Skip Navigation


Cardiovascular Research Advance Access originally published online on July 2, 2008
Cardiovascular Research 2008 79(4):545-546; doi:10.1093/cvr/cvn186
This Article
Right arrow Extract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
79/4/545    most recent
cvn186v2
cvn186v1
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Lochner, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lochner, A.
Related Collections
Right arrowRelated Article
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2008. For permissions please email: journals.permissions@oxfordjournals.org

Sarcolemmal permeability changes during ischaemia and reperfusion: release of survival factors

Amanda Lochner*

Department Biomedical Sciences, Division of Medical Physiology, Faculty of Health Sciences, University of Stellenbosch, PO Box 19063, Tygerberg, Republic of South Africa

* Corresponding author. Tel: +27 21 938 9391; fax: +27 21 938 9476. E-mail address: alo{at}sun.ac.za

This editorial refers to ‘Identification and physiological activity of survival factor released from cardiomyocytes during ischaemia and reperfusion’ by Y. Mizukami et al.,14 pp. 589–599, this issue.

Enzyme release by ischaemic myocardium has been used as a hallmark of the infarction process for several decades: in the clinical setting, deterioration of cell membrane integrity, as evidenced by the release of macromolecules such as creatine kinase and lactate dehydrogenase, has been used as quantitative indication of myocardial infarction. Leakage of membrane-impermeable molecules due to sarcolemmal rupture is considered to be the most prominent feature of irreversible injury, and the main mechanisms proposed to underlie this phenomenon are energy deficiency and calcium overload.1,2 However, changes in sarcolemmal permeabililty have been demonstrated to occur after exposure of the heart to relatively short periods of ischaemia. Using NMR spectroscopy, Askenasy et al.3 showed that sarcolemmal integrity deteriorated as a function of the duration of ischaemia and that even after as short a period as 10 min ischaemia cellular membrane permeability to osmolytes increased, although myocytes remained impermeable to polar and large molecules. Interestingly, before the onset of irreversible injury, enzyme release by the ischaemic perfused heart can be manipulated by the substrate present: for example, glucose reduces fatty acid-induced enzyme release, possibly via provision of glycolytic ATP.4,5 With the discovery of the phenomenon of ischaemic pre-conditioning, attention was again drawn to the potential of the myocardium to release a variety of substances (autocoids) after exposure to very short periods of ischaemia and reperfusion (e.g. 5 min), which may have either beneficial or detrimental effects on the heart. However, the causal stimulus for and the exact mechanism whereby the cardiomyocyte changes its sarcolemmal permeability properties during very short periods of ischaemia have not been resolved yet.

It is now well-established that the release of molecules such as adenosine, bradykinin, opioids, and catecholamines during the short episodes of ischaemia/reperfusion of a pre-conditioning protocol elicits, via their respective G-protein-coupled receptors and subsequent intracellular signalling processes, an adaptive response leading to resistance to a subsequent period of sustained ischaemia. In this regard, the significant involvement of adenosine, a breakdown product of ATP, in the response of the heart to ischaemia/reperfusion has been demonstrated in both pre- and post-conditioning.6 The copious amounts of catecholamines, particularly norepinephrine, which are released during reperfusion of the ischaemic myocardium7 have dual effects: both {alpha}1-adrenergic8 and β-adrenergic9 receptor stimulation may act as triggers during an ischaemic pre-conditioning protocol, while excessive accumulation during long periods of ischaemia aggravate the progression of cell injury and development of arrhythmias.10,11 Other substances of interest released by the ischaemic myocardium are the natriuretic peptides, atrial natriuretic peptide (ANP), and brain natriuretic peptide, e.g. an almost 3-fold increase in ANP release was reported after 5 min of ischaemia of the rat heart.12 The reduction in infarct size by these peptides was attributed to, amongst others, an increase in cyclic guanosine monophosphate levels and opening of the KATP channels.

In contrast to the above beneficial effects exerted by some substances released by the ischaemic myocardium, it is well-established that myocardial ischaemia also triggers the release of harmful substances such as the cytokines, tumour necrosis factor-{alpha}, interleukin-1β (IL-1β), and IL-6 and the platelet activating factor which depress myocardial contractility (for a review, see Stangl et al.13). However, in general, this seems to be a slower process, occurring during reperfusion after relatively longer periods of ischaemia.

