Ion channel trafficking implications in heart failure

Heart failure (HF) is recognized as an epidemic in the contemporary world, impacting around 1%–2% of the adult population and affecting around 6 million Americans. HF remains a major cause of mortality, morbidity, and poor quality of life. Several therapies are used to treat HF and improve the survival of patients; however, despite these substantial improvements in treating HF, the incidence of HF is increasing rapidly, posing a significant burden to human health. The total cost of care for HF is USD 69.8 billion in 2023, warranting a better understanding of the mechanisms involved in HF. Among the most serious manifestations associated with HF is arrhythmia due to the electrophysiological changes within the cardiomyocyte. Among these electrophysiological changes, disruptions in sodium and potassium currents’ function and trafficking, as well as calcium handling, all of which impact arrhythmia in HF. The mechanisms responsible for the trafficking, anchoring, organization, and recycling of ion channels at the plasma membrane seem to be significant contributors to ion channels dysfunction in HF. Variants, microtubule alterations, or disturbances of anchoring proteins lead to ion channel trafficking defects and the alteration of the cardiomyocyte's electrophysiology. Understanding the mechanisms of ion channels trafficking could provide new therapeutic approaches for the treatment of HF. This review provides an overview of the recent advances in ion channel trafficking in HF

Electrophysiological basis of cardiac arrhythmia in a mouse model of myotonic dystrophy type 1

Introduction: Myotonic dystrophy type 1 (DM1) is a multisystemic genetic disorder caused by the increased number of CTG repeats in 3′ UTR of Dystrophia Myotonia Protein Kinase (DMPK) gene. DM1 patients experience conduction abnormalities as well as atrial and ventricular arrhythmias with increased susceptibility to sudden cardiac death. The ionic basis of these electrical abnormalities is poorly understood.Methods: We evaluated the surface electrocardiogram (ECG) and key ion currents underlying the action potential (AP) in a mouse model of DM1, DMSXL, which express over 1000 CTG repeats. Sodium current (INa), L-type calcium current (ICaL), transient outward potassium current (Ito), and APs were recorded using the patch-clamp technique.Results: Arrhythmic events on the ECG including sinus bradycardia, conduction defects, and premature ventricular and atrial arrhythmias were observed in DMSXL homozygous mice but not in WT mice. PR interval shortening was observed in homozygous mice while ECG parameters such as QRS duration, and QTc did not change. Further, flecainide prolonged PR, QRS, and QTc visually in DMSXL homozygous mice. At the single ventricular myocyte level, we observed a reduced current density for Ito and ICaL with a positive shift in steady state activation of L-type calcium channels carrying ICaL in DMSXL homozygous mice compared with WT mice. INa densities and action potential duration did not change between DMSXL and WT mice.Conclusion: The reduced current densities of Ito, and ICaL and alterations in gating properties in L-type calcium channels may contribute to the ECG abnormalities in the DMSXL mouse model of DM1. These findings open new avenues for novel targeted therapeutics

Development and characterization of a human cardiac cell model of arrhythmogenic cardiomyopathy

