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Structure-Based Bioisosterism Design, Synthesis, Biological Evaluation and In Silico Studies of Benzamide Analogs as Potential Anthelmintics. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27092659. [PMID: 35566007 PMCID: PMC9102753 DOI: 10.3390/molecules27092659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 04/08/2022] [Accepted: 04/18/2022] [Indexed: 11/16/2022]
Abstract
A recent screen of 67,012 compounds identified a new family of compounds with excellent nematicidal activity: the ortho-substituted benzamide families Wact-11 and Wact-12. These compounds are active against Caenorhabditis elegans and parasitic nematodes by selectively inhibiting nematode complex II, and they display low toxicity in mammalian cells and vertebrate organisms. Although a big number of benzamides were tested against C. elegans in high-throughput screens, bioisosteres of the amide moiety were not represented in the chemical space examined. We thus identified an opportunity for the design, synthesis and evaluation of novel compounds, using bioisosteric replacements of the amide group present in benzamides. The compound Wact-11 was used as the reference scaffold to prepare a set of bioisosteres to be evaluated against C. elegans. Eight types of amide replacement were selected, including ester, thioamide, selenoamide, sulfonamide, alkyl thio- and oxo-amides, urea and triazole. The results allowed us to perform a structure-activity relationship, highlighting the relevance of the amide group for nematicide activity. Experimental evidence was complemented with in silico structural studies over a C. elegans complex II model as a molecular target of benzamides. Importantly, compound Wact-11 was active against the flatworm Echinococcus granulosus, suggesting a previously unreported pan-anthelmintic potential for benzamides.
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Boutin JA, Witt-Enderby PA, Sotriffer C, Zlotos DP. Melatonin receptor ligands: A pharmaco-chemical perspective. J Pineal Res 2020; 69:e12672. [PMID: 32531076 DOI: 10.1111/jpi.12672] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 05/19/2020] [Accepted: 06/04/2020] [Indexed: 12/14/2022]
Abstract
Melatonin MT1 and MT2 receptor ligands have been vigorously explored for the last 4 decades. Inspection of approximately 80 publications in the field revealed that most melatonergic ligands were structural analogues of melatonin combining three essential features of the parent compound: an aromatic ring bearing a methoxy group and an amide side chain in a relative arrangement similar to that present in melatonin. While several series of MT2 -selective agents-agonists, antagonists, or partial agonists-were reported, the field was lacking MT1 -selective agents. Herein, we describe various approaches toward the development of melatonergic ligands, keeping in mind that most of the molecules/pharmacophores obtained were essentially melatonin copies, even though diverse tri- or tetra-cyclic compounds were explored. In addition to lack of structural diversity, only few studies examined the activity of the reported melatonergic ligands in vivo. Moreover, an extensive pharmacological characterization including biopharmaceutical stability, pharmacokinetic properties, specificity toward other major receptors to name a few remained scarce. For example, many of the antagonists described were not stable in vivo, were not selective for the melatonin receptor subtype of interest, and were not fully characterized from a pharmacological standpoint. Indeed, virtual screening of large compound libraries has led to the recent discovery of potent and selective melatonin receptor agonists and partial agonists of new chemotypes. Having said this, the melatonergic field is still lacking subtype-selective melatonin receptor antagonists "active" in vivo, which are critical to our understanding of melatonin and melatonin receptors' role in basic physiology and disease.
