1
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Denaroso GE, Smith Z, Angeliu CG, Cheli VT, Wang C, Paez PM. Deletion of voltage-gated calcium channels in astrocytes decreases neuroinflammation and demyelination in a murine model of multiple sclerosis. J Neuroinflammation 2023; 20:263. [PMID: 37964385 PMCID: PMC10644533 DOI: 10.1186/s12974-023-02948-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 11/05/2023] [Indexed: 11/16/2023] Open
Abstract
The experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis was used in combination with a Cav1.2 conditional knock-out mouse (Cav1.2KO) to study the role of astrocytic voltage-gated Ca++ channels in autoimmune CNS inflammation and demyelination. Cav1.2 channels were specifically ablated in Glast-1-positive astrocytes by means of the Cre-lox system before EAE induction. After immunization, motor activity was assessed daily, and a clinical score was given based on the severity of EAE symptoms. Cav1.2 deletion in astrocytes significantly reduced the severity of the disease. While no changes were found in the day of onset and peak disease severity, EAE mean clinical score was lower in Cav1.2KO animals during the chronic phase of the disease. This corresponded to better performance on the rotarod and increased motor activity in Cav1.2KO mice. Furthermore, decreased numbers of reactive astrocytes, activated microglia, and infiltrating lymphocytes were found in the lumbar section of the spinal cord of Cav1.2KO mice 40 days after immunization. The degree of myelin protein loss and size of demyelinated lesions were also attenuated in Cav1.2KO spinal cords. Similar results were found in EAE animals treated with nimodipine, a Cav1.2 Ca++ channel inhibitor with high affinity to the CNS. Mice injected with nimodipine during the acute and chronic phases of the disease exhibited lower numbers of reactive astrocytes, activated microglial, and infiltrating immune cells, as well as fewer demyelinated lesions in the spinal cord. These changes were correlated with improved clinical scores and motor performance. In summary, these data suggest that antagonizing Cav1.2 channels in astrocytes during EAE alleviates neuroinflammation and protects the spinal cord from autoimmune demyelination.
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Affiliation(s)
- G E Denaroso
- Institute for Myelin and Glia Exploration, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY, 14203, USA
| | - Z Smith
- Institute for Myelin and Glia Exploration, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY, 14203, USA
| | - C G Angeliu
- Institute for Myelin and Glia Exploration, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY, 14203, USA
| | - V T Cheli
- Institute for Myelin and Glia Exploration, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY, 14203, USA
| | - C Wang
- Institute for Myelin and Glia Exploration, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY, 14203, USA
| | - P M Paez
- Institute for Myelin and Glia Exploration, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY, 14203, USA.
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2
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Cuong Tran NK, Jeong JH, Sharma N, Doan Nguyen YN, Phi Tran HY, Dang DK, Park JH, Byun JK, Jin D, Xiaoyan Z, Ko SK, Nah SY, Kim HC, Shin EJ. Ginsenoside Re blocks Bay k-8644-induced neurotoxicity via attenuating mitochondrial dysfunction and PKCδ activation in the hippocampus of mice: Involvement of antioxidant potential. Food Chem Toxicol 2023:113869. [PMID: 37308051 DOI: 10.1016/j.fct.2023.113869] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 06/01/2023] [Indexed: 06/14/2023]
Abstract
Although the anticonvulsant effects of ginsenosides are recognized, little is known about their effects on the convulsive behaviors induced by the activation of L-type Ca2+ channels. Here, we investigated whether ginsenoside Re (GRe) modulates excitotoxicity induced by the L-type Ca2+ channel activator Bay k-8644. GRe significantly attenuated Bay k-8644-induced convulsive behaviors and hippocampal oxidative stress in mice. GRe-mediated antioxidant potential was more pronounced in the mitochondrial fraction than cytosolic fraction. As L-type Ca2+ channels are thought to be targets of protein kinase C (PKC), we investigated the role of PKC under excitotoxic conditions. GRe attenuated Bay k-8644-induced mitochondrial dysfunction, PKCδ activation, and neuronal loss. The PKCδ inhibition and neuroprotection mediated by GRe were comparable to those by the ROS inhibitor N-acetylcysteine, the mitochondrial protectant cyclosporin A, the microglial inhibitor minocycline, or the PKCδ inhibitor rottlerin. Consistently, the GRe-mediated PKCδ inhibition and neuroprotection were counteracted by the mitochondrial toxin 3-nitropropionic acid or the PKC activator bryostatin-1. GRe treatment did not have additional effects on PKCδ gene knockout-mediated neuroprotection, suggesting that PKCδ is a molecular target of GRe. Collectively, our results suggest that GRe-mediated anticonvulsive/neuroprotective effects require the attenuation of mitochondrial dysfunction and altered redox status and inactivation of PKCδ.
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Affiliation(s)
- Ngoc Kim Cuong Tran
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chunchon, 24341, Republic of Korea.
| | - Ji Hoon Jeong
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, College of Medicine, Chung-Ang University, Seoul, 06974, Republic of Korea.
| | - Naveen Sharma
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chunchon, 24341, Republic of Korea; Department of Global Innovative Drugs, Graduate School of Chung-Ang University, College of Medicine, Chung-Ang University, Seoul, 06974, Republic of Korea
| | - Yen Nhi Doan Nguyen
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chunchon, 24341, Republic of Korea
| | - Hoang-Yen Phi Tran
- Physical Chemistry Department, University of Medicine and Pharmacy, Ho Chi Minh City, 760000, Viet Nam
| | - Duy-Khanh Dang
- Pharmacy Faculty, Can Tho University of Medicine and Pharmacy, Can Tho City, 900000, Viet Nam
| | - Jung Hoon Park
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chunchon, 24341, Republic of Korea
| | - Jae Kyung Byun
- Korea Society of Forest Environmental Research, Namyangju, 12106, Republic of Korea
| | - Dezhong Jin
- Department of Oriental Medical Food & Nutrition, Semyung University, Jecheon, 27316, Republic of Korea
| | - Zeng Xiaoyan
- Department of Oriental Medical Food & Nutrition, Semyung University, Jecheon, 27316, Republic of Korea
| | - Sung Kwon Ko
- Department of Oriental Medical Food & Nutrition, Semyung University, Jecheon, 27316, Republic of Korea
| | - Seung-Yeol Nah
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine, Konkuk University, Seoul, 05029, Republic of Korea
| | - Hyoung-Chun Kim
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chunchon, 24341, Republic of Korea.
| | - Eun-Joo Shin
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chunchon, 24341, Republic of Korea.
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3
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Needham H, Torpey G, Flores CC, Davis CJ, Vanderheyden WM, Gerstner JR. A Dichotomous Role for FABP7 in Sleep and Alzheimer's Disease Pathogenesis: A Hypothesis. Front Neurosci 2022; 16:798994. [PMID: 35844236 PMCID: PMC9280343 DOI: 10.3389/fnins.2022.798994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 05/10/2022] [Indexed: 11/15/2022] Open
Abstract
Fatty acid binding proteins (FABPs) are a family of intracellular lipid chaperone proteins known to play critical roles in the regulation of fatty acid uptake and transport as well as gene expression. Brain-type fatty acid binding protein (FABP7) is enriched in astrocytes and has been implicated in sleep/wake regulation and neurodegenerative diseases; however, the precise mechanisms underlying the role of FABP7 in these biological processes remain unclear. FABP7 binds to both arachidonic acid (AA) and docosahexaenoic acid (DHA), resulting in discrete physiological responses. Here, we propose a dichotomous role for FABP7 in which ligand type determines the subcellular translocation of fatty acids, either promoting wakefulness aligned with Alzheimer's pathogenesis or promoting sleep with concomitant activation of anti-inflammatory pathways and neuroprotection. We hypothesize that FABP7-mediated translocation of AA to the endoplasmic reticulum of astrocytes increases astrogliosis, impedes glutamatergic uptake, and enhances wakefulness and inflammatory pathways via COX-2 dependent generation of pro-inflammatory prostaglandins. Conversely, we propose that FABP7-mediated translocation of DHA to the nucleus stabilizes astrocyte-neuron lactate shuttle dynamics, preserves glutamatergic uptake, and promotes sleep by activating anti-inflammatory pathways through the peroxisome proliferator-activated receptor-γ transcriptional cascade. Importantly, this model generates several testable hypotheses applicable to other neurodegenerative diseases, including amyotrophic lateral sclerosis and Parkinson's disease.
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Affiliation(s)
- Hope Needham
- Department of Biology, Gonzaga University, Spokane, WA, United States
| | - Grace Torpey
- Department of Biology, Gonzaga University, Spokane, WA, United States
| | - Carlos C. Flores
- Department of Translational Medicine and Physiology, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - Christopher J. Davis
- Department of Translational Medicine and Physiology, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
- Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - William M. Vanderheyden
- Department of Translational Medicine and Physiology, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
- Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - Jason R. Gerstner
- Department of Translational Medicine and Physiology, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
- Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
- Steve Gleason Institute for Neuroscience, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
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4
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Perrillat-Mercerot A, Deliot N, Miranville A, Guillevin R, Constantin B. Mathematical Analysis of Membrane Transporters Dynamics: A Calcium Fluxes Case Study. Acta Biotheor 2022; 70:14. [PMID: 35482100 DOI: 10.1007/s10441-022-09437-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 04/03/2022] [Indexed: 12/07/2022]
Abstract
A tight control of intracellular [Ca[Formula: see text]] is essential for the survival and normal function of cells. In this study we investigate key mechanistic steps by which calcium is regulated and calcium oscillations could occur using in silico modeling of membrane transporters. To do so we give a deterministic description of intracellular Ca[Formula: see text] dynamics using nonlinear dynamics in order to understand Ca[Formula: see text] signaling. We first present the ordinary differential equations (ODEs) system for cell calcium kinetics and make a preliminary work on Sobol indices. We then describe and analyze complex transporters action. Besides, we analyze the whole system. We finally perform numerical simulations and compare our results to real data.
