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Ishijima T, Nakajima K. Mechanisms of Microglia Proliferation in a Rat Model of Facial Nerve Anatomy. BIOLOGY 2023; 12:1121. [PMID: 37627005 PMCID: PMC10452325 DOI: 10.3390/biology12081121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/27/2023] [Accepted: 08/09/2023] [Indexed: 08/27/2023]
Abstract
Although microglia exist as a minor glial cell type in the normal state of the brain, they increase in number in response to various disorders and insults. However, it remains unclear whether microglia proliferate in the affected area, and the mechanism of the proliferation has long attracted the attention of researchers. We analyzed microglial mitosis using a facial nerve transection model in which the blood-brain barrier is left unimpaired when the nerves are axotomized. Our results showed that the levels of macrophage colony-stimulating factor (M-CSF), cFms (the receptor for M-CSF), cyclin A/D, and proliferating cell nuclear antigen (PCNA) were increased in microglia in the axotomized facial nucleus (axotFN). In vitro experiments revealed that M-CSF induced cFms, cyclin A/D, and PCNA in microglia, suggesting that microglia proliferate in response to M-CSF in vivo. In addition, M-CSF caused the activation of c-Jun N-terminal kinase (JNK) and p38, and the specific inhibitors of JNK and p38 arrested the microglial mitosis. JNK and p38 were shown to play roles in the induction of cyclins/PCNA and cFms, respectively. cFms was suggested to be induced through a signaling cascade of p38-mitogen- and stress-activated kinase-1 (MSK1)-cAMP-responsive element binding protein (CREB) and/or p38-activating transcription factor 2 (ATF2). Microglia proliferating in the axotFN are anticipated to serve as neuroprotective cells by supplying neurotrophic factors and/or scavenging excite toxins and reactive oxygen radicals.
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Affiliation(s)
- Takashi Ishijima
- Graduate School of Science and Engineering, Soka University, Tokyo 192-8577, Japan;
| | - Kazuyuki Nakajima
- Graduate School of Science and Engineering, Soka University, Tokyo 192-8577, Japan;
- Glycan & Life Systems Integration Center, Soka University, Tokyo 192-8577, Japan
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2
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Sheng L, Shields EJ, Gospocic J, Sorida M, Ju L, Byrns CN, Carranza F, Berger SL, Bonini N, Bonasio R. Ensheathing glia promote increased lifespan and healthy brain aging. Aging Cell 2023; 22:e13803. [PMID: 36840361 PMCID: PMC10186613 DOI: 10.1111/acel.13803] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 02/07/2023] [Accepted: 02/08/2023] [Indexed: 02/26/2023] Open
Abstract
Glia have an emergent role in brain aging and disease. In the Drosophila melanogaster brain, ensheathing glia function as phagocytic cells and respond to acute neuronal damage, analogous to mammalian microglia. We previously reported changes in glia composition over the life of ants and fruit flies, including a decline in the relative proportion of ensheathing glia with time. How these changes influence brain health and life expectancy is unknown. Here, we show that ensheathing glia but not astrocytes decrease in number during Drosophila melanogaster brain aging. The remaining ensheathing glia display dysregulated expression of genes involved in lipid metabolism and apoptosis, which may lead to lipid droplet accumulation, cellular dysfunction, and death. Inhibition of apoptosis rescued the decline of ensheathing glia with age, improved the neuromotor performance of aged flies, and extended lifespan. Furthermore, an expanded ensheathing glia population prevented amyloid-beta accumulation in a fly model of Alzheimer's disease and delayed the premature death of the diseased animals. These findings suggest that ensheathing glia play a vital role in regulating brain health and animal longevity.
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Affiliation(s)
- Lihong Sheng
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceInstitutes of Brain Science, Fudan UniversityShanghaiChina
- Epigenetics InstituteUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Cell and Developmental BiologyUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
| | - Emily J. Shields
- Epigenetics InstituteUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Cell and Developmental BiologyUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Urology and Institute of NeuropathologyMedical Center–University of FreiburgFreiburgGermany
| | - Janko Gospocic
- Epigenetics InstituteUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Cell and Developmental BiologyUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Urology and Institute of NeuropathologyMedical Center–University of FreiburgFreiburgGermany
| | - Masato Sorida
- Epigenetics InstituteUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Cell and Developmental BiologyUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
| | - Linyang Ju
- Epigenetics InstituteUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Cell and Developmental BiologyUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
| | - China N. Byrns
- Medical Scientist Training ProgramUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Neuroscience Graduate GroupUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Faith Carranza
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Shelley L. Berger
- Epigenetics InstituteUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Cell and Developmental BiologyUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
- Department of GeneticsUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
| | - Nancy Bonini
- Neuroscience Graduate GroupUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Roberto Bonasio
- Epigenetics InstituteUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Cell and Developmental BiologyUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvaniaUSA
- Department of Urology and Institute of NeuropathologyMedical Center–University of FreiburgFreiburgGermany
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3
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Lu Y, Jarrahi A, Moore N, Bartoli M, Brann DW, Baban B, Dhandapani KM. Inflammaging, cellular senescence, and cognitive aging after traumatic brain injury. Neurobiol Dis 2023; 180:106090. [PMID: 36934795 PMCID: PMC10763650 DOI: 10.1016/j.nbd.2023.106090] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 03/01/2023] [Accepted: 03/16/2023] [Indexed: 03/19/2023] Open
Abstract
Traumatic brain injury (TBI) is associated with mortality and morbidity worldwide. Accumulating pre-clinical and clinical data suggests TBI is the leading extrinsic cause of progressive neurodegeneration. Neurological deterioration after either a single moderate-severe TBI or repetitive mild TBI often resembles dementia in aged populations; however, no currently approved therapies adequately mitigate neurodegeneration. Inflammation correlates with neurodegenerative changes and cognitive dysfunction for years post-TBI, suggesting a potential association between immune activation and both age- and TBI-induced cognitive decline. Inflammaging, a chronic, low-grade sterile inflammation associated with natural aging, promotes cognitive decline. Cellular senescence and the subsequent development of a senescence associated secretory phenotype (SASP) promotes inflammaging and cognitive aging, although the functional association between senescent cells and neurodegeneration is poorly defined after TBI. In this mini-review, we provide an overview of the pre-clinical and clinical evidence linking cellular senescence with poor TBI outcomes. We also discuss the current knowledge and future potential for senotherapeutics, including senolytics and senomorphics, which kill and/or modulate senescent cells, as potential therapeutics after TBI.
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Affiliation(s)
- Yujiao Lu
- Department of Neurosurgery, Medical College of Georgia, Augusta University, Augusta, GA 30912, United States of America.
| | - Abbas Jarrahi
- Department of Neurosurgery, Medical College of Georgia, Augusta University, Augusta, GA 30912, United States of America
| | - Nicholas Moore
- Department of Neurosurgery, Medical College of Georgia, Augusta University, Augusta, GA 30912, United States of America
| | - Manuela Bartoli
- Department of Ophthalmology, Medical College of Georgia, Augusta University, Augusta, GA 30912, United States of America
| | - Darrell W Brann
- Department of Neurosurgery, Medical College of Georgia, Augusta University, Augusta, GA 30912, United States of America
| | - Babak Baban
- Department of Oral Biology and Diagnostic Services, Dental College of Georgia, Augusta University, Augusta, GA 30912, United States of America
| | - Krishnan M Dhandapani
- Department of Neurosurgery, Medical College of Georgia, Augusta University, Augusta, GA 30912, United States of America.
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4
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Campos RMP, Barbosa-Silva MC, Ribeiro-Resende VT. A period of transient synaptic density unbalancing in the motor cortex after peripheral nerve injury and the involvement of microglial cells. Mol Cell Neurosci 2023; 124:103791. [PMID: 36372156 DOI: 10.1016/j.mcn.2022.103791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 11/05/2022] [Accepted: 11/06/2022] [Indexed: 11/13/2022] Open
Abstract
Some types of peripheral nerve injury lead to limb deafferentation, which leads to remodeling of body representation areas in different parts of the brain, such as in the primary motor cortex and primary sensory cortex. This plasticity is a consequence of several cellular events, such as the emergence and elimination of synapses in these areas. Beside neurons, microglial cells are intimately involved in synapse plasticity, especially in synaptic pruning. In this study, we investigated the transient changes in synaptic density in the primary motor and sensory cortex after different types of peripheral nerve injury, as well as the behavior of microglial cells in each scenario. Male C57/B6 mice were divided into a control group (no injury), sciatic-crush group, and sciatic-transection group, and treated with PBS or minocycline daily for different time points. Both types of sciatic lesion led to a significant decrease of synaptophysin and PSD-95 positive puncta counts compared to control animals 4 days after lesion (DAL), which recovered at 7 DAL and was sustained until 14 DAL. The changes in synaptic puncta density were concomitant with changes in the density and morphology of microglial cells, which were significantly more ramified in the primary motor cortex of injured animals at 1 and 4 DAL. Although the decreased synaptic puncta density overlapped with an increased number of microglial cells, the number of lysosomes per microglial cell did not increase on day 4 after lesion. Surprisingly, daily administration of minocycline increased microglial cell number and PSD-95 positive puncta density by 14 DAL. Taken together, we found evidence for transient changes in synaptic density in the primary motor, related to peripheral injury with possible participation of microglia in this plasticity process.
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Affiliation(s)
- Raquel Maria Pereira Campos
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil.
| | - Maria Carolina Barbosa-Silva
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
| | - Victor Túlio Ribeiro-Resende
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil; Núcleo Multidisciplinar de Pesquisa em Biologia (Numpex-Bio), Campus de Duque de Caxias Geraldo Guerra Cidade, Universidade Federal do Rio de Janeiro, Duque de Caxias, RJ 25255-030, Brazil
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5
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Mitochondrial Damage-Associated Molecular Patterns Content in Extracellular Vesicles Promotes Early Inflammation in Neurodegenerative Disorders. Cells 2022; 11:cells11152364. [PMID: 35954208 PMCID: PMC9367540 DOI: 10.3390/cells11152364] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 07/27/2022] [Accepted: 07/28/2022] [Indexed: 02/06/2023] Open
Abstract
Neuroinflammation is a common hallmark in different neurodegenerative conditions that share neuronal dysfunction and a progressive loss of a selectively vulnerable brain cell population. Alongside ageing and genetics, inflammation, oxidative stress and mitochondrial dysfunction are considered key risk factors. Microglia are considered immune sentinels of the central nervous system capable of initiating an innate and adaptive immune response. Nevertheless, the pathological mechanisms underlying the initiation and spread of inflammation in the brain are still poorly described. Recently, a new mechanism of intercellular signalling mediated by small extracellular vesicles (EVs) has been identified. EVs are nanosized particles (30–150 nm) with a bilipid membrane that carries cell-specific bioactive cargos that participate in physiological or pathological processes. Damage-associated molecular patterns (DAMPs) are cellular components recognised by the immune receptors of microglia, inducing or aggravating neuroinflammation in neurodegenerative disorders. Diverse evidence links mitochondrial dysfunction and inflammation mediated by mitochondrial-DAMPs (mtDAMPs) such as mitochondrial DNA, mitochondrial transcription factor A (TFAM) and cardiolipin, among others. Mitochondrial-derived vesicles (MDVs) are a subtype of EVs produced after mild damage to mitochondria and, upon fusion with multivesicular bodies are released as EVs to the extracellular space. MDVs are particularly enriched in mtDAMPs which can induce an immune response and the release of pro-inflammatory cytokines. Importantly, growing evidence supports the association between mitochondrial dysfunction, EV release and inflammation. Here, we describe the role of extracellular vesicles-associated mtDAMPS in physiological conditions and as neuroinflammation activators contributing to neurodegenerative disorders.
