Cellular Stress Response (Hormesis) in Response to Bioactive Nutraceuticals with Relevance to Alzheimer Disease.

Significance: Alzheimer's disease (AD) is the most common form of dementia associated with aging. As the large Baby Boomer population ages, risk of developing AD increases significantly, and this portion of the population will increase significantly over the next several decades. Recent Advances: Research suggests that a delay in the age of onset by 5 years can dramatically decrease both the incidence and cost of AD. In this review, the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in AD is examined in the context of heme oxygenase-1 (HO-1) and biliverdin reductase-A (BVR-A) and the beneficial potential of selected bioactive nutraceuticals. Critical Issues: Nrf2, a transcription factor that binds to enhancer sequences in antioxidant response elements (ARE) of DNA, is significantly decreased in AD brain. Downstream targets of Nrf2 include, among other proteins, HO-1. BVR-A is activated when biliverdin is produced. Both HO-1 and BVR-A also are oxidatively or nitrosatively modified in AD brain and in its earlier stage, amnestic mild cognitive impairment (MCI), contributing to the oxidative stress, altered insulin signaling, and cellular damage observed in the pathogenesis and progression of AD. Bioactive nutraceuticals exhibit anti-inflammatory, antioxidant, and neuroprotective properties and are potential topics of future clinical research. Specifically, ferulic acid ethyl ester, sulforaphane, epigallocatechin-3-gallate, and resveratrol target Nrf2 and have shown potential to delay the progression of AD in animal models and in some studies involving MCI patients. Future Directions: Understanding the regulation of Nrf2 and its downstream targets can potentially elucidate therapeutic options for delaying the progression of AD. Antioxid. Redox Signal. 38, 643-669.

Mitochondrial Oxidative and Nitrosative Stress and Alzheimer Disease.

Oxidative and nitrosative stress are widely recognized as critical factors in the pathogenesis and progression of Alzheimer disease (AD) and its earlier stage, amnestic mild cognitive impairment (MCI). A major source of free radicals that lead to oxidative and nitrosative damage is mitochondria. This review paper discusses oxidative and nitrosative stress and markers thereof in the brain, along with redox proteomics, which are techniques that have been pioneered in the Butterfield laboratory. Selected biological alterations in-and oxidative and nitrosative modifications of-mitochondria in AD and MCI and systems of relevance thereof also are presented. The review article concludes with a section on the implications of mitochondrial oxidative and nitrosative stress in MCI and AD with respect to imaging studies in and targeted therapies toward these disorders. Taken together, this review provides support for the notion that brain mitochondrial alterations in AD and MCI are key components of oxidative and nitrosative stress observed in these two disorders, and as such, they provide potentially promising therapeutic targets to slow-and hopefully one day stop-the progression of AD, which is a devastating dementing disorder.

Classics in Chemical Neuroscience: Chlorpromazine.

The discovery of chlorpromazine in the early 1950s revolutionized the clinical treatment of schizophrenia, galvanized the development of psychopharmacology, and standardized protocols used for testing the clinical efficacy of antipsychotics. Furthermore, chlorpromazine expanded our understanding of the role of chemical messaging in neurotransmission and reduced the stigma associated with mental illness, facilitating deinstitutionalization in the 1960s and 1970s. In this review, we will discuss the synthesis, manufacturing, metabolism and pharmacokinetics, pharmacology, structure-activity relationship, and adverse effects of chlorpromazine. In conclusion, we summarize the history and significant contributions of chlorpromazine that have resulted in this potent first-generation antipsychotic maintaining its clinical relevance for nearly 70 years.

Redox proteomics and amyloid ß-peptide: insights into Alzheimer disease.

