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Papay RS, Macdonald JD, Stauffer SR, Perez DM. Characterization of a novel positive allosteric modulator of the α 1A-Adrenergic receptor. CURRENT RESEARCH IN PHARMACOLOGY AND DRUG DISCOVERY 2022; 4:100142. [PMID: 36544813 PMCID: PMC9762201 DOI: 10.1016/j.crphar.2022.100142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/27/2022] [Accepted: 11/15/2022] [Indexed: 12/05/2022] Open
Abstract
α1-Adrenergic Receptors (ARs) are G-protein Coupled Receptors (GPCRs) that regulate the sympathetic nervous system via the binding and activation of norepinephrine (NE) and epinephrine (Epi). α1-ARs control various aspects of neurotransmission, cognition, cardiovascular functions as well as other organ systems. However, therapeutic drug development for these receptors, particularly agonists, has been stagnant due to unwanted effects on blood pressure regulation. We report the synthesis and characterization of the first positive allosteric modulator (PAM) for the α1-AR based upon the derivation of the α1A-AR selective imidazoline agonist, cirazoline. Compound 3 (Cmpd-3) binds the α1A-AR with high and low affinity sites (0.13pM; 54 nM) typical of GPCR agonists, and reverts to a single low affinity site of 100 nM upon the addition of GTP. Comparison of Cmpd-3 versus other orthosteric α1A-AR-selective imidazoline ligands reveal unique properties that are consistent with a type I PAM. Cmpd-3 is both conformationally and ligand-selective for the α1A-AR subtype. In competition binding studies, Cmpd-3 potentiates NE-binding at the α1A-AR only on the high affinity state of NE with no effect on the Epi-bound α1A-AR. Moreover, Cmpd-3 demonstrates signaling-bias and potentiates the NE-mediated cAMP response of the α1A-AR at nM concentrations with no effects on the NE-mediated inositol phosphate response. There are no effects of Cmpd-3 on the signaling at the α1B- or α1D-AR subtypes. Cmpd-3 displays characteristics of a pure PAM with no intrinsic agonist properties. Specific derivation of Cmpd-3 at the R1 ortho-position recapitulated PAM characteristics. Our results characterize the first PAM for the α1-AR and holds promise for a first-in-class therapeutic to treat various diseases without the side effect of increasing blood pressure intrinsic to classical orthosteric agonists.
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Affiliation(s)
- Robert S. Papay
- The Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH, 44195, USA
| | - Jonathan D. Macdonald
- Center for Therapeutics Discovery, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH, 44195, USA
| | - Shaun R. Stauffer
- Center for Therapeutics Discovery, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH, 44195, USA
| | - Dianne M. Perez
- The Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH, 44195, USA
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Li Y, Duan H, Yi J, Wang G, Cheng W, Feng L, Liu J. Kv4.2 phosphorylation by PKA drives Kv4.2 - KChIP2 dissociation, leading to Kv4.2 out of lipid rafts and internalization. Am J Physiol Cell Physiol 2022; 323:C190-C201. [PMID: 35508186 DOI: 10.1152/ajpcell.00307.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sympathetic regulation of the Kv4.2 transient outward potassium current is critical for the acute electrical and contractile response of the myocardium under physiological and pathological conditions. Previous studies have suggested that KChIP2, the key auxiliary subunit of Kv4 channels, is required for the sympathetic regulation of Kv4.2 current densities. Of interest, Kv4.2 and KChIP2, and key components mediating acute sympathetic signaling transduction are present in lipid rafts, which are profoundly involved in regulation of Ito densities in rat ventricular myocytes. However, little is known about the mechanisms of Kv4.2-raft association and its connection with acute sympathetic regulation. With the aid of high-resolution fluorescent microscope, we demonstrate that KChIP2 assists Kv4.2 localization in lipid rafts in HEK293 cells. Moreover, PKA-mediated Kv4.2 phosphorylation, the downstream signaling event of acute sympathetic stimulation, induced dissociation between Kv4.2 and KChIP2, resulting in Kv4.2 shifting out of lipid rafts in KChIP2-expressed HEK293.The mutation that mimics Kv4.2 phosphorylation by PKA similarly disrupted Kv4.2 interaction with KChIP2 and also decreased the surface stability of Kv4.2. The attenuated Kv4.2-KChIP2 interaction was also observed in native neonatal rat ventricular myocytes (NRVMs) upon acute adrenergic stimulation with phenylephrine (PE). Furthermore, PE accelerated internalization of Kv4.2 in native NRVMs, but disruption of lipid rafts dampens this reaction. In conclusion, KChIP2 contributes to targeting Kv4.2 to lipid rafts. Acute adrenergic stimulation induces Kv4.2 - KChIP2 dissociation, leading to Kv4.2 out of lipid rafts and internalization, reinforcing the critical role of Kv4.2-lipid raft association in the essential physiological response of Ito to acute sympathetic regulation.
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Affiliation(s)
- Ying Li
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Haixia Duan
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Jing Yi
- Department of Hepatobiliary and Pancreatic Surgery, Peking University Shenzhen Hospital, Shenzhen, Guangdong, China
| | - Gang Wang
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Wanwen Cheng
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Li Feng
- Department of Cardiology, Zhongshan People's Hospital, Zhongshan, Guangdong, China
| | - Jie Liu
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
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3
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Trum M, Islam MMT, Lebek S, Baier M, Hegner P, Eaton P, Maier LS, Wagner S. Inhibition of cardiac potassium currents by oxidation-activated protein kinase A contributes to early afterdepolarizations in the heart. Am J Physiol Heart Circ Physiol 2020; 319:H1347-H1357. [PMID: 33035439 PMCID: PMC7792712 DOI: 10.1152/ajpheart.00182.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Reactive oxygen species (ROS) have been shown to prolong cardiac action potential duration resulting in afterdepolarizations, the cellular basis of triggered arrhythmias. As previously shown, protein kinase A type I (PKA I) is readily activated by oxidation of its regulatory subunits. However, the relevance of this mechanism of activation for cardiac pathophysiology is still elusive. In this study, we investigated the effects of oxidation-activated PKA I on cardiac electrophysiology. Ventricular cardiomyocytes were isolated from redox-dead PKA-RI Cys17Ser knock-in (KI) and wild-type (WT) mice and exposed to H2O2 (200 µmol/L) or vehicle (Veh) solution. In WT myocytes, exposure to H2O2 significantly increased oxidation of the regulatory subunit I (RI) and thus its dimerization (threefold increase in PKA RI dimer). Whole cell current clamp and voltage clamp were used to measure cardiac action potentials (APs), transient outward potassium current (Ito) and inward rectifying potassium current (IK1), respectively. In WT myocytes, H2O2 exposure significantly prolonged AP duration due to significantly decreased Ito and IK1 resulting in frequent early afterdepolarizations (EADs). Preincubation with the PKA-specific inhibitor Rp-8-Br-cAMPS (10 µmol/L) completely abolished the H2O2-dependent decrease in Ito and IK1 in WT myocytes. Intriguingly, H2O2 exposure did not prolong AP duration, nor did it decrease Ito, and only slightly enhanced EAD frequency in KI myocytes. Treatment of WT and KI cardiomyocytes with the late INa inhibitor TTX (1 µmol/L) completely abolished EAD formation. Our results suggest that redox-activated PKA may be important for H2O2-dependent arrhythmias and could be important for the development of specific antiarrhythmic drugs.NEW & NOTEWORTHY Oxidation-activated PKA type I inhibits transient outward potassium current (Ito) and inward rectifying potassium current (IK1) and contributes to ROS-induced APD prolongation as well as generation of early afterdepolarizations in murine ventricular cardiomyocytes.
