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Boyko AN, Dolgushin MB, Karalkina MA. [New neuroimaging methods in assessing the activity of neuroinflammation in multiple sclerosis]. Zh Nevrol Psikhiatr Im S S Korsakova 2023; 123:8-14. [PMID: 37560828 DOI: 10.17116/jnevro20231230728] [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] [Indexed: 08/11/2023]
Abstract
The review presents current data on the use of positron emission tomography and single-photon emission computed tomography in multiple sclerosis (MS) to assess the activity of the pathological process, including neuroinflammation, demyelination, activation of microglia, neurodegeneration and local blood flow disorders. These methodologies are a new approach for studying the mechanisms of action and evaluating the clinical effect of disease modifying therapy of MS, especially those capable of penetrating into brain tissue. Among them, the most attention is attracted by cladribine tablets acting on the mechanism of immune reconstitution therapy, most likely with the modulation of immune reactions directly in the brain tissue.
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Affiliation(s)
- A N Boyko
- Federal Center of Brain and Neurotechnologies of the Federal Medical Biological Agency, Moscow, Russia
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - M B Dolgushin
- Federal Center of Brain and Neurotechnologies of the Federal Medical Biological Agency, Moscow, Russia
| | - M A Karalkina
- Federal Center of Brain and Neurotechnologies of the Federal Medical Biological Agency, Moscow, Russia
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2
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Pitombeira MS, Koole M, Campanholo KR, Souza AM, Duran FLS, Solla DJF, Mendes MF, Pereira SLA, Rimkus CM, Busatto GF, Callegaro D, Buchpiguel CA, de Paula Faria D. Innate immune cells and myelin profile in multiple sclerosis: a multi-tracer PET/MR study. Eur J Nucl Med Mol Imaging 2022; 49:4551-4566. [PMID: 35838758 DOI: 10.1007/s00259-022-05899-2] [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: 12/02/2021] [Accepted: 06/30/2022] [Indexed: 11/04/2022]
Abstract
PURPOSE Neuropathological studies have demonstrated distinct profiles of microglia activation and myelin injury among different multiple sclerosis (MS) phenotypes and disability stages. PET imaging using specific tracers may uncover the in vivo molecular pathology and broaden the understanding of the disease heterogeneity. METHODS We used the 18-kDa translocator protein (TSPO) tracer (R)-[11C]PK11195 and [11C]PIB PET images acquired in a hybrid PET/MR 3 T system to characterize, respectively, the profile of innate immune cells and myelin content in 47 patients with MS compared to 18 healthy controls (HC). For the volume of interest (VOI)-based analysis of the dynamic data, (R)-[11C]PK11195 distribution volume (VT) was determined for each subject using a metabolite-corrected arterial plasma input function while [11C]PIB distribution volume ratio (DVR) was estimated using a reference region extracted by a supervised clustering algorithm. A voxel-based analysis was also performed using Statistical Parametric Mapping. Functional disability was evaluated by the Expanded Disability Status Scale (EDSS), Multiple Sclerosis Functional Composite (MSFC), and Symbol Digit Modality Test (SDMT). RESULTS In the VOI-based analysis, [11C]PIB DVR differed between patients and HC in the corpus callosum (P = 0.019) while no differences in (R)-[11C]PK11195 VT were observed in patients relative to HC. Furthermore, no correlations or associations were observed between both tracers within the VOI analyzed. In the voxel-based analysis, high (R)-[11C]PK11195 uptake was observed diffusively in the white matter (WM) when comparing the progressive phenotype and HC, and lower [11C]PIB uptake was observed in certain WM regions when comparing the relapsing-remitting phenotype and HC. None of the tracers were able to differentiate phenotypes at voxel or VOI level in our cohort. Linear regression models adjusted for age, sex, and phenotype demonstrated that higher EDSS was associated with an increased (R)-[11C]PK11195 VT and lower [11C]PIB DVR in corpus callosum (P = 0.001; P = 0.023), caudate (P = 0.015; P = 0.008), and total T2 lesion (P = 0.007; P = 0.012), while better cognitive scores in SDMT were associated with higher [11C]PIB DVR in the corpus callosum (P = 0.001), and lower (R)-[11C]PK11195 VT (P = 0.013). CONCLUSIONS Widespread innate immune cells profile and marked loss of myelin in T2 lesions and regions close to the ventricles may occur independently and are associated with disability, in both WM and GM structures.
