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Zhang M, Meng H, Zhou Q, Chunyu H, He L, Meng H, Wang H, Wang Y, Sun C, Xi Y, Hai W, Huang Q, Li B, Chen S. Microglial Activation Imaging Using 18F-DPA-714 PET/MRI for Detecting Autoimmune Encephalitis. Radiology 2024; 310:e230397. [PMID: 38441089 DOI: 10.1148/radiol.230397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
Background Translocator protein (TSPO) PET has been used to visualize microglial activation in neuroinflammation and is a potential imaging tool for detecting autoimmune encephalitis (AIE). Purpose To compare the detection rate between TSPO radioligand fluorine 18 (18F) DPA-714 PET and conventional MRI and assess the relationship between 18F-DPA-714 uptake and clinical features in participants with AIE. Materials and Methods Healthy volunteers and patients with AIE were enrolled in this prospective study between December 2021 and April 2023. All participants underwent hybrid brain 18F-DPA-714 PET/MRI and antibody testing. Modified Rankin scale scoring and AIE-related symptoms were assessed in participants with AIE. Positive findings were defined as intensity of 18F-DPA-714 uptake above a threshold of the mean standardized uptake value ratio (SUVR) plus 2 SD inside the corresponding brain regions of healthy controls. The McNemar test was used to compare the positive detection rate between the two imaging modalities; the independent samples t test was used to compare continuous variables; and correlation with Bonferroni correction was used to assess the relationship between 18F-DPA-714 uptake and clinical features. Results A total of 25 participants with AIE (mean age, 39.24 years ± 19.03 [SD]) and 10 healthy controls (mean age, 28.70 years ± 5.14) were included. The positive detection rate of AIE was 72% (18 of 25) using 18F-DPA-714 PET compared to 44% (11 of 25) using conventional MRI, but the difference was not statistically significant (P = .065). Participants experiencing seizures exhibited significantly higher mean SUVR in the entire cortical region than those without seizures (1.23 ± 0.21 vs 1.15 ± 0.18; P = .003). Of the 13 participants with AIE who underwent follow-up PET/MRI, 11 (85%) demonstrated reduced uptake of 18F-DPA-714 accompanied by relief of symptoms after immunosuppressive treatment. Conclusion 18F-DPA-714 PET has potential value in supplementing MRI for AIE detection. Clinical trial registration no. NCT05293405 © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Zaharchuk in this issue.
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Affiliation(s)
- Min Zhang
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Huanyu Meng
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Qinming Zhou
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Hangxing Chunyu
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Lu He
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Hongping Meng
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Hanzhong Wang
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Yue Wang
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Chenwei Sun
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Yun Xi
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Wangxi Hai
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Qiu Huang
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Biao Li
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
| | - Sheng Chen
- From the Departments of Nuclear Medicine (M.Z., H.C., Hongping Meng, Y.W., C.S., Y.X., W.H., B.L.) and Neurology (Huanyu Meng, Q.Z., L.H., S.C.), Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, China; Shanxi Medical University-Collaborative Innovation Center for Molecular Imaging of Precision Medicine, Taiyuan, China (M.Z., B.L.); School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China (H.W., Q.H.); and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China (S.C.)
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Wheeler S, Bhardwaj M, Kenyon V, Ferraz MJ, Aerts JMFG, Sillence DJ. Mitochondrial dysfunction in NPC1-deficiency is not rescued by drugs targeting the glucosylceramidase GBA2 and the cholesterol-binding proteins TSPO and StARD1. FEBS Lett 2024; 598:477-484. [PMID: 38302739 DOI: 10.1002/1873-3468.14802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/04/2023] [Accepted: 12/14/2023] [Indexed: 02/03/2024]
Abstract
Niemann-Pick type C disease (NPCD) is a rare neurodegenerative disorder most commonly caused by mutations in the lysosomal protein Niemann-Pick C1 (NPC1), which is implicated in cholesterol export. Mitochondrial insufficiency forms a significant feature of the pathology of this disease, yet studies attempting to address this are rare. The working hypothesis is that mitochondria become overloaded with cholesterol which renders them dysfunctional. We examined two potential protein targets-translocator protein (TSPO) and steroidogenic acute regulatory protein D1 (StARD1)-which are implicated in cholesterol transport to mitochondria, in addition to glucocerbrosidase 2 (GBA2), the target of miglustat, which is currently the only approved treatment for NPCD. However, inhibiting these proteins did not correct the mitochondrial defect in NPC1-deficient cells.
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Affiliation(s)
- Simon Wheeler
- Leicester School of Pharmacy, De Montfort University, Leicester, UK
| | | | | | - Maria J Ferraz
- Leiden Institute of Chemistry, Leiden University, The Netherlands
| | | | - Dan J Sillence
- Leicester School of Pharmacy, De Montfort University, Leicester, UK
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Liere P, Liu GJ, Pianos A, Middleton RJ, Banati RB, Akwa Y. The Comprehensive Steroidome in Complete TSPO/PBR Knockout Mice under Basal Conditions. Int J Mol Sci 2023; 24:ijms24032474. [PMID: 36768796 PMCID: PMC9916858 DOI: 10.3390/ijms24032474] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 01/31/2023] Open
Abstract
The 18 kDa translocator protein (TSPO/PBR) is a multifunctional evolutionary highly conserved outer mitochondrial membrane protein. Decades of research has reported an obligatory role of TSPO/PBR in both mitochondrial cholesterol transport and, thus, steroid production. However, the strict dependency of steroidogenesis on TSPO/PBR has remained controversial. The aim of this study was to provide insight into the steroid profile in complete C57BL/6-Tspotm1GuWu(GuwiyangWurra)-knockout male mice (TSPO-KO) under basal conditions. The steroidome in the brain, adrenal glands, testes and plasma was measured by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). We found that steroids present in wild-type (WT) mice were also detected in TSPO-KO mice, including pregnenolone (PREG), progestogens, mineralo-glucocorticosteroids and androgens. The concentrations of PREG and most metabolites were similar between genotypes, except a significant decrease in the levels of the 5α-reduced metabolites of progesterone (PROG) in adrenal glands and plasma and of the 5α-reduced metabolites of corticosterone (B) in plasma in TSPO-KO compared to WT animals, suggesting other regulatory functions for the TSPO/PBR. The expression levels of the voltage-dependent anion-selective channel (VDAC-1), CYP11A1 and 5α-reductase were not significantly different between both groups. Thus, the complete deletion of the tspo gene in male mice does not impair de novo steroidogenesis in vivo.
