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Kim HL, Riew TR, Park J, Lee Y, Kim IB. Correlative Light and Electron Microscopy Using Frozen Section Obtained Using Cryo-Ultramicrotomy. Int J Mol Sci 2021; 22:ijms22084273. [PMID: 33924132 PMCID: PMC8074315 DOI: 10.3390/ijms22084273] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/13/2021] [Accepted: 04/17/2021] [Indexed: 11/16/2022] Open
Abstract
Immuno-electron microscopy (Immuno-EM) is a powerful tool for identifying molecular targets with ultrastructural details in biological specimens. However, technical barriers, such as the loss of ultrastructural integrity, the decrease in antigenicity, or artifacts in the handling process, hinder the widespread use of the technique by biomedical researchers. We developed a method to overcome such challenges by combining light and electron microscopy with immunolabeling based on Tokuyasu's method. Using cryo-sectioned biological specimens, target proteins with excellent antigenicity were first immunolabeled for confocal analysis, and then the same tissue sections were further processed for electron microscopy, which provided a well-preserved ultrastructure comparable to that obtained using conventional electron microscopy. Moreover, this method does not require specifically designed correlative light and electron microscopy (CLEM) devices but rather employs conventional confocal and electron microscopes; therefore, it can be easily applied in many biomedical studies.
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Affiliation(s)
- Hong-Lim Kim
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
| | - Tae-Ryong Riew
- Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea;
| | - Jieun Park
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
| | - Youngchun Lee
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
| | - In-Beom Kim
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
- Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea;
- Catholic Neuroscience Institute, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Catholic Institute for Applied Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Correspondence: ; Tel.: +82-2-2258-7263
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2
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Gundersen V. Parkinson's Disease: Can Targeting Inflammation Be an Effective Neuroprotective Strategy? Front Neurosci 2021; 14:580311. [PMID: 33716638 PMCID: PMC7946840 DOI: 10.3389/fnins.2020.580311] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 10/20/2020] [Indexed: 12/11/2022] Open
Abstract
The reason why dopamine neurons die in Parkinson’s disease remains largely unknown. Emerging evidence points to a role for brain inflammation in neurodegeneration. Essential questions are whether brain inflammation happens sufficiently early so that interfering with this process can be expected to slow down neuronal death and whether the contribution from inflammation is large enough so that anti-inflammatory agents can be expected to work. Here I discuss data from human PD studies indicating that brain inflammation is an early event in PD. I also discuss the role of T-lymphocytes and peripheral inflammation for neurodegeneration. I critically discuss the failure of clinical trials targeting inflammation in PD.
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Affiliation(s)
- Vidar Gundersen
- Section for Movement Disorders, Department of Neurology, Oslo University Hospital, Oslo, Norway
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3
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Das R, Chinnathambi S. Microglial remodeling of actin network by Tau oligomers, via G protein-coupled purinergic receptor, P2Y12R-driven chemotaxis. Traffic 2021; 22:153-170. [PMID: 33527700 DOI: 10.1111/tra.12784] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 01/05/2021] [Accepted: 01/25/2021] [Indexed: 12/13/2022]
Abstract
Alzheimer's disease (AD) is associated with age-related neurodegeneration, synaptic deformation and chronic inflammation mediated by microglia and infiltrated macrophages in the brain. Tau oligomers can be released from damaged neurons via various mechanisms such as exosomes, neurotransmitter, membrane leakage etc. Microglia sense the extracellular Tau through several cell-surface receptors and mediate chemotaxis and phagocytosis. The purinergic receptor P2Y12R recently gained interest in neurodegeneration for neuro-glial communication and microglial chemotaxis towards the site of plaque deposition. To understand the effect of extracellular Tau oligomers in microglial migration, the P2Y12R-mediated actin remodeling, reorientation of tubulin network and rate of migration were studied in the presence of ATP. The extracellular Tau species directly interacted with P2Y12R and also induced this purinoceptor expression in microglia. Microglial P2Y12R colocalized with remodeled membrane-associated actin network as a component of migration in response to Tau oligomers. As an inducer of P2Y12R, ATP facilitated the localization of P2Y12R in lamellipodia and filopodia during accelerated microglial migration. The direct interaction of extracellular Tau oligomers with microglial P2Y12R would facilitate the signal transduction in both way, directional chemotaxis and receptor-mediated phagocytosis. These unprecedented findings emphasize that microglia can modulate the membrane-associated actin structure and incorporate P2Y12R to perceive the axis and rate of chemotaxis in Tauopathy.
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Affiliation(s)
- Rashmi Das
- Neurobiology Group, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Subashchandrabose Chinnathambi
- Neurobiology Group, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
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4
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Yegla B, Boles J, Kumar A, Foster TC. Partial microglial depletion is associated with impaired hippocampal synaptic and cognitive function in young and aged rats. Glia 2021; 69:1494-1514. [PMID: 33586813 DOI: 10.1002/glia.23975] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/25/2021] [Accepted: 01/26/2021] [Indexed: 12/11/2022]
Abstract
The role of microglia in mediating age-related changes in cognition and hippocampal synaptic function was examined by microglial depletion and replenishment using PLX3397. We observed age-related differences in microglial number and morphology, as well as increased Iba-1 expression, indicating microglial activation. PLX3397 treatment decreased microglial number, with aged rats exhibiting the lowest density. Young rats exhibited increased expression of pro-inflammatory cytokines during depletion and repopulation and maintenance of Iba-1 levels despite reduced microglial number. For aged rats, several cytokines increased with depletion and recovered during repopulation; however, aged rats did not fully recover microglial cell number or Iba-1 expression during repopulation, with a recovery comparable to young control levels rather than aged controls. Hippocampal CA3-CA1 synaptic transmission was impaired with age, and microglial depletion was associated with decreased total synaptic transmission in young and aged rats. A robust decline in N-methyl-d-aspartate-receptor-mediated synaptic transmission arose in young depleted rats specifically. Microglial replenishment normalized depletion-induced synaptic function to control levels; however, recovery of aged animals did not mirror young. Microglial depletion was associated with decreased context-object discrimination memory in both age groups, which recovered with microglial repopulation. Aged rats displayed impaired contextual and cued fear memory, and microglial replenishment did not recover their memory to the level of young. The current study indicates that cognitive function and synaptic transmission benefit from the support of aged microglia and are hindered by removal of these cells. Replenishment of microglia in aging did not ameliorate age-related cognitive impairments or senescent synaptic function.