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Affiliation(s)
- Milena Sales Pitombeira
- Department of Neurology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil.,Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Michel Koole
- Department of Imaging and Pathology, Nuclear Medicine and Molecular Imaging, KU Leuven, Flanders, Belgium
| | - Kenia R Campanholo
- Department of Neurology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil.,Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Aline M Souza
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Fábio L S Duran
- Laboratory of Psychiatric Neuroimaging (LIM21), Department of Psychiatry, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Davi J Fontoura Solla
- Department of Neurology, Division of Neurosurgery, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Maria F Mendes
- Department of Neurology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | | | - Carolina M Rimkus
- Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Geraldo Filho Busatto
- Laboratory of Psychiatric Neuroimaging (LIM21), Department of Psychiatry, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Dagoberto Callegaro
- Department of Neurology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Carlos A Buchpiguel
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Daniele de Paula Faria
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, Brazil.
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de Souza AM, Pitombeira MS, de Souza LE, Marques FLN, Buchpiguel CA, Real CC, de Paula Faria D. 11C-PK11195 plasma metabolization has the same rate in multiple sclerosis patients and healthy controls: a cross-sectional study. Neural Regen Res 2021; 16:2494-2498. [PMID: 33907039 PMCID: PMC8374550 DOI: 10.4103/1673-5374.313062] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
11C-PK11195 is a positron emitter tracer used for Positron Emission Tomography (PET) imaging of innate immune cell activation in studies of neuroinflammatory diseases. For the image quantitative analysis, it is necessary to quantify the intact fraction of this tracer in the arterial plasma during imaging acquisition (plasma intact fraction). Due to the complexity and costs involved in this analysis it is important to evaluate the real necessity of individual analysis in each 11C-PK11195 PET imaging acquisition. The purpose of this study is to compare 11C-PK11195 plasma metabolization rate between healthy controls and multiple sclerosis (MS) patients and evaluate the interference of sex, age, treatment, and disease phenotype in the tracer intact fraction measured in arterial plasma samples. 11C-PK11195 metabolization rate in arterial plasma was quantified by high performance liquid chromatography in samples from MS patients (n = 50) and healthy controls (n = 23) at 20, 45, and 60 minutes after 11C-PK11195 injection. Analyses were also stratified by sex, age, treatment type, and MS phenotype. The results showed no significant differences in the metabolization rate of healthy controls and MS patients, or in the stratified samples. In conclusion, 11C-PK11195 metabolization has the same rate in patients with MS and healthy controls, which is not affected by sex, age, treatment, and disease phenotype. Thus, these findings could contribute to exempting the necessity for tracer metabolization determination in all 11C-PK11195 PET imaging acquisition, by using a population metabolization rate average. The study procedures were approved by the Ethics Committee for Research Projects Analysis of the Hospital das Clinicas of the University of Sao Paulo Medical School (approval No. 624.065) on April 23, 2014.
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Affiliation(s)
- Aline Morais de Souza
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Milena Sales Pitombeira
- Department of Neurology, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Larissa Estessi de Souza
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Fabio Luiz Navarro Marques
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Carlos Alberto Buchpiguel
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Caroline Cristiano Real
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Daniele de Paula Faria
- Laboratory of Nuclear Medicine (LIM43), Department of Radiology and Oncology; Department of Neurology, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
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Parente A, Maciel ES, J O Dierckx RA, Langendijk JA, de Vries EFJ, Doorduin J. Delayed effects of a single-dose whole-brain radiation therapy on glucose metabolism and myelin density: a longitudinal PET study. Int J Radiat Biol 2020; 96:1135-1143. [PMID: 32602390 DOI: 10.1080/09553002.2020.1787542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE Radiotherapy is an important treatment option for brain tumors, but the unavoidable irradiation of normal brain tissue can lead to delayed cognitive impairment. The mechanisms involved are still not well explained and, therefore, new tools to investigate the processes leading to the delayed symptoms of brain irradiation are warranted. In this study, positron emission tomography (PET) is used to explore delayed functional changes induced by brain irradiation. MATERIALS AND METHODS Male Wistar rats were subjected to a single 25-Gy dose of whole brain X-ray irradiation, or sham-irradiation. To investigate delayed effects of radiation on cerebral glucose metabolism and myelin density, 18F-fluorodeoxyglucose (18F-FDG) PET scans were performed at baseline and on day 64 and 94, whereas N-11C-methyl-4,4'-diaminostilbene (11C-MeDAS) PET scans were performed at baseline and on day 60 and 90 post-irradiation. In addition, the open field test (OFT) and novel spatial recognition (NSR) test were performed at baseline and on days 59 and 89 to investigate whether whole brain irradiation induces behavioral changes. RESULTS Whole-brain irradiation caused loss of bodyweight and delayed cerebral hypometabolism, with 18F-FDG uptake in all brain regions being significantly decreased in irradiated rat on day 64 while it remained unchanged in control animals. Only amygdala and cortical brain regions of irradiated rats still showed reduced 18F-FDG uptake on day 94. 11C-MeDAS uptake in control animals was significantly lower on days 60 and 90 than at the baseline, suggesting a reduction in myelin density in young adults. In irradiated animals, 11C-MeDAS uptake was similarly reduced on day 60, but on day 90 tracer uptake was somewhat increased and not significantly different from baseline anymore. Behavioral tests showed a similar pattern in control and irradiated animals. In both groups, the OFT showed significantly reduced mobility on days 59 and 89, whereas the NSR did not reveal any significant changes in spatial memory over time. Interestingly, a positive correlation between the NSR and 11C-MeDAS uptake was observed in irradiated rats. CONCLUSIONS Whole-brain irradiation causes delayed brain hypometabolism, which is not accompanied by white matter loss. Irradiated animals showed similar behavioral changes over time as control animals and, therefore, cerebral hypometabolism could not be linked to behavioral abnormalities. However, spatial memory seems to be associated with myelin density in irradiated rats.
