Age-related loss of cardiac preconditioning: Impact of protein kinase A

doi:10.1016/j.exger.2011.11.003

Experimental Gerontology

Volume 47, Issue 1, January 2012, Pages 116-121

https://doi.org/10.1016/j.exger.2011.11.003 Get rights and content

Abstract

Helium induces preconditioning (He-PC) by mitochondrial calcium-sensitive potassium (mK_Ca) channel-activation, but this effect is lost in the aged myocardium. Both, the upstream signalling pathway of He-PC and the underlying mechanisms for an age-related loss of preconditioning are unknown. A possible candidate as upstream regulator of mK_Ca channels is protein kinase A (PKA).

We investigated whether 1) regulation of PKA is involved in He-PC and 2) regulation of PKA is age-dependent.

Young (2–3 months) and aged (22–24 months) Wistar rats were randomised to eight groups (each n = 8). All animals underwent 25 min regional myocardial ischemia and 120 min reperfusion. Control (Con, Age Con) animals were not further treated. Young rats inhaled 70% helium for 3 × 5min (He-PC). The PKA-blocker H-89 (10 μg/kg) was administered with and without helium (He-PC + H-89, H-89). Furthermore, we tested the effect of direct activation of mK_Ca channels with NS1619. The adenylyl cyclase activator forskolin (For) was administered in young (300 μg/kg) and aged animals (300 and 1000 μg/kg).

He-PC reduced infarct size from 60 ± 4% (Con) to 37 ± 10% (p < 0.05). Infarct size reduction was completely abolished by H-89 (58 ± 5%; p < 0.05), but H-89 alone had no effect (57 ± 2%). NS1619 reduced infarct size in the same concentration in both, young and aged rats (35 ± 6%; p < 0.05 vs. Con and 34 ± 8%; p < 0.05 vs. Age Con). Forskolin in a concentration of 300 μg/kg reduced infarct size in young (37 ± 6%; p < 0.05) but not in aged rats (48 ± 13%; n.s.). In contrast, 1000 μg/kg Forskolin reduced infarct size also in aged rats (28 ± 3%; p < 0.05).

He-PC is mediated by activation of PKA. Alterations in PKA regulation might be an underlying mechanism for the age-dependent loss of preconditioning.

Highlights

► Activation of PKA is critically involved in helium preconditioning. ► Differences in AC/PKA regulation might cause an aged related loss of preconditioning. ► The aged heart can be protected by activation of mK_Ca, the downstream target of PKA.

Introduction

Ageing is associated with an increase in morbidity and mortality following myocardial infarction (Devlin et al., 1995, Haase et al., 2000, Maggioni et al., 1993). Loss of cardioprotective strategies, i.e. preconditioning, during senescence has been suggested as one of the underlying mechanisms (Abete et al., 1996, Juhaszova et al., 2005, Lee et al., 2002, Tani et al., 1997). The cardioprotective effect of preconditioning can be mimicked by the noble gas helium (Pagel et al., 2007). Helium confers cardioprotection via modulation of the mitochondrial permeability transition pore (mPTP) (Pagel et al., 2007). Recently, we demonstrated that the cardioprotective effect of helium was abrogated by the calcium-sensitive potassium (K_Ca) channel blocker iberiotoxin (Heinen et al., 2008). Furthermore, helium caused a mild uncoupling of mitochondrial respiration and oxidative phosphorylation, an effect that was also blocked by iberiotoxin (Heinen et al., 2008). Therefore, we concluded that activation of mitochondrial K_Ca (mK_Ca) channels with the consequence of altered mitochondrial bioenergetics is critically involved in the signalling pathway of helium preconditioning. In senescent rat hearts, no infarct size reducing effect of helium was detectable (Heinen et al., 2008). Interestingly, not only the protective effect of helium was lost in the aged heart, but also the mild uncoupling effect on mitochondrial respiration (Heinen et al., 2008). Based on these data, we hypothesised that the age-related loss of the protective potency of preconditioning is caused at the level of the mK_Ca channel and/or its upstream signalling pathway. The upstream pathway by which helium activates mK_Ca channels is unknown. A possible candidate as upstream regulator is protein kinase A (PKA). It has been demonstrated that mK_Ca channels can be activated by PKA (Nishida et al., 2008). PKA itself is regulated by cyclic adenosine 3′,5′-monophosphate (cAMP), which is a product of adenylyl cyclase (AC). Therefore, we aimed to investigate in the present study 1) whether PKA is critically involved in helium-induced preconditioning, and 2) whether the age-related loss of cardioprotection is caused by signalling defects at the level of AC/PKA activation.

