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Shi TH, Nagata Y, Akine S, Ohtani S, Kato K, Ogoshi T. A Twisted Chiral Cavitand with 5-Fold Symmetry and Its Length-Selective Binding Properties. J Am Chem Soc 2022; 144:23677-23684. [PMID: 36529936 DOI: 10.1021/jacs.2c11225] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Controlling bottom-up syntheses from chiral seeds to construct architectures with specific chiralities is currently challenging. Herein, a twisted chiral cavitand with 5-fold symmetry was constructed by bottom-up synthesis using corannulene as the chiral seed and pillar[5]arene as the chiral wall. After docking between the seed and the wall, their dynamic chiralities (M and P) are fixed. Moreover, the formed hedges also exhibit M and P chirality. Through dynamic covalent bonding, the thermodynamically stable product is obtained selectively as a pair of enantiomers (MMM and PPP), where all three subcomponents, i.e., the corannulene, hedges, and pillar[5]arene, are tilted in the same direction. Furthermore, the twisted cavitand exhibits length-selective binding to alkylene dibromides, with three maximum binding constants being unexpectedly observed.
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Affiliation(s)
- Tan-Hao Shi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yuuya Nagata
- WPI Institute for Chemical Reaction Design and Discovery (WPI- ICReDD), Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo 060-0810, Japan
| | - Shigehisa Akine
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.,Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Shunsuke Ohtani
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Kenichi Kato
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Tomoki Ogoshi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.,WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan
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Chen J, Campbell AP, Wakelin LPG, Finch AM. Characterisation of bis(4-aminoquinoline)s as α 1A adrenoceptor allosteric modulators. Eur J Pharmacol 2021; 916:174659. [PMID: 34871559 DOI: 10.1016/j.ejphar.2021.174659] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 11/19/2021] [Accepted: 11/29/2021] [Indexed: 11/30/2022]
Abstract
The development of sub-type selective α1 adrenoceptor ligands has been hampered by the high sequence similarity of the amino acids forming the orthosteric binding pocket of the three α1 adrenoceptor subtypes, along with other biogenic amine receptors. One possible approach to overcome this issue is to target allosteric sites on the α1 adrenoceptors. Previous docking studies suggested that one of the quinoline moieties of a bis(4-aminoquinoline), comprising a 9-carbon methylene linker attached via the amine groups, could interact with residues outside of the orthosteric binding site while, simultaneously, the other quinoline moiety bound within the orthosteric site. We therefore hypothesized that this compound could act in a bitopic manner, displaying both orthosteric and allosteric binding properties. To test this proposition, we investigated the allosteric activity of a series of bis(4-aminoquinoline)s with linker lengths ranging from 2 to 12 methylene units (designated C2-C12). A linear trend of increasing [3H]prazosin dissociation rate with increasing linker length between C7 and C11 was observed, confirming their action as allosteric modulators. These data suggest that the optimal linker length for the bis(4-aminoquinoline)s to occupy the allosteric site of the α1A adrenoceptor is between 7 and 11 methylene units. In addition, the ability of C9 bis(4-aminoquinoline) to modulate the activation of the α1A adrenoceptor by norepinephrine was subsequently examined, showing that C9 acted as a non-competitive antagonist. Our findings indicate that the bis(4-aminoquinolines) are acting as allosteric modulators of orthosteric ligand binding, but not efficacy, in a bitopic manner.
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Affiliation(s)
- Junli Chen
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, 2052, Australia
| | - Adrian P Campbell
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, 2052, Australia
| | - Laurence P G Wakelin
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, 2052, Australia
| | - Angela M Finch
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, 2052, Australia.
