Curcumin promotes renewal of intestinal epithelium by miR-195-3p

Ethnopharmacological relevance: Turmeric (Curcuma longa) has been used to treat gastrointestinal disorders in the Indian Ayurvedic medical system. According to the theory behind traditional Chinese medicine, turmeric can be distributed in the spleen meridian, for which it has been used as a digestive aid. Curcumin (Cur), a natural polyphenol compound originally derived from turmeric, has anti-inflammatory activity and can assist in treating inflammatory bowel disease. Aims of the study: To investigate curcumin's protective effects on intestinal epithelium and explore the underlying miR-195-3p-related mechanisms. Materials and methods: The miR-195-3p mimics were used to over-express miR-195-3p. The in vitro effects of Cur and miR-195-3p on the intestine were shown utilizing intestinal cryptlike epithelial cell line-6 (IEC-6) cells. By fasting for 48 h, an intestinal mucosal atrophy model of SD rats was created in vivo. Cur (25 or 50 mg/kg) was assessed for its protective effect on intestinal epithelium. Glycyrrhetinic acid (GA) with an intestinal protective effect reported in our previous research was adopted as a positive drug for the in vivo and in vitro bioactivity evaluation since there is no universally positive drug for either intestinal mucosal restitution or miR-195-3p modulation. Results: Cur protects the intestinal epithelium and promotes its repair after injury via down-regulating miR-1953p. In vitro experiments showed that Cur inhibited the apoptosis of IEC-6 cells, stimulated their growth, and down-regulated the level of miR-195-3p in cells. When miR-195-3p was overexpressed, the viability of IEC-6 cells decreased while the apoptosis rate increased. All the above detrimental effects were alleviated after curcumin intervention. Moreover, Cur reversed the effect of miR-195-3p on its downstream occludin. In vivo, results showed that 48-h fasting impaired the integrity of the small intestinal mucosa (abnormal crypt structure and reduced goblet cell number), which was ameliorated by Cur treatment. In addition, the Cur treatment reversed both the increased expression level of miR-195-3p and decreased levels of ki-67 and occludin caused by fasting. Conclusions: Cur could promote the proliferation and repair after injury of the intestinal mucosa by downregulating miR-195-3p.