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Weresa J, Pędzińska-Betiuk A, Schlicker E, Hirnle G, Mitrosz M, Malinowska B. Beneficial and harmful effects of CB 1 and CB 2 receptor antagonists on chronotropic and inotropic effects related to atrial β-adrenoceptor activation in humans and in rats with primary hypertension. Clin Exp Pharmacol Physiol 2021; 48:1547-1557. [PMID: 34333780 DOI: 10.1111/1440-1681.13560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 07/22/2021] [Accepted: 07/29/2021] [Indexed: 11/26/2022]
Abstract
We have previously shown that cannabinoid CB1 and CB2 receptor antagonists, AM251 and AM630, respectively, modulate cardiostimulatory effects of isoprenaline in atria of Wistar rats. The aim of the present study was to examine whether such modulatory effects can also be observed (a) in the human atrium and (b) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). Inotropic effects of isoprenaline and/or CGP12177 (that activate the high- and low-affinity site of β1 -adrenoceptors, respectively) were examined in paced human atrial trabeculae and rat left atria; chronotropic effects were studied in spontaneously beating right rat atria. AM251 modified cardiostimulatory effects more strongly than AM630. Therefore, AM251 (1 μM) enhanced the chronotropic effect of isoprenaline in WKY and SHR as well as inotropic action of isoprenaline in WKY and in human atria. It also increased the inotropic influence of CGP12177 in SHR. AM630 (1 μM) decreased the inotropic effect of isoprenaline and CGP12177 in WKY, but enhanced the isoprenaline-induced inotropic effect in SHR and human atria. Furthermore, AM251 (0.1 and 3 μM) and AM630 (0.1 μM) reduced the inotropic action of isoprenaline in human atria. In conclusion, cannabinoid receptor antagonists have potentially harmful and beneficial effects through their amplificatory effects on β-adrenoceptor-mediated positive chronotropic and inotropic actions, respectively.
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MESH Headings
- Animals
- Humans
- Rats
- Receptor, Cannabinoid, CB1/antagonists & inhibitors
- Receptor, Cannabinoid, CB1/metabolism
- Male
- Rats, Inbred SHR
- Heart Atria/drug effects
- Heart Atria/metabolism
- Heart Atria/physiopathology
- Receptor, Cannabinoid, CB2/antagonists & inhibitors
- Receptor, Cannabinoid, CB2/metabolism
- Isoproterenol/pharmacology
- Hypertension/physiopathology
- Hypertension/drug therapy
- Hypertension/metabolism
- Hypertension/chemically induced
- Piperidines/pharmacology
- Myocardial Contraction/drug effects
- Heart Rate/drug effects
- Pyrazoles/pharmacology
- Rats, Inbred WKY
- Receptors, Adrenergic, beta/metabolism
- Indoles/pharmacology
- Cannabinoid Receptor Antagonists/pharmacology
- Female
- Propanolamines
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Affiliation(s)
- Jolanta Weresa
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, Białystok, Poland
| | - Anna Pędzińska-Betiuk
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, Białystok, Poland
| | - Eberhard Schlicker
- Department of Pharmacology and Toxicology, University of Bonn, Bonn, Germany
| | - Grzegorz Hirnle
- Department of Cardiac Surgery, Medical University of Białystok, Białystok, Poland
| | - Maciej Mitrosz
- Department of Cardiac Surgery, Medical University of Białystok, Białystok, Poland
| | - Barbara Malinowska
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, Białystok, Poland
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Okeke K, Angers S, Bouvier M, Michel MC. Agonist-induced desensitisation of β 3 -adrenoceptors: Where, when, and how? Br J Pharmacol 2019; 176:2539-2558. [PMID: 30809805 DOI: 10.1111/bph.14633] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 01/27/2019] [Accepted: 02/11/2019] [Indexed: 12/13/2022] Open
Abstract
β3 -Adrenoceptor agonists have proven useful in the treatment of overactive bladder syndrome, but it is not known whether their efficacy during chronic administration may be limited by receptor-induced desensitisation. Whereas the β2 -adrenoceptor has phosphorylation sites that are important for desensitisation, the β3 -adrenoceptor lacks these; therefore, it had been assumed that β3 -adrenoceptors are largely resistant to agonist-induced desensitisation. While all direct comparative studies demonstrate that β3 -adrenoceptors are less susceptible to desensitisation than β2 -adrenoceptors, desensitisation of β3 -adrenoceptors has been observed in many models and treatment settings. Chimeric β2 - and β3 -adrenoceptors have demonstrated that the C-terminal tail of the receptor plays an important role in the relative resistance to desensitisation but is not the only relevant factor. While the evidence from some models, such as transfected CHO cells, is inconsistent, it appears that desensitisation is observed more often after long-term (hours to days) than short-term (minutes to hours) agonist exposure. When it occurs, desensitisation of β3 -adrenoceptors can involve multiple levels including down-regulation of its mRNA and the receptor protein and alterations in post-receptor signalling events. The relative contributions of these mechanistic factors apparently depend on the cell type under investigation. Which if any of these factors is applicable to the human urinary bladder remains to be determined. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.
