Synergic PDE3 and PDE4 control intracellular cAMP and cardiac excitation-contraction coupling in a porcine model.

AIMS: Cyclic AMP phosphodiesterases (PDEs) are important modulators of the cardiac response to ß-adrenergic receptor (ß-AR) stimulation. PDE3 is classically considered as the major cardiac PDE in large mammals and human, while PDE4 is preponderant in rodents. However, it remains unclear whether PDE4 also plays a functional role in large mammals. Our purpose was to understand the role of PDE4 in cAMP hydrolysis and excitation-contraction coupling (ECC) in the pig heart, a relevant pre-clinical model. METHODS AND RESULTS: Real-time cAMP variations were measured in isolated adult pig right ventricular myocytes (APVMs) using a Förster resonance energy transfer (FRET) biosensor. ECC was investigated in APVMs loaded with Fura-2 and paced at 1 Hz allowing simultaneous measurement of intracellular Ca2+ and sarcomere shortening. The expression of the different PDE4 subfamilies was assessed by Western blot in pig right ventricles and APVMs. Similarly to PDE3 inhibition with cilostamide (Cil), PDE4 inhibition with Ro 20-1724 (Ro) increased cAMP levels and inotropy under basal conditions. PDE4 inhibition enhanced the effects of the non-selective ß-AR agonist isoprenaline (Iso) and the effects of Cil, and increased spontaneous diastolic Ca2+ waves (SCWs) in these conditions. PDE3A, PDE4A, PDE4B and PDE4D subfamilies are expressed in pig ventricles. In APVMs isolated from a porcine model of repaired tetralogy of Fallot which leads to right ventricular failure, PDE4 inhibition also exerts inotropic and pro-arrhythmic effects. CONCLUSIONS: Our results show that PDE4 controls ECC in APVMs and suggest that PDE4 inhibitors exert inotropic and pro-arrhythmic effects upon PDE3 inhibition or ß-AR stimulation in our pre-clinical model. Thus, PDE4 inhibitors should be used with caution in clinics as they may lead to arrhythmogenic events upon stress.

Generation of a heterozygous SCN5A knockout human induced pluripotent stem cell line by CRISPR/Cas9 edition.

Mutations leading to haploinsufficiency in SCN5A, the gene encoding the cardiac sodium channel Nav1.5 α-subunit, are involved in life-threatening cardiac disorders. Using CRISPR/Cas9-mediated genome edition, we generated here a human induced-pluripotent stem cell (hiPSC) line carrying a heterozygous mutation in exon 2 of SCN5A, which leads to apparition of a premature stop codon. SCN5A-clone 5 line maintained normal karyotype, morphology and pluripotency and differentiated into three germ layers. Cardiomyocytes derived from these hiPSCs would be a useful model for investigating channelopathies related to SCN5A heterozygous deficiency.

Incomplete Assembly of the Dystrophin-Associated Protein Complex in 2D and 3D-Cultured Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CM) are increasingly used to study genetic diseases on a human background. However, the lack of a fully mature adult cardiomyocyte phenotype of hiPSC-CM may be limiting the scope of these studies. Muscular dystrophies and concomitant cardiomyopathies result from mutations in genes encoding proteins of the dystrophin-associated protein complex (DAPC), which is a multi-protein membrane-spanning complex. We examined the expression of DAPC components in hiPSC-CM, which underwent maturation in 2D and 3D culture protocols. The results were compared with human adult cardiac tissue and isolated cardiomyocytes. We found that similarly to adult cardiomyocytes, hiPSC-CM express dystrophin, in line with previous studies on Duchenne's disease. ß-dystroglycan was also expressed, but, contrary to findings in adult cardiomyocytes, none of the sarcoglycans nor α-dystroglycan were, despite the presence of their mRNA. In conclusion, despite the robust expression of dystrophin, the absence of several other DAPC protein components cautions for reliance on commonly used protocols for hiPSC-CM maturation for functional assessment of the complete DAPC.

Standard and Strain Measurements by Echocardiography Detect Early Overloaded Right Ventricular Dysfunction: Validation against Hemodynamic and Myocyte Contractility Changes in a Large Animal Model.