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MESH Headings
- Animals
- Humans
- Ligands
- Melatonin/chemistry
- Receptor, Melatonin, MT1/agonists
- Receptor, Melatonin, MT1/antagonists & inhibitors
- Receptor, Melatonin, MT1/chemistry
- Receptor, Melatonin, MT2/agonists
- Receptor, Melatonin, MT2/antagonists & inhibitors
- Receptor, Melatonin, MT2/chemistry
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Affiliation(s)
- Jean A Boutin
- Institut de Recherches Internationales SERVIER, Suresnes, France
| | - Paula A Witt-Enderby
- School of Pharmacy & Graduate School of Pharmaceutical, Administrative and Social Sciences, Duquesne University, Pittsburg, PA, USA
| | - Christoph Sotriffer
- Institute of Pharmacy and Food Chemistry, University of Würzburg, Würzburg, Germany
| | - Darius P Zlotos
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology, The German University in Cairo, New Cairo City, Egypt
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Ortiz C, Echeverri F, Robledo S, Lanari D, Curini M, Quiñones W, Vargas E. Synthesis and Evaluation of Antileishmanial and Cytotoxic Activity of Benzothiopyrane Derivatives. Molecules 2020; 25:molecules25040800. [PMID: 32059518 PMCID: PMC7094215 DOI: 10.3390/molecules25040800] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Revised: 01/21/2020] [Accepted: 01/30/2020] [Indexed: 02/07/2023] Open
Abstract
In continuation of our efforts to identify promising antileishmanial agents based on the chroman scaffold, we synthesized several substituted 2H-thiochroman derivatives, including thiochromenes, thichromanones and hydrazones substituted in C-2 or C-3 with carbonyl or carboxyl groups. Thirty-two compounds were thus obtained, characterized, and evaluated against intracellular amastigotes of Leishmania (V)panamensis. Twelve compounds were active, with EC50 values lower than 40 µM, but only four compounds displayed the highest antileishmanial activity, with EC50 values below 10 µM; these all compounds possess a good Selectivity Index > 2.6. Although two active compounds were thiochromenes, a clear structure-activity relationship was not detected since each active compound has a different substitution pattern.
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Affiliation(s)
- Cristian Ortiz
- Química Orgánica de Productos Naturales, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia, calle 70, No. 52–21, Medellín A. A 1226, Columbia; (C.O.); (F.E.)
| | - Fernando Echeverri
- Química Orgánica de Productos Naturales, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia, calle 70, No. 52–21, Medellín A. A 1226, Columbia; (C.O.); (F.E.)
| | - Sara Robledo
- PECET-Facultad de Medicina, Universidad de Antioquia, calle 70 No. 52–21, Medellín A. A 1226, Columbia;
| | - Daniela Lanari
- Dipartimento di Scienze Farmaceutiche, Università di Perugia, Via del Liceo, 1, 06123 Perugia, Italy; (D.L.); (M.C.)
| | - Massimo Curini
- Dipartimento di Scienze Farmaceutiche, Università di Perugia, Via del Liceo, 1, 06123 Perugia, Italy; (D.L.); (M.C.)
| | - Wiston Quiñones
- Química Orgánica de Productos Naturales, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia, calle 70, No. 52–21, Medellín A. A 1226, Columbia; (C.O.); (F.E.)
- Correspondence: (E.V.); (W.Q.); Tel.: +5-742-196-596 (E.V. & W.Q.)
| | - Esteban Vargas
- Química Orgánica de Productos Naturales, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia, calle 70, No. 52–21, Medellín A. A 1226, Columbia; (C.O.); (F.E.)
- Correspondence: (E.V.); (W.Q.); Tel.: +5-742-196-596 (E.V. & W.Q.)
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Chen CH, Tsai WY, Luo ZH. Highly Fluorescent Conjugated Copolymers Constructed by Alternating Heterocyclic Diazoles and Alkoxy Benzene. J CHIN CHEM SOC-TAIP 2017. [DOI: 10.1002/jccs.201700184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Chih-Hsien Chen
- Department of Chemical Engineering; Feng Chia University; Taichung Taiwan 407
| | - Wu-Yen Tsai
- Department of Chemical Engineering; Feng Chia University; Taichung Taiwan 407
| | - Zi-Huan Luo
- Department of Chemical Engineering; Feng Chia University; Taichung Taiwan 407
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Hu Y, Li CY, Wang XM, Yang YH, Zhu HL. 1,3,4-Thiadiazole: synthesis, reactions, and applications in medicinal, agricultural, and materials chemistry. Chem Rev 2014; 114:5572-610. [PMID: 24716666 DOI: 10.1021/cr400131u] [Citation(s) in RCA: 331] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yang Hu
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University , Nanjing 210093, People's Republic of China
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6
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New quinoxaline derivatives as potential MT₁ and MT₂ receptor ligands. Molecules 2012; 17:7737-57. [PMID: 22732886 PMCID: PMC6269071 DOI: 10.3390/molecules17077737] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/14/2012] [Accepted: 06/18/2012] [Indexed: 11/17/2022] Open
Abstract
Ever since the idea arose that melatonin might promote sleep and resynchronize circadian rhythms, many research groups have centered their efforts on obtaining new melatonin receptor ligands whose pharmacophores include an aliphatic chain of variable length united to an N-alkylamide and a methoxy group (or a bioisostere), linked to a central ring. Substitution of the indole ring found in melatonin with a naphthalene or quinoline ring leads to compounds of similar affinity. The next step in this structural approximation is to introduce a quinoxaline ring (a bioisostere of the quinoline and naphthalene rings) as the central nucleus of future melatoninergic ligands.
