[Oxidative Stress, Beta-amyloide Peptide and Alzheimer's Disease]

Alzheimer's disease, the leading cause of dementia in the elderly is characterized by the presence in the brain of senile plaques formed of insoluble fibrillar deposits of beta-amyloid peptide. This peptide is normally produced in a monomeric soluble form and it is present in low concentrations in the blood and spinal fluid. At physiological concentrations, this peptide is a neurotrophic and neuroprotector factor; nevertheless, with aging and particularly in Alzheimer's disease this peptide accumulates, favors the formation of insoluble fibrils and causes neurotoxicity. beta-Amyloid peptide toxicity has been associated with the generation of free radicals that in turn promote lipid peroxidation and protein oxidation. Through the recognition of specific receptors such as the scavenger receptor, the beta-amyloid peptide becomes internalized in the form of aggregates. Independently of the way the peptide enters the cell, it generates oxidative stress that eventually triggers a state of neurotoxicity and cell death. Recent studies in our laboratory have shown the effect caused by an extracellular oxidative stress upon the internalization of the scavenger receptor. We have also demonstrated that the process of protein translation of molecules implicated in the mechanism of endocytosis through the scavenger receptor, such as the case of beta-adaptin, is arrested in microglial cells treated with beta-amyloid.