title: Activation of soluble guanylyl cyclase by the nitrovasodilator 3-morpholinosydnonimine involves formation of S-nitrosoglutathione.
abstract: Soluble guanylyl cyclase (sGC) is the major physiological target of sydnonimine-based vasodilators such as molsidomine. Decomposition of sydnonimines results in the stoichiometric formation of nitric oxide (NO) and superoxide (O2-), which rapidly react to form peroxynitrite. Inasmuch as sGC is activated by NO but not by peroxynitrite, we investigated the mechanisms underlying sGC activation by 3-morpholinosydnonimine (SIN-1). Stimulation of purified bovine lung sGC by SIN-1 was found to be strongly dependent on glutathione (GSH). By contrast, GSH did not affect sGC activation by NO released from 2,2-diethyl-1-nitroso-oxyhydrazine, indicating that NO/O2- released from SIN-1 converted GSH to an activator of sGC. High performance liquid chromatography identified this product as the thionitrite S-nitrosoglutathione. Further, the reaction product decomposed to release NO upon addition of Cu(NO3)2 in the presence of GSH. Activation of sGC was antagonized by the Cu(I)-specific chelator neocuproine, whereas the Cu(II)-selective drug cuprizone was less potent. Carbon dioxide (delivered as NaHCO3) antagonized S-nitrosation by peroxynitrite but not by SIN-1. Thus, NO/O2- released from SIN-1 mediates a CO2-insensitive conversion of GSH to S-nitrosoglutathione, a thionitrite that activates sGC via trace metal-catalyzed release of NO. These results may provide novel insights into the molecular mechanism underlying the nitrovasodilator action of SIN-1.
authors.affiliation: Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, A-8010 Graz, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Schrammel
authors.forename: S
authors.initials: S
authors.lastname: Pfeiffer
authors.forename: K
authors.initials: K
authors.lastname: Schmidt
authors.forename: D
authors.initials: D
authors.lastname: Koesling
authors.forename: B
authors.initials: B
authors.lastname: Mayer
mesh_terms: D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism; D006162:Guanylate Cyclase / Q000187:drug effects* / Q000378:metabolism; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D009603:Nitroso Compounds / Q000378:metabolism*; D026422:S-Nitrosoglutathione; D013481:Superoxides / Q000378:metabolism; D014665:Vasodilator Agents / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D009603:Nitroso Compounds; D014665:Vasodilator Agents; D013481:Superoxides; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; C002385:linsidomine; D008981:Molsidomine; D006162:Guanylate Cyclase; D005978:Glutathione