1
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Gan Z, Guo Y, Zhao M, Ye Y, Liao Y, Liu B, Yin J, Zhou X, Yan Y, Yin Y, Ren W. Excitatory amino acid transporter supports inflammatory macrophage responses. Sci Bull (Beijing) 2024; 69:2405-2419. [PMID: 38614854 DOI: 10.1016/j.scib.2024.03.055] [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: 12/20/2023] [Revised: 01/28/2024] [Accepted: 03/25/2024] [Indexed: 04/15/2024]
Abstract
Excitatory amino acid transporters (EAATs) are responsible for excitatory amino acid transportation and are associated with auto-immune diseases in the central nervous system and peripheral tissues. However, the subcellular location and function of EAAT2 in macrophages are still obscure. In this study, we demonstrated that LPS stimulation increases expression of EAAT2 (coded by Slc1a2) via NF-κB signaling. EAAT2 is necessary for inflammatory macrophage polarization through sustaining mTORC1 activation. Mechanistically, lysosomal EAAT2 mediates lysosomal glutamate and aspartate efflux to maintain V-ATPase activation, which sustains macropinocytosis and mTORC1. We also found that mice with myeloid depletion of Slc1a2 show alleviated inflammatory responses in LPS-induced systemic inflammation and high-fat diet induced obesity. Notably, patients with type II diabetes (T2D) have a higher level of expression of lysosomal EAAT2 and activation of mTORC1 in blood macrophages. Taken together, our study links the subcellular location of amino acid transporters with the fate decision of immune cells, which provides potential therapeutic targets for the treatment of inflammatory diseases.
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Affiliation(s)
- Zhending Gan
- State Key Laboratory of Swine and Poultry Breeding Industry, Guangdong Laboratory of Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou 510642, China
| | - Yan Guo
- State Key Laboratory of Swine and Poultry Breeding Industry, Guangdong Laboratory of Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou 510642, China
| | - Muyang Zhao
- State Key Laboratory of Swine and Poultry Breeding Industry, Guangdong Laboratory of Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou 510642, China
| | - Yuyi Ye
- State Key Laboratory of Swine and Poultry Breeding Industry, Guangdong Laboratory of Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou 510642, China
| | - Yuexia Liao
- School of Nursing & School of Public Health, Yangzhou University, Yangzhou 225009, China
| | - Bingnan Liu
- State Key Laboratory of Swine and Poultry Breeding Industry, Guangdong Laboratory of Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou 510642, China
| | - Jie Yin
- College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China
| | - Xihong Zhou
- Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
| | - Yuqi Yan
- Department of Veterinary Medicine, College of Animal Sciences, Zhejiang University, Hangzhou 310058, China
| | - Yulong Yin
- Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
| | - Wenkai Ren
- State Key Laboratory of Swine and Poultry Breeding Industry, Guangdong Laboratory of Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
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2
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Lu HJ, Guo D, Wei QQ. Potential of Neuroinflammation-Modulating Strategies in Tuberculous Meningitis: Targeting Microglia. Aging Dis 2024; 15:1255-1276. [PMID: 37196131 PMCID: PMC11081169 DOI: 10.14336/ad.2023.0311] [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: 12/09/2022] [Accepted: 03/11/2023] [Indexed: 05/19/2023] Open
Abstract
Tuberculous meningitis (TBM) is the most severe complication of tuberculosis (TB) and is associated with high rates of disability and mortality. Mycobacterium tuberculosis (M. tb), the infectious agent of TB, disseminates from the respiratory epithelium, breaks through the blood-brain barrier, and establishes a primary infection in the meninges. Microglia are the core of the immune network in the central nervous system (CNS) and interact with glial cells and neurons to fight against harmful pathogens and maintain homeostasis in the brain through pleiotropic functions. However, M. tb directly infects microglia and resides in them as the primary host for bacillus infections. Largely, microglial activation slows disease progression. The non-productive inflammatory response that initiates the secretion of pro-inflammatory cytokines and chemokines may be neurotoxic and aggravate tissue injuries based on damages caused by M. tb. Host-directed therapy (HDT) is an emerging strategy for modulating host immune responses against diverse diseases. Recent studies have shown that HDT can control neuroinflammation in TBM and act as an adjunct therapy to antibiotic treatment. In this review, we discuss the diverse roles of microglia in TBM and potential host-directed TB therapies that target microglia to treat TBM. We also discuss the limitations of applying each HDT and suggest a course of action for the near future.
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Affiliation(s)
- Huan-Jun Lu
- Institute of Special Environmental Medicine, Nantong University, Jiangsu, China
| | - Daji Guo
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Qian-Qi Wei
- Department of Infectious Diseases, General Hospital of Tibet Military Command, Xizang, China
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3
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Nogueira CO, Rocha T, Messor DF, Souza INO, Clarke JR. Fundamental neurochemistry review: Glutamatergic dysfunction as a central mechanism underlying flavivirus-induced neurological damage. J Neurochem 2023; 166:915-927. [PMID: 37603368 DOI: 10.1111/jnc.15935] [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: 05/15/2023] [Revised: 07/06/2023] [Accepted: 07/26/2023] [Indexed: 08/22/2023]
Abstract
The Flaviviridae family comprises positive-sense single-strand RNA viruses mainly transmitted by arthropods. Many of these pathogens are especially deleterious to the nervous system, and a myriad of neurological symptoms have been associated with infections by Zika virus (ZIKV), West Nile virus (WNV), and Japanese encephalitis virus (JEV) in humans. Studies suggest that viral replication in neural cells and the massive release of pro-inflammatory mediators lead to morphological alterations of synaptic spine structure and changes in the balance of excitatory/inhibitory neurotransmitters and receptors. Glutamate is the predominant excitatory neurotransmitter in the brain, and studies propose that either enhanced release or impaired uptake of this amino acid contributes to brain damage in several conditions. Here, we review existing evidence suggesting that glutamatergic dysfunction-induced by flaviviruses is a central mechanism for neurological damage and clinical outcomes of infection. We also discuss current data suggesting that pharmacological approaches that counteract glutamatergic dysfunction show benefits in animal models of such viral diseases.
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Affiliation(s)
- Clara O Nogueira
- Programa de Pós-graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Tamires Rocha
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Daniel F Messor
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Isis N O Souza
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Julia R Clarke
- Programa de Pós-graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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4
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Wilson KM, He JJ. HIV Nef Expression Down-modulated GFAP Expression and Altered Glutamate Uptake and Release and Proliferation in Astrocytes. Aging Dis 2023; 14:152-169. [PMID: 36818564 PMCID: PMC9937695 DOI: 10.14336/ad.2022.0712] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 07/12/2022] [Indexed: 11/18/2022] Open
Abstract
HIV infection of astrocytes leads to restricted gene expression and replication but abundant expression of HIV early genes Tat, Nef and Rev. A great deal of neuroHIV research has so far been focused on Tat protein, its effects on astrocytes, and its roles in neuroHIV. In the current study, we aimed to determine effects of Nef expression on astrocytes and their function. Using transfection or infection of VSVG-pseudotyped HIV viruses, we showed that Nef expression down-modulated glial fibrillary acidic protein (GFAP) expression. We then showed that Nef expression also led to decreased GFAP mRNA expression. The transcriptional regulation was further confirmed using a GFAP promoter-driven reporter gene assay. We performed transcription factor profiling array to compare the expression of transcription factors between Nef-intact and Nef-deficient HIV-infected cells and identified eight transcription factors with expression changes of 1.5-fold or higher: three up-regulated by Nef (Stat1, Stat5, and TFIID), and five down-regulated by Nef (AR, GAS/ISRE, HIF, Sp1, and p53). We then demonstrated that removal of the Sp1 binding sites from the GFAP promoter resulted in a much lower level of the promoter activity and reversal of Nef effects on the GFAP promoter, confirming important roles of Sp1 in the GFAP promoter activity and for Nef-induced GFAP expression. Lastly, we showed that Nef expression led to increased glutamate uptake and decreased glutamate release by astrocytes and increased astrocyte proliferation. Taken together, these results indicate that Nef leads to down-modulation of GFAP expression and alteration of glutamate metabolism in astrocytes, and astrocyte proliferation and could be an important contributor to neuroHIV.
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Affiliation(s)
- Kelly M Wilson
- Department of Microbiology and Immunology, Center for Cancer Cell Biology, Immunology and Infection, School of Graduate and Postdoctoral Studies, Rosalind Franklin University, Chicago Medical School, North Chicago, IL 60064, USA
| | - Johnny J He
- Department of Microbiology and Immunology, Center for Cancer Cell Biology, Immunology and Infection, School of Graduate and Postdoctoral Studies, Rosalind Franklin University, Chicago Medical School, North Chicago, IL 60064, USA
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5
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Espinosa JM, Castellano JM, Garcia-Rodriguez S, Quintero-Flórez A, Carrasquilla N, Perona JS. Lipophilic Bioactive Compounds Transported in Triglyceride-Rich Lipoproteins Modulate Microglial Inflammatory Response. Int J Mol Sci 2022; 23:ijms23147706. [PMID: 35887052 PMCID: PMC9321013 DOI: 10.3390/ijms23147706] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 06/30/2022] [Accepted: 07/09/2022] [Indexed: 11/16/2022] Open
Abstract
Microglial cells can contribute to Alzheimer’s disease by triggering an inflammatory response that leads to neuronal death. In addition, the presence of amyloid-β in the brain is consistent with alterations in the blood–brain barrier integrity and triglyceride-rich lipoproteins (TRL) permeation. In the present work, we used lab-made TRL as carriers of lipophilic bioactive compounds that are commonly present in dietary oils, namely oleanolic acid (OA), α-tocopherol (AT) and β-sitosterol (BS), to assess their ability to modulate the inflammatory response of microglial BV-2 cells. We show that treatment with lab-made TRL increases the release and gene-expression of IL-1β, IL-6, and TNF-α, as well as NO and iNOS in microglia. On the other hand, TRL revealed bioactive compounds α-tocopherol and β-sitosterol as suitable carriers for oleanolic acid. The inclusion of these biomolecules in TRL reduced the release of proinflammatory cytokines. The inclusion of these biomolecules in TRL reduced the release of proinflammatory cytokines. AT reduced IL-6 release by 72%, OA reduced TNF-α release by approximately 50%, and all three biomolecules together (M) reduced IL-1β release by 35% and TNF-α release by more than 70%. In addition, NO generation was reduced, with the inclusion of OA by 45%, BS by 80% and the presence of M by 88%. Finally, a recovery of the basal glutathione content was observed with the inclusion of OA and M in the TRL. Our results open the way to exploiting the neuro-pharmacological potential of these lipophilic bioactive compounds through their delivery to the brain as part of TRL.
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6
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Abstract
Glutathione (GSH) is the most abundant non-protein thiol, and plays crucial roles in the antioxidant defense system and the maintenance of redox homeostasis in neurons. GSH depletion in the brain is a common finding in patients with neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease, and can cause neurodegeneration prior to disease onset. Excitatory amino acid carrier 1 (EAAC1), a sodium-dependent glutamate/cysteine transporter that is selectively present in neurons, plays a central role in the regulation of neuronal GSH production. The expression of EAAC1 is posttranslationally controlled by the glutamate transporter-associated protein 3–18 (GTRAP3-18) or miR-96-5p in neurons. The regulatory mechanism of neuronal GSH production mediated by EAAC1 may be a new target in therapeutic strategies for these neurodegenerative diseases. This review describes the regulatory mechanism of neuronal GSH production and its potential therapeutic application in the treatment of neurodegenerative diseases.
