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Tapilina SV, Ivanova AD, Filatova TS, Galenko-Yaroshevsky PA, Abramochkin DV. The role of M3 receptors in regulation of electrical activity deteriorates in the rat heart during ageing. Curr Res Physiol 2022; 5:1-7. [PMID: 34977599 PMCID: PMC8685909 DOI: 10.1016/j.crphys.2021.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 11/25/2021] [Accepted: 12/02/2021] [Indexed: 11/29/2022] Open
Abstract
Ageing is a complex process which affects all systems of the organism and therefore changes the environment where the heart is working. In this study we demonstrate the ageing-related changes in the mechanisms of parasympathetic regulation of mammalian heart. Electrophysiological effects produced by selective activation of M3-cholinoreceptors were compared in isolated cardiac preparations from young adult (4 months), adult (1 year) and ageing (2 years) rats using sharp glass microelectrode technique. M3-receptors were activated with muscarinic agonist pilocarpine (10-5M) in the presence of selective M2 antagonist AQ-RA741 (10-7M). In atrial and ventricular myocardium from young rats M3 stimulation induced shortening of action potentials(APs), while no significant effect was observed in both elder groups. The main mechanism of M3-induced AP shortening is inhibition of L-type Ca2+ current, estimated using whole-cell patch-clamp. It was negligible in atrial myocytes from ageing animals in comparison with young rats. The loss of sensitivity to stimulation of M3-receptors is due to decrease in M3 gene expression, shown by RT-PCR both in atrial and ventricular samples from ageing rats. Thus, in ageing rat heart M3-receptors are down-regulated and not involved in regulation of electrical activity. Stimulation of M3-receptors shortens action potentials (APs) in rat myocardium. This effect of M3-stimulation is diminished in 1 and 2-year old rats. Underlying M3-mediated inhibition of L-type Ca2+ current deteriorates in aged rats. These age-related changes are due to downregulation of M3 receptors.
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Affiliation(s)
- Svetlana V Tapilina
- Department of Human and Animal Physiology, Moscow State University, Leninskiye Gory 1, 12, Moscow, Russia
| | - Alexandra D Ivanova
- Department of Human and Animal Physiology, Moscow State University, Leninskiye Gory 1, 12, Moscow, Russia
| | - Tatiana S Filatova
- Department of Human and Animal Physiology, Moscow State University, Leninskiye Gory 1, 12, Moscow, Russia.,Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova Str 1, Moscow, Russia.,Laboratory of Cardiac Electrophysiology, National Medical Research Center for Cardiology, Moscow, Russia
| | | | - Denis V Abramochkin
- Department of Human and Animal Physiology, Moscow State University, Leninskiye Gory 1, 12, Moscow, Russia
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Roles Played by the Na +/Ca 2+ Exchanger and Hypothermia in the Prevention of Ischemia-Induced Carrier-Mediated Efflux of Catecholamines into the Extracellular Space: Implications for Stroke Therapy. Neurochem Res 2019; 45:16-33. [PMID: 31346893 PMCID: PMC6942591 DOI: 10.1007/s11064-019-02842-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 05/30/2019] [Accepted: 07/04/2019] [Indexed: 12/11/2022]
Abstract
The release of [3H]dopamine ([3H]DA) and [3H]noradrenaline ([3H]NA) in acutely perfused rat striatal and cortical slice preparations was measured at 37 °C and 17 °C under ischemic conditions. The ischemia was simulated by the removal of oxygen and glucose from the Krebs solution. At 37 °C, resting release rates in response to ischemia were increased; in contrast, at 17 °C, resting release rates were significantly reduced, or resting release was completely prevented. The removal of extracellular Ca2+ further increased the release rates of [3H]DA and [3H]NA induced by ischemic conditions. This finding indicated that the Na+/Ca2+ exchanger (NCX), working in reverse in the absence of extracellular Ca2+, fails to trigger the influx of Ca2+ in exchange for Na+ and fails to counteract ischemia by further increasing the