THE FUNCTION OF THE CYSTATHIONINE-GAMMA-LYASE/HYDROGEN SULFIDE AXIS IN THE PATHOGENESIS OF ULCERATIVE COLITIS

Abstract INTRODUCTION Current combination therapies in ulcerative colitis (UC) target different inflammatory cascades, including tumor necrosis factor-alpha (TNF-alpha) signaling. However, most patients do not achieve long-term remission, suggesting that the molecular pathophysiology of UC is still poorly understood. Endogenously produced hydrogen sulfide (H2S) has emerged as a critical physiological mediator of gastrointestinal homeostasis, limiting mucosal inflammation and promoting tissue healing in response to epithelial injury. Inhibition of cystathionine-gamma-lyase (CSE)-dependent H2S production in animal models of UC has been shown to exacerbate colitis and delay tissue repair. Our research group has strong evidence revealing that the CSE/H2S axis regulates TNF-alpha signaling in colonic epithelial cells. Therefore, we hypothesize that decreased CSE/H2S pathway activity in colonic mucosa cells leads to dysregulation of TNF-alpha signaling and uncontrolled inflammatory/immune responses with aberrant wound repair mechanisms contributing to the pathogenesis of UC. RESULTS We found a significant decrease in CSE mRNA and protein expression in colonic biopsies from patients with UC. Using a preclinical animal model of epithelium injury-induced chronic colitis (DSS), we confirmed a sustained downregulation of CSE, as well as upregulation of TNF-alpha and tumor necrosis receptor 2 expressions in colonic mucosa samples. Treatment with the slow-releasing H2S-donor GYY4137 significantly reduced the severity of DSS-induced inflammation and improved mucosal integrity and restitution responses. In epithelial cell and colonoid cultures, the inhibition of CSE-dependent H2S synthesis decreased the activation of extracellular-signal-regulated-kinase-1/2 (ERK1/2), increased IL-6 and TNF-alpha mRNA levels and suppressed basic and TNF-alpha–mediated colonocyte migration. CONCLUSION These studies demonstrate that CSE regulates mucosal TNF-alpha signaling, pro- and anti-inflammatory responses as well as colonic epithelial repair. Adding the H2S donor GYY4137 reduces inflammation, suggesting the restoration of normal TNF-alpha signaling function. Acknowledgments: KM is supported by the DoD Career Development Award (W81XWH2010641) and ACS Research Scholar Grant (RSG–21–027–01–CSM).