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Kelberman M, Keilholz S, Weinshenker D. What's That (Blue) Spot on my MRI? Multimodal Neuroimaging of the Locus Coeruleus in Neurodegenerative Disease. Front Neurosci 2020; 14:583421. [PMID: 33122996 PMCID: PMC7573566 DOI: 10.3389/fnins.2020.583421] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 09/16/2020] [Indexed: 01/04/2023] Open
Abstract
The locus coeruleus (LC) has long been underappreciated for its role in the pathophysiology of Alzheimer’s disease (AD), Parkinson’s disease (PD), and other neurodegenerative disorders. While AD and PD are distinct in clinical presentation, both are characterized by prodromal protein aggregation in the LC, late-stage degeneration of the LC, and comorbid conditions indicative of LC dysfunction. Many of these early studies were limited to post-mortem histological techniques due to the LC’s small size and location deep in the brainstem. Thus, there is a growing interest in utilizing in vivo imaging of the LC as a predictor of preclinical neurodegenerative processes and biomarker of disease progression. Simultaneously, neuroimaging in animal models of neurodegenerative disease holds promise for identifying early alterations to LC circuits, but has thus far been underutilized. While still in its infancy, a handful of studies have reported effects of single gene mutations and pathology on LC function in disease using various neuroimaging techniques. Furthermore, combining imaging and optogenetics or chemogenetics allows for interrogation of network connectivity in response to changes in LC activity. The purpose of this article is twofold: (1) to review what magnetic resonance imaging (MRI) and positron emission tomography (PET) have revealed about LC dysfunction in neurodegenerative disease and its potential as a biomarker in humans, and (2) to explore how animal models can be used to test hypotheses derived from clinical data and establish a mechanistic framework to inform LC-focused therapeutic interventions to alleviate symptoms and impede disease progression.
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Affiliation(s)
- Michael Kelberman
- Department of Human Genetics, Emory University, Atlanta, GA, United States
| | - Shella Keilholz
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
| | - David Weinshenker
- Department of Human Genetics, Emory University, Atlanta, GA, United States
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Alluri SR, Kim SW, Volkow ND, Kil KE. PET Radiotracers for CNS-Adrenergic Receptors: Developments and Perspectives. Molecules 2020; 25:molecules25174017. [PMID: 32899124 PMCID: PMC7504810 DOI: 10.3390/molecules25174017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/29/2020] [Accepted: 09/01/2020] [Indexed: 12/30/2022] Open
Abstract
Epinephrine (E) and norepinephrine (NE) play diverse roles in our body’s physiology. In addition to their role in the peripheral nervous system (PNS), E/NE systems including their receptors are critical to the central nervous system (CNS) and to mental health. Various antipsychotics, antidepressants, and psychostimulants exert their influence partially through different subtypes of adrenergic receptors (ARs). Despite the potential of pharmacological applications and long history of research related to E/NE systems, research efforts to identify the roles of ARs in the human brain taking advantage of imaging have been limited by the lack of subtype specific ligands for ARs and brain penetrability issues. This review provides an overview of the development of positron emission tomography (PET) radiotracers for in vivo imaging of AR system in the brain.
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Affiliation(s)
- Santosh Reddy Alluri
- University of Missouri Research Reactor, University of Missouri, Columbia, MO 65211-5110, USA;
| | - Sung Won Kim
- Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-1013, USA;
| | - Nora D. Volkow
- Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-1013, USA;
- National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD 20892-1013, USA
- Correspondence: (N.D.V.); (K.-E.K.); Tel.: +1-(301)-443-6480 (N.D.V.); +1-(573)-884-7885 (K.-E.K.)
| | - Kun-Eek Kil
- University of Missouri Research Reactor, University of Missouri, Columbia, MO 65211-5110, USA;
- Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO 65211, USA
- Correspondence: (N.D.V.); (K.-E.K.); Tel.: +1-(301)-443-6480 (N.D.V.); +1-(573)-884-7885 (K.-E.K.)