In this edition of Cardiovascular Research, the release of a novel survival factor from an embryonic rat heart-derived cell line H9c2 during simulated ischaemia/reperfusion is described.14 Interestingly, it appears that this substance is released by a mechanism other than via a damaged membrane, since the rate of cell death among cells exposed to ischaemia/reperfusion in this study was almost equal to that of control cells. These cells were exposed to simulated ischaemia for 2 h (oxygen and glucose deprivation) and reperfusion (oxygen and glucose addition) for 24 h. A p36 protein was purified from polypeptides released from these cells and identified as the lactate dehydrogenase muscle (M-LDH) subunit. This compound protects cardiomyocytes against oxidative stress: pre-treatment of adult cardiomyocytes with M-LDH reduced H2O2-induced morphological changes and preserved contractility in response to electrical stimulation. Using fura-2-loaded H9c2 cells, the authors demonstrated that M-LDH suppresses H2O2-induced oxidative stress Ca2+ overloading, while it also inhibited the frequency and amplitude of early afterdepolarizations. Finally, this compound, in nanomolar amounts (25 nM), attenuated ischaemia/reperfusion-induced reduction in contractility of isolated perfused working mouse hearts. How does this compound accomplish its beneficial actions? Indications are that it does not exert its survival activity as an enzyme. To evaluate the involvement of the survival kinases in the cardioprotective actions of M-LDH, H9c2 cells were incubated with M-LDH, which caused a concentration-dependent increase in ERK1/2 phosphorylation, however, phosphorylation of p38 mitogen activated protein kinase, JNK1/2, and phospholipase C{gamma} remained unchanged. It was also suggested, but not proven, that a receptor for M-LDH may be present in cardiomyocytes.

In view of the role of activation of the reperfusion injury salvage kinase (RISK) pathway in cardioprotection, it is tempting to speculate that M-LDH-induced ERK1/2 activation may play a pivotal role in its actions, and that this may occur via inhibition of the mitochondrial permeability transition pore (MPTP). It is well established that agents such as insulin, erythropoietin, adipocytokines, adenosine, volatile anaesthetics, natriuretic peptides, etc. reduce infarct size via activation of survival kinases such as PI3-K/Akt and ERK1/2, which in turn cause inhibition of opening of the MPTP (for a review, see Hausenloy and Yellon15). The exact mechanism whereby the activation of the RISK pathway accomplishes this is still unclear. Downstream phosphorylation of glycogen synthase kinase-3β,16 BAD,17 and endothelial nitric oxide synthase18 may be involved. However, whether M-LDH exerts its cardioprotective actions through ERK1/2 and closure of the MPTP was not addressed by Mizukami et al.14

ERK1/2 activation during ischaemia/reperfusion has been suggested to contribute to cardioprotection through induction of {alpha}-enolase, a rate-limiting enzyme in the glycolytic pathway. In an earlier study by Mizukami et al.,19 the authors used functional proteomics by 2-D electrophoresis to identify an intracellular target for ERK1/2 in response to ischaemic hypoxia. At least four spots were found to be inhibited by the MEK inhibitor PD 98059. A protein with a molecular mass of 52 kDa that was strongly induced by ERK1/2 activation in response to ischaemic hypoxia/reoxygenation was identified as {alpha}-enolase. Introduction of {alpha}-enolase into cells caused an increase in ATP levels and attenuated cell death associated with ischaemia/reperfusion. This particular investigation suggested that ERK1/2 activation has a novel function that involved stimulation of glycolysis and ATP generation in diseases related to ischaemia.

Thus, the significance of ERK1/2 activation by M-LDH in the scenario of ischaemia/reperfusion injury still needs to be established. The use of appropriate inhibitors (e.g. PD 98059) may contribute to the elucidation of unsolved questions. In addition, the role of PKB/Akt activation, if any, in the actions of M-LDH, may also shed some light on the mechanism of action of this novel prosurvival factor.

Discovery of yet another prosurvival factor released by the cardiomyocyte after exposure to relatively mild ischaemia, which, in turn, sets into motion intracellular signalling events known to be associated with protection, is intriguing. It is effective in nanomolar quantities, suggesting that further investigation into the clinical potential of this protein is obvious.


   Notes
 
The opinions expressed in this article are not necessarily those of the Editors of Cardiovascular Research or of the European Society of Cardiology.


