amyloid-beta-peptides and 3-nitrotyrosine

Glycation and nitrotyrosination are pathological posttranslational modifications that make proteins prone to losing their physiological properties. Since both modifications are increased in Alzheimer's disease (AD) due to amyloid-β peptide (Aβ) accumulation, we have studied their effect on albumin, the most abundant protein in cerebrospinal fluid and blood. Brain and plasmatic levels of glycated and nitrated albumin were significantly higher in AD patients than in controls. In vitro turbidometry and electron microscopy analyses demonstrated that glycation and nitrotyrosination promote changes in albumin structure and biochemical properties. Glycated albumin was more resistant to proteolysis and less uptake by hepatoma cells occurred. Glycated albumin also reduced the osmolarity expected for a solution containing native albumin. Both glycation and nitrotyrosination turned albumin cytotoxic in a cell type-dependent manner for cerebral and vascular cells. Finally, of particular relevance to AD, these modified albumins were significantly less effective in avoiding Aβ aggregation than native albumin. In summary, nitrotyrosination and especially glycation alter albumin structural and biochemical properties, and these modifications might contribute for the progression of AD.

Topics: Aged; Albumins; Alzheimer Disease; Amyloid beta-Peptides; Brain; Cells, Cultured; Dose-Response Relationship, Drug; Endothelial Cells; Female; Glycosylation; Humans; Male; Molsidomine; Neurons; Peptide Fragments; Protein Aggregates; Protein Processing, Post-Translational; tau Proteins; Trypsin; Tyrosine

Part of the inflammatory response in Alzheimer's disease (AD) is the upregulation of the inducible nitric oxide synthase (NOS2) resulting in increased NO production. NO contributes to cell signaling by inducing posttranslational protein modifications. Under pathological conditions there is a shift from the signal transducing actions to the formation of protein tyrosine nitration by secondary products like peroxynitrite and nitrogen dioxide. We identified amyloid β (Aβ) as an NO target, which is nitrated at tyrosine 10 (3NTyr(10)-Aβ). Nitration of Aβ accelerated its aggregation and was detected in the core of Aβ plaques of APP/PS1 mice and AD brains. NOS2 deficiency or oral treatment with the NOS2 inhibitor L-NIL strongly decreased 3NTyr(10)-Aβ, overall Aβ deposition and cognitive dysfunction in APP/PS1 mice. Further, injection of 3NTyr(10)-Aβ into the brain of young APP/PS1 mice induced β-amyloidosis. This suggests a disease modifying role for NOS2 in AD and therefore represents a potential therapeutic target.

Topics: Age Factors; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Animals; Biophysics; Brain; Disease Models, Animal; Drug Combinations; Electric Stimulation; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation; Hippocampus; Humans; Immunoprecipitation; In Vitro Techniques; Long-Term Potentiation; Maze Learning; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Neurons; Nitric Oxide Synthase Type II; Patch-Clamp Techniques; Peptide Fragments; Peroxynitrous Acid; Plaque, Amyloid; Presenilin-1; Tyrosine

Alzheimer disease (AD) is a neurodegenerative disorder characterized clinically by progressive memory loss and subsequent dementia and neuropathologically by senile plaques, neurofibrillary tangles, and synapse loss. Interestingly, a small percentage of individuals with normal antemortem psychometric scores meet the neuropathological criteria for AD (termed 'preclinical' AD (PCAD)). In this study, inferior parietal lobule (IPL) from PCAD and control subjects was compared for oxidative stress markers by immunochemistry, amyloid beta peptide by ELISA, and identification of protein expression differences by proteomics. We observed a significant increase in highly insoluble monomeric Abeta42, but no significant differences in oligomeric Abeta nor in oxidative stress measurements between controls and PCAD subjects. Expression proteomics identified proteins whose trends in PCAD are indicative of cellular protection, possibly correlating with previous studies showing no cell loss in PCAD. Our analyses may reveal processes involved in a period of protection from neurodegeneration that mimic the clinical phenotype of PCAD.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Case-Control Studies; Electrophoresis, Gel, Two-Dimensional; Enzyme-Linked Immunosorbent Assay; Female; Humans; Lipid Peroxidation; Male; Oxidative Stress; Parietal Lobe; Peptide Fragments; Protein Carbonylation; Proteomics; Spectrum Analysis; Tyrosine

