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Blaesi AH, Saka N. WITHDRAWN: Gastroretentive fibrous dosage forms for prolonged delivery of sparingly-soluble tyrosine kinase inhibitors. Part 1: Dosage form design, and models of expansion, post-expansion mechanical strength, and drug release. Int J Pharm 2024; 653:123428. [PMID: 37806505 DOI: 10.1016/j.ijpharm.2023.123428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 09/10/2023] [Accepted: 09/17/2023] [Indexed: 10/10/2023]
Affiliation(s)
- Aron H Blaesi
- Enzian Pharmaceutics Blaesi AG, CH-7078, Lenzerheide, Switzerland; Enzian Pharmaceutics, Inc., Cambridge, MA 02139, USA.
| | - Nannaji Saka
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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2
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Valentin JP, Hoffmann P, Ortemann-Renon C, Koerner J, Pierson J, Gintant G, Willard J, Garnett C, Skinner M, Vargas HM, Wisialowski T, Pugsley MK. OUP accepted manuscript. Toxicol Sci 2022; 187:3-24. [PMID: 35148401 PMCID: PMC9041548 DOI: 10.1093/toxsci/kfac013] [Citation(s) in RCA: 3] [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: 11/13/2022] Open
Abstract
The content of this article derives from a Health and Environmental Sciences Institute (HESI) consortium with a focus to improve cardiac safety during drug development. A detailed literature review was conducted to evaluate the concordance between nonclinical repolarization assays and the clinical thorough QT (TQT) study. Food and Drug Administration and HESI developed a joint database of nonclinical and clinical data, and a retrospective analysis of 150 anonymized drug candidates was reviewed to compare the performance of 3 standard nonclinical assays with clinical TQT study findings as well as investigate mechanism(s) potentially responsible for apparent discrepancies identified. The nonclinical assays were functional (IKr) current block (Human ether-a-go-go related gene), action potential duration, and corrected QT interval in animals (in vivo corrected QT). Although these nonclinical assays demonstrated good specificity for predicting negative clinical QT prolongation, they had relatively poor sensitivity for predicting positive clinical QT prolongation. After review, 28 discordant TQT-positive drugs were identified. This article provides an overview of direct and indirect mechanisms responsible for QT prolongation and theoretical reasons for lack of concordance between clinical TQT studies and nonclinical assays. We examine 6 specific and discordant TQT-positive drugs as case examples. These were derived from the unique HESI/Food and Drug Administration database. We would like to emphasize some reasons for discordant data including, insufficient or inadequate nonclinical data, effects of the drug on other cardiac ion channels, and indirect and/or nonelectrophysiological effects of drugs, including altered heart rate. We also outline best practices that were developed based upon our evaluation.
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Affiliation(s)
- Jean-Pierre Valentin
- Department of Investigative Toxicology, UCB Biopharma SRL, Braine-l’Alleud B-1420, Belgium
| | | | | | - John Koerner
- Center for Drug Evaluation and Research, FDA, Silver Spring, Maryland 20993, USA
| | - Jennifer Pierson
- To whom correspondence should be addressed at Health and Environmental Sciences Institute, 740 15th Street, N.W., Suite 600, Washington, DC 20005, USA. E-mail:
| | | | - James Willard
- Center for Drug Evaluation and Research, FDA, Silver Spring, Maryland 20993, USA
| | - Christine Garnett
- Center for Drug Evaluation and Research, FDA, Silver Spring, Maryland 20993, USA
| | | | - Hugo M Vargas
- Department of Safety Pharmacology & Animal Research Center, Amgen, Thousand Oaks, California 91320, USA
| | - Todd Wisialowski
- Department of Safety Pharmacology, Pfizer, Groton, Connecticut 06340, USA
| | - Michael K Pugsley
- Department of Toxicology, Cytokinetics, South San Francisco, California 94080, USA
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3
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Nalos L, Jarkovská D, Švíglerová J, Süß A, Záleský J, Rajdl D, Krejčová M, Kuncová J, Rosenberg J, Štengl M. TdP Incidence in Methoxamine-Sensitized Rabbit Model Is Reduced With Age but Not Influenced by Hypercholesterolemia. Front Physiol 2021; 12:692921. [PMID: 34234694 PMCID: PMC8255784 DOI: 10.3389/fphys.2021.692921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 05/17/2021] [Indexed: 11/13/2022] Open
Abstract
Metabolic syndrome is associated with hypercholesterolemia, cardiac remodeling, and increased susceptibility to ventricular arrhythmias. Effects of diet-induced hypercholesterolemia on susceptibility to torsades de pointes arrhythmias (TdP) together with potential indicators of arrhythmic risk were investigated in three experimental groups of Carlsson's rabbit model: (1) young rabbits (YC, young control, age 12-16 weeks), older rabbits (AC, adult control, age 20-24 weeks), and older age-matched cholesterol-fed rabbits (CH, cholesterol, age 20-24 weeks). TdP was induced by α-adrenergic stimulation by methoxamine and IKr block in 83% of YC rabbits, 18% of AC rabbits, and 21% of CH rabbits. High incidence of TdP was associated with high incidence of single (SEB) and multiple ectopic beats (MEB), but the QTc prolongation and short-term variability (STV) were similar in all three groups. In TdP-susceptible rabbits, STV was significantly higher compared with arrhythmia-free rabbits but not with rabbits with other than TdP arrhythmias (SEB, MEB). Amplitude-aware permutation entropy analysis of baseline ECG could identify arrhythmia-resistant animals with high sensitivity and specificity. The data indicate that the TdP susceptibility in methoxamine-sensitized rabbits is affected by the age of rabbits but probably not by hypercholesterolemia. Entropy analysis could potentially stratify the arrhythmic risk and identify the low-risk individuals.
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Affiliation(s)
- Lukáš Nalos
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia.,Biomedical Center, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
| | - Dagmar Jarkovská
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia.,Biomedical Center, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
| | - Jitka Švíglerová
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia.,Biomedical Center, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
| | - Annabell Süß
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
| | - Jakub Záleský
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
| | - Daniel Rajdl
- Institute of Clinical Biochemistry and Haematology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
| | - Milada Krejčová
- New Technologies for the Information Society, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czechia
| | - Jitka Kuncová
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia.,Biomedical Center, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
| | - Josef Rosenberg
- New Technologies for the Information Society, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czechia
| | - Milan Štengl
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia.,Biomedical Center, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czechia
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4
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Lee S, Kittleson MD. Naturally occurring torsades de pointes and QT interval prolongation in a domestic cat. J Vet Cardiol 2021; 35:42-47. [PMID: 33812132 DOI: 10.1016/j.jvc.2021.02.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 02/02/2021] [Accepted: 02/18/2021] [Indexed: 11/24/2022]
Abstract
A 10-year-old male American Shorthair cat was presented after a witnessed syncopal event. A Holter monitor demonstrated a long QT interval and revealed a rhythm characteristic of torsades de pointes (TdP) coincident with a bout of syncope. On subsequent Holter monitor recordings, sotalol did not prolong the QT interval further and did not reduce the severity of the underlying ventricular tachyarrhythmias, but no TdP was identified. When another syncopal event occurred, sotalol was discontinued, and oral amiodarone and magnesium were started. This resulted in improvement in the ventricular tachyarrhythmia. No syncopal events occurred in the ensuing 3 months, but the cat died of an unrelated disease shortly after. This is the first report of naturally occurring torsades de pointes in a domestic cat.
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Affiliation(s)
- S Lee
- Seoul Animal Heart Hospital, 542 Eonju-ro, Gangnam-gu, Seoul, Republic of Korea
| | - M D Kittleson
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA.
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5
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The electrophysiological effect of cannabidiol on hERG current and in guinea-pig and rabbit cardiac preparations. Sci Rep 2020; 10:16079. [PMID: 32999428 PMCID: PMC7528081 DOI: 10.1038/s41598-020-73165-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 09/10/2020] [Indexed: 12/28/2022] Open
Abstract
Cannabis use is associated with cardiovascular adverse effects ranging from arrhythmias to sudden cardiac death. The exact mechanism of action behind these activities is unknown. The aim of our work was to study the effect of cannabidiol (CBD), tetrahydrocannabinol and 11-nor-9-carboxy-tetrahydrocannabinol on cellular cardiac electrophysiological properties including ECG parameters, action potentials, hERG and IKr ion channels in HEK cell line and in rabbit and guinea pig cardiac preparations. CBD increased action potential duration in rabbit and guinea pig right ventricular papillary muscle at lower concentrations (1 µM, 2.5 µM and 5 µM) but did not significantly change it at 10 µM. CBD at high concentration (10 µM) decreased inward late sodium and L-type calcium currents as well. CBD inhibited hERG potassium channels with an IC50 value of 2.07 µM at room temperature and delayed rectifier potassium current with 6.5 µM at 37 °C, respectively. The frequency corrected QT interval (QTc) was significantly lengthened in anaesthetized guinea pig without significantly changing other ECG parameters. Although the IC50 value of CBD was higher than literary Cmax values after CBD smoking and oral intake, our results raise the possibility that hERG and potassium channel inhibition might have a role in the possible proarrhythmic adverse effects of cannabinoids in situations where metabolism of CBD impaired and/or the repolarization reserve is weakened.
