RESUMO
ObjectiveTo investigate the mechanism of ethyl acetate extract of Tibetan medicine dampness bud Gentianopsis paludosa in the prevention and treatment of recurrent ulcerative colitis （UC） in rats with dampness-heat in large intestine syndrome based on the apoptotic pathway mediated by the B-cell lymphoma-2 （Bcl-2） and Bcl-2-associated X protein （Bax）. MethodUsing the disease-syndrome combination method， a recurrent UC model of dampness-heat in large intestine syndrome was constructed in rats. Seventy SPF-grade male SD rats were randomly divided into control group， model group， high-， medium-， and low-dose ethyl acetate of G.paludosa groups （150， 75， 37.5 mg·kg-1）， and mesalazine group （135 mg·kg-1）. The rats were orally administered with respective drugs for 14 days. The general conditions of the rats were recorded， and colon length and mucosal damage were observed. The colon wet weight index and organ coefficients of the liver， spleen， and thymus were calculated. Enzyme-linked immunosorbent assay （ELISA） was used to measure the levels of interleukin-6 （IL-6） and interleukin-1β （IL-1β） in the serum of each group. Hematoxylin-eosin （HE） staining was performed to observe pathological changes in the colon. Terminal deoxynucleotidyl transferase dUTP nick end labeling （TUNEL） was used to detect apoptosis in colonic epithelial cells. Western blot was used to measure the expression levels of Bcl-2， Bax， Caspase-3， Caspase-9， Zona Occludens-1 （ZO-1）， Claudin3， and Occludin in colonic tissue. Immunohistochemistry （IHC） was used to observe the expression of Bax and Caspase-3 in colonic epithelial cells. ResultCompared with the control group， the model group showed significant increases in the disease activity index （DAI） score， colonic mucosal damage index （CMDI）， intestinal epithelial apoptosis， liver and spleen indexes， and levels of inflammatory factors IL-1β and IL-6 in the serum （P<0.01）， decreased expression of intestinal mucosal protective proteins ZO-1， Claudin3， and Occluding （P<0.01）， increased expression of pro-apoptotic proteins Bax， Caspase-3， and Caspase-9 （P<0.01）， and decreased expression of anti-apoptotic protein Bcl-2 （P<0.01）. Compared with the model group， the high-， medium-， and low-dose ethyl acetate of G.paludosa groups all significantly improved the general condition of the rats， reduced colonic lesions， decreased intestinal epithelial cell apoptosis， reduced liver and spleen indexes， upregulated the expression of ZO-1， Claudin3， Occludin， and Bcl-2 proteins， and downregulated the expression of Bax， Caspase-3， and Caspase-9 proteins， with the high- and medium-dose ethyl acetate of G.paludosa groups showing the superior effects （P<0.05， P<0.01）. ConclusionEthyl acetate of G.paludosa can alleviate colonic mucosal damage and exert a therapeutic effect on UC by regulating the Bcl-2/Bax signaling pathway.