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Nicotinic Acetylcholine Receptors and Microglia as Therapeutic and Imaging Targets in Alzheimer's Disease. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27092780. [PMID: 35566132 PMCID: PMC9102429 DOI: 10.3390/molecules27092780] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 04/21/2022] [Accepted: 04/25/2022] [Indexed: 12/12/2022]
Abstract
Amyloid-β (Aβ) accumulation and tauopathy are considered the pathological hallmarks of Alzheimer’s disease (AD), but attenuation in choline signaling, including decreased nicotinic acetylcholine receptors (nAChRs), is evident in the early phase of AD. Currently, there are no drugs that can suppress the progression of AD due to a limited understanding of AD pathophysiology. For this, diagnostic methods that can assess disease progression non-invasively before the onset of AD symptoms are essential, and it would be valuable to incorporate the concept of neurotheranostics, which simultaneously enables diagnosis and treatment. The neuroprotective pathways activated by nAChRs are attractive targets as these receptors may regulate microglial-mediated neuroinflammation. Microglia exhibit both pro- and anti-inflammatory functions that could be modulated to mitigate AD pathogenesis. Currently, single-cell analysis is identifying microglial subpopulations that may have specific functions in different stages of AD pathologies. Thus, the ability to image nAChRs and microglia in AD according to the stage of the disease in the living brain may lead to the development of new diagnostic and therapeutic methods. In this review, we summarize and discuss the recent findings on the nAChRs and microglia, as well as their methods for live imaging in the context of diagnosis, prophylaxis, and therapy for AD.
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Mori D, Kimura H, Kawashima H, Yagi Y, Arimitsu K, Ono M, Saji H. Development of 99mTc radiolabeled A85380 derivatives targeting cerebral nicotinic acetylcholine receptor: Novel radiopharmaceutical ligand 99mTc-A-YN-IDA-C4. Bioorg Med Chem 2019; 27:4200-4210. [PMID: 31401009 DOI: 10.1016/j.bmc.2019.07.053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 07/25/2019] [Accepted: 07/30/2019] [Indexed: 01/22/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels that have been implicated in higher brain functions. To elucidate the functional mechanisms underlying nAChRs and contribute significantly to development of drugs targeting neurological and neuropsychiatric diseases, non-invasive nuclear medical imaging can be used for evaluation. In addition, technetium-99m (99mTc) is a versatile radionuclide used clinically as a tracer in single-photon emission computed tomography. Because A85380 is known as a potent α4β2-nAChR agonist, we prepared A85380 derivatives labeled with 99mTc using a bifunctional chelate system. A computational scientific approach was used to design the probe efficiently. We used non-radioactive rhenium (Re) for a 99mTc analog and found that one of the derivatives, Re-A-YN-IDA-C4, exhibited high binding affinity at α4β2-nAChR in both the docking simulation (-19.3 kcal/mol) and binding assay (Ki = 0.4 ± 0.04 nM). Further, 99mTc-A-YN-IDA-C4 was synthesized using microwaves, and its properties were examined. Consequently, we found that 99mTc-A-YN-IDA-C4, with a structure optimized by using computational chemistry techniques, maintained affinity and selectivity for nAChR in vitro and possessed efficient characteristics as a nuclear medicine molecular imaging probe, demonstrated usefulness of computational scientific approach for molecular improvement strategy.
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Affiliation(s)
- Daisuke Mori
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Hiroyuki Kimura
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan; Department of Analytical and Bioinorganic Chemistry, Kyoto Pharmaceutical University, Kyoto, Japan.
| | - Hidekazu Kawashima
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan; Radioisotope Research Center, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Yusuke Yagi
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan; Department of Analytical and Bioinorganic Chemistry, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Kenji Arimitsu
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan; Department of Analytical and Bioinorganic Chemistry, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Masahiro Ono
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Hideo Saji
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
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Synthesis and biological evaluation of Tc-99m-cyclopentadienyltricarbonyl-technetium-labeled A-85380: An imaging probe for single-photon emission computed tomography investigation of nicotinic acetylcholine receptors in the brain. Bioorg Med Chem 2019; 27:2245-2252. [PMID: 31047775 DOI: 10.1016/j.bmc.2019.04.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 04/23/2019] [Accepted: 04/25/2019] [Indexed: 10/27/2022]
Abstract
We have designed (S)-(5-(azetidin-2-ylmethoxy)pyridine-3-yl)methyl cyclopentadienyltricarbonyl technetium carboxylate ([99mTc]CPTT-A-E) with high affinity for nicotinic acetylcholine receptors (nAChRs) using (2(S)-azetidinylmethoxy)-pyridine (A-85380) as the lead compound to develop a Tc-99m-cyclopentadienyltricarbonyl-technetium (99mTc)-labeled nAChR imaging probe. Because technetium does not contain a stable isotope, cyclopentadienyltricarbonyl rhenium (CPTR) was synthesized by coordinating rhenium, which is a homologous element having the same coordination structure as technetium. Further, the binding affinity to nAChR was evaluated. CPTR-A-E exhibited a high binding affinity to nAChR (Ki = 0.55 nM). Through the radiosynthesis of [99mTc]CPTT-A-E, an objective compound could be obtained with a radiochemical yield of 33% and a radiochemical purity of greater than 97%. In vitro autoradiographic study of the brain exhibited that the local nAChR density strongly correlated with the amount of [99mTc]CPTT-A-E that was accumulated in each region of interest. Further, the in vivo evaluation of biodistribution revealed a higher accumulation of [99mTc]CPTT-A-E in the thalamus (characterized by the high nAChR density) when compared with that in the cerebellum (characterized by the low nAChR density). Although additional studies will be necessary to improve the uptake of [99mTc]CPTT-A-E to the brain, [99mTc]CPTT-A-E met the basic requirements for nAChR imaging.