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3
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Li Z, Li J, Liu L, Deng W, Liu Q, Liu R, Zhang W, He Z, Fan L, Yang Y, Duan Y, Hou H, Wang X, Yang Z, Wang X, Chen S, Wang Y, Huang N, Chen J. Structural Insight into the Mechanism of 4-Aminoquinolines Selectivity for the alpha2A-Adrenoceptor. DRUG DESIGN DEVELOPMENT AND THERAPY 2020; 14:2585-2594. [PMID: 32694911 PMCID: PMC7340475 DOI: 10.2147/dddt.s214157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 09/19/2019] [Indexed: 11/23/2022]
Abstract
Background α2A-adrenoceptor (AR) is a potential target for the treatment of degenerative diseases of the central nervous system, and α2A-AR agonists are effective drugs for this condition. However, the lack of high selectivity for α2A-AR subtype of traditional drugs greatly limits their clinic usage. Methods A series of homobivalent 4-aminoquinolines conjugated by two 4-aminoquinoline moieties via varying alkane linker length (C2-C12) were characterized for their affinities for each α2-AR subtype. Subsequently, docking, molecular dynamics and mutagenesis were applied to uncover the molecular mechanism. Results Most 4-aminoquinolines (4-aminoquinoline monomer, C2-C6, C8-C10) were selective for α2A-AR over α2B- and α2C-ARs. Besides, the affinities are of similar linker length-dependence for each α2-AR subtype. Among all the compounds tested, C10 has the highest affinity for α2A-AR (pKi=−7.45±0.62), which is 12-fold and 60-fold selective over α2B-AR and α2C-AR, respectively. Docking and molecular dynamics suggest that C10 simultaneously interacts with orthosteric and “allosteric” sites of the α2A-AR. The mutation of F205 decreases the affinity by 2-fold. The potential allosteric residues include S90, N93, E94 and W99. Conclusion The specificity of C10 for the α2A-AR and the potential orthosteric and allosteric binding sites proposed in this study provide valuable guidance for the development of novel α2A-AR subtype selective compounds.
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Affiliation(s)
- Zaibing Li
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China.,Department of Pathophysiology, School of Basic Medical Science, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Jingyu Li
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Liyan Liu
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Wenyi Deng
- West China Medical School, Sichuan University, Chengdu 610041, People's Republic of China
| | - Qingrong Liu
- West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Ruofan Liu
- West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Wen Zhang
- West China Medical School, Sichuan University, Chengdu 610041, People's Republic of China
| | - Zaiqing He
- Department of Pathology, Nuclear of Industry 416 Hospital, Chengdu, Sichuan 610051, People's Republic of China
| | - Lei Fan
- Department of Occupational Medicine, Nuclear of Industry 416 Hospital, Chengdu, Sichuan 610051, People's Republic of China
| | - Yingzhuo Yang
- Department of Nuclear Medicine, Sichuan Cancer Hospital, Chengdu 610041, People's Republic of China
| | - Yun Duan
- Department of Nuclear Medicine, Sichuan Cancer Hospital, Chengdu 610041, People's Republic of China
| | - Huifang Hou
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Xinyuan Wang
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Zhimei Yang
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Xiaoying Wang
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Shanze Chen
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Yi Wang
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Ning Huang
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
| | - Junli Chen
- Department of Pathophysiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, People's Republic of China
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Campbell AP, Wakelin LPG, Denny WA, Finch AM. Homobivalent Conjugation Increases the Allosteric Effect of 9-aminoacridine at the α1-Adrenergic Receptors. Mol Pharmacol 2016; 91:135-144. [PMID: 27903755 DOI: 10.1124/mol.116.105874] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 11/28/2016] [Indexed: 12/14/2022] Open
Abstract
The α1-adrenergic receptors are targets for a number of cardiovascular and central nervous system conditions, but the current drugs for these receptors lack specificity to be of optimal clinical value. Allosteric modulators offer an alternative mechanism of action to traditional α1-adrenergic ligands, yet there is little information describing this drug class at the α1-adrenergic receptors. We have identified a series of 9-aminoacridine compounds that demonstrate allosteric modulation of the α1A- and α1B-adrenergic receptors. The 9-aminoacridines increase the rate of [3H]prazosin dissociation from the α1A- and α1B-adrenergic receptors and noncompetitively inhibit receptor activation by the endogenous agonist norepinephrine. The structurally similar compound, tacrine, which is a known allosteric modulator of the muscarinic receptors, is also shown to be a modulator of the α1-adrenergic receptors, which suggests a general lack of selectivity for allosteric binding sites across aminergic G protein-coupled receptor. Conjugation of two 9-aminoacridine pharmacophores, using linkers of varying length, increases the potency and efficacy of the allosteric effects of this ligand, likely through optimization of bitopic engagement of the allosteric and orthosteric binding sites of the receptor. Such a bivalent approach may provide a mechanism for fine tuning the efficacy of allosteric compounds in future drug design efforts.
