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Díaz RG, Escudero DS, Brea MS, Morgan PE, Pérez NG. p38 mitogen activated protein kinase mediates cardiac Na +/H + exchanger inhibition induced by Sildenafil. Eur J Pharmacol 2019; 849:96-105. [PMID: 30721701 DOI: 10.1016/j.ejphar.2019.01.070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 01/11/2019] [Accepted: 01/21/2019] [Indexed: 10/27/2022]
Abstract
Since the original description as potent antianginal compounds, phosphodiesterase 5A inhibitors have continuously increased their possible therapeutic applications. In the heart, Sildenafil was shown to protect against an ischemic insult by decreasing cardiac Na+/H+ exchanger (NHE1) activity, action that was mediated by protein kinase G. p38 mitogen activated protein kinase (p38MAPK) activation was described in cardiac ischemia, but its precise role remains elusive. It has been shown that p38MAPK is activated by protein kinase G (PKG) in certain non-cardiac tissues, while in others modulates NHE1 activity. Current study was aimed to seek the role of p38MAPK in the Sildenafil-triggered pathway leading to NHE1 inhibition in myocardium. Rat isolated papillary muscles were used to evaluate NHE1 activity during intracellular pH recovery from an acidic load. Protein kinases phosphorylation (activation) was determined by western blot. Sustained acidosis promoted NHE1 hyperactivity by enhancing Ser703 phosphorylation, effect that was blunted by Sildenafil. p38MAPK inhibition reversed the effect of Sildenafil on NHE1. Activation of p38MAPK, by Sodium Arsenite or Anisomycin, mimicked the inhibitory effect of Sildenafil on the exchanger. Consistently, Sildenafil induced p38MAPK phosphorylation/activation during acidosis. Neither Sildenafil nor p38MAPK inhibition affected extracellular signal-regulated kinases 1/2 phosphorylation, kinases upstream NHE1. Furthermore, inhibition of NHE1 after p38MAPK activation was precluded by preventing the activation of protein phosphatase 2A with Okadaic Acid. Taken together, these results suggest that activation of p38MAPK is a necessary step to trigger the inhibitory effect of Sildenafil on cardiac NHE1 activity, thorough a mechanism that involves protein phosphatase 2A-mediated exchanger dephosphorylation.
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Affiliation(s)
- Romina G Díaz
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina
| | - Daiana S Escudero
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina
| | - María S Brea
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina
| | - Patricio E Morgan
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina.
| | - Néstor G Pérez
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina.
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Malan D, Fleischmann BK. Functional expression and modulation of the L-type Ca2+ current in embryonic heart cells. Pediatr Cardiol 2012; 33:907-15. [PMID: 22639002 DOI: 10.1007/s00246-012-0360-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 04/30/2012] [Indexed: 11/28/2022]
Abstract
Voltage-dependent L-type Ca2+ channels (VDCCs) are critically involved in excitation contraction coupling and regulation of the force of contraction. An important mechanism contributing to the adaptation of heart function is modulation of the L-type Ca2+ current (I(Ca-L)) by hormones of the autonomous nervous system. The signaling pathways underlying this regulation in the adult heart are well understood. However, VDCC expression and its regulation in the embryonic heart are less understood. This report therefore provides a short overview of the current knowledge on this topic using embryonic stem cells and the mouse as model systems.
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Affiliation(s)
- Daniela Malan
- Institute of Physiology I, Life and Brain Center, University of Bonn, Sigmund-Freud-Strasse 25, 53105, Bonn, Germany.
