Although protein kinase C (PKC) and phosphatidylinositol 3 (PI3)-kinase are implicated in cardioprotective signal transduction mediated by ischemic preconditioning, their role in pharmacological preconditioning (PPC) has not been determined. Cultured neonatal rat cardiomyocytes (CMCs) were subjected to simulated ischemia for 2 h followed by 15 min of reoxygenation. PPC of CMCs consisted of administration of 50 μM adenosine, 50 μM diazoxide, and 50 μM S-nitroso- N-acetylpenicillamine (SNAP), each alone or in combination, for 15 min followed by 30 min of washout before simulated ischemia. Although PKC-ε and PI3-kinase were significantly activated during treatment with adenosine, activation of these kinases dissipated after washout. In contrast, PPC combined with adenosine, diazoxide, and SNAP elicited sustained activation of PKC-ε and PI-3 kinase after washout. The combined-PPC, but not the single-PPC, protocol conferred antiapoptotic and antinecrotic effects after reoxygenation. The PKC inhibitor chelerythrine (5 μM) or the PI3-kinase inhibitor LY-294002 (10 μM) given during the washout period partially blocked the activation of PKC-ε and PI3-kinase mediated by the combined-PPC protocol, whereas combined addition of chelerythrine and LY-294002 completely inhibited activation of PKC-ε and PI3-kinase. Chelerythrine or LY-294002 partially blocked antiapoptotic and antinecrotic effects mediated by the combined-PPC protocol, whereas combined addition of chelerythrine and LY-294002 completely abrogated antiapoptotic and antinecrotic effects. These results suggest that the combined-PPC protocol confers cardioprotective memory through sustained and interdependent activation of PKC and PI3-kinase.
Protein kinase C βII activation induces angiotensin converting enzyme expression in neonatal rat cardiomyocytes