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Mahemuti Y, Kadeer K, Su R, Abula A, Aili Y, Maimaiti A, Abulaiti S, Maimaitituerxun M, Miao T, Jiang S, Axier A, Aisha M, Wang Y, Cheng X. TSPO exacerbates acute cerebral ischemia/reperfusion injury by inducing autophagy dysfunction. Exp Neurol 2023; 369:114542. [PMID: 37717810 DOI: 10.1016/j.expneurol.2023.114542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 09/19/2023]
Abstract
Autophagy is considered a double-edged sword, with a role in the regulation of the pathophysiological processes of the central nervous system (CNS) after cerebral ischemia-reperfusion injury (CIRI). The 18-kDa translocator protein (TSPO) is a highly conserved protein, with its expression level in the nervous system closely associated with the regulation of pathophysiological processes. In addition, the ligand of TSPO reduces neuroinflammation in brain diseases, but the potential role of TSPO in CIRI is largely undiscovered. On this basis, we investigated whether TSPO regulates neuroinflammatory response by affecting autophagy in microglia. In our study, increased expression of TSPO was detected in rat brain tissues with transient middle cerebral artery occlusion (tMCAO) and in BV2 microglial cells exposed to oxygen-glucose deprivation or reoxygenation (OGD/R) treatment, respectively. In addition, we confirmed that autophagy was over-activated during CIRI by increased expression of autophagy activation related proteins with Beclin-1 and LC3B, while the expression of p62 was decreased. The degradation process of autophagy was inhibited, while the expression levels of LAMP-1 and Cathepsin-D were significantly reduced. Results of confocal laser microscopy and transmission electron microscopy (TEM) indicated that autophagy flux was disordered. In contrast, inhibition of TSPO prevented autophagy over-activation both in vivo and in vitro. Interestingly, suppression of TSPO alleviated nerve cell damage by reducing reactive oxygen species (ROS) and pro-inflammatory factors, including TNF-α and IL-6 in microglia cells. In summary, these results indicated that TSPO might affect CIRI by mediating autophagy dysfunction and thus might serve as a potential target for ischemic stroke treatment.
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Affiliation(s)
- Yusufu Mahemuti
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China; School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou 310058, Zhejiang, PR China; Liangzhu Laboratory, MOE Frontier Science Center for Brain Science & Brain-Machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou 311121, Zhejiang, PR China; NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University, Hangzhou 310058, Zhejiang, PR China
| | - Kaheerman Kadeer
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Riqing Su
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Abudureheman Abula
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Yirizhati Aili
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Aierpati Maimaiti
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Subinuer Abulaiti
- Department of Epidemiology and Biostatistics, Institute of Public Health, Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | | | - Tong Miao
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Shihao Jiang
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Aximujiang Axier
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Maimaitili Aisha
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Yongxin Wang
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China
| | - Xiaojiang Cheng
- Department of Neurosurgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, Xinjiang, PR China.
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2
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18F-Radiolabeled Translocator Protein (TSPO) PET Tracers: Recent Development of TSPO Radioligands and Their Application to PET Study. Pharmaceutics 2022; 14:pharmaceutics14112545. [PMID: 36432736 PMCID: PMC9697781 DOI: 10.3390/pharmaceutics14112545] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 11/16/2022] [Accepted: 11/17/2022] [Indexed: 11/23/2022] Open
Abstract
Translocator protein 18 kDa (TSPO) is a transmembrane protein in the mitochondrial membrane, which has been identified as a peripheral benzodiazepine receptor. TSPO is generally present at high concentrations in steroid-producing cells and plays an important role in steroid synthesis, apoptosis, and cell proliferation. In the central nervous system, TSPO expression is relatively modest under normal physiological circumstances. However, some pathological disorders can lead to changes in TSPO expression. Overexpression of TSPO is associated with several diseases, such as neurodegenerative diseases, neuroinflammation, brain injury, and cancers. TSPO has therefore become an effective biomarker of related diseases. Positron emission tomography (PET), a non-invasive molecular imaging technique used for the clinical diagnosis of numerous diseases, can detect diseases related to TSPO expression. Several radiolabeled TSPO ligands have been developed for PET. In this review, we describe recent advances in the development of TSPO ligands, and 18F-radiolabeled TSPO in particular, as PET tracers. This review covers pharmacokinetic studies, preclinical and clinical trials of 18F-labeled TSPO PET ligands, and the synthesis of TSPO ligands.
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Zhou R, Ji B, Kong Y, Qin L, Ren W, Guan Y, Ni R. PET Imaging of Neuroinflammation in Alzheimer's Disease. Front Immunol 2021; 12:739130. [PMID: 34603323 PMCID: PMC8481830 DOI: 10.3389/fimmu.2021.739130] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 08/27/2021] [Indexed: 12/15/2022] Open
Abstract
Neuroinflammation play an important role in Alzheimer's disease pathogenesis. Advances in molecular imaging using positron emission tomography have provided insights into the time course of neuroinflammation and its relation with Alzheimer's disease central pathologies in patients and in animal disease models. Recent single-cell sequencing and transcriptomics indicate dynamic disease-associated microglia and astrocyte profiles in Alzheimer's disease. Mitochondrial 18-kDa translocator protein is the most widely investigated target for neuroinflammation imaging. New generation of translocator protein tracers with improved performance have been developed and evaluated along with tau and amyloid imaging for assessing the disease progression in Alzheimer's disease continuum. Given that translocator protein is not exclusively expressed in glia, alternative targets are under rapid development, such as monoamine oxidase B, matrix metalloproteinases, colony-stimulating factor 1 receptor, imidazoline-2 binding sites, cyclooxygenase, cannabinoid-2 receptor, purinergic P2X7 receptor, P2Y12 receptor, the fractalkine receptor, triggering receptor expressed on myeloid cells 2, and receptor for advanced glycation end products. Promising targets should demonstrate a higher specificity for cellular locations with exclusive expression in microglia or astrocyte and activation status (pro- or anti-inflammatory) with highly specific ligand to enable in vivo brain imaging. In this review, we summarised recent advances in the development of neuroinflammation imaging tracers and provided an outlook for promising targets in the future.
