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Martínez-Moreno R, Carreras D, Sarquella-Brugada G, Pérez GJ, Selga E, Scornik FS, Brugada R. Loss of sodium current caused by a Brugada syndrome-associated variant is determined by patient-specific genetic background. Heart Rhythm 2024; 21:331-339. [PMID: 38008367 DOI: 10.1016/j.hrthm.2023.11.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 11/07/2023] [Accepted: 11/20/2023] [Indexed: 11/28/2023]
Abstract
BACKGROUND Brugada syndrome (BrS) is an inherited cardiac arrhythmogenic disease that predisposes patients to sudden cardiac death. It is associated with mutations in SCN5A, which encodes the cardiac sodium channel alpha subunit (NaV1.5). BrS-related mutations have incomplete penetrance and variable expressivity within families. OBJECTIVE The purpose of this study was to determine the role of patient-specific genetic background on the cellular and clinical phenotype among carriers of NaV1.5_p.V1525M. METHODS We studied sodium currents from patient-specific human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and heterologously transfected human embryonic kidney (HEK) tsA201 cells using the whole-cell patch-clamp technique. We determined gene and protein expression by quantitative polymerase chain reaction, RNA sequencing, and western blot and performed a genetic panel for arrhythmogenic diseases. RESULTS Our results showed a large reduction in INa density in hiPSC-CM derived from 2 V1525M single nucleotide variant (SNV) carriers compared with hiPSC-CM derived from a noncarrier, suggesting a dominant-negative effect of the NaV1.5_p.V1525M channel. INa was not affected in hiPSC-CMs derived from a V1525M SNV carrier who also carries the NaV1.5_p.H558R polymorphism. Heterozygous expression of V1525M in HEK-293T cells produced a loss of INa function, not observed when this variant was expressed together with H558R. In addition, the antiarrhythmic drug mexiletine rescued INa function in hiPSC-CM. SCN5A expression was increased in the V1525M carrier who also expresses NaV1.5_p.H558R. CONCLUSION Our results in patient-specific hiPSC-CM point to a dominant-negative effect of NaV1.5_p.V1525M, which can be reverted by the presence of NaV1.5_p.H558R. Overall, our data points to a role of patient-specific genetic background as a determinant for incomplete penetrance in BrS.
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Affiliation(s)
- Rebecca Martínez-Moreno
- Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, Girona, Spain; Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona Dr. Josep Trueta, Girona, Spain
| | - David Carreras
- Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona Dr. Josep Trueta, Girona, Spain
| | - Georgia Sarquella-Brugada
- Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, Girona, Spain; Arrhythmia, Inherited Cardiac Diseases and Sudden Death Unit, Hospital Sant Joan de Déu, Esplugues, Barcelona, Spain; Arrítmies pediàtriques, cardiologia genètica i mort sobtada. Institut de Recerca Sant Joan de Déu, Esplugues de Llobregat, Barcelona, Spain
| | - Guillermo J Pérez
- Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, Girona, Spain; Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona Dr. Josep Trueta, Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain.
| | - Elisabet Selga
- Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, Girona, Spain; Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona Dr. Josep Trueta, Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain; Faculty of Medicine, University of Vic-Central University of Catalonia (UVic-UCC), Vic, Spain.
| | - Fabiana S Scornik
- Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, Girona, Spain; Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona Dr. Josep Trueta, Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain.