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Affiliation(s)
- Katerina Okeke
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany
| | - Stephane Angers
- Leslie Dan Faculty of Pharmacy and Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Michel Bouvier
- Institute for Research in Immunology and Cancer, Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, QC, Canada
| | - Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany
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3
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Cross-regulation between cardiac muscarinic acetylcholine receptors and β-adrenoceptors: lessons for use of knock-out mice. Naunyn Schmiedebergs Arch Pharmacol 2012; 386:1-3. [PMID: 23143657 DOI: 10.1007/s00210-012-0805-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 10/19/2012] [Indexed: 01/25/2023]
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Mattsson CL, Csikasz RI, Chernogubova E, Yamamoto DL, Hogberg HT, Amri EZ, Hutchinson DS, Bengtsson T. β₁-Adrenergic receptors increase UCP1 in human MADS brown adipocytes and rescue cold-acclimated β₃-adrenergic receptor-knockout mice via nonshivering thermogenesis. Am J Physiol Endocrinol Metab 2011; 301:E1108-18. [PMID: 21878665 DOI: 10.1152/ajpendo.00085.2011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
With the finding that brown adipose tissue is present and negatively correlated to obesity in adult man, finding the mechanism(s) of how to activate brown adipose tissue in humans could be important in combating obesity, type 2 diabetes, and their complications. In mice, the main regulator of nonshivering thermogenesis in brown adipose tissue is norepinephrine acting predominantly via β(3)-adrenergic receptors. However, vast majorities of β(3)-adrenergic agonists have so far not been able to stimulate human β(3)-adrenergic receptors or brown adipose tissue activity, and it was postulated that human brown adipose tissue could be regulated instead by β(1)-adrenergic receptors. Therefore, we have investigated the signaling pathways, specifically pathways to nonshivering thermogenesis, in mice lacking β(3)-adrenergic receptors. Wild-type and β(3)-knockout mice were either exposed to acute cold (up to 12 h) or acclimated for 7 wk to cold, and parameters related to metabolism and brown adipose tissue function were investigated. β(3)-knockout mice were able to survive both acute and prolonged cold exposure due to activation of β(1)-adrenergic receptors. Thus, in the absence of β(3)-adrenergic receptors, β(1)-adrenergic receptors are effectively able to signal via cAMP to elicit cAMP-mediated responses and to recruit and activate brown adipose tissue. In addition, we found that in human multipotent adipose-derived stem cells differentiated into functional brown adipocytes, activation of either β(1)-adrenergic receptors or β(3)-adrenergic receptors was able to increase UCP1 mRNA and protein levels. Thus, in humans, β(1)-adrenergic receptors could play an important role in regulating nonshivering thermogenesis.