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3
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Lanzafame AA, Christopoulos A, Mitchelson F. Cellular Signaling Mechanisms for Muscarinic Acetylcholine Receptors. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820308263] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Ritchie RH, Irvine JC, Rosenkranz AC, Patel R, Wendt IR, Horowitz JD, Kemp-Harper BK. Exploiting cGMP-based therapies for the prevention of left ventricular hypertrophy: NO* and beyond. Pharmacol Ther 2009; 124:279-300. [PMID: 19723539 DOI: 10.1016/j.pharmthera.2009.08.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 08/14/2009] [Indexed: 02/07/2023]
Abstract
Left ventricular hypertrophy (LVH), an increased left ventricular (LV) mass, is common to many cardiovascular disorders, initially developing as an adaptive response to maintain myocardial function. In the longer term, this LV remodelling becomes maladaptive, with progressive decline in LV contractility and diastolic function. Indeed LVH is recognised as an important blood-pressure independent predictor of cardiovascular morbidity and mortality. The clinical efficacy of current treatments for LVH is reduced, however, by their tendency to slow disease progression rather than induce its reversal, and thus the development of new therapies for LVH is paramount. The signalling molecule cyclic guanosine-3',5'-monophosphate (cGMP), well-recognised for its role in regulating vascular tone, is now being increasingly identified as an important anti-hypertrophic mediator. This review is focused on the various means by which cGMP can be stimulated in the heart, such as via the natriuretic peptides, to exert anti-hypertrophic actions. In particular we address the limitations of traditional nitric oxide (NO*) donors in the face of the potential therapeutic advantages offered by novel alternatives; NO* siblings, ligands of the cGMP-generating enzymes, soluble (sGC) and particulate guanylyl cyclases (pGC), and phosphodiesterase inhibitors. Further impact of cGMP within the cardiovascular system is also discussed with a view to representing cGMP-based therapies as innovative pharmacotherapy, alone or concurrent with standard care, for the management of LVH.
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Affiliation(s)
- Rebecca H Ritchie
- Heart Failure Pharmacology, Baker IDI Heart & Diabetes Institute Melbourne, Victoria, Australia.
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Hünlich M, Hasenfuss G. Effects of the NO donor sodium nitroprusside on oxygen consumption and energetics in rabbit myocardium. Basic Res Cardiol 2009; 104:359-65. [PMID: 19190952 PMCID: PMC3085761 DOI: 10.1007/s00395-009-0777-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 12/22/2008] [Indexed: 12/05/2022]
Abstract
Nitric oxide (NO) has influence on various cellular functions. Little is known of the influence of NO on myocardial energetics. In the present study oxygen consumption and mechanical parameters of isometrically contracting rabbit papillary muscles (1 Hz stimulation frequency) were investigated at varying interventions while maintaining physiological conditions (37°C; 2.5 mM Ca2+) to study the effects of NO on energetics. The NO donor sodium nitroprusside (SNP) showed a negative inotropic effect. SNP decreased the maximal force in normal rabbit muscle strips by 30%, the force time integral (FTI) by 40% and the relaxation time by 20%. In addition the oxygen consumption decreased by 60%, a notably disproportional decrease compared to the mechanical parameters. Consequently, the economy as a ratio of FTI and oxygen consumption is significantly increased by SNP. In contrast the negative inotropic effect due to a reduction in extracellular Calcium (Ca2+) from 2.5 to 1.25 mM reduced FTI and oxygen consumption proportionally by 40% and did not change economy. The effect of NO on force and oxygen consumption could be reproduced by the application of the cyclic guanosine monophosphate (cGMP) analogue 8-bromo-cGMP. In summary, NO increased the economy of isometrically contracting papillary muscles. The improvement in contraction economy under NO seems to be mediated by cGMP as the secondary messenger and maybe due to alterations of the crossbridge cycle.
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Affiliation(s)
- Mark Hünlich
- Universitätsklinik Göttingen, Abteilung für Kardiologie, Robert-Koch-Strasse 40, 37099, Göttingen, Germany.
