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Joyce RL, Tibbs GR, David Warren J, Costa CJ, Aromolaran K, Lea Sanford R, Andersen OS, Li Z, Zhang G, Willis DE, Goldstein PA. Probucol is anti-hyperalgesic in a mouse peripheral nerve injury model of neuropathic pain. NEUROBIOLOGY OF PAIN (CAMBRIDGE, MASS.) 2023; 14:100141. [PMID: 38099280 PMCID: PMC10719523 DOI: 10.1016/j.ynpai.2023.100141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/25/2023] [Accepted: 08/01/2023] [Indexed: 12/17/2023]
Abstract
2,6-di-tert-butylphenol (2,6-DTBP) ameliorates mechanical allodynia and thermal hyperalgesia produced by partial sciatic nerve ligation in mice, and selectively inhibits HCN1 channel gating. We hypothesized that the clinically utilized non-anesthetic dimerized congener of 2,6-DTBP, probucol (2,6-di-tert-butyl-4-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)sulfanylpropan-2-ylsulfanyl]phenol), would relieve the neuropathic phenotype that results from peripheral nerve damage, and that the anti-hyperalgesic efficacy in vivo would correlate with HCN1 channel inhibition in vitro. A single oral dose of probucol (800 mg/kg) relieved mechanical allodynia and thermal hyperalgesia in a mouse spared-nerve injury neuropathic pain model. While the low aqueous solubility of probucol precluded assessment of its possible interaction with HCN1 channels, our results, in conjunction with recent data demonstrating that probucol reduces lipopolysaccharide-induced mechanical allodynia and thermal hyperalgesia, support the testing/development of probucol as a non-opioid, oral antihyperalgesic albeit one of unknown mechanistic action.
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Affiliation(s)
- Rebecca L. Joyce
- Dept. of Anesthesiology, 1300 York Ave., Weill Cornell Medicine, New York, NY, USA
| | - Gareth R. Tibbs
- Dept. of Anesthesiology, 1300 York Ave., Weill Cornell Medicine, New York, NY, USA
| | - J. David Warren
- Dept. of Biochemistry, 413 E. 69th Street, Weill Cornell Medicine, New York, NY, USA
| | | | - Kelly Aromolaran
- Dept. of Anesthesiology, 1300 York Ave., Weill Cornell Medicine, New York, NY, USA
| | - R. Lea Sanford
- Dept. of Physiology & Biophysics, 1300 York Ave., Weill Cornell Medicine, New York, NY, USA
| | - Olaf S. Andersen
- Dept. of Physiology & Biophysics, 1300 York Ave., Weill Cornell Medicine, New York, NY, USA
| | - Zhucui Li
- Dept. of Biochemistry, 413 E. 69th Street, Weill Cornell Medicine, New York, NY, USA
| | - Guoan Zhang
- Dept. of Biochemistry, 413 E. 69th Street, Weill Cornell Medicine, New York, NY, USA
| | - Dianna E. Willis
- Burke Neurological Institute, 785 Mamaroneck Avenue, White Plains, NY, USA
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, NY, USA
| | - Peter A. Goldstein
- Dept. of Anesthesiology, 1300 York Ave., Weill Cornell Medicine, New York, NY, USA
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, NY, USA
- Dept. of Medicine, Weill Cornell Medicine, New York, NY, USA
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2
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Downregulation of hERG Channel Expression By Tyrosine Kinase Inhibitors Nilotinib And Vandetanib Predominantly Contributes To Arrhythmogenesis. Toxicol Lett 2022; 365:11-23. [DOI: 10.1016/j.toxlet.2022.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 05/11/2022] [Accepted: 06/03/2022] [Indexed: 11/20/2022]
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3
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Valentin JP, Hoffmann P, Ortemann-Renon C, Koerner J, Pierson J, Gintant G, Willard J, Garnett C, Skinner M, Vargas HM, Wisialowski T, Pugsley MK. OUP accepted manuscript. Toxicol Sci 2022; 187:3-24. [PMID: 35148401 PMCID: PMC9041548 DOI: 10.1093/toxsci/kfac013] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The content of this article derives from a Health and Environmental Sciences Institute (HESI) consortium with a focus to improve cardiac safety during drug development. A detailed literature review was conducted to evaluate the concordance between nonclinical repolarization assays and the clinical thorough QT (TQT) study. Food and Drug Administration and HESI developed a joint database of nonclinical and clinical data, and a retrospective analysis of 150 anonymized drug candidates was reviewed to compare the performance of 3 standard nonclinical assays with clinical TQT study findings as well as investigate mechanism(s) potentially responsible for apparent discrepancies identified. The nonclinical assays were functional (IKr) current block (Human ether-a-go-go related gene), action potential duration, and corrected QT interval in animals (in vivo corrected QT). Although these nonclinical assays demonstrated good specificity for predicting negative clinical QT prolongation, they had relatively poor sensitivity for predicting positive clinical QT prolongation. After review, 28 discordant TQT-positive drugs were identified. This article provides an overview of direct and indirect mechanisms responsible for QT prolongation and theoretical reasons for lack of concordance between clinical TQT studies and nonclinical assays. We examine 6 specific and discordant TQT-positive drugs as case examples. These were derived from the unique HESI/Food and Drug Administration database. We would like to emphasize some reasons for discordant data including, insufficient or inadequate nonclinical data, effects of the drug on other cardiac ion channels, and indirect and/or nonelectrophysiological effects of drugs, including altered heart rate. We also outline best practices that were developed based upon our evaluation.
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Affiliation(s)
- Jean-Pierre Valentin
- Department of Investigative Toxicology, UCB Biopharma SRL, Braine-l’Alleud B-1420, Belgium
| | | | | | - John Koerner
- Center for Drug Evaluation and Research, FDA, Silver Spring, Maryland 20993, USA
| | - Jennifer Pierson
- To whom correspondence should be addressed at Health and Environmental Sciences Institute, 740 15th Street, N.W., Suite 600, Washington, DC 20005, USA. E-mail:
| | | | - James Willard
- Center for Drug Evaluation and Research, FDA, Silver Spring, Maryland 20993, USA
| | - Christine Garnett
- Center for Drug Evaluation and Research, FDA, Silver Spring, Maryland 20993, USA
| | | | - Hugo M Vargas
- Department of Safety Pharmacology & Animal Research Center, Amgen, Thousand Oaks, California 91320, USA
| | - Todd Wisialowski
- Department of Safety Pharmacology, Pfizer, Groton, Connecticut 06340, USA
| | - Michael K Pugsley
- Department of Toxicology, Cytokinetics, South San Francisco, California 94080, USA
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4
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Ríos-Pérez EB, Liu F, Stevens-Sostre WA, Eichel CA, Silignavong J, Robertson GA. A stable cell line inducibly expressing hERG1a/1b heteromeric channels. J Pharmacol Toxicol Methods 2021; 110:107081. [PMID: 34058320 DOI: 10.1016/j.vascn.2021.107081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 04/07/2021] [Accepted: 05/20/2021] [Indexed: 11/24/2022]
Abstract
Heterologously expressed hERG channels represent a mainstay of in vitro drug safety screens intended to mitigate risk of cardiac IKr block and sudden cardiac death. This is true even as more channel types are adopted as part of the Comprehensive in vitro Proarrhythmia Assay (CiPA) intended to elevate specificity and thus enhance throughput of promising lead drugs. Until now, hERG1a homomeric channels have been used as a proxy for IKr despite a wealth of evidence showing that hERG1a/1b heteromers better represent native channels in terms of protein abundance and channel biophysical and pharmacological properties. Past efforts to create a stable hERG1a/1b cell line were met with unpredictable silencing of hERG1b expression despite stable integration of the gene into the HEK293 cell genome. Here we report a new cell line stably expressing hERG1a, with hERG1b reliably controlled by an inducible promoter sensitive to doxycycline. Co-immunoprecipitation, Western blot analysis and patch-clamp electrophysiology confirm the heteromeric composition of the expressed channels. Association with hERG1b was found to promote hERG1a protein levels and enhance membrane current levels. Optimal conditions for drug screening and experimental investigation were achieved at 24 h exposure to 100 ng/ml doxycycline. Differences in pharmacological sensitivity between homomeric and heteromeric channels were observed for dofetilide and ebastine, but not fluoxetine, as evaluated by their IC50 values. Using these values in the O'Hara-Rudy-CiPA in silico model revealed discrepancies in pro-arrhythmia risk, implying the hERG1a homomeric platform overestimates risk for these two drugs. Dofetilide block was use-dependent and faster for hERG1a/1b than hERG1a channels, whereas ebastine showed considerable block at rest and had a slower progression for hERG1a/1b channels. The hERG1a/1b cell line thus represents an advanced model for contemporary drug safety screening assays such as CiPA that employ IC50 values to estimate risk of proarrhythmia in computational models of ventricular cardiomyocytes. This novel technology fulfills an unmet need to enhance specificity and foster a safe yet expanded drug development pipeline.
