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Campagna N, Wall E, Lee K, Guo J, Li W, Yang T, Baranchuk A, El-Diasty M, Zhang S. Differential Effects of Remdesivir and Lumacaftor on Homomeric and Heteromeric hERG Channels. Mol Pharmacol 2023; 104:164-173. [PMID: 37419691 DOI: 10.1124/molpharm.123.000708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/31/2023] [Accepted: 06/08/2023] [Indexed: 07/09/2023] Open
Abstract
The human ether-a-go-go-related gene (hERG) encodes for the pore-forming subunit of the channel that conducts the rapidly activating delayed K+ current (IKr) in the heart. The hERG channel is important for cardiac repolarization, and reduction of its expression in the plasma membrane due to mutations causes long QT syndrome type 2 (LQT2). As such, promoting hERG membrane expression is a strategy to rescue mutant channel function. In the present study, we applied patch clamp, western blots, immunocytochemistry, and quantitative reverse transcription polymerase chain reaction techniques to investigate the rescue effects of two drugs, remdesivir and lumacaftor, on trafficking-defective mutant hERG channels. As our group has recently reported that the antiviral drug remdesivir increases wild-type (WT) hERG current and surface expression, we studied the effects of remdesivir on trafficking-defective LQT2-causing hERG mutants G601S and R582C expressed in HEK293 cells. We also investigated the effects of lumacaftor, a drug used to treat cystic fibrosis, that promotes CFTR protein trafficking and has been shown to rescue membrane expression of some hERG mutations. Our results show that neither remdesivir nor lumacaftor rescued the current or cell-surface expression of homomeric mutants G601S and R582C. However, remdesivir decreased while lumacaftor increased the current and cell-surface expression of heteromeric channels formed by WT hERG and mutant G601S or R582C hERG. We concluded that drugs can differentially affect homomeric WT and heteromeric WT+G601S (or WT+R582C) hERG channels. These findings extend our understanding of drug-channel interaction and may have clinical implications for patients with hERG mutations. SIGNIFICANCE STATEMENT: Various naturally occurring mutations in a cardiac potassium channel called hERG can impair channel function by decreasing cell-surface channel expression, resulting in cardiac electrical disturbances and even sudden cardiac death. Promotion of cell-surface expression of mutant hERG channels represents a strategy to rescue channel function. This work demonstrates that drugs such as remdesivir and lumacaftor can differently affect homomeric and heteromeric mutant hERG channels, which have biological and clinical implications.
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Affiliation(s)
- Noah Campagna
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Erika Wall
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Kevin Lee
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Jun Guo
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Wentao Li
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Tonghua Yang
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Adrian Baranchuk
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Mohammad El-Diasty
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
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2
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Zhang HQ, Lin JL, Pan L, Mao L, Pang JL, Yuan Q, Li GY, Yi GS, Lin YB, Feng BL, Li YD, Wang Y, Jie LJ, Zhang YH. Enzastaurin cardiotoxicity: QT interval prolongation, negative inotropic responses and negative chronotropic action. Biochem Pharmacol 2023; 209:115443. [PMID: 36720353 DOI: 10.1016/j.bcp.2023.115443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/22/2023] [Accepted: 01/23/2023] [Indexed: 01/31/2023]
Abstract
Several clinical trials observed that enzastaurin prolonged QT interval in cancer patients. However, the mechanism of enzastaurin-induced QT interval prolongation is unclear. Therefore, this study aimed to assess the effect and mechanism of enzastaurin on QT interval and cardiac function. The Langendorff and Ion-Optix MyoCam systems were used to assess the effects of enzastaurin on QT interval, cardiac systolic function and intracellular Ca2+ transient in guinea pig hearts and ventricular myocytes. The effects of enzastaurin on the rapid delayed rectifier (IKr), the slow delayed rectifier K+ current (IKs), transient outward potassium current (Ito), action potentials, Ryanodine Receptor 2 (RyR2) and the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) expression and activity in HEK 293 cell system and primary cardiomyocytes were investigated using whole-cell recording technique and western blotting. We found that enzastaurin significantly prolonged QT interval in guinea pig hearts and increased the action potential duration (APD) in guinea pig cardiomyocytes in a dose-dependent manner. Enzastaurin potently inhibited IKr by binding to the human Ether-à-go-go-Related gene (hERG) channel in both open and closed states, and hERG mutant channels, including S636A, S631A, and F656V attenuated the inhibitory effect of enzastaurin. Enzastaurin also moderately decreased IKs. Additionally, enzastaurin also induced negative chronotropic action. Moreover, enzastaurin impaired cardiac systolic function and reduced intracellular Ca2+ transient via inhibition of RyR2 phosphorylation. Taken together, we found that enzastaurin prolongs QT, reduces heart rate and impairs cardiac systolic function. Therefore, we recommend that electrocardiogram (ECG) and cardiac function should be continuously monitored when enzastaurin is administered to cancer patients.
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Affiliation(s)
- He-Qiang Zhang
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Jia-le Lin
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Lei Pan
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Liang Mao
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China; Key Laboratory of Medical Electrophysiology, Southwest Medical University, Luzhou, Sichuan, China
| | - Jing-Long Pang
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Qian Yuan
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Gui-Yang Li
- Department of Cardiology, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Gang-Si Yi
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Yang-Bin Lin
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Bao-Long Feng
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Yun-da Li
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Yan Wang
- Department of Cardiology, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China.
| | - Ling-Jun Jie
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China; Department of Cardiology, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China.
| | - Yan-Hui Zhang
- Institute of Cardiovascular Diseases, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China.
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Pettini F, Domene C, Furini S. Early Steps in C-Type Inactivation of the hERG Potassium Channel. J Chem Inf Model 2023; 63:251-258. [PMID: 36512342 PMCID: PMC9832476 DOI: 10.1021/acs.jcim.2c01028] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Fast C-type inactivation confers distinctive functional properties to the hERG potassium channel, and its association to inherited and acquired cardiac arrythmias makes the study of the inactivation mechanism of hERG at the atomic detail of paramount importance. At present, two models have been proposed to describe C-type inactivation in K+-channels. Experimental data and computational work on the bacterial KcsA channel support the hypothesis that C-type inactivation results from a closure of the selectivity filter that sterically impedes ion conduction. Alternatively, recent experimental structures of a mutated Shaker channel revealed a widening of the extracellular portion of the selectivity filter, which might diminish conductance by interfering with the mechanism of ion permeation. Here, we performed molecular dynamics simulations of the wild-type hERG, a non-inactivating mutant (hERG-N629D), and a mutant that inactivates faster than the wild-type channel (hERG-F627Y) to find out which and if any of the two reported C-type inactivation mechanisms applies to hERG. Closure events of the selectivity filter were not observed in any of the simulated trajectories but instead, the extracellular section of the selectivity filter deviated from the canonical conductive structure of potassium channels. The degree of widening of the potassium binding sites at the extracellular entrance of the channel was directly related to the degree of inactivation with hERG-F627Y > wild-type hERG > hERG-N629D. These findings support the hypothesis that C-type inactivation in hERG entails a widening of the extracellular entrance of the channel rather than a closure of the selectivity filter.
