1
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Lee JM, Gadhe CG, Kang H, Pae AN, Lee CJ. Glutamate Permeability of Chicken Best1. Exp Neurobiol 2022; 31:277-288. [PMID: 36351838 PMCID: PMC9659495 DOI: 10.5607/en22038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 10/28/2022] [Accepted: 10/28/2022] [Indexed: 07/28/2023] Open
Abstract
Bestrophin-1 (Best1) is a calcium (Ca2+)-activated chloride (Cl-) channel which has a phylogenetically conserved channel structure with an aperture and neck in the ion-conducting pathway. Mammalian mouse Best1 (mBest1) has been known to have a permeability for large organic anions including gluconate, glutamate, and D-serine, in addition to several small monovalent anions, such as Cl‑, bromine (Br-), iodine (I-), and thiocyanate (SCN-). However, it is still unclear whether non-mammalian Best1 has a glutamate permeability through the ion-conducting pathway. Here, we report that chicken Best1 (cBest1) is permeable to glutamate in a Ca2+-dependent manner. The molecular docking and molecular dynamics simulation showed a glutamate binding at the aperture and neck of cBest1 and a glutamate permeation through the ion-conducting pore, respectively. Moreover, through electrophysiological recordings, we calculated the permeability ratio of glutamate to Cl- (PGlutamate/PCl) as 0.28 based on the reversal potential shift by ion substitution from Cl- to glutamate in the internal solution. Finally, we directly detected the Ca2+-dependent glutamate release through cBest1 using the ultrasensitive two-cell sniffer patch technique. Our results propose that Best1 homologs from non-mammalian (cBest1) to mammalian (mBest1) have a conserved permeability for glutamate.
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Affiliation(s)
- Jung Moo Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea
| | | | - Hyunji Kang
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea
- IBS School, University of Science and Technology, Daejeon 34113, Korea
| | - Ae Nim Pae
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Korea
- KIST School, University of Science and Technology, Seoul 02792, Korea
| | - C. Justin Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea
- IBS School, University of Science and Technology, Daejeon 34113, Korea
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2
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Chen TS, Lai MC, Huang HYI, Wu SN, Huang CW. Immunity, Ion Channels and Epilepsy. Int J Mol Sci 2022; 23:ijms23126446. [PMID: 35742889 PMCID: PMC9224225 DOI: 10.3390/ijms23126446] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 06/03/2022] [Accepted: 06/07/2022] [Indexed: 12/10/2022] Open
Abstract
Epilepsy is a common chronic neurological disorder in modern society. One of the major unmet challenges is that current antiseizure medications are basically not disease-modifying. Among the multifaceted etiologies of epilepsy, the role of the immune system has attracted considerable attention in recent years. It is known that both innate and adaptive immunity can be activated in response to insults to the central nervous system, leading to seizures. Moreover, the interaction between ion channels, which have a well-established role in epileptogenesis and epilepsy, and the immune system is complex and is being actively investigated. Some examples, including the interaction between ion channels and mTOR pathways, will be discussed in this paper. Furthermore, there has been substantial progress in our understanding of the pathophysiology of epilepsy associated with autoimmune encephalitis, and numerous neural-specific autoantibodies have been found and documented. Early recognition of immune-mediated epilepsy is important, especially in cases of pharmacoresistant epilepsy and in the presence of signs of autoimmune encephalitis, as early intervention with immunotherapy shows promise.
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Affiliation(s)
- Tsang-Shan Chen
- Department of Neurology, Tainan Sin-Lau Hospital, Tainan 701002, Taiwan;
| | - Ming-Chi Lai
- Department of Pediatrics, Chi-Mei Medical Center, Tainan 71004, Taiwan;
| | | | - Sheng-Nan Wu
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan 70101, Taiwan
| | - Chin-Wei Huang
- Department of Neurology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan
- Correspondence: ; Tel.: +886-6-2353535 (ext. 5485)
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3
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Dang R, Wang M, Li X, Wang H, Liu L, Wu Q, Zhao J, Ji P, Zhong L, Licinio J, Xie P. Edaravone ameliorates depressive and anxiety-like behaviors via Sirt1/Nrf2/HO-1/Gpx4 pathway. J Neuroinflammation 2022; 19:41. [PMID: 35130906 PMCID: PMC8822843 DOI: 10.1186/s12974-022-02400-6] [Citation(s) in RCA: 149] [Impact Index Per Article: 74.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 01/24/2022] [Indexed: 02/07/2023] Open
Abstract
Background The inflammation and oxidative stress (OS) have been considered crucial components of the pathogenesis of depression. Edaravone (EDA), a free radical scavenger, processes strong biological activities including antioxidant, anti-inflammatory and neuroprotective properties. However, its role and potential molecular mechanisms in depression remain unclear. The present study aimed to investigate the antidepressant activity of EDA and its underlying mechanisms. Methods A chronic social defeat stress (CSDS) depression model was performed to explore whether EDA could produce antidepressant effects. Behaviors tests were carried out to examine depressive, anxiety-like and cognitive behaviors including social interaction (SI) test, sucrose preference test (SPT), open field test (OFT), elevated plus maze (EPM), novel object recognition (NOR), tail suspension test (TST) and forced swim test (FST). Hippocampal and medial prefrontal cortex (mPFC) tissues were collected for Nissl staining, immunofluorescence, targeted energy metabolomics analysis, enzyme-linked immunosorbent assay (ELISA), measurement of MDA, SOD, GSH, GSH-PX, T-AOC and transmission electron microscopy (TEM). Western blotting (WB) and quantitative real-time polymerase chain reaction (qRT-PCR) detected the Sirt1/Nrf2/HO-1/Gpx4 signaling pathway. EX527, a Sirt1 inhibitor and ML385, a Nrf2 inhibitor were injected intraperitoneally 30 min before EDA injection daily. Knockdown experiments were performed to determine the effects of Gpx4 on CSDS mice with EDA treatment by an adeno-associated virus (AAV) vector containing miRNAi (Gpx4)–EGFP infusion. Results The administrated of EDA dramatically ameliorated CSDS-induced depressive and anxiety-like behaviors. In addition, EDA notably attenuated neuronal loss, microglial activation, astrocyte dysfunction, oxidative stress damage, energy metabolism and pro-inflammatory cytokines activation in the hippocampus (Hip) and mPFC of CSDS-induced mice. Further examination indicated that the application of EDA after the CSDS model significantly increased the protein expressions of Sirt1, Nrf2, HO-1 and Gpx4 in the Hip. EX527 abolished the antidepressant effect of EDA as well as the protein levels of Nrf2, HO-1 and Gpx4. Similarly, ML385 reversed the antidepressant and anxiolytic effects of EDA via decreased expressions of HO-1 and Gpx4. In addition, Gpx4 knockdown in CSDS mice abolished EDA-generated efficacy on depressive and anxiety-like behaviors. Conclusion These findings suggest that EDA possesses potent antidepressant and anxiolytic properties through Sirt1/Nrf2/HO-1/Gpx4 axis and Gpx4-mediated ferroptosis may play a key role in this effect. Supplementary Information The online version contains supplementary material available at 10.1186/s12974-022-02400-6.
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Affiliation(s)
- Ruozhi Dang
- NHC Key Laboratory of Diagnosis and Treatment on Brain Functional Diseases, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Yuzhong District, Chongqing, 400016, China.,Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Mingyang Wang
- NHC Key Laboratory of Diagnosis and Treatment on Brain Functional Diseases, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Yuzhong District, Chongqing, 400016, China
| | - Xinhui Li
- NHC Key Laboratory of Diagnosis and Treatment on Brain Functional Diseases, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Yuzhong District, Chongqing, 400016, China.,Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Haiyang Wang
- NHC Key Laboratory of Diagnosis and Treatment on Brain Functional Diseases, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Yuzhong District, Chongqing, 400016, China.,College of Stomatology and Affiliated Stomatological Hospital of Chongqing Medical University, Chongqing, 401147, China
| | - Lanxiang Liu
- NHC Key Laboratory of Diagnosis and Treatment on Brain Functional Diseases, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Yuzhong District, Chongqing, 400016, China.,Department of Neurology, Yongchuan Hospital of Chongqing Medical University, Chongqing, 402160, China
| | - Qingyuan Wu
- Department of Neurology, Chongqing University Three Gorges Hospital, Chongqing, 404100, China
| | - Jianting Zhao
- Department of Neurology, Xinxiang Central Hospital, Xinxiang, 453000, China
| | - Ping Ji
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, College of Stomatology and Affiliated Stomatological Hospital of Chongqing Medical University, Chongqing, 401147, China.,Key Laboratory of Psychoseomadsy, Stomatological Hospital of Chongqing Medical University, Chongqing, 401147, China
| | - Lianmei Zhong
- Department of Neurology, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Julio Licinio
- Department of Psychiatry and Behavioral Sciences, College of Medicine, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Peng Xie
- NHC Key Laboratory of Diagnosis and Treatment on Brain Functional Diseases, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Yuzhong District, Chongqing, 400016, China. .,Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China.
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4
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Lalo U, Koh W, Lee CJ, Pankratov Y. The tripartite glutamatergic synapse. Neuropharmacology 2021; 199:108758. [PMID: 34433089 DOI: 10.1016/j.neuropharm.2021.108758] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 07/25/2021] [Accepted: 08/20/2021] [Indexed: 12/31/2022]
Abstract
Astroglial cells were long considered as structural and metabolic supporting cells are which do not directly participate in information processing in the brain. Discoveries of responsiveness of astrocytes to synaptically-released glutamate and their capability to release agonists of glutamate receptors awakened extensive studies of glia-neuron communications and led to the revolutionary changes in our understanding of brain cellular networks. Nowadays, astrocytes are widely acknowledged as inseparable element of glutamatergic synapses and role for glutamatergic astrocyte-neuron interactions in the brain computation is emerging. Astroglial glutamate receptors, in particular of NMDA, mGluR3 and mGluR5 types, can activate a variety of molecular cascades leading astroglial-driven modulation of extracellular levels of glutamate and activity of neuronal glutamate receptors. Their preferential location to the astroglial perisynaptic processes facilitates interaction of astrocytes with individual excitatory synapses. Bi-directional glutamatergic communication between astrocytes and neurons underpins a complex, spatially-distributed modulation of synaptic signalling thus contributing to the enrichment of information processing by the neuronal networks. Still, further research is needed to bridge the substantial gaps in our understanding of mechanisms and physiological relevance of astrocyte-neuron glutamatergic interactions, in particular ability of astrocytes directly activate neuronal glutamate receptors by releasing glutamate and, arguably, d-Serine. An emerging roles for aberrant changes in glutamatergic astroglial signalling, both neuroprotective and pathogenic, in neurological and neurodegenerative diseases also require further investigation. This article is part of the special Issue on 'Glutamate Receptors - The Glutamatergic Synapse'.
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Affiliation(s)
- Ulyana Lalo
- School of Life Sciences, Immanuel Kant Baltic Federal University, Kaliningrad, Russia
| | - Wuhyun Koh
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, 34126, South Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, 34126, South Korea
| | - Yuriy Pankratov
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom.
