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Colom M, Vidal B, Zimmer L. Is There a Role for GPCR Agonist Radiotracers in PET Neuroimaging? Front Mol Neurosci 2019; 12:255. [PMID: 31680859 PMCID: PMC6813225 DOI: 10.3389/fnmol.2019.00255] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/02/2019] [Indexed: 12/30/2022] Open
Abstract
Positron emission tomography (PET) is a molecular imaging modality that enables in vivo exploration of metabolic processes and especially the pharmacology of neuroreceptors. G protein-coupled receptors (GPCRs) play an important role in numerous pathophysiologic disorders of the central nervous system. Thus, they are targets of choice in PET imaging to bring proof concept of change in density in pathological conditions or in pharmacological challenge. At present, most radiotracers are antagonist ligands. In vitro data suggest that properties differ between GPCR agonists and antagonists: antagonists bind to receptors with a single affinity, whereas agonists are characterized by two different affinities: high affinity for receptors that undergo functional coupling to G-proteins, and low affinity for those that are not coupled. In this context, agonist radiotracers may be useful tools to give functional images of GPCRs in the brain, with high sensitivity to neurotransmitter release. Here, we review all existing PET radiotracers used from animals to humans and their role for understanding the ligand-receptor paradigm of GPCR in comparison with corresponding antagonist radiotracers.
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Affiliation(s)
- Matthieu Colom
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France
| | - Benjamin Vidal
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France
| | - Luc Zimmer
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France.,Institut National des Sciences et Techniques Nucléaires, CEA Saclay, Gif-sur-Yvette, France
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Chiral resolution of serial potent and selective σ 1 ligands and biological evaluation of (-)-[ 18F]TZ3108 in rodent and the nonhuman primate brain. Bioorg Med Chem 2017; 25:1533-1542. [PMID: 28129990 DOI: 10.1016/j.bmc.2017.01.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 01/11/2017] [Accepted: 01/13/2017] [Indexed: 11/24/2022]
Abstract
Twelve optically pure enantiomers were obtained using either crystallization or chiral high performance liquid chromatography (HPLC) separation methodologies to resolve six racemic sigma-1 (σ1) receptor ligands. The in vitro binding affinities of each enantiomer for σ1, σ2 receptors and vesicular acetylcholine transporter (VAChT) were determined. Out of the 12 optically pure enantiomers, five displayed very high affinities for σ1 (Ki<2nM) and high selectivity for σ1 versus σ2 and VAChT (>100-fold). The minus enantiomer, (-)-14a ((-)-TZ3108) (Ki-σ1=1.8±0.4nM, Ki-σ2=6960±810nM, Ki-VAChT=980±87nM), was chosen for radiolabeling and further in vivo evaluation in rodents and nonhuman primates (NHPs). A biodistribution study in Sprague Dawley rats showed brain uptake (%ID/gram) of (-)-[18F]TZ3108 reached 1.285±0.062 at 5min and 0.802±0.129 at 120min. NHP microPET imaging studies revealed higher brain uptake of (-)-[18F]TZ3108 and more favorable pharmacokinetics compared to its racemic counterpart. Pretreatment of the animal using two structurally different σ1 ligands significantly decreased accumulation of (-)-[18F]TZ3108 in the brain. Together, our in vivo evaluation results suggest that (-)-[18F]TZ3108 is a promising positron emission tomography (PET) tracer for quantifying σ1 receptor in the brain.
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Banister SD, Manoli M, Kassiou M. The development of radiotracers for imaging sigma (σ) receptors in the central nervous system (CNS) using positron emission tomography (PET). J Labelled Comp Radiopharm 2014; 56:215-24. [PMID: 24285328 DOI: 10.1002/jlcr.3010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 11/19/2012] [Accepted: 11/20/2012] [Indexed: 11/10/2022]
Abstract
Sigma (σ) receptors are unique mammalian proteins, distributed in the central nervous system and elsewhere, which are increasingly implicated in the pathophysiology of virtually all major central nervous system disorders. The heterogeneous but wide distribution of σ1 in the brain has prompted the development of selective radiotracers for imaging these sites using positron emission tomography (PET). To date, some 50 carbon-11-labelled and fluorine-18-labelled candidate PET radioligands targeting σ receptors have been reported. The historical development of selective σ1 receptor ligands as potential PET imaging agents, as well as the radiochemistry and application of the most recently developed examples, is described herein.