Alzheimer disease (AD) is a progressive neurodegenerative disorder associated with aging and characterized pathologically by the presence of senile plaques, neurofibrillary tangles, and neurite and synapse loss. Amyloid beta-peptide (1-42) [Aß(1-42)], a major component of senile plaques, is neurotoxic and induces oxidative stress in vitro and in vivo. Redox proteomics has been used to identify proteins oxidatively modified by Aß(1-42) in vitro and in vivo. In this review, we discuss these proteins in the context of those identified to be oxidatively modified in animal models of AD, and human studies including familial AD, pre-clinical AD (PCAD), mild cognitive impairment (MCI), early AD, late AD, Down syndrome (DS), and DS with AD (DS/AD). These redox proteomics studies indicate that Aß(1-42)-mediated oxidative stress occurs early in AD pathogenesis and results in altered antioxidant and cellular detoxification defenses, decreased energy yielding metabolism and mitochondrial dysfunction, excitotoxicity, loss of synaptic plasticity and cell structure, neuroinflammation, impaired protein folding and degradation, and altered signal transduction. Improved access to biomarker imaging and the identification of lifestyle interventions or treatments to reduce Aß production could be beneficial in preventing or delaying the progression of AD. This article is part of the special issue "Proteomics".

Oxidative Stress, Amyloid-ß Peptide, and Altered Key Molecular Pathways in the Pathogenesis and Progression of Alzheimer's Disease.

Oxidative stress is implicated in the pathogenesis and progression of Alzheimer's disease (AD) and its earlier stage, amnestic mild cognitive impairment (aMCI). One source of oxidative stress in AD and aMCI brains is that associated with amyloid-ß peptide, Aß1-42 oligomers. Our laboratory first showed in AD elevated oxidative stress occurred in brain regions rich in Aß1-42, but not in Aß1-42-poor regions, and was among the first to demonstrate Aß peptides led to lipid peroxidation (indexed by HNE) in AD and aMCI brains. Oxidatively modified proteins have decreased function and contribute to damaged key biochemical and metabolic pathways in which these proteins normally play a role. Identification of oxidatively modified brain proteins by the methods of redox proteomics was pioneered in the Butterfield laboratory. Four recurring altered pathways secondary to oxidative damage in brain from persons with AD, aMCI, or Down syndrome with AD are interrelated and contribute to neuronal death. This "Quadrilateral of Neuronal Death" includes altered: glucose metabolism, mTOR activation, proteostasis network, and protein phosphorylation. Some of these pathways are altered even in brains of persons with preclinical AD. We opine that targeting these pathways pharmacologically and with lifestyle changes potentially may provide strategies to slow or perhaps one day, prevent, progression or development of this devastating dementing disorder. This invited review outlines both in vitro and in vivo studies from the Butterfield laboratory related to Aß1-42 and AD and discusses the importance and implications of some of the major achievements of the Butterfield laboratory in AD research.

Proteomics analysis of the Alzheimer's disease hippocampal proteome.

Alzheimer's disease (AD) is characterized by the presence of intracellular neurofibrillary tangles (NFT), extracellular senile plaques (SP), and synaptic loss. The hippocampus is a region that plays an important role in memory and cognitive function, and it is severely affected in AD. The levels of proteins in the hippocampus may provide a better understanding of the pathological changes known. In the present study we used two-dimensional gel electrophoresis and mass spectrometry techniques to determine changes in protein levels in AD and control hippocampus. We identified 18 proteins with altered protein levels that are involved in regulating different cellular functions. Protein levels were found to be significantly decreased for peptidyl prolyl cis/trans-isomerase (Pin 1) (0.6-fold compared to control, p<0.03), dihydropyrimidinase-like protein 2 (DRP-2) (0.74-fold compared to control, p<0.02), phosphoglycerate mutase 1 (PGM1) (0.7-fold compared to control, p<0.01), beta-tubulin (0.34-fold compared to control, p<0.01), and aldolase A (0.87-fold compared to control, p<0.0002), whereas the protein levels were found to be significantly increased for enolase (1.35-fold compared to control, p<0.05), ubiquitin carboxyl terminal hydrolase L-1 (UCH L1) (1.31-fold compared to control, p<0.02), triosephosphate isomerase (TPI) (1.38-fold compared to control, p<0.05), carbonic anhydrase II (CAH-II) (1.24-fold compared to control, p=0.05), heat shock protein 70 (1.14-fold compared to control, p<0.03), fructose bisphosphate aldolase (1.38-fold compared to control, p<0.05), ferritin heavy chain (1.23-fold compared to control, p=0.05), 2',3'-cyclic nucleotide 3' phosphodiestrase (CNPase) (1.12-fold compared to control, p<0.02), peroxiredoxin II (1.39-fold compared to control, p<0.05), and adenylate kinase I (1.19-fold compared to control, p<0.03). We found 2 proteins spots that were identified as glyceraldehyde 3-phosphate dehydrogenase (GAPDH). One of the spots showed a 1.28-fold increase in protein level compared to control (p<0.01), and the other spot showed a similar 1.26-fold increase in protein level compared to control (p<0.04). Thus, proteomics has provided knowledge of the levels of key proteins in AD brain. We discuss the functions regulated by these proteins with respect to AD pathology.