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Krzyczmonik A, Keller T, López-Picón FR, Forsback S, Kirjavainen AK, Takkinen JS, Wasilewska A, Scheinin M, Haaparanta-Solin M, Sączewski F, Solin O. Radiosynthesis and Preclinical Evaluation of an α 2A-Adrenoceptor Tracer Candidate, 6-[ 18F]Fluoro-marsanidine. Mol Imaging Biol 2020; 21:879-887. [PMID: 30710261 DOI: 10.1007/s11307-019-01317-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE The α2-adrenoceptors mediate many effects of norepinephrine and epinephrine, and participate in the regulation of neuronal, endocrine, cardiovascular, vegetative, and metabolic functions. Of the three receptor subtypes, only α2A and α2C are found in the brain in significant amounts. Subtype-selective positron emission tomography (PET) imaging of α2-adrenoceptors has been limited to the α2C subtype. Here, we report the synthesis of 6-[18F]fluoro-marsanidine, a subtype-selective PET tracer candidate for α2A-adrenoceptors, and its preclinical evaluation in rats and mice. PROCEDURES 6-[18F]Fluoro-marsanidine was synthesized using electrophilic F-18 fluorination with [18F]Selectfluor bis(triflate). The tracer was evaluated in Sprague Dawley rats and in α2A-knockout (KO) and wild-type (WT) mice for subtype selectivity. In vivo PET imaging and ex vivo brain autoradiography were performed to determine the tracer distribution in the brain. The specificity of the tracer for the target was determined by pretreatment with the subtype-non-selective α2-agonist medetomidine. The peripheral biodistribution and extent of metabolism of 6-[18F]fluoro-marsanidine were also analyzed. RESULTS 6-[18F]Fluoro-marsanidine was synthesized with [18F]Selectfluor bis(triflate) in a radiochemical yield of 6.4 ± 1.7 %. The molar activity was 3.1 to 26.6 GBq/μmol, and the radiochemical purity was > 99 %. In vivo studies in mice revealed lower uptake in the brains of α2A-KO mice compared to WT mice. The results for selectivity were confirmed by ex vivo brain autoradiography. Blocking studies revealed reduced uptake in α2A-adrenoceptor-rich brain regions in pretreated animals, demonstrating the specificity of the tracer. Metabolite analyses revealed very rapid metabolism of 6-[18F]fluoro-marsanidine with blood-brain barrier-permeable metabolites in both rats and mice. CONCLUSION 6-[18F]Fluoro-marsanidine was synthesized and evaluated as a PET tracer candidate for brain α2A-adrenoceptors. However, rapid metabolism, extensive presence of labeled metabolites in the brain, and high non-specific uptake in mouse and rat brain make 6-[18F]fluoro-marsanidine unsuitable for α2A-adrenoceptor targeting in rodents in vivo.
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Affiliation(s)
- Anna Krzyczmonik
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Thomas Keller
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Francisco R López-Picón
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Sarita Forsback
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,Department of Chemistry, University of Turku, Turku, Finland
| | - Anna K Kirjavainen
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Jatta S Takkinen
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Aleksandra Wasilewska
- Department of Chemical Technology of Drugs, Faculty of Pharmacy, Medical University of Gdańsk, Gdańsk, Poland
| | - Mika Scheinin
- Institute of Biomedicine, University of Turku, and Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland
| | - Merja Haaparanta-Solin
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Franciszek Sączewski
- Department of Chemical Technology of Drugs, Faculty of Pharmacy, Medical University of Gdańsk, Gdańsk, Poland
| | - Olof Solin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland. .,Department of Chemistry, University of Turku, Turku, Finland. .,Accelerator Laboratory, Turku PET Centre, Åbo Akademi University, Kiinamyllynkatu 4-8, FI-20520, Turku, Finland.