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MESH Headings
- Acclimatization/genetics
- Acclimatization/physiology
- Adipocytes, Brown/cytology
- Adipocytes, Brown/metabolism
- Animals
- Cell Differentiation/genetics
- Cell Differentiation/physiology
- Cells, Cultured
- Cold Temperature
- Down-Regulation/genetics
- Epistasis, Genetic/physiology
- Female
- Humans
- Ion Channels/genetics
- Ion Channels/metabolism
- Male
- Mice
- Mice, Knockout
- Mitochondrial Proteins/genetics
- Mitochondrial Proteins/metabolism
- Multipotent Stem Cells/cytology
- Multipotent Stem Cells/metabolism
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-1/physiology
- Receptors, Adrenergic, beta-3/genetics
- Shivering/genetics
- Shivering/physiology
- Thermogenesis/genetics
- Thermogenesis/physiology
- Uncoupling Protein 1
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Affiliation(s)
- Charlotte L Mattsson
- Department of Physiology, The Wenner-Gren Institute, Arrhenius Laboratories F3, Stockholm University, Stockholm, Sweden
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Hauton D, May S, Sabharwal R, Deveci D, Egginton S. Cold-impaired cardiac performance in rats is only partially overcome by cold acclimation. J Exp Biol 2011; 214:3021-31. [DOI: 10.1242/jeb.053587] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
SUMMARY
The consequences of acute hypothermia include impaired cardiovascular performance, ultimately leading to circulatory collapse. We examined the extent to which this results from intrinsic limitations to cardiac performance or physiological dysregulation/autonomic imbalance, and whether chronic cold exposure could ameliorate the impaired function. Wistar rats were held at a 12 h:12 h light:dark (L:D) photoperiod and room temperature (21°C; euthermic controls), or exposed to a simulated onset of winter in an environmental chamber by progressive acclimation to 1 h:23 h L:D and 4°C over 4 weeks. In vivo, acute cold exposure (core temperature, Tb=25°C) resulted in hypotension (approximately –20%) due to low cardiac output (approximately –30%) accompanying a bradycardia (approximately –50%). Cold acclimation (CA) induced only partial compensation for this challenge, including increased coronary flow at Tb=37°C (but not at Tb=25°C), maintenance of ventricular capillarity and altered sympathovagal balance (increased low:high frequency in power spectral analysis, PSA), suggesting physiological responses alone were insufficient to maintain cardiovascular performance. However, PSA showed maintenance of cardiorespiratory coupling on acute cold exposure in both groups. Ex vivo cardiac performance revealed no change in intrinsic heart rate, but a mechanical impairment of cardiac function at low temperatures following CA. While CA involved an increased capacity for β-oxidation, there was a paradoxical reduction in developed pressure as a result of adrenergic down-regulation. These data suggest that integrated plasticity is the key to cardiovascular accommodation of chronic exposure to a cold environment, but with the potential for improvement by intervention, for example with agents such as non-catecholamine inotropes.
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Affiliation(s)
- David Hauton
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Shaun May
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Rasna Sabharwal
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Durmus Deveci
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Stuart Egginton
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
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Christ T, Galindo-Tovar A, Thoms M, Ravens U, Kaumann AJ. Inotropy and L-type Ca2+ current, activated by beta1- and beta2-adrenoceptors, are differently controlled by phosphodiesterases 3 and 4 in rat heart. Br J Pharmacol 2009; 156:62-83. [PMID: 19133992 DOI: 10.1111/j.1476-5381.2008.00015.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE beta(1)- and beta(2)-adrenoceptors coexist in rat heart but beta(2)-adrenoceptor-mediated inotropic effects are hardly detectable, possibly due to phosphodiesterase (PDE) activity. We investigated the influence of the PDE3 inhibitor cilostamide (300 nmol x L(-1)) and the PDE4 inhibitor rolipram (1 micromol x L(-1)) on the effects of (-)-catecholamines. EXPERIMENTAL APPROACH Cardiostimulation evoked by (-)-noradrenaline (ICI118551 present) and (-)-adrenaline (CGP20712A present) through beta(1)- and beta(2)-adrenoceptors, respectively, was compared on sinoatrial beating rate, left atrial and ventricular contractile force in isolated tissues from Wistar rats. L-type Ca(2+)-current (I(Ca-L)) was assessed with whole-cell patch clamp. KEY RESULTS Rolipram caused sinoatrial tachycardia. Cilostamide and rolipram did not enhance chronotropic potencies of (-)-noradrenaline and (-)-adrenaline. Rolipram but not cilostamide potentiated atrial and ventricular inotropic effects of (-)-noradrenaline. Cilostamide potentiated the ventricular effects of (-)-adrenaline but not of (-)-noradrenaline. Concurrent cilostamide + rolipram uncovered left atrial effects of (-)-adrenaline. Both rolipram and cilostamide augmented the (-)-noradrenaline (1 micromol x L(-1)) evoked increase in I(Ca-L). (-)-Adrenaline (10 micromol x L(-1)) increased I(Ca-L) only in the presence of cilostamide but not rolipram. CONCLUSIONS AND IMPLICATIONS PDE4 blunts the beta(1)-adrenoceptor-mediated inotropic effects. PDE4 reduces basal sinoatrial rate in a compartment distinct from compartments controlled by beta(1)- and beta(2)-adrenoceptors. PDE3 and PDE4 jointly prevent left atrial beta(2)-adrenoceptor-mediated inotropy. Both PDE3 and PDE4 reduce I(Ca-L) responses through beta(1)-adrenoceptors but the PDE3 component is unrelated to inotropy. PDE3 blunts both ventricular inotropic and I(Ca-L) responses through beta(2)-adrenoceptors.