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Events Occurring in the Axotomized Facial Nucleus. Cells 2022; 11:cells11132068. [PMID: 35805151 PMCID: PMC9266054 DOI: 10.3390/cells11132068] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/26/2022] [Accepted: 06/27/2022] [Indexed: 01/27/2023] Open
Abstract
Transection of the rat facial nerve leads to a variety of alterations not only in motoneurons, but also in glial cells and inhibitory neurons in the ipsilateral facial nucleus. In injured motoneurons, the levels of energy metabolism-related molecules are elevated, while those of neurofunction-related molecules are decreased. In tandem with these motoneuron changes, microglia are activated and start to proliferate around injured motoneurons, and astrocytes become activated for a long period without mitosis. Inhibitory GABAergic neurons reduce the levels of neurofunction-related molecules. These facts indicate that injured motoneurons somehow closely interact with glial cells and inhibitory neurons. At the same time, these events allow us to predict the occurrence of tissue remodeling in the axotomized facial nucleus. This review summarizes the events occurring in the axotomized facial nucleus and the cellular and molecular mechanisms associated with each event.
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Microglia in Alzheimer’s Disease: A Favorable Cellular Target to Ameliorate Alzheimer’s Pathogenesis. Mediators Inflamm 2022; 2022:6052932. [PMID: 35693110 PMCID: PMC9184163 DOI: 10.1155/2022/6052932] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 05/09/2022] [Indexed: 11/18/2022] Open
Abstract
Microglial cells serve as molecular sensors of the brain that play a role in physiological and pathological conditions. Under normal physiology, microglia are primarily responsible for regulating central nervous system homeostasis through the phagocytic clearance of redundant protein aggregates, apoptotic cells, damaged neurons, and synapses. Furthermore, microglial cells can promote and mitigate amyloid β phagocytosis and tau phosphorylation. Dysregulation of the microglial programming alters cellular morphology, molecular signaling, and secretory inflammatory molecules that contribute to various neurodegenerative disorders especially Alzheimer’s disease (AD). Furthermore, microglia are considered primary sources of inflammatory molecules and can induce or regulate a broad spectrum of cellular responses. Interestingly, in AD, microglia play a double-edged role in disease progression; for instance, the detrimental microglial effects increase in AD while microglial beneficiary mechanisms are jeopardized. Depending on the disease stages, microglial cells are expressed differently, which may open new avenues for AD therapy. However, the disease-related role of microglial cells and their receptors in the AD brain remain unclear. Therefore, this review represents the role of microglial cells and their involvement in AD pathogenesis.
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8
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Guo L, Choi S, Bikkannavar P, Cordeiro MF. Microglia: Key Players in Retinal Ageing and Neurodegeneration. Front Cell Neurosci 2022; 16:804782. [PMID: 35370560 PMCID: PMC8968040 DOI: 10.3389/fncel.2022.804782] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 02/11/2022] [Indexed: 12/20/2022] Open
Abstract
Microglia are the resident immune cells of the central nervous system (CNS) and play a key role in maintaining the normal function of the retina and brain. During early development, microglia migrate into the retina, transform into a highly ramified phenotype, and scan their environment constantly. Microglia can be activated by any homeostatic disturbance that may endanger neurons and threaten tissue integrity. Once activated, the young microglia exhibit a high diversity in their phenotypes as well as their functions, which relate to either beneficial or harmful consequences. Microglial activation is associated with the release of cytokines, chemokines, and growth factors that can determine pathological outcomes. As the professional phagocytes in the retina, microglia are responsible for the clearance of pathogens, dead cells, and protein aggregates. However, their phenotypic diversity and phagocytic capacity is compromised with ageing. This may result in the accumulation of protein aggregates and myelin debris leading to retinal neuroinflammation and neurodegeneration. In this review, we describe microglial phenotypes and functions in the context of the young and ageing retina, and the mechanisms underlying changes in ageing. Additionally, we review microglia-mediated retinal neuroinflammation and discuss the mechanisms of microglial involvement in retinal neurodegenerative diseases.
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Affiliation(s)
- Li Guo
- Institute of Ophthalmology, University College London, London, United Kingdom
- *Correspondence: Li Guo,
| | - Soyoung Choi
- Institute of Ophthalmology, University College London, London, United Kingdom
| | | | - M. Francesca Cordeiro
- Institute of Ophthalmology, University College London, London, United Kingdom
- Imperial College Ophthalmology Research Group, Imperial College London, London, United Kingdom
- M. Francesca Cordeiro,
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9
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Sanchez K, Darling JS, Kakkar R, Wu SL, Zentay A, Lowry CA, Fonken LK. Mycobacterium vaccae immunization in rats ameliorates features of age-associated microglia activation in the amygdala and hippocampus. Sci Rep 2022; 12:2165. [PMID: 35140249 PMCID: PMC8828872 DOI: 10.1038/s41598-022-05275-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 01/05/2022] [Indexed: 12/14/2022] Open
Abstract
Aging and reduced exposure to environmental microbes can both potentiate neuroinflammatory responses. Prior studies indicate that immunization with the immunoregulatory and anti-inflammatory bacterium, Mycobacterium vaccae (M. vaccae), in aged rats limits neuroimmune activation and cognitive impairments. However, the mechanisms by which M. vaccae immunization ameliorates age-associated neuroinflammatory “priming” and whether microglia are a primary target remain unclear. Here, we investigated whether M. vaccae immunization protects against microglia morphological changes in response to aging. Adult (3 mos) and aged (24 mos) Fisher 344 × Brown Norway rats were immunized with either M. vaccae or vehicle once every week for 3 weeks. Aging led to elevated Iba1 immunoreactivity, microglial density, and deramification of microglia processes in the hippocampus and amygdala but not other brain regions. Additionally, aged rats exhibited larger microglial somas in the dorsal hippocampus, suggestive of a more activated phenotype. Notably, M. vaccae treatment ameliorated indicators of microglia activation in both the amygdala and hippocampus. While changes in morphology appeared to be region-specific, gene markers indicative of microglia activation were upregulated by age and lowered in response to M. vaccae in all brain regions evaluated. Taken together, these data suggest that peripheral immunization with M. vaccae quells markers of age-associated microglia activation.
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Affiliation(s)
- Kevin Sanchez
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 107 W Dean Keeton St 3.510C, Austin, TX, 78712, USA
| | - Jeffrey S Darling
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 107 W Dean Keeton St 3.510C, Austin, TX, 78712, USA
| | - Reha Kakkar
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 107 W Dean Keeton St 3.510C, Austin, TX, 78712, USA
| | - Sienna L Wu
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 107 W Dean Keeton St 3.510C, Austin, TX, 78712, USA
| | - Andrew Zentay
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 107 W Dean Keeton St 3.510C, Austin, TX, 78712, USA
| | - Christopher A Lowry
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, 80309, USA.,Center for Neuroscience, University of Colorado Boulder, Boulder, CO, 80309, USA
| | - Laura K Fonken
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 107 W Dean Keeton St 3.510C, Austin, TX, 78712, USA.
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10
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de Melo ASLF, Lima JLD, Malta MCS, Marroquim NF, Moreira ÁR, de Almeida Ladeia I, dos Santos Cardoso F, Gonçalves DB, Dutra BG, dos Santos JCC. The role of microglia in prion diseases and possible therapeutic targets: a literature review. Prion 2021; 15:191-206. [PMID: 34751640 PMCID: PMC8583147 DOI: 10.1080/19336896.2021.1991771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Accepted: 10/01/2021] [Indexed: 11/19/2022] Open
Abstract
Creutzfeldt-Jakob disease (CJD) is a rare and fatal condition that leads to progressive neurodegeneration due to gliosis, vacuolation of central nervous system tissue, and loss of neurons. Microglia play a crucial role in maintaining Central Nervous System (CNS) homoeostasis, both in health and disease, through phagocytosis and cytokine production. In the context of CJD, the immunomodulatory function of microglia turns it into a cell of particular interest. Microglia would be activated by infectious prion proteins, initially acquiring a phagocytic and anti-inflammatory profile (M2), and producing cytokines such as IL-4, IL-10, and TGF-β. Therefore, microglia are seen as a key target for the development of new treatment approaches, with many emerging strategies to guide it towards a beneficial role upon neuroinflammation, by manipulating its metabolic pathways. In such a setting, many cellular targets in microglia that can be involved in phenotype modulation, such as membrane receptors, have been identified and pointed out as possible targets for further experiments and therapeutic approaches. In this article, we review the major findings about the role of microglia in CJD, including its relationship to some risk factors associated with the development of the disease. Furthermore, considering its central role in neural immunity, we explore microglial connection with other elements of the immune system and cell signalling, such as inflammasomes, the complement and purinergic systems, and the latest finding strategies to guide these cells from harmful to beneficial roles.
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Affiliation(s)
| | | | | | | | - Álvaro Rivelli Moreira
- Department of Neurology, Centro Universitário Governador Ozanam Coelho, UniFacog, Ubá, MG, Brazil
| | | | - Fabrizio dos Santos Cardoso
- Núcleo de Pesquisas Tecnológicas, Universidade De Mogi Das Cruzes, Mogi das Cruzes, SP, Brazil
- Department of Psychology and Institute for Neuroscience, University of Texas (Ut), Austin, TX, USA
| | | | | | - Júlio César Claudino dos Santos
- Laboratório de Neurociências, Departamento De Neurologia E Neurocirurgia, Universidade Federal de São Paulo, São Paulo, Sp, Brazil
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11
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Schwab N, Leung E, Hazrati LN. Cellular Senescence in Traumatic Brain Injury: Evidence and Perspectives. Front Aging Neurosci 2021; 13:742632. [PMID: 34650425 PMCID: PMC8505896 DOI: 10.3389/fnagi.2021.742632] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 09/03/2021] [Indexed: 12/14/2022] Open
Abstract
Mild traumatic brain injury (mTBI) can lead to long-term neurological dysfunction and increase one's risk of neurodegenerative disease. Several repercussions of mTBI have been identified and well-studied, including neuroinflammation, gliosis, microgliosis, excitotoxicity, and proteinopathy – however the pathophysiological mechanisms activating these pathways after mTBI remains controversial and unclear. Emerging research suggests DNA damage-induced cellular senescence as a possible driver of mTBI-related sequalae. Cellular senescence is a state of chronic cell-cycle arrest and inflammation associated with physiological aging, mood disorders, dementia, and various neurodegenerative pathologies. This narrative review evaluates the existing studies which identify DNA damage or cellular senescence after TBI (including mild, moderate, and severe TBI) in both experimental animal models and human studies, and outlines how cellular senescence may functionally explain both the molecular and clinical manifestations of TBI. Studies on this subject clearly show accumulation of various forms of DNA damage (including oxidative damage, single-strand breaks, and double-strand breaks) and senescent cells after TBI, and indicate that cellular senescence may be an early event after TBI. Further studies are required to understand the role of sex, cell-type specific mechanisms, and temporal patterns, as senescence may be a pathway of interest to target for therapeutic purposes including prognosis and treatment.
