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Moreno-Manuel AI, Macías Á, Cruz FM, Gutiérrez LK, Martínez F, González-Guerra A, Martínez Carrascoso I, Bermúdez-Jimenez FJ, Sánchez-Pérez P, Vera-Pedrosa ML, Ruiz-Robles JM, Bernal JA, Jalife J. The Kir2.1E299V mutation increases atrial fibrillation vulnerability while protecting the ventricles against arrhythmias in a mouse model of short QT syndrome type 3. Cardiovasc Res 2024; 120:490-505. [PMID: 38261726 PMCID: PMC11060485 DOI: 10.1093/cvr/cvae019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 10/24/2023] [Accepted: 12/12/2023] [Indexed: 01/25/2024] Open
Abstract
AIMS Short QT syndrome type 3 (SQTS3) is a rare arrhythmogenic disease caused by gain-of-function mutations in KCNJ2, the gene coding the inward rectifier potassium channel Kir2.1. We used a multidisciplinary approach and investigated arrhythmogenic mechanisms in an in-vivo model of de-novo mutation Kir2.1E299V identified in a patient presenting an extremely abbreviated QT interval and paroxysmal atrial fibrillation. METHODS AND RESULTS We used intravenous adeno-associated virus-mediated gene transfer to generate mouse models, and confirmed cardiac-specific expression of Kir2.1WT or Kir2.1E299V. On ECG, the Kir2.1E299V mouse recapitulated the QT interval shortening and the atrial-specific arrhythmia of the patient. The PR interval was also significantly shorter in Kir2.1E299V mice. Patch-clamping showed extremely abbreviated action potentials in both atrial and ventricular Kir2.1E299V cardiomyocytes due to a lack of inward-going rectification and increased IK1 at voltages positive to -80 mV. Relative to Kir2.1WT, atrial Kir2.1E299V cardiomyocytes had a significantly reduced slope conductance at voltages negative to -80 mV. After confirming a higher proportion of heterotetrameric Kir2.x channels containing Kir2.2 subunits in the atria, in-silico 3D simulations predicted an atrial-specific impairment of polyamine block and reduced pore diameter in the Kir2.1E299V-Kir2.2WT channel. In ventricular cardiomyocytes, the mutation increased excitability by shifting INa activation and inactivation in the hyperpolarizing direction, which protected the ventricle against arrhythmia. Moreover, Purkinje myocytes from Kir2.1E299V mice manifested substantially higher INa density than Kir2.1WT, explaining the abbreviation in the PR interval. CONCLUSION The first in-vivo mouse model of cardiac-specific SQTS3 recapitulates the electrophysiological phenotype of a patient with the Kir2.1E299V mutation. Kir2.1E299V eliminates rectification in both cardiac chambers but protects against ventricular arrhythmias by increasing excitability in both Purkinje-fiber network and ventricles. Consequently, the predominant arrhythmias are supraventricular likely due to the lack of inward rectification and atrial-specific reduced pore diameter of the Kir2.1E299V-Kir2.2WT heterotetramer.
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MESH Headings
- Animals
- Humans
- Mice
- Action Potentials
- Arrhythmias, Cardiac/genetics
- Arrhythmias, Cardiac/physiopathology
- Arrhythmias, Cardiac/metabolism
- Atrial Fibrillation/genetics
- Atrial Fibrillation/physiopathology
- Atrial Fibrillation/metabolism
- Disease Models, Animal
- Genetic Predisposition to Disease
- Heart Rate/genetics
- Heart Ventricles/metabolism
- Heart Ventricles/physiopathology
- Mice, Inbred C57BL
- Mice, Transgenic
- Mutation
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Phenotype
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
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Affiliation(s)
- Ana I Moreno-Manuel
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Álvaro Macías
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Francisco M Cruz
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Lilian K Gutiérrez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Fernando Martínez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Andrés González-Guerra
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Isabel Martínez Carrascoso
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Francisco José Bermúdez-Jimenez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- Department of Cardiology, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain
| | - Patricia Sánchez-Pérez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | | | - Juan Manuel Ruiz-Robles
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Juan A Bernal
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - José Jalife
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
- Departments of Internal Medicine and Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 4810, USA
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2
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Blair GA, Wu X, Bain C, Warren M, Hoeker GS, Poelzing S. Mannitol and hyponatremia regulate cardiac ventricular conduction in the context of sodium channel loss of function. Am J Physiol Heart Circ Physiol 2024; 326:H724-H734. [PMID: 38214908 PMCID: PMC11221810 DOI: 10.1152/ajpheart.00211.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 01/04/2024] [Accepted: 01/09/2024] [Indexed: 01/13/2024]
Abstract
Scn5a heterozygous null (Scn5a+/-) mice have historically been used to investigate arrhythmogenic mechanisms of diseases such as Brugada syndrome (BrS) and Lev's disease. Previously, we demonstrated that reducing ephaptic coupling (EpC) in ex vivo hearts exacerbates pharmacological voltage-gated sodium channel (Nav)1.5 loss of function (LOF). Whether this effect is consistent in a genetic Nav1.5 LOF model is yet to be determined. We hypothesized that loss of EpC would result in greater reduction in conduction velocity (CV) for the Scn5a+/- mouse relative to wild type (WT). In vivo ECGs and ex vivo optical maps were recorded from Langendorff-perfused Scn5a+/- and WT mouse hearts. EpC was reduced with perfusion of a hyponatremic solution, the clinically relevant osmotic agent mannitol, or a combination of the two. Neither in vivo QRS duration nor ex vivo CV during normonatremia was significantly different between the two genotypes. In agreement with our hypothesis, we found that hyponatremia severely slowed CV and disrupted conduction for 4/5 Scn5a+/- mice, but 0/6 WT mice. In addition, treatment with mannitol slowed CV to a greater extent in Scn5a+/- relative to WT hearts. Unexpectedly, treatment with mannitol during hyponatremia did not further slow CV in either genotype, but resolved the disrupted conduction observed in Scn5a+/- hearts. Similar results in guinea pig hearts suggest the effects of mannitol and hyponatremia are not species specific. In conclusion, loss of EpC through either hyponatremia or mannitol alone results in slowed or disrupted conduction in a genetic model of Nav1.5 LOF. However, the combination of these interventions attenuates conduction slowing.NEW & NOTEWORTHY Cardiac sodium channel loss of function (LOF) diseases such as Brugada syndrome (BrS) are often concealed. We optically mapped mouse hearts with reduced sodium channel expression (Scn5a+/-) to evaluate whether reduced ephaptic coupling (EpC) can unmask conduction deficits. Data suggest that conduction deficits in the Scn5a+/- mouse may be unmasked by treatment with hyponatremia and perinexal widening via mannitol. These data support further investigation of hyponatremia and mannitol as novel diagnostics for sodium channel loss of function diseases.
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Affiliation(s)
- Grace A Blair
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, Virginia, United States
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Xiaobo Wu
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Chandra Bain
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Mark Warren
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Gregory S Hoeker
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Steven Poelzing
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, Virginia, United States
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
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3
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Sauer J, Marksteiner J, Lilliu E, Hackl B, Todt H, Kubista H, Dostal C, Podesser BK, Kiss A, Koenig X, Hilber K. Empagliflozin treatment rescues abnormally reduced Na + currents in ventricular cardiomyocytes from dystrophin-deficient mdx mice. Am J Physiol Heart Circ Physiol 2024; 326:H418-H425. [PMID: 38099845 PMCID: PMC11219046 DOI: 10.1152/ajpheart.00729.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 12/07/2023] [Accepted: 12/12/2023] [Indexed: 01/23/2024]
Abstract
Cardiac arrhythmias significantly contribute to mortality in Duchenne muscular dystrophy (DMD), a severe muscle illness caused by mutations in the gene encoding for the intracellular protein dystrophin. A major source for arrhythmia vulnerability in patients with DMD is impaired ventricular impulse conduction, which predisposes for ventricular asynchrony, decreased cardiac output, and the development of reentrant circuits. Using the dystrophin-deficient mdx mouse model for human DMD, we previously reported that the lack of dystrophin causes a significant loss of peak Na+ current (INa) in ventricular cardiomyocytes. This finding provided a mechanistic explanation for ventricular conduction defects and concomitant arrhythmias in the dystrophic heart. In the present study, we explored the hypothesis that empagliflozin (EMPA), an inhibitor of sodium/glucose cotransporter 2 in clinical use to treat type II diabetes and nondiabetic heart failure, rescues peak INa loss in dystrophin-deficient ventricular cardiomyocytes. We found that INa of cardiomyocytes derived from mdx mice, which had received clinically relevant doses of EMPA for 4 wk, was restored to wild-type level. Moreover, incubation of isolated mdx ventricular cardiomyocytes with 1 µM EMPA for 24 h significantly increased their peak INa. This effect was independent of Na+-H+ exchanger 1 inhibition by the drug. Our findings imply that EMPA treatment can rescue abnormally reduced peak INa of dystrophin-deficient ventricular cardiomyocytes. Long-term EMPA administration may diminish arrhythmia vulnerability in patients with DMD.NEW & NOTEWORTHY Dystrophin deficiency in cardiomyocytes leads to abnormally reduced Na+ currents. These can be rescued by long-term empagliflozin treatment.
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Affiliation(s)
- Jakob Sauer
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Jessica Marksteiner
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Elena Lilliu
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Benjamin Hackl
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Hannes Todt
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Helmut Kubista
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Christopher Dostal
- Center for Biomedical Research and Translational Surgery, Medical University of Vienna, Vienna, Austria
| | - Bruno K Podesser
- Center for Biomedical Research and Translational Surgery, Medical University of Vienna, Vienna, Austria
| | - Attila Kiss
- Center for Biomedical Research and Translational Surgery, Medical University of Vienna, Vienna, Austria
| | - Xaver Koenig
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Karlheinz Hilber
- Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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4
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Stevens TL, Coles S, Sturm AC, Hoover CA, Borzok MA, Mohler PJ, El Refaey M. Molecular Pathways and Animal Models of Arrhythmias. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1441:1057-1090. [PMID: 38884769 DOI: 10.1007/978-3-031-44087-8_67] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
Arrhythmias account for over 300,000 annual deaths in the United States, and approximately half of all deaths are associated with heart disease. Mechanisms underlying arrhythmia risk are complex; however, work in humans and animal models over the past 25 years has identified a host of molecular pathways linked with both arrhythmia substrates and triggers. This chapter will focus on select arrhythmia pathways solved by linking human clinical and genetic data with animal models.
