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Baker JG, Summers RJ. Adrenoceptors: Receptors, Ligands and Their Clinical Uses, Molecular Pharmacology and Assays. Handb Exp Pharmacol 2024. [PMID: 38926158 DOI: 10.1007/164_2024_713] [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: 06/28/2024]
Abstract
The nine G protein-coupled adrenoceptor subtypes are where the endogenous catecholamines adrenaline and noradrenaline interact with cells. Since they are important therapeutic targets, over a century of effort has been put into developing drugs that modify their activity. This chapter provides an outline of how we have arrived at current knowledge of the receptors, their physiological roles and the methods used to develop ligands. Initial studies in vivo and in vitro with isolated organs and tissues progressed to cell-based techniques and the use of cloned adrenoceptor subtypes together with high-throughput assays that allow close examination of receptors and their signalling pathways. The crystal structures of many of the adrenoceptor subtypes have now been determined opening up new possibilities for drug development.
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Affiliation(s)
- Jillian G Baker
- Cell Signalling, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham, UK.
- Department of Respiratory Medicine, Nottingham University Hospitals NHS Trust, Nottingham, UK.
| | - Roger J Summers
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia.
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The differential effects of low and high doses of apelin through opioid receptors on the blood pressure of rats with renovascular hypertension. Hypertens Res 2017; 40:732-737. [PMID: 28275232 DOI: 10.1038/hr.2017.28] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/28/2016] [Accepted: 01/05/2017] [Indexed: 01/25/2023]
Abstract
The apelin/APJ system has an important role in the regulation of vascular tone and blood pressure. Opioid receptors (OPRs) are also important cardiovascular regulators and exert many of their effects by modulating the function of other G-protein-coupled receptors. The aim of this study was to analyze the interaction of apelin and the opioid system with respect to vascular responses to apelin in rats with renovascular hypertension (two-kidney, one clip (2K1C)). Homodynamic studies were carried out in 2K1C rats. Naloxone (a nonselective OPR inhibitor) or nor-binaltorphimine dihydrochloride (norBNI, a kappa OPR inhibitor) and signaling pathway inhibitors PTX (a Gi path inhibitor) and chelerythrine (a protein kinase C (PKC) inhibitor) were administered before apelin at 20 and 40 μg kg-1. Apelin at 20 and 40 μg kg-1 decreased the systolic blood pressure by 15% and 20%, respectively (P<0.05). The pressure drop caused by apelin 20 was inhibited by naloxone, norBNI and PTX, but it was not affected by chelerythrine. The pressure drop caused by apelin 40 was augmented by naloxone and chelerythrine, and it was not affected by norBNI or PTX. The lowering effect of apelin 20 on blood pressure is exerted through OPRs and stimulation of Gi and PKC pathways. However, apelin 40 functions independently of OPRs, Gi and PKC. This dose-dependent differential effect of apelin may have potential clinical applications as opioids are currently used, and apelin has been introduced as a potential therapeutic agent in cardiovascular complications.
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Soave M, Stoddart LA, Brown A, Woolard J, Hill SJ. Use of a new proximity assay (NanoBRET) to investigate the ligand-binding characteristics of three fluorescent ligands to the human β1-adrenoceptor expressed in HEK-293 cells. Pharmacol Res Perspect 2016; 4:e00250. [PMID: 27588207 PMCID: PMC4988514 DOI: 10.1002/prp2.250] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 06/27/2016] [Accepted: 07/01/2016] [Indexed: 12/12/2022] Open
Abstract
Previous research has indicated that allosteric interactions across the dimer interface of β1‐adrenoceptors may be responsible for a secondary low affinity binding conformation. Here we have investigated the potential for probe dependence, in the determination of antagonist pKi values at the human β1‐adenoceptor, which may result from such allosterism interactions. Three fluorescent β1‐adrenoceptor ligands were used to investigate this using bioluminescence energy transfer (BRET) between the receptor‐bound fluorescent ligand and the N‐terminal NanoLuc tag of a human β1‐adrenoceptor expressed in HEK 293 cells (NanoBRET). This proximity assay showed high‐affinity‐specific binding to the NanoLuc‐ β1‐adrenoceptor with each of the three fluorescent ligands yielding KD values of 87.1 ± 10 nmol/L (n = 8), 38.1 ± 12 nmol/L (n = 7), 13.4 ± 2 nmol/L (n = 14) for propranolol‐Peg8‐BY630, propranolol‐ β(Ala‐Ala)‐BY630 and CGP‐12177‐TMR, respectively. Parallel radioligand‐binding studies with 3H‐CGP12177 and TIRF microscopy, to monitor NanoLuc bioluminescence, confirmed a high cell surface expression of the NanoLuc‐ β1‐adrenoceptor in HEK 293 cells (circa 1500 fmol.mg protein−1). Following a 1 h incubation with fluorescent ligands and β1‐adrenoceptor competing antagonists, there were significant differences (P < 0.001) in the pKi values obtained for CGP20712a and CGP 12177 with the different fluorescent ligands and 3H‐CGP 12177. However, increasing the incubation time to 2 h removed these significant differences. The data obtained show that the NanoBRET assay can be applied successfully to study ligand‐receptor interactions at the human β1‐adrenoceptor. However, the study also emphasizes the importance of ensuring that both the fluorescent and competing ligands are in true equilibrium before interpretations regarding probe dependence can be made.
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Affiliation(s)
- Mark Soave
- Cell Signalling and Pharmacology Research Group School of Life Sciences University of Nottingham Nottingham NG7 2UH United Kingdom
| | - Leigh A Stoddart
- Cell Signalling and Pharmacology Research Group School of Life Sciences University of Nottingham Nottingham NG7 2UH United Kingdom
| | - Alastair Brown
- Heptares Therapeutics Ltd. Bio Park Welwyn Garden City AL7 3AX United Kingdom
| | - Jeanette Woolard
- Cell Signalling and Pharmacology Research Group School of Life Sciences University of Nottingham Nottingham NG7 2UH United Kingdom
| | - Stephen J Hill
- Cell Signalling and Pharmacology Research Group School of Life Sciences University of Nottingham Nottingham NG7 2UH United Kingdom
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Gherbi K, Briddon SJ, Hill SJ. Detection of the secondary, low-affinity β1 -adrenoceptor site in living cells using the fluorescent CGP 12177 derivative BODIPY-TMR-CGP. Br J Pharmacol 2015; 171:5431-45. [PMID: 25052258 PMCID: PMC4261997 DOI: 10.1111/bph.12858] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 07/11/2014] [Accepted: 07/18/2014] [Indexed: 02/06/2023] Open
Abstract
Background and Purpose CGP 12177 not only inhibits agonist effects mediated through the catecholamine site of the β1-adrenoceptor with high affinity, but also exhibits agonist effects of its own at higher concentrations through a secondary, low-affinity β1-adrenoceptor site or conformation. β-blocker affinities for this ‘CGP 12177’ site of the human β1-adrenoceptor have thus far only been characterized in functional studies. Here, we used the fluorescent CGP 12177 analogue BODIPY-TMR-CGP to directly investigate receptor–ligand interactions at the secondary binding site of the β1-adrenoceptor. Experimental Approach The human β1-adrenoceptor was stably expressed in CHO cells containing a cAMP response element (CRE)-secreted placental alkaline phosphatase (SPAP) reporter gene construct. Functional responses of BODIPY-TMR-CGP were determined in the CRE-SPAP reporter gene assay, and manual and automated confocal microscopy platforms used to investigate the binding properties of BODIPY-TMR-CGP. Key Results BODIPY-TMR-CGP displayed a pharmacological profile similar to that of CGP 12177, retaining agonist activity at the secondary β1-adrenoceptor site. In confocal microscopy studies, specific BODIPY-TMR-CGP binding allowed clear visualization of β1-adrenoceptors in live cells. Using a wider concentration range of labelled ligand in a high-content fluorescence-based binding assay than is possible in radioligand binding assays, two-site inhibition binding curves of β-adrenoceptor antagonists were revealed in CHO cells expressing the human β1-adrenoceptor, but not the β2-adrenoceptor. Conclusions and Implications The fluorescent CGP 12177 analogue allowed the detection of the β1-adrenoceptor secondary site in both functional and binding studies. This suggests that BODIPY-TMR-CGP presents an important and novel fluorescent tool to investigate the nature of the secondary β1-adrenoceptor site.
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Affiliation(s)
- K Gherbi
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, UK
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Gherbi K, May LT, Baker JG, Briddon SJ, Hill SJ. Negative cooperativity across β1-adrenoceptor homodimers provides insights into the nature of the secondary low-affinity CGP 12177 β1-adrenoceptor binding conformation. FASEB J 2015; 29:2859-71. [PMID: 25837585 PMCID: PMC4478806 DOI: 10.1096/fj.14-265199] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 03/02/2015] [Indexed: 01/30/2023]
Abstract
At the β1-adrenoceptor, CGP 12177 potently antagonizes agonist responses at the primary high-affinity catecholamine conformation while also exerting agonist effects of its own through a secondary low-affinity conformation. A recent mutagenesis study identified transmembrane region (TM)4 of the β1-adrenoceptor as key for this low-affinity conformation. Others suggested that TM4 has a role in β1-adrenoceptor oligomerization. Here, assessment of the dissociation rate of a fluorescent analog of CGP 12177 [bordifluoropyrromethane-tetramethylrhodamine-(±)CGP 12177 (BODIPY-TMR-CGP)] at the human β1-adrenoceptor expressed in Chinese hamster ovary cells revealed negative cooperative interactions between 2 distinct β1-adrenoceptor conformations. The dissociation rate of 3 nM BODIPY-TMR-CGP was 0.09 ± 0.01 min−1 in the absence of competitor ligands, and this was enhanced 2.2- and 2.1-fold in the presence of 1 µM CGP 12177 and 1 µM propranolol, respectively. These effects on the BODIPY-TMR-CGP dissociation rate were markedly enhanced in β1-adrenoceptor homodimers constrained by bimolecular fluorescence complementation (9.8- and 9.9-fold for 1 µM CGP 12177 and 1 µM propranolol, respectively) and abolished in β1-adrenoceptors containing TM4 mutations vital for the second conformation pharmacology. This study suggests that negative cooperativity across a β1-adrenoceptor homodimer may be responsible for generating the low-affinity pharmacology of the secondary β1-adrenoceptor conformation.—Gherbi, K., May, L. T., Baker, J. G., Briddon, S. J., Hill, S. J. Negative cooperativity across β1-adrenoceptor homodimers provides insights into the nature of the secondary low-affinity CGP 12177 β1-adrenoceptor binding conformation.
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Affiliation(s)
- Karolina Gherbi
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Lauren T May
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Jillian G Baker
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Stephen J Briddon
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Stephen J Hill
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
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Kiriazis H, Tugiono N, Xu Q, Gao XM, Jennings NL, Ming Z, Su Y, Klenowski P, Summers RJ, Kaumann A, Molenaar P, Du XJ. Chronic activation of the low affinity site of β1-adrenoceptors stimulates haemodynamics but exacerbates pressure-overload cardiac remodelling. Br J Pharmacol 2014; 170:352-65. [PMID: 23750586 DOI: 10.1111/bph.12272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 04/22/2013] [Accepted: 06/07/2013] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE The β1-adrenoceptor has at least two binding sites, high and low affinity sites (β1H and β1L, respectively), which mediate cardiostimulation. While β1H-adrenoceptor can be blocked by all clinically used β-blockers, β1L-adrenoceptor is relatively resistant to blockade. Thus, chronic β1L-adrenoceptor activation may mediate persistent cardiostimulation, despite the concurrent blockade of β1H-adrenoceptors. Hence, it is important to determine the potential significance of β1L-adrenoceptors in vivo, particularly in pathological situations. EXPERIMENTAL APPROACH C57Bl/6 male mice were used. Chronic (4 or 8 weeks) β1L-adrenoceptor activation was achieved by treatment, via osmotic mini pumps, with (-)-CGP12177 (10 mg·kg(-1)·day(-1)). Cardiac function was assessed by echocardiography and micromanometry. KEY RESULTS (-)-CGP12177 treatment of healthy mice increased heart rate and left ventricular (LV) contractility. (-)-CGP12177 treatment of mice subjected to transverse aorta constriction (TAC), during weeks 4-8 or 4-12 after TAC, led to a positive inotropic effect and exacerbated fibrogenic signalling while cardiac hypertrophy tended to be more severe. (-)-CGP12177 treatment of mice with TAC also exacerbated the myocardial expression of hypertrophic, fibrogenic and inflammatory genes compared to untreated TAC mice. Washout of (-)-CGP12177 revealed a more pronounced cardiac dysfunction after 12 weeks of TAC. CONCLUSIONS AND IMPLICATIONS β1L-adrenoceptor activation provides functional support to the heart, in both normal and pathological (pressure overload) situations. Sustained β1L-adrenoceptor activation in the diseased heart exacerbates LV remodelling and therefore may promote disease progression from compensatory hypertrophy to heart failure.
