Inhaled nitric oxide (NO) has been reported to decrease the infarct size in cardiac ischemia reperfusion (I-R) injury. However, reactive nitrogen species (RNS) produced by NO causes myocardial dysfunction and injury. Since H2 is reported to eliminate peroxynitrite, it was expected to reduce the adverse effects of NO. In mice, left anterior descending coronary artery ligation for 60 min followed by reperfusion was performed with inhaled NO (80 ppm), H2 (2%), or NO + H2, starting 5 min before reperfusion for 35 min. After 24 hrs, left ventricular function, the infarct size and area at risk (AAR) were assessed. Oxidative stress associated with reactive oxygen species (ROS) was evaluated by staining for 8-hydroxy-2′-deoxyguanosine and 4-hydroxy-2-nonenal, that associated with RNS by staining for nitrotyrosine, and neutrophil infiltration by staining for granulocyte receptor-1. The infarct size/AAR decreased with breathing NO or H2 alone. NO inhalation plus H2 reduced the infarct size/AAR, with significant interaction between the two, reducing ROS and neutrophil infiltration, and improved the cardiac function to normal levels. While nitrotyrosine staining was prominent after NO inhalation alone, it was eliminated after breathing a mixture of H2 with NO. Preconditioning with NO significantly reduced the infarct size/AAR, but not preconditioning with H2. In conclusion, breathing NO + H2 during I-R reduced the infarct size and maintained cardiac function, and reduced the generation of myocardial nitrotyrosine associated with NO inhalation. Administration of NO + H2 gases for inhalation may be useful for planned coronary interventions or for the treatment of I-R injury.
Background: Exogenously administered hydrogen exerts cytoprotective effects through anti-oxidant, anti-inflammatory, and anti-apoptotic mechanisms in various disease settings, including organ transplantation. Our objective in this study was to evaluate the efficacy of a novel cold storage device equipped with a hydrogen-rich water bath. Methods: The study used an established rat heterotopic transplantation model. Syngeneic heart grafts from elderly donors (60- to 70-week-old Lewis rats) or allografts from adult donors (12-week-old Brown Norway rats) were exposed to prolonged cold preservation. The cardiac grafts were stored in plastic bags containing Celsior, which were immersed in the cold water bath equipped with an electrolyzer to saturate the water with hydrogen. The cardiac grafts then were heterotopically engrafted into Lewis rat recipients. Results: In both experimental settings, serum troponin I and creatine phosphokinase were markedly elevated 3 hours after reperfusion in the control grafts without hydrogen treatment. The grafts exhibited prominent inflammatory responses, including neutrophil infiltration and the upregulation of messenger RNAs for pro-inflammatory cytokines and chemokines. Myocardial injury and inflammatory events were significantly attenuated by organ storage in the hydrogen-rich water bath. The grafts stored using the hydrogen-rich water bath also exhibited less mitochondrial damage and a higher adenosine triphosphate content. Conclusions: Hydrogen delivery to cardiac grafts during cold preservation using a novel hydrogen-supplemented water bath efficiently ameliorated myocardial injury due to cold ischemia and reperfusion. This new device to saturate organs with hydrogen during cold storage merits further investigation for possible therapeutic and preventative use during transplantation.