Ulcerative colitis is a chronic inflammatory disease of colon with unclear mechanism. Generally, It has been believed that its pathogenesis involves the defect of epithelial barrier defects, dysregulated immune responses, and the disorder of intestinal microbiota. In TNBS-induced ulcerative colitis, UC rats are represented by diarrhea, ulceration of colon tissue, increase of IL-6 level and enhancement of MPO activity in serum [25, 26]. In this study, all UC model rats demonstrated clinical symptoms of diarrhea. Concurrently, overexpression of inflammatory factors and the disturbance of gut microbiota existed in UC model rats, indicating the UC model was successfully established in this study.
Colonic epithelial cells and mucosal barrier are strongly related to the pathogenesis of UC. By inhibiting the apoptosis of colonic epithelial cells, mucosal ulceration and mucosal epithelial cell damage in UC rats can be improved . As a famous formula for 900 years, SLBZS has been widely used in the treatment of gastrointestinal diseases. It’s has been reported that SLBZS might exhibit ameliorating effects against diarrhea by modulations on intestinal absorption function as well as mucosal ultra structure . From the pathological section of the colon and the change of the colon in each group of the experiment, high dose of SLBZS for UC had a certain recovery effect on the intestinal villi detachment, the over all structural damage of the colon, inflammatory cell infiltration and apoptosis induction, which was beneficial to regulate the reabsorption capacity and mucosal barrier of the colon. The level of inflammatory factors and activities of antioxidant enzymes in rats serum were also ascertained. Previous studies delineated that overexpression of IL-6 could lead to a continuous inflammatory response and in turn promote inflammatory bowel disease . IL-6 can promote inflammation by activating multiple target cells, including antigen-presenting cells and T cells . MPO is mainly located in aniline blue particles in neutrophils , which reflects the inflammatory state to some extent. Studies have found that reactive oxygen species (ROS) is closely related to UC colon mucosal tissue damage . Although low level of ROS are necessary for some physiological processes, excessive ROS are produced in UC patients . SOD and CAT can remove ROS, prevent lipid peroxidation and maintain the stability of cell membrane. In our study, we observed that low dose of SLBZS treatment could decrease the level of IL-6 and MPO (P < 0.05) and increase the activities of SOD and CAT (P > 0.05) while all dose SLBZS treatment could significantly decreased the level of MPO (P < 0.05) compared to TNBS group. Our study proved that SLBZS could treat UC by inhibiting inflammation and improving antioxidant capacity.
Abnormal microbial composition and reduced complexity of intestinal microbial ecosystem are common features of ulcerative colitis . To monitor the structural modulation of the gut microbiota during UC treatment with SLBZS, high-throughput sequencing analysis of 16S rRNA genes was performed in our study. As reflected by the chao1 estimator and shannon diversity index, we found that SLBZS treatment reduced the shannon diversity index but increased the chao1 estimator, suggesting SLBZS treated UC by reducing the diversity of gut microbiota while increasing its richness. PCA and NMDS showed that SLBZS treatment could change the structure and composition of the microbiota, and the structure of the microbiota can be closer to the normal state than the TNBS group. In order to analyze the further difference in the structure of gut microbiota after treatment, this study also carried out a comparative analysis of the gut microbiota at the phylum and genus levels of each group. We found that the relative abundance of Bilophila, Desulfovibrio and Bacteroides decreased in TNBS-L and TNBS-H compared to TNBS group while Oscillospira and Helicobacter increased in TNBS-M and Prevotella increased in TNBS-L and TNBS-H group. Prevotella and Oscillospira are short chain fatty acid (SCFA) producing bacteria [35, 36], and SCFA, important nutrients of colon mucosal, is capable of colon cell proliferation and mucosal growth . Undigested dietary fiber, protein and peptides can be fermented through gut microbiota in the cecum and colon, resulting in the generation of SCFA. SCFA can induce intestinal epithelial cells to secret IL-18, antimicrobial peptide, mucin and upregulate the expression of tight junction to regulate the integrity of intestinal barrier . Meanwhile, SCFA can induce neutrophil migration and enhance phagocytosis . Bacteroides is involved in metabolism and nutrient absorption in vivo , but promotes inflammation in inflammatory bowel disease . Both Desulfovibrio and Bilophila are conditional pathogens, creating H2S in combination with H2 by sulfuric acid or sulfur-containing compounds, which has an important relationship with the inflammatory state of the intestinal epithelium (such as UC) . Studies have shown that the body with Helicobacter removed is more susceptible to colitis than the untreated group, suggesting that Helicobacter has potential protective effects on colitis patients . Therefore, these result further indicated that the amelioration of UC using SLBZS may be mediated by the enrichment of beneficial bacteria to product SCFA for protection of colon mucosa and a reduction in bacteria, such as Bacteroides, Desulfovibrio and Bilophila, to inhibit inflammation.