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Affiliation(s)
- Philippe Liere
- Disease and Hormones of the Nervous System, U1195 Inserm-Université Paris Saclay, 80 rue du Général Leclerc, 94276 Kremlin-Bicêtre, France
| | - Guo-Jun Liu
- Australian Nuclear Science and Technology Organisation (ANSTO), Kirrawee, NSW 2232, Australia
- Faculty of Medicine and Health, Medical Imaging Sciences, Brain and Mind Centre, University of Sydney, Camperdown, NSW 2006, Australia
| | - Antoine Pianos
- Disease and Hormones of the Nervous System, U1195 Inserm-Université Paris Saclay, 80 rue du Général Leclerc, 94276 Kremlin-Bicêtre, France
| | - Ryan J. Middleton
- Australian Nuclear Science and Technology Organisation (ANSTO), Kirrawee, NSW 2232, Australia
| | - Richard B. Banati
- Australian Nuclear Science and Technology Organisation (ANSTO), Kirrawee, NSW 2232, Australia
- Faculty of Medicine and Health, Medical Imaging Sciences, Brain and Mind Centre, University of Sydney, Camperdown, NSW 2006, Australia
| | - Yvette Akwa
- Disease and Hormones of the Nervous System, U1195 Inserm-Université Paris Saclay, 80 rue du Général Leclerc, 94276 Kremlin-Bicêtre, France
- Correspondence: ; Tel.: +33-(0)1-49591878
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Conti E, Grana D, Angiulli F, Karantzoulis A, Villa C, Combi R, Appollonio I, Ferrarese C, Tremolizzo L. TSPO Modulates Oligomeric Amyloid-β-Induced Monocyte Chemotaxis: Relevance for Neuroinflammation in Alzheimer's Disease. J Alzheimers Dis 2023; 95:549-559. [PMID: 37574731 DOI: 10.3233/jad-230239] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
BACKGROUND Neuroinflammation is one of the cardinal mechanisms of Alzheimer's disease (AD). with amyloid-β (Aβ) playing a critical role by activating microglia to produce soluble inflammatory mediators, including several chemokines. Peripheral monocytes are, therefore, attracted into the central nervous system (CNS), where they change into blood-born microglia and participate in the attempt of removing toxic Aβ species. The translocator protein-18 kDa (TSPO) is a transmembrane protein overexpressed in response to neuroinflammation and known to regulate human monocyte chemotaxis. OBJECTIVE We aimed to evaluate the role of the oligomeric Aβ1-42 isoform at inducing peripheral monocyte chemotaxis, and the possible involvement of TSPO in this process. METHODS In vitro cell lines, and ex vivo monocytes from consecutive AD patients (n = 60), and comparable cognitively intact controls (n = 30) were used. Chemotaxis analyses were carried out through both μ-slide chambers and Boyden assays, using 125 pM oligomeric Aβ1-42 as chemoattractant. TSPO agonists and antagonists were tested (Ro5-4864, Emapunil, PK11195). RESULTS Oligomeric Aβ directly promoted chemotaxis in all our models. Interestingly, AD monocytes displayed a stronger response (about twofold) with respect to controls. Aβ-induced chemotaxis was prevented by the TSPO antagonist PK11195; the expression of the TSPO and of the C-C chemokine receptor type 2 (CCR2) was unchanged by drug exposure. CONCLUSION Oligomeric Aβ1-42 is able to recruit peripheral monocytes, and we provide initial evidence sustaining a role for TSPO in modulating this process. This data may be of value for future therapeutic interventions aimed at modulating monocytes motility toward the CNS.
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Affiliation(s)
- Elisa Conti
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
| | - Denise Grana
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
| | - Federica Angiulli
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
| | - Aristotelis Karantzoulis
- Milan Center for Neuroscience (NeuroMi), Italy
- Memory Clinic, Neurology Unit, IRCCS "San Gerardo dei Tintori", Monza, Italy
| | - Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
| | - Romina Combi
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
| | - Ildebrando Appollonio
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
- Memory Clinic, Neurology Unit, IRCCS "San Gerardo dei Tintori", Monza, Italy
| | - Carlo Ferrarese
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
- Memory Clinic, Neurology Unit, IRCCS "San Gerardo dei Tintori", Monza, Italy
| | - Lucio Tremolizzo
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
- Milan Center for Neuroscience (NeuroMi), Italy
- Memory Clinic, Neurology Unit, IRCCS "San Gerardo dei Tintori", Monza, Italy
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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: 81] [Impact Index Per Article: 27.0] [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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Georges E, Sottas C, Li Y, Papadopoulos V. Direct and specific binding of cholesterol to the mitochondrial translocator protein (TSPO) using PhotoClick cholesterol analogue. J Biochem 2021; 170:239-243. [PMID: 33846725 DOI: 10.1093/jb/mvab031] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 03/18/2021] [Indexed: 11/14/2022] Open
Abstract
The translocator protein (TSPO) is a five-helix transmembrane protein localized to the outer mitochondria membrane. Radioligand binding assays and chemical crosslinking showed TSPO to be a high affinity cholesterol-binding protein. In this report, we show that TSPO in mitochondrial fractions from MA-10 mouse tumour Leydig cells can interact directly and competitively with the clickable photoreactive cholesterol analogue. PhotoClick cholesterol showed saturable photoaffinity labelling of TSPO that could be specifically immunoprecipitated with anti-TSPO antibody, following the click reaction with the fluorescent-azide probe, tetramethylrhodamine (TAMRA)-azide. Moreover, excess cholesterol reduced the photolabelling of both total mitochondrial proteins and TSPO. Together, the results of this study demonstrated direct binding of PhotoClick cholesterol to TSPO and that this interaction occurs at physiologically relevant site(s).
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Affiliation(s)
- Elias Georges
- Institute of Parasitology, McGill University, Montreal, Quebec H9X1C0, Canada.,Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA
| | - Chantal Sottas
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA
| | - Yuchang Li
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA
| | - Vassilios Papadopoulos
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA
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7
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Marlow B, Kuenze G, Li B, Sanders CR, Meiler J. Structural determinants of cholesterol recognition in helical integral membrane proteins. Biophys J 2021; 120:1592-1604. [PMID: 33640379 DOI: 10.1016/j.bpj.2021.02.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 01/12/2021] [Accepted: 02/08/2021] [Indexed: 12/20/2022] Open
Abstract
Cholesterol is an integral component of mammalian membranes. It has been shown to modulate membrane fluidity and dynamics and alter integral membrane protein function. However, understanding the molecular mechanisms of how cholesterol impacts protein function is complicated by limited and conflicting structural data. Because of the nature of the crystallization and cryo-EM structure determination, it is difficult to distinguish between specific and biologically relevant interactions and a nonspecific association. The only widely recognized search algorithm for cholesterol-integral-membrane-protein interaction sites is sequence based, i.e., searching for the so-called "Cholesterol Recognition/interaction Amino acid Consensus" motif. Although these motifs are present in numerous integral membrane proteins, there is inconclusive evidence to support their necessity or sufficiency for cholesterol binding. Here, we leverage the increasing number of experimental cholesterol-integral-membrane-protein structures to systematically analyze putative interaction sites based on their spatial arrangement and evolutionary conservation. This analysis creates three-dimensional representations of general cholesterol interaction sites that form clusters across multiple integral membrane protein classes. We also classify cholesterol-integral-membrane-protein interaction sites as either likely-specific or nonspecific. Information gleaned from our characterization will eventually enable a structure-based approach to predict and design cholesterol-integral-membrane-protein interaction sites.
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Affiliation(s)
- Brennica Marlow
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee; Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee; Department of Chemistry, Vanderbilt University, Nashville, Tennessee; Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Bian Li
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee; Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee
| | - Charles R Sanders
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee; Department of Biochemistry, Vanderbilt University, Nashville, Tennessee
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee; Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee; Department of Chemistry, Vanderbilt University, Nashville, Tennessee; Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany.
