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Eickelmann C, Lieder HR, Sturek M, Heusch G, Kleinbongard P. Differences in vasomotor function of mesenteric arteries between Ossabaw minipigs with predisposition to metabolic syndrome and Göttingen minipigs. Am J Physiol Heart Circ Physiol 2024; 326:H408-H417. [PMID: 38133620 DOI: 10.1152/ajpheart.00719.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 12/08/2023] [Accepted: 12/20/2023] [Indexed: 12/23/2023]
Abstract
Metabolic syndrome predisposes and contributes to the development and progression of atherosclerosis. The minipig strain "Ossabaw" is characterized by a predisposition to develop metabolic syndrome. We compared vasomotor function in Ossabaw minipigs before they developed their diseased phenotype to that of Göttingen minipigs without such genetic predisposition. Mesenteric arteries of adult Ossabaw and Göttingen minipigs were dissected postmortem and mounted on a myograph for isometric force measurements. Maximal vasoconstriction to potassium chloride (KClmax) was induced. Cumulative concentration-response curves were determined in response to norepinephrine. Endothelium-dependent (with carbachol) and endothelium-independent (with nitroprusside) vasodilation were analyzed after preconstriction by norepinephrine. In a bioinformatic analysis, variants/altered base pairs within genes associated with cardiovascular disease were analyzed. KClmax was similar between the minipig strains (15.6 ± 6.7 vs. 14.1 ± 3.4 ΔmN). Vasoconstriction in response to norepinephrine was more pronounced in Ossabaw than in Göttingen minipigs (increase of force to 143 ± 48 vs. 108 ± 38% of KClmax). Endothelium-dependent and endothelium-independent vasodilation were less pronounced in Ossabaw than in Göttingen minipigs (decrease of force to 46.4 ± 29.6 vs. 16.0 ± 18.4% and to 36.7 ± 25.2 vs. 2.3 ± 3.7% of norepinephrine-induced preconstriction). Vasomotor function was not different between the sexes. More altered base pairs/variants were identified in Ossabaw than in Göttingen minipigs for the exon encoding adrenoceptor-α1A. Vasomotor function in lean Ossabaw minipigs is shifted toward vasoconstriction and away from vasodilation in comparison with Göttingen minipigs, suggesting a genetic predisposition for vascular dysfunction and atherosclerosis in Ossabaw minipigs. Thus, Ossabaw minipigs may be a better model for human cardiovascular disease than Göttingen minipigs.NEW & NOTEWORTHY Animal models with a predisposition to metabolic syndrome and atherosclerosis are attracting growing interest for translational research, as they may better mimic the variability of patients with cardiovascular disease. In Ossabaw minipigs, with a polygenic predisposition to metabolic syndrome, but without the diseased phenotype, vasoconstriction is more and vasodilation is less pronounced in mesenteric arteries than in Göttingen minipigs. Ossabaw minipigs may be a more suitable model of human cardiovascular disease.
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Affiliation(s)
- Chantal Eickelmann
- Institute for Pathophysiology, West German Heart and Vascular Center, University of Essen Medical School, Essen, Germany
| | - Helmut Raphael Lieder
- Institute for Pathophysiology, West German Heart and Vascular Center, University of Essen Medical School, Essen, Germany
| | - Michael Sturek
- CorVus Biomedical, LLC, and CorVus Foundation, Inc., Crawfordsville, Indiana, United States
| | - Gerd Heusch
- Institute for Pathophysiology, West German Heart and Vascular Center, University of Essen Medical School, Essen, Germany
| | - Petra Kleinbongard
- Institute for Pathophysiology, West German Heart and Vascular Center, University of Essen Medical School, Essen, Germany
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2
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Mastos C, Xu X, Keen AC, Halls ML. Signalling of Adrenoceptors: Canonical Pathways and New Paradigms. Handb Exp Pharmacol 2024. [PMID: 38227198 DOI: 10.1007/164_2023_704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2024]
Abstract
The concept of G protein-coupled receptors initially arose from studies of the β-adrenoceptor, adenylyl cyclase, and cAMP signalling pathway. Since then both canonical G protein-coupled receptor signalling pathways and emerging paradigms in receptor signalling have been defined by experiments focused on adrenoceptors. Here, we discuss the evidence for G protein coupling specificity of the nine adrenoceptor subtypes. We summarise the ability of each of the adrenoceptors to activate proximal signalling mediators including cAMP, calcium, mitogen-activated protein kinases, and protein kinase C pathways. Finally, we highlight the importance of precise spatial and temporal control of adrenoceptor signalling that is controlled by the localisation of receptors at intracellular membranes and in larger protein complexes.