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Affiliation(s)
- Rong Zhou
- Department of Nephrology, Yangpu Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Bin Ji
- Department of Radiopharmacy and Molecular Imaging, School of Pharmacy, Fudan University, Shanghai, China
| | - Yanyan Kong
- Positron Emission Tomography (PET) Center, Huashan Hospital, Fudan University, Shanghai, China
| | - Limei Qin
- Inner Mongolia Baicaotang Qin Chinese Mongolia Hospital, Hohhot, China
| | - Wuwei Ren
- School of Information Science and Technology, Shanghaitech University, Shanghai, China
| | - Yihui Guan
- Positron Emission Tomography (PET) Center, Huashan Hospital, Fudan University, Shanghai, China
| | - Ruiqing Ni
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
- Institute for Biomedical Engineering, University of Zurich & Eidgenössische Technische Hochschule Zürich (ETH Zurich), Zurich, Switzerland
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Mattner F, Katsifis A, Bourdier T, Loc'h C, Berghofer P, Fookes C, Hung TT, Jackson T, Henderson D, Pham T, Lee BJ, Shepherd R, Greguric I, Wyatt N, Le T, Poon J, Power C, Fulham M. Synthesis and pharmacological evaluation of [ 18F]PBR316: a novel PET ligand targeting the translocator protein 18 kDa (TSPO) with low binding sensitivity to human single nucleotide polymorphism rs6971. RSC Med Chem 2021; 12:1207-1221. [PMID: 34355185 PMCID: PMC8292990 DOI: 10.1039/d1md00035g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/15/2021] [Indexed: 02/04/2023] Open
Abstract
Radiopharmaceuticals that target the translocator protein 18 kDa (TSPO) have been investigated with positron emission tomography (PET) to study neuroinflammation, neurodegeneration and cancer. We have developed the novel, achiral, 2-phenylimidazo[1,2-a]pyridine, PBR316 that targets the translocator protein 18 kDa (TSPO) that addresses some of the limitations inherent in current TSPO ligands; namely specificity in binding, blood brain barrier permeability, metabolism and insensitivity to TSPO binding in subjects as a result of rs6971 polymorphism. PBR316 has high nanomolar affinity (4.7-6.0 nM) for the TSPO, >5000 nM for the central benzodiazepine receptor (CBR) and low sensitivity to rs6971 polymorphism with a low affinity binders (LABs) to high affinity binders (HABs) ratio of 1.5. [18F]PBR316 was prepared in 20 ± 5% radiochemical yield, >99% radiochemical purity and a molar activity of 160-400 GBq μmol-1. Biodistribution in rats showed high uptake of [18F]PBR316 in organs known to express TSPO such as heart (3.9%) and adrenal glands (7.5% ID per g) at 1 h. [18F]PBR316 entered the brain and accumulated in TSPO-expressing regions with an olfactory bulb to brain ratio of 3 at 15 min and 7 at 4 h. Radioactivity was blocked by PK11195 and Ro 5-4864 but not Flumazenil. Metabolite analysis showed that radioactivity in adrenal glands and the brain was predominantly due to the intact radiotracer. PET-CT studies in mouse-bearing prostate tumour xenografts indicated biodistribution similar to rats with radioactivity in the tumour increasing with time. [18F]PBR316 shows in vitro binding that is insensitive to human polymorphism and has specific and selective in vivo binding to the TSPO. [18F]PBR316 is suitable for further biological and clinical studies.
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Affiliation(s)
- Filomena Mattner
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Andrew Katsifis
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
- School of Pharmacy, University of Sydney Sydney NSW 2006 Australia
| | - Thomas Bourdier
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Christian Loc'h
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Paula Berghofer
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Christopher Fookes
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Tzong-Tyng Hung
- Biological Resources Imaging Laboratory, University of New South Wales Sydney NSW Australia
| | - Timothy Jackson
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - David Henderson
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Tien Pham
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Brendan J Lee
- Biological Resources Imaging Laboratory, University of New South Wales Sydney NSW Australia
| | - Rachael Shepherd
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Ivan Greguric
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Naomi Wyatt
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Thanh Le
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Jackson Poon
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Carl Power
- Biological Resources Imaging Laboratory, University of New South Wales Sydney NSW Australia
| | - Michael Fulham
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
- Faculty of Engineering and Information Technologies, University of Sydney Sydney NSW 2006 Australia
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Giordani A, Menziani MC, Moresco RM, Matarrese M, Paolino M, Saletti M, Giuliani G, Anzini M, Cappelli A. Exploring Translocator Protein (TSPO) Medicinal Chemistry: An Approach for Targeting Radionuclides and Boron Atoms to Mitochondria. J Med Chem 2021; 64:9649-9676. [PMID: 34254805 DOI: 10.1021/acs.jmedchem.1c00379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Translocator protein 18 kDa [TSPO or peripheral-type benzodiazepine receptor (PBR)] was identified in the search of binding sites for benzodiazepine anxiolytic drugs in peripheral regions. In these areas, binding sites for TSPO ligands were recognized in steroid-producing tissues. TSPO plays an important role in many cellular functions, and its coding sequence is highly conserved across species. TSPO is located predominantly on the membrane of mitochondria and is overexpressed in several solid cancers. TSPO basal expression in the CNS is low, but it becomes high in neurodegenerative conditions. Thus, TSPO constitutes not only as an outstanding drug target but also as a valuable marker for the diagnosis of a number of diseases. The aim of the present article is to show the lesson we have learned from our activity in TSPO medicinal chemistry and in approaching the targeted delivery to mitochondria by means of TSPO ligands.
