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

Figure 1 Isolation of hamster biliary epithelial cells. A: Phase contrast microscopy revealing a small amount of hamster gallbladder epithelial cells growing on the collagen gels 24 h after culture (× 100); B: High magnification of hamster gallbladder epithelial cells demonstrating cuboidal cells around the biliary fragments (× 400); C: Phase contrast microscopy showing widely extended gallbladder epithelial cells on the surface of the gel 7 d after culture (× 40).

Figure 2 High performance liquid chromatography showing significantly elevated NO₂^- + NO₃^- levels in the CM group compared with the control group, similar NO generation in the CM + L-NMMA group and control group, being significantly lower than that in the CM group.

Figure 3 iNOS mRNA expression in gallbladder epithelial cells in the CM group and no iNOS mRNA expression in the control group.

Figure 4 NO-dependent DNA damage evaluated by comet assay. A: Fluorescence microscopy showing the apparent comet tail in gallbladder cells stimulated by the cytokine mixture and intact spherical nuclei of the cells in the control group and CM + L-NMMA group; B: Analysis of the proportion of DNA migrated to comet tails using NIH image showing a significantly higher level of DNA damage in the CM group than in the control group, which decreased to the control level after the addition of L-NMMA.