| | - Ramon Brugada
- Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, Girona, Spain; Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona Dr. Josep Trueta, Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain; Hospital Josep Trueta, Girona, Spain
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Campostrini G, Kosmidis G, Ward-van Oostwaard D, Davis RP, Yiangou L, Ottaviani D, Veerman CC, Mei H, Orlova VV, Wilde AAM, Bezzina CR, Verkerk AO, Mummery CL, Bellin M. Maturation of hiPSC-derived cardiomyocytes promotes adult alternative splicing of SCN5A and reveals changes in sodium current associated with cardiac arrhythmia. Cardiovasc Res 2023; 119:167-182. [PMID: 35394010 PMCID: PMC10022870 DOI: 10.1093/cvr/cvac059] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 02/07/2022] [Accepted: 03/23/2022] [Indexed: 11/13/2022] Open
Abstract
AIMS Human-induced pluripotent stem cell-cardiomyocytes (hiPSC-CMs) are widely used to study arrhythmia-associated mutations in ion channels. Among these, the cardiac sodium channel SCN5A undergoes foetal-to-adult isoform switching around birth. Conventional hiPSC-CM cultures, which are phenotypically foetal, have thus far been unable to capture mutations in adult gene isoforms. Here, we investigated whether tri-cellular cross-talk in a three-dimensional (3D) cardiac microtissue (MT) promoted post-natal SCN5A maturation in hiPSC-CMs. METHODS AND RESULTS We derived patient hiPSC-CMs carrying compound mutations in the adult SCN5A exon 6B and exon 4. Electrophysiological properties of patient hiPSC-CMs in monolayer were not altered by the exon 6B mutation compared with isogenic controls since it is not expressed; further, CRISPR/Cas9-mediated excision of the foetal exon 6A did not promote adult SCN5A expression. However, when hiPSC-CMs were matured in 3D cardiac MTs, SCN5A underwent isoform switch and the functional consequences of the mutation located in exon 6B were revealed. Up-regulation of the splicing factor muscleblind-like protein 1 (MBNL1) drove SCN5A post-natal maturation in microtissues since its overexpression in hiPSC-CMs was sufficient to promote exon 6B inclusion, whilst knocking-out MBNL1 failed to foster isoform switch. CONCLUSIONS Our study shows that (i) the tri-cellular cardiac microtissues promote post-natal SCN5A isoform switch in hiPSC-CMs, (ii) adult splicing of SCN5A is driven by MBNL1 in these tissues, and (iii) this model can be used for examining post-natal cardiac arrhythmias due to mutations in the exon 6B. TRANSLATIONAL PERSPECTIVE The cardiac sodium channel is essential for conducting the electrical impulse in the heart. Postnatal alternative splicing regulation causes mutual exclusive inclusion of fetal or adult exons of the corresponding gene, SCN5A. Typically, immature hiPSCCMs fall short in studying the effect of mutations located in the adult exon. We describe here that an innovative tri-cellular three-dimensional cardiac microtissue culture promotes hiPSC-CMs maturation through upregulation of MBNL1, thus revealing the effect of a pathogenic genetic variant located in the SCN5A adult exon. These results help advancing the use of hiPSC-CMs in studying adult heart disease and for developing personalized medicine applications.
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Affiliation(s)
- Giulia Campostrini
- Department of Anatomy and Embryology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
| | - Georgios Kosmidis
- Department of Anatomy and Embryology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
| | - Dorien Ward-van Oostwaard
- Department of Anatomy and Embryology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
| | - Richard Paul Davis
- Department of Anatomy and Embryology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
| | - Loukia Yiangou
- Department of Anatomy and Embryology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
| | - Daniele Ottaviani
- Department of Biology, University of Padua, 35121 Padua, Italy
- Veneto Institute of Molecular Medicine, 35129 Padua, Italy
| | - Christiaan Cornelis Veerman
- Department of Clinical and Experimental Cardiology, Heart Centre, Amsterdam University Medical Centre, location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - Hailiang Mei
- Sequencing Analysis Support Core, Leiden University Medical Center, 2333 Leiden, The Netherlands
| | - Valeria Viktorovna Orlova
- Department of Anatomy and Embryology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
| | - Arthur Arnold Maria Wilde
- Department of Clinical and Experimental Cardiology, Heart Centre, Amsterdam University Medical Centre, location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - Connie Rose Bezzina
- Department of Clinical and Experimental Cardiology, Heart Centre, Amsterdam University Medical Centre, location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - Arie Otto Verkerk
- Department of Clinical and Experimental Cardiology, Heart Centre, Amsterdam University Medical Centre, location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - Christine Lindsay Mummery
- Department of Anatomy and Embryology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
- Department of Applied Stem Cell Technologies, University of Twente, 7500 AE, Enschede, The Netherlands
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Olaopa MA, Ai T, Chao B, Xiao X, Vatta M, Habecker BA. Phosphorylation of Lamin A/C at serine 22 modulates Na v 1.5 function. Physiol Rep 2021; 9:e15121. [PMID: 34806324 PMCID: PMC8606869 DOI: 10.14814/phy2.15121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 10/29/2021] [Accepted: 10/31/2021] [Indexed: 12/17/2022] Open
Abstract
Variants in the LMNA gene, which encodes for Lamin A/C, are associated with cardiac conduction disease (CCD). We previously reported that Lamin A/C variants p.R545H and p.A287Lfs*193, which were identified in CCD patients, decreased peak INa in HEK-293 cells expressing Nav 1.5. Decreased peak INa in the cardiac conduction system could account for patients' atrioventricular block. We found that serine 22 (Ser 22) phosphorylation of Lamin A/C was decreased in the p.R545H variant and hypothesized that lamin phosphorylation modulated Nav 1.5 activity. To test this hypothesis, we assessed Nav 1.5 function in HEK-293 cells co-transfected with LMNA variants or treated with the small molecule LBL1 (lamin-binding ligand 1). LBL1 decreased Ser 22 phosphorylation by 65% but did not affect Nav 1.5 function. To test the complete loss of phosphorylation, we generated a version of LMNA with serine 22 converted to alanine 22 (S22A-LMNA); and a version of mutant R545H-LMNA that mimics phosphorylation via serine 22 to aspartic acid 22 substitution (S22D-R545H-LMNA). We found that S22A-LMNA inhibited Lamin-mediated activation of peak INa by 63% and shifted voltage-dependency of steady-state inactivation of Nav 1.5. Conversely, S22D-R545H-LMNA abolished the effects of mutant R545H-LMNA on voltage-dependency but not peak INa . We conclude that Lamin A/C Ser 22 phosphorylation can modulate Nav 1.5 function and contributes to the mechanism by which R545H-LMNA alters Nav 1.5 function. The differential impact of complete versus partial loss of Ser 22 phosphorylation suggests a threshold of phosphorylation that is required for full Nav 1.5 modulation. This is the first study to link Lamin A/C phosphorylation to Nav 1.5 function.
