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Mo S, Yang C, Zheng X, Lv H, Mao S, Liu N, Yang Q, Liao B, Yang M, Lu Z, Tang L, Huang X, Jian C, Li X, Shang J. Neuroprotective Effects of AER-271 in a tMCAO Mouse Model: Modulation of Autophagy, Apoptosis, and Inflammation. Inflammation 2024:10.1007/s10753-024-02082-7. [PMID: 39117789 DOI: 10.1007/s10753-024-02082-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 06/10/2024] [Accepted: 06/12/2024] [Indexed: 08/10/2024]
Abstract
Following ischemic stroke, aquaporin 4 (AQP4) expression modifications have been associated with increased inflammation. However, the underlying mechanisms are not fully understood. This study aims to elucidate the mechanistic basis of post-cerebral ischemia-reperfusion (I/R) inflammation by employing the AQP4-specific inhibitor, AER-271. The middle cerebral artery occlusion (MCAO) model was used to induce ischemic stroke in mice. C57BL/6 mice were randomly allocated into four groups: sham operation, I/R, AER-271, and 2-(nicotinamide)-1,3,4-thiadiazole (TGN-020) treatment, with observations recorded at 1 day, 3 days, and 7 days post-tMCAO. Each group consisted of 15 mice. Procedures included histological examination through HE staining, neurological scoring, Western blot analysis, and immunofluorescence staining. AER-271 treatment yielded significant improvements in post-stroke weight recovery and neurological scores, accompanied by a reduction in cerebral infarction volume. Moreover, AER-271 exhibited a noticeable influence on autophagic and apoptotic pathways, affecting the activation of both pro-inflammatory and anti-inflammatory cytokines. Alterations in the levels of inflammatory biomarkers MCP-1, NLRP3, and caspase 1 were also detected. Finally, a comparative assessment of the effects of AER-271 and TGN-020 in mitigating apoptosis and microglial polarization in ischemic mice revealed neuroprotective effects with no significant difference in efficacy. This study provides essential insights into the neuroprotective mechanisms of AER-271 in cerebral ischemia-reperfusion injury, offering potential clinical applications in the treatment of ischemic cerebrovascular disorders.
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Affiliation(s)
- Shenglong Mo
- Department of Neurology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, 533000, Guangxi, China
- Biological Molecule Laboratory, Guangxi University Key Laboratory of High Incidence Prevention and Control Research in Western Guangxi, Baise, 53300, Guangxi, China
- Graduate School of Youjiang, Medical University for Nationalities, Baise, Guangxi, China
| | - Chengmin Yang
- Department of Neurology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, 533000, Guangxi, China
- Biological Molecule Laboratory, Guangxi University Key Laboratory of High Incidence Prevention and Control Research in Western Guangxi, Baise, 53300, Guangxi, China
| | - Xingwu Zheng
- Department of Geriatrics, Affiliated Hospital of Guilin Medical University, Guilin, Guangxi, China
| | - Hui Lv
- Modern Industrial College of Biomedicine and Great Health, Youjiang Medical University for Nationalities, Baise, Guangxi, China
| | - Sanyin Mao
- Department of Neurology, The First People's Hospital of Jiande, Hangzhou, China
| | - Ning Liu
- School of Basic Medical Sciences, Beihua University, Jilin, China
| | - Qin Yang
- Department of Neurology, BAISE PEOPLE'S HOSPITAL, Baise, Guangxi, China
| | - Bao Liao
- Department of Neurology, BAISE PEOPLE'S HOSPITAL, Baise, Guangxi, China
| | - Meiling Yang
- Graduate School of Youjiang, Medical University for Nationalities, Baise, Guangxi, China
| | - Zhicheng Lu
- Graduate School of Youjiang, Medical University for Nationalities, Baise, Guangxi, China
| | - Lina Tang
- Graduate School of Youjiang, Medical University for Nationalities, Baise, Guangxi, China
| | - Xiaorui Huang
- Department of Psychiatry and Psychology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, Guangxi, China
| | - Chongdong Jian
- Department of Neurology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, 533000, Guangxi, China.
- Biological Molecule Laboratory, Guangxi University Key Laboratory of High Incidence Prevention and Control Research in Western Guangxi, Baise, 53300, Guangxi, China.
| | - Xuebin Li
- Department of Neurology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, 533000, Guangxi, China.
- Biological Molecule Laboratory, Guangxi University Key Laboratory of High Incidence Prevention and Control Research in Western Guangxi, Baise, 53300, Guangxi, China.
| | - Jingwei Shang
- Department of Neurology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, 533000, Guangxi, China.
- Biological Molecule Laboratory, Guangxi University Key Laboratory of High Incidence Prevention and Control Research in Western Guangxi, Baise, 53300, Guangxi, China.
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Czyżewski W, Litak J, Sobstyl J, Mandat T, Torres K, Staśkiewicz G. Aquaporins: Gatekeepers of Fluid Dynamics in Traumatic Brain Injury. Int J Mol Sci 2024; 25:6553. [PMID: 38928258 PMCID: PMC11204105 DOI: 10.3390/ijms25126553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2024] [Revised: 06/10/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
Aquaporins (AQPs), particularly AQP4, play a crucial role in regulating fluid dynamics in the brain, impacting the development and resolution of edema following traumatic brain injury (TBI). This review examines the alterations in AQP expression and localization post-injury, exploring their effects on brain edema and overall injury outcomes. We discuss the underlying molecular mechanisms regulating AQP expression, highlighting potential therapeutic strategies to modulate AQP function. These insights provide a comprehensive understanding of AQPs in TBI and suggest novel approaches for improving clinical outcomes through targeted interventions.
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Affiliation(s)
- Wojciech Czyżewski
- Department of Neurosurgery, Maria Sklodowska-Curie National Research Institute of Oncology, ul. W.K. Roentgena 5, 02-781 Warsaw, Poland;
- Department of Didactics and Medical Simulation, Medical University of Lublin, 20-954 Lublin, Poland
| | - Jakub Litak
- Department of Clinical Immunology, Medical University of Lublin, 20-954 Lublin, Poland;
| | - Jan Sobstyl
- Department of Interventional Radiology and Neuroradiology, Medical University of Lublin, 20-954 Lublin, Poland;
| | - Tomasz Mandat
- Department of Neurosurgery, Maria Sklodowska-Curie National Research Institute of Oncology, ul. W.K. Roentgena 5, 02-781 Warsaw, Poland;
| | - Kamil Torres
- Department of Plastic, Reconstructive Surgery with Microsurgery, Medical University of Lublin, 20-954 Lublin, Poland;
| | - Grzegorz Staśkiewicz
- Department of Human, Clinical and Radiological Anatomy, Medical University, 20-954 Lublin, Poland;
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Pirici D, Mogoanta L, Ion DA, Kumar-Singh S. Fractal Analysis in Neurodegenerative Diseases. ADVANCES IN NEUROBIOLOGY 2024; 36:365-384. [PMID: 38468042 DOI: 10.1007/978-3-031-47606-8_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Neurodegenerative diseases are defined by progressive nervous system dysfunction and death of neurons. The abnormal conformation and assembly of proteins is suggested to be the most probable cause for many of these neurodegenerative disorders, leading to the accumulation of abnormally aggregated proteins, for example, amyloid β (Aβ) (Alzheimer's disease and vascular dementia), tau protein (Alzheimer's disease and frontotemporal lobar degeneration), α-synuclein (Parkinson's disease and Lewy body dementia), polyglutamine expansion diseases (Huntington disease), or prion proteins (Creutzfeldt-Jakob disease). An aberrant gain-of-function mechanism toward excessive intraparenchymal accumulation thus represents a common pathogenic denominator in all these proteinopathies. Moreover, depending upon the predominant brain area involvement, these different neurodegenerative diseases lead to either movement disorders or dementia syndromes, although the underlying mechanism(s) can sometimes be very similar, and on other occasions, clinically similar syndromes can have quite distinct pathologies. Non-Euclidean image analysis approaches such as fractal dimension (FD) analysis have been applied extensively in quantifying highly variable morphopathological patterns, as well as many other connected biological processes; however, their application to understand and link abnormal proteinaceous depositions to other clinical and pathological features composing these syndromes is yet to be clarified. Thus, this short review aims to present the most important applications of FD in investigating the clinical-pathological spectrum of neurodegenerative diseases.