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Affiliation(s)
- Francesco Pettini
- Department
of Medical Biotechnologies, University of
Siena, viale Mario Bracci 12, Siena 53100, Italy,Department
of Biotechnology, Chemistry and Pharmacy, University of Siena, viale Mario Bracci 12, Siena 53100, Italy
| | - Carmen Domene
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K.,Department
of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K.,
| | - Simone Furini
- Department
of Electrical, Electronic and Information Engineering ″Guglielmo
Marconi”, University of Bologna, via dell’Università
50, Cesena (FC) 47521, Italy,
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4
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Jie LJ, Li YD, Zhang HQ, Mao L, Xie HB, Zhou FG, Zhou TL, Xie D, Lin JL, Li GY, Cai BN, Zhang YH, Wang Y. Mechanisms of gefitinib-induced QT prolongation. Eur J Pharmacol 2021; 910:174441. [PMID: 34474028 DOI: 10.1016/j.ejphar.2021.174441] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 08/20/2021] [Accepted: 08/24/2021] [Indexed: 11/26/2022]
Abstract
Gefitinib, a tyrosine kinase inhibitor, was the first targeted therapy for non-small cell lung cancer (NSCLC). Gefitinib could block human Ether-à-go-go-Related Gene (hERG) channel, an important target in drug-induced long QT syndrome. However, it is unclear whether gefitinib could induce QT interval prolongation. Here, whole-cell patch-clamp technique was used for evaluating the effect of gefitinib on rapidly-activating delayed rectifier K+ current (IKr), slowly-activating delayed rectifier K+ current (IKs), transient outward potassium current (Ito), inward rectifier K+ current (IK1) and on action potentials in guinea pig ventricular myocytes. The Langendorff heart perfusion technique was used to determine drug effect on the ECG. Gefitinib depressed IKr by binding to open and closed hERG channels in a concentration-dependent way (IC50: 1.91 μM). The inhibitory effect of gefitinib on wildtype hERG channels was reduced at the hERG mutants Y652A, S636A, F656V and S631A (IC50: 8.51, 13.97, 18.86, 32.99 μM), indicating that gefitinib is a pore inhibitor of hERG channels. In addition, gefitinib accelerated hERG channel inactivation and decreased channel steady-state inactivation. Gefitinib also decreased IKs with IC50 of 23.8 μM. Moreover, gefitinib increased action potential duration (APD) in guinea pig ventricular myocytes and the corrected QT interval (QTc) in isolated perfused guinea pig hearts in a concentration-dependent way (1-30 μM). These findings indicate that gefitinib could prolong QTc interval by potently blocking hERG channel, modulating kinetic properties of hERG channel. Partial block of KCNQ1/KCNE1 could also contribute to delayed repolarization and prolonged QT interval. Thus, caution should be taken when gefitinib is used for NSCLC treatment.
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Affiliation(s)
- Ling-Jun Jie
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Yun-Da Li
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - He-Qiang Zhang
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Liang Mao
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China; Southwest Medical University, Luzhou, Sichuan, 646000, China
| | - Hua-Bin Xie
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Fa-Guang Zhou
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Tian-Li Zhou
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Dong Xie
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Jia-Le Lin
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Gui-Yang Li
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Bin-Ni Cai
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China
| | - Yan-Hui Zhang
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China.
| | - Yan Wang
- Xiamen Cardiovascular Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China.
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5
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Su S, Sun J, Wang Y, Xu Y. Cardiac hERG K + Channel as Safety and Pharmacological Target. Handb Exp Pharmacol 2021; 267:139-166. [PMID: 33829343 DOI: 10.1007/164_2021_455] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The human ether-á-go-go related gene (hERG, KCNH2) encodes the pore-forming subunit of the potassium channel responsible for a fast component of the cardiac delayed rectifier potassium current (IKr). Outward IKr is an important determinant of cardiac action potential (AP) repolarization and effectively controls the duration of the QT interval in humans. Dysfunction of hERG channel can cause severe ventricular arrhythmias and thus modulators of the channel, including hERG inhibitors and activators, continue to attract intense pharmacological interest. Certain inhibitors of hERG channel prolong the action potential duration (APD) and effective refractory period (ERP) to suppress premature ventricular contraction and are used as class III antiarrhythmic agents. However, a reduction of the hERG/IKr current has been recognized as a predominant mechanism responsible for the drug-induced delayed repolarization known as acquired long QT syndromes (LQTS), which is linked to an increased risk for "torsades de pointes" (TdP) ventricular arrhythmias and sudden cardiac death. Many drugs of different classes and structures have been identified to carry TdP risk. Hence, assessing hERG/IKr blockade of new drug candidates is mandatory in the drug development process according to the regulatory agencies. In contrast, several hERG channel activators have been shown to enhance IKr and shorten the APD and thus might have potential antiarrhythmic effects against pathological LQTS. However, these activators may also be proarrhythmic due to excessive shortening of APD and the ERP.
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Affiliation(s)
- Shi Su
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Jinglei Sun
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yi Wang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yanfang Xu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China.
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6
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Li J, Shen R, Reddy B, Perozo E, Roux B. Mechanism of C-type inactivation in the hERG potassium channel. SCIENCE ADVANCES 2021; 7:7/5/eabd6203. [PMID: 33514547 PMCID: PMC7846155 DOI: 10.1126/sciadv.abd6203] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 12/14/2020] [Indexed: 05/05/2023]
Abstract
The fast C-type inactivation displayed by the voltage-activated potassium channel hERG plays a critical role in the repolarization of cardiac cells, and malfunction caused by nonspecific binding of drugs or naturally occurring missense mutations affecting inactivation can lead to pathologies. Because of its impact on human health, understanding the molecular mechanism of C-type inactivation in hERG represents an advance of paramount importance. Here, long-time scale molecular dynamics simulations, free energy landscape calculations, and electrophysiological experiments are combined to address the structural and functional impacts of several disease-associated mutations. Results suggest that C-type inactivation in hERG is associated with an asymmetrical constricted-like conformation of the selectivity filter, identifying F627 side-chain rotation and the hydrogen bond between Y616 and N629 as key determinants. Comparison of hERG with other K+ channels suggests that C-type inactivation depends on the degree of opening of the intracellular gate via the filter-gate allosteric coupling.
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Affiliation(s)
- Jing Li
- Department of BioMolecular Sciences, Division of Medicinal Chemistry, School of Pharmacy, University of Mississippi, University, MS 38677, USA
| | - Rong Shen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Bharat Reddy
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
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7
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Tschirhart JN, Zhang S. Fentanyl-Induced Block of hERG Channels Is Exacerbated by Hypoxia, Hypokalemia, Alkalosis, and the Presence of hERG1b. Mol Pharmacol 2020; 98:508-517. [PMID: 32321735 DOI: 10.1124/mol.119.119271] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 04/08/2020] [Indexed: 01/19/2023] Open
Abstract
Human ether-a-go-go-related gene (hERG) encodes the pore-forming subunit of the rapidly activating delayed rectifier potassium current (IKr) important for repolarization of cardiac action potentials. Drug-induced disruption of hERG channel function is a main cause of acquired long QT syndrome, which can lead to ventricular arrhythmias and sudden death. Illicit fentanyl use is associated with sudden death. We have demonstrated that fentanyl blocks hERG current (IhERG) at concentrations that overlap with the upper range of postmortem blood concentrations in fentanyl-related deaths. Since fentanyl can cause respiratory depression and electrolyte imbalances, in the present study we investigated whether certain pathologic circumstances exacerbate fentanyl-induced block of IhERG Our results show that chronic hypoxia or hypokalemia additively reduced IhERG with fentanyl. As well, high pH potentiated the fentanyl-mediated block of hERG channels, with an IC50 at pH 8.4 being 7-fold lower than that at pH 7.4. Furthermore, although the full-length hERG variant, hERG1a, has been widely used to study hERG channels, coexpression with the short variant, hERG1b (which does not produce current when expressed alone), produces functional hERG1a/1b channels, which gate more closely resembling native IKr Our results showed that fentanyl blocked hERG1a/1b channels with a 3-fold greater potency than hERG1a channels. Thus, in addition to a greater susceptibility due to the presence of hERG1b in the human heart, hERG channel block by fentanyl can be exacerbated by certain conditions, such as hypoxia, hypokalemia, or alkalosis, which may increase the risk of fentanyl-induced ventricular arrhythmias and sudden death. SIGNIFICANCE STATEMENT: This work demonstrates that heterologously expressed human ether a-go-go-related gene (hERG) 1a/1b channels, which more closely resemble rapidly activating delayed rectifier potassium current in the human heart, are blocked by fentanyl with a 3-fold greater potency than the previously studied hERG1a expressed alone. Additionally, chronic hypoxia, hypokalemia, and alkalosis can increase the block of hERG current by fentanyl, potentially increasing the risk of cardiac arrhythmias and sudden death.
