A selective ε-protein kinase C antagonist inhibits protection of cardiac myocytes from hypoxia-induced cell death

Protein kinase C activation is thought to protect cardiac tissue from subsequent ischemic injury by a process termed preconditioning, The protein kinase C isozyme that mediates preconditioning has not yet been identified, Using a cell culture model of hypoxic preconditioning, we found that cardiac myocyte viability after 9 h of hypoxia was increased by more than 50% over control, Preconditioning activated protein kinase C isozymes as evidenced by translocation from one cell compartment to another as follows: there was a a,l-fold increase in epsilon-protein kinase C activation, a 2.8-fold increase in delta-protein kinase C activation, and no increase in beta(1)-protein kinase C activation, 4 beta-Phorbol la-myristate 13-acetate mimicked hypoxic preconditioning, increasing myocyte survival after prolonged hypoxia by 34% compared with control, We previously identified an epsilon-protein kinase C-selective antagonist, epsilon V1-2 peptide, that inhibits epsilon-protein kinase C translocation and function in cardiac myocytes (Johnson, J, A., Gray, M. O., Chen, C.-H,, and Mochly-Rosen, D. (1996) J, Biol, Chem, 271, 24962-24966), epsilon V1-2 peptide abolished hypoxic preconditioning and phorbol ester mediated cardiac protection, Therefore, preconditioning can be induced in this culture model, and activation of epsilon-protein kinase C is critical for cardiac myocyte protection.