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Affiliation(s)
- Daniel Pirici
- Department of Histology, University of Medicine and Pharmacy of Craiova, Craiova, Romania
| | - Laurentiu Mogoanta
- Department of Histology, University of Medicine and Pharmacy of Craiova, Craiova, Romania
| | - Daniela Adriana Ion
- Department of Physiopathology, University of Medicine and Pharmacy Carol Davila, Bucharest, Romania
| | - Samir Kumar-Singh
- Molecular Pathology Group, Faculty of Medicine and Health Sciences, Cell Biology & Histology and Translational Neuroscience Department, University of Antwerp, Antwerpen, Belgium
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Xin W, Pan Y, Wei W, Tatenhorst L, Graf I, Popa-Wagner A, Gerner ST, Huber S, Kilic E, Hermann DM, Bähr M, Huttner HB, Doeppner TR. Preconditioned extracellular vesicles from hypoxic microglia reduce poststroke AQP4 depolarization, disturbed cerebrospinal fluid flow, astrogliosis, and neuroinflammation. Theranostics 2023; 13:4197-4216. [PMID: 37554272 PMCID: PMC10405850 DOI: 10.7150/thno.84059] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 06/06/2023] [Indexed: 08/10/2023] Open
Abstract
Background: Stroke stimulates reactive astrogliosis, aquaporin 4 (AQP4) depolarization and neuroinflammation. Preconditioned extracellular vesicles (EVs) from microglia exposed to hypoxia, in turn, reduce poststroke brain injury. Nevertheless, the underlying mechanisms of such effects are elusive, especially with regards to inflammation, AQP4 polarization, and cerebrospinal fluid (CSF) flow. Methods: Primary microglia and astrocytes were exposed to oxygen-glucose deprivation (OGD) injury. For analyzing the role of AQP4 expression patterns under hypoxic conditions, a co-culture model of astrocytes and microglia was established. Further studies applied a stroke model, where some mice also received an intracisternal tracer infusion of rhodamine B. As such, these in vivo studies involved the analysis of AQP4 polarization, CSF flow, astrogliosis, and neuroinflammation as well as ischemia-induced brain injury. Results: Preconditioned EVs decreased periinfarct AQP4 depolarization, brain edema, astrogliosis, and inflammation in stroke mice. Likewise, EVs promoted postischemic CSF flow and cerebral blood perfusion, and neurological recovery. Under in vitro conditions, hypoxia stimulated M2 microglia polarization, whereas EVs augmented M2 microglia polarization and repressed M1 microglia polarization even further. In line with this, astrocytes displayed upregulated AQP4 clustering and proinflammatory cytokine levels when exposed to OGD, which was reversed by preconditioned EVs. Reduced AQP4 depolarization due to EVs, however, was not a consequence of unspecific inflammatory regulation, since LPS-induced inflammation in co-culture models of astrocytes and microglia did not result in altered AQP4 expression patterns in astrocytes. Conclusions: These findings show that hypoxic microglia may participate in protecting against stroke-induced brain damage by regulating poststroke inflammation, astrogliosis, AQP4 depolarization, and CSF flow due to EV release.
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Affiliation(s)
- Wenqiang Xin
- Department of Neurology, University of Göttingen Medical School, Göttingen, Germany
| | - Yongli Pan
- Department of Neurology, University of Göttingen Medical School, Göttingen, Germany
| | - Wei Wei
- Department of Neurology, University of Göttingen Medical School, Göttingen, Germany
| | - Lars Tatenhorst
- Department of Neurology, University of Göttingen Medical School, Göttingen, Germany
| | - Irina Graf
- Department of Neurology, University of Göttingen Medical School, Göttingen, Germany
| | - Aurel Popa-Wagner
- Department of Neurology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Stefan T Gerner
- Department of Neurology, University of Giessen Medical School, Giessen, Germany
| | - Sabine Huber
- Department of Neurology, University of Giessen Medical School, Giessen, Germany
| | - Ertugrul Kilic
- Department of Physiology, Istanbul Medeniyet University, Istanbul, Turkey
| | - Dirk M Hermann
- Department of Neurology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Mathias Bähr
- Department of Neurology, University of Göttingen Medical School, Göttingen, Germany
| | - Hagen B Huttner
- Department of Neurology, University of Giessen Medical School, Giessen, Germany
| | - Thorsten R Doeppner
- Department of Neurology, University of Göttingen Medical School, Göttingen, Germany
- Department of Neurology, University of Giessen Medical School, Giessen, Germany
- Department of Anatomy and Cell Biology, Medical University of Varna, Varna, Bulgaria
- Center for Mind, Brain and Behavior (CMBB), University of Marburg and Justus Liebig University Giessen, Germany
- Research Institute for Health Sciences and Technologies (SABITA), Medipol University, Istanbul, Turkey
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Forrest SL, Kim JH, Crockford DR, Huynh K, Cheong R, Knott S, Kane MA, Ittner LM, Halliday GM, Kril JJ. Distribution Patterns of Astrocyte Populations in the Human Cortex. Neurochem Res 2023; 48:1222-1232. [PMID: 35930103 PMCID: PMC10030423 DOI: 10.1007/s11064-022-03700-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 07/08/2022] [Accepted: 07/15/2022] [Indexed: 10/16/2022]
Abstract
Astrocytes are a major class of glial cell in the central nervous system that have a diverse range of types and functions thought to be based on their anatomical location, morphology and cellular properties. Recent studies highlight that astrocyte dysfunction contributes to the pathogenesis of neurological conditions. However, few studies have described the pattern, distribution and density of astrocytes in the adult human cortex. This study mapped the distribution and density of astrocytes immunolabelled with a range of cytoskeletal and membrane markers in the human frontal cortex. Distinct and overlapping astrocyte populations were determined. The frontal cortex from ten normal control cases (75 ± 9 years) was immunostained with glial fibrillary acidic protein (GFAP), aldehyde dehydrogenase-1 L1 (ALDH1L1), connexin-43 (Cx43), aquaporin-4 (AQP4), and glutamate transporter 1 (GLT-1). All markers labelled populations of astrocytes in the grey and white matter, separate cortical layers, subpial and perivascular regions. All markers were informative for labelling different cellular properties and cellular compartments of astrocytes. ALDH1L1 labelled the largest population of astrocytes, and Cx43-immunopositive astrocytes were found in all cortical layers. AQP4 and GLT-1 labelled distal astrocytic process and end-feet in the same population of astrocytes (98% of GLT-1-immunopositive astrocytes contained AQP4). In contrast, GFAP, the most widely used marker, predominantly labelled astrocytes in superficial cortical layers. This study highlights the diversity of astrocytes in the human cortex, providing a reference map of the distribution of distinct and overlapping astrocyte populations which can be used for comparative purposes in various disease, inflammatory and injury states involving astrocytes.
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Affiliation(s)
- Shelley L Forrest
- Dementia Research Centre, School of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 13A Research Park Drive, Sydney, NSW, 2109, Australia.