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Affiliation(s)
- M. Trum
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - M. M. T. Islam
- 2Department of Biochemistry and Molecular Biology, University of Dhaka, Bangladesh
- 3Department of Cardiology and Pneumology, University Medical Center Göttingen, Göttingen, Germany
| | - S. Lebek
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - M. Baier
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - P. Hegner
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - P. Eaton
- 4The William Harvey Research Institute, Charterhouse Square, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - L. S. Maier
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - S. Wagner
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
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4
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Saadeh K, Shivkumar K, Jeevaratnam K. Targeting the β-adrenergic receptor in the clinical management of congenital long QT syndrome. Ann N Y Acad Sci 2020; 1474:27-46. [PMID: 32901453 DOI: 10.1111/nyas.14425] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 05/10/2020] [Accepted: 06/09/2020] [Indexed: 01/01/2023]
Abstract
The long QT syndrome (LQTS) is largely treated pharmacologically with β-blockers, despite the role of sympathetic activity in LQTS being poorly understood. Using the trigger-substrate model of cardiac arrhythmias in this review, we amalgamate current experimental and clinical data from both animal and human studies to explain the mechanism of adrenergic stimulation and blockade on LQT arrhythmic risk and hence assess the efficacy of β-adrenoceptor blockade in the management of LQTS. In LQTS1 and LQTS2, sympathetic stimulation increases arrhythmic risk by enhancing early afterdepolarizations and transmural dispersion of repolarization. β-Blockers successfully reduce cardiac events by reducing these triggers and substrates; however, these effects are less marked in LQTS2 compared with LQTS1. In LQTS3, clinical and experimental investigations of the effects of sympathetic stimulation and β-blocker use have produced contradictory findings, resulting in significant clinical uncertainty. We offer explanations for these contradicting results relating to study sample size, the dose of the β-blocker administered associated with its off-target Na+ channel effects, as well as the type of β-blocker used. We conclude that the antiarrhythmic efficacy of β-blockers is a genotype-specific phenomenon, and hence the use of β-blockers in clinical practice should be genotype dependent.
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Affiliation(s)
- Khalil Saadeh
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,School of Clinical Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Kalyanam Shivkumar
- UCLA Cardiac Arrhythmia Centre, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
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5
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Martin RD, Sun Y, Bourque K, Audet N, Inoue A, Tanny JC, Hébert TE. Receptor- and cellular compartment-specific activation of the cAMP/PKA pathway by α 1-adrenergic and ETA endothelin receptors. Cell Signal 2018; 44:43-50. [PMID: 29329779 DOI: 10.1016/j.cellsig.2018.01.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 12/11/2017] [Accepted: 01/07/2018] [Indexed: 10/18/2022]
Abstract
The signalling functions of many G protein-coupled receptors (GPCRs) expressed in the myocardium are incompletely understood. Among these are the endothelin receptor (ETR) family and α1-adrenergic receptor (α1-AR), which are thought to couple to the G protein Gαq. In this study, we used transcriptome analysis to compare the signalling networks downstream of these receptors in primary neonatal rat cardiomyocytes. This analysis indicated increased expression of target genes of cAMP responsive element modulator (CREM) after 24 h treatment with the α1-AR agonist phenylephrine, but not the ETR agonist endothelin-1, suggesting a specific role for the α1-AR in promoting cAMP production in cardiomyocytes. To validate the difference observed between these two GPCRs, we used heterologous expression of the receptors and genetically encoded biosensors in HEK 293 cell lines. We validated that both α1A- and α1B-AR subtypes were able to lead to the accumulation of cAMP in response to phenylephrine in both the nucleus and cytoplasm in a Gαs-dependent manner. However, the ETR subtype ETA did not affect cAMP levels in either compartment. All three receptors were coupled to Gαq signalling as expected. Further, we showed that activation of PKA in different compartments was α1-AR subtype specific, with α1B-AR able to activate PKA in the cytoplasm and nucleus and α1A-AR only able to in the nucleus. We provide evidence for a pathway downstream of the α1-AR, and show that distinct pools of a receptor lead to differential activation of downstream effector proteins dependent on their cellular compartment.
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Affiliation(s)
- Ryan D Martin
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada
| | - Yalin Sun
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada
| | - Kyla Bourque
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada
| | - Nicolas Audet
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, Japan
| | - Jason C Tanny
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada.
| | - Terence E Hébert
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada.
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6
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Shen P, Feng X, Zhang X, Huang X, Liu S, Lu X, Li J, You J, Lu J, Li Z, Ye J, Liu P. SIRT6 suppresses phenylephrine-induced cardiomyocyte hypertrophy though inhibiting p300. J Pharmacol Sci 2016; 132:31-40. [DOI: 10.1016/j.jphs.2016.03.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 03/23/2016] [Accepted: 03/25/2016] [Indexed: 01/01/2023] Open
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7
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Peng SY, Zhuang QX, Zhang YX, Zhang XY, Wang JJ, Zhu JN. Excitatory effect of norepinephrine on neurons in the inferior vestibular nucleus and the underlying receptor mechanism. J Neurosci Res 2016; 94:736-48. [PMID: 27121461 DOI: 10.1002/jnr.23745] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 02/26/2016] [Accepted: 03/16/2016] [Indexed: 12/20/2022]
Abstract
The central noradrenergic system, originating mainly from the locus coeruleus in the brainstem, plays an important role in many physiological functions, including arousal and attention, learning and memory, anxiety, and nociception. However, little is known about the roles of norepinephrine (NE) in somatic motor control. Therefore, using extracellular recordings on rat brainstem slices and quantitative real-time RT-PCR, we investigate the effect and mechanisms of NE on neuronal activity in the inferior vestibular nucleus (IVN), the largest nucleus in the vestibular nuclear complex, which holds an important position in integration of information signals controlling body posture. Here, we report that NE elicits an excitatory response on IVN neurons in a concentration-dependent manner. Activation of α1 - and β2 -adrenergic receptors (ARs) induces an increase in firing rate of IVN neurons, whereas activation of α2 -ARs evokes a decrease in firing rate of IVN neurons. Therefore, the excitation induced by NE on IVN neurons is a summation of the excitatory components mediated by coactivation of α1 - and β2 -ARs and the inhibitory component induced by α2 -ARs. Accordingly, α1 -, α2 -, and β2 -AR mRNAs are expressed in the IVN. Although β1 -AR mRNAs are also detected, they are not involved in the direct electrophysiological effect of NE on IVN neurons. All these results demonstrate that NE directly regulates the activity of IVN neurons via α1 -, α2 -, and β2 -ARs and suggest that the central noradrenergic system may actively participate in IVN-mediated vestibular reflexes and postural control. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Shi-Yu Peng
- State Key Laboratory of Pharmaceutical Biotechnology and Department of Biological Science and Technology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Qian-Xing Zhuang
- State Key Laboratory of Pharmaceutical Biotechnology and Department of Biological Science and Technology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Yong-Xiao Zhang
- State Key Laboratory of Pharmaceutical Biotechnology and Department of Biological Science and Technology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Xiao-Yang Zhang
- State Key Laboratory of Pharmaceutical Biotechnology and Department of Biological Science and Technology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Jian-Jun Wang
- State Key Laboratory of Pharmaceutical Biotechnology and Department of Biological Science and Technology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Jing-Ning Zhu
- State Key Laboratory of Pharmaceutical Biotechnology and Department of Biological Science and Technology, School of Life Sciences, Nanjing University, Nanjing, China
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8
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Gallego M, Alday A, Alonso H, Casis O. Adrenergic regulation of cardiac ionic channels: role of membrane microdomains in the regulation of kv4 channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:692-9. [PMID: 23811359 DOI: 10.1016/j.bbamem.2013.06.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 06/13/2013] [Accepted: 06/17/2013] [Indexed: 11/18/2022]
Abstract
The heart must constantly adapt its activity to the needs of the body. In any potentially dangerous or physically demanding situation the activated sympathetic nervous system leads a very fast cardiac response. Under these circumstances, α1-adrenergic receptors activate intracellular signaling pathways that finally phosphorylate the caveolae-located subpopulation of Kv4 channels and reduce the transient outward K(+) current (Ito) amplitude. This reduction changes the shape of the cardiac action potential and makes the plateau phase to start at higher voltages. This means that there are more calcium ions entering the myocyte and the result is an increase in the strength of the contraction. However, an excessive reduction of Ito could dangerously prolong action potential duration and this could cause arrhythmias when the heart rate is high. This excessive current reduction does not occur because there is a second population of Ito channels located in non-caveolar membrane rafts that are not accessible for α1-AR mediated regulation. Thus, the location of the components of a given transduction signaling pathway in membrane domains determines the correct and safe behavior of the heart. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
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Affiliation(s)
- Mónica Gallego
- Lascaray Research Center, University of the Basque Country (UPV/EHU), Av. Miguel de Unamuno 3, 01006 Vitoria, Spain; Departamento de Fisiología, Facultad de Farmacia, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria, Spain.
| | - Aintzane Alday
- Departamento de Fisiología, Facultad de Farmacia, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria, Spain.
| | - Hiart Alonso
- Lascaray Research Center, University of the Basque Country (UPV/EHU), Av. Miguel de Unamuno 3, 01006 Vitoria, Spain; Departamento de Fisiología, Facultad de Farmacia, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria, Spain.
| | - Oscar Casis
- Lascaray Research Center, University of the Basque Country (UPV/EHU), Av. Miguel de Unamuno 3, 01006 Vitoria, Spain; Departamento de Fisiología, Facultad de Farmacia, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria, Spain.
