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Yu M, Zhao S. Functional role of translocator protein and its ligands in ocular diseases (Review). Mol Med Rep 2024; 29:33. [PMID: 38186312 PMCID: PMC10804439 DOI: 10.3892/mmr.2024.13157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 12/08/2023] [Indexed: 01/09/2024] Open
Abstract
The 18 kDa translocator protein (TSPO) is an essential outer mitochondrial membrane protein that is responsible for mitochondrial transport, maintenance of mitochondrial homeostasis and normal physiological cell function. The role of TSPO in the pathogenesis of ocular diseases is a growing area of interest. More notably, TSPO exerts positive effects in regulating various pathophysiological processes, such as the inflammatory response, oxidative stress, steroid synthesis and modulation of microglial function, in combination with a variety of specific ligands such as 1‑(2‑chlorophenyl‑N‑methylpropyl)‑3‑isoquinolinecarboxamide, 4'‑chlorodiazepam and XBD173. In the present review, the expression of TSPO in ocular tissues and the functional role of TSPO and its ligands in diverse ocular diseases was discussed.
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Affiliation(s)
- Mingyi Yu
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 30384, P.R. China
| | - Shaozhen Zhao
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 30384, P.R. China
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2
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Wei W, Wang S, Xu C, Zhou X, Lian X, He L, Li K. Gut microbiota, pathogenic proteins and neurodegenerative diseases. Front Microbiol 2022; 13:959856. [PMID: 36466655 PMCID: PMC9715766 DOI: 10.3389/fmicb.2022.959856] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 10/07/2022] [Indexed: 12/20/2023] Open
Abstract
As the world's population ages, neurodegenerative diseases (NDs) have brought a great burden to the world. However, effective treatment measures have not been found to alleviate the occurrence and development of NDs. Abnormal accumulation of pathogenic proteins is an important cause of NDs. Therefore, effective inhibition of the accumulation of pathogenic proteins has become a priority. As the second brain of human, the gut plays an important role in regulate emotion and cognition functions. Recent studies have reported that the disturbance of gut microbiota (GM) is closely related to accumulation of pathogenic proteins in NDs. On the one hand, pathogenic proteins directly produced by GM are transmitted from the gut to the central center via vagus nerve. On the other hand, The harmful substances produced by GM enter the peripheral circulation through intestinal barrier and cause inflammation, or cross the blood-brain barrier into the central center to cause inflammation, and cytokines produced by the central center cause the production of pathogenic proteins. These pathogenic proteins can produced by the above two aspects can cause the activation of central microglia and further lead to NDs development. In addition, certain GM and metabolites have been shown to have neuroprotective effects. Therefore, modulating GM may be a potential clinical therapeutic approach for NDs. In this review, we summarized the possible mechanism of NDs caused by abnormal accumulation of pathogenic proteins mediated by GM to induce the activation of central microglia, cause central inflammation and explore the therapeutic potential of dietary therapy and fecal microbiota transplantation (FMT) in NDs.
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Affiliation(s)
- Wei Wei
- The Mental Hospital of Yunnan Province, Mental Health Center Affiliated to Kunming Medical University, Kunming, China
- School of Forensic Medicine, Kunming Medical University, Kunming, China
| | - Shixu Wang
- School of Forensic Medicine, Kunming Medical University, Kunming, China
| | - Chongchong Xu
- School of Forensic Medicine, Kunming Medical University, Kunming, China
| | - Xuemei Zhou
- School of Forensic Medicine, Kunming Medical University, Kunming, China
| | - Xinqing Lian
- School of Forensic Medicine, Kunming Medical University, Kunming, China
| | - Lin He
- The Mental Hospital of Yunnan Province, Mental Health Center Affiliated to Kunming Medical University, Kunming, China
| | - Kuan Li
- School of Forensic Medicine, Kunming Medical University, Kunming, China
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Liu Q, Huang Y, Duan M, Yang Q, Ren B, Tang F. Microglia as Therapeutic Target for Radiation-Induced Brain Injury. Int J Mol Sci 2022; 23:ijms23158286. [PMID: 35955439 PMCID: PMC9368164 DOI: 10.3390/ijms23158286] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 07/22/2022] [Accepted: 07/25/2022] [Indexed: 12/10/2022] Open
Abstract
Radiation-induced brain injury (RIBI) after radiotherapy has become an increasingly important factor affecting the prognosis of patients with head and neck tumor. With the delivery of high doses of radiation to brain tissue, microglia rapidly transit to a pro-inflammatory phenotype, upregulate phagocytic machinery, and reduce the release of neurotrophic factors. Persistently activated microglia mediate the progression of chronic neuroinflammation, which may inhibit brain neurogenesis leading to the occurrence of neurocognitive disorders at the advanced stage of RIBI. Fully understanding the microglial pathophysiology and cellular and molecular mechanisms after irradiation may facilitate the development of novel therapy by targeting microglia to prevent RIBI and subsequent neurological and neuropsychiatric disorders.
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Affiliation(s)
- Qun Liu
- The School of Basic Medicine, Health Science Center, Yangtze University, Jingzhou 434023, China; (Q.L.); (Y.H.)
| | - Yan Huang
- The School of Basic Medicine, Health Science Center, Yangtze University, Jingzhou 434023, China; (Q.L.); (Y.H.)
| | - Mengyun Duan
- Department of Pharmacology, School of Medicine, Yangtze University, Jingzhou 434023, China; (M.D.); (Q.Y.)
| | - Qun Yang
- Department of Pharmacology, School of Medicine, Yangtze University, Jingzhou 434023, China; (M.D.); (Q.Y.)
| | - Boxu Ren
- The School of Basic Medicine, Health Science Center, Yangtze University, Jingzhou 434023, China; (Q.L.); (Y.H.)
- Correspondence: (B.R.); (F.T.)
| | - Fengru Tang
- Radiation Physiology Laboratory, Singapore Nuclear Research and Safety Initiative, National University of Singapore, Singapore 138602, Singapore
- Correspondence: (B.R.); (F.T.)
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Translocator Protein Regulate Polarization Phenotype Transformation of Microglia after Cerebral Ischemia-reperfusion Injury. Neuroscience 2021; 480:203-216. [PMID: 34624453 DOI: 10.1016/j.neuroscience.2021.09.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/26/2021] [Accepted: 09/28/2021] [Indexed: 12/12/2022]
Abstract
Microglia cells are activated after cerebral ischemia-reperfusion injury (CIRI), playing a dual role in aggravating the injury or promoting tissue repair by polarization. Translocator protein (TSPO) is a biomarker of neuroinflammation or microglia activation. Its expression is significantly increased while brain injury and neuroinflammation occur. However, the relationship between TSPO and microglia polarization in CIRI is still not clear. In the present study, the middle cerebral artery occlusion (MCAO) methods in rats were used to simulate CIRI. We found that the expressions of M1 markers (CD86, IL-1β, and TNF-α) and M2 markers (CD206, IL-10, and TGF-β) were significantly increased. Moreover, the injection of TSPO ligand, PK11195, inhibited the increase of M1 polarization markers but promoted the expressions of M2 polarization markers, which significantly ameliorated the neurological damage after MCAO in rats. In vitro studies showed that shRNA-mediated TSPO knock-down promoted M1 polarization but inhibited M2 polarization, accompanied by a significant decrease in cell viability. On the contrary, overexpression of TSPO inhibited M1 polarization, promoted M2 polarization, and significantly improved cell viability. In summary, TSPO plays a neuroprotective role in CIRI by inhibiting M1 polarization and promoting M2 polarization, which suggests that TSPO may have the potential to serve as a therapeutic target for stroke.
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Dominguini D, Steckert AV, Abatti MR, Generoso JS, Barichello T, Dal-Pizzol F. The Protective Effect of PK-11195 on Cognitive Impairment in Rats Survived of Polymicrobial Sepsis. Mol Neurobiol 2021; 58:2724-2733. [PMID: 33495933 DOI: 10.1007/s12035-021-02294-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 01/13/2021] [Indexed: 10/22/2022]
Abstract
Sepsis is an organ dysfunction caused by a host's unregulated response to infection, causing long-term brain dysfunction with microglial activation, the release of inflammatory components, and mitochondrial changes. Neuroinflammation can increase the expression of the 18-kD translocator protein (TSPO) in the mitochondria, leading to the activation of the microglia and the release of inflammatory components. The antagonist PK-11195 can modulate TSPO and reduce microglial activation and cognitive damage presented in an animal model of sepsis. The aim of this was to evaluate the effects of PK-11195 on long-term brain inflammation and cognitive impairment in an animal model of sepsis. Wistar rats, 60 days old, were submitted to cecal ligation and puncture (CLP) surgery, divided into groups control/saline, control/PK-11195, sepsis/saline, and sepsis/PK-11195. Immediately after surgery, the antagonist PK-11195 was administered at a dose of 3 mg/kg. Ten days after CLP surgery, the animals were submitted to behavioral tests and determination of brain inflammatory parameters. The sepsis/saline group presented cognitive damage. However, there was damage prevention in animals that received PK-11195. Besides, the sepsis increased the levels of cytokines and M1 microglia markers and caused oxidative damage. However, PK-11195 had the potential to decrease inflammation. These events show that the modulation of neuroinflammation during sepsis by PK-11195, possibly related to changes in TSPO, improves mitochondrial function in the animals' brains. In conclusion, the antagonist PK-11195 attenuated brain inflammation and prevented cognitive impairment in animals subjected to sepsis.