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The chemistry of labeling heterocycles with carbon-11 or fluorine-18 for biomedical imaging. ADVANCES IN HETEROCYCLIC CHEMISTRY 2020. [DOI: 10.1016/bs.aihch.2019.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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A new, simple and robust radioligand binding method used to determine kinetic off-rate constants for unlabeled ligands. Application at α 2A - and α 2C -adrenoceptors. Eur J Pharmacol 2016; 788:113-121. [DOI: 10.1016/j.ejphar.2016.06.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 06/12/2016] [Accepted: 06/15/2016] [Indexed: 10/21/2022]
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Leonard MG, Jung S, Andurkar SV, Gulati A. Centhaquin attenuates hyperalgesia and non-evoked guarding in a rat model of postoperative pain primarily through α2B-adrenoceptors. Eur J Pharmacol 2016; 789:81-87. [PMID: 27397429 DOI: 10.1016/j.ejphar.2016.07.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/27/2016] [Accepted: 07/07/2016] [Indexed: 10/21/2022]
Abstract
Centhaquin has been shown to produce antinociception in the mouse hot plate and tail flick assays through the opioid, the α2A and α2B adrenoceptors. Present study was conducted to determine the effects of centhaquin in a rat model of postoperative pain. Involvement of opioid, and adrenergic receptors was assessed by pretreating rats with antagonists at the opioid (naloxone), α2-(atipamezole) or α2B-(imiloxan) adrenergic receptors. Postoperative pain was induced by hind paw plantar incision in male Sprague Dawley rats. Antihyperalgesic effects were determined by measurement of paw withdrawal latencies and withdrawal force, using dynamic von Frey filaments; attenuation of non-evoked guarding was measured by assigning pain scores to spontaneous behaviors. Rotarod test was used to determine motor impairment. Animals received saline, centhaquin or antagonist plus centhaquin. Centhaquin produced dose-dependent antihyperalgesic effect and attenuation of non-evoked guarding behavior, versus saline treated rats (P<0.05). Naloxone partially blocked while atipamezole and imiloxan significantly reversed centhaquin's antihyperalgesic effects (P<0.05). Attenuation of non-evoked guarding behavior was also blocked, but was not statistically significant. Imiloxan produced a greater block compared to atipamezole while naloxone had no significant effect. Rotarod testing indicated that centhaquin did not cause motor impairment. This is the first report demonstrating centhaquin antinociception in the rat postoperative pain model. Opioid, α2 adrenergic, and particularly α2B adrenergic receptors are involved in mediating antihyperalgesia while attenuation of nonevoked guarding is mediated by α2B/α2 adrenergic receptors. Centhaquin could be an effective non-sedating alternative in treating postoperative pain in ambulatory surgeries.
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Affiliation(s)
- Mary G Leonard
- Department of Pharmaceutical Sciences, Chicago College of Pharmacy, Midwestern University, Downers Grove, IL 60515, USA
| | - Shawn Jung
- Department of Biomedical Sciences, Chicago College of Health Sciences, Midwestern University, Downers Grove, IL 60515, USA
| | - Shridhar V Andurkar
- Department of Pharmaceutical Sciences, Chicago College of Pharmacy, Midwestern University, Downers Grove, IL 60515, USA.