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Affiliation(s)
- Michael A. Olaopa
- Department of Chemical Physiology and BiochemistryOregon Health & Science UniversityPortlandOregonUSA
- Krannert Institute of CardiologyDepartment of MedicineIndiana University School of MedicineIndianapolisIndianaUSA
| | - Tomohiko Ai
- Krannert Institute of CardiologyDepartment of MedicineIndiana University School of MedicineIndianapolisIndianaUSA
- Department of Clinical Laboratory MedicineJuntendo UniversityTokyoJapan
| | - Bo Chao
- Department of Chemical Physiology and BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - Xiangshu Xiao
- Department of Chemical Physiology and BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - Matteo Vatta
- Krannert Institute of CardiologyDepartment of MedicineIndiana University School of MedicineIndianapolisIndianaUSA
| | - Beth A. Habecker
- Department of Chemical Physiology and BiochemistryOregon Health & Science UniversityPortlandOregonUSA
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Nowak MB, Poelzing S, Weinberg SH. Mechanisms underlying age-associated manifestation of cardiac sodium channel gain-of-function. J Mol Cell Cardiol 2021; 153:60-71. [PMID: 33373643 PMCID: PMC8026540 DOI: 10.1016/j.yjmcc.2020.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 12/04/2020] [Accepted: 12/06/2020] [Indexed: 10/22/2022]
Abstract
Cardiac action potentials are initiated by sodium ion (Na+) influx through voltage-gated Na+ channels. Na+ channel gain-of-function (GOF) can arise in inherited conditions due to mutations in the gene encoding the cardiac Na+ channel, such as Long QT syndrome type 3 (LQT3). LQT3 can be a "concealed" disease, as patients with LQT3-associated mutations can remain asymptomatic until later in life; however, arrhythmias can also arise early in life in LQT3 patients, demonstrating a complex age-associated manifestation. We and others recently demonstrated that cardiac Na+ channels preferentially localize at the intercalated disc (ID) in adult cardiac tissue, which facilitates ephaptic coupling and formation of intercellular Na+ nanodomains that regulate pro-arrhythmic early afterdepolarization (EAD) formation in tissue with Na+ channel GOF. Several properties related to ephaptic coupling vary with age, such as cell size and Na+ channel and gap junction (GJ) expression and distribution: neonatal cells have immature IDs, with Na+ channels and GJs primarily diffusively distributed, while adult myocytes have mature IDs with preferentially localized Na+ channels and GJs. Here, we perform an in silico study varying critical age-dependent parameters to investigate mechanisms underlying age-associated manifestation of Na+ channel GOF in a model of guinea pig cardiac tissue. Simulations predict that total Na+ current conductance is a critical factor in action potential duration (APD) prolongation. We find a complex cell size/ Na+ channel expression relationship: increases in cell size (without concurrent increases in Na+ channel expression) suppress EAD formation, while increases in Na+ channel expression (without concurrent increases in cell size) promotes EAD formation. Finally, simulations with neonatal and early age-associated parameters predict normal APD with minimal dependence on intercellular cleft width; however, variability in cellular properties can lead to EADs presenting in early developmental stages. In contrast, for adult-associated parameters, EAD formation is highly dependent on cleft width, consistent with a mechanism underlying the age-associated manifestation of the Na+ channel GOF.