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Molecular Imaging of the Cholinergic System in Parkinson's Disease. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2018; 141:211-250. [PMID: 30314597 DOI: 10.1016/bs.irn.2018.07.027] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
One of the first identified neurotransmitters in the brain, acetylcholine, is an important modulator that drives changes in neuronal and glial activity. For more than two decades, the main focus of molecular imaging of the cholinergic system in Parkinson's disease (PD) has been on cognitive changes. Imaging studies have confirmed that degeneration of the cholinergic system is a major determinant of dementia in PD. Within the last decade, the focus is expanding to studying cholinergic correlates of mobility impairments, dyskinesias, olfaction, sleep, visual hallucinations and risk taking behavior in this disorder. These studies increasingly recognize that the regional topography of cholinergic brain areas associates with specific functions. In parallel with this trend, more recent molecular cholinergic imaging approaches are investigating cholinergic modulatory functions and contributions to large-scale brain network functions. A novel area of research is imaging cholinergic innervation functions of peripheral autonomic organs that may have the potential of future prodromal diagnosis of PD. Finally, emerging evidence of hypercholinergic activity in prodromal and symptomatic leucine-rich repeat kinase 2 PD may reflect neuronal cholinergic compensation versus a response to neuro-inflammation. Molecular imaging of the cholinergic system has led to many new insights in the etiology of dopamine non-responsive symptoms of PD (more "malignant" hypocholinergic disease phenotype) and is poised to guide and evaluate future cholinergic drug development in this disorder.
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Abstract
In vivo molecular imaging is a powerful tool to analyze the human body. Precision medicine is receiving high attention these days, and molecular imaging plays an important role as companion diagnostics in precision medicine. Nuclear imaging with PET or SPECT and optical imaging technologies are used for in vivo molecular imaging. Nuclear imaging is superior for quantitative imaging, and whole-body analysis is possible even for humans. Optical imaging is superior due to its ease of use, and highly targeted specific imaging is possible with activatable agents. However, with optical imaging using fluorescence, it is difficult to obtain a signal from deep tissue and quantitation is difficult due to the attenuation and scattering of the fluorescent signal. Recently, to overcome these issues, optoacoustic imaging has been used in in vivo imaging. In this article, we review in vivo molecular imaging with nuclear and optical imaging and discuss their utility for precision medicine.
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Affiliation(s)
- Mikako Ogawa
- Laboratory for Bioanalysis and Molecular Imaging, Graduate School of Pharmaceutical Sciences, Hokkaido University.,JST, PRESTO
| | - Hideo Takakura
- Laboratory for Bioanalysis and Molecular Imaging, Graduate School of Pharmaceutical Sciences, Hokkaido University
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6
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Matsuura Y, Ueda M, Higaki Y, Sano K, Saji H, Enomoto S. Evaluation of the Relationship Between Cognitive Impairment, Glycometabolism, and Nicotinic Acetylcholine Receptor Deficits in a Mouse Model of Alzheimer’s Disease. Mol Imaging Biol 2018; 21:519-528. [DOI: 10.1007/s11307-018-1253-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Affiliation(s)
- Hideo Saji
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University
- Kyoto University Research Administration Office
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8
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Harada N, Kimura H, Onoe S, Watanabe H, Matsuoka D, Arimitsu K, Ono M, Saji H. Synthesis and Biologic Evaluation of Novel 18F-Labeled Probes Targeting Prostate-Specific Membrane Antigen for PET of Prostate Cancer. J Nucl Med 2016; 57:1978-1984. [PMID: 27417647 DOI: 10.2967/jnumed.116.175810] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 06/17/2016] [Indexed: 12/11/2022] Open
Abstract
Prostate-specific membrane antigen (PSMA) is a membrane protein highly expressed on prostate cancer cells and a potential imaging target for diagnosis. 18F-DCFPyL has been recently developed as an effective probe with high diagnostic accuracy for prostate cancer imaging. However, its radiochemical yield is low. We developed new PSMA probes using succinimidyl 4-18F-fluorobenzoate (18F-SFB), a rapid and effective 18F-labeling agent, taking advantage of the high radiochemical yield of this compound. We evaluated the probes as PET probes for PSMA imaging. METHODS Four 18F-labeled probes, 18F-8a, 18F-8b, 18F-10a, and 18F-10b, were synthesized using 18F-SFB, and their affinity for PSMA and partition coefficients (log D) were evaluated in vitro. Biodistribution studies were performed in human prostate cancer xenograft-bearing mice. PET images were obtained using 2 compounds, 18F-8a and 18F-10a, and a toxicologic study of 18F-10a was performed. RESULTS Four 18F-labeled asymmetric urea compounds, conjugated with 18F-SFB, were synthesized at a radiochemical yield of 30%-50% (decay-corrected), with a radiochemical purity greater than 95%. The radiochemical yield was 10-15 times higher than that of 18F-DCFPyL, the probe currently used in clinical studies. All 4 compounds showed high affinity for PSMA. 18F-8a and 18F-10a had a particularly high binding affinity (Ki values of 3.35 and 2.23 nM, respectively). In the biodistribution study, the accumulation of 18F-8a (13.3 ± 2.2 percentage injected dose per gram [%ID/g]) and 18F-10a (14.0 ± 3.1 %ID/g) in PSMA-positive human prostate (LNCaP) tumors was higher than that of the other 2 compounds and similar to that of 18F-DCFPyL (16.0 ± 2.9 %ID/g). 18F-10a showed the lowest hepatic and intestinal accumulation among the 4 compounds and slightly slower blood clearance than others. In the PET imaging studies, 18F-8a and 18F-10a were clearly visualized in LNCaP in xenograft-bearing mice. 18F-10a showed higher LNCaP-to-liver ratios than 18F-8a. We confirmed the safety profiles of 18F-10a; the no-observed-adverse-effects level was larger than 13.2 μg/kg. CONCLUSION A novel 18F-labeled asymmetric urea compound, 18F-10a, had a high radiochemical yield, high binding affinity for PSMA, and pharmacokinetic profiles suitable for a PSMA imaging probe. We believe that 18F-10a can be effectively and safely used in this type of imaging.
