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Adhikari A, Zhang MR, Tiwari AK. Acetamidobenzoxazolone scaffold as a promising translocator protein (18 kDa, TSPO) marker for neuroinflammation imaging: Advancement in last decennial period. Drug Dev Res 2022; 83:1519-1533. [PMID: 36074736 DOI: 10.1002/ddr.21989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 07/10/2022] [Accepted: 07/14/2022] [Indexed: 11/09/2022]
Abstract
Inflammation has been linked to the onset and progression of a wide range of neuropathological disorders. The well-conserved outer mitochondrial membrane 18 kDa translocator protein (TSPO) is perceived as an in vivo neuroinflammation marker. A dearth of a reference region, genetic disparity influencing the ligand's affinity for TSPO, and a substantial signal in the endothelium of the brain veins contributes toward complications in quantifying TSPO positron emission tomography (PET) image. Up to the present time several radiotracers based on different pharmacophore such as (R)[11 C]PK11195, [18 F]DPA714, [11 C]PBR28, [11 C]ER176, and many more have been recognized for envisaging the prominent TSPO level observed in neurological conditions. Recently acetamidobenzoxazolone (ABO) scaffold, a bicyclic ring system composed of a phenyl ring fused to a carbamate and its substituted radiolabelled analogues especially at C-5 position has evidenced encouraging outcomes as next generation of TSPO PET ligands. Diverse ABO framework-based TSPO ligands have been designed embracing imperative aspects such as lipophilicity, metabolic profile, and capability to penetrate the blood-brain barrier apart from least effect of polymorphism (rs6971). Over the years numerous systematic literature reviews compiling different structural class of TSPO ligands characterized on the grounds of their binding affinity and metabolite profile have been reported but none is especially focused toward a fascinating benzoxazolone scaffold. This review exclusively bestows an overview of the recent advancements on ABO derivatives with neuroinflammation imaging potential and emphases on the structural features accountable for visualizing TSPO in-vivo with collation of published reports during last 10 years.
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Affiliation(s)
- Anupriya Adhikari
- Department of Chemistry, Babasaheb Bhimrao Ambedkar University (A Central University), Lucknow, Uttar Pradesh, India
| | - Ming-Rong Zhang
- Department of Advanced Nuclear Medicine Sciences, National Institutes for Quantum Science and Technology, Chiba, Japan
| | - Anjani Kumar Tiwari
- Department of Chemistry, Babasaheb Bhimrao Ambedkar University (A Central University), Lucknow, Uttar Pradesh, India
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Viviano M, Barresi E, Siméon FG, Costa B, Taliani S, Da Settimo F, Pike VW, Castellano S. Essential Principles and Recent Progress in the Development of TSPO PET Ligands for Neuroinflammation Imaging. Curr Med Chem 2022; 29:4862-4890. [PMID: 35352645 PMCID: PMC10080361 DOI: 10.2174/0929867329666220329204054] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 12/21/2021] [Accepted: 01/25/2022] [Indexed: 11/22/2022]
Abstract
The translocator protein 18kDa (TSPO) is expressed in the outer mitochondrial membrane and is implicated in several functions, including cholesterol transport and steroidogenesis. Under normal physiological conditions, TSPO is present in very low concentrations in the human brain but is markedly upregulated in response to brain injury and inflammation. This upregulation is strongly associated with activated microglia. Therefore, TSPO is particularly suited for assessing active gliosis associated with brain lesions following injury or disease. For over three decades, TSPO has been studied as a biomarker. Numerous radioligands for positron emission tomography (PET) that target TSPO have been developed for imaging inflammatory progression in the brain. Although [11C]PK11195, the prototypical first-generation PET radioligand, is still widely used for in vivo studies, mainly now as its single more potent R-enantiomer, it has severe limitations, including low sensitivity and poor amenability to quantification. Second-generation radioligands are characterized by higher TSPO specific signals but suffer from other drawbacks, such as sensitivity to the TSPO single nucleotide polymorphism (SNP) rs6971. Therefore, their applications in human studies have the burden of needing to genotype subjects. Consequently, recent efforts are focused on developing improved radioligands that combine the optimal features of the second generation with the ability to overcome the differences in binding affinities across the population. This review presents essential principles in the design and development of TSPO PET ligands and discusses prominent examples among the main chemotypes.
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Affiliation(s)
- Monica Viviano
- Department of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
| | | | - Fabrice G. Siméon
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Barbara Costa
- Department of Pharmacy, University of Pisa, 56126, Pisa, Italy
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, 56126, Pisa, Italy
| | | | - Victor W. Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sabrina Castellano
- Department of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
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van der Geest KSM, Sandovici M, Nienhuis PH, Slart RHJA, Heeringa P, Brouwer E, Jiemy WF. Novel PET Imaging of Inflammatory Targets and Cells for the Diagnosis and Monitoring of Giant Cell Arteritis and Polymyalgia Rheumatica. Front Med (Lausanne) 2022; 9:902155. [PMID: 35733858 PMCID: PMC9207253 DOI: 10.3389/fmed.2022.902155] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 05/13/2022] [Indexed: 12/26/2022] Open
Abstract
Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are two interrelated inflammatory diseases affecting patients above 50 years of age. Patients with GCA suffer from granulomatous inflammation of medium- to large-sized arteries. This inflammation can lead to severe ischemic complications (e.g., irreversible vision loss and stroke) and aneurysm-related complications (such as aortic dissection). On the other hand, patients suffering from PMR present with proximal stiffness and pain due to inflammation of the shoulder and pelvic girdles. PMR is observed in 40-60% of patients with GCA, while up to 21% of patients suffering from PMR are also affected by GCA. Due to the risk of ischemic complications, GCA has to be promptly treated upon clinical suspicion. The treatment of both GCA and PMR still heavily relies on glucocorticoids (GCs), although novel targeted therapies are emerging. Imaging has a central position in the diagnosis of GCA and PMR. While [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) has proven to be a valuable tool for diagnosis of GCA and PMR, it possesses major drawbacks such as unspecific uptake in cells with high glucose metabolism, high background activity in several non-target organs and a decrease of diagnostic accuracy already after a short course of GC treatment. In recent years, our understanding of the immunopathogenesis of GCA and, to some extent, PMR has advanced. In this review, we summarize the current knowledge on the cellular heterogeneity in the immunopathology of GCA/PMR and discuss how recent advances in specific tissue infiltrating leukocyte and stromal cell profiles may be exploited as a source of novel targets for imaging. Finally, we discuss prospective novel PET radiotracers that may be useful for the diagnosis and treatment monitoring in GCA and PMR.
