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Vinogradova TM, Sirenko S, Lukyanenko YO, Yang D, Tarasov KV, Lyashkov AE, Varghese NJ, Li Y, Chakir K, Ziman B, Lakatta EG. Basal Spontaneous Firing of Rabbit Sinoatrial Node Cells Is Regulated by Dual Activation of PDEs (Phosphodiesterases) 3 and 4. Circ Arrhythm Electrophysiol 2019; 11:e005896. [PMID: 29880528 DOI: 10.1161/circep.117.005896] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 03/27/2018] [Indexed: 12/21/2022]
Abstract
BACKGROUND Spontaneous firing of sinoatrial node cells (SANCs) is regulated by cAMP-mediated, PKA (protein kinase A)-dependent (cAMP/PKA) local subsarcolemmal Ca2+ releases (LCRs) from RyRs (ryanodine receptors). LCRs occur during diastolic depolarization and activate an inward Na+/Ca2+ exchange current that accelerates diastolic depolarization rate prompting the next action potential. PDEs (phosphodiesterases) regulate cAMP-mediated signaling; PDE3/PDE4 represent major PDE activities in SANC, but how they modulate LCRs and basal spontaneous SANC firing remains unknown. METHODS Real-time polymerase chain reaction, Western blot, immunostaining, cellular perforated patch clamping, and confocal microscopy were used to elucidate mechanisms of PDE-dependent regulation of cardiac pacemaking. RESULTS PDE3A, PDE4B, and PDE4D were the major PDE subtypes expressed in rabbit SANC, and PDE3A was colocalized with α-actinin, PDE4D, SERCA (sarcoplasmic reticulum Ca2+ ATP-ase), and PLB (phospholamban) in Z-lines. Inhibition of PDE3 (cilostamide) or PDE4 (rolipram) alone increased spontaneous SANC firing by ≈20% (P<0.05) and ≈5% (P>0.05), respectively, but concurrent PDE3+PDE4 inhibition increased spontaneous firing by ≈45% (P<0.01), indicating synergistic effect. Inhibition of PDE3 or PDE4 alone increased L-type Ca2+ current (ICa,L) by ≈60% (P<0.01) or ≈5% (P>0.05), respectively, and PLB phosphorylation by ≈20% (P>0.05) each, but dual PDE3+PDE4 inhibition increased ICa,L by ≈100% (P<0.01) and PLB phosphorylation by ≈110% (P<0.05). Dual PDE3+PDE4 inhibition increased the LCR number and size (P<0.01) and reduced the SR (sarcoplasmic reticulum) Ca2+ refilling time (P<0.01) and the LCR period (time from action potential-induced Ca2+ transient to subsequent LCR; P<0.01), leading to decrease in spontaneous SANC cycle length (P<0.01). When RyRs were disabled by ryanodine and LCRs ceased, dual PDE3+PDE4 inhibition failed to increase spontaneous SANC firing. CONCLUSIONS Basal cardiac pacemaker function is regulated by concurrent PDE3+PDE4 activation which operates in a synergistic manner via decrease in cAMP/PKA phosphorylation, suppression of LCR parameters, and prolongation of the LCR period and spontaneous SANC cycle length.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD.