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Affiliation(s)
- Chantel Mastos
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Xiaomeng Xu
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Alastair C Keen
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Michelle L Halls
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia.
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Mechanisms for the α-Adrenoceptor-Mediated Positive Inotropy in Mouse Ventricular Myocardium: Enhancing Effect of Action Potential Prolongation. Int J Mol Sci 2023; 24:ijms24043926. [PMID: 36835338 PMCID: PMC9964142 DOI: 10.3390/ijms24043926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/09/2023] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
Mechanisms for the α-adrenoceptor-mediated positive inotropy in neonatal mouse ventricular myocardium were studied with isolated myocardial preparations. The phenylephrine-induced positive inotropy was suppressed by prazosin, nifedipine, and chelerythrine, a protein kinase C inhibitor, but not by SEA0400, a selective Na+/Ca2+ exchanger inhibitor. Phenylephrine increased the L-type Ca2+ channel current and prolonged the action potential duration, while the voltage-dependent K+ channel current was not influenced. In the presence of cromakalim, an ATP-sensitive K+ channel opener, the phenylephrine-induced prolongation of action potential duration, as well as the positive inotropy, were smaller than in the absence of cromakalim. These results suggest that the α-adrenoceptor-mediated positive inotropy is mediated by an increase in Ca2+ influx through the L-type Ca2+ channel, and the concomitant increase in action potential duration acts as an enhancing factor.
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Sandroni PB, Fisher-Wellman KH, Jensen BC. Adrenergic Receptor Regulation of Mitochondrial Function in Cardiomyocytes. J Cardiovasc Pharmacol 2022; 80:364-377. [PMID: 35170492 PMCID: PMC9365878 DOI: 10.1097/fjc.0000000000001241] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 02/01/2022] [Indexed: 01/31/2023]
Abstract
ABSTRACT Adrenergic receptors (ARs) are G protein-coupled receptors that are stimulated by catecholamines to induce a wide array of physiological effects across tissue types. Both α1- and β-ARs are found on cardiomyocytes and regulate cardiac contractility and hypertrophy through diverse molecular pathways. Acute activation of cardiomyocyte β-ARs increases heart rate and contractility as an adaptive stress response. However, chronic β-AR stimulation contributes to the pathobiology of heart failure. By contrast, mounting evidence suggests that α1-ARs serve protective functions that may mitigate the deleterious effects of chronic β-AR activation. Here, we will review recent studies demonstrating that α1- and β-ARs differentially regulate mitochondrial biogenesis and dynamics, mitochondrial calcium handling, and oxidative phosphorylation in cardiomyocytes. We will identify potential mechanisms of these actions and focus on the implications of these findings for the modulation of contractile function in the uninjured and failing heart. Collectively, we hope to elucidate important physiological processes through which these well-studied and clinically relevant receptors stimulate and fuel cardiac contraction to contribute to myocardial health and disease.
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Affiliation(s)
- Peyton B. Sandroni
- University of North Carolina School of Medicine, Department of Pharmacology
- University of North Carolina School of Medicine, McAllister Heart Institute
| | - Kelsey H. Fisher-Wellman
- East Carolina University Brody School of Medicine, Department of Physiology
- East Carolina University Diabetes and Obesity Institute
| | - Brian C. Jensen
- University of North Carolina School of Medicine, Department of Pharmacology
- University of North Carolina School of Medicine, McAllister Heart Institute
- University of North Carolina School of Medicine, Department of Medicine, Division of Cardiology
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Chronic isoprenaline/phenylephrine vs. exclusive isoprenaline stimulation in mice: critical contribution of alpha 1-adrenoceptors to early cardiac stress responses. Basic Res Cardiol 2022; 117:15. [PMID: 35286475 PMCID: PMC8921177 DOI: 10.1007/s00395-022-00920-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 02/04/2022] [Accepted: 02/07/2022] [Indexed: 01/31/2023]
Abstract
Hyperactivity of the sympathetic nervous system is a major driver of cardiac remodeling, exerting its effects through both α-, and β-adrenoceptors (α-, β-ARs). As the relative contribution of subtype α1-AR to cardiac stress responses remains poorly investigated, we subjected mice to either subcutaneous perfusion with the β-AR agonist isoprenaline (ISO, 30 mg/kg × day) or to a combination of ISO and the stable α1-AR agonist phenylephrine (ISO/PE, 30 mg/kg × day each). Telemetry analysis revealed similar hemodynamic responses under both ISO and ISO/PE treatment i.e., permanently increased heart rates and only transient decreases in mean blood pressure during the first 24 h. Echocardiography and single cell analysis after 1 week of exposure showed that ISO/PE-, but not ISO-treated animals established α1-AR-mediated inotropic responsiveness to acute adrenergic stimulation. Morphologically, additional PE perfusion limited concentric cardiomyocyte growth and enhanced cardiac collagen deposition during 7 days of treatment. Time-course analysis demonstrated a diverging development in transcriptional patterns at day 4 of treatment i.e., increased expression of selected marker genes Xirp2, Nppa, Tgfb1, Col1a1, Postn under chronic ISO/PE treatment which was either less pronounced or absent in the ISO group. Transcriptome analyses at day 4 via RNA sequencing demonstrated that additional PE treatment caused a marked upregulation of genes allocated to extracellular matrix and fiber organization along with a more pronounced downregulation of genes involved in metabolic processes, muscle adaptation and cardiac electrophysiology. Consistently, transcriptome changes under ISO/PE challenge more effectively recapitulated early transcriptional alterations in pressure overload-induced experimental heart failure and in human hypertrophic cardiomyopathy.