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Affiliation(s)
- Kornelis S. M. van der Geest
- Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Maria Sandovici
- Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Pieter H. Nienhuis
- Department of Nuclear Medicine and Molecular Imaging, Medical Imaging Center, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Riemer H. J. A. Slart
- Department of Nuclear Medicine and Molecular Imaging, Medical Imaging Center, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
- Department of Biomedical Photonic Imaging Group, University of Twente, Enschede, Netherlands
| | - Peter Heeringa
- Department of Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Elisabeth Brouwer
- Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - William F. Jiemy
- Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
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Singh P, Adhikari A, Singh D, Gond C, Tiwari AK. The 18-kDa Translocator Protein PET Tracers as a Diagnostic Marker for Neuroinflammation: Development and Current Standing. ACS OMEGA 2022; 7:14412-14429. [PMID: 35557664 PMCID: PMC9089361 DOI: 10.1021/acsomega.2c00588] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 04/05/2022] [Indexed: 05/13/2023]
Abstract
Translocator protein (TSPO, 18 kDa) is an evolutionary, well-preserved, and tryptophan-rich 169-amino-acid protein which localizes on the contact sites between the outer and inner mitochondrial membranes of steroid-synthesizing cells. This mitochondrial protein is implicated in an extensive range of cellular activities, including steroid synthesis, cholesterol transport, apoptosis, mitochondrial respiration, and cell proliferation. The upregulation of TSPO is well documented in diverse disease conditions including neuroinflammation, cancer, brain injury, and inflammation in peripheral organs. On the basis of these outcomes, TSPO has been assumed to be a fascinating subcellular target for early stage imaging of the diseased state and for therapeutic purposes. The main outline of this Review is to give an update on dealing with the advances made in TSPO PET tracers for neuroinflammation, synchronously emphasizing the approaches applied for the design and advancement of new tracers with reference to their structure-activity relationship (SAR).
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Affiliation(s)
- Priya Singh
- Department
of Chemistry, Babasaheb Bhimrao Ambedkar
University (A Central University), Lucknow, 226025, Uttar Pradesh, India
| | - Anupriya Adhikari
- Department
of Chemistry, Babasaheb Bhimrao Ambedkar
University (A Central University), Lucknow, 226025, Uttar Pradesh, India
| | - Deepika Singh
- Department
of Chemistry, Babasaheb Bhimrao Ambedkar
University (A Central University), Lucknow, 226025, Uttar Pradesh, India
| | - Chandraprakash Gond
- Department
of Chemistry, Babasaheb Bhimrao Ambedkar
University (A Central University), Lucknow, 226025, Uttar Pradesh, India
| | - Anjani Kumar Tiwari
- Department
of Chemistry, Babasaheb Bhimrao Ambedkar
University (A Central University), Lucknow, 226025, Uttar Pradesh, India
- Address:
Department of Chemistry,
Babasaheb Bhimrao Ambedkar University, Lucknow, Uttar Pradesh. Tel.: +91-7503381343. Fax: +91-522-2440821. E-mail:
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Yamasaki T, Kumata K, Hiraishi A, Zhang Y, Wakizaka H, Kurihara Y, Nengaki N, Zhang MR. Synthesis of [ 11C]carbonyl-labeled cyclohexyl (5-(2-acetamidobenzo[d]thiazol-6-yl)-2-methylpyridin-3-yl)carbamate ([ 11C-carbonyl]PK68) as a potential PET tracer for receptor-interacting protein 1 kinase. EJNMMI Radiopharm Chem 2022; 7:4. [PMID: 35290562 PMCID: PMC8924334 DOI: 10.1186/s41181-022-00156-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 03/02/2022] [Indexed: 11/28/2022] Open
Abstract
Background Receptor-interacting protein 1 kinase (RIPK1) is a key enzyme in the regulation of cellular necroptosis. Recently, cyclohexyl (5-(2-acetamidobenzo[d]thiazol-6-yl)-2-methylpyridin-3-yl)carbamate (PK68, 5) has been developed as a potent inhibitor of RIPK1. Herein, we synthesized [11C]carbonyl-labeled PK68 ([11C-carbonyl]PK68, [11C]PK68) as a potential PET tracer for imaging RIPK1 and evaluated its brain uptake in vivo. Results We synthesized [11C]PK68 by reacting amine precursor 14 with [11C]acetyl chloride. At the end of synthesis, we obtained [11C]PK68 of 1200–1790 MBq with a radiochemical yield of 9.1 ± 5.9% (n = 10, decay-corrected to the end of irradiation) and radiochemical purity of > 99%, and a molar activity of 37–99 GBq/μmol starting from 18–33 GBq of [11C]CO2. The fully automated synthesis took 30 min from the end of irradiation. In a small-animal PET study, [11C]PK68 was rapidly distributed in the liver and kidneys of healthy mice after injection, and subsequently cleared from their bodies via hepatobiliary excretion and the intestinal reuptake pathway. Although there was no obvious specific binding of RIPK1 in the PET study, [11C]PK68 demonstrated relatively high stability in vivo and provided useful structural information further candidate development. Conclusions In the present study, we successfully radiosynthesized [11C]PK68 as a potential PET tracer and evaluated its brain uptake. We are planning to optimize the chemical structure of [11C]PK68 and conduct further PET studies on it using pathological models.
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Affiliation(s)
- Tomoteru Yamasaki
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Katsushi Kumata
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Atsuto Hiraishi
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Yiding Zhang
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Hidekatsu Wakizaka
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Yusuke Kurihara
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.,SHI Accelerator Service Co. Ltd., 1-17-6 Osaki, Shinagawa-ku, Tokyo, 141-0032, Japan
| | - Nobuki Nengaki
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.,SHI Accelerator Service Co. Ltd., 1-17-6 Osaki, Shinagawa-ku, Tokyo, 141-0032, Japan
| | - Ming-Rong Zhang
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
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Zhang L, Hu K, Shao T, Hou L, Zhang S, Ye W, Josephson L, Meyer JH, Zhang MR, Vasdev N, Wang J, Xu H, Wang L, Liang SH. Recent developments on PET radiotracers for TSPO and their applications in neuroimaging. Acta Pharm Sin B 2021; 11:373-393. [PMID: 33643818 PMCID: PMC7893127 DOI: 10.1016/j.apsb.2020.08.006] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 07/15/2020] [Accepted: 07/29/2020] [Indexed: 12/12/2022] Open
Abstract
The 18 kDa translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor, is predominately localized to the outer mitochondrial membrane in steroidogenic cells. Brain TSPO expression is relatively low under physiological conditions, but is upregulated in response to glial cell activation. As the primary index of neuroinflammation, TSPO is implicated in the pathogenesis and progression of numerous neuropsychiatric disorders and neurodegenerative diseases, including Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), multiple sclerosis (MS), major depressive disorder (MDD) and obsessive compulsive disorder (OCD). In this context, numerous TSPO-targeted positron emission tomography (PET) tracers have been developed. Among them, several radioligands have advanced to clinical research studies. In this review, we will overview the recent development of TSPO PET tracers, focusing on the radioligand design, radioisotope labeling, pharmacokinetics, and PET imaging evaluation. Additionally, we will consider current limitations, as well as translational potential for future application of TSPO radiopharmaceuticals. This review aims to not only present the challenges in current TSPO PET imaging, but to also provide a new perspective on TSPO targeted PET tracer discovery efforts. Addressing these challenges will facilitate the translation of TSPO in clinical studies of neuroinflammation associated with central nervous system diseases.
