New Research on Alzheimer's Disease

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NEW RESEARCH ON ALZHEIMER’S DISEASE

No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.

NEW RESEARCH ON ALZHEIMER’S DISEASE

EILEEN M. WELSH EDITOR

Nova Science Publishers, Inc. New York

Copyright © 2006 by Nova Science Publishers, Inc.

All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. Library of Congress Cataloging-in-Publication Data New research on Alzheimer's disease / Eileen M. Welsh (editor). p. ; cm. Includes index. ISBN 978-1-60876-520-1 (E-Book) 1. Alzheimer's disease--Research. I. Welsh, Eileen M. [DNLM: 1. Alzheimer Disease. WT 155 N5315 2006] RC523.R472 616.8'310072--dc22

Published by Nova Science Publishers, Inc. New York

2006 2005035992

Contents Preface Chapter I

vii Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion of Amyloid-β Glenda M. Bishop and Stephen R. Robinson

Chapter II

The Role of Phospholipase A2 in Alzheimer's Disease Wagner F. Gattaz, Evelin L. Schaeffer and Orestes V. Forlenza

Chapter III

Low Molecular Weight Glycosaminoglycans and Apoptosis: Potential Treatment of Neurodegenerative Disorders Including Alzheimer’s Disease Bertalan Dudas

Chapter IV

Chapter V

Chapter VI

Chapter VII

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1): One of the Hallmarks ofAlzheimer’s Disease and Other Complex Degenerative Processes Christiane Gläser, Gerd Birkenmeier, Susanne Schulz and Klaus Huse

1 57

87

99

The Role of Peroxisome Proliferator-Activated Receptors in Alzheimer’s Disease Dokmeci Dikmen

125

Role of Sphingomyelin Cycle Signaling System in Alzheimer’s Disease A. V. Alessenko

165

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease Ryszard Pluta

183

vi

Chapter VIII

Index

Eileen M. Welsh

Amyloid Beta (Aβ) Peptides in Plasma as Biochemical Markers of Alzheimer's Disease and Mild Cognitive Impairment Tomasz Sobow, Marcin Flirski, Pawel P. Liberski and Iwona Kloszewska

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Preface Dementia is a brain disorder that seriously affects a person's ability to carry out daily activities. The most common form of dementia among older people is Alzheimer's Disease (AD), which involves the parts of the brain that contol memory, thought and language. Age is the most important known risk factor for AD. The number of people with the disease doubles every 5 years beyond age 65. AD is a slow disease, starting with mild memory loss and ending with severe brain damage. The course the disease takes and how fast changes occur vary from person to person. On average, AD patients live from 8 to 10 years after they are diagnosed, though the disease can last for as many as 20 years. Current research is aimed at understanding why AD occurs and who is at greatest risk for developing it, improving the accuracy of diagnosis and ability to identify who is at risk, developing, discovering and testing new treatments for behavioral problems in patients with AD. This new book gathers state-of-the-art research from leading scientists throughout the world which offers important information on understanding the underlying causes and discovering the most effective treatments for Alzheimer's Disease. The notion that the amyloid-beta (Aβ) peptide plays a role in the pathogenesis of Alzheimer’s disease (AD) has received strong support from in vitro demonstrations that Aβ is toxic to cultured neurones, but its support from in vivo models has been equivocal. In order to understand the reasons for this difference, the authors of chapter I have critically appraised the numerous in vivo studies that have investigated the toxicity of Aβ by injecting or infusing Aβ into the brains of rodents or primates. Taken together, these studies indicate that neuronal loss is not a consistent response to Aβ, yet it does induce subtle changes in neuronal function by altering several neurotransmitter systems, particularly the cholinergic system. Behavioural impairments are evident on spatial and discriminative learning tasks and are paralleled by a reduced capacity to induce LTP. In addition, Aβ induces astrocytic and microglial reactivity which may be associated with increased indices of oxidative stress. The Aβ injection/infusion models have also shown some brain regions to be more susceptible to the neuroactive properties of Aβ than others. The superior spatial and temporal resolution of injection/infusion models allows comparisons of the effects of individual isoforms or fragments of Aβ, and of agents that enhance or reduce the bioactivity of this peptide. They conclude that the Aβ injection/infusion models are a valuable adjunct to transgenic mouse

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models, and they may help to elucidate the physiological actions of Aβ and further our understanding of the pathogenesis of AD. Phospholipase A2 (PLA2) is a key enzyme in phospholipid metabolism. In the brain, PLA2 is involved in the liberation of membrane choline for acetylcholine synthesis, as well as in the processing of the amyloid precursor protein to form the beta-amyloid, the major component of senile plaques in Alzheimer's disease (AD) as described in chapter II. In previous post-mortem studies the authors reported on decreased PLA2 activity in the frontal and in the parietal cortex of patients with AD, suggesting reduced phospholipid metabolism in the disease. Interestingly, they found also a reduction of PLA2 activity in platelet membranes of AD patients, suggesting that reduced phospholipid turnover may also be observed in peripheral cells of AD patients. In an in vivo study they investigated the intracerebral phospholipid metabolism in 16 patients with probable AD and 18 age-matched controls through 31P-Magnetic Resonance Spectroscopy of the pre-frontal cortex. Cognitive assessment was performed by the CAMDEX schedule. PME resonance was significantly higher and PDE was lower among AD than controls. PME correlated negatively with cognitive performance. Higher PME indicates reduced breakdown of membrane phospholipids, which is in line with reduced PLA2 activity. The findings in the pre-frontal cortex suggest that reduced membrane phospholipid turnover may be a widespread cerebral phenomenon in AD brains, since the pre-frontal cortex is a region not as severely affected by the neurodegenerative process as temporal and parietal areas, specially in early stages of dementia. To investigate further the implications of reduced PLA2 in the neurobiology of AD, they carried out a series of in vitro and animal experiments, to respectively test the effects of the inhibition of PLA2 on neuronal homeostasis in cultured neurons, and in memory formation in rats. In primary cultures of cortical and hippocampal neurons, the inhibition of PLA2 precluded neurite outgrowth, and the sustained inhibition of the enzyme in mature cultures lead to loss of viability. These findings reinforce the involvement of PLA2 enzymes in neurodevelopment and neurodegeneration. In early stages of AD there is an impairment of episodic short-term (STM) and long-term memory (LTM). In rat hippocampal slices, PLA2 has been implicated in mechanisms of synaptic plasticity involved in memory formation. Using adult Wistar rats, we investigated the effects of injections of PLA2 inhibitors into rat hippocampus on the formation of STM and LTM of a one-trial step-down inhibitory avoidance task. Infusion of the PLA2 inhibitors impaired both STM and LTM in a dosedependent manner. Additionally, because memory function is largely dependent on the fluidity of brain membranes, they investigated the effects of in vivo PLA2 inhibition on the fluidity of hippocampal membranes from rats subjected to inhibitory avoidance training. Hippocampal tissue from rats injected with PLA2 inhibitor showed reduced membrane fluidity, and this reduction was highly correlated with PLA2 inhibition. Taken together, the findings suggest that reduced PLA2 activity, probably reducing membrane phospholipids breakdown, may contribute to the memory impairment in AD. Previous studies have shown that apoptosis (programmed cell death) plays a crucial role in the pathomechanism of neurodegenerative disorders. It is a general consensus that apoptosis can be triggered by dysregulation of nerve growth factor physiology and/or oxidative stress processes. As reported in chapter III, since both of these pathological changes are characteristic to AD, it is conceivable that influencing apoptosis can be a valuable tool in

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the treatment of neurodegenerative disorders. Glucosaminoglycans (GAGs) exhibit neuroprotective properties in several animal models of AD. Low molecular weight GAG, C3, attenuates Aβ(25-35)-induced tau-2 immunoreactivity, and AF64A-induced cholinergic lesion in rat brain. Recent studies have also revealed that C3 influences p75 nerve growth factor receptor expression. However, the exact mechanism of the neuroprotective attributes of C3 is not elucidated yet. Since apoptosis is believed to play a pivotal role in numerous neurodegenerative disorders, C3 may induce neuroprotection/neurorepair via affecting apoptotic processes. The neuroprotective effect of glucosaminoglycans including C3 thus may involve multiple mechanisms, including an influence on processes that lead to programmed cell death. Since apoptosis is a crucial event not only in neurodegenerative diseases but also in the general process of aging, C3 may be a valuable therapeutic agent in Alzheimer’s disease-related senile dementia and in other age-related malfunctions. Susceptibility to Alzheimer´s disease (AD) is governed by multiple factors. Remarkably, LDL receptor-related proteins (LRPs) and several of their numerous ligands were associated to AD. Alpha2-macroglobulin (A2M), apolipoprotein E (Apo E), but also amyloid precursor protein (APP) belong to the functionally and genetically interesting molecules involved in the complex degenerative processes resulting in AD as suggested by the findings in chapter IV. LRP1 (CD91) (MIM 107770) is a 4,544-amino acid protein containing a single transmembrane segment and is located on chromosome 12q13.1-12q13.3 within a region shown to be linked to AD. It consists of 84 exons and belongs to the largest human proteins and is highly evolutionary conserved. It could be demonstrated that several genomic variants of LRP1 were associated to AD but also to other degenerative diseases like atherosclerosis and cancer suggesting a complex role in fundamental cellular processes. LRP1 functions as a clearance receptor for several ligands, including amyloid ß (Aß), and mediates signaling pathways affecting the processes of neurite outgrowth and calcium influx. While clearance of Aß diminishes the extracellular Aß-load the interaction with APP may enhance formation of Aß. LRP1 is expressed in brain, blood vessels as well as in endothelial cells of the brainblood-barrier mediating the transcytosis of Aß between blood circulation and brain. Internalization via LRP1 concerns also extracellular proteases and protease-inhibitor complexes involved in Aß degradation. In AD as well as in other diseases genetic variations and structure-caused failure of LRP1 leading to dysfunctions as well as alteration in the expression of LRP1 ligands may determine common degenerative processes. Age-related changes in the level of LRP1 and its ligands may increase the risk for degenerative diseases. The modulation of LRP1 and its ligands by cytokines and growth factors was detected in and outside the brain. There are indications that also inflammatory processes play an important role in the development of degenerative diseases. Alzheimer’s disease (AD) is characterized by a progressive loss of cognitive function with cerebral deposits of amyloid-β (Aβ) senile plaques and neurofibrillary tangles (NFTs) surrounded by inflammatory cells. Neuroinflammation, oxidative stress and impaired glucose and lipid metabolism are postulated to be the mechanisms playing role in the pathophysiology of AD. Recent evidence suggests that inflammatory events are associated with plaque formation in the brains of patients with AD and non-steroid anti-inflammatory drugs (NSAIDs) might influence central nervous system (CNS) inflammation and AD pathology. Reactive oxygen and nitrogen species production may also participate in part to

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neurodegeneration in AD brains; antioxidant and/or free radical scavengers reduce inflammation in AD via free radical quenching and possess neuroprotective activity. In addition, AD patients show hyperinsulinemia and reduced insulin sensitivity during fasting and glucose tolerance tests; and insulin gene polymorphism might act as a modifier of AD progression. An increased number of insulin receptors are also observed in post-mortem brain tissues of AD patients. Furthermore, augmented plasma insulin levels and reduced cerebrospinal fluid (CSF) levels and CSF/plasma insulin ratio are observed in AD patients. Chapter V discusses treatment of insulin resistance may reduce the risk or retard the progression of AD. Peroxisome proliferator-activated receptors (PPARs), members of the nuclear receptor family, are ligand-activated transcription factors. To date, three isoforms, encoded by separated genes, have been identified: PPARα [NR1C1], PPARβ (NUC-1 or PPARδ) [NR1C2] and PPARγ [NR1C3]. All PPAR isotypes are detected and found to exhibit specific patterns of localization in the different areas of the brain. PPARs may have specific functions in regulating the expression of genes involved in neurotransmission, and therefore play roles in complex processes, such as neurodegeneration, learning and memory. It is likely that at least some effects of PPAR agonists and NSAIDs on AD pathology are mediated through PPARs, since both PPARs and cyclooxygenase (COX) expression are increased in AD brains. Recently, NSAIDs, activating PPARα and γ, have been identified. In addition, NSAIDs and PPARα and γ agonists have anti-inflammatory, antioxidant and neuroprotective effects. This neuroprotective effect correlates with the modulation of β-catenin levels, inhibition of glycogen synthase kinase-3β (GSK-3β) activity and increased mRNA levels of the Wnt-target genes engrailed-1, cyclin D1 and PPARδ. Thiazolidinediones (TZDs) such as pioglitazone and rosiglitazone are insulin sensitizers, used to control glucose concentrations in patients with type 2 diabetes. These are potent synthetic PPARγ agonists, which exert both anti-inflammatory and antioxidant effects. PPARα and γ ligands, NSAIDs and TZDs inhibit activation of nuclear factor (NF)-κB, signal transducers and activators of transcription-1 (STAT-1), the nuclear factor of activated T-cells (NFAT) and activating protein-1 (AP-1). Moreover, they prevent the expression of COX-2 and inducible nitric oxide synthase (iNOS) and production of inflammatory cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α in human monocytes and arrest the differentiation of monocytes into activated macrophages. In conclusion, the development of new drugs targeting PPARs would be a great interest for future treatments of AD. Alzheimer’s disease (AD) is characterized by a progressive decline in cognition, memory and intellect. Possible mechanisms for AD neurotoxicity include: alteration in Ca2+ homeostasis, activation of specific receptors affecting cellular homeostasis, activation of oxidative processes, direct disruption of membrane integrity and disorders in lipid metabolism, or a combination of two or more of the above mechanisms. It was established that conformational changes in amyloid-beta peptide (Aβ) may occur in lipid rafts under the control of specific sphingolipids. Chapter VI demonstrates a novel mechanism for development of AD. It has been hypothesized that Aβ and TNF-α may have a prominent role in neurodegeneration. It is well-known that neuronal death is developed according to apoptotic program. Most signaling pathways that trigger apoptosis remain unknown, but the sphingomyelin pathway has been recognized as an ubiquitous signaling system that links specific cell-surface receptors and environmental stresses to the nucleus. This pathway is

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initiated by the hydrolysis of sphingomyelin via the action of sphingomyelinases to generate ceramide. Ceramide then serves as a second messenger in this system, leading to apoptosis. Oxidative mechanisms have been implicated in this pathway. TNF-α activates receptors linked to multiple effector systems, including a sphingomyelin pathway and peroxide oxidation. Recently, it was shown that superoxide radicals are used as signaling molecules within the sphingomyelin pathway. It means that cross-talk between the oxidation system and sphingomyelin cycle exists in cells and could have important implications for the induction phase and evolution of AD. The role of TNF-α in the pathogenesis of AD is unclear, because it has been shown to be involved in both neuroprotection and neurodegeneration, depending on doses and the age of animals. Small doses of this cytokine induced a protective effect against Aβ neurotoxicity. It was suggested that using low doses of TNF-α in the clinic for the prevention of AD development might be a perspective. Identification of the N-SMaseceramide pathway may lead to the development of more effective therapeutic strategies, aimed at preventing Aβ-induced cell death. The study of neurobiology of Alzheimer’s disease, now more than ever, needs an infusion of a new concept. Despite ongoing interest in Alzheimer’s disease, the basis of this entity is not yet clear. For now, the best-established and accepted “culprit” in Alzheimer’s disease pathology by most scientists is the amyloid, as the main molecular factor of neurodegeneration in Alzheimer’s disease. Abnormal upregulation of amyloid production or a disturbed clearance mechanism may lead to pathological accumulation of amyloid in the brain. Chapter VII will critically review these observations and highlight inconsistencies between the predictions of the “amyloid hypothesis” and the published data. There is still controversy over the role of amyloid in the pathological process – is it responsible for the neurodegeneration or does it accumulate because of the neurodegeneration? Recent evidence suggests that the neuropathology of Alzheimer’s disease comprises more than amyloid accumulation, tau protein pathology and finally brain atrophy. At least one third of Alzheimer types of dementia cases exhibit different cerebrovascular diseases. In addition, micro- and macroinfarctions and ischemic white matter changes are also evident in brains of Alzheimer’s disease patients. The presence of vascular abnormalities seems usually ignored and regarded by researchers as insignificant or considered incidental in Alzheimer’s disease etiology. Interestingly, that Alzheimer, in his own report presenting changes in the brain of the first patient had described, that besides “storage of peculiar material in the cortex, one sees endothelial proliferation and also occasionally neovascularisation”. Endothelial proliferation and angiogenesis and moderate arteriosclerosis in the brain arteries of the first case, provide evidence that cerebrovascular diseases were also evident in Alzheimer’s original case, which now defines Alzheimer’s disease. These raise the question of what was the first cerebrovascular disease as trigger of Alzheimer’s disease or neurodegeneration of Alzheimer’s type itself? New findings propose an early and significant role for ischemiareperfusion factors contributing to the neurodegenerative processes in Alzheimer’s disease. The ischemia hypothesis was primarily aimed at stimulating research and redirecting the focus of studies towards ischemic cellular mechanisms of Alzheimer’s disease. In this review, the authors will show that experimental brain ischemia-reperfusion episode produces neurochemical and neuropathological changes that simulate the early stage of Alzheimer’s disease process. Presented data suggest that ischemic mechanisms of neuronal death with β-

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amyloid peptide from circulatory network modulate neuropathology of cerebral ischemiareperfusion injury via molecular events in common with Alzheimer-type neuropathology. These results indicate that ischemic brain processes might be a key factor in the development of the picture of Alzheimer-type dementia over years. The collective data summarized in this review strongly support the idea that sporadic from of Alzheimer’s disease is a neurovascular disorder. Considerable progress has been made in recent years by a handful of researchers in understanding the role of ischemia in the aging process generally and in contributing to the development of Alzheimer’s disease. To accommodate the recent progress of study in Alzheimer’s disease there is a need to synthesize all the divergent pieces of data into a coherent story. This review provides a synopsis of current information about ischemic cellular and molecular mediators involved in Alzheimer’s neuropathology as well as interactions between these mediators that influence pathology. In this review, current knowledge on the relation between ischemia-reperfusion factors and Alzheimer’s-type dementia will be reviewed. They will summarize the results with a special focus on Alzheimer lesions in experimental brain ischemia. Taken all together, evidence presented in this review suggests a scheme for Alzheimer’s pathogenesis with ischemia-reperfusion playing a crucial role in influencing and linking β-amyloid deposition to neuronal damage and clinical disease. Plasma levels of amyloid β peptides (Aβ) represent a potentially attractive biomarker of Alzheimer’s disease (AD). Although plasma Aβ levels are increased in patients with familial AD mutations, results of the studies encompassing sporadic AD cases are equivocal. In several studies elevated plasma Aβ42 levels could be detected long before the onset of symptoms, though the value of that effect in predicting progression to dementia in mildly cognitively impaired (MCI) subjects is not known. It has recently been proposed that plasma Aβ levels increase merely with age and are neither sensitive nor specific for AD or MCI. Additionally, an increase of Aβ42 plasma levels in women with MCI has been reported and thus suggested to represent a biologic explanation for the increased prevalence of females in the population of late-onset AD patients identified by epidemiologic studies. In chapter VIII the authors have assessed the levels of Aβ peptides in plasma of carefully selected AD patients and MCI subjects compared to healthy controls matched for age, gender and education. The selection procedure employed in the study has been aimed at excluding patients with mixed AD as well as patients fulfilling current diagnostic criteria for both AD and other specific forms of dementia (e.g. dementia with Lewy bodies). No difference in any of the evaluated parameters (Aβ40, Aβ42, Aβ40/Aβ42 ratio) was observed between the AD and control groups. In subjects with MCI plasma Aβ42 levels were significantly elevated versus both AD (p<0,001) and controls (p<0,001), whereas Aβ40 concentrations were not significantly altered; no correlation with age or gender was found. A hypothesis can be formulated that the elevation of plasma Aβ42 in MCI is a reflection of efforts to eliminate the pathological peptide from the central nervous system (CNS) through the yet viable bloodbrain barrier (BBB). It is therefore probable that in a very early stage of AD alterations in the catabolism of a β-amyloid precursor protein (βAPP) occur, resulting in a preferential synthesis of longer, more amyloidogenic isoform of Aβ peptide - Aβ42; Aβ42 is initially effectively removed via the BBB which brings about a gradual increase in plasma Aβ42, but

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not Aβ40, still competently transported backwards. The results of the study, indicating an elevation of Aβ42, but not Aβ40 in MCI subjects, would support this hypothesis.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp. 1-55

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter I

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion of Amyloid-β Glenda M. Bishop∗ and Stephen R. Robinson School of Psychology, Psychiatry and Psychological Medicine, Monash University, Victoria, Australia

Abstract The notion that the amyloid-beta (Aβ) peptide plays a role in the pathogenesis of Alzheimer’s disease (AD) has received strong support from in vitro demonstrations that Aβ is toxic to cultured neurones, but its support from in vivo models has been equivocal. In order to understand the reasons for this difference, we have critically appraised the numerous in vivo studies that have investigated the toxicity of Aβ by injecting or infusing Aβ into the brains of rodents or primates. Taken together, these studies indicate that neuronal loss is not a consistent response to Aβ, yet it does induce subtle changes in neuronal function by altering several neurotransmitter systems, particularly the cholinergic system. Behavioural impairments are evident on spatial and discriminative learning tasks and are paralleled by a reduced capacity to induce LTP. In addition, Aβ induces astrocytic and microglial reactivity which may be associated with increased indices of oxidative stress. The Aβ injection/infusion models have also shown some brain regions to be more susceptible to the neuroactive properties of Aβ than others. The superior spatial and temporal resolution of injection/infusion models allows comparisons of the effects of individual isoforms or fragments of Aβ, and of agents that enhance or reduce the bioactivity of this peptide. We conclude that the Aβ injection/infusion models

∗

Corresponding Author: Glenda Bishop, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Wellington Road, Clayton VIC 3800 Australia. Tel: 61-3-990-54565; Fax: 61-3990-53948; Email: [email protected]

Glenda M. Bishop and Stephen R. Robinson

2

are a valuable adjunct to transgenic mouse models, and they may help to elucidate the physiological actions of Aβ and further our understanding of the pathogenesis of AD.

Abbreviations ACh: AChE: AD: Alz50: Am: Aβ: ATCtx: A/TFA: BS: CD68: ChAT: CR: CSF: Ctx: DβH: ED1: ELISA: EM: FCtx: GFAP: GPx: H and E: HFS: Hipp: IL-1β: Immuno: iNOS: LTP: LTD: MAP-2: MNB: NA: NB: NE: Nissl: nNOS: NOS: OX-42:

acetylcholine; acetylcholinesterase; Alzheimer’s disease; antibody that recognises abnormally phosphorylated tau; amygdala; amyloid-β; anterior temporal cortex; acetonitrile plus trifluoacetic acid; Bielschowsky silver; factor expressed by microglia; choline acetyltransferase; Congo red; cerebrospinal fluid; cerebral cortex; dopamine β-hydroxylase; antibody that recognises microglia and macrophages; enzyme-linked immunosorbent assay; electron microscopy; frontal cortex; glial fibrillary acidic protein, an astrocytic protein; glutathione peroxidase; haematoxylin and eosin; high-frequency stimulation; hippocampus; interleukin-1β (cytokine expressed by microglia); immunohistochemical labelling; inducible nitric oxide synthase; long-term potentiation; long-term depression; microtubule-associated protein type 2 (expressed in neuronal dendrites); magnocellular layer of the nucleus basalis; nucleus accumbens; nucleus basalis; norepinephrine; a cell stain that labels ribosomes and DNA; neuronal nitric oxide synthase; nitric oxide synthase; a specific antibody clone that recognises CD11b in activated microglia;

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion … OX-6: PCtx: PHF: revAβ: ROS: scrAβ: SI: SOD: Th-T: ThS: TUNEL: VEGF: VP: WB:

3

a specific antibody clone that recognises MHC Class II in microglia; parietal cortex; paired helical filament; reverse sequence of Aβ peptide; reactive oxygen species; scrambled sequence of Aβ peptide; substantia innominata; superoxide dismutase; Thioflavin-T; thioflavin-S; terminal deoxynucleotide transferase (TdT)-mediated dUTP-biotin nick end labelling (marker of apoptosis); vascular endothelial growth factor; ventral pallidum; Western blot.

Introduction The brains of patients with Alzheimer’s disease (AD) are characterised by neurodegeneration, the presence of neurofibrillary tangles and the accumulation of senile plaques, which are extracellular deposits composed largely of the amyloid-β (Aβ) peptide. Aβ is a 39-43 amino acid peptide that is naturally produced by the brain; the most commonly detected variants are Aβ1-40 and Aβ1-42. Aβ is normally dissolved in the extracellular fluid of the brain and cerebrospinal fluid (CSF), but under certain circumstances it forms into small fibrils which adopt a β-sheet formation, that precipitate out of solution as fibrillar aggregates and are deposited extracellularly into plaques. The aggregation process of Aβ is one of the mechanisms believed to underpin the neurodegeneration in AD. Since the Aβ peptide was sequenced in the early 1980s [Glenner and Wong, 1984; Masters et al., 1985], the aggregation of Aβ and its effects on brain cells have been studied extensively in vitro. These studies have contributed to the prevailing view that Aβ is toxic to neurones [e.g. Pike et al., 1992; Roher et al., 1991], particularly when in a fibrillar state [Hartley et al., 1999; Pike et al., 1991]. Aβ toxicity has been conjectured to be due to the generation of free radicals which lead to oxidative damage [e.g. Harris et al., 1995], the influx of calcium via the formation of membrane-spanning channels [e.g. Durell et al., 1994], the potentiation of neuronal excitotoxicity [e.g. Koh et al., 1990], and the release of neurotoxic agents from activated microglia [e.g. Giulian et al., 1996]. The data obtained from in vitro studies have provided useful information regarding the mechanisms of Aβ toxicity and how this may relate to the pathology of AD. Their physiological relevance is limited however, by the necessary use of simplified conditions which employ neuronal cultures obtained from neonatal animals or cancerous cell lines. Such cultures differ greatly from the intact adult brain where the interactions between different neural cell types permit an integrated response to a potentially toxic agent.

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Another way to assess the effects of Aβ on the living brain is to utilise transgenic mice that overexpress mutant forms of the human Aβ precursor protein (APP) which are associated with familial cases of AD [e.g. Games et al., 1995; Hsiao et al., 1996]. In these mice, Aβ plaques begin to deposit around 4 months of age, gradually increasing in number until they occupy up to 30% of the cortical and hippocampal volume when the mice are 18 months old [Games et al., 1995; Schenk et al., 1999]. While much emphasis has been put on the value of these transgenic models, they are limited with respect to the information they can provide about the spatio-temporal relationships between Aβ deposition and neuronal and cognitive dysfunction. This is because while the average Aβ deposition rate in a transgenic line can be determined, the exact time and location of individual deposits cannot be known. Thus there is a need for other in vivo models that can examine the effects of Aβ on specific brain regions in a time-dependent manner. In vivo models have been developed that either inject or infuse synthetic human Aβ variants into specific brain regions. For discrete microinjections, a small burr hole is drilled in the skull and a fine-tipped bevelled needle is used to inject the Aβ solution into the desired brain region. For infusion studies, a cannula is inserted into the brain and then attached via synthetic tubing to a subcutaneously-implanted mini-osmotic pump that contains the Aβ solution, allowing continual infusion of Aβ into the brain. To control for potential toxicity of the solvent that the Aβ is dissolved in, as well as the unavoidable mechanical damage of the injection procedure, control injections are given in the contralateral hemisphere or in a control group of animals. The brain is usually analysed to determine whether Aβ was deposited at the site of injection, and is then assessed for neuronal degeneration. Alternatively the brain is assessed for inflammatory responses, specific neuronal markers, or other markers that may be affected by Aβ. Table 1. Comparison of the features of transgenic and injection/infusion models of AD. Transgenic mouse models of AD No direct tissue damage Physiological Aβ deposition due to up-regulation of genes Allows investigations of chronic Aβ deposition, but has little temporal resolution Has global effects rather than local target Allows intracellular Aβ deposition No control over the contaminants present in plaques Involves overexpression of mutant genes (not physiological) Effects of genes are present throughout development Promoter is present in specific cell types and regions – biases outcome Only possible in rodents, which have different Aβ sequence and a limited cognitive capacity

Aβ injection or infusion models Tissue damage (solvent, needle, etc) Non-physiological deposition of Aβ, primarily as a bolus Allows acute investigations of Aβ deposition with high temporal resolution Local effects rather than global target (spatial resolution) Aβ treatment is exclusively extracellular Allows Aβ to be co-injected or co-infused with other agents Allows comparison of specific Aβ isoforms Allows specific ages to be targeted after normal brain maturation Can equally affect all cells in the vicinity Possible in all species including primates

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

5

The main advantages of injection/infusion in vivo models (see Table 1) include the spatial resolution of Aβ deposition, the temporal resolution after Aβ deposition, and the ability to examine specific Aβ isoforms. By contrast, transgenic mouse models have the advantage of being non-invasive, Aβ accumulates both extracellularly and intracellularly in their brains, and they have a slow but chronic build-up of Aβ. Clearly each model has its own strengths, and their advantages are complementary. More than 180 in vivo studies have assessed the actions of Aβ that has been delivered to a specific region of the brain, potentially allowing for an investigation of spatio-temporal effects. However, no consensus has yet been reached concerning whether Aβ delivered in this way is toxic to living brain tissue. The purpose of this chapter is to search for trends among these studies, to review correlations between the results obtained by researchers using similar protocols, to gain a better understanding of the reason for the variations, and to achieve a greater appreciation of the effects that Aβ has on the living brain.

Critical Analysis of the in vivo Studies: Selection Criteria The published literature was searched using the PubMed website (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed) to find primary data papers that had either injected or infused Aβ into the brains of animals. There were five primary criteria that had to be met for inclusion in this review: (1) the research paper had to be published in English; (2) the animals used had to be of a wild-type strain which was readily available, had not been genetically modified and had not been put under experimental stress; (3) the Aβ that was injected or infused had to be in a pure form (not mixed with a carrier or co-injected with another substance; these studies are discussed at the end of this chapter); (4) an appropriate control must have been used to compare the effects of Aβ, such as a vehicle control or a control peptide. Occasionally studies were found that did not include such controls, normally because they had examined the effects of Aβ in previous work and in the new study chose to make comparisons between pure Aβ and co-injections of Aβ with another substance [e.g. Takata et al., 2003], thus assuming consistency with previous experimental work; and (5) the study had to assess the effects of Aβ, not simply measure the deposition and clearance of the peptide after injection. These criteria enabled us to identify 146 papers published from 1991 to 2005, with approximately 20 papers published each year from 2001 onwards (Figure 1). The primary purpose of most studies was to determine whether Aβ was toxic to the living brain, but the measure of ‘toxicity’ varied considerably and could be broadly grouped into 7 categories: (1) neuronal degeneration, determined primarily by histological stains that detect dead or living neurones (Tables 2A-D); (2) changes in neuronal subpopulations, determined primarily by examining the expression or activity of neurotransmitter-related enzymes or markers (Tables 3A and 3B); (3) induction of gliosis using markers of activated astrocytes and microglia (Tables 4A-D); (4) behavioural changes (Tables 5A and 5B); (5) changes in normal synaptic function, generally determined from electrophysiological recordings (Tables 6A and 6B); (6) indices of oxidative stress (Tables 7A and 7B); and (7) miscellaneous

Glenda M. Bishop and Stephen R. Robinson

6

expression of cytokines, growth factors, cell-signalling molecules and hormones (Tables 8A and 8B). When studies performed multiple investigations, they were assigned to several categories. For instance, a paper may have examined neuronal death, changes in neurotransmitter expression and behavioural changes. 22

Number of published studies

20 18 16 14 12 10 8 6 4 2

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

0

Year of Publication Figure 1. Published studies. Distribution of the published studies that met the criteria for inclusion in the present review, listed according to the year of publication.

Each of the tables include information about the species used, Aβ sequence, the use of a physiological solvent, the type of controls, the site of injection or infusion, whether Aβ deposition was analysed and the specific type of analysis that was performed. The analysis was described in terms of the quantitative or qualitative assay that was used. In recent years much emphasis has been placed on the influence of the secondary structure of Aβ on toxicity, yet there is a lack of agreement concerning the best way to encourage Aβ to assume a desired conformation. Furthermore, the terms ‘fibrillar’ and ‘aggregated’ are often applied differently by researchers, such that an aggregated preparation of Aβ generated by one researcher may have more or less fibrils than that generated by another researcher. For this reason, the secondary structure of Aβ was not defined in the summary tables, except in two cases where different secondary structures were examined and opposing results were observed for the two preparations [Geula et al., 1998; Weldon et al., 1998]. The summary tables show that an extraordinary degree of methodological variability exists.

Table 2A. Injection of Aβ induces neuronal degeneration. Physiological solvent?

Controls

Site of injection

Assay to detect Aβ

Type of analysis

Aβ25-35 Aβ25-35, Aβ142 Aβ25-35 Aβ25-35 Aβ1-40

N N

revAβ25-35 Vehicle

CA1 Right Am

None None

Nissl-qualitative Tau-2; tau protein levels

N N N

Hipp Right Am FCtx/Hipp, PCtx/Hipp

None None None

Nissl-qualitative Tau-2 cell counts in Hipp Nissl-lesion area

Y

FCtx, PCtx, ATCx

Aβ immuno

Nissl-lesion area; phosphorylated tau

rabbit

Aβ40, Aβ42 (fibrillar) Aβ1-42

Vehicle Vehicle Vehicle, revAβ1-40 Vehicle

Y

Vehicle

Cistern

None

Ghribi et al., 2003*

rabbit

Aβ1-42

Y

Vehicle

Cistern

None

Ghribi et al., 2004*

rabbit

Aβ1-42

Y

Vehicle

Cistern

None

rat young/old rat

Aβ1-40

N

Aβ1-40

Y

WB for apoptosis signals (Bcl-2, caspase cleavage) WB for apoptosis signals (Bcl-2, Bax, caspase cleavage) WB for apoptosis signals (caspase cleavage), tau phosphorylation; TUNELcell counts Nissl-living neurons (3×0.64µm2 sections); Alz50 Nissl-qualitative

rat

Aβ1-42

Y

rat

Aβ1-40, Aβ142 Aβ1-40

Y

Reference

Species

Aβ sequence

Bhagat et al., 2002 Chambers et al., 2000

rat rat

Chen et al., 1996 Dudas et al., 2002 Emre et al., 1992

rat rat rat

Geula et al., 1998*

monkey old

Ghribi et al., 2001*

Giordano et al., 1994 Gonzalo-Ruiz et al., 2003* Jantaratnotai et al., 2003* Jen et al., 1998* Kowall et al., 1991 Kowall et al., 1992

rat

rat, monkey Aβ1-40, Aβ25young/old 35

Vehicle, saline, FCtx revAβ1-40 Vehicle Retrosplenial granular Ctx Vehicle, Corpus callosum revAβ1-42 Vehicle Vitreous chamber

None Aβ immuno Aβ immuno None

N

revAβ1-40

Deep FCtx, or Hipp

Aβ immuno

N

revAβ1-40, scrAβ1-40

Deep Ctx; FCtx

Aβ immuno

Neurofilament medium subunit-fibre density; Luxol Fast Blue-demyelination Number of TUNEL positive-cells in retina Nissl-living neurons (3×0.64µm2 sections); Alz50, Gallays, tau Nissl-living neurons (3×0.64µm2 sections); Alz50, tau

Table 2A. Injection of Aβ induces neuronal degeneration. (Continued) Species

Aβ sequence

Physiological solvent?

rat

Aβ1-40

N

mice rat

Aβ25-35, Aβ1-28 Aβ1-40

Reyes et al., 2004*

rat

Rush et al., 1992

Reference

Controls

Site of injection

N N

Vehicle, revAβ1-42 Vehicle Vehicle

Hipp, 7 injections bilaterally Right ventricle ICV

Y

Vehicle

rat

Aβ1-40, RatAβ140 Aβ1-40, Aβ25-35

N

Vehicle

Dentate gyrus bilateral Dorsal Hipp

Ryu et al., 2004* Sigurdsson et al., 1996

rat rat

Aβ1-42 Aβ25-35

Y N

Right Hipp Right Am

Sigurdsson et al., 1997a Sigurdsson et al., 1997b Sigurdsson et al., 2000

rat

Aβ25-35

N

rat

Aβ25-35

N

revAβ1-42 Vehicle, revAβ25-35 Vehicle, revAβ25-35 Vehicle

rat

Aβ1-42

N

Vehicle

Am bilateral

Stepanichev et al., 2003b Stepanichev et al., 2004 Stephan et al., 2001

rat

Aβ25-35

N

Vehicle

Hipp

rat

Aβ25-35

N

Vehicle

ICV bilateral

rat

Aβ40+Aβ43

N

Vehicle

Stephan et al., 2003

rat

Aβ40+Aβ43

N

Vehicle

mouse

Aβ25-35

N

Saline, revAβ25-35

Dentate gyrus, 8 bilateral injections Dentate gyrus, 8 bilateral injections Right ventricle

Malin et al., 2001 Maurice et al., 1996 Minogue et al., 2003

Tohda et al., 2003

Am Am

Assay to detect Aβ

Type of analysis

Aβ immuno

Nissl-semi-quantitative

CR None

Nissl-Hipp living neurons in 5000µm2 Levels of Bax, cytochrome c, PARP, FasL (apoptosis) Nissl-living neurons

Aβ immuno, CR, ThS None Nissl-area of tissue loss, area of neuronal loss, total area of damage None NeuN-cell counts None Nissl-qualitative, neuronal size; tau-2, Alz50 CR Nissl-neuronal size; tau-2-cell counts in 6 sections CR Nissl-neuronal size; tau-2-cell counts in 6 sections Aβ immuno, Nissl-neuronal size CR None Nissl-area of degeneration; TUNELqualitative; caspase-3 activity None H&E-living neuron counts Aβ immuno, ThS Aβ immuno, ThS None

Nissl and NeuN-qualitative Nissl-qualitative Nissl-neuron density

Table 2A. Injection of Aβ induces neuronal degeneration. (Continued) Reference

Physiological solvent?

Species

Aβ sequence

Waite et al., 1992

rat

N

Walsh et al., 2002*

rat

Aβ1-40, Aβ1-42, RatAβ1-42 Aβ1-42

Walzer et al., 2002 Whitehead et al., 2005 Yagami et al., 2004*

rat rat rat

Aβ25-35 Aβ25-35 Aβ25-35, Aβ140, Aβ1-42

N Y Y

Zou et al., 2003

rat

Aβ1-42

N

Y

Controls

Site of injection

Vehicle, revAβ1-40 Vehicle, revAβ1-42 Vehicle Vehicle Vehicle, scrAβ25-35, revAβ25-35 PBS

Hipp

Assay to detect Aβ

Type of analysis

Right Am ICV bilateral Striatum

Aβ immuno, ThS Fluoresceintagged Aβ CR CR None

Number of TUNEL positive-cells and Nissl-stained cells in retina Tau-2 cell counts Tau-2 cell counts Nissl-area of degeneration

Entorhinal Ctx

CR

Tau phosphorylation (WB)

Vitreous chamber

Nissl-qualitative

Table 2B. Injection of Aβ does not induce neuronal degeneration Reference

Aβ25-35

*

rat

*

rat

Aβ1-40, Aβ1-42, RatAβ1-40 Aβ1-42, RatAβ1-42 Aβ1-42 Aβ1-43, Aβ1-40

N

Aβ25-35 Aβ1-40, Aβ1-38, Aβ25-35

Y Y or N

Bishop & Robinson, 2003b

Bishop & Robinson, 2004 Clemens & Stephenson, 1992

Games et al., 1992

*

Y

rat

Bishop & Robinson, 2003a

Dornan et al., 1993

revAβ25-35

Aβ sequence

Arias et al., 2002

*

Physiological solvent? Y

Species

rat rat young/ middle aged rat rat

Controls

Site of injection Assay to detect Aβ

Type of analysis

None

Nissl-lesion size

Vehicle

Hipp (dentate gyrus) Ctx

Aβ immuno, EM

Fluoro-Jade-total counts

Y

Vehicle

Ctx

Aβ immuno, EM

Fluoro-Jade-total counts

Y

Vehicle

Ctx

Aβ immuno

Fluoro-Jade-total counts

Aβ immuno

Nissl, H&E-qualitative lesion size; Alz50 Nissl-qualitative lesion size H&E-qualitative; BS Gallays, phosphorylated neurofilament, tau, Alz50

Prolactin in vehicle, Striatum, dorsal scrAβ1-40 Hipp Vehicle Hipp bilateral Vehicle, scrAβ1-40, Ctx or Hipp revAβ1-40, revAβ25 -35, scrAβ25-35

CR Aβ immuno, CR

Table 2B. Injection of Aβ does not induce neuronal degeneration. (Continued) Physiological solvent? rat young/old, Aβ40, Aβ42 (fibrillar Y monkey young or soluble) rat Aβ25-35, Aβ1-40 N rat Aβ1-40 N rat Aβ1-28 N

Reference Geula et al., 1998

Species

*

Giovannelli et al., 1995 Giovannelli et al., 1998 Miguel-Hidalgo et al., 1998

Aβ sequence

Controls

Site of injection

Vehicle Saline, scrAβ25-35 Saline Vehicle

FCtx, PCtx, ATCx Right NB Right NB Right Hipp

Vehicle, revAβ1-40

Hipp

Assay to detect Aβ Aβ immuno

Nissl-lesion area; phosphorylated tau

rat

Aβ25-35, Aβ1-40

rat

Aβ1-40

Y

Vehicle

Hipp

None

Nissl-qualitative lesion size Nissl-total neuronal counts in NB Haematoxylin, MAP2-lateromedial extension of neuronal loss Nissl, H&E-volume of depleted Hipp neurons; MAP-2, TUNEL Nissl-area of degeneration

rat

Aβ1-42

Y

Vehicle

Right ventricle

Aβ immuno, CR

H&E, Bodian’s stain-qualitative

Podlisny et al., 1992

sheep monkey

Aβ1-40 Aβ1-40, Aβ25-35

N Y or N

Vehicle Vehicle, revAβ1-40, scrAβ1-40, scrAβ25-35

Ctx Ctx

Aβ immuno Aβ immuno

Podlisny et al., 1993

monkey

Aβ1-40, Aβ25-35

Y or N

Vehicle, revAβ1-40, scrAβ1-40, scrAβ25-35

Ctx

Sigurdsson et al., 1995 Smyth et al., 1994 Soto et al., 1998

rat rat rat

Aβ25-35 Aβ1-42, Aβ25-35 Aβ1-42

Y or N N N

Vehicle Vehicle, scrAβ25-35 Vehicle

VP/SI Hipp Am

Stein-Behrens et al., 1992

rat

Aβ25-35

Y or N

Vehicle, scrAβ25-35

Stephenson & Clemens, 1992

rat

Aβ1-43

N

Prolactin in vehicle

rat

Y

Vehicle, revAβ1-40

rat

Aβ1-40, Aβ1-42, RatAβ1-42 RatAβ1-42

Y

Vehicle

rat

Aβ1-42+Aβ1-40

N

PBS

Morimoto et al., 1998

*

Morimoto & Oda, 2003

*

*

Nakagawa et al., 2004 Nelson & Saper, 1996 *

*

Waite et al., 1992

Winkler et al., 1994 *

Zou et al., 2003

*

Y

CR CR, EM None

Type of analysis

Aβ immuno, CR

Alz50, tau-qualitative dystrophic neurites H&E-lesion width, neuronal cell counts; tau, BS, Alz50, phosphorylated neurofilament Aβ immuno H&E-lesion width, neuronal cell counts; tau, BS, Alz50, phosphorylated neurofilament CR Nissl-size of cavitation Aβ immuno Nissl-lesion volume Aβ immuno, CR, Nissl-gross level description ThS, EM None Nissl-area/volume of damage

Hipp (dentate gyrus) Corpus striatum, Aβ immuno Nissl, H&E-semiquantitation of neuronal dorsal Hipp damage; BS Hipp Aβ immuno, ThS Nissl-qualitative CA1 or lateral ventricle Entorhinal Ctx

Aβ immuno

Nissl-qualitative extent of reaction

CR

Tau phosphorylation (WB)

Table 2C. Infusion of Aβ induces neuronal degeneration. Reference

Physiological solvent?

Species

Aβ sequence

rat

Y

Aguado-Llera et al., 2005 Frautschy et al., 1998*

rat

Aβ25-35, Aβ142 Aβ40

N

Nakamura et al., 2001*

rat

Aβ1-42

N

Wang et al., 2001*

rat

Aβ1-40

N

Controls

Site of infusion

Assay to detect Aβ

Type of analysis

Saline, revAβ2535 Vehicle

Right ventricle

None

Cell death detection ELISA kit

Ventricle

Aβ immuno. CR, ThS

Vehicle, revAβ140 Vehicle

Right ventricle

None

TUNEL cells in four fields in frontal cortex; phosphorylated tau Nissl-qualitative

Left ventricle, 3 injections over 8 days

CR

H&E, EM, TUNEL-qualitative; Bax, P53, Bcl-2 immunoquantitative

Table 2D. Infusion of Aβ does not induce neuronal degeneration. Species

Aβ sequence

Physiological solvent?

Controls

Site of infusion

Brining et al., 1996*

rat

Aβ1-40

N

Vehicle

Ventricle

Games et al., 1992*

rat

N

rat

N

Vehicle, aCSF, revAβ1-40 Vehicle

Hipp

Nag et al., 1999*

Aβ1-40, Aβ138, Aβ25-35 Aβ1-40

Nitta et al., 1997* Snow et al., 1994*

rat rat

Aβ1-40 Aβ1-40

N N

Vehicle Vehicle, saline

Reference

Left or right ventricle Right ventricle Hipp

Assay to detect Aβ

Aβ immuno, ThS Aβ immuno, CR Aβ immuno

Type of analysis

Silver staining – qualitative H&E, Gallays silver, Alz50, BS-qualitative Nissl-gross observations

None Nissl-gross observations Aβ immuno, BS/Nissl-neuron counts; Alz50CR, ThS intensity

Table 3A. Effect of Aβ injection on neuronal subpopulations. Controls

Site of injection

Assay to detect Aβ

Medial septum

CR

N Y N

Vehicle, scrAβ2535 Contralateral MNB Saline Vehicle

Right MNB ICV Right Am

None None None

Aβ1-40

N

Vehicle, revAβ1-40

None

rat

Aβ25-35, Aβ1-40

N

Giovannelli et al., 1998

rat

Aβ1-40

N

Contralateral NB, saline, scrAβ25-35 Saline

FCtx/Hipp, PCtx/Hipp Right NB Right NB

CR, EM

Giovannini et al., 2002

rat

Aβ1-42

N

Saline

Right NBM

Aβ, CR

Gonzalo-Ruiz et al., 2003* Gonzalo-Ruiz et al., 2005* Harkany et al., 1995a Harkany et al., 1995b Harkany et al., 1999a Harkany et al., 1999b Harkany et al., 2000 Harkany et al., 2001 Li et al., 2004a* O'Mahony et al., 1998

rat

Aβ1-40

Y

Vehicle

Aβ immuno

rat

Aβ1-40

Y

Vehicle

Aβ immuno

Decreased AChE fibre density

rat rat rat rat rat rat rat rat

Aβ1-42 Aβ1-42 Aβ1-42 Aβ1-42 Aβ1-42, Aβ25-35 Aβ1-42 Aβ1-40 Aβ1-42, Aβ25-35

N N N N N N Y N

Vehicle Vehicle Vehicle Vehicle Vehicle Vehicle Vehicle Vehicle

Retrosplenial granular Ctx FCtx or cingulate Ctx Medial septum Right MNB Right MNB Right MNB Right MNB MNB Hipp bilateral Right MNB

Decreased ACh release (in vivo), and ChAT cell count Decreased ACh release (in vivo), and ChAT cell count in NB Decreased ChAT immuno, and ACh release by K+ Decreased ChAT neurones (cell counts)

None None None None None None None ThS

Decreased ChAT immuno cell count Decreased AChE and ChAT activity in FCtx Decreased AChE fibre density in Ctx Decreased AChE and ChAT activity Decreased AChE fibre density Decreased AChE fibre density Decreased AChE fibre density Decreased AChE fibre density

Reference

Species

Aβ sequence

Cholinergic System Abe et al., 1991

rat

Abraham et al., 2000 Choi et al., 2001* Dudas et al., 2002

rat mouse rat

Aβ12-28, Aβ2535, Aβ1-40 Aβ1-42 Aβ1-42 Aβ25-35

Emre et al., 1992

rat

Giovannelli et al., 1995

Physiological solvent?

N

CR

Type of analysis

Decreased ACh release (in vivo); unchanged ChAT assay Decreased AChE fibres Unchanged ACh levels Unchanged ChAT immuno cell count in Hipp, and ChAT and AChE activity in Hipp Decreased number of AChE cells

Table 3A. Effect of Aβ injection on neuronal subpopulations. (Continued) Reference

Species

Aβ sequence

Physiologic al solvent?

Scali et al., 1999 Sigurdsson et al., 1995 Sigurdsson et al., 1997a

rat rat rat

Aβ1-40 Aβ25-35 Aβ25-35

N Y or N N

Yamaguchi & Kawashima, 2001 Yamaguchi et al., 2002

rat

Aβ25-35

rat

Yan et al., 2001* Winkler et al., 1994* Noradrenergic System Chen et al., 1996 Emre et al., 1992 Gonzalo-Ruiz et al., 2003* Song et al., 2001* Serotonergic System Chen et al., 1996 Gonzalo-Ruiz et al., 2003 Harkany et al., 2001

Controls

Site of injection

Assay to detect Aβ

Type of analysis

Right NB VP/SI Am

CR CR CR

Decreased Ach levels Unchanged ChAT activity Unchanged ChAT activity

N

Saline Vehicle Vehicle, revAβ2535 Vehicle

Left ventricle

None

Aβ25-35

N

Vehicle

Left ventricle

None

mice rat

Aβ1-42 RatAβ1-42

Y Y

revAβ1-42 Vehicle

ICV CA1 or lateral ventricle

None Aβ immuno

Decreased ChAT activity, and ChAT cell counts Decreased ChAT activity, and ChAT cell counts Decreased Ach levels Unchanged ChAT activity in Hipp

rat rat

Aβ25-35 Aβ1-40

N N

Increased levels of NE in locus coeruleus Decreased number of DβH cells

Aβ1-40

Y

Aβ immuno

Decreased DβH neurones (cell counts)

mouse

Aβ1-42, Aβ1-40, Aβ25-35, Aβ1-28

Y

Vehicle, revAβ142

Hipp FCtx/Hipp, PCtx/Hipp Retrosplenial granular Ctx ICV

None None

rat

Vehicle Vehicle, revAβ140 Vehicle

None

Increased NE turnover

rat

Aβ25-35

N

Vehicle

Hipp

None

rat

Aβ1-40

Y

Vehicle

Aβ immuno

rat

Aβ1-42

N

Vehicle

Retrosplenial granular Ctx MNB

Increased levels of 5-HT and 5-HIAA in locus coeruleus Decreased 5-HT neurones (cell counts)

None

Decreased 5-HT fibre density, levels of 5-HT and 5-HIAA levels, and 5-HT1A receptor binding sites

Table 3A. Effect of Aβ injection on neuronal subpopulations. (Continued) Reference

Species

Amino Acid Transmitters Harkany et al., 1999a rat

Aβ sequence

Physiologic al solvent?

Controls

Site of injection

Assay to detect Aβ

Aβ1-42

N

Vehicle

Right MNB

None

Harkany et al., 2000

rat

Aβ1-42, Aβ25-35

N

Vehicle

Right MNB

None

Scali et al., 1999

rat

Aβ1-40

N

Saline

Right NB

CR

Neuropeptides Yamamoto et al., 2003

rat

Aβ25-35

Y

Vehicle

NBM bilateral

None

Interneurones Harkany et al., 1995a

rat

Aβ1-42

N

Vehicle

None

Li et al., 2004a* O'Mahony et al., 1998

rat rat

Aβ1-40 Aβ1-42, Aβ25-35

Y N

Vehicle Vehicle

Medial septum Hipp bilateral Right MNB

Walsh et al., 2002*

rat

Aβ1-42

Y

Vehicle, revAβ142

Vitreous chamber

Type of analysis

Increased levels of glutamate, aspartate and taurine Increased levels of Ca2+, taurine, aspartate and glutamate in vivo Unchanged glutamate, aspartate, taurine levels in PCtx; increased GABA levels; decreased glutamic acid decarboxylase activity in PCtx Decreased somatostatin and proSS mRNA; increased cholecystokinin, unchanged proCCK mRNA; unchanged substance P; increased activity of neuropeptide-degrading enzyme PEP but EP24.15, PSA, LAP and APB are unchanged; increased neuropeptide-processing enzymes SPC and PAM but CPE is unchanged

Unchanged parvalbumin immuno-total cell count in MS None Decreased nNOS cell counts & WB ThS Increased NADPH-diaphorase immuno intensity (in nNOS neurons) and nNOS-activity Fluorescein- Decreased number of parvalbumin-positive cells tagged Aβ

Table 3B. Effect of Aβ infusion on neuronal subpopulations. Species

Aβ sequence

Physiological solvent?

Controls

Site of infusion

Assay to detect Aβ

rat (infant, adult, or aged)

Aβ1-40

N

Vehicle

Right ventricle

None

Itoh et al., 1996*

rat

Aβ1-40

N

Vehicle

Left ventricle

None

Nabeshima & Nitta, 1994* Nag et al., 1999*

rat

Aβ1-40

N

Vehicle

Left ventricle

None

rat

Aβ1-40

N

Vehicle

Nag & Tang, 2001*

rat

Aβ1-40

N

Vehicle

Nakamura et al., 2001*

rat

Aβ1-42

N

Nitta et al., 1994* Nitta et al., 1997* Olariu et al., 2001

rat rat rat

Aβ1-40 Aβ1-40 Aβ25-35

N N N

Vehicle, revAβ1-40 Vehicle Vehicle Vehicle

Left or right Aβ immuno ventricle Left or right None ventricle Right ventricle None

Pavia et al., 2000

rat

N

scrAβ25-35

Right ventricle

None

Saez-Valero et al., 2002 Tanaka et al., 1998* Tang et al., 2002*

rat

A/TFA then Aβ25-35 A/TFA then Aβ25-35 Aβ1-40 Aβ1-40

N

scrAβ25-35

Right ventricle

None

N N

Vehicle Vehicle

Right ventricle Ventricle

None None

Reference

Cholinergic System Fukuta et al., 2001*

rat rat

Left ventricle Aβ immuno Right ventricle None Right ventricle None

Type of analysis

Decreased ChAT activity in adult rats; unchanged ChAT activity in infant and aged rats. Decreased release of ACh by nicotine or K+ (dialysis) Decreased ChAT activity; unchanged AChE activity Decreased ChAT activity Decreased ChAT activity Decreased ChAT activity and hemicholinium-3 binding Decreased ChAT activity Decreased ChAT activity Decreased ACh release by nicotine (dialysis) Increased AChE immuno-cell counts; unchanged ChAT activity Altered AChE isoform ratio; unchanged AChE activity Unchanged ChAT activity Decreased ChAT activity

Table 3B. Effect of Aβ infusion on neuronal subpopulations. (Continued) Controls

Site of infusion

Assay to detect Aβ

N

Vehicle, revAβ1-40

Right ventricle

None

Decreased ACh release by nicotine (dialysis)

N

Vehicle

CR

Decreased ChAT activity

Aβ1-40 Aβ1-42

N N

Vehicle revAβ1-40

Left ventricle, 3 injections over 5 days Right ventricle Right ventricle

None None

Decreased ChAT activity Unchanged ChAT activity

rat

Aβ1-40

N

Vehicle

Left ventricle

None

Yamada et al., 1999b*

rat

Aβ1-42

N

revAβ1-40

Right ventricle

None

Decreased release of DA by nicotine or K+ (dialysis) Unchanged levels of dopamine, DOPAC, HVA, 5-HT, 5-HIAA, NA

Neuropeptides Aguado-Llera et al., 2005

rat

Aβ25-35, Aβ1-42

N

Saline, revAβ25-35

Right ventricle

None

Nag et al., 1999*

rat

Aβ1-40

N

Vehicle

Left or right ventricle

Nag & Tang, 2001*

rat

Aβ1-40

N

Vehicle

Left or right ventricle

Tang et al., 2002*

rat

Aβ1-40

N

Vehicle

Ventricle

Reference

Species

Aβ sequence

Tran et al., 2001*

rat

Wang et al., 2001*

rat

Aβ1-40, Aβ1-42, Aβ25-35 Aβ1-40

Yamada et al., 1998* Yamada et al., 1999b* Dopaminergic System Itoh et al., 1996*

rat rat

Physiological solvent?

Type of analysis

Decreased somatostatin levels; decreased density of somatostatin receptor sst2, but sst1, sst3 or sst4 are unchanged Aβ immuno Decreased somatostatin levels and mRNA; decreased substance P but unchanged neuropeptide Y levels None Decreased somatostatin and substance P levels but unchanged neuropeptide Y levels None Decreased somatostatin levels

Table 4A. Injection of Aβ induces gliosis. Assay to detect Aβ None

Microglia (F4/80-intensity)

Aβ immuno

Microglia (CD68-total counts)

Physiological solvent? Y

Controls

Site of injection

revAβ1-42

Ctx

Y

Vehicle

N

Saline

FCtx, PCtx, ATCx Right NBM

Aβ1-40

Y

Vehicle

rat

Aβ1-42

Y

mice

Aβ1-42

Y

Li et al., 2004a* Nakagawa et al., 2004* O'Hare et al., 1999 Reyes et al., 2004*

rat rat

Aβ1-40 Aβ1-42

Y Y

rat rat

Y Y

Richardson et al., 2002* Ryu et al., 2004*

rat

Aβ1-42 Aβ1-40, rat Aβ1-40 Aβ1-42

Y

rat

Aβ1-42

Y

revAβ1-42

Right Hipp

None

Scali et al., 1999 Sigurdsson et al., 1996

rat rat

Aβ1-40 Aβ25-35

N N

Saline Vehicle, revAβ25-35

Right NB Right Am

CR None

Reference El Khoury et al., 2003* Geula et al., 1998* Giovannini et al., 2002 Gonzalo-Ruiz et al., 2003* Jantaratnotai et al., 2003* Kim et al., 2004*

Species

Aβ sequence

mice

Aβ1-42

monkey old rat

Aβ40, Aβ42 (fibrillar) Aβ1-42

rat

Type of analysis

Aβ, CR

Astrocytes (GFAP-cell counts); Microglia (OX-6, COX-2, iNOS-cell counts) Aβ immuno Astrocytes (GFAP-qualitative)

Retrosplenial granular Ctx Vehicle, Corpus callosum Aβ immuno Astrocytes (GFAP-qualitative); Microglia revAβ1-42 (OX-42, OX-6-qualitative); Oligodendrocytes (CC1-cell counts) revAβ1-42 ICV None Microglia (OX-42 and interferon-γqualitative) Vehicle Hipp bilateral None iNOS-cell counts (glia), WB Vehicle Right ventricle Aβ immuno, Microglia (OX-42-qualitative) CR Sterile water CA3 Aβ immuno Astrocytes (GFAP-qualitative) Vehicle Dentate gyrus Aβ immuno, Astrocytes (GFAP-cell counts) bilateral CR, ThS Saline CA3 bilateral Aβ immuno Astrocytes (GFAP-intensity and number) Astrocytes (GFAP-cell counts) Microglia (ED1, COX-2-cell counts) Microglia (OX-42-qualitiative) Astrocytes (GFAP-branching)

Table 4A. Injection of Aβ induces gliosis. (Continued) Species

Aβ sequence

Physiological solvent?

Controls

Site of injection

Assay to detect Aβ

Sigurdsson et al., 1997a

rat

Aβ25-35

N

Am

CR

N N

Vehicle, revAβ25-35 Vehicle Vehicle

Sigurdsson et al., 1997b Sigurdsson et al., 2000

rat rat

Aβ25-35 Aβ1-42

Am Am bilateral

Soto et al., 1998

rat

Aβ1-42

N

Vehicle

Am

Stepanichev et al., 2003b

rat

Aβ25-35

N

Vehicle

Hipp

Stephan et al., 2001

rat

Aβ40+Aβ43

N

Vehicle

Stephan et al., 2003

rat

Aβ40+Aβ43

N

Vehicle

Walsh et al., 2002*

rat

Aβ1-42

Y

Walzer et al., 2002 Weldon et al., 1998*

rat rat

Aβ25-35 Aβ1-40 (fibrillar)

N Y

Vehicle, revAβ1-42 Vehicle Vehicle

Dentate gyrus, 8x bilateral Dentate gyrus, 8x bilateral Vitreous chamber Right Am Striatum

Whitehead et al., 2005

rat

Aβ25-35

Y

Vehicle

ICV bilateral

Yamamoto et al., 2003

rat

Aβ25-35

Y

Vehicle

NBM bilateral

Yan et al., 2001*

mice

Aβ1-42

Y

revAβ1-42

ICV

Zou et al., 2003

rat

Aβ1-42

N

PBS

Entorhinal Ctx

Reference

Type of analysis

Astrocytes (GFAP-branching); Microglia (IL1β) CR Astrocytes (GFAP-branching) Aβ immuno, Microglia (IL-1β, OX-42-semiquantitative) CR Aβ immuno, Astrocytes (GFAP-qualitative) CR, ThS None Astrocytes (GFAP-qualitative); Microglia (isolectin B4-qualitative) Aβ immuno, Astrocytes (GFAP-qualitative); Microglia ThS (OX-42-qualitative) Aβ immuno, Astrocytes (GFAP-qualitative); Microglia ThS (OX-42-qualitative) FluoresceinAstrocytes (GFAP) tagged Aβ CR Astrocytes (GFAP-cell counts) Aβ immuno, Astrocytes (GFAP, iNOS-intensity); CR, ThS Microglia (OX-42-cell counts; iNOSintensity) CR Astrocytes (GFAP-cell counts); Microglia (OX-6-cell counts) None Astrocytes (GFAP immuno and increased βglucuronidase activity) None Astrocytes (GFAP-qualitative); Microglia (IL1β-qualitative) CR Astrocytes (GFAP-quantitative)

Table 4B. Injection of Aβ does not gliosis. Reference

Species

Aβ sequence

Bishop & Robinson, 2003a*

rat

Games et al., 1992*

rat

Aβ1-40, Aβ142, RatAβ1-40 Aβ1-40, Aβ138, Aβ25-35

Geula et al., 1998*

Podlisny et al., 1992*

Podlisny et al., 1993*

rat Aβ40, Aβ42 young/old, (fibrillar or monkey soluble) young monkey Aβ1-40, Aβ2535

Physiologic al solvent? Y

Y or N

Y

Y or N

Controls Vehicle

Vehicle, scrAβ140, revAβ1-40, revAβ25 -35, scrAβ25-35 Vehicle

Vehicle, revAβ140, scrAβ1-40, scrAβ25-35 Vehicle, revAβ140, scrAβ1-40, scrAβ25-35 Prolactin in vehicle

monkey

Aβ1-40, Aβ2535

Y or N

Stephenson & Clemens, 1992

rat

Aβ1-43

N

Weldon et al., 1998

rat

Aβ1-40 (soluble)

N

Vehicle

Zou et al., 2003

rat

Aβ1-42+Aβ1-40

N

PBS

Site of injection Ctx

Assay to detect Aβ Aβ immuno, EM

Type of analysis Microglia (Ferritin-total counts)

Ctx or Hipp Aβ immuno, Astrocytes (GFAP-qualitative); Microglia CR (ED1-qualitative)

FCtx, PCtx, ATCx

Aβ immuno

Microglia (CD68-total counts)

Ctx

Aβ immuno

Astrocytes (GFAP-qualitative)

Ctx

Aβ immuno

Astrocytes (GFAP-qualitative)

Corpus striatum, dorsal Hipp Striatum

Entorhinal Ctx

Aβ immuno Astrocytes (GFAP-qualitative); Microglia (ED1-qualitative) Aβ immuno, CR, ThS CR

Astrocytes (GFAP, iNOS-intensity); Microglia (OX-42-cell counts; iNOSintensity) Astrocytes (GFAP-quantitative)

Table 4C. Infusion of Aβ induces gliosis. Reference

Species

Aβ sequence

Frautschy et al., 1998*

rat

Aβ40

Physiological solvent? Y

Matsunaga et al., 2003* Netland et al., 1998

rat

Aβ1-40

N

rat

Aβ

Y

Nitta et al., 1997* Snow et al., 1994*

rat rat

Aβ1-40 Aβ1-40

N N

Tran et al., 2001*

rat

Aβ1-40, Aβ142, Aβ25-35

N

Controls Vehicle

Vehicle, revAβ1-40 Vehicle Vehicle Vehicle, saline Vehicle, revAβ1-40

Site of infusion Ventricle

Assay to detect Aβ Aβ immuno, CR, ThS

Type of analysis

Astrocytes (GFAP-area of reactivity); Microglia (phosphotyrosine-area of reactivity) FCtx or Hipp Aβ immuno Astrocytes (GFAP-qualitative); Microglia (CD11b-qualitative) Ventricle Aβ immuno, Microglia (OX-6-counts) ThS Right ventricle None Astrocytes (GFAP-qualitative) Hipp Aβ immuno, Astrocytes (GFAP-intensity); Microglia CR, ThS (ED1-intensity) Right ventricle None Astrocytes (GFAP, iNOS-qualitative); Microglia (CD11b, iNOS-qualitative); iNOS mRNA and activity

Table 4D. Infusion of Aβ does not induce gliosis. Reference *

Games et al., 1992

Species

Aβ sequence

rat

Aβ1-40, Aβ1-38, Aβ25-35

Physiologica l solvent?

N

Controls

Site of infusion

Vehicle, aCSF, revAβ1-40

Hipp

Assay to detect Aβ

Type of analysis

Aβ immuno, Astrocytes (GFAP-qualitative); Microglia CR (ED1-qualitative)

Table 5A. Behavioural impairments induced by Aβ injection. Reference

Chen et al., 1996 Choi et al., 2001*

Species Aβ sequence

Physiological solvent?

Controls

Site of injection

Assay to detect Aβ

Timing of Aβ injection

Activity analysis

Behavioural assessment

rat mouse

Aβ25-35 Aβ1-42

N Y

Vehicle Saline

Hipp ICV

None None

7-14d prior 14d prior

None None

Delobette et al., 1997

rat

N

Vehicle

Right ventricle

None

14-28d prior

None

Dornan et al., 1993

rat

Aβ25-35, Aβ1-28 Aβ25-35

Y

Vehicle

Hipp bilateral

CR

8-10d prior

Locomotor

N,N, Y,N

Vehicle

Hipp, third ventricle

None

3min after

None

No change on radial arm maze or water maze Footshock avoidance

Y

Vehicle

Hipp, Am, thalamus, caudate, mamillary bodies, septum Right MNB Right MNB

None

3min after

None

Footshock avoidance

None None

14d prior 5-12d prior

Open-field Open-field

Passive avoidance Plus maze, passive avoidance Plus maze Water maze, passive avoidance Water maze

Flood et al., 1991

mice

Flood et al., 1994

mice

Aβ1-28, Aβ18-28, Aβ12-28, Aβ12-20 Aβ12-28

Harkany et al., 1999a Harkany et al., 1999b

rat rat

Aβ1-42 Aβ1-42

N N

Vehicle Vehicle

Harkany et al., 2001 Jhoo et al., 2004

rat mice

Aβ1-42 Aβ1-42

N N

MNB ICV

None None

7d prior 3d prior

None None

Jin et al., 2004

rat

N

NB

None

10d prior

None

Li et al., 2004b*

rat

Aβ1-42, Aβ25-35 Aβ1-40

Vehicle Vehicle, revAβ1-40 Vehicle

Y

Vehicle

Hipp bilateral

None

14d prior

Malin et al., 2001

rat

Aβ1-40

N

Vehicle, revAβ1-42

Hipp, 7x bilateral

Aβ immuno

14d prior

Water maze Water maze; no change on Y-maze Water maze

Open-field Open-field, Y-maze, passive avoidance None One-trial/day reward learning

Table 5A. Behavioural impairments induced by Aβ injection. (Continued) Reference

Species Aβ sequence

Maurice et al., 1996

mice

Mazzola et al., 2003*

mice

McDonald et al., 1996 Miguel-Hidalgo et al., 1998 Mileusnic et al., 2004

Physiological solvent?

Controls

Site of injection

Assay to detect Aβ

Timing of Aβ injection

Activity analysis

Behavioural assessment

N

Vehicle

Right ventricle

CR

6-14d prior

None

N,Y

Vehicle

Right ventricle

None

7d prior

None

Y-maze, passive avoidance, water maze Passive avoidance

rat

Aβ25-35, Aβ1-28 Aβ25-35, Aβ1-42 Aβ1-40

N

Dorsal Hipp

None

7d after, 7d prior

None

Y-maze

rat

Aβ1-28

N

Vehicle, revAβ1-40 Vehicle

Right Hipp

None

7d or 28d prior

None

Passive avoidance

chick

Aβ12-28

Y

Vehicle

Hyperstriatum

None

None

One-trial passive avoidance

O'Hare et al., 1999*

rat

Aβ1-42

Y

Sterile water

CA3

Aβ immuno

45min after, 1d prior After training

None

Pan et al., 2004 Perez-Severiano et al., 2004 Richardson et al., 2002*

rat rat

Aβ25-35 Aβ25-35

Y Y

Vehicle Vehicle

Left ventricle Hipp bilateral

None None

None None

rat

Aβ1-42

Y

Saline

CA3 bilateral

Aβ immuno

8d prior 2d prior, then testing 35d later After training

Two-lever operant chamber alternating lever cyclic-ratio Water maze Radial arm maze

Shen et al., 2002 Sigurdsson et al., 1995

rat rat

Aβ25-35 Aβ25-35

Y Y or N

Vehicle Vehicle

Hipp bilateral VP/SI

None CR

Stepanichev et al., 2003a

rat

Aβ25-35

N

Vehicle

ICV bilateral

None

Stepanichev et al., 2004 Stephan et al., 2001

rat rat

Aβ25-35 Aβ40+Aβ43

N N

Vehicle Vehicle

ICV bilateral Dentate gyrus, 8x bilateral

None ThS, Aβ immuno

None

Two-lever operant chamber alternating lever cyclic-ratio 7d prior None Water maze 12-37d prior Open field No change on water maze or conditioned avoidance 16-20d prior; None Y-maze, social recognition, 7d after, 60d prior but no change on passive to retraining avoidance; Radial arm maze 4w prior None Radial arm maze 4w prior None Radial arm maze, water maze

Table 5A. Behavioural impairments induced by Aβ injection. (Continued) Reference

Species Aβ sequence

Physiological solvent?

Controls

Site of injection

Assay to detect Aβ

Timing of Aβ injection

Activity analysis

N

Vehicle

Dentate gyrus, 8x bilateral ICV bilateral

ThS, Aβ immuno None

4w prior

None

3d prior

None

None

3d after, 1-14d prior to reexposure 21d prior

Swimming speed None

Locomotor

Water maze

None

7-10d prior

None

None

Y-maze, passive avoidance but no change on Porsolt forced swim test for behavioural despair Staircase test

None

No change on water maze Apomorphine-induced circling behaviour

Stephan et al., 2003

rat

Aβ40+Aβ43

Sun & Alkon, 2002

rat

Aβ25-35

Terranova et al., 1996

rat

N

Vehicle, revAβ25-35 Vehicle, Medial septum revAβ1-40, scrAβ25-35 Saline, Right ventricle revAβ25-35 scrAβ25-35 ICV

Tohda et al., 2003

mouse

Aβ1-40, Aβ1-42, Aβ25-35 Aβ25-35

Urani et al., 2002

rat

Aβ25-35

N

Whitehead et al., 2005

rat

Aβ25-35

Y

Vehicle

ICV bilateral

CR

Winkler et al., 1994*

rat

RatAβ1-42

Y

Vehicle

Aβ immuno

Yagami et al., 2004*

rat

Y

5d prior

None

rat

N

Vehicle, scrAβ25-35, revAβ25-35 Vehicle

None

Yamaguchi & Kawashima, 2001 Yamaguchi et al., 2002 Yan et al., 2001*

Aβ25-35, Aβ1-40, Aβ1-42 Aβ25-35

CA1 or lateral ventricle Striatum

8d after, 7d prior to retraining 15 months prior

Left ventricle

None

4d prior

None

rat mice

Aβ25-35 Aβ1-42

N Y

Vehicle revAβ1-42

Left ventricle ICV

None None

5d prior 1-3d prior

Yan et al., 2004*

mice

Aβ1-42

Y

revAβ1-42

ICV

None

1d prior

N

Behavioural assessment

Radial arm maze, water maze Water maze Social recognition

Passive avoidance, radial arm maze Locomotor Passive avoidance None Passive avoidance, Y-maze, water maze None Passive avoidance, Y-maze

Table 5B. Behavioural impairments induced by Aβ infusion. Reference

Species Aβ sequence

Physiological solvent?

Controls

Site of infusion

Assay to detect Aβ

Timing of Aβ infusion

Activity analysis

Behavioural assessment

2w infusion began 15d prior Trained and then daily injections 20min prior to testing 2w infusion began 8-14d prior 2w infusion began 10d prior 2w infusion began 10d prior 2w infusion began 16-21d prior

None

Wooden cross maze

None

No change on lever pressing and delayed conditional discrimination

None None

Water maze, passive avoidance Water maze

None

Water maze

Open field

Spontaneous object recognition but no change on acoustic startle reflex Y-maze, water maze, passive avoidance Water maze

Ammassari-Teule et al., 2002* Cleary et al., 1995*

rat

Aβ1-42

N

revAβ1-42

Right ventricle

None

rat

Aβ1-40

N

Vehicle

CA3

ThS

Nabeshima & Nitta, 1994* Nag et al., 1999*

rat

Aβ1-40

N

Vehicle

Left ventricle

None

rat

Aβ1-40

N

Vehicle

Nag & Tang, 2001*

rat

Aβ1-40

N

Vehicle

Aβ immuno None

Nag et al., 2001*

rat

Aβ1-40

N

Vehicle

Left or right ventricle Left or right ventricle Left or right ventricle

Nakamura et al., 2001* Nitta et al., 1994*

rat

Aβ1-42

N

Right ventricle

None

rat

Aβ1-40

N

Vehicle, revAβ1-40 Vehicle

Left ventricle

Nitta et al., 1997*

rat

Aβ1-40

N

Vehicle

Right ventricle

Aβ immuno None

Olariu et al., 2001

rat

Aβ25-35

N

Vehicle

Right ventricle

None

Tanaka et al., 1998*

rat

Aβ1-40

N

Vehicle

Right ventricle

None

None

3d infusion began None 20-25d prior 2w infusion began None 8-12d prior 2w infusion began None 8-14d prior 2w infusion began Locomoto 7-16d prior r 34d infusion began 10d prior

None

Water maze, passive avoidance Y-maze, elevated-plus maze, water maze, passive avoidance Water maze, passive avoidance but no change on Y-maze

Table 5B. Behavioural impairments induced by Aβ infusion. (Continued) Reference

Species Aβ sequence

Physiological solvent? N

Controls

Site of infusion

Vehicle

Ventricle

Assay to detect Aβ None

Timing of Aβ Activity Behavioural infusion analysis assessment 2w infusion began None Water maze 10d prior 10d infusion began Arm entry Radial eight-arm maze 6d prior

Tang et al., 2002*

rat

Aβ1-40

Tran et al., 2001*

rat

N

Vehicle, revAβ1-40

Right ventricle

None

Urani et al., 2004*

rat

Aβ1-40, Aβ1-42, Aβ25-35 Aβ1-40

N

revAβ1-40

Right ventricle

None

2w infusion began 14d prior

None

Wang et al., 2001*

rat

Aβ1-40

N

Vehicle

Left ventricle

CR

None

Yamada et al., 1998* Yamada et al., 1999a* Yamada et al., 1999b* Yamada et al., 1999c*

rat

Aβ1-40

N

Vehicle

Right ventricle

None

rat

Aβ1-42

N

revAβ1-40

Right ventricle

None

rat

Aβ1-42

N

revAβ1-40

Right ventricle

None

rat

Aβ1-42

N

revAβ1-40

Right ventricle

None

3 injections over 8d, last injection was 12d prior 2w infusion began 10-17d prior 2w infusion began 7-18d prior 2w infusion began 7-18d prior 2w infusion began 7-16d prior

No change on conditioned fear stress procedure Water maze

Locomotor Y-maze, water maze, passive avoidance Locomotor Y-maze, water maze, passive avoidance Locomotor Y-maze, water maze, passive avoidance Locomotor Y-maze, water maze

Table 6A. Effects of Aβ injection on synapse function. Controls

Site of injection

Assay to detect Aβ

Type of analysis

ICV

None

Decreased LTP in vivo after HFS for Aβ25-35 only

N N

Vehicle, revAβ2535 Vehicle Vehicle

ICV ICV

None None

N N

Vehicle Vehicle

Right ventricle Right ventricle

None

Aβ1-40 Aβ40+Aβ43

N N

Vehicle Vehicle

ICV None Dentate gyrus, Aβ immuno, 8x bilateral ThS

rat

Aβ40+Aβ43

N

Vehicle

Tohda et al., 2003

mouse

Aβ25-35

N

Trubetskaya et al., 2003

rat

Aβ25-35

N

Saline, revAβ2535 Vehicle

Dentate gyrus, Aβ immuno, 8x bilateral ThS Right ventricle None

Decreased LTP in vivo after HFS Decreased LTP in vivo after HFS for Aβ1-40 only; no change in baseline transmission Induction of LTD in vivo after HFS Decreased LTP in vivo after HFS; no change in baseline transmission Decreased LTP in vivo after HFS Decreased LTP in vivo after tetanus; no change in baseline transmission; no change in synaptophysin immuno Decreased LTP in vivo after tetanus; no change in baseline transmission No change in synaptophysin immuno-quantitative

Reference

Physiological solvent?

Species

Aβ sequence

Freir et al., 2001

rat

Aβ25-35, Aβ1525

N

Freir et al., 2003 Freir & Herron, 2003

rat rat

Kim et al., 2001 Klyubin et al., 2004

rat rat

Aβ25-35 Aβ1-40, Aβ1228 Aβ1-42 Aβ1-40

Minogue et al., 2003 Stephan et al., 2001

rat rat

Stephan et al., 2003

ICV bilateral

None

Increased LTP in vivo after tetanus; increased size of baseline evoked potential in vivo

Table 6B. Effects of Aβ infusion on synapse function. Reference

Species

Itoh et al., 1999*

rat

Aβ sequence Aβ1-40

Physiological solvent? N

Controls Vehicle

Site of infusion Ventricle

Assay to detect Aβ None

Type of analysis Decreased LTP in hippocampal slices obtained after infusion

Table 7A. Effect of Aβ injection on markers of oxidative stress.

rat

Aβ sequence Aβ1-42

Physiological solvent? N

Saline

Site of injection Right NB

Assay to detect Aβ None

rat

Aβ1-42

N

Vehicle

Right MNB

None

Jhoo et al., 2004

mice

Aβ1-42

N

Vehicle, revAβ1-40

ICV

None

Li et al., 2004b*

rat

Aβ1-40

Y

Vehicle

Hipp bilateral

None

Perez-Severiano et al., 2004

rat

Aβ25-35

Y

Vehicle

Hipp bilateral

None

Rosales-Corral et al., 2004* Shen et al., 2002

rat

Aβ1-40

Y

CA1

rat

Aβ25-35

Y

Vehicle, revAβ1-40 Vehicle

Hipp bilateral

Aβ immuno, CR None

Stepanichev et al., 2004

rat

Aβ25-35

N

Vehicle

ICV bilateral

None

Reference Boyd-Kimball et al., 2005 Harkany et al., 1999b

Species

Controls

Type of analysis Increased protein carbonyls by 2D gel with oxyblot analysis Increased Cu/Zn-SOD activity; decreased MnSOD activity Increased Cu/Zn-SOD, Mn-SOD, GPx, and glutathione reductase activity; increased levels of protein carbonyls and malondialdehyde. Increased malondialdehyde content; unchanged SOD activity Increased ROS content and lipid peroxidation; unchanged Cu/Zn-SOD, Mn-SOD and GPx activity Increased nitrites and lipid peroxidation products; decreased GPx activity Increased lipid peroxidation; decreased SOD and GPx activity; decreased glutathione levels Increased lipid peroxidation and superoxide generation.

Table 7B. Effect of Aβ infusion on markers of oxidative stress. Species

Aβ sequence

Kim et al., 2003*

rat

Aβ1-42

Physiological solvent? N

Yamada et al., 1999a*

rat

Aβ1-42

N

Reference

Controls Vehicle, revAβ1-40 revAβ1-40

Site of injection Right ventricle

Assay to detect Aβ None

Right ventricle

None

Type of analysis Decreased immuno intensity for MnSOD, glutathione, GPx, glutathione-Stransferase Unchanged lipid peroxidation levels

Table 8A. Miscellaneous markers that were examined after injection of Aβ. Reference *

Baltrons et al., 2002 *

Choi et al., 2001

*

Ghribi et al., 2001 Giovannini et al., 2002

*

Li et al., 2004b Minogue et al., 2003 *

Mohajeri et al., 2002 Pan et al., 2004

*

Reyes et al., 2004

*

Aβ sequence

rat

Aβ1-40

Physiological solvent? Y

mouse

Aβ1-42

Y

Saline

rabbit

Aβ1-42

Y

Vehicle

Cistern

None

Increased NF-kB (neurones)-cell count and WB

rat

Aβ1-42

N

Saline

Right NBM

Aβ, CR

rat

Aβ1-40

Y

Vehicle

Hipp bilateral

None

Phospho-p38, MAPK immuno but unchanged phosphoERK and phospho-SAPK/JNK immuno; increased IL1β in homogenates Decreased membrane fluidity

rat mice

Aβ1-40 Aβ42

N Y

None None

Increased IL-1β levels Increased neprilysin levels (WB) and mRNA

rat

Aβ25-35

Y

Vehicle ICV Vehicle, PCtx revAβ42, BSA Vehicle Left ventricle

None

rat

Aβ1-40, RatAβ140 Aβ1-40

Y

Vehicle

Increased mRNA and protein levels of voltage-gated K+ channels Kv2.1, Kv1.4, Kv4.2, but not Kv1.5, Kv4.3 Unchanged laminin expression (injury response)

Y

mouse Aβ1-42, Aβ1-40, Aβ25-35, Aβ1-28 mouse Aβ1-16, Aβ1-40, Aβ1-42, Aβ1740, Aβ25-35, Aβ17-42 mouse Aβ1-42

Y Y

Vehicle, revAβ1-40 Vehicle, revAβ1-42 Vehicle

Y N

rat

Rosales-Corral et al., 2004 *

Song et al., 2001

*

Szczepanik et al., 2001

*

Szczepanik & Ringheim, 2003 Urani et al., 2002

Species

rat

Aβ25-35

Controls Vehicle

Site of injection Hipp, cerebellar vermis ICV

Dentate gyrus bilateral CA1

Assay to detect Aβ None None

Type of analysis Decreased soluble guanylyl cyclase expression in astrocytes Mitochondrial pyruvate dehydrogenase content

ICV

Aβ immuno, CR, ThS Aβ immuno, CR None

ICV

None

Increased levels of IL-1α, IL-1β, IL-6, MCP-1, TNFα in homogenates

Vehicle

ICV

None

scrAβ25-35

ICV

None

Increased IL-1α, IL-1β, MCP-1 but TNF-α unchanged in homogenates Decreased levels of progesterone but unchanged pregnenolone and dehydroepiandrosterone in Hipp

Increased levels of IL-1β, IL-6, TNF-α Increased plasma levels of IL-6, IL-1β

Table 8A. Miscellaneous markers that were examined after injection of Aβ. Reference

Species

Whitehead et al., 2005 * Yagami et al., 2004

rat rat

*

rat

Zand et al., 2005

Physiologica Controls Site of injection l solvent? Aβ25-35 Y Vehicle ICV bilateral Aβ25-35, Aβ1Y Vehicle, scrAβ25Striatum 40, Aβ1-42 35, revAβ25-35 Aβ1-42 Y revAβ1-42 Dentate gyrus Aβ sequence

Assay to detect Aβ CR None None

Type of analysis Increased NFkB, TNF-α-intensity Increased thromboxane A2 content Increased laminin-positive blood vessels-counts; Increased VEGF in astrocytes and microgliaqualitative

Table 8B. Miscellaneous markers that were examined after infusion of Aβ. Reference

Aguado-Llera et al., 2005

Species

Aβ sequence

rat

Aβ25-35, Aβ142

Physiological solvent?

Controls

Site of injection

Assay to detect Aβ

N

Saline, revAβ25-35

Right ventricle

None

Fukuta et al., rat (infant, adult and aged) 2001* Olariu et al., 2001 rat

Aβ1-40

N

Vehicle

Right ventricle

None

Aβ25-35

N

Vehicle

Right ventricle

None

Olariu et al., 2002*

rat

Aβ1-40

N

revAβ1-40

Right ventricle

None

Reyes et al., 2004*

rat

Aβ1-40

Y

Vehicle

Dorsal Hipp

Tang et al., 2000*

rat

N

rat

N

Vehicle, revAβ1-40 revAβ1-40

Right ventricle

Urani et al., 2004*

Aβ1-40, Aβ142, Aβ25-35 Aβ1-40

Aβ immuno, CR, ThS None

Right ventricle

None

Zhang et al., 2004*

rat

Aβ1-40

N

Vehicle

Left ventricle, 3 injections over 5 days

None

Type of analysis

Decreased p-Akt but unchanged levels of IGF-1-levels and MAP-K; unchanged αi subunits of G-proteins Increased NGF levels in Hipp in adult rats, but unchanged in infant and aged rats Decreased activity and binding affinity of PKC Decreased activity and binding affinity of PKC Unchanged laminin expression (injury response) Increased BDNF mRNA but no change in NGF or neurotrophin-3 mRNA Decreased levels of progesterone but unchanged pregnenolone and dehydroepiandrosterone in Hipp Decreased APPs and PKC levels

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Solvents are an important consideration because they can affect the properties of Aβ. For example, Aβ is highly soluble in acetonitrile but precipitates out of solution if salts are present [Waite et al., 1992], indicating that the solvent can change the secondary structure of Aβ and potentially alter its physiological properties. That paper showed that when Aβ dissolved in acetonitrile and trifluoacetic acid (A/TFA) was injected into rat hippocampus it was very toxic, when dissolved in water it was less toxic, and no more toxic than the solvent when dissolved in phosphate-buffered saline (PBS) and cyclodextrin. One reason for the toxicity of acetonitrile is that it can be converted to cyanide in microsomes [Freeman & Hayes, 1988], which then compromises cellular metabolism [Goldberg et al., 1987]. Thus when Aβ dissolved in acetonitrile is delivered into the brain the Aβ will act upon cells that are under stress and have a reduced viability due to the solvent. The toxicity of Aβ observed under these circumstances may not necessarily be indicative of its toxicity to unstressed cells. It should be noted that when the solvent vehicle alone was injected into the hippocampus, A/TFA was the most toxic, water had some toxicity and PBS had only minimal toxicity [Waite et al., 1992]. This finding demonstrates that solvents themselves can cause neuronal degeneration and confirms the need to include vehicle control injections when assessing the toxicity of Aβ in vivo. Surprisingly, not all studies have controlled for vehicle effects but have instead made comparisons to untreated tissue that has not even suffered the mechanical damage associated with the injection procedure. Physiological solvents can be employed in most injection procedures, but organic solvents are favoured when performing constant infusions of Aβ via mini-osmotic pumps because this reduces the likelihood of the pumps becoming clogged. A model that can constantly infuse Aβ over long periods of time while still using a physiological solvent is possible however, as shown by Frautschy and colleagues who used HEPES buffer to dissolve Aβ for a 4-week infusion [Frautschy et al., 1998]. A useful additional control that has been included in some studies is the injection of reverse or scrambled forms of Aβ (see Figure 2), or the inclusion of rodent isoforms of the peptide to control for non-specific “peptide effects”, particularly with respect to the tendency of Aβ to form large, sticky deposits that displace nearby tissue. The rodent variants of Aβ are particularly useful controls because the primary peptide sequence differs from human Aβ by only three amino acids [Shivers et al., 1988]. Rodent Aβ is an ‘endogenous’ peptide for both rats and mice, and thus can serve as a peptide control, but can also control for the aggregational properties of full-length human Aβ peptide that the reverse or scrambled sequences are often unable to achieve. It is also worth considering that injection or infusion of Aβ into the lateral ventricles allows the peptide to interact with other agents contained within the CSF, such as metal ions, cytokines and proteins. In vitro studies have shown that Aβ interacts with acetylcholinesterase, iron, zinc, and aluminium; all change the properties of Aβ, altering its solubility, causing it to fibrillise and precipitate out of solution [Alvarez et al., 1998; Bush et al., 1995; Bush et al., 1994; Mantyh et al., 1993]. In addition, Aβ has been reported to be more toxic to cultured cells when mixed with some of these substances than when it is on its own [Alvarez et al., 1998; Schubert & Chevion, 1995]. This is an important consideration because when Aβ is discretely injected into brain tissue it has limited opportunity to interact with other proteins or molecules, except those within the immediate vicinity, whereas Aβ

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injected or infused into the lateral ventricles has a greater opportunity to interact with agents that can alter its properties.

Figure 2. Aβ peptide. The Aβ peptide contains 39-43 amino acids. It is normally present as Aβ1-40 or Aβ1-42, which contain 40 or 42 amino acids respectively. Rat Aβ varies from human Aβ by three amino acid substitutions at residues 5, 10, and 13. Truncated forms of Aβ are sometimes used, especially Aβ25-35, which contains only residues 25-35 of full-length Aβ. Reverse Aβ1-40 (revAβ1-40, or Aβ40-1) is often used as a control for Aβ1-40. RevAβ1-40 contains the same amino acids as Aβ1-40, but in the opposite order with the amino and carboxy groups to amino acid residues 40 and 1, respectively. Scrambled peptides contain the same amino acids as the selected peptide, but the amino acids are randomly arranged within the peptide.

Given the difficulty involved in comparing the results of studies that used differing methodologies to deliver Aβ, a stricter set of secondary exclusion criteria were employed to select a subset of studies that had used the most rigorous experimental designs: (1) a physiological solvent must have been used to dissolve Aβ. Artificial CSF, saline, PBS, HEPES buffer or cell culture media were defined as physiological solvents, while A/TFA, dimethyl sulfoxide (DMSO) or water were defined as non-physiological solvents; (2) there had to be a control condition where either the vehicle, a physiological solvent, or a reverse or scrambled form of Aβ was injected or infused for comparison; (3) a physiological full-length variant of Aβ had to be examined, which was defined as Aβ1-40, Aβ1-42 or Aβ1-43. Truncated forms of Aβ, such as Aβ25-35, can assist our understanding of particular amino acid sequences within the full-length peptide [e.g. Giulian et al., 1996; Yankner et al., 1990], but they are not physiological since they have never been detected in vivo. The studies that met these stricter criteria have been indicated in the summary tables with an asterisk (*). These secondary criteria were applied to studies that had injected Aβ, however nearly all of the studies that had infused Aβ into the brain used non-physiological solvents to prevent Aβ from clogging the pump. Consequently infusion studies that met criteria (2) and (3), such that they had appropriate control infusions and that they used full-length sequences of Aβ, are also indicated by an asterisk. In the following sections, the overall trends in each summary table are first discussed, and then the trends pertaining to the highlighted studies are further dissected for analysis. A full discussion of the data associated with each category could easily fill a chapter of this book, so we have been restricted by space limitations to a brief discussion of the most pertinent findings associated with each category. Nonetheless, we hope that the details

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included in the tables will serve as a resource which will allow the interested reader to follow up on aspects that we have not had the leisure to discuss.

Aβ-induced Neuronal Degeneration In this category of analysis, the presence or absence of neuronal degeneration can be considered an absolute finding, so for ease of understanding the results, we have separated the studies which observed neuronal degeneration (Tables 2A and 2C) from those that did not (Tables 2B and 2D). The studies that injected Aβ are listed in the first two tables (2A and 2B) and those which infused Aβ are in the second two tables (2C and 2D). It is important to note that three studies assessed neuronal degeneration using either different animals [Geula et al., 1998], different solvents [Waite et al., 1992], or different Aβ sequences [Zou et al., 2003], which resulted in both positive and negative effects in terms of neuronal degeneration. We have treated these findings as separate sets of data, and have listed them in both Tables 2A and 2B. 58 studies assessed neuronal degeneration resulting from injection of Aβ into the brain, which generated 61 sets of data. Most used Nissl or haematoxylin and eosin (H&E) stains to determine either the presence of dead neurones at injection sites or the remaining number of viable neurones. Some studies assessed the presence of tau phosphorylation or used highly specific markers of cell death such as TUNEL or Fluoro-Jade. In recent years, some studies have used Western blot (WB) analysis of apoptotic markers or ELISA cell detection kits. If all of the data sets are considered as if they are equivalent, then 59% detected neuronal degeneration after injection of Aβ. If however, we limit the comparison to the more rigorous physiological studies (asterisks), then only 49% of data sets found that injection of Aβ into the brain induces neuronal degeneration. Further analysis shows that only 22% of studies that injected Aβ into the cerebral cortex, and 29% of studies that injected Aβ into hippocampus, were able to detect increased neuronal degeneration. This analysis suggests that the injection of physiological variants of Aβ into the regions of the brain most commonly affected by AD does not result in a significant degree of neuronal loss. In contrast, Aβ was reported to induce neuronal degeneration in 60% of studies that injected it into the lateral ventricles (or cistern), and in each of the studies that injected Aβ into the striatum, corpus callosum or vitreous chamber of the eye. In order to be certain that the effects observed after injection of Aβ are due to the peptide, it is necessary to confirm that at least some Aβ has deposited near the site of injection. Of the papers surveyed, the most common methods used to detect Aβ deposition were the histological stains Congo red (CR) or Thioflavin-S (ThS), or immunohistochemistry using antibodies raised against Aβ. It is interesting that only 45% of the data sets reporting Aβ toxicity ascertained that Aβ was present at the site of injection, whereas 92% of the data sets reporting a lack of toxicity confirmed Aβ deposition. Thus a much greater proportion of the studies reporting a lack of Aβ toxicity were certain of the success of their injections than those that had reported toxicity. 8 out of 9 infusion studies met the secondary criteria of the more rigorous studies, allowing for the fact that infusion studies generally require the use of non-physiological

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solvents to keep Aβ dissolved for the duration of the infusion (see Tables 2C and 2D). 38% of these studies found that infusion of Aβ into the brain induces neuronal degeneration. Further analysis showed that neither of the studies which infused Aβ into the hippocampus reported neuronal degeneration, whereas half of those that infused Aβ into the lateral ventricles did. This supports the observation from injection studies that deposition of physiological variants of Aβ into a brain region commonly affected by AD does not result in significant death of neurones. It should be noted that only one infusion study used a physiological solvent to dissolve Aβ [Frautschy et al., 1998]. That study reported that Aβ killed cortical neurones after 4weeks of infusion into the lateral ventricle. The constant infusion of Aβ allows the peptide to gradually accumulate, which may be the way that Aβ deposits in AD. In an attempt to further increase the deposition of Aβ, Frautschy and coworkers have co-infused the protease inhibitors leupeptin or aprotinin with Aβ1-40 to increase the deposition of Aβ in the thalamus, cortex and hippocampus compared to infusion of Aβ alone [Frautschy et al., 1998]. These authors found that increased Aβ deposition does not guarantee increased toxicity since co-infusion with aprotinin decreased the amount of apoptosis, even though it increased the amount of Aβ deposition. On balance, the preceding observations indicate that Aβ deposits do not consistently cause a significant amount of neuronal degeneration after either injection or infusion into the brain, particularly when deposited in discrete regions such as the cerebral cortex or hippocampus. Furthermore, the amount of Aβ that has been deposited does not appear to be correlated with the resulting degree of neuronal degeneration. This outcome is similar to the observations from transgenic mouse models, which reported that high levels of Aβ deposition did not correlate with the extent of neuronal death [Irizarry et al., 1997a; Irizarry et al., 1997b].

Effects of Aβ on Neuronal Subpopulations The studies that have injected or infused Aβ and examined the effects on neuronal subpopulations are described in Tables 3A and 3B, respectively. Due to the central involvement of the cholinergic system in AD [e.g. Henke & Lang, 1983; Perry et al., 1978], this subpopulation of neurones has been the most widely studied after injection or infusion of Aβ. Reported impairments include decreased levels of acetylcholine (ACh), decreased activity of choline acetyltransferase (ChAT), or decreased numbers of cells or fibres containing ChAT or acetylcholinesterase (AChE), respectively. 80% of studies that have examined the cholinergic system after injection of Aβ have reported impairments in at least one aspect of cholinergic metabolism (Table 3A). Of the 6 studies that meet our physiological criteria, 67% reported decreased cholinergic functioning after injection of Aβ. A similar outcome was obtained after infusion of Aβ, with 86% of studies that used full-length Aβ sequences and appropriate control infusions indicating a decrease in cholinergic function. One of these studies reported decreased ChAT activity but no change in AChE activity after infusion of Aβ into the left ventricle of rats [Nabeshima & Nitta, 1994], while another

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reported that ChAT activity decreased after infusion of Aβ1-40 into the lateral ventricle of adult rats, but not when infused into infant or aged rats [Fukuta et al., 2001]. Giovannelli and colleagues showed that Aβ could temporarily impair cholinergic metabolism without actually killing cholinergic neurones [Giovannelli et al., 1998]. They reported that four months after injection of Aβ1-40 into the nucleus basalis (NB) there was decreased expression of ChAT in the NB and decreased ACh release from parietal cortex, yet two months later the levels had returned to normal. They also showed that neuronal death did not occur at any time point after Aβ injection (see Table 2B). These results demonstrate that functional changes can occur in the brain, and persist for several months after Aβ administration, without the Aβ causing any neuronal loss or permanent deficits. Other neurotransmitter systems that have been examined include the noradrenergic, dopaminergic and serotonergic systems, amino acid transmitters such as glutamate and GABA, and neuropeptides such as substance P, neuropeptide Y and somatostatin. The effect of Aβ on interneurones has also been investigated by examining the expression of neuronal nitric oxide synthase (nNOS) and parvalbumin. While few of these studies meet our physiological criteria, they indicate that injection of Aβ decreases the number of labelled noradrenergic and serotonergic neurones, and interneurones. Infusion studies appear to have placed greater emphasis on neuropeptides. Although none used physiological solvents, these studies indicate that infusion of Aβ may decrease the levels of somatostatin and substance P, but leave the levels of neuropeptide Y unaffected. It is not clear whether infusion of Aβ alters the dopaminergic system, since one study reported that Aβ1-40 decreased the release of dopamine [Itoh et al., 1996], while another reported that Aβ1-42 did not alter the levels of dopamine or its metabolites [Yamada et al., 1999b]. This discrepancy may be related to the length of Aβ used. In summary, Aβ appears to impair the function of pathways that use acetylcholine, serotonin, noradrenaline, somatostatin or substance P, and decreases the expression of nNOS and parvalbumin in interneurones. At least some of these effects are transient and it is not known whether these changes are due to the direct actions of Aβ, or to secondary effects such as cytokine release by activated neuroglia. It is not yet clear whether Aβ impairs the function of pathways that use dopamine or amino acid transmitters.