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Affiliation(s)
- Helen Kiriazis
- Experimental Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Vic., Australia
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Schlicker E, Pędzińska-Betiuk A, Kozłowska H, Szkaradek N, Żelaszczyk D, Baranowska-Kuczko M, Kieć-Kononowicz K, Marona H, Malinowska B. MH-3: evidence for non-competitive antagonism towards the low-affinity site of β1-adrenoceptors. Naunyn Schmiedebergs Arch Pharmacol 2014; 387:743-52. [DOI: 10.1007/s00210-014-0983-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 04/09/2014] [Indexed: 10/25/2022]
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Baker JG, Proudman RGW, Hill SJ. Identification of key residues in transmembrane 4 responsible for the secondary, low-affinity conformation of the human β1-adrenoceptor. Mol Pharmacol 2014; 85:811-29. [PMID: 24608857 DOI: 10.1124/mol.114.091587] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The β1-adrenoceptor exists in two agonist conformations/states: 1) a high-affinity state where responses to catecholamines and other agonists (e.g., cimaterol) are potently inhibited by β1-adrenoceptor antagonists, and 2) a low-affinity secondary conformation where agonist responses, particularly CGP12177 [(-)-4-(3-tert-butylamino-2-hydroxypropoxy)-benzimidazol-2-one] are relatively resistant to inhibition by β1-adrenoceptor antagonists. Although both states have been demonstrated in many species (including human), the precise nature of the secondary state is unknown and does not occur in the closely related β2-adrenoceptor. Here, using site-directed mutagenesis and functional measurements of production of a cyclic AMP response element upstream of a secreted placental alkaline phosphatase reporter gene and accumulation of (3)H-cAMP, we examined the pharmacological consequences of swapping transmembrane (TM) regions of the human β1- and β2-adrenoceptors, followed by single point mutations, to determine the key residues involved in the β1-adrenoceptor secondary conformation. We found that TM4 (particularly amino acids L195 and W199) had a major role in the generation of the secondary β1-adrenoceptor conformation. Thus, unlike at the human β1-wild-type adrenoceptor, at β1-TM4 mutant receptors, cimaterol and CGP12177 responses were both potently inhibited by antagonists. CGP12177 acted as a simple partial agonist with similar KB and EC50 values in the β1-TM4 but not β1-wild-type receptors. Furthermore pindolol switched from a biphasic concentration response at human β1-wild-type adrenoceptors to a monophasic concentration response in the β1-TM4 mutant receptors. Mutation of these amino acids to those found in the β2-adrenoceptor (L195Q and W199Y), or mutation of a single residue (W199D) in the human β1-adrenoceptor thus abolished this secondary conformation and created a β1-adrenoceptor with only one high-affinity agonist conformation.
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Affiliation(s)
- Jillian G Baker
- Cell Signalling, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
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Catus SL, Gibbs ME, Sato M, Summers RJ, Hutchinson DS. Role of β-adrenoceptors in glucose uptake in astrocytes using β-adrenoceptor knockout mice. Br J Pharmacol 2011; 162:1700-15. [PMID: 21138422 DOI: 10.1111/j.1476-5381.2010.01153.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE β(1) -, β(2) - and β(3) -adrenoceptors determined by functional, binding and reverse transcription polymerase chain reaction (RT-PCR) studies are present in chick astrocytes and activation of β(2) - or β(3) -adrenoceptors increase glucose uptake. The aims of the present study are to identify which β-adrenoceptor subtypes are present in mouse astrocytes, the signal transduction mechanisms involved and whether β-adrenoceptor stimulation regulates glucose uptake. EXPERIMENTAL APPROACH Astrocytes were prepared from four mouse strains: FVB/N, DBA/1 crossed with C57BL/6J, β(3) -adrenoceptor knockout and β(1) β(2) -adrenoceptor knockout mice. RT-PCR and radioligand binding studies were used to determine β-adrenoceptor expression. Glucose uptake and cAMP were assayed to elucidate the signalling pathways involved. KEY RESULTS mRNAs for all three β-adrenoceptors were identified in astrocytes from wild-type mice. Radioligand binding studies identified that β(1) - and β(3) -adrenoceptors were predominant. cAMP studies showed that β(1) - and β(2) -adrenoceptors coupled to G(s) whereas β(3) -adrenoceptors coupled to both G(s) and G(i) . However, activation of any of the three β-adrenoceptors increased glucose uptake in mouse astrocytes. Interestingly, there was no functional compensation for receptor subtype loss in knockout animals. CONCLUSIONS AND IMPLICATIONS This study demonstrates that although β(1) -adrenoceptors are the predominant β-adrenoceptor in mouse astrocytes and are primarily responsible for cAMP production in response to β-adrenoceptor stimulation, β(3) -adrenoceptors are also present in mouse astrocytes and activation of β(2) - and β(3) -adrenoceptors increases glucose uptake in mouse astrocytes.
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Affiliation(s)
- Stephanie L Catus
- Department of Pharmacology, Monash University, Clayton, Victoria, Australia
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Christ T, Molenaar P, Klenowski PM, Ravens U, Kaumann AJ. Human atrial β(1L)-adrenoceptor but not β₃-adrenoceptor activation increases force and Ca(2+) current at physiological temperature. Br J Pharmacol 2011; 162:823-39. [PMID: 20726983 DOI: 10.1111/j.1476-5381.2010.00996.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE It has been proposed that BRL37344, SR58611 and CGP12177 activate β₃-adrenoceptors in human atrium to increase contractility and L-type Ca(2+) current (I(Ca-L)). β₃-adrenoceptor agonists are potentially beneficial for the treatment of a variety of diseases but concomitant cardiostimulation would be potentially harmful. It has also been proposed that (-)-CGP12177 activates the low affinity binding site of the β₁-adrenoceptor in human atrium. We therefore used BRL37344, SR58611 and (-)-CGP12177 with selective β-adrenoceptor subtype antagonists to clarify cardiostimulant β-adrenoceptor subtypes in human atrium. EXPERIMENTAL APPROACH Human right atrium was obtained from patients without heart failure undergoing coronary artery bypass or valve surgery. Cardiomyocytes were prepared to test BRL37344, SR58611 and CGP12177 effects on I(Ca-L). Contractile effects were determined on right atrial trabeculae. KEY RESULTS BRL37344 increased force which was antagonized by blockade of β₁- and β₂-adrenoceptors but not by blockade of β₃-adrenoceptors with β₃-adrenoceptor-selective L-748,337 (1 µM). The β₃-adrenoceptor agonist SR58611 (1 nM-10 µM) did not affect atrial force. BRL37344 and SR58611 did not increase I(Ca-L) at 37°C, but did at 24°C which was prevented by L-748,337. (-)-CGP12177 increased force and I(Ca-L) at both 24°C and 37°C which was prevented by (-)-bupranolol (1-10 µM), but not L-748,337. CONCLUSIONS AND IMPLICATIONS We conclude that the inotropic responses to BRL37344 are mediated through β₁- and β₂-adrenoceptors. The inotropic and I(Ca-L) responses to (-)-CGP12177 are mediated through the low affinity site β(1L)-adrenoceptor of the β₁-adrenoceptor. β₃-adrenoceptor-mediated increases in I(Ca-L) are restricted to low temperatures. Human atrial β₃-adrenoceptors do not change contractility and I(Ca-L) at physiological temperature.
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Affiliation(s)
- Torsten Christ
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany
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Baker JG, Hill SJ, Summers RJ. Evolution of β-blockers: from anti-anginal drugs to ligand-directed signalling. Trends Pharmacol Sci 2011; 32:227-34. [PMID: 21429598 PMCID: PMC3081074 DOI: 10.1016/j.tips.2011.02.010] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 02/16/2011] [Accepted: 02/16/2011] [Indexed: 01/14/2023]
Abstract
Sir James Black developed β-blockers, one of the most useful groups of drugs in use today. Not only are they being used for their original purpose to treat angina and cardiac arrhythmias, but they are also effective therapeutics for hypertension, cardiac failure, glaucoma, migraine and anxiety. Recent studies suggest that they might also prove useful in diseases as diverse as osteoporosis, cancer and malaria. They have also provided some of the most useful tools for pharmacological research that have underpinned the development of concepts such as receptor subtype selectivity, agonism and inverse agonism, and ligand-directed signalling bias. This article examines how β-blockers have evolved and indicates how they might be used in the future.
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Affiliation(s)
- Jillian G. Baker
- Institute of Cell Signalling, School of Biomedical Sciences, Medical School, Queen's Medical Centre, Nottingham, UK
| | - Stephen J. Hill
- Institute of Cell Signalling, School of Biomedical Sciences, Medical School, Queen's Medical Centre, Nottingham, UK
| | - Roger J. Summers
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, 399, Royal Parade, Parkville, Vic 3052, Australia
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Baker JG. A full pharmacological analysis of the three turkey β-adrenoceptors and comparison with the human β-adrenoceptors. PLoS One 2010; 5:e15487. [PMID: 21152092 PMCID: PMC2994877 DOI: 10.1371/journal.pone.0015487] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 10/01/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND There are three turkey β-adrenoceptors: the original turkey β-adrenoceptor from erythrocytes (tβtrunc, for which the X-ray crystal structure has recently been determined), tβ3C and tβ4C-receptors. This study examined the similarities and differences between these avian receptors and mammalian receptors with regards to binding characteristics and functional high and low affinity agonist conformations. METHODOLOGY/PRINCIPAL FINDINGS Stable cell lines were constructed with each of the turkey β-adrenoceptors and 3H-CGP12177 whole cell binding, CRE-SPAP production and (3)H-cAMP accumulation assays performed. It was confirmed that the three turkey β-adrenoceptors are distinct from each other in terms of amino acid sequence and binding characteristics. The greatest similarity of any of the turkey β-adrenoceptors to human β-adrenoceptors is between the turkey β3C-receptor and the human β2-adrenoceptor. There are pharmacologically distinct differences between the binding of ligands for the tβtrunc and tβ4C and the human β-adrenoceptors (e.g. with CGP20712A and ICI118551). The tβtrunc and tβ4C-adrenoceptors appear to exist in at least two different agonist conformations in a similar manner to that seen at both the human and rat β1-adrenoceptor and human β3-adrenoceptors. The tβ3C-receptor, similar to the human β2-adrenoceptor, does not, at least so far, appear to exist in more than one agonist conformation. CONCLUSIONS/SIGNIFICANCE There are several similarities, but also several important differences, between the recently crystallised turkey β-adrenoceptor and the human β-adrenoceptors. These findings are important for those the field of drug discovery using the recently structural information from crystallised receptors to aid drug design. Furthermore, comparison of the amino-acid sequence for the turkey and human adrenoceptors may therefore shed more light on the residues involved in the existence of the secondary β-adrenoceptor conformation.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signalling, University of Nottingham, Nottingham, United Kingdom.
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Baker JG. The selectivity of beta-adrenoceptor agonists at human beta1-, beta2- and beta3-adrenoceptors. Br J Pharmacol 2010; 160:1048-61. [PMID: 20590599 DOI: 10.1111/j.1476-5381.2010.00754.x] [Citation(s) in RCA: 260] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE There are two important properties of receptor-ligand interactions: affinity (the ability of the ligand to bind to the receptor) and efficacy (the ability of the receptor-ligand complex to induce a response). Ligands are classified as agonists or antagonists depending on whether or not they have efficacy. In theory, it is possible to develop selective agonists based on selective affinity, selective intrinsic efficacy or both. This study examined the affinity and intrinsic efficacy of 31 beta-adrenoceptor agonists at the three human beta-adrenoceptors to determine whether the current agonists are subtype selective because of affinity or intrinsic efficacy. EXPERIMENTAL APPROACH Stable clonal CHO-K1 cell lines, transfected with either the human beta(1), beta(2) or beta(3)-adrenoceptor, were used, and whole-cell [(3)H]-CGP 12177 radioligand binding and [(3)H]-cAMP accumulation were measured. KEY RESULTS Several agonists were found to be highly subtype selective because of selective affinity (e.g. salmeterol and formoterol, for the beta(2)-adrenoceptor over the beta(1) or beta(3)), while others (e.g. isoprenaline) had little affinity-selectivity. However, the intrinsic efficacy of salmeterol, formoterol and isoprenaline was similar across all three receptor subtypes. Other ligands (e.g. denopamine for beta(1); clenbuterol, AZ 40140d, salbutamol for beta(2)) were found to have subtype-selective intrinsic efficacy. Several ligands appeared to activate two agonist conformations of the beta(1)- and beta(3)-adrenoceptors. CONCLUSIONS AND IMPLICATIONS There are agonists with subtype selectivity based upon both selective affinity and selective intrinsic efficacy. Therefore, there is scope to develop better selective agonists based upon both selective affinity and selective intrinsic efficacy.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signalling, C Floor Medical School, Queen's Medical Centre, University of Nottingham, Nottingham, UK.