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Key Words
- AD, Alzheimer's disease
- ALS, amyotrophic lateral sclerosis
- AMPA, α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid
- ANT, adenine nucleotide transporter
- Am, molar activities
- BBB, blood‒brain barrier
- BMSC, bone marrow stromal cells
- BP, binding potential
- BPND, non-displaceable binding potential
- BcTSPO, Bacillus cereus TSPO
- CBD, corticobasal degeneration
- CNS disorders
- CNS, central nervous system
- CRAC, cholesterol recognition amino acid consensus sequence
- DLB, Lewy body dementias
- EP, epilepsy
- FTD, frontotemporal dementia
- HAB, high-affinity binding
- HD, Huntington's disease
- HSE, herpes simplex encephalitis
- IMM, inner mitochondrial membrane
- KA, kainic acid
- LAB, low-affinity binding
- LPS, lipopolysaccharide
- MAB, mixed-affinity binding
- MAO-B, monoamine oxidase B
- MCI, mild cognitive impairment
- MDD, major depressive disorder
- MMSE, mini-mental state examination
- MRI, magnetic resonance imaging
- MS, multiple sclerosis
- MSA, multiple system atrophy
- Microglial activation
- NAA/Cr, N-acetylaspartate/creatine
- Neuroinflammation
- OCD, obsessive compulsive disorder
- OMM, outer mitochondrial membrane
- P2X7R, purinergic receptor P2X7
- PAP7, RIa-associated protein
- PBR, peripheral benzodiazepine receptor
- PCA, posterior cortical atrophy
- PD, Parkinson's disease
- PDD, PD dementia
- PET, positron emission tomography
- PKA, protein kinase A
- PRAX-1, PBR-associated protein 1
- PSP, progressive supranuclear palsy
- Positron emission tomography (PET)
- PpIX, protoporphyrin IX
- QA, quinolinic acid
- RCYs, radiochemical yields
- ROS, reactive oxygen species
- RRMS, relapsing remitting multiple sclerosis
- SA, specific activity
- SAH, subarachnoid hemorrhage
- SAR, structure–activity relationship
- SCIDY, spirocyclic iodonium ylide
- SNL, selective neuronal loss
- SNR, signal to noise ratio
- SUV, standard uptake volume
- SUVR, standard uptake volume ratio
- TBAH, tetrabutyl ammonium hydroxide
- TBI, traumatic brain injury
- TLE, temporal lobe epilepsy
- TSPO
- TSPO, translocator protein
- VDAC, voltage-dependent anion channel
- VT, distribution volume
- d.c. RCYs, decay-corrected radiochemical yields
- dMCAO, distal middle cerebral artery occlusion
- fP, plasma free fraction
- n.d.c. RCYs, non-decay-corrected radiochemical yields
- p.i., post-injection
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Kwon YD, Kang S, Park H, Cheong IK, Chang KA, Lee SY, Jung JH, Lee BC, Lim ST, Kim HK. Novel potential pyrazolopyrimidine based translocator protein ligands for the evaluation of neuroinflammation with PET. Eur J Med Chem 2018; 159:292-306. [PMID: 30296688 DOI: 10.1016/j.ejmech.2018.09.069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 09/06/2018] [Accepted: 09/28/2018] [Indexed: 01/06/2023]
Abstract
Translocator protein (TSPO) is an interesting biological target because TSPO overexpression is associated with microglial activation caused by neuronal damage or neuroinflammation, and these activated microglia are involved in several central nervous system diseases. Herein, novel fluorinated ligands (14a-c and 16a-c) based on a 2-phenylpyrazolo[1,5-a]pyrimidin-3-yl acetamide scaffold were synthesized, and in vitro characterization of each of the novel ligands was performed to elucidate structure activity relationships. All of the newly synthesized ligands displayed nano-molar affinity for TSPO. Particularly, an in vitro affinity study suggests that 2-(5,7-diethyl-2-(4-(3-fluoro-2-methylpropoxy)phenyl)pyrazolo[1,5-a]pyrimidin-3-yl)-N,N-diethylacetamide (14a), which exhibited high nano-molar affinity for TSPO and proper lipophilicity, was suitable for in vivo brain studies. Thus, radiosynthesis from tosylate precursor 13a using fluorine-18 was performed, and [18F]14a was obtained in a 31% radiochemical yield (decay-corrected). Dynamic positron emission tomography (PET) imaging studies were performed in a lipopolysaccharide (LPS)-induced neuroinflammation rat model using [18F]14a to identify the location of inflammation in the brain with a high target-to-background signal ratio. In addition, we validated that the locations of inflammatory lesions found by PET imaging were consistent with the locations observed by histological examination of dissected brains using antibodies. These results suggest that [18F]14a is a novel promising PET imaging agent for diagnosing neuroinflammation, and it may also prove to be applicable for diagnosing other diseases, including cancers associated with altered TSPO expression, using PET techniques.
