Superoxide anions mediate veratridine-induced cytochrome c release and caspase activity in bovine chromaffin cells

1 Mitochondrial mechanisms involved in veratridine-induced chromaffin cell death have been explored. 2 Exposure to veratridine (30 pm, 1 h) produces cytochrome c release to the cytoplasm that seems to be mediated by superoxide anions and that is blocked by cyclosporin A (10 pm), MnTBAP (10 nm), catalase (100 IU ml(-1)) and vitamin E (50 mum). 3 Following veratridine treatment, there is an increase in caspase-like activity, blocked by vitamin E (50 mum) and the mitochondrial permeability transition pore blocker cyclosporin A (10 mum). 4 Superoxide anions open the mitochondrial permeability transition pore in isolated mitochondria, an effect that is blocked by vitamin E (50 mum) and cyclosporin A (10 mum), but not by the Ca2+ uniporter blocker ruthenium red (5 mum). 5 These results strongly suggest that under the stress situation caused by veratridine, superoxide anions become important regulators of mitochondrial function in chromaffin cells. 6 Exposure of isolated bovine chromaffin mitochondria to Ca2+ results in mitochondrial swelling. This effect was prevented by ruthenium red (5 mum) and cyclosporin A (10 mum), while it was not modified by vitamin E (50 mum). 7 Veratridine (30 mum, 1 h) markedly decreased total glutathione and GSH content in bovine chromaffin cells. 8 In conclusion, superoxide anions seem to mediate veratridine-induced cytochrome e release, decrease in total glutathione, caspase activation and cell death in bovine chromaffin cells.