This study is to investigate the influence and mechanism of action of asymmetrical dimethylarginine (ADMA) and the induced oxidative stress level on Alzheimer's disease (AD) incidence. ADMA concentration, nitric oxide, Abeta(40)/Abeta(42) ratio, inducible NO synthase (iNOS) activity and the concentrations of the induced free radicals including malondialdehyde (MDA), 3-nitrotyrosine (3-NT) and peroxynitrite (ONOO-) in the cerebrospinal fluid (CSF) from 34 neurologically normal controls and 37 AD patients were quantitatively determined and statistically compared. The results showed that the ADMA concentration significantly decreased in AD patients, and it showed negative correlation with the NO, iNOS activity, and showed positive correlation with MMSE score. ADMA concentration was negatively correlated with Abeta(40)/Abeta(42) ratio (P<0.01) with the observation that Abeta(40)/Abeta(42) ratio increased while ADMA level decreased in CSF in AD patients. The concentration levels of MDA, 3-NT and ROS significantly increased compared with the control with all the P values less than 0.05. These findings suggested that the ADMA disorder and the oxidative damage effect of the induced free radicals in CSF of AD patients are an important mechanism of AD incidence, and their joint regulation may provide new idea for the prevention and clinical treatment of AD.

Topics: Aged; Alzheimer Disease; Amyloid beta-Peptides; Arginine; Female; Humans; Male; Malondialdehyde; Middle Aged; Nitric Oxide; Nitric Oxide Synthase Type II; Oxidative Stress; Peptide Fragments; Peroxynitrous Acid; Reactive Oxygen Species; Tyrosine

Amyloid beta (Abeta) is a critical factor involved in the pathogenesis of Alzheimer's disease (AD). We have previously demonstrated that continuous intracerebroventricular infusion of Abeta1-40 induced a time-dependent expression of the inducible nitric oxide (NO) synthase (iNOS) and an overproduction of NO in the rat hippocampus. The pathophysiological significance of the overproduction of NO on brain function was manifested by an impairment of nicotine-evoked acetylcholine(ACh) release and memory deficits.(4) Molecular mechanisms by which NO participates in the Abeta-induced brain dysfunction, however, remain to be determined. Here we show that chronic Abeta1-40 infusion caused a robust peroxynitrite formation and subsequent tyrosine nitration of proteins in the hippocampus. Immunoprecipitation and Western blot analyses further revealed that synaptophysin, a synaptic protein, was a main target of tyrosine nitration. Chronic infusion of Abeta1-40 resulted in an impairment of nicotine-evoked ACh release as analyzed by microdialysis. Daily treatment with the iNOS inhibitor aminoguanidine (AG) or the peroxynitrite scavenger uric acid (UA) prevented the tyrosine nitration of synaptophysin as well as the impairment of nicotine-evoked ACh release induced by Abeta. Our findings suggest that the tyrosine nitration of synaptophysin is related to Abeta-induced impairment of ACh release.

Topics: Acetylcholine; Amyloid beta-Peptides; Animals; Cerebral Ventricles; Hippocampus; Infusions, Parenteral; Male; Microdialysis; Peptide Fragments; Peroxynitrous Acid; Rats; Rats, Wistar; Synaptophysin; Tyrosine

Senile plaques (SP), a neuropathological hallmark of Alzheimer's disease (AD), are characterized by extracellular accumulations of beta amyloid (A beta). SP predominantly contain A beta 42 with a small amount of associated A beta 40. We determined the neurotoxic properties of A beta 42 as compared to A beta 40 by injections into the frontal cortex of three month old C57BL/6 mice. A beta 42 was associated with a significantly larger area of glial fibrillary acidic protein (GFAP) immunoreactivity and a greater density of reactive astrocytes than A beta 40. Immunohistochemical staining for markers of oxidative damage against 3-nitrotyrosine (3-NT) and 8-hydroxydeoxyguanosine (8-OHDG) were significantly more intense around the A beta 42 injection compared to the A beta 40 injection sites. These findings are consistent with previous in vitro studies and suggest that A beta 42 is more neurotoxic and may generate more free radical damage than A beta 40.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Amyloid beta-Peptides; Animals; Astrocytes; Brain; Deoxyguanosine; Free Radicals; Frontal Lobe; Glial Fibrillary Acidic Protein; Male; Mice; Mice, Inbred C57BL; Microinjections; Neurotoxins; Peptide Fragments; Tyrosine