title: L-cysteine inhibits insulin release from the pancreatic beta-cell: possible involvement of metabolic production of hydrogen sulfide, a novel gasotransmitter.
abstract: Hydrogen sulfide (H(2)S) was historically recognized as a toxic gas generated by natural resources. However, its enzymatic production from L-cysteine has recently been demonstrated in mammals. Cystathionine beta-synthase and cystathionine gamma-lyase, both of which can produce H(2)S, were expressed in mouse pancreatic islet cells and the beta-cell line, MIN6. L-cysteine and the H(2)S donor NaHS inhibited glucose-induced insulin release from islets and MIN6 cells. These inhibitory effects were reproduced when insulin release was stimulated by alpha-ketoisocaproate, tolbutamide, or high K+. L-cysteine and NaHS inhibited glucose-potentiated insulin release in the copresence of diazoxide and high K+. Real-time imaging of intracellular Ca2+ concentration ([Ca2+](i)) demonstrated that both L-cysteine and NaHS reversibly suppressed glucose-induced [Ca2+](i) oscillation in a single beta-cell without obvious changes in the mean value. These substances inhibited Ca2+ - or guanosine 5'-0-3-thiotriphosphate-induced insulin release from islets permeabilized with streptolysin-O. L-cysteine and NaHS reduced ATP production and attenuated glucose-induced hyperpolarization of the mitochondrial membrane potential. Finally, L-cysteine increased H(2)S content in MIN6 cells. We suggest here that L-cysteine inhibits insulin release via multiple actions on the insulin secretory process through H(2)S production. Because the activities of H(2)S-producing enzymes and the tissue H(2)S contents are known to increase under diabetic conditions, the inhibition may participate in the deterioration of insulin release in this disease.
authors.affiliation: Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Oita 879-5593, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kaneko
authors.forename: Yuka
authors.initials: Y
authors.lastname: Kimura
authors.forename: Hideo
authors.initials: H
authors.lastname: Kimura
authors.forename: Ichiro
authors.initials: I
authors.lastname: Niki
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D003541:Cystathionine beta-Synthase / Q000378:metabolism; D003542:Cystathionine gamma-Lyase / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008239:Lysine / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR
chemical_list: D007328:Insulin; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase; D008239:Lysine; D006862:Hydrogen Sulfide