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Siméon FG, Lee JH, Morse CL, Stukes I, Zoghbi SS, Manly LS, Liow JS, Gladding RL, Dick RM, Yan X, Taliani S, Costa B, Martini C, Da Settimo F, Castellano S, Innis RB, Pike VW. Synthesis and Screening in Mice of Fluorine-Containing PET Radioligands for TSPO: Discovery of a Promising 18F-Labeled Ligand. J Med Chem 2021; 64:16731-16745. [PMID: 34756026 PMCID: PMC8817670 DOI: 10.1021/acs.jmedchem.1c01562] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Translocator protein 18 kDa (TSPO) is a biomarker of neuroinflammation. [11C]ER176 robustly quantifies TSPO in the human brain with positron emission tomography (PET), irrespective of subject genotype. We aimed to develop an ER176 analog with potential for labeling with longer-lived fluorine-18 (t1/2 = 109.8 min). New fluoro and trifluoromethyl analogs of ER176 were prepared through a concise synthetic strategy. These ligands showed high TSPO affinity and low human genotype sensitivity. Each ligand was initially labeled by a generic 11C-methylation procedure, thereby enabling speedy screening in mice. Each radioligand was rapidly taken up and well retained in the mouse brain at baseline after intravenous injection. Preblocking of TSPO showed that high proportions of brain uptake were specifically bound to TSPO at baseline. Overall, the 3-fluoro analog of [11C]ER176 ([11C]3b) displayed the most promising imaging properties. Therefore, a method was developed to label 3b with [18F]fluoride ion. [18F]3b gave similarly promising PET imaging results and deserves evaluation in higher species.
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Affiliation(s)
- Fabrice G Siméon
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Jae-Hoon Lee
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
- Department of Nuclear Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 03772, South Korea
| | - Cheryl L Morse
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Ian Stukes
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Sami S Zoghbi
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Lester S Manly
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Jeih-San Liow
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Robert L Gladding
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Rachel M Dick
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Xuefeng Yan
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | - Barbara Costa
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | - Claudia Martini
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | | | - Sabrina Castellano
- Department of Pharmacy, University of Salerno, 84084 Fisciano, SA, Italy
| | - Robert B Innis
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Victor W Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
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Tjerkaski J, Cervenka S, Farde L, Matheson GJ. Kinfitr - an open-source tool for reproducible PET modelling: validation and evaluation of test-retest reliability. EJNMMI Res 2020; 10:77. [PMID: 32642865 PMCID: PMC7343683 DOI: 10.1186/s13550-020-00664-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 06/25/2020] [Indexed: 01/26/2023] Open
Abstract
Background In positron emission tomography (PET) imaging, binding is typically estimated by fitting pharmacokinetic models to the series of measurements of radioactivity in the target tissue following intravenous injection of a radioligand. However, there are multiple different models to choose from and numerous analytical decisions that must be made when modelling PET data. Therefore, it is important that analysis tools be adapted to the specific circumstances, and that analyses be documented in a transparent manner. Kinfitr, written in the open-source programming language R, is a tool developed for flexible and reproducible kinetic modelling of PET data, i.e. performing all steps using code which can be publicly shared in analysis notebooks. In this study, we compared outcomes obtained using kinfitr with those obtained using PMOD: a widely used commercial tool. Results Using previously collected test-retest data obtained with four different radioligands, a total of six different kinetic models were fitted to time-activity curves derived from different brain regions. We observed good correspondence between the two kinetic modelling tools both for binding estimates and for microparameters. Likewise, no substantial differences were observed in the test-retest reliability estimates between the two tools. Conclusions In summary, we showed excellent agreement between the open-source R package kinfitr, and the widely used commercial application PMOD. We, therefore, conclude that kinfitr is a valid and reliable tool for kinetic modelling of PET data.
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Affiliation(s)
- Jonathan Tjerkaski
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet & Stockholm Health Care Services, Stockholm County Council, Karolinska University Hospital, SE-171 76, Stockholm, Sweden.
| | - Simon Cervenka
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet & Stockholm Health Care Services, Stockholm County Council, Karolinska University Hospital, SE-171 76, Stockholm, Sweden
| | - Lars Farde
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet & Stockholm Health Care Services, Stockholm County Council, Karolinska University Hospital, SE-171 76, Stockholm, Sweden
| | - Granville James Matheson
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet & Stockholm Health Care Services, Stockholm County Council, Karolinska University Hospital, SE-171 76, Stockholm, Sweden
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Tong J, Williams B, Rusjan PM, Mizrahi R, Lacapère JJ, McCluskey T, Furukawa Y, Guttman M, Ang LC, Boileau I, Meyer JH, Kish SJ. Concentration, distribution, and influence of aging on the 18 kDa translocator protein in human brain: Implications for brain imaging studies. J Cereb Blood Flow Metab 2020; 40:1061-1076. [PMID: 31220997 PMCID: PMC7181090 DOI: 10.1177/0271678x19858003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Positron emission tomography (PET) imaging of the translocator protein (TSPO) is widely used as a biomarker of microglial activation. However, TSPO protein concentration in human brain has not been optimally quantified nor has its regional distribution been compared to TSPO binding. We determined TSPO protein concentration, change with age, and regional distribution by quantitative immunoblotting in autopsied human brain. Brain TSPO protein concentration (>0.1 ng/µg protein) was higher than those reported by in vitro binding assays by at least 2 to 70 fold. TSPO protein distributed widely in both gray and white matter regions, with distribution in major gray matter areas ranked generally similar to that of PET binding in second-generation radiotracer studies. TSPO protein concentration in frontal cortex was high at birth, declined precipitously during the first three months, and increased modestly during adulthood/senescence (10%/decade; vs. 30% for comparison astrocytic marker GFAP). As expected, TSPO protein levels were significantly increased (+114%) in degenerating putamen in multiple system atrophy, providing further circumstantial support for TSPO as a gliosis marker. Overall, findings show some similarities between TSPO protein and PET binding characteristics in the human brain but also suggest that part of the TSPO protein pool might be less available for radioligand binding.
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Affiliation(s)
- Junchao Tong
- Preclinical Imaging, Research Imaging
Centre, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Human Brain Laboratory, Research Imaging
Centre, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Research Imaging Centre and Campbell
Family Mental Health Research Institute, Centre for Addiction and Mental Health,
Toronto, Ontario, Canada
- Junchao Tong, Preclinical Imaging, Centre
for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8,
Canada.
| | - Belinda Williams
- Human Brain Laboratory, Research Imaging
Centre, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Addiction Imaging Research Group,
Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario,
Canada
| | - Pablo M. Rusjan
- Research Imaging Centre and Campbell
Family Mental Health Research Institute, Centre for Addiction and Mental Health,
Toronto, Ontario, Canada
| | - Romina Mizrahi
- Research Imaging Centre and Campbell
Family Mental Health Research Institute, Centre for Addiction and Mental Health,
Toronto, Ontario, Canada
| | - Jean-Jacques Lacapère
- Sorbonne Universités-UPMC University of
Paris 06, Département de Chimie, École Normale Supérieure-PSL Research University,
Paris, France
| | - Tina McCluskey
- Human Brain Laboratory, Research Imaging
Centre, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Research Imaging Centre and Campbell
Family Mental Health Research Institute, Centre for Addiction and Mental Health,
Toronto, Ontario, Canada
| | - Yoshiaki Furukawa
- Department of Neurology, Juntendo Tokyo
Koto Geriatric Medical Center, and Faculty of Medicine, University & Post
Graduate University of Juntendo, Tokyo, Japan
| | - Mark Guttman
- Centre for Movement Disorders, Toronto,
Ontario, Canada
| | - Lee-Cyn Ang
- Division of Neuropathology, London
Health Science Centre, University of Western Ontario, London, Ontario, Canada
| | - Isabelle Boileau
- Research Imaging Centre and Campbell
Family Mental Health Research Institute, Centre for Addiction and Mental Health,
Toronto, Ontario, Canada
- Addiction Imaging Research Group,
Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario,
Canada
| | - Jeffrey H Meyer
- Research Imaging Centre and Campbell
Family Mental Health Research Institute, Centre for Addiction and Mental Health,
Toronto, Ontario, Canada
| | - Stephen J Kish
- Human Brain Laboratory, Research Imaging
Centre, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Research Imaging Centre and Campbell
Family Mental Health Research Institute, Centre for Addiction and Mental Health,
Toronto, Ontario, Canada
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Effects of age, BMI and sex on the glial cell marker TSPO - a multicentre [ 11C]PBR28 HRRT PET study. Eur J Nucl Med Mol Imaging 2019; 46:2329-2338. [PMID: 31363804 PMCID: PMC6717599 DOI: 10.1007/s00259-019-04403-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 06/14/2019] [Indexed: 01/25/2023]
Abstract
Purpose The purpose of this study was to investigate the effects of ageing, sex and body mass index (BMI) on translocator protein (TSPO) availability in healthy subjects using positron emission tomography (PET) and the radioligand [11C]PBR28. Methods [11C]PBR28 data from 140 healthy volunteers (72 males and 68 females; N = 78 with HAB and N = 62 MAB genotype; age range 19–80 years; BMI range 17.6–36.9) were acquired with High Resolution Research Tomograph at three centres: Karolinska Institutet (N = 53), Turku PET centre (N = 62) and Yale University PET Center (N = 25). The total volume of distribution (VT) was estimated in global grey matter, frontal, temporal, occipital and parietal cortices, hippocampus and thalamus using multilinear analysis 1. The effects of age, BMI and sex on TSPO availability were investigated using linear mixed effects model, with TSPO genotype and PET centre specified as random intercepts. Results There were significant positive correlations between age and VT in the frontal and temporal cortex. BMI showed a significant negative correlation with VT in all regions. Additionally, significant differences between males and females were observed in all regions, with females showing higher VT. A subgroup analysis revealed a positive correlation between VT and age in all regions in male subjects, whereas age showed no effect on TSPO levels in female subjects. Conclusion These findings provide evidence that individual biological properties may contribute significantly to the high variation shown in TSPO binding estimates, and suggest that age, BMI and sex can be confounding factors in clinical studies. Electronic supplementary material The online version of this article (10.1007/s00259-019-04403-7) contains supplementary material, which is available to authorized users.
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Plavén-Sigray P, Cervenka S. Meta-analytic studies of the glial cell marker TSPO in psychosis - a question of apples and pears? Psychol Med 2019; 49:1624-1628. [PMID: 30739609 PMCID: PMC6601355 DOI: 10.1017/s003329171800421x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- P Plavén-Sigray
- Department of Clinical Neuroscience,Centre for Psychiatry Research, Karolinska Institutet & Stockholm Health Care Services, Stockholm County Council, Karolinska University Hospital,SE-171 76 Stockholm,Sweden
| | - S Cervenka
- Department of Clinical Neuroscience,Centre for Psychiatry Research, Karolinska Institutet & Stockholm Health Care Services, Stockholm County Council, Karolinska University Hospital,SE-171 76 Stockholm,Sweden
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Best L, Ghadery C, Pavese N, Tai YF, Strafella AP. New and Old TSPO PET Radioligands for Imaging Brain Microglial Activation in Neurodegenerative Disease. Curr Neurol Neurosci Rep 2019; 19:24. [DOI: 10.1007/s11910-019-0934-y] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Plavén-Sigray P, Matheson GJ, Cselényi Z, Jucaite A, Farde L, Cervenka S. Test-retest reliability and convergent validity of (R)-[ 11C]PK11195 outcome measures without arterial input function. EJNMMI Res 2018; 8:102. [PMID: 30498919 PMCID: PMC6265355 DOI: 10.1186/s13550-018-0455-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 11/02/2018] [Indexed: 12/29/2022] Open
Abstract
Purpose The PET radioligand (R)-[11C]PK11195 is used to quantify the 18-kDa translocator protein (TSPO), a marker for glial activation. Since there is no brain region devoid of TSPO, an arterial input function (AIF) is ideally required for quantification of binding. However, obtaining an AIF is experimentally demanding, is sometimes uncomfortable for participants, and can introduce additional measurement error during quantification. The objective of this study was to perform an evaluation of the test-retest reliability and convergent validity of techniques used for quantifying (R)-[11C]PK11195 binding without an AIF in clinical studies. Methods Data from six healthy individuals who participated in two PET examinations, 6 weeks apart, were analyzed. Regional non-displaceable binding potential (BPND) values were calculated using the simplified reference tissue model, with either cerebellum as reference region or a reference input derived using supervised cluster analysis (SVCA). Standardized uptake values (SUVs) were estimated for the time interval of 40–60 min. Results Test-retest reliability for BPND estimates were poor (80% of ICCs < 0.5). BPND estimates derived without an AIF were not correlated with BPND, total or specific distribution volume from the 2TCM using an AIF (all R2 < 12%). SUVs showed moderate reliability but no correlation to any other outcome measure. Conclusions Caution is warranted when interpreting patient-control comparisons employing (R)-[11C]PK11195 outcome measures obtained without an AIF. Electronic supplementary material The online version of this article (10.1186/s13550-018-0455-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Pontus Plavén-Sigray
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.