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Zhu X, Zhu X, Niu X, Pei J, Xiong L, Chen S, Lu SY, Wei J, Xing B, Liu L, Mei Q, Zhu M, Kaye AD. Inhibition of cardiomyocyte contractile/relaxation by MN9202 and mechanisms involved. Arch Med Res 2008; 39:489-95. [PMID: 18514093 DOI: 10.1016/j.arcmed.2008.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Accepted: 02/28/2008] [Indexed: 10/22/2022]
Abstract
BACKGROUND The cardiac contractile function of hypertensive patients is higher than non-hypertensive patients so that it is beneficial for lowering cardiac contractile function of hypertensive patients. It remains unclear if MN9202, a dihydropyridine calcium channel blocker, has effects on positive inotropic responses induced by tetraethylammonium chloride (TEA), an antagonist of calcium-activated potassium channels, forskolin (FSK), an activator of adenylyl cyclase, isoproterenol (Iso), an activator of beta-adrenergic receptors, and methylene blue (MB), an inhibitor of guanylyl cyclase, in electrically stimulated rat cardiomyocytes. Myocyte shortening and intracellular calcium transients were assessed and the underlying mechanisms were investigated. METHODS Twitch amplitude was measured by a video edge tracker method. Cell shortening/relengthening indexes including peak height (ph), peak height/baseline percent (ph/bl%), maximal velocity of shortening (+dL/dt), and maximal velocity of relengthening (-dL/dt) were recorded and analyzed by computer. Calcium transient amplitude (DeltaFFI) indicates intracellular calcium transients. RESULTS Iso, FSK, TEA, and MB enhanced electrical stimulation induced contraction as evidenced by increased ph, ph/bl%, +/- dL/dt, and calcium transient amplitude (DeltaFFI) compared with those in the control group. Under basal conditions, MN9202 decreased electrically induced contraction (ph, ph/bl%,+dL/dt,-dL/dt) in a concentration-dependent manner from 3 x 10(-10) to 3 x 10(-6) mol/L. MN9202 significantly decreased calcium transient amplitude. Moreover, MN9202 (3 x 10(-6) mol/L) partially but significantly blocked the positive inotropic effect induced by Iso, FSK, MB, and TEA through blocking DeltaFFI. CONCLUSIONS Iso, FSK, TEA, and MB increased the shortening and relengthening function of cardiomyocytes, which were partially blocked by MN9202. These results suggest that MN9202 may not only block the dihydropyridine receptor but may also inhibit other calcium influx. The exact mechanism of the action of MN9202 requires further study.
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Affiliation(s)
- Xiaoxing Zhu
- Department of Cardiology, Xi'an Jiaotong University, Xi'an, Shaanxi, PR China
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Wei SK, Ruknudin AM, Shou M, McCurley JM, Hanlon SU, Elgin E, Schulze DH, Haigney MCP. Muscarinic modulation of the sodium-calcium exchanger in heart failure. Circulation 2007; 115:1225-33. [PMID: 17339552 DOI: 10.1161/circulationaha.106.650416] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The Na-Ca exchanger (NCX) is a critical calcium efflux pathway in excitable cells, but little is known regarding its autonomic regulation. METHODS AND RESULTS We investigated beta-adrenergic receptor and muscarinic receptor regulation of the cardiac NCX in control and heart failure (HF) conditions in atrially paced pigs. NCX current in myocytes from control swine hearts was significantly increased by isoproterenol, and this response was reversed by concurrent muscarinic receptor stimulation with the addition of carbachol, demonstrating "accentuated antagonism." Okadaic acid eliminated the inhibitory effect of carbachol on isoproterenol-stimulated NCX current, indicating that muscarinic receptor regulation operates via protein phosphatase-induced dephosphorylation. However, in myocytes from atrially paced tachycardia-induced HF pigs, the NCX current was significantly larger at baseline but less responsive to isoproterenol compared with controls, whereas carbachol failed to inhibit isoproterenol-stimulated NCX current, and 8-Br-cGMP did not restore muscarinic responsiveness. Protein phosphatase type 1 dialysis significantly reduced NCX current in failing but not control cells, consistent with NCX hyperphosphorylation in HF. Protein phosphatase type 1 levels associated with NCX were significantly depressed in HF pigs compared with control, and total phosphatase activity associated with NCX was significantly decreased. CONCLUSIONS We conclude that the NCX is autonomically modulated, but HF reduces the level and activity of associated phosphatases; defective dephosphorylation then "locks" the exchanger in a highly active state.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Animals