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Affiliation(s)
- Andrea Parente
- Department of Nuclear Medicine and Molecular Imaging, Medical Imaging Center, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Elisa Scandiuzzi Maciel
- Department of Nuclear Medicine and Molecular Imaging, Medical Imaging Center, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Rudi A J O Dierckx
- Department of Nuclear Medicine and Molecular Imaging, Medical Imaging Center, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Johannes A Langendijk
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Erik F J de Vries
- Department of Nuclear Medicine and Molecular Imaging, Medical Imaging Center, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Janine Doorduin
- Department of Nuclear Medicine and Molecular Imaging, Medical Imaging Center, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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Coda AR, Anzilotti S, Boscia F, Greco A, Panico M, Gargiulo S, Gramanzini M, Zannetti A, Albanese S, Pignataro G, Annunziato L, Salvatore M, Brunetti A, De Berardinis P, Quarantelli M, Palma G, Pappatà S. In vivo imaging of CNS microglial activation/macrophage infiltration with combined [ 18F]DPA-714-PET and SPIO-MRI in a mouse model of relapsing remitting experimental autoimmune encephalomyelitis. Eur J Nucl Med Mol Imaging 2020; 48:40-52. [PMID: 32378022 PMCID: PMC7835304 DOI: 10.1007/s00259-020-04842-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 04/27/2020] [Indexed: 12/26/2022]
Abstract
Purpose To evaluate the feasibility and sensitivity of multimodality PET/CT and MRI imaging for non-invasive characterization of brain microglial/macrophage activation occurring during the acute phase in a mouse model of relapsing remitting multiple sclerosis (RR-MS) using [18F]DPA-714, a selective radioligand for the 18-kDa translocator protein (TSPO), superparamagnetic iron oxide particles (SPIO), and ex vivo immunohistochemistry. Methods Experimental autoimmune encephalomyelitis (EAE) was induced in female SJL/J mice by immunization with PLP139–151. Seven symptomatic EAE mice and five controls underwent both PET/CT and MRI studies between 11 and 14 days post-immunization. SPIO was injected i.v. in the same animals immediately after [18F]DPA-714 and MRI acquisition was performed after 24 h. Regional brain volumes were defined according to a mouse brain atlas on co-registered PET and SPIO-MRI images. [18F]DPA-714 standardized uptake value (SUV) ratios (SUVR), with unaffected neocortex as reference, and SPIO fractional volumes (SPIO-Vol) were generated. Both SUVR and SPIO-Vol values were correlated with the clinical score (CS) and among them. Five EAE and four control mice underwent immunohistochemical analysis with the aim of identifying activated microglia/macrophage and TSPO expressions. Results SUVR and SPIO-Vol values were significantly increased in EAE compared with controls in the hippocampus (p < 0.01; p < 0.02, respectively), thalamus (p < 0.02; p < 0.05, respectively), and cerebellum and brainstem (p < 0.02), while only SPIO-Vol was significantly increased in the caudate/putamen (p < 0.05). Both SUVR and SPIO-Vol values were positively significantly correlated with CS and among them in the same regions. TSPO/Iba1 and F4/80/Prussian blue staining immunohistochemistry suggests that increased activated microglia/macrophages underlay TSPO expression and SPIO uptake in symptomatic EAE mice. Conclusions These preliminary results suggest that both activated microglia and infiltrated macrophages are present in vulnerable brain regions during the acute phase of PLP-EAE and contribute to disease severity. Both [18F]DPA-714-PET and SPIO-MRI appear suitable modalities for preclinical study of neuroinflammation in MS mice models.
