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Wang T, Jiang R, Yao Y, Xu T, Li N. Anti-hypertensive therapy for preeclampsia: a network meta-analysis and systematic review. Hypertens Pregnancy 2024; 43:2329068. [PMID: 38488570 DOI: 10.1080/10641955.2024.2329068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 03/05/2024] [Indexed: 03/19/2024]
Abstract
BACKGROUND Preeclampsia (PE) is a pregnancy disorder that represents a major cause of maternal and perinatal morbidity and mortality. METHODS This network meta-analysis was registered with PROSPERO. We searched the PubMed, ClinicalTrials.gov. and Embase databases for studies published from inception to the 31st of March 2023. RevMan5.3 software provided by the Cochrane Collaboration was used for direct meta-analysis (DMA) statistical analysis. Funnel maps, network meta-analysis (NMA), the surface under the cumulative ranking curve (SUCRA) to rank the different interventions and publication bias were generated by STATA 17.0 software. RESULTS We included eight randomized controlled trials (RCTs) involving a total of 1192 women with PE; two studies were of high quality and six were of moderate quality. Eight interventions were addressed in the NMA. In the DMA, we found that blood pressure in the Ketanserin group were significantly higher than those in the Nicardipine group. NMA showed that blood pressure in the Dihydralazine group was significantly higher than that in the Methyldopa, Labetalol, Nicardipine and Diltiazem groups. And the blood pressure in the Labetalol group was significantly lower than that in the Nicardipine group. SUCRA values showed that Diltiazem was more effective in lowering blood pressure than other drugs looked at in this study. CONCLUSION According to the eight RCTs included in this study, Diltiazem was the most effective in reducing blood pressure in PE patients; Labetalol and Nicardipine also had good effects. Diltiazem is preferred for the treatment of patients with severe PE and high blood pressure.
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Affiliation(s)
- Ting Wang
- Department of Obstetrics and Gynecology, Women's Hospital Zhejiang University School of Medicine, Hangzhou, China
| | - Ruoan Jiang
- Department of Obstetrics and Gynecology, Women's Hospital Zhejiang University School of Medicine, Hangzhou, China
- Zhejiang Provincial Clinical Research Center for Obstetrics and Gynecology, Hangzhou, China
- Traditional Chinese Medicine for Reproductive Health Key Laboratory of Zhejiang Province, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Yingsha Yao
- Department of Obstetrics and Gynecology, Women's Hospital Zhejiang University School of Medicine, Hangzhou, China
| | - Ting Xu
- Department of Obstetrics and Gynecology, Women's Hospital Zhejiang University School of Medicine, Hangzhou, China
| | - Na Li
- Department of Obstetrics and Gynecology, Women's Hospital Zhejiang University School of Medicine, Hangzhou, China
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Arias-Hernández G, Vargas-De-León C, Calzada-Mendoza CC, Ocharan-Hernández ME. Efficacy of Diltiazem for the Control of Blood Pressure in Puerperal Patients with Severe Preeclampsia: A Randomized, Single-Blind, Controlled Trial. Int J Hypertens 2020; 2020:5347918. [PMID: 32774912 PMCID: PMC7397380 DOI: 10.1155/2020/5347918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 06/08/2020] [Accepted: 07/01/2020] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Postpartum preeclampsia is a serious disease related to high blood pressure that occurs commonly within the first six days after delivery. OBJECTIVE To evaluate if diltiazem improves blood pressure parameters in early puerperium patients with severe preeclampsia. Methodology. A randomized, single-blind longitudinal clinical trial of 42 puerperal patients with severe preeclampsia was carried out. Patients were randomized into two groups: the experimental group (n = 21) received diltiazem (60 mg) and the control group (n = 21) received nifedipine (10 mg). Both drugs were orally administered every 8 hours. Systolic, diastolic, and mean blood pressures as well as the heart rate were recorded and analyzed (two-way repeated measures ANOVA) at baseline and after 6, 12, 18, 24, 30, 36, 42, and 48 hours. Primary outcome measures were all the aforementioned blood pressure parameters. Secondary outcome measures included the number of hypertension and hypotension episodes along with the length of stay in the intensive care unit. RESULTS No statistical differences were found between groups (diltiazem vs. nifedipine) regarding basal blood pressure parameters. Interarm differences in blood pressure (systolic, diastolic, and mean) and heart rate were statistically significant between treatment groups from 6 to 48 hours. Patients in the diltiazem group had lower blood pressure levels than patients in the nifedipine group. Significantly, patients who received diltiazem had fewer hypertension and hypotension episodes and stayed fewer days in the intensive care unit than those treated with nifedipine. CONCLUSIONS Diltiazem controlled arterial hypertension in a more effective and uniform manner in patients under study than nifedipine. Patients treated with diltiazem had fewer collateral effects and spent less time in the hospital. This trial is registered with NCT04222855.
