1
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Favere K, Van Fraeyenhove J, Jacobs G, Bosman M, Eens S, De Sutter J, Miljoen H, Guns PJ, De Keulenaer GW, Segers VFM, Heidbuchel H. Cardiac electrophysiology studies in mice via the transjugular route: a comprehensive practical guide. Am J Physiol Heart Circ Physiol 2022; 323:H763-H773. [PMID: 36018757 DOI: 10.1152/ajpheart.00337.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac arrhythmias are associated with cardiovascular morbidity and mortality. Cardiac electrophysiology studies (EPS) use intracardiac catheter recording and stimulation for profound evaluation of the heart's electrical properties. The main clinical application is investigation and treatment of rhythm disorders. These techniques have been translated to the murine setting to open opportunities for detailed evaluation of the impact of different characteristics (including genetics) and interventions on cardiac electrophysiology and -pathology. Currently, a detailed description of the technique of murine transjugular EPS (which is the standard route of catheter introduction) is lacking. This article provides detailed information on EPS in mice via the transjugular route. This includes catheter placement, stimulation protocols, intracardiac tracing interpretation, artefact reduction and surface ECG recording. In addition, reference values as obtained in C57BL/6N mice are presented for common electrophysiological parameters. This detailed methodological description aims to increase accessibility and standardisation of EPS in mice. Ultimately, also human research and patient care may benefit from translation of the knowledge obtained in preclinical models using this technique.
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Affiliation(s)
- Kasper Favere
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium.,Research Group Cardiovascular Diseases, GENCOR, University of Antwerp, Antwerp, Belgium.,Department of Cardiology, Antwerp University Hospital, Antwerp, Belgium.,Department of Internal Medicine, Ghent University, Ghent, Belgium
| | - Jens Van Fraeyenhove
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium
| | - Griet Jacobs
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium
| | - Matthias Bosman
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium
| | - Sander Eens
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium.,Research Group Cardiovascular Diseases, GENCOR, University of Antwerp, Antwerp, Belgium
| | - Johan De Sutter
- Department of Internal Medicine, Ghent University, Ghent, Belgium
| | - Hielko Miljoen
- Department of Cardiology, Antwerp University Hospital, Antwerp, Belgium
| | - Pieter-Jan Guns
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium
| | - Gilles W De Keulenaer
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium.,Department of Cardiology, ZNA Middelheim Hospital, Antwerp, Belgium
| | - Vincent F M Segers
- Laboratory of Physiopharmacology, GENCOR, University of Antwerp, Antwerp, Belgium.,Research Group Cardiovascular Diseases, GENCOR, University of Antwerp, Antwerp, Belgium.,Department of Cardiology, Antwerp University Hospital, Antwerp, Belgium
| | - Hein Heidbuchel
- Research Group Cardiovascular Diseases, GENCOR, University of Antwerp, Antwerp, Belgium.,Department of Cardiology, Antwerp University Hospital, Antwerp, Belgium
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2
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Abstract
Advances in population-scale genomic sequencing have greatly expanded the understanding of the inherited basis of cardiovascular disease (CVD). Reanalysis of these genomic datasets identified an unexpected risk factor for CVD, somatically acquired DNA mutations. In this review, we provide an overview of somatic mutations and their contributions to CVD. We focus on the most common and well-described manifestation, clonal hematopoiesis of indeterminate potential. We also review the currently available data regarding how somatic mutations lead to tissue mosaicism in various forms of CVD, including atrial fibrillation and aortic aneurism associated with Marfan Syndrome. Finally, we highlight future research directions given current knowledge gaps and consider how technological advances will enhance the discovery of somatic mutations in CVD and management of patients with somatic mutations.
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Affiliation(s)
- J. Brett Heimlich
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center
| | - Alexander G. Bick
- Department of Medicine, Division of Genetic Medicine, Vanderbilt University Medical Center
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3
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Leiss V, Reisinger E, Speidel A, Beer-Hammer S, Nürnberg B. Analyses of Gnai3-iresGFP reporter mice reveal unknown Gα i3 expression sites. Sci Rep 2021; 11:14271. [PMID: 34253772 PMCID: PMC8275620 DOI: 10.1038/s41598-021-93591-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/21/2021] [Indexed: 12/01/2022] Open
Abstract
Inhibitory G proteins (Gi proteins) are highly homologous but play distinct biological roles. However, their isoform-specific detection remains challenging. To facilitate the analysis of Gαi3 expression, we generated a Gnai3- iresGFP reporter mouse line. An internal ribosomal entry site (IRES) was inserted behind the stop-codon of the Gnai3 gene to initiate simultaneous translation of the GFP cDNA together with Gαi3. The expression of GFP was confirmed in spleen and thymus tissue by immunoblot analysis. Importantly, the GFP knock-in (ki) did not alter Gαi3 expression levels in all organs tested including spleen and thymus compared to wild-type littermates. Flow cytometry of thymocytes, splenic and blood cell suspensions revealed significantly higher GFP fluorescence intensities in homozygous ki/ki animals compared to heterozygous mice (+/ki). Using cell-type specific surface markers GFP fluorescence was assigned to B cells, T cells, macrophages and granulocytes from both splenic and blood cells and additionally blood-derived platelets. Moreover, immunofluorescent staining of the inner ear from knock-in mice unraveled GFP expression in sensory and non-sensory cell types, with highest levels in Deiter’s cells and in the first row of Hensen’s cells in the organ of Corti, indicating a novel site for Gαi3 expression. In summary, the Gnai3- iresGFP reporter mouse represents an ideal tool for precise analyses of Gαi3 expression patterns and sites.