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Affiliation(s)
- A R Coda
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy
| | - S Anzilotti
- IRCCS SDN, Via E. Gianturco 113, 80143, Naples, Italy
| | - F Boscia
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, University "Federico II", Via S. Pansini 5, 80131, Naples, Italy
| | - A Greco
- Department of Advanced Biomedical Sciences, University "Federico II", Via S. Pansini 5, 80131, Naples, Italy
- Ceinge Biotecnologie Avanzate s. c. a. r. l., Via G. Salvatore 486, 80145, Naples, Italy
| | - M Panico
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy
| | - S Gargiulo
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy
| | - M Gramanzini
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy
| | - A Zannetti
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy
| | - S Albanese
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy
| | - G Pignataro
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, University "Federico II", Via S. Pansini 5, 80131, Naples, Italy
| | - L Annunziato
- IRCCS SDN, Via E. Gianturco 113, 80143, Naples, Italy
| | - M Salvatore
- IRCCS SDN, Via E. Gianturco 113, 80143, Naples, Italy
| | - A Brunetti
- Department of Advanced Biomedical Sciences, University "Federico II", Via S. Pansini 5, 80131, Naples, Italy
| | - P De Berardinis
- Institute of Biochemistry and Cell Biology, National Research Council, Via P. Castellino 111, 80131, Naples, Italy
| | - Mario Quarantelli
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy.
| | - G Palma
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy
| | - Sabina Pappatà
- Institute of Biostructure and Bioimaging, National Research Council, Via T. De Amicis 95, 80145, Naples, Italy.
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Evaluation of Myelin Radiotracers in the Lysolecithin Rat Model of Focal Demyelination: Beware of Pitfalls! CONTRAST MEDIA & MOLECULAR IMAGING 2019; 2019:9294586. [PMID: 31281236 PMCID: PMC6594279 DOI: 10.1155/2019/9294586] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 02/06/2019] [Accepted: 02/21/2019] [Indexed: 11/29/2022]
Abstract
The observation that amyloid radiotracers developed for Alzheimer's disease bind to cerebral white matter paved the road to nuclear imaging of myelin in multiple sclerosis. The lysolecithin (lysophosphatidylcholine (LPC)) rat model of demyelination proved useful in evaluating and comparing candidate radiotracers to target myelin. Focal demyelination following stereotaxic LPC injection is larger than lesions observed in experimental autoimmune encephalitis models and is followed by spontaneous progressive remyelination. Moreover, the contralateral hemisphere may serve as an internal control in a given animal. However, demyelination can be accompanied by concurrent focal necrosis and/or adjacent ventricle dilation. The influence of these side effects on imaging findings has never been carefully assessed. The present study describes an optimization of the LPC model and highlights the use of MRI for controlling the variability and pitfalls of the model. The prototypical amyloid radiotracer [11C]PIB was used to show that in vivo PET does not provide sufficient sensitivity to reliably track myelin changes and may be sensitive to LPC side effects instead of demyelination as such. Ex vivo autoradiography with a fluorine radiotracer should be preferred, to adequately evaluate and compare radiotracers for the assessment of myelin content.
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Bauckneht M, Capitanio S, Raffa S, Roccatagliata L, Pardini M, Lapucci C, Marini C, Sambuceti G, Inglese M, Gallo P, Cecchin D, Nobili F, Morbelli S. Molecular imaging of multiple sclerosis: from the clinical demand to novel radiotracers. EJNMMI Radiopharm Chem 2019; 4:6. [PMID: 31659498 PMCID: PMC6453990 DOI: 10.1186/s41181-019-0058-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 03/21/2019] [Indexed: 12/13/2022] Open
Abstract
Background Brain PET imaging with different tracers is mainly clinically used in the field of neurodegenerative diseases and brain tumors. In recent years, the potential usefulness of PET has also gained attention in the field of MS. In fact, MS is a complex disease and several processes can be selected as a target for PET imaging. The use of PET with several different tracers has been mainly evaluated in the research setting to investigate disease pathophysiology (i.e. phenotypes, monitoring of progression) or to explore its use a surrogate end-point in clinical trials. Results We have reviewed PET imaging studies in MS in humans and animal models. Tracers have been grouped according to their pathophysiological targets (ie. tracers for myelin kinetic, neuroinflammation, and neurodegeneration). The emerging clinical indication for brain PET imaging in the differential diagnosis of suspected tumefactive demyelinated plaques as well as the clinical potential provided by PET images in view of the recent introduction of PET/MR technology are also addressed. Conclusion While several preclinical and fewer clinical studies have shown results, full-scale clinical development programs are needed to translate molecular imaging technologies into a clinical reality that could ideally fit into current precision medicine perspectives.
