Department of Cardiology and Angiology, Justus Liebig University, Giessen, Germany.
Center for Cardiovascular Research, Charité, Berlin, Germany.
Biochim Biophys Acta Mol Basis Dis. 2019 Jan;1865(1):252-260. doi: 10.1016/j.bbadis.2018.07.021. Epub 2018 Jul 22.
Disturbance of mitochondrial function significantly contributes to the myocardial injury that occurs during reperfusion. Increasing evidence suggests a role of intra-mitochondrial cyclic AMP (cAMP) signaling in promoting respiration and ATP synthesis. Mitochondrial levels of cAMP are controlled by type 10 soluble adenylyl cyclase (sAC) and phosphodiesterase 2 (PDE2), however their role in the reperfusion-induced injury remains unknown. Here we aimed to examine whether sAC may support cardiomyocyte survival during reperfusion.
Adult rat cardiomyocytes or rat cardiac H9C2 cells were subjected to metabolic inhibition and recovery as a model of simulated ischemia and reperfusion. Cytosolic Ca, pH, mitochondrial cAMP (live-cell imaging), and cell viability were analyzed during a 15-min period of reperfusion. Suppression of sAC activity in cardiomyocytes and H9C2 cells, either by sAC knockdown, by pharmacological inhibition or by withdrawal of bicarbonate, a natural sAC activator, compromised cell viability and recovery of cytosolic Ca homeostasis during reperfusion. Contrariwise, overexpression of mitochondria-targeted sAC in H9C2 cells suppressed reperfusion-induced cell death. Analyzing cAMP concentration in mitochondrial matrix we found that inhibition of PDE2, a predominant mitochondria-localized PDE isoform in mammals, during reperfusion significantly increased cAMP level in mitochondrial matrix, but not in cytosol. Accordingly, PDE2 inhibition attenuated reperfusion-induced cardiomyocyte death and improved recovery of the cytosolic Ca homeostasis.
sAC plays an essential role in supporting cardiomyocytes viability during reperfusion. Elevation of mitochondrial cAMP pool either by sAC overexpression or by PDE2 inhibition beneficially affects cardiomyocyte survival during reperfusion.
线粒体功能障碍显著促进再灌注时发生的心肌损伤。越来越多的证据表明，线粒体环磷酸腺苷 (cAMP) 信号转导在促进呼吸和 ATP 合成中起作用。线粒体 cAMP 水平受 10 型可溶性腺苷酸环化酶 (sAC) 和磷酸二酯酶 2 (PDE2) 控制，但其在再灌注诱导损伤中的作用尚不清楚。本研究旨在探讨 sAC 是否可能在再灌注期间支持心肌细胞存活。
成年大鼠心肌细胞或大鼠心脏 H9C2 细胞在代谢抑制和恢复后作为模拟缺血和再灌注的模型。在 15 分钟的再灌注过程中分析细胞质 Ca、pH、线粒体 cAMP（活细胞成像）和细胞活力。心肌细胞和 H9C2 细胞中 sAC 活性的抑制，无论是通过 sAC 敲低、药理学抑制还是通过去除碳酸氢盐（天然 sAC 激活剂）来实现，都会损害再灌注期间细胞活力和细胞质 Ca 稳态的恢复。相反，在 H9C2 细胞中转染靶向线粒体的 sAC 过表达可抑制再灌注诱导的细胞死亡。分析线粒体基质中的 cAMP 浓度，我们发现再灌注期间抑制主要位于哺乳动物线粒体中的 PDE2，可显著增加线粒体基质中的 cAMP 水平，但细胞质中的 cAMP 水平不变。因此，PDE2 抑制减轻了再灌注诱导的心肌细胞死亡，并改善了细胞质 Ca 稳态的恢复。
sAC 在再灌注期间支持心肌细胞活力中发挥重要作用。通过 sAC 过表达或 PDE2 抑制增加线粒体 cAMP 池，有利于再灌注期间心肌细胞的存活。
