Carboxy-terminal fragment of fibroblast growth factor 23 induces heart hypertrophy in sickle cell disease

International audienc

Interventricular Differences in β‐Adrenergic Responses in the Canine Heart: Role of Phosphodiesterases

Background RV and LV have different embryologic, structural, metabolic, and electrophysiologic characteristics, but whether interventricular differences exist in β‐adrenergic (β‐AR) responsiveness is unknown. In this study, we examine whether β‐AR response and signaling differ in right (RV) versus left (LV) ventricles. Methods and Results Sarcomere shortening, Ca2+ transients, ICa,L and IKs currents were recorded in isolated dog LV and RV midmyocytes. Intracellular [cAMP] and PKA activity were measured by live cell imaging using FRET‐based sensors. Isoproterenol increased sarcomere shortening ≈10‐fold and Ca2+‐transient amplitude ≈2‐fold in LV midmyocytes (LVMs) versus ≈25‐fold and ≈3‐fold in RVMs. FRET imaging using targeted Epac2camps sensors revealed no change in subsarcolemmal [cAMP], but a 2‐fold higher β‐AR stimulation of cytoplasmic [cAMP] in RVMs versus LVMs. Accordingly, β‐AR regulation of ICa,L and IKs were similar between LVMs and RVMs, whereas cytoplasmic PKA activity was increased in RVMs. Both PDE3 and PDE4 contributed to the β‐AR regulation of cytoplasmic [cAMP], and the difference between LVMs and RVMs was abolished by PDE3 inhibition and attenuated by PDE4 inhibition. Finally LV and RV intracavitary pressures were recorded in anesthetized beagle dogs. A bolus injection of isoproterenol increased RV dP/dtmax≈5‐fold versus 3‐fold in LV. Conclusion Canine RV and LV differ in their β‐AR response due to intrinsic differences in myocyte β‐AR downstream signaling. Enhanced β‐AR responsiveness of the RV results from higher cAMP elevation in the cytoplasm, due to a decreased degradation by PDE3 and PDE4 in the RV compared to the LV

Phosphodiesterase 2 Protects against Catecholamine-induced Arrhythmias and Preserves Contractile Function after Myocardial Infarction

International audienceRationale: Phosphodiesterase 2 is a dual substrate esterase, which has the unique property to be stimulated by cGMP, but primarily hydrolyzes cAMP. Myocardial phosphodiesterase 2 is upregulated in human heart failure, but its role in the heart is unknown.Objective: To explore the role of phosphodiesterase 2 in cardiac function, propensity to arrhythmia, and myocardial infarction.Methods and Results: Pharmacological inhibition of phosphodiesterase 2 (BAY 60–7550, BAY) led to a significant positive chronotropic effect on top of maximal β-adrenoceptor activation in healthy mice. Under pathological conditions induced by chronic catecholamine infusions, BAY reversed both the attenuated β-adrenoceptor–mediated inotropy and chronotropy. Conversely, ECG telemetry in heart-specific phosphodiesterase 2-transgenic (TG) mice showed a marked reduction in resting and in maximal heart rate, whereas cardiac output was completely preserved because of greater cardiac contraction. This well-tolerated phenotype persisted in elderly TG with no indications of cardiac pathology or premature death. During arrhythmia provocation induced by catecholamine injections, TG animals were resistant to triggered ventricular arrhythmias. Accordingly, Ca2+-spark analysis in isolated TG cardiomyocytes revealed remarkably reduced Ca2+ leakage and lower basal phosphorylation levels of Ca2+-cycling proteins including ryanodine receptor type 2. Moreover, TG demonstrated improved cardiac function after myocardial infarction.Conclusions: Endogenous phosphodiesterase 2 contributes to heart rate regulation. Greater phosphodiesterase 2 abundance protects against arrhythmias and improves contraction force after severe ischemic insult. Activating myocardial phosphodiesterase 2 may, thus, represent a novel intracellular antiadrenergic therapeutic strategy protecting the heart from arrhythmia and contractile dysfunction