Aβ-induced Gliosis Astrocytes will normally form a scar around a site of damage in order to isolate it from the surrounding tissue, and microglia are recruited to phagocytose cellular debris and any other agents that are not normally present in healthy tissue. However, microglia and astrocytes can become activated by mild stimuli that do not cause neuronal loss. For example, microglia routinely respond to the presence of exogenous agents within the extracellular space, such as the Aβ that is deposited by injection or infusion [Halliday et al., 2000]. Astrocytes are sensitive to alterations in pH or osmotic pressure, and pro-inflammatory cytokines that have been released from neurones or microglia [Halliday et al., 2000]. Similar to the previous section (neuronal degeneration), the findings in this category of analysis can be considered absolute, thus the data has been separated into those that observed

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gliosis (Tables 4A and 4C) and those that did not (Tables 4B and 4D). The studies that injected Aβ are in Tables 4A and 4B and those that infused Aβ are in 4C and 4D. It is important to note that three studies assessed gliosis using either different animals [Geula et al., 1998], different solvents to derive different secondary structures [Weldon et al., 1998], or different Aβ sequences [Zou et al., 2003], giving both positive and negative effects. These findings have been treated as individual sets of data. 78% of the data sets that injected Aβ and assessed the reactivity of astrocytes using immunohistochemistry for glial fibrillary acidic protein (GFAP) reported an increased astrocytic reactivity (see Tables 4A and 4B). The physiological studies showed a similar pattern with 73% observing an induction of GFAP staining after injection of Aβ. Further analysis of these studies indicated a regional difference in that 75% of the studies which injected Aβ into the hippocampus, but only 25% of the studies that injected Aβ into the cerebral cortex, reported an induction of GFAP staining. One study each injected Aβ into the lateral ventricles, striatum, corpus callosum or vitreous chamber and all reported GFAP induction. Infusion of Aβ generated very similar results (see Tables 4C and 4D) with 83% of the more rigorous studies reporting an induction of GFAP. A smaller proportion (67%) reported an induction when Aβ was infused into the hippocampus while the one study that infused Aβ into the cerebral cortex and the three studies that infused Aβ into the lateral ventricles all reported an induction. In the one infusion study that met all three of our physiological criteria, it was reported that GFAP expression was induced around the injection cannula after Aβ infusion into the lateral ventricle [Frautschy et al., 1998]. Microglial reactivity can be assessed with a variety of markers, but most commonly researchers have used antibodies raised against immune-related markers such as CD11b (including the clone OX-42) and interleukin-1β (IL-1β), as well as specific markers for microglia such as lectins or phosphotyrosine. 76% of data sets have reported that injection of Aβ into the brain induces a microglial reaction. A similar pattern is observed with the physiological studies with 73% reporting microglial reactivity. In contrast to the findings for astrocytes, microgliosis has been observed in 40% of studies that injected Aβ into the cerebral cortex, and 50% of studies which injected Aβ into the hippocampus. Microgliosis was also observed in one study each that injected Aβ into the corpus callosum or vitreous chamber of the eye, and in the three studies which injected Aβ into the lateral ventricles. The results from infusion studies (see Tables 4C and 4D) were similar, with 80% of the more rigorous studies reporting an induction of microglia by Aβ. Again, 67% of studies that infused Aβ into the hippocampus observed microgliosis, as well as the one study which infused Aβ into the cerebral cortex and the two that infused Aβ into the lateral ventricles. In the only infusion study which met all three physiological criteria, it was reported that the numbers of phosphotyrosine-positive microglia were increased in the region of the injection cannula after infusion of Aβ1-40 into the lateral ventricle, and this was further enhanced if the Aβ was co-infused with protease inhibitors [Frautschy et al., 1998]. On balance, the majority of studies indicate that Aβ activates astrocytes and microglia, particularly when injected or infused into the lateral ventricles or hippocampus. There appears to be little difference in the responsiveness of astrocytes and microglia to injected or infused Aβ, except that astrocytes in the cerebral cortex may be more resistant to activation by Aβ than their hippocampal counterparts.

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Aβ-induced Behavioural Dysfunction The studies that have injected or infused Aβ and examined the effects on behaviour are described in Tables 5A and 5B, respectively. 92% of studies that have injected Aβ into the brain and then assessed behavioural functions, such as the ability to learn, have found that Aβ has deleterious effects on at least one behavioural test (see Table 5A). The physiological studies follow a similar pattern, with 89% reporting behavioural impairments on at least one test. Behavioural impairments were observed after Aβ was injected into the hippocampus in 75% of studies, the lateral ventricles in 80% of studies, and the striatum in one study. It is worth noting that one of these studies reported an impairment on the water maze, yet also reported a lack of impairment on the Y-maze, while using the same Aβ injection paradigm [Choi et al., 2001]. The most commonly used behavioural tests were the Morris water maze, the Y-maze and passive avoidance tasks. These tests can either examine the ability to learn or the ability to retrieve memories, depending on when the tests are applied in relation to when the Aβ is injected. For instance, if Aβ is administered prior to training, then performance on the task measures the ability of Aβ to influence the acquisition and consolidation of new memories. If the Aβ is administered after training, then performance on the task measures the capacity of Aβ to influence retrieval processes. Aβ was injected prior to training on all studies that used the water maze, Y-maze or passive avoidance tests, and problems in acquisition were reported in 67%, 75% and 100% of the studies that met the physiological criteria, respectively. Only 2 studies injected Aβ after training, both of which found impairments using a two-lever operant chamber, indicating an amnestic effect of Aβ. Infusion of Aβ into rat brain demonstrated similar findings, with 89% of studies reporting impairments on at least one behavioural test (see Tables 5C and 5D). Although these infusion studies used non-physiological solvents, most used the naturally occurring variants of Aβ, with 95% using either Aβ1-40 and/or Aβ1-42. By contrast, only 49% of injection studies used either Aβ1-40 and/or Aβ1-42, and one study examined rat Aβ1-42. It is worth noting that two studies reported impairments on at least one test, as well as a lack of impairment on other tests while using the same Aβ infusion paradigm [Nag et al., 2001; Tanaka et al., 1998]. The one infusion study that targeted the hippocampus did not report a behavioural impairment [Cleary et al., 1995], however 94% of those that infused Aβ into the lateral ventricles did. These studies infused Aβ into the lateral ventricles prior to training, thereby demonstrating the capacity of Aβ to impair acquisition in both discriminative and spatial learning tasks. In summary, an overwhelming proportion of studies reported impairments on at least one behavioural task, regardless of whether the Aβ was injected or infused into the brain. The strength of this result might be taken as clear evidence that Aβ does have amnestic properties. Caution is needed however, because we have no way of knowing how many other studies were not published because they obtained a negative result. In this context it is noteworthy that half of the negative outcomes reported in Table 5 were published in association with positive outcomes on another task. A further consideration is that spatial learning and passive avoidance tasks may have limited relevance to the behavioural dysfunction seen in AD. Other

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measures such as social recognition [Stepanichev et al., 2003a; Terranova et al., 1996] may have greater utility.

Aβ-induced Synaptic Dysfunction It has been suggested that neuronal dysfunction in AD may be related to changes in synapse number and function rather than to outright neuronal degeneration [Selkoe, 2002]. The first set of studies that examined synapse function after injection of Aβ were published in 2001, and a total of 10 studies have been included in the present analysis (see Table 6A). Unfortunately, all of these studies used non-physiological solvents. If we consider only the studies that used full-length Aβ and appropriate vehicle controls, there were 6 studies which investigated whether injection of Aβ into either the lateral ventricles or the dentate gyrus affects the induction of long-term potentiation (LTP) by neurones in the CA1. Five of these studies reported that Aβ impairs the induction of LTP after either high-frequency stimulation (HFS) or tetanic stimulation, and the other study reported an enhancement of long-term depression (LTD) after high-frequency stimulation [Kim et al., 2001]. A further study reported increased induction in LTP after tetanic stimulation following injection of a nonphysiological variant of Aβ [Trubetskaya et al., 2003]. While these results support the notion that Aβ can influence synaptic plasticity, the use of non-physiological solvents may have influenced the outcome. Only one study that injected full-length Aβ used immunohistochemistry to detect changes in the numbers of synapses. This study found no changes in the pattern of immunolabelling for the presynaptic terminal protein, synaptophysin, after Aβ injection [Tohda et al., 2003], suggesting that Aβ does not influence synaptogenesis or the maintenance of existing synapses. Only one study has infused Aβ (Table 6B) and then examined LTP [Itoh et al., 1999]. In contrast to the studies that injected Aβ, this study infused Aβ for 10-11 days and then collected slices of the hippocampus to perform an in vitro investigation of LTP. They found that LTP was decreased after tetanic stimulation when compared to the induction of LTP in hippocampal slices from vehicle-infused animals [Itoh et al., 1999]. While this is not strictly an in vivo study, it has been included in the present analysis since it is the only one that has examined LTP after Aβ infusion. There is clearly a need for more studies in this area, particularly physiological studies that examine hippocampal synaptic function after injection or infusion of Aβ. Nonetheless, the limited data available indicate that Aβ decreases LTP independently of synapse number.

Aβ-induced Oxidative Stress Structural oxidative damage to lipids or proteins is indicated by the presence of lipid peroxidation products such as malondialdehyde, or protein carbonyls, respectively. The presence of oxidative stress is also indicated by an increase in the activity or protein level of enzymes involved in generating free radicals, such as superoxide dismutase (SOD), or a

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decrease in the enzymes that are involved in neutralising free radicals, such as glutathione peroxidase (GPx) or glutathione reductase. Of the 8 studies that have investigated oxidative stress following Aβ injection, only two meet the criteria for physiological methodology (see Table 7A). Both studies reported an increase in lipid peroxidation products after injection of Aβ into the hippocampus. It was also reported that Aβ decreased the activity of GPx, an enzyme used to detoxify hydrogen peroxide [Rosales-Corral et al., 2004]. This result is consistent with a study that infused Aβ (Table 7B) into the lateral ventricle and observed a decrease in the extent of immunohistochemical label for GPx [Kim et al., 2003]. While the other injection studies in this category used non-physiological solvents, these studies consistently show that Aβ induces lipid peroxidation and protein carbonyl formation. It also appears that injection of Aβ may increase the activity of SOD, which may be a responsive mechanism to increased generation of superoxide after injection of Aβ [Stepanichev et al., 2004]. On balance, it appears likely that injection or infusion of Aβ into the brain does induce oxidative stress at the site of Aβ deposition. This may be due to the formation of free radicals by the peptide [e.g. Harris et al., 1995], to the production of reactive oxygen species (ROS) by activated glial cells, or simply due to increased rates of oxidative metabolism in cells exposed to Aβ. Further studies are required to investigate these possibilities.

Other Markers affected by Injection or Infusion of Aβ Researchers have examined aspects of brain function that go beyond the standard repertoire of assessment. These wide-ranging observations have been summarised in Tables 8A and 8B. For instance, injection of Aβ has been reported to decrease membrane fluidity [Li et al., 2004b], increase the expression of vascular endothelial growth factor (VEGF) in microglia and astrocytes [Zand et al., 2005] and increase the expression of the Aβ-degrading protein neprilysin and its mRNA [Mohajeri et al., 2002]. The levels of cytokines such as IL1α, IL-1β, IL-6, MCP-1 and TNFα have been found to be increased after injection of Aβ into the hippocampus or lateral ventricle [Rosales-Corral et al., 2004; Szczepanik et al., 2001; Szczepanik & Ringheim, 2003]. Infusion of Aβ has been reported to increase the expression of NGF in adult rats, but not in infant or aged rats [Fukuta et al., 2001]. It has also been reported that infusion of Aβ increases the mRNA levels of BDNF, but does not change those of NGF or neurotrophin-3 [Tang et al., 2000]. Infusion of Aβ into the lateral ventricle decreases hippocampal levels of progesterone, but does not alter hippocampal levels of pregnenolone and dehydroepiandrosterone [Urani et al., 2004]. These disparate studies indicate that Aβ exerts a wide variety of effects on the living brain; further investigation is required to verify these results, and to place them into a physiological context. In summary, Aβ appears to be capable of exerting effects on processes that lie outside of the parameters normally associated with toxicity. Further examination of such effects will help to elucidate the precise actions that Aβ has on neural cells in the living brain. Some in vivo and in vitro studies have begun to provide support for a physiological role for Aβ in the brain [see Bishop & Robinson, 2004b]. Evidence reviewed in this section, particularly the

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increased expression of growth factors following Aβ injection or infusion [Fukuta et al., 2001; Tang et al., 2000; Zand et al., 2005], provides further support for the notion that this peptide may also have beneficial effects.

Altering the Effects of Aβ with Other Agents While this chapter has focussed on studies that have injected or infused pure forms of Aβ into the brain, several studies have combined Aβ with other agents in an attempt to increase its rate of deposition or decrease its rate of clearance. For instance, some groups have prevented breakdown of the injected deposit with β-sheet breakers [Soto et al., 1998] and others have injected AlCl3 into the lateral ventricle prior to infusion of Aβ in order to increase its aggregation [e.g. Hashimoto et al., 2002; Oka et al., 1999]. Such procedures may result in the formation of a complex with very different properties to the original peptide. For example, co-infusion of Aβ with the protease inhibitor leupeptin into rat lateral ventricles not only increases the deposition of Aβ in the rat brain, it also greatly increases its toxicity and the microglial response [Frautschy et al., 1998]. By contrast, co-infusion of Aβ with perlecan into rat hippocampus increases the length of time that Aβ remains deposited at the injection site, yet this increased deposition is reported to have no effect on microglial reactivity when compared to infusion of Aβ alone [Snow et al., 1994]. Other studies that have seen little or no effect of Aβ on the brain have mixed the peptide with other toxic substances in the hope of making Aβ toxic. For instance, when Aβ is coinjected with ibotenic acid, an NMDA agonist, there is a significant increase in neuronal degeneration as seen by Nissl staining and a reduction in MAP-2-positive neurones [Morimoto et al., 1998]. Similarly, the present authors have observed that co-injection of Aβ1-42 with either iron or zinc increases the amount of neuronal death at cortical injection sites [Bishop & Robinson, 2003b; Bishop & Robinson, 2004a]. While co-injection of Aβ with another agent can increase the toxicity of Aβ, some researchers have instead primed the injection site with another agent and then infused or injected the Aβ peptide. An example of this is seen when A/TFA is injected into the lateral ventricle prior to Aβ infusion in order to compromise the viability of neurones and make them more vulnerable to any neurotoxicity of Aβ [Pavia et al., 2000]. After this priming, Aβ was then injected 15 minutes later and then injected daily for a period of 7 days [Pavia et al., 2000; Saez-Valero et al., 2002]. Surprisingly, neither of these studies observed detrimental effects on the cholinergic system after repeated Aβ injections, but instead saw an increased number of AChE-positive cortical fibres and neurones [Pavia et al., 2000] or a change in the isoforms of AChE [Saez-Valero et al., 2002]. Another reason for co-injecting agents with Aβ is to ameliorate the deleterious effects of Aβ on neurones. For example, when substance P was co-injected with Aβ1-40 into rat cerebral cortex, there was a decrease in the extent of neuronal loss compared to that caused by injection of Aβ alone [Kowall et al., 1991]. However in a similar study where substance P was instead co-injected with Aβ25-35 into rat hippocampus, no change was observed in the amount of neuronal death when compared to Aβ25-35 alone [Rush et al., 1992]. Another method of decreasing Aβ toxicity is the systemic administration of pharmaceutical

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compounds. For instance, administration of the NMDA antagonist MK-801 for 4 days after Aβ1-42 injection into the NB improved both AChE and ChAT activity and decreased Aβinduced anxiety, whereas treatment with vitamins C and E only improved ChAT activity [Harkany et al., 1999b]. Both treatment regimes improved the loss of MnSOD activity, but only the vitamins decreased the elevated Cu/ZnSOD activity. A different approach was taken by Netland and colleagues (1998) who reported that the microglial reactivity induced by Aβ could be reduced by administering the anti-inflammatory agent indomethacin twice daily to rats during their 14-day infusion of Aβ. Similarly, co-infusion of Aβ with indomethacin decreased microglial reactivity [Netland et al., 1998]. Propentofylline has been reported to improve behavioural deteriorations after infusion of Aβ, yet could not return ChAT activity to normal [Yamada et al., 1998]. In adrenalectomised rats, their decreased corticosterone levels increased the toxicity of Aβ1-42 injections to the NB, while replacement of corticosterone in the low to middle dosage range protected against the toxicity of Aβ1-42 [Abraham et al., 2000]. The data described above demonstrate the ease with which the effects of Aβ can be altered by subtle changes of experimental design. Furthermore, these studies show that injection and infusion models can be used to study interactions between Aβ and other agents that are present within plaques, as well as to test treatments that may ameliorate the negative effects of Aβ.

Conclusion In this chapter we have shown that injection/infusion models of AD are able to extend our understanding of aspects of AD pathogenesis in ways that are not possible with other techniques. Compared with transgenic mouse models, these in vivo techniques have superior temporal and spatial resolution, and they allow greater flexibility for investigating the physiological effects of different isoforms and fragments of Aβ. Perhaps their greatest advantage, yet the least exploited, is the capacity to deliver human isoforms of Aβ into primate brain. The collective results of Aβ injection/infusion studies clearly indicate strong and diverse bioactive effects of Aβ in vivo. When taken together, the studies have demonstrated that Aβ does not induce neuronal degeneration in the majority of cases, and that there is a regional variability in the susceptibility of neurones to Aβ toxicity. While neuronal death was not a prominent effect of Aβ, subtle changes were evident in a variety of neurotransmitter systems. Indeed, it appeared that the cholinergic system may be more vulnerable than other neurotransmitter systems such as the glutamatergic pathways. Aβ was quite proficient at increasing the reactivity of astrocytes and microglia, although the responsiveness varied across brain regions. A reasonable body of evidence indicates that Aβ can elicit behavioural changes, particularly the acquisition of memory on spatial and discriminative learning tasks, and these impairments are paralleled by a higher threshold for induction of LTP. There was also an indication of changes in markers of oxidative stress. The results reviewed in this chapter have highlighted some fundamental issues confronting AD research at the present time. While these issues have already been raised by findings from transgenic mouse models, it appears to us that injection/infusion models offer

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the greatest promise of their resolution. The most important of these issues relates to the varied effects that Aβ exerts on the brain and behaviour. It is critical to determine whether all of these effects are a direct result of Aβ deposition, or whether some of them are secondary effects brought about by a cascade of events. A cascade might be initiated for example, by the strongly pro-inflammatory nature of Aβ, which targets C1q receptors on microglia [Daly and Kotwal, 1998; Jiang et al., 1994; Rogers et al., 1992]. The resultant phagocytic response would lead to the release of cytokines and pro-oxidants which in turn would activate astrocytes and impair their homeostatic control of synaptic function. Most of the effects of Aβ reported in this chapter could be consequences of such a cascade. It would be difficult to detect such cascades in transgenic mice because the continuous production and deposition of Aβ would obscure the temporal sequence of events. With injection/infusion models however, it should be possible to establish whether such a series of events occurs, and then to use pharmacological interventions to block steps in this cascade. Aβ is produced continuously by the brain throughout life, and this ubiquity suggests that it has a physiological role. Several roles have been proposed, including the modulation of synaptic function [for reviews see Bishop and Robinson, 2004b; Robinson and Bishop, 2002]. A challenge facing researchers is to determine which of the effects of Aβ seen in animal models are pathological and which are physiologically relevant. Investigation of this issue has been limited by the need to administer abnormally high concentrations of Aβ in order to cause its deposition in the brain. For example, in order to obtain plaques, transgenic mouse models express mutant human APP, and presumably Aβ, at concentrations that are 510 times higher than are present under normal physiological conditions [Games et al., 1995; Hsiao et al., 1996]. Similarly, most injection/infusion models have delivered concentrations of Aβ that are intended to resemble those found in Aβ plaques (approximately 1-10mM [Selkoe et al., 1986]), rather than the levels normally found in the CSF, which are 6-9 orders of magnitude lower (approximately 50-500pM [Ida et al., 1996]). Nonetheless, injection/infusion models have the capacity to deliver Aβ into selected regions of the brain at concentrations which more closely approximate those found normally. Such approaches, particularly when combined with behavioural or electophysiological measures, will assist us to distinguish the beneficial effects from the deleterious effects of this peptide. At the outset of this chapter we noted that no consensus had yet been reached from injection/infusion models concerning the effects of Aβ on the living brain. A goal of the present chapter was to categorise studies according to the investigative approach used, in the hope that this would reduce the degree of variability in the results. While this approach was useful, substantial variability remained, even when the comparison was restricted to studies that had used physiological forms of Aβ, physiological solvents and rigorous control conditions. In Table 2 for example, 11 physiological studies reported that Aβ injection kills significant numbers of neurones while 12 reported that it does not. It is tempting to dismiss the results of discordant studies as being due to methodological differences but the real challenge is to determine why in some instances Aβ is toxic to neurones, whereas in almost identical paradigms, it is not. The solution to this conundrum may well hold the key to understanding the pathogenesis of AD.

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Acknowledgements We wish to acknowledge the support of a Dementia Grant from Alzheimer’s Australia Research Foundation Limited and a National Health and Medical Research Council Peter Doherty Fellowship to GB (ID: 284393).

References Abe, K., Tanzi, R. E. and Kogure, K. (1991) Selective induction of Kunitz-type protease inhibitor domain-containing amyloid precursor protein mRNA after persistent focal ischemia in rat cerebral cortex. Neurosci Lett, 125, 172-174. Abraham, I., Harkany, T., Horvath, K. M., Veenema, A. H., Penke, B., Nyakas, C. and Luiten, P. G. (2000) Chronic corticosterone administration dose-dependently modulates Aβ(1-42)- and NMDA-induced neurodegeneration in rat magnocellular nucleus basalis. J Neuroendocrinol, 12, 486-494. Aguado-Llera, D., Arilla-Ferreiro, E., Campos-Barros, A., Puebla-Jimenez, L. and Barrios, V. (2005) Protective effects of insulin-like growth factor-I on the somatostatinergic system in the temporal cortex of β-amyloid-treated rats. J Neurochem, 92, 607-615. Alvarez, A., Alarcon, R., Opazo, C., Campos, E. O., Munoz, F. J., Calderon, F. H., Dajas, F., Gentry, M. K., Doctor, B. P., De Mello, F. G. and Inestrosa, N. C. (1998) Stable complexes involving acetylcholinesterase and amyloid-β peptide change the biochemical properties of the enzyme and increase the neurotoxicity of Alzheimer's fibrils. J Neurosci, 18, 3213-3223. Ammassari-Teule, M., Middei, S., Passino, E. and Restivo, L. (2002) Enhanced procedural learning following β-amyloid protein (1-42) infusion in the rat. Neuroreport, 13, 16791682. Arias, C., Montiel, T., Quiroz-Baez, R. and Massieu, L. (2002) β-amyloid neurotoxicity is exacerbated during glycolysis inhibition and mitochondrial impairment in the rat hippocampus in vivo and in isolated nerve terminals: implications for Alzheimer's disease. Exp Neurol, 176, 163-174. Baltrons, M. A., Pedraza, C. E., Heneka, M. T. and Garcia, A. (2002) β-amyloid peptides decrease soluble guanylyl cyclase expression in astroglial cells. Neurobiol Dis, 10, 139149. Bhagat, Y. A., Obenaus, A., Richardson, J. S. and Kendall, E. J. (2002) Evolution of βamyloid induced neuropathology: magnetic resonance imaging and anatomical comparisons in the rodent hippocampus. Magma, 14, 223-232. Bishop, G. M. and Robinson, S. R. (2003a) Deposits of fibrillar Aβ do not cause neuronal loss or ferritin expression in adult rat brain. J Neural Transm, 110, 381-400. Bishop, G. M. and Robinson, S. R. (2003b) Human Aβ1-42 reduces iron-induced toxicity in rat cerebral cortex. J Neurosci Res, 73, 316-323. Bishop, G. M. and Robinson, S. R. (2004a) The amyloid paradox: amyloid-β-metal complexes can be neurotoxic and neuroprotective. Brain Pathol, 14, 448-452.

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

43

Bishop, G. M. and Robinson, S. R. (2004b) Physiological roles of amyloid-β and implications for its removal in Alzheimer's disease. Drugs Aging, 21, 621-630. Boyd-Kimball, D., Sultana, R., Fai Poon, H., Lynn, B. C., Casamenti, F., Pepeu, G., Klein, J. B. and Butterfield, D. A. (2005) Proteomic identification of proteins specifically oxidized by intracerebral injection of amyloid β-peptide (1-42) into rat brain: Implications for Alzheimer's disease. Neuroscience, 132, 313-324. Brining, S. K., Jones, C. R. and Chang, M. C. (1996) Effects of chronic β-amyloid treatment on fatty acid incorporation into rat brain. Neurobiol Aging, 17, 301-309. Bush, A. I., Moir, R. D., Rosenkranz, K. M. and Tanzi, R. E. (1995) Zinc and Alzheimer's disease. Science, 268, 1921-1923. Bush, A. I., Pettingell, W. H., Multhaup, G., d Paradis, M., Vonsattel, J. P., Gusella, J. F., Beyreuther, K., Masters, C. L. and Tanzi, R. E. (1994) Rapid induction of Alzheimer Aβ amyloid formation by zinc. Science, 265, 1464-1467. Chambers, C. B., Sigurdsson, E. M., Hejna, M. J., Lorens, S. A., Lee, J. M. and Muma, N. A. (2000) Amyloid-β injection in rat amygdala alters tau protein but not mRNA expression. Exp Neurol, 162, 158-170. Chen, S. Y., Wright, J. W. and Barnes, C. D. (1996) The neurochemical and behavioral effects of β-amyloid peptide(25-35). Brain Res, 720, 54-60. Choi, S. H., Park, C. H., Koo, J. W., Seo, J. H., Kim, H. S., Jeong, S. J., Lee, J. H., Kim, S. S. and Suh, Y. H. (2001) Memory impairment and cholinergic dysfunction by centrally administered Aβ and carboxyl-terminal fragment of Alzheimer's APP in mice. FASEB J, 15, 1816-1818. Cleary, J., Hittner, J. M., Semotuk, M., Mantyh, P. and O'Hare, E. (1995) β-amyloid(1-40) effects on behavior and memory. Brain Res, 682, 69-74. Clemens, J. A. and Stephenson, D. T. (1992) Implants containing β-amyloid protein are not neurotoxic to young and old rat brain. Neurobiol Aging, 13, 581-586. Daly, J. and Kotwal, G. J. (1998) Pro-inflammatory complement activation by the Aβ peptide of Alzheimer's disease is biologically significant and can be blocked by vaccinia virus complement control protein. Neurobiol Aging, 19, 619-627. Delobette, S., Privat, A. and Maurice, T. (1997) In vitro aggregation facilities β-amyloid peptide-(25-35)-induced amnesia in the rat. Eur J Pharmacol, 319, 1-4. Dornan, W. A., Kang, D. E., McCampbell, A. and Kang, E. E. (1993) Bilateral injections of βA(25-35) + IBO into the hippocampus disrupts acquisition of spatial learning in the rat. Neuroreport, 5, 165-168. Dudas, B., Cornelli, U., Lee, J. M., Hejna, M. J., Walzer, M., Lorens, S. A., Mervis, R. F., Fareed, J. and Hanin, I. (2002) Oral and subcutaneous administration of the glycosaminoglycan C3 attenuates Aβ(25-35)-induced abnormal tau protein immunoreactivity in rat brain. Neurobiol Aging, 23, 97-104. Durell, S. R., Guy, H. R., Arispe, N., Rojas, E. and Pollard, H. B. (1994) Theoretical models of the ion channel structure of amyloid β-protein. Biophys J, 67, 2137-2145. El Khoury, J. B., Moore, K. J., Means, T. K., Leung, J., Terada, K., Toft, M., Freeman, M. W. and Luster, A. D. (2003) CD36 mediates the innate host response to β-amyloid. J Exp Med, 197, 1657-1666.

44

Glenda M. Bishop and Stephen R. Robinson

Emre, M., Geula, C., Ransil, B. J. and Mesulam, M. M. (1992) The acute neurotoxicity and effects upon cholinergic axons of intracerebrally injected β-amyloid in the rat brain. Neurobiol Aging, 13, 553-559. Flood, J. F., Morley, J. E. and Roberts, E. (1991) Amnestic effects in mice of four synthetic peptides homologous to amyloid β protein from patients with Alzheimer disease. Proc Natl Acad Sci U S A, 88, 3363-3366. Flood, J. F., Morley, J. E. and Roberts, E. (1994) An amyloid β-protein fragment, Aβ[12-28], equipotently impairs post-training memory processing when injected into different limbic system structures. Brain Res, 663, 271-276. Frautschy, S. A., Horn, D. L., Sigel, J. J., Harris-White, M. E., Mendoza, J. J., Yang, F., Saido, T. C. and Cole, G. M. (1998) Protease inhibitor coinfusion with amyloid β-protein results in enhanced deposition and toxicity in rat brain. J Neurosci, 18, 8311-8321. Freeman, J. J. and Hayes, E. P. (1988) Microsomal metabolism of acetonitrile to cyanide. Effects of acetone and other compounds. Biochem Pharmacol, 37, 1153-1159. Freir, D. B., Costello, D. A. and Herron, C. E. (2003) Aβ25-35-induced depression of longterm potentiation in area CA1 in vivo and in vitro is attenuated by verapamil. J Neurophysiol, 89, 3061-3069. Freir, D. B. and Herron, C. E. (2003) Nicotine enhances the depressive actions of Aβ1-40 on long-term potentiation in the rat hippocampal CA1 region in vivo. J Neurophysiol, 89, 2917-2922. Freir, D. B., Holscher, C. and Herron, C. E. (2001) Blockade of long-term potentiation by βamyloid peptides in the CA1 region of the rat hippocampus in vivo. J Neurophysiol, 85, 708-713. Fukuta, T., Nitta, A., Itoh, A., Furukawa, S. and Nabeshima, T. (2001) Difference in toxicity of β-amyloid peptide with aging in relation to nerve growth factor content in rat brain. J Neural Transm, 108, 221-230. Games, D., Adams, D., Alessandrini, R., Barbour, R., Berthelette, P., Blackwell, C., Carr, T., Clemens, J., Donaldson, T., Gillespie, F., Guido, T., Hagoplan, S., Johnson-Wood, K., Khan, K., Lee, M., Leibowitz, P., Lieberburg, I., Little, S., Masliah, E., McConlogue, L., Montoya-Zavala, M., Mucke, L., Paganini, L., E., P., Power, M., Schenk, D., Seubert, P., Snyder, B., Soriano, F., Tan, H., Vitale, J., Wadsworth, S., Wolozin, B. and Zhao, J. (1995) Alzheimer-type neuropathology in transgenic mice overexpressing V717F βamyloid precursor protein. Nature, 373, 523-527. Games, D., Khan, K. M., Soriano, F. G., Keim, P. S., Davis, D. L., Bryant, K. and Lieberburg, I. (1992) Lack of Alzheimer pathology after β-amyloid protein injections in rat brain. Neurobiol Aging, 13, 569-576. Geula, C., Wu, C. K., Saroff, D., Lorenzo, A., Yuan, M. and Yankner, B. A. (1998) Aging renders the brain vulnerable to amyloid β-protein neurotoxicity. Nat Med, 4, 827-831. Ghribi, O., Herman, M. M., DeWitt, D. A., Forbes, M. S. and Savory, J. (2001) Aβ(1-42) and aluminum induce stress in the endoplasmic reticulum in rabbit hippocampus, involving nuclear translocation of gadd 153 and NF-κB. Brain Res Mol Brain Res, 96, 30-38. Ghribi, O., Herman, M. M., Pramoonjago, P., Spaulding, N. K. and Savory, J. (2004) GDNF regulates the Aβ-induced endoplasmic reticulum stress response in rabbit hippocampus

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

45

by inhibiting the activation of gadd 153 and the JNK and ERK kinases. Neurobiol Dis, 16, 417-427. Ghribi, O., Herman, M. M. and Savory, J. (2003) Lithium inhibits Aβ-induced stress in endoplasmic reticulum of rabbit hippocampus but does not prevent oxidative damage and tau phosphorylation. J Neurosci Res, 71, 853-862. Giordano, T., Pan, J. B., Monteggia, L. M., Holzman, T. F., Snyder, S. W., Krafft, G., Ghanbari, H. and Kowall, N. W. (1994) Similarities between β amyloid peptides 1-40 and 40-1: effects on aggregation, toxicity in vitro, and injection in young and aged rats. Exp Neurol, 125, 175-182. Giovannelli, L., Casamenti, F., Scali, C., Bartolini, L. and Pepeu, G. (1995) Differential effects of amyloid peptides β-(1-40) and β-(25-35) injections into the rat nucleus basalis. Neuroscience, 66, 781-792. Giovannelli, L., Scali, C., Faussone-Pellegrini, M. S., Pepeu, G. and Casamenti, F. (1998) Long-term changes in the aggregation state and toxic effects of β-amyloid injected into the rat brain. Neuroscience, 87, 349-357. Giovannini, M. G., Scali, C., Prosperi, C., Bellucci, A., Vannucchi, M. G., Rosi, S., Pepeu, G. and Casamenti, F. (2002) β-amyloid-induced inflammation and cholinergic hypofunction in the rat brain in vivo: involvement of the p38MAPK pathway. Neurobiol Dis, 11, 257274. Giulian, D., Haverkamp, L. J., Yu, J. H., Karshin, W., Tom, D., Li, J., Kirkpatrick, J., Kuo, L. M. and Roher, A. E. (1996) Specific domains of β-amyloid from Alzheimer plaque elicit neuron killing in human microglia. J Neurosci, 16, 6021-6037. Glenner, G. G. and Wong, C. W. (1984) Alzheimer's disease: initial report of the purification and characterization of a novel cerebrovascular amyloid protein. Biochem Biophys Res Commun, 120, 885-890. Goldberg, M. P., Weiss, J. H., Pham, P. C. and Choi, D. W. (1987) N-methyl-D-aspartate receptors mediate hypoxic neuronal injury in cortical culture. J Pharmacol Exp Ther, 243, 784-791. Gonzalo-Ruiz, A., Gonzalez, I. and Sanz-Anquela, J. M. (2003) Effects of β-amyloid protein on serotoninergic, noradrenergic, and cholinergic markers in neurons of the pontomesencephalic tegmentum in the rat. J Chem Neuroanat, 26, 153-169. Gonzalo-Ruiz, A., Sanz, J. M., Arevalo, J., Geula, C. and Gonzalo, P. (2005) Amyloid β peptide-induced cholinergic fibres loss in the cerebral cortex of the rat is modified by diet high in lipids and by age. J Chem Neuroanat, 29, 31-48. Halliday, G., Robinson, S. R., Shepherd, C. and Kril, J. (2000) Alzheimer's disease and inflammation: a review of cellular and therapeutic mechanisms. Clin Exp Pharmacol Physiol, 27, 1-8. Harkany, T., Abraham, I., Laskay, G., Timmerman, W., Jost, K., Zarandi, M., Penke, B., Nyakas, C. and Luiten, P. G. (1999a) Propionyl-IIGL tetrapeptide antagonizes β-amyloid excitotoxicity in rat nucleus basalis. Neuroreport, 10, 1693-1698. Harkany, T., Abraham, I., Timmerman, W., Laskay, G., Toth, B., Sasvari, M., Konya, C., Sebens, J. B., Korf, J., Nyakas, C., Zarandi, M., Soos, K., Penke, B. and Luiten, P. G. (2000) β-amyloid neurotoxicity is mediated by a glutamate-triggered excitotoxic cascade in rat nucleus basalis. Eur J Neurosci, 12, 2735-2745.

46

Glenda M. Bishop and Stephen R. Robinson

Harkany, T., De Jong, G. I., Soos, K., Penke, B., Luiten, P. G. and Gulya, K. (1995a) βamyloid (1-42) affects cholinergic but not parvalbumin-containing neurons in the septal complex of the rat. Brain Res, 698, 270-274. Harkany, T., Lengyel, Z., Soos, K., Penke, B., Luiten, P. G. and Gulya, K. (1995b) Cholinotoxic effects of β-amyloid (1-42) peptide on cortical projections of the rat nucleus basalis magnocellularis. Brain Res, 695, 71-75. Harkany, T., Mulder, J., Sasvari, M., Abraham, I., Konya, C., Zarandi, M., Penke, B., Luiten, P. G. and Nyakas, C. (1999b) N-Methyl-D-aspartate receptor antagonist MK-801 and radical scavengers protect cholinergic nucleus basalis neurons against β-amyloid neurotoxicity. Neurobiol Dis, 6, 109-121. Harkany, T., O'Mahony, S., Keijser, J., Kelly, J. P., Konya, C., Borostyankoi, Z. A., Gorcs, T. J., Zarandi, M., Penke, B., Leonard, B. E. and Luiten, P. G. (2001) β-amyloid(1-42)induced cholinergic lesions in rat nucleus basalis bidirectionally modulate serotonergic innervation of the basal forebrain and cerebral cortex. Neurobiol Dis, 8, 667-678. Harris, M. E., Hensley, K., Butterfield, D. A., Leedle, R. A. and Carney, J. M. (1995) Direct evidence of oxidative injury produced by the Alzheimer's β-amyloid peptide (1-40) in cultured hippocampal neurons. Exp Neurol, 131, 193-202. Hartley, D. M., Walsh, D. M., Ye, C. P., Diehl, T., Vasquez, S., Vassilev, P. M., Teplow, D. B. and Selkoe, D. J. (1999) Protofibrillar intermediates of amyloid β-protein induce acute electrophysiological changes and progressive neurotoxicity in cortical neurons. J Neurosci, 19, 8876-8884. Hashimoto, M., Hossain, S., Shimada, T., Sugioka, K., Yamasaki, H., Fujii, Y., Ishibashi, Y., Oka, J. and Shido, O. (2002) Docosahexaenoic acid provides protection from impairment of learning ability in Alzheimer's disease model rats. J Neurochem, 81, 1084-1091. Henke, H. and Lang, W. (1983) Cholinergic enzymes in neocortex, hippocampus and basal forebrain of non-neurological and senile dementia of Alzheimer-type patients. Brain Res, 267, 281-291. Hsiao, K., Chapman, P., Nilsen, S., Eckman, C., Harigaya, Y., Younkin, S., Yang, F. and Cole, G. (1996) Correlative memory deficits, Aβ elevation, and amyloid plaques in transgenic mice. Science, 274, 99-102. Ida, N., Hartmann, T., Pantel, J., Schroder, J., Zerfass, R., Forstl, H., Sandbrink, R., Masters, C. L. and Beyreuther, K. (1996) Analysis of heterogeneous A4 peptides in human cerebrospinal fluid and blood by a newly developed sensitive Western blot assay. J Biol Chem, 271, 22908-22914. Irizarry, M. C., McNamara, M., Fedorchak, K., Hsiao, K. and Hyman, B. T. (1997a) APPSw transgenic mice develop age-related Aβ deposits and neuropil abnormalities, but no neuronal loss in CA1. J Neuropathol Exp Neurol, 56, 965-973. Irizarry, M. C., Soriano, F., McNamara, M., Page, K. J., Schenk, D., Games, D. and Hyman, B. T. (1997b) Aβ deposition is associated with neuropil changes, but not with overt neuronal loss in the human amyloid precursor protein V717F (PDAPP) transgenic mouse. J Neurosci, 17, 7053-7059. Itoh, A., Akaike, T., Sokabe, M., Nitta, A., Iida, R., Olariu, A., Yamada, K. and Nabeshima, T. (1999) Impairments of long-term potentiation in hippocampal slices of β-amyloidinfused rats. Eur J Pharmacol, 382, 167-175.

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

47

Itoh, A., Nitta, A., Nadai, M., Nishimura, K., Hirose, M., Hasegawa, T. and Nabeshima, T. (1996) Dysfunction of cholinergic and dopaminergic neuronal systems in β-amyloid protein-infused rats. J Neurochem, 66, 1113-1117. Jantaratnotai, N., Ryu, J. K., Kim, S. U. and McLarnon, J. G. (2003) Amyloid β peptideinduced corpus callosum damage and glial activation in vivo. Neuroreport, 14, 14291433. Jen, L. S., Hart, A. J., Jen, A., Relvas, J. B., Gentleman, S. M., Garey, L. J. and Patel, A. J. (1998) Alzheimer's peptide kills cells of retina in vivo. Nature, 392, 140-141. Jhoo, J. H., Kim, H. C., Nabeshima, T., Yamada, K., Shin, E. J., Jhoo, W. K., Kim, W., Kang, K. S., Jo, S. A. and Woo, J. I. (2004) β-amyloid (1-42)-induced learning and memory deficits in mice: involvement of oxidative burdens in the hippocampus and cerebral cortex. Behav Brain Res, 155, 185-196. Jiang, H., Burdick, D., Glabe, C. G., Cotman, C. W. and Tenner, A. J. (1994) β-Amyloid activates complement by binding to a specific region of the collagen-like domain of the C1q A chain. J Immunol, 152, 5050-5059. Jin, D. Q., Park, B. C., Lee, J. S., Choi, H. D., Lee, Y. S., Yang, J. H. and Kim, J. A. (2004) Mycelial extract of Cordyceps ophioglossoides prevents neuronal cell death and ameliorates β-amyloid peptide-induced memory deficits in rats. Biol Pharm Bull, 27, 1126-1129. Kim, H. C., Yamada, K., Nitta, A., Olariu, A., Tran, M. H., Mizuno, M., Nakajima, A., Nagai, T., Kamei, H., Jhoo, W. K., Im, D. H., Shin, E. J., Hjelle, O. P., Ottersen, O. P., Park, S. C., Kato, K., Mirault, M. E. and Nabeshima, T. (2003) Immunocytochemical evidence that amyloid β (1-42) impairs endogenous antioxidant systems in vivo. Neuroscience, 119, 399-419. Kim, H. S., Cho, J. Y., Kim, D. H., Yan, J. J., Lee, H. K., Suh, H. W. and Song, D. K. (2004) Inhibitory effects of long-term administration of ferulic acid on microglial activation induced by intracerebroventricular injection of β-amyloid peptide (1-42) in mice. Biol Pharm Bull, 27, 120-121. Kim, J. H., Anwyl, R., Suh, Y. H., Djamgoz, M. B. and Rowan, M. J. (2001) Use-dependent effects of amyloidogenic fragments of β-amyloid precursor protein on synaptic plasticity in rat hippocampus in vivo. J Neurosci, 21, 1327-1333. Klyubin, I., Walsh, D. M., Cullen, W. K., Fadeeva, J. V., Anwyl, R., Selkoe, D. J. and Rowan, M. J. (2004) Soluble Arctic amyloid β protein inhibits hippocampal long-term potentiation in vivo. Eur J Neurosci, 19, 2839-2846. Koh, J. Y., Yang, L. L. and Cotman, C. W. (1990) β-amyloid protein increases the vulnerability of cultured cortical neurons to excitotoxic damage. Brain Res, 533, 315320. Kowall, N. W., Beal, M. F., Busciglio, J., Duffy, L. K. and Yankner, B. A. (1991) An in vivo model for the neurodegenerative effects of β amyloid and protection by substance P. Proc Natl Acad Sci U S A, 88, 7247-7251. Kowall, N. W., McKee, A. C., Yankner, B. A. and Beal, M. F. (1992) In vivo neurotoxicity of beta-amyloid [β(1-40)] and the β(25-35) fragment. Neurobiol Aging, 13, 537-542.

48

Glenda M. Bishop and Stephen R. Robinson

Li, L. X., Dai, J. P., Ru, L. Q., Yin, G. F. and Zhao, B. (2004a) Effects of tanshinone on neuropathological changes induced by amyloid β-peptide(1-40) injection in rat hippocampus. Acta Pharmacol Sin, 25, 861-868. Li, Y., Qin, H. Q., Chen, Q. S. and Wang, J. J. (2004b) Behavioral and neurochemical effects of the intrahippocampal co-injection of β-amyloid protein 1-40 and ibotenic acid in rats. Int J Neurosci, 114, 1521-1531. Malin, D. H., Crothers, M. K., Lake, J. R., Goyarzu, P., Plotner, R. E., Garcia, S. A., Spell, S. H., Tomsic, B. J., Giordano, T. and Kowall, N. W. (2001) Hippocampal injections of amyloid β-peptide 1-40 impair subsequent one-trial/day reward learning. Neurobiol Learn Mem, 76, 125-137. Mantyh, P. W., Ghilardi, J. R., Rogers, S., DeMaster, E., Allen, C. J., Stimson, E. R. and Maggio, J. E. (1993) Aluminum, iron, and zinc ions promote aggregation of physiological concentrations of β-amyloid peptide. J Neurochem, 61, 1171-1174. Masters, C. L., Simms, G., Weinman, N. A., Multhaup, G., McDonald, B. L. and Beyreuther, K. (1985) Amyloid plaque core protein in Alzheimer disease and Down syndrome. Proc Natl Acad Sci U S A, 82, 4245-4249. Matsunaga, W., Shirokawa, T. and Isobe, K. (2003) Specific uptake of Aβ1-40 in rat brain occurs in astrocyte, but not in microglia. Neurosci Lett, 342, 129-131. Maurice, T., Lockhart, B. P. and Privat, A. (1996) Amnesia induced in mice by centrally administered β-amyloid peptides involves cholinergic dysfunction. Brain Res, 706, 181193. Mazzola, C., Micale, V. and Drago, F. (2003) Amnesia induced by β-amyloid fragments is counteracted by cannabinoid CB1 receptor blockade. Eur J Pharmacol, 477, 219-225. McDonald, M. P., Overmier, J. B., Bandyopadhyay, S., Babcock, D. and Cleary, J. (1996) Reversal of β-amyloid-induced retention deficit after exposure to training and state cues. Neurobiol Learn Mem, 65, 35-47. Miguel-Hidalgo, J. J., Vecino, B., Fernandez-Novoa, L., Alvarez, A. and Cacabelos, R. (1998) Neuroprotective role of S12024 against neurodegeneration in the rat dentate gyrus. Eur Neuropsychopharmacol, 8, 203-208. Mileusnic, R., Lancashire, C. L. and Rose, S. P. (2004) The peptide sequence Arg-Glu-Arg, present in the amyloid precursor protein, protects against memory loss caused by Aβ and acts as a cognitive enhancer. Eur J Neurosci, 19, 1933-1938. Minogue, A. M., Schmid, A. W., Fogarty, M. P., Moore, A. C., Campbell, V. A., Herron, C. E. and Lynch, M. A. (2003) Activation of the c-Jun N-terminal kinase signaling cascade mediates the effect of amyloid-β on long term potentiation and cell death in hippocampus: a role for interleukin-1β? J Biol Chem, 278, 27971-27980. Mohajeri, M. H., Wollmer, M. A. and Nitsch, R. M. (2002) Aβ42-induced increase in neprilysin is associated with prevention of amyloid plaque formation in vivo. J Biol Chem, 277, 35460-35465. Morimoto, K. and Oda, T. (2003) Kainate exacerbates β-amyloid toxicity in rat hippocampus. Neurosci Lett, 340, 242-244. Morimoto, K., Yoshimi, K., Tonohiro, T., Yamada, N., Oda, T. and Kaneko, I. (1998) Coinjection of β-amyloid with ibotenic acid induces synergistic loss of rat hippocampal neurons. Neuroscience, 84, 479-487.

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

49

Nabeshima, T. and Nitta, A. (1994) Memory impairment and neuronal dysfunction induced by β-amyloid protein in rats. Tohoku J Exp Med, 174, 241-249. Nag, S. and Tang, F. (2001) The effect of age on the response of the rat brains to continuous β-amyloid infusion. Brain Res, 889, 303-307. Nag, S., Tang, F. and Yee, B. K. (2001) Chronic intracerebroventricular exposure to βamyloid(1-40) impairs object recognition but does not affect spontaneous locomotor activity or sensorimotor gating in the rat. Exp Brain Res, 136, 93-100. Nag, S., Yee, B. K. and Tang, F. (1999) Reduction in somatostatin and substance P levels and choline acetyltransferase activity in the cortex and hippocampus of the rat after chronic intracerebroventricular infusion of β-amyloid (1-40). Brain Res Bull, 50, 251-262. Nakagawa, Y., Yuzuriha, T. and Iwaki, T. (2004) Active clearance of human amyloid β1-42 peptide aggregates from the rat ventricular system. Neuropathology, 24, 194-200. Nakamura, S., Murayama, N., Noshita, T., Annoura, H. and Ohno, T. (2001) Progressive brain dysfunction following intracerebroventricular infusion of β1-42-amyloid peptide. Brain Res, 912, 128-136. Nelson, P. T. and Saper, C. B. (1996) Injections of okadaic acid, but not β-amyloid peptide, induce Alz-50 immunoreactive dystrophic neurites in the cerebral cortex of sheep. Neurosci Lett, 208, 77-80. Netland, E. E., Newton, J. L., Majocha, R. E. and Tate, B. A. (1998) Indomethacin reverses the microglial response to amyloid β-protein. Neurobiol Aging, 19, 201-204. Nitta, A., Fukuta, T., Hasegawa, T. and Nabeshima, T. (1997) Continuous infusion of βamyloid protein into the rat cerebral ventricle induces learning impairment and neuronal and morphological degeneration. Jpn J Pharmacol, 73, 51-57. Nitta, A., Itoh, A., Hasegawa, T. and Nabeshima, T. (1994) β-Amyloid protein-induced Alzheimer's disease animal model. Neurosci Lett, 170, 63-66. O'Hare, E., Weldon, D. T., Mantyh, P. W., Ghilardi, J. R., Finke, M. P., Kuskowski, M. A., Maggio, J. E., Shephard, R. A. and Cleary, J. (1999) Delayed behavioral effects following intrahippocampal injection of aggregated Aβ(1-42). Brain Res, 815, 1-10. Oka, J., Suzuki, E., Goto, N. and Kameyama, T. (1999) Endogenous GLP-1 modulates hippocampal activity in β-amyloid protein-treated rats. Neuroreport, 10, 2961-2964. Olariu, A., Tran, M. H., Yamada, K., Mizuno, M., Hefco, V. and Nabeshima, T. (2001) Memory deficits and increased emotionality induced by β-amyloid (25-35) are correlated with the reduced acetylcholine release and altered phorbol dibutyrate binding in the hippocampus. J Neural Transm, 108, 1065-1079. Olariu, A., Yamada, K., Mamiya, T., Hefco, V. and Nabeshima, T. (2002) Memory impairment induced by chronic intracerebroventricular infusion of β-amyloid (1-40) involves downregulation of protein kinase C. Brain Res, 957, 278-286. O'Mahony, S., Harkany, T., Rensink, A. A., Abraham, I., De Jong, G. I., Varga, J. L., Zarandi, M., Penke, B., Nyakas, C., Luiten, P. G. and Leonard, B. E. (1998) β-amyloidinduced cholinergic denervation correlates with enhanced nitric oxide synthase activity in rat cerebral cortex: reversal by NMDA receptor blockade. Brain Res Bull, 45, 405411.

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Pan, Y., Xu, X., Tong, X. and Wang, X. (2004) Messenger RNA and protein expression analysis of voltage-gated potassium channels in the brain of Aβ(25-35)-treated rats. J Neurosci Res, 77, 94-99. Pavia, J., Alberch, J., Alvarez, I., Toledano, A. and de Ceballos, M. L. (2000) Repeated intracerebroventricular administration of β-amyloid(25-35) to rats decreases muscarinic receptors in cerebral cortex. Neurosci Lett, 278, 69-72. Perez-Severiano, F., Salvatierra-Sanchez, R., Rodriguez-Perez, M., Cuevas-Martinez, E. Y., Guevara, J., Limon, D., Maldonado, P. D., Medina-Campos, O. N., Pedraza-Chaverri, J. and Santamaria, A. (2004) S-Allylcysteine prevents amyloid-β peptide-induced oxidative stress in rat hippocampus and ameliorates learning deficits. Eur J Pharmacol, 489, 197202. Perry, E. K., Tomlinson, B. E., Blessed, G., Bergmann, K., Gibson, P. H. and Perry, R. H. (1978) Correlation of cholinergic abnormalities with senile plaques and mental test scores in senile dementia. Br Med J, 2, 1457-1459. Pike, C. J., Cummings, B. J. and Cotman, C. W. (1992) β-amyloid induces neuritic dystrophy in vitro: similarities with Alzheimer pathology. Neuroreport, 3, 769-772. Pike, C. J., Walencewicz, A. J., Glabe, C. G. and Cotman, C. W. (1991) In vitro aging of βamyloid protein causes peptide aggregation and neurotoxicity. Brain Res, 563, 311-314. Podlisny, M. B., Stephenson, D. T., Frosch, M. P., Lieberburg, I., Clemens, J. A. and Selkoe, D. J. (1992) Synthetic amyloid β-protein fails to produce specific neurotoxicity in monkey cerebral cortex. Neurobiol Aging, 13, 561-567. Podlisny, M. B., Stephenson, D. T., Frosch, M. P., Tolan, D. R., Lieberburg, I., Clemens, J. A. and Selkoe, D. J. (1993) Microinjection of synthetic amyloid β-protein in monkey cerebral cortex fails to produce acute neurotoxicity. Am J Pathol, 142, 17-24. Reyes, A. E., Chacon, M. A., Dinamarca, M. C., Cerpa, W., Morgan, C. and Inestrosa, N. C. (2004) Acetylcholinesterase-Aβ complexes are more toxic than Aβ fibrils in rat hippocampus: effect on rat β-amyloid aggregation, laminin expression, reactive astrocytosis, and neuronal cell loss. Am J Pathol, 164, 2163-2174. Richardson, R. L., Kim, E. M., Shephard, R. A., Gardiner, T., Cleary, J. and O'Hare, E. (2002) Behavioural and histopathological analyses of ibuprofen treatment on the effect of aggregated Aβ(1-42) injections in the rat. Brain Res, 954, 1-10. Robinson, S. R. and Bishop, G. M. (2002) Aβ as a bioflocculant: implications for the amyloid hypothesis of Alzheimer's disease. Neurobiol Aging, 23, 1051-1072. Rogers, J., Cooper, N. R., Webster, S., Schultz, J., McGeer, P. L., Styren, S. D., Civin, W. H., Brachova, L., Bradt, B., Ward, P. and Lieberburg, I. (1992) Complement activation by βamyloid in Alzheimer disease. Proc Natl Acad Sci U S A, 89, 10016-10020. Roher, A. E., Ball, M. J., Bhave, S. V. and Wakade, A. R. (1991) β-amyloid from Alzheimer disease brains inhibits sprouting and survival of sympathetic neurons. Biochem Biophys Res Commun, 174, 572-579. Rosales-Corral, S., Tan, D. X., Reiter, R. J., Valdivia-Velazquez, M., Acosta-Martinez, J. P. and Ortiz, G. G. (2004) Kinetics of the neuroinflammation-oxidative stress correlation in rat brain following the injection of fibrillar amyloid-β onto the hippocampus in vivo. J Neuroimmunol, 150, 20-28.

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

51

Rush, D. K., Aschmies, S. and Merriman, M. C. (1992) Intracerebral β-amyloid(25-35) produces tissue damage: is it neurotoxic? Neurobiol Aging, 13, 591-594. Ryu, J. K., Franciosi, S., Sattayaprasert, P., Kim, S. U. and McLarnon, J. G. (2004) Minocycline inhibits neuronal death and glial activation induced by β-amyloid peptide in rat hippocampus. Glia, 48, 85-90. Saez-Valero, J., de Ceballos, M. L., Small, D. H. and de Felipe, C. (2002) Changes in molecular isoform distribution of acetylcholinesterase in rat cortex and cerebrospinal fluid after intracerebroventricular administration of amyloid β-peptide. Neurosci Lett, 325, 199-202. Scali, C., Prosperi, C., Giovannelli, L., Bianchi, L., Pepeu, G. and Casamenti, F. (1999) β(140) amyloid peptide injection into the nucleus basalis of rats induces microglia reaction and enhances cortical gamma-aminobutyric acid release in vivo. Brain Res, 831, 319321. Schenk, D., Barbour, R., Dunn, W., Gordon, G., Grajeda, H., Guido, T., Hu, K., Huang, J., Johnson-Wood, K., Khan, K., Kholodenko, D., Lee, M., Liao, Z., Lieberburg, I., Motter, R., Mutter, L., Soriano, F., Shopp, G., Vasquez, N., Vandevert, C., Walker, S., Wogulis, M., Yednock, T., Games, D. and Seubert, P. (1999) Immunization with amyloid-β attenuates Alzheimer-disease-like pathology in the PDAPP mouse. Nature, 400, 173-177. Schubert, D. and Chevion, M. (1995) The role of iron in beta amyloid toxicity. Biochem Biophys Res Commun, 216, 702-707. Selkoe, D. J. (2002) Alzheimer's disease is a synaptic failure. Science, 298, 789-791. Selkoe, D. J., Abraham, C. R., Podlisny, M. B. and Duffy, L. K. (1986) Isolation of lowmolecular-weight proteins from amyloid plaque fibers in Alzheimer's disease. J Neurochem, 46, 1820-1834. Shen, Y. X., Xu, S. Y., Wei, W., Sun, X. X., Liu, L. H., Yang, J. and Dong, C. (2002) The protective effects of melatonin from oxidative damage induced by amyloid β-peptide 2535 in middle-aged rats. J Pineal Res, 32, 85-89. Shivers, B. D., Hilbich, C., Multhaup, G., Salbaum, M., Beyreuther, K. and Seeburg, P. H. (1988) Alzheimer's disease amyloidogenic glycoprotein: expression pattern in rat brain suggests a role in cell contact. EMBO J, 7, 1365-1370. Sigurdsson, E. M., Hejna, M. J., Lee, J. M. and Lorens, S. A. (1995) β-Amyloid 25-35 and/or quinolinic acid injections into the basal forebrain of young male Fischer-344 rats: behavioral, neurochemical and histological effects. Behav Brain Res, 72, 141-156. Sigurdsson, E. M., Lee, J. M., Dong, X. W., Hejna, M. J. and Lorens, S. A. (1997a) Bilateral injections of amyloid-β 25-35 into the amygdala of young Fischer rats: behavioral, neurochemical, and time dependent histopathological effects. Neurobiol Aging, 18, 591608. Sigurdsson, E. M., Lee, J. M., Dong, X. W., Hejna, M. J. and Lorens, S. A. (1997b) Laterality in the histological effects of injections of amyloid-β 25-35 into the amygdala of young Fischer rats. J Neuropathol Exp Neurol, 56, 714-725. Sigurdsson, E. M., Lorens, S. A., Hejna, M. J., Dong, X. W. and Lee, J. M. (1996) Local and distant histopathological effects of unilateral amyloid-β 25-35 injections into the amygdala of young F344 rats. Neurobiol Aging, 17, 893-901.

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Sigurdsson, E. M., Permanne, B., Soto, C., Wisniewski, T. and Frangione, B. (2000) In vivo reversal of amyloid-β lesions in rat brain. J Neuropathol Exp Neurol, 59, 11-17. Smyth, M. D., Kesslak, J. P., Cummings, B. J. and Cotman, C. W. (1994) Analysis of brain injury following intrahippocampal administration of β-amyloid in streptozotocin-treated rats. Neurobiol Aging, 15, 153-159. Snow, A. D., Sekiguchi, R., Nochlin, D., Fraser, P., Kimata, K., Mizutani, A., Arai, M., Schreier, W. A. and Morgan, D. G. (1994) An important role of heparan sulfate proteoglycan (Perlecan) in a model system for the deposition and persistence of fibrillar A β-amyloid in rat brain. Neuron, 12, 219-234. Song, D. K., Im, Y. B., Jung, J. S., Cho, J., Suh, H. W. and Kim, Y. H. (2001) Central βamyloid peptide-induced peripheral interleukin-6 responses in mice. J Neurochem, 76, 1326-1335. Soto, C., Sigurdsson, E. M., Morelli, L., Kumar, R. A., Castano, E. M. and Frangione, B. (1998) β-sheet breaker peptides inhibit fibrillogenesis in a rat brain model of amyloidosis: implications for Alzheimer's therapy. Nat Med, 4, 822-826. Stein-Behrens, B., Adams, K., Yeh, M. and Sapolsky, R. (1992) Failure of β-amyloid protein fragment 25-35 to cause hippocampal damage in the rat. Neurobiol Aging, 13, 577-579. Stepanichev, M. Y., Moiseeva, Y. V., Lazareva, N. A., Onufriev, M. V. and Gulyaeva, N. V. (2003a) Single intracerebroventricular administration of amyloid-β (25-35) peptide induces impairment in short-term rather than long-term memory in rats. Brain Res Bull, 61, 197-205. Stepanichev, M. Y., Zdobnova, I. M., Yakovlev, A. A., Onufriev, M. V., Lazareva, N. A., Zarubenko, II and Gulyaeva, N. V. (2003b) Effects of tumor necrosis factor-α central administration on hippocampal damage in rat induced by amyloid β-peptide (25-35). J Neurosci Res, 71, 110-120. Stepanichev, M. Y., Zdobnova, I. M., Zarubenko, II, Moiseeva, Y. V., Lazareva, N. A., Onufriev, M. V. and Gulyaeva, N. V. (2004) Amyloid-β(25-35)-induced memory impairments correlate with cell loss in rat hippocampus. Physiol Behav, 80, 647-655. Stephan, A., Laroche, S. and Davis, S. (2001) Generation of aggregated β-amyloid in the rat hippocampus impairs synaptic transmission and plasticity and causes memory deficits. J Neurosci, 21, 5703-5714. Stephan, A., Laroche, S. and Davis, S. (2003) Learning deficits and dysfunctional synaptic plasticity induced by aggregated amyloid deposits in the dentate gyrus are rescued by chronic treatment with indomethacin. Eur J Neurosci, 17, 1921-1927. Stephenson, D. T. and Clemens, J. A. (1992) In vivo effects of β-amyloid implants in rodents: lack of potentiation of damage associated with transient global forebrain ischemia. Brain Res, 586, 235-246. Sun, M. K. and Alkon, D. L. (2002) Impairment of hippocampal CA1 heterosynaptic transformation and spatial memory by β-amyloid(25-35). J Neurophysiol, 87, 2441-2449. Szczepanik, A. M., Rampe, D. and Ringheim, G. E. (2001) Amyloid-β peptide fragments p3 and p4 induce pro-inflammatory cytokine and chemokine production in vitro and in vivo. J Neurochem, 77, 304-317.

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

53

Szczepanik, A. M. and Ringheim, G. E. (2003) IL-10 and glucocorticoids inhibit Aβ(1-42)and lipopolysaccharide-induced pro-inflammatory cytokine and chemokine induction in the central nervous system. J Alzheimers Dis, 5, 105-117. Takata, K., Kitamura, Y., Tsuchiya, D., Kawasaki, T., Taniguchi, T. and Shimohama, S. (2003) Heat shock protein-90-induced microglial clearance of exogenous amyloid-β1-42 in rat hippocampus in vivo. Neurosci Lett, 344, 87-90. Tanaka, T., Yamada, K., Senzaki, K., Narimatsu, H., Nishimura, K., Kameyama, T. and Nabeshima, T. (1998) NC-1900, an active fragment analog of arginine vasopressin, improves learning and memory deficits induced by β-amyloid protein in rats. Eur J Pharmacol, 352, 135-142. Tang, F., Nag, S., Shiu, S. Y. and Pang, S. F. (2002) The effects of melatonin and Ginkgo biloba extract on memory loss and choline acetyltransferase activities in the brain of rats infused intracerebroventricularly with β-amyloid 1-40. Life Sci, 71, 2625-2631. Tang, Y., Yamada, K., Kanou, Y., Miyazaki, T., Xiong, X., Kambe, F., Murata, Y., Seo, H. and Nabeshima, T. (2000) Spatiotemporal expression of BDNF in the hippocampus induced by the continuous intracerebroventricular infusion of β-amyloid in rats. Brain Res Mol Brain Res, 80, 188-197. Terranova, J. P., Kan, J. P., Storme, J. J., Perreaut, P., Le Fur, G. and Soubrie, P. (1996) Administration of amyloid β-peptides in the rat medial septum causes memory deficits: reversal by SR 57746A, a non-peptide neurotrophic compound. Neurosci Lett, 213, 7982. Tohda, C., Tamura, T. and Komatsu, K. (2003) Repair of amyloid β(25-35)-induced memory impairment and synaptic loss by a Kampo formula, Zokumei-to. Brain Res, 990, 141147. Tran, M. H., Yamada, K., Olariu, A., Mizuno, M., Ren, X. H. and Nabeshima, T. (2001) Amyloid β-peptide induces nitric oxide production in rat hippocampus: association with cholinergic dysfunction and amelioration by inducible nitric oxide synthase inhibitors. FASEB J, 15, 1407-1409. Trubetskaya, V. V., Stepanichev, M. Y., Onufriev, M. V., Lazareva, N. A., Markevich, V. A. and Gulyaeva, N. V. (2003) Administration of aggregated β-amyloid peptide (25-35) induces changes in long-term potentiation in the hippocampus in vivo. Neurosci Behav Physiol, 33, 95-98. Urani, A., Romieu, P., Roman, F. J. and Maurice, T. (2002) Enhanced antidepressant effect of sigma1 (σ1) receptor agonists in β25-35-amyloid peptide-treated mice. Behav Brain Res, 134, 239-247. Urani, A., Romieu, P., Roman, F. J., Yamada, K., Noda, Y., Kamei, H., Manh Tran, H., Nagai, T., Nabeshima, T. and Maurice, T. (2004) Enhanced antidepressant efficacy of sigma1 receptor agonists in rats after chronic intracerebroventricular infusion of βamyloid-(1-40) protein. Eur J Pharmacol, 486, 151-161. Waite, J., Cole, G. M., Frautschy, S. A., Connor, D. J. and Thal, L. J. (1992) Solvent effects on beta protein toxicity in vivo. Neurobiol Aging, 13, 595-599. Walsh, D. T., Montero, R. M., Bresciani, L. G., Jen, A. Y., Leclercq, P. D., Saunders, D., AN, E. L.-A., Gbadamoshi, L., Gentleman, S. M. and Jen, L. S. (2002) Amyloid-β peptide is toxic to neurons in vivo via indirect mechanisms. Neurobiol Dis, 10, 20-27.

54

Glenda M. Bishop and Stephen R. Robinson

Walzer, M., Lorens, S., Hejna, M., Fareed, J., Hanin, I., Cornelli, U. and Lee, J. M. (2002) Low molecular weight glycosaminoglycan blockade of β-amyloid induced neuropathology. Eur J Pharmacol, 445, 211-220. Wang, R., Zhang, H. Y. and Tang, X. C. (2001) Huperzine A attenuates cognitive dysfunction and neuronal degeneration caused by β-amyloid protein-(1-40) in rat. Eur J Pharmacol, 421, 149-156. Weldon, D. T., Rogers, S. D., Ghilardi, J. R., Finke, M. P., Cleary, J. P., O'Hare, E., Esler, W. P., Maggio, J. E. and Mantyh, P. W. (1998) Fibrillar β-amyloid induces microglial phagocytosis, expression of inducible nitric oxide synthase, and loss of a select population of neurons in the rat CNS in vivo. J Neurosci, 18, 2161-2173. Whitehead, S. N., Hachinski, V. C. and Cechetto, D. F. (2005) Interaction between a rat model of cerebral ischemia and β-amyloid toxicity: inflammatory responses. Stroke, 36, 107-112. Winkler, J., Connor, D. J., Frautschy, S. A., Behl, C., Waite, J. J., Cole, G. M. and Thal, L. J. (1994) Lack of long-term effects after β-amyloid protein injections in rat brain. Neurobiol Aging, 15, 601-607. Yagami, T., Takahara, Y., Ishibashi, C., Sakaguchi, G., Itoh, N., Ueda, K., Nakazato, H., Okamura, N., Hiramatsu, Y., Honma, T., Arimura, A., Sakaeda, T. and Katsuura, G. (2004) Amyloid β protein impairs motor function via thromboxane A2 in the rat striatum. Neurobiol Dis, 16, 481-489. Yamada, K., Tanaka, T., Han, D., Senzaki, K., Kameyama, T. and Nabeshima, T. (1999a) Protective effects of idebenone and alpha-tocopherol on β-amyloid-(1-42)-induced learning and memory deficits in rats: implication of oxidative stress in β-amyloidinduced neurotoxicity in vivo. Eur J Neurosci, 11, 83-90. Yamada, K., Tanaka, T., Mamiya, T., Shiotani, T., Kameyama, T. and Nabeshima, T. (1999b) Improvement by nefiracetam of β-amyloid-(1-42)-induced learning and memory impairments in rats. Br J Pharmacol, 126, 235-244. Yamada, K., Tanaka, T., Senzaki, K., Kameyama, T. and Nabeshima, T. (1998) Propentofylline improves learning and memory deficits in rats induced by β-amyloid protein-(1-40). Eur J Pharmacol, 349, 15-22. Yamada, K., Tanaka, T., Zou, L. B., Senzaki, K., Yano, K., Osada, T., Ana, O., Ren, X., Kameyama, T. and Nabeshima, T. (1999c) Long-term deprivation of oestrogens by ovariectomy potentiates β-amyloid-induced working memory deficits in rats. Br J Pharmacol, 128, 419-427. Yamaguchi, Y. and Kawashima, S. (2001) Effects of amyloid-β-(25-35) on passive avoidance, radial-arm maze learning and choline acetyltransferase activity in the rat. Eur J Pharmacol, 412, 265-272. Yamaguchi, Y., Matsuno, T. and Kawashima, S. (2002) Antiamnesic effects of azaindolizinone derivative ZSET845 on impaired learning and decreased ChAT activity induced by amyloid-β 25-35 in the rat. Brain Res, 945, 259-265. Yamamoto, M., Chikuma, T. and Kato, T. (2003) Changes in the levels of neuropeptides and their metabolizing enzymes in the brain regions of nucleus basalis magnocellularislesioned rats. J Pharmacol Sci, 92, 400-410.

Insights on Alzheimer’s Disease from the Intracerebral Injection and Infusion …

55

Yan, J. J., Cho, J. Y., Kim, H. S., Kim, K. L., Jung, J. S., Huh, S. O., Suh, H. W., Kim, Y. H. and Song, D. K. (2001) Protection against β-amyloid peptide toxicity in vivo with longterm administration of ferulic acid. Br J Pharmacol, 133, 89-96. Yan, J. J., Kim, D. H., Moon, Y. S., Jung, J. S., Ahn, E. M., Baek, N. I. and Song, D. K. (2004) Protection against β-amyloid peptide-induced memory impairment with long-term administration of extract of Angelica gigas or decursinol in mice. Prog Neuropsychopharmacol Biol Psychiatry, 28, 25-30. Yankner, B. A., Duffy, L. K. and Kirschner, D. A. (1990) Neurotrophic and neurotoxic effects of amyloid β protein: reversal by tachykinin neuropeptides. Science, 250, 279282. Zand, L., Ryu, J. K. and McLarnon, J. G. (2005) Induction of angiogenesis in the β-amyloid peptide-injected rat hippocampus. Neuroreport, 16, 129-132. Zhang, H. Y., Yan, H. and Tang, X. C. (2004) Huperzine A enhances the level of secretory amyloid precursor protein and protein kinase C-α in intracerebroventricular β-amyloid(1-40) infused rats and human embryonic kidney 293 Swedish mutant cells. Neurosci Lett, 360, 21-24. Zou, K., Kim, D., Kakio, A., Byun, K., Gong, J. S., Kim, J., Kim, M., Sawamura, N., Nishimoto, S., Matsuzaki, K., Lee, B., Yanagisawa, K. and Michikawa, M. (2003) Amyloid β-protein (Aβ)1-40 protects neurons from damage induced by Aβ1-42 in culture and in rat brain. J Neurochem, 87, 609-619.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp. 57-85

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter II

The Role of Phospholipase A2 in Alzheimer's Disease Wagner F. Gattaz∗, Evelin L. Schaeffer and Orestes V. Forlenza Laboratory of Neuroscience, Department and Institute of Psychiatry, Faculty of Medicine, University of São Paulo, S.P., Brazil

Abstract Phospholipase A2 (PLA2) is a key enzyme in phospholipid metabolism. In the brain, PLA2 is involved in the liberation of membrane choline for acetylcholine synthesis, as well as in the processing of the amyloid precursor protein to form the beta-amyloid, the major component of senile plaques in Alzheimer's disease (AD). In previous postmortem studies we reported on decreased PLA2 activity in the frontal and in the parietal cortex of patients with AD, suggesting reduced phospholipid metabolism in the disease. Interestingly, we found also a reduction of PLA2 activity in platelet membranes of AD patients, suggesting that reduced phospholipid turnover may also be observed in peripheral cells of AD patients. In an in vivo study we investigated the intracerebral phospholipid metabolism in 16 patients with probable AD and 18 age-matched controls through 31P-Magnetic Resonance Spectroscopy of the pre-frontal cortex. Cognitive assessment was performed by the CAMDEX schedule. PME resonance was significantly higher and PDE was lower among AD than controls. PME correlated negatively with cognitive performance. Higher PME indicates reduced breakdown of membrane phospholipids, which is in line with reduced PLA2 activity. Our findings in the prefrontal cortex suggest that reduced membrane phospholipid turnover may be a widespread cerebral phenomenon in AD brains, since the pre-frontal cortex is a region

∗

Corresponding author: Wagner F. Gattaz, Laboratory of Neuroscience (LIM-27), Department & Institute of Psychiatry, Faculty of Medicine, University of São Paulo, Rua Doutor Ovídio Pires de Campos 785, 05403-010 São Paulo - S.P. – Brasil; (E-mail: [email protected] / phone & fax: +55.11.3069 8010)

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Wagner F. Gattaz, Evelin F. Schaeffer and Orestes V. Forlenza not as severely affected by the neurodegenerative process as temporal and parietal areas, specially in early stages of dementia. To investigate further the implications of reduced PLA2 in the neurobiology of AD, we carried out a series of in vitro and animal experiments, to respectively test the effects of the inhibition of PLA2 on neuronal homeostasis in cultured neurons, and in memory formation in rats. In primary cultures of cortical and hippocampal neurons, the inhibition of PLA2 precluded neurite outgrowth, and the sustained inhibition of the enzyme in mature cultures lead to loss of viability. These findings reinforce the involvement of PLA2 enzymes in neurodevelopment and neurodegeneration. In early stages of AD there is an impairment of episodic short-term (STM) and long-term memory (LTM). In rat hippocampal slices, PLA2 has been implicated in mechanisms of synaptic plasticity involved in memory formation. Using adult Wistar rats, we investigated the effects of injections of PLA2 inhibitors into rat hippocampus on the formation of STM and LTM of a one-trial step-down inhibitory avoidance task. Infusion of the PLA2 inhibitors impaired both STM and LTM in a dosedependent manner. Additionally, because memory function is largely dependent on the fluidity of brain membranes, we investigated the effects of in vivo PLA2 inhibition on the fluidity of hippocampal membranes from rats subjected to inhibitory avoidance training. Hippocampal tissue from rats injected with PLA2 inhibitor showed reduced membrane fluidity, and this reduction was highly correlated with PLA2 inhibition. Taken together, our findings suggest that reduced PLA2 activity, probably reducing membrane phospholipids breakdown, may contribute to the memory impairment in AD.

Introduction Phospholipase A2 Enzymes Phospholipase A2 (PLA2) is a family of hydrolytic enzymes that catalyze the cleavage of fatty acids from the sn-2 position of phospholipids from both plasma and intracellular membranes to liberate free fatty acids and lysophospholipids (Dennis, 1994; Balsinde et al., 1999). Numerous PLA2 subtypes have been identified and characterized. They have been classified into several groups on the basis of their structure, cellular localization, requirement for Ca2+, and substrate specificity. The PLA2 subtypes are classified into three main groups: extracellular or secreted Ca2+-dependent PLA2 (sPLA2); cytosolic Ca2+-dependent PLA2 (cPLA2); and intracellular Ca2+-independent PLA2 (iPLA2) (Six and Dennis, 2000; Winstead et al., 2000; Kudo and Murakami, 2002; Chakraborti, 2003). The mRNA and/or the activity of sPLA2, cPLA2, and iPLA2 groups were detected in human and rodent brains (Yoshihara and Watanabe, 1990; Sharp and White, 1993; Chen et al., 1994; Owada et al., 1994; Larsson et al., 1998; Molloy et al., 1998; Underwood et al., 1998; Kishimoto et al., 1999; Larsson Forsell et al., 1999; Pickard et al., 1999; Song et al., 1999; Yang et al., 1999; Gelb et al., 2000; Mancuso et al., 2000; Suzuki et al., 2000; Tanaka et al., 2000). The sPLA2 enzymes are characterized by low molecular mass (~13-18 kDa), a requirement for millimolar Ca2+ concentrations for catalytic activity, and a broad specificity for phospholipids with different polar head groups and fatty acid chains at the sn-2 position (Farooqui et al., 1999). The 85 kDa cPLA2 shows a marked selectivity for phospholipids containing AA at the sn-2 position

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of phosphatidylcholine. Activation of cPLA2 is regulated by nanomolar or micromolar intracellular Ca2+ concentrations (Yoshihara and Watanabe, 1990; Underwood et al., 1998). The iPLA2 enzymes have high molecular mass (~88 kDa), do not require Ca2+ for catalytic activity, and show a preference, although slight, for AA over other fatty acids at the sn-2 position of phosphatidylcholine (Larsson et al., 1998; Mancuso et al., 2000; Tanaka et al., 2000). The heterogeneous nature of the PLA2 family means that subtype-specific methods need to be employed so as to distinguish the activity of one particular molecular form of the enzyme from another (Gattaz et al., 1995; Ross et al., 1997; Schaeffer and Gattaz, 2005).

PLA2 in Neuronal Homeostasis A wide range of physiological processes in which phospholipid metabolism plays a central role is regulated by PLA2 enzymes. For instance, cleavage of membrane phosphatidylcholine by PLA2 generates lysophosphatidylcholine and free arachidonic acid (AA) (Farooqui et al., 1997). The former is involved in the release of choline for the synthesis of acetylcholine (Maire and Wurtman, 1985; Blusztajn et al., 1987), whereas the latter causes a long-lasting facilitation of excitatory synaptic transmission after the induction of long-term potentiation (LTP) in the CA1 region of rat hippocampal slices (Nishizaki et al., 1999) and in pyramidal neurons of rat cerebral cortex (Nishikawa et al., 1994). LTP is a form of activity-dependent synaptic plasticity that is proposed as a basis of memory formation (Bliss and Collingridge, 1993). PLA2 metabolites participate in a wide variety of homeostatic functions, and the relationship between membrane fatty acid modification and neurite outgrowth has been evaluated in several recent tissue culture models (Ikemoto et al., 1997). PLA2-activated downstream pathways appear to have a general role in maintaining the ability of neurites to respond rapidly to external stimuli, possibly via regulating the ability of the cytoskeleton to remodel (Smalheiser et al., 1996). Arachidonic acid, one of the major products of PLA2 metabolism, has been implicated in the modulation of ion-channel conductance, the release of neurotransmitters (Kim & Clapham, 1989; Hwang et al., 1990; Miller et al, 1992) and neuritogenesis. In cultures of cerebellar neurones, arachidonic acid was shown to be involved in the intracellular signalling pathway leading to axonal growth, in a process dependent on the activation of calcium channels (Williams et al., 1994). Accordingly, neurite outgrowth was also stimulated in COX-2-overexpressing cells (Kadoyama et al., 2001). Finally, PLA2 inhibitors delayed the initial outgrowth of neurites on laminin, and exogenous arachidonic acid, conversely, enhanced neurite outgrowth (Smalheiser et al., 1996). In addition, in vitro studies have implicated PLA2 in the regulation of beta-amyloid precursor protein (APP) processing. Hence, PLA2 inhibition in cell cultures decreased the secretion of APP, whereas its activation potently increased APP secretion (Emmerling et al., 1993; Nitsch et al., 1997). In cultured cells, increased secretion of APP has been found to reduce the production of the beta-amyloid peptide (Caporaso et al., 1992; Fukushima et al., 1993; Fluhrer et al., 2002), the major component of amyloid plaques in Alzheimer’s disease (AD) (Alzheimer et al., 1995). AA was also found to increase APP secretion (Emmerling et al., 1996). Finally, the AA metabolites leukotrienes and 5-HPETE, generated by 5-

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lipoxygenase, and the metabolites prostaglandins and tromboxanes, generated by cyclooxygenase, are potent mediators of inflammation (Musser and Kreft, 1992; Yoshikai, 2001).

Phospholipid Metabolism and Neuropsychiatric Disorders Since PLA2 is the primary enzyme involved in the breakdown of membrane phosphomonoesters, abnormalities of PLA2 metabolism (possibly related to disease and/or to the processes involved in ageing) may affect membrane phospholipid turnover and arachidonic acid production in such a way as to cause cytoarchitectural changes and increased β-amyloid deposition within the brain. Research into biochemical processes affecting membrane composition and fluidity have generated models that fit relatively well in the pathophysiology of certain neurodegenerative diseases. Data from the 1990’ suggested decreased PLA2 activity in Alzheimer’s disease (Gattaz et al., 1995, Gattaz et al., 1996). Abnormalities of PLA2 metabolism have also been described in other neuropsychiatric diseases such as schizophrenia (Gattaz et al., 1987, Gattaz et al., 1990, Noponen et al., 1996, Ross et al., 1997), multiple sclerosis (Simonato, 1993), temporal-lobe epilepsy (Woelk & Peiler-Ichikawa, 1974, Visioli et al., 1994), and dyslexia (MacDonell et al., 2000). Accordingly to the “phospholipid hypothesis”, membrane changes play a primary role in the aetiology of neuropsychiatric disorders. Abnormal regulation of highly unsaturated fatty acid metabolism, mainly at the sn-2 position of phospholipid molecules, results in modifications of the neuronal membrane structure, affecting intracellular signalling from neurotransmitter- and ion channel-related functions (Horrobin, 1998).

PLA2 and Alzheimer’s Disease Rationale Because a wide range of physiological processes in which phospholipid metabolism plays a central role are regulated by phospholipase A2 (PLA2) enzymes, it is reasonable to hypothesise that abnormalities in PLA2-related functions may result in multiple pathological effects, ranging from intracellular signalling to neurotransmission. Choline, the precursor of acetylcholine, is released in cholinergic neurones by the PLA2 cleavage of membrane phosphatidylcholine (Blusztajn et al., 1987). PLA2 is involved in arachidonic acid (AA) release from membrane phospholipids, and thereby in the synthesis of major mediators of the inflammatory response, which secondarily participates in the maturation of neuritic plaques. It has also been reported that PLA2 appears to be involved in regulating the processing of amyloid precursor protein (APP) in cell culture (Emmerling et al., 1993). Thus, in cultured CHO-m1 cells, treatment with AA stimulated the secretory pathway of APP metabolism (Emmerling et al., 1996). It has also been demonstrated in cell culture models that PLA2 activation by mellitin led to an increase in the secretion of the APPs, whilst inhibition of PLA2 was reported to stop carbachol-stimulated production of APPs from CHO-m1 cells

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(Emmerling et al., 1993). In neurodegeneration models, it has been shown that arachidonic acid participates in the polymerization of hyperphosphorylated tau into neurofibrillary tangles, a critical step in the pathophysiology of dementia (Lukiw and Bazan, 2000).

Post-Mortem Studies Post-mortem studies have shown that PLA2 activity is decreased in AD brain (Gattaz et al., 1995ª, Gattaz et al., 1996). A reduction in cPLA2 activity in frontal and parietal cortices of AD patients was associated with an earlier onset of dementia, earlier age at death, and higher counts of senile plaques and neurofibrillary tangles. In the investigation of abnormalities in phospholipid metabolism, Skinner et al. (1989) demonstrated a marked reduction in the proportion of docosahexanoate in the parietal cortex of AD patients, and reduced total free fatty acid content in prefrontal areas. Since docosahexanoate is one of the main free fatty acids released following by PLA2 deacylation of membrane phospholipids, such finding is highly compatible with the reduction of PLA2 activity found in AD brains. Anisotropy studies have additionally demonstrated abnormal membrane fluidity in hippocampal synaptosomes of AD patients, which is also related with abnormal phospholipid turnover (Eckert et al., 2000). Finally, lower calcium-independent PLA2 (iPLA2) activity was identified in the prefrontal cortex of frontal-variant AD patients (Talbot et al., 2000). Taken together, such findings suggest that aberrations in the synthesis and degradation of membrane phospholipids are metabolic events that occur in AD.

Spectroscopy Studies The intracerebral availability of phospholipid precursors and metabolites, as well as the occurrence of high-energy phosphates, can be estimated by the analysis of the 31P spectral curve within a discrete brain area with the aid of magnetic resonance spectroscopy (MRS). Phosphomonoesters (PME) and phosphodiesters (PDE) are respectively the precursors and breakdown products of membrane phospholipids, and the ratio between both provides information on membrane phospholipid turnover. 31P-MRS studies of AD patients reported altered PME and PDE resonance in temporoparietal areas, which reflects changes in the biophysical state of membrane phospholipids (Pettegrew et al., 1988; Brown et al., 1989; Smith et al., 1993; Pettegrew et al., 1995). Pettegrew et al. (1988; 1995) found elevated PME levels in cortical areas of patients with mild AD, and increased PDE levels in severe AD, hypothesising that PME changes occur early in the disease, whereas PDE changes occur later. The authors further proposed that changes in membrane phospholipid and high-energy phosphate metabolism might precede the onset of dementia. Brown et al. (1989) showed that PME, PME/PDE ratio, and inorganic phosphate levels were elevated in temporoparietal areas of AD patients as compared to controls, although in another series addressing brain energy metabolism no significant difference between AD and controls was observed for either PME or PDE (Brown et al., 1993). Gonzalez et al. (1996) reported a 50% increase in PME/PDE

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ratio, but no changes in phosphocreatine, beta-nucleoside triphosphate (beta-NTP), and inorganic phosphate levels in AD brains. Correlations with morphologic data further suggested that elevations in PME levels precede the appearance of senile plaques in early stages of AD, whereas elevations in PDE levels, reflecting degeneration of neural membranes, correlate with the appearance of plaques in late stages of the disease (Pettegrew et al., 1988). In autopsy specimens of parietal gray matter from subjects with severe AD, spectroscopy abnormalities correlated with the density of neurofibrillary tangles (Smith et al., 1993). In a recent study conducted in our group (Forlenza et al., 2005), we investigated the intracerebral phospholipid metabolism in Alzheimer’s disease patients with the aid of 31PMRS, in a case control study comprising 18 patients with mild or moderate probable Alzheimer’s disease, and 16 healthy non-demented age-matched volunteers. Patients were recruited and assessed at the Alzheimer’s disease outpatient unit at the Institute of Psychiatry, University of Sao Paulo, and MRS scans were performed at the Division of Neruroimaging, Heart Institute, University of São Paulo. We used a 1.5T magnetic resonance imager addressing a 40mm3 voxell in the left pre-frontal cortex. Major outcome measures were mean relative peak areas of phosphate-rich cerebral metabolites within the 31P spectra of patients and controls, namely phosphomonoesters (PME), phosphodiesters (PDE), adenosinetriphosphate (alpha, beta, and gamma-ATP), phosphocreatine, and inorganic phosphate. Spectroscopy data were further correlated with parameters indicative of cognitive performance, as ascertained by the cognitive subscale of the Cambridge Examination for Mental Disorders of the Elderly (CAMCOG). The PME resonance and the PME/PDE ratio were increased in Alzheimer’s disease patients as compared to controls (p<0.05) (Figure 1). PME resonance was negatively correlated with global cognitive performance as shown by the total Mini-mental State Examination (rs=-0.36; p=0.05) and CAMCOG scores (rs=0.49; p=0.007), as well as with discrete neuropsychological functions, namely memory (rs=0.53; p=0.004), visual perception (rs=-0.54; p=0.003), orientation (rs=-0.36; p=0.05), and abstract thinking (rs=-0.48; p=0.01) (Figure 2). Other spectroscopy parameters were not significantly different between the two groups. We provided evidence of reduced membrane phospholipid breakdown in the pre-frontal cortex of mild and moderately demented Alzheimer’s disease patients. These abnormalities were correlated with neuropsychological deficits that are characteristic of Alzheimer’s disease, and reinforce the hypothesis that disordered cerebral phospholipid metabolism may play an etiological role in Alzheimer’s dementia, and further support the contention that alterations in brain membrane abnormalities can be non-invasively detected by 31P-MRS at early stages of clinical manifestations of the disease. Further research is needed in order to define whether this finding should be regarded as an etiological factor, or rather as an epiphenomenon of the neurodegenerative process.

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(A) PME % 20 16 12 8 4 0

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Figure 1. In vivo intracerebral availability of phospholipid precursors (PME) and metabolites (PDE), as determined by 31P-Magnetic resonance spectroscopy. Figures 1A and 1B represent the distribution of Alzheimer’s disease and control subjects according to percent areas of PME or PDE resonance, respectively; Figure 1C represent PME/PDE ratio.

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Figure 2. Negative correlations between prefrontal cortex phosphomonoesters (PME) and neuropsychological parameters. (A): CAMCOG: Cognitive subscale of the Cambridge Examination for Mental Disorders of the Elderly (total scores); (B): MMSE: Mini-mental State Examination (total scores); (C): Memory and (D): Visual Perception tasks of the CAMCOG schedule.

Platelet PLA2 Activity in AD: A Peripheral Correlate of Cerebral Phospholipid Abnormalities? Platelets and neurones possess certain membrane and receptor properties in common; platelets may therefore provide a useful model system in investigations of brain metabolic abnormalities in AD (Zubenko et al., 1999). The activity of cPLA2 in the brain may be indirectly assessed by measuring the activity of the enzyme in platelets. In the search for peripheral correlates of cerebral enzymatic abnormalities, several studies have focused on PLA2 activity in platelet membranes, where a reduction in PLA2 activity can also be detected in AD (Gattaz et al., 1996). In a recent study, we replicated previous findings of reduced platelet PLA2 activity in AD, and further demonstrated that such abnormality is correlated with the neuropsychological symptoms of the disease (Gattaz et al., 2004). We investigated PLA2 activity in platelets from 21 AD patients as compared to 17 healthy elderly controls and 11 individuals with mild cognitive impairment (MCI). Subjects were cognitively assessed by the

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Mini-Mental State Examination (MMSE) and the CAMDEX schedule. Platelet PLA2 activity was determined by radio-enzymatic assay, which mainly detected a calcium-independent form of the enzyme present also in the brain (iPLA2). PLA2 activity was significantly lower in AD than in controls (p<0.001). Mean PLA2 activity in MCI individuals was between the values of AD patients and controls, with a subgroup showing PLA as low as the lowest AD patients, but the differences from MCI were not significant from AD and control groups (Figure 3). 50

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Figure 3. PLA2 activity is decreased in patients with AD and MCI. Platelet PLA2 activity in individuals with Alzheimer’s disease (AD) (n=21), mild cognitive impairment (MCI) (n=11), and cognitively normal age-matched controls (n=17) was determined by radio-enzymatic assays (pmol / mg protein / minute). Significance levels: AD vs. controls: p<0.001.

Lower PLA2 activity was significantly correlated with a worse cognitive performance both at the MMSE (p=0.001) and the cognitive sub-scale of the CAMDEX inventory (p=0.002). Both reduced PLA2 activity and the correlation with impaired cognition were also reported in brain tissue of AD patients, suggesting thus that the present determinations in platelets may be related to a reduction in the brain. Further longitudinal studies in course will investigate whether those MCI individuals with the lowest PLA2 values in platelets would be at a higher risk to develop AD during a longitudinal follow up.

PLA2, Neuroplasticity and Memory Formation PLA2 in Neurodevelopment and in Neurodegeneration Whilst the importance of PLA2 in eicosanoid metabolism and signal transduction has been well established, much remains to be learned of its function and regulation within the brain. It has been shown in tissue culture models that neurite outgrowth and differentiation of neuroblastoma cells involve the participation of arachidonic acid (Williams et al., 1994).

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PLA2 is implicated in neurodevelopmental processes and in the early development of the nervous system. In embryonic rat brain, PLA2 activity peaks by the 12th gestational day, and progressive declines towards birth, maintaining basal levels in the post-natal period (Yoshihara et al., 1992; Forlenza et al., 2002). In primary cultures of embryonic rat cortical neurons, cPLA2 activity peaks on the 4th day in culture, and decreases after six days of incubation, when the cultures become mature. PLA2 activation in early developmental stages of cultures suggests its involvement in processes related to cell survival and development, particularly membrane recovering and neurite outgrowth (Forlenza et al., 2002). A

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Figure 4. Inhibition of PLA2 precludes neurite outgrowth . Primary cultures of rat cortical neurons at the 7th DIC, continuously treated with MAFP or BEL starting from the 4th DIC. Trypan blue staining. Cultures were imaged at 200x-manignification (Nikon TE300) corresponding to different experimental conditions: A – MAFP control (no treatment); B – treatment with MAFP 10µM; C – treatment with MAFP 100µM; D – treatment with MAFP 250µM; E – BEL control (no treatment); F – treatment with BEL 1µM; G – treatment with BEL 10µM; H – treatment with BEL 50µM.

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Cortical neurons - MTT assay

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In a recent study conducted in our lab, we addressed the effects of the pharmacological modulation of PLA2 in primary cultures of rat cortical neurons. Inhibition curves were obtained in 4 day-in-culture neurons treated for 30 minutes with either the dual PLA2 inhibitor methyl arachidonyl fluorophosphonate (MAFP), or the iPLA2 inhibitor bromoenol lactone (BEL). Full in vitro inhibition was achieved with 100 and 250µM of MAFP, or 10 and 20µM of BEL. Conversely, a dose-dependent activation of PLA2 was obtained with 1020µg/ml of mellitin. PLA2 inhibition with MAFP or BEL was not acutely toxic for cultured

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neurons. However, early and sustained inhibition of the enzyme precluded the development of neurites, and resulted in long-term loss of neuronal viability (Figure 4) (Mendes et al., 2005). When treatments with MAFP and BEL were applied to mature cultures of cortical and hippocampal neurons, i.e., after five days in culture, the inhibition of PLA2 was neurotoxic, as shown by a significant reduction in the number of viable neurons and neurite bearing cells (Figure 5) (Forlenza et al., in preparation).

Intracerebral PLA2 Inhibition in Rats and Affects Memory Formation and Membrane Fluidity In early AD there is an impairment of declarative episodic short-term (STM) and longterm memory (LTM) in correlation with reduced activity in hippocampus and cerebral cortex (Perani et al., 1993; Desgranges et al., 1998; Elgh et al., 2002). The biochemical cascade of memory has been extensively studied in the CA1 region of the dorsal hippocampus of rats in connection with one-trial step-down inhibitory avoidance task, which involves learning not to step-down from a platform in order to avoid a mild foot-shock. This task has a declarative component (increased avoidance latency), which crucially involves the hippocampus. In this paradigm the formation of STM (< 3 h) and LTM (at least 24 h) involves immediate posttraining activation of NMDA (and NMDA-mediated Ca2+ influx), AMPA, and metabotropic glutamate receptors, and modulation by muscarinic cholinergic receptors (Izquierdo and Medina, 1997; Izquierdo et al., 1997, 1999). It has been proposed that STM and LTM processes are mediated by mechanisms of synaptic plasticity referred to as short-term (STP) and long-term potentiation (LTP), respectively (Bliss and Collingridge, 1993; Izquierdo and Medina, 1997). Both cPLA2 and iPLA2 have been implicated in LTP induction in rat hippocampus. Hence, PLA2 inhibition in rat hippocampal slices prevented LTP induction in the CA1 region mediated by an NMDA-sensitive mechanism, and decreased [3H]AMPA binding observed after LTP induction (Bernard et al., 1994). In vivo LTP induction in rat hippocampus activated PLA2, which consequently reduced phosphatidylcholine and increased free AA levels (Clements et al., 1991). In addition, PLA2 inhibition in rat hippocampal slices blocked the NMDA-mediated release of lysophosphatidylcholine and, consequently, of choline (precursor of acetylcholine) (Weichel et al., 1999). Taken together, these data suggest an involvement of cPLA2 in LTP, due to their effects on glutamatergic and cholinergic systems. AA, which is formed by PLA2 activity, has also been implicated in LTP formation. Hence, Ca2+-sensitive LTP induction in rat hippocampal slices was facilitated by AA treatment (Nishizaki et al., 1999). In addition, selective iPLA2 inhibition in rat hippocampal slices prevented LTP induction in the CA1 region, which was restored by AA treatment (Wolf et al., 1995; Fujita et al., 2001). Besides the findings implicating PLA2 in LTP, some studies have suggested an involvement of the enzyme in memory function. For instance, injections of PLA2 inhibitors into the chick intermediate medial hyperstriatum ventrale impaired the learning of a passive avoidance task (Hölscher and Rose, 1994). Additionally, intraperitoneal injections of a PLA2 inhibitor in rats impaired spatial learning tested in the Morris water

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maze (Hölscher et al., 1995). Finally, intraperitoneal injections of a selective iPLA2 inhibitor in mice also impaired spatial learning (Fujita et al., 2000). A recent study examining brain phospholipid metabolism in the cPLA2 knockout mouse has suggested that altered AA metabolism influences membrane fluidity (Rosenberger et al., 2003). Membrane fluidity has also been implicated in LTP. Hence, treatment of aged rats with polyunsaturated fatty acids, which are known to increase membrane fluidity (Stubbs and Smith, 1984), reversed the age-related impairments in LTP (McGahon et al., 1999). Moreover, some studies showed that reduced fluidity of rat hippocampal membranes impaired memory (Hong, 1995; Clarke et al., 1999), whereas increased fluidity improved memory (Müller et al., 1997; Scheuer et al., 1999). Previous studies from our group showed reduced PLA2 activity in post-mortem brains of patients with AD, and this reduction correlated with the severity of dementia (Gattaz et al., 1995). In addition, reduced cPLA2 and iPLA2 activities were found in post-mortem hippocampus of AD patients (Ross et al., 1998). These data are in line with the in vivo NMR spectroscopy findings of decreased phospholipid metabolism in AD brains (Brown et al., 1989; Pettegrew et al., 1995), as well as with the finding on reduced membrane fluidity in post-mortem hippocampus of AD patients (Eckert et al., 2000). In face of these data, we performed a series of animal experiments to investigate the effects of injections of PLA2 inhibitors directly into rat hippocampus on the acquisition of STM and LTM, using as behavioural paradigm the step-down inhibitory avoidance task. Additionally, we investigated the effects of in vivo PLA2 inhibition on the fluidity of hippocampal membranes from rats subjected to inhibitory avoidance training. Male Wistar rats (2.5-3 months old) were intraperitoneally anaesthetized, placed in a stereotaxic frame, and bilaterally implanted with cannulae in the CA1 region of the dorsal hippocampus at stereotaxic coordinates anterior – 4.3 mm from bregma, lateral ± 4.0 mm from midline, and ventral 3.4 mm from dura (Paxinos and Watson, 1998). After recovering, the rats received intrahippocampal acute injections of a vehicle (DMSO/saline) or of one of three different PLA2 inhibitors dissolved in the vehicle: (a) methyl arachidonyl fluorophosphonate (MAFP), an irreversible dual cPLA2 and iPLA2 inhibitor (Balsinde and Dennis, 1996; Lio et al., 1996), (b) palmitoyl trifluoromethylketone (PACOCF3), a reversible dual cPLA2 and iPLA2 inhibitor (Ackermann et al., 1995; Balsinde and Dennis, 1997), or (c) bromoenol lactone (BEL), an irreversible selective iPLA2 inhibitor (Ackermann et al., 1995). Based on the findings showing that intracerebral injections of PLA2 inhibitors before but not after training produced amnesia for a passive avoidance task in chicks (Hölscher and Rose, 1994), and that treatment of rat hippocampal slices with a PLA2 inhibitor before tetanic stimulation prevented the induction of LTP but treatment after tetanic stimulation did not affect the maintenance phase of LTP (Fujita et al., 2001), in our study we decided to investigate the effects of the PLA2 inhibitors when injected before training in inhibitory avoidance task. Pre-training injections would be presumed to primarily affect the acquisition phase of memory formation (Izquierdo, 1989). At 30 min after injections into the CA1 region of (a) vehicle (n = 13) or 1 µM MAFP (n = 14) or 10 µM MAFP (n = 17), of (b) vehicle (n = 14) or 10 µM PACOCF3 (n = 11) or 100 µM PACOCF3 (n = 13), or of (c) vehicle (n = 14) or 1 µM BEL (n = 11) or 10 µM BEL (n = 12), the rats were submitted to one-session of step-down inhibitory avoidance training.

