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Ding Z, Guo S, Luo L, Zheng Y, Gan S, Kang X, Wu X, Zhu S. Emerging Roles of Microglia in Neuro-vascular Unit: Implications of Microglia-Neurons Interactions. Front Cell Neurosci 2021; 15:706025. [PMID: 34712121 PMCID: PMC8546170 DOI: 10.3389/fncel.2021.706025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 09/10/2021] [Indexed: 12/20/2022] Open
Abstract
Microglia, which serve as the defensive interface of the nervous system, are activated in many neurological diseases. Their role as immune responding cells has been extensively studied in the past few years. Recent studies have demonstrated that neuronal feedback can be shaped by the molecular signals received and sent by microglia. Altered neuronal activity or synaptic plasticity leads to the release of various communication messages from neurons, which in turn exert effects on microglia. Research on microglia-neuron communication has thus expanded from focusing only on neurons to the neurovascular unit (NVU). This approach can be used to explore the potential mechanism of neurovascular coupling across sophisticated receptor systems and signaling cascades in health and disease. However, it remains unclear how microglia-neuron communication happens in the brain. Here, we discuss the functional contribution of microglia to synapses, neuroimmune communication, and neuronal activity. Moreover, the current state of knowledge of bidirectional control mechanisms regarding interactions between neurons and microglia are reviewed, with a focus on purinergic regulatory systems including ATP-P2RY12R signaling, ATP-adenosine-A1Rs/A2ARs, and the ATP-pannexin 1 hemichannel. This review aims to organize recent studies to highlight the multifunctional roles of microglia within the neural communication network in health and disease.
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Affiliation(s)
- Zhe Ding
- Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Shaohui Guo
- Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Lihui Luo
- Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yueying Zheng
- Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Shuyuan Gan
- Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xianhui Kang
- Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiaomin Wu
- Department of Anesthesiology, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Shengmei Zhu
- Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
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52
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Lu H, Gallinaro JV, Normann C, Rotter S, Yalcin I. Time Course of Homeostatic Structural Plasticity in Response to Optogenetic Stimulation in Mouse Anterior Cingulate Cortex. Cereb Cortex 2021; 32:1574-1592. [PMID: 34607362 DOI: 10.1093/cercor/bhab281] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 07/09/2021] [Accepted: 07/12/2021] [Indexed: 11/13/2022] Open
Abstract
Plasticity is the mechanistic basis of development, aging, learning, and memory, both in healthy and pathological brains. Structural plasticity is rarely accounted for in computational network models due to a lack of insight into the underlying neuronal mechanisms and processes. Little is known about how the rewiring of networks is dynamically regulated. To inform such models, we characterized the time course of neural activity, the expression of synaptic proteins, and neural morphology employing an in vivo optogenetic mouse model. We stimulated pyramidal neurons in the anterior cingulate cortex of mice and harvested their brains at 1.5 h, 24 h, and $48\,\mathrm{h}$ after stimulation. Stimulus-induced cortical hyperactivity persisted up to 1.5 h and decayed to baseline after $24\,\mathrm{h}$ indicated by c-Fos expression. The synaptic proteins VGLUT1 and PSD-95, in contrast, were upregulated at $24\,\mathrm{h}$ and downregulated at $48\,\mathrm{h}$, respectively. Spine density and spine head volume were also increased at $24\,\mathrm{h}$ and decreased at $48\,\mathrm{h}$. This specific sequence of events reflects a continuous joint evolution of activity and connectivity that is characteristic of the model of homeostatic structural plasticity. Our computer simulations thus corroborate the observed empirical evidence from our animal experiments.
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Affiliation(s)
- Han Lu
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.,Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives UPR3212, Strasbourg 67000, France.,Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg 79104, Germany
| | - Júlia V Gallinaro
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.,Bioengineering Department, Imperial College London, London SW7 2AZ, United Kingdom
| | - Claus Normann
- Department of Psychiatry and Psychotherapy, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg 79104, Germany.,Center for Basics in Neuromodulation, Faculty of Medicine, University of Freiburg, Freiburg 79104, Germany
| | - Stefan Rotter
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg 79104, Germany
| | - Ipek Yalcin
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives UPR3212, Strasbourg 67000, France.,Department of Psychiatry and Neuroscience, Université Laval, Québec QC G1V 0A6, Canada
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53
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Bisht K, Okojie KA, Sharma K, Lentferink DH, Sun YY, Chen HR, Uweru JO, Amancherla S, Calcuttawala Z, Campos-Salazar AB, Corliss B, Jabbour L, Benderoth J, Friestad B, Mills WA, Isakson BE, Tremblay MÈ, Kuan CY, Eyo UB. Capillary-associated microglia regulate vascular structure and function through PANX1-P2RY12 coupling in mice. Nat Commun 2021; 12:5289. [PMID: 34489419 PMCID: PMC8421455 DOI: 10.1038/s41467-021-25590-8] [Citation(s) in RCA: 123] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 08/17/2021] [Indexed: 12/15/2022] Open
Abstract
Microglia are brain-resident immune cells with a repertoire of functions in the brain. However, the extent of their interactions with the vasculature and potential regulation of vascular physiology has been insufficiently explored. Here, we document interactions between ramified CX3CR1 + myeloid cell somata and brain capillaries. We confirm that these cells are bona fide microglia by molecular, morphological and ultrastructural approaches. Then, we give a detailed spatio-temporal characterization of these capillary-associated microglia (CAMs) comparing them with parenchymal microglia (PCMs) in their morphological activities including during microglial depletion and repopulation. Molecularly, we identify P2RY12 receptors as a regulator of CAM interactions under the control of released purines from pannexin 1 (PANX1) channels. Furthermore, microglial elimination triggered capillary dilation, blood flow increase, and impaired vasodilation that were recapitulated in P2RY12-/- and PANX1-/- mice suggesting purines released through PANX1 channels play important roles in activating microglial P2RY12 receptors to regulate neurovascular structure and function.
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Affiliation(s)
- Kanchan Bisht
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Kenneth A Okojie
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Kaushik Sharma
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Dennis H Lentferink
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Yu-Yo Sun
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Hong-Ru Chen
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Joseph O Uweru
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Saipranusha Amancherla
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Zainab Calcuttawala
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Antony Brayan Campos-Salazar
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Bruce Corliss
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Lara Jabbour
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Jordan Benderoth
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Bria Friestad
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - William A Mills
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, USA
- Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Marie-Ève Tremblay
- Axe Neurosciences, Centre de recherche du CHU de Québec-Université Laval, Québec, QC, Canada
- Département de médecine moléculaire, Université Laval, Québec, QC, Canada
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
- Biochemistry and Molecular Biology, Faculty of Medicine, The University of British Colombia, Vancouver, BC, Canada
| | - Chia-Yi Kuan
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA
| | - Ukpong B Eyo
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA.
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, USA.
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, USA.
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54
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Engel T, Smith J, Alves M. Targeting Neuroinflammation via Purinergic P2 Receptors for Disease Modification in Drug-Refractory Epilepsy. J Inflamm Res 2021; 14:3367-3392. [PMID: 34305404 PMCID: PMC8298823 DOI: 10.2147/jir.s287740] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 06/12/2021] [Indexed: 12/27/2022] Open
Abstract
Treatment of epilepsy remains a clinical challenge, with >30% of patients not responding to current antiseizure drugs (ASDs). Moreover, currently available ASDs are merely symptomatic without altering significantly the progression of the disease. Inflammation is increasingly recognized as playing an important role during the generation of hyperexcitable networks in the brain. Accordingly, the suppression of chronic inflammation has been suggested as a promising therapeutic strategy to prevent epileptogenesis and to treat drug-refractory epilepsy. As a consequence, a strong focus of ongoing research is identification of the mechanisms that contribute to sustained inflammation in the brain during epilepsy and whether these can be targeted. ATP is released in response to several pathological stimuli, including increased neuronal activity within the central nervous system, where it functions as a neuro- and gliotransmitter. Once released, ATP activates purinergic P2 receptors, which are divided into metabotropic P2Y and ionotropic P2X receptors, driving inflammatory processes. Evidence from experimental models and patients demonstrates widespread expression changes of both P2Y and P2X receptors during epilepsy, and critically, drugs targeting both receptor subtypes, in particular the P2Y1 and P2X7 subtypes, have been shown to possess both anticonvulsive and antiepileptic potential. This review provides a detailed summary of the current evidence suggesting ATP-gated receptors as novel drug targets for epilepsy and discusses how P2 receptor–driven inflammation may contribute to the generation of seizures and the development of epilepsy.
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Affiliation(s)
- Tobias Engel
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin, D02 YN77, Ireland.,FutureNeuro, Science Foundation Ireland Research Centre for Chronic and Rare Neurological Diseases, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin, D02 YN77, Ireland
| | - Jonathon Smith
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin, D02 YN77, Ireland.,FutureNeuro, Science Foundation Ireland Research Centre for Chronic and Rare Neurological Diseases, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin, D02 YN77, Ireland
| | - Mariana Alves
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin, D02 YN77, Ireland
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55
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Roufagalas I, Avloniti M, Fortosi A, Xingi E, Thomaidou D, Probert L, Kyrargyri V. Novel cell-based analysis reveals region-dependent changes in microglial dynamics in grey matter in a cuprizone model of demyelination. Neurobiol Dis 2021; 157:105449. [PMID: 34274460 DOI: 10.1016/j.nbd.2021.105449] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 06/25/2021] [Accepted: 07/13/2021] [Indexed: 02/07/2023] Open
Abstract
Microglia are key players in Multiple Sclerosis (MS), expressing many susceptibility genes for this disease. They constantly survey the brain microenvironment, but the precise functional relationships between microglia and pathological processes remain unknown. We performed a detailed assessment of microglial dynamics in three distinct grey matter regions in a cuprizone-induced demyelination model. We found that microglial activation preceded detectable demyelination and showed regional specificities, such as prominent phagocytic activity in cortical layer 5 and early hypertrophic morphology in hippocampal CA1. Demyelination happened earliest in cortical layer 5, although was more complete in CA1. In cortical layer 2/3, microglial activation and demyelination were less pronounced but microglia became hyper-ramified with slower process movement during remyelination, thereby maintaining local brain surveillance. Profiling of microglia using specific morphological and motility parameters revealed region-specific heterogeneity of microglial responses in the grey matter that might serve as sensitive indicators of progression in CNS demyelinating diseases.
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Affiliation(s)
- Ilias Roufagalas
- Department of Immunology, Laboratory of Molecular Genetics, Hellenic Pasteur Institute, Athens, Greece
| | - Maria Avloniti
- Department of Immunology, Laboratory of Molecular Genetics, Hellenic Pasteur Institute, Athens, Greece
| | - Alexandra Fortosi
- Department of Immunology, Laboratory of Molecular Genetics, Hellenic Pasteur Institute, Athens, Greece
| | - Evangelia Xingi
- Light Microscopy Unit, Hellenic Pasteur Institute, Athens, Greece
| | - Dimitra Thomaidou
- Light Microscopy Unit, Hellenic Pasteur Institute, Athens, Greece; Department of Neurobiology, Neural Stem Cells & Neuroimaging Group, Hellenic Pasteur Institute, Athens, Greece
| | - Lesley Probert
- Department of Immunology, Laboratory of Molecular Genetics, Hellenic Pasteur Institute, Athens, Greece
| | - Vasiliki Kyrargyri
- Department of Immunology, Laboratory of Molecular Genetics, Hellenic Pasteur Institute, Athens, Greece.
