Cardioprotection by H2S Donors: Nitric Oxide-Dependent and -Independent Mechanisms

Abstract

Hydrogen sulfide (H 2 S) is a signaling molecule with protective effects in the cardiovascular system. To harness the therapeutic potential of H 2 S, a number of donors have been developed. The present study compares the cardioprotective actions of representative H 2 S donors from different classes and studies their mechanisms of action in myocardial injury in vitro and in vivo. Exposure of cardiomyocytes to H 2 O 2 led to significant cytotoxicity, which was inhibited by sodium sulfide (Na 2 S), 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 Na 2 S and TV, but not GYY4137 and AP39, against H 2 O 2 -induced cardiomyocyte injury. Mice subjected to left anterior descending coronary ligation were protected from ischemia-reperfusion injury by the H 2 S donors tested. Inhibition of nitric oxide synthase (NOS) in vivo blocked only the beneficial effect of Na 2 S. Moreover, Na 2 S, but not AP39, administration enhanced the phosphorylation of endothelial NOS and vasodilator-associated phosphoprotein. Both Na 2 S 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 Ca 21 retention capacity, which is evidence of decreased propensity to undergo permeability transition. We conclude that although all the H 2 S donors we tested limited infarct size, the pathways involved were not conserved. Na 2 S 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.