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Affiliation(s)
- Torsten Christ
- Department of Pharmacology, Dresden University of Technology, Dresden, Germany
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7
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Cheng Y, Hauton D. Cold acclimation induces physiological cardiac hypertrophy and increases assimilation of triacylglycerol metabolism through lipoprotein lipase. Biochim Biophys Acta Mol Cell Biol Lipids 2008; 1781:618-26. [PMID: 18722549 PMCID: PMC2568868 DOI: 10.1016/j.bbalip.2008.07.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/15/2008] [Accepted: 07/15/2008] [Indexed: 12/24/2022]
Abstract
The contribution of triacylglycerol to energy provision in the hypertrophied heart, mediated through lipoprotein lipase (LPL) is largely unknown and the contribution of very-low-density lipoprotein (VLDL) receptor to control of LPL presentation at the endothelium is unclear. For isolated perfused rat hearts, cold acclimation (CA) induced volume-overload hypertrophy, with decreased developed pressure (P < 0.01), increased end-diastolic volume of the left ventricle (P < 0.001) and a loss of contractile reserve in response to dobutamine challenge (P < 0.01). Oleate utilisation by perfused hearts was unchanged by CA, however uptake of intralipid emulsion increased 3-fold (P < 0.01). CA increased the proportion of lipid deposited in tissue lipids from 10% in euthermic controls to 40% (P < 0.01) although the overall contribution of individual lipid classes was unaffected. Cold acclimation significantly increased heparin-releasable LPL (P < 0.05) and tissue residual LPL (P < 0.01). Western blot analysis indicated preserved expression of proteins coding for SERCA2, muscle-CPT1 and VLDL-receptor following CA, while AMPKα2 and phospho-AMPKα2 were unaffected. These observations indicate that for physiological hypertrophy AMPK phosphorylation does not mediate the enhanced translocation of LPL to cardiac endothelium.
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Affiliation(s)
- Y Cheng
- Department of Physiology, Division of Medical Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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8
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Osadchii OE. Cardiac hypertrophy induced by sustained β-adrenoreceptor activation: pathophysiological aspects. Heart Fail Rev 2007; 12:66-86. [PMID: 17387610 DOI: 10.1007/s10741-007-9007-4] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Accepted: 02/21/2007] [Indexed: 10/23/2022]
Abstract
Cardiac hypertrophy is promoted by adrenergic over-activation and represents an independent risk factor for cardiovascular morbidity and mortality. The basic knowledge about mechanisms by which sustained adrenergic activation promotes myocardial growth, as well as understanding how structural changes in hypertrophied myocardium could affect myocardial function has been acquired from studies using an animal model of chronic systemic beta-adrenoreceptor agonist administration. Sustained beta-adrenoreceptor activation was shown to enhance the synthesis of myocardial proteins, an effect mediated via stimulation of myocardial growth factors, up-regulation of nuclear proto-oncogenes, induction of cardiac oxidative stress, as well as activation of mitogen-activated protein kinases and phosphatidylinositol 3-kinase. Sustained beta-adrenoreceptor activation contributes to impaired cardiac autonomic regulation as evidenced by blunted parasympathetically-mediated cardiovascular reflexes as well as abnormal storage of myocardial catecholamines. Catecholamine-induced cardiac hypertrophy is associated with reduced contractile responses to adrenergic agonists, an effect attributed to downregulation of myocardial beta-adrenoreceptors, uncoupling of beta-adrenoreceptors and adenylate cyclase, as well as modifications of downstream cAMP-mediated signaling. In compensated cardiac hypertrophy, these changes are associated with preserved or even enhanced basal ventricular systolic function due to increased sarcoplasmic reticulum Ca(2+) content and Ca(2+)-induced sarcoplasmic reticulum Ca(2+) release. The increased availability of Ca(2+) to maintain cardiomyocyte contraction is attributed to prolongation of the action potential due to inhibition of the transient outward potassium current as well as stimulation of the reverse mode of the Na(+)-Ca(2+) exchange. Further progression of cardiac hypertrophy towards heart failure is due to abnormalities in Ca(2+) handling, necrotic myocardial injury, and increased myocardial stiffness due to interstitial fibrosis.