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Affiliation(s)
- Tyler L Stevens
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Sara Coles
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Amy C Sturm
- Genomic Medicine Institute, 23andMe, Sunnyvale, CA, USA
| | - Catherine A Hoover
- Department of Biochemistry, Chemistry, Engineering and Physics, Commonwealth University of Pennsylvania, Mansfield, PA, USA
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Maegen A Borzok
- Department of Biochemistry, Chemistry, Engineering and Physics, Commonwealth University of Pennsylvania, Mansfield, PA, USA
| | - Peter J Mohler
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- Department of Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Mona El Refaey
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
- Department of Surgery, Division of Cardiac Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
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5
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Liao Y, Xiang Y, Zheng M, Wang J. DeepMiceTL: a deep transfer learning based prediction of mice cardiac conduction diseases using early electrocardiograms. Brief Bioinform 2023; 24:bbad109. [PMID: 36935112 PMCID: PMC10422927 DOI: 10.1093/bib/bbad109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/10/2023] [Accepted: 03/01/2023] [Indexed: 03/21/2023] Open
Abstract
Cardiac conduction disease is a major cause of morbidity and mortality worldwide. There is considerable clinical significance and an emerging need of early detection of these diseases for preventive treatment success before more severe arrhythmias occur. However, developing such early screening tools is challenging due to the lack of early electrocardiograms (ECGs) before symptoms occur in patients. Mouse models are widely used in cardiac arrhythmia research. The goal of this paper is to develop deep learning models to predict cardiac conduction diseases in mice using their early ECGs. We hypothesize that mutant mice present subtle abnormalities in their early ECGs before severe arrhythmias present. These subtle patterns can be detected by deep learning though they are hard to be identified by human eyes. We propose a deep transfer learning model, DeepMiceTL, which leverages knowledge from human ECGs to learn mouse ECG patterns. We further apply the Bayesian optimization and $k$-fold cross validation methods to tune the hyperparameters of the DeepMiceTL. Our results show that DeepMiceTL achieves a promising performance (F1-score: 83.8%, accuracy: 84.8%) in predicting the occurrence of cardiac conduction diseases using early mouse ECGs. This study is among the first efforts that use state-of-the-art deep transfer learning to identify ECG patterns during the early course of cardiac conduction disease in mice. Our approach not only could help in cardiac conduction disease research in mice, but also suggest a feasibility for early clinical diagnosis of human cardiac conduction diseases and other types of cardiac arrythmias using deep transfer learning in the future.
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Affiliation(s)
- Ying Liao
- Department of Industrial, Manufacturing & Systems Engineering, Texas Tech University, Lubbock, Texas, USA
| | - Yisha Xiang
- Department of Industrial Engineering, University of Houston, Houston, Texas, USA
| | - Mingjie Zheng
- Department of Pediatrics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Jun Wang
- Department of Pediatrics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA
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6
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Berger V, Gabriel L, Lilliu E, Hackl B, Marksteiner J, Hilber K, Koenig X, Uhrin P, Todt H. Modulation of cardiac ventricular conduction: Impact on QRS duration, amplitude and dispersion. Eur J Pharmacol 2023; 941:175495. [PMID: 36621601 DOI: 10.1016/j.ejphar.2023.175495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 12/09/2022] [Accepted: 01/04/2023] [Indexed: 01/06/2023]
Abstract
Alterations in cardiac impulse conduction may exert both beneficial and detrimental effects. The assessment of ventricular conduction properties is of paramount importance both in clinical and in experimental settings. Currently the duration of the QRS complex is regarded as hallmark of in-vivo assessment of global ventricular conduction time. In addition, the amplitude of the QRS complex has been suggested to reflect ventricular conduction time in man and in rats. Here, for the first time, we systematically investigated the relationship between QRS duration ("QRS") and QRS amplitude ("RS-height"; RSh) in the murine ECG obtained during anesthesia. In mice harbouring a homozygous knockout of the transmembrane protein podoplanin (PDPN-/-; n = 10) we found both a shorter QRS and a greater RSh than in wild-type animals (n = 13). In both genotypes cumulative i.p. administration of 5 mg/kg and 10 mg/kg of the Na channel blocker flecainide resulted in dose-dependent QRS increase and RSh decrease, whereby the drug-induced changes in RSh were greater than in QRS. In both genotypes the flecainide-induced changes in QRS and in RSh were significantly correlated with each other (R = -0.56, P = 0.004). Whereas dispersion of QRS and RSh was similar between genotypes, dispersion of the ratio QRS/RSh was significantly smaller in PDPN-/- than in wild-types. We conclude that in the murine ECG QRS is inversely related to RSh. We suggest that both parameters should be considered in the analysis of ventricular conduction time in the murine ECG.
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Affiliation(s)
- Valerie Berger
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
| | - Ludwig Gabriel
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
| | - Elena Lilliu
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
| | - Benjamin Hackl
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
| | - Jessica Marksteiner
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
| | - Karlheinz Hilber
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
| | - Xaver Koenig
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
| | - Pavel Uhrin
- Center for Physiology and Pharmacology, Department of Vascular Biology and Thrombosis Research, Medical University of Vienna, Schwarzspanierstrasse 17, 1190, Vienna, Austria.
| | - Hannes Todt
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1190, Vienna, Austria.
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7
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Dorninger F, Kiss A, Rothauer P, Stiglbauer-Tscholakoff A, Kummer S, Fallatah W, Perera-Gonzalez M, Hamza O, König T, Bober MB, Cavallé-Garrido T, Braverman NE, Forss-Petter S, Pifl C, Bauer J, Bittner RE, Helbich TH, Podesser BK, Todt H, Berger J. Overlapping and Distinct Features of Cardiac Pathology in Inherited Human and Murine Ether Lipid Deficiency. Int J Mol Sci 2023; 24:1884. [PMID: 36768204 PMCID: PMC9914995 DOI: 10.3390/ijms24031884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/21/2023] Open
Abstract
Inherited deficiency in ether lipids, a subgroup of glycerophospholipids with unique biochemical and biophysical properties, evokes severe symptoms in humans resulting in a multi-organ syndrome. Mouse models with defects in ether lipid biosynthesis have widely been used to understand the pathophysiology of human disease and to study the roles of ether lipids in various cell types and tissues. However, little is known about the function of these lipids in cardiac tissue. Previous studies included case reports of cardiac defects in ether-lipid-deficient patients, but a systematic analysis of the impact of ether lipid deficiency on the mammalian heart is still missing. Here, we utilize a mouse model of complete ether lipid deficiency (Gnpat KO) to accomplish this task. Similar to a subgroup of human patients with rhizomelic chondrodysplasia punctata (RCDP), a fraction of Gnpat KO fetuses present with defects in ventricular septation, presumably evoked by a developmental delay. We did not detect any signs of cardiomyopathy but identified increased left ventricular end-systolic and end-diastolic pressure in middle-aged ether-lipid-deficient mice. By comprehensive electrocardiographic characterization, we consistently found reduced ventricular conduction velocity, as indicated by a prolonged QRS complex, as well as increased QRS and QT dispersion in the Gnpat KO group. Furthermore, a shift of the Wenckebach point to longer cycle lengths indicated depressed atrioventricular nodal function. To complement our findings in mice, we analyzed medical records and performed electrocardiography in ether-lipid-deficient human patients, which, in contrast to the murine phenotype, indicated a trend towards shortened QT intervals. Taken together, our findings demonstrate that the cardiac phenotype upon ether lipid deficiency is highly heterogeneous, and although the manifestations in the mouse model only partially match the abnormalities in human patients, the results add to our understanding of the physiological role of ether lipids and emphasize their importance for proper cardiac development and function.
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Affiliation(s)
- Fabian Dorninger
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Attila Kiss
- Center for Biomedical Research, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Peter Rothauer
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstrasse 13a, 1090 Vienna, Austria
| | - Alexander Stiglbauer-Tscholakoff
- Department of Biomedical Imaging and Image-Guided Therapy, Division of Molecular and Structural Preclinical Imaging, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Stefan Kummer
- Neuromuscular Research Department, Center for Anatomy and Cell Biology, Medical University of Vienna, Währinger Straße 13, 1090 Vienna, Austria
| | - Wedad Fallatah
- Department of Genetic Medicine, King AbdulAziz University, Jeddah 21589, Saudi Arabia
- Department of Human Genetics and Pediatrics, Montreal Children’s Hospital, McGill University, 1001 Décarie Blvd, Montreal, QC H4A 3J1, Canada
| | - Mireia Perera-Gonzalez
- Center for Biomedical Research, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Ouafa Hamza
- Center for Biomedical Research, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Theresa König
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Michael B. Bober
- Skeletal Dysplasia Program, Nemours Children’s Hospital, 1600 Rockland Road, Wilmington, DE 19803, USA
| | - Tiscar Cavallé-Garrido
- Department of Pediatrics, Division of Cardiology, Montreal Children’s Hospital, McGill University, 1001 Décarie Blvd, Montreal, QC H4A 3J1, Canada
| | - Nancy E. Braverman
- Department of Human Genetics and Pediatrics, Montreal Children’s Hospital, McGill University, 1001 Décarie Blvd, Montreal, QC H4A 3J1, Canada
| | - Sonja Forss-Petter
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Christian Pifl
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Jan Bauer
- Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Reginald E. Bittner
- Neuromuscular Research Department, Center for Anatomy and Cell Biology, Medical University of Vienna, Währinger Straße 13, 1090 Vienna, Austria
| | - Thomas H. Helbich
- Department of Biomedical Imaging and Image-Guided Therapy, Division of Molecular and Structural Preclinical Imaging, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Bruno K. Podesser
- Center for Biomedical Research, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Hannes Todt
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstrasse 13a, 1090 Vienna, Austria
| | - Johannes Berger
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
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8
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Barefield DY, Yamakawa S, Tahtah I, Sell JJ, Broman M, Laforest B, Harris S, Alvarez AA, Araujo KN, Puckelwartz MJ, Wasserstrom JA, Fishman GI, McNally EM. Partial and complete loss of myosin binding protein H-like cause cardiac conduction defects. J Mol Cell Cardiol 2022; 169:28-40. [PMID: 35533732 PMCID: PMC9329245 DOI: 10.1016/j.yjmcc.2022.04.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 03/25/2022] [Accepted: 04/15/2022] [Indexed: 02/04/2023]
Abstract
A premature truncation of MYBPHL in humans and a loss of Mybphl in mice is associated with dilated cardiomyopathy, atrial and ventricular arrhythmias, and atrial enlargement. MYBPHL encodes myosin binding protein H-like (MyBP-HL). Prior work in mice indirectly identified Mybphl expression in the atria and in small puncta throughout the ventricle. Because of its genetic association with human and mouse cardiac conduction system disease, we evaluated the anatomical localization of MyBP-HL and the consequences of loss of MyBP-HL on conduction system function. Immunofluorescence microscopy of normal adult mouse ventricles identified MyBP-HL-positive ventricular cardiomyocytes that co-localized with the ventricular conduction system marker contactin-2 near the atrioventricular node and in a subset of Purkinje fibers. Mybphl heterozygous ventricles had a marked reduction of MyBP-HL-positive cells compared to controls. Lightsheet microscopy of normal perinatal day 5 mouse hearts showed enrichment of MyBP-HL-positive cells within and immediately adjacent to the contactin-2-positive ventricular conduction system, but this association was not apparent in Mybphl heterozygous hearts. Surface telemetry of Mybphl-null mice revealed atrioventricular block and atrial bigeminy, while intracardiac pacing revealed a shorter atrial relative refractory period and atrial tachycardia. Calcium transient analysis of isolated Mybphl-null atrial cardiomyocytes demonstrated an increased heterogeneity of calcium release and faster rates of calcium release compared to wild type controls. Super-resolution microscopy of Mybphl heterozygous and homozygous null atrial cardiomyocytes showed ryanodine receptor disorganization compared to wild type controls. Abnormal calcium release, shorter atrial refractory period, and atrial dilation seen in Mybphl null, but not wild type control hearts, agree with the observed atrial arrhythmias, bigeminy, and atrial tachycardia, whereas the proximity of MyBP-HL-positive cells with the ventricular conduction system provides insight into how a predominantly atrial expressed gene contributes to ventricular arrhythmias and ventricular dysfunction.