La cardiomyopathie arythmogène est une maladie génétique rare. Elle est caractérisée par un dysfonctionnement cardiaque avec l’apparition d’arythmies ventriculaires, souvent responsables de mort subite par fibrillation ventriculaire et un remplacement progressif des cardiomyocytes par du tissu fibro-adipeux. Le remodelage cardiaque atteint préférentiellement le ventricule droit, mais des formes bi-ventriculaire existent. Une mutation sur un gène desmosomal est retrouvé dans 50% des cas. Parmi les gènes impliqués, la plakoglobine, la desmocolline-2, la desmogléine-2, la desmoplakine et la plakophiline-2 permettent l’ancrage et le maintien des cardiomyocytes entre eux. Une mutation sur l’un de ces gènes, entraîne la déstabilisation du desmosome et une fragilisation de la connexion entre les cardiomyocytes. Ceci conduit à un remodelage myocardique profond, maintenant bien définis, qui participe à l’initiation et au maintien des arythmies. Cependant, les mécanismes cellulaires restent insuffisament compris. Pour étudier cette pathologie, des cardiomyocytes issus de cellules souches pluripotentes induites (hiPSC-CM) ont été utilisés comme modèle cellulaire intéressant afin de comprendre les mécanismes sous-jacents pour une multitude de pathologies cardiaques héréditaires, et d’identifier de nouvelles voies thérapeutiques. L’apparition d’arythmies dans la cardiomyopathie arythmogène est souvent considérée comme étant le résultat d’un remodelage morpho-structurelle du myocarde. Cependant, les études sur le remodelage électrophysiologique font défaut. L’objectif principal de ma thèse était donc de valider notre modèle de cardiomyopathie arythmogène et d’étudier l’implication des altérations du couplage excitation-contraction dans le déclenchement des arythmies. Notre modèle d’étude a été capable de reproduire un phénotype cohérent avec des défauts de contractilité dûs à un remodelage électrophysiologique et calcique. Le test pharmacologique avec des anti-arythmiques, sotalol et flécaïnide, a permis de corriger les défauts de contraction et a amélioré notre compréhension de leur mécanisme d’action chez les patients atteints de la cardiomyopathie arythmogène. De plus, de nouvelles voies thérapeutiques testées sur les hiPSC-CM, ciblant la voie de signalisation PPAR et le système rénine-angiotensine-aldostérone ont montré des résultats prometteurs dans la prévention des arythmies et pourraient être pris en compte pour des études futures.Arrhythmogenic cardiomyopathy is a rare genetic disorder characterized by cardiac dysfunction with the onset of ventricular arrhythmias, often responsible for sudden cardiac death and progressive replacement of cardiomyocytes by fibro-adipose tissue. Cardiac remodeling preferentially affects the right ventricle, but there bi-ventricular forms may be present. A mutation in a desmosomal gene is found in 50% of cases. Among the genes involved, plakoglobin, desmocollin-2, desmoglein-2, desmoplakin, and plakophilin-2 allow the anchoring and maintenance of cardiomyocytes between them. A mutation in one of these genes destabilizes the desmosome, weakening the connection between the cardiomyocytes. This alteration leads to a profound remodeling of the heart, now well defined, which participates in the initiation of arrhythmias. However, the role and impact of cellular mechanisms are poorly understood. To study this pathology, cardiomyocytes derived from induced pluripotent stem cells (hiPSC-CM) were used as an exciting cell model to understand the underlying mechanisms for many hereditary cardiac pathologies and experiment with new therapeutic pathways. The development of arrhythmias in arrhythmogenic cardiomyopathy is often considered the result of morpho-structural remodeling of the myocardium. However, studies on electrophysiological remodeling are lacking. Therefore, the main objective of my thesis was to validate our cellular model of arrhythmogenic cardiomyopathy and to study the involvement of alterations in the excitation-contraction coupling in the onset of arrhythmias. Our study model reproduced a consistent phenotype with contractility defects due to electrophysiological and calcium remodeling. Testing anti-arrhythmic drugs, sotalol and flecainide, corrected contraction defects and improved our understanding of their mechanism of action in DSC2 patients. In addition, new therapeutic pathways tested on hiPSC-CMs, targeting the PPAR signaling pathway and the renin-angiotensin-aldosterone system, shown promising results in preventing arrhythmias and could be considered for future studies

Développement et caractérisation d’un modèle cellulaire cardiaque humain de cardiomyopathie arythmogène