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8
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Chung JY, Chen H, Papadopoulos V, Zirkin B. Cholesterol accumulation, lipid droplet formation, and steroid production in Leydig cells: Role of translocator protein (18-kDa). Andrology 2019; 8:719-730. [PMID: 31738001 DOI: 10.1111/andr.12733] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 11/06/2019] [Accepted: 11/14/2019] [Indexed: 02/06/2023]
Abstract
BACKGROUND Cholesterol import into the mitochondria of steroid-producing cells is the rate-determining step in steroidogenesis. Numerous studies have provided evidence that the cholesterol-binding translocator protein (18 kDa TSPO) plays an important role in cholesterol translocation into mitochondria and that it also might act on cholesterol homeostasis. Several TSPO-specific ligands have been shown to increase steroid production in vitro and in vivo. OBJECTIVES The present study assessed the effects of the TSPO drug ligand FGIN-1-27 on cholesterol accumulation and lipid droplet formation in relationship to steroid formation. MATERIALS AND METHODS Using MA-10 and primary Leydig cells, immunocytochemical and molecular methods were used to examine cholesterol accumulation, the formation of lipid droplets, and steroid formation in response to LH and FGIN-1-27. Additionally, we determined the effects of Tspo knockout by CRISPR/Cas9, and of siRNA knockdowns of Tspo and Plin2 (Perilipin 2; also known as adipose differentiation-related protein, ADFP) on LH- and FGIN-1-27-induced steroidogenesis. RESULTS In response to LH and FGIN-1-27, cultured MA-10 cells and primary Leydig cells increased steroid formation, cholesterol accumulation, and lipid droplet formation. Cholesterol accumulation in the lipid droplets also was increased in Tspo knockout cells. Knockout of Tspo or its knockdown in MA-10 cells resulted in reduced progesterone formation in response to both LH and FGIN-1-27, as did knockdown of Plin2. Steroid production also was inhibited by the cholesteryl ester hydrolase inhibitor diethylumbelliferyl phosphate. DISCUSSION AND CONCLUSION These results support the conclusion that FGIN-1-27 stimulates steroid formation by increasing TSPO-mediated cholesterol translocation into the inner mitochondria for steroidogenesis, as well as into the cytosol for lipid droplet formation. FGIN-1-27 also increased steroid formation at least in part by inducing the conversion of cholesteryl ester located in lipid droplets to cholesterol, thus making available more substrate for steroid formation.
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Affiliation(s)
- Jin-Yong Chung
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Haolin Chen
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.,Department of Anesthesiology, the Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Vassilios Papadopoulos
- Department of Pharmacology and Pharmaceutical Science, School of Pharmacy, University of Southern California, Los Angeles, CA, USA
| | - Barry Zirkin
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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Arbo B, Ribeiro M, Garcia-Segura L. Development of new treatments for Alzheimer's disease based on the modulation of translocator protein (TSPO). Ageing Res Rev 2019; 54:100943. [PMID: 31430564 DOI: 10.1016/j.arr.2019.100943] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 08/07/2019] [Accepted: 08/15/2019] [Indexed: 12/27/2022]
Abstract
The increase in life expectancy of the world population is associated with a higher prevalence of neurodegenerative diseases. Alzheimer's Disease (AD) is the most common neurodegenerative disease, affecting currently 43 million people over the world. To date, most of the pharmacological interventions in AD are intended for the alleviation of some of its symptoms, and there are no effective treatments to inhibit the progression of the disease. Translocator protein (TSPO) is present in contact points between the outer and the inner mitochondrial membranes and is involved in the control of steroidogenesis, inflammation and apoptosis. In the last decade, studies have shown that TSPO ligands present neuroprotective effects in different experimental models of AD, both in vitro and in vivo. The aim of this review is to analyze the data provided by these studies and to discuss if TSPO could be a viable therapeutic target for the development of new treatments for AD.
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10
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Kim S, Kim N, Park S, Jeon Y, Lee J, Yoo SJ, Lee JW, Moon C, Yu SW, Kim EK. Tanycytic TSPO inhibition induces lipophagy to regulate lipid metabolism and improve energy balance. Autophagy 2019; 16:1200-1220. [PMID: 31469345 PMCID: PMC7469491 DOI: 10.1080/15548627.2019.1659616] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Hypothalamic glial cells named tanycytes, which line the 3rd ventricle (3V), are components of the hypothalamic network that regulates a diverse array of metabolic functions for energy homeostasis. Herein, we report that TSPO (translocator protein), an outer mitochondrial protein, is highly enriched in tanycytes and regulates homeostatic responses to nutrient excess as a potential target for an effective intervention in obesity. Administration of a TSPO ligand, PK11195, into the 3V, and tanycyte-specific deletion of Tspo reduced food intake and elevated energy expenditure, leading to negative energy balance in a high-fat diet challenge. Ablation of tanycytic Tspo elicited AMPK-dependent lipophagy, breaking down lipid droplets into free fatty acids, thereby elevating ATP in a lipid stimulus. Our findings suggest that tanycytic TSPO affects systemic energy balance through macroautophagy/autophagy-regulated lipid metabolism, and highlight the physiological significance of TSPO in hypothalamic lipid sensing and bioenergetics in response to overnutrition. Abbreviations 3V: 3rd ventricle; ACAC: acetyl-Coenzyme A carboxylase; AGRP: agouti related neuropeptide; AIF1/IBA1: allograft inflammatory factor 1; AMPK: AMP-activated protein kinase; ARC: arcuate nucleus; Atg: autophagy related; Bafilo: bafilomycin A1; CAMKK2: calcium/calmodulin-dependent protein kinase kinase 2, beta; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CNS: central nervous system; COX4I1: cytochrome c oxidase subunit 4I1; FFA: free fatty acid; GFAP: glial fibrillary acidic protein; HFD: high-fat diet; ICV: intracerebroventricular; LAMP2: lysosomal-associated membrane protein 2; LD: lipid droplet; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MBH: mediobasal hypothalamus; ME: median eminence; MEF: mouse embryonic fibroblast; NCD: normal chow diet; NEFM/NFM: neurofilament medium; NPY: neuropeptide Y; OL: oleic acid; POMC: pro-opiomelanocortin-alpha; PRKN/Parkin: parkin RBR E3 ubiquitin protein ligase; Rax: retina and anterior neural fold homeobox; RBFOX3/NeuN: RNA binding protein, fox-1 homolog (C. elegans) 3; RER: respiratory exchange ratio; siRNA: small interfering RNA; SQSTM1: sequestosome 1; TG: triglyceride; TSPO: translocator protein; ULK1: unc-51 like kinase 1; VCO2: carbon dioxide production; VMH: ventromedial hypothalamus; VO2: oxygen consumption
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Affiliation(s)
- Seolsong Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Nayoun Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Seokjae Park
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea.,Neurometabolomics Research Center, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Yoonjeong Jeon
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea.,Neurometabolomics Research Center, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Jaemeun Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Seung-Jun Yoo
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea.,Convergence Research Advanced Centre for Olfaction, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Ji-Won Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Cheil Moon
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea.,Convergence Research Advanced Centre for Olfaction, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Seong-Woon Yu
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea.,Neurometabolomics Research Center, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
| | - Eun-Kyoung Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea.,Neurometabolomics Research Center, Daegu Gyeongbuk Institute of Science and Technology , Daegu, Republic of Korea
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11
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TSPO Ligands Promote Cholesterol Efflux and Suppress Oxidative Stress and Inflammation in Choroidal Endothelial Cells. Int J Mol Sci 2018; 19:ijms19123740. [PMID: 30477223 PMCID: PMC6321017 DOI: 10.3390/ijms19123740] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 11/16/2018] [Accepted: 11/21/2018] [Indexed: 02/06/2023] Open
Abstract
Choroidal endothelial cells supply oxygen and nutrients to retinal pigment epithelial (RPE) cells and photoreceptors, recycle metabolites, and dispose of metabolic waste through the choroidal blood circulation. Death of the endothelial cells of the choroid may cause abnormal deposits including unesterified and esterified cholesterol beneath RPE cells and within Bruch’s membrane that contribute to the progression of age-related macular degeneration (AMD), the most prevalent cause of blindness in older people. Translocator protein (TSPO) is a cholesterol-binding protein that is involved in mitochondrial cholesterol transport and other cellular functions. We have investigated the role of TSPO in choroidal endothelial cells. Immunocytochemistry showed that TSPO was localized to the mitochondria of choroidal endothelial cells. Choroidal endothelial cells exposed to TSPO ligands (Etifoxine or XBD-173) had significantly increased cholesterol efflux, higher expression of cholesterol homeostasis genes (LXRα, CYP27A1, CYP46A1, ABCA1 and ABCG1), and reduced biosynthesis of cholesterol and phospholipids from [14C]acetate, when compared to untreated controls. Treatment with TSPO ligands also resulted in reduced production of reactive oxygen species (ROS), increased antioxidant capacity, and reduced release of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α and VEGF) induced by oxidized LDL. These data suggest TSPO ligands may offer promise for the treatment of AMD.