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Affiliation(s)
- Brittney Yegla
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
| | - Jake Boles
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
| | - Ashok Kumar
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
| | - Thomas C Foster
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.,Genetics and Genomics Program, University of Florida, Gainesville, Florida, USA
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5
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Ward H, West SJ. Microglia: sculptors of neuropathic pain? ROYAL SOCIETY OPEN SCIENCE 2020; 7:200260. [PMID: 32742693 PMCID: PMC7353970 DOI: 10.1098/rsos.200260] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 06/01/2020] [Indexed: 05/02/2023]
Abstract
Neuropathic pain presents a huge societal and individual burden. The limited efficacy of current analgesics, diagnostic markers and clinical trial outcome measures arises from an incomplete understanding of the underlying mechanisms. A large and growing body of evidence has established the important role of microglia in the onset and possible maintenance of neuropathic pain, and these cells may represent an important target for future therapy. Microglial research has further revealed their important role in structural remodelling of the nervous system. In this review, we aim to explore the evidence for microglia in sculpting nervous system structure and function, as well as their important role in neuropathic pain, and finally integrate these studies to synthesize a new model for microglia in somatosensory circuit remodelling, composed of six key and inter-related mechanisms. Summarizing the mechanisms through which microglia modulate nervous system structure and function helps to frame a better understanding of neuropathic pain, and provide a clear roadmap for future research.
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Affiliation(s)
- Harry Ward
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Steven J. West
- Sainsbury Wellcome Centre, University College London, 25 Howland St, London WC1E 6BT, UK
- Author for correspondence: Steven J. West e-mail:
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6
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Yuan Y, Wu C, Ling EA. Heterogeneity of Microglia Phenotypes: Developmental, Functional and Some Therapeutic Considerations. Curr Pharm Des 2020; 25:2375-2393. [PMID: 31584369 DOI: 10.2174/1381612825666190722114248] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 07/12/2019] [Indexed: 02/06/2023]
Abstract
BACKGROUND Microglia play a pivotal role in maintaining homeostasis in complex brain environment. They first exist as amoeboid microglial cells (AMCs) in the developing brain, but with brain maturation, they transform into ramified microglial cells (RMCs). In pathological conditions, microglia are activated and have been classified into M1 and M2 phenotypes. The roles of AMCs, RMCs and M1/M2 microglia phenotypes especially in pathological conditions have been the focus of many recent studies. METHODS Here, we review the early development of the AMCs and RMCs and discuss their specific functions with reference to their anatomic locations, immunochemical coding etc. M1 and M2 microglia phenotypes in different neuropathological conditions are also reviewed. RESULTS Activated microglia are engaged in phagocytosis, production of proinflammatory mediators, trophic factors and synaptogenesis etc. Prolonged microglia activation, however, can cause damage to neurons and oligodendrocytes. The M1 and M2 phenotypes featured prominently in pathological conditions are discussed in depth. Experimental evidence suggests that microglia phenotype is being modulated by multiple factors including external and internal stimuli, local demands, epigenetic regulation, and herbal compounds. CONCLUSION Prevailing views converge that M2 polarization is neuroprotective. Thus, proper therapeutic designs including the use of anti-inflammatory drugs, herbal agents may be beneficial in suppression of microglial activation, especially M1 phenotype, for amelioration of neuroinflammation in different neuropathological conditions. Finally, recent development of radioligands targeting 18 kDa translocator protein (TSPO) in activated microglia may hold great promises clinically for early detection of brain lesion with the positron emission tomography.
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Affiliation(s)
- Yun Yuan
- Department of Anatomy and Histology/Embryology, Kunming Medical University, 1168 West Chunrong Road, Kunming, China
| | - Chunyun Wu
- Department of Anatomy and Histology/Embryology, Kunming Medical University, 1168 West Chunrong Road, Kunming, China
| | - Eng-Ang Ling
- Department of Anatomy, Yong Loo Lin School of Medicine, 4 Medical Drive, MD10, National University of Singapore, 117594, Singapore
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7
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Gheorghe RO, Deftu A, Filippi A, Grosu A, Bica-Popi M, Chiritoiu M, Chiritoiu G, Munteanu C, Silvestro L, Ristoiu V. Silencing the Cytoskeleton Protein Iba1 (Ionized Calcium Binding Adapter Protein 1) Interferes with BV2 Microglia Functioning. Cell Mol Neurobiol 2020; 40:1011-1027. [PMID: 31950314 DOI: 10.1007/s10571-020-00790-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 01/07/2020] [Indexed: 01/31/2023]
Abstract
Iba1 (ionized calcium binding adapter protein 1) is a cytoskeleton protein specific only for microglia and macrophages, where it acts as an actin-cross linking protein. Although frequently regarded as a marker of activation, its involvement in cell migration, membrane ruffling, phagocytosis or in microglia remodeling during immunological surveillance of the brain suggest that Iba1 is not a simple cytoskeleton protein, but a signaling molecule involved in specific signaling pathways. In this study we investigated if Iba1 could also represent a drug target, and tested the hypothesis that its specific silencing with customized Iba1-siRNA can modulate microglia functioning. The results showed that Iba1-silenced BV2 microglia migrate less due to reduced proliferation and cell adhesion, while their phagocytic activity and P2x7 functioning was significantly increased. Our data are the proof of concept that Iba1 protein is a new microglia target, which opens a new therapeutic avenue for modulating microglia behavior.