- Carbachol/pharmacology
- Cardiac Pacing, Artificial
- Cell Separation
- Cells, Cultured
- Cyclic GMP/analogs & derivatives
- Cyclic GMP/pharmacology
- Disease Models, Animal
- Drug Antagonism
- Female
- Heart Failure/complications
- Heart Failure/metabolism
- Isoproterenol/pharmacology
- Male
- Muscarinic Agonists/pharmacology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Niflumic Acid/pharmacology
- Patch-Clamp Techniques
- Phosphoprotein Phosphatases/metabolism
- Phosphorylation
- Receptors, Adrenergic, beta/drug effects
- Receptors, Adrenergic, beta/metabolism
- Receptors, Muscarinic/drug effects
- Receptors, Muscarinic/metabolism
- Sodium-Calcium Exchanger/metabolism
- Swine
- Tachycardia/complications
- Tachycardia/metabolism
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Affiliation(s)
- Shao-kui Wei
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd, Bethesda, MD 20814, USA
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Pitt GS, Dun W, Boyden PA. Remodeled cardiac calcium channels. J Mol Cell Cardiol 2006; 41:373-88. [PMID: 16901502 DOI: 10.1016/j.yjmcc.2006.06.071] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Revised: 05/26/2006] [Accepted: 06/22/2006] [Indexed: 10/24/2022]
Abstract
Cardiac calcium channels play a pivotal role in the proper functioning of cardiac cells. In response to various pathologic stimuli, they become remodeled, changing how they function, as they adapt to their new environment. Specific features of remodeled channels depend upon the particular disease state. This review will summarize what is known about remodeled cardiac calcium channels in three disease states: hypertrophy, heart failure and atrial fibrillation. In addition, it will review the recent advances made in our understanding of the function of the various molecular building blocks that contribute to the proper functioning of the cardiac calcium channel.
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Affiliation(s)
- Geoffrey S Pitt
- Department of Medicine, Columbia University, New York, NY, USA
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9
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Yu YC, Cao LH, Yang XL. Modulation by brain natriuretic peptide of GABA receptors on rat retinal ON-type bipolar cells. J Neurosci 2006; 26:696-707. [PMID: 16407567 PMCID: PMC6674405 DOI: 10.1523/jneurosci.3653-05.2006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Natriuretic peptides (NPs) may work as neuromodulators through their associated receptors [NP receptors (NPRs)]. By immunocytochemistry, we showed that NPR-A and NPR-B were expressed abundantly on both ON-type and OFF-type bipolar cells (BCs) in rat retina, including the dendrites, somata, and axon terminals. Whole-cell recordings made from isolated ON-type BCs further showed that brain natriuretic peptide (BNP) suppressed GABAA receptor-, but not GABAC receptor-, mediated currents of the BCs, which was blocked by the NPR-A antagonist anantin. The NPR-C agonist c-ANF [des(Gln18, Ser19, Gln20, Leu21, Gly22)ANF(4-23)-NH2] did not suppress GABAA currents. The BNP effect on GABAA currents was abolished with preincubation with the pGC-A/B antagonist HS-142-1 but mimicked by application of 8-bromoguanosine-3',5'-cyclomonophosphate. These results suggest that elevated levels of intracellular cGMP caused by activation of NPR-A may mediate the BNP effect. Internal infusion of the cGMP-dependent protein kinase G (PKG) inhibitor KT5823 essentially blocked the BNP-induced reduction of GABAA currents. Moreover, calcium imaging showed that BNP caused a significant elevation of intracellular calcium that could be caused by increased calcium release from intracellular stores by PKG. The BNP effect was blocked by the ryanodine receptor modulators caffeine, ryanodine, and ruthenium red but not by the IP3 receptor antagonists heparin and xestospongin-C. Furthermore, the BNP effect was abolished after application of the blocker of endoplasmic reticulum Ca2+-ATPase thapsigargin and greatly reduced by the calmodulin inhibitors W-7 and calmidazolium. We therefore conclude that the increased calcium release from ryanodine-sensitive calcium stores by BNP may be responsible for the BNP-caused GABAA response suppression in ON-type BCs through stimulating calmodulin.