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5
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Twible C, Abdo R, Zhang Q. Astrocyte Role in Temporal Lobe Epilepsy and Development of Mossy Fiber Sprouting. Front Cell Neurosci 2021; 15:725693. [PMID: 34658792 PMCID: PMC8514632 DOI: 10.3389/fncel.2021.725693] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/02/2021] [Indexed: 11/13/2022] Open
Abstract
Epilepsy affects approximately 50 million people worldwide, with 60% of adult epilepsies presenting an onset of focal origin. The most common focal epilepsy is temporal lobe epilepsy (TLE). The role of astrocytes in the presentation and development of TLE has been increasingly studied and discussed within the literature. The most common histopathological diagnosis of TLE is hippocampal sclerosis. Hippocampal sclerosis is characterized by neuronal cell loss within the Cornu ammonis and reactive astrogliosis. In some cases, mossy fiber sprouting may be observed. Mossy fiber sprouting has been controversial in its contribution to epileptogenesis in TLE patients, and the mechanisms surrounding the phenomenon have yet to be elucidated. Several studies have reported that mossy fiber sprouting has an almost certain co-existence with reactive astrogliosis within the hippocampus under epileptic conditions. Astrocytes are known to play an important role in the survival and axonal outgrowth of central and peripheral nervous system neurons, pointing to a potential role of astrocytes in TLE and associated cellular alterations. Herein, we review the recent developments surrounding the role of astrocytes in the pathogenic process of TLE and mossy fiber sprouting, with a focus on proposed signaling pathways and cellular mechanisms, histological observations, and clinical correlations in human patients.
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Affiliation(s)
- Carolyn Twible
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada
| | - Rober Abdo
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada.,Department of Anatomy and Cell Biology, Western University, London, ON, Canada
| | - Qi Zhang
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada.,Department of Pathology and Lab Medicine, London Health Sciences Centre, University Hospital, London, ON, Canada
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6
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Sherwood MW, Oliet SHR, Panatier A. NMDARs, Coincidence Detectors of Astrocytic and Neuronal Activities. Int J Mol Sci 2021; 22:7258. [PMID: 34298875 PMCID: PMC8307462 DOI: 10.3390/ijms22147258] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/30/2021] [Accepted: 06/30/2021] [Indexed: 12/18/2022] Open
Abstract
Synaptic plasticity is an extensively studied cellular correlate of learning and memory in which NMDARs play a starring role. One of the most interesting features of NMDARs is their ability to act as a co-incident detector. It is unique amongst neurotransmitter receptors in this respect. Co-incident detection is possible because the opening of NMDARs requires membrane depolarisation and the binding of glutamate. Opening of NMDARs also requires a co-agonist. Although the dynamic regulation of glutamate and membrane depolarization have been well studied in coincident detection, the role of the co-agonist site is unexplored. It turns out that non-neuronal glial cells, astrocytes, regulate co-agonist availability, giving them the ability to influence synaptic plasticity. The unique morphology and spatial arrangement of astrocytes at the synaptic level affords them the capacity to sample and integrate information originating from unrelated synapses, regardless of any pre-synaptic and post-synaptic commonality. As astrocytes are classically considered slow responders, their influence at the synapse is widely recognized as modulatory. The aim herein is to reconsider the potential of astrocytes to participate directly in ongoing synaptic NMDAR activity and co-incident detection.
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Affiliation(s)
- Mark W. Sherwood
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
| | | | - Aude Panatier
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
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7
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Gobbo D, Scheller A, Kirchhoff F. From Physiology to Pathology of Cortico-Thalamo-Cortical Oscillations: Astroglia as a Target for Further Research. Front Neurol 2021; 12:661408. [PMID: 34177766 PMCID: PMC8219957 DOI: 10.3389/fneur.2021.661408] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 05/11/2021] [Indexed: 12/21/2022] Open
Abstract
The electrographic hallmark of childhood absence epilepsy (CAE) and other idiopathic forms of epilepsy are 2.5-4 Hz spike and wave discharges (SWDs) originating from abnormal electrical oscillations of the cortico-thalamo-cortical network. SWDs are generally associated with sudden and brief non-convulsive epileptic events mostly generating impairment of consciousness and correlating with attention and learning as well as cognitive deficits. To date, SWDs are known to arise from locally restricted imbalances of excitation and inhibition in the deep layers of the primary somatosensory cortex. SWDs propagate to the mostly GABAergic nucleus reticularis thalami (NRT) and the somatosensory thalamic nuclei that project back to the cortex, leading to the typical generalized spike and wave oscillations. Given their shared anatomical basis, SWDs have been originally considered the pathological transition of 11-16 Hz bursts of neural oscillatory activity (the so-called sleep spindles) occurring during Non-Rapid Eye Movement (NREM) sleep, but more recent research revealed fundamental functional differences between sleep spindles and SWDs, suggesting the latter could be more closely related to the slow (<1 Hz) oscillations alternating active (Up) and silent (Down) cortical activity and concomitantly occurring during NREM. Indeed, several lines of evidence support the fact that SWDs impair sleep architecture as well as sleep/wake cycles and sleep pressure, which, in turn, affect seizure circadian frequency and distribution. Given the accumulating evidence on the role of astroglia in the field of epilepsy in the modulation of excitation and inhibition in the brain as well as on the development of aberrant synchronous network activity, we aim at pointing at putative contributions of astrocytes to the physiology of slow-wave sleep and to the pathology of SWDs. Particularly, we will address the astroglial functions known to be involved in the control of network excitability and synchronicity and so far mainly addressed in the context of convulsive seizures, namely (i) interstitial fluid homeostasis, (ii) K+ clearance and neurotransmitter uptake from the extracellular space and the synaptic cleft, (iii) gap junction mechanical and functional coupling as well as hemichannel function, (iv) gliotransmission, (v) astroglial Ca2+ signaling and downstream effectors, (vi) reactive astrogliosis and cytokine release.
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Affiliation(s)
- Davide Gobbo
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Anja Scheller
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Frank Kirchhoff
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
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8
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Cojocaru A, Burada E, Bălșeanu AT, Deftu AF, Cătălin B, Popa-Wagner A, Osiac E. Roles of Microglial Ion Channel in Neurodegenerative Diseases. J Clin Med 2021; 10:jcm10061239. [PMID: 33802786 PMCID: PMC8002406 DOI: 10.3390/jcm10061239] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 03/02/2021] [Accepted: 03/11/2021] [Indexed: 12/15/2022] Open
Abstract
As the average age and life expectancy increases, the incidence of both acute and chronic central nervous system (CNS) pathologies will increase. Understanding mechanisms underlying neuroinflammation as the common feature of any neurodegenerative pathology, we can exploit the pharmacology of cell specific ion channels to improve the outcome of many CNS diseases. As the main cellular player of neuroinflammation, microglia play a central role in this process. Although microglia are considered non-excitable cells, they express a variety of ion channels under both physiological and pathological conditions that seem to be involved in a plethora of cellular processes. Here, we discuss the impact of modulating microglia voltage-gated, potential transient receptor, chloride and proton channels on microglial proliferation, migration, and phagocytosis in neurodegenerative diseases.
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Affiliation(s)
- Alexandru Cojocaru
- Department of Physiology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; (A.C.); (E.B.); (A.-T.B.)
- Experimental Research Center for Normal and Pathological Aging, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
| | - Emilia Burada
- Department of Physiology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; (A.C.); (E.B.); (A.-T.B.)
| | - Adrian-Tudor Bălșeanu
- Department of Physiology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; (A.C.); (E.B.); (A.-T.B.)
- Experimental Research Center for Normal and Pathological Aging, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
| | - Alexandru-Florian Deftu
- Pain Center, Department of Anesthesiology, Lausanne University Hospital (CHUV), CH-1011 Lausanne, Switzerland;
- Faculty of Biology and Medicine (FBM), University of Lausanne (UNIL), CH-1011 Lausanne, Switzerland
| | - Bogdan Cătălin
- Department of Physiology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; (A.C.); (E.B.); (A.-T.B.)
- Experimental Research Center for Normal and Pathological Aging, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania
- Correspondence: (B.C.); (A.P.-W.)
| | - Aurel Popa-Wagner
- Chair of Vascular Neurology, Dementia and Ageing Research, University Hospital Essen, 45147 Essen, Germany
- Correspondence: (B.C.); (A.P.-W.)
| | - Eugen Osiac
- Department of Biophysics, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania;
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9
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Pham C, Hérault K, Oheim M, Maldera S, Vialou V, Cauli B, Li D. Astrocytes respond to a neurotoxic Aβ fragment with state-dependent Ca 2+ alteration and multiphasic transmitter release. Acta Neuropathol Commun 2021; 9:44. [PMID: 33726852 PMCID: PMC7968286 DOI: 10.1186/s40478-021-01146-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 02/28/2021] [Indexed: 12/13/2022] Open
Abstract
Excessive amounts of amyloid β (Aβ) peptide have been suggested to dysregulate synaptic transmission in Alzheimer's disease (AD). As a major type of glial cell in the mammalian brain, astrocytes regulate neuronal function and undergo activity alterations upon Aβ exposure. Yet the mechanistic steps underlying astrocytic responses to Aβ peptide remain to be elucidated. Here by fluorescence imaging of signaling pathways, we dissected astrocytic responses to Aβ25-35 peptide, a neurotoxic Aβ fragment present in AD patients. In native health astrocytes, Aβ25-35 evoked Ca2+ elevations via purinergic receptors, being also dependent on the opening of connexin (CX) hemichannels. Aβ25-35, however, induced a Ca2+ diminution in Aβ-preconditioned astrocytes as a result of the potentiation of the plasma membrane Ca2+ ATPase (PMCA). The PMCA and CX protein expression was observed with immunostaining in the brain tissue of hAPPJ20 AD mouse model. We also observed both Ca2+-independent and Ca2+-dependent glutamate release upon astrocytic Aβ exposure, with the former mediated by CX hemichannel and the latter by both anion channels and lysosome exocytosis. Our results suggest that Aβ peptide causes state-dependent responses in astrocytes, in association with a multiphasic release of signaling molecules. This study therefore helps to understand astrocyte engagement in AD-related amyloidopathy.
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10
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Li L, Acioglu C, Heary RF, Elkabes S. Role of astroglial toll-like receptors (TLRs) in central nervous system infections, injury and neurodegenerative diseases. Brain Behav Immun 2021; 91:740-755. [PMID: 33039660 PMCID: PMC7543714 DOI: 10.1016/j.bbi.2020.10.007] [Citation(s) in RCA: 132] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/22/2020] [Accepted: 10/06/2020] [Indexed: 02/07/2023] Open
Abstract
Central nervous system (CNS) innate immunity plays essential roles in infections, neurodegenerative diseases, and brain or spinal cord injuries. Astrocytes and microglia are the principal cells that mediate innate immunity in the CNS. Pattern recognition receptors (PRRs), expressed by astrocytes and microglia, sense pathogen-derived or endogenous ligands released by damaged cells and initiate the innate immune response. Toll-like receptors (TLRs) are a well-characterized family of PRRs. The contribution of microglial TLR signaling to CNS pathology has been extensively investigated. Even though astrocytes assume a wide variety of key functions, information about the role of astroglial TLRs in CNS disease and injuries is limited. Because astrocytes display heterogeneity and exhibit phenotypic plasticity depending on the effectors present in the local milieu, they can exert both detrimental and beneficial effects. TLRs are modulators of these paradoxical astroglial properties. The goal of the current review is to highlight the essential roles played by astroglial TLRs in CNS infections, injuries and diseases. We discuss the contribution of astroglial TLRs to host defense as well as the dissemination of viral and bacterial infections in the CNS. We examine the link between astroglial TLRs and the pathogenesis of neurodegenerative diseases and present evidence showing the pivotal influence of astroglial TLR signaling on sterile inflammation in CNS injury. Finally, we define the research questions and areas that warrant further investigations in the context of astrocytes, TLRs, and CNS dysfunction.
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Affiliation(s)
- Lun Li
- The Reynolds Family Spine Laboratory, Department of Neurosurgery, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States
| | - Cigdem Acioglu
- The Reynolds Family Spine Laboratory, Department of Neurosurgery, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States
| | - Robert F. Heary
- Department of Neurological Surgery, Hackensack Meridian School of Medicine, Nutley, NJ 07110, United States
| | - Stella Elkabes
- The Reynolds Family Spine Laboratory, Department of Neurosurgery, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States.
