Preconditioning blocks cardiocyte apoptosis: role of K_ATPchannels and PKC-ε

Abstract

The aims of this study were to determine whether preconditioning blocks cardiocyte apoptosis and to determine the role of mitochondrial ATP-sensitive K+(KATP) channels and the protein kinase C ε-isoform (PKC-ε) in this effect. Ventricular myocytes from 10-day-old chick embryos were used. In the control series, 10 h of simulated ischemia followed by 12 h of reoxygenation resulted in 42 ± 3% apoptosis ( n = 8). These results were consistent with DNA laddering and TdT-mediated dUTP nick-end labeling (TUNEL) assay. Preconditioning, elicited with three cycles of 1 min of ischemia separated by 5 min of reoxygenation before subjection to prolonged simulated ischemia, markedly attenuated the apoptotic process (28 ± 4%, n = 8). The selective mitochondrial KATP channel opener diazoxide (400 μmol/l), given before ischemia, mimicked preconditioning effects to prevent apoptosis (22 ± 4%, n = 6). Pretreatment with 5-hydroxydecanoate (100 μmol/l), a selective mitochondrial KATP channel blocker, abolished preconditioning (42 ± 2%, n = 6). In addition, the effects of preconditioning and diazoxide were blocked with the specific PKC inhibitors Gö-6976 (0.1 μmol/l) or chelerythrine (4 μmol/l), given at simulated ischemia and reoxygenation. Furthermore, preconditioning and diazoxide selectively activated PKC-ε in the particulate fraction before simulated ischemia without effect on the total fraction, cytosolic fraction, and PKC δ-isoform. The specific PKC activator phorbol 12-myristate 13-acetate (0.2 μmol/l), added during simulated ischemia and reoxygenation, mimicked preconditioning to block apoptosis. Opening mitochondrial KATP channels blocks cardiocyte apoptosis via activating PKC-ε in cultured ventricular myocytes. Through this signal transduction, preconditioning blocks apoptosis and preserves cardiac function in ischemia-reperfusion.

Volatile Anesthetic Preconditioning Attenuates Myocardial Apoptosis in Rabbits after Regional Ischemia and Reperfusion via Akt Signaling and Modulation of Bcl-2 Family Proteins

“…The protective actions of nitric oxide during ischemic and anesthetic preconditioning have been already demonstrated (Novalija et al, 2003a;Chiari et al, 2005b). In addition, phosphoinositide-dependent kinase 1 is a potent activator of other protein kinases, including protein kinase C, which has been implicated in the protection of myocardium against ischemia and reperfusion injury by reducing apoptosis as well as decreasing myocardial infarct size (Liu et al, 2002). Therefore, it seems that the PI3K signaling cascade may contribute to the recruitment of multiple endogenous cardioprotective pathways to reduce myocardial damage after ischemia and reperfusion.…”

Attenuation of fatty acid-induced apoptosis by low-dose alcohol in neonatal rat cardiomyocytes

“…Multiple studies also indicate that cardiac ischemic preconditioning inhibits both apoptosis and necrosis. The attenuation of apoptosis is mediated by PKC-⑀ in rat hearts and chick ventricular myocytes (29,38). Cardiac reperfusion after an ischemic event also exposes myocytes to a high level of circulating nonesterified fatty acids (35,40).…”

Sarcolemmal and mitochondrial KATP channels and myocardial ischemic preconditioning

“…In contrast, a recent study by Liu et al [40] demonstrated that PKC-e was downstream from mitoK ATP activation in IPC's apoptosis limiting effects. Using ventricular myocytes from chick embryos, Liu and collegues reported that both IPC and diazoxide treatment reduced cardiocyte apoptosis and that both of these effects were abolished by pretreatment with specific PKC inhibitors.…”

“…Thus, opening of mitoK ATP channels was associated with a downstream activation of ERK. The results of Wang and Ashraf, Samavati et al, and Liu et al suggest that mitoK ATP activation may also act as a trigger of the cardioprotection [40,41,47]. Further support for this hypothesis is given by Pain et al [48].…”

“…While it is generally accepted that the mitoK ATP is intimately involved in the cardioprotection afforded by IPC, it is still unclear as to whether its role is as a trigger/mediator or end effector. Recent reports support a role for mitoK ATP as both a trigger and end-effector [40,41,48,51].…”