101
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Acton D, Miles GB. Gliotransmission and adenosinergic modulation: insights from mammalian spinal motor networks. J Neurophysiol 2017; 118:3311-3327. [PMID: 28954893 DOI: 10.1152/jn.00230.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Astrocytes are proposed to converse with neurons at tripartite synapses, detecting neurotransmitter release and responding with release of gliotransmitters, which in turn modulate synaptic strength and neuronal excitability. However, a paucity of evidence from behavioral studies calls into question the importance of gliotransmission for the operation of the nervous system in healthy animals. Central pattern generator (CPG) networks in the spinal cord and brain stem coordinate the activation of muscles during stereotyped activities such as locomotion, inspiration, and mastication and may therefore provide tractable models in which to assess the contribution of gliotransmission to behaviorally relevant neural activity. We review evidence for gliotransmission within spinal locomotor networks, including studies indicating that adenosine derived from astrocytes regulates the speed of locomotor activity via metamodulation of dopamine signaling.
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Affiliation(s)
- David Acton
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
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102
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Al-Suwailem E, Abdi S, El-Ansary A. Sex differences in the glutamate signaling pathway in juvenile rats. J Neurosci Res 2017; 96:459-466. [PMID: 28861894 DOI: 10.1002/jnr.24144] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 08/04/2017] [Accepted: 08/07/2017] [Indexed: 12/19/2022]
Abstract
Females have been found to be at lower risk for the development of neurodevelopmental disorders than males. The greater neuroprotection in females is mostly due to female sex hormones. Estrogen is hypothesized to provide neuroprotection by suppressing the neuro-excitotoxicity induced by glutamate (Glu). This study was conducted to understand the effect of sex in modulating Glu signaling in juvenile rats. Brain tissue homogenate of 15 Wistar albino rats (9 males, 6 females) weighing 60 to 80 g and aged approximately 28 days was used. Biochemical parameters related to Glu signaling, such as the absolute and relative concentrations of Glu, gamma aminobutyric acid (GABA), and glutamine, as well as glutamate transporter 1 (GLT1), glutamine synthetase (GS), glutaminase (GLN), and glutamate decarboxylase-67 (GAD-67), were measured by ELISA. The data obtained demonstrated that compared with the levels in males, female rats exhibited significantly lower levels of Glu (p = .001) and GLN/GS (p = .021). The Glu/GABA and Glu/GLT1 ratios as well as the levels of GAD-67 were also lower in female rats, although the difference was not significant. The GLN/GAD-67 ratio (p = .027) and levels of GS (p = .019) were significantly higher in female rats than in males. Multiple regression analysis confirmed the role of GLN/GS, together with the much higher affinity of GLT1 to Glu, in avoiding excitotoxicity in females. In conclusion, there was a significant difference in Glu signaling between female and male rats. The females exhibited a lower susceptibility to develop Glu-induced excitotoxicity, an etiological mechanism for multiple neurodevelopmental disorders.
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Affiliation(s)
- Etidal Al-Suwailem
- Biochemistry Department, Science College, King Saud University, Riyadh, Saudi Arabia
| | - Saba Abdi
- Biochemistry Department, Science College, King Saud University, Riyadh, Saudi Arabia
| | - Afaf El-Ansary
- Central Laboratory, King Saud University, Riyadh, Saudi Arabia
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103
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Forsberg D, Thonabulsombat C, Jäderstad J, Jäderstad LM, Olivius P, Herlenius E. Functional Stem Cell Integration into Neural Networks Assessed by Organotypic Slice Cultures. ACTA ACUST UNITED AC 2017; 42:2D.13.1-2D.13.30. [PMID: 28806855 DOI: 10.1002/cpsc.34] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Re-formation or preservation of functional, electrically active neural networks has been proffered as one of the goals of stem cell-mediated neural therapeutics. A primary issue for a cell therapy approach is the formation of functional contacts between the implanted cells and the host tissue. Therefore, it is of fundamental interest to establish protocols that allow us to delineate a detailed time course of grafted stem cell survival, migration, differentiation, integration, and functional interaction with the host. One option for in vitro studies is to examine the integration of exogenous stem cells into an existing active neural network in ex vivo organotypic cultures. Organotypic cultures leave the structural integrity essentially intact while still allowing the microenvironment to be carefully controlled. This allows detailed studies over time of cellular responses and cell-cell interactions, which are not readily performed in vivo. This unit describes procedures for using organotypic slice cultures as ex vivo model systems for studying neural stem cell and embryonic stem cell engraftment and communication with CNS host tissue. © 2017 by John Wiley & Sons, Inc.