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Design and synthesis of 2-phenylimidazo[1,2-a]pyridines as a novel class of melatonin receptor ligands. Eur J Med Chem 2011; 46:4252-7. [DOI: 10.1016/j.ejmech.2011.06.030] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 06/22/2011] [Accepted: 06/23/2011] [Indexed: 12/15/2022]
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Dubocovich ML, Delagrange P, Krause DN, Sugden D, Cardinali DP, Olcese J. International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, classification, and pharmacology of G protein-coupled melatonin receptors. Pharmacol Rev 2010; 62:343-80. [PMID: 20605968 PMCID: PMC2964901 DOI: 10.1124/pr.110.002832] [Citation(s) in RCA: 400] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The hormone melatonin (5-methoxy-N-acetyltryptamine) is synthesized primarily in the pineal gland and retina, and in several peripheral tissues and organs. In the circulation, the concentration of melatonin follows a circadian rhythm, with high levels at night providing timing cues to target tissues endowed with melatonin receptors. Melatonin receptors receive and translate melatonin's message to influence daily and seasonal rhythms of physiology and behavior. The melatonin message is translated through activation of two G protein-coupled receptors, MT(1) and MT(2), that are potential therapeutic targets in disorders ranging from insomnia and circadian sleep disorders to depression, cardiovascular diseases, and cancer. This review summarizes the steps taken since melatonin's discovery by Aaron Lerner in 1958 to functionally characterize, clone, and localize receptors in mammalian tissues. The pharmacological and molecular properties of the receptors are described as well as current efforts to discover and develop ligands for treatment of a number of illnesses, including sleep disorders, depression, and cancer.
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Affiliation(s)
- Margarita L Dubocovich
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo State University of New York, 3435 Main Street, Buffalo, NY 14214, USA.
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Mor M, Rivara S, Pala D, Bedini A, Spadoni G, Tarzia G. Recent advances in the development of melatonin MT1and MT2receptor agonists. Expert Opin Ther Pat 2010; 20:1059-77. [DOI: 10.1517/13543776.2010.496455] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Tsotinis A, Afroudakis PA, Davidson K, Prashar A, Sugden D. Design, Synthesis, and Melatoninergic Activity of New Azido- and Isothiocyanato-Substituted Indoles. J Med Chem 2007; 50:6436-40. [DOI: 10.1021/jm7010723] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Andrew Tsotinis
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, 157 71 Athens, Greece, and Division of Reproduction and Endocrinology, School of Biomedical and Health Sciences, King’s College London, Guy’s Campus, London Bridge, London SE1 1UL, U.K
| | - Pandelis A. Afroudakis
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, 157 71 Athens, Greece, and Division of Reproduction and Endocrinology, School of Biomedical and Health Sciences, King’s College London, Guy’s Campus, London Bridge, London SE1 1UL, U.K
| | - Kathryn Davidson
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, 157 71 Athens, Greece, and Division of Reproduction and Endocrinology, School of Biomedical and Health Sciences, King’s College London, Guy’s Campus, London Bridge, London SE1 1UL, U.K
| | - Anjali Prashar
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, 157 71 Athens, Greece, and Division of Reproduction and Endocrinology, School of Biomedical and Health Sciences, King’s College London, Guy’s Campus, London Bridge, London SE1 1UL, U.K
| | - David Sugden
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, 157 71 Athens, Greece, and Division of Reproduction and Endocrinology, School of Biomedical and Health Sciences, King’s College London, Guy’s Campus, London Bridge, London SE1 1UL, U.K
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11
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Affiliation(s)
- Turan Ozturk
- Istanbul Technical University, Science Faculty, Chemistry Department, Organic Chemistry, 34469 Maslak, Istanbul, Turkey.