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11
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Verhoog QP, Holtman L, Aronica E, van Vliet EA. Astrocytes as Guardians of Neuronal Excitability: Mechanisms Underlying Epileptogenesis. Front Neurol 2020; 11:591690. [PMID: 33324329 PMCID: PMC7726323 DOI: 10.3389/fneur.2020.591690] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/26/2020] [Indexed: 12/11/2022] Open
Abstract
Astrocytes are key homeostatic regulators in the central nervous system and play important roles in physiology. After brain damage caused by e.g., status epilepticus, traumatic brain injury, or stroke, astrocytes may adopt a reactive phenotype. This process of reactive astrogliosis is important to restore brain homeostasis. However, persistent reactive astrogliosis can be detrimental for the brain and contributes to the development of epilepsy. In this review, we will focus on physiological functions of astrocytes in the normal brain as well as pathophysiological functions in the epileptogenic brain, with a focus on acquired epilepsy. We will discuss the role of astrocyte-related processes in epileptogenesis, including reactive astrogliosis, disturbances in energy supply and metabolism, gliotransmission, and extracellular ion concentrations, as well as blood-brain barrier dysfunction and dysregulation of blood flow. Since dysfunction of astrocytes can contribute to epilepsy, we will also discuss their role as potential targets for new therapeutic strategies.
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Affiliation(s)
- Quirijn P. Verhoog
- Leiden Academic Center for Drug Research, Leiden University, Leiden, Netherlands
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Linda Holtman
- Leiden Academic Center for Drug Research, Leiden University, Leiden, Netherlands
| | - Eleonora Aronica
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, Netherlands
| | - Erwin A. van Vliet
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
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12
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Li X, Li M, Tian L, Chen J, Liu R, Ning B. Reactive Astrogliosis: Implications in Spinal Cord Injury Progression and Therapy. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:9494352. [PMID: 32884625 PMCID: PMC7455824 DOI: 10.1155/2020/9494352] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 05/06/2020] [Accepted: 07/31/2020] [Indexed: 12/11/2022]
Abstract
Astrocytes are the most populous glial cells in the central nervous system (CNS). They are essential to CNS physiology and play important roles in the maintenance of homeostasis, development of synaptic plasticity, and neuroprotection. Nevertheless, under the influence of certain factors, astrocytes may also exert detrimental effects through a process of reactive astrogliosis. Previous studies have shown that astrocytes have more than one type of polarization. Two types have been extensively researched. One is a damaging change that occurs under inflammation and has been termed A1 astrocyte, while the other is a restorative change that occurs under ischemic induction and was termed A2 astrocyte. Researchers are now increasingly paying attention to the role of astrocytes in spinal cord injury (SCI), degenerative diseases, chronic pain, neurological tumors, and other CNS disorders. In this review, we discuss (a) the characteristics of polarized astrocytes, (b) the relationship between astrocyte polarization and SCI, and (c) new implications of reactive astrogliosis for future SCI therapies.
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Affiliation(s)
- Xinyu Li
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, No. 105, Jiefang Road, Jinan, Shandong 250013, China
| | - Meng Li
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, No. 105, Jiefang Road, Jinan, Shandong 250013, China
| | - Lige Tian
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, No. 105, Jiefang Road, Jinan, Shandong 250013, China
| | - Jianan Chen
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, No. 105, Jiefang Road, Jinan, Shandong 250013, China
| | - Ronghan Liu
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, No. 105, Jiefang Road, Jinan, Shandong 250013, China
| | - Bin Ning
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, No. 105, Jiefang Road, Jinan, Shandong 250013, China
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13
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Warnock A, Toomey LM, Wright AJ, Fisher K, Won Y, Anyaegbu C, Fitzgerald M. Damage Mechanisms to Oligodendrocytes and White Matter in Central Nervous System Injury: The Australian Context. J Neurotrauma 2020; 37:739-769. [DOI: 10.1089/neu.2019.6890] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Andrew Warnock
- Curtin Health Innovation Research Institute, Curtin University, Bentley, Western Australia, Australia
| | - Lillian M. Toomey
- Curtin Health Innovation Research Institute, Curtin University, Bentley, Western Australia, Australia
- Perron Institute for Neurological and Translational Science, Nedlands, Western Australia, Australia
| | - Alexander J. Wright
- Curtin Health Innovation Research Institute, Curtin University, Bentley, Western Australia, Australia
| | - Katherine Fisher
- School of Human Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Yerim Won
- School of Human Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Chidozie Anyaegbu
- Curtin Health Innovation Research Institute, Curtin University, Bentley, Western Australia, Australia
| | - Melinda Fitzgerald
- Curtin Health Innovation Research Institute, Curtin University, Bentley, Western Australia, Australia
- Perron Institute for Neurological and Translational Science, Nedlands, Western Australia, Australia
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14
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Walch E, Murphy TR, Cuvelier N, Aldoghmi M, Morozova C, Donohue J, Young G, Samant A, Garcia S, Alvarez C, Bilas A, Davila D, Binder DK, Fiacco TA. Astrocyte-Selective Volume Increase in Elevated Extracellular Potassium Conditions Is Mediated by the Na +/K + ATPase and Occurs Independently of Aquaporin 4. ASN Neuro 2020; 12:1759091420967152. [PMID: 33092407 PMCID: PMC7586494 DOI: 10.1177/1759091420967152] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 09/23/2020] [Indexed: 12/26/2022] Open
Abstract
Astrocytes and neurons have been shown to swell across a variety of different conditions, including increases in extracellular potassium concentration (^[K+]o). The mechanisms involved in the coupling of K+ influx to water movement into cells leading to cell swelling are not well understood and remain controversial. Here, we set out to determine the effects of ^[K+]o on rapid volume responses of hippocampal CA1 pyramidal neurons and stratum radiatum astrocytes using real-time confocal volume imaging. First, we found that elevating [K+]o within a physiological range (to 6.5 mM and 10.5 mM from a baseline of 2.5 mM), and even up to pathological levels (26 mM), produced dose-dependent increases in astrocyte volume, with absolutely no effect on neuronal volume. In the absence of compensating for addition of KCl by removal of an equal amount of NaCl, neurons actually shrank in ^[K+]o, while astrocytes continued to exhibit rapid volume increases. Astrocyte swelling in ^[K+]o was not dependent on neuronal firing, aquaporin 4, the inwardly rectifying potassium channel Kir 4.1, the sodium bicarbonate cotransporter NBCe1, , or the electroneutral cotransporter, sodium-potassium-chloride cotransporter type 1 (NKCC1), but was significantly attenuated in 1 mM barium chloride (BaCl2) and by the Na+/K+ ATPase inhibitor ouabain. Effects of 1 mM BaCl2 and ouabain applied together were not additive and, together with reports that BaCl2 can inhibit the NKA at high concentrations, suggests a prominent role for the astrocyte NKA in rapid astrocyte volume increases occurring in ^[K+]o. These findings carry important implications for understanding mechanisms of cellular edema, regulation of the brain extracellular space, and brain tissue excitability.
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Affiliation(s)
- Erin Walch
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, United States
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, United States
| | - Thomas R. Murphy
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
| | - Nicholas Cuvelier
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - Murad Aldoghmi
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
| | - Cristine Morozova
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Jordan Donohue
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - Gaby Young
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Anuja Samant
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Stacy Garcia
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Camila Alvarez
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Alex Bilas
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - David Davila
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
| | - Devin K. Binder
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, United States
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - Todd A. Fiacco
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, United States
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
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15
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López E, Lee-Rivera I, Alvarez-Arce A, López-Colomé AM. Thrombin induces Ca 2+-dependent glutamate release from RPE cells mediated by PLC/PKC and reverse Na +/Ca 2+ exchange. Mol Vis 2019; 25:546-558. [PMID: 31673221 PMCID: PMC6798708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 10/03/2019] [Indexed: 11/01/2022] Open
Abstract
Purpose We analyzed the molecular mechanisms leading to glutamate release from rat primary cultures of RPE cells, under isosmotic conditions. Thrombin has been shown to stimulate glutamate release from astrocytes and retinal glia; however, the effect of thrombin on glutamate release from RPE cells has not been examined. Our previous work showed that upon the alteration of the blood-retina barrier, the serine protease thrombin could contribute to the transformation, proliferation, and migration of RPE cells. In this condition, elevated extracellular glutamate causes neuronal loss in many retinal disorders, including glaucoma, ischemia, diabetic retinopathy, and inherited photoreceptor degeneration. Methods Primary cultures of rat RPE cells were preloaded with 1 µCi/ml 3H-glutamate in Krebs Ringer Bicarbonate (KRB) buffer for 30 min at 37 °C. Cells were rinsed and super-perfused with 1 ml/min KRB for 15 min. Stable release was reached at the 7th minute, and on the 8th minute, fresh KRB containing stimuli was added. Results This study showed for the first time that thrombin promotes specific, dose-dependent glutamate release from RPE cells, induced by the activation of protease-activated receptor 1 (PAR-1). This effect was found to depend on the Ca2+ increase mediated by the phospholipase C-β (PLC-β) and protein kinase C (PKC) pathways, as well as by the reverse activity of the Na+/Ca2+ exchanger. Conclusions Given the intimate contact of the RPE with the photoreceptor outer segments, diffusion of RPE-released glutamate could contribute to the excitotoxic death of retinal neurons, and the development of thrombin-induced eye pathologies.
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16
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Huang D, Li C, Zhang W, Qin J, Jiang W, Hu C. Dysfunction of astrocytic connexins 30 and 43 in the medial prefrontal cortex and hippocampus mediates depressive-like behaviours. Behav Brain Res 2019; 372:111950. [DOI: 10.1016/j.bbr.2019.111950] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 05/09/2019] [Accepted: 05/15/2019] [Indexed: 11/17/2022]
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17
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Halpern M, Brennand KJ, Gregory J. Examining the relationship between astrocyte dysfunction and neurodegeneration in ALS using hiPSCs. Neurobiol Dis 2019; 132:104562. [PMID: 31381978 DOI: 10.1016/j.nbd.2019.104562] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 06/28/2019] [Accepted: 07/31/2019] [Indexed: 02/07/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a complex and fatal neurodegenerative disease for which the causes of disease onset and progression remain unclear. Recent advances in human induced pluripotent stem cell (hiPSC)-based models permit the study of the genetic factors associated with ALS in patient-derived neural cell types, including motor neurons and glia. While astrocyte dysfunction has traditionally been thought to exacerbate disease progression, astrocytic dysfunction may play a more direct role in disease initiation and progression. Such non-cell autonomous mechanisms expand the potential targets of therapeutic intervention, but only a handful of ALS risk-associated genes have been examined for their impact on astrocyte dysfunction and neurodegeneration. This review summarizes what is currently known about astrocyte function in ALS and suggests ways in which hiPSC-based models can be used to more effectively study the role of astrocytes in neurodegenerative disease.
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Affiliation(s)
- Madeline Halpern
- Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America
| | - Kristen J Brennand
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America; Department of Genetics and Genomics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America; Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America; Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America.
| | - James Gregory
- Center for Genomics of Neurodegenerative Disease, New York Genome Center, New York, NY 10013, United States of America.