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Affiliation(s)
- Naoya Harada
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan
| | - Hiroyuki Kimura
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan.,Radioisotope Research Center of Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto, Japan.,Department of Analytical and Bioinorganic Chemistry, Kyoto Pharmaceutical University, 5 Nakauchicho, Misasagi, Yamashinaku, Kyoto, Japan; and
| | - Satoru Onoe
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan
| | - Hiroyuki Watanabe
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan
| | - Daiko Matsuoka
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan
| | - Kenji Arimitsu
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan.,School of Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Koshien Kyubancho, Nishinomiya, Hyogo, Japan
| | - Masahiro Ono
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan
| | - Hideo Saji
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto, Japan
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Noninvasive evaluation of nicotinic acetylcholine receptor availability in mouse brain using single-photon emission computed tomography with [123I]5IA. Nucl Med Biol 2016; 43:372-8. [DOI: 10.1016/j.nucmedbio.2016.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 01/31/2016] [Accepted: 02/22/2016] [Indexed: 11/20/2022]
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Ueda M. Development of Radiolabeled Molecular Imaging Probes for in Vivo Analysis of Biological Function. YAKUGAKU ZASSHI 2016; 136:659-68. [DOI: 10.1248/yakushi.15-00279] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Masashi Ueda
- Department of Pharmaceutical Analytical Chemistry, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University
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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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12
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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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Tavares AAS, Lewsey J, Dewar D, Pimlott SL. Radiotracer properties determined by high performance liquid chromatography: a potential tool for brain radiotracer discovery. Nucl Med Biol 2012; 39:127-35. [DOI: 10.1016/j.nucmedbio.2011.06.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 06/17/2011] [Accepted: 06/27/2011] [Indexed: 01/14/2023]
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Ueda M, Iida Y, Yoneyama T, Kawai T, Ogawa M, Magata Y, Saji H. In vivo relationship between thalamic nicotinic acetylcholine receptor occupancy rates and antiallodynic effects in a rat model of neuropathic pain: Persistent agonist binding inhibits the expression of antiallodynic effects. Synapse 2010; 65:77-83. [DOI: 10.1002/syn.20819] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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15
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Ueda M, Iida Y, Tominaga A, Yoneyama T, Ogawa M, Magata Y, Nishimura H, Kuge Y, Saji H. Nicotinic acetylcholine receptors expressed in the ventralposterolateral thalamic nucleus play an important role in anti-allodynic effects. Br J Pharmacol 2010; 159:1201-10. [PMID: 20136830 DOI: 10.1111/j.1476-5381.2009.00613.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Much interest is currently being focused on the anti-nociceptive effects mediated by nicotinic acetylcholine (nACh) receptors, including their location and mechanism of action. The purpose of this study was to elucidate these issues using 5-iodo-3-(2(S)-azetidinylmethoxy)pyridine (5IA), a nACh receptor agonist, and [(125)I]5IA. EXPERIMENTAL APPROACH We partially ligated the sciatic nerve of Sprague-Dawley rat to induce neuropathic pain [Seltzer's partial sciatic nerve ligation (PSL) model]. We then examined the changes in nACh receptor density in the CNS using [(125)I]5IA autoradiography and the involvement of nACh receptors in anti-nociceptive effects in the region where changes occurred. KEY RESULTS Autoradiographic studies showed that the accumulation of [(125)I]5IA and the number of nACh receptors in the thalamus of PSL rats were increased about twofold compared with those in the sham-operated rats. No change was observed in other brain regions. Rats injected in the ventral posterolateral thalamic nucleus (VPL) with 5IA demonstrated a significant and dose-dependent anti-allodynic effect and this effect was completely antagonized by mecamylamine, injected with 5IA, into the VPL. The blockade of nACh receptors in the VPL by mecamylamine decreased by 70% the anti-allodynic effect of 5IA, given i.c.v. Moreover, mecamylamine given intra-VPL by itself, induced significant hyperalgesia. CONCLUSIONS AND IMPLICATIONS Our findings suggest that the nACh receptors expressed in the VPL play an important role in the anti-allodynic effects produced by exogenous and endogenous agonists.