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9
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Zhou Y, Gong G, Yang W, Wang Y, Xu J, Xu Y. The cardioprotective effect of TG-6, a newly synthesized compound, on ischemia-reperfusion injury in rats. Eur J Pharmacol 2012; 683:190-6. [PMID: 22425651 DOI: 10.1016/j.ejphar.2012.01.047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 01/22/2012] [Accepted: 01/28/2012] [Indexed: 10/28/2022]
Abstract
We tested 3-nitro-4-((4-(2,3,4-trimethoxybenzyl)piperazin-1-yl)methyl) benzoylguanidine tartrate (TG-6) which is combinated of two known cardioprotective agents cariporide and trimetazidine, whether additively to reduce ischemia-reperfusion injury in rats. Using models of in vitro perfusion (Langendorff system) and in vivo open chest left anterior descending coronary artery ligation causing ischemia-reperfusion injury. We also used Fura-2 to measure the cytosolic Ca²⁺ concentrations ([Ca²⁺]i) in cardiomyocytes, western blot analysis the protein expression of Kv1.4, Kv4.2, Kv4.3 in myocardial ischemia-reperfusion rats. TG-6 improved the cardiac function in both in vivo and in vitro models, lowered Lactate Dehydrogenase (LDH), Creatine Kinase (CK), Malodialdehyed (MDA) activity while enhanced Superoxide Dismutase (SOD) activity. High dose of TG-6 improved the hypoxia injury of cardiomyocytes induced by sodium dithionite (Na₂S₂O₄), enhanced the viability and decreased the [Ca²⁺]i. It also down-regulated the expression of Kv1.4 and increased the expression of Kv4.2 and Kv4.3, so it might through regulating the expression of the transient outward potassium current (Ito) to improve the cardiac function.
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Affiliation(s)
- Yi Zhou
- Department of Pharmacology, China Pharmaceutical University, Nanjing, China
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10
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Harvey RD, Calaghan SC. Caveolae create local signalling domains through their distinct protein content, lipid profile and morphology. J Mol Cell Cardiol 2011; 52:366-75. [PMID: 21782827 DOI: 10.1016/j.yjmcc.2011.07.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 06/21/2011] [Accepted: 07/07/2011] [Indexed: 01/02/2023]
Abstract
Compartmentation of signalling allows multiple stimuli to achieve diverse cellular responses with only a limited pool of second messengers. This spatial control of signalling is achieved, in part, by cellular structures which bring together elements of a particular cascade. One such structure is the caveola, a flask-shaped lipid raft. Caveolae are well-recognised as signalosomes, platforms for assembly of signalling complexes of receptors, effectors and their targets, which can facilitate efficient and specific cellular responses. Here we extend this simple model and present evidence to show how the protein and lipid profiles of caveolae, as well as their characteristic morphology, define their roles in creating local signalling domains in the cardiac myocyte. This article is part of a Special Issue entitled "Local Signaling in Myocytes."
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Affiliation(s)
- Robert D Harvey
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA
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11
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Modulation of potassium channels via the α1B-adrenergic receptor in human osteoblasts. Neurosci Lett 2010; 485:102-6. [DOI: 10.1016/j.neulet.2010.08.073] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Revised: 08/11/2010] [Accepted: 08/25/2010] [Indexed: 12/29/2022]
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12
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Zhang L, Xu CQ, Hong Y, Zhang JL, Liu Y, Zhao M, Cao YX, Lu YJ, Yang BF, Shan HL. Propranolol regulates cardiac transient outward potassium channel in rat myocardium via cAMP/PKA after short-term but not after long-term ischemia. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:63-71. [PMID: 20499050 DOI: 10.1007/s00210-010-0520-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 04/25/2010] [Indexed: 10/19/2022]
Abstract
It was recently suggested that the antiarrhythmic effect of propranolol, a ss-adrenoceptor antagonist, on ischemic myocardium includes restoration of I(K1) current and Cx43 conductance; however, little is known whether effects on the transient outward current I(to) contribute. A model of myocardial infarction (MI) by ligating the left anterior descending coronary artery was established. Propranolol was given 1 h or daily for 3 months, whole-cell patch-clamp techniques were used to measure I(to). Kv4.2 and PKA levels were analyzed by Western blot and cAMP level was determined by radioimmunoassay. The results showed that propranolol decreased the incidence of arrhythmias induced by acute ischemia and mortality in 3 month MI rats. Propranolol restored the diminished I(to) density and Kv4.2 protein in MI hearts. In addition, neonatal cardiomyocyte pretreatment with propranolol or administrated after hypoxia can resume I(to) density. cAMP/PKA was enhanced in acute MI, the reason of decreased Kv4.2 expression. Treatment with propranolol prevented the increased cAMP/PKA in 1 h MI, whereas propranolol had little effect on decreased cAMP/PKA in 3 months MI. This study demonstrated that both short- and long-term propranolol administrations protect cardiomyocytes against arrhythmias and mortality caused by cardiac ischemia; the involvement of cAMP/PKA signal pathway in the regulation of propranolol on I(to) acted differently along with the ischemic progression.
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Affiliation(s)
- Li Zhang
- Department of Pharmacology, the State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
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13
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Sun Q, Zang WJ, Chen C. Growth hormone secretagogues reduce transient outward K+ current via phospholipase C/protein kinase C signaling pathway in rat ventricular myocytes. Endocrinology 2010; 151:1228-35. [PMID: 20056829 DOI: 10.1210/en.2009-0877] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Endogenous ghrelin and its synthetic counterpart hexarelin are peptide GH secretagogues (GHS) that exert a positive ionotropic effect in the cardiovascular system. The mechanism by which GHS modulate cardiac electrophysiology properties to alter myocyte contraction is poorly understood. In the present study, we examined whether GHS regulates the transient outward potassium current (I(to)) as well as the putative intracellular signaling cascade responsible for such regulation. GHS and experimental agents were applied locally onto freshly isolated adult Sprague-Dawley rat ventricular myocytes and action potential morphology and I(to) was recorded using nystatin-perforated whole-cell patch-clamp recording technique. Under current clamp, ghrelin and hexarelin (10 nm) significantly prolonged action potential duration. Under voltage clamp, hexarelin and ghrelin inhibited I(to) in a concentration-dependent manner. This inhibition was abolished in the presence of the GHS receptor (GHS-R) antagonist [D-Lys(3)]GH-releasing peptide-6 (10 microm) and GHS-R1a-specific antagonist BIM28163 (1 microm). GHS-induced I(to) inhibition was totally reversed by the phospholipase C inhibitor U73122 (5 microm) and protein kinase C inhibitors GO6983 (1 microm) and calphostin C (0.1 microm) but not by the cAMP antagonist Rp-cAMP (100 microm) or the PKA inhibitor H89 (1 microm). We conclude that hexarelin and ghrelin activate phospholipase C and protein kinase C signaling cascade through the stimulation of the GHS-R, resulting in a decrease in the I(to) current and subsequent prolongation of action potential duration.
