Ulcerative colitis (UC) is an inflammatory disease that mainly affects the colon and rectum. It is believed that genetic factors, host immune system disorders, intestinal microbiota dysbiosis, and environmental factors contribute to the pathogenesis of UC. However, studies on the role of intestinal microbiota in the pathogenesis of UC have been inconclusive. Studies have shown that probiotics improve intestinal mucosa barrier function and immune system function and promote secretion of anti-inflammatory factors, thereby inhibiting the growth of harmful bacteria in the intestine. Fecal microbiota transplantation (FMT) can reduce bowel permeability and thus the severity of disease by increasing the production of short-chain fatty acids, especially butyrate, which help maintain the integrity of the epithelial barrier. FMT can also restore immune dysbiosis by inhibiting Th1 differentiation, activity of T cells, leukocyte adhesion, and production of inflammatory factors. Probiotics and FMT are being increasingly used to treat UC, but their use is controversial because of uncertain efficacy. Here, we briefly review the role of intestinal microbiota in the pathogenesis and treatment of UC.

These findings suggest that R. intestinalis suppresses CD pathogenesis by inducing anti-inflammatory responses.

Roseburia intestinalis (R. intestinalis) is one of the dominant intestinal bacterial microbiota and is decreased in patients with inflammatory bowel disease (IBD). It helps protect colonic mucosa against the development of inflammation and subsequent IBD, however its underlying mechanisms are unclear. The aim of the present study was to evaluate the anti-inflammatory properties of R. intestinalis in vitro and in an animal model of IBD. The effects of R. intestinalis on disease activity index (DAI) scores, intestinal pathology, the expression of interleukin (IL)-17 and the frequency of CD4+CD25+Foxp3+ regulatory T cells (Treg) were evaluated in vivo in a model of 2,4,6-trinitrobenzenesulfonic acid solution (TNBS)-induced colitis. Compared with the control group, TNBS-treated mice had significantly higher secretion of IL-17, higher DAI scores, a lower ratio of Treg, reduced colon lengths and higher histological scores for colon inflammation. The administration of R. intestinalis significantly downregulated the expression of IL-17, increased the ratio of Treg and ameliorated the high DAI scores and the pathological signs of inflammation in the colon compared with mice treated with TNBS alone. Gene expression profiling was also used to detect the expression of IL-17 in human IBD and healthy control specimens. To extend these findings to an in vitro model of inflammation the human colon epithelial cell line NCM460 was stimulated with lipopolysaccharide (LPS) to induce inflammation and co-cultured with R. intestinalis and changes in IL-17 expression were evaluated. R. intestinalis inhibited the LPS-induced secretion of IL-17 by NCM460 cells. In conclusion, these results demonstrate that R. intestinalis inhibits IL-17 secretion and promotes Treg differentiation in colitis, suggesting that R. intestinalis could be of potential use in the treatment of IBD.