Oligomycin and antimycin A prevent nitric oxide-induced opoptosis by blocking cytochrome C leakage

Nitric oxide (NO) Is a potent inducer of apoptosis, and Its cytotoxicity is closely related to mitochondrial dysfunction. In this study we investigated the effects of a FOF1-ATPdse inhibitor, oligomycin, and a mitochondrial respiratory chain complex III inhibitor, antimycin A, on NO-induced apoptosis. We used a normal rat gastricepithelium cell line, RGM-1, treated with a pure NO donor, NOC-1-1-hydroxy-2oxo-3,3-bis(2-aminoethyl)- 1-triazene - in the presence or absence of oligomycin or antimycin A. Changes in the expressions of Bax or Bcl-2 proteins, release of cytochrome C from mitochondria into the cytosol, activation of caspase-3, and changes in the mitochondrial membrane potential (Deltapsi) were measured with the use of Western blotting, colorimetric assays, and a mitochondrial potential sensor, JC-1 dye. Treatment with NOC-18 Induced dose-dependent apoptotic cell death in RGM-1 cells. Cell death was accompanied by mitochondrial depolarization, increases in Bax protein expression and cytochrome C leakage, and, subsequently, caspase-3 activation. Ollgomycin and antimycin A prevented NO-induced apoptosis in a dose-dependent fashion by preventing cytochrome C-release independent of Bcl-2 expression. However, neither compound affected the up-regulation of Bax protein. On the one hand, oligomyclin treatment was not accompanied by a decline in Deltapsi. On the other hand, antimycin A treatment decreased Deltapsi regardless.of NOC-18 treatment. The findings of this study suggest that various functional molecules that constitute the mitochondrial respiratory chain may contribute to cytochrome C release that occurs during NO-induced apoptosis.