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Affiliation(s)
- Qiang Sun
- Department of Pharmacology, School of Medicine, Xi'an Jiaotong University, Xi'an 710061, China
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14
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Docherty JR. Subtypes of functional alpha1-adrenoceptor. Cell Mol Life Sci 2010; 67:405-17. [PMID: 19862476 PMCID: PMC11115521 DOI: 10.1007/s00018-009-0174-4] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 09/11/2009] [Accepted: 10/05/2009] [Indexed: 11/29/2022]
Abstract
In this review, subtypes of functional alpha1-adrenoceptor are discussed. These are cell membrane receptors, belonging to the seven-transmembrane-spanning G-protein-linked family of receptors, which respond to the physiological agonist noradrenaline. alpha1-Adrenoceptors can be divided into alpha1A-, alpha1B- and alpha1D-adrenoceptors, all of which mediate contractile responses involving Gq/11 and inositol phosphate turnover. A fourth alpha1-adrenoceptor, the alpha1L-, represents a functional phenotype of the alpha1A-adrenoceptor. alpha1-Adrenoceptor subtype knock-out mice have refined our knowledge of the functions of alpha-adrenoceptor subtypes, particuarly as subtype-selective agonists and antagonists are not available for all subtypes. alpha1-Adrenoceptors function as stimulatory receptors involved particularly in smooth muscle contraction, especially contraction of vascular smooth muscle, both in local vasoconstriction and in the control of blood pressure and temperature, and contraction of the prostate and bladder neck. Central actions are now being elucidated.
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MESH Headings
- Animals
- Blood Pressure/physiology
- Body Temperature Regulation
- Drug Inverse Agonism
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- Inositol Phosphates/metabolism
- Mice
- Mice, Knockout
- Muscle, Smooth/physiology
- Muscle, Smooth, Vascular/physiology
- Receptors, Adrenergic, alpha-1/classification
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Adrenergic, alpha-1/physiology
- Second Messenger Systems/physiology
- Vasoconstriction/physiology
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Affiliation(s)
- James R Docherty
- Department of Physiology, Royal College of Surgeons in Ireland, 123, St. Stephen's Green, Dublin 2, Ireland.
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15
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He YL, Zhan XQ, Yang G, Sun J, Mei YA. Amoxapine inhibits the delayed rectifier outward K+ current in mouse cortical neurons via cAMP/protein kinase A pathways. J Pharmacol Exp Ther 2009; 332:437-45. [PMID: 19915071 DOI: 10.1124/jpet.109.159160] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ion channels are known to be modulated by antidepressant drugs, but the molecular mechanisms are not known. We have shown that the antidepressant drug amoxapine suppresses rectifier outward K(+) (I(K)) currents in mouse cortical neurons. At a concentration of 10 to 500 muM, amoxapine reversibly inhibited I(K) in a dose-dependent manner and modulated both steady-state activation and inactivation properties. The application of forskolin or dibutyryl cAMP mimicked the inhibitory effect of amoxapine on I(K) and abolished further inhibition by amoxapine. N-[2-(p-Bromocinnamylamino)ethyl]-5-iso-quinolinesulphonamide (H-89), a protein kinase A (PKA) inhibitor, augmented I(K) amplitudes and completely eliminated amoxapine inhibition of I(K). Amoxapine was also found to significantly increase intracellular cAMP levels. The effects of amoxapine on I(K) were abolished by preincubation with 5-hydroxytryptamine (5-HT) and the antagonists of 5-HT(2) receptor. Moreover, intracellular application of guanosine 5'-[gammathio]-triphosphate increased I(K) amplitudes and prevented amoxapine-induced inhibition. The selective Kv2.1 subunit blocker Jingzhaotoxin-III reduced I(K) amplitudes by 30% and also significantly abolished the inhibitory effect of amoxapine. Together these results suggest that amoxapine inhibits I(K) in mouse cortical neurons by cAMP/PKA-dependent pathway associated with the 5-HT receptor, and suggest that the Kv2.1 alpha-subunit may be the target for this inhibition.
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Affiliation(s)
- Yan-Lin He
- nstitutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
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16
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Buchholz BM, Chanthaphavong RS, Bauer AJM. Nonhemopoietic cell TLR4 signaling is critical in causing early lipopolysaccharide-induced ileus. THE JOURNAL OF IMMUNOLOGY 2009; 183:6744-53. [PMID: 19846874 DOI: 10.4049/jimmunol.0901620] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Endotoxin-mediated ileus is poorly understood. Our objective was to mechanistically investigate the role of cell-specific TLR4 expression/signaling in causing gastrointestinal dysmotility. TLR4 chimeras and CSF-1-dependent macrophage-deficient mice were subjected to i.p. ultrapure (UP)-LPS (5 mg/kg). At 6 h, gastric emptying and gastrointestinal transit assessed in vivo motility, and jejunal circular muscle contractility was measured in vitro. Muscularis infiltration of neutrophils and monocytes were counted, and intestinal muscularis inflammatory mediators were quantified by quantitative PCR. Demonstrating TLR4 dependency, UP-LPS-induced gastric stasis and ileus of TLR4(WT) mice were absent in mutant TLR4(LPS-d) mice. Unexpectedly, engraftment of TLR4-mutant bone marrow into TLR4-competent mice (bmTLR4(LPS-d)/TLR4(WT)) exhibited a significant transit delay to UP-LPS similar to bmTLR4(WT)/TLR4(WT) mice. CSF-1(-/-) mice were not protected from ileus. Contrary, UP-LPS-treated bmTLR4(WT)/TLR4(LPS-d) and bmTLR4(LPS-d)/TLR4(LPS-d) mice had normal transit. No leukocytic infiltration was detected at 6 h. Spontaneous jejunal contractions were markedly suppressed in UP-LPS-treated TLR4-competent mice, but bethanechol-stimulated contractions were not altered by UP-LPS in any group. UP-LPS-induced inflammatory mRNAs in a TLR4-dependent manner, but TLR4 mRNA itself was not significantly altered. In chimera mice, UP-LPS induction of IL-1beta and IL-10 were hemopoietic dependent, and GM-CSF was nonhemopoietic dependent, whereas IL-6 and inducible NO synthase were derived from both cell types. Hemopoietic and nonhemopoietic cells contribute to TLR4-sensitive muscularis inflammatory signaling, but nonhemopoietic TLR4 signaling plays an exclusive primary role in causing functional UP-LPS-induced gastric stasis and ileus. Direct LPS suppression of spontaneous contractility participates in mediating early TLR4-transduced dysmotility.
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Affiliation(s)
- Bettina M Buchholz
- Department of Medicine/Gastroenterology, University of Pittsburgh, Pittsburgh, PA 15261, USA
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17
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Han J, Zou Z, Zhu C, Deng J, Wang J, Ran X, Shi C, Ai G, Li R, Cheng T, Su Y. DNA synthesis of rat bone marrow mesenchymal stem cells through alpha1-adrenergic receptors. Arch Biochem Biophys 2009; 490:96-102. [PMID: 19695215 DOI: 10.1016/j.abb.2009.08.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 08/06/2009] [Accepted: 08/12/2009] [Indexed: 11/16/2022]
Abstract
Multipotential bone marrow mesenchymal stem cells (BMSCs) are important in maintaining the microenvironment of the bone marrow (BM). Sympathetic nerves histologically innervate the BM; however, their role remains unclear. In this study, the effects of norepinephrine on DNA synthesis and the related signaling molecules involved in rBMSCs were examined. mRNA levels of the alpha1-adrenergic receptor subtypes increased following norepinephrine stimulation (10(-5) M for 30 min). DNA synthesis increased in dose- and time-dependent manners as determined by [(3)H]thymidine incorporation. Intracellular Ca(2+) concentration and translocation of protein kinase C from the cytosol to the membrane were also found to be elevated in rBMSCs. Phentolamine was able to suppress translocation of PKC. Norepinephrine also induced phosphorylation of ERK1/2, which was prevented by staurosporine treatment. Pretreatment with PD98059 inhibited ERK1/2 phosphorylation and DNA synthesis in rBMSCs. These findings indicate that norepinephrine stimulates DNA synthesis via alpha1-adrenergic receptors and downstream Ca(2+)/PKC and ERK1/2 activation in rBMSCs.