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia.
| | - Jordan Hanxi Kim
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Daniel R Crockford
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Katharine Huynh
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Rosie Cheong
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Samantha Knott
- Dementia Research Centre, School of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 13A Research Park Drive, Sydney, NSW, 2109, Australia
| | - Madison A Kane
- Dementia Research Centre, School of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 13A Research Park Drive, Sydney, NSW, 2109, Australia
| | - Lars M Ittner
- Dementia Research Centre, School of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 13A Research Park Drive, Sydney, NSW, 2109, Australia
| | - Glenda M Halliday
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia
- Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Jillian J Kril
- Dementia Research Centre, School of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 13A Research Park Drive, Sydney, NSW, 2109, Australia
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia
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Rotaru-Zavaleanu AD, Neacșu AI, Neacșu AD, Pirici D, Osiac E, Cătălin B, Gheonea DI. Effects of Acute Sepsis on Cellular Dynamics and Amyloid Formation in a Mouse Model of Alzheimer’s Disease. Curr Issues Mol Biol 2022; 44:3822-3834. [PMID: 36135174 PMCID: PMC9497925 DOI: 10.3390/cimb44090262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 08/19/2022] [Accepted: 08/21/2022] [Indexed: 11/18/2022] Open
Abstract
Our objective was to investigate how sepsis influences cellular dynamics and amyloid formation before and after plaque formation. As such, APP-mice were subjected to a polymicrobial abdominal infection resulting in sepsis at 2 (EarlySepsis) and 4 (LateSepsis) months of age. Behavior was tested before sepsis and at 5 months of age. We could not detect any short-term memory or exploration behavior alterations in APP-mice that were subjected to Early or LateSepsis. Immunohistochemical analysis revealed a lower area of NeuN+ and Iba1+ signal in the cortex of Late compared with EarlySepsis animals (p = 0.016 and p = 0.01), with an increased astrogliosis in LateSepsis animals compared with WT-Sepsis (p = 0.0028), EarlySepsis (p = 0.0032) and the APP-Sham animals (p = 0.048). LateSepsis animals had larger areas of amyloid compared with both EarlySepsis (p = 0.0018) and APP-Sham animals (p = 0.0024). Regardless of the analyzed markers, we were not able to detect any cellular difference at the hippocampal level between groups. We were able to detect an increased inflammatory response around hippocampal plaques in LateSepsis compared with APP-Sham animals (p = 0.0003) and a decrease of AQP4 signal far from Sma+ vessels. We were able to show experimentally that an acute sepsis event before the onset of plaque formation has a minimal effect; however, it could have a major impact after its onset.
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Affiliation(s)
- Alexandra Daniela Rotaru-Zavaleanu
- Department of Gastroenterology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
- Experimental Research Center for Normal and Pathological Aging, Department of Functional Sciences, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
| | - Alexandru Ionuț Neacșu
- Experimental Research Center for Normal and Pathological Aging, Department of Functional Sciences, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
- Department of Biophysics, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
| | - Adela-Daria Neacșu
- Experimental Research Center for Normal and Pathological Aging, Department of Functional Sciences, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
| | - Daniel Pirici
- Department of Histology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
| | - Eugen Osiac
- Experimental Research Center for Normal and Pathological Aging, Department of Functional Sciences, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
- Department of Biophysics, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
- Correspondence: (E.O.); (B.C.)
| | - Bogdan Cătălin
- Experimental Research Center for Normal and Pathological Aging, Department of Functional Sciences, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
- Department of Physiology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
- Correspondence: (E.O.); (B.C.)
| | - Dan Ionuț Gheonea
- Department of Gastroenterology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
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Szu JI, Binder DK. Mechanisms Underlying Aquaporin-4 Subcellular Mislocalization in Epilepsy. Front Cell Neurosci 2022; 16:900588. [PMID: 35734218 PMCID: PMC9207308 DOI: 10.3389/fncel.2022.900588] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
Epilepsy is a chronic brain disorder characterized by unprovoked seizures. Mechanisms underlying seizure activity have been intensely investigated. Alterations in astrocytic channels and transporters have shown to be a critical player in seizure generation and epileptogenesis. One key protein involved in such processes is the astrocyte water channel aquaporin-4 (AQP4). Studies have revealed that perivascular AQP4 redistributes away from astrocyte endfeet and toward the neuropil in both clinical and preclinical studies. This subcellular mislocalization significantly impacts neuronal hyperexcitability and understanding how AQP4 becomes dysregulated in epilepsy is beginning to emerge. In this review, we evaluate the role of AQP4 dysregulation and mislocalization in epilepsy.
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Sun C, Lin L, Yin L, Hao X, Tian J, Zhang X, Ren Y, Li C, Yang Y. Acutely Inhibiting AQP4 With TGN-020 Improves Functional Outcome by Attenuating Edema and Peri-Infarct Astrogliosis After Cerebral Ischemia. Front Immunol 2022; 13:870029. [PMID: 35592320 PMCID: PMC9110854 DOI: 10.3389/fimmu.2022.870029] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Accepted: 04/11/2022] [Indexed: 01/05/2023] Open
Abstract
Background Ischemic stroke is one of the leading causes of human death and disability. Brain edema and peri-infarct astrocyte reactivity are crucial pathological changes, both involving aquaporin-4 (AQP4). Studies revealed that acute inhibition of AQP4 after stroke diminishes brain edema, however, its effect on peri-infarct astrocyte reactivity and the subacute outcome is unclear. And if diffusion-weighted imaging (DWI) could reflect the AQP4 expression patterns is uncertain. Methods Rats were subjected to middle cerebral artery occlusion (MCAO) and allocated randomly to TGN 020-treated and control groups. One day after stroke, brain swelling and lesion volumes of the rats were checked using T2-weighted imaging (T2-WI). Fourteen days after stroke, the rats successively underwent neurological examination, T2-WI and DWI with standard b-values and ultra-high b-values, apparent diffusion coefficient (ADC) was calculated correspondingly. Finally, the rats’ brains were acquired and used for glial fibrillary acidic protein (GFAP) and AQP4 immunoreactive analysis. Results At 1 day after stroke, the TGN-020-treated animals exhibited reduced brain swelling and lesion volumes compared with those in the control group. At 14 days after stroke, the TGN-020-treated animals showed fewer neurological function deficits and smaller lesion volumes. In the peri-infarct region, the control group showed evident astrogliosis and AQP4 depolarization, which were reduced significantly in the TGN-020 group. In addition, the ultra-high b-values of ADC (ADCuh) in the peri-infarct region of the TGN-020 group was higher than that of the control group. Furthermore, correlation analysis revealed that peri-infarct AQP4 polarization correlated negatively with astrogliosis extent, and ADCuh correlated positively with AQP4 polarization. Conclusion We found that acutely inhibiting AQP4 using TGN-020 promoted neurological recovery by diminishing brain edema at the early stage and attenuating peri-infarct astrogliosis and AQP4 depolarization at the subacute stage after stroke. Moreover, ADCuh could reflect the AQP4 polarization.
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Affiliation(s)
- Chengfeng Sun
- Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China
| | - Luyi Lin
- Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China
| | - Lekang Yin
- Department of Radiology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xiaozhu Hao
- Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jiaqi Tian
- Department of Radiology, Renji Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaoxue Zhang
- Department of Radiotherapy, Shanghai Eastern Hepatobiliary Surgery Hospital, Shanghai, China
| | - Yan Ren
- Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chanchan Li
- Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China
| | - Yanmei Yang
- Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China
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Inhibition of Aquaporin 4 Decreases Amyloid Aβ40 Drainage Around Cerebral Vessels. Mol Neurobiol 2020; 57:4720-4734. [PMID: 32783141 PMCID: PMC7515968 DOI: 10.1007/s12035-020-02044-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 07/24/2020] [Indexed: 01/17/2023]
Abstract
Aquaporin-4 (AQP4) is located mainly in the astrocytic end-feet around cerebral blood vessels and regulates ion and water homeostasis in the brain. While deletion of AQP4 is shown to reduce amyloid-β (Aβ) clearance and exacerbate Aβ peptide accumulation in plaques and vessels of Alzheimer's disease mouse models, the mechanism and clearing pathways involved are debated. Here, we investigated how inhibiting the function of AQP4 in healthy male C57BL/6 J mice impacts clearance of Aβ40, the more soluble Aβ isoform. Using two-photon in vivo imaging and visualizing vessels with Sulfurodamine 101 (SR101), we first showed that Aβ40 injected as a ≤ 0.5-μl volume in the cerebral cortex diffused rapidly in parenchyma and accumulated around blood vessels. In animals treated with the AQP4 inhibitor TGN-020, the perivascular Aβ40 accumulation was significantly (P < 0.001) intensified by involving four times more vessels, thus suggesting a generalized clearance defect associated with vessels. Increasing the injecting volume to ≥ 0.5 ≤ 1 μl decreased the difference of Aβ40-positive vessels observed in non-treated and AQP4 inhibitor-treated animals, although the difference was still significant (P = 0.001), suggesting that larger injection volumes could overwhelm intramural vascular clearance mechanisms. While both small and large vessels accumulated Aβ40, for the ≤ 0.5-μl volume group, the average diameter of the Aβ40-positive vessels tended to be larger in control animals compared with TGN-020-treated animals, although the difference was non-significant (P = 0.066). Using histopathology and ultrastructural microscopy, no vascular structural change was observed after a single massive dose of TGN-020. These data suggest that AQP4 deficiency is directly involved in impaired Aβ brain clearance via the peri-/para-vascular routes, and AQP4-mediated vascular clearance might counteract blood-brain barrier abnormalities and age-related vascular amyloidopathy.
