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 ρ0 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.

A Comprehensive Review of the Carcinogenic and Anticarcinogenic Potential of Capsaicin

“…No mutagenic activity was observed in any of the five bacterial strains, in any of the activation conditions. Essentially identical results were reported by Proudlock et al (2004). Tsuchiya et al (2011) demonstrated mutagenicity of chili pepper extract in strain TA98, while pure capsaicin was inactive in the same assay; subsequent analysis of the chili pepper samples identified the presence of carcinogenic aflatoxins B1 and G1.…”

“…Arceo et al (1995) also showed a significant increase in number of peripheral blood cells with micronuclei. The micronucleus assay was repeated by groups with >98% pure capsaicin, both times yielding negative results: Chanda et al (2004) administered capsaicin orally to male mice at dose levels up to 800 mg/kg and females received 200 mg/kg; Proudlock et al (2004) administered capsaicin subcutaneously using an escalating dosing regime up to 500 mg/kg. Earlier, Villaseñor et al (1993) had also shown that capsaicin at a maximum tolerable dose of 1.22 mg/kg (intraperitoneally) was not mutagenic in the same assay.…”

Ablation of sensory neurons in a genetic model of pancreatic ductal adenocarcinoma slows initiation and progression of cancer

“…To examine how sensory neurons impact PDAC initiation and progression, we first determined if neonatal capsaicin had direct effects on pancreatic cells because previous studies using cancer-derived cell lines showed it affected apoptosis and proliferation (28)(29)(30)(31)(32)(33)(34). The neurotoxic effects of neonatal capsaicin treatment are assumed to be via binding to TRPV1, the vanilloid receptor specific for capsaicin.…”

Alantolactone induces apoptosis in glioblastoma cells via GSH depletion, ROS generation, and mitochondrial dysfunction

“…In addition to GSH, catalase and SOD play important role to detoxify hydrogen peroxide and super-oxides, respectively. A number of therapeutic agents have been shown to increase intracellular ROS generation by downregulating antioxidant enzymes such as catalase and SOD (7,20,23). However, some other studies have reported that reduction in intracellular GSH is necessary for the formation of ROS (10,24).…”

“…Cardiolipin oxidation was determined by staining the cells with 10-N-nonyl acridine orange (NAO), a probe specific for mitochondrial membrane cardiolipin (20). Briefly, U87 cells were incubated with 40 lM alantolactone for 0, 6, and 12 h. After treatment, cells were further incubated with DCFH-DA (10 lM), Rhodamine 123 (5 lg/ml), and NAO (5 lM) in the dark for 30 min.…”