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Affiliation(s)
- Gilberto Arias-Hernández
- Hospital De La Mujer, Prolongación Salvador Díaz Mirón 374, Colonia Santo Tomas, Delegación Miguel Hidalgo, C. P. 11340, México D. F., Mexico
| | - Cruz Vargas-De-León
- Facultad De Matemáticas, Universidad Autónoma De Guerrero, Chilpancingo, Av. Lázaro Cárdenas S/N, Cd. Universitaria, 39087 Chilpancingo, Guerrero, Mexico
- Instituto Politécnico Nacional Escuela Superior De Medicina, Plan De San Luis Y Díaz Mirón SN, Col. Casco De Santo Tomás, Delegación Miguel Hidalgo, C. P. 11340, México D. F, Mexico
| | - Claudia C Calzada-Mendoza
- Instituto Politécnico Nacional Escuela Superior De Medicina, Plan De San Luis Y Díaz Mirón SN, Col. Casco De Santo Tomás, Delegación Miguel Hidalgo, C. P. 11340, México D. F, Mexico
| | - María Esther Ocharan-Hernández
- Instituto Politécnico Nacional Escuela Superior De Medicina, Plan De San Luis Y Díaz Mirón SN, Col. Casco De Santo Tomás, Delegación Miguel Hidalgo, C. P. 11340, México D. F, Mexico
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Valli H, Ahmad S, Sriharan S, Dean LD, Grace AA, Jeevaratnam K, Matthews HR, Huang CLH. Epac-induced ryanodine receptor type 2 activation inhibits sodium currents in atrial and ventricular murine cardiomyocytes. Clin Exp Pharmacol Physiol 2017; 45:278-292. [PMID: 29027245 PMCID: PMC5814738 DOI: 10.1111/1440-1681.12870] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 09/23/2017] [Accepted: 09/27/2017] [Indexed: 12/16/2022]
Abstract
Acute RyR2 activation by exchange protein directly activated by cAMP (Epac) reversibly perturbs myocyte Ca2+ homeostasis, slows myocardial action potential conduction, and exerts pro‐arrhythmic effects. Loose patch‐clamp studies, preserving in vivo extracellular and intracellular conditions, investigated Na+ current in intact cardiomyocytes in murine atrial and ventricular preparations following Epac activation. Depolarising steps to varying test voltages activated typical voltage‐dependent Na+ currents. Plots of peak current against depolarisation from resting potential gave pretreatment maximum atrial and ventricular currents of −20.23 ± 1.48 (17) and −29.8 ± 2.4 (10) pA/μm2 (mean ± SEM [n]). Challenge by 8‐CPT (1 μmol/L) reduced these currents to −11.21 ± 0.91 (12) (P < .004) and −19.3 ± 1.6 (11) pA/μm2 (P < .04) respectively. Currents following further addition of the RyR2 inhibitor dantrolene (10 μmol/L) (−19.91 ± 2.84 (13) and −26.6 ± 1.7 (17)), and dantrolene whether alone (−19.53 ± 1.97 (8) and −27.6 ± 1.9 (14)) or combined with 8‐CPT (−19.93 ± 2.59 (12) and −29.9 ± 2.5(11)), were indistinguishable from pretreatment values (all P >> .05). Assessment of the inactivation that followed by applying subsequent steps to a fixed voltage 100 mV positive to resting potential gave concordant results. Half‐maximal inactivation voltages and steepness factors, and time constants for Na+ current recovery from inactivation in double‐pulse experiments, were similar through all the pharmacological conditions. Intracellular sharp microelectrode membrane potential recordings in intact Langendorff‐perfused preparations demonstrated concordant variations in maximum rates of atrial and ventricular action potential upstroke, (dV/dt)max. We thus demonstrate an acute, reversible, Na+ channel inhibition offering a possible mechanism for previously reported pro‐arrhythmic slowing of AP propagation following modifications of Ca2+ homeostasis, complementing earlier findings from chronic alterations in Ca2+ homeostasis in genetically‐modified RyR2‐P2328S hearts.
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Affiliation(s)
- Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Sujan Sriharan
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Lydia D Dean
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Kamalan Jeevaratnam
- Physiological Laboratory, University of Cambridge, Cambridge, UK.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK.,PU-RCSI School of Medicine, Perdana University, Serdang, Selangor Darul Ehsan, Malaysia
| | - Hugh R Matthews
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Cambridge, UK.,Department of Biochemistry, University of Cambridge, Cambridge, UK
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4
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Ahmad S, Valli H, Edling CE, Grace AA, Jeevaratnam K, Huang CLH. Effects of ageing on pro-arrhythmic ventricular phenotypes in incrementally paced murine Pgc-1β -/- hearts. Pflugers Arch 2017; 469:1579-1590. [PMID: 28821956 PMCID: PMC5691113 DOI: 10.1007/s00424-017-2054-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 01/07/2023]
Abstract
A range of chronic clinical conditions accompany cardiomyocyte energetic dysfunction and constitute independent risk factors for cardiac arrhythmia. We investigated pro-arrhythmic and arrhythmic phenotypes in energetically deficient C57BL mice with genetic ablation of the mitochondrial promoter peroxisome proliferator-activated receptor-γ coactivator-1β (Pgc-1β), a known model of ventricular arrhythmia. Pro-arrhythmic and cellular action potential (AP) characteristics were compared in intact Langendorff-perfused hearts from young (12–16 week) and aged (> 52 week), wild-type (WT) and Pgc-1β−/− mice. Simultaneous electrocardiographic and intracellular microelectrode recordings were made through successive trains of 100 regular stimuli at progressively incremented heart rates. Aged Pgc-1β−/− hearts displayed an increased incidence of arrhythmia compared to other groups. Young and aged Pgc-1β−/− hearts showed higher incidences of alternans in both AP activation (maximum AP upshoot velocity (dV/dt)max and latency), recovery (action potential duration (APD90) and resting membrane potential (RMP) characteristics compared to WT hearts. This was particularly apparent at lower pacing frequencies. These findings accompanied reduced (dV/dt)max and increased AP latency values in the Pgc-1β−/− hearts. APs observed prior to termination of the protocol showed lower (dV/dt)max and longer AP latencies, but indistinguishable APD90 and RMPs in arrhythmic compared to those in non-arrhythmic hearts. APD restitution analysis showed that Pgc-1β−/− and WT hearts showed similar limiting gradients. However, Pgc-1β−/− hearts had shortened plateau AP wavelengths, particularly in aged Pgc-1β−/− hearts. Pgc-1β−/− hearts therefore show pro-arrhythmic instabilities attributable to altered AP conduction and activation rather than recovery characteristics.
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Affiliation(s)
- Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
| | - Charlotte E Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7AL, UK
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Kamalan Jeevaratnam
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7AL, UK
- PU-RCSI School of Medicine, Perdana University, 43400, Serdang, Selangor Darul Ehsan, Malaysia
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, UK.
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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Tse G, Sun B, Wong ST, Tse V, Yeo JM. Anti-arrhythmic effects of hypercalcemia in hyperkalemic, Langendorff-perfused mouse hearts. Biomed Rep 2016; 5:301-310. [PMID: 27588173 PMCID: PMC4998139 DOI: 10.3892/br.2016.735] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 05/31/2016] [Indexed: 12/25/2022] Open
Abstract
The present study examined the ventricular arrhythmic and electrophysiological properties during hyperkalemia (6.3 mM [K+] vs. 4 mM in normokalemia) and anti-arrhythmic effects of hypercalcemia (2.2 mM [Ca2+]) in Langendorff-perfused mouse hearts. Monophasic action potential recordings were obtained from the left ventricle during right ventricular pacing. Hyperkalemia increased the proportion of hearts showing provoked ventricular tachycardia (VT) from 0 to 6 of 7 hearts during programmed electrical stimulation (Fisher's exact test, P<0.05). It shortened the epicardial action potential durations (APDx) at 90, 70, 50 and 30% repolarization and ventricular effective refractory periods (VERPs) (analysis of variance, P<0.05) without altering activation latencies. Endocardial APDx and VERPs were unaltered. Consequently, ∆APDx (endocardial APDx-epicardial APDx) was increased, VERP/latency ratio was decreased and critical intervals for reexcitation (APD90-VERP) were unchanged. Hypercalcemia treatment exerted anti-arrhythmic effects during hyperkalemia, reducing the proportion of hearts showing VT to 1 of 7 hearts. It increased epicardial VERPs without further altering the remaining parameters, returning VERP/latency ratio to normokalemic values and also decreased the critical intervals. In conclusion, hyperkalemia exerted pro-arrhythmic effects by shortening APDs and VERPs. Hypercalcemia exerted anti-arrhythmic effects by reversing VERP changes, which scaled the VERP/latency ratio and critical intervals.
