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Ranolazine: An Old Drug with Emerging Potential; Lessons from Pre-Clinical and Clinical Investigations for Possible Repositioning. Pharmaceuticals (Basel) 2021; 15:ph15010031. [PMID: 35056088 PMCID: PMC8777683 DOI: 10.3390/ph15010031] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 12/16/2021] [Accepted: 12/20/2021] [Indexed: 02/07/2023] Open
Abstract
Ischemic heart disease is a significant public health problem with high mortality and morbidity. Extensive scientific investigations from basic sciences to clinics revealed multilevel alterations from metabolic imbalance, altered electrophysiology, and defective Ca2+/Na+ homeostasis leading to lethal arrhythmias. Despite the recent identification of numerous molecular targets with potential therapeutic interest, a pragmatic observation on the current pharmacological R&D output confirms the lack of new therapeutic offers to patients. By contrast, from recent trials, molecules initially developed for other fields of application have shown cardiovascular benefits, as illustrated with some anti-diabetic agents, regardless of the presence or absence of diabetes, emphasizing the clear advantage of “old” drug repositioning. Ranolazine is approved as an antianginal agent and has a favorable overall safety profile. This drug, developed initially as a metabolic modulator, was also identified as an inhibitor of the cardiac late Na+ current, although it also blocks other ionic currents, including the hERG/Ikr K+ current. The latter actions have been involved in this drug’s antiarrhythmic effects, both on supraventricular and ventricular arrhythmias (VA). However, despite initial enthusiasm and promising development in the cardiovascular field, ranolazine is only authorized as a second-line treatment in patients with chronic angina pectoris, notwithstanding its antiarrhythmic properties. A plausible reason for this is the apparent difficulty in linking the clinical benefits to the multiple molecular actions of this drug. Here, we review ranolazine’s experimental and clinical knowledge on cardiac metabolism and arrhythmias. We also highlight advances in understanding novel effects on neurons, the vascular system, skeletal muscles, blood sugar control, and cancer, which may open the way to reposition this “old” drug alone or in combination with other medications.
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Xiao Y, Contaifer D, Huang W, Yang J, Hu Z, Guo Q, Bradley J, Peberdy MA, Ornato JP, Wijesinghe DS, Tang W. Cannabinoid Receptor Agonist WIN55, 212-2 Adjusts Lipid Metabolism in a Rat Model of Cardiac Arrest. Ther Hypothermia Temp Manag 2020; 10:192-203. [PMID: 31990631 DOI: 10.1089/ther.2019.0038] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The objective of this study was to investigate the effects of pharmacologically induced hypothermia with WIN55, 212-2 (WIN)on postresuscitation myocardial function, microcirculation, and metabolism-specific lipids in a rat cardiac arrest (CA) model. Ventricular fibrillation was electrically induced and untreated for 6 minutes in 24 Sprague-Dawley rats weighing 450-550 g. Cardiopulmonary resuscitation including chest compression and mechanical ventilation was then initiated and continued for 8 minutes, followed by defibrillation. At 5 minutes after restoration of spontaneous circulation (ROSC), animals were randomized into four groups: (1) normothermia with vehicle (NT); (2) physical hypothermia with vehicle (PH); (3) WIN55, 212-2 with normothermia (WN); and (4) WIN55, 212-2 with hypothermia (WH). For groups of WN and WH, WIN was administered by continuous intravenous infusion with a syringe pump for 4 hours. PH started at 5 minutes after resuscitation. NT maintained core temperature at 37°C ± 0.2°C with the aid of a heating blanket. Hypothermia groups maintained temperature at 33°C ± 0.5°C for 4 hours after ROSC. There was a significant improvement in myocardial function as measured by ejection fraction, cardiac output, and myocardial performance index in animals treated with WH and PH beginning at 1 hour after start of infusion. In the WH and PH groups, buccal microcirculation was significantly improved compared with NT and WN. Plasma at pre-CA and ROSC 4 hours was harvested for lipid metabolism. The WH group appeared to be closer to baseline than the other groups in lipid metabolism. lysophosphatidylcholine (LPC) 18:2, free fatty acid (FFA) 22:6, and ceramide (CER) (24:0) changed significantly among the lipidomic data compared with NT (p < 0.05). Postresuscitation hypothermia improved myocardial function and microcirculation. WH-mediated lipid metabolism had the best metabolic outcome to bring back the animals to normal metabolism, which may be protective to improve outcomes of CA. LPC 18:2, FFA 22:6, and CER (24:0) may be important predictors of outcomes of CA.