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Affiliation(s)
- Nicole Schwab
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.,The Hospital for Sick Children, Toronto, ON, Canada
| | - Emily Leung
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.,The Hospital for Sick Children, Toronto, ON, Canada
| | - Lili-Naz Hazrati
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.,The Hospital for Sick Children, Toronto, ON, Canada
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Moraes CA, Zaverucha-do-Valle C, Fleurance R, Sharshar T, Bozza FA, d’Avila JC. Neuroinflammation in Sepsis: Molecular Pathways of Microglia Activation. Pharmaceuticals (Basel) 2021; 14:ph14050416. [PMID: 34062710 PMCID: PMC8147235 DOI: 10.3390/ph14050416] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 03/31/2021] [Accepted: 04/01/2021] [Indexed: 12/11/2022] Open
Abstract
Frequently underestimated, encephalopathy or delirium are common neurological manifestations associated with sepsis. Brain dysfunction occurs in up to 80% of cases and is directly associated with increased mortality and long-term neurocognitive consequences. Although the central nervous system (CNS) has been classically viewed as an immune-privileged system, neuroinflammation is emerging as a central mechanism of brain dysfunction in sepsis. Microglial cells are major players in this setting. Here, we aimed to discuss the current knowledge on how the brain is affected by peripheral immune activation in sepsis and the role of microglia in these processes. This review focused on the molecular pathways of microglial activity in sepsis, its regulatory mechanisms, and their interaction with other CNS cells, especially with neuronal cells and circuits.
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Affiliation(s)
- Carolina Araújo Moraes
- Immunopharmacology Lab, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro 21045-900, Brazil;
| | - Camila Zaverucha-do-Valle
- National Institute of Infectious Disease Evandro Chagas, Oswaldo Cruz Foundation, Ministry of Health, Rio de Janeiro 21040-360, Brazil; (C.Z.-d.-V.); (F.A.B.)
| | - Renaud Fleurance
- UCB Biopharma SRL, 1420 Braine L’Alleud, Belgium;
- Experimental Neuropathology, Infection, and Epidemiology Department, Institut Pasteur, 75015 Paris, France;
- Université de Paris Sciences et Lettres, 75006 Paris Paris, France
| | - Tarek Sharshar
- Experimental Neuropathology, Infection, and Epidemiology Department, Institut Pasteur, 75015 Paris, France;
- Neuro-Anesthesiology and Intensive Care Medicine, Sainte-Anne Hospital, Paris-Descartes University, 75015 Paris, France
| | - Fernando Augusto Bozza
- National Institute of Infectious Disease Evandro Chagas, Oswaldo Cruz Foundation, Ministry of Health, Rio de Janeiro 21040-360, Brazil; (C.Z.-d.-V.); (F.A.B.)
- D’Or Institute for Research and Education, Rio de Janeiro 22281-100, Brazil
| | - Joana Costa d’Avila
- Immunopharmacology Lab, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro 21045-900, Brazil;
- School of Medicine, Universidade Iguaçu, Rio de Janeiro 26260-045, Brazil
- Correspondence:
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13
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Konishi H, Kiyama H. Non-pathological roles of microglial TREM2/DAP12: TREM2/DAP12 regulates the physiological functions of microglia from development to aging. Neurochem Int 2020; 141:104878. [DOI: 10.1016/j.neuint.2020.104878] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 10/03/2020] [Accepted: 10/06/2020] [Indexed: 01/01/2023]
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14
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Salas IH, Burgado J, Allen NJ. Glia: victims or villains of the aging brain? Neurobiol Dis 2020; 143:105008. [PMID: 32622920 DOI: 10.1016/j.nbd.2020.105008] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 06/14/2020] [Accepted: 06/29/2020] [Indexed: 12/11/2022] Open
Abstract
Aging is the strongest risk factor for metabolic, vascular and neurodegenerative diseases. Aging alone is associated with a gradual decline of cognitive and motor functions. Considering an increasing elderly population in the last century, understanding the cellular and molecular mechanisms contributing to brain aging is of vital importance. Recent genetic and transcriptomic findings strongly suggest that glia are the first cells changing with aging. Glial cells constitute around 50% of the total cells in the brain and play key roles regulating brain homeostasis in health and disease. Their essential functions include providing nutritional support to neurons, activation of immune responses, and regulation of synaptic transmission and plasticity. In this review we discuss how glia are altered in the aging brain and whether these alterations are protective or contribute to the age-related pathological cascade. We focus on the major morphological, transcriptional and functional changes affecting glia in a range of systems, including human, non-human primates, and rodents. We also highlight future directions for investigating the roles of glia in brain aging.
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Affiliation(s)
- Isabel H Salas
- Salk Institute for Biological Studies, Molecular Neurobiology Laboratory, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Jillybeth Burgado
- Salk Institute for Biological Studies, Molecular Neurobiology Laboratory, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Nicola J Allen
- Salk Institute for Biological Studies, Molecular Neurobiology Laboratory, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
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15
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Shaerzadeh F, Phan L, Miller D, Dacquel M, Hachmeister W, Hansen C, Bechtle A, Tu D, Martcheva M, Foster TC, Kumar A, Streit WJ, Khoshbouei H. Microglia senescence occurs in both substantia nigra and ventral tegmental area. Glia 2020; 68:2228-2245. [PMID: 32275335 DOI: 10.1002/glia.23834] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 03/19/2020] [Accepted: 03/24/2020] [Indexed: 02/06/2023]
Abstract
During aging humans lose midbrain dopamine neurons, but not all dopamine regions exhibit vulnerability to neurodegeneration. Microglia maintain tissue homeostasis and neuronal support, but microglia become senescent and likely lose some of their functional abilities. Since aging is the greatest risk factor for Parkinson's disease, we hypothesized that aging-related changes in microglia and neurons occur in the vulnerable substantia nigra pars compacta (SNc) but not the ventral tegmental area (VTA). We conducted stereological analyses to enumerate microglia and dopaminergic neurons in the SNc and VTA of 1-, 6-, 9-, 18-, and 24-month-old C57BL/J6 mice using sections double-stained with tyrosine hydroxylase (TH) and Iba1. Both brain regions show an increase in microglia with aging, whereas numbers of TH+ cells show no significant change after 9 months of age in SNc and 6 months in VTA. Morphometric analyses reveal reduced microglial complexity and projection area while cell body size increases with aging. Contact sites between microglia and dopaminergic neurons in both regions increase with aging, suggesting increased microglial support/surveillance of dopamine neurons. To assess neurotrophin expression in dopaminergic neurons, BDNF and TH mRNA were quantified. Results show that the ratio of BDNF to TH decreases in the SNc, but not the VTA. Gait analysis indicates subtle, aging-dependent changes in gait indices. In conclusion, increases in microglial cell number, ratio of microglia to dopamine neurons, and contact sites suggest that innate biological mechanisms compensate for the aging-dependent decline in microglia morphological complexity (senescence) to ensure continued neuronal support in the SNc and VTA.
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Affiliation(s)
- Fatemeh Shaerzadeh
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Leah Phan
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Douglas Miller
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Maxwell Dacquel
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - William Hachmeister
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Carissa Hansen
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Alexandra Bechtle
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Duan Tu
- Department of Mathematics, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Maia Martcheva
- Department of Mathematics, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Thomas C Foster
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Ashok Kumar
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Wolfgang J Streit
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Habibeh Khoshbouei
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
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16
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Rodriguez-Callejas JD, Fuchs E, Perez-Cruz C. Increased oxidative stress, hyperphosphorylation of tau, and dystrophic microglia in the hippocampus of aged Tupaia belangeri. Glia 2020; 68:1775-1793. [PMID: 32096580 DOI: 10.1002/glia.23804] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 02/04/2020] [Accepted: 02/07/2020] [Indexed: 12/26/2022]
Abstract
Aging is a major risk factor for the development of neurodegenerative diseases. Alzheimer's disease and other neurodegenerative diseases are characterized by abnormal and prominent protein aggregation in the brain, partially due to deficiency in protein clearance. It has been proposed that alterations in microglia phagocytosis and debris clearance hasten the onset of neurodegeneration. Dystrophic microglia are abundant in aged humans, and it has been associated with the onset of disease. Furthermore, alterations in microglia containing ferritin are associated with neurodegenerative conditions. To further understand the process of microglia dysfunction during the aging process, we used hippocampal sections from Tupaia belangeri (tree shrews). Adult (mean age 3.8 years), old (mean age 6 years), and aged (mean age 7.5 years) tree shrews were used for histochemical and immunostaining techniques to determine ferritin and Iba1 positive microglia, iron tissue content, tau hyperphosphorylation and oxidized-RNA in dentate gyrus, subiculum, and CA1-CA3 hippocampal regions. Our results indicated that aged tree shrews presented an increased number of activated microglia containing ferritin, but microglia labeled with Iba1 with a dystrophic phenotype was more abundant in aged individuals. With aging, oxidative damage to RNA (8OHG) increased significantly in all hippocampal regions, while tau hyperphosphorylation (AT100) was enhanced in DG, CA3, and SUB in aged animals. Phagocytic inclusions of 8OHG- and AT100-damaged cells were observed in activated M2 microglia in old and aged animals. These data indicate that aged tree shrew may be a suitable model for translational research to study brain and microglia alterations during the aging process.