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Affiliation(s)
- Samuel D Banister
- Brain and Mind Research Institute, The University of Sydney, NSW, 2050, Australia; School of Chemistry, The University of Sydney, NSW, 2006, Australia
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James ML, Shen B, Nielsen CH, Behera D, Buckmaster CL, Mesangeau C, Zavaleta C, Vuppala PK, Jamalapuram S, Avery BA, Lyons DM, McCurdy CR, Biswal S, Gambhir SS, Chin FT. Evaluation of σ-1 receptor radioligand 18F-FTC-146 in rats and squirrel monkeys using PET. J Nucl Med 2014; 55:147-53. [PMID: 24337599 PMCID: PMC4170105 DOI: 10.2967/jnumed.113.120261] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED The noninvasive imaging of σ-1 receptors (S1Rs) could provide insight into their role in different diseases and lead to novel diagnostic/treatment strategies. The main objective of this study was to assess the S1R radiotracer (18)F-FTC-146 in rats. Preliminary squirrel monkey imaging and human serum/liver microsome studies were performed to gain information about the potential of (18)F-FTC-146 for eventual clinical translation. METHODS The distribution and stability of (18)F-FTC-146 in rats were assessed via PET/CT, autoradiography, γ counting, and high-performance liquid chromatography (HPLC). Preliminary PET/MRI of squirrel monkey brain was conducted along with HPLC assessment of (18)F-FTC-146 stability in monkey plasma and human serum. RESULTS Biodistribution studies showed that (18)F-FTC-146 accumulated in S1R-rich rat organs, including the lungs, pancreas, spleen, and brain. Pretreatment with known S1R compounds, haloperidol, or BD1047, before radioligand administration, significantly attenuated (18)F-FTC-146 accumulation in all rat brain regions by approximately 85% (P < 0.001), suggesting radiotracer specificity for S1Rs. Similarly, PET/CT and autoradiography results demonstrated accumulation of (18)F-FTC-146 in rat brain regions known to contain S1Rs and that this uptake could be blocked by BD1047 pretreatment. Ex vivo analysis of (18)F-FTC-146 in the brain showed that only intact radiotracer was present at 15, 30, and 60 min, whereas rapid metabolism of residual (18)F-FTC-146 was observed in rat plasma. Preliminary monkey PET/MRI studies demonstrated specific accumulation of (18)F-FTC-146 in the brain (mainly in cortical structures, cerebellum, and vermis) that could be attenuated by pretreatment with haloperidol. HPLC of monkey plasma suggested radioligand metabolism, whereas (18)F-FTC-146 appeared to be stable in human serum. Finally, liver microsome studies revealed that (18)F-FTC-146 has a longer half-life in human microsomes, compared with rodents. CONCLUSION Together, these results indicate that (18)F-FTC-146 is a promising tool for visualizing S1Rs in preclinical studies and that it has potential for mapping these sites in the human brain.
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Affiliation(s)
- Michelle L. James
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
| | - Bin Shen
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
| | - Carsten H. Nielsen
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
- Cluster for Molecular Imaging and Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Deepak Behera
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
| | | | - Christophe Mesangeau
- Department of Medicinal Chemistry, University of Mississippi, University, Mississippi
| | - Cristina Zavaleta
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
| | - Pradeep K. Vuppala
- Department of Pharmaceutics, University of Mississippi, University, Mississippi
| | | | - Bonnie A. Avery
- Department of Pharmaceutics, University of Mississippi, University, Mississippi
| | - David M. Lyons
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, California
| | | | - Sandip Biswal
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
| | - Sanjiv S. Gambhir
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
- Department of Bioengineering, Department of Materials Science and Engineering, Stanford University, Stanford, California
| | - Frederick T. Chin
- Molecular Imaging Program at Stanford (MIPS) Department of Radiology, Stanford University, Stanford, California
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Jin H, Fan J, Zhang X, Li J, Flores HP, Perlmutter JS, Parsons SM, Tu Z. Radiosynthesis and in vivo evaluation of a novel σ 1 selective PET ligand. MEDCHEMCOMM 2014; 5:1669-1677. [PMID: 25584182 DOI: 10.1039/c4md00240g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The σ1 receptor is an important target for CNS disorders. We previously identified a σ1 ligand TZ3108 having highly potent (Ki-σ1 = 0.48 nM) and selective affinity for σ1 versus σ2 receptors. TZ3108 was 18F-labeled with F-18 for in vivo evaluation. Biodistribution and blocking studies of [18F]TZ3108 in male Sprague-Dawley rats demonstrated high brain uptake, which was σ1-specific with no in vivo defluorination. MicroPET studies in cynomolgus macaques showed high brain penetration of [18F]TZ3108; the regional brain distribution was consistent with that of the σ1 receptor. Pseudo-equilibrium in the brain was reached ~ 45 min post-injection. Metabolite analysis of [18F]TZ3108 in NHP blood and rodent blood and brain revealed that ~ 70% parent remained in the plasma of NHPs 60 min post-injection and the major radiometabolite did not cross the blood-brain barrier in rats. In summary, the potent, selective and metabolically stable σ1 specific radioligand [18F]TZ3108 represents a potentially useful PET radioligand for quantifying the σ1 receptor in the brain.