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Affiliation(s)
- Matteo Bauckneht
- Nuclear Medicine Unit, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi 10, 16132, Genoa, Italy.
| | - Selene Capitanio
- Nuclear Medicine Unit, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi 10, 16132, Genoa, Italy
| | - Stefano Raffa
- Department of Health Sciences (DISSAL), University of Genova, Genoa, Italy
| | - Luca Roccatagliata
- Department of Health Sciences (DISSAL), University of Genova, Genoa, Italy.,Neuroradiology, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Matteo Pardini
- Clinical Neurology, Department of Neuroscience (DINOGMI), University of Genoa, Genoa, Italy.,Clinica Neurologica, IRCCS Ospedale Policlinico, San Martino, Genoa, Italy
| | - Caterina Lapucci
- Clinical Neurology, Department of Neuroscience (DINOGMI), University of Genoa, Genoa, Italy
| | - Cecilia Marini
- Nuclear Medicine Unit, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi 10, 16132, Genoa, Italy.,CNR Institute of Molecular Bioimaging and Physiology, Milan, Italy
| | - Gianmario Sambuceti
- Nuclear Medicine Unit, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi 10, 16132, Genoa, Italy.,Department of Health Sciences (DISSAL), University of Genova, Genoa, Italy
| | - Matilde Inglese
- Clinical Neurology, Department of Neuroscience (DINOGMI), University of Genoa, Genoa, Italy.,Clinica Neurologica, IRCCS Ospedale Policlinico, San Martino, Genoa, Italy
| | - Paolo Gallo
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences DNS, University of Padua, Padua, Italy
| | - Diego Cecchin
- Nuclear Medicine Unit, Department of Medicine-DIMED, Padova University Hospital, Padua, Italy.,Padua Neuroscience Center, University of Padua, Padua, Italy
| | - Flavio Nobili
- Clinical Neurology, Department of Neuroscience (DINOGMI), University of Genoa, Genoa, Italy.,Clinica Neurologica, IRCCS Ospedale Policlinico, San Martino, Genoa, Italy
| | - Silvia Morbelli
- Nuclear Medicine Unit, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi 10, 16132, Genoa, Italy.,Department of Health Sciences (DISSAL), University of Genova, Genoa, Italy
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Salas JR, Chen BY, Wong A, Cheng D, Van Arnam JS, Witte ON, Clark PM. 18F-FAC PET Selectively Images Liver-Infiltrating CD4 and CD8 T Cells in a Mouse Model of Autoimmune Hepatitis. J Nucl Med 2018; 59:1616-1623. [PMID: 29700125 DOI: 10.2967/jnumed.118.210328] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 04/23/2018] [Indexed: 12/17/2022] Open
Abstract
Immune cell-mediated attack on the liver is a defining feature of autoimmune hepatitis and hepatic allograft rejection. Despite an assortment of diagnostic tools, invasive biopsies remain the only method for identifying immune cells in the liver. We evaluated whether PET imaging with radiotracers that quantify immune activation (18F-FDG and 18F-1-(2'-deoxy-2'-fluoro-arabinofuranosyl)cytosine [18F-FAC]) and hepatocyte biology (18F-2-deoxy-2-fluoroarabinose [18F-DFA]) can visualize and quantify liver-infiltrating immune cells and hepatocyte inflammation, respectively, in a preclinical model of autoimmune hepatitis. Methods: Mice treated with concanavalin A (ConA) to induce a model of autoimmune hepatitis or vehicle were imaged with 18F-FDG, 18F-FAC, and 18F-DFA PET. Immunohistochemistry, digital autoradiography, and ex vivo accumulation assays were used to localize areas of altered radiotracer accumulation in the liver. For comparison, mice treated with an adenovirus to induce a viral hepatitis were imaged with 18F-FDG, 18F-FAC, and 18F-DFA PET. 18F-FAC PET was performed on mice treated with ConA and vehicle or with ConA and dexamethasone. Biopsy samples of patients with autoimmune hepatitis were immunostained for deoxycytidine kinase. Results: Hepatic accumulation of 18F-FDG and 18F-FAC was 173% and 61% higher, respectively, and hepatic accumulation of 18F-DFA was 41% lower, in a mouse model of autoimmune hepatitis than in control mice. Increased hepatic 18F-FDG accumulation was localized to infiltrating leukocytes and inflamed sinusoidal endothelial cells, increased hepatic 18F-FAC accumulation was concentrated in infiltrating CD4 and CD8 cells, and decreased hepatic 18F-DFA accumulation was apparent in hepatocytes throughout the liver. In contrast, viral hepatitis increased hepatic 18F-FDG accumulation by 109% and decreased hepatic 18F-DFA accumulation by 20% but had no effect on hepatic 18F-FAC accumulation (nonsignificant 2% decrease). 18F-FAC PET provided a noninvasive biomarker of the efficacy of dexamethasone for treating the autoimmune hepatitis model. Infiltrating leukocytes in liver biopsy samples from patients with autoimmune hepatitis express high levels of deoxycytidine kinase, a rate-limiting enzyme in the accumulation of 18F-FAC. Conclusion: Our data suggest that PET can be used to noninvasively visualize activated leukocytes and inflamed hepatocytes in a mouse model of autoimmune hepatitis.
