Original article
CXCR4 modulates contractility in adult cardiac myocytes

https://doi.org/10.1016/j.yjmcc.2006.08.008Get rights and content

Abstract

The inflammatory response is critical to the development and progression of heart failure. Chemokines and their receptors are a distinct class of inflammatory modulators that may play a role in mediating myocardial dysfunction in heart failure. Levels of the chemokine CXCL12, also known as stromal cell-derived factor (SDF), and its receptor, CXCR4, are elevated in patients with heart failure, and we undertook this study to determine whether this chemokine system can directly affect cardiac function in the absence of leukocytes. Murine papillary muscles and adult rat cardiac myocytes treated with CXCL12, the only identified ligand of CXCR4, demonstrate blunted inotropic responses to physiologic concentrations of calcium. The negative inotropic effects on cardiac myocytes are accompanied by a proportional diminution of calcium transients. The effects are abrogated by AMD3100, a specific CXCR4 inhibitor. Overexpression of the receptor through adenoviral infection with a CXCR4 construct accentuates the negative inotropic effects of CXCL12 on cardiac myocytes during calcium stimulation. CXCR4 activation also attenuates beta-adrenergic-mediated increases in calcium mobilization and fractional shortening in cardiac myocytes. In electrophysiologic studies, CXCL12 decreases forskolin- and isoproterenol-induced voltage-gated L-type calcium channel activation. These studies demonstrate that activation of CXCR4 results in a direct negative inotropic modulation of cardiac myocyte function. The specific mechanism of action involves alterations of calcium channel activity on the membrane. The presence of functional CXCR4 on cardiac myocytes introduces a new target for treating cardiac dysfunction.

Introduction

Chemokines and their receptors are a relatively new class of inflammatory mediators that regulate inflammation by directing leukocytes to sites of injury. Chemokines and their receptors are up-regulated in patients with heart failure and therefore have been implicated in the development of this disease (reviewed in [1]). Contractile dysfunction is a prominent feature in heart failure, and there is an inverse relationship between chemokine levels and cardiac performance [2]. However, it is unclear whether these findings are merely coincidental or whether chemokines actually play a mechanistic role in mediating myocardial dysfunction. Furthermore, if chemokines mediate cardiac dysfunction, it is not clear whether the mechanism is via inflammatory cells or whether chemokines, through their receptors on the cardiac myocyte (CM) surface, can directly affect myocardial function.

The function of chemokines initially was thought to be limited to their migratory effects on inflammatory cells. However, as knowledge of the physiologic roles for chemokines and their receptors has markedly expanded, it is now appreciated that chemokine receptors mediate a myriad of important biological effects by activating their receptors on organs in a manner independent of inflammatory cells. CXCR4 exemplifies this concept. It is present on the mammalian heart and appears to play a critical role in cardiovascular development, in the mobilization of hematopoietic precursors and in vasculogenesis [3], [4]. CXCR4 is also a co-receptor for HIV infection and can modulate Ca2+ channel function in neuronal cell lines [5].

CXCR4 is one of several chemokine receptors that are up-regulated in patients with heart failure [2], [6], [7]. To our knowledge, it is the only chemokine receptor that has been shown to be up-regulated in the failing myocardium of patients by direct staining [6]. Other studies examining chemokine receptors in heart failure have analyzed whole heart specimens to assess mRNA levels and therefore cannot localize the cellular source of the receptor given that the heart is composed of heterogeneous cell types. In early cardiac allograft rejection, where myocardial dysfunction can be significant without an obviously discernible cause (such as significant myocyte necrosis), CXCR4 expression is also elevated [8], [9], [10], [11].

Given the increased expression of CXCR4 on dysfunctional myocardium in a variety of diseases and the specificity of CXCL12 (formerly known as stromal cell-derived factor (SDF-1)) for binding to CXCR4, this is an ideal model to demonstrate experimentally that a chemokine can directly affect myocardial function. The present study examines the effects of CXCR4 activation on myocardial contractility and explores the mechanisms at the cellular level. We demonstrate that CXCR4 negatively modulates myocardial contractility by binding its endogenous ligand, CXCL12. The mechanism of action involves an alteration of calcium (Ca2+) metabolism in response to β-adrenergic and Ca2+ stimulation in CM. These studies identify a potentially new class of receptors to target in the treatment of cardiac dysfunction.

