1
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Mineur YS, Picciotto MR. How can I measure brain acetylcholine levels in vivo? Advantages and caveats of commonly used approaches. J Neurochem 2023; 167:3-15. [PMID: 37621094 PMCID: PMC10616967 DOI: 10.1111/jnc.15943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 08/07/2023] [Accepted: 08/08/2023] [Indexed: 08/26/2023]
Abstract
The neurotransmitter acetylcholine (ACh) plays a central role in the regulation of multiple cognitive and behavioral processes, including attention, learning, memory, motivation, anxiety, mood, appetite, and reward. As a result, understanding ACh dynamics in the brain is essential for elucidating the neural mechanisms underlying these processes. In vivo measurements of ACh in the brain have been challenging because of the low concentrations and rapid turnover of this neurotransmitter. Here, we review a number of techniques that have been developed to measure ACh levels in the brain in vivo. We follow this with a deeper focus on use of genetically encoded fluorescent sensors coupled with fiber photometry, an accessible technique that can be used to monitor neurotransmitter release with high temporal resolution and specificity. We conclude with a discussion of methods for analyzing fiber photometry data and their respective advantages and disadvantages. The development of genetically encoded fluorescent ACh sensors is revolutionizing the field of cholinergic signaling, allowing temporally precise measurement of ACh release in awake, behaving animals. Use of these sensors has already begun to contribute to a mechanistic understanding of cholinergic modulation of complex behaviors.
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Affiliation(s)
- Yann S. Mineur
- Department of Psychiatry, Yale University School of Medicine, 34 Park Street, 3 Floor Research, New Haven, CT 06508, USA
| | - Marina R. Picciotto
- Department of Psychiatry, Yale University School of Medicine, 34 Park Street, 3 Floor Research, New Haven, CT 06508, USA
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2
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Zhang JJ, Fu H, Lin R, Zhou J, Haider A, Fang W, Elghazawy NH, Rong J, Chen J, Li Y, Ran C, Collier TL, Chen Z, Liang SH. Imaging Cholinergic Receptors in the Brain by Positron Emission Tomography. J Med Chem 2023; 66:10889-10916. [PMID: 37583063 PMCID: PMC10461233 DOI: 10.1021/acs.jmedchem.3c00573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Indexed: 08/17/2023]
Abstract
Cholinergic receptors represent a promising class of diagnostic and therapeutic targets due to their significant involvement in cognitive decline associated with neurological disorders and neurodegenerative diseases as well as cardiovascular impairment. Positron emission tomography (PET) is a noninvasive molecular imaging tool that has helped to shed light on the roles these receptors play in disease development and their diverse functions throughout the central nervous system (CNS). In recent years, there has been a notable advancement in the development of PET probes targeting cholinergic receptors. The purpose of this review is to provide a comprehensive overview of the recent progress in the development of these PET probes for cholinergic receptors with a specific focus on ligand structure, radiochemistry, and pharmacology as well as in vivo performance and applications in neuroimaging. The review covers the structural design, pharmacological properties, radiosynthesis approaches, and preclinical and clinical evaluations of current state-of-the-art PET probes for cholinergic receptors.
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Affiliation(s)
- Jing-Jing Zhang
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Hualong Fu
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Key
Laboratory of Radiopharmaceuticals, Ministry of Education, College
of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ruofan Lin
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Jingyin Zhou
- Key
Laboratory of Radiopharmaceuticals, Ministry of Education, College
of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ahmed Haider
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Weiwei Fang
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Nehal H. Elghazawy
- Department
of Pharmaceutical, Chemistry, Faculty of Pharmacy & Biotechnology, German University in Cairo, 11835 Cairo, Egypt
| | - Jian Rong
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Jiahui Chen
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Yinlong Li
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Chongzhao Ran
- Athinoula
A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02114, United States
| | - Thomas L. Collier
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Zhen Chen
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
| | - Steven H. Liang
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
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3
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Ozenil M, Aronow J, Millard M, Langer T, Wadsak W, Hacker M, Pichler V. Update on PET Tracer Development for Muscarinic Acetylcholine Receptors. Pharmaceuticals (Basel) 2021; 14:530. [PMID: 34199622 PMCID: PMC8229778 DOI: 10.3390/ph14060530] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 05/29/2021] [Accepted: 05/31/2021] [Indexed: 02/07/2023] Open
Abstract
The muscarinic cholinergic system regulates peripheral and central nervous system functions, and, thus, their potential as a therapeutic target for several neurodegenerative diseases is undoubted. A clinically applicable positron emission tomography (PET) tracer would facilitate the monitoring of disease progression, elucidate the role of muscarinic acetylcholine receptors (mAChR) in disease development and would aid to clarify the diverse natural functions of mAChR regulation throughout the nervous system, which still are largely unresolved. Still, no mAChR PET tracer has yet found broad clinical application, which demands mAChR tracers with improved imaging properties. This paper reviews strategies of mAChR PET tracer design and summarizes the binding properties and preclinical evaluation of recent mAChR tracer candidates. Furthermore, this work identifies the current major challenges in mAChR PET tracer development and provides a perspective on future developments in this area of research.