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56
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Koo JW, Wohleb ES. How Stress Shapes Neuroimmune Function: Implications for the Neurobiology of Psychiatric Disorders. Biol Psychiatry 2021; 90:74-84. [PMID: 33485589 PMCID: PMC8126571 DOI: 10.1016/j.biopsych.2020.11.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 11/09/2020] [Accepted: 11/11/2020] [Indexed: 12/13/2022]
Abstract
Chronic stress causes physiological and hormonal adaptations that lead to neurobiological consequences and behavioral and cognitive impairments. In particular, chronic stress has been shown to drive reduced neurogenesis and altered synaptic plasticity in brain regions that regulate mood and motivation. The neurobiological and behavioral effects of stress resemble the pathophysiology and symptoms observed in psychiatric disorders, suggesting that there are similar underlying mechanisms. Accumulating evidence indicates that neuroimmune systems, particularly microglia, have a critical role in regulating the neurobiology of stress. Preclinical models indicate that chronic stress provokes changes in microglia phenotype and increases inflammatory cytokine signaling, which affects neuronal function and leads to synaptic plasticity deficits and impaired neurogenesis. More recent work has shown that microglia can also phagocytose neuronal elements and contribute to structural remodeling of neurons in response to chronic stress. In this review we highlight work by the Duman research group (as well as others) that has revealed how chronic stress shapes neuroimmune function and, in turn, how inflammatory mediators and microglia contribute to the neurobiological effects of chronic stress. We also provide considerations to engage the therapeutic potential of neuroimmune systems, with the goal of improving treatment for psychiatric disorders.
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Affiliation(s)
- Ja Wook Koo
- Department of Neural Development and Disease, Korea Brain
Research Institute, Daegu, Korea,Department of Brain and Cognitive Sciences, Daegu Gyeongbuk
Institute of Science and Technology (DGIST), Daegu, Korea
| | - Eric S. Wohleb
- Department of Pharmacology & Systems Physiology,
University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of
America,Corresponding author: Eric S. Wohleb, Department
of Pharmacology & Systems Physiology, University of Cincinnati College of
Medicine, 2120 East Galbraith Road, Cincinnati, OH 45237 U.S.A.,
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57
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Ferro A, Auguste YSS, Cheadle L. Microglia, Cytokines, and Neural Activity: Unexpected Interactions in Brain Development and Function. Front Immunol 2021; 12:703527. [PMID: 34276699 PMCID: PMC8281303 DOI: 10.3389/fimmu.2021.703527] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 06/11/2021] [Indexed: 12/01/2022] Open
Abstract
Intercellular signaling molecules such as cytokines and their receptors enable immune cells to communicate with one another and their surrounding microenvironments. Emerging evidence suggests that the same signaling pathways that regulate inflammatory responses to injury and disease outside of the brain also play powerful roles in brain development, plasticity, and function. These observations raise the question of how the same signaling molecules can play such distinct roles in peripheral tissues compared to the central nervous system, a system previously thought to be largely protected from inflammatory signaling. Here, we review evidence that the specialized roles of immune signaling molecules such as cytokines in the brain are to a large extent shaped by neural activity, a key feature of the brain that reflects active communication between neurons at synapses. We discuss the known mechanisms through which microglia, the resident immune cells of the brain, respond to increases and decreases in activity by engaging classical inflammatory signaling cascades to assemble, remodel, and eliminate synapses across the lifespan. We integrate evidence from (1) in vivo imaging studies of microglia-neuron interactions, (2) developmental studies across multiple neural circuits, and (3) molecular studies of activity-dependent gene expression in microglia and neurons to highlight the specific roles of activity in defining immune pathway function in the brain. Given that the repurposing of signaling pathways across different tissues may be an important evolutionary strategy to overcome the limited size of the genome, understanding how cytokine function is established and maintained in the brain could lead to key insights into neurological health and disease.
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Affiliation(s)
| | | | - Lucas Cheadle
- Neuroscience Department, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, United States
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58
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De Schepper S, Crowley G, Hong S. Understanding microglial diversity and implications for neuronal function in health and disease. Dev Neurobiol 2021; 81:507-523. [PMID: 32757416 PMCID: PMC8438703 DOI: 10.1002/dneu.22777] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 06/21/2020] [Accepted: 07/31/2020] [Indexed: 12/22/2022]
Abstract
Genetic data implicate microglia as central players in brain health and disease, urging the need to better understand what microglia do in the brain. Microglia are critical partners in neuronal wiring and function during development and disease. Emerging literature suggests that microglia have diverse functional roles, raising the intriguing question of which functions of microglia become impaired in disease to undermine proper neuronal function. It is also becoming increasingly clear that microglia exist in heterogeneous cell states. Microglial cell states appear context-dependent, that is, age, sex, location, and health of their microenvironment; these are further influenced by external signaling factors including gut microbiota and lipid metabolites. These data altogether suggest that microglia exist in functional clusters that impact, and are impacted by, surrounding neuronal microenvironment. However, we still lack understanding of how we can translate microglia cell states into function. Here, we summarize the state-of-the-art on the diverse functions of microglia in relation to neuronal health. Then, we discuss heterogeneity during developing, healthy adult and diseased brains, and whether this may be predetermined by origin and/or regulated by local milieu. Finally, we propose that it is critical to gain high-resolution functional discernment into microglia-neuron interactions while preserving the spatial architecture of the tissue. Such insight will reveal specific targets for biomarker and therapeutic development toward microglia-neuron crosstalk in disease.
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Affiliation(s)
| | - Gerard Crowley
- UK Dementia Research InstituteUniversity College LondonLondonUK
| | - Soyon Hong
- UK Dementia Research InstituteUniversity College LondonLondonUK
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59
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Xi H, Tao T, Zhang R, Xue X, Zhu Y, Liu J, Xin X, Zeng X. The 2-(2-benzofuranyl)-2-imidazoline provides neuroprotection against focal cerebral ischemia-reperfusion injury in diabetic rats: Influence of microglia and possible mechanisms of action. Brain Res Bull 2021; 174:230-239. [PMID: 34175385 DOI: 10.1016/j.brainresbull.2021.06.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 06/19/2021] [Accepted: 06/21/2021] [Indexed: 01/16/2023]
Abstract
Increased microglial NADPH oxidase (NOX2) production may make an important contribution to the increased incidence and severity of ischemic stroke associated with diabetes. Imidazoline receptors are closely associated with neuroprotection, but the neuroprotective effects of the selective I2-imidazoline receptor ligand 2-(2-benzofuranyl)-2-imidazoline (2BFI) in diabetes has not been established. The effect of 2BFI on microglial NOX2 production was investigated using a co-culture of neurons and microglia, and the effect on cerebral ischemia-reperfusion (IR) injury was determined in diabetic rats. Garcia neurological scores, brain infarct volumes, brain water content, TUNEL staining, blood-brain barrier, and immunofluorescent labeling for microglia were evaluated. Western blots were used to determine gp91phox and Tyr1472 expression. Anti-inflammatory cytokine (IL-10) and inflammatory cytokine secretion was determined using ELISA kits. The brain infarct volumes, TUNEL-positive neurons, expression of microglia, brain water content, blood-brain barrier structure damage, and gp91phox and Tyr1472 expression were increased, the Garcia neurological scores were significantly decreased in the IR group, and 2BFI relieved these alterations. The IL-10 concentration was increased in the IR group; 2BFI significantly improved this increase. The neuron apoptosis and necrosis rates, and production of reactive oxygen species (ROS) and inflammatory cytokines, including IL-6, IL-8, TNF-α, and 8-iso-PGF2α, were significantly increased by high glucose stimulation combined with oxygen-glucose deprivation treatment, which were inhibited by 2BFI. The 2BFI ameliorated cerebral ischemia-reperfusion injury in diabetes and decreased neuron death in an in vitro model. The mechanism underlying these findings may be related to the decreased production of inflammatory factors and reactive oxygen species from microglia.
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Affiliation(s)
- Hongjie Xi
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
| | - Tao Tao
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
| | - Ruru Zhang
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
| | - Xinxin Xue
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
| | - Yana Zhu
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
| | - Jiuyang Liu
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
| | - Xianyi Xin
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
| | - Xianzhang Zeng
- Department of Anesthesiology, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
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60
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van Olst L, Rodriguez-Mogeda C, Picon C, Kiljan S, James RE, Kamermans A, van der Pol SMA, Knoop L, Michailidou I, Drost E, Franssen M, Schenk GJ, Geurts JJG, Amor S, Mazarakis ND, van Horssen J, de Vries HE, Reynolds R, Witte ME. Meningeal inflammation in multiple sclerosis induces phenotypic changes in cortical microglia that differentially associate with neurodegeneration. Acta Neuropathol 2021; 141:881-899. [PMID: 33779783 PMCID: PMC8113309 DOI: 10.1007/s00401-021-02293-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 02/15/2021] [Accepted: 03/03/2021] [Indexed: 12/21/2022]
Abstract
Meningeal inflammation strongly associates with demyelination and neuronal loss in the underlying cortex of progressive MS patients, thereby contributing significantly to clinical disability. However, the pathological mechanisms of meningeal inflammation-induced cortical pathology are still largely elusive. By extensive analysis of cortical microglia in post-mortem progressive MS tissue, we identified cortical areas with two MS-specific microglial populations, termed MS1 and MS2 cortex. The microglial population in MS1 cortex was characterized by a higher density and increased expression of the activation markers HLA class II and CD68, whereas microglia in MS2 cortex showed increased morphological complexity and loss of P2Y12 and TMEM119 expression. Interestingly, both populations associated with inflammation of the overlying meninges and were time-dependently replicated in an in vivo rat model for progressive MS-like chronic meningeal inflammation. In this recently developed animal model, cortical microglia at 1-month post-induction of experimental meningeal inflammation resembled microglia in MS1 cortex, and microglia at 2 months post-induction acquired a MS2-like phenotype. Furthermore, we observed that MS1 microglia in both MS cortex and the animal model were found closely apposing neuronal cell bodies and to mediate pre-synaptic displacement and phagocytosis, which coincided with a relative sparing of neurons. In contrast, microglia in MS2 cortex were not involved in these synaptic alterations, but instead associated with substantial neuronal loss. Taken together, our results show that in response to meningeal inflammation, microglia acquire two distinct phenotypes that differentially associate with neurodegeneration in the progressive MS cortex. Furthermore, our in vivo data suggests that microglia initially protect neurons from meningeal inflammation-induced cell death by removing pre-synapses from the neuronal soma, but eventually lose these protective properties contributing to neuronal loss.
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Affiliation(s)
- Lynn van Olst
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Carla Rodriguez-Mogeda
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Carmen Picon
- Division of Neuroscience, Department of Brain Sciences, Imperial College London, Hammersmith Hospital Campus, Burlington Danes Building, Du Cane Road, London, W12 0NN, UK
| | - Svenja Kiljan
- Department of Anatomy and Neurosciences, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Rachel E James
- Division of Neuroscience, Department of Brain Sciences, Imperial College London, Hammersmith Hospital Campus, Burlington Danes Building, Du Cane Road, London, W12 0NN, UK
| | - Alwin Kamermans
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Susanne M A van der Pol
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Lydian Knoop
- Department of Pathology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Iliana Michailidou
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
| | - Evelien Drost
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Marc Franssen
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Geert J Schenk
- Department of Anatomy and Neurosciences, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Jeroen J G Geurts
- Department of Anatomy and Neurosciences, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Sandra Amor
- Department of Pathology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Nicholas D Mazarakis
- Division of Neuroscience, Department of Brain Sciences, Imperial College London, Hammersmith Hospital Campus, Burlington Danes Building, Du Cane Road, London, W12 0NN, UK
| | - Jack van Horssen
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
| | - Helga E de Vries
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands
| | - Richard Reynolds
- Division of Neuroscience, Department of Brain Sciences, Imperial College London, Hammersmith Hospital Campus, Burlington Danes Building, Du Cane Road, London, W12 0NN, UK.
- Centre for Molecular Neuropathology, LKC School of Medicine, Nanyang Technological University, Singapore, Singapore.
| | - Maarten E Witte
- Department of Molecular Cell Biology and Immunology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands.
- Department of Pathology, Amsterdam UMC, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam, Netherlands.