Redox proteomics identification of oxidized proteins in Alzheimer's disease hippocampus and cerebellum: an approach to understand pathological and biochemical alterations in AD.

Alzheimer's disease (AD) is characterized by the presence of neurofibrillary tangles, senile plaques and loss of synapses. There is accumulating evidence that oxidative stress plays an important role in AD pathophysiology. Previous redox proteomics studies from our laboratory on AD inferior parietal lobule led to the identification of oxidatively modified proteins that were consistent with biochemical or pathological alterations in AD. The present study was focused on the identification of specific targets of protein oxidation in AD and control hippocampus and cerebellum using a redox proteomics approach. In AD hippocampus, peptidyl prolyl cis-trans isomerase, phosphoglycerate mutase 1, ubiquitin carboxyl terminal hydrolase 1, dihydropyrimidinase related protein-2 (DRP-2), carbonic anhydrase II, triose phosphate isomerase, alpha-enolase, and gamma-SNAP were identified as significantly oxidized protein with reduced enzyme activities relative to control hippocampus. In addition, no significant excessively oxidized protein spots were identified in cerebellum compared to control, consistent with the lack of pathology in this brain region in AD. The identification of oxidatively modified proteins in AD hippocampus was verified by immunochemical means. The identification of common oxidized proteins in different brain regions of AD brain suggests a potential role for these oxidized proteins and thereby oxidative stress in the pathogenesis of Alzheimer's disease.

Proteomic identification of proteins specifically oxidized in Caenorhabditis elegans expressing human Abeta(1-42): implications for Alzheimer's disease.

Protein oxidation has been shown to lead to loss of protein function, increased protein aggregation, decreased protein turnover, decreased membrane fluidity, altered cellular redox poteintial, loss of Ca2+ homeostaisis, and cell death. There is increasing evidence that protein oxidation is involved in the pathogenesis of Alzheimer's disease and amyloid beta-peptide (1-42) has been implicated as a mediator of oxidative stress in AD. However, the specific implications of the oxidation induced by Abeta(1-42) on the neurodegeneration evident in AD are unknown. In this study, we used proteomic techniques to identify specific targets of oxidation in transgenic Caenorhabditis elegans (C. elegans) expressing human Abeta(1-42). We identified 16 oxidized proteins involved in energy metabolism, proteasome function, and scavenging of oxidants that are more oxidized compared to control lines. These results are discussed with reference to Alzheimer's disease.

Oxidative modification and down-regulation of Pin1 in Alzheimer's disease hippocampus: A redox proteomics analysis.

Alzheimer disease (AD) is characterized neuropathologically by intracellular neurofibrillary tangles (NFT) and of extracellular senile plaques (SP), the central core of which is amyloid beta-peptide (Abeta) derived from amyloid precursor protein (APP), a transmembrane protein. AD brain has been reported to be under oxidative stress that may play an important role in the pathogenesis and progression of AD. The present proteomics study is focused on identification of a specific target of protein oxidation in AD hippocampus that has relevance to the role of oxidative stress in AD. Here, we report that the protein, Pin1, is significantly down-regulated and oxidized in AD hippocampus. The identity of Pin1 was confirmed immunochemically. Analysis of Pin1 activity in AD brain and separately as oxidized pure Pin1 demonstrated that oxidation of Pin1 led to loss of activity. Pin1 has been implicated in multiple aspects of cell cycle regulation and dephosphorylation of tau protein as well as in AD. The in vivo oxidative modification of Pin1 as found by proteomics in AD hippocampus in the present study suggests that oxidative modification may be related to the known loss of Pin1 isomerase activity that could be crucial in AD neurofibrillary pathology. Taken together, these results provide evidence supporting a direct link between oxidative damage to neuronal Pin1 and the pathobiology of AD.