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Briefly, the animals were placed on a platform in an inhibitory avoidance box whose floor was an electrified grid. In training sessions, immediately after stepping-down, placing the four paws on the grid, the animals received a 0.4 mA, 4.0 s scrambled foot-shock. Latencies to step-down were measured. Rats were tested for retention after 1.5 h and after 24 h, for STM and LTM, respectively. In test sessions, the animals were placed again on the platform and step-down latencies were measured up to a ceiling of 180 s, and no foot-shock was given. (a) Training session latencies were similar in animals injected with vehicle or with 1 µM or 10 µM MAFP (p > 0.1). After training, in animals injected with vehicle, latencies for STM and LTM significantly increased by 9 and 11-fold, respectively (p = 0.001). Injections of 10 µM MAFP (but not of 1 µM; p > 0.5) significantly prevented the increments of latencies for STM and LTM (p < 0.02, as compared to vehicle) (Figure 6A). (b) Training session latencies were similar in animals injected with vehicle or with 10 µM or 100 µM PACOCF3 (p > 0.1). After training, in animals injected with vehicle, latencies for STM and LTM significantly increased by 7 and 8-fold, respectively (p = 0.001). Injections of 100 µM PACOCF3 (but not of 10 µM; p > 0.5) significantly prevented the increments of latencies for STM and LTM (p < 0.02, as compared to vehicle) (Figure 6B). (c) Training session latencies were similar in animals injected with vehicle or with 1 µM or 10 µM BEL (p > 0.2). After training, in animals injected with vehicle, latencies for STM and LTM significantly increased by 11-fold (p = 0.001). Injections of 10 µM BEL (but not of 1 µM; p > 0.5) significantly prevented the increments of latencies for STM and LTM (p < 0.001 and p < 0.01, respectively, as compared to vehicle) (Figure 6C) (Schaeffer and Gattaz, 2005). As pre-training injections of MAFP, PACOCF3, and BEL impaired memory acquisition, we investigated whether the amnesic effects of the PLA2 inhibitors in inhibitory avoidance task were due to their action on general activity (locomotor and exploratory activities) during training performance. At 30 min after injections into the CA1 region of (a) vehicle or 10 µM MAFP, of (b) vehicle or 100 µM PACOCF3, or of (c) vehicle or 10 µM BEL (n = 10 per group), the rats were submitted to 3 min of free exploration of inhibitory avoidance apparatus. Crossings of three imaginary lines on the floor of inhibitory avoidance apparatus were counted. We found that the number of crossings was similar in animals injected with vehicle or with 10 µM MAFP, 100 µM PACOCF3, or 10 µM BEL (p > 0.1) (data not shown), indicating that the impairing effects of the pre-training injections of the PLA2 inhibitors were not caused by gross behavioral alterations on training performance (Schaeffer and Gattaz, 2005). After behavioral procedures, histological analyses were carried out to verify the injection placements and to investigate whether the observed effects of PLA2 inhibition on test session latencies in inhibitory avoidance task were a consequence of neuronal death. Rats injected with vehicle (n = 8) or with 10 µM MAFP (n = 6), 100 µM PACOCF3 (n = 6), or 10 µM BEL (n = 6) were deeply anaesthetized, transcardially perfused with saline and fixed with a 10% formaldehyde solution. The brains were withdrawn and fixed in the same fixative, embedded in paraffin, cut into consecutive 5 µm sections with a microtome, and placed on glass slides. The sections were stained with haematoxylin-eosin for histological localization of the injection sites as well as for histological analysis of neuronal death in the injection sites. Using a light microscope at 400X magnification, neuronal death was determined as the decrease in the percentage of purple-stained cell nuclei by haematoxylin-eosin in a delimited

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area of 2.0 mm2 corresponding to the injection sites in the CA1 region. In the remaining rats submitted to behavioural procedures a 10% trypan blue solution was injected into the brain sites implanted with cannulae. After 30 min the animals were killed by decapitation and the brains were withdrawn, fixed in a 10% formaldehyde solution, and cut manually for histological localization of the injection sites. Injections spread with a radius of 1.0-1.5 mm3 in each cannula-implanted site. On the whole, injections were found to be correct in 94% of the animals. We found that injections of the PLA2 inhibitors did not cause neuronal death as compared to vehicle (10 µM MAFP, p = 0.1; 100 µM PACOCF3 and 10 µM BEL, p > 0.5) (data not shown) (Schaeffer and Gattaz, 2005). Additionally, we investigated the degree of inhibition of PLA2 activity in the CA1 region of another group of rats injected with PLA2 inhibitors. Hence, at 30 min after injections into the CA1 region of (a) vehicle (n = 8) or 1 µM MAFP (n = 6) or 10 µM MAFP (n = 9), of (b) vehicle (n = 9) or 10 µM PACOCF3 (n = 9) or 100 µM PACOCF3 (n = 8), or of (c) vehicle or 1 µM or 10 µM BEL (n = 8 per group), the rats were submitted to inhibitory avoidance task as described above, but they were killed by decapitation immediately after receiving the footshock in order to dissect the CA1 region for PLA2 activity determination around the time of training. The brains were rapidly withdrawn and about 2.0 mm3 of the CA1 region corresponding to the injection sites were bilaterally dissected, homogenized in 5 mM TrisHCl (pH 7.4, 4°C), and stored at –70°C until use. PLA2 activity was determined by a radioenzymatic assay. Briefly, as enzyme substrate we used L-α-1-palmitoyl-2-arachidonylphosphatidylcholine labelled with [1-14C] in the arachidonyl tail at the sn-2 position (arachidonyl-1-14C-PC). We determined optimal assay conditions ([Ca2+] and pH value) for measuring cPLA2 plus iPLA2 activities in CA1 tissue homogenates of rats injected with MAFP or PACOCF3, and for measuring only iPLA2 activity in CA1 tissue homogenates of rats injected with BEL (data not shown). Hence, the assay samples (500 µl) contained 100 mM Tris-HCl (pH 8.5 for cPLA2 plus iPLA2; pH 7.5 for iPLA2), 1 µM CaCl2 (for cPLA2 plus iPLA2) or 100 µM EDTA (for iPLA2), 300 µg of protein from homogenates, and 0.06 µCi arachidonyl-1-14C-PC. After an incubation time of 30 min at 37°C the reaction was stopped and the liberated [1-14C]AA was extracted. The radioactivity of [1-14C]AA was measured in a liquid scintillation counter and used for calculating the PLA2 activity, which is expressed in pmol⋅mg protein⋅min– 1. The activity of cPLA2 plus iPLA2 in post-mortem CA1 region was significantly reduced by 28% by injections of 10 µM MAFP (p < 0.01) and by 26% by injections of 100 µM PACOCF3 (p = 0.002), but was not significantly reduced by injections of 1 µM MAFP (p > 0.2) or 10 µM PACOCF3 (p > 0.05), as compared to vehicle. The activity of iPLA2 in post-mortem CA1 region was significantly reduced by 17% by injections of 10 µM BEL (p = 0.002), but was not significantly reduced by injections of 1 µM BEL (p > 0.2), as compared to vehicle (Figure 7) (Schaeffer and Gattaz, 2005). As inhibition of hippocampal PLA2 activity impaired memory acquisition of inhibitory avoidance task, we carried out biochemical assays to evaluate directly whether the inhibitory avoidance is accompanied by changes in hippocampal PLA2 activity around the time of training. Nonimplanted male Wistar rats (2.5-3 months old) were divided into three groups: (a) naïve controls (n = 8), killed by decapitation immediately after withdrawal from their home cages; (b) shocked animals (n = 8), placed directly over the electrified grid, given a 0.4

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Figure 6. Acute PLA2 inhibition in rat CA1 region impairs acquisition of short- and long-term memory. Step-down latencies (seconds) are given as median (interquartile interval). Injections of 1 µM MAFP (A) (n = 14), 10 µM PACOCF3 (B) (n = 11), or 1 µM BEL (C) (n = 11) did not significantly prevent the increments of latencies for STM and LTM as compared to vehicle (n = 15, 15, 16, respectively). Injections of 10 µM MAFP (A) (n = 17), 100 µM PACOCF3 (B) (n = 13), or 10 µM BEL (C) (n = 12) significantly prevented the increments of latencies for STM and LTM as compared to vehicle (*p < 0.05 and **p < 0.01).

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mA, 4.0 s scrambled foot-shock, and immediately killed by decapitation; and (c) animals trained in the step-down inhibitory avoidance task (n = 10) as described above, and killed by decapitation immediately after receiving the foot-shock. Brain tissue preparation and PLA2 assay were carried out as described above. In this experiment, PLA2 assay was prepared using Tris-HCl pH 8.5 and 1 µM CaCl2. We found that inhibitory avoidance training increased significantly PLA2 activity during acquisition (14%; p = 0.002, as compared to naïve values). Additionally, inhibitory avoidance training increased significantly PLA2 activity as compared to shocked values (13%; p = 0.003), indicating that increments in PLA2 activity were specifically caused by the inhibitory avoidance training. Shocked animals had similar values of PLA2 activity as naïve controls (p > 0.5) (Figure 8) (Schaeffer and Gattaz, 2005). 8

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Figure 7. Dose-dependent inhibition of PLA2 activity in rat CA1 region. PLA2 activity (pmol⋅mg protein⋅min– 1) is given as mean (± standard deviation). Injections of 1 µM MAFP (n = 6), 10 µM PACOCF3 (n = 9), or 1 µM BEL (n = 8) did not significantly reduce PLA2 activity as compared to vehicle (n = 8, 9, 8, respectively). Injections of 10 µM MAFP (n = 9), 100 µM PACOCF3 (n = 8), or 10 µM BEL (n = 8) significantly reduced PLA2 activity as compared to vehicle (**p < 0.01).

Because memory function is largely dependent on the fluidity of brain membranes (Hong, 1995; Müller et al., 1997; Clarke et al., 1999; Scheuer et al., 1999), we investigated the effects of in vivo PLA2 inhibition on the fluidity of hippocampal membranes from rats subjected to inhibitory avoidance training. At 30 min after injections into the CA1 region of vehicle or 100 µM PACOCF3 (n = 24 per group), the rats were placed on the platform in the inhibitory avoidance box; when stepping-down the animals received a 0.4 mA, 4.0 s scrambled foot-shock. Rats were killed after 2.5 min, which was the time found to produce significant AA release mediated by PLA2 activity after in vivo LTP induction (Clements et al., 1991). The CA1 region at the injection sites was bilaterally dissected, homogenized (pools of 3 rats) in 5 mM Tris-HCl (pH 7.4, 4°C), and aliquots for PLA2 activity determination were separated and frozen at –70°C. The rest of homogenates was additionally diluted in 5 mM Tris-HCl (pH 7.4, 4°C) and centrifuged at 48,000 g for 20 min at 4°C (2x). The final membrane pellet was resuspended in 5 mM Tris-HCl (pH 7.4, 4°C) and aliquots for membrane fluidity determination were frozen at –20°C. Membrane fluidity was determined

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by anisotropy measurements. Briefly, we used the non-polar fluorescence probe 1,6diphenyl-1,3,5-hexatriene (DPH), which provides a measurement of anisotropy from the hydrophobic core of membranes. DPH anisotropy is inversely correlated with the fluidity of this membrane region. The assay samples (2 ml) containing 5 mM Tris-HCl (pH 7.4), 30 µg of protein from membrane suspensions, and 33 µM DPH were incubated for 45 min at 37°C. The steady-state anisotropy was measured in a Photon Technology International – PTI spectrofluorometer, using excitation and emission wavelengths of 360 nm and 450 nm, respectively. As expected, PACOCF3 significantly inhibited PLA2 activity in CA1 homogenates as compared to vehicle (p < 0.01; Figure 9A). Moreover, CA1 membranes from rats injected with PACOCF3 showed significantly reduced fluidity at the hydrophobic core, as indicated by increased DPH anisotropy, as compared to vehicle (p < 0.01; Figure 9B). Membrane fluidity was highly correlated with PLA2 activity in animals injected with PACOCF3 (r = 0.76, p < 0.03; Figure 10A) or with vehicle (r = 0.84, p < 0.01; Figure 10B) (Schaeffer et al., 2005). 6.0 5.5

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Figure 8. Effect of inhibitory avoidance training on PLA2 activity in rat CA1 region. PLA2 activity (pmol⋅mg protein⋅min– 1) is given as mean (± standard deviation). Animals trained in inhibitory avoidance task (n = 10) showed significant increase in PLA2 activity around the time of training as compared to naïve and shocked animals (n = 8 per group). Shocked animals had similar values of PLA2 activity as naïve controls (**p < 0.01).

The findings described above show that the inhibition of PLA2 activity in the CA1 region of the dorsal hippocampus of rats impaired the acquisition of STM and LTM of step-down inhibitory avoidance task. It should be noticed that impairment of memory was only observed when the concentrations of the inhibitors were enough to cause a significant inhibition of PLA2 activity. Memory impairment was not due to effects of the inhibition of PLA2 activity on locomotion and exploratory behaviour during training performance. Moreover, memory impairment did not result from neuronal death in the CA1 region after inhibition of PLA2 activity, suggesting thus a functional effect of PLA2 on memory neurochemistry. Our data confirm the previous findings showing that inhibitors of PLA2 impaired learning in chicks, rats, and mice (Hölscher and Rose, 1994; Hölscher et al., 1995; Fujita et al., 2000), and extend them by demonstrating that injections of PLA2 inhibitors directly into the hippocampus impaired memory acquisition of rats. The diversity of PLA2 family and its

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varied regulatory and functional properties emphasize the importance of considering different groups of PLA2 when investigating their physiological and pathological roles. The present findings show that the selective inhibition of iPLA2 activity by BEL in hippocampal CA1 region of rats impaired the acquisition of STM and LTM of inhibitory avoidance task. This result confirms and extends the previous finding showing that intraperitoneal injections of BEL in mice impaired spatial learning tested in the Morris water maze (Fujita et al., 2000). In our study we optimized some assay conditions for PLA2 activity determination. During these assays we found a dominant activity of iPLA2 in the dorsal hippocampus of rats towards 1palmitoyl-2-[1-14C]arachidonyl-phosphatidylcholine. The remaining PLA2 activity, likely of cPLA2 because of the assay conditions used (micromolar Ca2+ concentration), was about 11fold lower than the iPLA2 activity (data not shown). This finding is in line with previous data showing low levels of mRNA of cPLA2 (Molloy et al., 1998; Kishimoto et al., 1999) and a dominant iPLA2 activity over cPLA2 activity in rat hippocampus (Yang et al., 1999). Despite the low levels of mRNA and low activity of cPLA2, there are some evidences for an involvement of cPLA2 in LTP induction in rat hippocampus (Bernard et al., 1994; Weichel et al., 1999). The development of selective cPLA2 inhibitors is required for a better understanding of the involvement of cPLA2 in memory processes.

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Figure 9. PLA2 activity and anisotropy measurements in post-mortem CA1 region of rats. PLA2 activity (pmol⋅mg protein⋅min–1) and DPH anisotropy are given as mean (± standard deviation). All determinations were done in triplicate. Injections of 100 µM PACOCF3 (n = 8) significantly decreased PLA2 activity (A) and reduced membrane fluidity at the hydrophobic core, as indicated by increased DPH anisotropy (B), as compared to vehicle (n = 8) (**p < 0.01).

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Figure 10. Correlation between PLA2 activity and anisotropy in post-mortem CA1 region of rats. PLA2 activity (pmol⋅mg protein⋅min–1) and DPH anisotropy are given as the mean value from triplicate determinations. PLA2 activity correlated negatively with anisotropy (= positively with fluidity) at the hydrophobic core in rats injected with PACOCF3 (A; r = -.76, p < 0.03) or with vehicle (B; r = -.84, p < 0.01).

With the current experimental design (i.e. pre-training injections) our findings suggest that PLA2 inhibition blocked memory acquisition. Because STM and LTM are acquired at the same moment, one could argue that blocking acquisition there is no point to analyze the effects of drugs on both STM and LTM. However, it has been clearly shown that STM and LTM for the inhibitory avoidance task are established through partially independent molecular pathways in the hippocampus and related brain areas (Izquierdo et al., 1998). A recent study evaluating possible differential effects of drug injections before acquisition and during the early consolidation period of STM and LTM of inhibitory avoidance supports the view that consolidations of STM and LTM for inhibitory avoidance are parallel, independent processes (Quevedo et al., 2004). Further studies are required to clarify whether acquisition of STM and LTM would involve different mechanisms.

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It is noteworthy that in our study PLA2 activity increased in the CA1 region of rat hippocampus immediately after inhibitory avoidance training. Such increase may be caused by NMDA-stimulated Ca2+ influx (Yoshihara and Watanabe, 1990; Bernard et al., 1994; Underwood et al., 1998) and by phosphorylation mediated by mitogen-activated protein kinase and protein kinase C (Lin et al., 1993; Nemenoff et al., 1993) if considering an involvement of cPLA2. In the case of iPLA2, increased activity may also be mediated by protein kinase C-directed phosphorylation (Underwood et al., 1998; Akiba et al., 1999). Activation of PLA2 may result in increased glutamate binding to AMPA (Bernard et al., 1994) and metabotropic receptors (Collins et al., 1995). All these biochemical mechanisms (NMDA, AMPA, and metabotropic receptors, MAPK, PKC) in the hippocampus participate in the early stages of memory formation of inhibitory avoidance task in rats (Bianchin et al., 1994; Bernabeu et al., 1995; Cammarota et al., 1995, 2000; Alonso et al., 2002). The findings from anisotropy measurements suggest that apart from PLA2 cleaving membrane phospholipids generating arachidonic acid (Farooqui et al., 1997) – an important mediator in synaptic plasticity underlying memory processing (Nishizaki et al., 1999; Fujita et al., 2001) – it also influences membrane fluidity at the hydrophobic core. The increment of hydrophobic core fluidity of rat hippocampal membranes was found to improve memory function (Müller et al., 1997; Scheuer et al., 1999). In our experiments we used crude preparations of hippocampal membranes that probably contains plasma membranes as well as intracellular membranes. The inhibition of cPLA2 and iPLA2 by PACOCF3 (Ackermann et al., 1995; Balsinde and Dennis, 1997) in our study may reduce fluidity of both plasma and intracellular membranes, since cPLA2 translocates to nuclear and endoplasmic reticulum membranes where it releases AA (Schievella et al., 1995; Gijón et al., 1999; Hirabayashi et al., 1999; Perisic et al., 1999), and iPLA2 was found to release AA from the plasma membrane (Mizuno-Kamiya et al., 2001). At the plasma membrane, the effect of increased membrane fluidity on memory improvement (Müller et al., 1997; Scheuer et al., 1999) may be mediated by increased densities of NMDA and muscarinic receptors (Muccioli et al., 1996; Scheuer et al., 1999), which are both involved in memory formation (Izquierdo et al., 1997). Additionally, an increment in nuclear membrane fluidity was found to increase mRNA nucleocytoplasmic transport, whereas a reduction in nuclear membrane fluidity was found to decrease the mRNA efflux (Tomassoni et al., 1999). The mRNA-mediated gene expression is crucially involved in memory formation (Igaz et al., 2002, 2004). Taken together with these data, the present results suggest that the mechanism by which reduced PLA2 activity impairs memory formation involves also changes in membrane fluidity.

Conclusion The results of our study showing that PLA2 inhibition impaired memory acquisition and reduced membrane fluidity are of interest in face of previous reports from our and other laboratories showing decreased PLA2 activity in post-mortem brain, including the hippocampus, of patients with AD (Gattaz et al., 1995; Ross et al., 1998; Talbot et al., 2000), as well as reduced membrane fluidity in post-mortem hippocampus of AD patients (Eckert et al., 2000). In face of these data, we speculate that reduced membrane fluidity mediated by

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decreased PLA2 activity may contribute to memory impairment in AD. Further studies should clarify whether the stimulation of PLA2 does improve memory performance in animals, which could open new avenues for the development of treatment strategies in AD.

References Ackermann, EJ; Conde-Frieboes, K; Dennis, EA. Inhibition of macrophage Ca(2+)independent phospholipase A2 by bromoenol lactone and trifluoromethyl ketones. J Biol Chem. 1995;270(1):445-450. Akiba, S; Mizunaga, S; Kume, K; Hayama, M; Sato, T. Involvement of group VI Ca2+independent phospholipase A2 in protein kinase C-dependent arachidonic acid liberation in zymosan-stimulated macrophage-like P388D1 cells. J Biol Chem. 1999; 274(28):19906-19912. Alonso, M; Viola, H; Izquierdo, I; Medina, JH. Aversive experiences are associated with a rapid and transient activation of ERKs in the rat hippocampus. Neurobiol Learn Mem. 2002;77(1):119-124. Alzheimer, A; Stelzmann, RA; Schnitzlein, HN; Murtagh, FR. An English translation of Alzheimer's 1907 paper, "Uber eine eigenartige Erkankung der Hirnrinde". Clin Anat. 1995;8(6):429-431. Balsinde, J; Balboa, MA; Insel, PA; Dennis, EA. Regulation and inhibition of phospholipase A2. Annu Rev Pharmacol Toxicol. 1999;39:175-189. Balsinde, J; Dennis, EA. Distinct roles in signal transduction for each of the phospholipase A2 enzymes present in P388D1 macrophages. J Biol Chem. 1996;271(12):6758-6765. Balsinde, J; Dennis, EA. Function and inhibition of intracellular calcium-independent phospholipase A2. J Biol Chem. 1997;272(26):16069-16072. Bernabeu, R; Izquierdo, I; Cammarota, M; Jerusalinsky, D; Medina, JH. Learning-specific, time-dependent increase in [3H]phorbol dibutyrate binding to protein kinase C in selected regions of the rat brain. Brain Res. 1995;685(1-2):163-168. Bernard, J; Lahsaini, A; Massicotte, G. Potassium-induced long-term potentiation in area CA1 of the hippocampus involves phospholipase activation. Hippocampus. 1994;4(4):447-453. Bianchin, M; Da Silva, RC; Schmitz, PK; Medina, JH; Izquierdo, I. Memory of inhibitory avoidance in the rat is regulated by glutamate metabotropic receptors in the hippocampus. Behav Pharmacol. 1994;5(3):356-359. Bliss, TV; Collingridge, GL. A synaptic model of memory: long-term potentiation in the hippocampus. Nature. 1993;361(6407):31-39. Blusztajn, JK; Liscovitch, M; Mauron, C; Richardson, UI; Wurtman, RJ. Phosphatidylcholine as a precursor of choline for acetylcholine synthesis. J Neural Transm Suppl. 1987b;24:247-259. Brown, GG; Garcia, JH; Gdowski, JW; Levine, SR; Helpern, JA. Altered brain energy metabolism in demented patients with multiple subcortical ischemic lesions. Working hypotheses. Arch Neurol. 1993;50(4):384-388.

The Role of Phospholipase A2 in Alzheimer's Disease

79

Brown, GG; Levine, SR; Gorell, JM; Pettegrew, JW; Gdowski, JW; Bueri, JA; Helpern, JA; Welch, KM. In vivo 31P NMR profiles of Alzheimer's disease and multiple subcortical infarct dementia. Neurology. 1989;39(11):1423-1427. Cammarota, M; de Stein, ML; Paratcha, G; Bevilaqua, LR; Izquierdo, I; Medina, JH. Rapid and transient learning-associated increase in NMDA NR1 subunit in the rat hippocampus. Neurochem Res. 2000;25(5):567-572. Cammarota, M; Izquierdo, I; Wolfman, C; Levi de Stein, M; Bernabeu, R; Jerusalinsky, D; Medina, JH. Inhibitory avoidance training induces rapid and selective changes in 3[H]AMPA receptor binding in the rat hippocampal formation. Neurobiol Learn Mem. 1995;64(3):257-264. Caporaso, GL; Gandy, SE; Buxbaum, JD; Ramabhadran, TV; Greengard, P. Protein phosphorylation regulates secretion of Alzheimer beta/A4 amyloid precursor protein. Proc Natl Acad Sci U S A. 1992;89(7):3055-3059. Chakraborti, S. Phospholipase A(2) isoforms: a perspective. Cell Signal. 2003;15(7):637-665. Chen, J; Engle, SJ; Seilhamer, JJ; Tischfield, JA. Cloning and recombinant expression of a novel human low molecular weight Ca(2+)-dependent phospholipase A2. J Biol Chem. 1994;269(4):2365-2368. Clarke, MS; Prendergast, MA; Terry, AV Jr. Plasma membrane ordering agent pluronic F-68 (PF-68) reduces neurotransmitter uptake and release and produces learning and memory deficits in rats. Learn Mem. 1999;6(6):634-649. Clements, MP; Bliss, TV; Lynchl, MA. Increase in arachidonic acid concentration in a postsynaptic membrane fraction following the induction of long-term potentiation in the dentate gyrus. Neuroscience. 1991;45(2):379-389. Collins, DR; Smith, RC; Davies, SN. Interactions between arachidonic acid and metabotropic glutamate receptors in the induction of synaptic potentiation in the rat hippocampal slice. Eur J Pharmacol. 1995;294(1):147-154. Dennis, EA. Diversity of group types, regulation, and function of phospholipase A2. J Biol Chem. 1994;269(18):13057-13060. Desgranges, B; Baron, JC; de la Sayette, V; Petit-Taboue, MC; Benali, K; Landeau, B; Lechevalier, B; Eustache, F. The neural substrates of memory systems impairment in Alzheimer's disease. A PET study of resting brain glucose utilization. Brain. 1998;121(Pt 4):611-631. Eckert, GP; Cairns, NJ; Maras, A; Gattaz, WF; Müller, WE. Cholesterol modulates the membrane-disordering effects of beta-amyloid peptides in the hippocampus: specific changes in Alzheimer's disease. Dement Geriatr Cogn Disord. 2000;11(4):181-186. Elgh, E; Sundstrom, T; Nasman, B; Ahlstrom, R; Nyberg, L. Memory functions and rCBF (99m)Tc-HMPAO SPET: developing diagnostics in Alzheimer's disease. Eur J Nucl Med Mol Imaging. 2002;29(9):1140-1148. Emmerling, MR; Dudley, DT; Dyer, RD; Carroll, RT; Doyle, PD; Davis, RE. The role of arachidonic acid in the secretion of the amyloid precursor protein (APP). Ann N Y Acad Sci. 1996;777:310-315. Emmerling, MR; Moore, CJ; Doyle, PD; Carroll, RT; Davis, RE. Phospholipase A2 activation influences the processing and secretion of the amyloid precursor protein. Biochem Biophys Res Commun. 1993;197(1):292-297.

80

Wagner F. Gattaz, Evelin F. Schaeffer and Orestes V. Forlenza

Farooqui, AA; Litsky, ML; Farooqui, T; Horrocks, LA. Inhibitors of intracellular phospholipase A2 activity: their neurochemical effects and therapeutical importance for neurological disorders. Brain Res Bull. 1999;49(3):139-153. Farooqui, AA; Yang, HC; Rosenberger, TA; Horrocks, LA. Phospholipase A2 and its role in brain tissue. J Neurochem. 1997;69(3):889-901. Fluhrer, R; Capell, A; Westmeyer, G; Willem, M; Hartung, B; Condron, MM; Teplow, DB; Haass, C; Walter, J. A non-amyloidogenic function of BACE-2 in the secretory pathway. J Neurochem. 2002;81(5):1011-1020. Forlenza, OV; Schaeffer, EL; Gattaz, WF. Phospholipase A2 activity in rat embryonic brain and in primary cultures of cortical neurons. J Neural Transm. 2002;109(5-6):623-631. Forlenza, OV; Wacker, P; Nunes, PV; Yacubian, J; Castro, CC; Otaduy, MC; Gattaz, WF. Reduced phospholipid breakdown in Alzheimer's brains: a (31)P spectroscopy study. Psychopharmacology (Berl). 2005; [Epub ahead of print]. Fujita, S; Ikegaya, Y; Nishikawa, M; Nishiyama, N; Matsuki, N. Docosahexaenoic acid improves long-term potentiation attenuated by phospholipase A(2) inhibitor in rat hippocampal slices. Br J Pharmacol. 2001;132(7):1417-1422. Fujita, S; Ikegaya, Y; Nishiyama, N; Matsuki, N. Ca2+-independent phospholipase A2 inhibitor impairs spatial memory of mice. Jpn J Pharmacol. 2000;83(3):277-278. Fukushima, D; Konishi, M; Maruyama, K; Miyamoto, T; Ishiura, S; Suzuki, K. Activation of the secretory pathway leads to a decrease in the intracellular amyloidogenic fragments generated from the amyloid protein precursor. Biochem Biophys Res Commun. 1993;194(1):202-207. Gattaz, WF; Cairns, NJ; Levy, R; Forstl, H; Braus, DF; Maras, A. Decreased phospholipase A2 activity in the brain and in platelets of patients with Alzheimer's disease. Eur Arch Psychiatry Clin Neurosci. 1996;246(3):129-131. Gattaz, WF; Forlenza, OV; Talib, LL; Barbosa, NR; Bottino, CM. Platelet phospholipase A(2) activity in Alzheimer's disease and mild cognitive impairment. J Neural Transm. 2004;111(5):591-601. Gattaz, WF; Hübner, CK; Nevalainen, TJ; Thuren, T; Kinnunen, PKJ. Increased serum phospholipase A2 activity in schizophrenia: a replication study. Biol Psychiatry. 1990;28(6):495-501. Gattaz, WF; Köllisch, M; Thuren, T; Virtanen, JA; Kinnunen, PKJ. Increased plasma phospholipase-A2 activity in schizophrenic patients: reduction after neuroleptic therapy. Biol Psychiatry. 1987;22:421-426. Gattaz, WF; Steudle, A; Maras, A. Increased platelet phospholipase A2 in schizophrenia. Schizophr Res. 1995;16:1-6. Gattaz, WF; Maras, A; Cairns, NJ; Levy, R; Forstl, H. Decreased phospholipase A2 activity in Alzheimer brains. Biol Psychiatry. 1995;37(1):13-17. Gelb, MH; Valentin, E; Ghomashchi, F; Lazdunski, M; Lambeau, G. Cloning and recombinant expression of a structurally novel human secreted phospholipase A2. J Biol Chem. 2000;275(51):39823-39826. Gijón, MA; Spencer, DM; Kaiser, AL; Leslie, CC. Role of phosphorylation sites and the C2 domain in regulation of cytosolic phospholipase A2. J Cell Biol. 1999;145(6):1219-1232.

The Role of Phospholipase A2 in Alzheimer's Disease

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Gonzalez, RG; Guimaraes, AR; Moore, GJ; Crawley, A; Cupples, LA; Growdon, JH. Quantitative in vivo 31P magnetic resonance spectroscopy of Alzheimer disease. Alzheimer Dis Assoc Disord. 1996;10(1):46-52. Hirabayashi, T; Kume, K; Hirose, K; Yokomizo, T; Iino, M; Itoh, H; Shimizu, T. Critical duration of intracellular Ca2+ response required for continuous translocation and activation of cytosolic phospholipase A2. J Biol Chem. 1999;274(8):5163-5169. Hölscher, C; Canevari, L; Richter-Levin, G. Inhibitors of PLA2 and NO synthase cooperate in producing amnesia of a spatial task. Neuroreport. 1995;6(5):730-732. Hölscher, C; Rose, SP. Inhibitors of phospholipase A2 produce amnesia for a passive avoidance task in the chick. Behav Neural Biol. 1994;61(3):225-232. Hong, A. The neural basis of learning and memory declines in aged rats. Sheng Li Ke Xue Jin Zhan. 1995;26(3):240-242. Horrobin, DF. The membrane phospholipid hypothesis as a biochemical basis for the neurodevelopmental concept of schizophrenia. Schizophr Res. 1998;30(3):193-208. Hwang, TC; Guggino, SE; Guggino, WB. Direct modulation of secretory chloride channels by arachidonic and other cis unsaturated fatty acids. Proc Natl Acad Sci USA. 1990;87(15):5706-5709. Igaz, LM; Bekinschtein, P; Vianna, MM; Izquierdo, I; Medina, JH. Gene expression during memory formation. Neurotox Res. 2004;6(3):189-204. Igaz, LM; Vianna, MR; Medina, JH; Izquierdo, I. Two time periods of hippocampal mRNA synthesis are required for memory consolidation of fear-motivated learning. J Neurosci. 2002;22(15):6781-6789. Ikemoto, A; Kobayashi, T; Watanabe, S; Okuyama, H. Membrane fatty acid modifications of PC12 cells by arachidonate or docosahexaenoate affect neurite outgrowth but not norepinephrine release. Neurochem Res. 1997;22(6):671-678. Izquierdo, I. Mechanism of action of scopolamine as an amnestic. Trends Pharmacol Sci. 1989;10(5):175-177. Izquierdo, I; Barros, DM; Mello e Souza, T; de Souza, MM; Izquierdo, LA; Medina, JH. Mechanisms for memory types differ. Nature. 1998;393(6686):635-636. Izquierdo, I; Medina, JH. Memory formation: the sequence of biochemical events in the hippocampus and its connection to activity in other brain structures. Neurobiol Learn Mem. 1997;68(3):285-316. Izquierdo, I; Medina, JH; Vianna, MR; Izquierdo, LA; Barros, DM. Separate mechanisms for short- and long-term memory. Behav Brain Res. 1999;103(1):1-11. Izquierdo, I; Quillfeldt, JA; Zanatta, MS; Quevedo, J; Schaeffer, E; Schmitz, PK; Medina, JH. Sequential role of hippocampus and amygdala, entorhinal cortex and parietal cortex in formation and retrieval of memory for IA in rats. Eur J Neurosci. 1997;9(4):786-793. Kadoyama, K; Takahashi, Y; Higashida, H; Tanabe, T; Yoshimoto, T. Cyclooxygenase-2 stimulates production of amyloid beta-peptide in neuroblastoma x glioma hybrid NG10815 cells. Biochem Biophys Res Commun. 2000;281(2):483-490. Kim, D; Clapham, DE. Potassium channels in cardiac cells activated by arachidonic acid and phospholipids. Science. 1989;244(4909):1174-1176.

82

Wagner F. Gattaz, Evelin F. Schaeffer and Orestes V. Forlenza

Kishimoto, K; Matsumura, K; Kataoka, Y; Morii, H; Watanabe, Y. Localization of cytosolic phospholipase A2 messenger RNA mainly in neurons in the rat brain. Neuroscience. 1999;92(3):1061-1077. Kudo, I; Murakami, M. Phospholipase A2 enzymes. Prostaglandins Other Lipid Mediat. 2002;68-69:3-58. Larsson Forsell, PK; Kennedy, BP; Claesson, HE. The human calcium-independent phospholipase A2 gene multiple enzymes with distinct properties from a single gene. Eur J Biochem. 1999;262(2):575-585. Larsson, PK; Claesson, HE; Kennedy, BP. Multiple splice variants of the human calciumindependent phospholipase A2 and their effect on enzyme activity. J Biol Chem. 1998;273(1):207-214. Lin, LL; Wartmann, M; Lin, AY; Knopf, JL; Seth, A; Davis, RJ. cPLA2 is phosphorylated and activated by MAP kinase. Cell. 1993;72(2):269-278. Lio, YC; Reynolds, LJ; Balsinde, J; Dennis, EA. Irreversible inhibition of Ca(2+)independent phospholipase A2 by methyl arachidonyl fluorophosphonate. Biochim Biophys Acta. 1996;1302(1):55-60. Lukiw, WJ; Bazan, NG. Neuroinflammatory signaling upregulation in Alzheimer's disease. Neurochem Res. 2000;25(9-10):1173-1184. MacDonell, LE; Skinner, FK; Ward, PE; Glen, AI; Glen, AC; McDonald, DJ; Boyle, RM; Horrobin, DF. Increased levels of cytosolic phospholipase A2 in dyslexics. Prostagland Leukotr Essent Fatty Acids. 2000;63(1-2):37-39. Maire, JC; Wurtman, RJ. Effects of electrical stimulation and choline availability on the release and contents of acetylcholine and choline in superfused slices from rat striatum. J Physiol (Paris). 1985;80(3):189-195. Mancuso, DJ; Jenkins, CM; Gross, RW. The genomic organization, complete mRNA sequence, cloning, and expression of a novel human intracellular membrane-associated calcium-independent phospholipase A(2). J Biol Chem. 2000;275(14):9937-9945. McGahon, BM; Martin, DS; Horrobin, DF; Lynch, MA. Age-related changes in synaptic function: analysis of the effect of dietary supplementation with omega-3 fatty acids. Neuroscience. 1999;94(1):305-314. Mendes, CT; Gattaz, WF; Schaeffer, EL; Forlenza, OV. Modulation of phosopholipase A(2) activity in primary cultures of rat cortical neurons. J Neural Transm. 2005; [Epub ahead of print]. Miller, B; Sarantis, M; Traynelis, SF; Attwell, D. Potentiation of NMDA receptor currents by arachidonic acid. Nature. 1992;355(6362):722-725. Mizuno-Kamiya, M; Inokuchi, H; Kameyama, Y; Yashiro, K; Fujita, A. Ca2+-independent phospholipase A2 activity in apical plasma membranes from the rat parotid gland. Arch Oral Biol. 2001;46(9):789-799. Molloy, GY; Rattray, M; Williams, RJ. Genes encoding multiple forms of phospholipase A2 are expressed in rat brain. Neurosci Lett. 1998;258(3):139-142. Muccioli, G; Raso, GM; Ghe, C; Di Carlo, R. Effect of L-alpha glycerylphosphorylcholine on muscarinic receptors and membrane microviscosity of aged rat brain. Prog Neuropsychopharmacol Biol Psychiatry. 1996;20(2):323-339.

The Role of Phospholipase A2 in Alzheimer's Disease

83

Müller, WE; Koch, S; Scheuer, K; Rostock, A; Bartsch, R. Effects of piracetam on membrane fluidity in the aged mouse, rat, and human brain. Biochem Pharmacol. 1997;53(2):135140. Musser, JH; Kreft, AF. 5-lipoxygenase: properties, pharmacology, and the quinolinyl(bridged)aryl class of inhibitors. J Med Chem. 1992;35(14):2501-2524. Nemenoff, RA; Winitz, S; Qian, NX; Van Putten, V; Johnson, GL; Heasley, LE. Phosphorylation and activation of a high molecular weight form of phospholipase A2 by p42 microtubule-associated protein 2 kinase and protein kinase C. J Biol Chem. 1993;268(3):1960-1964. Nishikawa, M; Kimura, S; Akaike, N. Facilitatory effect of docosahexaenoic acid on Nmethyl-D-aspartate response in pyramidal neurones of rat cerebral cortex. J Physiol. 1994;475(1):83-93. Nishizaki, T; Nomura, T; Matsuoka, T; Tsujishita, Y. Arachidonic acid as a messenger for the expression of long-term potentiation. Biochem Biophys Res Commun. 1999;254(2): 446-449. Nitsch, RM; Deng, A; Wurtman, RJ; Growdon, JH. Metabotropic glutamate receptor subtype mGluR1alpha stimulates the secretion of the amyloid beta-protein precursor ectodomain. J Neurochem. 1997;69(2):704-712. Noponen, M; Sanfilipo, M; Samanich, K; Ryer, H; Ko, G; Angrist, B; Wolkin, A; Rotrosen J. Elevated PLA2 activity in schizophrenics and other psychiatric patients. Biol Psychiatry. 1993;34:641-649. Owada, Y; Tominaga, T; Yoshimoto, T; Kondo, H. Molecular cloning of rat cDNA for cytosolic phospholipase A2 and the increased gene expression in the dentate gyrus following transient forebrain ischemia. Brain Res Mol Brain Res. 1994;25(3-4):364-368. Paxinos, G; Watson, C. The Rat Brain in Stereotaxic Coordinates. San Diego: Academic Press; 1998. Perani, D; Bressi, S; Cappa, SF; Vallar, G; Alberoni, M; Grassi, F; Caltagirone, C; Cipolotti, L; Franceschi, M; Lenzi, GL; et al. Evidence of multiple memory systems in the human brain. A [18F]FDG PET metabolic study. Brain. 1993;116(Pt 4):903-919. Perisic, O; Paterson, HF; Mosedale, G; Lara-Gonzalez, S; Williams, RL. Mapping the phospholipid-binding surface and translocation determinants of the C2 domain from cytosolic phospholipase A2. J Biol Chem. 1999;274(21):14979-14987. Pettegrew, JW; Kanagasabai, P; Moossy, J; Martinez, J; Rao, G; Boller, F. Correlation of phosphorus-31 magnetic resonance spectroscopy and morphologic findings in Alzheimer’s disease. Arch Neurol. 1988;45:1093-1096. Pettegrew, JW; Klunk, WE; Kanal, E; Panchalingam, K; McClure, RJ. Changes in brain membrane phospholipid and high-energy phosphate metabolism precede dementia. Neurobiol Aging. 1995;16(6):973-975. Pickard, RT; Strifler, BA; Kramer, RM; Sharp, JD. Molecular cloning of two new human paralogs of 85-kDa cytosolic phospholipase A2. J Biol Chem. 1999;274(13):8823-8831. Quevedo, J; Vianna, MR; Martins, MR; Barichello, T; Medina, JH; Roesler, R; Izquierdo, I. Protein synthesis, PKA, and MAP kinase are differentially involved in short- and longterm memory in rats. Behav Brain Res. 2004;154(2):339-343.

84

Wagner F. Gattaz, Evelin F. Schaeffer and Orestes V. Forlenza

Rosenberger, TA; Villacreses, NE; Contreras, MA; Bonventre, JV; Rapoport, SI. Brain lipid metabolism in the cPLA2 knockout mouse. J Lipid Res. 2003;44(1):109-117. Ross, BM; Hudson, C; Erlich, J; Warsh, JJ; Kish, SJ. Increased phospholipid breakdown in schizophrenia. Evidence for the involvement of a calcium-independent phospholipase A2. Arch Gen Psychiatry. 1997;54(5):487-494. Ross, BM; Moszczynska, A; Erlich, J; Kish, SJ. Phospholipid-metabolizing enzymes in Alzheimer's disease: increased lysophospholipid acyltransferase activity and decreased phospholipase A2 activity. J Neurochem. 1998;70(2):786-793. Schaeffer, EL; Bassi, F Jr; Gattaz, WF. Inhibition of phospholipase A2 activity reduces membrane fluidity in rat hippocampus. J Neural Transm. 2005;112(5):641-647. Schaeffer, EL; Gattaz, WF. Inhibition of calcium-independent phospholipase A2 activity in rat hippocampus impairs acquisition of short- and long-term memory. Psychopharmacology (Berl). 2005; [Epub ahead of print]. Scheuer, K; Rostock, A; Bartsch, R; Müller, WE. Piracetam improves cognitive performance by restoring neurochemical deficits of the aged rat brain. Pharmacopsychiatry. 1999;32(Suppl 1):10-16. Schievella, AR; Regier, MK; Smith, WL; Lin, LL. Calcium-mediated translocation of cytosolic phospholipase A2 to the nuclear envelope and endoplasmic reticulum. J Biol Chem. 1995;270(51):30749-30754. Sharp, JD; White, DL. Cytosolic PLA2: mRNA levels and potential for transcriptional regulation. J Lipid Mediat. 1993;8(3):183-189. Simonato, M. A pathogenetic hypothesis of temporal lobe epilepsy. Pharmacol Res. 1993;27:217-225. Six, DA; Dennis, EA. The expanding superfamily of phospholipase A(2) enzymes: classification and characterization. Biochim Biophys Acta. 2000;1488(1-2):1-19. Skinner, ER; Watt, C; Besson, JAO; Best, PV. Lipid composition of different regions of the brain in patients with Alzheimer's disease. Biochem Soc Trans. 1989;17:213-214. Smalheiser, NR; Dissanayake, S; Kapil, A. Rapid regulation of neurite outgrowth and retraction by phospholipase A2-derived arachidonic acid and its metabolites. Brain Res. 1996;721(1-2):39-48. Smith, CD; Gallenstein, LG; Layton, WJ; Kryscio, RJ; Markesbery , WR. 31P magnetic resonance spectroscopy in Alzheimer's and Pick's disease. Neurobiol Aging. 1993;14(1):85-92. Song, C; Chang, XJ; Bean, KM; Proia, MS; Knopf, JL; Kriz, RW. Molecular characterization of cytosolic phospholipase A2-beta. J Biol Chem. 1999;274(24):17063-17067. Stubbs, CD; Smith, AD. The modification of mammalian membrane polyunsaturated fatty acid composition in relation to membrane fluidity and function. Biochim Biophys Acta. 1984;779(1):89-137. Suzuki, N; Ishizaki, J; Yokota, Y; Higashino, K; Ono, T; Ikeda, M; Fujii, N; Kawamoto, K; Hanasaki, K. Structures, enzymatic properties, and expression of novel human and mouse secretory phospholipase A(2)s. J Biol Chem. 2000;275(8):5785-5793. Talbot, K; Young, RA; Jolly-Tornetta, C; Lee, VM; Trojanowski, JQ; Wolf, BA. A frontal variant of Alzheimer's disease exhibits decreased calcium-independent phospholipase A2 activity in the prefrontal cortex. Neurochem Int. 2000;37(1):17-31.

The Role of Phospholipase A2 in Alzheimer's Disease

85

Tanaka, H; Takeya, R; Sumimoto, H. A novel intracellular membrane-bound calciumindependent phospholipase A(2). Biochem Biophys Res Commun. 2000;272(2):320-326. Tomassoni, ML; Amori, D; Magni, MV. Changes of nuclear membrane lipid composition affect RNA nucleocytoplasmic transport. Biochem Biophys Res Commun. 1999;258(2):476-481. Underwood, KW; Song, C; Kriz, RW; Chang, XJ; Knopf, JL; Lin, LL. A novel calciumindependent phospholipase A2, cPLA2-gamma, that is renylated and contains homology to cPLA2. J Biol Chem. 1998;273(34):21926-21932. Visioli, F, Rodriguez-de-Turco, EB, Kreisman, NR, Bazan, NG. Membrane lipid degradation is related to interictal cortical activity in a series of seizures. Metab Brain Dis. 1994;9:161-170. Weichel, O; Hilgert, M; Chatterjee, SS; Lehr, M; Klein, J. Bilobalide, a constituent of Ginkgo biloba, inhibits NMDA-induced phospholipase A2 activation and phospholipid breakdown in rat hippocampus. Naunyn Schmiedebergs Arch Pharmacol. 1999;360(6):609-615. Williams, EJ; Walsh, FS; Doherty, P. The production of arachidonic acid can account for calcium channel activation in the second messenger pathway underlying neurite outgrowth stimulated by NCAM, N-cadherin, and L1. J Neurochem. 1994;62(3):12311234. Winstead, MV; Balsinde, J; Dennis, EA. Calcium-independent phospholipase A(2): structure and function. Biochim Biophys Acta. 2000;1488(1-2):28-39. Woelk, H; Peiler-Ichikawa, K. Zur Aktivität der Phospholipase A2 gegenüber verschiedenen 1-Alk-1'-enyl-2-acyl- und 1-Alkyl-2-acyl-Verbindungen während der multiplen Sklerose. J Neurol. 1974;207:319-326. Wolf, MJ; Izumi, Y; Zorumski, CF; Gross, RW. Long-term potentiation requires activation of calcium-independent phospholipase A2. FEBS Lett. 1995;377(3):358-362. Yang, HC; Mosior, M; Ni, B; Dennis, EA. Regional distribution, ontogeny, purification, and characterization of the Ca2+-independent phospholipase A2 from rat brain. J Neurochem. 1999;73(3):1278-1287. Yoshihara, Y; Yamaji, M; Kawasaki, M; Watanabe, Y. Ontogeny of cytosolic phospholipase A2 activity in rat brain. Biochem Biophys Res Commun. 1992;185(1):350-355. Yoshihara, Y; Watanabe, Y. Translocation of phospholipase A2 from cytosol to membranes in rat brain induced by calcium ions. Biochem Biophys Res Commun. 1990;170(2):484490. Yoshikai, Y. Roles of prostaglandins and leukotrienes in acute inflammation caused by bacterial infection. Curr Opin Infect Dis. 2001;14(3):257-263. Zubenko, GS; Winwood, E; Jacobs, B; Teply, I; Stiffler, JS; Hughes, HB 3rd; Huff, FJ; Sunderland, T; Martinez, AJ. Prospective study of risk factors for Alzheimer's disease: results at 7.5 years. Am J Psychiatry. 1999;156(1):50-57.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp. 87-98

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter III

Low Molecular Weight Glycosaminoglycans and Apoptosis: Potential Treatment of Neurodegenerative Disorders Including Alzheimer’s Disease Bertalan Dudas Neuroendocrine Organization Laboratory (NEO), Lake Erie College of Osteopathic Medicine, Erie, PA 16509, USA.

Abstract Previous studies have shown that apoptosis (programmed cell death) plays a crucial role in the pathomechanism of neurodegenerative disorders. It is a general consensus that apoptosis can be triggered by dysregulation of nerve growth factor physiology and/or oxidative stress processes. Since both of these pathological changes are characteristic to AD, it is conceivable that influencing apoptosis can be a valuable tool in the treatment of neurodegenerative disorders. Glucosaminoglycans (GAGs) exhibit neuroprotective properties in several animal models of AD. Low molecular weight GAG, C3, attenuates Aβ(25-35)-induced tau-2 immunoreactivity, and AF64A-induced cholinergic lesion in rat brain. Recent studies have also revealed that C3 influences p75 nerve growth factor receptor expression. However, the exact mechanism of the neuroprotective attributes of C3 is not elucidated yet. Since apoptosis is believed to play a pivotal role in numerous neurodegenerative disorders, C3 may induce neuroprotection/neurorepair via affecting apoptotic processes. The neuroprotective effect of glucosaminoglycans including C3 thus may involve multiple mechanisms, including an influence on processes that lead to programmed cell death. Since apoptosis is a crucial event not only in neurodegenerative diseases but also

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Pathology of Alzheimer’s Disease: Introductory Comments Alzheimer’s disease (AD) is a progressive and irreversible brain disorder that is manifested in dementia, motor lesions and behavioral deficits. Since as many as 10% of the population above 65 years of age is affected by AD in the United States, AD is becoming a growing concern in health care. The unequivocal diagnosis of AD is based on histopathological evidence at brain autopsy or biopsy. The major pathological hallmarks of AD include abnormal biochemical alteration of regular proteins that leads to accumulation of the modified molecules in the brain. Intracellular deposition of hyperphosphorylated, polymerized tau protein, forming flame-like tangles disrupts axonal and dendritic transport by destroying the normal microtubular structure. Pathological cleavage of the amyloid precursor protein (APP) normally present in the brain results in beta amyloid fragments that are aggregated to form extracellular build-up of amyloid plaques. These histological hallmarks are associated with extensive loss of cholinergic neurons, which is believed to be the major cause of symptoms in AD. However, the exact patho-mechanism leading to neuronal death is not yet elucidated.

Apoptosis in Neurodegenerative Disorders Apoptosis (programmed cell death) is a natural process that ensures that damaged cells are packaged and removed by the surrounding cells cleanly, in order to prevent inflammation typical in necrotic processes. Apoptosis (Figure 1) is typically triggered by external stimuli (extrinsic pathway) and internal events (intrinsic pathway). The extrinsic pathway is initiated outside of the cell, when conditions in the extracellular environment determine that a cell must die. Extrinsic pathway is triggered by binding ligands to specific "death receptors" on the surface of the cells, leading to activation of cysteinyl proteases that are called initiator caspases. The intrinsic apoptosis pathway begins when an injury occurs within the cell. Mitochondrial damage, for example, can initiate the intrinsic pathway, when cytochrome-c, released from damaged mitochondria, activates an initiator caspase. The extrinsic and intrinsic pathways merge at caspase-3 that is activated by initiator caspases. Subsequent processes result in multiple events, including degradation of DNA, and packaging of the cell into small units that are easily taken up by neighboring cells. Several studies indicated that apoptosis is one of the crucial factors that may be responsible for neuronal loss, characteristic for neurodegeneratory disorders including AD. Caspases are believed to be involved in generation of toxic fragments of protein substrates, that can trigger the earlier stages of neuronal dysfunction including protein aggregation in Huntington's and Alzheimer's disease [1]. Thus, caspase inhibition may be a valuable adjunct

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in the treatment of neurodegenerative disorders. Previous findings also demonstrated dysregulation of apoptotic proteins in AD brain, that may play a crucial role in the neuropathology of AD [2,3]. Since the level of cytochrome c has been reported to be unchanged in the frontal cortex of patients suffering from AD [3], apoptosis may occur via the extrinsic death receptor pathway independent of cytochrome c. However, it is generally believed that multiple factors are responsible for the neuronal cell death in AD. For example, neurofibrillary tangles and amyloid plaques are not associated with caspase-3 induction, in contrast to hippocampal neurons, that exhibit vacuolar degeneration and caspase-3 activation [4]. Thus, caspase-3 may not have a significant role in the widespread neuronal apoptosis that occurs in AD, but may contribute to the specific loss of hippocampal neurons involved in learning and memory.

Figure 1. Major processes of the apoptotic pathway. Apoptosis is a natural process that ensures that damaged cells are packaged and removed by the surrounding cells thoroughly, in order to prevent inflammation typical in necrotic processes. Apoptosis is triggered by external stimuli (extrinsic pathway) and internal events (intrinsic pathway). The extrinsic pathway is activated by binding ligands (DL) to specific "death receptors" (DR) on the surface of the cells, leading to activation of initiator caspases of the external pathway (EIC). The intrinsic apoptosis pathway begins with an intracellular lesion that is typically mitochondrial damage, when cytochrome-c (Cc), released from damaged mitochondria, activates initiator caspases of the internal pathway (IIC). The extrinsic and intrinsic pathways merge at caspase-3 (CA3) that is activated by initiator caspases (EIC and IIC). Subsequent processes result in multiple events, including degradation of DNA in the nucleus, and packaging of the cell into small units that are easily taken up by neighboring cells.

It is a common consensus that there are two major pathways playing roles in triggering apoptosis in neurodegenerative disorders: oxidative stress and trophic factor dysregulation.

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Oxidative Stress in Alzheimer’s Disease Neuronal cell loss is believed to be responsible for the majority of the clinical symptoms of AD including dementia, motor lesions and behavioral deficits. One of the most important pathways known to trigger apoptosis in the brain is oxidative stress. Oxidative stress refers to the situation of a serious imbalance between production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), and antioxidant defense. ROS/RNS cause cell damage and neuronal death through lipid peroxidation (LPO), oxidation of nucleic acids, and oxidation and nitrosylation of proteins and aminoacids. It is generally thought that the amyloid deposit (i.e. the senile plaque), which accumulates in the brain of Alzheimer’s disease (AD) patients, is the cause of the neurodegenerative changes characteristic of AD, and that oxidative stress induced by amyloid beta peptide (Aβ) is a prominent feature of amyloid-induced neuronal cell death in the AD brain. Indeed, post-mortem studies have shown that 4-hydroxy-nonenal (4-HNE), a lipid peroxidation (LPO) end–product accumulates in the AD brain [5]. Moreover, a recent study has shown that iPF(2α)–IV, another marker of LPO (i.e. oxidative stress) was increased in the urine of patients with mild to moderate dementia and probable AD [6]. Studies have also demonstrated that Aβ can directly cause increases in reactive oxygen species (ROS) and produce 4-HNE [7]. These findings indicate that Aβ-induced oxidative stress is a key feature in AD. The contention that AD pathology is associated with increased levels of oxidative stress has also been confirmed in an animal model of Alzheimer amyloidosis [8]. Levels of urinary and plasma iPF(2α)–IV were higher in APP-transgenic mice than in littermate wild type animals as early as eight months of age, and remained high for the rest of the study. Furthermore, homogenates from the cerebral cortex and the hippocampus of APP-mice had higher levels of iPF(2α)–IV, and this increase in LPO preceded amyloid plaque formation. That increased oxidative damage may, indeed, be the earliest event in AD is suggested by findings showing that increases in 8-hydroxyguanosine, an oxidized nucleoside derived from DNA, and nitrotyrosine, an oxidized amino acid, were quantitatively greatest early in the disease [9]. Data confirming that oxidative stress-induced damage precedes the deposition of amyloid in the brain also come from a study of Down’s syndrome brains [10]. Oxidized nucleic acid, 8-hydroxy guanosine (8-OHG), oxidized protein and nitrotyrosine were found to be increased significantly in the teens and in the twenties, while Aβ deposits only occurred after age 30. These findings suggest that brain oxidative damage must contribute to AD pathogenesis before Aβ (i.e. senile plaques) accumulates in the AD brain. Several risk factors may facilitate oxidative stress in the AD brain. One study has showed reduced antioxidant enzyme activity in AD brain [11], and brains of transgenic mice expressing different Alzheimer-linked presenilin-1 gene (PS1) mutations have been shown to have decreased antioxidant enzyme activity [12]. Another risk factor that may facilitate Aβinduced oxidative brain damage is the epsilon4 allele of apolipoprotein E (APOE), an established risk factor for AD. Levels of LPO were found to be significantly increased in tissues from Alzheimer’s cases which were homozygous for the epsilon4 allele of APOE, compared to AD epsilon3/epsilon3 cases and controls [13], suggesting that oxidative stressinduced injury in the frontal cortex of AD cases is related to the APOE genotype.

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Activated astrocytes (and microglia) are observed in a wide range of CNS pathologies, including brain inflammation, trauma, ischemia, and stroke; neurodegenerative diseases including AD, and normal aging [14,15]. In AD, activated microglia and astrocytes expressing the inducible form of nitric oxide synthase (iNOS) are found in the amyloid plaques surrounded by dead and dystrophic neurites [16,17], and a growing body of evidence suggests that these activated glia contribute to neurotoxicity through the production of reactive nitrogen species (RNS) derived from increased production of iNOS. Moreover, aggregated Aβ peptide can also stimulate iNOS production in rat glial cell cultures [18]. The concentration of 3-nitrotyrosine, a marker of oxidative damage mediated by peroxynitrite, and the 3-nitrotyrosine/tyrosine ratio was also increased six-fold in AD patients when compared with cerebrospinal fluid samples from age matched controls, and increased significantly with decreasing cognitive function [19]. Strong nitrotyrosine (NT) immunoreactivity was also observed in the absence of tangle formation in most terminal deoxynucleotidyl transferase (TdT)-positive neurones in the visual cortex of AD patients, suggesting that neuronal DNA damage may precede tangle formation and is associated with up-regulation of nitrotyrosine in AD brain [20]. These studies indicate that increased oxidative damage must contribute to the pathogenesis of AD before amyloid deposits occur in the brain. Thus, oxidative stress and increased production of iNOS are early events that appear to be central in determining cell death in AD.

Neurotrophic Factors in Alzheimer’s Disease Since nerve growth factor (NGF) induces neuronal growth and regeneration [21-25], it is generally accepted that NGF may play a pivotal role in the repair processes of neurodegenerative disorders [26] and may be a crucial element of the neuronal loss in AD[27-30]. Several studies revealed that deficiency of NGF may directly trigger apoptosis. Neuronal PC12 cells underwent apoptosis within two days following withdrawal of nerve growth factor (NGF) from the culture medium. [31]. Anti-NGF transgenic mice develop neurodegeneratory lesions characteristic for AD including amyloid plaques and neurofibrillary tangles in cortical and hippocampal neurons associated with extensive neuronal loss [32]. Although NGF is commonly accepted as a major factor promoting neuronal regeneration and survival, recent findings indicated that NGF may also play a role in triggering apoptosis. The ambivalent nature of NGF may be explained by the physiology of the NGF receptors, the tropomyosin receptor kinase A (TrkA) and the 75 kDa NGF receptor (p75NTR). TrkA induces survival and regeneration, whereas p75NTR appears to be a death receptor mediating the apoptotic effect of NGF. Indeed, NGF induced apoptosis in p75NTR-expressing human neuroblastoma SK-N-MC cells, but neurotrophin-3 (NT-3) or brain-derived neurotrophic factor (BDNF) lacked apoptotic effect [33]. Moreover, betaamyloid peptide, commonly present in amyloid plaques in AD, specifically binds the p75NTR in rat cortical neurons, NIH-3T3 cell line and neuronal hybrid cells, and triggers apoptosis [34-36] indicating that neuronal death in Alzheimer's disease may be mediated by the interaction of beta-amyloid with p75NTR. Since p75NTR is up-regulated in

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neurodegeneratory disorders, p75NTR might be involved in neuronal cell death related to AD [33].

Alzheimer’s Disease and Glycosaminoglycans There is a growing body of evidence that glycosaminoglycans (GAGs) play a pivotal role in the pathogenesis of Alzheimer’s disease. Glycosaminoglycans are highly sulfated polysaccharides that are common constituents of the extracellular matrix. GAGs bind to Aβ, and attenuate the proteoglycan-mediated protection of Aβ against proteolysis. It has been also shown that GAGs inhibit the aggregation and toxicity of Aβ itself [37]. AteroidR, a mixture of low molecular weight GAGs recently used in Europe to reverse the symptoms of AD, improves age-related behavioral deficits in rats. Moreover, human studies revealed that AteroidR significantly improves dementia [38,39]. C3 is a novel low molecular weight GAG exerting neuroprotective property. C3 is synthesized from unfractionated heparin using a standardized process of γ-irradiation. The chemical and biological properties of C3 have been well characterized including its ability to protect against various lesions in rat animal models. Stereotaxic injection of Aβ fragments (Aβ[25-35]) into the amygdala increases tau-2 immunoreactivity in the rat hippocampus [40]. This phenomenon was blocked by administration of C3 [41]. Moreover, C3 attenuated the cholinergic lesions in the septum and cingulum bundle induced by intraventricular administration of a specific cholinotoxin, ethylcholine aziridinium (AF64A; [42,43]. It has been also shown that C3 increase axonal growth and arborization in the rat hippocampus [44]. Recent studies suggested that GAGs may act via modulating the release of nerve growth factor (NGF) by stimulating the effect of growth factors in cell culture [45,46] and/or reducing the expression of cholinotoxin-stimulated growth factor receptor expression in the rat septum [47]. Glial cell line-derived neurotrophic factor (GDNF), that is vital to the development and maintenance of neural tissues, requires heparan sulphate glycosaminoglycan to promote neuronal survival [48]. However, the exact mechanism of the neuroprotective/neurorepair effect of GAGs is not known. The bioavailability of various GAGs depends on their potential to traverse the blood bran barrier (BBB). Since C3 has been demonstrated to cross the BBB, it may be a valuable adjunct in the treatment of neurodegenerative disorders including AD. Indeed, C3 is in phase I clinical trials at the time of this writing.

Glycosaminoglycans and Apoptosis: Potential Treatment of Alzheimer’s Disease Previous studies revealed that GAGs express neuroprotective properties against various lesions in cell culture [49] and in vivo [41-43,50]. Since neural damage is often associated with apoptotic processes, it is possible that GAGs may protect against neural lesions via

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influencing stressor-induced apoptosis. Moreover, C3, the low molecular GAG derived from heparin has been shown to penetrate the blood-brain-barrier [51], thus, it is conceivable that C3 and similar molecules can be used as therapeutic agents to protect against neuronal apoptotic processes, that are major hallmarks of neurodegenerative disorders. It is a common premise that GAGs play a pivotal role in the molecular processes of programmed cell death in several cell types. However, the data are ambiguous. Numerous studies indicate that GAGs may participate in the inhibition of apoptotic pathways. Hyaluronan, a major glycosaminoglycan component of the extracellular matrix of the mammalian bone marrow, antagonizes dexamethasone-induced apoptosis of malignant multiplex myeloma (MM) cells [52]. Since GAGs are major constituents of the bone marrow, these findings support the idea that GAGs could play a major role in the survival of MM cells in vivo, and could explain why MM cells accumulate in the bone marrow of patients with MM and escape conventional chemotherapy. Apoptosis in fibroblasts was also attenuated by administration of chondroitin sulfate, and heparan sulfate. Platelet-derived growth factor (PDGF) and beta-D-xyloside treatment protected fetal lung fibroblasts against serum starvation-induced apoptosis probably by stimulating the GAG synthesis/secretion of the cells. Indeed, application of sulfated GAGs, chondroitin sulfate, and heparan sulfate, also resulted in diminished apoptosis in fetal lung fibroblasts, possibly via increasing Bclassociated death promoter phosphorylation and diminished caspase-3 and caspase-7 cleavage [53] Heparin inhibits mesangial cell apoptosis induced by staurosporine, pyrrolidine dithiocarbamate, and ultraviolet light, and also suppresses oxidant-induced apoptosis of NRK49F fibroblasts and Madin-Darby canine kidney epithelial cells. Furthermore, heparin attenuated spontaneous apoptosis of podocytes in explanted glomeruli. These results indicate the novel potential of heparin as an inhibitor of apoptosis in several cell types, including glomerular cells [54]. Moreover, heparin and aspirin has been shown to inhibit trophoblast apoptosis providing an additional mechanism to explain the clinical benefits of heparin and aspirin on recurrent pregnancy loss [55]. In contrast to these findings, induction of apoptosis by GAGs has been reported by several studies, suggesting that GAGs may be used for eliminating tumor cells. Heparin exerts a significant anti-proliferative and an apoptotic effect on human hepatoma cells in vitro [56], and induces apoptosis of human nasopharyngeal carcinoma CNE2 cells [57]. Internalized heparin induces apoptotic cell death probably by interfering with transcription factor function [58]. Derivatives of heparin and chondroitin sulphate substantially reduce cell viability by induction of apoptosis of myeloma and breast cancer cells in vitro [59]. Heparin also induces apoptosis in peripheral blood neutrophils. This phenomenon may help explain the anti-inflammatory effects resulting from the interaction between vessel wall heparan sulphate and chemoattracted peripheral blood neutrophils [60]. Moreover, heparin is not the only GAG exhibiting apoptotic features. A low molecular weight proteoglycan, lumican induced and/or increased the apoptosis of B16F1 cells, probably via the sulphated GAG component of the molecule [61]. Chondroitin sulphate also induces apoptosis of articular chondrocytes [62].

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Discussion and Summary Apoptosis is believed to play a pivotal role in the pathogenesis of neurodegenerative disorders including AD. Although the exact function of apoptotic processes in brain pathology is not known, it is a common consensus that two major pathways are responsible in triggering apoptosis in neurodegenerative disorders: (1) oxidative stress and (2) trophic factor dysregulation. Oxidative stress appears to be the major pathological hallmark of AD. Moreover, dysregulation in the release of nerve growth factors, and expression of their receptors are characteristic pathological changes attributed to AD. GAGs are known to exhibit neuroprotective properties in numerous animal models of AD. One possible explanation of the GAG-induced neuroprotection is that GAGs may affect apoptotic processes characteristic in neurodegenerative lesions. The pathomechanism of this phenomenon is not entirely understood; GAGs may affect apoptosis either directly, or via modulating growth factor pathology and/or oxidative stress, that are major hallmarks of AD. Thus, GAGs can be extremely veluable adjunct in the treatment of neurodegenerative disorders. Since a low molecular GAG, C3, is able to cross the blood-brain-barrier, C3 treatment may represent an entirely novel avenue in the therapy of AD. Indeed, C3 has successfully passed the toxicology tests as a low-risk compound, and it is currently in phase I clinical trials.

References [1] [2]

[3]

[4]

[5] [6]

[7]

Rideout HJ, Stefanis L. Caspase Inhibition: A Potential Therapeutic Strategy In Neurological Diseases Histol Histopathol 2001; 16: 895-908. Engidawork E, Gulesserian T, Seidl R, Cairns N, Lubec G. Expression Of Apoptosis Related Proteins In Brains Of Patients With Alzheimer's Disease Neurosci Lett 2001; 303: 79-82. Engidawork E, Gulesserian T, Yoo BC, Cairns N, Lubec G. Alteration Of Caspases And Apoptosis-Related Proteins In Brains Of Patients With Alzheimer's Disease Biochem Biophys Res Commun 2001; 281: 84-93. Selznick LA, Holtzman DM, Han BH, Gokden M, Srinivasan AN, Johnson EM, Roth KA. In Situ Immunodetection Of Neuronal Caspase-3 Activation In Alzheimer Disease J Neuropathol Exp Neurol 1999; 58: 1020-1026. Lovell MA, Ehmann WD, Mattson MP, Markesbery WR. Elevated 4-Hydroxynonenal In Ventricular Fluid In Alzheimer's Disease Neurobiol Aging 1997; 18: 457-461. Tuppo EE, Forman LJ, Spur BW, Chan-Ting RE, Chopra A, Cavalieri TA. Sign Of Lipid Peroxidation As Measured In The Urine Of Patients With Probable Alzheimer's Disease Brain Res Bull 2001; 54: 565-568. Mark RJ, Lovell MA, Markesbery WR, Uchida K, Mattson MP. A Role For 4Hydroxynonenal, An Aldehydic Product Of Lipid Peroxidation, In Disruption Of Ion Homeostasis And Neuronal Death Induced By Amyloid Beta-Peptide J Neurochem 1997; 68: 255-264.

Low Molecular Weight Glycosaminoglycans and Apoptosis [8]

[9]

[10]

[11]

[12]

[13]

[14] [15] [16]

[17]

[18]

[19]

[20]

[21]

95

Pratico D, Uryu K, Leight S, Trojanoswki JQ, Lee VM. Increased Lipid Peroxidation Precedes Amyloid Plaque Formation In An Animal Model Of Alzheimer Amyloidosis J Neurosci 2001; 21: 4183-4187. Nunomura A, Perry G, Aliev G, Hirai K, Takeda A, Balraj EK, Jones PK, Ghanbari H, Wataya T, Shimohama S, Chiba S, Atwood CS, Petersen RB, Smith MA. Oxidative Damage Is The Earliest Event In Alzheimer Disease J Neuropathol Exp Neurol 2001; 60: 759-767. Nunomura A, Perry G, Pappolla MA, Friedland RP, Hirai K, Chiba S, Smith MA. Neuronal Oxidative Stress Precedes Amyloid-Beta Deposition In Down Syndrome J Neuropathol Exp Neurol 2000; 59: 1011-1017. Marcus DL, Thomas C, Rodriguez C, Simberkoff K, Tsai JS, Strafaci JA, Freedman ML. Increased Peroxidation And Reduced Antioxidant Enzyme Activity In Alzheimer's Disease Exp Neurol 1998; 150: 40-44. Leutner S, Czech C, Schindowski K, Touchet N, Eckert A, Muller WE. Reduced Antioxidant Enzyme Activity In Brains Of Mice Transgenic For Human Presenilin-1 With Single Or Multiple Mutations Neurosci Lett 2000; 292: 87-90. Ramassamy C, Averill D, Beffert U, Bastianetto S, Theroux L, Lussier-Cacan S, Cohn JS, Christen Y, Davignon J, Quirion R, Poirier J. Oxidative Damage And Protection By Antioxidants In The Frontal Cortex Of Alzheimer's Disease Is Related To The Apolipoprotein E Genotype Free Radic Biol Med 1999; 27: 544-553. Eddleston M, Mucke L. Molecular Profile Of Reactive Astrocytes--Implications For Their Role In Neurologic Disease Neuroscience 1993; 54: 15-36. Kreutzberg GW. Microglia: A Sensor For Pathological Events In The CNS Trends Neurosci 1996; 19: 312-318. Lee SC, Zhao ML, Hirano A, Dickson DW. Inducible Nitric Oxide Synthase Immunoreactivity In The Alzheimer Disease Hippocampus: Association With Hirano Bodies, Neurofibrillary Tangles, And Senile Plaques J Neuropathol Exp Neurol 1999; 58: 1163-1169. Wallace MN, Geddes JG, Farquhar DA, Masson MR. Nitric Oxide Synthase In Reactive Astrocytes Adjacent To Beta-Amyloid Plaques Exp Neurol 1997; 144: 266272. Akama KT, Van Eldik LJ. Beta-Amyloid Stimulation Of Inducible Nitric-Oxide Synthase In Astrocytes Is Interleukin-1beta- And Tumor Necrosis Factor-Alpha (Tnfalpha)-Dependent, And Involves A Tnfalpha Receptor-Associated Factor- And Nfkappab-Inducing Kinase-Dependent Signaling Mechanism J Biol Chem 2000; 275: 7918-7924. Tohgi H, Abe T, Yamazaki K, Murata T, Ishizaki E, Isobe C. Alterations Of 3Nitrotyrosine Concentration In The Cerebrospinal Fluid During Aging And In Patients With Alzheimer's Disease Neurosci Lett 1999; 269: 52-54. Su JH, Deng G, Cotman CW. Neuronal DNA Damage Precedes Tangle Formation And Is Associated With Up-Regulation Of Nitrotyrosine In Alzheimer's Disease Brain Brain Res 1997; 774: 193-199. Damon DH, D'Amore PA, Wagner JA. Nerve Growth Factor And Fibroblast Growth Factor Regulate Neurite Outgrowth And Gene Expression In PC12 Cells Via Both

96

[22] [23]

[24]

[25]

[26] [27]

[28] [29] [30]

[31]

[32]

[33] [34]

[35]

[36]

Bertalan Dudas Protein Kinase C- And Camp-Independent Mechanisms J Cell Biol 1990; 110: 13331339. Gahwiler BH, Enz A, Hefti F. Nerve Growth Factor Promotes Development Of The Rat Septo-Hippocampal Cholinergic Projection In Vitro Neurosci Lett 1987; 75: 6-10. Hartikka J, Hefti F. Development Of Septal Cholinergic Neurons In Culture: Plating Density And Glial Cells Modulate Effects Of NGF On Survival, Fiber Growth, And Expression Of Transmitter-Specific Enzymes J Neurosci 1988; 8: 2967-2985. Hefti F, Knusel B, Lapchak PA. Protective Effects Of Nerve Growth Factor And BrainDerived Neurotrophic Factor On Basal Forebrain Cholinergic Neurons In Adult Rats With Partial Fimbrial Transections Prog Brain Res 1993; 98: 257-263. Junard EO, Montero CN, Hefti F. Long-Term Administration Of Mouse Nerve Growth Factor To Adult Rats With Partial Lesions Of The Cholinergic Septohippocampal Pathway Exp Neurol 1990; 110: 25-38. Hefti F, Knusel B. Chronic Administration Of Nerve Growth Factor And Other Neurotrophic Factors To The Brain Neurobiol Aging 1988; 9: 689-690. Hefti F, Will B. Nerve Growth Factor Is A Neurotrophic Factor For Forebrain Cholinergic Neurons; Implications For Alzheimer's Disease J Neural Transm Suppl 1987; 24: 309-315. Hefti F, Schneider LS. Nerve Growth Factor And Alzheimer's Disease Clin Neuropharmacol 1991; 14 Suppl 1: S62-S76. Lapchak PA, Hefti F. Emerging Pharmacology Of Nerve Growth Factor Prog Neuropsychopharmacol Biol Psychiatry 1991; 15: 851-860. Phelps CH, Gage FH, Growdon JH, Hefti F, Harbaugh R, Johnston MV, Khachaturian ZS, Mobley WC, Price DL, Raskind M. Potential Use Of Nerve Growth Factor To Treat Alzheimer's Disease Neurobiol Aging 1989; 10: 205-207. Araki W, Wurtman RJ. Increased Expression Of Amyloid Precursor Protein And Amyloid Precursor-Like Protein 2 During Trophic Factor Withdrawal-Induced Death Of Neuronal PC12 Cells Brain Res Mol Brain Resry 1998; 56: 169-177. Capsoni S, Ugolini G, Comparini A, Ruberti F, Berardi N, Cattaneo A. Alzheimer-Like Neurodegeneration In Aged Antinerve Growth Factor Transgenic Mice Proc Natl Acad Sci U S A 2000; 97: 6826-6831. Kuner P, Hertel C. NGF Induces Apoptosis In A Human Neuroblastoma Cell Line Expressing The Neurotrophin Receptor P75ntr J Neurosci Res 1998; 54: 465-474. Yaar M, Zhai S, Pilch PF, Doyle SM, Eisenhauer PB, Fine RE, Gilchrest BA. Binding Of Beta-Amyloid To The P75 Neurotrophin Receptor Induces Apoptosis. A Possible Mechanism For Alzheimer's Disease J Clin Invest 1997; 100: 2333-2340. Tsukamoto E, Hashimoto Y, Kanekura K, Niikura T, Aiso S, Nishimoto I. Characterization Of The Toxic Mechanism Triggered By Alzheimer's Amyloid-Beta Peptides Via P75 Neurotrophin Receptor In Neuronal Hybrid Cells J Neurosci Res 2003; 73: 627-636. Hashimoto Y, Kaneko Y, Tsukamoto E, Frankowski H, Kouyama K, Kita Y, Niikura T, Aiso S, Bredesen DE, Matsuoka M, Nishimoto I. Molecular Characterization Of Neurohybrid Cell Death Induced By Alzheimer's Amyloid-Beta Peptides Via P75ntr/PLAIDD J Neurochem 2004; 90: 549-558.

Low Molecular Weight Glycosaminoglycans and Apoptosis

97

[37] Kisilevsky R, Lemieux LJ, Fraser PE, Kong X, Hultin PG, Szarek WA. Arresting Amyloidosis In Vivo Using Small-Molecule Anionic Sulphonates Or Sulphates: Implications For Alzheimer's Disease Nat Med 1995; 1: 143-148. [38] Conti L, Re F, Lazzerini F, Morey LC, Ban TA, Santini V, Modafferi A, Postiglione A. Glycosaminoglycan Polysulfate (Ateroid) In Old-Age Dementias: Effects Upon Depressive Symptomatology In Geriatric Patients Prog Neuropsychopharmacol Biol Psychiatry 1989; 13: 977-981. [39] Conti L, Placidi GF, Cassano GB. Ateroid In The Treatment Of Dementia: Results Of A Clinical Trial Mod Probl Pharmacopsychiatry 1989; 23: 76-84. [40] Sigurdsson EM, Lorens SA, Hejna MJ, Dong XW, Lee JM. Local And Distant Histopathological Effects Of Unilateral Amyloid-Beta 25-35 Injections Into The Amygdala Of Young F344 Rats Neurobiol Aging 1996; 17: 893-901. [41] Dudas B, Cornelli U, Lee JM, Hejna MJ, Walzer M, Lorens SA, Mervis RF, Fareed J, Hanin I. Oral And Subcutaneous Administration Of The Glycosaminoglycan C3 Attenuates Abeta(25-35)-Induced Abnormal Tau Protein Immunoreactivity In Rat Brain Neurobiol Aging 2002; 23: 97-104. [42] Rose M, Dudas B, Cornelli U, Hanin I. Protective Effect Of The Heparin-Derived Oligosaccharide C3, On AF64A-Induced Cholinergic Lesion In Rats Neurobiol Aging 2003; 24: 481-490. [43] Rose M, Dudas B, Cornelli U, Hanin I. Glycosaminoglycan C3 Protects Against AF64A-Induced Cholinotoxicity In A Dose-Dependent And Time-Dependent Manner Brain Res 2004; 1015: 96-102. [44] Mervis RF, Mckean J, Zats S, Gum A, Reinhard R, Dudas B, Cornelli U, Lee JM, Lorens SA, Fareed J, Hanin I. Neurotrophic Effects Of The Glycosaminoglycan C3 On Dendritic Arborization And Spines In The Adult Rat Hippocampus: A Quantitative Golgi Study CNS Drug Reviews 2000; 44-46. [45] Damon DH, D'Amore PA, Wagner JA. Sulfated Glycosaminoglycans Modify Growth Factor-Induced Neurite Outgrowth In PC12 Cells J Cell Physiol 1988; 135: 293-300. [46] Lesma E, Di Giulio AM, Ferro L, Prino G, Gorio A. Glycosaminoglycans In Nerve Injury: 1. Low Doses Of Glycosaminoglycans Promote Neurite Formation J Neurosci Res 1996; 46: 565-571. [47] Dudas B, Rose M, Cornelli U, Hanin I. Low Molecular Weight Glycosaminoglycan C3 Attenuates AF64A-Stimulated, Low-Affinity Nerve Growth Factor ReceptorImmunoreactive Axonal Varicosities In The Rat Septum Brain Res 2005; 1033: 34-40. [48] Barnett MW, Fisher CE, Perona-Wright G, Davies JA. Signalling By Glial Cell LineDerived Neurotrophic Factor (GDNF) Requires Heparan Sulphate Glycosaminoglycan J Cell Sci 2002; 115: 4495-4503. [49] Kisilevsky R, Lemieux LJ, Fraser PE, Kong X, Hultin PG, Szarek WA. Arresting Amyloidosis In Vivo Using Small-Molecule Anionic Sulphonates Or Sulphates: Implications For Alzheimer's Disease Nat Med 1995; 1: 143-148. [50] Sigurdsson EM, Lorens SA, Hejna MJ, Dong XW, Lee JM. Local And Distant Histopathological Effects Of Unilateral Amyloid-Beta 25-35 Injections Into The Amygdala Of Young F344 Rats Neurobiol Aging 1996; 17: 893-901.

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[51] Ma Q, Dudas B, Hejna M, Cornelli U, Lee JM, Lorens S, Mervis R, Hanin I, Fareed J. The Blood-Brain Barrier Accessibility Of A Heparin-Derived Oligosaccharides C3 Thromb Res 2002; 105: 447-453. [52] Vincent T, Molina L, Espert L, Mechti N. Hyaluronan, A Major Non-Protein Glycosaminoglycan Component Of The Extracellular Matrix In Human Bone Marrow, Mediates Dexamethasone Resistance In Multiple Myeloma Br J Haematol 2003; 121: 259-269. [53] Cartel NJ, Post M. Abrogation Of Apoptosis Through PDGF-BB-Induced Sulfated Glycosaminoglycan Synthesis And Secretion Am J Physiol Lung Cell Mol Physiol 2005; 288: L285-L293. [54] Ishikawa Y, Kitamura M. Inhibition Of Glomerular Cell Apoptosis By Heparin Kidney Int 1999; 56: 954-963. [55] Bose P, Black S, Kadyrov M, Weissenborn U, Neulen J, Regan L, Huppertz B. Heparin And Aspirin Attenuate Placental Apoptosis In Vitro: Implications For Early Pregnancy Failure Am J Obstet Gynecol 2005; 192: 23-30. [56] Karti SS, Ovali E, Ozgur O, Yilmaz M, Sonmez M, Ratip S, Ozdemir F. Induction Of Apoptosis And Inhibition Of Growth Of Human Hepatoma Hepg2 Cells By Heparin Hepatogastroenterology 2003; 50: 1864-1866. [57] Li HL, Ye KH, Zhang HW, Luo YR, Ren XD, Xiong AH, Situ R. Effect Of Heparin On Apoptosis In Human Nasopharyngeal Carcinoma CNE2 Cells Cell Res 2001; 11: 311-315. [58] Berry D, Lynn DM, Sasisekharan R, Langer R. Poly(Beta-Amino Ester)S Promote Cellular Uptake Of Heparin And Cancer Cell Death Chem Biol 2004; 11: 487-498. [59] Pumphrey CY, Theus AM, Li S, Parrish RS, Sanderson RD. Neoglycans, Carbodiimide-Modified Glycosaminoglycans: A New Class Of Anticancer Agents That Inhibit Cancer Cell Proliferation And Induce Apoptosis Cancer Res 2002; 62: 37223728. [60] Manaster J, Chezar J, Shurtz-Swirski R, Shapiro G, Tendler Y, Kristal B, Shasha SM, Sela S. Heparin Induces Apoptosis In Human Peripheral Blood Neutrophils Br J Haematol 1996; 94: 48-52. [61] Vuillermoz B, Khoruzhenko A, D'Onofrio MF, Ramont L, Venteo L, Perreau C, Antonicelli F, Maquart FX, Wegrowski Y. The Small Leucine-Rich Proteoglycan Lumican Inhibits Melanoma Progression Exp Cell Res 2004; 296: 294-306. [62] Bali JP, Cousse H, Neuzil E. Biochemical Basis Of The Pharmacologic Action Of Chondroitin Sulfates On The Osteoarticular System Semin Arthritis Rheum 2001; 31: 58-68.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp. 99-123

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter IV

Low Density Lipoprotein ReceptorRelated Protein 1 (LRP1): One of the Hallmarks ofAlzheimer’s Disease and Other Complex Degenerative Processes Christiane Gläser(1,*), Gerd Birkenmeier(2), Susanne Schulz(1,3) and Klaus Huse(4) (1)

Institute of Human Genetics and Medical Biology, University of Halle, Halle, Germany (2) Institute of Biochemistry, University of Leipzig, Leipzig, Germany (3) Department of Medicine III, University of Halle, Halle, Germany (4) Leibniz Institute for Age Research - Fritz Lipmann Institute, Jena, Germany

Abstract Susceptibility to Alzheimer´s disease (AD) is governed by multiple factors. Remarkably, LDL receptor-related proteins (LRPs) and several of their numerous ligands were associated to AD. Alpha2-macroglobulin (A2M), apolipoprotein E (Apo E), but also amyloid precursor protein (APP) belong to the functionally and genetically interesting molecules involved in the complex degenerative processes resulting in AD. LRP1 (CD91) (MIM 107770) is a 4,544-amino acid protein containing a single transmembrane segment and is located on chromosome 12q13.1-12q13.3 within a region shown to be linked to AD. It consists of 84 exons and belongs to the largest human proteins and is highly evolutionary conserved. It could be demonstrated that several genomic variants of LRP1 were associated to AD but also to other degenerative diseases like atherosclerosis and cancer suggesting a complex role in fundamental cellular processes.

*

Correspondence: Dr. Christiane Gläser, Institute of Human Genetics and Medical Biology, Magdeburger Str. 2, D-06097 Halle, Phone +49-345-557 4296, Fax: +49-345-557 4293 e-mail: [email protected]

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Christiane Gläser, Gerd Birkenmeier, Susanne Schulz and Klaus Huse LRP1 functions as a clearance receptor for several ligands, including amyloid ß (Aß), and mediates signaling pathways affecting the processes of neurite outgrowth and calcium influx. While clearance of Aß diminishes the extracellular Aß-load the interaction with APP may enhance formation of Aß. LRP1 is expressed in brain, blood vessels as well as in endothelial cells of the brain-blood-barrier mediating the transcytosis of Aß between blood circulation and brain. Internalization via LRP1 concerns also extracellular proteases and protease-inhibitor complexes involved in Aß degradation. In AD as well as in other diseases genetic variations and structure-caused failure of LRP1 leading to dysfunctions as well as alteration in the expression of LRP1 ligands may determine common degenerative processes. Age-related changes in the level of LRP1 and its ligands may increase the risk for degenerative diseases. The modulation of LRP1 and its ligands by cytokines and growth factors was detected in and outside the brain. There are indications that also inflammatory processes play an important role in the development of degenerative diseases.

Abbreviations AD Aß α1-PI BACE1 CAD C. elegans CNS D. melanogaster EGF IDE IL LPS MMP NCBI NEP NPxY PAI-1 PDGF RAP u-PA t-PA TFPI HLA-DR

Alzheimer`s Disease amyloid ß protease inhibitor-1 (PI) ß site amyloid beta A4 precursor protein-cleavage enzyme coronary artery disease Caenorhabditis elegans central nervous system Drosophila melanogaster epidermal growth factor insulin-degrading enzyme interleukin lipopolysaccharide matrix metalloprotease National Center for Biotechnology Information neprilysin, membrane metalloendopeptidase (MME) amino acid motif asparagine-proline-x-tyrosine plasminogen activator-inhibitor-1 (PAI1) platelet-derived growth factor low density lipoprotein receptor-related protein-associated protein 1 (LRPAP1) plasminogen activator urinary (PLAU) plasminogen activator tissue (PLAT) tissue factor pathway inhibitor human leucocyte antigens-DR locus

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Common Features of Alzheimer´s Disease To date, the following four main risk markers have been characterized and related to Alzheimer´s disease (AD): amyloid precursor protein (APP, chromosome 21), apolipoprotein E (Apo E, chromosome 19), presenilin-1 (PSEN1, chromosome 14) and presenilin-2 (PSEN2, chromosome 1). It has been suggested that other genetic loci mapped to chromosome 10, 12, and 20, - including the polymorphic genetic variants of alpha-2 macroglobulin (A2M, chromosome 12) and its receptor the low density lipoprotein receptor-related protein (LRP1, chromosome 12), as well as to the mitochondrial genome, contribute to neurodegenerative processes (for review see Tanzi and Bertram, 2005).

Amyloid Precursor Protein The widely expressed cell surface protein, amyloid precursor protein (APP), in particular its proteolytic fragment amyloid ß (Aß) produced by γ-secretase cleavage, has been identified as playing a role in the formation of the plaque core in AD patients and also in older patients with Down syndrome (Masters et al., 1985). Investigations have described that different APP isoforms (Sandbrink et al., 1994) are created by alternative splicing (Yoshikai et al., 1990). Moreover, several mutations within the APP gene were found in familial AD, which denotes APP as being a significant candidate gene. Under physiological conditions clearance and degradation of soluble APP and Aß is mediated by an efficient “cargo” system, including LRP1 and its ligand A2M (Kounnas et al., 1995, Narita et al., 1997). And von Arnim et al. (2005) could demonstrate that LRP1 functions as a novel ß-secretase (BACE1) substrate.

Apolipoprotein E Apo E is an integral part of several lipoproteins involved in the lipid metabolism (Mahley 1988) and it is inherited in three common alleles, ε2, ε3, ε4 (Strittmatter et al., 1993). The Apo E ε4 allele is strongly associated with an increased amyloid burden in AD while Apo E ε2 considerably decreases the risk for AD (Hyman, 1996). The Apo E ε4 isoform was more frequently found in AD patients and was strongly related to a higher risk for late-onset familial AD and sporadic AD (Lendon et al., 1997; Pericak-Vance et al., 1997; Craig et al., 2004).

Presenilin 1 and 2 PSEN1 and PSEN2 are different in gene structure but display similar expression patterns in tissues and intracellular localization (Kovacs et al. 1996). PSEN1 and PSEN2 represent the fundamental features of a γ-secretase (Li et al., 2000) which is responsible for the APP cleavage producing Aß. Mutations found in PSEN1 and PSEN2 that result in functional

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aberration are considered to be the most common cause of familial AD (Berezowska et al., 2005).

Putative Role of LRP1 in Alzheimer´s Disease The Lipoprotein Receptor Family The low-density lipoprotein receptors are comprised of a family of cell-surface receptors which recognize multiple, structurally diverse extracellular ligands and internalize them for degradation by lysosomes (Hussain, 2001; Howell and Herz, 2001, Gliemann, 1998). They are also considered to be recruiting receptors and are able to interact with other proteins for signalling, realized by their cytoplasmic domains. The low-density lipoprotein receptor LDLR is the prototype of this family, whose paralogous members in the human genome are listed in Table 1. Most of these genes also have their orthologs in other vertebrates. Members of the family are even found in D. melanogaster and C. elegans. As the results of several duplications, deletions and subsequent alterations the human proteins are evolutionary distant (Figure 1) and their genes are scattered throughout the human genome. All proteins contain four major structural modules: variable numbers (between two and eleven) of cysteine-rich complement-type repeats, EGF-like repeats, a small cytoplasmic domain, and a membranespanning domain. They serve very different functions in distinct physiological systems among them are lipoprotein metabolism, vitamin transport, virus infection, fibrinolysis, angiogenesis, protease clearance, and intercellular communication. Mutations in these different genes, therefore, cause very different phenotypes. Mutations in the LDLR, for instance, which is mainly responsible for the control of cholesterol metabolism, cause familial hypercholesterolemia and premature coronary artery disease. Several of these types of mutations have been described including missense, some that affect the splice site and expression-relevant ones in the LDLR promoter region. With respect to AD it is noteworthy to mention that alterations in lipoprotein and cholesterol metabolism have been linked to brain Aß levels. Kuo et al. (1998) described that there is a correlation between LDL cholesterol and total serum cholesterol as regards to the amounts of Aß 1-42 in the brains of patients with AD and also reported that receptors involved in cholesterol homeostasis and lipoprotein metabolism are putatively and pathogenetically relevant. LRP2 (megalin) is a major receptor in the proximal tubules absorptive epithelial cells and also functions as an antigenic determinant for Heymann nephritis in rats. It also binds cubilin, which is the receptor for the intrinsic factor complex in vitamin B12, thus providing an uptake mechanism for dietary vitamin B12. Furthermore, homozygous knockout mice manifested abnormalities in epithelial tissues e.g. lung and kidney and died perinatally from respiratory insufficiency (Willnow et al., 1996). This has been suspected to be caused by an insufficient cholesterol supply to the brain; these animals also showed impaired brain development. It has also been suggested that megalin mediates cellular uptake and transport of apolipoprotein J, which is able to bind Aß and mediates transport of this protein across the blood-brain barrier and the blood-cerebrospinal fluid barrier (Zlokovic et al., 1996). The functional importance of

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individual receptors may lie in their differential tissue expression. Most of the LRP family members are tissue-specific expressed and some of them are highly expressed in the brain. This is the case concerning LRP8 which is predominantly expressed in brain and is also an apoliprotein E receptor. Although this has not yet been confirmed by independent studies, one synonymous polymorphism in LRP8 has been identified showing a difference in its allele frequencies between AD patients and controls (Ma et al., 2002). The expression regulation of these receptors occurs at the transcriptional level in different ways, for instance, expression of LDLR is regulated by intracellular sterol concentration. However, other members of the family are not regulated by sterols. Equally notable is that all the receptors are regulated by many hormones and growth factors, but the mechanisms of regulation involving hormones are not fully understood. In this context the most frequent studied member of the LRP family is LRP1.

LRP3 LRP12 LRP10 LRP11 LDLR VLDLR LRP8 LRP1 LRP1B LRP2 LRP5 LRP6 SORL1

Figure 1. Evolutionary relationship of the human paralogous members of the LRP protein family. The phylogenetic tree was constructed using ClustalW (Thompson et al., 1994)

LRP1: A Multi-ligand Clearance Receptor The binding of more than 30 different ligands to LRP1 suggests that this receptor affects complex degenerative cellular processes which proceed the onset of AD, Parkinson disease, coronary artery disease or cancer (Hussain 2001; Myllykangas et al., 2000; Boucher at al., 2002; May et al., 2003; Strickland et al., 2003). All these degenerative diseases could be described as cellular dysregulations resulting in the pathogenic accumulation of diverse risk factors.