| | - Anil Gulati
- Department of Pharmaceutical Sciences, Chicago College of Pharmacy, Midwestern University, Downers Grove, IL 60515, USA
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Lehto J, Hirvonen MM, Johansson J, Kemppainen J, Luoto P, Naukkarinen T, Oikonen V, Arponen E, Rouru J, Sallinen J, Scheinin H, Vuorilehto L, Finnema SJ, Halldin C, Rinne JO, Scheinin M. Validation of [(11) C]ORM-13070 as a PET tracer for alpha2c -adrenoceptors in the human brain. Synapse 2015; 69:172-81. [PMID: 25530024 DOI: 10.1002/syn.21798] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 12/03/2014] [Accepted: 12/10/2014] [Indexed: 12/24/2022]
Abstract
This study explored the use of the α2C -adrenoceptor PET tracer [(11) C]ORM-13070 to monitor α2C -AR occupancy in the human brain. The subtype-nonselective α2 -AR antagonist atipamezole was administered to eight healthy volunteer subjects to determine its efficacy and potency (Emax and EC50 ) at inhibiting tracer uptake. We also explored whether the tracer could reveal changes in the synaptic concentrations of endogenous noradrenaline in the brain, in response to several pharmacological and sensory challenge conditions. We assessed occupancy from the bound-to-free ratio measured during 5-30 min post injection. Based on extrapolation of one-site binding, the maximal extent of inhibition of striatal [(11) C]ORM-13070 uptake (Emax ) achievable by atipamezole was 78% (95% CI 69-87%) in the caudate nucleus and 65% (53-77%) in the putamen. The EC50 estimates of atipamezole (1.6 and 2.5 ng/ml, respectively) were in agreement with the drug's affinity to α2C -ARs. These findings represent clear support for the use of [(11) C]ORM-13070 for monitoring drug occupancy of α2C -ARs in the living human brain. Three of the employed noradrenaline challenges were associated with small, approximately 10-16% average reductions in tracer uptake in the dorsal striatum (atomoxetine, ketamine, and the cold pressor test; P < 0.05 for all), but insulin-induced hypoglycemia did not affect tracer uptake. The tracer is suitable for studying central nervous system receptor occupancy by α2C -AR ligands in human subjects. [(11) C]ORM-13070 also holds potential as a tool for in vivo monitoring of synaptic concentrations of noradrenaline, but this remains to be further evaluated in future studies.
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Affiliation(s)
- Jussi Lehto
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Turku, Finland; Clinical Research Services Turku CRST, Turku, Finland; Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland
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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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Fluorinated analogues of marsanidine, a highly α2-AR/imidazoline I1 binding site-selective hypotensive agent. Synthesis and biological activities. Eur J Med Chem 2014; 87:386-97. [PMID: 25282262 DOI: 10.1016/j.ejmech.2014.09.083] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 09/25/2014] [Accepted: 09/26/2014] [Indexed: 01/25/2023]
Abstract
The aim of these studies was to establish the influence of fluorination of the indazole ring on the pharmacological properties of two selective α2-adrenoceptor (α2-AR) agonists: 1-[(imidazolidin-2-yl)imino]-1H-indazole (marsanidine, A) and its methylene analogue 1-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-1H-indazole (B). Introduction of fluorine into the indazole ring of A and B reduced both binding affinity and α2-AR/I1 imidazoline binding site selectivity. The most α2-AR-selective ligands were 6-fluoro-1-[(imidazolidin-2-yl)imino]-1H-indazole (6c) and 7-fluoro-1-[(imidazolidin-2-yl)imino]-1H-indazole (6d). The in vivo cardiovascular properties of fluorinated derivatives of A and B revealed that in both cases the C-7 fluorination leads to compounds with the highest hypotensive and bradycardic activities. The α2-AR partial agonist 6c was prepared as a potential lead compound for development of a radiotracer for PET imaging of brain α2-ARs.
