1
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O'Neill KM, Saracino E, Barile B, Mennona NJ, Mola MG, Pathak S, Posati T, Zamboni R, Nicchia GP, Benfenati V, Losert W. Decoding Natural Astrocyte Rhythms: Dynamic Actin Waves Result from Environmental Sensing by Primary Rodent Astrocytes. Adv Biol (Weinh) 2023; 7:e2200269. [PMID: 36709481 DOI: 10.1002/adbi.202200269] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 12/07/2022] [Indexed: 01/30/2023]
Abstract
Astrocytes are key regulators of brain homeostasis, equilibrating ion, water, and neurotransmitter concentrations and maintaining essential conditions for proper cognitive function. Recently, it has been shown that the excitability of the actin cytoskeleton manifests in second-scale dynamic fluctuations and acts as a sensor of chemophysical environmental cues. However, it is not known whether the cytoskeleton is excitable in astrocytes and how the homeostatic function of astrocytes is linked to the dynamics of the cytoskeleton. Here it is shown that homeostatic regulation involves the excitable dynamics of actin in certain subcellular regions of astrocytes, especially near the cell boundary. The results further indicate that actin dynamics concentrate into "hotspot" regions that selectively respond to certain chemophysical stimuli, specifically the homeostatic challenges of ion or water concentration increases. Substrate topography makes the actin dynamics of astrocytes weaker. Super-resolution images demonstrate that surface topography is also associated with the predominant perpendicular alignment of actin filaments near the cell boundary, whereas flat substrates result in an actin cortex mainly parallel to the cell boundary. Additionally, coculture with neurons increases both the probability of actin dynamics and the strength of hotspots. The excitable systems character of actin thus makes astrocytes direct participants in neural cell network dynamics.
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Affiliation(s)
- Kate M O'Neill
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
| | - Emanuela Saracino
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Barbara Barile
- Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, 70125, Bari, Italy
| | - Nicholas J Mennona
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
- Physics Department, University of Maryland, College Park, MD, 20742, USA
| | - Maria Grazia Mola
- Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, 70125, Bari, Italy
| | - Spandan Pathak
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
| | - Tamara Posati
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Roberto Zamboni
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Grazia P Nicchia
- Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, 70125, Bari, Italy
| | - Valentina Benfenati
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Wolfgang Losert
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
- Physics Department, University of Maryland, College Park, MD, 20742, USA
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2
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Peng HR, Zhang YK, Zhou JW. The Structure and Function of Glial Networks: Beyond the Neuronal Connections. Neurosci Bull 2023; 39:531-540. [PMID: 36481974 PMCID: PMC10043088 DOI: 10.1007/s12264-022-00992-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 10/27/2022] [Indexed: 12/13/2022] Open
Abstract
Glial cells, consisting of astrocytes, oligodendrocyte lineage cells, and microglia, account for >50% of the total number of cells in the mammalian brain. They play key roles in the modulation of various brain activities under physiological and pathological conditions. Although the typical morphological features and characteristic functions of these cells are well described, the organization of interconnections of the different glial cell populations and their impact on the healthy and diseased brain is not completely understood. Understanding these processes remains a profound challenge. Accumulating evidence suggests that glial cells can form highly complex interconnections with each other. The astroglial network has been well described. Oligodendrocytes and microglia may also contribute to the formation of glial networks under various circumstances. In this review, we discuss the structure and function of glial networks and their pathological relevance to central nervous system diseases. We also highlight opportunities for future research on the glial connectome.
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Affiliation(s)
- Hai-Rong Peng
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yu-Kai Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jia-Wei Zhou
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China.
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3
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Freitag K, Eede P, Ivanov A, Sterczyk N, Schneeberger S, Borodina T, Sauer S, Beule D, Heppner FL. Diverse but unique astrocytic phenotypes during embryonic stem cell differentiation, culturing and development. Commun Biol 2023; 6:40. [PMID: 36639529 PMCID: PMC9839673 DOI: 10.1038/s42003-023-04410-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 01/03/2023] [Indexed: 01/14/2023] Open
Abstract
Astrocytes are resident glial cells of the central nervous system (CNS) that play complex and heterogeneous roles in brain development, homeostasis and disease. Since their vast involvement in health and disease is becoming increasingly recognized, suitable and reliable tools for studying these cells in vivo and in vitro are of utmost importance. One of the key challenges hereby is to adequately mimic their context-dependent in vivo phenotypes and functions in vitro. To better understand the spectrum of astrocytic variations in defined settings we performed a side-by-side-comparison of murine embryonic stem cell (ESC)-derived astrocytes as well as primary neonatal and adult astrocytes, revealing major differences on a functional and transcriptomic level, specifically on proliferation, migration, calcium signaling and cilium activity. Our results highlight the need to carefully consider the choice of astrocyte origin and phenotype with respect to age, isolation and culture protocols based on the respective biological question.
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Affiliation(s)
- Kiara Freitag
- grid.6363.00000 0001 2218 4662Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Neuropathology, Charitéplatz 1, 10117 Berlin, Germany ,grid.424247.30000 0004 0438 0426German Center for Neurodegenerative Diseases (DZNE) within the Helmholtz Association, Berlin, Germany
| | - Pascale Eede
- grid.6363.00000 0001 2218 4662Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Neuropathology, Charitéplatz 1, 10117 Berlin, Germany ,Present Address: Apollo Health Ventures, Schlüterstr. 36, 10629 Berlin, Germany
| | - Andranik Ivanov
- grid.6363.00000 0001 2218 4662Core Unit Bioinformatics, Berlin Institute of Health, Charité - University Hospital Berlin, 10117 Berlin, Germany
| | - Nele Sterczyk
- grid.6363.00000 0001 2218 4662Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Neuropathology, Charitéplatz 1, 10117 Berlin, Germany
| | - Shirin Schneeberger
- grid.6363.00000 0001 2218 4662Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Neuropathology, Charitéplatz 1, 10117 Berlin, Germany ,grid.517316.7Cluster of Excellence, NeuroCure, Berlin, Germany ,Present Address: Apollo Health Ventures, Schlüterstr. 36, 10629 Berlin, Germany
| | - Tatiana Borodina
- grid.419491.00000 0001 1014 0849Scientific Genomics Platforms, Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz Society, Berlin, Germany and Berlin Institute of Health (BIH), Berlin, Germany
| | - Sascha Sauer
- grid.419491.00000 0001 1014 0849Scientific Genomics Platforms, Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz Society, Berlin, Germany and Berlin Institute of Health (BIH), Berlin, Germany
| | - Dieter Beule
- grid.6363.00000 0001 2218 4662Core Unit Bioinformatics, Berlin Institute of Health, Charité - University Hospital Berlin, 10117 Berlin, Germany
| | - Frank L. Heppner
- grid.6363.00000 0001 2218 4662Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Neuropathology, Charitéplatz 1, 10117 Berlin, Germany ,grid.424247.30000 0004 0438 0426German Center for Neurodegenerative Diseases (DZNE) within the Helmholtz Association, Berlin, Germany ,grid.517316.7Cluster of Excellence, NeuroCure, Berlin, Germany
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4
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Zhang NN, Zhang Y, Wang ZZ, Chen NH. Connexin 43: insights into candidate pathological mechanisms of depression and its implications in antidepressant therapy. Acta Pharmacol Sin 2022; 43:2448-2461. [PMID: 35145238 PMCID: PMC9525669 DOI: 10.1038/s41401-022-00861-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 01/06/2022] [Indexed: 11/09/2022] Open
Abstract
Major depressive disorder (MDD), a chronic and recurrent disease characterized by anhedonia, pessimism or even suicidal thought, remains a major chronic mental concern worldwide. Connexin 43 (Cx43) is the most abundant connexin expressed in astrocytes and forms the gap junction channels (GJCs) between astrocytes, the most abundant and functional glial cells in the brain. Astrocytes regulate neurons' synaptic strength and function by expressing receptors and regulating various neurotransmitters. Astrocyte dysfunction causes synaptic abnormalities, which are related to various mood disorders, e.g., depression. Increasing evidence suggests a crucial role of Cx43 in the pathogenesis of depression. Depression down-regulates Cx43 expression in humans and rats, and dysfunction of Cx43 also induces depressive behaviors in rats and mice. Recently Cx43 has received considerable critical attention and is highly implicated in the onset of depression. However, the pathological mechanisms of depression-like behavior associated with Cx43 still remain ambiguous. In this review we summarize the recent progress regarding the underlying mechanisms of Cx43 in the etiology of depression-like behaviors including gliotransmission, metabolic disorders, and neuroinflammation. We also discuss the effects of antidepressants (monoamine antidepressants and ketamine) on Cx43. The clarity of the candidate pathological mechanisms of depression-like behaviors associated with Cx43 and its potential pharmacological roles for antidepressants will benefit the exploration of a novel antidepressant target.
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Affiliation(s)
- Ning-Ning Zhang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China
| | - Yi Zhang
- Department of Anatomy, School of Chinese Medicine, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Zhen-Zhen Wang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China.
| | - Nai-Hong Chen
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China.
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5
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Unique Astrocyte Cytoskeletal and Nuclear Morphology in a Three-Dimensional Tissue-Engineered Rostral Migratory Stream. NEUROGLIA (BASEL, SWITZERLAND) 2022; 3:41-60. [PMID: 36776937 PMCID: PMC9910099 DOI: 10.3390/neuroglia3010003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neural precursor cells (NPCs) are generated in the subventricular zone (SVZ) and travel through the rostral migratory stream (RMS) to replace olfactory bulb interneurons in the brains of most adult mammals. Following brain injury, SVZ-derived NPCs can divert from the RMS and migrate toward injured brain regions but arrive in numbers too low to promote functional recovery without experimental intervention. Our lab has biofabricated a "living scaffold" that replicates the structural and functional features of the endogenous RMS. This tissue-engineered rostral migratory stream (TE-RMS) is a new regenerative medicine strategy designed to facilitate stable and sustained NPC delivery into neuron-deficient brain regions following brain injury or neurodegenerative disease and an in vitro tool to investigate the mechanisms of neuronal migration and cell-cell communication. We have previously shown that the TE-RMS replicates the basic structure and protein expression of the endogenous RMS and can direct immature neuronal migration in vitro and in vivo. Here, we further describe profound morphological changes that occur following precise physical manipulation and subsequent self-assembly of astrocytes into the TE-RMS, including significant cytoskeletal rearrangement and nuclear elongation. The unique cytoskeletal and nuclear architecture of TE-RMS astrocytes mimics astrocytes in the endogenous rat RMS. Advanced imaging techniques reveal the unique morphology of TE-RMS cells that has yet to be described of astrocytes in vitro. The TE-RMS offers a novel platform to elucidate astrocyte cytoskeletal and nuclear dynamics and their relationship to cell behavior and function.