Table 1: Database summary of the members of the LRP family

Gene symbol

alternative symbols

LDLR

low density lipoprotein receptor precursor

VLDLR LRP1

LRP, A2MR, APR, APOER, CD91

LRP1B

LRP-DIT

LRP2

gp330, megalin

LRP3 LRP5

LR3, LRP7

LRP6 LRP8

APOER2

OMIM

Chromosomal location

mRNA RefSeq

protein RefSeq

606945

19p13.2

NM_000527

NP_000518

very low density lipoprotein receptor

192977

9p24

NM_003383

NP_003374

low density lipoprotein receptor-related protein 1

107770

12q13.1-q13.3

NM_002332

NP_002323

low density lipoprotein receptor-related protein 1B

608766

2q22.1-2q22.2

NM_018557

NP_061027

low density lipoprotein receptor-related protein 2

600073

2q31.1

NM_004525

NP_004516

low density lipoprotein receptor-related protein 3

603159

19q13.11

NM_002333

NP_002324

low density lipoprotein receptor-related protein 5

603506

11q13.2

NM_002335

NP_002326

low density lipoprotein receptor-related protein 6

603507

12p13.2

NM_002336*

NP_002327

low density lipoprotein receptor-related protein 8

602600

1p32.3

NM_004631

NP_004622 NP_054764

LRP10

low density lipoprotein receptor-related protein 10

14q11.2

NM_014045

LRP11

low density lipoprotein receptor-related protein 11

6q25.1

NM_032832

NP_116221

LRP12

low density lipoprotein receptor-related protein 12

8q22.3

NM_013437

NP_038465

11q23.3

NM_003105

NP_003096

SORL1 *

gene product

SORLA1, SORLA, LR11

the major mRNA isoforms only

sortilin-related receptor containing LDLR class

602005

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

105

The domain structure of LRP1 has been described in detail (Herz et al., 1988, Brown et al., 1991; Gaeta et al., 1994). Obviously, its huge size (600 kD) enables the binding of diverse ligands such as proteins, peptides and drugs to take place independently and simultaneously. To carry out functional studies the first attempts were made to create LRP1 knock-out mice. (Herz et al., 1992). However, these experiments failed due to impaired embryonic implantations. Now, new approaches involving short interfering RNA (siRNA) techniques were used and hence a selective decline in LRP1 expression was achieved (Laatsch et al., 2004). It has been shown that a decrease in LRP1 levels significantly reduced LRP1-mediated ligand uptake and degradation (Li and Bu, 2003). As a result of the proposed "cargo" function, it is not surprising that LRP1 is expressed in almost all cells with regards to regulating ligand homeostasis and most importantly, on cells of the vasculature, which enables the transcytosis of ligands. LRP1 ligands fall into several functional categories: (i) Pericellular proteolysis (e.g. A2M; α1-PI, MMPs, u-PA, t-PA, PAI-1); (ii) Lipid metabolism (Apo E, Lipoprotein lipase); (iii) Blood coagulation (Factor IXa, Factor VIIIa, TFPI, Antithrombin III; Heparin cofactor); (iv) Inflammation/immune response (complement factors, chaperons, beta2-integrins) (v) Drugs (suramin, saponin) and (vi) Membrane or intracellular scaffold proteins (Fe65, Disabled, PDGF-receptor, G-proteins, APP). It is well known that the deposition of Aß is a critical pathological feature in AD. A recent study has suggested that improper clearance of Aß is as important as Aß production in amyloid deposition (Glabe, 2001). Moreover, there are several interfaces where LRP1 may determine the balance between Aß synthesis and clearance mechanism:

LRP1 and Pericellular Proteolysis Lowering Aß levels may be achieved by inhibiting its generation from APP or by promoting its clearance by transport or degradation and to date three major proteases have been identified in playing a role in degrading Aß. They are as follows: the neutral endopeptidase, neprilysin (NEP), is located on the cell surface which allows hydrolysis of peptides on the extracellular side including Aß 1-40 (Howell et al., 1995) and Aß 1-42 (Iwata et al., 2000). In vivo inhibition of neprilysin by specific inhibitors results in an accumulation of endogenous Aß (Iwata et al., 2000). It has been suggested that age-related decreases of the neprilysin could lead to increased brain concentrations of Aß, plaque formation, and AD (Newell et al., 2003). A second important protease is the insulin-degrading enzyme (IDE); a zinc-containing metalloprotease found in the cytosol, on the cell surface and in the extracellular space (Qiu et al., 1996; Qiu et al., 1998). It cleaves small proteins many of them share the property to form amyloid fibrils, e.g. Aß, insulin, glucagon and amylin (Farris et al., 2003). Both NEP and IDE mediate degradation of soluble Aß but have less ability to degrade Aß once it becomes insoluble or oligomeric (Selkoe, 2001). The only protease that is capable of degrading soluble and fibrilar Aß seems to be plasmin (Tucker et al., 2002). In brain, tPA, uPA and plasminogen are present in low concentrations. Upregulation of plasminogen activators by aggregated Aß indicates that the

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plasmin system is activated in response to Aß deposition. Thus, plasmin confers neuroprotection which may continue until upregulation of the plasmin system is exhausted during the course of the disease (Ledesma et al., 2000). These findings are supported by a recent report showing an association of a single nucleotide polymorphism in the uPA gene with elevated Aß 1-42/40 (Ertekin-Taner at al., 2005). There are indications of a general proteases deficiency in the brain and blood of AD patients (Aoyagi et al., 1992), which has been found to be similar in healthy but elderly patients (Aoyagi et al., 1994). Although, so far a direct link of LRP1 to regulation of NEP and IDE metabolism has not yet been established, it can be anticipated that the activities of both enzymes are regulated by protease inhibitors as it is the case with the pan-protease inhibitor A2M and plasmin (Tucker et al., 2000). The inhibitory action of A2M is mediated by a unique trapping mechanism (SottrupJensen, 1989). Proteases are sterically trapped but retain their activity toward small proteins and peptides. Accompanying conformation changes make A2M ready to accommodate such peptides and to bind to LRP1 for endocytosis (Ashcom et al., 1990). A2M-protease complexes have been shown to degrade bound Aß initiating extracellular amyloid depletion and to continue intracellular lysosomal Aß degradation following receptor-mediated uptake of A2M-protease-Aß complexes (Qiu et al., 1996). This process is very unique and seems to be a common mechanism to down-modulate pathologically elevated levels of bioactive peptides such as Aß or other growth factors (Birkenmeier, 2001). It has recently been shown that the administration of small proteases such as trypsin or chymotrypsin to human blood leads to degradation of radiolabeled Aß mediated by formation of A2M-protease-Aß complexes (Lauer et al., 2001). Up-regulation of Aß catabolism via proteases delivery could probably reduce the risk of developing AD by preventing Aß accumulation in the brain and in the vasculature. Thus, clearance of Aß strongly depends on the presence of extracellular proteases as well as the level of its vehicle, A2M. The plasma concentration of A2M showed significant individual variations ranging from approximately 50mg/100 ml to 500mg/100ml (Birkenmeier et al., 2003). The reason for this diversity is not yet known, but is assumed to be related to different promoter activity. Most interestingly, a steep decline of the A2M level was manifested at an age when late-onset AD starts to develop (Figure 2). Since AD develops slowly over years, a progressive exhaustion of proteases and A2M in combination with an altered modulation of LRP1 would have a tremendous impact on the clearance system of AD-related ligands. Thus, one can speculate that a decreased A2M level in blood is a risk factor for AD. Various attempts to associate the level of A2M to different polymorphisms in the A2M gene have failed and genetic linkage and association studies of polymorphisms with AD have all provided conflicting results (Saunders et al., 2003). However, it cannot be excluded that known variants in A2M might be linked to pathogenic mutations/polymorphism in the A2M gene or in its neighbourhood that have not yet been identified (Saunders and Tanzi, 2003).

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

107

Total A2M in plasma (mg/100ml)

600 males females

500

400

300

200

100

0 0

20

40

60

80

100

Age (years)

Figure 2. Distribution of A2M level dependent on age and gender in a population of 400 healthy individuals. The concentration of total A2M was determined by ELISA using the test kits MacroNat (BioMac, Leipzig). Females (open circles), males (black circles) (with permission from Exp Neurol. 2003,184:153-61).

LRP1 and APP LRP1 interacts with APP and its expression facilitates APP processing via the amyloidogenic pathway (Kounnas et al., 1995). This is because receptor-mediated endocytosis brings APP into close proximity to the APP-cleaving enzyme, ß-secretase, which results in elevated generation and secretion of Aß (Ehehalt et al., 2003). Thus, dynamic interactions of APP with its clearance receptors determine the amyloid burden in the extracellular space. This is corroborated by recent results showing that expression of LRP1B, a homologue of LRP1, which also binds APP, produces less Aß probably due to the lower rate of endocytosis when compared to LRP1 (Cam et al., 2004). Similar effects were seen after treating cells with RAP, which blocks the binding of ligands to LRP1 (Ulery et al., 2000). Thus, the contribution of LRP1 to AD is complex because it influences both the production and the clearance of Aß. In addition to recognizing numerous extracellular ligands with the aid of the LRP1 ectodomain, the intracellular domain of LRP1 contains binding sites for many adaptor and scaffold proteins (Gotthardt et al., 2000). Phosphorylated NPxY motifs act as anchors for Fe65, Dab, Jip and Shc and are found in both the cytoplasmic tail of LRP1 as well as in APP. Tyrosine phosphorylation of LRP1 was found to result from interaction with the plateletderived growth factor BB which creates docking sites for Shc. By subsequent phosphorylation, different signalling pathways involving Ras and c-Myc are initiated (Loukinova et al., 2002).

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Similarities between LRP1 and APP also concern the proteolysis of the extra- and intracellular domain. Soluble APP ectodomains are obtained by the action of α- or ßsecretase, whereas the shedding of LRP1 is caused by an unknown metalloprotease (Quinn et al., 1999). Analogously to APP processing, the LRP1 cytoplasmic domain is cleaved by a γsecretase-like activity (May et al., 2002). The released proteolytic products may modulate signalling or may travel to other compartments of the cell.

LRP and ApoE It has been shown that ApoE binds to Aß and the isoform-specific effects of ApoE are related to this action with regards to fibrillogenesis and sequestration (Strittmatter et al., 1993; Sanan et al. 1994; Castano et al., 1995; Carter 2005). Cellular uptake of ApoE is mediated by LRP1, which also mediates the effect of ApoE on neurite outgrowth (Beisiegel et al., 1989; Nathan et al., 2002; Gylys et al. 2003).

LRP1 and Ligand Transcytosis at Blood-Brain-Barrier The expression of LRP1 in brain cells, vessel walls and in brain capillary endothelium has been well documented (Shibata et al., 2000). Late-onset AD patients, who do not have increased Aß production or APP overexpression, are likely to exhibit (i) a failure in Aß clearance from the brain to plasma, (ii) defects in Aß degradation in the CNS or (iii) an increased influx of circulating Aß into the CNS. Although the level of free Aß in extracellular brain fluid is higher than that found in plasma, the absolute amounts of Aß in body fluid exceeds the Aß level in brain fluid by factor 10. Thus, body fluids provide a large reservoir for accommodation and degradation of excessive Aß. Two main receptors are involved in shuttling Aß through the blood-brain barrier between both compartments: (i) AGER (advanced glycosylation end product-specific receptor) mediates influx of Aß into the brain (Mackic et al., 1998) and (ii) LRP1 mediates efflux of Aß into circulation (Shibata et al., 2000). In contrast to the brain, uptake and degradation of Aß in blood seems to be chaperoned by A2M or ApoE, two main ligands of LRP1.

LRP1 and Inflammation In AD and APP transgenic mouse models of AD LRP1 is down-regulated (Shibata et al., 2000). However, little information is available on factors that affect LRP1 expression in the brain. Considerable evidence which has been gained over the past decade has led scientists come to the conclusion that neuroinflammation is associated with AD. The main cellular players in inflammatory processes are microglia and the astrocytes (Akiyama et al., 2000). LRP1 is expressed in both cell types, but expression varies with regards to the state of the cellular activation (Hussaini et al., 1999).

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

109

Microglial cells e.g. can be activated by Aß, LPS or other cytokines and they respond to the following: reactive oxidant species, expression of NFkappaB, inflammatory cytokines and HLA-DR (Streit, 2004). Expression of IL-1, α1-antichymotrypsin and complement factors in the AD brain is another indication of ongoing inflammatory processes which take place during the development of AD (Shuguang and Janciauskiene, 2002; Mrak and Griffin, 2001). LPS decreases expression of LRP1 in monocyte lineage cells (LaMarre et al., 1993) and interferon-gamma was found to up-regulate LRP1 and A2M in astrocytoma cell lines (Businaro et al., 1997). Furthermore, LRP1 is a receptor for chaperoned peptides trafficking immunogenic peptides into antigen presenting cells for presentation (Binder et al., 2000). Thus, inflammatory processes will most likely affect the function of LRP1 in the brain and in the blood-brain-barrier, as well. Recent data have suggested that reduced LRP1 expression is a contributing risk factor for AD, possibly because it impedes the clearance of Aß by ApoE and A2M (Kang et al., 2000). Thus, conditions to increase LRP1 expression in the brain could systemically exert beneficial effects on the prevention of AD.

Expression of LRP1 in Alzheimer´s Disease and in Related Degenerative Diseases At present, only limited experimental data have been published describing the in vivo expression of LRP1 with regards to degenerative diseases. Most expression studies have been done on transgenic animals or on post mortem material. Handschug et al. (1998) first described results on in vivo expression of LRP1 in humans by measuring the LRP1 transcripts obtained from patients’ blood monocytes. A mild age-dependent increase in LRP1 expression within a group of healthy controls was recognized. LRP1 transcripts increased from 117.7 ag/cell to 150.2 ag/cell (attogram/cell) in healthy controls ranging in ages from 20-60r, respectively. Surprisingly, Schulz et al. (2003) could show that a high transcription rate was paralleled by a decrease in LRP1 protein concentration and vice versa. Furthermore, LRP1 gene and protein expression were shown to follow a circadian- and gender-specific rhythm, which have to be considered in studies investigating the LRP1 in vivo function. A similar expression profile was also corroborated for disease-related expression studies in patients with degenerative coronary atherosclerosis. A disease-associated significant increase in the LRP1 gene-expression in patients (223 ag/cell) versus controls (122,3 ag/cell) was associated with low LRP1 protein levels in the patient group (1.6 pg/cell) versus controls (6 pg/cell). These data suggest that low LRP1 protein levels are tried to be functionally compensated by a dramatically increased LRP1 transcription rate, acting as an incomplete in vivo feed back mechanism. Motivated by these results, we have done a comparative study of in vivo LRP1 gene expression in patients with degenerative diseases, AD and coronary artery disease (CAD), and compared our results to healthy controls. The impact of age, gender and circadian rhythm on LRP1 expression was taken into account in the statistical analysis (detailed description of materials and methods can be requested from the authors).

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In the whole group of 97 individuals a mean LRP1-mRNA expression of 187.20 ag/cell was detected (Table 2). AD patients showed the highest LRP1 gene expression levels (290.96 ag/cell) followed by patients with coronary degenerative disease (174.49 ag/cell). The healthy controls revealed the lowest levels of LRP1-mRNA expression among all of the three subgroups (158.79 ag/cell). The differences among the three patient groups were statistically significant (Kruskal-Wallis test, p=0.015). A correlation between age and LRP1 gene expression was not detected in any of the three groups (controls: p=0.453, CAD: p=0.650, AD: p=0.871) nor was a correlation found between gender and expression (controls: p=0. 348, CAD: p=0.123, AD: p=0.581); this suggests that the subgroup specific difference in the LRP1-mRNA level is really disease-related. The 83.2 % higher expression of LRP1 found in AD patients indicates that the disordered metabolism of patients suffering from this degenerative disease probably activates mechanisms to help compensate for the loss of function at the protein level. The molecular mechanism causing this inverse relation between the levels of LRP1 transcript and protein is not fully understood. It has been suggested that feed-back control mechanisms do exist (up-regulation of mRNA) but the translation into a protein may be blocked. Unravelling the underlying mechanism will be a challenge concerning therapeutic intervention. It is noteworthy that this is the first report demonstrating a relationship between a cellular blood marker and AD. Further studies are needed to test the feasibility of blood LRP1 as a marker for the onset, the severity or the susceptibility to develop AD. Table 2: Results of a study on in vivo gene expression of LRP1 in AD patients compared with patient suffering from (degenerative) coronary artery disease (CAD) versus healthy controls. There was neither a correlation between LRP1 gene expression and gender nor age.

Number Male Age SD Age min.-max. LRPgene expression (ag/cell) SD Correlation* age/LRP1 expression P Correlation* gender/LRP1 expression P *

All individuals

controls

CAD patients

AD patients

97 71 59.7 7.55 54-86 187.20 80.43

20 18 58.9 3.39 54-65 158.79† 52.12 0.178

68 49 58.4 4.09 54-68 174.49† 66.17 -0.056

9 4 71 8.62 54-86 290.96† 126.83 0.064

0.453 0.222

0.650 0.190

0.871 -0.214

0.348

0.123

0.581

Pearson. † The patient groups differ significantly in their expression levels: p=0.015 (Kruskall-Wallis).

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

111

Genetic Predisposition to Alzheimer’s Disease While investigating the possible genetic causes of AD, a variety of different genes was found to be involved in the pathogenesis of this degenerative disease (Bertram and Tanzi, 2004; Williamson and LaRusse, 2004). The autosomal dominant early onset AD was shown to be associated with genes coding for presenilin-1 and -2 as well as amyloid precursor protein. Mutations in these genes lead to the main clinical feature of AD, which is characterized by an increased generation of Aβ and amyloid deposition. However, genomic variations in these genes have been proven to be fully penetrant, but they are very rare events accounting for only 1% to 2% of all AD cases (Gaskell and Vance, 2004). On the other hand, genetic variations of the Apo E lead to an increased risk of late-onset sporadic and familial AD. The ε4 allele of this gene has been established worldwide as a genomic variant predisposing for AD and this allele has been demonstrated to increase for the risk of developing AD in a dose-dependent fashion (Corder et al., 1993). Since the gene encoding ApoE is highly polymorphic the influence of other single nucleotide polymorphisms on the risk of developing AD was studied. However, only a weak effect concerning other SNPs independent of ε4 allele could be demonstrated (Nicodemus et al., 2004). Since Apo E is reported to account for less than 50% of the genetic effects in AD it implies that the onset as well as the progression of the complex disorder AD is triggered by additional genetic and environmental factors which have already been suggested by Sjogren et al. (1952) and St George-Hyslop et al. (1990). A number of genome wide screens have been published investigating the genetic causes of AD. These studies used linkage- or association-based evaluation procedures and reported on genetic locations of interest on different chromosomes (for review see Bertram and Tanzi, 2004). The LRP1 locus on chromosome 12 has also been shown in different studies to be associated with a late-onset form of familial AD (OMIM 602096). Interestingly, a full genome scan for late onset AD which included 292 affected siblings revealed linkage of the locus on chromosome 12 with similar lod scores as for APP (Kehoe et al., 1999). As of June 2005 128 genomic variants of the LRP1 gene have been reported on in dbSNP database of the NCBI Entrez system. Numerous clinical studies were conducted in order to evaluate possible associations of these genomic variants of LRP1 with AD, however, results are conflicting and are controversially discussed (Table 3) (for review see Gläser et al., 2004). Nevertheless, ethnicity and population-specific differences in genotype distributions were shown for a variety of these genomic variants (Gläser et al., 2004) and may account at least in part for the reported conflicting results. To date, only a few studies have been conducted investigating the possible disease related functional consequences of genomic variants of LRP1 (Schulz et al., 2002; Kang et al., 2000). A polymorphism in the promoter region of the gene (c.1-25C>G) has been proven to increase the LRP1 expression on a transcriptional level due to the creation of a CG-box, which is recognized by the SP1 transcription factor (Schulz et al., 2002). For another polymorphism in exon 3 (c.766C>T) a significant increase in LRP1 level could be described for T-allele carriers suffering from AD (Kang et al., 2000).

Table 3: Published important clinical studies evaluating AD related to genomic variants of LRP1. Genomic Variant 5’ Tetranucleotidpolymorphism

Individuals investigated French: 144 sporadic late onset AD patients ↔ 153 controls Caucasians: 182 AD patients ↔ 118 controls French Caucasians: 600 AD patients ↔ 646 controls Americans: 168 AD patients ↔ 157 controls American Caucasians: 62 AD patients ↔ 282 controls American Whites: 216 sporadic late onset AD patients ↔ 106 controls 179 Familial multiplex late onset AD patients, 436 sporadic AD patients ↔ 240 controls Spaniards: 188 sporadic late onset AD patients ↔ 226 controls Japanese: 100 AD patients ↔ 246 controls North Irish: 219 AD patients ↔ 237 controls French Caucasians: 274 AD patients ↔ 290 controls American Whites: 505 late onset AD patients ↔ 522 controls

c.766C>T US Euorpean Whites: 157 late-onset AD patients ↔ 102 polymorphism in exon 3 controls Chinese: 143 AD patients ↔ 129 controls

Whites: 234 AD patients ↔ 103 controls American Whites: 432 AD patients ↔ 106 controls Whites: 558 AD patients ↔ 596 controls

Clinical association to AD Citations Significant decrease of 87bp-allele in AD patients Wavrant –DeVrieze et al., 1997 Significant increase of 87bp-allele in AD patients Lendon et al., 1997 Significant increase of 91bp-allele in AD patients Lambert et al., 1998 None Clathworthy et al., 1997 None Fallin et al., 1997 None Kamboh et al., 1998 None

Scott et al., 1998

None

Bullido et al., 2000

None None None None

Hatanaka et al., 2000 Mc Ilroy et al., 2001 Verpillat et al., 2001 Luedecking-Zimmer et al., 2003 Kang et al., 1997

Significant increase of CC-genotype in AD patients (more pronounced among AD patients with positive familial history of senile dementia Significantly decreased T-allele in AD patients diagnosed pathologically; no association in AD patients diagnosed clinically Significant increase of CC-genotype in AD patients, no correlation to age of onset Significant increase of TT-genotype in controls Increase of CC-genotype and C-allele in AD patients

Baum et al., 1998

Hollenbach et al., 1998 Kamboh et al., 1998 Lambert et al., 1998

Table 3: Published important clinical studies evaluating AD related to genomic variants of LRP1. (Continued) Genomic Variant Individuals investigated Clinical association to AD c.766C>T Caucasians: 225 neuropathologically confirmed AD patients Weak increase of CC-genotype in AD patients polymorphism in exon 3 ↔ 187 controls Japanese : 100 AD patients ↔ 246 controls Association with age of onset Spaniards: 305 sporadic AD patients ↔ 304 controls Weak increase of CC-genotype in AD patients in meta-analysis Caucasians : 212 AD patients ↔ 337 controls Increase of C-allele in controls Higher age of onset in C-allele carriers 133 late-onset AD patients ↔ 70 controls None Spaniards: 199 sporadic late-onset AD patients ↔ 243 None controls Taiwan Chinese: 82 AD patients ↔ 110 controls None North Irish: 219 AD patients ↔ 237 controls None French Caucasians: 274 AD patients ↔ 290 controls None A217V Northern French Caucasians: 648 AD patients ↔ 670 Weak increase of T-allele in controls polymorphism in exon 6 controls US Whites: 536 late-onset AD patients ↔ 511 controls None A775P mutation in exon 14 D2080N polymorphism in exon 39 D2632E mutation in exon 48 G4379S Mutation in exon 85

Citations Beffert et al., 1999 Hatanaka et al., 2000 Sanchez-Guerra et al., 2001 Kölsch et al., 2003 Woodward et al., 1998 Bullido et al., 2000

29 AD patients ↔ 22 controls

No carrier identified

Hu et al., 2000 Mc Ilroy et al., 2001 Verpillat et al., 2001 Wavrant-DeVrieze et al., 1999 Luedecking-Zimmer et al., 2003 Van Leuven et al., 2001

29 AD patients ↔ 22 controls

No carrier identified

Van Leuven et al., 2001

29 AD patients ↔ 22 controls

Only 1 carrier in control group

Van Leuven et al., 2001

29 AD patients ↔ 22 controls

No carrier identified

Van Leuven et al., 2001

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Brain (intracellular)

Brain (interstitial)

Blood

7 Aß

1 6

APP

4 8

10

5

11

A2M

11 LRP1

9

2

3

Figure 3. Schematic diagram of possible interventions by modulation of the LRP1-A2M axis of amyloid ß metabolism. (1)Aß processed via the amyloidogenic pathway (secretases) is released into the interstitial fluid for degradation by IDE, NEP or plasmin. (2) Soluble Aß is bound to proteolytically modified A2M by the action of proteases (e.g. plasmin) that mediates binding to LRP1 for endocytosis and lysosomal degradation (3). Soluble Aß (4) or A2M-Aß complexes (5) are transported via LRP1mediated efflux from the brain into the circulatory system. In blood, soluble Aß is subsequently degraded by proteases (6) or eliminated by LRP1-mediated endocytosis in conjunction with proteaseactivated A2M (9). Possible check points of intervention are the modulation of cytoplasmic binding of scaffold protein to LRP1/APP (10); increasing the expression of LRP1 (11) increasing the expression of A2M in brain and blood (7) and increasing the proteolytic potential in brain (1), and in blood (8) and (9) to support A2M-mediated elimination of Aß.

Clinical and Therapeutic Significance It seems indisputable that LRP1 is one of the most interesting candidate genes, not only for AD and other neurodegenerative diseases such as Parkinson disease but also for other degenerative processes affecting other organs, tissues and vessel-walls causing cellular dysfunctions as in CAD or cell degeneration as in cancer (Gläser et al., 2004). In current consolidated findings significant increased levels of LRP1-mRNA which correspond to a decrease in LRP1-protein expression could be a diagnostic marker in recognizing improper supply and/or disposal processes which are dangerous for cells, tissues and organs. Since an alteration in LRP1 expression is directly transmitted to the level of LRP1-ligands to be cleared in the blood, investigation should be done to determine whether or not a more timesaving analysis of LRP1 plasma ligands is to be preferred. Such a candidate ligand could be

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plasma A2M. It exists in two different forms, native A2M and transformed A2M (Birkenmeier, 2001). The latter is the receptor-recognizable species which can easily be determined by immunological assays (Birkenmeier and Stigbrand, 1993; Sinnreich et al., 2004). With respect to LRP1 and its Aß-clearing ligands possible therapeutic interventions should focus on (i) increasing the clearance capacity of LRP1 by elevating its peripheral expression, (ii) increasing the proteolytic activity in the brain and the blood circulation , (iii) increasing the level of A2M in blood and (iv) promoting the LRP1-mediated transfer of Aß from the brain to circulatory system. In addition to current trials and activities to tame AD progression with secretase inhibitors, inhibition of Aß-fibril formation or with vaccinations, the modulation of the LRP1-ligand system seems to be a promising approach (Figure 3).

Data Bases GeneCardsR, Weizman Institute of Science http://bioinfo.weizmann.ac.il/cardsbin/cardsearch.pl OMIMTM - Online Mendelian Inheritance in ManTM: http://www.ncbi.nlm.nih.gov/entrez/ query.fcgi?db=OMIM

References Akiyama H, Arai T, Kondo H, Tanno E, Haga C, Ikeda K. Cell mediators of inflammation in the Alzheimer disease brain. Alzheimer Dis Assoc Disord. 2000,14:47-53. Aoyagi T, Wada T, Kojima F, Nagai M, Harada S, Takeuchi T, Isse K, Ogura M, Hamamoto M, Tanaka K, et al. Deficiency of fibrinolytic enzyme activities in the serum of patients with Alzheimer-type dementia. Experientia. 1992,48:656-9. Aoyagi T, Wada T, Kojima F, Nagai M, Harada S, Takeuchi T. Age-dependent decreases in fibrinolytic enzyme activities in serum of healthy subjects. Biol Pharm Bull. 1994,17:348-51. Ashcom JD, Tiller SE, Dickerson K, Cravens JL, Argraves WS, Strickland DK. The human alpha 2-macroglobulin receptor: identification of a 420-kD cell surface glycoprotein specific for the activated conformation of alpha 2-macroglobulin. J Cell Biol. 1990,110:1041-8. Baum L, Dong ZY, Choy KW, Pang CP, Ng HK. Low density lipoprotein receptor related protein gene amplification and 766T polymorphism in astrocytomas. Neuroscience Letters. 1998,256:5-8. Beffert U, Arguin C, Poirier J. The polymorphism in exon 3 of the low density lipoprotein receptor-related protein gene is weakly associated with Alzheimers disease. Neuroscience Letters 1999,259:29-32. Beisiegel U, Weber W, Ihrke G, Herz J, Stanley KK. The LDL-receptor-related protein, LRP, is an apolipoprotein E-binding protein. Nature. 1989,341:162-4.

116

Christiane Gläser, Gerd Birkenmeier, Susanne Schulz and Klaus Huse

Berezovska O, Lleo A, Herl LD, Frosch MP, Stern EA, Bacskai BJ, Hyman BT. Familial Alzheimer's disease presenilin 1 mutations cause alterations in the conformation of presenilin and interactions with amyloid precursor protein. J Neurosci. 2005,25:3009-17. Bertram L, Tanzi RE. The current status of Alzheimer's disease genetics: what do we tell the patients? Pharmacol Res. 2004,50:385-96. Review. Binder RJ, Han DK, Srivastava PK. CD91: a receptor for heat shock protein gp96. Nat Immunol. 2000,1:151-5. Birkenmeier G. Targetting the proteinase inhibitor and immune modulatory function of human a2-macroglobulin. Mod Asp Immunbiol. 2001, 2:32-6. Birkenmeier G, Muller R, Huse K, Forberg J, Gläser C, Hedrich H, Nicklisch S,Reichenbach A. Human alpha2-macroglobulin: genotype-phenotype relation. Exp Neurol. 2003,184:153-61. Birkenmeier G, Stigbrand T. Production of conformation-specific monoclonal antibodies against alpha 2-macroglobulin and their use for quantitation of total and transformed alpha 2-macroglobulin in human blood. J Immunol Methods. 1993,162:59-67. Boucher P, Ducluzeau PH, Davelu P, Andreelli F, Vallier P, Riou JP, Laville M, Vidal H. Expression and regulation by insulin of low-density lipoprotein receptor related protein mRNA in human skeletal muscle. Biochim Biophys Acta. 2002,1588:226-31. Brown MS, Herz J, Kowal RC, Goldstein JL. The low density lipoprotein receptor-related protein: couble agent or decoy? Curr Opin Lipidol. 1991,2:65-72. Bullido MJ, Guallar-Castillon P, Artiga MJ, Ramos MC, Sastre I, Aldudo J, Frank A, Coria F, Rodriguez-Artalejo F, Valdivieso F. Alzheimer´s risk associated with human apolipoprotein E, alpha-2 macroglobulin and lipoproteinreceptor related protein polymorphisms: absence of genetic interactions, and modulation by gender. Neurosci Lett. 2000,289(3),213-6. Businaro R, Fabrizi C, Persichini T, Starace G, Ennas MG, Fumagalli L,. Lauro GM. Modulation of the alpha 2 macroglobulin receptor/low density lipoprotein receptor related protein by interferon-gamma in human astroglial cells. J Neuroimmunol. 1997,72:75–81. Cam JA, Zerbinatti CV, Knisely JM, Hecimovic S, Li Y, Bu G. The low density lipoprotein receptor-related protein 1B retains beta-amyloidprecursor protein at the cell surface and reduces amyloid-beta peptide production. J Biol Chem. 2004,279:29639-46. Carter DB.The interaction of amyloid-beta with ApoE. Subcell Biochem. 2005,38:255-72. Castano E.M., Prelli F., Wisniewski T., Golabek A., Kumar R.A., Soto C. and Frangione B. Fibrillogenesis in Alzheimer’s disease of amyloid beta peptides and apolipoprotein E. Biochem J. 1995,306:599–604. Clatworthy AE, Gomez-Isla T, Rebeck GW, Wallace RB, Hyman BT. Lack of association of a polymorphism in the low-density lipoprotein receptor-related protein gene with Alzheimer Disease. Arch Neurol. 1997,54,1289-92. Corder EH, Saunders AM, Strittmatter WJ, Schmechel DE, Gaskell PC, Small GW, Roses AD, Haines JL, Pericak-Vance MA. Gene dose of apolipoprotein E type 4 allele and the risk of Alzheimer's disease in late onset families. Science. 1993,261:921-3.

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

117

Craig D, Hart DJ, McCool K, McIlroy SP, Passmore AP. Apolipoprotein E e4 allele influences aggressive behaviour in Alzheimer's disease. J Neurol Neurosurg Psychiatry. 2004,75:1327-30. Ehehalt R, Keller P, Haass C, Thiele C, Simons K. Amyloidogenic processing of the Alzheimer beta-amyloid precursor protein dependson lipid rafts. J Cell Biol. 2003,160:113-23. Ertekin-Taner N, Ronald J, Feuk L, Prince J, Tucker M, Younkin L, Hella M, JainS, Hackett A, Scanlin L, Kelly J, Kihiko-Ehman M, Neltner M, Hersh L, Kindy M,Markesbery W, Hutton M, de Andrade M, Petersen RC, Graff-Radford N, Estus S,Brookes AJ, Younkin SG. Elevated amyloid beta protein (Abeta42) and late onset Alzheimer's disease areassociated with single nucleotide polymorphisms in the urokinase-type plasminogen activator gene. Hum Mol Genet. 2005,1:447-60. Fallin D, Kundtz A, Town T, Gauntlett AC, Duara F, Barker W, Crawford F, Mullan M. No association between the low density lipoprotein receptor-related protein (LRP) gene and late-onset Alzheimer´s disease in a community-based sample. Neuroscience Letters. 1997,233,145-147. Farris W, Mansourian S, Chang Y, Lindsley L, Eckman EA, Frosch MP, Eckman CB,Tanzi RE, Selkoe DJ, Guenette S. Insulin-degrading enzyme regulates the levels of insulin, amyloid beta-protein, and the beta-amyloid precursor protein intracellular domain in vivo. Proc Natl Acad Sci U S A. 2003,100:4162-7. Gaeta BA, Borthwick I, Stanley KK. The 5'-flanking region of the alpha 2MR/LRP gene contains an enhancer-like cluster of Sp1 binding sites. Biochim Biophys Acta. 1994,1219:307-13. Gaskell PC Jr, Vance JM. Alzheimer's disease genes and genetic testing in clinical practice. JAAPA. 2004,17:25-6. Review. Glabe C. Intracellular mechanisms of amyloid accumulation and pathogenesis in Alzheimer's disease. J Mol Neurosci. 2001,17:137-45. Gläser C, Schulz S, Handschug K, Huse K, Birkenmeier G. Genetic and functional characteristics of the human in vivo LRP1/A2MR receptor suggested as a risk marker for Alzheimer's disease and other complex (degenerative) diseases. Neurosci Res. 2004,50:85-101. Gliemann J, Receptors of the low density lipoprotein (LDL) receptor family in man. Multiple functions of the large family members via interaction with complex ligands. Biol Chem. 1998,379:951-64. Review. Gotthardt M, Trommsdorff M, Nevitt MF, Shelton J, Richardson JA, Stockinger W,Nimpf J, Herz J. Interactions of the low density lipoprotein receptor gene family with cytosolic adaptor and scaffold proteins suggest diverse biological functions in cellularcommunication and signal transduction. J Biol Chem. 2000,275:25616-24. Gylys KH, Fein JA, Tan AM, Cole GM. Apolipoprotein E enhances uptake of soluble but not aggregated amyloid-beta protein into synaptic terminals. J Neurochem. 2003,84:1442-51. Handschug K, Schulz S, Schnürer C, Köhler S, Wenzel K, Teichmann W, Gläser C. Lowdensity lipoprotein receptor-related protein in atherosclerosis development: up-regulation of gene expression in patients with coronary obstruction. J Mol Med. 1998,76:596-600.

118

Christiane Gläser, Gerd Birkenmeier, Susanne Schulz and Klaus Huse

Hatanaka Y, Kamino K, Fukuo K, Mitsuda N, Nishiwaki-Ueda Y, Sato N, Satoh T, Yamamoto H, Yoncda H, Imagawa M, Miki T, Ohta S, Ogihara T. Low density lipoprotein receptor-related protein gene polymorphisms and risk for late-onset Alzheimer´s disease in a Japanese population. Clin Genet. 2000, 58:319-23. Herz J, Clouthier DE, Hammer RE. LDL receptor related protein internalizes and degrades uPA-PAI-1 complexes and is essential for embryo implantation. Cell. 1992,71:411-21. Herz J, Hamann U, Rogne S, Myklebost O, Gausepohl H, Stanley KK. Surface location and high affinity for calcium of a 500-kd liver membrane protein closely related to LDL receptor suggest a physiological role as a lipoprotein receptor. EMBO J. 1988, 7:4119-27. Hollenbach E, Ackermann S, Hyman BT, Rebeck GW. Confirmation of an association between a polymorphism in exon 3 of the low-density lipoprotein receptor-related protein gene and Alzheimer´s disease. Neurology. 1998,50:1905-7. Howell BW, Herz J. The LDL receptor gene family: signaling functions during development. Curr Opin Neurobiol. 2001,11:74-81. Howell S, Nalbantoglu J, Crine P. Neutral endopeptidase can hydrolyze beta-amyloid(1-40) but shows no effect on beta-amyloid precursor protein metabolism. Peptides. 1995,16:647-52. Hu CJ, Sung SM, Liu HC, Hsu WC, Lee LS, Lee CC, Tsai CH, Chang JG. Genetic risk factors of sporadic Alzheimer´s disease among Chinese. Journal of Neurological Sciences. 2000,181:127-31. Hussain MM. Structural, biochemical and signaling properties of the low-density lipoprotein receptor gene family. Front Biosci. 2001,6:417-28. Review. Hussaini IM, Brown MD, Karns LR, Carpenter J, Redpath GT, Gonias SL, Vandenberg SR. Epidermal growth factor differentially regulates low density lipoprotein receptor-related protein gene expression in neoplastic and fetal human astrocytes. Glia. 1999,25:71–84. Hyman BT. Apolipoprotein E genotype: utility in clinical practice in Alzheimer´s disease. J Am Geriatr Soc. 1996,44:1469-71. Iwata N, Tsubuki S, Takaki Y, Watanabe K, Sekiguchi M, Hosoki E, Kawashima-Morishima M, Lee HJ, Hama E, Sekine-Aizawa Y, Saido TC. Identification of the major Abeta1-42degrading catabolic pathway in brain parenchyma: suppression leads to biochemical and pathological deposition. Nat Med. 2000,6:143-50. Kamboh MI, Ferrell RE, DeKosky ST. Genetic association studies between Alzheimer´s disease and two polymorphisms in the low density lipoprotein receptor-related protein gene. Neuroscience Letters. 1998,244:65-68. Kang DE, Saitoh T, Chen X, Xia Y, Masliah E, Hansen LA, Thomas RG, Thal LJ, Katzman R. Genetic association of the low-density lipoprotein receptor-related protein gene (LRP), an apolipoprotein E receptor, with late-onset Alzheimer's disease. Neurology. 1997,49:56-61. Kang DE, Pietrzik CU, Baum L, Chevallier N, Merriam DE, Kounnas MZ, Wagner SL, Troncoso JC, Kawas CH, Katzman R, Koo EH. Modulation of amyloid beta-protein clearance and Alzheimer's disease susceptibility by the LDL receptor-related protein pathway. J Clin Invest. 2000,106:1159-66. Kehoe P, Wavrant-De Vrieze F, Crook R, Wu WS, Holmans P, Fenton I, Spurlock G, Norton N, Williams H, Williams N, Lovestone S, Perez-Tur J, Hutton M, Chartier-Harlin MC,

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

119

Shears S, Roehl K, Booth J, Van Voorst W, Ramic D, Williams J, Goate A, Hardy J, Owen MJ. A full genome scan for late onset Alzheimer's disease. Hum Mol Genet. 1999,8:237-45. Kölsch H, Ptok U, Mohamed I, Schmitz S, Rao ML, Maier W, Hein R. Association of the C766T polymorphism of the low-density lipoprotein receptor-related protein gene with Alzheimer´s disease. Am J Med Genet. 2003,121:128-30. Kounnas MZ, Moir RD, Rebeck GW, Bush AI, Argraves WS, Tanzi RE, Hyman BT, Strickland DK. LDL receptor-related protein, a multifunctional ApoE receptor, binds secreted beta-amyloid precursor protein and mediates its degradation. Cell. 1995,82:33140. Kovacs DM, Fausett HJ, Page KJ, Kim TW, Moir RD, Merriam DE, Hollister RD, Hallmark OG, Mancini R, Felsenstein KM, Hyman BT, Tanzi RE, Wasco W. Alzheimer-associated presenilins 1 and 2: neuronal expression in brain and localization to intracellular membranes in mammalian cells. Nat Med. 1996,2:224-9. Kuo YM, Emmerling MR, Bisgaier CL, Essenburg AD, Lampert HC, Drumm D, Roher AE. Elevated low-density lipoprotein in Alzheimer's disease correlates with brain abeta 1-42 levels. Biochem Biophys Res Commun. 1998,52:711-5 Laatsch A, Ragozin S, Grewal T, Beisiegel U, Joerg H. Differential RNA interference: replacement of endogenous with recombinant low density lipoprotein receptor-related protein (LRP). Eur J Cell Biol. 2004,83:113-20. LaMarre J, Wolf BB, Kittler EL, Quesenberry PJ, Gonias SL. Regulation of macrophage alpha 2-macroglobulin receptor/low density lipoproteinreceptor-related protein by lipopolysaccharide and interferon-gamma. J Clin Invest. 1993,91 :1219-24. Lambert JC, Wavrant-De Vrièze F, Amouyel P, Chartier-Harlin MC. Association at LRP gene Locus with sporadic late-onset Alzheimer´s disease. The Lancet. 1998,351:1787-88. Lauer D, Reichenbach A, Birkenmeier G. Alpha 2-macroglobulin-mediated degradation of amyloid beta 1-42: a mechanism to enhance amyloid beta catabolism. Exp Neurol. 2001,167:385-92. Ledesma MD, Da Silva JS, Crassaerts K, Delacourte A, De Strooper B, Dotti CG. Brain plasmin enhances APP alpha-cleavage and Abeta degradation and is reduced inAlzheimer's disease brains. EMBO Rep. 2000,1:530-5. Lendon CL, Talbot CJ, Craddock NJ, Han SW, Wragg M, Morris JC, Goate AM. Genetic association studies between dementia of the Alzheimer´s type and three receptors for polipoprotein E in a Caucasian population. Neurosci Lett. 1997,222:187-90. Li Y, Lu W, Bu G. Essential role of the low density lipoprotein receptor-related protein in vascular smooth muscle cell migration. FEBS Lett. 2003,555:346-50. Li YM, Lai MT, Xu M, Huang Q, DiMuzio-Mower J, Sardana MK, Shi XP, Yin KC, Shafer JA, Gardell SJ. Presenilin 1 is linked with gamma-secretase activity in the detergent solubilized state. Proc Natl Acad Sci U S A. 2000, 97:6138-43. Loukinova E, Ranganathan S, Kuznetsov S, Gorlatova N, Migliorini MM, Loukinov D,Ulery PG, Mikhailenko I, Lawrence DA, Strickland DK. Platelet-derived growth factor (PDGF)-induced tyrosine phosphorylation of thelow density lipoprotein receptor-related protein (LRP). Evidence for integratedco-receptor function betwenn LRP and the PDGF. J Biol Chem. 2002,27715499-506.

120

Christiane Gläser, Gerd Birkenmeier, Susanne Schulz and Klaus Huse

Luedecking-Zimmer E, DeKosky ST, Nebes R, Kamboh MI. Asociation of the 3´UTR transcription factor LBP-1c/CP2/LSF polymorphism with late-onset Alzheimer´s disease. Am J Med Genet. 2003, 117:114-7. Ma SL, Ng HK, Baum L, Pang JC, Chiu HF, Woo J, Tang NL, Lam LC. Low-density lipoprotein receptor-related protein 8 (apolipoprotein E receptor 2) gene polymorphisms in Alzheimer's disease. Neurosci Lett. 2002,332:216-8. Mackic JB, Stins M, McComb JG, Calero M, Ghiso J, Kim KS, Yan SD, Stern D, Schmidt AM, Frangione B, Zlokovic BV. Human blood-brain barrier receptors for Alzheimer's amyloid-beta 1- 40.Asymmetrical binding, endocytosis, and transcytosis at the apical side of brainmicrovascular endothelial cell monolayer. J Clin Invest. 1998,102:734-43. Mahley RW. Apolipoprotein E: cholesterol transport protein with expanding role in cell biology. Science. 1988,240:622-30. Review. Masters CL, Simms G, Weinman NA, Multhaup G, McDonald BL, Beyreuther K. Amyloid plaque core protein in Alzheimer disease and Down syndrome. Proc Natl Acad Sci U S A. 1985,82:4245-9. May P, Herz J. LDL receptor-related proteins in neurodevelopment. Traffic. 2003,4:291-301. May P, Reddy YK, Herz J. Proteolytic processing of low density lipoprotein receptor-related protein mediates regulated release of its intracellular domain. J Biol Chem. 2002,277:18736-43. Marques MA, Crutcher KA. Apolipoprotein E-related neurotoxicity as a therapeutic target for Alzheimer's disease. J Mol Neurosci. 2003,20:327-37. McIlroy SP, Dynan KB, Vahidassr DJ, Lawson JT, Patterson CC, Passmore P. Common polymorphisms in LRP and A2M do not affect genetic risk for Alzheimer disease in Northern Ireland. American Journal of Medical Genetics (Neuropsychiatric Genetics). 2001,105;502-6. Mrak RE, Griffin WS. Interleukin-1, neuroinflammation, and Alzheimer's disease. Neurobiol Aging. 2001,22:903-8. Myllykangas L, Polvikoski T, Sulkava R, Verkkoniemi A, Tienari P, Niinistö L, Kontula K, Hardy J, Haltia M, Pérez-Tur J. Cardivascular risk factors and Alzheimer´s disease: a genetic association study in a population aged 85 or over. Neuroscience Letters. 2000, 292:195-8. Narita M, Holtzman DM, Schwartz AL, Bu G. Alpha2-macroglobulin complexes with and mediates the endocytosis of beta-amyloid peptide via cell surface low-density lipoprotein receptor-related protein. J Neurochem. 1997,69:1904-11. Nathan BP, Jiang Y, Wong GK, Shen F, Brewer GJ, Struble RG. Apolipoprotein E4 inhibits, and apolipoprotein E3 promotes neurite outgrowth in cultured adult mouse cortical neurons through the low-density lipoprotein receptor-related protein. Brain Res. 2002,928:96-105. Newell AJ, Sue LI, Scott S, Rauschkolb PK, Walker DG, Potter PE, Beach TG. Thiorphaninduced neprilysin inhibition raises amyloid beta levels in rabbit cortex and cerebrospinal fluid. Neurosci Lett. 2003,35:178-80. Nicodemus KK, Stenger JE, Schmechel DE, Welsh-Bohmer KA, Saunders AM, Roses AD, Gilbert JR, Vance JM, Haines JL, Pericak-Vance MA, Martin ER. Comprehensive

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

121

association analysis of APOE regulatory region polymorphisms in Alzheimer disease. Neurogenetics. 2004,5:201-8. Pericak-Vance MA, Bass MP, Yamaoka LH, Gaskell PC, Scott WK, Terwedow HA, Menold MM, Conneally PM, Small GW, Vance JM, Saunders AM, Roses AD, Haines JL. Complete genomic screen in late-onset familial Alzheimer disease. Evidence for a new locus on chromosome 12. JAMA. 1997,278,1237-41. Qiu WQ, Borth W, Ye Z, Haass C, Teplow DB, Selkoe DJ. Degradation of amyloid betaprotein by a serine protease-alpha2-macroglobulin complex. J Biol Chem. 1996,271:8443-51. Qiu WQ, Walsh DM, Ye Z, Vekrellis K, Zhang J, Podlisny MB, Rosner MR, Safavi A,Hersh LB, Selkoe DJ. Insulin-degrading enzyme regulates extracellular levels of amyloid betaprotein by degradation. J Biol Chem. 1998,273:32730-8. Quinn KA, Pye VJ, Dai YP, Chesterman CN, Owensby DA. Characterization of the soluble form of the low density lipoprotein receptor-related protein (LRP). Exp Cell Res. 1999,251:433-41. Sanan DA, Weisgraber KH, Russell SJ, Mahley RW, Huang D, Saunders A, Schmechel D, Wisniewski T, Frangione B, Roses AD, et al. Apolipoprotein E associates with beta amyloid peptide of Alzheimer's disease to form novel monofibrils. Isoform apoE4 associates more efficiently than apoE3. J Clin Invest. 1994,94,860-9. Sánchez-Guerra M, Combarros O, Infante J, Llorca J, Berciano J, Fontalba A, FernándezLuna JL, Pena N, Fernández-Viadero C. Case-Control study and meta-analysis of low density lipoprotein receptor-related protein gene exon 3 polymorphism in Alzheimer´s disease. Neuroscience Letters. 2001,316:17-20. Sandbrink R, Masters CL, Beyreuther K.. Similar alternative splicing of a non-homologous domain in beta A4-amyloid protein precursor-like proteins. J Biol Chem. 1994,269:14227-34. Saunders AJ, Tanzi RE.Welcome to the complex disease world. Alpha2-macroglobulin and Alzheimer's disease. Exp Neurol. 2003,184:50-3. Saunders AJ, Bertram L, Mullin K, Sampson AJ, Latifzai K, Basu S, Jones J, Kinney D, MacKenzie-Ingano L, Yu S, Albert MS, Moscarillo TJ, Go RC, Bassett SS,Daly MJ, Laird NM, Wang X, Velicelebi G, Wagner SL, Becker DK, Tanzi RE, Blacker D. Genetic association of Alzheimer's disease with multiple polymorphisms in alpha-2macroglobulin. Hum Mol Genet. 2003,12:2765-76. Schulz S, Birkenmeier G, Schagdarsurengin U, Wenzel K, Müller-Werdan U, Rehfeld D, Süß T, Kabisch A, Werdan K, Gläser C. The role of LDL receptor-related protein (LRP) in coronary atherosclerosis. Int J Cardiol. 2003,92:137-44. Schulz S, Schagdarsurengin U, Greiser P, Birkenmeier G, Müller-Werdan U, Hagemann M, Riemann D, Werdan K, Gläser C. The LDL receptor-related protein (LRP1/A2MR) and coronary atherosclerosis--novel genomic variants and functional consequences. Hum Mutat. 2002,20:404. Scott WK, Yamaoka LH, Bass MP, Gaskell PC, Conneally PM, Small GW, Farrer LA, Auerbach SA, Saunders AM, Roses AD, Haines JL, Pericak-Vance MA. No genetic association between the LRP receptor and sporadic or late-onset familial Alzheimer disease. Neurogenetics. 1998,1:179-183.

122

Christiane Gläser, Gerd Birkenmeier, Susanne Schulz and Klaus Huse

Selkoe DJ. Clearing the brain's amyloid cobwebs. Neuron. 2001,32:177-80. Shibata M, Yamada S, Kumar SR, Calero M, Bading J, Frangione B, Holtzman DM,Miller CA, Strickland DK, Ghiso J, Zlokovic BV. Clearance of Alzheimer's amyloid-ss(1-40) peptide from brain by LDL receptor-related protein-1 at the blood-brain barrier. J Clin Invest. 2000,106:1489-99. Shuguang Z and Janciauskiene S. Multi-functional capability of proteins: a1antichymotrypsin and the correlation with Alzheimer´s disease. J Alz Dis. 2002,4:15-122. Sinnreich O, Kratzsch J, Reichenbach A, Gläser C, Huse K, Birkenmeier G.Plasma levels of transforming growth factor-1beta and alpha2-macroglobulin before and after radical prostatectomy: association to clinicopathological parameters. Prostate. 2004,61:201-8. Sjogren, T.; Sjogren, H.; Lindgren, A. G. H.: Morbus Alzheimer and morbus Pick: a genetic, clinical and patho-anatomical study. Acta Psychiat. Neurol. Scand. 1952,82 (suppl.):1152. Sottrup-Jensen L. Alpha-macroglobulins: structure, shape, and mechanism of proteinase complex formation. J Biol Chem. 1989,264:11539-42. St George-Hyslop PH, Petit A. Molecular biology and genetics of Alzheimer's disease. C R Biol 2005,328(2):119-30. St. George-Hyslop, P. H.; Haines, J. L.; Farrer, L. A.; Polinsky, R.; Van Broeckhoven, C.; Goate, A.; Crapper McLachlan, D. R.; Orr, H.; Bruni, A. C.; Sorbi, S.; Rainero, I.; Foncin, J.-F.; and 54 others: Genetic linkage studies suggest that Alzheimer's disease is not a single homogeneous disorder. Nature. 1990,347:194-197. Streit WJ. Microglia and Alzheimer´s Disease. J Neurosci Res. 2004, 77:1-8. Strickland DK, Gonias SL, Argraves WS. Diverse roles for the LDL receptor family. Trends Endocrin Metab 2003,13:66-74. Strickland DK, Ranganathan S. Diverse role of LDL receptor-related protein in the clearance of proteases and in signaling. J Thromb Haemost. 2003,1(7):1663-70. Review. Strittmatter WJ, Saunders AM, Schmechel D, Pericak-Vance M, Enghild J, Salvesen GS, Roses AD. Apolipoprotein E: high-avidity binding to beta-amyloid and increased frequencyof type 4 allele in late-onset familial Alzheimer disease. Proc Natl Acad Sci U S A. 1993,90:1977-81. Tanzi RE, Bertram L. Twenty years of the Alzheimer's disease amyloid hypothesis: a genetic perspective. Cell. 2005,120(4):545-55. Review. Thompson JD, Higgins DG, Gibson TJ. CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight Matrix choice. Nucleic Acids Res. 1994,22:4673-80. Tucker HM, Kihiko-Ehmann M, Estus S. Urokinase-type plasminogen activator inhibits amyloid-beta neurotoxicity andfibrillogenesis via plasminogen. J Neurosci Res. 2002,70:249-55. Ulery PG, Beers J, Mikhailenko I, Tanzi RE, Rebeck GW, Hyman BT, Strickland DK. Modulation of beta-amyloid precursor protein processing by the low density lipoprotein receptor-related protein (LRP). Evidence that LRP contributes to the pathogenesis of Alzheimer's disease. J Biol Chem. 2000,275:7410-5.

Low Density Lipoprotein Receptor-Related Protein 1 (LRP1)

123

Van Leuven F, Thiry E, Lambrechts M, Stas L, Boon T, Bruynseels K, Muls E Decamps O. Sequencing of the coding exons of the LRP1 and LDLR genes an individual DNA samples reveals novel mutations in both genes. Atherosclerosis. 2001,154:567-77. Verpillat P, Bouley S, Campion D, Hanneqeuin D, Dubois B, Belliard S, Puel M, ThomasAntérion C, Agid Y, Brice A, Clerget-Darpoux F. Use of haplotype information to test involvement of the LRP gene in Alzheimer´s disease in the French population. European Journal of Human Genetics. 2001, 9:464-8. Wavrant-DeVrieze F, Lambert JC, Stas L, Crook R, Cottel D, Pasquier F, Frigard B, Lambrechts M, Thiry E, Amouyel P, Tur JP, Chartier-Harlin MC, Hardy J, Van Leuven F. Association between coding variability in the LRP gene and the risk of late-onset Alzheimer's disease. Hum Genet. 1999,104(5):432-4. Wavrant-De Vrièze F, Pérez-Tur J, Lambert JC, Frigard B, Pasquieir F, Delacourte A, Amouyel P, Hardy J, Chartier-Harlin MC. Association between the low density lipoprotein receptor-related protein (LRP) and Alzheimers´s disease. Neuroscience Letters. 1997,227:68-70. Williamson J, LaRusse S. Genetics and genetic counseling: recommendations for Alzheimer's disease, frontotemporal dementia, and Creutzfeldt-Jakob disease. Curr Neurol Neurosci Rep. 2004,4(5):351-7. Willnow TE, Hilpert J, Armstrong SA, Rohlmann A, Hammer RE, Burns DK, Herz J. Defective forebrain development in mice lacking gp330/megalin. Proc Natl Acad Sci U S A. 1996,93:8460-4 Woodward R, Singleton AB, Gibson AM, Edwardson JA, Morris CM. LRP gene and lateonset Alzheimer´s disease. The Lancet. 1998,352:239-40. Yoshikai S, Sasaki H, Doh-ura K, Furuya H, Sakaki Y. Genomic organization of the human amyloid beta-protein precursor gene. Gene. 1990,87(2):257-63. Erratum in: Gene. 1991, 102(2):291-2. Zlokovic BV, Deane R, Sallstrom J, Chow N, Miano JM. Neurovascular pathways and Alzheimer amyloid beta-peptide. Brain Pathol. 2005,15(1):78-83. Review. Zlokovic BV, Martel CL, Matsubara E, McComb JG, Zheng G, McCluskey RT, Frangione B, Ghiso J. Glycoprotein 330/megalin: probable role in receptor-mediated transport of apolipoprotein J alone and in a complex with Alzheimer disease amyloid beta at the blood-brain and blood-cerebrospinal fluid barriers. Proc Natl Acad Sci U S A. 1996,93(9):4229-34.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp.

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter V

The Role of Peroxisome Proliferator-Activated Receptors in Alzheimer’s Disease Dokmeci Dikmen∗ Department of Pharmacology, Faculty of Medicine, Trakya University, Edirne, Turkey

Abstract Alzheimer’s disease (AD) is characterized by a progressive loss of cognitive function with cerebral deposits of amyloid-β (Aβ) senile plaques and neurofibrillary tangles (NFTs) surrounded by inflammatory cells. Neuroinflammation, oxidative stress and impaired glucose and lipid metabolism are postulated to be the mechanisms playing role in the pathophysiology of AD. Recent evidence suggests that inflammatory events are associated with plaque formation in the brains of patients with AD and non-steroid antiinflammatory drugs (NSAIDs) might influence central nervous system (CNS) inflammation and AD pathology. Reactive oxygen and nitrogen species production may also participate in part to neurodegeneration in AD brains; antioxidant and/or free radical scavengers reduce inflammation in AD via free radical quenching and possess neuroprotective activity. In addition, AD patients show hyperinsulinemia and reduced insulin sensitivity during fasting and glucose tolerance tests; and insulin gene polymorphism might act as a modifier of AD progression. An increased number of insulin receptors are also observed in post-mortem brain tissues of AD patients. Furthermore, augmented plasma insulin levels and reduced cerebrospinal fluid (CSF) levels and CSF/plasma insulin ratio are observed in AD patients. Accordingly, treatment of insulin resistance may reduce the risk or retard the progression of AD.

∗

Correspondence: Assoc. Prof. Dikmen Dokmeci, M.D. Department of Pharmacology, Faculty of Medicine, Trakya University, 22030, Edirne, Turkey. Tel. no.: 90-284-2359742; Fax no.: 90-284-2352476; e-mail: [email protected], [email protected]

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Peroxisome proliferator-activated receptors (PPARs), members of the nuclear receptor family, are ligand-activated transcription factors. To date, three isoforms, encoded by separated genes, have been identified: PPARα [NR1C1], PPARβ (NUC-1 or PPARδ) [NR1C2] and PPARγ [NR1C3]. All PPAR isotypes are detected and found to exhibit specific patterns of localization in the different areas of the brain. PPARs may have specific functions in regulating the expression of genes involved in neurotransmission, and therefore play roles in complex processes, such as neurodegeneration, learning and memory. It is likely that at least some effects of PPAR agonists and NSAIDs on AD pathology are mediated through PPARs, since both PPARs and cyclooxygenase (COX) expression are increased in AD brains. Recently, NSAIDs, activating PPARα and γ, have been identified. In addition, NSAIDs and PPARα and γ agonists have anti-inflammatory, antioxidant and neuroprotective effects. This neuroprotective effect correlates with the modulation of β-catenin levels, inhibition of glycogen synthase kinase-3β (GSK-3β) activity and increased mRNA levels of the Wnt-target genes engrailed-1, cyclin D1 and PPARδ. Thiazolidinediones (TZDs) such as pioglitazone and rosiglitazone are insulin sensitizers, used to control glucose concentrations in patients with type 2 diabetes. These are potent synthetic PPARγ agonists, which exert both anti-inflammatory and antioxidant effects. PPARα and γ ligands, NSAIDs and TZDs inhibit activation of nuclear factor (NF)-κB, signal transducers and activators of transcription-1 (STAT-1), the nuclear factor of activated T-cells (NFAT) and activating protein-1 (AP-1). Moreover, they prevent the expression of COX-2 and inducible nitric oxide synthase (iNOS) and production of inflammatory cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α in human monocytes and arrest the differentiation of monocytes into activated macrophages. In conclusion, the development of new drugs targeting PPARs would be a great interest for future treatments of AD.

Keywords: Alzheimer’s disease, PPARs, neuroprotective effect, neuroinflammation, antioxidant effect, fibrates, thiazolidinediones, NSAIDs, Wnt signaling

Abbreviations AP-1 AGEs AD Aβ APP ApoE JNK CAT CNS CSF CoA COX DAT

activating protein-1 advanced glycation end-products Alzheimer’s disease amyloid-β amyloid precursor protein apolipoprotein E c-jun-NH2-terminal kinase catalase central nervous system cerebrospinal fluid coenzyme A cyclooxygenase dementia of Alzheimer type

The Role of Peroxisome Proliferator-Activated Receptors… DHA FDA GSH-Px GSSGR GSK HDL iNOS IRS IL LPS LDL LMWAs MMP MCI MAPK NFTs NADPH NO NSAIDs (NF)-κB NFAT PPARs PI3K PUFAs PS PG RXR RNS ROS STAT-1 SOD TZDs TNF VLDLs

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docosahexaenoic acid Food and Drug Administration glutathione peroxidase glutathione reductase glycogen synthase kinase high-density lipoprotein inducible nitric oxide synthase insulin receptor substrate interleukin lipopolysaccaride low-density lipoprotein low-molecular-weight antioxidants matrix metalloproteinase mild cognitive impairment mitogen-activated protein kinase neurofibrillary tangles nicotinamide adenine dinucleotide phosphate nitric oxide non-steroid anti-inflammatory drugs nuclear factor nuclear factor of activated T-cells peroxisome proliferator-activated receptors phosphatidylinositol 3-kinase polyunsaturated fatty acids presenilin prostaglandin retinoid X receptor reactive nitrogen species reactive oxygen species signal transducers and activators of transcription-1 superoxide dismutase thiazolidinediones tumor necrosis factor very-low-density lipoproteins

Introduction Alzheimer’s disease (AD), the most common form of dementia among the elderly population in the world, is a progressive, degenerative disorder of the central nervous system (CNS). Clinically, AD is characterized by impairment in memory, visuospatial skills, complex cognition, language, emotion and personality. Currently, AD affects ~5 million people in the United States and >30 million people worldwide. The prevalence of AD is expected to quadruple by the year 2047. Economically, AD is extremely costly to patients,

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their families, and society. In fact, the cost of caring for patients with AD was over $110 billion per year in the early 1990s in the United States, and the average annual cost per patient is about $45,000 [1]. There are no definitive diagnostic tests or biological markers of AD. Furthermore, there are no known cures or preventions for AD. Therefore, scientists from different disciplines have been trying to find new drugs for the prevention and treatment of AD for a long time. On the other hand, drug discovery for AD is complicated by the fact that the exact cause(s) of the disease is still unknown and early diagnosis of the disease is not currently available [2]. The early-onset, familial form of AD accounts for nearly 5-10% of all cases of AD and is characterized by early manifestations of dementia, in some cases in patients ~40 years of age. It is caused by multiple mutations in the major genes, such as amyloid precursor protein (APP) on chromosome 21, presenilin (PS)-1 on chromosome 14, and PS-2 on chromosome 1 [2, 3]. In contrast, although the initiating events are still unknown, late onset AD, which is sporadic and accounts for ~90-95% of all patients, results from the combination of genetic risk factors such as aging, apolipoprotein E (ApoE), and α2 macroglobulins, with different epigenetic events [4]. Diabetes, cardiovascular complications, arteriosclerosis, and hypertension are considered to be the risk factors in the development of AD [5, 6]. Neuroinflammation, oxidative stress and impaired glucose and lipid metabolism are also postulated to be the mechanisms playing role in the pathophysiology of AD. Furthermore, peroxisome proliferators-activated receptor (PPAR) expression is increased in AD brains and PPARs seem to play an important role in AD etiopathogenesis [7]. PPARs, a member of the nuclear hormone receptor superfamily, are involved in several physiological processes, such as glucose homeostasis, cellular differentiation, regulation of lipid and lipoprotein metabolism, neurodegeneration, learning and memory, as well as in pathological states including atherosclerosis, inflammation, cancer, diabetes, obesity, infertility, and demyelinization [8, 9]. Hipolipidemic fibrates, antidiabetic thiazolidinediones (TZDs) and non-steroid anti-inflammatory drugs (NSAIDs) are PPAR agonists. In addition, to date, several studies have confirmed the insulin sensitizer, hipolipidemic, antiinflammatory and antioxidant properties of various PPAR agonists in vivo and in vitro. Hence, it is of importance to determine if the efficacy of fibrates, TZDs and NSAIDs in reducing AD risk is a result of the action of these drugs on PPARs.

Neuropathology of AD AD is characterized by a progressive loss of cognitive function with senile plaques, vascular amyloid-β (Aβ) deposits and neurofibrillary tangles (NFTs) as the pathologic hallmarks of the disease. AD brains exhibit a number of other abnormalities: synaptic reduction, neuronal loss, volume loss (atrophy), gliosis, microglial activation, impaired energy metabolism, mitochondrial function, signs of inflammation, and damage secondary to oxygen radicals [10, 11]. NFTs are cytoskeletal lesions largely composed of paired helical and straight filaments, which are intraneuronal aggregates of hyperphosphorylated, microtubule-associated tau protein. After the neurofibrillary tangle-laden neurons die,

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extracellular "tombstone" tangles remain visible [12]. Aβ are deposited as extracellular senile plaques composed of the 39-42 amino-acid-long peptide, derived from the β-APP, caused by cleavage with β-secretase and γ-secretase. The α-secretase cleaves the middle of the Aβ region, releasing a secreted ectodomain that contains the first 16 amino acids of the Aβ (sAPPα). In contrast, β-secretase, the novel transmembrane asparatic protease, BACE, cleaves between Met-671 and Asp-672, producing the amino terminal end of the Aβ and ending with Met-671 (sAPPβ). Further processing of the carboxyl-terminal end of sAPPβ, by the activity of γ-secretase, leads to the release of Aβ [12, 13]. Brain levels of both 42-aminoacid form (Aβ42) and 40-amino-acid form (Aβ40) are increased in AD. The Aβ40 is the most abundantly produced Aβ peptide, whereas a slightly longer and less abundant Aβ42 has been implicated as the more pathogenic species. Despite being a minor Aβ species, Aβ42 is deposited earlier and more consistently than Aβ40 in the AD brain. Collectively, these observations provide a strong rationale for selective targeting of Aβ42 and indicate that reducing Aβ42 levels by as little as 20-30% might retard the development of AD [14]. Interestingly, Kitamura and collegues reported that PPARγ expression could be detected by Western analysis in the temporal cortex of the human brain. Significantly, they found approximately a 50% increase in the amount of immunoreactive PPARγ protein in the brains of AD patients [7]. In conclusion, PPARs play an important role in AD etiopathology and may be a promising new therapeutic approach for the treatment of AD.

PPARs PPARs are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors, which includes retinoid, steroid, vitamin D and thyroid hormone receptors that function as heterodimers with the retinoid X receptor (RXR) and contain a highly conserved DNA-binding domain and a carboxy-terminal ligand-binding domain. These receptors regulate the expression of specific target genes by binding as heterodimers with RXR to specific DNA sequences, which are referred to as PPAR response elements [8]. Intensive study of PPARs during recent years has suggested an important role for these nuclear receptors both in normal physiology and the pathology of various tissues [15]. There are three PPAR isotypes, namely PPARα [NR1C1], PPARβ (PPARδ, NUC-1 or FAAR) [NR1C2] and PPARγ [NR1C3], localized on chromosomes 22, 6 and 3, respectively, with distinct tissue distribution and biological activities [8, 9, 15, 16]. As a result of alternative splicing and alternative promoter usage generates three transcripts from the human PPARγ gene; PPARγ1, PPARγ2 and PPARγ3. Both PPARγ1 and PPARγ3 mRNA encode the same protein product expressed in most tissues, whereas the PPARγ2 mRNA encodes the PPARγ2 protein that contains an additional 28 amino acids and is specific to adipocytes [16]. PPARs have been found and identified so far in amphibians, cyclostoma, teleosts, rodents and humans. PPARs are implicated in many cellular processes, from cell cycle to cell proliferation, from inflammation to apoptosis, and crucial for energy homeostasis. In addition, PPARs act as transcription factors, and regulate the expression of numerous genes and affect glycaemic control, lipid metabolism, inflammation and oxidant status [17-19]. Meanwhile, all PPAR isotypes are detected and found to exhibit specific patterns of

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localization in the different areas of the brain. PPARs have specific functions in regulating the expression of genes involved in neurotransmission, and therefore play roles in complex processes, such as aging, neuroinflammation, neurodegeneration, learning and memory [20]. PPARs may act for a range of compounds including hypolipidemic, antihyperglycaemic drugs, insulin sensitizers, and NSAIDs.

PPARα The first discovered PPAR was PPARα (Issemann and Green, 1990) [21], followed by PPARβ and PPARγ. PPARα is expressed primarily in liver, kidney, heart, adipose tissue, intestine, skeletal muscle and vascular cells [18, 22, 23]. PPARα can be activated by a wide variety of saturated and unsaturated fatty acids including arachidonic acid, oleic acid, linoleic acid, palmitic acid, docosahexaenoic acid (DHA), and eicosapentaenoic acid. Recently, PPARα has also been shown to be activated by very-low-density lipoproteins (VLDLs) in the presence of enzymatically active lipoprotein lipase [24, 25]. PPARα has been shown to regulate lipid metabolism through the control of apolipoprotein expression. Ligand activation of PPARα in vivo lowers triglyceride levels, presumably through its effects on fatty acid and lipoprotein metabolism. PPARα activation is now recognized to be the mechanism of action of the fibrate class of hypolipidemic drugs. The fibrates, amphipathic carboxylic acids that have been proven useful in the treatment of hypertriglyceridemia, are PPARα ligands. Clofibrate is a prototype for this class. Clofibrate and fenofibrate have been shown to activate PPARα with a 10-fold selectivity over PPARγ. Bezafibrate is a pan-agonist that exerts similar potency on all three PPAR isoforms [8]. PPARα transcriptionally regulates fatty acid catabolism and the production of enzymes such as acyl-coenzyme A (CoA) oxidase, the key enzyme in peroxisomal β-oxidation pathway, carnitine palmitoyl transferase I, implicated in the translocation of fatty acids across the inner mitochondrial membrane, as well as CYP4A6, which is an important microsomal ωhydroxylase. Interestingly fatty acids directly affect transcription by activating PPARα [26]. In addition, PPARα is involved in inflammation and in the cell response to reactive oxygen and nitrogen species. PPARα activators also reduce the risk of atherosclerosis, decrease progression of atherosclerotic plaques, and reduce the incidence of mortality from cardiovascular disease [20, 22, 25]. Moreover, PPARα ligands inhibit the inflammatory response in aortic smooth muscle cells, an effect that is lost in the PPARα null mice. This occurs through the inhibition of interleukin (IL)-1-mediated expression of IL-6 and cyclooxygenase (COX)-2. The transcriptional inhibition of this key enzyme of the inflammation process occurs as a result of a PPARα-dependent repression of the nuclear factor (NF)-κB pathway [27].

PPAR β/δ PPARδ is a less well known PPAR isoform, widely distributed in the organism; it is abundant especially in skeletal muscle, skin, placenta and brain. PPARδ interacts with

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saturated and unsaturated fatty acids; its ligand selectivity is intermediate between PPARγ and PPARα. Arachidonic acid, palmitic acid, prostaglandin (PG) A1 and PGD2, eicosapentaenoic acid, dihomo-γ-linolenic acid and carbaprostacyclin have been shown to activate PPARδ [8, 25]. Recently, the antiepileptic drug valproic acid has also been shown to activate PPARδ [28-30]. Its physiological role is not well understood, but it has been suggested to play a role in lipid metabolism, myelination and neuronal signaling, particularly in CNS, carcinogenesis, wound repair, epithelial inflammatory response, obesity, reproductive function, fertility, embryo implantation, cell proliferation, apoptosis, keratinocyte, adipocyte, and oligodendrocyte differentiation [8, 20, 22, 25].

PPARγ PPARγ, the best characterized of the PPARs, is expressed in white adipose tissue, pancreas, intestine, spleen, lymphoid tissue, bone marrow, kidney, heart, ovary, testis, liver, bladder, skeletal muscle and vasculature, epithelial keratinocytes and brain [19]. Fatty acids and eicosanoid derivatives bind and activate PPARγ at micromolar concentrations. PPARγ clearly prefers polyunsaturated fatty acids (PUFAs) including the essential fatty acids linoleic acid, linolenic acid, arachidonic acid and eicosapentaenoic acid. LTD4 antagonists, such as pranlukast, are selective agonists for PPARγ [8, 16]. PPARγ is a key regulator of glucose homeostasis and adipogenic differentiation [31]. PPARγ also promotes lipogenesis and exerts anti-inflammatory and antiproliferative actions [20, 25]. PPARγ is also involved in atherosclerosis [9]. It was reported that PPARγ is markedly upregulated in activated macrophages and that natural and synthetic PPARγ ligands inhibit the induction of indicuble nitric oxide syntase (iNOS), matrix metalloproteinase (MMP, called also gelatinase B) and scavenger receptor A gene transcription [32]. Promoter studies have revealed that PPARγ inhibits the transcriptional activity of these genes by interfering with the activating protein-1 (AP-1), NF-κB, the nuclear factor of activated Tcells (NFAT) and signal transducers and activators of transcription-1 (STAT-1) transcription factors. Furthermore, Jiang et al. [33] have shown that incubation of human monocytes with the natural PPAR γ ligand PGJ2 or with synthetic agonists inhibits the production of proinflammatory cytokines, including tumor necrosis factor (TNF)-α, IL-1β, and IL-6. The pharmacological ligands for PPARγ are TZDs and a variety of NSAIDs. TZDs were primarily developed in an effort to improve the antidiabetic actions of the fibrate hypolipidemic agents [8]. These compounds are used as therapeutic agents for treatment of type 2 diabetes. There are currently two members of the TZD class (pioglitazone and rosiglitazone) that have been approved by Food and Drug Administration (FDA) for treatment of Type 2 diabetes [31]. TZDs decrease plasma triglyceride and free fatty acids levels by enhancing their catabolism via the induction of lipoprotein lipase gene expression in adipose tissue. TZDs such as troglitazone, pioglitazone, rosiglitazone, englitazone and ciglitazone also have been postulated to be promising drugs for the treatment of cancer, hypertension, atherosclerosis, multiple sclerosis, psoriasis, ulcerative colitis, asthma, atopic dermatitis, and

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chronic inflammatory processes. They are also potent neuroprotector compounds, which that inhibit inflammatory activation of cultured brain astrocytes and microglia by diminishing lipopolysaccharide (LPS)-induced IL-6, TNF-α, iNOS, and inducible COX-2 expression. In addition, glycogen synthase kinase (GSK)-3α/β has been recognized as a therapeutic target for the treatment of neuropathological disorders, such as AD. TZDs were first described as GSK-3β inhibitors and were postulated that could be of potential therapeutic use for the treatment of AD [9, 15, 18, 19, 25]. Nitric oxide (NO) is overproduced in adipose tissue and muscle by iNOS in conditions such as chronic inflammation and insulin resistance. Recently, it was shown that PPARγ results in a decrease in iNOS expression in mesangial cells and macrophages via its effects on the NFκB, AP-1 and STAT-1 pathways [31]. NSAIDs are well known COX inhibitors, and some have been indicated recently to activate the PPARs. Hence, NSAIDs were classified into the following theree groups: The first group including aspirin, acetaminophen, tiaramide, and piroxicam shows no agonistic activity for any subtype of PPAR. The second group including indomethacin and diclofenac shows high selectivity for the PPARγ. The last group, e.g. ibuprofen, exerts agonistic activity for all type PPARs [34-36]. NSAIDs exerting PPAR agonistic activity, inhibit activation of NF-κB, STAT-1 and AP-1, and prevent expression of iNOS and production of inflammatory cytokines such as TNF-α and IL-1β. PPAR activators inhibiting COX expression and inflammatory events may have beneficial effects in the treatment of AD patients [7].

The Roles of Glucose Metabolism and PPARs in Alzheimer’s Disease Diabetes mellitus is a metabolic disorder divided into two main types: insulin-dependent and non-insulin–dependent. The various subtypes of diabetes mellitus differ with respect to etiology, pathogenesis, and insulin availability, but share the same consequences of chronic hyperglycemia and impaired insulin actions. Insulin dependent diabetes mellitus (called also Type 1 diabetes) is caused by insulin deficiency as a result of autoimmune destruction of pancreatic islet beta cells. Non-insulin-dependent diabetes mellitus (called also Type 2 diabetes) is the most common form of diabetes that is characterized by hyperinsulinemia and insulin resistance in peripheral tissues. Individuals with Type 2 diabetes have hyperglycemia and hyperinsulinemia. The pathogenesis of insulin resistance in Type 2 diabetes is not completely understood. However, evidence suggests that the insulin resistance is partly mediated by reduced levels of insulin receptor expression (down regulation), insulin receptor tyrosine kinase activity, insulin receptor substrate (IRS)-1 expression, and/or phosphatidylinositol 3-kinase (PI3K) activation in skeletal muscle and adipocytes [37, 38]. Type 2 diabetes is also associated with hippocampal and amygdalar athropy and increasing insulin resistance is associated with more amygdalar atrophy on magnetic resonance imaging [39]. Insulin synthesis and insulin gene expression have been demonstrated in mammalian neuronal cells. Insulin mRNA is distributed in a highly specific pattern with the highest density in pyramidal cells of the hippocampus and a high density in the medial prefrontal

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cortex, the enthorinal cortex, perirhinal cortex, thalamus and the granule cell layer of the olfactory bulb. Neither insulin mRNA nor insulin synthesis is observed in glia cells [40]. In 1978, Havrankova et al. [41] localized the insulin receptor in the CNS for the first time, and later insulin receptors are expressed in neurons throughout the CNS, particularly in the cerebral cortex, cerebellar cortex, hippocampus, olfactory bulbs, thalamus, hypothalamus, brainstem nuclei, spinal cord, and retina. In neurons, the binding of insulin to its receptor initiates tyrosine kinase mediated intracellular signaling and this leads to autophosphorylation of the receptor, followed by tyrosine phosphorylation of IRS proteins, which induce the activation of downstream pathways such as the PI3K and the mitogen-activated protein kinase (MAPK) cascades [42-44]. Binding of tyrosine phosphorylated-IRS to p85 stimulates glucose transport and inhibits apoptosis by activating Akt/Protein kinase B and inhibiting GSK-3β. Akt kinase inhibits apoptosis by phosphorylating GSK-3β [45]. Low levels of Akt kinase and high levels of GSK-3β activity are associated with increased neuronal death [46, 47]. Furthermore, insulin inhibits neuronal apoptosis via activation of protein kinase B in vitro, and regulates phosphorylation of tau, metabolism of the APP and clearance of Aβ from the brain in vivo [44]. Glucose, transported from peripheral blood, is the primary nutrient for neurons and the major fuel for oxidative metabolism, and function in the CNS. However, insulin enters the cerebrospinal fluid (CSF) through the blood-brain barrier by insulin receptor-mediated transport process, and exerts neuromodulator, neuroendocrine and neurotropic effects [5, 47]. Margolis et al. [48] showed that peripheral infusion of insulin leads to an increase in insulin levels in CSF. However, the augmentation of the peripheral insulin concentration acutely increases the concentration in the brain and CSF, whereas prolonged peripheral hyperinsulinaemia downregulates blood-brain barrier insulin receptors and reduces insulin transport into the brain [49]. The transport of insulin across the blood-brain barrier shows a saturable character; however, the molecular identity of this transport mechanism remains obscure [50]. Insulin regulates growth, food intake, sympathetic activity, reproductive endocrinology, glucose homeostasis and peripheral insulin action through the inhibition of hepatic gluconeogenesis [44, 51, 52]. In addition, insulin interferes neuronal growth, survival, differentiation and signal transduction; and promotes neurite outgrowth, migration, protein synthesis, neuronal cytoskeletal protein expression, and nascent synapse formation [53]. The brain may utilize insulin from both locally produced and peripheral (pancreatic) sources for different functional requirements including learning and memory. Furthermore, intranasal administration of insulin rapidly augments the insulin concentration in CSF without affecting blood glucose levels [54], and facilitates brain cognitive functions and working memory [55, 56], suggesting that it influences brain function directly and independently of changes in peripheral glucose. Epidemiologic and clinical studies suggest an important interaction between diabetes mellitus, hyperinsulinemia, insulin resistance and the development of AD, and diabetes mellitus significantly increases the risk for the development of AD [5, 57-64]. Furthermore, AD patiens are also more vulnerable to Type 2 diabetes [65]. There is compelling clinical and pre-clinical evidence that abnormalities of glucose metabolism are related to cognitive impairment and specifically to the development of AD. It is likely that insulin and insulin

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resistance play important roles in this process [5]. Moreover, insulin dysregulation may contribute to AD pathology through several mechanisms including decreased cortical glucose utilization particularly in the hippocampus and entorhinal cortex; increased oxidative stress through the formation of advanced glycation endproducts; increased tau phosphorylation and NFT formation; and increased Aβ aggregation through inhibition of IDE (called also unsulysin) [5]. In addition, pathological filaments with histochemical properties of amyloid are found in human AD pancreas [66], and Aβ-immunoreactive intracellular deposits have been reported in the pancreases of mice overexpressing the 99-amino acid C-terminal fragment of APP [67]. Thus, accumulation of Aβ in islet cells may be an underlying cause of, or at least potentiate the development of, insulin resistance and impaired glucose tolerance in AD [68]. Brain glucose metabolism reduces in AD patients [47]. Individuals suffering from AD have higher plasma insulin and lower CSF insulin concentrations as well as the insulin insensitivity or resistance, indicating impairment in insulin metabolism in the brain [69-71]. Moreover, administration of insulin to Alzheimer’s patients has been demonstrated to result in an improvement on memory and performance [72]. Consistent with the insulin resistant pattern, insulin tyrosine kinase, an insulin transducer, was reduced in the AD brains. Frolich et al. [73] found that brain insulin concentration and insulin receptor densities both decrease with age. Moreover, insulin receptor density is up-regulated in AD disease, and the authors interpreted the increased receptor density as a compensatory upregulation for defective insulin signal transduction [73, 74]. Schubert et al. [75] showed that disruptions of the insulin receptor tyrosine kinase signaling leads to an accumulation of phosphorylated tau in the mice hippocampus. In fact, the reduced CNS expression of genes encoding insulin and its receptor, as well as related signaling molecules, in the AD brain prompted the researchers to consider sporadic AD as a neuroendocrine disease that resembles Type 2 diabetes which was termed ‘’brain diabetes or Type 3 diabetes’’ [47, 63, 76-78]. Aβ40 and Aβ42, the main physiological C-terminal cleavage products of APP, reduce insulin binding and insulin receptor auto-phosphorylation due to reduced affinity of insulin binding to its own receptor, thereby impairing insulin signaling [79]. Aβ accumulations can promote tau hyperphosphorylation and the formation of the AD dementia associated paired helical filament-containing neuronal cytoskeletal lesions (NFTs, neuritic plaques, and neuropil threads) through functional impairment of the insulin signaling cascade, leading to increased levels of GSK-3β activity. It has been shown that Aβ40 and Aβ42 reduce insulin binding to and autophosphorylation of its receptor [80]. Furthermore, insulin protects against Aβ-peptide toxicity in brain mitochondria of diabetic rats [81]. Insulin seems to be involved in clearing Aβ from the brain [82]; on the other hand, inhibits the breakdown of Aβ by competitively blocking IDE. IDE activity is influenced by insulin concentration. IDE is a protease that can cleave a variety of small proteins, such as insulin and glucagons, and regulates the levels of insulin, Aβ -protein, and the Aβ precursor protein [83, 84]. IDE can degrade both intra- and extracellular Aβ as well as APP intracellular domain fragment produced by γ-secretase cleavage of APP [85]. IDE is decreased in Tg2576 mice which will also enhance the accumulation of Aβ [86]. Since both insulin and Aβ are substrates of IDE, insulin may compete with Aβ for IDE and therefore prevent Aβ degradation [61]. IDE deficiency or hypofunction may play a role in the disease

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processes of both AD and diabetes mellitus [87], and the use of IDE inhibitors block the degradation of Aβ and may be beneficial in diabetes mellitus and AD therapy. Advanced glycation end-products (AGEs) are sugar-derived protein modifications formed through a series of non-enzymatic glycosylation reactions [5]. Both diabetes mellitus and AD are characterized by accumulation of extra- and intracellular AGEs with the glucose hypometabolism and the metabolic consequences of oxidative stress [88]. There is CNS neuronal insulin resistance in AD brains which is associated with reduced levels of IRS mRNA, IRS-associated PI3K, reduced activation of Akt, and increased activation of GSK-3β activity and APP mRNA expression [89]. Insulin modulates other enzymes involved in tau phosphorylation, such as GSK-3. GSK3 is a serine/threonine kinase originally identified as a protein destined to phosphorylate and inactivate glycogen synthase. There are two GSK-3 isoforms, termed GSK-3α and GSK-3β. The latter is specifically expressed in CNS [90]. Oxidative stress can result in the phosphorylation of GSK-3β and neuronal injury. Hence, Aβ exposure in cultured hippocampal neurons can activate GSK-3β [91]. In addition to the relationship of GSK-3β with Aβ toxicity, GSK-3β can also alter the processing of APP. Involvement of GSK-3β in AD has also been linked to the microtubule-associated protein tau. The hyperphosphorylated tau is the major component of NFT that are composed of paired helical filaments. On the other hand, GSK-3β and PS1 may have an additional relationship through β-catenin. PS-1 can regulate the stability of β-catenin, a substrate of GSK-3β. GSK-3β negatively regulates βcatenin through phosphorylation and degradation. The loss of β-catenin results in an increase in the susceptibility of cells to apoptosis [90]. TZDs were first described as GSK-3β inhibitors and were postulated that could be of potential therapeutic use for the treatment of AD [92]. In conclusion, the precise role of insulin in the pathophysiology of AD is as yet undetermined. Impaired insulin signal transduction pathways, insulin dysregulation and insulin resistance in AD brain play important role in development and progression of AD. Antidiabetic agents including TZDs that reduce hyperinsulinemia might have the effect of diminishing circulating insulin in the CNS and freeing IDE to metabolize Aβ. TZD class of agents is FDA-approved for diabetes mellitus [31]. They bind to the PPARγ, which regulate fat cell differentiation and glucose uptake in adipose tissue. TZDs improve insulin sensitivity, reduce lipid content in skeletal muscle and other non-adipose tissues, and reduce peripheral glucose levels in patients with Type 2 diabetes mellitus. TZDs may also reduce insulin resistance. The use of insulin sensitizers (preferably ones are CNSspecific) would probably provide the best form of therapeutic rescue in the early and intermediate stages of AD [8, 22]. It is possible that the reported salutary effects of PPARγ might arise from improved brain glucose utilization in AD. Interestingly, some studies suggest that treatment for insulin resistance may reduce the risk or retard the progression of AD. Since insulin resistance increases amyloidosis in AD brain, the amyloid-lowering effect of TZDs may also be due to enhanced insulin sensitivity [47, 61]. Activation of this receptor also results in inhibition of a broad range of proinflammatory genes [93]. Treatment of microglial cultures with PPARγ agonists reduces the neurotoxic Aβ-induced inflammatory response [47]. These agents might prove to be disease-modifying treatments in AD [18, 25].

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Adiponectin is a fat-derived hormone and reduced circulating adiponectin concentrations were found to be strongly associated with the progression or insulin resistance in humans. PPARγ activation enhances adiponectin expression and production in humans and insulin resistant mice, which could contribute to the mechanisms by which PPARγ ligands improve the sensitivity of glucose metabolism to insulin’s action [31]. Uryu et al. [94] suggested that troglitazone, TZD drug and PPARγ agonist, inhibits both post-glutamate neurotoxicity and low-potassium-induced apoptosis in cerebellar granule neurons. Gemma et al. [95] demonstrated that administration of a PPARγ agonist, rosiglitazone, reversed an age-related deficit in contextual fear conditioning. Furthermore, PPARγ activation might modulate the beneficial effects of NSAIDs on cognition. The authors attribute the improvement in verbal memory recovery to the insulin-sensitizing effects of rosiglitazone. The Wnt signaling pathway is one of the best-studied signaling cascades implicated in neural development and maintenance of the CNS [96]. Defects of Wnt signaling appears to play role in neurodegenerative disorders, such as AD, and some of these events may be related to the modulation of β-catenin and GSK-3. Moreover, a loss of function of the Wnt signaling pathway has also been found to play role during Aβ neurotoxicity, and the key components of such pathway are affected in AD, that is, β-catenin is reduced and GSK-3β is activated in preneurofibrillary lesions. Engrailed-1 is a Wnt target gene related with the activation of Wnt signaling pathway in hippocampal neurons. It was demonstrated that PPARγ agonists modulate Wnt signaling pathway components; hence, activation of PPARγ receptors increases the expression of the Wnt-target genes engrailed-1, cyclin D1 and PPARδ, and inhibits the GSK-3β activity [97, 98]. Inestrosa et al. [98] showed that PPARγ agonist troglitazone treatment of rat hippocampal neurons results in the modulation of Wnt signaling pathway components and prevents the neurodegenerative changes induced by Aβ. Furthermore, GSK-3β negatively regulates β-catenin through phosphorylation and degradation. The loss of β-catenin results in an increase in the susceptibility of cells to apoptosis. Farias et al. [99] showed that ibuprofen (NSAID and PPAR pan-agonist) and octyl-pyridostigmine (cholinesterase inhibitor) protects rat hippocampal neurons, inhibits GSK-3β and stabilized β-catenin in rat and mouse brain neurons exposed to Aβ as well as cortical neurons derived from transgenic mice that overexpressed GSK-3β. In addition, these drug combinations enhanced the non-amyloidogenic APP cleavage by increasing secreted APP and decreasing endogenous Aβ40 in rat hippocampal neurons. It has been recently shown that all three PPAR subtypes are activated by valproic acid and some of its analogues in a structure-dependent manner. Kim et al. [100] demonstrated that valproate protects cells from ER stress-induced lipid accumulation and apoptosis by inhibiting GSK-3α/β, a kinase involved in a diverse number of signaling pathways including those controling neuronal gene expression and survival. In addition, valproat has been shown to modulate gene expression by activating the AP-1 family of transcription factors. Loy et al. [101] suggested that pan-agonist valproat has potential benefit for AD and tauopathies by neuroprotective properties. In conclusion, PPAR agonists have potent neuroprotective effect and directly promote neuroprotection in primary neurons exposed to different pro-apoptotic stimuli in vitro. This neuroprotective effect correlates with the modulation of β-catenin levels, inhibition of GSK-

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3β activity and increased mRNA levels of the Wnt-target genes engrailed-1, cyclin D1 and PPARδ [98].

The Roles of Lipid Metabolism and PPARs in Alzheimer’s Disease Brain membranes have a very high content of essential PUFAs and cholesterol. Both PUFA and cholesterol metabolisms play important roles in brain development, maturation, differentiation and functioning. Almost three decades ago, it was realized that cholesterol metabolism is different in the brain than in the other tissues, limiting penetration of lipids into the brain through the blood-brain barrier. It is well known that PUFAs alter the blood–brain barrier, therefore PUFAs or cholesterol, which are present in the diet, modulate brain functions. It was shown that dietary cholesterol induces the transcription of genes coding for acute inflammatory proteins, adhesion molecules, cytokines and stress proteins [102, 103]. Recent studies suggest a link between lipid metabolism and the development of neurodegenerative disorders such as AD, but the mechanisms for these associations are unknown. AD patients show elevated serum total cholesterol levels in their midlives [104, 105], and hypercholesterolaemic rabbits have increased neuronal Aβ accumulation. Since high cholesterol was implicated in the pathogenesis of amyloid plaques in AD, high intake of dietary cholesterol and saturated fat increases the risk of AD and the deposition of Aβ in brains [106]. In addition, dietary factors and the use of cholesterol-reducing drugs may be associated with a low risk of AD and can be protective against the disease [107]. PPARs play a role in lipoprotein metabolism and regulate target genes involved in uptake, transport, catabolism and storage of fatty acids [108]. Synthetic agonists of PPARα, fibrates such as clofibrate, fenofibrate, bezafibrate, ciprofibrate are used in the treatment of hyperlipidemia. The use of fibrates results in a substantial decrease in plasma triglycerides and is usually associated with a moderate decrease in low-density lipoprotein (LDL) cholesterol and an increase in high-density lipoprotein (HDL) cholesterol concentrations. Recent investigations indicate that the effects of fibrates are mediated, at least in part, through alterations in transcription of genes encoding for proteins that control lipoprotein metabolism. Fibrates activate specific transcription factors belonging to the nuclear hormone receptor superfamily, termed PPARs. The PPARα form mediates fibrate action on HDL cholesterol levels via transcriptional induction of synthesis of the major HDL apolipoproteins, apoA-I and apoA-II. Fibrates lower hepatic apoC-III production and increase lipoprotein lipase-mediated lipolysis via PPARα. Fibrates also stimulate cellular fatty acid uptake, conversion to acyl-CoA derivatives, and catabolism by the β-oxidation pathways, which, combined with a reduction in fatty acid and triglyceride synthesis, results in a decrease in VLDL production [109-111]. The PPARα agonist fenofibrate reduces atherosclerosis in animal models of atherosclerosis [112], and also protects against cerebral injury by neuroprotective, antioxidant and anti-inflammatory mechanisms [113]. Brune at al. [114] showed that there is an association between the PPARα L162V V-allele and AD, however the mechanism is unclear.

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PPARα L162V polymorphism, especially in carriers of the insulin gene-1 allele, influences the risk for AD, possibly by altering Aβ42 CSF levels. ApoE is a lipid and cholesterol transport protein that is synthesized within the CNS. Furthermore, functions of ApoE include neuronal repair, dendritic growth, maintenance of synaptic plasticity, and anti-inflammatory activities. Of three principal alleles that exist for this protein, people with the ApoE ε4 allele, who are at a high risk of AD, have high cholesterol concentrations, whereas those with the ε2 allele, who are at a low risk of AD, have low cholesterol concentrations [115]. ApoE has also been shown to colocalize with neuropathological lesions of AD such as Aβ and NFTs. In addition, it has also been demonstrated that ApoE is essential for amyloid deposition in the APP(V717F) transgenic model of AD [2]. The risk for AD has been reported to correlate with transcriptional activity of the ApoE gene. Binding sites for putative transcriptional factors, such as AP-1, AP-2 and NF-κB, are present in the ApoE promoter. The promoter also contains sites for the inflammatory response transcription factors IL-6, STAT-1 and STAT-2. A functional PPARγ has been detected in the ApoE/ApoCI intergenic region. ApoE mRNA levels were shown to be regulated by ciglitazone, a PPARγ agonist [2]. ApoE is expressed in macrophages, where its expression increases when macrophages develop into foam cells [2]. The PPARγ is involved in this conversion. Galetto et al. [116] showed that ciglitazone doubled the levels of ApoEmRNA. In addition, the identification of a PPARδ-selective agonist allowed to link the action of PPARδ with reverse cholesterol transport. GW501516 is a potent and subtype-selective PPARδ agonist. In macrophages, fibroblasts, and intestinal cells, GW501516 increases expression of the reverse cholesterol transporter ATP-binding cassette A1 and induces apolipoprotein A1-specific cholesterol efflux [117]. 24S-hydroxycholesterol is the major elimination product of brain cholesterol and is released into the blood circulation. Most of plasma 24S-hydroxycholesterol originates from the brain and thus plasma 24S-hydroxycholesterol levels may reflect cholesterol turnover in the CNS. Altered 24S-hydroxycholesterol levels in the periphery might point to a neurodegenerative process in the CNS, as detected in AD. The levels of plasma 24Shydroxycholesterol are significantly lower in AD patients compared to healthy controls [118]. Sauder et al. [119] found that PPARγ Pro12Ala polymorphism influenced plasma 24Shydroxycholesterol/cholesterol ratios in AD patients in that carrier of the Ala allele presented with higher ratios than homozygote carriers of the Pro-allele. Furthermore the Pro allele of the PPAR γ Pro12Ala polymorphism is associated with an increased risk of Type 2 diabetes [120]. The unsaturated fatty acids bind to all three PPARs with PPARα exhibiting the highest affinity, while saturated fatty acids are poor PPAR ligands in general. On the other hand, there is a recent increase in the level of interest in the possible role of dietary fatty acids in age-related cognitive decline, and cognitive impairment of both degenerative (AD) or vascular origin. Intake of non-hydrogenated unsaturated fats, low intake of hydrogenated and saturated fats and high intake of PUFAs from fish or vegetable sources can lower the risk of AD and could act synergistically in improving cognitive functioning [106, 107]. In addition, epidemiological studies on the association between diet and cognitive decline also suggested

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a possible role of fatty acids intake in maintaining adequate cognitive functioning and possibly in preventing or delaying the onset of dementia, both of degenerative or vascular origin [121]. Dietary fats may also influence AD through other mechanisms. Higher intakes of hydrogenated and saturated fats are related to insulin resistance, and high insulin concentrations may be related to a high risk of AD. High intake of fats may also cause oxidation, which can result in AD [107]. Appropriate dietary measures or supplementation with specific micro- and macronutrients might open new ways for the prevention and management of cognitive decline and dementia [121]. Hashimoto et al. [122] investigated whether administration of DHA, PPAR agonist and major fatty acid of the brain, ameliorates the impairment of learning ability in an animal model of AD, in rats infused with Aβ40 into the cerebral ventricle. DHA administered for 12 weeks significantly reduced the increase in the number of reference and working memory errors in the Aβ-infused rats, and increased both the cortico-hippocampal level of DHA and the molar ratio of DHA/arachidonic acid, suggesting an amelioration of the impaired spatial cognition learning ability. Furthermore, DHA suppressed the increases in the levels of lipid peroxide and reactive oxygen species (ROS) in the cerebral cortex and the hippocampus of Aβ-infused rats, suggesting that DHA increases antioxidative defenses. DHA is thus a possible therapeutic agent for ameliorating learning deficiencies due to AD [122].

