1
|
Porta-Sánchez A, Mazzanti A, Tarifa C, Kukavica D, Trancuccio A, Mohsin M, Zanfrini E, Perota A, Duchi R, Hernandez-Lopez K, Jáuregui-Abularach ME, Pergola V, Fernandez E, Bongianino R, Tavazzani E, Gambelli P, Memmi M, Scacchi S, Pavarino LF, Franzone PC, Lentini G, Filgueiras-Rama D, Galli C, Santiago DJ, Priori SG. Unexpected impairment of INa underpins reentrant arrhythmias in a knock-in swine model of Timothy syndrome. NATURE CARDIOVASCULAR RESEARCH 2023; 2:1291-1309. [PMID: 38665938 PMCID: PMC11041658 DOI: 10.1038/s44161-023-00393-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 11/15/2023] [Indexed: 04/28/2024]
Abstract
Timothy syndrome 1 (TS1) is a multi-organ form of long QT syndrome associated with life-threatening cardiac arrhythmias, the organ-level dynamics of which remain unclear. In this study, we developed and characterized a novel porcine model of TS1 carrying the causative p.Gly406Arg mutation in CACNA1C, known to impair CaV1.2 channel inactivation. Our model fully recapitulated the human disease with prolonged QT interval and arrhythmic mortality. Electroanatomical mapping revealed the presence of a functional substrate vulnerable to reentry, stemming from an unforeseen constitutional slowing of cardiac activation. This signature substrate of TS1 was reliably identified using the reentry vulnerability index, which, we further demonstrate, can be used as a benchmark for assessing treatment efficacy, as shown by testing of multiple clinical and preclinical anti-arrhythmic compounds. Notably, in vitro experiments showed that TS1 cardiomyocytes display Ca2+ overload and decreased peak INa current, providing a rationale for the arrhythmogenic slowing of impulse propagation in vivo.
Collapse
Affiliation(s)
- Andreu Porta-Sánchez
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Andrea Mazzanti
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Carmen Tarifa
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Deni Kukavica
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Alessandro Trancuccio
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Muhammad Mohsin
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
| | | | | | | | - Kevin Hernandez-Lopez
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | | | - Valerio Pergola
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Department of Advanced Biomedical Sciences, University of Naples Federico II, Naples, Italy
| | - Eugenio Fernandez
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Rossana Bongianino
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
| | - Elisa Tavazzani
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
| | - Patrick Gambelli
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
| | - Mirella Memmi
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
| | - Simone Scacchi
- Department of Mathematics, University of Milan, Milano, Italy
| | | | - Piero Colli Franzone
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
- AVANTEA, Cremona, Italy
- Department of Advanced Biomedical Sciences, University of Naples Federico II, Naples, Italy
- Department of Mathematics, University of Milan, Milano, Italy
- Department of Mathematics, University of Pavia, Pavia, Italy
- Department of Pharmacology, University of Bari, Bari, Italy
- Cardiovascular Institute, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares, Madrid, Spain
| | | | - David Filgueiras-Rama
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Cardiovascular Institute, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares, Madrid, Spain
| | | | - Demetrio Julián Santiago
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Silvia G. Priori
- Novel Arrhythmogenic Mechanism Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| |
Collapse
|
2
|
Mokrov GV. Multitargeting in cardioprotection: An example of biaromatic compounds. Arch Pharm (Weinheim) 2023; 356:e2300196. [PMID: 37345968 DOI: 10.1002/ardp.202300196] [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: 04/05/2023] [Revised: 05/23/2023] [Accepted: 05/26/2023] [Indexed: 06/23/2023]
Abstract
A multitarget drug design approach is actively developing in modern medicinal chemistry and pharmacology, especially with regard to multifactorial diseases such as cardiovascular diseases, cancer, and neurodegenerative diseases. A detailed study of many well-known drugs developed within the single-target approach also often reveals additional mechanisms of their real pharmacological action. One of the multitarget drug design approaches can be the identification of the basic pharmacophore models corresponding to a wide range of the required target ligands. Among such models in the group of cardioprotectors is the linked biaromatic system. This review develops the concept of a "basic pharmacophore" using the biaromatic pharmacophore of cardioprotectors as an example. It presents an analysis of possible biological targets for compounds corresponding to the biaromatic pharmacophore and an analysis of the spectrum of biological targets for the five most known and most studied cardioprotective drugs corresponding to this model, and their involvement in the biological effects of these drugs.
Collapse
|
3
|
Experimental factors that impact CaV1.2 channel pharmacology-Effects of recording temperature, charge carrier, and quantification of drug effects on the step and ramp currents elicited by the "step-step-ramp" voltage protocol. PLoS One 2022; 17:e0276995. [PMID: 36417390 PMCID: PMC9683570 DOI: 10.1371/journal.pone.0276995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 10/18/2022] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE CaV1.2 channels contribute to action potential upstroke in pacemaker cells, plateau potential in working myocytes, and initiate excitation-contraction coupling. Understanding drug action on CaV1.2 channels may inform potential impact on cardiac function. However, literature shows large degrees of variability between CaV1.2 pharmacology generated by different laboratories, casting doubt regarding the utility of these data to predict or interpret clinical outcomes. This study examined experimental factors that may impact CaV1.2 pharmacology. EXPERIMENTAL APPROACH Whole cell recordings were made on CaV1.2 overexpression cells. Current was evoked using a "step-step-ramp" waveform that elicited a step and a ramp current. Experimental factors examined were: 1) near physiological vs. room temperature for recording, 2) drug inhibition of the step vs. the ramp current, and 3) Ca2+ vs. Ba2+ as the charge carrier. Eight drugs were studied. KEY RESULTS CaV1.2 current exhibited prominent rundown, exquisite temperature sensitivity, and required a high degree of series resistance compensation to optimize voltage control. Temperature-dependent effects were examined for verapamil and methadone. Verapamil's block potency shifted by up to 4X between room to near physiological temperature. Methadone exhibited facilitatory and inhibitory effects at near physiological temperature, and only inhibitory effect at room temperature. Most drugs inhibited the ramp current more potently than the step current-a preference enhanced when Ba2+ was the charge carrier. The slopes of the concentration-inhibition relationships for many drugs were shallow, temperature-dependent, and differed between the step and the ramp current. CONCLUSIONS AND IMPLICATIONS All experimental factors examined affected CaV1.2 pharmacology. In addition, whole cell CaV1.2 current characteristics-rundown, temperature sensitivity, and impact of series resistance-are also factors that can impact pharmacology. Drug effects on CaV1.2 channels appear more complex than simple pore block mechanism. Normalizing laboratory-specific approaches is key to improve inter-laboratory data reproducibility. Releasing original electrophysiology records is essential to promote transparency and enable the independent evaluation of data quality.
Collapse
|
4
|
Hermida A, Jedraszak G, Kubala M, Bourgain M, Bodeau S, Hermida JS. Use of ranolazine as rescue therapy in a patient with Timothy syndrome type 2. REVISTA ESPANOLA DE CARDIOLOGIA (ENGLISH ED.) 2022; 75:447-448. [PMID: 34844894 DOI: 10.1016/j.rec.2021.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 10/25/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Alexis Hermida
- Cardiology, Arrhythmia, and Cardiac Stimulation Service, Amiens-Picardie University Hospital, Amiens, France; EA4666 HEMATIM, University of Picardie-Jules Verne, Amiens, France.
| | - Guillaume Jedraszak
- EA4666 HEMATIM, University of Picardie-Jules Verne, Amiens, France; Molecular Genetics Laboratory, Amiens-Picardie University Hospital, Amiens, France
| | - Maciej Kubala
- Cardiology, Arrhythmia, and Cardiac Stimulation Service, Amiens-Picardie University Hospital, Amiens, France
| | - Marion Bourgain
- Pediatric Cardiology Department, Amiens-Picardie University Hospital, Amiens, France
| | - Sandra Bodeau
- Laboratory of Pharmacology and Toxicology, Amiens-Picardie University Hospital, Amiens, France
| | - Jean-Sylvain Hermida
- Cardiology, Arrhythmia, and Cardiac Stimulation Service, Amiens-Picardie University Hospital, Amiens, France
| |
Collapse
|
5
|
Hermida A, Jedraszak G, Kubala M, Bourgain M, Bodeau S, Hermida JS. Uso de ranolazina en paciente con síndrome de Timothy tipo 2. Rev Esp Cardiol 2022. [DOI: 10.1016/j.recesp.2021.10.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
6
|
Forouzandehmehr M, Koivumäki JT, Hyttinen J, Paci M. A mathematical model of hiPSC cardiomyocytes electromechanics. Physiol Rep 2021; 9:e15124. [PMID: 34825519 PMCID: PMC8617339 DOI: 10.14814/phy2.15124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/18/2021] [Accepted: 11/02/2021] [Indexed: 01/21/2023] Open
Abstract
Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are becoming instrumental in cardiac research, human-based cell level cardiotoxicity tests, and developing patient-specific care. As one of the principal functional readouts is contractility, we propose a novel electromechanical hiPSC-CM computational model named the hiPSC-CM-CE. This model comprises a reparametrized version of contractile element (CE) by Rice et al., 2008, with a new passive force formulation, integrated into a hiPSC-CM electrophysiology formalism by Paci et al. in 2020. Our simulated results were validated against in vitro data reported for hiPSC-CMs at matching conditions from different labs. Specifically, key action potential (AP) and calcium transient (CaT) biomarkers simulated by the hiPSC-CM-CE model were within the experimental ranges. On the mechanical side, simulated cell shortening, contraction-relaxation kinetic indices (RT50 and RT25 ), and the amplitude of tension fell within the experimental intervals. Markedly, as an inter-scale analysis, correct classification of the inotropic effects due to non-cardiomyocytes in hiPSC-CM tissues was predicted on account of the passive force expression introduced to the CE. Finally, the physiological inotropic effects caused by Verapamil and Bay-K 8644 and the aftercontractions due to the early afterdepolarizations (EADs) were simulated and validated against experimental data. In the future, the presented model can be readily expanded to take in pharmacological trials and genetic mutations, such as those involved in hypertrophic cardiomyopathy, and study arrhythmia trigger mechanisms.
