BETA-AMYLOID-INDUCED TOXICITY IN RAT HIPPOCAMPAL CELLS - IN-VITRO EVIDENCE FOR THE INVOLVEMENT OF FREE-RADICALS

The conditions under which amyloid is toxic to primary rat hippocampal neurons were investigated. Synthetic A beta(1-42) peptide elicited ne urotoxic activity following ''aging'' for 7 to 14 days at 37 degrees C in Modified Eagles Media. Neurotoxicity included decreases in neurite length, cell number, and a loss in 3-[4,5-dimethylthiazol-2-yl]-2,5-d iphenyl tetrazolium bromide reduction. In contrast, the addition of th e media supplement B27, during the aging process, promoted the neurotr ophic actions of aged A beta(1-42), as indicated by an increase in neu rite length and the number of cells possessing neurites, and attenuate d toxicity. The differences in the biological actions elicited by thes e two preparations of aged peptide were attributed to the presence of the B27 components. B27 consists of a mixture of agents that provide p rotection against oxidative damage. In support, aging A beta(1-42) in the presence of superoxide dismutase and catalase, two components of B 27, significantly reduced the the toxic actions of peptide; hence, sug gesting that free radicals may be required for the toxicity that accum ulates during the aging of the peptide. To determine the contribution of particular amino acid residues in amyloid toxicity, studies were ca rried out with an aged preparation of the A beta(1-42) analog, A beta( 1-42)Nle(35). Findings from these studies suggest that the methionine residue may play a part, but is not required, for amyloid toxicity to occur.