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Kumar M, Gaivin RJ, Khan S, Fedorov Y, Adams DJ, Zhao W, Lee HY, Dai X, Dealwis CG, Schelling JR. Definition of fatty acid transport protein-2 (FATP2) structure facilitates identification of small molecule inhibitors for the treatment of diabetic complications. Int J Biol Macromol 2023; 244:125328. [PMID: 37307967 PMCID: PMC10527240 DOI: 10.1016/j.ijbiomac.2023.125328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 06/06/2023] [Accepted: 06/08/2023] [Indexed: 06/14/2023]
Abstract
Diabetes is a major public health problem due to morbidity and mortality associated with end organ complications. Uptake of fatty acids by Fatty Acid Transport Protein-2 (FATP2) contributes to hyperglycemia, diabetic kidney and liver disease pathogenesis. Because FATP2 structure is unknown, a homology model was constructed, validated by AlphaFold2 prediction and site-directed mutagenesis, and then used to conduct a virtual drug discovery screen. In silico similarity searches to two low-micromolar IC50 FATP2 inhibitors, followed by docking and pharmacokinetics predictions, narrowed a diverse 800,000 compound library to 23 hits. These candidates were further evaluated for inhibition of FATP2-dependent fatty acid uptake and apoptosis in cells. Two compounds demonstrated nanomolar IC50, and were further characterized by molecular dynamic simulations. The results highlight the feasibility of combining a homology model with in silico and in vitro screening, to economically identify high affinity inhibitors of FATP2, as potential treatment for diabetes and its complications.
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Affiliation(s)
- Mukesh Kumar
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Robert J Gaivin
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Shenaz Khan
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Yuriy Fedorov
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Drew J Adams
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Weiyang Zhao
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Hsueh-Yun Lee
- School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei 110, Taiwan
| | - Xinghong Dai
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Chris G Dealwis
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, United States of America; Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, United States of America
| | - Jeffrey R Schelling
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106, United States of America; Department of Medicine, Case Western Reserve University, Cleveland, OH 44106, United States of America.
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Oz M, Lorke DE, Howarth FC. Transient receptor potential vanilloid 1 (TRPV1)-independent actions of capsaicin on cellular excitability and ion transport. Med Res Rev 2023. [PMID: 36916676 DOI: 10.1002/med.21945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 01/17/2023] [Accepted: 02/26/2023] [Indexed: 03/15/2023]
Abstract
Capsaicin is a naturally occurring alkaloid derived from chili pepper that is responsible for its hot pungent taste. Capsaicin is known to exert multiple pharmacological actions, including analgesia, anticancer, anti-inflammatory, antiobesity, and antioxidant effects. The transient receptor potential vanilloid subfamily member 1 (TRPV1) is the main receptor mediating the majority of the capsaicin effects. However, numerous studies suggest that the TRPV1 receptor is not the only target for capsaicin. An increasing number of studies indicates that capsaicin, at low to mid µM ranges, not only indirectly through TRPV1-mediated Ca2+ increases, but also directly modulates the functions of voltage-gated Na+ , K+ , and Ca2+ channels, as well as ligand-gated ion channels and other ion transporters and enzymes involved in cellular excitability. These TRPV1-independent effects are mediated by alterations of the biophysical properties of the lipid membrane and subsequent modulation of the functional properties of ion channels and by direct binding of capsaicin to the channels. The present study, for the first time, systematically categorizes this diverse range of non-TRPV1 targets and discusses cellular and molecular mechanisms mediating TRPV1-independent effects of capsaicin in excitable, as well as nonexcitable cells.