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Affiliation(s)
- Madison B Nowak
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States of America
| | - Steven Poelzing
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States of America; Fralin Biomedical Research Institute at Virginia Tech Carilion, Virginia Polytechnic Institute and State University, Roanoke, VA, United States of America
| | - Seth H Weinberg
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States of America; Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, United States of America.
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Kawano H, Kawamura K, Kohno M, Ishijima M, Fukae S, Ishikawa T, Makita N, Maemura K. Pathological findings of myocardium in a patient with cardiac conduction defect associated with an SCN5A mutation. Med Mol Morphol 2021; 54:259-264. [PMID: 33651170 DOI: 10.1007/s00795-021-00283-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 02/12/2021] [Indexed: 11/27/2022]
Abstract
A 16-year-old Japanese man was admitted to our hospital because of syncope during exercise. His father and his younger brother had permanent pacemaker implantation because of sick sinus syndrome. Several examinations revealed first-degree atrioventricular block, complete right bundle branch block, sick sinus syndrome, and ventricular tachycardia with normal cardiac function. As no abnormalities were evident on coronary angiography, right ventricular endomyocardial biopsy was performed. It showed myocardial disarrangement and lipofuscin accumulation in hypertrophic myocytes. Moreover, electron microscopy showed a few degenerative myocytes, Z-band streaming, disarrangement, increased small capillaries with Weibel-Palade bodies in endothelial cells, and endothelial proliferations. Genetic analysis of the proband, his father, and his younger brother revealed a missense mutation, D1275N, in SCN5A, a gene which encodes sodium ion channel protein, are related to cardiomyopathy and arrhythmia. The proband was diagnosed with a cardiac conduction defect (CCD) and underwent permanent pacemaker implantation. These pathological findings suggest various myocardial changes presented in CCD patients with a missense mutation, D1275N, in SCN5A.
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Affiliation(s)
- Hiroaki Kawano
- Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki, 852-8501, Japan.
| | - Koichi Kawamura
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Masaki Kohno
- Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki, 852-8501, Japan
| | - Mitsuaki Ishijima
- Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki, 852-8501, Japan
| | - Satoki Fukae
- Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki, 852-8501, Japan
| | - Taisuke Ishikawa
- Omics Research Center, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Naomasa Makita
- Omics Research Center, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Koji Maemura
- Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki, 852-8501, Japan
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Alvarez-Collazo J, López-Requena A, Alvarez JL, Talavera K. The Citrus Flavonoid Hesperetin Has an Inadequate Anti-Arrhythmic Profile in the ΔKPQ Na V1.5 Mutant of the Long QT Type 3 Syndrome. Biomolecules 2020; 10:biom10060952. [PMID: 32599724 PMCID: PMC7355927 DOI: 10.3390/biom10060952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/19/2020] [Accepted: 06/21/2020] [Indexed: 11/19/2022] Open
Abstract
Type 3 long QT syndromes (LQT3) are associated with arrhythmogenic gain-of-function mutations in the cardiac voltage-gated Na+ channel (hNaV1.5). The citrus flavanone hesperetin (HSP) was previously suggested as a template molecule to develop new anti-arrhythmic drugs, as it blocks slowly-inactivating currents carried by the LQT3-associated hNaV1.5 channel mutant R1623Q. Here we investigated whether HSP also has potentially beneficial effects on another LQT3 hNaV1.5 channel variant, the ΔKPQ, which is associated to lethal ventricular arrhythmias. We used whole-cell patch-clamp to record Na+ currents (INa) in HEK293T cells transiently expressing hNaV1.5 wild type or ΔKPQ mutant channels. HSP blocked peak INa and the late INa carried by ΔKPQ mutant channels with an effective concentration of ≈300 μM. This inhibition was largely voltage-independent and tonic. HSP decreased the rate of inactivation of ΔKPQ channels and, consequently, was relatively weak in reducing the intracellular Na+ load in this mutation. We conclude that, although HSP has potential value for the treatment of the R1623Q LQT3 variant, this compound is inadequate to treat the LQT3 associated to the ΔKPQ genetic variant. Our results underscore the precision medicine rationale of better understanding the basic pathophysiological and pharmacological mechanisms to provide phenotype- genotype-directed individualization of treatment.
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Abstract
The most common cause of death among adults with diabetes is cardiovascular disease (CVD). In this concise review on pathogenesis of CVD in diabetes, the 4 common conditions, atherosclerosis, microangiopathy, diabetic cardiomyopathy, and cardiac autonomic neuropathy, are explored and illustrated to be caused by interrelated pathogenetic factors. Each of these diagnoses can present alone or, commonly, along with others due to overlapping pathophysiology. Although the spectrum of physiologic abnormalities that characterize the diabetes milieu is broad and go beyond hyperglycemia, the authors highlight the most relevant evidence supporting the current knowledge of potent factors that contribute to CVD in diabetes.