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Affiliation(s)
- David Y. Barefield
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL;,Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL;,Correspondence to: David Y. Barefield, PhD, Department of Cell and Molecular Physiology Loyola University Chicago, 2160 S. 1st Ave. Maywood, IL 60153,
| | - Sean Yamakawa
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - Ibrahim Tahtah
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - Jordan J. Sell
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - Michael Broman
- Section of Cardiology, Department of Medicine, University of Chicago, Chicago, IL
| | - Brigitte Laforest
- Section of Cardiology, Department of Medicine, University of Chicago, Chicago, IL
| | - Sloane Harris
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - Alejandro A. Alvarez
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Kelly N. Araujo
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Megan J. Puckelwartz
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - J. Andrew Wasserstrom
- Department of Medicine and The Feinberg Cardiovascular and Renal Institute, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Glenn I. Fishman
- Division of Cardiology, NYU Grossman School of Medicine, New York, New York
| | - Elizabeth M. McNally
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL;,Correspondence to: Elizabeth McNally, MD, PhD, Center for Genetic Medicine, Northwestern University, 303 E. Superior St. Chicago, IL 60611,
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9
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Yu G, Chakrabarti S, Tischenko M, Chen AL, Wang Z, Cho H, French BA, Naga Prasad SV, Chen Q, Wang QK. Gene therapy targeting protein trafficking regulator MOG1 in mouse models of Brugada syndrome, arrhythmias, and mild cardiomyopathy. Sci Transl Med 2022; 14:eabf3136. [PMID: 35675436 DOI: 10.1126/scitranslmed.abf3136] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Brugada syndrome (BrS) is a fatal arrhythmia that causes an estimated 4% of all sudden death in high-incidence areas. SCN5A encodes cardiac sodium channel NaV1.5 and causes 25 to 30% of BrS cases. Here, we report generation of a knock-in (KI) mouse model of BrS (Scn5aG1746R/+). Heterozygous KI mice recapitulated some of the clinical features of BrS, including an ST segment abnormality (a prominent J wave) on electrocardiograms and development of spontaneous ventricular tachyarrhythmias (VTs), seizures, and sudden death. VTs were caused by shortened cardiac action potential duration and late phase 3 early afterdepolarizations associated with reduced sodium current density (INa) and increased Kcnd3 and Cacna1c expression. We developed a gene therapy using adeno-associated virus serotype 9 (AAV9) vector-mediated MOG1 delivery for up-regulation of MOG1, a chaperone that binds to NaV1.5 and traffics it to the cell surface. MOG1 was chosen for gene therapy because the large size of the SCN5A coding sequence (6048 base pairs) exceeds the packaging capacity of AAV vectors. AAV9-MOG1 gene therapy increased cell surface expression of NaV1.5 and ventricular INa, reversed up-regulation of Kcnd3 and Cacna1c expression, normalized cardiac action potential abnormalities, abolished J waves, and blocked VT in Scn5aG1746R/+ mice. Gene therapy also rescued the phenotypes of cardiac arrhythmias and contractile dysfunction in heterozygous humanized KI mice with SCN5A mutation p.D1275N. Using a small chaperone protein may have broad implications for targeting disease-causing genes exceeding the size capacity of AAV vectors.
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Affiliation(s)
- Gang Yu
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Susmita Chakrabarti
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Miroslava Tischenko
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Ai-Lan Chen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Cardiology, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 511436, P. R. China
| | - Zhijie Wang
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Hyosuk Cho
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Brent A French
- Department of Biomedical Engineering, University of Virginia Health System, Charlottesville, VA 22903, USA
| | - Sathyamangla V Naga Prasad
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Qiuyun Chen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Qing K Wang
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA.,Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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10
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Li Y, Lang S, Akin I, Zhou X, El-Battrawy I. Brugada Syndrome: Different Experimental Models and the Role of Human Cardiomyocytes From Induced Pluripotent Stem Cells. J Am Heart Assoc 2022; 11:e024410. [PMID: 35322667 PMCID: PMC9075459 DOI: 10.1161/jaha.121.024410] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Brugada syndrome (BrS) is an inherited and rare cardiac arrhythmogenic disease associated with an increased risk of ventricular fibrillation and sudden cardiac death. Different genes have been linked to BrS. The majority of mutations are located in the SCN5A gene, and the typical abnormal ECG is an elevation of the ST segment in the right precordial leads V1 to V3. The pathophysiological mechanisms of BrS were studied in different models, including animal models, heterologous expression systems, and human-induced pluripotent stem cell-derived cardiomyocyte models. Currently, only a few BrS studies have used human-induced pluripotent stem cell-derived cardiomyocytes, most of which have focused on genotype-phenotype correlations and drug screening. The combination of new technologies, such as clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 (CRISPR associated protein 9)-mediated genome editing and 3-dimensional engineered heart tissues, has provided novel insights into the pathophysiological mechanisms of the disease and could offer opportunities to improve the diagnosis and treatment of patients with BrS. This review aimed to compare different models of BrS for a better understanding of the roles of human-induced pluripotent stem cell-derived cardiomyocytes in current BrS research and personalized medicine at a later stage.
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Affiliation(s)
- Yingrui Li
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany
| | - Siegfried Lang
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany
| | - Ibrahim Akin
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany
| | - Xiaobo Zhou
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province Institute of Cardiovascular Research Southwest Medical University Luzhou Sichuan China.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany
| | - Ibrahim El-Battrawy
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany.,Department of Cardiology and Angiology Bergmannsheil Bochum Medical Clinic II Ruhr University Bochum Germany
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11
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Bonet-Luz E, Lyle JV, Huang CLH, Zhang Y, Nandi M, Jeevaratnam K, Aston PJ. Symmetric Projection Attractor Reconstruction analysis of murine electrocardiograms: Retrospective prediction of Scn5a +/- genetic mutation attributable to Brugada syndrome. Heart Rhythm O2 2021; 1:368-375. [PMID: 33748801 PMCID: PMC7962089 DOI: 10.1016/j.hroo.2020.08.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background Life-threatening arrhythmias resulting from genetic mutations are often missed in current electrocardiogram (ECG) analysis. We combined a new method for ECG analysis that uses all the waveform data with machine learning to improve detection of such mutations from short ECG signals in a mouse model. Objective We sought to detect consequences of Na+ channel deficiencies known to compromise action potential conduction in comparisons of Scn5a+/- mutant and wild-type mice using short ECG signals, examining novel and standard features derived from lead I and II ECG recordings by machine learning algorithms. Methods Lead I and II ECG signals from anesthetized wild-type and Scn5a+/- mutant mice of length 130 seconds were analyzed by extracting various groups of features, which were used by machine learning to classify the mice as wild-type or mutant. The features used were standard ECG intervals and amplitudes, as well as features derived from attractors generated using the novel Symmetric Projection Attractor Reconstruction method, which reformulates the whole signal as a bounded, symmetric 2-dimensional attractor. All the features were also combined as a single feature group. Results Classification of genotype using the attractor features gave higher accuracy than using either the ECG intervals or the intervals and amplitudes. However, the highest accuracy (96%) was obtained using all the features. Accuracies for different subgroups of the data were obtained and compared. Conclusion Detection of the Scn5a+/- mutation from short mouse ECG signals with high accuracy is possible using our Symmetric Projection Attractor Reconstruction method.