Role and regulation of phosphodiesterase type 2 in heart failure

L'AMP cyclique (AMPc) et le GMP cyclique (GMPc) sont des seconds messagers essentiels pour la régulation de la fonction cardiaque. Leurs niveaux sont régulés par l’adénylate cyclase et la guanylate cyclase, respectivement, et par les phosphodiestérases (PDEs). Cependant, une telle régulation est altérée dans l'insuffisance cardiaque (IC). En effet, la diminution de la signalisation de l’AMPc et l’augmentation de celle du GMPc est caractéristique des cœurs défaillants.Parmi la superfamille des PDEs, la PDE2 a la particularité d'être stimulée par le GMPc, conduisant ainsi à une augmentation remarquable de l'hydrolyse de l'AMPc. Ceci semble induire une interaction entre les voies de signalisation de l’AMPc et du GMPc. Cependant, le rôle de la PDE2 dans le cœur défaillant est très peu connu.Dans ce contexte, nous avons examiné si la PDE2 cardiaque est modifiée dans l’IC chez l’Homme et chez les modèles animaux d’IC, et déterminé le rôle de la PDE2 dans la signalisation β-adrénergique dans les cardiomyocytes. Grâce à l’utilisation de Western blot, de technique radioenzymatique, d’imagerie basée sur le FRET, de la planimétrie, de la microscopie à épifluorescence et des mesures du courant calcique de type L, réalisés sur les tissus myocardiques humains et/ou dans des cardiomyocytes isolés de cœurs des modèles animaux d’IC, respectivement, nous avons montré que l’expression et l’activité de la PDE2 sont augmentées dans les cœurs défaillants. Cette augmentation réduit l’effet d’une stimulation β-adrénergique aiguë, contribuant à la désensibilisation β-adrénergique observée dans l’IC. En accord avec ces résultats, la surexpression de la PDE2 dans des cardiomyocytes sains, réduit l’augmentation des taux d'AMPc et l’amplitude du courant ICa,L et abolit l'effet inotrope positif suite à une stimulation β-adrénergique aiguë, sans affecter la contractilité basale. Plus important, les cardiomyocytes surexprimant la PDE2, montrent une protection contre les réponses hypertrophiques induites par la noradrénaline et contre les arythmies induites par l'isoprotérénol.En conclusion, ce travail met en évidence l'altération de la PDE2 dans l’IC et nous laisse suggérer que l’augmentation de la PDE2 dans l’IC peut constituer un mécanisme de défense important dans des conditions de stress cardiaque, notamment en antagonisant la suractivation de la voie β-adrénergique. Ainsi, l'activation de PDE2 myocardique peut représenter une nouvelle stratégie thérapeutique anti-adrénergique intracellulaire dans l’IC.Cyclic AMP (cAMP) and cyclic GMP (cGMP) are critical second messengers for the regulation of cardiac function. Their levels are regulated by adenylyl and guanylyl cyclases, respectively, and by cyclic nucleotides phosphodiesterases (PDEs). However, such regulation is altered in heart failure (HF). Indeed diminished cAMP- and augmented cGMP-signaling is characteristic of failing hearts.Among the PDE superfamily, PDE2 has the unique property to be stimulated by cGMP, thus leading to a remarkable increase in cAMP hydrolysis. This appears to mediate a negative cross-talk between cAMP- and cGMP signaling pathways. However, the role of PDE2 in the failing heart is only poorly understood.In this context, we investigated whether myocardial PDE2 is altered in human and experimental HF and determined PDE2 mediated effects on β-adrenoceptor (β-AR) signaling in cardiomyocytes. Using immunoblotting, radioenzymatic- and FRET-based assays, video-edge-detection, epifluorescent microscopy and L-type Ca2+ current measurements, performed in myocardial tissues and/or isolated cardiomyocytes from human and/or experimental HF, respectively, we showed that PDE2 is markedly upregulated in failing hearts. This reduces the effect of an acute β-adrenergic stimulation, and contributes to the β-adrenergic desensitization which is a characteristic feature in HF. Accordingly, PDE2 overexpression in healthy cardiomyocytes reduced the rise in cAMP levels and ICa,L amplitude and abolished the inotropic effect following acute β-AR stimulation, without affecting basal contractility. Importantly, PDE2-overexpressing cardiomyocytes showed marked protection from norepinephrine-induced hypertrophic responses and from isoproterenol-induced arrhythmias.In conclusion, this work highlights the alteration of PDE2 in HF and lets us assume that PDE2 upregulation in HF may constitute an important defence mechanism during cardiac stress, e.g. by antagonizing excessive β-AR drive. Thus, activating myocardial PDE2 may represent a novel intracellular anti-adrenergic therapeutic strategy in HF