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Affiliation(s)
- Erick B Ríos-Pérez
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Fang Liu
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Whitney A Stevens-Sostre
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Catherine A Eichel
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Jonathan Silignavong
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Gail A Robertson
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America.
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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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Cao H, Zhou Y, Li T, Yao C, Yang W, Kong S, Wang Y, Yu B, Jiao Q, Sun Y, Jia X, Wang Y, Wang Z, Zhang X, Li J. The Prevalence, Risk Factors and Clinical Correlates of QTc Prolongation in Chinese Hospitalized Patients With Chronic Schizophrenia. Front Psychiatry 2021; 12:704045. [PMID: 34483996 PMCID: PMC8416174 DOI: 10.3389/fpsyt.2021.704045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 07/22/2021] [Indexed: 12/02/2022] Open
Abstract
Background: The QTc interval may be significantly prolonged in schizophrenia patients taking antipsychotics. Few studies have addressed QTc prolongation (QTP) in Chinese patients. Objectives: This study was designed to evaluate the prevalence of QTP and its clinical correlates in Chinese hospitalized patients with chronic schizophrenia. Methods: A total of 436 inpatients and 291 normal controls matched with age and sex were included. QTc prolongation was defined as 2 standard deviations (SD) above the mean value of normal controls. Positive and Negative Syndrome Scale (PANSS) and its five-factor model were used to evaluate psychopathological symptoms. Results: QTc interval was significantly longer in patients than in normal controls. The prevalence of QTP is 8.26% in Chinese hospitalized patients with chronic schizophrenia. More women than men displayed QTP. Compared with patients without QTP, the patients with QTP had significantly higher concrete/disorganized subscore, lower low density lipoprotein (LDL) and lower total protein (TP). Furthermore, binary logistic regression analysis showed that higher number of hospitalizations, higher concrete/disorganized subscore and lower LDL were risk factors for QTP. Correlation analysis indicated significant association between QTc interval and the following variables: sex, age, duration of illness, the number of hospitalizations, PANSS total score, fasting blood glucose (FPG). Finally, a multiple regression analysis showed that older age, antipsychotic polypharmacy, higher PANSS total score, and lower LDL were risk factors for QTP. Among them, LDL seemed to be a protective factor for QTP. Conclusions: QTc interval was longer in schizophrenia patients than in normal controls. The prevalence of QTP is 8.26% in Chinese hospitalized patients with chronic schizophrenia. Some clinical characteristics were risk factors for QTP. And LDL seemed to be a protective factor for QTP.
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Affiliation(s)
- Haiyan Cao
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Yongjie Zhou
- Department of Psychiatric Rehabilitation, Shenzhen Kangning Hospital, Shenzhen, China
| | - Tao Li
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Cong Yao
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Weiliang Yang
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Siying Kong
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Yanyan Wang
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Baoping Yu
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Qingyan Jiao
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Yun Sun
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Xiaoju Jia
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Yuting Wang
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
| | - Zhonggang Wang
- Department of Psychiatry, Jining Psychiatric Hospital, Jining, China
| | - Xiangyang Zhang
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
| | - Jie Li
- Institute of Mental Health, Tianjin Anding Hospital, Tianjin Medical University, Tianjin, China
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7
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Shi YQ, Fan P, Zhang GC, Zhang YH, Li MZ, Wang F, Li BX. Probucol-induced hERG Channel Reduction can be Rescued by Matrine and Oxymatrine in vitro. Curr Pharm Des 2020; 25:4606-4612. [PMID: 31657676 PMCID: PMC7327797 DOI: 10.2174/1381612825666191026170033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 10/19/2019] [Indexed: 01/24/2023]
Abstract
Background The human ether-a-go-go-related gene (hERG) potassium channel is the rapidly activating component of cardiac delayed rectifier potassium current (IKr), which is a crucial determinant of cardiac repolarization. The reduction of hERG current is commonly believed to cause Long QT Syndrome (LQTs). Probucol, a cholesterol-lowering drug, induces LQTs by inhibiting the expression of the hERG channel. Unfortunately, there is currently no effective therapeutic method to rescue probucol-induced LQTs. Methods Patch-clamp recording techniques were used to detect the action potential duration (APD) and current of hERG. Western blot was performed to measure the expression levels of proteins. Results In this study, we demonstrated that 1 μM matrine and oxymatrine could rescue the hERG current and hERG surface expression inhibited by probucol. In addition, matrine and oxymatrine significantly shortened the prolonged action potential duration induced by probucol in neonatal cardiac myocytes. We proposed a novel mechanism underlying the probucol induced decrease in the expression of transcription factor Specificity protein 1 (Sp1), which is an established transactivator of the hERG gene. We also demonstrated that matrine and oxymatrine were able to upregulate Sp1 expression which may be one of the possible mechanisms by which matrine and oxymatrine rescued probucol-induced hERG channel deficiency. Conclusion Our current results demonstrate that matrine and oxymatrine could rescue probucol-induced hERG deficiency in vitro, which may lead to potentially effective therapeutic drugs for treating acquired LQT2 by probucol in the future.