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Guo H, Yin A, Ma Y, Fan Z, Tao L, Tang W, Ma Y, Hou W, Cai G, Zhuo L, Zhang J, Li Y, Xiong L. Astroglial N-myc downstream-regulated gene 2 protects the brain from cerebral edema induced by stroke. Glia 2020; 69:281-295. [PMID: 32652708 PMCID: PMC7754347 DOI: 10.1002/glia.23888] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 06/16/2020] [Accepted: 06/26/2020] [Indexed: 01/14/2023]
Abstract
Brain edema is a grave complication of brain ischemia and is the main cause of herniation and death. Although astrocytic swelling is the main contributor to cytotoxic edema, the molecular mechanism involved in this process remains elusive. N‐myc downstream‐regulated gene 2 (NDRG2), a well‐studied tumor suppressor gene, is mainly expressed in astrocytes in mammalian brains. Here, we found that NDRG2 deficiency leads to worsened cerebral edema, imbalanced Na+ transfer, and astrocyte swelling after ischemia. We also found that NDRG2 deletion in astrocytes dramatically changed the expression and distribution of aquaporin‐4 and Na+‐K+‐ATPase β1, which are strongly associated with cell polarity, in the ischemic brain. Brain edema and astrocyte swelling were significantly alleviated by rescuing the expression of astrocytic Na+‐K+‐ATPase β1 in NDRG2‐knockout mouse brains. In addition, the upregulation of astrocytic NDRG2 by lentiviral constructs notably attenuated brain edema, astrocytic swelling, and blood–brain barrier destruction. Our results indicate a particular role of NDRG2 in maintaining astrocytic polarization to facilitate Na+ and water transfer balance and to protect the brain from ischemic edema. These findings provide insight into NDRG2 as a therapeutic target in cerebral edema.
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Affiliation(s)
- Hang Guo
- Department of Anesthesiology, The Seventh Medical Center of Chinese PLA General Hospital, Beijing, China.,Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Air Force Military Medical University, Xi'an, China
| | - Anqi Yin
- Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Air Force Military Medical University, Xi'an, China.,Department of Anesthesiology, Jinling Hospital, Nanjing, China
| | - Yulong Ma
- Anesthesia and Operation Center, The First Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Ze Fan
- Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Air Force Military Medical University, Xi'an, China
| | - Liang Tao
- Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Air Force Military Medical University, Xi'an, China
| | - Wenhong Tang
- Department of Anesthesiology, The 960th Hospital of PLA, Jinan, China
| | - Yaqun Ma
- Department of Anesthesiology, The Seventh Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Wugang Hou
- Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Air Force Military Medical University, Xi'an, China
| | - Guohong Cai
- Institute of Neuroscience, The Air Force Military Medical University, Xi'an, China
| | - Lixia Zhuo
- Department of Anesthesiology & Center for Brain Science, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Jian Zhang
- Department of Biochemistry and Molecular Biology, The Air Force Military Medical University, Xi'an, China
| | - Yan Li
- Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Air Force Military Medical University, Xi'an, China.,Department of Anesthesiology & Center for Brain Science, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Lize Xiong
- Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Air Force Military Medical University, Xi'an, China.,Department of Anesthesiology & Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, Tongji University School of Medicine, Shanghai, China
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11
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Hindeya Gebreyesus H, Gebrehiwot Gebremichael T. The Potential Role of Astrocytes in Parkinson's Disease (PD). Med Sci (Basel) 2020; 8:E7. [PMID: 32012713 PMCID: PMC7151567 DOI: 10.3390/medsci8010007] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 08/08/2019] [Accepted: 08/09/2019] [Indexed: 12/11/2022] Open
Abstract
Astrocytes are multi-functional cells, now recognized as critical participants in many brain functions. They play a critical physiological role in the clearance of neurotransmitters, such as glutamate and gamma-aminobutyric acid (GABA), and in the regulation of K+ from the space of synaptic clefts. Astrocytes also express the excitatory amino acid transporters (EAATs) and aquaporin-4 (AQP4) water channel, which are involved in both physiological functions and neurodegenerative diseases (ND). Some of the ND are the Alzheimer's (AD), Huntington's (HD), Parkinson's diseases (PD), Cerebral edema, amyotrophic lateral sclerosis (ALS), and epilepsy pathological conditions in specific regions of the CNS. Parkinson's disease is the second most common age-related neurodegenerative disorder, characterized by degeneration of dopaminergic neurons of the substantia nigra pars compacta (SNpc). These project to the striatum, forming an important pathway within the basal ganglia. Mostly, PD has no clear etiology, and the mechanism of dopaminergic (DA) neuron loss is not well illustrated. The results of various studies suggest that astrocytes are involved in the pathophysiology of PD. Evidence has shown that the down-regulation of EAAT-2/GLT-1 and AQP4 expression is associated with PD pathogenesis. However, controversial results were reported in different experimental studies about the expression and function of EAAT-2/GLT-1 and AQP4, as well as their colocalization in different brain regions, and their involvement in PD development. Therefore, under neurological disorders, Parkinson's disease is related to the genetic and phenotypic change of astrocytes' biology. In this review, the authors summarized recent their research findings, which revealed the involvement of EAAT-2/GLT-1 and AQP4 expression, the physical interaction between EAAT-2/GLT-1 and AQP4 in astrocyte function, and their potential role in the development of PD in SNpc and Subthalamic nucleus (STN) of the basal ganglia nuclei.
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Affiliation(s)
- Hiluf Hindeya Gebreyesus
- School of Medicine, Biomedical Sciences, College of Health Sciences, Mekelle University, P.O. Box: 1871 Mekelle, Tigray, Ethiopia
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12
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Zhou J, Tao K, Guo K, Wu L, Zhang Z, Feng D, Gao G, Qin H. Suppression of NDRG2 alleviates brain injury after intracerebral hemorrhage through mitigating astrocyte-drived glutamate neurotoxicity via NF-κB/GLT1 signaling. Brain Res 2019; 1729:146600. [PMID: 31843625 DOI: 10.1016/j.brainres.2019.146600] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 12/07/2019] [Accepted: 12/11/2019] [Indexed: 02/08/2023]
Abstract
N-myc downstream-regulated gene 2 (NDRG2), a newly identified astrocytic stress response gene, is involved in the regulation of astrocytic morphology and function, and has been indicated to be a potential therapeutic target for some central nervous system (CNS) diseases. However, the role of NDRG2 in intracerebral hemorrhage (ICH) remains unknown. Here, we reported that NDRG2 suppression exerted neuroprotection effect against hemorrhagic brain injury in ICH mice and in oxyhemoglobin (OxyHb)-treated cells. Ndrg2 knockout (Ndrg2-/-) mice exhibited reduced hematoma volume and neuronal apoptosis in perihematoma although Ndrg2 deficiency showed little effect on the initial hematoma volume after ICH induction by collagenase injection. Moreover, contrary to the increase in NDRG2 expression after ICH, the expression of glutamate transporter 1 (GLT1) in astrocytes was dramatically decreased in WT (Ndrg2+/+) mice, while which could be more maintained in Ndrg2 knockout mice following ICH. Furthermore, in terms of the mechanism of epigenetic regulation of GLT1 by NDRG2, the results showed that NDRG2 directly interacted with NF-κB, and inhibited the nuclear import and DNA binding activity of the NF-κB p65 subunit after OxyHb treatment in primary astrocytes, decreasing GLT1 transcription and impairing glutamate uptake. Overall, our findings indicate that NDRG2 plays a key role in the pathology of ICH by regulating astrocytic GLT1 expression; thus suppressing NDRG2 may be a potential therapeutic target for ICH.