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18
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Han YE, Kwon J, Won J, An H, Jang MW, Woo J, Lee JS, Park MG, Yoon BE, Lee SE, Hwang EM, Jung JY, Park H, Oh SJ, Lee CJ. Tweety-homolog ( Ttyh) Family Encodes the Pore-forming Subunits of the Swelling-dependent Volume-regulated Anion Channel (VRAC swell) in the Brain. Exp Neurobiol 2019; 28:183-215. [PMID: 31138989 PMCID: PMC6526117 DOI: 10.5607/en.2019.28.2.183] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 04/23/2019] [Accepted: 04/25/2019] [Indexed: 11/19/2022] Open
Abstract
In the brain, a reduction in extracellular osmolality causes water-influx and swelling, which subsequently triggers Cl-- and osmolytes-efflux via volume-regulated anion channel (VRAC). Although LRRC8 family has been recently proposed as the pore-forming VRAC which is activated by low cytoplasmic ionic strength but not by swelling, the molecular identity of the pore-forming swelling-dependent VRAC (VRACswell) remains unclear. Here we identify and characterize Tweety-homologs (TTYH1, TTYH2, TTYH3) as the major VRACswell in astrocytes. Gene-silencing of all Ttyh1/2/3 eliminated hypo-osmotic-solution-induced Cl- conductance (ICl,swell) in cultured and hippocampal astrocytes. When heterologously expressed in HEK293T or CHO-K1 cells, each TTYH isoform showed a significant ICl,swell with similar aquaporin-4 dependency, pharmacological properties and glutamate permeability as ICl,swell observed in native astrocytes. Mutagenesis-based structure-activity analysis revealed that positively charged arginine residue at 165 in TTYH1 and 164 in TTYH2 is critical for the formation of the channel-pore. Our results demonstrate that TTYH family confers the bona fide VRACswell in the brain.
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Affiliation(s)
- Young-Eun Han
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.,Department of Neuroscience, Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Jea Kwon
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.,KU-KIST, Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea
| | - Joungha Won
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.,Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Heeyoung An
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.,KU-KIST, Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea
| | - Minwoo Wendy Jang
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.,KU-KIST, Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea
| | - Junsung Woo
- Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Je Sun Lee
- Molecular Neurobiology Laboratory, Dept. of Structure and Function of Neural Network, Korea Brain Research Institute, Daegu 41068, Korea
| | - Min Gu Park
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.,KU-KIST, Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea
| | - Bo-Eun Yoon
- Department of molecular biology, Dankook University, Cheonan 31116, Korea
| | - Seung Eun Lee
- Virus Facility, Research Animal Resource Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Eun Mi Hwang
- Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Jae-Young Jung
- Department of Neuroscience, Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Hyungju Park
- Molecular Neurobiology Laboratory, Dept. of Structure and Function of Neural Network, Korea Brain Research Institute, Daegu 41068, Korea
| | - Soo-Jin Oh
- Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.,Convergence Research Center for Diagnosis, Treatment and Care System of Dementia, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.,Department of Neuroscience, Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea.,Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
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19
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Yang J, Vitery MDC, Chen J, Osei-Owusu J, Chu J, Qiu Z. Glutamate-Releasing SWELL1 Channel in Astrocytes Modulates Synaptic Transmission and Promotes Brain Damage in Stroke. Neuron 2019; 102:813-827.e6. [PMID: 30982627 DOI: 10.1016/j.neuron.2019.03.029] [Citation(s) in RCA: 132] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 12/14/2018] [Accepted: 03/19/2019] [Indexed: 01/01/2023]
Abstract
By releasing glutamate, astrocytes actively regulate synaptic transmission and contribute to excitotoxicity in neurological diseases. However, the mechanisms of astrocytic glutamate release have been debated. Here, we report non-vesicular release of glutamate through the glutamate-permeable volume-regulated anion channel (VRAC). Both cell swelling and receptor stimulation activated astrocytic VRAC, which requires its only obligatory subunit, Swell1. Astrocyte-specific Swell1 knockout mice exhibited impaired glutamatergic transmission due to the decreases in presynaptic release probability and ambient glutamate level. Consistently, the mutant mice displayed hippocampal-dependent learning and memory deficits. During pathological cell swelling, deletion of astrocytic Swell1 attenuated glutamate-dependent neuronal excitability and protected mice from brain damage after ischemic stroke. Our identification of a new molecular mechanism for channel-mediated glutamate release establishes a role for astrocyte-neuron interactions in both synaptic transmission and brain ischemia. It provides a rationale for targeting VRAC for the treatment of stroke and other neurological diseases associated with excitotoxicity.
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Affiliation(s)
- Junhua Yang
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Maria Del Carmen Vitery
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jianan Chen
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - James Osei-Owusu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jiachen Chu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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20
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Mahmoud S, Gharagozloo M, Simard C, Gris D. Astrocytes Maintain Glutamate Homeostasis in the CNS by Controlling the Balance between Glutamate Uptake and Release. Cells 2019; 8:E184. [PMID: 30791579 PMCID: PMC6406900 DOI: 10.3390/cells8020184] [Citation(s) in RCA: 322] [Impact Index Per Article: 64.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 02/15/2019] [Accepted: 02/19/2019] [Indexed: 01/26/2023] Open
Abstract
Glutamate is one of the most prevalent neurotransmitters released by excitatory neurons in the central nervous system (CNS); however, residual glutamate in the extracellular space is, potentially, neurotoxic. It is now well-established that one of the fundamental functions of astrocytes is to uptake most of the synaptically-released glutamate, which optimizes neuronal functions and prevents glutamate excitotoxicity. In the CNS, glutamate clearance is mediated by glutamate uptake transporters expressed, principally, by astrocytes. Interestingly, recent studies demonstrate that extracellular glutamate stimulates Ca2+ release from the astrocytes' intracellular stores, which triggers glutamate release from astrocytes to the adjacent neurons, mostly by an exocytotic mechanism. This released glutamate is believed to coordinate neuronal firing and mediate their excitatory or inhibitory activity. Therefore, astrocytes contribute to glutamate homeostasis in the CNS, by maintaining the balance between their opposing functions of glutamate uptake and release. This dual function of astrocytes represents a potential therapeutic target for CNS diseases associated with glutamate excitotoxicity. In this regard, we summarize the molecular mechanisms of glutamate uptake and release, their regulation, and the significance of both processes in the CNS. Also, we review the main features of glutamate metabolism and glutamate excitotoxicity and its implication in CNS diseases.
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Affiliation(s)
- Shaimaa Mahmoud
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - Marjan Gharagozloo
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - Camille Simard
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - Denis Gris
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
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21
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Taş YÇ, Solaroğlu İ, Gürsoy-Özdemir Y. Spreading Depolarization Waves in Neurological Diseases: A Short Review about its Pathophysiology and Clinical Relevance. Curr Neuropharmacol 2019; 17:151-164. [PMID: 28925885 PMCID: PMC6343201 DOI: 10.2174/1570159x15666170915160707] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 09/03/2017] [Accepted: 09/09/2017] [Indexed: 02/05/2023] Open
Abstract
Lesion growth following acutely injured brain tissue after stroke, subarachnoid hemorrhage and traumatic brain injury is an important issue and a new target area for promising therapeutic interventions. Spreading depolarization or peri-lesion depolarization waves were demonstrated as one of the significant contributors of continued lesion growth. In this short review, we discuss the pathophysiology for SD forming events and try to list findings detected in neurological disorders like migraine, stroke, subarachnoid hemorrhage and traumatic brain injury in both human as well as experimental studies. Pharmacological and non-pharmacological treatment strategies are highlighted and future directions and research limitations are discussed.
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Affiliation(s)
| | | | - Yasemin Gürsoy-Özdemir
- Address correspondence to these authors at the Department of Neurosurgery, School of Medicine, Koç University, İstanbul, Turkey; Tel: +90 850 250 8250; E-mails: ,
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22
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Hadley G, Beard DJ, Couch Y, Neuhaus AA, Adriaanse BA, DeLuca GC, Sutherland BA, Buchan AM. Rapamycin in ischemic stroke: Old drug, new tricks? J Cereb Blood Flow Metab 2019; 39:20-35. [PMID: 30334673 PMCID: PMC6311672 DOI: 10.1177/0271678x18807309] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 08/16/2018] [Accepted: 09/06/2018] [Indexed: 12/19/2022]
Abstract
The significant morbidity that accompanies stroke makes it one of the world's most devastating neurological disorders. Currently, proven effective therapies have been limited to thrombolysis and thrombectomy. The window for the administration of these therapies is narrow, hampered by the necessity of rapidly imaging patients. A therapy that could extend this window by protecting neurons may improve outcome. Endogenous neuroprotection has been shown to be, in part, due to changes in mTOR signalling pathways and the instigation of productive autophagy. Inducing this effect pharmacologically could improve clinical outcomes. One such therapy already in use in transplant medicine is the mTOR inhibitor rapamycin. Recent evidence suggests that rapamycin is neuroprotective, not only via neuronal autophagy but also through its broader effects on other cells of the neurovascular unit. This review highlights the potential use of rapamycin as a multimodal therapy, acting on the blood-brain barrier, cerebral blood flow and inflammation, as well as directly on neurons. There is significant potential in applying this old drug in new ways to improve functional outcomes for patients after stroke.
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Affiliation(s)
- Gina Hadley
- Acute Stroke Programme, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Daniel J Beard
- Acute Stroke Programme, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Yvonne Couch
- Acute Stroke Programme, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Ain A Neuhaus
- Acute Stroke Programme, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Bryan A Adriaanse
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Gabriele C DeLuca
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Brad A Sutherland
- Acute Stroke Programme, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- School of Medicine, College of Health and Medicine, University of Tasmania, Hobart, Tasmania, Australia
| | - Alastair M Buchan
- Acute Stroke Programme, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Acute Vascular Imaging Centre, University of Oxford, Oxford University Hospitals, Oxford, UK
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23
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Abudara V, Retamal MA, Del Rio R, Orellana JA. Synaptic Functions of Hemichannels and Pannexons: A Double-Edged Sword. Front Mol Neurosci 2018; 11:435. [PMID: 30564096 PMCID: PMC6288452 DOI: 10.3389/fnmol.2018.00435] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/08/2018] [Indexed: 01/18/2023] Open
Abstract
The classical view of synapses as the functional contact between presynaptic and postsynaptic neurons has been challenged in recent years by the emerging regulatory role of glial cells. Astrocytes, traditionally considered merely supportive elements are now recognized as active modulators of synaptic transmission and plasticity at the now so-called "tripartite synapse." In addition, an increasing body of evidence indicates that beyond immune functions microglia also participate in various processes aimed to shape synaptic plasticity. Release of neuroactive compounds of glial origin, -process known as gliotransmission-, constitute a widespread mechanism through which glial cells can either potentiate or reduce the synaptic strength. The prevailing vision states that gliotransmission depends on an intracellular Ca2+/exocytotic-mediated release; notwithstanding, growing evidence is pointing at hemichannels (connexons) and pannexin channels (pannexons) as alternative non-vesicular routes for gliotransmitters efflux. In concurrence with this novel concept, both hemichannels and pannexons are known to mediate the transfer of ions and signaling molecules -such as ATP and glutamate- between the cytoplasm and the extracellular milieu. Importantly, recent reports show that glial hemichannels and pannexons are capable to perceive synaptic activity and to respond to it through changes in their functional state. In this article, we will review the current information supporting the "double edge sword" role of hemichannels and pannexons in the function of central and peripheral synapses. At one end, available data support the idea that these channels are chief components of a feedback control mechanism through which gliotransmitters adjust the synaptic gain in either resting or stimulated conditions. At the other end, we will discuss how the excitotoxic release of gliotransmitters and [Ca2+]i overload linked to the opening of hemichannels/pannexons might impact cell function and survival in the nervous system.
