Emodin ameliorates ulcerative colitis by the flagellin-TLR5 dependent pathway in mice

Emodin is an anthraquinone compound derived from Rheum officinale Baill. Several reports showed that emodin had efficacy on acute pancreatitis, keratitis, myocarditis, and rheumatoid arthritis. However, the potency of emodin on ulcerative colitis(UC) remains unclear. In this study, we investigated the effect of emodin on dextran sodium sulfate (DSS)-induced ulcerative colitis in mice. Our results showed that emodin significantly alleviated the symptoms of DSS-induced UC in mice, involving prevented the loss of body weight and colon shortening, decreased the disease activity index (DAI), intestinal damages and the count of white blood cells (WBC) in peripheral blood. In addition, emodin treatment decreased the level of anti-flagellin antibody in serum and significantly down-regulated the expression of TLR5 and NF-κB p65 in colon of the UC mice. Further study in vitro showed that emodin down-regulated the expression of TLR5 and MyD88, up-regulated the expression of IκB, inhibited the nuclear translocation of NF-κB p65 and decreased the release of IL-8 in flagellin-stimulated HT-29 cells. These results, for the first time, demonstrated that emodin had the therapeutic potential to ameliorate UC symptoms possibly via regulating the flagellin-TLR5 signaling pathway. Emodin may be a potential candidate ingredient for ulcerative colitis.