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Affiliation(s)
- Adrian P Campbell
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia (A.P.C., L.P.G.W., A.M.F.); Auckland Cancer Society Research Centre, Faculty of Medicine and Health Science, University of Auckland, Auckland, New Zealand (W.A.D.)
| | - Laurence P G Wakelin
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia (A.P.C., L.P.G.W., A.M.F.); Auckland Cancer Society Research Centre, Faculty of Medicine and Health Science, University of Auckland, Auckland, New Zealand (W.A.D.)
| | - William A Denny
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia (A.P.C., L.P.G.W., A.M.F.); Auckland Cancer Society Research Centre, Faculty of Medicine and Health Science, University of Auckland, Auckland, New Zealand (W.A.D.)
| | - Angela M Finch
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia (A.P.C., L.P.G.W., A.M.F.); Auckland Cancer Society Research Centre, Faculty of Medicine and Health Science, University of Auckland, Auckland, New Zealand (W.A.D.)
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Chen J, Campbell AP, Urmi KF, Wakelin LPG, Denny WA, Griffith R, Finch AM. Human α1-adrenoceptor subtype selectivity of substituted homobivalent 4-aminoquinolines. Bioorg Med Chem 2014; 22:5910-6. [PMID: 25288493 DOI: 10.1016/j.bmc.2014.09.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Revised: 09/01/2014] [Accepted: 09/09/2014] [Indexed: 11/27/2022]
Abstract
A series of ring-substituted ethyl- and heptyl-linked 4-aminoquinoline dimers were synthesized and evaluated for their affinities at the 3 human α(1)-adrenoceptor (α(1)-AR) subtypes and the human serotonin 5-HT(1A)-receptor (5-HT(1A)-R). We find that the structure-specificity profiles are different for the two series at the α(1)-AR subtypes, which suggests that homobivalent 4-aminoquinolines can be developed with α(1)-AR subtype selectivity. The 8-methyl (8-Me) ethyl-linked analogue has the highest affinity for the α(1A)-AR, 7 nM, and the greatest capacity for discriminating between α(1A)-AR and α(1B)-AR (6-fold), α(1D)-AR (68-fold), and the 5-HT(1A)-R (168-fold). α(1B)-AR selectivity was observed with the 6-methyl (6-Me) derivative of the ethyl- and heptyl-linked 4-aminoquinoline dimers and the 7-methoxy (7-OMe) derivative of the heptyl-linked analogue. These substitutions result in 4- to 80-fold selectivity for α(1B)-AR over α(1A)-AR, α(1D)-AR, and 5-HT(1A)-R. In contrast, 4-aminoquinoline dimers with selectivity for α(1D)-AR are more elusive, since none studied to date has greater affinity for the α(1D)-AR over the other two α(1)-ARs. The selectivity of the 8-Me ethyl-linked 4-aminoquinoline dimer for the α(1A)-AR, and 6-Me ethyl-linked, and the 6-Me and 7-OMe heptyl-linked 4-aminoquinoline dimers for the α(1B)-AR, makes them promising leads for drug development of α(1A)-AR or α(1B)-AR subtype selective ligands with reduced 5-HT(1A)-R affinity.
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Affiliation(s)
- Junli Chen
- Department of Pharmacology, School of Medical Sciences, Wallace Wurth Building, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Adrian P Campbell
- Department of Pharmacology, School of Medical Sciences, Wallace Wurth Building, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Kaniz F Urmi
- Department of Pharmacology, School of Medical Sciences, Wallace Wurth Building, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Laurence P G Wakelin
- Department of Pharmacology, School of Medical Sciences, Wallace Wurth Building, UNSW Australia, Sydney, NSW 2052, Australia.
| | - William A Denny
- Auckland Cancer Society Research Centre, School of Medical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
| | - Renate Griffith
- Department of Pharmacology, School of Medical Sciences, Wallace Wurth Building, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Angela M Finch
- Department of Pharmacology, School of Medical Sciences, Wallace Wurth Building, UNSW Australia, Sydney, NSW 2052, Australia.