Rôle et régulation de la phosphodiestérase de type 2 dans l’insuffisance cardiaque

Cyclic AMP (cAMP) and cyclic GMP (cGMP) are critical second messengers for the regulation of cardiac function. Their levels are regulated by adenylyl and guanylyl cyclases, respectively, and by cyclic nucleotides phosphodiesterases (PDEs). However, such regulation is altered in heart failure (HF). Indeed diminished cAMP- and augmented cGMP-signaling is characteristic of failing hearts.Among the PDE superfamily, PDE2 has the unique property to be stimulated by cGMP, thus leading to a remarkable increase in cAMP hydrolysis. This appears to mediate a negative cross-talk between cAMP- and cGMP signaling pathways. However, the role of PDE2 in the failing heart is only poorly understood.In this context, we investigated whether myocardial PDE2 is altered in human and experimental HF and determined PDE2 mediated effects on β-adrenoceptor (β-AR) signaling in cardiomyocytes. Using immunoblotting, radioenzymatic- and FRET-based assays, video-edge-detection, epifluorescent microscopy and L-type Ca2+ current measurements, performed in myocardial tissues and/or isolated cardiomyocytes from human and/or experimental HF, respectively, we showed that PDE2 is markedly upregulated in failing hearts. This reduces the effect of an acute β-adrenergic stimulation, and contributes to the β-adrenergic desensitization which is a characteristic feature in HF. Accordingly, PDE2 overexpression in healthy cardiomyocytes reduced the rise in cAMP levels and ICa,L amplitude and abolished the inotropic effect following acute β-AR stimulation, without affecting basal contractility. Importantly, PDE2-overexpressing cardiomyocytes showed marked protection from norepinephrine-induced hypertrophic responses and from isoproterenol-induced arrhythmias.In conclusion, this work highlights the alteration of PDE2 in HF and lets us assume that PDE2 upregulation in HF may constitute an important defence mechanism during cardiac stress, e.g. by antagonizing excessive β-AR drive. Thus, activating myocardial PDE2 may represent a novel intracellular anti-adrenergic therapeutic strategy in HF.L'AMP cyclique (AMPc) et le GMP cyclique (GMPc) sont des seconds messagers essentiels pour la régulation de la fonction cardiaque. Leurs niveaux sont régulés par l’adénylate cyclase et la guanylate cyclase, respectivement, et par les phosphodiestérases (PDEs). Cependant, une telle régulation est altérée dans l'insuffisance cardiaque (IC). En effet, la diminution de la signalisation de l’AMPc et l’augmentation de celle du GMPc est caractéristique des cœurs défaillants.Parmi la superfamille des PDEs, la PDE2 a la particularité d'être stimulée par le GMPc, conduisant ainsi à une augmentation remarquable de l'hydrolyse de l'AMPc. Ceci semble induire une interaction entre les voies de signalisation de l’AMPc et du GMPc. Cependant, le rôle de la PDE2 dans le cœur défaillant est très peu connu.Dans ce contexte, nous avons examiné si la PDE2 cardiaque est modifiée dans l’IC chez l’Homme et chez les modèles animaux d’IC, et déterminé le rôle de la PDE2 dans la signalisation β-adrénergique dans les cardiomyocytes. Grâce à l’utilisation de Western blot, de technique radioenzymatique, d’imagerie basée sur le FRET, de la planimétrie, de la microscopie à épifluorescence et des mesures du courant calcique de type L, réalisés sur les tissus myocardiques humains et/ou dans des cardiomyocytes isolés de cœurs des modèles animaux d’IC, respectivement, nous avons montré que l’expression et l’activité de la PDE2 sont augmentées dans les cœurs défaillants. Cette augmentation réduit l’effet d’une stimulation β-adrénergique aiguë, contribuant à la désensibilisation β-adrénergique observée dans l’IC. En accord avec ces résultats, la surexpression de la PDE2 dans des cardiomyocytes sains, réduit l’augmentation des taux d'AMPc et l’amplitude du courant ICa,L et abolit l'effet inotrope positif suite à une stimulation β-adrénergique aiguë, sans affecter la contractilité basale. Plus important, les cardiomyocytes surexprimant la PDE2, montrent une protection contre les réponses hypertrophiques induites par la noradrénaline et contre les arythmies induites par l'isoprotérénol.En conclusion, ce travail met en évidence l'altération de la PDE2 dans l’IC et nous laisse suggérer que l’augmentation de la PDE2 dans l’IC peut constituer un mécanisme de défense important dans des conditions de stress cardiaque, notamment en antagonisant la suractivation de la voie β-adrénergique. Ainsi, l'activation de PDE2 myocardique peut représenter une nouvelle stratégie thérapeutique anti-adrénergique intracellulaire dans l’IC

