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Mawanda F, Wallace RB, McCoy K, Abrams TE. Systemic and localized extra-central nervous system bacterial infections and the risk of dementia among US veterans: A retrospective cohort study. ALZHEIMER'S & DEMENTIA (AMSTERDAM, NETHERLANDS) 2016; 4:109-117. [PMID: 27752534 PMCID: PMC5061465 DOI: 10.1016/j.dadm.2016.08.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Emerging evidence indicates associations between extra-central nervous system (CNS) bacterial infections and an increased risk for dementia; however, epidemiological evidence is still very limited. METHODS This study involved a retrospective cohort of a national sample of US veterans (N = 417,172) aged ≥56 years. Extended Cox proportional hazard models adjusted for demographic characteristics and medical and psychiatric comorbidities determined the associations between systemic and localized extra-CNS bacterial infections occurring >2 years before the initial dementia diagnosis and the risk for dementia. RESULTS Exposure to any extra-CNS bacterial infection was associated with a significantly increased risk for dementia (hazard ratio [HR] = 1.20 [95% confidence interval = 1.16-1.24]). Independently, septicemia (HR = 1.39 [1.16-1.66]), bacteremia (HR = 1.22 [1.00-1.49]), osteomyelitis (HR = 1.20 [1.06-1.37]), pneumonia (HR = 1.10 [1.02-1.19]), urinary tract infections (HR = 1.13 [1.08-1.18]), and cellulitis (HR = 1.14 [1.09-1.20]) were associated with a significantly increased risk for dementia. DISCUSSION Both systemic and localized extra-CNS bacterial infections are associated with an increased risk for developing dementia.
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Affiliation(s)
- Francis Mawanda
- Department of Epidemiology, University of Iowa, Iowa City, IA, USA
| | - Robert B. Wallace
- Department of Epidemiology, University of Iowa, Iowa City, IA, USA
- Department of Medicine, University of Iowa, Iowa City, IA, USA
| | - Kimberly McCoy
- Center for Comprehensive Access & Delivery Research and Evaluation, Iowa City VA Health Care System, Iowa City, IA, USA
| | - Thad E. Abrams
- Department of Epidemiology, University of Iowa, Iowa City, IA, USA
- Department of Medicine, University of Iowa, Iowa City, IA, USA
- Center for Comprehensive Access & Delivery Research and Evaluation, Iowa City VA Health Care System, Iowa City, IA, USA
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252
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Andreasson KI, Bachstetter AD, Colonna M, Ginhoux F, Holmes C, Lamb B, Landreth G, Lee DC, Low D, Lynch MA, Monsonego A, O’Banion MK, Pekny M, Puschmann T, Russek-Blum N, Sandusky LA, Selenica MLB, Takata K, Teeling J, Town T, Van Eldik LJ, Russek-Blum N, Monsonego A, Low D, Takata K, Ginhoux F, Town T, O’Banion MK, Lamb B, Colonna M, Landreth G, Andreasson KI, Sandusky LA, Selenica MLB, Lee DC, Holmes C, Teeling J, Lynch MA, Van Eldik LJ, Bachstetter AD, Pekny M, Puschmann T. Targeting innate immunity for neurodegenerative disorders of the central nervous system. J Neurochem 2016; 138:653-93. [PMID: 27248001 PMCID: PMC5433264 DOI: 10.1111/jnc.13667] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 04/01/2016] [Accepted: 04/30/2016] [Indexed: 12/21/2022]
Abstract
Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview of physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia and astrocyte cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article. Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer's disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview on physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Niva Russek-Blum
- The Dead Sea and Arava Science Center, Central Arava Branch, Yair Station, Hazeva, Israel
| | - Alon Monsonego
- The Shraga Segal Dept. of Microbiology, Immunology and Genetics, The Faculty of Health Sciences: The National Institute of Biotechnology in the Negev, and Zlotowski Center for Neuroscience, Ben-Gurion University, Beer-Sheva 84105, Israel
| | - Donovan Low
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore
| | - Kazuyuki Takata
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore
- Department of Clinical and Translational Physiology, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Florent Ginhoux
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore
| | - Terrence Town
- Departments of Physiology and Biophysics, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089,
| | - M. Kerry O’Banion
- Departments of Neuroscience and Neurology, Del Monte Neuromedicine Institute, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642,
| | - Bruce Lamb
- Department of Neurosciences, Cleveland Clinic, Cleveland, OH 44106
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Gary Landreth
- Department of Neurosciences, Case Western Reserve University 44106
| | - Katrin I. Andreasson
- Department of Neurology and Neurological Sciences, Stanford Neuroscience Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Leslie A. Sandusky
- USF Health Byrd Alzheimer’s Institute, Tampa, FL 33613
- College of Pharmacy & Pharmaceutical Sciences, Tampa, FL 33613
| | - Maj-Linda B. Selenica
- USF Health Byrd Alzheimer’s Institute, Tampa, FL 33613
- College of Pharmacy & Pharmaceutical Sciences, Tampa, FL 33613
| | - Daniel C. Lee
- USF Health Byrd Alzheimer’s Institute, Tampa, FL 33613
- College of Pharmacy & Pharmaceutical Sciences, Tampa, FL 33613
| | - Clive Holmes
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO16 7YD, United Kingdom
| | - Jessica Teeling
- Centre for Biological Sciences, University of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO16 7YD, United Kingdom
| | | | | | | | - Milos Pekny
- Center for Brain Repair and Rehabilitation, Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, SE-405 30 Gothenburg, Sweden
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Hunter Medical Research Institute, University of Newcastle, New South Wales, Australia
| | - Till Puschmann
- Center for Brain Repair and Rehabilitation, Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, SE-405 30 Gothenburg, Sweden
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253
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Zhang B, Bailey WM, McVicar AL, Gensel JC. Age increases reactive oxygen species production in macrophages and potentiates oxidative damage after spinal cord injury. Neurobiol Aging 2016; 47:157-167. [PMID: 27596335 DOI: 10.1016/j.neurobiolaging.2016.07.029] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Revised: 07/16/2016] [Accepted: 07/29/2016] [Indexed: 01/08/2023]
Abstract
Age potentiates neurodegeneration and impairs recovery from spinal cord injury (SCI). Previously, we observed that age alters the balance of destructive (M1) and protective (M2) macrophages; however, the age-related pathophysiology in SCI is poorly understood. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) contributes to reactive oxygen species (ROS)-mediated damage and macrophage activation in neurotrauma. Further, NOX and ROS increase with central nervous system age. Here, we found significantly higher ROS generation in 14 versus 4-month-old (MO) mice after contusion SCI. Notably, NOX2 increased in 14 MO ROS-producing macrophages suggesting that macrophages and NOX contribute to SCI oxidative stress. Indicators of lipid peroxidation, a downstream cytotoxic effect of ROS accumulation, were significantly higher in 14 versus 4 MO SCI mice. We also detected a higher percentage of ROS-producing M2 (Arginase-1-positive) macrophages in 14 versus 4 MO mice, a previously unreported SCI phenotype, and increased M1 (CD16/32-positive) macrophages with age. Thus, NOX and ROS are age-related mediators of SCI pathophysiology and normally protective M2 macrophages may potentiate secondary injury through ROS generation in the aged injured spinal cord.
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Affiliation(s)
- Bei Zhang
- Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky, Lexington, KY 40536, USA
| | - William M Bailey
- Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky, Lexington, KY 40536, USA
| | - Anna Leigh McVicar
- Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky, Lexington, KY 40536, USA
| | - John C Gensel
- Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky, Lexington, KY 40536, USA.
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254
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Abstract
Inflammatory activation of microglia is a hallmark of several disorders of the central nervous system. In addition to protecting the brain against inflammatory insults, microglia are neuroprotective and play a significant role in maintaining neuronal connectivity, but the prolongation of an inflammatory status may limit the beneficial functions of these immune cells. The finding that estrogen receptors are present in monocyte-derived cells and that estrogens prevent and control the inflammatory response raise the question of the role that this sex steroid plays in the manifestation and progression of pathologies that have a clear sex difference in prevalence, such as multiple sclerosis, Parkinson's disease, and Alzheimer's disease. The present review aims to provide a critical review of the current literature on the actions of estrogen in microglia and on the involvement of estrogen receptors in the manifestation of selected neurological disorders. This current understanding highlights a research area that should be expanded to identify appropriate replacement therapies to slow the progression of such diseases.
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Affiliation(s)
- Alessandro Villa
- Center of Excellence on Neurodegenerative Diseases and Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy
| | - Elisabetta Vegeto
- Center of Excellence on Neurodegenerative Diseases and Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy
| | - Angelo Poletti
- Center of Excellence on Neurodegenerative Diseases and Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy
| | - Adriana Maggi
- Center of Excellence on Neurodegenerative Diseases and Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy
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255
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Matt SM, Lawson MA, Johnson RW. Aging and peripheral lipopolysaccharide can modulate epigenetic regulators and decrease IL-1β promoter DNA methylation in microglia. Neurobiol Aging 2016; 47:1-9. [PMID: 27500965 DOI: 10.1016/j.neurobiolaging.2016.07.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 07/01/2016] [Accepted: 07/07/2016] [Indexed: 12/23/2022]
Abstract
In aged mice, peripheral stimulation of the innate immune system with lipopolysaccharide (LPS) causes exaggerated neuroinflammation and prolonged sickness behavior due in part to microglial dysfunction. Epigenetic changes to DNA may play a role in microglial dysfunction; therefore, we sought to determine whether aged microglia displayed DNA hypomethylation of the interleukin-1 beta (IL-1β) promoter and altered expression of epigenetic regulators. We further examined whether the demethylating agent 5-azacytidine induced IL-1β expression in BV2 and primary microglia similar to microglia from aged mice. Novel findings indicated that aged mice had decreased methylation of the IL-1β gene promoter in primary microglia basally or following systemic LPS that is associated with increased IL-1β mRNA, intracellular IL-1β production, as well as prolonged sickness behavior. Last, 5-azacytidine increased IL-1β gene expression and decreased DNA methylation of BV2 and primary microglial cells similar to microglia from aged mice. Taken together, these data indicate that DNA methylation promotes heightened microglial activation in the aged brain.
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Affiliation(s)
- Stephanie M Matt
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Marcus A Lawson
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Rodney W Johnson
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Integrative Immunology and Behavior Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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256
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Zabel MK, Zhao L, Zhang Y, Gonzalez SR, Ma W, Wang X, Fariss RN, Wong WT. Microglial phagocytosis and activation underlying photoreceptor degeneration is regulated by CX3CL1-CX3CR1 signaling in a mouse model of retinitis pigmentosa. Glia 2016; 64:1479-91. [PMID: 27314452 PMCID: PMC4958518 DOI: 10.1002/glia.23016] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Accepted: 05/20/2016] [Indexed: 12/20/2022]
Abstract
Retinitis pigmentosa (RP), a disease characterized by the progressive degeneration of mutation‐bearing photoreceptors, is a significant cause of incurable blindness in the young worldwide. Recent studies have found that activated retinal microglia contribute to photoreceptor demise via phagocytosis and proinflammatory factor production, however mechanisms regulating these contributions are not well‐defined. In this study, we investigate the role of CX3CR1, a microglia‐specific receptor, in regulating microglia‐mediated degeneration using the well‐established rd10 mouse model of RP. We found that in CX3CR1‐deficient (CX3CR1GFP/GFP) rd10 mice microglial infiltration into the photoreceptor layer was significantly augmented and associated with accelerated photoreceptor apoptosis and atrophy compared with CX3CR1‐sufficient (CX3CR1GFP/+) rd10 littermates. CX3CR1‐deficient microglia demonstrated increased phagocytosis as evidenced by (1) having increased numbers of phagosomes in vivo, (2) an increased rate of phagocytosis of fluorescent beads and photoreceptor cellular debris in vitro, and (3) increased photoreceptor phagocytosis dynamics on live cell imaging in retinal explants, indicating that CX3CR1 signaling in microglia regulates the phagocytic clearance of at‐risk photoreceptors. We also found that CX3CR1 deficiency in retinal microglia was associated with increased expression of inflammatory cytokines and microglial activation markers. Significantly, increasing CX3CL1‐CX3CR1 signaling in the rd10 retina via exogenous intravitreal delivery of recombinant CX3CL1 was effective in (1) decreasing microglial infiltration, phagocytosis and activation, and (2) improving structural and functional features of photoreceptor degeneration. These results indicate that CX3CL1‐CX3CR1 signaling is a molecular mechanism capable of modulating microglial‐mediated degeneration and represents a potential molecular target in therapeutic approaches to RP. GLIA 2016;64:1479–1491
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Affiliation(s)
- Matthew K Zabel
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland
| | - Lian Zhao
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland
| | - Yikui Zhang
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland
| | - Shaimar R Gonzalez
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland
| | - Wenxin Ma
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland
| | - Xu Wang
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland
| | - Robert N Fariss
- Biological Imaging Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland
| | - Wai T Wong
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland
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257
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Lückoff A, Caramoy A, Scholz R, Prinz M, Kalinke U, Langmann T. Interferon-beta signaling in retinal mononuclear phagocytes attenuates pathological neovascularization. EMBO Mol Med 2016; 8:670-8. [PMID: 27137488 PMCID: PMC4888856 DOI: 10.15252/emmm.201505994] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Age-related macular degeneration (AMD) is a leading cause of vision loss among the elderly. AMD pathogenesis involves chronic activation of the innate immune system including complement factors and microglia/macrophage reactivity in the retina. Here, we show that lack of interferon-β signaling in the retina accelerates mononuclear phagocyte reactivity and promotes choroidal neovascularization (CNV) in the laser model of neovascular AMD Complete deletion of interferon-α/β receptor (Ifnar) using Ifnar1(-/-) mice significantly enhanced early microglia and macrophage activation in lesion areas. This triggered subsequent vascular leakage and CNV at later stages. Similar findings were obtained in laser-treated Cx3cr1(Cre) (ER):Ifnar1(fl/fl) animals that allowed the tamoxifen-induced conditional depletion of Ifnar in resident mononuclear phagocytes only. Conversely, systemic IFN-β therapy of laser-treated wild-type animals effectively attenuated microgliosis and macrophage responses in the early stage of disease and significantly reduced CNV size in the late phase. Our results reveal a protective role of Ifnar signaling in retinal immune homeostasis and highlight a potential use for IFN-β therapy in the eye to limit chronic inflammation and pathological angiogenesis in AMD.
