Chlorpyrifos oxon crosslinking of amyloid beta 42 peptides is a new route for generation of self-aggregating amyloidogenic oligomers that promote Alzheimer's disease

Abstract

Epidemiological evidence suggests that people chronically exposed to organophosphorus pesticides are at increased risk of neurodegenerative disease. Covalently linked amyloid beta dimers have been isolated from the brains of Alzheimer's patients. The toxic forms of amyloid beta are amyloid dimers that spontaneously oligomerize. In the present report we treated recombinant and synthetic amyloid beta (1–42) with 1 mM chlorpyrifos oxon or 1 mM paraoxon. The trypsin-digested samples were analyzed by liquid chromatography tandem mass spectrometry on an Orbitrap Fusion Lumos mass spectrometer. Data were searched with Protein Prospector software. We found two new types of crosslinks in amyloid dimers. An isopeptide Asp-Asp link occurred between the N-terminal amine of Asp 1 in one peptide and the beta carboxyl group of Asp 1 in another peptide. An Asp-Arg link occurred between the guanidino group of Arg 5 in one peptide and the beta carboxyl group of Asp 1 in another peptide. These results show that the active metabolites of the pesticides chlorpyrifos and parathion catalyze the crosslinking of amyloid beta (1–42) into toxic dimers. It was concluded that the increased risk of neurodegenerative disease in people exposed to organophosphorus pesticides could be explained by the crosslinking activity of these chemicals. Data are available via ProteomeXchange with identifier PXD034163.