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Park M, Mun SY, Zhuang W, Jeong J, Kim HR, Park H, Han ET, Han JH, Chun W, Li H, Park WS. The antidiabetic drug ipragliflozin induces vasorelaxation of rabbit femoral artery by activating a Kv channel, the SERCA pump, and the PKA signaling pathway. Eur J Pharmacol 2024; 972:176589. [PMID: 38631503 DOI: 10.1016/j.ejphar.2024.176589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 03/29/2024] [Accepted: 04/11/2024] [Indexed: 04/19/2024]
Abstract
We explored the vasorelaxant effects of ipragliflozin, a sodium-glucose cotransporter-2 inhibitor, on rabbit femoral arterial rings. Ipragliflozin relaxed phenylephrine-induced pre-contracted rings in a dose-dependent manner. Pre-treatment with the ATP-sensitive K+ channel inhibitor glibenclamide (10 μM), the inwardly rectifying K+ channel inhibitor Ba2+ (50 μM), or the Ca2+-sensitive K+ channel inhibitor paxilline (10 μM) did not influence the vasorelaxant effect. However, the voltage-dependent K+ (Kv) channel inhibitor 4-aminopyridine (3 mM) reduced the vasorelaxant effect. Specifically, the vasorelaxant response to ipragliflozin was significantly attenuated by pretreatment with the Kv7.X channel inhibitors linopirdine (10 μM) and XE991 (10 μM), the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) pump inhibitors thapsigargin (1 μM) and cyclopiazonic acid (10 μM), and the cAMP/protein kinase A (PKA)-associated signaling pathway inhibitors SQ22536 (50 μM) and KT5720 (1 μM). Neither the cGMP/protein kinase G (PKG)-associated signaling pathway nor the endothelium was involved in ipragliflozin-induced vasorelaxation. We conclude that ipragliflozin induced vasorelaxation of rabbit femoral arteries by activating Kv channels (principally the Kv7.X channel), the SERCA pump, and the cAMP/PKA-associated signaling pathway independent of other K+ (ATP-sensitive K+, inwardly rectifying K+, and Ca2+-sensitive K+) channels, cGMP/PKG-associated signaling, and the endothelium.
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Affiliation(s)
- Minju Park
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Seo-Yeong Mun
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Wenwen Zhuang
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Junsu Jeong
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Hye Ryung Kim
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Hongzoo Park
- Institute of Medical Sciences, Department of Urology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Eun-Taek Han
- Department of Medical Environmental Biology and Tropical Medicine, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Jin-Hee Han
- Department of Medical Environmental Biology and Tropical Medicine, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Wanjoo Chun
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea
| | - Hongliang Li
- Institute of Translational Medicine, Medical College, Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment for Senile Diseases, Yangzhou University, Yangzhou, 225001, Jiangsu, China.
| | - Won Sun Park
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, South Korea.
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Chang PY, Chang SF, Chang TY, Su HM, Lu SC. Synergistic effects of electronegative-LDL- and palmitic-acid-triggered IL-1β production in macrophages via LOX-1- and voltage-gated-potassium-channel-dependent pathways. J Nutr Biochem 2021; 97:108767. [PMID: 34052311 DOI: 10.1016/j.jnutbio.2021.108767] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 03/16/2021] [Accepted: 04/16/2021] [Indexed: 12/22/2022]
Abstract
Electronegative LDL (LDL(-)) and free fatty acids (FFAs) are circulating risk factors for cardiovascular diseases (CVDs) and have been associated with inflammation. Interleukin-1 beta (IL-1β) represents a key cytokine in the development of CVD; however, the initial trigger of IL-1β in CVD remains to be explored. In this study, we investigated the combined effects of LDL(-) from the plasma of ST-segment elevation myocardial infarction (STEMI) patients or diet-induced hypercholesterolemic rabbits and bovine serum albumin bound palmitic acid (PA-BSA) on IL-1β production in macrophages. Macrophages derived from THP-1 cells or human peripheral blood mononuclear cells were independently treated with LDL(-), PA-BSA or cotreated with LDL(-) and PA-BSA. The results showed that nLDL and/or PA-BSA had no effect on IL-1β, and LDL(-) slightly increased IL-1β; however, cotreatment with LDL(-) and PA-BSA resulted in abundant secretion of IL-1β in macrophages. Rabbit LDL(-) induced the elevation of cellular pro-IL-1β and p-Iκ-Bα, but PA-BSA had no effect on pro-IL-1β or p-Iκ-Bα. In potassium-free buffer, LDL(-)-induced IL-1β reached a level similar to that induced by cotreatment with LDL(-) and PA-BSA. Moreover, LDL(-) and PA-BSA-induced IL-1β was inhibited in lectin-type oxidized LDL receptor-1 (LOX-1) knockdown cells and by blockers of voltage-gated potassium (Kv) channels. LDL(-) from diet-induced hypercholesterolemic rabbit had a similar effect as STEMI LDL(-) on IL-1β in macrophages. These results show that PA-BSA cooperates with LDL(-) to trigger IL-1β production in macrophages via a mechanism involving the LOX-1 and Kv channel pathways, which may play crucial roles in the regulation of inflammation in CVD.
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Affiliation(s)
- Po-Yuan Chang
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Shwu-Fen Chang
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Ting-Yu Chang
- Department of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Hui-Min Su
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Shao-Chun Lu
- Department of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan.
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An JR, Seo MS, Jung HS, Heo R, Kang M, Han ET, Park H, Jung WK, Choi IW, Park WS. Inhibition by Imipramine of the Voltage-Dependent K+ Channel in Rabbit Coronary Arterial Smooth Muscle Cells. Toxicol Sci 2020; 178:302-310. [PMID: 33010168 DOI: 10.1093/toxsci/kfaa149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Imipramine, a tricyclic antidepressant, is used in the treatment of depressive disorders. However, the effect of imipramine on vascular ion channels is unclear. Therefore, using a patch-clamp technique we examined the effect of imipramine on voltage-dependent K+ (Kv) channels in freshly isolated rabbit coronary arterial smooth muscle cells. Kv channels were inhibited by imipramine in a concentration-dependent manner, with an IC50 value of 5.55 ± 1.24 µM and a Hill coefficient of 0.73 ± 0.1. Application of imipramine shifted the steady-state activation curve in the positive direction, indicating that imipramine-induced inhibition of Kv channels was mediated by influencing the voltage sensors of the channels. The recovery time constants from Kv-channel inactivation were increased in the presence of imipramine. Furthermore, the application of train pulses (of 1 or 2 Hz) progressively augmented the imipramine-induced inhibition of Kv channels, suggesting that the inhibitory effect of imipramine is use (state) dependent. The magnitude of Kv current inhibition by imipramine was similar during the first, second, and third depolarizing pulses. These results indicate that imipramine-induced inhibition of Kv channels mainly occurs in the closed state. The imipramine-mediated inhibition of Kv channels was associated with the Kv1.5 channel, not the Kv2.1 or Kv7 channel. Inhibition of Kv channels by imipramine caused vasoconstriction. From these results, we conclude that imipramine inhibits vascular Kv channels in a concentration- and use (closed-state)-dependent manner by changing their gating properties regardless of its own function.
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Affiliation(s)
| | | | | | | | | | - Eun-Taek Han
- Department of Medical Environmental Biology and Tropical Medicine
| | - Hongzoo Park
- Department of Urology, Kangwon National University School of Medicine, Chuncheon 24341, South Korea
| | - Won-Kyo Jung
- Department of Biomedical Engineering, and Center for Marine-Integrated Biomedical Technology (BK21 Plus), Pukyong National University, Busan 48513, South Korea
| | - Il-Whan Choi
- Department of Microbiology, College of Medicine, Inje University, Busan 48516, South Korea
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Fontaine JT, Rosehart AC, Joutel A, Dabertrand F. HB-EGF depolarizes hippocampal arterioles to restore myogenic tone in a genetic model of small vessel disease. Mech Ageing Dev 2020; 192:111389. [PMID: 33127441 PMCID: PMC7683376 DOI: 10.1016/j.mad.2020.111389] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 10/16/2020] [Accepted: 10/22/2020] [Indexed: 12/26/2022]
Abstract
Vascular cognitive impairment, the second most common cause of dementia, profoundly affects hippocampal-dependent functions. However, while the growing literature covers complex neuronal interactions, little is known about the sustaining hippocampal microcirculation. Here we examined vasoconstriction to physiological pressures of hippocampal arterioles, a fundamental feature of small arteries, in a genetic mouse model of CADASIL, an archetypal cerebral small vessel disease. Using diameter and membrane potential recordings on isolated arterioles, we observed both blunted pressure-induced vasoconstriction and smooth muscle cell depolarization in CADASIL. This impairment was abolished in the presence of voltage-gated potassium (KV1) channel blocker 4-aminopyridine, or by application of heparin-binding EGF-like growth factor (HB-EGF), which promotes KV1 channel down-regulations. Interestingly, we observed that HB-EGF induced a depolarization of the myocyte plasma membrane within the arteriolar wall in CADASIL, but not wild-type, arterioles. Collectively, our results indicate that hippocampal arterioles in CADASIL mice display a blunted contractile response to luminal pressure, similar to the defect we previously reported in cortical arterioles and pial arteries, that is rescued by HB-EGF. Hippocampal vascular dysfunction in CADASIL could then contribute to the decreased vascular reserve associated with decreased cognitive performance, and its correction may provide a therapeutic option for treating vascular cognitive impairment.
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Affiliation(s)
- Jackson T Fontaine
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Amanda C Rosehart
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Anne Joutel
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA; Institute of Psychiatry and Neurosciences of Paris, INSERM UMR1266, University of Paris, GHU Paris Psychiatrie et Neurosciences, France
| | - Fabrice Dabertrand
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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Shih CH, Chen CM, Ko WC. Butylidenephthalide facilitates contractions via nonspecific binding to receptors in isolated guinea-pig vas deferens. Pharm Biol 2019; 57:380-384. [PMID: 31155999 PMCID: PMC6567070 DOI: 10.1080/13880209.2019.1619781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/04/2019] [Accepted: 05/10/2019] [Indexed: 06/09/2023]
Abstract
Context: Butylidenephthalide (Bdph) has been reported to inhibit rat uterine contractions, but significantly potentiate the noradrenaline (NA)-induced contractions in guinea-pig vas deferens (GPVDs). Objective: The present study elucidates the binding specificity of Bdph in GPVD to potentiate contractions. Materials and methods: Electrical field stimulation (EFS, supramaximal voltage, 1 ms and 1 Hz) or exogenous NA (50 μM) was applied to the GPVD in Krebs or 1/10 Mg-Tyrode's solution, respectively. After the clonidine (10 nM)-induced twitch inhibition or the exogenous NA-induced contractions reached a constant, Bdph (50 µM) was added 2 min prior to the subsequent addition of NA (50 µM). Three experiments were performed. In the presence of Bdph (100 μM), the release of NA in the medium and remaining NA content in the tissues were determined after EFS-stimulation. Results: Bdph (100 μM) significantly antagonized the clonidine (10 nM)-induced twitch inhibition from 22.5 ± 2.1 to -11.4 ± 1.6% (n = 6) and dibutyryl-cAMP (300 μM) from 25.7 ± 3.2 to 7.9 ± 4.0% (n = 8). Bdph (100 μM) significantly increased the electrically stimulated release of NA from 393.0 ± 109.5 to 1000.0 ± 219.1 ng/g (n = 6). Bdph (50 μM) potentiated the exogenous NA (50 μM)-induced contractions from 3.0 ± 0.06 to 3.9 ± 0.06 g (n = 3), but after washout of Bdph, the response to NA gradually curtailed. Discussion and conclusions: Bdph action may be through the nonspecific binding of the butylidene group to prejunctional α2- and postjunctional α1-adrenoceptors to reversibly block K+ channels, and irreversibly block VDCCs on the smooth muscle cell membrane, respectively.