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Affiliation(s)
| | - Eberhard Fuchs
- German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
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17
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Schwab N, Grenier K, Hazrati LN. DNA repair deficiency and senescence in concussed professional athletes involved in contact sports. Acta Neuropathol Commun 2019; 7:182. [PMID: 31727161 PMCID: PMC6857343 DOI: 10.1186/s40478-019-0822-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 09/29/2019] [Indexed: 12/11/2022] Open
Abstract
Mild traumatic brain injury (mTBI) leads to diverse symptoms including mood disorders, cognitive decline, and behavioral changes. In some individuals, these symptoms become chronic and persist in the long-term and can confer an increased risk of neurodegenerative disease and dementia diagnosis later in life. Despite the severity of its consequences, the pathophysiological mechanism of mTBI remains unknown. In this post-mortem case series, we assessed DNA damage-induced cellular senescence pathways in 38 professional athletes with a history of repeated mTBI and ten controls with no mTBI history. We assessed clinical presentation, neuropathological changes, load of DNA damage, morphological markers of cellular senescence, and expression of genes involved in DNA damage signaling, DNA repair, and cellular senescence including the senescence-associated secretory phenotype (SASP). Twenty-eight brains with past history of repeated mTBI history had DNA damage within ependymal cells, astrocytes, and oligodendrocytes. DNA damage burden was increased in brains with proteinopathy compared to those without. Cases also showed hallmark features of cellular senescence in glial cells including astrocytic swelling, beading of glial cell processes, loss of H3K27Me3 (trimethylation at lysine 27 of histone H3) and lamin B1 expression, and increased expression of cellular senescence and SASP pathways. Neurons showed a spectrum of changes including loss of emerin nuclear membrane expression, loss of Brahma-related gene-1 (BRG1 or SMARCA4) expression, loss of myelin basic protein (MBP) axonal expression, and translocation of intranuclear tau to the cytoplasm. Expression of DNA repair proteins was decreased in mTBI brains. mTBI brains showed substantial evidence of DNA damage and cellular senescence. Decreased expression of DNA repair genes suggests inefficient DNA repair pathways in this cohort, conferring susceptibly to cellular senescence and subsequent brain dysfunction after mTBI. We therefore suggest that brains of contact-sports athletes are characterized by deficient DNA repair and DNA damage-induced cellular senescence and propose that this may affect neurons and be the driver of brain dysfunction in mTBI, predisposing the progression to neurodegenerative diseases. This study provides novel targets for diagnostic and prognostic biomarkers, and represents viable targets for future treatments.
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Affiliation(s)
- Nicole Schwab
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 1 King's College Cir, Toronto, ON, M5S 1A8, Canada
- The Hospital for Sick Children, 555 University Ave, Toronto, ON, M5G 1X8, Canada
- Canadian Concussion Centre, Toronto Western Hospital, Toronto, ON, Canada
| | - Karl Grenier
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 1 King's College Cir, Toronto, ON, M5S 1A8, Canada
- The Hospital for Sick Children, 555 University Ave, Toronto, ON, M5G 1X8, Canada
| | - Lili-Naz Hazrati
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 1 King's College Cir, Toronto, ON, M5S 1A8, Canada.
- The Hospital for Sick Children, 555 University Ave, Toronto, ON, M5G 1X8, Canada.
- Canadian Concussion Centre, Toronto Western Hospital, Toronto, ON, Canada.
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18
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Catlin J, Leclerc JL, Shukla K, Marini SM, Doré S. Role of the PGE 2 receptor subtypes EP1, EP2, and EP3 in repetitive traumatic brain injury. CNS Neurosci Ther 2019; 26:628-635. [PMID: 31617678 PMCID: PMC7248542 DOI: 10.1111/cns.13228] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 09/16/2019] [Accepted: 09/18/2019] [Indexed: 01/02/2023] Open
Abstract
Aims The goal was to explore the signaling pathways of PGE2 to investigate therapeutic effects against secondary injuries following TBI. Methods Young (4.9 ± 1.0 months) and aged (20.4 ± 1.4 months) male wild type (WT) C57BL/6 and PGE2 EP1, 2, and 3 receptor knockout mice were selected to either receive sham or repetitive concussive head injury. Immunohistochemistry protocols with Iba1 and GFAP were performed to evaluate microgliosis and astrogliosis in the hippocampus, two critical components of neuroinflammation. Passive avoidance test measured memory function associated with the hippocampus. Results No differences in hippocampal microgliosis were found when aged EP2−/− and EP3−/− mice were compared with aged WT mice. However, the aged EP1−/− mice had 69.2 ± 7.5% less hippocampal microgliosis in the contralateral hemisphere compared with WT aged mice. Compared with aged EP2−/− and EP3−/−, EP1−/− aged mice had 78.9 ± 5.1% and 74.7 ± 6.2% less hippocampal microgliosis in the contralateral hemisphere. Within the EP1−/− mice, aged mice had 90.7 ± 2.7% and 81.1 ± 5.6% less hippocampal microgliosis compared with EP1−/− young mice in the contralateral and ipsilateral hemispheres, respectively. No differences were noted in all groups for astrogliosis. There was a significant difference in latency time within EP1−/−, EP2−/−, and EP3−/− on day 1 and day 2 in aged and young mice. Conclusion These findings demonstrate that the PGE2 EP receptors may be potential therapeutic targets to treat repetitive concussions and other acute brain injuries.
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Affiliation(s)
- James Catlin
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA
| | - Jenna L Leclerc
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA
| | - Krunal Shukla
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA
| | - Sarah M Marini
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA
| | - Sylvain Doré
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA.,Department of Neurology, Psychiatry, and Pharmaceutics, University of Florida, Gainesville, FL, USA
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19
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Duffy MF, Collier TJ, Patterson JR, Kemp CJ, Luk KC, Tansey MG, Paumier KL, Kanaan NM, Fischer DL, Polinski NK, Barth OL, Howe JW, Vaikath NN, Majbour NK, El-Agnaf OMA, Sortwell CE. Lewy body-like alpha-synuclein inclusions trigger reactive microgliosis prior to nigral degeneration. J Neuroinflammation 2018; 15:129. [PMID: 29716614 PMCID: PMC5930695 DOI: 10.1186/s12974-018-1171-z] [Citation(s) in RCA: 115] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 04/20/2018] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Converging evidence suggests a role for microglia-mediated neuroinflammation in Parkinson's disease (PD). Animal models of PD can serve as a platform to investigate the role of neuroinflammation in degeneration in PD. However, due to features of the previously available PD models, interpretations of the role of neuroinflammation as a contributor to or a consequence of neurodegeneration have remained elusive. In the present study, we investigated the temporal relationship of neuroinflammation in a model of synucleinopathy following intrastriatal injection of pre-formed alpha-synuclein fibrils (α-syn PFFS). METHODS Male Fischer 344 rats (N = 114) received unilateral intrastriatal injections of α-syn PFFs, PBS, or rat serum albumin with cohorts euthanized at monthly intervals up to 6 months. Quantification of dopamine neurons, total neurons, phosphorylated α-syn (pS129) aggregates, major histocompatibility complex-II (MHC-II) antigen-presenting microglia, and ionized calcium-binding adaptor molecule-1 (Iba-1) immunoreactive microglial soma size was performed in the substantia nigra. In addition, the cortex and striatum were also examined for the presence of pS129 aggregates and MHC-II antigen-presenting microglia to compare the temporal patterns of pSyn accumulation and reactive microgliosis. RESULTS Intrastriatal injection of α-syn PFFs to rats resulted in widespread accumulation of phosphorylated α-syn inclusions in several areas that innervate the striatum followed by significant loss (~ 35%) of substantia nigra pars compacta dopamine neurons within 5-6 months. The peak magnitudes of α-syn inclusion formation, MHC-II expression, and reactive microglial morphology were all observed in the SN 2 months following injection and 3 months prior to nigral dopamine neuron loss. Surprisingly, MHC-II immunoreactivity in α-syn PFF injected rats was relatively limited during the later interval of degeneration. Moreover, we observed a significant correlation between substantia nigra pSyn inclusion load and number of microglia expressing MHC-II. In addition, we observed a similar relationship between α-syn inclusion load and number of microglia expressing MHC-II in cortical regions, but not in the striatum. CONCLUSIONS Our results demonstrate that increases in microglia displaying a reactive morphology and MHC-II expression occur in the substantia nigra in close association with peak numbers of pSyn inclusions, months prior to nigral dopamine neuron degeneration, and suggest that reactive microglia may contribute to vulnerability of SNc neurons to degeneration. The rat α-syn PFF model provides an opportunity to examine the innate immune response to accumulation of pathological α-syn in the context of normal levels of endogenous α-syn and provides insight into the earliest neuroinflammatory events in PD.
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Affiliation(s)
- Megan F Duffy
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
- Neuroscience Graduate Training Program, Michigan State University, Grand Rapids, MI, USA
| | - Timothy J Collier
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
- Mercy Health Hauenstein Neuroscience Medical Center, Grand Rapids, MI, USA
| | - Joseph R Patterson
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
| | - Christopher J Kemp
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
| | - Kelvin C Luk
- Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Malú G Tansey
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA
| | - Katrina L Paumier
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
- Mercy Health Hauenstein Neuroscience Medical Center, Grand Rapids, MI, USA
| | - Nicholas M Kanaan
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
- Mercy Health Hauenstein Neuroscience Medical Center, Grand Rapids, MI, USA
| | - D Luke Fischer
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
- Neuroscience Graduate Training Program, Michigan State University, Grand Rapids, MI, USA
- MD/PhD Program, Michigan State University, Grand Rapids, MI, USA
| | - Nicole K Polinski
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
- Neuroscience Graduate Training Program, Michigan State University, Grand Rapids, MI, USA
| | - Olivia L Barth
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
| | - Jacob W Howe
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA
| | - Nishant N Vaikath
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Education City, Qatar
| | - Nour K Majbour
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Education City, Qatar
| | - Omar M A El-Agnaf
- Life Sciences Division, College of Science and Engineering, Hamad Bin Khalifa University (HBKU), Education City, Qatar
| | - Caryl E Sortwell
- Department of Translational Science and Molecular Medicine, Michigan State University, 400 Monroe Avenue NW, Grand Rapids, MI, 49503-2532, USA.
- Mercy Health Hauenstein Neuroscience Medical Center, Grand Rapids, MI, USA.
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20
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d’Avila JC, Siqueira LD, Mazeraud A, Azevedo EP, Foguel D, Castro-Faria-Neto HC, Sharshar T, Chrétien F, Bozza FA. Age-related cognitive impairment is associated with long-term neuroinflammation and oxidative stress in a mouse model of episodic systemic inflammation. J Neuroinflammation 2018; 15:28. [PMID: 29382344 PMCID: PMC5791311 DOI: 10.1186/s12974-018-1059-y] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 01/08/2018] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Microglia function is essential to maintain the brain homeostasis. Evidence shows that aged microglia are primed and show exaggerated response to acute inflammatory challenge. Systemic inflammation signals to the brain inducing changes that impact cognitive function. However, the mechanisms involved in age-related cognitive decline associated to episodic systemic inflammation are not completely understood. The aim of this study was to identify neuropathological features associated to age-related cognitive decline in a mouse model of episodic systemic inflammation. METHODS Young and aged Swiss mice were injected with low doses of LPS once a week for 6 weeks to induce episodic systemic inflammation. Sickness behavior, inflammatory markers, and neuroinflammation were assessed in different phases of systemic inflammation in young and aged mice. Behavior was evaluated long term after episodic systemic inflammation by open field, forced swimming, object recognition, and water maze tests. RESULTS Episodic systemic inflammation induced systemic inflammation and sickness behavior mainly in aged mice. Systemic inflammation induced depressive-like behavior in both young and aged mice. Memory and learning were significantly affected in aged mice that presented lower exploratory activity and deficits in episodic and spatial memories, compared to aged controls and to young after episodic systemic inflammation. Systemic inflammation induced acute microglia activation in young mice that returned to base levels long term after episodic systemic inflammation. Aged mice presented dystrophic microglia in the hippocampus and entorhinal cortex at basal level and did not change morphology in the acute response to SI. Regardless of their dystrophic microglia, aged mice produced higher levels of pro-inflammatory (IL-1β and IL-6) as well as pro-resolution (IL-10 and IL-4) cytokines in the brain. Also, higher levels of Nox2 expression, oxidized proteins and lower antioxidant defenses were found in the aged brains compared to the young after episodic systemic inflammation. CONCLUSIONS Our data show that aged mice have increased susceptibility to episodic systemic inflammation. Aged mice that showed cognitive impairments also presented higher oxidative stress and abnormal production of cytokines in their brains. These results indicate that a neuroinflammation and oxidative stress are pathophysiological mechanisms of age-related cognitive impairments.