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Affiliation(s)
- Antonio Giordani
- Rottapharm Biotech S.p.A., Via Valosa di Sopra 9, 20900 Monza, Italy
| | - Maria Cristina Menziani
- Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Via Campi 103, 41121 Modena, Italy
| | - Rosa Maria Moresco
- Department of Medicine and Surgery, University of Milan-Bicocca, Nuclear Medicine Department, San Raffaele Scientific Institute, IBFM-CNR, Via Olgettina 60, 20132 Milano, Italy
| | - Mario Matarrese
- Department of Medicine and Surgery, University of Milan-Bicocca, Nuclear Medicine Department, San Raffaele Scientific Institute, IBFM-CNR, Via Olgettina 60, 20132 Milano, Italy
| | - Marco Paolino
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022), Università di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Mario Saletti
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022), Università di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Germano Giuliani
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022), Università di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Maurizio Anzini
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022), Università di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Andrea Cappelli
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022), Università di Siena, Via A. Moro 2, 53100 Siena, Italy
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Cybulska KA, Bloemers V, Perk LR, Laverman P. Optimised GMP-compliant production of [ 18F]DPA-714 on the Trasis AllinOne module. EJNMMI Radiopharm Chem 2021; 6:20. [PMID: 34037896 PMCID: PMC8155128 DOI: 10.1186/s41181-021-00133-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 04/09/2021] [Indexed: 11/12/2022] Open
Abstract
Background The translocator protein 18 kDa is recognised as an important biomarker for neuroinflammation due to its soaring expression in microglia. This process is common for various neurological disorders. DPA-714 is a potent TSPO-specific ligand which found its use in Positron Emission Tomography following substitution of fluorine-19 with fluorine-18, a positron-emitting radionuclide. [18F]DPA-714 enables visualisation of inflammatory processes in vivo non-invasively. Radiolabelling of this tracer is well described in literature, including validation for clinical use. Here, we report significant enhancements to the process which resulted in the design of a fully GMP-compliant robust synthesis of [18F]DPA-714 on a popular cassette-based system, Trasis AllinOne, boosting reliability, throughput, and introducing a significant degree of simplicity. Results [18F]DPA-714 was synthesised using the classic nucleophilic aliphatic substitution on a good leaving group, tosylate, with [18F]fluoride using tetraethylammonium bicarbonate in acetonitrile at 100∘C. The process was fully automated on a Trasis AllinOne synthesiser using an in-house designed cassette and sequence. With a relatively small precursor load of 4 mg, [18F]DPA-714 was obtained with consistently high radiochemical yields of 55-71% (n=6) and molar activities of 117-350 GBq/µmol at end of synthesis. With a single production batch, starting with 31-42 GBq of [18F]fluoride, between 13-20 GBq of the tracer can be produced, enabling multi-centre studies. Conclusion To the best of our knowledge, the process presented herein is the most efficient [18F]DPA-714 synthesis, with advantageous GMP compliance. The use of a Trasis AllinOne synthesiser increases reliability and allows rapid training of production staff.
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Affiliation(s)
- Klaudia A Cybulska
- Radboud Translational Medicine B.V., Geert Grooteplein 21, Nijmegen, 6525 EZ, Netherlands. .,Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein 10, Nijmegen, 6525 GA, Netherlands.
| | - Vera Bloemers
- Radboud Translational Medicine B.V., Geert Grooteplein 21, Nijmegen, 6525 EZ, Netherlands
| | - Lars R Perk
- Radboud Translational Medicine B.V., Geert Grooteplein 21, Nijmegen, 6525 EZ, Netherlands
| | - Peter Laverman
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein 10, Nijmegen, 6525 GA, Netherlands
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Kim K, Kim H, Bae SH, Lee SY, Kim YH, Na J, Lee CH, Lee MS, Ko GB, Kim KY, Lee SH, Song IH, Cheon GJ, Kang KW, Kim SE, Chung JK, Kim EE, Paek SH, Lee JS, Lee BC, Youn H. [ 18F]CB251 PET/MR imaging probe targeting translocator protein (TSPO) independent of its Polymorphism in a Neuroinflammation Model. Am J Cancer Res 2020; 10:9315-9331. [PMID: 32802194 PMCID: PMC7415805 DOI: 10.7150/thno.46875] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 07/12/2020] [Indexed: 01/03/2023] Open
Abstract