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Affiliation(s)
- Verónica Abudara
- Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile.,Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States.,Programa de Comunicación Celular en Cáncer, Instituto de Ciencias e Innovación en Medicina, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Juan A Orellana
- Departamento de Neurología, Escuela de Medicina and Centro Interdisciplinario de Neurociencias, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación y Estudio del Consumo de Alcohol en Adolescentes, Santiago, Chile
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24
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Lee EJ, Park JS, Lee YY, Kim DY, Kang JL, Kim HS. Anti-inflammatory and anti-oxidant mechanisms of an MMP-8 inhibitor in lipoteichoic acid-stimulated rat primary astrocytes: involvement of NF-κB, Nrf2, and PPAR-γ signaling pathways. J Neuroinflammation 2018; 15:326. [PMID: 30470240 PMCID: PMC6260848 DOI: 10.1186/s12974-018-1363-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Accepted: 11/07/2018] [Indexed: 01/06/2023] Open
Abstract
Background Recent evidence suggests that reactive astrocytes play an important role in neuroinflammation and neurodegenerative diseases. Thus, controlling astrocyte reactivity has been suggested as a promising strategy for treating neurodegenerative diseases. In the present study, we investigated whether a matrix metalloproteinase (MMP)-8 inhibitor, M8I, could control neuroinflammation in lipoteichoic acid (LTA)-stimulated rat primary astrocytes. Methods The effects of M8I on the expression of inducible nitric oxide synthase, cytokines, and MMPs were examined in LTA-stimulated rat primary astrocytes by ELISA, RT-PCR, and Western blot analysis. The effects of M8I on reactive oxygen species (ROS) generation and phase II antioxidant enzyme expression were examined by the DCF-DA assay, RT-PCR, and Western blot analysis. The detailed molecular mechanisms underlying the anti-inflammatory and antioxidant effects of M8I were analyzed by the electrophoretic mobility shift assay, the reporter gene assay, Western blot, and RT-PCR analysis. Results Treatment with LTA, a major cell wall component of Gram-positive bacteria, led to astrocyte activation and induced the expression of inflammatory molecules such as iNOS, COX-2, and pro-inflammatory cytokines. In addition, LTA induced the expression of MMPs such as MMP-1, MMP-3, MMP-8, MMP-9, and MMP-13 in rat primary astrocytes. Based on previous reports showing that MMP-8 plays a role as a proinflammatory mediator in microglia, we investigated whether MMP-8 is also involved in inflammatory reactions of reactive astrocytes. We found that treatment of astrocytes with M8I significantly inhibited LTA-induced expression of iNOS, TNF-α, IL-1β, IL-6, and TLR-2. In addition, M8I inhibited LTA-induced NF-κB, MAP kinase, and Akt activities, while it increased the anti-inflammatory PPAR-γ activities. Moreover, M8I showed antioxidant effects by suppressing ROS production in LTA- or H2O2-stimulated astrocytes. Interestingly, M8I increased the expression of phase II antioxidant enzymes such as hemeoxygenase-1, NQO1, catalase, and MnSOD by modulating the Nrf2/ARE signaling pathway. Conclusions The data collectively suggest the therapeutic potential of an MMP-8 inhibitor in neuroinflammatory disorders that are associated with astrocyte reactivity. Electronic supplementary material The online version of this article (10.1186/s12974-018-1363-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Eun-Jung Lee
- Department of Molecular Medicine, Tissue Injury Defense Research Center, School of Medicine, Ewha Womans University, Mok-6-dong 911-1, Yangchun-Ku, Seoul, 158-710, South Korea
| | - Jin-Sun Park
- Department of Molecular Medicine, Tissue Injury Defense Research Center, School of Medicine, Ewha Womans University, Mok-6-dong 911-1, Yangchun-Ku, Seoul, 158-710, South Korea
| | - Yu-Young Lee
- Department of Molecular Medicine, Tissue Injury Defense Research Center, School of Medicine, Ewha Womans University, Mok-6-dong 911-1, Yangchun-Ku, Seoul, 158-710, South Korea
| | - Do-Yeon Kim
- Department of Molecular Medicine, Tissue Injury Defense Research Center, School of Medicine, Ewha Womans University, Mok-6-dong 911-1, Yangchun-Ku, Seoul, 158-710, South Korea
| | - Jihee Lee Kang
- Department of Physiology, Tissue Injury Defense Research Center, School of Medicine, Ewha Womans University, Seoul, South Korea
| | - Hee-Sun Kim
- Department of Molecular Medicine, Tissue Injury Defense Research Center, School of Medicine, Ewha Womans University, Mok-6-dong 911-1, Yangchun-Ku, Seoul, 158-710, South Korea.
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25
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Wilson CS, Mongin AA. Cell Volume Control in Healthy Brain and Neuropathologies. CURRENT TOPICS IN MEMBRANES 2018; 81:385-455. [PMID: 30243438 DOI: 10.1016/bs.ctm.2018.07.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Regulation of cellular volume is a critical homeostatic process that is intimately linked to ionic and osmotic balance in the brain tissue. Because the brain is encased in the rigid skull and has a very complex cellular architecture, even minute changes in the volume of extracellular and intracellular compartments have a very strong impact on tissue excitability and function. The failure of cell volume control is a major feature of several neuropathologies, such as hyponatremia, stroke, epilepsy, hyperammonemia, and others. There is strong evidence that such dysregulation, especially uncontrolled cell swelling, plays a major role in adverse pathological outcomes. To protect themselves, brain cells utilize a variety of mechanisms to maintain their optimal volume, primarily by releasing or taking in ions and small organic molecules through diverse volume-sensitive ion channels and transporters. In principle, the mechanisms of cell volume regulation are not unique to the brain and share many commonalities with other tissues. However, because ions and some organic osmolytes (e.g., major amino acid neurotransmitters) have a strong impact on neuronal excitability, cell volume regulation in the brain is a surprisingly treacherous process, which may cause more harm than good. This topical review covers the established and emerging information in this rapidly developing area of physiology.
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Affiliation(s)
- Corinne S Wilson
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY, United States
| | - Alexander A Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY, United States; Department of Biophysics and Functional Diagnostics, Siberian State Medical University, Tomsk, Russian Federation
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26
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Gómez-Gonzalo M, Zehnder T, Requie LM, Bezzi P, Carmignoto G. Insights into the release mechanism of astrocytic glutamate evoking in neurons NMDA receptor-mediated slow depolarizing inward currents. Glia 2018; 66:2188-2199. [DOI: 10.1002/glia.23473] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/27/2018] [Accepted: 05/25/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Marta Gómez-Gonzalo
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
| | - Tamara Zehnder
- Department of Fundamental Neurosciences; University of Lausanne; Lausanne Switzerland
| | - Linda Maria Requie
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
| | - Paola Bezzi
- Department of Fundamental Neurosciences; University of Lausanne; Lausanne Switzerland
| | - Giorgio Carmignoto
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
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27
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Osei-Owusu J, Yang J, Vitery MDC, Qiu Z. Molecular Biology and Physiology of Volume-Regulated Anion Channel (VRAC). CURRENT TOPICS IN MEMBRANES 2018; 81:177-203. [PMID: 30243432 DOI: 10.1016/bs.ctm.2018.07.005] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The Volume-Regulated Anion Channel (VRAC) is activated by cell swelling and plays a key role in cell volume regulation. VRAC is ubiquitously expressed in vertebrate cells and also implicated in many other physiological and cellular processes including fluid secretion, glutamate release, membrane potential regulation, cell proliferation, migration, and apoptosis. Although its biophysical properties have been well characterized, the molecular identity of VRAC remained a mystery for almost three decades. The field was transformed by recent discoveries showing that the leucine-rich repeat-containing protein 8A (LRRC8A, also named SWELL1) and its four other homologs form heteromeric VRAC channels. The composition of LRRC8 subunits determines channel properties and substrate selectivity of a large variety of different VRACs. Incorporating purified SWELL1-containing protein complexes into lipid bilayers is sufficient to reconstitute channel activities, a finding that supports the decrease in intracellular ionic strength as the mechanism of VRAC activation during cell swelling. Characterization of Swell1 knockout mice uncovers the important role of VRAC in T cell development, pancreatic β-cell glucose-stimulated insulin secretion, and adipocyte metabolic function. The ability to permeate organic osmolytes and metabolites is a major feature of VRAC. The list of VRAC substrates is expected to grow, now also including some cancer drugs and antibiotics even under non-cell swelling conditions. Therefore, a critical role of VRAC in drug resistance and cell-cell communication is emerging. This review summarizes the exciting recent progress on the structure-function relationship and physiology of VRAC and discusses key future questions to be solved.
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Affiliation(s)
- James Osei-Owusu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Junhua Yang
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Maria Del Carmen Vitery
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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28
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Formaggio F, Saracino E, Mola MG, Rao SB, Amiry-Moghaddam M, Muccini M, Zamboni R, Nicchia GP, Caprini M, Benfenati V. LRRC8A is essential for swelling-activated chloride current and for regulatory volume decrease in astrocytes. FASEB J 2018; 33:101-113. [PMID: 29957062 DOI: 10.1096/fj.201701397rr] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Consolidated evidence indicates that astroglial cells are critical in the homeostatic regulation of cellular volume by means of ion channels and aquaporin-4. Volume-regulated anion channel (VRAC) is the chloride channel that is activated upon cell swelling and critically contributes to cell volume regulation in astrocytes. The molecular identity of VRAC has been recently defined, revealing that it belongs to the leucine-rich repeat-containing 8 (LRRC8) protein family. However, there is a lack of evidence demonstrating that LRRC8A underpins VRAC currents in astrocyte. Nonetheless, direct evidence of the role of LRRC8A in astrocytic regulatory volume decrease remains to be proved. Here, we aim to bridge this gap in knowledge by combining RNA interference specific for LRRC8A with patch-clamp analyses and a water-permeability assay. We demonstrated that LRRC8A molecular expression is essential for swelling-activated chloride current via VRAC in primary-cultured cortical astrocytes. The knockdown of LRRC8A with a specific short interference RNA abolished the recovery of the cell volume after swelling induced by hypotonic challenge. In addition, immunoblotting, immunofluorescence, confocal imaging, and immunogold electron microscopy demonstrated that LRRC8A is expressed in the plasma membrane of primary cortical astrocytes and in situ in astrocytes at the perivascular interface with endothelial cells. Collectively, our results suggest that LRRC8A is an essential subunit of VRAC and a key factor for astroglial volume homeostasis.-Formaggio, F., Saracino, E., Mola, M. G., Rao, S. B., Amiry-Moghaddam, M., Muccini, M., Zamboni, R., Nicchia, G. P., Caprini, M., Benfenati, V. LRRC8A is essential for swelling-activated chloride current and for regulatory volume decrease in astrocytes.
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Affiliation(s)
- Francesco Formaggio
- Laboratory of Human and General Physiology, Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy.,Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy
| | - Emanuela Saracino
- Institute for the Organic Synthesis and Photoreactivity, National Research Council of Italy, Bologna, Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnologies, and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari Aldo Moro, Bari, Italy
| | - Shreyas Balachandra Rao
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Mahmood Amiry-Moghaddam
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Michele Muccini
- Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy
| | - Roberto Zamboni
- Institute for the Organic Synthesis and Photoreactivity, National Research Council of Italy, Bologna, Italy
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnologies, and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari Aldo Moro, Bari, Italy.,Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York, USA
| | - Marco Caprini
- Laboratory of Human and General Physiology, Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy.,Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy
| | - Valentina Benfenati
- Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy.,Institute for the Organic Synthesis and Photoreactivity, National Research Council of Italy, Bologna, Italy
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29
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Nasr B, Chatterton R, Yong JHM, Jamshidi P, D'Abaco GM, Bjorksten AR, Kavehei O, Chana G, Dottori M, Skafidas E. Self-Organized Nanostructure Modified Microelectrode for Sensitive Electrochemical Glutamate Detection in Stem Cells-Derived Brain Organoids. BIOSENSORS 2018; 8:E14. [PMID: 29401739 PMCID: PMC5872062 DOI: 10.3390/bios8010014] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 01/30/2018] [Accepted: 01/31/2018] [Indexed: 02/05/2023]
Abstract
Neurons release neurotransmitters such as glutamate to communicate with each other and to coordinate brain functioning. As increased glutamate release is indicative of neuronal maturation and activity, a system that can measure glutamate levels over time within the same tissue and/or culture system is highly advantageous for neurodevelopmental investigation. To address such challenges, we develop for the first time a convenient method to realize functionalized borosilicate glass capillaries with nanostructured texture as an electrochemical biosensor to detect glutamate release from cerebral organoids generated from human embryonic stem cells (hESC) that mimic various brain regions. The biosensor shows a clear catalytic activity toward the oxidation of glutamate with a sensitivity of 93 ± 9.5 nA·µM-1·cm-2. It was found that the enzyme-modified microelectrodes can detect glutamate in a wide linear range from 5 µM to 0.5 mM with a limit of detection (LOD) down to 5.6 ± 0.2 µM. Measurements were performed within the organoids at different time points and consistent results were obtained. This data demonstrates the reliability of the biosensor as well as its usefulness in measuring glutamate levels across time within the same culture system.