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Affiliation(s)
- David Forsberg
- Department of Women's and Children's Health, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden
| | - Charoensri Thonabulsombat
- Department of Clinical Sciences, Intervention and Technology (CLINTEC), Section of Otorhinolaryngology, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden.,Center for Hearing and Communication Research, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden.,Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Johan Jäderstad
- Department of Women's and Children's Health, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden
| | - Linda Maria Jäderstad
- Department of Women's and Children's Health, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden
| | - Petri Olivius
- Department of Clinical Sciences, Intervention and Technology (CLINTEC), Section of Otorhinolaryngology, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden.,Center for Hearing and Communication Research, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden
| | - Eric Herlenius
- Department of Women's and Children's Health, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden
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104
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Wang Y, Shi G, Miller DJ, Wang Y, Wang C, Broussard G, Wang Y, Tian L, Yu G. Automated Functional Analysis of Astrocytes from Chronic Time-Lapse Calcium Imaging Data. Front Neuroinform 2017; 11:48. [PMID: 28769780 PMCID: PMC5509822 DOI: 10.3389/fninf.2017.00048] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 06/30/2017] [Indexed: 01/12/2023] Open
Abstract
Recent discoveries that astrocytes exert proactive regulatory effects on neural information processing and that they are deeply involved in normal brain development and disease pathology have stimulated broad interest in understanding astrocyte functional roles in brain circuit. Measuring astrocyte functional status is now technically feasible, due to recent advances in modern microscopy and ultrasensitive cell-type specific genetically encoded Ca2+ indicators for chronic imaging. However, there is a big gap between the capability of generating large dataset via calcium imaging and the availability of sophisticated analytical tools for decoding the astrocyte function. Current practice is essentially manual, which not only limits analysis throughput but also risks introducing bias and missing important information latent in complex, dynamic big data. Here, we report a suite of computational tools, called Functional AStrocyte Phenotyping (FASP), for automatically quantifying the functional status of astrocytes. Considering the complex nature of Ca2+ signaling in astrocytes and low signal to noise ratio, FASP is designed with data-driven and probabilistic principles, to flexibly account for various patterns and to perform robustly with noisy data. In particular, FASP explicitly models signal propagation, which rules out the applicability of tools designed for other types of data. We demonstrate the effectiveness of FASP using extensive synthetic and real data sets. The findings by FASP were verified by manual inspection. FASP also detected signals that were missed by purely manual analysis but could be confirmed by more careful manual examination under the guidance of automatic analysis. All algorithms and the analysis pipeline are packaged into a plugin for Fiji (ImageJ), with the source code freely available online at https://github.com/VTcbil/FASP.