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Affiliation(s)
- Jessica R Salas
- Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California.,Crump Institute for Molecular Imaging, UCLA, Los Angeles, California
| | - Bao Ying Chen
- Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California.,Crump Institute for Molecular Imaging, UCLA, Los Angeles, California
| | - Alicia Wong
- Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California.,Crump Institute for Molecular Imaging, UCLA, Los Angeles, California
| | - Donghui Cheng
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, UCLA, Los Angeles, California
| | - John S Van Arnam
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Owen N Witte
- Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, UCLA, Los Angeles, California.,Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, California
| | - Peter M Clark
- Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California .,Crump Institute for Molecular Imaging, UCLA, Los Angeles, California.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, UCLA, Los Angeles, California
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Liu H, Jin H, Yue X, Luo Z, Liu C, Rosenberg AJ, Tu Z. PET Imaging Study of S1PR1 Expression in a Rat Model of Multiple Sclerosis. Mol Imaging Biol 2017; 18:724-32. [PMID: 26975859 DOI: 10.1007/s11307-016-0944-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
PURPOSE Upregulation of sphingosine-1-phosphate receptor 1 (S1PR1) expression in multiple sclerosis (MS) lesions is associated with neuroinflammatory response. This study investigated the correlation between neuroinflammation and S1PR1 expression in the spinal cord of an experimental autoimmune encephalomyelitis (EAE) rat model of MS, using the S1PR1 positron emission tomography (PET) radiotracer [(11)C]TZ3321. PROCEDURES MicroPET imaging studies of [(11)C]TZ3321 were performed to measure uptake of [(11)C]TZ3321 in the spinal cord of EAE rats. Immunohistochemical staining was performed to confirm the overexpression of S1PR1 and other inflammatory biomarkers. RESULTS MicroPET imaging demonstrated a 20-30 % increase in [(11)C]TZ3321 uptake in the lumbar spinal cord of EAE rats versus sham controls at 35-60 min post injection. The increased uptake of [(11)C]TZ3321 was correlated with the overexpression of S1PR1 in the lumbar spinal cord of EAE rats that was confirmed by immunohistochemical staining. Upregulated S1PR1 expression was associated with glial cell activation and immune cell infiltration. CONCLUSIONS MicroPET imaging modality with a specific radioligand [(11)C]TZ3321 is able to assess the expression of S1PR1 in EAE rat lumbar spinal cord. This may provide a new approach to the assessment of neuroinflammatory response in MS and other inflammatory diseases.
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Affiliation(s)
- Hui Liu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Hongjun Jin
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Xuyi Yue
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Zonghua Luo
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Chunling Liu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Adam J Rosenberg
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Zhude Tu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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Vállez García D, Doorduin J, de Paula Faria D, Dierckx RAJO, de Vries EFJ. Effect of Preventive and Curative Fingolimod Treatment Regimens on Microglia Activation and Disease Progression in a Rat Model of Multiple Sclerosis. J Neuroimmune Pharmacol 2017; 12:521-530. [PMID: 28361437 PMCID: PMC5527053 DOI: 10.1007/s11481-017-9741-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 03/23/2017] [Indexed: 11/29/2022]
Abstract
Fingolimod was the first oral drug approved for multiple sclerosis treatment. Its principal mechanism of action is blocking of lymphocyte trafficking. In addition, recent studies have shown its capability to diminish microglia activation. The effect of preventive and curative fingolimod treatment on the time-course of neuroinflammation was investigated in the experimental autoimmune encephalomyelitis rat model for multiple sclerosis. Neuroinflammatory progression was followed in Dark Agouti female rats after immunization. Positron-Emission tomography (PET) imaging with (R)-[11C]PK11195 was performed on day 11, 15, 19, 27, 29 and 34 during normal disease progression, preventive and curative treatments with fingolimod (1 mg/kg/day). Additionally, bodyweight and clinical symptoms were determined. Preventive treatment diminished bodyweight loss and inhibited the appearance of neurological symptoms. In non-treated rats, PET showed that neuroinflammation peaked in the brainstem at day 19, whereas the imaging signal was decreased in cortical regions. Both preventive and curative treatment reduced neuroinflammation in the brainstem at day 19. Eight days after treatment withdrawal, neuroinflammation had flared-up, especially in cortical regions. Preventive treatment with fingolimod suppressed clinical symptoms and neuroinflammation in the brainstem. After treatment withdrawal, clinical symptoms reappeared together with neuroinflammation in cortical regions, suggesting a different pathway of disease progression.
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Affiliation(s)
- David Vállez García
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, 9700 RB Groningen, The Netherlands
| | - Janine Doorduin
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, 9700 RB Groningen, The Netherlands
| | - Daniele de Paula Faria
- Department of Radiology and Oncology, Faculty of Medicine, University of Sao Paulo, Sao Paulo, Brazil
| | - Rudi A J O Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, 9700 RB Groningen, The Netherlands
| | - Erik F J de Vries
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, 9700 RB Groningen, The Netherlands.