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6
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Heit MC, Stallons LJ, Seewald W, Thompson CM, Toutain CE, King SB, Helbig R. Safety evaluation of the interchangeable use of robenacoxib in commercially-available tablets and solution for injection in cats. BMC Vet Res 2020; 16:355. [PMID: 32988403 PMCID: PMC7520961 DOI: 10.1186/s12917-020-02553-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 08/31/2020] [Indexed: 11/18/2022] Open
Abstract
Background Robenacoxib (Onsior™) is a non-steroidal anti-inflammatory drug developed for canine and feline use for the control of pain and inflammation. It is available as both tablets and solution for injection. The objective of this study was to evaluate the safety of the interchangeable use of commercially available robenacoxib formulations when administered to cats orally using 6 mg tablets and subcutaneously using a solution for injection containing 20 mg/mL. Thirty-four naïve healthy 4-month old cats were enrolled in this 37-day study and were randomized to four groups (three robenacoxib and one control). One robenacoxib group received the maximum recommended dose (MRD) rate of each formulation, while the other two received two and three times this dose rate. The cats underwent three 10-day treatment cycles comprised of seven days of once daily oral administration followed by three days of subcutaneous administration. The third cycle was followed by an additional seven days of oral treatment. The control group received oral empty gelatin capsules or subcutaneous saline injections. Assessment of safety was based on general health observations, clinical observations, physical, ophthalmic, electrocardiographic and neurological examinations, clinical pathology evaluations, food consumption, body weight, and macroscopic and microscopic examinations. Blood samples were collected for toxicokinetic evaluation. Results Blood concentrations of robenacoxib confirmed systemic exposure of all treated cats. All cats were in good health through study termination and there were no serious adverse events during the study. There were no changes in body weight, food consumption, ophthalmic, physical or neurological examinations during the study. Treatment-related abnormalities were of low occurrence at all doses and included injection site changes (transient edema with minimal or mild, subacute/chronic inflammation histologically) and prolongation of the QT interval. These findings were consistent with previously observed findings in studies with robenacoxib administered separately orally or subcutaneously in cats. Thus, there were no adverse effects that could be attributed specifically to the interchangeable use of oral and injectable robenacoxib. Conclusions This 37-day laboratory study supports the safety of interchanging robenacoxib injection at a daily dose of 2 mg/kg with robenacoxib tablets at a daily dose of 1 mg/kg, or vice versa.
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Affiliation(s)
- Mark C Heit
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN, 64140, USA.
| | - L Jay Stallons
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN, 64140, USA
| | - Wolfgang Seewald
- Elanco Animal Health, Mattenstrasse 24a, CH-4058, Basel, Switzerland
| | - Caryn M Thompson
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN, 64140, USA
| | - Céline E Toutain
- Elanco Animal Health, Mattenstrasse 24a, CH-4058, Basel, Switzerland
| | - Stephen B King
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN, 64140, USA
| | - Rainer Helbig
- Elanco Animal Health, Mattenstrasse 24a, CH-4058, Basel, Switzerland
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7
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Hornyik T, Castiglione A, Franke G, Perez-Feliz S, Major P, Hiripi L, Koren G, Bősze Z, Varró A, Zehender M, Brunner M, Bode C, Baczkó I, Odening KE. Transgenic LQT2, LQT5, and LQT2-5 rabbit models with decreased repolarisation reserve for prediction of drug-induced ventricular arrhythmias. Br J Pharmacol 2020; 177:3744-3759. [PMID: 32436214 PMCID: PMC7393202 DOI: 10.1111/bph.15098] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 04/09/2020] [Accepted: 04/23/2020] [Indexed: 12/21/2022] Open
Abstract
Background and Purpose Reliable prediction of pro‐arrhythmic side effects of novel drug candidates is still a major challenge. Although drug‐induced pro‐arrhythmia occurs primarily in patients with pre‐existing repolarisation disturbances, healthy animals are employed for pro‐arrhythmia testing. To improve current safety screening, transgenic long QT (LQTS) rabbit models with impaired repolarisation reserve were generated by overexpressing loss‐of‐function mutations of human HERG (HERG‐G628S, loss of IKr; LQT2), KCNE1 (KCNE1‐G52R, decreased IKs; LQT5), or both transgenes (LQT2‐5) in the heart. Experimental Approach Effects of K+ channel blockers on cardiac repolarisation and arrhythmia susceptibility were assessed in healthy wild‐type (WT) and LQTS rabbits using in vivo ECG and ex vivo monophasic action potential and ECG recordings in Langendorff‐perfused hearts. Key Results LQTS models reflect patients with clinically “silent” (LQT5) or “manifest” (LQT2 and LQT2‐5) impairment in cardiac repolarisation reserve: they were more sensitive in detecting IKr‐blocking (LQT5) or IK1/IKs‐blocking (LQT2 and LQT2‐5) properties of drugs compared to healthy WT animals. Impaired QT‐shortening capacity at fast heart rates was observed due to disturbed IKs function in LQT5 and LQT2‐5. Importantly, LQTS models exhibited higher incidence, longer duration, and more malignant types of ex vivo arrhythmias than WT. Conclusion and Implications LQTS models represent patients with reduced repolarisation reserve due to different pathomechanisms. As they demonstrate increased sensitivity to different specific ion channel blockers (IKr blockade in LQT5 and IK1 and IKs blockade in LQT2 and LQT2‐5), their combined use could provide more reliable and more thorough prediction of (multichannel‐based) pro‐arrhythmic potential of novel drug candidates.
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Affiliation(s)
- Tibor Hornyik
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Institute of Experimental Cardiovascular Medicine, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Alessandro Castiglione
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany
| | - Gerlind Franke
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany
| | - Stefanie Perez-Feliz
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Institute of Experimental Cardiovascular Medicine, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany
| | - Péter Major
- NARIC-Agricultural Biotechnology Institute, Animal Biotechnology Department, Gödöllő, Hungary
| | - László Hiripi
- NARIC-Agricultural Biotechnology Institute, Animal Biotechnology Department, Gödöllő, Hungary
| | - Gideon Koren
- Cardiovascular Research Center, Brown University, Providence, Rhode Island, USA
| | - Zsuzsanna Bősze
- NARIC-Agricultural Biotechnology Institute, Animal Biotechnology Department, Gödöllő, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Manfred Zehender
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany
| | - Michael Brunner
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Department of Cardiology and Medical Intensive Care, St. Josefskrankenhaus, Freiburg, Germany
| | - Christoph Bode
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Katja E Odening
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Institute of Experimental Cardiovascular Medicine, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Translational Cardiology, Department of Cardiology, Inselspital, Bern University Hospital, and Institute of Physiology, University of Bern, Bern, Switzerland
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8
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Bernikova OG, Sedova KA, Arteyeva NV, Ovechkin AO, Kharin SN, Shmakov DN, Azarov JE. Repolarization in perfused myocardium predicts reperfusion ventricular tachyarrhythmias. J Electrocardiol 2018; 51:542-548. [DOI: 10.1016/j.jelectrocard.2017.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Indexed: 11/30/2022]
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9
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Baburin I, Varkevisser R, Schramm A, Saxena P, Beyl S, Szkokan P, Linder T, Stary-Weinzinger A, van der Heyden MAG, Houtman M, Takanari H, Jonsson M, Beekman JHD, Hamburger M, Vos MA, Hering S. Dehydroevodiamine and hortiamine, alkaloids from the traditional Chinese herbal drug Evodia rutaecarpa, are I Kr blockers with proarrhythmic effects in vitro and in vivo. Pharmacol Res 2018; 131:150-163. [PMID: 29477480 DOI: 10.1016/j.phrs.2018.02.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 02/09/2018] [Accepted: 02/20/2018] [Indexed: 11/26/2022]
Abstract
Evodiae fructus is a widely used herbal drug in traditional Chinese medicine. Evodia extract was found to inhibit hERG channels. The aim of the current study was to identify hERG inhibitors in Evodia extract and to investigate their potential proarrhythmic effects. Dehydroevodiamine (DHE) and hortiamine were identified as IKr (rapid delayed rectifier current) inhibitors in Evodia extract by HPLC-microfractionation and subsequent patch clamp studies on human embryonic kidney cells. DHE and hortiamine inhibited IKr with IC50s of 253.2±26.3nM and 144.8±35.1nM, respectively. In dog ventricular cardiomyocytes, DHE dose-dependently prolonged the action potential duration (APD). Early afterdepolarizations (EADs) were seen in 14, 67, 100, and 67% of cells after 0.01, 0.1, 1 and 10μM DHE, respectively. The proarrhythmic potential of DHE was evaluated in 8 anesthetized rabbits and in 8 chronic atrioventricular block (cAVB) dogs. In rabbits, DHE increased the QT interval significantly by 12±10% (0.05mg/kg/5min) and 60±26% (0.5mg/kg/5min), and induced Torsade de Pointes arrhythmias (TdP, 0.5mg/kg/5min) in 2 rabbits. In cAVB dogs, 0.33mg/kg/5min DHE increased QT duration by 48±10% (P<0.05*) and induced TdP in 2/4 dogs. A higher dose did not induce TdP. In human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), methanolic extracts of Evodia, DHE and hortiamine dose-dependently prolonged APD. At 3μM DHE and hortiamine induced EADs. hERG inhibition at submicromolar concentrations, APD prolongation and EADs in hiPSC-CMs and dose-dependent proarrhythmic effects of DHE at micromolar plasma concentrations in cAVB dogs should increase awareness regarding proarrhythmic effects of widely used Evodia extracts.