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Affiliation(s)
- Jing Han
- Institute of Combined Injury, State Key Laboratory of Trauma, Burns and Combined Injury, College of Preventive Medicine, Third Military Medical University, Chongqing 400038, China
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18
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Niwa N, Nerbonne JM. Molecular determinants of cardiac transient outward potassium current (I(to)) expression and regulation. J Mol Cell Cardiol 2009; 48:12-25. [PMID: 19619557 DOI: 10.1016/j.yjmcc.2009.07.013] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 06/25/2009] [Accepted: 07/10/2009] [Indexed: 12/21/2022]
Abstract
Rapidly activating and inactivating cardiac transient outward K(+) currents, I(to), are expressed in most mammalian cardiomyocytes, and contribute importantly to the early phase of action potential repolarization and to plateau potentials. The rapidly recovering (I(t)(o,f)) and slowly recovering (I(t)(o,s)) components are differentially expressed in the myocardium, contributing to regional heterogeneities in action potential waveforms. Consistent with the marked differences in biophysical properties, distinct pore-forming (alpha) subunits underlie the two I(t)(o) components: Kv4.3/Kv4.2 subunits encode I(t)(o,f), whereas Kv1.4 encodes I(t)(o,s), channels. It has also become increasingly clear that cardiac I(t)(o) channels function as components of macromolecular protein complexes, comprising (four) Kvalpha subunits and a variety of accessory subunits and regulatory proteins that influence channel expression, biophysical properties and interactions with the actin cytoskeleton, and contribute to the generation of normal cardiac rhythms. Derangements in the expression or the regulation of I(t)(o) channels in inherited or acquired cardiac diseases would be expected to increase the risk of potentially life-threatening cardiac arrhythmias. Indeed, a recently identified Brugada syndrome mutation in KCNE3 (MiRP2) has been suggested to result in increased I(t)(o,f) densities. Continued focus in this area seems certain to provide new and fundamentally important insights into the molecular determinants of functional I(t)(o) channels and into the molecular mechanisms involved in the dynamic regulation of I(t)(o) channel functioning in the normal and diseased myocardium.
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Affiliation(s)
- Noriko Niwa
- Department of Developmental Biology, Washington University School of Medicine, 660 South Euclid Avenue, Box 8103, St. Louis, MO 63110-1093, USA
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19
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Zhang M, Fei XW, He YL, Yang G, Mei YA. Bradykinin inhibits the transient outward K+ current in mouse Schwann cells via the cAMP/PKA pathway. Am J Physiol Cell Physiol 2009; 296:C1364-72. [PMID: 19339513 DOI: 10.1152/ajpcell.00014.2009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bradykinin (BK) is an endogenous peptide with diverse biological actions and is considered to be an important mediator of the inflammatory response in both the peripheral and the central nervous systems. BK has attracted recent interest as a potential mediator of K(+) conductance, Cl(-) channels, and Ca(2+)-activated K(+) channels. However, few reports have associated BK with the voltage-gated K(+) current. In this study, we demonstrated that BK suppressed the transient outward potassium current (I(A)) in mouse Schwann cells using whole cell recording techniques. At a concentration of 0.1 muM to 5 muM, BK reversibly inhibited I(A) in a dose-dependent manner with the modulation of steady-state activation and inactivation properties. The effect of BK on I(A) current was abolished after preincubation with a B(2) receptor antagonist but could not be eliminated by B(1) receptor antagonist. Intracellular application of GTP-gammaS induced an irreversible decrease in I(A), and the inhibition of G(s) using NF449 provoked a gradual augmentation in I(A) and eliminated the BK-induced effect on I(A,) while the G(i)/(o) antagonist NF023 did not. The application of forskolin or dibutyryl-cAMP mimicked the inhibitory effect of BK on I(A) and abolished the BK-induced effect on I(A). H-89, an inhibitor of PKA, augmented I(A) amplitude and completely eliminated the BK-induced inhibitory effect on I(A). In contrast, activation of PKC by PMA augmented I(A) amplitude. A cAMP assay revealed that BK significantly increased intracellular cAMP level. It is therefore concluded that BK inhibits the I(A) current in Schwann cells by cAMP/PKA-dependent pathways via activation of the B(2) receptor.
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Affiliation(s)
- Man Zhang
- Institute of Brain Science, School of Life Sciences and State Key Lab of Medical Neurobiology, Fudan University, Shanghai 200433, P.R. China
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20
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El-Haou S, Balse E, Neyroud N, Dilanian G, Gavillet B, Abriel H, Coulombe A, Jeromin A, Hatem SN. Kv4 potassium channels form a tripartite complex with the anchoring protein SAP97 and CaMKII in cardiac myocytes. Circ Res 2009; 104:758-69. [PMID: 19213956 DOI: 10.1161/circresaha.108.191007] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Membrane-associated guanylate kinase (MAGUK) proteins are major determinants of the organization of ion channels in the plasma membrane in various cell types. Here, we investigated the interaction between the MAGUK protein SAP97 and cardiac Kv4.2/3 channels, which account for a large part of the outward potassium current, I(to), in heart. We found that the Kv4.2 and Kv4.3 channels C termini interacted with SAP97 via a SAL amino acid sequence. SAP97 and Kv4.3 channels were colocalized in the sarcolemma of cardiomyocytes. In CHO cells, SAP97 clustered Kv4.3 channels in the plasma membrane and increased the current independently of the presence of KChIP and dipeptidyl peptidase-like protein-6. Suppression of SAP97 by using short hairpin RNA inhibited I(to) in cardiac myocytes, whereas its overexpression by using an adenovirus increased I(to). Kv4.3 channels without the SAL sequence were no longer regulated by Ca2+/calmodulin kinase (CaMK)II inhibitors. In cardiac myocytes, pull-down and coimmunoprecipitation assays showed that the Kv4 channel C terminus, SAP97, and CaMKII interact together, an interaction suppressed by SAP97 silencing and enhanced by SAP97 overexpression. In HEK293 cells, SAP97 silencing reproduced the effects of CaMKII inhibition on current kinetics and suppressed Kv4/CaMKII interactions. In conclusion, SAP97 is a major partner for surface expression and CaMKII-dependent regulation of cardiac Kv4 channels.
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Affiliation(s)
- Saïd El-Haou
- UMRS-956, Faculté de Médecine Pierre-Marie Curie, 91 Boulevard de l'Hôpital, 75013 Paris, France
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21
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Gallego M, Alday A, Urrutia J, Casis O. Transient outward potassium channel regulation in healthy and diabetic heartsThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 1 of a 2-part Special Issue). Can J Physiol Pharmacol 2009; 87:77-83. [DOI: 10.1139/y08-106] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Diabetic patients have a higher incidence of cardiac arrhythmias, including ventricular fibrillation and sudden death, and show important alterations in the electrocardiogram, most of these related to the repolarization. In myocytes isolated from diabetic hearts, the transient outward K+ current (Ito) is the repolarizing current that is mainly affected. Type 1 diabetes alters Ito at 3 levels: the recovery of inactivation, the responsiveness to physiologic regulators, and the functional expression of the channel. Diabetes slows down Ito recovery of inactivation because it triggers the switching from fast-recovering Kv4.x channels to the slow-recovering Kv1.4. Diabetic animals also have decreased responsiveness of Ito towards the sympathetic nervous system; thus, the diabetic heart develops a resistance to its physiologic regulator. Finally, diabetes impairs support of various trophic factors required for the functional expression of the channel and reduces Ito amplitude by decreasing the amount of Kv4.2 and Kv4.3 proteins.