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Affiliation(s)
- Yan Xiao
- Department of Emergency Medicine, The Second Affiliated Hospital of Soochow University, Soochow, China.,Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Daniel Contaifer
- School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Weiping Huang
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Jin Yang
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Zhangle Hu
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Qinyue Guo
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Jennifer Bradley
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Mary Ann Peberdy
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA.,Department of Internal Medicine, Virginia Commonwealth University Health System, Richmond, Virginia, USA.,Department of Emergency Medicine, Virginia Commonwealth University Health System, Richmond, Virginia, USA
| | - Joseph P Ornato
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA.,Department of Emergency Medicine, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Dayanjan S Wijesinghe
- School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia, USA.,Institute for Structural Biology, Drug Discovery and Development, Virginia Commonwealth University, Richmond, Virginia, USA.,Da Vinci Center, School of Pharmacy, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.,Department of Pharmacotherapy and Outcomes Sciences, School of Pharmacy, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Wanchun Tang
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, Virginia, USA.,Department of Emergency Medicine, Virginia Commonwealth University, Richmond, Virginia, USA
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Yang KC, Kyle JW, Makielski JC, Dudley SC. Mechanisms of sudden cardiac death: oxidants and metabolism. Circ Res 2015; 116:1937-55. [PMID: 26044249 PMCID: PMC4458707 DOI: 10.1161/circresaha.116.304691] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 02/09/2015] [Indexed: 02/07/2023]
Abstract
Ventricular arrhythmia is the leading cause of sudden cardiac death (SCD). Deranged cardiac metabolism and abnormal redox state during cardiac diseases foment arrhythmogenic substrates through direct or indirect modulation of cardiac ion channel/transporter function. This review presents current evidence on the mechanisms linking metabolic derangement and excessive oxidative stress to ion channel/transporter dysfunction that predisposes to ventricular arrhythmias and SCD. Because conventional antiarrhythmic agents aiming at ion channels have proven challenging to use, targeting arrhythmogenic metabolic changes and redox imbalance may provide novel therapeutics to treat or prevent life-threatening arrhythmias and SCD.
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Affiliation(s)
- Kai-Chien Yang
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - John W Kyle
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - Jonathan C Makielski
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
| | - Samuel C Dudley
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
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Ben-Zeev G, Telias M, Nussinovitch I. Lysophospholipids modulate voltage-gated calcium channel currents in pituitary cells; effects of lipid stress. Cell Calcium 2010; 47:514-24. [PMID: 20510448 DOI: 10.1016/j.ceca.2010.04.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 04/28/2010] [Accepted: 04/28/2010] [Indexed: 01/26/2023]
Abstract
Voltage-gated calcium channels (VGCCs) are osmosensitive. The hypothesis that this property of VGCCs stems from their susceptibility to alterations in the mechanical properties of the bilayer was tested on VGCCs in pituitary cells using cone-shaped lysophospholipids (LPLs) to perturb bilayer lipid stress. LPLs of different head group size and charge were used: lysophosphatidylcholine (LPC), lysophosphatidylinositol (LPI), lysophosphatidylserine (LPS) and lysophosphatidylethanolamine (LPE). Phosphatidylcholine (PC) and LPC (C6:0) were used as controls. We show that partition of both LPC and LPI into the membrane of pituitary cells suppressed L-type calcium channel currents (I(L)). This suppression of I(L) was slow in onset, reversible upon washout with BSA and associated with a depolarizing shift in activation ( approximately 8mV). In contrast to these effects of LPC and LPI on I(L), LPS, LPE, PC and LPC (C6:0) exerted minimal or insignificant effects. This difference may be attributed to the prominent conical shape of LPC and LPI compared to the shapes of LPS and LPE (which have smaller headgroups), and to PC (which is cylindrical). The similar effects of LPC and LPI on I(L), despite differences in the structure and charge of their headgroups suggest a common lipid stress dependent mechanism in their action on VGCCs.
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Affiliation(s)
- Galia Ben-Zeev
- Department of Medical Neurobiology, Institute for Medical Research-Israel-Canada, Jerusalem, Israel
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Ghaly HA, Boyle PM, Vigmond EJ, Shimoni Y, Nygren A. Simulations of reduced conduction reserve in the diabetic rat heart: response to uncoupling and reduced excitability. Ann Biomed Eng 2009; 38:1415-25. [PMID: 19953318 DOI: 10.1007/s10439-009-9855-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Accepted: 11/20/2009] [Indexed: 10/20/2022]
Abstract
Experimental results have shown that action potential (AP) conduction in ventricular tissue from streptozotocin-diabetic (STZ) rats is compromised. This was manifest as increased sensitivity of conduction velocity (CV) to the gap junction uncoupler heptanol, as well as increased sensitivity of CV to reduced cellular excitability due to elevated extracellular K(+) concentration, in the STZ hearts. This "reduced conduction reserve" has been suggested to be due to lateralization of connexin43 (Cx43) proteins, rendering them nonfunctional, resulting in compromised intercellular electrical coupling. In this study, we have used computer simulations of one-dimensional AP conduction in a model of rat ventricular myocytes to verify this interpretation. Our results show that compromised intercellular coupling indeed reduces conduction reserve and predict a response to gap junction uncoupling with heptanol that is consistent with experiments. However, our simulations also show that compromised intercellular coupling is insufficient to explain the increased sensitivity to reduced cellular excitability. A thorough investigation of possible underlying mechanisms, suggests that subtle alterations in the voltage-dependence of steady-state gating for the Na(+) current (I (Na)), combined with compromised intercellular coupling, is a likely mechanism for these observations.
