Attenuation of Expression of γ-Glutamylcysteine Synthetase by Ribozyme Transfection Enhance Insulin Secretion by Pancreatic β Cell Line, MIN6☆

Abstract Low levels of intracellular antioxidant enzyme activities as well as glutathione (GSH) concentrations have been described in pancreatic β cells. We examined the effects of intracellular GSH depletion on insulin secretion and the role of intracellular GSH in signal transduction in β cell line, MIN6 cells. Anti-γ-glutamylcysteine synthetase (γ-GCS) heavy subunit ribozyme was stably transfected to MIN6 cells to reduce intracellular GSH concentration. In the presence of 10 mM glucose, ribozyme-transfected cells (RTC) increased insulin secretion from 0.58 μg/10 6 cells/h in control cells (CC) to 1.48 μg/10 6 cells/h. This was associated with increased intracellular Ca 2+ concentration in RTC, detected by fluo-3 staining. Our results demonstrated that intracellular GSH concentration might influence insulin secretion by MIN6 cells, and suggest that enhanced insulin secretion by β cells conditioned by chronic depletion of GSH is mediated by increased intracellular Ca 2+ concentration.