Pharmacological polysulfide suppresses glucose-stimulated insulin secretion in an ATP-sensitive potassium...

Hydrogen sulfide (H₂S) is an endogenous gaseous transmitter synthesized in various cell types. It is well established that H₂S functions in many physiological processes, including the relaxation of vascular smooth muscle, mediation of neurotransmission, regulation of inflammation, and modulation of insulin signaling. In recent years, it has been revealed that polysulfides, substances with a varying number of sulfur atoms (H₂Sn), are generated endogenously from H₂S in the presence of oxygen. A series of studies describes that sulfane sulfur has the unique ability to bind reversibly to other sulfur atoms to form hydropersulfides and polysulfides, and that polysulfides activate ion channels and promote calcium influx. Furthermore, polysulfides regulate tumor suppressor activity, promote the activation of transcription factors targeting antioxidant genes and regulate blood pressure by vascular smooth muscle relaxation. Insulin secretion from pancreatic β cells plays a critical role in response to increased blood glucose concentration. H₂S has emerged as an important regulator of glycemic control and exhibits characteristic regulation of glucose homeostasis. However, the effects of polysulfides on glucose-stimulated insulin secretion (GSIS) are largely unknown. In this study, we demonstrated that pharmacological polysulfide salts including Na₂S₂, Na₂S₃, and Na₂S₄ considerably inhibit GSIS in mouse and rat pancreatic β-cell-derived MIN6 and INS-1 cell lines, and that the effect is dependent on the activation of ATP-sensitive potassium channels. In addition, we demonstrated that a mixture of Na₂S and diethylamine NONOate inhibits GSIS in a similar way to the pharmacological administration of polysulfide salts.