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Affiliation(s)
- Haisam A Ghaly
- Department of Electrical & Computer Engineering, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
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Undrovinas A, Maltsev VA. Late sodium current is a new therapeutic target to improve contractility and rhythm in failing heart. Cardiovasc Hematol Agents Med Chem 2008; 6:348-59. [PMID: 18855648 PMCID: PMC2575131 DOI: 10.2174/187152508785909447] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Most cardiac Na+ channels open transiently within milliseconds upon membrane depolarization and are responsible for the excitation propagation. However, some channels remain active during hundreds of milliseconds, carrying the so-called persistent or late Na+ current (I(NaL)) throughout the action potential plateau. I(NaL) is produced by special gating modes of the cardiac-specific Na+ channel isoform. Experimental data accumulated over the past decade show the emerging importance of this late current component for the function of both normal and especially failing myocardium, where I(NaL) is reportedly increased. Na+ channels represent a multi-protein complex and its activity is determined not only by the pore-forming alpha subunit but also by its auxiliary beta subunits, cytoskeleton, and by Ca2+ signaling and trafficking proteins. Remodeling of this protein complex and intracellular signaling pathways may lead to alterations of I(NaL) in pathological conditions. Increased I(NaL) and the corresponding Na+ influx in failing myocardium contribute to abnormal repolarization and an increased cell Ca2+ load. Interventions designed to correct I(NaL) rescue normal repolarization and improve Ca2+ handling and contractility of the failing cardiomyocytes. New therapeutic strategies to target both arrhythmias and deficient contractility in HF may not be limited to the selective inhibition of I(NaL) but also include multiple indirect, modulatory (e.g. Ca(2+)- or cytoskeleton- dependent) mechanisms of I(NaL) function.
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Affiliation(s)
- Albertas Undrovinas
- Department of Internal Medicine, Henry Ford Hospital, Detroit, MI 48202-2689, USA.
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Lundbaek JA. Lipid bilayer-mediated regulation of ion channel function by amphiphilic drugs. ACTA ACUST UNITED AC 2008; 131:421-9. [PMID: 18411332 PMCID: PMC2346573 DOI: 10.1085/jgp.200709948] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Jens A Lundbaek
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY 10021, USA.
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Zebedin E, Koenig X, Radenkovic M, Pankevych H, Todt H, Freissmuth M, Hilber K. Effects of duramycin on cardiac voltage-gated ion channels. Naunyn Schmiedebergs Arch Pharmacol 2008; 377:87-100. [DOI: 10.1007/s00210-007-0248-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Accepted: 12/07/2007] [Indexed: 11/28/2022]
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9
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Maltsev VA, Undrovinas A. Late sodium current in failing heart: friend or foe? PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 96:421-51. [PMID: 17854868 PMCID: PMC2267741 DOI: 10.1016/j.pbiomolbio.2007.07.010] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Most cardiac Na+ channels open transiently upon membrane depolarization and then are quickly inactivated. However, some channels remain active, carrying the so-called persistent or late Na+ current (INaL) throughout the action potential (AP) plateau. Experimental data and the results of numerical modeling accumulated over the past decade show the emerging importance of this late current component for the function of both normal and failing myocardium. INaL is produced by special gating modes of the cardiac-specific Na+ channel isoform. Heart failure (HF) slows channel gating and increases INaL, but HF-specific Na+ channel isoform underlying these changes has not been found. Na+ channels represent a multi-protein complex and its activity is determined not only by the pore-forming alpha subunit but also by its auxiliary beta subunits, cytoskeleton, calmodulin, regulatory kinases and phosphatases, and trafficking proteins. Disruption of the integrity of this protein complex may lead to alterations of INaL in pathological conditions. Increased INaL and the corresponding Na+ flux in failing myocardium contribute to abnormal repolarization and an increased cell Ca2+ load. Interventions designed to correct INaL rescue normal repolarization and improve Ca2+ handling and contractility of the failing cardiomyocytes. This review considers (1) quantitative integration of INaL into the established electrophysiological and Ca2+ regulatory mechanisms in normal and failing cardiomyocytes and (2) a new therapeutic strategy utilizing a selective inhibition of INaL to target both arrhythmias and impaired contractility in HF.