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11
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Tremoleda JL, Thau-Zuchman O, Davies M, Foster J, Khan I, Vadivelu KC, Yip PK, Sosabowski J, Trigg W, Michael-Titus AT. In vivo PET imaging of the neuroinflammatory response in rat spinal cord injury using the TSPO tracer [(18)F]GE-180 and effect of docosahexaenoic acid. Eur J Nucl Med Mol Imaging 2016; 43:1710-22. [PMID: 27154521 PMCID: PMC4932147 DOI: 10.1007/s00259-016-3391-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 04/04/2016] [Indexed: 12/30/2022]
Abstract
Purpose Traumatic spinal cord injury (SCI) is a devastating condition which affects millions of people worldwide causing major disability and substantial socioeconomic burden. There are currently no effective treatments. Modulating the neuroinflammatory (NI) response after SCI has evolved as a major therapeutic strategy. PET can be used to detect the upregulation of the 18-kDa translocator protein (TSPO), a hallmark of activated microglia in the CNS. We investigated whether PET imaging using the novel TSPO tracer [18F]GE-180 can be used as a clinically relevant biomarker for NI in a contusion SCI rat model, and we present data on the modulation of NI by the lipid docosahexaenoic acid (DHA). Methods A total of 22 adult male Wistar rats were subjected to controlled spinal cord contusion at the T10 spinal cord level. Six non-injured and ten T10 laminectomy only (LAM) animals were used as controls. A subset of six SCI animals were treated with a single intravenous dose of 250 nmol/kg DHA (SCI-DHA group) 30 min after injury; a saline-injected group of six animals was used as an injection control. PET and CT imaging was carried out 7 days after injury using the [18F]GE-180 radiotracer. After imaging, the animals were killed and the spinal cord dissected out for biodistribution and autoradiography studies. In vivo data were correlated with ex vivo immunohistochemistry for TSPO. Results In vivo dynamic PET imaging revealed an increase in tracer uptake in the spinal cord of the SCI animals compared with the non-injured and LAM animals from 35 min after injection (P < 0.0001; SCI vs. LAM vs. non-injured). Biodistribution and autoradiography studies confirmed the high affinity and specific [18F]GE-180 binding in the injured spinal cord compared with the binding in the control groups. Furthermore, they also showed decreased tracer uptake in the T10 SCI area in relation to the non-injured remainder of the spinal cord in the SCI-DHA group compared with the SCI-saline group (P < 0.05), supporting a NI modulatory effect of DHA. Immunohistochemistry showed a high level of TSPO expression (38 %) at the T10 injury site in SCI animals compared with that in the non-injured animals (6 %). Conclusion [18F]GE-180 PET imaging can reveal areas of increased TSPO expression that can be visualized and quantified in vivo after SCI, offering a minimally invasive approach to the monitoring of NI in SCI models and providing a translatable clinical readout for the testing of new therapies. Electronic supplementary material The online version of this article (doi:10.1007/s00259-016-3391-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- J L Tremoleda
- Centre for Trauma Sciences, The Blizard Institute, London, UK.
| | - O Thau-Zuchman
- Centre for Trauma Sciences, The Blizard Institute, London, UK
| | - M Davies
- Centre for Trauma Sciences, The Blizard Institute, London, UK
| | - J Foster
- Barts Cancer Institute, Queen Mary University London, London, UK
| | - I Khan
- GE Healthcare Ltd, Amersham, UK
| | - K C Vadivelu
- Centre for Trauma Sciences, The Blizard Institute, London, UK
| | - P K Yip
- Centre for Trauma Sciences, The Blizard Institute, London, UK
| | - J Sosabowski
- Barts Cancer Institute, Queen Mary University London, London, UK
| | - W Trigg
- GE Healthcare Ltd, Amersham, UK
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12
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Martín A, Vázquez-Villoldo N, Gómez-Vallejo V, Padro D, Soria FN, Szczupak B, Plaza-García S, Arrieta A, Reese T, Llop J, Domercq M, Matute C. In vivo imaging of system xc- as a novel approach to monitor multiple sclerosis. Eur J Nucl Med Mol Imaging 2015; 43:1124-38. [PMID: 26659901 DOI: 10.1007/s00259-015-3275-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 11/27/2015] [Indexed: 01/24/2023]
Abstract
PURPOSE Glutamate excitotoxicity contributes to oligodendroglial and axonal damage in multiple sclerosis pathology. Extracellular glutamate concentration in the brain is controlled by cystine/glutamate antiporter (system xc-), a membrane antiporter that imports cystine and releases glutamate. Despite this, the system xc(-) activity and its connection to the inflammatory reaction in multiple sclerosis (MS) is largely unknown. METHODS Longitudinal in vivo magnetic resonance (MRI) and positron emission tomography (PET) imaging studies with 2-[(18)F]Fluoro-2-deoxy-D-glucose ([(18)F]FDG), [(11)C]-(R)-(1-(2-chlorophenyl)-N-methyl-N-1(1-methylpropyl)-3-isoquinolinecarboxamide ([(11)C]PK11195) and (4S)-4-(3-(18)F-fluoropropyl)-L-glutamate ([(18)F]FSPG) were carried out during the course of experimental autoimmune encephalomyelitis (EAE) induction in rats. RESULTS [(18)F]FSPG showed a significant increase of system xc(-) function in the lumbar section of the spinal cord at 14 days post immunization (dpi) that stands in agreement with the neurological symptoms and ventricle edema formation at this time point. Likewise, [(18)F]FDG did not show significant changes in glucose metabolism throughout central nervous system and [(11)C]PK11195 evidenced a significant increase of microglial/macrophage activation in spinal cord and cerebellum 2 weeks after EAE induction. Therefore, [(18)F]FSPG showed a major capacity to discriminate regions of the central nervous system affected by the MS in comparison to [(18)F]FDG and [(11)C]PK11195. Additionally, clodronate-treated rats showed a depletion in microglial population and [(18)F]FSPG PET signal in spinal cord confirming a link between neuroinflammatory reaction and cystine/glutamate antiporter activity in EAE rats. CONCLUSIONS Altogether, these results suggest that in vivo PET imaging of system xc(-) could become a valuable tool for the diagnosis and treatment evaluation of MS.