The 18 kDa translocator protein (TSPO) has been proposed as a biomarker for the detection of neuroinflammation. Although various PET probes targeting TSPO have been developed, a highly selective probe for detecting TSPO is still needed because single nucleotide polymorphisms in the human TSPO gene greatly affect the binding affinity of TSPO ligands. Here, we describe the visualization of neuroinflammation with a multimodality imaging system using our recently developed TSPO-targeting radionuclide PET probe [18F]CB251, which is less affected by TSPO polymorphisms. Methods: To test the selectivity of [18F]CB251 for TSPO polymorphisms, 293FT cells expressing polymorphic TSPO were generated by introducing the coding sequences of wild-type (WT) and mutant (Alanine → Threonine at 147th Amino Acid; A147T) forms. Competitive inhibition assay was conducted with [3H]PK11195 and various TSPO ligands using membrane proteins isolated from 293FT cells expressing TSPO WT or mutant-A147T, representing high-affinity binder (HAB) or low-affinity binder (LAB), respectively. IC50 values of each ligand to [3H]PK11195 in HAB or LAB were measured and the ratio of IC50 values of each ligand to [3H]PK11195 in HAB to LAB was calculated, indicating the sensitivity of TSPO polymorphism. Cellular uptake of [18F]CB251 was measured with different TSPO polymorphisms, and phantom studies of [18F]CB251-PET using 293FT cells were performed. To test TSPO-specific cellular uptake of [18F]CB251, TSPO expression was regulated with pCMV-TSPO (or shTSPO)/eGFP vector. Intracranial lipopolysaccharide (LPS) treatment was used to induce regional inflammation in the mouse brain. Gadolinium (Gd)-DOTA MRI was used to monitor the disruption of the blood-brain barrier (BBB) and infiltration by immune cells. Infiltration of peripheral immune cells across the BBB, which exacerbates neuroinflammation to produce higher levels of neurotoxicity, was also monitored with bioluminescence imaging (BLI). Peripheral immune cells isolated from luciferase-expressing transgenic mice were transferred to syngeneic inflamed mice. Neuroinflammation was monitored with [18F]CB251-PET/MR and BLI. To evaluate the effects of anti-inflammatory agents on intracranial inflammation, an inflammatory cytokine inhibitor, 2-cyano-3, 12-dioxooleana-1, 9-dien-28-oic acid methyl ester (CDDO-Me) was administered in intracranial LPS challenged mice. Results: The ratio of IC50 values of [18F]CB251 in HAB to LAB indicated similar binding affinity to WT and mutant TSPO and was less affected by TSPO polymorphisms. [18F]CB251 was specific for TSPO, and its cellular uptake reflected the amount of TSPO. Higher [18F]CB251 uptake was also observed in activated immune cells. Simultaneous [18F]CB251-PET/MRI showed that [18F]CB251 radioactivity was co-registered with the MR signals in the same region of the brain of LPS-injected mice. Luciferase-expressing peripheral immune cells were located at the site of LPS-injected right striatum. Quantitative evaluation of the anti-inflammatory effect of CDDO-Me on neuroinflammation was successfully monitored with TSPO-targeting [18F]CB251-PET/MR and BLI. Conclusion: Our results indicate that [18F]CB251-PET has great potential for detecting neuroinflammation with higher TSPO selectivity regardless of polymorphisms. Our multimodal imaging system, [18F]CB251-PET/MRI, tested for evaluating the efficacy of anti-inflammatory agents in preclinical studies, might be an effective method to assess the severity and therapeutic response of neuroinflammation.
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Keller T, López-Picón FR, Krzyczmonik A, Forsback S, Takkinen JS, Rajander J, Teperi S, Dollé F, Rinne JO, Haaparanta-Solin M, Solin O. Comparison of high and low molar activity TSPO tracer [ 18F]F-DPA in a mouse model of Alzheimer's disease. J Cereb Blood Flow Metab 2020; 40:1012-1020. [PMID: 31142224 PMCID: PMC7181084 DOI: 10.1177/0271678x19853117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
[18F]F-DPA, a novel translocator protein 18 kDa (TSPO)-specific radioligand for imaging neuroinflammation, has to date been synthesized with low to moderate molar activities (Am's). In certain cases, low Am can skew the estimation of specific binding. The high proportion of the non-radioactive component can reduce the apparent-specific binding by competitively binding to receptors. We developed a nucleophilic synthesis of [18F]F-DPA resulting in high Am (990 ± 150 GBq/µmol) and performed in vivo comparison with low Am (9.0 ± 2.9 GBq/µmol) [18F]F-DPA in the same APP/PS1-21 and wild-type mice (injected masses: 0.34 ± 0.13 µg/kg and 38 ± 15 µg/kg, respectively). The high level of microgliosis in the APP/PS1-21 mouse model enables good differentiation between diseased and healthy animals and serves better to distinguish the effect of differing Am on specific binding. The differing injected masses affect the washout profile and shape of the time-activity curves. Ratios of standardized uptake values obtained with high and low Am [18F]F-DPA demonstrate that there is a 1.5-fold higher uptake of radioactivity in the brains of APP/PS1-21 animals when imaging is carried out with high Am [18F]F-DPA. The differences between APP/PS1-21 and wild-type animals showed higher significance when high Am was used.