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Affiliation(s)
- Igor Baburin
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria.
| | - Rosanne Varkevisser
- Department of Medical Physiology, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Anja Schramm
- Division of Pharmaceutical Biology, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Priyanka Saxena
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Stanislav Beyl
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Phillip Szkokan
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; ChanPharm GmbH, Leidesdorfgasse 14, Top 6, 1190 Vienna, Austria
| | - Tobias Linder
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Marcel A G van der Heyden
- Department of Medical Physiology, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Marien Houtman
- Department of Medical Physiology, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Hiroki Takanari
- Department of Medical Physiology, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Malin Jonsson
- Department of Medical Physiology, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Jet H D Beekman
- Department of Medical Physiology, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Matthias Hamburger
- Division of Pharmaceutical Biology, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Marc A Vos
- Department of Medical Physiology, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Steffen Hering
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
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Ligneau X, Shah RR, Berrebi‐Bertrand I, Mirams GR, Robert P, Landais L, Maison‐Blanche P, Faivre J, Lecomte J, Schwartz J. Nonclinical cardiovascular safety of pitolisant: comparing International Conference on Harmonization S7B and Comprehensive in vitro Pro-arrhythmia Assay initiative studies. Br J Pharmacol 2017; 174:4449-4463. [PMID: 28941245 PMCID: PMC5715595 DOI: 10.1111/bph.14047] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 09/15/2017] [Accepted: 09/18/2017] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND AND PURPOSE We evaluated the concordance of results from two sets of nonclinical cardiovascular safety studies on pitolisant. EXPERIMENTAL APPROACH Nonclinical studies envisaged both in the International Conference on Harmonization (ICH) S7B guideline and Comprehensive in vitro Pro-arrhythmia Assay (CiPA) initiative were undertaken. The CiPA initiative included in vitro ion channels, stem cell-derived human ventricular myocytes, and in silico modelling to simulate human ventricular electrophysiology. ICH S7B-recommended assays included in vitro hERG (KV 11.1) channels, in vivo dog studies with follow-up investigations in rabbit Purkinje fibres and the in vivo Carlsson rabbit pro-arrhythmia model. KEY RESULTS Both sets of nonclinical data consistently excluded pitolisant from having clinically relevant QT-liability or pro-arrhythmic potential. CiPA studies revealed pitolisant to have modest calcium channel blocking and late INa reducing activities at high concentrations, which resulted in pitolisant reducing dofetilide-induced early after-depolarizations (EADs) in the ICH S7B studies. Studies in stem cell-derived human cardiomyocytes with dofetilide or E-4031 given alone and in combination with pitolisant confirmed these properties. In silico modelling confirmed that the ion channel effects measured are consistent with results from both the stem cell-derived cardiomyocytes and rabbit Purkinje fibres and categorized pitolisant as a drug with low torsadogenic potential. Results from the two sets of nonclinical studies correlated well with those from two clinical QT studies. CONCLUSIONS AND IMPLICATIONS Our findings support the CiPA initiative but suggest that sponsors should consider investigating drug effects on EADs and the use of pro-arrhythmia models when the results from CiPA studies are ambiguous.
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Affiliation(s)
| | | | | | - Gary R Mirams
- Centre for Mathematical Medicine and Biology, School of Mathematical SciencesUniversity of NottinghamNottinghamUK
| | | | | | | | - Jean‐François Faivre
- Laboratoire Signalisation et Transports Ioniques MembranairesUniversité de Poitiers‐CNRSPoitiersFrance
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Conlon K, De Maeyer JH, Bruce C, Schuurkes JAJ, Christie L, McRedmond J, Derakhchan K, Wade PR. Nonclinical Cardiovascular Studies of Prucalopride, a Highly Selective 5-Hydroxytryptamine 4 Receptor Agonist. J Pharmacol Exp Ther 2017; 364:156-169. [DOI: 10.1124/jpet.117.244079] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 10/31/2017] [Indexed: 11/22/2022] Open
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12
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Sandau KE, Funk M, Auerbach A, Barsness GW, Blum K, Cvach M, Lampert R, May JL, McDaniel GM, Perez MV, Sendelbach S, Sommargren CE, Wang PJ. Update to Practice Standards for Electrocardiographic Monitoring in Hospital Settings: A Scientific Statement From the American Heart Association. Circulation 2017; 136:e273-e344. [DOI: 10.1161/cir.0000000000000527] [Citation(s) in RCA: 121] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Hagiwara M, Shibuta S, Takada K, Kambayashi R, Nakajo M, Aimoto M, Nagasawa Y, Takahara A. The anaesthetized rabbit with acute atrioventricular block provides a new model for detecting drug-induced Torsade de Pointes. Br J Pharmacol 2017; 174:2591-2605. [PMID: 28547743 DOI: 10.1111/bph.13870] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 05/03/2017] [Accepted: 05/04/2017] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Several rabbit proarrhythmia models have been developed using genetic or pharmacological methods to suppress the slow component of delayed rectifier K+ currents in the ventricle, leading to reduction of the repolarization reserve. Here we have characterized a novel rabbit in vivo proarrhythmia model with severe bradycardia caused by acute atrioventricular block (AVB). EXPERIMENTAL APPROACH Bradycardia was induced in isoflurane-anaesthetized rabbits by inducing AVB with catheter ablation, and the ventricle was electrically driven at 60 beats min-1 throughout the experiment except when extrasystoles appeared. We assessed the effects of two antiarrhythmics, two quinolone antibiotics and one antipsychotic drug, which were chosen as positive drugs (dofetilide, sparfloxacin and haloperidol) and negative drugs (amiodarone and moxifloxacin) for induction of Torsades de Pointes (TdP). KEY RESULTS In our model, TdP arrhythmias appeared with high reproducibility after i.v. dofetilide (10-100 μg·kg-1 ) in five out of six rabbits, sparfloxacin (30 mg·kg-1 ) in three out of six rabbits and haloperidol (0.3-3 mg·kg-1 ) in two out of six rabbits. The lethal arrhythmias repeatedly appeared and were accompanied with prolongation of the QT interval and early afterdepolarization-like phenomena. Neither amiodarone (0.3-10 mg·kg-1 , n = 6) nor moxifloxacin (3-30 mg·kg-1 , n = 6) induced such arrhythmias, even when QT intervals were prolonged. CONCLUSIONS AND IMPLICATIONS These results suggest that our model of the unremodelled and bradycardic heart of the anaesthetized rabbit is a useful test system for the detection of drug-induced TdP arrhythmias.
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Affiliation(s)
- Mihoko Hagiwara
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
| | - Seiji Shibuta
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
| | - Kazuhiro Takada
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
| | - Ryuichi Kambayashi
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
| | - Misako Nakajo
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
| | - Megumi Aimoto
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
| | - Yoshinobu Nagasawa
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
| | - Akira Takahara
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan
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Wang J, Wang G, Quan X, Ruan L, Liu Y, Ruan Y, Liu N, Zhang C, Bai R. Fluconazole-induced long QT syndrome via impaired human ether-a-go-go-related gene (hERG) protein trafficking in rabbits. Europace 2017; 19:1244-1249. [PMID: 27189953 DOI: 10.1093/europace/euw091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 03/14/2016] [Indexed: 11/12/2022] Open
Abstract
Aims hERG protein trafficking deficiency has long been known in drug-induced long QT syndrome (LQTS). However, validated evidence from in vivo data kept scanty. Our goal was to investigate the proarrhythmic action of fluconazole and its underlying mechanism in an animal model. Methods and results Twenty female Japanese long-eared white rabbits were randomly distributed into a control group and a fluconazole group for a chronic 2-week treatment. The control group was treated with 0.5% sodium carboxymethylcellulose (CMCNa), and the fluconazole group was treated with fluconazole. Electrocardiograms (ECGs) were recorded during the experimental period. Isolated arterially perfused left ventricular wedge preparations from the rabbits were made 2 weeks after treatment, and the arrhythmia events, the transmural ECG, and action potential from both the endocardium and epicardium were recorded. The changes in hERG protein expression were measured by western blot. The fluconazole group showed a longer QT interval 1 week after treatment (P < 0.05) and a higher arrhythmia occurrence 2 weeks after treatment (P < 0.05) than the control group. The fluconazole group also showed a longer transmural dispersion of repolarization and a higher occurrence of life-threatening torsades de pointes in arterially perfused left ventricular preparations. Furthermore, western blot analysis showed that the density of mature hERG protein was lower in the fluconazole group than that in the control group. Conclusion Fluconazole can prolong the QT interval and possess proarrhythmic activity due to its inhibition of hERG protein trafficking in our experimental model. These findings may impact the clinical potential of fluconazole in humans.
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Affiliation(s)
- Jinli Wang
- Department of Geriatrics, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan 430030, P.R. China
| | - Guan Wang
- Department of Geriatrics, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan 430030, P.R. China
| | - Xiaoqing Quan
- Department of Geriatrics, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan 430030, P.R. China
| | - Lei Ruan
- Department of Geriatrics, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan 430030, P.R. China
| | - Yang Liu
- Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, P.R. China
| | - Yanfei Ruan
- Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, No. 2 Anzhen Rd, Beijing 100029, P.R. China
| | - Nian Liu
- Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, No. 2 Anzhen Rd, Beijing 100029, P.R. China
| | - Cuntai Zhang
- Department of Geriatrics, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan 430030, P.R. China
| | - Rong Bai
- Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, No. 2 Anzhen Rd, Beijing 100029, P.R. China.,Texas Cardiac Arrhythmia Institute at St David's Medical Center, Austin, TX, USA
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Abstract
This is a brief review of properties of cardiovascular function that should be considered for interrogation in studies of toxicology and/or safety pharmacology for non-cardiologists and non-physiologists. Since concern over the rarely occurring, unusual, and drug-induced tachycardia, Torsade de pointes, is a leading cause for cessation of development of potential drugs and for removal of drugs from the market, therefore, the toxic manifestation of drugs will be emphasized. The putative origin of torsade de pointes, and the origin of the electrocardiogram and electrocardiographic features of ventricular arrhythmias will be discussed.