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Affiliation(s)
- Mónica Gallego
- Department of Physiology, School of Pharmacy, Universidad del País Vasco, P.O. Box 699, Bilbao 48080, Spain
| | - Aintzane Alday
- Department of Physiology, School of Pharmacy, Universidad del País Vasco, P.O. Box 699, Bilbao 48080, Spain
| | - Janire Urrutia
- Department of Physiology, School of Pharmacy, Universidad del País Vasco, P.O. Box 699, Bilbao 48080, Spain
| | - Oscar Casis
- Department of Physiology, School of Pharmacy, Universidad del País Vasco, P.O. Box 699, Bilbao 48080, Spain
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22
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Kim MO, Na SI, Lee MY, Heo JS, Han HJ. Epinephrine increases DNA synthesis via ERK1/2s through cAMP, Ca(2+)/PKC, and PI3K/Akt signaling pathways in mouse embryonic stem cells. J Cell Biochem 2008; 104:1407-20. [PMID: 18275042 DOI: 10.1002/jcb.21716] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Epinephrine is a catecholamine that plays important roles in regulating a wide variety of physiological systems by acting through the adrenergic receptors (ARs). The cellular responses to AR stimulation are mediated through various signaling pathways. Therefore, this study examined the effects of epinephrine on DNA synthesis and related signaling molecules in mouse embryonic stem cells (ESCs). Epinephrine increased DNA synthesis in a dose- and time-dependent manner, as determined by the level of [(3)H]-thymidine incorporation. AR subtypes (alpha1(A), alpha2(A), beta1, beta2, and beta3) were expressed in mouse ESCs and their expression levels were increased by epinephrine. In this experiment, epinephrine increased cAMP levels, intracellular Ca(2+) concentration ([Ca(2+)](i)), and translocation of protein kinase C (PKC) from the cytosol to the membrane compartment. In addition, we observed Akt phosphorylation in response to epinephrine; this was stimulated by phosphorylation of the epidermal growth factor receptor (EGFR). Epinephrine also induced phosphorylation of ERK1/2 (p44/42 MAPKs), while inhibition of PKC or Akt blocked this phosphorylation. Epinephrine increased the mRNA levels of proto-oncogenes (c-fos, c-jun, c-myc), while inhibition of ERK1/2 decreased these mRNA levels. In experiments aimed at examining the involvement of cell cycle regulatory proteins, epinephrine increased the levels of cyclin E/cyclin-dependent kinase 2 (CDK2) and cyclin D1/cyclin-dependent kinase 4 (CDK4). In conclusion, epinephrine stimulates DNA synthesis via ERK1/2 through cAMP, Ca(2+)/PKC, and PI3K/Akt signaling pathways in mouse ESCs.
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Affiliation(s)
- Mi Ok Kim
- Department of Veterinary Physiology, Biotherapy Human Resources Center (BK 21), College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Korea
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Lu Z, Abe JI, Taunton J, Lu Y, Shishido T, McClain C, Yan C, Xu SP, Spangenberg TM, Xu H. Reactive oxygen species-induced activation of p90 ribosomal S6 kinase prolongs cardiac repolarization through inhibiting outward K+ channel activity. Circ Res 2008; 103:269-78. [PMID: 18599872 DOI: 10.1161/circresaha.107.166678] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
p90 ribosomal S6 kinase (p90RSK) is activated in cardiomyopathies caused by conditions such as ischemia/reperfusion injury and diabetes mellitus in which prolongation of cardiac repolarization and frequent arrhythmias are common. Molecular mechanisms underlying the electric remodeling in cardiac diseases are largely unknown. In the present study, we determined the role of p90RSK activation in the modulation of voltage-gated K+ channel activity determining cardiac repolarization. Mice with increased cardiac p90RSK activity due to transgenic expression of p90RSK (p90RSK-Tg) had prolongation of QT intervals and of ventricular myocyte action potential durations. Fast transient outward K+ current (I(to,f)), slow delayed outward K+ current (I(K,slow)), and steady-state K+ current (I(SS)) were significantly decreased in p90RSK-Tg mouse ventricular myocytes. mRNA levels of Kv4.3, Kv4.2, Kv1.5, Kv2.1, and KChIP2 from ventricles between p90RSK-Tg and nontransgenic littermate control mice were similar, as assessed by quantitative reverse transcriptase-polymerase chain reaction, indicating that p90RSK regulates voltage-gated K+ channels through posttranslational modification. Kv4.3- and Kv1.5- rather than Kv4.2- and Kv2.1-encoded channels in HEK 293 cells were inhibited by p90RSK. In vitro phosphorylation analysis showed that Kv4.3 was phosphorylated by p90RSK at 2 conserved sites, Ser516 and Ser550. p90RSK expression significantly inhibited Kv4.3- and Kv4.3 and KChIP2-encoded channel activities in HEK 293 cells, whereas p90RSK's effects were blocked by amino acid mutation(s) at phosphorylation site(s) in Kv4.3. Hydrogen peroxide, a mediator of induced cardiac p90RSK activation in ischemia/reperfusion injury and diabetes mellitus, had effects similar to those of p90RSK on Kv4.3- or Kv4.3- and KChIP2-encoded channels. Fluoromethylketone, a specific p90RSK inhibitor, abolished hydrogen peroxide effects. These findings indicate that p90RSK activation is critical for reactive oxygen species-mediated inhibition of voltage-gated K+ channel activity and leads to prolongation of cardiac repolarization.
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Affiliation(s)
- Zhibo Lu
- Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USA
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24
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Medei EH, Nascimento JHM, Pedrosa RC, Barcellos L, Masuda MO, Sicouri S, Elizari MV, de Carvalho ACC. Antibodies with beta-adrenergic activity from chronic chagasic patients modulate the QT interval and M cell action potential duration. Europace 2008; 10:868-76. [PMID: 18515284 PMCID: PMC2666256 DOI: 10.1093/europace/eun138] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
AIMS The aim of this study was to investigate whether the sera from chronic chagasic patients (CChPs) with beta-1 adrenergic activity (Ab-beta) can modulate ventricular repolarization. Beta-adrenergic activity has been described in CChP. It increases the L-type calcium current and heart rate in isolated hearts, but its effects on ventricular repolarization has not been described. METHODS AND RESULTS In isolated rabbit hearts, under pacing condition, QT interval was measured under Ab-beta perfusion. Beta-adrenergic activity was also tested in guinea pig ventricular M cells. Furthermore, the immunoglobulin fraction (IgG-beta) of the Ab-beta was tested on Ito, ICa, and Iks currents in rat, rabbit, and guinea pig myocytes, respectively. Beta-adrenergic activity shortened the QT interval. This effect was abolished in the presence of propranolol. In addition, sera from CChP without beta-adrenergic activity (Ab-beta) did not modulate QT interval. The M cell action potential duration (APD) was reversibly shortened by Ab-beta. Atenolol inhibited this effect of Ab-beta, and Ab- did not modulate the AP of M cells. Ito was not modulated by isoproterenol nor by IgG-beta. However, IgG-beta increased ICa and IKs. CONCLUSION The shortening of the QT interval and APD in M cells and the increase of IKs and ICa induced by IgG-beta contribute to repolarization changes that may trigger malignant ventricular arrhythmias observed in patients with chronic chagasic or idiopathic cardiomyopathy.
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Affiliation(s)
- Emiliano Horacio Medei
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Bloco G-CCS, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ 21949-900, Brasil.
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25
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Liu YY, Cai WF, Yang HZ, Cui B, Chen ZR, Liu HZ, Yan J, Jin W, Yan HM, Xin BM, Yuan B, Hua F, Hu ZW. Bacillus Calmette-Guérin and TLR4 Agonist Prevent Cardiovascular Hypertrophy and Fibrosis by Regulating Immune Microenvironment. THE JOURNAL OF IMMUNOLOGY 2008; 180:7349-57. [DOI: 10.4049/jimmunol.180.11.7349] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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26
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IMANI ALIREZA, FAGHIHI MAHDIEH, SADR SAYYEDSHAHABEDDIN, KESHAVARZ MANSOOR, NIARAKI SOMAYEHSADEGHI. Noradrenaline Reduces Ischemia-Induced Arrhythmia in Anesthetized Rats: Involvement of α1-Adrenoceptors and Mitochondrial KATPChannels. J Cardiovasc Electrophysiol 2008; 19:309-15. [DOI: 10.1111/j.1540-8167.2007.01031.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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27
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Borchert GH, Giggey M, Kolar F, Wong TM, Backx PH, Escriba PV. 2-hydroxyoleic acid affects cardiomyocyte [Ca2+]i transient and contractility in a region-dependent manner. Am J Physiol Heart Circ Physiol 2008; 294:H1948-55. [PMID: 18296566 DOI: 10.1152/ajpheart.01209.2007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Monounsaturated fatty acids such as oleic acid are cardioprotective, modify the physicochemical properties of cardiomyocyte membranes, and affect the electrical stability of these cells by regulating the conductance of ion channels. We have designed a nonhydrolysable oleic acid derivative, 2-hydroxyoleic acid (2-OHOA), which regulates membrane lipid structure and cell signaling, resulting in beneficial cardiovascular effects. We previously demonstrated that 2-OHOA induces PKA activation and PKCalpha translocation to the membrane; both pathways are thought to regulate transient outward K(+) current (I(to)) depending on the stimulus and the species used. This study was designed to investigate the effect of 2-OHOA on isolated cardiomyocytes. We examined the dose- and time-dependent effect of 2-OHOA on cytosolic Ca(2+) concentration ([Ca(2+)](i)) transient and contraction of myocytes isolated from different parts of the rat ventricular myocardium. Although this drug had no effect on [Ca(2+)](i) transient and cell shortening in myocytes isolated from the septum, it increased (up to 95%) [Ca(2+)](i) transient and cell shortening in subpopulations of myocytes from the right and left ventricles. The pattern of the effects of 2-OHOA was similar to that observed following the application of the I(to) blocker 4-aminopyridine, suggesting that the drug may act on this channel. Unlike the effect of 2-OHOA on [Ca(2+)](i) transient and cell shortening, PKCalpha translocation to membranes was not region specific. Thus 2-OHOA-induced effects on [Ca(2+)](i) transients and cell shortening are likely related to reductions in I(to) function, but PKCalpha translocation does not seem to play a role. The present results indicate that 2-OHOA selectively increases myocyte inotropic responsiveness, which could underlie its beneficial cardiovascular effects.
