Phosphodiesterase type 1 regulates adenosine 2A receptor-associated cAMP signaling at the plasma membrane to increase myocardial contractility

BACKGROUNDPhosphodiesterase type 1 (PDE1) inhibition exerts inodilatory effects in pre-clinical models and human heart failure patients with reduced ejection fraction (HFrEF). PDE1 hydrolyzes cyclic nucleotide cAMP in a soluble but not microsomal fraction of the human myocardium. PDE1 may exert domain-specific effects, but the mechanism whereby PDE1 compartmentalization induces an inotropic change remains unknown. We sought to elucidate PDE1 regulation of cAMP and contractility. METHODSPharmacologic modulators of PDEs or G-protein coupled receptors (GPCRs) were used to study PDE1 signaling mechanisms in healthy and failing guinea pig hearts. Tissue fractionation examined the localization of different PDE types. Live cell imaging experiments assessed cytosolic and sarcolemmal membrane cAMP level ([cAMP]) and protein kinase A (PKA) activity changes in cells transduced with Forster resonance energy transfer (FRET) biosensors. Sarcomere length and intracellular calcium changes monitored contractile changes in electrically paced cells. Coronary flow and left ventricular (LV) developed pressure were measured in ex vivo Langendorff perfusion heart studies. RESULTSPDE1 isoforms were found not only in the soluble, but also in the microsomal fractions of the guinea pig heart. PDE1 hydrolysis of cAMP was greater at the sarcolemma compared to the cytosol. PDE1 specifically regulated a pool of cAMP associated with the Gs protein coupled receptor adenosine 2A receptor (A2AR) at the sarcolemma, without activating PKA. A2AR/PDE1 regulation induced positive inotropic and lusitropic changes in healthy and failing guinea pig cardiomyocytes and in the myocardium ex vivo. CONCLUSIONSPDE1 is the major regulator of cAMP pools generated by A2AR activation at the sarcolemma. Functionally, this regulation induces inotropic and lusitropic effects in cardiomyocytes and at the whole organ level. Thus, PDE1 is compartmentalized at the membrane with A2AR, and this regulation determines cardiomyocyte contractility in healthy and failing hearts.