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7
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Balouch B, Funnell JL, Ziemba AM, Puhl DL, Lin K, Gottipati MK, Gilbert RJ. Conventional immunomarkers stain a fraction of astrocytes in vitro: A comparison of rat cortical and spinal cord astrocytes in naïve and stimulated cultures. J Neurosci Res 2020; 99:806-826. [PMID: 33295039 DOI: 10.1002/jnr.24759] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 11/14/2020] [Indexed: 11/05/2022]
Abstract
Astrocytes are responsible for a wide variety of essential functions throughout the central nervous system. The protein markers glial fibrillary acidic protein (GFAP), glutamate aspartate transporter (GLAST), glutamate transporter-1 (GLT-1), glutamine synthetase (GS), 10-formyltetrahydrofolate dehydrogenase (ALDH1L1), and the transcription factor SOX9 are routinely used to label astrocytes in primary rodent cultures. However, GLAST, GLT-1, GS, and SOX9 are also produced by microglia and oligodendrocytes and GFAP, GLAST, GLT-1, and GS production levels are affected by astrocyte phenotypic changes associated with reactive astrogliosis. No group has performed a comprehensive immunocytochemical evaluation to quantify the percentage of cells labeled by these markers in vitro, nor compared changes in staining between cortex- and spinal cord-derived cells in naïve and stimulated cultures. Here, we quantified the percentage of cells positively stained for these six markers in astrocyte, microglia, and oligodendrocyte cultures isolated from neonatal rat cortices and spinal cords. Additionally, we incubated the astrocytes with transforming growth factor (TGF)-β1 or TGF-β3 to determine if the labeling of these markers is altered by these stimuli. We found that only SOX9 in cortical cultures and ALDH1L1 in spinal cord cultures labeled more than 75% of the cells in naïve and stimulated astrocyte cultures and stained less than 5% of the cells in microglia and oligodendrocyte cultures. Furthermore, significantly more cortical than spinal cord astrocytes stained for GFAP, GLAST, and ALDH1L1 in naïve cultures, whereas significantly more spinal cord than cortical astrocytes stained for GLAST and GS in TGF-β1-treated cultures. These findings are important as variability in marker staining may lead to misinterpretation of the astrocyte response in cocultures, migration assays, or engineered disease models.
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Affiliation(s)
- Bailey Balouch
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.,Drexel University College of Medicine, Philadelphia, PA, USA
| | - Jessica L Funnell
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Alexis M Ziemba
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.,Neuroscience Program, Smith College, Northampton, MA, USA
| | - Devan L Puhl
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Kathy Lin
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Manoj K Gottipati
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Brain and Spinal Cord Repair, Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - Ryan J Gilbert
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA
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8
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Fatoba O, Itokazu T, Yamashita T. Microglia as therapeutic target in central nervous system disorders. J Pharmacol Sci 2020; 144:102-118. [PMID: 32921391 DOI: 10.1016/j.jphs.2020.07.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/19/2020] [Accepted: 07/07/2020] [Indexed: 12/17/2022] Open
Abstract
Chronic microglial activation is associated with the pathogenesis of several CNS disorders. Microglia show phenotypic diversity and functional complexity in diseased CNS. Thus, understanding the pathology-specific heterogeneity of microglial behavior is crucial for the future development of microglia-modulating therapy for variety of CNS disorders. This review summarizes up-to-date knowledge on how microglia contribute to CNS homeostasis during development and throughout adulthood. We discuss the heterogeneity of microglial phenotypes in the context of CNS disorders with an emphasis on neurodegenerative diseases, demyelinating diseases, CNS trauma, and epilepsy. We conclude this review with a discussion about the disease-specific heterogeneity of microglial function and how it could be exploited for therapeutic intervention.
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Affiliation(s)
- Oluwaseun Fatoba
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; WPI-Immunology Frontier Research Center, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Takahide Itokazu
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Department of Neuro-Medical Science, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Toshihide Yamashita
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; WPI-Immunology Frontier Research Center, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; Department of Neuro-Medical Science, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
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9
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Iovino L, Tremblay ME, Civiero L. Glutamate-induced excitotoxicity in Parkinson's disease: The role of glial cells. J Pharmacol Sci 2020; 144:151-164. [PMID: 32807662 DOI: 10.1016/j.jphs.2020.07.011] [Citation(s) in RCA: 155] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/30/2020] [Accepted: 07/27/2020] [Indexed: 12/11/2022] Open
Abstract
Glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamate transmission efficiency depends on the correct functionality and expression of a plethora of receptors and transporters, located both on neurons and glial cells. Of note, glutamate reuptake by dedicated transporters prevents its accumulation at the synapse as well as non-physiological spillover. Indeed, extracellular glutamate increase causes aberrant synaptic signaling leading to neuronal excitotoxicity and death. Moreover, extrasynaptic glutamate diffusion is strongly associated with glia reaction and neuroinflammation. Glutamate-induced excitotoxicity is mainly linked to an impaired ability of glial cells to reuptake and respond to glutamate, then this is considered a common hallmark in many neurodegenerative diseases, including Parkinson's disease (PD). In this review, we discuss the function of astrocytes and microglia in glutamate homeostasis, focusing on how glial dysfunction causes glutamate-induced excitotoxicity leading to neurodegeneration in PD.
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Affiliation(s)
- L Iovino
- Department of Biology, University of Padova, Italy
| | - M E Tremblay
- Division of Medical Sciences, University of Victoria, Victoria, Canada
| | - L Civiero
- Department of Biology, University of Padova, Italy; IRCCS San Camillo Hospital, Venice, Italy.
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10
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Rodríguez-Gómez JA, Kavanagh E, Engskog-Vlachos P, Engskog MK, Herrera AJ, Espinosa-Oliva AM, Joseph B, Hajji N, Venero JL, Burguillos MA. Microglia: Agents of the CNS Pro-Inflammatory Response. Cells 2020; 9:E1717. [PMID: 32709045 PMCID: PMC7407646 DOI: 10.3390/cells9071717] [Citation(s) in RCA: 168] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/14/2020] [Accepted: 07/15/2020] [Indexed: 12/21/2022] Open
Abstract
The pro-inflammatory immune response driven by microglia is a key contributor to the pathogenesis of several neurodegenerative diseases. Though the research of microglia spans over a century, the last two decades have increased our understanding exponentially. Here, we discuss the phenotypic transformation from homeostatic microglia towards reactive microglia, initiated by specific ligand binding to pattern recognition receptors including toll-like receptor-4 (TLR4) or triggering receptors expressed on myeloid cells-2 (TREM2), as well as pro-inflammatory signaling pathways triggered such as the caspase-mediated immune response. Additionally, new research disciplines such as epigenetics and immunometabolism have provided us with a more holistic view of how changes in DNA methylation, microRNAs, and the metabolome may influence the pro-inflammatory response. This review aimed to discuss our current knowledge of pro-inflammatory microglia from different angles, including recent research highlights such as the role of exosomes in spreading neuroinflammation and emerging techniques in microglia research including positron emission tomography (PET) scanning and the use of human microglia generated from induced pluripotent stem cells (iPSCs). Finally, we also discuss current thoughts on the impact of pro-inflammatory microglia in neurodegenerative diseases.
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Affiliation(s)
- José A. Rodríguez-Gómez
- Institute of Biomedicine of Seville (IBIS)-Hospital Universitario Virgen del Rocío/CSIC/University of Seville, 41012 Seville, Spain; (J.A.R.-G.); (A.J.H.); (A.M.E.-O.); (J.L.V.)
- Department of Medical Physiology and Biophysics, Faculty of Medicine, University of Seville, 41009 Sevilla, Spain
| | - Edel Kavanagh
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Seville, 41012 Seville, Spain;
| | - Pinelopi Engskog-Vlachos
- Institute of Environmental Medicine, Toxicology Unit, Karolinska Institute, 17177 Stockholm, Sweden; (P.E.-V.); (B.J.)
| | - Mikael K.R. Engskog
- Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry, Uppsala University, 751 23 Uppsala, Sweden;
| | - Antonio J. Herrera
- Institute of Biomedicine of Seville (IBIS)-Hospital Universitario Virgen del Rocío/CSIC/University of Seville, 41012 Seville, Spain; (J.A.R.-G.); (A.J.H.); (A.M.E.-O.); (J.L.V.)
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Seville, 41012 Seville, Spain;
| | - Ana M. Espinosa-Oliva
- Institute of Biomedicine of Seville (IBIS)-Hospital Universitario Virgen del Rocío/CSIC/University of Seville, 41012 Seville, Spain; (J.A.R.-G.); (A.J.H.); (A.M.E.-O.); (J.L.V.)
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Seville, 41012 Seville, Spain;
| | - Bertrand Joseph
- Institute of Environmental Medicine, Toxicology Unit, Karolinska Institute, 17177 Stockholm, Sweden; (P.E.-V.); (B.J.)
| | - Nabil Hajji
- Division of Brain Sciences, The John Fulcher Molecular Neuro-Oncology Laboratory, Imperial College London, London W12 ONN, UK;
| | - José L. Venero
- Institute of Biomedicine of Seville (IBIS)-Hospital Universitario Virgen del Rocío/CSIC/University of Seville, 41012 Seville, Spain; (J.A.R.-G.); (A.J.H.); (A.M.E.-O.); (J.L.V.)
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Seville, 41012 Seville, Spain;
| | - Miguel A. Burguillos
- Institute of Biomedicine of Seville (IBIS)-Hospital Universitario Virgen del Rocío/CSIC/University of Seville, 41012 Seville, Spain; (J.A.R.-G.); (A.J.H.); (A.M.E.-O.); (J.L.V.)
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Seville, 41012 Seville, Spain;
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11
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Microglial metabolic flexibility supports immune surveillance of the brain parenchyma. Nat Commun 2020; 11:1559. [PMID: 32214088 PMCID: PMC7096448 DOI: 10.1038/s41467-020-15267-z] [Citation(s) in RCA: 139] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 02/27/2020] [Indexed: 02/07/2023] Open
Abstract
Microglia are highly motile cells that continuously monitor the brain environment and respond to damage-associated cues. While glucose is the main energy substrate used by neurons in the brain, the nutrients metabolized by microglia to support surveillance of the parenchyma remain unexplored. Here, we use fluorescence lifetime imaging of intracellular NAD(P)H and time-lapse two-photon imaging of microglial dynamics in vivo and in situ, to show unique aspects of the microglial metabolic signature in the brain. Microglia are metabolically flexible and can rapidly adapt to consume glutamine as an alternative metabolic fuel in the absence of glucose. During insulin-induced hypoglycemia in vivo or in aglycemia in acute brain slices, glutaminolysis supports the maintenance of microglial process motility and damage-sensing functions. This metabolic shift sustains mitochondrial metabolism and requires mTOR-dependent signaling. This remarkable plasticity allows microglia to maintain their critical surveillance and phagocytic roles, even after brain neuroenergetic homeostasis is compromised. Glucose is the main source of fuel in the brain. Here, the authors show that in the absence of glucose, glutamine is required for microglia to maintain their immune surveillance function.