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Affiliation(s)
- Robert L Hamlin
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio 43210, USA.
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16
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Kui P, Orosz S, Takács H, Sarusi A, Csík N, Rárosi F, Csekő C, Varró A, Papp JG, Forster T, Farkas AS, Farkas A. New in vitro model for proarrhythmia safety screening: IKs inhibition potentiates the QTc prolonging effect of IKr inhibitors in isolated guinea pig hearts. J Pharmacol Toxicol Methods 2016; 80:26-34. [DOI: 10.1016/j.vascn.2016.04.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 04/01/2016] [Accepted: 04/04/2016] [Indexed: 01/25/2023]
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17
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Baczkó I, Jost N, Virág L, Bősze Z, Varró A. Rabbit models as tools for preclinical cardiac electrophysiological safety testing: Importance of repolarization reserve. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:157-68. [PMID: 27208697 DOI: 10.1016/j.pbiomolbio.2016.05.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/01/2016] [Indexed: 01/26/2023]
Abstract
It is essential to more reliably assess the pro-arrhythmic liability of compounds in development. Current guidelines for pre-clinical and clinical testing of drug candidates advocate the use of healthy animals/tissues and healthy individuals and focus on the test compound's ability to block the hERG current and prolong cardiac ventricular repolarization. Also, pre-clinical safety tests utilize several species commonly used in cardiac electrophysiological studies. In this review, important species differences in cardiac ventricular repolarizing ion currents are considered, followed by the discussion on electrical remodeling associated with chronic cardiovascular diseases that leads to altered ion channel and transporter expression and densities in pathological settings. We argue that the choice of species strongly influences experimental outcome and extrapolation of results to human clinical settings. We suggest that based on cardiac cellular electrophysiology, the rabbit is a useful species for pharmacological pro-arrhythmic investigations. In addition to healthy animals and tissues, the use of animal models (e.g. those with impaired repolarization reserve) is suggested that more closely resemble subsets of patients exhibiting increased vulnerability towards the development of ventricular arrhythmias and sudden cardiac death.
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Affiliation(s)
- István Baczkó
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary.
| | - Norbert Jost
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Dóm tér 12., 6720 Szeged, Hungary
| | - László Virág
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary
| | - Zsuzsanna Bősze
- Rabbit Genome and Biomodel Group, NARIC-Agricultural Biotechnology Institute, 2100 Gödöllő, Hungary
| | - András Varró
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Dóm tér 12., 6720 Szeged, Hungary
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Sedova KA, Vaykshnorayte MA, Ovechkin AO, Kneppo P, Bernikova OG, Vityazev VA, Azarov JE. Ventricular electrical heterogeneity in experimental diabetes mellitus: effect of myocardial ischemia. Physiol Res 2016; 65:437-45. [PMID: 27070744 DOI: 10.33549/physiolres.933161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Aims of the study were to compare the development of electrocardiographic responses of the ischemia-induced heterogeneities of activation and repolarization in the ventricular myocardium of normal and diabetic animals. Body surface ECGs and unipolar electrograms in 64 epicardial leads were recorded before and during 20 min after the ligation of the left anterior descending artery in diabetic (alloxan model, 4 weeks, n=8) and control (n=8) rabbits. Activation times (ATs), end of repolarization times (RTs) and repolarization durations (activation-recovery intervals, ARIs) were determined in ischemic and periischemic zones. In contrast to the controls, the diabetic rabbits demonstrated the significant prolongation of ATs and shortening of ARIs (P<0.05) during ischemia in the affected region resulting in the development and progressive increase of the ARI and RT gradients across the ischemic zone boundary. The alterations of global and local dispersions of the RTs in diabetics correlated with the T(peak)-T(end) interval changes in the limb leads ECGs. In the ischemic conditions, the diabetic animals differed from the controls by the activation delay, significant repolarization duration shortening, and the increase of local repolarization dispersion; the latter could be assessed by the T(peak)-T(end) interval measurements in the body surface ECGs.
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Affiliation(s)
- K A Sedova
- Department of Biomedical Technology, Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, Czech Republic.
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19
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DURGUT R, ÖZTÜRK OH, NACAR A, SAĞKAN-ÖZTÜRK A. Cardiotoxic effects of enrofloxacin on electrophysiological activity, cardiac markers, oxidative stress, and haematological findings in rabbits. TURK J ZOOL 2016. [DOI: 10.3906/zoo-1510-51] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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20
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Assessment of efficacy of proarrhythmia biomarkers in isolated rabbit hearts with attenuated repolarization reserve. J Cardiovasc Pharmacol 2015; 64:266-76. [PMID: 24887684 DOI: 10.1097/fjc.0000000000000116] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Isolated hearts with reduced repolarization reserve would be suitable for assessing the proarrhythmic liability of drugs. However, it is not known which proarrhythmia biomarkers indicate the increased susceptibility to torsades de pointes arrhythmia (TdP) in such experimental setting. Thus, we estimated the efficacy of proarrhythmia biomarkers in isolated hearts with attenuated repolarization reserve. Langendorff-perfused rabbit hearts were used. Repolarization reserve was reduced by concomitant inhibition of the rapid (IKr) and slow (IKs) delayed rectifier potassium currents by dofetilide and HMR-1556, respectively. Rate corrected QT (QTc) interval and beat-to-beat variability of the QT interval measured in sinus rhythm or irrespective of rhythm even during arrhythmias (sinus and absolute QT variability, respectively) were tested. QTc failed to predict increased proarrhythmic risk. Sinus QT variability indicated proarrhythmic liability when low concentration of dofetilide was used. However, when arrhythmias compromised sinus variability measurement during coperfusion of catecholamines and elevated concentration of dofetilide, only absolute QT variability indicated increased proarrhythmic risk. Absolute QT variability parameters seem to be the most practical and sensitive biomarkers of proarrhythmic liability in rabbit hearts with reduced repolarization reserve. Absolute QT variability parameters could serve as surrogates for torsades de pointes in drug-safety investigations in isolated rabbit hearts with attenuated repolarization reserve.
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Sedova K, Bernikova O, Azarov J, Shmakov D, Vityazev V, Kharin S. Effects of echinochrome on ventricular repolarization in acute ischemia. J Electrocardiol 2015; 48:181-6. [DOI: 10.1016/j.jelectrocard.2015.01.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Indexed: 11/27/2022]
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22
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Assessment of anti-arrhythmic activity of antipsychotic drugs in an animal model: Influence of non-cardiac α1-adrenergic receptors. Eur J Pharmacol 2015; 748:10-7. [DOI: 10.1016/j.ejphar.2014.12.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 11/28/2014] [Accepted: 12/10/2014] [Indexed: 01/09/2023]
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23
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Ovechkin AO, Vaykshnorayte MA, Sedova K, Shumikhin KV, Arteyeva NV, Azarov JE. Functional role of myocardial electrical remodeling in diabetic rabbits. Can J Physiol Pharmacol 2014; 93:245-52. [PMID: 25666101 DOI: 10.1139/cjpp-2014-0293] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The objective of the study was to investigate the role of electrical remodeling of the ventricular myocardium in hemodynamic impairment and the development of arrhythmogenic substrate. Experiments were conducted with 11 healthy and 12 diabetic (alloxan model, 4 weeks) rabbits. Left ventricular pressure was monitored and unipolar electrograms were recorded from 64 epicardial leads. Aortic banding was used to provoke arrhythmia. The diabetic rabbits had prolonged QTc, with activation-recovery intervals (surrogates for repolarization durations) being relatively short on the left ventricular base and long on the anterior apical portions of both ventricles (P < 0.05). In the diabetic rabbits, a negative correlation (-0.726 to -0.817) was observed between dP/dt(max), dP/dt(min), and repolarization dispersions. Under conditions of systolic overload (5 min), tachyarrhythmias were equally rare and the QTc and activation-recovery intervals were shortened in both groups (P < 0.05), whereas QRS was prolonged in the diabetic rabbits only. The repolarization shortening was more pronounced on the apex, which led to the development of apicobasal and interventricular end of repolarization gradients in the healthy animals, and to the flattening of the repolarization profile in the diabetic group. Thus, the diabetes-related pattern of ventricular repolarization was associated with inotropic and lusitropic impairment of the cardiac pump function.