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Arponen E, Helin S, Marjamäki P, Grönroos T, Holm P, Löyttyniemi E, Någren K, Scheinin M, Haaparanta-Solin M, Sallinen J, Solin O. A PET Tracer for Brain α2C Adrenoceptors, (11)C-ORM-13070: Radiosynthesis and Preclinical Evaluation in Rats and Knockout Mice. J Nucl Med 2014; 55:1171-7. [PMID: 24799619 DOI: 10.2967/jnumed.113.135574] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 03/17/2014] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED We report the development of a PET tracer for α2C adrenoceptor imaging and its preliminary preclinical evaluation. α2C adrenoceptors in the human brain may be involved in various neuropsychiatric disorders, such as depression, schizophrenia, and neurodegenerative diseases. PET tracers are needed for imaging of this receptor system in vivo. METHODS High-specific-activity (11)C-ORM-13070 (1-[(S)-1-(2,3-dihydrobenzo[1,4]dioxin-2-yl)methyl]-4-(3-(11)C-methoxymethylpyridin-2-yl)-piperazine) was synthesized by (11)C-methylation of O-desmethyl-ORM-13070 with (11)C-methyl triflate, which was prepared from cyclotron-produced (11)C-methane via (11)C-methyl iodide. Rats and mice were investigated in vivo with PET and ex vivo with autoradiography. The specificity of (11)C-ORM-13070 binding to α2 adrenoceptors was demonstrated in rats pretreated with atipamezole, an α2 adrenoceptor antagonist. The α2C adrenoceptor selectivity of the tracer was determined by comparing tracer binding in wild-type and α2A- and α2AC adrenoceptor knockout (KO) mice. (11)C-ORM-13070 and its radioactive metabolites in rat plasma and brain tissue were analyzed with radio-high-performance liquid chromatography and mass spectroscopy. Human radiation dose estimates were extrapolated from rat biodistribution data. RESULTS The radiochemical yield, calculated from initial cyclotron-produced (11)C-methane, was 9.6% ± 2.7% (decay-corrected to end of bombardment). The specific activity of the product was 640 ± 390 GBq/μmol (decay-corrected to end of synthesis). The radiochemical purity exceeded 99% in all syntheses. The highest levels of tracer binding were observed in the striatum and olfactory tubercle of rats and control and α2A KO mice-that is, in the brain regions known to contain the highest densities of α2C adrenoceptors. In rats pretreated with atipamezole and in α2AC KO mice, (11)C tracer binding in the striatum and olfactory tubercle was low, similar to that of the frontal cortex and thalamus, regions with low densities of α2C adrenoceptors. Two radioactive metabolites were found in rat plasma, but only one of them was found in the brain; their identity was not revealed. The estimated effective radiation dose was comparable with the average exposure level in PET studies with (11)C tracers. CONCLUSION An efficient method for the radiosynthesis of (11)C-ORM-13070 was developed. (11)C-ORM-13070 emerged as a potential novel radiotracer for in vivo imaging of brain α2C adrenoceptors.
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Affiliation(s)
- Eveliina Arponen
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Semi Helin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Päivi Marjamäki
- MediCity/PET Preclinical Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Tove Grönroos
- MediCity/PET Preclinical Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Patrik Holm
- Orion Pharma, Research and Development, Turku, Finland
| | | | - Kjell Någren
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Mika Scheinin
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, and Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland; and
| | - Merja Haaparanta-Solin
- MediCity/PET Preclinical Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | | | - Olof Solin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland Accelerator Laboratory, Åbo Akademi University, Turku, Finland
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Kawamura K, Akiyama M, Yui J, Yamasaki T, Hatori A, Kumata K, Wakizaka H, Takei M, Nengaki N, Yanamoto K, Fukumura T, Zhang MR. In vivo evaluation of limiting brain penetration of probes for α(2C)-adrenoceptor using small-animal positron emission tomography. ACS Chem Neurosci 2010; 1:520-8. [PMID: 22778842 DOI: 10.1021/cn1000364] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 05/25/2010] [Indexed: 11/30/2022] Open
Abstract
To evaluate in vivo brain penetration of α(2C)-adrenoceptor (α(2C)-AR) antagonists as a therapeutic agent, we synthesized two new (11)C-labeled selective α(2C)-AR antagonists 4-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-2-aryl-7-methoxybenzofuran ([(11)C]MBF) and acridin-9-yl-[4-(4-methylpiperazin-1-yl)phenyl]amine ([(11)C]JP-1302) as α(2C)-AR-selective positron emission tomography (PET) probes. The radiochemical yield, specific activity, and radiochemical purity of these probes was appropriate for injection. To evaluate whether the brain penetration of these probes is related to the function of two major drug efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), we performed PET studies using wild-type and P-gp/Bcrp knockout mice. In wild-type mice, the radioactivity level after injection with [(11)C]MBF initially increased and effluxed immediately from the brain, whereas that with [(11)C]JP-1302 was distributed throughout the brain. However, the regional distribution of radioactivity after injection with [(11)C]JP-1302 in the brain was different from that of α(2C)-ARs. In P-gp/Bcrp knockout mice, uptake of [(11)C]MBF was approximately 3.7-fold higher and that of [(11)C]JP-1302 was approximately 1.6-fold higher than those in wild-type mice. These results indicate that brain penetration of the two PET probes was affected by modulation of P-gp and Bcrp functions.
