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?2-adrenergic receptors mediate cardioprotection through crosstalk with mitochondrial cell death pathways.

ABSTRACT: ?-adrenergic receptors (?-ARs) modulate cardiotoxicity/cardioprotection through crosstalk with multiple signaling pathways. We have previously shown that ?2-ARs are cardioprotective during exposure to oxidative stress induced by doxorubicin (DOX). DOX cardiotoxicity is mediated in part through a Ca(2+)-dependent opening of the mitochondrial permeability transition (MPT), however the signals linking a cell surface receptor like the ?2-AR to regulators of mitochondrial function are not clear. The objective of this study was to assess mechanisms of crosstalk between ?2-ARs and mitochondrial cell death pathways. DOX administered to WT mice resulted in no acute mortality, however 85% of ?2-/- mice died within 30 min. Several pro- and anti-survival pathways were altered. The pro-survival kinase, ?PKC, was decreased by 64% in ?2-/- after DOX vs WT (p<0.01); the ?PKC activator ??RACK partially rescued these mice (47% reduction in mortality). Activity of the pro-survival kinase Akt decreased by 76% in ?2-/- after DOX vs WT (p<0.01). The ?1-antagonist prazosin restored Akt activity to normal and also partially reversed the mortality (45%). Deletion of the ?2-AR increased rate of Ca(2+) release by 75% and peak [Ca(2+)](i) by 20% respectively in isolated cardiomyocytes; the Ca(2+) channel blocker verapamil also partially rescued the ?2-/- (26%). Mitochondrial architecture was disrupted and complex I and II activities decreased by 40.9% and 34.6% respectively after DOX only in ?2-/-. The MPT blocker cyclosporine reduced DOX mortality by 41% and prazosin plus cyclosporine acted synergistically to decrease mortality by 85%. ?2-ARs activate pro-survival kinases and attenuate mitochondrial dysfunction during oxidative stress; absence of ?2-ARs enhances cardiotoxicity via negative regulation of survival kinases and enhancement of intracellular Ca(2+), thus predisposing the mitochondria to opening of the MPT.

SUBMITTER: Fajardo G

PROVIDER: S-EPMC3184305 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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β2-adrenergic receptors mediate cardioprotection through crosstalk with mitochondrial cell death pathways.

Fajardo Giovanni G Zhao Mingming M Berry Gerald G Wong Lee-Jun LJ Mochly-Rosen Daria D Bernstein Daniel D

Journal of molecular and cellular cardiology 20110702 5

β-adrenergic receptors (β-ARs) modulate cardiotoxicity/cardioprotection through crosstalk with multiple signaling pathways. We have previously shown that β2-ARs are cardioprotective during exposure to oxidative stress induced by doxorubicin (DOX). DOX cardiotoxicity is mediated in part through a Ca(2+)-dependent opening of the mitochondrial permeability transition (MPT), however the signals linking a cell surface receptor like the β2-AR to regulators of mitochondrial function are not clear. The ...[more]

PMID: 21756913

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Project description:Endothelial cells (EC) serve a paracrine function to enhance signaling in cardiomyocytes (CM), and conversely, CM secrete factors that impact EC function. Understanding how EC interact with CM may be critically important in the context of ischemia-reperfusion injury, where EC might promote CM survival. We used isoflurane as a pharmacological stimulus to enhance EC protection of CM against hypoxia and reoxygenation injury. Triggering of intracellular signal transduction pathways culminating in the enhanced production of nitric oxide (NO) appears to be a central component of pharmacologically induced cardioprotection. Although the endothelium is well recognized as a regulator for vascular tone, little attention has been given to its potential importance in mediating cardioprotection. In the current investigation, EC-CM in co-culture were used to test the hypothesis that EC contribute to isoflurane-enhanced protection of CM against hypoxia and reoxygenation injury and that this protection depends on hypoxia-inducible factor (HIF1?) and NO. CM were protected against cell injury [lactate dehydrogenase (LDH) release] to a greater extent in the presence vs. absence of isoflurane-stimulated EC (1.7 ± 0.2 vs. 4.58 ± 0.8 fold change LDH release), and this protection was NO-dependent. Isoflurane enhanced release of NO in EC (1103 ± 58 vs. 702 ± 92 pmol/mg protein) and EC-CM in co-culture sustained NO release during reoxygenation. In contrast, lentiviral mediated HIF1? knockdown in EC decreased basal and isoflurane stimulated NO release in an eNOS dependent manner (517 ± 32 vs. 493 ± 38 pmol/mg protein) and prevented the sustained increase in NO during reoxygenation when co-cultured. Opening of mitochondrial permeability transition pore (mPTP), an index of mitochondrial integrity, was delayed in the presence vs. absence of EC (141 ± 2 vs. 128 ± 2.5 arbitrary mPTP opening time). Isoflurane stimulated an increase in HIF1? in EC but not in CM under normal oxygen tension (3.5 ± 0.1 vs. 0.79 ± 0.15 fold change density) and this action was blocked by pretreatment with the Mitogen-activated Protein/Extracellular Signal-regulated Kinase inhibitor U0126. Expression and nuclear translocation of HIF1? were confirmed by Western blot and immunofluorescence. Taken together, these data support the concept that EC are stimulated by isoflurane to produce important cardioprotective factors that may contribute to protection of myocardium during ischemia and reperfusion injury.

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?2-adrenergic receptors mediate cardioprotection through crosstalk with mitochondrial cell death pathways.

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β2-adrenergic receptors mediate cardioprotection through crosstalk with mitochondrial cell death pathways.

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