Collapse
Affiliation(s)
| | - Jussi T. Koivumäki
- Faculty of Medicine and Health TechnologyTampere UniversityTampereFinland
| | - Jari Hyttinen
- Faculty of Medicine and Health TechnologyTampere UniversityTampereFinland
| | - Michelangelo Paci
- Faculty of Medicine and Health TechnologyTampere UniversityTampereFinland
| |
Collapse
|
7
|
Millet J, Aguilar-Sanchez Y, Kornyeyev D, Bazmi M, Fainstein D, Copello JA, Escobar AL. Thermal modulation of epicardial Ca2+ dynamics uncovers molecular mechanisms of Ca2+ alternans. J Gen Physiol 2021; 153:211659. [PMID: 33410862 PMCID: PMC7797898 DOI: 10.1085/jgp.202012568] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 11/02/2020] [Accepted: 11/30/2020] [Indexed: 01/16/2023] Open
Abstract
Ca2+ alternans (Ca-Alts) are alternating beat-to-beat changes in the amplitude of Ca2+ transients that frequently occur during tachycardia, ischemia, or hypothermia that can lead to sudden cardiac death. Ca-Alts appear to result from a variation in the amount of Ca2+ released from the sarcoplasmic reticulum (SR) between two consecutive heartbeats. This variable Ca2+ release has been attributed to the alternation of the action potential duration, delay in the recovery from inactivation of RYR Ca2+ release channel (RYR2), or an incomplete Ca2+ refilling of the SR. In all three cases, the RYR2 mobilizes less Ca2+ from the SR in an alternating manner, thereby generating an alternating profile of the Ca2+ transients. We used a new experimental approach, fluorescence local field optical mapping (FLOM), to record at the epicardial layer of an intact heart with subcellular resolution. In conjunction with a local cold finger, a series of images were recorded within an area where the local cooling induced a temperature gradient. Ca-Alts were larger in colder regions and occurred without changes in action potential duration. Analysis of the change in the enthalpy and Q10 of several kinetic processes defining intracellular Ca2+ dynamics indicated that the effects of temperature change on the relaxation of intracellular Ca2+ transients involved both passive and active mechanisms. The steep temperature dependency of Ca-Alts during tachycardia suggests Ca-Alts are generated by insufficient SERCA-mediated Ca2+ uptake into the SR. We found that Ca-Alts are heavily dependent on intra-SR Ca2+ and can be promoted through partial pharmacologic inhibition of SERCA2a. Finally, the FLOM experimental approach has the potential to help us understand how arrhythmogenesis correlates with the spatial distribution of metabolically impaired myocytes along the myocardium.
Collapse
Affiliation(s)
- Jose Millet
- Institute of Information and Communication Technologies, Universitat Politècnica de València and Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares, Valencia, Spain
| | - Yuriana Aguilar-Sanchez
- Department of Physiology and Biophysics, School of Medicine, Rush University Medical Center, Chicago, IL.,School of Natural Sciences, University of California, Merced, Merced, CA
| | - Dmytro Kornyeyev
- Department of Bioengineering, School of Engineering, University of California Merced, Merced, CA
| | - Maedeh Bazmi
- School of Natural Sciences, University of California, Merced, Merced, CA
| | - Diego Fainstein
- Facultad de Ingeniería, Universidad Nacional de Entre Ríos, Entre Ríos, Argentina.,Department of Bioengineering, School of Engineering, University of California Merced, Merced, CA
| | - Julio A Copello
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL
| | - Ariel L Escobar
- Department of Bioengineering, School of Engineering, University of California Merced, Merced, CA
| |
Collapse
|
8
|
Nakajima T, Tamura S, Kurabayashi M, Kaneko Y. Towards Mutation-Specific Precision Medicine in Atypical Clinical Phenotypes of Inherited Arrhythmia Syndromes. Int J Mol Sci 2021; 22:ijms22083930. [PMID: 33920294 PMCID: PMC8069124 DOI: 10.3390/ijms22083930] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 04/08/2021] [Indexed: 12/19/2022] Open
Abstract
Most causal genes for inherited arrhythmia syndromes (IASs) encode cardiac ion channel-related proteins. Genotype-phenotype studies and functional analyses of mutant genes, using heterologous expression systems and animal models, have revealed the pathophysiology of IASs and enabled, in part, the establishment of causal gene-specific precision medicine. Additionally, the utilization of induced pluripotent stem cell (iPSC) technology have provided further insights into the pathophysiology of IASs and novel promising therapeutic strategies, especially in long QT syndrome. It is now known that there are atypical clinical phenotypes of IASs associated with specific mutations that have unique electrophysiological properties, which raises a possibility of mutation-specific precision medicine. In particular, patients with Brugada syndrome harboring an SCN5A R1632C mutation exhibit exercise-induced cardiac events, which may be caused by a marked activity-dependent loss of R1632C-Nav1.5 availability due to a marked delay of recovery from inactivation. This suggests that the use of isoproterenol should be avoided. Conversely, the efficacy of β-blocker needs to be examined. Patients harboring a KCND3 V392I mutation exhibit both cardiac (early repolarization syndrome and paroxysmal atrial fibrillation) and cerebral (epilepsy) phenotypes, which may be associated with a unique mixed electrophysiological property of V392I-Kv4.3. Since the epileptic phenotype appears to manifest prior to cardiac events in this mutation carrier, identifying KCND3 mutations in patients with epilepsy and providing optimal therapy will help prevent sudden unexpected death in epilepsy. Further studies using the iPSC technology may provide novel insights into the pathophysiology of atypical clinical phenotypes of IASs and the development of mutation-specific precision medicine.
Collapse
|
9
|
Hermida A, Jedraszak G, Kubala M, Mathiron A, Berna P, Bennis Y, Hermida JS. Long-term follow-up of a patient with type 2 Timothy syndrome and the partial efficacy of mexiletine. Gene 2021; 777:145465. [PMID: 33524520 DOI: 10.1016/j.gene.2021.145465] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 12/23/2020] [Accepted: 01/22/2021] [Indexed: 11/15/2022]
Abstract
We report a detailed case of type 2 TS due to a p.(Gly402Ser) mutation in exon 8 of the CACNA1C gene. The patient shows a marked prolongation of repolarization with a mean QTc of 540 ms. He shows no structural heart disease, syndactyly, or cranio-facial abnormalities. However, he shows developmental delays, without autism, and dental abnormalities. The cardiac phenotype is very severe, with a resuscitated cardiac arrest at 2.5 years of age, followed by 26 appropriate shocks during nine years of follow-up. Adding mexiletine to nadolol resulted in a reduction of the QTc and a slight decrease in the number of appropriate shocks.
Collapse
Affiliation(s)
- Alexis Hermida
- Cardiology, Arrhythmia, and Cardiac Stimulation Service, Amiens-Picardie University Hospital, Amiens, France.
| | - Guillaume Jedraszak
- Molecular Genetics Laboratory, Amiens-Picardie University Hospital, Amiens, France; EA4666 HEMATIM, University of Picardie-Jules Verne, Amiens, France
| | - Maciej Kubala
- Cardiology, Arrhythmia, and Cardiac Stimulation Service, Amiens-Picardie University Hospital, Amiens, France
| | - Amel Mathiron
- Pediatric Cardiology Department, Amiens-Picardie University Hospital, Amiens, France
| | - Pascal Berna
- Department of Thoracic Surgery Service, Amiens-Picardie University Hospital, Amiens, France
| | - Youssef Bennis
- Laboratory of Pharmacology and Toxicology, Amiens-Picardie University Hospital, Amiens, France
| | - Jean-Sylvain Hermida
- Cardiology, Arrhythmia, and Cardiac Stimulation Service, Amiens-Picardie University Hospital, Amiens, France
| |
Collapse
|
10
|
Han D, Xu L, Liu P, Liu Y, Sun C, Yin Y. Allicin disrupts cardiac Cav1.2 channels via trafficking. PHARMACEUTICAL BIOLOGY 2019; 57:245-249. [PMID: 30929547 PMCID: PMC6450490 DOI: 10.1080/13880209.2019.1577469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 10/06/2018] [Accepted: 01/25/2019] [Indexed: 06/09/2023]
Abstract
CONTEXT Allicin is a potential antiarrhythmic agent. The antiarrhythmic properties of allicin rely on its blockade of various cardiac ion channels. The l-type calcium (Cav1.2) channel provides a pivotal substrate for cardiac electrophysiologic activities. The mechanism of allicin on Cav1.2 remains unclear. OBJECTIVE This study evaluated the potential of allicin on the synthesis and trafficking of Cav1.2 channels. MATERIALS AND METHODS Primary cardiomyocytes (CMs) from neonatal Sprague-Dawley (SD) rats were exposed to allicin (0, 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 μg/mL) for 24 and 48 h. The CellTiter-Glo assay was performed to measure CM viability. Western blot with grayscale analysis and confocal laser scanning microscopy were used to evaluate the effects of allicin on the synthesis and trafficking of Cav1.2 channel proteins in primary CMs. RESULTS There was no significant difference in apoptotic toxicity from the actual cell viability (p > 0.05) in any group (0, 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 μg/mL allicin), except that viability in the 0.001 and 0.01 μg/mL groups at 24 h were significantly greater (137.37 and 135.96%) (p < 0.05). Western blot with grayscale analysis revealed no substantial inhibition by allicin of the synthesis of Cav1.2 proteins. Confocal laser scanning microscopy revealed trafficking dysfunction of Cav1.2 channels caused by allicin in primary CMs. CONCLUSION This study is the first to demonstrate that allicin inhibits cardiac Cav1.2 channels by disrupting trafficking, possibly mediating its antiarrhythmic benefits. Therefore, allicin might serve as a new antiarrhythmic agent in the future.
Collapse
Affiliation(s)
- Dan Han
- Arrhythmia Unit, Department of Cardiology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Lingping Xu
- Arrhythmia Unit, Department of Cardiology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
- Xianyang Central Hospital, Xianyang, China
| | - Peng Liu
- Arrhythmia Unit, Department of Cardiology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Yingying Liu
- Arrhythmia Unit, Department of Cardiology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Chaofeng Sun
- Arrhythmia Unit, Department of Cardiology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Yanrong Yin
- Arrhythmia Unit, Department of Cardiology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| |
Collapse
|
11
|
Kushner J, Ferrer X, Marx SO. Roles and Regulation of Voltage-gated Calcium Channels in Arrhythmias. J Innov Card Rhythm Manag 2019; 10:3874-3880. [PMID: 32494407 PMCID: PMC7252866 DOI: 10.19102/icrm.2019.101006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 03/04/2019] [Indexed: 12/25/2022] Open
Abstract
Calcium flowing through voltage-dependent calcium channels into cardiomyocytes mediates excitation–contraction coupling, controls action-potential duration and automaticity in nodal cells, and regulates gene expression. Proper surface targeting and basal and hormonal regulation of calcium channels are vital for normal cardiac physiology. In this review, we discuss the roles of voltage-gated calcium channels in the heart and the mechanisms by which these channels are regulated by physiological signaling pathways in health and disease.