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61
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Mendes MS, Majewska AK. An overview of microglia ontogeny and maturation in the homeostatic and pathological brain. Eur J Neurosci 2021; 53:3525-3547. [PMID: 33835613 PMCID: PMC8225243 DOI: 10.1111/ejn.15225] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 03/17/2021] [Accepted: 04/01/2021] [Indexed: 12/21/2022]
Abstract
Microglia are the resident immune cells of the central nervous system (CNS) and are increasingly recognized as critical players in development, brain homeostasis, and disease pathogenesis. The lifespan, maintenance, proliferation, and turnover of microglia are important factors that regulate microglial behavior and affect their roles in the CNS. However, emerging evidence suggests that microglia are morphologically and phenotypically distinct in different brain areas, at different ages, and during disease. Ongoing research focuses on understanding how microglia acquire specific phenotypes in response to extrinsic cues in the environment and how phenotypes are specified by intrinsic properties of different populations of microglia. With the development of pharmacological and genetic tools that allow the investigation of microglia in vivo, there have been considerable advances in understanding molecular signatures of both homeostatic microglia and those reacting to injury and disease. Here, we review the master gene regulators that define microglia as well as discuss the evidence that microglia are heterogeneous and fall into distinct clusters that display specific intrinsic properties and perform unique tasks in different settings. Taken together, the information presented supports the idea that microglia morphology and transcriptional heterogeneity should be considered when studying the complex nature of microglia and their roles in brain health and disease.
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Affiliation(s)
- Monique S Mendes
- Department of Neuroscience, University of Rochester Medical Center, Rochester, NY, USA
| | - Ania K Majewska
- Department of Neuroscience, University of Rochester Medical Center, Rochester, NY, USA
- Center for Visual Science, University of Rochester, Rochester, NY, USA
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62
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Hippocampal subfield transcriptome analysis in schizophrenia psychosis. Mol Psychiatry 2021; 26:2577-2589. [PMID: 32152472 DOI: 10.1038/s41380-020-0696-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 01/16/2020] [Accepted: 02/19/2020] [Indexed: 12/18/2022]
Abstract
We have previously demonstrated functional and molecular changes in hippocampal subfields in individuals with schizophrenia (SZ) psychosis associated with hippocampal excitability. In this study, we use RNA-seq and assess global transcriptome changes in the hippocampal subfields, DG, CA3, and CA1 from individuals with SZ psychosis and controls to elucidate subfield-relevant molecular changes. We also examine changes in gene expression due to antipsychotic medication in the hippocampal subfields from our SZ ON- and OFF-antipsychotic medication cohort. We identify unique subfield-specific molecular profiles in schizophrenia postmortem samples compared with controls, implicating astrocytes in DG, immune mechanisms in CA3, and synaptic scaling in CA1. We show a unique pattern of subfield-specific effects by antipsychotic medication on gene expression levels with scant overlap of genes differentially expressed by SZ disease effect versus medication effect. These hippocampal subfield changes serve to confirm and extend our previous model of SZ and can explain the lack of full efficacy of conventional antipsychotic medication on SZ symptomatology. With future characterization using single-cell studies, the identified distinct molecular profiles of the DG, CA3, and CA1 in SZ psychosis may serve to identify further potential hippocampal-based therapeutic targets.
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63
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Hall S, Deurveilher S, Robertson GS, Semba K. Homeostatic state of microglia in a rat model of chronic sleep restriction. Sleep 2021; 43:5849344. [PMID: 32474610 DOI: 10.1093/sleep/zsaa108] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 05/13/2020] [Indexed: 12/29/2022] Open
Abstract
Chronic sleep restriction (CSR) negatively impacts brain functions. Whether microglia, the brain's resident immune cells, play any role is unknown. We studied microglia responses to CSR using a rat model featuring slowly rotating wheels (3 h on/1 h off), which was previously shown to induce both homeostatic and adaptive responses in sleep and attention. Adult male rats were sleep restricted for 27 or 99 h. Control rats were housed in locked wheels. After 27 and/or 99 h of CSR, the number of cells immunoreactive for the microglia marker ionized calcium-binding adaptor molecule-1 (Iba1) and the density of Iba1 immunoreactivity were increased in 4/10 brain regions involved in sleep/wake regulation and cognition, including the prelimbic cortex, central amygdala, perifornical lateral hypothalamic area, and dorsal raphe nucleus. CSR neither induced mitosis in microglia (assessed with bromodeoxyuridine) nor impaired blood-brain barrier permeability (assessed with Evans Blue). Microglia appeared ramified in all treatment groups and, when examined quantitatively in the prelimbic cortex, their morphology was not affected by CSR. After 27 h, but not 99 h, of CSR, mRNA levels of the anti-inflammatory cytokine interleukin-10 were increased in the frontal cortex. Pro-inflammatory cytokine mRNA levels (tumor necrosis factor-α, interleukin-1β, and interleukin-6) were unchanged. Furthermore, cortical microglia were not immunoreactive for several pro- and anti-inflammatory markers tested, but were immunoreactive for the purinergic P2Y12 receptor. These results suggest that microglia respond to CSR while remaining in a physiological state and may contribute to the previously reported homeostatic and adaptive responses to CSR.
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Affiliation(s)
- Shannon Hall
- Department of Medical Neuroscience, Dalhousie University, Halifax, NS, Canada
| | - Samüel Deurveilher
- Department of Medical Neuroscience, Dalhousie University, Halifax, NS, Canada
| | - George S Robertson
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada.,Department of Psychiatry, Dalhousie University, Halifax, NS, Canada
| | - Kazue Semba
- Department of Medical Neuroscience, Dalhousie University, Halifax, NS, Canada.,Department of Psychiatry, Dalhousie University, Halifax, NS, Canada.,Department of Psychology & Neuroscience, Dalhousie University, Halifax, NS, Canada
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64
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Ernest James Phillips T, Maguire E. Phosphoinositides: Roles in the Development of Microglial-Mediated Neuroinflammation and Neurodegeneration. Front Cell Neurosci 2021; 15:652593. [PMID: 33841102 PMCID: PMC8032904 DOI: 10.3389/fncel.2021.652593] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 03/08/2021] [Indexed: 12/11/2022] Open
Abstract
Microglia are increasingly recognized as vital players in the pathology of a variety of neurodegenerative conditions including Alzheimer’s (AD) and Parkinson’s (PD) disease. While microglia have a protective role in the brain, their dysfunction can lead to neuroinflammation and contributes to disease progression. Also, a growing body of literature highlights the seven phosphoinositides, or PIPs, as key players in the regulation of microglial-mediated neuroinflammation. These small signaling lipids are phosphorylated derivates of phosphatidylinositol, are enriched in the brain, and have well-established roles in both homeostasis and disease.Disrupted PIP levels and signaling has been detected in a variety of dementias. Moreover, many known AD disease modifiers identified via genetic studies are expressed in microglia and are involved in phospholipid metabolism. One of these, the enzyme PLCγ2 that hydrolyzes the PIP species PI(4,5)P2, displays altered expression in AD and PD and is currently being investigated as a potential therapeutic target.Perhaps unsurprisingly, neurodegenerative conditions exhibiting PIP dyshomeostasis also tend to show alterations in aspects of microglial function regulated by these lipids. In particular, phosphoinositides regulate the activities of proteins and enzymes required for endocytosis, toll-like receptor signaling, purinergic signaling, chemotaxis, and migration, all of which are affected in a variety of neurodegenerative conditions. These functions are crucial to allow microglia to adequately survey the brain and respond appropriately to invading pathogens and other abnormalities, including misfolded proteins. AD and PD therapies are being developed to target many of the above pathways, and although not yet investigated, simultaneous PIP manipulation might enhance the beneficial effects observed. Currently, only limited therapeutics are available for dementia, and although these show some benefits for symptom severity and progression, they are far from curative. Given the importance of microglia and PIPs in dementia development, this review summarizes current research and asks whether we can exploit this information to design more targeted, or perhaps combined, dementia therapeutics. More work is needed to fully characterize the pathways discussed in this review, but given the strength of the current literature, insights in this area could be invaluable for the future of neurodegenerative disease research.
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Affiliation(s)
| | - Emily Maguire
- UK Dementia Research Institute at Cardiff University, Cardiff, United Kingdom
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65
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Purinergic signaling in nervous system health and disease: Focus on pannexin 1. Pharmacol Ther 2021; 225:107840. [PMID: 33753132 DOI: 10.1016/j.pharmthera.2021.107840] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2021] [Indexed: 02/06/2023]
Abstract
Purinergic signaling encompasses the cycle of adenosine 5' triphosphate (ATP) release and its metabolism into nucleotide and nucleoside derivatives, the direct release of nucleosides, and subsequent receptor-triggered downstream intracellular pathways. Since the discovery of nerve terminal and glial ATP release into the neuropil, purinergic signaling has been implicated in the modulation of nervous system development, function, and disease. In this review, we detail our current understanding of the roles of the pannexin 1 (PANX1) ATP-release channel in neuronal development and plasticity, glial signaling, and neuron-glial-immune interactions. We additionally provide an overview of PANX1 structure, activation, and permeability to orientate readers and highlight recent research developments. We identify areas of convergence between PANX1 and purinergic receptor actions. Additional highlights include data on PANX1's participation in the pathophysiology of nervous system developmental, degenerative, and inflammatory disorders. Our aim in combining this knowledge is to facilitate the movement of our current understanding of PANX1 in the context of other nervous system purinergic signaling mechanisms one step closer to clinical translation.
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66
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Masuda T, Sankowski R, Staszewski O, Prinz M. Microglia Heterogeneity in the Single-Cell Era. Cell Rep 2021; 30:1271-1281. [PMID: 32023447 DOI: 10.1016/j.celrep.2020.01.010] [Citation(s) in RCA: 374] [Impact Index Per Article: 124.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 10/19/2019] [Accepted: 01/02/2020] [Indexed: 12/30/2022] Open
Abstract
Microglia are resident immune cells in the central nervous system (CNS) that are capable of carrying out prominent and various functions during development and adulthood under both homeostatic and disease conditions. Although microglia are traditionally thought to be heterogeneous populations, which potentially allows them to achieve a wide range of responses to environmental changes for the maintenance of CNS homeostasis, a lack of unbiased and high-throughput methods to assess microglia heterogeneity has prevented the study of spatially and temporally distributed microglia subsets. The recent emergence of novel single-cell techniques, such as cytometry by time-of-flight mass spectrometry (CyTOF) and single-cell RNA sequencing, enabled scientists to overcome such limitations and reveal the surprising context-dependent heterogeneity of microglia. In this review, we summarize the current knowledge about the spatial, temporal, and functional diversity of microglia during development, homeostasis, and disease in mice and humans.
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Affiliation(s)
- Takahiro Masuda
- Institute of Neuropathology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Roman Sankowski
- Institute of Neuropathology, Faculty of Medicine, University of Freiburg, Freiburg, Germany; Berta-Ottenstein-Programme for Clinician Scientists, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ori Staszewski
- Institute of Neuropathology, Faculty of Medicine, University of Freiburg, Freiburg, Germany; Berta-Ottenstein-Programme for Clinician Scientists, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marco Prinz
- Institute of Neuropathology, Faculty of Medicine, University of Freiburg, Freiburg, Germany; Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany; Center for Basics in NeuroModulation (NeuroModulBasics), Faculty of Medicine, University of Freiburg, Freiburg, Germany.
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67
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Andoh M, Koyama R. Microglia regulate synaptic development and plasticity. Dev Neurobiol 2021; 81:568-590. [PMID: 33583110 PMCID: PMC8451802 DOI: 10.1002/dneu.22814] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 01/13/2021] [Accepted: 02/09/2021] [Indexed: 12/12/2022]
Abstract
Synapses are fundamental structures of neural circuits that transmit information between neurons. Thus, the process of neural circuit formation via proper synaptic connections shapes the basis of brain functions and animal behavior. Synapses continuously undergo repeated formation and elimination throughout the lifetime of an organism, reflecting the dynamics of neural circuit function. The structural transformation of synapses has been described mainly in relation to neural activity-dependent strengthening and weakening of synaptic functions, that is, functional plasticity of synapses. An increasing number of studies have unveiled the roles of microglia, brain-resident immune cells that survey the brain parenchyma with highly motile processes, in synapse formation and elimination as well as in regulating synaptic function. Over the past 15 years, the molecular mechanisms underlying microglia-dependent regulation of synaptic plasticity have been thoroughly studied, and researchers have reported that the disruption of microglia-dependent regulation causes synaptic dysfunction that leads to brain diseases. In this review, we will broadly introduce studies that report the roles of microglia in synaptic plasticity and the possible underlying molecular mechanisms.
