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

Background: Recent evidence suggests that hydrogen sulfide is capable of mitigating the degree of cellular damage associated with ischemia-reperfusion injury (IRI). Methods: This 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. Results: In 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). Conclusions: These 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.