Abstract

Hydrogen sulfide (H₂S) is a signaling molecule with protective effects in the cardiovascular system. To harness the therapeutic potential of H₂S, a number of donors have been developed. The present study compares the cardioprotective actions of representative H₂S donors from different classes and studies their mechanisms of action in myocardial injury in vitro and in vivo. Exposure of cardiomyocytes to H₂O₂ led to significant cytotoxicity, which was inhibited by sodium sulfide (Na₂S), thiovaline (TV), GYY4137 [morpholin-4-ium 4 methoxyphenyl(morpholino) phosphinodithioate], and AP39 [(10-oxo-10-(4-(3-thioxo-3H-1,2-dithiol5yl)phenoxy)decyl) triphenylphospho-nium bromide]. Inhibition of nitric oxide (NO) synthesis prevented the cytoprotective effects of Na₂S and TV, but not GYY4137 and AP39, against H₂O₂-induced cardiomyocyte injury. Mice subjected to left anterior descending coronary ligation were protected from ischemia-reperfusion injury by the H₂S donors tested. Inhibition of nitric oxide synthase (NOS) in vivo blocked only the beneficial effect of Na₂S. Moreover, Na₂S, but not AP39, administration enhanced the phosphorylation of endothelial NOS and vasodilator-associated phosphoprotein. Both Na₂S and AP39 reduced infarct size in mice lacking cyclophilin-D (CypD), a modulator of the mitochondrial permeability transition pore (PTP). Nevertheless, only AP39 displayed a direct effect on mitochondria by increasing the mitochondrial Ca²⁺ retention capacity, which is evidence of decreased propensity to undergo permeability transition. We conclude that although all the H₂S donors we tested limited infarct size, the pathways involved were not conserved. Na₂S had no direct effects on PTP opening, and its action was nitric oxide dependent. In contrast, the cardioprotection exhibited by AP39 could result from a direct inhibitory effect on PTP acting at a site different than CypD.