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Affiliation(s)
| | | | - Joji Yui
- Department of Molecular Probes and
| | | | | | | | - Hidekatsu Wakizaka
- Department of Molecular Probes and
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555, Japan
| | - Makoto Takei
- Department of Molecular Probes and
- Tokyo Nuclear Services Co., Ltd., Tokyo 110-0005, Japan
| | - Nobuki Nengaki
- Department of Molecular Probes and
- SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Kazuhiko Yanamoto
- Department of Molecular Probes and
- Division of Health Sciences, Graduate School of Medicine, Osaka University, Suita 565-0871, Japan
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Prabhakaran J, Majo VJ, Milak MS, Mali P, Savenkova L, Mann JJ, Parsey RV, Kumar JD. Synthesis and in vivo evaluation of [11C]MPTQ: A potential PET tracer for alpha2A-adrenergic receptors. Bioorg Med Chem Lett 2010; 20:3654-7. [DOI: 10.1016/j.bmcl.2010.04.099] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 04/20/2010] [Accepted: 04/21/2010] [Indexed: 12/28/2022]
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Abstract
The aberrant expression and function of certain receptors in tumours and other diseased tissues make them preferable targets for molecular imaging. PET and SPECT radionuclides can be used to label specific ligands with high affinity for the target receptors. The functional information obtained from imaging these receptors can be used to better understand the systems under investigation and for diagnostic and therapeutic applications. This review discusses some of the aspects of receptor imaging with small molecule tracers by PET and SPECT and reviews some of the tracers for the receptor imaging of tumours and brain, heart and lung disorders.
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Affiliation(s)
- Aviv Hagooly
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S. Kingshighway Blvd., Campus Box 8225, St. Louis, MO 63110, USA.
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Van der Mey M, Windhorst AD, Klok RP, Herscheid JDM, Kennis LE, Bischoff F, Bakker M, Langlois X, Heylen L, Jurzak M, Leysen JE. Synthesis and biodistribution of [11C]R107474, a new radiolabeled α2-adrenoceptor antagonist. Bioorg Med Chem 2006; 14:4526-34. [PMID: 16517171 DOI: 10.1016/j.bmc.2006.02.029] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 02/09/2006] [Accepted: 02/14/2006] [Indexed: 10/24/2022]
Abstract
R107474, 2-methyl-3-[2-(1,2,3,4-tetrahydrobenzo[4,5]furo[3,2-c]pyridin-2-yl)ethyl]-4H-pyrido[1,2-a]pyrimidin-4-one, was investigated using in vitro and in vivo receptor assays and proved to be a potent and relatively selective alpha(2)-adrenoceptor antagonist. Performed assays in vitro were inhibition of binding to a large number of neurotransmitter receptor sites, drug receptor binding sites, ion channel binding sites, peptide receptor binding sites, and the monoamine transporters in membrane preparations of brain tissue or of cells expressing the cloned human receptors. The compound has subnanomolar affinity for halpha(2A)- and halpha(2C)-adrenoceptors (K(i) = 0.13 and 0.15 nM, respectively) and showed nanomolar affinity for the halpha(2B)-adrenoceptors and 5-hydroxytryptamine(7) (h5-HT(7)) receptors (K(i) = 1 and 5 nM, respectively). R107474 interacted weakly (K(i) values ranging between 81 and 920 nM) with dopamine-hD(2L), -hD(3) and -hD(4), h5-HT(1D)-, h5-HT(1F)-, h5-HT(2A)-, h5-HT(2C)-, and h5-HT(5A) receptors. The compound, tested up to 10 microM, interacted only at micromolar concentrations or not at all with any of the other receptor or transporter binding sites tested in this