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Affiliation(s)
- Alexey O Ovechkin
- Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya Street, 167982 Syktyvkar, Russia., First Department of Internal Diseases of Komi Branch of Kirov State Medical Academy, 11 Babushkin Street, Syktyvkar 167000, Russia., Department of Physiology, Medical Institute of Syktyvkar State University, 11 Babushkin Street, Syktyvkar 167000, Russia
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24
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Transmural dispersion of repolarization and cardiac remodeling in ventricles of rabbit with right ventricular hypertrophy. J Pharmacol Toxicol Methods 2014; 71:129-36. [PMID: 25305588 DOI: 10.1016/j.vascn.2014.09.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 09/26/2014] [Accepted: 09/30/2014] [Indexed: 11/23/2022]
Abstract
INTRODUCTION Recent publications demonstrated that rabbits with right ventricular hypertrophy (RVH) possess high sensitivity and specificity for drug-induced arrhythmias. However, the underlying mechanism has not been elucidated. This study aimed to evaluate RVH induced changes in cardiac remodeling especially the transmural dispersion of repolarization (TDR), epicardial monophasic action potentials (MAP), and hERG mRNA expression in rabbits. METHODS New Zealand White rabbits (n=13) were divided into 2 groups: sham operated (SHAM, n=6) and pulmonary artery banding (PAB, n=7). PAB was induced by narrowing the pulmonary artery. Twenty weeks after surgery, hemodynamic, cardiac function, electrocardiograms, and MAP were obtained from PAB compared with SHAM. After measurement, rabbits were sacrificed to collect ventricular myocardium for histopathological analysis and measurement of hERG mRNA expression by real time PCR. RESULTS After 20weeks, the % HW to BW ratio of whole heart and right ventricle (RV) and left and right ventricular free wall thickness was significantly increased in PAB when compared with those in SHAM. PAB has a significant electrical remodeling as demonstrated by lengthening of QT, QTc intervals, and increased Tp-Te duration. PAB also has a significant functional remodeling verified by decreased contractility index of RV and lengthened time constant of relaxation of LV. MAP of RV epicardium was significantly shortened in PAB consistently with increased hERG mRNA expression at the epicardium of RV. DISCUSSION The rabbit with PAB demonstrates cardiac remodeling diastolic and systolic dysfunctions. These rabbits also demonstrate increased TDR and electrical remodeling related to the change of hERG mRNA expression which may be prone to develop arrhythmias.
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VARKEVISSER ROSANNE, VOS MARCA, BEEKMAN JETD, TIELAND RALPHG, VAN DER HEYDEN MARCELA. AV-Block and Conduction Slowing Prevail Over TdP Arrhythmias in the Methoxamine-Sensitized Pro-Arrhythmic Rabbit Model. J Cardiovasc Electrophysiol 2014; 26:82-9. [DOI: 10.1111/jce.12533] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 08/14/2014] [Accepted: 08/19/2014] [Indexed: 11/27/2022]
Affiliation(s)
- ROSANNE VARKEVISSER
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - MARC A. VOS
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - JET D. BEEKMAN
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - RALPH G. TIELAND
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - MARCEL A. VAN DER HEYDEN
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
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Varkevisser R, van der Heyden MAG, Tieland RG, Beekman JDM, Vos MA. Vernakalant is devoid of proarrhythmic effects in the complete AV block dog model. Eur J Pharmacol 2013; 720:49-54. [PMID: 24211677 DOI: 10.1016/j.ejphar.2013.10.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 10/25/2013] [Accepted: 10/29/2013] [Indexed: 11/28/2022]
Abstract
The anesthetized chronic AV-blocked dog (cAVB) and methoxamine-sensitized rabbit model are widely used to determine pro-arrhythmic properties of drugs. In general, both models show similar results. However, conflicting data have also been reported; K201 and AZD1305 induced Torsade de Pointes (TdP) exclusively in cAVB dogs. Vernakalant, an antiarrhythmic drug that blocks several ion channels has been approved only in Europe. Its propensity to induce repolarization-dependent TdP arrhythmias has been evaluated solely in the methoxamine-sensitized rabbits. We therefore assessed the proarrhythmic potential of vernakalant in the cAVB dog model. Vernakalant was evaluated in 10 mongrel dogs (sinus rhythm (SR) 2mg/kg; chronic AV block (cAVB) 2+3mg/kg). The same dogs were challenged with dofetilide (25 μg/kg) to evaluate TdP inducibility. During the serial experiments the animals were paced from the right ventricular apex (60 beats/min). Short-term variability of repolarization (STV) was quantified for proarrhythmic risk. In SR (n=8) vernakalant prolonged QT (265 ± 11 to 311 ± 18 ms P<0.01(**)) but not PQ or QRS. In cAVB (n=8), 2mg/kg vernakalant prolonged QT (391 ± 43 to 519 ± 73 ms(**)) and QRS (103 ± 24 to 108 ± 23 ms(**)). After a 30 min lag-time, 3mg/kg vernakalant (n=4) increased QT to a lesser extent (413 ± 34 to 454 ± 27 ms(**)) while maintaining QRS prolongation (114 ± 18 to 122 ± 20 ms(**)). Neither dose increased STV or caused arrhythmias. Dofetilide prolonged QT (398 ± 51 to 615 ± 71 ms(**)), increased STV (1.0 ± 0.4 to 2.2 ± 1.0 ms P<0.05(⁎)) and induced TdP arrhythmias in 6/8(⁎) cAVB dogs. Vernakalant did not induce arrhythmias in the cAVB dog model. Higher dosages (3mg/kg) did not prolong repolarization further whereas negative inotropic effects were starting to become apparent precluding further increases in dose.
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Affiliation(s)
- Rosanne Varkevisser
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
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Li X, Wang T, Han K, Zhuo X, Lu Q, Ma A. Bisoprolol reverses down-regulation of potassium channel proteins in ventricular tissues of rabbits with heart failure. J Biomed Res 2013; 25:274-9. [PMID: 23554701 PMCID: PMC3597065 DOI: 10.1016/s1674-8301(11)60037-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 04/28/2011] [Accepted: 05/14/2011] [Indexed: 11/24/2022] Open
Abstract
Remodeling of ion channels is an important mechanism of arrhythmia induced by heart failure (HF). We investigated the expression of potassium channel encoding genes in the ventricles of rabbit established by volume-overload operation followed with pressure-overload. The reversible effect of these changes with bisoprolol was also evaluated. The HF group exhibited left ventricular enlargement, systolic dysfunction, prolongation of corrected QT interval (QTc), and increased plasma brain natriuretic peptide levels in the HF rabbits. Several potassium channel subunit encoding genes were consistently down-regulated in the HF rabbits. After bisoprolol treatment, heart function was improved significantly and QTc was shortened. Additionally, the mRNA expression of potassium channel subunit genes could be partially reversed. The down-regulated expression of potassium channel subunits Kv4.3, Kv1.4, KvLQT1, minK and Kir 2.1 may contribute to the prolongation of action potential duration in the heart of rabbits induced by volume combined with pressure overload HF. Bisoprolol could partially reverse these down-regulations and improve heart function.
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Affiliation(s)
- Xi Li
- Department of Cardiovascular Medicine, the First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China
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Han C, Pogwizd SM, Killingsworth CR, Zhou Z, He B. Noninvasive cardiac activation imaging of ventricular arrhythmias during drug-induced QT prolongation in the rabbit heart. Heart Rhythm 2013; 10:1509-15. [PMID: 23773986 DOI: 10.1016/j.hrthm.2013.06.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Indexed: 11/18/2022]
Abstract
BACKGROUND Imaging myocardial activation from noninvasive body surface potentials promises to aid in both cardiovascular research and clinical medicine. OBJECTIVE To investigate the ability of a noninvasive 3-dimensional cardiac electrical imaging technique for characterizing the activation patterns of dynamically changing ventricular arrhythmias during drug-induced QT prolongation in rabbits. METHODS Simultaneous body surface potential mapping and 3-dimensional intracardiac mapping were performed in a closed-chest condition in 8 rabbits. Data analysis was performed on premature ventricular complexes, couplets, and torsades de pointes (TdP) induced during intravenous administration of clofilium and phenylephrine with combinations of various infusion rates. RESULTS The drug infusion led to a significant increase in the QT interval (from 175 ± 7 to 274 ± 31 ms) and rate-corrected QT interval (from 183 ± 5 to 262 ± 21 ms) during the first dose cycle. All the ectopic beats initiated by a focal activation pattern. The initial beat of TdPs arose at the focal site, whereas the subsequent beats were due to focal activity from different sites or 2 competing focal sites. The imaged results captured the dynamic shift of activation patterns and were in good correlation with the simultaneous measurements, with a correlation coefficient of 0.65 ± 0.02 averaged over 111 ectopic beats. Sites of initial activation were localized to be ~5 mm from the directly measured initiation sites. CONCLUSIONS The 3-dimensional cardiac electrical imaging technique could localize the origin of activation and image activation sequence of TdP during QT prolongation induced by clofilium and phenylephrine in rabbits. It offers the potential to noninvasively investigate the proarrhythmic effects of drug infusion and assess the mechanisms of arrhythmias on a beat-to-beat basis.
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Affiliation(s)
- Chengzong Han
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota
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Negative electro-mechanical windows are required for drug-induced Torsades de Pointes in the anesthetized guinea pig. J Pharmacol Toxicol Methods 2012; 66:125-34. [DOI: 10.1016/j.vascn.2012.03.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/13/2012] [Accepted: 03/29/2012] [Indexed: 11/17/2022]
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Najafipour H, Joukar S. Combination of opium smoking and hypercholesterolemia augments susceptibility for lethal cardiac arrhythmia and atherogenesis in rabbit. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2012; 34:154-159. [PMID: 22522425 DOI: 10.1016/j.etap.2012.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 03/02/2012] [Accepted: 03/18/2012] [Indexed: 05/31/2023]
Abstract
Opium consumption is increasing in some eastern societies, where it is grown. We investigated the effect of opium smoking on plasma atherogenic index and incidence of lethal cardiac arrhythmia, i.e. ventricular tachycardia (VT) and ventricular fibrillation (VF) in rabbits. Animals were divided into two-, normo- and hyper-cholesterolemic main groups fed with normal or high cholesterol diet prior and during short-term and long-term exposure to opium smoke. Then, isoproterenol (3mg/kg, i.p.) was injected to induce cardiac ischemia and animals were followed for 3h for counting of lethal arrhythmia incidence. Long-term opium smoking significantly increased the plasma atherogenic index. In ischemic hearts, opium smoking along with hypercholesterolemia significantly enhanced the incidence of fatal arrhythmia. This vulnerability was not mediated by changes in QT interval. These data suggest that opium smoking, especially in hypercholesterolemic conditions, can be a predisposing factor for atherogenesis and lethal arrhythmia.