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Affiliation(s)
- Megumi Andoh
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
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68
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Andoh M, Koyama R. Assessing Microglial Dynamics by Live Imaging. Front Immunol 2021; 12:617564. [PMID: 33763064 PMCID: PMC7982483 DOI: 10.3389/fimmu.2021.617564] [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: 10/15/2020] [Accepted: 02/16/2021] [Indexed: 12/13/2022] Open
Abstract
Microglia are highly dynamic in the brain in terms of their ability to migrate, proliferate, and phagocytose over the course of an individual's life. Real-time imaging is a useful tool to examine how microglial behavior is regulated and how it affects the surrounding environment. However, microglia are sensitive to environmental stimuli, so they possibly change their state during live imaging in vivo, mainly due to surgical damage, and in vitro due to various effects associated with culture conditions. Therefore, it is difficult to perform live imaging without compromising the properties of the microglia under physiological conditions. To overcome this barrier, various experimental conditions have been developed; recently, it has become possible to perform live imaging of so-called surveillant microglia in vivo, ex vivo, and in vitro, although there are various limitations. Now, we can choose in vivo, ex vivo, or in vitro live imaging systems according to the research objective. In this review, we discuss the advantages and disadvantages of each experimental system and outline the physiological significance and molecular mechanisms of microglial behavior that have been elucidated by live imaging.
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Affiliation(s)
- Megumi Andoh
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
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69
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Gonçalves de Andrade E, Šimončičová E, Carrier M, Vecchiarelli HA, Robert MÈ, Tremblay MÈ. Microglia Fighting for Neurological and Mental Health: On the Central Nervous System Frontline of COVID-19 Pandemic. Front Cell Neurosci 2021; 15:647378. [PMID: 33737867 PMCID: PMC7961561 DOI: 10.3389/fncel.2021.647378] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 01/15/2021] [Indexed: 12/15/2022] Open
Abstract
Coronavirus disease 2019 (COVID-19) is marked by cardio-respiratory alterations, with increasing reports also indicating neurological and psychiatric symptoms in infected individuals. During COVID-19 pathology, the central nervous system (CNS) is possibly affected by direct severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) invasion, exaggerated systemic inflammatory responses, or hypoxia. Psychosocial stress imposed by the pandemic further affects the CNS of COVID-19 patients, but also the non-infected population, potentially contributing to the emergence or exacerbation of various neurological or mental health disorders. Microglia are central players of the CNS homeostasis maintenance and inflammatory response that exert their crucial functions in coordination with other CNS cells. During homeostatic challenges to the brain parenchyma, microglia modify their density, morphology, and molecular signature, resulting in the adjustment of their functions. In this review, we discuss how microglia may be involved in the neuroprotective and neurotoxic responses against CNS insults deriving from COVID-19. We examine how these responses may explain, at least partially, the neurological and psychiatric manifestations reported in COVID-19 patients and the general population. Furthermore, we consider how microglia might contribute to increased CNS vulnerability in certain groups, such as aged individuals and people with pre-existing conditions.
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Affiliation(s)
| | - Eva Šimončičová
- Division of Medical Science, University of Victoria, Victoria, BC, Canada
| | - Micaël Carrier
- Division of Medical Science, University of Victoria, Victoria, BC, Canada.,Axe Neurosciences, Centre de Recherche du CHU de Québec, Université de Laval, Québec City, QC, Canada
| | | | - Marie-Ève Robert
- Axe Neurosciences, Centre de Recherche du CHU de Québec, Université de Laval, Québec City, QC, Canada
| | - Marie-Ève Tremblay
- Division of Medical Science, University of Victoria, Victoria, BC, Canada.,Axe Neurosciences, Centre de Recherche du CHU de Québec, Université de Laval, Québec City, QC, Canada.,Neurology and Neurosurgery Department, McGill University, Montréal, QC, Canada.,Department of Molecular Medicine, Université de Laval, Québec City, QC, Canada.,Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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70
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Lowery RL, Mendes MS, Sanders BT, Murphy AJ, Whitelaw BS, Lamantia CE, Majewska AK. Loss of P2Y12 Has Behavioral Effects in the Adult Mouse. Int J Mol Sci 2021; 22:ijms22041868. [PMID: 33668516 PMCID: PMC7918634 DOI: 10.3390/ijms22041868] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 02/05/2021] [Accepted: 02/09/2021] [Indexed: 12/17/2022] Open
Abstract
While microglia have been established as critical mediators of synaptic plasticity, the molecular signals underlying this process are still being uncovered. Increasing evidence suggests that microglia utilize these signals in a temporally and regionally heterogeneous manner. Subsequently, it is necessary to understand the conditions under which different molecular signals are employed by microglia to mediate the physiological process of synaptic remodeling in development and adulthood. While the microglial purinergic receptor P2Y12 is required for ocular dominance plasticity, an adolescent form of experience-dependent plasticity, it remains unknown whether P2Y12 functions in other forms of plasticity at different developmental time points or in different brain regions. Using a combination of ex vivo characterization and behavioral testing, we examined how the loss of P2Y12 affects developmental processes and behavioral performance in adulthood in mice. We found P2Y12 was not required for an early form of plasticity in the developing visual thalamus and did not affect microglial migration into barrels in the developing somatosensory cortex. In adult mice, however, the loss of P2Y12 resulted in alterations in recognition and social memory, as well as anxiety-like behaviors, suggesting that while P2Y12 is not a universal regulator of synaptic plasticity, the loss of P2Y12 is sufficient to cause functional defects.
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Affiliation(s)
- Rebecca L. Lowery
- Center for Visual Science, Department of Neuroscience, University of Rochester, Rochester, NY 14642, USA; (R.L.L.); (M.S.M.); (B.T.S.); (A.J.M.); (B.S.W.); (C.E.L.)
| | - Monique S. Mendes
- Center for Visual Science, Department of Neuroscience, University of Rochester, Rochester, NY 14642, USA; (R.L.L.); (M.S.M.); (B.T.S.); (A.J.M.); (B.S.W.); (C.E.L.)
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Brandon T. Sanders
- Center for Visual Science, Department of Neuroscience, University of Rochester, Rochester, NY 14642, USA; (R.L.L.); (M.S.M.); (B.T.S.); (A.J.M.); (B.S.W.); (C.E.L.)
| | - Allison J. Murphy
- Center for Visual Science, Department of Neuroscience, University of Rochester, Rochester, NY 14642, USA; (R.L.L.); (M.S.M.); (B.T.S.); (A.J.M.); (B.S.W.); (C.E.L.)
| | - Brendan S. Whitelaw
- Center for Visual Science, Department of Neuroscience, University of Rochester, Rochester, NY 14642, USA; (R.L.L.); (M.S.M.); (B.T.S.); (A.J.M.); (B.S.W.); (C.E.L.)
| | - Cassandra E. Lamantia
- Center for Visual Science, Department of Neuroscience, University of Rochester, Rochester, NY 14642, USA; (R.L.L.); (M.S.M.); (B.T.S.); (A.J.M.); (B.S.W.); (C.E.L.)
| | - Ania K. Majewska
- Center for Visual Science, Department of Neuroscience, University of Rochester, Rochester, NY 14642, USA; (R.L.L.); (M.S.M.); (B.T.S.); (A.J.M.); (B.S.W.); (C.E.L.)
- Correspondence: ; Tel.: +1-585-276-2254
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71
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Picard K, St-Pierre MK, Vecchiarelli HA, Bordeleau M, Tremblay MÈ. Neuroendocrine, neuroinflammatory and pathological outcomes of chronic stress: A story of microglial remodeling. Neurochem Int 2021; 145:104987. [PMID: 33587954 DOI: 10.1016/j.neuint.2021.104987] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 02/07/2021] [Accepted: 02/08/2021] [Indexed: 02/07/2023]
Abstract
Microglia, the resident macrophage cells of the central nervous system (CNS), are involved in a myriad of processes required to maintain CNS homeostasis. These cells are dynamic and can adapt their phenotype and functions to the physiological needs of the organism. Microglia rapidly respond to changes occurring in their microenvironment, such as the ones taking place during stress. While stress can be beneficial for the organism to adapt to a situation, it can become highly detrimental when it turns chronic. Microglial response to prolonged stress may lead to an alteration of their beneficial physiological functions, becoming either maladaptive or pro-inflammatory. In this review, we aim to summarize the effects of chronic stress exerted on microglia through the neuroendocrine system and inflammation at adulthood. We also discuss how these effects of chronic stress could contribute to microglial involvement in neuropsychiatric and sleep disorders, as well as neurodegenerative diseases.
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Affiliation(s)
- Katherine Picard
- Axe Neurosciences, Centre de recherche du CHU de Québec-Université Laval, Québec, QC, Canada; Division of Medical Sciences, University of Victoria, Victoria, BC, Canada; Department of Molecular Medicine, Faculty of Medicine, Université Laval, Québec, QC, Canada
| | - Marie-Kim St-Pierre
- Axe Neurosciences, Centre de recherche du CHU de Québec-Université Laval, Québec, QC, Canada; Division of Medical Sciences, University of Victoria, Victoria, BC, Canada; Department of Molecular Medicine, Faculty of Medicine, Université Laval, Québec, QC, Canada
| | | | - Maude Bordeleau
- Axe Neurosciences, Centre de recherche du CHU de Québec-Université Laval, Québec, QC, Canada; Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
| | - Marie-Ève Tremblay
- Axe Neurosciences, Centre de recherche du CHU de Québec-Université Laval, Québec, QC, Canada; Division of Medical Sciences, University of Victoria, Victoria, BC, Canada; Department of Molecular Medicine, Faculty of Medicine, Université Laval, Québec, QC, Canada; Neurology and Neurosurgery Department, McGill University, Montréal, QC, Canada; Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada.
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72
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Gamma frequency activation of inhibitory neurons in the acute phase after stroke attenuates vascular and behavioral dysfunction. Cell Rep 2021; 34:108696. [PMID: 33535035 DOI: 10.1016/j.celrep.2021.108696] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 11/06/2020] [Accepted: 01/06/2021] [Indexed: 11/24/2022] Open
Abstract
Alterations in gamma oscillations occur in several neurological disorders, and the entrainment of gamma oscillations has been recently proposed as a treatment for neurodegenerative disease. Optogenetic stimulation enhances recovery in models of stroke when applied weeks after injury; however, the benefits of acute brain stimulation have not been investigated. Here, we report beneficial effects of gamma-frequency modulation in the acute phase, within 1 h, after stroke. Transgenic VGAT-ChR2 mice are subject to awake photothrombotic stroke in an area encompassing the forelimb sensory and motor cortex. Optogenetic stimulation at 40 Hz in the peri-infarct zone recovers neuronal activity 24 h after stroke in motor and parietal association areas, as well as blood flow over the first week after stroke. Stimulation significantly reduces lesion volume and improves motor function. Our results suggest that acute-phase modulation of cortical oscillatory dynamics may serve as a target for neuroprotection against stroke.
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73
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Changing Functional Signatures of Microglia along the Axis of Brain Aging. Int J Mol Sci 2021; 22:ijms22031091. [PMID: 33499206 PMCID: PMC7865559 DOI: 10.3390/ijms22031091] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 12/19/2022] Open
Abstract
Microglia, the innate immune cells of the brain, are commonly perceived as resident macrophages of the central nervous system (CNS). This definition, however, requires further specification, as under healthy homeostatic conditions, neither morphological nor functional properties of microglia mirror those of classical macrophages. Indeed, microglia adapt exceptionally well to their microenvironment, becoming a legitimate member of the cellular brain architecture. The ramified or surveillant microglia in the young adult brain are characterized by specific morphology (small cell body and long, thin motile processes) and physiology (a unique pattern of Ca2+ signaling, responsiveness to various neurotransmitters and hormones, in addition to classic “immune” stimuli). Their numerous physiological functions far exceed and complement their immune capabilities. As the brain ages, the respective changes in the microglial microenvironment impact the functional properties of microglia, triggering further rounds of adaptation. In this review, we discuss the recent data showing how functional properties of microglia adapt to age-related changes in brain parenchyma in a sex-specific manner, with a specific focus on early changes occurring at middle age as well as some strategies counteracting the aging of microglia.
