SLC6A4 and colitis: produce agonists that activate the aryl hydrocarbon receptor (AhR) pathway shown to be involved in intestinal homeostasis.30 Specifically, Bifidobacterium produce indole metabolites such as indole-3-lactate which is an agonist for the AhR and interacts with the serotonin reuptake transporter, Slc6a4.31,32 Decreases in Slc6a4 are associated with colitis whereby activation of AhR is associated with improved disease outcomes.33 Here we show that B.p. MP80 + 2ʹFL prevented the colonic DSS-induced decrease in AhR (p = .036, DSS vs DSS + B.p MP80 + 2ʹFL; Figure 4f, Supplemental Tables S18-S19).