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Cacciari B, Bolcato C, Spalluto G, Klotz KN, Bacilieri M, Deflorian F, Moro S. Pyrazolo-triazolo-pyrimidines as adenosine receptor antagonists: A complete structure-activity profile. Purinergic Signal 2007; 3:183-93. [PMID: 18404432 PMCID: PMC2096643 DOI: 10.1007/s11302-006-9027-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Revised: 09/05/2006] [Accepted: 09/07/2006] [Indexed: 12/31/2022] Open
Abstract
In the last 5 years, many efforts have been conducted searching potent and selective human A(3) adenosine antagonists. In this field several different classes of compounds, possessing very good affinity (nM range) and with a broad range of selectivity, have been proposed. Recently, our group synthesized a new series of pyrazolo-triazolo-pyrimidines bearing different substitutions at the N(5) and N(8) positions, which have been described as highly potent and selective human A(3) adenosine receptor antagonists. The present review summarizes available data and provides an overview of the structure-activity relationships found for this class of human A(3) adenosine receptor antagonists.
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Affiliation(s)
- Barbara Cacciari
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Ferrara, Via Fossato di Mortara 17–19, 44100 Ferrara, Italy
| | - Chiara Bolcato
- Dipartimento di Scienze Farmaceutiche, Università di Trieste, Piazzale Europa 1, 34127 Trieste, Italy
| | - Giampiero Spalluto
- Dipartimento di Scienze Farmaceutiche, Università di Trieste, Piazzale Europa 1, 34127 Trieste, Italy
| | - Karl-Norbet Klotz
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, 97078 Würzburg, Germany
| | - Magdalena Bacilieri
- Molecular Modeling Section, Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Francesca Deflorian
- Molecular Modeling Section, Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Stefano Moro
- Molecular Modeling Section, Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
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Desai ND. Synthesis and interconversion of isomeric pyrrolotriazolopyrimidines. HETEROATOM CHEMISTRY 2007. [DOI: 10.1002/hc.20295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Kim SK, Gao ZG, Jeong LS, Jacobson KA. Docking studies of agonists and antagonists suggest an activation pathway of the A3 adenosine receptor. J Mol Graph Model 2006; 25:562-77. [PMID: 16793299 PMCID: PMC6262875 DOI: 10.1016/j.jmgm.2006.05.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 05/03/2006] [Accepted: 05/03/2006] [Indexed: 10/24/2022]
Abstract
Structural determinants of ligand efficacy in the human A(3) adenosine receptor (AR) were studied using pharmacophore and docking analyses of various categories of A(3) selective ligands: inverse agonist, neutral antagonist (nonnucleoside and nucleoside), and agonist (partial and full). The homology modeling of GPCRs was adapted to provide two templates: the rhodopsin-based resting state for antagonist binding and a putative Meta I state, conformationally altered at a key residue (W6.48), for agonist binding. The preferential binding domains and/or local conformational changes associated with docking of three high affinity A(3)AR ligands were compared: inverse agonist PSB-11 1 ((R)-8-ethyl-4-methyl-2-phenyl-imidazo[2,1-i]purin-5-one); neutral antagonist MRE-3008F20 7 (5-[[(4-methoxyphenyl)amino]carbonyl]amino-8-methyl-2-(2-furyl)pyra-zolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine), and full agonist Cl-IB-MECA 21 (2-chloro-N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine) to define a distinct recognition mode for each. Ribose-containing agonists were more hydrophilic than nonnucleoside antagonists, and H-bonding ability at the ribose 3'- and 5'-positions was required for agonism. From the receptor perspective, common requirements for activation included the destabilization of H-bond networks at W6.48 and H7.43, the specific interactions of the ribose moiety in its putative hydrophilic pocket at T3.36, S7.42, and H7.43, the stabilization of the complex by inward movement of F5.43, and the characteristic rotation of W6.48. By analogy, outward rotation of the W6.48 side-chain upon activation of an internally-crosslinking mutant M(3) muscarinic receptor was indicated by constrained molecular dynamics (MD). Our results are consistent with an anti-clockwise rotation (from the extracellular view) of transmembrane domains 3, 5, 6, and 7, as proposed for other Family A GPCRs. Thus, the putative conformational changes associated with A(3)AR activation indicate a shared mechanism of GPCR activation similar to rhodopsin.