Collapse
Affiliation(s)
- Jared Kushner
- Division of Cardiology, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Xavier Ferrer
- Division of Cardiology, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Steven O Marx
- Division of Cardiology, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| |
Collapse
|
12
|
Han D, Xue X, Yan Y, Li G. Dysfunctional Cav1.2 channel in Timothy syndrome, from cell to bedside. Exp Biol Med (Maywood) 2019; 244:960-971. [PMID: 31324123 DOI: 10.1177/1535370219863149] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Timothy syndrome is a rare disorder caused by CACNA1C gene mutations and characterized by multi-organ system dysfunctions, including ventricular arrhythmias, syndactyly, dysmorphic facial features, intermittent hypoglycemia, immunodeficiency, developmental delay, and autism. Because of the low morbidity and high mortality at a young age, it remains a huge challenge to establish a diagnosis and treatment system to manage Timothy syndrome patients. Here, we aim to provide a detailed review of Timothy syndrome, discuss the mechanisms underlying dysfunctional Cav1.2 due to CACNA1C mutations, and provide some new emerging evidences in treating Timothy syndrome from cell to bedside, promoting the management of this rare disease. Impact statement The knowledge of Timothy syndrome (TS) caused by dysfunctional Cav1.2 channel due to CACNA1C mutations is rapidly evolving as novel technologies of electrophysiology are introduced and our understanding of the mechanisms of TS develops. In this review, we focus on the TS-related dysfunctional Cav1.2 and the underlying mechanisms. We update TS-related CACNA1C mutations in a precise way over the past 20 years and summarize all reported TS patients based on their clinical presentations and molecular mechanisms, respectively. We hope this review will provide a new comprehensive way to better understand the electrophysiological mechanisms underlying TS from cell to bedside, promoting the management of TS in practice.
Collapse
Affiliation(s)
- Dan Han
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China.,2 Department of Cardiovascular Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P.R. China*These authors contributed equally to this work and should be considered to share first authorship
| | - Xiaolin Xue
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China
| | - Yang Yan
- 2 Department of Cardiovascular Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P.R. China*These authors contributed equally to this work and should be considered to share first authorship
| | - Guoliang Li
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China
| |
Collapse
|
13
|
Walsh MA, Turner C, Timothy KW, Seller N, Hares DL, James AF, Hancox JC, Uzun O, Boyce D, Stuart AG, Brennan P, Sarton C, McGuire K, Newbury-Ecob RA, Mcleod K. A multicentre study of patients with Timothy syndrome. Europace 2018; 20:377-385. [PMID: 28371864 DOI: 10.1093/europace/euw433] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 12/20/2016] [Indexed: 11/13/2022] Open
Abstract
Aims Timothy syndrome (TS) is an extremely rare multisystem disorder characterized by marked QT prolongation, syndactyly, seizures, behavioural abnormalities, immunodeficiency, and hypoglycaemia. The aim of this study was to categorize the phenotypes and examine the outcomes of patients with TS. Methods and results All patients diagnosed with TS in the United Kingdom over a 24-year period were reviewed. Fifteen centres in the British Congenital Arrhythmia Group network were contacted to partake in the study. Six patients with TS were identified over a 24-year period (4 boys and 2 girls). Five out of the six patients were confirmed to have a CACNA1C mutation (p.Gly406Arg) and the other patient was diagnosed clinically. Early presentation with heart block, due to QT prolongation was frequently seen. Four are still alive, two of these have a pacemaker and two have undergone defibrillator implantation. Five out of six patients have had a documented cardiac arrest with three occurring under general anaesthesia. Two patients suffered a cardiac arrest while in hospital and resuscitation was unsuccessful, despite immediate access to a defibrillator. Surviving patients seem to have mild developmental delay and learning difficulties. Conclusion Timothy syndrome is a rare disorder with a high attrition rate if undiagnosed. Perioperative cardiac arrests are common and not always amenable to resuscitation. Longer-term survival is possible, however, patients invariably require pacemaker or defibrillator implantation.
Collapse
Affiliation(s)
- Mark A Walsh
- Bristol Royal Hospital for Children, University Hospital Bristol, Bristol, UK.,Bristol Heart Institute, University Hospital Bristol, Bristol, UK
| | - Christian Turner
- Department of Congenital Cardiology, Freeman Hospital, Newcastle upon Tyne, UK.,Children's Hospital at Westmead, Sydney, Australia
| | | | - Neil Seller
- Department of Congenital Cardiology, Freeman Hospital, Newcastle upon Tyne, UK
| | - Dominic L Hares
- Department of Cardiology, The Yorkshire Heart Centre, Leeds General Infirmary, Leeds, UK
| | - Andrew F James
- School of Physiology, Pharmacology and Neuroscience Cardiovascular Research Laboratories, University of Bristol, Bristol, UK
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience Cardiovascular Research Laboratories, University of Bristol, Bristol, UK
| | - Orhan Uzun
- Department of Cardiology, University Hospital Wales, Cardiff, UK
| | - Dean Boyce
- Department of Plastic Surgery, University Hospital Wales, Cardiff, UK
| | - Alan G Stuart
- Bristol Royal Hospital for Children, University Hospital Bristol, Bristol, UK.,Bristol Heart Institute, University Hospital Bristol, Bristol, UK
| | - Paul Brennan
- Department of Clinical Genetics, Freeman Hospital, Newcastle upon Tyne, UK
| | - Caroline Sarton
- Oxford Medical Genetics Laboratories, Cardiac Service, Oxford University Hospitals NHS Trust, The Churchill Hospital, Oxford, UK
| | - Karen McGuire
- Oxford Medical Genetics Laboratories, Cardiac Service, Oxford University Hospitals NHS Trust, The Churchill Hospital, Oxford, UK
| | | | - Karen Mcleod
- Department of Cardiology, Royal Hospital for Sick Children, Glasgow, UK
| |
Collapse
|
14
|
Sicouri S, Antzelevitch C. Mechanisms Underlying the Actions of Antidepressant and Antipsychotic Drugs That Cause Sudden Cardiac Arrest. Arrhythm Electrophysiol Rev 2018; 7:199-209. [PMID: 30416734 PMCID: PMC6141916 DOI: 10.15420/aer.2018.29.2] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 06/19/2018] [Indexed: 12/18/2022] Open
Abstract
A number of antipsychotic and antidepressant drugs are known to increase the risk of ventricular arrhythmias and sudden cardiac death. Based largely on a concern over the development of life-threatening arrhythmias, a number of antipsychotic drugs have been temporarily or permanently withdrawn from the market or their use restricted. While many antidepressants and antipsychotics have been linked to QT prolongation and the development of torsade de pointes arrhythmias, some have been associated with a Brugada syndrome phenotype and the development of polymorphic ventricular arrhythmias. This article examines the arrhythmic liability of antipsychotic and antidepressant drugs capable of inducing long QT and/or Brugada syndrome phenotypes. The goal of this article is to provide an update on the ionic and cellular mechanisms thought to be involved in, and the genetic and environmental factors that predispose to, the development of cardiac arrhythmias and sudden cardiac death among patients taking antidepressant and antipsychotic drugs that are in clinical use.
Collapse
Affiliation(s)
- Serge Sicouri
- Lankenau Institute for Medical ResearchWynnewood, PA, USA
| | - Charles Antzelevitch
- Lankenau Institute for Medical ResearchWynnewood, PA, USA
- Lankenau Heart InstituteWynnewood, PA
- Sidney Kimmel Medical College of Thomas Jefferson UniversityPhiladelphia, PA, USA
| |
Collapse
|
15
|
Bazoukis G, Tse G, Letsas KP, Thomopoulos C, Naka KK, Korantzopoulos P, Bazoukis X, Michelongona P, Papadatos SS, Vlachos K, Liu T, Efremidis M, Baranchuk A, Stavrakis S, Tsioufis C. Impact of ranolazine on ventricular arrhythmias - A systematic review. J Arrhythm 2018; 34:124-128. [PMID: 29657587 PMCID: PMC5891418 DOI: 10.1002/joa3.12031] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 11/29/2017] [Indexed: 12/15/2022] Open
Abstract
Ranolazine is a new medication for the treatment of refractory angina. However, except its anti-anginal properties, it has been found to act as an anti-arrhythmic. The aim of our systematic review is to present the existing data about the impact of ranolazine in ventricular arrhythmias. We searched MEDLINE and Cochrane databases as well clinicaltrials.gov until September 1, 2017 to find all studies (clinical trials, observational studies, case reports/series) reported data about the impact of ranolazine in ventricular arrhythmias. Our search revealed 14 studies (3 clinical trials, 2 observational studies, 8 case reports, 1 case series). These data reported a beneficial impact of ranolazine in ventricular tachycardia/fibrillation, premature ventricular beats, and ICD interventions in different clinical settings. The existing data highlight the anti-arrhythmic properties of ranolazine in ventricular arrhythmias.