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Tsang S, Wu S, Liu J, Wong TM. Testosterone protects rat hearts against ischaemic insults by enhancing the effects of alpha(1)-adrenoceptor stimulation. Br J Pharmacol 2007; 153:693-709. [PMID: 18157169 DOI: 10.1038/sj.bjp.0707624] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Testosterone alleviates symptoms in patients with ischaemic heart disease. Androgen receptors are present in the heart, and testosterone upregulates gene expression of cardiac beta(1)-adrenoceptors. We hypothesize that testosterone may confer cardioprotection by interacting with adrenoceptors. EXPERIMENTAL APPROACH In isolated perfused hearts and ventricular myocytes from orchidectomized rats without or with testosterone (200 microg/100 g) replacement, we first determined the effect of ischaemia/reperfusion in the presence of noradrenaline (10(-7) M). Then we determined the contribution of interactions between testosterone and alpha(1)- or beta(1)-adrenoceptors in cardiac injury/protection (infarct size, release of lactate dehydrogenase, viability of myocytes, recovery of contractile function and incidence of arrhythmias) upon ischaemia/reperfusion by pharmacological manipulation using selective adrenoceptor agonists (alpha(1)-adrenoceptor agonist: phenylephrine 10(-6) M; non-selective beta-adrenoceptor agonist: isoprenaline 10(-7) M) and antagonists (alpha(1): prazosin or benoxathian 10(-6) M; beta(1): CGP 20712A 5 x 10(-7) M). We also determined the expression of alpha(1) and beta(1)-adrenoceptor in the hearts from rats with and without testosterone. KEY RESULTS Testosterone reduced injury induced by ischaemia/reperfusion and noradrenaline. This was achieved by enhancing the beneficial effect of alpha(1)-adrenoceptor stimulation, which was greater than the deleterious effect of beta(1)-adrenoceptor stimulation (also enhanced by testosterone). The effects of testosterone were abolished or attenuated by blockade of androgen receptors. Testosterone also enhanced the expression of alpha(1A) and beta(1)-adrenoceptor. CONCLUSIONS AND IMPLICATIONS Testosterone conferred cardioprotection by upregulating the cardiac alpha(1)-adrenoceptor and enhancing the effects of stimulation of this adrenoceptor. The effect of testosterone was at least partly mediated by androgen receptors.
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Affiliation(s)
- S Tsang
- Department of Physiology, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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Zhou SS, Zhang LB, Sun WP, Xiao FC, Zhou YM, Li YJ, Li DL. Effects of monocarboxylic acid-derived Cl−channel blockers on depolarization-activated potassium currents in rat ventricular myocytes. Exp Physiol 2007; 92:549-59. [PMID: 17303647 DOI: 10.1113/expphysiol.2007.037069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effects of monocarboxylic acid-derived Cl(-) channel blockers on cardiac depolarization-activated K(+) currents were investigated. Membrane currents in rat ventricular myocytes were recorded using the whole-cell configuration of the patch-clamp technique. 5-Nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) and niflumic acid (NFA) induced an outward current at 0 mV. Both NPPB and NFA failed to induce any current when used intracellularly or after K(+) in the bath and pipette solutions was replaced by equimolar Cs(+). Voltage pulse protocols revealed that NPPB and NFA enhanced the steady-state K(+) current but inhibited the transient outward K(+) current. Genistein, a tyrosine kinase (PTK) inhibitor, inhibited NPPB- and NFA-induced outward current. Another PTK inhibitor, lavendustin A, produced a comparable effect. In contrast, the inactive analogue of genistein, daidzein, was ineffective. Orthovanadate, a tyrosine phosphatase inhibitor, markedly slowed the deactivation of the outward current induced by NPPB and NFA. The protein kinase A (PKA) inhibitor H-89 inhibited NPPB-induced outward current at 0 mV. In contrast, the protein kinase C (PKC) inhibitor H-7 was without significant effect on the action of NPPB. Pretreatment of the myocytes with genistein or H-89 prevented the enhancing effect of NPPB. Increasing intracellular Cl(-) from 22 to 132 mm slightly reduced NPPB-induced outward current at 0 mV. These results demonstrate that the monocarboxylic acid-derived Cl(-) channel blockers NPPB and NFA enhance cardiac steady-state K(+) current, and suggest that the enhancing effect of the Cl(-) channel blockers is mediated by stimulation of PKA and PTK signalling pathways.
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Affiliation(s)
- Shi-Sheng Zhou
- Institute of Basic Medical Sciences, Medical College, Dalian University, Dalian 116622, China
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Hein P, Michel MC. Signal transduction and regulation: are all alpha1-adrenergic receptor subtypes created equal? Biochem Pharmacol 2006; 73:1097-106. [PMID: 17141737 DOI: 10.1016/j.bcp.2006.11.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Revised: 10/30/2006] [Accepted: 11/01/2006] [Indexed: 02/06/2023]
Abstract
The current manuscript reviews the evidence whether and how subtypes of alpha(1)-adrenergic receptors, i.e. alpha(1A)-, alpha(1B)- and alpha(1D)-adrenergic receptors, differentially couple to signal transduction pathways and exhibit differential susceptibility to regulation. In both regards studies in tissues or cells natively expressing the subtypes are hampered because the relative expression of the subtypes is poorly controlled and the observed effects may be cell-type specific. An alternative approach, i.e. transfection of multiple subtypes into the same host cell line overcomes this limitation, but it often remains unclear whether results in such artificial systems are representative for the physiological situation. The overall evidence suggests that indeed subtype-intrinsic and cell type-specific factors interact to direct alpha(1)-adrenergic receptor signaling and regulation. This may explain why so many apparently controversial findings have been reported from various tissues and cells. One of the few consistent themes is that alpha(1D)-adrenergic receptors signal less effectively upon agonist stimulation than the other subtypes, most likely because they exhibit spontaneous internalization.
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Affiliation(s)
- Peter Hein
- Department of Pharmacology, University of Würzburg, Würzburg, Germany
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Li J, Marionneau C, Zhang R, Shah V, Hell JW, Nerbonne JM, Anderson ME. Calmodulin kinase II inhibition shortens action potential duration by upregulation of K+ currents. Circ Res 2006; 99:1092-9. [PMID: 17038644 DOI: 10.1161/01.res.0000249369.71709.5c] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is activated by elevated intracellular Ca(2+) (Ca(2+)(i)), and mice with chronic myocardial CaMKII inhibition (Inh) resulting from transgenic expression of a CaMKII inhibitory peptide (AC3-I) unexpectedly showed action potential duration (APD) shortening. Inh mice exhibit increased L-type Ca(2+) current (I(Ca)), because of upregulation of protein kinase A (PKA) activity, and decreased CaMKII-dependent phosphorylation of phospholamban (PLN). We hypothesized that CaMKII is a molecular signal linking Ca(2+)(i) to repolarization. Whole cell voltage-clamp recordings revealed that the fast transient outward current (I(to,f)) and the inward rectifier current (I(K1)) were selectively upregulated in Inh, compared with wild-type (WT) and transgenic control, mice. Breeding Inh mice with mice lacking PLN returned I(to,f) and I(K1) to control levels and equalized the APD and QT intervals in Inh mice to control and WT levels. Dialysis of AC3-I into WT cells did not result in increased I(to,f) or I(K1), suggesting that enhanced cardiac repolarization in Inh mice is an adaptive response to chronic CaMKII inhibition rather than an acute effect of reduced CaMKII activity. Increasing PKA activity, by cell dialysis with cAMP, or inhibition of PKA did not affect I(K1) in WT cells. Dialysis of WT cells with cAMP also reduced I(to,f), suggesting that PKA upregulation does not increase repolarizing K(+) currents in Inh mice. These findings provide novel in vivo and cellular evidence that CaMKII links Ca(2+)(i) to cardiac repolarization and suggest that PLN may be a critical CaMKII target for feedback regulation of APD in ventricular myocytes.