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MESH Headings
- Animals
- Atrial Natriuretic Factor/pharmacology
- Caffeine/pharmacology
- Calcium/metabolism
- Calcium Channels
- Calcium Signaling/drug effects
- Calcium-Transporting ATPases/antagonists & inhibitors
- Calmodulin/antagonists & inhibitors
- Calmodulin/physiology
- Carbazoles/pharmacology
- Cyclic GMP/analogs & derivatives
- Cyclic GMP/pharmacology
- Cyclic GMP-Dependent Protein Kinases/physiology
- GABA-A Receptor Antagonists
- Guanylate Cyclase/drug effects
- Guanylate Cyclase/physiology
- Heparin/pharmacology
- Imidazoles/pharmacology
- Indoles/pharmacology
- Inositol 1,4,5-Trisphosphate Receptors
- Macrocyclic Compounds
- Male
- Membrane Potentials/drug effects
- Natriuretic Peptide, Brain/antagonists & inhibitors
- Natriuretic Peptide, Brain/pharmacology
- Natriuretic Peptide, Brain/physiology
- Oxazoles/pharmacology
- Patch-Clamp Techniques
- Peptide Fragments/pharmacology
- Peptides, Cyclic/pharmacology
- Polysaccharides/pharmacology
- Protein Kinase Inhibitors/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, Atrial Natriuretic Factor/drug effects
- Receptors, Atrial Natriuretic Factor/physiology
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Receptors, GABA/physiology
- Receptors, GABA-A/drug effects
- Retinal Bipolar Cells/drug effects
- Retinal Bipolar Cells/physiology
- Ruthenium Red/pharmacology
- Ryanodine/pharmacology
- Ryanodine Receptor Calcium Release Channel/drug effects
- Thapsigargin/pharmacology
- gamma-Aminobutyric Acid/pharmacology
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Affiliation(s)
- Yong-Chun Yu
- Institute of Neurobiology, Fudan University, Shanghai 200433, China
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Wang X, Wu BW, Wu DM. Effects of AMP579 and adenosine on L-type Ca2+ current in isolated rat ventricular myocytes. Acta Pharmacol Sin 2005; 26:559-62. [PMID: 15842773 DOI: 10.1111/j.1745-7254.2005.00107.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
AIM To compare the effects of AMP579 and adenosine on L-type Ca2+ current (I(Ca-L)) in rat ventricular myocytes and explore the mechanism by which AMP579 acts on I(Ca-L). METHODS I(Ca-L) was recorded by patch-clamp technique in whole-cell configuration. RESULTS Adenosine (10 nmol/L to 50 micromol/L) showed no effect on basal I(Ca-L), but it inhibited the I(Ca-L) induced by isoproterenol 10 nmol/L in a concentration-dependent manner with the IC(50) of 13.06 micromol/L. Similar to adenosine, AMP579 also showed an inhibitory effect on the I(Ca-L) induced by isoproterenol. AMP579 and adenosine (both in 10 micromol/L) suppressed isoproterenol-induced ICa-L by 11.1% and 5.2%, respectively. In addition, AMP579 had a direct inhibitory effect on basal I(Ca-L) in a concentration-dependent manner with IC50 (1.17 micromol/L). PD116948 (30 micromol/L), an adenosine A1 receptor blocker, showed no action on the inhibitory effect of AMP579 on basal I(Ca-L). However, GF109203X (0.4 micromol/L), a special protein kinase C (PKC) blocker, could abolish the inhibitory effect of AMP579 on basal I(Ca-L). So the inhibitory effect of AMP579 on basal I(Ca-L) was induced through activating PKC, but not linked to adenosine A1 receptor. CONCLUSION AMP579 shows a stronger inhibitory effect than adenosine on the I(Ca-L) induced by isoproterenol. AMP579 also has a strong inhibitory effect on basal I(Ca-L) in rat ventricular myocytes. Activation of PKC is involved in the inhibitory effect of AMP579 on basal I(Ca-L) at downstream-mechanism.
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Affiliation(s)
- Xiong Wang
- Department of Physiology, Shanxi Medical University, Taiyuan 030001, China.