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Affiliation(s)
- Soo-Kyung Kim
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Lak Shin Jeong
- Laboratory of Medicinal Chemistry, College of Pharmacy, Ewha Womans University, Seoul 120-750, South Korea
| | - Kenneth A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA
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Biagi G, Bianucci AM, Coi A, Costa B, Fabbrini L, Giorgi I, Livi O, Micco I, Pacchini F, Santini E, Leonardi M, Nofal FA, Salerni OL, Scartoni V. 2,9-disubstituted-N6-(arylcarbamoyl)-8-azaadenines as new selective A3 adenosine receptor antagonists: synthesis, biochemical and molecular modelling studies. Bioorg Med Chem 2005; 13:4679-93. [PMID: 15908217 DOI: 10.1016/j.bmc.2005.04.063] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Revised: 04/22/2005] [Accepted: 04/22/2005] [Indexed: 11/19/2022]
Abstract
A number of N6-(N-arylcarbamoyl)-2-substituted-9-benzyl-8-azaadenines, obtained by a modification of the synthetic scheme used to prepare selective A1 ligands, by only three or two steps, are described. At first we prepared a series of 2-phenyl-9-benzyl-8-azaadenines having as N6 substituent a variously substituted N-phenylcarbamoyl group. Some of these derivatives demonstrated good affinity towards the A3 subtype but low selectivity. Compounds having p-CF3, p-F and p-OCH3, as substituents on the phenylcarbamoyl group were selected as lead compounds for the second part of this study. Without modifying the N6 substituent, which would assure A3 affinity, we varied the 9 and 2 positions on these molecules to enhance selectivity. Some compounds having a p-methyl group on the 2-phenyl substituent showed a very good affinity and selectivity for the A3 subtype, revealing the first class of A3 adenosine receptor selective antagonists with a bicyclic structure strictly correlated to the adenine nucleus. The molecular modelling work, carried out using the DOCK program, supplied two models which may be useful for a better understanding of the binding modes. Both models highlighted the preferred interacting tautomeric forms of the antagonists for human A1 and A3 receptors.
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Affiliation(s)
- Giuliana Biagi
- Dipartimento di Scienze Farmaceutiche, Università di Pisa, via Bonanno 6, 56126 Pisa, Italy
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New heterocyclic ligands for the adenosine receptors P1 and for the ATP receptors P2. ACTA ACUST UNITED AC 2005; 60:185-202. [PMID: 15784237 DOI: 10.1016/j.farmac.2004.09.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2004] [Revised: 07/08/2004] [Accepted: 09/15/2004] [Indexed: 11/26/2022]
Abstract
Extracellular adenosine and adenine nucleotides induce various cellular responses through activation of P1 and P2 receptors. P1 receptors preferentially recognize adenosine and four different G protein-coupled receptors (A(1), A(2A), A(2B), and A(3) subtypes) have been identified. On the other hand, P2 receptors are activated by adenine and/or uridine nucleotides and classified into two families: ionotropic P2X and G protein-coupled P2Y receptors. In this article, we summarize our studies which led to development of new potent and selective heterocyclic ligands for the adenosine receptors P1 and for the ATP receptors P2X(7).
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Okamura T, Kurogi Y, Hashimoto K, Nishikawa H, Nagao Y. Facile synthesis of fused 1,2,4-triazolo[1,5-c]pyrimidine derivatives as human adenosine A3 receptor ligands. Bioorg Med Chem Lett 2004; 14:2443-6. [PMID: 15109629 DOI: 10.1016/j.bmcl.2004.03.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Revised: 03/03/2004] [Accepted: 03/04/2004] [Indexed: 10/26/2022]
Abstract
A facile synthetic method for fused triazolopyrimidine derivatives having high affinity and selectivity for human adenosine A(3) receptors is reported. The fused triazolopyrimidine derivatives were easily prepared by one-pot reaction using acylhydrazines and imidates prepared from amine derivatives bearing cyano group and orthoesters in situ. This synthetic method was useful in finding new tricyclic adenosine A(3) receptor antagonists and also in diversifying the substituents at two positions on the fused triazolopyrimidine ring.
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Affiliation(s)
- Takashi Okamura
- Pharmaceutical Technology Institute, Otsuka Pharmaceutical Factory, Inc. Tateiwa, Muya-cho, Naruto, Tokushima 772-8601, Japan.