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Affiliation(s)
- M Ueda
- Radioisotopes Research Laboratory, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Kyoto, Japan
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16
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Brasić JR, Zhou Y, Musachio JL, Hilton J, Fan H, Crabb A, Endres CJ, Reinhardt MJ, Dogan AS, Alexander M, Rousset O, Maris MA, Galecki J, Nandi A, Wong DF. Single photon emission computed tomography experience with (S)-5-[(123)I]iodo-3-(2-azetidinylmethoxy)pyridine in the living human brain of smokers and nonsmokers. Synapse 2009; 63:339-58. [PMID: 19140167 PMCID: PMC2766259 DOI: 10.1002/syn.20611] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
(S)-5-[(123)I]iodo-3-(2-azetidinylmethoxy)pyridine (5-[(123)I]IA), a novel potent radioligand for high-affinity alpha4beta2* neuronal nicotinic acetylcholine receptors (nAChRs), provides a means to evaluate the density and the distribution of nAChRs in the living human brain. We sought in healthy adult smokers and nonsmokers to (1) evaluate the safety, tolerability, and efficacy of 5-[(123)I]IA in an open nonblind trial and (2) to estimate the density and the distribution of alpha(4)beta(2)* nAChRs in the brain. Single photon emission computed tomography (SPECT) was performed for 5 h after the i.v. administration of approximately 0.001 microg/kg ( approximately 10 mCi) 5-[(123)I]IA. Blood pressure, heart rate, and neurobehavioral status were monitored before, during, and after the administration of 5-[(123)I]IA to 12 healthy adults (8 men and 4 women) (6 smokers and 6 nonsmokers) ranging in age from 19 to 46 years (mean = 28.25, standard deviation = 8.20). High plasma-nicotine level was significantly associated with low 5-[(123)I]IA binding in: (1) the caudate head, the cerebellum, the cortex, and the putamen, utilizing both the Sign and Mann-Whitney U-tests; (2) the fusiform gyrus, the hippocampus, the parahippocampus, and the pons utilizing the Mann-Whitney U-test; and (3) the thalamus utilizing the Sign test. We conclude that 5-[(123)I]IA is a safe, well-tolerated, and effective pharmacologic agent for human subjects to estimate high-affinity alpha4/beta2 nAChRs in the living human brain.
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Affiliation(s)
- James Robert Brasić
- Division of Nuclear Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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Ogawa M, Tsukada H, Hatano K, Ouchi Y, Saji H, Magata Y. Central in vivo nicotinic acetylcholine receptor imaging agents for positron emission tomography (PET) and single photon emission computed tomography (SPECT). Biol Pharm Bull 2009; 32:337-340. [PMID: 19252274 DOI: 10.1248/bpb.32.337] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/07/2024]
Abstract
Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are useful for non-invasive investigation of brain receptors. With these imaging techniques, changes in brain receptor densities and distributions during chronic drug treatments and disease progressions can be tracked for a long period. Appropriate radiolabeled imaging agents are necessary for PET and SPECT molecular imaging. Nicotinic acetylcholine receptors (nAChRs) play important roles in brain functions. The alpha4beta2 and alpha7 are the major nAChR subtypes in the brain. To date, several subtype selective radiolabeled ligands for nAChR have been reported. For the alpha4beta2 subtype, some agents are already applied for human studies, but only a few agents are developed for the alpha7 subtype. Here, we overview our results of [(125/123)I]5-iodo-3-(2(S)-azetidinylmethoxy)pyridine and 5-[11C]methyl-3-(2-(S)-azetidinylmethoxy)pyridine ([11C]5MA) for alpha4beta2 subtype imaging, and [11C](R)-2-methylamino-benzoic acid 1-aza-bicyclo[2.2.2]oct-3-yl ester ([11C](R)-MeQAA) for alpha7 subtype imaging.
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Affiliation(s)
- Mikako Ogawa
- Photon Medical Research Center, Hamamatsu University School of Medicine, Japan
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Seibyl JP. Single-photon emission computed tomography and positron emission tomography evaluations of patients with central motor disorders. Semin Nucl Med 2008; 38:274-86. [PMID: 18514083 DOI: 10.1053/j.semnuclmed.2008.03.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Neuroimaging biomarkers in movement disorders during the past decade have served as diagnostic agents (Europe), tools for evaluation of novel therapeutics, and a powerful means for describing pathophysiology by revealing in vivo changes at different stages of disease and within the course of an individual patient's illness. As imaging with agents tracking dopaminergic function become more available, the next decade promises to enhance our clinical sophistication in the optimal use of dopaminergic imaging biomarkers for differential diagnosis, characterization of at-risk populations, guiding selection and management of appropriate treatments. The clinical role of these agents as clinical tools goes hand in hand with the development and availability of disease-modifying drugs, which carry the additional requirement for early and accurate diagnosis and improved clinical monitoring once treatment is initiated. Challenges remain in the ideal application of neuroimaging in the clinical algorithms for patient assessment and management. Further, the application of imaging to other targets, both monamineric and nonmonoaminergic, could serve a function beyond the important delineation of pathologic change occurring in patients with Parkinson's disease to suggest some role in improved phenotyping and classification of patients with Parkinson's disease presenting with different symptom clusters. New areas of focus based on the elucidation of mechanisms at the cellular and molecular level, including intense interest in alpha-synuclein and other protein inclusions in neurons and glia, have piqued interest in their in vivo assessment using scinitigraphic methods. Perhaps ultimately, treatment that is targeted to a better delineated pathophysiology-based characterization of movement disorder patients will emerge. The application of neuroimaging biomarkers to multiple ends in movement disorders provides an important model for the multiple roles diagnostic imaging agents can serve in neurodegenerative disorders; for diagnosis, for elaborating pathophysiology in patient populations, for developing new drugs, ultimately for improving clinical management.