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Affiliation(s)
- Veronika Leiss
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, 72074, Tübingen, Germany
| | - Ellen Reisinger
- Department of Otolaryngology-Head and Neck Surgery, Gene Therapy for Hearing Impairment Group, University of Tübingen, Medical Center, Elfriede-Aulhorn-Straße 5, 72076, Tübingen, Germany
| | - Annika Speidel
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, 72074, Tübingen, Germany
| | - Sandra Beer-Hammer
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, 72074, Tübingen, Germany.
| | - Bernd Nürnberg
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, 72074, Tübingen, Germany
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4
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Sebastian S, Nobles M, Tsisanova E, Ludwig A, Munroe PB, Tinker A. The role of resistance to inhibitors of cholinesterase 8b in the control of heart rate. Physiol Genomics 2021; 53:150-159. [PMID: 33719582 DOI: 10.1152/physiolgenomics.00157.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have assessed the role of ric-b8 in the control of heart rate after the gene was implicated in a recent genome-wide association study of resting heart rate. We developed a novel murine model in which it was possible to conditionally delete ric-8b in the sinoatrial (SA) node after the addition of tamoxifen. Despite this, we were unable to obtain homozygotes and thus studied heterozygotes. Haploinsufficiency of ric-8b in the sinoatrial node induced by the addition of tamoxifen in adult animals leads to mice with a reduced heart rate. However, other electrocardiographic intervals (e.g., PR and QRS) were normal, and there was no apparent arrhythmia such as heart block. The positive chronotropic response to isoprenaline was abrogated, whereas the response to carbachol was unchanged. The pacemaker current If (funny current) has an important role in regulating heart rate, and its function is modulated by both isoprenaline and carbachol. Using a heterologous system expressing HCN4, we show that ric-8b can modulate the HCN4 current. Overexpression of ric-8b led to larger HCN4 currents, whereas silencing ric-8b led to smaller currents. Ric-8b modulates heart rate responses in vivo likely via its actions on the stimulatory G-protein.
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Affiliation(s)
- Sonia Sebastian
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Muriel Nobles
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Elena Tsisanova
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Andreas Ludwig
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Patricia B Munroe
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Andrew Tinker
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
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5
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A modified approach for programmed electrical stimulation in mice: Inducibility of ventricular arrhythmias. PLoS One 2018; 13:e0201910. [PMID: 30133474 PMCID: PMC6104969 DOI: 10.1371/journal.pone.0201910] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 07/24/2018] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Electrophysiological studies in mice, the prevailing model organism in the field of basic cardiovascular research, are impeded by the low yield of programmed electrical stimulation (PES). OBJECTIVE To investigate a modified approach for ventricular arrhythmia (VA) induction and a novel scoring system in mice. METHOD A systematic review of literature on current methods for PES in mice searching the PubMed database revealed that VA inducibility was low and ranged widely (4.6 ± 10.7%). Based on this literature review, a modified PES protocol with 3 to 10 extrastimuli was developed and tested in comparison to the conventional PES protocol using up to 3 extrastimuli in anesthetized wildtype mice (C57BL/6J, n = 12). Induced VA, classified according to the Lambeth Convention, were assessed by established arrhythmia scores as well as a novel arrhythmia score based on VA duration. RESULTS PES with the modified approach raised both the occurrence and the duration of VA compared to conventional PES (0% vs 50%; novel VA score p = 0.0002). Particularly, coupling of >6 extrastimuli raised the induction of VA. Predominantly, premature ventricular complexes (n = 6) and ventricular tachycardia <1s (n = 4) were observed. Repeated PES after adrenergic stimulation using isoprenaline resulted in enhanced induction of ventricular tachycardia <1s in both protocols. CONCLUSION Our findings suggest that the presented approach of modified PES enables effective induction and quantification of VA in wildtype mice and may well be suited to document and evaluate detailed VA characteristics in mice.
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Nobles M, Montaigne D, Sebastian S, Birnbaumer L, Tinker A. Differential effects of inhibitory G protein isoforms on G protein-gated inwardly rectifying K + currents in adult murine atria. Am J Physiol Cell Physiol 2018; 314:C616-C626. [PMID: 29342363 DOI: 10.1152/ajpcell.00271.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
G protein-gated inwardly rectifying K+ (GIRK) channels are the major inwardly rectifying K+ currents in cardiac atrial myocytes and an important determinant of atrial electrophysiology. Inhibitory G protein α-subunits can both mediate activation via acetylcholine but can also suppress basal currents in the absence of agonist. We studied this phenomenon using whole cell patch clamping in murine atria from mice with global genetic deletion of Gαi2, combined deletion of Gαi1/Gαi3, and littermate controls. We found that mice with deletion of Gαi2 had increased basal and agonist-activated currents, particularly in the right atria while in contrast those with Gαi1/Gαi3 deletion had reduced currents. Mice with global genetic deletion of Gαi2 had decreased action potential duration. Tissue preparations of the left atria studied with a multielectrode array from Gαi2 knockout mice showed a shorter effective refractory period, with no change in conduction velocity, than littermate controls. Transcriptional studies revealed increased expression of GIRK channel subunit genes in Gαi2 knockout mice. Thus different G protein isoforms have differential effects on GIRK channel behavior and paradoxically Gαi2 act to increase basal and agonist-activated GIRK currents. Deletion of Gαi2 is potentially proarrhythmic in the atria.