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Affiliation(s)
- Diogo Dominguini
- Laboratory of Experimental Pathophysiology, Graduate Program in Health Sciences, University of Southern Santa Catarina (UNESC), Criciúma, SC, 88806-000, Brazil.
| | - Amanda V Steckert
- Laboratory of Experimental Pathophysiology, Graduate Program in Health Sciences, University of Southern Santa Catarina (UNESC), Criciúma, SC, 88806-000, Brazil
| | - Mariane R Abatti
- Laboratory of Experimental Pathophysiology, Graduate Program in Health Sciences, University of Southern Santa Catarina (UNESC), Criciúma, SC, 88806-000, Brazil
| | - Jaqueline S Generoso
- Laboratory of Experimental Pathophysiology, Graduate Program in Health Sciences, University of Southern Santa Catarina (UNESC), Criciúma, SC, 88806-000, Brazil
| | - Tatiana Barichello
- Laboratory of Experimental Pathophysiology, Graduate Program in Health Sciences, University of Southern Santa Catarina (UNESC), Criciúma, SC, 88806-000, Brazil
- Translational Psychiatry Program, Department of Psychiatry and Behavioral Sciences, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Felipe Dal-Pizzol
- Laboratory of Experimental Pathophysiology, Graduate Program in Health Sciences, University of Southern Santa Catarina (UNESC), Criciúma, SC, 88806-000, Brazil
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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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Fairley LH, Sahara N, Aoki I, Ji B, Suhara T, Higuchi M, Barron AM. Neuroprotective effect of mitochondrial translocator protein ligand in a mouse model of tauopathy. J Neuroinflammation 2021; 18:76. [PMID: 33740987 PMCID: PMC7980620 DOI: 10.1186/s12974-021-02122-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/02/2021] [Indexed: 12/13/2022] Open
Abstract
Background The translocator protein (TSPO) has been identified as a positron emission tomography (PET)-visible biomarker of inflammation and promising immunotherapeutic target for the treatment of Alzheimer’s disease (AD). While TSPO ligands have been shown to reduce the accumulation of the toxic Alzheimer’s beta-amyloid peptide, their effect on tau pathology has not yet been investigated. To address this, we analyzed the effects of TSPO ligand, Ro5-4864, on the progression of neuropathology in rTg4510 tau transgenic mice (TauTg). Methods Brain atrophy, tau accumulation, and neuroinflammation were assessed longitudinally using volumetric magnetic resonance imaging, tau-PET, and TSPO-PET, respectively. In vivo neuroimaging results were confirmed by immunohistochemistry for markers of neuronal survival (NeuN), tauopathy (AT8), and inflammation (TSPO, ionized calcium-binding adaptor molecule 1 or IBA-1, and complement component 1q or C1q) in brain sections from scanned mice. Results TSPO ligand treatment attenuated brain atrophy and hippocampal neuronal loss in the absence of any detected effect on tau depositions. Atrophy and neuronal loss were strongly associated with in vivo inflammatory signals measured by TSPO-PET, IBA-1, and levels of C1q, a regulator of the complement cascade. In vitro studies confirmed that the TSPO ligand Ro5-4864 reduces C1q expression in a microglial cell line in response to inflammation, reduction of which has been shown in previous studies to protect synapses and neurons in models of tauopathy. Conclusions These findings support a protective role for TSPO ligands in tauopathy, reducing neuroinflammation, neurodegeneration, and brain atrophy. Supplementary Information The online version contains supplementary material available at 10.1186/s12974-021-02122-1.
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Affiliation(s)
- Lauren H Fairley
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, Singapore, 308232, Singapore
| | - Naruhiko Sahara
- National Institute of Radiological Science, Chiba City, Chiba Province, 263-8555, Japan
| | - Ichio Aoki
- National Institute of Radiological Science, Chiba City, Chiba Province, 263-8555, Japan
| | - Bin Ji
- National Institute of Radiological Science, Chiba City, Chiba Province, 263-8555, Japan
| | - Tetsuya Suhara
- National Institute of Radiological Science, Chiba City, Chiba Province, 263-8555, Japan
| | - Makoto Higuchi
- National Institute of Radiological Science, Chiba City, Chiba Province, 263-8555, Japan
| | - Anna M Barron
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, Singapore, 308232, Singapore. .,National Institute of Radiological Science, Chiba City, Chiba Province, 263-8555, Japan.
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Ammer LM, Vollmann-Zwerenz A, Ruf V, Wetzel CH, Riemenschneider MJ, Albert NL, Beckhove P, Hau P. The Role of Translocator Protein TSPO in Hallmarks of Glioblastoma. Cancers (Basel) 2020; 12:cancers12102973. [PMID: 33066460 PMCID: PMC7602186 DOI: 10.3390/cancers12102973] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 10/09/2020] [Accepted: 10/09/2020] [Indexed: 12/18/2022] Open
Abstract
Simple Summary The translocator protein (TSPO) has been under extensive investigation as a specific marker in positron emission tomography (PET) to visualize brain lesions following injury or disease. In recent years, TSPO is increasingly appreciated as a potential novel therapeutic target in cancer. In Glioblastoma (GBM), the most malignant primary brain tumor, TSPO expression levels are strongly elevated and scientific evidence accumulates, hinting at a pivotal role of TSPO in tumorigenesis and glioma progression. The aim of this review is to summarize the current literature on TSPO with respect to its role both in diagnostics and especially with regard to the critical hallmarks of cancer postulated by Hanahan and Weinberg. Overall, our review contributes to a better understanding of the functional significance of TSPO in Glioblastoma and draws attention to TSPO as a potential modulator of treatment response and thus an important factor that may influence the clinical outcome of GBM. Abstract Glioblastoma (GBM) is the most fatal primary brain cancer in adults. Despite extensive treatment, tumors inevitably recur, leading to an average survival time shorter than 1.5 years. The 18 kDa translocator protein (TSPO) is abundantly expressed throughout the body including the central nervous system. The expression of TSPO increases in states of inflammation and brain injury due to microglia activation. Not least due to its location in the outer mitochondrial membrane, TSPO has been implicated with a broad spectrum of functions. These include the regulation of proliferation, apoptosis, migration, as well as mitochondrial functions such as mitochondrial respiration and oxidative stress regulation. TSPO is frequently overexpressed in GBM. Its expression level has been positively correlated to WHO grade, glioma cell proliferation, and poor prognosis of patients. Several lines of evidence indicate that TSPO plays a functional part in glioma hallmark features such as resistance to apoptosis, invasiveness, and proliferation. This review provides a critical overview of how TSPO could regulate several aspects of tumorigenesis in GBM, particularly in the context of the hallmarks of cancer proposed by Hanahan and Weinberg in 2011.
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Affiliation(s)
- Laura-Marie Ammer
- Wilhelm Sander-NeuroOncology Unit and Department of Neurology, University Hospital Regensburg, 93053 Regensburg, Germany; (L.-M.A.); (A.V.-Z.)
| | - Arabel Vollmann-Zwerenz
- Wilhelm Sander-NeuroOncology Unit and Department of Neurology, University Hospital Regensburg, 93053 Regensburg, Germany; (L.-M.A.); (A.V.-Z.)
| | - Viktoria Ruf
- Center for Neuropathology and Prion Research, Ludwig Maximilians University of Munich, 81377 Munich, Germany;
| | - Christian H. Wetzel
- Molecular Neurosciences, Department of Psychiatry and Psychotherapy, University of Regensburg, 93053 Regensburg, Germany;
| | | | - Nathalie L. Albert
- Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, 81377 Munich, Germany;
| | - Philipp Beckhove
- Regensburg Center for Interventional Immunology (RCI) and Department Internal Medicine III, University Hospital Regensburg, 93053 Regensburg, Germany;
| | - Peter Hau
- Wilhelm Sander-NeuroOncology Unit and Department of Neurology, University Hospital Regensburg, 93053 Regensburg, Germany; (L.-M.A.); (A.V.-Z.)
- Correspondence:
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Molecular Mechanisms of Glial Cells Related Signaling Pathways Involved in the Neuroinflammatory Response of Depression. Mediators Inflamm 2020; 2020:3497920. [PMID: 33100903 PMCID: PMC7569467 DOI: 10.1155/2020/3497920] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 09/17/2020] [Accepted: 09/28/2020] [Indexed: 02/07/2023] Open
Abstract
Dysfunction of the glial cells, such as astrocytes and microglia, is one of the pathological features in many psychiatric disorders, including depression, which emphasizes that glial cells driving neuroinflammation is not only an important pathological change in depression but also a potential therapeutic target. In this review, we summarized a recent update about several signaling pathways in which glial cells may play their roles in depression through neuroinflammatory reactions. We focused on the basic knowledge of these signaling pathways by elaborating each of them. This review may provide an updated image about the recent advances on these signaling pathways that are essential parts of neuroinflammation involved in depression.
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Betlazar C, Middleton RJ, Banati R, Liu GJ. The Translocator Protein (TSPO) in Mitochondrial Bioenergetics and Immune Processes. Cells 2020; 9:cells9020512. [PMID: 32102369 PMCID: PMC7072813 DOI: 10.3390/cells9020512] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 02/19/2020] [Accepted: 02/19/2020] [Indexed: 12/11/2022] Open
Abstract
The translocator protein (TSPO) is an outer mitochondrial membrane protein that is widely used as a biomarker of neuroinflammation, being markedly upregulated in activated microglia in a range of brain pathologies. Despite its extensive use as a target in molecular imaging studies, the exact cellular functions of this protein remain in question. The long-held view that TSPO plays a fundamental role in the translocation of cholesterol through the mitochondrial membranes, and thus, steroidogenesis, has been disputed by several groups with the advent of TSPO knockout mouse models. Instead, much evidence is emerging that TSPO plays a fundamental role in cellular bioenergetics and associated mitochondrial functions, also part of a greater role in the innate immune processes of microglia. In this review, we examine the more direct experimental literature surrounding the immunomodulatory effects of TSPO. We also review studies which highlight a more central role for TSPO in mitochondrial processes, from energy metabolism, to the propagation of inflammatory responses through reactive oxygen species (ROS) modulation. In this way, we highlight a paradigm shift in approaches to TSPO functioning.
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Affiliation(s)
- Calina Betlazar
- Human Health, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia; (R.J.M.); (R.B.)
- Discipline of Medical Imaging & Radiation Sciences, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW 2050, Australia
- Correspondence: (C.B.); (G-J.L.)
| | - Ryan J. Middleton
- Human Health, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia; (R.J.M.); (R.B.)
| | - Richard Banati
- Human Health, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia; (R.J.M.); (R.B.)
- Discipline of Medical Imaging & Radiation Sciences, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW 2050, Australia
| | - Guo-Jun Liu
- Human Health, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia; (R.J.M.); (R.B.)
- Discipline of Medical Imaging & Radiation Sciences, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW 2050, Australia
- Correspondence: (C.B.); (G-J.L.)
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Rojas A, Banik A, Chen D, Flood K, Ganesh T, Dingledine R. Novel Microglia Cell Line Expressing the Human EP2 Receptor. ACS Chem Neurosci 2019; 10:4280-4292. [PMID: 31469538 DOI: 10.1021/acschemneuro.9b00311] [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] [Indexed: 02/06/2023] Open
Abstract
Recently, EP2 signaling pathways were shown to regulate the classical activation and death of microglia in rat primary microglial culture. The study of microglial cells has been challenging because they are time-consuming to isolate in culture, they are demanding in their growth requirements, and they have a limited lifespan. To circumvent these difficulties, we created a murine BV2 microglial cell line stably expressing human EP2 receptors (BV2-hEP2) and further explored EP2 modulation of microglial functions. The BV2-hEP2 cells displayed cAMP elevation when exposed to the selective EP2 receptor agonists (ONO-AE1-259-1 and CP544326), and this response was competitively inhibited by TG4-155, a selective EP2 antagonist (Schild KB = 2.6 nM). By contrast, untransfected BV2 cells were unresponsive to selective EP2 agonists. Similar to the case of rat primary microglia, BV2-hEP2 microglia treated with lipopolysaccharide (LPS) (100 ng/mL) displayed rapid and robust induction of the inflammatory mediators COX-2, IL-1β, TNFα, and IL-6. EP2 activation depressed TNFα induction but exacerbated that of the other inflammatory mediators. Like primary microglia, classically activated BV2 microglia phagocytose fluorescent-labeled latex microspheres. The presence of EP2, but not its activation by agonists, in BV2-hEP2 microglia reduced phagocytosis and proliferation by 65% and 32%, respectively, compared to BV2 microglia. Thus, BV2-hEP2 is the first microglial cell line that retains the EP2 modulation of immune regulation and phagocytic ability of native microglia. Suppression of phagocytosis by the EP2 protein appears unrelated to classical EP2 signaling pathways, which has implications for therapeutic development of EP2 antagonists.