The Roles of Inflammation and PPARs in Alzheimer’s Disease AD is a progressive age-related neurodegenerative disorder that is the most common form of dementia affecting people 65 years and older. The exact etiologic factor of AD is unknown; however, evidence has been growing that supports the hypothesis that neuroinflammation may play a central role in the development of AD. It is not known whether neuroinflammation is primary in the disease process or a result of the disease, but it does appear that it is a part of the pathophysiologic process. Also, the CNS differs from other organs in that it contains a blood-brain barrier, a system of tight junctions at the capillaries within the CNS that obstructs the entry of inflammatory cells, pathogens, and some macromolecules into the subarachnoid space. Although not complete, this barrier acts to protect the sensitive, fragile, and post-mitotic neurons from the damages typically associated with inflammation [87, 92, 123]. Inflammatory activation of neuronal, as well as glial cells is believed to contribute to cell death and damage during this neurological disease. Inflammation develops as a consequence of activation of astrocytes and microglial cells. Over the last two decades, much evidence has accumulated which has demonstrated numerous markers for inflammation associated with plaques in the AD brain. Inflammatory components related to AD neuroinflammation include brain cells such as activated astrocytes, reactive microglia; cytokines; chemokines; interleukins; Aβ; pentraxins such as C-reactive protein; acute-phase proteins; reactive oxygen and nitrogen species; proteases; arachidonic acid derivatives; classical pathway complement proteins from C1q right through to membrane attack complex C5b-9; neuronal-type nicotinic acetylcholine receptors as well as PPARs which could be mediators of the so-called

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secondary damage [12, 124]. Both the microglia and astrocytes have been shown to generate Aβ, one of the main pathologic features of AD. Aβ itself has been shown to act as a proinflammatory agent causing the activation of many of the inflammatory components. Both in vitro and in vivo studies suggest that Aβ deposition induces abnormal τ immunoreactivity, and precedes NFT formation, and plays an important physiological function in the etiology of AD. Aβ aggregates appear to be capable of inciting an inflammatory response, and there is evidence that inflammation can promote increased Aβ production and also enhance Aβ deposition. Thus, an Aβ-induced inflammatory response could promote further Aβ accumulation and increased inflammation. On the basis of the notion that the inflammatory response to Aβ is harmful, anti-inflammatory drugs have been proposed as beneficial agents in AD therapy [125]. Accumulating evidence suggests that PPARs may play a role in inflammation. However, the molecular mechanisms mediating the anti-inflammatory action of PPARs, at present, are not fully understood. Several studies have shown that activation of these receptors may interfere with several signaling pathways regulating the expression of pro-inflammatory genes. More recently, PPAR activators were shown to inhibit the activation of inflammatory response genes (such as IL-1β, IL-2, IL-6, IL-8, iNOS, ICAM-1, COX-2, TNF-α and MMP) by negatively interfering with the NF-κB, C/EBPβ, STAT-1 and NFAT and AP-1 signalling pathways. Furthermore, PPARs interact with p65. PPARs, also induce a decrease in expression of pro-inflammatory cytokines by antagonizing the activities of c-jun-NH2terminal kinase (JNK) and p38 MAPK [9, 126-129]. PPAR activators exert these anti-inflammatory activities in different immunological and vascular wall cell types such as monocyte/macrophages, endothelial, epithelial and smooth muscle cells in which PPARs are expressed. These recent findings indicate a modulatory role for PPARs in the control of the inflammatory response with potential therapeutic applications in inflammation-related diseases, such as atherosclerosis [130], psoriasis [131], rheumatoid arthritis [132, 133], asthma [134], acute myocardial infarction [135] and inflammatory bowel disease [136]. PPAR agonists may also be effective in the treatment of chronic inflammatory disorders of the CNS including AD [137, 138], autoimmune encephalomyelitis [139], multiple sclerosis [140] and Parkinson’s disease [141]. A great amount of experimental evidence indicates that PPARs are related with the pathophysiology of AD [87, 137, 142]. On the contrary, the role of PPARs in the AD-related neuroinflammation process is still not well known. It has been recently shown that PPAR ligands, including fibrates, TZDs and NSAIDs have potent anti-inflammatory effects [143]. Of relevance to AD is that PPAR agonists have been demonstrated to have similar antiinflammatory effects on neurons, microglial cells and astrocytes. All PPAR isotypes are detected and found to exhibit specific patterns of localization in different areas of the brain. PPARs may have specific functions in regulating the expression of genes involved in neurotransmission and neuroinflammation. Kitamura et al. [7] suggested that PPARγ expression could be detected by Western analysis in the temporal cortex of the human brain. Significantly, they found an approximately 50% increase in the amount of immunoreactive PPARγ protein in brains of AD patients. Since PPARγ expression are increased in Alzheimer brains, it is likely that at least some effects of PPAR activators on AD pathology are mediated through changes in the activities of PPARs.

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It has been demonstrated that inflammatory processes play a critical role in AD risk and progression [144]. Furthermore, a large number of experimental, clinical and retrospective and prospective epidemiological studies indicate that chronically NSAIDs administered groups of individuals have a reduced risk for AD, delayed disease onset, ameliorated symptomatic severity and slowed cognitive decline. NSAIDs can also lower amyloidogenic Aβ42 [125, 145-147]. In addition, NSAID treatment has positively correlated with a reduction of plaque-associated, activated microglia in humans and transgenic mice [148-150]. The PPARs have been shown to play a role in the regulation of inflammatory processes in the body [151], and some NSAIDs directly bind to PPARs and activate its transcriptional regulatory activities. In addition, PPARs has been shown to inhibit the expression of wide range of proinflammatory genes, these receptors appears to be a good candidate to mediate the observed anti-inflammatory effects [34, 35, 126, 152]. It is very important that, Lehmann et al. [34] have identified a novel target of NSAID actions, the ligand-activated nuclear receptor PPARs. These findings suggest that the anti-inflammatory effects of NSAIDs may not occur exclusively through their inhibition of COXs, but also as a consequence of the ability of these drugs to directly activate PPARs and inhibit proinflammatory gene expression [126, 153-156]. Combs et al. [126] reported that a variety of PPARγ agonists, including the NSAIDs indomethacin and ibuprofen, the TZDs troglitazone and ciglitazone, and 15d-PGJ2, inhibited the Aβ-induced stimulation of IL-6 and TNF-α expression by monocytes/microglia. Heneka et al. [154] demonstrated that, in cerebellar granule cell cultures, the NSAID PPARγ agonists indomethacin and ibuprofen, as well as the natural PPARγ ligand 15d-PGJ2, inhibited LPSstimulated neuron death. Kim et al. [157] showed that troglitazone, ciglitazone and 15d-PGJ2 inhibited LPS-induced death of neurons in cortical neuron-glia cocultures. Furthermore, troglitazone inhibited glutamate toxicity of cerebellar granule neurons [94]. Specifically, indomethacin, fenoprofen, flufenamic acid and ibuprofen act as PPARγ agonists. Recent studies in AD mouse models have shown that chronic treatment with a subset of NSAIDs (e.g. ibuprofen, flurbiprofen, indomethacin) reduced brain inflammation and Aβ levels in addition to the deposition of Aβ in brain [158-161]. NSAID ibuprofen, a COX-1 and COX-2 inhibitor as well as a PPAR pan-agonist, decreases the production of NO, protects neurons against glutamate toxicity and decreases the production of proinflammatory cytokines. Ibuprofen crosses the blood-brain barrier and suppresses neuritic plaque pathology and inflammation in AD brain. Furthermore, it is a potent free radical scavenger, and could reduce lipid peroxidation and free radical generation [162]. Hence, ibuprofen treatment reduced the amount of Aβ deposited in the brains of an animal model of AD and acts to reduce microglial activation and cytokine production in transgenic mice overexpressing APP [158, 164, 165]. Sastre et al. [165] showed in vitro that NSAIDs, such as indomethacin and ibuprofen, as well as several structurally different PPARγ agonists, reduce immunostimulated Aβ production in a PPARγ-dependent manner. Similarly, Yao et al. [166] demonstrated that the combination of antiinflammatory (indomethacin) and antioxidant (vitamin E) drugs significantly decreased soluble and insoluble Aβ40 and Aβ41 in neocortex and hippocampus and suppressed brain inflammatory and oxidative stress responses in transgenic mice model of AD. Morihara et al. [167] demonstrated that PPAR pan-agonist and NSAID ibuprofen

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suppresses IL-1β induction of pro-amyloidogenic α1-antichymotrypsin to ameliorate Aβ pathology in APPsw (Tg2575) mice of Alzheimer's models. TZDs are potent neuroprotective and anti-inflammatory compounds in neuronal cells through, at least in part, activation of the nuclear receptor PPARγ. TZDs inhibit inflammatory activation of cultured brain astrocytes and microglia by diminishing LPS-induced IL-6, TNFα, iNOS, and inducible COX2 expression. In addition, TZDs inhibits TNF-α and NO production and, concomitantly, protects cortical neurons from cell death induced by cell-free supernatant from activated microglia. These effects are completely inhibited by GW9662, a PPARγ antagonist [92]. Heneka et al. [168] reported that 7 day oral treatment of the specific PPARγ agonist pioglitazone or PPAR pan-agonist and NSAID ibuprofen resulted in a reduction in the number of activated microglia and reactive astrocytes in the hippocampus and cortex in APPV7171 mice. Drug treatment also reduced the expression of the proinflammatory enzymes COX-2 and iNOS. In parallel to the suppression of inflammatory markers, pioglitazone and ibuprofen treatment decreased β-secretase-1 mRNA and protein levels. Importantly, the researchers observed a significant reduction of the total area and staining intensity of Aβ42-positive amyloid deposits in the hippocampus and cortex. Additionally, animals treated with pioglitazone revealed a 27% reduction in the levels of soluble Aβ42 peptide. These findings demonstrate that antiinflammatory drugs can act rapidly to inhibit inflammatory responses in the brain and negatively modulate amyloidogenesis. Bernardo et al. [169] demonstrated that 15d-PGJ2 attenuated TNF-α and NO production in primary cultures of microglia stimulated with LPS, as well as reducing INFγ-induced MHC class II expression. The effects of 15d-PGJ2 on LPS-induced NO and TNF-α production were found to be mediated by PPARγ, in that ciglitazone, a specific synthetic PPARγ agonist, induced similar responses in microglia. These researchers showed that PPARγ is activated in rat microglial cells by the anti-inflammatory drug HCT1026, a derivative of flurbiprofen [161].

The Roles of Oxidative Stress and PPARs in Alzheimer’s Disease Free radicals are atoms or molecules that have a single unpaired electron in their outer orbit. They are chemically unstable and highly reactive compounds, which are formed during normal cellular metabolism. The most important free radicals produced are ROS and reactive nitrogen species (RNS) [90, 170]. The average cell utilizes 1013 O2 per day. It is estimated that 1% of respired molecular oxygen will form O2−, thus approximately 1011 free radical species are produced by each cell in a day [171]. Free radicals may also be produced by endogenous and environmental sources. Due to their reactivity, they can be responsible for cellular and tissue damage anytime their generation exceeds the endogenous ability to destroy them. This condition is also known as oxidant or oxidative stress. ROS can attack PUFAs that lead to lipid peroxidation [87].

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Oxidative stress is very important in the CNS. Compared with other organs or tissues, the brain is more sensitive to ROS- and RNS-induced damage due to its high rate of oxygen consumption, high polyunsaturated lipid content, and relatively low antioxidant defense enzymes and antioxidants [172-175]. In addition, it contains high levels of transition metals, especially iron, which can catalyze the formation of oxygen radicals [173, 174]. The brain uses glucose for energy production and needs about 4 × 1021 molecules every minute. As the mitochondria in aerobes, are the fount of ATP synthesis, this provides an explanation as to why deep hypoglycemia and inhibitors of ATP synthesis can cause neuronal cell death [176, 177]. The production of radicals is thought to be higher in neuronal cells due to heightened oxygen metabolism. Although the brain only constitutes 2–3% of total body mass, it utilizes 20% of basal oxygen supplied to the body. While most of the radicals are sequestered in the mitochondria, oxidative damage is exacerbated by age, metabolic demand, and disease conditions such as AD [171]. The adult brain contains about 1011-1012 neurons, which are supported and protected by at least twice as many neuroglial cells. There are several types of glial cells, oligodendrocytes, microglia and astrocytes. Microglia are the equivalent in the nervous system as monocytes-macrophages [175]. ROS and RNS are the cause of oxidative stress in nervous system. Classically oxidative stress is described as an imbalance between generation and elimination of ROS and RNS. This imbalance between cellular production of ROS and the inability of cells to defend against them is called oxidative stress [178]. Oxidative stress can cause cellular damage and subsequent cell death because ROS oxidizes cardinal cellular components, such as lipids, proteins, and DNA [4, 170, 171]. When oxidative stress occurs, cells function to counteract the resulting oxidant effect and to restore the redox balance. Furthermore, detoxifying enzymes, e.g., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx) and glutathione reductase (GSSGR) may be altered in their activity or protein synthesis [179, 180]. All organisms have adaptive responses to oxidative stress, such as activation of genes encoding defensive enzymes, transcription factors, and structural proteins. Antioxidants are exogenous (natural or synthetic) or endogenous compounds acting in several ways, including removal of O2, scavenging ROS or their precursors, inhibiting ROS formation, and binding metal ions needed for the catalysis of ROS generation. In summary, the natural antioxidant system can be classified into two major groups: enzymatic (e.g., SOD, CAT), and nonenzymatic or low-molecular-weight antioxidants (LMWAs). The LMWA group of molecules can be further classified into directly acting antioxidants (e.g., scavengers and chain-breaking antioxidants) and indirectly acting antioxidants (e.g., chelating agents) [4]. Oxidative stress and free radical damage have been suggested to play role in several pathological processes including ischemia-reperfusion, inflammatory response and AD. In addition, oxidative stress increases with aging [181]. Lipids, proteins and nucleic acids that have been damaged by free radicals accumulate in the brain and other organs with age, and are implicated in many age-related diseases, including neurodegenerative diseases. Free radical theory of aging is postulated by Harman (1956) [182]. Many antioxidants such as vitamins have shown beneficial effects in different biological systems in which they were

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able to prevent age-associated damage, to lower the incidence of age-associated diseases and to increase lifespan [183]. AD is the most common, complex and challenging form of neurodegenerative disease with dementia in the elderly. Although oxidative damage is well documented in AD [185189], the sources of reactive oxygen and nitrogen species triggering such damage to various macromolecules is yet to be identified. It is not known whether oxidative damage is primary in the disease process or a result of the disease, but it is apparent that it is a part of the pathophysiologic process. Disturbance in the prooxidant/antioxidant balance increases during aging; moreover, the production of free radicals appear to play a significant role in this neurodegenerative process. These processes suggest that oxidative damage is one of the factors in neuronal death underlying the loss of cognition [171]. This is based on the premise that if oxidative stress occurs when there is an imbalance between free radical generation and antioxidant availability, then antioxidants may be used to scavenge excess free radicals and modulate the development and the progression of the AD [190]. Indeed, individuals affected by AD show significantly increased oxidative damage to every class of biological macromolecules including sugar (i.e., glycosylation and glycation), lipid (i.e., lipid peroxidation), protein (i.e., protein oxidation/ nitration) and nucleic acid (i.e., DNA/RNA oxidation) in the brain [171, 191]. There is considerable evidence indicating that oxidative stress is an early event in AD, occurring prior to cytopathology [192, 193]. Indeed, these oxidative mechanisms are involved in the cell loss and other neuropathology associated with AD is evidenced by the large number of metabolic signs of oxidative stress as well as by markers of oxidative damage [171, 192, 194, 195]. Moreover, both NFTs and Aβ-containing plaques seem to be closely associated with markers of oxidative stress, but the exact interrelations between oxidative stress and its pathology have not been determined. The Aβ peptide is the major component of the senile plaques that are hallmark findings in the AD-affected brain. Aβ is the proteolytic product of APP. Large soluble fragments of APPs that are the result of APP cleavage within its Aβ domain are secreted into the extracellular medium. Overexpression of APP can accelerate Aβ secretion, which can form insoluble amyloid aggregates in the presence of amyloidotrophic factors, contributing to the development of AD [189]. Free radicals are produced by the Aβ peptide once it is formed outside the neurons, and were found to be neurotoxic to hippocampal cells and the synaptosomal membranes. As a result, oxidative damage in AD pathogenesis may involve two known pathways. In vitro, direct Aβ application to neuronal cells increase hydrogen peroxide production through metal ion reduction [196], leading to Aβ neurotoxicity. Indirect Aβ neurotoxicity from microglia stimulates superoxide and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, iNOS and NO [197]. In summary, on one hand, Aβ was shown to be sensitive to the action of free radicals, contributing to aggregation. On the other hand, the effect of Aβ accumulation, including that arising from an Aβ-initiated inflammatory response, may include excessive generation of free radicals [197, 198]. Evidence for oxidative stress derives from both human (post-mortem and living patients) studies, and transgenic mouse models of the disease. There is a long list of surrogate markers of ROS-mediated injury that have been found to be increased in the brain, CSF and urine of

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AD patients. It includes malondialdehyde, 4-hydroxynonenal, F2-isoprostanes (lipid peroxidation); protein carbonyls, nitrotyrosine (protein oxidation); 8-hydroxy-2'deoxyguanosine (DNA oxidation) [170, 193, 199]. Transgenic animals show the same type of oxidative damage that is found in AD, and it directly correlates with the presence of Aβ deposits. Many studies also demonstrated that the prevalence of hippocampal atrophy increased with age and was very common in AD [200]. Moreover, several investigators detected changes in the antioxidant enzyme activity of SOD, CAT, GSH-Px, GSSGR and heme oxygenase-1 in several areas of the brain [201]. The direct measurement of a product of lipid peroxidation in the brain tissue and ventricular fluid of patients with AD provides important evidence of the occurrence of oxidative stress in the brain of AD patients. Assessment of free radical-induced oxidative stress in the brains of patients with AD has revealed an increase in thiobarbituric acidreactive substances in the hippocampus [202] and the temporal cortex [203, 204], indicative of significant lipid peroxidation. The aldehyde product of lipid peroxidation, 4hydroxynonenal, is significantly increased in the amygdala, the hippocampus, and the parahippocampal gyrus of the AD brain and coincides in these areas with histopathology characteristic of AD [205]. Elevated levels of 4-hydroxynonenal are also found in the cerebrospinal fluid of patients with probable AD [206]. Isoprostanes are members of a complex family of lipids, isomers of conventional enzymatically derived PGs, which are produced by oxygen radical-catalyzed peroxidation of PUFAs. Most of the work has been focused on a group of isomers of the PGF2α, called iPF2α, and an abundant literature has established that their measurement provides a reliable marker of in vivo lipid peroxidation and oxidative stress [188, 207]. Pratico et al. [209] found that, compared with controls, patients with a clinical diagnosis of AD had increased CSF, plasma, and urinary levels of a major isoprostane, 8,12-iso-iPF2α-VI. In addition, CSF tau protein levels increase and the percentage ratio of Aβ42 decreases with the progression of AD. These researchers showed a direct correlation between CSF 8,12-iso-iPF2α-VI levels and CSF tau and an inverse correlation with CSF Aβ42 in AD patients [208]. These findings suggest that elevation of isoprostane not only reflects an increase in CNS oxidative damage but also correlates with the progression of the disease. Levels of antioxidant enzymes were also measured in the AD-affected brain. Enzymes such as CAT, GSH-Px and GSSGR are important in preventing excessive build-up of free radicals. It was shown that levels of GSH-Px were elevated in the hippocampus; levels of GSSGR were elevated in the hippocampus and amygdala; and levels of CAT were elevated in the hippocampus and temporal neocortex of AD-affected brains as compared with controls [201]. These elevations correlated with increased lipid peroxidation in the same regions. This could indicate that the brain of a patient with AD is attempting to respond to the challenge of increased oxidative stress by increasing the availability of antioxidant enzymes. Upregulation of antioxidant enzymes found in vulnerable neurons in AD indicates that ROS not only cause damage to cellular structures but also provoke cellular response. Gsell et al. [210] measured activities of the enzymes, SOD and CAT, which detoxicate ROS. Enzyme activities were measured postmortem in basal ganglia, cortical and limbic brain regions of patients with dementia of Alzheimer type (DAT) and age-matched controls. SOD activity increased with age in basal nucleus of Meynert. However, there was no

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significant difference in SOD activity between DAT and controls. CAT activity was independent of age and postmortem time. There were significant reductions in CAT activity in parietotemporal cortex, basal ganglia, and amygdala in DAT compared to controls. Their findings are in line with the assumption that ROS could contribute to the pathogenesis of DAT. Over the past 15 years, numerous studies have identified hippocampal atrophy as a predictor of the decline from mild cognitive impairment (MCI) to AD [10, 200]. AD-related volume losses are most readily detected in the hippocampus in MCI, and indicate that in predicting the transition to dementia, it is important to consider both hippocampal and lateral temporal lobe volume reductions. Studies by Hampel et al. [211] suggest that elevated Ptau231 measurements may be specific for AD. The p-tau proteins in CSF come closest to fulfilling the criteria of a biological marker of AD. Antioxidants of widely varying chemical structures have been investigated as potential therapeutic agents for neurodegenerative diseases such as AD. In vitro and animal studies suggest that various compounds with antioxidant ability can attenuate the oxidative stress induced by Aβ [212-214]. Recently, clinical trials have demonstrated potential benefits for treatments with the antioxidants, vitamin E, ascorbic acid, carotenes, selegiline, curcumin, Gingko biloba, L-carnitine and idebenone [107, 215, 216]. Vitamin E, a fat-soluble vitamin, has been the most widely studied antioxidant [217]. Recent prospective studies have indicated that dietary intake of several exogenous antioxidants is associated with a lower risk for AD, suggesting that intervention with antioxidants might be beneficial in the early phases of AD or in people at risk for developing AD [218, 219]. Generally, to achieve efficacy, a candidate antioxidant must penetrate the blood-brain barrier to attain a critical therapeutic level within the CNS and must be given as early as possible, before the irreversible neuronal loss. It also should fit the precise oxidative stress physiology, for example, the type of ROS involved, the place of generation, and the severity of the damage. Thus, antioxidant cocktails or antioxidants combined with other drugs may have more successful synergistic effects [4]. Several studies demonstrated that PPARγ agonists ameliorated the lesions associated with ischemia-reperfusion of gastric tissue, heart, brain, lung, kidney and intestine possibly due to the antiinflammatory and antioxidant properties. Meanwhile, PPARs agonists have potent antioxidant effect [220-223]. Yao and colleagues examined whether the simultaneous administration of an antioxidant, vitamin E, with an anti-inflammatory drug, indomethacin, would exert an additive anti-amyloidogenic effect in the Tg2576 mouse model of AD-like Aβ brain amyloidosis, one of the most extensively studied mouse models of AD [166]. Villegas et al. [222] investigated the effects of the rosiglitazone on gastric injury caused by ischemia following reperfusion in rats. Rosiglitazone significantly reduced the myeloperoxidase, as a marker of neutrophils infiltration, and the levels of TNF-α. Rosiglitazone did not revert the reduced GSH-Px activity but enhanced significantly the decreased xanthine oxidase and SOD activities in gastric mucosa of ischemic rats. In conclusion, rosiglitazone reduces the damage in ischemia-reperfusion gastric injury and alleviates the inflammatory response and the oxidative events. Liu et al. [224] demonstrated that phenylbutyric acid activates PPARs in astrocytes, and binds to PPARα and γ. Phenylbutyric acid maintaines CAT protein levels in brain of ts1-infected mice, and delays the hindlimb paralysis caused by ts1 infection. The

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authors suggest that ts1-induced oxidative stress in infected astrocytes that is alleviated by phenylbutyric acid is mediated via PPARα and/or PPARγ. Uryu et al. [94] suggested that troglitazone inhibits both post-glutamate neurotoxicity and low-potassium-induced apoptosis in cerebellar granule neurons, and has neuroprotective and antioxidant effect; it acts as a dual-inhibitor against both exicotoxicity and apoptosis. Furthermore, in other studies rosiglitazone, PPARγ agonist, improved endothelium-dependent vasodilatation, preserved PVASP, suppressed gp91phox and iNOS expression, reduced superoxide and total NOx production, and inhibited nitrotyrosine formation most likely by attenuation of oxidative and nitrative stresses [108]. Tao et al. [108] showed that rosiglitazone enhanced PPAR expression, improved endothelium-dependent vasodilatation, preserved the phosphorylation of vasodilator-stimulated phosphoprotein, suppressed gp91phox and iNOS expression, reduced superoxide and total NOx production, and inhibited nitrotyrosine formation in hypercholesterolemic rabbits. Moreover, Klucis et al. [225] reported that administration of PPARα activators results in a drastic increase of the activity of CAT, an antioxidant enzyme. In conclusion, since oxidative damage is a key phenomenon in AD, treatment with antioxidants such as PPAR agonists seems to be a promising approach for slowing disease progression to the extend that oxidative damage may be responsible for the cognitive and functional decline observed in AD [226].

Conclusion AD is the most common, complex and challenging form of neurodegenerative disease with dementia in the elderly. Because of their anti-inflammatory and antioxidant activity, and modulating effects of glucose and lipid metabolism PPAR agonists are currently being developed for clinical use, and they may be a promising new therapeutic approach for the treatment of AD.

References [1]

[2]

[3] [4] [5]

Brookmeyer, R; Gray, S; Kawas, C. Projections of Alzheimer's disease in the United States and the public health impact of delaying disease onset. Am J Public Health, 1998 88, 1337-1342. Lahiri, DK. Apolipoprotein E as a target for developing new therapeutics for Alzheimer's disease based on studies from protein, RNA, and regulatory region of the gene. J Mol Neurosci, 2004 23, 225-233. Selkoe, DJ. Alzheimer's disease results from the cerebral accumulation and cytotoxicity of amyloid beta-protein. J Alzheimers Dis, 2001 3, 75-80. Gilgun-Sherki, Y; Melamed, E; Offen, D. Antioxidant treatment in Alzheimer's disease: current state. J Mol Neurosci, 2003 21, 1-11. Grossman, H. Does diabetes protect or provoke Alzheimer's disease? Insights into the pathobiology and future treatment of Alzheimer's disease. CNS Spectr, 2003 8, 815823.

148 [6] [7]

[8]

[9] [10]

[11]

[12]

[13] [14]

[15]

[16] [17] [18] [19]

[20]

[21]

Dokmeci Dikmen Ravona-Springer, R; Davidson, M; Noy, S. The role of cardiovascular risk factors in Alzheimer’s disease. CNS Spectr, 2003 8, 824-831. Kitamura, Y; Shimohama, S; Koike, H; Kakimura, J; Matsuoka, Y; Nomura, Y; Gebicke-Haerter, PJ; Taniguchi, T. Increased expression of cyclooxygenases and peroxisome proliferator-activated receptor-gamma in Alzheimer's disease brains. Biochem Biophys Res Commun, 1999 254, 582-586. Alarcon de, la Lastra C; Sanchez-Fidalgo, S; Villegas, I; Motilva, V. New pharmacological perspectives and therapeutic potential of PPAR-gamma agonists. Curr Pharm Des, 2004 10, 3505-3524. Berger, J; Moller DE. The mechanisms of action of PPARs. Annu Rev Med, 2002 53, 409-435. de Leon, MJ; DeSanti, S; Zinkowski, R; Mehta, PD; Pratico, D; Segal, S; Clark, C; Kerkman, D; DeBernardis, J; Li, J; Lair, L; Reisberg, B; Tsui, W; Rusinek, H. MRI and CSF studies in the early diagnosis of Alzheimer's disease. J Intern Med, 2004 256, 205223. Hwang, DY; Cho, JS; Lee, SH; Chae, KR; Lim, HJ; Min, SH; Seo, SJ; Song, YS; Song, CW; Paik, SG; Sheen, YY; Kim, YK. Aberrant expressions of pathogenic phenotype in Alzheimer's diseased transgenic mice carrying NSE-controlled APPsw. Exp Neurol, 2004 186, 20-32. Braak, E; Griffing, K; Arai, K; Bohl, J; Bratzke, H; Braak, H. Neuropathology of Alzheimer's disease: what is new since A. Alzheimer? Eur Arch Psychiatr Clin Neurosci, 1999 249, 14-22. Kitamura, Y; Nomura, Y. Stress proteins and glial functions: possible therapeutic targets for neurodegenerative disorders. Pharmacol Ther, 2003 97, 35-53. Golde, TE; Eckman, CB; Younkin, SG. Biochemical detection of Aβ isoforms: implications for pathogenesis, diagnosis, and treatment of Alzheimer's disease. Biochim Biophys Acta, 2000 1502, 172-187. Ehrmann, J Jr; Vavrusova, N; Collan, Y; Kolar, Z. Peroxisome proliferator-activated receptors (PPARs) in health and disease. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub, 2002 146, 11-14. Theocharis, S; Margeli, A; Vielh, P; Kouraklis, G. Peroxisome proliferator-activated receptor-gamma ligands as cell-cycle modulators. Cancer Treat Rev, 2004 30, 545-554. Desvergne, B; Wahli, W. Peroxisome proliferator-activated receptors: nuclear control of metabolism. Endocr Rev, 1999 20, 649-688. Martens, FM; Visseren, FL; Lemay, J; de Koning, EJ; Rabelink, TJ. Metabolic and additional vascular effects of thiazolidinediones. Drugs, 2002 62, 1463-1480. Pershadsingh, HA. Peroxisome proliferator-activated receptor-gamma: therapeutic target for diseases beyond diabetes: quo vadis? Expert Opin Investig Drugs, 2004 13, 215-228. Moreno, S; Farioli-Vecchioli, S; Ceru, MP. Immunolocalization of peroxisome proliferator-activated receptors and retinoid X receptors in the adult rat CNS. Neuroscience, 2004 123, 131-145. Issemann, I; Green, S. Activation of a member of the steroid hormone receptor superfamily by peroxisome proliferators. Nature, 1990 347, 645-650.

The Role of Peroxisome Proliferator-Activated Receptors…

149

[22] Hihi, AK; Michalik, L; Wahli, W. PPARs: transcriptional effectors of fatty acids and their derivatives. Cell Mol Life Sci, 2002 59, 790-798. [23] Bishop-Bailey, D; Wray, J. Peroxisome proliferator-activated receptors: a critical review on endogenous pathways for ligand generation. Prostaglandins Other Lipid Mediat, 2003 71, 1-22. [24] Ziouzenkova, O; Perrey, S; Asatryan, L; Hwang, J; MacNaul, KL; Moller, DE; Rader, DJ; Sevanian, A; Zechner, R; Hoefler, G; Plutzky, J. Lipolysis of triglyceride-rich lipoproteins generates PPAR ligands: evidence for an antiinflammatory role for lipoprotein lipase. Proc Natl Acad Sci U S A, 2003 100, 2730-2735. [25] Castrillo, A; Tontonoz, P. Nuclear receptors in macrophage biology: at the crossroads of lipid metabolism and inflammation. Annu Rev Cell Dev Biol, 2004 20, 455-480. [26] Dreyer, C; Keller, H; Mahfoudi, A; Laudet, V; Krey, G; Wahli, W. Positive regulation of the peroxisomal beta-oxidation pathway by fatty acids through activation of peroxisome proliferator-activated receptors (PPAR). Biol Cell, 1993 77, 67-76. [27] Delerive, P; De Bosscher, K; Besnard, S; Vanden Berghe, W; Peters, JM; Gonzalez, FJ; Fruchart, JC; Tedgui, A; Haegeman, G; Staels, B. Peroxisome proliferator-activated receptor alpha negatively regulates the vascular inflammatory gene response by negative cross-talk with transcription factors NF-kappaB and AP-1. J Biol Chem, 1999 274, 32048-32054. [28] Lampen, A; Siehler, S; Ellerbeck, U; Gottlicher, M; Nau, H. New molecular bioassays for the estimation of the teratogenic potency of valproic acid derivatives in vitro: activation of the peroxisomal proliferator-activated receptor (PPARdelta). Toxicol Appl Pharmacol, 1999 160, 238-249. [29] Werling, U; Siehler, S; Litfin, M; Nau, H; Gottlicher, M. Induction of differentiation in F9 cells and activation of peroxisome proliferator-activated receptor delta by valproic acid and its teratogenic derivatives. Mol Pharmacol, 2001 59, 1269-1276. [30] Lampen, A; Carlberg, C; Nau, H. Peroxisome proliferator-activated receptor delta is a specific sensor for teratogenic valproic acid derivatives. Eur J Pharmacol, 2001 431, 25-33. [31] Picard, F; Auwerx, J. PPAR(gamma) and glucose homeostasis. Annu Rev Nutr, 2002 22, 167-197. [32] Ricote, M; Welch, JS; Glass, CK. Regulation of macrophage gene expression by the peroxisome proliferator-activated receptor-gamma. Horm Res, 2000 54, 275-280. [33] Jiang, C; Ting, AT; Seed, B. PPAR-gamma agonists inhibit production of monocyte inflammatory cytokines. Nature, 1998 391, 82-86. [34] Lehmann, JM; Lenhard, JM; Oliver, BB; Ringold, GM; Kliewer, SA. Peroxisome proliferator-activated receptors alpha and gamma are activated by indomethacin and other non-steroidal anti-inflammatory drugs. J Biol Chem, 1997 272, 3406-3410. [35] Jaradat, MS; Wongsud, B; Phornchirasilp, S; Rangwala, SM; Shams, G; Sutton, M; Romstedt, KJ; Noonan, DJ; Feller, DR. Activation of peroxisome proliferator-activated receptor isoforms and inhibition of prostaglandin H(2) synthases by ibuprofen, naproxen, and indomethacin. Biochem Pharmacol, 2001 62, 1587-1595. [36] Kojo, H; Fukagawa, M; Tajima, K; Suzuki, A; Fujimura, T; Aramori, I; Hayashi, K; Nishimura, S. Evaluation of human peroxisome proliferator-activated receptor (PPAR)

150

[37] [38] [39]

[40]

[41] [42] [43] [44] [45] [46]

[47]

[48] [49]

[50] [51] [52]

[53]

[54]

Dokmeci Dikmen subtype selectivity of a variety of anti-inflammatory drugs based on a novel assay for PPAR delta(beta). J Pharmacol Sci, 2003 93, 347-355. Virkamaki, A; Ueki, K; Kahn, CR. Protein-protein interaction in insulin signaling and the molecular mechanisms of insulin resistance. J Clin Invest, 1999 103, 931-943. Zhu, X; Perry, G; Smith, MA. Insulin signaling, diabetes mellitus and risk of Alzheimer disease. J Alzheimers Dis, 2005 7, 81-84. den Heijer, T; Vermeer, SE; van Dijk, EJ; Prins, ND; Koudstaal, PJ; Hofman, A; Breteler, MM. Type 2 diabetes and atrophy of medial temporal lobe structures on brain MRI. Diabetologia, 2003 46, 1604-1610. Devaskar, SU; Giddings, SJ; Rajakumar, PA; Carnaghi, LR; Menon, RK; Zahm, DS. Insulin gene expression and insulin synthesis in mammalian neuronal cells. J Biol Chem, 1994 269, 8445-8454. Havrankova, J; Roth, J; Brownstein, M. Insulin receptors are widely distributed in the central nervous system of the rat. Nature, 1978 272, 827-829. Gerozissis, K. Brain insulin: regulation, mechanisms of action and functions. Cell Mol Neurobiol, 2003 23, 1-25. White, MF. Insulin signaling in health and disease. Science, 2003 302, 1710-1711. Plum, L; Schubert, M; Bruning, JC. The role of insulin receptor signaling in the brain. Trends Endocrinol Metab, 2005 16, 59-65. Pap, M; Cooper, GM. Role of glycogen synthase kinase-3 in the phosphatidylinositol 3-Kinase/Akt cell survival pathway. J Biol Chem, 1998 273, 19929-19932. Eves, EM; Xiong, W; Bellacosa, A; Kennedy, SG; Tsichlis, PN; Rosner, MR; Hay, N. Akt, a target of phosphatidylinositol 3-kinase, inhibits apoptosis in a differentiating neuronal cell line. Mol Cell Biol, 1998 18, 2143-2152. de la Monte, SM; Wands JR. Review of insulin and insulin-like growth factor expression, signaling, and malfunction in the central nervous system: relevance to Alzheimer's disease. J Alzheimers Dis, 2005 7, 45-61. Margolis, RU; Altszuler, N. Insulin in the cerebrospinal fluid. Nature, 1967 215, 13751376. Wallum, BJ; Taborsky, GJ Jr; Porte, D Jr; Figlewicz, DP; Jacobson, L; Beard, JC; Ward, WK; Dorsa, D. Cerebrospinal fluid insulin levels increase during intravenous insulin infusions in man. J Clin Endocrinol Metab, 1987 64, 190-194. Banks, WA. The source of cerebral insulin. Eur J Pharmacol, 2004 490, 5-12. Wozniak, M; Rydzewski, B; Baker, SP; Raizada, MK. The cellular and physiological actions of insulin in the central nervous system. Neurochem Int, 1993 22, 1-10. Unger, JW; Betz, M. Insulin receptors and signal transduction proteins in the hypothalamo-hypophyseal system: a review on morphological findings and functional implications. Histol Histopathol, 1998 13, 1215-1224. Stockhorst, U; de Fries, D; Steingrueber, HJ; Scherbaum, WA. Insulin and the CNS: effects on food intake, memory, and endocrine parameters and the role of intranasal insulin administration in humans.Physiol Behav, 2004 83, 47-54. Kern, W; Born, J; Schreiber, H; Fehm, HL. Central nervous system effects of intranasally administered insulin during euglycemia in men. Diabetes, 1999 48, 557563.

The Role of Peroxisome Proliferator-Activated Receptors…

151

[55] Zhao, WQ; Chen, H; Quon, MJ; Alkon, DL. Insulin and the insulin receptor in experimental models of learning and memory. Eur J Pharmacol, 2004 490, 71-81. [56] Watson, GS; Craft S. Modulation of memory by insulin and glucose: neuropsychological observations in Alzheimer's disease. Eur J Pharmacol, 2004 490, 97-113. [57] Leibson, CL; Rocca, WA; Hanson, VA; Cha, R; Kokmen, E; O'Brien, PC; Palumbo, PJ. The risk of dementia among persons with diabetes mellitus: a population-based cohort study. Ann N Y Acad Sci, 1997 826, 422-427. [58] Ott, A; Stolk, RP; van Harskamp, F; Pols, HA; Hofman, A; Breteler, MM. Diabetes mellitus and the risk of dementia: The Rotterdam Study. Neurology, 1999 53, 19371942. [59] Hoyer, S. The brain insulin signal transduction system and sporadic (type II) Alzheimer disease: an update. J Neural Transm, 2002 109, 341-360. [60] Peila, R; Rodriguez, BL; Launer, LJ; Honolulu-Asia Aging Study. Type 2 diabetes, APOE gene, and the risk for dementia and related pathologies: The Honolulu-Asia Aging Study. Diabetes, 2002 51, 1256-1262. [61] Watson, GS; Craft, S. The role of insulin resistance in the pathogenesis of Alzheimer's disease: implications for treatment. CNS Drugs, 2003 17, 27-45. [62] Arvanitakis, Z; Wilson, RS; Bienias, JL; Evans, DA; Bennett, DA. Diabetes mellitus and risk of Alzheimer disease and decline in cognitive function. Arch Neurol, 2004 61, 661-666. [63] Hoyer, S. Glucose metabolism and insulin receptor signal transduction in Alzheimer disease. Eur J Pharmacol, 2004 490, 115-125. [64] Luchsinger, JA; Tang, MX; Shea, S; Mayeux, R. Hyperinsulinemia and risk of Alzheimer disease. Neurology, 2004 63, 1187-1192. [65] Janson, J; Laedtke, T; Parisi, JE; O'Brien, P; Petersen, RC; Butler, PC. Increased risk of type 2 diabetes in Alzheimer disease. Diabetes, 2004 53, 474-481. [66] Miklossy, J; Taddei, K; Martins, R; Escher, G; Kraftsik, R; Pillevuit, O; Lepori, D; Campiche, M. Alzheimer disease: curly fibers and tangles in organs other than brain. J Neuropathol Exp Neurol, 1999 58, 803-814. [67] Fukuchi, K; Li, L; Hart, M; Lindsey, JR. Accumulation of amyloid-beta protein in exocrine glands of transgenic mice overexpressing a carboxyl terminal portion of amyloid protein precursor. Int J Exp Pathol, 2000 81, 231-239. [68] Pedersen, WA; Flynn ER. Insulin resistance contributes to aberrant stress responses in the Tg2576 mouse model of Alzheimer's disease. Neurobiol Dis, 2004 17, 500-506. [69] Craft, S; Peskind, E; Schwartz, MW; Schellenberg, GD; Raskind, M; Porte, D Jr. Cerebrospinal fluid and plasma insulin levels in Alzheimer's disease: relationship to severity of dementia and apolipoprotein E genotype. Neurology, 1998 50, 164-168. [70] Craft, S; Asthana, S; Schellenberg, G; Cherrier, M; Baker, LD; Newcomer, J; Plymate, S; Latendresse, S; Petrova, A; Raskind, M; Peskind, E; Lofgreen, C; Grimwood, K. Insulin metabolism in Alzheimer’s disease differs according to apolipoprotein E genotype and gender. Neuroendocrinology, 1999 70, 146-152. [71] Craft, S; Watson, GS. Insulin and neurodegenerative disease: shared and specific mechanisms. Lancet Neurol; 2004 3, 169-178.

152

Dokmeci Dikmen

[72] Craft, S; Asthana, S; Newcomer, JW; Wilkinson, CW; Matos, IT; Baker, LD; Cherrier, M; Lofgreen, C; Latendresse, S; Petrova, A; Plymate, S; Raskind, M; Grimwood, K; Veith, RC. Enhancement of memory in Alzheimer disease with insulin and somatostatin, but not glucose. Arch Gen Psychiatry, 1999 56, 1135-1140. [73] Frolich, L; Blum-Degen, D; Bernstein, HG; Engelsberger, S; Humrich, J; Laufer, S; Muschner, D; Thalheimer, A; Turk, A; Hoyer, S; Zochling, R; Boissl, KW; Jellinger, K; Riederer, P. Brain insulin and insulin receptors in aging and sporadic Alzheimer’s disease. J Neural Transm, 1998 105, 423-438. [74] Frolich, L; Blum-Degen, D; Riederer, P; Hoyer, S. A disturbance in the neuronal insulin receptor signal transduction in sporadic Alzheimer’s disease. Ann N Y Acad Sci, 1999 893, 290-293. [75] Schubert, M; Brazil, DP; Burks, DJ; Kushner, JA; Ye, J; Flint, CL; Farhang-Fallah, J; Dikkes, P; Warot, XM; Rio, C; Corfas, G; White, MF. Insulin receptor substrate-2 deficiency impairs brain growth and promotes tau phosphorylation. J Neurosci, 2003 23, 7084-7092. [76] Blass, JP; Gibson, GE; Hoyer, S. The role of the metabolic lesion in Alzheimer's disease. J Alzheimers Dis, 2002 4, 225-232. [77] Hoyer, S. Causes and consequences of disturbances of cerebral glucose metabolism in sporadic Alzheimer disease: therapeutic implications. Adv Exp Med Biol, 2004 541, 135-152. [78] Steen, E; Terry, BM; Rivera, EJ; Cannon, JL; Neely, TR; Tavares, R; Xu, XJ; Wands, JR; de la Monte, SM. Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer's disease--is this type 3 diabetes? J Alzheimers Dis, 2005 7, 63-80. [79] Mudher, A; Chapman, S; Richardson, J; Asuni, A; Gibb, G; Pollard, C; Killick, R; Iqbal, T; Raymond, L; Varndell, I; Sheppard, P; Makoff, A; Gower, E; Soden, PE; Lewis, P; Murphy, M; Golde, TE; Rupniak, HT; Anderton, BH; Lovestone, S. Dishevelled regulates the metabolism of amyloid precursor protein via protein kinase C/mitogen-activated protein kinase and c-Jun terminal kinase. J Neurosci, 2001 21, 4987-4995. [80] Xie, L; Helmerhorst, E; Taddei, K; Plewright, B; Van Bronswijk, W; Martins, R. Alzheimer's beta-amyloid peptides compete for insulin binding to the insulin receptor. J Neurosci, 2002 22, RC221. [81] Moreira, PI; Santos, MS; Sena, C; Seica, R; Oliveira, CR. Insulin protects against amyloid beta-peptide toxicity in brain mitochondria of diabetic rats. Neurobiol Dis, 2005 18, 628-637. [82] Boyt, AA; Taddei, TK; Hallmayer, J; Helmerhorst, E; Gandy, SE; Craft, S; Martins, RN. The effect of insulin and glucose on the plasma concentration of Alzheimer's amyloid precursor protein. Neuroscience, 2000 95, 727-734. [83] Qiu, WQ; Walsh, DM; Ye, Z; Vekrellis, K; Zhang, J; Podlisny, MB; Rosner, MR; Safavi, A; Hersh, LB; Selkoe, DJ. Insulin-degrading enzyme regulates extracellular levels of amyloid beta-protein by degradation. J Biol Chem, 1998 273, 32730-32738. [84] Zhao, L; Teter, B; Morihara, T; Lim, GP; Ambegaokar, SS; Ubeda, OJ; Frautschy, SA; Cole, GM. Insulin-degrading enzyme as a downstream target of insulin receptor

The Role of Peroxisome Proliferator-Activated Receptors…

[85]

[86]

[87] [88]

[89]

[90] [91]

[92]

[93] [94]

[95]

[96] [97]

153

signaling cascade: implications for Alzheimer's disease intervention. J Neurosci, 2004 24, 11120-11126. Farris, W; Mansourian, S; Chang, Y; Lindsley, L; Eckman, EA; Frosch, MP; Eckman, CB; Tanzi, RE; Selkoe, DJ; Guenette, S. Insulin-degrading enzyme regulates the levels of insulin, amyloid beta-protein, and the beta-amyloid precursor protein intracellular domain in vivo. Proc Natl Acad Sci U S A, 2003 100, 4162-4167. Ho, L; Qin, W; Pompl, PN; Xiang, Z; Wang, J; Zhao, Z; Peng, Y; Cambareri, G; Rocher, A; Mobbs, CV; Hof, PR; Pasinetti, GM. Diet-induced insulin resistance promotes amyloidosis in a transgenic mouse model of Alzheimer's disease. FASEB J, 2004 18, 902-904. Tuppo, EE; Arias, HR. The role of inflammation in Alzheimer's disease. Int J Biochem Cell Biol, 2005 37, 289-305. Onyango, IG; Tuttle, JB; Bennett, JP Jr. Altered intracellular signaling and reduced viability of Alzheimer's disease neuronal cybrids is reproduced by beta-amyloid peptide acting through receptor for advanced glycation end products (RAGE). Mol Cell Neurosci, 2005 29, 333-343. Schubert, M; Gautam, D; Surjo, D; Ueki, K; Baudler, S; Schubert, D; Kondo, T; Alber, J; Galldiks, N; Kustermann, E; Arndt, S; Jacobs, AH; Krone, W; Kahn, CR; Bruning, JC. Role for neuronal insulin resistance in neurodegenerative diseases. Proc Natl Acad Sci U S A, 2004 101, 3100-3105. Maiese, K; Chong, ZZ. Insights into oxidative stress and potential novel therapeutic targets for Alzheimer disease. Restor Neurol Neurosci, 2004 22, 87-104. Takashima, A; Honda, T; Yasutake, K; Michel, G; Murayama, O; Murayama, M; Ishiguro, K; Yamaguchi, H. Activation of tau protein kinase I/glycogen synthase kinase-3beta by amyloid beta peptide (25-35) enhances phosphorylation of tau in hippocampal neurons. Neurosci Res, 1998 31, 317-323. Luna-Medina, R; Cortes-Canteli, M; Alonso, M; Santos, A; Martinez, A; PerezCastillo, A. Regulation of inflammatory response in neural cells in vitro by thiadiazolidinones derivatives through peroxisome proliferator-activated receptor gamma activation. J Biol Chem, 2005 280, 21453-21462. Biondi-Zoccai, GG; Abbate, A; Liuzzo, G; Biasucci, LM. Atherothrombosis, inflammation, and diabetes. J Am Coll Cardiol, 2003 41, 1071-1077. Uryu, S; Harada, J; Hisamoto, M; Oda, T. Troglitazone inhibits both post-glutamate neurotoxicity and low-potassium-induced apoptosis in cerebellar granule neurons. Brain Res, 2002 924, 229-236. Gemma, C; Stellwagen, H; Fister, M; Coultrap, SJ; Mesches, MH; Browning, MD; Bickford, PC. Rosiglitazone improves contextual fear conditioning in aged rats. Neuroreport, 2004 15, 2255-2259. Patapoutian, A; Reichardt, LF. Roles of Wnt proteins in neural development and maintenance. Curr Opin Neurobiol, 2000 10, 392-399. Chong, ZZ; Maiese, K. Targeting WNT, protein kinase B, and mitochondrial membrane integrity to foster cellular survival in the nervous system. Histol Histopathol, 2004 19, 495-504.

154

Dokmeci Dikmen

[98] Inestrosa, NC; Godoy, JA; Quintanilla, RA; Koenig, CS; Bronfman, M. Peroxisome proliferator-activated receptor gamma is expressed in hippocampal neurons and its activation prevents beta-amyloid neurodegeneration: role of Wnt signaling. Exp Cell Res, 2005 304, 91-104. [99] Farias, GG; Godoy, JA; Vazquez, MC; Adani, R; Meshulam, H; Avila, J; Amitai, G; Inestrosa, NC. The anti-inflammatory and cholinesterase inhibitor bifunctional compound IBU-PO protects from beta-amyloid neurotoxicity by acting on Wnt signaling components. Neurobiol Dis, 2005 18, 176-183. [100] Kim, AJ; Shi, Y; Austin, RC; Werstuck, GH. Valproate protects cells from ER stressinduced lipid accumulation and apoptosis by inhibiting glycogen synthase kinase-3. J Cell Sci, 2005 118, 89-99. [101] Loy, R; Tariot, PN. Neuroprotective properties of valproate: potential benefit for AD and tauopathies. J Mol Neurosci, 2002 19, 303-307. [102] Puskas, LG; Bereczki, E; Santha, M; Vigh, L; Csanadi, G; Spener, F; Ferdinandy, P; Onochy, A; Kitajka, K. Cholesterol and cholesterol plus DHA diet-induced gene expression and fatty acid changes in mouse eye and brain. Biochimie, 2004 86, 817824. [103] Horrocks, LA; Farooqui, AA. Docosahexaenoic acid in the diet: its importance in maintenance and restoration of neural membrane function. Prostaglandins Leukot Essent Fatty Acids, 2004 70, 361-372. [104] Notkola, IL; Sulkava, R; Pekkanen, J; Erkinjuntti, T; Ehnholm, C; Kivinen, P; Tuomilehto, J; Nissinen, A. Serum total cholesterol, apolipoprotein E epsilon 4 allele, and Alzheimer's disease. Neuroepidemiology, 1998 17, 14-20. [105] Kivipelto, M; Helkala, EL; Laakso, MP; Hanninen, T; Hallikainen, M; Alhainen, K; Soininen, H; Tuomilehto, J; Nissinen, A. Midlife vascular risk factors and Alzheimer's disease in later life: longitudinal, population based study. BMJ, 2001 322, 1447-1451. [106] Lim, GP; Calon, F; Morihara, T; Yang, F; Teter, B; Ubeda, O; Salem, N Jr; Frautschy, SA; Cole, GM. A diet enriched with the omega-3 fatty acid docosahexaenoic acid reduces amyloid burden in an aged Alzheimer mouse model. J Neurosci, 2005 25, 3032-3040. [107] Luchsinger, JA; Mayeux, R. Dietary factors and Alzheimer's disease. Lancet Neurol, 2004 3, 579-587. [108] Tao, L; Liu, HR; Gao, E; Teng, ZP; Lopez, BL; Christopher, TA; Ma, XL; BatinicHaberle, I; Willette, RN; Ohlstein, EH; Yue, TL. Antioxidative, antinitrative, and vasculoprotective effects of a peroxisome proliferator-activated receptor-gamma agonist in hypercholesterolemia. Circulation, 2003 108, 2805-2811. [109] Staels, B; Dallongeville, J; Auwerx, J; Schoonjans, K; Leitersdorf, E; Fruchart, JC. Mechanism of action of fibrates on lipid and lipoprotein metabolism. Circulation, 1998 98, 2088-2093. [110] Fruchart, JC; Staels, B; Duriez, P. PPARS, metabolic disease and atherosclerosis. Pharmacol Res, 2001 44, 345-352. [111] Cullingford, TE; Dolphin, CT; Sato, H. The peroxisome proliferator-activated receptor alpha-selective activator ciprofibrate upregulates expression of genes encoding fatty

The Role of Peroxisome Proliferator-Activated Receptors…

155

acid oxidation and ketogenesis enzymes in rat brain. Neuropharmacology, 2002 42, 724-730. [112] Duez, H; Chao, YS; Hernandez, M; Torpier, G; Poulain, P; Mundt, S; Mallat, Z; Teissier, E; Burton, CA; Tedgui, A; Fruchart, JC; Fievet, C; Wright, SD; Staels, B. Reduction of atherosclerosis by the peroxisome proliferator-activated receptor alpha agonist fenofibrate in mice. J Biol Chem, 2002 277, 48051-48057. [113] Deplanque, D; Gele, P; Petrault, O; Six, I; Furman, C; Bouly, M; Nion, S; Dupuis, B; Leys, D; Fruchart, JC; Cecchelli, R; Staels, B; Duriez, P; Bordet, R. Peroxisome proliferator-activated receptor-alpha activation as a mechanism of preventive neuroprotection induced by chronic fenofibrate treatment. J Neurosci, 2003 23, 62646271. [114] Brune, S; Kolsch, H; Ptok, U; Majores, M; Schulz, A; Schlosser, R; Rao, ML; Maier, W; Heun, R. Polymorphism in the peroxisome proliferator-activated receptor alpha gene influences the risk for Alzheimer's disease. J Neural Transm, 2003 110, 10411050. [115] Rubin, J; Berglund, L. Apolipoprotein E and diets: a case of gene-nutrient interaction? Curr Opin Lipidol, 2002 13, 25-32. [116] Galetto, R; Albajar, M; Polanco, JI; Zakin, MM; Rodriguez-Rey, JC. Identification of a peroxisome-proliferator-activated-receptor response element in the apolipoprotein E gene control region. Biochem J, 2001 357, 521-527. [117] Oliver, WR Jr; Shenk, JL; Snaith, MR; Russell, CS; Plunket, KD; Bodkin, NL; Lewis, MC; Winegar, DA; Sznaidman, ML; Lambert, MH; Xu, HE; Sternbach, DD; Kliewer, SA; Hansen, BC; Willson, TM. A selective peroxisome proliferator-activated receptor delta agonist promotes reverse cholesterol transport. Proc Natl Acad Sci U S A 2001 98, 5306-5311. [118] Kolsch, H; Heun, R; Kerksiek, A; Bergmann, KV; Maier, W; Lutjohann D. Altered levels of plasma 24S- and 27-hydroxycholesterol in demented patients. Neurosci Lett, 2004 368, 303-308. [119] Sauder, S; Kolsch, H; Lutjohann, D; Schulz, A; von Bergmann, K; Maier, W; Heun, R. Influence of peroxisome proliferator-activated receptor gamma gene polymorphism on 24S-hydroxycholesterol levels in Alzheimer's patients. J Neural Transm, 2005 112, 1381-1389. [120] Altshuler, D; Hirschhorn, JN; Klannemark, M; Lindgren, CM; Vohl, MC; Nemesh, J; Lane, CR; Schaffner, SF; Bolk, S; Brewer, C; Tuomi, T; Gaudet, D; Hudson, TJ; Daly, M; Groop, L; Lander, ES. The common PPARgamma Pro12Ala polymorphism is associated with decreased risk of type 2 diabetes. Nat Genet, 2000 26, 76-80. [121] Solfrizzi, V; D'Introno, A; Colacicco, AM; Capurso, C; Del Parigi, A; Capurso, S; Gadaleta, A; Capurso, A; Panza, F. Dietary fatty acids intake: possible role in cognitive decline and dementia. Exp Gerontol, 2005 40, 257-270. [122] Hashimoto, M; Tanabe, Y; Fujii, Y; Kikuta, T; Shibata, H; Shido, O. Chronic administration of docosahexaenoic acid ameliorates the impairment of spatial cognition learning ability in amyloid beta-infused rats. J Nutr, 2005 135, 549-555. [123] Akiyama, H; Barger, S; Barnum, S; Bradt, B; Bauer, J; Cole, GM; Cooper, NR; Eikelenboom, P; Emmerling, M; Fiebich, BL; Finch, CE; Frautschy, S; Griffin, WS;

156

Dokmeci Dikmen

Hampel, H; Hull, M; Landreth, G; Lue, L; Mrak, R; Mackenzie, IR; McGeer, PL; O'Banion, MK; Pachter, J; Pasinetti, G; Plata-Salaman, C; Rogers, J; Rydel, R; Shen, Y; Streit, W; Strohmeyer, R; Tooyoma, I; Van Muiswinkel, FL; Veerhuis, R; Walker, D; Webster, S; Wegrzyniak, B; Wenk, G; Wyss-Coray, T. Inflammation and Alzheimer's disease. Neurobiol Aging, 2000 21, 383-421. [124] Yasojima, K; Schwab, C; McGeer, EG; McGeer, PL. Up-regulated production and activation of the complement system in Alzheimer's disease brain. Am J Pathol, 1999 154, 927-936. [125] Zhou, Y; Su, Y; Li, B; Liu, F; Ryder, JW; Wu, X; Gonzalez-DeWhitt, PA; Gelfanova, V; Hale, JE; May, PC; Paul, SM; Ni, B. Nonsteroidal anti-inflammatory drugs can lower amyloidogenic Abeta42 by inhibiting Rho. Science, 2003 302, 1215-1217. [126] Combs, CK; Johnson, DE; Karlo, JC; Cannady, SB; Landreth, GE. Inflammatory mechanisms in Alzheimer's disease: inhibition of beta-amyloid-stimulated proinflammatory responses and neurotoxicity by PPARgamma agonists. J Neurosci, 2000 20, 558-567. [127] Blanquart, C; Barbier, O; Fruchart, JC; Staels, B; Glineur, C. Peroxisome proliferatoractivated receptors: regulation of transcriptional activities and roles in inflammation. J Steroid Biochem Mol Biol, 2003 85, 267-273. [128] Chinetti, G; Fruchart, JC; Staels, B. Peroxisome proliferator-activated receptors and inflammation: from basic science to clinical applications. Int J Obes Relat Metab Disord, 2003 27, 41-45. [129] Valledor, AF; Ricote, M. Nuclear receptor signaling in macrophages. Biochem Pharmacol, 2004 67, 201-212. [130] Staels, B. PPARgamma and atherosclerosis. Curr Med Res Opin, 2005 21, 13-20. [131] Kuenzli, S; Saurat, JH. Peroxisome proliferator-activated receptors as new molecular targets in psoriasis. Curr Drug Targets Inflamm Allergy, 2004 3, 205-211. [132] Okamoto, H; Kamatani, N. Successful treatment with fenofibrate, a peroxisome proliferator activated receptor alpha ligand, for a patient with rheumatoid arthritis. Ann Rheum Dis, 2004 63, 1002-1003. [133] Kobayashi, T; Notoya, K; Naito, T; Unno, S; Nakamura, A; Martel-Pelletier, J; Pelletier, JP. Pioglitazone, a peroxisome proliferator-activated receptor gamma agonist, reduces the progression of experimental osteoarthritis in guinea pigs. Arthritis Rheum, 2005 52, 479-487. [134] Honda, K; Marquillies, P; Capron, M; Dombrowicz, D. Peroxisome proliferatoractivated receptor gamma is expressed in airways and inhibits features of airway remodeling in a mouse asthma model.J Allergy Clin Immunol, 2004 113, 882-888. [135] Takano, H; Hasegawa, H; Zou, Y; Komuro, I. Pleiotropic actions of PPAR gamma activators thiazolidinediones in cardiovascular diseases. Curr Pharm Des, 2004 10, 2779-2786. [136] Lytle, C; Tod, TJ; Vo, KT; Lee, JW; Atkinson, RD; Straus, DS. The peroxisome proliferator-activated receptor gamma ligand rosiglitazone delays the onset of inflammatory bowel disease in mice with interleukin 10 deficiency. Inflamm Bowel Dis, 2005 11, 231-243.

The Role of Peroxisome Proliferator-Activated Receptors…

157

[137] Kielian, T; Drew, PD. Effects of peroxisome proliferator-activated receptor-gamma agonists on central nervous system inflammation. J Neurosci Res, 2003 71, 315-325. [138] Feinstein DL. Therapeutic potential of peroxisome proliferator-activated receptor agonists for neurological disease. Diabetes Technol Ther, 2003 5, 67-73. [139] Feinstein, DL; Galea, E; Gavrilyuk, V; Brosnan, CF; Whitacre, CC; DumitrescuOzimek L; Landreth, GE; Pershadsingh, HA; Weinberg, G; Heneka, MT. Peroxisome proliferator-activated receptor-gamma agonists prevent experimental autoimmune encephalomyelitis. Ann Neurol, 2002 51, 694-702. [140] Storer, PD; Xu, J; Chavis, J; Drew, PD. Peroxisome proliferator-activated receptorgamma agonists inhibit the activation of microglia and astrocytes: implications for multiple sclerosis. J Neuroimmunol, 2005 161, 113-122. [141] Breidert, T; Callebert, J; Heneka, MT; Landreth, G; Launay, JM; Hirsch, EC. Protective action of the peroxisome proliferator-activated receptor-gamma agonist pioglitazone in a mouse model of Parkinson's disease. J Neurochem, 2002 82, 615-624. [142] Hull, M; Lieb, K; Fiebich, BL. Pathways of inflammatory activation in Alzheimer's disease: potential targets for disease modifying drugs. Curr Med Chem, 2002 9, 83-88. [143] Mrak, RE; Landreth, GE. PPARgamma, neuroinflammation, and disease. J Neuroinflammation, 2004 1, 5-7. [144] Breitner, JC. The role of anti-inflammatory drugs in the prevention and treatment of Alzheimer’s disease. Annu Rev Med, 1996 47,401-411. [145] McGeer, PL; Schulzer, M; McGeer, EG. Arthritis and anti-inflammatory agents as possible protective factors for Alzheimer's disease: a review of 17 epidemiologic studies. Neurology, 1996 47, 425-432. [146] Stewart, WF; Kawas, C; Corrada, M; Metter, EJ. Risk of Alzheimer’s disease and duration of NSAID use. Neurology, 1997 48, 626-632. [147] in t' Veld, BA; Ruitenberg, A; Hofman, A; Launer, LJ; van Duijn, CM; Stijnen, T; Breteler, MM; Stricker, BH. Nonsteroidal antiinflammatory drugs and the risk of Alzheimer's disease. N Engl J Med, 2001 345, 1515-1521. [148] Alafuzoff, I; Overmyer, M; Helisalmi, S; Soininen, H. Lower Counts of Astroglia and Activated Microglia in Patients with Alzheimer's Disease with Regular Use of NonSteroidal Anti-Inflammatory Drugs. J Alzheimers Dis, 2000 2, 37-46. [149] Asanuma, M; Miyazaki, I; Ogawa, N. Neuroprotective effects of nonsteroidal antiinflammatory drugs on neurodegenerative diseases. Curr Pharm Des, 2004 10, 695700. [150] Gasparini, L; Ongini, E; Wenk, G. Non-steroidal anti-inflammatory drugs (NSAIDs) in Alzheimer's disease: old and new mechanisms of action. J Neurochem, 2004 91, 521536. [151] Cabrero, A; Laguna, JC; Vazquez, M. Peroxisome proliferator-activated receptors and the control of inflammation. Curr Drug Targets Inflamm Allergy, 2002 1, 243-248. [152] Landreth, GE; Heneka, MT. Anti-inflammatory actions of peroxisome proliferatoractivated receptor gamma agonists in Alzheimer's disease. Neurobiol Aging, 2001 22, 937-944.

158

Dokmeci Dikmen

[153] Gelman, L; Fruchart, JC; Auwerx, J. An update on the mechanisms of action of the peroxisome proliferator-activated receptors (PPARs) and their roles in inflammation and cancer. Cell Mol Life Sci, 1999 55, 932-943. [154] Heneka, MT; Feinstein, DL; Galea, E; Gleichmann, M; Wullner, U; Klockgether, T. Peroxisome proliferator-activated receptor gamma agonists protect cerebellar granule cells from cytokine-induced apoptotic cell death by inhibition of inducible nitric oxide synthase. J Neuroimmunol, 1999 100, 156-168. [155] Heneka, MT; Klockgether, T; Feinstein, DL. PPARγ ligands reduce neuronal inducible nitric oxide synthase expression and cell death in vivo. J Neurosci, 2000 20, 68626867. [156] Murphy, GJ; Holder, JC. PPAR-gamma agonists: therapeutic role in diabetes, inflammation, and cancer. Trends Pharmacol Sci, 2000 21, 469-474. [157] Kim, EJ; Kwon, KJ; Park, JY; Lee, SH; Moon, CH; Baik, EJ. Effects of peroxisome proliferator-activated receptor agonists on LPS-induced neuronal death in mixed cortical neurons: associated with iNOS and COX-2. Brain Res, 2002 941, 1-10. [158] Lim, GP; Yang, F; Chu, T; Chen, P; Beech, W; Teter, B; Tran, T; Ubeda, O; Hsiao Ashe, K; Frautschy, SA; Cole, GM. Ibuprofen suppresses plaque pathology and inflammation in a mouse model of Alzheimer's disease. J Neurosci, 2000 20, 57095714. [159] Weggen, S; Eriksen, JL; Das, P; Sagi, SA; Wang, R; Pietrzik, CU; Findlay, KA; Smith, TE; Murphy, MP; Bulter, T; Kang, DE; Marquez-Sterling, N; Golde, TE; Koo, EH. A subset of NSAIDs lower amyloidogenic Abeta42 independently of cyclooxygenase activity. Nature, 2001 414, 212-216. [160] Jantzen, PT; Connor, KE; DiCarlo, G; Wenk, GL; Wallace, JL; Rojiani, AM; Coppola, D; Morgan, D; Gordon, MN. Microglial activation and beta -amyloid deposit reduction caused by a nitric oxide-releasing nonsteroidal anti-inflammatory drug in amyloid precursor protein plus presenilin-1 transgenic mice. J Neurosci, 2002 22, 2246-2254. [161] Bernardo, A; Ajmone-Cat, MA; Gasparini, L; Ongini, E; Minghetti, L. Nuclear receptor peroxisome proliferator-activated receptor-gamma is activated in rat microglial cells by the anti-inflammatory drug HCT1026, a derivative of flurbiprofen. J Neurochem, 2005 92, 895-903. [162] Dokmeci D. Ibuprofen and Alzheimer's disease. Folia Med (Plovdiv), 2004 46, 5-10. [163] Richardson, RL; Kim, EM; Shephard, RA; Gardiner, T; Cleary, J; O'Hare, E. Behavioural and histopathological analyses of ibuprofen treatment on the effect of aggregated Abeta(1-42) injections in the rat. Brain Res, 2002 954, 1-10. [164] Yan, Q; Zhang, J; Liu, H; Babu-Khan, S; Vassar, R; Biere, AL; Citron, M; Landreth, G. Anti-inflammatory drug therapy alters beta-amyloid processing and deposition in an animal model of Alzheimer's disease. J Neurosci, 2003 23, 7504-7509. [165] Sastre, M; Dewachter, I; Landreth, GE; Willson, TM; Klockgether, T; van Leuven, F; Heneka, MT. Nonsteroidal anti-inflammatory drugs and peroxisome proliferatoractivated receptor-gamma agonists modulate immunostimulated processing of amyloid precursor protein through regulation of beta-secretase. J Neurosci, 2003 23, 9796-9804.

The Role of Peroxisome Proliferator-Activated Receptors…

159

[166] Yao, Y; Chinnici, C; Tang, H; Trojanowski, JQ; Lee, VM; Pratico, D. Brain inflammation and oxidative stress in a transgenic mouse model of Alzheimer-like brain amyloidosis. J Neuroinflammation, 2004 1, 21. [167] Morihara, T; Teter, B; Yang, F; Lim, GP; Boudinot, S; Boudinot, FD; Frautschy, SA; Cole, GM. Ibuprofen suppresses interleukin-1beta induction of pro-amyloidogenic alpha(1)-antichymotrypsin to ameliorate beta-amyloid (Abeta) pathology in lzheimer's models. Neuropsychopharmacology, 2005 30, 1111-1120. [168] Heneka, MT; Sastre, M; Dumitrescu-Ozimek, L; Hanke, A; Dewachter, I; Kuiperi, C; O'Banion, K; Klockgether, T; Van Leuven, F; Landreth, GE. Acute treatment with the PPARgamma agonist pioglitazone and ibuprofen reduces glial inflammation and Abeta1-42 levels in APPV717I transgenic mice. Brain, 2005 128, 1442-1453. [169] Bernardo, A; Levi, G; Minghetti, L. Role of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and its natural ligand 15-deoxy-Delta12, 14prostaglandin J2 in the regulation of microglial functions. Eur J Neurosci, 2000 12, 2215-2223. [170] Pratico D. Peripheral biomarkers of oxidative damage in Alzheimer's disease: the road ahead. Neurobiol Aging, 2005 26, 581-583. [171] Zhu, X; Raina, AK; Lee, HG; Casadesus, G; Smith, MA; Perry, G. Oxidative stress signalling in Alzheimer's disease. Brain Res, 2004 1000, 32-39. [172] Hazel, JR; Williams, EE. The role of alterations in membrane lipid compositions in enabling physiological adaptation of organisms to their physical environment. Prog Lipid Res, 1990 26, 167-227. [173] Coyle, JT; Puttfarcken, P. Oxidative stress, glutamate, and neurodegenerative disorders. Science, 1993 262, 689-695. [174] Floyd, RA. Antioxidants, oxidative stress, and degenerative neurological disorders. Proc Soc Exper Biol Med, 1999 222, 236-245. [175] Emerit, J; Edeas, M; Bricaire, F. Neurodegenerative diseases and oxidative stress. Biomed Pharmacother, 2004 58, 39-46. [176] Beal, MF. Does impairment of energy metabolism result in excitotoxic neuronal death in neurodegenerative illnesses? Ann Neurol, 1992 31, 119-130. [177] Refolo, LM; Fillit, HM. New directions in neuroprotection: basic mechanisms, molecular targets and treatment strategies. J Alzheimers Dis, 2004 6, 1-2. [178] Metodiewa, D; Koska, C. Reactive oxygen species and reactive nitrogen species: relevance to cyto(neuro)toxic events and neurologic disorders. An overview. Neurotox Res, 2000 1, 197-233. [179] Berr, C; Richard, MJ; Roussel, AM; Bonithon-Kopp, C. Systemic oxidative stress and cognitive performance in the population-based EVA study, Free Radic Biol Med, 1998 24, 1202-1208. [180] Rinaldi, P; Polidori, MC; Metastasio, A; Mariani, E; Mattioli, P; Cherubini, A; Catani, M; Cecchetti, R; Senin, U; Mecocci, P. Plasma antioxidants are similarly depleted in mild cognitive impairment and in Alzheimer's disease. Neurobiol Aging, 2003 24, 915919.

160

Dokmeci Dikmen

[181] Pratico, D; Yao, Y; Rokach, J; Mayo, M; Silverberg, GG; McGuire, D. Reduction of brain lipid peroxidation by CSF drainage in Alzheimer's disease patients. J Alzheimers Dis, 2004 6, 385-389. [182] Harman D. Aging: a theory based on free radical and radiation chemistry. J. Gerontol, 1956 11, 298-300. [183] Beckman, KB; Ames, BN. The free radical theory of aging matures. Physiol Rev, 1998 78, 547-581. [184] Pietrini, P; Azari, NP; Grady, CL; Salerno, JA; Gonzales-Aviles, A; Heston, LL; Pettigrew, KD; Horwitz, B; Haxby, JV; Schapiro, MB. Pattern of cerebral metabolic interactions in a subject with isolated amnesia at risk for Alzheimer's disease: a longitudinal evaluation. Dementia, 1993 4, 94-101. [185] Berent, S; Giordani, B; Foster, N; Minoshima, S; Lajiness-O'Neill, R; Koeppe, R; Kuhl, DE. Neuropsychological function and cerebral glucose utilization in isolated memory impairment and Alzheimer's disease. J Psychiatr Res, 1999 33, 7-16. [186] Pratico, D; Delanty, N. Oxidative injury in diseases of the central nervous system: focus on Alzheimer's disease. Am J Med, 2000 109, 577-585. [187] Arnaiz, E; Jelic, V; Almkvist, O; Wahlund, LO; Winblad, B; Valind, S; Nordberg, A. Impaired cerebral glucose metabolism and cognitive functioning predict deterioration in mild cognitive impairment. Neuroreport, 2001 12, 851-855. [188] Pratico D. Alzheimer's disease and oxygen radicals: new insights. Biochem Pharmacol, 2002 63, 563-567. [189] Chong, ZZ; Kang, JQ; Maiese, K. Essential cellular regulatory elements of oxidative stress in early and late phases of apoptosis in the central nervous system. Antioxid Redox Signal, 2004 6, 277-287. [190] Marklund, SL; Adolfsson, R; Gottfries, CG; Winblad, B. Superoxide dismutase isoenzymes in normal brains and in brains from patients with dementia of Alzheimer type. J Neurol Sci, 1985 67, 319-325. [191] Zhu, X; Smith, MA; Perry, G; Aliev, G. Mitochondrial failures in Alzheimer's disease. Am J Alzheimers Dis Other Demen, 2004 19, 345-352. [192] Nunomura, A; Perry, G; Aliev, G; Hirai, K; Takeda, A; Balraj, EK; Jones, PK; Ghanbari, H; Wataya, T; Shimohama, S; Chiba, S; Atwood, CS; Petersen, RB; Smith, MA. Oxidative damage is the earliest event in Alzheimer disease. J Neuropathol Exp Neurol, 2001 60, 759-767. [193] Pratico, D; Sung, S. Lipid peroxidation and oxidative imbalance: early functional events in Alzheimer's disease. J Alzheimers Dis, 2004 6, 171-175. [194] Perry, G; Smith, MA. Is oxidative damage central to the pathogenesis of Alzheimer disease? Acta Neurol Belg, 1998 98, 175-179. [195] Pratico, D; Uryu, K; Leight, S; Trojanoswki, JQ; Lee, VM. Increased lipid peroxidation precedes amyloid plaque formation in an animal model of Alzheimer amyloidosis. J Neurosci, 2001 21, 4183-4187. [196] Behl, C; Davis, JB; Lesley, R; Schubert, D. Hydrogen peroxide mediates amyloid beta protein toxicity. Cell, 1994 77, 817-827. [197] Canevari, L; Abramov, AY; Duchen, MR. Toxicity of amyloid beta peptide: tales of calcium, mitochondria, and oxidative stress. Neurochem Res, 2004 29, 637-650.

The Role of Peroxisome Proliferator-Activated Receptors…

161

[198] Lahiri, DK; Greig, NH. Lethal weapon: amyloid beta-peptide, role in the oxidative stress and neurodegeneration of Alzheimer's disease. Neurobiol Aging, 2004 25, 581587. [199] Tuppo, EE; Forman, LJ; Spur, BW; Chan-Ting, RE; Chopra, A; Cavalieri, TA. Sign of lipid peroxidation as measured in the urine of patients with probable Alzheimer's disease. Brain Res Bull, 2001 54, 565-568. [200] De Leon, MJ; George, AE; Golomb, J; Tarshish, C; Convit, A; Kluger, A; De Santi, S; McRae, T; Ferris, SH; Reisberg, B; Ince, C; Rusinek, H; Bobinski, M; Quinn, B; Miller, DC; Wisniewski, HM. Frequency of hippocampal formation atrophy in normal aging and Alzheimer's disease. Neurobiol Aging, 1997 18, 1-11. [201] Markesbery, WR; Carney, JM. Oxidative alterations in Alzheimer's disease. Brain Pathol, 1999 9, 133-146. [202] Lovell, MA; Ehmann, WD; Butler, SM; Markesbery, WR. Elevated thiobarbituric acidreactive substances and antioxidant enzyme activity in the brain in Alzheimer's disease. Neurology, 1995 45, 1594-1601. [203] McIntosh, LJ; Trush, MA; Troncoso, JC. Increases susceptibility of Alzheimer’s disease temporal lobe cortex to oxygen free radical mediated processes. Free Radic Biol Med, 1997 23, 183-190. [204] Marcus, DL; Thomas, C; Rodriguez, C; Simberkoff, K; Tsai, JS; Strafaci, JA; Freedman, ML. Increased peroxidation and reduced antioxidant enzyme activity in Alzheimer’s disease. Exp Neurol, 1998 150, 40-44. [205] Markesbery, WR; Lovell, MA. Four-hydroxynonenal, a product of lipid peroxidation, is increased in the brain in Alzheimer’s disease. Neurobiol Aging, 1998 19, 33-36. [206] Lovell, MA; Ehmann WD; Mattson, MP; Markesbery, WR. Elevated 4hydroxynonenal in ventricular fluid in Alzheimer’s disease. Neurobiol Aging, 1997 18, 457-461. [207] Montine, TJ; Beal, MF; Cudkowicz, ME; O'Donnell, H; Margolin, RA; McFarland, L; Bachrach, AF; Zackert, WE; Roberts, LJ; Morrow, JD. Increased CSF F2- isoprostane concentration in probable AD. Neurology, 1999 52, 562-565. [208] Pratico, D; Clark, CM; Lee, VM; Trojanowski, JQ; Rokach, J; FitzGerald, GA. Increased 8,12-iso-iPF2alpha-VI in Alzheimer's disease: correlation of a noninvasive index of lipid peroxidation with disease severity. Ann Neurol, 2000 48, 809-812. [209] Pratico, D; Lee, VMY; Trojanowski, JQ; Rokach, J; Fitzgerald, GA. Increased F2isoprostanes in Alzheimer’s disease: evidence for enhanced lipid peroxidation in vivo. FASEB J, 1998 12, 1777-1783. [210] Gsell, W; Conrad, R; Hickethier, M; Sofic, E; Frolich, L; Wichart, I; Jellinger, K; Moll, G; Ransmayr, G; Beckmann, H; Riederer, P. Decreased catalase activity but unchanged superoxide dismutase activity in brains of patients with dementia of Alzheimer type. J Neurochem, 1995 64, 1216-1223. [211] Hampel, H; Buerger, K; Zinkowski, R; Teipel, SJ; Goernitz, A; Andreasen, N; Sjoegren, M; DeBernardis, J; Kerkman, D; Ishiguro, K; Ohno, H; Vanmechelen, E; Vanderstichele, H; McCulloch, C; Moller, HJ; Davies, P; Blennow, K. Measurement of phosphorylated tau epitopes in the differential diagnosis of Alzheimer disease: a comparative cerebrospinal fluid study. Arch Gen Psychiatry, 2004 61, 95-102.

162

Dokmeci Dikmen

[212] Frautschy, SA; Hu, W; Kim, P; Miller, SA; Chu, T; Harris-White, ME; Cole, GM. Phenolic anti-inflammatory antioxidant reversal of Abeta-induced cognitive deficits and neuropathology. Neurobiol Aging, 2001 22, 993-1005. [213] Cole, GM; Morihara, T; Lim, GP; Yang, F; Begum, A; Frautschy, SA. NSAID and antioxidant prevention of Alzheimer's disease: Lessons from in vitro and animal models. Ann N Y Acad Sci, 2004 1035, 68-84. [214] Bragin, V; Chemodanova, M; Dzhafarova, N; Bragin, I; Czerniawski, JL; Aliev, G. Integrated treatment approach improves cognitive function in demented and clinically depressed patients. Am J Alzheimers Dis Other Demen, 2005 20, 21-26. [215] Sano, M; Ernesto, C; Thomas, RG; Klauber, MR; Schafer, K; Grundman, M; Woodbury, P; Growdon, J; Cotman, CW; Pfeiffer, E; Schneider, LS; Thal, LJ. A controlled trial of selegiline, alpha-tocopherol, or both as treatment for Alzheimer's disease. The Alzheimer's Disease Cooperative Study. N Engl J Med, 1997 336, 12161222. [216] Yang, F; Lim, GP; Begum, AN; Ubeda, OJ; Simmons, MR; Ambegaokar, SS; Chen, PP; Kayed, R; Glabe, CG; Frautschy, SA; Cole, GM. Curcumin inhibits formation of amyloid beta oligomers and fibrils, binds plaques, and reduces amyloid in vivo. J Biol Chem, 2005 280, 5892-5901. [217] Vina, J; Lloret, A; Orti, R; Alonso, D. Molecular bases of the treatment of Alzheimer's disease with antioxidants: prevention of oxidative stress. Mol Aspects Med, 2004 25, 117-123. [218] Engelhart, MJ; Geerlings, MI; Ruitenberg, A; van Swieten, JC; Hofman, A; Witteman, JC; Breteler, MM. Dietary intake of antioxidants and risk of Alzheimer disease. JAMA, 2002 287, 3223-3239. [219] Morris, MC; Evans, DA; Bienias, JL; Tangney, CC; Bennett, DA; Aggarwal, N; Wilson, RS; Scherr, PA. Dietary intake of antioxidant nutrients and the risk of incident Alzheimer disease in a biracial community study. JAMA, 2002 287, 3230-3237. [220] Inoue, H; Jiang, XF; Katayama, T; Osada, S; Umesono, K; Namura, S. Brain protection by resveratrol and fenofibrate against stroke requires peroxisome proliferator-activated receptor alpha in mice. Neurosci Lett, 2003 352, 203-206. [221] Cuzzocrea, S. Peroxisome proliferator-activated receptors gamma ligands and ischemia and reperfusion injury. Vascul Pharmacol, 2004 41, 187-195. [222] Villegas, I; Martin, AR; Toma, W; de la Lastra, CA. Rosiglitazone, an agonist of peroxisome proliferator-activated receptor gamma, protects against gastric ischemiareperfusion damage in rats: role of oxygen free radicals generation. Eur J Pharmacol, 2004 505, 195-203. [223] Abdelrahman, M; Sivarajah, A; Thiemermann, C. Beneficial effects of PPAR-gamma ligands in ischemia-reperfusion injury, inflammation and shock. Cardiovasc Res, 2005 65, 772-781. [224] Liu, N; Qiang, W; Kuang, X; Thuillier, P; Lynn, WS; Wong, PK. The peroxisome proliferator phenylbutyric acid (PBA) protects astrocytes from ts1 MoMuLV-induced oxidative cell death. J Neurovirol, 2002 8, 318-325.

The Role of Peroxisome Proliferator-Activated Receptors…

163

[225] Klucis, E; Crane, D; Masters, C. Sequential alterations in the micro-localization of catalase in mouse liver after treatment with hypolipidemic drugs. Mol Cell Biochem, 1984 65, 73-82. [226] Moreira, PI; Smith, MA; Zhu, X; Honda, K; Lee, HG; Aliev, G; Perry, G. Oxidative damage and Alzheimer's disease: are antioxidant therapies useful? Drug News Perspect, 2005 18, 13-19.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp.

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter VI

Role of Sphingomyelin Cycle Signaling System in Alzheimer’s Disease A. V. Alessenko∗ Institute of Biochemical Physics of the Russian Academy of Sciences, Moscow, Russia

Abstract Alzheimer’s disease (AD) is characterized by a progressive decline in cognition, memory and intellect. Possible mechanisms for AD neurotoxicity include: alteration in Ca2+ homeostasis, activation of specific receptors affecting cellular homeostasis, activation of oxidative processes, direct disruption of membrane integrity and disorders in lipid metabolism, or a combination of two or more of the above mechanisms. It was established that conformational changes in amyloid-beta peptide (Aβ) may occur in lipid rafts under the control of specific sphingolipids. This review demonstrates a novel mechanism for development of AD. It has been hypothesized that Aβ and TNF-α may have a prominent role in neurodegeneration. It is well-known that neuronal death is developed according to apoptotic program. Most signaling pathways that trigger apoptosis remain unknown, but the sphingomyelin pathway has been recognized as an ubiquitous signaling system that links specific cell-surface receptors and environmental stresses to the nucleus. This pathway is initiated by the hydrolysis of sphingomyelin via the action of sphingomyelinases to generate ceramide. Ceramide then serves as a second messenger in this system, leading to apoptosis. Oxidative mechanisms have been implicated in this pathway. TNF-α activates receptors linked to multiple effector systems, including a sphingomyelin pathway and peroxide oxidation. Recently, it was shown that superoxide radicals are used as signaling ∗

Telephone: 7(495) 939 71 59; email: [email protected]

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A. V. Alessenko molecules within the sphingomyelin pathway. It means that cross-talk between the oxidation system and sphingomyelin cycle exists in cells and could have important implications for the induction phase and evolution of AD. The role of TNF-α in the pathogenesis of AD is unclear, because it has been shown to be involved in both neuroprotection and neurodegeneration, depending on doses and the age of animals. Small doses of this cytokine induced a protective effect against Aβ neurotoxicity. It was suggested that using low doses of TNF-α in the clinic for the prevention of AD development might be a perspective. Identification of the N-SMase-ceramide pathway may lead to the development of more effective therapeutic strategies, aimed at preventing Aβ-induced cell death.

Introduction Alzheimer’s disease (AD) affects about 15 million individuals worldwide. The prevalence of this disease doubles every 5 years after age 65 and approaches 50% by age 85. Because of the ongoing increase in life expectancy, the number of people affected by this disease is rapidly increasing. The major risk factor for late-onset AD is aging [1]. The molecular events that mediate the effect of aging on AD are the subjects of intensive study. AD is characterized neuropathologically by amyloid deposits, neurofibrillary tangles, and selective neuronal loss [2]. The major component of the amyloid deposits is β-amyloid peptide (Αβ - a family of 39-43-residue peptides proteolytically derived from the amyloid precursor protein (APP). APP is first cleaved by β-site APP –cleaving enzyme 1 (BACE1) at the N terminus of Aβ (β-cleavege), producing a C-terminal fragment (β-APP-CTF) of12 kDa, and subsequently in the transmembrane domain (γ-cleavage) by a presenilin-harboring protease complex. The two major sites of γ-cleavage are located at position 40 and 42 of Αβ, generating Aβ40 and Aβ42, respectively. Aβ in AD brains exist either as amorphous deposits called diffuse amyloid or as dense cores of deposits called senile plaques [3]. While diffuse amyloid is present in both normal-aged and AD brains, senile plaques are found only in AD brains, where they are associated with dystrophic neurons [4]. Increasing evidence from genetic [5], pathological [6] and cell culture [7] studies have implicated Aβ as a toxic agent in AD. The membrane lipid ceramide is the backbone of all complex sphingolipids and acts as a second messenger in many biological events. Ceramide is involved in stress-activated apoptosis. The intracellular levels of ceramide increase progressively during aging in both cultered cells and the whole organ [8-11]. In addition, brains from AD patients contain approximately three times more ceramide when compared with a normal brain [12]. The AD brain is subjected to increased oxidative stress resulting from free radical damage and the resulting cellular dysfunctions are widely believed to be responsible for neuronal degeneration in this disorder [13, 14]. Aβ-induced oxidative stress alters membrane lipid metabolism, resulting in increased amounts of ceramides [15]. Possible mechanisms for Aβ neurotoxicity include: alteration in Ca2+ homeostasis, activation of specific receptors affecting cellular homeostasis, activation of oxidative processes, direct disruption of membrane integrity and disorders in lipid metabolism, or a combination of two or more of the above mechanisms.

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Role of Membrain Sphingolipids and Cholesterol in Conformational Transition of the β −amyloid Peptide To understand the neurotoxic action of Aβ, it is essential to identify specific cellular components that interact with the peptide and mediate a biological response of the affected cells. A likely primary target of Aβ is the neuronal plasma membrane. Indeed, a rapidly growing number of observations indicate that the peptide may alter important physical and biological properties of the membranes [16, 17]. The mechanisms of Aβ-membrane interaction remain, however, elusive. It was demonstrated [18] that Aβ40 forms cationselective channels in membranes and have been speculated that these channels disrupt ion homeostasis and thus cause toxicity. Aβ underwent a conformational transition from an alpha-helix-rich structure to a betasheet-rich structure with the increase in protein density on the membrane. The experimental studies provide evidence suggesting that Aβ neurotoxicity stems from interactions of Aβ with membrane proteins or lipids. It was shown by biophysical techniques that phosphatidylcholine (PC) / phosphatidylglycerol (PG) vesicles interact with Aβ-peptide [19]. Several results indicate that Aβ neurotoxicity may be mediated, at least in part, by direct interaction between Aβ and membrane phospholipids and gangliosides. The major conformational transition of the Alzheimer beta-amyloid peptide has been observed upon interaction with sphingolipid-containing membranes. Alzheimer Aβ contains a mutation domain that was found to interact with monomolecular films of galacosylceramide and sphingomylin at the air-water interface. [20] It has been found that Aβ undergoes a conformational transition from random coil to ordered structure rich in β-sheet after the addition of lipid vesicles containing negatively charge lipids and when it binds to the membrane containing the ganglioside GM1 [21]. Aβ binds with high affinity and selectivity to gangliosides, which belong to the sphingomyelin family. Furthermore, in the presence of ganglioside-containing membrane vesicle, there is a dramatic increase in the rate of fibril formation by the peptide [22, 23]. It was postulated that the membrane-bound Aβ may act as a template that catalyzes the fibrogenesis reaction in vivo. Ganglioside-bound Aβ species were found in brains exhibiting early pathological changes of Alzheimer’s disease [24]. This form was identified as Aβ42 and speculated to be localized on the cell surface where it can act as a seed for amyloid fibril formation [22, 24]. Identification of factors that initiate formation of GM1/Aβ may be crucial for determination of the pathogenesis of AD and for development of preventive and curative treatment strategies. It was established that the gandlioside species-specificity is responsible for a conformational changes of Aβ by which ganglioside-bound Aβ acts as a seed for Aβ fibrillogenesis. Aβ recognized ganglioside clusters composed of major gangliosides occurring in brains (GM1, GD1a, GD1b and GT1b), the density of which increased with the number of sialic acid residue. Interestingly, however, mixing of gangliosides inhibited cluster formation. GM1- Aβ exhibited the strongest seeding potential, especially under beta-sheet-forming

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conditions [25]. This study suggested that lipid composition of rafts including gangliosides, sphingomyelin, cholesterol and ceramide strictly controls amyloid formation. So, it appears that the peptides β-sheet structure may facilitate the association with lipid membranes. Ganglioside forms clusters that Aβ can recognize. [21-25]. An important role in Aβ aggregation and neurotoxicity may play caveolae membrane domaines or rafts, specialized transmembrane exchange zones implicated in cell signaling. They are enriched in glycosphingolipids, cholesterol, sphingomyelin (SPM) and lipidenchored membrane proteins. [26]. It was established that conformational changes in Aβ may occur in lipid rafts under the control of specific sphingolipids [20]. Membrane rafts composed of sphingomyelin have van der Waals interactions and hydrogen bonds between the sugar head groups and the sphingosine backbones leading to stronger lateral cohesion resulting in a higher gel-to-liquid phase transition. The amidebounded fatty acid in ceramide ranges from 20 to 26 carbon atoms in length, compared with 16 to 22 for the fatty acids of glycerolipids. In addition, SPH fatty acids are more saturated compared with PtdCho fatty acids, resulting in less lateral packing of the PtdCho molecules. A putative galactosylceramide (GalCer)-binding motif was indentified in Alzheimer’s βamyloid peptide. Interaction of Aβ with GalCer and sphingomyelin was studied by monomolecular film binding assay [20]. Aβ recognizes sphingomyelin as well as GalCer. The ability of Aβ-peptide to recognize both sphingolipids is likely due to the presence of both sugar-binding residues (Tyr10, His13, His14, Phe20, Phe21) and acid residues (Asp7, Glu11) within peptide [20]. It is known that cell surface SM in rafts is mostly found in cholesterol-rich domains [27, 28]. The planar steroid ring of cholesterol can interact more closely with saturated fatty acids of SPH than with the fatty acids of PtdCho, which contains the kink at C9-C10. Hydrolysis of SM has been reported to reduce the clustering of cholesterol into cholesterol-rich domains and to induce retrotransport of cholesterol to the endoplasmic reticulum [27]. Cholesterol level has been reported to be reduced in the brains of AD patients [29]. The 30% reduction in cholesterol level was associated with 3-4 A reduction in the bilayer width of membrane prepared from AD brain [29]. However, it should be noted that post-mortern of an AD brain reflects only the last stage of a progressive neurodegenerative process that started decades before. But recently it was shown that treatment with cholesterol-lowering statins drastically lowered the risk of AD developing [30]. Changes in membrane cholesterol disrupts the formation and function of caveolae, suggesting that these membrane microdomains containing cholesterol are involved in a range of biological processes including the trafficking and proteolytic processing of embedded proteins. Biophysical properties of SPH/cholesterol enriched rafts probably influence the lipidlipid and lipid-protein interactions in the rafts [31, 32]. It is not known if amyloid precursor protein (APP) is transported and proteolytically processed by secretases (αβ or γ while inserted into SPH/cholesterol rafts, but if so, an alteration in rafts lipid composition could conceivably alter both the transport and processing of APP.

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To elucidate the molecular mechanisms underlying GM1/ Aβ formation, the effects of cholesterol and ethers lipid on the binding of Aβ to GM1-containing lipid bilayers were examined in detail using fluorescent dye-labeled human Aβ [33]. Increases in not only GM1 but also cholesterol contents in the lipid bilayers facilitated the binding of Aβ to the membrane by altering the binding capacity, but not binding affinity. An increase in membrane-bound Aβ concentration triggered its conformational transition from helix-rich to β-sheet rich structures [33]. It was suggested that increases in intramembrane cholesterol content, which are likely to occur during aging, appear to be a risk factor for amyloid fibril formation. It was reported [15] that alterations in sphingolipid and cholesterol metabolism during normal brain aging and in the brain of AD patients results in the accumulation of long-chain ceramides and cholesterol. Analysis of 10 different brain regions from patients affected by Alzheimer’s disease /senile demetia of Alzheimer’s type have shown that sphingomyelin content decreased in regions rich in myelin. Cholesterol amounts were highly variable, whereas ubiquinone concentrations increased by 30-100% in most regions of the brain was affected by AD. [34]. Treatment of neurons with alpha-tocopherol or an inhibitor synthesis prevents accumulation of ceramides and cholesterol and protects them against death induced by Aβ. In the endoplasmic reticulum excess cholesterol activates the enzyme acyl-coenzyme A:cholesterol acyltransferase which was implicated in Aβ generation [35]. At the same time it was shown that intracellular levels of ceramide- product of SM digestion regulate Aβ generation by modulation β-secretase cleavage of APP. N-SMase, fumonisin1 and NB-DGJ, general inhibitor of the SM/glycosphingolipid metabolic pathway, caused changes in the ceramide levels, which were consistently paralleled in Aβ generation. It was found that ceramide controls the processing of APP by affecting the molecular stability of the βsecretase, BACE1 [36]. Presented studies suggest that lipid composition of rafts including gangliosides, sphingomyelin, cholesterol and ceramide strictly controls amyloid processing and aggregation.

Role of the Neutral Sphingomyelinase-Ceramide Pathway in Neurodegenerative Damages Numerous molecules involed in cell signaling have been identified in caveolae, suggesting that these structures may serve to compartimentalize, modulate and integrate signaling events at the cell surface. Alteration in the expression of caveolin genes of signaling enzymes has been implicated in Alzheimer’s disease. One of such kind of enzyme is sphingomyelinase (SMase) that controls metabolism of sphingomyelin- the main component of membrane sphingolipids in the brain. Sphingolipids (SLs) are ubiquitous components of eukariotic cell membranes. Relatively high levels of them are located in the membranes of neuronal tissues [37]. Sialylated glycosphingolipids (GSLs), the gangliosides are essential membrane components. Except

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gangliosides, a large number of individual SL species exist, resulting from differences in both the hydrophobic ceramide moiety and in the polar head group. Ceramide consists of a long chain base (sphingosine, sphinganine or phytosphingosine) to which a variety of fatty acids are attached via N-acylation. The polar head group consists of phosphorylcholine, sugar or sulfatide residues. Equilibrium of balance between specific SLs is essential for normal neuronal function [37]. This becomes apparent when considering the SL storage diseases, such as Gaucher, Tay-Sachs and Nieman-Pick A and B diseases in which GleCer, ganglioside GM2 and sphingomyelin accumulate respectively due to a decreased activity of the lysosomal enzymes responsible for their degradation [38, 39]. Although SLs were generally assumed to be little more than inert components of cell membranes, it is now clear that they also act as important signaling molecules, and moreover, individual SL and GSL species are known to function in regulating specific biochemical events in signaling pathways. Over the past decade, relatively simple SLs, such as ceramide, sphingosine, sphingosine-1-phosphate and glucosylceramide play important roles in neuronal functions by regulating rates of neuronal growth, differentiation and death [37]. Ceramides can be generated either from de novo synthesis or by the action of sphingomyelinase (ceramide-phosphocholine phosphodiesterase, EC 3.1.4.12), which cleaves phosphorylcholine from SPH resulting in the formation of ceramide. Five major isoforms of SMases are known, classified primarily according to their pH optima, localization in cell structures (plasma membrane, lysosomas, inner membranes) and cation-dependency [40]. The best characterized Smase is the lysosomal acid SMase (A-SMase), whose deficiency is responsible for Nieman-Pick disease [39]. A-SMase is highly expressed in brain cells and its expression level does not change significantly during development. Neutral membrane-bound SMase (N-SMase) is expressed at the highest level in the brain, and its expression increases during neuronal development [41]. Various factors such as cytokines, growth factors, hormones, oxidative stress and radiation are known to activate SMases in non-neuronal tissues. Less is known about the mechanisms by which SMases are activated in neurons and glial cells. In our experiments we have shown that intracerebral and interperitoneal injection of TNF-α induced activity of NSMase in hippocampus [42, 43]. The mechanisms involved in the activation of N-SMase in response to TNF-α are becoming clear. TNF-α initiates the pathway through TNFR1 (55-kda receptor) leading to phospholipase A2 activation, generation of arachidonic acid, and subsequent activation of N-SMase [44]. In addition, proteases have also been implicated in the pathway leading from TNF-α to the activation of N-SMase. Nerve growth factor (NGF) caused an increase in ceramide levels in T9 glioma cells and hippocampal neurons [45]. Furthermore, in hippocampal neurons, it was shown that the response to NGF after the first 24 h in culture undergoes a switch from acceleration of axonal outgrowth [46] to apoptotic cell death [47], due to an increased level of ceramide generation. In hippocampal neurons, ceramide is generated via N-SMase in respose to NGF. Thus, in these primary neuronal cultures, N-SMase appears to be mainly responsible for ceramide generation in response to trophic factor [47]. In contrast, an excitotoxic stress-activated pathway of ceramide generation does involve A-SMase in hippocampal neurons [48]. It means that different SMases in the same neuron are activated for the generation of different ceramide pools in response to different stimuli.