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Affiliation(s)
- Young-Do Kwon
- Department of Nuclear Medicine, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea; Department of Nuclear Medicine, Molecular Imaging & Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, 54907, Republic of Korea
| | - Shinwoo Kang
- Department of Pharmacology, College of Medicine, Gachon University, Incheon, 21936, Republic of Korea; Neuroscience Research Institute, Gachon University, Incheon, 21565, Republic of Korea
| | - Hyunjun Park
- Department of Pharmacology, College of Medicine, Gachon University, Incheon, 21936, Republic of Korea; Neuroscience Research Institute, Gachon University, Incheon, 21565, Republic of Korea; Gachon Advanced Institute for Health Science and Technology, Graduate School, Gachon University, Incheon, 21936, Republic of Korea
| | - Il-Koo Cheong
- Neuroscience Research Institute, Gachon University, Incheon, 21565, Republic of Korea; Gachon Advanced Institute for Health Science and Technology, Graduate School, Gachon University, Incheon, 21936, Republic of Korea
| | - Keun-A Chang
- Department of Pharmacology, College of Medicine, Gachon University, Incheon, 21936, Republic of Korea; Neuroscience Research Institute, Gachon University, Incheon, 21565, Republic of Korea; Gachon Advanced Institute for Health Science and Technology, Graduate School, Gachon University, Incheon, 21936, Republic of Korea.
| | - Sang-Yoon Lee
- Neuroscience Research Institute, Gachon University, Incheon, 21565, Republic of Korea; Gachon Advanced Institute for Health Science and Technology, Graduate School, Gachon University, Incheon, 21936, Republic of Korea; Department of Neuroscience, College of Medicine, Gachon University, Incheon, 21936, Republic of Korea
| | - Jae Ho Jung
- Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, 13620, Republic of Korea
| | - Byung Chul Lee
- Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, 13620, Republic of Korea; Center for Nanomolecular Imaging and Innovative Drug Development, Advanced Institutes of Convergence Technology, Suwon, 16229, Republic of Korea
| | - Seok Tae Lim
- Department of Nuclear Medicine, Molecular Imaging & Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, 54907, Republic of Korea; Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, 54907, Republic of Korea
| | - Hee-Kwon Kim
- Department of Nuclear Medicine, Molecular Imaging & Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, 54907, Republic of Korea; Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, 54907, Republic of Korea.
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In Vivo Monitoring for Regional Changes of Metabotropic Glutamate Receptor Subtype 1 (mGluR1) in Pilocarpine-Induced Epileptic Rat Brain by Small-Animal PET. Sci Rep 2017; 7:14945. [PMID: 29097780 PMCID: PMC5668420 DOI: 10.1038/s41598-017-15015-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 10/19/2017] [Indexed: 11/24/2022] Open
Abstract
Metabotropic glutamate receptor subtype 1 (mGluR1) is a crucial pharmacological target for several central nervous system disorders. In this study, we aimed to monitor in vivo regional changes of mGluR1 related to neuroinflammation in the brains of rats after pilocarpine-induced status epilepticus (PISE) using longitudinal positron emission tomography (PET). PISE was induced in rats by administering lithium chloride, followed by repeated pilocarpine hydrochloride treatments. PET assessments were conducted using N-[4-[6-(isopropylamino)-pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methyl-4-[11C]methylbenzamide ([11C]ITDM), a selective radioligand for mGluR1, and N-benzyl-N-[11C]methyl-2-(7-methyl-8-oxo-2-phenyl-7,8-dihydro-9H-purin-9-yl)acetamide ([11C]DAC), a selective translocator protein PET ligand for neuroinflammation monitoring. PET scans were conducted on PISE rats at 1 day (acute), 1 week (subacute) and 3 weeks (chronic) after repeated seizures. PET with [11C]ITDM showed significant decreases of mGluR1 availability (BPND) in the thalamus and hippocampus after PISE over the chronic period. Conversely, PET with [11C]DAC exhibited a significant increase of radioactive uptake in the forebrain after the acute period, especially in the thalamus. These conflicting changes in the thalamus indicated negative correlation. In conclusion, PET with [11C]ITDM could successfully visualize hippocampal and thalamic declines of mGluR1 related to neuroinflammation, which would help further understanding for mGluR1 functions in neuroexcitotoxicity.
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Bar-Klein G, Klee R, Brandt C, Bankstahl M, Bascuñana P, Töllner K, Dalipaj H, Bankstahl JP, Friedman A, Löscher W. Isoflurane prevents acquired epilepsy in rat models of temporal lobe epilepsy. Ann Neurol 2017; 80:896-908. [PMID: 27761920 DOI: 10.1002/ana.24804] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 09/16/2016] [Accepted: 10/10/2016] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Acquired epilepsy is a devastating long-term risk of various brain insults, including trauma, stroke, infections, and status epilepticus (SE). There is no preventive treatment for patients at risk. Attributable to the complex alterations involved in epileptogenesis, it is likely that multitargeted approaches are required for epilepsy prevention. We report novel preclinical findings with isoflurane, which exerts various nonanesthetic effects that may be relevant for antiepileptogenesis. METHODS The effects of isoflurane were investigated in two rat models of SE-induced epilepsy: intrahippocampal kainate and systemic administration of paraoxon. Isoflurane was either administered during (kainate) or after (paraoxon) induction of SE. Magnetic resonance imaging was used to assess blood-brain barrier (BBB) dysfunction. Positron emission tomography was used to visualize neuroinflammation. Long-term electrocorticographic recordings were used to monitor spontaneous recurrent seizures. Neuronal damage was assessed histologically. RESULTS In the absence of isoflurane, spontaneous recurrent seizures were common in the majority of rats in both models. When isoflurane was administered during kainate injection, duration and severity of SE were not affected, but only few rats developed spontaneous recurrent seizures. A similar antiepileptogenic effect was found when paraoxon-treated rats were exposed to isoflurane after SE. Moreover, in the latter model, isoflurane prevented BBB dysfunction and neurodegeneration, whereas isoflurane reduced neuroinflammation in the kainate model. INTERPRETATION Given that isoflurane is a widely used volatile anesthetic, and is used for inhalational long-term sedation in critically ill patients at risk to develop epilepsy, our findings hold a promising potential to be successfully translated into the clinic. Ann Neurol 2016;80:896-908.