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Affiliation(s)
- Victor A Maltsev
- Gerontology Research Center, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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10
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Gautier M, Zhang H, Fearon IM. Peroxynitrite formation mediates LPC-induced augmentation of cardiac late sodium currents. J Mol Cell Cardiol 2007; 44:241-51. [PMID: 17961592 DOI: 10.1016/j.yjmcc.2007.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 08/31/2007] [Accepted: 09/10/2007] [Indexed: 12/17/2022]
Abstract
Lysophosphatidylcholine (LPC) accumulates in the ischaemic myocardium and is arrhythmogenic. We have examined the mechanisms underlying the effects of LPC on the late cardiac Na(+) current (I(L)Na). Na(+) currents were recorded in HEK293 cells expressing Na(V)1.5 and isolated rat ventricular myocytes. LPC enhanced recombinant I(L)Na, while it reduced peak Na(+) current. Computer modeling of human ventricular myocyte action potentials predicted a marked duration prolonging effect and arrhythmogenic potential due to these effects of LPC on peak and late currents. Enhancement of recombinant I(L)Na was suppressed by the antioxidant ascorbic acid and by the NADPH oxidase inhibitor DPI. Inhibitors of the mitochondrial electron transport chain (rotenone, TTFA and myxothiazol) were without effect on LPC responses. The superoxide donor pyrogallol was without effect on I(L)Na. Enhancement of I(L)Na was abrogated by the NOS inhibitors l-NAME and 7-nitroindazole, while LPC induced an l-NAME-sensitive production of NO, measured as enhanced DAF-FM fluorescence, in both HEK293 cells and ventricular myocytes. Despite this, the NO donors SNAP and SNP caused no change in I(L)Na. However, SNAP enhanced TTX-sensitive recombinant and native I(L)Na in the presence of pyrogallol, suggesting peroxynitrite formation as a mediator of the response to LPC. In support of this, the peroxynitrite scavenger FeTPPS prevented the response of I(L)Na to LPC. Peroxynitrite formation provides a novel mechanism by which LPC regulates the late cardiac Na(+) current.
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Affiliation(s)
- Mathieu Gautier
- Faculty of Life Sciences, The University of Manchester, Floor 2, Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, UK
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Makielski JC, Valdivia CR. Ranolazine and late cardiac sodium current--a therapeutic target for angina, arrhythmia and more? Br J Pharmacol 2007; 148:4-6. [PMID: 16520741 PMCID: PMC1617040 DOI: 10.1038/sj.bjp.0706713] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ranolazine is a new antianginal drug approved for clinical use in the United States in January 2006. A study published in this same issue of the British Journal of Pharmacology characterizes ranolazine block of late sodium current caused by the long QT syndrome 3 mutations. This commentary discusses the implications of that study and the background and implications for block of late cardiac sodium current in general.
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Affiliation(s)
- Jonathan C Makielski
- Department of Medicine, Cardiovascular Medicine Section, University of Wisconsin, Madison, WI 53705, USA.
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12
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Lundbæk JA. Regulation of membrane protein function by lipid bilayer elasticity-a single molecule technology to measure the bilayer properties experienced by an embedded protein. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:S1305-S1344. [PMID: 21690843 DOI: 10.1088/0953-8984/18/28/s13] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Membrane protein function is generally regulated by the molecular composition of the host lipid bilayer. The underlying mechanisms have long remained enigmatic. Some cases involve specific molecular interactions, but very often lipids and other amphiphiles, which are adsorbed to lipid bilayers, regulate a number of structurally unrelated proteins in an apparently non-specific manner. It is well known that changes in the physical properties of a lipid bilayer (e.g., thickness or monolayer spontaneous curvature) can affect the function of an embedded protein. However, the role of such changes, in the general regulation of membrane protein function, is unclear. This is to a large extent due to lack of a generally accepted framework in which to understand the many observations. The present review summarizes studies which have demonstrated that the hydrophobic interactions between a membrane protein and the host lipid bilayer provide an energetic coupling, whereby protein function can be regulated by the bilayer elasticity. The feasibility of this 'hydrophobic coupling mechanism' has been demonstrated using the gramicidin channel, a model membrane protein, in planar lipid bilayers. Using voltage-dependent sodium channels, N-type calcium channels and GABA(A) receptors, it has been shown that membrane protein function in living cells can be regulated by amphiphile induced changes in bilayer elasticity. Using the gramicidin channel as a molecular force transducer, a nanotechnology to measure the elastic properties experienced by an embedded protein has been developed. A theoretical and technological framework, to study the regulation of membrane protein function by lipid bilayer elasticity, has been established.
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Affiliation(s)
- Jens August Lundbæk
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
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Makielski JC, Farley AL. Na+ Current in Human Ventricle: Implications for Sodium Loading and Homeostasis. J Cardiovasc Electrophysiol 2006; 17 Suppl 1:S15-S20. [PMID: 16686671 DOI: 10.1111/j.1540-8167.2006.00380.x] [Citation(s) in RCA: 62] [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: 11/29/2022]
Abstract
The Na current (I(Na)) in human ventricle is carried through a specific isoform of the voltage gated Na channel in heart. The pore forming alpha-subunit is encoded by the gene SCN5A. Up to four beta-subunits may be associated, and the larger macromolecular complex may include attachments to cytoskeleton and scaffolding proteins, all of which may affect the gating kinetics of the current. I(Na) underlies initiation and propagation of action potentials in the heart and plays a prominent role in cardiac electrophysiology and arrhythmia. In addition, I(Na) also loads the ventricular cell with Na(+) ions and plays an important role in intracellular Na homeostasis. This review considers the structure and function of the human cardiac Na channel that carries I(Na) with a particular consideration of the implications of alterations in I(Na) in acquired cardiac diseases such as hypertrophy, failure, and ischemia, which affect Na loading.