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Affiliation(s)
- Hamid Najafipour
- Physiology Research Center, Kerman University of Medical Sciences, Kerman, Iran; Department of Physiology and Pharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Siyavash Joukar
- Physiology Research Center, Kerman University of Medical Sciences, Kerman, Iran; Department of Physiology and Pharmacology, Kerman University of Medical Sciences, Kerman, Iran.
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Wen D, Liu A, Chen F, Yang J, Dai R. Validation of visualized transgenic zebrafish as a high throughput model to assay bradycardia related cardio toxicity risk candidates. J Appl Toxicol 2012; 32:834-42. [PMID: 22744888 DOI: 10.1002/jat.2755] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 02/27/2012] [Accepted: 02/27/2012] [Indexed: 11/09/2022]
Abstract
Drug-induced QT prolongation usually leads to torsade de pointes (TdP), thus for drugs in the early phase of development this risk should be evaluated. In the present study, we demonstrated a visualized transgenic zebrafish as an in vivo high-throughput model to assay the risk of drug-induced QT prolongation. Zebrafish larvae 48 h post-fertilization expressing green fluorescent protein in myocardium were incubated with compounds reported to induce QT prolongation or block the human ether-a-go-go-related gene (hERG) K⁺ current. The compounds sotalol, indapaminde, erythromycin, ofoxacin, levofloxacin, sparfloxacin and roxithromycin were additionally administrated by microinjection into the larvae yolk sac. The ventricle heart rate was recorded using the automatic monitoring system after incubation or microinjection. As a result, 14 out of 16 compounds inducing dog QT prolongation caused bradycardia in zebrafish. A similar result was observed with 21 out of 26 compounds which block hERG current. Among the 30 compounds which induced human QT prolongation, 25 caused bradycardia in this model. Thus, the risk of compounds causing bradycardia in this transgenic zebrafish correlated with that causing QT prolongation and hERG K⁺ current blockage in established models. The tendency that high logP values lead to high risk of QT prolongation in this model was indicated, and non-sensitivity of this model to antibacterial agents was revealed. These data suggest application of this transgenic zebrafish as a high-throughput model to screen QT prolongation-related cardio toxicity of the drug candidates.
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Affiliation(s)
- Dingsheng Wen
- South China University of Technology, Guangzhou 510641, China
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Nalos L, Varkevisser R, Jonsson MKB, Houtman MJC, Beekman JD, van der Nagel R, Thomsen MB, Duker G, Sartipy P, de Boer TP, Peschar M, Rook MB, van Veen TAB, van der Heyden MAG, Vos MA. Comparison of the IKr blockers moxifloxacin, dofetilide and E-4031 in five screening models of pro-arrhythmia reveals lack of specificity of isolated cardiomyocytes. Br J Pharmacol 2012; 165:467-78. [PMID: 21718297 DOI: 10.1111/j.1476-5381.2011.01558.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND AND PURPOSE Drug development requires the testing of new chemical entities for adverse effects. For cardiac safety screening, improved assays are urgently needed. Isolated adult cardiomyocytes (CM) and human embryonic stem cell-derived cardiomyocytes (hESC-CM) could be used to identify pro-arrhythmic compounds. In the present study, five assays were employed to investigate their sensitivity and specificity for evaluating the pro-arrhythmic properties of I(Kr) blockers, using moxifloxacin (safe compound) and dofetilide or E-4031 (unsafe compounds). EXPERIMENTAL APPROACH Assays included the anaesthetized remodelled chronic complete AV block (CAVB) dog, the anaesthetized methoxamine-sensitized unremodelled rabbit, multi-cellular hESC-CM clusters, isolated CM obtained from CAVB dogs and isolated CM obtained from the normal rabbit. Arrhythmic outcome was defined as Torsade de Pointes (TdP) in the animal models and early afterdepolarizations (EADs) in the cell models. KEY RESULTS At clinically relevant concentrations (5-12 µM), moxifloxacin was free of pro-arrhythmic properties in all assays with the exception of the isolated CM, in which 10 µM induced EADs in 35% of the CAVB CM and in 23% of the rabbit CM. At supra-therapeutic concentrations (≥100 µM), moxifloxacin was pro-arrhythmic in the isolated rabbit CM (33%), in the hESC-CM clusters (18%), and in the methoxamine rabbit (17%). Dofetilide and E-4031 induced EADs or TdP in all assays (50-83%), and the induction correlated with a significant increase in beat-to-beat variability of repolarization. CONCLUSION AND IMPLICATIONS Isolated cardiomyocytes lack specificity to discriminate between TdP liability of the I(Kr) blocking drugs moxifloxacin and dofetilide or E4031.
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Affiliation(s)
- L Nalos
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, the Netherlands
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Johnson DM, de Jong MMJ, Crijns HJGM, Carlsson LG, Volders PGA. Reduced ventricular proarrhythmic potential of the novel combined ion-channel blocker AZD1305 versus dofetilide in dogs with remodeled hearts. Circ Arrhythm Electrophysiol 2011; 5:201-9. [PMID: 22080293 DOI: 10.1161/circep.111.963025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AZD1305 is an investigational antiarrhythmic agent for management of atrial fibrillation. It blocks various cardiac ion currents at different potencies and has atrial-predominant electrophysiological effects. We investigated the electrophysiological and proarrhythmic effects of AZD1305 versus dofetilide in dogs with chronic complete atrioventricular block and myocardial hypertrophic remodeling. METHODS AND RESULTS AZD1305 was administered to anesthetized mongrel dogs before and >2 weeks after the induction of atrioventricular block and ventricular and atrial electrophysiological parameters were assessed. In all dogs, the selective I(Kr) blocker dofetilide was used to examine susceptibility to acquired torsades de pointes in chronic atrioventricular block and for comparison. At normal sinus rhythm, AZD1305 increased QT and RR intervals from 290±7 to 397±15 ms (+37%, P<0.0001) and from 603±22 to 778±32 ms (+29%, P=0.002), respectively. In the same animals at chronic atrioventricular block, AZD1305 increased the QT interval from 535±28 to 747±36 ms (+40%, P<0.0001), similar to the QT prolongation by dofetilide (511±22 to 703±45 ms [+38%, P<0.0001]). AZD1305 slightly slowed the idioventricular rhythm. Whereas all (n=14) chronic atrioventricular block animals exhibited torsades de pointes on dofetilide, the arrhythmia was induced in only 4 of 11 dogs after AZD1305. Beat-to-beat variability of left-ventricular monophasic-action-potential duration increased after dofetilide (2.3±0.2 to 6.3±0.7 ms; P<0.0001) but not after AZD1305 (2.8±0.3 to 3.7±0.3 ms; P=0.20) despite similar left-ventricular monophasic-action-potential duration prolongations. CONCLUSIONS Despite causing similar degrees of repolarization delay as the selective I(Kr) blocker dofetilide, the combined ion-channel blocker AZD1305 induces less repolarization instability and has a lower ventricular proarrhythmic potential in the remodeled dog heart.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
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Zhang Y, Sun X, Zhang Y, Wang J, Lu Y, Yang B, Wang Z. Potential therapeutic value of antioxidants for abnormal prolongation of QT interval and the associated arrhythmias in a rabbit model of diabetes. Cell Physiol Biochem 2011; 28:97-102. [PMID: 21865852 DOI: 10.1159/000331718] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/04/2011] [Indexed: 12/27/2022] Open
Abstract
Abnormal QT prolongation is the major cardiac electrical disorder and a predictor of mortality in diabetic patients. Our previous studies suggest that dysfunction of delayed rectifier K(+) current (I(Kr)) is the main cause for the problem. Here we report the potential therapeutic role and mechanisms of vitamin E in the rabbit model of diabetes. The QT interval and action potential duration were considerably prolonged with frequent occurrence of ventricular tachyarrhythmias in diabetic rabbits. Administration of vitamin E corrected the abnormal QT prolongation and abolished the arrhythmic incidence. I(Kr) was found markedly reduced resulting in slowing of cardiac repolarization thereby QT prolongation in diabetic hearts. The diabetic depression of I(Kr) is primarily ascribed to oxidative damages to the cardiac membrane and proteins, as indicated by the overproduction of reactive oxygen species leading to severe lipid peroxidation and protein oxidation. Moreover, I(Kr) depression is most likely due to the dysfunction of HERG K(+) channel, the major subunit underlying native I(Kr), in response to oxidative stress, for peroxide anion-generating system produced similar depression of HERG channels. Vitamin E restored the depressed I(Kr) and HERG by its antioxidant actions which likely underlie its beneficial effects on diabetic QT prolongation and the associated arrhythmias. The data indicate that an antioxidant is sufficient for reversing the I(Kr)/I(HERG) dysfunction and the consequent electrical disorders in diabetic hearts. Our study also conceptually simplifies the complex nature of diabetic electrical disorders to primarily oxidative stress, and should stimulate interest in antioxidants as a therapeutic strategy for diabetic QT prolongation.
