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Ogunjirin AE, Fortunak JM, Brown LL, Xiao Y, Dávila-García MI. Competition, Selectivity and Efficacy of Analogs of A-84543 for Nicotinic Acetylcholine Receptors with Repositioning of Pyridine Nitrogen. Neurochem Res 2015; 40:2131-42. [PMID: 26508288 PMCID: PMC4741274 DOI: 10.1007/s11064-015-1705-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 08/13/2015] [Accepted: 08/18/2015] [Indexed: 01/17/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) play a crucial role in a number of clinically relevant mental and neurological pathways, as well as autonomic and immune functions. The development of subtype-selective ligands for nAChRs therefore is potentially useful for targeted therapeutic management of conditions where nAChRs are involved. We tested if selectivity for a particular nAChR subtype can be achieved through small structural modifications of a lead compound containing the nicotinic pharmacophore by changing the distance between the electronegative elements. For this purpose, analogs of A-84543 were designed, synthesized and characterized as potentially new nAChR subtype-selective ligands. Compounds were tested for their binding properties in rat cerebral cortical tissue homogenates, and subtype-selectivity was determined using stably transfected HEK cells expressing different nAChR subtypes. All compounds synthesized were found to competitively displace [(3)H]-epibatidine ([(3)H]EB) from the nAChR binding site. Of all the analogues, H-11MNH showed highest affinity for nAChRs compared to a ~ fivefold to tenfold lower affinity of A-84543. All other compounds had affinities >10,000 nM. Both A-84543 and H-11MNH have highest affinity for α2β2 and α4β2 nAChRs and show moderate affinity for β4- and α7-containing receptors. H-11MNH was found to be a full agonist with high potency at α3β4, while A-84543 is a partial agonist with low potency. Based on their unique pharmacological binding properties we suggest that A-84543 and its desmethylpyrrolidine analog can be useful as pharmacological ligands for studying nAChRs if selective pharmacological and/or genetic tools are used to mask the function of other receptors subtypes.
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Affiliation(s)
- Adebowale E Ogunjirin
- Department of Pharmaceutical Sciences, Howard University, Washington, DC, 20059, USA
| | - Joseph M Fortunak
- Department of Pharmaceutical Sciences, Howard University, Washington, DC, 20059, USA
- Department of Chemistry, Howard University, Washington, DC, 20059, USA
| | - LaVerne L Brown
- Department of Pharmaceutical Sciences, Howard University, Washington, DC, 20059, USA
| | - Yingxian Xiao
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, 20057, USA
| | - Martha I Dávila-García
- Department of Pharmacology, Howard University College of Medicine, Washington, DC, 20059, USA.
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2
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Tamborini L, Pinto A, Ettari R, Gotti C, Fasoli F, Conti P, De Micheli C. Synthesis and Pharmacological Evaluation of α4β2 Nicotinic Ligands with a 3-Fluoropyrrolidine Nucleus. ChemMedChem 2015; 10:1071-8. [PMID: 25882435 DOI: 10.1002/cmdc.201500073] [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: 02/17/2015] [Revised: 03/10/2015] [Indexed: 11/09/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) play an important role in many central nervous system disorders such as Alzheimer's and Parkinson's diseases, schizophrenia, and mood disorders. The α(4)β(2) subtype has emerged as an important target for the early diagnosis and amelioration of Alzheimer's disease symptoms. Herein we report a new class of α(4)β(2) receptor ligands characterized by a basic pyrrolidine nucleus, the basicity of which was properly decreased through the insertion of a fluorine atom at the 3-position, and a pyridine ring carrying at the 3-position substituents known to positively affect affinity and selectivity toward the α(4)β(2) subtype. Derivatives 3-(((2S,4R)-4-fluoropyrrolidin-2-yl)methoxy)-5-(phenylethynyl)pyridine (11) and 3-((4-fluorophenyl)ethynyl)-5-(((2S,4R)-4-fluoropyrrolidin-2-yl)methoxy)pyridine (12) were found to be the most promising ligands identified in this study, showing good affinity and selectivity for the α(4)β(2) subtype and physicochemical properties predictive of a relevant central nervous system penetration.
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Affiliation(s)
- Lucia Tamborini
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli 25, 20133 Milano (Italy)
| | - Andrea Pinto
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli 25, 20133 Milano (Italy).