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Affiliation(s)
- Jonathan C Makielski
- Department of Medicine, Cardiovascular Medicine Section, University of Wisconsin, Madison, Wisconsin 53792, USA.
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Zheng M, Uchino T, Kaku T, Kang L, Wang Y, Takebayashi S, Ono K. Lysophosphatidylcholine augments Ca(v)3.2 but not Ca(v)3.1 T-type Ca(2+) channel current expressed in HEK-293 cells. Pharmacology 2006; 76:192-200. [PMID: 16543777 DOI: 10.1159/000092041] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Accepted: 01/19/2006] [Indexed: 11/19/2022]
Abstract
Lysophosphatidylcholine (LPC) has been shown to induce electrophysiological disturbances to arrhythmogenesis. However, the effects of LPC on the low-voltage-activated T-type Ca(2+) channels in the heart are not understood yet. We found that LPC increases the T-type Ca(2+) channel current (I(Ca.T)) in neonatal rat cardiomyocytes. To further investigate the underlying modulatory mechanism of LPC on T-type Ca(2+) channels, we utilized HEK-293 cells stably expressing alpha1G and alpha1H subunits (HEK-293/alpha1G and HEK-293/alpha1H), by use of patch-clamp techniques. A low concentration of LPC (10 micromol/l) significantly increased Ca(v)3.2 I(Ca.T) (alpha1H) that were similar to those observed in neonatal rat cardiomyocytes. Activation and steady-state inactivation curves were shifted in the hyperpolarized direction by 5.1 +/- 0.2 and 4.6 +/- 0.4 mV, respectively, by application of 10 micromol/l LPC. The pretreatment of cells with a protein kinase C inhibitor (chelerythrine) attenuated the effects of LPC on I(Ca.T) (alpha1H). However, the application of LPC failed to modify Ca(v)3.1 (alpha1G) I(Ca.T) at concentrations of 10-50 micromol/l. In conclusion, these data demonstrate that extracellularly applied LPC augments Ca(v)3.2 I(Ca.T) (alpha1H) but not Ca(v)3.1 I(Ca.T) (alpha1G) in a heterologous expression system, possibly by modulating protein kinase C signaling.
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Affiliation(s)
- Mingqi Zheng
- Department of Cardiovascular Science, Oita University, Oita, Japan
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15
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Lundbaek JA, Birn P, Tape SE, Toombes GES, Søgaard R, Koeppe RE, Gruner SM, Hansen AJ, Andersen OS. Capsaicin regulates voltage-dependent sodium channels by altering lipid bilayer elasticity. Mol Pharmacol 2005; 68:680-9. [PMID: 15967874 DOI: 10.1124/mol.105.013573] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
At submicromolar concentrations, capsaicin specifically activates the TRPV1 receptor involved in nociception. At micro- to millimolar concentrations, commonly used in clinical and in vitro studies, capsaicin also modulates the function of a large number of seemingly unrelated membrane proteins, many of which are similarly modulated by the capsaicin antagonist capsazepine. The mechanism(s) underlying this widespread regulation of protein function are not understood. We investigated whether capsaicin could regulate membrane protein function by changing the elasticity of the host lipid bilayer. This was done by studying capsaicin's effects on lipid bilayer stiffness, measured using gramicidin A (gA) channels as molecular force-transducers, and on voltage-dependent sodium channels (VDSC) known to be regulated by bilayer elasticity. Capsaicin and capsazepine (10-100 microM) increase gA channel appearance rate and lifetime without measurably altering bilayer thickness or channel conductance, meaning that the changes in bilayer elasticity are sufficient to alter the conformation of an embedded protein. Capsaicin and capsazepine promote VDSC inactivation, similar to other amphiphiles that decrease bilayer stiffness, producing use-dependent current inhibition. For capsaicin, the quantitative relation between the decrease in bilayer stiffness and the hyperpolarizing shift in inactivation conforms to that previously found for other amphiphiles. Capsaicin's effects on gA channels and VDSC are similar to those of Triton X-100, although these amphiphiles promote opposite lipid monolayer curvature. We conclude that capsaicin can regulate VDSC function by altering bilayer elasticity. This mechanism may underlie the promiscuous regulation of membrane protein function by capsaicin and capsazepine-and by amphiphilic drugs generally.