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Affiliation(s)
- Asheebo Rojas
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia 30322, United States
| | - Avijit Banik
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia 30322, United States
| | - Di Chen
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia 30322, United States
| | - Kevin Flood
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia 30322, United States
| | - Thota Ganesh
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia 30322, United States
| | - Raymond Dingledine
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia 30322, United States
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Da Pozzo E, Tremolanti C, Costa B, Giacomelli C, Milenkovic VM, Bader S, Wetzel CH, Rupprecht R, Taliani S, Da Settimo F, Martini C. Microglial Pro-Inflammatory and Anti-Inflammatory Phenotypes Are Modulated by Translocator Protein Activation. Int J Mol Sci 2019; 20:ijms20184467. [PMID: 31510070 PMCID: PMC6770267 DOI: 10.3390/ijms20184467] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 09/06/2019] [Accepted: 09/09/2019] [Indexed: 12/13/2022] Open
Abstract
A key role of the mitochondrial Translocator Protein 18 KDa (TSPO) in neuroinflammation has been recently proposed. However, little is known about TSPO-activated pathways underlying the modulation of reactive microglia. In the present work, the TSPO activation was explored in an in vitro human primary microglia model (immortalized C20 cells) under inflammatory stimulus. Two different approaches were used with the aim to (i) pharmacologically amplify or (ii) silence, by the lentiviral short hairpin RNA, the TSPO physiological function. In the TSPO pharmacological stimulation model, the synthetic steroidogenic selective ligand XBD-173 attenuated the activation of microglia. Indeed, it reduces and increases the release of pro-inflammatory and anti-inflammatory cytokines, respectively. Such ligand-induced effects were abolished when C20 cells were treated with the steroidogenesis inhibitor aminoglutethimide. This suggests a role for neurosteroids in modulating the interleukin production. The highly steroidogenic ligand XBD-173 attenuated the neuroinflammatory response more effectively than the poorly steroidogenic ones, which suggests that the observed modulation on the cytokine release may be influenced by the levels of produced neurosteroids. In the TSPO silencing model, the reduction of TSPO caused a more inflamed phenotype with respect to scrambled cells. Similarly, during the inflammatory response, the TSPO silencing increased and reduced the release of pro-inflammatory and anti-inflammatory cytokines, respectively. In conclusion, the obtained results are in favor of a homeostatic role for TSPO in the context of dynamic balance between anti-inflammatory and pro-inflammatory mediators in the human microglia-mediated inflammatory response. Interestingly, our preliminary results propose that the TSPO expression could be stimulated by NF-κB during activation of the inflammatory response.
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Affiliation(s)
- Eleonora Da Pozzo
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Chiara Tremolanti
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Barbara Costa
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
- Correspondence:
| | - Chiara Giacomelli
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Vladimir M. Milenkovic
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Stefanie Bader
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Christian H. Wetzel
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Rainer Rupprecht
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Federico Da Settimo
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Claudia Martini
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
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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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Bonsack F, Sukumari-Ramesh S. TSPO: An Evolutionarily Conserved Protein with Elusive Functions. Int J Mol Sci 2018; 19:ijms19061694. [PMID: 29875327 PMCID: PMC6032217 DOI: 10.3390/ijms19061694] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 05/18/2018] [Indexed: 12/22/2022] Open
Abstract
TSPO (18 kDa translocator protein) was identified decades ago in a search for peripheral tissue binding sites for benzodiazepines, and was formerly called the peripheral benzodiazepine receptor. TSPO is a conserved protein throughout evolution and it is implicated in the regulation of many cellular processes, including inflammatory responses, oxidative stress, and mitochondrial homeostasis. TSPO, apart from its broad expression in peripheral tissues, is highly expressed in neuroinflammatory cells, such as activated microglia. In addition, emerging studies employing the ligands of TSPO suggest that TSPO plays an important role in neuropathological settings as a biomarker and therapeutic target. However, the precise molecular function of this protein in normal physiology and neuropathology remains enigmatic. This review provides an overview of recent advances in our understanding of this multifaceted molecule and identifies the knowledge gap in the field for future functional studies.
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Affiliation(s)
- Frederick Bonsack
- Department of Neurosurgery, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA.
| | - Sangeetha Sukumari-Ramesh
- Department of Neurosurgery, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA.
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15
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Larson TA. Sex Steroids, Adult Neurogenesis, and Inflammation in CNS Homeostasis, Degeneration, and Repair. Front Endocrinol (Lausanne) 2018; 9:205. [PMID: 29760681 PMCID: PMC5936772 DOI: 10.3389/fendo.2018.00205] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 04/12/2018] [Indexed: 01/16/2023] Open
Abstract
Sex steroidal hormones coordinate the development and maintenance of tissue architecture in many organs, including the central nervous systems (CNS). Within the CNS, sex steroids regulate the morphology, physiology, and behavior of a wide variety of neural cells including, but not limited to, neurons, glia, endothelial cells, and immune cells. Sex steroids spatially and temporally control distinct molecular networks, that, in turn modulate neural activity, synaptic plasticity, growth factor expression and function, nutrient exchange, cellular proliferation, and apoptosis. Over the last several decades, it has become increasingly evident that sex steroids, often in conjunction with neuroinflammation, have profound impact on the occurrence and severity of neuropsychiatric and neurodegenerative disorders. Here, I review the foundational discoveries that established the regulatory role of sex steroids in the CNS and highlight recent advances toward elucidating the complex interaction between sex steroids, neuroinflammation, and CNS regeneration through adult neurogenesis. The majority of recent work has focused on neuroinflammatory responses following acute physical damage, chronic degeneration, or pharmacological insult. Few studies directly assess the role of immune cells in regulating adult neurogenesis under healthy, homeostatic conditions. As such, I also introduce tractable, non-traditional models for examining the role of neuroimmune cells in natural neuronal turnover, seasonal plasticity of neural circuits, and extreme CNS regeneration.
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Affiliation(s)
- Tracy A. Larson
- Department of Biology, University of Virginia, Charlottesville, VA, United States
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16
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Partoazar A, Nasoohi S, Rezayat SM, Gilani K, Mehr SE, Amani A, Rahimi N, Dehpour AR. Nanoliposome containing cyclosporine A reduced neuroinflammation responses and improved neurological activities in cerebral ischemia/reperfusion in rat. Fundam Clin Pharmacol 2016; 31:185-193. [PMID: 27616018 DOI: 10.1111/fcp.12244] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 09/04/2016] [Accepted: 09/08/2016] [Indexed: 12/19/2022]
Abstract
Cyclosporine A (CsA) is known as a neuroprotective agent against cerebral ischemia/reperfusion (I/R) in animal models. However, the significant therapeutic effects of CsA have been observed in high systemic doses or manipulating the blood-brain barrier, resulting in systemic side effects and toxicity. As the liposome nanocarriers have been developed for efficient delivery of peptide and proteins, liposomal CsA (Lipo-CsA) could improve cerebral (I/R) injuries. In this study, the liposomal CsA formulation (CsA at dose of 2.5 mg/kg) was prepared to assess the brain injury outcomes in 90 min middle cerebral artery occlusion (MCAO) stroke model followed by 48 h reperfusion in treating rats. Five minutes after induction of cerebral ischemia in rats, intravenous (iv) administration of Lipo-CsA significantly (P < 0.001) recovered the infarct size, the brain edema, and the neurological activities compared to corresponding control groups following 48 h I/R. In addition, after 48 h cerebral I/R, Lipo-CsA potentially (P < 0.001) inhibited the inflammation responses including MPO activity and tumor necrosis factor-alpha level in comparison to other groups. In conclusion, the results indicate that the low dose of CsA in liposomal formulation is more effective compared to higher dose of free form of CsA in treatment of ischemic brain in rats.
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Affiliation(s)
- Alireza Partoazar
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran
| | - Sanaz Nasoohi
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Shahid Beheshti University of Medical Science, Poursina Street, Tehran, 1417613151, Iran
| | - Sayed M Rezayat
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran
| | - Kambiz Gilani
- Department of Pharmaceutics, School of Pharmacy, Tehran University of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran
| | - Shahram E Mehr
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran
| | - Amir Amani
- Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran university of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran
| | - Nastaran Rahimi
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran
| | - Ahmad R Dehpour
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Poursina Street, Tehran, 1417613151, Iran
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17
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Li Z, Zhang D, He Y, Ding Z, Mao F, Luo T, Zhang X. Lipopolysaccharide Compromises Human Sperm Function by Reducing Intracellular cAMP. TOHOKU J EXP MED 2016; 238:105-12. [PMID: 26782775 DOI: 10.1620/tjem.238.105] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A worldwide decline in the quality of human semen is currently occurring. In mammals, sperm are produced from diploid stem-cell spermatogonia by spermatogenesis in testes and become mature in epididymis. Nevertheless, these biological processes can be affected by Gram-negative bacterial infection mediated by lipopolysaccharide (LPS), the major endotoxin of Gram-negative bacteria. It is well known that LPS can disturb spermatogenesis and affect sperm maturation and quality in vivo. However, the effect of LPS on the ejaculated mature sperm in vitro remains unclear. Thus, this study aimed to assess the in vitro toxicity of LPS on human sperm function and to elucidate the underlying mechanism. Human sperm were incubated with LPS (0.1-100 μg/ml) for 1-12 h in vitro and, subsequently, sperm viability, motility and capacitation, and the acrosome reaction were examined. LPS dose-dependently inhibited total and progressive motility and the ability to move through a viscous medium of the sperm but did not affect sperm viability, capacitation, and the acrosome reaction. To explore the underlying mechanism of LPS's actions, we examined the effects of LPS on the intracellular concentrations of cyclic adenosine monophosphate (cAMP) and calcium ([Ca(2+)]i) and protein-tyrosine phosphorylation of human sperm, which are key regulators of human sperm function. LPS decreased intracellular cAMP dose-dependently but had no effect on [Ca(2+)]i and protein-tyrosine phosphorylation of human sperm. These findings suggest that LPS inhibits human sperm motility by decreasing intracellular cAMP.