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12
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Biswas L, Zhou X, Dhillon B, Graham A, Shu X. Retinal pigment epithelium cholesterol efflux mediated by the 18 kDa translocator protein, TSPO, a potential target for treating age-related macular degeneration. Hum Mol Genet 2018; 26:4327-4339. [PMID: 28973423 DOI: 10.1093/hmg/ddx319] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 08/06/2017] [Indexed: 12/13/2022] Open
Abstract
Cholesterol accumulation beneath the retinal pigment epithelium (RPE) cells is supposed to contribute the pathogenesis of age-related macular degeneration (AMD). Cholesterol efflux genes (APOE and ABCA1) were identified as risk factors for AMD, although how cholesterol efflux influences accumulation of this lipid in sub-RPE deposits remains elusive. The 18 kDa translocator protein, TSPO, is a cholesterol-binding protein implicated in mitochondrial cholesterol transport. Here, we investigate the function of TSPO in cholesterol efflux from the RPE cells. We demonstrate in RPE cells that TSPO specific ligands promoted cholesterol efflux to acceptor (apo)lipoprotein and human serum, while loss of TSPO resulted in impaired cholesterol efflux. TSPO-/- RPE cells also had significantly increased production of reactive oxygen species (ROS) and upregulated expression of proinflammatory cytokines (IL-1β and TNFα). Cholesterol (oxidized LDL) uptake and accumulation were markedly increased in TSPO-/- RPE cells. Finally, in aged RPE cells, TSPO expression was reduced and cholesterol efflux impaired. These findings provide a new pharmacological concept to treat early AMD patients by stimulating cellular cholesterol removal with TSPO specific ligands or by overexpression of TSPO in RPE cells.
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Affiliation(s)
- Lincoln Biswas
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4?0BA, UK
| | - Xinzhi Zhou
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4?0BA, UK
| | - Baljean Dhillon
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16?4SB, UK
| | - Annette Graham
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4?0BA, UK
| | - Xinhua Shu
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4?0BA, UK
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13
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Baez E, Guio-Vega GP, Echeverria V, Sandoval-Rueda DA, Barreto GE. 4'-Chlorodiazepam Protects Mitochondria in T98G Astrocyte Cell Line from Glucose Deprivation. Neurotox Res 2017; 32:163-171. [PMID: 28405935 DOI: 10.1007/s12640-017-9733-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/30/2017] [Accepted: 04/04/2017] [Indexed: 01/12/2023]
Abstract
The translocator protein (TSPO), formerly known as the peripheral-type benzodiazepine receptor (PBR), is considered an important regulator of steroidogenesis and a potential therapeutic target in neurological disorders. Previous evidence suggests that TSPO ligands can protect cells during injury and prevent apoptosis in central nervous system (CNS) cells. However, its actions on astrocytic cells under metabolic injury are not well understood. In this study, we explored whether 4'-chlorodiazepam (Ro5-4864), a TSPO ligand, might protect astrocyte mitochondria under glucose deprivation. Our results showed that 4'-chlorodiazepam preserved cell viability and reduced nuclear fragmentation in glucose-deprived cells. These effects were accompanied by a reduced production of free radicals and maintenance of mitochondrial functions in cells treated with 4'-chlorodiazepam. Finally, our findings suggest that TSPO might be involved in reducing oxidative stress by preserving mitochondrial functions in astrocytic cells exposed to glucose withdrawal.
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Affiliation(s)
- Eliana Baez
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - Gina Paola Guio-Vega
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | | | - Daniel Andres Sandoval-Rueda
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - George E Barreto
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia. .,Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Santiago, Chile.
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14
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Zhang M, Liu J, Zhou MM, Wu H, Hou Y, Li YF, Yin Y, Zheng L, Cai J, Liao FF, Liu FY, Yi M, Wan Y. Anxiolytic effects of hippocampal neurosteroids in normal and neuropathic rats with spared nerve injury. J Neurochem 2017; 141:137-150. [PMID: 28129443 DOI: 10.1111/jnc.13965] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 12/16/2016] [Accepted: 01/11/2017] [Indexed: 11/30/2022]
Affiliation(s)
- Meng Zhang
- Neuroscience Research Institute; Peking University; Beijing China
- Department of Pathology; Beijing Children's Hospital, Capital Medical University; Beijing China
| | - Jia Liu
- Institute of Systems Biomedicine; Peking University; Beijing China
| | - Meng-Meng Zhou
- Neuroscience Research Institute; Peking University; Beijing China
| | - Honghai Wu
- Department of Pharmacy; Bethune International Peace Hospital; Shijiazhuang China
| | - Yanning Hou
- Department of Pharmacy; Bethune International Peace Hospital; Shijiazhuang China
| | - Yun-Feng Li
- Department of New Drug Evaluation; Beijing Institute of Pharmacology and Toxicology; Beijing China
| | - Yuxin Yin
- Institute of Systems Biomedicine; Peking University; Beijing China
| | - Lemin Zheng
- Institute of Cardiovascular Sciences and Institute of Systems Biomedicine; Key Laboratory of Molecular Cardiovascular Sciences of the Ministry of Education; Peking University; Beijing China
| | - Jie Cai
- Neuroscience Research Institute; Peking University; Beijing China
| | - Fei-Fei Liao
- Neuroscience Research Institute; Peking University; Beijing China
| | - Feng-Yu Liu
- Neuroscience Research Institute; Peking University; Beijing China
| | - Ming Yi
- Neuroscience Research Institute; Peking University; Beijing China
| | - You Wan
- Neuroscience Research Institute; Peking University; Beijing China
- Key Laboratory for Neuroscience; Ministry of Education/National Health and Family Planning Commission; Peking University; Beijing China
- Department of Neurobiology; School of Basic Medical Sciences; Peking University; Beijing China
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15
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Hatty CR, Banati RB. Protein-ligand and membrane-ligand interactions in pharmacology: the case of the translocator protein (TSPO). Pharmacol Res 2015; 100:58-63. [PMID: 26238176 DOI: 10.1016/j.phrs.2015.07.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 07/28/2015] [Accepted: 07/29/2015] [Indexed: 11/30/2022]
Abstract
The targets of many small molecule drugs are membrane proteins, and traditionally the focus of pharmacology is on the interaction between such receptors and their small molecule drug ligands. However, the lipid membranes of cells and organelles are increasingly appreciated as diverse and dynamic structures that also specifically interact with small molecule drugs and peptides, causing profound changes in the properties of these membranes, and modulating the function of the membrane and the proteins within it. Drug-membrane interactions are likely to have a role in both the therapeutic and toxic activity of a variety of compounds, and their role in the overall pharmacological effect of a drug needs to be understood more clearly. This is the case for the 18 kDa translocator protein (TSPO) and its ligands, where functions that were established based on pharmacological studies are being called into question. Re-examining the putative functions of the TSPO and the effects of its ligands reveals a need to consider in more detail the interplay between protein-ligand and membrane-ligand interactions, and the modulatory relationship between TSPO and the lipid membrane.