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Affiliation(s)
- Yinxue Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State UniversityArlington, VA, United States
| | - Guilai Shi
- Department of Biochemistry and Molecular Medicine, University of California Davis School of MedicineDavis, CA, United States
| | - David J Miller
- Department of Electrical Engineering, School of Electrical Engineering and Computer Science, Pennsylvania State UniversityUniversity Park, PA, United States
| | - Yizhi Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State UniversityArlington, VA, United States
| | - Congchao Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State UniversityArlington, VA, United States
| | - Gerard Broussard
- Department of Biochemistry and Molecular Medicine, University of California Davis School of MedicineDavis, CA, United States
| | - Yue Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State UniversityArlington, VA, United States
| | - Lin Tian
- Department of Biochemistry and Molecular Medicine, University of California Davis School of MedicineDavis, CA, United States
| | - Guoqiang Yu
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State UniversityArlington, VA, United States
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105
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Losi G, Mariotti L, Sessolo M, Carmignoto G. New Tools to Study Astrocyte Ca 2+ Signal Dynamics in Brain Networks In Vivo. Front Cell Neurosci 2017; 11:134. [PMID: 28536505 PMCID: PMC5422467 DOI: 10.3389/fncel.2017.00134] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 04/20/2017] [Indexed: 11/19/2022] Open
Abstract
Sensory information processing is a fundamental operation in the brain that is based on dynamic interactions between different neuronal populations. Astrocytes, a type of glial cells, have been proposed to represent active elements of brain microcircuits that, through dynamic interactions with neurons, provide a modulatory control of neuronal network activity. Specifically, astrocytes in different brain regions have been described to respond to neuronal signals with intracellular Ca2+ elevations that represent a key step in the functional recruitment of astrocytes to specific brain circuits. Accumulating evidence shows that Ca2+ elevations regulate the release of gliotransmitters that, in turn, modulate synaptic transmission and neuronal excitability. Recent studies also provided new insights into the spatial and temporal features of astrocytic Ca2+ elevations revealing a surprising complexity of Ca2+ signal dynamics in astrocytes. Here we discuss how recently developed experimental tools such as the genetically encoded Ca2+ indicators (GECI), optogenetics and chemogenetics can be applied to the study of astrocytic Ca2+ signals in the living brain.
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Affiliation(s)
- Gabriele Losi
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy
| | - Letizia Mariotti
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy.,Division of Neurobiology, MRC Laboratory of Molecular BiologyCambridge, UK
| | - Michele Sessolo
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy.,Center for Drug Discovery & Development, Aptuit inc.Verona, Italy
| | - Giorgio Carmignoto
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy
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106
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Butt AM, Vanzulli I, Papanikolaou M, De La Rocha IC, Hawkins VE. Metabotropic Glutamate Receptors Protect Oligodendrocytes from Acute Ischemia in the Mouse Optic Nerve. Neurochem Res 2017; 42:2468-2478. [PMID: 28365868 PMCID: PMC5603641 DOI: 10.1007/s11064-017-2220-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/13/2017] [Accepted: 02/28/2017] [Indexed: 12/01/2022]
Abstract
Studies by Bruce Ransom and colleagues have made a major contribution to show that white matter is susceptible to ischemia/hypoxia. White matter contains axons and the glia that support them, notably myelinating oligodendrocytes, which are highly vulnerable to ischemic-hypoxic damage. Previous studies have shown that metabotropic GluRs (mGluRs) are cytoprotective for oligodendrocyte precursor cells and immature oligodendrocytes, but their potential role in adult white matter was unresolved. Here, we report that group 1 mGluR1/5 and group 2 mGluR3 subunits are expressed in optic nerves from mice aged postnatal day (P)8-12 and P30-35. We demonstrate that activation of group 1 mGluR protects oligodendrocytes against oxygen-glucose deprivation (OGD) in developing and young adult optic nerves. In contrast, group 2 mGluR are shown to be protective for oligodendrocytes against OGD in postnatal but not young adult optic nerves. The cytoprotective effect of group 1 mGluR requires activation of PKC, whilst group 2 mGluR are dependent on negatively regulating adenylyl cyclase and cAMP. Our results identify a role for mGluR in limiting injury of oligodendrocytes in developing and young adult white matter, which may be useful for protecting oligodendrocytes in neuropathologies involving excitoxicity and ischemia/hypoxia.
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Affiliation(s)
- Arthur M Butt
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK.
| | - Ilaria Vanzulli
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Maria Papanikolaou
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Irene Chacon De La Rocha
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Virginia E Hawkins
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK. .,Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, 06269, USA.