study. In vivo alpha(2A)- and alpha(2C)-adrenoceptor occupancy was measured by ex vivo autoradiography 1h after subcutaneous (sc) administration of R107474. It was found that R107474 occupies the alpha(2A)- and alpha(2C)-adrenoceptors with an ED(50) (95% confidence limits) of 0.014 mg/kg sc (0.009-0.019) and 0.026 mg/kg sc (0.022-0.030), respectively. Radiolabeled 2-methyl-3-[2-([1-(11)C]-1,2,3,4-tetrahydrobenzo[4,5]furo[3,2-c]pyridin-2-yl)ethyl]-4H-pyrido[1,2-a]pyrimidin-4-one ([(11)C]R107474) was prepared and evaluated as a potential positron emission tomography (PET) ligand for studying central alpha(2)-adrenoceptors. [(11)C]R107474 was obtained via a Pictet-Spengler reaction with [(11)C]formaldehyde in 33 +/- 4% overall decay-corrected radiochemical yield. The total synthesis time was 55 min and the specific activity was 24-28 GBq/micromol. The biodistribution of [(11)C]R107474 in rats revealed that the uptake of [(11)C]R107474 after in vivo intravenous administration is very rapid; in most tissues (including the brain) it reaches maximum concentration at 5 min after tracer injection. In agreement with the known distribution of alpha(2)-adrenoceptors in the brain, highest uptake of radioactivity was observed in septum (3.54 +/- 0.52 ID/g, 5 min pi) and entorhinal cortex (1.57 +/- 0.10 ID/g, 5 min pi). Tissue/cerebellum concentration ratios for septum (5.38 +/- 0.45, 30 min pi) and entorhinal cortex (3.43+/-0.24, 30 min pi) increased with time due to rapid uptake followed by a slow washout. In vivo blocking experiments using the non-selective alpha(2)-adrenoceptor antagonist mirtazapine demonstrated specific inhibition of [(11)C]R107474 binding in selective brain areas. The receptor binding profile of mirtazapine is reported and the selectivity of inhibition of binding is discussed. These results suggest that [(11)C]R107474 deserves further investigation as a potential radioligand for studying alpha(2)-adrenoceptors using PET.
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Affiliation(s)
- M Van der Mey
- VU University Medical Center, Department of Nuclear Medicine and PET Research, Amsterdam, The Netherlands.
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Elsinga PH, van Waarde A, Vaalburg W. Receptor imaging in the thorax with PET. Eur J Pharmacol 2005; 499:1-13. [PMID: 15363946 DOI: 10.1016/j.ejphar.2004.06.057] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2004] [Revised: 06/23/2004] [Accepted: 06/29/2004] [Indexed: 10/26/2022]
Abstract
This review focuses on positron emission tomography (PET)-imaging of receptors in the sympathetic and the parasympathetic systems of heart and lung and highlights the human applications of PET. For the alpha-adrenoceptor, only [11C]GB67 (N2-[6-[(4-amino-6,7-dimethoxy-2-quinazolinyl)(methyl)amino]hexyl]-N2-[11C]methyl-2-furamide hydrochloride) has been developed. Its potential for application in patients needs to be assessed. For both the beta-adrenergic and the muscarinic systems, potent PET radioligands have been prepared and evaluated in patients. It has been possible to measure receptor densities quantitatively in human heart [[11C]MQNB: [11C]methylquinuclidinyl benzilate, [11C]CGP12177: S-(3'-t-butylamino-2'-hydroxypropoxy)-benzimidazol-2-[11C]one and [11C]CGP12388: (S)-4-(3-(2'-[11C]isopropylamino)-2-hydroxypropoxy)-2H-benzimidazol-2-one] and qualitatively in lung [[11C]VC002: N-[11C]-methyl-piperidin-4-yl-2-cyclohexyl-2-hydroxy-2-phenylacetate and [11C]CGP12177]. Besides these subtype nonselective radioligands, the development of compounds that are selective for one subtype are ongoing and have not found successful application in humans yet.