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Affiliation(s)
- Gary Tse
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, SAR, P.R. China
| | - Bing Sun
- Department of Cardiology, Tongji University Affiliated Tongji Hospital, Shanghai 200065, P.R. China
| | | | - Vivian Tse
- Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Jie Ming Yeo
- School of Medicine, Imperial College London, London SW7 2AZ, UK
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7
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Surinkaew S, Chattipakorn S, Chattipakorn N. Roles of mitochondrial benzodiazepine receptor in the heart. Can J Cardiol 2011; 27:262.e3 -13. [PMID: 21459278 DOI: 10.1016/j.cjca.2010.12.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 06/02/2010] [Indexed: 12/01/2022] Open
Abstract
Mitochondrial benzodiazepine receptor (mBzR) is a type of peripheral benzodiazepine receptor that is located in the outer membrane of mitochondria. It is an 18-kDa protein that can form a multimeric complex with voltage-dependent anion channel (32 kDa) and adenine nucleotide translocator (30 kDa). mBzR is found in various species and abundantly distributed in peripheral tissues, including the cardiovascular system. The mitochondria are well known as the site of energy production, and the heart is the organ that highly requires this energy supply. In the past decades, it has been shown that mBzR plays a critical role in regulating mitochondrial and heart functions. A growing body of evidence demonstrates that mBzR is associated with regulation of mitochondrial respiration, mitochondrial membrane potential, apoptosis, and reactive oxygen species production. Moreover, mBzR has been suggested to play a role in alteration of physiological effects in the heart such as contractility and heart rate. mBzR is involved in the pathologic condition such as ischemia/reperfusion injury, responses to stress, and changes in electrophysiological properties and arrhythmogenesis. In this review, evidence of the roles of mBzR in the heart under both physiological and pathologic conditions is presented. Clinical studies regarding the use of pharmacologic intervention involving mBzR in the heart are also discussed as a possible target for the treatment of electrical and mechanical dysfunction in the heart.
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Affiliation(s)
- Sirirat Surinkaew
- Department of Physiology, Chiang Mai University, Chiang Mai, Thailand
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8
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Katz G, Khoury A, Kurtzwald E, Hochhauser E, Porat E, Shainberg A, Seidman JG, Seidman CE, Lorber A, Eldar M, Arad M. Optimizing catecholaminergic polymorphic ventricular tachycardia therapy in calsequestrin-mutant mice. Heart Rhythm 2010; 7:1676-82. [PMID: 20620233 DOI: 10.1016/j.hrthm.2010.07.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 07/10/2010] [Indexed: 11/17/2022]
Abstract
BACKGROUND Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a lethal arrhythmia provoked by physical or emotional stress and mediated by spontaneous Ca(2+) release and delayed after-depolarizations. Beta-adrenergic blockers are the therapy of choice but fail to control arrhythmia in up to 50% of patients. OBJECTIVE To optimize antiarrhythmic therapy in recessively inherited CPVT caused by calsequestrin (CASQ2) mutations. METHODS Murine heart rhythm telemetry was obtained at rest, during treadmill exercise, and after injection of epinephrine. The protocol was repeated after injection of different antiarrhythmic drugs. Results were then validated in human patients. RESULTS Adult CASQ2 mutant mice had complex ventricular arrhythmia at rest and developed bidirectional and polymorphic ventricular tachycardia on exertion. Class I antiarrhythmic agents (procainamide, lidocaine, flecainide) were ineffective in controlling arrhythmia. Propranolol and sotalol attenuated arrhythmia at rest but failed to prevent VT during sympathetic stimulation. The calcium channel blocker verapamil showed a dose-dependent protection against CPVT. Verapamil was more effective than the dihydropyridine L-type Ca(2+) channel blocker nifedipine, and its activity was markedly enhanced when combined with propranolol. Human patients homozygous for CASQ2(D307H) mutation, remaining symptomatic despite chronic β-blocker therapy, underwent exercise testing according to the Bruce protocol with continuous electrocardiogram recording. Verapamil was combined with propranolol at maximum tolerated doses. Adding verapamil attenuated ventricular arrhythmia and prolonged exercise duration in five of 11 patients. CONCLUSION Verapamil is highly effective against catecholamine-induced arrhythmia in mice with CASQ2 mutations and may potentiate the antiarrhythmic activity of β-blockers in humans with CPVT2.
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Affiliation(s)
- Guy Katz
- Heart Institute, Sheba Medical Center, Tel Hashomer and Sackler School of Medicine, Tel Aviv University, Israel
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Wang W, Zhang H, Gao H, Kubo H, Berretta RM, Chen X, Houser SR. {beta}1-Adrenergic receptor activation induces mouse cardiac myocyte death through both L-type calcium channel-dependent and -independent pathways. Am J Physiol Heart Circ Physiol 2010; 299:H322-31. [PMID: 20495143 DOI: 10.1152/ajpheart.00392.2010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac diseases persistently increase the contractility demands of cardiac myocytes, which require activation of the sympathetic nervous system and subsequent increases in myocyte Ca(2+) transients. Persistent exposure to sympathetic and/or Ca(2+) stress is associated with myocyte death. This study examined the respective roles of persistent beta-adrenergic receptor (beta-AR) agonist exposure and high Ca(2+) concentration in myocyte death. Ventricular myocytes (VMs) were isolated from transgenic (TG) mice with cardiac-specific and inducible expression of the beta(2a)-subunit of the L-type Ca(2+) channel (LTCC). VMs were cultured, and the rate of myocyte death was measured in the presence of isoproterenol (ISO), other modulators of Ca(2+) handling and the beta-adrenergic system, and inhibitors of caspases and reactive oxygen species generation. The rate of myocyte death was greater in TG vs. wild-type myocytes and accelerated by ISO in both groups, although ISO did not increase LTCC current (I(Ca-L)) in TG-VMs. Nifedipine, an LTCC antagonist, only partially prevented myocyte death. These results suggest both LTCC-dependent and -independent mechanisms in ISO induced myocyte death. ISO increased the contractility of wild type and TG-VMs by enhancing sarcoplasmic reticulum function and inhibiting sarco(endo)plasmic reticulum Ca(2+)-ATPase, Na(+)/Ca(2+) exchanger, and CaMKII partially protected myocyte from death induced by both Ca(2+) and ISO. Caspase and reactive oxygen species inhibitors did not, but beta(2)-AR activation did, reduce myocyte death induced by enhanced I(Ca-L) and ISO stimulation. Our results suggest that catecholamines induce myocyte necrosis primarily through beta(1)-AR-mediated increases in I(Ca-L), but other mechanisms are also involved in rodents.