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107
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Buscemi L, Ginet V, Lopatar J, Montana V, Pucci L, Spagnuolo P, Zehnder T, Grubišić V, Truttman A, Sala C, Hirt L, Parpura V, Puyal J, Bezzi P. Homer1 Scaffold Proteins Govern Ca2+ Dynamics in Normal and Reactive Astrocytes. Cereb Cortex 2017; 27:2365-2384. [PMID: 27075036 PMCID: PMC5963825 DOI: 10.1093/cercor/bhw078] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In astrocytes, the intracellular calcium (Ca2+) signaling mediated by activation of metabotropic glutamate receptor 5 (mGlu5) is crucially involved in the modulation of many aspects of brain physiology, including gliotransmission. Here, we find that the mGlu5-mediated Ca2+ signaling leading to release of glutamate is governed by mGlu5 interaction with Homer1 scaffolding proteins. We show that the long splice variants Homer1b/c are expressed in astrocytic processes, where they cluster with mGlu5 at sites displaying intense local Ca2+ activity. We show that the structural and functional significance of the Homer1b/c-mGlu5 interaction is to relocate endoplasmic reticulum (ER) to the proximity of the plasma membrane and to optimize Ca2+ signaling and glutamate release. We also show that in reactive astrocytes the short dominant-negative splice variant Homer1a is upregulated. Homer1a, by precluding the mGlu5-ER interaction decreases the intensity of Ca2+ signaling thus limiting the intensity and the duration of glutamate release by astrocytes. Hindering upregulation of Homer1a with a local injection of short interfering RNA in vivo restores mGlu5-mediated Ca2+ signaling and glutamate release and sensitizes astrocytes to apoptosis. We propose that Homer1a may represent one of the cellular mechanisms by which inflammatory astrocytic reactions are beneficial for limiting brain injury.
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Affiliation(s)
- Lara Buscemi
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Stroke Laboratory, Neurology Service, Department of Clinical Neurosciences, University Hospital Centre and University of Lausanne, CH-1011 Lausanne, Switzerland
| | - Vanessa Ginet
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Division of Neonatology, Department of Paediatrics and Paediatric Surgery, University Hospital Centre and University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Jan Lopatar
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
| | - Vedrana Montana
- Department of Biotechnology, University of Rijeka, 51000 Rijeka, Croatia
- Department of Neurobiology, Center for Glial Biology in Medicine, Civitan International Research Center, Atomic Force Microscopy and Nanotechnology Laboratories, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Luca Pucci
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
| | - Paola Spagnuolo
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Tamara Zehnder
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
| | - Vladimir Grubišić
- Department of Neurobiology, Center for Glial Biology in Medicine, Civitan International Research Center, Atomic Force Microscopy and Nanotechnology Laboratories, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Anita Truttman
- Division of Neonatology, Department of Paediatrics and Paediatric Surgery, University Hospital Centre and University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Carlo Sala
- CNR Institute of Neuroscience and Department of Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Lorenz Hirt
- Stroke Laboratory, Neurology Service, Department of Clinical Neurosciences, University Hospital Centre and University of Lausanne, CH-1011 Lausanne, Switzerland
| | - Vladimir Parpura
- Department of Neurobiology, Center for Glial Biology in Medicine, Civitan International Research Center, Atomic Force Microscopy and Nanotechnology Laboratories, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Julien Puyal
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Division of Neonatology, Department of Paediatrics and Paediatric Surgery, University Hospital Centre and University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Paola Bezzi
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
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108
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Astrocytic Pathological Calcium Homeostasis and Impaired Vesicle Trafficking in Neurodegeneration. Int J Mol Sci 2017; 18:ijms18020358. [PMID: 28208745 PMCID: PMC5343893 DOI: 10.3390/ijms18020358] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 02/08/2023] Open
Abstract
Although the central nervous system (CNS) consists of highly heterogeneous populations of neurones and glial cells, clustered into diverse anatomical regions with specific functions, there are some conditions, including alertness, awareness and attention that require simultaneous, coordinated and spatially homogeneous activity within a large area of the brain. During such events, the brain, representing only about two percent of body mass, but consuming one fifth of body glucose at rest, needs additional energy to be produced. How simultaneous energy procurement in a relatively extended area of the brain takes place is poorly understood. This mechanism is likely to be impaired in neurodegeneration, for example in Alzheimer’s disease, the hallmark of which is brain hypometabolism. Astrocytes, the main neural cell type producing and storing glycogen, a form of energy in the brain, also hold the key to metabolic and homeostatic support in the central nervous system and are impaired in neurodegeneration, contributing to the slow decline of excitation-energy coupling in the brain. Many mechanisms are affected, including cell-to-cell signalling. An important question is how changes in cellular signalling, a process taking place in a rather short time domain, contribute to the neurodegeneration that develops over decades. In this review we focus initially on the slow dynamics of Alzheimer’s disease, and on the activity of locus coeruleus, a brainstem nucleus involved in arousal. Subsequently, we overview much faster processes of vesicle traffic and cytosolic calcium dynamics, both of which shape the signalling landscape of astrocyte-neurone communication in health and neurodegeneration.