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Baker JG, Proudman RGW, Hawley NC, Fischer PM, Hill SJ. Role of key transmembrane residues in agonist and antagonist actions at the two conformations of the human beta1-adrenoceptor. Mol Pharmacol 2008; 74:1246-60. [PMID: 18687809 DOI: 10.1124/mol.108.048371] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Studies with 4-[3-[(1,1-dimethylethyl)amino]2-hydroxypropoxy]-1,3-dihydro-2H-benzimidazol-2-one hydrochloride (CGP 12177) at the human beta1-adrenoceptor have provided evidence for two binding modes or conformations that have markedly different pharmacological properties. Here, key transmembrane residues (Asp104, Asp138, Ser228, Ser229, Ser232, Phe341, Asn344 and Asn363) have been mutated to provide structural insights into the nature of these conformations. [(3)H]CGP 12177 binding and cAMP response element-mediated reporter gene studies confirmed that CGP 12177 was a neutral antagonist (log K(D) = -9.18) at the "catecholamine site" and an agonist at the "CGP 12177 site" (log EC(50) = -8.12). Agonist responses to isoprenaline and CGP 12177 had different sensitivities to beta1-antagonists (e.g., CGP 20712A; log K(D) = -8.65 and -7.26, respectively). Site-directed mutagenesis showed that Asn363 and Asp138 were key residues for binding of agonists and antagonists, and they were also essential for the agonist actions of CGP 12177. S228A and S229A in transmembrane-spanning region (TM) 5 reduced the binding of CGP 12177 and had an identical effect on its agonist and antagonist actions. Both N344A and F341A in TM6 abolished the ability of CGP 20712A to discriminate between responses elicited by isoprenaline and CGP 12177. The fact that both Asp138 and Asn363 are absolutely required for CGP 12117 binding in both agonist and antagonist modes leads to the conclusion that the secondary agonist binding site for CGP 12117 must overlap with the catecholamine binding site. Modeling studies provide a basis for these overlapping sites with either the tert-butylamino group or the hydroxyethyloxy and imidazolone portions of CGP 12177 capable of forming polar interactions with Asp138 and Asn363.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signaling, Queen's Medical Centre, Nottingham, NG7 2UH, UK
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15
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Baker JG. Antagonist affinity measurements at the Gi-coupled human histamine H3 receptor expressed in CHO cells. BMC Pharmacol 2008; 8:9. [PMID: 18538007 PMCID: PMC2430196 DOI: 10.1186/1471-2210-8-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Accepted: 06/06/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The H3 histamine receptor is a Gi-coupled GPCR that has been proven to exist in different agonist-induced states, including that defined by the protean agonist proxyfan. Several GPCRs are now known to exist in different states. For some of these, antagonist affinity measurement remain constant regardless of the state of the receptor, for others e.g. the beta-adrenoceptors, the antagonist affinity measurements vary considerably depending on which agonist-dependent state is being identified. The purpose of this study was to examine the antagonist affinity measurements at the Gi-coupling human H3 receptor, paying particular attention to measurements made in the presence of full agonists, partial agonists and the proxyfan protean agonist-induced state of the receptor. RESULTS CHO cells stably expressing the human histamine H3 receptor and a CRE-SPAP reporter were used. Measurements of CRE-gene transcription and 3H-cAMP accumulation were made. A range of ligands of different agonist efficacies were determined, including some partial agonists e.g. VUF 5681. Unlike other Gi-coupled receptors, no Gs-coupled state of the receptor was detected with these ligands. Antagonist affinity measurements were constant, whether the measurements were made in the presence of a full agonist, a partial agonist or the protean agonist proxyfan. CONCLUSION In contrast to all three subtypes of the beta-adrenoceptors, but in keeping with the traditional pharmacological dogma, antagonist affinity measurements remained constant at the human H3 receptor, including the medium-efficacy proxyfan-induced state of the receptor and the VUF5681-induced state of the receptor.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signalling, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK.
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16
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Kaumann AJ, Molenaar P. The low-affinity site of the β1-adrenoceptor and its relevance to cardiovascular pharmacology. Pharmacol Ther 2008; 118:303-36. [DOI: 10.1016/j.pharmthera.2008.03.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Accepted: 03/20/2008] [Indexed: 10/22/2022]
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17
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Baker JG. A study of antagonist affinities for the human histamine H2 receptor. Br J Pharmacol 2007; 153:1011-21. [PMID: 18157166 DOI: 10.1038/sj.bjp.0707644] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Ligand affinity has been a fundamental concept in the field of pharmacology and has traditionally been considered to be constant for a given receptor-ligand interaction. Recent studies have demonstrated that this is not true for all three members of the G(s)-coupled beta-adrenoceptor family. This study evaluated antagonist affinity measurements at a different G(s)-coupled receptor, the histamine H(2) receptor, to determine whether antagonist affinity measurements made at a different family of GPCRs were constant. EXPERIMENTAL APPROACH CHO cells stably expressing the human histamine H(2) receptor and a CRE-SPAP reporter were used and antagonist affinity was assessed in short-term cAMP assays and longer term CRE gene transcription assays. KEY RESULTS Nine agonists and seven antagonists, of sufficient potency at the H(2) receptor to examine in detail, were identified. Measurements of antagonist affinity were the same regardless of the efficacy of the competing agonist, time of agonist incubation, cellular response measured or presence of a PDE inhibitor. CONCLUSIONS AND IMPLICATIONS Antagonist affinity at the G(s)-coupled histamine H(2) receptor obeys the accepted dogma for antagonism at GPCRs. This study further confirms that something unusual is indeed happening with the beta-adrenoceptors and is not an artefact related to the transfected cell system used. As the human histamine H(2) receptor does not behave in a similar manner to any of the human beta-adrenoceptors, it is clear that information gathered from one GPCR cannot be simply extrapolated to predict the behaviour of another GPCR. Each GPCR therefore requires careful and detailed evaluation on its own.
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Affiliation(s)
- J G Baker
- Institute of Cell Signalling, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham, UK.
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18
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Hamilton BS, Doods HN. Identification of potent agonists acting at an endogenous atypical beta3-adrenoceptor state that modulate lipolysis in rodent fat cells. Eur J Pharmacol 2007; 580:55-62. [PMID: 18031735 DOI: 10.1016/j.ejphar.2007.10.065] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Revised: 10/17/2007] [Accepted: 10/22/2007] [Indexed: 11/28/2022]
Abstract
Small molecules interacting with aminergic G-protein coupled receptors represent a number of very successful drugs. G-protein coupled receptors continue to be a significant group of targets for pharmaceutical intervention, and modifying their activity through small molecules is a major focus of drug development. Previously, these small molecules could be easily fit in models, as agonists, partial agonists or antagonists. More recently, however, these lines have been blurred as it is increasingly recognized that ligands can interact with receptors in various ways. Analysis of beta-adrenoceptors has revealed that several sites or states exist for the individual receptors. The putative atypical beta(4)-adrenoceptor identified on heart and adipose tissue is now recognized as a unique beta(1)-adrenoceptor state. Similarly, a unique beta(3)-adrenoceptor state has been identified using the aryloxypropanolamine CGP-12,177 and cloned receptor systems. Here we expand upon these observations, by describing an atypical state of the beta(3)-adrenoceptor that exists endogenously in adipose tissue. Furthermore, we describe novel arylethanolamine ligands that interact with this atypical state of the beta(3)-adrenoceptor with high affinity and provide additional tools to investigate the atypical beta(3)-adrenoceptor state to determine whether it can be influenced for therapeutic purposes.
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Affiliation(s)
- Bradford S Hamilton
- Department of Metabolic Diseases, Boehringer Ingelheim Pharma GmbH & Co KG, 88397 Biberach an der Riss, Germany.
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19
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Molenaar P, Chen L, Semmler ABT, Parsonage WA, Kaumann AJ. HUMAN HEART ?-ADRENOCEPTORS: ?1-ADRENOCEPTOR DIVERSIFICATION THROUGH ?AFFINITY STATES? AND POLYMORPHISM. Clin Exp Pharmacol Physiol 2007; 34:1020-8. [PMID: 17714089 DOI: 10.1111/j.1440-1681.2007.04730.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. In atrium and ventricle from failing and non-failing human hearts, activation of beta(1)- or beta(2)-adrenoceptors causes increases in contractile force, hastening of relaxation, protein kinase A-catalysed phosphorylation of proteins implicated in the hastening of relaxation, phospholamban, troponin I and C-protein, consistent with coupling of both beta(1)- and beta(2)-adrenoceptors to stimulatory G(salpha)-protein but not inhibitory G(ialpha)-protein. 2. Two 'affinity states', namely beta(1H) and beta(1L), of the beta(1)-adrenoceptor exist. In human heart, noradrenaline elicits powerful increases in contractile force and hastening of relaxation. These effects are blocked with high affinity by beta-adenoceptor antagonists, including propranolol, (-)-pindolol, (-)-CGP 12177 and carvedilol. Some beta-blockers, typified by (-)-pindolol and (-)-CGP 12177, not only block the receptor, but also activate it, albeit at much higher concentrations (approximately 2 log units) than those required to antagonize the effects of catecholamines. In human heart, both (-)-CGP 12177 and (-)-pindolol increase contractile force and hasten relaxation. However, the involvement of the beta(1)-adrenoceptor was not immediately obvious because (-)-pindolol- and (-)-CGP 12177-evoked responses were relatively resistant to blockade by (-)-propranolol. Abrogation of cardiostimulant effects of (-)-CGP 12177 in beta(1)-/beta(2)-adrenoceptor double-knockout mice, but not beta(2)-adrenoceptor-knockout mice, revealed an obligatory role of the beta(1)-adrenoceptor. On the basis of these results, two 'affinity states' have been designated, the beta(1H)- and beta(1L)-adrenoceptor, where the beta(1H)-adrenoceptor is activated by noradrenaline and blocked with high affinity by beta-blockers and the beta(1L)-adrenoceptor is activated by drugs such as (-)-CGP 12177 and (-)-pindolol and blocked with low affinity by beta-blockers such as (-)-propranolol. The beta(1H)- and beta(1L)-adrenoceptor states are consistent with high- and low-affinity binding sites for (-)-[(3)H]-CGP 12177 radioligand binding found in cardiac muscle and recombinant beta(1)-adrenoceptors. 3. There are two common polymorphic locations of the beta(1)-adrenoceptor, at amino acids 49 (Ser/Gly) and 389 (Arg/Gly). Their existence has raised several questions, including their role in determining the effectiveness of heart failure treatment with beta-blockers. We have investigated the effect of long-term maximally tolerated carvedilol administration (> 1 year) on left ventricular ejection fraction (LVEF) in patients with non-ischaemic cardiomyopathy (mean left ventricular ejection fraction 23 +/- 7%; n = 135 patients). The administration of carvedilol improved LVEF to 37 +/- 13% (P < 0.005); however, the improvement was variable, with 32% of patients showing pound 5% improvement. Upon segregation of patients into Arg389Gly-beta(1)-adrenoceptors, it was found that carvedilol caused a greater increase in left ventricular ejection faction in patients carrying the Arg389 allele with Arg389Arg > Arg389Gly > Gly389Gly.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Adrenergic beta-Antagonists/pharmacology
- Animals
- Heart/drug effects
- Heart Atria/drug effects
- Heart Ventricles/drug effects
- Humans
- Myocardium/metabolism
- Polymorphism, Genetic/genetics
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/physiology
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/physiology
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/physiology
- Species Specificity
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Affiliation(s)
- P Molenaar
- Department of Medicine, The University of Queensland, The Prince Charles Hospital, Chermside, Queensland, Australia.
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20
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Baker JG, Hill SJ. Multiple GPCR conformations and signalling pathways: implications for antagonist affinity estimates. Trends Pharmacol Sci 2007; 28:374-81. [PMID: 17629959 PMCID: PMC2169386 DOI: 10.1016/j.tips.2007.06.011] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Revised: 05/22/2007] [Accepted: 06/26/2007] [Indexed: 01/27/2023]
Abstract
Antagonist affinity measurements have traditionally been considered important in characterizing the cell-surface receptors present in a particular cell or tissue. A central assumption has been that antagonist affinity is constant for a given receptor-antagonist interaction, regardless of the agonist used to stimulate that receptor or the downstream response that is measured. As a consequence, changes in antagonist affinity values have been taken as initial evidence for the presence of novel receptor subtypes. Emerging evidence suggests, however, that receptors can possess multiple binding sites and the same receptor can show different antagonist affinity measurements under distinct experimental conditions. Here, we discuss several mechanisms by which antagonists have different affinities for the same receptor as a consequence of allosterism, coupling to different G proteins, multiple (but non-interacting) receptor sites, and signal-pathway-dependent pharmacology (where the pharmacology observed varies depending on the signalling pathway measured).
