Phospholemman Ser69 phosphorylation contributes to sildenafil-induced cardioprotection against reperfusion injury

Madhani, M., Hall, A. R., Cuello, F., Charles, R. L., Burgoyne, J. R., Fuller, W. , Hobbs, A. J., Shattock, M. J. and Eaton, P. (2010) Phospholemman Ser69 phosphorylation contributes to sildenafil-induced cardioprotection against reperfusion injury. American Journal of Physiology: Heart and Circulatory Physiology, 299(3), H827-H836. (doi:10.1152/ajpheart.00129.2010) (PMID:20543084) (PMCID:PMC2944484)

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Abstract

The phosphodiesterase type-5 inhibitor sildenafil has powerful cardioprotective effects against ischemia-reperfusion injury. PKG-mediated signaling has been implicated in this protection, although the mechanism and the downstream targets of this kinase remain to be fully elucidated. In this study we assessed the role of phospholemman (PLM) phosphorylation, which activates the Na+/K+-ATPase, in cardioprotection afforded by sildenafil administered during reperfusion. Isolated perfused mouse hearts were optimally protected against infarction (indexed by tetrazolium staining) by 0.1 μM sildenafil treatment during the first 10 min of reperfusion. Extended sildenafil treatment (30, 60, or 120 min at reperfusion) did not alter the degree of protection provided. This protection was PKG dependent, since it was blocked by KT-5823. Western blot analysis using phosphospecific antibodies to PLM showed that sildenafil at reperfusion did not modulate PLM Ser63 or Ser68 phosphorylation but significantly increased Ser69 phosphorylation. The treatment of isolated rat ventricular myocytes with sildenafil or 8-bromo-cGMP (PKG agonist) enhanced PLM Ser69 phosphorylation, which was bisindolylmaleimide (PKC inhibitor) sensitive. Patch-clamp studies showed that sildenafil treatment also activated the Na+/K+-ATPase, which is anticipated in light of PLM Ser69 phosphorylation. Na+/K+-ATPase activation during reperfusion would attenuate Na+ overload at this time, providing a molecular explanation of how sildenafil guards against injury at this time. Indeed, using flame photometry and rubidium uptake into isolated mouse hearts, we found that sildenafil enhanced Na+/K+-ATPase activity during reperfusion. In this study we provide a molecular explanation of how sildenafil guards against myocardial injury during postischemic reperfusion.

Item Type:Articles
Additional Information:We thank The British Heart Foundation and The Wellcome Trust for their support.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Fuller, Dr Will
Authors: Madhani, M., Hall, A. R., Cuello, F., Charles, R. L., Burgoyne, J. R., Fuller, W., Hobbs, A. J., Shattock, M. J., and Eaton, P.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Journal Name:American Journal of Physiology: Heart and Circulatory Physiology
Publisher:American Physiological Society
ISSN:0363-6135
ISSN (Online):1522-1539
Published Online:01 September 2010

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