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Salazar BC, Castaño S, Sánchez JC, Romero M, Recio-Pinto E. Ganglioside GD1a increases the excitability of voltage-dependent sodium channels. Brain Res 2004; 1021:151-8. [PMID: 15342262 DOI: 10.1016/j.brainres.2004.06.055] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2004] [Indexed: 11/30/2022]
Abstract
The effect of the negatively charged ganglioside GD1a, one of the major brain gangliosides [H. Beitinger, W. Probst, R. Hilbig, H. Rahmann, Seasonal variability of sialo-glycoconjugates in the brain of the Djungarian hamster (Phodopus sungorus). Comp. Biochem. Physiol., B 86 (1987) 377-384] on the function of brain derived BTX-modified voltage-dependent sodium channel was studied using the planar lipid bilayer system. Bilayers were formed either with a mixture of neutral phospholipids (4 phosphoethanolamine (PE):1 phosphocholine (PC)) alone or with one containing 6% of the disialoganglioside GD1a. The permeation and activation properties of the channels were measured in the presence of symmetrical 200 mM NaCl. We found that the single channel conductance was not affected by GD1a, whereas the steady-state activation curve displayed a hyperpolarizing shift in the presence of GD1a. Since the lipid distribution in these membranes is symmetrical, then the GD1a effect on sodium channels may result either from an induction of channel conformational changes or from an asymmetrical interaction between the channel (extracellular vs. intracellular channel aspect) and GD1a. Regardless of the mechanism, the data indicate that differences in ganglioside content in neuronal cells may contribute to the previously observed sodium channel functional variability within (soma, dentritic, axon hillock) and between neuronal cells as well as to excitability changes in those physiological and pathological conditions where changes in the neuronal ganglioside content occur.
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Affiliation(s)
- Blanca C Salazar
- Centro de Estudios Cerebrales, Universidad del Valle, Calle 4B No.36-00, Barrio San Fernando, Cali, Colombia.
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Ma YP, Hu HJ, Hao XM, Zhou PA, Wu CH, Dai DZ. Reduced sodium currents in isolated mammalian myocytes treated with chronicL-thyroxine. Drug Dev Res 2003. [DOI: 10.1002/ddr.10138] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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Rodríguez B, Ferrero JM, Trénor B. Mechanistic investigation of extracellular K+ accumulation during acute myocardial ischemia: a simulation study. Am J Physiol Heart Circ Physiol 2002; 283:H490-500. [PMID: 12124193 DOI: 10.1152/ajpheart.00625.2001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study, we have used computer simulations to study the mechanisms of extracellular K+ accumulation during acute ischemia. A modified version of the Luo-Rudy phase II action potential model was used to simulate the electrical behavior of one ventricular myocyte during 14 min of simulated ischemia. Our results show the following: 1) only the integrated effect of activation of ATP-dependent K+ current, an ischemic Na+ inward current, and inhibition of Na(+)-K(+) pump activity in the absence of coronary flow replicates the biphasic time course of extracellular K+ concentration observed during acute ischemia; 2) the time to onset of the plateau phase and the plateau level value are determined by the rate of stimulation and by the rate of alteration of the three mechanisms. However, acidosis and reduction of extracellular volume produce only a slight anticipation of the plateau phase; and 3) cellular K+ loss is mainly due to an increase of K+ efflux via the time-independent K+ current and ATP-dependent K+ current rather than to a decrease of K+ influx.
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Affiliation(s)
- B Rodríguez
- Laboratorio Integrado de Bioingeniería, Departamento de Ingeniería Electrónica, Universidad Politécnica de Valencia, Camino de Vera s/n, 46021 Valencia, Spain
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19
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Ziolo MT, Sondgeroth KL, Harshbarger CH, Smith JM, Wahler GM. Effects of arrhythmogenic lipid metabolites on the L-type calcium current of diabetic vs. non-diabetic rat hearts. Mol Cell Biochem 2001; 220:169-75. [PMID: 11451378 DOI: 10.1023/a:1010992900387] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Accumulation of lipid metabolites, such as palmitoylcarnitine and lysophosphatidylcholine, is thought to be a major contributor to the development of cardiac arrhythmias during myocardial ischemia. This arrhythmogenicity is likely due to the effects of these metabolites on various ion channels. Diabetic hearts have been shown to accumulate much higher concentrations of these lipid metabolites during ischemia, which may be an important factor in the enhanced incidence of arrhythmias in diabetic hearts. However, it is not known whether these metabolites have similar effects on the ion channels of diabetic hearts as in non-diabetic hearts. Previous studies on myocytes from non-diabetic hearts have reported either enhancement or inhibition of L-type calcium current (I(Ca)) by these lipid metabolites. Thus, it is not clear whether the effects of palmitoylcarnitine and/or lysophosphatidlycholine on I(Ca) contribute to the enhanced arrhythmogenicity of diabetic hearts or protect against arrhythmias. We determined the effect of exogenous palmitoylcarnitine and lysophosphatidylcholine on the (I(Ca)) in ventricular myocytes from streptozotocin-diabetic and non-diabetic rat hearts under identical conditions. We found that palmitoylcarnitine and lysophosphatidylcholine exhibited a dose-dependent inhibition of I(Ca), which was virtually identical in diabetic and non-diabetic cardiac myocytes. Thus, we conclude that these arrhythmogenic lipid metabolites have similar actions on calcium channels in diabetic and non-diabetic hearts. Therefore, the greater susceptibility of diabetic hearts to arrhythmias during myocardial ischemia is not due to an altered sensitivity of the L-type calcium channels to lipid metabolites, but may be explained, in large part, by the greater accumulation of these metabolites during ischemia.