| | - Granville James Matheson
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden
| | - Zsolt Cselényi
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.,PET Imaging Centre, Precision Medicine and Genomics, IMED Biotech Unit, AstraZeneca, Karolinska Institutet, Stockholm, Sweden
| | - Aurelija Jucaite
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.,PET Imaging Centre, Precision Medicine and Genomics, IMED Biotech Unit, AstraZeneca, Karolinska Institutet, Stockholm, Sweden
| | - Lars Farde
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.,PET Imaging Centre, Precision Medicine and Genomics, IMED Biotech Unit, AstraZeneca, Karolinska Institutet, Stockholm, Sweden
| | - Simon Cervenka
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden
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Plavén-Sigray P, Matheson GJ, Collste K, Ashok AH, Coughlin JM, Howes OD, Mizrahi R, Pomper MG, Rusjan P, Veronese M, Wang Y, Cervenka S. Positron Emission Tomography Studies of the Glial Cell Marker Translocator Protein in Patients With Psychosis: A Meta-analysis Using Individual Participant Data. Biol Psychiatry 2018; 84:433-442. [PMID: 29653835 PMCID: PMC7893597 DOI: 10.1016/j.biopsych.2018.02.1171] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 02/13/2018] [Accepted: 02/20/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND Accumulating evidence suggests that the immune system may be an important target for new treatment approaches in schizophrenia. Positron emission tomography and radioligands binding to the translocator protein (TSPO), which is expressed in glial cells in the brain including immune cells, represents a potential method for patient stratification and treatment monitoring. This study examined whether patients with first-episode psychosis and schizophrenia had altered TSPO levels compared with healthy control subjects. METHODS PubMed was searched for studies comparing patients with psychosis with healthy control subjects using second-generation TSPO radioligands. The outcome measure was total distribution volume (VT), an index of TSPO levels, in frontal cortex, temporal cortex, and hippocampus. Bayes factors (BFs) were applied to examine the relative support for higher, lower, or no difference in patients' TSPO levels compared with healthy control subjects. RESULTS Five studies, with 75 participants with first-episode psychosis or schizophrenia and 77 healthy control subjects, were included. BFs showed strong support for lower VT in patients relative to no difference (all BFs > 32), or relative to higher VT (all BFs > 422), in all brain regions. From the posterior distributions, mean patient-control differences in standardized VT values were -0.48 for frontal cortex (95% credible interval [CredInt] = -0.88 to 0.09), -0.47 for temporal cortex (CredInt = -0.87 to -0.07), and -0.63 for hippocampus (CredInt = -1.00 to -0.25). CONCLUSIONS The lower levels of TSPO observed in patients may correspond to altered function or lower density of brain immune cells. Future studies should focus on investigating the underlying biological mechanisms and their relevance for treatment.
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Affiliation(s)
- Pontus Plavén-Sigray
- Centre for Psychiatry Research, Department of Clinical Neuroscience, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden.
| | - Granville J Matheson
- Centre for Psychiatry Research, Department of Clinical Neuroscience, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden
| | - Karin Collste
- Centre for Psychiatry Research, Department of Clinical Neuroscience, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden
| | - Abhishekh H Ashok
- Institute of Psychiatry, Psychology, & Neuroscience, King's College London, London, United Kingdom; Medical Research Council London Institute of Medical Sciences, Hammersmith Hospital, London, United Kingdom; Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Jennifer M Coughlin
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins Medical Institutions, Baltimore, Maryland; Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Oliver D Howes
- Institute of Psychiatry, Psychology, & Neuroscience, King's College London, London, United Kingdom; Medical Research Council London Institute of Medical Sciences, Hammersmith Hospital, London, United Kingdom; Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Romina Mizrahi
- Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - Martin G Pomper
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins Medical Institutions, Baltimore, Maryland; Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Pablo Rusjan
- Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - Mattia Veronese
- Department of Neuroimaging, Institute of Psychiatry, Psychology, & Neuroscience, King's College London, London, United Kingdom
| | - Yuchuan Wang
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Simon Cervenka
- Centre for Psychiatry Research, Department of Clinical Neuroscience, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden
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Betlazar C, Harrison-Brown M, Middleton RJ, Banati R, Liu GJ. Cellular Sources and Regional Variations in the Expression of the Neuroinflammatory Marker Translocator Protein (TSPO) in the Normal Brain. Int J Mol Sci 2018; 19:ijms19092707. [PMID: 30208620 PMCID: PMC6163555 DOI: 10.3390/ijms19092707] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Revised: 09/09/2018] [Accepted: 09/09/2018] [Indexed: 02/07/2023] Open
Abstract
The inducible expression of the mitochondrial translocator protein 18 kDa (TSPO) by activated microglia is a prominent, regular feature of acute and chronic-progressive brain pathology. This expression is also the rationale for the continual development of new TSPO binding molecules for the diagnosis of "neuroinflammation" by molecular imaging. However, there is in the normal brain an ill-defined, low-level constitutive expression of TSPO. Taking advantage of healthy TSPO knockout mouse brain tissue to validate TSPO antibody specificity, this study uses immunohistochemistry to determine the regional distribution and cellular sources of TSPO in the normal mouse brain. Fluorescence microscopy revealed punctate TSPO immunostaining in vascular endothelial cells throughout the brain. In the olfactory nerve layers and glomeruli of the olfactory bulb, choroid plexus and ependymal layers, we confirm constitutive TSPO expression levels similar to peripheral organs, while some low TSPO expression is present in regions of known neurogenesis, as well as cerebellar Purkinje cells. The distributed-sparse expression of TSPO in endothelial mitochondria throughout the normal brain can be expected to give rise to a low baseline signal in TSPO molecular imaging studies. Finally, our study emphasises the need for valid and methodologically robust verification of the selectivity of TSPO ligands through the use of TSPO knockout tissues.
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Affiliation(s)
- Calina Betlazar
- Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia.
- Discipline of Medical Imaging & Radiation Sciences, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW 2050, Australia.
| | - Meredith Harrison-Brown
- Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia.
- Discipline of Medical Imaging & Radiation Sciences, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW 2050, Australia.
| | - Ryan J Middleton
- Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia.
| | - Richard Banati
- Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia.
- Discipline of Medical Imaging & Radiation Sciences, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW 2050, Australia.
| | - Guo-Jun Liu
- Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia.
- Discipline of Medical Imaging & Radiation Sciences, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW 2050, Australia.
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TSPO in diverse CNS pathologies and psychiatric disease: A critical review and a way forward. Pharmacol Ther 2018; 194:44-58. [PMID: 30189290 DOI: 10.1016/j.pharmthera.2018.09.003] [Citation(s) in RCA: 101] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The use of Translocator Protein 18 kDa (TSPO) as a clinical neuroimaging biomarker of brain injury and neuroinflammation has increased exponentially in the last decade. There has been a furious pace in the development of new radiotracers for TSPO positron emission tomography (PET) imaging and its use has now been extensively described in many neurological and mental disorders. This fast pace of research and the ever-increasing number of new laboratories entering the field often times lack an appreciation of the historical perspective of the field and introduce dogmatic, but unproven facts, related to the underlying neurobiology of the TSPO response to brain injury and neuroinflammation. Paradoxically, while in neurodegenerative disorders and in all types of CNS pathologies brain TSPO levels increase, a new observation in psychiatric disorders such as schizophrenia is decreased brain levels of TSPO measured by PET. The neurobiological bases for this new finding is currently not known, but rigorous experimental design using multiple experimental approaches and careful interpretation of results is critically important to provide the methodological and/or biological underpinnings to this new observation. This review provides a perspective of the early history of validating TSPO as a biomarker of brain injury and neuroinflammation and a critical analysis of controversial topics in the literature related to the cellular sources of the TSPO response. The latter is important in order to provide the correct interpretation of PET studies in neurodegenerative and psychiatric disorders. Furthermore, this review proposes some yet to be explored explanations to new findings in psychiatric disorders and new approaches to quantitatively assess the glial sources of the TSPO response in order to move the field forward.
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Lillethorup TP, Glud AN, Landeck N, Alstrup AKO, Jakobsen S, Vang K, Doudet DJ, Brooks DJ, Kirik D, Hinz R, Sørensen JC, Landau AM. In vivo quantification of glial activation in minipigs overexpressing human α-synuclein. Synapse 2018; 72:e22060. [PMID: 30009467 DOI: 10.1002/syn.22060] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 07/06/2018] [Accepted: 07/11/2018] [Indexed: 12/25/2022]
Abstract
Parkinson's disease is characterized by a progressive loss of substantia nigra (SN) dopaminergic neurons and the formation of Lewy bodies containing accumulated alpha-synuclein (α-syn). The pathology of Parkinson's disease is associated with neuroinflammatory microglial activation, which may contribute to the ongoing neurodegeneration. This study investigates the in vivo microglial and dopaminergic response to overexpression of α-syn. We used positron emission tomography (PET) and the 18 kDa translocator protein radioligand, [11 C](R)PK11195, to image brain microglial activation and (+)-α-[11 C]dihydrotetrabenazine ([11 C]DTBZ), to measure vesicular monoamine transporter 2 (VMAT2) availability in Göttingen minipigs following injection with recombinant adeno-associated virus (rAAV) vectors expressing either mutant A53T α-syn or green fluorescent protein (GFP) into the SN (4 rAAV-α-syn, 4 rAAV-GFP, 5 non-injected control minipigs). We performed motor symptom assessment and immunohistochemical examination of tyrosine hydroxylase (TH) and transgene expression. Expression of GFP and α-syn was observed at the SN injection site and in the striatum. We observed no motor symptoms or changes in striatal [11 C]DTBZ binding potential in vivo or striatal or SN TH staining in vitro between the groups. The mean [11 C](R)PK11195 total volume of distribution was significantly higher in the basal ganglia and cortical areas of the α-syn group than the control animals. We conclude that mutant α-syn expression in the SN resulted in microglial activation in multiple sub- and cortical regions, while it did not affect TH stains or VMAT2 availability. Our data suggest that microglial activation constitutes an early response to accumulation of α-syn in the absence of dopamine neuron degeneration.
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Affiliation(s)
- Thea Pinholt Lillethorup
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Andreas Nørgaard Glud
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Natalie Landeck
- Brain Repair and Imaging in Neural Systems (BRAINS) Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Aage Kristian Olsen Alstrup
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Steen Jakobsen
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Kim Vang
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Doris J Doudet
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark.,Department of Medicine/Neurology, University of British Columbia, Vancouver, British Columbia, Canada
| | - David J Brooks
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark.,Division of Neuroscience, Department of Medicine, Imperial College London, London, United Kingdom.,Division of Neuroscience, Newcastle University, Newcastle, United Kingdom
| | - Deniz Kirik
- Brain Repair and Imaging in Neural Systems (BRAINS) Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Rainer Hinz
- Wolfson Molecular Imaging Centre, University of Manchester, Manchester, United Kingdom
| | - Jens Christian Sørensen
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Anne M Landau
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark.,Translational Neuropsychiatry Unit, Institute of Clinical Medicine, Aarhus University, Risskov, Denmark
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12
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Airas L, Nylund M, Rissanen E. Evaluation of Microglial Activation in Multiple Sclerosis Patients Using Positron Emission Tomography. Front Neurol 2018; 9:181. [PMID: 29632509 PMCID: PMC5879102 DOI: 10.3389/fneur.2018.00181] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 03/08/2018] [Indexed: 01/24/2023] Open
Abstract
Understanding the mechanisms underlying progression in multiple sclerosis (MS) is one of the key elements contributing to the identification of appropriate therapeutic targets for this under-managed condition. In addition to plaque-related focal inflammatory pathology typical for relapsing remitting MS there are, in progressive MS, widespread diffuse alterations in brain areas outside the focal lesions. This diffuse pathology is tightly related to microglial activation and is co-localized with signs of neurodegeneration. Microglia are brain-resident cells of the innate immune system and overactivation of microglia is associated with several neurodegenerative diseases. Understanding the role of microglial activation in relation to developing neurodegeneration and disease progression may provide a key to developing therapies to target progressive MS. 18-kDa translocator protein (TSPO) is a mitochondrial molecule upregulated in microglia upon their activation. Positron emission tomography (PET) imaging using TSPO-binding radioligands provides a method to assess microglial activation in patients in vivo. In this mini-review, we summarize the current status of TSPO imaging in the field of MS. In addition, the review discusses new insights into the potential use of this method in treatment trials and in clinical assessment of progressive MS.