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Affiliation(s)
- Jared N Tschirhart
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
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8
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Lee W, Windley MJ, Perry MD, Vandenberg JI, Hill AP. Protocol-Dependent Differences in IC 50 Values Measured in Human Ether-Á-Go-Go-Related Gene Assays Occur in a Predictable Way and Can Be Used to Quantify State Preference of Drug Binding. Mol Pharmacol 2019; 95:537-550. [PMID: 30770456 DOI: 10.1124/mol.118.115220] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 02/10/2019] [Indexed: 12/22/2022] Open
Abstract
Current guidelines around preclinical screening for drug-induced arrhythmias require the measurement of the potency of block of voltage-gated potassium channel subtype 11.1 (Kv11.1) as a surrogate for risk. A shortcoming of this approach is that the measured IC50 of Kv11.1 block varies widely depending on the voltage protocol used in electrophysiological assays. In this study, we aimed to investigate the factors that contribute to these differences and to identify whether it is possible to make predictions about protocol-dependent block that might facilitate the comparison of potencies measured using different assays. Our data demonstrate that state preferential binding, together with drug-binding kinetics and trapping, is an important determinant of the protocol dependence of Kv11.1 block. We show for the first time that differences in IC50 measured between protocols occurs in a predictable way, such that machine-learning algorithms trained using a selection of simple voltage protocols can indeed predict protocol-dependent potency. Furthermore, we also show that the preference of a drug for binding to the open versus the inactivated state of Kv11.1 can also be inferred from differences in IC50 values measured between protocols. Our work therefore identifies how state preferential drug binding is a major determinant of the protocol dependence of IC50 values measured in preclinical Kv11.1 assays. It also provides a novel method for quantifying the state dependence of Kv11.1 drug binding that will facilitate the development of more complete models of drug binding to Kv11.1 and improve our understanding of proarrhythmic risk associated with compounds that block Kv11.1.
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Affiliation(s)
- William Lee
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Monique J Windley
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Matthew D Perry
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
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9
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Tschirhart JN, Li W, Guo J, Zhang S. Blockade of the Human Ether A-Go-Go-Related Gene (hERG) Potassium Channel by Fentanyl. Mol Pharmacol 2019; 95:386-397. [PMID: 30665971 DOI: 10.1124/mol.118.114751] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 01/12/2019] [Indexed: 11/22/2022] Open
Abstract
The human ether-a-go-go-related gene (hERG) encodes the pore-forming subunit of the rapidly activating delayed rectifier potassium channel (IKr). Drug-mediated or medical condition-mediated disruption of hERG function is the primary cause of acquired long-QT syndrome, which predisposes affected individuals to ventricular arrhythmias and sudden death. Fentanyl abuse poses a serious health concern, with abuse and death rates rising over recent years. As fentanyl has a propensity to cause sudden death, we investigated its effects on the hERG channel. The effects of norfentanyl, the main metabolite, and naloxone, an antidote used in fentanyl overdose, were also examined. Currents of hERG channels stably expressed in HEK293 cells were recorded using the whole-cell voltage-clamp method. When hERG tail currents were analyzed upon -50 mV repolarization after a 50 mV depolarization, fentanyl and naloxone blocked hERG current (IhERG) with IC50 values of 0.9 and 74.3 μM, respectively, whereas norfentanyl did not block. However, fentanyl-mediated block of IhERG was voltage dependent. When a voltage protocol that mimics a human ventricular action potential (AP) was used, fentanyl blocked IhERG with an IC50 of 0.3 μM. Furthermore, fentanyl (0.5 μM) prolonged AP duration and blocked IKr in ventricular myocytes isolated from neonatal rats. The concentrations of fentanyl used in this study were higher than seen with clinical use but overlap with postmortem overdose concentrations. Although mechanisms of fentanyl-related sudden death need further investigation, blockade of hERG channels may contribute to the death of individuals with high-concentration overdose or compromised cardiac repolarization.
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Affiliation(s)
- Jared N Tschirhart
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Wentao Li
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Jun Guo
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
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10
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Thouta S, Lo G, Grajauskas L, Claydon T. Investigating the state dependence of drug binding in hERG channels using a trapped-open channel phenotype. Sci Rep 2018; 8:4962. [PMID: 29563525 PMCID: PMC5862968 DOI: 10.1038/s41598-018-23346-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 03/09/2018] [Indexed: 02/06/2023] Open
Abstract
The hERG channel is a key player in repolarization of the cardiac action potential. Pharmacological blockade of hERG channels depletes the cardiac repolarization reserve, increasing the risk of cardiac arrhythmias. The promiscuous nature of drug interactions with hERG presents a therapeutic challenge for drug design and development. Despite considerable effort, the mechanisms of drug binding remain incompletely understood. One proposed mechanism is that high-affinity drug binding preferentially occurs when channels are in the inactivated state. However, this has been difficult to test, since inactivation is rapid in hERG and access to the drug binding site is limited by slower opening of the activation gate. Here, we have directly assessed the role of inactivation in cisparide and terfenadine drug binding in mutant (I663P) hERG channels where the activation gate is trapped-open. We firstly demonstrate the utility of this approach by showing that inactivation, ion selectivity and high affinity drug binding are preserved in I663P mutant channels. We then assess the role of inactivation by applying cisapride and terfenadine at different membrane voltages, which induce varying degrees of inactivation. We show that the extent of block does not correlate with the extent of inactivation. These data suggest that inactivation is not a major determinant of cisapride or terfenadine binding in hERG channels.
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Affiliation(s)
- Samrat Thouta
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, B.C., Canada
| | - Garman Lo
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, B.C., Canada
| | - Lukas Grajauskas
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, B.C., Canada
| | - Tom Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, B.C., Canada.
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11
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Kratz JM, Grienke U, Scheel O, Mann SA, Rollinger JM. Natural products modulating the hERG channel: heartaches and hope. Nat Prod Rep 2017; 34:957-980. [PMID: 28497823 PMCID: PMC5708533 DOI: 10.1039/c7np00014f] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
This review covers natural products modulating the hERG potassium channel. Risk assessment strategies, structural features of blockers, and the duality target/antitarget are discussed.
Covering: 1996–December 2016 The human Ether-à-go-go Related Gene (hERG) channel is a voltage-gated potassium channel playing an essential role in the normal electrical activity in the heart. It is involved in the repolarization and termination of action potentials in excitable cardiac cells. Mutations in the hERG gene and hERG channel blockage by small molecules are associated with increased risk of fatal arrhythmias. Several drugs have been withdrawn from the market due to hERG channel-related cardiotoxicity. Moreover, as a result of its notorious ligand promiscuity, this ion channel has emerged as an important antitarget in early drug discovery and development. Surprisingly, the hERG channel blocking profile of natural compounds present in frequently consumed botanicals (i.e. dietary supplements, spices, and herbal medicinal products) is not routinely assessed. This comprehensive review will address these issues and provide a critical compilation of hERG channel data for isolated natural products and extracts over the past two decades (1996–2016). In addition, the review will provide (i) a solid basis for the molecular understanding of the physiological functions of the hERG channel, (ii) the translational potential of in vitro/in vivo results to cardiotoxicity in humans, (iii) approaches for the identification of hERG channel blockers from natural sources, (iv) future perspectives for cardiac safety guidelines and their applications within phytopharmaceuticals and dietary supplements, and (v) novel applications of hERG channel modulation (e.g. as a drug target).
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Affiliation(s)
- Jadel M Kratz
- Department of Pharmacognosy, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090 Vienna, Austria.
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12
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Jie LJ, Wu WY, Li G, Xiao GS, Zhang S, Li GR, Wang Y. Clemizole hydrochloride blocks cardiac potassium currents stably expressed in HEK 293 cells. Br J Pharmacol 2017; 174:254-266. [PMID: 27886373 DOI: 10.1111/bph.13679] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2016] [Revised: 11/21/2016] [Accepted: 11/22/2016] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND AND PURPOSE Clemizole, a histamine H1 receptor antagonist has a potential therapeutic effect on hepatitis C infection and also potently inhibits TRPC5 ion channels. The aim of the present study was to investigate whether clemizole blocks cardiac K+ currents and thus affects cardiac repolarization. EXPERIMENTAL APPROACH Whole-cell patch techniques was used to examine the effects of clemizole on hERG channel current, IKs and Kv 1.5 channel current in HEK 293 cell expression systems as well as on ventricular action potentials of guinea pig hearts. Isolated hearts from guinea pigs were used to determine the effect on the ECG. KEY RESULTS Clemizole decreased hERG current by blocking both open and closed states of the channel in a concentration-dependent manner (IC50 : 0.07 μM). The S631A, S636A, Y652A and F656V hERG mutant channels reduced the inhibitory effect of clemizole (IC50 : 0.82, 0.89, 1.49 and 2.98 μM, respectively), suggesting that clemizole is a pore blocker of hERG channels. Clemizole also moderately decreased IKs and human Kv 1.5 channel current. Moreover, clemizole increased the duration of the ventricular action potential in guinea pig hearts and the QTc interval in isolated perfused hearts from guinea pigs, in a concentration-dependent manner (0.1-1.0 μM). CONCLUSION AND IMPLICATIONS Our results provide the first evidence that clemizole potently blocks hERG channels, moderately inhibits cardiac IKs , delays cardiac repolarization and thereby prolongs QT interval. Thus, caution should be taken when clemizole is used as a TRPC5 channel blocker or for treating hepatitis C infection.
