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

Abstract

A B S T R A C TThe chemical interaction of sodium sulfide (Na2S) with the NO-donor S-nitrosoglutathione (GSNO) has been described to generate new reaction products, including polysulfides and nitrosopersulfide (SSNO -) via intermediacy of thionitrous acid (HSNO). The aim of the present work was to investigate the vascular effects of the longer-lived products of the Sulfide/GSNO interaction. Here we show that the products of this reaction relax precontracted isolated rings of rat thoracic aorta and mesenteric artery (but to a lesser degree rat uterus) with a >2-fold potency compared with the starting material, GSNO (50 nM), whereas Na2S and polysulfides have little effect at 1-5 μM. The onset of vasorelaxation of the reaction products was 7-10 times faster in aorta and mesenteric arteries compared with GSNO. Relaxation to GSNO (100-500 nM) was blocked by an inhibitor of soluble guanylyl cyclase, ODQ (0.1 and 10 μM), and by the NO scavenger cPTIO (100 μM), but less affected by prior acidification (pH 2-4), and unaffected by N-acetylcysteine (1 mM) or methemoglobin (20 μM heme). By contrast, relaxation to the Sulfide/GSNO reaction products (100-500 nM based on the starting material) was inhibited to a lesser extent by ODQ, only slightly decreased by cPTIO, more markedly inhibited by methemoglobin and N-acetylcysteine, and abolished by acidification before addition to the organ bath. The reaction mixture was found to generate NO as detected by EPR spectroscopy using N-(dithiocarboxy)-N-methyl-D-glucamine (MGD2)-Fe 2+ as spin trap. In conclusion, the Sufide/GSNO reaction products are faster and more pronounced vasorelaxants than GSNO itself. We conclude that in addition to NO formation from SSNO -, reaction products other than polysulfides may give rise to nitroxyl (HNO) and be involved in the pronounced relaxation induced by the Sulfide/GSNO cross-talk.

Key bioactive reaction products of the NO/H 2 S interaction are S/N-hybrid species, polysulfides, and nitroxyl

“…The different chemical properties attributed to SSNO − , HS n − , and SULFI/NO translate into distinct bioactivities in vitro and in vivo. As shown here and elsewhere (26,28), the SSNO − mixture (produced from either DEA/NO or SNAP with excess sulfide) contains high concentrations of SSNO − and HS n − , releases NO, is a potent sGC stimulator in the NO reporter cell line RFL-6 (26), induces NO-mediated vasorelaxation in isolated aortic tissue (28), and significantly decreases blood pressure in a dose-dependent fashion with minor effects on cardiac function. No changes in any of these parameters were observed by equivalent concentrations/doses of sulfide alone.…”

“…Chemical studies by Seel and Wagner (9,10) showed that NO readily reacts with HS − in basic aqueous solution or organic solvents under anoxic conditions to form the yellow nitrosopersulfide (SSNO − ). Accumulation of this product was also observed after reaction of RSNOs with sulfide at pH 7.4 (26,27); moreover, SSNO − -containing mixtures were found to release NO, activate soluble guanylyl cyclase (sGC) (26), and relax vascular tissue (28), although a contribution of other reaction products to these effects cannot be excluded. Meanwhile, other sulfane sulfur molecules, including persulfides (RSSH) and polysulfides (RSS n − and HS n − ), have come to the fore as potential mediators of sulfide's biological effects (29)(30)(31), but little is known about their pathways of formation, prevalence in biological systems, and relationship with NO.…”

“…Moreover, HSNO can undergo rapid nucleophilic attack by HS − to give HSSH and NO − (reacting with O 2 to form ONOO − ), whereas the electron density of the proximate sulfur in HSSNO is increased, making it less susceptible to nucleophilic attack by HS − and reaction with metals (e.g., Cu + ). Of note, SSNO − exerts faster and more prominent vasorelaxation compared with its precursor and the prototypical nitrosothiol, GSNO (28), indicative of the ease with which it can cross cell membranes and release NO.…”

Reactions between nitrosopersulfide and heme proteins

“…At neutral pH, unstored H 2 S is predominantly HS − due to a pKa of 6.8 [19]. Although NO and HS − are likely nonreactive, HS − and NO + , which occurs in S-nitrosothiol (RSNO), or sulfide radical (HS • ) and NO are reactive [19-21]. …”

Chloride channels mediate sodium sulphide‐induced relaxation in rat uteri

“…These findings suggest that NO may modulate sulphide's action on uterus contraction. Recently, it was shown that powerful inhibitory effect of sulphide on rat uterus is unaffected by the presence of polysulphides but that it is diminished by interaction with NO donors such as S-nitrosoglutathione (GSNO; Berenyiova et al, 2015). The NO donor SNP prevented H2S-induced relaxation of rat uterus (Filipovic et al, 2013).…”