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11
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Su J, Scholz PM, Weiss HR. Differential effects of cGMP produced by soluble and particulate guanylyl cyclase on mouse ventricular myocytes. Exp Biol Med (Maywood) 2005; 230:242-50. [PMID: 15792945 DOI: 10.1177/153537020523000403] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Particulate guanylyl cyclase (pGC) and soluble guanylyl cyclase (sGC) are cGMP-generation systems distributed in different intracellular locations. Our aim was to test the hypothesis that the functional effects of cGMP produced by pGC and sGC on contraction and Ca2+ transients would differ in ventricular myocytes. We measured myocyte shortening from adult mice using a video edge-detector and investigated the functional changes after stimulating pGC with C-type natriuretic peptide (CNP; 10(-8) M and 10(-7) M) or sGC with S-nitroso-N-acetyl-penicillamine (SNAP; nitric oxide donor; 10(-6) M and 10(-5) M). Significant concentration-dependent decreases in percentage shortening (PCS), maximal rate of shortening (RSmax), and relaxation (RRmax) were produced by CNP. To a similar degree, SNAP concentration-dependently reduced PCS, RSmax, and RRmax. The addition of Rp-8-[(4-chlorophenyl)thio]-cGMPS triethylamine (cGMP-dependent protein kinase inhibitor; 5 x 10(-6) M) or erythro-9-(2-hydroxy-3-nonyl) adenine (cGMP-stimulated cAMP phosphodiesterase inhibitor; 10(-5) M) reduced the responses induced by CNP or SNAP, suggesting that their actions were through cGMP-mediated pathways. While SNAP significantly increased intracellular cGMP concentration by 57%, CNP had little effect on cGMP production. We also found that CNP markedly decreased the amplitude of Ca2+ transients while SNAP had little effect, suggesting the cGMP generated by sGC may decrease myofilament Ca2+ sensitivity. The small amount of cGMP generated by pGC had a major effect in reducing Ca2+ level. This study suggested the existence of compartmentalization for cGMP in ventricular myocytes.
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Affiliation(s)
- Jun Su
- Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-5635, USA
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Brette F, Leroy J, Le Guennec JY, Sallé L. Ca2+ currents in cardiac myocytes: Old story, new insights. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2005; 91:1-82. [PMID: 16503439 DOI: 10.1016/j.pbiomolbio.2005.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Calcium is a ubiquitous second messenger which plays key roles in numerous physiological functions. In cardiac myocytes, Ca2+ crosses the plasma membrane via specialized voltage-gated Ca2+ channels which have two main functions: (i) carrying depolarizing current by allowing positively charged Ca2+ ions to move into the cell; (ii) triggering Ca2+ release from the sarcoplasmic reticulum. Recently, it has been suggested than Ca2+ channels also participate in excitation-transcription coupling. The purpose of this review is to discuss the physiological roles of Ca2+ currents in cardiac myocytes. Next, we describe local regulation of Ca2+ channels by cyclic nucleotides. We also provide an overview of recent studies investigating the structure-function relationship of Ca2+ channels in cardiac myocytes using heterologous system expression and transgenic mice, with descriptions of the recently discovered Ca2+ channels alpha(1D) and alpha(1E). We finally discuss the potential involvement of Ca2+ currents in cardiac pathologies, such as diseases with autoimmune components, and cardiac remodeling.
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Affiliation(s)
- Fabien Brette
- School of Biomedical Sciences, University of Leeds, Worsley Building Leeds, LS2 9NQ, UK.
