Anemoside B4 ameliorates TNBS-induced colitis involved suppressing the S100A9/NF-κB signaling pathway

Abstract

Background Despite the increased morbidity of ulcerative colitis (UC) in the developing countries, available treatments remain unsatisfactory. Therefore, it is urgent to discover more effective therapeutic strategies. Pulsatilla chinensis was widely used for the treatment of inflamed intestinal diseases including UC for thousands of years in China. However, it is unclear which compound in P. chinensis is responsible for the therapeutic effect. Our previous study reported that anemoside B4, the most abundant triterpenoid saponin isolated from P. chinensis, exerts anti-inflammatory and antioxidant effects. Methods Here, we used the 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-induced colitis rat model to evaluate the therapeutic effect of anemoside B4. Blood samples of colitis rat were collected for hematology analysis. The effects of anemoside B4 on inflammation-associated mediators were investigated by Enzyme-linked immunosorbent assay (ELISA) and hematoxylin and eosin staining (HE) staining. Cell proliferation or apoptosis was measured by immunofluorescence technique. The mechanisms of anemoside B4 was investigated using label-free quantitative proteomics. The level of proteins was quantified by western blotting. mRNA expression was quantified by quantitative real-time RT-PCR. Results The results showed that anemoside B4 ameliorated TNBS-induced colitis symptoms, including tissue damage, inflammatory cell infiltration, and pro-inflammatory cytokine production, apoptosis and slowed proliferation in the colon. Quantitative proteomic analyses discovered that 56 proteins were significantly altered by anemoside B4 in the TNBS-induced rats. These proteins were mainly clustered in tricarboxylic acid cycle (TCA) cycle and respiratory electron transport chain. Among the altered proteins, S100A9 is one of the most significantly downregulated proteins and associated with NF-κB and MAPK signaling pathways in the pathogenesis of UC. Further experiments revealed that anemoside B4 suppresses the expression of S100A9 and its downstream genes including TLR4, NF-κB, and p-JNK in colon. In vitro, S100A9 protein could active NF-κB signaling pathway in human intestinal epithelial Caco-2 cells. However, anemoside B4 could inhibit the NF-κB signaling pathway induced by S100A9 protein. Besides, it also inhibited active of NF-κB signaling pathway stimulated by LPS or IL-6. Conclusions Our results demonstrate that anemoside B4 prevents TNBS-induced colitis involved inhibiting the NF-κB signaling pathway through inactivating S100A9 suggesting that anemoside B4 is a promising therapeutic candidate for colitis.