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Affiliation(s)
- Yuan-Qi Shi
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, 23 Youzheng Street, Nangang District, Harbin 150001, China
| | - Pan Fan
- Department of Ophthalmology, the Second Affiliated Hospital of Harbin Medical University, No. 148 Baojian Road, Nangang District, Harbin 150081, China
| | - Guo-Cui Zhang
- Department of Pharmacology, Harbin Medical University, No. 157 Baojian Road, Harbin, 150086, China
| | - Yu-Hao Zhang
- Department of Pharmacology, Harbin Medical University, No. 157 Baojian Road, Harbin, 150086, China
| | - Ming-Zhu Li
- Department of Pharmacology, Harbin Medical University, No. 157 Baojian Road, Harbin, 150086, China
| | - Fang Wang
- Department of Pharmacology, Harbin Medical University, No. 157 Baojian Road, Harbin, 150086, China
| | - Bao-Xin Li
- Department of Pharmacology, Harbin Medical University, No. 157 Baojian Road, Harbin, 150086, China.,State-Province Key Laboratory of Biopharmaceutical Engineering, No. 157 Baojian Road, Harbin, 150086, China
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8
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Mutation-specific peripheral and ER quality control of hERG channel cell-surface expression. Sci Rep 2019; 9:6066. [PMID: 30988392 PMCID: PMC6465299 DOI: 10.1038/s41598-019-42331-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 03/28/2019] [Indexed: 12/11/2022] Open
Abstract
Impaired functional plasma membrane (PM) expression of the hERG K+-channel is associated with Long-QT syndrome type-2 (LQT2) and increased risk of cardiac arrhythmia. Reduced PM-expression is primarily attributed to retention and degradation of misfolded channels by endoplasmic reticulum (ER) protein quality control (QC) systems. However, as the molecular pathogenesis of LQT2 was defined using severely-misfolded hERG variants with limited PM-expression, the potential contribution of post-ER (peripheral) QC pathways to the disease phenotype remains poorly established. Here, we investigate the cellular processing of mildly-misfolded Per-Arnt-Sim (PAS)-domain mutant hERGs, which display incomplete ER-retention and PM-expression defects at physiological temperature. We show that the attenuated PM-expression of hERG is dictated by mutation-specific contributions from both the ER and peripheral QC systems. At the ER, PAS-mutants experience inefficient conformational maturation coupled with rapid ubiquitin-dependent proteasomal degradation. In post-ER compartments, they are rapidly endocytosed from the PM via a ubiquitin-independent mechanism and rapidly targeted for lysosomal degradation. Conformational destabilization underlies aberrant cellular processing at both ER- and post-ER compartments, since conformational correction by a hERG-specific pharmacochaperone or low-temperatures can restore WT-like trafficking. Our results demonstrate that the post-ER QC alone or jointly with the ER QC determines the loss-of-PM-expression phenotype of a subset of LQT2 mutations.
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9
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Feng PF, Zhang B, Zhao L, Fang Q, Liu Y, Wang JN, Xu XQ, Xue H, Li Y, Yan CC, Zhao X, Li BX. Intracellular Mechanism of Rosuvastatin-Induced Decrease in Mature hERG Protein Expression on Membrane. Mol Pharm 2019; 16:1477-1488. [DOI: 10.1021/acs.molpharmaceut.8b01102] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Pan-Feng Feng
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Bo Zhang
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Lei Zhao
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Qing Fang
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Yan Liu
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Jun-Nan Wang
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Xue-Qi Xu
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Hui Xue
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Yang Li
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Cai-Chuan Yan
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Xin Zhao
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
| | - Bao-Xin Li
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
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Yan M, Feng L, Shi Y, Wang J, Liu Y, Li F, Li B. Mechanism of As2O3-Induced Action Potential Prolongation and Using hiPS-CMs to Evaluate the Rescue Efficacy of Drugs With Different Rescue Mechanism. Toxicol Sci 2018; 158:379-390. [PMID: 28521025 DOI: 10.1093/toxsci/kfx098] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Arsenic trioxide (As2O3) has been verified as a breakthrough in the management of acute promyelocytic leukemia in recent decades. However, cardiotoxicity, especially long QT syndrome (LQTS) has become the most important issue during As2O3 treatment. The characterized mechanisms behind this adverse effect are inhibition of cardiac hERG channel trafficking and increase of cardiac calcium currents. In our study, we found a new pathway underlying As2O3-induced cardiotoxicity that As2O3 accelerates lysosomal degradation of hERG on plasma membrane after using brefeldin A (BFA) to block protein trafficking. Then we explored pharmacological rescue strategies on As2O3-induced LQTS, and found that 4 therapeutic agents exert rescue efficacy via 3 different pathways: fexofenadine and astemizole facilitate hERG trafficking via promotion of channel-chaperone formation after As2O3 incubation; ranolazine slows hERG degradation in the presence of As2O3; and resveratrol shows significant attenuation on calcium current increase triggered by As2O3. Moreover, we used human-induced pluripotent stem cell derived cardiomyocytes (hiPS-CMs) to evaluate the rescue effects of the above agents on As2O3-induced prolongation of action potential duration (APD) and demonstrated that fexofenadine and resveratrol significantly ameliorate the prolonged APD. These observations suggested that pharmacological chaperone like fexofenadine and resveratrol might have the potential to protect against the cardiotoxicity of As2O3.
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Affiliation(s)
- Meng Yan
- Department of Pharmacology Harbin Medical University, Nangang District, Harbin, Heilongjiang Province 150086, China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Nangang District, Harbin, Heilongjiang Province 150081, China
| | - Lifang Feng
- Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Nangang District, Harbin, Heilongjiang Province 150081, China
| | - Yanhui Shi
- Department of Pharmacology Harbin Medical University, Nangang District, Harbin, Heilongjiang Province 150086, China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Nangang District, Harbin, Heilongjiang Province 150081, China
| | - Junnan Wang
- Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Nangang District, Harbin, Heilongjiang Province 150081, China
| | - Yan Liu
- Department of Pharmacology Harbin Medical University, Nangang District, Harbin, Heilongjiang Province 150086, China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Nangang District, Harbin, Heilongjiang Province 150081, China
| | - Fengmei Li
- Department of Pharmacology Harbin Medical University, Nangang District, Harbin, Heilongjiang Province 150086, China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Nangang District, Harbin, Heilongjiang Province 150081, China
| | - Baoxin Li
- Department of Pharmacology Harbin Medical University, Nangang District, Harbin, Heilongjiang Province 150086, China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Nangang District, Harbin, Heilongjiang Province 150081, China
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11
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Schlüter KD, Wolf A, Weber M, Schreckenberg R, Schulz R. Oxidized low-density lipoprotein (oxLDL) affects load-free cell shortening of cardiomyocytes in a proprotein convertase subtilisin/kexin 9 (PCSK9)-dependent way. Basic Res Cardiol 2017; 112:63. [PMID: 28913715 PMCID: PMC5599470 DOI: 10.1007/s00395-017-0650-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 09/07/2017] [Indexed: 12/16/2022]
Abstract
Recent studies have documented that oxidized low-density lipoprotein cholesterol (oxLDL) levels directly impact myocardial structure and function. However, the molecular mechanisms by which oxLDL affects cardiac myocytes are not well established. We addressed the question whether oxLDL modifies load-free cell shortening, a standardized readout of cardiac cellular function, and investigated whether proprotein convertase subtilisin/kexin-9 (PCSK9) is involved on oxLDL-dependent processes. Adult rat ventricular cardiomyocytes were isolated and incubated for 24 h with oxLDL. PCSK9 was silenced by administration of siRNA. Load-free cell shortening was analyzed via a line camera at a beating frequency of 2 Hz. RT-PCR and immunoblots were used to identify molecular pathways. We observed a concentration-dependent reduction of load-free cell shortening that was independent of cell damage (apoptosis, necrosis). The effect of oxLDL was attenuated by silencing of oxLDL receptors (LOX-1), blockade of p38 MAP kinase activation, and silencing of PCSK9. oxLDL increased the expression of PCSK9 and caused oxidative modification of tropomyosin. In conclusion, we found that oxLDL significantly impaired contractile function via induction of PCSK9. This is the first report about the expression of PCSK9 in adult terminal differentiated ventricular cardiomyocytes. The data are important in the light of recent development of PCSK9 inhibitory strategies.