intracellular Na+ concentration ([Na+]i). KB-R7943, an inhibitor of NCX, significantly reduced the cytoplasmic resting release rate of catecholamines under ischemic conditions and under conditions where Ca2+ was removed. Hypothermia inhibited the excessive release of [3H]DA in response to ischemia, even in the absence of Ca2+. These findings further indicate that the NCX plays an important role in maintaining a high [Na+]i, a condition that may lead to the reversal of monoamine transporter functions; this effect consequently leads to the excessive cytoplasmic tonic release of monoamines and the reversal of the NCX. Using HPLC combined with scintillation spectrometry, hypothermia, which enhances the stimulation-evoked release of DA, was found to inhibit the efflux of toxic DA metabolites, such as 3,4-dihydroxyphenylacetaldehyde (DOPAL). In slices prepared from human cortical brain tissue removed during elective neurosurgery, the uptake and release values for [3H]NA did not differ from those measured at 37 °C in slices that were previously maintained under hypoxic conditions at 8 °C for 20 h. This result indicates that hypothermia preserves the functions of the transport and release mechanisms, even under hypoxic conditions. Oxidative stress (H2O2), a mediator of ischemic brain injury enhanced the striatal resting release of [3H]DA and its toxic metabolites (DOPAL, quinone). The study supports our earlier findings that during ischemia transmitters are released from the cytoplasm. In addition, the major findings of this study that hypothermia of brain slice preparations prevents the extracellular calcium concentration ([Ca2+]o)-independent non-vesicular transmitter release induced by ischemic insults, inhibiting Na+/Cl−-dependent membrane transport of monoamines and their toxic metabolites into the extracellular space, where they can exert toxic effects.
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Zhabyeyev P, McLean B, Chen X, Vanhaesebroeck B, Oudit GY. Inhibition of PI3Kinase-α is pro-arrhythmic and associated with enhanced late Na + current, contractility, and Ca 2+ release in murine hearts. J Mol Cell Cardiol 2019; 132:98-109. [PMID: 31095940 DOI: 10.1016/j.yjmcc.2019.05.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 04/11/2019] [Accepted: 05/09/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Phosphoinositide 3-kinase α (PI3Kα) is a proto-oncogene with high activity in the heart. BYL719 (BYL) is a PI3Kα-selective small molecule inhibitor and a prospective drug for advanced solid tumors. We investigated whether acute pharmacological inhibition of PI3Kα has pro-arrhythmic effects. METHODS & RESULTS In isolated wild-type (WT) cardiomyocytes, pharmacological inhibition of PI3Kα (BYL719) increased contractility by 28%, Ca2+ release by 20%, and prolonged action potential (AP) repolarization by 10-15%. These effects of BYL719 were abolished by inhibition of reverse-mode Na+/Ca2+ exchanger (NCX) (KB-R7943) or by inhibition of late Na+ current (INa-L) (ranolazine). BYL719 had no effect on PI3Kα-deficient cardiomyocytes, suggesting BYL719 effects were PI3Kα-dependent and mediated via NCX and INa-L. INa-L was suppressed by activation of PI3Kα, application of exogenous intracellular PIP3, or ranolazine. Investigation of AP and Ca2+ release in whole heart preparations using epicardial optical mapping showed that inhibition of PI3Kα similarly led to prolongation of AP and enhancement of Ca2+ release. In hearts of PI3Kα-deficient mice, β-adrenergic stimulation in the presence of high Ca2+ concentrations and 12-Hz burst pacing led to delayed afterdepolarizations and ventricular fibrillation. In vivo, administration of BYL719 prolonged QT interval [QTcF (Fridericia) increased by 15%] in WT, but not in PI3Kα-deficient mice. CONCLUSIONS Pharmacological inhibition of PI3Kα is arrhythmogenic due to activation of INa-L leading to increased sarcoplasmic reticulum Ca2+ load and prolonged QT interval. Therefore, monitoring of cardiac electrical activity in patients receiving PI3K inhibitors may provide further insights into the arrhythmogenic potential of PI3Ka inhibition.