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109
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Oschmann F, Mergenthaler K, Jungnickel E, Obermayer K. Spatial separation of two different pathways accounting for the generation of calcium signals in astrocytes. PLoS Comput Biol 2017; 13:e1005377. [PMID: 28192424 PMCID: PMC5330534 DOI: 10.1371/journal.pcbi.1005377] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 02/28/2017] [Accepted: 01/23/2017] [Indexed: 11/26/2022] Open
Abstract
Astrocytes integrate and process synaptic information and exhibit calcium (Ca2+) signals in response to incoming information from neighboring synapses. The generation of Ca2+ signals is mostly attributed to Ca2+ release from internal Ca2+ stores evoked by an elevated metabotropic glutamate receptor (mGluR) activity. Different experimental results associated the generation of Ca2+ signals to the activity of the glutamate transporter (GluT). The GluT itself does not influence the intracellular Ca2+ concentration, but it indirectly activates Ca2+ entry over the membrane. A closer look into Ca2+ signaling in different astrocytic compartments revealed a spatial separation of those two pathways. Ca2+ signals in the soma are mainly generated by Ca2+ release from internal Ca2+ stores (mGluR-dependent pathway). In astrocytic compartments close to the synapse most Ca2+ signals are evoked by Ca2+ entry over the plasma membrane (GluT-dependent pathway). This assumption is supported by the finding, that the volume ratio between the internal Ca2+ store and the intracellular space decreases from the soma towards the synapse. We extended a model for mGluR-dependent Ca2+ signals in astrocytes with the GluT-dependent pathway. Additionally, we included the volume ratio between the internal Ca2+ store and the intracellular compartment into the model in order to analyze Ca2+ signals either in the soma or close to the synapse. Our model results confirm the spatial separation of the mGluR- and GluT-dependent pathways along the astrocytic process. The model allows to study the binary Ca2+ response during a block of either of both pathways. Moreover, the model contributes to a better understanding of the impact of channel densities on the interaction of both pathways and on the Ca2+ signal.
