Protective role of soluble adenylyl cyclase against reperfusion-induced injury of cardiac cells
Abstract
Aims:Disturbance of mitochondrial function significantly contributes to the myocardial injury that occursduring reperfusion. Increasing evidence suggests a role of intra-mitochondrial cyclic AMP (cAMP) signaling inpromoting respiration and ATP synthesis. Mitochondrial levels of cAMP are controlled by type 10 solubleadenylyl cyclase (sAC) and phosphodiesterase 2 (PDE2), however their role in the reperfusion-induced injuryremains unknown. Here we aimed to examine whether sAC may support cardiomyocyte survival during re-perfusion.
Methods and results:Adult rat cardiomyocytes or rat cardiac H9C2 cells were subjected to metabolic inhibitionand recovery as a model of simulated ischemia and reperfusion. Cytosolic Ca2+, pH, mitochondrial cAMP (live-cell imaging), and cell viability were analyzed during a 15-min period of reperfusion. Suppression of sAC activityin cardiomyocytes and H9C2 cells, either by sAC knockdown, by pharmacological inhibition or by withdrawal ofbicarbonate, a natural sAC activator, compromised cell viability and recovery of cytosolic Ca2+homeostasisduring reperfusion. Contrariwise, overexpression of mitochondria-targeted sAC in H9C2 cells suppressed re-perfusion-induced cell death. Analyzing cAMP concentration in mitochondrial matrix we found that inhibition ofPDE2, a predominant mitochondria-localized PDE isoform in mammals, during reperfusion significantly in-creased cAMP level in mitochondrial matrix, but not in cytosol. Accordingly, PDE2 inhibition attenuated re-perfusion-induced cardiomyocyte death and improved recovery of the cytosolic Ca2+homeostasis.
Conclusion:sAC plays an essential role in supporting cardiomyocytes viability during reperfusion. Elevation ofmitochondrial cAMP pool either by sAC overexpression or by PDE2 inhibition beneficially affects cardiomyocyte survival during reperfusion