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Affiliation(s)
- Muriel Nobles
- The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry , London , United Kingdom
| | - David Montaigne
- Centre Hospitalier Régional Universitaire de Lille , Lille , France.,Université Lille 2 , Lille , France.,Institut National de la Santé et de la Recherche Médicale, U1011, Lille , France.,European Genomic Institute for Diabetes , Lille , France.,Institut Pasteur de Lille , Lille , France
| | - Sonia Sebastian
- The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry , London , United Kingdom
| | - Lutz Birnbaumer
- Division of Intramural Research, National Institute of Environmental Health Sciences , Research Triangle Park, North Carolina.,Institute of Biomedical Research, Catholic University of Argentina , Buenos Aires , Argentina
| | - Andrew Tinker
- The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry , London , United Kingdom
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7
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Lane JD, Tinker A. Have the Findings from Clinical Risk Prediction and Trials Any Key Messages for Safety Pharmacology? Front Physiol 2017; 8:890. [PMID: 29163223 PMCID: PMC5681497 DOI: 10.3389/fphys.2017.00890] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 10/20/2017] [Indexed: 01/28/2023] Open
Abstract
Anti-arrhythmic drugs are a mainstay in the management of symptoms related to arrhythmias, and are adjuncts in prevention and treatment of life-threatening ventricular arrhythmias. However, they also have the potential for pro-arrhythmia and thus the prediction of arrhythmia predisposition and drug response are critical issues. Clinical trials are the latter stages in the safety testing and efficacy process prior to market release, and as such serve as a critical safeguard. In this review, we look at some of the lessons to be learned from approaches to arrhythmia prediction in patients, clinical trials of drugs used in the treatment of arrhythmias, and the implications for the design of pre-clinical safety pharmacology testing.
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Affiliation(s)
- Jem D Lane
- William Harvey Heart Centre, Barts and The London School of Medicine and Dentistry, London, United Kingdom.,Department of Cardiac Electrophysiology, Barts Heart Centre, St Bartholomew's Hospital, London, United Kingdom
| | - Andrew Tinker
- William Harvey Heart Centre, Barts and The London School of Medicine and Dentistry, London, United Kingdom
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8
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Lane JD, Montaigne D, Tinker A. Tissue-Level Cardiac Electrophysiology Studied in Murine Myocardium Using a Microelectrode Array: Autonomic and Thermal Modulation. J Membr Biol 2017; 250:471-481. [PMID: 28766006 PMCID: PMC5613071 DOI: 10.1007/s00232-017-9973-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 07/25/2017] [Indexed: 01/01/2023]
Abstract
Cardiac electrophysiology is regulated by the autonomic nervous system, and this has both pathophysiological, and possibly therapeutic importance. Furthermore, chamber differences in electrophysiology exist between atria and ventricles, yet there have been few direct comparisons. There is substantial literature on ion channel modulation at the single-cell level but less work on how this affects tissue-level parameters. We used a microelectrode array system to explore these issues using murine atrial and ventricular tissue slices. Activation time, conduction velocity and repolarisation were measured, and their modulation by temperature and pharmacological autonomic agonists were assessed. The system recorded reliable measurements under control conditions in the absence of drug/thermal challenge, and significant baseline differences were found in chamber electrophysiology. The sodium channel blocker mexiletine, produced large magnitude changes in all three measured parameters. Carbachol and isoprenaline induced differing effects in atria and ventricles, whereas temperature produced similar effects on activation and repolarisation.
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Affiliation(s)
- Jem D Lane
- William Harvey Heart Centre, Barts & The London School of Medicine and Dentistry, London, UK
| | - David Montaigne
- William Harvey Heart Centre, Barts & The London School of Medicine and Dentistry, London, UK.,Department of Cardiac Functional Investigations, CHU Lille, 59000, Lille, France.,Univ. Lille, 59000, Lille, France.,Inserm, UMR 1011, 59000, Lille, France.,Institut Pasteur de Lille, Lille, France.,European Genomic Institute for Diabetes (E.G.I.D.), FR 3508, 59000, Lille, France
| | - Andrew Tinker
- William Harvey Heart Centre, Barts & The London School of Medicine and Dentistry, London, UK.