Collapse
Affiliation(s)
- George Bazoukis
- Department of Cardiology Catheterization Laboratory Evangelismos General Hospital of Athens Athens Greece
| | - Gary Tse
- Department of Medicine and Therapeutics Faculty of Medicine Chinese University of Hong Kong Hong Kong China.,Li Ka Shing Institute of Health Sciences Faculty of Medicine Chinese University of Hong Kong Hong Kong China
| | - Konstantinos P Letsas
- Department of Cardiology Catheterization Laboratory Evangelismos General Hospital of Athens Athens Greece
| | | | - Katerina K Naka
- Second Department of Cardiology School of Medicine University of Ioannina Ioannina Greece
| | | | - Xenophon Bazoukis
- Department of Cardiology General Hospital of Ioannina, "G Hatzikosta" Ioannina Greece
| | - Paschalia Michelongona
- Department of Cardiology Catheterization Laboratory Evangelismos General Hospital of Athens Athens Greece
| | - Stamatis S Papadatos
- Faculty Department of Internal Medicine Athens School of Medicine Sotiria General Hospital National and Kapodistrian University of Athens Athens Greece
| | - Konstantinos Vlachos
- Department of Cardiology Catheterization Laboratory Evangelismos General Hospital of Athens Athens Greece
| | - Tong Liu
- Department of Cardiology Tianjin Institute of Cardiology Second Hospital of Tianjin Medical University Tianjin China
| | - Michael Efremidis
- Department of Cardiology Catheterization Laboratory Evangelismos General Hospital of Athens Athens Greece
| | - Adrian Baranchuk
- Division of Cardiology, Electrophysiology and Pacing Kingston General Hospital Queen's University Kingston ON Canada
| | - Stavros Stavrakis
- University of Oklahoma Health Sciences Center Oklahoma City Oklahoma
| | - Costas Tsioufis
- First Cardiology Clinic Hippokration Hospital University of Athens Athens Greece
| |
Collapse
|
16
|
Tunca Sahin G, Ergul Y. A case report: Is mexiletine usage effective in the shortening of QTC interval and improving the T-wave alternans in Timothy syndrome? Ann Noninvasive Electrocardiol 2017; 23:e12522. [PMID: 29194862 DOI: 10.1111/anec.12522] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 10/14/2017] [Indexed: 01/12/2023] Open
Abstract
Timothy syndrome (TS) is a multisystemic disease that occurs because of a mutation in CACN1C gene and is characterized by prolonged QT interval. Mexiletine is a Class 1B antiarrhythmic drug that causes the disappearance of T-wave alternans by shortening QTc and peak-to-end of the T wave. It may block the development of torsades de pointes in a prolonged QT. This study presented the case of a patient diagnosed with TS and had a cardiac arrest history, prolonged QT, and T-wave alternans. After mexiletine treatment, the QTc interval shortened and T-wave alternans disappeared. Such a case has rarely been seen in the literature, and hence considered rare. This case presentation was of particular importance because it highlighted the use of mexiletine besides an initial beta-blocker treatment in the cases with TS.
Collapse
Affiliation(s)
- Gulhan Tunca Sahin
- Department of Pediatric Cardiology, Istanbul Mehmet Akif Ersoy Thoracic and Cardiovascular Surgery Education and Research Hospital, Istanbul Saglik Bilimleri University, Istanbul, Turkey
| | - Yakup Ergul
- Department of Pediatric Cardiology, Istanbul Mehmet Akif Ersoy Thoracic and Cardiovascular Surgery Education and Research Hospital, Istanbul Saglik Bilimleri University, Istanbul, Turkey
| |
Collapse
|
17
|
Ergül Y, Özyılmaz İ, Haydın S, Güzeltaş A, Tuzcu V. A rare association with suffered cardiac arrest, long QT interval, and syndactyly: Timothy syndrome (LQT-8). Anatol J Cardiol 2016; 15:672-4. [PMID: 26301350 PMCID: PMC5336871 DOI: 10.5152/anatoljcardiol.2015.6315] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- Yakup Ergül
- Clinic of Pediatric Cardiology, Mehmet Akif Ersoy Cardiovascular Training and Research Hospital; İstanbul-Turkey.
| | | | | | | | | |
Collapse
|
18
|
Bai J, Wang K, Li Q, Yuan Y, Zhang H. Pro-arrhythmogenic effects of CACNA1C G1911R mutation in human ventricular tachycardia: insights from cardiac multi-scale models. Sci Rep 2016; 6:31262. [PMID: 27502440 PMCID: PMC4977499 DOI: 10.1038/srep31262] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 07/14/2016] [Indexed: 01/11/2023] Open
Abstract
Mutations in the CACNA1C gene are associated with ventricular tachycardia (VT). Although the CACNA1C mutations were well identified in patients with cardiac arrhythmias, mechanisms by which cardiac arrhythmias are generated in such genetic mutation conditions remain unclear. In this study, we identified a novel mechanism of VT resulted from enhanced repolarization dispersion which is a key factor for arrhythmias in the CACNA1C G1911R mutation using multi-scale computational models of the human ventricle. The increased calcium influx in the mutation prolonged action potential duration (APD), produced steepened action potential duration restitution (APDR) curves as well as augmented membrane potential differences among different cell types during repolarization, increasing transmural dispersion of repolarization (DOR) and the spatial and temporal heterogeneity of cardiac electrical activities. Consequentially, the vulnerability to unidirectional conduction block in response to a premature stimulus increased at tissue level in the G1911R mutation. The increased functional repolarization dispersion anchored reentrant excitation waves in tissue and organ models, facilitating the initiation and maintenance of VT due to less meandering rotor tip. Thus, the increased repolarization dispersion caused by the G1911R mutation is a primary factor that may primarily contribute to the genesis of cardiac arrhythmias in Timothy Syndrome.
Collapse
Affiliation(s)
- Jieyun Bai
- School of Computer Science and Technology, Harbin Institute Technology, Harbin, 150001, China
| | - Kuanquan Wang
- School of Computer Science and Technology, Harbin Institute Technology, Harbin, 150001, China
| | - Qince Li
- School of Computer Science and Technology, Harbin Institute Technology, Harbin, 150001, China
| | - Yongfeng Yuan
- School of Computer Science and Technology, Harbin Institute Technology, Harbin, 150001, China
| | - Henggui Zhang
- School of Computer Science and Technology, Harbin Institute Technology, Harbin, 150001, China
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| |
Collapse
|
19
|
Badri M, Patel A, Patel C, Liu G, Goldstein M, Robinson VM, Xue X, Yang L, Kowey PR, Yan GX. Mexiletine Prevents Recurrent Torsades de Pointes in Acquired Long QT Syndrome Refractory to Conventional Measures. JACC Clin Electrophysiol 2015; 1:315-322. [DOI: 10.1016/j.jacep.2015.05.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 05/21/2015] [Indexed: 12/18/2022]
|
20
|
Guo K, Wang YP, Zhou ZW, Jiang YB, Li W, Chen XM, Li YG. Impact of phosphomimetic and non-phosphorylatable mutations of phospholemman on L-type calcium channels gating in HEK 293T cells. J Cell Mol Med 2015; 19:642-50. [PMID: 25656605 PMCID: PMC4369820 DOI: 10.1111/jcmm.12484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Accepted: 10/10/2014] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Phospholemman (PLM) is an important phosphorylation substrate for protein kinases A and C in the heart. Until now, the association between PLM phosphorylation status and L-type calcium channels (LTCCs) gating has not been fully understood. We investigated the kinetics of LTCCs in HEK 293T cells expressing phosphomimetic or nonphosphorylatable PLM mutants. METHODS The LTCCs gating was measured in HEK 293T cells transfected with LTCC and wild-type (WT) PLM, phosphomimetic or nonphosphorylatable PLM mutants: 6263AA, 6869AA, AAAA, 6263DD, 6869DD or DDDD. RESULTS WT PLM significantly slowed LTCCs activation and deactivation while enhanced voltage-dependent inactivation (VDI). PLM mutants 6869DD and DDDD significantly increased the peak of the currents. 6263DD accelerated channel activation, while 6263AA slowed it more than WT PLM. 6869DD significantly enhanced PLM-induced increase of VDI. AAAA slowed the channel activation more than 6263AA, and DDDD accelerated the channel VDI more than 6869DD. CONCLUSIONS Our results demonstrate that phosphomimetic PLM could stimulate LTCCs and alter their dynamics, while PLM nonphosphorylatable mutant produced the opposite effects.
Collapse
Affiliation(s)
- Kai Guo
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | | | | | | | | | | | | |
Collapse
|
21
|
Schmunk G, Gargus JJ. Channelopathy pathogenesis in autism spectrum disorders. Front Genet 2013; 4:222. [PMID: 24204377 PMCID: PMC3817418 DOI: 10.3389/fgene.2013.00222] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Accepted: 10/09/2013] [Indexed: 01/12/2023] Open
Abstract
Autism spectrum disorder (ASD) is a syndrome that affects normal brain development and is characterized by impaired social interaction as well as verbal and non-verbal communication and by repetitive, stereotypic behavior. ASD is a complex disorder arising from a combination of multiple genetic and environmental factors that are independent from racial, ethnic and socioeconomical status. The high heritability of ASD suggests a strong genetic basis for the disorder. Furthermore, a mounting body of evidence implies a role of various ion channel gene defects (channelopathies) in the pathogenesis of autism. Indeed, recent genome-wide association, and whole exome- and whole-genome resequencing studies linked polymorphisms and rare variants in calcium, sodium and potassium channels and their subunits with susceptibility to ASD, much as they do with bipolar disorder, schizophrenia and other neuropsychiatric disorders. Moreover, animal models with these genetic variations recapitulate endophenotypes considered to be correlates of autistic behavior seen in patients. An ion flux across the membrane regulates a variety of cell functions, from generation of action potentials to gene expression and cell morphology, thus it is not surprising that channelopathies have profound effects on brain functions. In the present work, we summarize existing evidence for the role of ion channel gene defects in the pathogenesis of autism with a focus on calcium signaling and its downstream effects.
Collapse
Affiliation(s)
- Galina Schmunk
- Department of Physiology and Biophysics, University of California Irvine, CA, USA ; UCI Center for Autism Research and Treatment, School of Medicine, University of California Irvine, CA, USA
| | | |
Collapse
|
22
|
Electronic "expression" of the inward rectifier in cardiocytes derived from human-induced pluripotent stem cells. Heart Rhythm 2013; 10:1903-10. [PMID: 24055949 DOI: 10.1016/j.hrthm.2013.09.061] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Indexed: 01/09/2023]
Abstract
BACKGROUND Human-induced pluripotent stem cell (h-iPSC)-derived cardiac myocytes are a unique model in which human myocyte function and dysfunction are studied, especially those from patients with genetic disorders. They are also considered a major advance for drug safety testing. However, these cells have considerable unexplored potential limitations when applied to quantitative action potential (AP) analysis. One major factor is spontaneous activity and resulting variability and potentially anomalous behavior of AP parameters. OBJECTIVE To demonstrate the effect of using an in silico interface on electronically expressed I(K1), a major component lacking in h-iPSC-derived cardiac myocytes. METHODS An in silico interface was developed to express synthetic I(K1) in cells under whole-cell voltage clamp. RESULTS Electronic I(K1) expression established a physiological resting potential, eliminated spontaneous activity, reduced spontaneous early and delayed afterdepolarizations, and decreased AP variability. The initiated APs had the classic rapid upstroke and spike and dome morphology consistent with data obtained with freshly isolated human myocytes as well as the readily recognizable repolarization attributes of ventricular and atrial cells. The application of 1 µM of BayK-8644 resulted in anomalous AP shortening in h-iPSC-derived cardiac myocytes. When I(K1) was electronically expressed, BayK-8644 prolonged the AP, which is consistent with the existing results on native cardiac myocytes. CONCLUSIONS The electronic expression of I(K1) is a simple and robust method to significantly improve the physiological behavior of the AP and electrical profile of h-iPSC-derived cardiac myocytes. Increased stability enables the use of this preparation for a controlled quantitative analysis of AP parameters, for example, drug responsiveness, genetic disorders, and dynamic behavior restitution profiles.