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74
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Lin SS, Tang Y, Illes P, Verkhratsky A. The Safeguarding Microglia: Central Role for P2Y 12 Receptors. Front Pharmacol 2021; 11:627760. [PMID: 33519493 PMCID: PMC7840491 DOI: 10.3389/fphar.2020.627760] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 11/30/2020] [Indexed: 12/14/2022] Open
Affiliation(s)
- Si-Si Lin
- Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- International Collaborative Center on Big Science Plan for Purine Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Yong Tang
- Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- International Collaborative Center on Big Science Plan for Purine Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Peter Illes
- Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- International Collaborative Center on Big Science Plan for Purine Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Rudolf Boehm Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
| | - Alexei Verkhratsky
- International Collaborative Center on Big Science Plan for Purine Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
- Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
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75
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Gagne C, Piot A, Brake WG. Depression, Estrogens, and Neuroinflammation: A Preclinical Review of Ketamine Treatment for Mood Disorders in Women. Front Psychiatry 2021; 12:797577. [PMID: 35115970 PMCID: PMC8804176 DOI: 10.3389/fpsyt.2021.797577] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 12/24/2021] [Indexed: 12/11/2022] Open
Abstract
Ketamine has been shown to acutely and rapidly ameliorate depression symptoms and suicidality. Given that women suffer from major depression at twice the rate of men, it is important to understand how ketamine works in the female brain. This review explores three themes. First, it examines our current understanding of the etiology of depression in women. Second, it examines preclinical research on ketamine's antidepressant effects at a neurobiological level as well as how ovarian hormones present a unique challenge in interpreting these findings. Lastly, the neuroinflammatory hypothesis of depression is highlighted to help better understand how ovarian hormones might interact with ketamine in the female brain.
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Affiliation(s)
- Collin Gagne
- Department of Psychology, Centre for Studies in Behavioural Neurobiology Concordia University, Montreal, QC, Canada
| | - Alexandre Piot
- Department of Psychology, Centre for Studies in Behavioural Neurobiology Concordia University, Montreal, QC, Canada
| | - Wayne G Brake
- Department of Psychology, Centre for Studies in Behavioural Neurobiology Concordia University, Montreal, QC, Canada
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76
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Umpierre AD, Wu LJ. How microglia sense and regulate neuronal activity. Glia 2020; 69:1637-1653. [PMID: 33369790 DOI: 10.1002/glia.23961] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 12/16/2022]
Abstract
Microglia are innate immune cells of the central nervous system that sense extracellular cues. Brain injuries, inflammation, and pathology evoke dynamic structural responses in microglia, altering their morphology and motility. The dynamic motility of microglia is hypothesized to be a critical first step in sensing local alterations and engaging in pattern-specific responses. Alongside their pathological responses, microglia also sense and regulate neuronal activity. In this review, we consider the extracellular molecules, receptors, and mechanisms that allow microglia to sense neuronal activity changes under both hypoactivity and hyperactivity. We also highlight emerging in vivo evidence that microglia regulate neuronal activity, ranging from physiological to pathophysiological conditions. In addition, we discuss the emerging role of calcium signaling in microglial responses to the extracellular environment. The dynamic function of microglia in monitoring and influencing neuronal activity may be critical for brain homeostasis and circuit modification in health and disease.
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Affiliation(s)
| | - Long-Jun Wu
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, USA.,Department of Immunology, Mayo Clinic, Rochester, Minnesota, USA
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77
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Cserép C, Pósfai B, Dénes Á. Shaping Neuronal Fate: Functional Heterogeneity of Direct Microglia-Neuron Interactions. Neuron 2020; 109:222-240. [PMID: 33271068 DOI: 10.1016/j.neuron.2020.11.007] [Citation(s) in RCA: 110] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/13/2020] [Accepted: 11/06/2020] [Indexed: 12/11/2022]
Abstract
The functional contribution of microglia to normal brain development, healthy brain function, and neurological disorders is increasingly recognized. However, until recently, the nature of intercellular interactions mediating these effects remained largely unclear. Recent findings show microglia establishing direct contact with different compartments of neurons. Although communication between microglia and neurons involves intermediate cells and soluble factors, direct membrane contacts enable a more precisely regulated, dynamic, and highly effective form of interaction for fine-tuning neuronal responses and fate. Here, we summarize the known ultrastructural, molecular, and functional features of direct microglia-neuron interactions and their roles in brain disease.
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Affiliation(s)
- Csaba Cserép
- "Momentum" Laboratory of Neuroimmunology, Institute of Experimental Medicine, Szigony u. 43, 1083 Budapest, Hungary
| | - Balázs Pósfai
- "Momentum" Laboratory of Neuroimmunology, Institute of Experimental Medicine, Szigony u. 43, 1083 Budapest, Hungary; Szentágothai János Doctoral School of Neurosciences, Semmelweis University, Üllői út 26, 1085 Budapest, Hungary
| | - Ádám Dénes
- "Momentum" Laboratory of Neuroimmunology, Institute of Experimental Medicine, Szigony u. 43, 1083 Budapest, Hungary.
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78
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Purinergic signaling orchestrating neuron-glia communication. Pharmacol Res 2020; 162:105253. [PMID: 33080321 DOI: 10.1016/j.phrs.2020.105253] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/29/2020] [Accepted: 10/09/2020] [Indexed: 12/12/2022]
Abstract
This review discusses the evidence supporting a role for ATP signaling (operated by P2X and P2Y receptors) and adenosine signaling (mainly operated by A1 and A2A receptors) in the crosstalk between neurons, astrocytes, microglia and oligodendrocytes. An initial emphasis will be given to the cooperation between adenosine receptors to sharpen information salience encoding across synapses. The interplay between ATP and adenosine signaling in the communication between astrocytes and neurons will then be presented in context of the integrative properties of the astrocytic syncytium, allowing to implement heterosynaptic depression processes in neuronal networks. The process of microglia 'activation' and its control by astrocytes and neurons will then be analyzed under the perspective of an interplay between different P2 receptors and adenosine A2A receptors. In spite of these indications of a prominent role of purinergic signaling in the bidirectional communication between neurons and glia, its therapeutical exploitation still awaits obtaining an integrated view of the spatio-temporal action of ATP signaling and adenosine signaling, clearly distinguishing the involvement of both purinergic signaling systems in the regulation of physiological processes and in the control of pathogenic-like responses upon brain dysfunction or damage.
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79
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Phosphoinositide-3-Kinase γ Is Not a Predominant Regulator of ATP-Dependent Directed Microglial Process Motility or Experience-Dependent Ocular Dominance Plasticity. eNeuro 2020; 7:ENEURO.0311-20.2020. [PMID: 33067365 PMCID: PMC7769883 DOI: 10.1523/eneuro.0311-20.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 09/16/2020] [Accepted: 10/09/2020] [Indexed: 12/18/2022] Open
Abstract
Microglia are dynamic cells whose extensive interactions with neurons and glia during development allow them to regulate neuronal development and function. The microglial P2Y12 receptor is crucial for microglial responsiveness to extracellular ATP and mediates numerous microglial functions, including ATP-dependent directional motility, microglia-neuron interactions, and experience-dependent synaptic plasticity. However, little is known about the downstream signaling effectors that mediate these diverse actions of P2Y12. Phosphoinositide-3-kinase γ (PI3Kγ), a lipid kinase activated downstream of Gi-protein-coupled receptors such as P2Y12, could translate localized extracellular ATP signals into directed microglial action and serve as a broad effector of P2Y12-dependent signaling. Here, we used pharmacological and genetic methods to manipulate P2Y12 and PI3Kγ signaling to determine whether inhibiting PI3Kγ phenocopied the loss of P2Y12 signaling in mouse microglia. While pan-inhibition of all PI3K activity substantially affected P2Y12-dependent microglial responses, our results suggest that PI3Kγ specifically is only a minor part of the P2Y12 signaling pathway. PI3Kγ was not required to maintain homeostatic microglial morphology or their dynamic surveillance in vivo Further, PI3Kγ was not strictly required for P2Y12-dependent microglial responses ex vivo or in vivo, although we did observe subtle deficits in the recruitment of microglial process toward sources of ATP. Finally, PI3Kγ was not required for ocular dominance plasticity, a P2Y12-dependent form of experience-dependent synaptic plasticity that occurs in the developing visual cortex. Overall, our results demonstrate that PI3Kγ is not the major mediator of P2Y12 function in microglia, but may have a role in amplifying or fine-tuning the chemotactic response.
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80
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Jia X, Gao Z, Hu H. Microglia in depression: current perspectives. SCIENCE CHINA-LIFE SCIENCES 2020; 64:911-925. [PMID: 33068286 DOI: 10.1007/s11427-020-1815-6] [Citation(s) in RCA: 120] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/09/2020] [Indexed: 12/11/2022]
Abstract
Major depressive disorder (MDD) is a prevalent psychiatric disease that involves malfunctions of different cell types in the brain. Accumulating studies started to reveal that microglia, the primary resident immune cells, play an important role in the development and progression of depression. Microglia respond to stress-triggered neuroinflammation, and through the release of proinflammatory cytokines and their metabolic products, microglia may modulate the function of neurons and astrocytes to regulate depression. In this review, we focused on the role of microglia in the etiology of depression. We discussed the dynamic states of microglia; the correlative and causal evidence of microglial abnormalities in depression; possible mechanisms of how microglia sense depression-related stress and modulate depression state; and how antidepressive therapies affect microglia. Understanding the role of microglia in depression may shed light on developing new treatment strategies to fight against this devastating mental illness.
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Affiliation(s)
- Xiaoning Jia
- Department of Psychiatry of First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310003, China.,The MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, 310012, China
| | - Zhihua Gao
- The MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, 310012, China. .,NHC and CAMS Key Laboratory of Medical Neurobiology, Mental Health Center, Zhejiang University, Hangzhou, 310058, China. .,Department of Neurobiology and Department of Neurology of Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310009, China.
| | - Hailan Hu
- Department of Psychiatry of First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310003, China. .,The MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, 310012, China. .,NHC and CAMS Key Laboratory of Medical Neurobiology, Mental Health Center, Zhejiang University, Hangzhou, 310058, China. .,Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, 510515, China. .,Fountain-Valley Institute for Life Sciences, Guangzhou, 510530, China. .,Research Units of Brain Mechanisms Underlying Emotion and Emotion disorders, Chinese Academy of Medical Sciences, Beijing, 100730, China.
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81
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Negative feedback control of neuronal activity by microglia. Nature 2020; 586:417-423. [PMID: 32999463 PMCID: PMC7577179 DOI: 10.1038/s41586-020-2777-8] [Citation(s) in RCA: 475] [Impact Index Per Article: 118.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 08/28/2020] [Indexed: 01/02/2023]
Abstract
Microglia, the brain’s resident macrophages, help to regulate brain function by removing dying neurons, pruning non-functional synapses, and producing ligands that support neuronal survival1. Here we show that microglia are also critical modulators of neuronal activity and associated behavioural responses in mice. Microglia respond to neuronal activation by suppressing neuronal activity, and ablation of microglia amplifies and synchronizes the activity of neurons, leading to seizures. Suppression of neuronal activation by microglia occurs in a highly region-specific fashion and depends on the ability of microglia to sense and catabolize extracellular ATP, which is released upon neuronal activation by neurons and astrocytes. ATP triggers the recruitment of microglial protrusions and is converted by the microglial ATP/ADP hydrolysing ectoenzyme CD39 into AMP; AMP is then converted into adenosine by CD73, which is expressed on microglia as well as other brain cells. Microglial sensing of ATP, the ensuing microglia-dependent production of adenosine, and the adenosine-mediated suppression of neuronal responses via the adenosine receptor A1R are essential for the regulation of neuronal activity and animal behaviour. Our findings suggest that this microglia-driven negative feedback mechanism operates similarly to inhibitory neurons and is essential for protecting the brain from excessive activation in health and disease.