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Affiliation(s)
- Claire R Hatty
- Medical Imaging & Radiation Sciences Faculty Research Group, Faculty of Health Sciences, The University of Sydney, Brain & Mind Research Institute, 94 Mallett Street, Camperdown, NSW 2050, Australia.
| | - Richard B Banati
- Medical Imaging & Radiation Sciences Faculty Research Group, Faculty of Health Sciences, The University of Sydney, Brain & Mind Research Institute, 94 Mallett Street, Camperdown, NSW 2050, Australia; Life Sciences, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia
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16
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Tu LN, Zhao AH, Stocco DM, Selvaraj V. PK11195 effect on steroidogenesis is not mediated through the translocator protein (TSPO). Endocrinology 2015; 156:1033-9. [PMID: 25535830 PMCID: PMC4330312 DOI: 10.1210/en.2014-1707] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Translocator protein (TSPO) is a mitochondrial outer membrane protein of unknown function with high physiological expression in steroidogenic cells. Using TSPO gene-deleted mice, we recently demonstrated that TSPO function is not essential for steroidogenesis. The first link between TSPO and steroidogenesis was established in studies showing modest increases in progesterone production by adrenocortical and Leydig tumor cell lines after treatment with PK11195. To reconcile discrepancies between physiological and pharmacological interpretations of TSPO function, we generated TSPO-knockout MA-10 mouse Leydig tumor cells (MA-10:TspoΔ/Δ) and examined their steroidogenic potential after exposure to either dibutyryl-cAMP or PK11195. Progesterone production in MA-10:TspoΔ/Δ after dibutyryl-cAMP was not different from control MA-10:Tspo+/+ cells, confirming that TSPO function is not essential for steroidogenesis. Interestingly, when treated with increasing concentrations of PK11195, both control MA-10:Tspo+/+ cells and MA-10:TspoΔ/Δ cells responded in a similar dose-dependent manner showing increases in progesterone production. These results show that the pharmacological effect of PK11195 on steroidogenesis is not mediated through TSPO.
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Affiliation(s)
- Lan N Tu
- Department of Animal Science, College of Agriculture and Life Sciences (L.N.T., A.H.Z., V.S.), Cornell University, Ithaca, New York 14853; and Department of Cell Biology and Biochemistry, School of Medicine (D.M.S.), Texas Tech University Health Sciences Center, Lubbock, Texas 79430
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17
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Taylor JMW, Allen AM, Graham A. Targeting mitochondrial 18 kDa translocator protein (TSPO) regulates macrophage cholesterol efflux and lipid phenotype. Clin Sci (Lond) 2014; 127:603-13. [PMID: 24814875 DOI: 10.1042/cs20140047] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The aim of the present study was to establish mitochondrial cholesterol trafficking 18 kDa translocator protein (TSPO) as a potential therapeutic target, capable of increasing macrophage cholesterol efflux to (apo)lipoprotein acceptors. Expression and activity of TSPO in human (THP-1) macrophages were manipulated genetically and by the use of selective TSPO ligands. Cellular responses were analysed by quantitative PCR (Q-PCR), immunoblotting and radiolabelling, including [3H]cholesterol efflux to (apo)lipoprotein A-I (apoA-I), high-density lipoprotein (HDL) and human serum. Induction of macrophage cholesterol deposition by acetylated low-density lipoprotein (AcLDL) increased expression of TSPO mRNA and protein, reflecting findings in human carotid atherosclerosis. Transient overexpression of TSPO enhanced efflux (E%) of [3H]cholesterol to apoA-I, HDL and human serum compared with empty vector (EV) controls, whereas gene knockdown of TSPO achieved the converse. Ligation of TSPO (using PK11195, FGIN-1-27 and flunitrazepam) triggered increases in [3H]cholesterol efflux, an effect that was amplified in TSPO-overexpressing macrophages. Overexpression of TSPO induced the expression of genes [PPARA (peroxisome-proliferator-activated receptor α), NR1H3 (nuclear receptor 1H3/liver X receptor α), ABCA1 (ATP-binding cassette A1), ABCG4 (ATP-binding cassette G4) and APOE (apolipoprotein E)] and proteins (ABCA1 and PPARα) involved in cholesterol efflux, reduced macrophage neutral lipid mass and lipogenesis and limited cholesterol esterification following exposure to AcLDL. Thus, targeting TSPO reduces macrophage lipid content and prevents macrophage foam cell formation, via enhanced cholesterol efflux to (apo)lipoprotein acceptors.
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Affiliation(s)
- Janice M W Taylor
- *Department of Life Sciences and the Diabetes Research Group, Institute for Applied Health Research, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, U.K
| | - Anne-Marie Allen
- *Department of Life Sciences and the Diabetes Research Group, Institute for Applied Health Research, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, U.K
| | - Annette Graham
- *Department of Life Sciences and the Diabetes Research Group, Institute for Applied Health Research, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, U.K
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18
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Eckmann J, Clemens LE, Eckert SH, Hagl S, Yu-Taeger L, Bordet T, Pruss RM, Muller WE, Leuner K, Nguyen HP, Eckert GP. Mitochondrial membrane fluidity is consistently increased in different models of Huntington disease: restorative effects of olesoxime. Mol Neurobiol 2014; 50:107-18. [PMID: 24633813 DOI: 10.1007/s12035-014-8663-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 02/18/2014] [Indexed: 12/12/2022]
Abstract
Huntington disease (HD) is a fatal neurodegenerative disorder caused by a CAG repeat expansion in exon 1 of the huntingtin gene (HTT). One prominent target of the mutant huntingtin protein (mhtt) is the mitochondrion, affecting its morphology, distribution, and function. Thus, mitochondria have been suggested as potential therapeutic targets for the treatment of HD. Olesoxime, a cholesterol-like compound, promotes motor neuron survival and neurite outgrowth in vitro, and its effects are presumed to occur via a direct interaction with mitochondrial membranes (MMs). We examined the properties of MMs isolated from cell and animal models of HD as well as the effects of olesoxime on MM fluidity and cholesterol levels. MMs isolated from brains of aged Hdh Q111/Q111 knock-in mice showed a significant decrease in 1,6-diphenyl-hexatriene (DPH) anisotropy, which is inversely correlated with membrane fluidity. Similar increases in MM fluidity were observed in striatal STHdh Q111/Q111 cells as well as in MMs isolated from brains of BACHD transgenic rats. Treatment of STHdh cells with olesoxime decreased the fluidity of isolated MMs. Decreased membrane fluidity was also measured in olesoxime-treated MMs isolated from brains of HD knock-in mice. In both models, treatment with olesoxime restored HD-specific changes in MMs. Accordingly, olesoxime significantly counteracted the mhtt-induced increase in MM fluidity of MMs isolated from brains of BACHD rats after 12 months of treatment in vivo, possibly by enhancing MM cholesterol levels. Thus, olesoxime may represent a novel pharmacological tool to treat mitochondrial dysfunction in HD.