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Affiliation(s)
- Thomas Keller
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku and Turku University Central Hospital, Turku, Finland.,Department of Chemistry, University of Turku, Turku, Finland
| | - Francisco R López-Picón
- MediCity Research Laboratory, University of Turku, Turku, Finland.,PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Anna Krzyczmonik
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku and Turku University Central Hospital, Turku, Finland.,Department of Chemistry, University of Turku, Turku, Finland
| | - Sarita Forsback
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku and Turku University Central Hospital, Turku, Finland.,Department of Chemistry, University of Turku, Turku, Finland
| | - Jatta S Takkinen
- MediCity Research Laboratory, University of Turku, Turku, Finland.,PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Johan Rajander
- Accelerator Laboratory, Turku PET Centre, Åbo Akademi University, Turku, Finland
| | - Simo Teperi
- Department of Biostatistics, University of Turku, Turku, Finland
| | - Frédéric Dollé
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France
| | - Juha O Rinne
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku and Turku University Central Hospital, Turku, Finland
| | - Merja Haaparanta-Solin
- MediCity Research Laboratory, University of Turku, Turku, Finland.,PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Olof Solin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku and Turku University Central Hospital, Turku, Finland.,Department of Chemistry, University of Turku, Turku, Finland.,Accelerator Laboratory, Turku PET Centre, Åbo Akademi University, Turku, Finland
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9
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Lacapere JJ, Duma L, Finet S, Kassiou M, Papadopoulos V. Insight into the Structural Features of TSPO: Implications for Drug Development. Trends Pharmacol Sci 2020; 41:110-122. [PMID: 31864680 PMCID: PMC7021566 DOI: 10.1016/j.tips.2019.11.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 11/13/2019] [Accepted: 11/18/2019] [Indexed: 01/01/2023]
Abstract
The translocator protein (TSPO), an 18-kDa transmembrane protein primarily found in the outer mitochondrial membrane, is evolutionarily conserved and widely distributed across species. In mammals, TSPO has been described as a key member of a multiprotein complex involved in many putative functions and, over the years, several classes of ligand have been developed to modulate these functions. In this review, we consider the currently available atomic structures of mouse and bacterial TSPO and propose a rationale for the development of new ligands for the protein. We provide a review of TSPO monomeric and oligomeric states and their conformational flexibility, together with ligand-binding site and interaction mechanisms. These data are expected to help considerably the development of high-affinity ligands for TSPO-based therapies or diagnostics.
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Affiliation(s)
- Jean-Jacques Lacapere
- Sorbonne Université, Ecole Normale Supérieure, PSL University, CNRS, Laboratoire des Biomolécules (LBM), 4 Place Jussieu, F-75005 Paris, France.
| | - Luminita Duma
- CNRS Enzyme and Cell Engineering Laboratory, Sorbonne Université, Université de Technologie de Compiègne, 60203 Compiègne Cedex, France
| | - Stephanie Finet
- IMPMC, UMR 7590 CNRS Sorbonne Université, 4 Place Jussieu, F-75005 Paris, France
| | - Michael Kassiou
- School of Chemistry, Faculty of Science, The University of Sydney, F11, Eastern Ave, Sydney, NSW 2006, Australia
| | - Vassilios Papadopoulos
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA
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10
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Murphy RB, Wyatt NA, Fraser BH, Yepuri NR, Holden PJ, Wotherspoon AT, Darwish TA. A rapid MS/MS method to assess the deuterium kinetic isotope effect and associated improvement in the metabolic stability of deuterated biological and pharmacological molecules as applied to an imaging agent. Anal Chim Acta 2019; 1064:65-70. [DOI: 10.1016/j.aca.2019.02.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 02/11/2019] [Accepted: 02/18/2019] [Indexed: 02/07/2023]
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11
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(R)-[ 18F]NEBIFQUINIDE: A promising new PET tracer for TSPO imaging. Eur J Med Chem 2019; 176:410-418. [PMID: 31125895 DOI: 10.1016/j.ejmech.2019.05.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 04/19/2019] [Accepted: 05/06/2019] [Indexed: 12/11/2022]
Abstract
Positron emission tomography (PET) imaging of the 18 kDa translocator protein (TSPO), has a high diagnostic potential in neurodegenerative disorders and cancer. However, TSPO is considered a challenge for molecular imaging due to the poor availability of suitable radiotracers with adequate pharmacokinetic properties. Here, we describe the development of a radiofluorinated pyridinyl isoquinoline analogue of the established TSPO PET tracer (R)-[11C]PK11195 with improved binding properties in all known human TSPO phenotypes. We conducted a complete preclinical evaluation using in vitro, in vivo and ex vivo methods to assess the performance of this novel radiotracer and observed high specific binding of the radiotracer to TSPO, as well as high metabolic stability. Therefore, we propose this radiolabeled compound for further evaluation in animal models as well as in clinical trials.
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12
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Stadulytė A, Alcaide-Corral CJ, Walton T, Lucatelli C, Tavares AAS. Analysis of PK11195 concentrations in rodent whole blood and tissue samples by rapid and reproducible chromatographic method to support target-occupancy PET studies. J Chromatogr B Analyt Technol Biomed Life Sci 2019; 1118-1119:33-39. [PMID: 31005772 PMCID: PMC6522057 DOI: 10.1016/j.jchromb.2019.04.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 04/05/2019] [Accepted: 04/11/2019] [Indexed: 12/24/2022]
Abstract
In Positron Emission Tomography (PET) research, it is important to assess not only pharmacokinetics of a radiotracer in vivo, but also of the drugs used in blocking/displacement PET studies. Typically, pharmacokinetic/pharmacodynamic (PK/PD) analyses of drugs used in rodent PET studies are based on population average pharmacokinetic profiles of the drugs due to limited blood volume withdrawal while simultaneously maintaining physiological homeostasis. This likely results in bias of PET data quantification, including unknown bias of target occupancy (TO) measurements. This study aimed to develop a High Performance Liquid Chromatography (HPLC) method for PK/PD quantification of drugs used in preclinical rodent PET research, specifically the translocator 18 kDa protein (TSPO) selective drug, PK11195, that used sub-millilitre blood volumes. The lowest detection limit for the proposed HPLC method ranged between 7.5 and 10 ng/mL depending on the method used to calculate the limit of detection, and the measured average relative standard deviation for intermediate precision was equal to 17.2%. Most importantly, we were able to demonstrate a significant difference between calculated PK11195 concentrations at 0.5, 1, 2, 3, 5, 15 and 30 min post-administration and individually measured whole blood levels (significance level range from p < 0.05 to p < 0.001; one-way ANOVA, Dunnet's post hoc test, p < 0.05). The HPLC method developed here uses sub-millilitre sample volumes to reproducibly assess PK/PD of PK11195 in rodent blood. This study highlights the importance of individually measured PK/PD drug concentrations when quantifying the TO from blocking/displacement rodent PET experiments.
