Effects of Bifidobacteria bifidum strains on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced acute colitis and its potential mechanism

Microbiota-based therapies for improving symptoms of Crohn's disease (CD) are receiving increasing attention. Probiotics and second-generation probiotics can potentially prevent this disease. However, the therapeutic action and underlying molecular mechanisms of probiotics remain largely unknown. Efficient screening of probiotics is also challenging. In this study, we screened eight B. bifidum strains with CD-relieving potential using a 2,4,6-trinitrobenzene sulfonic acid (TNBS) colitis mouse model. We also observed that B. bifidum CJ238 could prevent but not cure the colitis-symptoms (weight loss, colon shortening and connective tissue hyperplasia) in mice model. The 16S rRNA sequencing data showed that supplementation with B. bifidum did not alter the composition of the intestinal microbiota. B. bifidum CJ238 administration also provided full protection against acute colitis in pseudo germ-free mice. Therefore, we infered that the protective effect of B. bifidum strains does not depend on their interaction with the gut microbiota. Furthermore, heat-killed (95 °C for 20min) B. bifidum cells (109 CFU/mouse) also protected mice against acute colitis. In-vitro adhesion and immunomodulatory activities of the B. bifidum strains were measured. Combined with the in-vivo results, the anti-colitis effect of B. bifidum was positively associated with its strong anti-inflammatory and adhesion capacity in-vitro. This study provides insights into the in-vitro screening and clinical application of probiotics in CD prevention.