Differential regulation of C-type natriuretic peptide-induced cGMP and functional responses by PDE2 and PDE3 in failing myocardium

Abstract

Recently, we showed C-type natriuretic peptide (CNP)-induced negative inotropic (NIR) and positive lusitropic response (LR) in failing rat heart. We wanted to study whether, and if so, how phosphodiesterases (PDEs) regulate CNP-induced cyclic 3',5'-guanosine monophosphate (cGMP) elevation and functional responses. Inotropic and lusitropic responses were measured in left ventricular muscle strips and cyclic nucleotide levels, PDE activity and phospholamban (PLB) and troponin I (TnI) phosphorylation were measured in ventricular cardiomyocytes from Wistar rats with heart failure 6 weeks after myocardial infarction. CNP-mediated increase in global cGMP was mainly regulated by PDE2, as reflected by a marked amplification of the cGMP increase during PDE2 inhibition and by a high PDE2 activity in cardiomyocytes. PDE3 inhibition, on the other hand, caused no significant cGMP increase by CNP. The functional consequences did not correspond to the changes of cGMP. PDE3 inhibition increased the potency of the CNP-induced NIR and LR, while PDE2 inhibition desensitized the CNP-induced NIR, but not LR. A role for PDE2 on the maximal LR and PDE5 on the maximal NIR to CNP was revealed in the presence of PDE3 inhibition. CNP increased PLB phosphorylation about 25- to 30-fold and tended to increase TnI phosphorylation about twofold. As a whole, CNP-induced functional responses were only modestly regulated by PDEs compared to the cAMP-mediated functional responses to β1-adrenoceptor stimulation, which are highly regulated by PDEs. There is a mismatch between the CNP-induced cGMP increase and functional responses. Global cGMP levels are mainly regulated by PDE2 after CNP stimulation, whereas the functional responses are modestly regulated by both PDE2 and PDE3, indicating cGMP compartmentation by PDEs affecting CNP-induced responses in failing hearts.

Different Compartmentation of Responses to Brain Natriuretic Peptide and C-Type Natriuretic Peptide in Failing Rat Ventricle

“…Thus, PDE barriers are not a sufficient explanation for the inability of BNP stimulation to reach the same functional compartment as CNP stimulation, unless PDEs other than the ones tested could be involved. The cGMP increase by both BNP (this study) and CNP (Moltzau et al, 2014) is markedly and mainly regulated by PDE2, in line with earlier studies (Castro et al, 2006). Still, the effect of PDE2 inhibition on the cGMP elevation was significantly higher for CNP than BNP (P , 0.05), despite comparable cGMP elevation with the two NPs alone.…”

“…Further, we found that concerted effects of phospholamban (PLB) Ser16 and troponin I (TnI) Ser23/24 phosphorylation most likely represent the main mechanisms explaining the cGMP-protein kinase G (PKG)-mediated NIR and LR to CNP (Moltzau et al, 2013). Whereas PDE2 was the major phosphodiesterase-hydrolyzing cGMP generated by CNP, we also found a role for both PDE2 and PDE3 in the regulation of CNP-induced functional responses (Moltzau et al, 2014). Thus, a major discrepancy between cGMP levels and functional responses was revealed.…”

“…We earlier had found that the NIR and LR to CNP are regulated by PDEs (Moltzau et al, 2014). A possible explanation for the lack of NIR and LR to BNP could be PDE barriers protecting the contractile machinery from NPR-A-generated cGMP.…”

C-Type Natriuretic Peptide Improves Left Ventricular Functional Performance at Rest and Restores Normal Exercise Responses after Heart Failure

“…The cGMP generated by NPR-B has been reported to increase b 1 -adrenoceptor-mediated positive inotropic responses through inhibition of PDE3 (Moltzau et al, 2013). In HF, it is possible that cGMP may affect cAMP signaling via cross-talk regulation by cGMPregulated subtypes of PDEs (PDE2 or PDE3) (Takimoto, 2012;Moltzau et al, 2014b), which leads to an increase in intracellular cAMP and increased contractility; however, whether and to what extent administration of CNP affects the cGMP-cAMP pathway, improving b-adrenergic stimulation and thereby contributing to the beneficial action of CNP in HF, is unknown.…”

“…Fourth, we measured the plasma levels of cGMP, but we did not measure the cGMP or cAMP levels in the heart. It is possible that its beneficial actions are attributable to the alteration on b-adrenergic stimulation activated by subtype PDEs that regulated the CNP-activated cGMP/protein kinase G (PKG) pathway (Moltzau et al, 2013(Moltzau et al, , 2014b. Finally, the angiotensin receptor neprilysin inhibitor of LCZ696 has demonstrated greater efficacy than enalapril in a phase 3 trial in HF with reduced ejection fraction (Langenickel and Dole, 2012;Singh and Lang, 2015).…”