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Affiliation(s)
- Chung-Hung Shih
- Department of Internal Medicine, Division of Thoracic Medicine, Taipei Medical University Hospital, Taipei, Taiwan
- School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chi-Ming Chen
- Department of Medicinal Chemistry, School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, Taiwan
| | - Wun-Chang Ko
- Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
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Ran D, Luo Y, Gan Z, Liu J, Yang J. Neural mechanisms underlying the deficit of learning and memory by exposure to Di(2-ethylhexyl) phthalate in rats. Ecotoxicol Environ Saf 2019; 174:58-65. [PMID: 30822668 DOI: 10.1016/j.ecoenv.2019.02.043] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 01/20/2019] [Accepted: 02/13/2019] [Indexed: 06/09/2023]
Abstract
Di(2-ethylhexyl) phthalate (DEHP), as one of the most broadly representative phthalic acid esters, is used as a plasticizer in Polyvinyl chloride production. The exact neurotoxicologically effects of DEHP to human have not been adequately researched. In order to investigate the effects and mechanisms of DEHP exposure on neural circuit, the spatial learning and memory of Sprague Dawley (SD) rats was measured, and the cellular mechanisms underlying synaptic plasticity, cellular excitability and ion channels were detected. Our data showed that the spatial learning and memory was changed by DEHP (100 and 300 mg) treatment. Meanwhile, the frequency of mini Excitatory Postsynaptic Current (mEPSC) from CA3 pyramidal cells were significantly decreased by DEHP exposure (0.1 and 0.3 M); the firing threshold, membrane potential threshold, number, amplitude and latency of Action Potentials (Aps) of CA1 pyramidal cells were altered with the application of DEHP (0.1 and 0.3 M); furthermore, DEHP, both in 0.1 and 0.3 M could inhibit the voltage-gated potassium channel of CA1 pyramidal cells. Our results indicated that DEHP could impair the spatial learning and memory, and this impairment might due to the DEHP-induced suppression of the neuronal excitability and synaptic plasticity by inhibiting the voltage-gated potassium channel, supporting the hypothesis that DEHP could cause the disruption of neural function.
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Affiliation(s)
- Dongzhi Ran
- Department of Pharmacology, Chongqing Medical University, Chongqing 400016, PR China; The Key Laboratory of Biochemistry and Molecular Pharmacology, PR China
| | - Ying Luo
- Department of Pharmacology, Chongqing Medical University, Chongqing 400016, PR China; The Key Laboratory of Biochemistry and Molecular Pharmacology, PR China
| | - Zongjie Gan
- Department of Pharmacology, Chongqing Medical University, Chongqing 400016, PR China
| | - Jia Liu
- The Third Affiliated Hospital of Chongqing Medical University, Chongqing 401120, PR China
| | - Junqing Yang
- Department of Pharmacology, Chongqing Medical University, Chongqing 400016, PR China; The Key Laboratory of Biochemistry and Molecular Pharmacology, PR China.
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Li H, Kang H, An JR, Seo MS, Jung WK, Lee DS, Choi G, Yim MJ, Lee JM, Bae YM, Son YK, Choi IW, Park WS. Inhibitory Effect of Tricyclic Antidepressant Doxepin on Voltage-Dependent K + Channels in Rabbit Coronary Arterial Smooth Muscle Cells. Cardiovasc Toxicol 2019; 19:465-473. [PMID: 31030342 DOI: 10.1007/s12012-019-09519-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Doxepin, tricyclic antidepressant, is widely used for the treatment of depressive disorders. Our present study determined the inhibitory effect of doxepin on voltage-dependent K+ (Kv) channels in freshly isolated rabbit coronary arterial smooth muscle cells using a whole-cell patch clamp technique. Vascular Kv currents were inhibited by doxepin in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC50) value of 6.52 ± 1.35 μM and a Hill coefficient of 0.72 ± 0.03. Doxepin did not change the steady-state activation curve or inactivation curve, suggesting that doxepin does not alter the gating properties of Kv channels. Application of train pulses (1 or 2 Hz) slightly reduced the amplitude of Kv currents. However, the inhibition of Kv channels by train pulses were not changed in the presence of doxepin. Pretreatment with Kv1.5 inhibitor, DPO-1, effectively reduced the doxepin-induced inhibition of the Kv current. However, pretreatment with Kv2.1 inhibitor (guangxitoxin) or Kv7 inhibitor (linopirdine) did not change the inhibitory effect of doxepin on Kv currents. Inhibition of Kv channels by doxepin caused vasoconstriction and membrane depolarization. Therefore, our present study suggests that doxepin inhibits Kv channels in a concentration-dependent, but not use-, and state-dependent manners, irrespective of its own function.
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Affiliation(s)
- Hongliang Li
- Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 24341, South Korea
| | - Hojung Kang
- Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 24341, South Korea
| | - Jin Ryeol An
- Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 24341, South Korea
| | - Mi Seon Seo
- Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 24341, South Korea
| | - Won-Kyo Jung
- Department of Biomedical Engineering, and Center for Marine-Integrated Biomedical Technology (BK21 Plus), Pukyong National University, Busan, 48513, South Korea
| | - Dae-Sung Lee
- Department of Applied Research, National Marine Biodiversity Institute of Korea, Seocheon, 33662, South Korea
| | - Grace Choi
- Department of Applied Research, National Marine Biodiversity Institute of Korea, Seocheon, 33662, South Korea
| | - Mi-Jin Yim
- Department of Applied Research, National Marine Biodiversity Institute of Korea, Seocheon, 33662, South Korea
| | - Jeong Min Lee
- Department of Applied Research, National Marine Biodiversity Institute of Korea, Seocheon, 33662, South Korea
| | - Young Min Bae
- Department of Physiology, Konkuk University School of Medicine, Chungju, 27478, South Korea
| | - Youn Kyoung Son
- Biological and Genetic Resources Assessment Division, National Institute of Biological Resources, Incheon, 22689, South Korea
| | - Il-Whan Choi
- Department of Microbiology, College of Medicine, Inje University, Busan, 48516, South Korea
| | - Won Sun Park
- Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 24341, South Korea.
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Banijamali SE, Amininasab M, Zaeifi D. Structural characterization of PPTI, a kunitz-type protein from the venom of Pseudocerastes persicus. PLoS One 2019; 14:e0214657. [PMID: 30973886 PMCID: PMC6459475 DOI: 10.1371/journal.pone.0214657] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 03/19/2019] [Indexed: 01/22/2023] Open
Abstract
The main purpose of this report is to investigate the structural property and new potential function of PPTI (Pseudocerastes Persicus Trypsin Inhibitor), a kunitz-type protein with inhibitory effect against trypsin proteolytic activity. Besides kunitz-type serine protease inhibitors, PPTI shows clear-cut similarities with dendrotoxins (DTXs), the other kunitz-type protein subfamily. The most important reason is the presence of functionally important residues of DTXs at correspondingly the same positions in PPTI. As such, we proposed the new ability of PPTI for inhibiting voltage-gated potassium channels and consequently its dual functionality. At first, we determined the solution structure of PPTI via Nuclear Magnetic Resonance (NMR) spectroscopy. Then by homology modeling, we constructed the model structure of trypsin-PPTI complex to confirm the same interaction pattern as trypsin-BPTI at complex interface. Finally, by Brownian dynamics (BD) simulations of PPTI NMR derived ensemble structure as ligand against homology model of human Kv1.1 potassium channel as receptor, we evaluated the potential DTX-like activity of PPTI. The results of our study support the proposed dual functionality of PPTI.
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Affiliation(s)
- Seyede Elnaz Banijamali
- Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Mehriar Amininasab
- Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran, Iran
- * E-mail:
| | - Davood Zaeifi
- Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran, Iran
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Abstract
GABAergic inhibition plays a critical role in the regulation of neuronal activity. In the neocortex, inhibitory interneurons that target the dendrites of pyramidal cells influence both electrical and biochemical postsynaptic signaling. Voltage-gated ion channels strongly shape dendritic excitability and the integration of excitatory inputs, but their contribution to GABAergic signaling is less well understood. By combining 2-photon calcium imaging and focal GABA uncaging, we show that voltage-gated potassium channels normally suppress the GABAergic inhibition of calcium signals evoked by back-propagating action potentials in dendritic spines and shafts of cortical pyramidal neurons. Moreover, the voltage-dependent inactivation of these channels leads to enhancement of dendritic calcium inhibition following somatic spiking. Computational modeling reveals that the enhancement of calcium inhibition involves an increase in action potential depolarization coupled with the nonlinear relationship between membrane voltage and calcium channel activation. Overall, our findings highlight the interaction between intrinsic and synaptic properties and reveal a novel mechanism for the activity-dependent regulation of GABAergic inhibition.
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Affiliation(s)
- Jeremy T. Chang
- Department of NeuroscienceProgram in Cellular Neuroscience, Neurodegeneration and RepairKavli InstituteYale School of MedicineNew HavenConnecticut
| | - Michael J. Higley
- Department of NeuroscienceProgram in Cellular Neuroscience, Neurodegeneration and RepairKavli InstituteYale School of MedicineNew HavenConnecticut
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Moreels L, Peigneur S, Yamaguchi Y, Vriens K, Waelkens E, Zhu S, Thevissen K, Cammue BPA, Sato K, Tytgat J. Expanding the pharmacological profile of κ-hefutoxin 1 and analogues: A focus on the inhibitory effect on the oncogenic channel K v10.1. Peptides 2017; 98:43-50. [PMID: 27578329 DOI: 10.1016/j.peptides.2016.08.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/21/2016] [Accepted: 08/23/2016] [Indexed: 10/21/2022]
Abstract
Peptide toxins, such as scorpion peptides, are interesting lead compounds in the search for novel drugs. In this paper, the focus is on the scorpion peptide κ-hefutoxin 1. This peptide displays a cysteine-stabilized helix-loop-helix fold (CSα/α) and is known to be a weak Kv1.x inhibitor. Due to the low affinity of κ-hefutoxin 1 for these channels, it is assumed that the main target(s) of κ-hefutoxin 1 remain(s) unknown. In order to identify novel targets, electrophysiological measurements and antifungal assays were performed. The effect of κ-hefutoxin 1 was previously evaluated on a panel of 11 different voltage-gated potassium channels. Here, we extended this target screening with the oncogenic potassium channel Kv10.1. κ-Hefutoxin 1 was able to inhibit this channel in a dose-dependent manner (IC50∼26μM). Although the affinity is rather low, this is the first peptide toxin ever described to be a Kv10.1 inhibitor. The structure-activity relationship of κ-hefutoxin 1 on Kv10.1 was investigated by testing eight κ-hefutoxin 1 variants using the two-electrode voltage clamp technique. Several important amino acid residues were identified; the functional dyad residues (Tyr5 and Lys19), N-terminal residues (Gly1 and His2) and the amidated C-terminal residue (Cys22). Since the CSα/α fold is also found in a class of antifungal plant peptides, the α-hairpinines, we investigated the antifungal activity of κ-hefutoxin 1. κ-Hefutoxin 1 showed low activity against the plant pathogen Fusarium culmorum and no activity against three other yeast and fungal species, even at high concentrations (∼100μM).
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Affiliation(s)
- Lien Moreels
- Toxicology and Pharmacology, KU Leuven, Campus Gasthuisberg O&N2, Herestraat 49, PO Box 922, 3000 Leuven, Belgium.
| | - Steve Peigneur
- Toxicology and Pharmacology, KU Leuven, Campus Gasthuisberg O&N2, Herestraat 49, PO Box 922, 3000 Leuven, Belgium.
| | - Yoko Yamaguchi
- Department of Environmental Science, Fukuoka Women's University, Fukuoka 813-8529, Japan.
| | - Kim Vriens
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, PO Box 2460, 3001 Leuven, Belgium.
| | - Etienne Waelkens
- Laboratory of Protein Phosphorylation and Proteomics, KU Leuven, Campus Gasthuisberg, O&N1, Herestraat 49, PO Box 901, 3000 Leuven, Belgium.
| | - Shunyi Zhu
- Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
| | - Karin Thevissen
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, PO Box 2460, 3001 Leuven, Belgium.
| | - Bruno P A Cammue
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, PO Box 2460, 3001 Leuven, Belgium; VIB Department of Plant Systems Biology, Technologiepark 927, 9052 Ghent, Belgium.
| | - Kazuki Sato
- Department of Environmental Science, Fukuoka Women's University, Fukuoka 813-8529, Japan.
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, Campus Gasthuisberg O&N2, Herestraat 49, PO Box 922, 3000 Leuven, Belgium.
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Moreels L, Peigneur S, Galan DT, De Pauw E, Béress L, Waelkens E, Pardo LA, Quinton L, Tytgat J. APETx4, a Novel Sea Anemone Toxin and a Modulator of the Cancer-Relevant Potassium Channel K V10.1. Mar Drugs 2017; 15:md15090287. [PMID: 28902151 PMCID: PMC5618426 DOI: 10.3390/md15090287] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/05/2017] [Accepted: 09/07/2017] [Indexed: 12/31/2022] Open
Abstract
The human ether-à-go-go channel (hEag1 or KV10.1) is a cancer-relevant voltage-gated potassium channel that is overexpressed in a majority of human tumors. Peptides that are able to selectively inhibit this channel can be lead compounds in the search for new anticancer drugs. Here, we report the activity-guided purification and electrophysiological characterization of a novel KV10.1 inhibitor from the sea anemone Anthopleura elegantissima. Purified sea anemone fractions were screened for inhibitory activity on KV10.1 by measuring whole-cell currents as expressed in Xenopus laevis oocytes using the two-microelectrode voltage clamp technique. Fractions that showed activity on Kv10.1 were further purified by RP-HPLC. The amino acid sequence of the peptide was determined by a combination of MALDI- LIFT-TOF/TOF MS/MS and CID-ESI-FT-ICR MS/MS and showed a high similarity with APETx1 and APETx3 and was therefore named APETx4. Subsequently, the peptide was electrophysiologically characterized on KV10.1. The selectivity of the toxin was investigated on an array of voltage-gated ion channels, including the cardiac human ether-à-go-go-related gene potassium channel (hERG or Kv11.1). The toxin inhibits KV10.1 with an IC50 value of 1.1 μM. In the presence of a similar toxin concentration, a shift of the activation curve towards more positive potentials was observed. Similar to the effect of the gating modifier toxin APETx1 on hERG, the inhibition of Kv10.1 by the isolated toxin is reduced at more positive voltages and the peptide seems to keep the channel in a closed state. Although the peptide also induces inhibitory effects on other KV and NaV channels, it exhibits no significant effect on hERG. Moreover, APETx4 induces a concentration-dependent cytotoxic and proapoptotic effect in various cancerous and noncancerous cell lines. This newly identified KV10.1 inhibitor can be used as a tool to further characterize the oncogenic channel KV10.1 or as a scaffold for the design and synthesis of more potent and safer anticancer drugs.