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21
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Nelson CP, Challiss RAJ. “Phenotypic” pharmacology: The influence of cellular environment on G protein-coupled receptor antagonist and inverse agonist pharmacology. Biochem Pharmacol 2007; 73:737-51. [PMID: 17046719 DOI: 10.1016/j.bcp.2006.09.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Revised: 08/31/2006] [Accepted: 09/06/2006] [Indexed: 11/25/2022]
Abstract
A central dogma of G protein-coupled receptor (GPCR) pharmacology has been the concept that unlike agonists, antagonist ligands display equivalent affinities for a given receptor, regardless of the cellular environment in which the affinity is assayed. Indeed, the widespread use of antagonist pharmacology in the classification of receptor expression profiles in vivo has relied upon this 'antagonist assumption'. However, emerging evidence suggests that the same gene-product may exhibit different antagonist pharmacological profiles, depending upon the cellular context in which it is expressed-so-called 'phenotypic' profiles. In this commentary, we review the evidence relating to some specific examples, focusing on adrenergic and muscarinic acetylcholine receptor systems, where GPCR antagonist/inverse agonist pharmacology has been demonstrated to be cell- or tissue-dependent, before going on to examine some of the ways in which the cellular environment might modulate receptor pharmacology. In the majority of cases, the cellular factors responsible for generating phenotypic profiles are unknown, but there is substantial evidence that factors, including post-transcriptional modifications, receptor oligomerization and constitutive receptor activity, can influence GPCR pharmacology and these concepts are discussed in relation to antagonist phenotypic profiles. A better molecular understanding of the impact of cell background on GPCR antagonist pharmacology is likely to provide previously unrealized opportunities to achieve greater specificity in new drug discovery candidates.
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Affiliation(s)
- Carl P Nelson
- Department of Cell Physiology & Pharmacology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 9HN, UK.
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22
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Vargas ML, Hernandez J, Kaumann AJ. Phosphodiesterase PDE3 blunts the positive inotropic and cyclic AMP enhancing effects of CGP12177 but not of noradrenaline in rat ventricle. Br J Pharmacol 2007; 147:158-63. [PMID: 16331293 PMCID: PMC1615855 DOI: 10.1038/sj.bjp.0706498] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
1.--The cardiostimulant effects of CGP12177, mediated through a beta(1)-adrenoceptor site with low affinity for (-)-propranolol, are potentiated by the nonselective PDE inhibitor IBMX but the role of PDE isoenzymes is unknown. We studied the effects of the PDE3-selective inhibitor cilostamide (300 nM) and PDE4-selective inhibitor rolipram (1 microM) on the positive inotropic and cyclic AMP-enhancing effects of CGP12177 and noradrenaline in right ventricular strips of rat. 2.--CGP12177 (under (-)-propranolol 200 nM) only increased contractile force in the presence of either cilostamide or rolipram with -logEC(50)M 6.7 (E(max)=23% over basal) and 7.1 (E(max)=50%) respectively. The combination of cilostamide and rolipram caused CGP12177 to enhance contractile force with -logEC(50)M=7.7 and E(max)=178%. 3.--The positive inotropic effects of noradrenaline (-logEC(50)M=6.9) were potentiated by rolipram (-logEC(50)M=7.4) but not by cilostamide (-logEC(50)M=7.0). 4.--In the presence of rolipram and (-)-propranolol, noradrenaline (2 microM) and CGP12177 (10 microM) produced matching inotropic effects but failed to increase cyclic AMP levels. 20 microM (-)-noradrenaline increased cyclic AMP levels, a response further enhanced by rolipram. 5.--Both PDE3 and PDE4 of rat ventricle appear to hydrolyse cyclic AMP generated through the low-affinity beta(1)-adrenoceptor site, thereby preventing inotropic responses of CGP12177. When (-)-noradrenaline interacts with the beta(1)-adrenoceptor, the generated cyclic AMP is hydrolysed only by PDE4, thereby reducing cardiostimulation.
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Affiliation(s)
| | - Jesus Hernandez
- Department of Pharmacology, University of Murcia, Murcia, Spain
| | - Alberto J Kaumann
- Department of Physiology, University of Cambridge, Downing Street, Cambridge CB2 3EG
- Author for correspondence:
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23
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Baker JG, Hill SJ. A comparison of the antagonist affinities for the Gi- and Gs-coupled states of the human adenosine A1-receptor. J Pharmacol Exp Ther 2006; 320:218-28. [PMID: 17018691 DOI: 10.1124/jpet.106.113589] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The antagonist affinity for a given receptor is traditionally considered to be constant, reflecting the chemical nature of the specific ligand-receptor interaction. However, recent observations with all three beta-adrenoceptors have cast doubt on this basic pharmacological principle. The extent to which this finding applies to other G protein-coupled receptors and their interaction with different G proteins is unknown. Therefore, we studied the influence of different agonists on antagonist affinity measurements for Gi- and Gs-coupled conformations of the adenosine A1-receptor in Chinese hamster ovary cells stably expressing the human adenosine A1-receptor and a cAMP-response element (CRE)-secreted placental alkaline phosphatase reporter gene. Gi-coupled inhibition of [3H]cAMP accumulation via the A1-receptor was observed at low concentrations of agonist; however, a small increase in [3H]cAMP accumulation was also seen at higher agonist concentrations. This biphasic response was more evident for A1-stimulated CRE-gene transcription. The inhibitory component was abolished by pretreatment with pertussis toxin, whereas the stimulatory component was augmented, suggesting that the responses were due to an A1-Gi-coupled inhibition followed by an A1-Gs-coupled stimulation. However, the antagonist affinity values measured at the Gi-coupled and Gs-coupled conformations of the receptor were the same in both functional responses and whole-cell binding. Thus, in marked contrast to the beta-adrenoceptors, the A1-receptor conforms to the long-held principle of pharmacology that antagonist affinity measurements are constant regardless of the response being measured and the competing agonist used to stimulate that response. This was true even when the receptor was shown, in the same assay, to exist in two different conformational states coupled to two different G proteins.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signaling, Queen's Medical Centre, Nottingham NG7 2UH, UK.
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24
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Zakrzeska A, Schlicker E, Kwolek G, Kozłowska H, Malinowska B. Positive inotropic and lusitropic effects mediated via the low-affinity state of beta1-adrenoceptors in pithed rats. Br J Pharmacol 2006; 146:760-8. [PMID: 16151438 PMCID: PMC1751196 DOI: 10.1038/sj.bjp.0706382] [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: 11/09/2022] Open
Abstract
1 Activation by CGP 12177 and cyanopindolol of the human and rat low-affinity state of beta(1)-adrenoceptors increases frequency and contractile force and hastens relaxation in isolated cardiac tissues, and probably relaxes isolated vessels. In order to identify the positive inotropic, positive lusitropic and vasodilator effects of both agonists also in vivo, we have determined their effects on the left ventricular systolic pressure (LVSP), the rate of intraventricular pressure rise (+dP dt(-1)(max)) and decline (-dP dt(-1)(max)), the diastolic blood pressure (DBP) and the mesenteric blood flow (MBF) in pithed and vagotomized rats. 2 CGP 12177 (0.1-100 nmol kg(-1)) and cyanopindolol (1-1000 nmol kg(-1)) dose-dependently enhanced all cardiac parameters. The nonselective beta-adrenoceptor antagonist bupranolol 10 micromol kg(-1) diminished the CGP 12177 (100 nmol kg(-1))-stimulated increases in LVSP from 26.3+/-8.2 to 13.1+/-1.8 mmHg (P<0.05), +dP dt(-1)(max) from 5287+/-290 to 2439+/-296 mmHg s(-1) (P<0.001) and -dP dt(-1)(max) from -3836+/-301 to -2187+/-443 mmHg s(-1) (P<0.05), respectively. The beta(1)-adrenoceptor antagonist CGP 20712A 10 micromol kg(-1) (known to block the low-affinity state of beta(1)-adrenoceptors at high doses) inhibited increases in +/-dP dt(-1)(max) elicited by the highest dose of CGP 12177. 3 The highest doses of CGP 12177 and cyanopindolol increased DBP by about 10 mmHg and MBF by 1.4+/-0.3 and 0.6+/-0.3 ml min(-1), respectively. The vascular effects of CGP 12177 were not affected by bupranolol and CGP 20712A. 4 In conclusion, activation of the low-affinity state of beta(1)-adrenoceptors by CGP 12177 and cyanopindolol in pithed rats causes a positive inotropic and lusitropic effect. By contrast, the vascular effects of CGP 12177 and cyanopindolol are not mediated by these receptors and have only marginal influence under in vivo conditions.
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Affiliation(s)
- Agnieszka Zakrzeska
- Zakład Fizjologii Doświadczalnej, Akademia Medyczna w Białymstoku, ul. Mickiewicza 2A, 15-089 Białystok, Poland
| | - Eberhard Schlicker
- Institut für Pharmakologie und Toxikologie, Universität Bonn, Reuterstrasse 2b, 53113 Bonn, Germany
| | - Grzegorz Kwolek
- Zakład Fizjologii Doświadczalnej, Akademia Medyczna w Białymstoku, ul. Mickiewicza 2A, 15-089 Białystok, Poland
| | - Hanna Kozłowska
- Zakład Fizjologii Doświadczalnej, Akademia Medyczna w Białymstoku, ul. Mickiewicza 2A, 15-089 Białystok, Poland
| | - Barbara Malinowska
- Zakład Fizjologii Doświadczalnej, Akademia Medyczna w Białymstoku, ul. Mickiewicza 2A, 15-089 Białystok, Poland
- Author for correspondence:
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Abstract
There are three members of the beta-adrenoceptor family, all of which are primarily coupled to G(s) proteins. Recent studies using the huge range of beta-ligands now available have given remarkable new insights into their pharmacology. beta1-adrenoceptors exist in at least two active conformations, whereas beta2-adrenoceptors are able to induce signaling via different agonist-induced receptor conformational states, and their affinity for antagonists can be altered by highly efficacious agonists. This study therefore examined the pharmacology of the human beta3-adrenoceptor stably expressed in Chinese hamster ovary cells. Several compounds described previously as beta-antagonists have agonist properties at the beta3-adrenoceptor. Antagonist affinity measurements varied at the beta3-adrenoceptor in a manner similar to those observed at human beta1-adrenoceptors and unlike those seen at beta2-adrenoceptors. Some ligands (e.g., fenoterol and cimaterol) were more readily inhibited by all antagonists, whereas other ligands [e.g., alprenolol and 1-(2-ethylphenoxy)-3-[[(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]-(2S)-2-propanol hydrochloride [SR 59230A]) stimulated responses that were more resistant to antagonism. Alprenolol inhibited fenoterol-induced beta3-adrenoceptor responses while acting as an agonist at higher concentrations. This is highly suggestive of two active conformational states of the beta3-adrenoceptor. (S)-4-[2-Hydroxy-3-phenoxypropylaminoethoxy]-N-(2-methoxyethyl)phenoxyacetamide (ZD 7114) stimulated a two-component response, of which the first component was more readily antagonized than the second. Taken together, these experiments suggest that the human beta3-adrenoceptor exists in at least two different agonist conformations with a similar high- and low-affinity pharmacology analogous to, if not as pronounced as, the beta1-adrenoceptor. Both conformations are present in living cells and can be distinguished by their pharmacological characteristics. In this respect, the human beta3-adrenoceptor seems similar to the human beta1-adrenoceptor.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signaling, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, United Kingdom.
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26
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Santos IN, Sumitame M, Caceres VM, Moreira MF, Krieger MH, Spadari-Bratfisch RC. Evidence for two atypical conformations of beta-adrenoceptors and their interaction with Gi proteins. Eur J Pharmacol 2005; 513:109-18. [PMID: 15878715 DOI: 10.1016/j.ejphar.2005.03.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Accepted: 03/02/2005] [Indexed: 11/25/2022]
Abstract
In this study, we investigated whether the responses of right atria from sinoaortic denervated rats to CGP12177 (4(3-t-butylamino-2-hydroxypropoxy benzidimidazole-2 one, hydrochloride)), isoprenaline and norepinephrine desensitized in parallel and whether CGP12177 interacted with distinct conformations of beta-adrenoceptors. Right atria from rats 48 h after sinoaortic denervation were subsensitive to isoprenaline, norepinephrine and CGP12177. One week after sinoaortic denervation, the sensitivity to CGP12177 had recovered whereas the responses to isoprenaline and norepinephrine were still subsensitive, suggesting that the binding sites for these molecules showed independent behavior. In atria from 48 h sinoaortic-denervated rats, propranolol or 3 microM CGP20712A (2-hydroxy-5(2-((2-hydroxy-3-(4-((methyl-4-trifluormethyl)1H imidazole-2-yl)-phenoxypropyl) amino) ethoxy)-benzamide monomethane sulphonate)) blocked the responses to 10 nM-1 microM CGP12177 and steepened the curves. The concentration-response curves to CGP12177 in the presence of ICI118,551 (erythro-DL-1(-methylindan-4-yloxy)-3-isopropylamino-butan-2-ol) were biphasic, suggesting that CGP12177 interacted with at least two conformations of beta-adrenoceptors that showed negative cooperativism, one acting through beta(2)-adrenoceptor-Gi and the other via beta(1)-adrenoceptor-Gs. This hypothesis was confirmed in right atria from sinoaortic-denervated rats treated with pertussis toxin.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Adrenergic beta-Agonists/pharmacology
- Adrenergic beta-Antagonists/pharmacology
- Animals
- Dose-Response Relationship, Drug
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Heart/drug effects
- Heart/physiology
- Heart Atria/drug effects
- Heart Atria/innervation
- Imidazoles/pharmacology
- In Vitro Techniques
- Isoproterenol/pharmacology
- Male
- Myocardial Contraction/drug effects
- Norepinephrine/pharmacology
- Pertussis Toxin/pharmacology
- Propanolamines/pharmacology
- Protein Binding
- Protein Conformation
- Rats
- Rats, Wistar
- Receptors, Adrenergic, beta/chemistry
- Receptors, Adrenergic, beta/metabolism
- Receptors, Adrenergic, beta-1/chemistry
- Receptors, Adrenergic, beta-1/metabolism
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Affiliation(s)
- Iraídes N Santos
- Department of Physiology and Biophysics, Institute of Biology, State University of Campinas (UNICAMP), Campinas, SP, Brazil
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27
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Abstract
Antagonist affinity measurements have traditionally been considered important in defining the receptor or receptor subtypes present within cells or tissues. Any change in this value has normally been taken as evidence for the presence of a second receptor. However, highly efficacious ligands induce a time and phosphorylation-dependent change in the beta2-adrenoceptor resulting in 10-fold lower affinity for antagonists. Also the beta1-adrenoceptor is now considered to exist in two different active conformations which are distinguished by their pharmacological properties. In this study, the site of action of a range of beta-agonists and beta-antagonists was determined using the human beta1-adrenoceptor stably expressed in Chinese hamster ovary cells with cyclic AMP response element reporter genes. Adrenaline and noradrenaline were confirmed as having agonist actions via the catecholamine site, whereas all antagonists had higher affinity for the catecholamine rather than secondary site. However, the rank order of affinity for the two sites was different suggesting that they are indeed separate entities. The measurements of antagonist affinity at the catecholamine site, however, were found to depend upon the agonist present. For example, xamoterol, cimaterol, terbutaline, and formoterol agonist responses were more readily antagonized by CGP 20712A[2-hydroxy-5-(2-[{hydroxy-3-(4-[1-methyl-4-trifluoromethyl-2-imidazolyl]phenoxy)propyl}amino]ethoxy)benzamide] than the catecholamine responses themselves. This, however, was not related to agonist efficacy as has previously been reported for the human beta2-adrenoceptor. Therefore, it may be that some agonists (e.g., cimaterol) purely activate the catecholamine site and others purely activate the secondary site (e.g., CGP 12177 [(-)-4-(3-tert-butylamino-2-hydroxypropoxy)-benzimidazol-2-one]), whereas the others (e.g., catecholamines) activate both sites to differing degrees.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signaling, Queen's Medical Centre, Nottingham, UK.