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Affiliation(s)
- Laura Airas
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland.,Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland
| | - Marjo Nylund
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland.,Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland
| | - Eero Rissanen
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland.,Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland
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13
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García-Lorenzo D, Lavisse S, Leroy C, Wimberley C, Bodini B, Remy P, Veronese M, Turkheimer F, Stankoff B, Bottlaender M. Validation of an automatic reference region extraction for the quantification of [ 18F]DPA-714 in dynamic brain PET studies. J Cereb Blood Flow Metab 2018; 38:333-346. [PMID: 28178885 PMCID: PMC5951011 DOI: 10.1177/0271678x17692599] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 12/19/2016] [Accepted: 01/09/2017] [Indexed: 12/11/2022]
Abstract
There is a great need for a non-invasive methodology enabling the quantification of translocator protein overexpression in PET clinical imaging. [18F]DPA-714 has emerged as a promising translocator protein radiotracer as it is fluorinated, highly specific and returned reliable quantification using arterial input function. Cerebellum gray matter was proposed as reference region for simplified quantification; however, this method cannot be used when inflammation involves cerebellum. Here we adapted and validated a supervised clustering (supervised clustering algorithm (SCA)) for [18F]DPA-714 analysis. Fourteen healthy subjects genotyped for translocator protein underwent an [18F]DPA-714 PET, including 10 with metabolite-corrected arterial input function and three for a test-retest assessment. Two-tissue compartmental modelling provided [Formula: see text] estimates that were compared to either [Formula: see text] or [Formula: see text] generated by Logan analysis (using supervised clustering algorithm extracted reference region or cerebellum gray matter). The supervised clustering algorithm successfully extracted a pseudo-reference region with similar reliability using classes that were defined using either all subjects, or separated into HAB and MAB subjects. [Formula: see text], [Formula: see text] and [Formula: see text] were highly correlated (ICC of 0.91 ± 0.05) but [Formula: see text] were ∼26% higher and less variable than [Formula: see text]. Reproducibility was good with 5% variability in the test-retest study. The clustering technique for [18F]DPA-714 provides a simple, robust and reproducible technique that can be used for all neurological diseases.
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Affiliation(s)
- Daniel García-Lorenzo
- Sorbonne Université, UPMC Paris 06, Institut du Cerveau et de la Moelle Epinière, ICM, Hôpital de la Pitié Salpêtrière, Paris, France
| | - Sonia Lavisse
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), MIRCen, Fontenay-aux-Roses, France
- Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Université Paris-Saclay, Neurodegenerative Diseases Laboratory, Fontenay-aux-Roses, France
| | - Claire Leroy
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), Service Hospitalier Frédéric Joliot, Orsay, France
- Imagerie Moléculaire in Vivo, IMIV, CEA, Inserm, CNRS, Univ. Paris-Sud, Université Paris Saclay, Orsay, France
| | - Catriona Wimberley
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), Service Hospitalier Frédéric Joliot, Orsay, France
- Imagerie Moléculaire in Vivo, IMIV, CEA, Inserm, CNRS, Univ. Paris-Sud, Université Paris Saclay, Orsay, France
| | - Benedetta Bodini
- Sorbonne Université, UPMC Paris 06, Institut du Cerveau et de la Moelle Epinière, ICM, Hôpital de la Pitié Salpêtrière, Paris, France
| | - Philippe Remy
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), MIRCen, Fontenay-aux-Roses, France
- Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Université Paris-Saclay, Neurodegenerative Diseases Laboratory, Fontenay-aux-Roses, France
- Centre Expert Parkinson, Neurologie, CHU Henri Mondor, Assistance Publique Hôpitaux de Paris and Université Paris-Est, Créteil, France
| | - Mattia Veronese
- Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Federico Turkheimer
- Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Bruno Stankoff
- Sorbonne Université, UPMC Paris 06, Institut du Cerveau et de la Moelle Epinière, ICM, Hôpital de la Pitié Salpêtrière, Paris, France
- Hôpital Saint Antoine, AP-HP, Paris, France
| | - Michel Bottlaender
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), Service Hospitalier Frédéric Joliot, Orsay, France
- Imagerie Moléculaire in Vivo, IMIV, CEA, Inserm, CNRS, Univ. Paris-Sud, Université Paris Saclay, Orsay, France
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM),Neurospin, UNIACT, Gif-sur-Yvette, France
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14
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Holmes SE, Hinz R, Conen S, Gregory CJ, Matthews JC, Anton-Rodriguez JM, Gerhard A, Talbot PS. Elevated Translocator Protein in Anterior Cingulate in Major Depression and a Role for Inflammation in Suicidal Thinking: A Positron Emission Tomography Study. Biol Psychiatry 2018; 83:61-69. [PMID: 28939116 DOI: 10.1016/j.biopsych.2017.08.005] [Citation(s) in RCA: 195] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 08/04/2017] [Accepted: 08/06/2017] [Indexed: 12/27/2022]
Abstract
BACKGROUND Major depressive disorder is associated with raised peripheral inflammatory markers. Mounting evidence also suggests that inflammation is involved in suicidal behavior. However, the involvement of inflammation in the brains of individuals with depression, and its association with suicidal ideation, needs further clarification. Translocator protein (TSPO), which is upregulated in activated glia (predominantly microglia), can be measured as an indication of neuroinflammation in vivo using positron emission tomography and TSPO-specific radioligands. METHODS We used [11C](R)-PK11195 positron emission tomography to compare TSPO availability in the anterior cingulate cortex (ACC), prefrontal cortex, and insula between 14 medication-free patients in a major depressive episode of at least moderate severity and 13 matched healthy control subjects. In a post hoc analysis, we also compared TSPO availability between patients with and without suicidal thoughts. RESULTS Multivariate analysis of variance indicated significantly higher TSPO in patients compared with control subjects (p = .005). The elevation was of large effect size and significant in the ACC (p = .022, Cohen's d = 0.95), with smaller nonsignificant elevations in the prefrontal cortex (p = .342, Cohen's d = 0.38) and insula (p = .466, Cohen's d = 0.29). TSPO was not elevated in patients without suicidal thinking but was significantly increased in those with suicidal thoughts compared with those without, most robustly in the ACC (p = .008) and insula (p = .023). CONCLUSIONS We confirm evidence for increased TSPO availability, suggestive of predominantly microglial activation, in the ACC during a moderate to severe major depressive episode. Our findings provide further incentive for evaluating anti-inflammatory therapies in major depressive disorder.
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Affiliation(s)
- Sophie E Holmes
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Rainer Hinz
- Division of Informatics, Imaging and Data Sciences, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Silke Conen
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Catherine J Gregory
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Julian C Matthews
- Division of Informatics, Imaging and Data Sciences, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Jose M Anton-Rodriguez
- Division of Informatics, Imaging and Data Sciences, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Alexander Gerhard
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom; Salford Royal NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Peter S Talbot
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom; Greater Manchester Mental Health NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom.
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15
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Sakata M, Ishibashi K, Imai M, Wagatsuma K, Ishii K, Hatano K, Ishiwata K, Toyohara J. Assessment of safety, efficacy, and dosimetry of a novel 18-kDa translocator protein ligand, [ 11C]CB184, in healthy human volunteers. EJNMMI Res 2017; 7:26. [PMID: 28337723 PMCID: PMC5364125 DOI: 10.1186/s13550-017-0271-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 03/01/2017] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND N,N-di-n-propyl-2-[2-(4-[11C]methoxyphenyl)-6,8-dichloroimidazol[1,2-a]pyridine-3-yl]acetamide ([11C]CB184) is a novel selective radioligand for the 18-kD translocator protein (TSPO), which is upregulated in activated microglia in the brain, and may be useful in positron emission tomography (PET). We examined the safety, radiation dosimetry, and initial brain imaging with [11C]CB184 in healthy human volunteers. RESULTS Dynamic [11C]CB184 PET scans (90 min) were performed in five healthy male subjects. During the scan, arterial blood was sampled at various time intervals, and the fraction of the parent compound in plasma was determined with high-performance liquid chromatography. No serious adverse events occurred in any of the subjects throughout the study period. [11C]CB184 was metabolized in the periphery: 36.7% ± 5.7% of the radioactivity in plasma was detected as the unchanged form after 60 min. The total distribution volume (V T) was estimated with a two-tissue compartment model. The V T of [11C]CB184 was highest in the thalamus (5.1 ± 0.4), followed by the cerebellar cortex (4.4 ± 0.2), and others. Although regional differences were small, the observed [11C]CB184 binding pattern was consistent with the TSPO distribution in the normal human brain. Radiation dosimetry was determined in three healthy male subjects using a serial whole-body PET scan acquired over 2 h after [11C]CB184 injection. [11C]CB184 PET demonstrated high uptake in the gallbladder at a later time (>60 min). In urine obtained approximately 100 min post-injection, 0.3% of the total injected radioactivity was recovered, indicating hepatobiliary excretion of radioactivity. The absorbed dose (μGy/MBq) was highest in the kidneys (21.0 ± 0.5) followed by the lungs (16.8 ± 2.7), spleen (16.6 ± 6.6), and pancreas (16.5 ± 2.2). The estimated effective dose for [11C]CB184 was 5.9 ± 0.6 μSv/MBq. CONCLUSIONS This initial evaluation indicated that [11C]CB184 is feasible for imaging of TSPO in the brain.
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Affiliation(s)
- Muneyuki Sakata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015 Tokyo, Japan
| | - Kenji Ishibashi
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015 Tokyo, Japan
| | - Masamichi Imai
- Department of Radiology, Toranomon Hospital, Tokyo, Japan
| | - Kei Wagatsuma
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015 Tokyo, Japan
| | - Kenji Ishii
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015 Tokyo, Japan
| | - Kentaro Hatano
- Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Kiichi Ishiwata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015 Tokyo, Japan
- Institute of Cyclotron and Drug Discovery Research, Southern TOHOKU Research Institute for Neuroscience, Koriyama, Japan
- Department of Biofunctional Imaging, Fukushima Medical University, Fukushima, Japan
| | - Jun Toyohara
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015 Tokyo, Japan
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16
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Di Biase MA, Zalesky A, O'keefe G, Laskaris L, Baune BT, Weickert CS, Olver J, McGorry PD, Amminger GP, Nelson B, Scott AM, Hickie I, Banati R, Turkheimer F, Yaqub M, Everall IP, Pantelis C, Cropley V. PET imaging of putative microglial activation in individuals at ultra-high risk for psychosis, recently diagnosed and chronically ill with schizophrenia. Transl Psychiatry 2017; 7:e1225. [PMID: 28850113 PMCID: PMC5611755 DOI: 10.1038/tp.2017.193] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Accepted: 06/23/2017] [Indexed: 01/22/2023] Open
Abstract
We examined putative microglial activation as a function of illness course in schizophrenia. Microglial activity was quantified using [11C](R)-(1-[2-chrorophynyl]-N-methyl-N-[1-methylpropyl]-3 isoquinoline carboxamide (11C-(R)-PK11195) positron emission tomography (PET) in: (i) 10 individuals at ultra-high risk (UHR) of psychosis; (ii) 18 patients recently diagnosed with schizophrenia; (iii) 15 patients chronically ill with schizophrenia; and, (iv) 27 age-matched healthy controls. Regional-binding potential (BPND) was calculated using the simplified reference-tissue model with four alternative reference inputs. The UHR, recent-onset and chronic patient groups were compared to age-matched healthy control groups to examine between-group BPND differences in 6 regions: dorsal frontal, orbital frontal, anterior cingulate, medial temporal, thalamus and insula. Correlation analysis tested for BPND associations with gray matter volume, peripheral cytokines and clinical variables. The null hypothesis of equality in BPND between patients (UHR, recent-onset and chronic) and respective healthy control groups (younger and older) was not rejected for any group comparison or region. Across all subjects, BPND was positively correlated to age in the thalamus (r=0.43, P=0.008, false discovery rate). No correlations with regional gray matter, peripheral cytokine levels or clinical symptoms were detected. We therefore found no evidence of microglial activation in groups of individuals at high risk, recently diagnosed or chronically ill with schizophrenia. While the possibility of 11C-(R)-PK11195-binding differences in certain patient subgroups remains, the patient cohorts in our study, who also displayed normal peripheral cytokine profiles, do not substantiate the assumption of microglial activation in schizophrenia as a regular and defining feature, as measured by 11C-(R)-PK11195 BPND.
