Angiotensin II‐preconditioning is associated with increased PKCε/PKCδ ratio and prosurvival kinases in mitochondria

Abstract

Summary Angiotensin II-preconditioning (APC) has been shown to reproduce the cardioprotective effects of ischaemic preconditioning (IPC), however, the molecular mechanisms mediating the effects of APC remain unknown. In this study, Langendorff-perfused rat hearts were subjected to IPC, APC or both (IPC/APC) followed by ischaemia-reperfusion (IR), to determine translocation of PKCε, PKCδ, Akt, Erk1/2, JNK, p38 MAPK and GSK-3β to mitochondria as an indicator of activation of the protein kinases. In agreement with previous observations, IPC, APC and IPC/APC increased the recovery of left ventricular developed pressure (LVDP), reduced infarct size (IS) and lactate dehydrogenase (LDH) release, compared to controls. These effects were associated with increased mitochondrial PKCε/PKCδ ratio, Akt, Erk1/2, JNK, and inhibition of permeability transition pore (mPTP) opening. Chelerythrine, a pan-PKC inhibitor, abolished the enhancements of PKCε but increased PKCδ expression, and inhibited Akt, Erk1/2, and JNK protein levels. The drug had no effect on the APC- and IPC/APC-induced cardioprotection as previously reported, but enhanced the post-ischaemic LVDP in controls. Losartan, an angiotensin II type 1 receptor (AT1-R) blocker, abolished the APC-stimulated increase of LVDP and reduced PKCε, Akt, Erk1/2, JNK, and p38. Both drugs reduced ischaemic contracture and LDH release, and abolished the inhibition of mPTP by the preconditioning. Chelerythrine also prevented the reduction of IS by APC and IPC/APC. These results suggest that the cardioprotection induced by APC and IPC/APC involves an AT1-R-dependent translocation of PKCε and survival kinases to the mitochondria leading to mPTP inhibition. In chelerythrine-treated hearts, however, alternate mechanisms appear to maintain cardiac function.

Critical role of angiotensin II type 2 receptors in the control of mitochondrial and cardiac function in angiotensin II-preconditioned rat hearts

“…During the post-ischemic phase (Fig. 2d), APC improved cardiac recovery by 2.1-fold ( p <0.05) and this effect was abrogated by losartan as previously reported [35,36]. However, cardiac recovery significantly enhanced compared with the control or APC in the presence of PD with or without losartan (APC+PD versus Control: 3.7-fold, p <0.05; APC+L+PD versus APC: 72%, p <0.05).…”

“…We previously reported [36] that APC operates through a chelerythrine-sensitive, PKCε-dependent signaling in the mitochondria. For this reason, we then evaluated the effects of AT1-Rs and AT2-Rs blockade on the levels of protein kinases (PKCε, PKCδ, Akt, MAPKs, and PKG-1) involved in the APC-mediated signaling pathway in mitochondria from control and APC hearts.…”

“…Indeed, treatment with RAS inhibitors [ARBs, and angiotensin-converting enzyme (ACE) inhibitors] ameliorates the pathophysiological conditions associated with RAS upregulation. However, recent reports [13,30,35,36,44] indicate that brief and repetitive exposure of rat hearts to Ang II, known as Ang II preconditioning (APC), exerts cardioprotective effects against ischemia-reperfusion (IR) injury. The cardioprotective effect of APC is characterized by improved cardiac function, reduced mitochondrial permeability transition pore (mPTP) opening, improved respiratory control index (RCI), and reduced infarct size (IS) and LDH release [35].…”

“…The cardioprotective effect of APC is characterized by improved cardiac function, reduced mitochondrial permeability transition pore (mPTP) opening, improved respiratory control index (RCI), and reduced infarct size (IS) and LDH release [35]. APC also increased the PKCε/PKCδ ratio and promoted a chelerythrine-sensitive translocation of Akt, and MAPKs (ERK1/2, p38, JNK) to the mitochondria [36]. The AT1-R is required for APC because blockade of the receptor by losartan abolished the APC-induced post-ischemic recovery of cardiac function as well as PKCε-dependent signaling in heart mitochondria.…”

“…The AT1-R is required for APC because blockade of the receptor by losartan abolished the APC-induced post-ischemic recovery of cardiac function as well as PKCε-dependent signaling in heart mitochondria. Also, the reduction of IS by APC can be prevented by pretreatment with chelerythrine (pan-PKC inhibitor) or its infusion at reperfusion [36]. These studies indicated that the effects of APC include an AT1-R-mediated mechanism that promotes cardioprotection through the activation/translocation of PKCε-dependent survival kinases to the mitochondria and the inhibition of mPTP.…”