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9
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Zhang D, Tu H, Wang C, Cao L, Muelleman RL, Wadman MC, Li YL. Correlation of Ventricular Arrhythmogenesis with Neuronal Remodeling of Cardiac Postganglionic Parasympathetic Neurons in the Late Stage of Heart Failure after Myocardial Infarction. Front Neurosci 2017; 11:252. [PMID: 28533740 PMCID: PMC5420597 DOI: 10.3389/fnins.2017.00252] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Accepted: 04/20/2017] [Indexed: 01/06/2023] Open
Abstract
Introduction: Ventricular arrhythmia is a major cause of sudden cardiac death in patients with chronic heart failure (CHF). Our recent study demonstrates that N-type Ca2+ currents in intracardiac ganglionic neurons are reduced in the late stage of CHF rats. Rat intracardiac ganglia are divided into the atrioventricular ganglion (AVG) and sinoatrial ganglion. Only AVG nerve terminals innervate the ventricular myocardium. In this study, we tested the correlation of electrical remodeling in AVG neurons with ventricular arrhythmogenesis in CHF rats. Methods and Results: CHF was induced in male Sprague-Dawley rats by surgical ligation of the left coronary artery. The data from 24-h continuous radiotelemetry ECG recording in conscious rats showed that ventricular tachycardia/fibrillation (VT/VF) occurred in 3 and 14-week CHF rats but not 8-week CHF rats. Additionally, as an index for vagal control of ventricular function, changes of left ventricular systolic pressure (LVSP) and the maximum rate of left ventricular pressure rise (LV dP/dtmax) in response to vagal efferent nerve stimulation were blunted in 14-week CHF rats but not 3 or 8-week CHF rats. Results from whole-cell patch clamp recording demonstrated that N-type Ca2+ currents in AVG neurons began to decrease in 8-week CHF rats, and that there was also a significant decrease in 14-week CHF rats. Correlation analysis revealed that N-type Ca2+ currents in AVG neurons negatively correlated with the cumulative duration of VT/VF in 14-week CHF rats, whereas there was no correlation between N-type Ca2+ currents in AVG neurons and the cumulative duration of VT/VF in 3-week CHF. Conclusion: Malignant ventricular arrhythmias mainly occur in the early and late stages of CHF. Electrical remodeling of AVG neurons highly correlates with the occurrence of ventricular arrhythmias in the late stage of CHF.
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Affiliation(s)
- Dongze Zhang
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Huiyin Tu
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Chaojun Wang
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA.,Department of Cardiovascular Disease, The First Affiliated Hospital of Xi'an Jiaotong UniversityXi'an, China
| | - Liang Cao
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA.,Department of Cardiac Surgery, Second Xiangya Hospital, Central South UniversityChangsha, China
| | - Robert L Muelleman
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Michael C Wadman
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Yu-Long Li
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA.,Department of Cellular & Integrative Physiology, University of Nebraska Medical CenterOmaha, NE, USA
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10
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Ang R, Abramowitz J, Birnbaumer L, Gourine AV, Tinker A. The role of GαO-mediated signaling in the rostral ventrolateral medulla oblongata in cardiovascular reflexes and control of cardiac ventricular excitability. Physiol Rep 2017; 4:4/15/e12860. [PMID: 27528004 PMCID: PMC4985541 DOI: 10.14814/phy2.12860] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 06/20/2016] [Indexed: 12/02/2022] Open
Abstract
The heart is controlled by the sympathetic and parasympathetic limbs of the autonomic nervous system with inhibitory signaling mechanisms recruited in both limbs. The aim of this study was to determine the role of inhibitory heterotrimeric G proteins in the central nervous mechanisms underlying autonomic control of the heart and its potential role in arrhythmogenesis. Mice with conditional deletion of the inhibitory heterotrimeric G protein GαO in the presympathetic area of the rostral ventral lateral medulla (RVLM) were generated to determine the role of GαO‐mediated signalling in autonomic control and electrophysiological properties of the heart. GαO deletion within the RVLM was not associated with changes in heart rate (HR) or the arterial blood pressure at rest (home cage, normal behavior). However, exposure to stressful conditions (novel environment, hypoxia, or hypercapnia) in these mice was associated with abnormal HR responses and an increased baroreflex gain when assessed under urethane anesthesia. This was associated with shortening of the ventricular effective refractory period. This phenotype was reversed by systemic beta‐adrenoceptor blockade, suggesting that GαO depletion in the RVLM increases central sympathetic drive. The data obtained support the hypothesis that GαO‐mediated signaling within the presympathetic circuits of the RVLM contributes to the autonomic control of the heart. GαO deficiency in the RVLM has a significant impact on cardiovascular responses to stress, cardiovascular reflexes and electrical properties of the heart.