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Affiliation(s)
- Esther Bonet-Luz
- Department of Mathematics, University of Surrey, Guildford, United Kingdom
| | - Jane V Lyle
- Department of Mathematics, University of Surrey, Guildford, United Kingdom
| | - Christopher L-H Huang
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Yanmin Zhang
- Department of Paediatric Cardiology, Shaanxi Institute for Pediatric Diseases, Affiliate Children's Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Manasi Nandi
- School of Cancer and Pharmaceutical Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Philip J Aston
- Department of Mathematics, University of Surrey, Guildford, United Kingdom
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12
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Amstetter D, Badt F, Rubi L, Bittner RE, Ebner J, Uhrin P, Hilber K, Koenig X, Todt H. The bradycardic agent ivabradine decreases conduction velocity in the AV node and in the ventricles in-vivo. Eur J Pharmacol 2021; 893:173818. [PMID: 33345856 DOI: 10.1016/j.ejphar.2020.173818] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 12/02/2020] [Accepted: 12/10/2020] [Indexed: 10/22/2022]
Abstract
Ivabradine blocks hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels, thereby lowering the heart rate, an action that is used clinically for the treatment of heart failure and angina pectoris. We and others have shown previously that ivabradine, in addition to its HCN channel blocking activity, also inhibits voltage-gated Na channels in vitro at concentrations that may be clinically relevant. Such action may reduce conduction velocity in cardiac atria and ventricles. Here, we explore the effect of administration of ivabradine on parameters of ventricular conduction and repolarization in the surface ECG of anesthetized mice. We found that 5 min after i.p. administration of 10 mg/kg ivabradine spontaneous heart rate had declined by ~13%, which is within the range observed in human clinical studies. At the same time a significant increase in QRS duration by ~18% was observed, suggesting a reduction in ventricular conduction velocity. During transesophageal pacing at heart rates between 100 and 220 beats/min there was no obvious rate-dependence of ivabradine-induced QRS prolongation. On the other hand, ivabradine produced substantial rate-dependent slowing of AV nodal conduction. We conclude that ivabradine prolongs conduction in the AV-node and in the ventricles in vivo.
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Affiliation(s)
- Daniel Amstetter
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria
| | - Florian Badt
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria
| | - Lena Rubi
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria
| | - Reginald E Bittner
- Neuromuscular Research Department, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | - Janine Ebner
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria
| | - Pavel Uhrin
- Department of Vascular Biology and Thrombosis Research, Center for Physiology and Pharmacology, Austria
| | - Karlheinz Hilber
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria
| | - Xaver Koenig
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria
| | - Hannes Todt
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria.
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13
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Nieto-Marín P, Tinaquero D, Utrilla RG, Cebrián J, González-Guerra A, Crespo-García T, Cámara-Checa A, Rubio-Alarcón M, Dago M, Alfayate S, Filgueiras D, Peinado R, López-Sendón JL, Jalife J, Tamargo J, Bernal JA, Caballero R, Delpón E. Tbx5 variants disrupt Nav1.5 function differently in patients diagnosed with Brugada or Long QT Syndrome. Cardiovasc Res 2021; 118:1046-1060. [PMID: 33576403 DOI: 10.1093/cvr/cvab045] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 12/22/2020] [Accepted: 02/04/2021] [Indexed: 12/14/2022] Open
Abstract
AIMS The transcription factor Tbx5 controls cardiogenesis and drives Scn5a expression in mice. We have identified two variants in TBX5 encoding p.D111Y and p.F206L Tbx5, respectively, in two unrelated patients with structurally normal hearts diagnosed with Long QT (LQTS) and Brugada (BrS) Syndrome. Here we characterized the consequences of each variant to unravel the underlying disease mechanisms. METHODS AND RESULTS We combined clinical analysis with in vivo and in vitro electrophysiological and molecular techniques in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), HL-1 cells, and cardiomyocytes from mice trans-expressing human wildtype (WT) or mutant proteins. Tbx5 increased transcription of SCN5A encoding cardiac Nav1.5 channels, while repressing CAMK2D and SPTBN4 genes encoding Ca-calmodulin kinase IIδ (CaMKIIδ) and βIV-spectrin, respectively. These effects significantly increased Na current (INa) in hiPSC-CMs and in cardiomyocytes from mice trans-expressing Tbx5. Consequently, action potential (AP) amplitudes increased and QRS interval narrowed in the mouse electrocardiogram. p.F206L Tbx5 bound to the SCN5A promoter failed to transactivate it, thus precluding the pro-transcriptional effect of WT Tbx5. Therefore, p.F206L markedly decreased INa in hiPSC-CM, HL-1 cells, and mouse cardiomyocytes. The INa decrease in p.F206L trans-expressing mice translated into QRS widening and increased flecainide sensitivity. p.D111Y Tbx5 increased SCN5A expression but failed to repress CAMK2D and SPTBN4. The increased CaMKIIδ and βIV-spectrin significantly augmented the late component of INa (INaL) which, in turn, significantly prolonged AP duration in both hiPSC-CMs and mouse cardiomyocytes. Ranolazine, a selective INaL inhibitor, eliminated the QT and QTc intervals prolongation seen in p.D111Y trans-expressing mice. CONCLUSIONS In addition to peak INa, Tbx5 critically regulates INaL and the duration of repolarization in human cardiomyocytes. Our original results suggest that TBX5 variants associate with and modulate the intensity of the electrical phenotype in LQTS and BrS patients.
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Affiliation(s)
- Paloma Nieto-Marín
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - David Tinaquero
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - Raquel G Utrilla
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - Jorge Cebrián
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | | | - Teresa Crespo-García
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - Anabel Cámara-Checa
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - Marcos Rubio-Alarcón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - María Dago
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - Silvia Alfayate
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - David Filgueiras
- Fundación Centro Nacional de Investigaciones Cardiovasculares. 28029-Madrid, Spain
| | - Rafael Peinado
- Department of Cardiology. Hospital Universitario La Paz. Instituto de Investigación Sanitaria la Paz. 28046-Madrid Spain
| | - José Luis López-Sendón
- Department of Cardiology. Hospital Universitario La Paz. Instituto de Investigación Sanitaria la Paz. 28046-Madrid Spain
| | - José Jalife
- Fundación Centro Nacional de Investigaciones Cardiovasculares. 28029-Madrid, Spain.,Departments of Internal Medicine and Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Juan Tamargo
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - Juan Antonio Bernal
- Fundación Centro Nacional de Investigaciones Cardiovasculares. 28029-Madrid, Spain
| | - Ricardo Caballero
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
| | - Eva Delpón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid. Instituto de Investigación Gregorio Marañón. CIBERCV. 28040-Madrid, Spain
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14
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Ornelas-Loredo A, Kany S, Abraham V, Alzahrani Z, Darbar FA, Sridhar A, Ahmed M, Alamar I, Menon A, Zhang M, Chen Y, Hong L, Konda S, Darbar D. Association Between Obesity-Mediated Atrial Fibrillation and Therapy With Sodium Channel Blocker Antiarrhythmic Drugs. JAMA Cardiol 2021; 5:57-64. [PMID: 31774463 DOI: 10.1001/jamacardio.2019.4513] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Importance The association between obesity, an established risk factor for atrial fibrillation (AF), and response to antiarrhythmic drugs (AADs) remains unclear. Objective To test the hypothesis that obesity differentially mediates response to AADs in patients with symptomatic AF and in mice with diet-induced obesity (DIO) and pacing induced AF. Design, Setting, and Participants An observational cohort study was conducted including 311 patients enrolled in a clinical-genetic registry. Mice fed a high-fat diet for 10 weeks were also evaluated. The study was conducted from January 1, 2018, to June 2, 2019. Main Outcomes and Measures Symptomatic response was defined as continuation of the same AAD for at least 3 months. Nonresponse was defined as discontinuation of the AAD within 3 months of initiation because of poor symptomatic control of AF necessitating alternative rhythm control therapy. Outcome measures in DIO mice were pacing-induced AF and suppression of AF after 2 weeks of treatment with flecainide acetate or sotalol hydrochloride. Results A total of 311 patients (mean [SD] age, 65 [12] years; 120 women [38.6%]) met the entry criteria and were treated with a class I or III AAD for symptomatic AF. Nonresponse to class I AADs in patients with obesity was less than in those without obesity (30% [obese] vs 6% [nonobese]; difference, 0.24; 95% CI, 0.11-0.37; P = .001). Both groups had similar symptomatic response to a potassium channel blocker AAD. On multivariate analysis, obesity, AAD class (class I vs III AAD [obese] odds ratio [OR], 4.54; 95% Wald CI, 1.84-11.20; P = .001), female vs male sex (OR, 2.31; 95% Wald CI, 1.07-4.99; P = .03), and hyperthyroidism (OR, 4.95; 95% Wald CI, 1.23-20.00; P = .02) were significant indicators of the probability of failure to respond to AADs. Pacing induced AF in 100% of DIO mice vs 30% (P < .001) in controls. Furthermore, DIO mice showed a greater reduction in AF burden when treated with sotalol compared with flecainide (85% vs 25%; P < .01). Conclusions and Relevance Results suggest that obesity differentially mediates response to AADs in patients and in mice with AF, possibly reducing the therapeutic effectiveness of sodium channel blockers. These findings may have implications for the management of AF in patients with obesity.
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Affiliation(s)
- Aylin Ornelas-Loredo
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Shinwan Kany
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Vihas Abraham
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Zain Alzahrani
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Faisal A Darbar
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Arvind Sridhar
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Maha Ahmed
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Ihab Alamar
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Ambili Menon
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Meihang Zhang
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Yining Chen
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Liang Hong
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago
| | - Sreenivas Konda
- Division of Epidemiology and Biostatistics, University of Illinois at Chicago
| | - Dawood Darbar
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago.,Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
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15
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Kelly A, Salerno S, Connolly A, Bishop M, Charpentier F, Stølen T, Smith GL. Normal interventricular differences in tissue architecture underlie right ventricular susceptibility to conduction abnormalities in a mouse model of Brugada syndrome. Cardiovasc Res 2019; 114:724-736. [PMID: 29267949 PMCID: PMC5915948 DOI: 10.1093/cvr/cvx244] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 12/16/2017] [Indexed: 01/09/2023] Open
Abstract
Aims Loss-of-function of the cardiac sodium channel NaV1.5 is a common feature of Brugada syndrome. Arrhythmias arise preferentially from the right ventricle (RV) despite equivalent NaV1.5 downregulation in the left ventricle (LV). The reasons for increased RV sensitivity to NaV1.5 loss-of-function mutations remain unclear. Because ventricular electrical activation occurs predominantly in the transmural axis, we compare RV and LV transmural electrophysiology to determine the underlying cause of the asymmetrical conduction abnormalities in Scn5a haploinsufficient mice (Scn5a+/−). Methods and results Optical mapping and two-photon microscopy in isolated-perfused mouse hearts demonstrated equivalent depression of transmural conduction velocity (CV) in the LV and RV of Scn5a+/− vs. wild-type littermates. Only RV transmural conduction was further impaired when challenged with increased pacing frequencies. Epicardial dispersion of activation and beat-to-beat variation in activation time were increased only in the RV of Scn5a+/− hearts. Analysis of confocal and histological images revealed larger intramural clefts between cardiomyocyte layers in the RV vs. LV, independent of genotype. Acute sodium current inhibition in wild type hearts using tetrodotoxin reproduced beat-to-beat activation variability and frequency-dependent CV slowing in the RV only, with the LV unaffected. The influence of clefts on conduction was examined using a two-dimensional monodomain computational model. When peak sodium channel conductance was reduced to 50% of normal the presence of clefts between cardiomyocyte layers reproduced the activation variability and conduction phenotype observed experimentally. Conclusions Normal structural heterogeneities present in the RV are responsible for increased vulnerability to conduction slowing in the presence of reduced sodium channel function. Heterogeneous conduction slowing seen in the RV will predispose to functional block and the initiation of re-entrant ventricular arrhythmias.