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Affiliation(s)
- Ling-Jun Jie
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Wei-Yin Wu
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Gang Li
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Guo-Sheng Xiao
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
| | - Gui-Rong Li
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Yan Wang
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
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13
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Furlanello F, Serdoz LV, Cappato R, De Ambroggi L. Illicit drugs and cardiac arrhythmias in athletes. ACTA ACUST UNITED AC 2016; 14:487-94. [PMID: 17667636 DOI: 10.1097/hjr.0b013e3280ecfe3e] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The current management of athletes with cardiac arrhythmias has become complicated by the widespread use of illicit drugs, which can be arrhythmogenic.The World Anti-Doping Agency annually updates a list of prohibited substances and methods banned by the International Olympic Committee that includes different classes of substances namely, anabolic androgenic steroids, hormones and related substances, β2-agonists, diuretics, stimulants, narcotics, cannabinoids, glucocorticosteroids, alcohol, β-blockers and others. Almost all illicit drugs may cause, through a direct or indirect arrhythmogenic effect, a wide range of cardiac arrhythmias (focal or reentry type, supraventricular and/or ventricular) that can even be lethal and which are frequently sport activity related.A large use of illicit drugs has been documented in competitive athletes, but the arrhythmogenic effect of specific substances is not precisely known. Precipitation of cardiac arrhythmias, particularly in the presence of a latent electrophysiologic substrate including some inherited cardiomyopathies, at risk of sudden death or due to long-term consumption of the substances, should raise the suspicion that illicit drugs may be a possible cause and lead cardiologists to investigate carefully this relationship and appropriately prevent the clinical consequences.
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Affiliation(s)
- Francesco Furlanello
- Arrhythmias and Electrophysiology Center, Department of Cardiology, IRCCS Policlinico San Donato, University of Milan, Italy.
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14
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Zhang Y, Colenso CK, El Harchi A, Cheng H, Witchel HJ, Dempsey CE, Hancox JC. Interactions between amiodarone and the hERG potassium channel pore determined with mutagenesis and in silico docking. Biochem Pharmacol 2016; 113:24-35. [PMID: 27256139 PMCID: PMC4959829 DOI: 10.1016/j.bcp.2016.05.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 05/27/2016] [Indexed: 02/04/2023]
Abstract
The antiarrhythmic drug amiodarone delays cardiac repolarisation through inhibition of hERG-encoded potassium channels responsible for the rapid delayed rectifier potassium current (IKr). This study aimed to elucidate molecular determinants of amiodarone binding to the hERG channel. Whole-cell patch-clamp recordings were made at 37 °C of ionic current (IhERG) carried by wild-type (WT) or mutant hERG channels expressed in HEK293 cells. Alanine mutagenesis and ligand docking were used to investigate the roles of pore cavity amino-acid residues in amiodarone binding. Amiodarone inhibited WT outward IhERG tails with a half-maximal inhibitory concentration (IC50) of ∼45 nM, whilst inward IhERG tails in a high K+ external solution ([K+]e) of 94 mM were blocked with an IC50 of 117.8 nM. Amiodarone’s inhibitory action was contingent upon channel gating. Alanine-mutagenesis identified multiple residues directly or indirectly involved in amiodarone binding. The IC50 for the S6 aromatic Y652A mutation was increased to ∼20-fold that of WT IhERG, similar to the pore helical mutant S624A (∼22-fold WT control). The IC50 for F656A mutant IhERG was ∼17-fold its corresponding WT control. Computational docking using a MthK-based hERG model differentiated residues likely to interact directly with drug and those whose Ala mutation may affect drug block allosterically. The requirements for amiodarone block of aromatic residues F656 and Y652 within the hERG pore cavity are smaller than for other high affinity IhERG inhibitors, with relative importance to amiodarone binding of the residues investigated being S624A ∼ Y652A > F656A > V659A > G648A > T623A.
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Affiliation(s)
- Yihong Zhang
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Charlotte K Colenso
- School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Aziza El Harchi
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Hongwei Cheng
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Harry J Witchel
- Brighton and Sussex Medical School, University of Sussex, Falmer BN1 9PX, UK
| | - Chris E Dempsey
- School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK.
| | - Jules C Hancox
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK.
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15
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Schyman P, Liu R, Wallqvist A. General Purpose 2D and 3D Similarity Approach to Identify hERG Blockers. J Chem Inf Model 2016; 56:213-22. [DOI: 10.1021/acs.jcim.5b00616] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Patric Schyman
- DoD Biotechnology
High Performance
Computing Software Applications Institute, Telemedicine and Advanced
Technology Research Center, U.S. Army Medical Research and Materiel Command, 2405 Whittier Drive, Frederick, Maryland 21702, United States
| | - Ruifeng Liu
- DoD Biotechnology
High Performance
Computing Software Applications Institute, Telemedicine and Advanced
Technology Research Center, U.S. Army Medical Research and Materiel Command, 2405 Whittier Drive, Frederick, Maryland 21702, United States
| | - Anders Wallqvist
- DoD Biotechnology
High Performance
Computing Software Applications Institute, Telemedicine and Advanced
Technology Research Center, U.S. Army Medical Research and Materiel Command, 2405 Whittier Drive, Frederick, Maryland 21702, United States
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16
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Murthy V, Reyes S, Geng L, Gao Y, Brimijoin S. Cocaine Hydrolase Gene Transfer Demonstrates Cardiac Safety and Efficacy against Cocaine-Induced QT Prolongation in Mice. J Pharmacol Exp Ther 2015; 356:720-5. [PMID: 26669428 DOI: 10.1124/jpet.115.228825] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 12/14/2015] [Indexed: 11/22/2022] Open
Abstract
Cocaine addiction is associated with devastating medical consequences, including cardiotoxicity and risk-conferring prolongation of the QT interval. Viral gene transfer of cocaine hydrolase engineered from butyrylcholinesterase offers therapeutic promise for treatment-seeking drug users. Although previous preclinical studies have demonstrated benefits of this strategy without signs of toxicity, the specific cardiac safety and efficacy of engineered butyrylcholinesterase viral delivery remains unknown. Here, telemetric recording of electrocardiograms from awake, unrestrained mice receiving a course of moderately large cocaine doses (30 mg/kg, twice daily for 3 weeks) revealed protection against a 2-fold prolongation of the QT interval conferred by pretreatment with cocaine hydrolase vector. By itself, this prophylactic treatment did not affect QT interval duration or cardiac structure, demonstrating that viral delivery of cocaine hydrolase has no intrinsic cardiac toxicity and, on the contrary, actively protects against cocaine-induced QT prolongation.
