Copper enhances amyloid-beta peptide neurotoxicity and non beta-aggregation: a series of experiments conducted upon copper-bound and copper-free amyloid-beta peptide.

Alzheimer's disease is characterized by the abnormal aggregation of amyloid-beta peptide (Abeta) in extracellular deposits known as senile plaques. However, the nature of the toxic Abeta species and its precise mechanism of action remain unclear. Previous reports suggest that the histidine residues are involved in copper-Abeta interaction, by which resulting in the neurotoxicity of Abeta and free radical damage. Here, we employed a mutant Abeta (Abeta H13R) in which a histidine residue was replaced by arginine. Copper facilitated the precipitation of both wild-type and mutant Abeta in the spectrophotometric absorbance assay but suppressed beta-structure aggregates according to Thioflavine-T assay. Wild-type Abeta alone is more cytotoxic but produced less amount of H(2)O(2) than AbetaH13R-copper complexes, suggesting that Abeta-membrane interaction may also implicated in the pathologic progress. Abeta toxicity is in positive correlation to its competence to aggregate despite the aggregation is mainly composed of non-beta fibril substances. In short, these findings may provide further evidence on the role of copper in the pathogenesis of Alzheimer's disease.