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Affiliation(s)
- Klaus-Dieter Schlüter
- Institute of Physiology, Justus-Liebig-University Giessen, Aulweg 129, 35392, Giessen, Germany.
| | - Annemarie Wolf
- Institute of Physiology, Justus-Liebig-University Giessen, Aulweg 129, 35392, Giessen, Germany
| | - Martin Weber
- Institute of Physiology, Justus-Liebig-University Giessen, Aulweg 129, 35392, Giessen, Germany
| | - Rolf Schreckenberg
- Institute of Physiology, Justus-Liebig-University Giessen, Aulweg 129, 35392, Giessen, Germany
| | - Rainer Schulz
- Institute of Physiology, Justus-Liebig-University Giessen, Aulweg 129, 35392, Giessen, Germany
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Yu D, Lv L, Fang L, Zhang B, Wang J, Zhan G, Zhao L, Zhao X, Li B. Inhibitory effects and mechanism of dihydroberberine on hERG channels expressed in HEK293 cells. PLoS One 2017; 12:e0181823. [PMID: 28763460 PMCID: PMC5538702 DOI: 10.1371/journal.pone.0181823] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 07/09/2017] [Indexed: 12/20/2022] Open
Abstract
The human ether-a-go-go-related gene (hERG) potassium channel conducts rapid delayed rectifier potassium currents (IKr) and contributes to phase III cardiac action potential repolarization. Drugs inhibit hERG channels by binding to aromatic residues in hERG helixes. Berberine (BBR) has multiple actions, and its hydrogenated derivative dihydroberberine (DHB) is a potential candidate for developing new drugs. Previous studies have demonstrated that BBR blocks hERG channels and prolongs action potential duration (APD). Our present study aimed to investigate the effects and mechanism of DHB on hERG channels. Protein expression and the hERG current were analyzed using western blotting and patch-clamp, respectively. DHB inhibited the hERG current concentration-dependently after instantaneous perfusion, accelerated channel inactivation by directly binding tyrosine (Tyr652) and phenylalanine (Phe656), and decreased mature (155-kDa) and simultaneously increased immature (135-kDa) hERG expression, respectively. This suggests disruption of forward trafficking of hERG channels. Besides, DHB remarkably reduced heat shock protein 90 (Hsp90) expression and its interaction with hERG, indicating that DHB disrupted hERG trafficking by impairing channel folding. Meanwhie, DHB enhanced the expression of cleaved activating transcription factor-6 (ATF-6), a biomarker of unfolded protein response (UPR). Expression of calnexin and calreticulin, chaperones activated by ATF-6 to facilitate channel folding, were also increased, which indicating UPR activation. Additionally, the degradation rate of mature 155-kDa hERG increased following DHB exposure. In conclusion, we demonstrated that DHB acutely blocked hERG channels by binding the aromatic Tyr652 and Phe656. DHB may decrease hERG plasma membrane expression through two pathways involving disruption of forward trafficking of immature hERG channels and enhanced degradation of mature hERG channels. Furthermore, forward trafficking was disrupted by impaired channel folding associated with altered interactions between hERG proteins and chaperones. Finally, trafficking inhibition activated UPR, and mature hERG channel degradation was increased by DHB.
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Affiliation(s)
- Dahai Yu
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Lin Lv
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Li Fang
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Bo Zhang
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Junnan Wang
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Ge Zhan
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Lei Zhao
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Xin Zhao
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
| | - Baoxin Li
- Department of Pharmacology, College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang Province, People's Republic of China
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13
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Luo L, Hu P, Miao C, Ma A, Wang T. Clenbuterol Attenuates hERG Channel by Promoting the Mature Channel Degradation. Int J Toxicol 2017; 36:314-324. [PMID: 28535735 DOI: 10.1177/1091581817710786] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Clenbuterol, a β2-selective adrenergic receptor agonist, is illicitly used in weight loss and performance enhancement and animal production. Increasing evidence demonstrates that clenbuterol induces various kinds of arrhythmias and QTc interval prolongation. However, little is known about the underlying mechanism. Most drugs are associated with QTc prolongation through interfering with human ether-a-go-go-related gene (hERG) K+ channels. The present study aims to investigate the effects and underlying mechanisms of clenbuterol on the hERG channel. HEK 293 cells were transfected with wild type and Y652A or F656A mutants of the hERG channel and treated with clenbuterol. The hERG current was recorded using whole-cell patch-clamp technique, and protein level was evaluated by Western blot. We found that clenbuterol decreases the mature form of the hERG protein at the cell membrane in a concentration- and time-dependent manner, without affecting the immature form. Correspondingly, clenbuterol chronic treatment reduced hERG current to a greater extent compared to acute treatment. In the presence of Brefeldin A (BFA), which was used to block hERG channel trafficking to cell membrane, clenbuterol reduced hERG on plasma membrane to a greater extent than BFA alone. In addition, the hERG channel's drug binding sites mutant Y652A and F656A abolished clenbuterol-mediated hERG reduction and current blockade. In conclusion, clenbuterol reduces hERG channel expression and current by promoting the channel degradation. The effect of clenbuterol on the hERG channel is related to the drug-binding sites, Tyr-652 and Phe-656, located on the S6 domain. This biophysical mechanism may underlie clenbuterol-induced QTc prolongation or arrhythmia.
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Affiliation(s)
- Ling Luo
- 1 Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Peijing Hu
- 1 Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Changqing Miao
- 1 Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Aiqun Ma
- 1 Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China.,2 Key Laboratory of Molecular Cardiology, Shaanxi, China.,3 Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University), Ministry of Education, Xi'an, Shaanxi, China
| | - Tingzhong Wang
- 1 Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China.,2 Key Laboratory of Molecular Cardiology, Shaanxi, China.,3 Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University), Ministry of Education, Xi'an, Shaanxi, China
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Turker I, Ai T, Itoh H, Horie M. Drug-induced fatal arrhythmias: Acquired long QT and Brugada syndromes. Pharmacol Ther 2017; 176:48-59. [PMID: 28527921 DOI: 10.1016/j.pharmthera.2017.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Since the early 1990s, the concept of primary "inherited" arrhythmia syndromes or ion channelopathies has evolved rapidly as a result of revolutionary progresses made in molecular genetics. Alterations in genes coding for membrane proteins such as ion channels or their associated proteins responsible for the generation of cardiac action potentials (AP) have been shown to cause specific malfunctions which eventually lead to cardiac arrhythmias. These arrhythmic disorders include congenital long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, short QT syndrome, progressive cardiac conduction disease, etc. Among these, long QT and Brugada syndromes are the most extensively studied, and drugs cause a phenocopy of these two diseases. To date, more than 10 different genes have been reported to be responsible for each syndrome. More recently, it was recognized that long QT syndrome can be latent, even in the presence of an unequivocally pathogenic mutation (silent mutation carrier). Co-existence of other pathological conditions in these silent mutation carriers may trigger a malignant form of ventricular arrhythmia, the so called torsade de pointes (TdP) that is most commonly brought about by drugs. In analogy to the drug-induced long QT syndrome, Brugada type 1 ECG can also be induced or unmasked by a wide variety of drugs and pathological conditions; so physicians may encounter patients with a latent form of Brugada syndrome. Of particular note, Brugada syndrome is frequently associated with atrial fibrillation whose therapeutic agents such as Vaughan Williams class IC drugs can unmask the dormant and asymptomatic Brugada syndrome. This review describes two types of drug-induced arrhythmias: the long QT and Brugada syndromes.