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Gessi S, Varani K, Merighi S, Cattabriga E, Avitabile A, Gavioli R, Fortini C, Leung E, Mac Lennan S, Borea PA. Expression of A3 adenosine receptors in human lymphocytes: up-regulation in T cell activation. Mol Pharmacol 2004; 65:711-9. [PMID: 14978250 DOI: 10.1124/mol.65.3.711] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study investigates mRNA and protein levels of A3 adenosine receptors in resting (R) and activated (A) human lymphocytes. The receptors were evaluated by the antagonist radioligand [3H]5-N-(4-methoxyphenyl-carbamoyl)amino-8-propyl-2(2furyl)-pyrazolo-[4,3e]-1,2,4-triazolo-[1,5-c]-pyrimidine ([3H]MRE 3008F20), which yielded Bmax values of 125 +/- 15 and 225 +/- 23 fmol/mg of protein and KD values of 1.79 +/- 0.30 and 1.85 +/- 0.25 nM in R and A cells, respectively. The protein seems to be induced with remarkable rapidity starting at 15 min and reaches a plateau at 30 min. Western blot assays revealed that the up-regulation of the A3 subtype after lymphocyte activation was caused by an increase in an enriched CD4+ cell fraction. Real-time reverse transcription-polymerase chain reaction experiments confirmed the rapid increase of A3 mRNA after T cell activation. Competition of radioligand binding by adenosine ligands displayed a rank order of potency typical of the A3 subtype. Thermodynamic data indicated that the binding is enthalpy- and entropy-driven in both R and A cells, suggesting that the activation process does not involve, at a molecular level, receptor alterations leading to modifications in the A3-related binding mechanisms. Functionally, the up-regulation of A3 adenosine receptors in A versus R cells corresponded to a potency increase of the A3 agonist N6-(3-iodo-benzyl)-2-chloro-adenosine-5'-N-methyluronamide in inhibiting cAMP accumulation (IC50=1.5 +/- 0.4 and 2.7 +/- 0.3 nM, respectively); this effect was antagonized by MRE 3008F20 (IC50=5.0 +/- 0.3 nM). In conclusion, our results provide, for the first time, an in-depth investigation of A3 receptors in human lymphocytes and demonstrate that, under activating conditions, they are up-regulated and may contribute to the effects triggered by adenosine.
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Affiliation(s)
- Stefania Gessi
- Department of Clinical and Experimental Medicine, Pharmacology Unit, University of Ferrara, Ferrara, Italy
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Klotz KN, Kachler S, Lambertucci C, Vittori S, Volpini R, Cristalli G. 9-Ethyladenine derivatives as adenosine receptor antagonists: 2- and 8-substitution results in distinct selectivities. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2003; 367:629-34. [PMID: 12734636 DOI: 10.1007/s00210-003-0749-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2002] [Accepted: 03/21/2003] [Indexed: 10/25/2022]
Abstract
9-Ethyladenine was used as the basis for a series of non-xanthine adenosine receptor antagonists at human adenosine receptors. The adenine-based compounds were substituted in 2- or 8-position with a variety of side chains including some aryl or arylalkynyl groups previously tested as 2-substituents in adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) for their effect on agonist affinity. The affinity of the novel compounds was tested in radioligand binding assays (A1, A2A and A3) and inhibition of NECA-stimulated adenylyl cyclase activity (A2B) in membranes prepared from CHO cells stably transfected with the respective human receptor subtype. High affinity antagonists were identified for A1 (9-ethyl-8-phenyl-9H-adenine, compound 2; 6-(1-butylamino)-9-ethyl-8-phenyl-9H-purine, compound 3), A2A (8-ethoxy-9-ethyladenine; compound 8) and A3 (9-ethyl-8-phenylethynyl-9H-adenine, compound 5) with selectivities versus other receptor subtypes in the range of 10 to 600. These results demonstrate that adenine is a useful template for further development of high-affinity antagonists with distinct receptor selectivity profiles.
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Affiliation(s)
- Karl-Norbert Klotz
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany.
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Baraldi PG, Tabrizi MA, Fruttarolo F, Bovero A, Avitabile B, Preti D, Romagnoli R, Merighi S, Gessi S, Varani K, Borea PA. Recent developments in the field of A3 adenosine receptor antagonists. Drug Dev Res 2003. [DOI: 10.1002/ddr.10167] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Baraldi PG, Tabrizi MA, Bovero A, Avitabile B, Preti D, Fruttarolo F, Romagnoli R, Varani K, Borea PA. Recent developments in the field of A2A and A3 adenosine receptor antagonists. Eur J Med Chem 2003; 38:367-82. [PMID: 12750024 DOI: 10.1016/s0223-5234(03)00042-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In the last years adenosine receptors have been extensively studied, and mainly at present we understand the importance of A(2A) and A(3) adenosine receptors. A(2A) selective adenosine receptors antagonists are promising new drugs for the treatment of Parkinson's disease, while A(3) selective adenosine receptors antagonists have been postulated as novel anti-inflammatory and antiallergic agents; recent studies also indicated a possible employment of these derivatives as antitumour agents. Lately different classes of compounds have been identified as potent A(2A) and A(3) antagonists. In this article we report the past and present efforts which led to development of more potent and selective A(2A) and A(3) antagonists. Our group has mainly worked on the pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine nucleus both as A(2A) and A(3) antagonists, aiming to improve the affinity, selectivity and the hydrophilic profile. In fact, we have synthesised several compounds endowed with high affinity and selectivity versus A(2A) adenosine receptors, as 2, 2a-c (K(i)A(2A)=0.12-0.19 nM), or A(3) adenosine receptors, as 4p (K(i)A(3)=0.01 nM) and 4q (K(i)A(3)=0.04 nM).
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Affiliation(s)
- Pier Giovanni Baraldi
- Dipartimento di Scienze Farmaceutiche, Università di Ferrara, Via fossato di Mortara 17-19, 44100, Ferrara, Italy.
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