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Affiliation(s)
- M A Di Biase
- Melbourne Neuropsychiatry Centre, Department of Psychiatry, The University of Melbourne and Melbourne Health, Carlton South, VIC, Australia
- Department of Psychiatry, The University of Melbourne, Parkville, VIC Australia
| | - A Zalesky
- Melbourne Neuropsychiatry Centre, Department of Psychiatry, The University of Melbourne and Melbourne Health, Carlton South, VIC, Australia
- Department of Psychiatry, The University of Melbourne, Parkville, VIC Australia
- Melbourne School of Engineering, The University of Melbourne, Parkville, VIC Australia
| | - G O'keefe
- Department of Molecular Imaging and Therapy, The University of Melbourne, Heidelberg, VIC Australia
- Department of Medicine, The University of Melbourne, and La Trobe University, Austin Hospital, Heidelberg, VIC, Australia
| | - L Laskaris
- Melbourne Neuropsychiatry Centre, Department of Psychiatry, The University of Melbourne and Melbourne Health, Carlton South, VIC, Australia
- Department of Psychiatry, The University of Melbourne, Parkville, VIC Australia
| | - B T Baune
- Discipline of Psychiatry, The University of Adelaide, Adelaide, SA, Australia
| | - C S Weickert
- Melbourne Neuropsychiatry Centre, Department of Psychiatry, The University of Melbourne and Melbourne Health, Carlton South, VIC, Australia
- Neuroscience Research Australia, Randwick, NSW, Australia
- Schizophrenia Research Institute, Randwick, NSW, Australia
- School of Psychiatry, University of New South Wales, Sydney, NSW, Australia
| | - J Olver
- Department of Psychiatry, The University of Melbourne, Parkville, VIC Australia
- Department of Molecular Imaging and Therapy, The University of Melbourne, Heidelberg, VIC Australia
- Department of Medicine, The University of Melbourne, and La Trobe University, Austin Hospital, Heidelberg, VIC, Australia
| | - P D McGorry
- Orygen, The National Centre of Excellence in Youth Mental Health, Parkville, VIC, Australia
- Centre for Youth Mental Health, The University of Melbourne, Parkville, VIC, Australia
| | - G P Amminger
- Orygen, The National Centre of Excellence in Youth Mental Health, Parkville, VIC, Australia
| | - B Nelson
- Orygen, The National Centre of Excellence in Youth Mental Health, Parkville, VIC, Australia
| | - A M Scott
- Department of Molecular Imaging and Therapy, The University of Melbourne, Heidelberg, VIC Australia
- Department of Medicine, The University of Melbourne, and La Trobe University, Austin Hospital, Heidelberg, VIC, Australia
| | - I Hickie
- Brain & Mind Centre, The University of Sydney, Camperdown, NSW, Australia
| | - R Banati
- Medical Radiation Sciences, The University of Sydney, Camperdown, NSW, Australia
| | - F Turkheimer
- Department of Neuroimaging, King’s College London, London, UK
| | - M Yaqub
- VU University Medical Center, Amsterdam, The Netherlands
| | - I P Everall
- Department of Psychiatry, The University of Melbourne, Parkville, VIC Australia
- North Western Mental Health, Melbourne Health, Parkville, VIC, Australia
- Florey Institute for Neurosciences and Mental Health, Parkville, VIC, Australia
- Centre for Neural Engineering, Department of Electrical and Electronic Engineering, The University of Melbourne, Carlton South, VIC, Australia
- Cooperative Research Centre for Mental Health, Carlton, VIC, Australia
| | - C Pantelis
- Melbourne Neuropsychiatry Centre, Department of Psychiatry, The University of Melbourne and Melbourne Health, Carlton South, VIC, Australia
- Department of Psychiatry, The University of Melbourne, Parkville, VIC Australia
- North Western Mental Health, Melbourne Health, Parkville, VIC, Australia
- Florey Institute for Neurosciences and Mental Health, Parkville, VIC, Australia
- Centre for Neural Engineering, Department of Electrical and Electronic Engineering, The University of Melbourne, Carlton South, VIC, Australia
- Cooperative Research Centre for Mental Health, Carlton, VIC, Australia
| | - V Cropley
- Melbourne Neuropsychiatry Centre, Department of Psychiatry, The University of Melbourne and Melbourne Health, Carlton South, VIC, Australia
- Department of Psychiatry, The University of Melbourne, Parkville, VIC Australia
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17
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Matheson GJ, Plavén-Sigray P, Forsberg A, Varrone A, Farde L, Cervenka S. Assessment of simplified ratio-based approaches for quantification of PET [ 11C]PBR28 data. EJNMMI Res 2017; 7:58. [PMID: 28733954 PMCID: PMC5520824 DOI: 10.1186/s13550-017-0304-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/11/2017] [Indexed: 11/22/2022] Open
Abstract
Purpose Kinetic modelling with metabolite-corrected arterial plasma is considered the gold standard for quantification of [11C]PBR28 binding to the translocator protein (TSPO), since there is no brain region devoid of TSPO that can serve as reference. The high variability in binding observed using this method has motivated the use of simplified ratio-based approaches such as standardised uptake value ratios (SUVRs) and distribution volume (VT) ratios (DVRs); however, the reliability of these measures and their relationship to VT have not been sufficiently evaluated. Methods Data from a previously published [11C]PBR28 test-retest study in 12 healthy subjects were reanalysed. VT was estimated using a two-tissue compartment model. SUVR and DVR values for the frontal cortex were calculated using the whole brain and cerebellum as denominators. Test-retest reliability was assessed for all measures. Interregional correlations were performed for SUV and VT, and principal component analysis (PCA) was applied. Lastly, correlations between ratio-based outcomes and VT were assessed. Results Reliability was high for VT, moderate to high for SUV and SUVR, and poor for DVR. Very high interregional correlations were observed for both VT and SUV (all R2 > 85%). The PCA showed that almost all variance (>98%) was explained by a single component. Ratio-based methods correlated poorly with VT (all R2 < 34%, divided by genotype). Conclusions The reliability was good for SUVR, but poor for DVR. Both outcomes showed little to no association with VT, questioning their validity. The high interregional correlations for VT and SUV suggest that after dividing by a denominator region, most of the biologically relevant signal is lost. These observations imply that results from TSPO PET studies using SUVR or DVR estimates should be interpreted with caution.
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Affiliation(s)
- Granville J Matheson
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden
| | - Pontus Plavén-Sigray
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden
| | - Anton Forsberg
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden
| | - Andrea Varrone
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden
| | - Lars Farde
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden.,Personalised Healthcare and Biomarkers, AstraZeneca PET Science Centre, Karolinska Institutet, Stockholm, Sweden
| | - Simon Cervenka
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden. .,Department of Clinical Neuroscience, Karolinska Institutet, Karolinska University Hospital, R5:00, SE-171 76, Stockholm, Sweden.
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18
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Lower levels of the glial cell marker TSPO in drug-naive first-episode psychosis patients as measured using PET and [ 11C]PBR28. Mol Psychiatry 2017; 22:850-856. [PMID: 28194003 DOI: 10.1038/mp.2016.247] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 09/30/2016] [Accepted: 11/22/2016] [Indexed: 11/08/2022]
Abstract
Several lines of evidence are indicative of a role for immune activation in the pathophysiology of schizophrenia. Nevertheless, studies using positron emission tomography (PET) and radioligands for the translocator protein (TSPO), a marker for glial activation, have yielded inconsistent results. Whereas early studies using a radioligand with low signal-to-noise in small samples showed increases in patients, more recent studies with improved methodology have shown no differences or trend-level decreases. Importantly, all patients investigated thus far have been on antipsychotic medication, and as these compounds may dampen immune cell activity, this factor limits the conclusions that can be drawn. Here, we examined 16 drug-naive, first-episode psychosis patients and 16 healthy controls using PET and the TSPO radioligand [11C]PBR28. Gray matter (GM) volume of distribution (VT) derived from a two-tissue compartmental analysis with arterial input function was the main outcome measure. Statistical analyses were performed controlling for both TSPO genotype, which is known to affect [11C]PBR28 binding, and gender. There was a significant reduction of [11C]PBR28 VT in patients compared with healthy controls in GM as well as in secondary regions of interest. No correlation was observed between GM VT and clinical or cognitive measures after correction for multiple comparisons. The observed decrease in TSPO binding suggests reduced numbers or altered function of immune cells in brain in early-stage schizophrenia.
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19
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Lagarde J, Sarazin M, Bottlaender M. In vivo PET imaging of neuroinflammation in Alzheimer's disease. J Neural Transm (Vienna) 2017; 125:847-867. [PMID: 28516240 DOI: 10.1007/s00702-017-1731-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/01/2017] [Indexed: 12/15/2022]
Abstract
Increasing evidence suggests that neuroinflammation contributes to the pathophysiology of many neurodegenerative diseases, especially Alzheimer's disease (AD). Molecular imaging by PET may be a useful tool to assess neuroinflammation in vivo, thus helping to decipher the complex role of inflammatory processes in the pathophysiology of neurodegenerative diseases and providing a potential means of monitoring the effect of new therapeutic approaches. For this objective, the main target of PET studies is the 18 kDa translocator protein (TSPO), as it is overexpressed by activated microglia. In the present review, we describe the most widely used PET tracers targeting the TSPO, the methodological issues in tracer quantification and summarize the results obtained by TSPO PET imaging in AD, as well as in neurodegenerative disorders associated with AD, in psychiatric disorders and ageing. We also briefly describe alternative PET targets and imaging modalities to study neuroinflammation. Lastly, we question the meaning of PET imaging data in the context of a highly complex and multifaceted role of neuroinflammation in neurodegenerative diseases. This overview leads to the conclusion that PET imaging of neuroinflammation is a promising way of deciphering the enigma of the pathophysiology of AD and of monitoring the effect of new therapies.
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Affiliation(s)
- Julien Lagarde
- Unit of Neurology of Memory and Language, Centre de Psychiatrie et Neurosciences, INSERM UMR S894, Centre Hospitalier Sainte-Anne and Université Paris Descartes, Sorbonne Paris Cité, 75014, Paris, France
| | - Marie Sarazin
- Unit of Neurology of Memory and Language, Centre de Psychiatrie et Neurosciences, INSERM UMR S894, Centre Hospitalier Sainte-Anne and Université Paris Descartes, Sorbonne Paris Cité, 75014, Paris, France
| | - Michel Bottlaender
- UNIACT, NeuroSpin, Institut d'Imagerie Biomédicale, Direction de la Recherche Fondamentale, Commissariat à l'Energie Atomique, 91191, Gif-sur-Yvette, France. .,Laboratoire Imagerie Moléculaire in Vivo, UMR 1023, Service Hospitalier Frédéric Joliot, Institut d'Imagerie Biomédicale, Direction de la Recherche Fondamentale, Commissariat à l'Energie Atomique, 91400, Orsay, France.
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20
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Frankle WG, Narendran R, Wood AT, Suto F, Himes ML, Kobayashi M, Ohno T, Yamauchi A, Mitsui K, Duffy K, Bruce M. Brain translocator protein occupancy by ONO-2952 in healthy adults: A Phase 1 PET study using [11C]PBR28. Synapse 2017; 71. [DOI: 10.1002/syn.21970] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 02/10/2017] [Accepted: 02/22/2017] [Indexed: 11/12/2022]
Affiliation(s)
- W. Gordon Frankle
- Department of Psychiatry; NYU Langone Medical Center; New York New York
| | - Rajesh Narendran
- Department of Psychiatry; University of Pittsburgh; Pittsburgh Pennsylvania
- Department of Radiology; University of Pittsburgh; Pittsburgh Pennsylvania
| | | | | | - Michael L. Himes
- Department of Psychiatry; University of Pittsburgh; Pittsburgh Pennsylvania
| | | | | | | | | | | | - Mark Bruce
- Ono Pharma UK Ltd; London United Kingdom
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21
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Liu GJ, Middleton RJ, Banati RB. Subcellular distribution of the 18kDa translocator protein and transcript variant PBR-S in human cells. Gene 2017; 613:45-56. [PMID: 28263860 DOI: 10.1016/j.gene.2017.02.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 02/22/2017] [Accepted: 02/28/2017] [Indexed: 10/20/2022]
Abstract
Despite continued interest in the 18kDa translocator protein (PBR/TSPO) as a biomarker and a therapeutic target for a range of diseases, its functional role, such as in the steroid synthesis pathway and energy metabolism has either become contentious or remains to be described more precisely. The PBR/TSPO gene consists of four exons, while a shorter isoform termed PBR-S lacks exon 2. The PBR-S 102-codon open reading frame differs to that of PBR/TSPO, resulting in a protein that is completely unrelated to PBR/TSPO. To our knowledge, PBR-S protein has never been described and has no known or proposed function. To obtain possible clues on the role of this uncharacterised protein, we compared the subcellular distribution of PBR-S to that of PBR/TSPO. By expressing fluorescently tagged PBR/TSPO, we confirmed that full-length PBR/TSPO co-localises with mitochondria in HeLa, HEK-293, MDA-MB-231, BJ and U87-MG human cell lines. Unlike the strictly mitochondrial localisation of PBR/TSPO, PBR-S has a punctate distribution throughout the cytosol that co-localises with lysosomes in HeLa, HEK-293, MDA-MB-231, BJ and U87-MG cells. In summary, within the cell lines examined we confirm mitochondria rather than occasionally reported other localisations, such as the cell nucleus, to be the only site where PBR/TSPO resides. Due to the lack of any shared protein sequences and the different subcellular locations, we suggest that the previously uncharacterised PBR-S protein variant of the PBR/TSPO gene is likely to serve a different yet to be discovered function compared to PBR/TSPO.
