Cardiomyocyte-restricted overexpression of extracellular superoxide dismutase increases nitric oxide bioavailability and reduces infarct size after ischemia/reperfusion

Abstract

Increased levels of extracellular superoxide dismutase (ecSOD) induced by preconditioning or gene therapy protect the heart from ischemia/reperfusion injury. To elucidate the mechanism responsible for this action, we studied the effects of increased superoxide scavenging on nitric oxide (NO) bioavailability in a cardiac myocyte-specific ecSOD transgenic (Tg) mouse. Results indicated that ecSOD overexpression increased cardiac myocyte-specific ecSOD activity 27.5-fold. Transgenic ecSOD was localized to the sarcolemma and, notably, the cytoplasm of cardiac myocytes. Ischemia/reperfusion injury was attenuated in ecSOD Tg hearts, in which infarct size was decreased and LV functional recovery was improved. Using the ROS spin trap, DMPO, electron paramagnetic resonance (EPR) spectroscopy demonstrated a significant decrease in ROS in Tg hearts during the first 20 min of reperfusion. This decrease in ROS was accompanied by an increase in NO production determined by EPR using the NO spin trap, Fe-MGD. Attenuated ROS in ecSOD Tg myocytes was also supported by decreased production of peroxynitrite (ONOO−). Increased NO bioavailability was confirmed by attenuated guanylate cyclase-dependent (p-VASP) signaling. In conclusion, attenuation of ROS levels by cardiac-specific ecSOD overexpression increases NO bioavailability in response to ischemia/reperfusion and protects against reperfusion injury. These findings are the first to demonstrate increased NO bioavailability with attenuation of ROS by direct measurement of these reactive species (EPR, reactive fluorescent dyes) with cardiac-specific ecSOD expression. This is also the first indication that the predominantly extracellular SOD isoform is capable of cytosolic localization that affects myocardial intracellular signal transduction and function.Electronic supplementary materialThe online version of this article (doi:10.1007/s00395-012-0305-1) contains supplementary material, which is available to authorized users.

Molecular Basis of Cardioprotection

“…294 Gene transfer of these proteins also conferred protection against infarction. 279,[295][296][297] The upregulation of cardioprotective proteins in late IPC shares a protective phenotype with hibernating myocardium, which is also characterized by lack of infarction, despite reduced coronary blood flow, 298,299 and has increased expression of inducible NOS, 57 stress proteins, such as αB crystallin, 300 H11 kinase, HIF1α, and heat shock protein 70. 301 …”

Ischemia-Reperfusion Injury in Stroke

“…These most notably include therapy using superoxide dismutase and NADPH oxidase as agents, which have been shown in animal models of ischemia-reperfusion to lessen injury and improve function in multiple organ systems [39,105,106,107,108]. Multiple isoforms of NADPH oxidase have been identified with a variable pattern of expression across the central nervous system.…”

Repair of the Infarcted Myocardium

“…Free radical scavengers have been widely used to study the role of ROS in the pathophysiology of MI; their effects generated interest in [ 17 ] demonstrated protective effects of combining the antioxidant enzymes superoxide dismutase (SOD) and catalase in reduction of infarct size in dogs undergoing coronary occlusion and reperfusion. Recently, transgenic mice with specifi c overexpression of extracellular SOD (ecSOD) in cardiomyocytes exhibited signifi cant protection from post-ischemic/reperfusion injury [ 18 ]. In addition, mice overexpressing manganese SOD (MnSOD) demonstrated a signifi cant decrease in infarct size in Langendorff-perfused hearts undergoing coronary artery ligation [ 19 ].…”