Cyclic AMP Synthesis and Hydrolysis in the Normal and Failing Heart

International audienceCyclic AMP regulates a multitude of cellular responses and orchestrates a network of intracellular events. In the heart, cAMP is the main second messenger of the β-adrenergic receptor (β-AR) pathway producing positive chronotropic, inotropic and lusitropic effects during sympathetic stimulation. Whereas short term stimulation of β-AR/cAMP is beneficial for the heart, chronic activation of this pathway triggers pathological cardiac remodelling which may ultimately lead to heart failure (HF). Cyclic AMP is controlled by two families of enzymes with opposite actions: adenylyl cyclases which control cAMP production and phosphodiesterases which control its degradation. The large number of families and isoforms of these enzymes, their different localization within the cell and their organization in macromolecular complexes leads to a high level of compartmentation, both in space and time, of cAMP signaling in cardiac myocytes. Here, we review the expression level, molecular characteristics, functional properties and roles of the different adenylyl cyclase and phosphodiesterase families expressed in heart muscle and the changes that occur in cardiac hypertrophy and failure

Phosphodiesterase 2: anti-adrenergic friend or hypertrophic foe in heart disease?

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Dominant negative Ras (DN Ras) attenuates pathological ventricular remodeling in pressure overload cardiac hypertrophy

International audienc

Phosphodiesterase-2 Is Up-Regulated in Human Failing Hearts and Blunts β-Adrenergic Responses in Cardiomyocytes

International audienceObjectives: We investigated whether myocardial phosphodiesterase 2 (PDE2) is altered in heart failure (HF) and determined PDE2-mediated effects on β-adrenoceptor (AR) signaling in healthy and diseased cardiomyocytes.Background: Diminished cAMP- and augmented cGMP-signaling is characteristic for failing hearts. Among the PDE superfamily, PDE2 has the unique property to be stimulated by cGMP, thus leading to a remarkable increase in cAMP hydrolysis mediating a negative cross-talk between cGMP- and cAMP-signaling. However, the role of PDE2 in HF is poorly understood.Methods and Results: Immunoblotting and radioenzymatic assay revealed that myocardial PDE2 expression and activity were ~2-fold higher in advanced human HF. Chronic β-AR stimulation via catecholamine infusions in rats enhanced PDE2 expression 2-fold and cAMP hydrolytic activity 4-fold as determined by FRET-based sensors, which correlated with blunted cardiac β-AR responsiveness. Notably, in diseased cardiomyocytes the higher PDE2 activity could be further enhanced by stimulation of cGMP synthesis via NO donors whereas specific PDE2 inhibition partially restored β-AR responsiveness. Accordingly, PDE2 overexpression in healthy cardiomyocytes reduced the rise in cAMP levels and ICa,L amplitude and abolished the positive inotropic effect following acute β-AR stimulation, without affecting basal contractility. Importantly, PDE2-overexpressing cardiomyocytes showed marked protection from norepinephrine-induced hypertrophic responses.Conclusions: PDE2 is markedly upregulated in failing hearts and desensitizes against acute β-AR stimulation. This may constitute an important defence mechanism during cardiac stress, e.g. by antagonizing excessive β-AR drive. Thus, activating myocardial PDE2 may represent a novel intracellular anti-adrenergic therapeutic strategy in HF