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Affiliation(s)
- Zhongyuan Li
- Department of Urology, Xiangyang Hospital, Hubei University of Medicine
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18
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Santoro A, Mattace Raso G, Taliani S, Da Pozzo E, Simorini F, Costa B, Martini C, Laneri S, Sacchi A, Cosimelli B, Calignano A, Da Settimo F, Meli R. TSPO-ligands prevent oxidative damage and inflammatory response in C6 glioma cells by neurosteroid synthesis. Eur J Pharm Sci 2016; 88:124-31. [PMID: 27094781 DOI: 10.1016/j.ejps.2016.04.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 04/01/2016] [Accepted: 04/05/2016] [Indexed: 11/30/2022]
Abstract
Translocator protein 18kDa (TSPO) is predominantly located in the mitochondrial outer membrane, playing an important role in steroidogenesis, inflammation, cell survival and proliferation. Its expression in central nervous system, mainly in glial cells, has been found to be upregulated in neuropathology, and brain injury. In this study, we investigated the anti-oxidative and anti-inflammatory effects of a group of TSPO ligands from the N,N-dialkyl-2-phenylindol-3-ylglyoxylamide class (PIGAs), highlighting the involvement of neurosteroids in their pharmacological effects. To this aim we used a well-known in vitro model of neurosteroidogenesis: the astrocytic C6 glioma cell line, where TSPO expression and localization, as well as cell response to TSPO ligand treatment, have been established. All PIGAs reduced l-buthionine-(S,R)-sulfoximine (BSO)-driven cell cytotoxicity and lipid peroxidation. Moreover, an anti-inflammatory effect was observed due to the reduction of inducible nitric oxide synthase and cyclooxygenase-2 induction in LPS/IFNγ challenged cells. Both effects were blunted by aminoglutethimide (AMG), an inhibitor of pregnenolone synthesis, suggesting neurosteroids' involvement in PIGA protective mechanism. Finally, pregnenolone evaluation in PIGA exposed cells revealed an increase in its synthesis, which was prevented by AMG pre-treatment. These findings indicate that these TSPO ligands reduce oxidative stress and pro-inflammatory enzymes in glial cells through the de novo synthesis of neurosteroids, suggesting that these compounds could be potential new therapeutic tools for the treatment of inflammatory-based neuropathologies with beneficial effects possibly comparable to steroids, but potentially avoiding the negative side effects of long-term therapies with steroid hormones.
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Affiliation(s)
- Anna Santoro
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, University of Pisa, 56126 Pisa, Italy
| | - Giuseppina Mattace Raso
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, University of Pisa, 56126 Pisa, Italy
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | | | | | - Barbara Costa
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | - Claudia Martini
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | - Sonia Laneri
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, University of Pisa, 56126 Pisa, Italy
| | - Antonia Sacchi
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, University of Pisa, 56126 Pisa, Italy
| | - Barbara Cosimelli
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, University of Pisa, 56126 Pisa, Italy
| | - Antonio Calignano
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, University of Pisa, 56126 Pisa, Italy
| | | | - Rosaria Meli
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, University of Pisa, 56126 Pisa, Italy.
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19
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Yuan L, Liu S, Bai X, Gao Y, Liu G, Wang X, Liu D, Li T, Hao A, Wang Z. Oxytocin inhibits lipopolysaccharide-induced inflammation in microglial cells and attenuates microglial activation in lipopolysaccharide-treated mice. J Neuroinflammation 2016; 13:77. [PMID: 27075756 PMCID: PMC4831099 DOI: 10.1186/s12974-016-0541-7] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 04/06/2016] [Indexed: 12/21/2022] Open
Abstract
Background Overactivated microglia is involved in various kinds of neurodegenerative diseases. Suppression of microglial overactivation has emerged as a novel strategy for treatment of neuroinflammation-based neurodegeneration. In the current study, anti-inflammatory effects of oxytocin (OT), which is a highly conserved nonapeptide with hormone and neurotransmitter properties, were investigated in vitro and in vivo. Methods BV-2 cells and primary microglia were pre-treated with OT (0.1, 1, and 10 μM) for 2 h followed by LPS treatment (500 ng/ml); microglial activation and pro-inflammatory mediators were measured by Western blot, RT-PCR, and immunofluorescence. The MAPK and NF-κB pathway proteins were assessed by Western blot. The intracellular calcium concentration ([Ca2+]i) was determined using Fluo2-/AM assay. Intranasal application of OT was pre-treated in BALB/C mice (adult male) followed by injected intraperitoneally with LPS (5 mg/kg). The effect of OT on LPS-induced microglial activation and pro-inflammatory mediators was measured by Western blot, RT-PCR, and immunofluorescence in vivo. Results Using the BV-2 microglial cell line and primary microglia, we found that OT pre-treatment significantly inhibited LPS-induced microglial activation and reduced subsequent release of pro-inflammatory factors. In addition, OT inhibited phosphorylation of ERK and p38 but not JNK MAPK in LPS-induced microglia. OT remarkably reduced the elevation of [Ca2+]i in LPS-stimulated BV-2 cells. Furthermore, a systemic LPS-treated acute inflammation murine brain model was used to study the suppressive effects of OT against neuroinflammation in vivo. We found that pre-treatment with OT showed marked attenuation of microglial activation and pro-inflammatory factor levels. Conclusions Taken together, the present study demonstrated that OT possesses anti-neuroinflammatory activity and might serve as a potential therapeutic agent for treating neuroinflammatory diseases.
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Affiliation(s)
- Lin Yuan
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Song Liu
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Xuemei Bai
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Yan Gao
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Guangheng Liu
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Xueer Wang
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Dexiang Liu
- Department of Medical Psychology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Tong Li
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Aijun Hao
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Zhen Wang
- Department of Physiology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China. .,Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China.
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20
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Mirzaei N, Tang SP, Ashworth S, Coello C, Plisson C, Passchier J, Selvaraj V, Tyacke RJ, Nutt DJ, Sastre M. In vivo imaging of microglial activation by positron emission tomography with [(11)C]PBR28 in the 5XFAD model of Alzheimer's disease. Glia 2016; 64:993-1006. [PMID: 26959396 DOI: 10.1002/glia.22978] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 02/08/2016] [Indexed: 11/05/2022]
Abstract
Microglial activation has been linked with deficits in neuronal function and synaptic plasticity in Alzheimer's disease (AD). The mitochondrial translocator protein (TSPO) is known to be upregulated in reactive microglia. Accurate visualization and quantification of microglial density by PET imaging using the TSPO tracer [(11)C]-R-PK11195 has been challenging due to the limitations of the ligand. In this study, it was aimed to evaluate the new TSPO tracer [(11)C]PBR28 as a marker for microglial activation in the 5XFAD transgenic mouse model of AD. Dynamic PET scans were acquired following intravenous administration of [(11)C]PBR28 in 6-month-old 5XFAD mice and in wild-type controls. Autoradiography with [(3)H]PBR28 was carried out in the same brains to further confirm the distribution of the radioligand. In addition, immunohistochemistry was performed on adjacent brain sections of the same mice to evaluate the co-localization of TSPO with microglia. PET imaging revealed that brain uptake of [(11)C]PBR28 in 5XFAD mice was increased compared with control mice. Moreover, binding of [(3)H]PBR28, measured by autoradiography, was enriched in cortical and hippocampal brain regions, coinciding with the positive staining of the microglial marker Iba-1 and amyloid deposits in the same areas. Furthermore, double-staining using antibodies against TSPO demonstrated co-localization of TSPO with microglia and not with astrocytes in 5XFAD mice and human post-mortem AD brains. The data provided support of the suitability of [(11)C]PBR28 as a tool for in vivo monitoring of microglial activation and assessment of treatment response in future studies using animal models of AD.
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Affiliation(s)
- Nazanin Mirzaei
- Division of Brain Sciences, Imperial College London, Du Cane Road, London, W12 0NN, United Kingdom
| | - Sac Pham Tang
- Imanova Limited, Du Cane Road, London, W12 0NN, United Kingdom
| | - Sharon Ashworth
- Imanova Limited, Du Cane Road, London, W12 0NN, United Kingdom
| | | | | | - Jan Passchier
- Imanova Limited, Du Cane Road, London, W12 0NN, United Kingdom
| | - Vimal Selvaraj
- Department of Animal Science, Cornell University, Ithaca, New York
| | - Robin J Tyacke
- Division of Brain Sciences, Imperial College London, Du Cane Road, London, W12 0NN, United Kingdom
| | - David J Nutt
- Division of Brain Sciences, Imperial College London, Du Cane Road, London, W12 0NN, United Kingdom
| | - Magdalena Sastre
- Division of Brain Sciences, Imperial College London, Du Cane Road, London, W12 0NN, United Kingdom
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21
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Park JH, Kim JN, Jang BC, Im SS, Song DK, Bae JH. Glucosamine suppresses platelet-activating factor-induced activation of microglia through inhibition of store-operated calcium influx. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2016; 42:1-8. [PMID: 26745504 DOI: 10.1016/j.etap.2015.12.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 12/17/2015] [Accepted: 12/19/2015] [Indexed: 06/05/2023]
Abstract
Microglia activation and subsequent release of inflammatory mediators are implicated in the pathophysiology of neurodegenerative diseases. Platelet-activating factor (PAF), a potent lipid mediator synthesized by microglia, is known to stimulate microglia functional responses. In this study, we determined that endogenous PAF exert autocrine effects on microglia activation, as well as the underlying mechanism involved. We also investigated the effect of D-glucosamine (GlcN) on PAF-induced cellular activation in human HMO6 microglial cells. PAF induced sustained intracellular Ca(2+) ([Ca(2+)]i) increase through store-operated Ca(2+) channels (SOC) and reactive oxygen species (ROS) generation. PAF also induced pro-inflammatory markers through NFκB/COX-2 signaling. GlcN significantly inhibited PAF-induced Ca(2+) influx and ROS generation without significant cytotoxicity. GlcN downregulated excessive expression of pro-inflammatory markers and promoted filopodia formation through NFκB/COX-2 inhibition in PAF-stimulated HMO6 cells. Taken together, these data suggest that GlcN may offer substantial therapeutic potential for treating inflammatory and neurodegenerative diseases accompanied by microglial activation.
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Affiliation(s)
- Jae-Hyung Park
- Department of Physiology, Keimyung University School of Medicine, Daegu, South Korea
| | - Jeong-Nam Kim
- Department of Physiology, Keimyung University School of Medicine, Daegu, South Korea
| | - Byeong-Churl Jang
- Department of Molecular Medicine, Keimyung University School of Medicine, Daegu, South Korea
| | - Seung-Soon Im
- Department of Physiology, Keimyung University School of Medicine, Daegu, South Korea
| | - Dae-Kyu Song
- Department of Physiology, Keimyung University School of Medicine, Daegu, South Korea
| | - Jae-Hoon Bae
- Department of Physiology, Keimyung University School of Medicine, Daegu, South Korea.
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The hGFAP-driven conditional TSPO knockout is protective in a mouse model of multiple sclerosis. Sci Rep 2016; 6:22556. [PMID: 26925573 PMCID: PMC4772008 DOI: 10.1038/srep22556] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Accepted: 02/17/2016] [Indexed: 01/04/2023] Open
Abstract
The mitochondrial translocator protein (TSPO) has been implicated in CNS diseases. Here, we sought to determine the specific role of TSPO in experimental autoimmune encephalomyelitis (EAE), the most studied animal model of multiple sclerosis (MS). To fundamentally elucidate the functions of TSPO, we first developed a viable TSPO knockout mouse. A conditional TSPO knockout mouse was generated by utilizing the Cre-Lox system. We generated a TSPO floxed mouse, and then crossed this mouse with a Cre recombinase expressing mouse driven by the human glial fibrillary acidic protein (hGFAP) promoter. The resultant mouse was a neural linage line specific TSPO knockout. The loss of TSPO in the CNS did not result in overt developmental defects or phenotypes. The TSPO−/− mouse showed a decrease in GFAP expression, correlating with a decrease in astrogliosis in response to neural injury during EAE. This decrease in astrogliosis was also witnessed in the lessening of severity of EAE clinical scoring, indicating an in vivo functional role for TSPO in suppressing EAE. The TSPO−/− mouse could be a useful tool in better understanding the role of TSPO in CNS disease, and our results implicate TSPO as a potential therapeutic target in MS.