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Affiliation(s)
- Anika Lückoff
- Retinal Immunology Laboratory (RIL), Department of Ophthalmology, University of Cologne, Cologne, Germany
| | - Albert Caramoy
- Retinal Immunology Laboratory (RIL), Department of Ophthalmology, University of Cologne, Cologne, Germany
| | - Rebecca Scholz
- Retinal Immunology Laboratory (RIL), Department of Ophthalmology, University of Cologne, Cologne, Germany
| | - Marco Prinz
- Institute of Neuropathology and BIOSS Center for Biological Signaling Studies, University of Freiburg, Freiburg, Germany
| | - Ulrich Kalinke
- Institute for Experimental Infection Research, TWINCORE Centre for Experimental and Clinical Infection Research a joint venture between the Helmholtz Centre for Infection Research and the Hannover Medical School, Hannover, Germany
| | - Thomas Langmann
- Retinal Immunology Laboratory (RIL), Department of Ophthalmology, University of Cologne, Cologne, Germany
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258
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Zhao L, Zabel MK, Wang X, Ma W, Shah P, Fariss RN, Qian H, Parkhurst CN, Gan WB, Wong WT. Microglial phagocytosis of living photoreceptors contributes to inherited retinal degeneration. EMBO Mol Med 2016; 7:1179-97. [PMID: 26139610 PMCID: PMC4568951 DOI: 10.15252/emmm.201505298] [Citation(s) in RCA: 298] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Retinitis pigmentosa, caused predominantly by mutations in photoreceptor genes, currently lacks comprehensive treatment. We discover that retinal microglia contribute non-cell autonomously to rod photoreceptor degeneration by primary phagocytosis of living rods. Using rd10 mice, we found that the initiation of rod degeneration is accompanied by early infiltration of microglia, upregulation of phagocytic molecules in microglia, and presentation of “eat-me” signals on mutated rods. On live-cell imaging, infiltrating microglia interact dynamically with photoreceptors via motile processes and engage in rapid phagocytic engulfment of non-apoptotic rods. Microglial contribution to rod demise is evidenced by morphological and functional amelioration of photoreceptor degeneration following genetic ablation of retinal microglia. Molecular inhibition of microglial phagocytosis using the vitronectin receptor antagonist cRGD also improved morphological and functional parameters of degeneration. Our findings highlight primary microglial phagocytosis as a contributing mechanism underlying cell death in retinitis pigmentosa and implicate microglia as a potential cellular target for therapy.
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Affiliation(s)
- Lian Zhao
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye institute National Institutes of Health, Bethesda, MD, USA
| | - Matthew K Zabel
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye institute National Institutes of Health, Bethesda, MD, USA
| | - Xu Wang
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye institute National Institutes of Health, Bethesda, MD, USA
| | - Wenxin Ma
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye institute National Institutes of Health, Bethesda, MD, USA
| | - Parth Shah
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye institute National Institutes of Health, Bethesda, MD, USA
| | - Robert N Fariss
- Biological Imaging Core, National Eye institute National Institutes of Health, Bethesda, MD, USA
| | - Haohua Qian
- Visual Function Core, National Eye institute National Institutes of Health, Bethesda, MD, USA
| | - Christopher N Parkhurst
- Department of Neuroscience and Physiology, Skirball Institute New York University School of Medicine, New York, NY, USA
| | - Wen-Biao Gan
- Department of Neuroscience and Physiology, Skirball Institute New York University School of Medicine, New York, NY, USA
| | - Wai T Wong
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye institute National Institutes of Health, Bethesda, MD, USA
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259
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Tay TL, Savage JC, Hui CW, Bisht K, Tremblay MÈ. Microglia across the lifespan: from origin to function in brain development, plasticity and cognition. J Physiol 2016; 595:1929-1945. [PMID: 27104646 DOI: 10.1113/jp272134] [Citation(s) in RCA: 357] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/15/2016] [Indexed: 12/11/2022] Open
Abstract
Microglia are the only immune cells that permanently reside in the central nervous system (CNS) alongside neurons and other types of glial cells. The past decade has witnessed a revolution in our understanding of their roles during normal physiological conditions. Cutting-edge techniques revealed that these resident immune cells are critical for proper brain development, actively maintain health in the mature brain, and rapidly adapt their function to physiological or pathophysiological needs. In this review, we highlight recent studies on microglial origin (from the embryonic yolk sac) and the factors regulating their differentiation and homeostasis upon brain invasion. Elegant experiments tracking microglia in the CNS allowed studies of their unique roles compared with other types of resident macrophages. Here we review the emerging roles of microglia in brain development, plasticity and cognition, and discuss the implications of the depletion or dysfunction of microglia for our understanding of disease pathogenesis. Immune activation, inflammation and various other conditions resulting in undesirable microglial activity at different stages of life could severely impair learning, memory and other essential cognitive functions. The diversity of microglial phenotypes across the lifespan, between compartments of the CNS, and sexes, as well as their crosstalk with the body and external environment, is also emphasised. Understanding what defines particular microglial phenotypes is of major importance for future development of innovative therapies controlling their effector functions, with consequences for cognition across chronic stress, ageing, neuropsychiatric and neurological diseases.
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Affiliation(s)
- Tuan Leng Tay
- Institute of Neuropathology, University of Freiburg, Germany
| | - Julie C Savage
- Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, Canada
| | - Chin Wai Hui
- Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, Canada
| | - Kanchan Bisht
- Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, Canada
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260
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Leovsky C, Fabian C, Naaldijk Y, Jäger C, Jang HJ, Böhme J, Rudolph L, Stolzing A. Biodistribution of in vitro-derived microglia applied intranasally and intravenously to mice: effects of aging. Cytotherapy 2016; 17:1617-26. [PMID: 26432561 DOI: 10.1016/j.jcyt.2015.07.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 07/13/2015] [Accepted: 07/30/2015] [Indexed: 12/28/2022]
Abstract
BACKGROUND AIMS The age of both the donor and the recipient has a potential influence on the efficacy of various cell therapies, but the underlying mechanisms are still being charted. We studied the effect of donor and recipient age in the context of microglia migration. METHODS Microglia were in vitro--differentiated from bone marrow of young (3 months) and aged (12 months) mice and transplanted into young (∼ 3 months) and aged (∼ 17 months) C57BL/6 mice (n = 25) through intravenous and intranasal application routes. Recipients were not immune-suppressed or irradiated. Transplanted microglia were tracked through the use of a sex-mismatched setup or histologically with the use of cells from enhanced green fluorescent protein enhanced green fluorescent protein transgenic mice. RESULTS No acute rejections or transplant-associated toxicity was observed. After 10 days, both intravenously and intranasally transplanted cells were detected in the brain. Transplanted cells were also found in the blood and the lymph system. The applied cells were also tracked in lungs and kidney but only after intravenous injection subjected to a "pulmonary first-pass effect." After 28 days, intravenously delivered cells were also found in the bone marrow and other organs, especially in aged recipients. Whereas in young recipients the transplanted microglia did not appear to persist, in aged brains the transplanted cells could still be identified up to 28 days after transplantation. However, when cells from aged donors were used, no signals of transplanted cells could be detected in the recipients. CONCLUSIONS This study establishes proof of principle that in vitro--derived microglia from young but not from aged donors, intravenously or intranasally transplanted, migrate to the brain in young and aged recipients.
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Affiliation(s)
| | - Claire Fabian
- Fraunhofer Institute for Cell Therapy and Immunology, Leipzig, Germany; Translational Centre for Regenerative Medicine (TRM), University of Leipzig, Leipzig, Germany
| | - Yahaira Naaldijk
- Fraunhofer Institute for Cell Therapy and Immunology, Leipzig, Germany; Translational Centre for Regenerative Medicine (TRM), University of Leipzig, Leipzig, Germany
| | - Carsten Jäger
- Paul Flechsig Institute for Brain Research, University of Leipzig, Leipzig, Germany
| | - Hwa Jin Jang
- Korea Ministry of Food and Drug Safety (MFDS), Hangul, Korea
| | - Josephine Böhme
- Fraunhofer Institute for Cell Therapy and Immunology, Leipzig, Germany
| | - Lukas Rudolph
- Translational Centre for Regenerative Medicine (TRM), University of Leipzig, Leipzig, Germany
| | - Alexandra Stolzing
- Translational Centre for Regenerative Medicine (TRM), University of Leipzig, Leipzig, Germany; University of Loughborough, Centre for Biological Engineering, Wolfson School of Material and Manufacturing Engineering, Loughborough, United Kingdom.
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261
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Udeochu JC, Shea JM, Villeda SA. Microglia communication: Parallels between aging and Alzheimer's disease. ACTA ACUST UNITED AC 2016; 7:114-125. [PMID: 27840659 PMCID: PMC5084774 DOI: 10.1111/cen3.12307] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 04/05/2016] [Indexed: 12/25/2022]
Abstract
Aging alters the functional integrity of the adult brain, driving cognitive impairments and susceptibility to neurodegenerative disorders in healthy individuals. In fact, aging remains the most dominant risk factor for Alzheimer's disease (AD). Recent findings have expanded our understanding of microglia function in the normal aging and AD brain, provoking an appreciation for microglia involvement in remodeling neuronal connections and maintaining brain integrity. This homeostatic function of microglia is achieved in part through the ability of microglia to interact extensively with and rapidly respond to changes in the brain microenvironment to enable adequate phenotypic transformations. Here, we discuss pro‐inflammatory drivers of microglia transformation in aging and AD by focusing on the immune‐modulatory functions of secreted factors, such as cytokines, complement factors and extracellular vesicles. We highlight the involvement of these secreted factors in aging and AD‐associated cellular changes in microglia immune activation, surveillance function, and phagocytosis. Finally, we discuss how pro‐inflammatory phenotypic changes associated with altered immune communication could both facilitate and exacerbate impairments in synaptic plasticity and cognitive function observed in the aged and AD brain.
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Affiliation(s)
- Joe C Udeochu
- Department of Anatomy University of California San Francisco San Francisco CA USA; Biomedical Sciences Graduate Program University of California San Francisco San Francisco CA USA
| | - Jeremy M Shea
- Department of Anatomy University of California San Francisco San Francisco CA USA
| | - Saul A Villeda
- Department of Anatomy University of California San Francisco San Francisco CA USA; Biomedical Sciences Graduate Program University of California San Francisco San Francisco CA USA; The Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research San Francisco CA USA
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262
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Wes PD, Sayed FA, Bard F, Gan L. Targeting microglia for the treatment of Alzheimer's Disease. Glia 2016; 64:1710-32. [DOI: 10.1002/glia.22988] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/22/2016] [Accepted: 03/24/2016] [Indexed: 12/19/2022]
Affiliation(s)
- Paul D. Wes
- Neuroinflammation Department; Lundbeck Research USA; Paramus New Jersey
| | - Faten A. Sayed
- Gladstone Institute for Neurodegeneration; San Francisco California
| | | | - Li Gan
- Gladstone Institute for Neurodegeneration; San Francisco California
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263
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Grabert K, Michoel T, Karavolos MH, Clohisey S, Baillie JK, Stevens MP, Freeman TC, Summers KM, McColl BW. Microglial brain region-dependent diversity and selective regional sensitivities to aging. Nat Neurosci 2016; 19:504-16. [PMID: 26780511 PMCID: PMC4768346 DOI: 10.1038/nn.4222] [Citation(s) in RCA: 809] [Impact Index Per Article: 101.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 12/07/2015] [Indexed: 12/13/2022]
Abstract
Microglia have critical roles in neural development, homeostasis and neuroinflammation and are increasingly implicated in age-related neurological dysfunction. Neurodegeneration often occurs in disease-specific, spatially restricted patterns, the origins of which are unknown. We performed to our knowledge the first genome-wide analysis of microglia from discrete brain regions across the adult lifespan of the mouse, and found that microglia have distinct region-dependent transcriptional identities and age in a regionally variable manner. In the young adult brain, differences in bioenergetic and immunoregulatory pathways were the major sources of heterogeneity and suggested that cerebellar and hippocampal microglia exist in a more immune-vigilant state. Immune function correlated with regional transcriptional patterns. Augmentation of the distinct cerebellar immunophenotype and a contrasting loss in distinction of the hippocampal phenotype among forebrain regions were key features during aging. Microglial diversity may enable regionally localized homeostatic functions but could also underlie region-specific sensitivities to microglial dysregulation and involvement in age-related neurodegeneration.