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Affiliation(s)
- Agnė Stadulytė
- University/BHF Centre for Cardiovascular Science, University of Edinburgh, UK; Edinburgh Preclinical Imaging (EPI), University of Edinburgh, UK.
| | - Carlos José Alcaide-Corral
- University/BHF Centre for Cardiovascular Science, University of Edinburgh, UK; Edinburgh Preclinical Imaging (EPI), University of Edinburgh, UK
| | - Tashfeen Walton
- University/BHF Centre for Cardiovascular Science, University of Edinburgh, UK; Edinburgh Imaging, Queen's Medical Research Institute, University of Edinburgh, UK
| | - Christophe Lucatelli
- Edinburgh Imaging, Queen's Medical Research Institute, University of Edinburgh, UK
| | - Adriana Alexandre S Tavares
- University/BHF Centre for Cardiovascular Science, University of Edinburgh, UK; Edinburgh Preclinical Imaging (EPI), University of Edinburgh, UK
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13
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Synthesis and in vitro evaluation of new translocator protein ligands designed for positron emission tomography. Future Med Chem 2019; 11:539-550. [PMID: 30888874 DOI: 10.4155/fmc-2018-0444] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
AIM Dysregulated levels of the translocator protein TSPO 18 KDa have been reported in several disorders, particularly neurodegenerative diseases. This makes TSPO an interesting target for the development of diagnostic biomarkers. Even though several radioligands have already been developed for in vivo TSPO imaging, the ideal TSPO radiotracer has still not been found. RESULTS Here, we report the chemical synthesis of a set of new TSPO ligands designed for future application in positron emission tomography, together with the determination of their biological activity and applied 11C-labeling strategy. CONCLUSION The lead compound of our series, (R)-[11C]Me@NEBIQUINIDE, showed very promising results and is therefore proposed to be further evaluated under in vivo settings.
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14
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Mori W, Yamasaki T, Fujinaga M, Ogawa M, Zhang Y, Hatori A, Xie L, Kumata K, Wakizaka H, Kurihara Y, Ohkubo T, Nengaki N, Zhang MR. Development of 2-(2-(3-(4-([ 18F]Fluoromethoxy- d 2)phenyl)-7-methyl-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione for Positron-Emission-Tomography Imaging of Phosphodiesterase 10A in the Brain. J Med Chem 2018; 62:688-698. [PMID: 30516998 DOI: 10.1021/acs.jmedchem.8b01366] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Phosphodiesterase 10A (PDE10A) is a newly identified therapeutic target for central-nervous-system disorders. 2-(2-(3-(4-([18F]Fluoroethoxy)phenyl)-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione ([18F]MNI-659, [18F]5) is a useful positron-emission-tomography (PET) ligand for imaging of PDE10A in the human brain. However, the radiolabeled metabolite of [18F]5 can accumulate in the brain. In this study, using [18F]5 as a lead compound, we designed four new 18F-labeled ligands ([18F]6-9) to find one more suitable than [18F]5. Of these, 2-(2-(3-(4-([18F]fluoromethoxy- d2)phenyl)-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione ([18F]9) exhibited high in vitro binding affinity ( Ki = 2.9 nM) to PDE10A and suitable lipophilicity (log D = 2.2). In PET studies, the binding potential (BPND) of [18F]9 (5.8) to PDE10A in the striatum of rat brains was significantly higher than that of [18F]5 (4.6). Furthermore, metabolite analysis showed much lower levels of contamination with radiolabeled metabolites in the brains of rats given [18F]9 than in those given [18F]5. In conclusion, [18F]9 is a useful PET ligand for PDE10A imaging in brain.
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Affiliation(s)
| | | | | | - Masanao Ogawa
- SHI Accelerator Service, Ltd. , 1-17-6 Osaki , Shinagawa-ku, Tokyo 141-0032 , Japan
| | | | | | | | | | | | - Yusuke Kurihara
- SHI Accelerator Service, Ltd. , 1-17-6 Osaki , Shinagawa-ku, Tokyo 141-0032 , Japan
| | - Takayuki Ohkubo
- SHI Accelerator Service, Ltd. , 1-17-6 Osaki , Shinagawa-ku, Tokyo 141-0032 , Japan
| | - Nobuki Nengaki
- SHI Accelerator Service, Ltd. , 1-17-6 Osaki , Shinagawa-ku, Tokyo 141-0032 , Japan
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15
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Cumming P, Burgher B, Patkar O, Breakspear M, Vasdev N, Thomas P, Liu GJ, Banati R. Sifting through the surfeit of neuroinflammation tracers. J Cereb Blood Flow Metab 2018; 38:204-224. [PMID: 29256293 PMCID: PMC5951023 DOI: 10.1177/0271678x17748786] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 10/26/2017] [Accepted: 11/09/2017] [Indexed: 01/09/2023]
Abstract
The first phase of molecular brain imaging of microglial activation in neuroinflammatory conditions began some 20 years ago with the introduction of [11C]-( R)-PK11195, the prototype isoquinoline ligand for translocator protein (18 kDa) (TSPO). Investigations by positron emission tomography (PET) revealed microgliosis in numerous brain diseases, despite the rather low specific binding signal imparted by [11C]-( R)-PK11195. There has since been enormous expansion of the repertoire of TSPO tracers, many with higher specific binding, albeit complicated by allelic dependence of the affinity. However, the specificity of TSPO PET for revealing microglial activation not been fully established, and it has been difficult to judge the relative merits of the competing tracers and analysis methods with respect to their sensitivity for detecting microglial activation. We therefore present a systematic comparison of 13 TSPO PET and single photon computed tomography (SPECT) tracers belonging to five structural classes, each of which has been investigated by compartmental analysis in healthy human brain relative to a metabolite-corrected arterial input. We emphasize the need to establish the non-displaceable binding component for each ligand and conclude with five recommendations for a standard approach to define the cellular distribution of TSPO signals, and to characterize the properties of candidate TSPO tracers.