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Affiliation(s)
- Andrea V Haas
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA
| | - Marie E McDonnell
- Diabetes Section, Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, Room 381, Boston, MA 02115, USA.
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Abstract
E1784K is the most common mixed syndrome SCN5a mutation underpinning both Brugada syndrome type 1 (BrS1) and Long-QT syndrome type 3 (LQT3). The charge reversal mutant enhances the late sodium current (INa) passed by the cardiac voltage-gated sodium channel (NaV1.5), delaying cardiac repolarization. Exercise-induced triggers, like elevated temperature and cytosolic calcium, exacerbate E1784K late INa. In this study, we tested the effects of Ranolazine, the late INa blocker, on voltage-dependent and kinetic properties of E1784K at elevated temperature and cytosolic calcium. We used whole-cell patch clamp to measure INa from wild type and E1784K channels expressed in HEK293 cells. At elevated temperature, Ranolazine attenuated gain-of-function in E1784K by decreasing late INa, hyperpolarizing steady-state fast inactivation, and increasing use-dependent inactivation. Both elevated temperature and cytosolic calcium hampered the capacity of Ranolazine to suppress E1784K late INa. In-silico action potential (AP) simulations were done using a modified O'Hara Rudy (ORd) cardiac model. Simulations showed that Ranolazine failed to shorten AP duration, an effect augmented at febrile temperatures. The drug-channel interaction is clearly affected by external triggers, as reported previously with ischemia. Determining drug efficacy under various physiological states in SCN5a cohorts is crucial for accurate management of arrhythmias.
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Affiliation(s)
- Mena Abdelsayed
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Manpreet Ruprai
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Peter C Ruben
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
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Anderson HN, Bos JM, Kapplinger JD, Meskill JM, Ye D, Ackerman MJ. Lidocaine attenuation testing: An in vivo investigation of putative LQT3-associated variants in the SCN5A-encoded sodium channel. Heart Rhythm 2017; 14:1173-1179. [PMID: 28412158 DOI: 10.1016/j.hrthm.2017.04.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Indexed: 01/08/2023]
Abstract
BACKGROUND Long QT syndrome type 3 (LQT3) accounts for 5%-10% of long QT syndrome and results from gain-of-function mutations in the SCN5A-encoded sodium channel. Approximately 2% of healthy individuals host rare SCN5A variants of uncertain significance (VUS). Distinction of true LQT3-causative mutations from background genetic noise is essential. OBJECTIVE The purpose of this study was to assess the use of the lidocaine attenuation test (LAT) in evaluating patients with possible LQT3. METHODS We reviewed the LAT results and medical records for 25 patients with a possible LQT3-associated SCN5A variant. The LAT involved a loading dose of 1 mg/kg of intravenous lidocaine followed by continuous infusion at 50 μg/(kg⋅min) for 20 minutes. If the corrected QT interval shortened by ≥30 ms, the LAT was defined as positive. RESULTS Sixteen patients (64%) had a positive LAT, 6 of which demonstrated the E1784K variant. A positive LAT correlated in 86% of cases with abnormal in vitro channel function (mean corrected QT interval attenuation 43 ± 3 ms vs 25 ± 5 ms for wild-type variants; P = .03). Four of 5 patients (80%) with a VUS had a positive LAT (T1304M [2 patients], L1786P, and R800L). The T1304M variant demonstrated abnormal in vitro function and a positive LAT, opening the door for a potential variant promotion from VUS to likely pathogenic. CONCLUSION The LAT may help distinguish true LQT3-causative mutations from an otherwise noncontributory VUS. Given that lidocaine acts as a late sodium current blocker, a positive LAT may enable the early identification of a pathological accentuation of the late sodium current that could be targeted therapeutically.
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Affiliation(s)
- Heather N Anderson
- Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota
| | - J Martijn Bos
- Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota; Division of Heart Rhythm Services, Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota; Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic College of Biomedical Sciences, Mayo Clinic, Rochester, Minnesota
| | - Jamie D Kapplinger
- Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic College of Biomedical Sciences, Mayo Clinic, Rochester, Minnesota
| | - Jana M Meskill
- Division of Heart Rhythm Services, Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota
| | - Dan Ye
- Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic College of Biomedical Sciences, Mayo Clinic, Rochester, Minnesota
| | - Michael J Ackerman
- Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota; Division of Heart Rhythm Services, Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota; Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic College of Biomedical Sciences, Mayo Clinic, Rochester, Minnesota.
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