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Affiliation(s)
- Isik Turker
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Tomohiko Ai
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Clinical Laboratory Medicine, Juntendo University School of Medicine, Tokyo, Japan
| | - Hideki Itoh
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
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15
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Physiological and therapeutic regulation of PCSK9 activity in cardiovascular disease. Basic Res Cardiol 2017; 112:32. [PMID: 28439730 PMCID: PMC5403857 DOI: 10.1007/s00395-017-0619-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 04/07/2017] [Indexed: 12/14/2022]
Abstract
Ischemic heart disease is the main cause of death worldwide and is accelerated by increased levels of low-density lipoprotein cholesterol (LDL-C). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent circulating regulator of LDL-C through its ability to induce degradation of the LDL receptor (LDLR) in the lysosome of hepatocytes. Only in the last few years, a number of breakthroughs in the understanding of PCSK9 biology have been reported illustrating how PCSK9 activity is tightly regulated at several levels by factors influencing its transcription, secretion, or by extracellular inactivation and clearance. Two humanized antibodies directed against the LDLR-binding site in PCSK9 received approval by the European and US authorities and additional PCSK9 directed therapeutics are climbing up the phases of clinical trials. The first outcome data of the PCSK9 inhibitor evolocumab reported a significant reduction in the composite endpoint (cardiovascular death, myocardial infarction, or stroke) and further outcome data are awaited. Meanwhile, it became evident that PCSK9 has (patho)physiological roles in several cardiovascular cells. In this review, we summarize and discuss the recent biological and clinical data on PCSK9, the regulation of PCSK9, its extra-hepatic activities focusing on cardiovascular cells, molecular concepts to target PCSK9, and finally briefly summarize the data of recent clinical studies.
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16
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Abstract
Cardiac delayed rectifier potassium channels conduct outward potassium currents during the plateau phase of action potentials and play pivotal roles in cardiac repolarization. These include IKs, IKr and the atrial specific IKur channels. In this article, we will review their molecular identities and biophysical properties. Mutations in the genes encoding delayed rectifiers lead to loss- or gain-of-function phenotypes, disrupt normal cardiac repolarization and result in various cardiac rhythm disorders, including congenital Long QT Syndrome, Short QT Syndrome and familial atrial fibrillation. We will also discuss the prospect of using delayed rectifier channels as therapeutic targets to manage cardiac arrhythmia.
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Affiliation(s)
- Lei Chen
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Kevin J Sampson
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Robert S Kass
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA.
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17
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Yan M, Zhang K, Shi Y, Feng L, Lv L, Li B. Mechanism and pharmacological rescue of berberine-induced hERG channel deficiency. DRUG DESIGN DEVELOPMENT AND THERAPY 2015; 9:5737-47. [PMID: 26543354 PMCID: PMC4622489 DOI: 10.2147/dddt.s91561] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Berberine (BBR), an isoquinoline alkaloid mainly isolated from plants of Berberidaceae family, is extensively used to treat gastrointestinal infections in clinics. It has been reported that BBR can block human ether-a-go-go-related gene (hERG) potassium channel and inhibit its membrane expression. The hERG channel plays crucial role in cardiac repolarization and is the target of diverse proarrhythmic drugs. Dysfunction of hERG channel can cause long QT syndrome. However, the regulatory mechanisms of BBR effects on hERG at cell membrane level remain unknown. This study was designed to investigate in detail how BBR decreased hERG expression on cell surface and further explore its pharmacological rescue strategies. In this study, BBR decreases caveolin-1 expression in a concentration-dependent manner in human embryonic kidney 293 (HEK293) cells stably expressing hERG channel. Knocking down the basal expression of caveolin-1 alleviates BBR-induced hERG reduction. In addition, we found that aromatic tyrosine (Tyr652) and phenylalanine (Phe656) in S6 domain mediate the long-term effect of BBR on hERG by using mutation techniques. Considering both our previous and present work, we propose that BBR reduces hERG membrane stability with multiple mechanisms. Furthermore, we found that fexofenadine and resveratrol shorten action potential duration prolongated by BBR, thus having the potential effects of alleviating the cardiotoxicity of BBR.
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Affiliation(s)
- Meng Yan
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Kaiping Zhang
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Yanhui Shi
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Lifang Feng
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Lin Lv
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Baoxin Li
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China ; State-Province Key Laboratory of Biopharmaceutical Engineering, Harbin, Heilongjiang, People's Republic of China
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18
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Shi YQ, Yan CC, Zhang X, Yan M, Liu LR, Geng HZ, Lv L, Li BX. Mechanisms underlying probucol-induced hERG-channel deficiency. DRUG DESIGN DEVELOPMENT AND THERAPY 2015; 9:3695-704. [PMID: 26229434 PMCID: PMC4516208 DOI: 10.2147/dddt.s86724] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The hERG gene encodes the pore-forming α-subunit of the rapidly activating delayed rectifier potassium channel (I Kr), which is important for cardiac repolarization. Reduction of I hERG due to genetic mutations or drug interferences causes long QT syndrome, leading to life-threatening cardiac arrhythmias (torsades de pointes) or sudden death. Probucol is a cholesterol-lowering drug that could reduce hERG current by decreasing plasma membrane hERG protein expression and eventually cause long QT syndrome. Here, we investigated the mechanisms of probucol effects on I hERG and hERG-channel expression. Our data demonstrated that probucol reduces SGK1 expression, known as SGK isoform, in a concentration-dependent manner, resulting in downregulation of phosphorylated E3 ubiquitin ligase Nedd4-2 expression, but not the total level of Nedd4-2. As a result, the hERG protein reduces, due to the enhanced ubiquitination level. On the contrary, carbachol could enhance the phosphorylation level of Nedd4-2 as an alternative to SGK1, and thus rescue the ubiquitin-mediated degradation of hERG channels caused by probucol. These discoveries provide a novel mechanism of probucol-induced hERG-channel deficiency, and imply that carbachol or its analog may serve as potential therapeutic compounds for the handling of probucol cardiotoxicity.
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Affiliation(s)
- Yuan-Qi Shi
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Cai-Chuan Yan
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Xiao Zhang
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Meng Yan
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Li-Rong Liu
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Huai-Ze Geng
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Lin Lv
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
| | - Bao-Xin Li
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China ; State-Province Key Laboratory of Biopharmaceutical Engineering, Harbin, Heilongjiang, People's Republic of China
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19
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Computational investigations of hERG channel blockers: New insights and current predictive models. Adv Drug Deliv Rev 2015; 86:72-82. [PMID: 25770776 DOI: 10.1016/j.addr.2015.03.003] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 01/13/2015] [Accepted: 03/04/2015] [Indexed: 01/08/2023]
Abstract
Identification of potential human Ether-a-go-go Related-Gene (hERG) potassium channel blockers is an essential part of the drug development and drug safety process in pharmaceutical industries or academic drug discovery centers, as they may lead to drug-induced QT prolongation, arrhythmia and Torsade de Pointes. Recent reports also suggest starting to address such issues at the hit selection stage. In order to prioritize molecules during the early drug discovery phase and to reduce the risk of drug attrition due to cardiotoxicity during pre-clinical and clinical stages, computational approaches have been developed to predict the potential hERG blockage of new drug candidates. In this review, we will describe the current in silico methods developed and applied to predict and to understand the mechanism of actions of hERG blockers, including ligand-based and structure-based approaches. We then discuss ongoing research on other ion channels and hERG polymorphism susceptible to be involved in LQTS and how systemic approaches can help in the drug safety decision.
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20
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Zhang KP, Yang BF, Li BX. Translational toxicology and rescue strategies of the hERG channel dysfunction: biochemical and molecular mechanistic aspects. Acta Pharmacol Sin 2014; 35:1473-84. [PMID: 25418379 PMCID: PMC4261120 DOI: 10.1038/aps.2014.101] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/20/2014] [Indexed: 01/08/2023] Open
Abstract
The human ether-à-go-go related gene (hERG) potassium channel is an obligatory anti-target for drug development on account of its essential role in cardiac repolarization and its close association with arrhythmia. Diverse drugs have been removed from the market owing to their inhibitory activity on the hERG channel and their contribution to acquired long QT syndrome (LQTS). Moreover, mutations that cause hERG channel dysfunction may induce congenital LQTS. Recently, an increasing number of biochemical and molecular mechanisms underlying hERG-associated LQTS have been reported. In fact, numerous potential biochemical and molecular rescue strategies are hidden within the biogenesis and regulating network. So far, rescue strategies of hERG channel dysfunction and LQTS mainly include activators, blockers, and molecules that interfere with specific links and other mechanisms. The aim of this review is to discuss the rescue strategies based on hERG channel toxicology from the biochemical and molecular perspectives.