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Affiliation(s)
- Lien Moreels
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
| | - Steve Peigneur
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
| | - Diogo T Galan
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
| | - Edwin De Pauw
- Laboratory of Mass Spectrometry-MolSys, University of Liege, Liege 4000, Belgium.
| | - Lászlo Béress
- Immunology and Rheumatology, Section of Peptide Chemistry, Hannover Medical School (MHH), Hannover 30625, Germany.
| | - Etienne Waelkens
- Laboratory of Protein Phosphorylation and Proteomics, KU Leuven, Leuven 3000, Belgium.
| | - Luis A Pardo
- Oncophysiology Group, Max Planck Institute for Experimental Medicine; Göttingen 37075, Germany.
| | - Loïc Quinton
- Laboratory of Mass Spectrometry-MolSys, University of Liege, Liege 4000, Belgium.
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
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12
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Abstract
Inflammatory lesions of periodontal disease contain all the cellular components, including abundant activated/memory T- and B-cells, necessary to control immunological interactive networks and to accelerate bone resorption by RANKL-dependent and -independent mechanisms. Blockade of RANKL function has been shown to ameliorate periodontal bone resorption and other osteopenic disorders without affecting inflammation. Development of therapies aimed at decreasing the expression of RANKL and pro-inflammatory cytokines by T-cells constitutes a promising strategy to ameliorate not only bone resorption, but also inflammation. Several reports have demonstrated that the potassium channels Kv1.3 and IKCa1, through the use of selective blockers, play important roles in T-cell-mediated events, including T-cell proliferation and the production of pro-inflammatory cytokines. More recently, a potassium channel-blocker for Kv1.3 has been shown to down-regulate bone resorption by decreasing the ratio of RANKL-to-OPG expression by memory-activated T-cells. In this article, we first summarize the mechanisms by which chronically activated/memory T-cells, in concert with B-cells and macrophages, trigger inflammatory bone resorption. Then, we describe the main structural and functional characteristics of potassium channels Kv1.3 and IKCa1 in some of the cells implicated in periodontal disease progression. Finally, this review elucidates some recent advances in the use of potassium channel-blockers of Kv1.3 and IKCa1 to ameliorate the clinical signs or side-effects of several immunological disorders and to decrease inflammatory bone resorption in periodontal disease. ABBREVIATIONS: AICD, activation-induced cell death; APC, antigen-presenting cells; B(K), large conductance; CRAC, calcium release-activated calcium channels; DC, dendritic cell; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IFN-γ, interferon-γ; IP3, inositol (1,4,5)-triphosphate; (K)ir, inward rectifier; JNK, c-Jun N-terminal kinase; I(K), intermediate conductance; LPS, lipopolysaccharide; L, ligand; MCSF, macrophage colony-stimulating factor; MHC, major histocompatibility complex; NFAT, nuclear factor of activated T-cells; RANK, receptor activator of nuclear factor-κB; TCM, central memory T-cells; TEM, effector memory T-cells; TNF, tumor necrosis factor; TRAIL, TNF-related apoptosis-inducing ligand; OPG, osteoprotegerin; Omp29, 29-kDa outer membrane protein; PKC, protein kinase C; PLC, phospholipase C; RT-PCR, reverse-transcriptase polymerase chain-reaction; S(K), small conductance; TCR, T-cell receptor; and (K)v, voltage-gated.
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Affiliation(s)
- P Valverde
- Tufts University School of Dental Medicine, One Kneeland Street, Boston, MA 02111, USA.
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13
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Arsyad A, Dobson GP. Lidocaine relaxation in isolated rat aortic rings is enhanced by endothelial removal: possible role of K v, K ATP channels and A 2a receptor crosstalk. BMC Anesthesiol 2016; 16:121. [PMID: 27914476 PMCID: PMC5135802 DOI: 10.1186/s12871-016-0286-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 11/24/2016] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Lidocaine is an approved local anesthetic and Class 1B antiarrhythmic with a number of ancillary properties. Our aim was to investigate lidocaine's vasoreactivity properties in intact versus denuded rat thoracic aortic rings, and the effect of inhibitors of nitric oxide (NO), prostenoids, voltage-dependent Kv and KATP channels, membrane Na+/K+ pump, and A2a and A2b receptors. METHODS Aortic rings were harvested from adult male Sprague Dawley rats and equilibrated in an organ bath containing oxygenated, modified Krebs-Henseleit solution, pH 7.4, 37 °C. The rings were pre-contracted sub-maximally with 0.3 μM norepinephrine (NE), and the effect of increasing lidocaine concentrations was examined. Rings were tested for viability after each experiment with maximally dilating 100 μM papaverine. The drugs 4-aminopyridine (4-AP), glibenclamide, 5-hydroxydecanoate, ouabain, 8-(3-chlorostyryl) caffeine and PSB-0788 were examined. RESULTS All drugs tested had no significant effect on basal tension. Lidocaine relaxation in intact rings was biphasic between 1 and 10 μM (Phase 1) and 10 and 1000 μM (Phase 2). Mechanical removal of the endothelium resulted in further relaxation, and at lower concentrations ring sensitivity (% relaxation per μM lidocaine) significantly increased 3.5 times compared to intact rings. The relaxing factor(s) responsible for enhancing ring relaxation did not appear to be NO- or prostacyclin-dependent, as L-NAME and indomethacin had little or no effect on intact ring relaxation. In denuded rings, lidocaine relaxation was completely abolished by Kv channel inhibition and significantly reduced by antagonists of the MitoKATP channel, and to a lesser extent the SarcKATP channel. Curiously, A2a subtype receptor antagonism significantly inhibited lidocaine relaxation above 100 μM, but not the A2b receptor. CONCLUSIONS We show that lidocaine relaxation in rat thoracic aorta was biphasic and significantly enhanced by endothelial removal, which did not appear to be NO or prostacyclin dependent. The unknown factor(s) responsible for enhanced relaxation was significantly reduced by Kv inhibition, 5-HD inhibition, and A2a subtype inhibition indicating a potential role for crosstalk in lidocaine's vasoreactivity.
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Affiliation(s)
- Aryadi Arsyad
- Heart, Trauma and Sepsis Research Laboratory, Australian Institute of Tropical Health and Medicine, College of Medicine and Dentistry, James Cook University, 1 James Cook Drive, 4811 Queensland, Australia
- Physiology Department, Medical Faculty, Hasanuddin University, Jl. Perintis Kemerdekaan, Km. 10, 90213 Tamalanrea, Makassar Indonesia
| | - Geoffrey P. Dobson
- Heart, Trauma and Sepsis Research Laboratory, Australian Institute of Tropical Health and Medicine, College of Medicine and Dentistry, James Cook University, 1 James Cook Drive, 4811 Queensland, Australia
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14
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Dorn A, Hermann F, Ebneth A, Bothmann H, Trube G, Christensen K, Apfel C. Evaluation of a High-Throughput Fluorescence Assay Method for hERG Potassium Channel Inhibition. ACTA ACUST UNITED AC 2016; 10:339-47. [PMID: 15964935 DOI: 10.1177/1087057104272045] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The number of projects in drug development that fail in late phases because of cardiac side effects such as QT prolongation can impede drug discovery and development of projects. The molecular target responsible for QT prolongation by a wide range of pharmaceutical agents is the myocardial hERG potassium channel. It is therefore desirable to screen for compound interactions with the hERG channel at an early stage of drug development. Here, the authors report a cell-based fluorescence assay using membrane potential-sensitive fluorescent dyes and stably transfected hERG channels from CHO cells. The assay allows semiautomated screening of compounds for hERG activity on 384-well plates and is sufficiently rapid for testing a large number of compounds. The assay is robust as indicated by a Z′ factor larger than 0.6. The throughput is in the range of 10,000 data points per day, which is significantly higher than any other method presently available for hERG. The data obtained with the fluorescence assay were in qualitative agreement with those from patch-clamp electrophysiological analysis. There were no false-positive hits, and the rate of false-negative compounds is currently 12% but might be further reduced by testing compounds at higher concentration. Quantitative differences between fluorescence and electrophysiological methods may be due to the use- or voltage-dependentactivity of the antagonists.
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Affiliation(s)
- Arnulf Dorn
- Hoffmann-La Roche Ltd., Pharma Research, Basel, Switzerland.
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15
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ElFessi-Magouri R, Peigneur S, Khamessi O, Srairi-Abid N, ElAyeb M, Mille BG, Cuypers E, Tytgat J, Kharrat R. Kbot55, purified from Buthus occitanus tunetanus venom, represents the first member of a novel α-KTx subfamily. Peptides 2016; 80:4-8. [PMID: 26079392 DOI: 10.1016/j.peptides.2015.05.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/26/2015] [Accepted: 05/28/2015] [Indexed: 01/13/2023]
Abstract
Kbot55 is a 39 amino acid peptide isolated from the venom of the Tunisian scorpion Buthus occitanus tunetanus. This peptide is cross-linked by 3 disulfide bridges and has a molecular mass of 4128.65Da. Kbot55 is very low represented in the venom and thus represents a challenge for biochemical characterization. In this study, Kbot55 has been subjected to a screening on ion channels expressed in Xenopus laevis oocytes. It was found that Kbot55 targets voltage-gated potassium channels with high affinity. Kbot55 shows very low amino acid identity with other scorpion potassium toxins and therefore was considered a bona fide novel type of scorpion toxin. Sequence alignment analysis indicated that Kbot55 is the first representative of the new α-Ktx31 subfamily and therefore was classified as α-Ktx31.1.
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Affiliation(s)
- Rym ElFessi-Magouri
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis, Tunisia
| | - Steve Peigneur
- Toxicology & Pharmacology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, B-3000 Leuven, Belgium
| | - Oussema Khamessi
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis, Tunisia
| | - Najet Srairi-Abid
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis, Tunisia
| | - Mohamed ElAyeb
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis, Tunisia
| | - Bea Garcia Mille
- Toxicology & Pharmacology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, B-3000 Leuven, Belgium
| | - Eva Cuypers
- Toxicology & Pharmacology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, B-3000 Leuven, Belgium
| | - Jan Tytgat
- Toxicology & Pharmacology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, B-3000 Leuven, Belgium
| | - Riadh Kharrat
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis, Tunisia.
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16
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Li H, Kim HS, Kim HW, Shin SE, Jung WK, Ha KS, Han ET, Hong SH, Firth AL, Bae YM, Choi IW, Park WS. The class III anti-arrhythmic agent, amiodarone, inhibits voltage-dependent K(+) channels in rabbit coronary arterial smooth muscle cells. Naunyn Schmiedebergs Arch Pharmacol 2016; 389:713-21. [PMID: 27030392 DOI: 10.1007/s00210-016-1232-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 03/16/2016] [Indexed: 01/06/2023]
Abstract
We examined the inhibitory effect of amiodarone, a class III anti-arrhythmic agent, on voltage-dependent K(+) (Kv) currents in freshly isolated rabbit coronary arterial smooth muscle cells, using a whole-cell patch clamp technique. Amiodarone inhibited Kv currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC50) value of 3.9 ± 1.44 μM and a Hill coefficient of 0.45 ± 0.14. Amiodarone did not have a significant effect on the steady-state activation of Kv channels, but shifted the inactivation current toward a more negative potential. Application of consecutive pulses progressively augmented the amiodarone-induced Kv channel inhibition. Another class III anti-arrhythmic agent, dofetilide, did not inhibit the Kv current or change the inhibitory effect of amiodarone on Kv channels. Therefore, these results strongly suggest that amiodarone inhibits Kv currents in a concentration- and state-dependent manner.