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Affiliation(s)
- John P Seibyl
- Institute for Neurodegenerative Disorders, Molecular Neuroimaging, LLC, Yale University School of Medicine, New Haven, CT, USA.
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Ueda M, Iida Y, Kitamura Y, Kawashima H, Ogawa M, Magata Y, Saji H. 5-Iodo-A-85380, a specific ligand for alpha 4 beta 2 nicotinic acetylcholine receptors, prevents glutamate neurotoxicity in rat cortical cultured neurons. Brain Res 2008; 1199:46-52. [PMID: 18269932 DOI: 10.1016/j.brainres.2007.10.107] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 10/05/2007] [Accepted: 10/15/2007] [Indexed: 01/09/2023]
Abstract
5-iodo-3-(2(S)-azetidinylmethoxy)pyridine (5-iodo-A-85380, 5IA) has very high affinity and selectivity to nicotinic acetylcholine receptor (nAChR) alpha 4 beta 2 subtype, and a relative safe profile. To assess whether 5IA has neuroprotective properties, we examined the effect of 5IA on glutamate (Glu)-induced neurotoxicity using primary cultures of rat cortical neurons. A 10-min exposure of cultures to Glu followed by 2-h incubation with drug-free medium caused a marked loss of viability, as determined by trypan blue exclusion method. Glu-induced neurotoxicity was prevented by 5IA both in a time- and concentration-dependent manner. 5IA-induced neuroprotection required pretreatment of 5IA prior to Glu exposure with an optimal concentration of 10 nM and an optimal pretreatment time of 2 h. Treatment after Glu exposure could not rescue the cultured cells. The neuroprotective effect of 5IA was antagonized by mecamylamine, a nAChR antagonist, but not by scopolamine, a muscarinic acetylcholine receptor antagonist. Dihydro-beta-erythroidine, an alpha 4 beta 2 nAChR antagonist, completely inhibited 5IA-induced neuroprotection, whereas alpha-bungarotoxin, an alpha 7 nAChR antagonist, had no effect. Furthermore, 5IA did not show neuroprotective effects in the absence of extracellular Ca2+. These results suggest that the neuroprotective effects of 5IA are produced by activation of alpha 4 beta 2 nAChRs followed by the influx of extracellular Ca2+. In conclusion, 5IA is possibly not only useful for the treatment and prevention of glutamate neurotoxicity, but also as an available tool for elucidating the mechanism of neuroprotection associated with alpha 4 beta 2 nAChRs.
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Affiliation(s)
- Masashi Ueda
- Radioisotopes Research Laboratory, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Kyoto 606-8507, Japan
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Oishi N, Hashikawa K, Yoshida H, Ishizu K, Ueda M, Kawashima H, Saji H, Fukuyama H. Quantification of nicotinic acetylcholine receptors in Parkinson's disease with (123)I-5IA SPECT. J Neurol Sci 2007; 256:52-60. [PMID: 17367812 DOI: 10.1016/j.jns.2007.02.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Revised: 12/20/2006] [Accepted: 02/06/2007] [Indexed: 11/16/2022]
Abstract
We quantified in vivo brain nicotinic acetylcholine receptor (nAChR) distributions in patients with Parkinson's disease (PD) and evaluated correlations between nAChR distributions and clinical variables of the patients, especially dopaminergic medications. Ten patients with PD without dementia underwent 5-(123)I-iodo-3-(2(S)-azetidinylmethoxy)pyridine ((123)I-5IA) single photon emission computed tomography (SPECT) and the data were compared with those of 10 age-matched healthy volunteers. Correlation analyses between (123)I-5IA distribution volumes (DVs) in each brain region and clinical variables of the patients were also performed. The PD group showed a statistically significant decrease (20-25%) in the brainstem and frontal cortex as compared with the control group. Although age, duration of disease, daily dose of levodopa, duration of PD medication use, and scores on the motor section of Unified Parkinson's Disease Rating Scale were not significantly correlated with DV values in any brain regions, high daily doses of dopamine agonist showed a significant negative correlation with DVs in the cerebellum, and temporal, parietal and occipital cortices. These findings suggest that patients with PD without dementia can show reductions especially in the brainstem and frontal cortex. They also suggest that dopamine agonists can have a negative influence on the distribution of nAChRs.
