CELL-DEATH INDUCED BY BETA-AMYLOID-1-40 IN MES-23.5 HYBRID CLONE - THE ROLE OF NITRIC-OXIDE AND NMDA-GATED CHANNEL ACTIVATION LEADING TO APOPTOSIS

The molecular events associated with beta-amyloid-induced neuronal inj ury remain incompletely characterized. Using a substantia nigra/neurob lastoma hybrid cell line (MES 23.5) synthetic beta-amyloid 1-40 induce d a time and dose-dependent apoptotic cell death which was characteriz ed by cell shrinkage and fragmentation of DNA, and was inhibited by au rintricarboxylic acid (ATA), and cycloheximide (CHX). Following beta-a myloid 1-40 treatment, cyclic GMP, an index of NO synthesis, was incre ased in MES 23.5 cells. The NO scavenger hemoglobin, as well as the NO synthase inhibitors N-G-monomethyl-L-arginine acetate (L-NMMA) and L- N-5-(1-imin-oethyl)ornithine hydrochloride (L-NIO) attenuated such inc reases. These same inhibitors and scavengers also significantly preven ted cytotoxicity. beta-Amyloid also induced an early and transient inc rease in intracellular calcium as monitored with laser scanning confoc al microscopy and Fluo-3 imaging. These induced calcium transients cou ld be significantly blocked by the N-methyl-D-aspartic acid (NMDA) rec eptor antagonist MK-801. Pretreatment with MK-801 or removal of extrac ellular Ca2+ also reduced beta-amyloid-induced NO production and neuro toxicity. Furthermore, beta-amyloid neurotoxicity was greatly enhanced in the absence of Mg2+ or in the presence of glutamate or NMDA. These data suggest that beta-amyloid can lead to apoptotic cell death throu gh a NO mediated process possibly triggered by Ca2+ entry through acti vated NMDA-gated channels.