SLC6A4 and colitis: To further substantiate the intermediary effect of 5-HT in AR-induced colitis, SERT-deficient (SERT−/−) mice, which exhibit enhanced DSS-colitis severity due to augmented bioactivity of 5-HT41 were exposed to AR via diet for 12 weeks prior to induction of acute colitis with 3.5% DSS for 7 days (Supplementary Fig. 14a).