Cardioprotection mediated by urocortin is dependent upon PKCε activation

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Abstract
Urocortin (Ucn) is an endogenous cardioprotective agent that protects against the damaging effects of ischemia and reperfusion injury in vitro and in vivo. We have found that the mechanism of action of Ucn involves both acute activation of specific target molecules, and using Affymetrix (Santa Clara, CA) gene chip technology, altered gene expression of different end effector molecules. Here, from our gene chip data, we show that after a 24 h exposure to Ucn, there was a specific increase in mRNA and protein levels of the protein kinase C epsilon (PKCepsilon) isozyme in primary rat cardiomyocytes compared with untreated cells and in the Langendorff perfused ex vivo heart. Furthermore, a short 10 min exposure of these cells to Ucn caused a specific translocation/activation of PKCepsilon in vitro and in the Langendorff perfused ex vivo heart. The importance of the PKCepsilon isozyme in cardioprotection and its relationship to cardioprotection produced by Ucn was assessed using PKCepsilon-specific inhibitor peptides. The inhibitor peptide, when introduced into cardiomyocytes, caused an increase in apoptotic cell death compared with control peptide after ischemia and reperfusion. When the inhibitor peptide was present with Ucn, the cardioprotective effect of Ucn was lost. This loss of cardioprotection by Ucn was also seen in whole hearts from PKCepsilon knockout mice. These findings indicate that the cardioprotective effect of Ucn is dependent upon PKCepsilon.