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Affiliation(s)
- Philip H Elsinga
- Groningen University Hospital, PET-center, P.O. Box 30001, 9700 RB Groningen, The Netherlands.
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Roeda D, Sipilä H, Bramoullé Y, Enas JD, Vaufrey F, Dollé F, Crouzel C. Synthesis of [11C]atipamezole, a potential PET ligand for theα2-adrenergic receptor in the brain. J Labelled Comp Radiopharm 2001. [DOI: 10.1002/jlcr.532] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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McConathy J, Kilts CD, Goodman MM. Radioligands for PET and SPECT Imaging of the central noradrenergic system. CNS Spectr 2001; 6:704-9. [PMID: 15520617 DOI: 10.1017/s1092852900001401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In the central nervous system, the neurotransmitter norepinephrine is involved in normal physiology, neuropsychiatric disorders, and the effects of numerous drugs. Although alterations of the central noradrenergic system are involved in the pathophysiology and pharmacotherapy of mood disorders, the basis and nature of these changes remain unresolved. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging agents will be valuable for further elucidating the roles of norepinephrine in health and disease. This review discusses PET and SPECT radioligands that have been developed for the enzymes, receptors, and transporters involved in noradrenergic neurotransmission. Currently, imaging agents that exhibit specific in vivo uptake in the brain have been described for monoamine oxidase A and beta-adrenergic receptors, but have not undergone detailed evaluation or experimental application. Based on the successful development and utilization of in vivo imaging agents for elements of the central dopaminergic and serotoninergic systems, PET and SPECT radioligands are expected to serve as new tools for studying the physiology, pathophysiology, and pharmacology of the central noradrenergic system.
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Affiliation(s)
- J McConathy
- Neuroscience Program, Emory University, Atlanta, GA, USA.
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Qin X, Frech P. Liquid chromatography/mass spectrometry (LC/MS) identification of photooxidative degradates of crystalline and amorphous MK-912. J Pharm Sci 2001; 90:833-44. [PMID: 11458333 DOI: 10.1002/jps.1037] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
How and why the chemical stability of amorphous solid is different from crystalline solid is an important problem. In this study, this problem is addressed by evaluation of the photodegradation of both crystalline and amorphous MK-912 (an alpha-2 adrenoceptor antagonist) according to the photostability tests of the ICH (International Conference on Harmonization) guidelines. Under the ICH conditions, the photodegradation rate of the amorphous MK-912 was approximately 40 times faster than that of the crystalline MK-912. The photodegradation yielded isomeric, oxidative degradates. Three keto-degradates (molecular weight of 14 Da over MK-912) were observed for both forms. But, whereas five alcohol and one N-oxide degradates (molecular weight of 16 Da over MK-912) were observed for the amorphous form, only one alcohol degradate was observed for the crystalline form. Liquid chromatography/mass spectrometry (LC/MS) and LC/MS/MS were applied to identify these low-level photodegradates. A thorough analysis of the MS/MS data of protonated MK-912 was the key to the identification, and the special MS/MS features of the degradates due to the structural modifications from degradations were also important. Following this strategy, the structures of all the photodegradates were proposed. The structural identification of the photodegradates of MK-912 shed light on the different photostabilities between the crystalline and amorphous MK-912.
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Affiliation(s)
- X Qin
- Merck Research Laboratories, WP78-302, West Point, Pennsylvania 19486, USA
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Roeda D, Sipilä HT, Bramoullé Y, Enas JD, Vaufrey F, Dollé F, Crouzel C. Carbon-11 labelling of the α-2 antagonist atipamezole. J Labelled Comp Radiopharm 2001. [DOI: 10.1002/jlcr.25804401150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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