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Affiliation(s)
- Jiahua Zhou
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, PR China
| | - Kai Tao
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, PR China
| | - Kang Guo
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, PR China
| | - Lin Wu
- Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, PR China
| | - Zhiguo Zhang
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, PR China
| | - Dayun Feng
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, PR China
| | - Guodong Gao
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, PR China.
| | - Huaizhou Qin
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, PR China.
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13
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Stamatovic SM, Phillips CM, Martinez-Revollar G, Keep RF, Andjelkovic AV. Involvement of Epigenetic Mechanisms and Non-coding RNAs in Blood-Brain Barrier and Neurovascular Unit Injury and Recovery After Stroke. Front Neurosci 2019; 13:864. [PMID: 31543756 PMCID: PMC6732937 DOI: 10.3389/fnins.2019.00864] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/31/2019] [Indexed: 12/13/2022] Open
Abstract
Cessation of blood flow leads to a complex cascade of pathophysiological events at the blood-vascular-parenchymal interface which evolves over time and space, and results in damage to neural cells and edema formation. Cerebral ischemic injury evokes a profound and deleterious upregulation in inflammation and triggers multiple cell death pathways, but it also induces a series of the events associated with regenerative responses, including vascular remodeling, angiogenesis, and neurogenesis. Emerging evidence suggests that epigenetic reprograming could play a pivotal role in ongoing post-stroke neurovascular unit (NVU) changes and recovery. This review summarizes current knowledge about post-stroke recovery processes at the NVU, as well as epigenetic mechanisms and modifiers (e.g., DNA methylation, histone modifying enzymes and microRNAs) associated with stroke injury, and NVU repair. It also discusses novel drug targets and therapeutic strategies for enhancing post-stroke recovery.
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Affiliation(s)
- Svetlana M. Stamatovic
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Chelsea M. Phillips
- Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI, United States
| | | | - Richard F. Keep
- Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI, United States
- Department of Molecular Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Anuska V. Andjelkovic
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, United States
- Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI, United States
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14
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Distribution of Aquaporins 1 and 4 in the Central Nervous System. CURRENT HEALTH SCIENCES JOURNAL 2019; 45:218-226. [PMID: 31624651 PMCID: PMC6778305 DOI: 10.12865/chsj.45.02.14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 04/21/2019] [Indexed: 01/05/2023]
Abstract
The aquaporins (AQP), a protein family, were first discovered in the early 1990s. The primary role of aquaporins is to facilitate water transport across multiple cell types. In the spinal cord and brain responsible for most of the water diffusion are AQP4 and AQP1. In this paper, we describe the structure, localization and role of this water channel family, especially AQP4 and AQP1. AQP4 is involved in various pathologies such as: stroke, brain tumors, Neuromyelitis optica (NMO), Alzheimer’s Disease (AD), traumatic brain injury, Parkinson’s Disease, hydrocephalus, schizophrenia, epilepsy, major depressive disorder, autism. Brain edema is the most important acute complication of the hypoxic-ischemic and it has no pathogenic treatment. Imaging and histopathology studies have shown that inhibition of AQP4 reduces brain edema.
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15
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Hoshi A, Tsunoda A, Yamamoto T, Tada M, Kakita A, Ugawa Y. Altered expression of glutamate transporter-1 and water channel protein aquaporin-4 in human temporal cortex with Alzheimer's disease. Neuropathol Appl Neurobiol 2018; 44:628-638. [PMID: 29405337 DOI: 10.1111/nan.12475] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 01/11/2018] [Indexed: 12/13/2022]
Abstract
AIMS Glutamate neurotoxicity plays an important role in the pathogenesis of various neurodegenerative disorders. Many studies have demonstrated that glutamate transporter-1 (GLT-1), the dominant astrocytic glutamate transporter, is significantly reduced in the cerebral cortex of patients with Alzheimer's disease (AD), suggesting that glutamate-mediated excitotoxicity might contribute to the pathogenesis of AD. In a previous study, we have demonstrated marked alterations in the expression of the astrocytic water channel protein aquaporin-4 (AQP4) in relation to amyloid β deposition in human AD brains. As a functional complex, GLT-1 and AQP4 in astrocytes may play a neuroprotective role in the progression of AD pathology. However, few studies have examined the correlation between the expression of GLT-1 and that of AQP4 in human AD brain. METHODS Here, using immunohistochemistry with antibodies against GLT-1 and AQP4, we studied the expression levels and distribution patterns of GLT-1 in areas showing various patterns of AQP4 expression in autopsied temporal lobes from eight patients with AD and five controls without neurological disorders. RESULTS GLT-1 staining in the control group was present throughout the neocortex as uniform neuropil staining with co-localized AQP4. The AD group showed a significant reduction in GLT-1 expression, whereas cortical AQP4 immunoreactivity was more intense in the AD group than in the control group. There were two different patterns of GLT-1 and AQP4 expression in the AD group: (i) uneven GLT-1 expression in the neuropil where diffuse but intense AQP4 expression was evident, and (ii) senile plaque-like co-expression of GLT-1 and AQP4. CONCLUSIONS These findings suggest disruption of glutamate/water homoeostasis in the AD brain.
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Affiliation(s)
- A Hoshi
- Department of Neurology, Fukushima Medical University, Fukushima, Japan.,IMS Shin Katsushika Royal Clinic, Tokyo, Japan
| | - A Tsunoda
- Department of Neurology, Fukushima Medical University, Fukushima, Japan
| | - T Yamamoto
- Department of Neurology, Fukushima Medical University, Fukushima, Japan
| | - M Tada
- Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
| | - A Kakita
- Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
| | - Y Ugawa
- Department of Neurology, Fukushima Medical University, Fukushima, Japan.,Fukushima Global Medical Science Center, Advanced Clinical Research Center, Fukushima Medical University, Fukushima, Japan
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16
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Inhibition of Aquaporin-4 Improves the Outcome of Ischaemic Stroke and Modulates Brain Paravascular Drainage Pathways. Int J Mol Sci 2017; 19:ijms19010046. [PMID: 29295526 PMCID: PMC5795996 DOI: 10.3390/ijms19010046] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 12/18/2017] [Accepted: 12/20/2017] [Indexed: 01/09/2023] Open
Abstract
Aquaporin-4 (AQP4) is the most abundant water channel in the brain, and its inhibition before inducing focal ischemia, using the AQP4 inhibitor TGN-020, has been showed to reduce oedema in imaging studies. Here, we aimed to evaluate, for the first time, the histopathological effects of a single dose of TGN-020 administered after the occlusion of the medial cerebral artery (MCAO). On a rat model of non-reperfusion ischemia, we have assessed vascular densities, albumin extravasation, gliosis, and apoptosis at 3 and 7 days after MCAO. TGN-020 significantly reduced oedema, glial scar, albumin effusion, and apoptosis, at both 3 and 7 days after MCAO. The area of GFAP-positive gliotic rim decreased, and 3D fractal analysis of astrocytic processes revealed a less complex architecture, possibly indicating water accumulating in the cytoplasm. Evaluation of the blood vessels revealed thicker basement membranes colocalizing with exudated albumin in the treated animals, suggesting that inhibition of AQP4 blocks fluid flow towards the parenchyma in the paravascular drainage pathways of the interstitial fluid. These findings suggest that a single dose of an AQP4 inhibitor can reduce brain oedema, even if administered after the onset of ischemia, and AQP4 agonists/antagonists might be effective modulators of the paravascular drainage flow.