Proteomic identification of proteins oxidized by Abeta(1-42) in synaptosomes: implications for Alzheimer's disease.

Protein oxidation has been implicated in Alzheimer's disease (AD) and can lead to loss of protein function, abnormal protein turnover, interference with cell cycle, imbalance of cellular redox potential, and eventually cell death. Recent proteomics work in our laboratory has identified specifically oxidized proteins in AD brain such as: creatine kinase BB, glutamine synthase, ubiquitin carboxy-terminal hydrolase L-1, dihydropyrimidase-related protein 2, alpha-enolase, and heat shock cognate 71, indicating that a number of cellular mechanisms are affected including energy metabolism, excitotoxicity and/or synaptic plasticity, protein turnover, and neuronal communication. Synapse loss is known to be an early pathological event in AD, and incubation of synaptosomes with amyloid beta peptide 1-42 (Abeta 1-42) leads to the formation of protein carbonyls. In order to test the involvement of Abeta(1-42) in the oxidation of proteins in AD brain, we utilized two-dimensional gel electrophoresis, immunochemical detection of protein carbonyls, and mass spectrometry to identify proteins from synaptosomes isolated from Mongolian gerbils. Abeta(1-42) treatment leads to oxidatively modified proteins, consistent with the notion that Abeta(1-42)-induced oxidative stress plays an important role in neurodegeneration in AD brain. In this study, we identified beta-actin, glial fibrillary acidic protein, and dihydropyrimidinase-related protein-2 as significantly oxidized in synaptosomes treated with Abeta(1-42). Additionally, H+-transporting two-sector ATPase, syntaxin binding protein 1, glutamate dehydrogenase, gamma-actin, and elongation factor Tu were identified as increasingly carbonylated. These results are discussed with respect to their potential involvement in the pathogenesis of AD.

Neurotoxicity and oxidative stress in D1M-substituted Alzheimer's A beta(1-42): relevance to N-terminal methionine chemistry in small model peptides.

Small model peptides containing N-terminal methionine are reported to form sulfur-centered-free radicals that are stabilized by the terminal N atom. To test whether a similar chemistry would apply to a disease-relevant longer peptide, Alzheimer's disease (AD)-associated amyloid beta-peptide 1-42 was employed. Methionine at residue 35 of this 42-mer has been shown to be a key amino acid residue involved in amyloid beta-peptide 1-42 [A beta1-42]-mediated toxicity and therefore, the pathogenesis of AD. Previous studies have shown that mutation of the methionine residue to norleucine abrogates the oxidative stress and neurotoxic properties of A beta(1-42). In the current study, we examined if the position of methionine at residue 35 is a criterion for toxicity. In doing so, we tested the effects of moving methionine to the N-terminus of the peptide in a synthetic peptide, A beta(1-42)D1M, in which methionine was substituted for aspartic acid at the N-terminus of the peptide and all subsequent residues from D1 to L34 were shifted one position towards the carboxy-terminus. A beta(1-42)D1M exhibited oxidative stress and neurotoxicity properties similar to those of the native peptide, A beta(1-42), all of which are inhibited by the free radical scavenger Vitamin E, suggesting that reactive oxygen species may play a role in the A beta-mediated toxicity. Additionally, substitution of methionine at the N-terminus by norleucine, A beta(1-42)D1Nle, completely abrogated the oxidative stress and neurotoxicity associated with the A beta(1-42)D1M peptide. The results of this study validate the chemistry reported for short peptides with N-terminal methionines in a disease-relevant peptide.

Proteomic analysis of oxidatively modified proteins induced by the mitochondrial toxin 3-nitropropionic acid in human astrocytes expressing the HIV protein tat.