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Affiliation(s)
- Franziska Oschmann
- Technische Universität Berlin, Neural Information Processing Group, Berlin, Germany
- Bernstein Center for Computational Neuroscience, Berlin, Germany
| | | | - Evelyn Jungnickel
- Technische Universität Berlin, Neural Information Processing Group, Berlin, Germany
| | - Klaus Obermayer
- Technische Universität Berlin, Neural Information Processing Group, Berlin, Germany
- Bernstein Center for Computational Neuroscience, Berlin, Germany
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110
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Gómez-Gonzalo M, Martin-Fernandez M, Martínez-Murillo R, Mederos S, Hernández-Vivanco A, Jamison S, Fernandez AP, Serrano J, Calero P, Futch HS, Corpas R, Sanfeliu C, Perea G, Araque A. Neuron-astrocyte signaling is preserved in the aging brain. Glia 2017; 65:569-580. [PMID: 28130845 DOI: 10.1002/glia.23112] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Revised: 11/23/2016] [Accepted: 12/21/2016] [Indexed: 12/18/2022]
Abstract
Astrocytes play crucial roles in brain homeostasis and are emerging as regulatory elements of neuronal and synaptic physiology by responding to neurotransmitters with Ca2+ elevations and releasing gliotransmitters that activate neuronal receptors. Aging involves neuronal and astrocytic alterations, being considered risk factor for neurodegenerative diseases. Most evidence of the astrocyte-neuron signaling is derived from studies with young animals; however, the features of astrocyte-neuron signaling in adult and aging brain remain largely unknown. We have investigated the existence and properties of astrocyte-neuron signaling in physiologically and pathologically aging mouse hippocampal and cortical slices at different lifetime points (0.5 to 20 month-old animals). We found that astrocytes preserved their ability to express spontaneous and neurotransmitter-dependent intracellular Ca2+ signals from juvenile to aging brains. Likewise, resting levels of gliotransmission, assessed by neuronal NMDAR activation by glutamate released from astrocytes, were largely preserved with similar properties in all tested age groups, but DHPG-induced gliotransmission was reduced in aged mice. In contrast, gliotransmission was enhanced in the APP/PS1 mouse model of Alzheimer's disease, indicating a dysregulation of astrocyte-neuron signaling in pathological conditions. Disruption of the astrocytic IP3 R2 mediated-signaling, which is required for neurotransmitter-induced astrocyte Ca2+ signals and gliotransmission, boosted the progression of amyloid plaque deposits and synaptic plasticity impairments in APP/PS1 mice at early stages of the disease. Therefore, astrocyte-neuron interaction is a fundamental signaling, largely conserved in the adult and aging brain of healthy animals, but it is altered in Alzheimer's disease, suggesting that dysfunctions of astrocyte Ca2+ physiology may contribute to this neurodegenerative disease. GLIA 2017 GLIA 2017;65:569-580.
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Affiliation(s)
| | | | | | | | | | - Stephanie Jamison
- Department of Neuroscience, University of Minnesota, Minneapolis, 55455
| | | | | | | | - Hunter S Futch
- College of Medicine, University of Florida, Gainesville, Florida, 32610-0261
| | - Rubén Corpas
- Aging and Neurodegeneration Unit, Biomedical Research Institute of Barcelona (IIBB), CSIC and IDIBAPS, Barcelona, 08036, Spain
| | - Coral Sanfeliu
- Aging and Neurodegeneration Unit, Biomedical Research Institute of Barcelona (IIBB), CSIC and IDIBAPS, Barcelona, 08036, Spain
| | | | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, 55455
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111
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Sherwood MW, Arizono M, Hisatsune C, Bannai H, Ebisui E, Sherwood JL, Panatier A, Oliet SHR, Mikoshiba K. Astrocytic IP 3 Rs: Contribution to Ca 2+ signalling and hippocampal LTP. Glia 2017; 65:502-513. [PMID: 28063222 DOI: 10.1002/glia.23107] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 11/26/2016] [Accepted: 12/01/2016] [Indexed: 12/22/2022]
Abstract
Astrocytes regulate hippocampal synaptic plasticity by the Ca2+ dependent release of the N-methyl d-aspartate receptor (NMDAR) co-agonist d-serine. Previous evidence indicated that d-serine release would be regulated by the intracellular Ca2+ release channel IP3 receptor (IP3 R), however, genetic deletion of IP3 R2, the putative astrocytic IP3 R subtype, had no impact on synaptic plasticity or transmission. Although IP3 R2 is widely believed to be the only functional IP3 R in astrocytes, three IP3 R subtypes (1, 2, and 3) have been identified in vertebrates. Therefore, to better understand gliotransmission, we investigated the functionality of IP3 R and the contribution of the three IP3 R subtypes to Ca2+ signalling. As a proxy for gliotransmission, we found that long-term potentiation (LTP) was impaired by dialyzing astrocytes with the broad IP3 R blocker heparin, and rescued by exogenous d-serine, indicating that astrocytic IP3 Rs regulate d-serine release. To explore which IP3 R subtypes are functional in astrocytes, we used pharmacology and two-photon Ca2+ imaging of hippocampal slices from transgenic mice (IP3 R2-/- and IP3 R2-/- ;3-/- ). This approach revealed that underneath IP3 R2-mediated global Ca2+ events are an overlooked class of IP3 R-mediated local events, occurring in astroglial processes. Notably, multiple IP3 Rs were recruited by high frequency stimulation of the Schaffer collaterals, a classical LTP induction protocol. Together, these findings show the dependence of LTP and gliotransmission on Ca2+ release by astrocytic IP3 Rs. GLIA 2017;65:502-513.