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Affiliation(s)
- A Perrillat-Mercerot
- R&D Scientist at Novadiscovery, 1 Place Giovanni da Verrazzano, Lyon, 69009, France.
| | - N Deliot
- Université de Poitiers, Laboratoire Signalisation et Transports Ioniques Membranaires, ERL CNRS 7003, Equipe 4CS, Bâtiment B36 - TSA 51106, 1 Rue Georges Bonnet, Poitiers Cedex 9, 86073, France
| | - A Miranville
- Université de Poitiers, Laboratoire commun I3M (CNRS-UP-CHU-SIEMENS), Laboratoire de Mathématiques et Applications, UMR CNRS 7348, Equipe DACTIM-MIS, Site du Futuroscope - Téléport 2, 11 Boulevard Marie et Pierre Curie, Bâtiment H3 - TSA 61125, Poitiers Cedex 9, 86073, France
| | - R Guillevin
- Université de Poitiers, Laboratoire commun I3M (CNRS-UP-CHU-SIEMENS), Laboratoire de Mathématiques et Applications, UMR CNRS 7348, Equipe DACTIM-MIS, Site du Futuroscope - Téléport 2, 11 Boulevard Marie et Pierre Curie, Bâtiment H3 - TSA 61125, Poitiers Cedex 9, 86073, France
- CHU de Poitiers, 2 Rue de la Milétrie, Poitiers, 86021, France
| | - B Constantin
- Université de Poitiers, Laboratoire Signalisation et Transports Ioniques Membranaires, ERL CNRS 7003, Equipe 4CS, Bâtiment B36 - TSA 51106, 1 Rue Georges Bonnet, Poitiers Cedex 9, 86073, France
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5
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Bistability and Chaos Emergence in Spontaneous Dynamics of Astrocytic Calcium Concentration. MATHEMATICS 2022. [DOI: 10.3390/math10081337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this work, we consider a mathematical model describing spontaneous calcium signaling in astrocytes. Based on biologically relevant principles, this model simulates experimentally observed calcium oscillations and can predict the emergence of complicated dynamics. Using analytical and numerical analysis, various attracting sets were found and investigated. Employing bifurcation theory analysis, we examined steady state solutions, bistability, simple and complicated periodic limit cycles and also chaotic attractors. We found that astrocytes possess a variety of complex dynamical modes, including chaos and multistability, that can further provide different modulations of neuronal circuits, enhancing their plasticity and flexibility.
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6
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Moura DMS, Brennan EJ, Brock R, Cocas LA. Neuron to Oligodendrocyte Precursor Cell Synapses: Protagonists in Oligodendrocyte Development and Myelination, and Targets for Therapeutics. Front Neurosci 2022; 15:779125. [PMID: 35115904 PMCID: PMC8804499 DOI: 10.3389/fnins.2021.779125] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 12/17/2021] [Indexed: 12/17/2022] Open
Abstract
The development of neuronal circuitry required for cognition, complex motor behaviors, and sensory integration requires myelination. The role of glial cells such as astrocytes and microglia in shaping synapses and circuits have been covered in other reviews in this journal and elsewhere. This review summarizes the role of another glial cell type, oligodendrocytes, in shaping synapse formation, neuronal circuit development, and myelination in both normal development and in demyelinating disease. Oligodendrocytes ensheath and insulate neuronal axons with myelin, and this facilitates fast conduction of electrical nerve impulses via saltatory conduction. Oligodendrocytes also proliferate during postnatal development, and defects in their maturation have been linked to abnormal myelination. Myelination also regulates the timing of activity in neural circuits and is important for maintaining the health of axons and providing nutritional support. Recent studies have shown that dysfunction in oligodendrocyte development and in myelination can contribute to defects in neuronal synapse formation and circuit development. We discuss glutamatergic and GABAergic receptors and voltage gated ion channel expression and function in oligodendrocyte development and myelination. We explain the role of excitatory and inhibitory neurotransmission on oligodendrocyte proliferation, migration, differentiation, and myelination. We then focus on how our understanding of the synaptic connectivity between neurons and OPCs can inform future therapeutics in demyelinating disease, and discuss gaps in the literature that would inform new therapies for remyelination.
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Affiliation(s)
- Daniela M. S. Moura
- Department of Biology, Santa Clara University, Santa Clara, CA, United States
| | - Emma J. Brennan
- Department of Biology, Santa Clara University, Santa Clara, CA, United States
| | - Robert Brock
- Department of Biology, Santa Clara University, Santa Clara, CA, United States
| | - Laura A. Cocas
- Department of Biology, Santa Clara University, Santa Clara, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
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7
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Heuser K, Enger R. Astrocytic Ca 2+ Signaling in Epilepsy. Front Cell Neurosci 2021; 15:695380. [PMID: 34335188 PMCID: PMC8320018 DOI: 10.3389/fncel.2021.695380] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 06/16/2021] [Indexed: 01/10/2023] Open
Abstract
Epilepsy is one of the most common neurological disorders – estimated to affect at least 65 million worldwide. Most of the epilepsy research has so far focused on how to dampen neuronal discharges and to explain how changes in intrinsic neuronal activity or network function cause seizures. As a result, pharmacological therapy has largely been limited to symptomatic treatment targeted at neurons. Given the expanding spectrum of functions ascribed to the non-neuronal constituents of the brain, in both physiological brain function and in brain disorders, it is natural to closely consider the roles of astrocytes in epilepsy. It is now widely accepted that astrocytes are key controllers of the composition of the extracellular fluids, and may directly interact with neurons by releasing gliotransmitters. A central tenet is that astrocytic intracellular Ca2+ signals promote release of such signaling substances, either through synaptic or non-synaptic mechanisms. Accruing evidence suggests that astrocytic Ca2+ signals play important roles in both seizures and epilepsy, and this review aims to highlight the current knowledge of the roles of this central astrocytic signaling mechanism in ictogenesis and epileptogenesis.
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Affiliation(s)
- Kjell Heuser
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Rune Enger
- Letten Centre and GliaLab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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8
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das Neves SP, Sousa JC, Sousa N, Cerqueira JJ, Marques F. Altered astrocytic function in experimental neuroinflammation and multiple sclerosis. Glia 2020; 69:1341-1368. [PMID: 33247866 DOI: 10.1002/glia.23940] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 11/14/2020] [Accepted: 11/17/2020] [Indexed: 12/11/2022]
Abstract
Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that affects about 2.5 million people worldwide. In MS, the patients' immune system starts to attack the myelin sheath, leading to demyelination, neurodegeneration, and, ultimately, loss of vital neurological functions such as walking. There is currently no cure for MS and the available treatments only slow the initial phases of the disease. The later-disease mechanisms are poorly understood and do not directly correlate with the activity of immune system cells, the main target of the available treatments. Instead, evidence suggests that disease progression and disability are better correlated with the maintenance of a persistent low-grade inflammation inside the CNS, driven by local glial cells, like astrocytes and microglia. Depending on the context, astrocytes can (a) exacerbate inflammation or (b) promote immunosuppression and tissue repair. In this review, we will address the present knowledge that exists regarding the role of astrocytes in MS and experimental animal models of the disease.
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Affiliation(s)
- Sofia Pereira das Neves
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga, Portugal
| | - João Carlos Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga, Portugal.,Clinical Academic Center, Braga, Portugal
| | - João José Cerqueira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga, Portugal.,Clinical Academic Center, Braga, Portugal
| | - Fernanda Marques
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga, Portugal
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9
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Cho J, Huh Y. Astrocytic Calcium Dynamics Along the Pain Pathway. Front Cell Neurosci 2020; 14:594216. [PMID: 33192331 PMCID: PMC7596274 DOI: 10.3389/fncel.2020.594216] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 09/14/2020] [Indexed: 12/30/2022] Open
Abstract
Astrocytes, once thought to be passive cells merely filling the space between neurons in the nervous system, are receiving attention as active modulators of the brain and spinal cord physiology by providing nutrients, maintaining homeostasis, and modulating synaptic transmission. Accumulating evidence indicates that astrocytes are critically involved in chronic pain regulation. Injury induces astrocytes to become reactive, and recent studies suggest that reactive astrocytes can have either neuroprotective or neurodegenerative effects. While the exact mechanisms underlying the transition from resting astrocytes to reactive astrocytes remain unknown, astrocytic calcium increase, coordinated by inflammatory molecules, has been suggested to trigger this transition. In this mini review article, we will discuss the roles of astrocytic calcium, channels contributing to calcium dynamics in astrocytes, astrocyte activations along the pain pathway, and possible relationships between astrocytic calcium dynamics and chronic pain.
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Affiliation(s)
- Jeiwon Cho
- Brain and Cognitive Science, Scranton College, Ewha Womans University, Seoul, South Korea
| | - Yeowool Huh
- Department of Medical Science, College of Medicine, Catholic Kwandong University, Incheon, South Korea.,Translational Brain Research Center, Catholic Kwandong University, International St. Mary's Hospital, Incheon, South Korea
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10
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Direct monitoring of ER Ca 2+ dynamics reveals that Ca 2+ entry induces ER-Ca 2+ release in astrocytes. Pflugers Arch 2020; 472:439-448. [PMID: 32246199 DOI: 10.1007/s00424-020-02364-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/29/2020] [Accepted: 03/12/2020] [Indexed: 12/23/2022]
Abstract
Excitability in astroglia is controlled by Ca2+ fluxes from intracellular organelles, mostly from the endoplasmic reticulum (ER). Astrocytic ER possesses inositol 1,4,5-trisphosphate receptors (InsP3R) that can be activated upon stimulation through a vast number of metabotropic G-protein-coupled receptors. By contrast, the role of Ca2+-gated Ca2+ release channels is less explored in astroglia. Here we address this process by monitoring Ca2+ dynamics directly in the cytosol and the ER of astroglial cells. Cultured astrocytes exhibited spontaneous and high-K-evoked cytosolic Ca2+ transients, both of them reversibly abolished by external Ca2+ removal, addition of plasma membrane channel blockers or ER Ca2+ depletion with SERCA inhibitors. Resting astrocyte [Ca2+]ER averaged 400 μM and maximal stimulation with ATP provoked a complete and reversible ER discharge. Direct monitoring of Ca2+ in the lumen of ER showed that high-K induced a Ca2+ release from the ER, and its amplitude was proportional to the [K]. Furthermore, by combining the low affinity GAP3 indicator targeted to the ER with the high affinity cytosolic Rhod-2, we simultaneously imaged ER- and cytosolic-Ca2+ signals, in astrocytes in culture and in situ. Plasma membrane Ca2+ entry triggered a fast ER Ca2+ release coordinated with an increase in cytosolic Ca2+. Thus, we identify a Ca2+-induced Ca2+-release (CICR) mechanism that is likely to participate in spontaneous astroglial oscillations, providing a graded amplification of the cytosolic Ca2+ signal.