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Affiliation(s)
- Pavel Zhabyeyev
- Department of Medicine, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
| | - Brent McLean
- Department of Medicine, University of Alberta, Edmonton, Canada; Department of Physiology, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
| | - Xueyi Chen
- Department of Medicine, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
| | | | - Gavin Y Oudit
- Department of Medicine, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada.
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Inhibition of potassium currents is involved in antiarrhythmic effect of moderate ethanol on atrial fibrillation. Toxicol Appl Pharmacol 2017; 322:89-96. [DOI: 10.1016/j.taap.2017.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 03/01/2017] [Accepted: 03/07/2017] [Indexed: 12/27/2022]
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Sibarov DA, Abushik PA, Poguzhelskaya EE, Bolshakov KV, Antonov SM. Inhibition of Plasma Membrane Na/Ca-Exchanger by KB-R7943 or Lithium Reveals Its Role in Ca-Dependent N-methyl-d-aspartate Receptor Inactivation. J Pharmacol Exp Ther 2015; 355:484-95. [PMID: 26391160 DOI: 10.1124/jpet.115.227173] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 09/18/2015] [Indexed: 01/09/2023] Open
Abstract
To evaluate the possible role of the plasma membrane Na(+)/Ca(2+)-exchanger (NCX) in regulation of N-methyl-d-aspartate (NMDA) receptors (NMDARs), we studied effects of 2-[2-[4-(4-nitrobenzyloxy) phenyl]ethyl]isothiourea methanesulfonate (KB-R7943; KBR) and lithium (inhibitors of NCX) on NMDA-elicited whole-cell currents using the patch-clamp technique on rat cortical neurons and human embryonic kidney 293T cells expressing recombinant NMDARs. KBR inhibited NMDAR currents in a voltage-independent manner with similar potency for receptors of GluN1/2A and GluN1/2B subunit compositions that excludes open-channel block and GluN2B-selective inhibition. The inhibition by KBR depended on glycine (Gly) concentration. At 30 μM NMDA, the KBR IC50 values were 5.3 ± 0.1 and 41.2 ± 8.8 μM for 1 and 300 μM Gly, respectively. Simultaneous application of NMDA + KBR in the absence of Gly induced robust inward NMDAR currents that peaked and then rapidly decreased. KBR, therefore, is an agonist (EC50 is 1.18 ± 0.16 µM) of the GluN1 subunit coagonist binding sites. The decrease of NMDA-elicited currents in the presence of KBR was abolished in Ca(2+)-free solution and was not observed in the presence of extracellular Ca(2+) on 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-loaded neurons, suggesting that Ca(2+) affects NMDARs from the cytosol. In agreement, the substitution of Li(+) for extracellular Na(+) caused a considerable decrease of NMDAR currents, which was not observed in the absence of extracellular Ca(2+). Most likely, the accumulation of intracellular Ca(2+) is caused by the inhibition of Ca(2+) extrusion via NCX. Thus, KBR and Li(+) provoke Ca(2+)-dependent receptor inactivation due to the disruption of Ca(2+) extrusion by the NCX. The data reveal the role of NCX in regulation of Ca(2+)-dependent inactivation of NMDARs.