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Affiliation(s)
- Vishakantha Murthy
- Department of Molecular Pharmacology and Experimental Therapeutics, Robert and Arlene Kogod Center on Aging (V.M., L.G., Y.G., S.B.), and Marriott Heart Disease Research Program, Division of Cardiovascular Diseases (S.R.), Mayo Clinic, Rochester, Minnesota
| | - Santiago Reyes
- Department of Molecular Pharmacology and Experimental Therapeutics, Robert and Arlene Kogod Center on Aging (V.M., L.G., Y.G., S.B.), and Marriott Heart Disease Research Program, Division of Cardiovascular Diseases (S.R.), Mayo Clinic, Rochester, Minnesota
| | - Liyi Geng
- Department of Molecular Pharmacology and Experimental Therapeutics, Robert and Arlene Kogod Center on Aging (V.M., L.G., Y.G., S.B.), and Marriott Heart Disease Research Program, Division of Cardiovascular Diseases (S.R.), Mayo Clinic, Rochester, Minnesota
| | - Yang Gao
- Department of Molecular Pharmacology and Experimental Therapeutics, Robert and Arlene Kogod Center on Aging (V.M., L.G., Y.G., S.B.), and Marriott Heart Disease Research Program, Division of Cardiovascular Diseases (S.R.), Mayo Clinic, Rochester, Minnesota
| | - Stephen Brimijoin
- Department of Molecular Pharmacology and Experimental Therapeutics, Robert and Arlene Kogod Center on Aging (V.M., L.G., Y.G., S.B.), and Marriott Heart Disease Research Program, Division of Cardiovascular Diseases (S.R.), Mayo Clinic, Rochester, Minnesota
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17
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Liu H, Yang L, Chen KH, Sun HY, Jin MW, Xiao GS, Wang Y, Li GR. SKF-96365 blocks human ether-à-go-go-related gene potassium channels stably expressed in HEK 293 cells. Pharmacol Res 2015; 104:61-9. [PMID: 26689773 DOI: 10.1016/j.phrs.2015.12.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 11/19/2015] [Accepted: 12/07/2015] [Indexed: 11/18/2022]
Abstract
SKF-96365 is a TRPC channel antagonist commonly used to characterize the potential functions of TRPC channels in different systems, which was recently reported to induce QTc prolongation on ECG by inhibiting TRPC channels. The present study investigates whether the blockade of cardiac repolarization currents would be involved in the increase of QTc interval. Cardiac repolarization currents were recorded in HEK 293 cells stably expressing human ether-à-go-go-related gene potassium (hERG or hKv11.1) channels, hKCNQ1/hKCNE1 channels (IKs) or hKir2.1 channels and cardiac action potentials were recorded in guinea pig ventricular myocytes using a whole-cell patch technique. The potential effect of SKF-96365 on QT interval was evaluated in ex vivo guinea pig hearts. It was found that SKF-96365 inhibited hERG current in a concentration-dependent manner (IC50, 3.4μM). The hERG mutants S631A in the pore helix and F656V of the S6 region reduced the inhibitory sensitivity with IC50s of 27.4μM and 11.0μM, suggesting a channel pore blocker. In addition, this compound inhibited IKs and hKir2.1currents with IC50s of 10.8 and 8.7μM. SKF-96365 (10μM) significantly prolonged ventricular APD90 in guinea pig ventricular myocytes and QTc interval in ex vivo guinea pig hearts. These results indicate that the TRPC channel antagonist SKF-96365 exerts blocking effects on hERG, IKs, and hKir2.1 channels. Prolongation of ventricular APD and QT interval is related to the inhibition of multiple repolarization potassium currents, especially hERG channels.
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Affiliation(s)
- Hui Liu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Departments of Physiology and Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Lei Yang
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Departments of Physiology and Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Kui-Hao Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Departments of Physiology and Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Hai-Ying Sun
- Departments of Physiology and Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Man-Wen Jin
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Guo-Sheng Xiao
- Xiamen Cardiovascular Hospital, Medical College of Xiamen University, Xiamen, China
| | - Yan Wang
- Xiamen Cardiovascular Hospital, Medical College of Xiamen University, Xiamen, China.
| | - Gui-Rong Li
- Departments of Physiology and Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China; Xiamen Cardiovascular Hospital, Medical College of Xiamen University, Xiamen, China.
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18
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High incidence of functional ion-channel abnormalities in a consecutive Long QT cohort with novel missense genetic variants of unknown significance. Sci Rep 2015; 5:10009. [PMID: 26066609 PMCID: PMC4464365 DOI: 10.1038/srep10009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 03/23/2015] [Indexed: 01/08/2023] Open
Abstract
The Long QT syndrome (LQTS) is a disorder characterized by a prolongation of the QT interval and a propensity to ventricular tachyarrhythmias, which may lead to syncope, cardiac arrest, or sudden death. Our objective was to (1) determine the incidence of variants with unknown significance (VUS) in a cohort of consecutive LQTS patients and (2) to determine the percentage of those with novel missense VUS that have demonstrable functional channel abnormalities from a single referral center. We performed genetic screening of candidate genes in 39 probands with a diagnosis of LQTS to identify mutations and variants. Seven variants of unknown significance were identified, six were missense variants and one was a splice site variant. We investigated the six novel missense VUS in five patients; three missense variants in KCNQ1 (L236R, W379R, Y522S) and three missense variants in KCNH2 (R35W, S620G, V491I). We employed two-electrode voltage-clamp experiments in Xenopus laevis oocytes and confocal imaging to characterize the novel missense mutations functionally. We revealed electrophysiological and trafficking loss-of-function phenotypes. This report emphasizes the frequency of adverse channel function in patients with LQTS and the importance of heterologous studies to define channel function.
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19
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Wu W, Gardner A, Sanguinetti MC. The Link between Inactivation and High-Affinity Block of hERG1 Channels. Mol Pharmacol 2015; 87:1042-50. [PMID: 25855787 DOI: 10.1124/mol.115.098111] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 04/08/2015] [Indexed: 11/22/2022] Open
Abstract
Block of human ether-à-go-go-related gene 1 (hERG1) K(+) channels by many drugs delays cardiac repolarization, prolongs QT interval, and is associated with an increased risk of cardiac arrhythmia. Preferential block of hERG1 channels in an inactivated state has been assumed because inactivation deficient mutant channels can exhibit dramatically reduced drug sensitivity. Here we reexamine the link between inactivation gating and potency of channel block using concatenated hERG1 tetramers containing a variable number (0-4) of subunits harboring a point mutation (S620T or S631A) that disrupts inactivation. Concatenated hERG1 tetramers containing four wild-type subunits exhibited high-affinity block by cisapride, dofetilide, and MK-499, similar to wild-type channels formed from hERG1 monomers. A single S620T subunit within a tetramer was sufficient to fully disrupt inactivation gating, whereas S631A suppressed inactivation as a graded function of the number of mutant subunits present in a concatenated tetramer. Drug potency was positively correlated to the number of S620T subunits contained within a tetramer but unrelated to mutation-induced disruption of channel inactivation. Introduction of a second point mutation (Y652W) into S620T hERG1 partially rescued drug sensitivity. The potency of cisapride was not altered for tetramers containing 0 to 3 S631A subunits, whereas the potency of dofetilide was a graded function of the number of S631A subunits contained within a tetramer. Together these findings indicate that S620T or S631A substitutions can allosterically disrupt drug binding by a mechanism that is independent of their effects on inactivation gating.