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12
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Robinson RR, Dietz AK, Maroof AM, Asmis R, Forsthuber TG. The role of glial-neuronal metabolic cooperation in modulating progression of multiple sclerosis and neuropathic pain. Immunotherapy 2019; 11:129-147. [PMID: 30730270 DOI: 10.2217/imt-2018-0153] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
While the etiology of multiple sclerosis (MS) remains unclear, research from the clinic and preclinical models identified the essential role of inflammation and demyelination in the pathogenesis of MS. Current treatments focused on anti-inflammatory processes are effective against acute episodes and relapsing-remitting MS, but patients still move on to develop secondary progressive MS. MS progression is associated with activation of microglia and astrocytes, and importantly, metabolic dysfunction leading to neuronal death. Neuronal death also contributes to chronic neuropathic pain. Metabolic support of neurons by glia may play central roles in preventing progression of MS and chronic neuropathic pain. Here, we review mechanisms of metabolic cooperation between glia and neurons and outline future perspectives exploring metabolic support of neurons by glia.
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Affiliation(s)
- Rachel R Robinson
- Department of Biology, University of Texas at San Antonio, TX 78249, USA
| | - Alina K Dietz
- Department of Biology, University of Texas at San Antonio, TX 78249, USA
| | - Asif M Maroof
- Department of Biology, University of Texas at San Antonio, TX 78249, USA
| | - Reto Asmis
- Department of Internal Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA
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13
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Geiß C, Alanis-Lobato G, Andrade-Navarro M, Régnier-Vigouroux A. Assessing the reliability of gene expression measurements in very-low-numbers of human monocyte-derived macrophages. Sci Rep 2019; 9:17908. [PMID: 31784632 PMCID: PMC6884563 DOI: 10.1038/s41598-019-54500-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 11/14/2019] [Indexed: 12/14/2022] Open
Abstract
Tumor-derived primary cells are essential for in vitro and in vivo studies of tumor biology. The scarcity of this cellular material limits the feasibility of experiments or analyses and hence hinders basic and clinical research progress. We set out to determine the minimum number of cells that can be analyzed with standard laboratory equipment and that leads to reliable results, unbiased by cell number. A proof-of-principle study was conducted with primary human monocyte-derived macrophages, seeded in decreasing number and constant cell density. Gene expression of cells stimulated to acquire opposite inflammatory states was analyzed by quantitative PCR. Statistical analysis indicated the lack of significant difference in the expression profile of cells cultured at the highest (100,000 cells) and lowest numbers (3,610 cells) tested. Gene Ontology, pathway enrichment and network analysis confirmed the reliability of the data obtained with the lowest cell number. This statistical and computational analysis of gene expression profiles indicates that low cell number analysis is as dependable and informative as the analysis of a larger cell number. Our work demonstrates that it is possible to employ samples with a scarce number of cells in experimental studies and encourages the application of this approach on other cell types.
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Affiliation(s)
- Carsten Geiß
- Institute of Developmental Biology and Neurobiology, Faculty of Biology, Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 13, 55128, Mainz, Germany
| | - Gregorio Alanis-Lobato
- Human Embryo and Stem Cell Laboratory, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.,Institute of Organismic and Molecular Evolution, Faculty of Biology, Johannes Gutenberg University of Mainz, Hans-Dieter-Hüsch-Weg 15, 55128, Mainz, Germany
| | - Miguel Andrade-Navarro
- Institute of Organismic and Molecular Evolution, Faculty of Biology, Johannes Gutenberg University of Mainz, Hans-Dieter-Hüsch-Weg 15, 55128, Mainz, Germany
| | - Anne Régnier-Vigouroux
- Institute of Developmental Biology and Neurobiology, Faculty of Biology, Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 13, 55128, Mainz, Germany.
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14
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Carvalho PLPF, Yamamoto FY, Barros MM, Gatlin Iii DM. l-glutamine in vitro supplementation enhances Nile tilapia Oreochromis niloticus (Linnaeus, 1758) leukocyte function. FISH & SHELLFISH IMMUNOLOGY 2018; 80:592-599. [PMID: 29960065 DOI: 10.1016/j.fsi.2018.06.043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 06/22/2018] [Accepted: 06/26/2018] [Indexed: 06/08/2023]
Abstract
Under appropriate conditions, glutamine (Gln) is an essential nutrient for immunological responses, acting as a metabolic substrate for proliferation of enterocytes and lymphocytes, and having positive effects on the function of stimulated immune cells. Thus, specific components of both innate and adaptive immune systems of Nile tilapia were evaluated after supplementing Gln to cell culture media. Primary cell cultures of kidney leukocytes were used for respiratory burst and phagocytic activity assessment. The ability of macrophages to kill Streptococcus iniae also was evaluated. Additionally, a proliferation assay was conducted with peripheral blood lymphocytes (PBL) exposed to non-specific mitogens. Results showed that macrophage phagocytosis, anion superoxide production, and bactericidal capacity were significantly (P < 0.05) enhanced by Gln supplementation to the culture media. The proliferation of lymphocytes upon mitogenic exposure also was significantly (P < 0.05) enhanced by Gln supplementation to the media. Our results suggest that in vitro, different levels of Gln were necessary for optimal immunological responses of leukocytes and lymphocytes. As such, Gln supplementation was able to enhance and modulate both innate and adaptive responses of Nile tilapia leukocytes, highlighting its potential application as an immunonutrient.
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Affiliation(s)
- Pedro L P F Carvalho
- Faculdade de Medicina Veterinária e Zootecnia, Departamento de Melhoramento e Nutrição Animal, Universidade Estadual Paulista "Júlio de Mesquita Filho", São Paulo, Brazil; Department of Wildlife and Fisheries Sciences, Texas A&M University System, College Station, TX, 77843-2258, USA.
| | - Fernando Y Yamamoto
- Department of Wildlife and Fisheries Sciences, Texas A&M University System, College Station, TX, 77843-2258, USA.
| | - Margarida M Barros
- Faculdade de Medicina Veterinária e Zootecnia, Departamento de Melhoramento e Nutrição Animal, Universidade Estadual Paulista "Júlio de Mesquita Filho", São Paulo, Brazil.
| | - Delbert M Gatlin Iii
- Department of Wildlife and Fisheries Sciences, Texas A&M University System, College Station, TX, 77843-2258, USA.
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15
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Palmieri EM, Menga A, Martín-Pérez R, Quinto A, Riera-Domingo C, De Tullio G, Hooper DC, Lamers WH, Ghesquière B, McVicar DW, Guarini A, Mazzone M, Castegna A. Pharmacologic or Genetic Targeting of Glutamine Synthetase Skews Macrophages toward an M1-like Phenotype and Inhibits Tumor Metastasis. Cell Rep 2018; 20:1654-1666. [PMID: 28813676 PMCID: PMC5575233 DOI: 10.1016/j.celrep.2017.07.054] [Citation(s) in RCA: 229] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 05/30/2017] [Accepted: 07/19/2017] [Indexed: 12/18/2022] Open
Abstract
Glutamine-synthetase (GS), the glutamine-synthesizing enzyme from glutamate, controls important events, including the release of inflammatory mediators, mammalian target of rapamycin (mTOR) activation, and autophagy. However, its role in macrophages remains elusive. We report that pharmacologic inhibition of GS skews M2-polarized macrophages toward the M1-like phenotype, characterized by reduced intracellular glutamine and increased succinate with enhanced glucose flux through glycolysis, which could be partly related to HIF1α activation. As a result of these metabolic changes and HIF1α accumulation, GS-inhibited macrophages display an increased capacity to induce T cell recruitment, reduced T cell suppressive potential, and an impaired ability to foster endothelial cell branching or cancer cell motility. Genetic deletion of macrophagic GS in tumor-bearing mice promotes tumor vessel pruning, vascular normalization, accumulation of cytotoxic T cells, and metastasis inhibition. These data identify GS activity as mediator of the proangiogenic, immunosuppressive, and pro-metastatic function of M2-like macrophages and highlight the possibility of targeting this enzyme in the treatment of cancer metastasis. GS expression and activity are induced by M2 stimuli, especially under starvation Inhibition of GS activity skews M2 macrophages toward an M1-like phenotype Metabolic rewiring by GS loss favors immunostimulatory and antiangiogenic features GS ablation in macrophages blocks vessels, immunosuppression, and metastasis
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Affiliation(s)
- Erika M Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; The Cancer and Inflammation Program, National Cancer Institute-Frederick, Frederick, MD 21702, USA
| | - Alessio Menga
- Hematology Unit, National Cancer Research Center, Istituto Tumori "Giovanni Paolo II," 70124 Bari, Italy; Laboratory of Tumor Inflammation and Angiogenesis, Center for Cancer Biology (CCB), VIB, 3000 Leuven, Belgium; Laboratory of Tumor Inflammation and Angiogenesis, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Rosa Martín-Pérez
- Laboratory of Tumor Inflammation and Angiogenesis, Center for Cancer Biology (CCB), VIB, 3000 Leuven, Belgium; Laboratory of Tumor Inflammation and Angiogenesis, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Annamaria Quinto
- Hematology Unit, National Cancer Research Center, Istituto Tumori "Giovanni Paolo II," 70124 Bari, Italy
| | - Carla Riera-Domingo
- Laboratory of Tumor Inflammation and Angiogenesis, Center for Cancer Biology (CCB), VIB, 3000 Leuven, Belgium; Laboratory of Tumor Inflammation and Angiogenesis, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Giacoma De Tullio
- Hematology Unit, National Cancer Research Center, Istituto Tumori "Giovanni Paolo II," 70124 Bari, Italy
| | - Douglas C Hooper
- Department of Cancer Biology, Department of Neurological Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Wouter H Lamers
- Department of Anatomy & Embryology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University, 6211 LK Maastricht, the Netherlands; Nutrigenomics Consortium, Top Institute Food and Nutrition, Wageningen, the Netherlands; Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, University of Amsterdam, 1012 WX Amsterdam, the Netherlands
| | - Bart Ghesquière
- Metabolomics Expertise Center, Vesalius Research Center, VIB, 3000 Leuven, Belgium; Metabolomics Expertise Center, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Daniel W McVicar
- The Cancer and Inflammation Program, National Cancer Institute-Frederick, Frederick, MD 21702, USA
| | - Attilio Guarini
- Hematology Unit, National Cancer Research Center, Istituto Tumori "Giovanni Paolo II," 70124 Bari, Italy
| | - Massimiliano Mazzone
- Laboratory of Tumor Inflammation and Angiogenesis, Center for Cancer Biology (CCB), VIB, 3000 Leuven, Belgium; Laboratory of Tumor Inflammation and Angiogenesis, Department of Oncology, KU Leuven, 3000 Leuven, Belgium.
| | - Alessandra Castegna
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; Hematology Unit, National Cancer Research Center, Istituto Tumori "Giovanni Paolo II," 70124 Bari, Italy.
