Nattokinase mitigated dextran sulfate sodium-induced chronic colitis by regulating microbiota and suppressing tryptophan metabolism via inhibiting IDO-1

In this study, we investigated the protective effect of Nattokinase (NK), the most active ingredient in natto used for healthcare, on dextran sulfate sodium (DSS)-induced chronic colitis and unraveled the potential mechanisms. NK dramatically attenuated clinical symptoms and pathological damage of DSS-induced chronic colitis. NK also inhibited proinflammatory cytokines production in DSS-induced colonic tissues. Mucosal integrity was maintained by NK. Moreover, nattokinase reversed DSS-induced decline of bacteria community diversity and intestinal microbial imbalance by decreasing levels of Firmicutes and increasing levels of Bacteroidetes . Tryptophan (Trp) metabolism analysis demonstrated that NK suppressed Trp catabolism especially the Kynurenine (Kyn) pathway in chronic colitis. Furthermore, NK strikingly down-regulated the protein expression of IDO-1 in chronic colitis mice. Taken together, the study demonstrated that NK relieved DSS-induced chronic colitis by regulating gut microbiota and suppressing Trp metabolism via inhibiting IDO-1. This study indicated that NK might be a promising and effective agent for IBD.