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Affiliation(s)
- Allen Kelly
- Department of Circulation and Medical Imaging, St Olav's Hospital, Norwegian University of Science and Technology (NTNU), Postboks 8905, 7491 Trondheim, Norway.,Institute of Cardiovascular & Medical Sciences, University of Glasgow G12 8QQ, UK
| | - Simona Salerno
- Department of Circulation and Medical Imaging, St Olav's Hospital, Norwegian University of Science and Technology (NTNU), Postboks 8905, 7491 Trondheim, Norway
| | - Adam Connolly
- Division of Imaging Sciences and Biomedical Engineering, Department of Biomedical Engineering, Kings College London SE1 7EH, UK
| | - Martin Bishop
- Division of Imaging Sciences and Biomedical Engineering, Department of Biomedical Engineering, Kings College London SE1 7EH, UK
| | | | - Tomas Stølen
- Department of Circulation and Medical Imaging, St Olav's Hospital, Norwegian University of Science and Technology (NTNU), Postboks 8905, 7491 Trondheim, Norway
| | - Godfrey L Smith
- Department of Circulation and Medical Imaging, St Olav's Hospital, Norwegian University of Science and Technology (NTNU), Postboks 8905, 7491 Trondheim, Norway.,Institute of Cardiovascular & Medical Sciences, University of Glasgow G12 8QQ, UK
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16
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Korantzopoulos P, Bechlioulis A, Lakkas L, Naka KK. Brugada syndrome in a young patient with type 1 myotonic dystrophy requiring an implantable cardioverter defibrillator for primary prevention: a case report. Eur Heart J Case Rep 2019; 3:5519818. [PMID: 31449644 PMCID: PMC6601169 DOI: 10.1093/ehjcr/ytz086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 01/26/2019] [Accepted: 04/30/2019] [Indexed: 11/14/2022]
Abstract
Abstract
Background
Cardiac electrical disturbances represent the most frequent cardiac manifestations of myotonic dystrophy Type 1 (MD1). Limited data suggest that the prevalence of Brugada syndrome in MD1 may be increased compared to the general population.
Case summary
We report a case of a 22-year-old asymptomatic man with repolarization abnormalities in leads V1–V3 suggestive of Type III Brugada pattern. The patient had a family history of MD and incidents of sudden death in relatives. Drug-induced Brugada Type 1 syndrome was revealed after procainamide challenge. A ventricular stimulation study was positive since a polymorphic ventricular tachycardia was induced after two extrastimuli. The patient underwent implantation of a single chamber cardiac defibrillator (ICD). Eight months after the procedure he suffered an appropriate ICD shock due to rapid polymorphic ventricular tachycardia.
Discussion
Brugada syndrome is linked with MD1. Potential life-threatening arrhythmias may develop in the adult life of MD1 patients. Electrocardiographic surveillance and tailored invasive treatment with ICDs can prevent sudden cardiac death in this setting.
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Affiliation(s)
- Panagiotis Korantzopoulos
- 1st Department of Cardiology, University of Ioannina, Stavros Niarchos Avenue, Ioannina, Greece
- Laboratory of Pacing and Electrophysiology, 1st and 2nd Department of Cardiology, University Hospital of Ioannina, Greece
| | - Aris Bechlioulis
- Laboratory of Pacing and Electrophysiology, 1st and 2nd Department of Cardiology, University Hospital of Ioannina, Greece
- 2nd Department of Cardiology, University of Ioannina, Stavros Niarchos Avenue, Ioannina, Greece
| | - Lampros Lakkas
- 2nd Department of Cardiology, University of Ioannina, Stavros Niarchos Avenue, Ioannina, Greece
| | - Katerina K Naka
- 2nd Department of Cardiology, University of Ioannina, Stavros Niarchos Avenue, Ioannina, Greece
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17
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Abstract
Brugada syndrome is an inherited, rare cardiac arrhythmogenic disease, associated with sudden cardiac death. It accounts for up to 20% of sudden deaths in patients without structural cardiac abnormalities. The majority of mutations involve the cardiac sodium channel gene SCN5A and give rise to classical abnormal electrocardiogram with ST segment elevation in the right precordial leads V1 to V3 and a predisposition to ventricular fibrillation. The pathophysiological mechanisms of Brugada syndrome have been investigated using model systems including transgenic mice, canine heart preparations, and expression systems to study different SCN5A mutations. These models have a number of limitations. The recent development of pluripotent stem cell technology creates an opportunity to study cardiomyocytes derived from patients and healthy individuals. To date, only a few studies have been done using Brugada syndrome patient-specific iPS-CM, which have provided novel insights into the mechanisms and pathophysiology of Brugada syndrome. This review provides an evaluation of the strengths and limitations of each of these model systems and summarizes the key mechanisms that have been identified to date.
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18
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Waldau B. Using miniature brain implants in rodents for novel drug discovery. Expert Opin Drug Discov 2019; 14:379-386. [DOI: 10.1080/17460441.2019.1577816] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Ben Waldau
- Department of Neurological Surgery, University of California, Davis Medical Center, Sacramento, CA, USA
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19
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Ahmad S, Valli H, Salvage SC, Grace AA, Jeevaratnam K, Huang CLH. Age-dependent electrocardiographic changes in Pgc-1β deficient murine hearts. Clin Exp Pharmacol Physiol 2017; 45:174-186. [PMID: 28949414 PMCID: PMC5814877 DOI: 10.1111/1440-1681.12863] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 07/06/2017] [Accepted: 09/19/2017] [Indexed: 01/08/2023]
Abstract
Increasing evidence implicates chronic energetic dysfunction in human cardiac arrhythmias. Mitochondrial impairment through Pgc-1β knockout is known to produce a murine arrhythmic phenotype. However, the cumulative effect of this with advancing age and its electrocardiographic basis have not been previously studied. Young (12-16 weeks) and aged (>52 weeks), wild type (WT) (n = 5 and 8) and Pgc-1β-/- (n = 9 and 6), mice were anaesthetised and used for electrocardiographic (ECG) recordings. Time intervals separating successive ECG deflections were analysed for differences between groups before and after β1-adrenergic (intraperitoneal dobutamine 3 mg/kg) challenge. Heart rates before dobutamine challenge were indistinguishable between groups. The Pgc-1β-/- genotype however displayed compromised nodal function in response to adrenergic challenge. This manifested as an impaired heart rate response suggesting a functional defect at the level of the sino-atrial node, and a negative dromotropic response suggesting an atrioventricular conduction defect. Incidences of the latter were most pronounced in the aged Pgc-1β-/- mice. Moreover, Pgc-1β-/- mice displayed electrocardiographic features consistent with the existence of a pro-arrhythmic substrate. Firstly, ventricular activation was prolonged in these mice consistent with slowed action potential conduction and is reported here for the first time. Additionally, Pgc-1β-/- mice had shorter repolarisation intervals. These were likely attributable to altered K+ conductance properties, ultimately resulting in a shortened QTc interval, which is also known to be associated with increased arrhythmic risk. ECG analysis thus yielded electrophysiological findings bearing on potential arrhythmogenicity in intact Pgc-1β-/- systems in widespread cardiac regions.
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Affiliation(s)
- Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Samantha C Salvage
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Kamalan Jeevaratnam
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom.,PU-RCSI School of Medicine, Perdana University, Selangor Darul Ehsan, Malaysia
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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20
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Wang X, Tang H, Wei EQ, Wang Z, Yang J, Yang R, Wang S, Zhang Y, Pitt GS, Zhang H, Wang C. Conditional knockout of Fgf13 in murine hearts increases arrhythmia susceptibility and reveals novel ion channel modulatory roles. J Mol Cell Cardiol 2017; 104:63-74. [PMID: 28119060 DOI: 10.1016/j.yjmcc.2017.01.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 01/13/2017] [Accepted: 01/17/2017] [Indexed: 01/06/2023]
Abstract
The intracellular fibroblast growth factors (iFGF/FHFs) bind directly to cardiac voltage gated Na+ channels, and modulate their function. Mutations that affect iFGF/FHF-Na+ channel interaction are associated with arrhythmia syndromes. Although suspected to modulate other ionic currents, such as Ca2+ channels based on acute knockdown experiments in isolated cardiomyocytes, the in vivo consequences of iFGF/FHF gene ablation on cardiac electrical activity are still unknown. We generated inducible, cardiomyocyte-restricted Fgf13 knockout mice to determine the resultant effects of Fgf13 gene ablation. Patch clamp recordings from ventricular myocytes isolated from Fgf13 knockout mice showed a ~25% reduction in peak Na+ channel current density and a hyperpolarizing shift in steady-state inactivation. Electrocardiograms on Fgf13 knockout mice showed a prolonged QRS duration. The Na+ channel blocker flecainide further prolonged QRS duration and triggered ventricular tachyarrhythmias only in Fgf13 knockout mice, suggesting that arrhythmia vulnerability resulted, at least in part, from a loss of functioning Na+ channels. Consistent with these effects on Na+ channels, action potentials in Fgf13 knockout mice, compared to Cre control mice, exhibited slower upstrokes and reduced amplitude, but unexpectedly had longer durations. We investigated candidate sources of the prolonged action potential durations in myocytes from Fgf13 knockout mice and found a reduction of the transient outward K+ current (Ito). Fgf13 knockout did not alter whole-cell protein levels of Kv4.2 and Kv4.3, the Ito pore-forming subunits, but did decrease Kv4.2 and Kv4.3 at the sarcolemma. No changes were seen in the sustained outward K+ current or voltage-gated Ca2+ current, other candidate contributors to the increased action potential duration. These results implicate that FGF13 is a critical cardiac Na+ channel modulator and Fgf13 knockout mice have increased arrhythmia susceptibility in the setting of Na+ channel blockade. The unanticipated effect on Ito revealed new FGF13 properties and the unexpected lack of an effect on voltage-gated Ca2+ channels highlight potential compensatory changes in vivo not readily revealed with acute Fgf13 knockdown in cultured cardiomyocytes.