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Conventional and advanced echocardiographic assessment of systolic function in dogs sedated with dexmedetomidine or acepromazine. Res Vet Sci 2021; 141:129-137. [PMID: 34740044 DOI: 10.1016/j.rvsc.2021.09.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 08/25/2021] [Accepted: 09/26/2021] [Indexed: 01/16/2023]
Abstract
Dexmedetomidine and acepromazine, sedatives commonly used in dogs have opposite vascular effects, resulting in afterload increase and decrease, respectively. This could variably affect systolic myocardial function. Previous echocardiographic studies assessing the cardiovascular effects of these drugs used conventional echocardiography, while advanced techniques such as speckle tracking echocardiography (STE) and tissue Doppler imaging (TDI), which are known to provide a more accurate assessment of systolic function, have been rarely used for this aim. Moreover, in the few studies using advanced techniques, the drugs where combined with opioids. Therefore, the main objective of this prospective study was to assess systolic myocardial function by conventional and advanced echocardiography (STE and TDI), in dogs sedated exclusively with dexmedetomidine or acepromazine not combined with other drugs. Twenty healthy dogs were randomly divided into two groups, Group A (acepromazine, 20 μg/kg IM), and Group D (dexmedetomidine, 5 μg/kg IM), cardiovascular parameters were assessed before sedation (T0), and thirty minutes afterwards (T1). Systolic arterial pressure and heart rate decreased in both groups at T1 as compared to T0. Only one conventional echocardiographic raw variable (left ventricular internal dimension in systole) and three out of five advanced echocardiographic variables (radial TDI systolic velocities at the epicardial region of the left ventricular free wall, longitudinal TDI systolic velocities of the septal mitral valve annulus and the STE-derived left ventricular global strain), were affected in Group D. A systolic impairment was observed in Group D and better estimated by advanced echocardiography. In Group A, only the end diastolic voume index (conventional echocardiography) was decreased. Both protocols seem to induce echocardiographic changes more likely secondary to their vascular action.
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Targeting Adrenergic Receptors in Metabolic Therapies for Heart Failure. Int J Mol Sci 2021; 22:ijms22115783. [PMID: 34071350 PMCID: PMC8198887 DOI: 10.3390/ijms22115783] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 05/20/2021] [Accepted: 05/22/2021] [Indexed: 12/14/2022] Open
Abstract
The heart has a reduced capacity to generate sufficient energy when failing, resulting in an energy-starved condition with diminished functions. Studies have identified numerous changes in metabolic pathways in the failing heart that result in reduced oxidation of both glucose and fatty acid substrates, defects in mitochondrial functions and oxidative phosphorylation, and inefficient substrate utilization for the ATP that is produced. Recent early-phase clinical studies indicate that inhibitors of fatty acid oxidation and antioxidants that target the mitochondria may improve heart function during failure by increasing compensatory glucose oxidation. Adrenergic receptors (α1 and β) are a key sympathetic nervous system regulator that controls cardiac function. β-AR blockers are an established treatment for heart failure and α1A-AR agonists have potential therapeutic benefit. Besides regulating inotropy and chronotropy, α1- and β-adrenergic receptors also regulate metabolic functions in the heart that underlie many cardiac benefits. This review will highlight recent studies that describe how adrenergic receptor-mediated metabolic pathways may be able to restore cardiac energetics to non-failing levels that may offer promising therapeutic strategies.
