Physiological Function of Cyclic Nucleotide Phosphodiesterases in Atrial Myocytes and their Potential as Targets in Atrial Fibrillation.

Cyclic nucleotide hy drolysing phosphodiesterases (PDEs) are key regulators of cyclic nucleotide (e.g. cAMP and cGMP) signalling. Here we examine the role of PDEs in the physiology of atrial myocytes (AMs), the pathogenesis of atrial fibrillation (AF) and the potential of PDEs as therapeutic targets for AF. PDE1-5 and 8 are present and functional in AMs. PDE2-4 are important regulators of AM contraction but their role beyond atrial contractility is unclear. The role of PDE1,5 and 8 in healthy AMs is unknown but of interest because of their roles in ventricular myocytes. We propose that PDE2-5 and PDE8 are potential targets to prevent the triggering of AF considering their effects on Ca²⁺ handling and /or electrical activity. PDE1-5 are possible targets to treat patients with paroxysmal or persistent AF caused by pulmonary vein automaticity. PDE8B2 is a possible target for patients with persistent AF due to its altered expression. Research should aim to identify the presence, localisation, and function of specific PDE isoforms in human atria. Ultimately, the paucity of PDE isoform-specific small molecule modulators and the difficulty of delivering PDE-targeted medications or therapies to particular cell types limit current research and its application.