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82
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Das R, Chinnathambi S. Actin-mediated Microglial Chemotaxis via G-Protein Coupled Purinergic Receptor in Alzheimer's Disease. Neuroscience 2020; 448:325-336. [PMID: 32941933 DOI: 10.1016/j.neuroscience.2020.09.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/05/2020] [Accepted: 09/07/2020] [Indexed: 02/08/2023]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disease mainly associated with aging, oxidative stress and genetic mutations. There are two pathological proteins involved in AD; Amyloid-β peptide and microtubule-associated protein Tau (MAPT). The β- and γ-secretase enzyme cleaves the Amyloid precursor protein, which results in the formation of extracellular plaques in brain. While, Tau undergoes hyperphosphorylation and other post-translational modifications (PTMs), which eventually generates Tau oligomers, and intracellular neurofibrillary tangles (NFTs) in neurons. Moreover, the brain-resident glia and infiltrated macrophages elevate the level of CNS inflammation, which trigger the oxidative damage of neuronal circuits by reactive oxygen species (ROS) and Nitric oxide (NO). Microglia is the primary immune cell in the CNS, which is continuously surveilling the neuronal synapses and pathogen invasion. Microglia in the resting state is called 'Ramified', which possess long surveilling extensions with a small cell body. But, upon activation, microglia retracts the cellular extensions and transform into round migratory cells, called as 'Amoeboid' state. Activated microglia undergoes actin remodeling by forming lamellipodia and filopodia, which directs the migratory axis while podosomes formed are involved in extracellular matrix degradation for invasion. Protein-aggregates in malfunctioning synapses and in CNS milieu can be detected by microglia, which results in its activation and migration. Subsequently, the phagocytosis of synapses leads to the inflammatory burst and memory loss. The extracellular nucleotides released from damaged neurons and the cytokine-chemokine gradients allow the neighboring microglia and macrophages to migrate-infiltrate at the site of neuronal-damage. The ionotropic (P2XR) and metabotropic (P2YR) purinergic receptor recognize extracellular ATP/ADP, which propagates through the intracellular calcium signaling, chemotaxis, phagocytosis and inflammation. The P2Y receptors give 'find me' or 'eat me' signals to microglia to either migrate or phagocytose cellular debris. Further, the actin cytoskeleton helps microglia to mediate directed chemotaxis and neuronal repair during neurodegeneration. Hence, we aim to emphasize the connection between purinergic signaling and actin-driven mechanical movements of microglia for migration and inflammation in AD.
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Affiliation(s)
- Rashmi Das
- Neurobiology Group, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, 411008 Pune, India; Academy of Scientific and Innovative Research (AcSIR), 411008 Pune, India
| | - Subashchandrabose Chinnathambi
- Neurobiology Group, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, 411008 Pune, India; Academy of Scientific and Innovative Research (AcSIR), 411008 Pune, India.
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83
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Bollinger JL, Horchar MJ, Wohleb ES. Diazepam limits microglia-mediated neuronal remodeling in the prefrontal cortex and associated behavioral consequences following chronic unpredictable stress. Neuropsychopharmacology 2020; 45:1766-1776. [PMID: 32454511 PMCID: PMC7419496 DOI: 10.1038/s41386-020-0720-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 04/27/2020] [Accepted: 05/14/2020] [Indexed: 11/09/2022]
Abstract
Chronic stress induces neuronal atrophy and synaptic loss in the medial prefrontal cortex (PFC), and this leads to behavioral and cognitive impairments. Our recent findings indicate that microglia contribute to structural remodeling of neurons via increased colony-stimulating factor (CSF)-1 in the medial PFC. Other work shows that chronic stress induces aberrant neuronal activity in the medial PFC, and that neuronal hyperactivity increases CSF1 signaling and alters microglia function. Thus, the present studies were designed to examine the role of neuronal activity in stress-induced CSF1 signaling and microglia-mediated neuronal remodeling in the medial PFC. Additional analyses probed stress effects on the dorsal hippocampus (HPC), basolateral amygdala (BLA), and somatosensory cortex (SSCTX). Mice were exposed to chronic unpredictable stress (CUS) or handled intermittently as controls, and received daily injection of vehicle or diazepam (1 mg/kg). As anticipated, diazepam attenuated CUS-induced behavioral despair and cognitive impairments. Further studies showed that diazepam normalized Csf1 and C3 mRNA in the PFC, and prevented increases in Csf1r and Cd11b in frontal cortex microglia following CUS. Stress had no effect on neuroimmune gene expression in the HPC. Confocal imaging in Thy1-GFP(M) mice demonstrated that diazepam limited microglial engulfment of neuronal elements and blocked CUS-induced dendritic spine loss in the medial PFC. Altogether, these findings indicate that modulation of chronic stress-induced neuronal activity limits microglia-mediated neuronal remodeling in the medial PFC, and subsequent behavioral and cognitive consequences.
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Affiliation(s)
- Justin L Bollinger
- Department of Pharmacology & Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Matthew J Horchar
- Department of Pharmacology & Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Eric S Wohleb
- Department of Pharmacology & Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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84
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Pinto MV, Fernandes A. Microglial Phagocytosis-Rational but Challenging Therapeutic Target in Multiple Sclerosis. Int J Mol Sci 2020; 21:ijms21175960. [PMID: 32825077 PMCID: PMC7504120 DOI: 10.3390/ijms21175960] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 08/12/2020] [Accepted: 08/17/2020] [Indexed: 12/14/2022] Open
Abstract
Multiple sclerosis (MS) is the most common autoimmune and demyelinating disease of the central nervous system (CNS), characterized, in the majority of cases, by initial relapses that later evolve into progressive neurodegeneration, severely impacting patients’ motor and cognitive functions. Despite the availability of immunomodulatory therapies effective to reduce relapse rate and slow disease progression, they all failed to restore CNS myelin that is necessary for MS full recovery. Microglia are the primary inflammatory cells present in MS lesions, therefore strongly contributing to demyelination and lesion extension. Thus, many microglial-based therapeutic strategies have been focused on the suppression of microglial pro-inflammatory phenotype and neurodegenerative state to reduce disease severity. On the other hand, the contribution of myelin phagocytosis advocating the neuroprotective role of microglia in MS has been less explored. Indeed, despite the presence of functional oligodendrocyte precursor cells (OPCs), within lesioned areas, MS plaques fail to remyelinate as a result of the over-accumulation of myelin-toxic debris that must be cleared away by microglia. Dysregulation of this process has been associated with the impaired neuronal recovery and deficient remyelination. In line with this, here we provide a comprehensive review of microglial myelin phagocytosis and its involvement in MS development and repair. Alongside, we discuss the potential of phagocytic-mediated therapeutic approaches and encourage their modulation as a novel and rational approach to ameliorate MS-associated pathology.
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Affiliation(s)
- Maria V. Pinto
- Neuron-Glia Biology in Health and Disease, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, 1649-003 Lisboa, Portugal;
| | - Adelaide Fernandes
- Neuron-Glia Biology in Health and Disease, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, 1649-003 Lisboa, Portugal;
- Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, 1649-003 Lisboa, Portugal
- Correspondence: ; Tel.: +351-217946400
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85
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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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86
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Hristovska I, Verdonk F, Comte JC, Tsai ES, Desestret V, Honnorat J, Chrétien F, Pascual O. Ketamine/xylazine and barbiturates modulate microglial morphology and motility differently in a mouse model. PLoS One 2020; 15:e0236594. [PMID: 32760073 PMCID: PMC7410236 DOI: 10.1371/journal.pone.0236594] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/08/2020] [Indexed: 12/30/2022] Open
Abstract
Microglia, the resident immune cells of the brain, are highly ramified and motile and their morphology is strongly linked to their function. Microglia constantly monitor the brain parenchyma and are crucial for maintaining brain homeostasis and fine-tuning neuronal networks. Besides affecting neurons, anesthetics may have wide-ranging effects mediated by non-neuronal cells and in particular microglia. We thus examined the effect of two commonly used anesthetic agents, ketamine/xylazine and barbiturates, on microglial motility and morphology. A combination of two-photon in vivo imaging and electroencephalography (EEG) recordings in unanesthetized and anesthetized mice as well as automated analysis of ex vivo sections were used to assess morphology and dynamics of microglia. We found that administration of ketamine/xylazine and pentobarbital anesthesia resulted in quite distinct EEG profiles. Both anesthetics reduced microglial motility, but only ketamine/xylazine administration led to reduction of microglial complexity in vivo. The change of cellular dynamics in vivo was associated with a region-dependent reduction of several features of microglial cells ex vivo, such as the complexity index and the ramification length, whereas thiopental altered the size of the cytoplasm. Our results show that anesthetics have considerable effects on neuronal activity and microglial morphodynamics and that barbiturates may be a preferred anesthetic agent for the study of microglial morphology. These findings will undoubtedly raise compelling questions about the functional relevance of anesthetics on microglial cells in neuronal physiology and anesthesia-induced neurotoxicity.
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Affiliation(s)
- Ines Hristovska
- Equipe Synaptopathies et Autoanticorps (SynatAc), Institut NeuroMyoGène, INSERM U1217/UMR CNRS 5310, Lyon, France
- Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
| | - Franck Verdonk
- Unité Neuropathologie Expérimentale, Département Infection et Epidémiologie, Institut Pasteur, Paris, France
- Department d’anesthésiologie et de Soins Intensifs, Hôpital Saint Antoine, Assistance Publique-Hôpitaux de Paris, Paris, France
- Sorbonne Université, Paris, France
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California, United States of America
| | - Jean-Christophe Comte
- Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
- Equipe Processus d’oubli et Dynamique Corticale, Centre de Recherche en Neuroscience de Lyon (CRNL), INSERM U1028, CNRS UMR5292, Lyon, France
| | - Eileen S. Tsai
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California, United States of America
| | - Virginie Desestret
- Equipe Synaptopathies et Autoanticorps (SynatAc), Institut NeuroMyoGène, INSERM U1217/UMR CNRS 5310, Lyon, France
- Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
- Centre maladies rares sur les syndromes neurologiques paranéoplasiques, Hospices Civils de Lyon, Lyon, France
| | - Jérôme Honnorat
- Equipe Synaptopathies et Autoanticorps (SynatAc), Institut NeuroMyoGène, INSERM U1217/UMR CNRS 5310, Lyon, France
- Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
- Centre maladies rares sur les syndromes neurologiques paranéoplasiques, Hospices Civils de Lyon, Lyon, France
| | - Fabrice Chrétien
- Unité Neuropathologie Expérimentale, Département Infection et Epidémiologie, Institut Pasteur, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Laboratoire Hospitalo-Universitaire de Neuropathologie, Centre Hospitalier Sainte Anne, Paris, France
- * E-mail: (FC); (OP)
| | - Olivier Pascual
- Equipe Synaptopathies et Autoanticorps (SynatAc), Institut NeuroMyoGène, INSERM U1217/UMR CNRS 5310, Lyon, France
- Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
- * E-mail: (FC); (OP)
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87
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Bernier LP, Bohlen CJ, York EM, Choi HB, Kamyabi A, Dissing-Olesen L, Hefendehl JK, Collins HY, Stevens B, Barres BA, MacVicar BA. Nanoscale Surveillance of the Brain by Microglia via cAMP-Regulated Filopodia. Cell Rep 2020; 27:2895-2908.e4. [PMID: 31167136 DOI: 10.1016/j.celrep.2019.05.010] [Citation(s) in RCA: 125] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 03/14/2019] [Accepted: 04/30/2019] [Indexed: 02/07/2023] Open
Abstract
Microglia, the brain's immune cells, maintain homeostasis and sense pathological changes by continuously surveying the parenchyma with highly motile large processes. Here, we demonstrate that microglia also use thin actin-dependent filopodia that allow fast nanoscale sensing within discrete regions. Filopodia are distinct from large processes by their size, speed, and regulation mechanism. Increasing cyclic AMP (cAMP) by activating norepinephrine Gs-coupled receptors, applying nitric oxide, or inhibiting phosphodiesterases rapidly increases filopodia but collapses large processes. Alternatively, Gi-coupled P2Y12 receptor activation collapses filopodia but triggers large processes extension with bulbous tips. Similar control of cytoskeletal dynamics and microglial morphology by cAMP is observed in ramified primary microglia, suggesting that filopodia are intrinsically generated sensing structures. Therefore, nanoscale surveillance of brain parenchyma by microglia requires localized cAMP increases that drive filopodia formation. Shifting intracellular cAMP levels controls the polarity of microglial responses to changes in brain homeostasis and alters the scale of immunosurveillance.