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Affiliation(s)
- Richard Ang
- William Harvey Heart Centre, Barts & The London School of Medicine and Dentistry, London, UK Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Joel Abramowitz
- Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Lutz Birnbaumer
- Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Alexander V Gourine
- William Harvey Heart Centre, Barts & The London School of Medicine and Dentistry, London, UK
| | - Andrew Tinker
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
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11
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Bissinger R, Lang E, Ghashghaeinia M, Singh Y, Zelenak C, Fehrenbacher B, Honisch S, Chen H, Fakhri H, Umbach AT, Liu G, Rexhepaj R, Liu G, Schaller M, Mack AF, Lupescu A, Birnbaumer L, Lang F, Qadri SM. Blunted apoptosis of erythrocytes in mice deficient in the heterotrimeric G-protein subunit Gαi2. Sci Rep 2016; 6:30925. [PMID: 27499046 PMCID: PMC4976336 DOI: 10.1038/srep30925] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 07/11/2016] [Indexed: 01/09/2023] Open
Abstract
Putative functions of the heterotrimeric G-protein subunit Gαi2-dependent signaling include ion channel regulation, cell differentiation, proliferation and apoptosis. Erythrocytes may, similar to apoptosis of nucleated cells, undergo eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine (PS) exposure. Eryptosis may be triggered by increased cytosolic Ca2+ activity and ceramide. In the present study, we show that Gαi2 is expressed in both murine and human erythrocytes and further examined the survival of erythrocytes drawn from Gαi2-deficient mice (Gαi2−/−) and corresponding wild-type mice (Gαi2+/+). Our data show that plasma erythropoietin levels, erythrocyte maturation markers, erythrocyte counts, hematocrit and hemoglobin concentration were similar in Gαi2−/− and Gαi2+/+ mice but the mean corpuscular volume was significantly larger in Gαi2−/− mice. Spontaneous PS exposure of circulating Gαi2−/− erythrocytes was significantly lower than that of circulating Gαi2+/+ erythrocytes. PS exposure was significantly lower in Gαi2−/− than in Gαi2+/+ erythrocytes following ex vivo exposure to hyperosmotic shock, bacterial sphingomyelinase or C6 ceramide. Erythrocyte Gαi2 deficiency further attenuated hyperosmotic shock-induced increase of cytosolic Ca2+ activity and cell shrinkage. Moreover, Gαi2−/− erythrocytes were more resistant to osmosensitive hemolysis as compared to Gαi2+/+ erythrocytes. In conclusion, Gαi2 deficiency in erythrocytes confers partial protection against suicidal cell death.
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Affiliation(s)
- Rosi Bissinger
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Elisabeth Lang
- Department of Gastroenterology, Hepatology and Infectious Diseases, University of Duesseldorf, Germany
| | - Mehrdad Ghashghaeinia
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Yogesh Singh
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Christine Zelenak
- Department of Internal Medicine, Charité Medical University, Berlin, Germany
| | | | - Sabina Honisch
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Hong Chen
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Hajar Fakhri
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Anja T Umbach
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Guilai Liu
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Rexhep Rexhepaj
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany.,Institute of Biochemistry and Molecular Biology, University of Bonn, Germany
| | - Guoxing Liu
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | | | | | - Adrian Lupescu
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Lutz Birnbaumer
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC, USA
| | - Florian Lang
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany
| | - Syed M Qadri
- Institute of Cardiology, Vascular Medicine and Physiology, University of Tuebingen, Germany.,Institute of Biomedical Research (BIOMED), School of Medical Sciences, Catholic University of Argentina, Buenos Aires, Argentina.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
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12
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Gourine AV, Machhada A, Trapp S, Spyer KM. Cardiac vagal preganglionic neurones: An update. Auton Neurosci 2016; 199:24-8. [DOI: 10.1016/j.autneu.2016.06.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 06/17/2016] [Indexed: 01/06/2023]
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Opel A, Nobles M, Montaigne D, Finlay M, Anderson N, Breckenridge R, Tinker A. Absence of the Regulator of G-protein Signaling, RGS4, Predisposes to Atrial Fibrillation and Is Associated with Abnormal Calcium Handling. J Biol Chem 2015; 290:19233-44. [PMID: 26088132 PMCID: PMC4521044 DOI: 10.1074/jbc.m115.666719] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 06/15/2015] [Indexed: 01/11/2023] Open
Abstract
The description of potential molecular substrates for predisposition to atrial fibrillation (AF) is incomplete, and it is unknown what role regulators of G-protein signaling might play. We address whether the attenuation of RGS4 function may promote AF and the mechanism through which this occurs. For this purpose, we studied a mouse with global genetic deletion of RGS4 (RGS4(-/-)) and the normal littermate controls (RGS4(+/+)). In vivo electrophysiology using atrial burst pacing revealed that mice with global RGS4 deletion developed AF more frequently than control littermates. Isolated atrial cells from RGS4(-/-) mice show an increase in Ca(2+) spark frequency under basal conditions and after the addition of endothelin-1 and abnormal spontaneous Ca(2+) release events after field stimulation. Isolated left atria studied on a multielectrode array revealed modest changes in path length for re-entry but abnormal electrical events after a pacing train in RGS4(-/-) mice. RGS4 deletion results in a predisposition to atrial fibrillation from enhanced activity in the Gαq/11-IP3 pathway, resulting in abnormal Ca(2+) release and corresponding electrical events.