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Affiliation(s)
- Roxana-Olimpia Gheorghe
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, Sector 5, 050095, Bucharest, Romania
| | - Alexandru Deftu
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, Sector 5, 050095, Bucharest, Romania
| | - Alexandru Filippi
- Institute of Cellular Biology and Pathology 'Nicolae Simionescu' of the Romanian Academy, Bucharest, Romania
| | - Andreea Grosu
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, Sector 5, 050095, Bucharest, Romania
| | - Melania Bica-Popi
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, Sector 5, 050095, Bucharest, Romania
| | - Marioara Chiritoiu
- Department of Molecular Cell Biology, Institute of Biochemistry, Romanian Academy, Splaiul Independentei 296, 06003, Bucharest, Romania
| | - Gabriela Chiritoiu
- Department of Molecular Cell Biology, Institute of Biochemistry, Romanian Academy, Splaiul Independentei 296, 06003, Bucharest, Romania
| | - Cristian Munteanu
- Department of Molecular Cell Biology, Institute of Biochemistry, Romanian Academy, Splaiul Independentei 296, 06003, Bucharest, Romania
| | - Luigi Silvestro
- Pharma Serv International, Sabinelor 52, 050853, Bucharest, Romania
| | - Violeta Ristoiu
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, Sector 5, 050095, Bucharest, Romania.
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8
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Das R, Balmik AA, Chinnathambi S. Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia. J Neuroinflammation 2020; 17:10. [PMID: 31915009 PMCID: PMC6950897 DOI: 10.1186/s12974-019-1694-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 12/29/2019] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Alzheimer's disease is associated with the accumulation of intracellular Tau tangles within neurons and extracellular amyloid-β plaques in the brain parenchyma, which altogether results in synaptic loss and neurodegeneration. Extracellular concentrations of oligomers and aggregated proteins initiate microglial activation and convert their state of synaptic surveillance into a destructive inflammatory state. Although Tau oligomers have fleeting nature, they were shown to mediate neurotoxicity and microglial pro-inflammation. Due to the instability of oligomers, in vitro experiments become challenging, and hence, the stability of the full-length Tau oligomers is a major concern. METHODS In this study, we have prepared and stabilized hTau40WT oligomers, which were purified by size-exclusion chromatography. The formation of the oligomers was confirmed by western blot, thioflavin-S, 8-anilinonaphthaalene-1-sulfonic acid fluorescence, and circular dichroism spectroscopy, which determine the intermolecular cross-β sheet structure and hydrophobicity. The efficiency of N9 microglial cells to phagocytose hTau40WT oligomer and subsequent microglial activation was studied by immunofluorescence microscopy with apotome. The one-way ANOVA was performed for the statistical analysis of fluorometric assay and microscopic analysis. RESULTS Full-length Tau oligomers were detected in heterogeneous globular structures ranging from 5 to 50 nm as observed by high-resolution transmission electron microscopy, which was further characterized by oligomer-specific A11 antibody. Immunocytochemistry studies for oligomer treatment were evidenced with A11+ Iba1high microglia, suggesting that the phagocytosis of extracellular Tau oligomers leads to microglial activation. Also, the microglia were observed with remodeled filopodia-like actin structures upon the exposure of oligomers and aggregated Tau. CONCLUSION The peri-membrane polymerization of actin filament and co-localization of Iba1 relate to the microglial movements for phagocytosis. Here, these findings suggest that microglia modified actin cytoskeleton for phagocytosis and rapid clearance of Tau oligomers in Alzheimer's disease condition.
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Affiliation(s)
- Rashmi Das
- Neurobiology Group, Division of Biochemical Sciences, CSIR-National Chemical Laboratory (CSIR-NCL), Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Pune, 411008, India
| | - Abhishek Ankur Balmik
- Neurobiology Group, Division of Biochemical Sciences, CSIR-National Chemical Laboratory (CSIR-NCL), Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Pune, 411008, India
| | - Subashchandrabose Chinnathambi
- Neurobiology Group, Division of Biochemical Sciences, CSIR-National Chemical Laboratory (CSIR-NCL), Pune, 411008, India. .,Academy of Scientific and Innovative Research (AcSIR), Pune, 411008, India.
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9
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Pavlov D, Bettendorff L, Gorlova A, Olkhovik A, Kalueff AV, Ponomarev ED, Inozemtsev A, Chekhonin V, Lesсh KP, Anthony DC, Strekalova T. Neuroinflammation and aberrant hippocampal plasticity in a mouse model of emotional stress evoked by exposure to ultrasound of alternating frequencies. Prog Neuropsychopharmacol Biol Psychiatry 2019; 90:104-116. [PMID: 30472146 DOI: 10.1016/j.pnpbp.2018.11.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 11/08/2018] [Accepted: 11/21/2018] [Indexed: 02/06/2023]
Abstract
Emotional stress is a form of stress evoked by processing negative mental experience rather than an organic or physical disturbance and is a frequent cause of neuropsychiatric pathologies, including depression. Susceptibility to emotional stress is commonly regarded as a human-specific trait that is challenging to model in other species. Recently, we showed that a 3-week-long exposure to ultrasound of unpredictable alternating frequencies within the ranges of 20-25 kHz and 25-45 kHz can induce depression-like characteristics in laboratory mice and rats. In an anti-depressant sensitive manner, exposure decreases sucrose preference, elevates behavioural despair, increases aggression, and alters serotonin-related gene expression. To further investigate this paradigm, we studied depression/distress-associated markers of neuroinflammation, neuroplasticity, oxidative stress and the activity of glycogen synthase kinase-3 (GSK-3) isoforms in the hippocampus of male mice. Stressed mice exhibited a decreased density of Ki67-positive and DCX-positive cells in the subgranular zone of hippocampus, and altered expression of brain-derived neurotrophic factor (BDNF), its receptor TrkB, and anti-apoptotic protein kinase B phosphorylated at serine 473 (AktpSer473). The mice also exhibited increased densities of Iba-1-positive cells, increased oxidative stress, increased levels of interleukin-1β (IL-1β), interleukin-6 (IL-6) in the hippocampus and plasma, and elevated activity of GSK-3 isoforms. Together, the results of our investigation have revealed that unpredictable alternating ultrasound evokes behavioural and molecular changes that are characteristic of the depressive syndrome and validates this new and simple method of modeling emotional stress in rodents.