   References
Top
 References
 

  1. Jennings RB, Reimer KA, Steenbergen C. Myocardial ischaemia revisited: the osmolar load, membrane damage and reperfusion. J Mol Cell Cardiol (1986) 18:769–780.[CrossRef][Web of Science][Medline]
  2. Farber JL. Biology of disease: membrane injury and calcium homeostasis in the pathogenesis of coagulative necrosis. Lab Invest (1982) 47:114–123.[Web of Science][Medline]
  3. Askenasy N, Vivi A, Tassini M, Navon G, Farkas DL. NMR spectroscopic characterization of sarcolemmal permeability during myocardial ischaemia and reperfusion. J Mol Cell Cardiol (2001) 33:1420–1433.
  4. Opie LH, Bricknell OL. Role of glycolytic flux in effect of glucose in decreasing fatty acid-induced release of lactate dehydrogenase from isolated coronary ligated rat heart. Cardiovasc Res (1979) 13:693–702.[Abstract/Free Full Text]
  5. Lochner A, Pentz A, Williams K, Tromp E, Harper IS. Substrate effects on sarcolemmal permeability in the normoxic and hypoxic perfused rat heart. Bas Res Cardiol (1996) 91:64–78.[Web of Science][Medline]
  6. Downey JM, Krieg T, Cohen MV. Mapping preconditioning's signaling pathways. An engineering approach. Ann N Y Acad Sci (2008) 1123:187–196.[CrossRef][Web of Science][Medline]
  7. Schömig A, Dart AM, Dietz R, Mayer E, Kubler W. Release of endogenous catecholamines in the ischemic myocardium of the rat. Part A: locally mediated release. Circ Res (1984) 55:689–701.[Abstract/Free Full Text]
  8. Hu K, Nattel S. Mechanisms of ischemic preconditioning in rat hearts. Involvement of alpha 1B-adrenoceptors, pertussis toxin-sensitive G proteins and protein kinase C. Circulation (1995) 92:2259–2265.[Abstract/Free Full Text]
  9. Lochner A, Genade S, Tromp E, Podzuweit T, Moolman JA. Ischemic preconditioning and the beta-adrenergic signal transduction pathway. Circulation (1999) 100:958–966.[Abstract/Free Full Text]
  10. Penny WJ. The deleterious effects of myocardial catecholamines on cellular electrophysiology and arrhythmias during ischemia and reperfusion. Eur Heart J (1984) 5:960–973.[Abstract/Free Full Text]
  11. Waldenstrom AP, Hjalmarson AC, Thornell L. A possible role of noradrenaline in the development of myocardial infarction: an experimental study in the isolated rat heart. Am Heart J (1978) 95:43–51.[CrossRef][Web of Science][Medline]
  12. Uusimaa PA, Peuhkurinen KJ, Vuolteenaho O, Ruskoaho H, Hassinen IE. Role of myocardial and energy states in ischemia-stimulated release of atrial natriuretic peptide. J Mol Cell Cardiol (1992) 24:191–205.[Web of Science][Medline]
  13. Stangl V, Baumann G, Stangl K, Felix SB. Negative inotropic mediators released from the heart after myocardial ischaemia–reperfusion. Cardiovasc Res (2001) 53:12–30.[CrossRef][Web of Science]
  14. Mizukami Y, Ono K, Du C-K, Aki T, Hatano N, Okamoto Y, et al. Identification and physiological activity of survival factor released from cardiomyocytes during ischaemia and reperfusion. Cardiovasc Res (2008) 79:589–599.[Abstract/Free Full Text]
  15. Hausenloy DJ, Yellon DM. Reperfusion injury salvage kinase signalling: taking a RISK for cardioprotection. Heart Fail Rev (2007) 12:217–234.[CrossRef][Medline]
  16. Juhaszova M, Zorov DB, Kim SH, Pepe S, Fu Q, Fishbein KW, et al. Glycogen synthase kinase-3 beta mediates convergence of protection signaling to inhibit the mitochondrial permeability transition pore. J Clin Invest (2004) 113:1535–1549.[CrossRef][Web of Science][Medline]
  17. Jonassen AK, Mjos OD, Sack MN. p70s6kinase is a functional target of insulin activated Akt cell-survival signaling. Biochem Biophys Commun (2004) 315:160–165.[CrossRef][Web of Science][Medline]
  18. Kim JS, Ohshima S, Pediaditakis P, Lemasters JJ. Nitric oxide protects rat hepatocytes against reperfusion injury mediated by the mitochondrial permeability transition. Hepatology (2004) 39:1533–1543.[CrossRef][Web of Science][Medline]
  19. Mizukami Y, Iwamatsu A, Aki T, Kimura M, Nakamura K, Nao T, et al. ERK1/2 regulates intracellular ATP levels through {alpha}-enolase expression in cardiomyocytes exposed to ischemic hypoxia and reoxygenation. J Biol Chem (2004) 279:50120–50131.[Abstract/Free Full Text]

Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?

Related Article

Identification and physiological activity of survival factor released from cardiomyocytes during ischaemia and reperfusion
Yoichi Mizukami, Kyoichi Ono, Cheng-Kun Du, Toshihiko Aki, Naoya Hatano, Yosuke Okamoto, Yasuhiro Ikeda, Hiroshi Ito, Kimikazu Hamano, and Sachio Morimoto
Cardiovasc Res 2008 79: 589-599. [Abstract] [Full Text] [PDF]




This Article
Right arrow Extract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
79/4/545    most recent
cvn186v2
cvn186v1
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Lochner, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lochner, A.
Related Collections
Right arrowRelated Article
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?