Abstract
PURPOSE: The aim of this study was to evaluate the effect of inflammation on NAD(P)H: quinone oxidoreductase-1 (NQO1), the xenobiotic metabolizing and antioxidant enzyme protecting cells against electrophiles and reactive oxygen species in biliary cancer (cholangiocarcinoma) cells. METHODS: Human cholangiocarcinoma cell line, KKU-OCA17 and HeLa Chang liver cells were treated with inflammatory cytokine combinations (interferon-gamma, interleukin-1beta and tumor necrosis factor-alpha) for 48 h before NQO1 activity was assayed. Oxidant status was examined by assays of formation of nitric oxide (NO) and superoxide, and glutathione (GSH) levels. Expression of NQO1 was assessed by a reverse transcription and polymerase chain reaction. Effects of S-nitroso-glutathione (GSNO) were examined if the effects of inflammatory cytokines could be mimicked by nitric oxide donor. RESULTS: NQO1 activity in KKU-OCA17 and HeLa Chang liver cells was suppressed by cytokine combination. Cytokines induced formation of NO and suppression of redox ratios of GSH and glutathione disulfide (GSSG). GSNO produced the similar effects as cytokines on KKU-OCA17, in contrast, GSNO induced increase of NQO1 activity in HeLa Chang liver cells. The treatment of cytokines or GSNO suppressed expression of NQO1 in KKU-OCA17 and HeLa Chang liver cells. CONCLUSIONS: Inflammatory cytokines induced oxidative stress and this is associated with suppression of NQO1, whereas may contribute to differential susceptibility of biliary epithelial cells to chemical-induced cytotoxicity and carcinogenesis.