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Perez DM. Current Developments on the Role of α 1-Adrenergic Receptors in Cognition, Cardioprotection, and Metabolism. Front Cell Dev Biol 2021; 9:652152. [PMID: 34113612 PMCID: PMC8185284 DOI: 10.3389/fcell.2021.652152] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/29/2021] [Indexed: 12/13/2022] Open
Abstract
The α1-adrenergic receptors (ARs) are G-protein coupled receptors that bind the endogenous catecholamines, norepinephrine, and epinephrine. They play a key role in the regulation of the sympathetic nervous system along with β and α2-AR family members. While all of the adrenergic receptors bind with similar affinity to the catecholamines, they can regulate different physiologies and pathophysiologies in the body because they couple to different G-proteins and signal transduction pathways, commonly in opposition to one another. While α1-AR subtypes (α1A, α1B, α1C) have long been known to be primary regulators of vascular smooth muscle contraction, blood pressure, and cardiac hypertrophy, their role in neurotransmission, improving cognition, protecting the heart during ischemia and failure, and regulating whole body and organ metabolism are not well known and are more recent developments. These advancements have been made possible through the development of transgenic and knockout mouse models and more selective ligands to advance their research. Here, we will review the recent literature to provide new insights into these physiological functions and possible use as a therapeutic target.
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Affiliation(s)
- Dianne M Perez
- The Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH, United States
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9
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Rodrigues da Silva R, Baptista de Souza Filho O, Bassani JWM, Bassani RA. The ForceLAB simulator: Application to the comparison of current models of cardiomyocyte contraction. Comput Biol Med 2021; 131:104240. [PMID: 33556894 DOI: 10.1016/j.compbiomed.2021.104240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/20/2021] [Accepted: 01/20/2021] [Indexed: 10/22/2022]
Abstract
Mathematical models are useful tools in the study of physiological phenomena. However, due to differences in assumptions and formulations, discrepancy in simulations may occur. Among the models for cardiomyocyte contraction based on Huxley's cross-bridge cycling, those proposed by Negroni and Lascano (NL) and Rice et al. (RWH) are the most frequently used. This study was aimed at developing a computational tool, ForceLAB, which allows implementing different contraction models and modifying several functional parameters. As an application, electrically-stimulated twitches triggered by an equal Ca2+ input and steady-state force x pCa relationship (pCa = -log of the molar free Ca2+ concentration) simulated with the NL and RWH models were compared. The equilibrium Ca2+-troponin C (TnC) dissociation constant (Kd) was modified by changing either the association (kon) or the dissociation (koff) rate constant. With the NL model, raising Kd by either maneuver decreased monotonically twitch amplitude and duration, as expected. With the RWH model, in contrast, the same Kd variation caused increase or decrease of peak force depending on which rate constant was modified. Additionally, force x pCa curves simulated using Ca2+ binding constants estimated in cardiomyocytes bearing wild-type and mutated TnC were compared to curves previously determined in permeabilized fibers. Mutations increased kon and koff, and decreased Kd. Both models produced curves fairly comparable to the experimental ones, although sensitivity to Ca2+ was greater, especially with RWH model. The NL model reproduced slightly better the qualitative changes associated with the mutations. It is expected that this tool can be useful for teaching and investigation.
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Affiliation(s)
- Robson Rodrigues da Silva
- Research and Technology Center, University of Mogi Das Cruzes, Mogi Das Cruzes, SP, Brazil; LabNECC, Center for Biomedical Engineering, University of Campinas, Campinas, SP, Brazil.
