Amyloid beta-peptide (1-42)-mediated oxidative stress and neurotoxicity: I. The role of methionine 35. II. Proteomic identification of specifically oxidized proteins in models of Alzheimer's disease

The studies described in this dissertation were conducted with the objective of gaining greater insight into the role of amyloid beta-peptide (1--42) [Abeta(1--42)]-induced oxidative stress in the pathogenesis of Alzheimer's disease (AD), a neurodegenerative disorder associated with aging and cognitive decline. Senile plaques are a hallmark AD and are composed primarily of Abeta(1--42). AD brain is under extensive oxidative stress and Abeta(1--42) has been shown to induce oxidative stress in vitro and in vivo. In this dissertation, the mechanisms of Abeta(1--42)-induced oxidative stress and neurotoxicity were evaluated. Additionally, specific targets of in vitro and in vivo Abeta(1--42)-induced protein oxidation were identified by proteomic analysis. Finally, upregulation of glutathione by gamma-glutamylcysteine ethyl ester was shown to protect neurons against Abeta(1--42)-mediated protein oxidation.; Methionine 35 was shown to play a primary role in the oxidative stress and neurotoxicity exhibited by Abeta(1--42). Moreover, the thioether chemistry of methionine was shown to contribute to the oxidative stress and neurotoxicity of Abeta(1--42) Further, vitamin E protected neurons against the oxidative stress induced by Abeta(1--42) and all of the methionine containing peptide studied, suggesting the mechanism is associated with reactive oxygen species.; It was demonstrated that upregulation of glutathione by gamma-glutamylcysteine ethyl ester protected neurons against Abeta(1--42)-induced protein oxidation, but not lipid peroxidation. Proteomic analysis showed that gamma-glutamylcysteine ethyl ester protected specific neuronal proteins against oxidation induced by Abeta(1--42), supporting the role for antioxidant intervention as a therapeutic in AD. Additional proteomic studies were conducted to investigate the oxidative effects of Abeta(1--42) in synaptosomal preparations and in transgenic Caenorhabditis elegans (C. elegans ) expressing Abeta(1--42). Finally, proteomics techniques were used to evaluate the specific regional protein oxidation induced by Abeta(1--42) injected into rat brain.; Taken together, these findings support the role of Abeta(1--42) as a mediator of oxidative stress and as a causative agent in the pathogenesis of AD. The proteins identified in these studies are involved in a variety of cellular functions including: energy metabolism, proteasome function, excitotoxicity, neuronal communication, antioxidant functions, and cytoskeletal integrity, all of which are affected in AD brain.