Anesthetic-induced Preconditioning Delays Opening of Mitochondrial Permeability Transition Pore via Protein Kinase C-ϵ–mediated Pathway

Background:Cardioprotection by volatile anesthetic-induced preconditioning (APC) involves activation of protein kinase C (PKC). This study investigated the importance of APC-activated PKC in delaying mitochondrial permeability transition pore (mPTP) opening. Methods:Rat ventricular myocytes were exposed to isoflurane in the presence or absence of nonselective PKC inhibitor chelerythrine or isoform-specific inhibitors of PKC-&dgr; (rottlerin) and PKC-ϵ (myristoylated PKC-ϵ V1–2 peptide), and the mPTP opening time was measured by using confocal microscopy. Ca2+-induced mPTP opening was measured in mitochondria isolated from rats exposed to isoflurane in the presence and absence of chelerythrine or in mitochondria directly treated with isoflurane after isolation. Translocation of PKC-ϵ was assessed in APC and control cardiomyocytes by Western blotting. Results:In cardiomyocytes, APC prolonged time necessary to induce mPTP opening (261 ± 26 s APC vs. 216 ± 27 s control; P < 0.05), and chelerythrine abolished this delay to 213 ± 22 s. The effect of isoflurane was also abolished when PKC-ϵ inhibitor was applied (210 ± 22 s) but not in the presence of PKC-&dgr; inhibitor (269 ± 31 s). Western blotting revealed translocation of PKC-ϵ toward mitochondria in APC cells. The Ca2+ concentration required for mPTP opening was significantly higher in mitochondria from APC rats (45 ± 8 &mgr;m · mg−1 control vs. 64 ± 8 &mgr;m · mg−1 APC), and APC effect was reversed with chelerythrine. In contrast, isoflurane did not protect directly treated mitochondria. Conclusion:APC induces delay of mPTP opening through PKC-ϵ–mediated inhibition of mPTP opening, but not through PKC-&dgr;. These results point to the connection between cytosolic and mitochondrial components of cardioprotection by isoflurane.