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Affiliation(s)
- Guy Bar-Klein
- Departments of Physiology and Cell Biology, Cognitive and Brain Sciences, the Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Rebecca Klee
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.,Center for Systems Neuroscience, Hannover, Germany
| | - Claudia Brandt
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Marion Bankstahl
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.,Center for Systems Neuroscience, Hannover, Germany
| | - Pablo Bascuñana
- Department of Nuclear Medicine, Hannover Medical School, Germany
| | - Kathrin Töllner
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Hotjensa Dalipaj
- Department of Medical Neuroscience, Dalhousie University, Halifax, Canada
| | - Jens P Bankstahl
- Department of Nuclear Medicine, Hannover Medical School, Germany
| | - Alon Friedman
- Departments of Physiology and Cell Biology, Cognitive and Brain Sciences, the Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Department of Medical Neuroscience, Dalhousie University, Halifax, Canada
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.,Center for Systems Neuroscience, Hannover, Germany
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Alam MM, Lee J, Lee SY. Recent Progress in the Development of TSPO PET Ligands for Neuroinflammation Imaging in Neurological Diseases. Nucl Med Mol Imaging 2017; 51:283-296. [PMID: 29242722 DOI: 10.1007/s13139-017-0475-8] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 12/08/2016] [Accepted: 02/06/2017] [Indexed: 12/13/2022] Open
Abstract
Neuroinflammation is heavily associated with various neurological diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and stroke. It is strongly characterized by the activation of microglia which can be visualized using position emission tomography (PET). Traditionally, translocator protein 18 kDa (TSPO) has been the preferred target for imaging the inflammatory progression of the microglial component. TSPO is expressed in the outer mitochondrial membrane and present in very low concentrations in the healthy human brain, but is markedly upregulated in response to brain injury and inflammation. Due to its value as a marker of microglial activation and subsequent utility for evaluating neuroinflammation in CNS disorders, several classes of TSPO radioligands have been developed and evaluated. However, the application of these second-generation TSPO radiotracers has been subject to several limiting factors, including a polymorphism that affects TSPO binding. This review focuses on recent developments in TSPO imaging, as well as current limitations and suggestions for future directions from a medical imaging perspective.
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Affiliation(s)
- Md Maqusood Alam
- Neuroscience Research Institute, Gachon University, Incheon, 20565 South Korea
| | - Jihye Lee
- Neuroscience Research Institute, Gachon University, Incheon, 20565 South Korea
| | - Sang-Yoon Lee
- Neuroscience Research Institute, Gachon University, Incheon, 20565 South Korea.,Department of Neuroscience, College of Medicine, Gachon University, Incheon, 21936 South Korea
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11
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Lee J, Jung JH, Lee BC, Lee SY. Design and Synthesis of Phenoxypyridyl Acetamide or Aryl-oxodihydropurine Derivatives for the Development of Novel PET Ligands Targeting the Translocator Protein 18 kDa (TSPO). B KOREAN CHEM SOC 2016. [DOI: 10.1002/bkcs.10979] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Jihye Lee
- Neuroscience Research Institute; Gachon University; Incheon 21565 Korea
| | - Jae Ho Jung
- Department of Nuclear Medicine; Seoul National University College of Medicine, Seoul National University Bundang Hospital; Seongnam 13620 Korea
| | - Byung Chul Lee
- Department of Nuclear Medicine; Seoul National University College of Medicine, Seoul National University Bundang Hospital; Seongnam 13620 Korea
- Center for Nanomolecular Imaging and Innovative Drug Development; Advanced Institutes of Convergence Technology; Suwon 16229 Korea
| | - Sang-Yoon Lee
- Neuroscience Research Institute; Gachon University; Incheon 21565 Korea
- Department of Neuroscience, College of Medicine; Gachon University; Incheon 21936 Korea
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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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Kawamura K, Kumata K, Takei M, Furutsuka K, Hashimoto H, Ito T, Shiomi S, Fujishiro T, Watanabe R, Igarashi N, Muto M, Yamasaki T, Yui J, Xie L, Hatori A, Zhang Y, Nemoto K, Fujibayashi Y, Zhang MR. Efficient radiosynthesis and non-clinical safety tests of the TSPO radioprobe [(18)F]FEDAC: Prerequisites for clinical application. Nucl Med Biol 2016; 43:445-53. [PMID: 27183465 DOI: 10.1016/j.nucmedbio.2016.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 04/19/2016] [Accepted: 04/24/2016] [Indexed: 12/17/2022]
Abstract
INTRODUCTION [(18)F]FEDAC ([(18)F]1) has potent binding affinity and selectivity for translocator protein (18kDa, TSPO), and has been used to noninvasively visualize neuroinflammation, lung inflammation, acute liver damage, nonalcoholic fatty liver disease, and liver fibrosis. We had previously synthesized [(18)F]1 in two steps: (i) preparation of [(18)F]fluoroethyl bromide and (ii) coupling of [(18)F]fluoroethyl bromide with the appropriate precursor (2) for labeling. In this study, to clinically utilize [(18)F]1 as a PET radiopharmaceutical and to transfer the production technique of [(18)F]1 to other PET centers, we simplified its preparation by using a direct, one-step, tosyloxy-for-fluorine substitution. We also performed an acute toxicity study as a major non-clinical safety test, and determined radiometabolites using human liver microsomes. METHODS [(18)F]1 was prepared via direct (18)F-fluorination by heating the corresponding tosylated derivative (3) with [(18)F]fluoride as its Kryptofix 222 complex in dimethyl sulfoxide at 110°C for 15min, following by HPLC purification. Non-clinical safety tests were performed for the extended single-dose toxicity study in rats, and for the in vitro metabolite analysis with human liver microsomal incubation. RESULTS High quality batches of [(18)F]1, compatible with clinical applications, were obtained. At the end of irradiation, the decay-corrected radiochemical yield of [(18)F]1 using 1 and 5mg of precursor based on [(18)F]fluoride was 18.5±7.9% (n=10) and 52.0±5.8% (n=3), respectively. A single-dose of [(18)F]1 did not show toxicological effects for 14 days after the injection in male and female rats. In human liver microsomal incubations, [(18)F]1 was easily metabolized to [(18)F]desbenzyl-FEDAC ([(18)F]10) by CYPs (4.2% of parent compound left 60min after incubation). CONCLUSION We successfully synthesized clinical grade batches of [(18)F]1 and verified the absence of innocuity of this radiotracer. [(18)F]1 will be used to first-in-human studies in our facility.
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Affiliation(s)
- Kazunori Kawamura
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan.