Collapse
|
23
|
Late sodium current inhibition in acquired and inherited ventricular (dys)function and arrhythmias. Cardiovasc Drugs Ther 2013; 27:91-101. [PMID: 23292167 DOI: 10.1007/s10557-012-6433-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The late sodium current has been increasingly recognized for its mechanistic role in various cardiovascular pathologies, including angina pectoris, myocardial ischemia, atrial fibrillation, heart failure and congenital long QT syndrome. Although relatively small in magnitude, the late sodium current (I(NaL)) represents a functionally relevant contributor to cardiomyocyte (electro)physiology. Many aspects of I(NaL) itself are as yet still unresolved, including its distribution and function in different cell types throughout the heart, and its regulation by sodium channel accessory proteins and intracellular signalling pathways. Its complexity is further increased by a close interrelationship with the peak sodium current and other ion currents, hindering the development of inhibitors with selective and specific properties. Thus, increased knowledge of the intricacies of the complex nature of I(NaL) during distinct cardiovascular conditions and its potential as a pharmacological target is essential. Here, we provide an overview of the functional and electrophysiological effects of late sodium current inhibition on the level of the ventricular myocyte, and its potential cardioprotective and anti-arrhythmic efficacy in the setting of acquired and inherited ventricular dysfunction and arrhythmias.
Collapse
|
24
|
Gao Y, Xue X, Hu D, Liu W, Yuan Y, Sun H, Li L, Timothy KW, Zhang L, Li C, Yan GX. Inhibition of Late Sodium Current by Mexiletine. Circ Arrhythm Electrophysiol 2013; 6:614-22. [PMID: 23580742 DOI: 10.1161/circep.113.000092] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Yuanfeng Gao
- Heart Center, Peking University People's Hospital, Beijing, People's Republic of China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Kim GH. MicroRNA regulation of cardiac conduction and arrhythmias. Transl Res 2013; 161:381-92. [PMID: 23274306 PMCID: PMC3619003 DOI: 10.1016/j.trsl.2012.12.004] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 12/04/2012] [Accepted: 12/06/2012] [Indexed: 01/01/2023]
Abstract
MicroRNAs are now recognized as important regulators of cardiovascular genes with critical roles in normal development and physiology, as well as disease development. MicroRNAs (miRNAs) are small noncoding RNAs approximately 22 nucleotides in length that regulate expression of target genes through sequence-specific hybridization to the 3' untranslated region of messenger RNAs and either block translation or direct degradation of their target messenger RNA. They have been shown to participate in cardiovascular disease pathogenesis including atherosclerosis, coronary artery disease, myocardial infarction, heart failure, and cardiac arrhythmias. Broadly defined, cardiac arrhythmias are a variation from the normal heart rate or rhythm. Arrhythmias are common and result in significant morbidity and mortality. Ventricular arrhythmias constitute a major cause for cardiac death, particularly sudden cardiac death in the setting of myocardial infarction and heart failure. As advances in pharmacologic, device, and ablative therapy continue to evolve, the molecular insights into the basis of arrhythmia is growing with the ambition of providing additional therapeutic options. Electrical remodeling and structural remodeling are identified mechanisms underlying arrhythmia generation; however, published studies focusing on miRNAs and cardiac conduction are sparse. Recent studies have highlighted the role of miRNAs in cardiac rhythm through regulation of key ion channels, transporters, and cellular proteins in arrhythmogenic conditions. This article aims to review the studies linking miRNAs to cardiac excitability and other processes pertinent to arrhythmia.
Collapse
Affiliation(s)
- Gene H Kim
- University of Chicago, Institute for Cardiovascular Research, Chicago, IL 60637, USA.
| |
Collapse
|
26
|
Sicouri S, Belardinelli L, Antzelevitch C. Antiarrhythmic effects of the highly selective late sodium channel current blocker GS-458967. Heart Rhythm 2013; 10:1036-43. [PMID: 23524321 DOI: 10.1016/j.hrthm.2013.03.023] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Indexed: 12/14/2022]
Abstract
BACKGROUND Previous studies have shown that late sodium channel current (INa) blockers such as ranolazine can exert antiarrhythmic effects by suppressing early and delayed afterdepolarization (EAD and DAD)-induced triggered activity. OBJECTIVE To evaluate the electrophysiological properties of GS-458967 (GS967), a potent and highly selective late INa blocker, in canine Purkinje fibers (PFs) and pulmonary vein (PV) and superior vena cava (SVC) sleeve preparations. METHODS Transmembrane action potentials were recorded from canine PFs and PV and SVC sleeve preparations by using standard microelectrode techniques. The rapidly activating delayed rectifier potassium channel current blocker E-4031 (2.5-5 µM) and the late INa agonist ATX-II (10 nM) were used to induce EADs in PFs. Isoproterenol (1 µM), high calcium ([Ca(2+)]o = 5.4 mM), or their combination was used to induce DADs and triggered activity. RESULTS In PFs, GS967 (10-300 nM) caused a significant concentration-dependent reduction in action potential duration without altering the maximum rate of rise of the action potential upstroke, action potential amplitude, or resting membrane potential at any rate studied (basic cycle lengths of 1000, 500, and 300 ms) or concentration evaluated (n = 5; P < .05). GS967 (30-100 nM) abolished EADs and EAD-induced triggered activity elicited in PFs by exposure to E-4031 (n = 4) or ATX-II (n = 4). In addition, GS967 reduced or abolished DADs and suppressed DAD-induced triggered activity elicited in PFs (n = 4) and PV (n = 4) and SVC (n = 3) sleeve preparations by exposure to isoproterenol, high calcium, or their combination. CONCLUSIONS Our data suggest that the selective inhibition of late INa with GS967 can exert antiarrhythmic effects by suppressing EAD- and DAD-mediated extrasystolic activity in PFs and PV and SVC sleeve preparations.
Collapse
Affiliation(s)
- Serge Sicouri
- Masonic Medical Research Laboratory, Utica, New York 13501-1787, USA.
| | | | | |
Collapse
|
27
|
Xue X, Guo D, Sun H, Wang D, Li J, Liu T, Yang L, Shu J, Yan GX. Wenxin Keli suppresses ventricular triggered arrhythmias via selective inhibition of late sodium current. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2013; 36:732-40. [PMID: 23438075 DOI: 10.1111/pace.12109] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 12/14/2012] [Accepted: 12/28/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND Wenxin Keli is a popular Chinese herb extract that approximately five million Asians are currently taking for the treatment of a variety of ventricular arrhythmias. However, its electrophysiological mechanisms remain poorly understood. METHODS AND RESULTS The concentration-dependent electrophysiological effects of Wenxin Keli were evaluated in the isolated rabbit left ventricular myocytes and wedge preparation. Wenxin Keli selectively inhibited late sodium current (INa) with an IC50 of 3.8 ± 0.4 mg/mL, which was significantly lower than the IC50 of 10.6 ± 0.9 mg/mL (n = 6, P < 0.05) for the fast INa. Wenxin Keli produced a small but statistically significant QT prolongation at 0.3 mg/mL, but shortened the QT and Tp-e interval at concentrations ≥ 1 mg/mL. Wenxin Keli increased QRS duration by 10.1% from 34.8 ± 1.0 ms to 38.3 ± 1.1 ms (n = 6, P < 0.01) at 3 mg/mL at a basic cycle length of 2,000 ms. However, its effect on the QRS duration exhibited weak use-dependency, that is, QRS remained less changed at increased pacing rates than other classic sodium channel blockers, such as flecainide, quinidine, and lidocaine. On the other hand, Wenxin Keli at 1-3 mg/mL markedly reduced dofetilide-induced QT and Tp-e prolongation by attenuation of its reverse use-dependence and abolished dofetilide-induced early afterdepolarization (EAD) in four of four left ventricular wedge preparations. It also suppressed digoxin-induced delayed after depolarization (DAD) and ventricular tachycardias without changing the positive staircase pattern in contractility at 1-3 mg/mL in a separate experimental series (four of four). CONCLUSIONS Wenxin Keli suppressed EADs, DADs, and triggered ventricular arrhythmias via selective inhibition of late INa.
Collapse
Affiliation(s)
- Xiaolin Xue
- Department of Cardiology, the First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Hsiao PY, Tien HC, Lo CP, Juang JMJ, Wang YH, Sung RJ. Gene mutations in cardiac arrhythmias: a review of recent evidence in ion channelopathies. APPLICATION OF CLINICAL GENETICS 2013; 6:1-13. [PMID: 23837003 PMCID: PMC3699290 DOI: 10.2147/tacg.s29676] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the past 15 years, molecular genetic studies have linked gene mutations to many inherited arrhythmogenic disorders, in particular, “ion channelopathies”, in which mutations in genes encode functional units of ion channels and/or their transporter-associated proteins in patients without primary cardiac structural abnormalities. These disorders are exemplified by congenital long QT syndrome (LQTS), short QT syndrome, Brugada syndrome (BrS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). Functional and pathophysiological studies have led to better understanding of the clinical spectrum, ion channel structures and cellular electrophysiology involving dynamics of intracellular calcium cycling in many subtypes of these disorders and more importantly, development of potentially more effective pharmacological agents and even curative gene therapy. In this review, we have summarized (1) the significance of unveiling mutations in genes encoding transporter-associated proteins as the cause of congenital LQTS, (2) the technique of catheter ablation applied at the right ventricular outflow tract may be curative for severely symptomatic BrS, (3) mutations with channel function modulated by protein Kinase A-dependent phosphorylation can be the culprit of CPVT mimicry in Andersen-Tawil syndrome (LQT7), (4) ablation of the ion channel anchoring protein may prevent arrhythmogenesis in Timothy syndrome (LQT8), (5) altered intracellular Ca2+ cycling can be the basis of effective targeted pharmacotherapy in CPVT, and (6) the technology of induced pluripotent stem cells is a promising diagnostic and research tool as it has become a new paradigm for pathophysiological study of patient- and disease-specific cells aimed at screening new drugs and eventual clinical application of gene therapy. Lastly, we have discussed (7) genotype-phenotype correlation in relation to risk stratification of patients with congenital LQTS in clinical practice.