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Affiliation(s)
- Naoya Oishi
- Human Brain Research Center, Kyoto University Graduate School of Medicine, Shogoin, Kyoto, Japan
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Waterhouse RN, Zhao J. In vivo tomographic imaging studies of neurodegeneration and neuroprotection: a review. Methods Mol Biol 2007; 399:215-233. [PMID: 18309935 DOI: 10.1007/978-1-59745-504-6_15] [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] [Indexed: 05/26/2023]
Abstract
Noninvasive tomographic imaging methods including positron emission tomography (PET) and single photon emission computed tomography (SPECT) are extremely sensitive and are capable of measuring biochemical processes that occur at concentrations in the nanomolar range. Inherent to neurodegenerative processes is neuronal loss. Thus, PET or SPECT monitoring of biochemical processes altered by neuronal loss (changes in neurotransmitter turnover, alterations in receptor, transporter or enzyme concentrations) can provide unique information not attainable by other methods. Such imaging techniques can also be used to longtitudinally monitor the effects of neuroprotective treatments. This review highlights current imaging probes used to evaluate patients with specific neurodegenerative disorders (e.g., Alzheimer's Disease, Parkinson's Disease, Huntington's Chorea), including those that image receptors of the dopaminergic, cholinergic and glutamatergic systems. Areas of future research focus are also defined. It is clear that monitoring the progression of neurodegenerative disorders and the impact of neuroprotective treatments are two different but related goals for which noninvasive imaging via PET and SPECT methods plays a powerful and unique role.
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Affiliation(s)
- Rikki N Waterhouse
- Neurobiology and Imaging Program, Department of Biological Psychiatry, New York State Psychiatric Institute, New York, NY, USA
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Ogawa M, Iida Y, Nakagawa M, Kuge Y, Kawashima H, Tominaga A, Ueda M, Magata Y, Saji H. Change of central cholinergic receptors following lesions of nucleus basalis magnocellularis in rats: search for an imaging index suitable for the early detection of Alzheimer's disease. Nucl Med Biol 2006; 33:249-54. [PMID: 16546680 DOI: 10.1016/j.nucmedbio.2005.06.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2005] [Revised: 06/05/2005] [Accepted: 06/06/2005] [Indexed: 11/29/2022]
Abstract
Cholinergic system in the central nervous system is involved in the memory function. Thus, because the dysfunction of cholinergic system that project to the cerebral cortex from nucleus basalis of Meynert (nbM) would be implicated in the memory function deficits in Alzheimer's disease (AD), evaluating cholinergic function may be useful for the early detection of AD. In this study, because the nucleus basalis magnocellularis (NBM) in rats is equivalent to nbM in human, we investigated the change in cholinergic receptors in the frontal cortex of rats with unilateral lesion to the NBM to find an appropriate index for the early detection of AD using techniques of nuclear medicine. The right NBM was injected with ibotenic acid. [(18)F]FDG-PET images were obtained 3 days later. Some rats were sacrificed at 1 week, whereas others were subjected to a second [(18)F]FDG-PET at 4 weeks then sacrificed for membrane preparation. The prepared membranes were subjected to radioreceptor assays to measure the density of nicotinic and muscarinic acetylcholine receptors. Glucose metabolism had decreased on the damaged side compared to the control side at 3 days, but at 4 weeks, there was no difference between the sides. Nicotinic acetylcholine receptors had significantly decreased in density compared to the control side at both 1 and 4 weeks. However, muscarinic receptors were not affected. These results suggested that neuronal dysfunction in AD could be diagnosed at an early stage by imaging nicotinic acetylcholine receptors.
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Affiliation(s)
- Mikako Ogawa
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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Gozzi A, Schwarz A, Reese T, Bertani S, Crestan V, Bifone A. Region-specific effects of nicotine on brain activity: a pharmacological MRI study in the drug-naïve rat. Neuropsychopharmacology 2006; 31:1690-703. [PMID: 16292320 DOI: 10.1038/sj.npp.1300955] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have applied pharmacological magnetic resonance imaging (phMRI) methods to map the functional response to nicotine in drug-naïve rats. Nicotine (0.35 mg/kg intravenous (i.v.)) increased relative cerebral blood volume (rCBV) in cortical (including medial prefrontal, cingulate orbitofrontal, insular) and subcortical (including amygdala and dorsomedial hippocampus) structures. The pharmacological specificity of the effect was demonstrated by acute pretreatment with the nicotinic acetylcholine receptor (nAChR) ion-channel-blocking agent mecamylamine, which suppressed the rCBV response to nicotine. Control experiments with norepinephrine, a potent non-brain-penetrant vasopressor, at a dose that mimics the cardiovascular response induced by nicotine were performed to assess the potential confounding effects of peripheral blood pressure changes induced by nicotine. In an attempt to highlight the relative contribution of different nAChR subtypes to the observed activation pattern of nicotine, we also investigated the central phMRI response to an acute challenge with (R)-N-(1-azabicyclo[2.2.2]oct-3-yl)(5-(2-pyridyl)thiophene-2-carboxamide) (cpdA, at 5, 10, 20, and 30 mg/kg i.v.) and 5-iodo-A-85380 (5IA, 5 mg/kg i.v.). CpdA is a selective agonist at homomeric alpha7 nAChRs, while 5IA features high in vivo affinity for the alpha4beta2* and other less-abundant beta2-containing nicotinic receptors. CpdA did not produce significant rCBV changes at any of the doses tested, whereas 5IA induced a pattern of activation very similar to that induced by nicotine. The lack of phMRI response to cpdA together with the high spatial overlap between the activation profile of nicotine and 5IA, suggest that the acute functional response to nicotine in drug-naïve rats is mediated by beta2-containing nAChR isoforms, presumably belonging to the alpha4beta2* subtype.
