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Gouilly D, Vrillon A, Bertrand E, Goubeaud M, Catala H, Germain J, Ainaoui N, Rafiq M, Nogueira L, Mouton-Liger F, Planton M, Salabert AS, Hitzel A, Méligne D, Jasse L, Sarton B, Silva S, Lemesle B, Péran P, Payoux P, Thalamas C, Paquet C, Pariente J. Translocator protein (TSPO) genotype does not change cerebrospinal fluid levels of glial activation, axonal and synaptic damage markers in early Alzheimer's disease. Neuroimage Clin 2024; 43:103626. [PMID: 38850834 PMCID: PMC11201347 DOI: 10.1016/j.nicl.2024.103626] [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: 02/29/2024] [Revised: 05/10/2024] [Accepted: 05/29/2024] [Indexed: 06/10/2024]
Abstract
BACKGROUND PET imaging of the translocator protein (TSPO) is used to assess in vivo brain inflammation. One of the main methodological issues with this method is the allelic dependence of the radiotracer affinity. In Alzheimer's disease (AD), previous studies have shown similar clinical and patho-biological profiles between TSPO genetic subgroups. However, there is no evidence regarding the effect of the TSPO genotype on cerebrospinal-fluid biomarkers of glial activation, and synaptic and axonal damage. METHOD We performed a trans-sectional study in early AD to compare cerebrospinal-fluid levels of GFAP, YKL-40, sTREM2, IL-6, IL-10, NfL and neurogranin between TSPO genetic subgroups. RESULTS We recruited 33 patients with early AD including 16 (48%) high affinity binders, 13 (39%) mixed affinity binders, and 4/33 (12%) low affinity binders. No difference was observed in terms of demographics, and cerebrospinal fluid levels of each biomarker for the different subgroups. CONCLUSION TSPO genotype is not associated with a change in glial activation, synaptic and axonal damage in early AD. Further studies with larger numbers of participants will be needed to confirm that the inclusion of specific TSPO genetic subgroups does not introduce selection bias in studies and trials of AD that combine TSPO imaging with cerebrospinal fluid biomarkers.
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Affiliation(s)
- Dominique Gouilly
- Department of Cognitive Neurology, Epilepsy, Sleep and Movement Disorders, CHU Toulouse Purpan, Toulouse, France.
| | - Agathe Vrillon
- Université de Paris, Cognitive Neurology Center, GHU Nord, APHP, Hospital Lariboisière Fernand Widal, Paris, France; Université de Paris, Inserm UMRS11-44 Therapeutic Optimization in Neuropsychopharmacology, Paris, France
| | - Elsa Bertrand
- Center of Clinical Investigation, CHU Toulouse Purpan (CIC 1436), Toulouse, France
| | - Marie Goubeaud
- Center of Clinical Investigation, CHU Toulouse Purpan (CIC 1436), Toulouse, France
| | - Hélène Catala
- Center of Clinical Investigation, CHU Toulouse Purpan (CIC 1436), Toulouse, France
| | - Johanne Germain
- Center of Clinical Investigation, CHU Toulouse Purpan (CIC 1436), Toulouse, France
| | - Nadéra Ainaoui
- Center of Clinical Investigation, CHU Toulouse Purpan (CIC 1436), Toulouse, France
| | - Marie Rafiq
- Department of Cognitive Neurology, Epilepsy, Sleep and Movement Disorders, CHU Toulouse Purpan, Toulouse, France; Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France
| | - Leonor Nogueira
- Laboratory of Cell Biology and Cytology, CHU Toulouse Purpan, Toulouse, France
| | - François Mouton-Liger
- Université de Paris, Inserm UMRS11-44 Therapeutic Optimization in Neuropsychopharmacology, Paris, France
| | - Mélanie Planton
- Department of Cognitive Neurology, Epilepsy, Sleep and Movement Disorders, CHU Toulouse Purpan, Toulouse, France; Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France
| | - Anne-Sophie Salabert
- Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France; Department of Nuclear Medicine, CHU Toulouse Purpan, Toulouse, France
| | - Anne Hitzel
- Department of Nuclear Medicine, CHU Toulouse Purpan, Toulouse, France
| | - Déborah Méligne
- Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France
| | - Laurence Jasse
- Department of Cognitive Neurology, Epilepsy, Sleep and Movement Disorders, CHU Toulouse Purpan, Toulouse, France
| | - Benjamine Sarton
- Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France; Critical Care Unit, CHU Toulouse Purpan, Toulouse, France
| | - Stein Silva
- Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France; Critical Care Unit, CHU Toulouse Purpan, Toulouse, France
| | - Béatrice Lemesle
- Department of Cognitive Neurology, Epilepsy, Sleep and Movement Disorders, CHU Toulouse Purpan, Toulouse, France
| | - Patrice Péran
- Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France
| | - Pierre Payoux
- Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France; Department of Nuclear Medicine, CHU Toulouse Purpan, Toulouse, France
| | - Claire Thalamas
- Center of Clinical Investigation, CHU Toulouse Purpan (CIC 1436), Toulouse, France
| | - Claire Paquet
- Université de Paris, Cognitive Neurology Center, GHU Nord, APHP, Hospital Lariboisière Fernand Widal, Paris, France; Université de Paris, Inserm UMRS11-44 Therapeutic Optimization in Neuropsychopharmacology, Paris, France
| | - Jérémie Pariente
- Department of Cognitive Neurology, Epilepsy, Sleep and Movement Disorders, CHU Toulouse Purpan, Toulouse, France; Center of Clinical Investigation, CHU Toulouse Purpan (CIC 1436), Toulouse, France; Toulouse Neuroimaging Center, UMR 1214, Inserm/UPS, Toulouse, France
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An Update on the Effects of Vitamin D on the Immune System and Autoimmune Diseases. Int J Mol Sci 2022; 23:ijms23179784. [PMID: 36077185 PMCID: PMC9456003 DOI: 10.3390/ijms23179784] [Citation(s) in RCA: 49] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 08/24/2022] [Accepted: 08/26/2022] [Indexed: 12/16/2022] Open
Abstract
Vitamin D intervenes in calcium and phosphate metabolism and bone homeostasis. Experimental studies have shown that 1,25-dihydroxyvitamin D (calcitriol) generates immunologic activities on the innate and adaptive immune system and endothelial membrane stability. Low levels of serum 25-hydroxyvitamin D (25(OH)D) are associated with an increased risk of developing immune-related diseases such as psoriasis, type 1 diabetes, multiple sclerosis, and autoimmune diseases. Various clinical trials describe the efficacy of supplementation of vitamin D and its metabolites for treating these diseases that result in variable outcomes. Different disease outcomes are observed in treatment with vitamin D as high inter-individual difference is present with complex gene expression in human peripheral blood mononuclear cells. However, it is still not fully known what level of serum 25(OH)D is needed. The current recommendation is to increase vitamin D intake and have enough sunlight exposure to have serum 25(OH)D at a level of 30 ng/mL (75 nmol/L) and better at 40–60 ng/mL (100–150 nmol/L) to obtain the optimal health benefits of vitamin D.
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Nutma E, Ceyzériat K, Amor S, Tsartsalis S, Millet P, Owen DR, Papadopoulos V, Tournier BB. Cellular sources of TSPO expression in healthy and diseased brain. Eur J Nucl Med Mol Imaging 2021; 49:146-163. [PMID: 33433698 PMCID: PMC8712293 DOI: 10.1007/s00259-020-05166-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 12/13/2020] [Indexed: 12/11/2022]
Abstract
The 18 kDa translocator protein (TSPO) is a highly conserved protein located in the outer mitochondrial membrane. TSPO binding, as measured with positron emission tomography (PET), is considered an in vivo marker of neuroinflammation. Indeed, TSPO expression is altered in neurodegenerative, neuroinflammatory, and neuropsychiatric diseases. In PET studies, the TSPO signal is often viewed as a marker of microglial cell activity. However, there is little evidence in support of a microglia-specific TSPO expression. This review describes the cellular sources and functions of TSPO in animal models of disease and human studies, in health, and in central nervous system diseases. A discussion of methods of analysis and of quantification of TSPO is also presented. Overall, it appears that the alterations of TSPO binding, their cellular underpinnings, and the functional significance of such alterations depend on many factors, notably the pathology or the animal model under study, the disease stage, and the involved brain regions. Thus, further studies are needed to fully determine how changes in TSPO binding occur at the cellular level with the ultimate goal of revealing potential therapeutic pathways.
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Affiliation(s)
- Erik Nutma
- Department of Pathology, Amsterdam UMC, VUmc, Amsterdam, The Netherlands
| | - Kelly Ceyzériat
- Division of Adult Psychiatry, Department of Psychiatry, University Hospitals of Geneva, Avenue de la Roseraie, 64, 1206, Geneva, Switzerland
- Division of Nuclear medicine and Molecular Imaging, University Hospitals of Geneva, Geneva, Switzerland
- Division of Radiation Oncology, Department of Oncology, University Hospitals of Geneva, Geneva, Switzerland
| | - Sandra Amor
- Department of Pathology, Amsterdam UMC, VUmc, Amsterdam, The Netherlands
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Stergios Tsartsalis
- Division of Adult Psychiatry, Department of Psychiatry, University Hospitals of Geneva, Avenue de la Roseraie, 64, 1206, Geneva, Switzerland
- Department of Brain Sciences, Faculty of Medicine, Imperial College London, London, UK
| | - Philippe Millet
- Division of Adult Psychiatry, Department of Psychiatry, University Hospitals of Geneva, Avenue de la Roseraie, 64, 1206, Geneva, Switzerland
- Department of Psychiatry, University of Geneva, Geneva, Switzerland
| | - David R Owen
- Department of Brain Sciences, Faculty of Medicine, Imperial College London, London, UK
| | - Vassilios Papadopoulos
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, USA
| | - Benjamin B Tournier
- Division of Adult Psychiatry, Department of Psychiatry, University Hospitals of Geneva, Avenue de la Roseraie, 64, 1206, Geneva, Switzerland.
- Department of Psychiatry, University of Geneva, Geneva, Switzerland.
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Guilarte TR, Rodichkin AN, McGlothan JL, Acanda De La Rocha AM, Azzam DJ. Imaging neuroinflammation with TSPO: A new perspective on the cellular sources and subcellular localization. Pharmacol Ther 2021; 234:108048. [PMID: 34848203 DOI: 10.1016/j.pharmthera.2021.108048] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 11/04/2021] [Accepted: 11/24/2021] [Indexed: 12/14/2022]
Abstract
Translocator Protein 18 kDa (TSPO), previously named Peripheral Benzodiazepine Receptor, is a well-validated and widely used biomarker of neuroinflammation to assess diverse central nervous system (CNS) pathologies in preclinical and clinical studies. Many studies have shown that in animal models of human neurological and neurodegenerative disease and in the human condition, TSPO levels increase in the brain neuropil, and this increase is driven by infiltration of peripheral inflammatory cells and activation of glial cells. Therefore, a clear understanding of the dynamics of the cellular sources of the TSPO response is critically important in the interpretation of Positron Emission Tomography (PET) studies and for understanding the pathophysiology of CNS diseases. Within the normal brain compartment, there are tissues and cells such as the choroid plexus, ependymal cells of the lining of the ventricles, and vascular endothelial cells that also express TSPO at even higher levels than in glial cells. However, there is a paucity of knowledge if these cell types respond and increase TSPO in the diseased brain. These cells do provide a background signal that needs to be accounted for in TSPO-PET imaging studies. More recently, there are reports that TSPO may be expressed in neurons of the adult brain and TSPO expression may be increased by neuronal activity. Therefore, it is essential to study this topic with a great deal of detail, methodological rigor, and rule out alternative interpretations and imaging artifacts. High levels of TSPO are present in the outer mitochondrial membrane. Recent studies have provided evidence of its localization in other cellular compartments including the plasma membrane and perinuclear regions which may define functions that are different from that in mitochondria. A greater understanding of the TSPO subcellular localization in glial cells and infiltrating peripheral immune cells and associated function(s) may provide an additional layer of information to the understanding of TSPO neurobiology. This review is an effort to outline recent advances in understanding the cellular sources and subcellular localization of TSPO in brain cells and to examine remaining questions that require rigorous investigation.