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Affiliation(s)
- Louis-Philippe Bernier
- University of British Columbia, Djavad Mowafaghian Centre for Brain Health, Vancouver, BC V6T 1Z3, Canada.
| | - Christopher J Bohlen
- Stanford University School of Medicine, Department of Neurobiology, Stanford, CA 94305, USA
| | - Elisa M York
- University of British Columbia, Djavad Mowafaghian Centre for Brain Health, Vancouver, BC V6T 1Z3, Canada
| | - Hyun B Choi
- University of British Columbia, Djavad Mowafaghian Centre for Brain Health, Vancouver, BC V6T 1Z3, Canada
| | - Alireza Kamyabi
- University of British Columbia, Djavad Mowafaghian Centre for Brain Health, Vancouver, BC V6T 1Z3, Canada
| | - Lasse Dissing-Olesen
- University of British Columbia, Djavad Mowafaghian Centre for Brain Health, Vancouver, BC V6T 1Z3, Canada; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School Boston, MA 02115, USA
| | - Jasmin K Hefendehl
- University of British Columbia, Djavad Mowafaghian Centre for Brain Health, Vancouver, BC V6T 1Z3, Canada
| | - Hannah Y Collins
- Stanford University School of Medicine, Department of Neurobiology, Stanford, CA 94305, USA
| | - Beth Stevens
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School Boston, MA 02115, USA
| | - Ben A Barres
- Stanford University School of Medicine, Department of Neurobiology, Stanford, CA 94305, USA
| | - Brian A MacVicar
- University of British Columbia, Djavad Mowafaghian Centre for Brain Health, Vancouver, BC V6T 1Z3, Canada.
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88
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Neves AF, Farias FH, de Magalhães SF, Araldi D, Pagliusi M, Tambeli CH, Sartori CR, Lotufo CMDC, Parada CA. Peripheral Inflammatory Hyperalgesia Depends on P2X7 Receptors in Satellite Glial Cells. Front Physiol 2020; 11:473. [PMID: 32523543 PMCID: PMC7261868 DOI: 10.3389/fphys.2020.00473] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 04/17/2020] [Indexed: 12/23/2022] Open
Abstract
Peripheral inflammatory hyperalgesia depends on the sensitization of primary nociceptive neurons. Inflammation drives molecular alterations not only locally but also in the dorsal root ganglion (DRG) where interleukin-1 beta (IL-1β) and purinoceptors are upregulated. Activation of the P2X7 purinoceptors by ATP is essential for IL-1β maturation and release. At the DRG, P2X7R are expressed by satellite glial cells (SGCs) surrounding sensory neurons soma. Although SGCs have no projections outside the sensory ganglia these cells affect pain signaling through intercellular communication. Therefore, here we investigated whether activation of P2X7R by ATP and the subsequent release of IL-1β in DRG participate in peripheral inflammatory hyperalgesia. Immunofluorescent images confirmed the expression of P2X7R and IL-1β in SGCs of the DRG. The function of P2X7R was then verified using a selective antagonist, A-740003, or antisense for P2X7R administered in the L5-DRG. Inflammation was induced by CFA, carrageenan, IL-1β, or PGE2 administered in rat's hind paw. Blockage of P2X7R at the DRG reduced the mechanical hyperalgesia induced by CFA, and prevented the mechanical hyperalgesia induced by carrageenan or IL-1β, but not PGE2. It was also found an increase in P2X7 mRNA expression at the DRG after peripheral inflammation. IL-1β production was also increased by inflammatory stimuli in vivo and in vitro, using SGC-enriched cultures stimulated with LPS. In LPS-stimulated cultures, activation of P2X7R by BzATP induced the release of IL-1β, which was blocked by A-740003. In summary, our data suggest that peripheral inflammation leads to the activation of P2X7R expressed by SGCs at the DRG. Then, ATP-induced activation of P2X7R mediates the release of IL-1β from SGC. This evidence places the SGC as an active player in the establishment of peripheral inflammatory hyperalgesia and highlights the importance of the events in DRG for the treatment of inflammatory diseases.
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Affiliation(s)
- Amanda Ferreira Neves
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
| | - Felipe Hertzing Farias
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
| | | | - Dionéia Araldi
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
| | - Marco Pagliusi
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
| | - Claudia Herrera Tambeli
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
| | - Cesar Renato Sartori
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
| | | | - Carlos Amílcar Parada
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
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89
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Regulation of Microglial Functions by Purinergic Mechanisms in the Healthy and Diseased CNS. Cells 2020; 9:cells9051108. [PMID: 32365642 PMCID: PMC7290360 DOI: 10.3390/cells9051108] [Citation(s) in RCA: 112] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 04/25/2020] [Accepted: 04/27/2020] [Indexed: 02/07/2023] Open
Abstract
Microglial cells, the resident macrophages of the central nervous system (CNS), exist in a process-bearing, ramified/surveying phenotype under resting conditions. Upon activation by cell-damaging factors, they get transformed into an amoeboid phenotype releasing various cell products including pro-inflammatory cytokines, chemokines, proteases, reactive oxygen/nitrogen species, and the excytotoxic ATP and glutamate. In addition, they engulf pathogenic bacteria or cell debris and phagocytose them. However, already resting/surveying microglia have a number of important physiological functions in the CNS; for example, they shield small disruptions of the blood–brain barrier by their processes, dynamically interact with synaptic structures, and clear surplus synapses during development. In neurodegenerative illnesses, they aggravate the original disease by a microglia-based compulsory neuroinflammatory reaction. Therefore, the blockade of this reaction improves the outcome of Alzheimer’s Disease, Parkinson’s Disease, multiple sclerosis, amyotrophic lateral sclerosis, etc. The function of microglia is regulated by a whole array of purinergic receptors classified as P2Y12, P2Y6, P2Y4, P2X4, P2X7, A2A, and A3, as targets of endogenous ATP, ADP, or adenosine. ATP is sequentially degraded by the ecto-nucleotidases and 5′-nucleotidase enzymes to the almost inactive inosine as an end product. The appropriate selective agonists/antagonists for purinergic receptors as well as the respective enzyme inhibitors may profoundly interfere with microglial functions and reconstitute the homeostasis of the CNS disturbed by neuroinflammation.
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90
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Yeung AK, Patil CS, Jackson MF. Pannexin‐1 in the CNS: Emerging concepts in health and disease. J Neurochem 2020; 154:468-485. [DOI: 10.1111/jnc.15004] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 02/26/2020] [Accepted: 03/09/2020] [Indexed: 12/15/2022]
Affiliation(s)
- Albert K. Yeung
- Department of Pharmacology and Therapeutics Max Rady College of Medicine Rady Faculty of Health Sciences University of Manitoba Winnipeg Manitoba Canada
- Neuroscience Research Program Kleysen Institute for Advanced Medicine University of Manitoba Winnipeg Manitoba Canada
| | - Chetan S. Patil
- Department of Pharmacology and Therapeutics Max Rady College of Medicine Rady Faculty of Health Sciences University of Manitoba Winnipeg Manitoba Canada
- Neuroscience Research Program Kleysen Institute for Advanced Medicine University of Manitoba Winnipeg Manitoba Canada
| | - Michael F. Jackson
- Department of Pharmacology and Therapeutics Max Rady College of Medicine Rady Faculty of Health Sciences University of Manitoba Winnipeg Manitoba Canada
- Neuroscience Research Program Kleysen Institute for Advanced Medicine University of Manitoba Winnipeg Manitoba Canada
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91
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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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92
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Abstract
Microglia dynamically interact with neurons influencing the development, structure, and function of neuronal networks. Recent studies suggest microglia may also influence neuronal activity by physically interacting with axonal domains responsible for action potential initiation and propagation. However, the nature of these microglial process interactions is not well understood. Microglial-axonal contacts are present early in development and persist through adulthood, implicating microglial interactions in the regulation of axonal integrity in both the developing and mature central nervous system. Moreover, changes in microglial-axonal contact have been described in disease states such as multiple sclerosis (MS) and traumatic brain injury (TBI). Depending on the disease state, there are increased associations with specific axonal segments. In MS, there is enhanced contact with the axon initial segment and node of Ranvier, while, in TBI, microglia alter interactions with axons at the site of injury, as well as at the axon initial segment. In this article, we review the interactions of microglial processes with axonal segments, analyzing their associations with various axonal domains and how these interactions may differ between MS and TBI. Furthermore, we discuss potential functional consequences and molecular mechanisms of these interactions and how these may differ among various types of microglial-axonal interactions.
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Affiliation(s)
- Savannah D Benusa
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Audrey D Lafrenaye
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA 23298, USA
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93
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Neuroinflammation in CNS diseases: Molecular mechanisms and the therapeutic potential of plant derived bioactive molecules. PHARMANUTRITION 2020. [DOI: 10.1016/j.phanu.2020.100176] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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94
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The VGF-derived Peptide TLQP21 Impairs Purinergic Control of Chemotaxis and Phagocytosis in Mouse Microglia. J Neurosci 2020; 40:3320-3331. [PMID: 32060170 DOI: 10.1523/jneurosci.1458-19.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 12/20/2019] [Accepted: 01/23/2020] [Indexed: 11/21/2022] Open
Abstract
Microglial cells are considered as sensors of brain pathology by detecting any sign of brain lesions, infections, or dysfunction and can influence the onset and progression of neurological diseases. They are capable of sensing their neuronal environment via many different signaling molecules, such as neurotransmitters, neurohormones and neuropeptides. The neuropeptide VGF has been associated with many metabolic and neurological disorders. TLQP21 is a VGF-derived peptide and has been shown to signal via C3aR1 and C1qBP receptors. The effect of TLQP21 on microglial functions in health or disease is not known. Studying microglial cells in acute brain slices, we found that TLQP21 impaired metabotropic purinergic signaling. Specifically, it attenuated the ATP-induced activation of a K+ conductance, the UDP-stimulated phagocytic activity, and the ATP-dependent laser lesion-induced process outgrowth. These impairments were reversed by blocking C1qBP, but not C3aR1 receptors. While microglia in brain slices from male mice lack C3aR1 receptors, both receptors are expressed in primary cultured microglia. In addition to the negative impact on purinergic signaling, we found stimulating effects of TLQP21 in cultured microglia, which were mediated by C3aR1 receptors: it directly evoked membrane currents, stimulated basal phagocytic activity, evoked intracellular Ca2+ transient elevations, and served as a chemotactic signal. We conclude that TLQP21 has differential effects on microglia depending on C3aR1 activation or C1qBP-dependent attenuation of purinergic signaling. Thus, TLQP21 can modulate the functional phenotype of microglia, which may have an impact on their function in health and disease.SIGNIFICANCE STATEMENT The neuropeptide VGF and its peptides have been associated with many metabolic and neurological disorders. TLQP21 is a VGF-derived peptide that activates C1qBP receptors, which are expressed by microglia. We show here, for the first time, that TLQP21 impairs P2Y-mediated purinergic signaling and related functions. These include modulation of phagocytic activity and responses to injury. As purinergic signaling is central for microglial actions in the brain, this TLQP21-mediated mechanism might regulate microglial activity in health and disease. We furthermore show that, in addition to C1qBP, functional C3aR1 responses contribute to TLQP21 action on microglia. However, C3aR1 responses were only present in primary cultures but not in situ, suggesting that the expression of these receptors might vary between different microglial activation states.