Collapse
Affiliation(s)
- Pi-Yin Hsiao
- Institute of Life Sciences, National Central University, Taoyuan, Taiwan
| | | | | | | | | | | |
Collapse
|
29
|
Di Diego JM, Sicouri S, Myles RC, Burton FL, Smith GL, Antzelevitch C. Optical and electrical recordings from isolated coronary-perfused ventricular wedge preparations. J Mol Cell Cardiol 2012; 54:53-64. [PMID: 23142540 DOI: 10.1016/j.yjmcc.2012.10.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 10/22/2012] [Accepted: 10/29/2012] [Indexed: 01/06/2023]
Abstract
The electrophysiological heterogeneity that exists across the ventricular wall in the mammalian heart has long been recognized, but remains an area that is incompletely understood. Experimental studies of the mechanisms of arrhythmogenesis in the whole heart often examine the epicardial surface in isolation and thereby disregard transmural electrophysiology. Significant heterogeneity exists in the electrophysiological properties of cardiomyocytes isolated from different layers of the ventricular wall, and given that regional heterogeneities of membrane repolarization properties can influence the electrophysiological substrate for re-entry, the diversity of cell types and characteristics spanning the ventricular wall is important in the study of arrhythmogenesis. For these reasons, coronary-perfused left ventricular wedge preparations have been developed to permit the study of transmural electrophysiology in the intact ventricle. Since the first report by Yan and Antzelevitch in 1996, electrical recordings from the transmural surface of canine wedge preparations have provided a wealth of data regarding the cellular basis for the electrocardiogram, the role of transmural heterogeneity in arrhythmogenesis, and differences in the response of the different ventricular layers to drugs and neurohormones. Use of the wedge preparation has since been expanded to other species and more recently it has also been widely used in optical mapping studies. The isolated perfused wedge preparation has become an important tool in cardiac electrophysiology. In this review, we detail the methodology involved in recording both electrical and optical signals from the coronary-perfused wedge preparation and review the advances in cardiac electrophysiology achieved through study of the wedge.
Collapse
Affiliation(s)
- José M Di Diego
- Masonic Medical Research Laboratory, 2150 Bleecker St., Utica, NY 13501, USA
| | | | | | | | | | | |
Collapse
|
30
|
Lu YY, Cheng CC, Chen YC, Chen SA, Chen YJ. ATX-II-induced pulmonary vein arrhythmogenesis related to atrial fibrillation and long QT syndrome. Eur J Clin Invest 2012; 42:823-31. [PMID: 22339387 DOI: 10.1111/j.1365-2362.2012.02655.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Long QT syndrome (LQTS) is associated with a high incidence of atrial fibrillation (AF), but the underlying mechanisms are unclear. Pulmonary veins (PVs) play a critical role in AF genesis. Type 3 LQTS increases late sodium current (I(Na,L) ), which may increase PV arrhythmogenesis and AF. Therefore, this study examines PV arrhythmogenesis in anemonia sulcata toxin II (ATX-II)-induced type 3 LQTS and evaluates whether the I(Na,L) inhibitor ranolazine can suppress PV arrhythmogenesis. MATERIALS AND METHODS Conventional microelectrodes were used to record the action potentials (AP) and contractility in isolated rabbit PV specimens before and after ATX-II administration with or without ranolazine. RESULTS Anemonia sulcata toxin II (100 nM) increased the PV spontaneous rates from 2·0 ± 0·1 to 2·9 ± 0·2 Hz (n = 7), induced PV burst firing (100%) with the genesis of early afterdepolarization (EAD) (86%) and prolonged the AP duration. Ranolazine (0·1, 1 and 10 μM) dose dependently reduced the PV spontaneous rates from 2·5 ± 0·2 to 2·3 ± 0·2 Hz, 1·9 ± 0·2 and 1·5 ± 0·3 Hz (P < 0·05) and decreased the diastolic tension by 40 ± 19%, 87 ± 26% and 113 ± 28%. In the presence of ranolazine (10 μM), ATX-II (100 nM) further increased the AP duration. However, ATX-II neither increased the PV spontaneous rates (1·6 ± 0·1 vs. 1·7 ± 0·2 Hz, n = 7) nor induced PV burst firing or EAD. Moreover, ranolazine (10 μM) reduced ATX-II-induced PV acceleration and EAD. CONCLUSIONS The I(Na,L) enhancer ATX-II can increase PV arrhythmogenesis, which can be attenuated or blocked by ranolazine. This suggests that AF may be related to type 3 LQTS through increased I(Na,L) .
Collapse
Affiliation(s)
- Yen-Yu Lu
- Division of Cardiology, Sijhih Cathay General Hospital, Sijhih, Taiwan
| | | | | | | | | |
Collapse
|
31
|
Venetucci L, Denegri M, Napolitano C, Priori SG. Inherited calcium channelopathies in the pathophysiology of arrhythmias. Nat Rev Cardiol 2012; 9:561-75. [DOI: 10.1038/nrcardio.2012.93] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
|
32
|
Vizzardi E, D'Aloia A, Quinzani F, Bonadei I, Rovetta R, Bontempi L, Curnis A, Dei Cas L. A focus on antiarrhythmic properties of ranolazine. J Cardiovasc Pharmacol Ther 2012; 17:353-6. [PMID: 22492919 DOI: 10.1177/1074248412442000] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Ranolazine is an antianginal drug that inhibits a number of ion currents that are important for the genesis of transmembrane cardiac action potential. It was initially developed as an antianginal agent but was found to additionally exert antiarrhythmic actions, due to its multichannel-blocking properties. In recent years, several studies about the antiarrhythmic properties of ranolazine were conducted, demonstrating the beneficial effects of this drug in both atrial and ventricular arrhythmias, such as atrial fibrillation, ventricular premature beats, ventricular tachycardia, torsades de pointes, and ventricular fibrillation. Our aim is to briefly review the main points of these studies, most more experimental than clinical.
Collapse
Affiliation(s)
- Enrico Vizzardi
- Department of Applied and Experimental Medicine, Chair of Cardiology University of Brescia, Brescia, Italy.
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Tamargo J, Caballero R, Delpón E. Ranolazine: an antianginal drug with antiarrhythmic properties. Expert Rev Cardiovasc Ther 2011; 9:815-27. [PMID: 21809962 DOI: 10.1586/erc.11.91] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Ranolazine is an agent approved for the symptomatic treatment of chronic stable angina that inhibits the late inward sodium current (I(NaL)). I(NaL) amplitude is increased under several pathological conditions, including increased oxidative stress, myocardial ischemia, cardiac hypertrophy, heart failure, long-QT syndrome variant 3 and atrial fibrillation. Experimental and preliminary clinical evidence suggests that ranolazine may represent a new therapeutic strategy in the treatment of a broad spectrum of cardiac arrhythmias. This article reviews the role of the I(NaL) and provides an update on experimental and clinical evidence supporting the efficacy and safety of ranolazine across a broad spectrum of arrhythmias.
Collapse
Affiliation(s)
- Juan Tamargo
- Department of Pharmacology, School of Medicine, Universidad Complutense, 28040 Madrid, Spain.
| | | | | |
Collapse
|
34
|
Krause U, Gravenhorst V, Kriebel T, Ruschewski W, Paul T. A rare association of long QT syndrome and syndactyly: Timothy syndrome (LQT 8). Clin Res Cardiol 2011; 100:1123-7. [PMID: 21915623 PMCID: PMC3222804 DOI: 10.1007/s00392-011-0358-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 08/25/2011] [Indexed: 02/06/2023]
|
35
|
Napolitano C, Antzelevitch C. Phenotypical manifestations of mutations in the genes encoding subunits of the cardiac voltage-dependent L-type calcium channel. Circ Res 2011; 108:607-18. [PMID: 21372292 DOI: 10.1161/circresaha.110.224279] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The L-type cardiac calcium channel (LTCC) plays a prominent role in the electric and mechanical function of the heart. Mutations in the LTCC have been associated with a number of inherited cardiac arrhythmia syndromes, including Timothy, Brugada, and early repolarization syndromes. Elucidation of the genetic defects associated with these syndromes has led to a better understanding of molecular and cellular mechanisms and the development of novel therapeutic approaches to dealing with the arrhythmic manifestations. This review provides an overview of the molecular structure and function of the LTCC, the genetic defects in these channels known to contribute to inherited disorders, and the underlying molecular and cellular mechanisms contributing to the development of life-threatening arrhythmias.
Collapse
Affiliation(s)
- Carlo Napolitano
- Executive Director and Director of Research, Gordon K. Moe Scholar, Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY 13501, USA.
| | | |
Collapse
|
36
|
Szél T, Koncz I, Jost N, Baczkó I, Husti Z, Virág L, Bussek A, Wettwer E, Ravens U, Papp JG, Varró A. Class I/B antiarrhythmic property of ranolazine, a novel antianginal agent, in dog and human cardiac preparations. Eur J Pharmacol 2011; 662:31-9. [PMID: 21550338 DOI: 10.1016/j.ejphar.2011.04.042] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 03/11/2011] [Accepted: 04/14/2011] [Indexed: 11/28/2022]
Abstract
The aim of this study was to investigate the cellular electrophysiological effects of ranolazine on action potential characteristics. The experiments were carried out in dog and human cardiac preparations using the conventional microelectrode technique. In dog Purkinje fibres ranolazine produced a concentration- and frequency-dependent depression of the maximum rate of depolarization (V(max)) while action potential duration (APD) was shortened. In dog and human right ventricular papillary muscle ranolazine exerted no significant effect on APD, while it produced, like mexiletine, use-dependent depression of V(max) with relatively fast onset and offset kinetics. In dog midmyocardial preparations the drug did not exert statistically significant effect on repolarization at 10 μM, although a tendency toward prolongation was observed at 20 μM. A moderate lengthening of APD(90) by ranolazine was noticed in canine atrial preparations obtained from dogs in sinus rhythm and in tachypacing induced remodelled preparations. Use-dependent depression of V(max) was more pronounced in atria from dogs in sinus rhythm than those in remodelled atria or in the ventricle. These findings indicate that ranolazine, in addition to its known late sodium current blocking effect, also depresses peak I(Na) with class I/B antiarrhythmic characteristics. Although peak I(Na) inhibition by ranolazine is stronger in the atria, it is also substantial (at fast stimulation frequencies) in ventricular preparations. Ranolazine also decreased the dispersion of ventricular repolarization (the difference in APD(90) values between Purkinje fibres and papillary muscles), which can contribute to the antiarrhythmic property of the drug.