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Affiliation(s)
- Hongliang Li
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 200-701, South Korea
| | - Han Sol Kim
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 200-701, South Korea
| | - Hye Won Kim
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 200-701, South Korea
| | - Sung Eun Shin
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 200-701, South Korea
| | - Won-Kyo Jung
- Department of Biomedical Engineering, and Center for Marine-Integrated Biomedical Technology (BK21 Plus), Pukyong National University, Busan, 608-737, South Korea
| | - Kwon-Soo Ha
- Department of Molecular and Cellular Biochemistry, Kangwon National University School of Medicine, Chuncheon, 200-701, South Korea
| | - Eun-Taek Han
- Department of Medical Environmental Biology and Tropical Medicine, Kangwon National University School of Medicine, Chuncheon, 200-701, South Korea
| | - Seok-Ho Hong
- Institute of Medical Sciences, Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, 200-701, South Korea
| | - Amy L Firth
- Department of Pulmonary, Critical Care and Sleep Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA, 90033, USA
| | - Young Min Bae
- Department of Physiology, Konkuk University School of Medicine, Chungju, 380-701, South Korea
| | - Il-Whan Choi
- Department of Microbiology, Inje University College of Medicine, Busan, 614-735, South Korea.
| | - Won Sun Park
- Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon, 200-701, South Korea.
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17
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Hu XM, Li XQ, Li XT. The Tau-Induced Reduction of mRNA Levels of Kv Channels in Human Neuroblastoma SK-N-SH Cells. J Mol Neurosci 2015; 58:306-11. [PMID: 26576773 DOI: 10.1007/s12031-015-0683-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2015] [Accepted: 11/09/2015] [Indexed: 11/25/2022]
Abstract
Previous findings indicated that microtubule-binding protein tau and voltage-gated K(+) (Kv) channels exhibit a regulatory role in cell proliferation. However, the possible interaction of tau with Kv channels remained obscure. In this report, transfection of tau plasmids into human neuroblastoma SK-N-SH cells caused a significant reduction in the messenger RNA (mRNA) levels of several Kv channels, including Kv2.1, Kv3.1, Kv5.1, Kv9.2, and KCNH4. Correspondingly, the Kv currents recorded using patch-clamp techniques were substantially declined in the tau-transfected SK-N-SH cells. Moreover, tau induction and treatment with the Kv channel blocker TEA (tetraethylammonium) were able to improve proliferation rates of SK-N-SH cells by 43.1 and 66.2%, respectively. These data suggested that the tau-mediated alteration of Kv channels could be involved in its action on neural proliferation.
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Affiliation(s)
- Xi-Mu Hu
- Graduate Institute of South-Central University for Nationalities, Wuhan, 430074, China
| | - Xiao-Qing Li
- Graduate Institute of South-Central University for Nationalities, Wuhan, 430074, China
| | - Xian-Tao Li
- Department of Neurobiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, China.
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18
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Stas JI, Bocksteins E, Labro AJ, Snyders DJ. Modulation of Closed-State Inactivation in Kv2.1/Kv6.4 Heterotetramers as Mechanism for 4-AP Induced Potentiation. PLoS One 2015; 10:e0141349. [PMID: 26505474 PMCID: PMC4623978 DOI: 10.1371/journal.pone.0141349] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 10/06/2015] [Indexed: 12/26/2022] Open
Abstract
The voltage-gated K+ (Kv) channel subunits Kv2.1 and Kv2.2 are expressed in almost every tissue. The diversity of Kv2 current is increased by interacting with the electrically silent Kv (KvS) subunits Kv5-Kv6 and Kv8-Kv9, into functional heterotetrameric Kv2/KvS channels. These Kv2/KvS channels possess unique biophysical properties and display a more tissue-specific expression pattern, making them more desirable pharmacological and therapeutic targets. However, little is known about the pharmacological properties of these heterotetrameric complexes. We demonstrate that Kv5.1, Kv8.1 and Kv9.3 currents were inhibited differently by the channel blocker 4-aminopyridine (4-AP) compared to Kv2.1 homotetramers. In contrast, Kv6.4 currents were potentiated by 4-AP while displaying moderately increased affinities for the channel pore blockers quinidine and flecainide. We found that the 4-AP induced potentiation of Kv6.4 currents was caused by modulation of the Kv6.4-mediated closed-state inactivation: suppression by 4-AP of the Kv2.1/Kv6.4 closed-state inactivation recovered a population of Kv2.1/Kv6.4 channels that was inactivated at resting conditions, i.e. at a holding potential of -80 mV. This modulation also resulted in a slower initiation and faster recovery from closed-state inactivation. Using chimeric substitutions between Kv6.4 and Kv9.3 subunits, we demonstrated that the lower half of the S6 domain (S6c) plays a crucial role in the 4-AP induced potentiation. These results demonstrate that KvS subunits modify the pharmacological response of Kv2 subunits when assembled in heterotetramers and illustrate the potential of KvS subunits to provide unique pharmacological properties to the heterotetramers, as is the case for 4-AP on Kv2.1/Kv6.4 channels.
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Affiliation(s)
- Jeroen I. Stas
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, CDE, Universiteitsplein 1, Antwerp, Belgium
| | - Elke Bocksteins
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, CDE, Universiteitsplein 1, Antwerp, Belgium
| | - Alain J. Labro
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, CDE, Universiteitsplein 1, Antwerp, Belgium
| | - Dirk J. Snyders
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, CDE, Universiteitsplein 1, Antwerp, Belgium
- * E-mail:
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19
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ElFessi-Magouri R, Peigneur S, Othman H, Srairi-Abid N, ElAyeb M, Tytgat J, Kharrat R. Characterization of Kbot21 Reveals Novel Side Chain Interactions of Scorpion Toxins Inhibiting Voltage-Gated Potassium Channels. PLoS One 2015; 10:e0137611. [PMID: 26398235 PMCID: PMC4580410 DOI: 10.1371/journal.pone.0137611] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 08/19/2015] [Indexed: 11/18/2022] Open
Abstract
Scorpion toxins are important pharmacological tools for probing the physiological roles of ion channels which are involved in many physiological processes and as such have significant therapeutic potential. The discovery of new scorpion toxins with different specificities and affinities is needed to further characterize the physiology of ion channels. In this regard, a new short polypeptide called Kbot21 has been purified to homogeneity from the venom of Buthus occitanus tunetanus scorpion. Kbot21 is structurally related to BmBKTx1 from the venom of the Asian scorpion Buthus martensii Karsch. These two toxins differ by only two residues at position 13 (R /V) and 24 (D/N).Despite their very similar sequences, Kbot21 and BmBKTx1 differ in their electrophysiological activities. Kbot21 targets KV channel subtypes whereas BmBKTx1 is active on both big conductance (BK) and small conductance (SK) Ca2+-activated K+ channel subtypes, but has no effects on Kv channel subtypes. The docking model of Kbot21 with the Kv1.2 channel shows that the D24 and R13 side-chain of Kbot21 are critical for its interaction with KV channels.
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Affiliation(s)
- Rym ElFessi-Magouri
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis,13 Place Pasteur, BP-74, 1002, Tunis, Tunisie
| | - Steve Peigneur
- Laboratory of Toxicology & Pharmacology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, B-3000, Leuven, Belgium
| | - Houcemeddine Othman
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis,13 Place Pasteur, BP-74, 1002, Tunis, Tunisie
| | - Najet Srairi-Abid
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis,13 Place Pasteur, BP-74, 1002, Tunis, Tunisie
| | - Mohamed ElAyeb
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis,13 Place Pasteur, BP-74, 1002, Tunis, Tunisie
| | - Jan Tytgat
- Laboratory of Toxicology & Pharmacology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, B-3000, Leuven, Belgium
| | - Riadh Kharrat
- Laboratoire des Venins et Molécules Thérapeutiques, Institut Pasteur de Tunis,13 Place Pasteur, BP-74, 1002, Tunis, Tunisie
- * E-mail:
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20
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Sánchez-Carranza O, Torres-Rodríguez P, Darszon A, Treviño CL, López-González I. Pharmacology of hSlo3 channels and their contribution in the capacitation-associated hyperpolarization of human sperm. Biochem Biophys Res Commun 2015; 466:554-9. [PMID: 26381170 DOI: 10.1016/j.bbrc.2015.09.073] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 09/12/2015] [Indexed: 01/01/2023]
Abstract
Slo3 channels (mSlo3) primarily mediate mouse sperm K(+) currents and are essential for the capacitation-associated hyperpolarization (CAH). Whether Slo3 and/or Slo1, two Slo family K(+) channels are functionally expressed in human sperm is controversial. Our recent pharmacological studies of the human sperm CAH suggested the participation of both. Lack of a detailed pharmacology of heterologously expressed human Slo3 (hSlo3) prevented precisely identifying the K(+) channel(s) involved. In the present report, we compare the pharmacological profile of expressed hSlo3 in CHO cells with that of the CAH to advance this matter. Whole-cell patch-clamp recordings showed that hSlo3 currents are inhibited: significantly by progesterone, Ba(2+) and quinidine; partially by Penitrem A and Charybdotoxin; and poorly by Iberiotoxin and Slotoxin. Surprisingly, hSlo3 currents were resistant to Clofilium and 60 mM TEA(+) which inhibit mSlo3. Pharmacological comparison of the CAH and hSlo3 profiles indicates in addition to hSlo3, other K(+) channels, possibly Slo1, may participate in CAH. The pharmacological profile of heterologously expressed hSlo3 channels differs from that of mSlo3 K(+) channels, consistent with species-specific differences observed among other sperm ion channels. While the pharmacological correlation analysis of the hSlo3 currents and the CAH confirmed the participation of hSlo3 channels, it suggests that additional K(+) channels may be involved, in particular Slo1 channels.
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Affiliation(s)
- Oscar Sánchez-Carranza
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Paulina Torres-Rodríguez
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Alberto Darszon
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Claudia L Treviño
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico.
| | - Ignacio López-González
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico.
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21
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Hu Y, Chen J, Wang B, Yang W, Zhang C, Hu J, Xie Z, Cao Z, Li W, Wu Y, Chen Z. Engineering a peptide inhibitor towards the KCNQ1/KCNE1 potassium channel (IKs). Peptides 2015; 71:77-83. [PMID: 26188173 DOI: 10.1016/j.peptides.2015.07.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 07/05/2015] [Accepted: 07/07/2015] [Indexed: 11/27/2022]
Abstract
The KCNQ1/KCNE1 channel (IKs) plays important roles in the physiological and pathological process of heart, but no potent peptide acting on this channel has been reported. In this work, we found that the natural scorpion venom hardly inhibited KCNQ1/KCNE1 channel currents. Based on this observation, we attempted to use three natural scorpion toxins ChTX, BmKTX and OmTx2 with two different structural folds as templates to engineer potent peptide inhibitors towards the KCNQ1/KCNE1 channel. Pharmacological experiments showed that when we screen with 1μM MT2 peptide, an analog derived from BmKTX toxin, KCNQ1/KCNE1 channel currents could be effectively inhibited. Concentration-dependent experiments showed that MT2 inhibited the KCNQ1/KCNE1 channel with an IC50 value of 4.6±1.9μM. The mutagenesis experiments indicated that MT2 peptide likely used Lys26 residue to interact with the KCNQ1/KCNE1 channel. With MT2 as a new template, we further designed a more potent MT2-2 peptide, which selectively inhibited the KCNQ1/KCNE1 channel with an IC50 of 1.51±0.62μM. Together, this work provided a much potent KCNQ1/KCNE1 channel peptide inhibitor so far, and highlighted the role of molecular strategy in developing potent peptide inhibitors for the natural toxin-insensitive orphan receptors.
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Affiliation(s)
- Youtian Hu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Jing Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Bin Wang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Weishan Yang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Chuangeng Zhang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Jun Hu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Zili Xie
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Zhijian Cao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China
| | - Wenxin Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China
| | - Yingliang Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China.
| | - Zongyun Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.
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Sakakibara K, Feng GG, Li J, Akahori T, Yasuda Y, Nakamura E, Hatakeyama N, Fujiwara Y, Kinoshita H. Kynurenine causes vasodilation and hypotension induced by activation of KCNQ-encoded voltage-dependent K(+) channels. J Pharmacol Sci 2015; 129:31-7. [PMID: 26318674 DOI: 10.1016/j.jphs.2015.07.042] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 07/25/2015] [Accepted: 07/31/2015] [Indexed: 12/23/2022] Open
Abstract
Kynurenine is a potential contributor to hypotension in animal and human sepsis. The present study was designed to examine whether the voltage-dependent K(+) channels encoded by the KCNQ gene family (Kv7 channels) mediate vasodilator effects of kynurenine and whether modulation of these channels ameliorates hypotension caused by this compound. Rat aortas and mesenteric arteries or human omental arteries without endothelium were used. Some rings were incubated with the selective Kv7 channel inhibitor linopirdine (10 μM). l-Kynurenine (10 μM-1 mM) induced concentration-dependent relaxation in rat aortas and mesenteric arteries as well as human omental arteries, whereas linopirdine abolished the relaxation. l-Kynurenine (1 mM) produced hyperpolarization of vascular smooth muscle, which was reversed by linopirdine (10 μM). Wistar rats received l-kynurenine (1 mM) iv and subsequent linopirdine (10 μM) iv under 3% sevoflurane inhalation. l-Kynurenine iv caused hypotension, whereas linopirdine iv partially reversed it. In conclusion, kynurenine dilates arteries from rats as well as humans via Kv7 channels in the vascular smooth muscle. In rats, this tryptophan metabolite causes hypotension, which is partly counteracted by Kv7 channel inhibition. These results suggest that modulation of Kv7 channels may be a novel strategy to treat hypotension induced by the kynurenine.