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Affiliation(s)
- Dmitrii Pavlov
- Department of Neuroscience, Maastricht University, Universiteitssingel 40, NL 6229ER, Maastricht, Netherlands; Department of Biology, Lomonosov Moscow State University, Leninskie Gory1-12, Moscow 119991, Russia; Laboratory of Neurophysiology, GIGA-Neurosciences, University of Liège, Av. Hippocrate 15, Liège 4000, Belgium; Institute of General Pathology and Pathophysiology, Baltiiskaya str, 8, Moscow 125315, Russia
| | - Lucien Bettendorff
- Laboratory of Neurophysiology, GIGA-Neurosciences, University of Liège, Av. Hippocrate 15, Liège 4000, Belgium
| | - Anna Gorlova
- Department of Biology, Lomonosov Moscow State University, Leninskie Gory1-12, Moscow 119991, Russia; Laboratory of Neurophysiology, GIGA-Neurosciences, University of Liège, Av. Hippocrate 15, Liège 4000, Belgium; Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Laboratory of Psychiatric Neurobiology and Department of Normal Physiology, Trubetskaya street 8-2, 119991, Moscow, Russia
| | - Andrey Olkhovik
- Department of Biology, Lomonosov Moscow State University, Leninskie Gory1-12, Moscow 119991, Russia
| | - Allan V Kalueff
- Institute of Translational Biomedicine, St.Petersburg State University, Universitetskaya nab. 7-9, St.-Petersburg 199034, Russia
| | - Eugene D Ponomarev
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Anatoly Inozemtsev
- Department of Biology, Lomonosov Moscow State University, Leninskie Gory1-12, Moscow 119991, Russia
| | - Vladimir Chekhonin
- Department of Basic and Applied Neurobiology, Serbsky Federal Medical Research Center for Psychiatry and Narcology, Kropotkinsky per 23, Moscow 119034, Russia
| | - Klaus-Peter Lesсh
- Department of Neuroscience, Maastricht University, Universiteitssingel 40, NL 6229ER, Maastricht, Netherlands; Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Laboratory of Psychiatric Neurobiology and Department of Normal Physiology, Trubetskaya street 8-2, 119991, Moscow, Russia; Division of Molecular Psychiatry, Center of Mental Health University of Wuerzburg, Josef-Schneider-Straße 2, Wuerzburg 97080, Germany
| | - Daniel C Anthony
- Department of Pharmacology, Oxford University, Mansfield Road, Oxford OX1 3QT, UK.
| | - Tatyana Strekalova
- Department of Neuroscience, Maastricht University, Universiteitssingel 40, NL 6229ER, Maastricht, Netherlands; Institute of General Pathology and Pathophysiology, Baltiiskaya str, 8, Moscow 125315, Russia; Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Laboratory of Psychiatric Neurobiology and Department of Normal Physiology, Trubetskaya street 8-2, 119991, Moscow, Russia.
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10
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Uweru JO, Eyo UB. A decade of diverse microglial-neuronal physical interactions in the brain (2008-2018). Neurosci Lett 2019; 698:33-38. [PMID: 30625349 DOI: 10.1016/j.neulet.2019.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 12/29/2018] [Accepted: 01/01/2019] [Indexed: 12/17/2022]
Abstract
Microglia are unique cells of the central nervous system (CNS) with a distinct ontogeny and molecular profile. They are the predominant immune resident cell in the CNS. Recent studies have revealed a diversity of transient and terminal physical interactions between microglia and neurons in the vertebrate brain. In this review, we follow the historical trail of the discovery of these interactions, summarize their notable features, provide implications of these discoveries to CNS function, emphasize emerging themes along the way and peak into the future of what outstanding questions remain to move the field forward.
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Affiliation(s)
- Joseph O Uweru
- Department of Neuroscience, University of Virginia, Charlottesville, VA, United States; Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, United States; Center for Brain Immunology and Glia (BIG), University of Virginia, Charlottesville, VA, United States
| | - Ukpong B Eyo
- Department of Neuroscience, University of Virginia, Charlottesville, VA, United States; Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, United States; Center for Brain Immunology and Glia (BIG), University of Virginia, Charlottesville, VA, United States.
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11
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Abstract
The concept of the immunological privilege of the central nervous system (CNS) has had a profound influence on studies of interactions between the immune system and the CNS. At one time there was considerable debate as to whether there were any cells in the CNS of myeloid origin, but we now know that there are a number of populations of myeloid cells in specialized compartments of the CNS and that there is an ongoing bidirectional dialogue between the CNS and the immune system. We briefly review what we know of the different myeloid populations, in particular the microglia: their phenotype and function; their role in CNS homeostasis; and also their role in pathology, focusing on chronic neurodegeneration.
