MPO and colitis: As shown in Figures 4A–D, HO treatment at a dose of 40 μg/kg significantly attenuated DSS-induced colitis in mice, as demonstrated by reducing body weight change, macroscopic scores (p < 0.0001), and histological scores (p = 0.0001), as well as colonic MPO activity (p = 0.0045), which were inhibited by pretreatment of NH.