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Affiliation(s)
- Babak Nasr
- Centre for Neural Engineering, The University of Melbourne, Melbourne, VIC 3053, Australia.
- The Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia.
- ARC Centre of Excellence for Integrative Brain Function, The University of Melbourne, Melbourne, VIC 3010, Australia.
| | - Rachael Chatterton
- Centre for Neural Engineering, The University of Melbourne, Melbourne, VIC 3053, Australia.
| | - Jason Hsien Ming Yong
- Centre for Neural Engineering, The University of Melbourne, Melbourne, VIC 3053, Australia.
- The Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia.
| | - Pegah Jamshidi
- Centre for Neural Engineering, The University of Melbourne, Melbourne, VIC 3053, Australia.
| | - Giovanna Marisa D'Abaco
- The Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia.
| | - Andrew Robin Bjorksten
- The Department of Anaesthesia & Pain Management, Royal Melbourne Hospital, Parkville, VIC 3050, Australia.
| | - Omid Kavehei
- Faculty of Engineering and Information Technology, The University of Sydney, Sydney, NSW 2006, Australia.
| | - Gursharan Chana
- Centre for Neural Engineering, The University of Melbourne, Melbourne, VIC 3053, Australia.
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Melbourne, VIC 3050, Australia.
| | - Mirella Dottori
- Centre for Neural Engineering, The University of Melbourne, Melbourne, VIC 3053, Australia.
- The Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia.
- Illawarra Health and Medical Research Institute, Centre for Molecular and Medical Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia.
| | - Efstratios Skafidas
- Centre for Neural Engineering, The University of Melbourne, Melbourne, VIC 3053, Australia.
- The Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia.
- ARC Centre of Excellence for Integrative Brain Function, The University of Melbourne, Melbourne, VIC 3010, Australia.
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30
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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31
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 899] [Impact Index Per Article: 149.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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32
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Bai W, Zhou YG. Homeostasis of the Intraparenchymal-Blood Glutamate Concentration Gradient: Maintenance, Imbalance, and Regulation. Front Mol Neurosci 2017; 10:400. [PMID: 29259540 PMCID: PMC5723322 DOI: 10.3389/fnmol.2017.00400] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 11/20/2017] [Indexed: 12/25/2022] Open
Abstract
It is widely accepted that glutamate is the most important excitatory neurotransmitter in the central nervous system (CNS). However, there is also a large amount of glutamate in the blood. Generally, the concentration gradient of glutamate between intraparenchymal and blood environments is stable. However, this gradient is dramatically disrupted under a variety of pathological conditions, resulting in an amplifying cascade that causes a series of pathological reactions in the CNS and peripheral organs. This eventually seriously worsens a patient’s prognosis. These two “isolated” systems are rarely considered as a whole even though they mutually influence each other. In this review, we summarize what is currently known regarding the maintenance, imbalance and regulatory mechanisms that control the intraparenchymal-blood glutamate concentration gradient, discuss the interrelationships between these systems and further explore their significance in clinical practice.
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Affiliation(s)
- Wei Bai
- Molecular Biology Center, State Key Laboratory of Trauma, Burn, and Combined Injury, Research Institute of Surgery and Daping Hospital, Third Military Medical University, Chongqing, China
| | - Yuan-Guo Zhou
- Molecular Biology Center, State Key Laboratory of Trauma, Burn, and Combined Injury, Research Institute of Surgery and Daping Hospital, Third Military Medical University, Chongqing, China
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33
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Lohman AW, Weilinger NL, Santos SM, Bialecki J, Werner AC, Anderson CL, Thompson RJ. Regulation of pannexin channels in the central nervous system by Src family kinases. Neurosci Lett 2017; 695:65-70. [PMID: 28911820 DOI: 10.1016/j.neulet.2017.09.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 07/24/2017] [Accepted: 09/10/2017] [Indexed: 02/06/2023]
Abstract
Pannexins form single membrane channels that regulate the passage of ions, small molecules and metabolites between the intra- and extracellular compartments. In the central nervous system, these channels are integrated into numerous signaling cascades that shape brain physiology and pathology. Post-translational modification of pannexins is complex, with phosphorylation emerging as a prominent form of functional regulation. While much is still not known regarding the specific kinases and modified amino acids, recent reports support a role for Src family tyrosine kinases (SFK) in regulating pannexin channel activity. This review outlines the current evidence supporting SFK-dependent pannexin phosphorylation in the CNS and examines the importance of these modifications in the healthy and diseased brain.
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Affiliation(s)
- Alexander W Lohman
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Nicholas L Weilinger
- Djavad Mowafaghian Centre for Brain Health, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Silva Mf Santos
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Jennifer Bialecki
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Allison C Werner
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Connor L Anderson
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Roger J Thompson
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
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34
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Ferrer I. Diversity of astroglial responses across human neurodegenerative disorders and brain aging. Brain Pathol 2017; 27:645-674. [PMID: 28804999 PMCID: PMC8029391 DOI: 10.1111/bpa.12538] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 05/24/2017] [Indexed: 12/11/2022] Open
Abstract
Astrogliopathy refers to alterations of astrocytes occurring in diseases of the nervous system, and it implies the involvement of astrocytes as key elements in the pathogenesis and pathology of diseases and injuries of the central nervous system. Reactive astrocytosis refers to the response of astrocytes to different insults to the nervous system, whereas astrocytopathy indicates hypertrophy, atrophy/degeneration and loss of function and pathological remodeling occurring as a primary cause of a disease or as a factor contributing to the development and progression of a particular disease. Reactive astrocytosis secondary to neuron loss and astrocytopathy due to intrinsic alterations of astrocytes occur in neurodegenerative diseases, overlap each other, and, together with astrocyte senescence, contribute to disease-specific astrogliopathy in aging and neurodegenerative diseases with abnormal protein aggregates in old age. In addition to the well-known increase in glial fibrillary acidic protein and other proteins in reactive astrocytes, astrocytopathy is evidenced by deposition of abnormal proteins such as β-amyloid, hyper-phosphorylated tau, abnormal α-synuclein, mutated huntingtin, phosphorylated TDP-43 and mutated SOD1, and PrPres , in Alzheimer's disease, tauopathies, Lewy body diseases, Huntington's disease, amyotrophic lateral sclerosis and Creutzfeldt-Jakob disease, respectively. Astrocytopathy in these diseases can also be manifested by impaired glutamate transport; abnormal metabolism and release of neurotransmitters; altered potassium, calcium and water channels resulting in abnormal ion and water homeostasis; abnormal glucose metabolism; abnormal lipid and, particularly, cholesterol metabolism; increased oxidative damage and altered oxidative stress responses; increased production of cytokines and mediators of the inflammatory response; altered expression of connexins with deterioration of cell-to-cell networks and transfer of gliotransmitters; and worsening function of the blood brain barrier, among others. Increased knowledge of these aspects will permit a better understanding of brain aging and neurodegenerative diseases in old age as complex disorders in which neurons are not the only players.
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Affiliation(s)
- Isidro Ferrer
- Department of Pathology and Experimental TherapeuticsUniversity of BarcelonaBarcelonaSpain
- Institute of NeuropathologyPathologic Anatomy Service, Bellvitge University Hospital, IDIBELL, Hospitalet de LlobregatBarcelonaSpain
- Institute of NeurosciencesUniversity of BarcelonaBarcelonaSpain
- Biomedical Network Research Center on Neurodegenerative Diseases (CIBERNED), Institute Carlos IIIMadridSpain
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Inhibition of Gap Junction Elevates Glutamate Uptake in Cultured Astrocytes. Neurochem Res 2017; 43:59-65. [PMID: 28589517 DOI: 10.1007/s11064-017-2316-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 05/26/2017] [Accepted: 05/27/2017] [Indexed: 10/19/2022]
Abstract
Glutamate uptake is a main function of astrocytes to keep extracellular glutamate levels low and protect neurons against glutamate-induced excitotoxicity. On the other hand, astrocyte networks formed by gap junctions, which are consisted with connexins and connecting neighboring cells, are reported to play a critical role in maintaining the homeostasis in the brain. In the present study, we examined the effects of gap junction inhibitors on the glutamate uptake activity in cultured rat cortical astrocytes. At first, we confirmed the effects of gap junction inhibitors, 1-octanol and carbenoxolone, on cell-cell communication by the scrape-loading assay using a fluorescent dye Lucifer yellow. Both of 1-octanol and carbenoxolone treatments for 20 min in cultured astrocytes significantly suppressed the cell-cell communication assessed as the distance of dye-spreading. 1-octanol and carbenoxolone increased the glutamate uptake by astrocytes and glutamate aspartate transporter (GLAST) expression on the cell membrane. These results suggest that gap junction inhibitors increase the glutamate uptake activity through the increase of GLAST proteins located on the cell membrane. The regulation of gap junction in astrocytes might protect neurons against glutamate-induced excitotoxicity.
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Kaczor PT, Mozrzymas JW. Key Metabolic Enzymes Underlying Astrocytic Upregulation of GABAergic Plasticity. Front Cell Neurosci 2017; 11:144. [PMID: 28559800 PMCID: PMC5432623 DOI: 10.3389/fncel.2017.00144] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 05/02/2017] [Indexed: 11/30/2022] Open
Abstract
GABAergic plasticity is recognized as a key mechanism of shaping the activity of the neuronal networks. However, its description is challenging because of numerous neuron-specific mechanisms. In particular, while essential role of glial cells in the excitatory plasticity is well established, their involvement in GABAergic plasticity only starts to emerge. To address this problem, we used two models: neuronal cell culture (NC) and astrocyte-neuronal co-culture (ANCC), where we chemically induced long-term potentiation at inhibitory synapses (iLTP). iLTP could be induced both in NC and ANCC but in ANCC its extent was larger. Importantly, this functional iLTP manifestation was accompanied by an increase in gephyrin puncta size. Furthermore, blocking astrocyte Krebs cycle with fluoroacetate (FA) in ANCC prevented enhancement of both mIPSC amplitude and gephyrin puncta size but this effect was not observed in NC, indicating a key role in neuron-astrocyte cross-talk. Blockade of monocarboxylate transport with α-Cyano-4-hydroxycinnamic acid (4CIN) abolished iLTP both in NC and ANCC and in the latter model prevented also enlargement of gephyrin puncta. Similarly, blockade of glycogen phosphorylase with BAYU6751 prevented enlargement of gephyrin puncta upon iLTP induction. Finally, block of glutamine synthetase with methionine sulfoxide (MSO) nearly abolished mIPSC increase in both NMDA stimulated cell groups but did not prevent enlargement of gephyrin puncta. In conclusion, we provide further evidence that GABAergic plasticity is strongly regulated by astrocytes and the underlying mechanisms involve key metabolic enzymes. Considering the strategic role of GABAergic interneurons, the plasticity described here indicates possible mechanism whereby metabolism regulates the network activity.
