Bifidobacterium bifidum relieved DSS-induced colitis in mice potentially by activating the aryl hydrocarbon receptor.

Inflammatory bowel disease (IBD) characterized by relapsed intestinal inflammation and barrier function disruption is still a great therapeutic challenge. This study aimed to screen probiotics that have the potential to help alleviate IBD and further elucidate their mechanism of action. Caco-2 cell differentiated monolayers and RAW264.7 cells stimulated by lipopolysaccharide (LPS) were used for probiotic screening in vitro , and then the efficacies of the obtained six bacterial strains were evaluated in mice with dextran sulfate sodium (DSS)-induced colitis. The results showed that all of the strains at varying degrees could increase the transepithelial electrical resistance (TEER) value, decrease the influx of FITC-dextran in Caco-2 cell monolayers and attenuate the production of nitric oxide (NO), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in LPS-stimulated RAW264.7 cells. In vivo experiments indicated that Bifidobacterium bifidum FL-276.1 (FL-276.1) and Bifidobacterium bifidum FL-228.1 (FL-228.1) showed the best efficacies to ameliorate body weight loss, colon shortening, and intestinal barrier disruption. Accordingly, in FL-276.1 and FL-228.1 groups, the genes of zonula occludens-1 (ZO-1), claudin-4, occludin and mucin 2 (Muc2) in mouse colonic tissues were significantly upregulated, while TNF-α, IL-1β and IL-6 were downregulated. Further results showed that strains FL-276.1 and FL-228.1 could activate the aryl hydrocarbon receptor (AhR) in the intestine. Our study showed that the two Bifidobacterium bifidum strains, FL-276.1 and FL-228.1, ameliorated DSS-induced colitis by enhancing the intestinal barrier and anti-inflammation potentially via the AhR pathway.