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23
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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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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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Targeting the 18-kDa translocator protein: recent perspectives for neuroprotection. Biochem Soc Trans 2015; 43:559-65. [DOI: 10.1042/bst20150028] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Indexed: 12/14/2022]
Abstract
The translocator protein (TSPO, 18 kDa), mainly localized in the outer mitochondrial membrane of steroidogenic tissues, is involved in several cellular functions. TSPO level alterations have been reported in a number of human disorders, particularly in cancer, psychiatric and neurological diseases. In the central nervous system (CNS), TSPO is usually expressed in glial cells, but also in some neuronal cell types. Interestingly, the expression of TSPO on glial cells rises after brain injury and increased TSPO expression is often observed in neurological disorders, gliomas, encephalitis and traumatic injury. Since TSPO is up-regulated in brain diseases, several structurally different classes of ligands targeting TSPO have been described as potential diagnostic or therapeutic agents. Recent researches have reported that TSPO ligands might be valuable in the treatment of brain diseases. This review focuses on currently available TSPO ligands, as useful tools for the treatment of neurodegeneration, neuro-inflammation and neurotrauma.
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Banati RB, Middleton RJ, Chan R, Hatty CR, Wai-Ying Kam W, Quin C, Graeber MB, Parmar A, Zahra D, Callaghan P, Fok S, Howell NR, Gregoire M, Szabo A, Pham T, Davis E, Liu GJ. Positron emission tomography and functional characterization of a complete PBR/TSPO knockout. Nat Commun 2014; 5:5452. [PMID: 25406832 PMCID: PMC4263137 DOI: 10.1038/ncomms6452] [Citation(s) in RCA: 186] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 10/01/2014] [Indexed: 12/17/2022] Open
Abstract
The evolutionarily conserved peripheral benzodiazepine receptor (PBR), or 18-kDa translocator protein (TSPO), is thought to be essential for cholesterol transport and steroidogenesis, and thus life. TSPO has been proposed as a biomarker of neuroinflammation and a new drug target in neurological diseases ranging from Alzheimer's disease to anxiety. Here we show that global C57BL/6-Tspo(tm1GuWu(GuwiyangWurra))-knockout mice are viable with normal growth, lifespan, cholesterol transport, blood pregnenolone concentration, protoporphyrin IX metabolism, fertility and behaviour. However, while the activation of microglia after neuronal injury appears to be unimpaired, microglia from (GuwiyangWurra)TSPO knockouts produce significantly less ATP, suggesting reduced metabolic activity. Using the isoquinoline PK11195, the ligand originally used for the pharmacological and structural characterization of the PBR/TSPO, and the imidazopyridines CLINDE and PBR111, we demonstrate the utility of (GuwiyangWurra)TSPO knockouts to provide robust data on drug specificity and selectivity, both in vitro and in vivo, as well as the mechanism of action of putative TSPO-targeting drugs.
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Affiliation(s)
- Richard B. Banati
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Medical Imaging & Radiation Sciences, Faculty of Health Science and Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- National Imaging Facility, Sydney, Camperdown, New South Wales 2006, Australia
| | - Ryan J. Middleton
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Ronald Chan
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Medical Imaging & Radiation Sciences, Faculty of Health Science and Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Claire R. Hatty
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Medical Imaging & Radiation Sciences, Faculty of Health Science and Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Winnie Wai-Ying Kam
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Medical Imaging & Radiation Sciences, Faculty of Health Science and Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Candice Quin
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Medical Imaging & Radiation Sciences, Faculty of Health Science and Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Manuel B. Graeber
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Medical Imaging & Radiation Sciences, Faculty of Health Science and Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Sydney Medical School, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Arvind Parmar
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - David Zahra
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Paul Callaghan
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Sandra Fok
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Nicholas R. Howell
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Marie Gregoire
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Alexander Szabo
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
- Centre for Translational Neuroscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Tien Pham
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Emma Davis
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Guo-Jun Liu
- Life Sciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
- Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
- Medical Imaging & Radiation Sciences, Faculty of Health Science and Brain & Mind Research Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
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Microglia in Alzheimer's disease. BIOMED RESEARCH INTERNATIONAL 2014; 2014:437483. [PMID: 25197646 PMCID: PMC4150406 DOI: 10.1155/2014/437483] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 05/28/2014] [Accepted: 06/03/2014] [Indexed: 12/30/2022]
Abstract
Alzheimer's disease (AD) is a familiar neurodegenerative disease in the elderly. In this paper, we will review current viewpoints of microglial activation, inflammatory regulatory systems, and their relationship with AD pathology and etiology. Microglia cells are macrophage and representative of the innate immune system in brain. AD brain is marked by obvious inflammatory features, in which microglial activation is the driving force. β-amyloid protein sedimentation activates microglia cells, which causes the inflammation in AD. Microglia cells have dual roles: they provoke the release of inflammatory factors and cytotoxins leading to neuronal injuries and death; on the other hand, they have the neuroprotective effects. Through this, we hope to illustrate that the anti-inflammatory defenses of neurons can be practiced in the future strategy for recuperating the balance between the levels of inflammatory mediators and immune regulators in AD.
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Macroglia-microglia interactions via TSPO signaling regulates microglial activation in the mouse retina. J Neurosci 2014; 34:3793-806. [PMID: 24599476 DOI: 10.1523/jneurosci.3153-13.2014] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chronic retinal inflammation in the form of activated microglia and macrophages are implicated in the etiology of neurodegenerative diseases of the retina, including age-related macular degeneration, diabetic retinopathy, and glaucoma. However, molecular biomarkers and targeted therapies for immune cell activation in these disorders are currently lacking. To address this, we investigated the involvement and role of translocator protein (TSPO), a biomarker of microglial and astrocyte gliosis in brain degeneration, in the context of retinal inflammation. Here, we find that TSPO is acutely and specifically upregulated in retinal microglia in separate mouse models of retinal inflammation and injury. Concomitantly, its endogenous ligand, diazepam-binding inhibitor (DBI), is upregulated in the macroglia of the mouse retina such as astrocytes and Müller cells. In addition, we discover that TSPO-mediated signaling in microglia via DBI-derived ligands negatively regulates features of microglial activation, including reactive oxygen species production, TNF-α expression and secretion, and microglial proliferation. The inducibility and effects of DBI-TSPO signaling in the retina reveal a mechanism of coordinated macroglia-microglia interactions, the function of which is to limit the magnitude of inflammatory responses after their initiation, facilitating a return to baseline quiescence. Our results indicate that TSPO is a promising molecular marker for imaging inflammatory cell activation in the retina and highlight DBI-TSPO signaling as a potential target for immodulatory therapies.
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Sharma P, Ping L. Calcium ion influx in microglial cells: physiological and therapeutic significance. J Neurosci Res 2014; 92:409-23. [PMID: 24464907 DOI: 10.1002/jnr.23344] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 11/09/2013] [Accepted: 11/12/2013] [Indexed: 01/16/2023]
Abstract
Microglial cells, the immunocompetent cells of the central nervous system (CNS), exhibit a resting phenotype under healthy conditions. In response to injury, however, they transform into an activated state, which is a hallmark feature of many CNS diseases. Factors or agents released from the neurons, blood vessels, and/or astrocytes could activate these cells, leading to their functional and structural modifications. Microglial cells are well equipped to sense environmental changes within the brain under both physiological and pathological conditions. Entry of calcium ions (Ca(2+)) plays a critical role in the process of microglial transformation; several channels and receptors have been identified on the surface of microglial cells. These include store-operated channel, Orai1, and its sensor protein, stromal interaction molecule 1 (STIM1), in microglial cells, and their functions are modulated under pathological stimulations. Transient receptor potential (TRP) channels and voltage- and ligand-gated channels (ionotropic and metabotropic receptors) are also responsible for Ca(2+) influx into the microglial cells. An elevation of intracellular Ca(2+) concentration subsequently regulates microglial cell functions by activating a diverse array of Ca(2+)-sensitive signaling cascades. Perturbed Ca(2+) homeostasis contributes to the progression of a number of CNS disorders. Thus, regulation of Ca(2+) entry into microglial cells could be a pharmacological target for several CNS-related pathological conditions. This Review addresses the recent insights into microglial cell Ca(2+) influx mechanisms, their roles in the regulation of functions, and alterations of Ca(2+) entry in specific CNS disorders.
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Affiliation(s)
- Purnima Sharma
- All India Institute of Medical Sciences-Physiology, Basni Industrial Area Phase II Jodhpur, Rajasthan, India
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Karlstetter M, Nothdurfter C, Aslanidis A, Moeller K, Horn F, Scholz R, Neumann H, Weber BHF, Rupprecht R, Langmann T. Translocator protein (18 kDa) (TSPO) is expressed in reactive retinal microglia and modulates microglial inflammation and phagocytosis. J Neuroinflammation 2014; 11:3. [PMID: 24397957 PMCID: PMC3895821 DOI: 10.1186/1742-2094-11-3] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 12/23/2013] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The translocator protein (18 kDa) (TSPO) is a mitochondrial protein expressed on reactive glial cells and a biomarker for gliosis in the brain. TSPO ligands have been shown to reduce neuroinflammation in several mouse models of neurodegeneration. Here, we analyzed TSPO expression in mouse and human retinal microglia and studied the effects of the TSPO ligand XBD173 on microglial functions. METHODS TSPO protein analyses were performed in retinoschisin-deficient mouse retinas and human retinas. Lipopolysaccharide (LPS)-challenged BV-2 microglial cells were treated with XBD173 and TSPO shRNAs in vitro and pro-inflammatory markers were determined by qRT-PCR. The migration potential of microglia was determined with wound healing assays and the proliferation was studied with Fluorescence Activated Cell Sorting (FACS) analysis. Microglial neurotoxicity was estimated by nitrite measurement and quantification of caspase 3/7 levels in 661 W photoreceptors cultured in the presence of microglia-conditioned medium. The effects of XBD173 on filopodia formation and phagocytosis were analyzed in BV-2 cells and human induced pluripotent stem (iPS) cell-derived microglia (iPSdM). The morphology of microglia was quantified in mouse retinal explants treated with XBD173. RESULTS TSPO was strongly up-regulated in microglial cells of the dystrophic mouse retina and also co-localized with microglia in human retinas. Constitutive TSPO expression was high in the early postnatal Day 3 mouse retina and declined to low levels in the adult tissue. TSPO mRNA and protein were also strongly induced in LPS-challenged BV-2 microglia while the TSPO ligand XBD173 efficiently suppressed transcription of the pro-inflammatory marker genes chemokine (C-C motif) ligand 2 (CCL2), interleukin 6 (IL6) and inducible nitric oxide (NO)-synthase (iNOS). Moreover, treatment with XBD173 significantly reduced the migratory capacity and proliferation of microglia, their level of NO secretion and their neurotoxic activity on 661 W photoreceptor cells. Furthermore, XBD173 treatment of murine and human microglial cells promoted the formation of filopodia and increased their phagocytic capacity to ingest latex beads or photoreceptor debris. Finally, treatment with XBD173 reversed the amoeboid alerted phenotype of microglial cells in explanted organotypic mouse retinal cultures after challenge with LPS. CONCLUSIONS These findings suggest that TSPO is highly expressed in reactive retinal microglia and a promising target to control microglial reactivity during retinal degeneration.