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Affiliation(s)
- Joana Costa d’Avila
- Laboratory of Immunopharmacology, Oswaldo Cruz Foundation (FIOCRUZ), Rio de Janeiro, Brazil
| | - Luciana Domett Siqueira
- Institute of Medical Biochemistry Leopoldo DeMeis, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Aurélien Mazeraud
- Human Histopathology and Animal Models, Pasteur Institute, Paris, France
| | - Estefania Pereira Azevedo
- Institute of Medical Biochemistry Leopoldo DeMeis, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Debora Foguel
- Institute of Medical Biochemistry Leopoldo DeMeis, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Tarek Sharshar
- Human Histopathology and Animal Models, Pasteur Institute, Paris, France
| | - Fabrice Chrétien
- Human Histopathology and Animal Models, Pasteur Institute, Paris, France
| | - Fernando Augusto Bozza
- National Institute of Infectious Diseases Evandro Chagas, Oswaldo Cruz Foundation (FIOCRUZ), Ministry of Health, Rio de Janeiro, Brazil
- D’Or Institute for Research and Education (IDOR), Rio de Janeiro, Brazil
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21
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Clayton KA, Van Enoo AA, Ikezu T. Alzheimer's Disease: The Role of Microglia in Brain Homeostasis and Proteopathy. Front Neurosci 2017; 11:680. [PMID: 29311768 PMCID: PMC5733046 DOI: 10.3389/fnins.2017.00680] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Accepted: 11/21/2017] [Indexed: 01/15/2023] Open
Abstract
Brain aging is central to late-onset Alzheimer's disease (LOAD), although the mechanisms by which it occurs at protein or cellular levels are not fully understood. Alzheimer's disease is the most common proteopathy and is characterized by two unique pathologies: senile plaques and neurofibrillary tangles, the former accumulating earlier than the latter. Aging alters the proteostasis of amyloid-β peptides and microtubule-associated protein tau, which are regulated in both autonomous and non-autonomous manners. Microglia, the resident phagocytes of the central nervous system, play a major role in the non-autonomous clearance of protein aggregates. Their function is significantly altered by aging and neurodegeneration. This is genetically supported by the association of microglia-specific genes, TREM2 and CD33, and late onset Alzheimer's disease. Here, we propose that the functional characterization of microglia, and their contribution to proteopathy, will lead to a new therapeutic direction in Alzheimer's disease research.
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Affiliation(s)
- Kevin A Clayton
- Department of Pharmacology and Experimental Therapeutics, Medical School, Boston University, Boston, MA, United States
| | - Alicia A Van Enoo
- Department of Pharmacology and Experimental Therapeutics, Medical School, Boston University, Boston, MA, United States
| | - Tsuneya Ikezu
- Department of Pharmacology and Experimental Therapeutics, Medical School, Boston University, Boston, MA, United States.,Department of Neurology, Medical School, Boston University, Boston, MA, United States
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22
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Beier EE, Neal M, Alam G, Edler M, Wu LJ, Richardson JR. Alternative microglial activation is associated with cessation of progressive dopamine neuron loss in mice systemically administered lipopolysaccharide. Neurobiol Dis 2017; 108:115-127. [PMID: 28823928 DOI: 10.1016/j.nbd.2017.08.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 07/17/2017] [Accepted: 08/16/2017] [Indexed: 12/12/2022] Open
Abstract
Inflammation arising from central and/or peripheral sources contributes to the pathogenesis of multiple neurodegenerative diseases including Parkinson's disease (PD). Emerging data suggest that differential activation of glia could lead to the pathogenesis and progression of PD. Here, we sought to determine the relationship between lipopolysaccharide (LPS) treatment, loss of dopaminergic neurons and differential activation of glia. Using a model of repeated injections with LPS (1mg/kg, i.p. for 4days), we found that LPS induced a 34% loss of dopamine neurons in the substantia nigra 19days after initiation of treatment, but no further cell loss was observed at 36days. LPS induced a strong pro-inflammatory response with increased mRNA expression of pro-inflammatory markers, including tumor necrosis factor-α (4.8-fold), inducible nitric oxide synthase (2.0-fold), interleukin-1 beta (8.9-fold), interleukin-6 (10.7-fold), and robust glial activation were observed at 1day after final dose of LPS. These pro-inflammatory genes were then reduced at 19days after treatment, when there was a rise in the anti-inflammatory genes Ym1 (1.8-fold) and arginase-1 (2.6-fold). Additionally, 36days after the last LPS injection there was a significant increase in interleukin-10 (2.1-fold) expression. The qPCR data results were supported by protein data, including cytokine measurements, western blotting, and immunofluorescence in brain microglia. Taken together, these data demonstrate that progressive neurodegeneration in the substantia nigra following LPS is likely arrested by microglia shifting to an anti-inflammatory phenotype. Thus, strategies to promote resolution of neuroinflammation may be a promising avenue to slow the progressive loss of dopamine neurons in PD.
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Affiliation(s)
- Eric E Beier
- Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, United States
| | - Matthew Neal
- Department of Pharmaceutical Sciences, Center for Neurodegenerative Disease and Aging, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Gelerah Alam
- Department of Pharmaceutical Sciences, Center for Neurodegenerative Disease and Aging, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Melissa Edler
- Department of Pharmaceutical Sciences, Center for Neurodegenerative Disease and Aging, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Long-Jun Wu
- Department of Neurology, Mayo Clinic, Rochester, MN, United States
| | - Jason R Richardson
- Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, United States; Department of Pharmaceutical Sciences, Center for Neurodegenerative Disease and Aging, Northeast Ohio Medical University, Rootstown, OH, United States.
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23
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Mangold CA, Wronowski B, Du M, Masser DR, Hadad N, Bixler GV, Brucklacher RM, Ford MM, Sonntag WE, Freeman WM. Sexually divergent induction of microglial-associated neuroinflammation with hippocampal aging. J Neuroinflammation 2017; 14:141. [PMID: 28732515 PMCID: PMC5521082 DOI: 10.1186/s12974-017-0920-8] [Citation(s) in RCA: 116] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 07/13/2017] [Indexed: 01/11/2023] Open
Abstract
Background The necessity of including both males and females in molecular neuroscience research is now well understood. However, there is relatively limited basic biological data on brain sex differences across the lifespan despite the differences in age-related neurological dysfunction and disease between males and females. Methods Whole genome gene expression of young (3 months), adult (12 months), and old (24 months) male and female C57BL6 mice hippocampus was analyzed. Subsequent bioinformatic analyses and confirmations of age-related changes and sex differences in hippocampal gene and protein expression were performed. Results Males and females demonstrate both common expression changes with aging and marked sex differences in the nature and magnitude of the aging responses. Age-related hippocampal induction of neuroinflammatory gene expression was sexually divergent and enriched for microglia-specific genes such as complement pathway components. Sexually divergent C1q protein expression was confirmed by immunoblotting and immunohistochemistry. Similar patterns of cortical sexually divergent gene expression were also evident. Additionally, inter-animal gene expression variability increased with aging in males, but not females. Conclusions These findings demonstrate sexually divergent neuroinflammation with aging that may contribute to sex differences in age-related neurological diseases such as stroke and Alzheimer’s, specifically in the complement system. The increased expression variability in males suggests a loss of fidelity in gene expression regulation with aging. These findings reveal a central role of sex in the transcriptomic response of the hippocampus to aging that warrants further, in depth, investigations. Electronic supplementary material The online version of this article (doi:10.1186/s12974-017-0920-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Colleen A Mangold
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, State College, PA, USA
| | - Benjamin Wronowski
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Mei Du
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Dustin R Masser
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Niran Hadad
- Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Georgina V Bixler
- Genome Sciences Facility, Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Robert M Brucklacher
- Genome Sciences Facility, Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Matthew M Ford
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, Oregon, USA
| | - William E Sonntag
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Willard M Freeman
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA. .,Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA. .,Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, USA. .,, SLY-BRC 1370, 975 NE 10th St, Oklahoma City, OK, 73104, USA.
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Kwon IS, Kim J, Rhee DK, Kim BO, Pyo S. Pneumolysin induces cellular senescence by increasing ROS production and activation of MAPK/NF-κB signal pathway in glial cells. Toxicon 2017; 129:100-112. [DOI: 10.1016/j.toxicon.2017.02.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 02/15/2017] [Accepted: 02/17/2017] [Indexed: 02/01/2023]
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25
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Yeh TY, Wang SM, Tseng GF, Liu PH. Differential regulation of glial reactions in the central facial tract and the facial nucleus after facial neurorrhaphy. J Chem Neuroanat 2017; 79:38-50. [DOI: 10.1016/j.jchemneu.2016.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Revised: 10/01/2016] [Accepted: 11/14/2016] [Indexed: 01/01/2023]
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26
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Barzilai A, Schumacher B, Shiloh Y. Genome instability: Linking ageing and brain degeneration. Mech Ageing Dev 2017; 161:4-18. [DOI: 10.1016/j.mad.2016.03.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/23/2016] [Accepted: 03/26/2016] [Indexed: 02/06/2023]
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Cornejo F, von Bernhardi R. Age-Dependent Changes in the Activation and Regulation of Microglia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:205-226. [DOI: 10.1007/978-3-319-40764-7_10] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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28
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Hogg EL, Müller J, Corrêa SAL. Does the MK2-dependent Production of TNFα Regulate mGluR-dependent Synaptic Plasticity? Curr Neuropharmacol 2016; 14:474-80. [PMID: 27296641 PMCID: PMC4983755 DOI: 10.2174/1570159x13666150624165939] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 04/22/2015] [Accepted: 06/26/2015] [Indexed: 11/22/2022] Open
Abstract
The molecular mechanisms and signalling cascades that trigger the induction of group I metabotropic glutamate receptor (GI-mGluR)-dependent long-term depression (LTD) have been the subject of intensive investigation for nearly two decades. The generation of genetically modified animals has played a crucial role in elucidating the involvement of key molecules regulating the induction and maintenance of mGluR-LTD. In this review we will discuss the requirement of the newly discovered MAPKAPK-2 (MK2) and MAPKAPK-3 (MK3) signalling cascade in regulating GI-mGluR-LTD. Recently, it has been shown that the absence of MK2 impaired the induction of GI-mGluR-dependent LTD, an effect that is caused by reduced internalization of AMPA receptors (AMPAR). As the MK2 cascade directly regulates tumour necrosis factor alpha (TNFα) production, this review will examine the evidence that the release of TNFα acts to regulate glutamate receptor expression and therefore may play a functional role in the impairment of GI-mGluRdependent LTD and the cognitive deficits observed in MK2/3 double knockout animals. The strong links of increased TNFα production in both aging and neurodegenerative disease could implicate the action of MK2 in these processes.