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Affiliation(s)
- Marius Ozenil
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Jonas Aronow
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Marlon Millard
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, 1090 Wien, Austria; (M.M.); (T.L.)
| | - Thierry Langer
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, 1090 Wien, Austria; (M.M.); (T.L.)
| | - Wolfgang Wadsak
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Marcus Hacker
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Verena Pichler
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, 1090 Wien, Austria; (M.M.); (T.L.)
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4
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Naganawa M, Nabulsi N, Henry S, Matuskey D, Lin SF, Slieker L, Schwarz AJ, Kant N, Jesudason C, Ruley K, Navarro A, Gao H, Ropchan J, Labaree D, Carson RE, Huang Y. First-in-Human Assessment of 11C-LSN3172176, an M1 Muscarinic Acetylcholine Receptor PET Radiotracer. J Nucl Med 2020; 62:553-560. [PMID: 32859711 DOI: 10.2967/jnumed.120.246967] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 07/09/2020] [Indexed: 01/25/2023] Open
Abstract
This was a first-in-human study of the PET radiotracer 11C-LSN3172176 for the muscarinic acetylcholine receptor subtype M1. The objectives of the study were to determine the appropriate kinetic model to quantify binding of the tracer to M1 receptors, and the reliability of the chosen quantification method. Methods: Six healthy subjects completed the test-retest protocol, and 5 healthy subjects completed the baseline-scopolamine blocking protocol. Multiple modeling methods were applied to calculate total distribution volume (V T) and nondisplaceable binding potential (BP ND) in various brain regions. The reference region was selected from the blocking study. The occupancy plot was applied to compute receptor occupancy by scopolamine and nondisplaceable distribution volume. Results: Tracer uptake was highest in the striatum, followed by neocortical regions and white matter, and lowest in the cerebellum. Regional time-activity curves were fitted well by all models. The 2-tissue-compartment (2TC) model fits were good, but the 2TC parameters often could not be reliably estimated. Because V T correlated well between the 2TC and 1-tissue-compartment (1TC) models after exclusion of unreliable estimates, the 1TC model was chosen as the most appropriate. The cerebellum showed the lowest V T, consistent with preclinical studies showing little to no specific binding in the region. Further, cerebellar V T did not change between baseline and blocking scans, indicating that the cerebellum is a suitable reference region. The simplified reference tissue model (SRTM) slightly underestimated 1TC BP ND, and the simplified reference tissue model 2 (SRTM2) improved BP ND estimation. An 80-min scan was sufficient to quantify V T and BP ND The test-retest study showed excellent absolute test-retest variability for 1TC V T (≤5%) and BP ND (≤10%). In the baseline and blocking studies, occupancy values were lower in the striatum than in nonstriatal regions, as may be attributed to differences in regional acetylcholine concentrations. Conclusion: The 1TC and SRTM2 models are appropriate for quantitative analysis of 11C-LSN3172176 imaging data. 11C-LSN3172176 displayed excellent test-retest reproducibility and is a highly promising ligand to quantify M1 receptors in the human brain.