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Affiliation(s)
- M T Ziolo
- Department of Physiology, Midwestern University, Downers Grove, IL 60515, USA
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20
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Eigel BN, Hadley RW. Contribution of the Na(+) channel and Na(+)/H(+) exchanger to the anoxic rise of [Na(+)] in ventricular myocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:H1817-22. [PMID: 10564135 DOI: 10.1152/ajpheart.1999.277.5.h1817] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to quantify the contribution of the Na(+)/H(+) exchanger (NHE) and the Na(+) channel to the rise in cytosolic Na(+) concentration ([Na(+)]) that is seen in anoxic guinea pig ventricular myocytes. [Na(+)] was measured with the use of microfluorometry and was found to rise to 44 mM after prolonged anoxia. This rise was partially sensitive to either TTX or HOE-642, selective inhibitors of the Na(+) channel and NHE1, respectively. [Na(+)] did not significantly rise when both drugs were present, suggesting that other routes of Na(+) entry were insignificant. However, the relative contributions of the NHE and the Na(+) channel were found to be remarkably sensitive to ionic conditions expected to occur during ischemia. The Na(+) channel was the dominant Na(+) source during acidic anoxia. However, the NHE was the dominant Na(+) source during both hyperkalemic anoxia and simulated ischemia (hyperkalemia, low pH, and anoxia). The data suggest that the NHE may prove to be the best pharmacological target to reduce Na(+) entry during true ischemia and that inhibition of Na(+) influx could contribute strongly to the cardioprotective effects of NHE inhibitors.
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Affiliation(s)
- B N Eigel
- Department of Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky 40536-0084, USA
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Wilson HA, Waldrip JB, Nielson KH, Judd AM, Han SK, Cho W, Sims PJ, Bell JD. Mechanisms by which elevated intracellular calcium induces S49 cell membranes to become susceptible to the action of secretory phospholipase A2. J Biol Chem 1999; 274:11494-504. [PMID: 10206954 DOI: 10.1074/jbc.274.17.11494] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Exposure of S49 lymphoma cells to exogenous group IIA or V secretory phospholipase A2 (sPLA2) caused an initial release of fatty acid followed by resistance to further hydrolysis by the enzyme. This refractoriness was overcome by exposing cells to palmitoyl lysolecithin. This effect was specific in terms of lysophospholipid structure. Induction of membrane susceptibility by lysolecithin involved an increase in cytosolic calcium and was duplicated by incubating the cells with calcium ionophores such as ionomycin. Lysolecithin also activated cytosolic phospholipase A2 (cPLA2). Inhibition of this enzyme attenuated the ability of lysolecithin (but not ionomycin) to induce susceptibility to sPLA2. Lysolecithin or ionomycin caused concurrent hydrolysis of both phosphatidylethanolamine and phosphatidylcholine implying that transbilayer movement of phosphatidylethanolamine occurred upon exposure to these agents but that susceptibility is not simply due to exposure of a preferred substrate (i.e. phosphatidylethanolamine) to the enzyme. Microvesicles were apparently released from the cells upon addition of lysolecithin or ionomycin. Both these vesicles and the remnant cell membranes were susceptible to sPLA2. Together these data suggest that lysolecithin induces susceptibility through both cPLA2-dependent and -independent pathways. Whereas elevated cytosolic calcium was required for both pathways, it was sufficient only for the cPLA2-independent pathway. This cPLA2-independent pathway involved changes in cell membrane structure associated with transbilayer phospholipid migration and microvesicle release.
