J Am Coll Cardiol. 2012 Jun 12;59(24):2182-90.

Cyclic adenosine monophosphate phosphodiesterase type 4 protects against atrial arrhythmias.

Molina CE, Leroy J, Richter W, Xie M, Scheitrum C, Lee IO, Maack C, Rucker-Martin C, Donzeau-Gouge P, Verde I, Llach A, Hove-Madsen L, Conti M, Vandecasteele G, Fischmeister R.

INSERM UMR-S 769, LabEx LERMIT, DHU-Torino, Châtenay-Malabry, France.

Abstract

OBJECTIVES: This study was designed to examine whether a cyclic adenosine monophosphate (cAMP) phosphodiesterase (PDE), PDE4, is expressed in human atrium and contributes to the control of electrical stability.
BACKGROUND: Atrial fibrillation is accompanied by a profound remodeling of membrane receptors and alterations in cAMP-dependent regulation of Ca(2+) handling. Being responsible for cAMP hydrolysis, PDEs are likely to play a role in this setting. In the rodent heart, PDE4 contributes up to 60% of total cAMP-hydrolytic activity. However, its role in the human heart remains controversial.
METHODS: L-type Ca(2+) current and spontaneous Ca(2+) release were recorded in isolated human atrial myocytes. Intracellular cAMP was measured by live cell imaging using a fluorescence resonance energy transfer-based sensor. Contractile force and arrhythmias were recorded in human atrial trabeculae. PDE activity was measured in human atrial tissue from patients in sinus rhythm and permanent atrial fibrillation.
RESULTS: PDE4 is expressed in human atrial myocytes and accounts for approximately 15% of total PDE activity. PDE4D represents the major PDE4 subtype. PDE4 inhibition increased intracellular cAMP and L-type Ca(2+) current and dramatically delayed their decay after a brief β-adrenergic stimulation. PDE4 inhibition also increased the frequency of spontaneous Ca(2+) release at baseline, as well as the contractile response and the incidence of arrhythmias in human atrial strips during β-adrenergic stimulation. Total PDE activity decreased with age, and the relative PDE4 activity was lower in patients with permanent atrial fibrillation than in age-matched sinus rhythm controls.
CONCLUSIONS: PDE4 is critical in controlling cAMP levels and thereby Ca(2+) influx and release in human atrial muscle, hence limiting the susceptibility to arrhythmias.

Comment in: Phosphodiesterase-4 activity: a critical modulator of atrial contractility and arrhythmogenesis. [J Am Coll Cardiol. 2012]

PMID:22676938