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Affiliation(s)
- Yiqiang Zhang
- Research Center, Montreal Heart Institute, Montreal, Canada
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Tsuji Y, Hojo M, Voigt N, El-Armouche A, Inden Y, Murohara T, Dobrev D, Nattel S, Kodama I, Kamiya K. Ca
2+
-Related Signaling and Protein Phosphorylation Abnormalities Play Central Roles in a New Experimental Model of Electrical Storm. Circulation 2011; 123:2192-203. [DOI: 10.1161/circulationaha.110.016683] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Yukiomi Tsuji
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Mayumi Hojo
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Niels Voigt
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Ali El-Armouche
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Yasuya Inden
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Toyoaki Murohara
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Dobromir Dobrev
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Stanley Nattel
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Itsuo Kodama
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
| | - Kaichiro Kamiya
- From the Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University (Y.T., M.H., I.K., K.K.), and Department of Cardiology, Nagoya Graduate School of Medicine (Y.I., T.M.), Nagoya, Japan; Department of Pharmacology, University Medical Center Göttingen of the Georg-August Universität, Göttingen, Germany (A.E.-A.); Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany (N.V., D.D.); Division of Experimental Cardiology,
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Abstract
The drug-induced long QT syndrome is a distinct clinical entity that has evolved from an electrophysiologic curiosity to a centerpiece in drug regulation and development. This evolution reflects an increasing recognition that a rare adverse drug effect can profoundly upset the balance between benefit and risk that goes into the prescription of a drug by an individual practitioner as well as the approval of a new drug entity by a regulatory agency. This review will outline how defining the central mechanism, block of the cardiac delayed-rectifier potassium current I(Kr), has contributed to defining risk in patients and in populations. Models for studying risk, and understanding the way in which clinical risk factors modulate cardiac repolarization at the molecular level are discussed. Finally, the role of genetic variants in modulating risk is described.
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Affiliation(s)
- Prince Kannankeril
- Oates Institute for Experimental Therapeutics, Vanderbilt University School of Medicine, Nashville, TN 37232-0575, USA
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37
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Vos MA. The quest for an anti-arrhythmic drug against atrial fibrillation that combines efficacy with safety. Europace 2010; 12:925-6. [PMID: 20488855 DOI: 10.1093/europace/euq142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Graff C, Struijk JJ, Matz J, Kanters JK, Andersen MP, Nielsen J, Toft E. Covariate analysis of QTc and T-wave morphology: new possibilities in the evaluation of drugs that affect cardiac repolarization. Clin Pharmacol Ther 2010; 88:88-94. [PMID: 20485337 DOI: 10.1038/clpt.2010.51] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This study adds the dimension of a T-wave morphology composite score (MCS) to the QTc interval-based evaluation of drugs that affect cardiac repolarization. Electrocardiographic recordings from 62 subjects on placebo and 400 mg moxifloxacin were compared with those from 21 subjects on 160 and 320 mg D,L-sotalol. T-wave morphology changes, as assessed by DeltaMCS, are larger after 320 mg D,L-sotalol than after 160 mg D,L-sotalol; and the changes associated with 160 mg D,L-sotalol are, in turn, larger than those associated with moxifloxacin and placebo. Covariate analyses of DeltaQTc and DeltaMCS showed that changes in T-wave morphology are a significant effect of D,L-sotalol. By contrast, moxifloxacin was found to have no significant effect on T-wave morphology (DeltaMCS) at any given change in QTc. This study offers new insights into the repolarization behavior of a drug associated with low cardiac risk vs. one associated with a high risk and describes the added benefits of a T-wave MCS as a covariate to the assessment of the QTc interval.
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Affiliation(s)
- C Graff
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
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Drew BJ, Ackerman MJ, Funk M, Gibler WB, Kligfield P, Menon V, Philippides GJ, Roden DM, Zareba W. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. J Am Coll Cardiol 2010; 55:934-47. [PMID: 20185054 DOI: 10.1016/j.jacc.2010.01.001] [Citation(s) in RCA: 272] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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40
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Drew BJ, Ackerman MJ, Funk M, Gibler WB, Kligfield P, Menon V, Philippides GJ, Roden DM, Zareba W. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. Circulation 2010; 121:1047-60. [PMID: 20142454 DOI: 10.1161/circulationaha.109.192704] [Citation(s) in RCA: 375] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Rokutan H, Anker SD, Springer J. In vivomodels of cardiac diseases: application to drug development and screening. Expert Opin Drug Discov 2009; 5:65-78. [DOI: 10.1517/17460440903460299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Report and recommendations of the workshop of the European Centre for the Validation of Alternative Methods for Drug-Induced Cardiotoxicity. Cardiovasc Toxicol 2009; 9:107-25. [PMID: 19572114 DOI: 10.1007/s12012-009-9045-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Accepted: 04/17/2009] [Indexed: 10/20/2022]
Abstract
Cardiotoxicity is among the leading reasons for drug attrition and is therefore a core subject in non-clinical and clinical safety testing of new drugs. European Centre for the Validation of Alternative Methods held in March 2008 a workshop on "Alternative Methods for Drug-Induced Cardiotoxicity" in order to promote acceptance of alternative methods reducing, refining or replacing the use of laboratory animals in this field. This review reports the outcome of the workshop. The participants identified the major clinical manifestations, which are sensitive to conventional drugs, to be arrhythmias, contractility toxicity, ischaemia toxicity, secondary cardiotoxicity and valve toxicity. They gave an overview of the current use of alternative tests in cardiac safety assessments. Moreover, they elaborated on new cardiotoxicological endpoints for which alternative tests can have an impact and provided recommendations on how to cover them.
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Zankov DP, Yoshida H, Tsuji K, Toyoda F, Ding WG, Matsuura H, Horie M. Adrenergic regulation of the rapid component of delayed rectifier K+ current: implications for arrhythmogenesis in LQT2 patients. Heart Rhythm 2009; 6:1038-46. [PMID: 19419905 DOI: 10.1016/j.hrthm.2009.02.045] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2008] [Accepted: 02/25/2009] [Indexed: 11/26/2022]
Abstract
BACKGROUND KCNH2 gene mutations disrupting rapid component of I(K) (I(Kr)) underlie type 2 congenital long QT syndrome (LQT2). Startled auditory stimuli are specific symptomatic triggers in LQT2, thus suggesting fast arrhythmogenic mechanism. OBJECTIVE We investigated acute alpha(1A)- and cyclic adenosine monophosphate (cAMP)-related beta-adrenergic modulation of I(Kr) in HL-1 cardiomyocytes, wild type (WT)- and 2 LQT2-associated mutant Kv11.1 channels (Y43D- and K595E-Kv11.1) reconstituted in Chinese hamster ovary (CHO) cells. METHODS I(Kr) and Kv11.1 currents were recorded using the whole-cell patch-clamp technique and confocal microscopy of HL-1 cardiomyocytes transfected with green fluorescent protein (GFP)-tagged pleckstrin homology domain of phospholipase C-delta(1) visualized fluctuations of membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)) content. RESULTS In HL-1 cardiomyocytes expressing human alpha(1A)-adrenoceptor, superfusion with phenylephrine significantly reduced I(Kr) amplitude, shifted current activation to more positive potentials, and accelerated kinetics of deactivation. Confocal images showed a decline of membrane PIP(2) content during phenylephrine exposure. Simultaneous application of adenylyl cyclase activator forskolin and phosphodiesterase inhibitor 3-isobutyl-1-methylxantine (IBMX) shifted I(Kr) activation to more negative potentials and decreased tail current amplitudes after depolarizations between +10 and +50 mV. In CHO cells, alpha(1A)-adrenoceptor activation downregulated WT-Kv11.1 channels and forskolin/IBMX produced a dual effect. Expressed alone, the Y43D-Kv11.1 or K595E-Kv11.1 channel had no measurable function. However, co-expression of WT-Kv11.1 and each mutant protein evoked currents with loss-of-function alterations but identical to WT-Kv11.1 alpha(1A)- and forskolin/IBMX-induced regulation. CONCLUSION Acute adrenergic regulation of at least 2 Kv11.1 mutant channels is preserved as in WT-Kv11.1 and native I(Kr). Suppression of alpha(1A)-adrenoceptor-related transduction might have therapeutic implications in some cases of LQT2.
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Affiliation(s)
- Dimitar P Zankov
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan
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Abstract
The term torsade de pointes refers to polymorphic ventricular tachycardia that occurs in the setting of an abnormally long QT interval. While the most common cause is treatment with QT prolonging drugs, torsade de pointes also occurs in the congenital long QT syndromes and in the setting of acquired heart block or severe electrolyte disturbance, notably hypokalemia. Among QT prolonging drugs that cause torsade de pointes, both antiarrhythmics and "noncardioactive" drugs have been recognized. The electrocardiographic features of torsade de pointes include labile QT intervals, prominent U waves, and a "pause-dependent" onset of the arrhythmia. Treatment consists of recognition of the syndrome, correction of underlying electrolyte abnormalities, and withdrawal of any offending drugs. Magnesium, isoproterenol, or cardiac pacing provides specific antiarrhythmic therapy in torsade de pointes.