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Affiliation(s)
- Wei Wu
- Nora Eccles Harrison Cardiovascular Research & Training Institute (W.W., A.G., M.C.S.), Department of Internal Medicine, Division of Cardiovascular Medicine (M.C.S.), University of Utah, Salt Lake City, Utah
| | - Alison Gardner
- Nora Eccles Harrison Cardiovascular Research & Training Institute (W.W., A.G., M.C.S.), Department of Internal Medicine, Division of Cardiovascular Medicine (M.C.S.), University of Utah, Salt Lake City, Utah
| | - Michael C Sanguinetti
- Nora Eccles Harrison Cardiovascular Research & Training Institute (W.W., A.G., M.C.S.), Department of Internal Medicine, Division of Cardiovascular Medicine (M.C.S.), University of Utah, Salt Lake City, Utah
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20
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Linder T, Saxena P, Timin E, Hering S, Stary-Weinzinger A. Structural Insights into Trapping and Dissociation of Small Molecules in K+ Channels. J Chem Inf Model 2014; 54:3218-28. [DOI: 10.1021/ci500353r] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tobias Linder
- Department for Pharmacology and Toxicology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Priyanka Saxena
- Department for Pharmacology and Toxicology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Eugen Timin
- Department for Pharmacology and Toxicology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Steffen Hering
- Department for Pharmacology and Toxicology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Anna Stary-Weinzinger
- Department for Pharmacology and Toxicology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
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21
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Thurner P, Stary-Weinzinger A, Gafar H, Gawali VS, Kudlacek O, Zezula J, Hilber K, Boehm S, Sandtner W, Koenig X. Mechanism of hERG channel block by the psychoactive indole alkaloid ibogaine. J Pharmacol Exp Ther 2013; 348:346-58. [PMID: 24307198 DOI: 10.1124/jpet.113.209643] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ibogaine is a psychoactive indole alkaloid. Its use as an antiaddictive agent has been accompanied by QT prolongation and cardiac arrhythmias, which are most likely caused by human ether a go-go-related gene (hERG) potassium channel inhibition. Therefore, we studied in detail the interaction of ibogaine with hERG channels heterologously expressed in mammalian kidney tsA-201 cells. Currents through hERG channels were blocked regardless of whether ibogaine was applied via the extracellular or intracellular solution. The extent of inhibition was determined by the relative pH values. Block occurred during activation of the channels and was not observed for resting channels. With increasing depolarizations, ibogaine block grew and developed faster. Steady-state activation and inactivation of the channel were shifted to more negative potentials. Deactivation was slowed, whereas inactivation was accelerated. Mutations in the binding site reported for other hERG channel blockers (Y652A and F656A) reduced the potency of ibogaine, whereas an inactivation-deficient double mutant (G628C/S631C) was as sensitive as wild-type channels. Molecular drug docking indicated binding within the inner cavity of the channel independently of the protonation of ibogaine. Experimental current traces were fit to a kinetic model of hERG channel gating, revealing preferential binding of ibogaine to the open and inactivated state. Taken together, these findings show that ibogaine blocks hERG channels from the cytosolic side either in its charged form alone or in company with its uncharged form and alters the currents by changing the relative contribution of channel states over time.
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Affiliation(s)
- Patrick Thurner
- Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna, Austria (H.G., V.S.G., K.H., S.B., X.K.), Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria (P.T., O.K., J.Z., W.S.), Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria (A.S.-W.)
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22
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Han SN, Yang SH, Zhang Y, Duan YY, Sun XY, Chen Q, Fan TL, Ye ZK, Huang CZ, Hu XJ, Zhang Z, Zhang LR. Blockage of hERG current and the disruption of trafficking as induced by roxithromycin. Can J Physiol Pharmacol 2013; 91:1112-8. [DOI: 10.1139/cjpp-2012-0456] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Roxithromycin is an oral macrolide antibiotic agent that has been repeatedly reported to provoke excessive prolongation of the Q–T interval and torsades de pointes in clinical settings. To investigate the mechanisms underlying the arrhythmogenic side effects of roxithromycin, we studied the molecular mechanisms of roxithromycin on human ether-à-go-go-related gene (hERG) K+ channels expressed in human embryonic kidney (HEK293) cells. Roxithromycin was found to inhibit wild-type (WT) hERG currents in a concentration-dependent manner with a half-maximum block concentration (IC50) of 55.8 ± 9.1 μmol/L. S6 residue hERG mutants (Y652A and F656C) showed reduced levels of hERG current blockage attributable to roxithromycin. Roxithromycin also inhibited the trafficking of hERG protein to the cell membrane, as confirmed by Western blot analysis and confocal microscopy. These findings indicate that roxithromycin may cause acquired long-QT syndrome via direct inhibition of hERG current and by disruption of hERG protein trafficking. Mutations in drug-binding sites (Y652A or F656C) of the hERG channel were found to attenuate hERG current blockage by roxithromycin, but did not significantly alter the disruption of trafficking.
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Affiliation(s)
- Sheng-Na Han
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Song-Hua Yang
- The First Affiliated Hospital, Zhengzhou University, Zhengzhou, China
| | - Yu Zhang
- Pharmacy College of Zhengzhou Railway Vocational, Zhengzhou, China
| | - Yan-Yan Duan
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Xiao-Yan Sun
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Qiu Chen
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Tian-Li Fan
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Zhen-Kun Ye
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Chen-Zheng Huang
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Xiang-Jie Hu
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
| | - Zhao Zhang
- Jiangsu the Key Laboratory for Molecular and Medical Biotechnology, College of Life Science in Nanjing Normal University, Nanjing, China
| | - Li-Rong Zhang
- Department of Pharmacology, School of Medicine, Zhengzhou University, Zhengzhou, China
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23
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In silico analysis of conformational changes induced by mutation of aromatic binding residues: consequences for drug binding in the hERG K+ channel. PLoS One 2011; 6:e28778. [PMID: 22194911 PMCID: PMC3240635 DOI: 10.1371/journal.pone.0028778] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 11/15/2011] [Indexed: 01/24/2023] Open
Abstract
Pharmacological inhibition of cardiac hERG K+ channels is associated with increased risk of lethal arrhythmias. Many drugs reduce hERG current by directly binding to the channel, thereby blocking ion conduction. Mutation of two aromatic residues (F656 and Y652) substantially decreases the potency of numerous structurally diverse compounds. Nevertheless, some drugs are only weakly affected by mutation Y652A. In this study we utilize molecular dynamics simulations and docking studies to analyze the different effects of mutation Y652A on a selected number of hERG blockers. MD simulations reveal conformational changes in the binding site induced by mutation Y652A. Loss of π-π-stacking between the two aromatic residues induces a conformational change of the F656 side chain from a cavity facing to cavity lining orientation. Docking studies and MD simulations qualitatively reproduce the diverse experimentally observed modulatory effects of mutation Y652A and provide a new structural interpretation for the sensitivity differences.
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24
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Es-Salah-Lamoureux Z, Xiong PY, Goodchild SJ, Ahern CA, Fedida D. Blockade of permeation by potassium but normal gating of the G628S nonconducting hERG channel mutant. Biophys J 2011; 101:662-70. [PMID: 21806934 DOI: 10.1016/j.bpj.2011.06.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 06/10/2011] [Accepted: 06/17/2011] [Indexed: 12/21/2022] Open
Abstract
G628S is a mutation in the signature sequence that forms the selectivity filter of the human ether-a-go-go-related gene (hERG) channel (GFG) and is associated with long-QT2 syndrome. G628S channels are known to have a dominant-negative effect on hERG currents, and the mutant is therefore thought to be nonfunctional. This study aims to assess the physiological mechanism that prevents the surface-expressing G628S channels from conducting ions. We used voltage-clamp fluorimetry along with two-microelectrode voltage clamping in Xenopus oocytes to confirm that the channels express well at the surface, and to show that they are actually functional, with activation kinetics comparable to that of wild-type, and that the mutation leads to a reduced selectivity to potassium. Although ionic currents are not detected in physiological solutions, removing extracellular K(+) results in the appearance of an inward Na(+)-dependent current. Using whole-cell patch clamp in mammalian transfected cells, we demonstrate that the G628S channels conduct Na(+), but that this can be blocked by both intracellular and higher-than-physiological extracellular K(+). Using solutions devoid of K(+) allows the appearance of nA-sized Na(+) currents with activation and inactivation gating analogous to wild-type channels. The G628S channels are functionally conducting but are normally blocked by intracellular K(+).
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Affiliation(s)
- Zeineb Es-Salah-Lamoureux
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
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25
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O'Leary ME, Hancox JC. Role of voltage-gated sodium, potassium and calcium channels in the development of cocaine-associated cardiac arrhythmias. Br J Clin Pharmacol 2011; 69:427-42. [PMID: 20573078 DOI: 10.1111/j.1365-2125.2010.03629.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cocaine is a highly active stimulant that alters dopamine metabolism in the central nervous system resulting in a feeling of euphoria that with time can lead to addictive behaviours. Cocaine has numerous deleterious effects in humans including seizures, vasoconstriction, ischaemia, increased heart rate and blood pressure, cardiac arrhythmias and sudden death. The cardiotoxic effects of cocaine are indirectly mediated by an increase in sympathomimetic stimulation to the heart and coronary vasculature and by a direct effect on the ion channels responsible for maintaining the electrical excitability of the heart. The direct and indirect effects of cocaine work in tandem to disrupt the co-ordinated electrical activity of the heart and have been associated with life-threatening cardiac arrhythmias. This review focuses on the direct effects of cocaine on cardiac ion channels, with particular focus on sodium, potassium and calcium channels, and on the contributions of these channels to cocaine-induced arrhythmias. Companion articles in this edition of the journal examine the epidemiology of cocaine use (Wood & Dargan) and the treatment of cocaine-associated arrhythmias (Hoffmann).
