Activation of Soluble Guanylyl Cyclase by the Nitrovasodilator 3-Morpholinosydnonimine Involves Formation ofS-Nitrosoglutathione
- 1Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, A-8010 Graz, Austria (A.S., S.P., K.S., B.M), and 2Institut für Pharmakologie, Freie Universität Berlin, D-14195 Berlin, Germany (D.K.)
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.
Footnotes
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Send reprint requests to: Dr. Bernd Mayer, Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria. E-mail: mayer{at}kfungigraz.ac.at
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This work was supported by grants P 10859, P 11478, P 10655 (B.M.), and P 12191 (K.S.) from the Fonds zur Förderung der Wissenschaftlichen Forschung in Austria and SFB 366 from the Deutsche Forschungsgemeinschaft.
- Abbreviations:
- SIN-1
- 3-morpholino-sydnonimine
- DEA/NO
- 2,2-diethyl-1-nitroso-oxyhydrazine
- DTT
- dithiothreitol
- GSH
- glutathione
- GSNO
- S-nitrosoglutathione
- HPLC
- high performance liquid chromatography
- NO
- nitric oxide
- O2⨪
- superoxide
- sGC
- soluble guanylyl cyclase
- SIN-1A
- N-morpholino-N-nitrosoaminoacetonitrile
- SIN-1C
- N-morpholinoiminoacetonitrile
- SOD
- superoxide dismutase
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- Received November 7, 1997.
- Accepted March 26, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