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Affiliation(s)
- Marcus Karlstetter
- Department of Ophthalmology, University of Cologne, D-50931 Cologne, Germany
| | - Caroline Nothdurfter
- Department of Psychiatry and Psychotherapy, University of Regensburg, D-93053 Regensburg, Germany
| | - Alexander Aslanidis
- Department of Ophthalmology, University of Cologne, D-50931 Cologne, Germany
| | - Katharina Moeller
- Department of Ophthalmology, University of Cologne, D-50931 Cologne, Germany
| | - Felicitas Horn
- Department of Ophthalmology, University of Cologne, D-50931 Cologne, Germany
| | - Rebecca Scholz
- Department of Ophthalmology, University of Cologne, D-50931 Cologne, Germany
| | - Harald Neumann
- Institute of Reconstructive Neurobiology, University of Bonn, D-53127 Bonn, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, D-93053 Regensburg, Germany
| | - Rainer Rupprecht
- Department of Psychiatry and Psychotherapy, University of Regensburg, D-93053 Regensburg, Germany
| | - Thomas Langmann
- Department of Ophthalmology, University of Cologne, D-50931 Cologne, Germany
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Abstract
Ligands of the translocator protein (TSPO) elicit pleiotropic neuroprotective effects that represent emerging treatment strategies for several neurodegenerative conditions. To investigate the potential of TSPO as a therapeutic target for Alzheimer's disease (AD), the current study assessed the effects of the TSPO ligand Ro5-4864 on the development of neuropathology in 3xTgAD mice. The effects of the TSPO ligand on neurosteroidogenesis and AD-related neuropathology, including β-amyloid accumulation, gliosis, and behavioral impairment, were examined under both early intervention (7-month-old young-adult male mice with low pathology) and treatment (24-month-old, aged male mice with advanced neuropathology) conditions. Ro5-4864 treatment not only effectively attenuated development of neuropathology and behavioral impairment in young-adult mice but also reversed these indices in aged 3xTgAD mice. Reduced levels of soluble β-amyloid were also observed by the combination of TSPO ligands Ro5-4864 and PK11195 in nontransgenic mice. These findings suggest that TSPO is a promising target for the development of pleiotropic treatment strategies for the management of AD.
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Daugherty DJ, Selvaraj V, Chechneva OV, Liu XB, Pleasure DE, Deng W. A TSPO ligand is protective in a mouse model of multiple sclerosis. EMBO Mol Med 2013; 5:891-903. [PMID: 23681668 PMCID: PMC3779450 DOI: 10.1002/emmm.201202124] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 03/15/2013] [Accepted: 03/18/2013] [Indexed: 12/18/2022] Open
Abstract
Local production of neurosteroids such as progesterone and allopregnanolone confers neuroprotection in central nervous system (CNS) inflammatory diseases. The mitochondrial translocator protein (TSPO) performs a rate-limiting step in the conversion of cholesterol to pregnenolone and its steroid derivatives. Previous studies have shown that TSPO is upregulated in microglia and astroglia during neural inflammation, and radiolabelled TSPO ligands such as PK11195 have been used to image and localize injury in the CNS. Recent studies have shown that modulating TSPO activity with pharmacological ligands such as etifoxine can initiate the production of neurosteroids locally in the injured CNS. In this study, we examined the effects of etifoxine, a clinically available anxiolytic drug, in the development and progression of mouse experimental autoimmune encephalomyelitis (EAE), an experimental model for multiple sclerosis (MS). Our results showed that etifoxine attenuated EAE severity when administered before the development of clinical signs and also improved symptomatic recovery when administered at the peak of the disease. In both cases, recovery was correlated with diminished inflammatory pathology in the lumbar spinal cord. Modulation of TSPO activity by etifoxine led to less peripheral immune cell infiltration of the spinal cord, and increased oligodendroglial regeneration after inflammatory demyelination in EAE. Our results suggest that a TSPO ligand, e.g. etifoxine, could be a potential new therapeutic option for MS with benefits that could be comparable to the administration of systemic steroids but potentially avoiding the detrimental side effects of long-term direct use of steroids.
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Affiliation(s)
- Daniel J Daugherty
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA, USA
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Beppu K, Kosai Y, Kido MA, Akimoto N, Mori Y, Kojima Y, Fujita K, Okuno Y, Yamakawa Y, Ifuku M, Shinagawa R, Nabekura J, Sprengel R, Noda M. Expression, subunit composition, and function of AMPA-type glutamate receptors are changed in activated microglia; possible contribution of GluA2 (GluR-B)-deficiency under pathological conditions. Glia 2013; 61:881-91. [PMID: 23468421 DOI: 10.1002/glia.22481] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 01/23/2013] [Indexed: 01/01/2023]
Abstract
Microglia express AMPA (α-amino-hydroxy-5-methyl-isoxazole-4-propionate)-type of glutamate (Glu) receptors (AMPAR), which are highly Ca(2+) impermeable due to the expression of GluA2. However, the functional importance of AMPAR in microglia remains to be investigated, especially under pathological conditions. As low expression of GluA2 was reported in some neurodegenerative diseases, GluA2(-/-) mice were used to show the functional change of microglial AMPARs in response to Glu or kainate (KA). Here we found that Glu-induced currents in the presence of 100 μM cyclothiazide, an inhibitor of AMPAR desensitization, showed time-dependent decrease after activation of microglia with lipopolysaccharide (LPS) in GluA2(+/+) microglia, but not in GluA2(-/-) microglia. Upon activation of microglia, expression level of GluA2 subunits significantly increased, while expression of GluA1, A3 and A4 subunits on membrane surface significantly decreased. These results suggest that nearly homomeric GluA2 subunits were the main reason for low conductance of AMPAR in activated microglia. Increased expression of GluA2 in microglia was also detected partially in brain slices from LPS-injected mice. Cultured microglia from GluA2(-/-) mice showed higher Ca(2+) -permeability, consequently inducing significant increase in the release of proinflammatory cytokine, such as TNF-α. The conditioning medium from KA-treated GluA2(-/-) microglia had more neurotoxic effect on wild type cultured neurons than that from KA-treated GluA2(+/+) microglia. These results suggest that membrane translocation of GluA2-containing AMPARs in activated microglia has functional importance and thus, dysfunction or decreased expression of GluA2 may accelerate Glu neurotoxicity via excess release of proinflammatory cytokines from microglia.
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Affiliation(s)
- Kaoru Beppu
- Laboratory of Pathophysiology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
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Mendonça-Torres MC, Roberts SS. The translocator protein (TSPO) ligand PK11195 induces apoptosis and cell cycle arrest and sensitizes to chemotherapy treatment in pre- and post-relapse neuroblastoma cell lines. Cancer Biol Ther 2013; 14:319-26. [PMID: 23358477 DOI: 10.4161/cbt.23613] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
High-risk neuroblastoma (NB) has a poor prognosis. Even with intensive myeloablative chemotherapy, relapse is common and almost uniformly fatal, and new treatments are needed. Translocator protein 18kDa (TSPO) ligands have been studied as potential new therapeutic agents in many cancers, but not in NB. We studied the effects of TSPO ligands on cell proliferation, cell cycle progression and apoptosis using paired cell lines derived from the same patient at the time of initial surgery and again after development of progressive disease or relapse post-chemotherapy. We found that TSPO expression was significantly increased 2- to 10-fold in post-relapse cell lines compared with pre-treatment lines derived from the same individual. Subsequently, these cell lines were treated with the specific TSPO ligand 1-(2-chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide (PK11195) (0-160µM) as a single agent, with cytotoxic chemotherapy agents alone (carboplatin, etoposide or melphalan), or with combinations of PK11195 and chemotherapy drugs. We found that PK11195 inhibited proliferation in a dose-dependent manner, induced apoptosis and caused G 1/S cell cycle arrest in all tested NB cell lines at micromolar concentrations. In addition, PK11195 significantly decreased mRNA expression of the chemotherapy resistance efflux pumps ABCA3, ABCB1 and ABCC1 in two post-relapse NB cell lines. We also found that pre-treatment with PK11195 sensitized these cell lines to treatment with cytotoxic chemotherapy agents. These results suggest that PK11195 alone or in combination with standard chemotherapeutic drugs warrants further study for the treatment of neuroblastoma.
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Affiliation(s)
- Maria C Mendonça-Torres
- Department of Pediatrics, Division of Hematology/Oncology, Uniformed Services University of the Health Sciences, Bethesda, MD USA
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Zawadzka M, Dabrowski M, Gozdz A, Szadujkis B, Sliwa M, Lipko M, Kaminska B. Early steps of microglial activation are directly affected by neuroprotectant FK506 in both in vitro inflammation and in rat model of stroke. J Mol Med (Berl) 2012; 90:1459-71. [PMID: 22806180 PMCID: PMC3506835 DOI: 10.1007/s00109-012-0925-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 05/10/2012] [Accepted: 05/30/2012] [Indexed: 02/05/2023]
Abstract
Neuroprotective and/or neuroregenerative activity of FK506, its derivatives, and to a lesser extent cyclosporin A (CsA) in animal models of neurodegenerative diseases of different etiology have been reported. Here, we verified a hypothesis that the most likely mechanism of their neuroprotective action is inhibition of the early steps of inflammatory activation of microglia by interference with mitogen-activated protein kinase (MAPK) signaling. The effect of immunosuppressants on lipopolysaccharide (LPS)-induced changes in morphology, proliferation, and motility of rat primary microglial cultures was evaluated. FK506 and CsA directly inhibited LPS-induced microglia activation and inflammatory responses. While both drugs efficiently reduced the expression of iNOS and the release of nitric oxide, only FK506 strongly inhibited the expression of Cox-2 and secretion of the mature form of IL-1β. FK506 strongly reduced LPS-induced activation of MAPK, and its downstream signaling crucial for inflammatory responses. Comparative analysis of global gene expression in rat ischemic brains and in LPS-stimulated microglial cultures revealed many genes and signaling pathways regulated in the same way in both systems. FK506 treatment blocked a majority of genes induced by an ischemic insult in the cortex, in particular inflammatory/innate immunity and apoptosis-related genes. Microglia-mediated inflammation is considered as one of the most important components of brain injury after trauma or stroke; thus, effective and multifaceted blockade of microglial activation by FK506 has clinical relevance and potential therapeutic implications.