Arrhythmogenic cardiomyopathy is a rare genetic disorder characterized by cardiac dysfunction with the onset of ventricular arrhythmias, often responsible for sudden cardiac death and progressive replacement of cardiomyocytes by fibro-adipose tissue. Cardiac remodeling preferentially affects the right ventricle, but there bi-ventricular forms may be present. A mutation in a desmosomal gene is found in 50% of cases. Among the genes involved, plakoglobin, desmocollin-2, desmoglein-2, desmoplakin, and plakophilin-2 allow the anchoring and maintenance of cardiomyocytes between them. A mutation in one of these genes destabilizes the desmosome, weakening the connection between the cardiomyocytes. This alteration leads to a profound remodeling of the heart, now well defined, which participates in the initiation of arrhythmias. However, the role and impact of cellular mechanisms are poorly understood. To study this pathology, cardiomyocytes derived from induced pluripotent stem cells (hiPSC-CM) were used as an exciting cell model to understand the underlying mechanisms for many hereditary cardiac pathologies and experiment with new therapeutic pathways. The development of arrhythmias in arrhythmogenic cardiomyopathy is often considered the result of morpho-structural remodeling of the myocardium. However, studies on electrophysiological remodeling are lacking. Therefore, the main objective of my thesis was to validate our cellular model of arrhythmogenic cardiomyopathy and to study the involvement of alterations in the excitation-contraction coupling in the onset of arrhythmias. Our study model reproduced a consistent phenotype with contractility defects due to electrophysiological and calcium remodeling. Testing anti-arrhythmic drugs, sotalol and flecainide, corrected contraction defects and improved our understanding of their mechanism of action in DSC2 patients. In addition, new therapeutic pathways tested on hiPSC-CMs, targeting the PPAR signaling pathway and the renin-angiotensin-aldosterone system, shown promising results in preventing arrhythmias and could be considered for future studies.La cardiomyopathie arythmogène est une maladie génétique rare. Elle est caractérisée par un dysfonctionnement cardiaque avec l’apparition d’arythmies ventriculaires, souvent responsables de mort subite par fibrillation ventriculaire et un remplacement progressif des cardiomyocytes par du tissu fibro-adipeux. Le remodelage cardiaque atteint préférentiellement le ventricule droit, mais des formes bi-ventriculaire existent. Une mutation sur un gène desmosomal est retrouvé dans 50% des cas. Parmi les gènes impliqués, la plakoglobine, la desmocolline-2, la desmogléine-2, la desmoplakine et la plakophiline-2 permettent l’ancrage et le maintien des cardiomyocytes entre eux. Une mutation sur l’un de ces gènes, entraîne la déstabilisation du desmosome et une fragilisation de la connexion entre les cardiomyocytes. Ceci conduit à un remodelage myocardique profond, maintenant bien définis, qui participe à l’initiation et au maintien des arythmies. Cependant, les mécanismes cellulaires restent insuffisament compris. Pour étudier cette pathologie, des cardiomyocytes issus de cellules souches pluripotentes induites (hiPSC-CM) ont été utilisés comme modèle cellulaire intéressant afin de comprendre les mécanismes sous-jacents pour une multitude de pathologies cardiaques héréditaires, et d’identifier de nouvelles voies thérapeutiques. L’apparition d’arythmies dans la cardiomyopathie arythmogène est souvent considérée comme étant le résultat d’un remodelage morpho-structurelle du myocarde. Cependant, les études sur le remodelage électrophysiologique font défaut. L’objectif principal de ma thèse était donc de valider notre modèle de cardiomyopathie arythmogène et d’étudier l’implication des altérations du couplage excitation-contraction dans le déclenchement des arythmies. Notre modèle d’étude a été capable de reproduire un phénotype cohérent avec des défauts de contractilité dûs à un remodelage électrophysiologique et calcique. Le test pharmacologique avec des anti-arythmiques, sotalol et flécaïnide, a permis de corriger les défauts de contraction et a amélioré notre compréhension de leur mécanisme d’action chez les patients atteints de la cardiomyopathie arythmogène. De plus, de nouvelles voies thérapeutiques testées sur les hiPSC-CM, ciblant la voie de signalisation PPAR et le système rénine-angiotensine-aldostérone ont montré des résultats prometteurs dans la prévention des arythmies et pourraient être pris en compte pour des études futures

Spironolactone as a Potential New Treatment to Prevent Arrhythmias in Arrhythmogenic Cardiomyopathy Cell Model

International audienceArrhythmogenic cardiomyopathy (ACM) is a rare genetic disease associated with ventricular arrhythmias in patients. The occurrence of these arrhythmias is due to direct electrophysiological remodeling of the cardiomyocytes, namely a reduction in the action potential duration (APD) and a disturbance of Ca2+ homeostasis. Interestingly, spironolactone (SP), a mineralocorticoid receptor antagonist, is known to block K+ channels and may reduce arrhythmias. Here, we assess the direct effect of SP and its metabolite canrenoic acid (CA) in cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) of a patient bearing a missense mutation (c.394C>T) in the DSC2 gene coding for desmocollin 2 and for the amino acid replacement of arginine by cysteine at position 132 (R132C). SP and CA corrected the APD in the muted cells (vs. the control) in linking to a normalization of the hERG and KCNQ1 K+ channel currents. In addition, SP and CA had a direct cellular effect on Ca2+ homeostasis. They reduced the amplitude and aberrant Ca2+ events. In conclusion, we show the direct beneficial effects of SP on the AP and Ca2+ homeostasis of DSC2-specific hiPSC-CMs. These results provide a rationale for a new therapeutical approach to tackle mechanical and electrical burdens in patients suffering from ACM