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Affiliation(s)
- Hongjun Jin
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Jinda Fan
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Xiang Zhang
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Junfeng Li
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Hubert P Flores
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Joel S Perlmutter
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA. ; Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Stanley M Parsons
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, 93106, USA
| | - Zhude Tu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
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Lever SZ, Xu R, Fan KH, Fergason-Cantrell EA, Carmack TL, Watkinson LD, Lever JR. Synthesis, radioiodination and in vitro and in vivo sigma receptor studies of N-1-allyl-N´-4-phenethylpiperazine analogs. Nucl Med Biol 2012; 39:401-14. [PMID: 22172395 DOI: 10.1016/j.nucmedbio.2011.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/25/2011] [Accepted: 10/05/2011] [Indexed: 10/14/2022]
Abstract
INTRODUCTION Sigma-1 (σ(1)) receptor radioligands are useful for basic pharmacology studies and for imaging studies in neurology, psychiatry and oncology. We derived a hybrid structure, N-1-allyl-N´-4-phenethylpiperazine, from known ligands TPCNE and SA4503 for use as a scaffold for development of radioiodinated σ(1) receptor ligands. METHODS E-and Z-N-1-(3'-iodoallyl)-N´-4-(3″,4″-dimethoxyphenethyl)-piperazine (E-1 and Z-1), N-1-allyl-N´-4-(3',4'-dimethoxyphenethyl)-piperazine (2) and E-N-1-(3'-iodoallyl)-N´-4-(3″-methoxy-4'´-hydroxyphenethyl)-piperazine (3) were synthesized. Affinities for σ(1) and σ(2) receptors were determined. [(125)I]E-1 and [(125)I]Z-1 were prepared and evaluated in vivo in mice. [(125)I]E-1 was further evaluated in σ(1) receptor binding assays in vitro. RESULTS E-1 displayed moderately high apparent affinity (15 nM) for σ(1) sites and 84-fold selectivity against σ(2) sites. Z-1 showed similar σ(1) affinity, but only 23-fold selectivity. In contrast, 2 exhibited poor binding to both subtypes, while 3 had good affinities but poor selectivity. E-1 profiled as a probable antagonist in the phenytoin shift assay. [(125)I]E-1 and [(125)I]Z-1 were prepared in good yields and with high specific radioactivities. Log D(7.4) values (2.25 and 2.27) fall within the optimal range for in vivo studies. Both radioligands selectively labeled σ(1) receptors in mouse brain and peripheral organs in vivo. [(125)I]E-1 showed a higher level of specific binding than [(125)I]Z-1 and displayed good metabolic stability. Further, [(125)I]E-1 selectively labeled σ(1) receptors in mouse brain homogenates (K(d) 3.79 nM; B(max)=599 fmol/mg protein). CONCLUSIONS [(125)I]E-1 is a selective σ(1) receptor radioligand that exhibits properties amenable to in vitro and in vivo studies, with possible extension to single photon emission computed tomography using iodine-123.
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Affiliation(s)
- Susan Z Lever
- Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA.