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12
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Induction of hippocampal long-term potentiation increases the morphological dynamics of microglial processes and prolongs their contacts with dendritic spines. Sci Rep 2016; 6:32422. [PMID: 27604518 PMCID: PMC5015055 DOI: 10.1038/srep32422] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 07/27/2016] [Indexed: 11/23/2022] Open
Abstract
Recently microglia, the resident immune cells of the brain, have been recognized as multi-tasking talents that are not only essential in the diseased brain, but also actively contribute to synaptic circuit remodeling during normal brain development. It is well established that microglia dynamically scan their environment and thereby establish transient physical contacts with neuronal synapses, which may allow them to sense and influence synaptic function. However, it is unknown whether and how the morphological dynamics of microglia and their physical interactions with synapses are affected by the induction of synaptic plasticity in the adult brain. To this end, we characterized the morphological dynamics of microglia and their interactions with synapses before and after the induction of synaptic plasticity (LTP) in the hippocampus by time-lapse two-photon imaging and electrophysiological recordings in acute brain slices. We demonstrate that during hippocampal LTP microglia alter their morphological dynamics by increasing the number of their processes and by prolonging their physical contacts with dendritic spines. These effects were absent in the presence of an NMDA receptor antagonist. Taken together, this altered behavior could reflect an active microglial involvement in circuit remodeling during activity-dependent synaptic plasticity in the healthy adult brain.
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13
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Sherpa AD, Xiao F, Joseph N, Aoki C, Hrabetova S. Activation of β-adrenergic receptors in rat visual cortex expands astrocytic processes and reduces extracellular space volume. Synapse 2016; 70:307-16. [PMID: 27085090 DOI: 10.1002/syn.21908] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 03/11/2016] [Accepted: 04/13/2016] [Indexed: 12/18/2022]
Abstract
Brain extracellular space (ECS) is an interconnected channel that allows diffusion-mediated transport of signaling molecules, metabolites, and drugs. We tested the hypothesis that β-adrenergic receptor (βAR) activation impacts extracellular diffusion-mediated transport of molecules through alterations in the morphology of astrocytes. Two structural parameters of ECS-volume fraction and tortuosity-govern extracellular diffusion. Volume fraction (α) is the volume of ECS relative to the total tissue volume. Tortuosity (λ) is a measure of the hindrance that molecules experience in the ECS, compared to a free medium. The real-time iontophoretic (RTI) method revealed that treatment of acutely prepared visual cortical slices of adult female rats with a βAR agonist, DL-isoproterenol (ISO), decreases α significantly, from 0.22 ± 0.03 (mean ± SD) for controls without agonist to 0.18 ± 0.03 with ISO, without altering λ (control: 1.64 ± 0.04; ISO: 1.63 ± 0.04). Electron microscopy revealed that the ISO treatment significantly increased the cytoplasmic area of astrocytic distal endings per unit area of neuropil by 54%. These findings show that norepinephrine decreases α, in part, through an increase in astrocytic volume following βAR activation. Norepinephrine is recognized to be released within the brain during the awake state and increase neurons' signal-to-noise ratio through modulation of neurons' biophysical properties. Our findings uncover a new mechanism for noradrenergic modulation of neuronal signals. Through astrocytic activation leading to a reduction of α, noradrenergic modulation increases extracellular concentration of neurotransmitters and neuromodulators, thereby facilitating neuronal interactions, especially during wakefulness. Synapse 70:307-316, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Ang Doma Sherpa
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York, 11203
- Neural and Behavioral Science Graduate Program, The School of Graduate Studies, State University of New York Downstate Medical Center, Brooklyn, New York, 11203
| | - Fanrong Xiao
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York, 11203
| | | | - Chiye Aoki
- Center for Neural Science, New York University, New York, New York, 10003
| | - Sabina Hrabetova
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York, 11203
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York, 11203
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P2Y Receptors in Synaptic Transmission and Plasticity: Therapeutic Potential in Cognitive Dysfunction. Neural Plast 2016; 2016:1207393. [PMID: 27069691 PMCID: PMC4812485 DOI: 10.1155/2016/1207393] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 02/10/2016] [Indexed: 01/02/2023] Open
Abstract
ATP released from neurons and astrocytes during neuronal activity or under pathophysiological circumstances is able to influence information flow in neuronal circuits by activation of ionotropic P2X and metabotropic P2Y receptors and subsequent modulation of cellular excitability, synaptic strength, and plasticity. In the present paper we review cellular and network effects of P2Y receptors in the brain. We show that P2Y receptors inhibit the release of neurotransmitters, modulate voltage- and ligand-gated ion channels, and differentially influence the induction of synaptic plasticity in the prefrontal cortex, hippocampus, and cerebellum. The findings discussed here may explain how P2Y1 receptor activation during brain injury, hypoxia, inflammation, schizophrenia, or Alzheimer's disease leads to an impairment of cognitive processes. Hence, it is suggested that the blockade of P2Y1 receptors may have therapeutic potential against cognitive disturbances in these states.
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Defining the Microglia Response during the Time Course of Chronic Neurodegeneration. J Virol 2016; 90:3003-17. [PMID: 26719249 PMCID: PMC4810622 DOI: 10.1128/jvi.02613-15] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 12/23/2015] [Indexed: 01/09/2023] Open
Abstract
UNLABELLED Inflammation has been proposed as a major component of neurodegenerative diseases, although the precise role it plays has yet to be defined. We examined the role of key contributors to this inflammatory process, microglia, the major resident immune cell population of the brain, in a prion disease model of chronic neurodegeneration. Initially, we performed an extensive reanalysis of a large study of prion disease, where the transcriptome of mouse brains had been monitored throughout the time course of disease. Our analysis has provided a detailed classification of the disease-associated genes based on cell type of origin and gene function. This revealed that the genes upregulated during disease, regardless of the strain of mouse or prion protein, are expressed predominantly by activated microglia. In order to study the microglia contribution more specifically, we established a mouse model of prion disease in which the 79A murine prion strain was introduced by an intraperitoneal route into BALB/cJ(Fms-EGFP/-) mice, which express enhanced green fluorescent protein under the control of the c-fms operon. Samples were taken at time points during disease progression, and histological analysis of the brain and transcriptional analysis of isolated microglia was carried out. The analysis of isolated microglia revealed a disease-specific, highly proinflammatory signature in addition to an upregulation of genes associated with metabolism and respiratory stress. This study strongly supports the growing recognition of the importance of microglia within the prion disease process and identifies the nature of the response through gene expression analysis of isolated microglia. IMPORTANCE Inflammation has been proposed as a major component of neurodegenerative diseases. We have examined the role of key contributors to this inflammatory process, microglia, the major resident immune cell population of the brain, in a murine prion disease model of chronic neurodegeneration. Our study demonstrates that genes upregulated throughout the disease process are expressed predominantly by microglia. A disease-specific, highly proinflammatory signature was observed in addition to an upregulation of genes associated with metabolism and respiratory stress. This study strongly supports the growing recognition of the important contribution of microglia to a chronic neurodegenerative disease process.