BACKGROUND: Early detection of right ventricular (RV) failure is required to improve the management of patients with congenital heart diseases. The aim of this study was to validate echocardiography for the early detection of overloaded RV dysfunction, compared with hemodynamic and myocyte contractility assessment. METHODS: Using a porcine model reproducing repaired tetralogy of Fallot, RV function was evaluated over 4 months using standard echocardiography and speckle-tracking compared with hemodynamic parameters (conductance catheter). Sarcomere shortening and calcium transients were recorded in RV isolated myocytes. Contractile reserve (ΔEmax) was assessed by ß-adrenergic stimulation in vivo (dobutamine 5 µg/kg) and ex vivo (isoproterenol 100 nM). RESULTS: Six operated animals were compared with four age- and sex-matched controls. In the operated group, hemodynamic RV efficient ejection fraction was significantly decreased (29.7% [26.2%-34%] vs 42.9% [40.7%-48.6%], P < .01), and inotropic responses to dobutamine were attenuated (ΔEmax was 51% vs 193%, P < .05). Echocardiographic measurements of fraction of area change, tricuspid annular plane systolic excursion, tricuspid annular peak systolic velocity (S') and RV free wall longitudinal systolic strain and strain rate were significantly decreased. Strain rate, S', and tricuspid annular plane systolic excursion were correlated with ΔEmax (r = 0.75, r = 0.78, and r = 0.65, respectively, P < .05). These alterations were associated in RV isolated myocytes with the decrease of sarcomere shortening in response to isoproterenol and perturbations of calcium homeostasis assessed by the increase of spontaneous calcium waves. CONCLUSIONS: In this porcine model, both standard and strain echocardiographic parameters detected early impairments of RV function and cardiac reserve, which were associated with cardiomyocyte excitation-contraction coupling alterations.

Calmodulin kinase II inhibition limits the pro-arrhythmic Ca2+ waves induced by cAMP-phosphodiesterase inhibitors.

AIMS: A major concern of using phosphodiesterase (PDE) inhibitors in heart failure is their potential to increase mortality by inducing arrhythmias. By diminishing cyclic adenosine monophosphate (cAMP) hydrolysis, they promote protein kinase A (PKA) activity under ß-adrenergic receptor (ß-AR) stimulation, hence enhancing Ca(2+) cycling and contraction. Yet, cAMP also activates CaMKII via PKA or the exchange protein Epac, but it remains unknown whether these pathways are involved in the pro-arrhythmic effect of PDE inhibitors. METHODS AND RESULTS: Excitation-contraction coupling was investigated in isolated adult rat ventricular myocytes loaded with Fura-2 and paced at 1 Hz allowing coincident measurement of intracellular Ca(2+) and sarcomere shortening. The PDE4 inhibitor Ro 20-1724 (Ro) promoted the inotropic effects of the non-selective ß-AR agonist isoprenaline (Iso) and also spontaneous diastolic Ca(2+) waves (SCWs). PDE4 inhibition potentiated RyR2 and PLB phosphorylation at specific PKA and CaMKII sites increasing sarcoplasmic reticulum (SR) Ca(2+) load and SR Ca(2+) leak measured in a 0Na(+)/0Ca(2+) solution ± tetracaine. PKA inhibition suppressed all the effects of Iso ± Ro, whereas CaMKII inhibition prevented SR Ca(2+) leak and diminished SCW incidence without affecting the inotropic effects of Ro. Inhibition of Epac2 but not Epac1 diminished the occurrence of SCWs. PDE3 inhibition with cilostamide induced an SR Ca(2+) leak, which was also blocked by CaMKII inhibition. CONCLUSION: Our results show that PDE inhibitors exert inotropic effects via PKA but lead to SCWs via both PKA and CaMKII activation partly via Epac2, suggesting the potential use of CaMKII inhibitors as adjuncts to PDE inhibition to limit their pro-arrhythmic effects.

Cyclic nucleotide phosphodiesterases in heart and vessels: A therapeutic perspective.