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Affiliation(s)
- Tomás R Guilarte
- Brain, Behavior, & the Environment Program, Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, United States of America.
| | - Alexander N Rodichkin
- Brain, Behavior, & the Environment Program, Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, United States of America
| | - Jennifer L McGlothan
- Brain, Behavior, & the Environment Program, Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, United States of America
| | - Arlet Maria Acanda De La Rocha
- Brain, Behavior, & the Environment Program, Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, United States of America
| | - Diana J Azzam
- Brain, Behavior, & the Environment Program, Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, United States of America
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Neuroinflammation in Parkinson's disease: a meta-analysis of PET imaging studies. J Neurol 2021; 269:2304-2314. [PMID: 34724571 DOI: 10.1007/s00415-021-10877-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/24/2021] [Accepted: 10/25/2021] [Indexed: 10/20/2022]
Abstract
Increasingly, evidence implicates an important role of neuroinflammation in neurodegeneration progression. Yet, brain imaging has not reached a consistent conclusion that neuroinflammation is involved in the pathogenesis of Parkinson's disease (PD). We aimed to review the evidence to quantitatively assess the existence and spatial distribution of neuroinflammation in the brain of PD patients. We systematically searched literature databases for case-control studies which used positron emission tomography to detect neuroinflammation represented by translocator protein (TSPO) levels in PD patients compared with healthy controls (HC). Standardized mean differences (SMD) were selected as effect sizes and random-effects models were used to combine effect sizes. Subgroup analyses for separate brain regions were conducted. Fifteen studies comprising 455 (HC = 198, PD = 238) participants and 19 brain regions were included. Compared to HC, PD patients had elevated TSPO levels in midbrain, putamen, anterior cingulate, posterior cingulate, thalamus, striatum, frontal, temporal, parietal, occipital, cortex, hippocampus, substantia nigra, pons, cerebellum, and caudate when using 1st-generation ligands. TSPO levels were elevated in the midbrain of PD patients when 2nd-generation ligands were used. We discussed the possible explanations of contrasting difference between these outcomes.
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Troike KM, Acanda de la Rocha AM, Alban TJ, Grabowski MM, Otvos B, Cioffi G, Waite KA, Barnholtz Sloan JS, Lathia JD, Guilarte TR, Azzam DJ. The Translocator Protein ( TSPO) Genetic Polymorphism A147T Is Associated with Worse Survival in Male Glioblastoma Patients. Cancers (Basel) 2021; 13:cancers13184525. [PMID: 34572751 PMCID: PMC8471762 DOI: 10.3390/cancers13184525] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/27/2021] [Accepted: 09/02/2021] [Indexed: 12/20/2022] Open
Abstract
Simple Summary The translocator protein 18 kDa (TSPO) gene is highly expressed in glioblastoma (GBM), the most common primary malignant brain tumor, which remains one of the most difficult tumors to treat. TSPO is located in the outer mitochondrial membrane and binds cholesterol through its C-terminal domain. One frequent single-nucleotide polymorphism (SNP) rs6971, which changes the alanine 147 into threonine (Ala147Thr), has been found in the C-terminal domain of the TSPO region and dramatically alters the affinity with which TSPO binds drug ligands. However, the potential association between the TSPO genetic variants and GBM clinical outcomes is not known. Here, we evaluated the effects of the Ala147Thr SNP localized in this TSPO region on biological, sex-specific, overall, and progression-free GBM survival. Our findings suggest an association between the TSPO rs6971 variant and adverse outcomes in male GBM patients but not in females. These findings also suggest that the TSPO rs6971 SNP could be used as a prognostic marker of survival in GBM patients. Abstract Glioblastoma (GBM) is the most common primary brain tumor in adults, with few available therapies and a five-year survival rate of 7.2%. Hence, strategies for improving GBM prognosis are urgently needed. The translocator protein 18kDa (TSPO) plays crucial roles in essential mitochondria-based physiological processes and is a validated biomarker of neuroinflammation, which is implicated in GBM progression. The TSPO gene has a germline single nucleotide polymorphism, rs6971, which is the most common SNP in the Caucasian population. High TSPO gene expression is associated with reduced survival in GBM patients; however, the relation between the most frequent TSPO genetic variant and GBM pathogenesis is not known. The present study retrospectively analyzed the correlation of the TSPO polymorphic variant rs6971 with overall and progression-free survival in GBM patients using three independent cohorts. TSPO rs6971 polymorphism was significantly associated with shorter overall survival and progression-free survival in male GBM patients but not in females in one large cohort of 441 patients. We observed similar trends in two other independent cohorts. These observations suggest that the TSPO rs6971 polymorphism could be a significant predictor of poor prognosis in GBM, with a potential for use as a prognosis biomarker in GBM patients. These results reveal for the first time a biological sex-specific relation between rs6971 TSPO polymorphism and GBM.
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Affiliation(s)
- Katie M. Troike
- Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (K.M.T.); (T.J.A.); (M.M.G.); (B.O.); (J.D.L.)
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
| | - Arlet M. Acanda de la Rocha
- Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, USA;
| | - Tyler J. Alban
- Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (K.M.T.); (T.J.A.); (M.M.G.); (B.O.); (J.D.L.)
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
| | - Matthew M. Grabowski
- Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (K.M.T.); (T.J.A.); (M.M.G.); (B.O.); (J.D.L.)
- Department of Neurosurgery, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Balint Otvos
- Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (K.M.T.); (T.J.A.); (M.M.G.); (B.O.); (J.D.L.)
- Department of Neurosurgery, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Gino Cioffi
- National Cancer Institute, Division of Cancer Epidemiology and Genetics, Trans-Divisional Research Program, Bethesda, MD 20892, USA; (G.C.); (K.A.W.); (J.S.B.S.)
| | - Kristin A. Waite
- National Cancer Institute, Division of Cancer Epidemiology and Genetics, Trans-Divisional Research Program, Bethesda, MD 20892, USA; (G.C.); (K.A.W.); (J.S.B.S.)
| | - Jill S. Barnholtz Sloan
- National Cancer Institute, Division of Cancer Epidemiology and Genetics, Trans-Divisional Research Program, Bethesda, MD 20892, USA; (G.C.); (K.A.W.); (J.S.B.S.)
- National Cancer Institute, Center for Biomedical Informatics and Information Technology, Bethesda, MD 20892, USA
| | - Justin D. Lathia
- Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (K.M.T.); (T.J.A.); (M.M.G.); (B.O.); (J.D.L.)
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
- Case Comprehensive Cancer Center, School of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
- Rose Ella Burkhardt Brain Tumor and Neuro-Oncology Center, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Tomás R. Guilarte
- Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, USA;
- Brain, Behavior & the Environment Program, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, USA
- Correspondence: (T.R.G.); (D.J.A.)
| | - Diana J. Azzam
- Department of Environmental Health Sciences, Robert Stempel College of Public Health & Social Work, Florida International University, Miami, FL 33199, USA;
- Correspondence: (T.R.G.); (D.J.A.)
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Mattner F, Katsifis A, Bourdier T, Loc'h C, Berghofer P, Fookes C, Hung TT, Jackson T, Henderson D, Pham T, Lee BJ, Shepherd R, Greguric I, Wyatt N, Le T, Poon J, Power C, Fulham M. Synthesis and pharmacological evaluation of [ 18F]PBR316: a novel PET ligand targeting the translocator protein 18 kDa (TSPO) with low binding sensitivity to human single nucleotide polymorphism rs6971. RSC Med Chem 2021; 12:1207-1221. [PMID: 34355185 PMCID: PMC8292990 DOI: 10.1039/d1md00035g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/15/2021] [Indexed: 02/04/2023] Open
Abstract
Radiopharmaceuticals that target the translocator protein 18 kDa (TSPO) have been investigated with positron emission tomography (PET) to study neuroinflammation, neurodegeneration and cancer. We have developed the novel, achiral, 2-phenylimidazo[1,2-a]pyridine, PBR316 that targets the translocator protein 18 kDa (TSPO) that addresses some of the limitations inherent in current TSPO ligands; namely specificity in binding, blood brain barrier permeability, metabolism and insensitivity to TSPO binding in subjects as a result of rs6971 polymorphism. PBR316 has high nanomolar affinity (4.7-6.0 nM) for the TSPO, >5000 nM for the central benzodiazepine receptor (CBR) and low sensitivity to rs6971 polymorphism with a low affinity binders (LABs) to high affinity binders (HABs) ratio of 1.5. [18F]PBR316 was prepared in 20 ± 5% radiochemical yield, >99% radiochemical purity and a molar activity of 160-400 GBq μmol-1. Biodistribution in rats showed high uptake of [18F]PBR316 in organs known to express TSPO such as heart (3.9%) and adrenal glands (7.5% ID per g) at 1 h. [18F]PBR316 entered the brain and accumulated in TSPO-expressing regions with an olfactory bulb to brain ratio of 3 at 15 min and 7 at 4 h. Radioactivity was blocked by PK11195 and Ro 5-4864 but not Flumazenil. Metabolite analysis showed that radioactivity in adrenal glands and the brain was predominantly due to the intact radiotracer. PET-CT studies in mouse-bearing prostate tumour xenografts indicated biodistribution similar to rats with radioactivity in the tumour increasing with time. [18F]PBR316 shows in vitro binding that is insensitive to human polymorphism and has specific and selective in vivo binding to the TSPO. [18F]PBR316 is suitable for further biological and clinical studies.
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Affiliation(s)
- Filomena Mattner
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Andrew Katsifis
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
- School of Pharmacy, University of Sydney Sydney NSW 2006 Australia
| | - Thomas Bourdier
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Christian Loc'h
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Paula Berghofer
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Christopher Fookes
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Tzong-Tyng Hung
- Biological Resources Imaging Laboratory, University of New South Wales Sydney NSW Australia
| | - Timothy Jackson
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - David Henderson
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Tien Pham
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Brendan J Lee
- Biological Resources Imaging Laboratory, University of New South Wales Sydney NSW Australia
| | - Rachael Shepherd
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Ivan Greguric
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Naomi Wyatt
- Australian Nuclear Science and Technology Organisation Lucas Heights NSW Australia
| | - Thanh Le
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Jackson Poon
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
| | - Carl Power
- Biological Resources Imaging Laboratory, University of New South Wales Sydney NSW Australia
| | - Michael Fulham
- Department of Molecular Imaging, Royal Prince Alfred Hospital Camperdown NSW 2050 Australia
- Faculty of Engineering and Information Technologies, University of Sydney Sydney NSW 2006 Australia
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Postlethwaite AE, Tuckey RC, Kim TK, Li W, Bhattacharya SK, Myers LK, Brand DD, Slominski AT. 20 S-Hydroxyvitamin D3, a Secosteroid Produced in Humans, Is Anti-Inflammatory and Inhibits Murine Autoimmune Arthritis. Front Immunol 2021; 12:678487. [PMID: 34276665 PMCID: PMC8278399 DOI: 10.3389/fimmu.2021.678487] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 06/15/2021] [Indexed: 12/12/2022] Open
Abstract
The ability to use large doses of vitamin D3 (D3) to chronically treat autoimmune diseases such as rheumatoid arthritis (RA) is prohibitive due to its calcemic effect which can damage vital organs. Cytochrome P450scc (CYP11A1) is able to convert D3 into the noncalcemic analog 20S-hydroxyvitamin D3 [20S(OH)D3]. We demonstrate that 20S(OH)D3 markedly suppresses clinical signs of arthritis and joint damage in a mouse model of RA. Furthermore, treatment with 20S(OH)D3 reduces lymphocyte subsets such as CD4+ T cells and CD19+ B cells leading to a significant reduction in inflammatory cytokines. The ratio of T reg cells (CD4+CD25+Foxp3+ T cells) to CD3+CD4+ T cells is increased while there is a decrease in critical complement-fixing anti-CII antibodies. Since pro-inflammatory cytokines and antibodies against type II collagen ordinarily lead to destruction of cartilage and bone, their decline explains why arthritis is attenuated by 20(OH) D3. These results provide a basis for further consideration of 20S(OH)D3 as a potential treatment for RA and other autoimmune disorders.
