title: Role of mitochondrial electron transport chain complexes in capsaicin mediated oxidative stress leading to apoptosis in pancreatic cancer cells.
abstract: We evaluated the mechanism of capsaicin-mediated ROS generation in pancreatic cancer cells. The generation of ROS was about 4-6 fold more as compared to control and as early as 1 h after capsaicin treatment in BxPC-3 and AsPC-1 cells but not in normal HPDE-6 cells. The generation of ROS was inhibited by catalase and EUK-134. To delineate the mechanism of ROS generation, enzymatic activities of mitochondrial complex-I and complex-III were determined in the pure mitochondria. Our results shows that capsaicin inhibits about 2.5-9% and 5-20% of complex-I activity and 8-75% of complex-III activity in BxPC-3 and AsPC-1 cells respectively, which was attenuable by SOD, catalase and EUK-134. On the other hand, capsaicin treatment failed to inhibit complex-I or complex-III activities in normal HPDE-6 cells. The ATP levels were drastically suppressed by capsaicin treatment in both BxPC-3 and AsPC-1 cells and attenuated by catalase or EUK-134. Oxidation of mitochondria-specific cardiolipin was substantially higher in capsaicin treated cells. BxPC-3 derived ρ(0) cells, which lack mitochondrial DNA, were completely resistant to capsaicin mediated ROS generation and apoptosis. Our results reveal that the release of cytochrome c and cleavage of both caspase-9 and caspase-3 due to disruption of mitochondrial membrane potential were significantly blocked by catalase and EUK-134 in BxPC-3 cells. Our results further demonstrate that capsaicin treatment not only inhibit the enzymatic activity and expression of SOD, catalase and glutathione peroxidase but also reduce glutathione level. Over-expression of catalase by transient transfection protected the cells from capsaicin-mediated ROS generation and apoptosis. Furthermore, tumors from mice orally fed with 2.5 mg/kg capsaicin show decreased SOD activity and an increase in GSSG/GSH levels as compared to controls. Taken together, our results suggest the involvement of mitochondrial complex-I and III in capsaicin-mediated ROS generation and decrease in antioxidant levels resulting in severe mitochondrial damage leading to apoptosis in pancreatic cancer cells.
authors.affiliation: Department of Biomedical Sciences and Cancer Biology Center, School of Pharmacy, Texas Tech University of Health Sciences Center, Amarillo, Texas, United States of America.
authors.forename: Kartick C
authors.initials: KC
authors.lastname: Pramanik
authors.forename: Srinivas Reddy
authors.initials: SR
authors.lastname: Boreddy
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Srivastava
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002211:Capsaicin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002374:Catalase / Q000378:metabolism; D045744:Cell Line, Tumor; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D019803:Glutathione Disulfide / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects*; D010190:Pancreatic Neoplasms / Q000473:pathology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; D002211:Capsaicin; D019803:Glutathione Disulfide