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Affiliation(s)
- Murat Oz
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Kuwait University, Safat, Kuwait
| | - Dietrich E Lorke
- Department of Anatomy and Cellular Biology, College of Medicine and Health Sciences, Khalifa University, Abu Dhabi, United Arab Emirates.,Center for Biotechnology, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
| | - Frank C Howarth
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates
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Isaev D, Yang KHS, Shabbir W, Howarth FC, Oz M. Capsaicin Inhibits Multiple Voltage-Gated Ion Channels in Rabbit Ventricular Cardiomyocytes in TRPV1-Independent Manner. Pharmaceuticals (Basel) 2022; 15:ph15101187. [PMID: 36297299 PMCID: PMC9611941 DOI: 10.3390/ph15101187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/19/2022] [Accepted: 09/20/2022] [Indexed: 11/17/2022] Open
Abstract
Capsaicin is a naturally occurring alkaloid derived from chili pepper which is responsible for its hot, pungent taste. It exerts multiple pharmacological actions, including pain-relieving, anti-cancer, anti-inflammatory, anti-obesity, and antioxidant effects. Previous studies have shown that capsaicin significantly affects the contractility and automaticity of the heart and alters cardiovascular functions. In this study, the effects of capsaicin were investigated on voltage-gated ion currents in rabbit ventricular myocytes. Capsaicin inhibited rapidly activated (IKr) and slowly activated (IKs) K+ currents and transient outward (Ito) K+ current with IC50 values of 3.4 µM,14.7 µM, and 9.6 µM, respectively. In addition, capsaicin, at higher concentrations, suppressed voltage-gated Na+ and Ca2+ currents and inward rectifier IK1 current with IC50 values of 42.7 µM, 34.9 µM, and 38.8 µM, respectively. Capsaicin inhibitions of INa, IL-Ca, IKr, IKs, Ito, and IK1 were not reversed in the presence of capsazepine (3 µM), a TRPV1 antagonist. The inhibitory effects of capsaicin on these currents developed gradually, reaching steady-state levels within 3 to 6 min, and the recoveries were usually incomplete during washout. In concentration-inhibition curves, apparent Hill coefficients higher than unity suggested multiple interaction sites of capsaicin on these channels. Collectively, these findings indicate that capsaicin affects cardiac electrophysiology by acting on a diverse range of ion channels and suggest that caution should be exercised when capsaicin is administered to carriers of cardiac channelopathies or to individuals with arrhythmia-prone conditions, such as ischemic heart diseases.
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Affiliation(s)
- Dmytro Isaev
- Department of Cellular Membranology, Bogomoletz Institute of Physiology, 01024 Kiev, Ukraine
| | - Keun-Hang Susan Yang
- Department of Biological Sciences, Schmid College of Science and Technology, Chapman University, One University Drive, Orange, CA 92866, USA
| | - Waheed Shabbir
- Department of Cellular Membranology, Bogomoletz Institute of Physiology, 01024 Kiev, Ukraine
| | - Frank Christopher Howarth
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Abu Dhabi 15551, United Arab Emirates
| | - Murat Oz
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Kuwait University, Safat 13110, Kuwait
- Correspondence: ; Tel.: +965-99758003
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Shan M, Jiang C, Qin L, Cheng G. A Review of Computational Methods in Predicting hERG Channel Blockers. ChemistrySelect 2022. [DOI: 10.1002/slct.202201221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mengyi Shan
- School of Pharmaceutical Sciences Zhejiang Chinese Medical University Hangzhou 310053 People's Republic of China
| | - Chen Jiang
- QuanMin RenZheng (HangZhou) Technology Co. Ltd. China
| | - Lu‐Ping Qin
