Xanthones from Gentianopsispaludosa(Hook. f.) Ma ameliorates colonic epithelial-mesenchymal transition through regulating autophagy

Abstract Ethnopharmacological relevance: Ulcerative colitis (UC) is an immune-mediated, idiopathic, chronic, recurrent inflammatory bowel disease inflammatory bowel diseases (IBD). Gentianopsis paludosa (Hook. f.) Ma, a traditional Tibetan medicine, is commonly used to treat hepatitis, cholecystitis, diarrhea, gastroenteritis, conjunctivitis, scabies, swollen poison and other diseases. The research group replicated the ulcerative colitis (UC) rat model through (2,4-dinitrobenzenesulfonic acid, DNBS）in the early stage, and it was clear that xanthone is the main active components, but the mechanism is still unclear and needs to be further elucidated. Aim of the study: Inflammatory bowel disease (IBD) is considered as one of the most intractable diseases worldwide. Intestinal fibrosis, as the most serious complication of IBD, can easily lead to intestinal scarring, intestinal stricture and even intestinal obstruction. Therefore, there is an urgent need to accelerate the development of anti-fibrotic drugs for IBD. The purpose of this study was to investigate the protective effect of xanthone from Gentianopsis paludosa (GPX) on the colonic epithelial-mesenchymal transition and its specific mechanism. Methods: The damage to colonic epithelium was caused by intraperitoneally injecting DNBS, and the therapeutic potential of GPX on colonic fibrosis was detected, which was verified by macroscopic evaluation of rats (disease activity index, DAI;colonic mucosal damage index,CMDI), histopathological staining and Western blotting. In addition, the effect of GPX was tested on NCM460 cells in vitro. The expression levels of EMT-related proteins, mRNAs and autophagy-related proteins, mRNAs in colon epithelial cells were detected by immunofluorescence assay, western blotting, quantitative real-time PCR and other techniques, and the possible mechanisms were explored. Result: GPX significantly inhibited colonic fibrosis, as preliminarily demonstrated by DNBS-induced body weight gain, DAI, CMDI score reduction and colonic fibrosis area reduction in rats. Moreover, GPX could down-regulate the expression of mesenchymal transition-related genes and proteins, and up-regulate the level of autophagy in colonocytes. Mechanistic studies showed that GPX could affect EMT by regulating autophagy, as evidenced by autophagy inhibitors (3-MA) or agonists (Rapa) that inhibit or enhance this effect of GPX. Conclusion: Herein, the evidence was provided to support that GPX could effectively inhibit colonic fibrosis, and its mechanism of action may be related to the inhibition of epithelial-mesenchymal transition and the regulation of autophagy in intestinal epithelial cells.