| | | | - José Wilson Magalhães Bassani
- LabNECC, Center for Biomedical Engineering, University of Campinas, Campinas, SP, Brazil; Department of Biomedical Engineering, School of Electrical and Computing Engineering, University of Campinas, Campinas, São Paulo, Brazil
| | - Rosana Almada Bassani
- LabNECC, Center for Biomedical Engineering, University of Campinas, Campinas, SP, Brazil
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Joyce W, Scholman KT, Jensen B, Wang T, Boukens BJ. α 1-adrenergic stimulation increases ventricular action potential duration in the intact mouse heart. Facets (Ott) 2021. [DOI: 10.1139/facets-2020-0081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of α1-adrenergic receptors (α-ARs) in the regulation of myocardial function is less well-understood than that of β-ARs. Previous reports in the mouse heart have described that α1-adrenergic stimulation shortens action potential duration in isolated cells or tissues, in contrast to prolongation of the action potential reported in most other mammalian hearts. It has since become appreciated, however, that the mouse heart exhibits marked variation in inotropic response to α1-adrenergic stimulation between ventricles and even individual cardiomyocytes. We investigated the effects of α1-adrenergic stimulation on action potential duration at 80% of repolarization in the right and left ventricles of Langendorff-perfused mouse hearts using optical mapping. In hearts under β-adrenergic blockade (propranolol), phenylephrine or noradrenaline perfusion both increased action potential duration in both ventricles. The increased action potential duration was partially reversed by subsequent perfusion with the α-adrenergic antagonist phentolamine (1 μmol L−1). These data show that α1-receptor stimulation may lead to a prolonging of action potential in the mouse heart and thereby refine our understanding of how action potential duration adjusts during sympathetic stimulation.
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Affiliation(s)
- William Joyce
- Department of Biology—Zoophysiology, Aarhus University, DK-8000 Aarhus C, Denmark
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada
| | - Koen T. Scholman
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, 11005 AZ Amsterdam, the Netherlands
| | - Bjarke Jensen
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, 11005 AZ Amsterdam, the Netherlands
| | - Tobias Wang
- Department of Biology—Zoophysiology, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Bastiaan J. Boukens
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, 11005 AZ Amsterdam, the Netherlands
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, 1100 DD Amsterdam, the Netherlands
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Zhang J, Simpson PC, Jensen BC. Cardiac α1A-adrenergic receptors: emerging protective roles in cardiovascular diseases. Am J Physiol Heart Circ Physiol 2020; 320:H725-H733. [PMID: 33275531 DOI: 10.1152/ajpheart.00621.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
α1-Adrenergic receptors (ARs) are catecholamine-activated G protein-coupled receptors (GPCRs) that are expressed in mouse and human myocardium and vasculature, and play essential roles in the regulation of cardiovascular physiology. Though α1-ARs are less abundant in the heart than β1-ARs, activation of cardiac α1-ARs results in important biologic processes such as hypertrophy, positive inotropy, ischemic preconditioning, and protection from cell death. Data from the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) indicate that nonselectively blocking α1-ARs is associated with a twofold increase in adverse cardiac events, including heart failure and angina, suggesting that α1-AR activation might also be cardioprotective in humans. Mounting evidence implicates the α1A-AR subtype in these adaptive effects, including prevention and reversal of heart failure in animal models by α1A agonists. In this review, we summarize recent advances in our understanding of cardiac α1A-ARs.
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Affiliation(s)
- Jiandong Zhang
- McAllister Heart Institute, University of North Carolina, School of Medicine, Chapel Hill, North Carolina
| | - Paul C Simpson
- Department of Medicine and Research Service, San Francisco Veterans Affairs Medical Center and Cardiovascular Research Institute, University of California, San Francisco, California
| | - Brian C Jensen
- McAllister Heart Institute, University of North Carolina, School of Medicine, Chapel Hill, North Carolina
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12
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Abstract
In the 1950s, Arthur C. Guyton removed the heart from its pedestal in cardiovascular physiology by arguing that cardiac output is primarily regulated by the peripheral vasculature. This is counterintuitive, as modulating heart rate would appear to be the most obvious means of regulating cardiac output. In this Review, we visit recent and classic advances in comparative physiology in light of this concept. Although most vertebrates increase heart rate when oxygen demands rise (e.g. during activity or warming), experimental evidence suggests that this tachycardia is neither necessary nor sufficient to drive a change in cardiac output (i.e. systemic blood flow, Q̇ sys) under most circumstances. Instead, Q̇ sys is determined by the interplay between vascular conductance (resistance) and capacitance (which is mainly determined by the venous circulation), with a limited and variable contribution from heart function (myocardial inotropy). This pattern prevails across vertebrates; however, we also highlight the unique adaptations that have evolved in certain vertebrate groups to regulate venous return during diving bradycardia (i.e. inferior caval sphincters in diving mammals and atrial smooth muscle in turtles). Going forward, future investigation of cardiovascular responses to altered metabolic rate should pay equal consideration to the factors influencing venous return and cardiac filling as to the factors dictating cardiac function and heart rate.