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Chen J, Murad AK, Wakelin LPG, Denny WA, Griffith R, Finch AM. α₁-Adrenoceptor and serotonin 5-HT(1A) receptor affinity of homobivalent 4-aminoquinoline compounds: an investigation of the effect of linker length. Biochem Pharmacol 2013; 85:1534-41. [PMID: 23524075 DOI: 10.1016/j.bcp.2013.03.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 03/12/2013] [Accepted: 03/13/2013] [Indexed: 11/18/2022]
Abstract
α₁-adrenoceptor (α₁-AR) subtype-selective ligands lacking off-target affinity for the 5-HT(1A) receptor (5-HT(1A)-R) will provide therapeutic benefits in the treatment of urogenital conditions such as benign prostatic hyperplasia. In this study we determined the affinity of 4-aminoquinoline and eleven homobivalent 4-aminoquinoline ligands (diquinolines) with alkane linkers of 2-12 atoms (C2-C12) for α(1A), α(1B) and α(1D)-ARs and the 5-HT(1A)-R. These ligands are α(1A)-AR antagonists with nanomolar affinity for α(1A) and α(1B)-ARs. They display linker-length dependent selectivity for α(1A/B)-ARs over α(1D)-AR and the 5-HT(1A)-R. The C2 diquinoline has the highest affinity for α1A-AR (pKi 7.60±0.26) and greater than 30-fold and 600-fold selectivity for α(1A)-AR over α(1D)-AR and 5-HT(1A)-R respectively. A decrease in affinity for α₁-ARs is observed as the linker length increases, reaching a nadir at 5 (α(1A/1B)-ARs) or 6 (α(1D)-AR) atoms; after which affinity increases as the linker is lengthened, peaking at 9 (α(1A/1B/1D)-ARs) or 8 (5-HT(1A)-R) atoms. Docking studies suggest that 4-aminoquinoline and C2 bind within the orthosteric binding site, while for C9 one end is situated within the orthosteric binding pocket, while the other 4-aminoquinoline moiety interacts with the extracellular surface. The limited α(1D)-AR and 5-HT(1A)-R affinity of these compounds makes them promising leads for future drug development of α(1A)-AR selective ligands without α(1D)-AR and the 5-HT(1A)-R off-target activity.
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Affiliation(s)
- Junli Chen
- Department of Pharmacology, School of Medical Sciences, UNSW, Sydney, NSW 2052, Australia
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Hamilton CA, Yakubu MA, Howie CA, Reid JL. Do centrally-acting antihypertensive drugs act at non-adrenergic as well as alpha-2 adrenoceptor sites? CLINICAL AND EXPERIMENTAL HYPERTENSION. PART A, THEORY AND PRACTICE 1992; 14:815-35. [PMID: 1327589 DOI: 10.3109/10641969209036221] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Rabbits were treated with guanabenz, clonidine and rilmenidine for 6 days via osmotic minipumps. Blood pressure, heart rate and responses to intracisternal clonidine were measured after 1 and 6 days treatment. Radioligand binding to forebrain and hindbrain membranes after 6 days treatment was examined using [3H]yohimbine to measure the number of adrenergic binding sites and [3H]clonidine and [3H]idazoxan to assess nonadrenergic imidazoline sites. No change in nonadrenergic imidazoline binding was observed but adrenergic binding was decreased in forebrain and hindbrain by guanabenz and in hindbrain by clonidine treatment. Resting heart rate was decreased after 1 day's treatment with partial recovery by day 6. At this time heart rate significantly reduced in the clonidine and rilmenidine treated groups but not the guanabenz group. No significant change in baseline blood pressure was observed in normotensive rabbits. Both depressor and bradycardia responses to intracisternal clonidine were attenuated after 1 day's dosing but only depressor responses were influenced after 6 days. Blood pressure and heart rate thus appeared to be regulated independently. It is possible that imidazoline receptors predominate in the central control of blood pressure while central alpha-2 adrenoceptors play a greater part in heart rate regulation.