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Affiliation(s)
- Wei Wang
- Institute of Burn Research, Southwest Hospital, State Key Laboratory of Trauma, Burns and Combined Injury, Third Military Medical University, Chongqing, China
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10
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Zhang Y, Fraser JA, Schwiening C, Zhang Y, Killeen MJ, Grace AA, Huang CLH. Acute atrial arrhythmogenesis in murine hearts following enhanced extracellular Ca(2+) entry depends on intracellular Ca(2+) stores. Acta Physiol (Oxf) 2010; 198:143-58. [PMID: 19886909 PMCID: PMC3763207 DOI: 10.1111/j.1748-1716.2009.02055.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Aim To investigate the effect of increases in extracellular Ca2+ entry produced by the L-type Ca2+ channel agonist FPL-64176 (FPL) upon acute atrial arrhythmogenesis in intact Langendorff-perfused mouse hearts and its dependence upon diastolic Ca2+ release from sarcoplasmic reticular Ca2+ stores. Methods Confocal microscope studies of Fluo-3 fluorescence in isolated atrial myocytes were performed in parallel with electrophysiological examination of Langendorff-perfused mouse hearts. Results Atrial myocytes stimulated at 1 Hz and exposed to FPL (0.1 μm) initially showed (<10 min) frequent, often multiple, diastolic peaks following the evoked Ca2+ transients whose amplitudes remained close to control values. With continued pacing (>10 min) this reverted to a regular pattern of evoked transients with increased amplitudes but in which diastolic peaks were absent. Higher FPL concentrations (1.0 μm) produced sustained and irregular patterns of cytosolic Ca2+ activity, independent of pacing. Nifedipine (0.5 μm), and caffeine (1.0 mm) and cyclopiazonic acid (CPA) (0.15 μm) pre-treatments respectively produced immediate and gradual reductions in the F/F0 peaks. Such nifedipine and caffeine, or CPA pre-treatments, abolished, or reduced, the effects of 0.1 and 1.0 μm FPL on cytosolic Ca2+ signals. FPL (1.0 μm) increased the incidence of atrial tachycardia and fibrillation in intact Langendorff-perfused hearts without altering atrial effective refractory periods. These effects were inhibited by nifedipine and caffeine, and reduced by CPA. Conclusion Enhanced extracellular Ca2+ entry exerts acute atrial arrhythmogenic effects that is nevertheless dependent upon diastolic Ca2+ release. These findings complement reports that associate established, chronic, atrial arrhythmogenesis with decreased overall inward Ca2+ current.
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Affiliation(s)
- Y Zhang
- Physiological Laboratory, University of Cambridge, Cambridge, UK
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11
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Blayney LM, Lai FA. Ryanodine receptor-mediated arrhythmias and sudden cardiac death. Pharmacol Ther 2009; 123:151-77. [PMID: 19345240 PMCID: PMC2704947 DOI: 10.1016/j.pharmthera.2009.03.006] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Accepted: 03/03/2009] [Indexed: 12/25/2022]
Abstract
The cardiac ryanodine receptor-Ca2+ release channel (RyR2) is an essential sarcoplasmic reticulum (SR) transmembrane protein that plays a central role in excitation–contraction coupling (ECC) in cardiomyocytes. Aberrant spontaneous, diastolic Ca2+ leak from the SR due to dysfunctional RyR2 contributes to the formation of delayed after-depolarisations, which are thought to underlie the fatal arrhythmia that occurs in both heart failure (HF) and in catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT is an inherited disorder associated with mutations in either the RyR2 or a SR luminal protein, calsequestrin. RyR2 shows normal function at rest in CPVT but the RyR2 dysfunction is unmasked by physical exercise or emotional stress, suggesting abnormal RyR2 activation as an underlying mechanism. Several potential mechanisms have been advanced to explain the dysfunctional RyR2 observed in HF and CPVT, including enhanced RyR2 phosphorylation status, altered RyR2 regulation at luminal/cytoplasmic sites and perturbed RyR2 intra/inter-molecular interactions. This review considers RyR2 dysfunction in the context of the structural and functional modulation of the channel, and potential therapeutic strategies to stabilise RyR2 function in cardiac pathology.
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Affiliation(s)
- Lynda M Blayney
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF144XN, UK.
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12
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Zhang Y, Schwiening C, Killeen MJ, Zhang Y, Ma A, Lei M, Grace AA, Huang CLH. Pharmacological changes in cellular Ca2+ homeostasis parallel initiation of atrial arrhythmogenesis in murine Langendorff-perfused hearts. Clin Exp Pharmacol Physiol 2009; 36:969-80. [PMID: 19298534 PMCID: PMC2841827 DOI: 10.1111/j.1440-1681.2009.05170.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
1. Intracellular Ca(2+) overload has been associated with established atrial arrhythmogenesis. The present experiments went on to correlate acute initiation of atrial arrhythmogenesis in Langendorff-perfused mouse hearts with changes in Ca(2+) homeostasis in isolated atrial myocytes following pharmacological procedures that modified the storage or release of sarcoplasmic reticular (SR) Ca(2+) or inhibited entry of extracellular Ca(2+). 2. Caffeine (1 mmol/L) elicited diastolic Ca(2+) waves in regularly stimulated atrial myocytes immediately following addition. This was followed by a decline in the amplitude of the evoked transients and the disappearance of such diastolic events, suggesting partial SR Ca(2+) depletion. 3. Cyclopiazonic acid (CPA; 0.15 micromol/L) produced more gradual reductions in evoked Ca(2+) transients and abolished diastolic Ca(2+) events produced by the further addition of caffeine. 4. Nifedipine (0.5 micromol/L) produced immediate reductions in evoked Ca(2+) transients. Further addition of caffeine produced an immediate increase followed by a decline in the amplitude of the evoked Ca(2+) transients, without eliciting diastolic Ca(2+) events. 5. These findings correlated with changes in spontaneous and provoked atrial arrhythmogenecity in mouse isolated Langendorf-perfused hearts. Thus, caffeine was pro-arrhythmogenic immediately following but not > 5 min after application and both CPA and nifedipine pretreatment inhibited such arrhythmogenesis. 6. Together, these findings relate acute atrial arrhythmogenesis in intact hearts to diastolic Ca(2+) events in atrial myocytes that, in turn, depend upon a finite SR Ca(2+) store and diastolic Ca(2+) release following Ca(2+)-induced Ca(2+) release initiated by the entry of extracellular Ca(2+).