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Ceramide is a lipid second messenger involved in many biological events that regulate terminal differentiation of neurons, cellular senescence, proliferation and death [37, 49, 50]. Chronic increase in intracellular ceramide can inhibit axonal elongation and receptormediated internalization of nerve growth factor [51]. Ceramide has been implicated in several apoptotic paradigms including trophic factor withdrawal and exposure to proinflammatory molecules [47]. Ceramide can stimulate both protein kinase and phosphatase pathways in neuronal cells. [37]. Ceramidase cleaves the acyl-amide bond of ceramide resulting in sphingosine and free fatty acid. Sphingosine can be phosphorylated by ATP and ceramide kinase to form sphingosine 1-phosphate. Sphingosine and sphingosine1-phosphate also are cell signaling molecules [52]. It is presently not known if sphingosine and sphingosine 1-phosphate levels are altered in the AD brain. Aβ and ceramide share cell death signaling characteristics. Aβ-induced apoptosis involves TNF-α p75 neurotrophin receptor, and FAS ligand [37, 53], which are cell surface receptors that transmit death signals through the sphingomyelin-ceramide pathway. [53, 54, 55, 56, 57]. Moreover, both Aβ [58] and ceramide [59] cause mitochondrial disfunction and induce oxidative stress. Cellular ceramide synthesis increases in response to stress or death signals [37, 55]. It was indicated that membrane-associated oxidative stress occurs in association with lipid alterations, and exposure of hippocampal neurons to Aβ induces membrane oxidative stress and the accumulation of ceramide species and cholesterol [15]. These findings suggest a sequence of events in the pathogenesis of AD in which Aβ induces membrane-associated oxidative stress, resulting in perturbed ceramide and cholesterol metabolism which, in turn, triggers neurodegenerative cascade that leads to clinical disease. [15]. Lower sphingomyelin level [34, 60] and higher ceramide levels [12, 34] in the AD brain have been reported. Examination of ceramide levels in the cerebrospinal fluid (CSF) or brain tissues from neurodegenerative disorders have been shown that ceramide was significantly increased in patients with Alzheimer’s disease than in patients with age-matched amyotrophic lateral sclerosis (ALS) and other neurological controls [6, 61]. In AD brains, ceramide was aberrantly expressed in astroglia in the frontal cortices, but not detected in ALS and control brains [62]. Maximal changes in ceramide contents after single intracerebral administration of TNF-α and Aβ were found in the hippocampus, and were less expressed in the cerebral cortex and cerebellum [42]. Remarkable increases in sphingomyelinase activity and content of ceramide were found after 7 days of injection of Aβ. In this study a link was found between activation of sphingomyelinase and accumulation of ceramide after 7 days injection of fibrillar A25−35 [ 42 ]. Aβ1-42 peptides, but not reverse (Aβ42-1) induce activation of sphingomyelinases and the production of ceramide in neurons [63]. Within 15 min of treatment, fibrillar Aβ1−42 peptides were able to induce the level of ceramide by more than 2-fold. After 10 h of treatment of Aβa 12-fold increase in ceramide production was observed. In contrast to fibrillar form, soluble Aβ1-42 peptides were weakly efficient in inducing the level of ceramide [63]. Several lines of evidence support the suggestion that ceramide mediates at least in part, Aβ-induced oligodenrocytes (OLG) death [64]. Both Aβ and C2-ceramide caused OLG death

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in time dependent manner. Aβ treatment increased ceramide formation in OLGs. In addition, increasing cellular ceramide release from sphingomyelin by exogenous bacterial SMase, which mimics cellular N-SMase action, also induced OLG death. Furthermore, the N-SMase inhibitors, 3-0-methyl-sphingomyelin was effective in protecting OLGs against Aβ cytotoxicity. Aβ 25-35 and Aβ 1-40 activated N-SMase, but not A-SMase, in OLGs. Antisense oligonucleotides specific for N-SMase also attenuated Aβ-induced OLG cell death, further implicating N-SMase as a mediator. Glutathione (GSH) depletion has been shown to activate N-SMase activity [66]. Buthonine sulfoximine (BSO) and diethyl maleate (DEM) have been shown to deplete GSH in various cell types [65]. Both BSO and DEM selectively increased N-SMase activity, increased ceramide level, decreased cellular GSH levels and were cytotoxic to OLGs [64]. Inhibition of ceramide degradation by ceramidase inhibitors, enhanced Aβ cytotoxicity in OLGs [65]. Although the local concentration of fibrillar Aβ peptides present in the brain of AD patients may differ from the concentration of Aβ in primary neurons used in the experiments of this study, nevertheless, these results cleary point out N-SMase as a possible therapeutic target for the prevention of neuronal damage in AD and other neurodegenerative disorders. The physiological response of neurons and other neuronal cells to ceramide generation very little is known. However, research in this area will be stimulated by recent observation that ceramides, together with cholesterol esters appear to mediate oxidative stress-induced death of neurons and apoptosis of oligodendrocytes.

Involvement of Oxidative Stress-induced Abnormalities in Sphingomyelinase Activity and Ceramide Level in Alzheimer’s Disease Oxidative stress plays a prominent role in Aβ-mediated neuronal [66] and OLG death [67]. The involvement of free radicals in the pathogenesis of AD is accepted for the following reasons: 1. Brain metabolism requires substantial quantities of oxygen. 2. Neurons are particularly sensitive to free radicals attack, because their glutathione content is very low, but their membranes contain a high proportion of polyunsaturated fatty acids. 3. β-Amyloid is sensitive to the action of free radicals, contributing to its aggregation. 4. Traces of metals (iron, copper, zinc and aluminium) capable of catalyzing reactions that produce free radicals have been found in the brain of AD patients. 5. AD is related to mitochondrial anomalies, particularly for cytochrome-c-oxidase, and these anomalies may explain the abnormal production of free radicals. 6. Aging is the principal AD risk factor and is itself related to accumulated free radical attacks. 7. Free radical scavengers reduce the toxicity of β-amyloid.

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8. The clinical use of many free scavengers (vitamin E, Ginkgo biloba extract drugs, estrogens, and the iron-chelating agents is quite successful. This evidence clearly supports the involvement of free radicals and ROS in AD. However, it is unknown whether free radicals are really one of the basic causes of the pathogenesis and neuronal damage in AD. Brain tissue is especially sensitive to oxidative injury because of its higher metabolic rate driven by glucose, lower concentration of protective antioxidants, and higher level of polyunsaturated fatty acids that are susceptible to lipid peroxidation. The Aβ cascade hypothesis postulates that Aβ generates free radicals and, thereby, oxidative disorders in cellular constituents [13]. The lipoperoxidation phenomena could have a major, or even causal, influence on the pathogenesis of the AD [68, 69]. Using postmortem material, it was reported that oxidative cellular damage (lipid peroxidation, oxidative damage of protein and DNA) is increased in certain AD brain areas [68]. Free-radical mediated long-lasting oxidative stress might play a primary role in the aggregation of Aβ and formation of extracellular amyloid plaques [68]. The effect of ROS on membrane phospholipids aggregation of Aβ could prove to be important because some alterations to membrane phospholipids may be specific to the pathogenesis of AD [14, 70]. It was shown [71] that lipid peroxidation is a major cause of the depletion of membrane phospholipids in AD. One of the products of lipid peroxidation, 4hydroxynonenal, which is found in high concentration in AD patients, proved to be toxic to hippocampal cells in culture [72]. This highly reactive product, β-aldehyde is thought to cause neuronal death by altering the ATPases involved in ionic transfers and calcium homeostasis [71]. The involvement of reactive oxygen species in the pathogenesis of AD is indicated by activation of catalase, superoxide dismutase and glutathione reductase in the hippocampus and amygdala (regions of the brain that are most affected in AD pathogenesis) [73, 74]. The increased calcium concentration could itself cause of intracellular events, resulting in increased ROS and cellular death. Recently, it was shown [75] that cerebrospinal fluid F2-isoprostane concentrations are elevated in AD patients. These compounds are produced by free radical-catalyzed peroxidation of arachidonic acid, independent of cyclooxygenase enzyme. This discovery is important because it confirms that lipid peroxidation is elevated in AD, but also because it suggests the possible use of the quantification of cerebrospinal fluid F2-isoprostane concentrations as a biomarker of this disease. Although Aβ-mediated oxidative stress induces DNA damage and activates selected transcription factors, including NF-κB and AP-1 the mechanism, by which Aβ induces oxidative stress in the AD brain remains unknown. Nitric acid and peroxynitrite appear to play a crucial role in pathogenesis of AD [76]. The observed increased expression of inducible nitric oxide synthase (iNOS) in the microglia and astrocytes surrounding the Aβ plagues and the significant increase in peroxynitrite in neurons suggest a role for peroxynitrite (ONOO-; a reaction product of NO. and O2 -.) mediated pathology in the AD brain [77]. Peroxynitrite is known to be cytotoxic because it inactivates various cellular processes by nitrosylating proteins, lipids and nucleic acids.

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Aβ(1-42 fibrous form) was reported to upregulate the induction of iNOS in astrocytes [77]. Cytokines, as well as Aβ peptides are known to induce iNOS. Cytokine-induced iNOS were reported to activate the sphingomyelin-ceramide, signal transduction pathway, generating ceramide, which, in turn, was reported to mediate the induction of manganese superoxide dismutase (MnSOD) [78]. It is by direct indications that ceramide induces expression of iNOS [79]. Ceramide-mediated upregulation of iNOS by NFκB activation and its inhibition by antioxidants as N-acetylcysteine and vitamin E suggest a role for cellular redox in the SM-ceramide cascade and induction of MnSOD and iNOS [61, 77, 78]. Presented reports demonstrating an increase in intracellular levels of ceramide in Alzheimer’s disease and the other, showing that ceramide can promote β-peptide biogenesis, substantiate the possible role of ceramide in the pathobiology of AD. Several mechanisms for induction of apoptosis by ROS have been proposed, but an integral model is not established. A growing body of evidence is slowly emerging, indicating that oxidative stress and activation of sphingomyelin pathway are intimately connected in cell cycle and apoptotic signaling [15, 61, 77, 78]. The sphingomyelin pathway has been recognized as an ubiquitous signaling system that links specific cell-surface receptors and environmental stresses to the nucleus [80]. This pathway is initiated by the hydrolysis of sphingomyelin via the action of sphingomyelinases to generate ceramide. Ceramide then serves as a second messenger in this system, leading to apoptosis. Biochemical analysis of recombinant and partially purified mouse N-SMase showed that the enzyme has reactive cysteine residues and that its enzymatic activity is redox-regulated. Indeed, N-SMase is reversibly activated by H2O2 and reversibly inhibited by GSH [81]. It means that cross-talk between the oxidation system and sphingomyelin cycle exists in living cells and could have important implications for developing apoptosis which plays an important role in many kinds of diseases including Alzheimer’s disease. It was shown that fibrillar Aβ induces the activation of N-SMase but not A-SMase in human primary neurons through NADPH-oxidase-sensitive superoxide production [63]. It was shown that, antioxidants inhibited Aβ-induced neuronal activation of N-SMase, but not A-SMase. Aβ1-42, but not Aβ42-1 peptides induced the production of superoxide in neurons. Then DPI, a specific inhibitor of NADPH oxidase, inhibited the Aβ1-42-induced production of superoxide. Primary neurons expressed p22phox, a subunit of NADPH oxidase, and antisense knockdown of p22phox strongly inhibited Aβ induced production of superoxide, suggesting that Aβ induces the production of superoxide via NADPH oxidase. Aβ1-42 peptides also induced the production of H2O2 in neurons, and antisense knockdown of p22phox reduced Aβ-induced production of H2O2, suggesting that superoxide generated from NADPH oxidase was actually converted to H2O2 [63]. Because H2O2 is responsible for the activation of N-SMase, but not A-SMase [81], antisense knockdown of p22phox inhibited Aβ1-42-induced activation of N-Smase, but not A-SMase. The generation of superoxide radicals by hypoxanthine and xanthine oxidase was sufficient to induce the activation of N-SMase in neurons via H2O2. Furthermore, fibrillar Aβ peptides were unable to induce apoptosis and cell death inp22phox knockout human primary neurons. Taken together, these studies [63] support the model in which Aβ peptides induce neuronal apoptosis via the NADPH oxidase-superoxide-H2O2-N-SMase pathway.

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The exact mechanism underlying Aβ-mediated N-SMase activation remains to be elucidated but may involve changes in the cellular redox state and/or GSH metabolism [81]. N-SMase enzymatic activity is directly regulated by cellular GSH content [81]. Aβ has been shown to deplete GSH in cultured cortical neurons [82] and the depletion of cellular GSH stores by oxidative stress has been proposed as a prime mechanism underlying the Aβ cytotoxicity [82]. Although the above sets of observation link sphingomyelin pathway and oxidative stress in cell death, relatively little is known regarding specific mechanisms through which oxidative stress acts on sphingolipid signaling. One could speculate that ROS have direct protein targets. Whether this protein is SMase or a protein with phospholipase, protein kinase, or protease activity, which, in turn regulate SMase, still remains unknown. Many of the relationships between oxidative stress and SM-signaling still remain obscure. It will be of special interest to determine the exact molecular mechanism and the subcellular localization of these interactions. This will allow a better understanding of the roles of ROS and ceramide production as mediators of cell death and of their functions in the pathophysiology of AD and various disease implicating apoptosis. In summary, this review demonstrates a novel mechanism for the development of AD. Presented results of different groups of scientists reveal a causal relationship between Aβ toxicity to various types of brain cells and activation of the N-SMase-ceramide pathway, which is likely to involve oxidative stress. Identification of this pathway may lead to the development of more effective therapeutic strategies, aimed at preventing Aβ-induced cell death. Pharmacological modulation of N-SMase activity can block the Aβ-activated death signaling process and prevent development neurodegenerative damage of the brain during AD disease.

References [1]

[2] [3]

[4]

[5] [6]

Morris, JC. Is Alzheimer's disease inevitable with age?: Lessons from clinicopathologic studies of healthy aging and very mild Alzheimer's disease. J. Clin Invest., 1999, 104, 1171-1173. Selkoe, D. Translating cell biology into therapeutic advances in Alzheimer's disease. Nature, 1999, 399, 23-31. Esch, F; Keim, PS; Beattie, EC; Blacher, RW; Culwell, AR; Oltersdorf, T; McClure D, and Ward, PJ. Cleavage of amyloid beta peptide during constitutive processing of its precursor. Science, 1990, 248, 1122-1128. Wang, D, and Munoz, DG. Qualitative and quantitative differences in senile plaque dystrophic neurites of Alzheimer's disease and normal aged brain. J. Neuropathol. Exp. Neurol., 1995, 54, 548-556. Games, D; Adams, D, et.al. Alzheimer-type neuropathology in transgenic mice overexpressing V717F beta-amyloid precursor protein. Nature, 1995, 373, 523-527. Masliah E; Mallory, M; Deerinck, T, and De’Teresa, R. Re-evaluation of the structural organization of neuritic plaques in Alzheimer's disease. J. Neuropathol. Exp. Neurol., 1993, 619-632.

176 [7]

[8] [9]

[10]

[11]

[12]

[13]

[14] [15]

[16]

[17]

[18]

[19] [20]

[21]

A. V. Alessenko Suzuki, N; Cheung, TT; Cai, X-D; Okada, A; Otvos, LJr; Eckman, C; Gelde, TE, and Younkin, SG. An increased percentage of long amyloid beta protein secreted by familial amyloid beta protein precursor (beta APP717) mutants. Science, 1994, 264, 1336-1340. Venable, ME; Lee, JY; Smyth, MJ; Bielawska, A, and Obeid, LM. Role of ceramide in cellular senescence. J. Biol. Chem., 1995, 270, 39701-39708. Lightle, SA; Oakley, JI, and Nikolova-Karakashin, MN. Activation of sphingolipid turnover and chronic generation of ceramide and sphingosine in liver during aging. Mech. Ageing Dev., 2000, 120, 111-125. Mouton, RE, and Venable, ME. Ceramide induces expression of the senescence histochemical marker, beta-galactosidase, in human fibroblasts. Mech. Ageing Dev., 2000, 113, 169-181. Miller, CJ, and Stein, GH. Human diploid fibroblasts that undergo a senescent-like differentiation have elevated ceramide and diacylglycerol. J. Gerontol A Biol. Sci. Med. Sci., 2001, 56, 8-19. Han, X; Holtzman, DM; McKeel, DWJr, and Morris, JC. Substantial sulfatide deficiency and ceramide elevation in very early Alzheimer’s disease: potential role in disease pathogenesis. J. Neurochem., 2002, 82, 809-818. Varadarajan, S; Yatin, S; Aksenova, M, and Butterfield DA. Rewiev: Alzheimer’s Amyloid β-peptide-associated free-radical oxidative stress and neurotoxicity. J. Structural Biol., 2000, 130, 184-208. Chisten Y. Oxidative stress and Alzheimer disease Am. J. Clin. Nutr., 2000, 71, 621S629S. Cutler, RG; Kelly, J; Storie, K; Pedersen, WA; Tammara, A; Hatanpaa, K; Troncoso, JC, and Mattson, MP. Involvement of oxidative stress-induced abnormalities in ceramide and cholesterol metabolism in brain aging and Alzheimer’s disease. Proc. Natl. Acad. Sci. USA, 2004, 101, 2070-2075. Arispe, N; Rojas, E, and Pollard, HB. Alzheimer disease amyloid beta protein forms calcium channels in bilayer membranes: blockade by tromethamine and aluminum. Proc. Natl. Acad. Sci. USA, 1993, 90, 467-571. Davidson, RM; Shajenko, L, and Donta, TS. Amyloid beta-peptide (A beta P) potentiates a nimodipine-sensitive L-type barium conductance in N1E-115 neuroblastoma cells. Brain Res., 1994, 643, 324-327. Arispe, N; Pollard, HB, and Rojas, E. Giant multilevel cation channels formed by Alzheimer disease amyloid beta-protein [A beta P-(1-40)] in bilayer membranes. Proc. Natl. Acad. Sci. USA, 1993, 90, 10573-10577. Terzi, E; Holzemann, G, and Seeling, J. Self-association of beta-amyloid peptide (1-40) in solution and binding to lipid membranes. J. Mol. Biol., 1995, 252, 633-642. Mahfoud, R; Garmy, N; Maresca, M; Yahi, N; Puigserver, A, and Fantini, J. Identification of a common sphingolipid-binding domain in Alzheimer, prion, and HIV1 proteins. J. Biol. Chem., 2002, 277, 11292-11296. Choo-Smith, LP, and Surewicz, WK. The interaction between Alzheimer amyloid b(140) peptide and ganglioside GM1-containing membranes. FEBS Lett., 1997, 402, 9598.

Role of Sphingomyelin Cycle Signaling System in Alzheimer’s Disease

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[22] Choo-Smith, LP; Garzon-Rodriguez, W; Glabe, CG, and Surewicz, WK. Acceleration of amyloid fibril formation by specific binding of Abeta (1-40) peptide to gangliosidecontaining membrane vesicles. J. Biol. Chem., 1997, 272, 22987-22990. [23] Kurganov, B; Doh, M, and Arispe, N. Aggregation of liposome induced by the toxic peptides Alzheimer’s Aβs, human amylin and prion (1065-126): facilitation by membrane-bound GM1 ganglioside. Peptides, 2004, 25, 217-232. [24] Yanagisava, K; Odaka, A; Suzuki, N, and Ihara, Y. GM1 ganglioside-bound amyloid beta-protein (A beta): a possible form of preamyloid in Alzheimer's disease. Nat. Med., 1995, 1, 1062-1066. [25] Kakio, A; Nishimoto, S; Yanagisawa, K; Kozutsumi, Y, and Matsuzaki, K. Interactions of amyloid beta-protein with various gangliosides in raft-like membranes: importance of GM1 ganglioside-bound form as an andogenous seed for Alzheimer amyloid. Biochemistry, 2002, 41, 7385-7390. [26] Slotte, JP; Porn, MS, and Hermala, A-S. in Current topics in Membranes: Cell Lipids (Hoekstra, D., ed), p. 483-502, Academic Press. Inc., New York. [27] Kaneko, K; Vey, M; Scott, M; Pilkuhn, S; Cohen, FE, and Prusiner, SB. COOHterminal sequence of the cellular prion protein directs subcellular trafficking and controls conversion into the scrapie isoform. Proc. Natl. Acad. Sci. USA, 1997, 84, 2333-2338. [28] Kakio, A; Nishimoto, S; Kozutsumi, Y, and Matsuzaki, K. Formation of a membraneactive form of amyloid beta-protein in raft-like model membranes Biochem. Biophys. Res. Commun., 2003, 303, 514-518. [29] Svennerholm, L, and Gottfries, CG. Membrane lipids, selectively diminished in Alzheimer brains suggest synapse loss as a primary event in early-onset (type1) and demyelination in late0onset form (typeII). Neurochem., 1994, 62, 1039-1047. [30] Hartman, T. Cholesterol, Aβ, and Alzheimer’s disease. TINS, 2001 24, (suppl), S45S48. [31] Eckert, GP; Cairns, NJ; Maras, A; Gattas, WF, and Muller, WE. Cholesterol modulate the membrane-disordering effect of beta-amyloid peptide in the hippocampus: specific changes in Alzheimer’s disease. Dement. Geriatr. Cogn. Disord., 2000, 11, 181-186. [32] Bittman, R; Kasireddy, CR; Mattjus, P, and Slotte, JP. Interaction of cholesterol with sphingomyelin in monolayers and vesicles. Biochemistry, 1994, 33, 11776-11781. [33] Kakio, A; Nishimoto, A-I; Yanagisawa, K; Kozutsumi, Y, and Matsuzaki, K. Cholesterol-dependent formation of GM1 ganglioside-bound amyloid β-protein, an endogenous seed for Alzheimer amyloid. J. Biol. Chem., 2001, 276, 24985-24990. [34] Soderberg, M; Edlund, C; Alafuzoff, I; Kristensson K, and Dallner G. Lipid composition in different regions of the brain in Alzheimer's disease/senile dementia of Alzheimer's type. J. Neurochem., 199, 259, 1646-1653. [35] Puglielli, L; Konopka, G; Pack-Chung, E; Ingano, LA; Berezovska, O; Hyman, BT; Chang, TY; Tanzi, RE, and Kovacs, DM. Acyl-coenzyme A: cholesterol acyltransferase modulates the generation of the amyloid beta-peptide. Natl. Cell Biol., 2001, 3, 905-912.

178

A. V. Alessenko

[36] Puglielli, L; Ellis, BC; Saunders, AJ, and Kovacs, DM. Ceramide stabilizes β-site amyloid precursor protein-cleaving enzyme1 and promotes amyloid β-peptide biogenesis. J. Biol. Chem., 2003, 278, 19777-19783. [37] Buccoliero, R, and Futterman, AH. The role of ceramide and complex sphingolipids in neuronal cell function. Pharmacological Res., 2003, 47, 409-419. [38] Bodennec, J; Pelled, D; Riedeling, C; Trajkovoc, S, and Futerma, AH. Phosphatidylcholine synthesis is elevated in neuronal models of Gaucher disease due to direct activation of CTP:phosphocholine cytidyltransferase by glucosylceramide. FASEB J., 2002, 16, 1814-1816. [39] Schuchman, EH, and Desnik, RJ. Nieman-Pick disease types A and B acid sphingomyelinase deficiecies. In: CR, Sly WS, Childs B, Beaudet, A.L., Valle, D., Kinzler, K.W., Vogelstein, D. Editors. The metabolic and molecular bases of inherited disease, vol.3. New York: McGraw-Hill, Inc. 2001, p.3589-3610. [40] Levade, T, and Jaffrezou, JP. Signalling sphingomyelinases: which, where, how and why? Biochim. Biophys. Acta, 1999, 1438, 1-17. [41] Spence, MW, and Burges, JK. Acid and neutral sphingomyelinases of rat brain. Activity in developing brain and regional distribution in adult brain. J. Neurochem., 1978, 30, 917-918. [42] Alessenko AV; Bugrova AE, and Dudnik LB. Connection of lipid peroxide oxidation with sphingomyelin cycle pathway in the development of Alzheimer’s disease. Biochem. Soc. Transaction, 2004, vol.32, 144-146. [43] Gutner UA; Dudnik LB; Korobko VG, and Alesenko AV. The influence of tumor necrosis factor alpha on the processes of sphingomyelin cycle and lipid peroxidation in brain. Zh. Nevrol. Psikhiatr. Im. SS Korsakova, 2005, 105, 48-54. [44] Jayadev S; Linardic CM, and Hannun YA. Identification of arachidonic acid as a mediator of sphingomyelin hydrolysis in response to tumor necrosis factor alpha. J. Biol. Chem., 1994, 269, 5757-5763. [45] Dobrowsky, RT; Werner, MH; Castellino, AM; Cao, MV, and Hannun, YA. Activation of sphingomyelin cycle through the low-affinity neurotrophin receptor, Science, 1994, 265, 1596-1599. [46] Brann, AB; Scott, R; Neuberger, Y; Abulafia, D; Boldin, S; Fainzilber, M, et. al. Ceramide signaling downstream of the p75 neurotrophin receptor mediates the effect of nerve growth factor on outgrowth of cultured hippocampal neurons. J. Neurosci., 1999, 19, 8199-8206. [47] Brann, AB; Tcherpakov, M; Williams, IM; Futerman, AH, and Fainzilber, M. Nerve growth factor-induced p75-mediated death of cultured hippocampal neurons is agedependent and transduced thrugh ceramide generated by neutral sphingomyelinase J. Biol. Chem., 2002, 277, 9812-9818. [48] Yu, ZF; Nikolaeva-Karakashian, M; Zhou, D; Cheng, G; Schuchman, EH, and Mattson, MP. Pivotal role for acidic sphingomyelinase in cerebral ischemia-induced ceramide and cytokine production, and neuronal apoptosis. J. Mol. Neurosci., 2000, 15, 85-97.

Role of Sphingomyelin Cycle Signaling System in Alzheimer’s Disease

179

[49] Irie, F, and Hirabayashi, YJ. Application of exogenous ceramide to cultured rat spinal motoneurons promotes survival or death by regulation of apoptosis depending on its concentrations. Neurosci. Res., 1998, 54, 475-485. [50] Ito, A, and Horigome, K. Ceramide prevents neuronal programmed cell death induced by nerve growth factor deprivation. J. Neurochem., 1995, 65, 463-466. [51] de Chaves, EP; Bussiere; M, MacInnis, B; Vance, DE; Campeton, RB, and Vance, J.E. Ceramide inhibits axonal growth and nerve growth factor uptake without compromising the viability of sympathetic neurons. J. Biol. Chem., 2001, 276, 36207-36214. [52] Spiegel, S, and Pyne, NJ. Sphingosine-1-phosphate signaling in mammalian cells. Biochem J., 2002, 16, 15596-15602. [53] Obeid, LM; Lenardic, CM; Karolak, LA, and Hannun, YA. Programmed cell death induced by ceramide. Science, 1993, 259, 1769-1771. [54] Merrill, AHJr; Schmelz, E-M; Dillehay, DL; Spigel, S; Shayman, JA, et. al. Sphingolipids-the enigmatic lipid class: biochemistry, physiology and pathophysiology. Toxicol. Appl. Pharmacol., 1997, 142, 208-225. [55] Gill, JS, and Windebank, AJ. Ceramide initiates NFkB-mediated caspase activation in neuronal apoptosis. Neurobiology of Disease 2000, 7, 448-461. [56] Ariga, T; Jarvis, WD, and Yu, RK. Role of sphingolipid-mediated cell death in neurodegenerative disease. J. Lipid Res., 1998, 39, 1-16. [57] Albers, DS, and Beal, MF. Mitochondrial dysfunction and oxidative stress in aging and neurodegenerative diseases. J. Neural. Transm. Suppl., 59. 133-154. [58] Ditaranto-Desimone, K; Saito, M; Tekirian, TL; Saito, M; Berg, M; Dubowchik, G; Soreghan, B; Thomas, S; Marks, N, and Yang, AJ. Neuronal endosomal’lysosomal membrane destabilization activates caspases and induces abnormal accumulation of the lipid secondary messenger ceramide. Brain Res Bull., 2003, 59, 523-531. [59] Singh, IK; Pahan, K; Khan, M, and Singh, AK. Cytokine-mediated induction of ceramide production is redox-sensitive.Implications to proinflammatory cytokinemediated apoptosis in demyelinating disease. J.Biol. Chem., 1998, 273, 20354-20360. [60] Sawamura, N; Morishima-Kawashima, M; Waki, H; Kobayashi, K., et. al. Mutant presenilin 2 transgenic mice. A large increase in the level of Abeta 42 is presumably associated with the low densoty membrane domein that contains decreased level of glycerophospholipids and sphingomyelin. J. Biol. Chem., 2000, 275, 27901-27908. [61] Ayasola, K; Khan, M; Singh, AK, and Singh, I. Inflamatory mediator and β-amyloid (25-35)-induced ceramide generation and iNOS expression are inhibited by vitamin E. Free Rad. Biol. Med., 2004, 37, 325-338. [62] Satoi H; Tomimoto H; Ohtani R; Kitano T; Kondo T; Watanabe M; Oka N; Akiguchi I; Furuya S; Hirabayashi Y; Okazaki T. Astroglial expression of ceramide in Alzheimer's disease brains: a role during neuronal apoptosis. Neuroscience, 2005, 130, 657-666. [63] Jana, A, and Pahan, K. Fibrillar amyloid-β peptides kill human primary neurons via NADPH oxidase-mediated activation of neutral sphingomyelinase. Implication for Alzheimer’s disease. J. Biol. Chem., 2004, 279, 51451-51459. [64] Lee, J-T; Xu, J; Ku, G; Han,X; Yang, D-I, Chen, S, and Hsu, CY. Amyloid-β−peptide induces oligodendrocyte death by activating the neutral sphingomyelinase-ceramide pathway. J. Cell Biol., 2004, 164, 123-131.

180

A. V. Alessenko

[65] Liu, BN, and Hannun, YA. Inhibition of the neutral magnesium-dependent sphingomyelinase by glutathione. J. Biol. Chem., 1997, 272, 16281-16287. [66] Behl, C, and Sagara, Y. Mechanism of amyloid beta protein induced neuronal cell death:current concepts and future perspectives J. Neural. Transm. Suppl., 1997 49, 125-134. [67] Xu, J; Chen S; Ahmed, SH; Chen, H; Ku, G; Goldberg MP, and Hsu, CY. Amyloidbeta peptides are cytotoxic to oligodendrocytes. J. Neurosci. 2001, 21, RC118. [68] Karelson, E; Bogdanovic, N; Garlind, A; Winblad, B; Zilmer, K, et.al. The cerebrocortical area in nirmal brain aging and in Alzheimer’s disease: noticeable differences in the lipid peroxidation level and in antioxidant defence. Neurochem. Res., 2001, 26, 353-361. [69] Mark, RJ; Lovell, MA; Markersbery, WR; Uchida, K, and Mattson, MP. A role for 4hydroxynonenal, an aldehydic product of lipid peroxidation, in disruption of ion homeostasis and neuronal death induced by amyloid β-peptide. J. Neurochem., 1997, 68, 255-264. [70] Nitsch, RM; Blusztajn, JK; Pittas, AG; Slack, BE; Growdon, JH, and Wurtman, RJ. Evidence for a membrane defect in Alzheimer’s disease brain. Proc. Natl. Acad. Sci. USA, 1992, 89, 1671-1675. [71] Markesbery, WR. Oxidative stress hypothesis in Alzheimer’s disease. Free Radic. Biol. Med., 1997, 23, 134-147. [72] Markesbery, WR, and Lovell, MA. Four-hydroxynonenal, a product of lipid peroxidation, is increased in the brain in Alzheimer’s disease. Neurobiol. Aging, 1998, 19, 33-36. [73] Gilgun-Sherki, Y; Melamed, E, and Offen, D. Oxidative stress-induced neurodegenerative diseases:the need for antioxidants that penetrate the bloodbrain barrier. Neuropharmacology, 2001, 40, 959-975. [74] Zemlan, FP; Thienhaus, OJ, and Bosman, HB. Superoxide dismutase activity in Alzheimer’s disease:possible mechanism for paired helical filament formation. Brain Res., 1989, 476, 160. [75] Montine, TJ; Markesbery, WR; Morrow, JD, and Roberts, LJ. Cerebrospinal fluidF2isoprostane levels are increased in Alzheimer’s disease. Ann. Neurol., 1998, 44, 410413. [76] Law, A; Gauthier, S, and Quirion, R. Say NO to Alzheimer’s disease: the putative links between nitric oxide and demetia of the Alzheimer’s type. Brain Res. Brain Res. Rev., 2001, 35, 73-96. [77] Akama, KT; Albanese, C; Pestell, RG, and Van Eldik, LJ.Amyloid beta-peptide stimulates nitric oxide production in astrocytes through an Nfkappa B-dependent mechanism. Proc. Natl. Acad. Sci. USA, 1998, 95, 5795-5800. [78] Pahan, K; Sheikh, FG; Khan, M; Namboodiri, AM, and Singh, I. Sphingomyelinase and ceramide stimulate the expression of inducible nitric-oxide synthase in rat primary astrocytes. J. Biol. Chem., 1998, 273, 2591-2600. [79] Pahan, K; Dobashi, K; Ghosh, B, and Singh, I. Induction of the manganese superoxide dismutase gene by sphingomyelinase and ceramide. J. Neurochem., 1999, 73, 513-520.

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[80] Hannun, YA. Functions of ceramide in coordinating cellular responses to stress. Science, 1996, 274, 1855-1890. [81] Liu, B; Andrieu-Abadie N; Levade T; Zhang, P; Obeid, LM, and Hannun, YA. Glutathione regulation of neutral sphingomyelinase in tumor necrosis factor-alphainduced cell death. J. Biol. Chem., 1998, 273, 11313-11320. [82] Medina S; Martinez M, and Hernanz A. Antioxidants inhibit the human cortical neuron apoptosis induced by hydrogen peroxide, tumor necrosis factor alpha, dopamine and beta-amyloid peptide 1-42. Free Radic. Res., 2002, 36, 1179-1184.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp.

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter VII

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease Ryszard Pluta∗ Department of Neurodegenerative Disorders, Medical Research Centre, Polish Academy of Sciences, 02-106 Warsaw, Pawinskiego 5 Str., Poland

Abstract The study of neurobiology of Alzheimer’s disease, now more than ever, needs an infusion of a new concept. Despite ongoing interest in Alzheimer’s disease, the basis of this entity is not yet clear. For now, the best-established and accepted “culprit” in Alzheimer’s disease pathology by most scientists is the amyloid, as the main molecular factor of neurodegeneration in Alzheimer’s disease. Abnormal upregulation of amyloid production or a disturbed clearance mechanism may lead to pathological accumulation of amyloid in the brain. We will critically review these observations and highlight inconsistencies between the predictions of the “amyloid hypothesis” and the published data. There is still controversy over the role of amyloid in the pathological process – is it responsible for the neurodegeneration or does it accumulate because of the neurodegeneration? Recent evidence suggests that the neuropathology of Alzheimer’s disease comprises more than amyloid accumulation, tau protein pathology and finally brain atrophy. At least one third of Alzheimer types of dementia cases exhibit different cerebrovascular diseases. In addition, micro- and macroinfarctions and ischemic white matter changes are also evident in brains of Alzheimer’s disease patients. The presence of vascular abnormalities seems usually ignored and regarded by researchers as insignificant or considered incidental in Alzheimer’s disease etiology. Interestingly, that Alzheimer, in his own report presenting changes in the brain of the first patient had

∗

Address correspondence: Prof. Ryszard Pluta, MD, PhD, Department of Neurodegenerative Disorders, Medical Research Centre, Polish Academy of Sciences, 02-106 Warsaw, Pawinskiego 5 Str., Poland; Tel: 48 (22) 6086-540; Fax: 48 (22) 668-55-32; E-mail: [email protected]

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Ryszard Pluta described, that besides “storage of peculiar material in the cortex, one sees endothelial proliferation and also occasionally neovascularisation”. Endothelial proliferation and angiogenesis and moderate arteriosclerosis in the brain arteries of the first case, provide evidence that cerebrovascular diseases were also evident in Alzheimer’s original case, which now defines Alzheimer’s disease. These raise the question of what was the first cerebrovascular disease as trigger of Alzheimer’s disease or neurodegeneration of Alzheimer’s type itself? New findings propose an early and significant role for ischemiareperfusion factors contributing to the neurodegenerative processes in Alzheimer’s disease. The ischemia hypothesis was primarily aimed at stimulating research and redirecting the focus of studies towards ischemic cellular mechanisms of Alzheimer’s disease. In this review, we will show that experimental brain ischemia-reperfusion episode produces neurochemical and neuropathological changes that simulate the early stage of Alzheimer’s disease process. Presented data suggest that ischemic mechanisms of neuronal death with β-amyloid peptide from circulatory network modulate neuropathology of cerebral ischemia-reperfusion injury via molecular events in common with Alzheimer-type neuropathology. These results indicate that ischemic brain processes might be a key factor in the development of the picture of Alzheimer-type dementia over years. The collective data summarized in this review strongly support the idea that sporadic from of Alzheimer’s disease is a neurovascular disorder. Considerable progress has been made in recent years by a handful of researchers in understanding the role of ischemia in the aging process generally and in contributing to the development of Alzheimer’s disease. To accommodate the recent progress of study in Alzheimer’s disease there is a need to synthesize all the divergent pieces of data into a coherent story. This review provides a synopsis of current information about ischemic cellular and molecular mediators involved in Alzheimer’s neuropathology as well as interactions between these mediators that influence pathology. In this review, current knowledge on the relation between ischemia-reperfusion factors and Alzheimer’s-type dementia will be reviewed. We will summarize the results with a special focus on Alzheimer lesions in experimental brain ischemia. Taken all together, evidence presented in this review suggests a scheme for Alzheimer’s pathogenesis with ischemia-reperfusion playing a crucial role in influencing and linking β-amyloid deposition to neuronal damage and clinical disease.

Qui vivra verra

Introduction It is estimated that almost 400 million individuals suffer from neurological diseases in the world. These disorders consist of both acute and chronic neurodegenerative diseases that e.g. include brain ischemia, brain trauma, presenile and senile dementia and Alzheimer’s disease. In addition, some endogenous and exogenous toxin exposure has also become increasingly prominent as a precipitant of degenerative disorders in the central nervous system with dementia (Table 1).

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease Table 1. Some causes of dementia in human clinic. Degenerative − Alzheimer’s disease − Parkinson’s disease − Down’s syndrome − Huntington’s disease − Wilson’s disease − Pick’s disease − Lewy body disease − Steel-Richardson-Olszewski syndrome − Frontotemporal dementia − Batten disease Vascular − Cardiac arrest − Multi-infarct dementia − Binswanger’s disease − Lacunar state Neurological lesions − Cerebral hypoxia/anoxia − Brain trauma − Dementia pugilistica Space increasing lesions − Intracranial tumors − Metastatic intracranial tumors − Chronic subdural hematoma Toxic − Alcoholism Metabolic − Diabetes mellitus − Hypothyroidism − Hyperthyroidism − Addison’s disease − Deficit of vitamin B12 − Deficit of vitamin B1 − Deficit of folic acid Infective − HIV infection − Neurosyphilis − Creutzfeldt-Jakob disease − Gerstmann-Sträussler-Scheinker syndrome Other − Normal pressure hydrocephalus

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Dementia is a general term for symptoms exhibited by people with various kinds of cognitive impairment [Burns et al., 1990a; Carlyle et al., 1993; Clark et at., 1998; Lyketsos et al., 2000]. These symptoms may include impaired mental functioning in areas such as memory, learning, judgment, attention, concentration, language and thinking. They are often accompanied by personality and behavioral changes [Burns et al., 1990b; Carlyle et al., 1993; Stewart, 1995; Lyketsos et al., 2000]. There seem to be peaks in the incidence of dementia; one, in patients in their early 40s and another in patients in their 70s and 80s. Dementia may be caused by more than 60 different diseases (Table 1), and affects a significant proportion of the elderly population. Alzheimer’s disease is the most common, accounting for over 60 percent of all cases of dementia over the age of 65. The second most common form is vascular dementia, usually resulting from different neurovascular disorders. Although dementia is not caused by aging, nor is it an inevitable part of the aging process, it is age-related. Between the ages of 65 and 95, the prevalence of all dementias rises with age and nearly doubles every five years. Population projections indicate that the number of aging persons will increase significantly over the next 50 years. The number of European Union elderly with dementia is expected to double by the middle of the 21st century. Fifty years ago, people with dementia were considered an annoyance to be locked away in institutions or hidden at home. Attitude has changed considerably in the past half-century due in no small part to the changing demographics. Now we recognize the serious problems posed by Alzheimer’s-type dementia and vascular dementia to the planet’s population [Barclay et al, 1985; Villardita, 1993; Schumock, 1998; Groves et al., 2000; Vuorinen et al., 2000; Erkinjuntti, 2001]. This review is intended to provide a profile of these dementias and possible etiology. Dementia is already responsible for significant social and economic costs [Schumock 1998], projected to rise exponentially in the coming decades as the elderly part of the society continues to increase. Knowledge of neurological disorder processes, especially among the aging part of the population is increasing rapidly. Dementia is a rising tide and a neglected problem at the same time. Dementia is a ticking bomb in the 21st century. In most countries, dementia has not been a policy priority. There is still a great deal of ignorance about Alzheimer’s disease and other dementias. Primary care physicians may know little about diseases of aging [Barrett et al., 1997]. Diagnosis may be late. Although most primary care physicians are able to diagnose the disease in the moderate stage, it is still very difficult to detect early dementia with the result that treatment and support may be delayed. The substantial increase in the absolute and relative numbers of older people, both in developed and developing countries, can be considered as one of the main features characterizing the world society in the 21st century. By 2025, the population of world aged, 65 years and older will exceed one billion with more than 700 million living in developing countries. It is estimated that the total number of people actually affected by the different forms of dementia stands at 29 million. Yet, by 2025 this number may well surpass 55 million. In some of the oldest age groups, dementia can reach the astonishing prevalence of 25 percent. Society aging has become an important development issue requiring urgent action. As the population ages and people live longer, these findings indicate that the developed countries can expect to have nearly half a million-dementia patients every year. Taken together, dementia affects more than one-quarter of the 85 and over population and a one-third to a half of those aged 90 and over.

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Alzheimer-type Dementia Named for Alois Alzheimer who first described the disease in 1907 [Alzheimer, 1907] Alzheimer’s disease is a chronic and silent neurodegenerative disorder characterized by widespread neuronal loss in specific areas of the brain [Hyman et al., 1984] and synaptic pathology, deposition of the β-amyloid peptide into plaques in parenchyma and blood vessel walls, tau protein pathology and finally brain atrophy. Patients with Alzheimer’s disease show a number of abnormalities on brain imaging. These include cortical atrophy, ventricular dilation and leukoaraiosis. Leukoaraiosis is frequently reported as evidence of cerebrovascular disease. Alzheimer’s disease, the most common of the dementias [Kasckow, 2002], is estimated to account for approximately 60 percent of all dementia [Small et al., 1997]. Increasing age is the greatest risk factor for Alzheimer’s disease and 10 percent of society over 65, and nearly half of those over 85 years old are affected by dementia [Bird et al., 1989; Small et al., 1997; Brookmeyer et al,. 1998; Hebert et al., 2003b]. Although there are rare cases with familial forms of Alzheimer’s disease, the majority of patients have the sporadic (> 90%) form of the disease [Smith, Perry, 1998; Blennow and Skoog, 1999]. However, rare forms of Alzheimer’s disease can strike patients as early as their 30s and 40s [Bird et al., 1989]. Now there are an estimated 4.5 million cases of Alzheimer’s disease in the United States [Fratiglioni et al, 1999; Hebert et al., 2003b]. Due to the increase in longevity, the prevalence of Alzheimer’s disease will rise dramatically within the next few decades so that an estimated 14 to 30 million people in the USA will be living with Alzheimer’s disease by the year 2030-2050 [Fratiglioni et al., 1999; Hebert et al., 2003b]. The degenerative process probably starts 20 to 30 years before the clinical onset of Alzheimer’s disease [Davies et al., 1988]. After the preclinical phase of the disease, the first symptoms generally affect episodic memory. The clinical course of Alzheimer’s disease is characterized by gradual onset and slow progression. Disease progression may be far more rapid in patients with early onset illness. Conversely, the duration of illness of 15-20 years has been reported in alter onset cases [Spisacka and Pluta, 2003]. Not surprisingly, survival is generally the shortest in patients with early onset forms of Alzheimer’s disease and tends to be longer in patients with late onset forms. Alzheimer’s disease is accompanied by the impairment of short- and long-term memory and other intellectual capabilities [Cummings et al., 1987; Deutsch et al., 1991; Paulsen et al., 2000; Rizzo et al., 2000; Vuorinen et al., 2000]. As the neuronal cells die slowly, the individual’s ability to function worsens progressively leading eventually to a loss of most functional skills, including the ability to read, reason, communicate and understand spatial relationships. Alzheimer’s disease is the most common cause of dementia and the fourth most common cause of death [Kuhlman et al., 1991]. Development of Alzheimer’s disease now is looking like the silent epidemic. Despite considerable resources now targeted on research of Alzheimer’s disease little is known about causes [Doraiswamy, 2003] and treatment [Hebert et al., 2003b] for this disorder. After nearly a century of inquiry the cause of Alzheimer’s disease remains to be found [Pluta et al., 1996b; Glabe, 2000; Selkoe, 2001b; Ghiso and Frangione, 2002; Hardy and Selkoe, 2002; Mudher and Lovestone, 2002; Rosenblum, 2002; Silverberg et al., 2003; Zlokovic, 2004]. Even diagnosis is difficult. With this diverse background and in the absence of sensitive and reliable biological markers it is perhaps not surprising that the clinical

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diagnosis of Alzheimer’s disease presents many problems for the practitioner. At this time there are no tests that predict whether a person will develop Alzheimer’s disease. The disorder is diagnosed by a process of elimination and by examination of a patient’s physical and mental state. Although early diagnosis is difficult, in many cases it can allow some patients to make necessary arrangements for care. Some can also benefit from new treatments that may provide a measure of symptomatic relief. Unfortunately, many general practitioners are not trained to recognize the disease [Barrett et al., 1997] and do not diagnose it until the condition has become severe. In addition, the availability and quality of specialist care varies greatly from country to country as well as within countries. A physical examination can rule out other dementias (Table 1). Physicians look for signs of deterioration in memory, language [Vuorinen et al., 2000] and thought. For example, people suffering from Alzheimer’s disease tend to lose short-term memory, forget what words mean, become unable to recognize familiar people and objects, and are unable to orient them spatially. As deterioration continues, their ability to carry out such simple activities of daily living as dressing, bathing, and toileting or even chewing and swallowing is increasingly impaired. Changes in mood [Burns et al., 1990a], behavior [Burns et al., 1990b; Lyketsos et al., 2000] and personality are all too common. People with Alzheimer’s disease are prone to wander at any time of the day or night. They may be incontinent, disoriented in time and space and/or demonstrate uncharacteristically aggressive activity [Carlyle et al., 1993; Clark et al., 1998]. These patients tend to lose weight and muscle tone. Vision is also often affected [Rizzo et al., 2000]. The role of the physician will be fundamentally changed by the introduction of effective reasonable tests and treatment for Alzheimer’s disease. A definitive diagnosis depends on presence neurofibrillary tangles in neurons and senile plaques in brain parenchyma after the death of patients. A careful clinical examination, however, can result in a possible or probable diagnosis based on deficits in cognitive abilities and the presence or absence of a second illness that can cause dementia. There is no known cure for Alzheimer’s disease, but symptomatic treatments are being developed [Sandman, 1990]. Drugs designed to interfere with progression of the disease and to alleviate some symptoms are available, but they have been of limited benefit and only for short periods of time. It has been projected that finding a treatment that could delay the onset of Alzheimer’s disease by two years could reduce the number of patients with Alzheimer’s disease by nearly 50 percent after 50 years [Brookmeyer et al., 1998]. Alzheimer’s disease now is the single most important and probably in the future, most successful area of research in human clinic and neurobiology.

Neurovascular Changes in the First Case of Alzheimer’s Disease Alzheimer in his own report presenting changes in the brain of Augusta D., the first patient, had described that, besides “numerous minute miliary foci which are caused by the deposition of a special substance in the cortex”, “a growth appears on the endothelia, in some places also a proliferation of vessels” and “the larger vascular tissues show arteriosclerotic changes” [Alzheimer 1907]. It seems that the endothelial proliferation and neovascularisation

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were a consequence of the brain ischemia. Endothelial proliferation and angiogenesis and moderate arteriosclerosis in the brain arteries of the first case provide evidence that cerebrovascular diseases were also evident in the original case of Alzheimer [Alzheimer 1907], which now defines Alzheimer’s disease.

Vascular Dementia Cardiovascular diseases still represent the leading cause of death worldwide. Here the morbidity and mortality due to different acute and chronic cerebrovascular diseases play a major role. A further contributing factor is the increasing proportion of aged population with geriatric diseases. Maintenance of cerebral blood flow on physiological range is essential to the preservation of normal mental activity, consciousness and life. There are age-related decreases for cerebral blood flow, measured in gray matter and to a less marked degree for white matter. These declines are accentuated by the presence of risk factors, long before symptoms of brain ischemia become evident. Sudden changes in blood pressure due to impairment of heart activity may provoke complete brain ischemia. However, the major factor in the pathophysiology of acute and/or chronic neurovascular disease is not the total blood flow, but rather a regional circulatory impairment, i.e., the regional and/or focal brain ischemia with a tendency to recur. Another frequent cause is hemodynamic crises due to hypertension and diabetes mellitus and arteriosclerosis (Table 2) that are the major risk factors contributing to the incidence of complete and focal ischemia-reperfusion injury. Lacunar lesions in the brain are small, well-defined neurovascular lesions, which may lead to vascular dementia and/or multiinfarct dementia. Ischemic diffuse white matter disease in subcortical and periventricular area is also associated with low density of the white matter (leukoaraiosis) and dementia. Stroke is the third leading cause of mortality in the United States and other Western countries and is the leading cause of chronic disability [Vukovic et al., 2003] and secondary cause of dementia [Gorelick, 1997]. One study has shown that cerebrovascular disease may be an important determinant in the manifestation of dementia in the presence of Alzheimerlike pathology [Snowdon et al., 1997]. Accumulating evidences from clinical studies suggest that brain stroke is a major risk factor of dementia, ranking only second to age [Gorelick, 1997]. The incidence of dementia in the first year following a cerebral infarct is nine times greater than expected and after the first year, a 50 percent increase is observed in Alzheimer’s disease [Kokmen et al., 1996]. Yearly, approximately 700 thousand patients in the United States are afflicted with a new stroke. Most victims survive the initial stroke, but are left with some degree of significant sensory, motor and cognitive disability. Women account for approximately 60 percent of stroke deaths in the United States due to the fact that women live longer than men. A majority of strokes (approx. 80 percent) are ischemic in nature and the aging population in Western countries suggests that a decline in stroke-related deaths and disabilities will not be seen in the near future. As effect of this, the socioeconomic burden of stroke will increase every year.

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Table 2. The same proven risk factors in vascular dementia and Alzheimer’s disease Vascular dementia − − − − − − − − − − − − − − − − − − − − − − − −

Aging Silent brain infarcts Arteriosclerosis Ischemic stroke Head injury Transient ischemic attacks Microvessel pathology Cardiac disease Atrial fibrillation Hypertension Hypotension Migraine Diabetes mellitus High serum cholesterol levels High serum viscosity Thrombotic episodes High fibrinogen concentration High fat intake Menopause Smoking Alcoholism Hemorheologic abnormalities Gender Low level of education

Alzheimer’s disease − − − − − − − − − − − − − − − − − − − − − − − −

Aging Silent brain infarcts Arteriosclerosis Ischemic stroke Head injury Transient ischemic attacks Microvessel pathology Cardiac disease Atrial fibrillation Hypertension Hypotension Migraine Diabetes mellitus High serum cholesterol levels High serum viscosity Thrombotic episodes High fibrinogen concentration High fat intake Menopause Smoking Alcoholism Hemorheologic abnormalities Gender Low level of education

Chronic and silent forms of cerebrovascular diseases include neuromicrovascular dementia. Etiology and neuropathogenesis show that vascular dementia does not occur with brain arteriosclerosis alone, but in association with organic brain parenchyma lesions [Kalaria, 2000; Kalaria, 2002]. Neurovascular dementia is related to a single, large infarction, to multiple middle-sized and/or small infarcts and/or to diffuse white matter lacunes [Kalaria, 2000; Kalaria, 2002]. Advancing age with different vascular brain injuries [Kalaria, 2000; Kalaria, 2002] may often be associated with impairment of higher brain function [Cummings et al., 1987; Vuorinen et al., 2000]. Numerous studies have indicated that age related decrease in cerebral blood flow becomes slowly accentuated to a significant degree by the presence of risk factors (Table 2) long before symptoms of brain ischemia become evident. Maintenance of physiological cerebral blood flow is essential for the maintenance of normal mental function and good life. One of the major problems in an aged society is that of memory [Cummings et al., 1987] and behavior deficits [Vuorinen et al., 2000; Erkinjuntti, 2001]. The severe forms are described as dementia and actually present a considerable social and medical problem. Chronic cerebrovascular diseases afflict more frequently the elderly population of the globe. Assessment of the intellectual and psychological stage of aged patients, however, is

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difficult due to the great number of variables involved. The symptoms of chronic cerebrovascular disease can be subdivided as follows: 1) Disorders of brain activity: impairment of memory (immediate and deferred) [Cummings et al., 1987], concentration difficulty and orientation (space and time). 2) Behavioral problems: low drive, resignation, emotional instability, aggressivity, anxiety, depression, poor cooperation and poor sociability [Vuorinen et al., 2000]. 3) Somatic symptoms: sleep disorders, headache, tinnitus, fatigue and vertigo [Erkinjuntti, 2001]. The clinical condition in vascular dementia shows unexpected and sudden onset with step-wise deterioration. The sudden occurrence of an episode of fleeting and recurring amnesia is mostly the first symptoms that are not forcing the patient to visit the physician. Impairment of memory is an early characteristic feature [Cummings et al., 1987]. The shortterm memory is particularly affected. Impairment of long-term memory is involved only at a later phase. The most alarming symptom is the loss of orientation (space and time) that forces the patient to go to the physician. Under neuropathological conditions the patients are unable to recall recent events, past experience and even important data: the amnesic syndrome can be characterized by loss of recent memory, involving retrograde and anterograde memory recall which leads to difficulties in concentration and orientation [Cummings et al., 1987]. Forgetfulness of the physiologically aging brain can be described as the transient inability to recall relatively unimportant data and/or parts of an experience, these missing mosaics may, however, be recalled at another later time. The deterioration of memory retrieval involves the acquisition and retention of new information. The behavioral problems in vascular dementia, which also arise at an early stage, imply emotional disorders and personality changes [Erkinjuntti, 2001]. Emotional disorders are characterized by low drive and emotional liability, including the increased predisposition to tears and to impatience. Personality changes are usually due to an impairment of higher control. Thus, a moody person becomes depressed and an impatient one aggressive [Erkinjuntti, 2001]. Somatic problems very frequently occur in vascular dementia as well as in chronic cerebrovascular diseases and in chronic and silent brain ischemia. The most common complaints are headache and vertigo. The neuropathological findings in patients with vascular dementia have been associated with the characteristic changes in the brain in Alzheimer’s disease patients with the Alzheimer-type dementia [Jendroska et al., 1995; Wisniewski and Maslinska, 1996; Jendroska et al., 1997; Snowdon et al., 1997; Erkinjuntti, 2001]. More recent evidence suggests that the neuropathology of post-mortem brain of Alzheimer’s disease comprises more than amyloid accumulation, tau protein pathology and finally brain atrophy. At least one-third of Alzheimer type of dementia cases exhibit different neurovascular diseases [Kalaria, 2000; Kalaria, 2002]. In addition, micro- and macroinfarctions and ischemic diffuse white matter changes are also evident in brains of Alzheimer’s disease patients [Kalaria 2000, Kalaria 2002]. Epidemiological data revealed that the prevalence of severe dementia in people aged 65 years and older was estimated at 4 to 10 percent, increasing to more than 20 percent above the age of 80 years. About 10 percent of people aged 65 years and over were estimated to suffer from mild to moderate forms of memory loss. No figures are known about the prevalence of presenile dementia, either in severe and/or in mild to moderate forms. Memory loss and dementia may be caused either by neurodegenerative processes of brain parenchyma (Alzheimer’s disease) and/or by changes in neurovasculature including acute and

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chronic transient and complete/global brain ischemia as well as cerebrovascular disease (multiple infarcts) (Table 1). Alzheimer’s disease and vascular dementia, which may both arise from chronic post ischemia-reperfusion injury, are the most common causes of cognitive decline and dementia in the elderly part of the population. Current thinking dictates that cerebromicrovascular factors are associated directly with vascular dementia, several next studies solely suggest that there may be a statistically increased risk of developing Alzheimer’s disease following ischemia-reperfusion injury and/or a previous history of neurovascular risk factor normally associated with brain ischemia, including arteriosclerosis and different forms of cardiovascular diseases [Kokmen et al., 1996; Gorelick, 1997; Snowdon et al., 1997]. It has been presented that about 80 percent of patients with Alzheimer’s disease have cardiovascular problems defined by the presence of arteriosclerosis of the different arterial vessels [Honig et al., 2005]. These effects may be compounded by profound injuries involving pathological changes in cellular components of the cerebral blood vessel wall. Conversely, at least one third of patients with vascular dementia will bear Alzheimer’s neuropathology in brains after autopsy [Wisniewski and Maslinska, 1996; Jendroska et al., 1997]. It is looking that now is the beginning of a new era for vascular dementia in solving the mystery of Alzheimer’s disease.

Vascular Risk Factors in Alzheimer’s Disease and Vascular Dementia Some data present that Alzheimer’s disease and vascular dementia share similar risk factors (Table 2) [De la Torre 2002]. Other studies show of overlapping clinical symptoms in Alzheimer’s disease and vascular dementia [Kalaria and Ballard; 1999] as effect of this is mixed dementia [Korczyn, 2002]. Epidemiological investigation linking vascular factors to cerebromicrovascular pathology that can set in motion neurodegenerative pathology and cognitive changes in patient’s brains with Alzheimer’s disease. In effect, Alzheimer’s disease and vascular dementia shows parallel neuromicrovascular and neurodegenerative etiology that is developing over years (Table 2). In the end, some studies suggest that brain hypoperfusion can trigger cognitive and degenerative changes [De la Torre, 2000]. Based on the epidemiological data it can be concluded that vascular risk factors and indicators of neurovascular disease have an established association with vascular and Alzheimer’s-type dementia (Table 2). The risk factors for Alzheimer’s disease and vascular dementia include silent brain infarcts [Vermeer et al., 2003], diabetes mellitus [Ott et al., 1996; Ott et al., 1999], thrombotic episodes [Bots et al., 1998], smoking [Graves et al., 1991; Van Duijn et al., 1995; Ott et al., 1998], alcoholism [Graves et al., 1991], atrial fibrillation [Ott et al., 1997], low level of education [Ott et al., 1995; Letenneur et al., 2000], high serum cholesterol levels [Breteler et al., 1998; Breteler, 2000], arteriosclerosis [Hofman et al., 1997], high fat intake [De la Torre, 2002], migraine [Tyas et al., 2001], transient ischemic attacks [Meyer et al., 2000], menopause [Ohkura et al., 1994, Waring et al., 1999], high fibrinogen concentration [Ajmani et al., 2000], hemorheologic abnormalities [Fioravanti et al., 1998; Solerte et al., 2000], hypertension [Breteler 2000; Launer et al., 2000] and

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hypotension [Morrison et al., 1996; Guo et al., 1997; Passant et al., 1997; Fioravanti et al., 1998], ischemic stroke [Wisniewski and Maslinska, 1996; Jendroska et al., 1997; Snowdon et al., 1997], head injury [Guo et al., 2000; Lye and Shores, 2000; Plassman et al., 2000], cardiac disease including arrhythmias [Deklunder et al., 1998; Kilander et al., 1998], gender [Fratiglioni et al., 1997] and aging [Kawas et al., 2000] (Table 2). Most of presented risk factors are present not only in the early phases of reported dementias, but often decades before any cognitive abnormalities develop. All presented risk factors are vascular related and all are known to impair and/or reduce cerebral blood flow [De la Torre, 2000]. The presence of silent brain infarcts at base line more than doubled the risk of dementia [Vermeer et al., 2003]. Elderly people with silent brain infarcts have an increased risk of dementia and a steeper decline in cognitive function than those without such lesions [Vermeer et al., 2003]. The relationship of risk factors in vascular and Alzheimer’s dementia (Table 2) suggests that these two dementias share a common etiology/origin. It should be noted that about 30 percent of all Alzheimer’s disease brains show neurovascular pathology [Kalaria, 2000; Kalaria, 2002] and practically all Alzheimer’s disease brains reveal periventricualar diffuse white matter changes, microcirculation degeneration, cerebral amyloid angiopathy or combinations of these pathologies in this situation the connection between Alzheimer’s- and vascular-type dementia appears more than coincidental [Kalaria and Ballard, 1999]. Interestingly, about 40 percent of brains with clinical vascular dementia diagnosis have concurrent Alzheimer’s-type dementia neuropathology hallmarks involving diffuse and senile plaques and tau protein pathology [Jendroska et al., 1995; Wisniewski and Maslinska, 1996; Jendroska et al., 1997; Snowdon et al., 1997; Skoog et al., 1999; Erkinjuntti, 2001]. Upon final reflection of interest to us in these correlations is the fusing of these two dementias as mixed dementia [Korczyn, 2002]. However, this argument today does not explain directly and completely why pure Alzheimer’s dementia still retains a powerful vascular basis. Reported by us, risk factors appear to convert just as easily to vascular dementia as they do to Alzheimer’s dementia (Table 2) [Villardita, 1993; Hofman et al., 1997; Launer et al., 2000; Kivipelto et al., 2001].

Hypothesis It is clear that dementia of Alzheimer’s- and vascular-type continue to burden the planet’s population with not only increasing morbidity and mortality, but also with a significant financial drain [Schumock, 1998] through increasing medical care costs coupled with a progressive loss in economic productivity. A considerable and growing body of evidence suggests that hallmarks of ischemic mechanism(s) are present in Alzheimer’s disease [Pluta et al., 1995b; Pluta et al., 1996c; Kalaria, 2000]. Introducing a human wild type or mutant amyloid precursor protein gene to rodent models of Alzheimer’s disease does not result in clear and complete neurodegeneration, suggesting that contributory factors lowering the threshold of neuronal death may be present in Alzheimer’s disease. Recently, brain ischemia-reperfusion has been recognized as a factor in lowering the threshold of neuronal death [Koistinaho et al., 2002]. Other studies from transgenic animals are surprising too since they suggest neuronal death may be a common feature of Alzheimer’s disease that is not dependent on β-amyloid peptide [Games et al., 1995]. The next study suggests that the

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secreted amyloid precursor protein fragments has acted as a growth factor that protects neurons in the CA1 sector against ischemic injury [Smith-Swintosky et al., 1994]. Transgenic mice expressing different fragments of human amyloid precursor protein exhibited decreased changes to the hippocampus after excitotoxic injuries [Masliah et al., 1997]. Not surprisingly, β-amyloid peptide is produced in response to neuronal injury [Ishimaru et al., 1996a] and probably produces its effects by interacting with cell surface molecules commonly encountered in the ischemic nervous system. The neuropathogenesis of Alzheimer’s-type dementia is not fully understood although two main theories have been proposed: traditional “amyloid hypothesis” and new “ischemia-reperfusion hypothesis”. More recent work has begun to focus on elucidating the complexities of Alzheimer’s disease that involve ischemic mechanisms in killing neurons and developing dementia. I would like to propose a theoretical scheme that fits very well with the ischemia basis of Alzheimer’s disease. In my proposal, Alzheimer’s disease would start to develop when at least two neuropathological events converge: brain ischemia and ischemic chronic opening of blood-brain barrier for serum βamyloid peptide. These two events create two main pathologies that brain ischemia is responsible for; neuronal death in hippocampus and ischemic chronic blood-brain barrier insufficiency which creates amyloid pathology in brain parenchyma. Transgenic mice that accumulate amyloid without neuronal loss in hippocampus support this idea. Additionally, we found overlapping features in both disorders of vascular dementia and Alzheimer’s disease. For example, Alzheimer’s disease and vascular dementia share hallmarks like brain hypoperfusion, diffuse white matter changes, neuropathological markers and overlapping symptoms. Constantly growing evidence indicating that the neuropathogenesis of Alzheimer’s disease is rooted in vascular pathology [Pluta et al., 1995b; Pluta 1997b; Kalaria, 2000; Pluta, 2004a; Pluta, 2004b]. The “amyloid toxicity hypothesis” of Alzheimer’s disease and the “ischemic-reperfusion theory” of Alzheimer’s disease may together explain Alzheimer-type neurodegeneration in brain. Therefore, the ischemic overexpression of amyloid precursor protein and ischemia alone may constitute a vicious cycle that leads to neurodegeneration. Progressing death of neurons following ischemia-reperfusion may be caused not only by a degeneration processes of neurons destroyed during ischemia insult but also by ischemic opening of blood-brain barrier vessels with deposition and influence of cytotoxic fragments of amyloid precursor protein on increase vulnerability of neurons to ischemic excitotoxicity. In this article, we discuss the role of novel cellular pathways that are invoked during ischemia-reperfusion process and may potentially mediate/develop injury in Alzheimer’s disease brain. The fundamental thesis of my proposal is that the neuropathology seen in Alzheimer’s disease is a continuous process from initial ischemic neuronal changes [Pluta, 1997b; Pluta, 2000a] to the well-established extravasations of β-amyloid protein across ischemic blood-brain barrier culminating in the formation of amyloid plaques and dystrophic neurites.

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Mosaic of Alzheimer’s Proteins in Ischemia-reperfusion Injury DNA, an extraordinary molecule present in the nucleus of every body and brain cell, controls the growth and development of the human and animal body and brain as genes. DNA carries all the genetic information necessary for developing not just a brain but also a complete human and animal being. DNA controls the processes of learning and maturation that turn the young brain into an adult brain. Once maturity is reached, DNA controls the metabolic processes that maintain the brain in its homoeostatic balance with some physiological correction during aging. It is also possible that DNA may hold a darker secret. It may hold the codes for the neurodegeneration of the brain with age for loss of memory and intelligence and for the clinical syndrome termed dementia. The neuropathological changes of some proteins seen in brain parenchyma from demented patients (e.g. widespread βamyloid peptide accumulation as diffuse and senile plaques and tau protein pathology as neurofibrillary tangles) may be a reflection of this dark and secret information in specific brain genes.

Amyloid Precursor Protein β-amyloid peptide is derived from the larger parent transmembrane molecule amyloid precursor protein. The gene coding for amyloid precursor protein has been identified on chromosome 21. Amyloid precursor protein mRNA increased over 200 percent and 150 percent in the penumbra and core ischemic regions, respectively on the fourth day after focal brain ischemia and remained high through the seventh day of ischemic insult. This study suggests focal brain ischemic insult enhances amyloid precursor protein mRNA expression and may contribute to the progression of cognitive impairment after ischemic injury [Shi et al., 2000]. After focal ischemia, the Kunitz protease inhibitor-bearing isoforms were increased whereas amyloid precursor protein 695 that lacks Kunitz protease inhibitor domain was decreased. These results show that focal ischemia alters Kunitz protease inhibitor-amyloid precursor protein/amyloid precursor protein 695 ratio in cerebral cortex and this shift in amyloid precursor protein isoforms could be related to neurodegeneration and/or activation of astrocytes during the ischemic process [Kim et al., 1998]. In persistent focal ischemia amyloid precursor protein mRNA species that contain a Kunitz-type protease inhibitor domain were induced in the rat cortex from 1 to 21 days after the injury with maximum at 4 days, while total amounts of amyloid precursor protein mRNA did not change. These results suggest a selective role of amyloid precursor protein species that contain the Kunitz protease inhibitor domain in focal brain ischemia [Abe et al., 1991]. At 7 days postischemia amyloid precursor protein 770 and amyloid precursor protein 751 mRNAs were induced in the infarct core and in a thin perifocal zone [Koistinaho et al., 1996]. Brain samples from ischemic core and penumbra of cortex at one hour and 24 hours following focal ischemia with ovariectomia were investigated for amyloid precursor protein

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mRNA. At one hour after ischemia rats had significant increase in amyloid precursor protein mRNA in the penumbra and core. Estrogen treatment reduced the amyloid precursor protein mRNA over-expression in these two areas [Shi et al., 1998]. This data demonstrates that estrogen may have an important role in reducing the over-expression of amyloid precursor protein mRNA following transient focal ischemia. Thus, these studies suggest a profound effect of estrogen on the brain that may be able to interrupt a vicious cycle of ischemia and neurodegeneration [Shi et al., 1998]. Animals with global and/or focal brain ischemia and followed by reperfusion showed strong, abnormal brain staining to the N-terminal of amyloid precursor protein and to the βamyloid peptide and as well as to the C-terminal of amyloid precursor protein. The staining was noted not only intracellularly (Figure 1B-D) [Pluta et al., 1994b; Hall et al., 1995; Horsburgh and Nicoll, 1996a; Tomimoto et al., 1995; Yokota et al., 1996; Pluta et al., 1997a; Pluta et al., 1998a; Lin et al., 1999; Pluta, 2000a; Lin et al., 2001; Sinigaglia-Coimbra et al., 2002], but also extracellularly (Figure 1A, C, D) [Pluta et al., 1994b; Ishimaru et al., 1996a; Pluta et al., 1997a; Pluta et al., 1998a; Pluta 2000a; Fujioka et al., 2003].

Figure 1. Extracellular β-amyloid peptide plaque-like deposits in enthorhinal cortex (A). Strong immunoreactivity to β-amyloid peptide in astrocytes in hippocampus. Other astrocytes exhibited immunostained processes in contact with capillary (B). Perivascular β-amyloid peptide- (C) and Cterminal of amyloid precursor protein-positive (D) material in hippocampus and frontal cortex respectively. 10-min brain ischemia – 6 months survival. Magnifications; A, B, C, D. x400. Reprinted from Pluta (2004) Curr Neurovasc Res, 1, 441-453 with permission from Bentham Science Publishers Ltd.

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Various fragments of amyloid precursor protein were observed within neuronal cells. Immunoreactivity was seen mainly in undamaged neurons. Animals after ischemia with short-term survival up to 7 days manifested the strongest labeling to the β-amyloid peptide and C-terminal of amyloid precursor protein and weaker staining to the N-terminal of amyloid precursor protein [Pluta et al., 1994b]. Rats with very long survival after ischemia 6 and 12 months presented abnormal brain staining only to the C-terminal of amyloid precursor protein as well as to the β-amyloid peptide domain (Figure 1A-D) [Pluta et al., 1997a; Pluta et al., 1998a; Pluta, 2000a]. Amyloid precursor protein may be expressed abnormally by microglia, astrocytes and oligodendrocytes (Figure 1B, C) [Banati et al., 1995; Palacios et al., 1995; Pluta et al., 1997c; Nihashi et al., 2001; Pluta, 2002a; Pluta, 2002b; Badan et al,. 2003; Badan et al., 2004]. Postischemic amyloid precursor protein overexpression may occur in activated microglial cells [Banati et al., 1995] and reactive astrocytes [Palacios et al., 1995; Pluta et al., 1997c; Nihashi et al., 2001; Pluta, 2002a; Pluta, 2002b]. Following focal brain ischemia and reperfusion amyloid precursor, protein increased expression has been noted mainly in reactive astrocytes [Nihashi et al., 2001]. After complete brain ischemia amyloid precursor protein staining occurs predominantly in reactive astrocytes in the hippocampus (Figure 1B) [Pluta et al., 1997c; Pluta, 2002a; Pluta, 2002b]. Following global brain ischemia with longterm survival, animals showed increased staining in the reactive astrocytes only to the cytotoxic C-terminal of amyloid precursor protein as well as to the β-amyloid peptide region (Figure 1B) [Pluta, 2000a; Pluta, 2002a; Pluta, 2002b]. Especially perivascular astrocytes showed very intense labeling of numerous very long, delicate, thin and widespread processes, which embraced or adjoined mainly the capillaries (Figure 1B) [Pluta, 2002b; Pluta, 2004b]. The reactive astrocytes with different fragments of amyloid precursor protein might be involved in the development of glial scars [Nihashi et al., 2001; Pluta, 2002b; Badan et al., 2003; Badan et al., 2004]. Reactive astrocytes with abnormal level of β-amyloid peptide (Figure 1B) might play an important role in pathological repairing of the host tissue after ischemia including amyloid accumulation and astrocytic death [Pluta et al., 1994b; Pluta, 2002b; Wyss-Coray et al., 2003; Takuma et al., 2004]. Increased amyloid precursor protein staining has been observed within white matter following transient focal brain ischemia. Amyloid precursor protein immunoreactivity was frequently noted in swollen axons between core and penumbra [Yam et al., 1997]. Abnormal amyloid precursor protein expression has been found in the white matter after embolic stroke in animals [Dietrich et al., 1998]. After global brain ischemia in subcortical and periventricular areas was frequently localized labeling for C-terminal of amyloid precursor protein and β-amyloid peptide in rats with very long survival [Pluta et al., 1997a; Pluta, 2003a]. Moreover, the larger and more intense ischemic insult, the more extensive staining of amyloid precursor protein in white matter [Yam et al., 1997]. Amyloid precursor protein staining has been used to detect axonal injury at the side of ischemic injury. The presence of amyloid precursor protein within axons after ischemic brain damage is thought to be due to its accumulation following inhibition of axoplasmic flow. The amyloid precursor protein associated swelling reflect a disturbance of flow in intact axons, but the development of amyloid precursor protein positive granule-like aggregation presents that axotomy and

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irreversible injury has occurred. These processes may be secondary to neuronal degeneration of axons. Extracellular amyloid precursor protein deposits ranged from numerous widespread small dots to irregular diffuse plaques (Figure 1A) [Pluta et al., 1994b; Pluta et al., 1997a; Pluta et al., 1998a; Pluta, 2000a; Pluta, 2002b; Pluta, 2003a]. Widespread and multifocal diffuse plaques predominated in the hippocampus, brain and entorhinal cortex and corpus callosum and around the lateral ventricles. Inside diffuse plaques have been found frequently glial and neuronal cells.

Brain ischemia

Blood-brain barrier Macrophages Microglial cells

Cytokines

Cytokines

Amyloid precursor protein Soluble β-amyloid peptide

Neurotoxicity

Neuronal death

Fibrillar β-amyloid peptide

Figure 2. The potential role of brain ischemia on activated microglial cells and microglia-derived proinflammatory factors in the ischemic pathogenesis of amyloid precursor protein and neuronal death.

The localization of the C-terminal of amyloid precursor protein within ischemic neurons and especially in astrocytes underscores the likely importance of the C-terminal of amyloid precursor protein in the neuropathogenesis of brain ischemia as in Alzheimer’s disease [Pluta et al., 1994b; Yokota et al., 1996; Pluta et al., 1997a; Pluta, 2002b; Badan et al., 2003; Badan et al., 2004]. This supports the possibility that the C-terminal of amyloid precursor protein is activated because the C-terminal of amyloid precursor protein is critical for the seeding and development of amyloid plaques in the brain [Estus et al., 1992]. Additionally, this fragment accumulation indicates that this part of amyloid precursor protein may promote synaptic degeneration and neuronal death [Oster-Granite et al., 1999]. These observations indicate that late C-terminal of amyloid precursor protein and β-amyloid peptide accumulation/ aggregation postischemia may represent a secondary injuring factor that could exacerbate insult outcome [Pluta et al., 1997e; Pluta et al., 1998a]. Not surprisingly, β-amyloid peptide is

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produced in response to neuronal damage [Ishimaru et al., 1996a] and probably produces its effects by interacting with ischemic nerve (Figure 2) and glial cells (Figure 3) surface molecules in the brain adding additional pathology as well as dementia. It is generally believed that β-amyloid peptide participates in the neuronal killing (Figures 2, 3) [Cotter et al., 1999]. β-amyloid peptide is a strong and direct neurotoxic protein and it develops ischemic cascade of intracellular processes including activation of these processes in microglial cells and astrocytes that leads to nerve and glial cells damage (Figures 2, 3) [Giulian et al., 1995]. This supports the additional role of the “amyloid toxicity hypothesis” in Alzheimer’s disease. Extracellular accumulation of β-amyloid peptide is detected only upon neuronal cell death [Ishimaru et al., 1996a] initially as halos of β-amyloid peptide staining around individual dying neurons and subsequently as β-amyloid peptide plaques containing numerous neuronal cell ghosts. Based on presented data we conclude that neuronal cell death likely occurs before the extracellular accumulation of β-amyloid peptide in Alzheimer’s disease brains [LaFerla et al., 1997].

Brain ischemia

Blood-brain barrier β-amyloid peptide

Astrocytes β-amyloid peptide

Astrocytic death

Protection

β-amyloid peptide

No protection

Ischemic neurons

Neuronal death Figure 3. Role of astrocytes in influence of β-amyloid peptide on neurons following ischemiareperfusion brain injury.

Apolipoproteins The apolipoprotein E gene is on chromosome 19. Since β-amyloid peptide binds with high affinity to apolipoprotein E, it has been suggested that apolipoprotein E may promote

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formation of β-amyloid peptide fibrils by acting as a “pathological chaperone” [Wisniewski and Frangione, 1992]. In an experimental study on gerbils, there was an increase in astrocytic apolipoprotein E mRNA with the levels being the highest on 7 days postischemia. This suggests that neuronal injury or insult results in the induction of certain genes in the surrounding reactive astrocytes and these proteins may contribute to post injury amyloidogenesis [Ali et al., 1996]. Apolipoprotein E mRNA expression in glial cells, but not in neurons was seen in ischemic penumbra with a peak at 21 days. In core marked apolipoprotein E mRNA expression was observed in macrophages [Kamada et al., 2003]. Some data present increased expression in apolipoprotein J, particularly by astrocytes that provide neuroprotection against brain ischemia as an anti-stress protein chaperone [Wiggins et al., 2003]. Increased expression of clusterin mRNA was noted in permanent focal cerebral ischemia in the mouse. Clusterin mRNA was located in the perifocal area. Reactive astrocytes within the cortex were found to be strongly immunoreactive for clusterin. It was concluded that local expression of apolipoprotein J mRNA might contribute to the inflammation representing an important process in secondary injury mechanisms after focal cerebral ischemia [Van Beek et al., 2000]. The severe ischemic insult leads primarily to necrotic neuronal death and showed very little if any clusterin mRNA. However, following the moderate insult there was a dramatic time-dependent accumulation of clusterin protein in neurons of the CA1 and CA2 sector in the hippocampus and cortical layers 3-5 regions undergoing delayed neuronal death. Clusterin mRNA expression in contrast to neuronal protein accumulation appeared to be glial in origin with increases in mRNA in and around the hippocampal fissure and only a weak signal over the CA1 and CA2 pyramidal cell layer. These results support the theory that the clusterin protein is synthesized in the astrocytes, secreted and then taken up by dying neurons [Nishio et al., 2003]. Clusterin was accumulating in neurons destined to die by programmed cell death. However, clusterin expression suggests that clusterin production was a result of the selective delayed neuronal death rather than being involved in the neurochemical cascade of events that cause it [Walton et al., 1996]. Apolipoprotein E immunoreactivity was recognized in astrocytes and neurons 3-14 days after transient focal cerebral ischemia. Apolipoprotein E was also detected in macrophages in the ischemic core. In contrast, apolipoprotein E mRNA was expressed in astrocytes and macrophages, but not in neurons. These results suggest that neuronal apolipoprotein E was not synthesized in neurons, but derived from astrocytes [Nishio et al., 2003]. Recent findings support this observation that astroglial cells regulate apolipoprotein E expression in neurons [Harris et al., 2004]. The abnormal staining for apolipoproteins E, A1 and J was noted intracellularly [Kida et al., 1995; Hall et al., 1995; Pluta et al., 1995a; Horsburgh and Nicoll, 1996a; Horsburgh and Nicoll 1996b; Ishimaru et al., 1996b; Pluta, 2000a; Kamada et al., 2003] and extracellularly [Kida et al., 1995; Pluta, 2000a]. Intracellular staining was observed in both slightly as well as markedly damaged neurons, exhibiting signs of ischemic changes [Pluta, 2000a]. Less often immunoreactivity for apolipoproteins was found in glial cells [Kamada et al., 2003]. Apolipoprotein extracellular deposits were well delineated and irregular. Diffuse, broad but faint areas were also seen. Strong staining was found also in irregular, spider-like,

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acellular, necrotic foci [Kida et al., 1995; Pluta et al., 1995a; Ishimaru et al., 1996a]. Extracellular apolipoprotein E and apolipoprotein J deposits were heavily labeled by antibody to apolipoproteinn A1, stronger than by apolipoprotein E antibody [Kida et al., 1995]. They were stained stronger by antibody to apolipoprotein E than apolipoprotein J [Kida et al., 1995]. It is of interest to notice that deposits of apolipoproteins colocalize with deposits of different fragments of amyloid precursor protein [Kida et al., 1995; Pluta et al., 1995c]. Apolipoprotein E can modulate and/or promote the aggregation of soluble β-amyloid peptide into the β-pleated sheet conformation. It is proposed that apolipoprotein E can function as a “pathological chaperone” in formation amyloid deposits [Wisniewski and Frangione, 1992]. Apolipoprotein J is implicated in the transport of β-amyloid peptide across the blood-brain barrier. On other hand, clusterin production was a result of the selective delayed neuronal death [Walton et al., 1996]. The main role of apolipoproteins E, A1 and J in controlling the levels of soluble β-amyloid peptide in the extracellular and intracellular compartments of brain as well as their influence on fibrillar β-amyloid peptide formation is suggested. It is also possible that stable apolipoprotein E and β-amyloid peptide complexes or two proteins separately adhere to the neuronal remnant after neuronal death and develop amyloid plaques. Interestingly we found in experimental brain ischemia faint staining for apolipoprotein E remaining in the pyramidal cell layer of hippocampus even long after their disappearance [Ishimaru et al., 1996a]. On the other hand, apolipoprotein E fragments present in Alzheimer’s disease brains induce neurofibrillary tangle-like intracellular inclusions in neurons [Huang et al., 2001]. Apolipoprotein E potentates β-amyloid peptide-induced lysosomal leakage and apoptosis in neuronal cells [Ji et al., 2002]. Apolipoprotein E-derived peptide produces neuronal toxicity [Moulder et al., 1999]. Neuronal cell death in Alzheimer’s disease correlates with apolipoprotein E uptake and intracellular β-amyloid peptide stabilization [LaFerla et al., 1997]. Apolipoprotein E and J can influence structure, toxicity and accumulation of the βamyloid peptide in the ischemic brain. Both proteins may also be involved in β-amyloid peptide metabolism prior to its deposition. These data demonstrate additive effects of both apolipoproteins on influencing β-amyloid peptide deposition and that they play an important role in regulating extracellular brain β-amyloid peptide metabolism independent of β-amyloid peptide synthesis. Another function, especially for apolipoprotein E in the brain is suggested clearance of ischemic tissue that would be an important process for tissue repair [Kitagawa et al., 2001]. Delayed clearance may hamper healing and reconstruction of the blood-brain barrier and glial boundary formation. The recent study supports current thinking that apolipoprotein E is a key protein for brain parenchyma remodeling after injury. Clearance of irreversible damaged tissue may be one of the important activities of apolipoprotein E in the central nervous system [Kitagawa et al., 2001]. These observations indicate that apolipoproteins E and J accumulation postischemia may represent a secondary injuring factor that could exacerbate healing of ischemic neurons. Extracellular apolipoproteins E and J deposition is noted mainly following neuronal death [Ishimaru et al., 1996a; Walton et al., 1996].

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Presenilins The protein products of the genes on chromosomes 14 and 1 were subsequently termed presenilin 1 and presenilin 2, respectively. Information regarding the genetic factors and environmental conditions that influence presenilins gene expression is essential for the elucidation of its pathophysiological role in Alzheimer’s disease. In one paper, the changes of presenilin 1 mRNA expression in the gerbil hippocampus following complete brain ischemia were studied [Tanimukai et al., 1998]. After ischemia, the selective induction of presenilin 1 gene in neurons of CA3 and dentate gyrus were observed which might be related to the resistant areas after ischemia. In this investigation, presenilin 1 mRNA was induced 1 day postischemia and reached the greatest levels at day 3 in the presented regions. These observations suggest that the expression of presenilin 1 mRNA may be associated with some response of nerve cells injured by ischemia insult. In another study, the induction of presenilins mRNA was examined in the rat hippocampus, cortex, striatum and cerebellum in experimental model of transient focal brain ischemia [Pennypacker et al., 1999]. The levels of presenilins mRNA exhibited the maximal expression in the hippocampus and cortex regions of plaque development in Alzheimer’s disease while the presenilin 1 and 2 genes content in cerebellum and striatum, regions unaffected by Alzheimer’s disease, presented generally no significant increase. The greatest expression for presenilins mRNA was observed in the cortex. Presenilins genes in the hippocampus and striatum show a pattern of expression similar to that seen in the cortex but with smaller intensities. Generally, the expressions were larger on the contralateral side to the focal ischemic injury. This difference may reflect a loss of brain cells expressing presenilins genes on the ipsilateral side. Staining of presenilin was more marked in glial than in neuronal cells and in a trace of the pyramidal cells of hippocampus after global brain ischemia-reperfusion injury [Pluta, 2001]. Presenilin 1 mutation increases neuronal cells’ vulnerability to focal ischemia by elevation of intracellular calcium [Mattson et al., 2000]. A recent study showed that presenilin 1 and intracellular calcium stores regulate neuronal glutamate uptake [Yang et al., 2004]. Taken together, these findings indicate that presenilins and intracellular calcium stores may play a significant role in regulating glutamate uptake and therefore, may be important in limiting glutamate toxicity in the brain. The finding of presenilins in ischemic brain suggest that presenilins may be regulated by conditions of neurodegeneration, a condition which both the ischemic brain and the brain in Alzheimer’s disease may experience.

Tau Protein Neurons expressing tau protein were noted in the hippocampus and brain cortex after cerebral ischemia with hyperthermia during reperfusion [Sinigaglia-Coimbra et al., 2002]. It was reported that tau immunoreactivity within glial cells is increased and that tau protein is degraded in axons in insult region after focal brain ischemia [Dewar and Dawson, 1995; Irving et al., 1997]. There was a noted increase of full-length tau protein staining in oligodendrocytes following focal ischemia-reperfusion injury of the rat brain [Irving et al., 1997]. Another study presented pathological modification of tau protein by microglia around

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ischemic foci [Uchihara et al., 2004]. The somal accumulation of tau protein in neuronal cell bodies throughout the ischemic hippocampal formation has been shown [Geddes et al., 1994]. Other data showed changes in tau protein and ubiquitin in some ischemic neurons [Dewar et al., 1993; Dewar et al., 1994]. Both proteins are components of neurofibrillary tangles in Alzheimer disease brains. These results indicate that only in some neurons are changes in tau protein shortly following brain ischemia [Dewar and Dawson, 1995] that may reflect an early phase of the ischemic processes in these cells [Irving et al., 1997]. Other investigations presented a complete dephosphorylation of microtubule-associated tau proteins after brain ischemia with incomplete rephosphorylation during recirculation period [Mailliot et al., 2000]. The dephosphorylation/phosphorylation of tau protein may alter its distribution between axon and cell body and affect its susceptibility to proteolysis [Shackelford and Yeh, 1998]. The next study presented that tau protein itself blocking transport of amyloid precursor protein from body of neurons into their axons and dendrites causing amyloid precursor protein deposition in the neuronal cell body [Stamer et al., 2002]. The recent study presented that after a brain ischemia, hyperphosphorylated tau accumulates in cortical neurons and colocalizes largely with sings of apoptosis. This process may be involved in the pathogenesis of neurodegenerative disorders. Further, these data indicate that ischemic neuronal damage and apoptosis associates with tau hyperphosphorylation and potentially neurofibrillary tangles formation [Wen et al., 2004b]. Wen et al. [2004c] reported for the first time that reversible brain ischemia induces aberrant mitotic proteins and hyperphosphorylation of tau protein with neurofibrillary tangle-like conformational epitopes in the adult female rat cortex. These data provide a pathological ground for development of dementia in patients with ischemic brain and support the theory that apoptosis and aberrant mitosis are integrated neuropathological events in neuronal cells that may play a important role in the formation of Alzheimer’s disease and other taupathy-related neuropathological changes [Wen et al., 2004c].

β- and γ-secretases The pathological processing of the amyloid precursor protein by β- and γ-secretases is key to β-amyloid peptide plaque development in Alzheimer’s disease. Recent data present that both experimental cerebral ischemia and experimental traumatic brain injury stimulate the expression, production and activity of Alzheimer’s disease β-secretase in animal brain [Blasko et al., 2004; Chen et al., 2004; Wen et al., 2004a]. Additionally, presenilin is involved in the processing of amyloid precursor protein to produce β-amyloid peptide through the γ-secretase complex [Wolfe et al., 1999]. The idea that presenilin the elusive γsecretase was proposed [Wolfe et at., 1999]. Another data has shown that full-length presenilin interacts with immature β-secretase. This observation suggests that presenilin regulates β-secretase activity via direct interaction and facilitated trafficking of β-secretase to different compartments of cells [Hebert et al., 2003a].

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Cytokines Brain ischemia resulted in a concomitant overexpression of cytokines in astroglial cells especially in the CA1 sector of hippocampus [Orzyłowska et al., 1999]. This study suggests that regional increase in cytokines may be involved in the pathology in selective regions of brain [Yamasaki et al., 1995; Orzyłowska et al., 1999; Touzani et al., 1999; Boutin et al., 2001; Touzani et al., 2002]. The main sources of interleukin-1β are astrocytes, oligodendrocytes, microglia and scattered perivascular macrophages (Figure 2) and monocytes. Instead, neurons and some microvessels endothelial cells showed interleukin-1R staining [Saito et al., 1996; Sairanen et al., 1997; Davies et al., 1999; Orzyłowska et al., 1999; Touzani et al., 2002]. These data indicate that neuronal cells in vulnerable areas (Figure 2) and probably the endothelial cells are target cells for ischemia-induced glial interleukin-1β production. It is clear that interleukin-1β may play an important function in ischemic cell damage and development of brain edema [Yamasaki et al., 1995]. Brain ischemia itself produces the glial cytokines that are important in repairing and healing and/or remodeling of ischemically injured parenchyma [Orzyłowska et al., 1999]. However, chronic stimulation of these processes may produce a self-sustaining cycle that gives rise to the characteristic brain pathological changes of Alzheimer’s disease (Figure 2). In this process interleukin-1 is a key agent that promotes neuronal abnormal processing of the amyloid precursor protein [Griffin et al., 1998] thus favoring constant deposition of β-amyloid peptide and release of a number of inflammatory and neurotoxic molecules (Figure 2). As effect of these is noted neuronal dysfunction and death (Figure 2). Neuronal damage arising from these cytokine-induced nerve cell injuries activate microglia with further amplification and self-propagation of this cytokine cycle (Figure 2). Taken together, these results suggest that interleukin-1 is an important factor in ischemia-reperfusion brain injury [Yamasaki et al., 1995; Touzani et al., 1999; Boutin et al., 2001; Touzani et al., 2002]. Several lines of evidence have been found that β-amyloid peptide stimulate microglial cells to release neurotoxins (Figure 2) [Giulian et al., 1995; Giulian et al., 1996]. Microglial cells produce multiple proinflammatory and neurotoxic factors including cytokines. Hypothetically, these factors exert direct neurotoxic effects and may trigger a positive feedback loop that ultimately results in the propagation of a local brain inflammatory response and a further dysregulation of amyloid precursor protein metabolism the conversion of soluble β-amyloid peptide into fibrillar β-amyloid peptide and hence to an aggregation of the disease process (Figure 2).

α-synuclein Transient brain ischemia developed changes in a presynaptic protein α-synuclein in the hippocampus [Ishimaru et al., 1998; Kitamura et al., 2001]. Strong α-synuclein immunoreactivity was observed in perivascular area in the CA1 sector of hippocampus in animals with long survival after injury [Kitamura et al., 2001]. In neurodegenerative areas after ischemia glial cells presented strong staining for α-synuclein [Ishimaru et al., 1998]. These observations support the idea that α-synuclein may be an important protein in the

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molecular ischemic processes [Goedert, 2001]. Abnormal α-synuclein deposition might stop synaptic activity, resulting in memory problems [Hashimoto and Masliah, 1999]. Studies have showed that disruption in the synaptic system is associated with cognitive disturbance and is an early phase in Alzheimer’s disease. Abnormal metabolism of α-synuclein impairs synaptic function, which additionally promote/support neuronal death in ischemic brain and Alzheimer’s disease [Goedert, 2001]. Neurodegeneration may be caused by the loss of αsynuclein function [Han et al., 1995]. In the Alzheimer’s disease, neocortex α-synuclein was colocalized with the dystrophic neuritic component of the plaques [Masliah et al., 1996]. This study suggests that there is a connection between metabolism of presynaptic proteins and amyloid formation and that fragments of α-synuclein might follow diffuse β-amyloid peptide accumulation resulting in the formation of compact amyloid and mature plaques [Masliah et al., 1996]. Thus, the induction of amyloid precursor protein, apolipoproteins and presenilin 1 and 2 and probably other Alzheimer’s disease-related genes during brain ischemia may be the molecular link between Alzheimer’s disease and ischemia-reperfusion brain injury [Pluta, 2001]. As an effect of induction of these genes it was noted long-term abnormal coaccumulation of amyloid precursor protein with β-site amyloid precursor protein-cleaving enzyme and presenilin-1 in damaged axons. The pathological concentration of these proteins may lead to amyloid precursor protein proteolysis and β-amyloid peptide formation within the axonal membrane compartment. It is rather clear that amyloid abnormal metabolism and tau protein pathology can both be triggered by vascular factors, such as ischemia-reperfusion brain injury. It is also interesting to note that microischemic brain insults and small, silent strokes in Alzheimer’s disease patients develop because of chronic brain hypoperfusion due to vascular risk factors. These observations raise a possibility that a neurovascular diseases can participate and trigger/amplify the β-amyloid peptide and tau protein changes and could be an important additional neuropathogenic mechanism contributing to neuropathology and cognitive decline in Alzheimer’s disease. In sum experimental data on ischemic brains show that Alzheimer’s disease-related changes render the brain more susceptible to ischemic damage and in consequence developing neurodegenerative changes.

Alzheimer’s Neuropathological Picture in Ischemia-reperfusion Injury Blood-brain Barrier In short, survival after cerebral ischemia-reperfusion injury blood-brain barrier microvessels showed plenty of changes: vasospastic events, increased numbers of endothelial microvillars, cellular invaginations, microthrombe formation and focal permeability for cellular and uncellular blood elements (Table 3) [Pluta et al., 1991b; Pluta et al., 1994a; Pluta et al., 1994b; Pluta et al., 1994c; Wisniewski et al., 1995; Shinnou et al., 1998; Ueno et al., 2002]. Instead, animals with long-term survival after ischemic brain insults demonstrated chronic insufficiency of blood-brain barrier for cellular and acellular blood components

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(Table 3). Permeability changes were spotty and dispersedly and involved arterioles, microcirculation, venules and veins [Pluta, 2003a; Pluta et al., 2003b]. Blood-brain barrier alterations predominate in hippocampus, brain cortex and white matter.

Table 3. Immunoreactivity for horseradish peroxidase (HRP), rat’s N- and C-terminal of amyloid precursor protein (NAPP, CAPP) and β-amyloid peptide (βA) and human βamyloid peptide 1-42 (βA1-42) in perivascular space following experimental 10-min brain ischemia. Groups Control Short-term survival Long-term survival Brain ischemia Short-term survival Long-term survival

HRP

NAPP

βA

CAPP

βA1-42

-

-

-

-

-

+ +

++ -

++ ++/+++

++ ++/+++

+++ +++

The staining intensity was categorized into four grades as follows: - no staining; + a single and diffuse areas; ++ a few and diffuse areas; +++ many strong and diffuse areas.

Other studies revealed numerous platelet aggregates of varying sizes within both venous and arterial brain tissue vessels following ischemia-reperfusion injury [Pluta et al., 1994c; Pluta 2003a]. Some platelets were observed outside cerebral vessels in the perivascular space [Pluta et al., 1994c; Pluta, 2003a]. Abnormally aggregating platelets like blood-brain barrier alterations were focal, widespread, random and dispersedly. Changes of blood-brain barrier and platelets predominated in vessel branches and bifurcations. Recent evidence suggests that platelets play a major role in ischemia-reperfusion injury not only through thrombus formation but also through participation in inflammatory reactions. Platelets may contribute to the recruitment of inflammatory cells to tissue after ischemia as effect of short life and source of β-amyloid peptide. Platelets pathology and microvascular deficiency [Grammas, 2000] was observed in brains early during the course of Alzheimer’s disease thus supporting a further link between related processes and Alzheimer’s disease [Borroni et al., 2002]. In short-term survival, animals after brain ischemia in the perivascular space were observed widespread and multifocal diffuse N-terminal of amyloid precursor protein, βamyloid peptide and C-terminal of amyloid precursor protein deposits (Table 3) predominantly in the hippocampus, brain cortex and white matter [Pluta et al., 1994b]. Multiple, abundant, extracellular deposits embraced or adjoined the blood-brain barrier vessels. Perivascular deposits formed irregular, often asymmetric, well-delineated areas that frequently encircled microvessels, forming round, perivascular cuffs or hallo. Diffuse, broad, but faintly positive perivascular zones were also found. Endothelial and pericyte cells were stained, too. In long-term survival after brain ischemia perivascular deposits ranged from numerous small-diffused areas to irregular diffuse plaques [Pluta et al., 1997a; Pluta et al., 1997c; Pluta et al., 1997e; Pluta, 2003a]. Deposits in brain vessels and around them stained only for C-terminal of amyloid precursor protein and β-amyloid peptide (Table 3) [Pluta et al., 1997a Pluta et al., 1997c; Pluta et al., 1997e; Pluta, 2003a]. Immunoreactivity in the

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perivascular space suggested diffusion of different fragments of amyloid precursor protein out of the vascular system. Especially staining for C-terminal of amyloid precursor protein in long-lived animals underscores the likely importance of the C-terminal of amyloid precursor protein in the neuropathogenesis of ischemia as in Alzheimer’s disease [Estus et al., 1992]. In other experiments it was tested permeability for human β-amyloid peptide 1-42 in ischemically open blood-brain barrier after single or repeated episodes of global brain ischemia (Table 3). In this study, it was seen multifocal and widespread accumulation of amyloid around and in contact with blood-brain barrier vessels (Table 3) especially in hippocampus and brain cortex and occasionally in white matter [Pluta et al., 1996a; Pluta et al., 1997d; Pluta et al., 1999a; Pluta et al., 2000c]. Amyloid peptide penetration involved arterioles, veins and venules. Endothelial, pericyte, glial and neuronal cells were observed filled with human β-amyloid peptide [Pluta et al., 1996a; Pluta et al., 1997d; Pluta et al., 1999a; Pluta et al., 2000c]. Direct evidence that soluble β-amyloid peptide crosses the ischemic blood-brain barrier and enters the brain parenchyma from the circulation is thus provided.