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6
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Orts-Del'Immagine A, Dhanasekar M, Lejeune FX, Roussel J, Wyart C. A norepinephrine-dependent glial calcium wave travels in the spinal cord upon acoustovestibular stimuli. Glia 2021; 70:491-507. [PMID: 34773299 DOI: 10.1002/glia.24118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 10/27/2021] [Accepted: 11/01/2021] [Indexed: 02/06/2023]
Abstract
Although calcium waves have been widely observed in glial cells, their occurrence in vivo during behavior remains less understood. Here, we investigated the recruitment of glial cells in the hindbrain and spinal cord after acousto-vestibular (AV) stimuli triggering escape responses using in vivo population calcium imaging in larval zebrafish. We observed that gap-junction-coupled spinal glial network exhibits large and homogenous calcium increases that rose in the rostral spinal cord and propagated bi-directionally toward the spinal cord and toward the hindbrain. Spinal glial calcium waves were driven by the recruitment of neurons and in particular, of noradrenergic signaling acting through α-adrenergic receptors. Noradrenergic neurons of the medulla-oblongata (NE-MO) were revealed in the vicinity of where the calcium wave started. NE-MO were recruited upon AV stimulation and sent dense axonal projections in the rostro-lateral spinal cord, suggesting these cells could trigger the glial wave to propagate down the spinal cord. Altogether, our results revealed that a simple AV stimulation is sufficient to recruit noradrenergic neurons in the brainstem that trigger in the rostral spinal cord two massive glial calcium waves, one traveling caudally in the spinal cord and another rostrally into the hindbrain.
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Affiliation(s)
| | | | | | | | - Claire Wyart
- Institut du cerveau, Sorbonne Université, Paris, France
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7
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Xu Q, Ford NC, He S, Huang Q, Anderson M, Chen Z, Yang F, Crawford LK, Caterina MJ, Guan Y, Dong X. Astrocytes contribute to pain gating in the spinal cord. SCIENCE ADVANCES 2021; 7:eabi6287. [PMID: 34730998 PMCID: PMC8565904 DOI: 10.1126/sciadv.abi6287] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
Various pain therapies have been developed on the basis of the gate control theory of pain, which postulates that nonpainful sensory inputs mediated by large-diameter afferent fibers (Aβ-fibers) can attenuate noxious signals relayed to the brain. To date, this theory has focused only on neuronal mechanisms. Here, we identified an unprecedented function of astrocytes in the gating of nociceptive signals transmitted by neurokinin 1 receptor–positive (NK1R+) projection neurons in the spinal cord. Electrical stimulation of peripheral Aβ-fibers in naïve mice activated spinal astrocytes, which in turn induced long-term depression (LTD) in NK1R+ neurons and antinociception through activation of endogenous adenosinergic mechanisms. Suppression of astrocyte activation by pharmacologic, chemogenetic, and optogenetic manipulations blocked the induction of LTD in NK1R+ neurons and pain inhibition by Aβ-fiber stimulation. Collectively, our study introduces astrocytes as an important component of pain gating by activation of Aβ-fibers, which thus exert nonneuronal control of pain.
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Affiliation(s)
- Qian Xu
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Neil C. Ford
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Shaoqiu He
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Qian Huang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michael Anderson
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Zhiyong Chen
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Fei Yang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - LaTasha K. Crawford
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michael J. Caterina
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Neurological Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Neurological Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Neurological Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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8
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Lim D, Semyanov A, Genazzani A, Verkhratsky A. Calcium signaling in neuroglia. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 362:1-53. [PMID: 34253292 DOI: 10.1016/bs.ircmb.2021.01.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glial cells exploit calcium (Ca2+) signals to perceive the information about the activity of the nervous tissue and the tissue environment to translate this information into an array of homeostatic, signaling and defensive reactions. Astrocytes, the best studied glial cells, use several Ca2+ signaling generation pathways that include Ca2+ entry through plasma membrane, release from endoplasmic reticulum (ER) and from mitochondria. Activation of metabotropic receptors on the plasma membrane of glial cells is coupled to an enzymatic cascade in which a second messenger, InsP3 is generated thus activating intracellular Ca2+ release channels in the ER endomembrane. Astrocytes also possess store-operated Ca2+ entry and express several ligand-gated Ca2+ channels. In vivo astrocytes generate heterogeneous Ca2+ signals, which are short and frequent in distal processes, but large and relatively rare in soma. In response to neuronal activity intracellular and inter-cellular astrocytic Ca2+ waves can be produced. Astrocytic Ca2+ signals are involved in secretion, they regulate ion transport across cell membranes, and are contributing to cell morphological plasticity. Therefore, astrocytic Ca2+ signals are linked to fundamental functions of the central nervous system ranging from synaptic transmission to behavior. In oligodendrocytes, Ca2+ signals are generated by plasmalemmal Ca2+ influx, or by release from intracellular stores, or by combination of both. Microglial cells exploit Ca2+ permeable ionotropic purinergic receptors and transient receptor potential channels as well as ER Ca2+ release. In this contribution, basic morphology of glial cells, glial Ca2+ signaling toolkit, intracellular Ca2+ signals and Ca2+-regulated functions are discussed with focus on astrocytes.
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Affiliation(s)
- Dmitry Lim
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale, Novara, Italy.
| | - Alexey Semyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia; Faculty of Biology, Moscow State University, Moscow, Russia; Sechenov First Moscow State Medical University, Moscow, Russia
| | - Armando Genazzani
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale, Novara, Italy
| | - Alexei Verkhratsky
- Sechenov First Moscow State Medical University, Moscow, Russia; Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom; Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
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9
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Chen C, Jiang Z, Fu X, Yu D, Huang H, Tasker JG. Astrocytes Amplify Neuronal Dendritic Volume Transmission Stimulated by Norepinephrine. Cell Rep 2020; 29:4349-4361.e4. [PMID: 31875545 PMCID: PMC7010232 DOI: 10.1016/j.celrep.2019.11.092] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 10/10/2019] [Accepted: 11/22/2019] [Indexed: 11/03/2022] Open
Abstract
In addition to their support role in neurotransmitter and ion buffering, astrocytes directly regulate neurotransmission at synapses via local bidirectional signaling with neurons. Here, we reveal a form of neuronal-astrocytic signaling that transmits retrograde dendritic signals to distal upstream neurons in order to activate recurrent synaptic circuits. Norepinephrine activates α1 adrenoreceptors in hypothalamic corticotropin-releasing hormone (CRH) neurons to stimulate dendritic release, which triggers an astrocytic calcium response and release of ATP; ATP stimulates action potentials in upstream glutamate and GABA neurons to activate recurrent excitatory and inhibitory synaptic circuits to the CRH neurons. Thus, norepinephrine activates a retrograde signaling mechanism in CRH neurons that engages astrocytes in order to extend dendritic volume transmission to reach distal presynaptic glutamate and GABA neurons, thereby amplifying volume transmission mediated by dendritic release.
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Affiliation(s)
- Chun Chen
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
| | - ZhiYing Jiang
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
| | - Xin Fu
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA; Tulane Brain Institute, Tulane University, New Orleans, LA 70118, USA
| | - Diankun Yu
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA; Tulane Brain Institute, Tulane University, New Orleans, LA 70118, USA
| | - Hai Huang
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA; Tulane Brain Institute, Tulane University, New Orleans, LA 70118, USA
| | - Jeffrey G Tasker
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA; Tulane Brain Institute, Tulane University, New Orleans, LA 70118, USA.
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10
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Wakida NM, Gomez-Godinez V, Li H, Nguyen J, Kim EK, Dynes JL, Othy S, Lau AL, Ding P, Shi L, Carmona C, Thompson LM, Cahalan MD, Berns MW. Calcium Dynamics in Astrocytes During Cell Injury. Front Bioeng Biotechnol 2020; 8:912. [PMID: 32984268 PMCID: PMC7481337 DOI: 10.3389/fbioe.2020.00912] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 07/15/2020] [Indexed: 12/31/2022] Open
Abstract
The changes in intracellular calcium concentration ([Ca2+]) following laser-induced cell injury in nearby cells were studied in primary mouse astrocytes selectively expressing the Ca2+ sensitive GFAP-Cre Salsa6f fluorescent tandem protein, in an Ast1 astrocyte cell line, and in primary mouse astrocytes loaded with Fluo4. Astrocytes in these three systems exhibit distinct changes in [Ca2+] following induced death of nearby cells. Changes in [Ca2+] appear to result from release of Ca2+ from intracellular organelles, as opposed to influx from the external medium. Salsa6f expressing astrocytes displayed dynamic Ca2+ changes throughout the phagocytic response, including lamellae protrusion, cytosolic signaling during vesicle formation, vesicle maturation, and vesicle tract formation. Our results demonstrate local changes in [Ca2+] are involved in the process of phagocytosis in astrocytes responding to cell corpses and/or debris.
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Affiliation(s)
- Nicole M Wakida
- Beckman Laser Institute & Medical Clinic, University of California, Irvine, Irvine, CA, United States
| | - Veronica Gomez-Godinez
- Institute of Engineering in Medicine, University of California, San Diego, San Diego, CA, United States
| | - Huayan Li
- Institute of Engineering in Medicine, University of California, San Diego, San Diego, CA, United States
| | - Jessica Nguyen
- Beckman Laser Institute & Medical Clinic, University of California, Irvine, Irvine, CA, United States
| | - Edward K Kim
- Beckman Laser Institute & Medical Clinic, University of California, Irvine, Irvine, CA, United States
| | - Joseph L Dynes
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA, United States
| | - Shivashankar Othy
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA, United States
| | - Alice L Lau
- Department of Psychiatry and Human Behavior, University of California, Irvine, Irvine, CA, United States
| | - Peng Ding
- Institute of Engineering in Medicine, University of California, San Diego, San Diego, CA, United States
| | - Linda Shi
- Institute of Engineering in Medicine, University of California, San Diego, San Diego, CA, United States
| | - Christopher Carmona
- Institute of Engineering in Medicine, University of California, San Diego, San Diego, CA, United States
| | - Leslie M Thompson
- Department of Psychiatry and Human Behavior, University of California, Irvine, Irvine, CA, United States.,Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA, United States.,Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States.,Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA, United States
| | - Michael D Cahalan
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA, United States.,Institute for Immunology, University of California, Irvine, Irvine, CA, United States
| | - Michael W Berns
- Beckman Laser Institute & Medical Clinic, University of California, Irvine, Irvine, CA, United States.,Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, United States.,Department of Developmental and Cell Biology, School of Biological Sciences, University of California, Irvine, Irvine, CA, United States
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11
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Wypych D, Pomorski P. Calcium Signaling in Glioma Cells: The Role of Nucleotide Receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1202:67-86. [PMID: 32034709 DOI: 10.1007/978-3-030-30651-9_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Calcium signaling is probably one of the evolutionary oldest and the most common way by which the signal can be transmitted from the cell environment to the cytoplasmic calcium binding effectors. Calcium signal is fast and due to diversity of calcium binding proteins it may have a very broad effect on cell behavior. Being a crucial player in neuronal transmission it is also very important for glia physiology. It is responsible for the cross-talk between neurons and astrocytes, for microglia activation and motility. Changes in calcium signaling are also crucial for the behavior of transformed glioma cells. The present chapter summarizes molecular mechanisms of calcium signal formation present in glial cells with a strong emphasis on extracellular nucleotide-evoked signaling pathways. Some aspects of glioma C6 signaling such as the cross-talk between P2Y1 and P2Y12 nucleotide receptors in calcium signal generation will be discussed in-depth, to show complexity of machinery engaged in formation of this signal. Moreover, possible mechanisms of modulation of the calcium signal in diverse environments there will be presented herein. Finally, the possible role of calcium signal in glioma motility is also discussed. This is a very important issue, since glioma cells, contrary to the vast majority of neoplastic cells, cannot spread in the body with the bloodstream and, at least in early stages of tumor development, may expand only by means of sheer motility.