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Affiliation(s)
- Oleg E Osadchii
- Cardiology Group, School of Clinical Sciences, University Clinical Departments, University of Liverpool, The Duncan Building, Daulby Street, Liverpool, L69 3GA, UK.
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9
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Hohimer AR, Davis LE, Hatton DC. Repeated daily injections and osmotic pump infusion of isoproterenol cause similar increases in cardiac mass but have different effects on blood pressure. Can J Physiol Pharmacol 2005; 83:191-7. [PMID: 15791293 DOI: 10.1139/y04-137] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We found in mice that repeated single daily subcutaneous (s.c.) isoproterenol (ISO) injections, like constant infusions using osmotic minipumps, caused increased biventricular mass or weight relative to body weight (VW/BW). We found that 5 (1/d) s.c. injections of 2, 10, or 20 microg/g body weight caused equivalent VW/BW increases as compared with 5-d infusions at 20 microg/(g.d)). While it is often presumed that ISO elicits hypertrophy by a direct effect on the myocytes, growth may also be secondary to systemic hemodynamic effects. The 2 modes of ISO administration had different effects on mean arterial blood pressure (MABP) and heart rate. Using telemetry we observed that single injections of ISO (0, 0.5, 2, and 10 microg/g) were associated with hypotension and tachycardia with a duration but not a magnitude that was dose dependent. MABP dropped rapidly to 60 mm Hg for more than 2 h at the highest dose. Constant s.c. infusion of ISO at 20 microg/(g.d) initially lowered MABP to about 70 mm Hg for 24 h. At 48 h MABP was normal, but rose 10 mm Hg higher than baseline by day 5. Thus, different routes of administration of ISO that cause comparable increases in VW/BW had different effects on MABP. Thus when evaluating mouse models of ISO-induced cardiac hypertrophy, both repeated daily injections or infusions can cause similar increases in VW/BW, but the daily doses that are required are not the same. Furthermore, these different routes of administration have different hemodynamic sequelae and could potentially evoke different cardiac phenotypes.
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Affiliation(s)
- A Roger Hohimer
- Department of OB/GYN, Division of Perinatology, Oregon Health & Science University, Portland 97239-3098, USA.