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Affiliation(s)
- Arnold E. Postlethwaite
- Research Service, Department of Veterans Affairs Medical Center, Memphis, TN, United States
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Robert C. Tuckey
- School of Molecular Sciences, The University of Western Australia, Perth, WA, Australia
| | - Tae-Kang Kim
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Wei Li
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Syamal K. Bhattacharya
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Linda K. Myers
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - David D. Brand
- Research Service, Department of Veterans Affairs Medical Center, Memphis, TN, United States
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Andrzej T. Slominski
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, United States
- Research Service, Department of Veterans Affairs Medical Center, Birmingham, AL, United States
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Vaht M. Variation rs6971 in the Translocator Protein Gene ( TSPO) is Associated with Aggressiveness and Impulsivity but Not with Anxiety in a Population-Representative Sample of Young Adults. The Journal of Genetic Psychology 2021; 182:149-162. [PMID: 33769215 DOI: 10.1080/00221325.2021.1896470] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Expression of the 18-kDa translocator protein (TSPO), originally identified as a peripheral benzodiazepine receptor, has been found to be altered in several psychiatric disorders. A common single nucleotide polymorphism (rs6971) in the TSPO gene leads to an amino acid substitution, Ala147Thr, which dramatically alters the affinity with which TSPO binds drug ligands. As cholesterol also binds TSPO in the same transmembrane domain, it is suggested that this substitution may impair the ability of TSPO to bind or import cholesterol, and hence may affect steroid synthesis and hypothalamic-pituitary-adrenal function. The analysis was carried out on older birth cohort (n = 655) of the longitudinal Estonian Children Personality, Behavior and Health Study sample. Anxiety, aggressive behavior, impulsiveness, and history of stressful life events were self-reported in various data collection waves. Psychiatric assessment of lifetime prevalence of anxiety disorders was carried out at 25 years of age by experienced clinical psychologists. TSPO rs6971 was genotyped in all participants. TSPO rs6971 was not associated with self-reported levels of anxiety or lifetime prevalence of anxiety disorders. However, participants homozygous for the minor A allele displayed the highest aggressiveness and dysfunctional impulsivity scores. The positive, adaptive aspect of impulsivity was sensitive to stressful life events, as the AA genotype was associated with functional impulsivity only when the participants had experienced a low number of stressful life events during childhood. TSPO rs6971 polymorphism may be related to development of aggressiveness and impulsivity by adulthood, regardless of the participants' gender.
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Affiliation(s)
- Mariliis Vaht
- Institute of Psychology, University of Tartu, Tartu, Estonia.,Institute of Genomics, University of Tartu, Tartu, Estonia
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10
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De novo Neurosteroidogenesis in Human Microglia: Involvement of the 18 kDa Translocator Protein. Int J Mol Sci 2021; 22:ijms22063115. [PMID: 33803741 PMCID: PMC8003294 DOI: 10.3390/ijms22063115] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 03/06/2021] [Accepted: 03/15/2021] [Indexed: 12/14/2022] Open
Abstract
Neuroactive steroids are potent modulators of microglial functions and are capable of counteracting their excessive reactivity. This action has mainly been ascribed to neuroactive steroids released from other sources, as microglia have been defined unable to produce neurosteroids de novo. Unexpectedly, immortalized murine microglia recently exhibited this de novo biosynthesis; herein, de novo neurosteroidogenesis was characterized in immortalized human microglia. The results demonstrated that C20 and HMC3 microglial cells constitutively express members of the neurosteroidogenesis multiprotein machinery-in particular, the transduceosome members StAR and TSPO, and the enzyme CYP11A1. Moreover, both cell lines produce pregnenolone and transcriptionally express the enzymes involved in neurosteroidogenesis. The high TSPO expression levels observed in microglia prompted us to assess its role in de novo neurosteroidogenesis. TSPO siRNA and TSPO synthetic ligand treatments were used to reduce and prompt TSPO function, respectively. The TSPO expression downregulation compromised the de novo neurosteroidogenesis and led to an increase in StAR expression, probably as a compensatory mechanism. The pharmacological TSPO stimulation the de novo neurosteroidogenesis improved in turn the neurosteroid-mediated release of Brain-Derived Neurotrophic Factor. In conclusion, these results demonstrated that de novo neurosteroidogenesis occurs in human microglia, unravelling a new mechanism potentially useful for future therapeutic purposes.
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11
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Barron AM, Higuchi M, Hattori S, Kito S, Suhara T, Ji B. Regulation of Anxiety and Depression by Mitochondrial Translocator Protein-Mediated Steroidogenesis: the Role of Neurons. Mol Neurobiol 2021; 58:550-563. [PMID: 32989676 DOI: 10.1007/s12035-020-02136-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 09/17/2020] [Indexed: 12/29/2022]
Abstract
Pharmacological studies have implicated the translocator protein (TSPO) in the regulation of complex behaviors including anxiety and depression, effects thought to be mediated by increased synthesis of neuroactive steroid hormones. However, TSPO function in the brain remains to be corroborated in vivo via genetic studies. To address this, we developed global TSPO knockout (TSPO-KO) and neuronal TSPO transgenic (TSPO-Tg) mouse models to investigate TSPO function in the regulation of anxiety- and depression-related behaviors using elevated plus maze and forced swim test paradigms. Neuroactive steroid hormones were measured in the brain by mass spectrometry. In vivo TSPO ligand pharmacokinetics was investigated using competitive PET with 18F-FE-DAA1106. Genetic TSPO deficiency increased anxiety-related behavior and impaired brain steroidogenesis but did not affect depressive behaviors. Using the TSPO-KO model, we then demonstrated the specificity of Ac-5216, also known as XBD-173 or Emapunil, as an anxiolytic targeting TSPO at doses optimized by competitive PET for high cortical occupancy. Neuronal TSPO overexpression decreased depressive behaviors, an effect that was dependent on steroidogenesis, and partially reversed anxiogenic behavior in TSPO-KO mice. These findings demonstrate that TSPO is critical for brain steroidogenesis and modulates anxiety- and depression-related behaviors. However, we demonstrate that key differences in the contribution of neuronal TSPO to the modulation of these complex behaviors, illustrating the tissue- and cell-specific importance of TSPO. The TSPO-KO and TSPO-Tg mice provide the tools and rationale for the development of therapeutic approaches targeting TSPO in the brain for treatment of neuropsychiatric conditions.
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Affiliation(s)
- Anna M Barron
- Department of Functional Brain Imaging Research, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, Singapore, 308232, Singapore
| | - Makoto Higuchi
- Department of Functional Brain Imaging Research, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Satoko Hattori
- Department of Functional Brain Imaging Research, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Seiji Kito
- Research, Development and Support Center, National Institutes for Quantum and Radiological Science and Technology, Chiba, 263-0024, Japan
| | - Tetsuya Suhara
- Department of Functional Brain Imaging Research, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Bin Ji
- Department of Functional Brain Imaging Research, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.
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12
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Microglia Implicated in Tauopathy in the Striatum of Neurodegenerative Disease Patients from Genotype to Phenotype. Int J Mol Sci 2020; 21:ijms21176047. [PMID: 32842621 PMCID: PMC7503242 DOI: 10.3390/ijms21176047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 08/19/2020] [Accepted: 08/20/2020] [Indexed: 12/12/2022] Open
Abstract
We found interactions between dopamine and oxidative damage in the striatum involved in advanced neurodegeneration, which probably change the microglial phenotype. We observed possible microglia dystrophy in the striatum of neurodegenerative brains. To investigate the interactions between oxidative damage and microglial phenotype, we quantified myeloperoxidase (MPO), poly (ADP-Ribose) (PAR), and triggering receptors expressed on myeloid cell 2 (TREM2) using enzyme-linked immunosorbent assay (ELISA). To test the correlations of microglia dystrophy and tauopathy, we quantified translocator protein (TSPO) and tau fibrils using autoradiography. We chose the caudate and putamen of Lewy body diseases (LBDs) (Parkinson’s disease, Parkinson’s disease dementia, and Dementia with Lewy body), Alzheimer’s disease (AD), and control brains and genotyped for TSPO, TREM2, and bridging integrator 1 (BIN1) genes using single nucleotide polymorphisms (SNP) assays. TREM2 gene variants were absent across all samples. However, associations between TSPO and BIN1 gene polymorphisms and TSPO, MPO, TREM2, and PAR level variations were found. PAR levels reduced significantly in the caudate of LBDs. TSPO density and tau fibrils decreased remarkably in the striatum of LBDs but increased in AD. Oxidative damage, induced by misfolded tau proteins and dopamine metabolism, causes microglia dystrophy or senescence during the late stage of LBDs. Consequently, microglia dysfunction conversely reduces tau propagation. The G allele of the BIN1 gene is a potential risk factor for tauopathy.
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13
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18-kDa translocator protein association complexes in the brain: From structure to function. Biochem Pharmacol 2020; 177:114015. [PMID: 32387458 DOI: 10.1016/j.bcp.2020.114015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 05/04/2020] [Indexed: 12/14/2022]
Abstract
The outer mitochondrial membrane 18-kDa translocator protein (TSPO) is highly conserved in organisms of different species and ubiquitously expressed throughout tissues, including the nervous system. In the healthy adult brain, TSPO expression levels are low and promptly modulated under different pathological conditions, such as cancer, inflammatory states, and neurological and psychiatric disorders. Not surprisingly, several endogenous and synthetic molecules capable of binding TSPO have been proposed as drugs or diagnostic tools for brain diseases. The most studied biochemical function of TSPO is cholesterol translocation into mitochondria, which in turn affects the synthesis of steroids in the periphery and neurosteroids in the brain. In the last 30 years, roles for TSPO have also been suggested in other cellular processes, such as heme synthesis, apoptosis, autophagy, calcium signalling and reactive oxygen species production. Herein, we provide an overview of TSPO associations with different proteins, focusing particular attention on their related functions. Furthermore, recent TSPO-targeted therapeutic interventions are explored and discussed as prospect for innovative treatments in mental and brain diseases.
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14
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Extra-adrenal glucocorticoid biosynthesis: implications for autoimmune and inflammatory disorders. Genes Immun 2020; 21:150-168. [PMID: 32203088 PMCID: PMC7276297 DOI: 10.1038/s41435-020-0096-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 03/05/2020] [Accepted: 03/09/2020] [Indexed: 12/11/2022]
Abstract
Glucocorticoid synthesis is a complex, multistep process that starts with cholesterol being delivered to the inner membrane of mitochondria by StAR and StAR-related proteins. Here its side chain is cleaved by CYP11A1 producing pregnenolone. Pregnenolone is converted to cortisol by the enzymes 3-βHSD, CYP17A1, CYP21A2 and CYP11B1. Glucocorticoids play a critical role in the regulation of the immune system and exert their action through the glucocorticoid receptor (GR). Although corticosteroids are primarily produced in the adrenal gland, they can also be produced in a number of extra-adrenal tissue including the immune system, skin, brain, and intestine. Glucocorticoid production is regulated by ACTH, CRH, and cytokines such as IL-1, IL-6 and TNFα. The bioavailability of cortisol is also dependent on its interconversion to cortisone which is inactive, by 11βHSD1/2. Local and systemic glucocorticoid biosynthesis can be stimulated by ultraviolet B, explaining its immunosuppressive activity. In this review, we want to emphasize that dysregulation of extra-adrenal glucocorticoid production can play a key role in a variety of autoimmune diseases including multiple sclerosis (MS), lupus erythematosus (LE), rheumatoid arthritis (RA), and skin inflammatory disorders such as psoriasis and atopic dermatitis (AD). Further research on local glucocorticoid production and its bioavailability may open doors into new therapies for autoimmune diseases.
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15
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Binding Affinity of Some Endogenous and Synthetic TSPO Ligands Regarding the rs6971 Polymorphism. Int J Mol Sci 2019; 20:ijms20030563. [PMID: 30699908 PMCID: PMC6387295 DOI: 10.3390/ijms20030563] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 01/22/2019] [Accepted: 01/24/2019] [Indexed: 12/15/2022] Open
Abstract
An intriguing target involved in several pathophysiological processes is the 18 kDa translocator protein (TSPO), of which exact functions remained elusive until now. A single nucleotide polymorphism in the TSPO gene influences the binding affinity of endogenous and synthetic TSPO ligands by facilitating a lower-affinity conformation, which modifies a potential ligand binding site, ultimately leading to a binding profile classification according to each genotype. For instance, some clinical effects of the distinctive binding affinity profile of cholesterol toward the TSPO of individuals with different genotypes have been extensively discussed. Therefore, we conducted an investigation based on a radioligand binding assay, to determine the inhibition constants of some reported endogenous TSPO ligands (diazepam binding inhibitor and protoporphyrin IX), as well as synthetic ligands (disulfiram and derivatives). We observed no dependency of the polymorphism on the binding affinity of the evaluated endogenous ligands, whereas a high dependency on the binding affinity of the tested synthetic ligands was evident.