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11
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Deletion of Voltage-Gated Calcium Channels in Astrocytes during Demyelination Reduces Brain Inflammation and Promotes Myelin Regeneration in Mice. J Neurosci 2020; 40:3332-3347. [PMID: 32169969 DOI: 10.1523/jneurosci.1644-19.2020] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 02/28/2020] [Accepted: 03/03/2020] [Indexed: 12/28/2022] Open
Abstract
To determine whether Cav1.2 voltage-gated Ca2+ channels contribute to astrocyte activation, we generated an inducible conditional knock-out mouse in which the Cav1.2 α subunit was deleted in GFAP-positive astrocytes. This astrocytic Cav1.2 knock-out mouse was tested in the cuprizone model of myelin injury and repair which causes astrocyte and microglia activation in the absence of a lymphocytic response. Deletion of Cav1.2 channels in GFAP-positive astrocytes during cuprizone-induced demyelination leads to a significant reduction in the degree of astrocyte and microglia activation and proliferation in mice of either sex. Concomitantly, the production of proinflammatory factors such as TNFα, IL1β and TGFβ1 was significantly decreased in the corpus callosum and cortex of Cav1.2 knock-out mice through demyelination. Furthermore, this mild inflammatory environment promotes oligodendrocyte progenitor cells maturation and myelin regeneration across the remyelination phase of the cuprizone model. Similar results were found in animals treated with nimodipine, a Cav1.2 Ca2+ channel inhibitor with high affinity to the CNS. Mice of either sex injected with nimodipine during the demyelination stage of the cuprizone treatment displayed a reduced number of reactive astrocytes and showed a faster and more efficient brain remyelination. Together, these results indicate that Cav1.2 Ca2+ channels play a crucial role in the induction and proliferation of reactive astrocytes during demyelination; and that attenuation of astrocytic voltage-gated Ca2+ influx may be an effective therapy to reduce brain inflammation and promote myelin recovery in demyelinating diseases.SIGNIFICANCE STATEMENT Reducing voltage-gated Ca2+ influx in astrocytes during brain demyelination significantly attenuates brain inflammation and astrocyte reactivity. Furthermore, these changes promote myelin restoration and oligodendrocyte maturation throughout remyelination.
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12
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Denizot A, Arizono M, Nägerl UV, Soula H, Berry H. Simulation of calcium signaling in fine astrocytic processes: Effect of spatial properties on spontaneous activity. PLoS Comput Biol 2019; 15:e1006795. [PMID: 31425510 PMCID: PMC6726244 DOI: 10.1371/journal.pcbi.1006795] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 09/04/2019] [Accepted: 07/08/2019] [Indexed: 12/20/2022] Open
Abstract
Astrocytes, a glial cell type of the central nervous system, have emerged as detectors and regulators of neuronal information processing. Astrocyte excitability resides in transient variations of free cytosolic calcium concentration over a range of temporal and spatial scales, from sub-microdomains to waves propagating throughout the cell. Despite extensive experimental approaches, it is not clear how these signals are transmitted to and integrated within an astrocyte. The localization of the main molecular actors and the geometry of the system, including the spatial organization of calcium channels IP3R, are deemed essential. However, as most calcium signals occur in astrocytic ramifications that are too fine to be resolved by conventional light microscopy, most of those spatial data are unknown and computational modeling remains the only methodology to study this issue. Here, we propose an IP3R-mediated calcium signaling model for dynamics in such small sub-cellular volumes. To account for the expected stochasticity and low copy numbers, our model is both spatially explicit and particle-based. Extensive simulations show that spontaneous calcium signals arise in the model via the interplay between excitability and stochasticity. The model reproduces the main forms of calcium signals and indicates that their frequency crucially depends on the spatial organization of the IP3R channels. Importantly, we show that two processes expressing exactly the same calcium channels can display different types of calcium signals depending on the spatial organization of the channels. Our model with realistic process volume and calcium concentrations successfully reproduces spontaneous calcium signals that we measured in calcium micro-domains with confocal microscopy and predicts that local variations of calcium indicators might contribute to the diversity of calcium signals observed in astrocytes. To our knowledge, this model is the first model suited to investigate calcium dynamics in fine astrocytic processes and to propose plausible mechanisms responsible for their variability.
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Affiliation(s)
- Audrey Denizot
- INRIA, F-69603, Villeurbanne, France
- Univ Lyon, LIRIS, UMR5205 CNRS, F-69621, Villeurbanne, France
| | - Misa Arizono
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France
| | - U. Valentin Nägerl
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France
| | - Hédi Soula
- INRIA, F-69603, Villeurbanne, France
- Univ P&M Curie, CRC, INSERM UMRS 1138, F-75006, Paris, France
| | - Hugues Berry
- INRIA, F-69603, Villeurbanne, France
- Univ Lyon, LIRIS, UMR5205 CNRS, F-69621, Villeurbanne, France
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13
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Calcium(II) oscillations to glucose: An astrocyte relation. Biophys Chem 2019; 252:106195. [PMID: 31195340 DOI: 10.1016/j.bpc.2019.106195] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/28/2019] [Accepted: 05/29/2019] [Indexed: 11/22/2022]
Abstract
Astrocytes, the most common type of glial cell, are critical to the health of the central nervous system. Evidence implies that changes in the astrocyte's cytosolic calcium concentration is part of a central mechanism by which information is passed and processed in the cell, and it is linked to both external stimuli impacting the cell as well as downstream events such as metabolism and neurotransmitter release. This work proposes a novel chemical model to further the understanding of how extracellular signals could affect intracellular calcium dynamics and metabolic processes within the cell.
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14
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Kalita J, Uniyal R, Misra UK, Bhoi SK. Neuronal Dysexcitability May Be a Biomarker of Migraine: A Visual Evoked Potential Study. Clin EEG Neurosci 2018; 49:342-350. [PMID: 28974100 DOI: 10.1177/1550059417734106] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We report neuronal sensitization and impaired habituation in migraine using pattern reversal visual evoked potential (PRVEP) and correlate these with clinical characteristics of migraine. Sixty-five migraineurs and 30 healthy controls were included. A detailed clinical examination was done and migraine characteristics, including migraine trigger, photophobia, phonophobia, and allodynia were noted. Consecutive 5 blocks of PRVEP were recorded averaging 100 epochs at 3 Hz stimuli. The amplitude of N75 and P100 were measured. Amplitude of first block was considered for sensitization, and impaired habituation was considered if any subsequent block was not suppressed. Migraineurs had sensitization of P100 (14.01 ± 6.02 vs 11.60 ± 5.17 µV; P = .049), but not of N75 (42.22 ± 4.79 vs 11.08 ± 4.56 µV; P = .27) compared with the controls. Impaired habituation of N75 was more marked and persisted up to fourth block of VEP recoding. Impaired habituation of P100 was significant only in the third block. Baseline N75 and P100 amplitudes were higher in females, and N75 was also higher in those with longer duration of illness. These phenomena did not correlate with visual triggers. Sensitization and impaired habituation were marked during headache. Based on the PRVEP findings, it may be concluded that migraineurs have sensitization of P100 and impaired habituation of N75 especially during headache. These phenomena may be useful for therapeutic monitoring.
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Affiliation(s)
- Jayantee Kalita
- 1 Department of Neurology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Ravi Uniyal
- 1 Department of Neurology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Usha K Misra
- 1 Department of Neurology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Sanjeev K Bhoi
- 1 Department of Neurology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
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15
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Maneshi MM, Sachs F, Hua SZ. Heterogeneous Cytoskeletal Force Distribution Delineates the Onset Ca 2+ Influx Under Fluid Shear Stress in Astrocytes. Front Cell Neurosci 2018; 12:69. [PMID: 29615869 PMCID: PMC5864927 DOI: 10.3389/fncel.2018.00069] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 02/27/2018] [Indexed: 01/13/2023] Open
Abstract
Mechanical perturbations increase intracellular Ca2+ in cells, but the coupling of mechanical forces to the Ca2+ influx is not well understood. We used a microfluidic chamber driven with a high-speed pressure servo to generate defined fluid shear stress to cultured astrocytes, and simultaneously measured cytoskeletal forces using a force sensitive actinin optical sensor and intracellular Ca2+. Fluid shear generated non-uniform forces in actinin that critically depended on the stimulus rise time emphasizing the presence of viscoelasticity in the activating sequence. A short (ms) shear pulse with fast rise time (2 ms) produced an immediate increase in actinin tension at the upstream end of the cell with minimal changes at the downstream end. The onset of Ca2+ rise began at highly strained areas. In contrast to stimulus steps, slow ramp stimuli produced uniform forces throughout the cells and only a small Ca2+ response. The heterogeneity of force distribution is exaggerated in cells having fewer stress fibers and lower pre-tension in actinin. Disruption of cytoskeleton with cytochalasin-D (Cyt-D) eliminated force gradients, and in those cells Ca2+ elevation started from the soma. Thus, Ca2+ influx with a mechanical stimulus depends on local stress within the cell and that is time dependent due to viscoelastic mechanics.
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Affiliation(s)
- Mohammad M Maneshi
- Department of Physiology and Biophysics, University at Buffalo, Buffalo, NY, United States.,Department of Mechanical and Aerospace Engineering, University at Buffalo, Buffalo, NY, United States
| | - Frederick Sachs
- Department of Physiology and Biophysics, University at Buffalo, Buffalo, NY, United States
| | - Susan Z Hua
- Department of Physiology and Biophysics, University at Buffalo, Buffalo, NY, United States.,Department of Mechanical and Aerospace Engineering, University at Buffalo, Buffalo, NY, United States
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16
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Smith NA, Kress BT, Lu Y, Chandler-Militello D, Benraiss A, Nedergaard M. Fluorescent Ca 2+ indicators directly inhibit the Na,K-ATPase and disrupt cellular functions. Sci Signal 2018; 11:11/515/eaal2039. [PMID: 29382785 DOI: 10.1126/scisignal.aal2039] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Fluorescent Ca2+ indicators have been essential for the analysis of Ca2+ signaling events in various cell types. We showed that chemical Ca2+ indicators, but not a genetically encoded Ca2+ indicator, potently suppressed the activity of Na+- and K+-dependent adenosine triphosphatase (Na,K-ATPase), independently of their Ca2+ chelating activity. Loading of commonly used Ca2+ indicators, including Fluo-4 acetoxymethyl (AM), Rhod-2 AM, and Fura-2 AM, and of the Ca2+ chelator BAPTA AM into cultured mouse or human neurons, astrocytes, cardiomyocytes, or kidney proximal tubule epithelial cells suppressed Na,K-ATPase activity by 30 to 80%. Ca2+ indicators also suppressed the agonist-induced activation of the Na,K-ATPase, altered metabolic status, and caused a dose-dependent loss of cell viability. Loading of Ca2+ indicators into mice, which is carried out for two-photon imaging, markedly altered brain extracellular concentrations of K+ and ATP. These results suggest that a critical review of data obtained with chemical Ca2+ indicators may be necessary.
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Affiliation(s)
- Nathan A Smith
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA.,Center for Neuroscience Research, Children's Research Institute, Children's National Health System, Washington, DC 20010, USA
| | - Benjamin T Kress
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Yuan Lu
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Devin Chandler-Militello
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Abdellatif Benraiss
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA.