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Affiliation(s)
- Guo-Jun Liu
- Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia; National Imaging Facility, Brain and Mind Centre and Faculty of Health Sciences, University of Sydney, Camperdown, NSW 2050, Australia
| | - Ryan J Middleton
- Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia
| | - Richard B Banati
- Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia; National Imaging Facility, Brain and Mind Centre and Faculty of Health Sciences, University of Sydney, Camperdown, NSW 2050, Australia.
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22
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Holmes SE, Hinz R, Drake RJ, Gregory CJ, Conen S, Matthews JC, Anton-Rodriguez JM, Gerhard A, Talbot PS. In vivo imaging of brain microglial activity in antipsychotic-free and medicated schizophrenia: a [ 11C](R)-PK11195 positron emission tomography study. Mol Psychiatry 2016; 21:1672-1679. [PMID: 27698434 DOI: 10.1038/mp.2016.180] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 08/24/2016] [Accepted: 08/26/2016] [Indexed: 12/11/2022]
Abstract
Positron emission tomography (PET) imaging of the 18 kDa translocator protein (TSPO) has been used to investigate whether microglial activation, an indication of neuroinflammation, is evident in the brain of adults with schizophrenia. Interpretation of these studies is confounded by potential modulatory effects of antipsychotic medication on microglial activity. In the first such study in antipsychotic-free schizophrenia, we have used [11C](R)-PK11195 PET to compare TSPO availability in a predominantly antipsychotic-naive group of moderate-to-severely symptomatic unmedicated patients (n=8), similarly symptomatic medicated patients with schizophrenia taking risperidone or paliperidone by regular intramuscular injection (n=8), and healthy comparison subjects (n=16). We found no evidence for increased TSPO availability in antipsychotic-free patients compared with healthy controls (mean difference 4%, P=0.981). However, TSPO availability was significantly elevated in medicated patients (mean increase 88%, P=0.032) across prefrontal (dorsolateral, ventrolateral, orbital), anterior cingulate and parietal cortical regions. In the patients, TSPO availability was also strongly correlated with negative symptoms measured using the Positive and Negative Syndrome Scale across all the brain regions investigated (r=0.651-0.741). We conclude that the pathophysiology of schizophrenia is not associated with microglial activation in the 2-6 year period following diagnosis. The elevation in the medicated patients may be a direct effect of the antipsychotic, although this study cannot exclude treatment resistance and/or longer illness duration as potential explanations. It also remains to be determined whether it is present only in a subset of patients, represents a pro- or anti-inflammatory state, its association with primary negative symptoms, and whether there are significant differences between antipsychotics.
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Affiliation(s)
- S E Holmes
- Wolfson Molecular Imaging Centre, Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - R Hinz
- Wolfson Molecular Imaging Centre, Division of Informatics, Imaging & Data Sciences, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - R J Drake
- Division of Psychology & Mental Health, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - C J Gregory
- Wolfson Molecular Imaging Centre, Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - S Conen
- Wolfson Molecular Imaging Centre, Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - J C Matthews
- Wolfson Molecular Imaging Centre, Division of Informatics, Imaging & Data Sciences, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - J M Anton-Rodriguez
- Wolfson Molecular Imaging Centre, Division of Informatics, Imaging & Data Sciences, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - A Gerhard
- Wolfson Molecular Imaging Centre, Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - P S Talbot
- Wolfson Molecular Imaging Centre, Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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23
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Brouwer C, Jenko KJ, Zoghbi SS, Morse CL, Innis RB, Pike VW. Translocator protein ligands based on N-methyl-(quinolin-4-yl)oxypropanamides with properties suitable for PET radioligand development. Eur J Med Chem 2016; 124:677-688. [PMID: 27622910 DOI: 10.1016/j.ejmech.2016.08.046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 07/28/2016] [Accepted: 08/21/2016] [Indexed: 11/17/2022]
Abstract
Modifications to an N-methyl-(quinolin-4-yl)oxypropanamide scaffold were explored to discover leads for developing new radioligands for PET imaging of brain TSPO (translocator protein), a biomarker of neuroinflammation. Whereas contraction of the quinolinyl portion of the scaffold or cyclization of the tertiary amido group abolished high TSPO affinity, insertion of an extra nitrogen atom into the 2-arylquinolinyl portion was effective in retaining sub-nanomolar affinity for rat TSPO, while also decreasing lipophilicity to within the moderate range deemed preferable for a PET radioligand. Replacement of a phenyl group on the amido nitrogen with an isopropyl group was similarly effective. Among others, compound 20 (N-methyl-N-phenyl-2-[2-(pyridin-2-yl)-1,8-naphthyridin-4-yloxy]propanamide) appears especially appealing for PET radioligand development, based on high selectivity and high affinity (Ki = 0.5 nM) for rat TSPO, moderate lipophilicity (logD = 2.48), and demonstrated amenability to labeling with carbon-11.
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Affiliation(s)
- Chad Brouwer
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3 C346A, 10 Center Drive, Bethesda, MD 20892, United States
| | - Kimberly J Jenko
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3 C346A, 10 Center Drive, Bethesda, MD 20892, United States
| | - Sami S Zoghbi
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3 C346A, 10 Center Drive, Bethesda, MD 20892, United States
| | - Cheryl L Morse
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3 C346A, 10 Center Drive, Bethesda, MD 20892, United States
| | - Robert B Innis
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3 C346A, 10 Center Drive, Bethesda, MD 20892, United States
| | - Victor W Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3 C346A, 10 Center Drive, Bethesda, MD 20892, United States.
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24
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Toyohara J, Sakata M, Hatano K, Yanai S, Endo S, Ishibashi K, Wagatsuma K, Ishii K, Ishiwata K. Preclinical and first-in-man studies of [(11)C]CB184 for imaging the 18-kDa translocator protein by positron emission tomography. Ann Nucl Med 2016; 30:534-43. [PMID: 27329083 DOI: 10.1007/s12149-016-1094-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 05/30/2016] [Indexed: 01/17/2023]
Abstract
OBJECTIVE We performed preclinical and first-in-man clinical positron emission tomography (PET) studies in human brain using N,N-di-n-propyl-2-[2-(4-[(11)C]methoxyphenyl)-6,8-dichloroimidazol[1,2-a]pyridine-3-yl]acetamide ([(11)C]CB184) to image the 18-kDa translocator protein (TSPO), which is overexpressed in activated microglia in neuroinflammatory conditions. METHODS In vitro selectivity of CB184 was characterized. The radiation absorbed dose by [(11)C]CB184 in humans was calculated from murine distribution data. Acute toxicity of CB184 hydrochloride in rats at a dose of 5.81 mg/kg body weight, which is >10,000-fold higher than the clinical equivalent dose of [(11)C]CB184, was evaluated. Acute toxicity of [(11)C]CB184 injection of a 400-fold dose to administer a postulated dose of 740 MBq [(11)C]CB184 was also evaluated after the decay-out of (11)C. The mutagenicity of CB184 was studied with a reverse mutation test (Ames test). The pharmacological effect of CB184 injection in mice was studied with an open field test. The first PET imaging of TSPO with [(11)C]CB184 in a normal human volunteer was performed. RESULTS A suitable preparation method for [(11)C]CB184 injection was established. CB184 showed low activity in a 28-standard receptor binding profile. The radiation absorbed dose by [(11)C]CB184 in humans was sufficiently low for clinical use, and no acute toxicity of CB184 or [(11)C]CB184 injection was found. No mutagenicity or apparent effect on locomotor activity or anxiety status was observed for CB184. We safely performed brain imaging with PET following administration of [(11)C]CB184 in a normal human volunteer. A 90-min dynamic scan showed rapid initial uptake of radioactivity in the brain followed by prompt clearance. [(11)C]CB184 was homogeneously distributed in the gray matter. The total distribution volume of [(11)C]CB184 was highest in the thalamus followed by the cerebellar cortex and elsewhere. Although regional differences were small, the observed [(11)C]CB184 binding pattern was consistent with the TSPO distribution in normal human brain. Peripherally, [(11)C]CB184 was metabolized in humans: 30 % of the radioactivity in plasma was detected as the unchanged form after 60 min. CONCLUSIONS [(11)C]CB184 is suitable for imaging TSPO in human brain and provides an acceptable radiation dose. Pharmacological safety was noted at the dose required for PET imaging.
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Affiliation(s)
- Jun Toyohara
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan.
| | - Muneyuki Sakata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Kentaro Hatano
- Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Shuichi Yanai
- Research Team for Aging Neuroscience, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Shogo Endo
- Research Team for Aging Neuroscience, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Kenji Ishibashi
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Kei Wagatsuma
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Kenji Ishii
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Kiichi Ishiwata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan.,Institute of Cyclotron and Drug Discovery Research, Southern Tohoku Research Institute for Neuroscience, Koriyama, Japan.,Department of Biofunctional Imaging, Fukushima Medical University, Fukushima, Japan
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25
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Fan Z, Calsolaro V, Atkinson RA, Femminella GD, Waldman A, Buckley C, Trigg W, Brooks DJ, Hinz R, Edison P. Flutriciclamide (18F-GE180) PET: First-in-Human PET Study of Novel Third-Generation In Vivo Marker of Human Translocator Protein. J Nucl Med 2016; 57:1753-1759. [DOI: 10.2967/jnumed.115.169078] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 05/10/2016] [Indexed: 12/27/2022] Open
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26
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Airas L, Rissanen E, Rinne JO. Imaging neuroinflammation in multiple sclerosis using TSPO-PET. Clin Transl Imaging 2015; 3:461-473. [PMID: 27331049 PMCID: PMC4887541 DOI: 10.1007/s40336-015-0147-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 09/22/2015] [Indexed: 12/15/2022]
Abstract
Conventional MR imaging (MRI) techniques form the cornerstone of multiple sclerosis (MS) diagnostics and clinical follow-up today. MRI is sensitive in demonstrating focal inflammatory lesions and diffuse atrophy. However, especially in progressive MS, there is increasingly widespread diffuse pathology also outside the plaques, often related to microglial activation and neurodegeneration. This cannot be detected using conventional MRI. Positron emission tomography (PET) imaging using 18-kDa translocator protein (TSPO) binding radioligands has recently shown promise as a tool to detect this diffuse pathology in vivo, and for the first time allows one to follow its development longitudinally. It is becoming evident that the more advanced the MS disease is, the more pronounced is microglial activation. PET imaging allows the detection of MS-related pathology at molecular level in vivo. It has potential to enable measurement of effects of new disease-modifying drugs aimed at reducing neurodegeneration and neuroinflammation. PET imaging could thus be included in the design of future clinical trials of progressive MS. There are still technical issues related to the quality of TSPO radioligands and post-processing methodology, and comparison of studies from different PET centres is challenging. In this review, we summarise the main evidence supporting the use of TSPO-PET as a tool to explore the diffuse inflammation in MS.
