Protective effects of Semen Crotonis Pulveratum on trinitrobenzene sulphonic acid-induced colitis in rats and H2O2-induced intestinal cell apoptosis in vitro

Abstract

Ulcerative colitis (UC) is a chronic inflammatory bowel disease. Semen Crotonis Pulveratum (SCP) has been used as a traditional medicine for the treatment of UC. However, its molecular mechanisms of action have not yet been elucidated. In the present study, we aimed to investigate the preliminary mechanisms of the role of SCP on trinitrobenzene sulphonic acid (TNBS)-induced UC in rats and hydrogen peroxide (H2O2)-induced intestinal cell apoptosis in vitro. Wistar rats (n=9 per group) were randomly divided into 4 groups: the normal control group, the UC group, the UC + SCP group and the UC + sulfasalazine group as a positive control. The proportion of CD4+CD25+ T cells and CD4+CD25+Foxp3+ Tregs, and the expression levels of interleukin (IL)-6 and IL-10 in the peripheral blood, as well as the expression levels of cyclooxygenase-2 (COX-2) and intercellular adhesion molecule-1 (ICAM-1) in the colon tissues were determined by flow cytometry, ELISA and immunohistochemical staining, respectively. Rat intestinal epithelial (IEC-6) cell apoptosis induced by H2O2 was determined by TUNEL assay, flow cytometry using Annexin V/propidium iodide (PI) staining and western blot analysis of caspase-3 activation, respectively. Significantly higher proportions of circulating CD4+CD25+ T cells and CD4+CD25+Foxp3+ Tregs were present in the UC + SCP group compared with the UC group. A significantly decreased expression of IL-6 and an increased expression of IL-10 were also observed in the UC + SCP group compared with UC group. SCP significantly reduced the UC-induced increase in the expression of COX-2 and ICAM-1 in the colon tissues. SCP inhibited cell apoptosis and caspase-3 activation induced by H2O2 in the ICE-6 cells. Our data thus indicate that SCP inhibits inflammation in UC by increasing the proportion of circulating Tregs, altering cytokine production and decreasing COX-2 and ICAM-1 expression. In addition it protects against H2O2-induced intestinal cell apoptosis in vitro.