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7
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Moussa IA, Banister SD, Giboureau N, Meikle SR, Kassiou M. Synthesis and in vivo evaluation of [18F]N-(2-benzofuranylmethyl)-N'-[4-(2-fluoroethoxy)benzyl]piperazine, a novel σ1 receptor PET imaging agent. Bioorg Med Chem Lett 2011; 21:6820-3. [PMID: 21962578 DOI: 10.1016/j.bmcl.2011.09.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 09/07/2011] [Accepted: 09/07/2011] [Indexed: 11/17/2022]
Abstract
N-(2-Benzofuranylmethyl)-N'-[4-(2-fluoroethoxy)benzyl]piperazine (6, σ(1)K(i)=2.6 nM) was radiolabeled with fluorine-18 to provide a potential σ(1) receptor radioligand for use in positron emission tomography (PET). Radiofluorination of the appropriate tosylate precursor furnished [(18)F]6 with a specific activity of 45 GBq/μmol, in an average radiochemical yield of 18% and greater than 98% radiochemical purity. MicroPET imaging in Papio hamadryas baboon brain revealed [(18)F]6 uptake consistent with σ receptor distribution, and specificity for σ receptors was demonstrated in a haloperidol pre-treated animal. [(18)F]6 possesses suitable properties for PET imaging of σ(1) receptors, and further investigation of this σ(1) receptor tracer is warranted.
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Affiliation(s)
- Iman A Moussa
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
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Ishiwata K, Kimura Y, Oda K, Ishii K, Sakata M, Kawasaki K, Nariai T, Suzuki Y, Ishibashi K, Mishina M, Hashimoto M, Ishikawa M, Toyohara J. Development of PET radiopharmaceuticals and their clinical applications at the Positron Medical Center. Geriatr Gerontol Int 2010; 10 Suppl 1:S180-96. [PMID: 20590833 DOI: 10.1111/j.1447-0594.2010.00594.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Positron Medical Center has developed a large number of radiopharmaceuticals and 36 radiopharmaceuticals have been approved for clinical use for studying aging and geriatric diseases, especially brain functions. Positron emission tomography (PET) has been used to provide a highly advanced PET-based diagnosis. The current status of the development of radiopharmaceuticals, and representative clinical and methodological results are reviewed.
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Affiliation(s)
- Kiichi Ishiwata
- Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.
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Kortekaas R, Maguire RP, van Waarde A, Leenders KL, Elsinga PH. Despite irreversible binding, PET tracer [11C]-SA5845 is suitable for imaging of drug competition at sigma receptors—The cases of ketamine and haloperidol. Neurochem Int 2008; 53:45-50. [DOI: 10.1016/j.neuint.2008.04.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 04/18/2008] [Accepted: 04/25/2008] [Indexed: 12/01/2022]
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Colabufo NA, Abate C, Contino M, Inglese C, Niso M, Berardi F, Perrone R. PB183, a sigma receptor ligand, as a potential PET probe for the imaging of prostate adenocarcinoma. Bioorg Med Chem Lett 2008; 18:1990-3. [PMID: 18276137 DOI: 10.1016/j.bmcl.2008.01.109] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 01/25/2008] [Accepted: 01/29/2008] [Indexed: 11/21/2022]
Abstract
PB183, a non-selective sigma receptor ligand displaying high sigma-1 and sigma-2 receptor affinity, was evaluated in prostate tumour cell lines for its suitability as PET radiotracer. The pharmacodynamic and pharmacokinetic properties suggested PB183 as a potential PET radiotracer to visualize prostate adenocarcinoma.
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Affiliation(s)
- Nicola Antonio Colabufo
- Dipartimento Farmacochimico, Università degli Studi di Bari, via Orabona 4, 70125 Bari, Italy.
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Kawamura K, Tsukada H, Shiba K, Tsuji C, Harada N, Kimura Y, Ishiwata K. Synthesis and evaluation of fluorine-18-labeled SA4503 as a selective sigma1 receptor ligand for positron emission tomography. Nucl Med Biol 2007; 34:571-7. [PMID: 17591557 DOI: 10.1016/j.nucmedbio.2007.03.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 03/07/2007] [Accepted: 03/15/2007] [Indexed: 11/20/2022]
Abstract
The [(18)F]fluoromethyl analog of the sigma(1) selective ligand 1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine dihydrochloride (SA4503) ([(18)F]FM-SA4503) was prepared and its potential evaluated for the in vivo measurement of sigma(1) receptors with positron emission tomography (PET). FM-SA4503 had selective affinity for the sigma(1) receptor (K(i) for sigma(1) receptor, 6.4 nM; K(i) for sigma(2) receptor, 250 nM) that was compatible with the affinity of SA4503 (K(i) for sigma(1) receptor, 4.4 nM; K(i) for sigma(2) receptor, 242 nM). [(18)F]FM-SA4503 was synthesized by (18)F-fluoromethylation of O-demethyl SA4503 in the radiochemical yield of 2.9-16.6% at the end of bombardment with a specific activity of 37.8-283 TBq/mmol at the end of synthesis. In mice, the uptake of [(18)F]FM-SA4503 in the brain was gradually increased for 30 min after injection, and then decreased. In the blocking study, brain uptake was significantly decreased by co-injection of haloperidol to 32% of control, and FM-SA4503 to 52% of control. In PET study of the monkey brain, high uptake was found in the cerebral cortex, thalamus and striatum. The radioactivity level of [(18)F]FM-SA4503 in the brain regions gradually increased over a period of 120 min after injection, followed by a stable plateau phase until 180 min after injection. In pretreatment with haloperidol measurement of the monkey brain, the radioactivity level was 22-32% and 11-25% of the baseline at 60 and 180 min, respectively, after injection, suggesting high receptor-specific binding. [(18)F]FM-SA4503 showed specific binding to sigma(1) receptors in mice and monkeys; therefore, [(18)F]FM-SA4503 has the potential for mapping sigma(1) receptors in the brain.