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16
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Albrecht D, Ahmed S, Kettner N, Borra R, Cohen-Adad J, Deng H, Houle T, Opalacz A, Roth S, Melo MV, Chen L, Mao J, Hooker J, Loggia ML, Zhang Y. Neuroinflammation of the spinal cord and nerve roots in chronic radicular pain patients. Pain 2018; 159:968-977. [PMID: 29419657 PMCID: PMC5908728 DOI: 10.1097/j.pain.0000000000001171] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Numerous preclinical studies support the role of spinal neuroimmune activation in the pathogenesis of chronic pain, and targeting glia (eg, microglia/astrocyte)- or macrophage-mediated neuroinflammatory responses effectively prevents or reverses the establishment of persistent nocifensive behaviors in laboratory animals. However, thus far, the translation of those findings into novel treatments for clinical use has been hindered by the scarcity of data supporting the role of neuroinflammation in human pain. Here, we show that patients suffering from a common chronic pain disorder (lumbar radiculopathy), compared with healthy volunteers, exhibit elevated levels of the neuroinflammation marker 18 kDa translocator protein, in both the neuroforamina (containing dorsal root ganglion and nerve roots) and spinal cord. These elevations demonstrated a pattern of spatial specificity correlating with the patients' clinical presentation, as they were observed in the neuroforamen ipsilateral to the symptomatic leg (compared with both contralateral neuroforamen in the same patients as well as to healthy controls) and in the most caudal spinal cord segments, which are known to process sensory information from the lumbosacral nerve roots affected in these patients (compared with more superior segments). Furthermore, the neuroforaminal translocator protein signal was associated with responses to fluoroscopy-guided epidural steroid injections, supporting its role as an imaging marker of neuroinflammation, and highlighting the clinical significance of these observations. These results implicate immunoactivation at multiple levels of the nervous system as a potentially important and clinically relevant mechanism in human radicular pain, and suggest that therapies targeting immune cell activation may be beneficial for chronic pain patients.
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Affiliation(s)
- Daniel Albrecht
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114
| | - Shihab Ahmed
- MGH Translational Pain Research Center, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Norman Kettner
- Department of Radiology, Logan University, Chesterfield, MO, 63017
| | - Ronald Borra
- Medical Imaging Centre of Southwest Finland, Turku University Hospital, Turku, Finland; Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Julien Cohen-Adad
- Department of Electrical Engineering, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, Quebec, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, Quebec, Canada
| | - Hao Deng
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Timothy Houle
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Arissa Opalacz
- MGH Translational Pain Research Center, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Sarah Roth
- MGH Translational Pain Research Center, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Marcos Vidal Melo
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Lucy Chen
- MGH Translational Pain Research Center, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Jianren Mao
- MGH Translational Pain Research Center, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
| | - Jacob Hooker
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129
| | - Marco L Loggia
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129
| | - Yi Zhang
- MGH Translational Pain Research Center, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114
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17
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Milenkovic VM, Bader S, Sudria-Lopez D, Siebert R, Brandl C, Nothdurfter C, Weber BHF, Rupprecht R, Wetzel CH. Effects of genetic variants in the TSPO gene on protein structure and stability. PLoS One 2018; 13:e0195627. [PMID: 29641545 PMCID: PMC5895031 DOI: 10.1371/journal.pone.0195627] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 03/25/2018] [Indexed: 11/18/2022] Open
Abstract
The 18 kDa translocator protein (TSPO) is an evolutionary conserved cholesterol binding protein localized in the outer mitochondrial membrane. Expression of TSPO is upregulated in activated microglia in various neuroinflammatory, neurodegenerative, and neoplastic disorders. Therefore, TSPO radioligands are used as biomarkers in positron emission tomography (PET) studies. In particular, a common A147T polymorphism in the TSPO gene affects binding of several high affinity TSPO radioligands. Given the relevance of TSPO as a diagnostic biomarker in disease processes, we systematically searched for mutations in the human TSPO gene by a wide array of evolution and structure based bioinformatics tools and identified potentially deleterious missense mutations. The two most frequently observed missense mutations A147T and R162H were further analysed in structural models of human wildtype and mutant TSPO proteins. The effects of missense mutations were studied on the atomic level using molecular dynamics simulations. To analyse putative effects of A147T and R162H variants on protein stability we established primary dermal fibroblast cultures from wt and homozygous A147T and R162H donors. Stability of endogenous TSPO protein, which is abundantly expressed in fibroblasts, was studied using cycloheximide protein degradation assay. Our data show that the A147T mutation significantly alters the flexibility and stability of the mutant protein. Furthermore both A147T and R162H mutations decreased the half-life of the mutant proteins by about 25 percent, which could in part explain its effect on reduced pregnenolone production and susceptibility to neuropsychiatric disorders. The present study is the first comprehensive bioinformatic analysis of genetic variants in the TSPO gene, thereby extending the knowledge about the clinical relevance of TSPO nsSNPs.
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Affiliation(s)
- Vladimir M. Milenkovic
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, Regensburg, Germany
- * E-mail:
| | - Stefanie Bader
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, Regensburg, Germany
| | - Daniel Sudria-Lopez
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, Regensburg, Germany
| | - Ramona Siebert
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, Regensburg, Germany
| | - Caroline Brandl
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
- Department of Ophthalmology, University Hospital Regensburg, Regensburg, Germany
| | - Caroline Nothdurfter
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, Regensburg, Germany
| | | | - Rainer Rupprecht
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, Regensburg, Germany
| | - Christian H. Wetzel
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, Regensburg, Germany
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18
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Translocator protein and steroidogenesis. Biochem J 2018; 475:901-904. [PMID: 29511094 DOI: 10.1042/bcj20170766] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Revised: 01/16/2018] [Accepted: 01/18/2018] [Indexed: 02/07/2023]
Abstract
Two interesting papers by Barren et al. and Owen et al. have been very recently published in Biochemical Journal, reporting the role of translocator protein (TSPO) in steroidogenesis. The involvement of TSPO in the steroid biosynthesis has been suggested by 30 years of researches, using biochemical, pharmacological and genetic experimental approaches. In the last 3 years, however, the TSPO involvement in steroidogenesis has been intensively and profoundly discussed. Using in vivo genetic manipulations aimed at deleting TSPO, some researchers have excluded its role in steroid production. Other research groups, using similar genetic manipulation techniques, have presented different results, corroborating the role of TSPO in steroidogenesis, in particular, when hormonal stimulation occurs. In this scenario, the publications by Barron et al. about 'Steroidogenic abnormalities in translocator protein knockout mice and significance in the aging male' and by Owen et al. about 'TSPO mutations in rats and a human polymorphism impair the rate of steroid synthesis' are part of this debate and provide further and more accurate information supporting the importance of TSPO as a steroidogenesis regulator.
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19
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Prossin AR, Chandler M, Ryan KA, Saunders EF, Kamali M, Papadopoulos V, Zöllner S, Dantzer R, McInnis MG. Functional TSPO polymorphism predicts variance in the diurnal cortisol rhythm in bipolar disorder. Psychoneuroendocrinology 2018; 89:194-202. [PMID: 29414032 PMCID: PMC6048960 DOI: 10.1016/j.psyneuen.2018.01.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 01/11/2018] [Accepted: 01/17/2018] [Indexed: 12/23/2022]
Abstract
INTRODUCTION Psychosocial stress contributes to onset/exacerbation of mood episodes and alcohol use, suggesting dysregulated diurnal cortisol rhythms underlie episodic exacerbations in Bipolar Disorder (BD). However, mechanisms underlying dysregulated HPA rhythms in BD and alcohol use disorders (AUD) are understudied. Knowledge of associated variance factors have great clinical translational potential by facilitating development of strategies to reduce stress-related relapse in BD and AUD. Evidence suggests structural changes to mitochondrial translocator protein (TSPO) (a regulator of steroid synthesis) due to the single nucleotide polymorphism rs6971, may explain much of this variance. However, whether rs6971 is associated with abnormal HPA rhythms and clinical exacerbation in humans is unknown. METHODS To show this common TSPO polymorphism impacts HPA rhythms in BD, we tested whether rs6971 (dichotomized: presence/absence of polymorphism) predicted variance in diurnal cortisol rhythm (saliva: morning and evening for 3 days) in 107 BD (50 with and 57 without AUD) and 28 healthy volunteers of similar age and ethno-demographic distribution. RESULTS Repeated measures ANOVA confirmed effects BD (F5,525 = 3.0, p = 0.010) and AUD (F5,525 = 2.9, p = 0.012), but not TSPO polymorphism (p > 0.05). Interactions were confirmed for TSPO × BD (F5,525 = 3.9, p = 0.002) and for TSPO × AUD (F5,525 = 2.8, p = 0.017). DISCUSSION We identified differences in diurnal cortisol rhythm depending on presence/absence of common TSPO polymorphism in BD volunteers with or without AUD and healthy volunteers. These results have wide ranging implications but further validation is needed prior to optimal clinical translation.
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Affiliation(s)
- Alan R Prossin
- Department of Psychiatry, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA; Houston Methodist Research Institute, Houston, TX, USA.
| | - Matthew Chandler
- Department of Psychiatry, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Kelly A Ryan
- Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Erika F Saunders
- Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Psychiatry, Medical School, Penn State College of Medicine and the Milton S. Hershey Medical Center, Hershey, PA, USA
| | - Masoud Kamali
- Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA
| | | | - Sebastian Zöllner
- Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Robert Dantzer
- Department of Symptom Research, Division of Internal Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Melvin G McInnis
- Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI, USA
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20
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Steroidogenic abnormalities in translocator protein knockout mice and significance in the aging male. Biochem J 2018; 475:75-85. [PMID: 29127254 DOI: 10.1042/bcj20170645] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 11/07/2017] [Accepted: 11/09/2017] [Indexed: 11/17/2022]
Abstract
The translocator protein (TSPO) has been proposed to act as a key component in a complex important for mitochondrial cholesterol importation, which is the rate-limiting step in steroid hormone synthesis. However, TSPO function in steroidogenesis has recently been challenged by the development of TSPO knockout (TSPO-KO) mice, as they exhibit normal baseline gonadal testosterone and adrenal corticosteroid production. Here, we demonstrate that despite normal androgen levels in young male TSPO-KO mice, TSPO deficiency alters steroidogenic flux and results in reduced total steroidogenic output. Specific reductions in the levels of progesterone and corticosterone as well as age-dependent androgen deficiency were observed in both young and aged male TSPO-KO mice. Collectively, these findings indicate that while TSPO is not critical for achieving baseline testicular and adrenal steroidogenesis, either indirect effects of TSPO on steroidogenic processes, or compensatory mechanisms and functional redundancy, lead to subtle steroidogenic abnormalities which become exacerbated with aging.
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21
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Frankle WG, Narendran R, Wood AT, Suto F, Himes ML, Kobayashi M, Ohno T, Yamauchi A, Mitsui K, Duffy K, Bruce M. Brain translocator protein occupancy by ONO-2952 in healthy adults: A Phase 1 PET study using [11C]PBR28. Synapse 2017; 71. [DOI: 10.1002/syn.21970] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 02/10/2017] [Accepted: 02/22/2017] [Indexed: 11/12/2022]
Affiliation(s)
- W. Gordon Frankle
- Department of Psychiatry; NYU Langone Medical Center; New York New York
| | - Rajesh Narendran
- Department of Psychiatry; University of Pittsburgh; Pittsburgh Pennsylvania
- Department of Radiology; University of Pittsburgh; Pittsburgh Pennsylvania
| | | | | | - Michael L. Himes
- Department of Psychiatry; University of Pittsburgh; Pittsburgh Pennsylvania
| | | | | | | | | | | | - Mark Bruce
- Ono Pharma UK Ltd; London United Kingdom
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Ghadery C, Koshimori Y, Coakeley S, Harris M, Rusjan P, Kim J, Houle S, Strafella AP. Microglial activation in Parkinson's disease using [ 18F]-FEPPA. J Neuroinflammation 2017; 14:8. [PMID: 28086916 PMCID: PMC5234135 DOI: 10.1186/s12974-016-0778-1] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 12/13/2016] [Indexed: 11/12/2022] Open
Abstract
Background Neuroinflammatory processes including activated microglia have been reported to play an important role in Parkinson’s disease (PD). Increased expression of translocator protein (TSPO) has been observed after brain injury and inflammation in neurodegenerative diseases. Positron emission tomography (PET) radioligand targeting TSPO allows for the quantification of neuroinflammation in vivo. Methods Based on the genotype of the rs6791 polymorphism in the TSPO gene, we included 25 mixed-affinity binders (MABs) (14 PD patients and 11 age-matched healthy controls (HC)) and 27 high-affinity binders (HABs) (16 PD patients and 11 age-matched HC) to assess regional differences in the second-generation radioligand [18F]-FEPPA between PD patients and HC. FEPPA total distribution volume (VT) values in cortical as well as subcortical brain regions were derived from a two-tissue compartment model with arterial plasma as an input function. Results Our results revealed a significant main effect of genotype on [18F]-FEPPA VT in every brain region, but no main effect of disease or disease × genotype interaction in any brain region. The overall percentage difference of the mean FEPPA VT between HC-MABs and HC-HABs was 32.6% (SD = 2.09) and for PD-MABs and PD-HABs was 43.1% (SD = 1.21). Conclusions Future investigations are needed to determine the significance of [18F]-FEPPA as a biomarker of neuroinflammation as well as the importance of the rs6971 polymorphism and its clinical consequence in PD.