The PPARγ pathway determines electrophysiological remodelling and arrhythmia risks in DSC2 arrhythmogenic cardiomyopathy

International audienceNo abstract availabl

Table1_Electrophysiological basis of cardiac arrhythmia in a mouse model of myotonic dystrophy type 1.DOCX

Introduction: Myotonic dystrophy type 1 (DM1) is a multisystemic genetic disorder caused by the increased number of CTG repeats in 3′ UTR of Dystrophia Myotonia Protein Kinase (DMPK) gene. DM1 patients experience conduction abnormalities as well as atrial and ventricular arrhythmias with increased susceptibility to sudden cardiac death. The ionic basis of these electrical abnormalities is poorly understood.Methods: We evaluated the surface electrocardiogram (ECG) and key ion currents underlying the action potential (AP) in a mouse model of DM1, DMSXL, which express over 1000 CTG repeats. Sodium current (INa), L-type calcium current (ICaL), transient outward potassium current (Ito), and APs were recorded using the patch-clamp technique.Results: Arrhythmic events on the ECG including sinus bradycardia, conduction defects, and premature ventricular and atrial arrhythmias were observed in DMSXL homozygous mice but not in WT mice. PR interval shortening was observed in homozygous mice while ECG parameters such as QRS duration, and QTc did not change. Further, flecainide prolonged PR, QRS, and QTc visually in DMSXL homozygous mice. At the single ventricular myocyte level, we observed a reduced current density for Ito and ICaL with a positive shift in steady state activation of L-type calcium channels carrying ICaL in DMSXL homozygous mice compared with WT mice. INa densities and action potential duration did not change between DMSXL and WT mice.Conclusion: The reduced current densities of Ito, and ICaL and alterations in gating properties in L-type calcium channels may contribute to the ECG abnormalities in the DMSXL mouse model of DM1. These findings open new avenues for novel targeted therapeutics.</p

Deciphering DSC2 arrhythmogenic cardiomyopathy electrical instability: From ion channels to ECG and tailored drug therapy

International audienceBackground: Severe ventricular rhythm disturbances are the hallmark of arrhythmogenic cardiomyopathy (ACM), and are often explained by structural conduction abnormalities. However, comprehensive investigations of ACM cell electrical instability are lacking. This study aimed to elucidate early electrical myogenic signature of ACM.Methods: We investigated a 41‐year‐old ACM patient with a missense mutation (c.394C>T) in the DSC2 gene, which encodes desmocollin 2. Pathogenicity of this variant was confirmed using a zebrafish DSC2 model system. Control and DSC2 patient‐derived pluripotent stem cells were reprogrammed and differentiated into cardiomyocytes (hiPSC‐CM) to examine the specific electromechanical phenotype and its modulation by antiarrhythmic drugs (AADs). Samples of the patient's heart and hiPSC‐CM were examined to identify molecular and cellular alterations.Results: A shortened action potential duration was associated with reduced Ca2+ current density and increased K+ current density. This finding led to the elucidation of previously unknown abnormal repolarization dynamics in ACM patients. Moreover, the Ca2+ mobilised during transients was decreased, and the Ca2+ sparks frequency was increased. AAD testing revealed the following: (1) flecainide normalised Ca2+ transients and significantly decreased Ca2+ spark occurrence and (2) sotalol significantly lengthened the action potential and normalised the cells’ contractile properties.Conclusions: Thorough analysis of hiPSC‐CM derived from the DSC2 patient revealed abnormal repolarization dynamics, prompting the discovery of a short QT interval in some ACM patients. Overall, these results confirm a myogenic origin of ACM electrical instability and provide a rationale for prescribing class 1 and 3 AADs in ACM patients with increased ventricular repolarization reserve