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Affiliation(s)
- Kensuke Sakakibara
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Guo-Gang Feng
- Department of Pharmacology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Jiazheng Li
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Takahiko Akahori
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Yoshitaka Yasuda
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Emi Nakamura
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Noboru Hatakeyama
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Yoshihiro Fujiwara
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan
| | - Hiroyuki Kinoshita
- Department of Anesthesiology, Aichi Medical University School of Medicine, 1-1 Yazako Karimata, Nagakute, Aichi 480-1195, Japan.
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Hu Z, Ma A, Zhang Y, Xi Y, Fan L, Wang T, Zhang T. Voltage-gated potassium+ channel expression in coronary artery smooth muscle cells of SHR and WKY. Cell Biochem Biophys 2015; 70:1725-31. [PMID: 25030407 DOI: 10.1007/s12013-014-0120-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study aims to compare the expression of genes and the molecular characteristic of voltage-gated K(+) channels, which make great effort in maintaining and controlling smooth muscle contraction, cellular membrane potential, and intracellular calcium ion currents in artery smooth muscle cells of SHR and WKY. Expression of potassium ions family in coronary artery was detected through reverse transcription polymerase chain reaction quantitatively. Significant levels of voltage-gated K(+) channels α1.2, α1.5, and β1.1 expression were all proved to be significantly higher in smooth muscles of SHR than WKY. Whole-cell voltage-gated K(+) channel currents were larger in SHR artery smooth muscles than the ones of WKY. Moreover, the voltage dependence of voltage-gated potassium channel activation was more negative in artery smooth muscle of SHR than that of WKY, while voltage dependence of availability was not different. The above diversity of voltage-gated potassium channel detected in gene expression and electrical character in coronary artery smooth muscle of SHR than that of WKY might be an underling mechanism associated with the membrane potential depolarization in artery smooth muscle of SHR.
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Affiliation(s)
- Zhi Hu
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, No. 277 West Yanta Road, Xi'an, 710061, Shaanxi, China
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24
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Meng XM, Huang X, Zhang CM, Liu DH, Lu HL, Kim YC, Xu WX. Hydrogen sulfide-induced enhancement of gastric fundus smooth muscle tone is mediated by voltage-dependent potassium and calcium channels in mice. World J Gastroenterol 2015; 21:4840-4851. [PMID: 25944997 PMCID: PMC4408456 DOI: 10.3748/wjg.v21.i16.4840] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 10/17/2014] [Accepted: 12/22/2014] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effect of hydrogen sulfide (H2S) on smooth muscle motility in the gastric fundus.
METHODS: The expression of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) in cultured smooth muscle cells from the gastric fundus was examined by the immunocytochemistry technique. The tension of the gastric fundus smooth muscle was recorded by an isometric force transducer under the condition of isometric contraction with each end of the smooth muscle strip tied with a silk thread. Intracellular recording was used to identify whether hydrogen sulfide affects the resting membrane potential of the gastric fundus in vitro. Cells were freshly separated from the gastric fundus of mice using a variety of enzyme digestion methods and whole-cell patch-clamp technique was used to find the effects of hydrogen sulfide on voltage-dependent potassium channel and calcium channel. Calcium imaging with fura-3AM loading was used to investigate the mechanism by which hydrogen sulfide regulates gastric fundus motility in cultured smooth muscle cells.
RESULTS: We found that both CBS and CSE were expressed in the cultured smooth muscle cells from the gastric fundus and that H2S increased the smooth muscle tension of the gastric fundus in mice at low concentrations. In addition, nicardipine and aminooxyacetic acid (AOAA), a CBS inhibitor, reduced the tension, whereas Nω-nitro-L-arginine methyl ester, a nonspecific nitric oxide synthase, increased the tension. The AOAA-induced relaxation was significantly recovered by H2S, and the NaHS-induced increase in tonic contraction was blocked by 5 mmol/L 4-aminopyridine and 1 μmol/L nicardipine. NaHS significantly depolarized the membrane potential and inhibited the voltage-dependent potassium currents. Moreover, NaHS increased L-type Ca2+ currents and caused an elevation in intracellular calcium ([Ca2+]i).
CONCLUSION: These findings suggest that H2S may be an excitatory modulator in the gastric fundus in mice. The excitatory effect is mediated by voltage-dependent potassium and L-type calcium channels.
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MESH Headings
- Animals
- Calcium Channel Agonists/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/drug effects
- Cells, Cultured
- Cystathionine gamma-Lyase/metabolism
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/pharmacology
- Gastric Fundus/drug effects
- Gastric Fundus/metabolism
- Gastrointestinal Motility/drug effects
- Hydrogen Sulfide/pharmacology
- Lyases/antagonists & inhibitors
- Lyases/metabolism
- Male
- Membrane Potentials
- Mice, Inbred ICR
- Muscle Contraction/drug effects
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Nitric Oxide Synthase/antagonists & inhibitors
- Nitric Oxide Synthase/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Voltage-Gated/antagonists & inhibitors
- Potassium Channels, Voltage-Gated/metabolism
- Time Factors
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Yu CC, Ai T, Weiss JN, Chen PS. Apamin does not inhibit human cardiac Na+ current, L-type Ca2+ current or other major K+ currents. PLoS One 2014; 9:e96691. [PMID: 24798465 PMCID: PMC4010514 DOI: 10.1371/journal.pone.0096691] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 04/10/2014] [Indexed: 12/03/2022] Open
Abstract
Background Apamin is commonly used as a small-conductance Ca2+-activated K+ (SK) current inhibitor. However, the specificity of apamin in cardiac tissues remains unclear. Objective To test the hypothesis that apamin does not inhibit any major cardiac ion currents. Methods We studied human embryonic kidney (HEK) 293 cells that expressed human voltage-gated Na+, K+ and Ca2+ currents and isolated rabbit ventricular myocytes. Whole-cell patch clamp techniques were used to determine ionic current densities before and after apamin administration. Results Ca2+ currents (CACNA1c+CACNB2b) were not affected by apamin (500 nM) (data are presented as median [25th percentile;75th percentile] (from –16 [–20;–10] to –17 [–19;–13] pA/pF, P = NS), but were reduced by nifedipine to –1.6 [–3.2;–1.3] pA/pF (p = 0.008). Na+ currents (SCN5A) were not affected by apamin (from –261 [–282;–145] to –268 [–379;–132] pA/pF, P = NS), but were reduced by flecainide to –57 [–70;–47] pA/pF (p = 0.018). None of the major K+ currents (IKs, IKr, IK1 and Ito) were inhibited by 500 nM of apamin (KCNQ1+KCNE1, from 28 [20]; [37] to 23 [18]; [32] pA/pF; KCNH2+KCNE2, from 28 [24]; [30] to 27 [24]; [29] pA/pF; KCNJ2, from –46 [–48;–40] to –46 [–51;–35] pA/pF; KCND3, from 608 [505;748] to 606 [454;684]). Apamin did not inhibit the INa or ICaL in isolated rabbit ventricular myocytes (INa, from –67 [–75;–59] to –68 [–71;–59] pA/pF; ICaL, from –16 [–17;–14] to –14 [–15;–13] pA/pF, P = NS for both). Conclusions Apamin does not inhibit human cardiac Na+ currents, L-type Ca2+ currents or other major K+ currents. These findings indicate that apamin is a specific SK current inhibitor in hearts as well as in other organs.
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Affiliation(s)
- Chih-Chieh Yu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Integrated Diagnostic & Therapeutics, National Taiwan University, Taipei, Taiwan
| | - Tomohiko Ai
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Molecular Pathogenesis, Division of Pathophysiology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - James N. Weiss
- Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- * E-mail:
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26
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Li X, Guo Q, Gao J, Yang J, Zhang W, Liang Y, Wu D, Liu Y, Weng J, Li Q, Zhang Y. The adenylyl cyclase inhibitor MDL-12,330A potentiates insulin secretion via blockade of voltage-dependent K(+) channels in pancreatic beta cells. PLoS One 2013; 8:e77934. [PMID: 24205033 PMCID: PMC3812155 DOI: 10.1371/journal.pone.0077934] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 09/06/2013] [Indexed: 12/25/2022] Open
Abstract
Objective Adenylyl cyclases (ACs) play important role in regulating pancreatic beta cell growth, survival and secretion through the synthesis of cyclic AMP (cAMP). MDL-12,330A and SQ 22536 are two AC inhibitors used widely to establish the role of ACs. The goal of this study was to examine the effects of MDL-12,330A and SQ 22536 on insulin secretion and underlying mechanisms. Methods Patch-clamp recording, Ca2+ fluorescence imaging and radioimmunoassay were used to measure outward K+ currents, action potentials (APs), intracellular Ca2+ ([Ca2+]i) and insulin secretion from rat pancreatic beta cells. Results MDL-12,330A (10 µmol/l) potentiated insulin secretion to 1.7 times of control in the presence of 8.3 mmol/l glucose, while SQ 22536 did not show significant effect on insulin secretion. MDL-12,330A prolonged AP durations (APDs) by inhibiting voltage-dependent K+ (KV) channels, leading to an increase in [Ca2+]i levels. It appeared that these effects induced by MDL-12,330A did not result from AC inhibition, since SQ 22536 did not show such effects. Furthermore, inhibition of the downstream effectors of AC/cAMP signaling by PKA inhibitor H89 and Epac inhibitor ESI-09, did not affect KV channels and insulin secretion. Conclusion The putative AC inhibitor MDL-12,330A enhances [Ca2+]i and insulin secretion via inhibition of KV channels rather than AC antagonism in beta cells, suggesting that the non-specific effects is needed to be considered for the right interpretation of the experimental results using this agent in the analyses of the role of AC in cell function.
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Affiliation(s)
- Xiaodong Li
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Qing Guo
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Jingying Gao
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Jing Yang
- Department of Endocrinology, the First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China
| | - Wan Zhang
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Yueqin Liang
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Dongmei Wu
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Yunfeng Liu
- Department of Endocrinology, the First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China
- * E-mail: (YL); (YZ)
| | - Jianping Weng
- Department of Endocrinology, the Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China
| | - Qingshan Li
- School of Pharmaceutical Sciences, Shanxi Medical University, Taiyuan, China
| | - Yi Zhang
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
- * E-mail: (YL); (YZ)
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27
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Orts DJB, Peigneur S, Madio B, Cassoli JS, Montandon GG, Pimenta AMC, Bicudo JEPW, Freitas JC, Zaharenko AJ, Tytgat J. Biochemical and electrophysiological characterization of two sea anemone type 1 potassium toxins from a geographically distant population of Bunodosoma caissarum. Mar Drugs 2013; 11:655-79. [PMID: 23466933 PMCID: PMC3705364 DOI: 10.3390/md11030655] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 01/23/2013] [Accepted: 02/15/2013] [Indexed: 12/12/2022] Open
Abstract
Sea anemone (Cnidaria, Anthozoa) venom is an important source of bioactive compounds used as tools to study the pharmacology and structure-function of voltage-gated K+ channels (KV). These neurotoxins can be divided into four different types, according to their structure and mode of action. In this work, for the first time, two toxins were purified from the venom of Bunodosoma caissarum population from Saint Peter and Saint Paul Archipelago, Brazil. Sequence alignment and phylogenetic analysis reveals that BcsTx1 and BcsTx2 are the newest members of the sea anemone type 1 potassium channel toxins. Their functional characterization was performed by means of a wide electrophysiological screening on 12 different subtypes of KV channels (KV1.1-KV1.6; KV2.1; KV3.1; KV4.2; KV4.3; hERG and Shaker IR). BcsTx1 shows a high affinity for rKv1.2 over rKv1.6, hKv1.3, Shaker IR and rKv1.1, while Bcstx2 potently blocked rKv1.6 over hKv1.3, rKv1.1, Shaker IR and rKv1.2. Furthermore, we also report for the first time a venom composition and biological activity comparison between two geographically distant populations of sea anemones.
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Affiliation(s)
- Diego J. B. Orts
- Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, SP, 05508-090, Brazil; E-Mails: (D.J.B.O.); (B.M.); (J.E.P.W.B.); (J.C.F.)