| | - Katsushi Kumata
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Makoto Takei
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Kenji Furutsuka
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Hiroki Hashimoto
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Takehito Ito
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Satoshi Shiomi
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; Tokyo Nuclear Services, Tokyo 110-0016, Japan
| | - Tomoya Fujishiro
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; Tokyo Nuclear Services, Tokyo 110-0016, Japan
| | - Ryuji Watanabe
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; Tokyo Nuclear Services, Tokyo 110-0016, Japan
| | - Nobuyuki Igarashi
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; Tokyo Nuclear Services, Tokyo 110-0016, Japan
| | - Masatoshi Muto
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; Tokyo Nuclear Services, Tokyo 110-0016, Japan
| | - Tomoteru Yamasaki
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Joji Yui
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Lin Xie
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Akiko Hatori
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Yiding Zhang
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Kazuyoshi Nemoto
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Yasuhisa Fujibayashi
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Ming-Rong Zhang
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
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Tracking neuroinflammation in Alzheimer's disease: the role of positron emission tomography imaging. J Neuroinflammation 2014; 11:120. [PMID: 25005532 PMCID: PMC4099095 DOI: 10.1186/1742-2094-11-120] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 06/20/2014] [Indexed: 12/02/2022] Open
Abstract
Alzheimer’s disease (AD) has been reconceptualized as a dynamic pathophysiological process, where the accumulation of amyloid-beta (Aβ) is thought to trigger a cascade of neurodegenerative events resulting in cognitive impairment and, eventually, dementia. In addition to Aβ pathology, various lines of research have implicated neuroinflammation as an important participant in AD pathophysiology. Currently, neuroinflammation can be measured in vivo using positron emission tomography (PET) with ligands targeting diverse biological processes such as microglial activation, reactive astrocytes and phospholipase A2 activity. In terms of therapeutic strategies, despite a strong rationale and epidemiological studies suggesting that the use of non-steroidal anti-inflammatory drugs (NSAIDs) may reduce the prevalence of AD, clinical trials conducted to date have proven inconclusive. In this respect, it has been hypothesized that NSAIDs may only prove protective if administered early on in the disease course, prior to the accumulation of significant AD pathology. In order to test various hypotheses pertaining to the exact role of neuroinflammation in AD, studies in asymptomatic carriers of mutations deterministic for early-onset familial AD may prove of use. In this respect, PET ligands for neuroinflammation may act as surrogate markers of disease progression, allowing for the development of more integrative models of AD, as well as for the measuring of target engagement in the context of clinical trials using NSAIDs. In this review, we address the biological basis of neuroinflammatory changes in AD, underscore therapeutic strategies using anti-inflammatory compounds, and shed light on the possibility of tracking neuroinflammation in vivo using PET imaging ligands.
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Ng TS, Lin AP, Koerte IK, Pasternak O, Liao H, Merugumala S, Bouix S, Shenton ME. Neuroimaging in repetitive brain trauma. ALZHEIMERS RESEARCH & THERAPY 2014; 6:10. [PMID: 25031630 PMCID: PMC3978843 DOI: 10.1186/alzrt239] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Sports-related concussions are one of the major causes of mild traumatic brain injury. Although most patients recover completely within days to weeks, those who experience repetitive brain trauma (RBT) may be at risk for developing a condition known as chronic traumatic encephalopathy (CTE). While this condition is most commonly observed in athletes who experience repetitive concussive and/or subconcussive blows to the head, such as boxers, football players, or hockey players, CTE may also affect soldiers on active duty. Currently, the only means by which to diagnose CTE is by the presence of phosphorylated tau aggregations post-mortem. Non-invasive neuroimaging, however, may allow early diagnosis as well as improve our understanding of the underlying pathophysiology of RBT. The purpose of this article is to review advanced neuroimaging methods used to investigate RBT, including diffusion tensor imaging, magnetic resonance spectroscopy, functional magnetic resonance imaging, susceptibility weighted imaging, and positron emission tomography. While there is a considerable literature using these methods in brain injury in general, the focus of this review is on RBT and those subject populations currently known to be susceptible to RBT, namely athletes and soldiers. Further, while direct detection of CTE in vivo has not yet been achieved, all of the methods described in this review provide insight into RBT and will likely lead to a better characterization (diagnosis), in vivo, of CTE than measures of self-report.
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Affiliation(s)
- Thomas Sc Ng
- Center for Clinical Spectroscopy, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 4 Blackfan Circle, Boston, MA 02115, USA ; Keck School of Medicine of the University of Southern California, 1975 Zonal Ave, Los Angeles, CA 90033, USA
| | - Alexander P Lin
- Center for Clinical Spectroscopy, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 4 Blackfan Circle, Boston, MA 02115, USA ; Psychiatric Neuroimaging Laboratory, Departments of Psychiatry and Radiology, Brigham and Women's Hospital, Harvard Medical School, 1249 Boylston Street, Boston, MA 02215, USA
| | - Inga K Koerte
- Psychiatric Neuroimaging Laboratory, Departments of Psychiatry and Radiology, Brigham and Women's Hospital, Harvard Medical School, 1249 Boylston Street, Boston, MA 02215, USA ; Institute for Clinical Radiology, Ludwig-Maximilians-University, Marchioninistrasse 15, 81377 Munich, Germany
| | - Ofer Pasternak
- Psychiatric Neuroimaging Laboratory, Departments of Psychiatry and Radiology, Brigham and Women's Hospital, Harvard Medical School, 1249 Boylston Street, Boston, MA 02215, USA
| | - Huijun Liao
- Center for Clinical Spectroscopy, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 4 Blackfan Circle, Boston, MA 02115, USA
| | - Sai Merugumala
- Center for Clinical Spectroscopy, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 4 Blackfan Circle, Boston, MA 02115, USA
| | - Sylvain Bouix
- Psychiatric Neuroimaging Laboratory, Departments of Psychiatry and Radiology, Brigham and Women's Hospital, Harvard Medical School, 1249 Boylston Street, Boston, MA 02215, USA
| | - Martha E Shenton
- Psychiatric Neuroimaging Laboratory, Departments of Psychiatry and Radiology, Brigham and Women's Hospital, Harvard Medical School, 1249 Boylston Street, Boston, MA 02215, USA ; Research and Development, VA Boston Healthcare System, 850 Belmont Street, Brockton, MA 02130, USA
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Harhausen D, Sudmann V, Khojasteh U, Müller J, Zille M, Graham K, Thiele A, Dyrks T, Dirnagl U, Wunder A. Specific imaging of inflammation with the 18 kDa translocator protein ligand DPA-714 in animal models of epilepsy and stroke. PLoS One 2013; 8:e69529. [PMID: 23936336 PMCID: PMC3732268 DOI: 10.1371/journal.pone.0069529] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 06/10/2013] [Indexed: 11/19/2022] Open
Abstract
Inflammation is a pathophysiological hallmark of many diseases of the brain. Specific imaging of cells and molecules that contribute to cerebral inflammation is therefore highly desirable, both for research and in clinical application. The 18 kDa translocator protein (TSPO) has been established as a suitable target for the detection of activated microglia/macrophages. A number of novel TSPO ligands have been developed recently. Here, we evaluated the high affinity TSPO ligand DPA-714 as a marker of brain inflammation in two independent animal models. For the first time, the specificity of radiolabeled DPA-714 for activated microglia/macrophages was studied in a rat model of epilepsy (induced using Kainic acid) and in a mouse model of stroke (transient middle cerebral artery occlusion, tMCAO) using high-resolution autoradiography and immunohistochemistry. Additionally, cold-compound blocking experiments were performed and changes in blood-brain barrier (BBB) permeability were determined. Target-to-background ratios of 2 and 3 were achieved in lesioned vs. unaffected brain tissue in the epilepsy and tMCAO models, respectively. In both models, ligand uptake into the lesion corresponded well with the extent of Ox42- or Iba1-immunoreactive activated microglia/macrophages. In the epilepsy model, ligand uptake was almost completely blocked by pre-injection of DPA-714 and FEDAA1106, another high-affinity TSPO ligand. Ligand uptake was independent of the degree of BBB opening and lesion size in the stroke model. We provide further strong evidence that DPA-714 is a specific ligand to image activated microglia/macrophages in experimental models of brain inflammation.