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17
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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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18
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 899] [Impact Index Per Article: 149.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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19
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Mestre ALG, Cerquido M, Inácio PMC, Asgarifar S, Lourenço AS, Cristiano MLS, Aguiar P, Medeiros MCR, Araújo IM, Ventura J, Gomes HL. Ultrasensitive gold micro-structured electrodes enabling the detection of extra-cellular long-lasting potentials in astrocytes populations. Sci Rep 2017; 7:14284. [PMID: 29079771 PMCID: PMC5660243 DOI: 10.1038/s41598-017-14697-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 10/17/2017] [Indexed: 12/13/2022] Open
Abstract
Ultra-sensitive electrodes for extracellular recordings were fabricated and electrically characterized. A signal detection limit defined by a noise level of 0.3-0.4 μV for a bandwidth of 12.5 Hz was achieved. To obtain this high sensitivity, large area (4 mm2) electrodes were used. The electrode surface is also micro-structured with an array of gold mushroom-like shapes to further enhance the active area. In comparison with a flat gold surface, the micro-structured surface increases the capacitance of the electrode/electrolyte interface by 54%. The electrode low impedance and low noise enable the detection of weak and low frequency quasi-periodic signals produced by astrocytes populations that thus far had remained inaccessible using conventional extracellular electrodes. Signals with 5 μV in amplitude and lasting for 5-10 s were measured, with a peak-to-peak signal-to-noise ratio of 16. The electrodes and the methodology developed here can be used as an ultrasensitive electrophysiological tool to reveal the synchronization dynamics of ultra-slow ionic signalling between non-electrogenic cells.
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Affiliation(s)
- Ana L G Mestre
- Universidade do Algarve, Faculdade de Ciências e Tecnologia, 8005-139, Faro, Portugal
- Instituto de Telecomunicações, Avenida Rovisco Pais 1, 1049-001, Lisboa, Portugal
| | - Mónica Cerquido
- Instituto de Física dos Materiais da Universidade do Porto, Instituto de Nanociências e Nanotecnologia, Departamento de Física e Astronomia, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal
| | - Pedro M C Inácio
- Universidade do Algarve, Faculdade de Ciências e Tecnologia, 8005-139, Faro, Portugal
- Instituto de Telecomunicações, Avenida Rovisco Pais 1, 1049-001, Lisboa, Portugal
| | - Sanaz Asgarifar
- Universidade do Algarve, Faculdade de Ciências e Tecnologia, 8005-139, Faro, Portugal
- Instituto de Telecomunicações, Avenida Rovisco Pais 1, 1049-001, Lisboa, Portugal
| | - Ana S Lourenço
- Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, 8005-139, Faro, Portugal
- Centro de Investigação em Biomedicina, Universidade do Algarve, 8005-139, Faro, Portugal
| | - Maria L S Cristiano
- Universidade do Algarve, Faculdade de Ciências e Tecnologia, 8005-139, Faro, Portugal
- Centro de Ciências do Mar, Universidade do Algarve, 8005-139, Faro, Portugal
| | - Paulo Aguiar
- Instituto de Engenharia Biomédica, Universidade do Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal
| | - Maria C R Medeiros
- Instituto de Telecomunicações, Departamento de Engenharia Electrotécnica e Computadores, Universidade de Coimbra, 3030-290, Coimbra, Portugal
| | - Inês M Araújo
- Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, 8005-139, Faro, Portugal
- Centro de Investigação em Biomedicina, Universidade do Algarve, 8005-139, Faro, Portugal
| | - João Ventura
- Instituto de Física dos Materiais da Universidade do Porto, Instituto de Nanociências e Nanotecnologia, Departamento de Física e Astronomia, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal
| | - Henrique L Gomes
- Universidade do Algarve, Faculdade de Ciências e Tecnologia, 8005-139, Faro, Portugal.
- Instituto de Telecomunicações, Avenida Rovisco Pais 1, 1049-001, Lisboa, Portugal.
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20
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Manninen T, Havela R, Linne ML. Reproducibility and Comparability of Computational Models for Astrocyte Calcium Excitability. Front Neuroinform 2017; 11:11. [PMID: 28270761 PMCID: PMC5318440 DOI: 10.3389/fninf.2017.00011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Accepted: 01/25/2017] [Indexed: 11/13/2022] Open
Abstract
The scientific community across all disciplines faces the same challenges of ensuring accessibility, reproducibility, and efficient comparability of scientific results. Computational neuroscience is a rapidly developing field, where reproducibility and comparability of research results have gained increasing interest over the past years. As the number of computational models of brain functions is increasing, we chose to address reproducibility using four previously published computational models of astrocyte excitability as an example. Although not conventionally taken into account when modeling neuronal systems, astrocytes have been shown to take part in a variety of in vitro and in vivo phenomena including synaptic transmission. Two of the selected astrocyte models describe spontaneous calcium excitability, and the other two neurotransmitter-evoked calcium excitability. We specifically addressed how well the original simulation results can be reproduced with a reimplementation of the models. Additionally, we studied how well the selected models can be reused and whether they are comparable in other stimulation conditions and research settings. Unexpectedly, we found out that three of the model publications did not give all the necessary information required to reimplement the models. In addition, we were able to reproduce the original results of only one of the models completely based on the information given in the original publications and in the errata. We actually found errors in the equations provided by two of the model publications; after modifying the equations accordingly, the original results were reproduced more accurately. Even though the selected models were developed to describe the same biological event, namely astrocyte calcium excitability, the models behaved quite differently compared to one another. Our findings on a specific set of published astrocyte models stress the importance of proper validation of the models against experimental wet-lab data from astrocytes as well as the careful review process of models. A variety of aspects of model development could be improved, including the presentation of models in publications and databases. Specifically, all necessary mathematical equations, as well as parameter values, initial values of variables, and stimuli used should be given precisely for successful reproduction of scientific results.
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Affiliation(s)
- Tiina Manninen
- Computational Neuroscience Group, Faculty of Biomedical Sciences and Engineering and BioMediTech Institute, Tampere University of Technology Tampere, Finland
| | - Riikka Havela
- Computational Neuroscience Group, Faculty of Biomedical Sciences and Engineering and BioMediTech Institute, Tampere University of Technology Tampere, Finland
| | - Marja-Leena Linne
- Computational Neuroscience Group, Faculty of Biomedical Sciences and Engineering and BioMediTech Institute, Tampere University of Technology Tampere, Finland
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21
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Coppola G, Ambrosini A, Clemente LD, Magis D, Fumal A, Gérard P, Pierelli F, Schoenen J. Interictal Abnormalities of Gamma Band Activity in Visual Evoked Responses in Migraine: An Indication of Thalamocortical Dysrhythmia? Cephalalgia 2016; 27:1360-7. [DOI: 10.1111/j.1468-2982.2007.01466.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Between attacks, migraineurs lack habituation in standard visual evoked potentials (VEPs). Visual stimuli also evoke high-frequency oscillations in the gamma band range (GBOs, 20–35 Hz) assumed to be generated both at subcortical (early GBOs) and cortical levels (late GBOs). The consecutive peaks of GBOs were analysed regarding amplitude and habituation in six successive blocks of 100 averaged pattern reversal (PR)-VEPs in healthy volunteers and interictally in migraine with (MA) or without aura patients. Amplitude of the two early GBO components in the first PR-VEP block was significantly increased in MA patients. There was a significant habituation deficit of the late GBO peaks in migraineurs. The increased amplitude of early GBOs could be related to the increased interictal visual discomfort reported by patients. We hypothesize that the hypo-functioning serotonergic pathways may cause, in line with the thalamocortical dysrhythmia theory, a functional disconnection of the thalamus leading to decreased intracortical lateral inhibition, which can induce dishabituation.
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Affiliation(s)
- G Coppola
- G.B. Bietti Eye Foundation-IRCCS, Department of Neurophysiology of Vision and Neurophthalmology
| | | | - L Di Clemente
- Headache Clinic, Department of Neurological Sciences, University ‘La Sapienza’, Rome, Italy
| | - D Magis
- Headache Research Unit, University Department of Neurology
| | - A Fumal
- Headache Research Unit, University Department of Neurology
| | - P Gérard
- Headache Research Unit, University Department of Neurology
| | - F Pierelli
- IRCCS-Neuromed, Pozzilli (IS)
- University ‘La Sapienza’, Polo Pontino—I.C.O.T., Rome, Italy
| | - J Schoenen
- Headache Research Unit, University Department of Neurology
- Res Ctr for Cell & Mol Neurobiology, Liège University, Liège, Belgium
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22
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Cheli VT, Santiago González DA, Smith J, Spreuer V, Murphy GG, Paez PM. L-type voltage-operated calcium channels contribute to astrocyte activation In vitro. Glia 2016; 64:1396-415. [PMID: 27247164 DOI: 10.1002/glia.23013] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 03/11/2016] [Accepted: 05/12/2016] [Indexed: 12/20/2022]
Abstract
We have found a significant upregulation of L-type voltage-operated Ca(++) channels (VOCCs) in reactive astrocytes. To test if VOCCs are centrally involved in triggering astrocyte reactivity, we used in vitro models of astrocyte activation in combination with pharmacological inhibitors, siRNAs and the Cre/lox system to reduce the activity of L-type VOCCs in primary cortical astrocytes. The endotoxin lipopolysaccharide (LPS) as well as high extracellular K(+) , glutamate, and ATP promote astrogliosis in vitro. L-type VOCC inhibitors drastically reduce the number of reactive cells, astrocyte hypertrophy, and cell proliferation after these treatments. Astrocytes transfected with siRNAs for the Cav1.2 subunit that conducts L-type Ca(++) currents as well as Cav1.2 knockout astrocytes showed reduce Ca(++) influx by ∼80% after plasma membrane depolarization. Importantly, Cav1.2 knock-down/out prevents astrocyte activation and proliferation induced by LPS. Similar results were found using the scratch wound assay. After injuring the astrocyte monolayer, cells extend processes toward the cell-free scratch region and subsequently migrate and populate the scratch. We found a significant increase in the activity of L-type VOCCs in reactive astrocytes located in the growing line in comparison to quiescent astrocytes situated away from the scratch. Moreover, the migration of astrocytes from the scratching line as well as the number of proliferating astrocytes was reduced in Cav1.2 knock-down/out cultures. In summary, our results suggest that Cav1.2 L-type VOCCs play a fundamental role in the induction and/or proliferation of reactive astrocytes, and indicate that the inhibition of these Ca(++) channels may be an effective way to prevent astrocyte activation. GLIA 2016. GLIA 2016;64:1396-1415.
