Addition of dietary I3C rescues AhRΔIEC mice induced with chronic DSS, and removal worsens inflammation phenotypes in WT mice. WT and AhRΔIEC mice were induced with chronic DSS and fed a diet purified of all AhR ligands (−I3C) or the purified diet supplemented with I3C (200 ppm, +I3C). (A) Survival curve of WT and AhRΔIEC mice induced with chronic DSS and fed −I3C or +I3C diets. WT mice treated with or without DSS and fed −I3C or +I3C diets. (B) Photographs of colons of WT mice after consuming −I3C or +I3C diets and DSS treatment and quantifications of (C) colon length (cm), (D) colon weight/length (g/cm), and (E) spleen/body weight (g). (F) H&E stains of distal colon and (G) their histological scores. Histological scores: 0—no inflammation, 1—quiescent, 2—mildly active, 3—moderately active, 4—severe. Values are mean ± standard error of mean. Data were analyzed by one-way ANOVA; * p < 0.05, ** p < 0.01, *** p < 0.001.