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Affiliation(s)
- Denise Harhausen
- Department of Experimental Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
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Abstract
Diagnosis and treatment strategies for dementia are based on the sensitive and specific detection of the incipient neuropathological characteristics, combined with emerging treatments that counteract molecular processes in its pathogenesis. Positron emission tomography (PET) is used for diverse clinical and basic studies on dementia with a wide range of radiotracers. Approaches to visualize amyloid deposition in human brains non-invasively with PET depend on imaging agents reacting with amyloid fibrils. The most widely used tracer is [(11) C]-6-OH-BTA-1, also known as Pittsburgh Compound-B, which has a high affinity to amyloid β peptide (Aβ) aggregates. Some (18) F-labeled amyloid ligands with a longer radioactive half-life have also been developed for broader clinical applications. In addition, there have been demonstrated advantages of tracers with high specific radioactivity in the sensitive detection of amyloid, which have indicated the significance of Aβ-N3-pyroglutamate as a new diagnostic and therapeutic target. Furthermore, beneficial outcomes of Aβ and tau immunization in humans and mouse models have highlighted crucial roles of immunocompetent glia in the protection of neurons against amyloid toxicities. The utility of PET with a radioligand for translocator protein as a biomarker for tau-triggered toxicity, and as a complement to amyloid and tau imaging for diagnostic assessment of tauopathies with and without Aβ pathologies, has also been demonstrated. Meanwhile, brain cholinergic function can be estimated by measuring acetylcholinesterase activity in the brain with PET and radiolabeled acetylcholine analogues. It has been reported that patients with early Parkinson's disease exhibit a reduction in acetylcholinesterase activity in the cerebral cortex, and this decline is more profound in patients with Parkinson's disease with dementia and dementia with Lewy bodies than in patients with Parkinson's disease without dementia. The Alzheimer's Disease Neuroimaging Initiative was a multicentre research project conducted over 6 years that studied changes in cognition, brain structure, and biomarkers in healthy elderly controls and subjects with mild cognitive impairment and Alzheimer's disease. An international workgroup of the National Institute on Aging-Alzheimer's Association has suggested that Alzheimer's disease would be optimally treated before significant cognitive impairment, defined as a 'presymptomatic' or 'preclinical' stage. Therefore, PET will be of technical importance for both clinical and basic research aimed at prodromal pathologies of Alzheimer's disease.
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Affiliation(s)
- Takaaki Mori
- Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
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Virdee K, Cumming P, Caprioli D, Jupp B, Rominger A, Aigbirhio FI, Fryer TD, Riss PJ, Dalley JW. Applications of positron emission tomography in animal models of neurological and neuropsychiatric disorders. Neurosci Biobehav Rev 2012; 36:1188-216. [PMID: 22342372 DOI: 10.1016/j.neubiorev.2012.01.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 01/26/2012] [Accepted: 01/31/2012] [Indexed: 01/08/2023]
Abstract
Positron emission tomography (PET) provides dynamic images of the biodistribution of radioactive tracers in the brain. Through application of the principles of compartmental analysis, tracer uptake can be quantified in terms of specific physiological processes such as cerebral blood flow, cerebral metabolic rate, and the availability of receptors in brain. Whereas early PET studies in animal models of brain diseases were hampered by the limited spatial resolution of PET instruments, dedicated small-animal instruments now provide molecular images of rodent brain with resolution approaching 1mm, the theoretic limit of the method. Major applications of PET for brain research have consisted of studies of animal models of neurological disorders, notably Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD), stroke, epilepsy and traumatic brain injury; these studies have particularly benefited from selective neurochemical lesion models (PD), and also transgenic rodent models (AD, HD). Due to their complex and uncertain pathophysiologies, corresponding models of neuropsychiatric disorders have proven more difficult to establish. Historically, there has been an emphasis on PET studies of dopamine transmission, as assessed with a range of tracers targeting dopamine synthesis, plasma membrane transporters, and receptor binding sites. However, notable recent breakthroughs in molecular imaging include the development of greatly improved tracers for subtypes of serotonin, cannabinoid, and metabotropic glutamate receptors, as well as noradrenaline transporters, amyloid-β and neuroinflammatory changes. This article reviews the considerable recent progress in preclinical PET and discusses applications relevant to a number of neurological and neuropsychiatric disorders in humans.