The human immunodeficiency virus (HIV)-Tat protein has been implicated in the neuropathogenesis of HIV infection. However, its role in modulating astroglial function is poorly understood. Astrocyte infection with HIV has been associated with rapid progression of dementia. Intracellularly expressed Tat is not toxic to astrocytes. In fact, intracellularly expressed Tat offers protection against oxidative stress-related toxins such as the mitochondrial toxin 3-nitroproprionic acid (3-NP). In the current study, human astrocytes expressing Tat (SVGA-Tat) and vector controls (SVGA-pcDNA) were each treated with the irreversible mitochondrial complex II inhibitor 3-NP. Proteomics analysis was utilized to identify changes in protein expression levels. By coupling 2D fingerprinting and identification of proteins by mass spectrometry, actin, heat shock protein 90, and mitochondrial single-stranded DNA binding protein were identified as proteins with increased expression, while lactate dehydrogenase had decreased protein expression levels in SVGA-Tat cells treated with 3-NP compared to SVGA-pcDNA cells treated with 3-NP. Oxidative damage can lead to several events including loss in specific protein function, abnormal protein clearance, depletion of the cellular redox-balance and interference with the cell cycle, ultimately leading to neuronal death. Identification of specific proteins protected from oxidation is a crucial step in understanding the interaction of Tat with astrocytes. In the current study, proteomics also was used to identify proteins that were specifically oxidized in SVGA-pcDNA cells treated with 3-NP compared to SVGA-Tat cells treated with 3-NP. We found beta-actin, calreticulin precursor protein, and synovial sarcoma X breakpoint 5 isoform A to have increased oxidation in control SVGA-pcDNA cells treated with 3-NP compared to SVGA-Tat cells treated with 3-NP. These results are discussed with reference to potential involvement of these proteins in HIV dementia and protection of astrocytes against oxidative stress by the HIV virus, a prerequisite for survival of a viral host cell.

Proteomics analysis of human astrocytes expressing the HIV protein Tat.

Astrocyte infection in HIV has been associated with rapid progression of dementia in a subset of HIV/AIDS patients. Astrogliosis and microglial activation are observed in areas of axonal and dendritic damage in HIVD. In HIV-infected astrocytes, the regulatory gene tat is over expressed and mRNA levels for Tat are elevated in brain extracts from individuals with HIV-1 dementia. Tat can be detected in HIV-infected astrocytes in vivo. The HIV-1 protein Tat transactivates viral and cellular gene expression, is actively secreted mainly from astrocytes, microglia and macrophages, into the extracellular environment, and is taken up by neighboring uninfected cells such as neurons. The HIV-1 protein Tat released from astrocytes reportedly produces trimming of neurites, mitochondrial dysfunction and cell death in neurons, while protecting its host, the astrocyte. We utilized proteomics to investigate protein expression changes in human astrocytes intracellularly expressing Tat (SVGA-Tat). By coupling 2D fingerprinting and identification of proteins by mass spectrometry, we identified phosphatase 2A, isocitrate dehydrogenase, nuclear ribonucleoprotein A1, Rho GDP dissociation inhibitor alpha, beta-tubulin, crocalbin like protein/calumenin, and vimentin/alpha-tubulin to have decreased protein expression levels in SVGA-Tat cells compared to the SVGA-pcDNA cells. Heat shock protein 70, heme oxygenase-1, and inducible nitric oxide synthase were found to have increased protein expression in SVGA-Tat cells compared to controls by slotblot technique. These findings are discussed with reference to astrocytes serving as a reservoir for the HIV virus and how Tat promotes survival of the astrocytic host.

The critical role of methionine 35 in Alzheimer's amyloid beta-peptide (1-42)-induced oxidative stress and neurotoxicity.

Amyloid beta-peptide (1-42) [Abeta(1-42)] has been proposed to play a central role in the pathogenesis of Alzheimer's disease, a neurodegenerative disorder associated with cognitive decline and aging. AD brain is under extensive oxidative stress, and Abeta(1-42) has been shown to induce protein oxidation, lipid peroxidation, and reactive oxygen species formation in neurons and synaptosomes, all of which are inhibited by the antioxidant vitamin E. Additional studies have shown that Abeta(1-42) induces oxidative stress when expressed in vivo in Caenorhabditis elegans, but when methionine 35 is replaced by cysteine, the oxidative stress is attenuated. This finding coupled with in vitro studies using mutant peptides have demonstrated a critical role for methionine 35 in the oxidative stress and neurotoxic properties of Abeta(1-42). In this review, we discuss the role of methionine 35 in the oxidative stress and neurotoxicity induced by Abeta(1-42) and the implications of these findings in the pathogenesis of AD.