- Center of Marine Biology, University of São Paulo, São Sebastião, SP, 11600-000, Brazil
| | - Steve Peigneur
- Laboratory of Toxicology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium; E-Mail:
| | - Bruno Madio
- Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, SP, 05508-090, Brazil; E-Mails: (D.J.B.O.); (B.M.); (J.E.P.W.B.); (J.C.F.)
| | - Juliana S. Cassoli
- Laboratory of Venoms and Animals Toxins, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil; E-Mails: (J.S.C.); (G.G.M.); (A.M.C.P.)
| | - Gabriela G. Montandon
- Laboratory of Venoms and Animals Toxins, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil; E-Mails: (J.S.C.); (G.G.M.); (A.M.C.P.)
| | - Adriano M. C. Pimenta
- Laboratory of Venoms and Animals Toxins, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil; E-Mails: (J.S.C.); (G.G.M.); (A.M.C.P.)
| | - José E. P. W. Bicudo
- Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, SP, 05508-090, Brazil; E-Mails: (D.J.B.O.); (B.M.); (J.E.P.W.B.); (J.C.F.)
| | - José C. Freitas
- Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, SP, 05508-090, Brazil; E-Mails: (D.J.B.O.); (B.M.); (J.E.P.W.B.); (J.C.F.)
| | - André J. Zaharenko
- Laboratorio de Genetica, Instituto Butantan, São Paulo, SP, 05503-900, Brazil
| | - Jan Tytgat
- Laboratory of Toxicology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium; E-Mail:
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28
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Brereton MF, Wareing M, Jones RL, Greenwood SL. Characterisation of K+ channels in human fetoplacental vascular smooth muscle cells. PLoS One 2013; 8:e57451. [PMID: 23437391 PMCID: PMC3578819 DOI: 10.1371/journal.pone.0057451] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 01/24/2013] [Indexed: 11/18/2022] Open
Abstract
Adequate blood flow through placental chorionic plate resistance arteries (CPAs) is necessary for oxygen and nutrient transfer to the fetus and a successful pregnancy. In non-placental vascular smooth muscle cells (SMCs), K(+) channels regulate contraction, vascular tone and blood flow. Previous studies showed that K(+) channel modulators alter CPA tone, but did not distinguish between effects on K(+) channels in endothelial cells and SMCs. In this study, we developed a preparation of freshly isolated CPASMCs of normal pregnancy and investigated K(+) channel expression and function. CPASMCs were isolated from normal human term placentas using enzymatic digestion. Purity and phenotype was confirmed with immunocytochemistry. Whole-cell patch clamp was used to assess K(+) channel currents, and mRNA and protein expression was determined in intact CPAs and isolated SMCs with RT-PCR and immunostaining. Isolated SMCs expressed α-actin but not CD31, a marker of endothelial cells. CPASMCs and intact CPAs expressed h-caldesmon and non-muscle myosin heavy chain-2; phenotypic markers of contractile and synthetic SMCs respectively. Whole-cell currents were inhibited by 4-AP, TEA, charybdotoxin and iberiotoxin implicating functional K(v) and BK(Ca) channels. 1-EBIO enhanced whole cell currents which were abolished by TRAM-34 and reduced by apamin indicating activation of IK(Ca) and SK(Ca) respectively. BK(Ca), IK(Ca) and SK(Ca)3 mRNA and/or protein were expressed in CPASMCs and intact CPAs. This study provides the first direct evidence for functional K(v), BK(Ca,) IK(Ca) and SK(Ca) channels in CPASMCs. These cells display a mixed phenotype implicating a dual role for CPASMCs in controlling both fetoplacental vascular resistance and vasculogenesis.
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MESH Headings
- Actins/genetics
- Actins/metabolism
- Calcium/metabolism
- Calmodulin-Binding Proteins/genetics
- Calmodulin-Binding Proteins/metabolism
- Chorion/blood supply
- Chorion/cytology
- Chorion/drug effects
- Chorion/metabolism
- Female
- Fetus
- Gene Expression/drug effects
- Humans
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Myosin Heavy Chains/genetics
- Myosin Heavy Chains/metabolism
- Patch-Clamp Techniques
- Placenta/blood supply
- Placenta/cytology
- Placenta/drug effects
- Placenta/metabolism
- Potassium/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/classification
- Potassium Channels, Calcium-Activated/genetics
- Potassium Channels, Calcium-Activated/metabolism
- Potassium Channels, Voltage-Gated/antagonists & inhibitors
- Potassium Channels, Voltage-Gated/classification
- Potassium Channels, Voltage-Gated/genetics
- Potassium Channels, Voltage-Gated/metabolism
- Pregnancy
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Affiliation(s)
- Melissa F Brereton
- Maternal and Fetal Health Research Centre, Institute of Human Development, University of Manchester, St. Mary's Hospital, Manchester, United Kingdom.
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Kodera SY, Yoshida M, Dezaki K, Yada T, Murayama T, Kawakami M, Kakei M. Inhibition of insulin secretion from rat pancreatic islets by dexmedetomidine and medetomidine, two sedatives frequently used in clinical settings. Endocr J 2013; 60:337-46. [PMID: 23171706 DOI: 10.1507/endocrj.ej12-0308] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The aim of this study was to determine whether dexmedetomidine (DEX) and medetomidine (MED), α2-adrenergic agonists clinically used as sedatives, influence insulin secretion from rat pancreatic islets. Islets were isolated from adult male Wistar rats after collagenase digestion. Static incubation was used to determine effects of DEX or MED on insulin secretion and ionic-channel currents of β-cells. Results indicate that both drugs dose-dependently inhibit insulin secretion, DEX more potently than MED. The inhibitory effects were attenuated by addition of yohimbine or by pretreatment of rats with pertussis toxin (PTX). 10 nM DEX decreased the current amplitude of voltage-dependent Ca2+ channels, but this did not occur when the N-type Ca2+ channel blocker ω-conotoxin was added. In the presence of tetraethylammonium, a classical voltage-gated K+ channel (Kv channel) blocker, the magnitude of inhibition of insulin secretion by MED was reduced. However, when tolbutamide, a specific blocker of the ATP-sensitive K+ channel (KATP channel), was present, the magnitude of MED inhibition of insulin secretion was not influenced, suggesting that Kv-channel activity alteration, but not that of KATP channels, is involved in MED-associated insulin secretory inhibition. The Kv-channel currents were increased during 1 nM MED exposure at membrane potentials ranging from -30 mV to -10 mV, where action potentials were generated in response to glucose stimulation. These results indicate that DEX and MED inhibit insulin secretion through an α2-adrenoceptor and PTX-sensitive GTP-binding protein pathway that eventually involves Kv channel activation and Ca2+ channel inhibition.
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Affiliation(s)
- Shiho Yamato Kodera
- Division of Anesthesiology, Second Department of General Medicine, Saitama Medical Center, Jichi Medical University School of Medicine, Omiya 330-8503, Japan
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30
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Franco D. Wiring the developing heart: a serious matter for adulthood. Cardiovasc Res 2013; 97:4-5. [PMID: 23175775 DOI: 10.1093/cvr/cvs341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
Incorporation of photoisomerizable chromophores into small molecule ligands represents a general approach for reversibly controlling protein function with light. Illumination at different wavelengths produces photostationary states (PSSs) consisting of different ratios of photoisomers. Thus optimal implementation of photoswitchable ligands requires knowledge of their wavelength sensitivity. Using an azobenzene-based ion channel blocker as an example, this protocol describes a (1)H NMR assay that can be used to precisely determine the isomeric content of photostationary states (PSSs) as a function of illumination wavelength. Samples of the photoswitchable ligand are dissolved in deuterated water and analyzed by UV/VIS spectroscopy to identify the range of illumination wavelengths that produce PSSs. The PSSs produced by these wavelengths are quantified using (1)H NMR spectroscopy under continuous irradiation through a monochromator-coupled fiber-optic cable. Because aromatic protons of azobenzene trans and cis isomers exhibit sufficiently different chemical shifts, their relative abundances at each PSS can be readily determined by peak integration. Constant illumination during spectrum acquisition is essential to accurately determine PSSs from molecules that thermally relax on the timescale of minutes or faster. This general protocol can be readily applied to any photoswitch that exhibits distinct (1)H NMR signals in each photoisomeric state.
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Baskakov MB, Zheludeva AS, Gusakova SV, Smagliĭ LV, Aleĭnik AN, Ianchuk PI, Medvedev MA, Orlov SN. [Ionic mechanisms of carbon monoxide action on the contractile properties of smooth muscles of the blood vessels]. Fiziol Zh (1994) 2013; 59:18-24. [PMID: 23957160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Carbon monoxide (CO) is one of a family of gas transmitters. In this article we present the results of mechanographic investigations of the mechanisms of CO action on a rat thoracic aorta segments. We found that relaxing effect of CO donor CORM-2 on vascular smooth muscles is mediated mainly by opening of voltage-dependent potassium channels in smooth muscle cells: 4-aminopyridine, blocking these channels, almost completely eliminated the CO-induced vasorelaxation of the segments precontracted by depolarization of the smooth muscle cells membranes with high potassium (30 mM KCl) solution or by phenylephrine (10 microM). For the first time we documented that CORM-2 reduces the nicardipine-sensitive input of 45Ca2+ in freshly isolated aorta cells. There are reasons to suggest that the L-type voltage-dependent calcium channels of vascular smooth muscle cells are another target for CO, which is implemented in the relaxing effect of this gas transmitter. Additional research is needed to determine the influence of ruthenium complexes (Ru(II)) on phenomenology of carbon monoxide effects.
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Hong DH, Son YK, Choi IW, Park WS. The inhibitory effect of curcumin on voltage-dependent K⁺ channels in rabbit coronary arterial smooth muscle cells. Biochem Biophys Res Commun 2012; 430:307-12. [PMID: 23146635 DOI: 10.1016/j.bbrc.2012.10.132] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 10/31/2012] [Indexed: 11/19/2022]
Abstract
We investigated the effects of curcumin, the principal active compound of turmeric, on voltage-dependent K(+) (Kv) channels in freshly isolated rabbit coronary arterial smooth muscle cells using the voltage-clamp technique. Curcumin reduced the Kv current in a dose-dependent manner with an apparent K(d) value of 1.07 ± 0.03 μM. Although curcumin did not alter the kinetics of Kv current activation, it predominantly accelerated the decay rate of channel inactivation. The association and dissociation rate constants of curcumin were 1.35 ± 0.05 μM(-1)s(-1) and 1.47 ± 0.17s(-1), respectively. Curcumin did not alter the steady-state activation or inactivation curves. Application of train pulses (1 or 2 Hz) increased curcumin-induced blockade of the Kv current, and the recovery time constant also increased in the presence of curcumin suggesting, that the inhibitory action of Kv currents by curcumin was use-dependent. From these results, we concluded that curcumin inhibited vascular Kv current in a state-, time-, and use-dependent manner.
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Affiliation(s)
- Da Hye Hong
- Department of Physiology, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon 200-701, South Korea
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Abstract
CONTEXT Wogonin is a flavone derivative isolated from Scutellaria baicalensis Georgi (Labiatae) root, which is a traditional Chinese drug used as an anti-inflammatory and for management of dysmenorrhea. OBJECTIVE The effect of wogonin on the uterus has not yet been examined. We investigated the relaxant effects of wogonin on contractile activity of isolated uterine strips of rats. MATERIALS AND METHODS The effect of wogonin on spontaneous uterine contraction, and uterine contraction induced by agonists, K⁺-depolarization and oxytocin in Ca²⁺-free solution was observed. To clarify the type of potassium channel, we tested the effects of 4-aminopyridine, tetraethylammonium and glibenclamide. RESULTS Wogonin reduced the contractile amplitude of uterine strip smooth muscle of rats in a dose-dependent manner. The concentration of wogonin for reducing the contraction amplitude by 50% (IC₅₀) on spontaneous contractions was 60.5 μM. Wogonin also inhibited the contraction induced by three agonists (oxytocin, prostaglandin F(2α) and acetylcholine). For the uterine strips pretreated with oxytocin in Ca²⁺-free solution or K⁺-depolarization, wogonin showed relaxant effect on the induced uterine contractions. In addition, whereas the inhibitive effect of wogonin on the contraction of uterine smooth muscle in rats could be partly blocked by 4-aminopyridine and tetraethylammonium, it was not influenced by glibenclamide. DISCUSSION AND CONCLUSION Wogonin significantly inhibited the contraction of rat uterine smooth muscle probably through the inhibition of the inflow of extracellular calcium into cells via cell membrane, and intracellular release of calcium ions. In addition, the relaxant effect induced by wogonin might be due in part to the opening of voltage-dependent and large conductance Ca²⁺-activated K⁺ channels.