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Affiliation(s)
- Malgorzata Zawadzka
- Laboratory of Transcription Regulation, Department Cell Biology, Nencki Institute of Experimental Biology, 3 Pasteur Str., 02-093 Warsaw, Poland
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Politis M, Su P, Piccini P. Imaging of microglia in patients with neurodegenerative disorders. Front Pharmacol 2012; 3:96. [PMID: 22661951 PMCID: PMC3361961 DOI: 10.3389/fphar.2012.00096] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 05/01/2012] [Indexed: 01/13/2023] Open
Abstract
Microglia constitute the main immune defense in the central nervous system. In response to neuronal injury, microglia become activated, acquire phagocytic properties, and release a wide range of pro-inflammatory mediators that are essential for the annihilation of the neuronal insult. Although the role of microglial activation in acute neuronal damage is well defined, the pathophysiological processes underlying destructive or protective role to neurons following chronic exposure to microglial activation is still a subject of debate. It is likely that chronic exposure induces detrimental effects by promoting neuronal death through the release of neurotoxic factors. Positron emission tomography (PET) imaging with the use of translocator protein (TSPO) radioligands provides an in vivo tool for tracking the progression and severity of neuroinflammation in neurodegenerative disease. TSPO expression is correlated to the extent of microglial activation and the measurement of TSPO uptake in vivo with PET is a useful indicator of active disease. Although understanding of the interaction between radioligands and TSPO is not completely clear, there is a wide interest in application of TSPO imaging in neurodegenerative disease. In this article, we aim to review the applications of in vivo microglia imaging in neurodegenerative disorders such as Parkinson's disease, Huntington's disease, Dementias, and Multiple Sclerosis.
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Affiliation(s)
- Marios Politis
- Division of Experimental Medicine, Faculty of Medicine, Centre for Neuroscience, Hammersmith Hospital, Imperial College London London, UK
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Xie L, Yamasaki T, Ichimaru N, Yui J, Kawamura K, Kumata K, Hatori A, Nonomura N, Zhang MR, Li XK, Takahara S. [11C]DAC-PET for Noninvasively Monitoring Neuroinflammation and Immunosuppressive Therapy Efficacy in Rat Experimental Autoimmune Encephalomyelitis Model. J Neuroimmune Pharmacol 2011; 7:231-42. [DOI: 10.1007/s11481-011-9322-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2011] [Accepted: 10/17/2011] [Indexed: 11/30/2022]
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Choi J, Ifuku M, Noda M, Guilarte TR. Translocator protein (18 kDa)/peripheral benzodiazepine receptor specific ligands induce microglia functions consistent with an activated state. Glia 2011; 59:219-30. [PMID: 21125642 DOI: 10.1002/glia.21091] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In the brain, translocator protein (18 kDa) (TSPO), previously called peripheral benzodiazepine receptor (PBR), is a glial protein that has been extensively used as a biomarker of brain injury and inflammation. However, the functional role of TSPO in glial cells is not well characterized. In this study, we show that the TSPO-specific ligands R-PK11195 (PK) and Ro5-4864 (Ro) increased microglia proliferation and phagocytosis with no effect on migration. Both ligands increased reactive oxygen species (ROS) production, and this effect may be mediated by NADPH-oxidase. PK and Ro also produced a small but detectable increase in IL-1β release. We also examined the effect of PK and Ro on the expression of proinflammatory genes and cytokine release in lipopolysaccharide (LPS) and adenosine triphosphate (ATP) activated microglia. PK or Ro had no effect on LPS-induced increase of pro-inflammatory genes, but they both decreased the ATP-induced increase of COX-2 gene expression. Ro, but not PK, enhanced the LPS-induced release of IL-1β. However, Ro decreased the ATP-induced release of IL-1β and TNF-α, and PK decreased the ATP-induced release of TNF-α. Exposure to Ro in the presence of LPS increased the number of apoptotic microglia, an effect that could be blocked by PK. These findings show that TSPO ligands modulate cellular functions consistent with microglia activation. Further, when microglia are activated, these ligands may have therapeutic potential by reducing the expression of pro-inflammatory genes and cytokine release. Finally, Ro-like ligands may be involved in the elimination of activated microglia via apoptosis.
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Affiliation(s)
- Judy Choi
- Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
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Ostuni MA, Issop L, Péranzi G, Walker F, Fasseu M, Elbim C, Papadopoulos V, Lacapere JJ. Overexpression of translocator protein in inflammatory bowel disease: potential diagnostic and treatment value. Inflamm Bowel Dis 2010; 16:1476-87. [PMID: 20222126 PMCID: PMC2930116 DOI: 10.1002/ibd.21250] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND Inflammatory bowel diseases (IBDs), such as ulcerative colitis and Crohn's disease, are chronic inflammatory disorders that increase the risk for colorectal cancer. The mitochondrial translocator protein (TSPO) is a high-affinity drug- and cholesterol-binding protein expressed in the colon and its expression is increased in colon cancers. The aim of this study was to investigate TSPO expression in IBD biopsies and to establish an animal model of IBD to examine the role of TSPO. In addition, we evaluated the potential use of TSPO drug ligands in diagnosing and treating IBD. METHODS TSPO expression in IBD biopsies was evaluated using immunohistochemistry. IBD was induced in a rat experimental model via treatment with dextran sodium sulfate (DSS). Colon morphology, TSPO expression, and proinflammatory cytokine production were evaluated in addition to the effect of TSPO drug ligands on disease pathology. RESULTS TSPO protein levels were elevated in the enterocytes of IBD biopsies. TSPO expression was localized to the enterocyte mitochondria. DSS treatment induced a time-dependent phenotype mimicking IBD with tissue injury and subsequent tissue regeneration. Coadministration of DSS and the TSPO drug ligands PK 11195 or Ro5-4864 increased both the rate of colon ulceration and regeneration, whereas administration of the TSPO drug ligand flunitrazepam partially prevented this pathology. These data correlated with changes in proinflammatory cytokine plasma levels, as well as increased cytokine production and secretion from the colon. CONCLUSIONS TSPO may serve as a marker of the IBD repair process, and TSPO drug ligands should be further evaluated for IBD treatment.
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Affiliation(s)
- Mariano A Ostuni
- Unité INSERM U773, Centre de Recherche Biomédicale Bichat Beaujon CRB3, Université Paris 7 Denis Diderot, Paris, France.
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Peripheral benzodiazepine receptors in patients with chronic schizophrenia: a PET study with [11C]DAA1106. Int J Neuropsychopharmacol 2010; 13:943-50. [PMID: 20350336 DOI: 10.1017/s1461145710000313] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Inflammatory/immunological process and glial contribution are suggested in the pathophysiology of schizophrenia. We investigated peripheral benzodiazepine receptors in brains of patients with chronic schizophrenia, which were reported to be located on mitochondria of glial cells, using [11C]DAA1106 with positron emission tomography. Fourteen patients and 14 age- and sex-matched normal controls participated in this study. PET data were analysed by two-tissue compartment model with metabolite-corrected plasma input. Clinical symptoms were assessed using the Positive and Negative Syndrome Scale. There was no significant difference between [11C]DAA1106 binding of the cortical regions of normal controls and patients with schizophrenia, whereas the patients showed a positive correlation between cortical [11C]DAA1106 binding and positive symptom scores. There was also a positive correlation between [11C]DAA1106 binding and duration of illness. Although the correlations need to be interpreted very cautiously, involvement of glial reaction process in the pathophysiology of positive symptoms or progressive change of schizophrenia might be suggested.
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Lee M, Cho T, Jantaratnotai N, Wang YT, McGeer E, McGeer PL. Depletion of GSH in glial cells induces neurotoxicity: relevance to aging and degenerative neurological diseases. FASEB J 2010; 24:2533-45. [PMID: 20228251 DOI: 10.1096/fj.09-149997] [Citation(s) in RCA: 177] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Oxidative stress induced by inhibition of glutathione (GSH) biosynthesis with D,L-buthionine-S,R-sulfoximine (BSO) causes human microglia, human astrocytes, THP-1 cells, and U373 cells to secrete materials toxic to human neuroblastoma SH-SY5Y cells and stimulates them to release TNF-alpha, IL-6, and nitrite ions. The effect is correlated with activation of the inflammatory pathways P38 MAP- kinase, Jun-N-terminal kinase, and NF-kappaB. The effect is reduced by adding to the medium GSH or clotrimazole (CTM), an inhibitor of Ca(2+)-influx through TRPM2 channels. It is also produced by inhibiting TRPM2 protein expression in microglia and astrocytes through introduction of its small inhibitory RNA (siRNA). TRPM2 mRNA is expressed by glial cells but not by SH-SY5Y cells. BSO in the culture medium causes an almost 3-fold increase in [Ca(2+)](i) in microglia and astrocytes over a 24-h period, which is reduced to half by the addition of CTM. The data strongly suggest that inhibiting intracellular GSH synthesis induces a neuroinflammatory response in human microglia and astrocytes, which is linked to Ca(2+) influx through TRPM2 channels. It represents a new model for inducing neuroinflammation and suggests that increasing GSH levels in glial cells may confer neuroprotection in neurodegenerative diseases, such as Alzheimer disease, which have a prominent neuroinflammatory component.
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Affiliation(s)
- Moonhee Lee
- Kinsmen Laboratory of Neurological Research, University of British Columbia, 2255 Wesbrook Mall, Vancouver, BC, Canada V6T 1Z3
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Yuan D, Ma B, Yang JY, Xie YY, Wang L, Zhang LJ, Kano Y, Wu CF. Anti-inflammatory effects of rhynchophylline and isorhynchophylline in mouse N9 microglial cells and the molecular mechanism. Int Immunopharmacol 2009; 9:1549-54. [PMID: 19781666 DOI: 10.1016/j.intimp.2009.09.010] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2009] [Revised: 09/04/2009] [Accepted: 09/15/2009] [Indexed: 11/17/2022]
Abstract
Excessive production of nitric oxide (NO) and proinflammatory cytokines from activated microglia contributes to human neurodegenerative disorders. Our previous study demonstrated the potent inhibition of lipopolysaccharide (LPS)-induced NO production in rat primary microglial cells by rhynchophylline (RIN) and isorhynchophylline (IRN), a pair of isomeric alkaloids of Uncaria rhynchophylla (Miq.) Jacks. that has been used in China for centuries as a "cognitive enhancer" as well as to treat strokes. We further investigated whether RIN and IRN effectively suppress release of proinflammatory cytokines in LPS-activated microglial cells and the underling molecular mechanism for the inhibition of microglial activation. RIN and IRN concentration-dependently attenuated LPS-induced production of proinflammatory cytokines such as TNF-alpha and IL-1beta as well as NO in mouse N9 microglial cells, with IRN showing more potent inhibition of microglial activation. The western blotting analysis indicated that the potential molecular mechanism for RIN or IRN-mediated attenuation was implicated in suppressions of iNOS protein level, phosphorylation of ERK and p38 MAPKs, and degradation of IkappaBalpha. In addition, the differential regulation of the three signaling pathways by two isomers was shown. Our results suggest that RIN and IRN may be effective therapeutic candidates for use in the treatment of neurodegenerative diseases accompanied by microglial activation.