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Affiliation(s)
- Dorota Wypych
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Paweł Pomorski
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
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12
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Heterogeneity of Astrocytes in Grey and White Matter. Neurochem Res 2019; 46:3-14. [PMID: 31797158 DOI: 10.1007/s11064-019-02926-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 11/21/2019] [Accepted: 11/28/2019] [Indexed: 02/07/2023]
Abstract
Astrocytes are a diverse and heterogeneous type of glial cells. The major task of grey and white matter areas in the brain are computation of information at neuronal synapses and propagation of action potentials along axons, respectively, resulting in diverse demands for astrocytes. Adapting their function to the requirements in the local environment, astrocytes differ in morphology, gene expression, metabolism, and many other properties. Here we review the differential properties of protoplasmic astrocytes of grey matter and fibrous astrocytes located in white matter in respect to glutamate and energy metabolism, to their function at the blood-brain interface and to coupling via gap junctions. Finally, we discuss how this astrocytic heterogeneity might contribute to the different susceptibility of grey and white matter to ischemic insults.
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Verkhratsky A, Parpura V, Vardjan N, Zorec R. Physiology of Astroglia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1175:45-91. [PMID: 31583584 DOI: 10.1007/978-981-13-9913-8_3] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Astrocytes are principal cells responsible for maintaining the brain homeostasis. Additionally, these glial cells are also involved in homocellular (astrocyte-astrocyte) and heterocellular (astrocyte-other cell types) signalling and metabolism. These astroglial functions require an expression of the assortment of molecules, be that transporters or pumps, to maintain ion concentration gradients across the plasmalemma and the membrane of the endoplasmic reticulum. Astrocytes sense and balance their neurochemical environment via variety of transmitter receptors and transporters. As they are electrically non-excitable, astrocytes display intracellular calcium and sodium fluctuations, which are not only used for operative signalling but can also affect metabolism. In this chapter we discuss the molecules that achieve ionic gradients and underlie astrocyte signalling.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK. .,Faculty of Health and Medical Sciences, Center for Basic and Translational Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark. .,Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
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Zhao W, Cheong LZ, Cui W, Xu S, Shen C. A case study of the electrical properties of astrocytes by multimode AFM. J Microsc 2019; 275:75-81. [PMID: 31074501 DOI: 10.1111/jmi.12804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 05/04/2019] [Accepted: 05/07/2019] [Indexed: 12/12/2022]
Abstract
Astrocytes play an important role in the physiological functions of the central nervous system. In this study, contact potential differences (CPD) and capacitance gradients of the cell bodies and glial filaments of astrocytes were measured. Charge propagation properties in the astrocyte gap junctions were also studied using multimode Atomic Force Microscopy (AFM) at nanometre resolution. The CPD of the cell bodies and glial filaments were 324.2 ± 138.4 and 119.1 ± 31.7 mV, respectively. The measured capacitance gradients were 1.51 ± 0.31 and 1.98 ± 0.32 zF nm-1 , respectively. The gap junctions in the astrocytes showed no charge propagation and were not electrically sensitive. This furthers our understanding of astrocytes and other types of neuroglia. LAY DESCRIPTION: Neuroglia cells play important structural and functional roles in central nervous system (CNS). Neuroglia cells exceed the number of neurons by 10∼50 and can be divided into macroglia and microglia. Astrocytes are macroglia and are the largest and most abundant cells in the CNS. Astrocytes lack axons and dendrites and do not propagate action potentials. They have few cytoplasmic organelles, but possess abundant glial filaments, the main components of the cytoskeleton. Glial filaments are composed of the glial fibrillary acidic protein (GFAP). Astrocytes produce intercellular calcium waves in their gap junctions mediated through receptor activator (such as glutamate) to permit signal transduction._ENREF_5 In addition to their role in the support and nutrition of neurons, astrocytes are involved in various types of CNS activity including: (1) cytokine secretion for neuronal survival, growth and differentiation; (2) protection from brain injury; (3) modulation of the blood brain barrier; and (4) neuronal immunity. Bidirectional crosstalk between the astrocytes and neurons exists. Astrocytes can be activated by neurotransmitters released and can themselves release gliotransmitters to act upon neurons. Astrocytes are closely related to various disease states, including epilepsy and Alzheimer's disease. In this study, the electrical properties of astrocytes, including the contact potential difference (CPD) and capacitance gradients of the cell bodies and glial filaments, and charge propagation in the gap junctions were investigated at the nanometer level using quantitative Kelvin Probe Force Microscopy (KPFM) and Electrostatic Force Microscopy (EFM). The CPD of the cell bodies and glial filaments of the astrocytes were 324.2 mV and 119.1 mV, respectively. Capacitance gradients of the cell bodies and glial filaments of the astrocytes were 1.51 zF/nm and 1.98 zF/nm, respectively. Gap junctions in the astrocytes do not perform charge propagation functions and the astrocytes are not electrically sensitive. One should note that these results from KPFM and EFM were measured on dried cell and the situation might be different when studying in operando environment, still these findings aid our understanding of the electrical properties and functions of astrocytes, and further our knowledge of the electrical properties of the CNS.
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Affiliation(s)
- Weidong Zhao
- Chinese Academy of Sciences, Ningbo Institute of Materials Technology & Engineering, Ningbo, Zhejiang, China
| | - Ling-Zhi Cheong
- College of Food and Pharmaceutical Sciences, Ningbo University, Ningbo, China
| | - Wei Cui
- Ningbo Key Laboratory of Behavioral Neuroscience, Provincial Key Laboratory of Pathophysiology, School of Medicine, Ningbo University, Ningbo, Zhejiang, China
| | - Shujun Xu
- Ningbo Key Laboratory of Behavioral Neuroscience, Provincial Key Laboratory of Pathophysiology, School of Medicine, Ningbo University, Ningbo, Zhejiang, China
| | - Cai Shen
- Chinese Academy of Sciences, Ningbo Institute of Materials Technology & Engineering, Ningbo, Zhejiang, China
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15
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Abstract
Astrocytes, the neural homeostatic cells, play a key role in the information processing in the central nervous system. They express multiple receptors which respond to a number of chemical messengers and get excited as evidenced by an increase in second messengers in short and delayed time domains. Astrocytes secrete numerous neuroactive agents and mount various homeostatic responses. These signal integrating functions are key factors of neuropathology (better termed astroneuropathology): they provide for neuroprotection through both homeostatic support and astroglial reactivity; failure in astroglial defensive or supporting capabilities facilitates evolution of neurological disorders.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark; Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain; Celica, BIOMEDICAL, Technology Park 24, 1000 Ljubljana, Slovenia.
| | - Robert Zorec
- University of Ljubljana, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Zaloška cesta 4, SI-1000, Ljubljana, Slovenia; Celica, BIOMEDICAL, Technology Park 24, 1000 Ljubljana, Slovenia.
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Verkhratsky A, Trebak M, Perocchi F, Khananshvili D, Sekler I. Crosslink between calcium and sodium signalling. Exp Physiol 2018; 103:157-169. [PMID: 29210126 PMCID: PMC6813793 DOI: 10.1113/ep086534] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 11/24/2017] [Indexed: 12/12/2022]
Abstract
NEW FINDINGS What is the topic of this review? This paper overviews the links between Ca2+ and Na+ signalling in various types of cells. What advances does it highlight? This paper highlights the general importance of ionic signalling and overviews the molecular mechanisms linking Na+ and Ca2+ dynamics. In particular, the narrative focuses on the molecular physiology of plasmalemmal and mitochondrial Na+ -Ca2+ exchangers and plasmalemmal transient receptor potential channels. Functional consequences of Ca2+ and Na+ signalling for co-ordination of neuronal activity with astroglial homeostatic pathways fundamental for synaptic transmission are discussed. ABSTRACT Transmembrane ionic gradients, which are an indispensable feature of life, are used for generation of cytosolic ionic signals that regulate a host of cellular functions. Intracellular signalling mediated by Ca2+ and Na+ is tightly linked through several molecular pathways that generate Ca2+ and Na+ fluxes and are in turn regulated by both ions. Transient receptor potential (TRP) channels bridge endoplasmic reticulum Ca2+ release with generation of Na+ and Ca2+ currents. The plasmalemmal Na+ -Ca2+ exchanger (NCX) flickers between forward and reverse mode to co-ordinate the influx and efflux of both ions with membrane polarization and cytosolic ion concentrations. The mitochondrial calcium uniporter channel (MCU) and mitochondrial Na+ -Ca2+ exchanger (NCLX) mediate Ca2+ entry into and release from this organelle and couple cytosolic Ca2+ and Na+ fluctuations with cellular energetics. Cellular Ca2+ and Na+ signalling controls numerous functional responses and, in the CNS, provides for fast regulation of astroglial homeostatic cascades that are crucial for maintenance of synaptic transmission.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
- Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Mohamed Trebak
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Fabiana Perocchi
- Gene Center/Department of Biochemistry, Ludwig-Maximilians Universität München, Munich, Germany
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
| | - Daniel Khananshvili
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Ramat-Aviv, Israel
| | - Israel Sekler
- Department of Physiology and Cell Biology, Faculty of Health Science, Ben-Gurion University, Beer-Sheva, Israel
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Bose A, Basu R, Maulik M, Das Sarma J. Loss of Cx43-Mediated Functional Gap Junction Communication in Meningeal Fibroblasts Following Mouse Hepatitis Virus Infection. Mol Neurobiol 2018; 55:6558-6571. [PMID: 29327203 PMCID: PMC7090783 DOI: 10.1007/s12035-017-0861-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 12/21/2017] [Indexed: 10/28/2022]
Abstract
Mouse hepatitis virus (MHV) infection causes meningoencephalitis by disrupting the neuro-glial and glial-pial homeostasis. Recent studies suggest that MHV infection alters gap junction protein connexin 43 (Cx43)-mediated intercellular communication in brain and primary cultured astrocytes. In addition to astrocytes, meningeal fibroblasts also express high levels of Cx43. Fibroblasts in the meninges together with the basal lamina and the astrocyte endfeet forms the glial limitans superficialis as part of the blood-brain barrier (BBB). Alteration of glial-pial gap junction intercellular communication (GJIC) in MHV infection has the potential to affect the integrity of BBB. Till date, it is not known if viral infection can modulate Cx43 expression and function in cells of the brain meninges and thus affect BBB permeability. In the present study, we have investigated the effect of MHV infection on Cx43 localization and function in mouse brain meningeal cells and primary meningeal fibroblasts. Our results show that MHV infection reduces total Cx43 levels and causes its intracellular retention in the perinuclear compartments reducing its surface expression. Reduced trafficking of Cx43 to the cell surface in MHV-infected cells is associated with loss functional GJIC. Together, these data suggest that MHV infection can directly affect expression and cellular distribution of Cx43 resulting in loss of Cx43-mediated GJIC in meningeal fibroblasts, which may be associated with altered BBB function observed in acute infection.
