Objective: To investigate the efficacy and its mechanism of rhein on dextran sulphate sodium(DSS )- induced ulcerative colitis in mice. Method: C57BL/6 male mice were randomly divided into 6 groups: normal control group

model group

mesalazine treatment group

low-dose rhein group

middle-dose rhein group and the high-dose rhein group (6.25

12.5

25 mg·kg-1)

n=10 in each group. The mice in normal control group received distilled water

while all the other mice were treated with 3% dextra sulfate sodium for 7 days to induce the ulcerative colitis model. From the first day of modeling

mesalazine and different concentrations of rhein were given by gavage for 14 days continuously

and equal volume of distilled water was given in normal group and model group. The body weight

defecation condition and hematochezia of the mice were observed and recorded everyday; scores of disease activity index (DAI) were calculated and evaluated; colon was taken and its length was measured; colon paraffin slices were prepared and their pathological changes were observed under microscope after HE staining. Peripheral blood was taken and the serum was collected to detect the level of anti-flagellin antibody by using ELISA kit. The expression levels of Toll like receptor 5(TLR5) and nuclear factor (NF )-κB p65 in colon were measured by Western blot. Result: As compared with the normal control group

DAI scores were significantly increased in model group (P<0.01); the colon length was significantly shortened(P<0.01); meanwhile

epithelium and intestinal gland disappeared

with a large number of lymphocyte infiltration and local vascular dilation in submucous layer. Above symptoms were ameliorated after giving mesalazine and different concentrations of rhein (P<0.05

P<0.01). The anti-flagellin antibody in serum

the expression levels of TLR5 and NF-κB p65 were significantly increased in model group (P<0.01) as compared with the normal group; while these levels were decreased after treatment by mesalazine and different concentrations of rhein (P<0.05

P<0.01). Conclusion: Rhein could treat DSS-induced ulcerative colitis in mice

and its mechanism may be related to inhibiting the expression of TLR5/NF-κB p65 pathway.