The present study investigated the effects of the Sijunzi decoction (SJZD) at various dosages on the immunological function of rats with 3% dextran sulfate sodium (DSS; molecular weight 5,000)-induced ulcerative colitis (UC). A total of 40 male Wistar rats were randomly divided into 5 groups: Normal, model, low-dose SJZD, moderate-dose SJZD and high-dose SJZD groups. The 3% DSS was intragastrically administered for 7 consecutive days in order to induce the UC model. The normal group consumed distilled water. Subsequently, SJZD (5.0, 10.0 and 30.0 g/kg) was intragastrically administered, and scores of the disease activity index (DAI) were calculated. After 2 weeks, all the rats were sacrificed. Scores of the colon mucosa damage index (CMDI) were evaluated; and secretory immunoglobulin A (sIgA) and interleukin-2 (IL-2) were measured in intestinal tissue by ELISA assays. The model group rats had ulcers, hyperemia and interstitial edema and infiltrated inflammatory cells. SJZD attenuated the severity of the gross lesions and reduced the histopathological injuries. Compared with the normal group, DAI and CMDI were significantly increased (P<0.01), and levels of determined sIgA in the intestinal mucosa and IL-2 in the intestinal tissue were significantly decreased (P<0.05) in the model group. Compared with the model group, moderate and high doses of SJZD showed a restoration effect on all the aforementioned indexes, and the high dose was the most effective. In conclusion, SJZD can ameliorate inflammation in DSS-induced UC rats. The mechanism is most likely due to enhancing intestinal local immunity.
Keywords: Sijunzi decoction; interleukin-2; intestinal mucosa immunity; secretory immunoglobulin A; ulcerative colitis.