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Manitz MP, Plümper J, Demir S, Ahrens M, Eßlinger M, Wachholz S, Eisenacher M, Juckel G, Friebe A. Flow cytometric characterization of microglia in the offspring of PolyI:C treated mice. Brain Res 2016; 1636:172-182. [PMID: 26872595 DOI: 10.1016/j.brainres.2016.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 11/16/2015] [Accepted: 02/02/2016] [Indexed: 02/07/2023]
Abstract
The neuropathology of schizophrenia has been reported to be closely associated with microglial activation. In a previous study, using the prenatal PolyI:C schizophrenia animal model, we showed an increase in cell numbers and a reduction in microglial branching in 30-day-old PolyI:C descendants, which suggests that there is microglial activation during adolescence. To provide more information about the activation state, we aimed to examine the expression levels of Iba1, which was reported to be up-regulated in activated microglia. We used a flow cytometric approach and investigated CD11b and CD45, two additional markers for the identification of microglial cells. We demonstrated that intracellular staining against Iba1 can be used as a reliable flow cytometric method for identification of microglial cells. Prenatal PolyI:C treatment had long-term effects on CD11b and CD45 expression. It also resulted in a trend towards increased Iba1 expression. Imbalance in CD11b, CD45, and Iba1 expression might contribute to impaired synaptic surveillance and enhanced activation/inflammatory activity of microglia in adult offspring.
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Affiliation(s)
- Marie Pierre Manitz
- Department of Psychiatry, LWL University Hospital, Ruhr-University Bochum, Alexandrinenstr. 1, D-44791 Bochum, Germany.
| | - Jennifer Plümper
- Department of Psychiatry, LWL University Hospital, Ruhr-University Bochum, Alexandrinenstr. 1, D-44791 Bochum, Germany
| | - Seray Demir
- Department of Neuroimmunology, Ruhr-University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany.
| | - Maike Ahrens
- Medizinisches Proteom-Center, Ruhr-University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany.
| | - Manuela Eßlinger
- Department of Psychiatry, LWL University Hospital, Ruhr-University Bochum, Alexandrinenstr. 1, D-44791 Bochum, Germany.
| | - Simone Wachholz
- Department of Psychiatry, LWL University Hospital, Ruhr-University Bochum, Alexandrinenstr. 1, D-44791 Bochum, Germany.
| | - Martin Eisenacher
- Medizinisches Proteom-Center, Ruhr-University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany.
| | - Georg Juckel
- Department of Psychiatry, LWL University Hospital, Ruhr-University Bochum, Alexandrinenstr. 1, D-44791 Bochum, Germany.
| | - Astrid Friebe
- Department of Psychiatry, LWL University Hospital, Ruhr-University Bochum, Alexandrinenstr. 1, D-44791 Bochum, Germany.
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Iida T, Tanaka S, Okabe S. C4-P-09Three-dimensional analysis of microglia and synapses with large-volume optical reconstruction. Microscopy (Oxf) 2015. [DOI: 10.1093/jmicro/dfv327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Abstract
Neuroglia, the "glue" that fills the space between neurons in the central nervous system, takes active part in nerve cell signaling. Neuroglial cells, astroglia, oligodendroglia, and microglia, are together about as numerous as neurons in the brain as a whole, and in the cerebral cortex grey matter, but the proportion varies widely among brain regions. Glial volume, however, is less than one-fifth of the tissue volume in grey matter. When stimulated by neurons or other cells, neuroglial cells release gliotransmitters by exocytosis, similar to neurotransmitter release from nerve endings, or by carrier-mediated transport or channel flux through the plasma membrane. Gliotransmitters include the common neurotransmitters glutamate and GABA, the nonstandard amino acid d-serine, the high-energy phosphate ATP, and l-lactate. The latter molecule is a "buffer" between glycolytic and oxidative metabolism as well as a signaling substance recently shown to act on specific lactate receptors in the brain. Complementing neurotransmission at a synapse, neuroglial transmission often implies diffusion of the transmitter over a longer distance and concurs with the concept of volume transmission. Transmission from glia modulates synaptic neurotransmission based on energetic and other local conditions in a volume of tissue surrounding the individual synapse. Neuroglial transmission appears to contribute significantly to brain functions such as memory, as well as to prevalent neuropathologies.