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Affiliation(s)
- Jingdong Li
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, USA
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Colinas O, Gallego M, Setién R, López-López JR, Pérez-García MT, Casis O. Differential modulation of Kv4.2 and Kv4.3 channels by calmodulin-dependent protein kinase II in rat cardiac myocytes. Am J Physiol Heart Circ Physiol 2006; 291:H1978-87. [PMID: 16648177 DOI: 10.1152/ajpheart.01373.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this work we have combined biochemical and electrophysiological approaches to explore the modulation of rat ventricular transient outward K+ current ( Ito) by calmodulin kinase II (CaMKII). Intracellular application of CaMKII inhibitors KN93, calmidazolium, and autocamtide-2-related inhibitory peptide II (ARIP-II) accelerated the inactivation of Ito, even at low [Ca2+]. In the same conditions, CaMKII coimmunoprecipitated with Kv4.3 channels, suggesting that phosphorylation of Kv4.3 channels modulate inactivation of Ito. Because channels underlying Ito are heteromultimers of Kv4.2 and Kv4.3, we have explored the effect of CaMKII on human embryonic kidney (HEK) cells transfected with either of those Kvα-subunits. Whereas Kv4.3 inactivated faster upon inhibition of CaMKII, Kv4.2 inactivation was insensitive to CaMKII inhibitors. However, Kv4.2 inactivation became slower when high Ca2+ was used in the pipette or when intracellular [Ca2+] ([Ca2+]i) was transiently increased. This effect was inhibited by KN93, and Western blot analysis demonstrated Ca2+-dependent phosphorylation of Kv4.2 channels. On the contrary, CaMKII coimmunoprecipitated with Kv4.3 channels without a previous Ca2+ increase, and the association was inhibited by KN93. These results suggest that both channels underlying Ito are substrates of CaMKII, although with different sensitivities; Kv4.2 remain unphosphorylated unless [Ca2+]i increases, whereas Kv4.3 are phosphorylated at rest. In addition to the functional impact that phosphorylation of Kv4 channels could cause on the shape of action potential, association of CaMKII with Kv4.3 provides a new role of Kv4.3 subunits as molecular scaffolds for concentrating CaMKII in the membrane, allowing Ca2+-dependent modulation by this enzyme of the associated Kv4.2 channels.
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Affiliation(s)
- Olaia Colinas
- Departamento de Bioquímica y Biología Molecular y Fisiología, Edificio IBGM, Universidad de Valladolid, C/ Sanz y Forés s/n, 47003 Valladolid, Spain
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Pearman C, Kent W, Bracken N, Hussain M. H-89 inhibits transient outward and inward rectifier potassium currents in isolated rat ventricular myocytes. Br J Pharmacol 2006; 148:1091-8. [PMID: 16799649 PMCID: PMC1752020 DOI: 10.1038/sj.bjp.0706810] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
1. Voltage clamp was used to investigate the effects of N-[2-p-bromo-cinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), a potent inhibitor of PKA, on transient outward K(+) current (I(to)) and inward rectifying K(+) current (I(K1)) in rat cardiac muscle. 2. Initial experiments, performed using descending voltage ramps, showed that H-89 inhibited both the outward and inward ramp currents in a concentration-dependent manner at concentrations between 5 and 60 micromol l(-1). A similar degree of inhibition was observed when I(to) and I(K1) were recorded using square wave depolarising and hyperpolarising voltage steps, respectively. 3. The IC(50) was 35.8 micromol l(-1) for I(to) and 27.8 micromol l(-1) for I(K1) compared to 5.4 micromol l(-1) for L-type Ca(2+) current (I(Ca)). The Hill coefficients for I(to), I(K1) and I(Ca) were -1.97, -1.60 and -1.21, respectively. In addition to inhibiting I(to) amplitude, H-89 also accelerated the time to peak and the rate of voltage-dependent inactivation so that the time course of I(to) was abbreviated. 4. Paired-pulse protocols were performed to study the effects of H-89 on steady-state activation and inactivation as well as recovery from voltage-dependent inactivation. H-89 produced a concentration-dependent rightward shift in voltage-dependent activation but had no significant effect on steady-state inactivation. Recovery from voltage-dependent inactivation was delayed, although this was only visible at the highest concentration (60 micromol l(-1)) used. In experiments investigating the effects of elevated cyclic AMP, the beta-adrenergic agonist isoprenaline and the phosphatase inhibitor calyculin A had no major effects on I(to) or I(K1). 6. Data suggest that the effects of H-89 on K(+) currents are more complex than simple inhibition of PKA-mediated phosphorylation.
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Affiliation(s)
- Charles Pearman
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
| | - William Kent
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
| | - Nicolas Bracken
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
| | - Munir Hussain
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
- Author for correspondence:
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Scarparo AC, Visconti MA, Castrucci AMDL. Signalling pathways evoked by alpha1-adrenoceptors in human melanoma cells. Cell Biochem Funct 2006; 24:119-29. [PMID: 16444773 DOI: 10.1002/cbf.1309] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The biological effects of catecholamines in mammalian pigment cells are poorly understood, but in poikilothermic vertebrates they regulate the translocation of pigment granules. We have previously demonstrated in SK-Mel 23-human melanoma cells the presence of low affinity alpha(1)-adrenoceptors, which mediate a decrease in cell proliferation and increase in tyrosinase activity, with no change of tyrosinase expression. In this report, we investigated the signalling pathways involved in these responses. Calcium mobilization in response to phenylephrine (PHE), an alpha(1)-adrenergic agonist, was investigated by confocal microscopy, and no change of fluorescence during the treatment was observed, suggesting that calcium is not involved in the signalling pathway activated by alpha(1)-adrenoceptors in SK-Mel 23 cells. cAMP levels, determined by enzyme-immunoassay, were significantly increased by PHE (10(-5)-10(-4)M), that could be blocked by the alpha(1)-adrenergic antagonist benoxathian (10(-5)-10(-4)M). Several biological assays were then performed with PHE, for 72 h, in the absence or presence of various signalling pathway inhibitors, in an attempt to determine the intracellular messengers involved in the responses of proliferation and tyrosinase activity. Our results suggest the participation of p38 and ERKs in PHE-induced decrease of proliferation, and possibly also of cAMP and protein kinase A. Regarding PHE-induced increase of tyrosinase activity, it is suggested that the following signalling components are involved: cAMP/PKA, PKC, PI3K, p38 and ERKs.
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Affiliation(s)
- Ana Cristina Scarparo
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, Brasil
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Harley CW, Darby-King A, McCann J, McLean JH. Beta1-adrenoceptor or alpha1-adrenoceptor activation initiates early odor preference learning in rat pups: support for the mitral cell/cAMP model of odor preference learning. Learn Mem 2006; 13:8-13. [PMID: 16452650 DOI: 10.1101/lm.62006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We proposed that mitral cell beta1-adrenoceptor activation mediates rat pup odor preference learning. Here we evaluate beta1-, beta2-, alpha1-, and alpha2-adrenoceptor agonists in such learning. The beta1-adrenoceptor agonist, dobutamine, and the alpha1-adrenoceptor agonist, phenylephrine, induced learning, and both exhibited an inverted U-curve dose-response relationship to odor preference learning. Phenylephrine-induced learning occurred in the presence of propranolol to prevent indirect activation of beta-adrenoceptors. Alpha1-adrenoceptor mediation may represent a novel mechanism inducing learning or may increase cAMP in mitral cells via indirect activation of GABA(B) receptors. Neither the beta2-adrenoceptor agonist, salbutamol, nor the alpha2-adrenoceptor agonist, clonidine, induced learning.
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Affiliation(s)
- Carolyn W Harley
- Department of Psychology, Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, NL A1B 3V6, Canada
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