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Affiliation(s)
- Veronica T Cheli
- Department of Pharmacology and Toxicology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo. NYS Center of Excellence, 701 Ellicott St., Buffalo, New York
| | - Diara A Santiago González
- Department of Pharmacology and Toxicology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo. NYS Center of Excellence, 701 Ellicott St., Buffalo, New York
| | - Jessica Smith
- Department of Pharmacology and Toxicology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo. NYS Center of Excellence, 701 Ellicott St., Buffalo, New York
| | - Vilma Spreuer
- Department of Pharmacology and Toxicology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo. NYS Center of Excellence, 701 Ellicott St., Buffalo, New York
| | - Geoffrey G Murphy
- Department of Physiology, Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, Michigan
| | - Pablo M Paez
- Department of Pharmacology and Toxicology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo. NYS Center of Excellence, 701 Ellicott St., Buffalo, New York
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23
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Scofield MD, Boger HA, Smith RJ, Li H, Haydon PG, Kalivas PW. Gq-DREADD Selectively Initiates Glial Glutamate Release and Inhibits Cue-induced Cocaine Seeking. Biol Psychiatry 2015; 78:441-51. [PMID: 25861696 PMCID: PMC4547911 DOI: 10.1016/j.biopsych.2015.02.016] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 02/10/2015] [Accepted: 02/10/2015] [Indexed: 01/24/2023]
Abstract
BACKGROUND Glial cells of the central nervous system directly influence neuronal activity by releasing neuroactive small molecules, including glutamate. Long-lasting cocaine-induced reductions in extracellular glutamate in the nucleus accumbens core (NAcore) affect synaptic plasticity responsible for relapse vulnerability. METHODS We transduced NAcore astrocytes with an adeno-associated virus vector expressing hM3D designer receptor exclusively activated by a designer drug (DREADD) under control of the glial fibrillary acidic protein promoter in 62 male Sprague Dawley rats, 4 dominant-negative soluble N-ethylmaleimide-sensitive factor attachment protein receptor mice, and 4 wild-type littermates. Using glutamate biosensors, we measured NAcore glutamate levels following intracranial or systemic administration of clozapine N-oxide (CNO) and tested the ability of systemic CNO to inhibit reinstated cocaine or sucrose seeking following self-administration and extinction training. RESULTS Administration of CNO in glial fibrillary acidic protein-hM3D-DREADD transfected animals increased NAcore extracellular glutamate levels in vivo. The glial origin of released glutamate was validated by an absence of CNO-mediated release in mice expressing a dominant-negative soluble N-ethylmaleimide-sensitive factor attachment protein receptor variant in glia. Also, CNO-mediated release was relatively insensitive to N-type calcium channel blockade. Systemic administration of CNO inhibited cue-induced reinstatement of cocaine seeking in rats extinguished from cocaine but not sucrose self-administration. The capacity to inhibit reinstated cocaine seeking was prevented by systemic administration of the group II metabotropic glutamate receptor antagonist LY341495. CONCLUSIONS DREADD-mediated glutamate gliotransmission inhibited cue-induced reinstatement of cocaine seeking by stimulating release-regulating group II metabotropic glutamate receptor autoreceptors to inhibit cue-induced synaptic glutamate spillover.
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Affiliation(s)
- Michael D Scofield
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina.
| | - Heather A Boger
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina
| | - Rachel J Smith
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina
| | - Hao Li
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina
| | - Philip G Haydon
- Department of Neurosciences, Tufts University, Boston, Massachusetts
| | - Peter W Kalivas
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina
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24
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Yang J, Yu H, Zhou D, Zhu K, Lou H, Duan S, Wang H. Na+–Ca2+ exchanger mediates ChR2-induced [Ca2+]i elevation in astrocytes. Cell Calcium 2015; 58:307-16. [DOI: 10.1016/j.ceca.2015.06.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 05/21/2015] [Accepted: 06/19/2015] [Indexed: 01/15/2023]
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25
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Astrocyte and Neuronal Plasticity in the Somatosensory System. Neural Plast 2015; 2015:732014. [PMID: 26345481 PMCID: PMC4539490 DOI: 10.1155/2015/732014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/09/2015] [Indexed: 11/17/2022] Open
Abstract
Changing the whisker complement on a rodent's snout can lead to two forms of experience-dependent plasticity (EDP) in the neurons of the barrel cortex, where whiskers are somatotopically represented. One form, termed coding plasticity, concerns changes in synaptic transmission and connectivity between neurons. This is thought to underlie learning and memory processes and so adaptation to a changing environment. The second, called homeostatic plasticity, serves to maintain a restricted dynamic range of neuronal activity thus preventing its saturation or total downregulation. Current explanatory models of cortical EDP are almost exclusively neurocentric. However, in recent years, increasing evidence has emerged on the role of astrocytes in brain function, including plasticity. Indeed, astrocytes appear as necessary partners of neurons at the core of the mechanisms of coding and homeostatic plasticity recorded in neurons. In addition to neuronal plasticity, several different forms of astrocytic plasticity have recently been discovered. They extend from changes in receptor expression and dynamic changes in morphology to alteration in gliotransmitter release. It is however unclear how astrocytic plasticity contributes to the neuronal EDP. Here, we review the known and possible roles for astrocytes in the barrel cortex, including its plasticity.
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Komin N, Moein M, Ellisman MH, Skupin A. Multiscale Modeling Indicates That Temperature Dependent [Ca2+]i Spiking in Astrocytes Is Quantitatively Consistent with Modulated SERCA Activity. Neural Plast 2015; 2015:683490. [PMID: 26347125 PMCID: PMC4539483 DOI: 10.1155/2015/683490] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 03/19/2015] [Indexed: 11/17/2022] Open
Abstract
Changes in the cytosolic Ca(2+) concentration ([Ca(2+)]i) are the most predominant active signaling mechanism in astrocytes that can modulate neuronal activity and is assumed to influence neuronal plasticity. Although Ca(2+) signaling in astrocytes has been intensively studied in the past, our understanding of the signaling mechanism and its impact on tissue level is still incomplete. Here we revisit our previously published data on the strong temperature dependence of Ca(2+) signals in both cultured primary astrocytes and astrocytes in acute brain slices of mice. We apply multiscale modeling to test the hypothesis that the temperature dependent [Ca(2+)]i spiking is mainly caused by the increased activity of the sarcoendoplasmic reticulum ATPases (SERCAs) that remove Ca(2+) from the cytosol into the endoplasmic reticulum. Quantitative comparison of experimental data with multiscale simulations supports the SERCA activity hypothesis. Further analysis of multiscale modeling and traditional rate equations indicates that the experimental observations are a spatial phenomenon where increasing pump strength leads to a decoupling of Ca(2+) release sites and subsequently to vanishing [Ca(2+)]i spikes.
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Affiliation(s)
- Niko Komin
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 7 Avenue des Hauts-Fourneaux, 4362 Esch-sur-Alzette, Luxembourg
- National Centre for Microscopy and Imaging Research, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0608, USA
| | - Mahsa Moein
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 7 Avenue des Hauts-Fourneaux, 4362 Esch-sur-Alzette, Luxembourg
| | - Mark H. Ellisman
- National Centre for Microscopy and Imaging Research, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0608, USA
| | - Alexander Skupin
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 7 Avenue des Hauts-Fourneaux, 4362 Esch-sur-Alzette, Luxembourg
- National Centre for Microscopy and Imaging Research, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0608, USA
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Restuccia D, Coppola G. Auditory stimulation enhances thalamic somatosensory high-frequency oscillations in healthy humans: a neurophysiological marker of cross-sensory sensitization? Eur J Neurosci 2015; 41:1079-85. [PMID: 25784489 DOI: 10.1111/ejn.12873] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 02/11/2015] [Accepted: 02/12/2015] [Indexed: 12/13/2022]
Abstract
Electrical stimulation of upper limb nerves evokes a train of high-frequency wavelets (high-frequency oscillations, HFOs) on the human scalp. These HFOs are related to the influence of arousal-promoting structures on somatosensory input processing, and are generated in the primary somatosensory cortex (post-synaptic HFOs) and the terminal tracts of thalamocortical radiations (pre-synaptic HFOs). We previously reported that HFOs do not undergo habituation to repeated stimulations; here, we verified whether HFOs could be modulated by external sensitizing stimuli. We recorded somatosensory evoked potentials (SSEPs) in 15 healthy volunteers before and after sensitization training with an auditory stimulus. Pre-synaptic HFO amplitudes, reflecting somatosensory thalamic/thalamocortical activity, significantly increased after the sensitizing acoustic stimulation, whereas both the low-frequency N20 SSEP component and post-synaptic HFOs were unaffected. Cross-talk between subcortical arousal-related structures is a probable mechanism for the pre-synaptic HFO effect observed in this study. We propose that part of the ascending somatosensory input encoded in HFOs is specifically able to convey sensitized inputs. This preferential involvement in sensitization mechanisms suggests that HFOs play a critical role in the detection of potentially relevant stimuli, and act at very early stages of somatosensory input processing.
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Affiliation(s)
- Domenico Restuccia
- Department of Neurosciences, Catholic University, Largo A. Gemelli 8, Rome, 00168, Italy
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Koide M, Wellman GC. Activation of TRPV4 channels does not mediate inversion of neurovascular coupling after SAH. ACTA NEUROCHIRURGICA. SUPPLEMENT 2015; 120:111-6. [PMID: 25366609 DOI: 10.1007/978-3-319-04981-6_19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Neurovascular coupling (NVC) allows increased blood flow to metabolically active neurons and involves the Ca²⁺ -dependent release of vasodilator influences by astrocyte endfeet that encase parenchymal arterioles. We previously reported inversion of NVC from dilation to constriction in brain slices from subarachnoid hemorrhage (SAH) model rats. Corresponding to NVC inversion, there was a marked increase in the amplitude of spontaneous Ca²⁺ oscillations in astrocyte endfeet. Calcium-permeable transient receptor potential vanilloid (TRPV)-4 channels have been reported in astrocyte endfeet, and activators of these channels enhance Ca²⁺ oscillations in healthy animals. Here, we examined the role of TRPV4 channels in the development of high-amplitude spontaneous Ca²⁺ oscillations in astrocyte endfeet and the inversion of neurovascular coupling after SAH. Treatment of brain slices with the TRPV4 channel antagonist, HC-067047 (10 μM), did not alter the amplitude of spontaneous Ca²⁺ oscillations after SAH. In addition, HC-067047 did not inhibit or change SAH-induced inversion of neurovascular coupling. In summary, TRPV4 channels do not appear to be involved in the inversion of neurovascular coupling after SAH. Further studies examining the impact of SAH on additional Ca²⁺ signaling pathways in astrocytes are likely to reveal valuable insights into new therapeutic strategies to advance SAH treatments.