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Affiliation(s)
- Abhishek Bose
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata (IISER-K), Mohanpur, Nadia, West Bengal, 741246, India
| | - Rahul Basu
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata (IISER-K), Mohanpur, Nadia, West Bengal, 741246, India
| | - Mahua Maulik
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata (IISER-K), Mohanpur, Nadia, West Bengal, 741246, India
| | - Jayasri Das Sarma
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata (IISER-K), Mohanpur, Nadia, West Bengal, 741246, India.
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18
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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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19
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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: 876] [Impact Index Per Article: 146.0] [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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20
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Szilvásy-Szabó A, Varga E, Beliczai Z, Lechan RM, Fekete C. Localization of connexin 43 gap junctions and hemichannels in tanycytes of adult mice. Brain Res 2017; 1673:64-71. [PMID: 28803831 DOI: 10.1016/j.brainres.2017.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 06/22/2017] [Accepted: 08/09/2017] [Indexed: 12/22/2022]
Abstract
Tanycytes are specialized glial cells lining the lateral walls and the floor of the third ventricle behind the optic chiasm. In addition to functioning as barrier cells, they also have an important role in the regulation of neuroendocrine axes and energy homeostasis. To determine whether tanycytes communicate with each other via Connexin 43 (Cx43) gap junctions, individual tanycytes were loaded with Lucifer yellow (LY) through a patch pipette. In all cases, LY filled a larger group of tanycytes as well as blood vessels adjacent to tanycyte processes. The Cx43-blocker, carbenoxolone, inhibited spreading of LY. The greatest density of Cx43-immunoreactive spots was observed in the cell membrane of α-tanycyte cell bodies. Cx43-immunoreactivity was also present in the membrane of β-tanycyte cell bodies, but in lower density. Processes of both types of tanycytes also contained Cx43-immunoreactivity. At the ultrastructural level, Cx43-immunoreactivity was present in the cell membrane of all types of tanycytes including their ventricular surface, but gap junctions were more frequent among α-tanycytes. Cx43-immunoreactivity was also observed in the cell membrane between contacting tanycyte endfeet processes, and between tanycyte endfeet process and axon varicosities in the external zone of the median eminence and capillaries in the arcuate nucleus and median eminence. These results suggest that gap junctions are present not only among tanycytes, but also between tanycytes and the axons of hypophysiotropic neurons. Cx43 hemichannels may also facilitate the transport between tanycytes and extracellular fluids, including the cerebrospinal fluid, extracellular space of the median eminence and bloodstream.
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Affiliation(s)
- Anett Szilvásy-Szabó
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary; Semmelweis University Neurosciences Doctoral School, Neuroendocrinology Program, Budapest, Hungary
| | - Edina Varga
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zsuzsa Beliczai
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Ronald M Lechan
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, MA, USA; Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Csaba Fekete
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary; Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, MA, USA.
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21
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Basu R, Bose A, Thomas D, Das Sarma J. Microtubule-assisted altered trafficking of astrocytic gap junction protein connexin 43 is associated with depletion of connexin 47 during mouse hepatitis virus infection. J Biol Chem 2017; 292:14747-14763. [PMID: 28566289 DOI: 10.1074/jbc.m117.786491] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/16/2017] [Indexed: 11/06/2022] Open
Abstract
Gap junctions (GJs) are important for maintenance of CNS homeostasis. GJ proteins, connexin 43 (Cx43) and connexin 47 (Cx47), play a crucial role in production and maintenance of CNS myelin. Cx43 is mainly expressed by astrocytes in the CNS and forms gap junction intercellular communications between astrocytes-astrocytes (Cx43-Cx43) and between astrocytes-oligodendrocytes (Cx43-Cx47). Mutations of these connexin (Cx) proteins cause dysmyelinating diseases in humans. Previously, it has been shown that Cx43 localization and expression is altered due to mouse hepatitis virus (MHV)-A59 infection both in vivo and in vitro; however, its mechanism and association with loss of myelin protein was not elaborated. Thus, we explored potential mechanisms by which MHV-A59 infection alters Cx43 localization and examined the effects of viral infection on Cx47 expression and its association with loss of the myelin marker proteolipid protein. Immunofluorescence and total internal reflection fluorescence microscopy confirmed that MHV-A59 used microtubules (MTs) as a conduit to reach the cell surface and restricted MT-mediated Cx43 delivery to the cell membrane. Co-immunoprecipitation experiments demonstrated that Cx43-β-tubulin molecular interaction was depleted due to protein-protein interaction between viral particles and MTs. During acute MHV-A59 infection, oligodendrocytic Cx47, which is mainly stabilized by Cx43 in vivo, was down-regulated, and its characteristic staining remained disrupted even at chronic phase. The loss of Cx47 was associated with loss of proteolipid protein at the chronic stage of MHV-A59 infection.
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Affiliation(s)
- Rahul Basu
- From the Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur-741246, India
| | - Abhishek Bose
- From the Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur-741246, India
| | - Deepthi Thomas
- From the Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur-741246, India
| | - Jayasri Das Sarma
- From the Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur-741246, India
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López-Hidalgo M, Kellner V, Schummers J. Astrocyte Calcium Responses to Sensory Input: Influence of Circuit Organization and Experimental Factors. Front Neural Circuits 2017; 11:16. [PMID: 28381991 PMCID: PMC5360724 DOI: 10.3389/fncir.2017.00016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 02/24/2017] [Indexed: 01/08/2023] Open
Affiliation(s)
| | - Vered Kellner
- Max Planck Florida Institute for Neuroscience Jupiter, FL, USA
| | - James Schummers
- Max Planck Florida Institute for Neuroscience Jupiter, FL, USA
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23
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Brunet T, Fischer AH, Steinmetz PR, Lauri A, Bertucci P, Arendt D. The evolutionary origin of bilaterian smooth and striated myocytes. eLife 2016; 5. [PMID: 27906129 PMCID: PMC5167519 DOI: 10.7554/elife.19607] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 12/01/2016] [Indexed: 12/25/2022] Open
Abstract
The dichotomy between smooth and striated myocytes is fundamental for bilaterian musculature, but its evolutionary origin is unsolved. In particular, interrelationships of visceral smooth muscles remain unclear. Absent in fly and nematode, they have not yet been characterized molecularly outside vertebrates. Here, we characterize expression profile, ultrastructure, contractility and innervation of the musculature in the marine annelid Platynereis dumerilii and identify smooth muscles around the midgut, hindgut and heart that resemble their vertebrate counterparts in molecular fingerprint, contraction speed and nervous control. Our data suggest that both visceral smooth and somatic striated myocytes were present in the protostome-deuterostome ancestor and that smooth myocytes later co-opted the striated contractile module repeatedly – for example, in vertebrate heart evolution. During these smooth-to-striated myocyte conversions, the core regulatory complex of transcription factors conveying myocyte identity remained unchanged, reflecting a general principle in cell type evolution. DOI:http://dx.doi.org/10.7554/eLife.19607.001
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Affiliation(s)
- Thibaut Brunet
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Antje Hl Fischer
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Patrick Rh Steinmetz
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Antonella Lauri
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Paola Bertucci
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Detlev Arendt
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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24
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Tang Y, Illes P. Regulation of adult neural progenitor cell functions by purinergic signaling. Glia 2016; 65:213-230. [PMID: 27629990 DOI: 10.1002/glia.23056] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 08/20/2016] [Accepted: 08/23/2016] [Indexed: 01/30/2023]
Abstract
Extracellular purines are signaling molecules in the neurogenic niches of the brain and spinal cord, where they activate cell surface purinoceptors at embryonic neural stem cells (NSCs) and adult neural progenitor cells (NPCs). Although mRNA and protein are expressed at NSCs/NPCs for almost all subtypes of the nucleotide-sensitive P2X/P2Y, and the nucleoside-sensitive adenosine receptors, only a few of those have acquired functional significance. ATP is sequentially degraded by ecto-nucleotidases to ADP, AMP, and adenosine with agonistic properties for distinct receptor-classes. Nucleotides/nucleosides facilitate or inhibit NSC/NPC proliferation, migration and differentiation. The most ubiquitous effect of all agonists (especially of ATP and ADP) appears to be the facilitation of cell proliferation, usually through P2Y1Rs and sometimes through P2X7Rs. However, usually P2X7R activation causes necrosis/apoptosis of NPCs. Differentiation can be initiated by P2Y2R-activation or P2X7R-blockade. A key element in the transduction mechanism of either receptor is the increase of the intracellular free Ca2+ concentration, which may arise due to its release from intracellular storage sites (G protein-coupling; P2Y) or due to its passage through the receptor-channel itself from the extracellular space (ATP-gated ion channel; P2X). Further research is needed to clarify how purinergic signaling controls NSC/NPC fate and how the balance between the quiescent and activated states is established with fine and dynamic regulation. GLIA 2017;65:213-230.