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Affiliation(s)
- Kathleen Grabert
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Tom Michoel
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
| | | | - Sara Clohisey
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
| | - J Kenneth Baillie
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Mark P Stevens
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Tom C Freeman
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Kim M Summers
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Barry W McColl
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, UK
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264
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Kim SY, Assawachananont J. A New Method to Visualize the Intact Subretina From Retinal Pigment Epithelium to Retinal Tissue in Whole Mount of Pigmented Mouse Eyes. Transl Vis Sci Technol 2016; 5:6. [PMID: 26929886 PMCID: PMC4757471 DOI: 10.1167/tvst.5.1.6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 01/06/2016] [Indexed: 01/24/2023] Open
Abstract
Purpose The subretinal layer between apical retinal pigment epithelium (RPE) and the apices of the photoreceptor outer segments is important to aging and degenerative pathogenesis, but current protocols do not provide intact horizontal images of this retinal space. Thus, an RPE/retina whole mount staining protocol was developed to observe integral subretinal regions. Methods RPE/retina whole mounts were stained instead of separated retina or RPE whole mounts. Hydrogen peroxide (H2O2) treatment was applied in different conditions of concentration, time, and temperature for the bleaching of RPE and choroidal melanocyte pigmentation in the pigmented RPE/retina whole mounts before antibody staining. Results An RPE/retina whole mount staining protocol provided better morphology of the photoreceptor outer segment than current retina whole mount. For the pigmented eyes, 10% H2O2 pretreatment effectively bleached melanin at 55°C less than 2 hours, or at 4°C within 7 days, without significant effect on immunolabeling efficacy of most antibodies tested. Actually, 55°C bleaching improved immunolabeling intensities compared to the nonbleaching control. This melanin bleaching RPE/retina protocol was applied further to observe macrophage/microglia extending from the sclera to outer plexiform layer in the CX3CR1+/GFP retina. Conclusions The pigment bleaching RPE/retina whole mount allowed integral horizontal imaging between choroid to photoreceptor layers, which could not be accomplished with existing methods of separated retina or RPE whole mount. Under these procedures, antigenicity of most antibodies also was well preserved. Translational Relevance This efficient protocol provides a tool to observe an integral view of subretinal structures including macrophage/microglia and transplanted cells, and further allows study of the interrelationship between the choroid and photoreceptor in models of aging, disease, and retinal degeneration.
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Affiliation(s)
- Soo-Young Kim
- Neurobiology-Neurodegeneration & Repair Laboratory National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Juthaporn Assawachananont
- Neurobiology-Neurodegeneration & Repair Laboratory National Eye Institute, National Institutes of Health, Bethesda, MD, USA
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265
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Rawji KS, Mishra MK, Michaels NJ, Rivest S, Stys PK, Yong VW. Immunosenescence of microglia and macrophages: impact on the ageing central nervous system. Brain 2016; 139:653-61. [PMID: 26912633 DOI: 10.1093/brain/awv395] [Citation(s) in RCA: 177] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Accepted: 11/18/2015] [Indexed: 01/21/2023] Open
Abstract
Ageing of the central nervous system results in a loss of both grey and white matter, leading to cognitive decline. Additional injury to both the grey and white matter is documented in many neurological disorders with ageing, including Alzheimer's disease, traumatic brain and spinal cord injury, stroke, and multiple sclerosis. Accompanying neuronal and glial damage is an inflammatory response consisting of activated macrophages and microglia, innate immune cells demonstrated to be both beneficial and detrimental in neurological repair. This article will propose the following: (i) infiltrating macrophages age differently from central nervous system-intrinsic microglia; (ii) several mechanisms underlie the differential ageing process of these two distinct cell types; and (iii) therapeutic strategies that selectively target these diverse mechanisms may rejuvenate macrophages and microglia for repair in the ageing central nervous system. Most responses of macrophages are diminished with senescence, but activated microglia increase their expression of pro-inflammatory cytokines while diminishing chemotactic and phagocytic activities. The senescence of macrophages and microglia has a negative impact on several neurological diseases, and the mechanisms underlying their age-dependent phenotypic changes vary from extrinsic microenvironmental changes to intrinsic changes in genomic integrity. We discuss the negative effects of age on neurological diseases, examine the response of senescent macrophages and microglia in these conditions, and propose a theoretical framework of therapeutic strategies that target the different mechanisms contributing to the ageing phenotype in these two distinct cell types. Rejuvenation of ageing macrophage/microglia may preserve neurological integrity and promote regeneration in the ageing central nervous system.
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Affiliation(s)
- Khalil S Rawji
- 1 Hotchkiss Brain Institute and the Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Manoj K Mishra
- 1 Hotchkiss Brain Institute and the Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Nathan J Michaels
- 1 Hotchkiss Brain Institute and the Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Serge Rivest
- 2 Neuroscience Laboratory, CHU de Québec Research Centre, Department of Molecular Medicine, Faculty of Medicine, Laval University, Québec City, Québec G1V 4G2, Canada
| | - Peter K Stys
- 1 Hotchkiss Brain Institute and the Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - V Wee Yong
- 1 Hotchkiss Brain Institute and the Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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266
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Aging Changes in Retinal Microglia and their Relevance to Age-related Retinal Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 854:73-8. [PMID: 26427396 DOI: 10.1007/978-3-319-17121-0_11] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Age-related retinal diseases, such as age-related macular degeneration (AMD) and glaucoma, contain features of chronic retinal inflammation that may promote disease progression. However, the relationship between aging and neuroinflammation is unclear. Microglia are long-lived, resident immune cells of the retina, and mediate local neuroinflammatory reactions. We hypothesize that aging changes in microglia may be causally linked to neuroinflammatory changes underlying age-dependent retinal diseases. Here, we review the evidence for (1) how the retinal microglial phenotype changes with aging, (2) the factors that drive microglial aging in the retina, and (3) aging-related changes in microglial gene expression. We examine how these aspects of microglial aging changes may relate to pathogenic mechanisms of immune dysregulation driving the progression of age-related retinal disease. These relationships can highlight microglial aging as a novel target for the prevention and treatment of retinal disease.
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267
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Lee S, Wu Y, Shi XQ, Zhang J. Characteristics of spinal microglia in aged and obese mice: potential contributions to impaired sensory behavior. IMMUNITY & AGEING 2015; 12:22. [PMID: 26604973 PMCID: PMC4657254 DOI: 10.1186/s12979-015-0049-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/12/2015] [Indexed: 12/30/2022]
Abstract
Background Both aging and obesity have been recognized widely as health conditions that profoundly affect individuals, families and the society. Aged and obese people often report altered pain responses while underlying mechanisms have not been fully elucidated. We aim to understand whether spinal microglia could potentially contribute to altered sensory behavior in aged and obese population. Results In this study, we monitored pain behavior in adult (6 months) and aged (17 months) mice fed with diet containing 10 % or 60 % Kcal fat. The group of young adult (3 months) mice was included as theoretical baseline control. Compared with lean adult animals, diet-induced-obese (DIO) adult, lean and DIO-aged mice showed enhanced painful response to heat and cold stimuli, while exhibiting hyposensitivity to mechanical stimulation. The impact of aging and obesity on microglia properties was evidenced by an increased microglial cell density in the spinal cords, stereotypic morphological changes and polarization towards pro-inflammatory phenotype. Obesity strikingly exacerbated the effect of aging on spinal microglia. Conclusion Aging/obesity altered microglia properties in the spinal cords, which can dysregulate neuron-microglia crosstalk and impair physiological pain signal transmission. The inflammatory functions of microglia have special relevance for understanding of abnormal pain behavior in aged/obese populations.
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Affiliation(s)
- SeungHwan Lee
- The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada ; Department of Neurology & Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC H3A 2B4 Canada ; Faculty of Dentistry, McGill University, Montreal, QC H3A 0C7 Canada
| | - YaSi Wu
- The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada ; Department of Neurology & Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC H3A 2B4 Canada ; Faculty of Dentistry, McGill University, Montreal, QC H3A 0C7 Canada
| | - Xiang Qun Shi
- The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada ; Department of Neurology & Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC H3A 2B4 Canada ; Faculty of Dentistry, McGill University, Montreal, QC H3A 0C7 Canada
| | - Ji Zhang
- The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada
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268
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Scholz R, Sobotka M, Caramoy A, Stempfl T, Moehle C, Langmann T. Minocycline counter-regulates pro-inflammatory microglia responses in the retina and protects from degeneration. J Neuroinflammation 2015; 12:209. [PMID: 26576678 PMCID: PMC4650866 DOI: 10.1186/s12974-015-0431-4] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 11/12/2015] [Indexed: 12/20/2022] Open
Abstract
Background Microglia reactivity is a hallmark of retinal degenerations and overwhelming microglial responses contribute to photoreceptor death. Minocycline, a semi-synthetic tetracycline analog, has potent anti-inflammatory and neuroprotective effects. Here, we investigated how minocycline affects microglia in vitro and studied its immuno-modulatory properties in a mouse model of acute retinal degeneration using bright white light exposure. Methods LPS-treated BV-2 microglia were stimulated with 50 μg/ml minocycline for 6 or 24 h, respectively. Pro-inflammatory gene transcription was determined by real-time RT-PCR and nitric oxide (NO) secretion was assessed using the Griess reagent. Caspase 3/7 levels were determined in 661W photoreceptors cultured with microglia-conditioned medium in the absence or presence of minocycline supplementation. BALB/cJ mice received daily intraperitoneal injections of 45 mg/kg minocycline, starting 1 day before exposure to 15.000 lux white light for 1 hour. The effect of minocycline treatment on microglial reactivity was analyzed by immunohistochemical stainings of retinal sections and flat-mounts, and messenger RNA (mRNA) expression of microglia markers was determined using real-time RT-PCR and RNA-sequencing. Optical coherence tomography (OCT) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) stainings were used to measure the extent of retinal degeneration and photoreceptor apoptosis. Results Stimulation of LPS-activated BV-2 microglia with minocycline significantly diminished the transcription of the pro-inflammatory markers CCL2, IL6, and inducible nitric oxide synthase (iNOS). Minocycline also reduced the production of NO and dampened microglial neurotoxicity on 661W photoreceptors. Furthermore, minocycline had direct protective effects on 661W photoreceptors by decreasing caspase 3/7 activity. In mice challenged with white light, injections of minocycline strongly decreased the number of amoeboid alerted microglia in the outer retina and down-regulated the expression of the microglial activation marker translocator protein (18 kDa) (TSPO), CD68, and activated microglia/macrophage whey acidic protein (AMWAP) already 1 day after light exposure. Furthermore, RNA-seq analyses revealed the potential of minocycline to globally counter-regulate pro-inflammatory gene transcription in the light-damaged retina. The severe thinning of the outer retina and the strong induction of photoreceptor apoptosis induced by light challenge were nearly completely prevented by minocycline treatment as indicated by a preserved retinal structure and a low number of apoptotic cells. Conclusions Minocycline potently counter-regulates microgliosis and light-induced retinal damage, indicating a promising concept for the treatment of retinal pathologies. Electronic supplementary material The online version of this article (doi:10.1186/s12974-015-0431-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Rebecca Scholz
- Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University of Cologne, 50931, Cologne, Germany.
| | - Markus Sobotka
- Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University of Cologne, 50931, Cologne, Germany.
| | - Albert Caramoy
- Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University of Cologne, 50931, Cologne, Germany.
| | - Thomas Stempfl
- Center of Excellence for Fluorescent Bioanalytics, University of Regensburg, 93053, Regensburg, Germany.
| | - Christoph Moehle
- Center of Excellence for Fluorescent Bioanalytics, University of Regensburg, 93053, Regensburg, Germany.
| | - Thomas Langmann
- Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University of Cologne, 50931, Cologne, Germany.
