HMOX1 and colitis: On the other side, DSS-induced colitis in COX-2−/− KO mice was less severe compared to WT control mice, showing a decrease of heme oxygenase-1 (HO-1) and increase of NADPH quinone oxidoreductase-1 (NQO-1), demonstrating the tight association between inflammation and the antioxidant system [63].