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Affiliation(s)
- Christine Ghadery
- Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.,Division of Brain, Imaging and Behaviour - Systems Neuroscience, Krembil Research Institute, UHN, University of Toronto, Ontario, Canada
| | - Yuko Koshimori
- Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.,Division of Brain, Imaging and Behaviour - Systems Neuroscience, Krembil Research Institute, UHN, University of Toronto, Ontario, Canada
| | - Sarah Coakeley
- Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.,Division of Brain, Imaging and Behaviour - Systems Neuroscience, Krembil Research Institute, UHN, University of Toronto, Ontario, Canada
| | - Madeleine Harris
- Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Pablo Rusjan
- Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Jinhee Kim
- Neurology Division, Department of Medicine, Morton and Gloria Shulman Movement Disorder Unit & E.J. Safra Parkinson Disease Program, Toronto Western Hospital, UHN, University of Toronto, Ontario, Canada.,Division of Brain, Imaging and Behaviour - Systems Neuroscience, Krembil Research Institute, UHN, University of Toronto, Ontario, Canada
| | - Sylvain Houle
- Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Antonio P Strafella
- Neurology Division, Department of Medicine, Morton and Gloria Shulman Movement Disorder Unit & E.J. Safra Parkinson Disease Program, Toronto Western Hospital, UHN, University of Toronto, Ontario, Canada. .,Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada. .,Division of Brain, Imaging and Behaviour - Systems Neuroscience, Krembil Research Institute, UHN, University of Toronto, Ontario, Canada. .,Toronto Western Hospital and Institute, CAMH-Research Imaging Centre, University of Toronto, Toronto, Ontario, M5T 2S8, Canada.
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23
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Kosek E, Martinsen S, Gerdle B, Mannerkorpi K, Löfgren M, Bileviciute-Ljungar I, Fransson P, Schalling M, Ingvar M, Ernberg M, Jensen KB. The translocator protein gene is associated with symptom severity and cerebral pain processing in fibromyalgia. Brain Behav Immun 2016; 58:218-227. [PMID: 27448744 DOI: 10.1016/j.bbi.2016.07.150] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 06/17/2016] [Accepted: 07/19/2016] [Indexed: 12/12/2022] Open
Abstract
The translocator protein (TSPO) is upregulated during glia activation in chronic pain patients. TSPO constitutes the rate-limiting step in neurosteroid synthesis, thus modulating synaptic transmission. Related serotonergic mechanisms influence if pro- or anti-nociceptive neurosteroids are produced. This study investigated the effects of a functional genetic polymorphism regulating the binding affinity to the TSPO, thus affecting symptom severity and cerebral pain processing in fibromyalgia patients. Gene-to-gene interactions with a functional polymorphism of the serotonin transporter gene were assessed. Fibromyalgia patients (n=126) were genotyped regarding the polymorphisms of the TSPO (rs6971) and the serotonin transporter (5-HTTLPR/rs25531). Functional magnetic resonance imaging (n=24) was used to study brain activation during individually calibrated pressure pain. Compared to mixed/low TSPO affinity binders, the high TSPO affinity binders rated more severe pain (p=0.016) and fibromyalgia symptoms (p=0.02). A significant interaction was found between the TSPO and the serotonin transporter polymorphisms regarding pain severity (p<0.0001). Functional connectivity analyses revealed that the TSPO high affinity binding group had more pronounced pain-evoked functional connectivity in the right frontoparietal network, between the dorsolateral prefrontal area and the parietal cortex. In conclusion, fibromyalgia patients with the TSPO high affinity binding genotype reported a higher pain intensity and more severe fibromyalgia symptoms compared to mixed/low affinity binders, and this was modulated by interaction with the serotonin transporter gene. To our knowledge this is the first evidence of functional genetic polymorphisms affecting pain severity in FM and our findings are in line with proposed glia-related mechanisms. Furthermore, the functional magnetic resonance findings indicated an effect of translocator protein on the affective-motivational components of pain perception.
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Affiliation(s)
- Eva Kosek
- Department of Clinical Neuroscience and Osher Center, Karolinska Insitutet, Department of Neuroradiology, Karolinska University Hospital, SE-171 77 Stockholm, Sweden; Stockholm Spine Center, Löwenströmska Hospital, 198 84 Upplands Väsby, Sweden.
| | - Sofia Martinsen
- Department of Clinical Neuroscience and Osher Center, Karolinska Insitutet, Department of Neuroradiology, Karolinska University Hospital, SE-171 77 Stockholm, Sweden.
| | - Björn Gerdle
- Pain and Rehabilitation Centre, and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
| | - Kaisa Mannerkorpi
- Department of Health and Rehabilitation/Physiotherapy, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden; University of Gothenburg Centre for Person-centred Care (GPCC), Sahlgrenska Academy, Gothenburg, Sweden.
| | - Monika Löfgren
- Department of Clinical Sciences, Karolinska Institutet and Department of Rehabilitation Medicine, Danderyd Hospital, SE-182 88 Stockholm, Sweden.
| | - Indre Bileviciute-Ljungar
- Department of Clinical Sciences, Karolinska Institutet and Department of Rehabilitation Medicine, Danderyd Hospital, SE-182 88 Stockholm, Sweden.
| | - Peter Fransson
- Department of Clinical Neuroscience and Osher Center, Karolinska Insitutet, Department of Neuroradiology, Karolinska University Hospital, SE-171 77 Stockholm, Sweden.
| | - Martin Schalling
- Department of Molecular Medicine and Surgery, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
| | - Martin Ingvar
- Department of Clinical Neuroscience and Osher Center, Karolinska Insitutet, Department of Neuroradiology, Karolinska University Hospital, SE-171 77 Stockholm, Sweden.
| | - Malin Ernberg
- Department of Dental Medicine, Karolinska Institutet, and Scandinavian Center for Orofacial Neurosciences (SCON), SE-141 04 Huddinge, Sweden.
| | - Karin B Jensen
- Department of Clinical Neuroscience and Osher Center, Karolinska Insitutet, Department of Neuroradiology, Karolinska University Hospital, SE-171 77 Stockholm, Sweden.
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24
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Selvaraj V, Tu LN. Current status and future perspectives: TSPO in steroid neuroendocrinology. J Endocrinol 2016; 231:R1-R30. [PMID: 27422254 DOI: 10.1530/joe-16-0241] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 07/15/2016] [Indexed: 12/21/2022]
Abstract
The mitochondrial translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), has received significant attention both as a diagnostic biomarker and as a therapeutic target for different neuronal disease pathologies. Recently, its functional basis believed to be mediating mitochondrial cholesterol import for steroid hormone production has been refuted by studies examining both in vivo and in vitro genetic Tspo-deficient models. As a result, there now exists a fundamental gap in the understanding of TSPO function in the nervous system, and its putative pharmacology in neurosteroid production. In this review, we discuss several recent findings in steroidogenic cells that are in direct contradiction to previous studies, and necessitate a re-examination of the purported role for TSPO in de novo neurosteroid biosynthesis. We critically examine the pharmacological effects of different TSPO-binding drugs with particular focus on studies that measure neurosteroid levels. We highlight the basis of key misconceptions regarding TSPO that continue to pervade the literature, and the need for interpretation with caution to avoid negative impacts. We also summarize the emerging perspectives that point to new directions that need to be investigated for understanding the molecular function of TSPO, only after which the true potential of this therapeutic target in medicine may be realized.
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Affiliation(s)
- Vimal Selvaraj
- Department of Animal ScienceCornell University, Ithaca, New York, USA
| | - Lan N Tu
- Department of Animal ScienceCornell University, Ithaca, New York, USA
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25
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Li F, Liu J, Liu N, Kuhn LA, Garavito RM, Ferguson-Miller S. Translocator Protein 18 kDa (TSPO): An Old Protein with New Functions? Biochemistry 2016; 55:2821-31. [PMID: 27074410 DOI: 10.1021/acs.biochem.6b00142] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Translocator protein 18 kDa (TSPO) was previously known as the peripheral benzodiazepine receptor (PBR) in eukaryotes, where it is mainly localized to the mitochondrial outer membrane. Considerable evidence indicates that it plays regulatory roles in steroidogenesis and apoptosis and is involved in various human diseases, such as metastatic cancer, Alzheimer's and Parkinson's disease, inflammation, and anxiety disorders. Ligands of TSPO are widely used as diagnostic tools and treatment options, despite there being no clear understanding of the function of TSPO. An ortholog in the photosynthetic bacterium Rhodobacter was independently discovered as the tryptophan-rich sensory protein (TspO) and found to play a role in the response to changes in oxygen and light conditions that regulate photosynthesis and respiration. As part of this highly conserved protein family found in all three kingdoms, the rat TSPO is able to rescue the knockout phenotype in Rhodobacter, indicating functional as well as structural conservation. Recently, a major breakthrough in the field was achieved: the determination of atomic-resolution structures of TSPO from different species by several independent groups. This now allows us to reexamine the function of TSPO with a molecular perspective. In this review, we focus on recently determined structures of TSPO and their implications for potential functions of this ubiquitous multifaceted protein. We suggest that TSPO is an ancient bacterial receptor/stress sensor that has developed additional interactions, partners, and roles in its mitochondrial outer membrane environment in eukaryotes.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Molecular Biology, Michigan State University , East Lansing, Michigan 48824, United States
| | - Jian Liu
- Department of Biochemistry and Molecular Biology, Michigan State University , East Lansing, Michigan 48824, United States
| | - Nan Liu
- Department of Biochemistry and Molecular Biology, Michigan State University , East Lansing, Michigan 48824, United States.,Department of Computer Science and Engineering, Michigan State University , East Lansing, Michigan 48824-1319, United States.,Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1319, United States
| | - Leslie A Kuhn
- Department of Biochemistry and Molecular Biology, Michigan State University , East Lansing, Michigan 48824, United States.,Department of Computer Science and Engineering, Michigan State University , East Lansing, Michigan 48824-1319, United States
| | - R Michael Garavito
- Department of Biochemistry and Molecular Biology, Michigan State University , East Lansing, Michigan 48824, United States
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology, Michigan State University , East Lansing, Michigan 48824, United States
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26
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TSPO: kaleidoscopic 18-kDa amid biochemical pharmacology, control and targeting of mitochondria. Biochem J 2016; 473:107-21. [PMID: 26733718 DOI: 10.1042/bj20150899] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The 18-kDa translocator protein (TSPO) localizes in the outer mitochondrial membrane (OMM) of cells and is readily up-regulated under various pathological conditions such as cancer, inflammation, mechanical lesions and neurological diseases. Able to bind with high affinity synthetic and endogenous ligands, its core biochemical function resides in the translocation of cholesterol into the mitochondria influencing the subsequent steps of (neuro-)steroid synthesis and systemic endocrine regulation. Over the years, however, TSPO has also been linked to core cellular processes such as apoptosis and autophagy. It interacts and forms complexes with other mitochondrial proteins such as the voltage-dependent anion channel (VDAC) via which signalling and regulatory transduction of these core cellular events may be influenced. Despite nearly 40 years of study, the precise functional role of TSPO beyond cholesterol trafficking remains elusive even though the recent breakthroughs on its high-resolution crystal structure and contribution to quality-control signalling of mitochondria. All this along with a captivating pharmacological profile provides novel opportunities to investigate and understand the significance of this highly conserved protein as well as contribute the development of specific therapeutics as presented and discussed in the present review.