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16
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Glutamine Synthetase: Localization Dictates Outcome. Genes (Basel) 2018; 9:genes9020108. [PMID: 29463059 PMCID: PMC5852604 DOI: 10.3390/genes9020108] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 02/14/2018] [Accepted: 02/15/2018] [Indexed: 01/03/2023] Open
Abstract
Glutamine synthetase (GS) is the adenosine triphosphate (ATP)-dependent enzyme that catalyses the synthesis of glutamine by condensing ammonium to glutamate. In the circulatory system, glutamine carries ammonia from muscle and brain to the kidney and liver. In brain reduction of GS activity has been suggested as a mechanism mediating neurotoxicity in neurodegenerative disorders. In cancer, the delicate balance between glutamine synthesis and catabolism is a critical event. In vitro evidence, confirmed in vivo in some cases, suggests that reduced GS activity in cancer cells associates with a more invasive and aggressive phenotype. However, GS is known to be highly expressed in cells of the tumor microenvironment, such as fibroblasts, adipocytes and immune cells, and their ability to synthesize glutamine is responsible for the acquisition of protumoral phenotypes. This has opened a new window into the complex scenario of the tumor microenvironment, in which the balance of glutamine consumption versus glutamine synthesis influences cellular function. Since GS expression responds to glutamine starvation, a lower glutamine synthesizing power due to the absence of GS in cancer cells might apply a metabolic pressure on stromal cells. This event might push stroma towards a GS-high/protumoral phenotype. When referred to stromal cells, GS expression might acquire a ‘bad’ significance to the point that GS inhibition might be considered a conceivable strategy against cancer metastasis.
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17
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Mazzone M, Menga A, Castegna A. Metabolism and TAM functions-it takes two to tango. FEBS J 2017; 285:700-716. [DOI: 10.1111/febs.14295] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/25/2017] [Accepted: 10/17/2017] [Indexed: 12/16/2022]
Affiliation(s)
- Massimiliano Mazzone
- Laboratory of Tumor Inflammation and Angiogenesis; Center for Cancer Biology (CCB); VIB; Leuven Belgium
- Laboratory of Tumor Inflammation and Angiogenesis; Department of Oncology; KU Leuven; Belgium
| | - Alessio Menga
- Hematology Unit; National Cancer Research Center; Istituto Tumori ‘Giovanni Paolo II’; Bari Italy
| | - Alessandra Castegna
- Hematology Unit; National Cancer Research Center; Istituto Tumori ‘Giovanni Paolo II’; Bari Italy
- Department of Biosciences, Biotechnologies and Biopharmaceutics; University of Bari; Italy
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18
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Palmieri EM, Menga A, Lebrun A, Hooper DC, Butterfield DA, Mazzone M, Castegna A. Blockade of Glutamine Synthetase Enhances Inflammatory Response in Microglial Cells. Antioxid Redox Signal 2017; 26:351-363. [PMID: 27758118 PMCID: PMC5346956 DOI: 10.1089/ars.2016.6715] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
AIMS Microglial cells are brain-resident macrophages engaged in surveillance and maintained in a constant state of relative inactivity. However, their involvement in autoimmune diseases indicates that in pathological conditions microglia gain an inflammatory phenotype. The mechanisms underlying this change in the microglial phenotype are still unclear. Since metabolism is an important modulator of immune cell function, we focused our attention on glutamine synthetase (GS), a modulator of the response to lipopolysaccharide (LPS) activation in other cell types, which is expressed by microglia. RESULTS GS inhibition enhances release of inflammatory mediators of LPS-activated microglia in vitro, leading to perturbation of the redox balance and decreased viability of cocultured neurons. GS inhibition also decreases insulin-mediated glucose uptake in microglia. In vivo, microglia-specific GS ablation enhances expression of inflammatory markers upon LPS treatment. In the spinal cords from experimental autoimmune encephalomyelitis (EAE), GS expression levels and glutamine/glutamate ratios are reduced. INNOVATION Recently, metabolism has been highlighted as mediator of immune cell function through the discovery of mechanisms that (behind these metabolic changes) modulate the inflammatory response. The present study shows for the first time a metabolic mechanism mediating microglial response to a proinflammatory stimulus, pointing to GS activity as a master modulator of immune cell function and thus unraveling a potential therapeutic target. CONCLUSIONS Our study highlights a new role of GS in modulating immune response in microglia, providing insights into the pathogenic mechanisms associated with inflammation and new strategies of therapeutic intervention. Antioxid. Redox Signal. 26, 351-363.
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Affiliation(s)
- Erika M Palmieri
- 1 Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari , Bari, Italy
| | - Alessio Menga
- 2 National Cancer Research Center, Istituto Tumori 'Giovanni Paolo II,' Bari, Italy
| | - Aurore Lebrun
- 3 Department of Cancer Biology, Thomas Jefferson University , Philadelphia, Pennsylvania.,4 Department of Neurological Surgery, Thomas Jefferson University , Philadelphia, Pennsylvania
| | - Douglas C Hooper
- 3 Department of Cancer Biology, Thomas Jefferson University , Philadelphia, Pennsylvania.,4 Department of Neurological Surgery, Thomas Jefferson University , Philadelphia, Pennsylvania
| | - D Allan Butterfield
- 5 Department of Chemistry, University of Kentucky , Lexington, Kentucky.,6 Sanders-Brown Center on Aging, University of Kentucky , Lexington, Kentucky
| | - Massimiliano Mazzone
- 7 Laboratory of Tumor Inflammation and Angiogenesis, Department of Oncology, University of Leuven , Leuven, Belgium .,8 Laboratory of Tumor Inflammation and Angiogenesis, Vesalius Research Center, VIB, Leuven, Belgium
| | - Alessandra Castegna
- 1 Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari , Bari, Italy .,2 National Cancer Research Center, Istituto Tumori 'Giovanni Paolo II,' Bari, Italy
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19
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Microglia derived from the axotomized adult rat facial nucleus uptake glutamate and metabolize it to glutamine in vitro. Neurochem Int 2016; 102:1-12. [PMID: 27816478 DOI: 10.1016/j.neuint.2016.10.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 09/12/2016] [Accepted: 10/31/2016] [Indexed: 11/22/2022]
Abstract
Microglia in the axotomized adult rat facial nucleus (axoFN) have been shown to highly express a glutamate transporter (GLT-1). The microglia appear to serve as glutamate (Glu) scavengers in the axoFN. However, there is no evidence that the microglia actually have the ability to uptake Glu and convert it to Gln. In this study, we investigated whether axoFN-derived microglia (axoFN-microglia) can uptake Glu and metabolize it to Gln. Microglia obtained by explant culture of axoFN on poly(N-isopropylacrylamide)-grafted dishes were non-invasively sub-cultured onto dishes or wells. Immunoblotting and Glu-uptake experiments revealed that the axoFN-microglia uptake 14C-Glu mainly by GLT-1 activity. Immunoblotting and immunocytochemical methods clarified that axoFN-microglia express the Gln synthetase (GS) protein in the same manner as newborn rat brain-derived primary microglia (NRB-microglia). Biochemical analysis demonstrated that the specific activity of GS of axoFN-microglia is similar to that of NRB-microglia, suggesting that these microglia play equivalent roles in the metabolic conversion of Glu to Gln. Nuclear magnetic resonance analysis clarified that NRB-microglia metabolize [13C]Glu to [13C]Gln depending on the incubation time, inferring the similar potential of axoFN-microglia. Taken together, these results demonstrate that axoFN-microglia express functional GLT-1 and GS proteins, and are strongly suggested to serve as Glu scavengers in vivo.
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20
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Verma AK, Ghosh S, Pradhan S, Basu A. Microglial activation induces neuronal death in Chandipura virus infection. Sci Rep 2016; 6:22544. [PMID: 26931456 PMCID: PMC4773833 DOI: 10.1038/srep22544] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 02/15/2016] [Indexed: 12/22/2022] Open
Abstract
Neurotropic viruses induce neurodegeneration either directly by activating host death domains or indirectly through host immune response pathways. Chandipura Virus (CHPV) belonging to family Rhabdoviridae is ranked among the emerging pathogens of the Indian subcontinent. Previously we have reported that CHPV induces neurodegeneration albeit the root cause of this degeneration is still an open question. In this study we explored the role of microglia following CHPV infection. Phenotypic analysis of microglia through lectin and Iba-1 staining indicated cells were in an activated state post CHPV infection in cortical region of the infected mouse brain. Cytokine Bead Array (CBA) analysis revealed comparatively higher cytokine and chemokine levels in the same region. Increased level of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), Nitric Oxide (NO) and Reactive Oxygen species (ROS) in CHPV infected mouse brain indicated a strong inflammatory response to CHPV infection. Hence it was hypothesized through our analyses that this inflammatory response may stimulate the neuronal death following CHPV infection. In order to validate our hypothesis supernatant from CHPV infected microglial culture was used to infect neuronal cell line and primary neurons. This study confirmed the bystander killing of neurons due to activation of microglia post CHPV infection.
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Affiliation(s)
| | - Sourish Ghosh
- National Brain Research Centre, Manesar, Haryana-122051, India
| | | | - Anirban Basu
- National Brain Research Centre, Manesar, Haryana-122051, India
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21
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Choi J, Stradmann-Bellinghausen B, Yakubov E, Savaskan NE, Régnier-Vigouroux A. Glioblastoma cells induce differential glutamatergic gene expressions in human tumor-associated microglia/macrophages and monocyte-derived macrophages. Cancer Biol Ther 2015; 16:1205-13. [PMID: 26047211 PMCID: PMC4623498 DOI: 10.1080/15384047.2015.1056406] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Glioblastoma cells produce and release high amounts of glutamate into the extracellular milieu and subsequently can trigger seizure in patients. Tumor-associated microglia/macrophages (TAMs), consisting of both parenchymal microglia and monocytes-derived macrophages (MDMs) recruited from the blood, are known to populate up to 1/3 of the glioblastoma tumor environment and exhibit an alternative, tumor-promoting and supporting phenotype. However, it is unknown how TAMs respond to the excess extracellular glutamate in the glioblastoma microenvironment. We investigated the expressions of genes related to glutamate transport and metabolism in human TAMs freshly isolated from glioblastoma resections. Quantitative real-time PCR analysis showed (i) significant increases in the expressions of GRIA2 (GluA2 or AMPA receptor 2), SLC1A2 (EAAT2), SLC1A3 (EAAT1), (ii) a near-significant decrease in the expression of SLC7A11 (cystine-glutamate antiporter xCT) and (iii) a remarkable increase in GLUL expression (glutamine synthetase) in these cells compared to adult primary human microglia. TAMs co-cultured with glioblastoma cells also exhibited a similar glutamatergic profile as freshly isolated TAMs except for a slight increase in SLC7A11 expression. We next analyzed these genes expressions in cultured human MDMs derived from peripheral blood monocytes for comparison. In contrast, MDMs co-cultured with glioblastoma cells compared to MDMs co-cultured with normal astrocytes exhibited decreased expressions in the tested genes except for GLUL. This is the first study to demonstrate transcriptional changes in glutamatergic signaling of TAMs in a glioblastoma microenvironment, and the findings here suggest that TAMs and MDMs might potentially elicit different cellular responses in the presence of excess extracellular glutamate.