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Affiliation(s)
- Dmitry A Sibarov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Polina A Abushik
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Ekaterina E Poguzhelskaya
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Konstantin V Bolshakov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Sergei M Antonov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
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Changes in Electrical Activity of Working Myocardium Under Condition of If Current Inhibition. Bull Exp Biol Med 2015; 158:600-3. [DOI: 10.1007/s10517-015-2815-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Indexed: 10/23/2022]
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Inhibition of the cardiac ATP-dependent potassium current by KB-R7943. Comp Biochem Physiol A Mol Integr Physiol 2014; 175:38-45. [PMID: 24845199 DOI: 10.1016/j.cbpa.2014.05.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 05/12/2014] [Accepted: 05/13/2014] [Indexed: 11/23/2022]
Abstract
KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea) was developed as a specific inhibitor of the sarcolemmal sodium-calcium exchanger (NCX) with potential experimental and therapeutic use. However, in cardiomyocytes KB-R7943 also effectively blocks several K(+) currents including the delayed rectifier, IKr, and background inward rectifier, IK1. In the present study we analyze the effects of KB-R7943 on the ATP-dependent potassium current (IKATP) recorded by whole-cell patch-clamp in ventricular cardiomyocytes from a mammal (mouse) and a fish (crucian carp). IKATP was induced by external application of a mitochondrial uncoupler CCCP (3×10(-7) M) and internal perfusion of the cell with ATP-free pipette solution. A weakly inwardly rectifying current with a large outward component, recorded in the presence of CCCP, was blocked with 10(-5) M glibenclamide by 56.1±4.6% and 56.9±3.6% in crucian carp and mouse ventricular myocytes, respectively. In fish cardiomyocytes IKATP was blocked by KB-R7943 with an IC50 value of 3.14×10(-7) M, while in mammalian cells IC50 was 2.8×10(-6) M (P<0.05). 10(-5) M KB-R7943 inhibited CCCP-induced IKATP by 99.9±0.13% and 97.5±1.2% in crucian carp and mouse ventricular myocytes, respectively. In crucian carp the IKATP is about an order of magnitude more sensitive to KB-R7943 than the background IK1, but in mammals IKATP and IK1 are almost equally sensitive to KB-R7943. Therefore, the ability of KB-R7943 to block IKATP should be taken into account together with INCX inhibition when investigating possible cardioprotective effects of this compound.
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Tauber P, Penton D, Stindl J, Humberg E, Tegtmeier I, Sterner C, Beuschlein F, Reincke M, Barhanin J, Bandulik S, Warth R. Pharmacology and pathophysiology of mutated KCNJ5 found in adrenal aldosterone-producing adenomas. Endocrinology 2014; 155:1353-62. [PMID: 24506072 DOI: 10.1210/en.2013-1944] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Somatic mutations of the potassium channel KCNJ5 are found in 40% of aldosterone producing adenomas (APAs). APA-related mutations of KCNJ5 lead to a pathological Na(+) permeability and a rise in cytosolic Ca(2+), the latter presumably by depolarizing the membrane and activating voltage-gated Ca(2+) channels. The aim of this study was to further investigate the effects of mutated KCNJ5 channels on intracellular Na(+) and Ca(2+) homeostasis in human adrenocortical NCI-H295R cells. Expression of mutant KCNJ5 led to a 2-fold increase in intracellular Na(+) and, in parallel, to a substantial rise in intracellular Ca(2+). The increase in Ca(2+) appeared to be caused by activation of voltage-gated Ca(2+) channels and by an impairment of Ca(2+) extrusion by Na(+)/Ca(2+) exchangers. The mutated KCNJ5 exhibited a pharmacological profile that differed from the one of wild-type channels. Mutated KCNJ5 was less Ba(2+) and tertiapin-Q sensitive but was inhibited by blockers of Na(+) and Ca(2+)-transporting proteins, such as verapamil and amiloride. The clinical use of these drugs might influence aldosterone levels in APA patients with KCNJ5 mutations. This might implicate diagnostic testing of APAs and could offer new therapeutic strategies.
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Affiliation(s)
- P Tauber
- Medical Cell Biology (P.T., J.S., E.H., I.T., C.S., S.B., R.W.), University of Regensburg, 93053 Regensburg, Germany; Laboratoire de PhysioMédecine Moléculaire (D.P., J.B.), Centre National de la Recherche Scientifique, and Université de Nice Sophia Antipolis, FRE3472-Laboratoire de PhysioMédecine Moléculaire, 06108 Nice Cedex, France; Laboratories of Excellence, Ion Channel Science and Therapeutics (D.P., J.B.), France; and Medizinische Klinik und Poliklinik IV (F.B., M.R.), Ludwig-Maximilians-Universität, 80336 Munich, Germany
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