- School of Pharmaceutical Sciences Zhejiang Chinese Medical University Hangzhou 310053 People's Republic of China
| | - Gang Cheng
- School of Pharmaceutical Sciences Zhejiang Chinese Medical University Hangzhou 310053 People's Republic of China
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Inhibition of the hERG potassium channel by phenanthrene: a polycyclic aromatic hydrocarbon pollutant. Cell Mol Life Sci 2021; 78:7899-7914. [PMID: 34727194 PMCID: PMC8629796 DOI: 10.1007/s00018-021-03967-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/25/2021] [Accepted: 10/01/2021] [Indexed: 11/07/2022]
Abstract
The lipophilic polycyclic aromatic hydrocarbon (PAH) phenanthrene is relatively abundant in polluted air and water and can access and accumulate in human tissue. Phenanthrene has been reported to interact with cardiac ion channels in several fish species. This study was undertaken to investigate the ability of phenanthrene to interact with hERG (human Ether-à-go-go-Related Gene) encoded Kv11.1 K+ channels, which play a central role in human ventricular repolarization. Pharmacological inhibition of hERG can be proarrhythmic. Whole-cell patch clamp recordings of hERG current (IhERG) were made from HEK293 cells expressing wild-type (WT) and mutant hERG channels. WT IhERG1a was inhibited by phenanthrene with an IC50 of 17.6 ± 1.7 µM, whilst IhERG1a/1b exhibited an IC50 of 1.8 ± 0.3 µM. WT IhERG block showed marked voltage and time dependence, indicative of dependence of inhibition on channel gating. The inhibitory effect of phenanthrene was markedly impaired by the attenuated inactivation N588K mutation. Remarkably, mutations of S6 domain aromatic amino acids (Y652, F656) in the canonical drug binding site did not impair the inhibitory action of phenanthrene; the Y652A mutation augmented IhERG block. In contrast, the F557L (S5) and M651A (S6) mutations impaired the ability of phenanthrene to inhibit IhERG, as did the S624A mutation below the selectivity filter region. Computational docking using a cryo-EM derived hERG structure supported the mutagenesis data. Thus, phenanthrene acts as an inhibitor of the hERG K+ channel by directly interacting with the channel, binding to a distinct site in the channel pore domain.
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Hamburger M. HPLC-based activity profiling for pharmacologically and toxicologically relevant natural products - principles and recent examples. PHARMACEUTICAL BIOLOGY 2019; 57:328-334. [PMID: 31057026 PMCID: PMC6507960 DOI: 10.1080/13880209.2019.1606261] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 04/02/2019] [Indexed: 05/30/2023]
Abstract
CONTEXT Discovery of pharmacologically active natural products as starting points for drug development remains important and, for reasons of consumer safety, the identification of toxicologically relevant compounds in herbal drugs. OBJECTIVE To explain, with the aid of relevant examples from our own research, how these goals can be achieved. METHODS An in-house technology platform comprising pre-formatted extract libraries in 96-well format, miniaturized tracking of activity in extracts via HPLC-activity profiling, structure elucidation with microprobe NMR, and in vitro and in vivo pharmacological methods were used. RESULTS Piperine was identified as a new scaffold for allosteric GABAA receptor modulators with in vivo activity that interacts at a benzodiazepine-independent binding site. Selectivity and potency were improved by iterative optimization towards synthetic piperine analogues. Dehydroevodiamine and hortiamine from the traditional Chinese herbal drug Evodiae fructus were identified as potent hERG channel blockers in vitro. The compounds induced torsades de pointes arrhythmia in animal models. CONCLUSIONS The allosteric binding site for piperine analogues remains to be characterized and cardiac risks of herbal drugs need to be further evaluated to ensure consumer safety.
