In vitro aging of beta-amyloid protein causes peptide aggregation and neurotoxicity.

beta-Amyloid peptide forms the senile plaques of Alzheimer's disease and has been previously demonstrated to have both trophic and toxic effects on neurons in vitro. We report here that synthetic beta-amyloid peptide shows both aggregation and neurotoxicity after a 2-4 day incubation period, but is neurite-promoting and not toxic in its initially solubilized state. SDS-PAGE characterization shows that newly solubilized beta-amyloid is predominantly monomeric whereas incubated peptide has several high molecular weight species.