| | - Roberta Ettari
- Dipartimento di Scienze del Farmaco e Prodotti per la Salute, Università degli Studi di Messina, Viale Annunziata 98168, Messina (Italy)
| | - Cecilia Gotti
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, CNR, Istituto di Neuroscienze, Università degli Studi di Milano, Via Vanvitelli 32, 20129 Milan (Italy)
| | - Francesca Fasoli
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, CNR, Istituto di Neuroscienze, Università degli Studi di Milano, Via Vanvitelli 32, 20129 Milan (Italy)
| | - Paola Conti
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli 25, 20133 Milano (Italy)
| | - Carlo De Micheli
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli 25, 20133 Milano (Italy)
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3
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Pandey SK, Pan S, Kant R, Kuruvilla SA, Pan ML, Mukherjee J. Synthesis and evaluation of 3-¹²³I-iodo-5-[2-(S)-3-pyrrolinylmethoxy]-pyridine (niodene) as a potential nicotinic α4β2 receptor imaging agent. Bioorg Med Chem Lett 2012; 22:7610-4. [PMID: 23116890 DOI: 10.1016/j.bmcl.2012.10.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 09/27/2012] [Accepted: 10/01/2012] [Indexed: 11/27/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are downregulated in disease conditions such as Alzheimer's and substance abuse. Presently, (123)I-5-IA-85380 is used in human studies and requires over 6h of scanning time, thus increases patient discomfort. We have designed and synthesized 3-iodo-5-[2-(S)-3-pyrrolinylmethoxy]pyridine (niodene) with the aim to have faster binding kinetics compared to (123)I-5-IA-85380, which may reduce scanning time and help in imaging studies. Binding affinity K(i) of niodene for rat brain α4β2 receptors in brain homogenate assays using (3)H-cytisine was 0.27 nM. Niodene, 10nM displaced >95% of (18)F-nifene bound to α4β2 receptors in rat brain slices. By using the iododestannylation method, (123)I-niodene was obtained in high radiochemical purity (>95%) but with low radiochemical yield (<5%) and low specific activity (∼100 Ci/mmol). Autoradiograms show (123)I-niodene localized in the thalamus and cortex, which was displaced by nicotine (thalamus to cerebellum ratio=4; cortex to cerebellum ratio=1.6). Methods of radioiodination need to be further evaluated in order to obtain (123)I-niodene in higher radiochemical yields and higher specific activity of this potentially useful new SPECT imaging agent.
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Affiliation(s)
- Suresh K Pandey
- Preclinical Imaging, B140 Medical Sciences, Department of Radiological Sciences, University of California - Irvine, Irvine, CA 92697, United States
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4
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Amartey JK, Esguerra C. A facile method for post-conjugation prosthetic radioiodination of “mini-peptides”. Appl Radiat Isot 2006; 64:1549-54. [PMID: 16300955 DOI: 10.1016/j.apradiso.2005.09.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2005] [Revised: 09/13/2005] [Accepted: 09/14/2005] [Indexed: 11/27/2022]
Abstract
Prosthetic radioiodination methods were developed to facilitate the labeling of proteins devoid of tyrosine(s) or when these moieties are crucial for biological activity. This method involves the use of the so-called Bolton-Hunter-type reagents. However, the in vivo instability of the label prompted the search for more stable groups. Although these second generation reagents have worked well with proteins and peptides, the current reaction scheme takes a long time to perform. A simplified method may be more appropriate especially from radiation safety point of view. More importantly, for short-lived halogens, advantage may be gained utilizing a shorter reaction time. Recently we reported on the radioiodination of interleukin-8 (IL-8) using the pyridine carboxylate-derived activated ester. We have successfully conjugated this prosthetic group to tri- and tetrapeptides harboring the somatostatin (SST) receptor recognition units and characterized by HPLC and MS. The radioiodination was accomplished using the Iodogen method in a reasonable yield (mean=60%). The total synthesis time was approximately 60 min, which was 3-4 times shorter than the classical two-step method. Preliminary biodistribution of the radiolabeled peptide showed uptake in some of the organs known to express SST receptors. Injection of a low specific activity tracer significantly decreased the retention of radioactivity in these organs.
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Affiliation(s)
- J K Amartey
- Cyclotron and Radiopharmaceuticals Department, King Faisal Specialist Hospital and Research Centre, MBC-03, P.O. Box 3354, Riyadh 11211, Kingdom of Saudi Arabia.
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Baldwin RM, Zoghbi SS, Staley JK, Brenner E, Al-Tikriti MS, Amici L, Fujita M, Innis RB, Tamagnan G. Chemical fate of the nicotinic acetylcholinergic radiotracer [123I]5-IA-85380 in baboon brain and plasma. Nucl Med Biol 2006; 33:549-54. [PMID: 16720248 DOI: 10.1016/j.nucmedbio.2006.03.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Revised: 02/21/2006] [Accepted: 03/06/2006] [Indexed: 11/26/2022]
Abstract
The fate of the nicotinic acetylcholinergic receptor radiotracer [123I]5-IA-85380 ([123I]5-IA) was studied in baboon by analyzing the chemical composition of brain tissue and plasma after intravenous administration of the tracer. Acetonitrile denaturation and high-performance liquid chromatography (HPLC) analysis showed predominantly unchanged (91-98%) parent tracer in all brain tissues examined, compared to significant metabolism (23% parent) in the plasma at 90 min postinjection, and control tissue recovery of 95-98%. [123I]5-IA was distributed to the thalamus with a standardized uptake value of 9.2 (0.04% dose/g) or a concentration 5.8 times higher than that of the cerebellum. The HPLC behavior of a synthesized sample of one hypothesized metabolite, 5-iodo-3-pyridinol (5-IP), was consistent with plasma radiometabolite fraction. Since only parent radiotracer compound was found in brain tissue, these results add confidence that information derived from single photon emission computed tomography images of 123I activity in the brain after [123I]5-IA administration can be interpreted as distribution of an intact radiotracer.