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27
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Porcu P, Barron AM, Frye CA, Walf AA, Yang SY, He XY, Morrow AL, Panzica GC, Melcangi RC. Neurosteroidogenesis Today: Novel Targets for Neuroactive Steroid Synthesis and Action and Their Relevance for Translational Research. J Neuroendocrinol 2016; 28:12351. [PMID: 26681259 PMCID: PMC4769676 DOI: 10.1111/jne.12351] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 12/12/2015] [Accepted: 12/12/2015] [Indexed: 12/19/2022]
Abstract
Neuroactive steroids are endogenous neuromodulators synthesised in the brain that rapidly alter neuronal excitability by binding to membrane receptors, in addition to the regulation of gene expression via intracellular steroid receptors. Neuroactive steroids induce potent anxiolytic, antidepressant, anticonvulsant, sedative, analgesic and amnesic effects, mainly through interaction with the GABAA receptor. They also exert neuroprotective, neurotrophic and antiapoptotic effects in several animal models of neurodegenerative diseases. Neuroactive steroids regulate many physiological functions, such as the stress response, puberty, the ovarian cycle, pregnancy and reward. Their levels are altered in several neuropsychiatric and neurological diseases and both preclinical and clinical studies emphasise a therapeutic potential of neuroactive steroids for these diseases, whereby symptomatology ameliorates upon restoration of neuroactive steroid concentrations. However, direct administration of neuroactive steroids has several challenges, including pharmacokinetics, low bioavailability, addiction potential, safety and tolerability, which limit its therapeutic use. Therefore, modulation of neurosteroidogenesis to restore the altered endogenous neuroactive steroid tone may represent a better therapeutic approach. This review summarises recent approaches that target the neuroactive steroid biosynthetic pathway at different levels aiming to promote neurosteroidogenesis. These include modulation of neurosteroidogenesis through ligands of the translocator protein 18 kDa and the pregnane xenobiotic receptor, as well as targeting of specific neurosteroidogenic enzymes such as 17β-hydroxysteroid dehydrogenase type 10 or P450 side chain cleavage. Enhanced neurosteroidogenesis through these targets may be beneficial not only for neurodegenerative diseases, such as Alzheimer's disease and age-related dementia, but also for neuropsychiatric diseases, including alcohol use disorders.
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Affiliation(s)
- Patrizia Porcu
- Neuroscience Institute, National Research Council of Italy (CNR), Cagliari, Italy
| | - Anna M. Barron
- Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Inage-ku, Chiba, Japan
| | - Cheryl Anne Frye
- Institute of Arctic Biology, The University of Alaska–Fairbanks, Fairbanks, AK, USA
- The University at Albany, Albany, NY, USA
| | - Alicia A. Walf
- Institute of Arctic Biology, The University of Alaska–Fairbanks, Fairbanks, AK, USA
- The University at Albany, Albany, NY, USA
- Department of Cognitive Science, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Song-Yu Yang
- Department of Developmental Biochemistry, NYS Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA
| | - Xue-Ying He
- Department of Developmental Biochemistry, NYS Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA
| | - A. Leslie Morrow
- Departments of Psychiatry and Pharmacology, Bowles Center for Alcohol Studies, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| | - Gian Carlo Panzica
- Department of Neuroscience, University of Turin, and NICO - Neuroscience Institute Cavalieri Ottolenghi, Orbassano, Italy
| | - Roberto C. Melcangi
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy
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28
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Midzak A, Papadopoulos V. Adrenal Mitochondria and Steroidogenesis: From Individual Proteins to Functional Protein Assemblies. Front Endocrinol (Lausanne) 2016; 7:106. [PMID: 27524977 PMCID: PMC4965458 DOI: 10.3389/fendo.2016.00106] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 07/18/2016] [Indexed: 12/13/2022] Open
Abstract
The adrenal cortex is critical for physiological function as the central site of glucocorticoid and mineralocorticoid synthesis. It possesses a great degree of specialized compartmentalization at multiple hierarchical levels, ranging from the tissue down to the molecular levels. In this paper, we discuss this functionalization, beginning with the tissue zonation of the adrenal cortex and how this impacts steroidogenic output. We then discuss the cellular biology of steroidogenesis, placing special emphasis on the mitochondria. Mitochondria are classically known as the "powerhouses of the cell" for their central role in respiratory adenosine triphosphate synthesis, and attention is given to mitochondrial electron transport, in both the context of mitochondrial respiration and mitochondrial steroid metabolism. Building on work demonstrating functional assembly of large protein complexes in respiration, we further review research demonstrating a role for multimeric protein complexes in mitochondrial cholesterol transport, steroidogenesis, and mitochondria-endoplasmic reticulum contact. We aim to highlight with this review the shift in steroidogenic cell biology from a focus on the actions of individual proteins in isolation to the actions of protein assemblies working together to execute cellular functions.
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Affiliation(s)
- Andrew Midzak
- Research Institute of the McGill University, Montreal, QC, Canada
- *Correspondence: Andrew Midzak, ; Vassilios Papadopoulos,
| | - Vassilios Papadopoulos
- Research Institute of the McGill University, Montreal, QC, Canada
- Department of Biochemistry, McGill University, Montreal, QC, Canada
- Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
- *Correspondence: Andrew Midzak, ; Vassilios Papadopoulos,
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29
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30
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Arbo BD, Benetti F, Garcia-Segura LM, Ribeiro MF. Therapeutic actions of translocator protein (18 kDa) ligands in experimental models of psychiatric disorders and neurodegenerative diseases. J Steroid Biochem Mol Biol 2015. [PMID: 26200949 DOI: 10.1016/j.jsbmb.2015.07.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Translocator protein (TSPO) is an 18kDa protein located at contact sites between the outer and the inner mitochondrial membrane. Numerous studies have associated TSPO with the translocation of cholesterol across the aqueous mitochondrial intermembrane space and the regulation of steroidogenesis, as well as with the control of some other mitochondrial functions, such as mitochondrial respiration, mitochondrial permeability transition pore opening, apoptosis and cell proliferation. In the brain, changes in TSPO expression occur in several neuropathological conditions including neurodegenerative diseases and psychiatric disorders. Furthermore, TSPO ligands have been shown to promote neuroprotection in animal models of brain pathology. At least in some cases, the mechanisms of neuroprotection are associated with modifications in brain steroidogenesis. In addition, regulation of neuroinflammation seems to be a common mechanism in the neuroprotective actions of TSPO ligands in different animal models of brain pathology.
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Affiliation(s)
- B D Arbo
- Laboratório de Interação Neuro-Humoral, Department of Physiology, ICBS, Universidade Federal do Rio Grande do Sul (UFRGS), Rua Sarmento Leite, 500, CEP 90050-170 Porto Alegre, RS, Brazil; Cajal Institute, CSIC, Avenida Doctor Arce, 37, 28002 Madrid, Spain.
| | - F Benetti
- Laboratório de Neurofisiologia Cognitiva e do Desenvolvimento, Department of Physiology, ICBS, Universidade Federal do Rio Grande do Sul (UFRGS), Rua Sarmento Leite, 500, CEP 90050-170 Porto Alegre, RS, Brazil
| | | | - M F Ribeiro
- Laboratório de Interação Neuro-Humoral, Department of Physiology, ICBS, Universidade Federal do Rio Grande do Sul (UFRGS), Rua Sarmento Leite, 500, CEP 90050-170 Porto Alegre, RS, Brazil
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31
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Narlawar R, Werry EL, Scarf AM, Hanani R, Chua SW, King VA, Barron ML, Martins RN, Ittner LM, Rendina LM, Kassiou M. First Demonstration of Positive Allosteric-like Modulation at the Human Wild Type Translocator Protein (TSPO). J Med Chem 2015; 58:8743-9. [PMID: 26461041 DOI: 10.1021/acs.jmedchem.5b01288] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We show that changing the number and position of nitrogen atoms in the heteroatomic core of a pyrazolopyrimidine acetamide is sufficient to induce complex binding to wild type human TSPO. Only compounds with this complex binding profile lacked intrinsic effect on glioblastoma proliferation but positively modulated the antiproliferative effects of a synthetic TSPO ligand. To the best of our knowledge this is the first demonstration of allosteric-like interaction at the wild type human TSPO.
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Affiliation(s)
| | | | | | | | - Sook Wern Chua
- Dementia Research Unit, School of Medical Sciences, University of New South Wales , Sydney, NSW 2052, Australia
| | | | | | - Ralph N Martins
- School of Medical Sciences, Edith Cowan University , Joondalup, WA 6027, Australia
| | - Lars M Ittner
- Dementia Research Unit, School of Medical Sciences, University of New South Wales , Sydney, NSW 2052, Australia
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32
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Koshimori Y, Ko JH, Mizrahi R, Rusjan P, Mabrouk R, Jacobs MF, Christopher L, Hamani C, Lang AE, Wilson AA, Houle S, Strafella AP. Imaging Striatal Microglial Activation in Patients with Parkinson's Disease. PLoS One 2015; 10:e0138721. [PMID: 26381267 PMCID: PMC4575151 DOI: 10.1371/journal.pone.0138721] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 09/02/2015] [Indexed: 01/22/2023] Open
Abstract
This study investigated whether the second-generation translocator protein 18kDa (TSPO) radioligand, [18F]-FEPPA, could be used in neurodegenerative parkinsonian disorders as a biomarker for detecting neuroinflammation in the striatum. Neuroinflammation has been implicated as a potential mechanism for the progression of Parkinson’s disease (PD). Positron Emission Tomography (PET) radioligand targeting for TSPO allows for the quantification of neuroinflammation in vivo. Based on genotype of the rs6791 polymorphism in the TSPO gene, 16 mixed-affinity binders (MABs) (8 PD and age-matched 8 healthy controls (HCs)), 16 high-affinity binders (HABs) (8 PD and age-matched 8 HCs) and 4 low-affinity binders (LABs) (3 PD and 1 HCs) were identified. Total distribution volume (VT) values in the striatum were derived from a two-tissue compartment model with arterial plasma as an input function. There was a significant main effect of genotype on [18F]-FEPPA VT values in the caudate nucleus (p = 0.001) and putamen (p < 0.001), but no main effect of disease or disease x genotype interaction in either ROI. In the HAB group, the percentage difference between PD and HC was 16% in both caudate nucleus and putamen; in the MAB group, it was -8% and 3%, respectively. While this PET study showed no evidence of increased striatal TSPO expression in PD patients, the current findings provide some insights on the possible interactions between rs6791 polymorphism and neuroinflammation in PD.
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Affiliation(s)
- Yuko Koshimori
- Division of Brain, Imaging and Behaviour—Systems Neuroscience, Toronto Western Research Institute, University Hospital Network, University of Toronto, Toronto, Ontario, Canada
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Ji-Hyun Ko
- Department of Human Anatomy and Cell Science, Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Romina Mizrahi
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Pablo Rusjan
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Rostom Mabrouk
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Mark F. Jacobs
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Leigh Christopher
- Division of Brain, Imaging and Behaviour—Systems Neuroscience, Toronto Western Research Institute, University Hospital Network, University of Toronto, Toronto, Ontario, Canada
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Clement Hamani
- Division of Neurosurgery, Toronto Western Hospital, University Hospital Network, University of Toronto, Toronto, Ontario, Canada
| | - Anthony E. Lang
- Morton and Gloria Shulman Movement Disorder Unit & Edmond.J. Safra Program in Parkinson Disease, Toronto Western Hospital, University Hospital Network, University of Toronto, Toronto, Ontario, Canada
| | - Alan A. Wilson
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Sylvain Houle
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
| | - Antonio P. Strafella
- Division of Brain, Imaging and Behaviour—Systems Neuroscience, Toronto Western Research Institute, University Hospital Network, University of Toronto, Toronto, Ontario, Canada
- Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada
- Morton and Gloria Shulman Movement Disorder Unit & Edmond.J. Safra Program in Parkinson Disease, Toronto Western Hospital, University Hospital Network, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Abstract
The translocator protein (TSPO; 18k Da) is an evolutionarily conserved outer mitochondrial membrane (OMM) protein highly expressed in steroid-synthesizing cells and found to possess a number of physiological and drug-binding partners. Extensive pharmacological, biochemical and cell biological research over the years has led to a model of TSPO involvement in mitochondrial cholesterol transport and promotion of steroid synthesis, a model guiding the design of drugs useful in stimulating neurosteroid synthesis and alleviating psychopathological symptoms. The involvement of TSPO in these processes has been called into question; however, with the publication of TSPO-deletion mouse models which saw no changes in steroid production. Here, we review work characterizing TSPO in steroidogenesis and offer perspective to research into TSPO pharmacology and its involvement in steroid biosynthesis.
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34
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Enigmatic Translocator protein (TSPO) and cellular stress regulation. Trends Biochem Sci 2015; 40:497-503. [PMID: 26228316 DOI: 10.1016/j.tibs.2015.07.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 06/25/2015] [Accepted: 07/06/2015] [Indexed: 11/23/2022]
Abstract
Translocator proteins (TSPOs) are conserved, ubiquitous membrane proteins identified initially as benzodiazepine-binding proteins in mammalian cells. Recent genetic and biochemical studies have challenged the accepted model that TSPOs are essential and required for steroidogenesis in animal cells. Instead, evidence from different kingdoms of life suggests that TSPOs are encoded by nonessential genes that are temporally upregulated in cells encountering conditions of oxidative stress, including inflammation and tissue injury. Here we discuss how TSPOs may be involved in complex homeostasis signaling mechanisms. We suggest that the main physiological role of TSPOs may be to modulate oxidative stress, irrespective of the cell type or subcellular localization, in part through the subtle regulation of tetrapyrrole metabolism.
