Apurinic/apyrimidinic endonuclease 1 prevents oxidative DNA damage in intestinal epithelial cells induced by genotoxic Escherichia coli NC101.

BACKGROUND

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional protein that regulates host responses to oxidative stress. We investigated its role in controlling DNA damage following infection with a genotoxic intestinal microbe.

METHODS

Mice rendered hypomorphic for APE1 were crossed with tamoxifen (TMX)-inducible or constitutive Vil1ACre mice to yield intestinal epithelial cell-targeted knockout mice (Apex1iΔIEC or Apex1cΔIEC). Mice were infected with a genotoxic strain of E. coli (pks + E. coli NC101) to determine the APE1-sensitive effects on the accumulation of reactive oxygen species (ROS) and oxidative DNA damage. Murine and human primary colonic epithelial cell lines genetically altered to reduce APE1 expression were infected with a pks-deficient, the genotoxic E. coli strain or its synthetic colibactin genotoxin.

RESULTS

APE1 expression was markedly diminished in enterocytes of Apex1iΔIEC mice, which was accompanied by increased constitutive epithelial cell DNA damage comparable to that observed in APE1 hypomorphic mice. The DNA damage, as indicated by γH2AX levels, was attenuated in germ-free Apex1iΔIEC mice and in APE1-hypomorphic mice treated with broad-spectrum antibiotics, indicating that commensal bacteria exert genotoxic effects that are unmasked by the loss of APE1 function. Levels of ROS and oxidative DNA damage in APE1-deficient primary colonic epithelial cells were increased significantly by pks + E. coli NC101 or its synthetic colibactin 742 genotoxin and this damage was prevented by prior treatment with an antioxidant.

CONCLUSIONS

APE1 protects epithelial cells by inhibiting the accumulation of ROS and oxidative DNA damage induced by intestinal bacteria, including the colibactin produced by E. coli NC101.