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Friedrich U, Datta S, Schubert T, Plössl K, Schneider M, Grassmann F, Fuchshofer R, Tiefenbach KJ, Längst G, Weber BHF. Synonymous variants in HTRA1 implicated in AMD susceptibility impair its capacity to regulate TGF-β signaling. Hum Mol Genet 2015; 24:6361-73. [PMID: 26310622 DOI: 10.1093/hmg/ddv346] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 08/19/2015] [Indexed: 12/16/2023] Open
Abstract
High-temperature requirement A1 (HTRA1) is a secreted serine protease reported to play a role in the development of several cancers and neurodegenerative diseases. Still, the mechanism underlying the disease processes largely remains undetermined. In age-related macular degeneration (AMD), a common cause of vision impairment and blindness in industrialized societies, two synonymous polymorphisms (rs1049331:C>T, and rs2293870:G>T) in exon 1 of the HTRA1 gene were associated with a high risk to develop disease. Here, we show that the two polymorphisms result in a protein with altered thermophoretic properties upon heat-induced unfolding, trypsin accessibility and secretion behavior, suggesting unique structural features of the AMD-risk-associated HTRA1 protein. Applying MicroScale Thermophoresis and protease digestion analysis, we demonstrate direct binding and proteolysis of transforming growth factor β1 (TGF-β1) by normal HTRA1 but not the AMD-risk-associated isoform. As a consequence, both HTRA1 isoforms strongly differed in their ability to control TGF-β mediated signaling, as revealed by reporter assays targeting the TGF-β1-induced serpin peptidase inhibitor (SERPINE1, alias PAI-1) promoter. In addition, structurally altered HTRA1 led to an impaired autocrine TGF-β signaling in microglia, as measured by a strong down-regulation of downstream effectors of the TGF-β cascade such as phosphorylated SMAD2 and PAI-1 expression. Taken together, our findings demonstrate the effects of two synonymous HTRA1 variants on protein structure and protein interaction with TGF-β1. As a consequence, this leads to an impairment of TGF-β signaling and microglial regulation. Functional implications of the altered properties on AMD pathogenesis remain to be clarified.
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Affiliation(s)
- Ulrike Friedrich
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Shyamtanu Datta
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Thomas Schubert
- Department of Biochemistry, University of Regensburg, 2bind GmbH, Josef Engert Straße 13, 93053 Regensburg, Germany
| | - Karolina Plössl
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | | | - Felix Grassmann
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | | | - Klaus-Jürgen Tiefenbach
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany and
| | - Gernot Längst
- Department of Biochemistry, University of Regensburg
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany,
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Scholz R, Caramoy A, Bhuckory MB, Rashid K, Chen M, Xu H, Grimm C, Langmann T. Targeting translocator protein (18 kDa) (TSPO) dampens pro-inflammatory microglia reactivity in the retina and protects from degeneration. J Neuroinflammation 2015; 12:201. [PMID: 26527153 PMCID: PMC4630900 DOI: 10.1186/s12974-015-0422-5] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 10/26/2015] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND Reactive microglia are commonly seen in retinal degenerative diseases, and neurotoxic microglia responses can contribute to photoreceptor cell death. We and others have previously shown that translocator protein (18 kDa) (TSPO) is highly induced in retinal degenerations and that the selective TSPO ligand XBD173 (AC-5216, emapunil) exerts strong anti-inflammatory effects on microglia in vitro and ex vivo. Here, we investigated whether targeting TSPO with XBD173 has immuno-modulatory and neuroprotective functions in two mouse models of acute retinal degeneration using bright white light exposure. METHODS BALB/cJ and Cx3cr1(GFP/+) mice received intraperitoneal injections of 10 mg/kg XBD173 or vehicle for five consecutive days, starting 1 day prior to exposure to either 15,000 lux white light for 1 h or 50,000 lux focal light for 10 min, respectively. The effects of XBD173 treatment on microglia and Müller cell reactivity were analyzed by immuno-stainings of retinal sections and flat mounts, fluorescence-activated cell sorting (FACS) analysis, and mRNA expression of microglia markers using quantitative real-time PCR (qRT-PCR). Optical coherence tomography (OCT), terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) stainings, and morphometric analyses were used to quantify the extent of retinal degeneration and photoreceptor apoptosis. RESULTS Four days after the mice were challenged with bright white light, a large number of amoeboid-shaped alerted microglia appeared in the degenerating outer retina, which was nearly completely prevented by treatment with XBD173. This treatment also down-regulated the expression of TSPO protein in microglia but did not change the TSPO levels in the retinal pigment epithelium (RPE). RT-PCR analysis showed that the microglia/macrophage markers Cd68 and activated microglia/macrophage whey acidic protein (Amwap) as well as the pro-inflammatory genes Ccl2 and Il6 were reduced after XBD173 treatment. Light-induced degeneration of the outer retina was nearly fully blocked by XBD173 treatment. We further confirmed these findings in an independent mouse model of focal light damage. Retinas of animals receiving XBD173 therapy displayed significantly more ramified non-reactive microglia and more viable arrestin-positive cone photoreceptors than vehicle controls. CONCLUSIONS Targeting TSPO with XBD173 effectively counter-regulates microgliosis and ameliorates light-induced retinal damage, highlighting a new pharmacological concept for the treatment of retinal degenerations.
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Affiliation(s)
- Rebecca Scholz
- Department of Ophthalmology, Laboratory for Experimental Immunology of the Eye, University of Cologne, 50931, Cologne, Germany.
| | - Albert Caramoy
- Department of Ophthalmology, Laboratory for Experimental Immunology of the Eye, University of Cologne, 50931, Cologne, Germany.
| | - Mohajeet B Bhuckory
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, BT12 6BA, UK.
| | - Khalid Rashid
- Department of Ophthalmology, Laboratory for Experimental Immunology of the Eye, University of Cologne, 50931, Cologne, Germany.
| | - Mei Chen
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, BT12 6BA, UK.
| | - Heping Xu
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, BT12 6BA, UK.
| | - Christian Grimm
- Department of Ophthalmology, Lab for Retinal Cell Biology, University of Zürich, 8057, Zürich, Switzerland.
| | - Thomas Langmann
- Department of Ophthalmology, Laboratory for Experimental Immunology of the Eye, University of Cologne, 50931, Cologne, Germany.
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Kohno H, Koso H, Okano K, Sundermeier TR, Saito S, Watanabe S, Tsuneoka H, Sakai T. Expression pattern of Ccr2 and Cx3cr1 in inherited retinal degeneration. J Neuroinflammation 2015; 12:188. [PMID: 26458944 PMCID: PMC4603985 DOI: 10.1186/s12974-015-0408-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 10/02/2015] [Indexed: 12/27/2022] Open
Abstract
Background Though accumulating evidence suggests that microglia, resident macrophages in the retina, and bone marrow-derived macrophages can cause retinal inflammation which accelerates photoreceptor cell death, the details of how these cells are activated during retinal degeneration (RD) remain uncertain. Therefore, it is important to clarify which cells play a dominant role in fueling retinal inflammation. However, distinguishing between microglia and macrophages is difficult using conventional techniques such as cell markers (e.g., Iba-1). Recently, two mouse models for visualizing chemokine receptors were established, Cx3cr1GFP/GFP and Ccr2RFP/RFP mice. As Cx3cr1 is expressed in microglia and Ccr2 is reportedly expressed in activated macrophages, these mice have the potential to distinguish microglia and macrophages, yielding novel information about the activation of these inflammatory cells and their individual roles in retinal inflammation. Methods In this study, c-mer proto-oncogene tyrosine kinase (Mertk)−/− mice, which show photoreceptor cell death due to defective retinal pigment epithelium phagocytosis, were employed as an animal model of RD. Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice were established by breeding Mertk−/−, Cx3cr1GFP/GFP, and Ccr2RFP/RFP mice. The retinal morphology and pattern of inflammatory cell activation and invasion of Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice were evaluated using retina and retinal pigment epithelium (RPE) flat mounts, retinal sections, and flow cytometry. Results Four-week-old Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice showed Cx3cr1-GFP-positive microglia in the inner retina. Cx3cr1-GFP and Ccr2-RFP dual positive activated microglia were observed in the outer retina and subretinal space of 6- and 8-week-old animals. Ccr2-RFP single positive bone marrow-derived macrophages were observed to migrate into the retina of Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice. These invading cells were still observed in the subretinal space in 18-week-old animals. Conclusions Cx3cr1-GFP-positive microglia and Ccr2-RFP-positive macrophages were distinguishable in the retinas of Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice. In addition, Ccr2 expression in Cx3cr1 positive microglia is a feature of microglial activation in RD. Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice enabled observation of microglial activation over time during RD and may be useful for developing inflammation-targeted treatment strategies for RD in the future.
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Affiliation(s)
- Hideo Kohno
- Department of Ophthalmology, The Jikei University School of Medicine, 105-8461, Tokyo, Japan. .,Tokyu Hospital, 145-0062, Tokyo, Japan.
| | - Hideto Koso
- Division of Molecular and Developmental Biology, The Institute of Medical Science, The University of Tokyo, 108-8639, Tokyo, Japan
| | - Kiichiro Okano
- Department of Ophthalmology, The Jikei University School of Medicine, 105-8461, Tokyo, Japan
| | - Thomas R Sundermeier
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Saburo Saito
- Department of Molecular Immunology, The Jikei University School of Medicine, 105-8461, Tokyo, Japan
| | - Sumiko Watanabe
- Division of Molecular and Developmental Biology, The Institute of Medical Science, The University of Tokyo, 108-8639, Tokyo, Japan
| | - Hiroshi Tsuneoka
- Department of Ophthalmology, The Jikei University School of Medicine, 105-8461, Tokyo, Japan
| | - Tsutomu Sakai
- Department of Ophthalmology, The Jikei University School of Medicine, 105-8461, Tokyo, Japan.
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272
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Lafrenaye AD, Todani M, Walker SA, Povlishock JT. Microglia processes associate with diffusely injured axons following mild traumatic brain injury in the micro pig. J Neuroinflammation 2015; 12:186. [PMID: 26438203 PMCID: PMC4595283 DOI: 10.1186/s12974-015-0405-6] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/23/2015] [Indexed: 01/08/2023] Open
Abstract
Background Mild traumatic brain injury (mTBI) is an all too common occurrence that exacts significant personal and societal costs. The pathophysiology of mTBI is complex, with reports routinely correlating diffuse axonal injury (DAI) with prolonged morbidity. Progressive chronic neuroinflammation has also recently been correlated to morbidity, however, the potential association between neuroinflammatory microglia and DAI is not well understood. The majority of studies exploring neuroinflammatory responses to TBI have focused on more chronic phases of injury involving phagocytosis associated with Wallerian change. Little, however, is known regarding the neuroinflammatory response seen acutely following diffuse mTBI and its potential relationship to early DAI. Additionally, while inflammation is drastically different in rodents compared to humans, pigs and humans share very similar inflammatory profiles and responses. Methods In the current study, we employed a modified central fluid percussion model in micro pigs. Using this model of diffuse mTBI, paired with various immunohistological endpoints, we assessed the potential association between acute thalamic DAI and neuroinflammation 6 h following injury. Results Injured micro pigs displayed substantial axonal damage reflected in the presence of APP+ proximal axonal swellings, which were particularly prominent in the thalamus. In companion, the same thalamic sites displayed extensive neuroinflammation, which was observed using Iba-1 immunohistochemistry. The physical relationship between microglia and DAI, assessed via confocal 3D analysis, revealed a dramatic increase in the number of Iba-1+ microglial processes that contacted APP+ proximal axonal swellings compared to uninjured myelinated thalamic axons in sham animals. Conclusions In aggregate, these studies reveal acute microglial process convergence on proximal axonal swellings undergoing DAI, an interaction not previously recognized in the literature. These findings transform our understanding of acute neuroinflammation following mTBI and may suggest its potential as a diagnostic and/or a therapeutic target. Electronic supplementary material The online version of this article (doi:10.1186/s12974-015-0405-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Audrey D Lafrenaye
- Department of Anatomy and Neurobiology, Virginia Commonwealth University Medical Center, P.O. Box 980709, Richmond, VA, 23298, USA.
| | - Masaki Todani
- Department of Anatomy and Neurobiology, Virginia Commonwealth University Medical Center, P.O. Box 980709, Richmond, VA, 23298, USA. .,Advanced Medical Emergency and Critical Care Center, Yamaguchi University Hospital, Yamaguchi, Japan.
| | - Susan A Walker
- Department of Anatomy and Neurobiology, Virginia Commonwealth University Medical Center, P.O. Box 980709, Richmond, VA, 23298, USA.
| | - John T Povlishock
- Department of Anatomy and Neurobiology, Virginia Commonwealth University Medical Center, P.O. Box 980709, Richmond, VA, 23298, USA.