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Key Words
- GS, glutamine synthetase
- HBSS, Hanks' Balance Salts Solution
- IL-10, interleukin-10
- MACS, magnetic-activated cell sorting
- MDMs, monocytes-derived macrophages
- MRC1, mannose receptor
- NHA, normal human astrocytes
- TAMs, Tumor-associated microglia/macrophages
- VEGF, vascular endothelial growth factor
- glioblastoma
- glutamate
- monocyte-derived macrophages
- qRT-PCR, quantitative real-time PCR
- tumor-associated microglia/macrophages
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Affiliation(s)
- Judy Choi
- a Johannes Gutenberg University of Mainz; Mainz, Germany
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22
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Mayhew J, Beart PM, Walker FR. Astrocyte and microglial control of glutamatergic signalling: a primer on understanding the disruptive role of chronic stress. J Neuroendocrinol 2015; 27:498-506. [PMID: 25737228 DOI: 10.1111/jne.12273] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Revised: 02/23/2015] [Accepted: 02/27/2015] [Indexed: 01/23/2023]
Abstract
It is now well established that chronic stress can induce significant structural remodelling of astrocytes and microglia. Until recently, however, the full significance of these morphological disturbances has remained unclear. Clues to the significance of astroglial re-organisation following stress are beginning to emerge from a compelling literature describing how astrocytes contribute to glutamatergic neurotransmission. The present review briefly summarises these two fields of research, identifies points of overlap and, in doing so, pin-points future research directions for stress neurobiology. Ultimately, understanding how chronic stress can disrupt the interactions of astrocytes and microglia with neurones has the potential in the future to improve the development of therapeutics designed to treat stress-related illnesses such as depression.
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Affiliation(s)
- J Mayhew
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
- Centre for Translational Neuroscience and Mental Health Research, University of Newcastle, Callaghan, NSW, Australia
- Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - P M Beart
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Vic., Australia
| | - F R Walker
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
- Centre for Translational Neuroscience and Mental Health Research, University of Newcastle, Callaghan, NSW, Australia
- Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
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Astroglia-Microglia Cross Talk during Neurodegeneration in the Rat Hippocampus. BIOMED RESEARCH INTERNATIONAL 2015; 2015:102419. [PMID: 25977914 PMCID: PMC4419226 DOI: 10.1155/2015/102419] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Revised: 01/16/2015] [Accepted: 03/09/2015] [Indexed: 01/30/2023]
Abstract
Brain injury triggers a progressive inflammatory response supported by a dynamic astroglia-microglia interplay. We investigated the progressive chronic features of the astroglia-microglia cross talk in the perspective of neuronal effects in a rat model of hippocampal excitotoxic injury. N-Methyl-D-aspartate (NMDA) injection triggered a process characterized within 38 days by atrophy, neuronal loss, and fast astroglia-mediated S100B increase. Microglia reaction varied with the lesion progression. It presented a peak of tumor necrosis factor-α (TNF-α) secretion at one day after the lesion, and a transient YM1 secretion within the first three days. Microglial glucocorticoid receptor expression increased up to day 5, before returning progressively to sham values. To further investigate the astroglia role in the microglia reaction, we performed concomitant transient astroglia ablation with L-α-aminoadipate and NMDA-induced lesion. We observed a striking maintenance of neuronal death associated with enhanced microglial reaction and proliferation, increased YM1 concentration, and decreased TNF-α secretion and glucocorticoid receptor expression. S100B reactivity only increased after astroglia recovery. Our results argue for an initial neuroprotective microglial reaction, with a direct astroglial control of the microglial cytotoxic response. We propose the recovery of the astroglia-microglia cross talk as a tissue priority conducted to ensure a proper cellular coordination that retails brain damage.
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24
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Nakajima K, Kanamatsu T, Takezawa Y, Kohsaka S. Up-regulation of glutamine synthesis in microglia activated with endotoxin. Neurosci Lett 2015; 591:99-104. [DOI: 10.1016/j.neulet.2015.02.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Revised: 01/31/2015] [Accepted: 02/10/2015] [Indexed: 11/24/2022]
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25
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Palmieri EM, Spera I, Menga A, Infantino V, Iacobazzi V, Castegna A. Glutamine synthetase desensitizes differentiated adipocytes to proinflammatory stimuli by raising intracellular glutamine levels. FEBS Lett 2014; 588:4807-14. [PMID: 25451225 DOI: 10.1016/j.febslet.2014.11.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 10/09/2014] [Accepted: 11/11/2014] [Indexed: 01/16/2023]
Abstract
The role of glutamine synthetase (GS) during adipocyte differentiation is unclear. Here, we assess the impact of GS on the adipocytic response to a proinflammatory challenge at different differentiation stages. GS expression at the late stages of differentiation desensitized mature adipocytes to bacterial lipopolysaccharide (LPS) by increasing intracellular glutamine levels. Furthermore, LPS-activated mature adipocytes were unable to produce inflammatory mediators; LPS sensitivity was rescued following GS inhibition and the associated drop in intracellular glutamine levels. The ability of adipocytes to differentially respond to LPS during differentiation negatively correlates to GS expression and intracellular glutamine levels. Hence, modulation of intracellular glutamine levels by GS expression represents an endogenous mechanism through which mature adipocytes control the inflammatory response.
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Affiliation(s)
- Erika Mariana Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Iolanda Spera
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Alessio Menga
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | | | - Vito Iacobazzi
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy; CNR Institute of Biomembranes and Bioenergetics, Bari, Italy
| | - Alessandra Castegna
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy.
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26
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Abstract
The multifunctional properties of astrocytes signify their importance in brain physiology and neurological function. In addition to defining the brain architecture, astrocytes are primary elements of brain ion, pH and neurotransmitter homoeostasis. GS (glutamine synthetase), which catalyses the ATP-dependent condensation of ammonia and glutamate to form glutamine, is an enzyme particularly found in astrocytes. GS plays a pivotal role in glutamate and glutamine homoeostasis, orchestrating astrocyte glutamate uptake/release and the glutamate-glutamine cycle. Furthermore, astrocytes bear the brunt of clearing ammonia in the brain, preventing neurotoxicity. The present review depicts the central function of astrocytes, concentrating on the importance of GS in glutamate/glutamine metabolism and ammonia detoxification in health and disease.
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Bell-Temin H, Zhang P, Chaput D, King MA, You M, Liu B, Stevens SM. Quantitative Proteomic Characterization of Ethanol-Responsive Pathways in Rat Microglial Cells. J Proteome Res 2013; 12:2067-77. [DOI: 10.1021/pr301038f] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Harris Bell-Temin
- Department
of Cell Biology,
Microbiology, and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620,
United States
| | | | - Dale Chaput
- Department
of Cell Biology,
Microbiology, and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620,
United States
| | - Michael A. King
- Department of Veterans Affairs Medical Center, 1601 SW Archer Road, Gainesville,
Florida 32608, United States
| | - Min You
- Department of Molecular Pharmacology
and Physiology, University of South Florida, 12901 Bruce B. Downs Boulevard, Tampa, Florida 33612, United States
| | | | - Stanley M. Stevens
- Department
of Cell Biology,
Microbiology, and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620,
United States
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Venugopal AK, Ghantasala SSK, Selvan LDN, Mahadevan A, Renuse S, Kumar P, Pawar H, Sahasrabhuddhe NA, Suja MS, Ramachandra YL, Prasad TSK, Madhusudhana SN, HC H, Chaerkady R, Satishchandra P, Pandey A, Shankar SK. Quantitative proteomics for identifying biomarkers for Rabies. Clin Proteomics 2013; 10:3. [PMID: 23521751 PMCID: PMC3660221 DOI: 10.1186/1559-0275-10-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 03/14/2013] [Indexed: 12/25/2022] Open
Abstract
INTRODUCTION Rabies is a fatal acute viral disease of the central nervous system, which is a serious public health problem in Asian and African countries. Based on the clinical presentation, rabies can be classified into encephalitic (furious) or paralytic (numb) rabies. Early diagnosis of this disease is particularly important as rabies is invariably fatal if adequate post exposure prophylaxis is not administered immediately following the bite. METHODS In this study, we carried out a quantitative proteomic analysis of the human brain tissue from cases of encephalitic and paralytic rabies along with normal human brain tissues using an 8-plex isobaric tags for relative and absolute quantification (iTRAQ) strategy. RESULTS AND CONCLUSION We identified 402 proteins, of which a number of proteins were differentially expressed between encephalitic and paralytic rabies, including several novel proteins. The differentially expressed molecules included karyopherin alpha 4 (KPNA4), which was overexpressed only in paralytic rabies, calcium calmodulin dependent kinase 2 alpha (CAMK2A), which was upregulated in paralytic rabies group and glutamate ammonia ligase (GLUL), which was overexpressed in paralytic as well as encephalitic rabies. We validated two of the upregulated molecules, GLUL and CAMK2A, by dot blot assays and further validated CAMK2A by immunohistochemistry. These molecules need to be further investigated in body fluids such as cerebrospinal fluid in a larger cohort of rabies cases to determine their potential use as antemortem diagnostic biomarkers in rabies. This is the first study to systematically profile clinical subtypes of human rabies using an iTRAQ quantitative proteomics approach.
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Affiliation(s)
- Abhilash K Venugopal
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
- Department of Biotechnology, Kuvempu University, Shimoga, 577451, India
| | - S Sameer Kumar Ghantasala
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
- Department of Biotechnology, Kuvempu University, Shimoga, 577451, India
| | - Lakshmi Dhevi N Selvan
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, 690525, India
| | - Anita Mahadevan
- Department of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bangalore, 560029, India
| | - Santosh Renuse
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, 690525, India
| | - Praveen Kumar
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
| | - Harsh Pawar
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
- Rajiv Gandhi University of Health Sciences, Bangalore, 560041, India
| | - Nandini A Sahasrabhuddhe
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
- Manipal University, Madhav Nagar, Manipal, Karnataka, 576104, India
| | - Mooriyath S Suja
- Department of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bangalore, 560029, India
| | | | - Thottethodi S Keshava Prasad
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, 690525, India
- Manipal University, Madhav Nagar, Manipal, Karnataka, 576104, India
- Bioinformatics Centre, School of Life Sciences, Pondicherry University, Pondicherry, 605014, India
| | - Shampur N Madhusudhana
- Department of Neurovirology, National Institute of Mental Health and Neuro Sciences, Bangalore, 560029, India
| | - Harsha HC
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
| | - Raghothama Chaerkady
- Institute of Bioinformatics, International Technology Park, Bangalore, 560066, India
| | | | - Akhilesh Pandey
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University, 733 N. Broadway, BRB 527, Baltimore, MD, 21205, USA
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Susarla K Shankar
- Department of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bangalore, 560029, India
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Liu C, Wu W, Zhang B, Xiang J, Zou J. Temporospatial expression and cellular localization of glutamine synthetase following traumatic spinal cord injury in adult rats. Mol Med Rep 2013; 7:1431-6. [PMID: 23525248 DOI: 10.3892/mmr.2013.1383] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 03/13/2013] [Indexed: 11/06/2022] Open
Abstract
Glutamine synthetase (GS) is an enzyme involved in an endogenous mechanism of protection against glutamate neurotoxicity and is important in the regulation of astrocyte migration. To date, limited information is available concerning the expression of GS in normal spinal cords and following injury. In the present study, GS expression was identified in astrocytes, oligodendrocytes and microglia in normal rat spinal cords. Following traumatic spinal cord injury (SCI), the glutamate concentration increased rapidly at 1 h and returned to baseline rapidly. However, the GS activity and protein levels were found to decrease at 4 h and then increase gradually from day 3 following SCI. The quantification of astrocytes, oligodendrocytes and activated microglia/macrophages, as well as immunohistochemistry staining of day 7 post‑injured spinal cords, indicated that the astrocytes and microglia/macrophages contributed to the increase in GS. Collectively, the results provided evidence for the temporospatial expression and location of GS following SCI and suggested that the changes in GS levels may contribute to glutamate neurotoxicity and glial cell response following SCI.