Gamma-glutamylcysteine ethyl ester-induced up-regulation of glutathione protects neurons against Abeta(1-42)-mediated oxidative stress and neurotoxicity: implications for Alzheimer's disease.

Glutathione (GSH) is an important endogenous antioxidant found in millimolar concentrations in the brain. GSH levels have been shown to decrease with aging. Alzheimer's disease (AD) is a neurodegenerative disorder associated with aging and oxidative stress. Abeta(1-42) has been shown to induce oxidative stress and has been proposed to play a central role in the oxidative damage detected in AD brain. It has been shown that administration of gamma-glutamylcysteine ethyl ester (GCEE) increases cellular levels of GSH, circumventing the regulation of GSH biosynthesis by providing the limiting substrate. In this study, we evaluated the protective role of up-regulation of GSH by GCEE against the oxidative and neurotoxic effects of Abeta(1-42) in primary neuronal culture. Addition of GCEE to neurons led to an elevated mean cellular GSH level compared with untreated control. Inhibition of gamma-glutamylcysteine synthetase by buthionine sulfoximine (BSO) led to a 98% decrease in total cellular GSH compared with control, which was returned to control levels by addition of GCEE. Taken together, these results suggest that GCEE up-regulates cellular GSH levels which, in turn, protects neurons against protein oxidation, loss of mitochondrial function, and DNA fragmentation induced by Abeta(1-42). These results are consistent with the notion that up-regulation of GSH by GCEE may play a viable protective role in the oxidative and neurotoxicity induced by Abeta(1-42) in AD brain.

Gamma-glutamylcysteine ethyl ester protection of proteins from Abeta(1-42)-mediated oxidative stress in neuronal cell culture: a proteomics approach.

Protein oxidation mediated by amyloid beta-peptide (1-42) (Abeta[1-42]) has been proposed to play a central role in the pathogenesis of Alzheimer's disease (AD), a neurodegenerative disorder associated with aging and the loss of cognitive function. The specific mechanism by which Abeta(1-42), the primary component of the senile plaque and a pathologic hallmark of AD, contributes to the oxidative damage evident in AD brain is unknown. Moreover, the specific proteins that are vulnerable to oxidative damage induced by Abeta(1-42) are unknown. Identification of such proteins could contribute to our understanding of not only the role of Abeta(1-42) in the pathogenesis of AD, but also provide insight into the mechanisms of neurodegeneration at the protein level in AD. We report the proteomic identification of two proteins found to be oxidized significantly in neuronal cultures treated with Abeta(1-42): 14-3-3zeta and glyceraldehyde-3-phosphate dehydrogenase. We also report that pretreatment of neuronal cultures with gamma-glutamylcysteine ethyl ester, a compound that supplies the limiting substrate for the synthesis of glutathione and results in the upregulation of glutathione in neuronal cultures, protects both proteins against Abeta(1-42)-mediated protein oxidation.

Amyloid beta-peptide(1-42) contributes to the oxidative stress and neurodegeneration found in Alzheimer disease brain.

Oxidative stress is extensive in Alzheimer disease (AD) brain. Amyloid beta-peptide (1-42) has been shown to induce oxidative stress and neurotoxicity in vitro and in vivo. Genetic mutations that result in increased production of Abeta1-42 from amyloid precursor protein are associated with an early onset and accelerated pathology of AD. Consequently, Abeta1-42 has been proposed to play a central role in the pathogenesis of AD as a mediator of oxidative stress. In this review, we discuss the role of Abeta1-42 in the lipid peroxidation and protein oxidation evident in AD brain and the implications of such oxidative stress for the function of various proteins that we have identified as specifically oxidized in AD brain compared to control, using proteomics methods. Additionally, we discuss the critical role of methionine 35 in the oxidative stress and neurotoxic properties exhibited by Abeta1-42.

Role of phenylalanine 20 in Alzheimer's amyloid beta-peptide (1-42)-induced oxidative stress and neurotoxicity.