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Affiliation(s)
- Yong Tang
- Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, China
| | - Peter Illes
- Rudolf Boehm Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, 04107, Germany
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25
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L-Type Calcium Channels Modulation by Estradiol. Mol Neurobiol 2016; 54:4996-5007. [PMID: 27525676 DOI: 10.1007/s12035-016-0045-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 08/08/2016] [Indexed: 01/29/2023]
Abstract
Voltage-gated calcium channels are key regulators of brain function, and their dysfunction has been associated with multiple conditions and neurodegenerative diseases because they couple membrane depolarization to the influx of calcium-and other processes such as gene expression-in excitable cells. L-type calcium channels, one of the three major classes and probably the best characterized of the voltage-gated calcium channels, act as an essential calcium binding proteins with a significant biological relevance. It is well known that estradiol can activate rapidly brain signaling pathways and modulatory/regulatory proteins through non-genomic (or non-transcriptional) mechanisms, which lead to an increase of intracellular calcium that activate multiple kinases and signaling cascades, in the same way as L-type calcium channels responses. In this context, estrogens-L-type calcium channels signaling raises intracellular calcium levels and activates the same signaling cascades in the brain probably through estrogen receptor-independent modulatory mechanisms. In this review, we discuss the available literature on this area, which seems to suggest that estradiol exerts dual effects/modulation on these channels in a concentration-dependent manner (as a potentiator of these channels in pM concentrations and as an inhibitor in nM concentrations). Indeed, estradiol may orchestrate multiple neurotrophic responses, which open a new avenue for the development of novel estrogen-based therapies to alleviate different neuropathologies. We also highlight that it is essential to determine through computational and/or experimental approaches the interaction between estradiol and L-type calcium channels to assist these developments, which is an interesting area of research that deserves a closer look in future biomedical research.
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Abstract
Astrocytes are activated during both excitatory and inhibitory synaptic transmission and respond with intracellular Ca2+i elevations. Ca2+i oscillations and waves in astrocytes now appear to represent the glial arm of a dynamic neuronal-glial signaling process. Advances within the last year have shown that stimuli that elevate Ca2+i in astrocytes have the potential to modulate synaptic function. Recent studies have shown that astrocytic calcium waves, initially believed to depend on the integrity of functional gap junction channels for the passage of intercellular signals, are actually mediated by release of ATP and subsequent activation of purinergic receptors on neighboring cells. ATP release is in turn regulated by the expression of gap junction proteins, establishing a novel dimension between gap junctions and extracellular-mediated signaling events. The role of ATP and its breakdown product, adenosine, on synaptic transmission are discussed.
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Affiliation(s)
- M. L. Cotrina
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, New York
| | - M. Nedergaard
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, New York
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28
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Abstract
Throughout the nervous system, neurons are closely surrounded by glial cells, leaving only a 20-nm wide extracellular space filled with interstitial fluid. Ions, transmitters, hormones, nutrients, and waste products all share this narrow diffusion pathway. Because the interstitial space occupies only a small volume, neuronal activity can lead to appreciable changes in the extracellular concentration of ions, protons, and neurotrans mitters. These changes can affect neuronal activity and are believed to be influenced by glial cells. The proximity of glial processes to synapses and axons make glial cells ideal partners to sequester ions and transmitters released by neurons. The failure of glial cells to perform such essential homeostatic functions can have profound effects, and these homeostatic activities may constitute one way in which glial cells can influence neuronal signaling. In addition, glial cells, which, unlike most neurons, are coupled to each other through gap-junctions, communicate with each other and possibly also with adjacent neurons through prop agated intracellular Ca2+waves. The importance of such interglial signaling is not understood. Additionally, glial cells and neurons mutually modulate their expression of ion channels, most likely through factors re leased into the extracellular space. The range of responses observed in glial cells and their intimate anatomical relationship with neurons suggest a broader role for glia than is currently appreciated. It also emphasizes the importance of a better understanding of glial-neuronal interactions to an understanding of brain function. The Neuroscientist 1:328-337, 1995
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Affiliation(s)
- Harald Sontheimer
- Neurobiology Research Center and Department of Physiology and Biophysics The University of Alabama at Birmingham Birmingham, Alabama
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Zhao J, Zhang Y, Zhao J, Wang C, Mao J, Li T, Wang X, Nie X, Jiang S, Wu Q. 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure influence the expression of glutamate transporter GLT-1 in C6 glioma cells via the Ca(2+) /protein kinase C pathway. J Appl Toxicol 2016; 36:1409-17. [PMID: 26988466 DOI: 10.1002/jat.3294] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 12/16/2015] [Accepted: 12/29/2015] [Indexed: 12/20/2022]
Abstract
The widespread environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is considered one of the most toxic dioxin-like compounds. Although epidemiological studies have shown that TCDD exposure is linked to some neurological and neurophysiological disorders, the underlying mechanism of TCDD-mediated neurotoxicity has remained unclear. Astrocytes are the most abundant cells in the nervous systems, and are recognized as the important mediators of normal brain functions as well as neurological, neurodevelopmental and neurodegenerative brain diseases. In this study, we investigated the role of TCDD in regulating the expression of glutamate transporter GLT-1 in astrocytes. TCDD, at concentrations of 0.1-100 nm, had no significantly harmful effect on the viability of C6 glioma cells. However, the expression of GLT-1 in C6 glioma cells was downregulated in a dose- and time-dependent manner. TCDD also caused activation of protein kinase C (PKC), as TCDD induced translocation of the PKC from the cytoplasm or perinuclear to the membrane. The translocation of PKC was inhibited by one Ca(2+) blocker, nifedipine, suggesting that the effects are triggered by the initial elevated intracellular concentration of free Ca(2+) . Finally, we showed that inhibition of the PKC activity reverses the TCDD-triggered reduction of GLT-1. In summary, our results suggested that TCDD exposure could downregulate the expression of GLT-1 in C6 via Ca(2+) /PKC pathway. The downregulation of GLT-1 might participate in TCDD-mediated neurotoxicity. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Jianya Zhao
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Yan Zhang
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Jianmei Zhao
- Department of Pediatrics, Affiliated Hospital of Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Cheng Wang
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Jiamin Mao
- Department of Labor and Environmental Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Ting Li
- Department of Labor and Environmental Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Xiaoke Wang
- Department of Labor and Environmental Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Xiaoke Nie
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Shengyang Jiang
- Department of Labor and Environmental Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China
| | - Qiyun Wu
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, 226001, People's Republic of China.
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Mouse Hepatitis Virus Infection Remodels Connexin43-Mediated Gap Junction Intercellular Communication In Vitro and In Vivo. J Virol 2015; 90:2586-99. [PMID: 26676788 DOI: 10.1128/jvi.02420-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 12/12/2015] [Indexed: 01/31/2023] Open
Abstract
UNLABELLED Gap junctions (GJs) form intercellular channels which directly connect the cytoplasm between neighboring cells to facilitate the transfer of ions and small molecules. GJs play a major role in the pathogenesis of infection-associated inflammation. Mutations of gap junction proteins, connexins (Cxs), cause dysmyelination and leukoencephalopathy. In multiple sclerosis (MS) patients and its animal model experimental autoimmune encephalitis (EAE), Cx43 was shown to be modulated in the central nervous system (CNS). The mechanism behind Cx43 alteration and its role in MS remains unexplored. Mouse hepatitis virus (MHV) infection-induced demyelination is one of the best-studied experimental animal models for MS. Our studies demonstrated that MHV infection downregulated Cx43 expression at protein and mRNA levels in vitro in primary astrocytes obtained from neonatal mouse brains. After infection, a significant amount of Cx43 was retained in endoplasmic reticulum/endoplasmic reticulum Golgi intermediate complex (ER/ERGIC) and GJ plaque formation was impaired at the cell surface, as evidenced by a reduction of the Triton X-100 insoluble fraction of Cx43. Altered trafficking and impairment of GJ plaque formation may cause the loss of functional channel formation in MHV-infected primary astrocytes, as demonstrated by a reduced number of dye-coupled cells after a scrape-loading Lucifer yellow dye transfer assay. Upon MHV infection, a significant downregulation of Cx43 was observed in the virus-infected mouse brain. This study demonstrates that astrocytic Cx43 expression and function can be modulated due to virus stress and can be an appropriate model to understand the basis of cellular mechanisms involved in the alteration of gap junction intercellular communication (GJIC) in CNS neuroinflammation. IMPORTANCE We found that MHV infection leads to the downregulation of Cx43 in vivo in the CNS. In addition, results show that MHV infection impairs Cx43 expression in addition to gap junction communication in primary astrocytes. After infection, Cx43 did not traffic normally to the membrane to form gap junction plaques, and that could be the basis of reduced functional gap junction coupling between astrocytes. This is an important first step toward understanding how viruses affect Cx43 expression and trafficking at the cellular level. This may provide a basis for understanding how structural alterations of astrocytic gap junctions can disrupt gap junction communication between other CNS cells in altered CNS environments due to infection and inflammation. More specifically, alteration of Cx43 may be the basis of the destabilization of Cx47 in oligodendrocytes seen in and around inflammatory demyelinating plaques in MS patients.
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Stavermann M, Meuth P, Doengi M, Thyssen A, Deitmer JW, Lohr C. Calcium-induced calcium release and gap junctions mediate large-scale calcium waves in olfactory ensheathing cells in situ. Cell Calcium 2015; 58:215-25. [DOI: 10.1016/j.ceca.2015.05.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 05/04/2015] [Accepted: 05/26/2015] [Indexed: 02/06/2023]
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Fleischer W, Theiss S, Slotta J, Holland C, Schnitzler A. High-frequency voltage oscillations in cultured astrocytes. Physiol Rep 2015; 3:3/5/e12400. [PMID: 25969464 PMCID: PMC4463829 DOI: 10.14814/phy2.12400] [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] [Indexed: 01/01/2023] Open
Abstract
Because of their close interaction with neuronal physiology, astrocytes can modulate brain function in multiple ways. Here, we demonstrate a yet unknown astrocytic phenomenon: Astrocytes cultured on microelectrode arrays (MEAs) exhibited extracellular voltage fluctuations in a broad frequency spectrum (100–600 Hz) after electrical stimulation. These aperiodic high-frequency oscillations (HFOs) could last several seconds and did not spread across the MEA. The voltage-gated calcium channel antagonist cilnidipine dose-dependently decreased the power of the oscillations. While intracellular calcium was pivotal, incubation with bafilomycin A1 showed that vesicular release of transmitters played only a minor role in the emergence of HFOs. Gap junctions and volume-regulated anionic channels had just as little functional impact, which was demonstrated by the addition of carbenoxolone (100 μmol/L) and NPPB (100 μmol/L). Hyperpolarization with low potassium in the extracellular solution (2 mmol/L) dramatically raised oscillation power. A similar effect was seen when we added extra sodium (+50 mmol/L) or if we replaced it with NMDG+ (50 mmol/L). The purinergic receptor antagonist PPADS suppressed the oscillation power, while the agonist ATP (100 μmol/L) had only an increasing effect when the bath solution pH was slightly lowered to pH 7.2. From these observations, we conclude that astrocytic voltage oscillations are triggered by activation of voltage-gated calcium channels and driven by a downstream influx of cations through channels that are permeable for large ions such as NMDG+. Most likely candidates are subtypes of pore-forming P2X channels with a low affinity for ATP.