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Affiliation(s)
- Mika Naganawa
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - Nabeel Nabulsi
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - Shannan Henry
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - David Matuskey
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - Shu-Fei Lin
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | | | | | - Nancy Kant
- Eli Lilly and Company, Indianapolis, Indiana
| | | | - Kevin Ruley
- Eli Lilly and Company, Indianapolis, Indiana
| | | | - Hong Gao
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - Jim Ropchan
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - David Labaree
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - Richard E Carson
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
| | - Yiyun Huang
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut; and
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5
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Pain CD, O'Keefe GJ, Ackermann U, Dore V, Villemagne VL, Rowe CC. Human biodistribution and internal dosimetry of 4-[ 18F]fluorobenzyl-dexetimide: a PET radiopharmaceutical for imaging muscarinic acetylcholine receptors in the brain and heart. EJNMMI Res 2020; 10:61. [PMID: 32533449 PMCID: PMC7292855 DOI: 10.1186/s13550-020-00641-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/04/2020] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND 4-[18F] fluorobenzyl dexetimide (F-DEX) is the first non-subtype selective fluorine-18 labelled tracer for muscarinic receptors (mAChR) used in humans. A recent first-in-human study found high regional brain uptake with low variation in normal subjects. Disturbance of mAChR has been reported in Alzheimer's and Parkinson's disease, schizophrenia and depression and various cardiac diseases. The following work assesses the biodistribution, organ tracer kinetics and radiation dose associated with F-DEX. METHOD Dose calculations were based on activity uptake derived from multiple time point whole body PET CT imaging and the organ-specific dosimetric S-factors derived from the ICRP 133 standard man and woman mathematical phantoms. Effective doses were calculated using the latest ICRP tissue weighting factors. RESULTS Serial images and time activity curves demonstrate high brain and left ventricular myocardial uptake (5% and 0.65% of injected activity, respectively) with greater retention in brain than myocardium. The mean effective dose was in concordance with other 18F labelled tracers at 19.70 ± 2.27 μSv/MBq. The largest absorbed doses were in the liver (52.91 ± 1.46 μGy/MBq) and heart wall (43.94 ± 12.88 μGy/MBq) for standard man and the liver (61.66 ± 13.61 μGy/MBq) and lungs (40.93 ± 3.11 μGy/MBq) for standard woman. The absorbed dose to all organs, most notably, the red bone marrow (20.03 ± 2.89 μGy/MBq) was sufficiently low to ensure no toxicity after numerous follow-up procedures. CONCLUSIONS The radiation dose associated with an administration of F-DEX is comparable to that of other 18F labelled tracers such as FDG (19.0 μSv/MBq) and lower than tracers used for SPECT imaging of muscarinic receptors (I-DEX 28.5 μSv/MBq). Clinical use would likely result in an effective dose less than 4 mSv for the ICRP 133 standard phantoms after dose optimisation allowing justification for numerous follow-up procedures. Recent results from first in-human studies and a comparatively low radiation dose make F-DEX an attractive option for future applications of imaging muscarinic receptors in the brain. Further investigation of the potential of F-DEX for imaging parasympathetic innervation of the heart may be warranted.
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Affiliation(s)
- Cameron D Pain
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Australia.
| | - Graeme J O'Keefe
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Australia
| | - Uwe Ackermann
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Australia
- University of Melbourne, Melbourne, Australia
| | - Vincent Dore
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Australia
- CSIRO, Heidelberg, Australia
| | - Victor L Villemagne
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Australia
- University of Melbourne, Melbourne, Australia
| | - Christopher C Rowe
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Australia
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6
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Nabulsi NB, Holden D, Zheng MQ, Bois F, Lin SF, Najafzadeh S, Gao H, Ropchan J, Lara-Jaime T, Labaree D, Shirali A, Slieker L, Jesudason C, Barth V, Navarro A, Kant N, Carson RE, Huang Y. Evaluation of 11C-LSN3172176 as a Novel PET Tracer for Imaging M 1 Muscarinic Acetylcholine Receptors in Nonhuman Primates. J Nucl Med 2019; 60:1147-1153. [PMID: 30733324 DOI: 10.2967/jnumed.118.222034] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 12/29/2018] [Indexed: 11/16/2022] Open
Abstract