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Affiliation(s)
- Przemysław T Kaczor
- Department of Molecular Physiology and Neurobiology, Faculty of Biological Sciences, University of WrocławWrocław, Poland
| | - Jerzy W Mozrzymas
- Department of Molecular Physiology and Neurobiology, Faculty of Biological Sciences, University of WrocławWrocław, Poland.,Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical UniversityWrocław, Poland
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Role of Nonneuronal TRPV4 Signaling in Inflammatory Processes. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 79:117-139. [PMID: 28528666 DOI: 10.1016/bs.apha.2017.03.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Transient receptor potential (TRP) ion channels are important signaling components in nociceptive and inflammatory pathways. This is attributed to their ability to function as polymodal sensors of environmental stimuli (chemical and mechanical) and as effector molecules in receptor signaling pathways. TRP vanilloid 4 (TRPV4) is a nonselective cation channel that is activated by multiple endogenous stimuli including shear stress, membrane stretch, and arachidonic acid metabolites. TRPV4 contributes to many important physiological processes and dysregulation of its activity is associated with chronic conditions of metabolism, inflammation, peripheral neuropathies, musculoskeletal development, and cardiovascular regulation. Mechanosensory and receptor- or lipid-mediated signaling functions of TRPV4 have historically been attributed to central and peripheral neurons. However, with the development of potent and selective pharmacological tools, transgenic mice and improved molecular and imaging techniques, many new roles for TRPV4 have been revealed in nonneuronal cells. In this chapter, we discuss these recent findings and highlight the need for greater characterization of TRPV4-mediated signaling in nonneuronal cell types that are either directly associated with neurons or indirectly control their excitability through release of sensitizing cellular factors. We address the integral role of these cells in sensory and inflammatory processes as well as their importance when considering undesirable on-target effects that may be caused by systemic delivery of TRPV4-selective pharmaceutical agents for treatment of chronic diseases. In future, this will drive a need for targeted drug delivery strategies to regulate such a diverse and promiscuous protein.
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Turning down the volume: Astrocyte volume change in the generation and termination of epileptic seizures. Neurobiol Dis 2017; 104:24-32. [PMID: 28438505 DOI: 10.1016/j.nbd.2017.04.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 04/18/2017] [Accepted: 04/20/2017] [Indexed: 12/20/2022] Open
Abstract
Approximately 1% of the global population suffers from epilepsy, a class of disorders characterized by recurrent and unpredictable seizures. Of these cases roughly one-third are refractory to current antiepileptic drugs, which typically target neuronal excitability directly. The events leading to seizure generation and epileptogenesis remain largely unknown, hindering development of new treatments. Some recent experimental models of epilepsy have provided compelling evidence that glial cells, especially astrocytes, could be central to seizure development. One of the proposed mechanisms for astrocyte involvement in seizures is astrocyte swelling, which may promote pathological neuronal firing and synchrony through reduction of the extracellular space and elevated glutamate concentrations. In this review, we discuss the common conditions under which astrocytes swell, the resultant effects on neural excitability, and how seizure development may ultimately be influenced by these effects.
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Ryoo K, Park JY. Two-pore Domain Potassium Channels in Astrocytes. Exp Neurobiol 2016; 25:222-232. [PMID: 27790056 PMCID: PMC5081468 DOI: 10.5607/en.2016.25.5.222] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 09/01/2016] [Accepted: 09/15/2016] [Indexed: 12/23/2022] Open
Abstract
Two-pore domain potassium (K2P) channels have a distinct structure and channel properties, and are involved in a background K+ current. The 15 members of the K2P channels are identified and classified into six subfamilies on the basis of their sequence similarities. The activity of the channels is dynamically regulated by various physical, chemical, and biological effectors. The channels are expressed in a wide variety of tissues in mammals in an isoform specific manner, and play various roles in many physiological and pathophysiological conditions. To function as channels, the K2P channels form dimers, and some isoforms form heterodimers that provide diversity in channel properties. In the brain, TWIK1, TREK1, TREK2, TRAAK, TASK1, and TASK3 are predominantly expressed in various regions, including the cerebral cortex, dentate gyrus, CA1-CA3, and granular layer of the cerebellum. TWIK1, TREK1, and TASK1 are highly expressed in astrocytes, where they play specific cellular roles. Astrocytes keep leak K+ conductance, called the passive conductance, which mainly involves TWIK1-TREK1 heterodimeric channel. TWIK1 and TREK1 also mediate glutamate release from astrocytes in an exocytosis-independent manner. The expression of TREK1 and TREK2 in astrocytes increases under ischemic conditions, that enhance neuroprotection from ischemia. Accumulated evidence has indicated that astrocytes, together with neurons, are involved in brain function, with the K2P channels playing critical role in these astrocytes.
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Affiliation(s)
- Kanghyun Ryoo
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Korea
| | - Jae-Yong Park
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Korea
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Bang J, Kim HY, Lee H. Optogenetic and Chemogenetic Approaches for Studying Astrocytes and Gliotransmitters. Exp Neurobiol 2016; 25:205-221. [PMID: 27790055 PMCID: PMC5081467 DOI: 10.5607/en.2016.25.5.205] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 08/19/2016] [Accepted: 08/19/2016] [Indexed: 12/20/2022] Open
Abstract
The brain consists of heterogeneous populations of neuronal and non-neuronal cells. The revelation of their connections and interactions is fundamental to understanding normal brain functions as well as abnormal changes in pathological conditions. Optogenetics and chemogenetics have been developed to allow functional manipulations both in vitro and in vivo to examine causal relationships between cellular changes and functional outcomes. These techniques are based on genetically encoded effector molecules that respond exclusively to exogenous stimuli, such as a certain wavelength of light or a synthetic ligand. Activation of effector molecules provokes diverse intracellular changes, such as an influx or efflux of ions, depolarization or hyperpolarization of membranes, and activation of intracellular signaling cascades. Optogenetics and chemogenetics have been applied mainly to the study of neuronal circuits, but their use in studying non-neuronal cells has been gradually increasing. Here we introduce recent studies that have employed optogenetics and chemogenetics to reveal the function of astrocytes and gliotransmitters.
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Affiliation(s)
- Juwon Bang
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Hak Yeong Kim
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Hyosang Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
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Orellana JA. Physiological Functions of Glial Cell Hemichannels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:93-108. [DOI: 10.1007/978-3-319-40764-7_5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bazargani N, Attwell D. Astrocyte calcium signaling: the third wave. Nat Neurosci 2016; 19:182-9. [PMID: 26814587 DOI: 10.1038/nn.4201] [Citation(s) in RCA: 559] [Impact Index Per Article: 69.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 11/10/2015] [Indexed: 02/06/2023]
Abstract
The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function.
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Affiliation(s)
- Narges Bazargani
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
| | - David Attwell
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
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Abeysinghe HCS, Phillips EL, Chin-Cheng H, Beart PM, Roulston CL. Modulating Astrocyte Transition after Stroke to Promote Brain Rescue and Functional Recovery: Emerging Targets Include Rho Kinase. Int J Mol Sci 2016; 17:288. [PMID: 26927079 PMCID: PMC4813152 DOI: 10.3390/ijms17030288] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 01/26/2016] [Accepted: 02/05/2016] [Indexed: 01/13/2023] Open
Abstract
Stroke is a common and serious condition, with few therapies. Whilst previous focus has been directed towards biochemical events within neurons, none have successfully prevented the progression of injury that occurs in the acute phase. New targeted treatments that promote recovery after stroke might be a better strategy and are desperately needed for the majority of stroke survivors. Cells comprising the neurovascular unit, including blood vessels and astrocytes, present an alternative target for supporting brain rescue and recovery in the late phase of stroke, since alteration in the unit also occurs in regions outside of the lesion. One of the major changes in the unit involves extensive morphological transition of astrocytes resulting in altered energy metabolism, decreased glutamate reuptake and recycling, and retraction of astrocyte end feed from both blood vessels and neurons. Whilst globally inhibiting transitional change in astrocytes after stroke is reported to result in further damage and functional loss, we discuss the available evidence to suggest that the transitional activation of astrocytes after stroke can be modulated for improved outcomes. In particular, we review the role of Rho-kinase (ROCK) in reactive gliosis and show that inhibiting ROCK after stroke results in reduced scar formation and improved functional recovery.
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Affiliation(s)
- Hima Charika S Abeysinghe
- Neurotrauma Research, Department of Medicine, St Vincent's Campus, University of Melbourne, Parkville, VIC 3065, Australia.
- Department of Surgery, St Vincent's Campus, University of Melbourne, Parkville, VIC 3065, Australia.
| | - Ellie L Phillips
- Department of Biochemistry and Molecular Biology, Bio21 Insitute, University of Melbourne, Parkville, VIC 3010, Australia.
| | - Heung Chin-Cheng
- Department of Biochemistry and Molecular Biology, Bio21 Insitute, University of Melbourne, Parkville, VIC 3010, Australia.
| | - Philip M Beart
- The Florey Institute of Neuroscience and Mental Health, Melbourne Brain Centre, Parkville, VIC 3010, Australia.
| | - Carli L Roulston
- Neurotrauma Research, Department of Medicine, St Vincent's Campus, University of Melbourne, Parkville, VIC 3065, Australia.
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Del Rio R, Quintanilla RA, Orellana JA, Retamal MA. Neuron-Glia Crosstalk in the Autonomic Nervous System and Its Possible Role in the Progression of Metabolic Syndrome: A New Hypothesis. Front Physiol 2015; 6:350. [PMID: 26648871 PMCID: PMC4664731 DOI: 10.3389/fphys.2015.00350] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 11/09/2015] [Indexed: 01/26/2023] Open
Abstract
Metabolic syndrome (MS) is characterized by the following physiological alterations: increase in abdominal fat, insulin resistance, high concentration of triglycerides, low levels of HDL, high blood pressure, and a generalized inflammatory state. One of the pathophysiological hallmarks of this syndrome is the presence of neurohumoral activation, which involve autonomic imbalance associated to hyperactivation of the sympathetic nervous system. Indeed, enhanced sympathetic drive has been linked to the development of endothelial dysfunction, hypertension, stroke, myocardial infarct, and obstructive sleep apnea. Glial cells, the most abundant cells in the central nervous system, control synaptic transmission, and regulate neuronal function by releasing bioactive molecules called gliotransmitters. Recently, a new family of plasma membrane channels called hemichannels has been described to allow the release of gliotransmitters and modulate neuronal firing rate. Moreover, a growing amount of evidence indicates that uncontrolled hemichannel opening could impair glial cell functions, affecting synaptic transmission and neuronal survival. Given that glial cell functions are disturbed in various metabolic diseases, we hypothesize that progression of MS may relies on hemichannel-dependent impairment of glial-to-neuron communication by a mechanism related to dysfunction of inflammatory response and mitochondrial metabolism of glial cells. In this manuscript, we discuss how glial cells may contribute to the enhanced sympathetic drive observed in MS, and shed light about the possible role of hemichannels in this process.
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Affiliation(s)
- Rodrigo Del Rio
- Centro de Investigación Biomédica, Universidad Autónoma de Chile Santiago, Chile ; Dirección de Investigación, Universidad Científica del Sur Lima, Perú
| | | | - Juan A Orellana
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina. Clínica Alemana Universidad del Desarrollo Santiago, Chile
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Mongin AA. Volume-regulated anion channel--a frenemy within the brain. Pflugers Arch 2015; 468:421-41. [PMID: 26620797 DOI: 10.1007/s00424-015-1765-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/16/2015] [Accepted: 11/20/2015] [Indexed: 10/22/2022]
Abstract
The volume-regulated anion channel (VRAC) is a ubiquitously expressed yet highly enigmatic member of the superfamily of chloride/anion channels. It is activated by cellular swelling and mediates regulatory cell volume decrease in a majority of vertebrate cells, including those in the central nervous system (CNS). In the brain, besides its crucial role in cellular volume regulation, VRAC is thought to play a part in cell proliferation, apoptosis, migration, and release of physiologically active molecules. Although these roles are not exclusive to the CNS, the relative significance of VRAC in the brain is amplified by several unique aspects of its physiology. One important example is the contribution of VRAC to the release of the excitatory amino acid neurotransmitters glutamate and aspartate. This latter process is thought to have impact on both normal brain functioning (such as astrocyte-neuron signaling) and neuropathology (via promoting the excitotoxic death of neuronal cells in stroke and traumatic brain injury). In spite of much work in the field, the molecular nature of VRAC remained unknown until less than 2 years ago. Two pioneer publications identified VRAC as the heterohexamer formed by the leucine-rich repeat-containing 8 (LRRC8) proteins. These findings galvanized the field and are likely to result in dramatic revisions to our understanding of the place and role of VRAC in the brain, as well as other organs and tissues. The present review briefly recapitulates critical findings in the CNS and focuses on anticipated impact on the LRRC8 discovery on further progress in neuroscience research.