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Affiliation(s)
- Aaisha Opel
- From the British Heart Foundation Laboratories, Department of Medicine, University College London, Rayne Institute, London WC1E 6JJ, United Kingdom and the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Muriel Nobles
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - David Montaigne
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Malcolm Finlay
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Naomi Anderson
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Ross Breckenridge
- From the British Heart Foundation Laboratories, Department of Medicine, University College London, Rayne Institute, London WC1E 6JJ, United Kingdom and
| | - Andrew Tinker
- From the British Heart Foundation Laboratories, Department of Medicine, University College London, Rayne Institute, London WC1E 6JJ, United Kingdom and the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
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14
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Machhada A, Ang R, Ackland GL, Ninkina N, Buchman VL, Lythgoe MF, Trapp S, Tinker A, Marina N, Gourine AV. Control of ventricular excitability by neurons of the dorsal motor nucleus of the vagus nerve. Heart Rhythm 2015; 12:2285-93. [PMID: 26051529 PMCID: PMC4631809 DOI: 10.1016/j.hrthm.2015.06.005] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Indexed: 01/09/2023]
Abstract
BACKGROUND The central nervous origins of functional parasympathetic innervation of cardiac ventricles remain controversial. OBJECTIVE This study aimed to identify a population of vagal preganglionic neurons that contribute to the control of ventricular excitability. An animal model of synuclein pathology relevant to Parkinson's disease was used to determine whether age-related loss of the activity of the identified group of neurons is associated with changes in ventricular electrophysiology. METHODS In vivo cardiac electrophysiology was performed in anesthetized rats in conditions of selective inhibition of the dorsal vagal motor nucleus (DVMN) neurons by pharmacogenetic approach and in mice with global genetic deletion of all family members of the synuclein protein. RESULTS In rats anesthetized with urethane (in conditions of systemic beta-adrenoceptor blockade), muscarinic and neuronal nitric oxide synthase blockade confirmed the existence of a tonic parasympathetic control of cardiac excitability mediated by the actions of acetylcholine and nitric oxide. Acute DVMN silencing led to shortening of the ventricular effective refractory period (vERP), a lowering of the threshold for triggered ventricular tachycardia, and prolongation of the corrected QT (QTc) interval. Lower resting activity of the DVMN neurons in aging synuclein-deficient mice was found to be associated with vERP shortening and QTc interval prolongation. CONCLUSION Activity of the DVMN vagal preganglionic neurons is responsible for tonic parasympathetic control of ventricular excitability, likely to be mediated by nitric oxide. These findings provide the first insight into the central nervous substrate that underlies functional parasympathetic innervation of the ventricles and highlight its vulnerability in neurodegenerative diseases.
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Affiliation(s)
- Asif Machhada
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom; Centre for Advanced Biomedical Imaging, University College London, London, United Kingdom
| | - Richard Ang
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom; William Harvey Heart Centre, Barts & The London School of Medicine and Dentistry, London, United Kingdom
| | - Gareth L Ackland
- Department of Medicine, University College London, London, United Kingdom
| | - Natalia Ninkina
- School of Biosciences, University of Cardiff, Cardiff, United Kingdom
| | | | - Mark F Lythgoe
- Centre for Advanced Biomedical Imaging, University College London, London, United Kingdom
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Andrew Tinker
- William Harvey Heart Centre, Barts & The London School of Medicine and Dentistry, London, United Kingdom
| | - Nephtali Marina
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
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Cheung JW, Ip JE, Yarlagadda RK, Liu CF, Thomas G, Xu L, Wilkes D, Markowitz SM, Lerman BB. Adenosine-insensitive right ventricular tachycardia: Novel variant of idiopathic outflow tract tachycardia. Heart Rhythm 2014; 11:1770-8. [DOI: 10.1016/j.hrthm.2014.06.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Indexed: 11/16/2022]
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Posokhova E, Ng D, Opel A, Masuho I, Tinker A, Biesecker LG, Wickman K, Martemyanov KA. Essential role of the m2R-RGS6-IKACh pathway in controlling intrinsic heart rate variability. PLoS One 2013; 8:e76973. [PMID: 24204714 PMCID: PMC3812209 DOI: 10.1371/journal.pone.0076973] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/05/2013] [Indexed: 11/18/2022] Open
Abstract
Normal heart function requires generation of a regular rhythm by sinoatrial pacemaker cells and the alteration of this spontaneous heart rate by the autonomic input to match physiological demand. However, the molecular mechanisms that ensure consistent periodicity of cardiac contractions and fine tuning of this process by autonomic system are not completely understood. Here we examined the contribution of the m2R-IKACh intracellular signaling pathway, which mediates the negative chronotropic effect of parasympathetic stimulation, to the regulation of the cardiac pacemaking rhythm. Using isolated heart preparations and single-cell recordings we show that the m2R-IKACh signaling pathway controls the excitability and firing pattern of the sinoatrial cardiomyocytes and determines variability of cardiac rhythm in a manner independent from the autonomic input. Ablation of the major regulator of this pathway, Rgs6, in mice results in irregular cardiac rhythmicity and increases susceptibility to atrial fibrillation. We further identify several human subjects with variants in the RGS6 gene and show that the loss of function in RGS6 correlates with increased heart rate variability. These findings identify the essential role of the m2R-IKACh signaling pathway in the regulation of cardiac sinus rhythm and implicate RGS6 in arrhythmia pathogenesis.