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Affiliation(s)
- Yanmin Zhang
- Physiological Laboratory, University of Cambridge, Cambridge, UK
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Anti-arrhythmic effects of cyclopiazonic acid in Langendorff-perfused murine hearts. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2009; 98:281-8. [PMID: 19351518 DOI: 10.1016/j.pbiomolbio.2009.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigated the effects of reducing sarcoplasmic reticular (SR) Ca(2+) stores using the Ca(2+)-ATPase inhibitor cyclopiazonic acid (CPA) in Langendorff-perfused mouse hearts exposed to different pro-arrhythmic agents all known to produce Ca(2+)-mediated arrhythmogenesis. CPA (100 and 150 nM) produced progressive (beginning over approximately 1 min) and significant (P<0.0001) reductions in peak amplitudes of Ca(2+) transients evoked by regular stimulation in isolated Fluo-3 loaded myocytes from F/F(0)=3.2+/-0.16 (n=12 cells) to 1.62+/-0.012 (n=6 cells) and 1.53+/-0.06 (n=12 cells), respectively, consistent with previous reports describing reductions of store Ca(2+) in other cell systems. The corresponding effects of CPA were then examined in intact hearts exposed to isoproterenol (100 nM), elevated extracellular [Ca(2+)] (5mM) and caffeine (1mM). All three agents produced ventricular tachycardia either when added alone or simultaneously with CPA during programmed electrical stimulation. However, arrhythmogenicity was not observed when such agents were added approximately 10 min after introduction of CPA. CPA thus antagonized this Ca(2+)-mediated arrhythmogenesis but only under circumstances of SR Ca(2+) depletion. These alterations in arrhythmogenic tendency took place despite an absence of alterations in electrogram and monophasic action potential characteristics. This was in sharp contrast to previous observations in murine, DeltaKPQ-Scn5a (LQT3) and KCNE1(-/-) (LQT5), systems where re-entry has been implicated in arrhythmogenesis.
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Ghais NS, Zhang Y, Grace AA, Huang CLH. Arrhythmogenic actions of the Ca2+ channel agonist FPL-64716 in Langendorff-perfused murine hearts. Exp Physiol 2008; 94:240-54. [PMID: 18978037 PMCID: PMC2705814 DOI: 10.1113/expphysiol.2008.044669] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The experiments explored the extent to which alterations in L-type Ca(2+) channel-mediated Ca(2+) entry triggers Ca(2+)-mediated arrhythmogenesis in Langendorff-perfused murine hearts through use of the specific L-type Ca(2+) channel modulator FPL-64716 (FPL). Introduction of FPL (1 microm) resulted in a gradual development (>10 min) of diastolic electrical events and alternans in spontaneously beating hearts from which monophasic action potentials were recorded. In regularly paced hearts, they additionally led to non-sustained and sustained ventricular tachycardia (nsVT and sVT). Programmed electrical stimulation (PES) resulted in nsVT and sVT after 5-10 and >10 min perfusion, respectively. Pretreatments with nifedipine, diltiazem and cyclopiazonic acid abolished arrhythmogenic tendency induced by subsequent introduction of FPL, consistent with its dependence upon both extracellular Ca(2+) entry and the degree of filling of the sarcoplasmic reticular Ca(2+) store. Values for action potential duration at 90% repolarization when any of these agents were applied to FPL-treated hearts became indistinguishable from those shown by untreated control hearts, in contrast to earlier reports of their altering in long QT syndrome type 3 and hypokalaemic murine models for re-entrant arrhythmogenesis. These arrhythmic effects instead correlated with alterations in Ca(2+) homeostasis at the single-cell level found in investigations of the effects of both FPL and the same agents in regularly stimulated fluo-3 loaded myocytes. These findings are compatible with a prolonged extracellular Ca(2+) entry that potentially results in an intracellular Ca(2+) overload and produces the cardiac arrhythmogenecity following addition of FPL.
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Affiliation(s)
- Nina S Ghais
- Physiological Laboratory, University of Cambridge, UK
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Hothi SS, Gurung IS, Heathcote JC, Zhang Y, Booth SW, Skepper JN, Grace AA, Huang CLH. Epac activation, altered calcium homeostasis and ventricular arrhythmogenesis in the murine heart. Pflugers Arch 2008; 457:253-70. [PMID: 18600344 PMCID: PMC3714550 DOI: 10.1007/s00424-008-0508-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2007] [Revised: 03/03/2008] [Accepted: 03/23/2008] [Indexed: 11/02/2022]
Abstract
The recently described exchange protein directly activated by cAMP (Epac) has been implicated in distinct protein kinase A-independent cellular signalling pathways. We investigated the role of Epac activation in adrenergically mediated ventricular arrhythmogenesis. In contrast to observations in control conditions (n = 20), monophasic action potentials recorded in 2 of 10 intrinsically beating and 5 of 20 extrinsically paced Langendorff-perfused wild-type murine hearts perfused with the Epac activator 8-pCPT-2'-O-Me-cAMP (8-CPT, 1 microM) showed spontaneous triggered activity. Three of 20 such extrinsically paced hearts showed spontaneous ventricular tachycardia (VT). Programmed electrical stimulation provoked VT in 10 of 20 similarly treated hearts (P < 0.001; n = 20). However, there were no statistically significant accompanying changes (P > 0.05) in left ventricular epicardial (40.7 +/- 1.2 versus 44.0 +/- 1.7 ms; n = 10) or endocardial action potential durations (APD(90); 51.8 +/- 2.3 versus 51.9 +/- 2.2 ms; n = 10), transmural (DeltaAPD(90)) (11.1 +/- 2.6 versus 7.9 +/- 2.8 ms; n = 10) or apico-basal repolarisation gradients, ventricular effective refractory periods (29.1 +/- 1.7 versus 31.2 +/- 2.4 ms in control and 8-CPT-treated hearts, respectively; n = 10) and APD(90) restitution characteristics. Nevertheless, fluorescence imaging of cytosolic Ca(2+) levels demonstrated abnormal Ca(2+) homeostasis in paced and resting isolated ventricular myocytes. Epac activation using isoproterenol in the presence of H-89 was also arrhythmogenic and similarly altered cellular Ca(2+) homeostasis. Epac-dependent effects were reduced by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibition with 1 microM KN-93. These findings associate VT in an intact cardiac preparation with altered cellular Ca(2+) homeostasis and Epac activation for the first time, in the absence of altered repolarisation gradients previously implicated in reentrant arrhythmias through a mechanism dependent on CaMKII activity.