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Affiliation(s)
- Laura Airas
- Division of Clinical Neurosciences, Turku University Hospital, Kiinamyllynkatu 4-8, 20521 Turku, Finland
- Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland
| | - Eero Rissanen
- Division of Clinical Neurosciences, Turku University Hospital, Kiinamyllynkatu 4-8, 20521 Turku, Finland
- Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland
| | - Juha O. Rinne
- Division of Clinical Neurosciences, Turku University Hospital, Kiinamyllynkatu 4-8, 20521 Turku, Finland
- Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland
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27
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28
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Sérrière S, Doméné A, Vercouillie J, Mothes C, Bodard S, Rodrigues N, Guilloteau D, Routier S, Page G, Chalon S. Assessment of the Protection of Dopaminergic Neurons by an α7 Nicotinic Receptor Agonist, PHA 543613 Using [(18)F]LBT-999 in a Parkinson's Disease Rat Model. Front Med (Lausanne) 2015; 2:61. [PMID: 26389120 PMCID: PMC4556971 DOI: 10.3389/fmed.2015.00061] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/17/2015] [Indexed: 12/02/2022] Open
Abstract
The inverse association between nicotine intake and Parkinson's disease (PD) is well established and suggests that this molecule could be neuroprotective through anti-inflammatory action mediated by nicotinic receptors, including the α7-subtype (α7R). The objective of this study was to evaluate the effects of an agonist of α7R, PHA 543613, on striatal dopaminergic neurodegeneration and neuroinflammation in a rat model of PD induced by 6-hydroxydopamine (6-OHDA) lesion. Adult male Wistar rats were lesioned in the right striatum and assigned to either the PHA group (n = 7) or the Sham group (n = 5). PHA 543613 hydrochloride at the concentration of 6 mg/kg (PHA group) or vehicle (Sham group) was intra-peritoneally injected 2 h before 6-OHDA lesioning and then at days 2, 4, and 6 post-lesion. Positron emission tomography (PET) imaging was performed at 7 days post-lesion using [(18)F]LBT-999 to quantify the striatal dopamine transporter (DAT). After PET imaging, neuroinflammation was evaluated in same animals in vitro through the measurement of the microglial activation marker 18 kDa translocator protein (TSPO) by quantitative autoradiography with [(3)H]PK-11195. The DAT density reflecting the integrity of dopaminergic neurons was significantly decreased while the intensity of neuroinflammation measured by TSPO density was significantly increased in the lesioned compared to intact striatum in both groups. However, these both modifications were partially reversed in the PHA group compared to Sham. In addition, a significant positive correlation between the degree of lesion and the intensity of neuroinflammation was evidenced. These findings indicate that PHA 543613 exerts neuroprotective effects on the striatal dopaminergic neurons associated with a reduction in microglial activation in this model of PD. This reinforces the hypothesis that an α7R agonist could provide beneficial effects for the treatment of PD.
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Affiliation(s)
- Sophie Sérrière
- UMR INSERM U930, Université François Rabelais, Tours, France
| | - Aurélie Doméné
- UMR INSERM U930, Université François Rabelais, Tours, France
| | | | | | - Sylvie Bodard
- UMR INSERM U930, Université François Rabelais, Tours, France
| | - Nuno Rodrigues
- UMR CNRS 7311, Institut de Chimie Organique et Analytique, Université d’Orléans, Orléans, France
| | - Denis Guilloteau
- UMR INSERM U930, Université François Rabelais, Tours, France
- CHRU de Tours, Hopital Bretonneau, Tours, France
| | - Sylvain Routier
- UMR CNRS 7311, Institut de Chimie Organique et Analytique, Université d’Orléans, Orléans, France
| | - Guylène Page
- EA3808 – CiMoTheMA, Université de Poitiers, Poitiers, France
| | - Sylvie Chalon
- UMR INSERM U930, Université François Rabelais, Tours, France
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29
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Jucaite A, Svenningsson P, Rinne JO, Cselényi Z, Varnäs K, Johnström P, Amini N, Kirjavainen A, Helin S, Minkwitz M, Kugler AR, Posener JA, Budd S, Halldin C, Varrone A, Farde L. Effect of the myeloperoxidase inhibitor AZD3241 on microglia: a PET study in Parkinson’s disease. Brain 2015; 138:2687-700. [DOI: 10.1093/brain/awv184] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 05/05/2015] [Indexed: 11/12/2022] Open
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30
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Zanotti-Fregonara P, Zhang Y, Jenko KJ, Gladding RL, Zoghbi SS, Fujita M, Sbardella G, Castellano S, Taliani S, Martini C, Innis RB, Da Settimo F, Pike VW. Synthesis and evaluation of translocator 18 kDa protein (TSPO) positron emission tomography (PET) radioligands with low binding sensitivity to human single nucleotide polymorphism rs6971. ACS Chem Neurosci 2014; 5:963-71. [PMID: 25123416 PMCID: PMC4210126 DOI: 10.1021/cn500138n] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
![]()
The imaging of translocator 18 kDa
protein (TSPO) in living human
brain with radioligands by positron emission tomography (PET) has
become an important means for the study of neuroinflammatory conditions
occurring in several neuropsychiatric disorders. The widely used prototypical
PET radioligand [11C](R)-PK 11195 ([11C](R)-1; [N-methyl-11C](R)-N-sec-butyl-1-(2-chlorophenyl)-N-methylisoquinoline-3-carboxamide) gives a low PET signal and is
difficult to quantify, whereas later generation radioligands have
binding sensitivity to a human single nucleotide polymorphism (SNP)
rs6971, which imposes limitations on their utility for comparative
quantitative PET studies of normal and diseased subjects. Recently,
azaisosteres of 1 have been developed with improved drug-like
properties, including enhanced TSPO affinity accompanied by moderated
lipophilicity. Here we selected three of these new ligands (7–9) for labeling with carbon-11 and for
evaluation in monkey as candidate PET radioligands for imaging brain
TSPO. Each radioligand was readily prepared by 11C-methylation
of an N-desmethyl precursor and was found to give
a high proportion of TSPO-specific binding in monkey brain. One of
these radioligands, [11C]7, the direct 4-azaisostere
of 1, presents many radioligand properties that are superior
to those reported for [11C]1, including higher
affinity, lower lipophilicity, and stable quantifiable PET signal.
Importantly, 7 was also found to show very low sensitivity
to the human SNP rs6971 in vitro. Therefore, [11C]7 now warrants evaluation in human subjects with PET to assess
its utility for imaging TSPO in human brain, irrespective of subject
genotype.
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Affiliation(s)
- Paolo Zanotti-Fregonara
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Yi Zhang
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Kimberly J. Jenko
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Robert L. Gladding
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Sami S. Zoghbi
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Masahiro Fujita
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Gianluca Sbardella
- Department
of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
| | - Sabrina Castellano
- Department
of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
| | - Sabrina Taliani
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Claudia Martini
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Robert B. Innis
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Federico Da Settimo
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Victor W. Pike
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
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Brouwer C, Jenko K, Zoghbi SS, Innis RB, Pike VW. Development of N-methyl-(2-arylquinolin-4-yl)oxypropanamides as leads to PET radioligands for translocator protein (18 kDa). J Med Chem 2014; 57:6240-51. [PMID: 24949670 PMCID: PMC4216211 DOI: 10.1021/jm5007947] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Translocator protein (18 kDa), known
as TSPO, is a recognized biomarker
of neuroinflammation. Radioligands with PET accurately quantify TSPO
in neuroinflammatory conditions. However, the existence of three human
TSPO genotypes that show differential affinity to almost all useful
TSPO PET radioligands hampers such studies. There is an unmet need
for genotype-insensitive, high-affinity, and moderately lipophilic
TSPO ligands that may serve as leads for PET radioligand development.
To address this need, we varied the known high-affinity TSPO ligand
(l)-N,N-diethyl-2-methyl-3-(2-phenylquinolin-4-yl)propanamide
in its aryl scaffold, side chain tether, and pendant substituted amido
group while retaining an N-methyl group as a site
for labeling with carbon-11. From this effort, oxygen-tethered N-methyl-aryloxypropanamides emerged as new high-affinity
TSPO ligands with attenuated lipophilicity, including one example
with attractive properties for PET radioligand development, namely N-methyl-N-phenyl-2-{[2-(pyridin-2-yl)quinolin-4-yl]oxy}propanamide
(22a; rat Ki = 0.10 nM; human
TSPO genotypes Ki = 1.4 nM; clogD = 4.18).
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Affiliation(s)
- Chad Brouwer
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health , Building 10, Room B3 C346A, 10 Center Drive, Bethesda, Maryland 20892, United States
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Su Z, Herholz K, Gerhard A, Roncaroli F, Du Plessis D, Jackson A, Turkheimer F, Hinz R. [¹¹C]-(R)PK11195 tracer kinetics in the brain of glioma patients and a comparison of two referencing approaches. Eur J Nucl Med Mol Imaging 2013; 40:1406-19. [PMID: 23715902 PMCID: PMC3738844 DOI: 10.1007/s00259-013-2447-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 04/30/2013] [Indexed: 12/22/2022]
Abstract
PURPOSE Translocator protein (TSPO) is a biomarker of neuroinflammation that can be imaged by PET using [¹¹C]-(R)PK11195. We sought to characterize the [¹¹C]-(R)PK11195 kinetics in gliomas of different histotypes and grades, and to compare two reference tissue input functions (supervised cluster analysis versus cerebellar grey matter) for the estimation of [¹¹C]-(R)PK11195 binding in gliomas and surrounding brain structures. METHODS Twenty-three glioma patients and ten age-matched controls underwent structural MRI and dynamic [¹¹C]-(R)PK11195 PET scans. Tissue time-activity curves (TACs) were extracted from tumour regions as well as grey matter (GM) and white matter (WM) of the brains. Parametric maps of binding potential (BPND) were generated with the simplified reference tissue model using the two input functions, and were compared with each other. TSPO expression was assessed in tumour tissue sections by immunohistochemistry. RESULTS Three types of regional kinetics were observed in individual tumour TACs: GM-like kinetics (n=6, clearance of the tracer similar to that in cerebellar GM), WM-like kinetics (n=8, clearance of the tracer similar to that in cerebral WM) and a form of mixed kinetics (n=9, intermediate rate of clearance). Such kinetic patterns differed between low-grade astrocytomas (WM-like kinetics) and oligodendrogliomas (GM-like and mixed kinetics), but were independent of tumour grade. There was good agreement between parametric maps of BPND derived from the two input functions in all controls and 10 of 23 glioma patients. In 13 of the 23 patients, BPND values derived from the supervised cluster input were systematically smaller than those using the cerebellar input. Immunohistochemistry confirmed that TSPO expression increased with tumour grade. CONCLUSION The three types of [¹¹C]-(R)PK11195 kinetics in gliomas are determined in part by tracer delivery, and indicated that kinetic analysis is a valuable tool in the study of gliomas with the potential for in vivo discrimination between low-grade astrocytomas and oligodendrogliomas. Supervised cluster and cerebellar input functions produced consistent BPND estimates in approximately half of the gliomas investigated, but had a systematic difference in the remainder. The cerebellar input is preferred based on theoretical and practical considerations.
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Affiliation(s)
- Zhangjie Su
- Wolfson Molecular Imaging Centre, University of Manchester, 27 Palatine Road, Manchester, UK.
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Kalk NJ, Owen DR, Tyacke RJ, Reynolds R, Rabiner EA, Lingford-Hughes AR, Parker CA. Are prescribed benzodiazepines likely to affect the availability of the 18 kDa translocator protein (TSPO) in PET studies? Synapse 2013; 67:909-12. [PMID: 23666806 DOI: 10.1002/syn.21681] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 04/13/2013] [Accepted: 05/03/2013] [Indexed: 11/07/2022]
Affiliation(s)
- N J Kalk
- Imperial College London, Centre for Neuropsychopharmacology, London, United Kingdom
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Guo WZ, Miao YL, An LN, Wang XY, Pan NL, Ma YQ, Chen HX, Zhao N, Zhang H, Li YF, Mi WD. Midazolam provides cytoprotective effect during corticosterone-induced damages in rat astrocytes by stimulating steroidogenesis. Neurosci Lett 2013; 547:53-8. [DOI: 10.1016/j.neulet.2013.05.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 04/30/2013] [Accepted: 05/03/2013] [Indexed: 10/26/2022]
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Jučaite A, Cselényi Z, Arvidsson A, Ahlberg G, Julin P, Varnäs K, Stenkrona P, Andersson J, Halldin C, Farde L. Kinetic analysis and test-retest variability of the radioligand [11C](R)-PK11195 binding to TSPO in the human brain - a PET study in control subjects. EJNMMI Res 2012; 2:15. [PMID: 22524272 PMCID: PMC3350394 DOI: 10.1186/2191-219x-2-15] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 04/23/2012] [Indexed: 12/02/2022] Open
Abstract
Background Positron-emission tomography and the radioligand [11C](R)-PK11195 have been used for the imaging of the translocator protein (TSPO) and applied to map microglia cells in the brain in neuropsychiatric disorders. [11C](R)-PK11195 binding has been quantified using reference region approaches, with the reference defined anatomically or using unsupervised or supervised clustering algorithms. Kinetic compartment modelling so far has not been presented. In the present test-retest study, we examine the characteristics of [11C](R)-PK11195 binding in detail, using the classical compartment analysis with a metabolite-corrected arterial input function. Methods [11C](R)-PK11195 binding was examined in six control subjects at two separate occasions, 6 weeks apart. Results of one-tissue and two-tissue compartment models (1TCM, 2TCM) were compared using the Akaike criteria and F-statistics. The reproducibility of binding potential (BPND) estimates was evaluated by difference in measurements (error in percent) and intraclass correlation coefficients (ICCs). Results [11C](R)-PK11195 binding could be described by 2TCM which was the preferred model. Measurement error (in percent) indicated good reproducibility in large brain regions (mean error: whole brain 4%, grey matter 5%), but not in smaller subcortical regions (putamen 25%, caudate 55%). The ICC values were moderate to low, highest for the white matter (0.73), whole brain and thalamus (0.57), and cortical grey matter (0.47). Sizeable [11C](R)-PK11195 BPND could be identified throughout the human brain (range 1.11 to 2.21). Conclusions High intra-subject variability of [11C](R)-PK11195 binding limits longitudinal monitoring of TSPO changes. The interpretation of [11C](R)-PK11195 binding by 2TCM suggests that the presence of specific binding to TSPO cannot be excluded at physiological conditions.