Senile plaques are a hallmark of Alzheimer's disease (AD), a neurodegenerative disease associated with cognitive decline and aging. Abeta(1-42) is the primary component of the senile plaque in AD brain and has been shown to induce protein oxidation in vitro and in vivo. Oxidative stress is extensive in AD brain. As a result, Abeta(1-42) has been proposed to play a central role in the pathogenesis of AD; however, the specific mechanism of neurotoxicity remains unknown. Recently, it has been proposed that long distance electron transfer from methionine 35 to the Cu(II) bound at the N terminus of Abeta(1-42) occurs via phenylalanine 20. Additionally, it was proposed that substitution of phenylalanine 20 of Abeta(1-42) by alanine [Abeta(1-42)F20A] would lessen the neurotoxicity induced by Abeta(1-42). In this study, we evaluate the predictions of this theoretical study by determining the oxidative stress and neurotoxic properties of Abeta(1-42)F20A relative to Abeta(1-42) in primary neuronal cell culture. Abeta(1-42)F20A induced protein oxidation and lipid peroxidation similar to Abeta(1-42) but to a lesser extent and in a manner inhibited by pretreatment of neurons with vitamin E. Additionally, Abeta(1-42)F20A affected mitochondrial function similar to Abeta(1-42), albeit to a lesser extent. Furthermore, the mutation does not appear to abolish the ability of the native peptide to reduce Cu(II). Abeta(1-42)F20A did not compromise neuronal morphology at 24 h incubation with neurons, but did so after 48 h incubation. Taken together, these results suggest that long distance electron transfer from methionine 35 through phenylalanine 20 may not play a pivotal role in Abeta(1-42)-mediated oxidative stress and neurotoxicity.

Rodent Abeta(1-42) exhibits oxidative stress properties similar to those of human Abeta(1-42): Implications for proposed mechanisms of toxicity.

Alzheimer's disease is a neurodegenerative disorder associated with aging and cognitive decline. Amyloid beta peptide (1-42) [Abeta(1-42)] is a primary constituent of senile plaques - a hallmark of Alzheimer's disease - and has been implicated in the pathogenesis of the disease. Previous studies have shown that methionine residue 35 of beta(1-42) may play a critical role in Abeta(1-42)-mediated oxidative stress and neurotoxicity. Several additional mechanisms of neurotoxicity have been proposed, including the role of Cu(II) binding and reduction to produce hydrogen peroxide and the role of peptide aggregation. It has been reported that rodent Abeta is less likely to form larger beta-sheet structures, and consequently, large aggregates. As a consequence of the lack of deposition of the peptide in rodent brain, rodent Abeta has been proposed to be non-toxic. Additionally, the sequence of the rodent variety of Abeta(1-42) contains three amino acid substitutions compared to the human sequence. These substitutions include the shift of arginine 5, trysosine 10, and histidine 13 to glycine, phenylalanine, and arginine, respectively. This shift in sequence within the Cu(II) binding region of the peptide results in a decrease in the ability of the rodent Abeta peptide to reduce Cu(II) to Cu(I) compared to the human Abeta peptide. As a result of the effect of the amino acid variations on the ability of the rodent peptide to reduce Cu(II) to Cu(I) compared to the human peptide, the rodent beta has been proposed to lack oxidative stress properties. In this study, the oxidative stress and neurotoxic properties of rodent beta(1-42) [Abeta(1-42)Rat] were evaluated and compared to those of human Abeta(1-42). Both human Abeta(1-42) and beta(1-42)Rat were found to have a significant effect on neuronal DNA fragmentation, loss of neuritic networks, and cell viability. beta(1-42) Rat was found to cause a significant increase in both protein oxidation and lipid peroxidation, similar to Abeta(1-42), both of which were inhibited by the lipid-soluble, chain breaking antioxidant vitamin E, suggesting that reactive oxygen species play a role in the Abeta-mediated toxicity. Taken together, these results suggest that Cu(II) reduction may not play a critical role inbeta(1-42)Rat-induced oxidative stress, and that the oxidative stress exhibited by this peptide may be a consequence of the presence of methionine 35, similar to the findings associated with the native human beta(1-42) peptide.