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Affiliation(s)
- Sandeep S Hothi
- University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
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Brown DA, Aon MA, Akar FG, Liu T, Sorarrain N, O'Rourke B. Effects of 4'-chlorodiazepam on cellular excitation-contraction coupling and ischaemia-reperfusion injury in rabbit heart. Cardiovasc Res 2008; 79:141-9. [PMID: 18304929 DOI: 10.1093/cvr/cvn053] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
AIMS Recent evidence indicates that the activity of energy-dissipating ion channels in the mitochondria can influence the susceptibility of the heart to ischaemia-reperfusion injury. In this study, we describe the effects of 4'-chlorodiazepam (4-ClDzp), a well-known ligand of the mitochondrial benzodiazepine receptor, on the physiology of both isolated cardiomyocytes and intact hearts. METHODS AND RESULTS We used current- and voltage-clamp methods to determine the effects of 4-ClDzp on excitation-contraction coupling in isolated rabbit heart cells. At the level of the whole heart, we subjected rabbit hearts to ischaemia/reperfusion in order to determine how 4-ClDzp influenced the susceptibility to arrhythmias and contractile dysfunction. In isolated rabbit cardiomyocytes, 4-ClDzp evoked a significant reduction in the cardiac action potential that was associated with a decrease in calcium currents and peak intracellular calcium transients. In intact perfused normoxic rabbit hearts, 4-ClDzp mediated a dose-dependent negative inotropic response, consistent with the observation that 4-ClDzp was reducing calcium influx. Hearts that underwent 30 min of global ischaemia and 30 min of reperfusion were protected against reperfusion arrhythmias and post-ischaemic contractile impairment when 4-ClDzp (24 microM) was administered throughout the protocol or as a single bolus dose given at the onset of reperfusion. In contrast, hearts treated with cyclosporin-A, a classical blocker of the mitochondrial permeability transition pore, were not protected against reperfusion arrhythmias. CONCLUSION The findings indicate that the effects of 4-ClDzp on both mitochondrial and sarcolemmal ion channels contribute to protection against post-ischaemic cardiac dysfunction. Of clinical relevance, the compound is effective when given upon reperfusion, unlike other pre-conditioning agents.
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Affiliation(s)
- David A Brown
- Department of Medicine, Division of Cardiology, Institute of Molecular Cardiobiology, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, 1059 Ross Building, Baltimore, MD 21205, USA
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Killeen MJ, Gurung IS, Thomas G, Stokoe KS, Grace AA, Huang CLH. Separation of early afterdepolarizations from arrhythmogenic substrate in the isolated perfused hypokalaemic murine heart through modifiers of calcium homeostasis. Acta Physiol (Oxf) 2007; 191:43-58. [PMID: 17524066 PMCID: PMC2040229 DOI: 10.1111/j.1748-1716.2007.01715.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS We resolved roles for early afterdepolarizations (EADs) and transmural gradients of repolarization in arrhythmogenesis in Langendorff-perfused hypokalaemic murine hearts paced from the right ventricular epicardium. METHODS Left ventricular epicardial and endocardial monophasic action potentials (MAPs) and arrhythmogenic tendency were compared in the presence and absence of the L-type Ca(2+) channel blocker nifedipine (10 nm-1 microm) and the calmodulin kinase type II inhibitor KN-93 (2 microm). RESULTS All the hypokalaemic hearts studied showed prolonged epicardial and endocardial MAPs, decreased epicardial-endocardial APD(90) difference, EADs, triggered beats and ventricular tachycardia (VT) (n = 6). In all spontaneously beating hearts, 100 (but not 10) nm nifedipine reduced both the incidence of EADs and triggered beats from 66.9 +/- 15.7% to 28.3 +/- 8.7% and episodes of VT from 10.8 +/- 6.3% to 1.2 +/- 0.7% of MAPs (n = 6 hearts, P < 0.05); 1 microm nifedipine abolished all these phenomena (n = 6). In contrast programmed electrical stimulation (PES) still triggered VT in six of six hearts with 0, 10 and 100 nm but not 1 microm nifedipine. 1 microm nifedipine selectively reduced epicardial (from 66.1 +/- 3.4 to 46.2 +/- 2.5 ms) but not endocardial APD(90), thereby restoring DeltaAPD(90) from -5.9 +/- 2.5 to 15.5 +/- 3.2 ms, close to normokalaemic values. KN-93 similarly reduced EADs, triggered beats and VT in spontaneously beating hearts to 29.6 +/- 8.9% and 1.7 +/- 1.1% respectively (n = 6) yet permitted PES-induced VT (n = 6), in the presence of a persistently negative DeltaAPD(90). CONCLUSIONS These findings empirically implicate both EADs and triggered beats alongside arrhythmogenic substrate of DeltaAPD(90) in VT pathogenesis at the whole heart level.
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Affiliation(s)
- M J Killeen
- Physiological Laboratory, University of Cambridge, Cambridge, UK.
