Abstract 264: Nitrite Therapy Ameliorates Myocardial Injury via H2S and Nuclear Factor-Erythroid 2-Related Factor 2 (Nrf2)-Dependent Signaling in Chronic Heart Failure

Abstract

Background: Nitric oxide (NO) and hydrogen sulfide (H 2 S) are reduced in congestive heart failure. Recent studies suggest cross-talk between NO and H 2 S signaling. We previously reported that sodium nitrite (NaNO 2 ) significantly ameliorates myocardial ischemia-reperfusion injury and heart failure. Nrf2 regulates the expression of antioxidant protein genes and is upregulated by H 2 S. We examined the effects of NaNO 2 therapy on endogenous H 2 S bioavailability and Nrf2 activation in mice subjected to ischemia-induced heart failure. Materials and Methods: Mice underwent 60 min. of left coronary artery occlusion and 4 weeks (WKS) of reperfusion. NaNO 2 (165 μg/kg) or saline vehicle (VEH) was administered at reperfusion and then in drinking water (100 mg/L) for 4 wks. Left ventricular ejection fraction (LVEF) was determined at baseline and 4 wks of reperfusion. Myocardial tissue was collected and analyzed for oxidative stress status and respective gene/protein levels. Results: NaNO 2 therapy preserved LVEF (47 ± 4% vs. 32 ± 4%, p < 0.01) and LV diastolic and systolic dimensions (LVEDD/LVESD; 4.0/3.1 mm vs. 4.5/3.9 mm, p < 0.05) at 4 wks. MDA and protein carbonyl contents were significantly reduced in NaNO 2 treated mice as compared to VEH. NaNO 2 markedly increased expression of CuZn-superoxide dismutase and catalase at 4 wks. Furthermore, NaNO 2 increased mRNA levels of H 2 S producing enzymes and H 2 S bioavailabilty. Cardiac Nrf2 activation was also observed with NaNO 2 therapy. Conclusions: Our results demonstrate that NaNO 2 therapy significantly improves left ventricular function via by increasing H 2 S bioavailability, activation of Nrf2, and increased antioxidant defenses.1