Functional and cardioprotective effects of simultaneous and individual activation of protein kinase A and Epac.

Igor Khaliulin,M‐Saadeh Suleiman,Zara Dyar,Mark Bond,Andrew F James,Jason L Johnson,Raheleh Amini

doi:10.1111/bph.13709

Igor Khaliulin, M‐Saadeh Suleiman + Show 5 more

Open Access

https://doi.org/10.1111/bph.13709

Copy DOI

Abstract

Background and PurposeMyocardial cAMP elevation confers cardioprotection against ischaemia/reperfusion (I/R) injury. cAMP activates two independent signalling pathways, PKA and Epac. This study investigated the cardiac effects of activating PKA and/or Epac and their involvement in cardioprotection against I/R.Experimental ApproachHearts from male rats were used either for determination of PKA and PKC activation or perfused in the Langendorff mode for either cardiomyocyte isolation or used to monitor functional activity at basal levels and after 30 min global ischaemia and 2 h reperfusion. Functional recovery and myocardial injury during reperfusion (LDH release and infarct size) were evaluated. Activation of PKA and/or Epac in perfused hearts was induced using cell permeable cAMP analogues in the presence or absence of inhibitors of PKA, Epac and PKC. H9C2 cells and cardiomyocytes were used to assess activation of Epac and effect on Ca2+ transients.Key ResultsSelective activation of either PKA or Epac was found to trigger a positive inotropic effect, which was considerably enhanced when both pathways were simultaneously activated. Only combined activation of PKA and Epac induced marked cardioprotection against I/R injury. This was accompanied by PKCε activation and repressed by inhibitors of PKA, Epac or PKC.Conclusion and ImplicationsSimultaneous activation of both PKA and Epac induces an additive inotropic effect and confers optimal and marked cardioprotection against I/R injury. The latter effect is mediated by PKCε activation. This work has introduced a new therapeutic approach and targets to protect the heart against cardiac insults.

Highlights

Cardiac ischaemia/reperfusion (I/R) injury can occur during coronary angioplasty, cardiac surgery and heart transplantation (Depre and Taegtmeyer, 2000) contributing to morbidity and mortality (Eltzschig and Eckle, 2011)
The aim of these experiments was to establish whether the strong inotropic response produced by 8-Br, which activates both PKA and Epac, is mediated by an increase in intracellular Ca2+ transients that is comparable with isoprenaline, which we have previously found to induce a strong cardioprotective effect (Khaliulin et al, 2014)
Optimization and validation of the effects of cAMP analogues and inhibitors The indirect or direct activation of PKA and Epac caused a significant increase in the amplitude of Ca2+ transients measured in electrically stimulated and superfused cardiomyocytes (Supplementary Information Fig. S1)

Summary

Introduction

Cardiac ischaemia/reperfusion (I/R) injury can occur during coronary angioplasty, cardiac surgery and heart transplantation (Depre and Taegtmeyer, 2000) contributing to morbidity and mortality (Eltzschig and Eckle, 2011). This injury is mediated by the opening of the mitochondria permeability transition pore (MPTP), which can be triggered by Ca2+ overload (Halestrap et al, 2004) and ROS (Honda et al, 2005; Halestrap and Pasdois, 2009). We investigated the cardioprotective efficacy of cAMP/PKA and cAMP/Epac signalling pathways using cell permeable cAMP analogues that are selective activators of either PKA or Epac or both and assessed the involvement of PKC in the cAMP-induced cardioprotection. H9C2 cells and cardiomyocytes were used to assess activation of Epac and effect on Ca2+ transients

Methods

Results

Discussion

Conclusion