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28
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Mallem MY, Toumaniantz G, Serpillon S, Gautier F, Gogny M, Desfontis JC, Gauthier C. Impairment of the low-affinity state beta1-adrenoceptor-induced relaxation in spontaneously hypertensive rats. Br J Pharmacol 2004; 143:599-605. [PMID: 15466443 PMCID: PMC1575435 DOI: 10.1038/sj.bjp.0705990] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1 In hypertension, a decrease of the vascular beta-adrenergic relaxation has been described. However, the specific involvement of each beta-adrenoceptor (beta-AR) subtype, in particular the low-affinity state of beta1-AR, has not yet been evaluated. We investigated whether the low-affinity state of beta1-AR-induced relaxation was impaired in Spontaneously Hypertensive Rats (SHR). 2 The relaxant responses to CGP 12177 and cyanopindolol, low-affinity state beta1-AR agonists (with beta1-/beta2-AR antagonistic and partial beta3-AR agonistic properties) were evaluated on thoracic aortic rings isolated from 12-weeks-old Wistar Kyoto rats (WKY) and SHR. 3 In WKY, CGP 12177 and cyanopindolol produced an endothelium and nitric oxide (NO)-independent relaxation. CGP 12177-induced endothelium-independent relaxation was not modified either by beta1-, beta2-AR (nadolol) or beta3-AR (L-748337 or SR 59230A) antagonists but was significantly reduced by high concentrations of CGP 20712A (P<0.05). This relaxation was also reduced by adenylyl cyclase inhibitors, SQ 22536 or MDL 12330A. 4 In SHR, CGP 12177 produced mainly an endothelium and NO-dependent relaxation. This effect was not modified by nadolol, but was strongly reduced by beta3-AR blockade. Endothelium-independent relaxation to CGP 12177 was not altered by adenylyl cyclase inhibition, but was amplified in preparations from pertussis toxin-pretreated SHR. 5 The immunohistochemical analysis revealed an upregulation of beta3-AR in the endothelial layer of SHR aorta, whereas the beta3-AR-induced relaxation was not modified. 6 In conclusion, we demonstrated an impaired low-affinity state of the beta1-AR-induced relaxation and an upregulation of the beta3-AR in hypertension. Some clinical implications of those findings are discussed.
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MESH Headings
- Adrenergic beta-Antagonists/pharmacology
- Animals
- Aorta, Thoracic/drug effects
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/pharmacology
- Hypertension/physiopathology
- Immunohistochemistry
- In Vitro Techniques
- Male
- Muscle Relaxation/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiopathology
- Nitric Oxide Synthase/antagonists & inhibitors
- Nitric Oxide Synthase Type III
- Pindolol/analogs & derivatives
- Pindolol/pharmacology
- Propanolamines/pharmacology
- Rats
- Rats, Inbred SHR
- Rats, Inbred WKY
- Receptors, Adrenergic, beta-1/drug effects
- omega-N-Methylarginine/pharmacology
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Affiliation(s)
- Mohamed Yassine Mallem
- UPSP 5304 de Physiopathologie Animale et de Pharmacologie Fonctionnelle, Ecole Nationale Vétérinaire, Nantes, France
| | | | - Sabrina Serpillon
- UPSP 5304 de Physiopathologie Animale et de Pharmacologie Fonctionnelle, Ecole Nationale Vétérinaire, Nantes, France
- Institut du Thorax, Inserm U533, Nantes, France
| | - Freddy Gautier
- UPSP 5304 de Physiopathologie Animale et de Pharmacologie Fonctionnelle, Ecole Nationale Vétérinaire, Nantes, France
| | - Marc Gogny
- UPSP 5304 de Physiopathologie Animale et de Pharmacologie Fonctionnelle, Ecole Nationale Vétérinaire, Nantes, France
| | - Jean-Claude Desfontis
- UPSP 5304 de Physiopathologie Animale et de Pharmacologie Fonctionnelle, Ecole Nationale Vétérinaire, Nantes, France
- Author for correspondence:
| | - Chantal Gauthier
- Institut du Thorax, Inserm U533, Nantes, France
- Faculté des Sciences et Techniques, Nantes, France
- Author for correspondence:
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29
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Joseph SS, Lynham JA, Colledge WH, Kaumann AJ. Binding of (-)-[3H]-CGP12177 at two sites in recombinant human beta 1-adrenoceptors and interaction with beta-blockers. Naunyn Schmiedebergs Arch Pharmacol 2004; 369:525-32. [PMID: 15060759 DOI: 10.1007/s00210-004-0884-y] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2003] [Accepted: 02/06/2004] [Indexed: 12/18/2022]
Abstract
To verify the hypothesis that the non-conventional partial agonist (-)-CGP12177 binds at two beta(1)-adrenoceptor sites, human beta(1)-adrenoceptors, expressed in CHO cells, were labelled with (-)-[(3)H]-CGP12177. We compared the binding affinity and antagonist potency of 12 clinically used beta-blockers against the cyclic AMP-enhancing effects of (-)-isoprenaline and (-)-CGP12177.(-)-[(3)H]-CGP12177 bound to a high affinity site (H; K(H)=0.47 nM) and low affinity site (L); K(L)=235 nM). (-)-[(3)H]-CGP12177 dissociated from the beta(1)-adrenoceptors with a fast component (k(off)=0.45 min(-1)), consistent with the L-site, and a slow component (k(off)=0.017-0.033 min(-1)), consistent with the H-site. (-)-Isoprenaline and (-)-CGP12177 caused 96-fold and 12-fold maximal increases in cyclic AMP levels with -logEC(50)M of 8.2 and 7.6. (-)-CGP12177 antagonised the effects of (-)-isoprenaline with a pK(B) of 9.9. The beta-blockers antagonised the effects of (-)-isoprenaline more than the effects of (-)-CGP12177 with potency ratios: (-)-atenolol 1,000, (+/-)-metropolol 676, (-)-pindolol 631, (-)-timolol 589, (+/-)-carvedilol 204, (+/-)-oxprenolol 138, (+/-)-sotalol 132, (-)-propranolol 120, (+/-)-bisoprolol 95, (+/-)-alprenolol 81, (+/-)-nadolol 68 and (-)-bupranolol 56. In intact cells the binding constants of beta-blockers, estimated from competition with 3-5 nM (-)-[(3)H]-CGP12177 (binding to the H-site), correlated with the corresponding affinities estimated from antagonism of the (-)-isoprenaline effects. We conclude that (-)-[(3)H]-CGP12177 binds at two sites in the recombinant beta(1)-adrenoceptor. (-)-CGP12177 is an antagonist of catecholamine effects through the H-site and a non-conventional partial agonist through the L-site. beta-blockers are more potent antagonists through the H-site than the L-site.
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Affiliation(s)
- Shirin S Joseph
- Department of Physiology, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
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30
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Lewis CJ, Gong H, Brown MJ, Harding SE. Overexpression of beta 1-adrenoceptors in adult rat ventricular myocytes enhances CGP 12177A cardiostimulation: implications for 'putative' beta 4-adrenoceptor pharmacology. Br J Pharmacol 2004; 141:813-24. [PMID: 14757703 PMCID: PMC1574257 DOI: 10.1038/sj.bjp.0705668] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. CGP 12177A mediates cardiostimulation by activation of the 'putative' beta(4)-adrenoceptor; however, it has recently been reported that disruption of the beta(1)-adrenoceptor gene abolishes this effect. We have adenovirally overexpressed beta(1)-adrenoceptors in isolated, cultured adult rat ventricular cardiomyocytes and observed the inotropic potency of isoprenaline and CGP 12177A (in the presence of 1 microm propranolol). 2. Isoprenaline was a full inotropic agonist at rat ventricular myocytes (pD(2) 7.69+/-0.12). CGP 12177A was a nonconventional partial agonist (pD(2) 6.34+/-0.09), increasing inotropy and lusitropy, with an intrinsic activity of 0.34 and antagonised by bupranolol. 3. beta(1)-adrenoceptor overexpression enhanced the inotropic potency of isoprenaline by 11.7-fold (pD(2) 8.76+/-0.14) and CGP 12177A by 5.9-fold (7.11+/-0.10), respectively. Green fluorescent protein (GFP) overexpression did not alter the potency of isoprenaline or CGP 12177A (pD(2) 7.41+/-0.24 and pD(2) 6.60+/-0.50, respectively). 4. The cardiostimulant effects of CGP 12177A were enhanced by IBMX (phosphodiesterase inhibitor) and decreased by Rp-cAMPS (cAMP antagonist). CGP 12177A also increased cAMP levels. CGP 12177A but not isoprenaline initiated arrhythmias at lower concentrations following beta(1)-adrenoceptor overexpression. 5. (125)I-Cyanopindolol saturation binding in Adv.beta(1) myocytes demonstrated approximately 18-fold increase in beta(1)-adrenoceptors. (3)H-CGP 12177A saturation binding, in the presence of propranolol, increased approximately 5-fold following overexpression of beta(1)-adrenoceptors. 6. This study demonstrates enhanced cardiostimulation by CGP 12177A (in the presence of propranolol) in rat ventricular myocytes overexpressing beta(1)-adrenoceptors, mediated by a Gs/cAMP signalling pathway. 'Putative' beta(4)-adrenoceptor pharmacology appears to be mediated by activation of a novel affinity state of the beta(1)-adrenoceptor.
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Affiliation(s)
- Clive J Lewis
- Clinical Pharmacology Unit, Department of Medicine, Cambridge University, Cambridge.
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31
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Joseph SS, Lynham JA, Molenaar P, Grace AA, Colledge WH, Kaumann AJ. Intrinsic sympathomimetic activity of (-)-pindolol mediated through a (-)-propranolol-resistant site of the beta1-adrenoceptor in human atrium and recombinant receptors. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2003; 368:496-503. [PMID: 14608456 DOI: 10.1007/s00210-003-0835-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2003] [Accepted: 09/16/2003] [Indexed: 10/26/2022]
Abstract
The beta-blocker (-)-pindolol produces intrinsic sympathomimetic activity manifested clinically by cardiostimulation, but the beta-adrenoceptor subtype, which mediates these effects, is unknown. Recent work indicates the existence of a (-)-propranolol-resistant site of the cardiac beta(1)-adrenoceptor and we propose that it mediates the cardiostimulation evoked by (-)-pindolol. We compared the interaction of (-)-pindolol both with human atrial myocardium and with recombinant beta(1)-adrenoceptors. The effects of (-)-pindolol on paced human atrial trabeculae were studied in the presence of 3-isobutyl-1-methylxanthine (IBMX; 20 microM). (-)-Pindolol caused small negative and positive inotropic effects at nanomolar and micromolar concentrations respectively, which were unaffected by N(G)-monomethyl-L-arginine (L-NMMA, 10 microM), inconsistent with an involvement of nitric oxide. (-)-Pindolol, in the presence of (-)-propranolol, increased atrial contractile force and cAMP through recombinant beta(1)-adrenoceptors with identical potency (-logEC(50)M=6.5). The positive inotropic effects of (-)-pindolol were resistant to blockade by L-748,337 (100 nM), a beta(3)-adrenoceptor antagonist. (-)-CGP12177, known to act through the (-)-propranolol-resistant site of the beta(1)-adrenoceptor, also increased with similar potency atrial contractile force (-logEC(50)M=7.6) and cAMP at recombinant beta(1)-adrenoceptors (-logEC(50)M=7.7). (-)-Pindolol blocked the effects of (-)-CGP12177 in human atrium and recombinant beta(1)-adrenoceptors with similar equilibrium dissociation constants (pK(B)=6.5 and 6.3). Thus, stimulant potency and blocking potency of (-)-pindolol against (-)-CGP12177 agree. In contrast, (-)-pindolol was 200-400 times more effective at blocking the effects of a catecholamine than the effects of (-)-CGP12177 in both human atrium (pK(B)=9.1) and at recombinant beta(1)-adrenoceptors (pK(B)=8.6). We conclude that the cardiostimulant effects of (-)-pindolol in human atrial myocardium are mediated through a (-)-propranolol-resistant site of the beta(1)-adrenoceptor with low affinity for (-)-pindolol. In contrast, (-)-pindolol blocks the effects of catecholamines through a high-affinity site of the beta(1)-adrenoceptor. beta(3)-Adrenoceptors are not involved in the atrial effects of (-)-pindolol.