The M1 muscarinic acetylcholine receptor (mAChR) plays an important role in learning and memory, and therefore is a target for development of drugs for treatment of cognitive impairments in Alzheimer disease and schizophrenia. The availability of M1-selective radiotracers for PET will help in developing therapeutic agents by providing an imaging tool for assessment of drug dose-receptor occupancy relationship. Here we report the synthesis and evaluation of 11C-LSN3172176 (ethyl 4-(6-(methyl-11 C)-2-oxoindolin-1-yl)-[1,4'-bipiperidine]-1'-carboxylate) in nonhuman primates. Methods: 11C-LSN3172176 was radiolabeled via the Suzuki-Miyaura cross-coupling method. PET scans in rhesus macaques were acquired for 2 h with arterial blood sampling and metabolite analysis to measure the input function. Blocking scans with scopolamine (50 μg/kg) and the M1-selective agent AZD6088 (0.67 and 2 mg/kg) were obtained to assess tracer binding specificity and selectivity. Regional brain time-activity curves were analyzed with the 1-tissue-compartment model and the multilinear analysis method (MA1) to calculate regional distribution volume. Nondisplaceable binding potential values were calculated using the cerebellum as a reference region. Results: 11C-LSN3172176 was synthesized with greater than 99% radiochemical purity and high molar activity. In rhesus monkeys, 11C-LSN3172176 metabolized rapidly (29% ± 6% parent remaining at 15 min) and displayed fast kinetics and extremely high uptake in the brain. Imaging data were modeled well with the 1-tissue-compartment model and MA1 methods. MA1-derived distribution volume values were high (range, 10-81 mL/cm3) in all known M1 mAChR-rich brain regions. Pretreatment with scopolamine and AZD6088 significantly reduced the brain uptake of 11C-LSN3172176, thus demonstrating its binding specificity and selectivity in vivo. The cerebellum appeared to be a suitable reference region for derivation of nondisplaceable binding potential, which ranged from 2.42 in the globus pallidus to 8.48 in the nucleus accumbens. Conclusion: 11C-LSN3172176 exhibits excellent in vivo binding and imaging characteristics in nonhuman primates and appears to be the first appropriate radiotracer for PET imaging of human M1 AChR.
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Affiliation(s)
- Nabeel B Nabulsi
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Daniel Holden
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Ming-Qiang Zheng
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Frederic Bois
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Shu-Fei Lin
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Soheila Najafzadeh
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Hong Gao
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Jim Ropchan
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Teresa Lara-Jaime
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - David Labaree
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Anupama Shirali
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | | | | | | | | | - Nancy Kant
- Eli Lilly and Co., Indianapolis, Indiana
| | - Richard E Carson
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
| | - Yiyun Huang
- Yale PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; and
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7
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Franco Machado J, Silva RD, Melo R, G Correia JD. Less Exploited GPCRs in Precision Medicine: Targets for Molecular Imaging and Theranostics. Molecules 2018; 24:E49. [PMID: 30583594 PMCID: PMC6337414 DOI: 10.3390/molecules24010049] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 12/07/2018] [Accepted: 12/09/2018] [Indexed: 12/18/2022] Open
Abstract
Precision medicine relies on individually tailored therapeutic intervention taking into account individual variability. It is strongly dependent on the availability of target-specific drugs and/or imaging agents that recognize molecular targets and patient-specific disease mechanisms. The most sensitive molecular imaging modalities, Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), rely on the interaction between an imaging radioprobe and a target. Moreover, the use of target-specific molecular tools for both diagnostics and therapy, theranostic agents, represent an established methodology in nuclear medicine that is assuming an increasingly important role in precision medicine. The design of innovative imaging and/or theranostic agents is key for further accomplishments in the field. G-protein-coupled receptors (GPCRs), apart from being highly relevant drug targets, have also been largely exploited as molecular targets for non-invasive imaging and/or systemic radiotherapy of various diseases. Herein, we will discuss recent efforts towards the development of innovative imaging and/or theranostic agents targeting selected emergent GPCRs, namely the Frizzled receptor (FZD), Ghrelin receptor (GHSR-1a), G protein-coupled estrogen receptor (GPER), and Sphingosine-1-phosphate receptor (S1PR). The pharmacological and clinical relevance will be highlighted, giving particular attention to the studies on the synthesis and characterization of targeted molecular imaging agents, biological evaluation, and potential clinical applications in oncology and non-oncology diseases. Whenever relevant, supporting computational studies will be also discussed.