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Affiliation(s)
- Kazunori Kawamura
- Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo 173-0022, Japan.
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Przegaliński E, Filip M, Zajac D, Pokorski M. N-oleoyl-dopamine increases locomotor activity in the rat. Int J Immunopathol Pharmacol 2007; 19:897-904. [PMID: 17166411 DOI: 10.1177/039463200601900419] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
N-oleoyl-dopamine (OLDA), a condensation product of oleic acid and dopamine (DA), is a bioactive lipid whose biological functions are not yet fully explored. The compound crosses the blood-brain barrier and might be considered as a carrier of DA into the brain. In this study we sought to determine whether OLDA would influence locomotor behavior and whether the central DA system would be involved in such influence. We addressed this issue by investigating horizontal locomotor activity in male Wistar rats after intraperitoneal administration of OLDA, 5-20 mg/kg, before and after pre-treatment with haloperidol, a D2 receptor antagonist. We found that OLDA caused a prompt stimulation of locomotor activity, with a bell-shaped dose-response. The maximum stimulatory effect was observed after 10 mg/kg of OLDA where the mean distance traveled by rats during a 2-hour test increased to 1213+/-196(SE) cm from the 403+/-89 cm in the vehicle-treated rats (P<0.05). This effect was dose-dependently antagonized by haloperidol (0.1-0.2 mg/kg). The results support the hypothesis that the OLDA-induced hyperlocomotion was mediated by the stimulation of DA systems. Using in vitro assays, we further demonstrated that OLDA is a stable compound that resists hydrolysis over a 2-hour period and thus the integral OLDA compound exerted DA-like effects. We conclude that OLDA is a potential brain modifier of motor behavior, the biological consequences of which remain to be explored.
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Affiliation(s)
- E Przegaliński
- Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
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Lever JR, Gustafson JL, Xu R, Allmon RL, Lever SZ. Sigma1 and sigma2 receptor binding affinity and selectivity of SA4503 and fluoroethyl SA4503. Synapse 2006; 59:350-8. [PMID: 16463398 DOI: 10.1002/syn.20253] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
SA4503, a potent sigma(1) receptor agonist, is reported as having 103-fold higher affinity for sigma(1) (IC(50) = 17.4 nM) than sigma(2) (IC(50) = 1,784 nM) sites in guinea pig brain membranes. Modest structural changes appear to have major effects on sigma(1)/sigma(2) selectivity. The fluoroethyl analog, FE-SA4503, is described as having high primary affinity for sigma(2) sites (IC(50) = 2.11 nM) and a weaker interaction with sigma(1) sites (IC(50) = 6.48 nM). SA4503 and FE-SA4503 have been radiolabeled for PET studies, and both bind selectively to sigma(1) receptors in animal and human brain in vivo. We prepared SA4503 and FE-SA4503 as reference compounds for radioligand development efforts. In our hands, SA4503 is 14-fold selective for sigma(1) (K(i) = 4.6 nM) over sigma(2) (K(i) = 63.1 nM) sites in guinea pig brain homogenates. Further, FE-SA4503 exhibits the same 14-fold selectivity for sigma(1) (K(i) = 8.0 nM) over sigma(2) (K(i) = 113.2 nM) receptors. The main differences from previously reported values stem from sigma(2) affinity determinations. This protocol, displacement of [(3)H]DTG binding to sigma(2) sites using (+)-pentazocine (200 nM) to mask sigma(1) sites, was validated by the proper rank order of sigma(2) inhibitory potencies shown by a panel of additional ligands: ifenprodil > haloperidol > DTG >> (+)-pentazocine. Robust Pearson correlation (r = 1.0, P = 0.002; slope = 0.97) was observed for our pK(i) values against those from a prior study by others. The findings have bearing on structure-activity relationships for this active series, and on conclusions that might be drawn from experiments relying upon defined sigma(1)/sigma(2) binding selectivity.