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Affiliation(s)
- Janett Eckmann
- Department of Pharmacology, Biocenter, Goethe-University Campus Riedberg, Biocentre Geb. N260, R.1.09, Max-von-Laue Str. 9, 60438, Frankfurt, Germany
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19
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Paradis S, Leoni V, Caccia C, Berdeaux A, Morin D. Cardioprotection by the TSPO ligand 4'-chlorodiazepam is associated with inhibition of mitochondrial accumulation of cholesterol at reperfusion. Cardiovasc Res 2013; 98:420-7. [PMID: 23554458 DOI: 10.1093/cvr/cvt079] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
AIMS The translocator protein (TSPO) is located on the outer mitochondrial membrane where it is responsible for the uptake of cholesterol into mitochondria of steroidogenic organs. TSPO is also present in the heart where its role remains uncertain. We recently showed that TSPO ligands reduced infarct size and improved mitochondrial functions after ischaemia-reperfusion. This study, thus, sought to determine whether cholesterol could play a role in the cardioprotective effect of TSPO ligands. METHODS AND RESULTS In a model of 30 min coronary occlusion/15 min reperfusion in Wistar rat, we showed that reperfusion induced lipid peroxidation as demonstrated by the increase in conjugated diene and thiobarbituric acid reactive substance formation and altered mitochondrial function (decrease in oxidative phosphorylation and increase in the sensitivity of mitochondrial permeability transition pore opening) in ex-vivo isolated mitochondria. This was associated with an increase in mitochondrial cholesterol uptake (89.5 ± 12.2 vs. 39.9 ± 3.51 nmol/mg protein in controls, P < 0.01) and a subsequent strong generation of auto-oxidized oxysterols, i.e. 7α- and 7β-hydroxycholesterol, 7-ketocholesterol, cholesterol-5α,6α-epoxide, and 5β,6β-epoxide (+173, +149, +165, +165, and +193% vs. controls, respectively; P < 0.01). Administration of the selective TSPO ligand 4'-chlorodiazepam inhibited oxidative stress, improved mitochondrial function, and abolished both mitochondrial cholesterol accumulation and oxysterol production. This was also observed with the new TSPO ligand TRO40303. CONCLUSION These data suggest that 4'-chlorodiazepam inhibits oxidative stress and oxysterol formation by reducing the accumulation of cholesterol in the mitochondrial matrix at reperfusion and prevents mitochondrial injury. This new and original mechanism may contribute to the cardioprotective properties of TSPO ligands.
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Affiliation(s)
- Stéphanie Paradis
- INSERM, U955, Equipe 3, 8 rue du Général Sarrail, Créteil Cedex 94000, France
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Falchi AM, Sogos V, Saba F, Piras M, Congiu T, Piludu M. Astrocytes shed large membrane vesicles that contain mitochondria, lipid droplets and ATP. Histochem Cell Biol 2012; 139:221-31. [PMID: 23108569 DOI: 10.1007/s00418-012-1045-x] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2012] [Indexed: 12/24/2022]
Abstract
Various cells types, including stem and progenitor cells, can exchange complex information via plasma membrane-derived vesicles, which can carry signals both in their limiting membrane and lumen. Astrocytes, traditionally regarded as mere supportive cells, play previously unrecognized functions in neuronal modulation and are capable of releasing signalling molecules of different functional significance. In the present study, we provide direct evidence that human fetal astrocytes in culture, expressing the same feature as immature and reactive astrocytes, release membrane vesicles larger than the microvesicles described up to now. We found that these large vesicles, ranging from 1-5 to 8 μm in diameter and expressing on their surface β1-integrin proteins, contain mitochondria and lipid droplets together with ATP. We documented vesicle content with fluorescent-specific dyes and with the immunocytochemistry technique we confirmed that mitochondria and lipid droplets were co-localized in the same vesicle. Scanning electron microscopy and transmission electron microscopy confirmed that astrocytes shed from surface membrane vesicles of the same size as the ones detected by fluorescence microscopy. Our results report for the first time that cultured astrocytes, activated by repetitive stimulation of ATP released from neighboring cells, shed from their surface large membrane vesicles containing mitochondria and lipid droplets.
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Affiliation(s)
- Angela Maria Falchi
- Department of Biomedical Sciences, University of Cagliari, Cittadella Universitaria Monserrato, 09042 Monserrato, CA, Italy.
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21
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Doperalski NJ, Martyniuk CJ, Prucha MS, Kroll KJ, Denslow ND, Barber DS. Cloning and expression of the translocator protein (18 kDa), voltage-dependent anion channel, and diazepam binding inhibitor in the gonad of largemouth bass (Micropterus salmoides) across the reproductive cycle. Gen Comp Endocrinol 2011; 173:86-95. [PMID: 21600210 PMCID: PMC3144257 DOI: 10.1016/j.ygcen.2011.04.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 04/30/2011] [Accepted: 04/30/2011] [Indexed: 01/14/2023]
Abstract
Cholesterol transport across the mitochondrial membrane is rate-limiting for steroidogenesis in vertebrates. Previous studies in fish have characterized expression of the steroidogenic acute regulatory protein, however the function and regulation of other genes and proteins involved in piscine cholesterol transport have not been evaluated. In the current study, mRNA sequences of the 18 kDa translocator protein (tspo; formerly peripheral benzodiazepine receptor), voltage-dependent anion channel (vdac), and diazepam binding inhibitor (dbi; also acyl-CoA binding protein) were cloned from largemouth bass. Gonadal expression was examined across reproductive stages to determine if expression is correlated with changes in steroid levels and with indicators of reproductive maturation. In testis, transcript abundance of tspo and dbi increased with reproductive maturation (6- and 23-fold maximal increase, respectively) and expression of tspo and dbi was positively correlated with reproductive stage, gonadosomatic index (GSI), and circulating levels of testosterone. Testis vdac expression was positively correlated with reproductive stage and GSI. In females, gonadal tspo and vdac expression was negatively correlated with GSI and levels of plasma testosterone and 17β-estradiol. Ovarian dbi expression was not correlated with indicators of reproductive maturation. These studies represent the first investigation of the steroidogenic role of tspo, vdac, and dbi in fish. Findings suggest that cholesterol transport in largemouth bass testis, but not in ovary, may be transcriptionally-regulated, however further investigation will be necessary to fully elucidate the role of these genes in largemouth bass steroidogenesis.