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Affiliation(s)
- João Franco Machado
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
- Centro de Química Estrutural, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| | - Rúben D Silva
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
| | - Rita Melo
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
- Center for Neuroscience and Cell Biology; Rua Larga, Faculdade de Medicina, Polo I, 1ºandar, Universidade de Coimbra, 3004-504 Coimbra, Portugal.
| | - João D G Correia
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
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8
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Shalgunov V, van Waarde A, Booij J, Michel MC, Dierckx RAJO, Elsinga PH. Hunting for the high-affinity state of G-protein-coupled receptors with agonist tracers: Theoretical and practical considerations for positron emission tomography imaging. Med Res Rev 2018; 39:1014-1052. [PMID: 30450619 PMCID: PMC6587759 DOI: 10.1002/med.21552] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 10/02/2018] [Accepted: 10/19/2018] [Indexed: 12/15/2022]
Abstract
The concept of the high‐affinity state postulates that a certain subset of G‐protein‐coupled receptors is primarily responsible for receptor signaling in the living brain. Assessing the abundance of this subset is thus potentially highly relevant for studies concerning the responses of neurotransmission to pharmacological or physiological stimuli and the dysregulation of neurotransmission in neurological or psychiatric disorders. The high‐affinity state is preferentially recognized by agonists in vitro. For this reason, agonist tracers have been developed as tools for the noninvasive imaging of the high‐affinity state with positron emission tomography (PET). This review provides an overview of agonist tracers that have been developed for PET imaging of the brain, and the experimental paradigms that have been developed for the estimation of the relative abundance of receptors configured in the high‐affinity state. Agonist tracers appear to be more sensitive to endogenous neurotransmitter challenge than antagonists, as was originally expected. However, other expectations regarding agonist tracers have not been fulfilled. Potential reasons for difficulties in detecting the high‐affinity state in vivo are discussed.
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Affiliation(s)
- Vladimir Shalgunov
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Aren van Waarde
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jan Booij
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany
| | - Rudi A J O Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.,Department of Nuclear Medicine, Ghent University, University Hospital, Ghent, Belgium
| | - Philip H Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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9
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Mogg AJ, Eessalu T, Johnson M, Wright R, Sanger HE, Xiao H, Crabtree MG, Smith A, Colvin EM, Schober D, Gehlert D, Jesudason C, Goldsmith PJ, Johnson MP, Felder CC, Barth VN, Broad LM. In Vitro Pharmacological Characterization and In Vivo Validation of LSN3172176 a Novel M1 Selective Muscarinic Receptor Agonist Tracer Molecule for Positron Emission Tomography. J Pharmacol Exp Ther 2018; 365:602-613. [PMID: 29643252 DOI: 10.1124/jpet.117.246454] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Accepted: 04/05/2018] [Indexed: 12/20/2022] Open
Abstract
In the search for improved symptomatic treatment options for neurodegenerative and neuropsychiatric diseases, muscarinic acetylcholine M1 receptors (M1 mAChRs) have received significant attention. Drug development efforts have identified a number of novel ligands, some of which have advanced to the clinic. However, a significant issue for progressing these therapeutics is the lack of robust, translatable, and validated biomarkers. One valuable approach to assessing target engagement is to use positron emission tomography (PET) tracers. In this study we describe the pharmacological characterization of a selective M1 agonist amenable for in vivo tracer studies. We used a novel direct binding assay to identify nonradiolabeled ligands, including LSN3172176, with the favorable characteristics required for a PET tracer. In vitro functional and radioligand binding experiments revealed that LSN3172176 was a potent partial agonist (EC50 2.4-7.0 nM, Emax 43%-73%), displaying binding selectivity for M1 mAChRs (Kd = 1.5 nM) that was conserved across species (native tissue Kd = 1.02, 2.66, 8, and 1.03 at mouse, rat, monkey, and human, respectively). Overall selectivity of LSN3172176 appeared to be a product of potency and stabilization of the high-affinity state of the M1 receptor, relative to other mAChR subtypes (M1 > M2, M4, M5 > M3). In vivo, use of wild-type and mAChR knockout mice further supported the M1-preferring selectivity profile of LSN3172176 for the M1 receptor (78% reduction in cortical occupancy in M1 KO mice). These findings support the development of LSN3172176 as a potential PET tracer for assessment of M1 mAChR target engagement in the clinic and to further elucidate the function of M1 mAChRs in health and disease.
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Affiliation(s)
- Adrian J Mogg
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Thomas Eessalu
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Megan Johnson
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Rebecca Wright
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Helen E Sanger
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Hongling Xiao
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Michael G Crabtree
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Alex Smith
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Ellen M Colvin
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Douglas Schober
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Donald Gehlert
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Cynthia Jesudason
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Paul J Goldsmith
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Michael P Johnson
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Christian C Felder
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Vanessa N Barth
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
| | - Lisa M Broad
- Eli Lilly & Co. Ltd., Lilly Research Centre, Windlesham, Surrey, United Kingdom (A.J.M., H.E.S., M.G.C., A.S., E.M.C., P.J.G., L.M.B.) and Eli Lilly & Co. Ltd., Lilly Corporate Center, Indianapolis, Indiana (T.E., M.J., R.W., H.X., D.S., D.G., C.J., M.P.J., C.C.F., V.N.B.)