Collapse
Affiliation(s)
- Tamás Szél
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Hungary
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Antzelevitch C, Burashnikov A, Sicouri S, Belardinelli L. Electrophysiologic basis for the antiarrhythmic actions of ranolazine. Heart Rhythm 2011; 8:1281-90. [PMID: 21421082 DOI: 10.1016/j.hrthm.2011.03.045] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 03/11/2011] [Indexed: 12/19/2022]
Abstract
Ranolazine is a Food and Drug Administration-approved antianginal agent. Experimental and clinical studies have shown that ranolazine has antiarrhythmic effects in both ventricles and atria. In the ventricles, ranolazine can suppress arrhythmias associated with acute coronary syndrome, long QT syndrome, heart failure, ischemia, and reperfusion. In atria, ranolazine effectively suppresses atrial tachyarrhythmias and atrial fibrillation (AF). Recent studies have shown that the drug may be effective and safe in suppressing AF when used as a pill-in-the pocket approach, even in patients with structurally compromised hearts, warranting further study. The principal mechanism underlying ranolazine's antiarrhythmic actions is thought to be primarily via inhibition of late I(Na) in the ventricles and via use-dependent inhibition of peak I(Na) and I(Kr) in the atria. Short- and long-term safety of ranolazine has been demonstrated in the clinic, even in patients with structural heart disease. This review summarizes the available data regarding the electrophysiologic actions and antiarrhythmic properties of ranolazine in preclinical and clinical studies.
Collapse
|
38
|
Doshi AN, Idriss SF. Effect of resistive barrier location on the relationship between T-wave alternans and cellular repolarization alternans: a 1-D modeling study. J Electrocardiol 2011; 43:566-71. [PMID: 21040826 DOI: 10.1016/j.jelectrocard.2010.07.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Indexed: 10/18/2022]
Abstract
Structural inhomogeneities in cardiac tissue have been associated with increased cellular repolarization alternans in animal experiments and increased T-wave alternans (TWA) in clinical studies. However, the effect of structural inhomogeneities on the relationship between cellular alternans and TWA has not been thoroughly investigated. We created 1-dimensional multicellular fiber models with and without a resistive barrier in various fiber regions and paced each model to induce cellular alternans. The models demonstrate that a resistive barrier in one fiber region substantially alters cellular repolarization alternans throughout the fiber. A midmyocardial or subepicardial barrier increase both TWA amplitude and maximum cellular alternans magnitude, relative to a fiber without a barrier. In addition, a direct relationship exists between TWA amplitude and maximum cellular alternans magnitude, which was highly dependent on barrier location. These results suggest that the position of a structural inhomogeneity within the myocardium may have substantial effects on dynamic repolarization instability and arrhythmogenicity.
Collapse
Affiliation(s)
- Ashish N Doshi
- Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281, USA.
| | | |
Collapse
|
39
|
Salama G, Akar FG. Deciphering Arrhythmia Mechanisms - Tools of the Trade. Card Electrophysiol Clin 2011; 3:11-21. [PMID: 21572551 PMCID: PMC3093299 DOI: 10.1016/j.ccep.2010.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Pathophysiological remodeling of cardiac function occurs at multiple levels, spanning the spectrum from molecular and sub-cellular changes to those occurring at the organ-system levels. Of key importance to arrhythmias are changes in electrophysiological and calcium handling properties at the tissue level. In this review, we discuss how high-resolution optical action potential and calcium transient imaging has advanced our understanding of basic arrhythmia mechanisms associated with multiple cardiovascular disorders, including the long QT syndrome, heart failure, and ischemia-reperfusion injury. We focus on the role of repolarization gradients (section 1) and calcium mediated triggers (section 2) in the initiation and maintenance of complex arrhythmias in these settings.
Collapse
Affiliation(s)
- Guy Salama
- University of Pittsburgh, The Cardiovascular Institute, Pittsburgh, PA, 15261
| | - Fadi G. Akar
- Mount Sinai School of Medicine, New York, NY 10029, Tel: 212-241-9251; FAX: 212-241-4080
| |
Collapse
|
40
|
Suppression of re-entrant and multifocal ventricular fibrillation by the late sodium current blocker ranolazine. J Am Coll Cardiol 2011; 57:366-75. [PMID: 21232675 DOI: 10.1016/j.jacc.2010.07.045] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 07/06/2010] [Accepted: 07/17/2010] [Indexed: 12/16/2022]
Abstract
OBJECTIVES The purpose of this study was to test the hypothesis that the late Na current blocker ranolazine suppresses re-entrant and multifocal ventricular fibrillation (VF). BACKGROUND VF can be caused by either re-entrant or focal mechanism. METHODS Simultaneous voltage and intracellular Ca(+)² optical mapping of the left ventricular epicardial surface along with microelectrode recordings was performed in 24 isolated-perfused aged rat hearts. Re-entrant VF was induced by rapid pacing and multifocal VF by exposure to oxidative stress with 0.1 mM hydrogen peroxide (H₂O₂). RESULTS Rapid pacing induced sustained VF in 7 of 8 aged rat hearts, characterized by 2 to 4 broad propagating wavefronts. Ranolazine significantly (p < 0.05) reduced the maximum slope of action potential duration restitution curve and converted sustained to nonsustained VF lasting 24 ± 8 s in all 7 hearts. Exposure to H₂O₂ initiated early afterdepolarization (EAD)-mediated triggered activity that led to sustained VF in 8 out of 8 aged hearts. VF was characterized by multiple foci, appearing at an average of 6.8 ± 3.2 every 100 ms, which remained confined to a small area averaging 2.8 ± 0.85 mm² and became extinct after a mean of 43 ± 16 ms. Ranolazine prevented (when given before H₂O₂) and suppressed H₂O₂-mediated EADs by reducing the number of foci, causing VF to terminate in 8 out of 8 hearts. Simulations in 2-dimensional tissue with EAD-mediated multifocal VF showed progressive reduction in the number of foci and VF termination by blocking the late Na current. CONCLUSIONS Late Na current blockade with ranolazine is effective at suppressing both pacing-induced re-entrant VF and EAD-mediated multifocal VF.
Collapse
|
41
|
Wang X, Gao G, Guo K, Yarotskyy V, Huang C, Elmslie KS, Peterson BZ. Phospholemman modulates the gating of cardiac L-type calcium channels. Biophys J 2010; 98:1149-59. [PMID: 20371314 DOI: 10.1016/j.bpj.2009.11.032] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 11/17/2009] [Accepted: 11/18/2009] [Indexed: 10/19/2022] Open
Abstract
Ca(2+) entry through L-type calcium channels (Ca(V)1.2) is critical in shaping the cardiac action potential and initiating cardiac contraction. Modulation of Ca(V)1.2 channel gating directly affects myocyte excitability and cardiac function. We have found that phospholemman (PLM), a member of the FXYD family and regulator of cardiac ion transport, coimmunoprecipitates with Ca(V)1.2 channels from guinea pig myocytes, which suggests PLM is an endogenous modulator. Cotransfection of PLM in HEK293 cells slowed Ca(V)1.2 current activation at voltages near the threshold for activation, slowed deactivation after long and strong depolarizing steps, enhanced the rate and magnitude of voltage-dependent inactivation (VDI), and slowed recovery from inactivation. However, Ca(2+)-dependent inactivation was not affected. Consistent with slower channel closing, PLM significantly increased Ca(2+) influx via Ca(V)1.2 channels during the repolarization phase of a human cardiac action potential waveform. Our results support PLM as an endogenous regulator of Ca(V)1.2 channel gating. The enhanced VDI induced by PLM may help protect the heart under conditions such as ischemia or tachycardia where the channels are depolarized for prolonged periods of time and could induce Ca(2+) overload. The time and voltage-dependent slowed deactivation could represent a gating shift that helps maintain Ca(2+) influx during the cardiac action potential waveform plateau phase.
Collapse
Affiliation(s)
- Xianming Wang
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | | | | | | | | | | | | |
Collapse
|
42
|
Shah DP, Baez-Escudero JL, Weisberg IL, Beshai JF, Burke MC. Ranolazine safely decreases ventricular and atrial fibrillation in Timothy syndrome (LQT8). PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2010; 35:e62-4. [PMID: 20883512 DOI: 10.1111/j.1540-8159.2010.02913.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Long QT eight (LQT8), otherwise known as Timothy syndrome (TS), is a genetic disorder causing hyper-activation of the L-type calcium channel Cav 1.2. This calcium load and the resultant increase in the QT interval provide the substrate for ventricular arrhythmias. We previously presented a case in a patient with TS who had a profound decrease in his burden of ventricular arrhythmias after institution of an L-type calcium channel blocker. Although this patient's arrhythmia burden had decreased, he displayed an increasing burden of atrial fibrillation and still had bouts of ventricular fibrillation requiring defibrillator therapy. Basic research has recently shown that ranolazine, a multipotent ion-channel blocker, may be of benefit in patients with LQT8 syndrome. This case report details the decrease of atrial fibrillation and ventricular fibrillation events in our LQT8 patient with the addition of ranolazine.
Collapse
Affiliation(s)
- Dipak P Shah
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | | | | | | | | |
Collapse
|
43
|
|
44
|
Antoons G, Oros A, Beekman JDM, Engelen MA, Houtman MJC, Belardinelli L, Stengl M, Vos MA. Late na(+) current inhibition by ranolazine reduces torsades de pointes in the chronic atrioventricular block dog model. J Am Coll Cardiol 2010; 55:801-9. [PMID: 20170820 DOI: 10.1016/j.jacc.2009.10.033] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 09/23/2009] [Accepted: 10/05/2009] [Indexed: 11/28/2022]
Abstract
OBJECTIVES This study investigated whether ranolazine reduces dofetilide-induced torsades de pointes (TdP) in a model of long QT syndrome with down-regulated K(+) currents due to hypertrophic remodeling in the dog with chronic atrioventricular block (cAVB). BACKGROUND Ranolazine inhibits the late Na(+) current (I(NaL)) and is effective against arrhythmias in long QT3 syndromes despite its blocking properties of the rapid component of delayed rectifying potassium current. METHODS Ranolazine was administered to cAVB dogs before or after TdP induction with dofetilide and electrophysiological parameters were determined including beat-to-beat variability of repolarization (BVR). In single ventricular myocytes, effects of ranolazine were studied on I(NaL), action potential duration, and dofetilide-induced BVR and early afterdepolarizations. RESULTS After dofetilide, ranolazine reduced the number of TdP episodes from 10 +/- 3 to 3 +/- 1 (p < 0.05) and partially reversed the increase of BVR with no abbreviation of the dofetilide-induced QT prolongation. Likewise, pre-treatment with ranolazine, or using lidocaine as a specific Na(+) channel blocker, attenuated TdP, but failed to prevent dofetilide-induced increases in QT, BVR, and ectopic activity. In cAVB myocytes, ranolazine suppressed dofetilide-induced early afterdepolarizations in 25% of cells at 5 micromol/l, in 75% at 10 micromol/l, and in 100% at 15 micromol/l. At 5 micromol/l, ranolazine blocked 26 +/- 3% of tetrodotoxin-sensitive I(NaL), and 49 +/- 3% at 15 micromol/l. Despite a 54% reduction of I(NaL) amplitude in cAVB compared with control cells, I(NaL) inhibition by 5 micromol/l tetrodotoxin equally shortened relative action potential duration and completely abolished dofetilide-induced early afterdepolarizations. CONCLUSIONS Despite down-regulation of I(NaL) in remodeled cAVB hearts, ranolazine is antiarrhythmic against drug-induced TdP. The antiarrhythmic effects are reflected in concomitant changes of BVR.
