TY - JOUR T1 - Mechanisms Underlying Activation of Soluble Guanylate Cyclase by the Nitroxyl Donor Angeli's Salt JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1115 LP - 1122 DO - 10.1124/mol.109.059915 VL - 76 IS - 5 AU - Andreas Zeller AU - M. Verena Wenzl AU - Matteo Beretta AU - Heike Stessel AU - Michael Russwurm AU - Doris Koesling AU - Kurt Schmidt AU - Bernd Mayer Y1 - 2009/11/01 UR - http://molpharm.aspetjournals.org/content/76/5/1115.abstract N2 - Nitroxyl (HNO) may be formed endogenously by uncoupled nitric-oxide (NO) synthases, enzymatic reduction of NO or as product of vascular nitroglycerin bioactivation. The established HNO donor Angeli's salt (trioxodinitrate, AS) causes cGMP-dependent vasodilation through activation of soluble guanylate cyclase (sGC). We investigated the mechanisms underlying this effect using purified sGC and cultured endothelial cells. AS (up to 0.1 mM) had no significant effect on sGC activity in the absence of superoxide dismutase (SOD) or dithiothreitol (DTT). In the presence of SOD, AS caused biphasic sGC activation (apparent EC50 ∼10 nM, maximum at 1 μM) that was accompanied by the formation of NO. DTT (2 mM) inhibited the effects of <10 μM AS but led to sGC activation and NO release at 0.1 mM AS even without SOD. AS had no effect on ferric sGC, excluding activation of the oxidized enzyme by HNO. The NO scavenger carboxy-PTIO inhibited endothelial cGMP accumulation induced by AS in the presence but not in the absence of SOD (EC50 ∼50 nM and ∼16 μM, respectively). Carboxy-PTIO (0.1 mM) inhibited the effect of ≤10 μM AS in the presence of SOD but caused NO release from 0.1 mM AS in the absence of SOD. These data indicate that AS activates sGC exclusively via NO, formed either via SOD-catalyzed oxidation of HNO or through a minor AS decomposition pathway that is unmasked in the presence of HNO scavenging thiols. © 2009 The American Society for Pharmacology and Experimental Therapeutics ER -