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Affiliation(s)
- C A Hamilton
- University Department of Medicine and Therapeutics Western Infirmary, Glasgow
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Uhlén S, Wikberg JE. Delineation of three pharmacological subtypes of alpha 2-adrenoceptor in the rat kidney. Br J Pharmacol 1991; 104:657-64. [PMID: 1665747 PMCID: PMC1908229 DOI: 10.1111/j.1476-5381.1991.tb12485.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
1. Simultaneous computer modelling of plain and ARC 239- and guanoxabenz-masked [3H]-RX821002 saturation curves, plain ARC 239 and guanoxabenz competition curves as well as ARC 239-masked guanoxabenz competition curves revealed that the drugs bound to three alpha 2-adrenoceptor subtypes in the rat kidney with grossly differing selectivities. These alpha 2-adrenoceptor subtypes were termed alpha 2 A, alpha 2B1 and alpha 2B2. The order of affinities for [3H]-RX821002 for the adrenoceptor sites was alpha 2A greater than alpha 2B1 greater than alpha 2B2, the KdS being 0.62 +/- 0.05, 2.52 +/- 0.11 and 6.74 +/- 1.21 nM, respectively. The order of affinities for ARC 239 was alpha 2B1 greater than alpha 2B2 much greater than alpha 2A with KdS 4.78 +/- 1.04, 28.8 +/- 4.1 and 1460 +/- 270 nM, respectively. For guanoxabenz the order of affinities was alpha 2A greater than alpha 2B1 much greater than alpha 2B2 with KdS 99.7 +/- 15.1, 508 +/- 135 and 25,400 +/- 2400 nM, respectively. 2. Binding constants for 14 compounds for the three rat kidney alpha 2-adrenoceptor subtypes were determined by the simultaneous computer modelling of plain and ARC 239- and guanoxabenz-masked drug competition curves, plain ARC 239 and guanoxabenz competition curves as well as ARC 239-masked guanoxabenz competition curves. Of the 14 compounds tested, oxymetazoline and guanfacine were found to bind with low affinities to both of the alpha 2B1- and alpha 2B2-adrenoceptor but with high affinity to the alpha 2A-adrenoceptor. 3. (-)-Adrenaline and (-)-noradrenaline showed dissimilar order of affinities for the three alpha2-adrenoceptors. For (-)-adrenaline the order of affinities was alpha2Bl >- alpha2A> alpha2B2 and for (-)-noradrenaline alpha2B2 > alpha2Bl > alpha2A. All three alpha2-adrenoceptors showed the expected stereoselective binding for adrenaline enantiomers, the (+)-form being 7-10 fold less potent than the (-)form. 4. [3H]-yohimbine was also used as radioligand. The data with this ligand were fully compatible with the [3H]-RX821002 data. However, [3H]-yohimbine appeared to label only alpha2Bl- and alpha2B2-adrenoceptors presumably because it had too low an affinity for alpha2A-adrenoceptors. 5. We conclude that three pharmacological subtypes of alpha2-adrenoceptors are labelled by [3H]-RX821002 in the rat kidney. Guanoxabenz and ARC 239 may be used in competition studies to delineate between these three alpha2-adrenoceptor subtypes. Moreoever, we here present a method allowing the determination of binding constants for an arbitrary drug to the three alpha2-adrenoceptor subtypes.