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Affiliation(s)
- Alessandro Gozzi
- Department of Neuroimaging, Centre of Excellence for Drug Discovery, Psychiatry, GlaxoSmithKline Medicines Research Centre, Verona, Italy.
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Ueda M, Iida Y, Mukai T, Mamede M, Ishizu K, Ogawa M, Magata Y, Konishi J, Saji H. 5-[123I]Iodo-A-85380: assessment of pharmacological safety, radiation dosimetry and SPECT imaging of brain nicotinic receptors in healthy human subjects. Ann Nucl Med 2005; 18:337-44. [PMID: 15359928 DOI: 10.1007/bf02984473] [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] [Indexed: 10/21/2022]
Abstract
Recently, 5-[123I]iodo-3-(2(S)-azetidinylmethoxy)pyridine ([123I]5IA) was developed as a ligand for imaging the nicotinic acetylcholine receptor (nAChR) in human brain using single photon emission computed tomography (SPECT). In the present study, the toxicity and radiation absorbed dose of [123I]5IA were investigated. Behavior and physiological parameters were examined in mice and rats after administration of 5IA. There were no changes in these parameters in animals administered 1 microg/kg of 5IA or less, indicating that the no observed effect level (NOEL) of 5IA was 1 microg/kg. [123I]5IA was then administered to healthy human subjects and serial whole-body images were acquired over 24 hr. Initially, high levels of radioactivity were observed in the liver and urinary bladder and moderate levels in the lungs, kidneys, and brain. Whole brain activity at 1 hr was 4.6 +/- 0.4% of the injected dose and this value gradually decreased with time. The majority (-75%) of the radioactivity was excreted in urine within 24 hr, and less than 1% remained in all organs tested. The biological half-life of [1231]51A averaged 7.2 +/- 4.0 hr. Based on the biodistribution data, radiation absorbed doses were estimated using MIRDOSE 3.1 software with the dynamic bladder model and the ICRP gastrointestinal (GI) tract model. Consequently, the effective dose equivalent was estimated to be 30 +/- 1.4 microSv/MBq, which is an acceptable radiation burden. Having determined the safety of this compound, we performed SPECT imaging in a healthy human subject using 171 MBq of [123I]5IA. SPECT images clearly revealed a cerebral distribution of radioactivity that was consistent with the known distribution of central nAChRs in humans. These results suggest that [123I]5IA is a promising ligand for imaging nAChRs in humans, with an acceptable dosimetry and pharmacological safety at the dose required for adequate SPECT imaging.
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Affiliation(s)
- Masashi Ueda
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Japan
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Affiliation(s)
- Hidenao Fukuyama
- Human Brain Research Center, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
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Kiyono Y, Kanegawa N, Kawashima H, Kitamura Y, Iida Y, Saji H. Evaluation of radioiodinated (R)-N-methyl-3-(2-iodophenoxy)-3-phenylpropanamine as a ligand for brain norepinephrine transporter imaging. Nucl Med Biol 2004; 31:147-53. [PMID: 15013479 DOI: 10.1016/j.nucmedbio.2003.09.004] [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: 07/02/2003] [Revised: 09/10/2003] [Accepted: 09/19/2003] [Indexed: 11/24/2022]
Abstract
(R)-N-methyl-3-(2-iodophenoxy)-3-phenylpropanamine (MIPP) was evaluated as a radiopharmaceutical for investigating brain norepinephrine transporters (NET) by single photon emission computed tomography (SPECT). (R)-[(125)I]MIPP was synthesized with high radiochemical yield (60%) and high radiochemical purity (> 98%). In biodistribution experiments, (R)-[(125)I]MIPP indicated that the brain uptake of (R)-[(125)I]MIPP was rapid and retained, and that the regional cerebral distribution was consistent with the density of NET. Moreover, the administration of desipramine decreased the accumulation of (R)-[(125)I]MIPP in the brain. HPLC analysis of brain radioactivity showed that more than 90% was intact (R)-MIPP. These results suggested that (R)-[(123)I]MIPP is a potential radiopharmaceutical for imaging brain NET.
