Ding's herbal enema treats dextran sulfate sodium-induced colitis in mice by regulating the gut microbiota and maintaining the Treg/Th17 cell balance

Ding's herbal enema (DHEP) is a traditional Chinese medicinal therapy that has been used to treat ulcerative colitis (UC) in China. The present study determined the molecular mechanism of the effect of DHEP in UC treatment. C57BL/6J mice were treated with 3.5% (w/v) dextran sulfate sodium (DSS) for 7 days to establish an animal model of colitis. The mice were divided into five groups (n=5): Control, vehicle, DHEP, mesalazine and beta-sitosterol. After oral administration for 7 days, the body weight, disease activity index, histopathology and inflammatory factors were analyzed. The fractions of CD4(+)Foxp3(+) regulatory T (Treg) cells and CD4(+)IL-17A(+) T helper (Th) cells were determined by flow cytometry. Gut microbiota composition was analyzed by next-generation sequencing. The results revealed that DHEP and beta-sitosterol could significantly alleviate the symptoms of DSS-induced UC. Furthermore, the levels of IL-6, cyclooxygenase-2, TNF-alpha and p65 were reduced after administration of DHEP. Additionally, the data indicated that DHEP could increase the abundance of seven operational taxonomic units (OTUs) and decrease the abundance of 12 OTUs in the gut microbiota. The content of short-chain fatty acids in the colon remodeled the balance of Treg/Th17 cells in DSS-induced UC in mice. The present study preliminarily defined the mechanism of action of DHEP in UC that may be associated with the regulation of the gut microbiota composition, and maintenance of the balance between Treg and Th17 cells. Furthermore, beta-sitosterol exhibited the same effects with DHEP and it could be a possible substitute for DHEP in UC treatment.