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Affiliation(s)
- Wiebke Fleischer
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Stephan Theiss
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany RESULT Medical GmbH, Düsseldorf, Germany
| | - Johannes Slotta
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Christine Holland
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Alfons Schnitzler
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
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33
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Crunelli V, Carmignoto G, Steinhäuser C. Novel astrocyte targets: new avenues for the therapeutic treatment of epilepsy. Neuroscientist 2015; 21:62-83. [PMID: 24609207 PMCID: PMC4361461 DOI: 10.1177/1073858414523320] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
During the last 20 years, it has been well established that a finely tuned, continuous crosstalk between neurons and astrocytes not only critically modulates physiological brain functions but also underlies many neurological diseases. In particular, this novel way of interpreting brain activity is markedly influencing our current knowledge of epilepsy, prompting a re-evaluation of old findings and guiding novel experimentation. Here, we review recent studies that have unraveled novel and unique contributions of astrocytes to the generation and spread of convulsive and nonconvulsive seizures and epileptiform activity. The emerging scenario advocates an overall framework in which a dynamic and reciprocal interplay among astrocytic and neuronal ensembles is fundamental for a fuller understanding of epilepsy. In turn, this offers novel astrocytic targets for the development of those really novel chemical entities for the control of convulsive and nonconvulsive seizures that have been acknowledged as a key priority in the management of epilepsy.
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Affiliation(s)
- Vincenzo Crunelli
- Neuroscience Division, School of Biosciences, Cardiff University, Cardiff, UK
| | - Giorgio Carmignoto
- Centro Nazionale della Ricerca, Neuroscience Institute and Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
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34
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Scherf JM, Hu XS, Tepp WH, Ichtchenko K, Johnson EA, Pellett S. Analysis of gene expression in induced pluripotent stem cell-derived human neurons exposed to botulinum neurotoxin A subtype 1 and a type A atoxic derivative. PLoS One 2014; 9:e111238. [PMID: 25337697 PMCID: PMC4206481 DOI: 10.1371/journal.pone.0111238] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 09/19/2014] [Indexed: 11/18/2022] Open
Abstract
Botulinum neurotoxin type A1 (BoNT/A1) is a potent protein toxin responsible for the potentially fatal human illness botulism. Notwithstanding, the long-lasting flaccid muscle paralysis caused by BoNT/A has led to its utility as a powerful and versatile bio-pharmaceutical. The flaccid paralysis is due to specific cleavage of neuronal SNAREs by BoNTs. However, actions of BoNTs on intoxicated neurons besides the cleavage of SNAREs have not been studied in detail. In this study we investigated by microarray analysis the effects of BoNT/A and a catalytically inactive derivative (BoNT/A ad) on the transcriptome of human induced pluripotent stem cell (hiPSC)-derived neurons at 2 days and 2 weeks after exposure. While there were only minor changes in expression levels at 2 days post exposure, at 2 weeks post exposure 492 genes were differentially expressed more than 2-fold in BoNT/A1-exposed cells when compared to non-exposed populations, and 682 genes were differentially expressed in BoNT/A ad-exposed cells. The vast majority of genes were similarly regulated in BoNT/A1 and BoNT/A ad-exposed neurons, and the few genes differentially regulated between BoNT/A1 and BoNT/A ad-exposed neurons were differentially expressed less than 3.5 fold. These data indicate a similar response of neurons to BoNT/A1 and BoNT/A ad exposure. The most highly regulated genes in cells exposed to either BoNT/A1 or BoNT/A ad are involved in neurite outgrowth and calcium channel sensitization.
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Affiliation(s)
- Jacob M. Scherf
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Xiaoyang Serene Hu
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - William H. Tepp
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Konstantin Ichtchenko
- Department of Pharmacology, New York University School of Medicine, New York, New York, United States of America
| | - Eric A. Johnson
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Sabine Pellett
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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35
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Orellana JA, Stehberg J. Hemichannels: new roles in astroglial function. Front Physiol 2014; 5:193. [PMID: 24987373 PMCID: PMC4060415 DOI: 10.3389/fphys.2014.00193] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 05/07/2014] [Indexed: 01/16/2023] Open
Abstract
The role of astrocytes in brain function has evolved over the last decade, from support cells to active participants in the neuronal synapse through the release of "gliotransmitters."Astrocytes express receptors for most neurotransmitters and respond to them through Ca(2+) intracellular oscillations and propagation of intercellular Ca(2+) waves. While such waves are able to propagate among neighboring astrocytes through gap junctions, thereby activating several astrocytes simultaneously, they can also trigger the release of gliotransmitters, including glutamate, d-serine, glycine, ATP, adenosine, or GABA. There are several mechanisms by which gliotransmitter release occurs, including functional hemichannels. These gliotransmitters can activate neighboring astrocytes and participate in the propagation of intercellular Ca(2+) waves, or activate pre- and post-synaptic receptors, including NMDA, AMPA, and purinergic receptors. In consequence, hemichannels could play a pivotal role in astrocyte-to-astrocyte communication and astrocyte-to-neuron cross-talk. Recent evidence suggests that astroglial hemichannels are involved in higher brain functions including memory and glucose sensing. The present review will focus on the role of hemichannels in astrocyte-to-astrocyte and astrocyte-to neuron communication and in brain physiology.
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Affiliation(s)
- Juan A Orellana
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Jimmy Stehberg
- Laboratorio de Neurobiología, Centro de Investigaciones Médicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andrés Bello Santiago, Chile
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36
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Wilkinson NM, Metta G. Capture of fixation by rotational flow; a deterministic hypothesis regarding scaling and stochasticity in fixational eye movements. Front Syst Neurosci 2014; 8:29. [PMID: 24616670 PMCID: PMC3935396 DOI: 10.3389/fnsys.2014.00029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 02/09/2014] [Indexed: 11/13/2022] Open
Abstract
Visual scan paths exhibit complex, stochastic dynamics. Even during visual fixation, the eye is in constant motion. Fixational drift and tremor are thought to reflect fluctuations in the persistent neural activity of neural integrators in the oculomotor brainstem, which integrate sequences of transient saccadic velocity signals into a short term memory of eye position. Despite intensive research and much progress, the precise mechanisms by which oculomotor posture is maintained remain elusive. Drift exhibits a stochastic statistical profile which has been modeled using random walk formalisms. Tremor is widely dismissed as noise. Here we focus on the dynamical profile of fixational tremor, and argue that tremor may be a signal which usefully reflects the workings of oculomotor postural control. We identify signatures reminiscent of a certain flavor of transient neurodynamics; toric traveling waves which rotate around a central phase singularity. Spiral waves play an organizational role in dynamical systems at many scales throughout nature, though their potential functional role in brain activity remains a matter of educated speculation. Spiral waves have a repertoire of functionally interesting dynamical properties, including persistence, which suggest that they could in theory contribute to persistent neural activity in the oculomotor postural control system. Whilst speculative, the singularity hypothesis of oculomotor postural control implies testable predictions, and could provide the beginnings of an integrated dynamical framework for eye movements across scales.
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Affiliation(s)
| | - Giorgio Metta
- iCub Facility, Fondazione Istituto Italiano di Tecnologia Genova, Italy ; Centre for Robotics and Neural Systems, School of Computing and Mathematics, University of Plymouth Plymouth, UK
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37
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Wu YW, Tang X, Arizono M, Bannai H, Shih PY, Dembitskaya Y, Kazantsev V, Tanaka M, Itohara S, Mikoshiba K, Semyanov A. Spatiotemporal calcium dynamics in single astrocytes and its modulation by neuronal activity. Cell Calcium 2014; 55:119-29. [DOI: 10.1016/j.ceca.2013.12.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 12/27/2013] [Accepted: 12/28/2013] [Indexed: 12/20/2022]
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38
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Gibbons M, Smeal R, Takahashi D, Vargas J, Wilcox K. Contributions of astrocytes to epileptogenesis following status epilepticus: opportunities for preventive therapy? Neurochem Int 2013; 63:660-9. [PMID: 23266599 PMCID: PMC4353644 DOI: 10.1016/j.neuint.2012.12.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 12/09/2012] [Accepted: 12/13/2012] [Indexed: 12/22/2022]
Abstract
Status epilepticus (SE) is a life threatening condition that often precedes the development of epilepsy. Traditional treatments for epilepsy have been focused on targeting neuronal mechanisms contributing to hyperexcitability, however, approximately 30% of patients with epilepsy do not respond to existing neurocentric pharmacotherapies. A growing body of evidence has demonstrated that profound changes in the morphology and function of astrocytes accompany SE and persist in epilepsy. Astrocytes are increasingly recognized for their diverse roles in modulating neuronal activity, and understanding the changes in astrocytes following SE could provide important clues about the mechanisms underlying seizure generation and termination. By understanding the contributions of astrocytes to the network changes underlying epileptogenesis and the development of epilepsy, we will gain a greater appreciation of the contributions of astrocytes to dynamic circuit changes, which will enable us to develop more successful therapies to prevent and treat epilepsy. This review summarizes changes in astrocytes following SE in animal models and human temporal lobe epilepsy and addresses the functional consequences of those changes that may provide clues to the process of epileptogenesis.