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Papadopoulos V, Aghazadeh Y, Fan J, Campioli E, Zirkin B, Midzak A. Translocator protein-mediated pharmacology of cholesterol transport and steroidogenesis. Mol Cell Endocrinol 2015; 408:90-8. [PMID: 25818881 PMCID: PMC4417383 DOI: 10.1016/j.mce.2015.03.014] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 03/16/2015] [Accepted: 03/17/2015] [Indexed: 12/17/2022]
Abstract
Steroidogenesis begins with cholesterol transfer into mitochondria through the transduceosome, a complex composed of cytosolic proteins that include steroidogenesis acute regulatory protein (STAR), 14-3-3 adaptor proteins, and the outer mitochondrial membrane proteins Translocator Protein (TSPO) and Voltage-Dependent Anion Channel (VDAC). TSPO is a drug- and cholesterol-binding protein found at particularly high levels in steroid synthesizing cells. Its aberrant expression has been linked to cancer, neurodegeneration, neuropsychiatric disorders and primary hypogonadism. Brain steroids serve as local regulators of neural development and excitability. Reduced levels of these steroids have been linked to depression, anxiety and neurodegeneration. Reduced serum testosterone is common among subfertile young men and aging men, and is associated with depression, metabolic syndrome and reduced sexual function. Although testosterone-replacement therapy is available, there are undesired side-effects. TSPO drug ligands have been proposed as therapeutic agents to regulate steroid levels in the brain and testis.
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Affiliation(s)
- Vassilios Papadopoulos
- The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada; Department of Medicine, McGill University, Montreal, Quebec, Canada; Department of Pharmacology & Therapeutics, McGill University, Montreal, Quebec, Canada; Departments of Biochemistry, McGill University, Montreal, Quebec, Canada.
| | - Yasaman Aghazadeh
- The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada; Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Jinjiang Fan
- The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada; Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Enrico Campioli
- The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada; Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Barry Zirkin
- Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA
| | - Andrew Midzak
- The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada; Departments of Biochemistry, McGill University, Montreal, Quebec, Canada
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Jaremko M, Jaremko Ł, Giller K, Becker S, Zweckstetter M. Structural Integrity of the A147T Polymorph of Mammalian TSPO. Chembiochem 2015; 16:1483-9. [PMID: 25974690 DOI: 10.1002/cbic.201500217] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Indexed: 01/27/2023]
Abstract
Ligands of the transmembrane protein TSPO are used for imaging of brain inflammation, but a common polymorphism in TSPO complicates their application to humans. Here we determined the three-dimensional structure and side-chain dynamics of the A147T polymorph of mammalian TSPO in complex with the first-generation ligand PK11195. We show that A147T TSPO is able to retain the same structural and dynamic profile as the wild-type protein and thus binds PK11195 with comparable affinity. Our study is important for the design of more potent diagnostic and therapeutic ligands of TSPO.
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Affiliation(s)
- Mariusz Jaremko
- Department for NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen (Germany)
| | - Łukasz Jaremko
- Department for NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen (Germany).,German Center for Neurodegenerative Diseases (DZNE), 37077 Göttingen (Germany)
| | - Karin Giller
- Department for NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen (Germany)
| | - Stefan Becker
- Department for NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen (Germany)
| | - Markus Zweckstetter
- Department for NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen (Germany). .,German Center for Neurodegenerative Diseases (DZNE), 37077 Göttingen (Germany). .,DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University Medical Center Göttingen, 37073 Göttingen (Germany).
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Conditional steroidogenic cell-targeted deletion of TSPO unveils a crucial role in viability and hormone-dependent steroid formation. Proc Natl Acad Sci U S A 2015; 112:7261-6. [PMID: 26039990 DOI: 10.1073/pnas.1502670112] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Translocator protein (TSPO) is a key member of the mitochondrial cholesterol transport complex in steroidogenic tissues. To assess the function of TSPO, we generated two lines of Cre-mediated Tspo conditional knockout (cKO) mice. First, gonadal somatic cell-targeting Amhr2-Cre mice were crossed with Tspo-floxed mice to obtain F1 Tspo Amhr2 cKO mice (Tspo(fl/fl);Amhr2-Cre(/+)). The unexpected Mendelian ratio of 4.4% cKO mice was confirmed by genotyping of 12.5-day-postcoitum (dpc) embryos. As Amhr2-Cre is expressed in gonads at 12.5 dpc, these findings suggest preimplantation selection of embryos. Analysis of expression databases revealed elevated levels of Amhr2 in two- and eight-cell zygotes, suggesting ectopic Tspo silencing before the morula stage and demonstrating elevated embryonic lethality and involvement of TSPO in embryonic development. To circumvent this issue, steroidogenic cell-targeting Nr5a1-Cre mice were crossed with Tspo-floxed mice. The resulting Tspo(fl/fl);Nr5a1-Cre(/+) mice were born at a normal Mendelian ratio. Nr5a1-driven Tspo cKO mice exhibited highly reduced Tspo levels in adrenal cortex and gonads. Treatment of mice with human chorionic gonadotropin (hCG) resulted in increased circulating testosterone levels despite extensive lipid droplet depletion. In contrast, Nr5a1-driven Tspo cKO mice lost their ability to form corticosterone in response to adrenocorticotropic hormone (ACTH). Important for ACTH-dependent steroidogenesis, Mc2r, Stard1, and Cypa11a1 levels were unaffected, whereas Scarb1 levels were increased and accumulation of lipid droplets was observed, indicative of a blockade of cholesterol utilization for steroidogenesis. TSPO expression in the adrenal medulla and increased epinephrine production were also observed. In conclusion, TSPO was found necessary for preimplantation embryo development and ACTH-stimulated steroid biosynthesis.
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2-Phenylimidazo[1,2-a]pyridine-containing ligands of the 18-kDa translocator protein (TSPO) behave as agonists and antagonists of steroidogenesis in a mouse leydig tumor cell line. Eur J Pharm Sci 2015; 76:231-7. [PMID: 26002041 DOI: 10.1016/j.ejps.2015.05.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 05/04/2015] [Accepted: 05/19/2015] [Indexed: 12/20/2022]
Abstract
Ligands of 18-kDa translocator protein (TSPO) are known for their ability to potently and dose-dependently stimulate steroid biosynthesis in steroidogenic cells. In this study, we investigated a number of 2-phenyl-imidazo[1,2-a]pyridine acetamide derivatives, analogs of alpidem, for their ability to bind TSPO and to affect steroidogenesis in a mouse Leydig tumor cell line. We observed that not only some compounds behaved as agonists, stimulating steroidogenesis (e.g., 3 and 4) with EC50 values (15.9 and 6.99μM) close to that determined for FGIN-1-27 used as positive control (7.24μM), but two compounds, namely 5 and 6, which on the other hand are the most lipophilic ones in the investigated series, behaved as antagonists, by significantly inhibiting steroid production at concentrations at least twenty times lower than the cytotoxic ones. To our surprise, the newly synthesized compound 3, which is a strict analog of alpidem bearing at the para position of the 2-phenyl group a methoxy group instead of chlorine, achieved a ten-fold stimulation of the steroid production (for comparison FGIN-1-27 achieved 1.6-fold stimulation). Within the limits of the examined property space, some unprecedented SARs were unveiled, which can help in understanding the key molecular factors underlying the transition from agonism to antagonism in the steroidogenesis process. Besides the substitution pattern and the physicochemical features (mainly hydrogen bonding potential) of the substituents at the positions C(6) and C(8) of the imidazo[1,2-a]pyridine nucleus, and at the para position of the 2-phenyl group, the structure-activity relationship analysis suggested lipophilicity, whose increase seems to be generally related to steroidogenesis inhibition, and steric hindrance, which appeared as a stimulation-limiting factor, as two main properties to control in the design or optimization of novel imidazo[1,2-a]pyridine-based TSPO ligands endowed with potential in modulating the steroidogenesis process.
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Li F, Liu J, Garavito RM, Ferguson-Miller S. Evolving understanding of translocator protein 18 kDa (TSPO). Pharmacol Res 2015; 99:404-9. [PMID: 25882248 DOI: 10.1016/j.phrs.2015.03.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 03/25/2015] [Accepted: 03/27/2015] [Indexed: 02/01/2023]
Abstract
The translocator protein 18 kDa (TSPO) has been the focus of intense research by the biomedical community and the pharmaceutical industry because of its apparent involvement in many disease-related processes. These include steroidogenesis, apoptosis, inflammation, neurological disease and cancer, resulting in the use of TSPO as a biomarker and its potential as a drug target. Despite more than 30 years of study, the precise function of TSPO remains elusive. A recent breakthrough in determining the high-resolution crystal structures of bacterial homologs of mitochondrial TSPO provides new insight into the structural and functional properties at a molecular level and new opportunities for investigating the significance of this ancient and highly conserved protein family. The availability of atomic level structural information from different species also provides a platform for structure-based drug development. Here we briefly review current knowledge regarding TSPO and the implications of the new structures with respect to hypotheses and controversies in the field.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Jian Liu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - R Michael Garavito
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
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Fan Z, Harold D, Pasqualetti G, Williams J, Brooks DJ, Edison P. Can Studies of Neuroinflammation in a TSPO Genetic Subgroup (HAB or MAB) Be Applied to the Entire AD Cohort? J Nucl Med 2015; 56:707-13. [PMID: 25840980 DOI: 10.2967/jnumed.114.149443] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 02/25/2015] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Neuroinflammation plays a significant role in Alzheimer disease (AD), and translocator protein (TSPO) PET imaging allows us to quantify this process. However, the binding of second-generation TSPO tracers depends on the TSPO genotype coded by the rs6971 single-nucleotide polymorphism, with a 40%-50% increase in BP in high-affinity binders (HABs) compared with mixed-affinity binders (MABs), whereas low-affinity binders (LABs) are unsuitable for evaluation. Hence, several studies are using either HAB alone or HAB and MAB subjects. To translate the findings of neuroinflammation studies to the entire population, it is crucial to establish the influence of TSPO genotypes on AD. Here, we investigated whether different TSPO genotypes influence cognitive function, amyloid load, and disease progression over time. METHODS We evaluated 798 subjects (225 control, 388 with mild cognitive impairment [MCI], and 185 with AD) from the Alzheimer's Disease Neuroimaging Initiative database at baseline and during follow-up. All subjects were screened for TSPO genotype and underwent detailed clinical and neuropsychologic assessments yearly for 4 y. Of the 798 subjects, 255 also had T1- and T2-weighted MR imaging and amyloid PET with (11)C-Pittsburgh compound B or (18)F-florbetapir. RESULTS We demonstrated that all TSPO binding groups (HAB, MAB, and LAB) have same level of amyloid load in AD and MCI subjects. We also demonstrated that the prevalence is 50.3% for HAB, 41.2% for MAB, and 8.5% for LAB, without a statistical difference among the AD, MCI, and control groups. During longitudinal follow-up, the mean change in neuropsychometric test scores on the Mini-Mental State Examination, the cognitive and modified Alzheimer Disease Assessment Scales (ADASs), and the Geriatric Depression Scale over time were similar in AD and MCI subjects among the 3 TSPO binding groups. Analysis of the covariates showed that diagnostic group (control, MCI, AD), apolipoprotein E4 status, and sex had a significant effect on decline on the modified Alzheimer Disease Assessment Scale (>3 points of the scale), but age and TSPO genotype did not. CONCLUSION This study suggests that information obtained from evaluating a subgroup of AD or MCI subject using second-generation TSPO tracers can be translated to the entire AD and MCI population. Thus, we can study fewer AD subjects in evaluating new antineuroinflammatory and antimicroglial agents in intervention studies and in observational studies evaluating the role of neuroinflammation.