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Affiliation(s)
- John R Lever
- Department of Radiology, University of Missouri-Columbia, 65211, USA.
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14
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Mach RH, Gage HD, Buchheimer N, Huang Y, Kuhner R, Wu L, Morton TE, Ehrenkaufer RL. N-[18F]4'-fluorobenzylpiperidin-4yl-(2-fluorophenyl) acetamide ([18F]FBFPA): a potential fluorine-18 labeled PET radiotracer for imaging sigma-1 receptors in the CNS. Synapse 2005; 58:267-74. [PMID: 16206186 DOI: 10.1002/syn.20207] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A series of brain uptake studies and PET imaging studies were conducted with the sigma(1) selective imaging agent, [(18)F]FBFPA. The results of the study indicate that this radiotracer readily crosses the blood-brain barrier and labels sigma(1) receptors in vivo. In vivo blocking studies with a sigma(1) selective ligand and a nonselective sigma(1)/sigma(2) receptor ligand indicates that [(18)F]FBFPA labels sigma(1) and not sigma(2) receptors in rodent brain. PET imaging studies demonstrated a high uptake in regions of rhesus monkey brain having a high density of sigma(1) receptors. The uptake of [(18)F]FBFPA was displaced by the sigma ligand, haloperidol (1 mg/kg, i.v.). In vivo blocking studies indicate that the progesterone blocked the brain uptake of [(18)F]FBFPA in rat brain. These data indicate that [(18)F]FBFPA is a potential radiotracer for imaging sigma(1) receptors in the CNS in vivo with PET.
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Affiliation(s)
- Robert H Mach
- Department of Radiology-PET Center Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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Kawamura K, Kubota K, Kobayashi T, Elsinga PH, Ono M, Maeda M, Ishiwata K. Evaluation of [11C]SA5845 and [11C]SA4503 for imaging of sigma receptors in tumors by animal PET. Ann Nucl Med 2005; 19:701-9. [PMID: 16444997 DOI: 10.1007/bf02985120] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Sigma receptors are expressed in a wide variety of tumor cell lines, and are expressed in proliferating cells. A radioligand for the visualization of sigma receptors could be useful for selective detection of primary tumors and their metastases, and for non-invasive assessment of tumor proliferative status. To this end we evaluated two sigma receptor ligands, [11C]SA5845 and [11C]SA4503. In an in vitro study, AH109A hepatoma showed moderate densities of sigma1 and sigma2 receptors, and VX-2 carcinoma showed a high density of sigma2 receptors: Bmax (fmol/mg protein) for sigma1 vs. sigma2, 1,700 vs. 1,200 for AH109A hepatoma and 800 vs. 10,000 for VX-2 carcinoma. In a cell growth assay in vitro, neither SA5845 nor SA4503 (<10 microM) showed any inhibitory effect on proliferation of the AH109A hepatoma cells. In rats, the uptake of [11C]SA5845 and [11C]SA4503 in AH109A tissues was accumulated over the first 60 minutes; however, the uptake of both tracers increased by co-injection with haloperidol as a sigma receptor ligand. On the other hand, in the PET studies of rabbits, the uptake of [11C]SA5845 in the VX-2 carcinoma was relatively higher than that of [11C]SA4503, because of a much higher density of sigma2 receptors compared to sigma1 receptors in the VX-2 tissue, and the uptake of both tracers in the VX-2 tissue was decreased by carrier-loading and pre-treatment with haloperidol ([11C]SA5845, 53% and 26%, respectively; [11C]SA4503, 41% and 22%, respectively at 30 minutes after injection). Therefore, [11C]SA5845 and [11C]SA4503 may be potential ligands for PET imaging of sigma receptor-rich tumors.
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Affiliation(s)
- Kazunori Kawamura
- Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Naka-cho 1-1, Itabashi-ku, Tokyo 173-0022, Japan.
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