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Affiliation(s)
- Shirin S Joseph
- Department of Physiology, University of Cambridge, Downing Street, CB2 3EG, Cambridge, UK
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32
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Affiliation(s)
- Peter Molenaar
- The National Heart Foundation, Chermside, Queensland 4032, Australia.
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33
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Baker JG, Hall IP, Hill SJ. Agonist actions of "beta-blockers" provide evidence for two agonist activation sites or conformations of the human beta1-adrenoceptor. Mol Pharmacol 2003; 63:1312-21. [PMID: 12761341 DOI: 10.1124/mol.63.6.1312] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous work with 4-[3-[(1,1-dimethylethyl)amino]2-hydroxypropoxy]-1,3-dihydro-2H-benzimidazol-2-one (CGP 12177) has led to the suggestion that there are two different agonist conformations of the human beta1-adrenoceptor: 1) where classic agonists (catecholamines) and beta-antagonists act, and 2) where CGP 12177 is an agonist and relatively resistant to inhibition by beta-adrenoceptor antagonists. In the present study, we have used studies of cAMP response element-regulated gene transcription to confirm the presence of these two beta1-adrenoceptor sites/conformations and to provide strong evidence that a range of clinically used beta-adrenoceptor blockers (beta-blockers) exhibit differential agonists and/or antagonist actions at the two sites. [2-(3-Carbamoyl-4-hydroxyphenoxy)-ethylamino]-3-[4-(1-methyl-4-trifluormethyl-2-imidazolyl)-phenoxy]-2-propanolmethanesulphonate (CGP 20712A) and atenolol act as classic antagonists at the catecholamine binding site but have much lower affinity for the secondary CGP 12177 site. CGP 12177 and carvedilol are potent antagonists at the catecholamine site but mediate substantial agonist actions on gene transcription via the secondary antagonist-resistant site at higher concentrations. Agonist effects of beta-blockers are not, however, confined to this secondary site, and we show that some (particularly acebutolol and labetolol) act primarily via the catecholamine site, whereas others (pindolol and alprenolol) can stimulate both. The different responses to beta-blockers seen in the clinic may therefore be caused in part by these beta-blocker agonist responses and the differential activation of the two sites or conformations.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signaling, Queen's Medical Centre, Nottingham NG7 2UH, UK
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34
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Santos IN, Marcondes FK, Spadari-Bratfisch RC. The beta1-adrenoceptor site activated by CGP12177 varies in behavior according to the estrous cycle phase and stress. Can J Physiol Pharmacol 2003; 81:459-68. [PMID: 12774852 DOI: 10.1139/y03-057] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this work was to assess whether stress and estrous cycle phases affected the beta1-adrenoceptor (beta1-AR) site activated by CGP12177 in the right atria of rats. The chronotropic response to CGP12177 in the absence or presence of antagonists was determined in atria from rats submitted to one daily foot-shock session for 3 consecutive days. Blood was collected for hormonal assays. The pD2 for CGP12177 in atria from females was lower than in atria from males and was unaltered by stress or the estrous cycle. Propranolol (200 nM) or CGP20712A (3 microM) shifted the concentration-response curves to CGP12177 to the right in control and stressed estrus or control diestrus rats. Atria from stressed diestrus rats were resistant to blockade by propranolol or CGP20712A, indicating that the effect of beta-adrenoceptor antagonists on the response to CGP12177 is influenced by estrous cycle phases. The stress-induced increase in serum corticosterone levels was independent of the estrous cycle or gender, but the estradiol/progesterone ratio was affected differently in the two groups of female rats. In the diestrus group, serum estradiol levels decreased after the first foot-shock session and remained low until the day of sacrifice, whereas in the estrus group the serum levels of estradiol did not decrease after stress and peaked on the second day, which corresponded to proestrus. These data do not indicate whether there is a direct or indirect effect of stress hormones and (or) sex steroids on cardiac beta1-AR sensitivity. However, they do show that the classic and low-affinity binding sites of the beta1-AR are independently regulated and that the beta1-AR atypical site affinity for antagonists depends on the estrous cycle.
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Affiliation(s)
- I N Santos
- Laboratório do Estudo do Estresse (LABEEST), Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6110, CEP 13081-970, Campinas, SP, Brasil
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35
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Baker JG, Hall IP, Hill SJ. Pharmacology and direct visualisation of BODIPY-TMR-CGP: a long-acting fluorescent beta2-adrenoceptor agonist. Br J Pharmacol 2003; 139:232-42. [PMID: 12770928 PMCID: PMC1573863 DOI: 10.1038/sj.bjp.0705287] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2003] [Revised: 03/03/2003] [Accepted: 03/18/2003] [Indexed: 11/09/2022] Open
Abstract
1 Fluorescence techniques offer a way to circumvent several problems associated with many radioligand binding and functional assays and the need for large numbers of cells. Fluorescent ligands also offer the advantage of allowing real time direct visualisation of ligand - receptors interactions. A fluorescent analogue of CGP 12177 (BODIPY-TMR-CGP) has thus been evaluated as a beta(2)-adrenoceptor ligand in CHO-K1 cells expressing the human beta(2)-adrenoceptor. 2 Studies of (3)H-cAMP accumulation showed that BODIPY-TMR-CGP stimulated an increase in cAMP accumulation and cyclic AMP response element (CRE)-mediated gene transcription with an EC(50) of 21-28 nM. Both of these responses were antagonised by the selective beta(2)-adrenoceptor antagonist ICI 118551. 3 Binding studies with (3)H-CGP 12177, and functional studies of CRE-regulated gene transcription showed that the BODIPY-TMR-CGP interaction with the human beta(2)-adrenoceptor is of very long duration. 4 Visualisation of the binding of BODIPY-TMR-CGP to single living mammalian cells was clearly demonstrated by confocal microscopy and showed that this ligand was able to selectively label cell surface beta(2)-adrenoceptors in living CHO-K1 cells transfected with the human beta(2)-adrenoceptor with an apparent K(D) of 27 nM. Studies with cells expressing a beta(2)-adrenoceptor-green fluorescent protein (GFP) fusion protein provided further strong evidence that BODIPY-TMR-CGP was binding to the beta(2)-adrenoceptor. 5 BODIPY-TMR-CGP is therefore a long-acting fluorescent beta(2)-adrenoceptor agonist that can be used to label beta(2)-adrenoceptors in the plasma membrane of living cells.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signalling, C Floor, Medical School, Queen's Medical Centre, Nottingham NG7 2UH, U.K
| | - Ian P Hall
- Institute of Cell Signalling, C Floor, Medical School, Queen's Medical Centre, Nottingham NG7 2UH, U.K
| | - Stephen J Hill
- Institute of Cell Signalling, C Floor, Medical School, Queen's Medical Centre, Nottingham NG7 2UH, U.K
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36
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Baker JG, Hall IP, Hill SJ. Pharmacological characterization of CGP 12177 at the human beta(2)-adrenoceptor. Br J Pharmacol 2002; 137:400-8. [PMID: 12237261 PMCID: PMC1573492 DOI: 10.1038/sj.bjp.0704855] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2002] [Revised: 05/27/2002] [Accepted: 06/24/2002] [Indexed: 11/09/2022] Open
Abstract
1 It has recently been reported that CGP 12177 can act as an agonist at a novel secondary site within the human beta(1)-adrenoceptor. The aim of this study was to undertake a detailed pharmacological study of the effects of CGP 12177 on the human beta(2)-adrenoceptor. 2 CGP 12177 acted as a potent partial agonist of (3)H-cyclic AMP accumulation (log EC(50)-8.90+/-0.06) and CRE-mediated reporter gene transcription (log EC(50)-9.66+/-0.04) in CHO-K1 cells expressing the human beta(2)-adrenoceptor. These CGP-induced responses were antagonized by the beta(2)-selective antagonist ICI 118551 (apparent log K(D) values of -8.84+/-0.15 and -9.51+/-0.02 for the cyclic AMP and reporter gene responses respectively). 3 CGP 12177 was also able to antagonize both cyclic AMP and reporter gene responses to more efficacious beta(2)-agonists with similar log K(D) values (e.g. -9.57+/-0.15 and -10.04+/-0.096 respectively with salbutamol as agonist). 4 (3)H-CGP 12177 binding to beta(2)-adrenoceptors in intact CHO-beta(2) cells yielded a log K(D) value of -9.84+/-0.06, but indicated that the ligand dissociates very slowly from the receptor (t(1/2) for dissociation=65 min). However, studies with a Green Fluorescent Protein (GFP)-tagged beta(2)-adrenoceptor indicated that CGP 12177 does not stimulate beta(2)-adrenoceptor internalization. 5 This study demonstrates that CGP 12177 is a high affinity partial agonist of both cAMP accumulation and CRE-mediated gene transcription at the human beta(2)-adrenoceptor. It provides no evidence that CGP 12177 can discriminate a secondary site on the beta(2)-adrenoceptor analogous to that observed for the human beta(1)-adrenoceptor. However, despite its very weak actions on cAMP accumulation, the potent agonist effects of CGP 12177 on CRE-mediated gene transcription at the human beta(2)-adrenoceptor, coupled with its long duration of action, offers a potential lead for drug development for the treatment of chronic inflammatory airway diseases.
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Affiliation(s)
- Jillian G Baker
- Institute of Cell Signalling, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH
| | - Ian P Hall
- Institute of Cell Signalling, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH
| | - Stephen J Hill
- Institute of Cell Signalling, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH
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37
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Jost P, Fasshauer M, Kahn CR, Benito M, Meyer M, Ott V, Lowell BB, Klein HH, Klein J. Atypical beta-adrenergic effects on insulin signaling and action in beta(3)-adrenoceptor-deficient brown adipocytes. Am J Physiol Endocrinol Metab 2002; 283:E146-53. [PMID: 12067855 DOI: 10.1152/ajpendo.00531.2001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cross talk between adrenergic and insulin signaling systems may represent a fundamental molecular basis of insulin resistance. We have characterized a newly established beta(3)-adrenoceptor-deficient (beta(3)-KO) brown adipocyte cell line and have used it to selectively investigate the potential role of novel-state and typical beta-adrenoceptors (beta-AR) on insulin signaling and action. The novel-state beta(1)-AR agonist CGP-12177 strongly induced uncoupling protein-1 in beta(3)-KO brown adipocytes as opposed to the beta(3)-selective agonist CL-316,243. Furthermore, CGP-12177 potently reduced insulin-induced glucose uptake and glycogen synthesis. Neither the selective beta(1)- and beta(2)-antagonists metoprolol and ICI-118,551 nor the nonselective antagonist propranolol blocked these effects. The classical beta(1)-AR agonist dobutamine and the beta(2)-AR agonist clenbuterol also considerably diminished insulin-induced glucose uptake. In contrast to CGP-12177 treatment, these negative effects were completely abrogated by metoprolol and ICI-118,551. Stimulation with CGP-12177 did not impair insulin receptor kinase activity but decreased insulin receptor substrate-1 binding to phosphatidylinositol (PI) 3-kinase and activation of protein kinase B. Thus the present study characterizes a novel cell system to selectively analyze molecular and functional interactions between novel and classical beta-adrenoceptor types with insulin action. Furthermore, it indicates insulin receptor-independent, but PI 3-kinase-dependent, potent negative effects of the novel beta(1)-adrenoceptor state on diverse biological end points of insulin action.
