Intestinal inflammation induces genotoxicity to extraintestinal tissues and cell types in mice

Chronic intestinal inflammation leads to increased risk of colorectal and small intestinal cancers and is also associated with extraintestinal manifestations such as lymphomas, other solid cancers and autoimmune disorders. We have previously found that acute and chronic intestinal inflammation causes DNA damage to circulating peripheral leukocytes, manifesting a systemic effect in genetically and chemically induced models of intestinal inflammation. Our study addresses the scope of tissue targets and genotoxic damage induced by inflammation-associated genotoxicity. Using several experimental models of intestinal inflammation, we analyzed various types of DNA damage in leukocyte subpopulations of the blood, spleen, mesenteric and peripheral lymph nodes and in intestinal epithelial cells, hepatocytes and the brain. Genotoxicity in the form of DNA single- and double-stranded breaks accompanied by oxidative base damage was found in leukocyte subpopulations of the blood, diverse lymphoid organs, intestinal epithelial cells and hepatocytes. The brain did not demonstrate significant levels of DNA double-stranded breaks as measured by γ-H2AX immunostaining. CD4(+) and CD8(+) T-cells were most sensitive to DNA damage versus other cell types in the peripheral blood. In vivo measurements and in vitro modeling suggested that genotoxicity was induced by increased levels of systemically circulating proinflammatory cytokines. Moreover, genotoxicity involved increased damage rather than reduced repair, as it is not associated with decreased expression of the DNA double-strand break recognition and repair protein, ataxia telangiectasia mutated. These findings suggest that levels of intestinal inflammation contribute to the remote tissue burden of genotoxicity, with potential effects on nonintestinal diseases and cancer.