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Affiliation(s)
- Huey-Chuan Shih
- School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan
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Lefranc F, Pouleau HB, Rynkowski M, De Witte O. Voltage-dependent K+ channels as oncotargets in malignant gliomas. Oncotarget 2012; 3:516-7. [PMID: 22695512 PMCID: PMC3388180 DOI: 10.18632/oncotarget.514] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 05/31/2012] [Indexed: 11/25/2022] Open
Abstract
Because both imipramine and citalopram have been commonly used to treat depression, which commonly occurs in glioma patients, it would be interesting to conduct large epidemiological studies to investigate the actual benefit that these two drugs would provide for malignant glioma patients when delivered during their glioma treatment. Such large-scale epidemiological studies have recently revealed the actual benefit provided by digoxin, a Na+/K+ ATPase inhibitor used to treat heart failure, in prostate cancer patients treated for both prostate cancer and heart failure.
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Gong CL, Wong KL, Cheng KS, Kuo CS, Chao CC, Tsai MF, Leung YM. Inhibitory effects of magnolol on voltage-gated Na+ and K+ channels of NG108-15 cells. Eur J Pharmacol 2012; 682:73-8. [PMID: 22374258 DOI: 10.1016/j.ejphar.2012.02.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 01/31/2012] [Accepted: 02/09/2012] [Indexed: 11/19/2022]
Abstract
Magnolol, a polyphenolic compound isolated from Houpu, a Chinese herb from the bark of Magnolia officinalis, has been reported to have in vitro and in vivo neuroprotective effects. In spite of these reported beneficial effects, studies on the direct impact of magnolol on neuronal ion channels have been scarce. Whether magnolol affects voltage-gated Na(+) channels (VGSC) and voltage-gated K(+) (Kv) channels is unknown. Using the whole-cell voltage-clamp method, we studied the effects of magnolol on voltage-gated ion channels in neuronal NG108-15 cells. Magnolol inhibited VGSC channels with mild state-dependence (IC(50) of 15 and 30 μM, at holding potentials of -70 and -100 mV, respectively). No frequency-dependence was observed in magnolol block. Magnolol caused a left-shift of 18 mV in the steady-state inactivation curve but did not affect the voltage-dependence of activation. Magnolol inhibited Kv channels with an IC(50) of 21 μM, and it caused a 20-mV left-shift in the steady-state inactivation curve without affecting the voltage-dependence of activation. In conclusion, magnolol is an inhibitor of both VGSC and Kv channels and these inhibitory effects may in part contribute to some of the reported neuroprotective effects of magnolol.
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Affiliation(s)
- Chi-Li Gong
- Department of Physiology, China Medical University, Taichung 40402, Taiwan
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van Vliet J, Meulstee J, Hartong EGTM, Mulleners WM. [Autoimmune limbic encephalitis: importance of early diagnosis and treatment]. Ned Tijdschr Geneeskd 2012; 156:A4455. [PMID: 22510418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BACKGROUND Autoimmune limbic encephalitis is a rare disorder, characterised by the subacute onset of seizures, short-term memory loss, and psychiatric and behavioural symptoms. Initially, it was recognised as a paraneoplastic disorder, but recently a subgroup of patients without systemic cancer was identified. This type of limbic encephalitis is associated with voltage-gated potassium channel (VGKC) or N-methyl-D-aspartate receptor (NMDAR) antibodies. CASE DESCRIPTION We describe a 69-year-old man with anti-VGKC limbic encephalitis suffering from generalised tonic-clonic seizures, severe insomnia, increasing memory deficits, visual hallucinations and depression. We also describe a 22-year-old woman, suffering from complex partial seizures and dysphasia, and displaying inappropriate behaviour. She was diagnosed with anti-NMDAR limbic encephalitis. Both showed marked improvement after starting prednisone and intravenous immunoglobulin therapy. CONCLUSION These case descriptions emphasise the importance of timely recognition of autoimmune limbic encephalitis in order to rule out malignancy and to quickly initiate treatment. This potentially life-threatening disease responds well to immunomodulatory therapy.
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Affiliation(s)
- Judith van Vliet
- Canisius-Wilhelmina Ziekenhuis, Afd. Neurologie, Nijmegen, the Netherlands.
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Buxton SK, Neveu C, Charvet CL, Robertson AP, Martin RJ. On the mode of action of emodepside: slow effects on membrane potential and voltage-activated currents in Ascaris suum. Br J Pharmacol 2011; 164:453-70. [PMID: 21486286 PMCID: PMC3188918 DOI: 10.1111/j.1476-5381.2011.01428.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 01/17/2011] [Accepted: 03/28/2011] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Anthelmintics are required for treatment and prophylaxis of nematode parasites of humans and domestic animals. Emodepside, a cyclooctadepsipeptide, is a modern anthelmintic that has a novel mode of action involving a Ca-activated K channel (SLO-1) in Caenorhabditis elegans, sometimes mediated by a latrophilin (LAT) receptor. We examined mechanisms of action of emodepside in a parasitic nematode, Ascaris suum. EXPERIMENTAL APPROACH RT-PCR was used to investigate expression of slo-1 and lat-1 in A. suum muscle flaps, and two-micropipette current-clamp and voltage-clamp techniques were used to record electrophysiological effects of emodepside. KEY RESULTS Expression of slo-1 and lat-1 were detected. Emodepside produced a slow time-dependent (20 min), 4-aminopyridine sensitive, concentration-dependent hyperpolarization and increase in voltage-activated K currents. Sodium nitroprusside increased the hyperpolarizations and K currents. N-nitro-L-arginine inhibited the hyperpolarizations and K currents. Phorbol-12-myristate-13 acetate increased the K currents, while staurosporine inhibited the hyperpolarizations and K currents. Iberiotoxin reduced these emodepside K currents. The effect of emodepside was reduced in Ca-free solutions. Emodepside had no effect on voltage-activated Ca currents. CONCLUSIONS AND IMPLICATIONS Asu-slo-1 and Asu-lat-1 are expressed in adult A. suum muscle flaps and emodepside produces slow activation of voltage-activated Ca-dependent SLO-1-like K channels. The effect of emodepside was enhanced by stimulation of protein kinase C and NO pathways. The data are consistent with a model in which NO, PKC and emodepside signalling pathways are separate and converge on the K channels, or in which emodepside activates NO and PKC signalling pathways to increase opening of the K channels.
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Affiliation(s)
- S K Buxton
- Department of Biomedical Sciences, Iowa State University, Ames, IA, USA
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Beleznai TZ, Yarova PL, Yuill KH, Dora KA. Smooth muscle Ca(2+) -activated and voltage-gated K+ channels modulate conducted dilation in rat isolated small mesenteric arteries. Microcirculation 2011; 18:487-500. [PMID: 21535295 PMCID: PMC4826745 DOI: 10.1111/j.1549-8719.2011.00109.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To assess the influence of blocking smooth muscle large conductance Ca(2+) -activated K+ channels and voltage-gated K+ channels on the conducted dilation to ACh and isoproterenol. MATERIALS AND METHODS Rat mesenteric arteries were isolated with a bifurcation, triple-cannulated, pressurized and imaged using confocal microscopy. Phenylephrine was added to the superfusate to generate tone, and agonists perfused into a sidebranch to evoke local dilation and subsequent conducted dilation into the feed artery. RESULTS Both ACh- and isoproterenol-stimulated local and conducted dilation with similar magnitudes of decay with distance along the feed artery (2000μm: ∼15% maximum dilation). The gap junction uncoupler carbenoxolone prevented both conducted dilation and intercellular spread of dye through gap junctions. IbTx, TEA or 4-AP, blockers of large conductance Ca(2+) -activated K+ channels and voltage-gated K+ channels, did not affect conducted dilation to either agonist. A combination of either IbTx or TEA with 4-AP markedly improved the extent of conducted dilation to both agonists (2000μm: >50% maximum dilation). The enhanced conducted dilation was reflected in the hyperpolarization to ACh (2000μm: Control, 4±1 mV, n = 3; TEA with 4-AP, 14±3mV, n=4), and was dependent on the endothelium. CONCLUSIONS These data show that activated BK(Ca) and K(V) -channels serve to reduce the effectiveness of conducted dilation.
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Affiliation(s)
- Timea Z Beleznai
- Department of Pharmacology, University of Oxford, Oxford, UK Department of Pharmacy and Pharmacology, University of Bath, Bath, UK
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Schöne C, Venner A, Knowles D, Karnani MM, Burdakov D. Dichotomous cellular properties of mouse orexin/hypocretin neurons. J Physiol 2011; 589:2767-79. [PMID: 21486780 PMCID: PMC3112554 DOI: 10.1113/jphysiol.2011.208637] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 04/06/2011] [Indexed: 11/08/2022] Open
Abstract
Hypothalamic hypocretin/orexin (Hcrt/Orx) neurons recently emerged as critical regulators of sleep–wake cycles, reward seeking and body energy balance. However, at the level of cellular and network properties, it remains unclear whether Hcrt/Orx neurons are one homogeneous population, or whether there are several distinct types of Hcrt/Orx cells. Here, we collated diverse structural and functional information about individual Hcrt/Orx neurons in mouse brain slices, by combining patch-clamp analysis of spike firing, membrane currents and synaptic inputs with confocal imaging of cell shape and subsequent 3-dimensional Sholl analysis of dendritic architecture. Statistical cluster analysis of intrinsic firing properties revealed that Hcrt/Orx neurons fall into two distinct types. These two cell types also differ in the complexity of their dendritic arbour, the strength of AMPA and GABAA receptor-mediated synaptic drive that they receive, and the density of low-threshold, 4-aminopyridine-sensitive, transient K+ current. Our results provide quantitative evidence that, at the cellular level, the mouse Hcrt/Orx system is composed of two classes of neurons with different firing properties, morphologies and synaptic input organization.
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Affiliation(s)
- Cornelia Schöne
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK
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Abstract
A 25-year-old woman complained of numbness of the extremities, following muscle rigidity and tenderness. The presence of anti-voltage-gated potassium channel antibody led to the diagnosis of Isaacs' syndrome. Twenty-seven months after the first symptom, she developed a pricking pain sensation in the lateral left foot, and then gradually developed a purple skin lesion resembling frostbite. The lesion completely disappeared 2 days later. An incidental episode occurred at the same site 8 months later. Frostbite-like skin lesions may be a rare autonomic manifestation in Isaacs' syndrome.
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Affiliation(s)
- Hikaru Doi
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Japan
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Leung YM, Tsou YH, Kuo CS, Lin SY, Wu PY, Hour MJ, Kuo YH. Arylnaphthalene lignans from Taiwania cryptomerioides as novel blockers of voltage-gated K+ channels. Phytomedicine 2010; 18:46-51. [PMID: 20684875 DOI: 10.1016/j.phymed.2010.04.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 03/19/2010] [Accepted: 04/01/2010] [Indexed: 05/29/2023]
Abstract
Lignans are natural phytochemicals which exhibit multiple pharmacological effects such as anti-inflammation, antivirus and anti-tumor activities. Whether they have effects on neural tissues and ion channels is still unknown. The effects of several arylnaphathalene lignans purified from Taiwania cryptomerioides on voltage-gated K(+) (Kv) channels in mouse neuroblastoma N2A cells were examined. These lignans included Taiwanin E, helioxanthin (HXT) and diphyllin. All lignans showed inhibitory effects on Kv channels and HXT was the most potent compound (IC(50)=1.7 μM). The mechanism of HXT block was further investigated. Its action was found to be extracellular but not intracellular. HXT accelerated current decay, caused a left-shift in steady-state inactivation curve but had no effect on voltage-dependence of activation. HXT block was unaffected by intracellular K(+) concentrations. Further, it did not affect ATP-sensitive K(+) channels. Our data therefore suggest that HXT is a potent and specific blocker of Kv channels, possibly with an inhibitory mechanism involving acceleration of slow inactivation.
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Affiliation(s)
- Yuk-Man Leung
- Graduate Institute of Neural and Cognitive Sciences, China Medical University, Taichung, Taiwan.
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Spigelman AF, Dai X, MacDonald PE. Voltage-dependent K(+) channels are positive regulators of alpha cell action potential generation and glucagon secretion in mice and humans. Diabetologia 2010; 53:1917-26. [PMID: 20446079 DOI: 10.1007/s00125-010-1759-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 03/23/2010] [Indexed: 01/22/2023]
Abstract
AIMS/HYPOTHESIS The regulation of glucagon secretion from alpha cells is poorly understood. Since action potential firing at low glucose is required for glucagon secretion, we hypothesised that voltage-dependent K(+) (Kv) currents limit glucagon secretion under these conditions, similarly to their role in insulin secretion. METHODS Kv currents and action potential firing of mouse and human alpha cells, identified by immunostaining, were examined by whole-cell patch-clamp. Glucagon secretion from mouse and human islets was measured by ELISA. RESULTS Kv current density was 35% larger in alpha than in beta cells. Alpha cell Kv channels were sensitive to block by tetraethylammonium (TEA) and 4-aminopyridine. Surprisingly, Kv channel inhibition reduced glucagon release to the same extent as glucose. Robust action potential firing was observed in beta cells when ATP-sensitive K(+) channels were closed, but in alpha cells a negative current (-8 pA) injection was required for action potential firing. TEA (0.5 mmol/l) impaired alpha cell action potential firing, which could be restored by further hyperpolarising current injection (-16 pA). Kv currents were more sensitive to the Kv2 inhibitor stromatoxin (100 nmol/l) in mouse (80%) than in human (45%) alpha cells. Finally, the maxi-K (BK) channel inhibitor iberiotoxin (100 nmol/l) blocked 55% of the current in human alpha cells and inhibited glucagon release from human islets. CONCLUSIONS/INTERPRETATION Kv currents in alpha cells are positive regulators of glucagon secretion. These currents, mediated by Kv2 and BK channels, limit membrane depolarisation, and prevent inactivation of alpha cell action potentials and suppression of glucagon release.