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Xiong W, Ferrier GR, Howlett SE. Diminished Inotropic Response to Amrinone in Ventricular Myocytes from Myopathic Hamsters Is Linked to Depression of High-Gain Ca2+-Induced Ca2+Release. J Pharmacol Exp Ther 2004; 310:761-73. [PMID: 15064331 DOI: 10.1124/jpet.103.064873] [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] [Indexed: 11/22/2022] Open
Abstract
This study investigates whether amrinone (100-1000 microM), a phosphodiesterase-III inhibitor, can alleviate depression of contractions in ventricular myocytes from prefailure cardiomyopathic (CM) hamsters (80-100 days). Cell shortening and ion currents were measured in voltage-clamped cells at 37 degrees C. Normal myocytes exhibited low-gain Ca(2+)-induced Ca(2+) release (CICR) initiated by test steps from -40 mV and high-gain CICR initiated from more negative potentials. In normal myocytes, amrinone selectively increased contractions initiated by high-gain CICR (fractional shortening increased from 3.6 +/- 0.5% to 5.3 +/- 0.6%, 300 microM amrinone) but had no effect on low-gain CICR. Amrinone decreased L-type Ca(2+) current (I(Ca-L); -5.5 +/- 0.8 to -3.7 +/- 0.5 picoAmp/picoFarad, 300 microM amrinone). In contrast, in CM myocytes, high-gain CICR was virtually absent, and amrinone had no inotropic effect. Amrinone inhibited I(Ca-L) less in CM than normal myocytes. Sarcoplasmic reticulum (SR) Ca(2+) stores, assessed by caffeine, were significantly increased by amrinone in normal but not CM myocytes. Thus, the positive inotropic effect of amrinone in normal hamster myocytes was mediated by selective enhancement of high-gain CICR. This effect was not mediated by stimulation of I(Ca-L) because I(Ca-L) is inhibited by this drug in hamster. High-gain CICR, which is depressed in CM myocytes, cannot be restored by amrinone. However, minimal stimulation of adenylyl cyclase with forskolin restored the positive inotropic effect of amrinone in CM cells. This positive inotropic effect of amrinone may reflect increased SR Ca(2+) stores because increased stores accompanied the positive inotropic effect in normal myocytes but were absent in CM myocytes.
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Affiliation(s)
- Wei Xiong
- Department of Pharmacology, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, Nova Scotia Canada B3H 4H7
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14
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Abstract
The parasympathetic component of the autonomic nervous system plays an important role in the physiological regulation of cardiac function by exerting significant influence over the initiation as well as propagation of electrical impulses, in addition to being able to regulate contractile force. These effects are mediated in whole or in part through changes in ion channel activity that occur in response to activation of M(2) muscarinic cholinergic receptors following release of the neurotransmitter acetylcholine. The coupling of M(2) receptor activation to most changes in cardiac ion channel function can be explained by one of two general paradigms. The first involves direct G protein-dependent regulation of ion channel activity. The second involves indirect regulation of ion channel activity through modulation of cAMP-dependent responses. This review focuses on recent advances in our understanding of the mechanisms by which M(2) muscarinic receptor activation both inhibits and facilitates cAMP-dependent ion channel responses in the heart.
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Affiliation(s)
- Robert D Harvey
- Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970, U.S.A.
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15
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Liu Q, Hofmann PA. Modulation of protein phosphatase 2a by adenosine A1 receptors in cardiomyocytes: role for p38 MAPK. Am J Physiol Heart Circ Physiol 2003; 285:H97-103. [PMID: 12649078 DOI: 10.1152/ajpheart.00956.2002] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adenosine A1 receptor activation causes protein phosphatase 2a (PP2a) activation in ventricular myocytes. This attenuates beta-adrenergic functional effects in the heart (Liu Q and Hofmann PA. Am J Physiol Heart Circ Physiol 283: H1314-H1321, 2002). The purpose of the present study was to identify the signaling pathway involved in the translocation/activation of PP2a by adenosine A1 receptors in ventricular myocytes. We found that N6-cyclopentyladenosine (CPA; an adenosine A1 receptor agonist)-induced PP2a translocation was blocked by p38 MAPK inhibition but not by JNK inhibition. CPA increased phosphorylation of p38 MAPK, and this effect was abolished by pertussis toxin and inhibitors of the cGMP pathway. Moreover, CPA-induced PP2a translocation was blocked by inhibition of the cGMP pathway. Guanylyl cyclase activation mimicked the effects of CPA and caused p38 MAPK phosphorylation and PP2a translocation. Finally, CPA-induced dephosphorylations of troponin I and phospholamban were blocked by pertussis toxin and attenuated by p38 MAPK inhibition. These results suggest that adenosine A1 receptor-mediated PP2a activation uses a pertussis toxin-sensitive Gi protein-guanylyl cyclase-p38 MAPK pathway. This proposed, novel pathway may play a role in acute modulation of cardiac function.
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Affiliation(s)
- Qinghang Liu
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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