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Affiliation(s)
- Kai-ping Zhang
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
| | - Bao-feng Yang
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
| | - Bao-xin Li
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
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21
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Nogawa H, Kawai T. hERG trafficking inhibition in drug-induced lethal cardiac arrhythmia. Eur J Pharmacol 2014; 741:336-9. [DOI: 10.1016/j.ejphar.2014.06.044] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 06/16/2014] [Accepted: 06/23/2014] [Indexed: 02/01/2023]
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22
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Cai Y, Wang Y, Xu J, Zuo X, Xu Y. Down-regulation of ether-a-go-go-related gene potassium channel protein through sustained stimulation of AT1 receptor by angiotensin II. Biochem Biophys Res Commun 2014; 452:852-7. [PMID: 25218469 DOI: 10.1016/j.bbrc.2014.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 09/03/2014] [Indexed: 01/26/2023]
Abstract
We investigated the effects of AT1 receptor stimulation by angiotensin II (Ang II) on human ether-a-go-go-related gene (hERG) potassium channel protein in a heterogeneous expression system with the human embryonic kidney (HEK) 293 cells which stably expressed hERG channel protein and were transiently transfected with the human AT1 receptors (HEK293/hERG). Western-blot analysis showed that Ang II significantly decreased the expression of mature hERG channel protein (155-kDa band) in a time- and dose-dependent manner without affecting the level of immature hERG channel protein (135-kDa band). The relative intensity of 155-kDa band was 64.7±6.8% of control (P<0.01) after treatment of Ang II at 100nM for 24h. To investigate the effect of Ang II on the degradation of mature hERG channel protein, we blocked forward trafficking from ER to Golgi with a Golgi transit inhibitor brefeldin A (10μM). Ang II significantly enhanced the time-dependent reduction of mature hERG channel protein. In addition, the proteasomal inhibitor lactacystin (5μM) inhibited Ang II-mediated the reduction of mature hERG channel protein, but the lysosomal inhibitor bafilomycin A1 (1μM) had no effect on the protein. The protein kinase C (PKC) inhibitor bisindolylmaleimide 1 (1μM) antagonized the reduction of mature hERG channel protein induced by Ang II. The results indicate that sustained stimulation of AT1 receptors by Ang II reduces the mature hERG channel protein via accelerating channel proteasomal degradation involving the PKC pathway.
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Affiliation(s)
- Yue Cai
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China
| | - Yuhong Wang
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China
| | - Jia Xu
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China
| | - Xu Zuo
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China
| | - Yanfang Xu
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China.
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23
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Wang T, Hogan-Cann A, Kang Y, Cui Z, Guo J, Yang T, Lamothe SM, Li W, Ma A, Fisher JT, Zhang S. Muscarinic receptor activation increases hERG channel expression through phosphorylation of ubiquitin ligase Nedd4-2. Mol Pharmacol 2014; 85:877-86. [PMID: 24688054 DOI: 10.1124/mol.113.091553] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The human ether-à-go-go-related gene (hERG) encodes the pore-forming subunit of the rapidly activating delayed rectifier potassium channel, which is important for cardiac repolarization. Reduction of hERG current due to genetic mutations or drug interferences causes long QT syndrome, leading to cardiac arrhythmias and sudden death. To date, there is no effective therapeutic method to restore or enhance hERG channel function. Using cell biology and electrophysiological methods, we found that the muscarinic receptor agonist carbachol increased the expression and function of hERG, but not ether-à-go-go or Kv1.5 channels stably expressed in human embryonic kidney cells. The carbachol-mediated increase in hERG expression was abolished by the selective M3 antagonist 4-DAMP (1,1-dimethyl-4-diphenylacetoxypiperidinium iodide) but not by the M2 antagonist AF-DX 116 (11[[2-[(diethylamino)methyl]-1-piperidinyl]-acetyl]-5,11-dihydro-6H-pyrido[2,3-b] [1,4]benzodiazepine-6-one). Treatment of cells with carbachol reduced the hERG-ubiquitin interaction and slowed the rate of hERG degradation. We previously showed that the E3 ubiquitin ligase Nedd4-2 mediates degradation of hERG channels. Here, we found that disrupting the Nedd4-2 binding domain in hERG completely eliminated the effect of carbachol on hERG channels. Carbachol treatment enhanced the phosphorylation level, but not the total level, of Nedd4-2. Blockade of the protein kinase C (PKC) pathway abolished the carbachol-induced enhancement of hERG channels. Our data suggest that muscarinic activation increases hERG channel expression by phosphorylating Nedd4-2 via the PKC pathway.
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Affiliation(s)
- Tingzhong Wang
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, China (T.W., A.M.); and Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada (T.W., A.H.-C., Y.K., Z.C., J.G., T.Y., S.M.L., W.L., J.T.F., S.Z.)
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Hihara T, Yamazaki K, Taniguchi T, Yoshinaga T, Ito M, Sawada K. Use of Human Embryonic Stem Cell-Derived Cardiomyocyte Clusters to Assess Potential for Chronic Treatment with Compounds to Cause QT Prolongation. ACTA ACUST UNITED AC 2014. [DOI: 10.4236/pp.2014.54044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Karnik R, Ludlow MJ, Abuarab N, Smith AJ, Hardy MEL, Elliott DJS, Sivaprasadarao A. Endocytosis of HERG is clathrin-independent and involves arf6. PLoS One 2013; 8:e85630. [PMID: 24392021 PMCID: PMC3877390 DOI: 10.1371/journal.pone.0085630] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 12/05/2013] [Indexed: 01/02/2023] Open
Abstract
The hERG potassium channel is critical for repolarisation of the cardiac action potential. Reduced expression of hERG at the plasma membrane, whether caused by hereditary mutations or drugs, results in long QT syndrome and increases the risk of ventricular arrhythmias. Thus, it is of fundamental importance to understand how the density of this channel at the plasma membrane is regulated. We used antibodies to an extracellular native or engineered epitope, in conjunction with immunofluorescence and ELISA, to investigate the mechanism of hERG endocytosis in recombinant cells and validated the findings in rat neonatal cardiac myocytes. The data reveal that this channel undergoes rapid internalisation, which is inhibited by neither dynasore, an inhibitor of dynamin, nor a dominant negative construct of Rab5a, into endosomes that are largely devoid of the transferrin receptor. These results support a clathrin-independent mechanism of endocytosis and exclude involvement of dynamin-dependent caveolin and RhoA mechanisms. In agreement, internalised hERG displayed marked overlap with glycosylphosphatidylinositol-anchored GFP, a clathrin-independent cargo. Endocytosis was significantly affected by cholesterol extraction with methyl-β-cyclodextrin and inhibition of Arf6 function with dominant negative Arf6-T27N-eGFP. Taken together, we conclude that hERG undergoes clathrin-independent endocytosis via a mechanism involving Arf6.