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17
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Hubbard JA, Binder DK. Unaltered Glutamate Transporter-1 Protein Levels in Aquaporin-4 Knockout Mice. ASN Neuro 2017; 9:1759091416687846. [PMID: 28078912 PMCID: PMC5315234 DOI: 10.1177/1759091416687846] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Maintenance of glutamate and water homeostasis in the brain is crucial to healthy brain activity. Astrocytic glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4) are the main regulators of extracellular glutamate and osmolarity, respectively. Several studies have reported colocalization of GLT1 and AQP4, but the existence of a physical interaction between the two has not been well studied. Therefore, we used coimmunoprecipitation to determine whether a strong interaction exists between these two important molecules in mice on both a CD1 and C57BL/6 background. Furthermore, we used Western blot and immunohistochemistry to examine GLT1 levels in AQP4 knockout (AQP4−/−) mice. An AQP4-GLT1 precipitate was not detected, suggesting the lack of a strong physical interaction between AQP4 and GLT1. In addition, GLT1 protein levels remained unaltered in tissue from CD1 and C57BL/6 AQP4−/− mice. Finally, immunohistochemical analysis revealed that AQP4 and GLT1 do colocalize, but only in a region-specific manner. Taken together, these findings suggest that AQP4 and GLT1 do not have a strong physical interaction between them and are, instead, differentially regulated.
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Affiliation(s)
- Jacqueline A Hubbard
- 1 Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, University of California, Riverside, CA, USA
| | - Devin K Binder
- 1 Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, University of California, Riverside, CA, USA
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18
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Dai J, Lin W, Zheng M, Liu Q, He B, Luo C, Lu X, Pei Z, Su H, Yao X. Alterations in AQP4 expression and polarization in the course of motor neuron degeneration in SOD1G93A mice. Mol Med Rep 2017. [PMID: 28627708 PMCID: PMC5562093 DOI: 10.3892/mmr.2017.6786] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by selective degeneration of upper and lower motor neurons. The disease progression is associated with the astrocytic environment. Aquaporin-4 (AQP4) water channels are the most abundant AQPs expressed in astrocytes, exerting important influences on central nervous system homeostasis. The present study aimed to characterize the alterations in AQP4 expression and localization in superoxide dismutase 1 (SOD1) G93A transgenic mice. SOD1G93A mice were sacrificed during the presymptomatic, disease onset and end stages and immunostaining was performed on spinal cord sections to investigate neuronal loss, glial activation and AQP4 expression in the spinal cord. It was observed that global AQP4 expression increased in the spinal cord of SOD1G93A mice as the disease progressed. However, AQP4 polarization decreased as the disease progressed, and AQP4 polarized localization at the endfeet of astrocytes was decreased in the spinal ventral horn of SOD1G93A mice at the disease onset and end stages. Meanwhile, motor neuron degeneration and decreased glutamate transporter 1 expression in astrocytes in SOD1G93A mice were observed as the disease progressed. The results of the present study demonstrated that AQP4 depolarization is a widespread pathological condition and may contribute to motor neuron degeneration in ALS.
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Affiliation(s)
- Jiaying Dai
- Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Weihao Lin
- Department of Breast and Thyroid Surgery, The First Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Minying Zheng
- Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Qiang Liu
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR 999078, P.R. China
| | - Baixuan He
- Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Chuanming Luo
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR 999078, P.R. China
| | - Xilin Lu
- Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Zhong Pei
- Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Huanxing Su
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR 999078, P.R. China
| | - Xiaoli Yao
- Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
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19
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Shi Z, Zhang W, Lu Y, Lu Y, Xu L, Fang Q, Wu M, Jia M, Wang Y, Dong L, Yan X, Yang S, Yuan F. Aquaporin 4-Mediated Glutamate-Induced Astrocyte Swelling Is Partially Mediated through Metabotropic Glutamate Receptor 5 Activation. Front Cell Neurosci 2017; 11:116. [PMID: 28503134 PMCID: PMC5408017 DOI: 10.3389/fncel.2017.00116] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 04/07/2017] [Indexed: 12/17/2022] Open
Abstract
Astrocytes are one of the most abundant cell types in the mammalian central nervous system (CNS), and astrocyte swelling is the primary event associated with brain edema. Glutamate, the principal excitatory amino acid neurotransmitter in the CNS, is released at high levels after brain injury including cerebral ischemia. This leads to astrocyte swelling, which we previously demonstrated is related to metabotropic glutamate receptor (mGluR) activation. Aquaporin 4 (AQP4), the predominant water channel in the brain, is expressed in astrocyte endfeet and plays an important role in brain edema following ischemia. Studies recently showed that mGluR5 is also expressed on astrocytes. Therefore, it is worth investigating whether AQP4 mediates the glutamate-induced swelling of astrocytes via mGluR5. In the present study, we found that 1 mM glutamate induced astrocyte swelling, quantified by the cell perimeter, but it had no effect on astrocyte viability measured by the cell counting kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays. Quantitative reverse transcription polymerase chain reaction analyses revealed that AQP4, among AQP1, 4, 5, 9 and 11, was the main molecular expressed in cultured astrocytes. Glutamate-induced cell swelling was accompanied by a concentration-dependent change in AQP4 expression. Furthermore, RNAi technology revealed that AQP4 gene silencing inhibited glutamate-induced astrocyte swelling. Moreover, we found that mGluR5 expression was greatest among the mGluRs in cultured astrocytes and was co-expressed with AQP4. Activation of mGluR5 in cultured astrocytes using (S)-3,5-dihydroxyphenylglycine (DHPG), an mGluR5 agonist, mimicked the effect of glutamate. This effect was abolished by co-incubation with the mGluR5 antagonist fenobam but was not influenced by DL-threo-β-benzyloxyaspartic acid (DL-TBOA), a glutamate transporter inhibitor. Finally, experiments in a rat model of transient middle cerebral artery occlusion (tMCAO) revealed that co-expression of mGluR5 and AQP4 was increased in astrocyte endfeet around capillaries in the penumbra, and this was accompanied by brain edema. Collectively, these results suggest that glutamate induces cell swelling and alters AQP4 expression in astrocytes via mGluR5 activation, which may provide a novel approach for the treatment of edema following brain injury.
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Affiliation(s)
- Zhongfang Shi
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Wei Zhang
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Yang Lu
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Yi Lu
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Lixin Xu
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Qing Fang
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Min Wu
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Mei Jia
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Yujiao Wang
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Liping Dong
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Xu Yan
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
| | - Shaohua Yang
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China.,Department of Pharmacology and Neuroscience, University of North Texas Health Science CenterFort Worth, TX, USA
| | - Fang Yuan
- Department of Pathophysiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical UniversityBeijing, China.,China National Clinical Research Center for Neurological DiseasesBeijing, China.,Beijing Key Laboratory of Central Nervous System InjuryBeijing, China.,Center of Stroke, Beijing Institute for Brain DisordersBeijing, China.,Beijing Key Laboratory of Translational Medicine for Cerebrovascular DiseaseBeijing, China
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20
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Hubbard JA, Szu JI, Binder DK. The role of aquaporin-4 in synaptic plasticity, memory and disease. Brain Res Bull 2017; 136:118-129. [PMID: 28274814 DOI: 10.1016/j.brainresbull.2017.02.011] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 12/25/2022]
Abstract
Since the discovery of aquaporins, it has become clear that the various mammalian aquaporins play critical physiological roles in water and ion balance in multiple tissues. Aquaporin-4 (AQP4), the principal aquaporin expressed in the central nervous system (CNS, brain and spinal cord), has been shown to mediate CNS water homeostasis. In this review, we summarize new and exciting studies indicating that AQP4 also plays critical and unanticipated roles in synaptic plasticity and memory formation. Next, we consider the role of AQP4 in Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), multiple sclerosis (MS), neuromyelitis optica (NMO), epilepsy, traumatic brain injury (TBI), and stroke. Each of these conditions involves changes in AQP4 expression and/or distribution that may be functionally relevant to disease physiology. Insofar as AQP4 is exclusively expressed on astrocytes, these data provide new evidence of "astrocytopathy" in the etiology of diverse neurological diseases.