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Current status of muscarinic M1 and M4 receptors as drug targets for neurodegenerative diseases. Neuropharmacology 2018; 136:449-458. [PMID: 29374561 DOI: 10.1016/j.neuropharm.2018.01.028] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 01/09/2018] [Accepted: 01/21/2018] [Indexed: 01/17/2023]
Abstract
The cholinergic signalling system has been an attractive pathway to seek targets for modulation of arousal, cognition, and attention which are compromised in neurodegenerative and neuropsychiatric diseases. The acetylcholine muscarinic receptor M1 and M4 subtypes which are highly expressed in the central nervous system, in cortex, hippocampus and striatum, key areas of cognitive and neuropsychiatric control, have received particular attention. Historical muscarinic drug development yielded first generation agonists with modest selectivity for these two receptor targets over M2 and M3 receptors, the major peripheral sub-types hypothesised to underlie the dose-limiting clinical side effects. More recent compound screening and medicinal chemistry optimization of orthosteric and allosteric agonists, and positive allosteric modulators binding to sites distinct from the highly homologous acetylcholine binding pocket have yielded a collection of highly selective tool compounds for preclinical validation studies. Several M1 selective ligands have progressed to early clinical development and in time will hopefully lead to useful therapeutics for treating symptoms of Alzheimer's disease and related disorders. This article is part of the Special Issue entitled 'Neuropharmacology on Muscarinic Receptors'.
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Sander CY, Hesse S. News and views on in-vivo imaging of neurotransmission using PET and MRI. THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING : OFFICIAL PUBLICATION OF THE ITALIAN ASSOCIATION OF NUCLEAR MEDICINE (AIMN) [AND] THE INTERNATIONAL ASSOCIATION OF RADIOPHARMACOLOGY (IAR), [AND] SECTION OF THE SOCIETY OF... 2017; 61:414-428. [PMID: 28750497 PMCID: PMC5916779 DOI: 10.23736/s1824-4785.17.03019-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Molecular neuroimaging with PET is an integrated tool in psychiatry research and drug-development for as long as this modality has been available, in particular for studying neurotransmission and endogenous neurotransmitter release. Pharmacologic, behavioral and other types of challenges are currently applied to induce changes in neurochemical levels that can be inferred through their effects on changes in receptor binding and related outcome measures. Based on the availability of tracers that are sensitive for measuring neurotransmitter release these experiments have focused on the brain's dopamine system, while recent developments have extended those studies to other targets such as the serotonin or choline system. With the introduction of hybrid, truly simultaneous PET/MRI systems, in-vivo imaging of the dynamics of neuroreceptor signal transmission in the brain using PET and functional MRI (fMRI) has become possible. fMRI has the ability to provide information about the effects of receptor function that are complementary to the PET measurement. Dynamic acquisition of both PET and fMRI signals enables not only an in-vivo real-time assessment of neurotransmitter or drug binding to receptors but also dynamic receptor adaptations and receptor-specific neurotransmission. While fMRI temporal resolution is comparatively fast in relation to PET, the timescale of observable biological processes is highly dependent on the kinetics of radiotracers and study design. Overall, the combination of the specificity of PET radiotracers to neuroreceptors, fMRI signal as a functional readout and integrated study design promises to expand our understanding of the location, propagation and connections of brain activity in health and disease.
