Triptolide induces suppressor of cytokine signaling-3 expression and promotes lamina propria mononuclear cells apoptosis in Crohn's colitis

Background: IL-6/STAT3/SOCS3 signaling pathway plays an important role in the pathogenesis of Crohn's disease by induction of the antiapoptotic factors Bcl-2 and Bcl-xl in lamina propria mononuclear cells (LPMCs). We previously reported that triptolide showed therapeutic activity in mouse colitis by mechanisms involving suppression of IL-6 trans-signaling. IL-10 gene-deficient mice with established colitis were used for the experiments with triptolide administration. Methods: This study further investigates the mechanism by which triptolide attenuates Crohn's colitis. IL-10 gene-deficient mice (IL-10(-)/(-)) of 10-12 weeks with established colitis were used for the experiments with chronic triptolide administration. Apoptosis of lamina propria mononuclear cells (LPMCs) were measured by flow cytometry. SOCS, Bcl-2, Bcl-xl and Bax were determined by Western blot. Furthermore, an in vitro study was performed by using cultured intestine from CD patients to observe the direct effects of triptolide. Results: Our data indicated triptolide promoted apoptosis in LPMCs in vivo. Interestingly, triptolide significantly induced the apoptosis of LP-CD4-positive but not LP-CD4-negative cells. Triptolide significantly induced SOCS3 protein and reduced STAT3 target anti-apoptotic genes Bcl-2 and Bcl-xl in LPMCs. The results were confirmed by an in vitro study using colonic explants cultured with triptolide. Conclusions: Our results indicated that triptolide therapy may restore the homeostatic balance of LP-T cell apoptosis within the gut, and demonstrate a novel mechanism of action of triptolide therapy mediated through regulation IL-6/STAT3/SOCS3 signaling pathway. (c) 2013 Elsevier B.V. All rights reserved.