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MESH Headings
- Adipocytes/cytology
- Adipocytes/drug effects
- Adipocytes/metabolism
- Adipose Tissue, Brown/cytology
- Adipose Tissue, Brown/drug effects
- Adipose Tissue, Brown/metabolism
- Adrenergic beta-1 Receptor Agonists
- Adrenergic beta-1 Receptor Antagonists
- Adrenergic beta-2 Receptor Agonists
- Adrenergic beta-2 Receptor Antagonists
- Adrenergic beta-Agonists/pharmacology
- Adrenergic beta-Antagonists/pharmacology
- Animals
- Carrier Proteins/biosynthesis
- Cell Line
- Enzyme Activation/drug effects
- Glucose/pharmacokinetics
- Glycogen/biosynthesis
- Insulin/pharmacology
- Insulin Receptor Substrate Proteins
- Insulin Resistance/physiology
- Intracellular Signaling Peptides and Proteins
- Ion Channels
- Membrane Proteins/biosynthesis
- Mice
- Mice, Knockout
- Mitochondrial Proteins
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphoproteins/metabolism
- Protein Serine-Threonine Kinases
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-akt
- Receptor Cross-Talk/drug effects
- Receptor Cross-Talk/physiology
- Receptor, Insulin/metabolism
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Adrenergic, beta-3/deficiency
- Receptors, Adrenergic, beta-3/genetics
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Uncoupling Protein 1
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Affiliation(s)
- Petra Jost
- Department of Internal Medicine I, Medical University of Lübeck, 23538 Lübeck, Germany
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38
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Lowe MD, Lynham JA, Grace AA, Kaumann AJ. Comparison of the affinity of beta-blockers for two states of the beta 1-adrenoceptor in ferret ventricular myocardium. Br J Pharmacol 2002; 135:451-61. [PMID: 11815381 PMCID: PMC1573134 DOI: 10.1038/sj.bjp.0704450] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We compared the potency of 11 clinically available beta-blockers as antagonists of the positive inotropic effects of (-)-isoprenaline and CGP12177 on ferret ventricular myocardium. (-)-CGP12177, (-)-pindolol and (-)-alprenolol were non-conventional partial agonists with intrinsic activity of 0.7, 0.2 and 0.1 respectively. All beta-blockers antagonized in a concentration-dependent and surmountable manner the positive inotropic effects of both (-)-isoprenaline and CGP12177. The potency of each beta-blocker was consistently higher against (-)-isoprenaline than against CGP12177. Two groups of beta-blockers were identified. In one group the difference between the pK(B) values of blockade against (-)-isoprenaline and CGP12177 was 1.1 - 1.6 log units ((-)-alprenolol, (-)-pindolol, (-)-bupranolol, nadolol and carvedilol). In the other group the pK(B) difference was of 2.1 - 3.0 log units ((-)-atenolol, metoprolol, bisoprolol, sotalol, (-)-propranolol and (-)-timolol). The beta-blockers competed with (-)-[(125)I]-cyanopindolol for binding to ventricular beta(1)-adrenoceptors. The binding affinities correlated with the corresponding blocking potencies against (-)-isoprenaline. On average the pK(i) values were 0.5 log units smaller than the pK(B) values against (-)-isoprenaline but 1.6 log units greater than the pK(B) values against CGP12177. In ferret ventricle the effects of (-)-isoprenaline appear to be antagonized by beta-blockers through the state of the beta(1)-adrenoceptor for which (-)-[(125)I]-cyanopindolol and beta-blockers have high affinity. The cardiostimulant effects of CGP12177 appear to be mediated through a low-affinity state of the beta(1)-adrenoceptor for which beta-blockers have low affinity.
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Affiliation(s)
- Martin D Lowe
- Section of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW
| | - James A Lynham
- Department of Physiology, University of Cambridge, Cambridge CB2 3EG
| | - Andrew A Grace
- Section of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW
| | - Alberto J Kaumann
- Department of Physiology, University of Cambridge, Cambridge CB2 3EG
- Author for correspondence:
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39
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Leavitt M, Setola V, Fishman PH. Protein kinase C-mediated down-regulation of beta(2)-adrenergic receptor and gene expression in rat C6 glioma cells. J Neurochem 2001; 77:823-9. [PMID: 11331411 DOI: 10.1046/j.1471-4159.2001.00279.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the regulation of beta(2)-adrenergic receptors (beta(2)AR) by protein kinase C (PKC) in rat C6 glioma cells at the levels of receptor activity, protein expression and gene expression. Cells exposed to 4beta-phorbol-12-myristate-13-acetate (PMA), a potent activator of PKC, exhibited a time- and concentration-dependent decrease in beta(2)AR binding activity. Maximum down-regulation was approximately 50% by 24 h and western blot analysis revealed a parallel decrease in beta(2)AR protein. In addition, PMA treatment resulted in an acute desensitization of beta(2)AR-stimulated cyclic AMP response prior to any reduction in receptor levels. PMA exposure also affected steady-state beta(2)AR mRNA levels in a time-dependent, biphasic manner. During the first 4 h, levels decreased by approximately 60% and then slowly recovered to approximately 75% of control by 24 h. As the reduction in receptor mRNA was not due to a decrease in its stability, we examined beta(2)AR gene transcription by nuclear run-on assays. Transcriptional activity in nuclei from C6 cells treated with PMA for 2 h was reduced by 70% compared to controls. Thus PKC can regulate beta(2)AR at least two levels: the first being an acute desensitization of receptor function, and the second being a more prolonged repression of receptor gene transcription that in turn results in decreased receptor expression.
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Affiliation(s)
- M Leavitt
- Membrane Biochemistry Section, Laboratory of Molecular and Cellular Neurobiology, National Institute of Neurological Disorders and Stroke, The National Institutes of Health, Bethesda, Maryland 20892-4440, USA
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40
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Santos IN, Spadari-Bratfisch RC. Chronotropic response to (±)-CGP12177 in right atria of stressed rats. Can J Physiol Pharmacol 2001. [DOI: 10.1139/y01-007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Foot-shock stress changes the sensitivity of the rat right atria to β1- and β2-adrenoceptor (AR) agonists. We investigated whether the same stress protocol also changes the atrial sensitivity to the non conventional agonist, (±)-CGP12177. Concentration-response curves to (±)-CGP12177, a β1- and β2-adrenoceptor antagonist with agonist properties at the putative β4-adrenoceptors, were obtained in the absence and presence of propranolol (200 nM or 2 µM), CGP20712A 10 nM plus ICI118,551 50 nM, or CGP20712A (1 µM or 3 µM), in right atria from rats submitted to three daily foot-shock sessions (120 mA pulses of 1.0 s duration applied at random intervals of 5-25 s over 30 min) and killed after the third session. The pD2 for (±)-CGP12177 was not influenced by foot-shock stress. The stimulant effect of (±)-CGP12177 was resistant to blockade by 200 nM and 2 µM (±)-propranolol, and to combined blockade by CGP20712A and ICI118,551. However, in right atria from stressed rats given 200 nM propranolol, the concentration-response curve to the agonist was shifted 2.0-fold to the right. CGP20712A shifted the concentration-response curve to (±)-CGP12177 to the right by 4.6- (1 µM) and 19-fold (3 µM) in atria of control rats, and by 2.2- (1 µM) and 43-fold (3 µM) in atria of stressed rats. Maximum response to CGP12177 was not affected by propranolol or CGP20712A in concentrations ranging from 0.1 nM to 10 µM. These results show that the chronotropic effect of (±)-CGP12177 is mediated by atypical β4-adrenoceptors. In constrast with to β1-and (or) β2-AR, this receptor is resistant to the effects of foot-shock stress, suggesting that the putative β4-AR is a different receptor from a low affinity state of β1-adrenoceptor, as previously proposed, unless both proposed isoforms of β1-adrenoceptor show independent stress-induced behavior.Key words: putative β4-adrenoceptor, low affinity β1-adrenoceptor isoform, stress, right atria, chronotropic response.
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41
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Granneman JG. The putative beta4-adrenergic receptor is a novel state of the beta1-adrenergic receptor. Am J Physiol Endocrinol Metab 2001; 280:E199-202. [PMID: 11158920 DOI: 10.1152/ajpendo.2001.280.2.e199] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The atypical beta3-adrenergic receptor (AR) agonist CGP-12177 has been used to define a novel atypical beta-AR subtype, the putative beta4-AR. Recent evaluation of recombinant beta-AR subtypes and beta-AR-deficient mice, however, has established the identity of the pharmacological beta4-AR as a novel state of the beta1-AR protein. The ability of aryloxypropanolamine ligands like CGP-12177 to independently interact with agonist and antagonist states of the beta1-AR has important implications regarding receptor classification and the potential development of tissue-specific beta-AR agonists.
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Affiliation(s)
- J G Granneman
- Cellular and Clinical Neurobiology Program, Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, 2309 Scott Hall, Detroit, Michigan 48201, USA.
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Hutchinson DS, Evans BA, Summers RJ. beta(1)-Adrenoceptors compensate for beta(3)-adrenoceptors in ileum from beta(3)-adrenoceptor knock-out mice. Br J Pharmacol 2001; 132:433-42. [PMID: 11159692 PMCID: PMC1572575 DOI: 10.1038/sj.bjp.0703828] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. This study examines beta(1)-, beta(2)- and beta(3)-adrenoceptor (AR)-mediated responses, mRNA levels and radioligand binding in ileum from beta(3)-AR knock-out (-/-) (KO) and wild type (+/+) (FVB) mice. 2. In KO and FVB mice, SR59230A (100 nM) (beta(3)-AR antagonist) antagonized responses to (-)-isoprenaline in both KO and FVB mice. (-)-Isoprenaline mediated relaxation of ileum was antagonized weakly by ICI118551 (100 nM) (beta(2)-AR antagonist). Responses to (-)-isoprenaline were more strongly antagonized by CGP20712A (100 nM) (beta(1)-AR antagonist), propranolol (1 microM) (beta(1)-/beta(2)-AR antagonist), carvedilol (100 nM) (non-specific beta-AR antagonist), and CGP12177A (100 nM) (beta(1)-/beta(2)-AR antagonist) in ileum from KO than in FVB mice. 3. Responses to CL316243 (beta(3)-AR agonist) in ileum from FVB mice were antagonized by SR59230A (100 nM) but not by propranolol (1 microM) or carvedilol (100 nM). CL316243 was ineffective in relaxing ileum from KO mice. 4. CGP12177A had no agonist actions in ileum from either KO or FVB mice. 5. beta(1)-AR mRNA levels were increased 3 fold in ileum from KO compared to FVB mice. This was associated with an increased maximum number of beta(1)-/beta(2)-AR binding sites (B(max)). beta(2)-AR mRNA levels were unaffected while no beta(3)-AR mRNA was detected in KO mice. 6. In mouse ileum, beta(3)-ARs and to a lesser extent beta(1)-ARs are the predominant adrenoceptor subtypes mediating relaxation in ileum from FVB mice. In KO mice beta(1)-ARs functionally compensate for the lack of beta(3)-ARs, and this is associated with increased beta(1)-AR mRNA and levels of binding.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Adrenergic beta-Antagonists/pharmacology
- Animals
- Dioxoles/pharmacology
- Genotype
- Ileum/drug effects
- In Vitro Techniques
- Isoproterenol/pharmacology
- Mice
- Mice, Knockout
- Muscle Relaxation/drug effects
- Muscle, Smooth/drug effects
- Pindolol/analogs & derivatives
- Pindolol/pharmacology
- Propranolol/pharmacology
- RNA, Messenger/biosynthesis
- Receptors, Adrenergic, beta-1/drug effects
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-3/drug effects
- Receptors, Adrenergic, beta-3/genetics
- Receptors, Adrenergic, beta-3/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- D S Hutchinson
- Department of Pharmacology, Monash University, Victoria, Australia 3800
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Oostendorp J, Preitner F, Moffatt J, Jimenez M, Giacobino JP, Molenaar P, Kaumann AJ. Contribution of beta-adrenoceptor subtypes to relaxation of colon and oesophagus and pacemaker activity of ureter in wildtype and beta(3)-adrenoceptor knockout mice. Br J Pharmacol 2000; 130:747-58. [PMID: 10864880 PMCID: PMC1572127 DOI: 10.1038/sj.bjp.0703365] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2000] [Revised: 03/13/2000] [Accepted: 03/15/2000] [Indexed: 11/09/2022] Open
Abstract
The smooth muscle relaxant responses to the mixed beta(3)-, putative beta(4)-adrenoceptor agonist, (-)-CGP 12177 in rat colon are partially resistant to blockade by the beta(3)-adrenoceptor antagonist SR59230A suggesting involvement of beta(3)- and putative beta(4)-adrenoceptors. We now investigated the function of the putative beta(4)-adrenoceptor and other beta-adrenoceptor subtypes in the colon, oesophagus and ureter of wildtype (WT) and beta(3)-adrenoceptor knockout (beta(3)KO) mice. (-)-Noradrenaline and (-)-adrenaline relaxed KCl (30 mM)-precontracted colon mostly through beta(1)-and beta(3)-adrenoceptors to a similar extent and to a minor extent through beta(2)-adrenoceptors. In colon from beta(3)KO mice, (-)-noradrenaline was as potent as in WT mice but the effects were mediated entirely through beta(1)-adrenoceptors. (-)-CGP 12177 relaxed colon from beta(3)KO mice with 2 fold greater potency than in WT mice. The maintenance of potency for (-)-noradrenaline and increase for (-)-CGP 12177 indicate compensatory increases in beta(1)- and putative beta(4)-adrenoceptor function in beta(3)KO mice. In oesophagi precontracted with 1 microM carbachol, (-)-noradrenaline caused relaxation mainly through beta(1)-and beta(3)-adrenoceptors. (-)-CGP 12177 (2 microM) relaxed oesophagi from WT by 61.4+/-5.1% and beta(3)KO by 67.3+/-10.1% of the (-)-isoprenaline-evoked relaxation, consistent with mediation through putative beta(4)-adrenoceptors. In ureter, (-)-CGP 12177 (2 microM) reduced pacemaker activity by 31.1+/-2.3% in WT and 31.3+/-7. 5% in beta(3)KO, consistent with mediation through putative beta(4)-adrenoceptors. Relaxation of mouse colon and oesophagus by catecholamines are mediated through beta(1)- and beta(3)-adrenoceptors in WT. The putative beta(4)-adrenoceptor, which presumably is an atypical state of the beta(1)-adrenoceptor, mediates the effects of (-)-CGP 12177 in colon, oesophagus and ureter.