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Affiliation(s)
| | | | - Sônia A L Corrêa
- School of Life Sciences, Bradford University, Bradford, BD18 3LX.
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29
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von Bernhardi R, Eugenín-von Bernhardi J, Flores B, Eugenín León J. Glial Cells and Integrity of the Nervous System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:1-24. [PMID: 27714682 DOI: 10.1007/978-3-319-40764-7_1] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Today, there is enormous progress in understanding the function of glial cells, including astroglia, oligodendroglia, Schwann cells, and microglia. Around 150 years ago, glia were viewed as a glue among neurons. During the course of the twentieth century, microglia were discovered and neuroscientists' views evolved toward considering glia only as auxiliary cells of neurons. However, over the last two to three decades, glial cells' importance has been reconsidered because of the evidence on their involvement in defining central nervous system architecture, brain metabolism, the survival of neurons, development and modulation of synaptic transmission, propagation of nerve impulses, and many other physiological functions. Furthermore, increasing evidence shows that glia are involved in the mechanisms of a broad spectrum of pathologies of the nervous system, including some psychiatric diseases, epilepsy, and neurodegenerative diseases to mention a few. It appears safe to say that no neurological disease can be understood without considering neuron-glia crosstalk. Thus, this book aims to show different roles played by glia in the healthy and diseased nervous system, highlighting some of their properties while considering that the various glial cell types are essential components not only for cell function and integration among neurons, but also for the emergence of important brain homeostasis.
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Affiliation(s)
- Rommy von Bernhardi
- Department of Neurology, School of Medicine, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile.
| | - Jaime Eugenín-von Bernhardi
- Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Pettenkoferstr.12, 80336, Munich, Germany.,Graduate School of Systemic Neuroscience, Ludwig-Maximilians-University, 82152, Planegg-Martinsried, Munich, Germany
| | - Betsi Flores
- Department of Neurology, School of Medicine, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile
| | - Jaime Eugenín León
- Department of Biology, Faculty of Chemistry and Biology, USACH, Santiago, Chile
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30
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Liu L, Luo XG, Yu HM, Feng Y, Ren Y, Yin YF, Shang H, He ZY. Repeated intra-nigrostriatal injection of phorbol myristate acetate induces microglial senescence in adult rats. Mol Med Rep 2015; 12:7271-8. [PMID: 26459397 PMCID: PMC4626136 DOI: 10.3892/mmr.2015.4412] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 08/17/2015] [Indexed: 11/18/2022] Open
Abstract
Phorbol myristate acetate (PMA), as a potent tumor promoter, may induce microglial senescence. The present study investigated the effect of PMA infection on microglial senescence. From 58 male Sprague-Dawley rats, 10 were randomly selected and divided into a PMA injection group, containing five rats (0.5 µg/µl PMA) and a control group, containing five rats (commensurable 0.9% saline). Immunofluorescent staining of Iba-1 and enzyme-linked immunosorbent assay analyses of the expression levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1 β were performed in these two groups. The remaining 48 rats were randomly divided into the following three groups, each containing 16 rats: Repeated injection control group (commensurable normal saline, once a week for 4 weeks), single PMA injection group (0.5 µg/µl PMA, once in the first week) and repeated injection PMA group (0.5 µg/µl PMA, once a week for 4 weeks). The expression levels of p21, detected using double immunofluorescence staining with Iba-1, and β-galactosidase, via double immunohistochemical staining of Iba-1, were examined in these three groups. The results indicated that a single injection of PMA did not change the microglial morphology and had no significant effects on the expression levels of TNF-α and IL-1β, compared with the control group (P>0.05). Following four repeated injections of PMA, the microglia in the substantia nigra presented with features of senescence, characterized by increased expression levels of β-galactosidase (P<0.001) and p21 (P<0.001), compared with the repeated injection control group. In conclusion, repeated intra-nigrostriatal treatment with PMA induced microglial senescence with increased expression levels of β-galactosidase and p21 in the substantia nigra of the rats.
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Affiliation(s)
- Lin Liu
- Department of Neurology, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Xiao-Guang Luo
- Department of Neurology, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Hong-Mei Yu
- Department of Neurology, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Yu Feng
- Department of Neurology, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Yan Ren
- Department of Neurology, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Ya-Fu Yin
- Department of Nuclear Medicine, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Hong Shang
- Department of Laboratory Medicine, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Zhi-Yi He
- Department of Neurology, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
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31
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Galbavy W, Kaczocha M, Puopolo M, Liu L, Rebecchi MJ. Neuroimmune and Neuropathic Responses of Spinal Cord and Dorsal Root Ganglia in Middle Age. PLoS One 2015; 10:e0134394. [PMID: 26241743 PMCID: PMC4524632 DOI: 10.1371/journal.pone.0134394] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 07/08/2015] [Indexed: 02/07/2023] Open
Abstract
Prior studies of aging and neuropathic injury have focused on senescent animals compared to young adults, while changes in middle age, particularly in the dorsal root ganglia (DRG), have remained largely unexplored. 14 neuroimmune mRNA markers, previously associated with peripheral nerve injury, were measured in multiplex assays of lumbar spinal cord (LSC), and DRG from young and middle-aged (3, 17 month) naïve rats, or from rats subjected to chronic constriction injury (CCI) of the sciatic nerve (after 7 days), or from aged-matched sham controls. Results showed that CD2, CD3e, CD68, CD45, TNF-α, IL6, CCL2, ATF3 and TGFβ1 mRNA levels were substantially elevated in LSC from naïve middle-aged animals compared to young adults. Similarly, LSC samples from older sham animals showed increased levels of T-cell and microglial/macrophage markers. CCI induced further increases in CCL2, and IL6, and elevated ATF3 mRNA levels in LSC of young and middle-aged adults. Immunofluorescence images of dorsal horn microglia from middle-aged naïve or sham rats were typically hypertrophic with mostly thickened, de-ramified processes, similar to microglia following CCI. Unlike the spinal cord, marker expression profiles in naïve DRG were unchanged across age (except increased ATF3); whereas, levels of GFAP protein, localized to satellite glia, were highly elevated in middle age, but independent of nerve injury. Most neuroimmune markers were elevated in DRG following CCI in young adults, yet middle-aged animals showed little response to injury. No age-related changes in nociception (heat, cold, mechanical) were observed in naïve adults, or at days 3 or 7 post-CCI. The patterns of marker expression and microglial morphologies in healthy middle age are consistent with development of a para-inflammatory state involving microglial activation and T-cell marker elevation in the dorsal horn, and neuronal stress and satellite cell activation in the DRG. These changes, however, did not affect the establishment of neuropathic pain.
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Affiliation(s)
- William Galbavy
- Department of Anesthesiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Martin Kaczocha
- Department of Anesthesiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Michelino Puopolo
- Department of Anesthesiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Lixin Liu
- Department of Anesthesiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Mario J Rebecchi
- Department of Anesthesiology, Stony Brook University, Stony Brook, New York, United States of America
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32
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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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33
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Villacampa N, Almolda B, Vilella A, Campbell IL, González B, Castellano B. Astrocyte-targeted production of IL-10 induces changes in microglial reactivity and reduces motor neuron death after facial nerve axotomy. Glia 2015; 63:1166-84. [PMID: 25691003 DOI: 10.1002/glia.22807] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 01/28/2015] [Indexed: 12/30/2022]
Abstract
Interleukin-10 (IL-10) is a cytokine that plays a crucial role in regulating the inflammatory response and immune reactions. In the central nervous system (CNS), IL-10 is mainly produced by astrocytes and microglia and it is upregulated after various insults, such as experimental autoimmune encephalomyelitis, middle cerebral artery occlusion, excitotoxicity and traumatic brain injury. To better understand the effects of IL-10 in the normal and injured CNS, we generated transgenic mice (termed GFAP-IL-10Tg) that expressed the murine IL-10 gene under the transcriptional control of the glial fibrillary acidic protein (GFAP) promoter. Previous studies demonstrated marked changes in the microglial phenotype in these mice under basal conditions. The objective of the present study was to investigate the effects of local astrocyte-targeted IL-10 production on glial activation, neuronal degeneration and leukocyte recruitment after axotomy. GFAP-IL-10Tg mice had marked changes in the phenotype of activated microglial cells, as well as in the number of microglial clusters and in microglial cell density. These microglial changes are accompanied by a twofold increase in lymphocyte infiltration in GFAP-IL-10Tg mice and around twofold decrease in neuronal cell death at 21 dpi. Altogether, our findings suggested that astrocyte-targeted production of IL-10 impacted the microglial response and lymphocyte recruitment and culminated in a beneficial effect on neuronal survival.
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Affiliation(s)
- Nàdia Villacampa
- Department of Cell Biology, Physiology and Immunology, Institute of Neuroscience, Universitat Autònoma de Barcelona, Bellaterra, 08193, Barcelona, Spain
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Leonardo CC, Mendes M, Ahmad AS, Doré S. Efficacy of prophylactic flavan-3-ol in permanent focal ischemia in 12-mo-old mice. Am J Physiol Heart Circ Physiol 2015; 308:H583-91. [PMID: 25576625 DOI: 10.1152/ajpheart.00239.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The consumption of flavan-3-ol-containing foods, including (-)-epicatechin (EC), has been linked to lower incidence of cardiovascular disease and stroke. We previously demonstrated nuclear transcription factor erythroid 2p45-related factor-2 (Nrf2) -dependent EC efficacy in reducing stroke-induced deficits in 2-mo-old mice; yet stroke is primarily a disease of the elderly. Because neuroinflammation, oxidative stress, and vascular dysfunction are hallmarks of aging, we tested whether Nrf2 mediates EC efficacy in aging mice through modulation of glial responses and blood brain barrier permeability. First, we compared anastomosis in naïve wild-type and C57BL/6 Nrf2(-/-) mice to identify potential differences in cerebrovascular architecture. Data showed no significant differences in the number of anastomoses or mean intersection points, indicating similar gross vascular physiology. To assess efficacy and mechanisms of protection, wild-type or Nrf2(-/-) mice were administered the minimum effective EC dose established in our previous studies before the permanent distal middle cerebral artery occlusion. Similar to previous results with young mice, 12-mo-old wild types also showed significant reductions in infarct volume (41.01 ± 29.57%) and improved performance in removing adhesive tape relative to vehicle-treated controls, whereas a trend toward protection was observed in Nrf2(-/-). However, EC did not reduce immunoreactivity for the microglia/macrophage marker anti-ionized calcium-binding adapter molecule 1, suggesting that dampened activation/recruitment did not account for EC protection. Furthermore, there were no differences in mouse IgG extravasation or spontaneous hemorrhage between EC-treated groups. These data demonstrate that EC protection occurs independent of microglia/macrophage modulation or blood brain barrier preservation, suggesting that the glial cell responses in young mice are compensatory to another, and potentially novel, protective mechanism.