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. NS, . SMS, . TM. Effects of Diltiazem on Electrolytes Homeostasis in Streptozotocin-Induced Diabetic Rats. INT J PHARMACOL 2007. [DOI: 10.3923/ijp.2007.319.326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Stokoe KS, Balasubramaniam R, Goddard CA, Colledge WH, Grace AA, Huang CLH. Effects of flecainide and quinidine on arrhythmogenic properties of Scn5a+/- murine hearts modelling the Brugada syndrome. J Physiol 2007; 581:255-75. [PMID: 17303635 PMCID: PMC2075209 DOI: 10.1113/jphysiol.2007.128785] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Brugada syndrome (BrS) is associated with a loss of Na+ channel function and an increased incidence of rapid polymorphic ventricular tachycardia (VT) and sudden cardiac death. A programmed electrical stimulation (PES) technique assessed arrhythmic tendency in Langendorff-perfused wild-type (WT) and genetically modified (Scn5a+/-) 'loss-of-function' murine hearts in the presence and absence of flecainide and quinidine, and the extent to which Scn5a+/- hearts model the human BrS. Extra-stimuli (S2), applied to the right ventricular epicardium, followed trains of pacing stimuli (S1) at progressively reduced S1-S2 intervals. These triggered VT in 16 out of 29 untreated Scn5a+/- and zero out of 31 WT hearts. VT occurred in 11 out of 16 (10 microM) flecainide-treated WT and nine out of the 13 initially non-arrhythmogenic Scn5a+/- hearts treated with (1.0 microM) flecainide. Quinidine (10 microM) prevented VT in six out of six flecainide-treated WT and 13 out of the 16 arrhythmogenic Scn5a+/- hearts in parallel with its clinical effects. Paced electrogram fractionation analysis demonstrated increased electrogram durations, expressed as electrogram duration (EGD) ratios, with shortening S1-S2 intervals in arrhythmogenic Scn5a+/- hearts, and prolonged ventricular effective refractory periods (VERPs) in non-arrhythmogenic Scn5a+/- hearts. Flecainide increased EGD ratios in WT (at 10 microM) and non-arrhythmogenic Scn5a+/- hearts (at 1.0 microM), whereas quinidine (10 microM) reduced EGD ratios and prolonged VERPs in WT and arrhythmogenic Scn5a+/- hearts. However, epicardial and endocardial monophasic action potential recordings consistently demonstrated positive gradients of repolarization in WT, arrhythmogenic and non-arrhythmogenic Scn5a+/- hearts under all pharmacological conditions. Together, these findings demonstrate proarrhythmic effects of flecainide in WT and Scn5a+/- murine hearts that recapitulate its clinical effects. They further attribute the arrhythmogenic phenomena observed here to re-entrant substrates resulting from delayed epicardial activation despite an absence of transmural heterogeneities of repolarization, in sharp contrast to recent characterizations in 'gain-of-function' Scn5a+/Delta murine hearts modelling the long-QT(3) syndrome.
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Affiliation(s)
- Kate S Stokoe
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
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Thomas G, Gurung IS, Killeen MJ, Hakim P, Goddard CA, Mahaut-Smith MP, Colledge WH, Grace AA, Huang CLH. Effects of L-type Ca2+ channel antagonism on ventricular arrhythmogenesis in murine hearts containing a modification in the Scn5a gene modelling human long QT syndrome 3. J Physiol 2006; 578:85-97. [PMID: 17110414 PMCID: PMC2075124 DOI: 10.1113/jphysiol.2006.121921] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Ventricular arrhythmogenesis in long QT 3 syndrome (LQT3) involves both triggered activity and re-entrant excitation arising from delayed ventricular repolarization. Effects of specific L-type Ca2+ channel antagonism were explored in a gain-of-function murine LQT3 model produced by a DeltaKPQ 1505-1507 deletion in the SCN5A gene. Monophasic action potentials (MAPs) were recorded from epicardial and endocardial surfaces of intact, Langendorff-perfused Scn5a+/Delta hearts. In untreated Scn5a+/Delta hearts, epicardial action potential duration at 90% repolarization (APD90) was 60.0 +/- 0.9 ms compared with 46.9 +/- 1.6 ms in untreated wild-type (WT) hearts (P < 0.05; n = 5). The corresponding endocardial APD(90) values were 52.0 +/- 0.7 ms and 53.7 +/- 1.6 ms in Scn5a+/Delta and WT hearts, respectively (P > 0.05; n = 5). Epicardial early afterdepolarizations (EADs), often accompanied by spontaneous ventricular tachycardia (VT), occurred in 100% of MAPs from Scn5a+/Delta but not in any WT hearts (n = 10). However, EAD occurrence was reduced to 62 +/- 7.1%, 44 +/- 9.7%, 10 +/- 10% and 0% of MAPs following perfusion with 10 nm, 100 nm, 300 nm and 1 mum nifedipine, respectively (P < 0.05; n = 5), giving an effective IC50 concentration of 79.3 nm. Programmed electrical stimulation (PES) induced VT in all five Scn5a+/Delta hearts (n = 5) but not in any WT hearts (n = 5). However, repeat PES induced VT in 3, 2, 2 and 0 out of 5 Scn5a+/Delta hearts following perfusion with 10 nm, 100 nm, 300 nm and 1 mum nifedipine, respectively. Patch clamp studies in isolated ventricular myocytes from Scn5a+/Delta and WT hearts confirmed that nifedipine (300 nm) completely suppressed the inward Ca2+ current but had no effect on inward Na+ currents. No significant effects were seen on epicardial APD90, endocardial APD90 or ventricular effective refractory period in Scn5a+/Delta and WT hearts following perfusion with nifedipine at 1 nm, 10 nm, 100 nm, 300 nm and 1 microm nifedipine concentrations. We conclude that L-type Ca2+ channel antagonism thus exerts specific anti-arrhythmic effects in Scn5a+/Delta hearts through suppression of EADs.