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Affiliation(s)
- Alexander A Mongin
- Center for Neuropharmacology and Neuroscience, Albany Medical College, 47 New Scotland Ave., Albany, NY, 12208, USA.
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Sahlender DA, Savtchouk I, Volterra A. What do we know about gliotransmitter release from astrocytes? Philos Trans R Soc Lond B Biol Sci 2015; 369:20130592. [PMID: 25225086 PMCID: PMC4173278 DOI: 10.1098/rstb.2013.0592] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Astrocytes participate in information processing by actively modulating synaptic properties via gliotransmitter release. Various mechanisms of astrocytic release have been reported, including release from storage organelles via exocytosis and release from the cytosol via plasma membrane ion channels and pumps. It is still not fully clear which mechanisms operate under which conditions, but some of them, being Ca2+-regulated, may be physiologically relevant. The properties of Ca2+-dependent transmitter release via exocytosis or via ion channels are different and expected to produce different extracellular transmitter concentrations over time and to have distinct functional consequences. The molecular aspects of these two release pathways are still under active investigation. Here, we discuss the existing morphological and functional evidence in support of either of them. Transgenic mouse models, specific antagonists and localization studies have provided insight into regulated exocytosis, albeit not in a systematic fashion. Even more remains to be uncovered about the details of channel-mediated release. Better functional tools and improved ultrastructural approaches are needed in order fully to define specific modalities and effects of astrocytic gliotransmitter release pathways.
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Affiliation(s)
- Daniela A Sahlender
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, Lausanne 1005, Switzerland
| | - Iaroslav Savtchouk
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, Lausanne 1005, Switzerland
| | - Andrea Volterra
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, Lausanne 1005, Switzerland
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Ropert N, Jalil A, Li D. Expression and cellular function of vSNARE proteins in brain astrocytes. Neuroscience 2015; 323:76-83. [PMID: 26518463 DOI: 10.1016/j.neuroscience.2015.10.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 10/07/2015] [Accepted: 10/21/2015] [Indexed: 12/27/2022]
Abstract
Gray matter protoplasmic astrocytes, a major type of glial cell in the mammalian brain, extend thin processes ensheathing neuronal synaptic terminals. Albeit electrically silent, astrocytes respond to neuronal activity with Ca(2+) signals that trigger the release of gliotransmitters, such as glutamate, d-serine, and ATP, which modulate synaptic transmission. It has been suggested that the astrocytic processes, together with neuronal pre- and post-synaptic elements, constitute a tripartite synapse, and that astrocytes actively regulate information processing. Astrocytic vesicles expressing VAMP2 and VAMP3 vesicular SNARE (vSNARE) proteins have been suggested to be a key feature of the tripartite synapse and mediate gliotransmitter release through Ca(2+)-regulated exocytosis. However, the concept of exocytotic release of gliotransmitters by astrocytes has been challenged. Here we review studies investigating the expression profile of VAMP2 and VAMP3 vSNARE proteins in rodent astrocytes, and the functional implication of VAMP2/VAMP3 vesicles in astrocyte signaling. We also discuss our recent data suggesting that astrocytic VAMP3 vesicles regulate the trafficking of glutamate transporters at the plasma membrane and glutamate uptake. A better understanding of the functional consequences of the astrocytic vSNARE vesicles on glutamate signaling, neuronal excitability and plasticity, will require the development of new strategies to selectively interrogate the astrocytic vesicles trafficking in vivo.
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Affiliation(s)
- N Ropert
- Brain Physiology Laboratory, CNRS UMR8118, Paris F-75006, France; Fédération de Recherche en Neurosciences, FR 3636, Université Paris Descartes, 45 rue des Saints Pères, Paris F-75006, France; Sorbonne Paris Cité, 190, avenue de France, Paris F-75013, France
| | - A Jalil
- Brain Physiology Laboratory, CNRS UMR8118, Paris F-75006, France; Fédération de Recherche en Neurosciences, FR 3636, Université Paris Descartes, 45 rue des Saints Pères, Paris F-75006, France; Sorbonne Paris Cité, 190, avenue de France, Paris F-75013, France
| | - D Li
- Brain Physiology Laboratory, CNRS UMR8118, Paris F-75006, France; Fédération de Recherche en Neurosciences, FR 3636, Université Paris Descartes, 45 rue des Saints Pères, Paris F-75006, France; Sorbonne Paris Cité, 190, avenue de France, Paris F-75013, France.
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Lauderdale K, Murphy T, Tung T, Davila D, Binder DK, Fiacco TA. Osmotic Edema Rapidly Increases Neuronal Excitability Through Activation of NMDA Receptor-Dependent Slow Inward Currents in Juvenile and Adult Hippocampus. ASN Neuro 2015; 7:7/5/1759091415605115. [PMID: 26489684 PMCID: PMC4623564 DOI: 10.1177/1759091415605115] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cellular edema (cell swelling) is a principal component of numerous brain disorders including ischemia, cortical spreading depression, hyponatremia, and epilepsy. Cellular edema increases seizure-like activity in vitro and in vivo, largely through nonsynaptic mechanisms attributable to reduction of the extracellular space. However, the types of excitability changes occurring in individual neurons during the acute phase of cell volume increase remain unclear. Using whole-cell patch clamp techniques, we report that one of the first effects of osmotic edema on excitability of CA1 pyramidal cells is the generation of slow inward currents (SICs), which initiate after approximately 1 min. Frequency of SICs increased as osmolarity decreased in a dose-dependent manner. Imaging of real-time volume changes in astrocytes revealed that neuronal SICs occurred while astrocytes were still in the process of swelling. SICs evoked by cell swelling were mainly nonsynaptic in origin and NMDA receptor-dependent. To better understand the relationship between SICs and changes in neuronal excitability, recordings were performed in increasingly physiological conditions. In the absence of any added pharmacological reagents or imposed voltage clamp, osmotic edema induced excitatory postsynaptic potentials and burst firing over the same timecourse as SICs. Like SICs, action potentials were blocked by NMDAR antagonists. Effects were more pronounced in adult (8-20 weeks old) compared with juvenile (P15-P21) mice. Together, our results indicate that cell swelling triggered by reduced osmolarity rapidly increases neuronal excitability through activation of NMDA receptors. Our findings have important implications for understanding nonsynaptic mechanisms of epilepsy in relation to cell swelling and reduction of the extracellular space.
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Affiliation(s)
- Kelli Lauderdale
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
| | - Thomas Murphy
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
| | - Tina Tung
- Department of Cell Biology and Neuroscience, Riverside, CA, USA
| | - David Davila
- Department of Cell Biology and Neuroscience, Riverside, CA, USA
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA Division of Biomedical Sciences, UC Riverside School of Medicine, CA, USA
| | - Todd A Fiacco
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
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Li H, Xie Y, Zhang N, Yu Y, Zhang Q, Ding S. Disruption of IP₃R2-mediated Ca²⁺ signaling pathway in astrocytes ameliorates neuronal death and brain damage while reducing behavioral deficits after focal ischemic stroke. Cell Calcium 2015; 58:565-76. [PMID: 26433454 DOI: 10.1016/j.ceca.2015.09.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 09/19/2015] [Accepted: 09/21/2015] [Indexed: 12/12/2022]
Abstract
Inositol trisphosphate receptor (IP3R)-mediated intracellular Ca(2+) increase is the major Ca(2+) signaling pathway in astrocytes in the central nervous system (CNS). Ca(2+) increases in astrocytes have been found to modulate neuronal function through gliotransmitter release. We previously demonstrated that astrocytes exhibit enhanced Ca(2+) signaling in vivo after photothrombosis (PT)-induced ischemia, which is largely due to the activation of G-protein coupled receptors (GPCRs). The aim of this study is to investigate the role of astrocytic IP3R-mediated Ca(2+) signaling in neuronal death, brain damage and behavior outcomes after PT. For this purpose, we conducted experiments using homozygous type 2 IP3R (IP3R2) knockout (KO) mice. Histological and immunostaining studies showed that IP3R2 KO mice were indeed deficient in IP3R2 in astrocytes and exhibited normal brain cytoarchitecture. IP3R2 KO mice also had the same densities of S100β+ astrocytes and NeuN+ neurons in the cortices, and exhibited the same glial fibrillary acidic protein (GFAP) and glial glutamate transporter (GLT-1) levels in the cortices and hippocampi as compared with wild type (WT) mice. Two-photon (2-P) imaging showed that IP3R2 KO mice did not exhibit ATP-induced Ca(2+) waves in vivo in the astrocytic network, which verified the disruption of IP3R-mediated Ca(2+) signaling in astrocytes of these mice. When subject to PT, IP3R2 KO mice had smaller infarction than WT mice in acute and chronic phases of ischemia. IP3R2 KO mice also exhibited less neuronal apoptosis, reactive astrogliosis, and tissue loss than WT mice. Behavioral tests, including cylinder, hanging wire, pole and adhesive tests, showed that IP3R2 KO mice exhibited reduced functional deficits after PT. Collectively, our study demonstrates that disruption of astrocytic Ca(2+) signaling by deleting IP3R2s has beneficial effects on neuronal and brain protection and functional deficits after stroke. These findings reveal a novel non-cell-autonomous neuronal and brain protective function of astrocytes in ischemic stroke, whereby suggest that the astrocytic IP3R2-mediated Ca(2+) signaling pathway might be a promising target for stroke therapy.
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Affiliation(s)
- Hailong Li
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States; Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Yicheng Xie
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States; Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Nannan Zhang
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States
| | - Yang Yu
- Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Qiao Zhang
- Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Shinghua Ding
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States; Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States.
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Abstract
Neuroglia, the "glue" that fills the space between neurons in the central nervous system, takes active part in nerve cell signaling. Neuroglial cells, astroglia, oligodendroglia, and microglia, are together about as numerous as neurons in the brain as a whole, and in the cerebral cortex grey matter, but the proportion varies widely among brain regions. Glial volume, however, is less than one-fifth of the tissue volume in grey matter. When stimulated by neurons or other cells, neuroglial cells release gliotransmitters by exocytosis, similar to neurotransmitter release from nerve endings, or by carrier-mediated transport or channel flux through the plasma membrane. Gliotransmitters include the common neurotransmitters glutamate and GABA, the nonstandard amino acid d-serine, the high-energy phosphate ATP, and l-lactate. The latter molecule is a "buffer" between glycolytic and oxidative metabolism as well as a signaling substance recently shown to act on specific lactate receptors in the brain. Complementing neurotransmission at a synapse, neuroglial transmission often implies diffusion of the transmitter over a longer distance and concurs with the concept of volume transmission. Transmission from glia modulates synaptic neurotransmission based on energetic and other local conditions in a volume of tissue surrounding the individual synapse. Neuroglial transmission appears to contribute significantly to brain functions such as memory, as well as to prevalent neuropathologies.
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Affiliation(s)
- Vidar Gundersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Jon Storm-Mathisen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Linda Hildegard Bergersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
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