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Affiliation(s)
- Nicholas J. Doperalski
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P. O. Box 110885, 471 Mowry Road, Gainesville, FL 32611, USA
| | - Christopher J. Martyniuk
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P. O. Box 110885, 471 Mowry Road, Gainesville, FL 32611, USA
| | - Melinda S. Prucha
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P. O. Box 110885, 471 Mowry Road, Gainesville, FL 32611, USA
| | - Kevin J. Kroll
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P. O. Box 110885, 471 Mowry Road, Gainesville, FL 32611, USA
| | - Nancy D. Denslow
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P. O. Box 110885, 471 Mowry Road, Gainesville, FL 32611, USA
| | - David S. Barber
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P. O. Box 110885, 471 Mowry Road, Gainesville, FL 32611, USA
- Corresponding author; Tel.: +1 352 294-4636; fax: +1 352 392 4707;
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Midazolam inhibits hippocampal long-term potentiation and learning through dual central and peripheral benzodiazepine receptor activation and neurosteroidogenesis. J Neurosci 2011; 30:16788-95. [PMID: 21159950 DOI: 10.1523/jneurosci.4101-10.2010] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Benzodiazepines (BDZs) enhance GABA(A) receptor inhibition by direct actions on central BDZ receptors (CBRs). Although some BDZs also bind mitochondrial receptors [translocator protein (18 kDa) (TSPO)] and promote the synthesis of GABA-enhancing neurosteroids, the role of neurosteroids in the clinical effects of BDZs is unknown. In rat hippocampal slices, we compared midazolam, an anesthetic BDZ, with clonazepam, an anticonvulsant/anxiolytic BDZ that activates CBRs selectively. Midazolam, but not clonazepam, increased neurosteroid levels in CA1 pyramidal neurons without changing TSPO immunostaining. Midazolam, but not clonazepam, also augmented a form of spike inhibition after stimulation adjacent to the pyramidal cell layer and inhibited induction of long-term potentiation. These effects were prevented by finasteride, an inhibitor of neurosteroid synthesis, or 17PA [17-phenyl-(3α,5α)-androst-16-en-3-ol], a blocker of neurosteroid effects on GABA(A) receptors. Moreover, the synaptic effects were mimicked by a combination of clonazepam with FGIN (2-[2-(4-fluorophenyl)-1H-indol-3-yl]-N,N-dihexylacetamide), a selective TSPO agonist, or a combination of clonazepam with exogenous allopregnanolone. Consistent with these in vitro results, finasteride abolished the effects of midazolam on contextual fear learning when administrated 1 d before midazolam injection. Thus, dual activation of CBRs and TSPO appears to result in unique actions of clinically important BDZs. Furthermore, endogenous neurosteroids are shown to be important regulators of pyramidal neuron function and synaptic plasticity.
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Giannaccini G, Betti L, Palego L, Pirone A, Schmid L, Lanza M, Fabbrini L, Pelosini C, Maffei M, Santini F, Pinchera A, Lucacchini A. Serotonin transporter (SERT) and translocator protein (TSPO) expression in the obese ob/ob mouse. BMC Neurosci 2011; 12:18. [PMID: 21299850 PMCID: PMC3044656 DOI: 10.1186/1471-2202-12-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 02/07/2011] [Indexed: 02/03/2023] Open
Abstract
Background An ever growing body of evidences is emerging concerning metabolism hormones, neurotransmitters or stress-related biomarkers as effective modulators of eating behavior and body weight in mammals. The present study sought at examining the density and affinity of two proteins related to neurotransmission and cell metabolism, the serotonin transporter SERT and the cholesterol import-benzodiazepine site TSPO (translocator protein), in a rodent leptin-lacking mutant, the obese ob/ob mouse. Binding studies were thus carried out in brain or peripheral tissues, blood platelets (SERT) and kidneys (TSPO), of ob/ob and WT mice supplied with a standard diet, using the selective radiochemical ligands [3H]-paroxetine and [3H]-PK11195. Results We observed comparable SERT number or affinity in brain and platelets of ob/ob and WT mice, whilst a significantly higher [3H]-PK11195 density was reported in the brain of ob/ob animals. TSPO binding parameters were similar in the kidneys of all tested mice. By [3H]-PK11195 autoradiography of coronal hypothalamic-hippocampal sections, an increased TSPO signal was detected in the dentate gyrus (hippocampus) and choroids plexus of ob/ob mice, without appreciable changes in the cortex or hypothalamic-thalamic regions. Conclusions These findings show that TSPO expression is up-regulated in cerebral regions of ob/ob leptin-deficient mice, suggesting a role of the translocator protein in leptin-dependent CNS trophism and metabolism. Unchanged SERT in mutant mice is discussed herein in the context of previous literature as the forerunner to a deeper biochemical investigation.
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Affiliation(s)
- Gino Giannaccini
- Department of Psychiatry, Neurobiology, Pharmacology and Biotechnology, University of Pisa, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy.
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Effects of different doses and schedules of diazepam treatment on lymphocyte parameters in rats. Int Immunopharmacol 2010; 10:1335-43. [PMID: 20846531 DOI: 10.1016/j.intimp.2010.08.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Revised: 07/30/2010] [Accepted: 08/20/2010] [Indexed: 11/20/2022]
Abstract
Benzodiazepines (BZD) are widely used for the treatment of anxiety. They enhance GABA-ergic neurotransmission through the binding on specific BDZ recognition sites, within the GABA(A) receptor-ion channel complex. However, recent studies showed that BZD also act on peripheral benzodiazepine receptor sites (PBR) or translocator protein 18 kDa (TSPO). Evidence for a direct immunomodulatory action for BZD emerged from studies that demonstrated the presence of TSPO on immune/inflammatory cells. The present study was designed to analyze the effects of diazepam on rat lymphocyte parameters, specifically on phenotype, cell proliferation and cell death. The effects of both acute and long-term (21 days) diazepam (1 and 10 mg/kg/day) administrations were evaluated. Results showed that diazepam (1 mg/kg) treatment did not change the immune parameters analyzed. However, both diazepam (10 mg/kg) acute and long-term treatments decreased the number of apoptotic cells; they also increased the percentage of T cytotoxic cells; decreased the percentage of B cells and increased the corticosterone serum levels. The induction of functional tolerance was suggested for the highest dose of diazepam (10 mg/kg), but not for the smaller dose (1 mg/kg) used, at least for diazepam effects on corticosterone serum levels. Diazepam effects were discussed as being related to the number of TSPO sites present on immune cells and/or to the increased levels of serum corticosterone observed after the treatments used.
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Guillaumot D, Guillon S, Déplanque T, Vanhee C, Gumy C, Masquelier D, Morsomme P, Batoko H. The Arabidopsis TSPO-related protein is a stress and abscisic acid-regulated, endoplasmic reticulum-Golgi-localized membrane protein. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 60:242-56. [PMID: 19548979 DOI: 10.1111/j.1365-313x.2009.03950.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The Arabidopsis gene At2g47770 encodes a membrane-bound protein designated AtTSPO (Arabidopsis thaliana TSPO-related). AtTSPO is related to the bacterial outer membrane tryptophan-rich sensory protein (TspO) and the mammalian mitochondrial 18-kDa translocator protein (18 kDa TSPO), members of the group of TspO/MBR domain-containing membrane proteins. In this study we show that AtTSPO is mainly detected in dry seeds, but can be induced in vegetative tissues by osmotic or salt stress or abscisic acid (ABA) treatment, corroborating available transcriptome data. Using subcellular fractionation, immunocytochemistry and fluorescent protein tagging approaches we present evidence that AtTSPO is targeted to the secretory pathway in plants. Induced or constitutively expressed AtTSPO can be detected in the endoplasmic reticulum and the Golgi stacks of plant cells. AtTSPO tagged with fluorescent protein in transgenic plants (Arabidopsis and tobacco) was mainly detected in the Golgi stacks of leaf epidermal cells. Constitutive expression of AtTSPO resulted in increased sensitivity to NaCl, but not to osmotic stress, and in reduced greening of cultured Arabidopsis cells under light growing conditions. Transgenic Arabidopsis plants overexpressing AtTSPO were more sensitive to ABA-induced growth inhibition, indicating that constitutive expression of AtTSPO may enhance ABA sensitivity. AtTSPO is rapidly downregulated during seed imbibition, and the ABA-dependent induction in plant is transient. Downregulation of AtTSPO seems to be boosted by treatment with aminolevulinic acid. Taken together, these results suggest that AtTSPO is a highly regulated protein, induced by abiotic stress to modulate, at least in part, transient intracellular ABA-dependent stress perception and/or signalling.