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Tsotinis A, Eleutheriades A, Hough KA, Davidson K, Sugden D. Design, synthesis and melatoninergic potency of new N-acyl 8,9-dihydro-4-methoxy-7H-2-benzo[de]quinolinalkanamines. Bioorg Chem 2007; 35:189-204. [PMID: 17223160 DOI: 10.1016/j.bioorg.2006.11.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Revised: 11/24/2006] [Accepted: 11/30/2006] [Indexed: 10/23/2022]
Abstract
A series of new N-acyl 8,9-dihydro-4-methoxy-7H-2-benzo[de]quinolinalkanamines have been prepared and tested for their ability to activate pigment granule aggregation in Xenopus laevis melanophores and bind to the recombinant human MT(1) and MT(2) melatonin receptor subtypes expressed in NIH 3T3 cells. Compounds with a single methylene spacer in the side chain (7) have no agonist activity, but are weak antagonists in the Xenopus melanophore assay, irrespectively of the size or shape of the R substituent (R=CH(3) to c-C(4)H(7)). In contrast, compounds with two (8) or three (9) methylene spacers show partial agonist activity, though this does vary with the nature of the R substituent. Interestingly, the cyclopropane and cyclobutane R substituents, which are usually linked with antagonism, render the cyclopropanecarboxamido analog 9d and its cyclobutanecarboxamido congener 9e weak agonists. It seems, therefore, that in these compounds the R substituent constitutes a functional probe in the dynamic agonist-antagonist conformational equilibrium. One of the new molecules, antagonist 8c, exhibits a noteworthy MT(2) subtype selectivity (13-fold), whereas the acetamido analog 9a (with a three methylene units spacer) also acts as an antagonist and is the only analog exhibiting MT(1) selectivity (>10-fold). In contrast to the analogous N1-C7 annulated indole derivatives, recently reported, the new C1-C8 condensed isoquinolines are not all pure antagonists. Despite their modest receptor affinity at the binding site these compounds demonstrate that the nature of the response (agonist or antagonist activity) is dependent, in this case, on both the side chain spacer's length and the size and shape of the R group.
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Affiliation(s)
- Andrew Tsotinis
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, 157 71 Athens, Greece.
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Chugunov AO, Farce A, Chavatte P, Efremov RG. Differences in Binding Sites of Two Melatonin Receptors Help to Explain Their Selectivity to Some Melatonin Analogs: A Molecular Modeling Study. J Biomol Struct Dyn 2006; 24:91-107. [PMID: 16928133 DOI: 10.1080/07391102.2006.10507103] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Numerous diseases have been linked to the malfunction of G-protein coupled receptors (GPCRs). Their adequate treatment requires rational design of new high-affinity and high-selectivity drugs targeting these receptors. In this work, we report three-dimensional models of the human MT(1) and MT(2) melatonin receptors, members of the GPCR family. The models are based on the X-ray structure of bovine rhodopsin. The computational approach employs an original procedure for optimization of receptor-ligand structures. It includes rotation of one of the transmembrane alpha-helices around its axis with simultaneous assessment of quality of the resulting complexes according to a number of criteria we have developed for this purpose. The optimal geometry of the receptor-ligand binding is selected based on the analysis of complementarity of hydrophobic/hydrophilic properties between the ligand and its protein environment in the binding site. The elaborated "optimized" models are employed to explore the details of protein-ligand interactions for melatonin and a number of its analogs with known affinity to MT(1) and MT(2) receptors. The models permit rationalization of experimental data, including those that were not used in model building. The perspectives opened by the constructed models and by the optimization procedure in the design of new drugs are discussed.
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Affiliation(s)
- Anton O Chugunov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ul. Miklukho-Maklaya 16/10, GSP Moscow, 117997, Russia.
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Tsotinis A, Vlachou M, Papahatjis DP, Calogeropoulou T, Nikas SP, Garratt PJ, Piccio V, Vonhoff S, Davidson K, Teh MT, Sugden D. Mapping the Melatonin Receptor. 7. Subtype Selective Ligands Based on β-SubstitutedN-Acyl-5-methoxytryptamines and β-SubstitutedN-Acyl-5-methoxy-1-methyltryptamines. J Med Chem 2006; 49:3509-19. [PMID: 16759094 DOI: 10.1021/jm0512544] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of beta-substituted and beta,beta-disubstituted N-acyl 5-methoxy-1-methyltryptamines and 5-methoxytryptamines have been prepared as melatonin analogues to investigate the nature of the binding site of the melatonin receptor. The affinity of analogues was determined in a radioligand binding assay using cloned human MT(1) and MT(2) receptor subtypes expressed in NIH 3T3 cells. Agonist and antagonist potency of all analogues was measured using the pigment aggregation response of a clonal line of Xenopus laevis melanophores. beta-Methylmelatonin (17a) and beta,beta-dimethylmelatonin (17b), though showing a slight decrease in binding at human receptors, show an increase in potency on Xenopus. N-Butanoyl 5-methoxy-1-methyl-beta,beta-trimethylenetryptamine (12c) is an antagonist at human MT(1) receptors but an agonist at MT(2), while N-butanoyl 5-methoxy-1-methyl-beta,beta-tetramethylenetryptamine (13c) is an antagonist at MT(1) but had no action at MT(2) and is one of the first examples of an MT(1) selective antagonist.