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Affiliation(s)
- Aurelija Jučaite
- AstraZeneca Global Clinical Development, Södertälje 151 85, Sweden.
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Initial evaluation in healthy humans of [18F]DPA-714, a potential PET biomarker for neuroinflammation. Nucl Med Biol 2011; 39:570-8. [PMID: 22172392 DOI: 10.1016/j.nucmedbio.2011.10.012] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/04/2011] [Accepted: 10/17/2011] [Indexed: 11/22/2022]
Abstract
INTRODUCTION The translocator protein 18 kDa (TSPO), although minimally expressed in healthy brain, is up-regulated in pathological conditions, coinciding with microglial activation. It is thereby a suitable in vivo biomarker of neuroinflammation for detection, evaluation and therapeutic monitoring of brain diseases. We aimed to estimate the radiation dosimetry of the positron emission tomography (PET) TSPO radioligand [(18)F]DPA-714, and we evaluated in healthy volunteers its whole-body uptake and cerebral kinetics. METHODS Biodistribution data from mice were used for the prediction of radiation dosimetry. In human studies, a 90-min dynamic PET scan was performed in seven healthy volunteers after injection of [(18)F]DPA-714 (245±45 MBq). Arterial and venous samples were collected from two subjects, and two additional subjects were submitted to whole-body acquisition. Regions of interest were defined over cerebral structures to obtain mean time-activity curves and to estimate the distribution volume ratios by Logan graphical analysis, and over peripheral organs to obtain standard uptake values. RESULTS The effective dose estimated from biodistribution in mice was 17.2 μSv/MBq. Modeling of regional brain and plasma data showed good in vivo stability of [(18)F]DPA-714 in humans, with only 20% of blood metabolites 20 min postinjection (p.i.). Maximum cerebral uptake was observed 5 min p.i., followed by two decreasing phases: a rapid washout (5-30 min) followed by a slower phase for the remainder of PET acquisition. Whole-body images demonstrate high activity in the gallbladder, heart, spleen and kidneys. CONCLUSIONS This initial study in humans shows that [(18)F]DPA-714 is a promising PET radioligand with excellent in vivo stability and biodistribution, and acceptable effective dose estimation. Therefore, [(18)F]DPA-714 could provide a sensitive measure of neuroinflammatory changes in subsequent clinical investigations.
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Quantitation of translocator protein binding in human brain with the novel radioligand [18F]-FEPPA and positron emission tomography. J Cereb Blood Flow Metab 2011; 31:1807-16. [PMID: 21522163 PMCID: PMC3170950 DOI: 10.1038/jcbfm.2011.55] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This article describes the kinetic modeling of [(18)F]-FEPPA binding to translocator protein 18 kDa in the human brain using high-resolution research tomograph (HRRT) positron emission tomography. Positron emission tomography scans were performed in 12 healthy volunteers for 180 minutes. A two-tissue compartment model (2-CM) provided, with no exception, better fits to the data than a one-tissue model. Estimates of total distribution volume (V(T)), specific distribution volume (V(S)), and binding potential (BP(ND)) demonstrated very good identifiability (based on coefficient of variation (COV)) for all the regions of interest (ROIs) in the gray matter (COV V(T)<7%, COV V(S)<8%, COV BP(ND)<11%). Reduction of the length of the scan to 2 hours is feasible as V(S) and V(T) showed only a small bias (6% and 7.5%, respectively). Monte Carlo simulations showed that, even under conditions of a 500% increase in specific binding, the identifiability of V(T) and V(S) was still very good with COV<10%, across high-uptake ROIs. The excellent identifiability of V(T) values obtained from an unconstrained 2-CM with data from a 2-hour scan support the use of V(T) as an appropriate and feasible outcome measure for [(18)F]-FEPPA.
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Schüle C, Eser D, Baghai TC, Nothdurfter C, Kessler JS, Rupprecht R. Neuroactive steroids in affective disorders: target for novel antidepressant or anxiolytic drugs? Neuroscience 2011; 191:55-77. [PMID: 21439354 DOI: 10.1016/j.neuroscience.2011.03.025] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 03/13/2011] [Accepted: 03/14/2011] [Indexed: 11/18/2022]
Abstract
In the past decades considerable evidence has emerged that so-called neuroactive steroids do not only act as transcriptional factors in the regulation of gene expression but may also alter neuronal excitability through interactions with specific neurotransmitter receptors such as the GABA(A) receptor. In particular, 3α-reduced neuroactive steroids such as allopregnanolone or allotetrahydrodeoxycorticosterone have been shown to act as positive allosteric modulators of the GABA(A) receptor and to play an important role in the pathophysiology of depression and anxiety. During depression, the concentrations of 3α,5α-tetrahydroprogesterone and 3α,5β-tetrahydroprogesterone are decreased, while the levels of 3β,5α-tetrahydroprogesterone, a stereoisomer of 3α,5α-tetrahydroprogesterone, which may act as an antagonist for GABAergic steroids, are increased. Antidepressant drugs such as selective serotonin reuptake inhibitors (SSRIs) or mirtazapine apparently have an impact on key enzymes of neurosteroidogenesis and have been shown to normalize the disequilibrium of neuroactive steroids in depression by increasing 3α-reduced pregnane steroids and decreasing 3β,5α-tetrahydroprogesterone. Moreover, 3α-reduced neuroactive steroids have been demonstrated to possess antidepressant- and anxiolytic-like effects both in animal and human studies for themselves. In addition, the translacator protein (18 kDa) (TSPO), previously called peripheral benzodiazepine receptor, is the key element of the mitochondrial import machinery supplying the substrate cholesterol to the first steroidogenic enzyme (P450scc), which transforms cholesterol into pregnenolone, the precursor of all neurosteroids. TSPO ligands increase neurosteroidogenesis and are a target of novel anxiolytic drugs producing anxiolytic effects without causing the side effects normally associated with conventional benzodiazepines such as sedation or tolerance. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain.
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Affiliation(s)
- C Schüle
- Department of Psychiatry and Psychotherapy, Ludwig-Maximilian-University, Nussbaumstrasse 7, 80336 Munich, Germany.
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Barron AM, Hojo Y, Mukai H, Higo S, Ooishi Y, Hatanaka Y, Ogiue-Ikeda M, Murakami G, Kimoto T, Kawato S. Regulation of synaptic plasticity by hippocampus synthesized estradiol. Horm Mol Biol Clin Investig 2011; 7:361-75. [PMID: 25961274 DOI: 10.1515/hmbci.2011.118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 07/21/2011] [Indexed: 01/29/2023]
Abstract
Estradiol is synthesized from cholesterol in hippocampal neurons of adult rats by cytochrome P450 and hydroxysteroid dehydrogenase enzymes. These enzymes are expressed in the glutamatergic neurons of the hippocampus. Surprisingly, the concentration of estradiol and androgen in the hippocampus is significantly higher than that in circulation. Locally synthesized estradiol rapidly and potently modulates synaptic plasticity within the hippocampus. E2 rapidly potentiates long-term depression and induces spinogenesis through synaptic estrogen receptors and kinases. The rapid effects of estradiol are followed by slow genomic effects mediated by both estrogen receptors located at the synapse and nucleus, modulating long-term potentiation and promoting the formation of new functional synaptic contacts. Age-related changes in hippocampally derived estradiol synthesis and distribution of estrogen receptors may alter synaptic plasticity, and could potentially contribute to age-related cognitive decline. Understanding factors which regulate hippocampal estradiol synthesis could lead to the identification of alternatives to conventional hormone therapy to protect against age-related cognitive decline.
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Abstract
Magnetic resonance imaging (MRI) has had a profound impact on both research and clinical management of multiple sclerosis (MS), but signal changes reflect underlying neuropathology only indirectly and often non-specifically. Positron emission tomography (PET) offers the potential to complement MRI with quantitative measures of molecularly specific markers of cellular and metabolic processes. PET radiotracers already available promise new insights into the dynamics of the innate immune response, neuronal function, neurodegeneration and remyelination. Because PET is an exquisitely sensitive technique (able to image even picomolar concentrations), only microdoses of radioligand (<10 µg) are needed for imaging. This facilitates rapid implementation of novel radioligands because extensive toxicology data is not required. In the future, molecular imaging could assist clinical decision-making with patient stratification for optimization of treatment selection.
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Affiliation(s)
- David RJ Owen
- Division of Experimental Medicine, Imperial College, Hammersmith Hospital, London UK
- GSK Clinical Imaging Centre, Hammersmith Hospital, London, UK
| | - Paola Piccini
- Centre for Neuroscience, Imperial College, London, UK
| | - Paul M Matthews
- GSK Clinical Imaging Centre, Hammersmith Hospital, London, UK
- Centre for Neuroscience, Imperial College, London, UK
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Imaging Brain Microglial Activation Using Positron Emission Tomography and Translocator Protein-Specific Radioligands. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2011; 101:19-39. [DOI: 10.1016/b978-0-12-387718-5.00002-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Two binding sites for [3H]PBR28 in human brain: implications for TSPO PET imaging of neuroinflammation. J Cereb Blood Flow Metab 2010; 30:1608-18. [PMID: 20424634 PMCID: PMC2949260 DOI: 10.1038/jcbfm.2010.63] [Citation(s) in RCA: 164] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
[(11)C]PBR28, a radioligand targeting the translocator protein (TSPO), does not produce a specific binding signal in approximately 14% of healthy volunteers. This phenomenon has not been reported for [(11)C]PK11195, another TSPO radioligand. We measured the specific binding signals with [(3)H]PK11195 and [(3)H]PBR28 in brain tissue from 22 donors. Overall, 23% of the samples did not generate a visually detectable specific autoradiographic signal with [(3)H]PBR28, although all samples showed [(3)H]PK11195 binding. There was a marked reduction in the affinity of [(3)H]PBR28 for TSPO in samples with no visible [(3)H]PBR28 autoradiographic signal (K(i)=188+/-15.6 nmol/L), relative to those showing normal signal (K(i)=3.4+/-0.5 nmol/L, P<0.001). Of this latter group, [(3)H]PBR28 bound with a two-site fit in 40% of cases, with affinities (K(i)) of 4.0+/-2.4 nmol/L (high-affinity site) and 313+/-77 nmol/L (low-affinity site). There was no difference in K(d) or B(max) for [(3)H]PK11195 in samples showing no [(3)H]PBR28 autoradiographic signal relative to those showing normal [(3)H]PBR28 autoradiographic signal. [(3)H]PK11195 bound with a single site for all samples. The existence of three different binding patterns with PBR28 (high-affinity binding (46%), low-affinity binding (23%), and two-site binding (31%)) suggests that a reduction in [(11)C]PBR28 binding may not be interpreted simply as a reduction in TSPO density. The functional significance of differences in binding characteristics warrants further investigation.