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Affiliation(s)
- Masayo Koide
- Department of Pharmacology, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT, USA,
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Verkhratsky A, Parpura V. Physiology of Astroglia: Channels, Receptors, Transporters, Ion Signaling and Gliotransmission. ACTA ACUST UNITED AC 2015. [DOI: 10.4199/c00123ed1v01y201501ngl004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Muñoz MF, Puebla M, Figueroa XF. Control of the neurovascular coupling by nitric oxide-dependent regulation of astrocytic Ca(2+) signaling. Front Cell Neurosci 2015; 9:59. [PMID: 25805969 PMCID: PMC4354411 DOI: 10.3389/fncel.2015.00059] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/07/2015] [Indexed: 12/28/2022] Open
Abstract
Neuronal activity must be tightly coordinated with blood flow to keep proper brain function, which is achieved by a mechanism known as neurovascular coupling. Then, an increase in synaptic activity leads to a dilation of local parenchymal arterioles that matches the enhanced metabolic demand. Neurovascular coupling is orchestrated by astrocytes. These glial cells are located between neurons and the microvasculature, with the astrocytic endfeet ensheathing the vessels, which allows fine intercellular communication. The neurotransmitters released during neuronal activity reach astrocytic receptors and trigger a Ca2+ signaling that propagates to the endfeet, activating the release of vasoactive factors and arteriolar dilation. The astrocyte Ca2+ signaling is coordinated by gap junction channels and hemichannels formed by connexins (Cx43 and Cx30) and channels formed by pannexins (Panx-1). The neuronal activity-initiated Ca2+ waves are propagated among neighboring astrocytes directly via gap junctions or through ATP release via connexin hemichannels or pannexin channels. In addition, Ca2+ entry via connexin hemichannels or pannexin channels may participate in the regulation of the astrocyte signaling-mediated neurovascular coupling. Interestingly, nitric oxide (NO) can activate connexin hemichannel by S-nitrosylation and the Ca2+-dependent NO-synthesizing enzymes endothelial NO synthase (eNOS) and neuronal NOS (nNOS) are expressed in astrocytes. Therefore, the astrocytic Ca2+ signaling triggered in neurovascular coupling may activate NO production, which, in turn, may lead to Ca2+ influx through hemichannel activation. Furthermore, NO release from the hemichannels located at astrocytic endfeet may contribute to the vasodilation of parenchymal arterioles. In this review, we discuss the mechanisms involved in the regulation of the astrocytic Ca2+ signaling that mediates neurovascular coupling, with a special emphasis in the possible participation of NO in this process.
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Affiliation(s)
- Manuel F Muñoz
- Facultad de Ciencias Biológicas, Departamento de Fisiología, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Mariela Puebla
- Facultad de Ciencias Biológicas, Departamento de Fisiología, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Xavier F Figueroa
- Facultad de Ciencias Biológicas, Departamento de Fisiología, Pontificia Universidad Católica de Chile Santiago, Chile
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Detection, characterization and biological activities of [bisphospho-thr3,9]ODN, an endogenous molecular form of ODN released by astrocytes. Neuroscience 2015; 290:472-84. [PMID: 25639232 DOI: 10.1016/j.neuroscience.2015.01.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 12/29/2014] [Accepted: 01/05/2015] [Indexed: 11/23/2022]
Abstract
Astrocytes synthesize and release endozepines, a family of regulatory neuropeptides, including diazepam-binding inhibitor (DBI) and its processing fragments such as the octadecaneuropeptide (ODN). At the molecular level, ODN interacts with two types of receptors, i.e. it acts as an inverse agonist of the central-type benzodiazepine receptor (CBR), and as an agonist of a G protein-coupled receptor (GPCR). ODN exerts a wide range of biological effects mediated through these two receptors and, in particular, it regulates astrocyte activity through an autocrine/paracrine mechanism involving the metabotropic receptor. More recently, it has been shown that Müller glial cells secrete phosphorylated DBI and that bisphosphorylated ODN ([bisphospho-Thr(3,9)]ODN, bpODN) has a stronger affinity for CBR than ODN. The aim of the present study was thus to investigate whether bpODN is released by mouse cortical astrocytes and to compare its potency to ODN. Using a radioimmunoassay and mass spectrometry analysis we have shown that bpODN as well as ODN were released in cultured astrocyte supernatants. Both bpODN and ODN increased astrocyte calcium event frequency but in a very different range of concentration. Indeed, ODN stimulatory effect decreased at concentrations over 10(-10)M whereas bpODN increased the calcium event frequency at similar doses. In vivo effects of bpODN and ODN were analyzed in two behavioral paradigms involving either the metabotropic receptor (anorexia) or the CBR (anxiety). As previously described, ODN (100ng, icv) induced a significant reduction of food intake. Similar effect was achieved with bpODN but at a 10 times higher dose (1000 ng, icv). Similarly, and contrasting with our hypothesis, bpODN was also 10 times less potent than ODN to induce anxiety-related behavior in the elevated zero maze test. Thus, the present data do not support that phosphorylation of ODN is involved in receptor selectivity but indicate that it rather weakens ODN activity.
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32
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The involvement of mitochondrial apoptotic pathway in eugenol-induced cell death in human glioblastoma cells. Toxicol Lett 2015; 232:122-32. [DOI: 10.1016/j.toxlet.2014.10.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 09/30/2014] [Accepted: 10/15/2014] [Indexed: 12/27/2022]
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Terunuma M, Haydon PG, Pangalos MN, Moss SJ. Purinergic receptor activation facilitates astrocytic GABAB receptor calcium signalling. Neuropharmacology 2014; 88:74-81. [PMID: 25261019 DOI: 10.1016/j.neuropharm.2014.09.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/04/2014] [Accepted: 09/06/2014] [Indexed: 12/11/2022]
Abstract
Gamma-aminobutyric acid B receptors (GABABRs) are heterodimeric G-protein coupled receptors, which mediate slow synaptic inhibition in the brain. Emerging evidence suggests astrocytes also express GABABRs, although their physiological significance remains unknown. To begin addressing this issue, we have used imaging and biochemical analysis to examine the role GABABRs play in regulating astrocytic Ca(2+) signalling. Using live imaging of cultured cortical astrocytes loaded with calcium indicator Fluo-4/AM, we found that astrocytic GABABRs are able to induce astrocytic calcium transients only if they are pre-activated by P2 purinoceptors (P2YRs). The GABABR-mediated calcium transients were attenuated by the removal of extracellular calcium. Furthermore, P2YRs enhance the phosphorylation of astrocytic GABABR R2 subunits on both serine 783 (S783) and serine 892 (S892), two phosphorylation sites that are well known to regulate the activity and the cell surface stability of GABABRs. Collectively these results suggest that P2YR mediated signalling is an important determinant of GABABR activity and phosphorylation in astrocytes.
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Affiliation(s)
- Miho Terunuma
- Department of Cell Physiology and Pharmacology, College of Medicine, Biological Sciences and Psychology, University of Leicester, University Road, Leicester LE1 9HN, UK.
| | - Philip G Haydon
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Menelas N Pangalos
- Innovative Medicines, AstraZeneca, Mereside, Alderley Park, Cheshire SK10 4TG, UK
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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Lee L, Kosuri P, Arancio O. Picomolar amyloid-β peptides enhance spontaneous astrocyte calcium transients. J Alzheimers Dis 2014; 38:49-62. [PMID: 23948929 DOI: 10.3233/jad-130740] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Amyloid-β (Aβ) peptides are constitutively produced in the brain throughout life via mechanisms that can be regulated by synaptic activity. Although Aβ has been extensively studied as the pathological plaque-forming protein species in Alzheimer's disease (AD), little is known about the normal physiological function(s) and signaling pathway(s). We previously discovered that physiologically-relevant, low picomolar amounts of Aβ can enhance synaptic plasticity and hippocampal-dependent cognition in mice. In this study, we demonstrated that astrocytes are cellular candidates for participating in this type of Aβ signaling. Using calcium imaging of primary astrocyte cultures, we observed that picomolar amounts of Aβ peptides can enhance spontaneous intracellular calcium transient signaling. After application of 200 pM Aβ42 peptides, the frequency and amplitude averages of spontaneous cytosolic calcium transients were significantly increased. These effects were dependent on α7 nicotinic acetylcholine receptors (α7-nAChRs), as the enhancement effects were blocked by a pharmacological α7-nAChR inhibitor and in astrocytes from an α7 deficient mouse strain. We additionally examined evoked intercellular calcium wave signaling but did not detect significant picomolar Aβ-induced alterations in propagation parameters. Overall, these results indicate that at a physiologically-relevant low picomolar concentration, Aβ peptides can enhance spontaneous astrocyte calcium transient signaling via α7-nAChRs. Since astrocyte-mediated gliotransmission has been previously found to have neuromodulatory roles, Aβ peptides may have a normal physiological function in regulating neuron-glia signaling. Dysfunction of this signaling process may underlie glia-based aspects of AD pathogenesis.
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Affiliation(s)
- Linda Lee
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University, New York, NY, USA Department of Pathology and Cell Biology, Columbia University, New York, NY, USA Center for Neurobiology and Behavior, Columbia University, New York, NY, USA
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35
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Astrocyte calcium microdomains are inhibited by Bafilomycin A1 and cannot be replicated by low-level Schaffer collateral stimulation in situ. Cell Calcium 2014; 55:1-16. [DOI: 10.1016/j.ceca.2013.10.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 10/09/2013] [Indexed: 11/20/2022]
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36
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Tadesse T, Derby CD, Schmidt M. Mechanisms underlying odorant-induced and spontaneous calcium signals in olfactory receptor neurons of spiny lobsters, Panulirus argus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2013; 200:53-76. [PMID: 24178131 DOI: 10.1007/s00359-013-0861-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 10/03/2013] [Accepted: 10/04/2013] [Indexed: 12/19/2022]
Abstract
We determined if a newly developed antennule slice preparation allows studying chemosensory properties of spiny lobster olfactory receptor neurons under in situ conditions with Ca(2+) imaging. We show that chemical stimuli reach the dendrites of olfactory receptor neurons but not their somata, and that odorant-induced Ca(2+) signals in the somata are sufficiently stable over time to allow stimulation with a substantial number of odorants. Pharmacological manipulations served to elucidate the source of odorant-induced Ca(2+) transients and spontaneous Ca(2+) oscillations in the somata of olfactory receptor neurons. Both Ca(2+) signals are primarily mediated by an influx of extracellular Ca(2+) through voltage-activated Ca(2+) channels that can be blocked by CoCl2 and the L-type Ca(2+) channel blocker verapamil. Intracellular Ca(2+) stores contribute little to odorant-induced Ca(2+) transients and spontaneous Ca(2+) oscillations. The odorant-induced Ca(2+) transients as well as the spontaneous Ca(2+) oscillations depend on action potentials mediated by Na(+) channels that are largely TTX-insensitive but blocked by the local anesthetics tetracaine and lidocaine. Collectively, these results corroborate the conclusion that odorant-induced Ca(2+) transients and spontaneous Ca(2+) oscillations in the somata of olfactory receptor neurons closely reflect action potential activity associated with odorant-induced phasic-tonic responses and spontaneous bursting, respectively. Therefore, both types of Ca(2+) signals represent experimentally accessible proxies of spiking.