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10
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Garofolo MC, Seidler FJ, Auman JT, Slotkin TA. beta-Adrenergic modulation of muscarinic cholinergic receptor expression and function in developing heart. Am J Physiol Regul Integr Comp Physiol 2002; 282:R1356-63. [PMID: 11959676 DOI: 10.1152/ajpregu.00598.2001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Imbalances of beta-adrenoceptor (beta-AR) and muscarinic ACh receptor (mAChR) input are thought to underlie perinatal cardiovascular abnormalities in conditions such as sudden infant death syndrome. Administration of isoproterenol, a beta(1)/beta(2)-AR agonist, to neonatal rats on postnatal days (PN) 2-5 caused downregulation of cardiac m(2)AChRs and a corresponding decrement in their control of adenylyl cyclase activity. Terbutaline, a beta(2)-selective agonist that crosses the placenta and the blood-brain barrier, was also effective when given either on PN 2-5 or during gestational days 17-20. Terbutaline failed to downregulate brain m(2)AChRs, even though it downregulated beta-ARs; beta-ARs and m(2)AChRs are located on different cell populations in the brain, but they are on the same cells in the heart. Destruction of catecholaminergic neurons with neonatal 6-hydroxydopamine upregulated cardiac but not brain m(2)AChRs. These results suggest that perinatal beta-AR stimulation shifts cardiac receptor production away from the generation of m(2)AChRs so that the development of sympathetic innervation acts as a negative modulator of cholinergic function. Accordingly, tocolytic therapy with beta-AR agonists may compromise the perinatal balance of adrenergic and cholinergic inputs.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Adrenergic Agents/pharmacology
- Adrenergic beta-Agonists/pharmacology
- Animals
- Animals, Newborn/metabolism
- Brain/metabolism
- Down-Regulation
- Embryo, Mammalian/drug effects
- Embryo, Mammalian/metabolism
- Heart/embryology
- Isoproterenol/pharmacology
- Myocardium/metabolism
- Oxidopamine/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor Cross-Talk
- Receptor, Muscarinic M2
- Receptors, Adrenergic, beta/drug effects
- Receptors, Adrenergic, beta/physiology
- Receptors, Muscarinic/drug effects
- Receptors, Muscarinic/physiology
- Terbutaline/pharmacology
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Affiliation(s)
- M C Garofolo
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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11
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Broadley KJ. Review of mechanisms involved in the apparent differential desensitization of beta1- and beta2-adrenoceptor-mediated functional responses. JOURNAL OF AUTONOMIC PHARMACOLOGY 1999; 19:335-45. [PMID: 10961739 DOI: 10.1111/j.1365-2680.1999.tb00006.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. There has been considerable debate whether responses mediated via beta1- and beta2-adrenoceptors (beta1ARs and beta2ARs) display the same degree of desensitization after prolonged or repeated exposure to agonists. 2. Examples are provided for selective desensitization of functional responses and loss of binding sites for beta1ARs. Equally, examples are given of selective desensitization and down-regulation involving beta2ARs. 3. This review examines whether receptor subtype-selective desensitization of betaAR-mediated responses can occur and whether even within the same subtype, there may be tissue-selective desensitization. Possible reasons why apparent selectivity of desensitization of functional responses may occur are considered and are divided into methodological and non-methodological factors. 4. Methodological factors discussed are: the concentration of agonist used for inducing desensitization and the washout times before construction of the post-incubation concentration-response curve (CRC), the need for correction of CRCs from time-matched controls, and the methods adopted for plotting CRCs. 5. Four non-methodological factors are considered. Firstly, the roles of different receptor reserves for the responses of each tissue can have an important effect on whether desensitization is apparent; a large reserve will make desensitization less likely to be apparent. Secondly, there is more than one site at which desensitization occurs; receptors are uncoupled from adenylyl cyclase activation, there is an additional site at the level of stimulation of cyclic AMP-dependent protein kinase and betaARs may ultimately be down-regulated. These processes may differ depending on the tissue and conditions and this may influence whether differential desensitization occurs between tissues. Thirdly, the apparent degree of desensitization after washout of an agonist can depend upon the rate of resensitization. Experiments to overcome this problem are described which demonstrate betaAR desensitization in the continued presence of agonist. Finally, the role of up-regulation of PDE in desensitization is discussed.