| | - Syevda Sirenko
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Yevgeniya O Lukyanenko
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Dongmei Yang
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Kirill V Tarasov
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Alexey E Lyashkov
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Nevin J Varghese
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Yue Li
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Khalid Chakir
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Bruce Ziman
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
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Vinogradova TM, Kobrinsky E, Lakatta EG. Dual Activation of Phosphodiesterases 3 and 4 Regulates Basal Spontaneous Beating Rate of Cardiac Pacemaker Cells: Role of Compartmentalization? Front Physiol 2018; 9:1301. [PMID: 30356755 PMCID: PMC6189467 DOI: 10.3389/fphys.2018.01301] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 08/29/2018] [Indexed: 12/17/2022] Open
Abstract
Spontaneous firing of sinoatrial (SA) node cells (SANCs) is regulated by cyclic adenosine monophosphate (cAMP)-mediated, protein kinase A (PKA)-dependent (cAMP/PKA) local subsarcolemmal Ca2+ releases (LCRs) from ryanodine receptors (RyR). The LCRs occur during diastolic depolarization (DD) and activate an inward Na+/Ca2+ exchange current that accelerates the DD rate prompting the next action potential (AP). Basal phosphodiesterases (PDEs) activation degrades cAMP, reduces basal cAMP/PKA-dependent phosphorylation, and suppresses normal spontaneous firing of SANCs. The cAMP-degrading PDE1, PDE3, and PDE4 represent major PDE activities in rabbit SANC, and PDE inhibition by 3-isobutyl-1-methylxanthine (IBMX) increases spontaneous firing of SANC by ∼50%. Though inhibition of single PDE1–PDE4 only moderately increases spontaneous SANC firing, dual PDE3 + PDE4 inhibition produces a synergistic effect hastening the spontaneous SANC beating rate by ∼50%. Here, we describe the expression and distribution of different PDE subtypes within rabbit SANCs, several specific targets (L-type Ca2+ channels and phospholamban) regulated by basal concurrent PDE3 + PDE4 activation, and critical importance of RyR Ca2+ releases for PDE-dependent regulation of spontaneous SANC firing. Colocalization of PDE3 and PDE4 beneath sarcolemma or in striated patterns inside SANCs strongly suggests that PDE-dependent regulation of cAMP/PKA signaling might be executed at the local level; this idea, however, requires further verification.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Intramural Research Program, NIA, NIH, Baltimore, MD, United States
| | - Evgeny Kobrinsky
- Laboratory of Cardiovascular Science, Intramural Research Program, NIA, NIH, Baltimore, MD, United States
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Intramural Research Program, NIA, NIH, Baltimore, MD, United States
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Distinct patterns of constitutive phosphodiesterase activity in mouse sinoatrial node and atrial myocardium. PLoS One 2012; 7:e47652. [PMID: 23077656 PMCID: PMC3471891 DOI: 10.1371/journal.pone.0047652] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 09/14/2012] [Indexed: 01/13/2023] Open
Abstract
Phosphodiesterases (PDEs) are critical regulators of cyclic nucleotides in the heart. In ventricular myocytes, the L-type Ca(2+) current (I(Ca,L)) is a major target of regulation by PDEs, particularly members of the PDE2, PDE3 and PDE4 families. Conversely, much less is known about the roles of PDE2, PDE3 and PDE4 in the regulation of action potential (AP) properties and I(Ca,L) in the sinoatrial node (SAN) and the atrial myocardium, especially in mice. Thus, the purpose of our study was to measure the effects of global PDE inhibition with Isobutyl-1-methylxanthine (IBMX) and selective inhibitors of PDE2, PDE3 and PDE4 on AP properties in isolated mouse SAN and right atrial myocytes. We also measured the effects of these inhibitors on I(Ca,L) in SAN and atrial myocytes in comparison to ventricular myocytes. Our data demonstrate that IBMX markedly increases spontaneous AP frequency in SAN myocytes and AP duration in atrial myocytes. Spontaneous AP firing in SAN myocytes was also increased by the PDE2 inhibitor erythro-9-[2-hydroxy-3-nonyl] adenine (EHNA), the PDE3 inhibitor milrinone (Mil) and the PDE4 inhibitor rolipram (Rol). In contrast, atrial AP duration was increased by EHNA and Rol, but not by Mil. IBMX also potently, and similarly, increased I(Ca,L) in SAN, atrial and ventricular myocytes; however, important differences emerged in terms of which inhibitors could modulate I(Ca,L) in each myocyte type. Consistent with our AP measurements, EHNA, Mil and Rol each increased I(Ca,L) in SAN myocytes. Also, EHNA and Rol, but not Mil, increased atrial I(Ca,L). In complete contrast, no selective PDE inhibitors increased I(Ca,L) in ventricular myocytes when given alone. Thus, our data show that the effects of selective PDE2, PDE3 and PDE4 inhibitors are distinct in the different regions of the myocardium indicating important differences in how each PDE family constitutively regulates ion channel function in the SAN, atrial and ventricular myocardium.
