Abstract 1877: Involvement of mitochondrial respiratory complexes in capsaicin mediated ROS generation and apoptosis in pancreatic cancer cells

Abstract

Abstract Capsaicin (N-vanillyl-8-methyl-nonenamide) is a homovanillic acid derivative and the spicy component of chili pepper. In our previous study, we have shown that capsaicin induced apoptosis in pancreatic cancer cells was associated with the generation of ROS and persistent disruption of mitochondrial membrane potential. However, the exact mechanism by which capsaicin causes ROS generation and cell death was not fully clear. We now evaluated the effect of capsaicin on mitochondrial respiratory complexes and ROS generation. The generation of ROS was about 3 fold and as early as 2h after capsaicin treatment in BxPC-3 cells and inhibited by rotenone and antimycin-A but not by 4-nitropropionic acid or sodium azide. Rotenone, 4-nitropropionic acid, antimycin A and sodium azide are the inhibitors of NADH-ubiquinone oxidoreductase (Complex I), succinate ubiquinone oxidoreductase (Complex II), ubiquinol cytochrome c reductase (Complex III) and cytochrome c oxidase (Complex IV) respectively. To further delineate the mechanism of ROS generation, effect of capsaicin was evaluated on the enzymatic activities of above-mentioned mitochondrial complexes in BxPC-3 cells. Our results show that capsaicin treatment significantly reduced complex I and complex III enzymatic activities suggesting the involvement of mitochondrial complex I and III in capsaicin mediated ROS generation. Capsaicin however did not affected complex II or complex IV activities. Our results further revealed that about 3 fold apoptosis induced by capsaicin in BxPC-3 cells was inhibited by rotenone and antimycin-A. Moreover, capsaicin mediated release of cytochrome c and AIF and cleavage of caspase-9 and caspase-3 were significantly inhibited by rotenone and antimycin-A. On the other hand, catalase or EUK (a mimetic of catalase) pretreatment block capsaicin-mediated ROS generation and apoptosis. Taken together, our results suggest the involvement of mitochondrial complex I and III in capsaicin mediated ROS generation and apoptosis. [Supported in part by RO1 grants CA 106953 and CA129038 (to SKS) awarded by National Cancer Institute]. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1877.