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Affiliation(s)
- Rucha Karnik
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Melanie J. Ludlow
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
- Faculty of Biological Sciences, Multidisciplinary Cardiovascular Centre, University of Leeds, Leeds, United Kingdom
| | - Nada Abuarab
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Andrew J. Smith
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | | | | | - Asipu Sivaprasadarao
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
- Faculty of Biological Sciences, Multidisciplinary Cardiovascular Centre, University of Leeds, Leeds, United Kingdom
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Townsend C, Brown BS. Predicting drug-induced QT prolongation and torsades de pointes: a review of preclinical endpoint measures. ACTA ACUST UNITED AC 2013; Chapter 10:Unit 10.16. [PMID: 23744708 DOI: 10.1002/0471141755.ph1016s61] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Compound-induced prolongation of the cardiac QT interval is a major concern in drug development and this unit discusses approaches that can predict QT effects prior to undertaking clinical trials. The majority of compounds that prolong the QT interval block the cardiac rapid delayed rectifier potassium current, IKr (hERG). Described in this overview are different ways to measure hERG, from recent advances in automated electrophysiology to the quantification of channel protein trafficking and binding. The contribution of other cardiac ion channels to hERG data interpretation is also discussed. In addition, endpoint measures of the integrated activity of cardiac ion channels at the single-cell, tissue, and whole-animal level, including for example the well-established action potential to the more recent beat-to-beat variability, transmural dispersion of repolarization, and field potential duration, are described in the context of their ability to predict QT prolongation and torsadogenicity in humans.
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Affiliation(s)
- Claire Townsend
- GlaxoSmithKline Biological Reagents and Assay Development, Research Triangle Park, NC, USA
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Ma Q, Yu H, Lin J, Sun Y, Shen X, Ren L. Screening for cardiac HERG potassium channel interacting proteins using the yeast two-hybrid technique. Cell Biol Int 2013; 38:239-45. [PMID: 24154981 DOI: 10.1002/cbin.10196] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 09/25/2013] [Indexed: 12/12/2022]
Abstract
The human ERG protein (HERG or Kv 11.1) encoded by the human ether-a-go-go-related gene (herg) is the pore-forming subunit of the cardiac delayed rectifier potassium current (IKr) responsible for action potential (AP) repolarization. Mutations in HERG lead to long-QT syndrome, a major cause of arrhythmias. Protein-protein interactions are fundamental for ion channel trafficking, membrane localization, and functional modulation. To identify proteins involved in the regulation of the HERG channel, we conducted a yeast two-hybrid screen of a human heart cDNA library using the C-terminus or N-terminus of HERG as bait. Fifteen proteins were identified as HERG amino terminal (HERG-NT)-interacting proteins, including Caveolin-1 (a membrane scaffold protein with multiple interacting partners, including G-proteins, kinases and NOS), the zinc finger protein, FHL2 and PTPN12 (a non-receptor tyrosine phosphatase). Eight HERG carboxylic terminal (HERG-CT)-interacting proteins were also identified, including the NF-κB-interacting protein myotrophin, We have identified multiple potential interacting proteins that may regulate cardiac IKr through cytoskeletal interactions, G-protein modulation, phosphorylation and downstream second messenger and transcription cascades. These findings provide further insight into dynamic modulation of HERG under physiological conditions and arrhythmogenesis.
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Affiliation(s)
- Qingyan Ma
- Department of Cardiology, Guangdong Provincial Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, 510080, China
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Nogawa H, Kawai T, Yajima M, Miura M, Ogawa T, Murakami K. Effects of probucol, a typical hERG expression inhibitor, on in vivo QT interval prolongation in conscious dogs. Eur J Pharmacol 2013; 720:29-37. [DOI: 10.1016/j.ejphar.2013.10.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 10/25/2013] [Accepted: 10/29/2013] [Indexed: 01/08/2023]
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Cardiac ion channel trafficking defects and drugs. Pharmacol Ther 2013; 139:24-31. [DOI: 10.1016/j.pharmthera.2013.03.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 03/14/2013] [Indexed: 01/19/2023]
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30
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He F, Luo J, Luo Z, Fan L, He Y, Zhu D, Gao J, Deng S, Wang Y, Qian Y, Zhou H, Chen X, Zhang W. The KCNH2 genetic polymorphism (1956, C>T) is a novel biomarker that is associated with CCB and α,β-ADR blocker response in EH patients in China. PLoS One 2013; 8:e61317. [PMID: 23613831 PMCID: PMC3632552 DOI: 10.1371/journal.pone.0061317] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 03/08/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND KCNH2 (hERG) potassium channels have an integral role in regulating the excitability of smooth muscle cells. Some pathways driven by angiotensin II, nitric oxide and adrenergic receptors blocker are involved in modulating the properties of KCNH2 potassium channels. And these pathways are closely related to blood pressure regulation. Therefore, we hypothesized that KCNH2 genetic polymorphisms may affect blood pressure response to the antihypertensive drug therapies. MATERIALS AND METHODS To evaluate the interactions between KCNH2 genetic polymorphisms and individual blood pressure response to antihypertensive drugs, 370 subjects with essential hypertension (EH) were studied. In evaluating the interactions between KCNH2 genetic polymorphisms and drug response to blood pressure, multivariable ANOVA analysis followed by Bonferroni correction were carried out. RESULTS There were statistically significant interactions between KCNH2 (1956, C>T) polymorphism and DBP change (P = 0.010), MAP change (P = 0.014) on azelnidipine or nitrendipine therapy patients at the end of 6 weeks. We found that the KCNH2 (1956,C>T) polymorphism was associated with the hypotensive effects of α,β-ADR blockers of DBP change at the end of 4 and 6 weeks' treatment in an age- and gender-dependent manner (P = 0.007 and 0.019, respectively). Similar results were also observed for changes in MAP at the end of 4 and 6 weeks (P-values were 0.035 and 0.078, respectively). While patients who received imidapril, candesartan and irbesartan therapy, no significant difference in drug response among KCNH2(1956,C>T) genotype was observed. CONCLUSION We have reported for the first time that KCNH2 (1956, C>T) polymorphism is associated with efficacy of antihypertensive drugs CCBs and ADR blockers, and may serve as a novel biomarker for individualized therapy for certain antihypertensive drugs.
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Affiliation(s)
- Fazhong He
- Pharmacogenetics Research Institute, Institute of Clinical Pharmacology, Hunan Key laboratory of Pharmacogenetics, Central South University, Changsha, Hunan, PRC
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Hihara T, Taniguchi T, Ueda M, Yoshinaga T, Miyamoto N, Sawada K. Probucol and the cholesterol synthesis inhibitors simvastatin and triparanol regulate I ks channel function differently. Hum Exp Toxicol 2013; 32:1028-37. [PMID: 23424208 DOI: 10.1177/0960327112474848] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Channels responsible for slowly activating delayed-rectifier potassium current (I(Ks)) are composed of KCNQ1 and KCNE1 subunits, and these channels play a role in the repolarization of cardiac action potentials. Recently, we showed that the antihyperlipidemic drug probucol, which induces QT prolongation, decreases the I(Ks) after 24-h treatment. In the present study, we investigated the effects of three cholesterol-lowering agents (probucol, an enhancer of cholesterol efflux; simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor; and triparanol, a 3β-hydroxysterol-▵24-reductase inhibitor) on cholesterol synthesis, the KCNQ1 current (I KCNQ1), and the I(Ks) to clarify the differences in the modes of action of these agents on the I(Ks). Probucol did not inhibit cholesterol synthesis and had no effect on I KCNQ1, while I(Ks) decreased after 24-h treatment. Simvastatin inhibited cholesterol synthesis and decreased I KCNQ1 and I(Ks). Additionally, the activation kinetics of I(Ks) became faster, compared with that of control I(Ks). Triparanol inhibited cholesterol synthesis but did not reduce I KCNQ1 and I(Ks). However, the activation kinetics of I(Ks) became faster. Our data indicated that the mechanism by which probucol inhibits I(Ks) was not mediated by the inhibition of cholesterol synthesis but depended on an interaction with the KCNQ1/KCNE1 complex. Meanwhile, the reduction in cholesterol induced by simvastatin and triparanol is one of the mechanisms that affects the kinetics of I(ks).