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Affiliation(s)
- Michael E O'Leary
- Department of Pathology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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Zhang XH, Jin MW, Sun HY, Zhang S, Li GR. The calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide directly blocks human ether à-go-go-related gene potassium channels stably expressed in human embryonic kidney 293 cells. Br J Pharmacol 2010; 161:872-84. [PMID: 20860665 DOI: 10.1111/j.1476-5381.2010.00916.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide (W-7) is a well-known calmodulin inhibitor used to study calmodulin regulation of intracellular Ca(2+) signalling-related process. Here, we have determined whether W-7 would inhibit human ether gene (hERG or K(v) 11.1) potassium channels, hK(v) 1.5 channels or hK(IR) 2.1 channels expressed in human embryonic kidney (HEK) 293 cells. EXPERIMENTAL APPROACH The hERG channel current, hK(v) 1.5 channel current or hK(IR) 2.1 channel current was recorded with a whole-cell patch clamp technique. KEY RESULTS It was found that the calmodulin inhibitor W-7 blocked hERG, hK(v) 1.5 and hK(IR) 2.1 channels. W-7 decreased the hERG current (I(hERG) ) in a concentration-dependent manner (IC(50) : 3.5 µM), and the inhibition was more significant at depolarization potentials between +10 and +60 mV. The hERG mutations in the S6 region Y652A and F656V, and in the pore helix S631A, had the IC(50) s of 5.5, 9.8 and 25.4 µM respectively. In addition, the compound inhibited hK(v) 1.5 and hK(IR) 2.1 channels with IC(50) s of 6.5 and 13.4 µM respectively. CONCLUSION AND IMPLICATIONS These results indicate that the calmodulin inhibitor W-7 exerts a direct channel-blocking effect on hERG, hK(v) 1.5 and hK(IR) 2.1 channels stably expressed in HEK 293 cells. Caution should be taken in the interpretation of calmodulin regulation of ion channels with W-7.
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Affiliation(s)
- Xiao-Hua Zhang
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
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27
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Massaeli H, Guo J, Xu J, Zhang S. Extracellular K
+
Is a Prerequisite for the Function and Plasma Membrane Stability of HERG Channels. Circ Res 2010; 106:1072-82. [DOI: 10.1161/circresaha.109.215970] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Hamid Massaeli
- From the Department of Physiology, Queen’s University, Kingston, Ontario, Canada
| | - Jun Guo
- From the Department of Physiology, Queen’s University, Kingston, Ontario, Canada
| | - Jianmin Xu
- From the Department of Physiology, Queen’s University, Kingston, Ontario, Canada
| | - Shetuan Zhang
- From the Department of Physiology, Queen’s University, Kingston, Ontario, Canada
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28
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Lucena J, Blanco M, Jurado C, Rico A, Salguero M, Vazquez R, Thiene G, Basso C. Cocaine-related sudden death: a prospective investigation in south-west Spain. Eur Heart J 2010; 31:318-29. [PMID: 20071326 DOI: 10.1093/eurheartj/ehp557] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS With an estimated 12 million consumers in Europe, cocaine (COC) is the illicit drug leading to the most emergency department visits. The aim of this study was to examine a consecutive series of sudden deaths (SDs) to focus on the prevalence, the toxicological characteristics, and the causes of death in COC-related fatalities. METHODS AND RESULTS Prospective case-control study of forensic autopsies was carried out in the time interval November 2003 to June 2006 at the Institute of Legal Medicine, Seville, south-west Spain, with a reference population of 1 875 462 inhabitants. Toxicology included blood ethanol analysis and blood and urine investigation for drugs of abuse and medical drugs. Autopsy was performed according to the European standardized protocol. Ten age- and sex-matched patients who died of violent causes with no antecedents of COC consumption and negative toxicology served as controls. During the study period, 2477 forensic autopsies were performed, including 1114 natural deaths. Among the latter, 668 fulfilled the criteria of SD and 21 (all males, mean age 34.6 +/- 7.3 years) resulted to be COC-related (3.1%). Cocaine was detected in 67.1% of the blood (median 0.17 mg/L, interquartile range 0.08-0.42) and in 83.0% of the urine samples (median 1.15 mg/L, interquartile range 0.37-17.34). A concomitant use of ethanol was found in 76.0% and cigarette smoking in 81.0%. Causes of SD were cardiovascular in 62.0%, cerebrovascular in 14.0%, excited delirium in 14.0%, respiratory and metabolic in 5.0% each. Left ventricular hypertrophy was observed in 57.0%, small vessels disease in 42.9%, severe atherosclerotic coronary artery disease in 28.6%, and coronary thrombosis in 14.3%. CONCLUSION Systematic toxicology investigation indicates that 3.1% of SDs are COC-related and are mainly due to cardio-cerebrovascular causes. Left ventricular hypertrophy, small vessel disease, and premature coronary artery atherosclerosis, with or without lumen thrombosis, are frequent findings that may account for myocardial ischaemia at risk of cardiac arrest in COC addicts.
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Affiliation(s)
- Joaquin Lucena
- Forensic Pathology Service, Institute of Legal Medicine, Seville, Spain.
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29
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Polak S, Wiśniowska B, Brandys J. Collation, assessment and analysis of literature in vitro data on hERG receptor blocking potency for subsequent modeling of drugs' cardiotoxic properties. J Appl Toxicol 2009; 29:183-206. [PMID: 18988205 DOI: 10.1002/jat.1395] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The assessment of the torsadogenic potency of a new chemical entity is a crucial issue during lead optimization and the drug development process. It is required by the regulatory agencies during the registration process. In recent years, there has been a considerable interest in developing in silico models, which allow prediction of drug-hERG channel interaction at the early stage of a drug development process. The main mechanism underlying an acquired QT syndrome and a potentially fatal arrhythmia called torsades de pointes is the inhibition of potassium channel encoded by hERG (the human ether-a-go-go-related gene). The concentration producing half-maximal block of the hERG potassium current (IC(50)) is a surrogate marker for proarrhythmic properties of compounds and is considered a test for cardiac safety of drugs or drug candidates. The IC(50) values, obtained from data collected during electrophysiological studies, are highly dependent on experimental conditions (i.e. model, temperature, voltage protocol). For the in silico models' quality and performance, the data quality and consistency is a crucial issue. Therefore the main objective of our work was to collect and assess the hERG IC(50) data available in accessible scientific literature to provide a high-quality data set for further studies.
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Affiliation(s)
- Sebastian Polak
- Toxicology Department, Faculty of Pharmacy, Medical Collage, Jagiellonian University, Poland.
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30
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Kamiya K, Niwa R, Morishima M, Honjo H, Sanguinetti MC. Molecular determinants of hERG channel block by terfenadine and cisapride. J Pharmacol Sci 2008; 108:301-7. [PMID: 18987434 DOI: 10.1254/jphs.08102fp] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Block of cardiac hERG K+ channels by the antihistamine terfenadine and the prokinetic agent cisapride is associated with prolonged ventricular repolarization and an increased risk of ventricular arrhythmia. Here, we used a site-directed mutagenesis approach to determine the molecular determinants of hERG block by terfenadine and cisapride. Wild-type and mutant hERG channels were heterologously expressed in Xenopus laevis oocytes and characterized by measuring whole cell currents with two-microelectrode voltage clamp techniques. Mutation of T623, S624, Y652, or F656 to Ala reduced channel sensitivity to block by terfenadine. The same mutations reduced sensitivity to cisapride. These data confirm our previous findings that polar residues (T623, S624) located near the base of the pore helix and aromatic residues (Y652, F656) located in the S6 domain are key molecular determinants of the hERG drug binding site. Unlike methanesulfonanilides (dofetilide, MK-499, E-4031, ibutilide) or clofilium, mutation of V625, G648, or V659 did not alter the sensitivity of hERG channels to terfenadine or cisapride. As previously proposed by molecular modeling studies (Farid R, et al. Bioorg Med Chem. 2006;14:3160-3173), our findings suggest that different drugs can adopt distinct modes of binding to the central cavity of hERG.
