Direct evidence that protein kinase C plays an essential role in the development of late preconditioning against myocardial stunning in conscious rabbits and that epsilon is the isoform involved.

Abstract

Brief ischemic episodes confer marked protection against myocardial stunning 1-3 d later (late preconditioning [PC] against stunning). The mechanism of this powerful protective effect is poorly understood. Although protein kinase C (PKC) has been implicated in PC against infarction, it is unknown whether it triggers late PC against stunning. In addition, the entire PKC hypothesis of ischemic PC remains controversial, possibly because the effects of PKC inhibitors on PC protection have not been correlated with their effects on PKC activity and/or translocation in vivo. Thus, conscious rabbits underwent a sequence of six 4-min coronary occlusion (O)/4-min reperfusion (R) cycles for three consecutive days (days 1, 2, and 3). In the control group (group I, n ϭ 7), the recovery of systolic wall thickening after the six O/R cycles was markedly improved on days 2 and 3 compared with day 1, indicating the development of late PC against stunning. Administration of the PKC inhibitor chelerythrine at a dose of 5 mg/kg before the first O on day 1 (group II, n ϭ 10) abrogated the late PC effect against stunning, whereas a 10-fold lower dose (0.5 mg/kg; group III, n ϭ 7) did not. Administration of 5 mg/kg of chelerythrine 10 min after the sixth reperfusion on day 1 (group IV, n ϭ 6) failed to block late PC against stunning. When rabbits were given 5 mg/kg of chelerythrine in the absence of O/R (group V, n ϭ 5), the severity of myocardial stunning 24 h later was not modified. Pretreatment with phorbol 12-myristate 13-acetate (4 g/kg) on day 1 without ischemia (group VI, n ϭ 11) induced late PC against stunning on day 2 and the magnitude of this effect was equivalent to that observed after ischemic PC. In vehicle-treated rabbits (group VIII, n ϭ 5), the six O/R cycles caused translocation of PKC isoforms ⑀ and from the cytosolic to the particulate fraction without significant changes in total PKC activity, in the subcellular distribution of total PKC activity, or in the subcellular distribution of the ␣ , ␤ 1 , ␤ 2 , ␥ , ␦ , , , , and isoforms. The higher dose of chelerythrine (5 mg/kg; group X, n ϭ 5) prevented the translocation of both PKC ⑀ and induced by ischemic PC, whereas the lower dose (0.5 mg/kg; group XI, n ϭ 5) prevented the translocation of PKC but not that of ⑀ , indicating that the activation of ⑀ is necessary for late PC to occur whereas that of is not. To our knowledge, this is the first demonstration that a PKC inhibitor actually prevents the translocation of PKC induced by ischemic PC in vivo, and that this inhibition of PKC translocation results in loss of PC protection. Taken together, the results demonstrate that the mechanism of late PC against myocardial stunning in conscious rabbits involves a PKCmediated signaling pathway, and implicate ⑀ as the specific PKC isoform responsible for the development of this cardioprotective phenomenon.

Protein kinase Cϵ interacts with cytochrome c oxidase subunit IV and enhances cytochrome c oxidase activity in neonatal cardiac myocyte preconditioning

“…18 kDa protein. In contrast, the PKCε translocation inhibitor inhibited the in vitro 32 P labelling of the approx. 18 kDa protein by 79 + − 15 % (n = 3, P < 0.05).…”

“…Ping et al [31] have established that induction of the early or late phases of PC in conscious rabbits triggered the translocation of the PKCε and PKCη isoenzymes to the cardiac particulate fraction. Qiu et al [32] found that differential inhibition of PKCη, but not PKCε, translocation by low concentrations of the PKC inhibitor chelerythrine allowed the recovery of systolic ventricular wall thickening in rabbits, while elevated concentrations of chelerythrine blocked PKCε translocation and PC. This same group demonstrated that nitric oxide was responsible for PC-induced PKCε activation and protection in rabbits [28] by a mechanism involving nitric oxideinduced nitration of PKCε and enhanced PKCε interaction with its intracellular RACK [28,29].…”

Intermittent hypoxia-induced delayed cardioprotection is mediated by PKC and triggered by p38 MAP kinase and Erk1/2

“…Furthermore, activation of PKC after ischemic PC is isoform selective. Notably, the epsilon isoform appears to be responsible for the development of delayed cardioprotection in the rabbit [28]. Thus assessment of the PKC isoform relevant to protection induced by IH should be of interest.…”

Protein Kinase C-β and Oxygen Deprivation

“…Recent studies have particularly focussed attention on the ␤-isoforms because of their potential role in cardiovascular dysfunction, especially as relates to endothelial cells and cardiac myocytes (45)(46)(47)(48)(49)(50)(51)(52)(53). Most studies analyzing PKC␤ isoforms have relied on inhibitors that show apparent specificity for ␤I/␤II versus other members of the PKC family (44, 45, 54 -59).…”