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Kaumann AJ. Phosphodiesterases reduce spontaneous sinoatrial beating but not the 'fight or flight' tachycardia elicited by agonists through Gs-protein-coupled receptors. Trends Pharmacol Sci 2011; 32:377-83. [PMID: 21481950 DOI: 10.1016/j.tips.2011.03.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 03/07/2011] [Accepted: 03/09/2011] [Indexed: 01/01/2023]
Abstract
Cyclic AMP (cAMP) steers the generation of basal heart beat in the sinoatrial node. It also induces sinoatrial tachycardia and increased cardiac force, elicited through activation of Gs-protein-coupled receptors (GsPCRs). Phosphodiesterases (PDEs) hydrolyse cAMP. In the heart mainly PDE3 and PDE4 would be expected to limit those functions, and the PDE isoenzymes do indeed reduce basal sinoatrial beating rate and blunt the positive inotropic effects of agonists, mediated by GsPCRs. By contrast, recent evidence shows that GsPCR-mediated sinoatrial tachycardia is not controlled by PDE1-5. A PDE-resistant cAMP pool in sinoatrial cells, generated through activation of GsPCRs, including β(1)- and β(2)-adrenoceptors, appears to guarantee unrestrained tachycardia during fight or flight stress.
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Affiliation(s)
- Alberto J Kaumann
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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Vinogradova TM, Lakatta EG. Regulation of basal and reserve cardiac pacemaker function by interactions of cAMP-mediated PKA-dependent Ca2+ cycling with surface membrane channels. J Mol Cell Cardiol 2009; 47:456-74. [PMID: 19573534 PMCID: PMC2757791 DOI: 10.1016/j.yjmcc.2009.06.014] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 06/23/2009] [Indexed: 01/01/2023]
Abstract
Decades of intensive research of primary cardiac pacemaker, the sinoatrial node, have established potential roles of specific membrane channels in the generation of the diastolic depolarization, the major mechanism allowing sinoatrial node cells to generate spontaneous beating. During the last three decades, multiple studies made either in the isolated sinoatrial node or sinoatrial node cells have demonstrated a pivotal role of Ca(2+) and, specifically Ca(2+) release from sarcoplasmic reticulum, for spontaneous beating of cardiac pacemaker. Recently, spontaneous, rhythmic local subsarcolemmal Ca(2+) releases from ryanodine receptors during late half of the diastolic depolarization have been implicated as a vital factor in the generation of sinoatrial node cell spontaneous firing. Local Ca(2+) releases are driven by a unique combination of high basal cAMP production by adenylyl cyclases, high basal cAMP degradation by phosphodiesterases and a high level of cAMP-mediated PKA-dependent phosphorylation. These local Ca(2+) releases activate an inward Na(+)-Ca(2+) exchange current which accelerates the terminal diastolic depolarization rate and, thus, controls the spontaneous pacemaker firing. Both the basal primary pacemaker beating rate and its modulation via beta-adrenergic receptor stimulation appear to be critically dependent upon intact RyR function and local subsarcolemmal sarcoplasmic reticulum generated Ca(2+) releases. This review aspires to integrate the traditional viewpoint that has emphasized the supremacy of the ensemble of surface membrane ion channels in spontaneous firing of the primary cardiac pacemaker, and these novel perspectives of cAMP-mediated PKA-dependent Ca(2+) cycling in regulation of the heart pacemaker clock, both in the basal state and during beta-adrenergic receptor stimulation.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Gerontology Research Center, NIA, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825, USA