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Affiliation(s)
- M.B. Gibbons
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT
| | - R.M. Smeal
- Department of Pharmacology & Toxicology, University of Utah, Salt Lake City, UT
| | - D.K. Takahashi
- Department of Neurology, Stanford University, Palo Alto, CA
| | - J.R. Vargas
- Department of Neurology, University of Utah, Salt Lake City, UT
| | - K.S. Wilcox
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT
- Department of Pharmacology & Toxicology, University of Utah, Salt Lake City, UT
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39
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Gao K, Wang CR, Jiang F, Wong AYK, Su N, Jiang JH, Chai RC, Vatcher G, Teng J, Chen J, Jiang YW, Yu ACH. Traumatic scratch injury in astrocytes triggers calcium influx to activate the JNK/c-Jun/AP-1 pathway and switch on GFAP expression. Glia 2013; 61:2063-77. [PMID: 24123203 DOI: 10.1002/glia.22577] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 08/11/2013] [Accepted: 08/21/2013] [Indexed: 01/25/2023]
Abstract
Astrocyte activation is a hallmark of central nervous system injuries resulting in glial scar formation (astrogliosis). The activation of astrocytes involves metabolic and morphological changes with complex underlying mechanisms, which should be defined to provide targets for astrogliosis intervention. Astrogliosis is usually accompanied by an upregulation of glial fibrillary acidic protein (GFAP). Using an in vitro scratch injury model, we scratched primary cultures of cerebral cortical astrocytes and observed an influx of calcium in the form of waves spreading away from the wound through gap junctions. Using the calcium blocker BAPTA-AM and the JNK inhibitor SP600125, we demonstrated that the calcium wave triggered the activation of JNK, which then phosphorylated the transcription factor c-Jun to facilitate the binding of AP-1 to the GFAP gene promoter to switch on GFAP upregulation. Blocking calcium mobilization with BAPTA-AM in an in vivo stab wound model reduced GFAP expression and glial scar formation, showing that the calcium signal, and the subsequent regulation of downstream signaling molecules, plays an essential role in brain injury response. Our findings demonstrated that traumatic scratch injury to astrocytes triggered a calcium influx from the extracellular compartment and activated the JNK/c-Jun/AP-1 pathway to switch on GFAP expression, identifying a previously unreported signaling cascade that is important in astrogliosis and the physiological response following brain injury.
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Affiliation(s)
- Kai Gao
- Neuroscience Research Institute, Key Laboratory for Neuroscience (Ministry of Education), Key Laboratory for Neuroscience (National Health and Family Planning Commission), Department of Neurobiology, School of Basic Medical Sciences, Health Science Center, Peking University, Beijing, China
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40
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Giaume C, Leybaert L, Naus CC, Sáez JC. Connexin and pannexin hemichannels in brain glial cells: properties, pharmacology, and roles. Front Pharmacol 2013; 4:88. [PMID: 23882216 PMCID: PMC3713369 DOI: 10.3389/fphar.2013.00088] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 06/21/2013] [Indexed: 12/22/2022] Open
Abstract
Functional interaction between neurons and glia is an exciting field that has expanded tremendously during the past decade. Such partnership has multiple impacts on neuronal activity and survival. Indeed, numerous findings indicate that glial cells interact tightly with neurons in physiological as well as pathological situations. One typical feature of glial cells is their high expression level of gap junction protein subunits, named connexins (Cxs), thus the membrane channels they form may contribute to neuroglial interaction that impacts neuronal activity and survival. While the participation of gap junction channels in neuroglial interactions has been regularly reviewed in the past, the other channel function of Cxs, i.e., hemichannels located at the cell surface, has only recently received attention. Gap junction channels provide the basis for a unique direct cell-to-cell communication, whereas Cx hemichannels allow the exchange of ions and signaling molecules between the cytoplasm and the extracellular medium, thus supporting autocrine and paracrine communication through a process referred to as “gliotransmission,” as well as uptake and release of metabolites. More recently, another family of proteins, termed pannexins (Panxs), has been identified. These proteins share similar membrane topology but no sequence homology with Cxs. They form multimeric membrane channels with pharmacology somewhat overlapping with that of Cx hemichannels. Such duality has led to several controversies in the literature concerning the identification of the molecular channel constituents (Cxs versus Panxs) in glia. In the present review, we update and discuss the knowledge of Cx hemichannels and Panx channels in glia, their properties and pharmacology, as well as the understanding of their contribution to neuroglial interactions in brain health and disease.
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Affiliation(s)
- Christian Giaume
- Collège de France, Center for Interdisciplinary Research in Biology/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050 Paris, France ; University Pierre et Marie Curie Paris, France ; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University Paris, France
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41
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Iwabuchi S, Kawahara K. Extracellular ATP-prinoceptor signaling and AMP-activated protein kinase regulate astrocytic glucose transporter 3 in an in vitro ischemia. Neurochem Int 2013; 63:259-68. [PMID: 23851016 DOI: 10.1016/j.neuint.2013.07.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 06/15/2013] [Accepted: 07/01/2013] [Indexed: 11/16/2022]
Abstract
Astrocytes become hypertrophic reactive in response to the ischemic stress, and they contribute to either protect or exacerbate neuronal damage, depending on the depth or duration of the stress. Astrocytes have more resistance to the ischemic stress than neurons, which is apparently due to active anerobic metabolic pathway in the emergency situation. We have been focused on the functional role of astrocytic glucose transporters in the ischemic condition. Under the physiological conditions, cultured astrocytes primarily express glucose transporter1 (GLUT1), and GLUT3 is only detected at extremely low levels. But astrocytes enhance GLUT3 expression through the signaling of nuclear factor-κ-light-chain-enhancer of activated B cells (NF-κB) under mild ischemic condition. It is reasonable since GLUT3 transports extracellular glucose about seven times faster than GLUT1, so astrocytes enhance the storage of intracellular glucose during the ischemia. However, other signaling cascades that regulate GLUT3 production remain unknown. Here we demonstrate that extracellular adenosine 5'-triphosphate (ATP)-P2Y receptor signaling also regulates GLUT3 expression. Under mild ischemic condition, astrocytes positively released existing intracellular or newly synthesized ATP by AMP-activated protein kinase (AMPK) signaling. The released extracellular ATP from pore channels activated ATP-sensitive P2Y receptor signaling, resulting in an increase in c-Fos and c-Jun proteins. Newly synthesized GLUT3 was regulated by those signaling since the inhibition of P2Y receptors or c-Fos/c-Jun signaling significantly reduced GLUT3 expression. Furthermore, the inhibition of P2Y receptors during the ischemic condition sustained intracellular ATP concentration, leading to a decrease in AMPK proteins. These results suggest AMPK-regulated ATP production triggers the release of ATP to activate P2Y receptor signaling, which is another candidate that regulates GLUT3 expression under the ischemic condition.
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Affiliation(s)
- Sadahiro Iwabuchi
- Department of Molecular Physiology & Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
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Gap junction channels and hemichannels in the CNS: regulation by signaling molecules. Neuropharmacology 2013; 75:567-82. [PMID: 23499663 DOI: 10.1016/j.neuropharm.2013.02.020] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 02/08/2013] [Accepted: 02/26/2013] [Indexed: 11/20/2022]
Abstract
Coordinated interaction among cells is critical to develop the extremely complex and dynamic tasks performed by the central nervous system (CNS). Cell synchronization is in part mediated by connexins and pannexins; two different protein families that form gap junction channels and hemichannels. Whereas gap junction channels connect the cytoplasm of contacting cells and coordinate electric and metabolic activities, hemichannels communicate intra- and extra-cellular compartments and serve as diffusional pathways for ions and small molecules. Cells in the CNS depend on paracrine/autocrine communication via several extracellular signaling molecules, such as, cytokines, growth factors, transmitters and free radical species to sense changes in microenvironment as well as to adapt to them. These signaling molecules modulate crucial processes of the CNS, including, cellular migration and differentiation, synaptic transmission and plasticity, glial activation, cell viability and microvascular blood flow. Gap junction channels and hemichannels are affected by different signaling transduction pathways triggered by these paracrine/autocrine signaling molecules. Most of the modulatory effects induced by these signaling molecules are specific to the cell type and the connexin and pannexin subtype expressed in different brain areas. In this review, we summarized and discussed most of the relevant and recently published information on the effects of signaling molecules on connexin or pannexin based channels and their possible relevance in CNS physiology and pathology. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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D'hondt C, Iyyathurai J, Wang N, Gourdie RG, Himpens B, Leybaert L, Bultynck G. Negatively charged residues (Asp378 and Asp379) in the last ten amino acids of the C-terminal tail of Cx43 hemichannels are essential for loop/tail interactions. Biochem Biophys Res Commun 2013; 432:707-12. [PMID: 23376080 DOI: 10.1016/j.bbrc.2013.01.066] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 01/17/2013] [Indexed: 01/08/2023]
Abstract
Connexin 43 (Cx43)-hemichannel activity is controlled by intramolecular interactions between cytoplasmic loop and C-terminal tail. We previously identified the last 10 amino acids of the C-terminal tail of Cx43 as essential for Cx43-hemichannel activity. We developed a cell-permeable peptide covering this sequence (TAT-Cx43CT). In this study, we examined the critical molecular determinants in TAT-Cx43CT to restore Cx43-hemichannel activity. Using amino acid substitutions in TAT-Cx43CT, we identified the two aspartate (Asp378 and Asp379) and two proline (Pro375 and Pro377) residues as critical for TAT-Cx43CT activity, since TAT-Cx43CT(DD/AA) and TAT-Cx43CT(PP/GG) did not overcome the inhibition of Cx43-hemichannel activity induced by thrombin, micromolar cytoplasmic Ca(2+) concentration or truncation of Cx43 at M(239). Consistent with this, we found that biotin-Cx43CT(DD/AA) was much less efficient than biotin-Cx43CT to bind the purified CL domain of Cx43 in surface plasmon resonance experiments. In conclusion, we postulate that Asp378 and Asp379 in the C-terminal part of Cx43 are essential for loop/tail interactions in Cx43 hemichannels, while Pro375 and Pro377 may help to properly coordinate the critical Asp residues.
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Affiliation(s)
- Catheleyne D'hondt
- Laboratory of Molecular and Cellular Signalling, Department Cellular and Molecular Medicine, Campus Gasthuisberg O/N-1 Bus 802, Herestraat 49, BE-3000 Leuven, Belgium
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Calcium signaling in glioma cells--the role of nucleotide receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 986:61-79. [PMID: 22879064 DOI: 10.1007/978-94-007-4719-7_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calcium signaling is probably one of the evolutionary oldest and the most common way by which the signal can be transmitted from the cell environment to the cytoplasmic calcium binding effectors. Calcium signal is fast and due to diversity of calcium binding proteins it may have a very broad effect on cell behavior. Being a crucial player in neuronal transmission it is also very important for glia physiology. It is responsible for the cross-talk between neurons and astrocytes, for microglia activation and motility. Changes in calcium signaling are also crucial for the behavior of transformed glioma cells. The present Chapter summarizes molecular mechanisms of calcium signal formation present in glial cells with a strong emphasis on extracellular nucleotide-evoked signaling pathways. Some aspects of glioma C6 signaling such as the cross-talk between P2Y(1) and P2Y(12) nucleotide receptors in calcium signal generation will be discussed in-depth, to show complexity of machinery engaged in formation of this signal. Moreover, possible mechanisms of modulation of the calcium signal in diverse environments there will be presented herein. Finally, the possible role of calcium signal in glioma motility is also discussed. This is a very important issue, since glioma cells, contrary to the vast majority of neoplastic cells, cannot spread in the body with the bloodstream and, at least in early stages of tumor development, may expand only by means of sheer motility.