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Affiliation(s)
- Jacqueline A Hubbard
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, United States
| | - Jenny I Szu
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, United States
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, United States.
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21
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Boulay AC, Cisternino S, Cohen-Salmon M. Immunoregulation at the gliovascular unit in the healthy brain: A focus on Connexin 43. Brain Behav Immun 2016; 56:1-9. [PMID: 26674996 DOI: 10.1016/j.bbi.2015.11.017] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 10/26/2015] [Accepted: 11/28/2015] [Indexed: 01/18/2023] Open
Abstract
In the brain, immune cell infiltration is normally kept at a very low level and a unique microenvironment strictly restricts immune reactions and inflammation. Even in such quiescent environment, a constant immune surveillance is at work allowing the brain to rapidly react to threats. To date, knowledge about the factors regulating the brain-immune system interrelationship in healthy conditions remains elusive. Interestingly, astrocytes, the most abundant glial cells in the brain, may participate in many aspects of this unique homeostasis, in particular due to their close interaction with the brain vascular system and expression of a specific molecular repertoire. Indeed, astrocytes maintain the blood-brain barrier (BBB) integrity, interact with immune cells, and participate in the regulation of intracerebral liquid movements. We recently showed that Connexin 43 (Cx43), a gap junction protein highly expressed by astrocytes at the BBB interface, is an immunoregulating factor. The absence of astroglial Cx43 leads to a transient endothelial activation, a continuous immune recruitment as well as the development of a specific humoral autoimmune response against the von Willebrand factor A domain-containing protein 5a, an extracellular matrix protein expressed by astrocytes. In this review, we propose to gather current knowledge on how astrocytes may influence the immune system in the healthy brain, focusing on their roles at the gliovascular interface. We will also consider pathological situations involving astrocyte-specific autoimmunities. Finally, we will discuss the specific role of astroglial Cx43 and the physiological consequences of immune regulations taking place on inflammation, cognition and behavior in the absence of Cx43.
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Affiliation(s)
- Anne-Cécile Boulay
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB), Centre National de la Recherche Scientifique CNRS, Unité Mixte de Recherche 7241, Institut National de la Santé et de la Recherche Médicale INSERM, U1050, Neuroglial Interactions in Cerebral Physiopathology, 75231 Paris Cedex 05, France; University Pierre et Marie Curie, ED, N°158, 75005 Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, 75005 Paris, France
| | - Salvatore Cisternino
- Variabilité de réponse aux psychotropes, INSERM, U1144, Paris F-75006, France; Université Paris Descartes, Faculté de Pharmacie, UMR-S 1144, 75006 Paris, France; Université Paris Diderot, UMR-S 1144, 75013 Paris, France
| | - Martine Cohen-Salmon
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB), Centre National de la Recherche Scientifique CNRS, Unité Mixte de Recherche 7241, Institut National de la Santé et de la Recherche Médicale INSERM, U1050, Neuroglial Interactions in Cerebral Physiopathology, 75231 Paris Cedex 05, France; University Pierre et Marie Curie, ED, N°158, 75005 Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, 75005 Paris, France.
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22
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Wang YF, Parpura V. Central Role of Maladapted Astrocytic Plasticity in Ischemic Brain Edema Formation. Front Cell Neurosci 2016; 10:129. [PMID: 27242440 PMCID: PMC4865516 DOI: 10.3389/fncel.2016.00129] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 04/29/2016] [Indexed: 12/24/2022] Open
Abstract
Brain edema formation and the ensuing brain damages are the major cause of high mortality and long term disability following the occurrence of ischemic stroke. In this process, oxygen and glucose deprivation and the resulting reperfusion injury play primary roles. In response to the ischemic insult, the neurovascular unit experiences both intracellular and extracellular edemas, associated with maladapted astrocytic plasticity. The astrocytic plasticity includes both morphological and functional plasticity. The former involves a reactive gliosis and the subsequent glial retraction. It relates to the capacity of astrocytes to buffer changes in extracellular chemical levels, particularly K+ and glutamate, as well as the integrity of the blood-brain barrier (BBB). The latter involves the expression and activity of a series of ion and water transport proteins. These molecules are grouped together around glial fibrillary acidic protein (GFAP) and water channel protein aquaporin 4 (AQP4) to form functional networks, regulate hydromineral balance across cell membranes and maintain the integrity of the BBB. Intense ischemic challenges can disrupt these capacities of astrocytes and result in their maladaptation. The maladapted astrocytic plasticity in ischemic stroke cannot only disrupt the hydromineral homeostasis across astrocyte membrane and the BBB, but also leads to disorders of the whole neurovascular unit. This review focuses on how the maladapted astrocytic plasticity in ischemic stroke plays the central role in the brain edema formation.
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Affiliation(s)
- Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University Harbin, China
| | - Vladimir Parpura
- Department of Neurobiology, University of Alabama at Birmingham Birmingham, AL, USA
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Jia SW, Liu XY, Wang SC, Wang YF. Vasopressin Hypersecretion-Associated Brain Edema Formation in Ischemic Stroke: Underlying Mechanisms. J Stroke Cerebrovasc Dis 2016; 25:1289-300. [PMID: 27068863 DOI: 10.1016/j.jstrokecerebrovasdis.2016.02.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 01/21/2016] [Accepted: 02/01/2016] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Brain edema formation is a major cause of brain damages and the high mortality of ischemic stroke. The aim of this review is to explore the relationship between ischemic brain edema formation and vasopressin (VP) hypersecretion in addition to the oxygen and glucose deprivation and the ensuing reperfusion injury. METHODS Pertinent studies involving ischemic stroke, brain edema formation, astrocytes, and VP were identified by a search of the PubMed and the Web of Science databases in January 2016. Based on clinical findings and reports of animal experiments using ischemic stroke models, this systematic review reanalyzes the implication of individual reports in the edema formation and then establishes the inherent links among them. RESULTS This systematic review reveals that cytotoxic edema and vasogenic brain edema in classical view are mainly under the influence of a continuous malfunction of astrocytic plasticity. Adaptive VP secretion can modulate membrane ion transport, water permeability, and blood-brain barrier integrity, which are largely via changing astrocytic plasticity. Maladaptive VP hypersecretion leads to disruptions of ion and water balance across cell membranes as well as the integrity of the blood-brain barrier. This review highlights our current understandings of the cellular mechanisms underlying ischemic brain edema formation and its association with VP hypersecretion. CONCLUSIONS VP hypersecretion promotes brain edema formation in ischemic stroke by disrupting hydromineral balance in the neurovascular unit; suppressing VP hypersecretion has the potential to alleviate ischemic brain edema.
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Affiliation(s)
- Shu-Wei Jia
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Xiao-Yu Liu
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Stephani C Wang
- Department of Surgery, Albany Medical Center, Albany, New York
| | - Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China.