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Affiliation(s)
- Paul Cumming
- School of Psychology and Counselling and IHBI, Faculty of Health, Queensland University of Technology, Brisbane, Australia
- QIMR Berghofer Institute, Brisbane, Australia
| | - Bjorn Burgher
- QIMR Berghofer Institute, Brisbane, Australia
- Metro North Mental Health Service, Brisbane, Australia
| | - Omkar Patkar
- School of Psychology and Counselling and IHBI, Faculty of Health, Queensland University of Technology, Brisbane, Australia
- QIMR Berghofer Institute, Brisbane, Australia
| | - Michael Breakspear
- QIMR Berghofer Institute, Brisbane, Australia
- Metro North Mental Health Service, Brisbane, Australia
| | - Neil Vasdev
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, MA, USA
- Department of Radiology, Harvard Medical School, Boston, MA, USA
| | - Paul Thomas
- Herston Imaging Research Facility, Faculty of Medicine, University of Queensland Centre for Clinical Research, Herston, Australia
| | - Guo-Jun Liu
- Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia
- National Imaging Facility, Brain and Mind Centre and Faculty of Health Sciences, University of Sydney, Camperdown, Australia
| | - Richard Banati
- Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia
- National Imaging Facility, Brain and Mind Centre and Faculty of Health Sciences, University of Sydney, Camperdown, Australia
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Ottoy J, De Picker L, Verhaeghe J, Deleye S, Wyffels L, Kosten L, Sabbe B, Coppens V, Timmers M, van Nueten L, Ceyssens S, Stroobants S, Morrens M, Staelens S. 18F-PBR111 PET Imaging in Healthy Controls and Schizophrenia: Test-Retest Reproducibility and Quantification of Neuroinflammation. J Nucl Med 2018; 59:1267-1274. [PMID: 29326362 DOI: 10.2967/jnumed.117.203315] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 12/13/2017] [Indexed: 01/03/2023] Open
Abstract
Activated microglia express the translocator protein (TSPO) on the outer mitochondrial membrane. 18F-PBR111 is a second-generation PET ligand that specifically binds the TSPO, allowing in vivo visualization and quantification of neuroinflammation. The aim of this study was to evaluate whether the test-retest variability of 18F-PBR111 in healthy controls is acceptable to detect a psychosis-associated neuroinflammatory signal in schizophrenia. Methods: Dynamic 90-min 18F-PBR111 scans were obtained in 17 healthy male controls (HCs) and 11 male schizophrenia patients (SPs) during a psychotic episode. Prior genotyping for the rs6917 polymorphism distinguished high-affinity binders (HABs) and mixed-affinity binders (MABs). Total volume of distribution (VT) was determined from 2-tissue-compartment modeling with vascular trapping and a metabolite-corrected plasma input function. A subgroup of HCs (n = 12; 4 HABs and 8 MABs) was scanned twice to assess absolute test-retest variability and intraclass correlation coefficients of the regional VT values. Differences in TSPO binding between HC and SP were assessed using mixed model analysis adjusting for age, genotype, and age*cohort. The effect of using different scan durations (VT-60 min versus VT-90 min) was determined based on Pearson r. Data were mean ± SD. Results: Mean absolute variability in VT ranged from 16% ± 14% (19% ± 20% HAB; 15% ± 11% MAB) in the cortical gray matter to 22% ± 15% (23% ± 15% HAB; 22% ± 16% MAB) in the hippocampus. Intraclass correlation coefficients were consistently between 0.64 and 0.82 for all tested regions. TSPO binding in SP compared with HC depended on age (cohort*age: P < 0.05) and was increased by +14% ± 4% over the regions. There was a significant effect of genotype on TSPO binding, and VT of HABs was 31% ± 8% (HC: 17% ± 5%, SP: 61% ± 14%) higher than MABs. Across all clinical groups, VT-60 min and VT-90 min were strongly correlated (r > 0.7, P < 0.0001). Conclusion:18F-PBR111 can be used for monitoring of TSPO binding, as shown by medium test-retest variability and reliability of VT in HCs. Microglial activation is present in SPs depending on age and needs to be adjusted for genotype.