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Affiliation(s)
- Vidar Gundersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Jon Storm-Mathisen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Linda Hildegard Bergersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
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CHF5074 (CSP-1103) induces microglia alternative activation in plaque-free Tg2576 mice and primary glial cultures exposed to beta-amyloid. Neuroscience 2015; 302:112-20. [DOI: 10.1016/j.neuroscience.2014.10.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 10/06/2014] [Accepted: 10/13/2014] [Indexed: 11/19/2022]
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Tremblay MÈ, Lecours C, Samson L, Sánchez-Zafra V, Sierra A. From the Cajal alumni Achúcarro and Río-Hortega to the rediscovery of never-resting microglia. Front Neuroanat 2015; 9:45. [PMID: 25926775 PMCID: PMC4396411 DOI: 10.3389/fnana.2015.00045] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 03/24/2015] [Indexed: 12/30/2022] Open
Abstract
Under the guidance of Ramón y Cajal, a plethora of students flourished and began to apply his silver impregnation methods to study brain cells other than neurons: the neuroglia. In the first decades of the twentieth century, Nicolás Achúcarro was one of the first researchers to visualize the brain cells with phagocytic capacity that we know today as microglia. Later, his pupil Pío del Río-Hortega developed modifications of Achúcarro's methods and was able to specifically observe the fine morphological intricacies of microglia. These findings contradicted Cajal's own views on cells that he thought belonged to the same class as oligodendroglia (the so called “third element” of the nervous system), leading to a long-standing discussion. It was only in 1924 that Río-Hortega's observations prevailed worldwide, thus recognizing microglia as a unique cell type. This late landing in the Neuroscience arena still has repercussions in the twenty first century, as microglia remain one of the least understood cell populations of the healthy brain. For decades, microglia in normal, physiological conditions in the adult brain were considered to be merely “resting,” and their contribution as “activated” cells to the neuroinflammatory response in pathological conditions mostly detrimental. It was not until microglia were imaged in real time in the intact brain using two-photon in vivo imaging that the extreme motility of their fine processes was revealed. These findings led to a conceptual revolution in the field: “resting” microglia are constantly surveying the brain parenchyma in normal physiological conditions. Today, following Cajal's school of thought, structural and functional investigations of microglial morphology, dynamics, and relationships with neurons and other glial cells are experiencing a renaissance and we stand at the brink of discovering new roles for these unique immune cells in the healthy brain, an essential step to understand their causal relationship to diseases.
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Affiliation(s)
- Marie-Ève Tremblay
- Centre de Recherche du CHU de Québec, Axe Neurosciences Québec, QC, Canada ; Département de médecine moléculaire, Université Laval Québec, QC, Canada
| | - Cynthia Lecours
- Centre de Recherche du CHU de Québec, Axe Neurosciences Québec, QC, Canada ; Département de médecine moléculaire, Université Laval Québec, QC, Canada
| | - Louis Samson
- Centre de Recherche du CHU de Québec, Axe Neurosciences Québec, QC, Canada ; Département de médecine moléculaire, Université Laval Québec, QC, Canada
| | - Víctor Sánchez-Zafra
- Achúcarro Basque Center for Neuroscience, Bizkaia Science and Technology Park Zamudio, Spain ; Department of Neurosciences, University of the Basque Country Leioa, Spain
| | - Amanda Sierra
- Achúcarro Basque Center for Neuroscience, Bizkaia Science and Technology Park Zamudio, Spain ; Department of Neurosciences, University of the Basque Country Leioa, Spain ; Ikerbasque Foundation Bilbao, Spain
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21
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Gomez-Nicola D, Perry VH. Microglial dynamics and role in the healthy and diseased brain: a paradigm of functional plasticity. Neuroscientist 2014; 21:169-84. [PMID: 24722525 PMCID: PMC4412879 DOI: 10.1177/1073858414530512] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The study of the dynamics and functions of microglia in the healthy and diseased brain is a matter of intense scientific activity. The application of new techniques and new experimental approaches has allowed the identification of novel microglial functions and the redefinition of classic ones. In this review, we propose the study of microglial functions, rather than their molecular profiles, to better understand and define the roles of these cells in the brain. We review current knowledge on the role of surveillant microglia, proliferating microglia, pruning/neuromodulatory microglia, phagocytic microglia, and inflammatory microglia and the molecular profiles that are associated with these functions. In the remodeling scenario of microglial biology, the analysis of microglial functional states will inform about the roles in health and disease and will guide us to a more precise understanding of the multifaceted roles of this never-resting cells.
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Affiliation(s)
- Diego Gomez-Nicola
- Centre for Biological Sciences, University of Southampton, Southampton, UK
| | - V Hugh Perry
- Centre for Biological Sciences, University of Southampton, Southampton, UK
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22
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Abstract
Under physiological conditions, the number and function of microglia--the resident macrophages of the CNS--is tightly controlled by the local microenvironment. In response to neurodegeneration and the accumulation of abnormally folded proteins, however, microglia multiply and adopt an activated state--a process referred to as priming. Studies using preclinical animal models have shown that priming of microglia is driven by changes in their microenvironment and the release of molecules that drive their proliferation. Priming makes the microglia susceptible to a secondary inflammatory stimulus, which can then trigger an exaggerated inflammatory response. The secondary stimulus can arise within the CNS, but in elderly individuals, the secondary stimulus most commonly arises from a systemic disease with an inflammatory component. The concept of microglial priming, and the subsequent exaggerated response of these cells to secondary systemic inflammation, opens the way to treat neurodegenerative diseases by targeting systemic disease or interrupting the signalling pathways that mediate the CNS response to systemic inflammation. Both lifestyle changes and pharmacological therapies could, therefore, provide efficient means to slow down or halt neurodegeneration.
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Affiliation(s)
- V Hugh Perry
- Centre for Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Tremona Road, Southampton SO16 6YD, UK
| | - Clive Holmes
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Tremona Road, Southampton SO16 6YD, UK
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23
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Evans AK, Strassmann PS, Lee IP, Sapolsky RM. Patterns of Toxoplasma gondii cyst distribution in the forebrain associate with individual variation in predator odor avoidance and anxiety-related behavior in male Long-Evans rats. Brain Behav Immun 2014; 37:122-33. [PMID: 24269877 PMCID: PMC3951684 DOI: 10.1016/j.bbi.2013.11.012] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 11/05/2013] [Accepted: 11/15/2013] [Indexed: 12/14/2022] Open
Abstract
Toxoplasma gondii (T. gondii) is one of the world's most successful brain parasites. T. gondii engages in parasite manipulation of host behavior and infection has been epidemiologically linked to numerous psychiatric disorders. Mechanisms by which T. gondii alters host behavior are not well understood, but neuroanatomical cyst presence and the localized host immune response to cysts are potential candidates. The aim of these studies was to test the hypothesis that T. gondii manipulation of specific host behaviors is dependent on neuroanatomical location of cysts in a time-dependent function post-infection. We examined neuroanatomical cyst distribution (53 forebrain regions) in infected rats after predator odor aversion behavior and anxiety-related behavior in the elevated plus maze and open field arena, across a 6-week time course. In addition, we examined evidence for microglial response to the parasite across the time course. Our findings demonstrate that while cysts are randomly distributed throughout the forebrain, individual variation in cyst localization, beginning 3 weeks post-infection, can explain individual variation in the effects of T. gondii on behavior. Additionally, not all infected rats develop cysts in the forebrain, and attenuation of predator odor aversion and changes in anxiety-related behavior are linked with cyst presence in specific forebrain areas. Finally, the immune response to cysts is striking. These data provide the foundation for testing hypotheses about proximate mechanisms by which T. gondii alters behavior in specific brain regions, including consequences of establishment of a homeostasis between T. gondii and the host immune response.