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The Neuroprotective Effect of the Association of Aquaporin-4/Glutamate Transporter-1 against Alzheimer's Disease. Neural Plast 2016; 2016:4626593. [PMID: 27057365 PMCID: PMC4736756 DOI: 10.1155/2016/4626593] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Revised: 11/21/2015] [Accepted: 11/30/2015] [Indexed: 11/21/2022] Open
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by memory loss and cognitive dysfunction. Aquaporin-4 (AQP4), which is primarily expressed in astrocytes, is the major water channel expressed in the central nervous system (CNS). This protein plays an important role in water and ion homeostasis in the normal brain and in various brain pathological conditions. Emerging evidence suggests that AQP4 deficiency impairs learning and memory and that this may be related to the expression of glutamate transporter-1 (GLT-1). Moreover, the colocalization of AQP4 and GLT-1 has long been studied in brain tissue; however, far less is known about the potential influence that the AQP4/GLT-1 complex may have on AD. Research on the functional interaction of AQP4 and GLT-1 has been demonstrated to be of great significance in the study of AD. Here, we review the interaction of AQP4 and GLT-1 in astrocytes, which might play a pivotal role in the regulation of distinct cellular responses that involve neuroprotection against AD. The association of AQP4 and GLT-1 could greatly supplement previous research regarding neuroprotection against AD.
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The Potential Roles of Aquaporin 4 in Alzheimer's Disease. Mol Neurobiol 2015; 53:5300-9. [PMID: 26433375 DOI: 10.1007/s12035-015-9446-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 09/16/2015] [Indexed: 01/28/2023]
Abstract
Aquaporin 4 (AQP4) is the major water channel expressed in the central nervous system (CNS), and it is primarily expressed in astrocytes. It has been studied in various brain pathological conditions. However, the potential for AQP4 to influence Alzheimer's disease (AD) is still unclear. Research regarding AQP4 functions related to AD can be traced back several years and has gradually progressed toward a better understanding of the potential mechanisms. Currently, it has been suggested that AQP4 influences synaptic plasticity, and AQP4 deficiency may impair learning and memory, in part, through glutamate transporter-1 (GLT-1). AQP4 may mediate the clearance of amyloid beta peptides (Aβ). In addition, AQP4 may influence potassium (K(+)) and calcium (Ca(2+)) ion transport, which could play decisive roles in the pathogenesis of AD. Furthermore, AQP4 knockout is involved in neuroinflammation and interferes with AD. To date, no specific therapeutic agents have been developed to inhibit or enhance AQP4. However, experimental results strongly emphasize the importance of this topic for future investigations.
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Stokum JA, Mehta RI, Ivanova S, Yu E, Gerzanich V, Simard JM. Heterogeneity of aquaporin-4 localization and expression after focal cerebral ischemia underlies differences in white versus grey matter swelling. Acta Neuropathol Commun 2015; 3:61. [PMID: 26419740 PMCID: PMC4588314 DOI: 10.1186/s40478-015-0239-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 09/17/2015] [Indexed: 12/21/2022] Open
Abstract
INTRODUCTION Ischemic stroke, a major cause of mortality, is frequently accompanied by life-threatening cerebral edema. Aquaporin-4 (Aqp4), an astrocytic transmembrane water channel, is an important molecular contributor to cerebral edema formation. Past studies of Aqp4 expression and localization after ischemia examined grey matter exclusively. However, as white matter astrocytes differ developmentally, physiologically, and molecularly from grey matter astrocytes, we hypothesized that functionally important regional heterogeneity exists in Aqp4 expression and subcellular localization following cerebral ischemia. RESULTS Subcellular localization of Aqp4 was compared between cortical and white matter astrocytes in postmortem specimens of patients with focal ischemic stroke versus controls. Subcellular localization and expression of Aqp4 was examined in rats subjected to experimental stroke. Volumetric analysis was performed on the cortex and white matter of rats subjected to experimental stroke. Following cerebral ischemia, cortical astrocytes exhibited reduced perivascular Aqp4 and unchanged Aqp4 protein abundance. In contrast, white matter astrocytes exhibited increased perivascular and plasmalemmal Aqp4 and a 2.2- to 6.2-fold increase in Aqp4 isoform abundance. Ischemic white matter swelled by approximately 40 %, while cortex swelled by approximately 9 %. CONCLUSIONS The findings reported here raise the possibility that cerebral white matter may play a heretofore underappreciated role in the formation of cerebral edema following ischemia.
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Vella J, Zammit C, Di Giovanni G, Muscat R, Valentino M. The central role of aquaporins in the pathophysiology of ischemic stroke. Front Cell Neurosci 2015; 9:108. [PMID: 25904843 PMCID: PMC4389728 DOI: 10.3389/fncel.2015.00108] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 04/10/2015] [Indexed: 11/16/2022] Open
Abstract
Stroke is a complex and devastating neurological condition with limited treatment options. Brain edema is a serious complication of stroke. Early edema formation can significantly contribute to infarct formation and thus represents a promising target. Aquaporin (AQP) water channels contribute to water homeostasis by regulating water transport and are implicated in several disease pathways. At least 7 AQP subtypes have been identified in the rodent brain and the use of transgenic mice has greatly aided our understanding of their functions. AQP4, the most abundant channel in the brain, is up-regulated around the peri-infarct border in transient cerebral ischemia and AQP4 knockout mice demonstrate significantly reduced cerebral edema and improved neurological outcome. In models of vasogenic edema, brain swelling is more pronounced in AQP4-null mice than wild-type providing strong evidence of the dual role of AQP4 in the formation and resolution of both vasogenic and cytotoxic edema. AQP4 is co-localized with inwardly rectifying K(+)-channels (Kir4.1) and glial K(+) uptake is attenuated in AQP4 knockout mice compared to wild-type, indicating some form of functional interaction. AQP4-null mice also exhibit a reduction in calcium signaling, suggesting that this channel may also be involved in triggering pathological downstream signaling events. Associations with the gap junction protein Cx43 possibly recapitulate its role in edema dissipation within the astroglial syncytium. Other roles ascribed to AQP4 include facilitation of astrocyte migration, glial scar formation, modulation of inflammation and signaling functions. Treatment of ischemic cerebral edema is based on the various mechanisms in which fluid content in different brain compartments can be modified. The identification of modulators and inhibitors of AQP4 offer new therapeutic avenues in the hope of reducing the extent of morbidity and mortality in stroke.
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Affiliation(s)
| | | | | | | | - Mario Valentino
- Department of Physiology and Biochemistry, University of MaltaMsida, Malta
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GLT-1 transporter: an effective pharmacological target for various neurological disorders. Pharmacol Biochem Behav 2014; 127:70-81. [PMID: 25312503 DOI: 10.1016/j.pbb.2014.10.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 09/01/2014] [Accepted: 10/03/2014] [Indexed: 11/23/2022]
Abstract
L-Glutamate is the predominant excitatory neurotransmitter in the central nervous system (CNS) and is directly and indirectly involved in a variety of brain functions. Glutamate is released in the synaptic cleft at a particular concentration that further activates the various glutaminergic receptors. This concentration of glutamate in the synapse is maintained by either glutamine synthetase or excitatory amino acid proteins which reuptake the excessive glutamate from the synapse and named as excitatory amino acid transporters (EAATs). Out of all the subtypes GLT-1 (glutamate transporter 1) is abundantly distributed in the CNS. Down-regulation of GLT-1 is reported in various neurological diseases such as, epilepsy, stroke, Alzheimer's disease and movement disorders. Therefore, positive modulators of GLT-1 which up-regulate the GLT-1 expression can serve as a potential target for the treatment of neurological disorders. GLT-1 translational activators such as ceftriaxone are found to have significant protective effects in ALS and epilepsy animal models, suggesting that this translational activation approach works well in rodents and that these compounds are worth further pursuit for various neurological disorders. This drug is currently in human clinical trials for ALS. In addition, a thorough understanding of the mechanisms underlying translational regulation of GLT-1, such as identifying the molecular targets of the compounds, signaling pathways involved in the regulation, and translational activation processes, is very important for this novel drug-development effort. This review mainly emphasizes the role of glutamate and its transporter, GLT-1 subtype in excitotoxicity. Further, recent reports on GLT-1 transporters for the treatment of various neurological diseases, including a summary of the presumed physiologic mechanisms behind the pharmacology of these disorders are also explained.
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