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Affiliation(s)
- Christin Y Sander
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA -
- Harvard Medical School, Boston, MA, USA -
| | - Swen Hesse
- Department of Nuclear Medicine, University of Leipzig, Leipzig, Germany
- Integrated Treatment and Research Center (IFB) Adiposity Diseases, Leipzig University Medical Center, Leipzig, Germany
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Ahmed T, Zahid S, Mahboob A, Farhat SM. Cholinergic System and Post-translational Modifications: An Insight on the Role in Alzheimer's Disease. Curr Neuropharmacol 2017; 15:480-494. [PMID: 27012953 PMCID: PMC5543671 DOI: 10.2174/1570159x14666160325121145] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 12/02/2015] [Accepted: 03/03/2016] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Alzheimer's disease (AD) is the most common form of old age dementia. The formation of amyloid plaques (Aβ), neurofibrillary tangles and loss of basal forebrain cholinergic neurons are the hallmark events in the pathology of AD. LITERATURE REVIEW Cholinergic system is one of the most important neurotransmitter system involved in learning and memory which preferentially degenerates in the initial stages of AD. Activation of cholinergic receptors (muscarinic and nicotinic) activates multiple pathways which result in post translational modifications (PTMs) in multiple proteins which bring changes in nervous system. Cholinergic receptors-mediated PTMs "in-part" substantially affect the biosynthesis, proteolysis, degradation and expression of many proteins and in particular, amyloid precursor protein (APP). APP is subjected to several PTMs (proteolytic processing, glycosylation, sulfation, and phosphorylation) during its course of processing, resulting in Aβ deposition, leading to AD. Aβ also alters the PTMs of tau which is a microtubule associated protein. Therefore, post-translationally modified tau and Aβ collectively aggravate the neuronal loss that leads to cholinergic hypofunction. CONCLUSION Despite the accumulating evidences, the interaction between cholinergic neurotransmission and the physiological significance of PTM events remain speculative and still needs further exploration. This review focuses on the role of cholinergic system and discusses the significance of PTMs in pathological progression of AD and highlights some important future directions.
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Affiliation(s)
- Touqeer Ahmed
- Neurobiology Laboratory, Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad, 44000, Pakistan
| | - Saadia Zahid
- Neurobiology Laboratory, Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad, 44000, Pakistan
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13
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Optimising PET approaches to measuring 5-HT release in human brain. Synapse 2015; 69:505-11. [DOI: 10.1002/syn.21835] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 05/28/2015] [Accepted: 06/08/2015] [Indexed: 01/16/2023]
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14
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Finnema SJ, Scheinin M, Shahid M, Lehto J, Borroni E, Bang-Andersen B, Sallinen J, Wong E, Farde L, Halldin C, Grimwood S. Application of cross-species PET imaging to assess neurotransmitter release in brain. Psychopharmacology (Berl) 2015; 232:4129-57. [PMID: 25921033 PMCID: PMC4600473 DOI: 10.1007/s00213-015-3938-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 04/09/2015] [Indexed: 01/03/2023]
Abstract
RATIONALE This review attempts to summarize the current status in relation to the use of positron emission tomography (PET) imaging in the assessment of synaptic concentrations of endogenous mediators in the living brain. OBJECTIVES Although PET radioligands are now available for more than 40 CNS targets, at the initiation of the Innovative Medicines Initiative (IMI) "Novel Methods leading to New Medications in Depression and Schizophrenia" (NEWMEDS) in 2009, PET radioligands sensitive to an endogenous neurotransmitter were only validated for dopamine. NEWMEDS work-package 5, "Cross-species and neurochemical imaging (PET) methods for drug discovery", commenced with a focus on developing methods enabling assessment of changes in extracellular concentrations of serotonin and noradrenaline in the brain. RESULTS Sharing the workload across institutions, we utilized in vitro techniques with cells and tissues, in vivo receptor binding and microdialysis techniques in rodents, and in vivo PET imaging in non-human primates and humans. Here, we discuss these efforts and review other recently published reports on the use of radioligands to assess changes in endogenous levels of dopamine, serotonin, noradrenaline, γ-aminobutyric acid, glutamate, acetylcholine, and opioid peptides. The emphasis is on assessment of the availability of appropriate translational tools (PET radioligands, pharmacological challenge agents) and on studies in non-human primates and human subjects, as well as current challenges and future directions. CONCLUSIONS PET imaging directed at investigating changes in endogenous neurochemicals, including the work done in NEWMEDS, have highlighted an opportunity to further extend the capability and application of this technology in drug development.
