Nitration of cytochrome c attenuates its ability for the caspase cascade activation.

Peroxynitrite is now known as one of the most prominent reactive nitrogen species. It inhibits the mitochondrial electron transfer reaction, and induces cell death in various types of cells. However, the intracellular mechanisms involved in the cell death process are still unclear. In this paper, the nitration of cytochrome c was examined in peroxynitrite-treated C6 rat glioma cells, and the effect of peroxynitrite treatment on the ability of cytochrome c for the activation of caspase cascades was evaluated in vitro. It was shown that the viability of C6 rat glioma cells was decreased by the treatment of SIN-1, a continuous peroxynitrite generator, in a dose-dependent manner. Under this condition, the activation of caspase-3 and the fragmentation of poly-(ADP-ribose) polymerase (PARP) were not observed. It was also shown that cytochrome c was nitrated in C6 glioma cells under the same condition. With the cytosolic fraction from C6 cells, it was found that the nitrated cytochrome c, prepared by a repetitive low dose treatment with peroxynitrite, was less active in the cleavage of procaspase-3 in vitro, whereas the cytochrome c prepared by a single high dose treatment of peroxynitrite showed the normal activity. It was suggested that the peroxynitrite at low concentration for long duration induces the nitration of cytochrome c, and that that cytochrome c loses the ability for the induction of the caspase cascade activation.9th Biennial Meeting of the SFRR Internationa