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Fujimura Y, Zoghbi SS, Simèon FG, Taku A, Pike VW, Innis RB, Fujita M. Quantification of translocator protein (18 kDa) in the human brain with PET and a novel radioligand, (18)F-PBR06. J Nucl Med 2009; 50:1047-53. [PMID: 19525468 DOI: 10.2967/jnumed.108.060186] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Translocator protein (TSPO) (18 kDa), formerly called the peripheral benzodiazepine receptor, is upregulated on activated microglia and macrophages and is, thus, a biomarker of inflammation. We previously reported that an (11)C-labeled aryloxyanilide (half-life, 20 min) was able to quantify TSPOs in the healthy human brain. Because many PET centers would benefit from a longer-lived (18)F-labeled radioligand (half-life, 110 min), the objective of this study was to evaluate the ability of a closely related aryloxyanilide ((18)F-N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline [(18)F-PBR06]) to quantify TSPOs in the healthy human brain. METHODS A total of 9 human subjects were injected with (18)F-PBR06 (approximately 185 MBq) and scanned for 5 h, with rest periods outside the camera. The concentrations of (18)F-PBR06, separated from radiometabolites, were measured in arterial plasma. RESULTS Modeling of regional brain and plasma data showed that a 2-tissue-compartment model was superior to a 1-tissue-compartment model. Even if data for all time points were used for the fitting, concentrations of brain activity measured with PET were consistently greater than the modeled values at late (280-300 min) but not at early time points. The greater values may have been caused by the slow accumulation of radiometabolites in the brain. To determine an adequate time for more accurate measurement of distribution volume (V(T)), which is the summation of receptor binding and nondisplaceable activity, we investigated which scan duration would be associated with maximal or near-maximal identifiability. We found that a scan of 120 min provided the best identifiability of V(T) (approximately 2%). The images showed no significant defluorination. CONCLUSION (18)F-PBR06 can quantify TSPOs in the healthy human brain using 120 min of image acquisition and concurrent measurements of radioligand in plasma. Although brain activity is likely contaminated with radiometabolites, the percentage contamination is thought to be small (<10%), because values of distribution volume are stable during 60-120 min and vary by less than 10%. (18)F-PBR06 is a longer-lived and promising alternative to (11)C-labeled radioligands to measure TSPOs as a biomarker of inflammation in the brain.
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Affiliation(s)
- Yota Fujimura
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-2035, USA
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Diazepam neuroprotection in excitotoxic and oxidative stress involves a mitochondrial mechanism additional to the GABAAR and hypothermic effects. Neurochem Int 2009; 55:164-73. [DOI: 10.1016/j.neuint.2009.01.024] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 01/27/2009] [Accepted: 01/30/2009] [Indexed: 11/19/2022]
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Kita A, Furukawa K. Involvement of neurosteroids in the anxiolytic-like effects of AC-5216 in mice. Pharmacol Biochem Behav 2008; 89:171-8. [DOI: 10.1016/j.pbb.2007.12.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Revised: 11/26/2007] [Accepted: 12/05/2007] [Indexed: 10/22/2022]
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Fujita M, Imaizumi M, Zoghbi SS, Fujimura Y, Farris AG, Suhara T, Hong J, Pike VW, Innis RB. Kinetic analysis in healthy humans of a novel positron emission tomography radioligand to image the peripheral benzodiazepine receptor, a potential biomarker for inflammation. Neuroimage 2007; 40:43-52. [PMID: 18093844 DOI: 10.1016/j.neuroimage.2007.11.011] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 11/09/2007] [Accepted: 11/13/2007] [Indexed: 11/17/2022] Open
Abstract
The peripheral benzodiazepine receptor (PBR) is upregulated on activated microglia and macrophages and thereby is a useful biomarker of inflammation. We developed a novel PET radioligand, [(11)C]PBR28, that was able to image and quantify PBRs in healthy monkeys and in a rat model of stroke. The objective of this study was to evaluate the ability of [(11)C]PBR28 to quantify PBRs in brain of healthy human subjects. Twelve subjects had PET scans of 120 to 180 min duration as well as serial sampling of arterial plasma to measure the concentration of unchanged parent radioligand. One- and two-tissue compartmental analyses were performed. To obtain stable estimates of distribution volume, which is a summation of B(max)/K(D) and nondisplaceable activity, 90 min of brain imaging was required. Distribution volumes in human were only approximately 5% of those in monkey. This comparatively low amount of receptor binding required a two-rather than a one-compartment model, suggesting that nonspecific binding was a sizeable percentage compared to specific binding. The time-activity curves in two of the twelve subjects appeared as if they had no PBR binding-i.e., rapid peak of uptake and fast washout from brain. The cause(s) of these unusual findings are unknown, but both subjects were also found to lack binding to PBRs in peripheral organs such as lung and kidney. In conclusion, with the exception of those subjects who appeared to have no PBR binding, [(11)C]PBR28 is a promising ligand to quantify PBRs and localize inflammation associated with increased densities of PBRs.
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Affiliation(s)
- Masahiro Fujita
- Molecular Imaging Branch, National Institute of Mental Health, 31 Center Drive, MSC-2035, Bethesda, MD 20892-2035, USA.
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Schuitemaker A, van Berckel BNM, Kropholler MA, Veltman DJ, Scheltens P, Jonker C, Lammertsma AA, Boellaard R. SPM analysis of parametric (R)-[11C]PK11195 binding images: Plasma input versus reference tissue parametric methods. Neuroimage 2007; 35:1473-9. [PMID: 17363280 DOI: 10.1016/j.neuroimage.2007.02.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Revised: 02/08/2007] [Accepted: 02/08/2007] [Indexed: 11/26/2022] Open
Abstract
(R)-[11C]PK11195 has been used for quantifying cerebral microglial activation in vivo. In previous studies, both plasma input and reference tissue methods have been used, usually in combination with a region of interest (ROI) approach. Definition of ROIs, however, can be labourious and prone to interobserver variation. In addition, results are only obtained for predefined areas and (unexpected) signals in undefined areas may be missed. On the other hand, standard pharmacokinetic models are too sensitive to noise to calculate (R)-[11C]PK11195 binding on a voxel-by-voxel basis. Linearised versions of both plasma input and reference tissue models have been described, and these are more suitable for parametric imaging. The purpose of this study was to compare the performance of these plasma input and reference tissue parametric methods on the outcome of statistical parametric mapping (SPM) analysis of (R)-[11C]PK11195 binding. Dynamic (R)-[11C]PK11195 PET scans with arterial blood sampling were performed in 7 younger and 11 elderly healthy subjects. Parametric images of volume of distribution (Vd) and binding potential (BP) were generated using linearised versions of plasma input (Logan) and reference tissue (Reference Parametric Mapping) models. Images were compared at the group level using SPM with a two-sample t-test per voxel, both with and without proportional scaling. Parametric BP images without scaling provided the most sensitive framework for determining differences in (R)-[11C]PK11195 binding between younger and elderly subjects. Vd images could only demonstrate differences in (R)-[11C]PK11195 binding when analysed with proportional scaling due to intersubject variation in K1/k2 (blood-brain barrier transport and non-specific binding).
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Affiliation(s)
- Alie Schuitemaker
- Department of Nuclear Medicine and PET Research, VU University Medical Centre, P.O. Box 7057, 1081 MB Amsterdam, The Netherlands
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Imaizumi M, Briard E, Zoghbi SS, Gourley JP, Hong J, Musachio JL, Gladding R, Pike VW, Innis RB, Fujita M. Kinetic evaluation in nonhuman primates of two new PET ligands for peripheral benzodiazepine receptors in brain. Synapse 2007; 61:595-605. [PMID: 17455247 DOI: 10.1002/syn.20394] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Peripheral benzodiazepine receptors (PBRs) are upregulated on activated microglia and are, thereby, biomarkers of cellular inflammation in brain. We recently developed two PET ligands with an aryloxyanilide structure to image PBRs and now evaluate the kinetics of these radiotracers in monkey to determine whether they are suitable to explore in human. Baseline and receptor-blocking scans were performed with [(11)C]PBR01 and [(18)F]PBR06 in conjunction with serial measurements of the arterial plasma concentration of parent radiotracer separated from radiometabolite. We used brain and plasma data with compartmental modeling to calculate regional brain distribution volume, which is equal to the ratio at equilibrium of the concentration of radioligand in brain to that of plasma. The distribution volume of [(11)C]PBR01 was inaccurately estimated in the baseline scans, possibly because of the short half-life of (11)C or the presence of radiometabolite in brain. In contrast, the distribution volume of [(18)F]PBR06 was stably determined within 200 min of scanning, and nondisplaceable uptake was only approximately 10% of total brain uptake. [(18)F]PBR06 is promising for use in human because brain activity could be quantified with standard compartmental models and showed higher ratios ( approximately 10:1) of specific to nonspecific uptake. A critical factor for human use will be whether the tracer has adequately fast wash out from brain relative to the half-life of the radionuclide to obtain stable values of distribution volume.
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Affiliation(s)
- Masao Imaizumi
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-2035, USA
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Versijpt J, Debruyne JC, Van Laere KJ, De Vos F, Keppens J, Strijckmans K, Achten E, Slegers G, Dierckx RA, Korf J, De Reuck JL. Microglial imaging with positron emission tomography and atrophy measurements with magnetic resonance imaging in multiple sclerosis: a correlative study. Mult Scler 2005; 11:127-34. [PMID: 15794383 DOI: 10.1191/1352458505ms1140oa] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE The objectives of the present study were to assess brain atrophy in multiple sclerosis (MS) patients during different disease stages and to investigate by PET and [11C]PK11195, a marker of microglial activation, the relationship between inflammation, atrophy and clinically relevant measures. METHODS Eight healthy subjects and 22 MS patients were included. Semiquantitative [11C]PK11195 uptake values, with normalization on cortical grey matter, were measured for magnetic resonance imaging T2- and T1-lesions and normal appearing white matter (NAWM). As atrophy index we used the ratio of the amount of white and grey matter divided by the ventricular size, using an optimized a priori based segmentation algorithm (SPM99). RESULTS Atrophy was significantly greater in MS patients compared to age-matched controls. A significant correlation was found between brain atrophy and both disease duration and disability, as measured with the Expanded Disability Status Scale. For NAWM, [11C]PK11195 uptake increased with the amount of atrophy, while T2-lesional [11C]PK11195 uptake values decreased according to increasing brain atrophy. CONCLUSIONS The present study suggests that brain atrophy, correlating with disease duration and disability, is directly related to NAWM and T2-lesional inflammation as measured by microglial activation.
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Affiliation(s)
- J Versijpt
- Ghent University Hospital, Ghent, the Netherlands
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Kita A, Kohayakawa H, Kinoshita T, Ochi Y, Nakamichi K, Kurumiya S, Furukawa K, Oka M. Antianxiety and antidepressant-like effects of AC-5216, a novel mitochondrial benzodiazepine receptor ligand. Br J Pharmacol 2004; 142:1059-72. [PMID: 15249420 PMCID: PMC1575165 DOI: 10.1038/sj.bjp.0705681] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We investigated the ability of N-benzyl-N-ethyl-2-(7,8-dihydro-7-methyl-8-oxo-2-phenyl-9H-purin-9-yl)acetamide (AC-5216), a novel mitochondrial benzodiazepine receptor (MBR) ligand, to produce anti-anxiety and antidepressant-like effects in various animal models. AC-5216 showed high affinity for MBRs prepared from rat whole brain (Ki 0.297 nm), rat glioma cells (IC50 3.04 nm) and human glioma cells (IC50 2.73 nm), but only negligible affinity for the other main receptors including central benzodiazepine receptors. AC-5216 produced anti-anxiety effects in the Vogel-type conflict test in rats, and in the light/dark box and social interaction tests in mice at 0.1-3, 0.003-0.01 and 0.01-0.3 mg kg(-1), p.o., respectively. These effects of AC-5216 were antagonized by PK11195, an MBR antagonist. In the forced swimming test in rats, AC-5216 (3-30 mg kg(-1), p.o.) reduced the immobility time, and this effect was blocked by PK11195. AC-5216 had no myorelaxant effects, did not affect the memory or prolong hexobarbitone-induced sleep in mice, even at doses as high as 1000 mg kg(-1), p.o. Although it did slightly prolong the ethanol-induced sleep time at 1000 mg kg(-1), AC-5216 (1-100 mg kg(-1), p.o.) produced no distinct change in the rat electroencephalogram. These results indicate that AC-5216 produces anti-anxiety and antidepressant-like effects that are mediated by MBR, but does not cause the side effects normally associated with conventional benzodiazepines. Hence, AC-5216 shows potential for the treatment of stress-related disorders including anxiety and depression.
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Affiliation(s)
- Atsuko Kita
- Pharmacology & Microbiology Research Laboratories, Dainippon Pharmaceutical Co., Ltd, 33-94 Enoki, Suita 564-0053, Osaka, Japan.
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