Section snippets

Papillary muscle contractility measurements

Papillary muscles (PM) from 10-week-old male FVBN-1 mice (Jackson Laboratories) were excised, loaded onto a force-transducer (Grass Instruments) and immersed in a circulating tissue bath at 37 °C. PM were field stimulated with platinum electrodes at 2× pacing threshold amplitude with a pacing frequency of 0.3 Hz and a stimulus duration of 0.3 ms. PM were then equilibrated in a modified Tyrode solution (containing the following in mM: K+, 5.9; Na+, 135.0; Cl, 126.0; Ca2+, 1.0; HCO3, 15.0; PO4

CXCR4 activation decreases PM contractility

Control and CXCL-12-treated papillary muscles were subjected to a first Ca2+ challenge to establish baseline function. They were then equilibrated at baseline Ca2+e prior to a second Ca2+ challenge. Prior to the second Ca2+ challenge, control PM were treated for 5 min with either diluent or CXCL12. Control PM demonstrated similar Log ED50 during the second (1.5 ±  0.13) and first (0.90 ± 0.23) Ca2+ challenges (p > 0.05) (Fig. 1A). In contrast, exposure to CXCL12 significantly blunted the PM response

Discussion

Heart failure is a clinical syndrome characterized by the inability of the heart to produce an adequate cardiac output [19]. A key contributor to the dysfunction may be depressed myocardial contractility [20], [21]. Studies that have examined the function of cardiac myocytes (CM) isolated from failing hearts suggest that a defect in CM contractility may contribute to the overall cardiac dysfunction [22]. The responsible agents or mechanisms, however, remain incompletely characterized.

Acknowledgments

We thank Dr. Federica del Monte for providing human cardiomyocytes and for providing insightful comments in manuscript preparation. This work was supported in part by grants from NIH: HL073458, HL054469 to ADS and HL057623, HL071763, HL078691 to RJH.

References (52)

  • S.D. Anker et al.

    How to RECOVER from RENAISSANCE? The significance of the results of RECOVER, RENAISSANCE, RENEWAL and ATTACH

    Int. J. Cardiol.

    (2002)
  • Y. Seino et al.

    Expression of leukocyte chemotactic cytokines in myocardial tissue

    Cytokine

    (1995)
  • C. Akekawatchai et al.

    Transactivation of CXCR4 by the insulin-like growth factor-1 receptor (IGF-1R) in human MDA-MB-231 breast cancer epithelial cells

    J. Biol. Chem.

    (2005)
  • T. Gudjonsson et al.

    Relation of “inotropic reserve” to functional capacity in heart failure secondary to ischemic or nonischemic cardiomyopathy

    Am. J. Cardiol.

    (2002)
  • A.P. Beltrami et al.

    Adult cardiac stem cells are multipotent and support myocardial regeneration

    Cell

    (2003)
  • P. Aukrust et al.

    Chemokines in myocardial failure-pathogenic importance and potential therapeutic targets

    Clin. Exp. Immunol.

    (2001)
  • P. Aukrust et al.

    Elevated circulating levels of C-C chemokines in patients with congestive heart failure

    Circulation

    (1998)
  • Y.-R. Zou et al.

    Function of the chemokine receptor CXCR4 in haematopoiesis and in cerebellar development

    Nature

    (1998)
  • K. Tachibana et al.

    The chemokine receptor CXCR4 is essential for vascularization of the gastrointestinal tract

    Nature

    (1998)
  • J.K. Damas et al.

    Myocardial expression of CC- and CXC-chemokines and their receptors in human end-stage heart failure

    Cardiovasc. Res.

    (2000)
  • N.M. Fahmy et al.

    Chemokine and receptor-gene expression during early and late acute rejection episodes in human cardiac allografts

    Transplantation

    (2003)
  • C. Communal et al.

    beta1 integrins expression in adult rat ventricular myocytes and its role in the regulation of beta-adrenergic receptor-stimulated apoptosis

    J. Cell Biochem.

    (2003)
  • R.J. Hajjar et al.

    Adenoviral gene transfer of phospholamban in isolated rat cardiomyocytes: rescue effects by concomitant gene transfer of sarcoplasmic reticulum Ca2+-ATPase

    Circ. Res.

    (1997)
  • F. del Monte et al.

    Improvement in survival and cardiac metabolism after gene transfer of sarcoplasmic reticulum Ca (2+)-ATPase in a rat model of heart failure

    Circulation

    (2001)
  • F. del Monte et al.

    Restoration of contractile function in isolated cardiomyocytes from failing human hearts by gene transfer of SERCA2a

    Circulation

    (1999)
  • G.A. Donzella et al.

    AMD3100, a small molecule inhibitor of HIV-1 entry via the CXCR4 co-receptor

    Nat. Med.

    (1998)
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