P35 Sodium sulfide therapy attenuates myocardial ischemia–reperfusion injury in the type-2 diabetic heart via the activation of Nrf2 signaling

Abstract

Background Hydrogen sulfide (H2S) therapy protects non-diabetic animals in various models of myocardial injury, including acute myocardial infarction and heart failure. However, it has yet to be determined if H2S therapeutic strategies have similar cardioprotective effects in the setting of type-2 diabetes. Here we sought to examine if H2S therapy could provide cardioprotection in the db/db diabetic mouse model. Methods Diabetic (db/db; 12 weeks of age) mice were subjected to transient myocardial ischemia for a period of 30 min followed by reperfusion. Sodium Sulfide (Na2S) or vehicle (saline) was administered either daily for 7 days before ischemia or 24 h prior to ischemia. Results Na2S therapy significantly decreased myocardial injury in the db/db diabetic mouse, as evidenced by a reduction in infarct size, circulating troponin-I levels, oxidative stress, and cleaved caspase-3 expression. In an effort to evaluate the signaling mechanism responsible for the observed cardioprotection, mice were administered (via tail vein) a single injection of Na2S or daily injections of either vehicle or Na2S for 7 days. Heart tissue was then excised and processed for Western blot analysis. Analysis uncovered a complication in the ability of Na2S to activate a Nuclear factor erythroid 2-related factor (Nrf2) signaling cascade in the diabetic heart. Specifically, the results indicate that the ability of Na2S to increase the nuclear localization of Nrf2 is not altered by diabetes. However, we did find that diabetes impaired Nrf2 transcriptional activity, as evidenced by the finding that it takes 7 days of Na2S therapy to increase Heme oxygenase-1 (HO-1) levels in the diabetic heart. Further analysis revealed that Nrf2 was unable to bind to the antioxidant response element (ARE). This appears to have been caused by Bach1, a known repressor of HO-1 transcription, as evidenced by the increased levels of Bach1 in the nucleus of the diabetic heart and the finding that 7 days of Na2S treatment reduced its nuclear expression. Conclusions Our findings demonstrate that Na2S therapy attenuates myocardial ischemia–reperfusion injury in the db/db diabetic mouse model, confirming the therapeutic potential of using Na2S to treat a heart attack in the setting of diabetes. Our results also demonstrate that Na2S activates Nrf2 signaling in the diabetic heart by removing Bach1 from the nucleus.