4-hydroxy-2-nonenal mediates genotoxicity and bystander effects caused by enterococcus faecalis-infected macrophages

Abstract

Background & Aims: Enterococcus faecalis is a human intestinal commensal that produces extracellular superoxide and promotes chromosome instability via macrophage-induced bystander effects. We investigated the ability of 4-hydroxy-2-nonenal (4-HNE), a diffusible breakdown product of ω-6 polyunsaturated fatty acids, to mediate these effects. Methods: 4-HNE was purified from E faecalisinfected macrophages; its genotoxicity was assessed in human colon cancer (HCT116) and primary murine colon epithelial (YAMC) cell lines. Results: 4-HNE induced G2M cell cycle arrest, led to formation γH2AX foci, and disrupted the mitotic spindle in both cell lines. Binucleate tetraploid cells that formed after incubation with 4-HNE were associated with the activation of stathmin and microtubule catastrophe. Silencing glutathione S-transferase α4, a scavenger of 4-HNE, increased the susceptibility of epithelial cells to 4-HNEinduced genotoxicity. Interleukin-10 knockout mice colonized with superoxide-producing E faecalis developed inflammation and colorectal cancer, whereas colonization with a superoxide-deficient strain resulted in inflammation but not cancer. 4-HNEprotein adducts were found in the lamina propria and macrophages in areas of colorectal inflammation. Conclusions: 4-HNE can act as an autochthonous mitotic spindle poison in normal colonic epithelial and colon cancer cells. This finding links the macrophage-induced bystander effects to colorectal carcinogenesis. © 2012 AGA Institute.