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Affiliation(s)
- Tizeta Tadesse
- Neuroscience Institute and Department of Biology, Georgia State University, P.O. Box 5030, Atlanta, GA, 30302-5030, USA
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Yan E, Li B, Gu L, Hertz L, Peng L. Mechanisms for L-channel-mediated increase in [Ca(2+)]i and its reduction by anti-bipolar drugs in cultured astrocytes combined with its mRNA expression in freshly isolated cells support the importance of astrocytic L-channels. Cell Calcium 2013; 54:335-42. [PMID: 24079970 DOI: 10.1016/j.ceca.2013.08.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 08/08/2013] [Accepted: 08/10/2013] [Indexed: 12/17/2022]
Abstract
The importance of Ca(2+) signaling in astrocytes is undisputed but a potential role of Ca(2+) influx via L-channels in the brain in vivo is disputed, although expression of these channels in cultured astrocytes is recognized. This study shows that an increase in free cytosolic Ca(2+) concentration ([Ca(2+)]i) in astrocytes in primary cultures in response to an increased extracellular K(+) concentration (45mM) is inhibited not only by nifedipine (confirming previous observations) but also to a very large extent by ryanodine, inhibiting ryanodine receptor-mediated release of Ca(2+), known to occur in response to an elevation in [Ca(2+)]i. This means that the actual influx of Ca(2+) is modest, which may contribute to the difficulty in demonstrating L-channel-mediated Ca(2+) currents in astrocytes in intact brain tissue. Chronic treatment with any of the 3 conventional anti-bipolar drugs lithium, carbamazepine or valproic acid similarly causes a pronounced inhibition of K(+)-mediated increase in [Ca(2+)]i. This is shown to be due to an inhibition of capacitative Ca(2+) influx, reflected by decreased mRNA and protein expression of the 'transient receptor potential channel' (TRPC1), a constituent of store-operated channels (SOCEs). Literature data are cited (i) showing that depolarization-mediated Ca(2+) influx in response to an elevated extracellular K(+) concentration is important for generation of Ca(2+) oscillations and for the stimulatory effect of elevated K(+) concentrations in intact, non-cultured brain tissue, and (ii) that Ca(2+) channel activity is dependent upon availability of metabolic substrates, including glycogen. Finally, expression of mRNA for Cav1.3 is demonstrated in freshly separated astrocytes from normal brain.
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Affiliation(s)
- Enzhi Yan
- Department of Clinical Pharmacology and Institute of Pathology and Pathophysiology, China Medical University, Shenyang, PR China
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Rubio N, Almanza A, Mercado F, Arévalo MÁ, Garcia-Segura LM, Vega R, Soto E. Upregulation of voltage-gated Ca2+ channels in mouse astrocytes infected with Theiler's murine encephalomyelitis virus (TMEV). Neuroscience 2013; 247:309-18. [PMID: 23742846 DOI: 10.1016/j.neuroscience.2013.05.049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 05/15/2013] [Accepted: 05/20/2013] [Indexed: 11/25/2022]
Abstract
Theiler's murine encephalomyelitis virus (TMEV) induces demyelination in susceptible strains of mice through a CD4(+) Th1 T cell-mediated immunopathological process. TMEV infection produces a syndrome in mice that resembles multiple sclerosis. In this work, we focused on the increased expression of the genes encoding voltage-gated Ca(2+) channel subunits in SJL/J mouse astrocytes infected in culture with a BeAn strain of TMEV. Affymetrix DNA murine genome U74v2 DNA microarray hybridized with cRNA from mock- and TMEV-infected astrocytes revealed the upregulation of four sequences encoding Ca(2+)-binding and Ca(2+) channel subunit proteins. The DNA hybridization results were further validated using conventional RT-PCR and quantitative RT-PCR, demonstrating the increased expression of mRNA encoding channel subunit proteins. Western blotting also showed the increased synthesis of L- and N-type channel subunit specific proteins after infection. The reduced expression and the functional upregulation of functional voltage-gated Ca(2+) channels in mock- and TMEV-infected cells, respectively, was demonstrated using voltage clamp experiments. TMEV infection in mouse astrocytes induced a Ca(2+) current with a density proportional to the amount of viral particles used for infection. The use of Ca(2+) channel blockers, nimodipine and ω-conotoxin-GVIA, showed that both functional L- and N-type Ca(2+) channels were upregulated in infected astrocytes. The upregulation of Ca(2+) channels in astrocytes after TMEV infection provides insight into the molecular processes and potential role of astrocyte Ca(2+) dysregulation in the pathophysiology of encephalomyelitis and is important for the development of novel therapeutic strategies leading to prevention of neurodegeneration.
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Affiliation(s)
- N Rubio
- Instituto Cajal, CSIC, Madrid, Spain
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Porcaro C, Coppola G, Pierelli F, Seri S, Di Lorenzo G, Tomasevic L, Salustri C, Tecchio F. Multiple frequency functional connectivity in the hand somatosensory network: An EEG study. Clin Neurophysiol 2013; 124:1216-24. [DOI: 10.1016/j.clinph.2012.12.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 11/12/2012] [Accepted: 12/08/2012] [Indexed: 01/01/2023]
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40
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TRPV4 channels stimulate Ca2+-induced Ca2+ release in astrocytic endfeet and amplify neurovascular coupling responses. Proc Natl Acad Sci U S A 2013; 110:6157-62. [PMID: 23530219 DOI: 10.1073/pnas.1216514110] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In the CNS, astrocytes are sensory and regulatory hubs that play important roles in cerebral homeostatic processes, including matching local cerebral blood flow to neuronal metabolism (neurovascular coupling). These cells possess a highly branched network of processes that project from the soma to neuronal synapses as well as to arterioles and capillaries, where they terminate in "endfeet" that encase the blood vessels. Ca(2+) signaling within the endfoot mediates neurovascular coupling; thus, these functional microdomains control vascular tone and local perfusion in the brain. Transient receptor potential vanilloid 4 (TRPV4) channels--nonselective cation channels with considerable Ca(2+) conductance--have been identified in astrocytes, but their function is largely unknown. We sought to characterize the influence of TRPV4 channels on Ca(2+) dynamics in the astrocytic endfoot microdomain and assess their role in neurovascular coupling. We identified local TRPV4-mediated Ca(2+) oscillations in endfeet and further found that TRPV4 Ca(2+) signals are amplified and propagated by Ca(2+)-induced Ca(2+) release from inositol trisphosphate receptors (IP3Rs). Moreover, TRPV4-mediated Ca(2+) influx contributes to the endfoot Ca(2+) response to neuronal activation, enhancing the accompanying vasodilation. Our results identify a dynamic synergy between TRPV4 channels and IP3Rs in astrocyte endfeet and demonstrate that TRPV4 channels are engaged in and contribute to neurovascular coupling.
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41
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The astrocytic contribution to neurovascular coupling – Still more questions than answers? Neurosci Res 2013; 75:171-83. [DOI: 10.1016/j.neures.2013.01.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 12/15/2012] [Accepted: 12/30/2012] [Indexed: 01/03/2023]
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42
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Chen H, Ye H, Meng DQ, Cai PC, Chen F, Zhu LP, Tang Q, Long ZX, Zhou Q, Jin Y, Xin JB, Tao XN, Ma WL. Reactive oxygen species and x-ray disrupted spontaneous [Ca²⁺]I oscillation in alveolar macrophages. Radiat Res 2013; 179:485-92. [PMID: 23421826 DOI: 10.1667/rr3006.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Radiation leads to a rapid burst of reactive oxygen species (ROS), which is considered to be one of the major causes of radiation-induced injury. ROS have previously been shown to induce changes in cytosolic Ca²⁺ ([Ca²⁺]i) including [Ca²⁺]i oscillation. However, the role of radiation in [Ca²⁺]i oscillation is poorly understood. The purpose of this study was to identify the effect of ROS and X ray on [Ca²⁺]i oscillation, as well as their role in radiation-induced lung injury. Alveolar macrophages were cultured in the absence and presence of different doses of hydrogen peroxide (H₂O₂) or exposed to X-ray irradiation with or without pretreatment of diphenyleneiodonium chloride (DPI, an inhibitor of NADPH oxidases) or tetrandrine (TET, a calcium entry blocker) and cytosolic Ca²⁺ concentration was detected by fluorescent Ca²⁺ indicator Fura-2. Rat radiation lung injury was induced in vivo by using 40 Gy X ray and DPI or TET was used to prevent radiation-induced lung injury. The results showed that there was spontaneous [Ca²⁺]i oscillation in alveolar macrophages under normal conditions, and treatment of H₂O₂ (100-500 μM) or 2 Gy X ray inhibited the spontaneous [Ca²⁺]i oscillation and induced [Ca²⁺]i rise. TET abolished H₂O₂ or X ray induced [Ca²⁺]i rise in alveolar macrophages, and attenuated X ray- induced rat alveolitis in vivo. DPI prevented X-ray-induced inhibition of [Ca²⁺]i oscillation in alveolar macrophages and prevented X-ray-induced rat alveolitis. Taken together, the data suggest that the disruption of [Ca²⁺]i oscillation and induction of [Ca²⁺]i rise through ROS is involved in the mechanism of radiation-induced lung injury.
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Affiliation(s)
- Hao Chen
- Department of Respiratory Diseases, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, China
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Li B, Chen S, Zeng S, Luo Q, Li P. Modeling the contributions of Ca2+ flows to spontaneous Ca2+ oscillations and cortical spreading depression-triggered Ca2+ waves in astrocyte networks. PLoS One 2012; 7:e48534. [PMID: 23119049 PMCID: PMC3485305 DOI: 10.1371/journal.pone.0048534] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 09/26/2012] [Indexed: 11/18/2022] Open
Abstract
Astrocytes participate in brain functions through Ca(2+) signals, including Ca(2+) waves and Ca(2+) oscillations. Currently the mechanisms of Ca(2+) signals in astrocytes are not fully clear. Here, we present a computational model to specify the relative contributions of different Ca(2+) flows between the extracellular space, the cytoplasm and the endoplasmic reticulum of astrocytes to the generation of spontaneous Ca(2+) oscillations (CASs) and cortical spreading depression (CSD)-triggered Ca(2+) waves (CSDCWs) in a one-dimensional astrocyte network. This model shows that CASs depend primarily on Ca(2+) released from internal stores of astrocytes, and CSDCWs depend mainly on voltage-gated Ca(2+) influx. It predicts that voltage-gated Ca(2+) influx is able to generate Ca(2+) waves during the process of CSD even after depleting internal Ca(2+) stores. Furthermore, the model investigates the interactions between CASs and CSDCWs and shows that the pass of CSDCWs suppresses CASs, whereas CASs do not prevent the generation of CSDCWs. This work quantitatively analyzes the generation of astrocytic Ca(2+) signals and indicates different mechanisms underlying CSDCWs and non-CSDCWs. Research on the different types of Ca(2+) signals might help to understand the ways by which astrocytes participate in information processing in brain functions.
