cGMP Catabolism by Phosphodiesterase 5A Regulates Cardiac Adrenergic Stimulation by NOS3-Dependent Mechanism

Abstract

Abstract-␤-Adrenergic agonists stimulate cardiac contractility and simultaneously blunt this response by coactivating NO synthase (NOS3) to enhance cGMP synthesis and activate protein kinase G (PKG-1). cGMP is also catabolically regulated by phosphodiesterase 5A (PDE5A). PDE5A inhibition by sildenafil (Viagra) increases cGMP and is used widely to treat erectile dysfunction; however, its role in the heart and its interaction with ␤-adrenergic and NOS3/cGMP stimulation is largely unknown. In nontransgenic (control) murine in vivo hearts and isolated myocytes, PDE5A inhibition (sildenafil) minimally altered rest function. However, when the hearts or isolated myocytes were stimulated with isoproterenol, PDE5A inhibition was associated with a suppression of contractility that was coupled to elevated cGMP and increased PKG-1 activity. In contrast, NOS3-null hearts or controls with NOS inhibited by N G -nitro-Larginine methyl ester, or soluble guanylate cyclase (sGC) inhibited by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one, showed no effect of PDE5A inhibition on ␤-stimulated contractility or PKG-1 activation. This lack of response was not attributable to altered PDE5A gene or protein expression or in vitro PDE5A activity, but rather to an absence of sGC-generated cGMP specifically targeted to PDE5A catabolism and to a loss of PDE5A localization to z-bands. Re-expression of active NOS3 in NOS3-null hearts by adenoviral gene transfer restored PDE5A z-band localization and the antiadrenergic efficacy of PDE5A inhibition. These data support a novel regulatory role of PDE5A in hearts under adrenergic stimulation and highlight specific coupling of PDE5A catabolic regulation with NOS3-derived cGMP attributable to protein subcellular localization and targeted synthetic/catabolic coupling. Key Words: PDE5 Ⅲ phosphodiesterase Ⅲ sildenafil Ⅲ nitric oxide synthase Ⅲ contractility Ⅲ z-band B eta-adrenergic regulation of cardiac contraction is coupled to elevations in adenosine (cAMP) and guanosine (cGMP) cyclic nucleotides. Increased cAMP enhances contractility 1,2 by activating protein kinase A (PKA), whereas concomitant stimulation of cGMP opposes this in part by activating protein kinase G (PKG-1). 3,4 The latter response is thought to be attributable to stimulation of soluble guanylate cyclase (sGC) by NO. 3-9 Cyclic GMP is also synthesized by receptor GC (rGC) coupled to natriuretic peptide stimulation, and both sources can modulate cardiac function and structure, particularly in hearts stimulated by neurohormones or mechanical stress. 3-5,10 -13 cGMP is also regulated by catabolic phosphodiesterases such as phosphodiesterase 5A (PDE5A), and PDE5A inhibition by sildenafil (Viagra; SIL) and similar compounds augments cGMP in vascular tissue and is the primary therapy for erectile dysfunction. 14,15 However, the role for PDE5A in regulating cardiac function has remained unclear. 16 -18 Such clarification has become increasingly important because PDE5A inhibitors are poised to become chronic treatments for diseases such as pul...

Cyclic GMP signaling in rat urinary bladder, prostate, and epididymis: tissue-specific changes with aging and in response to Leydig cell depletion

“…Interestingly, these data, indicating pronounced cellular activity under conditions of low PDE5 (and other cGMP pathway proteins), resemble findings in heart tissue. Chronic PDE5 inhibition prevents cardiac hypertrophy (Takimoto et al 2005a) despite a poor local Pde5 gene expression, which is 100-fold lower than in lung (Takimoto et al 2005b). Likewise, ANP-cGMP signaling inhibits cardiac hypertrophy (Bubikat et al 2005), although the ANP receptor, GC-A, is of unusually low abundance in the heart (D Mü ller, unpublished results).…”

Ventricular Arterial Stiffening

“…Similarly, increasing cGMP/PKG activation in the heart reduces fibrosis and can be anti-hypertrophic. 57,58 In mice, PDE5a inhibition markedly inhibits the development of cardiac hypertrophy and fibrosis while improving ventricular function despite sustained ventricular afterload increase 59 (Figure 5B). Furthermore, this treatment reversed hypertrophy and fibrosis once established ( Figure 5C).…”

Endothelial Nitric Oxide Synthase Keeps Erection Regulatory Function Balance in the Penis

“…Protein concentration was determined by the BCA kit (Pierce), and 30 μg of penile lysates from each sample was used for the measurement of PKG activity. PKG activity was expressed as a percentage of WT control PKG activity [18].…”