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Affiliation(s)
- D M Roden
- Vanderbilt University School of Medicine, Department of Medicine, Nashville, Tennessee 37232-6602, USA
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Schneider HJ, Husser O, Rihm M, Fredersdorf S, Birner C, Dhein S, Muders F, Jeron A, Goegelein H, Riegger GA, Luchner A. Safety of the novel atrial-selective K+-channel blocker AVE0118 in experimental heart failure. Naunyn Schmiedebergs Arch Pharmacol 2008; 379:225-32. [PMID: 18972103 DOI: 10.1007/s00210-008-0361-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 09/29/2008] [Indexed: 11/28/2022]
Abstract
Congestive heart failure (CHF) is often associated with atrial fibrillation. The safety of many antiarrhythmic drugs in CHF is limited by proarrhythmic effects. We aimed to assess the safety of a novel atrial-selective K(+)-channel blocker AVE0118 in CHF compared to a selective (dofetilide) and a non-selective IKr blocker (terfenadine). For the induction of CHF, rabbits (n = 12) underwent rapid right ventricular pacing (330-380 bpm for 30 days). AVE0118 (1 mg/kg) dofetilide (0.02 mg/kg) and terfenadine (2 mg/kg) were administered in baseline (BL) and CHF. A six-lead ECG was continuously recorded digitally for 30 min after each drug administration. At BL, dofetilide and terfenadine significantly prolonged QTc interval (218 +/- 30 ms vs 155 +/- 8 ms, p = 0.001 and 178 +/- 23 ms vs. 153 +/- 12 ms, p = 0.01, respectively) while QTc intervals were constant after administration of AVE0118 (p = n.s.). In CHF, dofetilide and terfenadine caused torsades de pointes and symptomatic bradycardia, respectively, and prolonged QTc interval (178 +/- 30 ms vs. 153 +/- 14 ms, p = 0.02 and 157 +/- 7 ms vs. 147 +/- 10 ms, p = 0.02, respectively) even at reduced dosages, whereas no QTc-prolongation or arrhythmia was observed after full-dose administration of AVE0118. In conclusion, atrial-selective K(+)-channel blockade by AVE0118 appears safe in experimental CHF.
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Affiliation(s)
- H-J Schneider
- Klinik und Poliklinik für Innere Medizin II, University of Regensburg, Franz-Josef-Strauss Allee 11, 93053, Regensburg, Germany
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Pugsley MK, Hancox JC, Curtis MJ. Perception of validity of clinical and preclinical methods for assessment of torsades de pointes liability. Pharmacol Ther 2008; 119:115-7. [DOI: 10.1016/j.pharmthera.2008.05.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 05/15/2008] [Indexed: 01/08/2023]
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Brunner M, Peng X, Liu GX, Ren XQ, Ziv O, Choi BR, Mathur R, Hajjiri M, Odening KE, Steinberg E, Folco EJ, Pringa E, Centracchio J, Macharzina RR, Donahay T, Schofield L, Rana N, Kirk M, Mitchell GF, Poppas A, Zehender M, Koren G. Mechanisms of cardiac arrhythmias and sudden death in transgenic rabbits with long QT syndrome. J Clin Invest 2008; 118:2246-59. [PMID: 18464931 DOI: 10.1172/jci33578] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Accepted: 03/19/2008] [Indexed: 11/17/2022] Open
Abstract
Long QT syndrome (LQTS) is a heritable disease associated with ECG QT interval prolongation, ventricular tachycardia, and sudden cardiac death in young patients. Among genotyped individuals, mutations in genes encoding repolarizing K+ channels (LQT1:KCNQ1; LQT2:KCNH2) are present in approximately 90% of affected individuals. Expression of pore mutants of the human genes KCNQ1 (KvLQT1-Y315S) and KCNH2 (HERG-G628S) in the rabbit heart produced transgenic rabbits with a long QT phenotype. Prolongations of QT intervals and action potential durations were due to the elimination of IKs and IKr currents in cardiomyocytes. LQT2 rabbits showed a high incidence of spontaneous sudden cardiac death (>50% at 1 year) due to polymorphic ventricular tachycardia. Optical mapping revealed increased spatial dispersion of repolarization underlying the arrhythmias. Both transgenes caused downregulation of the remaining complementary IKr and IKs without affecting the steady state levels of the native polypeptides. Thus, the elimination of 1 repolarizing current was associated with downregulation of the reciprocal repolarizing current rather than with the compensatory upregulation observed previously in LQTS mouse models. This suggests that mutant KvLQT1 and HERG interacted with the reciprocal wild-type alpha subunits of rabbit ERG and KvLQT1, respectively. These results have implications for understanding the nature and heterogeneity of cardiac arrhythmias and sudden cardiac death.
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Affiliation(s)
- Michael Brunner
- Innere Medizin III-Kardiologie und Angiologie, Universitätsklinikum Freiburg, Freiburg, Germany
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Gintant GA. Preclinical Torsades-de-Pointes screens: advantages and limitations of surrogate and direct approaches in evaluating proarrhythmic risk. Pharmacol Ther 2008; 119:199-209. [PMID: 18621077 DOI: 10.1016/j.pharmthera.2008.04.010] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 04/28/2008] [Indexed: 11/17/2022]
Abstract
The successful development of novel drugs requires the ability to detect (and avoid) compounds that may provoke Torsades-de-Pointes (TdeP) arrhythmia while endorsing those compounds with minimal torsadogenic risk. As TdeP is a rare arrhythmia not readily observed during clinical or post-marketing studies, numerous preclinical models are employed to assess delayed or altered ventricular repolarization (surrogate markers linked to enhanced proarrhythmic risk). This review evaluates the advantages and limitations of selected preclinical models (ranging from the simplest cellular hERG current assay to the more complex in vitro perfused ventricular wedge and Langendorff heart preparations and in vivo chronic atrio-ventricular (AV)-node block model). Specific attention is paid to the utility of concentration-response relationships and "risk signatures" derived from these studies, with the intention of moving beyond predicting clinical QT prolongation and towards prediction of TdeP risk. While the more complex proarrhythmia models may be suited to addressing questionable or conflicting proarrhythmic signals obtained with simpler preclinical assays, further benchmarking of proarrhythmia models is required for their use in the robust evaluation of safety margins. In the future, these models may be able to reduce unwarranted attrition of evolving compounds while becoming pivotal in the balanced integrated risk assessment of advancing compounds.
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Affiliation(s)
- Gary A Gintant
- Department of Integrative Pharmacology, Abbott Laboratories (Dept. R46R, Bldg AP-9), 100 Abbott Park Road, Abbott Park, IL 60064-6119, United States.
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Sensitive and reliable proarrhythmia in vivo animal models for predicting drug-induced torsades de pointes in patients with remodelled hearts. Br J Pharmacol 2008; 154:1528-37. [PMID: 18552873 DOI: 10.1038/bjp.2008.240] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
As an increasing number of non-cardiac drugs have been reported to cause QT interval prolongation and torsades de pointes (TdP), we extensively studied the utility of atrioventricular (AV) block animals as a model to predict their torsadogenic action in human. The present review highlights such in vivo proarrhythmia models. In the case of the canine model, test substances were administered p.o. at conscious state >4 weeks after the induction of AV block, with subsequent Holter ECG monitoring to evaluate drug effects. Control AV block dogs (no pharmacological treatment) survive for several years without TdP attack. For pharmacologically treated dogs, drugs were identified as high, low or no risk. High-risk drugs induced TdP at 1-3 times the therapeutic dose. Low-risk drugs did not induce TdP at this dose range, but induced it at higher doses. No-risk drugs never induced TdP at any dose tested. Electrophysiological, anatomical histological and biochemical adaptations against persistent bradycardia-induced chronic heart failure were observed in AV block dogs. Recently, we have developed another highly sensitive proarrhythmia model using a chronic AV block cynomolgus monkey, which possesses essentially the same pathophysiological adaptations and drug responses as those demonstrated in the canine model. As a common remodelling process leading to a diminished repolarization reserve may present in patients who experience drug-induced TdP and in the AV block animals, the in vivo proarrhythmia models described in this review may be useful for predicting the risk of pharmacologically induced TdP in humans.
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Michael G, Kane KA, Coker SJ. Adrenaline reveals the torsadogenic effect of combined blockade of potassium channels in anaesthetized guinea pigs. Br J Pharmacol 2008; 154:1414-26. [PMID: 18493252 DOI: 10.1038/bjp.2008.169] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Torsade de pointes (TdP) can be induced in several species by a reduction in cardiac repolarizing capacity. The aim of this study was to assess whether combined I(Kr) and I(Ks) blockade could induce TdP in anaesthetized guinea pigs and whether short-term variability (STV) or triangulation of action potentials could predict TdP. EXPERIMENTAL APPROACH Experiments were performed in open-chest, pentobarbital-anaesthetized, adrenaline-stimulated male Dunkin Hartley guinea pigs, which received three consecutive i.v. infusions of either vehicle, the I(Kr) blocker E-4031 (3, 10 and 30 nmol kg(-1) min(-1)), the I(Ks) blocker HMR1556 (75, 250, 750 nmol kg(-1) min(-1)) or E-4031 and HMR1556 combined. Phenylephrine-stimulated guinea pigs were also treated with the K(+) channel blockers in combination. Arterial blood pressure, ECGs and epicardial monophasic action potential (MAP) were recorded. KEY RESULTS TdP was observed in 75% of adrenaline-stimulated guinea pigs given the K(+) channel blockers in combination, but was not observed in guinea pigs treated with either I(K) blocker alone, or in phenylephrine-stimulated guinea pigs. Salvos and ventricular tachycardia occurred with adrenaline but not with phenylephrine. No changes in STV or triangulation of the MAP signals were observed before TdP. CONCLUSIONS AND IMPLICATIONS Combined blockade of both I(Kr) and I(Ks) plus the addition of adrenaline were required to induce TdP in anaesthetized guinea pigs. This suggests that there must be sufficient depletion of repolarization reserve and an appropriate trigger for TdP to occur.
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Affiliation(s)
- G Michael
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
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