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Affiliation(s)
- Christopher C Leonardo
- Department of Anesthesiology and Center for Translational Research and Neurodegenerative Disease, College of Medicine, University of Florida, Gainesville, Florida; and
| | - Monique Mendes
- Department of Anesthesiology and Center for Translational Research and Neurodegenerative Disease, College of Medicine, University of Florida, Gainesville, Florida; and
| | - Abdullah S Ahmad
- Department of Anesthesiology and Center for Translational Research and Neurodegenerative Disease, College of Medicine, University of Florida, Gainesville, Florida; and
| | - Sylvain Doré
- Department of Anesthesiology and Center for Translational Research and Neurodegenerative Disease, College of Medicine, University of Florida, Gainesville, Florida; and Departments of Neurology, Psychiatry and Neuroscience, College of Medicine, University of Florida, Gainesville, Florida
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Abstract
Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Despite extensive preclinical research supporting the effectiveness of neuroprotective therapies for brain trauma, there have been no successful randomized controlled clinical trials to date. TBI results in delayed secondary tissue injury due to neurochemical, metabolic and cellular changes; modulating such effects has provided the basis for neuroprotective interventions. To establish more effective neuroprotective treatments for TBI it is essential to better understand the complex cellular and molecular events that contribute to secondary injury. Here we critically review relevant research related to causes and modulation of delayed tissue damage, with particular emphasis on cell death mechanisms and post-traumatic neuroinflammation. We discuss the concept of utilizing multipotential drugs that target multiple secondary injury pathways, rather than more specific "laser"-targeted strategies that have uniformly failed in clinical trials. Moreover, we assess data supporting use of neuroprotective drugs that are currently being evaluated in human clinical trials for TBI, as well as promising emerging experimental multipotential drug treatment strategies. Finally, we describe key challenges and provide suggestions to improve the likelihood of successful clinical translation.
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Affiliation(s)
- David J Loane
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), National Study Center for Trauma and EMS, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Bogdan A Stoica
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), National Study Center for Trauma and EMS, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Alan I Faden
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), National Study Center for Trauma and EMS, University of Maryland School of Medicine, Baltimore, MD, USA.
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Song IU, Cho HJ, Kim JS, Park IS, Lee KS. Serum hs-CRP levels are increased in de Novo Parkinson's disease independently from age of onset. Eur Neurol 2014; 72:285-9. [PMID: 25323302 DOI: 10.1159/000363570] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 05/11/2014] [Indexed: 11/19/2022]
Abstract
BACKGROUND Microglia in the brain are the counterpart of macrophages and it functions as a first defense in the brain. The double-edged feature of microglia has explained that the inflammatory state of microglia in aged brains induces them to over-respond to small stimuli that are otherwise well controlled in young brains. The clinical effect of microglia in patients with Parkinson's disease (PD) is poorly defined. This prospective study assessed the peripheral concentrations of hs-CRP, a protein able to reflect neuroinflammation in the CNS, in de novo PD patients with varying ages of onset. METHODS We examined 435 patients with de novo PD and 221 healthy subjects and the differences in hs-CRP between these groups were investigated. The PD group was classified into 4 subgroups according to the age of de novo PD to investigate the relationship between hs-CRP and the aging process in de novo PD. RESULTS There were significantly higher serum hs-CRP levels in patients with PD compared with healthy subjects. A post-hoc analysis of the 4 PD subgroups showed no significant differences in serum hs-CRP level. CONCLUSION We assumed that neuroinflammatory reactions play a role in the pathogenesis of PD, but found no clinical evidence of a neuroprotective effect against PD in young brains. To clarify the role of microglia and aging in the pathogenesis of PD, future longitudinal studies involving a large cohort are required.
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Affiliation(s)
- In-Uk Song
- Department of Neurology, College of Medicine, The Catholic University of Korea, Seoul, Korea
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37
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Are there roles for brain cell senescence in aging and neurodegenerative disorders? Biogerontology 2014; 15:643-60. [PMID: 25305051 DOI: 10.1007/s10522-014-9532-1] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 09/13/2014] [Indexed: 12/30/2022]
Abstract
The term cellular senescence was introduced more than five decades ago to describe the state of growth arrest observed in aging cells. Since this initial discovery, the phenotypes associated with cellular senescence have expanded beyond growth arrest to include alterations in cellular metabolism, secreted cytokines, epigenetic regulation and protein expression. Recently, senescence has been shown to play an important role in vivo not only in relation to aging, but also during embryonic development. Thus, cellular senescence serves different purposes and comprises a wide range of distinct phenotypes across multiple cell types. Whether all cell types, including post-mitotic neurons, are capable of entering into a senescent state remains unclear. In this review we examine recent data that suggest that cellular senescence plays a role in brain aging and, notably, may not be limited to glia but also neurons. We suggest that there is a high level of similarity between some of the pathological changes that occur in the brain in Alzheimer's and Parkinson's diseases and those phenotypes observed in cellular senescence, leading us to propose that neurons and glia can exhibit hallmarks of senescence previously documented in peripheral tissues.
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Chinta SJ, Woods G, Rane A, Demaria M, Campisi J, Andersen JK. Cellular senescence and the aging brain. Exp Gerontol 2014; 68:3-7. [PMID: 25281806 DOI: 10.1016/j.exger.2014.09.018] [Citation(s) in RCA: 181] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 09/18/2014] [Accepted: 09/30/2014] [Indexed: 12/31/2022]
Abstract
Cellular senescence is a potent anti-cancer mechanism that arrests the proliferation of mitotically competent cells to prevent malignant transformation. Senescent cells accumulate with age in a variety of human and mouse tissues where they express a complex 'senescence-associated secretory phenotype' (SASP). The SASP includes many pro-inflammatory cytokines, chemokines, growth factors and proteases that have the potential to cause or exacerbate age-related pathology, both degenerative and hyperplastic. While cellular senescence in peripheral tissues has recently been linked to a number of age-related pathologies, its involvement in brain aging is just beginning to be explored. Recent data generated by several laboratories suggest that both aging and age-related neurodegenerative diseases are accompanied by an increase in SASP-expressing senescent cells of non-neuronal origin in the brain. Moreover, this increase correlates with neurodegeneration. Senescent cells in the brain could therefore constitute novel therapeutic targets for treating age-related neuropathologies.
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Affiliation(s)
| | - Georgia Woods
- Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Anand Rane
- Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Marco Demaria
- Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Judith Campisi
- Buck Institute for Research on Aging, Novato, CA 94945, USA; Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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Streit WJ, Xue QS, Tischer J, Bechmann I. Microglial pathology. Acta Neuropathol Commun 2014; 2:142. [PMID: 25257319 PMCID: PMC4180960 DOI: 10.1186/s40478-014-0142-6] [Citation(s) in RCA: 228] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 09/11/2014] [Indexed: 02/06/2023] Open
Abstract
This paper summarizes pathological changes that affect microglial cells in the human brain during aging and in aging-related neurodegenerative diseases, primarily Alzheimer’s disease (AD). It also provides examples of microglial changes that have been observed in laboratory animals during aging and in some experimentally induced lesions and disease models. Dissimilarities and similarities between humans and rodents are discussed in an attempt to generate a current understanding of microglial pathology and its significance during aging and in the pathogenesis of Alzheimer dementia (AD). The identification of dystrophic (senescent) microglia has created an ostensible conflict with prior work claiming a role for activated microglia and neuroinflammation during normal aging and in AD, and this has raised a basic question: does the brain’s immune system become hyperactive (inflamed) or does it become weakened (senescent) in elderly and demented people, and what is the impact on neuronal function and cognition? Here we strive to reconcile these seemingly contradictory notions by arguing that both low-grade neuroinflammation and microglial senescence are the result of aging-associated free radical injury. Both processes are damaging for microglia as they synergistically exhaust this essential cell population to the point where the brain’s immune system is effete and unable to support neuronal function.
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Mosher KI, Wyss-Coray T. Microglial dysfunction in brain aging and Alzheimer's disease. Biochem Pharmacol 2014; 88:594-604. [PMID: 24445162 PMCID: PMC3972294 DOI: 10.1016/j.bcp.2014.01.008] [Citation(s) in RCA: 412] [Impact Index Per Article: 41.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 01/06/2014] [Accepted: 01/07/2014] [Indexed: 12/23/2022]
Abstract
Microglia, the immune cells of the central nervous system, have long been a subject of study in the Alzheimer's disease (AD) field due to their dramatic responses to the pathophysiology of the disease. With several large-scale genetic studies in the past year implicating microglial molecules in AD, the potential significance of these cells has become more prominent than ever before. As a disease that is tightly linked to aging, it is perhaps not entirely surprising that microglia of the AD brain share some phenotypes with aging microglia. Yet the relative impacts of both conditions on microglia are less frequently considered in concert. Furthermore, microglial "activation" and "neuroinflammation" are commonly analyzed in studies of neurodegeneration but are somewhat ill-defined concepts that in fact encompass multiple cellular processes. In this review, we have enumerated six distinct functions of microglia and discuss the specific effects of both aging and AD. By calling attention to the commonalities of these two states, we hope to inspire new approaches for dissecting microglial mechanisms.
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Affiliation(s)
- Kira Irving Mosher
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California 94305, USA; Neuroscience IDP Program, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Tony Wyss-Coray
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California 94305, USA; Center for Tissue Regeneration, Repair and Restoration, Veterans Administration Palo Alto Health Care System, Palo Alto, California 94304, USA.
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Immunity and Alzheimer's disease: immunological perspectives on the development of novel therapies. Drug Discov Today 2013; 18:1212-20. [DOI: 10.1016/j.drudis.2013.07.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Revised: 07/19/2013] [Accepted: 07/30/2013] [Indexed: 02/07/2023]
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Abstract
The identification of microglia-associated, neurological disease-causing mutations in patients, combined with studies in mouse models has highlighted microglia, the brain’s intrinsic myeloid cells, as key modulators of pathogenesis and disease progression in neurodegenerative diseases. In Alzheimer’s disease (AD) in particular, the activation and accumulation of microglial cells around b-Amyloid (Ab) plaques has long been described and is believed to result in chronic neuroinflammation—a term that, despite being commonly used, lacks a precise definition. This seemingly directed response of microglia to amyloid deposits conflicts with the fact that the increasing buildup of Ab plaques is not inhibited by these cells during disease progression. While recent evidence suggests that microglia lose their intrinsic beneficial function during the course of AD and may even acquire a ‘‘toxic’’ phenotype over time, Ab may also simply not be an appropriate trigger to induce phagocytosis and degradation by microglia in vivo. As recent experimental evidence has indicated the importance of the microglia in AD pathogenesis, future efforts aimed at tackling this disease via utilization or modulation of microglia or factors therefrom appear to be an exciting and challenging research front.
