Abstract:Objective To investigate the mechanism of action of Shaoyao Decoction (SYD) in the treatment of ulcerative colitis based on its effects on the mechanical barrier and inflammatory cytokines of colon tissue. Methods Sprague-Dawley rats were randomly divided into control group, model group, mesalazine group, and SYD group. A rat model of ulcerative colitis was established by 2,4,6-trinitrobenzenesulfonic acid/ethanol, and the model group, mesalazine group, and SYD group were treated with normal saline, mesalazine, and SYD, respectively. General condition and disease activity index (DAI) score were compared between groups. The morphological changes in colon tissue and colonic epithelial tight junction were evaluated. The expression levels of serum interleukin-4 (IL-4), endotoxin (ET), and tumor necrosis factor-α (TNF-α) were determined by ELISA. Results Compared with the model group, the SYD group showed gradually increased body weight and reduced occurrence of diarrhea and hematochezia, and the mesalazine group and SYD group had significantly decreased DAI score, histomorphological score, IL-4, ET, and TNF-α (P<0.05). Under the transmission electron microscope, the model group showed obvious colonic epithelial tight junction injury, which was milder in the mesalazine group and the SYD group. Conclusion SYD may play a role in the treatment of ulcerative colitis by repairing the damaged colonic epithelial tight junction, reducing inflammatory response, and protecting the colonic mucosal mechanical barrier.