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Affiliation(s)
- Andrew K Evans
- Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
| | | | - I-Ping Lee
- Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Robert M Sapolsky
- Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA
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24
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Janz P, Illing RB. A role for microglial cells in reshaping neuronal circuitry of the adult rat auditory brainstem after its sensory deafferentation. J Neurosci Res 2014; 92:432-45. [DOI: 10.1002/jnr.23334] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 10/24/2013] [Accepted: 11/06/2013] [Indexed: 11/07/2022]
Affiliation(s)
- Philipp Janz
- Neurobiological Research Laboratory; Department of Otorhinolaryngology; University of Freiburg; Freiburg Germany
| | - Robert-Benjamin Illing
- Neurobiological Research Laboratory; Department of Otorhinolaryngology; University of Freiburg; Freiburg Germany
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25
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Šišková Z, Tremblay MÈ. Microglia and synapse: interactions in health and neurodegeneration. Neural Plast 2013; 2013:425845. [PMID: 24392228 PMCID: PMC3874338 DOI: 10.1155/2013/425845] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 09/30/2013] [Accepted: 10/19/2013] [Indexed: 01/04/2023] Open
Abstract
A series of discoveries spanning for the last few years has challenged our view of microglial function, the main form of immune defense in the brain. The surveillance of neuronal circuits executed by each microglial cell overseeing its territory occurs in the form of regular, dynamic interactions. Microglial contacts with individual neuronal compartments, such as dendritic spines and axonal terminals, ensure that redundant or dysfunctional elements are recognized and eliminated from the brain. Microglia take on a new shape that is large and amoeboid when a threat to brain integrity is detected. In this defensive form, they migrate to the endangered sites, where they help to minimize the extent of the brain insult. However, in neurodegenerative diseases that are associated with misfolding and aggregation of synaptic proteins, these vital defensive functions appear to be compromised. Many microglial functions, such as phagocytosis, might be overwhelmed during exposure to the abnormal levels of misfolded proteins in their proximity. This might prevent them from attending to their normal duties, such as the stripping of degenerating synaptic terminals, before neuronal function is irreparably impaired. In these conditions microglia become chronically activated and appear to take on new, destructive roles by direct or indirect inflammatory attack.
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Affiliation(s)
- Zuzana Šišková
- German Center for Neurodegenerative Diseases (DZNE), Ludwig-Erhard-Allee 2, 53175 Bonn, Germany
| | - Marie-Ève Tremblay
- Axe Neurosciences, Centre de Recherche du CHU de Québec, Département de Médecine Moléculaire, Université Laval, 2705 Boulevard Laurier, Québec, QC, Canada G1V 4G2
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26
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GABA is localized in dopaminergic synaptic vesicles in the rodent striatum. Brain Struct Funct 2013; 219:1901-12. [DOI: 10.1007/s00429-013-0609-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 07/03/2013] [Indexed: 11/24/2022]
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Morris GP, Clark IA, Zinn R, Vissel B. Microglia: a new frontier for synaptic plasticity, learning and memory, and neurodegenerative disease research. Neurobiol Learn Mem 2013; 105:40-53. [PMID: 23850597 DOI: 10.1016/j.nlm.2013.07.002] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/03/2013] [Indexed: 12/25/2022]
Abstract
We focus on emerging roles for microglia in synaptic plasticity, cognition and disease. We outline evidence that ramified microglia, traditionally thought to be functionally "resting" (i.e. quiescent) in the normal brain, in fact are highly dynamic and plastic. Ramified microglia continually and rapidly extend processes, contact synapses in an activity and experience dependent manner, and play a functionally dynamic role in synaptic plasticity, possibly through release of cytokines and growth factors. Ramified microglial also contribute to structural plasticity through the elimination of synapses via phagocytic mechanisms, which is necessary for normal cognition. Microglia have numerous mechanisms to monitor neuronal activity and numerous mechanisms also exist to prevent them transitioning to an activated state, which involves retraction of their surveying processes. Based on the evidence, we suggest that maintaining the ramified state of microglia is essential for normal synaptic and structural plasticity that supports cognition. Further, we propose that change of their ramified morphology and function, as occurs in inflammation associated with numerous neurological disorders such as Alzheimer's and Parkinson's disease, disrupts their intricate and essential synaptic functions. In turn altered microglia function could cause synaptic dysfunction and excess synapse loss early in disease, initiating a range of pathologies that follow. We conclude that the future of learning and memory research depends on an understanding of the role of non-neuronal cells and that this should include using sophisticated molecular, cellular, physiological and behavioural approaches combined with imaging to causally link the role of microglia to brain function and disease including Alzheimer's and Parkinson's disease and other neuropsychiatric disorders.
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Affiliation(s)
- Gary P Morris
- Neurodegenerative Disorders, Garvan Institute of Medical Research, Neuroscience Department, Sydney, Australia; Faculty of Medicine, University of New South Wales, Sydney, Australia.
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