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Chinta SJ, Lieu CA, Demaria M, Laberge RM, Campisi J, Andersen JK. Environmental stress, ageing and glial cell senescence: a novel mechanistic link to Parkinson's disease? J Intern Med 2013; 273:429-36. [PMID: 23600398 PMCID: PMC3633085 DOI: 10.1111/joim.12029] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Exposure to environmental toxins is associated with a variety of age-related diseases including cancer and neurodegeneration. For example, in Parkinson's disease (PD), chronic environmental exposure to certain toxins has been linked to the age-related development of neuropathology. Neuronal damage is believed to involve the induction of neuroinflammatory events as a consequence of glial cell activation. Cellular senescence is a potent anti-cancer mechanism that occurs in a number of proliferative cell types and causes the arrest of proliferation of cells at risk of malignant transformation following exposure to potentially oncogenic stimuli. With age, senescent cells accumulate and express a senescence-associated secretory phenotype (SASP; that is the robust secretion of many inflammatory cytokines, growth factors and proteases). Whereas cell senescence in peripheral tissues has been causally linked to a number of age-related pathologies, little is known about the induction of cellular senescence and the SASP in the brain. On the basis of recently reported findings, we propose that environmental stressors associated with PD may act in part by eliciting senescence and the SASP within non neuronal glial cells in the ageing brain, thus contributing to the characteristic decline in neuronal integrity that occurs in this disorder.
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Affiliation(s)
- S J Chinta
- Buck Institute for Research on Aging, Novato, CA, USA
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Liu Y, Zhang M, Hao W, Mihaljevic I, Liu X, Xie K, Walter S, Fassbender K. Matrix metalloproteinase-12 contributes to neuroinflammation in the aged brain. Neurobiol Aging 2013; 34:1231-9. [DOI: 10.1016/j.neurobiolaging.2012.10.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 10/09/2012] [Accepted: 10/19/2012] [Indexed: 01/02/2023]
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Wong WT. Microglial aging in the healthy CNS: phenotypes, drivers, and rejuvenation. Front Cell Neurosci 2013; 7:22. [PMID: 23493481 PMCID: PMC3595516 DOI: 10.3389/fncel.2013.00022] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Accepted: 02/21/2013] [Indexed: 12/12/2022] Open
Abstract
Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and age-related macular degeneration (AMD), share two characteristics in common: (1) a disease prevalence that increases markedly with advancing age, and (2) neuroinflammatory changes in which microglia, the primary resident immune cell of the CNS, feature prominently. These characteristics have led to the hypothesis that pathogenic mechanisms underlying age-related neurodegenerative disease involve aging changes in microglia. If correct, targeting features of microglial senescence may constitute a feasible therapeutic strategy. This review explores this hypothesis and its implications by considering the current knowledge on how microglia undergo change during aging and how the emergence of these aging phenotypes relate to significant alterations in microglial function. Evidence and theories on cellular mechanisms implicated in driving senescence in microglia are reviewed, as are “rejuvenative” measures and strategies that aim to reverse or ameliorate the aging microglial phenotype. Understanding and controlling microglial aging may represent an opportunity for elucidating disease mechanisms and for formulating novel therapies.
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Affiliation(s)
- 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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Kumar A, Stoica BA, Sabirzhanov B, Burns MP, Faden AI, Loane DJ. Traumatic brain injury in aged animals increases lesion size and chronically alters microglial/macrophage classical and alternative activation states. Neurobiol Aging 2012; 34:1397-411. [PMID: 23273602 DOI: 10.1016/j.neurobiolaging.2012.11.013] [Citation(s) in RCA: 188] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 10/22/2012] [Accepted: 11/22/2012] [Indexed: 12/01/2022]
Abstract
Traumatic brain injury (TBI) causes chronic microglial activation that contributes to subsequent neurodegeneration, with clinical outcomes declining as a function of aging. Microglia/macrophages (MG/Mɸ) have multiple phenotypes, including a classically activated, proinflammatory (M1) state that might contribute to neurotoxicity, and an alternatively activated (M2) state that might promote repair. In this study we used gene expression, immunohistochemical, and stereological analyses to show that TBI in aged versus young mice caused larger lesions associated with an M1/M2 balance switch and increased numbers of reactive (bushy and hypertrophic) MG/Mɸ in the cortex, hippocampus, and thalamus. Chitinase3-like 3 (Ym1), an M2 phenotype marker, displayed heterogeneous expression after TBI with amoeboid-like Ym1-positive MG/Mɸ at the contusion site and ramified Ym1-positive MG/Mɸ at distant sites; this distribution was age-related. Aged-injured mice also showed increased MG/Mɸ expression of major histocompatibility complex II and NADPH oxidase, and reduced antioxidant enzyme expression which was associated with lesion size and neurodegeneration. Thus, altered relative M1/M2 activation and an nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase)-mediated shift in redox state might contribute to worse outcomes observed in older TBI animals by creating a more proinflammatory M1 MG/Mɸ activation state.
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Affiliation(s)
- Alok Kumar
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
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Kumar A, Loane DJ. Neuroinflammation after traumatic brain injury: opportunities for therapeutic intervention. Brain Behav Immun 2012; 26:1191-201. [PMID: 22728326 DOI: 10.1016/j.bbi.2012.06.008] [Citation(s) in RCA: 473] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 05/27/2012] [Accepted: 06/14/2012] [Indexed: 12/11/2022] Open
Abstract
Traumatic brain injury (TBI) remains one of the leading causes of mortality and morbidity worldwide, yet despite extensive efforts to develop neuroprotective therapies for this devastating disorder there have been no successful outcomes in human clinical trials to date. Following the primary mechanical insult TBI results in delayed secondary injury events due to neurochemical, metabolic and cellular changes that account for many of the neurological deficits observed after TBI. The development of secondary injury represents a window of opportunity for therapeutic intervention to prevent progressive tissue damage and loss of function after injury. To establish effective neuroprotective treatments for TBI it is essential to fully understand the complex cellular and molecular events that contribute to secondary injury. Neuroinflammation is well established as a key secondary injury mechanism after TBI, and it has been long considered to contribute to the damage sustained following brain injury. However, experimental and clinical research indicates that neuroinflammation after TBI can have both detrimental and beneficial effects, and these likely differ in the acute and delayed phases after injury. The key to developing future anti-inflammatory based neuroprotective treatments for TBI is to minimize the detrimental and neurotoxic effects of neuroinflammation while promoting the beneficial and neurotrophic effects, thereby creating optimal conditions for regeneration and repair after injury. This review outlines how post-traumatic neuroinflammation contributes to secondary injury after TBI, and discusses the complex and varied responses of the primary innate immune cells of the brain, microglia, to injury. In addition, emerging experimental anti-inflammatory and multipotential drug treatment strategies for TBI are discussed, as well as some of the challenges faced by the research community to translate promising neuroprotective drug treatments to the clinic.
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Affiliation(s)
- Alok Kumar
- Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research (STAR), National Study Center for Trauma and EMS, University of Maryland School of Medicine, Baltimore, MD, United States
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Streit WJ, Xue QS. Alzheimer's disease, neuroprotection, and CNS immunosenescence. Front Pharmacol 2012; 3:138. [PMID: 22822399 PMCID: PMC3398410 DOI: 10.3389/fphar.2012.00138] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 06/25/2012] [Indexed: 01/07/2023] Open
Abstract
This review is focused on discussing in some detail possible neuroprotective functions of microglial cells. We strive to explain how loss of these essential microglial functions might contribute toward the development of characteristic neuropathological features that characterize Alzheimer’s disease. The conceptual framework guiding our thinking is provided by the hypothesis that microglial senescence accounts for impaired neuronal protection and consequent neurodegeneration.
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Affiliation(s)
- Wolfgang J Streit
- Department of Neuroscience, University of Florida College of Medicine and McKnight Brain Institute Gainesville, FL, USA
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Madhusudan A, Vogel P, Knuesel I. Impact of prenatal immune system disturbances on brain development. J Neuroimmune Pharmacol 2012; 8:79-86. [PMID: 22580757 DOI: 10.1007/s11481-012-9374-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 04/27/2012] [Indexed: 12/30/2022]
Abstract
As research into various aging-associated neurodegenerative disorders reveals their immense pathophysiological complexity, the focus is currently shifting from studying changes in an advanced disease state to investigations involving pre-symptomatic periods, possible aberrations in early life, and even abnormalities in brain development. Recent studies on the etiology of schizophrenia and autism spectrum disorders revealed a profound impact of neurodevelopmental disturbances on disease predisposition, onset and progression. Here, we discuss how a prenatal immune challenge can affect the developing brain-with a selective focus on the impact on microglia, the brain's immune cells-and the implications for brain aging and its associated risk of developing Alzheimer's disease.
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Affiliation(s)
- Amrita Madhusudan
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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50
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Luo XG, Chen SD. The changing phenotype of microglia from homeostasis to disease. Transl Neurodegener 2012; 1:9. [PMID: 23210447 PMCID: PMC3514090 DOI: 10.1186/2047-9158-1-9] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Accepted: 04/24/2012] [Indexed: 12/20/2022] Open
Abstract
It has been nearly a century since the early description of microglia by Rio-Hortega; since then many more biological and pathological features of microglia have been recognized. Today, microglia are generally considered to be beneficial to homeostasis at the resting state through their abilities to survey the environment and phagocytose debris. However, when activated microglia assume diverse phenotypes ranging from fully inflamed, which involves the release of many pro-inflammatory cytokines, to alternatively activated, releasing anti-inflammatory cytokines or neurotrophins, the consequences to neurons can range from detrimental to supportive. Due to the different experimental sets and conditions, contradictory results have been obtained regarding the controversial question of whether microglia are “good” or “bad.” While it is well understood that the dual roles of activated microglia depend on specific situations, the underlying mechanisms have remained largely unclear, and the interpretation of certain findings related to diverse microglial phenotypes continues to be problematic. In this review we discuss the functions of microglia in neuronal survival and neurogenesis, the crosstalk between microglia and surrounding cells, and the potential factors that could influence the eventual manifestation of microglia.
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Affiliation(s)
- Xiao-Guang Luo
- Department of Neurology & Institute of Neurology, Ruijin Hospital affiliated to Shanghai Jiao Tong University, Shanghai, 200025, China.
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