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Affiliation(s)
- K J Broadley
- Division of Pharmacology, Welsh School of Pharmacy, Cardiff University, Cathays Park, UK
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12
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McMartin L, Summers RJ. Functional analysis of desensitization of the beta-adrenoceptor signalling pathway in rat cardiac tissues following chronic isoprenaline infusion. Br J Pharmacol 1999; 127:1012-20. [PMID: 10433510 PMCID: PMC1566094 DOI: 10.1038/sj.bjp.0702618] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. This study examined beta-adrenoceptor signalling in cardiac tissues following infusion of isoprenaline (400 microg kg(-1) h(-1)) or vehicle to rats for 14 days. 2. Isoprenaline infusion caused marked hypertrophy of atria and ventricles and reduced the resting rate of spontaneously beating right atria and the basal force of left atrial contraction. 3. In spontaneously beating right atria, concentration-response curves to isoprenaline and forskolin were shifted 7.9 and 3.2 fold to the right following treatment whereas responses to the cyclic AMP analogue 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-3', 5'-cyclic monophosphorothioate were unchanged. 4. In electrically driven left atria, concentration-response curves to isoprenaline and forskolin were shifted 4 fold to the right and maximum responses reduced. Responses to dibutyryl cyclic AMP were shifted 3.2 fold to the right but those to Ca2+ were unchanged. 5. Inotropic responses of left and right ventricular papillary muscles to isoprenaline were abolished and markedly reduced respectively by isoprenaline treatment. Responses to forskolin were shifted 5 fold to the right. Responses to dibutyryl cyclic AMP were shifted to the right 3.2 and 2 fold in left and right ventricular papillary muscles. Responses to isobutyl methyl xanthine were shifted to the right 15.8 and 6.3 fold in left and right papillary muscles whereas those to Ca2+ were not significantly altered. 6. This study indicates differences in beta-adrenoceptor desensitization in different regions of the heart following chronic infusion of isoprenaline. Chronotropic responses showed impaired signalling between the receptor and adenylate cyclase whereas inotropic responses exhibited additional desensitization at the level of cyclic AMP dependent protein kinase.
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Affiliation(s)
- L McMartin
- Department of Pharmacology, University of Melbourne, Parkville 3052, Australia
| | - R J Summers
- Department of Pharmacology, Monash University Clayton 3168, Australia
- Author for correspondence:
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Molenaar P, Sarsero D, Kaumann AJ. Proposal for the interaction of non-conventional partial agonists and catecholamines with the 'putative beta 4-adrenoceptor' in mammalian heart. Clin Exp Pharmacol Physiol 1997; 24:647-56. [PMID: 9315364 DOI: 10.1111/j.1440-1681.1997.tb02107.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
1. Evidence for a 'putative beta 4-adrenoceptor' originated over 20 years ago when cardiostimulant effects were observed to non-conventional partial agonists. These agonists were originally described as beta 1- and beta 2-adrenoceptor antagonists; however, they cause cardiostimulant effects at much higher concentrations than those required to block beta 1- and beta 2-adrenoceptors. Cardiostimulant effects of non-conventional partial agonists have been observed in mouse, rat, guinea-pig, cat, ferret and human heart tissues. 2. The receptor is expressed in several heart regions, including the sinoatrial node, atrium and ventricle. 3. The receptor is resistant to blockade by most antagonists that possess high affinity for beta 1- and beta 2-adrenoceptors, but is blocked with moderate affinity by (-)-bupranolol and CGP 20712A. 4. The receptor is pharmacologically distinct from the beta 3-adrenoceptor. Micromolar concentrations of beta 3-adrenoceptor agonists have no agonist or blocking activity. The receptor is also resistant to blockade by a beta 3-adrenoceptor-selective antagonist. 5. The receptor mediates increases in cAMP levels and cAMP-dependent protein kinase (PK) A activity in cardiac tissues. Phosphodiesterase inhibition potentiates the positive chronotropic and inotropic effects of non-conventional partial agonists. 6. The receptor mediates hastening of atrial and ventricular relaxation, which is consistent with involvement of a cAMP-dependent pathway. 7. The non-conventional partial agonist (-)-[3H]-CGP 12177A labels the cardiac putative beta 4-adrenoceptor. Non-conventional partial agonists compete for binding with affinities that are closely similar to their agonist potencies. Catecholamines compete for binding in a stereoselective manner with a rank order of affinity of (-)-RO363 > (-)-isoprenaline > (-)-noradrenaline > or = (-)-adrenaline >> (+)-isoprenaline, suggesting that catecholamines can interact with the receptor. 8. The putative beta 4-adrenoceptor appears to be coupled to the Gs-adenylyl cyclase system, which could serve as a guide to its future cloning. Activation of the receptor may plausibly improve diastolic function but could also mediate arrhythmias.
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Affiliation(s)
- P Molenaar
- Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia.
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