Cardiovascular Research Advance Access first published online on November 24, 2008
This version [Corrected Proof] published online on December 18, 2008
Cardiovascular Research, doi:10.1093/cvr/cvn324
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Phosphodiesterase 5 inhibition blocks pressure overload-induced cardiac hypertrophy independent of the calcineurin pathway
1 Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Ross-Building, Room 850, Baltimore, MD 21205, USA
2 Department of Comparative Medicine and Comparative Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
3 Division of Molecular Cardiovascular Biology, Department of Pediatrics, Children’s Hospital Medical Center, Cincinnati, OH, USA
* Corresponding author. Tel: +1 410 955 4813; fax: +1 410 502 2558. E-mail address: etakimo1{at}jhmi.edu
Aims: Cyclic GMP (cGMP)-specific phosphodiesterase 5 (PDE5) inhibition by sildenafil (SIL) activates myocardial cGMP-dependent protein kinase G (PKG) and blunts cardiac hypertrophy. To date, the only documented target of PKG in myocardium is the serine–threonine phosphatase calcineurin (Cn), which is central to pathological cardiac hypertrophy. We tested whether Cn suppression is necessary in order to observe anti-hypertrophic effects of SIL.
Methods and results: Mice lacking the Cn-Aβ subunit (CnAβ–/–) and wild-type (WT) controls were subjected to transverse aorta constriction (TAC) with or without SIL (200 mg/kg/day, p.o.) for 3 weeks. TAC-induced elevation of Cn expression and activity in WT was absent in CnAβ–/– hearts, and the latter accordingly developed less cardiac hypertrophy (50 vs. 100% increase in heart weight/tibia length, P < 0.03) and chamber dilation. SIL remained effective in CnAβ–/– mice, increasing PKG activity similarly as in WT, suppressing hypertrophy and fetal gene expression, and enhancing heart function without altering afterload. TAC-stimulated calcium–calmodulin kinase II, Akt, and glycogen synthase kinase 3β in both groups (the first rising more in CnAβ–/– hearts), and SIL also suppressed these similarly. Activation of extracellular signal-regulated kinase observed in WT-TAC but not CnAβ–/– hearts was also suppressed by SIL.
Conclusion: PDE5A inhibition and its accompanying PKG activation blunt hypertrophy and improve heart function even without Cn activation. This occurs by its modulation of several alternative pathways which may result from concomitant distal targeting, or activity against a common proximal node.
KEYWORDS Calcineurin; Phosphodiesterase 5; Cyclic GMP; CGMP-dependent protein kinase; Sildenafil; Heart; Hypertrophy
Time for primary review: 15 days
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  T. Reffelmann and R. A. Kloner Phosphodiesterase 5 inhibitors: are they cardioprotective? Cardiovasc Res, July 15, 2009; 83(2): 204 - 212. [Abstract] [Full Text] [PDF]
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