Cell Death In ischemic brain pathological focus centers on the hippocampus because it is part of the brain selectively vulnerable to ischemia-reperfusion injury. In Alzheimer’s disease, brain structural abnormalities centers on hippocampus, too. Many small areas of pyramidal neuronal cell death were observed in the CA1 region of hippocampus two days after ischemic episode in rats [Pluta, 2000a]. In these cases complete disappearance of vulnerable neurons in the CA1 sector was noted from 7 to 14 days later [Butler et al., 2002]. About one-third of brains after ischemia-reperfusion injury did not present complete disappearance of CA1 sector in short-term survival time. These animals developed death of all nerve cells of CA1 area in late stages (Figure 4) [Pluta, 2000a; Pluta, 2002a; Pluta, 2002b]. Additionally, some data presented distinct pathology in brain regions considered to be resistant to ischemia, such as: CA2, CA3 and CA4 sectors of hippocampus and dentate gyrus. These regions showed early postischemic changes in nerve cells at 1, 6, 9 and 12 months after ischemic insult [Pluta, 2000a]. Pyramidal neurons are more frequently targeted in hippocampus [Pluta, 2000a; Butler et al., 2002; Pluta, 2002a; Pluta, 2002b]. These nerve cells have very long axons that connect different structures of the brain together through many synaptic connections. Pathology in pyramidal neurons may be of significant relevance to Alzheimer’s disease development. Actually, it has become recognized that pathological processes in ischemic nerve cells continue well beyond the acute stages [Pluta, 2000a; Pluta, 2002a]. Data indicate that brain ischemia regardless of survival time is followed by acute neuronal changes in brain parts belonging or not, to selectively vulnerable areas. In ischemic brains neurodegenerative alterations in neurons took the form of “burn faintly phenomenon” [Pluta, 2000a; Pluta, 2002a].

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Figure 4. Dilatation of subarachnoid space around and between brain hemispheres. Enlargement of the ventricular system with atrophy of hippocampus and in atrophic hippocampus complete disappearance of the CA1 sector. 10-min brain ischemia – 1 year survival. H&E. x20.

Recent studies show that astrocytes apoptosis may contribute to neuropathogenesis of many acute and chronic neurodegenerative diseases such as brain ischemia and Alzheimer’s disease [Takuma et al., 2004]. Astrocytes have many functions, such as formation of bloodbrain barrier, angiogenesis, immune response and finally formation of scar tissue after neuronal death (Figure 5). Common astrocytic reactions that occur in the brain ischemia and Alzheimer’s disease are cellular swelling, hypertrophy-hyperplasia (astrogliosis) and proliferation (astrocytosis) [Bernaudin et al., 1998; Stoltzner et al,. 2000]. It is widely believed that reactive astrocytes at the early stage of brain injury have a beneficial effect on neurons by participating in several biological processes, such as the repair of the extracellular matrix, control of the blood-brain interface, and trophic support of neurons (Figure 3). However, whether prolonged reactive astrocytic response is beneficial in neuronal recovery is still controversial. Some experiments showed after brain ischemia the early import from brain parenchyma and circulatory network to the astrocytes different fragments of amyloid precursor protein and in the late stage the export from astrocytes to the brain tissue of the

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toxic C-terminal of amyloid precursor protein and β-amyloid peptide [Pluta, 2002b; Pluta, 2004a; Pluta, 2004b]. We considered that in early stages astrocytes were removed from neuronal cells and their neighborhood through phagocytosis toxic fragments of amyloid precursor protein. In their cytoplasm is going degradation of various fragments of amyloid precursor protein. In the late stages when ischemic abnormal metabolism of amyloid precursor protein took on a chronic form and astrocytic metabolism began to be inefficient, we can observe first disruption of astrocyte processes [Pluta et al., 1994b; Pluta, 2002b]. On the other hand, disruption of astrocyte processes indicated degradation of different toxic fragments of amyloid precursor protein in the astroglial cytoplasm. The late observations of astroglial behavior support the idea that astrocytes produce amyloid precursor protein, a source of β-amyloid peptide. When this process developed, atrophy of the brains began at the same time. In an early stage, noted was vigorous incorporation of N-terminal of amyloid precursor protein into the developing astroglial scar around the infarct core [Badan et al., 2004]. Functional recovery after ischemia may reflect the balance between growth phenomena and degenerative processes, including an inflammatory reaction leading to glial scar formation (Figure 5) as well as the release of neurotoxic factors such as the C-terminal of amyloid precursor protein. At the early stages of infarct development the N-terminal of amyloid precursor protein may be synthesized by cells derived from the vascular endothelium that became fragmented after injury [Badan et al., 2004]. Over time, these cells change shape and size to become incorporated into the glial scar in a close spatial relationship with astrocytes and surprisingly formed new brain vessels that penetrated the scar. Concurrently, with the expression of scar-forming N-terminal of amyloid precursor protein there is expression of potentially neurotoxic factors such as C-terminal of amyloid precursor protein [Hsiao et al., 1996; Uetsuki et al., 1999]. Evidence derived from mice overexpressing the Cterminal of amyloid precursor protein indicates that this fragment may promote synaptic degeneration and neuronal death [Oster-Granite et al., 1996]. Some experiments clearly show that C-terminal of amyloid precursor protein steadily accumulates in neurons in the infarcted region as the infarct progresses the C-terminal of amyloid precursor protein immunoreactive elements become increasingly larger in the core even though the neurons are dying and the core becomes largely acellular [Badan et al., 2004]. The same study suggests that C-terminal of amyloid precursor protein identified in microglial cells could be due to the phagocytosis of dead, C-terminal of amyloid precursor protein containing neurons by microglia [Badan et al., 2004; D’Andrea et al., 2004]. Most interestingly, there are recent reports showing that astrocytes, not microglial cells can take up β-amyloid peptide [Matsunaga et al., 2003; WyssCoray et al., 2003]. Additionally, more recent work shows that C-terminal of amyloid precursor protein induces the death of astrocytes whereas the loss of neurons is a secondary consequence of the neuronal dependence on astrocytes for antioxidant protection [Abramov et al., 2003]. The localization of some fragments of amyloid precursor protein to astrocytes may be of significant relevance to Alzheimer’s disease in which chronic astrocytosis is thought to play a key role in the evolution of amyloid plaques and in repairing host tissue through development of glial scars (Figure 5). The study of astrocytes is particularly important considering the co-existence of the apoptotic death of neurons and astrocytes in damaged brains suffering from ischemia [Pluta, 1991a] and neurodegenerative disorders.

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Furthermore, significant astrocyte death occurs after reactive astrocytosis [Eddleston and Muckel, 1993] and dying astrocytes kill neighboring cells in brain injury [Lin et al., 1998]. Brain ischemia β-secretase Tau Cytokines

Apolipoproteins Presenilins

βA

BBB

Gliosis Ischemic neurons Platelets βA

Neuronal death

Neuronal remnants

Scar

CAMA

Physiological scar

Pathological scar

Diffuse plaques

Senile plaques

VD

MD

AD

Figure 5. Propose role of brain ischemia in the development of sporadic Alzheimer’s disease. βA - βamyloid peptide; BBB – blood-brain barrier; CAMA – cerebral amyloid microangiopathy; VD – vascular dementia; MD – mixed dementia; AD – Alzheimer’s disease.

Brain Atrophy Gross examination of animal brains performed about 1 year after ischemia-reperfusion injury revealed hydrocephalic features of brain ventricles, dilatation of the subarachnoid space around and between the hemispheres (Figure 4) [Pluta et al., 1997a; Pluta, 2003a;

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Pluta, 2004a; Pluta, 2004b]. Atrophy of the dorsal hippocampus with complete disappearance of the CA1 area was found after ischemia (Figure 4) [Hossmann et al., 1987; Pluta, 2000a; Pluta, 2002b; Pluta, 2004b]. The presence of new infarcts in experimental brain ischemiareperfusion injury with very long survival has been shown [Pluta, 2003a]. The cortex of the brain was narrow, expressing increased neuronal density. White matter was narrow and in some places with advanced spongiosis [Pluta, 2000a]. Generally, the atrophic brain is indicative of an active progressing neurodegenerative processes.

Treatment of Brain Amyloidosis The primary treatment is not pharmacological and care related. There is as yet no known cure for Alzheimer’s-type amyloidosis but symptomatic treatments are now available. These symptomatic therapies only provide symptomatic relief. These treatments are of modest benefit and do not prevent progression of the disease. These drugs that work by inhibiting the production of acetylcholinesterase an enzyme implicated in Alzheimer’s disease have been of benefit to some patients for short periods of time but side effects often prove difficult. Longterm outcomes of drug therapy are not yet known. A further difficulty is the importance of introducing drug therapy early in the disease. Most general practitioners, however, do not diagnose Alzheimer’s disease early enough for any treatment to be effective. In addition, too many doctors do not treat their older patients aggressively attributing diseases amenable to cure to old age. Although there is as yet no definitive evidence of its effectiveness against Alzheimer’s disease, some investigators are also researching the preventative value of vigorous mental and physical activity. Keeping the brain and the body active particularly in old age may help the brain become more resistant to damage and can reduce the negative effects of stress. Extensive research on new treatments is ongoing. Investigators are evaluating other potentially promising approaches including looking at drugs now used to treat other diseases studying the female hormone estrogen, NMDA receptor antagonist and trying combinations of treatments and studying relationships between Alzheimer’s and vascular dementia

Symptomatic Therapy Four approved drugs in the USA and European Union such as Aricept, Cognex, Exelon and Reminyl are therapies for Alzheimer’s disease. These drugs have a similar mechanism of action the inhibition of acetylcholinesterase activity [De la Torre, 2004]. They may help slow the progression of symptoms for a limited period. A recently approved drug memantine (Namenda) is an NMDA antagonist [Reisberg et al., 2003; Tariot et al., 2004]. The main effect of Namenda is to delay progression of the symptoms of moderate to severe Alzheimer’s disease.

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β-amyloid Peptide Therapy β-amyloid peptide clearance treatments had remarkable results in ischemic model of Alzheimer’s disease [Pluta et al., 1998b; Pluta et al., 1998c; Pluta et al., 1999a; Pluta et al., 1999b] and fewer effects in transgenic mice with overexpression of amyloid precursor protein in experimental immunization trials [Schenk et al., 1999]. In clinical trials, vaccination effects were less conclusive [Nicoll et al., 2003]. Recently, it has been shown that antibodies against β-amyloid peptide are present in human immunoglobulin, which specifically recognize and inhibit the neurotoxic effects of β-amyloid peptide [Dodel et al., 2004]. The paper by Dodel and coworkers highlights a novel and interesting therapeutic option for Alzheimer’s disease. In the past decade, strategies of treatment have been focused on inhibitors of β-secretase and γ-secretase responsible for proteolytic process of amyloid precursor protein and formation of β-amyloid peptide [Dovey et al., 2001; Selkoe, 2001a; Roberts, 2002]. Other investigations have used small particle libraries to screen for molecules that either interfere with assembly of β-amyloid peptide particles into fibrils [Lashuel et al., 2002; De Felice et al., 2004] or disaggregate existing fibrils [Soto, 2001; Gong et al., 2003; Blanchard et al., 2004].

Tau Protein Therapy Experimental therapies have been directed against hyperphosphorylation of tau protein either by inhibiting various protein kinases or promoting phosphatase activities [Lau et al., 2002; Iqbal and Grudke-Iqbal, 2004]. A recent in vitro study presented a small molecule that inhibited tau protein filament nucleation and fibrillization making this molecule a promising candidate to test in experimental animal models [Chirita et al., 2004]. A new interesting fact about β-amyloid peptide vaccination has been noted lastly in experimental condition, in which were passively immunized triple transgenic mice with antibodies to β-amyloid peptide [Oddo et al., 2004]. β-amyloid peptide immunotherapy leads to clearance of early but not late hyperphosphorylated tau protein aggregates via the proteasome [Oddo et al., 2004].

Other Therapies Drugs that protect neurovascular network could be important in the prevention and treatment of Alzheimer’s disease [Pluta et al., 1997c; Pluta, 2000b]. Recently, statins [Deane et al., 2004a] present some influence on blood-brain barrier vessels. Other drugs used in Alzheimer’s disease treatment may help to control some behavioral symptoms [Ohkura et al., 1994; Waring et al., 1999; Vukovic et al., 2003], which have an influence on daily activity. Using this treatment makes patients’ care easier. However, all these presented drugs today do not stop the progression of the Alzheimer’s disease.

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Table 4. Comparison of pathological cascade of events leading to development of dementia in experimental brain ischemia and Alzheimer’s disease. Brain ischemia Alzheimer’s disease Neuropathophysiological abnormalities N-terminal of amyloid precursor protein N-terminal of amyloid precursor protein C-terminal of amyloid precursor protein C-terminal of amyloid precursor protein β-amyloid peptide β-amyloid peptide β-secretase β-secretase γ-secretase γ-secretase Apolipoprotein E Apolipoprotein E Apolipoprotein J Apolipoprotein J Apolipoprotein A1 Apolipoprotein A1 Presenilins Presenilins Tau protein Tau protein Cytokines Cytokines α-synuclein α-synuclein Blood-brain barrier Blood-brain barrier Neuropathological abnormalities Pathology of platelets Pathology of platelets Diffuse amyloid plaques Diffuse amyloid plaques Gliosis Gliosis Microglial activity Microglial activity Necrosis Necrosis Apoptosis Apoptosis Neuronal death Neuronal death Astrocytic death Astrocytic death Leukoaraiosis Leukoaraiosis Final consequences Atrophy of hippocampus Atrophy of hippocampus Brain atrophy Brain atrophy Dementia Dementia

Conclusion Though Alzheimer’s disease is primarily a human disorder, other animal models need to be developed in order to study the mechanism of Alzheimer’s disease etiology. Over the years, attempts have been made to develop several experimental models that at the best display some but not all neuropathological hallmarks of Alzheimer’s disease. Nevertheless, these models are quite useful to study the cascade of neurochemical processes leading to neurodegeneration and to discover potential therapeutic agents. Among them is ischemic model of Alzheimer’s disease that has shed new light on neurovascular dysfunction as a likely contributor to dementia and chronic neurodegenerative situation in Alzheimer’s disease

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(Figure 5, Table 4). In Alzheimer’s disease, we should explain two main problems: first is neuronal death in a specific area, such as hippocampus and the next is amyloid accumulation in the brain. Neuronal death can be explained by direct influence of brain ischemia on selective vulnerable areas such as hippocampus and cortex and it is rather clear. In this condition, Alzheimer’s disease may be primarily centered on neuronal cells and originate from a primary neuronal disease (Figure 5). The integrity of the microvessels and the supply of the nutritious substances to the ischemic brain, as well as impede catabolic outflow of waste products are crucial for the future pathology and for the recovery and survival after that. Brain ischemia induces vascular changes and a sequence of processes that probably promote in early stage healing of bloodbrain barrier vessels [Atwood et al., 2003]. These alterations include β-amyloid peptide accumulation and its clearance during the healing processes. Mechanisms of sealing the vessels that rely on the platelets aggregation and sticking and disaggregation in the site of a leak would lead to temporal integrity of some vessels with the blood-brain barrier function [Pluta et al., 1994c]. Some data suggest that such process also involves the amyloid precursor protein from disaggregated platelets and its cleavage product β-amyloid peptide. Both proteins are known to accumulate in the cerebrovasculature wall following ischemia and Alzheimer’s disease. β-amyloid peptide aggregates and deposits form vessel scab for structural integrity of the blood-brain barrier and brain tissue (Figure 5) [Nihashi et al., 2001; Pluta 2002b]. Such a mechanism would allow delivery of blood to the ischemic brain by sealing cerebrovascular injuries and preventing cellular and acellular pathological blood components entering the brain parenchyma. It can be physiologically purposive deposits of βamyloid peptide [Pluta et al., 1996b], when this situation is going to be chronic we probably can observe pathological deposits in vessels as effects of inefficient process in cells especially vulnerable to ischemic injury in this situation endothelial [Thomas et al., 1996], pericyte [Lupo et al., 2001; Anfuso et al., 2004] and astoglial cells (Figure 5) [Takuma et al., 2004]. We suggest that chronic sealing of β-amyloid peptide may lead especially to the degeneration and disappearance of the blood-brain barrier vessels. It is also possible that decreased number of blood-brain barrier vessels can diminish the brain capillary network and surface area available for β-amyloid peptide influx and efflux and may further amplify the insufficiency of the neurovascular system to filter β-amyloid peptide from the brain parenchyma in to systemic circulation. Thus, β-amyloid peptide in senile plaques can originate primarily from the neurovascular tissue and either escape into the parenchyma across damaged blood-brain barrier or the β-amyloid peptide-laden small vessels as an effect of the blood-brain barrier sealing finally remains there following degeneration of the brain vessels (Figure 5). Given the extensive network of vessels in the brain, it seems improbable that neuritic plaques are not associated with such vessels. β-amyloid peptide that remain there after degeneration of the vessel become core of neuritic plaques. Massive vascular deposition of β-amyloid peptide results in recurrent ischemia-reperfusion injury. Another factor that supports this idea is the pattern of accumulation of β-amyloid peptide perpendicularly to the axis of the microvessels. Another source from bloodstream of β-amyloid peptide [Mehta and Pirttila, 2002] may be released directly from platelets that carry more than 90 percent of the

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plasma amyloid [Davies et al., 1997]. During degradation of platelet, β-amyloid peptide may be delivered and deposited in the brain vessel wall and parenchyma (Figure 5). On the other hand, the above processes can partly explain chronic blood-brain barrier opening in ischemia. Since leaking blood-brain barrier vessels were found inside the diffuse plaques, it is likely that they are the cause of senile plaques. This observation supported the possibility that the plasma β-amyloid peptide [Mehta and Pirttila, 2002] can be the source of amyloid fibers in Alzheimer’s disease. Other elements of the plaques that showed strong positive reaction for β-amyloid peptide were the astrocytes and their processes inside the area of the diffuse plaques and around blood-brain barrier vessels (Figure 1B) [Nihashi et al., 2001 Pluta 2002b; Pluta, 2004b]. The functional consequences of the chronic disturb leakage of the blood-brain barrier vessels following ischemia are not known. However, it can be expected that the chronic flooding of ischemic neurons with plasma β-amyloid peptide would affect their performance. Deposits in ischemic neurons of β-amyloid peptide for a long time following transient brain injury would be an important additional factor that probably limits the survival of terminally injured neurons. Accumulation of two overlapping pathogenic processes/mechanisms may produce selective delayed vulnerability of hippocampal neurons after ischemia. The increased accumulation of β-amyloid peptide in Alzheimer’s disease suggests excessive and pathological remodeling [Nihashi et al., 2001; Pluta, 2002b] within the sick brain triggered by e.g. repetitive ischemic episodes (Figure 5). Therefore, it is likely that fragments of amyloid precursor protein are involved in the initial healing and subsequent rebuilding of brain tissue [Nihashi et al., 2001; Pluta, 2002b] especially in blood-brain barrier vessels after ischemic injury. Finally, if β-amyloid peptide mediated remodeling is going to be abnormal in susceptible individuals very likely results in neurite and synapse withdrawal and hence the loss of neuronal networks activity (Figure 5). In this review, we presented several lines of evidence that relate ischemia-reperfusion injury of the brain to the development of sporadic Alzheimer’s disease (Table 4). The importance of microischemic episode in the etiology of Alzheimer’s disease has been supported by many recent observations. These observations presented abnormal amyloid precursor protein metabolism and expression as effect of transient brain ischemia [Kim et al., 1998; Lin et al., 1999; Bennett et al., 2000; Pluta, 2000a; Shi et al., 2000; Nihashi et al., 2001; Pluta, 2002b]. This affect was influenced by various risk factors such as age [BaidenAmissah et al., 1998; Popa-Wagner et al., 1998; Kawarabayashi et al., 2001, Badan et al. 2003, Badan et al. 2004] female gander [Pluta 2000a, Pluta 2002b, Pluta 2003b; Wen et al., 2004a; Wen et al., 2004c] hyperthermia [Sinigaglia-Coimbra et al., 2002] hyperglycemia [Lin et al., 2001] and menopause lack of estrogens [Shi et al., 1998]. As for the mechanism that ischemic episode influence Alzheimer’s disease it is suggested that β-amyloid peptide deposition in brain parenchyma may be caused mainly by permeability of ischemic blood-brain barrier for blood β-amyloid peptide (Figure 1C, D, Figure 5). New evidence supports this mechanism that transport β-amyloid peptide between the blood and brain and across the blood-brain barrier regulates brain tissue β-amyloid peptide deposition [Pluta, 2003a; Zlokovic, 2004]. Ischemic insult destabilizes neurons and synapses and makes them more sensitive for toxic parts of amyloid precursor protein. Repeated brain circulatory insufficiency probably explains the heterogeneic profile of Alzheimer’s disease [Etiene et al., 1998]. This data supports the idea of late impairment of

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brain parenchyma and function even though the first acute transient ischemia is followed by temporal neurological recovery. The general knowledge suggests that ischemia plays a principal role in the neuronal death in Alzheimer’s disease brains (Figure 5). On the other hand, associations between the ischemic neurons and aberrant ischemic β-amyloid peptide homeostasis have been shown in animal ischemic model of Alzheimer’s disease (Figure 5). We present that ischemic neuronal injury results at first in the induction of brain ischemia and next in the induction by ischemia certain genes and therefore protein synthesis and these proteins may contribute to postischemic amyloidogenesis as additional repairing hallmark of Alzheimer’s disease brain (Figure 5). These Alzheimer’s disease-related genes are induced in ischemic-reperfusion brain injury suggesting that these Alzheimer’s disease-related genes may be complex components of post-ischemic response. Tge relationship between ischemic neuronal and glial death and synaptic alteration and amyloidogenesis is rather clear. Recent studies have strongly suggested the possible pathogenic interactions between ischemic neurons and Alzheimer’s proteins such as βamyloid peptide, presenilin and α-synuclein. For example, data suggest that presenilin may promote neuronal degeneration in brain ischemia and Alzheimer’s disease by increasing the sensitivity of neurons to ischemia. As effects, we have molecular cascades that result in synaptic dysfunction and neuronal degeneration. An increased level of soluble β-amyloid peptide renders ischemic neurons more vulnerable to apoptosis and excitotoxicity. Presenilin additionally disturbs calcium regulation in cells in a way that sensitizes ischemic nerve cells to apoptosis and excitotoxicity. Links between aberrant calcium homeostasis and altered amyloid precursor protein metabolism are emerging in brain ischemia and Alzheimer’s disease pathology. In summary, the acute generation of β-amyloid peptide has evolved as a probable sealant molecule required during early times after ischemic injury for physiological repairing e.g. leaking blood-brain barrier vessels. The chronic generation of β-amyloid peptide has evolved probably in the pathological healing process in ischemic brain with subsequent damage of blood-brain barrier vessels and deposition/maturation of β-amyloid peptide as senile plaques (Figure 5). In late onset so-called sporadic no genetic Alzheimer’s disease the amassment of βamyloid peptide is not related to amyloid precursor protein neuronal overexpression and overproduction [Selkoe 2001a, Tanzi et al. 2004, Zlokovic 2004]. In addition, a relatively small number of Alzheimer’s disease brains have increased β-amyloid peptide production in the brain that is limited to familial cases of the disease [Zlokovic et al., 2005]. Studies presented that neurovascular dysregulation may result in increased β-amyloid peptide accumulation strongly support the view that neuronal alterations are primarily and observed β-amyloid peptide deposition may be rather secondary to neurovascular problems associated with Alzheimer’s disease. β-amyloid peptide is destroying the blood-brain barrier vessels leaving the brain without its important nutrition and clearance mechanisms. Impaired vascular clearance of β-amyloid peptide across the blood-brain barrier leads to an increased β-amyloid peptide capillary deposition and formation of amyloid lesions [Davis et al., 2004; Deane et al., 2004b]. As an effect of neurovascular β-amyloidosis noted was a decrease of LRP1 receptor levels in brain capillaries [Deane et al., 2004b]. What is creating an increase in the levels of soluble β-amyloid peptide in the brain by regulating its bi-directional

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trafficking across the blood-brain barrier [Pluta et al., 1996a; Pluta et al., 1997d; Pluta et al., 1999a; Pluta et al., 2000c; Deane et al., 2004b; Tanzi et al., 2004]. On the other hand, neuroinflammatory response increased cytokine expression and neuronal co-localization of circulating β-amyloid peptide mediates transcytosis of β-amyloid peptide through RAGE receptor across the blood-brain barrier under pathological conditions such as brain ischemia. At later stages in the Alzheimer’s disease development these two processes may work synergistically to form an interrelated and irreversible pathogenic circle that completely devastates the brain. In summary, it is possible that microneurovascular β-amyloidosis in Alzheimer’s disease develops slowly as a result of a progressive β-amyloid peptide clearance disorder rather than due to its uncontrolled production from amyloid precursor protein. Recent knowledge regarding the neuropathophysiology and neuropathology of brain ischemia and Alzheimer’s disease indicates that similar processes contribute to neuronal death and brain parenchyma disintegration (Table 2, 4, Figure 5).

Acknowledgements This review is being dedicated to three prominent internationally recognized neuropathologists who have departed from our world of neuroscience and with whom I had the great pleasure of working and knowing personally. Professors Henry M. Wisniewski MD, PhD, Mirosław J. Mossakowski MD, PhD, and Józef Kałuża MD, PhD, met untimely deaths in September 1999, December 2001 and July 2003, respectively. These neuroscientists were internationally acclaimed neuropathologists and served as mentors and professional advisors to me and who played prominent roles in influencing my career in the field of neurodegenerative diseases, such as brain ischemia and Alzheimer’s disease. This study was supported in part by funds from the European Community, Polish Comity of Scientific Research and Medical Research Centre. I would like to express my deep gratitude to Mr. Sławomir Januszewski, a collaborator in most experiments described in this review article.

References Abe, K., Tanzi, R.E. & Kogure, K. (1991). Selective induction of Kunitz-type protease inhibitor domain-containing amyloid precursor protein mRNA after persistent focal ischemia in rat cerebral cortex. Neurosci Lett, 125, 172-174. Abramov, A.Y., Canevari, L. & Duchen, M.R. (2003). Changes in intracellular calcium and glutathione in astrocytes as the primary mechanism of amyloid neurotoxicity. J Neurosci 23, 5088-5095. Ajmani, R.S., Metter, E.J., Jaykumar, R., Ingram, D.K., Spangler, E.L., Abugo, O.O. & Rifikind, J.M. (2000). Hemodynamic changes during aging associated with cerebral blood flow and impaired cognitive function. Neurobiol Aging, 21, 257-269.

218

Ryszard Pluta

Ali, S.M., Dunn, E., Oostveen, J.A., Hall, E.D. & Carter, D.B. (1996). Induction of apolipoprotein E mRNA in the hippocampus of the gerbil after transient global ischemia. Mol Brain Res, 38, 37-44. Alzheimer, A. (1907). Über eine eigenartige Erkrankung der Hirnrinde. Allg Z Psychiatr Psych Gericht Med (Berlin), 64, 146-148. Anfuso, C.D., Assero, G., Lupo, G., Nicota, A., Cannavo, G., Strosznajder, R.P., Rapisarda, P., Pluta, R. & Alberghia, M. (2004). Amyloid beta(1-42) and its beta(25-35) fragment induce activation and membrane translocation of cytosolic phospholipase A(2) in bovine retina capillary pericytes. Biochim Biophys Acta, 1686, 125-138. Atwood, C.S., Bowen, R.L., Smith, M.A. & Perry, G. (2003). Cerebrovascular requirement for sealant, anti-coagulant and remodeling molecules that allow for the maintenance of vascular integrity and blood supply. Brain Res Rev, 43, 164-178. Badan, I., Platt, D., Kessler, C. & Popa-Wagner, A. (2003). Temporal dynamics of degenerative and regenerative events associated with cerebral ischemia in aged rats. Gerontology, 49, 356-365. Badan, I., Dinca, I., Buchhold, B., Suofu, Y., Walker, L., Gratz, M., Platt, D., Kessler, C.H. & Popa-Wagner, A. (2004). Accelerated accumulation of N- and C-terminal beta APP fragments and delayed recovery of microtubule-associated protein 1B expression following stroke in aged rats. Eur J Neurosci, 19, 2270-2280. Baiden-Amissah, K., Joashi, U., Blumberg, R., Mehmet, H., Edwards, A.D. & Cox, P.M. (1998). Expression of amyloid precursor protein (beta-APP) in the neonatal brain following hypoxic ischaemic injury. Neuropathol Appl Neurobiol, 24, 346-352. Banati, R.B., Gehrmann, J., Wießner, C., Hossmann, K.A. & Kreutzberg, GW. (1995). Glial expression of the β-amyloid precursor protein (APP) in global ischemia. J Cereb Blood Flow Metab, 15, 647-654. Barclay, L.L., Zemcov, A., Blass, J.P. & Sansone, J. (1985). Survival in Alzheimer’s disease and vascular dementias. Neurology, 35, 834-840. Barrett, J.J., Haley, W.E., Harrell, L.E. & Powers, RE. (1997). Knowledge about Alzheimer disease among primary care physicians, psychologists, nurses, and social workers. Alzheimer Dis Assoc Disord, 11, 99-106. Bennett, S.A., Pappas, B.A., Stevens, W.D., Davidsion, C.M., Fortin, T. & Chen, J. (2000). Cleavage of amyloid precursor protein elicited by chronic cerebral hypoperfusion. Neurobiol Aging, 21, 207-214. Bernaudin, M., Nouvelot, A., MacKensie, E.T. & Petit, E. (1998). Selective neuronal vulnerability and specific glial reactions in hippocampal and neocortical organotypic cultures submitted to ischemia. Exp Neurol, 150, 30-39. Bird, T.D., Sumi, S.M., Nemens, E.J., Nochlin, D., Schellenberg, G., Lampe, T.H., Sadovnick, A., Chui, H., Milner, G.W. & Tinklenberg, J. (1989). Phenotypic heterogeneity in familial Alzheimer’s disease: a study of 24 kindreds. Ann Neurol, 25, 12-25. Blanchard, B.J., Chen, A., Rozenboom, L.M., Stafford, K.A., Weigele, P. & Ingram, V.M. (2004). Efficient reversal of Alzheimer’s disease fibril formation and elimination of neurotoxicity by a small molecule. Proc Natl Acad Sci USA, 101, 14326-14332.

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

219

Blasko, I., Beer, R., Bigl, M., Apelt, J., Franz, G., Rudzki, D., Ransmayr, G., Kampfl, A. & Schliebs, R. (2004). Experimental traumatic brain injury in rats stimulates the expression, production and activity of Alzheimer’s disease β-secretase (BACE-1). J Neural Transm, 111, 523-536. Blennow, K. & Skoog, I. (1999). Genetic testing for Alzheimer’s disease: how close is reality? Curr Opin Psychiatry, 12, 487-493. Borroni, B., Akkawi, N., Martini, G., Colciaghi, F., Prometti, P., Rozzini, L., Di Luca, M., Lenzi, G.L., Romanelli, G., Caimi, L. & Padovani, A. (2002). Microvascular damage and platelets abnormalities in early Alzheimer’s disease. J Neurol Sci, 203-204, 189-193. Bots, M.L., Breteler, M.M., van Kooten, F., Haverkate, F., Meijer, P., Koudstaal, P.J., Grobbee, D.E. & Kluft, C. (1998). Coagulation and fibrinolysis markers and risk of dementia. The Dutch Vascular Factors in Dementia Study. Haemostasis, 28, 216-222. Boutin, H., LeFeuvre, R.A., Horai, R., Asano, M., Iwakura, Y. & Rothwell, N.J. (2001). Role of IL-1α and IL-1β in ischemic brain damage. J Neurosci, 21, 5528-5534. Breteler, M.M., Bots, M.L., Ott, A. & Hofman, A. (1998). Risk factors for vascular disease and dementia. Haemostasis, 28, 167-173. Breteler, M.M. (2000). Vascular risk factors for Alzheimer’s disease: an epidemiologic perspective. Neurobiol Aging, 21, 153-160. Brookmeyer, R., Gray, S. & Kawas, C. (1998). Projections of Alzheimer’s disease in the United States and the public health impact of delaying disease onset. Am J Public Health, 88, 1337-1342. Burns, A., Jacoby, R. & Levy, R. (1990a). Psychiatric phenomena in Alzheimer’s disease. III. Disorders of mood. Br J Psychiatry, 157, 81-86. Burns, A., Jacoby, R. & Levy, R. (1990b) Psychiatric phenomena in Alzheimer’s disease. IV. Disorders of behavior. Br J Psychiatry, 157, 86-94. Butler, T.L., Kassed, C.A., Sanberg, P.R., Willing, A.E. & Pennypacker, K.R. (2002). Neurodegeneration in the rat hippocampus and striatum after middle cerebral artery occlusion. Brain Res, 929, 252-260. Carlyle, W., Ancill, R.J. & Sheldon, L. (1993). Aggression in the demented patient: a doubleblind study of loxapine versus haloperidol. Int Clin Psychopharmacol, 8, 103-108. Chen, X.H., Siman, R., Iwata, A., Meaney, D.F., Trojanowski, J.Q. & Smith, D.H. (2004). Long-term accumulation of amyloid-β, β-secretase, presenilin-1, and caspase-3 in damaged axons following brain trauma. Am J Pathol, 165, 357-371. Chirita, C., Necula, M. & Kuret, J. (2004). Ligand-dependent inhibition and reversal of tau filament formation. Biochemistry, 43, 2879-2887. Clark, M.E., Lipe, A.W. & Bilbrey, M. (1998). Use of music to decrease aggressive behaviors in people with dementia. J Gerontol Nurs, 24, 10-17. Cotter, R.L., Burke, W.J., Thomas, V.S., Potter, J.F., Zheng, J. & Gendelman, H.E. (1999). Insights into the neurodegenerative process of Alzheimer’s disease: a role for mononuclear phagocyte-associated inflammation and neurotoxicity. J Leukoc Biol, 65, 416-427. Cummings, J.L., Miller, B., Hill, M.A. & Neshkes, R. (1987). Neuropsychiatric aspects of multi-infarct dementia and dementia of the Alzheimer type. Arch Neurol, 44, 389-393.

220

Ryszard Pluta

Davies, L., Wolska, B., Hilbich, C., Multhaup, G., Martins, R., Simms, G., Beyreuther, K. & Masters, C. (1988). A4 amyloid protein deposition and the diagnosis of Alzheimer’s disease: prevalence in aged brains determined by immunocytochemistry compared with conventional neuropathologic techniques. Neurology, 38, 1688-1693. Davies, T.A., Long, H.J., Sgro, K., Rathbun, W.H., McMenamin, M.E., Seetoo, K., Tibbles, H., Billingslea, A.M., Fine, R.E., Fishman, J.B., Levesque, C.A., Smith, S.J., Wells, J.H. & Simons, E.R. (1997). Activated Alzheimer disease platelets retain more beta amyloid precursor protein. Neurobiol Aging, 18, 147-153. Davies, C.A., Loddick, S.A., Toulmond, S., Stroemer, R.P., Hunt, J. & Rothwell, N.J. (1999). The progression and topographic distribution of interleukin-1 beta expression after permanent middle cerebral artery occlusion in the rat. J Cereb Blood Flow Metab, 19, 87-98. Davis, J., Xu, F., Deane, R., Romanov, G., Previti, M.L., Zeigler, K., Zlokovic, B.V. & Van Nostrand, W.E. (2004). Early-onset and robust cerebral microvascular accumulation of amyloid β-protein in transgenic mice expressing low levels of a vasculotrophic Dutch/Iowa mutant form of amyloid β-protein precursor. J Biol Chem, 279, 2029620306. D’Andrea, M.R., Cole, G.M. & Ard, M.D. (2004). The microglial phagocytic role with specific plaque types in the Alzheimer disease brain. Neurobiol Aging, 25, 675-683. De Felice, F.G., Vieira, M.N., Saraiva, L.M., Figueroa-Villar, J.D., Garcia-Abreu, J., Liu, R., Chang, L., Klein, W.L. & Ferreira, S.T. (2004). Targeting the neurotoxic species in Alzheimer’s disease: inhibitors of Abeta oligomerization. FASEB J, 18, 1366-1372. De la Torre, J.C. (2000). Critically attained threshold of cerebral hypoperfusion: the CATCH hypothesis of Alzheimer’s pathogenesis. Neurobiol Aging, 21, 331-342. De la Torre, J.C. (2002). Vascular basis of Alzheimer’s pathogenesis. Ann NY Acad Sci, 977, 196-215. De la Torre, J.C. (2004). Alzheimer’s disease is a vasocognopathy: a new term to describe its nature. Neurol Res, 26, 517-524. Deane, R., Wu, Z., Sagare, A., Davis, J., Du Yan, S., Hamm, K., Xu, F., Parisi, M., LeRue, B., Hu, H.W., Spijkers, P., Guo, H., Song, X., Lenting, P.J., Van Nostrand, W.E. & Zlokovic, B.V. (2004a). LRP/amyloid β-peptide interaction mediates differentional brain efflux of aβ isoforms. Neuron, 43, 333-344. Deane, R., Wu, Z. & Zlokovic, B.V. (2004b). RAGE (yin) versus LRP (yang) balance regulates alzheimer amyloid β-peptide clearance through transport across the blood-brain barrier. Stroke, 35, Suppl.1, 2628-2631. Deklunder, G., Roussel, M., Lecroart, J.L., Prat, A. & Gautier, C. (1998). Microemboli in cerebral circulation and alteration of cognitive abilities in patients with mechanical prosthetic heart valves. Stroke, 29, 1821-1826. Dewar, D., Graham, D.I., Teasdale, G.M. & McCulloch, J. (1993). Alz-50 and ubiquitin immunoreactivity is induced by permanent focal cerebral ischaemia in the cat. Acta Neuropathol, 86, 623-629. Dewar, D., Graham, D.I., Teasdale, G.M. & McCulloch, J. (1994). Cerebral ischemia induces alterations in tau and ubiquitin proteins. Dementia, 5, 168-173.

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

221

Dewar, D. & Dawson, D. (1995). Tau protein is altered by focal cerebral ischaemia in the rat: an immunohistochemical and immunoblotting study. Brain Res, 684, 70-78. Deutsch, L.H., Bylsma, F.W., Rovner, B.W., Steele, C. & Folstein, M.F. (1991). Psychosis and physical aggression in probable Alzheimer’s disease. Am J Psychiatry, 148, 11591163. Dietrich, W.D., Kraydieh, S., Prado, R. & Stagliano, N.E. (1998). White matter alterations following thromboembolic stroke: a β-amyloid precursor protein immunocytochemical study in rats. Acta Neuropathol, 95, 524-531. Dodel, RC., Du, Y., Depboylu, C., Hampel, H., Frolich, L., Haag, A., Hemmeter, U., Paulsen, S., Teipel, SJ., Brettschneider, S., Spottke, A., Nolker, C., Moller, HJ., Wie, X., Farlow, M., Sommer, N. & Oertel, WH. (2004). Intravenous immunoglobulins containing antibodies against β-amyloid for the treatment of Alzheimer’s disease. J Neurol Neurosurg Psychiatry, 75, 1472-1474. Doraiswamy, P.M. (2003). The role of the N-methyl-D-aspartate receptor in Alzheimer’s disease: therapeutic potential. Curr Neurol Neurosci Rep, 3, 373-378. Dovey, H.F., John, V., Anderson, J.P., Chen, L.Z., de Saint Andrieu, P., Fang, L.Y., Freedman, S.B., Folmer, B., Goldbach, E., Holsztynska, E.J., Hu, K.L., Johnson-Wood, K.L., Kennedy, S.L., Kholodenko, D., Knops, J.E., Latimer, L.H., Lee, M., Liao, Z., Lieberburg, I.M., Motter, R.N., Mutter, L.C., Nietz, J., Quinn, K.P., Sacchi, K.L., Seubert, P.A., Shopp, G.M., Thorsett, E.D., Tung, J.S., Wu, J., Yang, S., Yin, C.T., Schenk, D.B., May, P.C., Altstiel, L.D., Bender, M.H., Boggs, L.N., Britton, T.C., Clemens, J.C., Czilli, D.L., Dieckman-McGinty, D.K., Droste, J.J., Fuson, K.S., Gitter, B.D., Hyslop, P.A., Johnstone, E.M., Li, W.Y., Little, S.P., Mabry, T.E., Miller, F.D. & Audia, J.E. (2001). Functional gamma-secretase inhibitors reduce beta-amyloid peptide levels in the brain. J Neurochem, 76, 173-181. Eddleston, M. & Muckel, L. (1993). Molecular profile of reactive astrocytes: implications for their role in neurologic disease. Neuroscience, 54,15-36. Erkinjuntti, T. (2001). Clinical deficits of Alzheimer’s disease with cerebrovascular disease and probable VaD. Int J Clin Pract, Suppl. 120, 14-23, 2001. Estus, S., Golde, T.E., Kunishita, T., Blades, D., Lowery, D., Eisen, M., Usiak, M., Qu, X., Tabira, T., Greenberg, B.D. & Younkin, S.G. (1992). Potentially amyloidogenic, carboxyl-terminal derivatives of the amyloid protein precursor. Science, 255, 726-728. Etiene, D., Kraft, J., Ganju, N., Gomez-Isla, T., Hyman, B., Hedley-Whyte, E.T., Wands, J.R. & Monte, S.M. de la. (1998). Cerebrovascular pathology contributes to heterogeneity of Alzheimer’s disease. J Alzheimer Dis, 1, 119-134. Fioravanti, M., Ricciardi, T. & Cottinelli, M. (1998). Hemorheologic alterations and acutephase reaction are related to recent-onset patients with senile dementia of the Alzheimer’s type. Neurobiol Aging, 19, S246-S247. Fratiglioni, L., Viitanen, M., von Strauss, E., Tontodonati, V., Herlitz, A. & Winbland, B. (1997). Very old women at highest risk of dementia and Alzheimer’s disease: incidence data from the Kungsholmen Project, Stockholm. Neurology, 48, 132-138. Fratiglioni, L., De Ronchi, D. & Aquero-Torres, H. (1999). Worldwide prevalence and incidence of dementia. Drugs Aging, 15, 365-375.

222

Ryszard Pluta

Fujioka, M., Taoka, T., Matsuo, Y., Mishima, K., Ogoshi, K., Kondo, Y., Isuda, M., Fujiwara, M., Asano, T., Sakaki, T., Miyasaki, A., Park, D. & Siesjo, BK. (2003). Magnetic resonance imaging shows delayed ischemic striatal neurodegeneration. Ann Neurol, 54, 732-747. Games, D., Adams, D., Alessandrini, R., Barbour, R., Berthelette, P., Blackwell, C., Carr, T., Clements, J., Donaldson, T., Gillespie, F., Guido, T., Hagopian, S., Johnson-Wood, K., Khan, K., Lee, M., Leibowitz, P., Lieberburg, I., Little, S., Masliah, E., McConlogue, L., Montoya-Zavala, M., Mucke, L., Paganini, L., Penuiman, E., Power, M., Schenk, D., Seubert, P., Snyder, B., Soriano, F., Tan, H., Vitale, J., Wadsworth, S., Wolozin, B. & Zhao, J. (1995). Alzheimer-type neuropathology in transgenic mice overexpressing V717F beta-amyloid precursor protein. Nature, 373, 523-527. Geddes, J.W., Schwab, C., Craddock, S., Wilson, J.L. & Pettigrew, L.C. (1994). Alterations in tau immunostaining in the rat hippocampus following transient cerebral ischemia. J Cereb Blood Flow Metab, 14, 554-564. Ghiso, J. & Frangione, B. (2002). Amyloidosis in Alzheimer’s disease. Adv Drug Deliv Rev, 54, 1539-1551. Giulian, D., Haverkamp, L.J., Li, J., Karshin, W.L., Yu, J., Tom, D., Li, X. & Kirkpatrick, J.B. (1995). Senile plaques stimulate microglia to release a neurotoxin found in Alzheimer brain. Neurochem Int, 27, 119-137. Giulian, D., Haverkamp, L.J., Yu, J.H., Karshin, W., Tom, D., Li, J., Kirkpatrick, J., Kuo, L.M. & Roher, A.E. (1996). Specific domains of beta-amyloid from Alzheimer plaque elicit neuron killing in human microglia. J Neurosci, 16, 6021-6037. Glabe, C. (2000). Does Alzheimer disease tilt the scales of amyloid degradation versus accumulation? Nat Med, 6, 133-134. Goedert, M. (2001). Alpha-synuclein and neurodegenerative diseases. Nat Rev Neurosci, 2, 492-501. Gong, Y., Chang, L., Viola, K.L., Loacor, P.N., Lambert, M.P., Finch, C.E., Krafft, G.A. & Klein, W.L. (2003). Alzheimer’s disease-affected brain: presence of oligomeric A beta ligands (ADDLs) suggests a molecular basis for reversible memory loss. Proc Natl Acad Sci USA, 100, 10417-10422. Gorelick, P.B. (1997). Status of risk factors for dementia associated with stroke. Stroke, 28, 459-463. Grammas, P. (2000). A damaged microcirculation contributes to neuronal cell death in Alzheimer’s disease. Neurobiol Aging, 21, 199-205. Graves, A.B., van Duijn, C.M., Chandra, V., Fratiglioni, L., Heyman, A., Jorm, A.F., Kokmen, E., Kondo, K., Mortimer, J.A. & Rocca, W.A. (1991). Alcohol and tobacco consumption as risk factors for Alzheimer’s disease: a collaborative re-analysis of casecontrol studies. EURODEM Risk Factors Research Group. Int J Epidemiol, 20, Suppl 2, S48-57. Griffin, W.S., Sheng, J.G., Royston, M.C., Gentleman, S.M., McKenzie, J.E., Graham, D.I., Roberts, G.W. & Mrak, R.E. (1998). Glial-neuronal interactions in Alzheimer‘s disease: the potential role of a „Cytokine Cycle“ in disease progression. Brain Pathol, 8, 65-72. Groves, W.C., Brandt, J., Steinberg, M., Warren, A., Rosenblatt, A., Baker, A. & Lyketsos, C.G. (2000). Vascular dementia and Alzheimer’s disease: is there a difference? A

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

223

comparison of symptoms by disease duration. J Neuropsychiatry Clin Neurosci, 12, 305315. Guo, Z., Viitanen, M., Fratiglioni, L. & Winblad, B. (1997). Blood pressure and dementia in the elderly: epidemiologic perspectives. Biomed Pharmacother, 51, 68-73. Guo, Z., Cupples, L.A., Kurz, A., Auerbach, S.H., Volicer, L., Chui, H., Green, R.C., Sadovnick, A.D., Duara, R., DeCarli, C., Johanson, K., Go, R.C., Growdon, J.H., Haines, J.L., Kukull, W.A. & Farrer, L.A. (2000). Head injury and the risk of AD in the MIRAGE study. Neurology, 54, 1316-1323. Hall, E.D., Oostveen, J.A., Dunn, E. & Carter, D.B. (1995). Increased amyloid protein precursor and apolipoprotein E immunoreactivity in the selectively vulnerable hippocampus following transient forebrain ischemia in gerbils. Exp Neurol, 135, 17-27. Han, H., Weinreb, P.H. & Lansbury, P.T.Jr. (1995). The core Alzheimer’s peptide NAC forms amyloid fibrils, which seed and are seeded by beta-amyloid: is NAC common trigger or target in neurodegenerative disease? Chem Biol, 2, 163-169. Hardy, J. & Selkoe, D.J. (2002). The amyloid hypothesis of Alzheimer’s disease: progress and problems on the road to therapeutics. Science, 297, 353-356. Harris, F.M., Tesseur, I., Brecht, W.J., Xu, O., Mullendorff, K., Chang, S., Wyss-Coray, T., Mahley, R.W. & Huang, Y. (2004). Asroglial regulation of apolipoprotein E expression in neuronal cells. Implications for Alzheimer’s disease. J Biol Chem, 279, 3862-3868. Hashimoto, M. & Masliah, E. (1999). Alpha-synuclein in Lewy body disease and Alzheimer’s disease. Brain Pathol, 9, 707-720. Hebert, S.S., Bourdages, V., Godin, C., Ferland, M., Carreau, M. & Levesque, G. (2003a). Presenilin-1 interacts directly with the beta-site amyloid protein precursor-cleaving enzyme (BACE1). Neurobiol Dis, 13, 238-245. Hebert, L.E., Scherr, P.A., Bienias, J.L., Bennett, D.A. & Evans, D.A. (2003b). Alzheimer disease in the US population: prevalence estimates using the 2000 census. Arch Neurol, 60, 1119-1122. Hofman, A., Ott, A., Breteler, M.M., Bots, M.L., Slooter, A.J., van Harskamp, F., van Duijn, C.N., Van Broeckhoven, C. & Grobbee, D.E. (1997). Atherosclerosis, apolipoprotein E, and prevalence of dementia and Alzheimer’s disease in the Rotterdam Study. Lancet, 349, 151-154. Honig, L.S., Kukull, W. & Mayeux, R. (2005). Atherosclerosis and Alzheimer’s disease. Analysis of data from the US National Alzheimer’s Coordinating Center. Neurology, 64, 494-500. Horsburgh, K. & Nicoll, J.A.R. (1996a). Selective cellular alterations in amyloid precursor protein and apolipoprotein E following transient cerebral ischaemia in the rat. Alzheimer’s Res, 2, 37-42. Horsburgh, K. & Nicoll, J.A.R. (1996b). Selective alterations in the cellular distribution of apolipoprotein E immunoreactivity following transient cerebral ischemia in the rat. Neuropathol Appl Neurobiol, 22, 342-349. Hossmann, K.A., Schmidt-Kastner. R. & Grosse Ophoff, B. (1987). Recovery of integrative central nervous function after one hour global cerebro-circulatory arrest in normothermic cat. J Neurol Sci, 77, 305-320.

224

Ryszard Pluta

Hsiao, K., Chapman, P., Nilsen, S., Eckman, C., Harigaya, Y., Younkin, S., Yang, F. & Cole, G. (1996). Correlative memory deficits, Abeta elevation, and amyloid plaques in transgenic mice. Science, 274, 99-102. Huang, Y., Liu, X.Q., Wyss-Coray, T., Brecht, W.J., Sanan, D.A. & Mahley, RW. (2001). Apolipoprotein E fragments present in Alzheimer’s disease brains induce neurofibrillary tangle-like intracellular inclusions in neurons. Proc Natl Acad Sci USA, 98, 8838-8843. Hyman, B.T., Van Horsen, G.W., Damasio, A.R. & Barnes, C.L. (1984). Alzheimer’s disease: cell specific pathology isolates the hippocampal formation. Science, 225, 11681170. Irving, E.A., Yatsushiro, K., McCulloch, J. & Dewar, D. (1997). Rapid alteration of tau in oligodendrocytes after focal ischemic injury in the rat: involvement of free radicals. J Cereb Blood Flow Metab, 17, 612-622. Iqbal, K. & Grudke-Iqbal, I. (2004). Inhibition of neurofibrillary degeneration: a promising approach to Alzheimer’s disease and other tauopathies. Curr Drug Targets, 5, 495-502. Ishimaru, H., Ishikawa, K., Haga, S., Shoji, M., Ohe, Y., Haga, C., Sasaki, A., Takahashi, A. & Maruyama, Y. (1996a). Accumulation of apolipoprotein E and β-amyloid-like protein in a trace of the hippocampal CA1 pyramidal cell layer after ischaemic delayed neuronal death. NeuroReport, 7, 3063-3067. Ishimaru, H., Ishikawa, K., Ohe, Y., Takahashi, A. & Maruyama, Y. (1996b). Cystatin C and apolipoprotein E immunoreactivities in CA1 neurons in ischemic gerbil hippocampus. Brain Res, 709, 155-162. Ishimaru, H., Ueda, K., Takahashi, A. & Maruyama, Y. (1998). Changes in presynaptic protein NACP/alpha-synuclein in an ischemic gerbil hippocampus. Brain Res, 788, 311314. Jendroska, K., Poewe, W., Daniel, S.E., Pluess, J., Iwerssen-Schmidt, H., Paulsen, J., Barthel, S., Schelosky, L., Cervos-Navarro, J. & DeArmond, S.J. (1995). Ischemic stress induces deposition of amyloid beta immunoreactivity in human brain. Acta Neuropathol, 90, 461466. Jendroska, K., Hoffmann, O.M. & Patt, S. (1997). Amyloid β peptide and precursor protein (APP) in mild and severe brain ischemia. Ann NY Acad Sci, 826, 401-405. Ji, Z.S., Miranda, R.D., Newhouse, Y.M., Weisgraber, K.H., Huang, Y. & Mahley, R.W. (2002). Apolipoprotein E4 potentates amyloid β peptide-induced lysosomal leakage and apoptosis in neuronal cells. J Biol Chem, 277, 21821-21828. Kalaria, R.N. & Ballard, C. (1999). Overlap between pathology of Alzheimer disease and vascular dementia. Alzheimer Dis Assoc Disord, 13, Suppl. 3, S115-S123. Kalaria, RN. (2000). The role of cerebral ischemia in Alzheimer’s disease. Neurobiol Aging, 21, 321-330. Kalaria, R.N. (2002). Small vessel disease and Alzheimer’s dementia: pathological considerations. Cerebrovasc Dis, 13, Suppl. 2, 48-52. Kamada, H., Sato, K., Zhang, W.R., Omori, N., Nagano, I., Shoji, M. & Abe, K. (2003). Spatiotemporal changes of apolipoprotein E immunoreactivity and apolipoprotein E mRNA expression after transient middle cerebral artery occlusion in rat brain. J Neurosci Res, 73, 545-556.

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

225

Kasckow, J.W. (2002). Cognitive enhancers for dementia: do they work? Curr Psychiatry, 1, 22-28. Kawarabayashi, T., Younkin, L.H., Saido, T.C., Shoji, M., Ashe, K.H. & Younkin, S.G. (2001). Age-dependent changes in brain, CSF, and plasma amyloid β protein in the Tg2576 transgenic mouse model of Alzheimer’s disease. J Neurosci, 21, 372-381. Kawas, C., Gray, S., Brookmeyer, R., Fozard, J. & Zonderman, A. (2000). Age-specific incidence rates of Alzheimer’s disease: the Boltimore longitudinal study of aging. Neurology, 54, 2072-2077. Kida, E., Pluta, R., Lossinsky, A.S., Golabek, A.A., Choi-Miura, N.H., Wisniewski, H.M. & Mossakowski, M.J. (1995). Complete cerebral ischemia with short-term survival in rat induced by cardiac arrest. II. Extracellular and intracellular accumulation of apolipoproteins E and J in the brain. Brain Res, 674, 341-346. Kilander, L., Andren, B., Nyman, H., Lind, L., Boberg, M. & Lithell, H. (1998). Atrial fibrillation is an independent determinant of low cognitive function: a cross-sectional study in elderly men. Stroke, 29, 1816-1820. Kim, H.S., Lee, S.H., Kim, S.S., Kim, Y.K., Jeong, S.J., Ma, J., Han, D.H., Cho, B.K. & Suh, Y.H. (1998). Post-ischemic changes in the expression of Alzheimer’s APP isoforms in rat cerebral cortex. NeuroReport, 9, 533-537. Kitagawa, K., Matsumoto, M., Kuwabara, K., Ohtsuki, T. & Hori, M. (2001). Delayed, but marked, expression of apolipoprotein E is involved in tissue clearance after cerebral infarction. J Cereb Blood Flow Metab, 21, 1199-1207. Kitamura, Y., Ishida, Y., Takata, K., Kakimura, J., Mizutani, H., Shimohama, S., Akaike, A. & Taniguchi, T. (2001). Alpha-synuclein protein is not scavenged in neuronal loss induced by kainic acid or focal ischemia. Brain Res, 898, 181-185. Kivipelto, M., Helkala, E.L., Hanninen, T., Laakso, M.P., Hallikainen, M., Alhainen, K., Soininen, H., Tuomilehto, J. & Nissinen, A. (2001). Midlife vascular risk factors and late-life mild cognitive impairment: A population-based study. Neurology, 56, 16831689. Koistinaho, J., Pyykonen, I., Keinanen, R. & Hokfelt, T. (1996). Expression of β-amyloid precursor protein mRNAs following transient focal ischaemia. NeuroReport, 7, 27272731. Koistinaho, M., Kettunen, M.I., Goldsteins, G., Keinanen, R., Salminen, A., Ort, M., Bures, J., Liu, D., Kauppinen, R.A., Higgins, L.S. & Koistinaho, J. (2002). β-amyloid precursor protein transgenic mice that harbor diffuse Aβ deposits but do not form plaques show increased ischemic vulnerability: Role of inflammation. Proc Natl Acad Sci USA, 99, 1610-1615. Kokmen, E., Whisnant, J.P., O’Fallon, W.M., Chu, C.P. & Beard, C.M. (1996). Dementia after ischemic stroke: a population-based study in Rochester, Minnesota, (1960-1984). Neurology, 46, 154-159. Korczyn, A.D. (2002). Mixed dementia-the most common cause of dementia. Ann NY Acad Sci, 977, 129-134. Kuhlman, G.J., Wilson, H.S., Hutchinson, S.A. & Wallhagen, M. (1991). Alzheimer’s disease and family caregiving: critical synthesis of the literature and research agenda. Nurs Res, 40, 331-337.

226

Ryszard Pluta

LaFerla, F.M., Troncoso, J.C., Strickland, D.K., Kawas, C.H. & Jay, G. (1997). Neuronal cell death in Alzheimer’s disease correlates with apoE uptake and intracellular Aβ stabilization. J Clin Invest, 100, 310-320. Lashuel, H.A., Hartley, D.M., Balakhaneh, D., Aggarwal, A., Teichberg, S. & Callaway, D.J. (2002). New class of inhibitors of amyloid-beta fibril formation. Implications for the mechanism of pathogenesis in Alzheimer’s disease. J Biol Chem, 277, 42881-42890. Lau, L.F., Schachter, J.B., Seymour, P.A. & Sanner, M.A. (2002). Tau protein phosphorylation as a therapeutic target in Alzheimer’s disease. Curr Top Med Chem, 2, 395-415. Launer, L.J., Ross, G.W., Petrovitch, H., Masaki, K., Foley, D., White, L.R. & Havlik, R. J. 2000. Midlife blood pressure and dementia: the Honolulu-Asia aging study. Neurobiol Aging, 21, 49-55. Letenneur, L., Launer, L.J., Adersen, K., Dewey, M.E., Ott, A., Copeland, J.R., Dartigues, J.F., Kragh-Sorensen, P., Baldereschi, M., Brayne, C., Lobo, A., Martinez-Lage, J.M., Stijnen, T. & Hofman, A. (2000). Education and the risk for Alzheimer’s disease: sex makes a difference. EURODEM pooled analyses. EURODERM Incidence Research Group. Am J Epidemiol, 151, 1064-1071. Lin, B., Schmidt-Kastner, R., Busto, R. & Ginsberg, M.D. (1999). Progressive parenchymal deposition of β-amyloid precursor protein in rat brain following global cerebral ischemia. Acta Neuropathol, 97, 359-368. Lin, B., Ginsberg, M.D. & Busto, R. (2001). Hyperglycemic but not normoglycemic global ischemia induces marked early intraneuronal expression of β-amyloid precursor protein. Brain Res, 888, 107-116. Lin, J.H., Weigel, H., Contrine, M.L., Liu, S., Bueno, E., Hansen, A.J., Hansen, T.W., Goldman, S. & Nedergaard, M. (1998). Gap-junction-mediated propagation and amplification of cell injury. Nat Neurosci, 1, 494-500. Lupo, G., Anfuso, C.D., Assero, G., Strosznajder, R.P., Walski, M., Pluta, R. & Alberghina, M. (2001). Amyloid β(1-42) and its β(25-25) fragment induce in vitro phosphatidylcholine hydrolysis in bovine retina capillary pericytes. Neurosci Lett, 303, 185-188. Lye, T.C. & Shores, E.A. (2000). Traumatic brain injury as a risk factor for Alzheimer’s disease: a review. Neuropsychol Rev, 10, 115-129. Lyketsos, C.G., Steinberg, M., Tschanz, J.T., Norton, M.C., Steffens, D.C. & Breitner, J.C. (2000). Mental and behavioral disturbances in dementia: findings from the Cache Country Study on Memory in Aging. Am J Psychiatry, 157, 708-714. Mailliot, C., Podevin-Dimster, V., Rosenthal, R.E., Sergeant, N., Delacourte, A., Fiskum, G. & Buee, L. (2000). Rapid tau protein dephosphorylation and differential rephosphorylation during cardiac arrest-induced cerebral ischemia and reperfusion. J Cereb Blood Flow Metab, 20, 543-549. Masliah, E., Iwai, A., Mallory, M., Ueda, K. & Saitoh, T. (1996). Altered presynaptic protein NACP is associated with plaque formation and neurodegeneration in Alzheimer’s disease. Am J Pathol, 148, 201-210. Masliah, E., Westland, C.E., Rockenstein, E.M., Abraham, C.R., Mallory, M., Veiberg, I., Sheldon, E. & Mucke, L. (1997). Amyloid precursor proteins protect neurons of

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

227

transgenic mice against acute and chronic excitotoxic injuries in vivo. Neuroscience, 78, 135-146. Matsunaga, W., Shirokawa, T. & Isobe, K. (2003). Specific uptake of Abeta 1-40 in rat brain occurs in astrocyte, but not in microglia. Neurosci Lett, 342, 129-131. Mattson, M.P., Zhu, H.Y., Yu, J. & Kindy, M.S. (2000). Presenilin-1 mutation increases neuronal vulnerability to focal ischemia in vivo and to hypoxia and glucose deprivation in cell culture: Involvement of perturbed calcium homeostasis. J Neurosci, 20, 13581364. Mehta, P.D. & Pirttila, T. (2002). Biological markers of Alzheimer’s disease. Drug Dev Res, 56, 74-84. Meyer, J.S., Rauch, G., Rauch, R.A. & Haque, A. (2000). Risk factors for cerebral hypoperfusion, mild cognitive impairment, and dementia. Neurobiol Aging, 21, 161-169. Morrison, R.A., McGrath, A., Davidson, G., Brown, J.J., Murray, G.D. & Lever, A.F. (1996). Low blood pressure in Down’s syndrome, a link with Alzheimer’s disease? Hypertension, 28, 569-575. Moulder, K.L., Narita, M., Chang, L.K., Bu, G. & Johanson, E.M.Jr. (1999). Analysis of a novel mechanism of neuronal toxicity produced by an apolipoprotein E-derived peptide. J Neurochem, 72, 1069-1080. Mudher, A. & Lovestone, S. (2002). Alzheimer’s disease-do tauists and baptists finally shake hands? Trends Neurosci, 25, 22-26. Nicoll, J.A., Wilkinson, D., Holmes, C., Steart, P., Markham, H. & Weller, R.O. (2003). Neuropathology of human Alzheimer disease after immunization with amyloid-β peptide: a case report. Nat Med, 9, 448-452. Nihashi, T., Inao, S., Kajita, Y., Kawai, T., Sugimoto, T., Niwa, M., Kabeya, R., Hata, N., Hayashi, S. & Yoshida, J. (2001). Expression and distribution of beta amyloid precursor protein and beta amyloid peptide in reactive astrocytes after transient middle cerebral artery occlusion. Acta Neurochir, 143, 287-295. Nishio, M., Kohmura, E., Yuguchi, T., Nakajima, Y., Fujinaka, T., Akiyama, C., Iwata, A. & Yoshimine, T. (2003). Neuronal apolipoprotein E is not synthesized in neuron after focal ischemia in rat brain. Neurol Res, 25, 390-394. Oddo, S., Billings, L., Kesslak, J.P., Cribbs, D.H. & LaFerla, F.M. (2004). Abeta immunotherapy leads to clearance of early, but not late, hyperphosphorylated tau aggregates via the proteasome. Neuron, 43, 321-332. Ohkura, T., Isse, K., Akazawa, K., Hamamoto, M., Yaoi, Y. & Hagino, N. (1994). Evaluation of estrogen treatment in female patients with dementia of the Alzheimer type. Endocr J, 41, 361-371. Orzyłowska, O., Oderfeld-Nowak, B., Zaremba, M., Januszewski, S. & Mossakowski, M. (1999). Prolonged and concomitant induction of astroglial immunoreactivity of interleukin-1beta and interleukin-6 in the rat hippocampus after transient global ischemia. Neurosci Lett, 263, 72-76. Oster-Granite, M.L., McPhie, D.L., Greenan, J. & Neve, R.L. (1996). Age-dependent neuronal and synaptic degeneration in mice transgenic for the C terminus of the amyloid precursor protein. J Neurosci, 16, 6732-6741.

228

Ryszard Pluta

Ott, A., Breteler, M.M., van Harskamp, F., Claus, J.J., van der Cammen, T.J., Grobbee, D.E. & Hofman, A. (1995). Prevalence of Alzheimer’s disease and vascular dementia: association with education. The Rotterdam study. Br Med J, 310, 970-973. Ott, A., Stolk, R.P., Hofman, A., van Harskamp, F., Grobbee, D.E. & Breteler, M.M. (1996). Association of diabetes mellitus and dementia: the Rotterdam Study. Diabetologia, 39, 1392-1397. Ott, A., Breteler, M.M., de Bruyne, M.C., van Harskamp, F., Grobbee, D.E. & Hofman, A. (1997). Atrial fibrillation and dementia in a population-based study. The Rotterdam Study. Stroke, 28, 316-321. Ott, A., Slooter, A.J., Hofman, A., van Harskamp, F., Witteman, J.C., Van Broeckhoven, C., van Duijn, C.M. & Breteler, M.M. (1998). Smoking and risk of dementia and Alzheimer’s disease in a population-based cohort study: the Rotterdam Study. Lancet, 351, 1840-1843. Ott, A., Stolk, R.P., van Harskamp, F., Polas, H.A., Hofman, A. & Breteler, M.M. (1999). Diabetes mellitus and the risk of dementia: The Rotterdam Study. Neurology, 53, 19371942. Palacios, G., Mengod, G., Tortosa, A., Ferrer, I. & Palacios, J.M. (1995). Increased βamyloid precursor protein expression in astrocytes in the gerbil hippocampus following ischaemia: Association with proliferation of astrocytes. Eur J Neurosci, 7, 501-510. Passant, U., Warkentin, S. & Gustafson, L. (1997). Orthostatic hypotension and low blood pressure in organic dementia: a study of prevalence and related clinical characteristics. Int J Geriatr Psychiatry, 12, 395-403. Paulsen, J.S., Salmon, D.P., Thal, L.J., Romero, R., Weisstein-Jenkins, C., Galasko, D., Hofstetter, C.R., Thomas, R., Grant, I. & Jeste, D.V. (2000). Incidence of and risk factors for hallucinations and delusions in patients with probable AD. Neurology, 54, 19651971. Pennypacker, K.R., Hernandez, H., Benkovic, S., Morgan, D.G., Willing, A.E. & Sanberg, P.R. (1999). Induction of presenilins in the rat brain after middle cerebral arterial occlusion. Brain Res Bull, 48, 539-543. Plassman, B.L., Havlik, R.J., Steffens, D.C., Helms, M.J., Newman, T.N., Drosdick, D., Phillips, C., Gau, B.A., Welsh-Bohmer, K.A., Burke, J.R., Guralnik, J.M. & Breitner, J.C. (2000). Documented head injury in early adulthood and risk of Alzheimer’s disease and other dementias. Neurology, 55, 1158-1166. Pluta, R. (1991a). The effects of prostacyclin on early ultrastructural changes in the cytoplasm and nuclei of neuroglial cells following complete cerebral ischemia. J Hirnforsch, 32, 175-184. Pluta, R., Lossinsky, A.S., Mossakowski, M.J., Faso, L. & Wisniewski, H.M. (1991b). Reassessment of new model of complete cerebral ischemia in rats. Method of induction of clinical death, pathophysiology and cerebrovascular pathology. Acta Neuropathol, 83, 1-11. Pluta, R., Lossinsky, A.S., Wisniewski, H.M. & Mossakowski, M.J. (1994a). Early bloodbrain barrier changes in the rat following transient complete cerebral ischemia induced by cardiac arrest. Brain Res, 633, 41-52.

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

229

Pluta, R., Kida, E., Lossinsky, A.S., Golabek, A.A., Mossakowski, M.J. & Wisniewski, H.M. (1994b). Complete cerebral ischemia with short-term survival in rats induced by cardiac arrest. I. Extracellular accumulation of Alzheimer’s β-amyloid protein precursor in the brain. Brain Res, 649, 323-328. Pluta, R., Lossinsky, A.S., Walski, M., Wisniewski, H.M. & Mossakowski, M.J. (1994c). Platelet occlusion phenomenon after short- and long-term survival following complete cerebral ischemia in rats produced by cardiac arrest. J Brain Res, 35, 463-471. Pluta, R., Kida, E., Golabek, A.A. & Mossakowski, M.J. (1995a). Accumulation of Alzheimer’s β-amyloid associated proteins: apolipoproteins E, J and A-1 in rat brain after global cerebral ischemia. J Cereb Blood Flow Metab, 15, Suppl. 1, S227. Pluta, R., Kida, E., Golabek, A.A. & Mossakowski, M.J. (1995b). Possible involvement of pathomechanism(s) operating in brain ischemia, in Alzheimer’s disease pathology. J Cereb Blood Flow Metab, 15, Suppl. 1, S803. Pluta, R., Kida, E., Golabek, A.A. & Mossakowski, M.J. (1995c). Apolipoproteins E and J in rat ischemic brain: colocalization with amyloid protein precursor. Eur J Neurosci, Suppl. 8, 170. Pluta, R., Barcikowska, M., Januszewski, S., Misicka, A. & Lipkowski, A.W. (1996a). Evidence of blood-brain barrier permeability/leakage for circulating human Alzheimer’s β-amyloid- (1-42)-peptide. NeuroReport, 7, 1261-1265. Pluta, R., Osęka, M., Januszewski, S., Misicka, A., Barcikowska, M., Lipkowski, A.W. & Koźniewska, E. (1996b). Circulating human β-amyloid-(1-42)-peptide increases cerebral blood flow in anaesthetized rats. Alzheimer’s Res, 2, 233-236. Pluta, R., Barcikowska, M., Januszewski, S., Misicka, A. & Lipkowski, A.W. (1996c). Ischemia with open blood-brain barrier and circulating human β-amyloid peptide trigger Alzheimer’s disease-like neuropathology. Neurobiol Aging, 17, Suppl. 4S, S24-S25. Pluta, R., Barcikowska, M., Kida, E., Zelman, I. & Mossakowski, M.J. (1997a). Late extracellular deposits of β-amyloid precursor protein in ischaemic rat brain show different immunoreactivity to the N- and C-terminal. Alzheimer’s Res, 3, 51-57. Pluta, R. (1997b). Experimental model of neuropathological changes characteristic for Alzheimer’s disease. Folia Neuropathol, 35, 94-98. Pluta, R., Barcikowska, M., Dębicki, G., Ryba, M. & Januszewski, S. (1997c). Changes in amyloid precursor protein and apolipoprotein E immunoreactivity following ischemic brain injury in rat with long-term survival: influence of idebenone treatment. Neurosci Lett, 232, 95-98. Pluta, R., Misicka, A., Januszewski, S., Barcikowska, M. & Lipkowski, A.W. (1997d). Transport of human β-amyloid peptide through the rat blood-brain barrier after global cerebral ischemia. Acta Neurochir, (Suppl.), 70, 247-249. Pluta, R., Barcikowska, M., Mossakowski, M.J. & Zelman, I. (1997e). Beta-amyloid peptide and C-terminal of beta-amyloid precursor protein persist for over 1 year in rat brain after global ischemia. J Cereb Blood Flow Metab, 17, Suppl. 1, S775. Pluta, R., Barcikowska, M., Mossakowski, M.J. & Zelman, I. (1998a). Cerebral accumulation of beta-amyloid following ischemic brain injury with long-term survival. Acta Neurochir, (Suppl.), 71, 206-208.

230

Ryszard Pluta

Pluta, R., Barcikowska, M., Misicka, A., Januszewski, S. & Lipkowski, A.W. (1998b). Disappearing diffuse amyloid plaques. Neurobiol Aging, 19, S131. Pluta, R., Misicka, A., Barcikowska, M., Lipkowski, A.W. & Januszewski, S. (1998c). Ischemic rats as model in the study of the neurobiological role of Alzheimer’s β-amyloid peptide. Clin Neurosci, (Hungary), 51, 20-21. Pluta, R., Barcikowska, M., Misicka, A., Lipkowski, A.W., Spisacka, S. & Januszewski, S. (1999a). Ischemic rats as a model in the study of the neurobiological role of human βamyloid peptide. Time-dependent disappearing diffuse amyloid plaques in brain. NeuroReport, 10, 3615-3619. Pluta, R., Misicka, A., Lipkowski, A.W., Januszewski, S. & Barcikowska, M. (1999b). Disappearing amyloid deposits in extracerebral organs in rat model of Alzheimer’s disease. J Cereb Blood Flow Metab, 19, Suppl.1, S13. Pluta, R. (2000a). The role of apolipoprotein E in the deposition of β-amyloid peptide during ischemia-reperfusion brain injury. A model of early Alzheimer’s disease. Ann NY Acad Sci, 903, 324-334. Pluta, R. (2000b). No effect of anti-oxidative therapy on cerebral amyloidosis following ischemia-reperfusion brain injury. Folia Neuropathol, 38, 188-190. Pluta, R., Misicka, A., Barcikowska, M., Spisacka, S., Lipkowski, A.W. & Januszewski, S. (2000c). Possible reverse transport of β-amyloid peptide across the blood-brain barrier. Acta Neurochir, (Suppl.), 76, 73-77. Pluta, R. (2001). Proteins associated with Alzheimer’s disease in conditions predisposing to Alzheimer’s-type neurodegeneration. J Cereb Blood Flow Metab, 21, Suppl. 1, S424. Pluta, R. (2002a). Glial expression of the β-amyloid peptide in cardiac arrest. J Neurol Sci, 203-204, 277-280. Pluta, R. (2002b). Astroglial expression of the beta-amyloid in ischemia-reperfusion brain injury. Ann NY Acad Sci, 977, 102-108. Pluta, R. (2003a). Blood-brain barrier dysfunction and amyloid precursor protein accumulation in microvascular compartment following ischemia-reperfusion brain injury with 1-year survival. Acta Neurochir, (Suppl.), 86, 117-122. Pluta, R., Ułamek, M., Łuczyk, W., Hodun, R., Niczyporuk, P., Smyrgała, B. & Januszewski, S. (2003b). Chronic blood-brain barrier opening following ischemia-reperfusion brain injury with 1-year survival. J Cereb Blood Flow Metab, 23, Suppl. 1, 165. Pluta, R. (2004a). Alzheimer lesions after ischemia-reperfusion brain injury. Folia Neuropathol, 42, 181-186. Pluta, R. (2004b). From brain ischemia-reperfusion injury to possible sporadic Alzheimer’s disease. Curr Neurovasc Res, 1, 441-453. Popa-Wagner, A., Schroder, E., Walker, L.C. & Kessler, C. (1998). Beta-amyloid precursor protein and beta-amyloid peptide immunoreactivity in the rat brain after middle cerebral artery occlusion: effect of age. Stroke, 29, 2196-2202. Reisberg, B., Doody, R., Stoffler, A., Schmitt, F., Ferris, S., Mobius, H.J. & Memantine Study Group. (2003). Memantine in moderate-to-severe Alzheimer’s disease. N Engl J Med, 348, 1333-1341. Rizzo, M., Anderson, S.W., Dawson, J., Myers, R. & Ball, K. (2000). Visual attention impairments in Alzheimer’s disease. Neurology, 54, 1954-1959.

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

231

Roberts, S.B. (2002). γ-secretase inhibitors and Alzheimer’s disease. Adv Drug Deliv Rev, 54, 1579-1588. Rosenblum, W.I. (2002). Structure and location of amyloid beta peptide chains and arrays in Alzheimer’s disease: new findings require reevaluation of the amyloid hypothesis and of tests of the hypothesis. Neurobiol Aging, 23, 225-230. Sairanen, T.R., Lindsberg, P.J., Brenner, M. & Siren, A.L. (1997). Global forebrain ischemia results in differential cellular expression of interleukin-1 beta (IL-1 beta) and its receptor at mRNA and protein level. J Cereb Blood Flow Metab, 17, 1107-1120. Saito, K., Suyama, K., Nishida, K., Sei, Y. & Basile, A.S. (1996). Early increases in TNFalpha, IL-6 and IL-1 beta levels following transient cerebral ischemia in gerbil brain. Neurosci Lett, 206, 149-152. Sandman, P.O. (1990). Is good care the best treatment for the Alzheimer patient? Acta Neurol Scand, (Suppl.), 129, 37-39. Schenk, D., Barbour, R., Dunn, W., Gordon, G., Grajeda, H., Guido, T., Hu, K., Huang, J., Johnson-Wood, K., Khan, K., Kholodenko, D., Lee, M., Liao, Z., Lieberburg, I., Motter, R., Mutter, L., Soriano, F., Shopp, G., Vasquez, N., Vandevert, C., Walker, S., Wogulis, M., Yednock, T., Games, D. & Seubert, P. (1999). Immunization with amyloid-beta attenuates Alzheimer-disease-like pathology in the PDAPP mouse. Nature, 400, 173-177. Schumock, G.T. (1998). Economic considerations in the treatment and management of Alzheimer’s disease. Am J Health Syst Pharm, 55, Suppl. 2, S17-S21. Selkoe, D.J. (2001a). Clearing the brain’s amyloid cobwebs. Neuron, 32, 177-180. Selkoe, D.J. (2001b). Alzheimer’s disease results from the cerebral accumulation and cytotoxicity of amyloid β-protein. J Alzheimers Dis, 3, 75-80. Shackelford, D.A. & Yeh, R.Y. (1998). Dephosphorylation of tau during transient forebrain ischemia in the rat. Mol Chem Neuropathol, 34, 1003-120. Shi, J., Panickar, K.S., Yang, S.H., Rabbani, O., Day, A.L. & Simpkins, J.W. (1998). Estrogen attenuates over-expression of beta-amyloid precursor protein messenger RNA in an animal model of focal ischemia. Brain Res, 810, 87-92. Shi, J., Yang, S.H., Stubley, L., Day, A.L. & Simpkins, J.W. (2000). Hypoperfusion induces overexpression of β-amyloid precursor protein mRNA in a focal ischemic rodent model. Brain Res, 853, 1-4. Shinnou, M., Ueno, M., Sakamoto, H. & Ide, M. (1998). Blood-brain barrier damage in reperfusion following ischemia in the hippocampus of the Mongolian gerbil brain. Acta Neurol Scand, 98, 406-411. Silverberg, G., Mayo, M., Saul, T., Rubenstein, E. & McGuire, D. (2003). Alzheimer’s disease, normal-pressure hydrocephalus, and senescent changes in CSF circulatory physiology: a hypothesis. Lancet Neurol, 2, 506-511. Sinigaglia-Coimbra, R., Cavalheiro, E.A. & Coimbra, C.G. (2002). Postischemic hypertermia induces Alzheimer-like pathology in the rat brain. Acta Neuropathol, 103, 444-452. Skoog, I., Kalaria, R.N. & Breteler, M.M. (1999). Vascular factors and Alzheimer disease. Alzheimer Dis Assoc Disord, 13, Suppl. 3, S106-S114. Small, G.W., Rabins, P.V., Bany, P.P., Buckholtz, N.S., DeKosky, S.T., Ferris, S.H., Finkel, S.I., Gwyther, L.P., Khachaturian, Z.S., Lebowitz, B.D., McRae, T.D., Morris, J.C., Oakley, F., Schneider, L.S., Streim, J.E., Sunderland, T., Teri, L.A. & Tune, L.E. (1997).

232

Ryszard Pluta

Diagnosis and treatment of Alzheimer’s disease and related disorders. Consensus statement of the American Association for Geriatric Psychiatry, the Alzheimer’s Association and the American Geriatrics Society. JAMA, 278, 1363-1371. Smith, M.A. & Perry, G. (1998). What are the facts and artifacts of the pathogenesis and etiology of Alzheimer disease? J Chem Neuroanat, 16, 35-41. Smith-Swintosky, V.L., Pettigrew, L.C., Craddock, S.D., Culwell, A.R., Rydel, R.E. & Mattson, M.P. (1994). Secreted forms of beta-amyloid precursor protein protect against ischemic injury. J Nuerochem, 63, 781-784. Snowdon, D.A., Greiner, L.H., Mortimer, J.A., Riley, K.P., Greiner, P.A. & Markesbery, W.R. (1997). Brain infarction and the clinical expression of Alzheimer disease. The nun study. JAMA, 277, 813-817. Solerte, S.B., Ceresini, G., Ferrari, E. & Fioravanti, M. (2000). Hemorheologic changes and overproduction of cytokines from immune cells in mild to moderate dementia of the Alzheimer’s type: adverse effects on cerebromicrovascular system. Neurobiol Aging, 21, 271-281. Soto, C. (2001). Protein misfolding and disease; protein refolding and therapy. FEBS Lett, 498, 204-207. Spisacka, S. & Pluta, R. (2003). Demographic and epidemiological profile of patients with Alzheimer’s disease. Ann Univ M Curie-Sklodowska, Vol LVIII, Suppl. XIII, 157-162. Stamer, K., Vogel, R., Thies, E., Mandelkow, E. & Mandelkow, E.M. (2002). Tau blocks traffic of organelles, neurofilaments, and APP vesicles in neurons and enhances oxidative stress. J Cell Biol, 156, 1051-1063. Stewart, J.T. (1995). Management of behavior problems in the demented patient. Am Fam Physician, 52, 2311-2317, 2321-2322. Stoltzner, S.E., Grenfell, T.J., Mori, C., Wisniewski, K.E., Wisniewski, T.M., Selkoe, D.J. & Lemere, C.A. (2000). Temporal accrual of complement proteins in amyloid plaques in Down’s syndrome with Alzheimer’s disease. Am J Pathol, 156, 489-499. Takuma, K., Baba, A. & Matsuda, T. (2004). Astrocyte apoptosis: Implications for neuroprotection. Prog Neurobiol, 72, 111-127. Tanimukai, H., Imaizumi, K., Kudo, T., Katayama, T., Tsuda, M., Takagi, T., Tohyama, M. & Takeda, M. (1998). Alzheimer-associated presenilin-1 gene is induced in gerbil hippocampus after transient ischemia. Mol Brain Res, 54, 212-218. Tanzi, R.E., Moir, R.D. & Wagner, S.L. (2004). Clearance of Alzheimer’s Aβ peptide: the many roads to perdition. Neuron, 43, 605-608. Tariot, P.N., Farlow, M.R., Grossberg, G.T., Graham, S.M., McDonald, S., Gergel, I. & Memantine Study Group. (2004). Memantine treatment in patients with moderate to severe Alzheimer disease already receiving donepezil: a randomized controlled trail. JAMA, 291, 317-324. Thomas, T., Thomas, G., McLendon, C., Sutton, T. & Mullan, M. (1996). β-amyloidmediated vasoactivity and vascular endothelial damage. Nature, 380, 168-171. Tomimoto, H., Akiguchi, I., Wakita, H., Nakamura, S. & Kimura, J. (1995). Ultrastructural localization of amyloid protein precursor in the normal and postischemic gerbil brain. Brain Res, 672, 187-195.

Ischemia-Reperfusion Factors in Sporadic Alzheimer’s Disease

233

Touzani, O., Boutin, H., Chuquet, J. & Rothwell, N. (1999). Potential mechanisms of interleukin-1 involvement in cerebral ischaemia. J Neuroimmunol, 100, 203-215. Touzani, O., Boutin, H., LeFeuvre, R., Parker, L., Miller, A., Luheshi, G. & Rothwell, N. (2002). Interleukin-1 influences ischemic brain damage in the mouse independently of the interleukin-1 type I receptor. J Neurosci, 22, 38-43. Tyas, S.L., Manfreda, J., Strain, L.A. & Montgomery, P.R. (2001). Risk factors for Alzheimer’s disease: a population-based, longitudinal study in Manitoba, Canada. Int J Epidemiol, 30, 590-597. Uchihara, T., Nakamura, A., Arai, T., Ikeda, K. & Tsuchiya, K. (2004). Microglial tau undergoes phosphorylation-independent modification after ischemia. Glia, 45, 180-187. Ueno, M., Tomimoto, H., Akiguchi, I., Wakita, H. & Sakamoto, H. (2002). Blood-brain barrier disruption in white matter lesions in a rat model of chronic cerebral hypoperfusion. J Cereb Blood Flow Metab, 22, 97-104. Uetsuki, T., Takemoto, K., Nishimura, I., Okamoto, M., Niinobe, M., Momoi, T., Miura, M. & Yoshikawa, K. (1999). Activation of neuronal caspase-3 by intracellular accumulation of wild-type Alzheimer amyloid precursor protein. J Neurosci, 19, 6955-6964. Van Beek, J., Chan, P., Bernaudin, M., Petit, E., MacKenzie, E.T. & Fontaine, M. (2000). Glial responses, clusterin, and complement in permanent focal cerebral ischemia in the mouse. Glia, 31, 39-50. Van Duijn, C.M., Havekes, L.M., Van Broeckhoven, C., de Knijff, P. & Hofman, A. (1995). Apolipoprotein E genotype and association between smoking and early onset Alzheimer’s disease. Br Med J, 310, 627-631. Vermeer, S.E., Prins, N.D., den Heijer, T., Hofman, A., Koudstaal, P.J. & Breteler, M.M.B. (2003). Silent brain infarcts and the risk of dementia and cognitive decline. N Engl J Med, 348, 1215-1222. Villardita, C. (1993). Alzheimer’s disease compared with cerebrovascular dementia. Neuropsychological similarities and differences. Acta Neurol Scand, 87, 299-308. Vukovic, V., Lovrencic-Huzjan, A., Solter, V.V., Dordevic, V. & Demarin, V. (2003). Hormone replacement therapy – is there a place for its use in neurology? Coll Antropol, 27, 413-424. Vuorinen, E., Laine, M. & Rinne, J. (2000). Common pattern of language impairment in vascular dementia and in Alzheimer disease. Alzheimer Dis Assoc Disord, 14, 81-86. Walton, M., Young, D., Sirimanne, E., Dodd, J., Christie, D., Williams, C., Gluckman, P. & Dragunow, M. (1996). Induction of clusterin in the immature brain following a hypoxicischemic injury. Mol Brain Res, 39, 137-152. Waring, S.C., Rocca, W.A., Petersen, R.C., O’Brien, P.C., Tangalos, E.G. & Kokmen, E. (1999). Postmenopausal estrogen replacement therapy and risk of AD: a populationbased study. Neurology, 52, 965-970. Wen, Y., Onyewuchi, O., Yang, S., Liu, R. & Simpkins, J.W. (2004a). Increased betasecretase activity and expression in rats following transient cerebral ischemia. Brain Res, 1009, 1-8. Wen, Y., Yang, S., Liu, R. & Simpkins, J.W. (2004b). Transient cerebral ischemia induces site-specific hyperphosphorylation of tau protein. Brain Res, 1022, 30-38.

234

Ryszard Pluta

Wen, Y., Yang, S., Liu, R., Brun-Zinkernagel, A.M., Koulen, P. & Simpkins, J.W. (2004c). Transient cerebral ischemia induces aberrant neuronal cell cycle re-entry and Alzheimer’s disease-like tauopathy in female rats. J Biol Chem, 279, 22684-22692. Wiggins, A.K., Shen, P.J. & Gundlach, A.L. (2003). Delayed, but prolonged increases in astrocytic clusterin (ApoJ) mRNA expression following acute cortical spreading depression in the rat: evidence for a role of clusterin in ischemic tolerance. Mol Brain Res, 114, 20-30. Wisniewski, H.M., Pluta, R., Lossinsky, A.S. & Mossakowski, M.J. (1995). Ultrastructural studies of cerebral vascular spasm after cardiac arrest-related global cerebral ischemia in rats. Acta Neuropathol, 90, 432-440. Wisniewski, H.M. & Maslinska, D. (1996). Beta-protein immunoreactivity in the human brain after cardiac arrest. Folia Neuropathol, 34, 65-71. Wisniewski, T. & Frangione, B. (1992). Apolipoprotein E: a pathological chaperone protein in patients with cerebral and systemic amyloid. Neurosci Lett, 135, 235-238. Wolfe, M.S., Xia, W., Ostaszewski, B.L., Diehl, T.S., Kimberly, W.T. & Selkoe, D.J. (1999). Two transmembrane aspartates in presenilin-1 required for presenilin endoproteolysis and gamma-secretase activity. Nature, 398, 513-517. Wyss-Coray, T., Loike, J.D., Brionne, T.C., Lu, E., Anankov, R., Yan, F., Silverstein, S.C. & Husemann, J. (2003). Adult mouse astrocytes degrade amyloid-beta in vitro and in situ. Nat Med, 9, 453-457. Yam, P.S., Takasago, T., Dewar, D., Graham, D.I. & McCulloch, J. (1997). Amyloid precursor protein accumulates in white matter at the margin of a focal ischaemic lesion. Brain Res, 760, 150-157. Yamasaki, Y., Matsuura, N., Shozuhara, H., Onodera, H., Itoyama, Y. & Kogure, K. (1995). Interleukin-1 as a pathogenetic mediator of ischemic brain damage in rats. Stroke, 26, 676-680. Yang, Y., Kinney, G.A., Spain, W.J., Breitner, J.C.S. & Cook, D.G. (2004). Presenilin-1 and intracellular calcium stores regulate neuronal glutamate uptake. J Neurochem, 88, 13611372 Yokota, M., Saido, T.C., Tani, E., Yamaura, I. & Minami, N. (1996). Cytotoxic fragment of amyloid precursor protein accumulates in hippocampus after global forebrain ischemia. J Cereb Blood Flow Metab, 16, 1219-1223. Zlokovic, B.V. (2004). Clearing amyloid through the blood-brain barrier. J Neurochem, 89, 807-811. Zlokovic, B.V., Deane, R., Sallstrom, J., Chow, N. & Miano, J.M. (2005). Neurovascular pathways and Alzheimer amyloid β-peptide. Brain Pathol, 15, 78-83.

In: New Research on Alzheimer’s Disease Editor: Eileen M. Welsh, pp.

ISBN 1-59454-939-7 © 2006 Nova Science Publishers, Inc.

Chapter VIII

Amyloid Beta (Aβ) Peptides in Plasma as Biochemical Markers of Alzheimer's Disease and Mild Cognitive Impairment Tomasz Sobow1∗, Marcin Flirski1, Pawel P. Liberski2 and Iwona Kloszewska1 1 2

Department of Old Age Psychiatry & Psychotic Disorders; Department of Molecular Pathology and Neuropathology, Medical University of Lodz, Poland

Abstract Plasma levels of amyloid β peptides (Aβ) represent a potentially attractive biomarker of Alzheimer’s disease (AD). Although plasma Aβ levels are increased in patients with familial AD mutations, results of the studies encompassing sporadic AD cases are equivocal. In several studies elevated plasma Aβ42 levels could be detected long before the onset of symptoms, though the value of that effect in predicting progression to dementia in mildly cognitively impaired (MCI) subjects is not known. It has recently been proposed that plasma Aβ levels increase merely with age and are neither sensitive nor specific for AD or MCI. Additionally, an increase of Aβ42 plasma levels in women with MCI has been reported and thus suggested to represent a biologic explanation for the increased prevalence of females in the population of late-onset AD patients identified by epidemiologic studies. In our study we have assessed the levels of Aβ peptides in plasma of carefully selected AD patients and MCI subjects compared to healthy controls matched for age, gender and education. The selection procedure employed in the study has been aimed at excluding patients with mixed AD as well as patients fulfilling current diagnostic criteria for both ∗

Corresponding author, Czechoslowacka 8/10, 92-216 Lodz, Poland. [email protected]

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Tomasz Sobow, Marcin Flirski, Pawel P. Liberski and Iwona Kloszewska AD and other specific forms of dementia (e.g. dementia with Lewy bodies). No difference in any of the evaluated parameters (Aβ40, Aβ42, Aβ40/Aβ42 ratio) was observed between the AD and control groups. In subjects with MCI plasma Aβ42 levels were significantly elevated versus both AD (p<0,001) and controls (p<0,001), whereas Aβ40 concentrations were not significantly altered; no correlation with age or gender was found. A hypothesis can be formulated that the elevation of plasma Aβ42 in MCI is a reflection of efforts to eliminate the pathological peptide from the central nervous system (CNS) through the yet viable blood-brain barrier (BBB). It is therefore probable that in a very early stage of AD alterations in the catabolism of a β-amyloid precursor protein (βAPP) occur, resulting in a preferential synthesis of longer, more amyloidogenic isoform of Aβ peptide - Aβ42; Aβ42 is initially effectively removed via the BBB which brings about a gradual increase in plasma Aβ42, but not Aβ40, still competently transported backwards. The results of our study, indicating an elevation of Aβ42, but not Aβ40 in MCI subjects, would support this hypothesis.

Introduction Dementia is one of the strongest predictors of mortality, with a risk two to three times those of other life-shortening illnesses, thus constituting a major medical and socioeconomic burden (Tschanz et al. 2004). Alzheimer’s disease (AD) is the most prevalent cause of dementia in the developed countries, occupying the eighth place among the ten leading causes of death (Fitzpatrick et al. 2004; Minino et al. 2002). The prevalence of AD in the population of developed countries has been estimated at 5-11 % of those aged 65 years or over, rising to as much as 50 % among those aged over 85 years [Evans et al., 1989]. With the development of new therapeutic strategies for Alzheimer’s disease, there is an increasing need and justification for an early diagnosis. Diagnosis of sporadic AD is based on clinical exclusion criteria [McKhann et al., 1984], and the required diagnostic work-up is timeconsuming and expensive, at best resulting in a diagnosis of probable AD. In specialised centres, a diagnostic accuracy of maximally 65-90 % is obtained [Andreasen et al., 1999]. Most studies evaluating accuracy rates are based on follow-up periods of several years, so that a much lower diagnostic accuracy can be expected in the earliest stages of the disease. Besides, diagnosis is only definite on brain biopsy or post-mortem neuropathological examination of the brain. Therefore, a marker allowing positive diagnosis of AD at an early stage of the disease is highly desirable. According to the Ronald and Nancy Reagan Research Institute of the Alzheimer’s Association and the National Institute on Aging Working Group [The Ronald and Nancy Reagan Research Institute of the Alzheimer’s Association and the National Institute on Aging Working Group, 1998], an ideal diagnostic marker would also allow predictive testing, monitoring of disease progression and measuring effects of (new potential) therapeutic compounds during treatment (trials). A diagnostic marker of AD should reflect a central pathogenic process of the disorder, like degeneration of neurons and synapses or the development of typical lesions as neuritic plaques and neurofibrillary tangles (NFT). Markers should be validated in neuropathologically confirmed AD cases and should have a sensitivity

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of at least 80 % for detecting AD and a specificity of at least 80 % for distinguishing other dementias. Moreover, the biological marker should be present in body fluids that are easily accessible like urine, blood or cerebrospinal fluid (CSF). Neurodegenerative disorders, along with cancer and cerebrovascular disease, now form a major focus for drug development. Since clinical presentations of different disorders often overlap, the reliable biomarker, at best case scenario reflecting unique pathogenetic features of the disease, is of urgent need. At the phase of clinically overt dementia, AD pathological process is already advanced, massive neuronal loss is obvious and the typical neuropathological changes, including amyloid plaques and neurofibrillary tangles (NFT), full-blown. Consequently, in recent years there is quite an interest in characterizing early stages of AD, clinically, neuropathologically and neuropsychologically. At a clinical level, the concept of mild cognitive impairment (MCI) as a preclinical stage of the disease has emerged [Petersen et al., 2001]. MCI is, however, undoubtedly heterogenous, and, although high rates of “conversion” to dementia have been reported, it is not clear which cases in fact represent early stages of dementia and which are quite benign and stable over time [Amieva et al., 2004; Larrieu et al., 2002]. This heterogenous MCI group comprises disorders associated with an increased risk of progression to dementia. Still, their conceptualization in flux, with equivocal assumptions about aging, the relationship between impairment and disease, and how concomitant functional impairment is classified. Amongst patients with MCI, especially its amnestic form, many will progress to AD. In contrast with clinic-based studies, where progression is more uniform, population-based studies suggest that the MCI classification is unstable in that context. In addition to amnestic MCI, other syndromes exist and can progress to dementia. For example, an identifiable group with vascular cognitive impairment without dementia shows a higher risk of progression to vascular dementia, Alzheimer's disease and mixed dementia [Davis & Rockwood, 2004].

Neurobiology of AD: The Role of Aβ Aβ is derived, after proteolytic cleavage, from a larger precursor protein – amyloid precursor protein (APP). The APP gene is located on chromosome 21. The Aβ domain of APP is partly embedded in the cellular membrane [Selkoe, 1994]. Aβ is believed to be metabolized along two putatively discrete pathways. In the first, APP is cleaved within the Aβ domain by a protease referred to as α-secretase [Seubert et al., 1993]. As a result α-secretase-cleaved soluble APP (α-sAPP) is released, alongside peptide C83 comprising 83 amino acid-residue-long C-terminal endodomain. Importantly, cleavage of APP by α-secretase precludes generation of Aβ, which is why it is sometimes called “the non-amyloidogenic pathway”. The C83 C-terminal fragment (CTF) of APP is then subject to cleavage by γ-secretase releasing a shorter peptide called p3, with a putative activity of a transcription regulator analogous to Notch [Dewachter et al., 2002]. In the second pathway, APP is cleaved at the N-terminus of the Aβ domain by another protease - β-secretase [Vassar et al., 1999]. This cleavage results in the release of β-secretasecleaved soluble APP (β-sAPP) and a 99 amino acid CTF of APP (C93). In the second step,

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C93 is cleaved by γ-secretase to form free Aβ. Due to the pivotal role Aβ plays in the formation of neuritic plaques, the β-secretase metabolic route is often called “the amyloidogenic pathway”. According to the popular, though controversial “amyloid cascade hypothesis”, mismetabolism of APP and Aβ, with subsequent aggregation and incorporation of Aβ into highly insoluble fibrils which are the main constituents of neuritic plaques, initiates a complex cascade of biochemical and cellular changes that leads to neurodegeneration, culminating in cognitive impairment [Joachim et al., 1992]. Extracellular neuritic plaques, together with intracellular NFTs are major neuropathological hallmarks of AD. Of the different forms of Aβ, the one containing 42 amino acids (Aβ42) aggregates more rapidly and predominates in amyloid plaques, although the 40 amino acid isoform (Aβ40) is present in higher concentrations in the brain [Iwatsubo et al., 1994]. The deposition of Aβ is a specific, early event in the development of AD, preceding NFT and clinical dementia. The highly ordered, insoluble, fibrillar Aβ is highly cytotoxic, acting as a proinflammatory agent, inducing oxidative stress, and contributing to neuronal loss [Weldon et al., 1998; Butterfield, 2002]. Recent data suggest that soluble, pre-fibrillar aggregates of Aβ - Aβ oligomers - may be even more effective in mediating neuronal injury [Walsh et al., 2002]. Aβ42 is more neurotoxic than Aβ40, is more likely to generate H2O2 than Aβ40 [Huang et al., 1999] which may be central to its observed cytotoxicity. Increased levels of Aβ42 are suggested to be an initiating factor for both sporadic and familial forms of AD [Scheuner et al., 1996].

