H2S and HS− donor NaHS releases nitric oxide from nitrosothiols, metal nitrosyl complex, brain homogenate and murine L1210 leukaemia cells

Abstract

Nitrosoglutathione [(GSNO), 500 nmol/l] relaxed the norepinephrine precontracted rat aortic rings. The relaxation effect was pronouncedly enhanced by H(2)S- and HS(-)-donor NaHS (30 micromol/l) at 7.5 pH but not at 6.3 pH. To study molecular mechanism of this effect, we investigated whether NaHS can release NO from NO donors. Using an electron paramagnetic resonance spectroscopy method of spin trap and by measuring the NO oxidation product, which is nitrite, by the Griess reaction, we report that NaHS released NO from nitrosothiols, namely from GSNO, S-nitroso-N-acetyl-DL: -penicillamine (SNAP), from metal nitrosyl complex nitroprusside (SNP) and from rat brain homogenate and murine L1210 leukaemia cells. From the observation that the releasing effect was more pronounced at 8.0 pH than 6.0 pH, we suppose that HS(-), rather than H(2)S, is responsible for the NO-releasing effect. Since in mammals, H(2)S and HS(-) are produced endogenously, we assume that their effect to release NO from nitrosothiols and from metal nitrosyl complexes are responsible for some of their biological activities and that this mechanism may be involved in S-nitrosothiol-signalling reactions.

The reaction products of sulfide and S-nitrosoglutathione are potent vasorelaxants

“…Experiments were carried out as previously described [8,9]. Briefly, preparations of thoracic aorta and arteria mesenterica superior (main branch) were prepared from male Wistar rats and mounted for recording of isometric tension changes in oxygenated (95% O2/5% CO2; 37°C) Krebsbicarbonate solution comprising (in mM) 118 NaCl, 5 KCl, 25 NaHCO3, 1.2 MgSO4, 1.2 KH2PO4, 2.5 CaCl2, 11 glucose, 0.032 CaNa2EDTA, pH 7.5.…”

“…Similarly, H2S can be stored in the form of sulfane sulfur and transported and released in response to a physiological stimulus [3]. A number of publications reported on the molecular interaction between H2S and NO or NO-donors [4][5][6][7][8][9][10][11][12][13][14], and H2S and NO were found to cooperatively regulate vascular tone by activating a neuroendocrine signaling pathway in which formation of nitroxyl (HNO) appears to play an important role [13]. Products of this H2S/NO interaction appear to have pronounced biological effects; however the nature of the reaction intermediates is currently unclear and many inconsistencies remain; for example, H2S donors were found to either potentiate or attenuate relaxation effect of NO donors in isolated aortic rings in vitro [15,16], or result in complete loss of vasodepressor activity in anesthetized rats [16].…”

The hypothesis of the main role of H2S in coupled sulphide-nitroso signalling pathway

“…The proportion of H 2 S and HS − at 37°C and pH 7.4 is 30% and 70%, respectively. In the present work, though, the term H 2 S will refer to the total mixture of H 2 S, HS − and S 2− (Ondrias et al 2008). Nitroso-cysteine (Cys-NO) and nitroso-N-acetylcysteine (NAC-NO) were synthesised by combining 200 mmol/l NaNO 2 and 200 mmol/l L-cysteine or N-acetyl-L-cysteine in 0.5 mol/l HCl in the dark at room temperature for 10 min.…”

“…Experiments were carried out as previously described (Ondrias et al 2008). Briefly, the rings of thoracic aorta were prepared from male Wistar rats (250-300 g, 12 weeks old) and were mounted for recording of isometric tension changes in pneumoxid-oxygenated (95% O 2 : CO 2 ; 37°C) Krebs-bicarbonate solution.…”

“…The samples were incubated for 15 min, and absorption spectra at 540 nm were measured (Ondrias et al 2008). Concentration of NO 2 − was calibrated by NaNO 2 .…”