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273
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Bilateral retinal microglial response to unilateral optic nerve transection in rats. Neuroscience 2015; 311:56-66. [PMID: 26432953 DOI: 10.1016/j.neuroscience.2015.09.067] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 09/07/2015] [Accepted: 09/24/2015] [Indexed: 01/17/2023]
Abstract
When retinal ganglion cells undergo apoptosis after optic nerve (ON) injury, microglial cells proliferate and promptly clear the degenerated debris in the ipsilateral retina. However, microglial changes in the contralateral retina have not been fully elucidated. This study characterized the long-term bilateral retinal microglial responses after unilateral ON transection. We analyzed the time course of proliferation and morphology changes of microglial cells, between 3 days and 12 weeks post ON transection, of undisturbed and reactive microglia in bilateral retinas of adult Fischer rats with unilateral ON transection. Microglia in retinas without ON transection were distributed homogeneously and possessed a highly ramified morphology, as judged by immunohistochemistry for ionized calcium-binding adapter molecule 1 (Iba1). After ON transection, microglia density in the ipsilateral retina increased gradually from 3 days to 2 weeks, and decreased from 3 weeks to 12 weeks, along with dramatic inverted alteration of process branch points of microglia in the ganglion cell layer (GCL). Transformation of ramified microglia into ameboid-like macrophages with few branching processes was observed in the ipsilateral retina from 1 week to 3 weeks. Though an increase in microglial density was weak in the contralateral retina and could only be statistically detected in the central retina, the morphological alteration over time was obvious and similar to that of the ipsilateral retina. In the inner plexiform layer (IPL), cell density and morphological changes of microglia in both the ipsilateral and contralateral retina were not prominent. These findings indicates that, though proliferation of microglial cells is weak in the contralateral retina after unilateral ON transection, conspicuous alterations in microglial morphology occur bilaterally. These suggest that using the contralateral retina as a control in studies of retinal degeneration should be considered with caution.
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274
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Choi I, Kim B, Byun JW, Baik SH, Huh YH, Kim JH, Mook-Jung I, Song WK, Shin JH, Seo H, Suh YH, Jou I, Park SM, Kang HC, Joe EH. LRRK2 G2019S mutation attenuates microglial motility by inhibiting focal adhesion kinase. Nat Commun 2015; 6:8255. [PMID: 26365310 PMCID: PMC4647842 DOI: 10.1038/ncomms9255] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 08/03/2015] [Indexed: 01/20/2023] Open
Abstract
In response to brain injury, microglia rapidly extend processes that isolate lesion sites and protect the brain from further injury. Here we report that microglia carrying a pathogenic mutation in the Parkinson's disease (PD)-associated gene, G2019S-LRRK2 (GS-Tg microglia), show retarded ADP-induced motility and delayed isolation of injury, compared with non-Tg microglia. Conversely, LRRK2 knockdown microglia are highly motile compared with control cells. In our functional assays, LRRK2 binds to focal adhesion kinase (FAK) and phosphorylates its Thr–X–Arg/Lys (TXR/K) motif(s), eventually attenuating FAK activity marked by decreased pY397 phosphorylation (pY397). GS-LRRK2 decreases the levels of pY397 in the brain, microglia and HEK cells. In addition, treatment with an inhibitor of LRRK2 kinase restores pY397 levels, decreased pTXR levels and rescued motility of GS-Tg microglia. These results collectively suggest that G2019S mutation of LRRK2 may contribute to the development of PD by inhibiting microglial response to brain injury. In response to brain injury, microglia extend processes to isolate the lesion. Here Choi et al. show that microglia expressing a pathogenic mutation in the Parkinson's disease-associated LRRK2 gene show reduced motility and delayed lesion isolation in vitro and in vivo due to attenuated focal adhesion kinase activity.
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Affiliation(s)
- Insup Choi
- Department of Biomedical Sciences, Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Beomsue Kim
- Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Ji-Won Byun
- Department of Biomedical Sciences, Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Sung Hoon Baik
- Department of Biochemistry and Biomedical Sciences, College of Medicine, Seoul National University, Seoul 110-799, Korea
| | - Yun Hyun Huh
- Bio Imaging and Cell Dynamics Research Center, School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Jong-Hyeon Kim
- Department of Biomedical Sciences, Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Inhee Mook-Jung
- Department of Biochemistry and Biomedical Sciences, College of Medicine, Seoul National University, Seoul 110-799, Korea
| | - Woo Keun Song
- Bio Imaging and Cell Dynamics Research Center, School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Joo-Ho Shin
- Division of Pharmacology, Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do 440-746, Korea
| | - Hyemyung Seo
- Department of Molecular and Life Sciences, Hanyang University, Ansan 426-791, Korea
| | - Young Ho Suh
- Department of Biomedical Sciences, Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Ilo Jou
- Department of Biomedical Sciences, Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Sang Myun Park
- Department of Biomedical Sciences, Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Ho Chul Kang
- Department of Physiology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
| | - Eun-Hye Joe
- Department of Biomedical Sciences, Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Department of Brain Science, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea.,Brain Disease Research Center, Ajou University School of Medicine, Suwon, Gyeonggi-do 443-380, Korea
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275
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Loane DJ, Kumar A. Microglia in the TBI brain: The good, the bad, and the dysregulated. Exp Neurol 2015; 275 Pt 3:316-327. [PMID: 26342753 DOI: 10.1016/j.expneurol.2015.08.018] [Citation(s) in RCA: 480] [Impact Index Per Article: 53.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 08/05/2015] [Accepted: 08/25/2015] [Indexed: 01/24/2023]
Abstract
As the major cellular component of the innate immune system in the central nervous system (CNS) and the first line of defense whenever injury or disease occurs, microglia play a critical role in neuroinflammation following a traumatic brain injury (TBI). In the injured brain microglia can produce neuroprotective factors, clear cellular debris and orchestrate neurorestorative processes that are beneficial for neurological recovery after TBI. However, microglia can also become dysregulated and can produce high levels of pro-inflammatory and cytotoxic mediators that hinder CNS repair and contribute to neuronal dysfunction and cell death. The dual role of microglial activation in promoting beneficial and detrimental effects on neurons may be accounted for by their polarization state and functional responses after injury. In this review article we discuss emerging research on microglial activation phenotypes in the context of acute brain injury, and the potential role of microglia in phenotype-specific neurorestorative processes such as neurogenesis, angiogenesis, oligodendrogenesis and regeneration. We also describe some of the known molecular mechanisms that regulate phenotype switching, and highlight new therapeutic approaches that alter microglial activation state balance to enhance long-term functional recovery after TBI. An improved understanding of the regulatory mechanisms that control microglial phenotypic shifts may advance our knowledge of post-injury recovery and repair, and provide opportunities for the development of novel therapeutic strategies for TBI.
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Affiliation(s)
- David J Loane
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD, United States; Shock, Trauma, and Anesthesiology Research (STAR) Center, University of Maryland School of Medicine, Baltimore, MD, United States.
| | - Alok Kumar
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD, United States; Shock, Trauma, and Anesthesiology Research (STAR) Center, University of Maryland School of Medicine, Baltimore, MD, United States
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276
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von Bernhardi R, Eugenín-von Bernhardi L, Eugenín J. Microglial cell dysregulation in brain aging and neurodegeneration. Front Aging Neurosci 2015; 7:124. [PMID: 26257642 PMCID: PMC4507468 DOI: 10.3389/fnagi.2015.00124] [Citation(s) in RCA: 357] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Accepted: 06/22/2015] [Indexed: 12/29/2022] Open
Abstract
Aging is the main risk factor for neurodegenerative diseases. In aging, microglia undergoes phenotypic changes compatible with their activation. Glial activation can lead to neuroinflammation, which is increasingly accepted as part of the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD). We hypothesize that in aging, aberrant microglia activation leads to a deleterious environment and neurodegeneration. In aged mice, microglia exhibit an increased expression of cytokines and an exacerbated inflammatory response to pathological changes. Whereas LPS increases nitric oxide (NO) secretion in microglia from young mice, induction of reactive oxygen species (ROS) predominates in older mice. Furthermore, there is accumulation of DNA oxidative damage in mitochondria of microglia during aging, and also an increased intracellular ROS production. Increased ROS activates the redox-sensitive nuclear factor kappa B, which promotes more neuroinflammation, and can be translated in functional deficits, such as cognitive impairment. Mitochondria-derived ROS and cathepsin B, are also necessary for the microglial cell production of interleukin-1β, a key inflammatory cytokine. Interestingly, whereas the regulatory cytokine TGFβ1 is also increased in the aged brain, neuroinflammation persists. Assessing this apparent contradiction, we have reported that TGFβ1 induction and activation of Smad3 signaling after inflammatory stimulation are reduced in adult mice. Other protective functions, such as phagocytosis, although observed in aged animals, become not inducible by inflammatory stimuli and TGFβ1. Here, we discuss data suggesting that mitochondrial and endolysosomal dysfunction could at least partially mediate age-associated microglial cell changes, and, together with the impairment of the TGFβ1-Smad3 pathway, could result in the reduction of protective activation and the facilitation of cytotoxic activation of microglia, resulting in the promotion of neurodegenerative diseases.
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Affiliation(s)
- Rommy von Bernhardi
- Department of Neurology, Faculty of Medicine, Pontificia Universidad Católica de Chile Santiago, Chile
| | | | - Jaime Eugenín
- Laboratory of Neural Systems, Department of Biology, Faculty of Chemistry and Biology, Universidad de Santiago de Chile (USACH) Santiago, Chile
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277
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Vecino E, Rodriguez FD, Ruzafa N, Pereiro X, Sharma SC. Glia-neuron interactions in the mammalian retina. Prog Retin Eye Res 2015; 51:1-40. [PMID: 26113209 DOI: 10.1016/j.preteyeres.2015.06.003] [Citation(s) in RCA: 493] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 05/18/2015] [Accepted: 06/02/2015] [Indexed: 02/07/2023]
Abstract
The mammalian retina provides an excellent opportunity to study glia-neuron interactions and the interactions of glia with blood vessels. Three main types of glial cells are found in the mammalian retina that serve to maintain retinal homeostasis: astrocytes, Müller cells and resident microglia. Müller cells, astrocytes and microglia not only provide structural support but they are also involved in metabolism, the phagocytosis of neuronal debris, the release of certain transmitters and trophic factors and K(+) uptake. Astrocytes are mostly located in the nerve fibre layer and they accompany the blood vessels in the inner nuclear layer. Indeed, like Müller cells, astrocytic processes cover the blood vessels forming the retinal blood barrier and they fulfil a significant role in ion homeostasis. Among other activities, microglia can be stimulated to fulfil a macrophage function, as well as to interact with other glial cells and neurons by secreting growth factors. This review summarizes the main functional relationships between retinal glial cells and neurons, presenting a general picture of the retina recently modified based on experimental observations. The preferential involvement of the distinct glia cells in terms of the activity in the retina is discussed, for example, while Müller cells may serve as progenitors of retinal neurons, astrocytes and microglia are responsible for synaptic pruning. Since different types of glia participate together in certain activities in the retina, it is imperative to explore the order of redundancy and to explore the heterogeneity among these cells. Recent studies revealed the association of glia cell heterogeneity with specific functions. Finally, the neuroprotective effects of glia on photoreceptors and ganglion cells under normal and adverse conditions will also be explored.
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Affiliation(s)
- Elena Vecino
- Department of Cell Biology and Histology, University of the Basque Country UPV/EHU, Leioa 48940, Vizcaya, Spain
| | - F David Rodriguez
- Department of Biochemistry and Molecular Biology, E-37007, University of Salamanca, Salamanca, Spain
| | - Noelia Ruzafa
- Department of Cell Biology and Histology, University of the Basque Country UPV/EHU, Leioa 48940, Vizcaya, Spain
| | - Xandra Pereiro
- Department of Cell Biology and Histology, University of the Basque Country UPV/EHU, Leioa 48940, Vizcaya, Spain
| | - Sansar C Sharma
- Department of Ophthalmology, Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA; IKERBASQUE, Basque Foundation for Science at Dept. Cell Biology and Histology, UPV/EHU, Spain
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278
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Deleidi M, Jäggle M, Rubino G. Immune aging, dysmetabolism, and inflammation in neurological diseases. Front Neurosci 2015; 9:172. [PMID: 26089771 PMCID: PMC4453474 DOI: 10.3389/fnins.2015.00172] [Citation(s) in RCA: 180] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Accepted: 04/28/2015] [Indexed: 12/17/2022] Open
Abstract
As we age, the immune system undergoes a process of senescence accompanied by the increased production of proinflammatory cytokines, a chronic subclinical condition named as “inflammaging”. Emerging evidence from human and experimental models suggest that immune senescence also affects the central nervous system and promotes neuronal dysfunction, especially within susceptible neuronal populations. In this review we discuss the potential role of immune aging, inflammation and metabolic derangement in neurological diseases. The discovery of novel therapeutic strategies targeting age-linked inflammation may promote healthy brain aging and the treatment of neurodegenerative as well as neuropsychiatric disorders.