Section snippets

Material and methods

The investigation is in accordance with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication No. 85–23, revised 1996), and was performed after approval of the Animal Ethics Committee of the University of Amsterdam, Amsterdam, The Netherlands.

Infarct size measurement

Infarct size was reduced by helium-induced preconditioning in young rats (37 ± 10% in He-PC vs. 60 ± 4% in controls, p < 0.05, Fig. 2). Administration of H-89 before the preconditioning stimulus completely abolished cardioprotection (58 ± 5%; p < 0.05 vs. He-PC). H-89 alone had no effect on infarct size (57 ± 2%; ns vs. Con). Administration of the mK_Ca channel activator NS1619 reduced infarct size to 35 ± 6% (p < 0.05 vs. Con). Activation of PKA by adenylyl cyclase activator forskolin reduced infarct size to

Discussion

Preconditioning is a cardioprotective phenomenon in which short periods of myocardial ischemia protect the heart against a subsequent longer ischemia and reduces the deleterious consequences of ischemia/reperfusion injury (Murry et al., 1986). Preconditioning consists of two phases: an early phase lasting up to 2–3 h after the preconditioning stimulus and a late phase reoccurring after 24 h and lasting up to 3–4 days. However, most studies that investigated the protective effects of

Funding

This study was funded in part by a research starter grant (9772429) of the research committee of the medical faculty of the Heinrich-Heine-University Düsseldorf to Ragnar Huhn, André Heinen and Inge Bauer.

Acknowledgements

The authors wish to thank Yvonne Grüber for her technical support with this study.

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Opening of mitochondrial calcium-activated potassium channels (BK_Ca) reduces infarct size after myocardial ischemia/reperfusion injury (I/R). It is unknown if targeting BK_Ca-channels improves cardiac performance in the long-term after I/R.
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Until recently, He-PC was used in animal studies, and results demonstrated that this modality may exert protective effects in some animal models [3–7]. The cardioprotective effects of He-PC are the most extensively investigated, and have been found to be associated with prosurvival signaling kinases [10], mitochondrial permeability transition pore (MPTP) opening [22], mitochondrial uncoupling [23], Ca2+-sensitive potassium channel [23], ROS [9,10], mitochondrial ATP-regulated K+ channel [22], mitochondrial permeability transition [24], opioid receptors [24] and protein kinase A (PKA) [25], but not with a mechanism involving glycogen synthase kinase 3 beta (GSK-3β) and protein kinase C-epsilon (PKC-ε) [26]. More recently, a clinical study revealed that helium induced early and late preconditioning of human endothelium in vivo, which had no influence on the plasma levels of cytokines, adhesion molecules, or microparticles and were independent of endothelial NO synthase [27].
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Age-related loss of cardiac preconditioning: Impact of protein kinase A

Abstract

Highlights

Introduction

Section snippets

Material and methods

Infarct size measurement

Discussion

Funding

Acknowledgements

J. Am. Coll. Cardiol.

Am. J. Cardiol.

J. Biol. Chem.

Mech. Ageing Dev.

Hypoxia induces late preconditioning in the rat heart in vivo

Anesthesiology

In-hospital mortality of elderly patients with acute myocardial infarction: data from the MITRA (Maximal Individual Therapy in Acute Myocardial Infarction) registry

Clin. Cardiol.

Helium-induced preconditioning in young and old rat heart: impact of mitochondrial Ca(2 +) -sensitive potassium channel activation

Anesthesiology

Protection in the aged heart: preventing the heart-break of old age?

Cardiovasc. Res.

Minimum alveolar concentrations of noble gases, nitrogen, and sulfur hexafluoride in rats: helium and neon as nonimmobilizers (nonanesthetics)

Anesth. Analg.

Loss of preconditioning by attenuated activation of myocardial ATP-sensitive potassium channels in elderly patients undergoing coronary angioplasty

Circulation