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Vinogradova TM, Sirenko S, Lyashkov AE, Younes A, Li Y, Zhu W, Yang D, Ruknudin AM, Spurgeon H, Lakatta EG. Constitutive phosphodiesterase activity restricts spontaneous beating rate of cardiac pacemaker cells by suppressing local Ca2+ releases. Circ Res 2008; 102:761-9. [PMID: 18276917 DOI: 10.1161/circresaha.107.161679] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Spontaneous beating of rabbit sinoatrial node cells (SANCs) is controlled by cAMP-mediated, protein kinase A-dependent local subsarcolemmal ryanodine receptor Ca(2+) releases (LCRs). LCRs activated an inward Na(+)/Ca(2+) exchange current that increases the terminal diastolic depolarization rate and, therefore, the spontaneous SANC beating rate. Basal cAMP in SANCs is elevated, suggesting that cAMP degradation by phosphodiesterases (PDEs) may be low. Surprisingly, total suppression of PDE activity with a broad-spectrum PDE inhibitor, 3'-isobutylmethylxanthine (IBMX), produced a 9-fold increase in the cAMP level, doubled cAMP-mediated, protein kinase A-dependent phospholamban phosphorylation, and increased SANC firing rate by approximately 55%, indicating a high basal activity of PDEs in SANCs. A comparison of specific PDE1 to -5 inhibitors revealed that the specific PDE3 inhibitor, milrinone, accelerated spontaneous firing by approximately 47% (effects of others were minor) and increased amplitude of L-type Ca(2+) current (I(Ca,L)) by approximately 46%, indicating that PDE3 was the major constitutively active PDE in the basal state. PDE-dependent control of the spontaneous SANC firing was critically dependent on subsarcolemmal LCRs, ie, PDE inhibition increased LCR amplitude and size and decreased LCR period, leading to earlier and augmented LCR Ca(2+) release, Na(+)/Ca(2+) exchange current, and an increase in the firing rate. When ryanodine receptors were disabled by ryanodine, neither IBMX nor milrinone was able to amplify LCRs, accelerate diastolic depolarization rate, or increase the SANC firing rate, despite preserved PDE inhibition-induced augmentation of I(Ca,L) amplitude. Thus, basal constitutive PDE activation provides a novel and powerful mechanism to decrease cAMP, limit cAMP-mediated, protein kinase A-dependent increase of diastolic ryanodine receptor Ca(2+) release, and restrict the spontaneous SANC beating rate.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Gerontology Research Center, NIA, NIH, 5600 Nathan Shock Dr, Baltimore, MD 21224-6825, USA.
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Sugiyama A, Satoh Y, Hashimoto K. Electropharmacologic effects of a new phosphodiesterase III inhibitor, toborinone (OPC-18790), assessed in an in vivo canine model. J Cardiovasc Pharmacol 2001; 38:268-77. [PMID: 11483877 DOI: 10.1097/00005344-200108000-00013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Electropharmacologic effects of a new phosphodiesterase (PDE) III inhibitor toborinone (OPC-18790) were assessed in a halothane-anesthetized, closed-chest canine model. Toborinone, 0.03 mg/kg, increased ventricular contractility, decreased total peripheral resistance, and inhibited intraventricular conduction without changing other cardiovascular parameters. A clinically relevant dose of 0.3 mg/kg increased heart rate, systolic blood pressure, and cardiac output, decreased preload to the left ventricle, enhanced atrioventricular nodal conduction, and shortened repolarization and the vulnerable period of the ventricle, in addition to enhancing the effects observed after the low dose. A high dose of 3 mg/kg of toborinone decreased systolic, mean, and diastolic pressures and prolonged the effective refractory period (ERP) in addition to the effects observed after the middle dose. No further change was detected in ventricular repolarization. Most of the cardiohemodynamic effects can be explained by the PDE III inhibition by toborinone. With regard to electrophysiologic properties, the prolongation of intraventricular conduction time and ERP by toborinone suggests sodium channel inhibition. The lack of the prolongation of ventricular repolarization suggests that previously demonstrated inhibition of I(Kr) and I(K1) and increased I(Ca-L) by toborinone might be counteracted by factors such as the cyclic AMP-dependent outward currents, I(Ks) and I(C1).
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Affiliation(s)
- A Sugiyama
- Department of Pharmacology, Yamanashi Medical University, Japan.
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