Epoxypukalide Induces Proliferation and Protects against Cytokine-Mediated Apoptosis in Primary Cultures of Pancreatic β-Cells

Abstract

There is an urgency to find new treatments for the devastating epidemic of diabetes. Pancreatic beta-cells viability and function are impaired in the two most common forms of diabetes, type 1 and type 2. Regeneration of pancreatic beta-cells has been proposed as a potential therapy for diabetes. In a preliminary study, we screened a collection of marine products for beta-cell proliferation. One unique compound (epoxypukalide) showed capability to induce beta-cell replication in the cell line INS1 832/13 and in primary rat cell cultures. Epoxypukalide was used to study beta-cell proliferation by [H-3] thymidine incorporation and BrdU incorporation followed by BrdU/insulin staining in primary cultures of rat islets. AKT and ERK1/2 signalling pathways were analyzed. Cell cycle activators, cyclin D2 and cyclin E, were detected by western-blot. Apoptosis was studied by TUNEL and cleaved caspase 3. beta-cell function was measured by glucose-stimulated insulin secretion. Epoxypukalide induced 2.5-fold increase in beta-cell proliferation; this effect was mediated by activation of ERK1/2 signalling pathway and upregulation of the cell cycle activators, cyclin D2 and cyclin E. Interestingly, epoxypukalide showed protection from basal (40% lower versus control) and cytokine-induced apoptosis (80% lower versus control). Finally, epoxypukalide did not impair beta-cell function when measured by glucose-stimulated insulin secretion. In conclusion, epoxypukalide induces beta-cell proliferation and protects against basal and cytokine-mediated beta-cell death in primary cultures of rat islets. These findings may be translated into new treatments for diabetes.