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Affiliation(s)
- H A Wilson
- Department of Zoology, Brigham Young University, Provo, Utah 84602, USA
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Caldwell RA, Baumgarten CM. Plasmalogen-derived lysolipid induces a depolarizing cation current in rabbit ventricular myocytes. Circ Res 1998; 83:533-40. [PMID: 9734476 DOI: 10.1161/01.res.83.5.533] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Plasmalogen rather than diacyl phospholipids are the preferred substrate for the cardiac phospholipase A2 (PLA2) isoform activated during ischemia. The diacyl metabolite, lysophosphatidylcholine, is arrhythmogenic, but the effects of the plasmalogen metabolite, lysoplasmenylcholine (LPLC), are essentially unknown. We found that 2.5 and 5 micromol/L LPLC induced spontaneous contractions of intact isolated rabbit ventricular myocytes (median times, 27.4 and 16.4 minutes, respectively) significantly faster than lysophosphatidylcholine (>60 and 37.8 minutes, respectively). Whole-cell recordings revealed that LPLC depolarized the resting membrane potential from -83.5+/-0.2 to -21.5+/-1.0 mV. Depolarization was due to a guanidinium toxin-insensitive Na+ influx. The LPLC-induced current reversed at -18.5+/-0.9 mV and was shifted 26.7+/-4.2 mV negative by a 10-fold reduction of bath Na+ (Na+/K+ permeability ratio, approximately 0.12+/-0.06). In contrast, block of Ca2+ channels with Cd2+ and reducing bath Cl failed to affect the current. The actions of LPLC were opposed by lanthanides. Gd3+ and La3+ were equally effective inhibitors of the LPLC-induced current and equally delayed the onset of spontaneous contractions. However, the characteristics of lanthanide block imply that Gd3+-sensitive, poorly selective, stretch-activated channels were not involved. Instead, the data are consistent with the view that lanthanides increase phospholipid ordering and may thereby oppose membrane perturbations caused by LPLC. Plasmalogens constitute a significant fraction of cardiac sarcolemmal choline phospholipids. In light of their subclass-specific catabolism by phospholipase A2 and the present results, it is suggested that LPLC accumulation may contribute to ventricular dysrhythmias during ischemia.
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Affiliation(s)
- R A Caldwell
- Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0551, USA
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Coronel R, Wilms-Schopman FJ, Janse MJ. Profibrillatory effects of intracoronary thrombus in acute regional ischemia of the in situ porcine heart. Circulation 1997; 96:3985-91. [PMID: 9403623 DOI: 10.1161/01.cir.96.11.3985] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND An intracoronary thrombus during regional ischemia is related to life-threatening arrhythmias. The electrophysiological consequences of a thrombus are unknown. METHODS AND RESULTS In open chest pigs, regional ischemia was induced by intracoronary injection of a thrombus (protocol 1). In protocol 2, coronary ligation was followed by injection of heparinized blood. Three consecutive episodes of ischemia (10 minutes) and reperfusion (20 minutes) were studied in protocols 3 and 4 (ligation). During the former, an intracoronary thrombus started the third period of ischemia. Multiple (78) local electrograms were recorded simultaneously, and activation patterns were determined. In a first period of ischemia, ventricular fibrillation (during the first 10 minutes) occurred more often after intracoronary thrombosis than during the other protocols (4/7 versus 2/19, P<.05) despite similar size of the ischemic tissue. The incidence of delayed arrhythmias (between 15 and 30 minutes) was not different. Epicardial activation delay was larger 2 to 4 minutes after intracoronary thrombosis compared with ligation. ST elevation was larger with than without a thrombus (2 minutes of ischemia, 12.9+/-4.1 versus 8.2+/-3.0 mV; +/-SD, P<.05). In protocols 3 and 4 the second period and third period of ischemia were similar irrespective of the presence of an intracoronary thrombus. CONCLUSIONS More conduction slowing underlies the profibrillatory effect of an intracoronary thrombus relative to coronary ligation. After preconditioning with ischemia, the profibrillatory effects are no longer detectable.
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Affiliation(s)
- R Coronel
- Department of Experimental Cardiology, Academic Medical Centre, Amsterdam, The Netherlands.
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24
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Abstract
Lysophosphatidylcholine (LPC) is a naturally occurring intracellular phospholipid metabolite that has been implicated in arrhythmogenesis during ischemia. LPC has been shown to affect the cardiac Na+ current (I(Na)), but the mechanism of modulation remains undescribed. Recently, low concentrations of LPC have been shown to activate protein kinase C (PKC) independent of the receptor-delineated pathway. The purposes of this study were to describe the effects of intracellularly introduced LPC on I(Na) and to determine if these effects were mediated by kinases. Modulation of I(Na) was studied in ventricular cells with LPC (1 nmol/L to 1 micromol/L) internally applied using whole-cell patch-clamp techniques. Intracellular LPC caused a dose-dependent depolarizing shift of steady state inactivation that was accompanied by a change in slope factor. The development of resting inactivation from closed states was delayed 40%, whereas the recovery from inactivation was significantly accelerated. These results were mimicked by another bioactive lipid, lysophosphatidylethanolamine, or by a peptide analogue of PKC, which is a potent stimulator of endogenous PKC activity. Maximal recruitable current was significantly increased by LPC but not by PKC activation. Some of the effects of LPC on I(Na) could be partially inhibited by the specific PKC inhibitor chelerythrine chloride or by downregulation of PKC with phorbol ester pretreatment. However, genistein, a specific tyrosine kinase inhibitor, completely inhibited all the modulation of I(Na) caused by LPC. These data suggest that LPC modulates I(Na) in cardiac myocytes by a pathway that involves both PKC-dependent and tyrosine kinase- dependent phosphorylation.
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Affiliation(s)
- C L Watson
- Department of Medicine, University of Maryland, Baltimore, USA
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