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Affiliation(s)
- Abraham Martín
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain.
| | - Nuria Vázquez-Villoldo
- Department of Neurosciences, University of the Basque Country, Barrio Sarriena s/n, 48940, Leioa, Spain.,Achucarro Basque Center for Neuroscience, UPV/EHU, 48170, Zamudio, Spain.,Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 48940, Leioa, Spain
| | - Vanessa Gómez-Vallejo
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain.,Radiochemistry and Nuclear Imaging, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain
| | - Daniel Padro
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain.,Magnetic Resonance Imaging, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain
| | - Federico N Soria
- Department of Neurosciences, University of the Basque Country, Barrio Sarriena s/n, 48940, Leioa, Spain.,Achucarro Basque Center for Neuroscience, UPV/EHU, 48170, Zamudio, Spain.,Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 48940, Leioa, Spain
| | - Boguslaw Szczupak
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain
| | - Sandra Plaza-García
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain.,Magnetic Resonance Imaging, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain
| | - Ander Arrieta
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain
| | - Torsten Reese
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain.,Magnetic Resonance Imaging, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain
| | - Jordi Llop
- Molecular Imaging Unit, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain.,Radiochemistry and Nuclear Imaging, CIC biomaGUNE, P° Miramon 182, San Sebastian, Spain
| | - Maria Domercq
- Department of Neurosciences, University of the Basque Country, Barrio Sarriena s/n, 48940, Leioa, Spain.,Achucarro Basque Center for Neuroscience, UPV/EHU, 48170, Zamudio, Spain.,Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 48940, Leioa, Spain
| | - Carlos Matute
- Department of Neurosciences, University of the Basque Country, Barrio Sarriena s/n, 48940, Leioa, Spain. .,Achucarro Basque Center for Neuroscience, UPV/EHU, 48170, Zamudio, Spain. .,Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 48940, Leioa, Spain.
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13
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Janssen B, Vugts DJ, Funke U, Molenaar GT, Kruijer PS, van Berckel BNM, Lammertsma AA, Windhorst AD. Imaging of neuroinflammation in Alzheimer's disease, multiple sclerosis and stroke: Recent developments in positron emission tomography. Biochim Biophys Acta Mol Basis Dis 2015; 1862:425-41. [PMID: 26643549 DOI: 10.1016/j.bbadis.2015.11.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 10/09/2015] [Accepted: 11/19/2015] [Indexed: 12/13/2022]
Abstract
Neuroinflammation is thought to play a pivotal role in many diseases affecting the brain, including Alzheimer's disease, multiple sclerosis and stroke. Neuroinflammation is characterised predominantly by microglial activation, which can be visualised using positron emission tomography (PET). Traditionally, translocator protein 18kDa (TSPO) is the target for imaging of neuroinflammation using PET. In this review, recent preclinical and clinical research using PET in Alzheimer's disease, multiple sclerosis and stroke is summarised. In addition, new molecular targets for imaging of neuroinflammation, such as monoamine oxidases, adenosine receptors and cannabinoid receptor type 2, are discussed. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.
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Affiliation(s)
- Bieneke Janssen
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands.
| | - Danielle J Vugts
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Uta Funke
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands; BV Cyclotron VU, Amsterdam, The Netherlands
| | - Ger T Molenaar
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands; BV Cyclotron VU, Amsterdam, The Netherlands
| | | | - Bart N M van Berckel
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Adriaan A Lammertsma
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Albert D Windhorst
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands.
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