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Affiliation(s)
- Sjoerd J. Finnema
- />Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Stockholm, Sweden
| | - Mika Scheinin
- />Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Turku, Finland , />Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland
| | - Mohammed Shahid
- />Research and Development, Orion Corporation, Orion Pharma, Turku, Finland
| | - Jussi Lehto
- />Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Turku, Finland
| | - Edilio Borroni
- />Neuroscience Department, Hoffman-La Roche, Basel, Switzerland
| | | | - Jukka Sallinen
- />Research and Development, Orion Corporation, Orion Pharma, Turku, Finland
| | - Erik Wong
- />Neuroscience Innovative Medicine Unit, AstraZeneca, Wilmington, DE USA
| | - Lars Farde
- />Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Stockholm, Sweden , />Translational Science Center at Karolinska Institutet, AstraZeneca, Stockholm, Sweden
| | - Christer Halldin
- />Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Stockholm, Sweden
| | - Sarah Grimwood
- Neuroscience Research Unit, Pfizer Inc, Cambridge, MA, USA. .,, 610 Main Street, Cambridge, MA, 02139, USA.
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Verbeek J, Eriksson J, Syvänen S, Labots M, de Lange ECM, Voskuyl RA, Mooijer MPJ, Rongen M, Lammertsma AA, Windhorst AD. [11C]phenytoin revisited: synthesis by [11C]CO carbonylation and first evaluation as a P-gp tracer in rats. EJNMMI Res 2012; 2:36. [PMID: 22747744 PMCID: PMC3506555 DOI: 10.1186/2191-219x-2-36] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 06/09/2012] [Indexed: 01/06/2023] Open
Abstract
UNLABELLED BACKGROUND At present, several positron emission tomography (PET) tracers are in use for imaging P-glycoprotein (P-gp) function in man. At baseline, substrate tracers such as R-[11C]verapamil display low brain concentrations with a distribution volume of around 1. [11C]phenytoin is supposed to be a weaker P-gp substrate, which may lead to higher brain concentrations at baseline. This could facilitate assessment of P-gp function when P-gp is upregulated. The purpose of this study was to synthesize [11C]phenytoin and to characterize its properties as a P-gp tracer. METHODS [11C]CO was used to synthesize [11C]phenytoin by rhodium-mediated carbonylation. Metabolism and, using PET, brain pharmacokinetics of [11C]phenytoin were studied in rats. Effects of P-gp function on [11C]phenytoin uptake were assessed using predosing with tariquidar. RESULTS [11C]phenytoin was synthesized via [11C]CO in an overall decay-corrected yield of 22 ± 4%. At 45 min after administration, 19% and 83% of radioactivity represented intact [11C]phenytoin in the plasma and brain, respectively. Compared with baseline, tariquidar predosing resulted in a 45% increase in the cerebral distribution volume of [11C]phenytoin. CONCLUSIONS Using [11C]CO, the radiosynthesis of [11C]phenytoin could be improved. [11C]phenytoin appeared to be a rather weak P-gp substrate.
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Affiliation(s)
- Joost Verbeek
- Department of Nuclear Medicine & PET Research, Radionuclide Centre, VU University Medical Center, P.O. box 7057, Amsterdam 1081, HV, The Netherlands
| | - Jonas Eriksson
- Department of Nuclear Medicine & PET Research, Radionuclide Centre, VU University Medical Center, P.O. box 7057, Amsterdam 1081, HV, The Netherlands
| | - Stina Syvänen
- Division of Pharmacology, LACDR, Leiden University, Leiden, 2300, RA, The Netherlands
| | - Maaike Labots
- Division of Pharmacology, LACDR, Leiden University, Leiden, 2300, RA, The Netherlands
| | | | - Rob A Voskuyl
- Division of Pharmacology, LACDR, Leiden University, Leiden, 2300, RA, The Netherlands
- Epilepsy Institutes of The Netherlands Foundation (SEIN), Heemstede, 2103, SW, The Netherlands
| | - Martinus P J Mooijer
- Department of Nuclear Medicine & PET Research, Radionuclide Centre, VU University Medical Center, P.O. box 7057, Amsterdam 1081, HV, The Netherlands
| | - Marissa Rongen
- Department of Nuclear Medicine & PET Research, Radionuclide Centre, VU University Medical Center, P.O. box 7057, Amsterdam 1081, HV, The Netherlands
| | - Adriaan A Lammertsma
- Department of Nuclear Medicine & PET Research, Radionuclide Centre, VU University Medical Center, P.O. box 7057, Amsterdam 1081, HV, The Netherlands
| | - Albert D Windhorst
- Department of Nuclear Medicine & PET Research, Radionuclide Centre, VU University Medical Center, P.O. box 7057, Amsterdam 1081, HV, The Netherlands
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