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Affiliation(s)
- Chunxing Liu
- Department of Clinical Testing, Huadong Sanitarium, Wuxi, Jiangsu 214065, PR China
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30
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Glutamine in the pathogenesis of acute hepatic encephalopathy. Neurochem Int 2012; 61:575-80. [DOI: 10.1016/j.neuint.2012.01.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 01/11/2012] [Accepted: 01/12/2012] [Indexed: 01/28/2023]
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Hauser KF, Fitting S, Dever SM, Podhaizer EM, Knapp PE. Opiate drug use and the pathophysiology of neuroAIDS. Curr HIV Res 2012; 10:435-52. [PMID: 22591368 PMCID: PMC3431547 DOI: 10.2174/157016212802138779] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 01/12/2012] [Accepted: 01/14/2012] [Indexed: 11/22/2022]
Abstract
Opiate abuse and HIV-1 have been described as interrelated epidemics, and even in the advent of combined anti-retroviral therapy, the additional abuse of opiates appears to result in greater neurologic and cognitive deficits. The central nervous system (CNS) is particularly vulnerable to interactive opiate-HIV-1 effects, in part because of the unique responses of microglia and astroglia. Although neurons are principally responsible for behavior and cognition, HIV-1 infection and replication in the brain is largely limited to microglia, while astroglia and perhaps glial progenitors can be latently infected. Thus, neuronal dysfunction and injury result from cellular and viral toxins originating from HIV-1 infected/exposed glia. Importantly, subsets of glial cells including oligodendrocytes, as well as neurons, express µ-opioid receptors and therefore can be direct targets for heroin and morphine (the major metabolite of heroin in the CNS), which preferentially activate µ-opioid receptors. This review highlights findings that neuroAIDS is a glially driven disease, and that opiate abuse may act at multiple glial-cell types to further compromise neuron function and survival. The ongoing, reactive cross-talk between opiate drug and HIV-1 co-exposed microglia and astroglia appears to exacerbate critical proinflammatory and excitotoxic events leading to neuron dysfunction, injury, and potentially death. Opiates enhance synaptodendritic damage and a loss of synaptic connectivity, which is viewed as the substrate of cognitive deficits. We especially emphasize that opioid signaling and interactions with HIV-1 are contextual, differing among cell types, and even within subsets of the same cell type. For example, astroglia even within a single brain region are heterogeneous in their expression of µ-, δ-, and κ-opioid receptors, as well as CXCR4 and CCR5, and Toll-like receptors. Thus, defining the distinct targets engaged by opiates in each cell type, and among brain regions, is critical to an understanding of how opiate abuse exacerbates neuroAIDS.
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Affiliation(s)
- Kurt F Hauser
- Department of Pharmacology and Toxicology, 1217 East Marshall Street, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, USA.
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Persson M, Rönnbäck L. Microglial self-defence mediated through GLT-1 and glutathione. Amino Acids 2011; 42:207-19. [PMID: 21373770 DOI: 10.1007/s00726-011-0865-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 11/27/2022]
Abstract
Glutamate is stored in synaptic vesicles in presynaptic neurons. It is released into the synaptic cleft to provide signalling to postsynaptic neurons. Normally, the astroglial glutamate transporters GLT-1 and GLAST take up glutamate to mediate a high signal-to-noise ratio in the synaptic signalling, and also to prevent excitotoxic effects by glutamate. In astrocytes, glutamate is transformed into glutamine, which is safely transported back to neurons. However, in pathological conditions, such as an ischemia or virus infection, astroglial transporters are down-regulated which could lead to excitotoxicity. Lately, it was shown that even microglia can express glutamate transporters during pathological events. Microglia have two systems for glutamate transport: GLT-1 for transport into the cells and the x (c) (-) system for transport out of the cells. We here review results from our work and others, which demonstrate that microglia in culture express GLT-1, but not GLAST, and transport glutamate from the extracellular space. We also show that TNF-α can induce increased microglial GLT-1 expression, possibly associating the expression with inflammatory systems. Furthermore, glutamate taken up through GLT-1 may be used for direct incorporation into glutathione and to fuel the intracellular glutamate pool to allow cystine uptake through the x (c) (-) system. This can lead to a defence against oxidative stress and have an antiviral function.
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Affiliation(s)
- Mikael Persson
- Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Per Dubbsgatan 14, 1tr, 41345, Gothenburg, Sweden
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Gras G, Samah B, Hubert A, Léone C, Porcheray F, Rimaniol AC. EAAT expression by macrophages and microglia: still more questions than answers. Amino Acids 2011; 42:221-9. [PMID: 21373769 DOI: 10.1007/s00726-011-0866-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 01/07/2023]
Abstract
Glutamate is the main excitatory amino acid, but its presence in the extracellular milieu has deleterious consequences. It may induce excitotoxicity and also compete with cystine for the use of the cystine-glutamate exchanger, blocking glutathione neosynthesis and inducing an oxidative stress-induced cell death. Both mechanisms are critical in the brain where up to 20% of total body oxygen consumption occurs. In normal conditions, the astrocytes ensure that extracellular concentration of glutamate is kept in the micromolar range, thanks to their coexpression of high-affinity glutamate transporters (EAATs) and glutamine synthetase (GS). Their protective function is nevertheless sensitive to situations such as oxidative stress or inflammatory processes. On the other hand, macrophages and microglia do not express EAATs and GS in physiological conditions and are the principal effector cells of brain inflammation. Since the late 1990s, a number of studies have now shown that both microglia and macrophages display inducible EAAT and GS expression, but the precise significance of this still remains poorly understood. Brain macrophages and microglia are sister cells but yet display differences. Both are highly sensitive to their microenvironment and can perform a variety of functions that may oppose each other. However, in the very particular environment of the healthy brain, they are maintained in a repressed state. The aim of this review is to present the current state of knowledge on brain macrophages and microglial cells activation, in order to help clarify their role in the regulation of glutamate under pathological conditions as well as its outcome.
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Affiliation(s)
- Gabriel Gras
- Division of Immuno-Virology, Institute of Emerging Diseases and Innovative Therapies, UMR E1 CEA DSV/IMETI/SIV and University Paris South-Paris 11, 18, route du Panorama, 92265, Fontenay-aux Roses, France.
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Melone M, Bellesi M, Ducati A, Iacoangeli M, Conti F. Cellular and Synaptic Localization of EAAT2a in Human Cerebral Cortex. Front Neuroanat 2011; 4:151. [PMID: 21258616 PMCID: PMC3024003 DOI: 10.3389/fnana.2010.00151] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 12/24/2010] [Indexed: 11/23/2022] Open
Abstract
We used light and electron microscopic immunocytochemical techniques to analyze the distribution, cellular and synaptic localization of EAAT2, the main glutamate transporter, in normal human neocortex. EAAT2a-immunoreactivity (ir) was in all layers and consisted of small neuropilar puncta and rare cells. In white matter EAAT2a+ cells were numerous. Electron microscopic studies showed that in gray matter ∼77% of immunoreactive elements were astrocytic processes, ∼14% axon terminals, ∼2.8% dendrites, whereas ∼5% were unidentifiable. In white matter, ∼81% were astrocytic processes, ∼17% were myelinated axons, and ∼2.0% were unidentified. EAAT2a-ir was never in microglial cells and oligodendrocytes. Pre-embedding electron microscopy showed that ∼67% of EAAT2a expressed at (or in the vicinity of) asymmetric synapses was in astrocytes, ∼17% in axon terminals, while ∼13% was both in astrocytes and in axons. Post-embedding electron microscopy studies showed that in astrocytic processes contacting asymmetric synapses and in axon terminals, gold particle density was ∼25.1 and ∼2.8 particles/μm2, respectively, and was concentrated in a membrane region extending for ∼300 nm from the active zone edge. Besides representing the first detailed description of EAAT2a in human cerebral cortex, these findings may contribute to understanding its role in the pathophysiology of neuropsychiatric diseases.
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Affiliation(s)
- Marcello Melone
- Department of Neuroscience, Section of Physiology, Università Politecnica delle Marche Ancona, Italy
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Helluy S, Thomas F. Parasitic manipulation and neuroinflammation: Evidence from the system Microphallus papillorobustus (Trematoda) - Gammarus (Crustacea). Parasit Vectors 2010; 3:38. [PMID: 20398322 PMCID: PMC2874546 DOI: 10.1186/1756-3305-3-38] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2010] [Accepted: 04/15/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Neuropathological consequences of neuroinflammatory processes have been implicated in a wide range of diseases affecting the central nervous system (CNS). Glial cells, the resident immune cells of the CNS, respond to tissue injury by releasing proinflammatory cytokines and free radicals such as nitric oxide. We explored the possibility that neuroimmune responses are involved in parasitic manipulation of host behavior in a trematode-crustacean association. The cerebral larva of the flatworm Microphallus papillorobustus alters responses to environmental stimuli - and thus reflex pathways - in the crustacean Gammarus insensibilis, in a way that enhances predation of the crustacean by birds, definitive hosts of the parasite. RESULTS Immunocytochemical experiments followed by confocal microscopy were performed to study the distribution of glutamine synthetase, a glial cell marker, and nitric oxide synthase in the brain of gammarids. Astrocyte-like glia and their processes were abundant at the surface of the parasites while levels of nitric oxide synthase were elevated at the host-parasite interface in the brain of gammarids harboring mature cerebral larvae and demonstrating altered behavior. CONCLUSION Taken together these results lend support to the neuroinflammation hypothesis whereby a chronic CNS specific immune response induced by the parasite plays a role in the disruption of neuromodulation, neuronal integrity, and behavior in infected hosts.
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Affiliation(s)
- Simone Helluy
- Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA.