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Affiliation(s)
- Ekaterina Posokhova
- Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - David Ng
- Genetic Diseases Research Branch, National Human Genome Research Institute, Bethesda, Maryland, United States of America
| | - Aaisha Opel
- Department of Medicine, University College London, London, United Kingdom
| | - Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Andrew Tinker
- The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Charterhouse Square, London, United Kingdom
| | - Leslie G. Biesecker
- Genetic Diseases Research Branch, National Human Genome Research Institute, Bethesda, Maryland, United States of America
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Kirill A. Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida, United States of America
- * E-mail:
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17
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Ward JA, Esa N, Pidikiti R, Freedman JE, Keaney JF, Tanriverdi K, Vitseva O, Ambros V, Lee R, McManus DD. Circulating Cell and Plasma microRNA Profiles Differ between Non-ST-Segment and ST-Segment-Elevation Myocardial Infarction. ACTA ACUST UNITED AC 2013; 2:108. [PMID: 24432306 PMCID: PMC3890357 DOI: 10.4172/2327-4972.1000108] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Differences in plasma and whole blood expression microRNAs (miRNAs) in patients with an acute coronary syndrome (ACS) have been determined in both in vitro and in vivo studies. Although most circulating miRNAs are located in the cellular components of whole blood, little is known about the miRNA profiles of whole blood subcomponents, including plasma, platelets and leukocytes in patients with myocardial ischemia. METHODS Thirteen patients with a ST-segment-elevation (STEMI) or non-ST-segment elevation (NSTEMI) myocardial infarction were identified in the University of Massachusetts Medical Center Emergency Department (ED) or cardiac catheterization laboratory between February and June of 2012. Whole blood was obtained from arterial blood samples at the time of cardiac catheterization and cell-specific miRNA profiling was performed. Expression of 343 miRNAs was quantified from whole blood, plasma, platelets, and peripheral blood mononuclear cells using a high-throughput, quantitative Real-Time polymerase-chain reaction system (qRT-PCR). RESULTS MiRNAs associated with STEMI as compared to NSTEMI patients included miR-25-3p, miR-221-3p, and miR-374b-5p. MiRNA 30d-5p was associated with plasma, platelets, and leukocytes in both STEMI and NSTEMI patients; miRNAs 221-3p and 483-5p were correlated with plasma and platelets only in NSTEMI patients. CONCLUSIONS Cell-specific miRNA profiles differed between patients with STEMI and NSTEMI. The miRNA distribution is also unique amongst plasma, platelets, and leukocytes in patients with ischemic heart disease or ACS. Our findings suggest unique miRNA profiles among the circulating subcomponents in patients presenting with myocardial ischemia.
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Affiliation(s)
- Jeanine A Ward
- Department of Emergency Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Nada Esa
- Cardiac Electrophysiology Section, Cardiovascular Medicine Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Rahul Pidikiti
- Cardiac Electrophysiology Section, Cardiovascular Medicine Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jane E Freedman
- Cardiac Electrophysiology Section, Cardiovascular Medicine Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - John F Keaney
- Cardiac Electrophysiology Section, Cardiovascular Medicine Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Kahraman Tanriverdi
- Cardiac Electrophysiology Section, Cardiovascular Medicine Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Olga Vitseva
- Cardiac Electrophysiology Section, Cardiovascular Medicine Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Victor Ambros
- Department of Molecular Biology, University of Massachusetts Medical School, Worcester, MA USA
| | - Rosalind Lee
- Department of Molecular Biology, University of Massachusetts Medical School, Worcester, MA USA
| | - David D McManus
- Cardiac Electrophysiology Section, Cardiovascular Medicine Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA ; Department of Quantitative Health Sciences, University of Massachusetts, Medical School, Worcester, MA, USA ; Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA, USA
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18
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Hussain RI, Aronsen JM, Afzal F, Sjaastad I, Osnes JB, Skomedal T, Levy FO, Krobert KA. The functional activity of inhibitory G protein (G(i)) is not increased in failing heart ventricle. J Mol Cell Cardiol 2012; 56:129-38. [PMID: 23220156 DOI: 10.1016/j.yjmcc.2012.11.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 11/22/2012] [Accepted: 11/24/2012] [Indexed: 11/16/2022]
Abstract
Beta-adrenergic receptor (βAR) inotropic effects are attenuated and muscarinic receptor-mediated inhibition thereof is enhanced in heart failure. We investigated if increased G(i) activity contributes to attenuated βAR-inotropic effects and potentiates muscarinic accentuated antagonism in failing rat ventricle. Contractility was measured in ventricular strips and adenylyl cyclase (AC) activity in ventricular membranes from rats with post-infarction heart failure (HF) or Sham-operated controls (Sham). The maximal βAR-mediated inotropic effect of isoproterenol was reduced by ~70% and basal, βAR- & forskolin-stimulated AC activity was significantly lower in HF vs. Sham. Carbachol-evoked antagonism of the βAR-mediated inotropic response was complete only in HF despite a ~40% reduction in the ability of carbachol to inhibit βAR-stimulated AC. However, neither the relative efficacy (contractility decreased by ~46%) nor the potency of carbachol to inhibit the βAR inotropic response differed between Sham and HF ventricle. Pertussis toxin (PTX) inactivation of G(i) did not increase the maximal βAR inotropic effect or the attenuated basal, βAR- & forskolin-stimulated AC activity in HF, but increased the potency of isoproterenol only in Sham (~0.5 log unit). In HF ventricle pretreated with PTX, simultaneous inhibition of phosphodiesterases 3,4 (PDE3,4) alone produced a larger inotropic response than isoproterenol in ventricle untreated with PTX (84% and 48% above basal respectively). In the absence of PTX, PDE3,4 inhibition evoked negligible inotropic effects in HF. These data are not consistent with the hypothesis that increased G(i) activity contributes to the reduced βAR-mediated inotropic response and AC activity in failing ventricle. The data, however, support the hypothesis that G(i), through chronic receptor independent inhibition of AC, together with PDE3,4 activity, is necessary to maintain a low basal level of contractility.