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Affiliation(s)
- Matthias Hamburger
- Pharmaceutical Biology, Pharmacenter, University of Basel, Basel, Switzerland
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Bai F, Pi X, Li P, Zhou P, Yang H, Wang X, Li M, Gao Z, Jiang H. A Statistical Thermodynamic Model for Ligands Interacting With Ion Channels: Theoretical Model and Experimental Validation of the KCNQ2 Channel. Front Pharmacol 2018; 9:150. [PMID: 29593528 PMCID: PMC5855359 DOI: 10.3389/fphar.2018.00150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 02/13/2018] [Indexed: 12/01/2022] Open
Abstract
Ion channels are important therapeutic targets, and their pharmacology is becoming increasingly important. However, knowledge of the mechanism of interaction of the activators and ion channels is still limited due to the complexity of the mechanisms. A statistical thermodynamic model has been developed in this study to characterize the cooperative binding of activators to ion channels. By fitting experimental concentration-response data, the model gives eight parameters for revealing the mechanism of an activator potentiating an ion channel, i.e., the binding affinity (KA), the binding cooperative coefficients for two to four activator molecules interacting with one channel (γ, μ, and ν), and the channel conductance coefficients for four activator binding configurations of the channel (a, b, c, and d). Values for the model parameters and the mechanism underlying the interaction of ztz240, a proven KCNQ2 activator, with the wild-type channel have been obtained and revealed by fitting the concentration-response data of this activator potentiating the outward current amplitudes of KCNQ2. With these parameters, our model predicted an unexpected bi-sigmoid concentration-response curve of ztz240 activation of the WT-F137A mutant heteromeric channel that was in good agreement with the experimental data determined in parallel in this study, lending credence to the assumptions on which the model is based and to the model itself. Our model can provide a better fit to the measured data than the Hill equation and estimates the binding affinity, as well as the cooperative coefficients for the binding of activators and conductance coefficients for binding states, which validates its use in studying ligand-channel interaction mechanisms.
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Affiliation(s)
- Fang Bai
- Department of Engineering Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, and Faculty of Chemical, Environmental, and Biological Science and Technology, Dalian University of Technology, Dalian, China.,Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xiaoping Pi
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Ping Li
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Pingzheng Zhou
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Huaiyu Yang
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xicheng Wang
- Department of Engineering Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, and Faculty of Chemical, Environmental, and Biological Science and Technology, Dalian University of Technology, Dalian, China
| | - Min Li
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD, United States
| | - Zhaobing Gao
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hualiang Jiang
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
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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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Xing J, Zhang C, Jiang W, Hao J, Liu Z, Luo A, Zhang P, Fan X, Ma J. The Inhibitory Effects of Ketamine on Human Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels and Action Potential in Rabbit Sinoatrial Node. Pharmacology 2017; 99:226-235. [DOI: 10.1159/000452975] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 11/01/2016] [Indexed: 11/19/2022]
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Sube R, Ertel EA. Cardiomyocytes Derived from Human Induced Pluripotent Stem Cells: An In-Vitro Model to Predict Cardiac Effects of Drugs. ACTA ACUST UNITED AC 2017. [DOI: 10.4236/jbise.2017.1011040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Omari SA, Adams MJ, Geraghty DP. TRPV1 Channels in Immune Cells and Hematological Malignancies. ADVANCES IN PHARMACOLOGY 2017; 79:173-198. [DOI: 10.1016/bs.apha.2017.01.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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He FZ, McLeod HL, Zhang W. Current pharmacogenomic studies on hERG potassium channels. Trends Mol Med 2013; 19:227-38. [PMID: 23369369 DOI: 10.1016/j.molmed.2012.12.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 12/18/2012] [Accepted: 12/27/2012] [Indexed: 11/25/2022]
Abstract
Genetic polymorphisms in human ether-a-go-go-related gene (hERG) potassium channels are associated with many complex diseases and sensitivity to channel-related drugs. Genotypes may underlie different sensitivities to the same drug, and different drugs selectively repair the functional deficits caused by individual mutations. In fact, not all drugs that block hERG function have adverse effects as previously thought. This suggests that the severe adverse reactions observed clinically may only occur in subjects with a particular genotype, but to others may be safe. Similarly, a drug that is ineffective in one population may be both safe and effective in another. Therefore, detecting polymorphisms in KCNH2 encoding hERG1 is of great significance in guiding the prevention and treatment of related diseases, re-evaluating drug safety, and individualizing treatment. This article reviews current pharmacogenomic studies on hERG potassium channels to provide a reference for developing individualized treatments and evaluating their safety.