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Affiliation(s)
- Michela Deleidi
- Department of Neurodegenerative Diseases, German Center for Neurodegenerative Diseases (DZNE), Hertie Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany
| | - Madeline Jäggle
- Department of Neurodegenerative Diseases, German Center for Neurodegenerative Diseases (DZNE), Hertie Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany
| | - Graziella Rubino
- Department of Internal Medicine II, Center for Medical Research, University of Tübingen Tübingen, Germany
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279
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Reichenbach A, Bringmann A. Purinergic signaling in retinal degeneration and regeneration. Neuropharmacology 2015; 104:194-211. [PMID: 25998275 DOI: 10.1016/j.neuropharm.2015.05.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/07/2015] [Accepted: 05/07/2015] [Indexed: 02/01/2023]
Abstract
Purinergic signaling is centrally involved in mediating the degeneration of the injured and diseased retina, the induction of retinal gliosis, and the protection of the retinal tissue from degeneration. Dysregulated calcium signaling triggered by overactivation of P2X7 receptors is a crucial step in the induction of neuronal and microvascular cell death under pathogenic conditions like ischemia-hypoxia, elevated intraocular pressure, and diabetes, respectively. Overactivation of P2X7 plays also a pathogenic role in inherited and age-related photoreceptor cell death and in the age-related dysfunction and degeneration of the retinal pigment epithelium. Gliosis of micro- and macroglial cells, which is induced and/or modulated by purinergic signaling and associated with an impaired homeostatic support to neurons, and the ATP-mediated propagation of retinal gliosis from a focal injury into the surrounding noninjured tissue are involved in inducing secondary cell death in the retina. On the other hand, alterations in the glial metabolism of extracellular nucleotides, resulting in a decreased level of ATP and an increased level of adenosine, may be neuroprotective in the diseased retina. Purinergic signals stimulate the proliferation of retinal glial cells which contributes to glial scarring which has protective effects on retinal degeneration and adverse effects on retinal regeneration. Pharmacological modulation of purinergic receptors, e.g., inhibition of P2X and activation of adenosine receptors, may have clinical importance for the prevention of photoreceptor, neuronal, and microvascular cell death in diabetic retinopathy, retinitis pigmentosa, age-related macular degeneration, and glaucoma, respectively, for the clearance of retinal edema, and the inhibition of dysregulated cell proliferation in proliferative retinopathies. This article is part of a Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Affiliation(s)
- Andreas Reichenbach
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany.
| | - Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
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280
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Li L, Eter N, Heiduschka P. The microglia in healthy and diseased retina. Exp Eye Res 2015; 136:116-30. [PMID: 25952657 DOI: 10.1016/j.exer.2015.04.020] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 04/28/2015] [Accepted: 04/29/2015] [Indexed: 12/25/2022]
Abstract
The microglia are the immune cells of the central nervous system and, also the retina. They fulfil several tasks of surveillance in the healthy retina. In case of an injury or disease, microglia become activated and tries to repair the damage. However, in a lot of cases it does not work, and microglia deteriorate the situation by releasing toxic and pro-inflammatory compounds. Moreover, they further promote degenerative processes by attacking and phagocytosing damaged neurones and photoreceptors that otherwise would possibly have the chance to survive. Such deleterious action of the microglia has been observed in degeneration of retinal ganglion cells and photoreceptors, and it takes place in hereditary diseases, infections as well as in case of traumatic or light injuries. Therefore, a number of attempts has been undertaken so far to inhibit the microglia, with varying success. The task remains to study behaviour of the microglia and their interaction with other retinal cell populations in more detail with respect to released factors and expressed receptors including the time points of the corresponding events. The goal has to be to find a better balance between helpful and detrimental actions of the microglia.
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Affiliation(s)
- Lu Li
- University of Münster Medical School, Department of Ophthalmology, Domagkstr. 15, D-48149 Münster, Germany
| | - Nicole Eter
- University of Münster Medical School, Department of Ophthalmology, Domagkstr. 15, D-48149 Münster, Germany
| | - Peter Heiduschka
- University of Münster Medical School, Department of Ophthalmology, Domagkstr. 15, D-48149 Münster, Germany.
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281
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Poliani PL, Wang Y, Fontana E, Robinette ML, Yamanishi Y, Gilfillan S, Colonna M. TREM2 sustains microglial expansion during aging and response to demyelination. J Clin Invest 2015; 125:2161-70. [PMID: 25893602 DOI: 10.1172/jci77983] [Citation(s) in RCA: 344] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 03/17/2015] [Indexed: 12/31/2022] Open
Abstract
Microglia contribute to development, homeostasis, and immunity of the CNS. Like other tissue-resident macrophage populations, microglia express the surface receptor triggering receptor expressed on myeloid cells 2 (TREM2), which binds polyanions, such as dextran sulphate and bacterial LPS, and activates downstream signaling cascades through the adapter DAP12. Individuals homozygous for inactivating mutations in TREM2 exhibit demyelination of subcortical white matter and a lethal early onset dementia known as Nasu-Hakola disease. How TREM2 deficiency mediates demyelination and disease is unknown. Here, we addressed the basis for this genetic association using Trem2(-/-) mice. In WT mice, microglia expanded in the corpus callosum with age, whereas aged Trem2(-/-) mice had fewer microglia with an abnormal morphology. In the cuprizone model of oligodendrocyte degeneration and demyelination, Trem2(-/-) microglia failed to amplify transcripts indicative of activation, phagocytosis, and lipid catabolism in response to myelin damage. As a result, Trem2(-/-) mice exhibited impaired myelin debris clearance, axonal dystrophy, oligodendrocyte reduction, and persistent demyelination after prolonged cuprizone treatment. Moreover, myelin-associated lipids robustly triggered TREM2 signaling in vitro, suggesting that TREM2 may directly sense lipid components exposed during myelin damage. We conclude that TREM2 is required for promoting microglial expansion during aging and microglial response to insults of the white matter.
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282
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Tremblay MÈ, Lecours C, Samson L, Sánchez-Zafra V, Sierra A. From the Cajal alumni Achúcarro and Río-Hortega to the rediscovery of never-resting microglia. Front Neuroanat 2015; 9:45. [PMID: 25926775 PMCID: PMC4396411 DOI: 10.3389/fnana.2015.00045] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 03/24/2015] [Indexed: 12/30/2022] Open
Abstract
Under the guidance of Ramón y Cajal, a plethora of students flourished and began to apply his silver impregnation methods to study brain cells other than neurons: the neuroglia. In the first decades of the twentieth century, Nicolás Achúcarro was one of the first researchers to visualize the brain cells with phagocytic capacity that we know today as microglia. Later, his pupil Pío del Río-Hortega developed modifications of Achúcarro's methods and was able to specifically observe the fine morphological intricacies of microglia. These findings contradicted Cajal's own views on cells that he thought belonged to the same class as oligodendroglia (the so called “third element” of the nervous system), leading to a long-standing discussion. It was only in 1924 that Río-Hortega's observations prevailed worldwide, thus recognizing microglia as a unique cell type. This late landing in the Neuroscience arena still has repercussions in the twenty first century, as microglia remain one of the least understood cell populations of the healthy brain. For decades, microglia in normal, physiological conditions in the adult brain were considered to be merely “resting,” and their contribution as “activated” cells to the neuroinflammatory response in pathological conditions mostly detrimental. It was not until microglia were imaged in real time in the intact brain using two-photon in vivo imaging that the extreme motility of their fine processes was revealed. These findings led to a conceptual revolution in the field: “resting” microglia are constantly surveying the brain parenchyma in normal physiological conditions. Today, following Cajal's school of thought, structural and functional investigations of microglial morphology, dynamics, and relationships with neurons and other glial cells are experiencing a renaissance and we stand at the brink of discovering new roles for these unique immune cells in the healthy brain, an essential step to understand their causal relationship to diseases.
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Affiliation(s)
- Marie-Ève Tremblay
- Centre de Recherche du CHU de Québec, Axe Neurosciences Québec, QC, Canada ; Département de médecine moléculaire, Université Laval Québec, QC, Canada
| | - Cynthia Lecours
- Centre de Recherche du CHU de Québec, Axe Neurosciences Québec, QC, Canada ; Département de médecine moléculaire, Université Laval Québec, QC, Canada
| | - Louis Samson
- Centre de Recherche du CHU de Québec, Axe Neurosciences Québec, QC, Canada ; Département de médecine moléculaire, Université Laval Québec, QC, Canada
| | - Víctor Sánchez-Zafra
- Achúcarro Basque Center for Neuroscience, Bizkaia Science and Technology Park Zamudio, Spain ; Department of Neurosciences, University of the Basque Country Leioa, Spain
| | - Amanda Sierra
- Achúcarro Basque Center for Neuroscience, Bizkaia Science and Technology Park Zamudio, Spain ; Department of Neurosciences, University of the Basque Country Leioa, Spain ; Ikerbasque Foundation Bilbao, Spain
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283
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Madry C, Attwell D. Receptors, ion channels, and signaling mechanisms underlying microglial dynamics. J Biol Chem 2015; 290:12443-50. [PMID: 25855789 DOI: 10.1074/jbc.r115.637157] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Microglia, the innate immune cells of the CNS, play a pivotal role in brain injury and disease. Microglia are extremely motile; their highly ramified processes constantly survey the brain parenchyma, and they respond promptly to brain damage with targeted process movement toward the injury site. Microglia play a key role in brain development and function by pruning synapses during development, phagocytosing apoptotic newborn neurons, and regulating neuronal activity by direct microglia-neuron or indirect microglia-astrocyte-neuron interactions, which all depend on their process motility. This review highlights recent discoveries about microglial dynamics, focusing on the receptors, ion channels, and signaling pathways involved.
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Affiliation(s)
- Christian Madry
- From the Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - David Attwell
- From the Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom
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284
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SIRT1 deficiency in microglia contributes to cognitive decline in aging and neurodegeneration via epigenetic regulation of IL-1β. J Neurosci 2015; 35:807-18. [PMID: 25589773 DOI: 10.1523/jneurosci.2939-14.2015] [Citation(s) in RCA: 183] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Aging is the predominant risk factor for neurodegenerative diseases. One key phenotype as the brain ages is an aberrant innate immune response characterized by proinflammation. However, the molecular mechanisms underlying aging-associated proinflammation are poorly defined. Whether chronic inflammation plays a causal role in cognitive decline in aging and neurodegeneration has not been established. Here we report a mechanistic link between chronic inflammation and aging microglia and a causal role of aging microglia in neurodegenerative cognitive deficits. We showed that SIRT1 is reduced with the aging of microglia and that microglial SIRT1 deficiency has a causative role in aging- or tau-mediated memory deficits via IL-1β upregulation in mice. Interestingly, the selective activation of IL-1β transcription by SIRT1 deficiency is likely mediated through hypomethylating the specific CpG sites on IL-1β proximal promoter. In humans, hypomethylation of IL-1β is strongly associated with chronological age and with elevated IL-1β transcription. Our findings reveal a novel epigenetic mechanism in aging microglia that contributes to cognitive deficits in aging and neurodegenerative diseases.
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285
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Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in industrial countries. Vision loss caused by AMD results from geographic atrophy (dry AMD) and/or choroidal neovascularization (wet AMD). Presently, the etiology and pathogenesis of AMD is not fully understood and there is no effective treatment. Oxidative stress in retinal pigment epithelial (RPE) cells is considered to be one of the major factors contributing to the pathogenesis of AMD. Also retinal glia, as scavengers, are deeply related with diseases and could play a role. Therefore, therapeutic approaches for microglia and Müller glia, as well as RPE, may lead to new strategies for AMD treatment. This review summarizes the pathological findings observed in RPE cells, microglia and Müller glia of AMD murine models.
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Affiliation(s)
- Soo-Young Kim
- Neurobiology-Neurodegeneration & Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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286
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Contribution of microglia-mediated neuroinflammation to retinal degenerative diseases. Mediators Inflamm 2015; 2015:673090. [PMID: 25873768 PMCID: PMC4385698 DOI: 10.1155/2015/673090] [Citation(s) in RCA: 161] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 12/16/2014] [Indexed: 12/27/2022] Open
Abstract
Retinal degenerative diseases are major causes of vision loss and blindness worldwide and are characterized by chronic and progressive neuronal loss. One common feature of retinal degenerative diseases and brain neurodegenerative diseases is chronic neuroinflammation. There is growing evidence that retinal microglia, as in the brain, become activated in the course of retinal degenerative diseases, having a pivotal role in the initiation and propagation of the neurodegenerative process. A better understanding of the events elicited and mediated by retinal microglia will contribute to the clarification of disease etiology and might open new avenues for potential therapeutic interventions. This review aims at giving an overview of the roles of microglia-mediated neuroinflammation in major retinal degenerative diseases like glaucoma, age-related macular degeneration, and diabetic retinopathy.
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287
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7-Ketocholesterol increases retinal microglial migration, activation, and angiogenicity: a potential pathogenic mechanism underlying age-related macular degeneration. Sci Rep 2015; 5:9144. [PMID: 25775051 PMCID: PMC4360733 DOI: 10.1038/srep09144] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 02/23/2015] [Indexed: 11/26/2022] Open
Abstract
Age-related macular degeneration (AMD) has been associated with both accumulation of lipid and lipid oxidative products, as well as increased neuroinflammatory changes and microglial activation in the outer retina. However, the relationships between these factors are incompletely understood. 7-Ketocholesterol (7KCh) is a cholesterol oxidation product localized to the outer retina with prominent pro-inflammatory effects. To explore the potential relationship between 7KCh and microglial activation, we localized 7KCh and microglia to the outer retina of aged mice and investigated 7KCh effects on retinal microglia in both in vitro and in vivo systems. We found that retinal microglia demonstrated a prominent chemotropism to 7KCh and readily internalized 7KCh. Sublethal concentrations of 7KCh resulted in microglial activation and polarization to a pro-inflammatory M1 state via NLRP3 inflammasome activation. Microglia exposed to 7KCh reduced expression of neurotrophic growth factors but increased expression of angiogenic factors, transitioning to a more neurotoxic and pro-angiogenic phenotype. Finally, subretinal transplantation of 7KCh-exposed microglia promoted choroidal neovascularization (CNV) relative to control microglia in a Matrigel-CNV model. The interaction of retinal microglia with 7KCh in the aged retina may thus underlie how outer retinal lipid accumulation in intermediate AMD results in neuroinflammation that ultimately drives progression towards advanced AMD.