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Kawashima H, Oguchi M, Ioi H, Amaha M, Yamanaka G, Kashiwagi Y, Takekuma K, Yamazaki Y, Hoshika A, Watanabe Y. PRIMARY BIOMARKERS IN CEREBRAL SPINAL FLUID OBTAINED FROM PATIENTS WITH INFLUENZA-ASSOCIATED ENCEPHALOPATHY ANALYZED BY METABOLOMICS. Int J Neurosci 2009; 116:927-36. [PMID: 16861158 DOI: 10.1080/00207450600550519] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In order to search for the specific biomarkers of patients with influenza-associated encephalopathy this article analyzed all metabolites in cerebrospinal fluid (CSF) by using metabolome analysis. In all metabolites, the peaks of two molecular weights, 246.0092 and 204.0611, were significantly higher than those in other diseases including influenza without convulsion (p < .05). The peak of a molecular weight 228.0247 in all of the patients except one was less than that in other patients. These results indicate that the new metabolites detected in CSF would be primary markers for the diagnosis of influenza-associated encephalopathy.
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Beschorner R, Pantazis G, Jeibmann A, Boy J, Meyermann R, Mittelbronn M, Schittenhelm J. Expression of EAAT-1 distinguishes choroid plexus tumors from normal and reactive choroid plexus epithelium. Acta Neuropathol 2009; 117:667-75. [PMID: 19283393 DOI: 10.1007/s00401-009-0519-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Revised: 03/05/2009] [Accepted: 03/05/2009] [Indexed: 12/26/2022]
Abstract
Microscopic distinction of normal choroid plexus (CP) from choroid plexus tumors (CPT) may be difficult, especially in small samples of well-differentiated CP papillomas. So far, there are no established markers that reliably distinguish normal and neoplastic CP epithelium. Recently, a correlation between expression/function of glial glutamate transporters EAAT-1 (GLAST) and EAAT-2 (Glt-1) and tumor proliferation has been reported. Furthermore, we previously found that CPTs frequently express EAAT-1, but not EAAT-2. We now compared expression of EAAT-1, EAAT-2 and GFAP in non-neoplastic CP (n = 68) and CPT (n = 79) by immunohistochemistry. Tissue of normal CP was obtained from 50 autopsy cases (20 normal and 30 pathologic brains) and 18 neurosurgical specimens that included 17 fetal, 21 pediatric and 30 adult cases. In non-neoplastic postnatal CP (n = 51), focal expression of EAAT-1 was found in only two pediatric cases (4%). In CPT, expression of EAAT-1 was found in 64 of 79 (81%) tumor samples and was significantly age-dependent (P < 0.0001). Hence, EAAT-1 expression distinguishes neoplastic from normal CP, both in children (P = 0.0032) and in adults (P < 0.0001). Immunostaining for EAAT-2 in selected samples from cases of different ages showed that normal CP (n = 15) or CPT (n = 16) lacked EAAT-2 expression. GFAP expression was found in 3 of 32 (10%) normal CP and in 28 of 73 (38%) tumor samples. In conclusion, in contrast to neoplastic CP samples, expression of EAAT-1 is exceptionally rare in non-neoplastic CP. Thus, EAAT-1 is superior to GFAP as a helpful diagnostic tool in CP samples.
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Persson M, Pekna M, Hansson E, Rönnbäck L. The complement-derived anaphylatoxin C5a increases microglial GLT-1 expression and glutamate uptake in a TNF-α-independent manner. Eur J Neurosci 2009; 29:267-74. [DOI: 10.1111/j.1460-9568.2008.06575.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Impaired astrocytes and diffuse activation of microglia in the cerebral cortex in simian immunodeficiency virus-infected Macaques without simian immunodeficiency virus encephalitis. J Neuropathol Exp Neurol 2008; 67:600-11. [PMID: 18520778 DOI: 10.1097/nen.0b013e3181772ce0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Various types of neuronal damage have been reported in acquired immunodeficiency syndrome (AIDS) dementia. We previously demonstrated that inflammation and cortical damage occur independently according to viral tropism in a simian immunodeficiency virus (SIV)-infected macaque model of AIDS dementia. To elucidate the pathogenesis of cortical degeneration, we examined the frontal cortex of SIV-infected macaques and found apoptosis and decreased expression of the excitatory amino acid transporter 2 in astrocytes and diffuse activation of microglia in association with limited neuronal damage. Some activated microglia also expressed excitatory amino acid transporter 2 but not proinflammatory cytokines. No inflammatory changes were seen in the cortex or the white matter, and SIV-infected cells were not detected in or around cortical lesions either by immunohistochemistry or by the polymerase chain reaction detection of SIV genomes of extracted DNA from microdissected tissue samples. These results indicate that an astrocytic abnormality and a compensatory activation of microglia might provide a protective effect against neuronal degeneration in the frontal cortex of SIV-infected macaques without SIV encephalitis.
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Garg SK, Banerjee R, Kipnis J. Neuroprotective immunity: T cell-derived glutamate endows astrocytes with a neuroprotective phenotype. THE JOURNAL OF IMMUNOLOGY 2008; 180:3866-73. [PMID: 18322194 DOI: 10.4049/jimmunol.180.6.3866] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A well-controlled T cell response to CNS injury may result in increased neuronal survival. However, the precise mechanism of T cell-induced neuroprotection is unknown. In this study, we report the unexpected finding that during culture of T cells, high levels of glutamate accumulate, which are efficiently cleared if T cells are cocultured with astrocytes. The T cell-derived glutamate elicits in turn, the release of neuroprotective thiols (cysteine, glutathione, and cysteinyl-glycine) and lactate from astrocytes. Media obtained from astrocytes conditioned in the presence of T cells reduce neuronal apoptosis induced by oxidative stress in primary neuronal cultures from 48 +/- 14 to 9 +/- 4% (p < 0.001). Inhibition of glutamate-dependent signaling during astrocyte-T cell cocultivation by a glutamate uptake inhibitor, l-aspartic acid beta-hydroxamate, abolishes this neuroprotective effect. The ability of astrocytes to clear extracellular glutamate is impaired under conditions of oxidative stress. We demonstrate that T cells, via secreted cytokines, restore glutamate clearance capacity of astrocytes under oxidative conditions. Furthermore, under normoxic conditions, glutamate-buffering capacity of astrocytes is increased upon cocultivation with T cells. It is known that, following CNS injury, astrocytes can respond with beneficial or destructive effects on neurons. However, the context and signaling mechanisms for this dual astrocytic response are unknown. Our results implicate T cells as potential determinants of the context that elicits a protective role for astrocytes in the damaged CNS.
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Affiliation(s)
- Sanjay K Garg
- Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA
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Nitrated alpha-synuclein and microglial neuroregulatory activities. J Neuroimmune Pharmacol 2008; 3:59-74. [PMID: 18202920 DOI: 10.1007/s11481-008-9100-z] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Accepted: 01/02/2008] [Indexed: 10/22/2022]
Abstract
Microglial neuroinflammatory responses affect the onset and progression of Parkinson's disease (PD). We posit that such neuroinflammatory responses are, in part, mediated by microglial interactions with nitrated and aggregated alpha-synuclein (alpha-syn) released from Lewy bodies as a consequence of dopaminergic neuronal degeneration. As disease progresses, secretions from alpha-syn-activated microglia can engage neighboring glial cells in a cycle of autocrine and paracrine amplification of neurotoxic immune products. Such pathogenic processes affect the balance between a microglial neurotrophic and neurotoxic signature. We now report that microglia secrete both neurotoxic and neuroprotective factors after exposure to nitrated alpha-syn (N-alpha-syn). Proteomic (surface enhanced laser desorption-time of flight, 1D sodium dodecyl sulfate electrophoresis, and liquid chromatography-tandem mass spectrometry) and limited metabolomic profiling demonstrated that N-alpha-syn-activated microglia secrete inflammatory, regulatory, redox-active, enzymatic, and cytoskeletal proteins. Increased extracellular glutamate and cysteine and diminished intracellular glutathione and secreted exosomal proteins were also demonstrated. Increased redox-active proteins suggest regulatory microglial responses to N-alpha-syn. These were linked to discontinuous cystatin expression, cathepsin activity, and nuclear factor-kappa B activation. Inhibition of cathepsin B attenuated, in part, N-alpha-syn microglial neurotoxicity. These data support multifaceted microglia functions in PD-associated neurodegeneration.
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Meisner F, Neuen-Jacob E, Sopper S, Schmidt M, Schlammes S, Scheller C, Vosswinkel D, Ter Meulen V, Riederer P, Koutsilieri E. Disruption of excitatory amino acid transporters in brains of SIV-infected rhesus macaques is associated with microglia activation. J Neurochem 2007; 104:202-9. [PMID: 17986224 DOI: 10.1111/j.1471-4159.2007.05007.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Glutamate-mediated neurodysfunction in human immunodeficiency virus (HIV) infection has been primarily suggested by in vitro studies. The regulation of glutamatergic neurotransmission in inflammation is a complex interaction between activation of immune mediators and adaptive changes in the functional elements of the glutamatergic synapse. We have used simian immunodeficiency virus (SIV)-infected macaques to answer the questions (i) whether perturbation of glutamate neurotransmission is evident during progression of immunodeficiency disease and (ii) what are the mechanisms underlying this impairment. Disease progression in SIV-infected macaques both in the periphery and in the brain was documented by clinical and general pathological examination, plasma and brain viral RNA load, T-cell analysis and brain histopathology. We report for the first time, disruption of excitatory amino acid transporters (EAATs), the cardinal glutamate clearing system, during SIV infection and a dramatic loss of EAATs associated with development of rapid acquired immunodeficiency syndrome (AIDS). EAATs impairment was correlated with activation status of microglia. Our data support the glutamate hypothesis for the development of HIV dementia and suggest that the pathogenetic mechanism for the neurodysfunction is the impairment of glutamate clearing which occurs in the stage of AIDS and which is associated with activated microglia.
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Affiliation(s)
- Falko Meisner
- Institute of Virology and Immunobiology, University of Würzburg, Würzburg, Germany
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Newcombe J, Uddin A, Dove R, Patel B, Turski L, Nishizawa Y, Smith T. Glutamate receptor expression in multiple sclerosis lesions. Brain Pathol 2007; 18:52-61. [PMID: 17924980 DOI: 10.1111/j.1750-3639.2007.00101.x] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Blockade of receptors for the excitatory neurotransmitter glutamate ameliorates neurological clinical signs in models of the CNS inflammatory demyelinating disease multiple sclerosis (MS). To investigate whether glutamate excitoxicity may play a role in MS pathogenesis, the cellular localization of glutamate and its receptors, transporters and enzymes was examined. Expression of glutamate receptor (GluR) 1, a Ca(++)-permeable ionotropic AMPA receptor subunit, was up-regulated on oligodendrocytes in active MS lesion borders, but Ca(++)-impermeable AMPA GluR2 subunit levels were not increased. Reactive astrocytes in active plaques expressed AMPA GluR3 and metabotropic mGluR1, 2/3 and 5 receptors and the GLT-1 transporter, and a subpopulation was immunostained with glutamate antibodies. Activated microglia and macrophages were immunopositive for GluR2, GluR4 and NMDA receptor subunit 1. Kainate receptor GluR5-7 immunostaining showed endothelial cells and dystrophic axons. Astrocyte and macrophage populations expressed glutamate metabolizing enzymes and unexpectedly the EAAC1 transporter, which may play a role in glutamate uptake in lesions. Thus, reactive astrocytes in MS white matter lesions are equipped for a protective role in sequestering and metabolizing extracellular glutamate. However, they may be unable to maintain glutamate at levels low enough to protect oligodendrocytes rendered vulnerable to excitotoxic damage because of GluR1 up-regulation.