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Affiliation(s)
- Fa-Zhong He
- Pharmacogenetics Research Institute, Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha, Hunan 410078, PR China
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Raffa RB, Burmeister JJ, Yuvasheva E, Pergolizzi JV. QTc interval prolongation byd-propoxyphene: what about other analgesics? Expert Opin Pharmacother 2012; 13:1397-409. [DOI: 10.1517/14656566.2012.682150] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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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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Zhou J, Hu G. Effect of lead ion on the function of the human ether-à-go-go-related gene K+ channel. Biol Trace Elem Res 2011; 143:131-42. [PMID: 20890732 DOI: 10.1007/s12011-010-8856-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 09/15/2010] [Indexed: 11/24/2022]
Abstract
Lead (Pb) is a trace metal element in the human body. In order to understand the hazard mechanism of the elevated blood lead level on the human body, the effect of Pb(2+) on the human ether-à-go-go-related gene (hERG) K(+) channel in the HEK 293 cell was investigated for the first time using whole-cell patch clamp technique, molecular dynamics simulation, and quantum chemistry calculation methods. We found that Pb(2+) obviously inhibits the current of the hERG K(+) channel, and delays the "activation" and "deactivation" of the hERG K(+) channel, indicating that Pb(2+) evidently decreases the function of the K(+) channel in the cell. The effect is increased with increasing the concentration of Pb(2+). When the concentration of Pb(2+) is 400 μg L(-1), the function of the K(+) channel is entirely lost. The results from the molecular dynamics simulation and quantum chemistry calculation indicated that Pb(2+) can coordinate with the oxygen/sulfur atoms in the K(+) channel protein, leading to the decrease in the function of the K(+) channel. According to the experimental results, we suggested that once the K(+) channel in the human body was irreversibly inactivated by Pb(2+), it would affect the treatment and prognosis of Pb(2+) intoxication.
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Affiliation(s)
- Jiemin Zhou
- The First School of Clinical Medicine, Nanjing Medical University, Nanjing 210097, People's Republic of China
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Choi S, Sun JM, Shahi PK, Zuo DC, Kim HI, Jun JY. Capsaicin inhibits the spontaneous pacemaker activity in interstitial cells of cajal from the small intestine of mouse. J Neurogastroenterol Motil 2010; 16:265-73. [PMID: 20680165 PMCID: PMC2912119 DOI: 10.5056/jnm.2010.16.3.265] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 04/22/2010] [Accepted: 04/28/2010] [Indexed: 11/25/2022] Open
Abstract
Background/Aims Capsaicin (8-methyl-N-vanillyl-6-ninenamide), a compound found in hot peppers, has been reported to have different physiological actions on different cell types. Not much work has been done about the effect of capsaicin on the function of interstitial cells of Cajal (ICC). In the present study, we examined the action of external application of capsaicin on pacemaker activity in the cultured ICC from the small intestine of mouse. Methods We investigated the effect of capsaicin on pacemaker currents in cultured ICC from the small intestine of mouse using a whole cell patch-clamp technique and Ca2+-imaging analysis. Results When capsaicin was applied externally to the pacemaker generating ICC, it completely inhibited the pacemaker potential under current-clamp mode (I = 0) and the pacemaker current under voltage-clamp mode at a -70 mV of holding potentials. The effect of capsaicin on pacemaker activity in ICC was shown dose dependently. The effect of capsaicin was not through the transient receptor potential of the vanilloid type 1 (TRPV1) channel as capsazepine did not block the effect of capsaicin. L-NAME, an inhibitor of nitric oxide synthase, also did not block the capsaicin-induced effects. When the action of capsaicin was examined in the intracellular calcium oscillation, it completely abolished the calcium oscillation. Conclusions These results prove that the capsaicin has the inhibitory effects on the ICC which is carried out neither through TRPV channel nor the nitric oxide production. Intracellular Ca2+ was also an important target for actions of capsaicin on ICC.
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Affiliation(s)
- Seok Choi
- Department of Physiology, College of Medicine, Chosun University, Gwangju, Korea
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