Brusatol ameliorates intestinal mucosal injury in ulcerative colitis via activating IL-22/STAT3 pathway

Brusatol (BR) is an active compounds isolated from Brucea javanica, a Chinese herbal medicine that is famous for its anti-diarrheal effect. We have previously reported that BR mitigated inflammation in murine ulcerative colitis (UC) models. However, BR's role in intestinal mucosal healing, which is recently established as central strategy for the prevention and treatment of UC, remains unknown. In this study, the ameliorative effect of BR on intestinal mucosal damage was investigated in DSS-induced UC mice. BR significantly alleviated colitis symptoms, improved intestinal barrier function by preventing loss of goblet cells and downregulation of mucins and tight junction proteins, as well as maintained proliferative and apoptotic homeostasis in the colonic epithelium of UC mice. Mechanistically, BR enhanced the level and secretion of IL-22, but inhibited IL-22BP, an inhibitory protein of IL-22, in the blood serum and intestinal tissues of UC mice, as well as in MNK3 cells which is an effective cell model for studying ILC3s. Additionally, BR elevated the expressions of receptors for IL-22 (IL-10R2 and IL-22R1), and activated its downstream STAT3 signaling pathway. Furthermore, the involvement of IL-22 was further investigated by using recombinant IL-22 (rIL-22) and IL-22 antibody (anti-IL-22). BR demonstrated comparable effects with rIL-22 on alleviating intestinal inflammation and repairing intestinal mucosal injury. Treatment with anti-IL-22 abrogated the mucosal protective effects of BR. The present findings shed novel insights into the role of BR in intestinal mucosal healing via activating IL-22/STAT3 signaling pathway in UC.