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MESH Headings
- Adrenergic beta-1 Receptor Antagonists
- Adrenergic beta-2 Receptor Antagonists
- Adrenergic beta-Agonists/pharmacology
- Adrenergic beta-Antagonists/pharmacology
- Animals
- Colon/physiology
- Dioxoles/pharmacology
- Dose-Response Relationship, Drug
- Epinephrine/pharmacology
- Esophagus/physiology
- Female
- Imidazoles/pharmacology
- In Vitro Techniques
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Inbred Strains
- Mice, Knockout
- Muscle Relaxation/drug effects
- Norepinephrine/pharmacology
- Propanolamines/pharmacology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Adrenergic, beta/drug effects
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/physiology
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/physiology
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/physiology
- Receptors, Adrenergic, beta-3
- Ureter/physiology
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Affiliation(s)
| | - Frédéric Preitner
- Département de Biochimie Médicale, Centre Médical Universitaire, CH-1211 Genève 4, Switzerland
| | - James Moffatt
- Department of Pharmacology, The University of Melbourne, Victoria 3052, Australia
| | - Maria Jimenez
- Département de Biochimie Médicale, Centre Médical Universitaire, CH-1211 Genève 4, Switzerland
| | - Jean Paul Giacobino
- Département de Biochimie Médicale, Centre Médical Universitaire, CH-1211 Genève 4, Switzerland
| | - Peter Molenaar
- Department of Pharmacology, The University of Melbourne, Victoria 3052, Australia
- Department of Medicine, University of Queensland, The Prince Charles Hospital, Chermside, Queensland 4032, Australia
| | - Alberto Julio Kaumann
- The Babraham Institute, Cambridge CB2 4AT
- Physiological Laboratory, Department of Physiology, University of Cambridge, Cambridge CB2 3EG
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Kompa AR, Summers RJ. Desensitization and resensitization of beta 1- and putative beta 4-adrenoceptor mediated responses occur in parallel in a rat model of cardiac failure. Br J Pharmacol 1999; 128:1399-406. [PMID: 10602318 PMCID: PMC1571772 DOI: 10.1038/sj.bjp.0702920] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Cardiostimulant effects of the non-conventional partial agonist, CGP 12177A, are mediated by a receptor distinct from the beta3-adrenoceptor and termed the putative beta4-adrenoceptor. Using a rat model of cardiac failure, induced by myocardial infarction (MI), we compared the desensitization and resensitization of responses to CGP 12177A with those to isoprenaline and RO 363 in left (LA) and right atria (RA). We also examined the ability of beta-adrenoceptor antagonists to block responses to CGP 12177A. 2. MI reduced the maximum inotropic response to isoprenaline by 48% (sham 4.1+/-0.6 mN, n=10; MI 2.1+/-0.4 mN, n=8, P<0.02), RO 363 by 61% (sham 4.2+/-0.5 mN, n=10; MI 1.8+/-0.3 mN, n=8, P<0.005) and CGP 12177A by 49% (sham 1.4+/-0.1 mN, n=5; MI 0.7+/-0.2 mN, n=7, P<0.05) in electrically stimulated LA. MI also reduced the sensitivity to isoprenaline (pEC50: sham 8.79+/-0.08, n=10; MI 8.30+/-0.10, n=8; P=0.001) and RO 363 (pEC50: sham 8.69+/-0.07, n=10; MI 8.33+/-0.10, n=8; P<0.01). The maximum chronotropic responses to isoprenaline, RO 363 and CGP 12177A in RA were unaffected. 3. Pertussis toxin treatment (10 microg kg-1, i.p.) restored the maximum inotropic response and sensitivity to isoprenaline (sham 3.5+/-0.5 mN, n=9; MI 3.2+/-0.6 mN, n=11, P=0.702) and CGP 12177A (sham 1.6+/-0.3 mN, n=6; MI 1.9+/-0.4 mN, n=7, P=0.537) in MI animals to levels similar to those in the sham group. 4. CGP 20712A (pKB: LA 6.7+/-0.2, n=6; RA 7. 1+/-0.1, n=4), ICI 118,551 (pKB: LA 6.4+/-0.1, n=5; RA 6.3+/-0.1, n=6), propranolol (pKB: LA 6.6+/-0.1, n=5; RA 6.8+/-0.1, n=6) and bupranolol (pKB: LA 7.2+/-0.1, n=6; RA 7.7+/-0.1, n=8), showed moderate affinity for the putative beta4-adrenoceptor. 5. Desensitization after MI and resensitization (after pertussis toxin treatment) to isoprenaline and CGP 12177A therefore occur in parallel, suggesting that the beta1- and putative beta4-adrenoceptor use the same signalling pathway. Antagonist affinity studies confirmed that drugs acting at beta1-adrenoceptors also interact with putative beta4-adrenoceptors with approximately 100 times lower affinity. We suggest that CGP 12177A produces its cardiac effects by interacting with a low affinity state of the beta1-adrenoceptor.
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MESH Headings
- Animals
- Disease Models, Animal
- Heart Failure/metabolism
- Heart Failure/physiopathology
- Kinetics
- Myocardial Contraction/drug effects
- Myocardial Contraction/physiology
- Myocardial Infarction/metabolism
- Myocardial Infarction/physiopathology
- Pertussis Toxin
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic, beta/metabolism
- Receptors, Adrenergic, beta/physiology
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-1/physiology
- Virulence Factors, Bordetella/pharmacology
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Affiliation(s)
- Andrew R Kompa
- Department of Pharmacology, Monash University, Wellington Road, Clayton, Victoria, 3168, Australia
| | - Roger J Summers
- Department of Pharmacology, Monash University, Wellington Road, Clayton, Victoria, 3168, Australia
- Author for correspondence:
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Sarsero D, Molenaar P, Kaumann AJ, Freestone NS. Putative beta 4-adrenoceptors in rat ventricle mediate increases in contractile force and cell Ca2+: comparison with atrial receptors and relationship to (-)-[3H]-CGP 12177 binding. Br J Pharmacol 1999; 128:1445-60. [PMID: 10602323 PMCID: PMC1571781 DOI: 10.1038/sj.bjp.0702936] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
1. We identified putative beta4-adrenoceptors by radioligand binding, measured increases in ventricular contractile force by (-)-CGP 12177 and (+/-)-cyanopindolol and demonstrated increased Ca2+ transients by (-)-CGP 12177 in rat cardiomyocytes. 2. (-)-[3H]-CGP 12177 labelled 13 - 22 fmol mg-1 protein ventricular beta1, beta2-adrenoceptors (pKD approximately 9.0) and 50 - 90 fmol mg-1 protein putative beta4-adrenoceptors (pKD approximately 7.3). The affinity values (pKi) for (beta1,beta2-) and putative beta4-adrenoceptors, estimated from binding inhibition, were (-)-propranolol 8.4, 5.7; (-)-bupranolol 9.7, 5.8; (+/-)-cyanopindolol 10.0,7.4. 3. In left ventricular papillary muscle, in the presence of 30 microM 3-isobutyl-1-methylxanthine, (-)-CGP 12177 and (+/-)-cyanopindolol caused positive inotropic effects, (pEC50, (-)-CGP 12177, 7.6; (+/-)-cyanopindolol, 7.0) which were antagonized by (-)-bupranolol (pKB 6.7 - 7.0) and (-)-CGP 20712A (pKB 6.3 - 6.6). The cardiostimulant effects of (-)-CGP 12177 in papillary muscle, left and right atrium were antagonized by (+/-)-cyanopindolol (pKP 7.0 - 7.4). 4. (-)-CGP 12177 (1 microM) in the presence of 200 nM (-)-propranolol increased Ca2+ transient amplitude by 56% in atrial myocytes, but only caused a marginal increase in ventricular myocytes. In the presence of 1 microM 3-isobutyl-1-methylxanthine and 200 nM (-)-propranolol, 1 microM (-)-CGP 12177 caused a 73% increase in Ca2+ transient amplitude in ventricular myocytes. (-)-CGP 12177 elicited arrhythmic transients in some atrial and ventricular myocytes. 5. Probably by preventing cyclic AMP hydrolysis, 3-isobutyl-1-methylxanthine facilitates the inotropic function of ventricular putative beta4-adrenoceptors, suggesting coupling to Gs protein-adenylyl cyclase. The receptor-mediated increases in contractile force are related to increases of Ca2+ in atrial and ventricular myocytes. The agreement of binding affinities of agonists with cardiostimulant potencies is consistent with mediation through putative beta4-adrenoceptors labelled with (-)-[3H]-CGP 12177.
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Affiliation(s)
- Doreen Sarsero
- Department of Pharmacology, University of Melbourne, Parkville, 3052, Victoria, Australia
| | - Peter Molenaar
- Department of Pharmacology, University of Melbourne, Parkville, 3052, Victoria, Australia
- Cardiovascular Research Unit, Department of Medicine, University of Queensland, Prince Charles Hospital, Chermside, 4032, Queensland, Australia
- Author for correspondence:
| | - Alberto J Kaumann
- Laboratory of Molecular Signalling, The Babraham Institute, Cambridge, CB2 4AT, U.K
- Physiological Laboratory, University of Cambridge, Cambridge, CB2 3EG, U.K
| | - Nicholas S Freestone
- Laboratory of Molecular Signalling, The Babraham Institute, Cambridge, CB2 4AT, U.K
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Bronnikov G, Bengtsson T, Kramarova L, Golozoubova V, Cannon B, Nedergaard J. beta1 to beta3 switch in control of cyclic adenosine monophosphate during brown adipocyte development explains distinct beta-adrenoceptor subtype mediation of proliferation and differentiation. Endocrinology 1999; 140:4185-97. [PMID: 10465291 DOI: 10.1210/endo.140.9.6972] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To explain the distinctive pharmacological profiles observed for adrenergic stimulation of cell proliferation (beta1) and cell differentiation (beta3), the adrenergic control of cAMP accumulation was investigated during brown adipocyte development. In preadipocytes, norepinephrine (NE) increased cAMP levels but the beta3-agonists BRL-37344 and CGP-12177 did not; in contrast, when the cells had differentiated into mature brown adipocytes, a large cAMP response to the beta3-agonists had emerged and was now double that to NE (although the affinity of NE had increased 10-fold). Beta1-messenger RNA (mRNA) levels were high in both pre- and mature brown adipocytes; beta3-mRNA did not appear until maturation but then abruptly. Although beta1-receptors remained detectable by [3H]CGP-12177 binding in the mature brown adipocytes, the cAMP response to NE (based on propranolol inhibitory potency) switched from beta1 to beta3. Even the established beta1-agonist dobutamine acted through beta3-receptors in the mature brown adipocytes. The increases in cAMP levels could adequately explain the increased cell proliferation in NE-stimulated preadipocytes and the NE-induced UCP1 gene expression in mature brown adipocytes. The distinctive adrenergic profiles for stimulation of proliferation and of differentiation were thus not due to the existence of additional pathways but to a switch in the type of beta-receptor mediating the NE response, coordinated with an alteration in the nuclear response to increased cAMP levels. The study implies that full recruitment of brown adipose tissue cannot be induced by exclusive beta3-stimulation.
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Affiliation(s)
- G Bronnikov
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, Sweden
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47
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Evans BA, Agar L, Summers RJ. The role of the sympathetic nervous system in the regulation of leptin synthesis in C57BL/6 mice. FEBS Lett 1999; 444:149-54. [PMID: 10050748 DOI: 10.1016/s0014-5793(99)00049-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The objectives of this study were to determine whether leptin synthesis is regulated by the sympathetic nervous system and if so whether beta-adrenergic receptors mediate this effect. We show that sympathetic blockade by reserpine increases leptin mRNA levels in brown but not white adipose tissue, while acute cold-exposure decreases leptin expression 10-fold in brown adipose tissue and 2-fold in white adipose tissue. The cold-induced reduction in leptin mRNA can be prevented by a combination of propranolol and SR 59230A but not by either antagonist alone, indicating that beta3-adrenergic receptors and classical beta1/beta2-adrenergic receptors both mediate responses to sympathetic stimulation. Circulating leptin levels reflect synthesis in white adipose tissue but not in brown adipose tissue.
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Affiliation(s)
- B A Evans
- Department of Pharmacology, Monash University, Clayton, Victoria, Australia.
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48
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