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Affiliation(s)
- Xiangchong Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China; The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China, Shijiazhuang, 050017, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province, Shijiazhuang 050017, China
| | - He Tang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China; The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China, Shijiazhuang, 050017, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province, Shijiazhuang 050017, China
| | - Eric Q Wei
- Ion Channel Research Unit, Department of Medicine/Cardiology and Pharmacology, Duke University Medical Center, Durham, NC 27710, USA
| | - Zhihua Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China; The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China, Shijiazhuang, 050017, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province, Shijiazhuang 050017, China
| | - Jing Yang
- Department of Physiology, Hebei Medical University, Shijiazhuang 050017, China
| | - Rong Yang
- Department of Cardiology, The Second Hospital of Hebei Medical University, Shijiazhuang 050000, China
| | - Sheng Wang
- Department of Physiology, Hebei Medical University, Shijiazhuang 050017, China
| | - Yongjian Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China; The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China, Shijiazhuang, 050017, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province, Shijiazhuang 050017, China
| | - Geoffrey S Pitt
- Ion Channel Research Unit, Department of Medicine/Cardiology and Pharmacology, Duke University Medical Center, Durham, NC 27710, USA
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China; The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China, Shijiazhuang, 050017, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province, Shijiazhuang 050017, China.
| | - Chuan Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China; The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China, Shijiazhuang, 050017, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province, Shijiazhuang 050017, China.
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21
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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22
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Männ L, Kochupurakkal N, Martin C, Verjans E, Klingberg A, Sody S, Kraus A, Dalimot J, Bergmüller E, Jung S, Voortman S, Winterhager E, Brandau S, Garbi N, Kurrer M, Eriksson U, Gunzer M, Hasenberg M. CD11c.DTR mice develop a fatal fulminant myocarditis after local or systemic treatment with diphtheria toxin. Eur J Immunol 2016; 46:2028-42. [PMID: 27184067 DOI: 10.1002/eji.201546245] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 04/05/2016] [Accepted: 05/11/2016] [Indexed: 12/21/2022]
Abstract
To assess the role of alveolar macrophages (AMs) during a pulmonary Aspergillus fumigatus infection AMs were depleted by intratracheal application of diphtheria toxin (DTX) to transgenic CD11c.DTR mice prior to fungal infection. Unexpectedly, all CD11c.DTR mice treated with DTX died within 4-5 days, whether being infected with A. fumigatus or not. Despite measurable impact of DTX on lung functional parameters, these constrictions could not explain the high mortality rate. Instead, DTX-treated CD11c.DTR animals developed fulminant myocarditis (FM) characterized by massive leukocyte infiltration and myocardial cell destruction, including central parts of the heart's stimulus transmission system. In fact, standard limb lead ECG recordings of diseased but not healthy mice showed a "Brugada"-like pattern with an abnormally high ST segment pointing to enhanced susceptibility for potential lethal arrhythmias. While CD11c.DTR mice are extensively used for the characterization of CD11c(+) cells, including dendritic cells, several studies have already mentioned adverse side effects following DTX treatment. Our results demonstrate that this limitation is based on severe myocarditis but not on the expected lung constrictions, and has to be taken into consideration if this animal model is used. Based on these properties, however, the CD11c.DTR mouse might serve as useful animal model for FM.
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Affiliation(s)
- Linda Männ
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Nora Kochupurakkal
- Department of Research, Experimental Critical Care Medicine, University Hospital, Basel, Switzerland
| | - Christian Martin
- Institute of Pharmacology and Toxicology, University Hospital Aachen, Aachen, Germany
| | - Eva Verjans
- Institute of Pediatrics, University Hospital Aachen, Aachen, Germany
| | - Anika Klingberg
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Simon Sody
- Department of Otorhinolaryngology, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Andreas Kraus
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Jill Dalimot
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Eileen Bergmüller
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Steffen Jung
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Sylvia Voortman
- Imaging Center Essen, Electron Microscopy Unit, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Elke Winterhager
- Imaging Center Essen, Electron Microscopy Unit, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Sven Brandau
- Department of Otorhinolaryngology, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Natalio Garbi
- Institute of Experimental Immunology, Rheinische Friedrich Wilhelms University, Bonn, Germany
| | | | - Urs Eriksson
- Division of Cardioimmunology, Center for Molecular Cardiology, University of Zurich, Schlieren, Switzerland.,Department of Medicine, GZO-Zurich Regional Health Center, Wetzikon, Switzerland
| | - Matthias Gunzer
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany
| | - Mike Hasenberg
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany
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Peters CH, Abdelsayed M, Ruben PC. Triggers for arrhythmogenesis in the Brugada and long QT 3 syndromes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 120:77-88. [DOI: 10.1016/j.pbiomolbio.2015.12.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/27/2015] [Accepted: 12/15/2015] [Indexed: 01/16/2023]
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24
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Rudic B, Schimpf R, Veltmann C, Doesch C, Tülümen E, Schoenberg SO, Borggrefe M, Papavassiliu T. Brugada syndrome: clinical presentation and genotype—correlation with magnetic resonance imaging parameters. Europace 2015; 18:1411-9. [DOI: 10.1093/europace/euv300] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 08/07/2015] [Indexed: 01/23/2023] Open
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Abnormal sodium current properties contribute to cardiac electrical and contractile dysfunction in a mouse model of myotonic dystrophy type 1. Neuromuscul Disord 2014; 25:308-20. [PMID: 25613807 DOI: 10.1016/j.nmd.2014.11.018] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 11/14/2014] [Accepted: 11/24/2014] [Indexed: 11/21/2022]
Abstract
Myotonic dystrophy type 1 (DM1) is the most common neuromuscular disorder and is associated with cardiac conduction defects. However, the mechanisms of cardiac arrhythmias in DM1 are unknown. We tested the hypothesis that abnormalities in the cardiac sodium current (INa) are involved, and used a transgenic mouse model reproducing the expression of triplet expansion observed in DM1 (DMSXL mouse). The injection of the class-I antiarrhythmic agent flecainide induced prominent conduction abnormalities and significantly lowered the radial tissular velocities and strain rate in DMSXL mice compared to WT. These abnormalities were more pronounced in 8-month-old mice than in 3-month-old mice. Ventricular action potentials recorded by standard glass microelectrode technique exhibited a lower maximum upstroke velocity [dV/dt](max) in DMSXL. This decreased [dV/dt](max) was associated with a 1.7 fold faster inactivation of INa in DMSXL myocytes measured by the whole-cell patch-clamp technique. Finally in the DMSXL mouse, no mutation in the Scn5a gene was detected and neither cardiac fibrosis nor abnormalities of expression of the sodium channel protein were observed. Therefore, alterations in the sodium current markedly contributed to electrical conduction block in DM1. This result should guide pharmaceutical and clinical research toward better therapy for the cardiac arrhythmias associated with DM1.
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26
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Zhang Y, Guzadhur L, Jeevaratnam K, Salvage SC, Matthews GDK, Lammers WJ, Lei M, Huang CL, Fraser JA. Arrhythmic substrate, slowed propagation and increased dispersion in conduction direction in the right ventricular outflow tract of murine Scn5a+/- hearts. Acta Physiol (Oxf) 2014; 211:559-73. [PMID: 24913289 PMCID: PMC4296345 DOI: 10.1111/apha.12324] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 05/23/2014] [Accepted: 06/03/2014] [Indexed: 12/18/2022]
Abstract
Aim To test a hypothesis attributing arrhythmia in Brugada Syndrome to right ventricular (RV) outflow tract (RVOT) conduction abnormalities arising from Nav1.5 insufficiency and fibrotic change. Methods Arrhythmic properties of Langendorff-perfused Scn5a+/− and wild-type mouse hearts were correlated with ventricular effective refractory periods (VERPs), multi-electrode array (MEA) measurements of action potential (AP) conduction velocities and dispersions in conduction direction (CD), Nav1.5 expression levels, and fibrotic change, as measured at the RVOT and RV. Two-way anova was used to test for both independent and interacting effects of anatomical region and genotype on these parameters. Results Scn5a+/− hearts showed greater arrhythmic frequencies during programmed electrical stimulation at the RVOT but not the RV. The Scn5a+/− genotype caused an independent increase of VERP regardless of whether the recording site was the RVOT or RV. Effective AP conduction velocities (CV†s), derived from fitting regression planes to arrays of observed local activation times were reduced in Scn5a+/− hearts and at the RVOT independently. AP conduction velocity magnitudes derived by averaging MEA results from local vector analyses, CV*, were reduced by the Scn5a+/− genotype alone. In contrast, dispersions in conduction direction, were greater in the RVOT than the RV, when the atrioventricular node was used as the pacing site. The observed reductions in Nav1.5 expression were attributable to Scn5a+/−, whereas increased levels of fibrosis were associated with the RVOT. Conclusions The Scn5a+/− RVOT recapitulates clinical findings of increased arrhythmogenicity through reduced CV† reflecting reduced CV* attributable to reduced Nav1.5 expression and increased CD attributable to fibrosis.