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Affiliation(s)
- Taro Hihara
- 1Department of Genomics-Based Drug Discovery, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Japan
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Guo J, Wang T, Li X, Shallow H, Yang T, Li W, Xu J, Fridman MD, Yang X, Zhang S. Cell surface expression of human ether-a-go-go-related gene (hERG) channels is regulated by caveolin-3 protein via the ubiquitin ligase Nedd4-2. J Biol Chem 2012; 287:33132-41. [PMID: 22879586 DOI: 10.1074/jbc.m112.389643] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The human ether-a-go-go-related gene (hERG) encodes the rapidly activating delayed rectifier potassium channel (I(Kr)) which plays an important role in cardiac repolarization. A reduction or increase in hERG current can cause long or short QT syndrome, respectively, leading to fatal cardiac arrhythmias. The channel density in the plasma membrane is a key determinant of the whole cell current amplitude. To gain insight into the molecular mechanisms for the regulation of hERG density at the plasma membrane, we used whole cell voltage clamp, Western blotting, and immunocytochemical methods to investigate the effects of an integral membrane protein, caveolin-3 (Cav3) on hERG expression levels. Our data demonstrate that Cav3, hERG, and ubiquitin-ligase Nedd4-2 interact with each other and form a complex. Expression of Cav3 thus enhances the hERG-Nedd4-2 interaction, leading to an increased ubiquitination and degradation of mature, plasma-membrane localized hERG channels. Disrupting Nedd4-2 interaction with hERG by mutations eliminates the effects of Cav3 on hERG channels. Knockdown of endogenous Cav3 or Nedd4-2 in cultured neonatal rat ventricular myocytes using siRNA led to an increase in native I(Kr). Our data demonstrate that hERG expression in the plasma membrane is regulated by Cav3 via Nedd4-2. These findings extend our understanding of the regulation of hERG channels and cardiac electrophysiology.
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Affiliation(s)
- Jun Guo
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, Ontario, Canada
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Targeted cancer therapy: giving histone deacetylase inhibitors all they need to succeed. Future Med Chem 2012; 4:505-24. [PMID: 22416777 DOI: 10.4155/fmc.12.3] [Citation(s) in RCA: 296] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Histone deacetylase inhibitors (HDACis) have now emerged as a powerful new class of small-molecule therapeutics acting through the regulation of the acetylation states of histone proteins (a form of epigenetic modulation) and other non-histone protein targets. Over 490 clinical trials have been initiated in the last 10 years, culminating in the approval of two structurally distinct HDACis - SAHA (vorinostat, Zolinza™) and FK228 (romidepsin, Istodax™). However, the current HDACis have serious limitations, including ineffectively low concentrations in solid tumors and cardiac toxicity, which is hindering their progress in the clinic. Herein, we review the primary paradigms being pursued to overcome these hindrances, including HDAC isoform selectivity, localized administration, and targeting cap groups to achieve selective tissue and cell type distribution.
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Chronic Probucol Treatment Decreases the Slow Component of the Delayed-Rectifier Potassium Current in CHO Cells Transfected With KCNQ1 and KCNE1. J Cardiovasc Pharmacol 2012; 59:377-86. [DOI: 10.1097/fjc.0b013e318245e0c5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Dennis AT, Wang L, Wan H, Nassal D, Deschenes I, Ficker E. Molecular determinants of pentamidine-induced hERG trafficking inhibition. Mol Pharmacol 2011; 81:198-209. [PMID: 22046004 DOI: 10.1124/mol.111.075135] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Pentamidine is an antiprotozoal compound that clinically causes acquired long QT syndrome (acLQTS), which is associated with prolonged QT intervals, tachycardias, and sudden cardiac arrest. Pentamidine delays terminal repolarization in human heart by acutely blocking cardiac inward rectifier currents. At the same time, pentamidine reduces surface expression of the cardiac potassium channel I(Kr)/human ether à-go-go-related gene (hERG). This is unusual in that acLQTS is caused most often by direct block of the cardiac potassium current I(Kr)/hERG. The present study was designed to provide a more complete picture of how hERG surface expression is disrupted by pentamidine at the cellular and molecular levels. Using biochemical and electrophysiological methods, we found that pentamidine exclusively inhibits hERG export from the endoplasmic reticulum to the cell surface in a heterologous expression system as well as in cardiomyocytes. hERG trafficking inhibition could be rescued in the presence of the pharmacological chaperone astemizole. We used rescue experiments in combination with an extensive mutational analysis to locate an interaction site for pentamidine at phenylalanine 656, a crucial residue in the canonical drug binding site of terminally folded hERG. Our data suggest that pentamidine binding to a folding intermediate of hERG arrests channel maturation in a conformational state that cannot be exported from the endoplasmic reticulum. We propose that pentamidine is the founding member of a novel pharmacological entity whose members act as small molecule antichaperones.
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Affiliation(s)
- Adrienne T Dennis
- Rammelkamp Center for Education and Research, MetroHealth Campus, Cleveland, OH 44109, USA
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Dennis AT, Nassal D, Deschenes I, Thomas D, Ficker E. Antidepressant-induced ubiquitination and degradation of the cardiac potassium channel hERG. J Biol Chem 2011; 286:34413-25. [PMID: 21832094 PMCID: PMC3190784 DOI: 10.1074/jbc.m111.254367] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Revised: 07/30/2011] [Indexed: 11/06/2022] Open
Abstract
The most common cause for adverse cardiac events by antidepressants is acquired long QT syndrome (acLQTS), which produces electrocardiographic abnormalities that have been associated with syncope, torsade de pointes arrhythmias, and sudden cardiac death. acLQTS is often caused by direct block of the cardiac potassium current I(Kr)/hERG, which is crucial for terminal repolarization in human heart. Importantly, desipramine belongs to a group of tricyclic antidepressant compounds that can simultaneously block hERG and inhibit its surface expression. Although up to 40% of all hERG blockers exert combined hERG block and trafficking inhibition, few of these compounds have been fully characterized at the cellular level. Here, we have studied in detail how desipramine inhibits hERG surface expression. We find a previously unrecognized combination of two entirely different mechanisms; desipramine increases hERG endocytosis and degradation as a consequence of drug-induced channel ubiquitination and simultaneously inhibits hERG forward trafficking from the endoplasmic reticulum. This unique combination of cellular effects in conjunction with acute channel block may explain why tricyclic antidepressants as a compound class are notorious for their association with arrhythmias and sudden cardiac death. Taken together, we describe the first example of drug-induced channel ubiquitination and degradation. Our data are directly relevant to the cardiac safety of not only tricyclic antidepressants but also other therapeutic compounds that exert multiple effects on hERG, as hERG trafficking and degradation phenotypes may go undetected in most preclinical safety assays designed to screen for acLQTS.
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Affiliation(s)
- Adrienne T. Dennis
- From the Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, Cleveland Ohio 44109
| | - Drew Nassal
- From the Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, Cleveland Ohio 44109
- the Department of Physiology and Biophysics, Case Western Reserve University, Cleveland Ohio 44106, and
| | - Isabelle Deschenes
- From the Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, Cleveland Ohio 44109
- the Department of Physiology and Biophysics, Case Western Reserve University, Cleveland Ohio 44106, and
| | - Dierk Thomas
- the Department of Cardiology, Medical University Hospital Heidelberg, D-69120 Heidelberg, Germany
| | - Eckhard Ficker
- From the Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, Cleveland Ohio 44109
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