Collapse
Affiliation(s)
- Gudrun Antoons
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, University of Utrecht, Utrecht, the Netherlands
| | | | | | | | | | | | | | | |
Collapse
|
45
|
A novel mechanism for the treatment of angina, arrhythmias, and diastolic dysfunction: inhibition of late I(Na) using ranolazine. J Cardiovasc Pharmacol 2010; 54:279-86. [PMID: 19333133 DOI: 10.1097/fjc.0b013e3181a1b9e7] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Inhibition of the persistent or late Na current (INa) using ranolazine (Ranexa) represents a novel mechanism of action that was approved in the United States in 2006 and only recently in the European Union for use in patients with stable angina pectoris. In general, myocardial ischemia is associated with reduced adenosine triphosphate fluxes and decreased energy supply, resulting in severe disturbances of intracellular ion homeostasis in cardiac myocytes. In the recent years, increased late INa was suggested to contribute to this phenomenon by elevating intracellular Na concentration with subsequent rise in diastolic Ca levels by means of the sarcolemmal Na-Ca exchange system. Ranolazine, a specific inhibitor of late INa, reduces Na influx and hence ameliorates disturbed Na and Ca homeostasis. This is associated with a symptomatic improvement of angina in patients unlike other antianginal drugs without affecting heart rate or systemic blood pressure as shown in placebo-controlled studies. Therefore, ranolazine is a useful new option for patients with chronic stable angina not only as an add-on therapy. New clinical and experimental studies even point to potential antiarrhythmic effects, beneficial effects in diastolic heart failure, and under hyperglycemic conditions. In the present article, the relevant pathophysiological concepts for the role of late INa inhibition are reviewed and the most recent data from basic studies and clinical trials are summarized.
Collapse
|
46
|
Farkas AS, Nattel S. Minimizing Repolarization-Related Proarrhythmic Risk in Drug Development and Clinical Practice. Drugs 2010; 70:573-603. [DOI: 10.2165/11535230-000000000-00000] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
47
|
Tadross MR, Ben Johny M, Yue DT. Molecular endpoints of Ca2+/calmodulin- and voltage-dependent inactivation of Ca(v)1.3 channels. ACTA ACUST UNITED AC 2010; 135:197-215. [PMID: 20142517 PMCID: PMC2828906 DOI: 10.1085/jgp.200910308] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ca2+/calmodulin- and voltage-dependent inactivation (CDI and VDI) comprise vital prototypes of Ca2+ channel modulation, rich with biological consequences. Although the events initiating CDI and VDI are known, their downstream mechanisms have eluded consensus. Competing proposals include hinged-lid occlusion of channels, selectivity filter collapse, and allosteric inhibition of the activation gate. Here, novel theory predicts that perturbations of channel activation should alter inactivation in distinctive ways, depending on which hypothesis holds true. Thus, we systematically mutate the activation gate, formed by all S6 segments within CaV1.3. These channels feature robust baseline CDI, and the resulting mutant library exhibits significant diversity of activation, CDI, and VDI. For CDI, a clear and previously unreported pattern emerges: activation-enhancing mutations proportionately weaken inactivation. This outcome substantiates an allosteric CDI mechanism. For VDI, the data implicate a “hinged lid–shield” mechanism, similar to a hinged-lid process, with a previously unrecognized feature. Namely, we detect a “shield” in CaV1.3 channels that is specialized to repel lid closure. These findings reveal long-sought downstream mechanisms of inactivation and may furnish a framework for the understanding of Ca2+ channelopathies involving S6 mutations.
Collapse
Affiliation(s)
- Michael R Tadross
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | | | | |
Collapse
|
48
|
Sicouri S, Burashnikov A, Belardinelli L, Antzelevitch C. Synergistic electrophysiologic and antiarrhythmic effects of the combination of ranolazine and chronic amiodarone in canine atria. Circ Arrhythm Electrophysiol 2009; 3:88-95. [PMID: 19952329 DOI: 10.1161/circep.109.886275] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Amiodarone and ranolazine have been characterized as inactivated- and activated-state blockers of cardiac sodium channel current (I(Na)), respectively, and shown to cause atrial-selective depression of I(Na)-related parameters. This study tests the hypothesis that their combined actions synergistically depress I(Na)-dependent parameters in atria but not ventricles. METHODS AND RESULTS The effects of acute ranolazine (5 to 10 micromol/L) were studied in coronary-perfused right atrial and left ventricular wedge preparations and superfused left atrial pulmonary vein sleeves isolated from chronic amiodarone-treated (40 mg/kg daily for 6 weeks) and untreated dogs. Floating and standard microelectrode techniques were used to record transmembrane action potentials. When studied separately, acute ranolazine and chronic amiodarone caused atrial-predominant depression of I(Na)-dependent parameters. Ranolazine produced a much greater reduction in V(max) and much greater increase in diastolic threshold of excitation and effective refractory period in atrial preparations isolated from amiodarone-treated versus untreated dogs, leading to a marked increase in postrepolarization refractoriness. The drug combination effectively suppressed triggered activity in pulmonary vein sleeves but produced relatively small changes in I(Na)-dependent parameters in the ventricle. Acetylcholine (0.5 micromol/L) and burst pacing induced atrial fibrillation in 100% of control atria, 75% of ranolazine-treated (5 micromol/L) atria, 16% of atria from amiodarone-treated dogs, and in 0% of atria from amiodarone-treated dogs exposed to 5 micromol/L ranolazine. CONCLUSIONS The combination of chronic amiodarone and acute ranolazine produces a synergistic use-dependent depression of I(Na)-dependent parameters in isolated canine atria, leading to a potent effect of the drug combination to prevent the induction of atrial fibrillation.
Collapse
|
49
|
Liao P, Soong TW. CaV1.2 channelopathies: from arrhythmias to autism, bipolar disorder, and immunodeficiency. Pflugers Arch 2009; 460:353-9. [PMID: 19916019 DOI: 10.1007/s00424-009-0753-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 10/22/2009] [Accepted: 10/23/2009] [Indexed: 11/28/2022]
Abstract
Mutations of human CaV1.2 channel gene were identified only recently. The gain-of-function mutations were found at two mutually exclusive exons in patients with Timothy syndrome (TS). These patients exhibit prolonged QT interval and lethal cardiac arrhythmias. In contrast, the loss-of-function mutations of CaV1.2 channel in patients with Brugada syndrome produce short QT interval that could result in sudden cardiac death. TS patients also suffer from multi-organ dysfunction that includes neurological disorder such as autism and mental retardation reflecting the wide tissue distribution of CaV1.2 channel. Mutations found on different mutually exclusive exons determine the severity of the disease. Unexpectedly, TS patients may develop recurrent infections and bronchitis that suggests a role of CaV1.2 channel in the immune system. Furthermore, recent reports revealed a linkage of CaV1.2 channel polymorphism with multiple central nervous system disorders including bipolar disorder, depression, and schizophrenia. Here, we will discuss how alternative splicing modulates CaV1.2 channelopathy and the role of CaV1.2 channel in both excitable and non-excitable tissues.
Collapse
Affiliation(s)
- Ping Liao
- National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433, Singapore.
| | | |
Collapse
|
50
|
Sicouri S, Glass A, Ferreiro M, Antzelevitch C. Transseptal dispersion of repolarization and its role in the development of Torsade de Pointes arrhythmias. J Cardiovasc Electrophysiol 2009; 21:441-7. [PMID: 19909385 DOI: 10.1111/j.1540-8167.2009.01641.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE This study was designed to quantitate transseptal dispersion of repolarization (DR) and delineate its role in arrhythmogenesis using the calcium agonist BayK 8644 to mimic the gain of function of calcium channel current responsible for Timothy syndrome. BACKGROUND Amplification of transmural dispersion of repolarization (TDR) has been shown to contribute to development of Torsade de Pointes (TdP) arrhythmias under long-QT conditions. METHODS An arterially perfused septal wedge preparation was developed via cannulation of the septal artery. Action potentials (APs) were recorded using floating microelectrodes together with a transseptal electrocardiogram (ECG). These data were compared to those recorded from arterially perfused canine left ventricular (LV) wedge preparations. RESULTS Under control conditions, the shortest AP duration measured at 90% repolarization (APD(90)) was observed in right ventricular (RV) endocardium (181.8 +/- 15 ms), APD(90) peaked close to midseptum (278.0 +/- 32 ms), and abbreviated again as LV endocardium was approached (207.3 +/- 9 ms). Transseptal DR averaged 106 +/- 24 ms and T(peak)-T(end) 84 +/- 7 ms (n = 6). TDR and T(peak)-T(end) recorded from LV wedge were 36 +/- 9 ms and 34 +/- 19 ms, respectively (n = 30). BayK 8644 increased transseptal DR to 123.2 +/- 35 ms (n = 5) and induced early and delayed afterdepolarizations (3/5), rate-dependent ST-T-wave alternans (5/5), and TdP arrhythmias (3/5). CONCLUSIONS Our data indicate that dispersion of repolarization across the interventricular septum is twice that of the LV free wall, predisposing to development of TdP under long-QT conditions. Our findings suggest that the coronary-perfused ventricular septal preparation may be a sensitive model in which to assess the potential arrhythmogenic effects of drugs and pathophysiological conditions.
Collapse
Affiliation(s)
- Serge Sicouri
- Masonic Medical Research Laboratory, Utica, New York 13501, USA.
| | | | | | | |
Collapse
|