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Affiliation(s)
- Y. Zhang
- Physiological Laboratory University of Cambridge Cambridge UK
- Heart Centre Northwest Women's and Children's Hospital Xi'an China
| | - L. Guzadhur
- Physiological Laboratory University of Cambridge Cambridge UK
| | - K. Jeevaratnam
- Physiological Laboratory University of Cambridge Cambridge UK
- Perdana University‐Royal College of Surgeons Ireland Selangor Malaysia
| | - S. C. Salvage
- Physiological Laboratory University of Cambridge Cambridge UK
| | | | - W. J. Lammers
- Department of Physiology College of Medicine and Health Sciences Al Ain UAE
| | - M. Lei
- Department of Pharmacology University of Oxford Oxford UK
| | - C. L.‐H. Huang
- Physiological Laboratory University of Cambridge Cambridge UK
- Department of Biochemistry University of Cambridge Cambridge UK
| | - J. A. Fraser
- Physiological Laboratory University of Cambridge Cambridge UK
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27
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Zhang Y, Wang J, Chang S, Zhou N, Xing H, Wang L, Huang C, Ma A, Huang CLH, Lei M, Fraser JA. The SCN5A mutation A1180V is associated with electrocardiographic features of LQT3. Pediatr Cardiol 2014; 35:295-300. [PMID: 23963187 DOI: 10.1007/s00246-013-0773-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 07/25/2013] [Indexed: 12/19/2022]
Abstract
Mutations of the SCN5A gene are associated with several arrhythmic syndromes including the Brugada syndrome, conduction disease, long QT syndrome type 3 (LQT3), atrial fibrillation, and dilated cardiomyopathy. We report LQT3 associated with an A1180V cardiac sodium channel mutation, previously associated with cardiac conduction block, and dilated cardiomyopathy in three generations of a Chinese family. Clinical, electrocardiographic (ECG), and echocardiographic examination was followed by direct sequencing of SCN5A and HERG to screen genomic DNA from blood samples. The proband presented with multiple syncopes from the age of 7 years and was found to share a mutation with two other members of his family. Continuous ECG monitoring after presentation showed prolonged QTc and biphasic T waves, multiple episodes of ventricular tachycardia and torsades de pointes. The other two mutation carriers showed ECG features of LQT3 without clinical symptoms. Transthoracic echocardiography showed normal cardiac structure in all three mutation carriers. This study shows LQT3 features associated with an A1180V cardiac sodium channel mutation, expanding the spectrum of phenotypes resulting from this mutation in which biophysical study has shown a persistent late Na(+) current.
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Affiliation(s)
- Yanmin Zhang
- Department of Paediatrics, Center of Shaanxi Province Children Cardiovascular Disease, The Shaanxi Provincial People's Hospital, The Third Affiliated Hospital of Xi'an Jiaotong University, Xi'an, People's Republic of China,
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28
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Matthews GDK, Guzadhur L, Sabir IN, Grace AA, Huang CLH. Action potential wavelength restitution predicts alternans and arrhythmia in murine Scn5a(+/-) hearts. J Physiol 2013; 591:4167-88. [PMID: 23836691 PMCID: PMC3779110 DOI: 10.1113/jphysiol.2013.254938] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Reductions in cardiac action potential wavelength, and the consequent wavebreak, have been implicated in arrhythmogenesis. Tachyarrhythmias are more common in the Brugada syndrome, particularly following pharmacological challenge, previously modelled using Scn5a+/− murine hearts. Propagation latencies and action potential durations (APDs) from monophasic action potential recordings were used to assess wavelength changes with heart rate in Langendorff-perfused wild-type (WT) and Scn5a+/− hearts. Recordings were obtained from right (RV) and left (LV) ventricular, epicardial and endocardial surfaces during incremental pacing, before and following flecainide or quinidine challenge. Conduction velocities (θ′), action potential wavelengths (λ′= APD ×θ′), and their corresponding alternans depended non-linearly upon diastolic interval (DI). Maximum θ′ was lower in Scn5a+/− RV epicardium than endocardium. Flecainide further reduced θ′, accentuating this RV conduction block. Quinidine reduced maximum θ′ in WT and caused earlier conduction failure in the RV of both Scn5a+/− and WT. Use of recovery wavelengths (λ′0= DI ×θ′) rather than DI, provided novel λ restitution plots of λ′ against λ′0, which sum to a basic cycle distance permitting feedback analysis. λ′ restitution gradient better correlated with alternans magnitude than either APD or θ restitution gradient. The large differences in θ′ and APD restitution contrasted with minor differences in maximum λ′ between epi- and endocardia of untreated hearts, and quinidine-treated WT hearts. Strikingly, all regions and conditions converged to a common instability point, implying a conserved relationship. Flecainide or quinidine decreased the pacing rates at which this occurred, through reducing basic cycle distance, in the Scn5a+/− RV epicardium, directly predictive of its arrhythmic phenotype.
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Affiliation(s)
- Gareth D K Matthews
- G. D. K. Matthews: Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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Abstract
The abrupt cessation of effective cardiac function due to an aberrant heart rhythm can cause sudden and unexpected death at any age, a syndrome called sudden cardiac death (SCD). Annually, more than 300,000 cases of SCD occur in the United States alone, making this a major public health concern. Our current understanding of the mechanisms responsible for SCD has emerged from decades of basic science investigation into the normal electrophysiology of the heart, the molecular physiology of cardiac ion channels, fundamental cellular and tissue events associated with cardiac arrhythmias, and the molecular genetics of monogenic disorders of heart rhythm. This knowledge has helped shape the current diagnosis and treatment of inherited arrhythmia susceptibility syndromes associated with SCD and has provided a pathophysiological framework for understanding more complex conditions predisposing to this tragic event. This Review presents an overview of the molecular basis of SCD, with a focus on monogenic arrhythmia syndromes.
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Affiliation(s)
- Alfred L George
- Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA.
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Cerrone M, Noorman M, Lin X, Chkourko H, Liang FX, van der Nagel R, Hund T, Birchmeier W, Mohler P, van Veen TA, van Rijen HV, Delmar M. Sodium current deficit and arrhythmogenesis in a murine model of plakophilin-2 haploinsufficiency. Cardiovasc Res 2012; 95:460-8. [PMID: 22764151 DOI: 10.1093/cvr/cvs218] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
AIMS The shRNA-mediated loss of expression of the desmosomal protein plakophilin-2 leads to sodium current (I(Na)) dysfunction. Whether pkp2 gene haploinsufficiency leads to I(Na) deficit in vivo remains undefined. Mutations in pkp2 are detected in arrhythmogenic right ventricular cardiomyopathy (ARVC). Ventricular fibrillation and sudden death often occur in the 'concealed phase' of the disease, prior to overt structural damage. The mechanisms responsible for these arrhythmias remain poorly understood. We sought to characterize the morphology, histology, and ultrastructural features of PKP2-heterozygous-null (PKP2-Hz) murine hearts and explore the relation between PKP2 abundance, I(Na) function, and cardiac electrical synchrony. METHODS AND RESULTS Hearts of PKP2-Hz mice were characterized by multiple methods. We observed ultrastructural but not histological or gross anatomical differences in PKP2-Hz hearts compared with wild-type (WT) littermates. Yet, in myocytes, decreased amplitude and a shift in gating and kinetics of I(Na) were observed. To further unmask I(Na) deficiency, we exposed myocytes, Langendorff-perfused hearts, and anaesthetized animals to a pharmacological challenge (flecainide). In PKP2-Hz hearts, the extent of flecainide-induced I(Na) block, impaired ventricular conduction, and altered electrocardiographic parameters were larger than controls. Flecainide provoked ventricular arrhythmias and death in PKP2-Hz animals, but not in the WT. CONCLUSIONS PKP2 haploinsufficiency leads to I(Na) deficit in murine hearts. Our data support the notion of a cross-talk between desmosome and sodium channel complex. They also suggest that I(Na) dysfunction may contribute to generation and/or maintenance of arrhythmias in PKP2-deficient hearts. Whether pharmacological challenges could help unveil arrhythmia risk in patients with mutations or variants in PKP2 remains undefined.
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Affiliation(s)
- Marina Cerrone
- Division of Cardiology, New York University School of Medicine, New York, NY, USA
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Derangeon M, Montnach J, Baró I, Charpentier F. Mouse Models of SCN5A-Related Cardiac Arrhythmias. Front Physiol 2012; 3:210. [PMID: 22737129 PMCID: PMC3381239 DOI: 10.3389/fphys.2012.00210] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 05/29/2012] [Indexed: 12/19/2022] Open
Abstract
Mutations of SCN5A gene, which encodes the α-subunit of the voltage-gated Na+ channel NaV1.5, underlie hereditary cardiac arrhythmic syndromes such as the type 3 long QT syndrome, cardiac conduction diseases, the Brugada syndrome, the sick sinus syndrome, a trial standstill, and numerous overlap syndromes. Patch-clamp studies in heterologous expression systems have provided important information to understand the genotype-phenotype relationships of these diseases. However, they could not clarify how SCN5A mutations can be responsible for such a large spectrum of diseases, for the late age of onset or the progressiveness of some of these diseases and for the overlapping syndromes. Genetically modified mice rapidly appeared as promising tools for understanding the pathophysiological mechanisms of cardiac SCN5A-related arrhythmic syndromes and several mouse models have been established. This review presents the results obtained on these models that, for most of them, recapitulate the clinical phenotypes of the patients. This includes two models knocked out for Nav1.5 β1 and β3 auxiliary subunits that are also discussed. Despite their own limitations that we point out, the mouse models still appear as powerful tools to elucidate the pathophysiological mechanisms of SCN5A-related diseases and offer the opportunity to investigate the secondary cellular consequences of SCN5A mutations such as the expression remodeling of other genes. This points out the potential role of these genes in the overall human phenotype. Finally, they constitute useful tools for addressing the role of genetic and environmental modifiers on cardiac electrical activity.
