Inflammatory cytokines promote inducible nitric oxide synthase-mediated DNA damage in hamster gallbladder epithelial cells

AIM:To investigate the link between chronic biliary inflammation and carcinogenesis using hamster gallbladder epithelial cells. METHODS:Gallbladder epithelial cells were isolated from hamsters and cultured with a mixture of inflammatory cytokines including interleukin-1β, interferon-γ, and tumor necrosis factor-α.Inducible nitric oxide synthase (iNOS) expression, nitric oxide (NO) generation, and DNA damage were evaluated. RESULTS:NO generation was increased significantly following cytokine stimulation, and suppressed by an iNOS inhibitor.iNOS mRNA expression was demonstrated in the gallbladder epithelial cells during exposure to inflammatory cytokines.Furthermore, NO-dependent DNA damage, estimated by the comet assay, was significantly increased by cytokines, and decreased to control levels by an iNOS inhibitor. CONCLUSION:Cytokine stimulation induced iNOS expression and NO generation in normal hamster gallbladder epithelial cells, which was sufficient to cause DNA damage.These results indicate that NO-mediated genotoxicity induced by inflammatory cytokines through activation of iNOS may be involved in the process of biliary carcinogenesis in response to chronic inflammation of the biliary tree.