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Affiliation(s)
- William Joyce
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark .,Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
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Glucocorticoid stimulation increases cardiac contractility by SGK1-dependent SOCE-activation in rat cardiac myocytes. PLoS One 2019; 14:e0222341. [PMID: 31498847 PMCID: PMC6733454 DOI: 10.1371/journal.pone.0222341] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Accepted: 08/27/2019] [Indexed: 01/28/2023] Open
Abstract
Aims Glucocorticoid (GC) stimulation has been shown to increase cardiac contractility by elevated intracellular [Ca] but the sources for Ca entry are unclear. This study aims to determine the role of store-operated Ca entry (SOCE) for GC-mediated inotropy. Methods and results Dexamethasone (Dex) pretreatment significantly increased cardiac contractile force ex vivo in Langendorff-perfused Sprague-Dawley rat hearts (2 mg/kg BW i.p. Dex 24 h prior to experiment). Moreover, Ca transient amplitude as well as fractional shortening were significantly enhanced in Fura-2-loaded isolated rat ventricular myocytes exposed to Dex (1 mg/mL Dex, 24 h). Interestingly, these Dex-dependent effects could be abolished in the presence of SOCE-inhibitors SKF-96356 (SKF, 2 μM) and BTP2 (5 μM). Ca transient kinetics (time to peak, decay time) were not affected by SOCE stimulation. Direct SOCE measurements revealed a negligible magnitude in untreated myocytes but a dramatic increase in SOCE upon Dex-pretreatment. Importantly, the Dex-dependent stimulation of SOCE could be blocked by inhibition of serum and glucocorticoid-regulated kinase 1 (SGK1) using EMD638683 (EMD, 50 μM). Dex preincubation also resulted in increased mRNA expression of proteins involved in SOCE (stromal interaction molecule 2, STIM2, and transient receptor potential cation channels 3/6, TRPC 3/6), which were also prevented in the presence of EMD. Conclusion Short-term GC-stimulation with Dex improves cardiac contractility by a SOCE-dependent mechanism, which appears to involve increased SGK1-dependent expression of the SOCE-related proteins. Since Ca transient kinetics were unaffected, SOCE appears to influence Ca cycling more by an integrated response across multiple cardiac cycles but not on a beat-to-beat basis.
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Goswami S. G protein-coupled receptor signaling in cardiovascular system: Specificity versus diversity. JOURNAL OF THE PRACTICE OF CARDIOVASCULAR SCIENCES 2019. [DOI: 10.4103/jpcs.jpcs_37_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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15
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Janssen PM, Canan BD, Kilic A, Whitson BA, Baker AJ. Human Myocardium Has a Robust α1A-Subtype Adrenergic Receptor Inotropic Response. J Cardiovasc Pharmacol 2018; 72:136-142. [PMID: 29923888 PMCID: PMC6126952 DOI: 10.1097/fjc.0000000000000604] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Recent studies report that a single subtype of α1-adrenergic receptor (α1-AR), the α1A-subtype, mediates robust cardioprotective effects in multiple experimental models of heart failure, suggesting that the α1A-subtype is a potential therapeutic target for an agonist to treat heart failure. Moreover, we recently found that the α1A-subtype is present in human heart. The goal of this study was to assess the inotropic response mediated by the α1A-subtype in human myocardium, and to determine whether the response is downregulated in myocardium from failing human heart. We measured in vitro contractile responses of cardiac muscle preparations (trabeculae) isolated from the right ventricle from nonfailing and failing human hearts. Addition of the α1A-subtype agonist A61603 (100 nM) resulted in a large positive inotropic response (force increased ≈ 2-fold). This response represented ≈70% of the response mediated by the β-adrenergic receptor agonist isoproterenol (1 μM). Moreover, in myocardium from failing hearts, α1A-subtype responses remained robust, and only slightly reduced relative to nonfailing hearts. We conclude that α1A-subtype-mediated inotropy could represent a significant source of inotropic support in the human heart. Furthermore, the α1A-subtype remains functional in myocardium from failing human hearts and thus, might be a therapeutic target to support cardioprotective effects in patients with heart failure.
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Affiliation(s)
- Paul M.L. Janssen
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio
| | - Benjamin D. Canan
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio
| | - Ahmet Kilic
- Department of Surgery, The Ohio State University, Columbus, Ohio
| | - Bryan A Whitson
- Department of Surgery, The Ohio State University, Columbus, Ohio
| | - Anthony J. Baker
- Veterans Affairs Medical Center, San Francisco, and Department of Medicine, Univ. Calif. San Francisco, San Francisco
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