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Affiliation(s)
- Bing Li
- Britton Chance Center of Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, People’s Republic of China
- Key Laboratory of Biomedical Photonics of Ministry of Education, Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People’s Republic of China
| | - Shangbin Chen
- Britton Chance Center of Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, People’s Republic of China
- Key Laboratory of Biomedical Photonics of Ministry of Education, Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People’s Republic of China
| | - Shaoqun Zeng
- Britton Chance Center of Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, People’s Republic of China
- Key Laboratory of Biomedical Photonics of Ministry of Education, Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People’s Republic of China
| | - Qingming Luo
- Britton Chance Center of Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, People’s Republic of China
- Key Laboratory of Biomedical Photonics of Ministry of Education, Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People’s Republic of China
| | - Pengcheng Li
- Britton Chance Center of Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, People’s Republic of China
- Key Laboratory of Biomedical Photonics of Ministry of Education, Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People’s Republic of China
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Parpura V, Verkhratsky A. The astrocyte excitability brief: From receptors to gliotransmission. Neurochem Int 2012; 61:610-21. [DOI: 10.1016/j.neuint.2011.12.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Revised: 11/14/2011] [Accepted: 12/01/2011] [Indexed: 01/23/2023]
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Ben Achour S, Pascual O. Astrocyte-neuron communication: functional consequences. Neurochem Res 2012; 37:2464-73. [PMID: 22669630 DOI: 10.1007/s11064-012-0807-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Revised: 05/07/2012] [Accepted: 05/21/2012] [Indexed: 12/17/2022]
Abstract
Astrocyte-neuron communication has recently been proposed as a potential mechanism participating to synaptic transmission. With the development of this concept and accumulating evidences in favor of a modulation of synaptic transmission by astrocytes, has emerged the term gliotransmission. It refers to the capacity of astrocytes to release various transmitters, such as ATP, glutamate, D-serine, and GABA in the vicinity of synapses. While the cellular mechanisms involved in gliotransmission still need to be better described and, for some, identified, the aim of more and more studies is to determine the role of astrocytes from a functional point of view. This review will summarize the principal studies that have investigated a potential role of astrocytes in the various functions regulated by the brain (sleep, breathing, perception, learning and memory…). This will allow us to highlight the similarities and discrepancies in the signaling pathways involved in the different areas of the brain related to these functions.
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Affiliation(s)
- Sarrah Ben Achour
- Ecole Normale Supérieure, Institut de Biologie de l'ENS, IBENS, 75005 Paris, France
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Inversion of neurovascular coupling by subarachnoid blood depends on large-conductance Ca2+-activated K+ (BK) channels. Proc Natl Acad Sci U S A 2012; 109:E1387-95. [PMID: 22547803 DOI: 10.1073/pnas.1121359109] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cellular events that cause ischemic neurological damage following aneurysmal subarachnoid hemorrhage (SAH) have remained elusive. We report that subarachnoid blood profoundly impacts communication within the neurovascular unit-neurons, astrocytes, and arterioles-causing inversion of neurovascular coupling. Elevation of astrocytic endfoot Ca(2+) to ∼400 nM by neuronal stimulation or to ∼300 nM by Ca(2+) uncaging dilated parenchymal arterioles in control brain slices but caused vasoconstriction in post-SAH brain slices. Inhibition of K(+) efflux via astrocytic endfoot large-conductance Ca(2+)-activated K(+) (BK) channels prevented both neurally evoked vasodilation (control) and vasoconstriction (SAH). Consistent with the dual vasodilator/vasoconstrictor action of extracellular K(+) ([K(+)](o)), [K(+)](o) <10 mM dilated and [K(+)](o) >20 mM constricted isolated brain cortex parenchymal arterioles with or without SAH. Notably, elevation of external K(+) to 10 mM caused vasodilation in brain slices from control animals but caused a modest constriction in brain slices from SAH model rats; this latter effect was reversed by BK channel inhibition, which restored K(+)-induced dilations. Importantly, the amplitude of spontaneous astrocytic Ca(2+) oscillations was increased after SAH, with peak Ca(2+) reaching ∼490 nM. Our data support a model in which SAH increases the amplitude of spontaneous astrocytic Ca(2+) oscillations sufficiently to activate endfoot BK channels and elevate [K(+)](o) in the restricted perivascular space. Abnormally elevated basal [K(+)](o) combined with further K(+) efflux stimulated by neuronal activity elevates [K(+)](o) above the dilation/constriction threshold, switching the polarity of arteriolar responses to vasoconstriction. Inversion of neurovascular coupling may contribute to the decreased cerebral blood flow and development of neurological deficits that commonly follow SAH.
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Verkhratsky A, Rodríguez JJ, Parpura V. Calcium signalling in astroglia. Mol Cell Endocrinol 2012; 353:45-56. [PMID: 21945602 DOI: 10.1016/j.mce.2011.08.039] [Citation(s) in RCA: 171] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Revised: 08/28/2011] [Accepted: 08/31/2011] [Indexed: 12/15/2022]
Abstract
Astroglia possess excitability based on movements of Ca(2+) ions between intracellular compartments and plasmalemmal Ca(2+) fluxes. This "Ca(2+) excitability" is controlled by several families of proteins located in the plasma membrane, within the cytosol and in the intracellular organelles, most notably in the endoplasmic reticulum (ER) and mitochondria. Accumulation of cytosolic Ca(2+) can be caused by the entry of Ca(2+) from the extracellular space through ionotropic receptors and store-operated channels expressed in astrocytes. Plasmalemmal Ca(2+) ATP-ase and sodium-calcium exchanger extrude cytosolic Ca(2+) to the extracellular space; the exchanger can also operate in reverse, depending of the intercellular Na(+) concentration, to deliver Ca(2+) to the cytosol. The ER internal store possesses inositol 1,4,5-trisphosphate receptors which can be activated upon stimulation of astrocytes through a multiple plasma membrane metabotropic G-protein coupled receptors. This leads to release of Ca(2+) from the ER and its elevation in the cytosol, the level of which can be modulated by mitochondria. The mitochondrial uniporter takes up Ca(2+) into the matrix, while free Ca(2+) exits the matrix through the mitochondrial Na(+)/Ca(2+) exchanger as well as via transient openings of the mitochondrial permeability transition pore. One of the prominent consequences of astroglial Ca(2+) excitability is gliotransmission, a release of transmitters from astroglia which can lead to signalling to adjacent neurones.
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Abstract
Astroglial cells, due to their passive electrical properties, were long considered subservient to neurons and to merely provide the framework and metabolic support of the brain. Although astrocytes do play such structural and housekeeping roles in the brain, these glial cells also contribute to the brain's computational power and behavioural output. These more active functions are endowed by the Ca2+-based excitability displayed by astrocytes. An increase in cytosolic Ca2+ levels in astrocytes can lead to the release of signalling molecules, a process termed gliotransmission, via the process of regulated exocytosis. Dynamic components of astrocytic exocytosis include the vesicular-plasma membrane secretory machinery, as well as the vesicular traffic, which is governed not only by general cytoskeletal elements but also by astrocyte-specific IFs (intermediate filaments). Gliotransmitters released into the ECS (extracellular space) can exert their actions on neighbouring neurons, to modulate synaptic transmission and plasticity, and to affect behaviour by modulating the sleep homoeostat. Besides these novel physiological roles, astrocytic Ca2+ dynamics, Ca2+-dependent gliotransmission and astrocyte–neuron signalling have been also implicated in brain disorders, such as epilepsy. The aim of this review is to highlight the newer findings concerning Ca2+ signalling in astrocytes and exocytotic gliotransmission. For this we report on Ca2+ sources and sinks that are necessary and sufficient for regulating the exocytotic release of gliotransmitters and discuss secretory machinery, secretory vesicles and vesicle mobility regulation. Finally, we consider the exocytotic gliotransmission in the modulation of synaptic transmission and plasticity, as well as the astrocytic contribution to sleep behaviour and epilepsy.
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Abstract
Astrocytes participate in all essential CNS functions, including blood flow regulation, energy metabolism, ion and water homeostasis, immune defence, neurotransmission, and adult neurogenesis. It is thus not surprising that astrocytic morphology and function differ between regions, and that different subclasses of astrocytes exist within the same brain region. Recent lines of work also show that the complexity of protoplasmic astrocytes increases during evolution. Human astrocytes are structurally more complex, larger, and propagate calcium signals significantly faster than rodent astrocytes. In this chapter, we review the diversity of astrocytic form and function, while considering the markedly expanded roles of astrocytes with phylogenetic evolution. We also define major challenges for the future, which include determining how astrocytic functions are locally specified, defining the molecular controls upon astrocytic fate and physiology and establishing how evolutionary changes in astrocytes contribute to higher cognitive functions.
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Affiliation(s)
- Nancy Ann Oberheim
- Center for Translational Neuromedicine, Department of Neurology, University of Rochester Medical Center, Rochester, NY, USA
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Calcium signaling in cerebral vasoregulation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:833-58. [PMID: 22453972 DOI: 10.1007/978-94-007-2888-2_37] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The tight coupling of regional neurometabolic activity with synaptic activity and regional cerebral blood perfusion constitutes a single functional unit, described generally as a neurovascular unit. This is central to any discussion of haemodynamic response linked to any neuronal activation. In normal as well as in pathologic conditions, neurons, astrocytes and endothelial cells of the vasculature interact to generate the complex activity-induced cerebral haemodynamic responses, with astrocytes not only partaking in the signaling but actually controlling it in many cases. Neurons and astrocytes have highly integrated signaling mechanisms, yet they form two separate networks. Bidirectional neuron-astrocyte interactions are crucial for the function and survival of the central nervous system. The primary purpose of such regulation is the homeostasis of the brain's microenvironment. In the maintenance of such homeostasis, astrocytic calcium response is a crucial variable in determining neurovascular control. Future work will be directed towards resolving the nature and extent of astrocytic calcium-mediated mechanisms for gene transcription, in modelling neurovascular control, and in determining calcium sensitive imaging assays that can capture disease variables.
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