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Affiliation(s)
- Kaichiro Kamiya
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
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31
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Perrin MJ, Kuchel PW, Campbell TJ, Vandenberg JI. Drug Binding to the Inactivated State Is Necessary but Not Sufficient for High-Affinity Binding to Human Ether-à-go-go-Related Gene Channels. Mol Pharmacol 2008; 74:1443-52. [DOI: 10.1124/mol.108.049056] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Tang Q, Li ZQ, Li W, Guo J, Sun HY, Zhang XH, Lau CP, Tse HF, Zhang S, Li GR. The 5-HT2 antagonist ketanserin is an open channel blocker of human cardiac ether-à-go-go-related gene (hERG) potassium channels. Br J Pharmacol 2008; 155:365-73. [PMID: 18574455 DOI: 10.1038/bjp.2008.261] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Ketanserin, a selective 5-HT receptor antagonist, prolongs the QT interval of ECG in patients. The purpose of the present study was to determine whether ketanserin would block human cardiac ether-à-go-go-related gene (hERG) potassium channels. EXPERIMENTAL APPROACH Whole-cell patch voltage-clamp technique was used to record membrane currents in HEK 293 cells expressing wild type or mutant hERG channel genes. KEY RESULTS Ketanserin blocked hERG current (I(hERG)) in a concentration-dependent manner (IC50=0.11 microM). The drug showed an open channel blocking property, the block increasing significantly at depolarizing voltages between +10 to +60 mV. Voltage-dependence for inactivation of hERG channels was negatively shifted by 0.3 microM ketanserin. A 2.8 fold attenuation of inhibition by elevation of external K+ concentration (from 5.0 to 20 mM) was observed, whereas the inactivation-deficient mutants S620T and S631A had the IC50s of 0.84 +/- 0.2 and 1.7 +/-0.4 microM (7.6 and 15.4 fold attenuation of block). In addition, the hERG mutants in pore helix and S6 also significantly reduced the channel block (2-59 fold) by ketanserin. CONCLUSIONS AND IMPLICATIONS These results suggest that ketanserin binds to and blocks the open hERG channels in the pore helix and the S6 domain; channel inactivation is also involved in the blockade of hERG channels. Blockade of hERG channels most likely contributes to the prolongation of QT intervals in ECG observed clinically at therapeutic concentrations of ketanserin.
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Affiliation(s)
- Q Tang
- Department of Medicine, and Research Centre of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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Lucena JS, Rico A, Salguero M, Blanco M, Vázquez R. Commotio cordis as a result of a fight: Report of a case considered to be imprudent homicide. Forensic Sci Int 2008; 177:e1-4. [DOI: 10.1016/j.forsciint.2007.09.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 01/23/2007] [Accepted: 09/17/2007] [Indexed: 11/29/2022]
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Tang Q, Jin MW, Xiang JZ, Dong MQ, Sun HY, Lau CP, Li GR. The membrane permeable calcium chelator BAPTA-AM directly blocks human ether a-go-go-related gene potassium channels stably expressed in HEK 293 cells. Biochem Pharmacol 2007; 74:1596-607. [PMID: 17826747 DOI: 10.1016/j.bcp.2007.07.042] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2007] [Revised: 07/14/2007] [Accepted: 07/30/2007] [Indexed: 11/29/2022]
Abstract
BAPTA-AM is a well-known membrane permeable Ca(2+) chelator. The present study found that BAPTA-AM rapidly and reversibly suppressed human ether a-go-go-related gene (hERG or Kv11.1) K(+) current, human Kv1.3 and human Kv1.5 channel currents stably expressed in HEK 293 cells, and the effects were not related to Ca(2+) chelation. The externally applied BAPTA-AM inhibited hERG channels in a concentration-dependent manner (IC(50): 1.3 microM). Blockade of hERG channels was dependent on channel opening, and tonic block was minimal. Steady-state activation V(0.5) of hERG channels was negatively shifted by 8.5 mV (from -3.7+/-2.8 of control to -12.2+/-3.1 mV, P<0.01), while inactivation V(0.5) was negatively shifted by 6.1 mV (from -37.9+/-2.0 mV of control to -44.0+/-1.6 mV, P<0.05) with application of 3 microM BAPTA-AM. The S6 mutant Y652A and the pore helix mutant S631A significantly attenuated blockade by BAPTA-AM at 10 microM causing profound blockade of wild-type hERG channels. In addition, BAPTA-AM inhibited hKv1.3 and hKv1.5 channels in a concentration-dependent manner (IC(50): 1.45 and 1.23 microM, respectively), and the blockade of these two types of channels was also dependent on channel opening. Moreover, EGTA-AM was found to be an open channel blocker of hERG, hKv1.3, hKv1.5 channels, though its efficacy is weaker than that of BAPTA-AM. These results indicate that the membrane permeable Ca(2+) chelator BAPTA-AM (also EGTA-AM) exerts an open channel blocking effect on hERG, hKv1.3 and hKv1.5 channels.
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Affiliation(s)
- Qiang Tang
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
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Yohannan S, Hu Y, Zhou Y. Crystallographic study of the tetrabutylammonium block to the KcsA K+ channel. J Mol Biol 2006; 366:806-14. [PMID: 17196615 DOI: 10.1016/j.jmb.2006.11.081] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 11/21/2006] [Accepted: 11/28/2006] [Indexed: 11/29/2022]
Abstract
K(+) channels play essential roles in regulating membrane excitability of many diverse cell types by selectively conducting K(+) ions through their pores. Many diverse molecules can plug the pore and modulate the K(+) current. Quaternary ammonium (QA) ions are a class of pore blockers that have been used for decades by biophysicists to probe the pore, leading to important insights into the structure-function relation of K(+) channels. However, many key aspects of the QA-blocking mechanisms remain unclear to date, and understanding these questions requires high resolution structural information. Here, we address the question of whether intracellular QA blockade causes conformational changes of the K(+) channel selectivity filter. We have solved the structures of the KcsA K(+) channel in complex with tetrabutylammonium (TBA) and tetrabutylantimony (TBSb) under various ionic conditions. Our results demonstrate that binding of TBA or TBSb causes no significant change in the KcsA structure at high concentrations of permeant ions. We did observe the expected conformational change of the filter at low concentration of K(+), but this change appears to be independent of TBA or TBSb blockade.
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Affiliation(s)
- Sarah Yohannan
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA
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37
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Response to Dr. Bauman’s Letter. South Med J 2006. [DOI: 10.1097/01.smj.0000223668.28038.f1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Abstract
The inactivation gating of hERG channels is important for the channel function and drug–channel interaction. Whereas hERG channels are highly selective for K+, we have found that inactivated hERG channels allow Na+ to permeate in the absence of K+. This provides a new way to directly monitor and investigate hERG inactivation. By using whole cell patch clamp method with an internal solution containing 135 mM Na+ and an external solution containing 135 mM NMG+, we recorded a robust Na+ current through hERG channels expressed in HEK 293 cells. Kinetic analyses of the hERG Na+ and K+ currents indicate that the channel experiences at least two states during the inactivation process, an initial fast, less stable state followed by a slow, more stable state. The Na+ current reflects Na+ ions permeating through the fast inactivated state but not through the slow inactivated state or open state. Thus the hERG Na+ current displayed a slow inactivation as the channels travel from the less stable, fast inactivated state into the more stable, slow inactivated state. Removal of fast inactivation by the S631A mutation abolished the Na+ current. Moreover, acceleration of fast inactivation by mutations T623A, F627Y, and S641A did not affect the hERG Na+ current, but greatly diminished the hERG K+ current. We also found that external Na+ potently blocked the hERG outward Na+ current with an IC50 of 3.5 mM. Mutations in the channel pore and S6 regions, such as S624A, F627Y, and S641A, abolished the inhibitory effects of external Na+ on the hERG Na+ current. Na+ permeation and blockade of hERG channels provide novel ways to extend our understanding of the hERG gating mechanisms.
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Affiliation(s)
- Hongying Gang
- Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, University of Manitoba, Winnipeg, Canada
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