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288
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289
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Lourbopoulos A, Ertürk A, Hellal F. Microglia in action: how aging and injury can change the brain's guardians. Front Cell Neurosci 2015; 9:54. [PMID: 25755635 PMCID: PMC4337366 DOI: 10.3389/fncel.2015.00054] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 02/03/2015] [Indexed: 01/03/2023] Open
Abstract
Neuroinflammation, the inflammatory response in the central nervous system (CNS), is a major determinant of neuronal function and survival during aging and disease progression. Microglia, as the resident tissue-macrophages of the brain, provide constant support to surrounding neurons in healthy brain. Upon any stress signal (such as trauma, ischemia, inflammation) they are one of the first cells to react. Local and/or peripheral signals determine microglia stress response, which can vary within a continuum of states from beneficial to detrimental for neuronal survival, and can be shaped by aging and previous insults. In this review, we discuss the roles of microglia upon an ischemic or traumatic injury, and give our perspective how aging may contribute to microglia behavior in the injured brain. We speculate that a deeper understanding of specific microglia identities will pave the way to develop more potent therapeutics to treat the diseases of aging brain.
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Affiliation(s)
- Athanasios Lourbopoulos
- Laboratory of Experimental Stroke Research, Institute for Stroke and Dementia Research (ISD), University of Munich Medical School Munich, Germany
| | - Ali Ertürk
- Laboratory of Acute Brain Injury, Institute for Stroke and Dementia Research (ISD), University of Munich Medical School Munich, Germany
| | - Farida Hellal
- Laboratory of Experimental Stroke Research, Institute for Stroke and Dementia Research (ISD), University of Munich Medical School Munich, Germany
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290
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Delpech JC, Madore C, Nadjar A, Joffre C, Wohleb ES, Layé S. Microglia in neuronal plasticity: Influence of stress. Neuropharmacology 2015; 96:19-28. [PMID: 25582288 DOI: 10.1016/j.neuropharm.2014.12.034] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/24/2014] [Accepted: 12/29/2014] [Indexed: 01/17/2023]
Abstract
The central nervous system (CNS) has previously been regarded as an immune-privileged site with the absence of immune cell responses but this dogma was not entirely true. Microglia are the brain innate immune cells and recent findings indicate that they participate both in CNS disease and infection as well as facilitate normal CNS function. Microglia are highly plastic and play integral roles in sculpting the structure of the CNS, refining neuronal circuitry and connectivity, and contribute actively to neuronal plasticity in the healthy brain. Interestingly, psychological stress can perturb the function of microglia in association with an impaired neuronal plasticity and the development of emotional behavior alterations. As a result it seemed important to describe in this review some findings indicating that the stress-induced microglia dysfunction may underlie neuroplasticity deficits associated to many mood disorders. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.
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Affiliation(s)
- Jean-Christophe Delpech
- Nutrition et Neurobiologie Intégrée, INRA 1286, 33077 Bordeaux Cedex, France; Nutrition et Neurobiologie Intégrée, University of Bordeaux, Bordeaux 33077, France
| | - Charlotte Madore
- Nutrition et Neurobiologie Intégrée, INRA 1286, 33077 Bordeaux Cedex, France; Nutrition et Neurobiologie Intégrée, University of Bordeaux, Bordeaux 33077, France
| | - Agnes Nadjar
- Nutrition et Neurobiologie Intégrée, INRA 1286, 33077 Bordeaux Cedex, France; Nutrition et Neurobiologie Intégrée, University of Bordeaux, Bordeaux 33077, France
| | - Corinne Joffre
- Nutrition et Neurobiologie Intégrée, INRA 1286, 33077 Bordeaux Cedex, France; Nutrition et Neurobiologie Intégrée, University of Bordeaux, Bordeaux 33077, France
| | - Eric S Wohleb
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06519, USA
| | - Sophie Layé
- Nutrition et Neurobiologie Intégrée, INRA 1286, 33077 Bordeaux Cedex, France; Nutrition et Neurobiologie Intégrée, University of Bordeaux, Bordeaux 33077, France.
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291
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The L-type voltage-gated calcium channel modulates microglial pro-inflammatory activity. Mol Cell Neurosci 2014; 64:104-15. [PMID: 25497271 DOI: 10.1016/j.mcn.2014.12.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 11/06/2014] [Accepted: 12/11/2014] [Indexed: 02/02/2023] Open
Abstract
Under pathological conditions, microglia, the resident CNS immune cells, become reactive and release pro-inflammatory cytokines and neurotoxic factors. We investigated whether this phenotypic switch includes changes in the expression of the L-type voltage-gated calcium channel (VGCC) in a rat model of N-methyl-D-aspartate-induced hippocampal neurodegeneration. Double immunohistochemistry and confocal microscopy evidenced that activated microglia express the L-type VGCC. We then analyzed whether BV2 microglia express functional L-type VGCC, and investigated the latter's role in microglial cytokine release and phagocytic capacity. Activated BV2 microglia express the CaV1.2 and CaV1.3 subunits of the L-type VGCC determined by reverse transcription-polymerase chain reaction, Western blot and immunocytochemistry. Depolarization with KCl induced a Ca2+ entry facilitated by Bay k8644 and partially blocked with nifedipine, which also reduced TNF-α and NO release by 40%. However, no nifedipine effect on BV2 microglia viability or phagocytic capacity was observed. Our results suggest that in CNS inflammatory processes, the L-type VGCC plays a specific role in the control of microglial secretory activity.
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292
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Schilling T, Eder C. Microglial K(+) channel expression in young adult and aged mice. Glia 2014; 63:664-72. [PMID: 25472417 PMCID: PMC4359010 DOI: 10.1002/glia.22776] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 11/20/2014] [Indexed: 02/02/2023]
Abstract
The K(+) channel expression pattern of microglia strongly depends on the cells' microenvironment and has been recognized as a sensitive marker of the cells' functional state. While numerous studies have been performed on microglia in vitro, our knowledge about microglial K(+) channels and their regulation in vivo is limited. Here, we have investigated K(+) currents of microglia in striatum, neocortex and entorhinal cortex of young adult and aged mice. Although almost all microglial cells exhibited inward rectifier K(+) currents upon membrane hyperpolarization, their mean current density was significantly enhanced in aged mice compared with that determined in young adult mice. Some microglial cells additionally exhibited outward rectifier K(+) currents in response to depolarizing voltage pulses. In aged mice, microglial outward rectifier K(+) current density was significantly larger than in young adult mice due to the increased number of aged microglial cells expressing these channels. Aged dystrophic microglia exhibited outward rectifier K(+) currents more frequently than aged ramified microglia. The majority of microglial cells expressed functional BK-type, but not IK- or SK-type, Ca(2+) -activated K(+) channels, while no differences were found in their expression levels between microglia of young adult and aged mice. Neither microglial K(+) channel pattern nor K(+) channel expression levels differed markedly between the three brain regions investigated. It is concluded that age-related changes in microglial phenotype are accompanied by changes in the expression of microglial voltage-activated, but not Ca(2+) -activated, K(+) channels.
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Affiliation(s)
- Tom Schilling
- Institute for Infection and Immunity, St. George's, University of London; Cranmer Terrace, London, SW17 0RE, United Kingdom
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293
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Karlstetter M, Scholz R, Rutar M, Wong WT, Provis JM, Langmann T. Retinal microglia: just bystander or target for therapy? Prog Retin Eye Res 2014; 45:30-57. [PMID: 25476242 DOI: 10.1016/j.preteyeres.2014.11.004] [Citation(s) in RCA: 374] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 11/20/2014] [Accepted: 11/25/2014] [Indexed: 10/24/2022]
Abstract
Resident microglial cells can be regarded as the immunological watchdogs of the brain and the retina. They are active sensors of their neuronal microenvironment and rapidly respond to various insults with a morphological and functional transformation into reactive phagocytes. There is strong evidence from animal models and in situ analyses of human tissue that microglial reactivity is a common hallmark of various retinal degenerative and inflammatory diseases. These include rare hereditary retinopathies such as retinitis pigmentosa and X-linked juvenile retinoschisis but also comprise more common multifactorial retinal diseases such as age-related macular degeneration, diabetic retinopathy, glaucoma, and uveitis as well as neurological disorders with ocular manifestation. In this review, we describe how microglial function is kept in balance under normal conditions by cross-talk with other retinal cells and summarize how microglia respond to different forms of retinal injury. In addition, we present the concept that microglia play a key role in local regulation of complement in the retina and specify aspects of microglial aging relevant for chronic inflammatory processes in the retina. We conclude that this resident immune cell of the retina cannot be simply regarded as bystander of disease but may instead be a potential therapeutic target to be modulated in the treatment of degenerative and inflammatory diseases of the retina.
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Affiliation(s)
- Marcus Karlstetter
- Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University of Cologne, Cologne, Germany
| | - Rebecca Scholz
- Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University of Cologne, Cologne, Germany
| | - Matt Rutar
- The John Curtin School of Medical Research, The Australian National University (ANU), Canberra, Australian Capital Territory, Australia
| | - Wai T Wong
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jan M Provis
- The John Curtin School of Medical Research, The Australian National University (ANU), Canberra, Australian Capital Territory, Australia
| | - Thomas Langmann
- Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University of Cologne, Cologne, Germany.
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294
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Chamniansawat S, Chongthammakun S. Inhibition of hippocampal estrogen synthesis by reactive microglia leads to down-regulation of synaptic protein expression. Neurotoxicology 2014; 46:25-34. [PMID: 25447322 DOI: 10.1016/j.neuro.2014.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 11/12/2014] [Accepted: 11/12/2014] [Indexed: 12/31/2022]
Abstract
Activation of microglia may facilitate age-related impairment in cognitive functions including hippocampal-dependent memory. Considerable evidence indicates that hippocampal-derived estrogen improves hippocampal-dependent learning and memory. We hypothesize that activated microglia may inhibit de novo hippocampal estrogen synthesis and in turn suppress hippocampal synaptic protein expression. The present study aimed to elucidate the role of lipopolysaccharide (LPS)-activated microglial HAPI cells on estrogen synthesis and expression of synaptic proteins using H19-7 hippocampal neurons with a neuron-microglia co-culture system. LPS induced expression of the microglial activation markers major histocompatibility complex II (MHC II), CD11b, and ionized calcium-binding adapter molecule 1 (Iba1). Prolonged LPS exposure also enhanced the secretion of interleukin (IL)-6 and nitric oxide (NO) from microglial HAPI cells. Exposure to either LPS-activated microglia or IL-6, significantly suppressed the expression of synaptic proteins and the secretion of de novo hippocampal estrogen in H19-7 hippocampal neurons. In addition, LPS-activated microglia also decreased the expression of estrogen receptors (ERα and ERβ) in H19-7 hippocampal neurons. Our findings demonstrate a potential mechanism of microglia activation underlying the reduction in estrogen-mediated signaling on synaptic proteins in hippocampal neurons, which may be involved in hippocampal-dependent memory formation.
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Affiliation(s)
- Siriporn Chamniansawat
- Division of Anatomy, Department of Biomedical Sciences, Faculty of Allied Health Sciences, Burapha University, 169 Long-Hard Bangsaen Road, SaenSook Sub-district, Mueang District, Chonburi 20131, Thailand.
| | - Sukumal Chongthammakun
- Department of Anatomy and Center for Neuroscience, Faculty of Science, Mahidol University, 272 Rama VI Rd., Ratchathewi District, Bangkok 10400, Thailand
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295
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Norden DM, Muccigrosso MM, Godbout JP. Microglial priming and enhanced reactivity to secondary insult in aging, and traumatic CNS injury, and neurodegenerative disease. Neuropharmacology 2014; 96:29-41. [PMID: 25445485 DOI: 10.1016/j.neuropharm.2014.10.028] [Citation(s) in RCA: 279] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 10/26/2014] [Accepted: 10/30/2014] [Indexed: 12/14/2022]
Abstract
Glia of the central nervous system (CNS) help to maintain homeostasis in the brain and support efficient neuronal function. Microglia are innate immune cells of the brain that mediate responses to pathogens and injury. They have key roles in phagocytic clearing, surveying the local microenvironment and propagating inflammatory signals. An interruption in homeostasis induces a cascade of conserved adaptive responses in glia. This response involves biochemical, physiological and morphological changes and is associated with the production of cytokines and secondary mediators that influence synaptic plasticity, cognition and behavior. This reorganization of host priorities represents a beneficial response that is normally adaptive but may become maladaptive when the profile of microglia is compromised. For instance, microglia can develop a primed or pro-inflammatory mRNA, protein and morphological profile with aging, traumatic brain injury and neurodegenerative disease. As a result, primed microglia exhibit an exaggerated inflammatory response to secondary and sub-threshold challenges. Consequences of exaggerated inflammatory responses by microglia include the development of cognitive deficits, impaired synaptic plasticity and accelerated neurodegeneration. Moreover, impairments in regulatory systems in these circumstances may make microglia more resistant to negative feedback and important functions of glia can become compromised and dysfunctional. Overall, the purpose of this review is to discuss key concepts of microglial priming and immune-reactivity in the context of aging, traumatic CNS injury and neurodegenerative disease. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.
