Cardiac Overexpression of PDE4B Blunts ß-Adrenergic Response and Maladaptive Remodeling in Heart Failure.

BACKGROUND: The cyclic AMP (adenosine monophosphate; cAMP)-hydrolyzing protein PDE4B (phosphodiesterase 4B) is a key negative regulator of cardiac ß-adrenergic receptor stimulation. PDE4B deficiency leads to abnormal Ca2+ handling and PDE4B is decreased in pressure overload hypertrophy, suggesting that increasing PDE4B in the heart is beneficial in heart failure. METHODS: We measured PDE4B expression in human cardiac tissues and developed 2 transgenic mouse lines with cardiomyocyte-specific overexpression of PDE4B and an adeno-associated virus serotype 9 encoding PDE4B. Myocardial structure and function were evaluated by echocardiography, ECG, and in Langendorff-perfused hearts. Also, cAMP and PKA (cAMP dependent protein kinase) activity were monitored by Förster resonance energy transfer, L-type Ca2+ current by whole-cell patch-clamp, and cardiomyocyte shortening and Ca2+ transients with an Ionoptix system. Heart failure was induced by 2 weeks infusion of isoproterenol or transverse aortic constriction. Cardiac remodeling was evaluated by serial echocardiography, morphometric analysis, and histology. RESULTS: PDE4B protein was decreased in human failing hearts. The first PDE4B-transgenic mouse line (TG15) had a ≈15-fold increase in cardiac cAMP-PDE activity and a ≈30% decrease in cAMP content and fractional shortening associated with a mild cardiac hypertrophy that resorbed with age. Basal ex vivo myocardial function was unchanged, but ß-adrenergic receptor stimulation of cardiac inotropy, cAMP, PKA, L-type Ca2+ current, Ca2+ transients, and cell contraction were blunted. Endurance capacity and life expectancy were normal. Moreover, these mice were protected from systolic dysfunction, hypertrophy, lung congestion, and fibrosis induced by chronic isoproterenol treatment. In the second PDE4B-transgenic mouse line (TG50), markedly higher PDE4B overexpression, resulting in a ≈50-fold increase in cardiac cAMP-PDE activity caused a ≈50% decrease in fractional shortening, hypertrophy, dilatation, and premature death. In contrast, mice injected with adeno-associated virus serotype 9 encoding PDE4B (1012 viral particles/mouse) had a ≈50% increase in cardiac cAMP-PDE activity, which did not modify basal cardiac function but efficiently prevented systolic dysfunction, apoptosis, and fibrosis, while attenuating hypertrophy induced by chronic isoproterenol infusion. Similarly, adeno-associated virus serotype 9 encoding PDE4B slowed contractile deterioration, attenuated hypertrophy and lung congestion, and prevented apoptosis and fibrotic remodeling in transverse aortic constriction. CONCLUSIONS: Our results indicate that a moderate increase in PDE4B is cardioprotective and suggest that cardiac gene therapy with PDE4B might constitute a new promising approach to treat heart failure.

Cyclic nucleotide signalling compartmentation by PDEs in cultured vascular smooth muscle cells.

BACKGROUND AND PURPOSE: Up-regulation of phosphodiesterases (PDEs) is associated with several vascular diseases, and better understanding of the roles of each PDE isoform in controlling subcellular pools of cyclic nucleotides in vascular cells is needed. We investigated the respective role of PDE1, PDE5, and PDE9 in controlling intracellular cAMP and/or cGMP concentrations ([cAMP]i , [cGMP]i ) in cultured rat aortic smooth muscle cells (RASMCs). EXPERIMENTAL APPROACH: We used selective inhibitors of PDE1 (PF-04471141), PDE5 (sildenafil), and PDE9 (PF-04447943) to measure cAMP- and cGMP-PDE activities with a radioenzymatic assay, in RASMC extracts. Real-time [cAMP]i and [cGMP]i were recorded by Förster resonance energy transfer-imaging in single living cells, and cell proliferation was assessed in FBS-stimulated cells. KEY RESULTS: PDE1, PDE5, and PDE9 represented the major cGMP-hydrolyzing activity in RASMCs. Basal PDE1 exerted a functional role in degrading in situ the cGMP produced in response to activation of particulate GC by C-type natriuretic peptide. In high intracellular Ca2+ concentrations, PDE1 also regulated the NO/soluble GC-dependent cGMP response, as well as the ß-adrenoceptor-mediated cAMP response. PDE5 exerted a major role in degrading cGMP produced by NO and the natriuretic peptides. PDE9 only regulated the NO-induced [cGMP]i increase. All three PDEs contributed differently to regulate cell proliferation under basal conditions and upon cGMP-elevating stimuli. CONCLUSIONS AND IMPLICATIONS: Our data emphasize the distinct roles of PDE1, PDE5, and PDE9 in local regulation of [cAMP]i and [cGMP]i , in vascular smooth muscle cells, strengthening the concept of PDEs as key actors in the subcellular compartmentation of cyclic nucleotides.