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Affiliation(s)
- Kanwar Virdee
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, CB2 3EB, UK
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Wu C, Li R, Dearborn D, Wang Y. Reductive Amination with [<sup>11</sup>C]Formaldehyde: A Versatile Approach to Radiomethylation of Amines. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/ijoc.2012.23030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Xie L, Yamasaki T, Ichimaru N, Yui J, Kawamura K, Kumata K, Hatori A, Nonomura N, Zhang MR, Li XK, Takahara S. [11C]DAC-PET for Noninvasively Monitoring Neuroinflammation and Immunosuppressive Therapy Efficacy in Rat Experimental Autoimmune Encephalomyelitis Model. J Neuroimmune Pharmacol 2011; 7:231-42. [DOI: 10.1007/s11481-011-9322-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2011] [Accepted: 10/17/2011] [Indexed: 11/30/2022]
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Kumata K, Yui J, Hatori A, Fujinaga M, Yanamoto K, Yamasaki T, Kawamura K, Wakizaka H, Nengaki N, Yoshida Y, Ogawa M, Fukumura T, Zhang MR. Synthesis and Evaluation of Novel Carbon-11 Labeled Oxopurine Analogues for Positron Emission Tomography Imaging of Translocator Protein (18 kDa) in Peripheral Organs. J Med Chem 2011; 54:6040-9. [DOI: 10.1021/jm200516a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Katsushi Kumata
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Joji Yui
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Akiko Hatori
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Masayuki Fujinaga
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Kazuhiko Yanamoto
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Tomoteru Yamasaki
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Kazunori Kawamura
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Hidekatsu Wakizaka
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Nobuki Nengaki
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
- SHI Accelerator Service Co. Ltd., 5-9-11 Kitashinagawa, Shinagawa-ku, Tokyo 141-8686, Japan
| | - Yuichiro Yoshida
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
- SHI Accelerator Service Co. Ltd., 5-9-11 Kitashinagawa, Shinagawa-ku, Tokyo 141-8686, Japan
| | - Masanao Ogawa
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
- SHI Accelerator Service Co. Ltd., 5-9-11 Kitashinagawa, Shinagawa-ku, Tokyo 141-8686, Japan
| | - Toshimitsu Fukumura
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Ming-Rong Zhang
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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In vivo positron emission tomographic imaging of glial responses to amyloid-beta and tau pathologies in mouse models of Alzheimer's disease and related disorders. J Neurosci 2011; 31:4720-30. [PMID: 21430171 DOI: 10.1523/jneurosci.3076-10.2011] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Core pathologies of Alzheimer's disease (AD) are aggregated amyloid-β peptides (Aβ) and tau, and the latter is also characteristic of diverse neurodegenerative tauopathies. These amyloid lesions provoke microglial activation, and recent neuroimaging technologies have enabled visualization of this response in living brains using radioligands for the peripheral benzodiazepine receptor also known as the 18 kDa translocator protein (TSPO). Here, we elucidated contributions of Aβ and tau deposits to in vivo TSPO signals in pursuit of mechanistic and diagnostic significance of TSPO imaging in AD and other tauopathies. A new antibody to human TSPO revealed induction of TSPO-positive microgliosis by tau fibrils in tauopathy brains. Emergence of TSPO signals before occurrence of brain atrophy and thioflavin-S-positive tau amyloidosis was also demonstrated in living mice transgenic for mutant tau by positron emission tomography (PET) with two classes of TSPO radioligands, [(11)C]AC-5216 and [(18)F]fluoroethoxy-DAA1106. Meanwhile, only modest TSPO elevation was observed in aged mice modeling Aβ plaque deposition, despite the notably enhanced in vivo binding of amyloid radiotracer, [(11)C]Pittsburgh Compound-B, to plaques. In these animals, [(11)C]AC-5216 yielded better TSPO contrasts than [(18)F]fluoroethoxy-DAA1106, supporting the possibility of capturing early neurotoxicity with high-performance TSPO probes. Furthermore, an additional line of mice modeling intraneuronal Aβ accumulation displayed elevated TSPO signals following noticeable neuronal loss, unlike TSPO upregulation heralding massive neuronal death in tauopathy model mice. Our data corroborate the utility of TSPO-PET imaging as a biomarker for tau-triggered toxicity, and as a complement to amyloid scans for diagnostic assessment of tauopathies with and without Aβ pathologies.
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Thominiaux C, Damont A, Kuhnast B, Demphel S, Le Helleix S, Boisnard S, Rivron L, Chauveau F, Boutin H, Van Camp N, Boisgard R, Roy S, Allen J, Rooney T, Benavides J, Hantraye P, Tavitian B, Dollé F. Radiosynthesis of 7-chloro-N,N-dimethyl-5-[11C]methyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide, [11C]SSR180575, a novel radioligand for imaging the TSPO (peripheral benzodiazepine receptor) with PET. J Labelled Comp Radiopharm 2010. [DOI: 10.1002/jlcr.1794] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Yui J, Hatori A, Kawamura K, Yanamoto K, Yamasaki T, Ogawa M, Yoshida Y, Kumata K, Fujinaga M, Nengaki N, Fukumura T, Suzuki K, Zhang MR. Visualization of early infarction in rat brain after ischemia using a translocator protein (18 kDa) PET ligand [11C]DAC with ultra-high specific activity. Neuroimage 2010; 54:123-30. [PMID: 20705143 DOI: 10.1016/j.neuroimage.2010.08.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 07/23/2010] [Accepted: 08/04/2010] [Indexed: 10/19/2022] Open
Abstract
The aim of this study was to visualize early infarction in the rat brain after ischemia using a translocator protein (TSPO) (18 kDa) PET ligand [(11)C]DAC with ultra-high specific activity (SA) of 3670-4450 GBq/μmol. An infarction model of rat brain was prepared by ischemic surgery and evaluated 2 days after ischemia using small-animal PET and in vitro autoradiography. Early infarction with a small increase of TSPO expression in the brain was visualized using PET with high SA [(11)C]DAC (average 4060 GBq/μmol), but was not distinguished clearly with usually reported SA [(11)C]DAC (37 GBq/μmol). Infarction in the rat brain 4 days after ischemia was visualized using high and usually reported SAs [(11)C]DAC. Displacement experiments with unlabeled TSPO-selective AC-5216 or PK11195 diminished the difference in radioactivity between ipsilateral and contralateral sides, confirming that the increased uptake on the infracted brain was specific to TSPO. In vitro autoradiography with high SA [(11)C]DAC showed that the TSPO expression increased on early infarction in the rat brain. High SA [(11)C]DAC is a useful and sensitive biomarker for the visualization of early infarction and the characterization of TSPO expression which was slightly elevated in the infarcted brain using PET.
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Affiliation(s)
- Joji Yui
- Molecular Imaging Center, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan
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Yui J, Hatori A, Yanamoto K, Takei M, Nengaki N, Kumata K, Kawamura K, Yamasaki T, Suzuki K, Zhang MR. Imaging of the translocator protein (18kDa) in rat brain after ischemia using [11C]DAC with ultra-high specific activity. Synapse 2010; 64:488-93. [DOI: 10.1002/syn.20761] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Stevenson L, Tavares AAS, Brunet A, McGonagle FI, Dewar D, Pimlott SL, Sutherland A. New iodinated quinoline-2-carboxamides for SPECT imaging of the translocator protein. Bioorg Med Chem Lett 2009; 20:954-7. [PMID: 20045646 DOI: 10.1016/j.bmcl.2009.12.061] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 12/14/2009] [Accepted: 12/14/2009] [Indexed: 11/17/2022]
Abstract
With the aim of developing new SPECT imaging agents for the translocator protein (TSPO), a small library of iodinated quinoline-2-carboxamides have been prepared and tested for binding affinity with TSPO. N,N-Diethyl-3-iodomethyl-4-phenylquinoline-2-carboxamide was found to have excellent affinity (K(i) 12.0 nM), comparable to that of the widely used TSPO imaging agent PK11195.
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Affiliation(s)
- Louise Stevenson
- WestCHEM, Department of Chemistry, The Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK
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