Therapeutic delivery of hydrogen sulfide for salvage of ischemic skeletal muscle after the onset of critical ischemia

BackgroundRecent evidence suggests that hydrogen sulfide is capable of mitigating the degree of cellular damage associated with ischemia-reperfusion injury (IRI).MethodsThis study evaluated the potential utility of hydrogen sulfide in preventing IRI in skeletal muscle by using in vitro (cultured myotubes subjected to sequential hypoxia and normoxia) and in vivo (mouse hind limb ischemia, followed by reperfusion) models to determine whether intravenous hydrogen sulfide delivered after the ischemic event had occurred (pharmacologic postconditioning) conferred protection against IRI. Injury score and apoptotic index were determined by analysis of specimens stained with hematoxylin and eosin and terminal deoxynucleotide transferase-mediated deoxy-uridine triphosphate nick-end labeling, respectively.ResultsIn vitro, hydrogen sulfide reduced the apoptotic index after 1, 3, or 5 hours of hypoxia by as much as 75% (P = .002), 80% (P = .006), and 83% (P < .001), respectively. In vivo, hydrogen sulfide delivered after the onset of hind limb ischemia and before reperfusion resulted in protection against IRI-induced cellular changes, which was validated by significant decreases in the injury score and apoptotic index. The timing of hydrogen sulfide delivery was crucial: when delivered 20 minutes before reperfusion, hydrogen sulfide conferred significant cytoprotection (P < .001), but treatment 1 minute before reperfusion did not provide protection (P = NS).ConclusionsThese findings confirm that hydrogen sulfide limits IRI-induced cellular damage in myotubes and skeletal muscle, even when delivered after the onset of ischemia in this murine model. These data suggest that when given in the appropriate dose and within the proper time frame, hydrogen sulfide may have significant therapeutic applications in multiple clinical scenarios.Clinical RelevanceExtremity ischemia is a limb- and life-threatening clinical scenario that must be treated expeditiously. Although rapid recognition and revascularization is crucial, there are few options regarding pharmacologic means to mitigate the effect of ischemia and subsequent reperfusion (ischemia-reperfusion injury). This is particularly true in situations of unanticipated ischemia, where no interventions can be undertaken before the onset of ischemia. Hydrogen sulfide is protective of muscle cells against ischemia-reperfusion injury when delivered before the onset of ischemia, and this study evaluated the effect of hydrogen sulfide delivered after the onset of ischemia. The promising results of the in vitro and in vivo studies suggest that hydrogen sulfide may in the future be an important adjunct to prompt surgical or endovascular intervention in episodes of unanticipated extremity ischemia