Withaferin A inhibits pro-inflammatory cytokine-induced damage to islets in culture and following transplantation

Abstract

Beta cell death triggered by pro-inflammatory cytokines plays a central role in the pathogenesis of type 1 diabetes and loss of transplanted islets. The nuclear factor κB (NF-κB) signalling pathway is a key regulator of beta cell stress response, survival and apoptosis. Withaferin A (WA), a steroidal lactone derived from Withania somnifera, has been demonstrated to be a potent, safe, anti-inflammatory molecule that can inhibit NF-κB signalling. Therefore, we evaluated the ability of WA to protect mouse and human islets from the damaging effects of pro-inflammatory cytokines in vitro and following intraportal transplantation. Mouse and human islets were treated with a cytokine cocktail, and NF-κB activation was measured by immunoblots, p65 nuclear translocation and chromatin immunoprecipitation of p65-bound DNA. Intraportal transplantation of a marginal mass of syngeneic mouse islets was performed to evaluate the in vivo protective effect of WA. Treatment with WA substantially improved islet engraftment of syngeneic islets (83% for infusion with 200 islets + WA; 0% for 200 islets + vehicle) in a mouse model of diabetes, compared with marginal graft controls with superior islet function in WA-treated mice confirmed by glucose tolerance test. Treatment of human and mouse islets with WA prevented cytokine-induced cell death, inhibited inflammatory cytokine secretion and protected islet potency. WA was shown to be a strong inhibitor of the inflammatory response in islets, protecting against cytokine-induced cell damage while improving survival of transplanted islets. These results suggest that WA could be incorporated as an adjunctive treatment to improve islet transplant outcome.