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Affiliation(s)
- Ronald M Baldwin
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06510, USA.
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6
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Daly JW. Nicotinic Agonists, Antagonists, and Modulators From Natural Sources. Cell Mol Neurobiol 2005; 25:513-52. [PMID: 16075378 DOI: 10.1007/s10571-005-3968-4] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Accepted: 04/14/2004] [Indexed: 10/25/2022]
Abstract
1. Acetylcholine receptors were initially defined as nicotinic or muscarinic, based on selective activation by two natural products, nicotine and muscarine. Several further nicotinic agonists have been discovered from natural sources, including cytisine, anatoxin, ferruginine, anabaseine, epibatidine, and epiquinamide. These have provided lead structures for the design of a wide range of synthetic agents. 2. Natural sources have also provided competitive nicotinic antagonists, such as the Erythrina alkaloids, the tubocurarines, and methyllycaconitine. Noncompetitive antagonists, such as the histrionicotoxins, various izidines, decahydroquinolines, spiropyrrolizidine oximes, pseudophrynamines, ibogaine, strychnine, cocaine, and sparteine have come from natural sources. Finally, galanthamine, codeine, and ivermectin represent positive modulators of nicotinic function, derived from natural sources. 3. Clearly, research on acetylcholine receptors and functions has been dependent on key natural products and the synthetic agents that they inspired.
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Affiliation(s)
- John W Daly
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892, USA.
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Henderson DJ, Eberl S, Thomson S, Smith A, Allan RD, Fulham MJ, Loiacono R, Kassiou M. 3-Pyridyl ethers as SPECT radioligands for imaging nicotinic acetylcholine receptors. Appl Radiat Isot 2004; 60:669-76. [PMID: 15082045 DOI: 10.1016/j.apradiso.2004.01.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Revised: 01/05/2004] [Accepted: 01/06/2004] [Indexed: 10/26/2022]
Abstract
To develop a suitable single photon emission computed tomography (SPECT) radioligand for neuronal nicotinic acetylcholine receptors (nAChRs) that displays faster in vivo kinetics than 5-[123I]iodo-A-85380, we synthesised the radioiodinated analogue of A-84543. 5-[123I]Iodo-A-84543 was prepared by electrophilic iododestannylation in a modest yield of 23%. In the baboon brain, 5-[123I]iodo-A-85380 displayed a profile consistent with the known distribution of nAChRs, however, 5-[123I]iodo-A-84543 displayed a homogenous uptake with no preferential localisation in regions known to contain nAChRs. To examine the effect of halogen substitution on the 3-pyridyl ether, A-84543, the 5-chloro, 5-bromo and 5-iodo analogues were synthesised and evaluated with respect to nAChR binding. In vitro binding data revealed that halogen substitution at the 5-position of A-84543 was not well tolerated with an increase in halogen size resulting in lower binding towards nAChRs. The 5-chloro analogue 4 displayed highest affinity, Ki =1.3 nM, compared to the 5-bromo and 5-iodo compounds, 5 Ki =3.3 nM and 3 Ki =40.8 nM, respectively. Taken together, these results clearly indicate that 5-[123I]iodo-A-84543 is not suitable for the study of nAChRs in vivo using SPECT.
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Affiliation(s)
- D J Henderson
- Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW, Sydney 2050, Australia
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8
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Romanelli MN, Gualtieri F. Cholinergic nicotinic receptors: competitive ligands, allosteric modulators, and their potential applications. Med Res Rev 2003; 23:393-426. [PMID: 12710018 DOI: 10.1002/med.10037] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Discovery of the important role played by nicotinic acetylcholine receptors (nAChRs) in several CNS disorders has called attention to these membrane proteins and to ligands able to modulate their functions. The existence of different subtypes at multiple levels has complicated the understanding of this receptor's physiological role, but at the same time has increased the efforts to discover selective compounds in order to improve the pharmacological characterization of this kind of receptor and to make the possible therapeutical use of its modulators safer. This review focuses on the structure of new ligands for nAChRs, agonists, antagonists and allosteric modulators, and on their possible applications.
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Affiliation(s)
- M Novella Romanelli
- Dipartimento di Scienze Farmaceutiche, Università di Firenze, via Gino Capponi 9, 50121 Firenze, Italy.
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Dumont F, Sultana A, Balter A, Waterhouse RN. Synthesis of [18F]3-[1-(3-fluoropropyl)-(S)-pyrrolidin-2-ylmethoxy]pyridine ([18F]NicFP): a potential?4?2 nicotinic acetylcholine receptor radioligand for PET. J Labelled Comp Radiopharm 2003. [DOI: 10.1002/jlcr.785] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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