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Affiliation(s)
- A F Spigelman
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
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El Harchi A, McPate MJ, Zhang YH, Zhang H, Hancox JC. Action potential clamp and mefloquine sensitivity of recombinant 'I KS' channels incorporating the V307L KCNQ1 mutation. J Physiol Pharmacol 2010; 61:123-131. [PMID: 20436212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Accepted: 03/19/2010] [Indexed: 05/29/2023]
Abstract
The slow delayed rectifier potassium current, 'I(Ks)', contributes to repolarisation of cardiac ventricular action potentials and thereby to the duration of the QT interval of the electrocardiogram. Mutations to I(Ks) channel subunits occur in clinically significant cardiac repolarisation disorders. The short QT syndrome (SQTS) is associated with accelerated ventricular repolarisation and with an increased risk of arrhythmia and sudden death. The SQT2 variant of the SQTS has been linked to a gain-of-function amino-acid substitution (V307L) in the KCNQ1-encoded I(Ks) channel alpha-subunit. This study reports the first action potential (AP) voltage-clamp comparison between wild-type (WT) and V307L KCNQ1 (co-expressed with KCNE1 to recapitulate I(Ks)) and identifies an effective pharmacological inhibitor of recombinant 'I(Ks)' channels incorporating the V307L KCNQ1 mutation. Perforated-patch voltage-clamp recordings at 37 degrees C of whole-cell current carried by co-expressed KCNQ1 and KCNE1 showed a marked (-36 mV) shift in half-maximal activation for V307L compared to WT KCNQ1; a significant slowing of current deactivation was also observed. Under AP clamp, peak repolarising current was significantly augmented for V307L KCNQ1 compared to WT KCNQ1 for both ventricular and atrial AP commands, consistent with an ability of the V307L mutation to increase repolarising I(Ks) in both regions. The quinoline agent mefloquine inhibited WT KCNQ1+KCNE1 with an IC(50) of 3.4 muM compared to 3.3 muM for V307L KCNQ1+KCNE1 (P >0.05). This establishes mefloquine as an effective inhibitor of recombinant 'I(Ks)' channels incorporating this SQT2 KCNQ1 mutation.
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Affiliation(s)
- A El Harchi
- Department of Physiology and Pharmacology and Cardiovascular Research Laboratories, School of Medical Sciences, University Walk, University of Bristol, UK
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Calderone V, Testai L, Martinotti E, Del Tacca M, Breschi MC. Drug-induced block of cardiac HERG potassium channels and development of torsade de pointes arrhythmias: the case of antipsychotics. J Pharm Pharmacol 2010; 57:151-61. [PMID: 15720777 DOI: 10.1211/0022357055272] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Abstract
The prolongation of the cardiac repolarization process, a result of the blocking of the Human Ether-a-go-go Related Gene potassium channel, is an undesired accessory property shared by many pharmacological classes of non-cardiovascular drugs. Often the delayed cardiac repolarization process can be identified by a prolongation of the QT interval of the electrocardiograph. In these conditions, premature action potentials can trigger a dangerous polymorphic ventricular tachyarrhythmia, known as torsade de pointes, which occasionally can result in lethal ventricular fibrillation. In this work, brief descriptions of the electrophysiological basis of torsade de pointes and of the several pharmacological classes of torsadogenic drugs are given. Attention is focused on antipsychotics, with a deeper overview on the experimental and clinical reports about their torsadogenic properties.
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Affiliation(s)
- Vincenzo Calderone
- Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, Università degli Studi di Pisa, Via Bonanno 6, I-56126, Pisa, Italy.
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Morecroft I, Murray A, Nilsen M, Gurney AM, MacLean MR. Treatment with the Kv7 potassium channel activator flupirtine is beneficial in two independent mouse models of pulmonary hypertension. Br J Pharmacol 2009; 157:1241-9. [PMID: 19508393 PMCID: PMC2743843 DOI: 10.1111/j.1476-5381.2009.00283.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 02/16/2009] [Accepted: 02/23/2009] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE Voltage-gated potassium (K(v)) channels contribute to resting membrane potential in pulmonary artery smooth muscle cells and are down regulated in patients with pulmonary arterial hypertension (PAH) and a contribution from K(v)7 channels has been recently proposed. We investigated the effect of the K(v)7 channel activator, flupirtine, on PAH in two independent mouse models: PAH induced by hypoxia and spontaneous PAH in mice over-expressing the 5-HT transporter (SERT(+) mice). EXPERIMENTAL APPROACH Right ventricular pressure was assessed in vivo in mice chronically treated with flupirtine (30 mg.kg(-1).day(-1)). In separate in vitro experiments, pulmonary arteries from untreated mice were mounted in a wire myograph. Relaxations to acute administration of flupirtine and contractions to K(v) channel blocking drugs, including the K(v)7 channel blocker linopirdine, were measured. KEY RESULTS In wild-type (WT) mice, hypoxia increased right ventricular pressure, pulmonary vascular remodelling and right ventricular hypertrophy. These effects were attenuated by flupirtine, which also attenuated these indices of PAH in SERT(+) mice. In the in vitro experiments, flupirtine induced a potent relaxant response in arteries from untreated WT and SERT(+) mice. The relaxation was fully reversed by linopirdine, which potently contracted mouse pulmonary arteries while other K(v) channel blockers did not. CONCLUSIONS AND IMPLICATIONS Flupirtine significantly attenuated development of chronic hypoxia-induced PAH in mice and reversed established PAH in SERT(+) mice, apparently via K(v)7 channel activation. These results provide the first direct evidence that drugs activating K(v)7 channels may be of benefit in the treatment of PAH with different aetiologies.
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MESH Headings
- Aminopyridines/therapeutic use
- Animals
- Disease Models, Animal
- Female
- Hypertension, Pulmonary/drug therapy
- Hypertension, Pulmonary/etiology
- Hypertension, Pulmonary/physiopathology
- Hypoxia/complications
- In Vitro Techniques
- Mice
- Muscle Contraction/drug effects
- Muscle Relaxation/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiopathology
- Potassium Channels, Voltage-Gated/agonists
- Potassium Channels, Voltage-Gated/antagonists & inhibitors
- Pulmonary Artery/drug effects
- Pulmonary Artery/physiopathology
- Serotonin Plasma Membrane Transport Proteins/genetics
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Affiliation(s)
- I Morecroft
- Integrative and Systems Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, UK.
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Xu LJ, Zhao JX, Zhang T, Ren GG, Yang Z. In vitro study on influence of nano particles of CuO on CA1 pyramidal neurons of rat hippocampus potassium currents. Environ Toxicol 2009; 24:211-217. [PMID: 18623077 DOI: 10.1002/tox.20418] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The effects of nano particles of CuO on voltage-dependent potassium currents were studied in acutely isolated CA1 pyramidal neurons of rat hippocampus using the whole-cell patch-clamp techniques. Nano particles of CuO had small effects on transient outward potassium current (I(A), no statistical significance) and mainly inhibited delayed rectifier potassium current (I(K)) in the concentration of 5 x 10(-5) g/mL. Nano particles of CuO didn't shift the steady-state activation curve of I(K) and I(A) but negatively shifted the inactivation curve of I(K). The effects on inactivation curve of I(A) had no statistical significance. These results suggested that blockades of K+ currents by nano particles of CuO could be preferential for I(k) for the first time. This may interfere with the normal function of nerve cells.
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Affiliation(s)
- Lan-Ju Xu
- College of Medicine, Nankai University, Tianjin 300071, China
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48
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Bender SB, Tune JD, Borbouse L, Long X, Sturek M, Laughlin MH. Altered mechanism of adenosine-induced coronary arteriolar dilation in early-stage metabolic syndrome. Exp Biol Med (Maywood) 2009; 234:683-92. [PMID: 19307464 DOI: 10.3181/0812-rm-350] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Onset of the combined metabolic syndrome (MetS) is a complex progressive process involving numerous cardiovascular risk factors. Although patients with established MetS exhibit reduced coronary flow reserve and individual components of the MetS reduce microvascular vasodilation, little is known concerning the impact of early-stage MetS on the mechanisms of coronary flow control. Therefore, we tested the hypothesis that coronary arteriolar dilation to adenosine is attenuated in early-stage MetS by reduced A2 receptor function and diminished K+ channel involvement. Pigs were fed control or high-fat/cholesterol diet for 9 weeks to induce early-stage MetS. Coronary atheroma was determined in vivo with intravascular ultrasound. In vivo coronary dilation was determined by intracoronary adenosine infusion. Further, apical coronary arterioles were isolated, cannulated and pressurized to 60 cmH2O for in vitro pharmacologic assessment of adenosine dilation. Coronary atheroma was not different between groups, indicating early-stage MetS. Coronary arteriolar dilation to adenosine (in vivo) and 2-chloroadenosine (2-CAD; in vitro) was similar between groups. In control arterioles, 2-CAD-mediated dilation was reduced only by selective A(2A) receptor inhibition, whereas only dual A(2A/2B) inhibition reduced this response in MetS arterioles. Arteriolar A(2B), but not A(2A), receptor protein expression was reduced by MetS. Blockade of voltage-dependent K+ (K(v)) channels reduced arteriolar sensitivity to 2-CAD in both groups, whereas ATP-sensitive K+ (K(ATP)) channel inhibition reduced sensitivity only in control arterioles. Our data indicate that the mechanisms mediating coronary arteriolar dilation to adenosine are altered in early-stage MetS prior to overt decrements in coronary vasodilator reserve.
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Affiliation(s)
- Shawn B Bender
- E102 Vet Med Bldg, Dept. of Biomedical Sciences, University of Missouri, Columbia, MO 65211, USA.
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Radicke S, Cotella D, Sblattero D, Ravens U, Santoro C, Wettwer E. The transmembrane beta-subunits KCNE1, KCNE2, and DPP6 modify pharmacological effects of the antiarrhythmic agent tedisamil on the transient outward current Ito. Naunyn Schmiedebergs Arch Pharmacol 2009; 379:617-26. [PMID: 19153714 DOI: 10.1007/s00210-008-0389-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 12/25/2008] [Indexed: 11/28/2022]
Abstract
Accessory beta-subunits modulate the pharmacology of ion channel blockers. The aim was to investigate differences in effects of the antiarrhythmic agent and open-channel blocker tedisamil on transient outward current I(to) (Kv4.3) when coexpressed with beta-subunits potassium voltage-gated channel, Isk-related family, member 1 (KCNE1), potassium voltage-gated channel, Isk-related family, member 2 (KCNE2), or dipeptidyl-aminopeptidase-like protein 6 (DPP6) which modulate I(to) kinetics. Tedisamil inhibited I(to) with IC(50) values of 16 microM for Kv4.3+KChIP2, 11 microM in the presence of KCNE1, and 14 microM for KCNE2. Values were higher in the presence of DPP6 or DPP6+KCNE2 (35 and 26 microM). K(d) values of tedisamil binding and rate constants were not affected by KCNE or DPP6. I(to) kinetics were accelerated by KCNE and DPP6, inactivation to a larger extent with DPP6. Tedisamil did not affect activation time course but apparently accelerated inactivation in all channel subunit combinations tested. Deletion of the intracellular domain of KCNE2 or DPP6 resulted in slowing of kinetics and increased tedisamil sensitivity (IC(50) 4 and 7 microM). It is concluded that apparent effects of DPP6 and deletion mutants (KCNE2 and DPP6) are due to the acceleration or slowing effects of the beta-subunits on I(to) kinetics.
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Affiliation(s)
- Susanne Radicke
- Department of Pharmacology and Toxicology, Medical Faculty, Dresden University of Technology, Fetscherstr. 74, 01307, Dresden, Germany
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Affiliation(s)
- Matthew R. Banghart
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (USA)
| | - Alexandre Mourot
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California 94720 (USA), Fax: (+1) 510 643-6791
| | - Doris L. Fortin
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California 94720 (USA), Fax: (+1) 510 643-6791
| | - Jennifer Z. Yao
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (USA)
| | - Richard H. Kramer
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California 94720 (USA), Fax: (+1) 510 643-6791
| | - Dirk Trauner
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (USA); University of Munich, Butenandtstr. 5-13 (F4.086), D-81377 Munich, Germany, Fax: (+49) (0)89 2180-77972
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