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Affiliation(s)
- Zhen Fan
- Neurology Imaging Unit, Imperial College London, Hammersmith Campus, London, United Kingdom
| | - Denise Harold
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, United Kingdom; and
| | - Giuseppe Pasqualetti
- Neurology Imaging Unit, Imperial College London, Hammersmith Campus, London, United Kingdom
| | - Julie Williams
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, United Kingdom; and
| | - David J Brooks
- Neurology Imaging Unit, Imperial College London, Hammersmith Campus, London, United Kingdom Department of Nuclear Medicine, Aarhus University, Denmark
| | - Paul Edison
- Neurology Imaging Unit, Imperial College London, Hammersmith Campus, London, United Kingdom MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, United Kingdom; and
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Selvaraj V, Stocco DM, Tu LN. Minireview: translocator protein (TSPO) and steroidogenesis: a reappraisal. Mol Endocrinol 2015; 29:490-501. [PMID: 25730708 DOI: 10.1210/me.2015-1033] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The 18-kDa translocator protein (TSPO), also known as the peripheral benzodiazepine receptor, is a transmembrane protein in the outer mitochondrial membrane. TSPO has long been described as being indispensable for mitochondrial cholesterol import that is essential for steroid hormone production. In contrast to this initial proposition, recent experiments reexamining TSPO function have demonstrated that it is not involved in steroidogenesis. This fundamental change has forced a reexamination of the functional interpretations made for TSPO that broadly impacts both basic and clinical research across multiple fields. In this minireview, we recapitulate the key studies from 25 years of TSPO research and concurrently examine their limitations that perhaps led towards the incorrect association of TSPO and steroid hormone production. Although this shift in understanding raises new questions regarding the molecular function of TSPO, these recent developments are poised to have a significant positive impact for research progress in steroid endocrinology.
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Affiliation(s)
- Vimal Selvaraj
- Department of Animal Science (V.S., L.N.T.), Cornell University, Ithaca, New York 14853; and Department of Cell Biology and Biochemistry (D.M.S.), Texas Tech University Health Sciences Center, Lubbock, Texas 79430
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Li F, Liu J, Valls L, Hiser C, Ferguson-Miller S. Identification of a key cholesterol binding enhancement motif in translocator protein 18 kDa. Biochemistry 2015; 54:1441-3. [PMID: 25635829 PMCID: PMC5125615 DOI: 10.1021/bi5015453] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Translocator protein 18 kDa (TSPO) in the mitochondrial outer membrane has been implicated in cholesterol transport regulating steroidogenesis. A human single polymorphism associated with anxiety disorders (A147T) and reduced pregnenolone production is adjacent to TSPO's cholesterol binding motif. In a mutant mimicking this polymorphism, we observe a lower level of binding of cholesterol. Further, three residues preceding A147 are more hydrophilic in a bacterial TSPO that has an affinity for cholesterol 1000-fold lower than that of the human form. Converting these residues to the human form in the bacterial homologue strikingly increases the affinity for cholesterol. An important role for this extended motif is further supported by covariance analysis.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
| | - Jian Liu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
| | - Lance Valls
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
| | - Carrie Hiser
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
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Li F, Liu J, Zheng Y, Garavito RM, Ferguson-Miller S. Protein structure. Crystal structures of translocator protein (TSPO) and mutant mimic of a human polymorphism. Science 2015; 347:555-8. [PMID: 25635101 DOI: 10.1126/science.1260590] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The 18-kilodalton translocator protein (TSPO), proposed to be a key player in cholesterol transport into mitochondria, is highly expressed in steroidogenic tissues, metastatic cancer, and inflammatory and neurological diseases such as Alzheimer's and Parkinson's. TSPO ligands, including benzodiazepine drugs, are implicated in regulating apoptosis and are extensively used in diagnostic imaging. We report crystal structures (at 1.8, 2.4, and 2.5 angstrom resolution) of TSPO from Rhodobacter sphaeroides and a mutant that mimics the human Ala(147)→Thr(147) polymorphism associated with psychiatric disorders and reduced pregnenolone production. Crystals obtained in the lipidic cubic phase reveal the binding site of an endogenous porphyrin ligand and conformational effects of the mutation. The three crystal structures show the same tightly interacting dimer and provide insights into the controversial physiological role of TSPO and how the mutation affects cholesterol binding.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Jian Liu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Yi Zheng
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - R Michael Garavito
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
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Cocaine abuse in humans is not associated with increased microglial activation: an 18-kDa translocator protein positron emission tomography imaging study with [11C]PBR28. J Neurosci 2014; 34:9945-50. [PMID: 25057196 DOI: 10.1523/jneurosci.0928-14.2014] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Basic science investigations have consistently shown that repeated exposure to psychostimulant drugs, such as cocaine, activate the immune response and lead to inflammatory changes in the brain. No previous in vivo studies have confirmed this observation in chronic cocaine-abusing humans. To test this hypothesis, we used positron emission tomography imaging to measure the binding of [(11)C]PBR28 to the 18 kDa translocator protein (TSPO), a marker for microglial activation in a group of 15 recently abstinent cocaine abusers and 17 matched healthy controls. [(11)C]PBR28 volumes of distribution expressed relative to total plasma ligand concentration (VT) were measured in subjects with kinetic analysis using the arterial input function. Subjects were also genotyped for the TSPO alanine147 threonine (Ala147Thr, rs6971) polymorphism that has been shown to influence the in vivo binding of PBR28 to TSPO. Consistent with previous reports, the TSPO Ala147Thr genotype predicted the in vivo binding of [(11)C]PBR28. No significant differences in [(11)C]PBR28 VT were observed in the cortical and subcortical regions in cocaine abusers compared with healthy controls. The results of this in vivo study do not support increased TSPO expression and, by extension, microglial activation in chronic cocaine-abusing humans. Further research with more direct markers of microglial activation is necessary to conclusively rule out neuroinflammation in cocaine dependence.
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Affiliation(s)
- Vassilios Papadopoulos
- Research Institute of the McGill University Health Centre and Departments of Medicine, Biochemistry, Pharmacology & Therapeutics, McGill University, Montreal, Quebec, H3G 1A4, Canada
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Bipolar Disorder is associated with the rs6971 polymorphism in the gene encoding 18 kDa Translocator Protein (TSPO). Psychoneuroendocrinology 2013; 38:2826-9. [PMID: 23942012 PMCID: PMC3820042 DOI: 10.1016/j.psyneuen.2013.07.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 07/12/2013] [Accepted: 07/13/2013] [Indexed: 12/17/2022]
Abstract
TSPO mediated transport of cholesterol into the mitochondrion is a necessary step in steroid synthesis. The rs6971 polymorphism in the TSPO gene causes an amino acid substitution (Ala147Thr) within the transmembrane domain where the cholesterol-binding pocket is located, and has been shown to affect the steroidogenic pathway. We report a nominal association between this TSPO polymorphism and the diagnosis of Bipolar Disorder in both the genome-wide dataset of the Wellcome Trust Case-Control Consortium and the Psychiatric Genome-Wide Association Study Consortium Bipolar Disorder group (OR=1.11, p=0.007; OR=1.10, p=0.011, respectively). We propose that the amino acid substitution affects hypothalamic-pituitary-adrenal (HPA) regulation, and hence may predispose to Bipolar Disorder. This supports the hypothesis that HPA dysregulation has a causal role in Bipolar Disorder, and is not just a consequence of the disease.
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Li F, Xia Y, Meiler J, Ferguson-Miller S. Characterization and modeling of the oligomeric state and ligand binding behavior of purified translocator protein 18 kDa from Rhodobacter sphaeroides. Biochemistry 2013; 52:5884-99. [PMID: 23952237 PMCID: PMC3756528 DOI: 10.1021/bi400431t] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
![]()
Translocator
Protein 18 kDa (TSPO), previously known as the peripheral-type
benzodiazepine receptor (PBR), is a mitochondrial outer membrane protein
that has been identified as a key player in cholesterol and porphyrin
transport, apoptotic signaling, and cancer development, as well as
neurological inflammation and disease. Despite a number of TSPO ligands
whose effects have been studied with respect to these varied biological
activities, the nature of their interactions with TSPO and the molecular
mechanism of their effects remain controversial, in part because of
the lack of an atomic-resolution structure. We expressed and purified
the homologue of mammalian TSPO from Rhodobacter sphaeroides (RsTSPO), as well as a mutant form in a proposed
drug binding loop, RsTSPOW38C. We characterized their
binding behaviors with endogenous ligands and a series of compounds
that affect apoptosis by using a sensitive tryptophan fluorescence
quenching assay. Our results show that RsTSPO behaves
as a dimer in the purified state and binds with low micromolar affinity
to many of these ligands, including retinoic acid, curcumin, and a
known Bcl-2 inhibitor, gossypol, suggesting a possible direct role
for TSPO in their regulation of apoptosis. A computational model of
the RsTSPO dimer is constructed using EM-Fold, Rosetta,
and a cryo-electron microscopy density map. Binding behaviors of known
ligands are discussed in the context of the model with respect to
regions that may be involved in binding.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
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Ginter C, Kiburu I, Boudker O. Chemical catalysis by the translocator protein (18 kDa). Biochemistry 2013; 52:3609-11. [PMID: 23651039 DOI: 10.1021/bi400364z] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Translocator proteins (18 kDa) (TSPOs) are conserved integral membrane proteins. In both eukaryotes and prokaryotes, TSPOs interact with porphyrins, precursors of heme, and photosynthetic pigments. Here we demonstrate that bacterial TSPOs catalyze rapid porphyrin degradation in a light- and oxygen-dependent manner. The reaction is inhibited by a synthetic TSPO ligand PK11195 and by mutations of conserved residues, which affect either porphyrin binding or catalytic activity. We hypothesize that TSPOs are ancient enzymes mediating porphyrin catabolism with the consumption of reactive oxygen species.
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Affiliation(s)
- Christopher Ginter
- Department of Physiology and Biophysics, Weill Cornell Medical College , New York, New York 10021, United States
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Kreisl WC, Jenko KJ, Hines CS, Lyoo CH, Corona W, Morse CL, Zoghbi SS, Hyde T, Kleinman JE, Pike VW, McMahon FJ, Innis RB. A genetic polymorphism for translocator protein 18 kDa affects both in vitro and in vivo radioligand binding in human brain to this putative biomarker of neuroinflammation. J Cereb Blood Flow Metab 2013; 33:53-8. [PMID: 22968319 PMCID: PMC3597372 DOI: 10.1038/jcbfm.2012.131] [Citation(s) in RCA: 186] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Second-generation radioligands for translocator protein (TSPO), an inflammation marker, are confounded by the codominant rs6971 polymorphism that affects binding affinity. The resulting three groups are homozygous for high-affinity state (HH), homozygous for low-affinity state (LL), or heterozygous (HL). We tested if in vitro binding to leukocytes distinguished TSPO genotypes and if genotype could affect clinical studies using the TSPO radioligand [(11)C]PBR28. In vitro binding to leukocytes and [(11)C]PBR28 brain imaging were performed in 27 human subjects with known TSPO genotype. Specific [(3)H]PBR28 binding was measured in prefrontal cortex of 45 schizophrenia patients and 47 controls. Leukocyte binding to PBR28 predicted genotype in all subjects. Brain uptake was ∼40% higher in HH than HL subjects. Specific [(3)H]PBR28 binding in LL controls was negligible, while HH controls had ∼80% higher binding than HL controls. After excluding LL subjects, specific binding was 16% greater in schizophrenia patients than controls. This difference was insignificant by itself (P=0.085), but was significant after correcting for TSPO genotype (P=0.011). Our results show that TSPO genotype influences PBR28 binding in vitro and in vivo. Correcting for this genotype increased statistical power in our postmortem study and is recommended for in vivo positron emission tomography studies.
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Affiliation(s)
- William C Kreisl
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, MD 20892-1026, USA.
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Abstract
Adrenal gonadal, placental and brain mitochondria contain several steroidogenic enzymes, notably the cholesterol side chain cleavage enzyme, P450scc, which is the enzymatic rate-limiting step in steroidogenesis which determines cellular steroidogenic capacity. Even before this step, the access of cholesterol to this enzyme system is both rate-limiting and the site of acute regulation via the steroidogenic acute regulatory protein (StAR) which interacts with a complex multi-component 'transduceosome' on the outer mitochondrial membrane (OMM). The components of the transduceosome include the 18 kDa translocator protein (TSPO), the voltage-dependent anion channel (VDAC-1), TSPO-associated protein 7 (PAP7, ACBD3 for acyl-CoA-binding-domain 3), and protein kinase A regulatory subunit 1α (PKAR1A). The precise fashion in which these proteins interact and move cholesterol from the OMM to P450scc, and the means by which cholesterol is loaded into the OMM, remain unclear. Human deficiency diseases have been described for StAR and for P450scc. Mitochondria also contain several 'downstream' steroidogenic enzymes.
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Affiliation(s)
- Vassilios Papadopoulos
- The Research Institute of the McGill University Health Centre, Department of Medicine, McGill University, Montreal, Quebec H3G 1A4, Canada.
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