Cyclic nucleotide phosphodiesterases (PDEs) degrade the second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), thereby regulating multiple aspects of cardiac and vascular muscle functions. This highly diverse class of enzymes encoded by 21 genes encompasses 11 families that are not only responsible for the termination of cyclic nucleotide signalling, but are also involved in the generation of dynamic microdomains of cAMP and cGMP, controlling specific cell functions in response to various neurohormonal stimuli. In the myocardium and vascular smooth muscle, the PDE3 and PDE4 families predominate, degrading cAMP and thereby regulating cardiac excitation-contraction coupling and smooth muscle contractile tone. PDE3 inhibitors are positive inotropes and vasodilators in humans, but their use is limited to acute heart failure and intermittent claudication. PDE5 is particularly important for the degradation of cGMP in vascular smooth muscle, and PDE5 inhibitors are used to treat erectile dysfunction and pulmonary hypertension. There is experimental evidence that these PDEs, as well as other PDE families, including PDE1, PDE2 and PDE9, may play important roles in cardiac diseases, such as hypertrophy and heart failure, as well as several vascular diseases. After a brief presentation of the cyclic nucleotide pathways in cardiac and vascular cells, and the major characteristics of the PDE superfamily, this review will focus on the current use of PDE inhibitors in cardiovascular diseases, and the recent research developments that could lead to better exploitation of the therapeutic potential of these enzymes in the future.

[Cyclic nucleotide phosphodiesterases: role in the heart and therapeutic perspectives]. / Phosphodiestérases des nucléotides cycliques : rôle dans le cœur et potentiel thérapeutique.

Cyclic nucleotide phosphodiesterases (PDEs) degrade the second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), thereby regulating multiple aspects of cardiac function. This highly diverse class of enzymes encoded by 21 genes encompasses 11 families that are not only responsible for the termination of cyclic nucleotide signalling, but are also involved in the generation of dynamic microdomains of cAMP and cGMP, controlling specific cell functions in response to various neurohormonal stimuli. In the myocardium, the PDE3 and PDE4 families predominate, degrading cAMP and thereby regulating cardiac excitation-contraction coupling. PDE3 inhibitors are positive inotropes and vasodilators in humans, but their use is limited to acute heart failure and intermittent claudication. PDE5 inhibitors, which are used with success to treat erectile dysfunction and pulmonary hypertension, do not seem efficient in heart failure with preserved ejection fraction. There is experimental evidence however that these PDE, as well as other PDE families including PDE1, PDE2 and PDE9, may play important roles in cardiac diseases, such as hypertrophy and heart failure (HF). After a brief presentation of the cyclic nucleotide pathways in cardiac myocytes and the major characteristics of the PDE superfamily, this review will focus on the potential use of PDE inhibitors in HF, and the recent research developments that could lead to a better exploitation of the therapeutic potential of these enzymes in the future.

Differential regulation of cardiac excitation-contraction coupling by cAMP phosphodiesterase subtypes.

AIMS: Multiple phosphodiesterases (PDEs) hydrolyze cAMP in cardiomyocytes, but the functional significance of this diversity is not well understood. Our goal here was to characterize the involvement of three different PDEs (PDE2-4) in cardiac excitation-contraction coupling (ECC). METHODS AND RESULTS: Sarcomere shortening and Ca(2+) transients were recorded simultaneously in adult rat ventricular myocytes and ECC protein phosphorylation by PKA was determined by western blot analysis. Under basal conditions, selective inhibition of PDE2 or PDE3 induced a small but significant increase in Ca(2+) transients, sarcomere shortening, and troponin I phosphorylation, whereas PDE4 inhibition had no effect. PDE3 inhibition, but not PDE2 or PDE4, increased phospholamban phosphorylation. Inhibition of either PDE2, 3, or 4 increased phosphorylation of the myosin-binding protein C, but neither had an effect on L-type Ca(2+) channel or ryanodine receptor phosphorylation. Dual inhibition of PDE2 and PDE3 or PDE2 and PDE4 further increased ECC compared with individual PDE inhibition, but the most potent combination was obtained when inhibiting simultaneously PDE3 and PDE4. This combination also induced a synergistic induction of ECC protein phosphorylation. Submaximal ß-adrenergic receptor stimulation increased ECC, and this effect was potentiated by individual PDE inhibition with the rank order of potency PDE4 = PDE3 > PDE2. Identical results were obtained on ECC protein phosphorylation. CONCLUSION: Our results demonstrate that PDE2, PDE3, and PDE4 differentially regulate ECC in adult cardiomyocytes. PDE2 and PDE3 play a more prominent role than PDE4 in regulating basal cardiac contraction and Ca(2+) transients. However, PDE4 becomes determinant when cAMP levels are elevated, for instance, upon ß-adrenergic stimulation or PDE3 inhibition.