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Affiliation(s)
- Diana M Norden
- Department of Neuroscience, The Ohio State University, 333 W. 10th Ave, Columbus, OH 43210, USA
| | - Megan M Muccigrosso
- Department of Neuroscience, The Ohio State University, 333 W. 10th Ave, Columbus, OH 43210, USA
| | - Jonathan P Godbout
- Department of Neuroscience, The Ohio State University, 333 W. 10th Ave, Columbus, OH 43210, USA; Institute for Behavioral Medicine Research, The Ohio State University, 460 Medical Center Dr., Columbus, OH 43210, USA; Center for Brain and Spinal Cord Repair, The Ohio State University, 460 W. 12th Ave, Columbus, OH 43210, USA.
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296
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Microglia as a critical player in both developmental and late-life CNS pathologies. Acta Neuropathol 2014; 128:333-45. [PMID: 25056803 PMCID: PMC4131160 DOI: 10.1007/s00401-014-1321-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 06/17/2014] [Accepted: 07/01/2014] [Indexed: 02/04/2023]
Abstract
Microglia, the tissue-resident macrophages of the brain, are attracting increasing attention as key players in brain homeostasis from development through aging. Recent works have highlighted new and unexpected roles for these once-enigmatic cells in both healthy central nervous system function and in diverse pathologies long thought to be primarily the result of neuronal malfunction. In this review, we have chosen to focus on Rett syndrome, which features early neurodevelopmental pathology, and Alzheimer’s disease, a disorder associated predominantly with aging. Interestingly, receptor-mediated microglial phagocytosis has emerged as a key function in both developmental and late-life brain pathologies. In a mouse model of Rett syndrome, bone marrow transplant and CNS engraftment of microglia-like cells were associated with surprising improvements in pathology—these benefits were abrogated by block of phagocytic function. In Alzheimer’s disease, large-scale genome-wide association studies have been brought to bear as a method of identifying previously unknown susceptibility genes, which highlight microglial receptors as promising novel targets for therapeutic modulation. Multi-photon in vivo microscopy has provided a method of directly visualizing the effects of manipulation of these target genes. Here, we review the latest findings and concepts emerging from the rapidly growing body of literature exemplified for Rett syndrome and late-onset, sporadic Alzheimer’s disease.
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297
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Zhao W, Zhang J, Davis EG, Rebeck GW. Aging reduces glial uptake and promotes extracellular accumulation of Aβ from a lentiviral vector. Front Aging Neurosci 2014; 6:210. [PMID: 25177293 PMCID: PMC4133689 DOI: 10.3389/fnagi.2014.00210] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 07/28/2014] [Indexed: 01/27/2023] Open
Abstract
We used a lentiviral system for expressing secreted human Aβ in the brains of young and old APOE knock-in mice. This system allowed us to examine Aβ metabolism in vivo, and test the effects of both aging and APOE genotype, two of the strongest risk factors for Alzheimer’s disease. We injected the Aβ1-42 lentivirus into the motor cortex of young (2 month old) and old (20–22 month old) APOE3 and APOE4 mice. After 2 weeks of lentiviral expression, we analyzed the pattern of Aβ accumulation, glial activation, and phosphor-tau. In young mice, Aβ accumulated mainly within neurons with no evidence of extracellular Aβ. Significantly higher levels of intraneuronal Aβ were observed in APOE4 mice compared to APOE3 mice. In old mice, APOE4 predisposed again to higher levels of Aβ accumulation, but the Aβ was mainly in extracellular spaces. In younger mice, we also observed Aβ in microglia but not astrocytes. The numbers of microglia containing Aβ were significantly higher in APOE3 mice compared to APOE4 mice, and were significantly lower in both genetic backgrounds with aging. The astrocytes in old mice were activated to a greater extent in the brain regions where Aβ was introduced, an effect that was again increased by the presence of APOE4. Finally, phospho-tau accumulated in the region of Aβ expression, with evidence of extracellular phospho-tau increasing with aging. These data suggest that APOE4 predisposes to less microglial clearance of Aβ, leading to more intraneuronal accumulation. In older brains, decreased clearance leads to more extracellular Aβ, and more downstream consequences relating to astrocyte activation and phospho-tau accumulation. We conclude that both aging and APOE genotype affect pathways related to Aβ metabolism by microglia.
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Affiliation(s)
- Wenjuan Zhao
- School of Pharmacy, Shanghai Jiao Tong University Shanghai, China
| | - Jiguo Zhang
- Department of Pharmacology, School of Pharmacy, Taishan Medical University Taian, China
| | - Elizabeth G Davis
- Department of Neuroscience, Georgetown University Medical Center Washington, DC, USA
| | - G William Rebeck
- Department of Neuroscience, Georgetown University Medical Center Washington, DC, USA
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298
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Heuss ND, Pierson MJ, Montaniel KRC, McPherson SW, Lehmann U, Hussong SA, Ferrington DA, Low WC, Gregerson DS. Retinal dendritic cell recruitment, but not function, was inhibited in MyD88 and TRIF deficient mice. J Neuroinflammation 2014; 11:143. [PMID: 25116321 PMCID: PMC4149240 DOI: 10.1186/s12974-014-0143-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Accepted: 07/29/2014] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Immune system cells are known to affect loss of neurons due to injury or disease. Recruitment of immune cells following retinal/CNS injury has been shown to affect the health and survival of neurons in several models. We detected close, physical contact between dendritic cells and retinal ganglion cells following an optic nerve crush, and sought to understand the underlying mechanisms. METHODS CD11c-DTR/GFP mice producing a chimeric protein of diphtheria toxin receptor (DTR) and GFP from a transgenic CD11c promoter were used in conjunction with mice deficient in MyD88 and/or TRIF. Retinal ganglion cell injury was induced by an optic nerve crush, and the resulting interactions of the GFPhi cells and retinal ganglion cells were examined. RESULTS Recruitment of GFPhi dendritic cells to the retina was significantly compromised in MyD88 and TRIF knockout mice. GFPhi dendritic cells played a significant role in clearing fluorescent-labeled retinal ganglion cells post-injury in the CD11c-DTR/GFP mice. In the TRIF and MyD88 deficient mice, the resting level of GFPhi dendritic cells was lower, and their influx was reduced following the optic nerve crush injury. The reduction in GFPhi dendritic cell numbers led to their replacement in the uptake of fluorescent-labeled debris by GFPlo microglia/macrophages. Depletion of GFPhi dendritic cells by treatment with diphtheria toxin also led to their displacement by GFPlo microglia/macrophages, which then assumed close contact with the injured neurons. CONCLUSIONS The contribution of recruited cells to the injury response was substantial, and regulated by MyD88 and TRIF. However, the presence of these adaptor proteins was not required for interaction with neurons, or the phagocytosis of debris. The data suggested a two-niche model in which resident microglia were maintained at a constant level post-optic nerve crush, while the injury-stimulated recruitment of dendritic cells and macrophages led to their transient appearance in numbers equivalent to or greater than the resident microglia.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Dale S Gregerson
- Department of Ophthalmology & Visual Neurosciences, University of Minnesota, Lions Research Bldg, Rm 314, 2001 6th St SE, Minneapolis 55455, MN, USA.
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299
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Baron R, Babcock AA, Nemirovsky A, Finsen B, Monsonego A. Accelerated microglial pathology is associated with Aβ plaques in mouse models of Alzheimer's disease. Aging Cell 2014; 13:584-95. [PMID: 24641683 PMCID: PMC4326940 DOI: 10.1111/acel.12210] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2014] [Indexed: 02/06/2023] Open
Abstract
Microglia integrate within the neural tissue with a distinct ramified morphology through which they scan the surrounding neuronal network. Here, we used a digital tool for the quantitative morphometric characterization of fine cortical microglial structures in mice, and the changes they undergo with aging and in Alzheimer's-like disease. We show that, compared with microglia in young mice, microglia in old mice are less ramified and possess fewer branches and fine processes along with a slightly increased proinflammatory cytokine expression. A similar microglial pathology appeared 6-12 months earlier in mouse models of Alzheimer's disease (AD), along with a significant increase in brain parenchyma lacking coverage by microglial processes. We further demonstrate that microglia near amyloid plaques acquire unique activated phenotypes with impaired process complexity. We thus show that along with a chronic proinflammatory reaction in the brain, aging causes a significant reduction in the capacity of microglia to scan their environment. This type of pathology is markedly accelerated in mouse models of AD, resulting in a severe microglial process deficiency, and possibly contributing to enhanced cognitive decline.
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Affiliation(s)
- Rona Baron
- The Shraga Segal Department of Microbiology and Immunology Faculty of Health Sciences and the National Institute of Biotechnology in the Negev Ben‐Gurion University of the Negev Beer‐Sheva 84105Israel
| | - Alicia A. Babcock
- Department of Neurobiology Research Institute of Molecular Medicine University of Southern Denmark DK‐5000Odense Denmark
| | - Anna Nemirovsky
- The Shraga Segal Department of Microbiology and Immunology Faculty of Health Sciences and the National Institute of Biotechnology in the Negev Ben‐Gurion University of the Negev Beer‐Sheva 84105Israel
| | - Bente Finsen
- Department of Neurobiology Research Institute of Molecular Medicine University of Southern Denmark DK‐5000Odense Denmark
| | - Alon Monsonego
- The Shraga Segal Department of Microbiology and Immunology Faculty of Health Sciences and the National Institute of Biotechnology in the Negev Ben‐Gurion University of the Negev Beer‐Sheva 84105Israel
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Caldeira C, Oliveira AF, Cunha C, Vaz AR, Falcão AS, Fernandes A, Brites D. Microglia change from a reactive to an age-like phenotype with the time in culture. Front Cell Neurosci 2014; 8:152. [PMID: 24917789 PMCID: PMC4040822 DOI: 10.3389/fncel.2014.00152] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 05/13/2014] [Indexed: 01/25/2023] Open
Abstract
Age-related neurodegenerative diseases have been associated with chronic neuroinflammation and microglia activation. However, cumulative evidence supports that inflammation only occurs at an early stage once microglia change the endogenous characteristics with aging and switch to irresponsive/senescent and dystrophic phenotypes with disease progression. Thus, it will be important to have the means to assess the role of reactive and aged microglia when studying advanced brain neurodegeneration processes and age-associated related disorders. Yet, most studies are done with microglia from neonates since there are no adequate means to isolate degenerating microglia for experimentation. Indeed, only a few studies report microglia isolation from aged animals, using either short-term cultures or high concentrations of mitogens in the medium, which trigger microglia reactivity. The purpose of this study was to develop an experimental process to naturally age microglia after isolation from neonatal mice and to characterize the cultured cells at 2 days in vitro (DIV), 10 DIV, and 16 DIV. We found that 2 DIV (young) microglia had predominant amoeboid morphology and markers of stressed/reactive phenotype. In contrast, 16 DIV (aged) microglia evidenced ramified morphology and increased matrix metalloproteinase (MMP)-2 activation, as well as reduced MMP-9, glutamate release and nuclear factor kappa-B activation, in parallel with decreased expression of Toll-like receptor (TLR)-2 and TLR-4, capacity to migrate and phagocytose. These findings together with the reduced expression of microRNA (miR)-124, and miR-155, decreased autophagy, enhanced senescence associated beta-galactosidase activity and elevated miR-146a expression, are suggestive that 16 DIV cells mainly correspond to irresponsive/senescent microglia. Data indicate that the model represent an opportunity to understand and control microglial aging, as well as to explore strategies to recover microglia surveillance function.
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Affiliation(s)
- Cláudia Caldeira
- Research Institute for Medicines - iMed.ULisboa, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal ; Centro de Investigação Interdisciplinar Egas Moniz, Egas Moniz - Cooperativa de Ensino Superior, CRL, Campus Universitário Monte de Caparica, Portugal
| | - Ana F Oliveira
- Research Institute for Medicines - iMed.ULisboa, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal
| | - Carolina Cunha
- Research Institute for Medicines - iMed.ULisboa, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal
| | - Ana R Vaz
- Research Institute for Medicines - iMed.ULisboa, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal ; Department of Biochemistry and Human Biology, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal
| | - Ana S Falcão
- Research Institute for Medicines - iMed.ULisboa, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal ; Department of Biochemistry and Human Biology, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal
| | - Adelaide Fernandes
- Research Institute for Medicines - iMed.ULisboa, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal ; Department of Biochemistry and Human Biology, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal
| | - Dora Brites
- Research Institute for Medicines - iMed.ULisboa, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal ; Department of Biochemistry and Human Biology, Faculdade de Farmácia, Universidade de Lisboa Lisboa, Portugal
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