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Activation of KATP channels by H2S in rat insulin‐secreting cells and the underlying mechanisms

H2S is an important gasotransmitter, generated in mammalian cells from l‐cysteine metabolism. As it stimulates KATP channels in vascular smooth muscle cells, H2S may also function as an endogenous opener of KATP channels in INS‐1E cells, an insulin‐secreting cell line. In the present study, KATP channel currents in INS‐1E cells were recorded using the whole‐cell and single‐channel recording configurations of the patch‐clamp technique. KATP channels in INS‐1E cells have a single‐channel conductance of 78 pS. These channels were activated by diazoxide and inhibited by gliclazide. ATP (3 mm) in the pipette solution inhibited KATP channels in INS‐1E cells. Significant amount of H2S was produced from INS‐1E cells in which the expression of cystathinonie gamma‐lyase (CSE) was confirmed. After INS‐1E cells were transfected with CSE‐targeted short interfering RNA (CSE‐siRNA) or treated with dl‐propargylglycine (PPG; 1–5 mm) to inhibit CSE, endogenous production of H2S was abolished. Increase in extracellular glucose concentration significantly decreased endogenous production of H2S in INS‐1E cells, and increased insulin secretion. After transfection of INS‐1E cells with adenovirus containing the CSE gene (Ad‐CSE) to overexpress CSE, high glucose‐stimulated insulin secretion was virtually abolished. Basal KATP channel currents were significantly reduced after incubating INS‐1E cells with a high glucose concentration (16 mm) or lowering endogenous H2S level by CSE‐siRNA transfection. Under these conditions, exogenously applied H2S significantly increased whole‐cell KATP channel currents at concentrations equal to or lower than 100 μm. H2S (100 μm) markedly increased open probability by more than 2‐fold of single KATP channels (inside‐out recording) in native INS‐1E cells (n= 4, P < 0.05). Single‐channel conductance and ATP sensitivity of KATP channels were not changed by H2S. In conclusion, endogenous H2S production from INS‐1E cells varies with in vivo conditions, which significantly affects insulin secretion from INS‐1E cells. H2S stimulates KATP channels in INS‐1E cells, independent of activation of cytosolic second messengers, which may underlie H2S‐inhibited insulin secretion from these cells. Interaction among H2S, glucose and the KATP channel may constitute an important and novel mechanism for the fine control of insulin secretion from pancreatic β‐cells.