Overall, our data show that key features associated with TNFα-induced colitis, including production of KC, high infiltration of neutrophils, redox imbalance, and activation of redox-sensitive MAP kinases, could be mediated through ROS produced by NOX1 and NOX2 from epithelial cells and neutrophils, respectively, and that these processes can be inhibited by apocynin, an NADPH oxidase inhibitor with antioxidant properties. The gene discussed is FMO5; the disease is colitis.