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Fiori MC, Figueroa V, Zoghbi ME, Saéz JC, Reuss L, Altenberg GA. Permeation of calcium through purified connexin 26 hemichannels. J Biol Chem 2012; 287:40826-34. [PMID: 23048025 DOI: 10.1074/jbc.m112.383281] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Indirect evidence suggests that connexin hemichannels are permeable to Ca(2+), but direct demonstration is lacking. RESULTS Calcium moves into liposomes containing purified Cx26 in response to a concentration gradient. CONCLUSION Cx26 hemichannels are permeable to Ca(2+). SIGNIFICANCE Cx26 hemichannels may play a role in Ca(2+) influx into cells under conditions that lead to hemichannel activation, such as ischemic damage. Gap junction channels communicate the cytoplasms of two cells and are formed by head to head association of two hemichannels, one from each of the cells. Gap junction channels and hemichannels are permeable to ions and hydrophilic molecules of up to M(r) 1,000, including second messengers and metabolites. Intercellular Ca(2+) signaling can occur by movement of a number of second messengers, including Ca(2+), through gap junction channels, or by a paracrine pathway that involves activation of purinergic receptors in neighboring cells following ATP release through hemichannels. Understanding Ca(2+) permeation through Cx26 hemichannels is important to assess the role of gap junction channels and hemichannels in health and disease. In this context, it is possible that increased Ca(2+) influx through hemichannels under ischemic conditions contributes to cell damage. Previous studies suggest Ca(2+) permeation through hemichannels, based on indirect arguments. Here, we demonstrate for the first time hemichannel permeability to Ca(2+) by measuring Ca(2+) transport through purified Cx26 hemichannels reconstituted in liposomes. We trapped the low affinity Ca(2+)-sensitive fluorescent probe Fluo-5N into the liposomes and followed the increases in intraliposomal [Ca(2+)] in response to an imposed [Ca(2+)] gradient. We show that Ca(2+) does move through Cx26 hemichannels and that the permeability of the hemichannels to Ca(2+) is high, similar to that for Na(+). We suggest that hemichannels can be a significant pathway for Ca(2+) influx into cells under conditions such as ischemia.
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Affiliation(s)
- Mariana C Fiori
- Department of Cell Physiology and Molecular Biophysics, Texas Tech Health Sciences Center, Lubbock, TX 79430-6551, USA
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Abstract
Intercellular calcium (Ca(2+)) waves (ICWs) represent the propagation of increases in intracellular Ca(2+) through a syncytium of cells and appear to be a fundamental mechanism for coordinating multicellular responses. ICWs occur in a wide diversity of cells and have been extensively studied in vitro. More recent studies focus on ICWs in vivo. ICWs are triggered by a variety of stimuli and involve the release of Ca(2+) from internal stores. The propagation of ICWs predominately involves cell communication with internal messengers moving via gap junctions or extracellular messengers mediating paracrine signaling. ICWs appear to be important in both normal physiology as well as pathophysiological processes in a variety of organs and tissues including brain, liver, retina, cochlea, and vascular tissue. We review here the mechanisms of initiation and propagation of ICWs, the key intra- and extracellular messengers (inositol 1,4,5-trisphosphate and ATP) mediating ICWs, and the proposed physiological functions of ICWs.
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Affiliation(s)
- Luc Leybaert
- Department of Basic Medical Sciences, Physiology Group, Faculty of Medicine & Health Sciences, Ghent University, Ghent, Belgium.
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Hill EJ, Jiménez-González C, Tarczyluk M, Nagel DA, Coleman MD, Parri HR. NT2 derived neuronal and astrocytic network signalling. PLoS One 2012; 7:e36098. [PMID: 22567128 PMCID: PMC3342170 DOI: 10.1371/journal.pone.0036098] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 03/30/2012] [Indexed: 12/16/2022] Open
Abstract
A major focus of stem cell research is the generation of neurons that may then be implanted to treat neurodegenerative diseases. However, a picture is emerging where astrocytes are partners to neurons in sustaining and modulating brain function. We therefore investigated the functional properties of NT2 derived astrocytes and neurons using electrophysiological and calcium imaging approaches. NT2 neurons (NT2Ns) expressed sodium dependent action potentials, as well as responses to depolarisation and the neurotransmitter glutamate. NT2Ns exhibited spontaneous and coordinated calcium elevations in clusters and in extended processes, indicating local and long distance signalling. Tetrodotoxin sensitive network activity could also be evoked by electrical stimulation. Similarly, NT2 astrocytes (NT2As) exhibited morphology and functional properties consistent with this glial cell type. NT2As responded to neuronal activity and to exogenously applied neurotransmitters with calcium elevations, and in contrast to neurons, also exhibited spontaneous rhythmic calcium oscillations. NT2As also generated propagating calcium waves that were gap junction and purinergic signalling dependent. Our results show that NT2 derived astrocytes exhibit appropriate functionality and that NT2N networks interact with NT2A networks in co-culture. These findings underline the utility of such cultures to investigate human brain cell type signalling under controlled conditions. Furthermore, since stem cell derived neuron function and survival is of great importance therapeutically, our findings suggest that the presence of complementary astrocytes may be valuable in supporting stem cell derived neuronal networks. Indeed, this also supports the intriguing possibility of selective therapeutic replacement of astrocytes in diseases where these cells are either lost or lose functionality.
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Affiliation(s)
- Eric J. Hill
- Aston Research Centre into Healthy Ageing (ARCHA), Aston University, Birmingham, West Midlands, United Kingdom
| | | | - Marta Tarczyluk
- Aston Research Centre into Healthy Ageing (ARCHA), Aston University, Birmingham, West Midlands, United Kingdom
| | - David A. Nagel
- School of Life and Health Sciences, Aston University, Birmingham, West Midlands, United Kingdom
| | - Michael D. Coleman
- School of Life and Health Sciences, Aston University, Birmingham, West Midlands, United Kingdom
| | - H. Rheinallt Parri
- School of Life and Health Sciences, Aston University, Birmingham, West Midlands, United Kingdom
- * E-mail:
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Ishihara Y, Sugawara Y, Kamioka H, Kawanabe N, Kurosaka H, Naruse K, Yamashiro T. In situ imaging of the autonomous intracellular Ca(2+) oscillations of osteoblasts and osteocytes in bone. Bone 2012; 50:842-52. [PMID: 22316656 DOI: 10.1016/j.bone.2012.01.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 12/15/2011] [Accepted: 01/24/2012] [Indexed: 10/14/2022]
Abstract
Bone cells form a complex three-dimensional network consisting of osteoblasts and osteocytes embedded in a mineralized extracellular matrix. Ca(2+) acts as a ubiquitous secondary messenger in various physiological cellular processes and transduces numerous signals to the cell interior and between cells. However, the intracellular Ca(2+) dynamics of bone cells have not been evaluated in living bone. In the present study, we developed a novel ex-vivo live Ca(2+) imaging system that allows the dynamic intracellular Ca(2+) concentration ([Ca(2+)](i)) responses of intact chick calvaria explants to be observed without damaging the bone network. Our live imaging analysis revealed for the first time that both osteoblasts and osteocytes display repetitive and autonomic [Ca(2+)](i) oscillations ex vivo. Thapsigargin, an inhibitor of the endoplasmic reticulum that induces the emptying of intracellular Ca(2+) stores, abolished these [Ca(2+)](i) responses in both osteoblasts and osteocytes, indicating that Ca(2+) release from intracellular stores plays a key role in the [Ca(2+)](i) oscillations of these bone cells in intact bone explants. Another possible [Ca(2+)](i) transient system to be considered is gap junctional communication through which Ca(2+) and other messenger molecules move, at least in part, across cell-cell junctions; therefore, we also investigated the role of gap junctions in the maintenance of the autonomic [Ca(2+)](i) oscillations observed in the intact bone. Treatment with three distinct gap junction inhibitors, 18α-glycyrrhetinic acid, oleamide, and octanol, significantly reduced the proportion of responsive osteocytes, indicating that gap junctions are important for the maintenance of [Ca(2+)](i) oscillations in osteocytes, but less in osteoblasts. Taken together, we found that the bone cells in intact bone explants showed autonomous [Ca(2+)](i) oscillations that required the release of intracellular Ca(2+) stores. In addition, osteocytes specifically modulated these oscillations via cell-cell communication through gap junctions, which maintains the observed [Ca(2+)](i) oscillations of bone cells.
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Affiliation(s)
- Yoshihito Ishihara
- Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, 700-8525, Japan.
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Beyer T, Thumberger T, Schweickert A, Blum M. Connexin26-mediated transfer of laterality cues in Xenopus. Biol Open 2012; 1:473-81. [PMID: 23213439 PMCID: PMC3507211 DOI: 10.1242/bio.2012760] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A cilia-driven leftward flow of extracellular fluid breaks bilateral symmetry in the dorsal midline of the neurula stage vertebrate embryo. The left-specific Nodal signaling cascade in the lateral plate mesoderm (LPM) is key to asymmetric morphogenesis and placement of organs during subsequent development. The nature of the initial asymmetric cue(s) as well as the transfer of information from the midline to the left side has remained elusive. Gap junctional communication has been previously involved in Xenopus left-right (LR) development, however a function at cleavage stages was inferred from inhibitor experiments. Here we show by heptanol-mediated block of connexin function that flow stages during neurulation represent the critical time window. Flow in Xenopus occurs at the gastrocoel roof plate (GRP), a ciliated sheath of cells of mesodermal fate transiently positioned within the dorsal epithelial lining of the forming archenteron. We reasoned that endodermal cells immediately adjacent to the GRP are important for transfer of asymmetry. A systematic screen identified two connexin genes, Cx26 and Cx32, which were co-expressed in these lateral endodermal cells. Gain- and loss-of-function experiments pinpointed Cx26 as the critical connexin for LR development, while Cx32 had no effect on laterality. Importantly, GRP morphology, ciliation and flow were not affected in Cx26 morphants. Our results demonstrate a decisive role of Cx26 in the transfer of laterality cues from the GRP to the left LPM, providing a novel access to the identification of the initial asymmetric signal generated by flow.
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Affiliation(s)
- Tina Beyer
- University of Hohenheim, Institute of Zoology, Garbenstrasse 30, 70593 Stuttgart, Germany
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Amiri M, Bahrami F, Janahmadi M. On the role of astrocytes in epilepsy: A functional modeling approach. Neurosci Res 2012; 72:172-80. [DOI: 10.1016/j.neures.2011.11.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/27/2011] [Accepted: 11/15/2011] [Indexed: 11/28/2022]
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