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Affiliation(s)
- Andrew Tsotinis
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Athens, Panepistimioupoli-Zografou, Athens 157 71, Greece.
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Abstract
Melatonin is a hormone exerting its multiple actions mainly through two G-protein-coupled receptors MT(1) and MT(2). Exploring the physiological role of each of these subtypes requires subtype selective MT(1) and MT(2) ligands. While several MT(2)-selective ligands were developed in the 1990s, no selective agonists and antagonists for the MT(1) subtype were described. The present article reviews mela toninergic ligands developed in the current millennium focusing on subtype selective agents and on drug candidates. Notable compounds are the MT(1)-selective agonists 35 and 134, MT(1)-selective antagonists 117 and 131, MT(2)-selective agonists 58, 70, 79, 97 and 125, MT(2)-selective antagonists 27, 73 and 119, and the highly potent non-selective agonist 120. The non-selective agonists agomelatine 2, and ramelteon 87 are drug candidates as antidepressive agent and for the treatment of insomnia and circadian rhythm disfunction, respectively.
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MESH Headings
- Animals
- Chemistry, Pharmaceutical/methods
- Chemistry, Pharmaceutical/trends
- Humans
- Ligands
- Molecular Structure
- Receptor, Melatonin, MT1/agonists
- Receptor, Melatonin, MT1/chemistry
- Receptor, Melatonin, MT1/physiology
- Receptor, Melatonin, MT2/agonists
- Receptor, Melatonin, MT2/chemistry
- Receptor, Melatonin, MT2/physiology
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Sugden D, Davidson K, Hough KA, Teh MT. Melatonin, melatonin receptors and melanophores: a moving story. ACTA ACUST UNITED AC 2005; 17:454-60. [PMID: 15357831 DOI: 10.1111/j.1600-0749.2004.00185.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Melatonin (5-methoxy N-acetyltryptamine) is a hormone synthesized and released from the pineal gland at night, which acts on specific high affinity G-protein coupled receptors to regulate various aspects of physiology and behaviour, including circadian and seasonal responses, and some retinal, cardiovascular and immunological functions. In amphibians, such as Xenopus laevis, another role of melatonin is in the control of skin coloration through an action on melanin-containing pigment granules (melanosomes) in melanophores. In these cells, very low concentrations of melatonin activate the Mel(1c) receptor subtype triggering movement of granules toward the cell centre thus lightening skin colour. Mel(1c) receptor activation reduces intracellular cAMP via a pertussis toxin-sensitive inhibitory G-protein (Gi), but how this and other intracellular signals regulate pigment movement is not yet fully understood. However, melanophores have proven an excellent model for the study of the molecular mechanisms which coordinate intracellular transport. Melanosome transport is reversible and involves both actin- (myosin V) and microtubule-dependent (kinesin II and dynein) motors. Melanosomes retain both kinesin and dynein during anterograde and retrograde transport, but the myosin V motor seems to be recruited to melanosomes during dispersion, where it assists kinesin II in dominating dynein thus driving net dispersion. Recent work suggests an important role for dynactin in coordinating the activity of the opposing microtubule motors. The melanophore pigment aggregation response has also played a vital role in the ongoing effort to devise specific melatonin receptor antagonists. Much of what has been learnt about the parts of the melatonin molecule required for receptor binding and activation has come from detailed structure-activity data using novel melatonin ligands. Work aiming to devise ligands specific for the distinct melatonin receptor subtypes stands poised to deliver selective agonists and antagonists which will be valuable tools in understanding the role of this enigmatic hormone in health and disease.
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Affiliation(s)
- David Sugden
- Division of Reproductive Health, Endocrinology and Development, School of Biomedical Sciences, New Hunts House, Kings College London, London Bridge, London SE1 1UL, UK.
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