A cell-based method for the detection of nanomolar concentrations of bioactive amyloid

A cell-based method for the detection of nanomolar concentrations of bioact ive amyloid peptide is described. The method is based upon the observation that fibrillogenic amyloid peptides specifically and dramatically enhance t he exocytosis of the intracellular vesicles that are involved in transporti ng the reduced tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltet razolium bromide (MTT formazan), with the formation of unique formazan crys tals on the cell surface. It is found that the ability of amyloid peptides to induce MTT formazan exocytosis is closely associated with both their neu rotoxicity and their ability to activate glia cells, two biological activit ies of amyloid peptides that are believed to cause neurodegeneration. This simple assay for bioactive amyloid species can be of great value in the scr eening of anti-amyloid drugs and in the study of amyloid fibrillogenesis wi th a cell-based model. (C) 2001 Academic Press.