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Affiliation(s)
- Jia Newcombe
- Department of Neuroinflammation, Institute of Neurology, University College London, London, UK.
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Peterson KE, Chesebro B. Influence of proinflammatory cytokines and chemokines on the neuropathogenesis of oncornavirus and immunosuppressive lentivirus infections. Curr Top Microbiol Immunol 2007; 303:67-95. [PMID: 16570857 DOI: 10.1007/978-3-540-33397-5_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Retroviral infection of the CNS can lead to severe debilitating neurological diseases in humans and other animals. Four general types of pathogenic effects with various retroviruses have been observed including: hemorrhage (TR1.3), spongiform encephalopathy (CasBrE, FrCasE, PVC211, NT40, Mol-ts1), demyelination with inflammatory lesions (HTLV-1, visna, CAEV), and encephalopathy with gliosis and proinflammatory chemokines and cytokines, usually with microglial giant cells and nodules [human immunodeficiencyvirus (HIV), feline immunodeficiencyvirus (FIV), simian immunodeficiency virus (SIV), Fr98]. This review focuses on this fourth group of retroviruses. In this latter group, proinflammatory cytokine and chemokine upregulation accompanies the disease process, and may influence pathogenesis by direct effects on resident CNS cells. The review first discusses the Fr98 murine polytropic virus system with particular reference to the roles of cytokines and chemokines in the pathogenic process. The Fr98 data are then compared and contrasted to the cytokine and chemokine data in the lentivirus systems, HIV, SIV, and FIV. Finally, various mechanisms are presented by which tumor necrosis factor (TNF) and several chemokines may alter the pathogenesis of retrovirus infection of the CNS.
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Affiliation(s)
- K E Peterson
- Dept. of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
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Persson M, Brantefjord M, Liljeqvist JA, Bergström T, Hansson E, Rönnbäck L. Microglial GLT-1 is upregulated in response to herpes simplex virus infection to provide an antiviral defence via glutathione. Glia 2007; 55:1449-58. [PMID: 17680651 DOI: 10.1002/glia.20560] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Herpes simplex virus (HSV) can enter the central nervous system and cause encephalitis (HSV-1) or meningitis (HSV-2). Microglia, the immunocompetent cells of the central nervous system, are potentially able to detect viral infections. Microglia have been shown to express the glutamate transporter GLT-1 during pathological events, leading to increased microglial glutamate uptake and glutathione synthesis. This study aims to address the role of GLT-1 and glutathione, a major antioxidant with antiviral properties, during HSV infections. Using neuron-enriched mixed primary cultures from rat, it was found that microglia have higher resistance to HSV infections than neurons or astrocytes after 24 h incubation with HSV. Purified microglia in culture were used to further address this. It was found that microglia were able to detect HSV and responded by releasing tumor necrosis factor-alpha (TNF-alpha) and upregulating GLT-1 after 24 h incubation with 1 PFU/cell HSV-1 or HSV-2. Furthermore, the microglial glutathione levels were not significantly diminished after 24 h. Inhibition of the microglial glutathione synthesis with 200 microM buthionine sulfoximide (BSO) led to significantly more infected cells after 24 h incubation with 1 PFU/cell HSV-1 or HSV-2. These data indicate that the higher resistance in microglia against HSV infections may be due to the expression of GLT-1, which can maintain the glutathione levels and provide a mechanism for microglial self-defense against HSV.
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Affiliation(s)
- Mikael Persson
- Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Göteborg University, Göteborg, Sweden.
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de Yebra L, Malpesa Y, Ursu G, Pugliese M, Liévens JC, Kerkerian-Le Goff L, Mahy N. Dissociation between hippocampal neuronal loss, astroglial and microglial reactivity after pharmacologically induced reverse glutamate transport. Neurochem Int 2006; 49:691-7. [PMID: 16965840 DOI: 10.1016/j.neuint.2006.06.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Revised: 05/23/2006] [Accepted: 06/12/2006] [Indexed: 11/20/2022]
Abstract
The inflammatory central nervous system response that involves activated microglia and reactive astrocytes may both heal and harm neurons, as inflammatory mediators lead to neuroprotection or excitation at one dose but to injury at a different concentration. To investigate these complex cellular interactions, L-trans-pyrrolidine-2,4-dicarboxylate (PDC), a selective substrate inhibitor of glutamate transport, was infused during 14 days in the rat hippocampus at three different rates: 5, 10 and 25 nmol/h. A microglial reaction appeared at the 5 nmol/h PDC rate in absence of astroglial reaction and neuronal loss. Microgliosis and neuronal death were observed at PDC 10 nmol/h in absence of astrogliosis and calcium precipitation, whereas all four aspects were present at the highest rate. This dissociation between neuronal loss and astroglial reactivity took place in presence of a permanent microglial reaction. These data suggest a specific response of microglia to PDC whose neuronal effects may differ with the infused dose.
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Affiliation(s)
- Lluïsa de Yebra
- Unitat de Bioquímica, IDIBAPS, Facultat de Medicina, Universitat de Barcelona, C/ Casanova 143, Barcelona E-08036, Spain
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Beart PM, O'Shea RD. Transporters for L-glutamate: an update on their molecular pharmacology and pathological involvement. Br J Pharmacol 2006; 150:5-17. [PMID: 17088867 PMCID: PMC2013845 DOI: 10.1038/sj.bjp.0706949] [Citation(s) in RCA: 299] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
L-Glutamate (Glu) is the major excitatory neurotransmitter in the mammalian CNS and five types of high-affinity Glu transporters (EAAT1-5) have been identified. The transporters EAAT1 and EAAT2 in glial cells are responsible for the majority of Glu uptake while neuronal EAATs appear to have specialized roles at particular types of synapses. Dysfunction of EAATs is specifically implicated in the pathology of neurodegenerative conditions such as amyotrophic lateral sclerosis, epilepsy, Huntington's disease, Alzheimer's disease and ischemic stroke injury, and thus treatments that can modulate EAAT function may prove beneficial in these conditions. Recent advances have been made in our understanding of the regulation of EAATs, including their trafficking, splicing and post-translational modification. This article summarises some recent developments that improve our understanding of the roles and regulation of EAATs.
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Affiliation(s)
- P M Beart
- Howard Florey Institute, The University of Melbourne, Parkville, Victoria 3800, Australia.
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Gras G, Porcheray F, Samah B, Leone C. The glutamate-glutamine cycle as an inducible, protective face of macrophage activation. J Leukoc Biol 2006; 80:1067-75. [PMID: 16912070 DOI: 10.1189/jlb.0306153] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Neuronal damage in HIV infection results mainly from chronic activation of brain tissue and involves inflammation, oxidative stress, and glutamate-related neurotoxicity. Glutamate toxicity acts via two distinct pathways: an excitotoxic one, in which glutamate receptors are hyperactivated, and an oxidative one, in which cystine uptake is inhibited, resulting in glutathione depletion, oxidative stress, and cell degeneration. A number of studies have shown that astrocytes normally take up glutamate, keeping extracellular glutamate concentration low in the brain and preventing excitotoxicity. They, in turn, provide the trophic amino acid glutamine via their expression of glutamine synthetase. These protective and trophic actions are inhibited in HIV infection, probably as a result of the effects of inflammatory mediators and viral proteins. In vitro and in vivo studies have demonstrated that activated microglia and brain macrophages (AMM) express the transporters and enzymes of the glutamate cycle. This suggests that in addition to their recognized neurotoxic properties in HIV infection, these cells exhibit some neuroprotective properties, which may partly compensate for the inhibited astrocytic function. This hypothesis might explain the discrepancy between microglial activation, which occurs early in the disease, and neuronal apoptosis and neuronal loss, which are late events. In this review, we discuss the possible neuroprotective and neurotrophic roles of AMM and their relationships with inflammation and oxidative stress.
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Affiliation(s)
- Gabriel Gras
- CEA, DSV, DRM, SNV, UMR E-01 Université Paris-Sud XI, Laboratoire de Neuro-Immuno-Virologie, F92265 Fontenay-aux Roses, France.
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Persson M, Sandberg M, Hansson E, Rönnbäck L. Microglial glutamate uptake is coupled to glutathione synthesis and glutamate release. Eur J Neurosci 2006; 24:1063-70. [PMID: 16925588 DOI: 10.1111/j.1460-9568.2006.04974.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The physiological function of microglial glutamate uptake has been debated as it is about 10% of that measured for astrocytes. This study addresses how glutamate, taken up from the extracellular space, is utilized by microglia. It was found that purified rat microglia incubated for 60 min with (3)H-glutamate had an increased intracellular accumulation of (3)H-glutamate after 12 h incubation with tumour necrosis factor alpha (TNF-alpha) but not after incubation with lipopolysaccharide (LPS). Furthermore, LPS- but not TNF-alpha-treated cells showed an increased efflux of (3)H-labelled compounds, presumably glutamate through the X(C) (-) system and treatment with LPS or TNF-alpha increased the microglial glutathione concentrations and led to an increased incorporation of (3)H-glutamate into glutathione. Depending on the stimuli, 3-6% of the total labelled contents were found in the form of glutathione and 25-35% in the form of glutamate. These results show that microglial glutamate uptake is directly coupled to glutathione synthesis and release of glutamate and/or glutamate metabolites. Additionally, the increased glutathione contents after LPS or TNF-alpha treatment were able to reduce microglial cell death after H(2)O(2) challenge, showing a potential (self)-protective function for microglial glutamate transporter expression and glutathione synthesis.
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Affiliation(s)
- Mikael Persson
- Institute of Neuroscience and Physiology, Department of Clinical Neuroscience and Rehabilitation, the Sahlgrenska Academy at Göteborg University, Guldhedsgatan 19, SE-41 45 Göteborg, Sweden.
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Berger UV, Hediger MA. Distribution of the glutamate transporters GLT-1 (SLC1A2) and GLAST (SLC1A3) in peripheral organs. ACTA ACUST UNITED AC 2006; 211:595-606. [PMID: 16868771 DOI: 10.1007/s00429-006-0109-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2006] [Indexed: 10/24/2022]
Abstract
The glutamate transporters GLT-1 and GLAST are widely expressed in astrocytes in the brain where they fulfill important functions during glutamatergic neurotransmission. The present study examines their distribution in peripheral organs using in situ hybridization (ISH) and immunocytochemistry. GLAST was found to be more widely distributed than GLT-1. GLAST was expressed primarily in epithelial cells, cells of the macrophage-lineage, lymphocytes, fat cells, interstitial cells, and salivary gland acini. GLT-1 was primarily expressed in glandular tissue, including mammary gland, lacrimal gland, and ducts and acini in salivary glands, but also by perivenous hepatocytes and follicular dendritic cells in spleen and lymph nodes. The findings demonstrate that, although expressed by the same cells in the brain, these two glutamate transporters have different distribution patterns in peripheral tissues and that they fulfill glutamate transport functions apart from glutamatergic neurotransmission in these areas.
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Affiliation(s)
- Urs V Berger
- Membrane Biology Program and Renal Division, Brigham and Women's Hospital, Boston, MA 02115, USA
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