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95
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Raghunatha P, Vosoughi A, Kauppinen TM, Jackson MF. Microglial NMDA receptors drive pro-inflammatory responses via PARP-1/TRMP2 signaling. Glia 2020; 68:1421-1434. [PMID: 32036619 DOI: 10.1002/glia.23790] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 01/16/2020] [Accepted: 01/23/2020] [Indexed: 12/16/2022]
Abstract
Chronic neuroinflammation driven by microglia is a characteristic feature associated with numerous neurodegenerative diseases. While acute inflammation can assist with recovery and repair, prolonged microglial pro-inflammatory responses are known to exacerbate neurodegenerative processes. Yet, detrimental outcomes of extended microglial activation are counterbalanced by beneficial outcomes including phagocytosis and release of trophic factors promoting neuronal viability. Our past work has shown that the nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) is a key signaling hub driving pro-inflammatory microglia responses, but the signaling pathway maintaining PARP-1 activation remains elusive. While best understood for its role in promoting DNA repair, our group has shown that PARP-1 activity can be stimulated via Ca2+ influx-dependent ERK1/2-mediated phosphorylation. However, to date, the route of Ca2+ entry responsible for stimulating PARP-1 has not been identified. A likely candidate is via Ca2+ -permeable transient receptor potential melastatin 2 (TRPM2) channels activated downstream of PARP-1 in a cascade that involves ADP-ribose (ADPR) production by poly(ADP-ribose) glycohydrolase (PARG). Here we demonstrate that NMDA receptor (NMDAR) stimulation in primary cultured microglia induces their proliferation, morphological activation and release of pro-inflammatory mediators. These responses were contingent on the recruitment of PARP-1, PARG and Ca2+ permeable TRPM2 channels. Furthermore, we show that Ca2+ influx is necessary to activate PARP-1/TRPM2 signaling, in an ERK1/2-dependent, but DNA damage independent, manner. Our findings, showing that PARP-1/TRPM2 mediate the pro-inflammatory effects of NMDAR stimulation, provides a unifying mechanism linking elevated glutamate levels to chronic neuroinflammation.
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Affiliation(s)
- Prajwal Raghunatha
- Department of Pharmacology and Therapeutics, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.,Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, Winnipeg, Manitoba, Canada
| | - Amir Vosoughi
- Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, Winnipeg, Manitoba, Canada
| | - Tiina M Kauppinen
- Department of Pharmacology and Therapeutics, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.,Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, Winnipeg, Manitoba, Canada.,The Children's Hospital Research Institute of Manitoba, Winnipeg, Manitoba, Canada
| | - Michael F Jackson
- Department of Pharmacology and Therapeutics, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.,Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, Winnipeg, Manitoba, Canada
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96
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Peña-Ortega F. Brain Arrhythmias Induced by Amyloid Beta and Inflammation: Involvement in Alzheimer’s Disease and Other Inflammation-related Pathologies. Curr Alzheimer Res 2020; 16:1108-1131. [DOI: 10.2174/1567205017666191213162233] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 10/29/2019] [Accepted: 11/05/2019] [Indexed: 12/13/2022]
Abstract
A variety of neurological diseases, including Alzheimer’s disease (AD), involve amyloid beta (Aβ) accumulation and/or neuroinflammation, which can alter synaptic and neural circuit functions. Consequently, these pathological conditions induce changes in neural network rhythmic activity (brain arrhythmias), which affects many brain functions. Neural network rhythms are involved in information processing, storage and retrieval, which are essential for memory consolidation, executive functioning and sensory processing. Therefore, brain arrhythmias could have catastrophic effects on circuit function, underlying the symptoms of various neurological diseases. Moreover, brain arrhythmias can serve as biomarkers for a variety of brain diseases. The aim of this review is to provide evidence linking Aβ and inflammation to neural network dysfunction, focusing on alterations in brain rhythms and their impact on cognition and sensory processing. I reviewed the most common brain arrhythmias characterized in AD, in AD transgenic models and those induced by Aβ. In addition, I reviewed the modulations of brain rhythms in neuroinflammatory diseases and those induced by immunogens, interleukins and microglia. This review reveals that Aβ and inflammation produce a complex set of effects on neural network function, which are related to the induction of brain arrhythmias and hyperexcitability, both closely related to behavioral alterations. Understanding these brain arrhythmias can help to develop therapeutic strategies to halt or prevent these neural network alterations and treat not only the arrhythmias but also the symptoms of AD and other inflammation-related pathologies.
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Affiliation(s)
- Fernando Peña-Ortega
- Departamento de Neurobiologia del Desarrollo y Neurofisiologia, Instituto de Neurobiologia, Universidad Nacional Autonoma de Mexico, Queretaro, Qro., 76230, Mexico
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97
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Distinct P2Y Receptors Mediate Extension and Retraction of Microglial Processes in Epileptic and Peritumoral Human Tissue. J Neurosci 2020; 40:1373-1388. [PMID: 31896671 DOI: 10.1523/jneurosci.0218-19.2019] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 09/27/2019] [Accepted: 09/30/2019] [Indexed: 12/12/2022] Open
Abstract
Microglia exhibit multiple, phenotype-dependent motility patterns often triggered by purinergic stimuli. However, little data exist on motility of human microglia in pathological situations. Here we examine motility of microglia stained with a fluorescent lectin in tissue slices from female and male epileptic patients diagnosed with mesial temporal lobe epilepsy or cortical glioma (peritumoral cortex). Microglial shape varied from ramified to amoeboid cells predominantly in regions of high neuronal loss or closer to a tumor. Live imaging revealed unstimulated or purine-induced microglial motilities, including surveillance movements, membrane ruffling, and process extension or retraction. At different concentrations, ADP triggered opposing motilities. Low doses triggered process extension. It was suppressed by P2Y12 receptor antagonists, which also reduced process length and surveillance movements. Higher purine doses caused process retraction and membrane ruffling, which were blocked by joint application of P2Y1 and P2Y13 receptor antagonists. Purinergic effects on motility were similar for all microglia tested. Both amoeboid and ramified cells from mesial temporal lobe epilepsy or peritumoral cortex tissue expressed P2Y12 receptors. A minority of microglia expressed the adenosine A2A receptor, which has been linked with process withdrawal of rodent cells. Laser-mediated tissue damage let us test the functional significance of these effects. Moderate damage induced microglial process extension, which was blocked by P2Y12 receptor antagonists. Overall, the purine-induced motility of human microglia in epileptic tissue is similar to that of rodent microglia in that the P2Y12 receptor initiates process extension. It differs in that retraction is triggered by joint activation of P2Y1/P2Y13 receptors.SIGNIFICANCE STATEMENT Microglial cells are brain-resident immune cells with multiple functions in healthy or diseased brains. These diverse functions are associated with distinct phenotypes, including different microglial shapes. In the rodent, purinergic signaling is associated with changes in cell shape, such as process extension toward tissue damage. However, there are little data on living human microglia, especially in diseased states. We developed a reliable technique to stain microglia from epileptic and glioma patients to examine responses to purines. Low-intensity purinergic stimuli induced process extension, as in rodents. In contrast, high-intensity stimuli triggered a process withdrawal mediated by both P2Y1 and P2Y13 receptors. P2Y1/P2Y13 receptor activation has not previously been linked to microglial morphological changes.
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98
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Bourgognon JM, Cavanagh J. The role of cytokines in modulating learning and memory and brain plasticity. Brain Neurosci Adv 2020; 4:2398212820979802. [PMID: 33415308 PMCID: PMC7750764 DOI: 10.1177/2398212820979802] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 11/18/2020] [Indexed: 12/28/2022] Open
Abstract
Cytokines are proteins secreted in the central nervous system by neurons, microglia, astrocytes and infiltrating peripheral immune cells under physiological and pathological conditions. Over the last 20 years, a growing number of reports have investigated the effects of these molecules on brain plasticity. In this review, we describe how the key cytokines interleukin 1β, interleukin 6 and tumour necrosis factor α were found to support long-term plasticity and learning and memory processes in physiological conditions. In contrast, during inflammation where cytokines levels are elevated such as in models of brain injury or infection, depression or neurodegeneration, the effects of cytokines are mostly detrimental to memory mechanisms, associated behaviours and homeostatic plasticity.
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Affiliation(s)
| | - Jonathan Cavanagh
- Institute of Infection, Immunity &
Inflammation, University of Glasgow, Glasgow, UK
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99
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Cannella LA, Andrews AM, Tran F, Razmpour R, McGary H, Collie C, Tsegaye T, Maynard M, Kaufman MJ, Rawls SM, Ramirez SH. Experimental Traumatic Brain Injury during Adolescence Enhances Cocaine Rewarding Efficacy and Dysregulates Dopamine and Neuroimmune Systems in Brain Reward Substrates. J Neurotrauma 2020; 37:27-42. [PMID: 31347447 PMCID: PMC6921296 DOI: 10.1089/neu.2019.6472] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Although clinical studies identify traumatic brain injury (TBI) as a risk factor for the development of substance use disorder, much remains unknown about the possible underlying pathogenesis and age-specific effects. Thus, the aim of this study is to test the hypothesis that at an age of ongoing maturation, adolescent TBI alters elements of the reward pathway, resulting in increased sensitivity to the rewarding effects of a subthreshold dose of cocaine that does not induce significant behavioral changes in naïve, non-injured mice. Specifically, these results were derived from the combination of the controlled cortical impact model of TBI, performed on either adolescent (6 weeks) or young adult (8 weeks) mice, followed by the cocaine-induced conditioned place preference assay 2 weeks later. Using three-dimensional isosurface rendering and volumetric image analysis, TBI was found to induce neuromorphological changes such as decreased dendritic complexity and reduced spine density in brain regions essential for reward perception and processing of drug-induced euphoria. Further, we demonstrated that these neuronal changes may affect the differential expression of dopamine-associated genes. Our analysis also provided evidence for age-related differences in immune response and the distinct involvement of augmented microglial phagocytic activity in the remodeling of neuronal structures in the adolescent TBI brain. Our studies suggest that TBI during adolescence, a period associated with ongoing maturation of dopaminergic systems, may subsequently enhance the abuse liability of cocaine in adulthood.
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Affiliation(s)
- Lee Anne Cannella
- Department of Pathology and Laboratory Medicine, Temple University, Philadelphia Pennsylvania
| | - Allison M. Andrews
- Department of Pathology and Laboratory Medicine, Temple University, Philadelphia Pennsylvania
| | - Fionya Tran
- Department of Pathology and Laboratory Medicine, Temple University, Philadelphia Pennsylvania
| | - Roshanak Razmpour
- Department of Pathology and Laboratory Medicine, Temple University, Philadelphia Pennsylvania
| | - Hannah McGary
- Department of Pathology and Laboratory Medicine, Temple University, Philadelphia Pennsylvania
| | - Ceryce Collie
- Department of Biology, Lincoln University, Philadelphia Pennsylvania
| | - Tarik Tsegaye
- Department of Biology, Lincoln University, Philadelphia Pennsylvania
| | - Marquis Maynard
- Department of Pathology and Laboratory Medicine, Temple University, Philadelphia Pennsylvania
| | - Marc J. Kaufman
- McLean Imaging Center, McLean Hospital, Harvard Medical School, Belmont, Massachusetts
| | - Scott M. Rawls
- Center for Substance Abuse Research, Temple University, Philadelphia Pennsylvania
| | - Servio H. Ramirez
- Department of Pathology and Laboratory Medicine, Temple University, Philadelphia Pennsylvania
- Center for Substance Abuse Research, Temple University, Philadelphia Pennsylvania
- Shriners Hospital for Pediatric Research Center, Temple University, Philadelphia Pennsylvania
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100
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Synaptic Pruning by Microglia in Epilepsy. J Clin Med 2019; 8:jcm8122170. [PMID: 31818018 PMCID: PMC6947403 DOI: 10.3390/jcm8122170] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 11/27/2019] [Accepted: 12/05/2019] [Indexed: 12/16/2022] Open
Abstract
Structural and functional collapse of the balance between excitatory (E) and inhibitory (I) synapses, i.e., synaptic E/I balance, underlies the pathogeneses of various central nervous system (CNS) disorders. In epilepsy, the synaptic E/I balance tips toward excitation; thus, most of the existing epileptic remedies have focused on how to directly suppress the activity of neurons. However, because as many as 30% of patients with epilepsy are drug resistant, the discovery of new therapeutic targets is strongly desired. Recently, the roles of glial cells in epilepsy have gained attention because glial cells manipulate synaptic structures and functions in addition to supporting neuronal survival and growth. Among glial cells, microglia, which are brain-resident immune cells, have been shown to mediate inflammation, neuronal death and aberrant neurogenesis after epileptic seizures. However, few studies have investigated the involvement of synaptic pruning—one of the most important roles of microglia—in the epileptic brain. In this review, we propose and discuss the hypothesis that synaptic pruning by microglia is enhanced in the epileptic brain, drawing upon the findings of previous studies. We further discuss the possibility that aberrant synaptic pruning by microglia induces synaptic E/I imbalance, promoting the development and aggravation of epilepsy.
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