Aβ as a Biochemical Marker of AD and MCI: CSF Studies Aβ, generated continuously as a soluble protein as part of the normal constitutive APP metabolism [Haass et al., 1992], is secreted into the extracellular space, allowing its detection in CSF and plasma [Seubert et al., 2002]. A selective reduction of CSF Aβ42 was shown by Motter et al. [Motter et al., 1995] . The statistically significant decrease of Aβ42 concentrations in the CSF of AD patients has later been confirmed in several studies [for an extensive review see Sobow et al., 2004]. A certain explanation of this finding is lacking. There are several hypotheses, the most probable of which comprise: −

−

an increased deposition of Aβ in the plaques, with lower levels remaining to diffuse into the CSF; this hypothesis has been challenged since the finding of reduced CSF Aβ42 in Lewy body dementia (DLB) [Kanemaru et al., 2000; Andreasen et al., 2001; Gomez-Tortosa et al., 2003], Creutzfeld-Jakob disease (CJD), also in cases without Aβ positive plaques [Otto et al., 2000; Kapaki et al., 2001], a percentage of patients with frontotemporal dementia (FTD) [Sjogren et al., 2000; Riemenschneider et al., 2002a] and vascular dementia (VaD) [Hulstaert et al., 1999; Nagga et al., 2002]; decreased clearance of Aβ from the brain;

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−

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disturbance in the metabolism of APP and Aβ leading to neuronal dysfunction and secondary CSF Aβ42 reduction; again, the stability of Aβ42 concentrations in the CSF after acute stroke [Hesse et al., 2000] proves that Aβ42 is not simply a marker of neuronal damage (unlike CSF microtubule associated protein-tau); methodological difficulties, specifically inability to quantify large Aβ aggregates found in CSF in AD in the same way as Aβ monomers [Pitschke et al., 1998].

The decrease in CSF Aβ42 has even been observed as early as in the stage of MCI [Andreasen et al., 1999a; Riemenschneider et al., 2002a; Andreasen et al., 2003]. Moreover, the value of low CSF Aβ42 for both separating MCI patients from cognitively healthy controls and predicting conversion from MCI to AD has also been pretty high (70-80 %), suggesting that low levels of CSF Aβ42 might be useful in the earliest stages of the disease, even before clinical dementia. In one study, CSF Aβ42 levels were examined in elderly nondemented individuals in relation to a later development of dementia [Skoog et al., 2003]. It appeared that those in the lower 50th percentile of CSF Aβ42 had a higher incidence of dementia than those in the higher 50th percentile, with an odds ratio of 8.2. None of those in the highest 33rd percentile of CSF Aβ42 developed dementia. The use of low CSF Aβ42 as a diagnostic marker of AD is greatly limited by its poor specificity. as decreased CSF Aβ42 levels can also be found even in major depression [Hock et al., 1998], not to mention other dementias including DLB, CJD, VaD, and a percentage of FTD cases [Hulstaert et al., 1999; Kanemaru et al., 2000; Otto et al., 2000; Sjogren et al., 2000; Andreasen et al., 2001; Kapaki et al., 2001; Nagga et al., 2002; Riemenschneider et al., 2002a; Gomez-Tortosa et al., 2003]. There also exists a substantial overlap in CSF Aβ42 concentrations between AD subjects and controls. Moreover, in many countries, lumbar puncture is recognized by both patients and doctors as a potentially dangerous and uninvited procedure that strongly limits its prospective widespread use.

Aβ as a Biochemical Marker of AD and MCI: Plasma Studies Studies evaluating β-amyloid levels in plasma are more scarce and their results are conflicting. In both Down syndrome [Schupf et al., 2001] (with neuropathological changes virtually identical to AD) and familial AD [Scheuner et al., 1996; Kosaka et al., 1997] increased plasma Aβ42 has been reported. The results in sporadic AD have been much more contradictory. Both an increase (although with a large overlap with non-AD cases) [Kuo et al., 1999; Matsubara et al., 1999] and lack of changes [Ida et al., 1996; Tamaoka et al., 1996; Mehta et al., 2000; Vanderstichele et al., 2000] in Aβ42 plasma levels of AD patients compared to age-matched controls have been reported. In another study, healthy people with plasma Aβ42 concentrations in the upper two quartiles have had a three to four fold increased risk of developing AD compared to subjects from the lowest quartile [Mayeux et al., 1999]. However, although the mean values differed, there was an almost complete overlap in plasma Aβ42 concentrations between the groups. In another most recent paper age, not diagnosis,

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has appeared the only variable correlated with plasma Aβ40 and Aβ42 levels, with higher values in older patients regardless of diagnostic category (AD, MCI, Parkinson’s disease), duration or severity of the disease, or APOE genotype [Fukumoto et al., 2003]. Since there is evidence that plasma Aβ levels are at least in part heritable [Ertekin-Taner et al., 2001], the influence of genetic factors other than APOE cannot be ruled out. No correlation between plasma Aβ42 and medication use, including statins, estrogen, acetylcholinesterase inhibitors, non-steroid anti-inflammatory drugs, and antioxidants has been reported [Tokuda et al., 2001; Basun et al., 2002; Fukumoto et al., 2003]. The above data are concordant with the preliminary results of our longitudinal study on plasma Aβ42 [Sobow et al., 2003]. We have observed similar plasma Aβ42 in AD and age-matched healthy controls, while in carefully diagnosed MCI patients of the pure amnestic type (excluding subjects with multiple domains and single domains other than memory deficits) the concentration has been significantly increased. Whether this elevation is of predictive value of future development of AD needs to established. Unfortunately, due to substantial variations in Aβ42 levels among participants, this measurement could be more useful as a “personal” marker rather than for the population screening purposes. Another possible explanation of the lack of change in plasma Aβ in AD is a hypothetical peripheral origin of a major part of Aβ in the blood. In another study, the increase of plasma Aβ levels in MCI has been shown but only among women [Assini et al., 2004]. Potential sources of plasma Aβ42 are skeletal muscle [Kuo et al., 2000] and platelets [Li et al., 1998]. However, contrary to previous hypotheses, plasma Aβ40 and Aβ42 concentrations are not related to platelet activation [Olsson et al., 2003], thus rigorous sample techniques to prevent platelet stimulation are not necessary for plasma Aβ42 determination.

Study Methods Patients Evaluation and Selection It’s been repetitively shown that a considerable proportion of subjects with other than AD types of dementia tend to fulfill internationally accepted AD criteria, e.g. those of NINCDS-ADRDA working group. Therefore, one of the major obstacles in getting reliable results in AD clinical studies might be patients selection. Here, we attempted to overcome this source of potential bias by using restrictive patients selection method targeted to exclude patients with mixed AD and patients fulfilling diagnostic criteria for other specific forms of dementia, e.g. dementia with Lewy bodies or frontotemporal dementia. Since it is the amnestic form of MCI which is most probably a clinical precursor of AD, only subjects with a preliminary diagnosis of amnestic MCI were recruited. That way we hoped to enrich our sample in “pure” AD cases. All the patients involved in the study were diagnosed in the specialized university-based Alzheimer’s Clinic during the period of 2001-2003. Initially, a total number of 132 newly diagnosed patients fulfilling the NINCDS-ADRDA diagnostic criteria for AD were found eligible. To ensure that our sample is not “contaminated” by cases with high probability of suffering from non-AD or mixed dementia we excluded, 36 patients fulfilling ICD-10 criteria

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for mixed AD dementia, 11 patients fulfilling diagnostic criteria for dementia with Lewy bodies, 5 subjects fulfilling criteria for frontotemporal dementia, and 8 patients with a longterm history of addiction (or harmful use) to alcohol, benzodiazepines or barbiturates, alone or in combination. As the goal of our study was to evaluate a diagnostic marker in subjects with sporadic AD, from the remaining cohort of 72 participants we excluded another 18 with a family history of AD. From the preliminarily recruited group of 70 subjects fulfilling Petersen’s criteria for MCI we excluded 31 cases for the following reasons, presence of an isolated deficit in a single cognitive domain other than memory (N=4), multiple domain deficits (N=7), clinically significant or badly controlled cardiovascular disorders, the influence of which on the development of the observed deficits could not be excluded (N=11), long-term history of addiction (or harmful use) to alcohol, benzodiazepines or barbiturates, alone or in combination (N=2), and family history of AD (N=7). All the participants or their caregivers (in case of AD patients) were provided with detailed information on the study protocol and signed an informed consent form which, along with the study protocol, was approved by the Ethical Committee of the Medical University of Lodz.

Sample Characteristics and Plasma Aβ Levels Measurements Finally, 128 participants were enrolled in the study, 54 patients with sporadic AD (17 men, mean age 77,5 ± 4,4 years, mean MMSE 17,5 ± 3,4), 39 subjects with amnestic MCI (13 men, mean age 74 ± 3,4, mean MMSE 27,3 ± 0,9), and 35 cognitively intact elderly without clinically significant vascular dementia risk factors or family history of dementia (11 men, mean age 75 ± 2,9, mean MMSE 29,5 ± 0,6) (Table 1).

Table 1: Demographic characteristics of the study participants

Study group

AD MCI Controls Total

N

Age (mean ± standard deviation)

Gender (fraction of women)

Years of formal education (mean ± standard deviation)

54 39 35 128

77,5±4,4 74,0±3,4 75,0±2,9 75,6±4,1

0,69 0,66 0,68 0,68

7,3±3,3 10,0±3,2 8,6±2,9 8,5±3,3

MMSE score ADAS-cog score (mean ± standard (mean ± standard deviation) deviation)

17,5±3,4 27,3±0,9 29,5±0,6 23,8±5,9

30,5±10,6 10,4±2,7 3,0±1,9 16,9±13,9

Whole blood was collected from fasting subjects in EDTA-containing recipients and cellular material was pelleted by centrifugation. Platelets have been regarded a primary source of circulating βAPP and Aβ. However, no sampling technique modification preventing the activation of platelets was applied, based on data indicating lack of any associations between platelet activation and plasma Aβ levels measured with a similar method (Olsson et al. 2003). As an increasing number of reports fail to observe a correlation between statins treatment and plasma Aβ levels, we did not introduce any additional procedures in cases of hypercholesterolemia treated with statins (Hoglund et al. 2004). Plasma was stored at -4°C for a maximum of 8 hours and then frozen in 1 ml aliquots and

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stored at -70°C until measurements. The concentrations of Aβ peptides (Aβ40 and Aβ42) in plasma were measured using commercially available sandwich ELISA colorimetric assay (BioSource Intl, Inc) which has been shown to be sensitive enough (range 15,6-1000 pg/ml) to ensure an accurate result in plasma.

Results Mean plasma concentrations of Aβ peptides (values in pg/ml ± standard deviation) in AD, MCI and control subjects are presented in Table 2; Aβ40 / Aβ42 quotient – by some authors considered more sensitive than Aβ42 levels alone – was calculated as well. The statistical analysis of between-group differences was performed using a nonparametric U Mann-Whitney test; the differences between groups in age, years of formal education and MMSE test scores (see table 1) were adjusted for. No difference in any of the evaluated parameters (Aβ40, Aβ42, Aβ40 / Aβ42) was observed between the AD and control groups. In subjects with MCI plasma Aβ42 levels were significantly elevated versus both AD (p<0,001) and controls (p<0,001), whereas Aβ40 concentrations were not significantly altered. This pattern of changes resulted in a significantly lower Aβ40 / Aβ42 ratio in the MCI group compared to both AD (p<0,001) and control groups (p<0,001) (Fig.1). Contrary to some previous reports, a linear regression method analysis (ANOVA) did not reveal any correlation between age of the participants and plasma Aβ levels; the observed differences were also unrelated to subjects’ gender.

Table 2: Mean values of plasma levels of Aβ peptides (pg/ml ± standard deviation) and Aβ1-40/Aβ1-42 ratio in the study groups Study group

AD MCI Controls * †

N

Aβ1-40 *

Aβ1-42 †

Aβ1-40/Aβ1-42 †

54 39 35

168,7 ± 32,2 160,1 ± 20,2 160,1 ± 15,2

37,8 ± 10,3 56,8 ± 9,3 36,3 ± 6,3

4,6 ± 0,9 2,9 ± 0,6 4,5 ± 0,6

differences not significant (U Mann-Whitney test) differences significant between MCI and both AD and controls at p<0.001(U Mann-Whitney test)

Both visual inspection of the boxplots (Figure 1) and the comparison of means using independent samples nonparametric tests revealed that Aβ40 / Aβ42 ratio and Aβ42 levels alone could almost perfectly separate MCI subjects from both AD and controls. As a next step, we have performed area under the curve ROC analyses to estimate the cut-off values of Aβ42 and Aβ40 / Aβ42 ratio that yield a highest accuracy in discriminating the samples. The value of Aβ40 / Aβ42 ratio lower than 3,8 discriminated MCI from AD with a sensitivity of 97,4% (95%CI=86,5-99,6) and specificity of 83,3% (70,7-92,1), and MCI from controls with a sensitivity of 97,4% (86,5-99,6) and specificity of 88,6% (73,2-96,7). The level of Aβ42 higher than 45 pg/ml discriminated MCI from AD with a sensitivity of 94,9% (82,6-99,2) and specificity of 75,9% (62,4-86,5), while MCI from controls with a sensitivity of 94,4% (82,699,2) and specificity of 91,4% (76,9-98,1).

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Figure 1. Comparison of Aβ40/Aβ42 ratios between AD, MCI (pure amnestic type) and control groups. Although an overlaps do exist, in amnestic MCI sample the ratio is significantly lower than both in AD and control groups.

Discussion The comparison of concentrations of Aβ peptides in plasma of AD subjects versus carefully selected control group presented in our study indicates the lack of applicability of this assessment in the differential diagnosis of sporadic AD. The absence of statistically significant differences is in concordance with some of the previous papers (Tamaoka et al. 1996; Vanderstichele et al. 2000; Fukumoto et al. 2003). We did not observe a formerly reported correlation between plasma Aβ levels and age of the study participants (Fukumoto et al. 2003) or any other demographic variable, like MMSE score, gender or years of formal education (Assini et al. 2004). We found an increase in Aβ42 concentrations in plasma of MCI subjects compared to either AD patients or controls; therefore, alterations in plasma Aβ42 might represent a potentially sensitive biochemical marker in that group of patients (Mayeux et al. 1999; Graff-Radford et al. 2002; Assini et al. 2004). In an attempt to explain the obtained results, a hypothesis can be formulated that the elevation of plasma Aβ42 in MCI is a reflection of efforts to eliminate the pathological peptide from the CNS through the yet viable BBB. In the later stages of disease, when the BBB is impaired, elimination of Aβ42 from the brain would become ineffective which might lead to its accumulation, toxicity towards neurons, and progressive cell death. The efficiency of Aβ peptides’ elimination in earlier stages of AD has indirectly been proven on animal models (Das et al. 2001); this mechanism can be responsible for the efficacy of both active

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and passive immunization in diminishing the number of amyloid deposits in the brains of experimental animals (DeMattos et al. 2001; DeMattos et al. 2002). Moreover, there is a substantial evidence for a progressive damage of the BBB in the course of neurodegeneration in AD (Claudio 1996; Kalaria 1999). Some authors point out the possibility of functional changes in the BBB associated with passage of Aβ peptides and their putative indirect influence on its permeability (Pluta et al. 1996; Strazielle et al. 2000; Shibata et al. 2000). It is therefore probable that in a very early stage of AD alterations in the catabolism of βAPP occur, resulting in a preferential synthesis of longer, more amyloidogenic isoform of Aβ peptide – Aβ42; Aβ42 is initially effectively removed via the BBB (by means of mechanisms associated with the LRP-1 receptor and proteins influencing lipid metabolism, such as α2macroglobulin and apolipoprotein E) which brings about a gradual increase in plasma Aβ42, but not Aβ40, still competently transported backwards (Shibata et al. 2000; Strazielle et al. 2000). The results of our study, indicating an elevation of Aβ42, but not Aβ40 in MCI subjects, would support this hypothesis. In later stages of AD, owing to a progressive destruction of the BBB and changes in a brain/plasma amyloid balance, both failure in the removal of Aβ42 from the brain (and its increased deposition in amyloid plaques) and retrograde transport of Aβ peptides from plasma to the brain (mainly responsible for vascular amyloidosis) would occur (Bading et al. 2002; Mackic et al 2002). With this theoretical sequence of events the lack of changes in plasma concentrations of Aβ peptides can be explained.

Conclusion The plasma level of Aβ42 or Aβ40 / Aβ42 quotient allow – with around 95 % sensitivity and at least 75 % specificity – the discrimination of MCI subjects from healthy controls and AD patients; unfortunately, that does not necessarily impose that a subgroup with “progressive” MCI (evolving towards AD) can be singled out with these parameters. For this purpose, a long term follow-up is inevitable; we have initiated it on the described study group. It is also possible that the elevation of plasma Aβ42 will constitute a personal indicator of the risk of conversion into AD rather than a classical biomarker of the trait. Studies in plasma and serum biomarkers in either AD or MCI have not yielded a consistent, reproducible, sensitive and specific marker for diagnosis, progression or treatment effects [Flirski & Sobow, 2005]. However, measures of β-APP metabolism appear to be altered and further research is needed to validate their possible use in clinical practice.

References Amieva, H; Letenneur, L; Dartigues, JF; Rouch-Leroyer, I; Sourgen, C; D'Alchee-Biree, F; Dib, M; Barberger-Gateau, P; Orgogozo, JM; Fabrigoule C. (2004) Annual rate and predictors of conversion to dementia in subjects presenting mild cognitive impairment criteria defined according to a population-based study. Dement Geriatr Cogn Disord, 18, 87-93.

Amyloid Beta (Aβ) Peptides in Plasmaas Biochemical Markers …

245

Andreasen, N; Minthon, L; Clarberg, A; Davidsson, P; Gottfries, J; Vanmechelen, E; Vanderstichele, H; Winblad, B; Blennow, K. (1999) Sensitivity, specificity, and stability of CSF-tau in AD in a community-based patient sample. Neurology, 57, 1488-1494. Andreasen, N; Minthon, L; Vanmechelen, E; Vanderstichele, H; Davidsson, P; Winblad, B; Blennow, K. (1999a) Cerebrospinal fluid tau and Abeta42 as predictors of development of Alzheimer’s disease in patients with mild cognitive impairment. Neurosci Lett, 273, 58. Andreasen, N; Minthon, L; Davidsson, P; Vanmechelen, E; Vanderstichele, H; Winblad, B; Blennow, K. (2001) Evaluation of CSF-tau and CSF-Aβ42 as diagnostic markers for Alzheimer disease in clinical practice. Arch Neurol, 58, 373-379. Andreasen, N; Vanmechelen, E; Vanderstichele, H; Davidsson, P; Blennow, K. (2003) Cerebrospinal fluid levels of total-tau, phospho-tau and Abeta42 predicts development of Alzheimer's disease in patients with mild cognitive impairment. Acta Neurol Scand, 107, 47-51. Assini, A; Cammarata, S; Vitali, A; Colucci, M; Giliberto, L; Borghi, R; Inglese, ML; Volpe, S; Ratto, S; Dagna-Bricarelli, F; Baldo, C; Argusti, A; Odetti, P; Piccini, A; Tabaton, M. (2004) Plasma levels of amyloid beta-protein 42 are increased in women with mild cognitive impairment. Neurology, 63, 828-31. Bading, JR; Yamada, S; Mackic, JB; Kirkman, L; Miller, C; Calero, M; Ghiso, J; Frangione, B; Zlokovic, BV. (2002) Brain clearance of Alzheimer's amyloid-beta40 in the squirrel monkey, a SPECT study in a primate model of cerebral amyloid angiopathy. J Drug Target, 10; 359-368. Basun, H; Nilsberth, C; Eckman, C; Lannfelt, L; Younkin, S. (2002) Plasma levels of Aβ42 and Aβ40 in Alzheimer patients during treatment with the acetylcholinesterase inhibitor tacrine. Dement Geriatr Cogn Disord, 14, 156-160. Butterfield DA (2002) Amyloid β-peptide(1-42) – induced oxidative stress and neurotoxicity, implications for neurodegeneration in Alzheimer’s disease brain. A review. Free Radic Res, 36, 1307-1313. Claudio L (1996) Ultrastructural features of the blood-brain barrier in biopsy tissue from Alzheimer's disease patients. Acta Neuropathol (Berl), 91, 6-14. Das, P; Murphy, MP; Younkin, LH; Younkin, SG; Golde TE. (2001) Reduced effectiveness of Abeta1-42 immunization in APP transgenic mice with significant amyloid deposition. Neurobiol Aging, 22, 721-727. Davis, HS; Rockwood, K. (2004) Conceptualization of mild cognitive impairment, a review. Int J Geriatr Psychiatry, 19, 313-9. DeMattos, RB; Bales, KR; Cummins, DJ; Dodart, JC; Paul, SM; Holtzman, DM (2001) Peripheral anti-A beta antibody alters CNS and plasma A beta clearance and decreases brain A beta burden in a mouse model of Alzheimer's disease. Proc Natl Acad Sci USA, 98, 8850-8855. DeMattos, RB; Bales, KR; Cummins, DJ; Paul, SM; Holtzman DM (2002) Brain to plasma amyloid-beta efflux, a measure of brain amyloid burden in a mouse model of Alzheimer's disease. Science, 295, 2264-2267. Dewachter, I; Van Leuven, F. (2002) Secretases as targets for the treatment of Alzheimer's disease; the prospects. Lancet Neurol, 1; 409-16.

246

Tomasz Sobow, Marcin Flirski, Pawel P. Liberski and Iwona Kloszewska

Ertekin-Taner, N; Graff-Radford, N; Younkin, LH; Eckman, C; Adamson, J; Schaid, DJ; Blangero, J; Hutton, M; Younkin, SG. (2001) Heritability of plasma amyloid beta in typical late-onset Alzheimer’s disease pedigrees. Genet Epidemiol, 21, 19-30. Evans, DA; Funkenstein, HH; Albert, MS; Scherr, PA; Cook, NR; Chown, MJ; Hebert, LE; Hennekens, CH; Taylor, JO. (1989) Prevalence of Alzheimer’s disease in a community population of older persons. JAMA, 262, 2551-2556. Flirski, M; Sobow, T. (2005) Biochemical Markers and Risk Factors of Alzheimer’s Disease. Curr Alz Res, 2, 47-64. Fukumoto, H; Tennis, M; Locascio, JJ; Hyman, BT; Growdon, JH; Irizarry, MC. (2003) Age but not diagnosis is the main predictor of plasma amyloid β-protein levels. Arch Neurol, 60, 958-964. Gomez-Tortosa, E; Gonzalo, I; Fanjul, S; Sainz, MJ; Cantarero, S; Cemillan, C; Yebenes, JG; del Ser, T. (2003) Cerebrospinal fluid markers in dementia with Lewy bodies compared with Alzheimer disease. Arch Neurol, 60, 1218-1222. Graff-Radford, N; Ertekin-Taner, N; Jadeja, N; Younkin, L; Younkin, S. (2002) Evidence that plasma amyloid beta protein may be useful as a premorbid biomarker for Alzheimer’s disease. Neurobiol Aging, 23, S384. Haass, C; Schlossmacher, MG; Hung, AY; Vigo-Pelfrey, C; Mellon, A; Ostaszewski, BL; Lieberburg, I; Koo, EH; Schenk, D; Teplow, DB. (1992) Amyloid beta-peptide is produced by cultured cells during normal cellular metabolism. Nature, 359, 322-325. Hesse, C; Rosengren, L; Vanmechelen, E; Vanderstichele, H; Jensen, C; Davidsson, P; Blennow, K. (2000) Cerebrospinal fluid markers for Alzheimer’s disease evaluated after acute ischaemic stroke. J Alzheimer Dis, 2, 199-206. Hock, C; Golombowski, S; Muller-Spahn, F; Naser, W; Beyreuther, K; Monning, U; Schenk, D; Vigo-Pelfrey, C; Bush, AM; Moir, R; Tanzi, RE; Growdon, JH; Nitsch, RM. (1998) Cerebrospinal fluid levels of amyloid precursor protein and amyloid beta-peptide in Alzheimer’s disease and major depression – inverse correlation with dementia severity. Eur Neurol, 39, 111-118. Hoglund, K; Wiklund, O; Vanderstichele, H; Eikenberg, O; Vanmechelen, E; Blennow, K. (2004) Plasma levels of beta-amyloid(1-40); beta-amyloid(1-42); and total beta-amyloid remain unaffected in adult patients with hypercholesterolemia after treatment with statins. Arch Neurol, 61, 333-337. Huang, X; Atwood, CS; Hartshorn, MA; Multhaup, G; Goldstein, LE; Scarpa, RC; Cuajungco, MP; Gray, DN; Lim, J; Moir, RD; Tanzi, RE; Bush, AI. (1999) The Aβ peptide of Alzheimer’s disease directly produces hydrogen peroxide through metal ion reduction. Biochemistry, 38, 7609-7616. Hulstaert, F; Blennow, K; Ivanoiu, A; Schoonderwaldt, HC; Riemenschneider, M; De Deyn, PP; Bancher, C; Cras, P; Wiltfang, J; Mehta, PD; Iqbal, K; Pottel, H; Vanmechelen, E; Vanderstichele, H. (1999) Improved discrimination of AD patients using β-amyloid (142) and tau levels in CSF. Neurology, 52, 1555-1562. Ida, N; Hartmann, T; Pantel, J; Schroder, J; Zerfass, R; Forstl, H; Sandbrink, R; Masters, CL; Beyreuther, K. (1996) Analysis of heterogenous A4 peptides in human cerebrospinal fluid and blood by a newly developed sensitive Western blot assay. J Biol Chem, 271, 22908-22914.

Amyloid Beta (Aβ) Peptides in Plasmaas Biochemical Markers …

247

Iwatsubo, T; Odaka, A; Suzuki, N; Mizusawa, H; Nukina, N; Ihara, Y. (1994) Visualization of A beta 42(43) and A beta 40 in senile plaques with end-specific A beta monoclonals, evidence that an initially deposited species is A beta 42(43). Neuron, 13, 45-53. Joachim, CL & Selkoe, DJ. (1992) The seminal role of beta-amyloid in the pathogenesis of Alzheimer disease. Alzheimer Dis Assoc Disord, 6, 7-34. Kalaria, RN. (1999) The blood-brain barrier and cerebrovascular pathology in Alzheimer's disease. Ann N Y Acad Sci, 893, 113-125. Kanemaru, K; Kameda, N; Yamanouchi, H. (2000) Decreased CSF amyloid beta42 and normal tau levels in dementia with Lewy bodies. Neurology, 54, 1875-1876. Kapaki, E; Kilidireas, K; Paraskevas, GP. (2001) Highly increased CSF tau protein and decreased β-amyloid (1-42) in sporadic CJD, a discrimination from Alzheimer’s disease? J Neurol Neurosurg Psychiatry, 71, 401-403. Kosaka, T; Imagawa, M; Seki, K; Arai, H; Sasaki, H; Tsuji, S; Asami-Odaka, A; Fukushima, T; Imai, K; Iwatsubo, T. (1997) The beta APP717 Alzheimer mutation increases the percentage of plasma amyloid-beta protein ending at Aβ42(43). Neurology, 48, 741-745. Kuo, YM; Emmerling, MR; Lampert, HC; Hempelman, SR; Kokjohn, TA; Woods, AS; Cotter, RJ; Roher, AE. (1999) High levels of circulating Abeta42 are sequestered by plasma proteins in Alzheimer’s disease. Biochem Biophys Res Commun, 257, 787-791. Kuo, YM; Kokjohn, TA; Watson, MD; Woods, AS; Cotter, RJ; Sue, LI; Kalback, WM; Emmerling, MR; Beach, TG; Roher, AE. (2000) Elevated abeta42 in skeletal muscle of Alzheimer disease patients suggests peripheral alterations of AbetaPP metabolism. Am J Pathol, 156, 797-805. Larrieu, S; Letenneur, L; Orgogozo, JM; Fabrigoule, C; Amieva, H; Le Carret, N; BarbergerGateau, P; Dartigues, JF. Incidence and outcome of mild cognitive impairment in a population-based prospective cohort. Neurology, 59, 1594-9. Li, QX; Whyte, S; Tanner, JE; Evin, G; Beyreuther, K; Masters, CL. (1998) Secretion of Alzheimer’s disease Abeta amyloid peptide by activated human platelets. Lab Invest, 78, 461-469. Mackic, JB; Bading, J; Ghiso, J; Walker, L; Wisniewski, T; Frangione, B; Zlokovic, BV. (2002) Circulating amyloid-beta peptide crosses the blood-brain barrier in aged monkeys and contributes to Alzheimer's disease lesions. Vascul Pharmacol, 38, 303-313. Matsubara, E; Ghiso, J; Frangione, B; Amari, M; Tomidokoro, Y; Ikeda, Y; Harigaya, Y; Okamoto, K; Shoji, M. (1999) Lipoprotein-free amyloidogenic peptides in plasma are elevated in patients with sporadic Alzheimer’s disease and Down syndrome. Ann Neurol, 45, 537-541. Mayeux, R; Tang, MX; Jacobs, DM; Manly, J; Bell, K; Merchant, C; Small, SA; Stern, Y; Wisniewski, HM; Mehta, PD. (1999) Plasma amyloid beta-peptide 1-42 and incipient Alzheimer’s disease. Ann Neurol, 46, 412-416. McKhann, G; Drachman, D; Folstein, M; Katzman, R; Price, D; Stadlan, EM. (1984) Clinical diagnosis of Alzheimer’s disease, report of the NINCDS-ADRDA Work Group under the auspices of Department of Health and Human Services Task Force on Alzheimer’s disease. Neurology, 34, 939-944.

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Mehta, PD; Pirttila, T; Mehta, SP; Sersen, EA; Aisen, PS; Wisniewski, HM. (2000) Plasma and cerebrospinal fluid levels of amyloid beta proteins 1-40 and 1-42 in Alzheimer disease. Arch Neurol, 57, 100-105. Motter, R; Vigo-Pelfrey, C; Kholodenko, D; Barbour, R; Johnson-Wood, K; Galasko, D; Chang, L; Miller, B; Clark, C; Green, R. (1995) Reduction of β -amyloid peptide 42 in the cerebrospinal fluid of patients with Alzheimer’s disease. Ann Neurol, 38, 643-648. Nagga, K; Gottfries, J; Blennow, K; Marcusson, J. (2002) Cerebrospinal fluid phospho-tau; total tau and β-amyloid1-42 in the differentiation between Alzheimer’s disease and vascular dementia. Dement Geriatr Cogn Disord, 14, 183-190. Olsson, A; Vanmechelen, E; Vanderstichele, H; Davidsson, P; Blennow, K. (2003) Unaltered plasma levels of beta-amyloid(1-40) and beta-amyloid(1-42) upon stimulation of human platelets. Dement Geriatr Cogn Disord, 16, 93-97. Otto, M; Esselmann, H; Schulz-Shaeffer, W; Neumann, M; Schroter, A; Ratzka, P; Cepek, L; Zerr, I; Steinacker, P; Windl, O; Kornhuber, J; Kretzschmar, HA; Poser, S; Wiltfang, J. (2000) Decreased beta-amyloid 1-42 in cerebrospinal fluid of patients with CreutzfeldJakob disease. Neurology, 54, 1099-1102. Petersen, RC; Doody, R; Kurz, A; Mohs, RC; Morris, JC; Rabins, PV; Ritchie, K; Rossor, M; Thal, L; Winblad, B. (2001) Current concepts in mild cognitive impairment. Arch Neurol, 58, 1985-92. Pitschke, M; Prior, R; Haupt, M; Riesner, D. (1998) Detection of single amyloid beta-protein aggregates in the cerebrospinal fluid of Alzheimer’s patients by fluorescence correlation spectroscopy. Nat Med, 4, 832-834. Pluta, R; Barcikowska, M; Januszewski, S; Misicka, A; Lipkowski, AW (1996) Evidence of blood-brain barrier permeability/leakage for circulating human Alzheimer's betaamyloid-(1-42)-peptide. Neuroreport, 7, 1261-1265. Riemenschneider, M; Lautenschlager, N; Wagenpfeil, S; Diehl, J; Drzezga, A; Kurz, A. (2002) Cerebrospinal fluid tau and β-amyloid 42 proteins identify Alzheimer disease in subjects with mild cognitive impairment. Arch Neurol, 59, 1729-1734. Riemenschneider, M; Wagenpfeil, S; Diehl, J; Lautenschlager, N; Theml, T; Heldmann, B; Drzezga, A; Jahn, T; Forstl, H; Kurz, A. (2002a) Tau and Aβ42 protein in CSF of patients with frontotemporal degeneration. Neurology, 58, 1622-1628. Scheuner, D; Eckman, C; Jensen, M; Song, X; Citron, M; Suzuki, N; Bird, TD; Hardy, J; Hutton, M; Kukull, W; Larson, E; Levy-Lahad, E; Viitanen, M; Peskind, E; Poorkaj, P; Schellenberg, G; Tanzi, R; Wasco, W; Lannfelt, L; Selkoe, D; Younkin, S. (1996) Secreted amyloid beta-protein similar to that in the senile plaques of Alzheimer’s disease is increased in vivo by the presenilin 1 and 2 and APP mutations linked to familial Alzheimer’s disease. Nat Med, 2, 864-870. Schupf, N; Patel, B; Silverman, W; Zigman, WB; Zhong, N; Tycko, B; Mehta, PD; Mayeux, R. (2001) Elevated plasma amyloid β-peptide 1-42 and onset of dementia in adults with Down syndrome. Neurosci Lett, 301, 199-203. Selkoe, DJ. (1994) Normal and abnormal biology of the beta-amyloid precursor protein. Annu Rev Neurosci, 17, 489-517.

Amyloid Beta (Aβ) Peptides in Plasmaas Biochemical Markers …

249

Seubert, P; Oltersdorf, T; Lee, MG; Barbour, R; Blomquist, C; Davis, DL; Bryant, K; Fritz, LC; Galasko, D; Thal, LJ. (1993) Secretion of beta-amyloid precursor protein cleaved at the amino terminus of the beta-amyloid peptide. Nature, 361, 260-3. Seubert, P; Vigo-Pelfrey, C; Esch, F; Lee, M; Dovey, H; Davis, D; Sinha, S; Schlossmacher, M; Whaley, J; Swindlehurst, C. (2002) Isolation and quantification of soluble Alzheimer’s beta-peptide from biological fluids. Nature, 359, 325-327. Shibata, M; Yamada, S; Kumar, SR; Calero, M; Bading, J; Frangione, B; Holtzman, DM; Miller, CA; Strickland, DK; Ghiso, J; Zlokovic, BV. (2000) Clearance of Alzheimer's amyloid-ss(1-40) peptide from brain by LDL receptor-related protein-1 at the blood-brain barrier. J Clin Invest, 106, 1489-1499. Sjogren, M; Minthon, L; Davidsson, P; Granerus, A-K; Clarberg, A; Vanderstichele, H; Vanmechelen, E; Wallin, A; Blennow, K. (2000) CSF levels of tau; beta-amyloid(1-42) and GAP-43 in frontotemporal dementia; other types of dementia and normal aging. J Neural Transm, 107, 563-579. Skoog, I; Davidsson, P; Aevarsson, O; Vanderstichele, H; Vanmechelen, E; Blennow, K. (2003) Cerebrospinal fluid beta-amyloid 42 is reduced before the onset of clinical dementia. Dement Geriatr Cogn Disord, 15, 169-176. Sobow, T; Flirski, M; Liberski, PP. (2004) Amyloid-beta and tau proteins as biochemical markers of Alzheimer's disease. Acta Neurobiol Exp (Wars), 64, 53-70. Sobow, T & Kloszewska, I. (2003) Plasma amyloid beta peptides levels in sporadic Alzheimer’s disease and amnestic mild cognitive impairment. Int Psychogeriatr, 15, 357. Strazielle, N; Ghersi-Egea, JF; Ghiso, J; Dehouck, MP; Frangione, B; Patlak, C; Fenstermacher, J; Gorevic, P (2000) In vitro evidence that beta-amyloid peptide 1-40 diffuses across the blood-brain barrier and affects its permeability. J Neuropathol Exp Neurol, 59, 29-38. Tamaoka, A; Fukushima, T; Sawamura, N; Ishikawa, K; Oguni, E; Komatsuzaki, Y; Shoji, S. (1996) Amyloid beta protein in plasma from patients with sporadic Alzheimer’s disease. J Neurol Sci, 141, 65-68. The Ronald and Nancy Reagan Research Institute of the Alzheimer’s Association and the National Institute on Aging Working Group (1998) Consensus Report of the Working Group on Molecular and Biochemical Markers for Alzheimer’s disease. Neurobiol Aging, 19, 109-116. Tokuda, T; Tamaoka, A; Matsuno, S; Sakurai, S; Shimada, H; Morita, H; Ikeda, S. (2001) Plasma levels of amyloid beta proteins did not differ between subjects taking statins and those not taking statins. Ann Neurol, 49, 546-547. Vanderstichele, H; Van Kerschaver, E; Hesse, C; Davidsson, P; Buyse, MA; Andreasen, N; Minthon, L; Wallin, A; Blennow, K; Vanmechelen, E. (2000), Standardization of measurement of beta-amyloid(1-42) in cerebrospinal fluid and plasma. Amyloid, 7, 245258. Vassar, R; Bennett, BD; Babu-Khan, S; Kahn, S; Mendiaz, EA; Denis, P; Teplow, DB; Ross, S; Amarante, P; Loeloff, R; Luo, Y; Fisher, S; Fuller, J; Edenson, S; Lile, J; Jarosinski, MA; Biere, AL; Curran, E; Burgess, T; Louis, JC; Collins, F; Treanor, J; Rogers, G; Citron, M. (1999) Beta-secretase cleavage of Alzheimer's amyloid precursor protein by the transmembrane aspartic protease BACE. Science, 286, 735-41.

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Walsh, DM; Klyubin, I; Fadeeva, JV; Rowan, MJ; Selkoe, DJ. (2002) Amyloid β-oligomers, their production; toxicity and therapeutic inhibition. Biochem Soc Trans, 30, 552-557. Weldon, DT; Rogers, SD; Ghilardi, JR; Finke, MP; Cleary, JP; O'Hare, E; Esler, WP; Maggio, JE; Mantyh, PW. (1998) Fibrillar beta-amyloid induces microglial phagocytosis; expression of inducible nitric oxide synthase; and loss of a select population of neurons in the rat CNS in vivo. J Neurosci, 18, 2161-73.

Index A abnormal, 43, 61, 88, 140, 172, 179, 196, 197, 200, 204, 205, 209, 215, 248 accuracy, vii, 236, 242 acetaminophen, 132 acetylcholine, viii, 2, 33, 34, 49, 57, 59, 60, 68, 78, 82, 139 acetylcholinesterase, 2, 30, 33, 42, 51, 211, 240, 245 acetylcholinesterase inhibitor, 240, 245 acid, ix, 2, 3, 14, 30, 31, 34, 39, 43, 46, 47, 48, 49, 51, 55, 58, 59, 60, 61, 65, 77, 78, 79, 80, 81, 82, 83, 84, 85, 90, 99, 100, 127, 129, 130, 131, 134, 136, 137, 139, 141, 144, 145, 146, 149, 154, 155, 161, 162, 167, 168, 170, 171, 173, 178, 185, 225, 237, 238 acquisition phase, 69 acquisition., 76 activation, x, 35, 43, 45, 47, 50, 51, 59, 60, 66, 67, 68, 78, 79, 81, 83, 85, 88, 89, 108, 126, 128, 130, 132, 133, 135, 136, 139, 140, 141, 142, 143, 149, 153, 154, 155, 156, 157, 158, 165, 166, 170, 171, 173, 174, 175, 178, 179, 195, 199, 218, 240, 241 addiction, 241 adenine, 127, 144 adipocyte, 131 adiponectin, 136 adipose, 130, 131, 132, 135 adipose tissue, 130, 131, 132, 135 adult(s), 96, 97, 234, 248 adulthood, 228 age, vii, viii, ix, xi, xii, 4, 45, 46, 49, 57, 61, 62, 65, 69, 88, 90, 91, 92, 105, 106, 107, 109, 110, 112, 113, 128, 134, 136, 138, 139, 143, 145, 166, 171,

175, 178, 186, 187, 189, 190, 191, 195, 211, 215, 230, 235, 239, 241, 242, 243 age-related, ix, 46, 69, 88, 92, 105, 136, 138, 139, 143, 186, 189 aggressive behavior, 117, 219 aging, ix, xii, 44, 50, 88, 128, 130, 143, 144, 152, 160, 166, 169, 175, 176, 179, 180, 184, 186, 189, 191, 193, 195, 217, 225, 226, 237 agonist, 39, 130, 136, 137, 138, 139, 141, 142, 147, 154, 155, 156, 157, 159, 162 airways, 156 alcohol, 241 alcoholism, 192 allele, 90, 101, 103, 111, 112, 113, 116, 117, 122, 137, 138, 154 alpha-2-macroglobulin (alpha2-mg), 121 alters, 34, 43, 158, 166, 195, 245 amino acid(s), ix, 3, 30, 31, 34, 90, 99, 100, 129, 134, 237, 238 amnesia, 43, 69, 81, 160, 191 amygdala, 2, 43, 51, 81, 92, 145, 146, 173 amyloidosis, 52, 90, 135, 146, 153, 159, 160, 211, 216, 244 amyotrophic lateral sclerosis, 171 angiogenesis, xi, 55, 102, 184, 189, 208 anisotropy, 74, 75, 76, 77 ANOVA, 242 anoxia, 185 anterior, 2, 69 antibodies (Ab), 2, 3, 32, 35, 42, 43, 44, 45, 46, 48, 49, 50, 53, 55, 60, 64, 116, 172, 201, 212, 221, 245 antidepressant, 53 anti-inflammatory, ix, 40, 93, 125, 126, 127, 128, 131, 137, 138, 140, 141, 142, 146, 147, 150, 154, 156, 157, 158, 162, 240

Index

252

anti-inflammatory agents, 40, 157 anti-inflammatory drugs, ix, 125, 127, 128, 140, 150, 156, 157, 158, 240 antioxidant, x, 47, 90, 125, 126, 128, 141, 143, 144, 145, 146, 147, 161, 162, 163, 180, 209 anxiety, 40, 191 apical, 82, 120 apoptosis, viii, x, 3, 7, 8, 33, 87, 88, 89, 90, 91, 93, 94, 129, 131, 133, 135, 136, 147, 150, 153, 154, 160, 165, 166, 171, 172, 174, 175, 178, 179, 181, 201, 203, 208, 216, 224, 232 arrhythmias, 193 arterioles, 206, 207 arteriosclerosis, xi, 128, 184, 189, 190, 192 artery(ies), xi, 184, 189, 219, 220, 224, 227, 230 arthritis, 140, 156 ascorbic acid, 146 assessment, viii, 21, 22, 23, 24, 25, 38, 57, 243 association, 36, 53, 106, 111, 112, 113, 116, 117, 118, 119, 120, 121, 122, 137, 138, 168, 171, 176, 190, 192, 228, 233 asthma, 131, 140, 156 astrocytoma, 109 astrogliosis, 208 atherosclerosis, ix, 99, 109, 117, 121, 128, 130, 131, 137, 140, 154, 155, 156 atherosclerotic plaque, 130 atopic dermatitis, 131 atrial fibrillation, 192 atrophy, xi, 128, 132, 145, 146, 150, 161, 183, 187, 191, 208, 209, 213 autoimmune, 132, 140 autopsy, 62, 88, 192 autosomal dominant, 111 avoidance, viii, 21, 22, 23, 24, 25, 36, 54, 58, 68, 69, 70, 71, 73, 74, 76, 77, 78, 79, 81 axon, 203

B bacterial, 85, 172 bacterial infection, 85 barbiturates, 241 basal forebrain, 46, 51 basal ganglia, 145 behavior, 43, 188, 190, 209, 219, 232 behavioral change, 186 behavioral problems, vii, 191 beneficial effect, 39, 41, 109, 132, 136, 143, 208 benzodiazepines, 241

bilateral, 8, 9, 12, 14, 17, 18, 21, 22, 23, 26, 27, 28, 29 binding, 13, 15, 29, 47, 49, 68, 77, 78, 79, 83, 88, 89, 103, 105, 107, 114, 115, 117, 120, 122, 129, 133, 134, 138, 143, 152, 168, 169, 176, 177 biological processes, 168, 208 biology, 120, 122, 149, 175, 248 biomarkers, 159, 244 biopsy, 88, 236, 245 bladder, 131 blocking, 76, 134, 203 blood, ix, xii, 29, 46, 92, 93, 94, 100, 102, 106, 108, 109, 110, 114, 115, 116, 120, 122, 123, 133, 137, 138, 139, 141, 146, 187, 189, 190, 192, 194, 201, 205, 206, 207, 208, 210, 212, 214, 215, 216, 218, 220, 226, 227, 228, 229, 230, 234, 236, 237, 240, 241, 245, 246, 247, 248, 249 blood flow, 189, 190, 193, 217, 229 blood monocytes, 109 blood pressure, 189, 226, 227, 228 blood vessels, ix, 29, 100 blood-brain barrier (BBB), xii, 92, 102, 108, 120, 122, 133, 137, 139, 141, 146, 194, 201, 205, 206, 207, 208, 210, 212, 214, 215, 216, 220, 228, 229, 230, 234, 236, 243, 244, 245, 247, 248, 249 bloodstream, 214 body, 40, 91, 92, 108, 141, 143, 174, 185, 193, 195, 203, 211, 223, 237, 238 body fluid, 108, 237 body mass, 143 bone marrow, 93, 131 brain, vii, viii, ix, x, xi, xii, 1, 3, 4, 5, 30, 31, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 61, 62, 64, 65, 69, 71, 73, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 87, 88, 89, 90, 91, 93, 94, 100, 102, 105, 106, 108, 109, 114, 115, 118, 119, 120, 122, 123, 125, 126, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 150, 151, 152, 154, 155, 156, 159, 160, 161, 166, 168, 169, 170, 171, 172, 173, 175, 176, 177, 178, 180, 183, 184, 187, 188, 189, 190, 191, 192, 193, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 236, 238, 243, 244, 245, 247, 248, 249 brain activity, 191 brain functions, 137 brainstem, 133

Index breast cancer, 93

C calcium, ix, 3, 59, 61, 65, 78, 82, 84, 85, 100, 118, 160, 173, 176, 202, 216, 217, 227, 234 cancer, ix, 93, 99, 103, 114, 128, 131, 158, 237 capillary(ies), 108, 139, 196, 197, 214, 216, 218, 226 carcinogenesis, 131 cardiac arrest, 225, 226, 228, 229, 230, 234 cardiovascular disease, 130, 156, 192 cardiovascular risk, 148 caregivers, 241 catabolism, xii, 106, 119, 130, 131, 137, 236, 244 Caucasian population, 119 cell(s), viii, x, xi, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 28, 30, 31, 32, 33, 38, 42, 47, 48, 50, 51, 52, 55, 57, 59, 60, 65, 66, 68, 70, 78, 81, 87, 88, 89, 90, 91, 92, 93, 101, 102, 105, 107, 108, 109, 110, 114, 115, 116, 119, 120, 126, 127, 129, 130, 131, 133, 134, 135, 136, 138, 139, 140, 141, 142, 143, 144, 148, 150, 153, 154, 158, 162, 165, 166, 167, 168, 169, 170, 171, 172, 174, 175, 176, 178, 179, 180, 181, 187, 194, 195, 197, 198, 199, 200, 201, 202, 203, 204, 206, 207, 209, 214, 216, 222, 224, 226, 227, 228, 232, 234, 243, 246 cell body, 203 cell cycle, 129, 174, 234 cell death, viii, xi, 32, 47, 48, 87, 88, 89, 90, 91, 92, 93, 139, 142, 143, 158, 162, 166, 170, 171, 172, 174, 175, 179, 180, 181, 199, 200, 201, 207, 222, 226, 243 cell line(s), 3, 91, 92, 109, 150 cell membranes, 169, 170 cell signaling, 168, 169, 171 cell surface, 101, 105, 115, 116, 120, 167, 168, 169, 171, 194 central nervous system (CNS), ix, xii, 53, 54, 91, 95, 97, 100, 108, 125, 126, 127, 131, 133, 134, 135, 136, 138, 139, 140, 143, 145, 146, 147, 148, 150, 151, 157, 160, 184, 201, 236, 243, 245, 250 cerebellum, 171, 202 cerebral amyloid angiopathy, 193, 245 cerebral amyloidosis, 230 cerebral blood flow, 189, 190, 193, 217, 229 cerebral cortex, 2, 32, 33, 35, 39, 42, 45, 46, 47, 49, 50, 59, 68, 83, 90, 133, 139, 171, 195, 217, 225 cerebrospinal fluid (CSF), x, 2, 3, 30, 31, 41, 46, 51, 91, 102, 120, 123, 125, 126, 133, 134, 138, 144,

253

145, 146, 148, 150, 160, 161, 171, 173, 225, 231, 237, 238, 239, 245, 246, 247, 248, 249 cerebrovascular disease, xi, 183, 187, 189, 190, 191, 192, 221, 237 chemokines, 139 chemotherapy, 93 cholesterol, 102, 120, 137, 138, 154, 155, 168, 169, 171, 172, 176, 177, 190, 192 cholinergic, vii, ix, 1, 33, 34, 39, 40, 43, 44, 45, 46, 47, 48, 49, 50, 53, 60, 68, 87, 88, 92 cholinesterase, 136, 154 chromosome(s), ix, 99, 101, 111, 121, 128, 129, 195, 199, 202, 237 chronic, 4, 5, 43, 49, 52, 53, 132, 140, 141, 155, 176, 184, 187, 189, 191, 192, 194, 204, 205, 208, 213, 214, 215, 216, 218, 227, 233 cleavage, 7, 58, 59, 60, 88, 93, 100, 101, 119, 129, 134, 136, 144, 166, 169, 214, 237, 249 clinical presentation, 237 clinical trials, 92, 94, 146, 212 cloning, 82, 83 cluster of differentiation (CD), 84 clustering, 168 clusters, 167, 168 coagulation, 105 coding, 111, 123, 137, 195 coenzyme, 126, 130, 169, 177 cognition, x, 65, 127, 136, 139, 144, 155, 165 cognitive abilities, 188, 220 cognitive deficit, 162 cognitive dysfunction, 4, 54 cognitive function, ix, 91, 125, 128, 133, 138, 151, 160, 162, 193, 217, 225 cognitive impairment, 64, 65, 80, 127, 133, 138, 146, 159, 160, 186, 195, 225, 227, 237, 238, 244, 245, 247, 248, 249 cognitive performance, viii, 57, 62, 65, 84, 159 community, 117, 162, 217, 245, 246 complementary DNA (cDNA), 83 complex, ix, x, 39, 46, 99, 102, 103, 107, 111, 117, 121, 122, 123, 126, 127, 130, 139, 144, 145, 147, 166, 178, 203, 216, 238 composition, 60, 84, 85, 168, 169, 177 concentration, 75, 79, 91, 103, 106, 107, 109, 133, 134, 152, 161, 169, 172, 173, 186, 190, 191, 192, 205, 240 consequence(s), 41, 70, 111, 121, 132, 135, 139, 141, 152, 189, 205, 209, 213, 215 consumption, 143, 222 context, 36, 38, 103, 237

Index

254

contralateral, 4, 202 contralateral hemisphere, 4 control, x, xii, 4, 5, 30, 31, 33, 41, 43, 62, 63, 65, 66, 102, 110, 113, 126, 129, 130, 137, 140, 148, 155, 157, 165, 168, 171, 191, 208, 212, 222, 236, 242, 243 control condition, 31, 41 control group, xii, 4, 65, 113, 236, 242, 243 controlled trial, 162 core, 48, 74, 75, 76, 77, 101, 120, 195, 197, 200, 209, 214, 223 coronary artery disease, 100, 102, 103, 109, 110 corpus callosum, 32, 35, 47, 198 correlation, xii, 50, 65, 68, 102, 110, 112, 122, 145, 161, 236, 240, 241, 242, 243, 246, 248 cortex, viii, xi, 2, 3, 11, 32, 33, 34, 35, 39, 42, 45, 46, 47, 49, 50, 51, 57, 59, 61, 62, 64, 68, 81, 83, 84, 89, 90, 91, 120, 129, 133, 134, 139, 140, 142, 145, 146, 161, 171, 184, 188, 195, 196, 198, 200, 202, 206, 207, 211, 214, 217, 225 cortical neurons, 46, 47, 66, 67, 80, 82, 91, 120, 136, 142, 158, 175, 203 counseling, 123 cross-sectional study, 225 culture(s), viii, 3, 31, 45, 55, 58, 59, 60, 65, 66, 67, 80, 82, 91, 92, 135, 141, 142, 166, 170, 173, 218, 227 cultured, vii, viii, 1, 30, 46, 47, 58, 59, 60, 67, 120, 132, 135, 142, 175, 178, 179, 246 cytochrome, 8, 88, 89, 172 cytokine(s), ix, x, 2, 6, 30, 34, 38, 41, 52, 53, 100, 109, 126, 131, 132, 137, 139, 140, 141, 149, 158, 166, 170, 178, 179, 204, 217, 232 cytoplasm, 209, 228 cytoplasmic tail, 107 cytotoxic, 172, 173, 180, 194, 197, 238

D damage, vii, xii, 3, 4, 8, 10, 30, 34, 37, 45, 47, 51, 52, 55, 88, 89, 90, 91, 92, 128, 139, 142, 143, 144, 145, 146, 147, 159, 160, 162, 163, 166, 172, 173, 175, 184, 197, 199, 203, 204, 205, 211, 216, 219, 231, 232, 233, 234, 239, 244 death, ix, x, xi, 6, 11, 33, 34, 39, 40, 51, 61, 70, 74, 88, 89, 90, 91, 93, 133, 141, 144, 158, 159, 165, 169, 170, 171, 172, 173, 175, 178, 179, 180, 184, 187, 188, 189, 193, 197, 198, 200, 201, 204, 205, 207, 208, 213, 214, 216, 217, 224, 228, 236

degradation, ix, 61, 85, 88, 89, 100, 101, 102, 105, 106, 108, 114, 119, 121, 134, 135, 136, 152, 170, 172, 209, 215, 222 delusions, 228 dementia, vii, viii, ix, xi, xii, 46, 50, 58, 61, 62, 69, 79, 83, 88, 90, 92, 112, 115, 119, 123, 126, 127, 128, 134, 139, 144, 145, 146, 147, 151, 155, 160, 161, 177, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 195, 199, 203, 210, 211, 213, 219, 221, 222, 223, 224, 225, 226, 227, 228, 232, 233, 235, 236, 237, 238, 239, 240, 241, 244, 246, 247, 248, 249 demyelinating disease, 179 demyelination, 7, 177 demyelinization, 128 dendrites, 2, 203 dendritic cell (DC), 161 dephosphorylation, 203, 226 depression, 2, 37, 44, 191, 234, 239, 246 developed countries, 186, 236 developing brain, 178 developing countries, 186 diabetes, x, 128, 131, 132, 133, 134, 135, 138, 147, 148, 150, 151, 152, 153, 158, 189, 192, 228 diabetes mellitus, 132, 133, 135, 150, 151, 189, 192, 228 diabetic, 134, 152 diacylglycerol, 176 diagnosis, vii, 88, 128, 145, 148, 187, 193, 220, 236, 239, 240, 244, 246, 247 diagnostic criteria, xii, 235, 240 diagnostic markers, 245 dialysis, 15, 16 diet, 45, 137, 138, 154 dietary fat, 138 dietary intake, 146 dietary supplementation, 82 differential diagnosis, 161, 243 differentiation, x, 65, 126, 128, 131, 133, 135, 137, 149, 170, 171, 176, 248 digestion, 169 diploid, 176 disabilities, 189 discrimination, 24, 244, 246, 247 disease, iv, vii, viii, ix, x, xi, xii, 1, 2, 3, 42, 43, 44, 45, 46, 48, 49, 50, 51, 57, 59, 60, 61, 62, 63, 64, 65, 79, 80, 81, 82, 83, 84, 85, 88, 90, 91, 92, 99, 100, 101, 102, 103, 106, 109, 110, 111, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 125, 126, 127, 128, 134, 135, 137, 139, 140, 141, 143, 144,

Index 145, 147, 148, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 165, 166, 167, 169, 170, 171, 173, 174, 175, 176, 177, 178, 179, 180, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 198, 201, 202, 203, 204, 205, 206, 207, 208, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 243, 245, 246, 247, 248, 249 DNA, 2, 88, 89, 90, 91, 95, 123, 129, 143, 144, 145, 173, 195 docosahexaenoic acid, 83, 127, 130, 154, 155 dopamine, 2, 16, 34, 181 dorsal, 9, 10, 19, 68, 69, 74, 211 dosage, 40 double-blind, 219 Down syndrome, 48, 101, 120, 239, 247, 248 drug therapy, 158, 211 drugs, ix, 76, 105, 125, 126, 127, 128, 130, 131, 136, 137, 140, 141, 142, 146, 149, 150, 156, 157, 158, 163, 173, 211, 212, 237, 240 duration, 33, 81, 157, 187, 223, 240 dyslexia, 60

E edema, 204 education, xii, 190, 192, 228, 235, 241, 242, 243 efficacy, 53, 128, 146, 243 eicosapentaenoic acid, 130, 131 elderly, 64, 106, 127, 144, 147, 186, 190, 192, 223, 225, 239, 241 elderly population, 127, 186, 190 embryo, 118, 131 emotion, 127 emotional disorders, 191 encephalomyelitis, 140 encoding, 82, 111, 134, 137, 143, 154 endocrine, 150 endogenous, 47, 105, 119, 136, 142, 143, 149, 177, 184 endothelial cells, ix, 100, 204 endothelium, 108, 147, 209 energy, 61, 78, 83, 128, 129, 143, 159 English, 5, 78 entorhinal cortex, 81, 134, 198 environment, 88 environmental conditions, 202 environmental factors, 111 enzymatic activity, 174, 175

255

enzyme(s), viii, 2, 5, 14, 37, 38, 42, 46, 54, 57, 58, 59, 60, 64, 65, 68, 71, 78, 82, 84, 90, 100, 105, 106, 107, 115, 117, 121, 130, 135, 142, 143, 145, 147, 152, 153, 155, 161, 166, 169, 170, 173, 174, 205, 211, 223 enzyme-linked immunosorbent assay (ELISA), 2, 11, 32, 107, 242 epidemic, 187 epilepsy, 60, 84 episodic, viii, 58, 68, 187 episodic memory, 187 epithelial cells, 93, 102 essential fatty acids, 131 estrogen, 196, 211, 227, 233, 240 ethnicity, 111 etiology, xi, 132, 140, 183, 186, 192, 193, 213, 215, 232 evaluation, 111, 160, 175 evolution, xi, 166, 209 excitotoxicity, 3, 45, 194, 216 exogenous, 34, 53, 59, 143, 146, 172, 179, 184 exon, 111, 112, 113, 115, 118, 121 experimental autoimmune encephalomyelitis (EAE), 157 experimental condition, 66, 212 experimental design, 31, 40, 76 expression, ix, x, 5, 28, 29, 34, 35, 38, 39, 42, 43, 50, 51, 53, 54, 77, 79, 80, 81, 82, 83, 84, 87, 92, 94, 100, 101, 102, 105, 107, 108, 109, 110, 111, 114, 115, 117, 118, 119, 126, 128, 129, 130, 131, 132, 133, 134, 135, 136, 138, 140, 141, 142, 147, 148, 149, 150, 152, 154, 158, 169, 170, 173, 174, 176, 179, 180, 195, 196, 197, 200, 202, 203, 209, 215, 217, 218, 219, 220, 223, 224, 225, 226, 228, 230, 231, 232, 233, 234, 250 extracellular, ix, 3, 4, 34, 58, 88, 92, 93, 100, 102, 105, 106, 107, 108, 121, 129, 134, 144, 152, 173, 199, 200, 201, 206, 208, 229, 238 extracellular matrix (ECM), 92, 93, 208

F factors, ix, x, xi, 6, 39, 88, 92, 94, 99, 100, 103, 105, 106, 108, 109, 126, 129, 131, 136, 137, 138, 143, 144, 148, 149, 154, 167, 170, 173, 184, 189, 192, 193, 198, 204, 205, 209, 219, 227, 231, 233 failure, ix, 51, 100, 108, 244 familial hypercholesterolemia, 102 family, x, 58, 59, 74, 102, 103, 104, 116, 117, 118, 122, 126, 128, 136, 145, 166, 167, 225, 241

Index

256

family history, 241 family members, 103, 117 fasting, x, 125, 241 fat, 135, 136, 146, 190, 192 fatigue, 191 fatty acid(s), 43, 58, 59, 60, 61, 69, 81, 82, 127, 130, 131, 137, 138, 149, 154, 155, 168, 170, 171, 172, 173 fear, 25, 81, 136, 153 female(s), xii, 203, 211, 215, 227, 234, 235 ferritin, 42 fertility, 131 fibrate, 130, 131, 137 fibrillation, 190, 225, 228 fibrinogen, 190, 192 fibrinolysis, 102, 219 fibroblasts, 93, 138, 176 fibrogenesis, 167 filament, 3, 134, 180, 212, 219 fish, 138 flexibility, 40 fluorescence, 74, 248 folic acid, 185 follow-up, 236, 244 food intake, 133, 150 forebrain, 46, 51, 52, 83, 123, 223, 231, 234 frequency, 2, 37 frontal cortex, viii, 2, 11, 57, 62, 89, 90, 196 functional, 34, 74, 101, 102, 105, 111, 117, 121, 122, 133, 134, 138, 147, 150, 160, 187, 215, 237, 244 functional changes, 34, 244

G gastric, 146, 162 gastric mucosa, 146 gender, xii, 107, 109, 110, 116, 151, 193, 235, 242, 243 gene(s), x, 4, 77, 82, 83, 90, 101, 102, 106, 109, 110, 111, 114, 115, 116, 117, 118, 119, 120, 121, 123, 125, 126, 128, 129, 131, 132, 134, 135, 136, 137, 138, 140, 141, 143, 147, 149, 150, 151, 154, 155, 169, 180, 193, 195, 199, 202, 205, 216, 232, 237 gene amplification, 115 gene expression, 77, 83, 109, 110, 117, 118, 131, 132, 136, 141, 149, 150, 154, 202 general knowledge, 216 general practitioner, 188, 211

generation, 3, 27, 38, 88, 105, 107, 111, 141, 142, 143, 144, 146, 149, 162, 169, 170, 172, 174, 176, 177, 179, 216, 237 genes, x, 4, 102, 111, 114, 117, 123, 126, 128, 129, 131, 134, 135, 136, 137, 140, 141, 143, 154, 169, 195, 200, 202, 205, 216 genetic factors, 202, 240 genetic information, 195 genetic testing, 117 genetics, 116, 122 genome, 101, 102, 111, 119 genotype, 90, 111, 112, 113, 116, 118, 151, 233, 240 glands, 151 glatiramer acetate (GA), 161 glia, 17, 91, 133, 141 glial cells, 38, 139, 143, 170, 199, 200, 202, 204 glioma, 81, 170 glucagon, 105 glucocorticoids, 53 glucose, ix, 79, 125, 126, 128, 131, 133, 134, 135, 136, 143, 147, 149, 151, 152, 160, 173, 227 glucose tolerance, x, 125, 134 glucose tolerance test, x, 125 glutamate, 14, 34, 45, 68, 77, 78, 79, 83, 136, 141, 147, 153, 159, 202, 234 glutathione, 2, 27, 38, 127, 143, 172, 173, 180, 217 glycogen, x, 126, 127, 132, 135, 150, 153, 154 glycolysis, 42 glycoprotein, 51, 115 gray matter, 62, 189 growth, viii, ix, 3, 6, 38, 39, 42, 44, 59, 87, 91, 92, 93, 94, 100, 103, 106, 107, 118, 119, 122, 133, 138, 150, 152, 170, 171, 178, 179, 188, 194, 195, 209 growth factor(s), ix, 3, 6, 39, 42, 91, 92, 93, 94, 100, 103, 106, 107, 118, 119, 150, 152, 170, 178, 194

H hallucinations, 228 head injury, 193, 228 headache, 191 healing, 201, 204, 214, 215, 216 heart valves, 220 heat shock protein, 116 heme oxygenase, 145 heparin, 92, 93 hepatic, 133, 137 hepatoma, 93 heterogeneity, 218, 221

Index heterogenous, 237, 246 hippocampus, viii, 2, 30, 32, 33, 35, 36, 37, 38, 39, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 58, 68, 69, 74, 76, 77, 78, 79, 81, 84, 85, 90, 92, 132, 134, 139, 141, 142, 145, 146, 170, 171, 173, 177, 194, 196, 197, 198, 200, 201, 202, 204, 206, 207, 208, 211, 213, 214, 218, 219, 222, 223, 224, 227, 228, 231, 232, 234 HIV infection, 185 HIV-1, 176 HIV-1 proteins, 176 homeostasis, viii, x, 58, 59, 94, 102, 105, 128, 129, 131, 133, 149, 165, 166, 167, 173, 180, 216, 227 homologous, 44, 121 homozygote, 138 homozygous, 90, 102 hormone(s), 6, 103, 128, 129, 136, 137, 148, 170, 211 human brain, 83, 129, 140, 224, 234 human genome, 102 human immunodeficiency virus (HIV), 176, 185 human leukocyte antigen (HLA), 100, 109 hybrid cell, 91 hydrocephalus, 185, 231 hydrogen peroxide, 38, 144, 181, 246 hydrolysis, xi, 105, 165, 174, 178, 226 hypercholesterolemia, 154, 241, 246 hyperglycemia, 132, 215 hyperinsulinemia, x, 125, 132, 133, 135 hyperlipidemia, 137 hyperplasia, 208 hypertension, 128, 131, 189, 192 hyperthermia, 202, 215 hypertriglyceridemia, 130 hypertrophy, 208 hypoglycemia, 143 hypotension, 193, 228 hypothalamus, 133 hypothesis, xi, xii, 50, 60, 62, 81, 84, 122, 139, 173, 180, 183, 194, 199, 220, 223, 231, 236, 238, 243, 244 hypoxia, 185, 227

I ibuprofen, 50, 132, 136, 141, 142, 149, 158, 159 identification, 43, 115, 138 IL-6, x, 28, 38, 126, 130, 131, 132, 138, 140, 141, 142, 231 IL-8, 140

257

immune response, 105, 208 immunization, 212, 227, 244, 245 immunoglobulin (Ig), 212 immunohistochemistry, 32, 35, 37 immunoreactivity, ix, 43, 87, 91, 92, 140, 196, 197, 200, 202, 204, 220, 223, 224, 227, 229, 230, 234 immunostaining, 222 immunotherapy, 212, 227 in vitro, vii, viii, 1, 3, 37, 38, 44, 45, 50, 52, 58, 59, 67, 93, 128, 133, 136, 140, 141, 149, 153, 162, 212, 226, 234 in vivo, vii, viii, 1, 4, 5, 12, 14, 26, 30, 31, 37, 38, 40, 42, 44, 45, 47, 48, 50, 51, 52, 53, 54, 55, 57, 69, 73, 81, 92, 93, 109, 110, 117, 128, 130, 133, 140, 145, 153, 158, 161, 162, 167, 227, 248, 250 incubation time, 71 infant, 15, 29, 34, 38 infarction, 190, 225, 232 infection, 146 infertility, 128 inflammation, ix, 45, 60, 85, 88, 89, 91, 115, 125, 128, 129, 130, 132, 139, 140, 141, 149, 153, 156, 157, 158, 159, 162, 200, 219, 225 inflammatory, ix, 4, 34, 41, 43, 52, 53, 54, 60, 100, 108, 109, 125, 126, 128, 130, 131, 132, 135, 137, 138, 139, 140, 141, 142, 143, 144, 146, 149, 153, 156, 157, 158, 204, 206, 209 inflammatory bowel disease (IBD), 140, 156 inflammatory cells, ix, 125, 139, 206 inflammatory response(s), 4, 54, 60, 130, 131, 135, 138, 140, 142, 143, 144, 146, 153, 204 influence, ix, xii, 6, 36, 37, 87, 111, 125, 139, 168, 173, 178, 184, 194, 199, 201, 202, 212, 214, 215, 229, 240, 241, 244 inhibition, viii, x, 42, 58, 59, 60, 67, 68, 69, 70, 71, 72, 73, 74, 76, 77, 78, 82, 88, 93, 105, 115, 120, 126, 130, 133, 134, 135, 136, 141, 149, 156, 158, 174, 197, 211, 219, 250 inhibitor, viii, ix, 44, 58, 67, 68, 69, 80, 93, 100, 106, 116, 136, 141, 147, 154, 169, 174, 195 injury, xii, 28, 29, 45, 46, 52, 88, 90, 135, 137, 144, 146, 160, 162, 173, 184, 189, 190, 192, 193, 194, 195, 197, 199, 200, 201, 202, 204, 205, 206, 207, 208, 210, 214, 215, 216, 218, 223, 224, 226, 228, 229, 230, 232, 233, 238 insulin, x, 42, 100, 105, 116, 117, 125, 126, 127, 128, 130, 132, 133, 134, 135, 136, 138, 139, 150, 151, 152, 153 insulin resistance, x, 125, 132, 133, 135, 136, 139, 150, 151, 153

Index

258

insulin sensitivity, x, 125, 135 insulin signaling, 134, 150 integrity, x, 153, 165, 166, 214, 218 intellect, x, 165 intelligence, 195 intensity, 11, 14, 17, 18, 19, 20, 27, 29, 142, 206 interaction(s), ix, xii, 3, 40, 91, 93, 100, 107, 116, 117, 133, 150, 155, 160, 167, 168, 175, 176, 184, 203, 216, 220, 222 intercellular, 102 intercellular adhesion molecule (ICAM), 140 interference, 119 interferon, 17, 109, 116, 119 interferon-γ, 17 interleukin (IL), x, 2, 18, 28, 35, 38, 48, 52, 53, 100, 109, 126, 127, 130, 131, 132, 138, 140, 141, 142, 154, 156, 159, 204, 219, 220, 227, 231, 233 intervention(s), 41, 110, 114, 146, 153 intestine, 130, 131, 146 intracellular, 4, 58, 59, 60, 77, 78, 80, 81, 82, 85, 89, 101, 103, 105, 106, 107, 108, 117, 119, 120, 133, 134, 135, 153, 166, 169, 171, 173, 174, 199, 201, 202, 217, 224, 225, 226, 233, 234, 238 intravenous (IV), v, ix, 90, 99, 150, 219 ion channel, 43, 60 ipsilateral, 202 iron, 30, 39, 42, 48, 51, 143, 172, 173 ischemia, xi, 42, 52, 54, 83, 91, 143, 146, 162, 178, 184, 189, 190, 191, 192, 193, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 210, 213, 214, 215, 216, 217, 218, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234 ischemic, xi, 78, 146, 183, 189, 190, 191, 193, 195, 197, 198, 200, 201, 202, 203, 204, 205, 207, 209, 212, 213, 214, 215, 216, 219, 222, 224, 225, 229, 231, 232, 233, 234

J Japanese, 112, 113, 118 judgment, 186 justification, 236

K keratinocyte, 131 ketones, 78 kidney, 55, 93, 102, 130, 131, 146 kinase activity, 132

L Langerhans cells (LC), 97, 120, 249 language, vii, 127, 186, 188, 233 latency, 68 later life, 154 LDL, ix, 99, 102, 115, 117, 118, 119, 120, 121, 122, 127, 137, 249 learning, vii, x, 1, 21, 36, 40, 42, 43, 46, 47, 48, 49, 50, 53, 54, 68, 74, 79, 81, 89, 126, 128, 130, 133, 139, 151, 155, 186, 195 learning and memory, x, 47, 53, 54, 79, 81, 89, 126, 128, 130, 133, 151 left ventricle, 33 leisure, 32 lesion(s), ix, xii, 7, 9, 10, 46, 52, 78, 87, 88, 89, 90, 91, 92, 94, 128, 134, 136, 138, 146, 152, 184, 185, 189, 190, 193, 216, 230, 233, 234, 236, 247 leukotrienes, 59, 85 liberation, viii, 57, 78 life expectancy, 166 lifespan, 144 ligands, ix, x, 88, 89, 99, 100, 102, 103, 105, 106, 107, 108, 114, 115, 117, 126, 130, 131, 136, 148, 158, 162, 222 limbic system, 44 linkage, 106, 111, 122 lipase, 105, 130, 131, 137, 149 lipid(s), ix, x, 27, 37, 38, 45, 84, 85, 90, 101, 117, 125, 128, 129, 130, 131, 135, 136, 137, 138, 139, 141, 142, 143, 144, 145, 147, 149, 154, 159, 160, 161, 165, 166, 167, 168, 169, 171, 173, 176, 177, 178, 179, 180, 244 lipid peroxidation, 27, 37, 38, 90, 141, 142, 144, 145, 160, 161, 173, 178, 180 lipids, 37, 45, 137, 143, 145, 167, 173, 177 lipolysis, 137 lipoproteins, 101, 149 liver, 118, 130, 131, 163, 176 location, 4, 118, 231 locus, 13, 100, 111, 121 longevity, 187 longitudinal study, 225, 233, 240 long-term memory, viii, 52, 58, 68, 72, 81, 83, 84, 187, 191 low density lipoprotein, 100, 101, 115, 116, 117, 118, 119, 120, 121, 122, 123 low risk, 137, 138 low-density lipoprotein, 102, 116, 118, 119, 120, 127, 130, 137

Index lumbar puncture, 239 lymphoid tissue, 131

M macronutrients, 139 macrophage(s), x, 2, 78, 119, 126, 131, 132, 138, 140, 143, 149, 156, 200, 204 magnesium, 180 magnetic resonance imaging (MRI), 42, 132, 148, 150 magnetic resonance spectroscopy (MRS), 61, 62, 81, 83, 84 major depression, 239, 246 major histocompatibility complex (MHC), 3, 142 males, 51, 71, 107 matrix, 92, 93, 100, 127, 131, 208 matrix metalloproteinases (MMP), 100, 105, 127, 131, 140 maturation, 4, 60, 137, 195, 216 maze learning, 54 medication, 240 melatonin, 51, 53 memory, vii, viii, x, 40, 43, 44, 46, 47, 48, 52, 53, 54, 55, 58, 59, 62, 68, 69, 70, 71, 72, 73, 74, 76, 77, 78, 79, 80, 81, 83, 84, 89, 126, 127, 128, 130, 133, 134, 136, 139, 150, 151, 152, 160, 165, 186, 187, 188, 190, 191, 195, 205, 222, 224, 240, 241 memory formation, viii, 58, 59, 69, 77, 81 memory processes, 75 memory retrieval, 191 men, 150, 189, 225, 241 menopause, 192, 215 mental activity, 189 mental disorders, 62, 64 messenger RNA (mRNA), x, 14, 16, 20, 28, 29, 38, 42, 43, 58, 75, 77, 81, 82, 84, 104, 110, 114, 116, 126, 129, 132, 135, 137, 138, 142, 195, 196, 200, 202, 217, 218, 224, 231, 234 meta-analysis, 113, 121 metabolic disorder, 132 metabolism, viii, ix, x, 30, 33, 34, 38, 44, 57, 59, 60, 61, 62, 65, 69, 78, 83, 84, 101, 102, 105, 106, 110, 114, 118, 125, 128, 129, 130, 131, 133, 134, 136, 137, 142, 143, 147, 148, 149, 151, 152, 154, 159, 160, 165, 166, 169, 171, 172, 175, 176, 201, 204, 205, 209, 215, 216, 238, 239, 244, 246, 247 metabolites, 34, 59, 61, 62, 63, 84 metabolizing, 54, 84 methodology, 38

259

microcirculation, 193, 206, 222 microsomes, 30 microtome, 70 mitochondria, 88, 89, 134, 143, 152, 160 mitogen, 77, 127, 133, 152 mitosis, 203 models, vii, ix, 1, 4, 5, 33, 40, 41, 43, 59, 60, 65, 87, 92, 94, 108, 137, 141, 142, 144, 146, 151, 159, 162, 193, 212, 213, 243 molecule, 93, 195, 212, 216, 218 monocyte chemoattractant protein (MCP), 28, 38 monolayer, 120 mood, 188, 219 morbidity, 189, 193 mortality, 130, 189, 193, 236 multi-infarct dementia, 219 multiple factors, ix, 89, 99 multiple sclerosis (MS), 14, 60, 79, 81, 84, 116, 121, 131, 140, 149, 152, 157, 177, 246 muscarinic receptor, 50, 77, 82 music, 219 mutations, xii, 90, 101, 102, 106, 116, 123, 128, 235, 248 myelin, 169 myocardial infarction, 140

N nasopharyngeal carcinoma, 93 negative outcomes, 36 neocortex, 46, 141, 145, 205 nephritis, 102 nerve, viii, 42, 44, 87, 91, 92, 94, 171, 178, 179, 199, 202, 204, 207, 216 nerve growth factor, viii, 44, 87, 91, 92, 94, 171, 178, 179 nervous system, 66, 100, 143, 150, 153, 194 neural development, 136, 153 neurobiology, viii, xi, 58, 183, 188 neuroblastoma, 65, 81, 91, 176 neurodegenerative disorders, viii, 87, 89, 91, 92, 93, 94, 136, 137, 148, 159, 171, 172, 203, 209 neurofibrillary tangles, ix, 3, 61, 62, 89, 91, 125, 127, 128, 166, 188, 195, 203, 236, 237 neurologic, 159, 221 neurological disease, 139, 157, 184 neuronal density, 211 neuronal models, 178 neuronal systems, 47

Index

260

neurons, viii, 7, 8, 10, 11, 14, 45, 46, 47, 48, 50, 53, 54, 55, 58, 59, 66, 67, 80, 82, 88, 89, 91, 120, 128, 133, 135, 136, 139, 140, 141, 142, 143, 144, 145, 147, 153, 154, 158, 166, 169, 170, 171, 172, 173, 174, 175, 178, 179, 181, 188, 194, 197, 198, 199, 200, 201, 202, 203, 204, 207, 208, 215, 216, 222, 224, 226, 227, 232, 236, 243, 250 neuropeptides, 14, 16, 34, 54, 55 neuroprotection, ix, xi, 87, 94, 106, 136, 155, 159, 166, 200, 232 neuroscience, 217 neurotoxicity, x, 39, 42, 44, 45, 46, 47, 50, 54, 91, 120, 122, 136, 144, 147, 153, 154, 156, 165, 166, 167, 168, 176, 217, 218, 219, 245 neurotransmitter, vii, 1, 5, 34, 40, 59, 60, 79 neurotrophic, 53, 91, 92 neurovascular, xii, 184, 186, 189, 191, 192, 205, 212, 213, 214, 216 neutrophils, 93, 146 nicotinamide, 127, 144 nicotine, 15, 16 nitric oxide, x, 2, 34, 49, 53, 54, 91, 126, 127, 131, 158, 173, 180, 250 nitric oxide synthase, x, 2, 34, 49, 53, 54, 91, 126, 127, 158, 173, 250 nitrogen, ix, 90, 91, 125, 127, 130, 139, 142, 144, 159 non-steroidal anti-inflammatory drugs, 149 norepinephrine (NE), 2, 13, 81, 84 normal aging, 91, 161, 249 NSAIDs, ix, 125, 126, 127, 128, 130, 131, 132, 136, 140, 141, 142, 157, 158, 162 nuclear receptors, 129 nucleic acid, 90, 143, 144, 173 nucleotide, 106, 111, 117 nucleus, x, 2, 34, 42, 45, 46, 51, 54, 89, 145, 165, 174, 195 nurses, 218 nutrients, 162 nutrition, 216

O obesity, 128, 131 observations, xi, 11, 33, 38, 129, 151, 167, 183, 198, 201, 202, 204, 205, 209, 215 obstruction, 117 occlusion, 219, 220, 224, 227, 228, 229, 230 old age, 211 omega-3, 82, 154

organic, 30, 190, 228 organism, 130 organization, 82, 123, 175 osmotic pressure, 34 osteoarthritis, 156 ovariectomy, 54 ovary, 131 oxidation, xi, 90, 130, 137, 139, 144, 145, 149, 155, 165, 174, 178 oxidative damage, 3, 37, 45, 51, 90, 91, 143, 144, 145, 147, 159, 160, 173 oxidative stress, vii, viii, ix, 1, 5, 27, 37, 38, 40, 50, 54, 87, 89, 90, 91, 94, 125, 128, 134, 135, 141, 142, 143, 144, 145, 146, 147, 153, 159, 160, 161, 162, 166, 170, 171, 172, 173, 174, 175, 176, 179, 232, 238, 245 oxygen, ix, 125, 128, 142, 143, 145, 159, 160, 161, 162, 172

P pancreas, 131, 134 paralysis, 146 parenchyma, 118, 187, 188, 190, 191, 194, 195, 201, 204, 207, 208, 214, 215, 217 parietal cortex, viii, 3, 34, 57, 61, 81 Parkinson’s disease, 140, 185, 240 parotid, 82 parotid gland, 82 parvalbumin, 14, 34, 46 pathogenesis, vii, xi, xii, 1, 40, 41, 90, 91, 92, 94, 111, 117, 122, 132, 137, 144, 146, 148, 151, 160, 166, 167, 171, 172, 173, 176, 184, 198, 203, 220, 226, 232, 247 pathogenic, 103, 106, 129, 148, 215, 216, 217, 236 pathogens, 139 pathology, ix, xi, 3, 44, 50, 51, 90, 94, 125, 126, 129, 134, 140, 141, 142, 144, 158, 159, 173, 183, 187, 189, 190, 191, 192, 193, 194, 195, 199, 204, 205, 206, 207, 214, 216, 221, 224, 228, 229, 231, 247 pathophysiology, ix, 60, 61, 125, 128, 135, 140, 175, 179, 189, 228 pathways, 34, 40, 59, 76, 88, 89, 90, 93, 94, 107, 123, 132, 133, 135, 137, 140, 144, 149, 171, 194, 234, 237 penalties, 122 peptide(s), vii, x, xii, 1, 3, 5, 30, 31, 32, 33, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 59, 79, 81, 90, 91, 105, 106, 109, 116, 120,

Index 121, 122, 123, 129, 134, 142, 144, 152, 153, 160, 161, 165, 166, 167, 168, 171, 172, 174, 175, 176, 177, 178, 179, 180, 181, 184, 187, 193, 195, 196, 197, 198, 199, 201, 203, 204, 205, 206, 207, 209, 210, 212, 213, 214, 215, 216, 220, 221, 223, 224, 227, 229, 230, 231, 232, 234, 235, 236, 237, 242, 243, 244, 245, 246, 247, 248, 249 perception, 62 performance, 36, 70, 74, 134, 215 peripheral blood, 93, 133 peroxisome proliferator-activated receptors (PPARs), 158 peroxynitrite, 91, 173 personality, 127, 186, 188, 191 perspective, xi, 79, 122, 166, 219 pH, 34, 71, 73, 170 phagocytosis, 54, 209, 250 pharmacology, 83 phenotype, 116, 148 phosphate, 30, 61, 62, 83, 127, 144, 170, 171, 179 phosphatidylcholine, 59, 60, 68, 71, 75, 167, 226 phospholipids, viii, 57, 58, 60, 61, 77, 81, 167, 173 phosphorylation, 7, 9, 10, 32, 45, 77, 79, 80, 93, 107, 119, 133, 134, 135, 136, 147, 152, 153, 203, 226, 233 physical activity, 211 physical aggression, 221 physical environment, 159 physiology, viii, 87, 91, 129, 146, 179, 231 pigs, 156 pioglitazone, x, 126, 131, 142, 157, 159 placenta, 130 plasma, x, xii, 28, 58, 77, 80, 82, 90, 106, 108, 114, 125, 131, 134, 137, 138, 145, 151, 152, 155, 167, 170, 215, 225, 235, 236, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249 plasma levels, xii, 28, 235, 239, 242, 248 plasma membrane, 77, 82, 167, 170 plasma proteins, 247 plasmin, 105, 106, 114, 119 plasminogen, 100, 105, 117, 122 plasticity, viii, 37, 47, 52, 58, 59, 68, 77, 138 platelet(s), viii, 57, 64, 65, 80, 100, 107, 206, 213, 214, 215, 219, 220, 240, 241, 247, 248 polymorphism(s), x, 103, 106, 111, 112, 113, 115, 116, 117, 118, 119, 120, 121, 125, 138, 155 polysaccharides, 92 polyunsaturated fatty acids, 69, 127, 131, 172, 173 population, xii, 54, 88, 107, 111, 118, 119, 120, 123, 127, 151, 154, 159, 186, 189, 190, 192, 193, 223,

261

225, 228, 233, 235, 236, 237, 240, 244, 246, 247, 250 positive feedback, 204 potassium, 50, 136, 147, 153 PPAR agonists, x, 126, 128, 136, 140, 147 PPAR ligands, 138, 140, 149 predictors, 236, 244, 245 prefrontal cortex, 61, 64, 84, 133 pregnancy, 93 prevention, xi, 48, 109, 128, 139, 157, 162, 166, 172, 212 production, ix, xi, 38, 41, 52, 53, 59, 60, 81, 85, 90, 91, 105, 107, 108, 116, 125, 126, 130, 131, 132, 136, 137, 140, 141, 142, 143, 144, 147, 149, 156, 171, 172, 174, 175, 178, 179, 180, 183, 200, 201, 203, 204, 211, 216, 219, 250 progesterone, 28, 29, 38 progression, x, xii, 111, 115, 125, 130, 135, 136, 141, 144, 145, 147, 156, 187, 188, 195, 211, 212, 220, 222, 235, 236, 237, 244 proliferating fraction (PF), 79, 96 proliferation, xi, 129, 131, 171, 184, 188, 208, 228 promoter, 93, 102, 106, 111, 129, 138 prostaglandin(s), 60, 85, 127, 131, 149, 159 prostatectomy, 122 protease, ix, 33, 35, 39, 42, 100, 102, 105, 106, 114, 121, 129, 134, 166, 175, 195, 217, 237, 249 protease inhibitor, 33, 35, 39, 42, 100, 106, 195, 217 protective factors, 157 protein(s), viii, ix, x, xi, xii, 2, 4, 7, 27, 28, 29, 30, 35, 37, 38, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 57, 59, 60, 65, 67, 71, 73, 74, 75, 76, 77, 78, 79, 80, 83, 88, 90, 99, 100, 101, 102, 103, 105, 106, 107, 109, 110, 111, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 126, 127, 128, 129, 131, 133, 134, 135, 137, 138, 139, 140, 142, 143, 144, 145, 146, 147, 148, 150, 151, 152, 153, 158, 160, 166, 167, 168, 171, 173, 175, 176, 177, 178, 180, 183, 187, 191, 193, 195, 196, 197, 198, 200, 201, 202, 203, 204, 205, 206, 208, 212, 213, 214, 215, 216, 217, 218, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 236, 237, 238, 239, 244, 245, 246, 247, 248, 249 protein family, 103 protein oxidation, 144, 145 protein synthesis, 133, 143, 216 proteinase, 116, 122 proteolysis, 92, 105, 108, 203, 205 psoriasis, 131, 140, 156 psychiatric patients, 83

Index

262

rodents, vii, 1, 4, 52, 129 rosiglitazone, x, 126, 131, 136, 146, 156

pyramidal cells, 132, 202

Q S quinolinic acid, 51

R radiation, 160, 170 radical, x, 46, 122, 125, 141, 142, 143, 144, 145, 160, 161, 166, 172, 173, 176 radius, 71 range, 40, 59, 60, 91, 130, 135, 141, 168, 189, 242 reactive oxygen, 3, 38, 90, 127, 130, 139, 144, 173 receptor(s), ix, x, 13, 16, 41, 45, 46, 48, 49, 50, 53, 64, 68, 77, 78, 79, 82, 83, 87, 88, 89, 91, 92, 94, 99, 100, 101, 102, 103, 105, 106, 107, 108, 109, 115, 116, 117, 118, 119, 120, 121, 122, 123, 125, 126, 127, 128, 129, 131, 132, 133, 134, 135, 137, 139, 141, 142, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 162, 170, 171, 178, 211, 216, 221, 231, 233, 244, 249 recognition, 22, 23, 24, 37, 49 recovery, 136, 208, 214, 216, 218 regeneration, 91 regression method, 242 relationship(s), 4, 59, 103, 110, 135, 151, 175, 187, 193, 209, 211, 216, 237 respiratory, 102 response, vii, 1, 3, 28, 29, 39, 41, 43, 44, 49, 60, 81, 83, 105, 106, 129, 130, 131, 135, 138, 140, 143, 144, 145, 146, 149, 153, 155, 167, 170, 171, 172, 178, 194, 199, 202, 204, 208, 216, 217 retention, 48, 70, 191 reticulum, 44, 45, 77, 84, 168, 169 retina, 7, 9, 47, 133, 218, 226 reward, 21, 48 rheumatoid arthritis, 140, 156 rhythm, 109 right ventricle, 11, 15, 16, 24 risk, vii, ix, x, 65, 85, 90, 94, 100, 101, 103, 106, 109, 111, 116, 117, 118, 120, 123, 125, 128, 130, 133, 135, 137, 138, 141, 146, 148, 150, 151, 154, 155, 157, 160, 162, 166, 168, 169, 172, 187, 189, 190, 192, 205, 215, 219, 221, 222, 223, 225, 226, 228, 233, 236, 237, 239, 241, 244 risk factor(s), vii, 85, 90, 103, 106, 109, 118, 120, 128, 148, 154, 166, 169, 172, 187, 189, 190, 192, 205, 215, 219, 222, 225, 226, 228, 241 RNA, 50, 85, 105, 119, 144, 147

saturated fatty acids, 138, 168 schizophrenia, 60, 80, 81, 84 secretion, 59, 60, 79, 83, 93, 107, 144 seeding, 167, 198 seizures, 85 senile dementia, ix, 46, 50, 88, 112, 177, 184, 221 sensitivity, x, 122, 125, 135, 136, 216, 236, 242, 244 septum, 12, 14, 21, 23, 53, 92 series, viii, 41, 58, 61, 69, 85, 135 serotonin, 34 serum, 80, 93, 102, 115, 137, 190, 192, 194, 244 severity, 69, 110, 141, 146, 151, 161, 240, 246 shock, 53, 68, 70, 71, 73, 162 short-term memory, 188, 191 sialic acid, 167 siblings, 111 side effects, 211 signaling pathways, ix, x, 100, 107, 136, 140, 165, 170 situation, 90, 193, 213, 214 skeletal muscle, 116, 130, 131, 132, 135, 240, 247 skin, 130 smoking, 192, 233 smooth muscle, 119, 130, 140 smooth muscle cells, 130, 140 social workers, 218 solvent, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 33 spatial learning, 36, 43, 68, 75 species, ix, 3, 4, 6, 38, 90, 91, 109, 115, 125, 127, 129, 130, 139, 142, 144, 159, 167, 170, 171, 173, 195, 220, 247 specificity, 58, 167, 237, 239, 242, 244, 245 spinal cord, 133 spleen, 131 stabilization, 201, 226 stages, viii, 58, 62, 66, 77, 88, 135, 207, 209, 217, 236, 237, 239, 243, 244 standard deviation, 67, 73, 74, 75, 241, 242 statins, 168, 212, 240, 241, 246, 249 steroid, ix, 125, 127, 128, 129, 148, 168, 240 sterols, 103 stimuli, 34, 59, 88, 89, 136, 170 strain, 5

Index stress, vii, viii, ix, 1, 5, 25, 27, 30, 37, 38, 40, 44, 45, 50, 54, 87, 89, 90, 91, 94, 125, 128, 134, 135, 136, 137, 141, 142, 143, 144, 145, 146, 147, 151, 153, 154, 159, 160, 161, 162, 166, 170, 171, 172, 173, 174, 175, 176, 179, 180, 181, 200, 211, 224, 232, 238, 245 striatum, 10, 19, 32, 35, 36, 54, 82, 202, 219 stroke, 91, 162, 189, 190, 193, 197, 218, 221, 222, 225, 239, 246 structural protein, 143 subcutaneous (SC), 43, 95 subdural hematoma, 185 substrate, 58, 71, 101, 127, 132, 135, 152 suppression, 118, 142 surrogate, 144 survival, 50, 66, 91, 92, 93, 133, 136, 150, 153, 179, 187, 196, 197, 204, 205, 206, 207, 208, 211, 214, 215, 225, 229, 230 symptomatic treatment, 188, 211 symptoms, xii, 64, 88, 90, 92, 186, 187, 188, 189, 190, 191, 192, 194, 211, 212, 223, 235 synapse, 26, 37, 133, 177, 215 synaptic plasticity, viii, 37, 47, 52, 58, 59, 68, 77, 138 syndrome, 90, 185, 191, 227, 232 synergistic, 48, 146

T temporal, vii, viii, 1, 2, 4, 5, 40, 41, 42, 58, 60, 84, 129, 140, 145, 146, 150, 161, 214, 216 temporal lobe, 84, 146, 150, 161 temporal lobe epilepsy, 84 test scores, 50, 242 testis, 131 tetanus, 26 thalamus, 21, 33, 133 T-helper cell (Th), 3 theory, 143, 160, 194, 200, 203 therapeutic agents, 93, 131, 146, 213 therapeutic interventions, 115 therapeutic targets, 148, 153 therapeutics, 147, 223 therapy, 52, 80, 94, 135, 140, 158, 211, 212, 230, 232, 233 thiazolidinediones, 126, 127, 128, 148, 156 thrombus, 206 thyroid, 129

263

time, 4, 30, 34, 39, 40, 51, 71, 73, 74, 78, 81, 92, 114, 128, 133, 146, 169, 172, 186, 188, 191, 200, 203, 207, 209, 211, 215, 236, 237 time periods, 81 tinnitus, 191 tissue(s), viii, x, 4, 5, 8, 30, 34, 51, 58, 59, 65, 71, 73, 80, 90, 92, 100, 101, 102, 103, 114, 125, 129, 132, 135, 137, 142, 143, 145, 146, 169, 170, 171, 173, 188, 197, 201, 206, 208, 214, 215, 225, 245 TNF-α, 28, 29, 132, 140, 141, 142, 146 total cholesterol, 137, 154 toxicity, vii, 1, 3, 4, 6, 30, 32, 33, 38, 39, 40, 42, 44, 45, 48, 51, 53, 54, 55, 92, 134, 135, 141, 152, 160, 167, 172, 175, 194, 199, 201, 202, 227, 243, 250 training, viii, 22, 36, 44, 48, 58, 68, 69, 70, 71, 73, 74, 76, 77, 79 transcription factors, x, 126, 129, 131, 136, 137, 138, 143, 149, 173 transforming growth factor (TGF), 122 transient ischemic attack, 192 translocation, 44, 81, 83, 84, 130, 218 transmission, 26, 52, 59 trauma, 91, 184, 185, 219 traumatic brain injury, 203, 219 treatment(s), vii, ix, x, 4, 40, 43, 50, 52, 60, 66, 67, 68, 69, 78, 87, 89, 92, 93, 94, 125, 126, 128, 129, 130, 131, 132, 135, 136, 137, 140, 141, 142, 146, 147, 148, 151, 155, 156, 157, 158, 159, 162, 163, 167, 168, 171, 172, 186, 187, 188, 196, 211, 212, 221, 227, 229, 231, 232, 236, 241, 244, 245, 246 triggers, 91, 171 triglycerides, 137 trophic, 89, 94, 170, 171, 208 trypsin, 106 tumor, x, 52, 93, 126, 127, 131, 178, 181 tumor cells, 93 tumor necrosis factor (TNF), x, 28, 29, 52, 126, 127, 131, 132, 140, 141, 142, 146, 165, 170, 171, 178, 181, 231 tumors, 185 turnover, viii, 13, 57, 60, 61, 138, 176 type 2 diabetes, x, 126, 131, 151, 155 tyrosine, 91, 100, 119, 132, 133, 134

U ulcerative colitis, 131 urine, 90, 144, 161, 237 urokinase, 117

Index

264

V values, 65, 67, 73, 74, 239, 242 vascular, xi, 3, 38, 119, 128, 130, 138, 140, 148, 149, 154, 183, 186, 188, 189, 190, 191, 192, 193, 205, 207, 209, 210, 211, 214, 216, 218, 219, 224, 225, 228, 232, 233, 234, 237, 238, 241, 244, 248 vascular dementia, 186, 189, 190, 191, 192, 194, 210, 211, 218, 224, 228, 233, 237, 238, 241, 248 vascular endothelial growth factor (VEGF), 38 vasculature, 105, 106, 131 vasodilator, 147 vasopressin, 53 veins, 206, 207 venous, 206 ventricle(s), 8, 10, 11, 13, 15, 16, 17, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 37, 38, 39, 49, 139, 198, 210 venules, 206, 207 vertebrates, 102 vertigo, 191 vesicles, 167, 177, 232 vessels, 188, 192, 194, 206, 207, 209, 212, 214, 215, 216 victims, 189 virus, 43, 102

virus infection, 102 vitamin(s), 40, 102, 129, 141, 143, 146, 173, 174, 179, 185 vitamin B12, 102, 185 vitamin D, 129 vitamin E, 141, 146, 173, 174, 179 vulnerability, 47, 194, 202, 215, 218, 225, 227

W white matter, xi, 183, 189, 190, 191, 193, 194, 197, 206, 207, 233, 234 wild type, 90, 193 withdrawal, 71, 91, 171, 215 women, xii, 189, 221, 235, 240, 241, 245 working memory, 54, 133, 139

Y yang, 220 yin, 220

Z zinc, 30, 39, 43, 48, 105, 172