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Affiliation(s)
- Glyn Thomas
- Section of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
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Thomas G, Killeen MJ, Gurung IS, Hakim P, Balasubramaniam R, Goddard CA, Grace AA, Huang CLH. Mechanisms of ventricular arrhythmogenesis in mice following targeted disruption of KCNE1 modelling long QT syndrome 5. J Physiol 2006; 578:99-114. [PMID: 17095567 PMCID: PMC2075126 DOI: 10.1113/jphysiol.2006.118133] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mutations within KCNE1 encoding a transmembrane protein which coassembles with K+ channels mediating slow K+, I(Ks), currents are implicated in cardiac action potential prolongation and ventricular arrhythmogenicity in long QT syndrome 5. We demonstrate the following potentially arrhythmogenic features in simultaneously recorded, left ventricular, endocardial and epicardial monophasic action potentials from Langendorff-perfused murine KCNE1-/- hearts for the first time. (1) Prolonged epicardial (57.1 +/- 0.5 ms cf. 36.1 +/- 0.07 ms in wild-type (WT), P < 0.001; n = 5) and endocardial action potential duration at 90% repolarication (APD90) (54.4 +/- 2.4 ms cf. 48.5 +/- 0.3 ms, P < 0.05; n = 5). (2) Negative transmural repolarization gradients (DeltaAPD90: endocardial minus epicardial APD90) (-2.5 +/- 2.4 ms, compared with 12.4 +/- 1.1 ms in WT, P < 0.001; n = 5). (3) Frequent epicardial early afterdepolarizations (EADs) and spontaneous ventricular tachycardia (VT) in 4 out of 5 KCNE1-/- hearts but not WT (n = 5). EADs were especially frequent following temporary cessations of ventricular pacing. (4) Monomorphic VT lasting 1.36 +/- 0.2 s in 5 out of 5 KCNE1-/- hearts, following premature stimuli but not WT (n = 5). (5) Epicardial APD alternans. Perfusion of KCNE1-/- hearts with 1 mum nifedipine induced potentially anti-arrhythmic changes including: (1) restored epicardial APD90 (from 57.1 +/- 0.5 ms to 42.3 +/- 0.4 ms, P < 0.001; n = 5); (2) altered DeltaAPD90 to values (11.2 +/- 2.6) close to WT (P > 0.05; n = 5); (3) EAD suppression during both spontaneous activity and following cessation of ventricular pacing (n = 5) to give similar features to WT controls (n = 5); (4) suppression of programmed electrical stimulation-induced VT; and (5) suppression of APD alternans. These findings suggest arrhythmic effects of reduced outward currents expected in KCNE1-/- hearts and their abolition by antagonism of inward L-type Ca2+ current.
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Affiliation(s)
- Glyn Thomas
- Section of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
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Stokoe KS, Thomas G, Goddard CA, Colledge WH, Grace AA, Huang CLH. Effects of flecainide and quinidine on arrhythmogenic properties of Scn5a+/Delta murine hearts modelling long QT syndrome 3. J Physiol 2006; 578:69-84. [PMID: 17023504 PMCID: PMC1810389 DOI: 10.1113/jphysiol.2006.117945] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Long QT3 (LQT3) syndrome is associated with incomplete Na+ channel inactivation, abnormal repolarization kinetics and prolonged cardiac action potential duration (APD). Electrophysiological effects of flecainide and quinidine were compared in Langendorff-perfused wild-type (WT), and genetically modified (Scn5a+/Delta) murine hearts modelling LQT3. Extra stimuli (S2) following trains of pacing stimuli (S1) applied to the right ventricular epicardium triggered ventricular tachycardia (VT) in 16 out of 28 untreated Scn5a+/Delta and zero out of 12 WT hearts. Paced electrogram fractionation analysis then demonstrated increased electrogram durations (EGD), expressed as EGD ratios, in arrhythmogenic Scn5a+/Delta hearts, and prolonged ventricular effective refractory periods in initially non-arrhythmogenic Scn5a+/Delta hearts. Nevertheless, comparisons of epicardial and endocardial monophasic action potential recordings demonstrated negative transmural repolarization gradients in both groups, giving DeltaAPD(90) values at 90% repolarization of -20.88 +/- 1.93 ms (n = 11) and -16.91 +/- 1.43 ms (n = 23), respectively. Flecainide prevented initiation of VT in 13 out of 16 arrhythmogenic Scn5a+/Delta hearts, reducing EGD ratio and restoring DeltaAPD90 to + 7.55 +/- 2.24 ms (n = 9) (P < 0.05). VT occurred in four out of eight non-arrhythmogenic Scn5a+/Delta hearts in the presence of quinidine, which increased EGD ratio but left DeltaAPD90 unchanged. In contrast (P < 0.05), WT hearts had positive DeltaAPD90 values (+ 11.72 +/- 2.17 ms) (n = 20). Flecainide then increased arrhythmic tendency and EGD ratio but conserved DeltaAPD90; reduced EGD ratios and unaltered DeltaAPD90 values accompanied the lower arrhythmogenicity associated with quinidine treatment. In addition to the changes in EGD ratio shown by WT hearts, these findings attribute arrhythmogenesis and its modification by flecainide and quinidine to alterations in DeltaAPD90 in Scn5a+/Delta hearts. This is consistent with a hypothesis in which incomplete Na+ channel inactivation in Scn5a+/Delta hearts generates functional substrates dependent on altered refractoriness that cause abnormalities in activation and conduction of subsequent cardiac impulses. Any spatial heterogeneities between the epicardial and endocardial layers would thus cause fragmentation of the activation wavefront and contribute to electrogram spreading.
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Affiliation(s)
- Kate S Stokoe
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
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Howlett SE, Grandy SA, Ferrier GR. Calcium spark properties in ventricular myocytes are altered in aged mice. Am J Physiol Heart Circ Physiol 2006; 290:H1566-74. [PMID: 16327019 DOI: 10.1152/ajpheart.00686.2005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study determined whether whole cell Ca2+ transients and unitary sarcoplasmic reticulum (SR) Ca2+ release events are constant throughout adult life or whether Ca2+ release is altered in aging ventricular myocytes. Myocytes were isolated from young adult (∼5 mo old) and aged (∼24 mo old) mice. Spontaneous Ca2+ sparks and Ca2+ transients initiated by field stimulation were detected with fluo-4. All experiments were conducted at 37°C. Ca2+ transient amplitudes were reduced, and Ca2+ transient rise times were abbreviated in aged cells stimulated at 8 Hz compared with young adult myocytes. Furthermore, the incidence and frequency of spontaneous Ca2+ sparks were markedly higher in aged myocytes compared with young adult cells. Spark amplitudes and spatial widths were similar in young adult and aged myocytes. However, spark half-rise times and half-decay times were abbreviated in aged cells compared with younger cells. Resting cytosolic Ca2+ levels and SR Ca2+ stores were assessed by rapid application of caffeine in fura-2-loaded cells. Neither resting Ca2+ levels nor SR Ca2+ content differed between young adult and aged cells. Thus increased spark frequency in aging cells was not attributable to increased SR Ca2+ stores. Furthermore, the decrease in Ca2+ transient amplitude was not due to a decrease in SR Ca2+ load. These results demonstrate that alterations in fundamental SR Ca2+ release units occur in aging ventricular myocytes and raise the possibility that alterations in Ca2+ release may reflect age-related changes in fundamental release events rather than changes in SR Ca2+ stores and diastolic Ca2+ levels.
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Affiliation(s)
- Susan E Howlett
- Dept. of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5.
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