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Affiliation(s)
- Yasushi Kiyono
- Radioisotopes Research Laboratory, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Kyoto, Japan
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Itier V, Schönbächler R, Tribollet E, Honer M, Prinz K, Marguerat A, Bertrand S, Bunnelle WH, Schubiger PA, Meyer MD, Sullivan JP, Bertrand D, Westera G. A-186253, a specific antagonist of the α4β2 nAChRs: its properties and potential to study brain nicotinic acetylcholine receptors. Neuropharmacology 2004; 47:538-57. [PMID: 15380372 DOI: 10.1016/j.neuropharm.2004.05.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2003] [Revised: 04/20/2004] [Accepted: 05/07/2004] [Indexed: 11/25/2022]
Abstract
Imaging the living brain and the distribution of the ligand gated channels that participate in the neurotransmission is one of the challenges that is hoped to bring new insights for the treatment of neurological diseases. Herein, we probed a new nicotinic derivative, A-186253 as a potential molecule to discriminate with high resolution the different neuronal nicotinic receptor subtypes that are expressed in distinct brain areas. Binding with a high affinity of 440 pM at the major brain alpha4beta2 receptor subtype and presenting an excellent safety margin, properties of the A-186253 were thoroughly evaluated. While autoradiography confirmed its specificity for the alpha4beta2 subtype, functional investigations revealed for short exposures a broader spectrum of action at receptors including the ganglionic alpha3beta4 and the homomeric alpha7 subtypes. Specificity was, however, observed at alpha4beta2 when receptors were exposed for several minutes with low concentration of the A-186253. In view of these promising results, the A-186253 was radiolabeled and tested in positron emission tomography on rats and pigs. Despite the high selectivity observed in vitro, the A-186253 displayed a complex binding profile and little displacement by the agonist cytisine. While the A-186253 can be valuable to discriminate receptor subtypes, improvements of this molecule must be brought for in vivo measurements.
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Affiliation(s)
- Valérie Itier
- Department of Physiology, Medical Faculty, CMU, University of Geneva, 1, rue Michel Servet, CH-1211 Geneva 4, Switzerland
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Roger G, Lagnel B, Rouden J, Besret L, Valette H, Demphel S, Gopisetti J, Coulon C, Ottaviani M, Wrenn LA, Letchworth SR, Bohme GA, Benavides J, Lasne MC, Bottlaender M, Dollé F. Synthesis of a [2-Pyridinyl-18F]-labelled fluoro derivative of (−)-Cytisine as a candidate radioligand for brain nicotinic α4β2 receptor imaging with PET. Bioorg Med Chem 2003; 11:5333-43. [PMID: 14642577 DOI: 10.1016/j.bmc.2003.09.042] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In recent years, there has been considerable effort to design and synthesize radiotracers suitable for use in Positron Emission Tomography (PET) imaging of the alpha4beta2 neuronal nicotinic acetylcholine receptor (nAChR) subtype. A new fluoropyridinyl derivative of (-)-cytisine (1), namely (-)-9-(2-fluoropyridinyl)cytisine (3, K(i) values of 24 and 3462 nM for the alpha4beta2 and alpha7 nAChRs subtypes, respectively) has been synthesized in four chemical steps from (-)-cytisine and labelled with fluorine-18 (T(1/2): 119.8 min) using an efficient two-step radiochemical process [(a). nucleophilic heteroaromatic ortho-radiofluorination using the corresponding N-Boc-protected nitro-derivative, (b). TFA removal of the Boc protective group]. Typically, 20-45 mCi (0.74-1.67 GBq) of (-)-9-(2-[18F]fluoropyridinyl)cytisine ([18F]-3, 2-3 Ci/micromol or 74-111 GBq/micromol) were easily obtained in 70-75 min starting from a 100 mCi (3.7 GBq) aliquot of a cyclotron-produced [18F]fluoride production batch (20-45% non decay-corrected yield based on the starting [18F]fluoride). The in vivo pharmacological profile of (-)-9-(2-[18F]fluoropyridinyl)cytisine ([18F]-3) was evaluated in rats with biodistribution studies and brain radioactivity monitoring using intracerebral radiosensitive beta-microprobes. The observed in vivo distribution of the radiotracer in brain was rather uniform, and did not match with the known regional densities of nAChRs. It was also significantly different from that of the parent compound (-)-[3H]cytisine. Moreover, competition studies with (-)-nicotine (5 mg/kg, 5 min before the radiotracer injection) did not reduce brain uptake of the radiotracer. These experiments clearly indicate that (-)-9-(2-[18F]fluoropyridinyl)cytisine ([18F]-3) does not have the required properties for imaging nAChRs using PET.
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Affiliation(s)
- Gaëlle Roger
- Département de Recherche Médicale, CEA/DSV, 4 place du Général Leclerc, F-91401 Orsay, France
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Saji H, Iida Y. [Biomedical imaging in pharmacology with nuclear medical imaging methodologies: positron emission tomography (PET) and single photon emission computed tomography (SPECT)]. Nihon Yakurigaku Zasshi 2003; 121:181-91. [PMID: 12673952 DOI: 10.1254/fpj.121.181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The nuclear imaging technologies, positron emission tomography (PET) and single photon emission computed tomography (SPECT), have the power to non-invasively obtain dynamic and real-time information on the in vivo behaviors of radiolabeled molecules not only in humans but also in experimental animals. Thus, PET and SPECT can image molecular interactions of biological processes in vivo directly and reveal biological phenomena that are hidden from view. Furthermore, these imaging procedures also can be repeatedly performed before and after interventions, thereby allowing each subject to be used as its own control. In these studies, the radiolabeled compounds used as imaging probes for non-invasive assays of biochemical processes should have defined in vivo behaviors that can provide valuable information on the physiological and pharmacological processes. This paper describes the principle of the nuclear medical imaging systems, rational design of radiolabeled imaging probes, and the application to in vivo investigation of the change of various neurotransmission systems under disease and drug treatment. The efficient utilization of these nuclear medical imaging technologies will accelerate biomedical studies and drug development.
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Affiliation(s)
- Hideo Saji
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan.
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