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Affiliation(s)
- R I Hussain
- Department of Pharmacology, Faculty of Medicine, University of Oslo, Oslo, Norway
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Ang R, Opel A, Tinker A. The Role of Inhibitory G Proteins and Regulators of G Protein Signaling in the in vivo Control of Heart Rate and Predisposition to Cardiac Arrhythmias. Front Physiol 2012; 3:96. [PMID: 22783193 PMCID: PMC3390690 DOI: 10.3389/fphys.2012.00096] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 03/27/2012] [Indexed: 12/17/2022] Open
Abstract
Inhibitory heterotrimeric G proteins and the control of heart rate. The activation of cell signaling pathways involving inhibitory heterotrimeric G proteins acts to slow the heart rate via modulation of ion channels. A large number of Regulators of G protein signalings (RGSs) can act as GTPase accelerating proteins to inhibitory G proteins and thus it is important to understand the network of RGS\G-protein interaction. We will review our recent findings on in vivo heart rate control in mice with global genetic deletion of various inhibitory G protein alpha subunits. We will discuss potential central and peripheral contributions to the phenotype and the controversies in the literature.
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Affiliation(s)
- Richard Ang
- Centre for Clinical Pharmacology, Division of Medicine, University College LondonLondon, UK
| | - Aaisha Opel
- Centre for Clinical Pharmacology, Division of Medicine, University College LondonLondon, UK
| | - Andrew Tinker
- William Harvey Heart Centre, Barts and The London School of Medicine and DentistryLondon, UK
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Abstract
The following are highlights from
Circulation: Heart Failure
's Topic Review. This series summarizes the most important manuscripts, as selected by the editors, that have been published in the
Circulation
portfolio. The objective of this series is to provide our readership with a timely, comprehensive selection of important papers that are relevant to the heart failure audience. The studies included in this article represent the most noteworthy research in the areas of pathophysiology and genetics.
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Gαi2- and Gαi3-specific regulation of voltage-dependent L-type calcium channels in cardiomyocytes. PLoS One 2011; 6:e24979. [PMID: 21966394 PMCID: PMC3180279 DOI: 10.1371/journal.pone.0024979] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 08/23/2011] [Indexed: 11/19/2022] Open
Abstract
Background Two pertussis toxin sensitive Gi proteins, Gi2 and Gi3, are expressed in cardiomyocytes and upregulated in heart failure. It has been proposed that the highly homologous Gi isoforms are functionally distinct. To test for isoform-specific functions of Gi proteins, we examined their role in the regulation of cardiac L-type voltage-dependent calcium channels (L-VDCC). Methods Ventricular tissues and isolated myocytes were obtained from mice with targeted deletion of either Gαi2 (Gαi2−/−) or Gαi3 (Gαi3−/−). mRNA levels of Gαi/o isoforms and L-VDCC subunits were quantified by real-time PCR. Gαi and Cavα1 protein levels as well as protein kinase B/Akt and extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation levels were assessed by immunoblot analysis. L-VDCC function was assessed by whole-cell and single-channel current recordings. Results In cardiac tissue from Gαi2−/− mice, Gαi3 mRNA and protein expression was upregulated to 187±21% and 567±59%, respectively. In Gαi3−/− mouse hearts, Gαi2 mRNA (127±5%) and protein (131±10%) levels were slightly enhanced. Interestingly, L-VDCC current density in cardiomyocytes from Gαi2−/− mice was lowered (−7.9±0.6 pA/pF, n = 11, p<0.05) compared to wild-type cells (−10.7±0.5 pA/pF, n = 22), whereas it was increased in myocytes from Gαi3−/− mice (−14.3±0.8 pA/pF, n = 14, p<0.05). Steady-state inactivation was shifted to negative potentials, and recovery kinetics slowed in the absence of Gαi2 (but not of Gαi3) and following treatment with pertussis toxin in Gαi3−/−. The pore forming Cavα1 protein level was unchanged in all mouse models analyzed, similar to mRNA levels of Cavα1 and Cavβ2 subunits. Interestingly, at the cellular signalling level, phosphorylation assays revealed abolished carbachol-triggered activation of ERK1/2 in mice lacking Gαi2. Conclusion Our data provide novel evidence for an isoform-specific modulation of L-VDCC by Gαi proteins. In particular, loss of Gαi2 is reflected by alterations in channel kinetics and likely involves an impairment of the ERK1/2 signalling pathway.
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