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Affiliation(s)
- Damien Guillaumot
- Institut des Sciences de la Vie, Molecular Physiology Group, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
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Rone MB, Liu J, Blonder J, Ye X, Veenstra TD, Young JC, Papadopoulos V. Targeting and insertion of the cholesterol-binding translocator protein into the outer mitochondrial membrane. Biochemistry 2009; 48:6909-20. [PMID: 19552401 DOI: 10.1021/bi900854z] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Translocator protein (18 kDa, TSPO), previously known as the peripheral-type benzodiazepine receptor, is an outer mitochondrial membrane (OMM) protein necessary for cholesterol import and steroid production. We reconstituted the mitochondrial targeting and insertion of TSPO into the OMM to analyze the signals and mechanisms required for this process. Initial studies indicated the formation of a mitochondrial 66 kDa complex through Blue Native-PAGE analysis. The formation of this complex was found to be dependent on the presence of ATP and the cytosolic chaperone Hsp90. Through mutational analysis we identified two areas necessary for TSPO targeting, import, and function: amino acids 103-108 (Schellman motif), which provide the necessary structural orientation for import, and the cholesterol-binding C-terminus required for insertion. Although the translocase of the outer mitochondrial membrane (TOM) complex proteins Tom22 and Tom40 were present in the OMM, the TOM complex did not interact with TSPO. In search of proteins involved in TSPO import, we analyzed complexes known to interact with TSPO by mass spectrometry. Formation of the 66 kDa complex was found to be dependent on an identified protein, Metaxin 1, for formation and TSPO import. The level of import of TSPO into steroidogenic cell mitochondria was increased following treatment of the cells with cAMP. These findings suggest that the initial targeting of TSPO to mitochondria is dependent upon the presence of cytosolic chaperones interacting with the import receptor Tom70. The C-terminus plays an important role in targeting TSPO to mitochondria, whereas its import into the OMM is dependent upon the presence of the Schellman motif. Final integration of TSPO into the OMM occurs via its interaction with Metaxin 1. Import of TSPO into steroidogenic cell mitochondria is regulated by cAMP.
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Affiliation(s)
- Malena B Rone
- Department of Biochemistry, Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC 20007, USA
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Do Rego JL, Seong JY, Burel D, Leprince J, Luu-The V, Tsutsui K, Tonon MC, Pelletier G, Vaudry H. Neurosteroid biosynthesis: enzymatic pathways and neuroendocrine regulation by neurotransmitters and neuropeptides. Front Neuroendocrinol 2009; 30:259-301. [PMID: 19505496 DOI: 10.1016/j.yfrne.2009.05.006] [Citation(s) in RCA: 282] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 05/12/2009] [Accepted: 05/21/2009] [Indexed: 01/09/2023]
Abstract
Neuroactive steroids synthesized in neuronal tissue, referred to as neurosteroids, are implicated in proliferation, differentiation, activity and survival of nerve cells. Neurosteroids are also involved in the control of a number of behavioral, neuroendocrine and metabolic processes such as regulation of food intake, locomotor activity, sexual activity, aggressiveness, anxiety, depression, body temperature and blood pressure. In this article, we summarize the current knowledge regarding the existence, neuroanatomical distribution and biological activity of the enzymes responsible for the biosynthesis of neurosteroids in the brain of vertebrates, and we review the neuronal mechanisms that control the activity of these enzymes. The observation that the activity of key steroidogenic enzymes is finely tuned by various neurotransmitters and neuropeptides strongly suggests that some of the central effects of these neuromodulators may be mediated via the regulation of neurosteroid production.
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Affiliation(s)
- Jean Luc Do Rego
- Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 413, 76821 Mont-Saint-Aignan, France
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Rone MB, Fan J, Papadopoulos V. Cholesterol transport in steroid biosynthesis: role of protein-protein interactions and implications in disease states. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:646-58. [PMID: 19286473 DOI: 10.1016/j.bbalip.2009.03.001] [Citation(s) in RCA: 258] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Revised: 02/28/2009] [Accepted: 03/03/2009] [Indexed: 12/20/2022]
Abstract
The transfer of cholesterol from the outer to the inner mitochondrial membrane is the rate-limiting step in hormone-induced steroid formation. To ensure that this step is achieved efficiently, free cholesterol must accumulate in excess at the outer mitochondrial membrane and then be transferred to the inner membrane. This is accomplished through a series of steps that involve various intracellular organelles, including lysosomes and lipid droplets, and proteins such as the translocator protein (18 kDa, TSPO) and steroidogenic acute regulatory (StAR) proteins. TSPO, previously known as the peripheral-type benzodiazepine receptor, is a high-affinity drug- and cholesterol-binding mitochondrial protein. StAR is a hormone-induced mitochondria-targeted protein that has been shown to initiate cholesterol transfer into mitochondria. Through the assistance of proteins such as the cAMP-dependent protein kinase regulatory subunit Ialpha (PKA-RIalpha) and the PKA-RIalpha- and TSPO-associated acyl-coenzyme A binding domain containing 3 (ACBD3) protein, PAP7, cholesterol is transferred to and docked at the outer mitochondrial membrane. The TSPO-dependent import of StAR into mitochondria, and the association of TSPO with the outer/inner mitochondrial membrane contact sites, drives the intramitochondrial cholesterol transfer and subsequent steroid formation. The focus of this review is on (i) the intracellular pathways and protein-protein interactions involved in cholesterol transport and steroid biosynthesis and (ii) the roles and interactions of these proteins in endocrine pathologies and neurological diseases where steroid synthesis plays a critical role.
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Affiliation(s)
- Malena B Rone
- The Research Institute of the McGill University Health Centre and Department of Medicine, McGill University, 1650 Cedar Avenue, Montreal, Quebec, Canada H3G 1A4
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Chen MK, Guilarte TR. Translocator protein 18 kDa (TSPO): molecular sensor of brain injury and repair. Pharmacol Ther 2008; 118:1-17. [PMID: 18374421 DOI: 10.1016/j.pharmthera.2007.12.004] [Citation(s) in RCA: 397] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Accepted: 12/21/2007] [Indexed: 11/25/2022]
Abstract
For over 15 years, the peripheral benzodiazepine receptor (PBR), recently named translocator protein 18 kDa (TSPO) has been studied as a biomarker of reactive gliosis and inflammation associated with a variety of neuropathological conditions. Early studies documented that in the brain parenchyma, TSPO is exclusively localized in glial cells. Under normal physiological conditions, TSPO levels are low in the brain neuropil but they markedly increase at sites of brain injury and inflammation making it uniquely suited for assessing active gliosis. This research has generated significant efforts from multiple research groups throughout the world to apply TSPO as a marker of "active" brain pathology using in vivo imaging modalities such as Positron Emission Tomography (PET) in experimental animals and humans. Further, in the last few years, there has been an increased interest in understanding the molecular and cellular function(s) of TSPO in glial cells. The latest evidence suggests that TSPO may not only serve as a biomarker of active brain disease but also the use of TSPO-specific ligands may have therapeutic implications in brain injury and repair. This review presents an overview of the history and function of TSPO focusing on studies related to its use as a sensor of active brain disease in experimental animals and in human studies.
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Affiliation(s)
- Ming-Kai Chen
- Neurotoxicology & Molecular Imaging Laboratory, Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
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