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Martin CA, Siedlecka U, Kemmerich K, Lawrence J, Cartledge J, Guzadhur L, Brice N, Grace AA, Schwiening C, Terracciano CM, Huang CLH. Reduced Na(+) and higher K(+) channel expression and function contribute to right ventricular origin of arrhythmias in Scn5a+/- mice. Open Biol 2012; 2:120072. [PMID: 22773948 PMCID: PMC3390792 DOI: 10.1098/rsob.120072] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/11/2012] [Indexed: 12/17/2022] Open
Abstract
Brugada syndrome (BrS) is associated with ventricular tachycardia originating particularly in the right ventricle (RV). We explore electrophysiological features predisposing to such arrhythmic tendency and their possible RV localization in a heterozygotic Scn5a+/- murine model. Na(v)1.5 mRNA and protein expression were lower in Scn5a+/- than wild-type (WT), with a further reduction in the RV compared with the left ventricle (LV). RVs showed higher expression levels of K(v)4.2, K(v)4.3 and KChIP2 in both Scn5a+/- and WT. Action potential upstroke velocity and maximum Na(+) current (I(Na)) density were correspondingly decreased in Scn5a+/-, with a further reduction in the RV. The voltage dependence of inactivation was shifted to more negative values in Scn5a+/-. These findings are predictive of a localized depolarization abnormality leading to slowed conduction. Persistent Na(+) current (I(pNa)) density was decreased in a similar pattern to I(Na). RV transient outward current (I(to)) density was greater than LV in both WT and Scn5a+/-, and had larger time constants of inactivation. These findings were also consistent with the observation that AP durations were smallest in the RV of Scn5a+/-, fulfilling predictions of an increased heterogeneity of repolarization as an additional possible electrophysiological mechanism for arrhythmogenesis in BrS.
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Affiliation(s)
- Claire A Martin
- Physiological Laboratory, University of Cambridge, Downing Site, Cambridge CB2 3EG, UK.
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Matthews GDK, Guzadhur L, Grace A, Huang CLH. Nonlinearity between action potential alternans and restitution, which both predict ventricular arrhythmic properties in Scn5a+/- and wild-type murine hearts. J Appl Physiol (1985) 2012; 112:1847-63. [PMID: 22461438 DOI: 10.1152/japplphysiol.00039.2012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Electrocardiographic QT- and T-wave alternans, presaging ventricular arrhythmia, reflects compromised adaptation of action potential (AP) duration (APD) to altered heart rate, classically attributed to incomplete Na(v)1.5 channel recovery prior to subsequent stimulation. The restitution hypothesis suggests a function whose slope directly relates to APD alternans magnitude, predicting a critical instability condition, potentially generating arrhythmia. The present experiments directly test for such correlations among arrhythmia, APD alternans and restitution. Mice haploinsufficient in the Scn5a, cardiac Na(+) channel gene (Scn5a(+/-)), previously used to replicate Brugada syndrome, were used, owing to their established arrhythmic properties increased by flecainide and decreased by quinidine, particularly in right ventricular (RV) epicardium. Monophasic APs, obtained during pacing with progressively decrementing cycle lengths, were systematically compared at RV and left ventricular epicardial and endocardial recording sites in Langendorff-perfused Scn5a(+/-) and wild-type hearts before and following flecainide (10 μM) or quinidine (5 μM) application. The extent of alternans was assessed using a novel algorithm. Scn5a(+/-) hearts showed greater frequencies of arrhythmic endpoints with increased incidences of ventricular tachycardia, diminished by quinidine, and earlier onsets of ventricular fibrillation, particularly following flecainide challenge. These features correlated directly with increased refractory periods, specifically in the RV, and abnormal restitution and alternans properties in the RV epicardium. The latter variables were related by a unique, continuous higher-order function, rather than a linear relationship with an unstable threshold. These findings demonstrate a specific relationship between alternans and restitution, as well as confirming their capacity to predict arrhythmia, but implicate mechanisms additional to the voltage feedback suggested in the restitution hypothesis.
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Affiliation(s)
- Gareth D K Matthews
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.
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Martin CA, Grace AA, Huang CLH. Refractory dispersion promotes conduction disturbance and arrhythmias in a Scn5a (+/-) mouse model. Pflugers Arch 2011; 462:495-504. [PMID: 21779762 PMCID: PMC3170477 DOI: 10.1007/s00424-011-0989-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 06/10/2011] [Accepted: 06/15/2011] [Indexed: 11/29/2022]
Abstract
Accentuated right ventricular (RV) gradients in action potential duration (APD) have been implicated in the arrhythmogenicity observed in Brugada syndrome in studies assuming that ventricular effective refractory periods (VERPs) vary in concert with APDs. The present experiments use a genetically modified mouse model to explore spatial heterogeneities in VERP that in turn might affect conduction velocity, thereby causing arrhythmias. Activation latencies, APDs and VERPs recorded during programmed S1S2 protocols were compared in RV and left ventricular (LV) epicardia and endocardia of Langendorff-perfused wild-type (WT) and Scn5a+/− hearts. Scn5a+/− and WT hearts showed similar patterns of shorter VERPs in RV than LV epicardia, and in epicardia than endocardia. However, Scn5a+/− hearts showed longer VERPs, despite shorter APD90s, than WT in all regions examined. The pro- and anti-arrhythmic agents flecainide and quinidine increased regional VERPs despite respectively decreasing and increasing the corresponding APD90s particularly in Scn5a+/− RV epicardia. In contrast, Scn5a+/− hearts showed greater VERP gradients between neighbouring regions, particularly RV transmural gradients, than WT (9.1 ± 1.1 vs. 5.7 ± 0.5 ms, p < 0.05, n = 12). Flecainide increased (to 21 ± 0.9 ms, p < 0.05, n = 6) but quinidine decreased (to 4.5 ± 0.5 ms, p < 0.05, n = 6) these gradients, particularly across the Scn5a+/− RV. Finally, Scn5a+/− hearts showed greater conduction slowing than WT following S2 stimuli, particularly with flecainide administration. Rather than arrhythmogenesis resulting from increased transmural repolarization gradients in an early, phase 2, reentrant excitation mechanism, the present findings implicate RV VERP gradients in potential reentrant mechanisms involving impulse conduction slowed by partial refractoriness.
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Affiliation(s)
- Claire A Martin
- Physiological Laboratory, University of Cambridge, Downing Site, Cambridge, CB2 3EG, UK.
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Martin CA, Guzadhur L, Grace AA, Lei M, Huang CLH. Mapping of reentrant spontaneous polymorphic ventricular tachycardia in a Scn5a+/- mouse model. Am J Physiol Heart Circ Physiol 2011; 300:H1853-62. [PMID: 21378142 PMCID: PMC3094090 DOI: 10.1152/ajpheart.00034.2011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two major mechanisms have been postulated for the arrhythmogenic tendency observed in Brugada Syndrome (BrS): delays in conduction or increased heterogeneities in repolarization. We use a contact mapping system to directly investigate the interacting roles of these two mechanisms in arrhythmogenesis using a genetic murine model for BrS for the first time. Electrograms were obtained from a multielectrode recording array placed against the left ventricle and right ventricle (RV) of spontaneously beating Langendorff-perfused wild type (WT) and Scn5a+/− mouse hearts. Scn5a+/− hearts showed activation waves arriving at the epicardial surface consistent with slowed conduction, which was exacerbated in the presence of flecainide. Lines of conduction block across the RV resulting from premature ventricular beats led to the formation of reentrant circuits and polymorphic ventricular tachycardia. WT hearts showed an inverse relationship between activation times and activation recovery intervals measured at the epicardial surface, which resulted in synchronicity of repolarization times. In contrast, Scn5a+/− hearts, despite having smaller mean activation recovery intervals, demonstrated a greater heterogeneity compared with WT. Isochronal maps showed that their normal activation recovery interval gradients at the epicardial surface were disrupted, leading to heterogeneity in repolarization times. We thus directly demonstrate the initiation of arrhythmia in the RV of Scn5a+/− hearts. This occurs as a result of the combination of repolarization heterogeneities leading to lines of conduction block and unidirectional conduction, with conduction slowing allowing the formation of reentrant circuits. The repolarization heterogeneities may also be responsible for the changing pattern of block, leading to the polymorphic character of the resulting ventricular tachycardia.
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Affiliation(s)
- Claire A Martin
- Physiological Laboratory, University of Cambridge, Cambridge, UK.
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Kofune M, Watanabe I, Ohkubo K, Ashino S, Okumura Y, Nagashima K, Mano H, Nakai T, Kasamaki Y, Hirayama A. Clarifying the Arrhythmogenic Substrate for Brugada Syndrome Electroanatomic Mapping Study of the Right Ventricle. Int Heart J 2011; 52:290-4. [DOI: 10.1536/ihj.52.290] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Masayoshi Kofune
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Ichiro Watanabe
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Kimie Ohkubo
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Sonoko Ashino
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Yasuo Okumura
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Koichi Nagashima
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Hiroaki Mano
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Toshiko Nakai
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Yuji Kasamaki
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
| | - Atsushi Hirayama
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine
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Martin CA, Grace AA, Huang CLH. Spatial and temporal heterogeneities are localized to the right ventricular outflow tract in a heterozygotic Scn5a mouse model. Am J Physiol Heart Circ Physiol 2010; 300:H605-16. [PMID: 21097662 PMCID: PMC3044044 DOI: 10.1152/ajpheart.00824.2010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ventricular tachycardia (VT) in Brugada Syndrome patients often originates in the right ventricular outflow tract (RVOT). We explore the physiological basis for this observation using murine whole heart preparations. Ventricular bipolar electrograms and monophasic action potentials were recorded from seven epicardial positions in Langendorff-perfused wild-type and Scn5a+/− hearts. VT first appeared in the RVOT, implicating it as an arrhythmogenic focus in Scn5a+/− hearts. RVOTs showed the greatest heterogeneity in refractory periods, response latencies, and action potential durations, and the most fractionated electrograms. However, incidences of concordant alternans in dynamic pacing protocol recordings were unaffected by the Scn5a+/− mutation or pharmacological intervention. Conversely, particularly at the RVOT, Scn5a+/− hearts showed earlier and more frequent transitions into discordant alternans. This was accentuated by flecainide, but reduced by quinidine, in parallel with their respective pro- and anti-arrhythmic effects. Discordant alternans preceded all episodes of VT. The RVOT of Scn5a+/− hearts also showed steeper restitution curves, with the diastolic interval at which the gradient equaled one strongly correlating with the diastolic interval at which discordant alternans commenced. We attribute the arrhythmic tendency within the RVOT to the greater spatial heterogeneities in baseline electrophysiological properties. These, in turn, give rise to a tendency to drive concordant alternans phenomena into an arrhythmogenic discordant alternans. Our findings may contribute to future work investigating possible pharmacological treatments for a disease in which the current mainstay of treatment is implantable cardioverter defibrillator implantation.
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Affiliation(s)
- Claire A Martin
- Physiological Laboratory, Department of Biochemistry, University of Cambridge, Downing Site, Cambridge CB2 3EG, UK.
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