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Affiliation(s)
- Dan Yuan
- Department of Traditional Chinese Medicines, Shenyang Pharmaceutical University, 103 Wenhua Rd., Shenyang, 110016, China
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Papadopoulos V, Lecanu L. Translocator protein (18 kDa) TSPO: an emerging therapeutic target in neurotrauma. Exp Neurol 2009; 219:53-7. [PMID: 19409385 DOI: 10.1016/j.expneurol.2009.04.016] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 04/22/2009] [Indexed: 12/11/2022]
Abstract
Traumatic brain injury (TBI) induces physical, cognitive, and psychosocial deficits that affect millions of patients. TBI activates numerous cellular mechanisms and molecular cascades that produce detrimental outcomes, including neuronal death and loss of function. The mitochondrion is one of the major targets of TBI, as seen by increased mitochondrial activity in activated and proliferating microglia (due to high energy requirements and/or calcium overload) as well as increased reactive oxygen species, changes in mitochondrial permeability transition, release of cytochrome c, caspase activation, reduced ATP levels, and cell death in neurons. Translocator protein (TSPO) is an 18-kDa outer mitochondrial membrane protein that interacts with the mitochondria permeability transition pore and binds with high affinity to cholesterol and various classes of drug ligands, including some benzodiazepines such as 4'-chlorodiazepam (Ro5-4864). Although TSPO levels in the brain are low, they are increased after brain injury and inflammation. This finding has led to the proposed use of TSPO expression as a marker of brain injury and repair. TSPO drug ligands have been shown to participate in the control of mitochondrial respiration and function, mitochondrial steroid and neurosteroid formation, as well as apoptosis. This review and commentary will outline our current knowledge of the benefits of targeting TSPO for TBI treatment and the mechanisms underlying the neuroprotective effects of TSPO drug ligands in neurotrauma.
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Affiliation(s)
- Vassilios Papadopoulos
- 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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Scarf AM, Ittner LM, Kassiou M. The Translocator Protein (18 kDa): Central Nervous System Disease and Drug Design. J Med Chem 2009; 52:581-92. [DOI: 10.1021/jm8011678] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alana M. Scarf
- Brain and Mind Research Institute, 100 Mallett Street, Camperdown, NSW 2050, Australia, and Department of Pharmacology, School of Medical Sciences, Discipline of Medical Radiation Sciences, and School of Chemistry, University of Sydney, NSW 2006, Australia
| | - Lars M. Ittner
- Brain and Mind Research Institute, 100 Mallett Street, Camperdown, NSW 2050, Australia, and Department of Pharmacology, School of Medical Sciences, Discipline of Medical Radiation Sciences, and School of Chemistry, University of Sydney, NSW 2006, Australia
| | - Michael Kassiou
- Brain and Mind Research Institute, 100 Mallett Street, Camperdown, NSW 2050, Australia, and Department of Pharmacology, School of Medical Sciences, Discipline of Medical Radiation Sciences, and School of Chemistry, University of Sydney, NSW 2006, Australia
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Cosenza-Nashat M, Zhao ML, Suh HS, Morgan J, Natividad R, Morgello S, Lee SC. Expression of the translocator protein of 18 kDa by microglia, macrophages and astrocytes based on immunohistochemical localization in abnormal human brain. Neuropathol Appl Neurobiol 2008; 35:306-28. [PMID: 19077109 DOI: 10.1111/j.1365-2990.2008.01006.x] [Citation(s) in RCA: 328] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
AIMS Microglia are involved in neurodegeneration, are prime targets for anti-inflammatory therapy and are potential biomarkers of disease progression. For example, positron emission tomography imaging employing radioligands for the mitochondrial translocator protein of 18 kDa (TSPO, formerly known as the peripheral benzodiazepine receptor) is being scrutinized to detect neuroinflammation in various diseases. TSPO is presumably present in activated microglia, but may be present in other neural cells. METHODS We sought to elucidate the protein expression in normal human central nervous system, several neurological diseases (HIV encephalitis, Alzheimer's disease, multiple sclerosis and stroke) and simian immunodeficiency virus encephalitis by performing immunohistochemistry with two anti-TSPO antibodies. RESULTS Although the overall parenchymal staining was minimal in normal brain, endothelial and smooth muscle cells, subpial glia, intravascular monocytes and ependymal cells were TSPO-positive. In disease states, elevated TSPO was present in parenchymal microglia, macrophages and some hypertrophic astrocytes, but the distribution of TSPO varied depending on the disease, disease stage and proximity to the lesion or relation to infection. Staining with the two antibodies correlated well in white matter, but one antibody also stained cortical neurones. Quantitative analysis demonstrated a significant increase in TSPO in the white matter of HIV encephalitis compared with brains without encephalitis. TSPO expression was also increased in simian immunodeficiency virus encephalitis. CONCLUSIONS This report provides the first comprehensive immunohistochemical analysis of the expression of TSPO. The results are useful for informing the usage of positron emission tomography as an imaging modality and have an impact on the potential use of TSPO as an anti-inflammatory pharmacological target.
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Affiliation(s)
- M Cosenza-Nashat
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Gottfried-Blackmore A, Sierra A, Jellinck PH, McEwen BS, Bulloch K. Brain microglia express steroid-converting enzymes in the mouse. J Steroid Biochem Mol Biol 2008; 109:96-107. [PMID: 18329265 PMCID: PMC2423427 DOI: 10.1016/j.jsbmb.2007.12.013] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the CNS, steroid hormones play a major role in the maintenance of brain homeostasis and it's response to injury. Since activated microglia are the pivotal immune cell involved in neurodegeneration, we investigated the possibility that microglia provide a discrete source for the metabolism of active steroid hormones. Using RT-PCR, our results showed that mouse microglia expressed mRNA for 17beta-hydroxysteroid dehydrogenase type 1 and steroid 5alpha-reductase type 1, which are involved in the metabolism of androgens and estrogens. Microglia also expressed the peripheral benzodiazepine receptor and steroid acute regulatory protein; however, the enzymes required for de novo formation of progesterone and DHEA from cholesterol were not expressed. To test the function of these enzymes, primary microglia cultures were incubated with steroid precursors, DHEA and AD. Microglia preferentially produced delta-5 androgens (Adiol) from DHEA and 5alpha-reduced androgens from AD. Adiol behaved as an effective estrogen receptor agonist in neuronal cells. Activation of microglia with pro-inflammatory factors, LPS and INFgamma did not affect the enzymatic properties of these proteins. However, PBR ligands reduced TNFalpha production signifying an immunomodulatory role for PBR. Collectively, our results suggest that microglia utilize steroid-converting enzymes and related proteins to influence inflammation and neurodegeneration within microenvironments of the brain.
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Affiliation(s)
| | - Amanda Sierra
- Laboratory of Neuroendocrinology, Rockefeller University, 1230 York Ave, New York, NY 10065
| | - Peter H. Jellinck
- Department of Biochemistry, Queen’s University, Kingston, Ontario K7L 3N6 Canada
| | - Bruce S. McEwen
- Laboratory of Neuroendocrinology, Rockefeller University, 1230 York Ave, New York, NY 10065
| | - Karen Bulloch
- Laboratory of Cell Physiology and Immunology, Rockefeller University, 1230 York Ave, New York, NY 10065
- CORRESPONDING AUTHOR: Karen Bulloch, Laboratory of Cell Physiology and Immunology, Rockefeller University (box 165), 1230 York Ave, New York, NY 10065. E-mail:
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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: 394] [Impact Index Per Article: 24.6] [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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Immunosuppression after traumatic or ischemic CNS damage: it is neuroprotective and illuminates the role of microglial cells. Prog Neurobiol 2007; 84:211-33. [PMID: 18262323 DOI: 10.1016/j.pneurobio.2007.12.001] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 11/15/2007] [Accepted: 12/11/2007] [Indexed: 01/08/2023]
Abstract
Acute traumatic and ischemic events in the central nervous system (CNS) invariably result in activation of microglial cells as local representatives of the immune system. It is still under debate whether activated microglia promote neuronal survival, or whether they exacerbate the original extent of neuronal damage. Protagonists of the view that microglial cells cause secondary damage have proposed that inhibition of microglial activation by immunosuppression is beneficial after acute CNS damage. It is the aim of this review to analyse the effects of immunosuppressants on isolated microglial cells and neurons, and to scrutinize the effects of immunosuppression in different in vivo models of acute CNS trauma or ischemia. It is found that the immunosuppressants cytosine-arabinoside, different steroids, cyclosporin A, FK506, rapamycin, mycophenolate mofetil, and minocycline all have direct inhibitory effects on microglial cells. These effects are mainly exerted by inhibiting microglial proliferation or microglial secretion of neurotoxic substances such as proinflammatory cytokines and nitric oxide. Furthermore, immunosuppression after acute CNS trauma or ischemia results in improved structure preservation and, mostly, in enhanced function. However, all investigated immunosuppressants also have direct effects on neurons, and some immunosuppressants affect other glial cells such as astrocytes. In summary, it is safe to conclude that immunosuppression after acute CNS trauma or ischemia is neuroprotective. Furthermore, circumferential evidence indicates that microglial activation after traumatic or ischemic CNS damage is not beneficial to adjacent neurons in the immediate aftermath of such acute lesions. Further experiments with more specific agents or genetic approaches that specifically inhibit microglial cells are needed in order to fully answer the question of whether microglial activation is "good or bad".
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Veiga S, Carrero P, Pernia O, Azcoitia I, Garcia-Segura LM. Translocator protein 18 kDa is involved in the regulation of reactive gliosis. Glia 2007; 55:1426-36. [PMID: 17674368 DOI: 10.1002/glia.20558] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Translocator protein (18 kDa) (TSPO), previously known as peripheral-type benzodiazepine receptor, is a critical component of the mitochondrial permeability transition pore. Brain inflammation results in the induction of the expression of TSPO in glial cells and some TSPO ligands decrease reactive gliosis after brain injury. However, since some TSPO ligands are neuroprotective, their effects on reactive gliosis may be the consequence of a reduced neurodegeneration. To assess whether TSPO ligands can modulate reactive gliosis in absence of neuronal death, we have tested their effects on the inflammatory response induced in the hippocampus of male rats by the intracerebroventricular infusion of lipopolysaccharide (LPS). LPS treatment did not induce neuronal death, assessed by Fluoro jade-B staining, but increased the number of cells immunoreactive for vimentin and MHC-II, used as markers of reactive astrocytes and reactive microglia, respectively. Furthermore, LPS produced an increase in the number of proliferating microglia. The TSPO ligand PK11195 reduced the number of MHC-II immunoreactive cells and the proliferation of microglia in LPS treated rats. In contrast, another TSPO ligand, Ro5-4864, did not significantly affect the response of microglia to LPS. Neither PK11195 nor Ro5-4864 affected the LPS-mediated increase in the number of vimentin-immunoreactive astrocytes at the time point studied, although PK11195 reduced vimentin immunoreactivity. These findings identify TSPO as a potential target for controlling neural inflammation, showing that the TSPO ligand PK11195 may reduce microglia activation by a mechanism that is independent of the regulation of neuronal survival.
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