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Affiliation(s)
- Julie Ottoy
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Livia De Picker
- Collaborative Antwerp Psychiatric Research Institute, University of Antwerp, Antwerp, Belgium.,University Department of Psychiatry, Campus Duffel, Duffel, Belgium
| | - Jeroen Verhaeghe
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Steven Deleye
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Leonie Wyffels
- Department of Nuclear Medicine, Antwerp University Hospital, Edegem, Belgium
| | - Lauren Kosten
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Bernard Sabbe
- Collaborative Antwerp Psychiatric Research Institute, University of Antwerp, Antwerp, Belgium.,University Department of Psychiatry, Campus Duffel, Duffel, Belgium
| | - Violette Coppens
- Collaborative Antwerp Psychiatric Research Institute, University of Antwerp, Antwerp, Belgium.,University Department of Psychiatry, Campus Duffel, Duffel, Belgium
| | - Maarten Timmers
- Janssen Research and Development, Janssen Pharmaceutica N.V., Beerse, Belgium; and.,Reference Center for Biological Markers of Dementia (BIODEM), Institute Born-Bunge, University of Antwerp, Antwerp, Belgium
| | - Luc van Nueten
- Janssen Research and Development, Janssen Pharmaceutica N.V., Beerse, Belgium; and
| | - Sarah Ceyssens
- Department of Nuclear Medicine, Antwerp University Hospital, Edegem, Belgium
| | - Sigrid Stroobants
- Department of Nuclear Medicine, Antwerp University Hospital, Edegem, Belgium
| | - Manuel Morrens
- Collaborative Antwerp Psychiatric Research Institute, University of Antwerp, Antwerp, Belgium.,University Department of Psychiatry, Campus Duffel, Duffel, Belgium
| | - Steven Staelens
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
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Regulation of Mitochondrial, Cellular, and Organismal Functions by TSPO. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 82:103-136. [PMID: 29413517 DOI: 10.1016/bs.apha.2017.09.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In 1999, the enigma of the 18kDa mitochondrial translocator protein (TSPO), also known as the peripheral-type benzodiazepine receptor, was the seeming disparity of the many functions attributed to TSPO, ranging from the potential of TSPO acting as a housekeeping gene at molecular biological levels to adaptations to stress, and even involvement in higher emotional and cognitive functioning, such as anxiety and depression. In the years since then, knowledge regarding the many functions modulated by TSPO has expanded, and understanding has deepened. In addition, new functions could be firmly associated with TSPO, such as regulation of programmed cell death and modulation of gene expression. Interestingly, control by the mitochondrial TSPO over both of these life and death functions appears to include Ca++ homeostasis, generation of reactive oxygen species (ROS), and ATP production. Other mitochondrial functions under TSPO control are considered to be steroidogenesis and tetrapyrrole metabolism. As TSPO effects on gene expression and on programmed cell death can be related to the wide range of functions that can be associated with TSPO, several of these five elements of Ca++, ROS, ATP, steroids, and tetrapyrroles may indeed form the basis of TSPO's capability to operate as a multifunctional housekeeping gene to maintain homeostasis of the cell and of the whole multicellular organism.
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18
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Zanderigo F, Mann JJ, Ogden RT. A hybrid deconvolution approach for estimation of in vivo non-displaceable binding for brain PET targets without a reference region. PLoS One 2017; 12:e0176636. [PMID: 28459878 PMCID: PMC5411064 DOI: 10.1371/journal.pone.0176636] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 04/13/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND AND AIM Estimation of a PET tracer's non-displaceable distribution volume (VND) is required for quantification of specific binding to its target of interest. VND is generally assumed to be comparable brain-wide and is determined either from a reference region devoid of the target, often not available for many tracers and targets, or by imaging each subject before and after blocking the target with another molecule that has high affinity for the target, which is cumbersome and involves additional radiation exposure. Here we propose, and validate for the tracers [11C]DASB and [11C]CUMI-101, a new data-driven hybrid deconvolution approach (HYDECA) that determines VND at the individual level without requiring either a reference region or a blocking study. METHODS HYDECA requires the tracer metabolite-corrected concentration curve in blood plasma and uses a singular value decomposition to estimate the impulse response function across several brain regions from measured time activity curves. HYDECA decomposes each region's impulse response function into the sum of a parametric non-displaceable component, which is a function of VND, assumed common across regions, and a nonparametric specific component. These two components differentially contribute to each impulse response function. Different regions show different contributions of the two components, and HYDECA examines data across regions to find a suitable common VND. HYDECA implementation requires determination of two tuning parameters, and we propose two strategies for objectively selecting these parameters for a given tracer: using data from blocking studies, and realistic simulations of the tracer. Using available test-retest data, we compare HYDECA estimates of VND and binding potentials to those obtained based on VND estimated using a purported reference region. RESULTS For [11C]DASB and [11C]CUMI-101, we find that regardless of the strategy used to optimize the tuning parameters, HYDECA provides considerably less biased estimates of VND than those obtained, as is commonly done, using a non-ideal reference region. HYDECA test-retest reproducibility is comparable to that obtained using a VND determined from a non-ideal reference region, when considering the binding potentials BPP and BPND. CONCLUSIONS HYDECA can provide subject-specific estimates of VND without requiring a blocking study for tracers and targets for which a valid reference region does not exist.
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Affiliation(s)
- Francesca Zanderigo
- Molecular Imaging and Neuropathology Division, New York State Psychiatric Institute, New York, New York, United States of America
- Department of Psychiatry, Columbia University, New York, New York, United States of America
| | - J. John Mann
- Molecular Imaging and Neuropathology Division, New York State Psychiatric Institute, New York, New York, United States of America
- Department of Psychiatry, Columbia University, New York, New York, United States of America
- Department of Radiology, Columbia University, New York, New York, United States of America
| | - R. Todd Ogden
- Molecular Imaging and Neuropathology Division, New York State Psychiatric Institute, New York, New York, United States of America
- Department of Psychiatry, Columbia University, New York, New York, United States of America
- Department of Biostatistics, Columbia University, Mailman School of Public Health, New York, New York, United States of America
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