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Affiliation(s)
- S Uhlén
- Department of Pharmacology, Umeå University, Sweden
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9
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Uhlén S, Persson ML, Alari L, Post C, Axelsson KL, Wikberg JE. Antinociceptive actions of alpha 2-adrenoceptor agonists in the rat spinal cord: evidence for antinociceptive alpha 2-adrenoceptor subtypes and dissociation of antinociceptive alpha 2-adrenoceptors from cyclic AMP. J Neurochem 1990; 55:1905-14. [PMID: 1977885 DOI: 10.1111/j.1471-4159.1990.tb05775.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The antinociceptive actions of intrathecal injections of two alpha 2-adrenergic agonists, UK-14,304 and guanfacine, were investigated in rats after pretreatment of the animals with the noradrenaline neurotoxin N-2-chloroethyl-N-ethyl-2-bromobenzylamine (DSP4) 14 days in advance. The chronic noradrenaline depletion induced by DSP4 caused a marked increase in sensitivity of the antinociceptive action of UK-14,304 in the tail-flick test. By contrast, the antinociceptive effect of guanfacine was not appreciably affected by the DSP4 treatment. The antinociceptive effects of both UK-14,304 and guanfacine were blocked by intraperitoneal injections of yohimbine, a result indicating that both drugs induced their actions by activating alpha 2-adrenoceptors. Both UK-14,304 and guanfacine were found to reduce the production of cyclic AMP (cAMP) in the spinal cord, as determined using an in vitro radioisotopic method. The cAMP inhibitory effects of both agonists were effectively blocked by yohimbine, but not by prazosin, a finding indicating the alpha 2-adrenergic nature of the response. However, the cAMP inhibitory effect of UK-14,304 was not potentiated by pretreatment with DSP4, a finding in marked contrast with the strong potentiation of the antinociceptive action of UK-14,304 induced by the chronic depletion of endogenous noradrenaline. Moreover, intrathecal injections of forskolin, which increased the endogenous levels of spinal cord cAMP fivefold, did not modify the antinociceptive effects of UK-14,304 or guanfacine in neither normal nor DSP4-treated animals. It is suggested that there exist pharmacologically differing alpha 2-adrenergic receptor pathways capable of mediating antinociceptive effects at the level of the spinal cord. The cAMP inhibitory actions of spinal cord alpha 2-adrenoceptors appear not to be directly linked with the antinociceptive actions of these receptors.
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Affiliation(s)
- S Uhlén
- Department of Pharmacology, Umeå University, Sweden
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10
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Van Megen YJ, Rodrigues de Miranda JF, Klaassen AB, Wentges BT, Van Ginneken CA. Alpha 2-adrenoceptors in homogenates of rat nasal mucosa. Eur J Pharmacol 1990; 182:561-7. [PMID: 2171951 DOI: 10.1016/0014-2999(90)90056-c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The specific binding of [3H]rauwolscine to rat nasal mucosa membranes was saturable, stereoselective and of high affinity. The Scatchard plot pointed to a homogeneous population of binding sites (Kd = 3.6 +/- 0.6 nM; Bmax = 5.1 +/- 0.7 pmol/g). The non-specific binding appeared to be non-linear, probably due to filter binding. Inhibition of [3H]rauwolscine binding with the subtype-selective antagonist, prazosin, suggested the presence of alpha 2-adrenoceptor subclasses in rat nasal mucosa. The (-)-epinephrine inhibition curves demonstrated high- and low-affinity agonist binding sites. A monophasic (-)-epinephrine inhibition curve was obtained in the presence of guanine nucleotides.
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Affiliation(s)
- Y J Van Megen
- Department of Otorhinolaryngology, University of Nijmegen, The Netherlands
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van Megen YJ, Klaassen AB, Rodrigues de Miranda JF, Wentges RT, van Ginneken CA. Demonstration of alpha 1-adrenoceptors in rat nasal mucosa. JOURNAL OF RECEPTOR RESEARCH 1989; 9:221-34. [PMID: 2570146 DOI: 10.3109/10799898909066056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
3H-Prazosin was used to demonstrate alpha 1-adrenoceptors in rat nasal mucosa. Specific binding is saturable and occurs to a homogeneous class of binding sites with high affinity (Kd = 0.07 +/- 0.01 nmol/l and with a receptor density of 0.36 +/- 0.02 pmol/g tissue or 14 +/- 1 fmol/mg protein. Kinetic experiments resulted in a Kd-value of 0.03 nmol/l. The binding is stereoselectively inhibited by epinephrine enantiomers. The antagonist prazosin inhibits 3H-Prazosin binding with high affinity, in contrast to yohimbine, classifying the binding sites as alpha 1-adrenoceptors. Inhibition experiments with WB4101 indicated the presence of alpha 1a- (31 +/- 9%) and alpha 1b-adrenoceptor subtypes in the rat nasal mucosa. The order of potencies of agonists determined in competition experiments was (-)epinephrine greater than (+)epinephrine greater than (-)phenylephrine.
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Affiliation(s)
- Y J van Megen
- Department of Otorhinolaryngology, St. Radboud Hospital, Nijmegen, The Netherlands
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