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Affiliation(s)
- Mark William Sherwood
- INSERM U1215, Neurocentre Magendie, Bordeaux, 33077, France.,Université de Bordeaux, Bordeaux, 33077, France.,Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Misa Arizono
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Chihiro Hisatsune
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Hiroko Bannai
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Division of Biological Sciences, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8602, Japan
| | - Etsuko Ebisui
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - John Lawrence Sherwood
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Aude Panatier
- INSERM U1215, Neurocentre Magendie, Bordeaux, 33077, France.,Université de Bordeaux, Bordeaux, 33077, France
| | | | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
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112
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Metabotropic glutamate receptors and neurodegenerative diseases. Pharmacol Res 2017; 115:179-191. [DOI: 10.1016/j.phrs.2016.11.013] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 11/11/2016] [Accepted: 11/15/2016] [Indexed: 12/21/2022]
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113
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Jackson MP, Rahman A, Lafon B, Kronberg G, Ling D, Parra LC, Bikson M. Animal models of transcranial direct current stimulation: Methods and mechanisms. Clin Neurophysiol 2016; 127:3425-3454. [PMID: 27693941 PMCID: PMC5083183 DOI: 10.1016/j.clinph.2016.08.016] [Citation(s) in RCA: 191] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 08/05/2016] [Accepted: 08/08/2016] [Indexed: 12/28/2022]
Abstract
The objective of this review is to summarize the contribution of animal research using direct current stimulation (DCS) to our understanding of the physiological effects of transcranial direct current stimulation (tDCS). We comprehensively address experimental methodology in animal studies, broadly classified as: (1) transcranial stimulation; (2) direct cortical stimulation in vivo and (3) in vitro models. In each case advantages and disadvantages for translational research are discussed including dose translation and the overarching "quasi-uniform" assumption, which underpins translational relevance in all animal models of tDCS. Terminology such as anode, cathode, inward current, outward current, current density, electric field, and uniform are defined. Though we put key animal experiments spanning decades in perspective, our goal is not simply an exhaustive cataloging of relevant animal studies, but rather to put them in context of ongoing efforts to improve tDCS. Cellular targets, including excitatory neuronal somas, dendrites, axons, interneurons, glial cells, and endothelial cells are considered. We emphasize neurons are always depolarized and hyperpolarized such that effects of DCS on neuronal excitability can only be evaluated within subcellular regions of the neuron. Findings from animal studies on the effects of DCS on plasticity (LTP/LTD) and network oscillations are reviewed extensively. Any endogenous phenomena dependent on membrane potential changes are, in theory, susceptible to modulation by DCS. The relevance of morphological changes (galvanotropy) to tDCS is also considered, as we suggest microscopic migration of axon terminals or dendritic spines may be relevant during tDCS. A majority of clinical studies using tDCS employ a simplistic dose strategy where excitability is singularly increased or decreased under the anode and cathode, respectively. We discuss how this strategy, itself based on classic animal studies, cannot account for the complexity of normal and pathological brain function, and how recent studies have already indicated more sophisticated approaches are necessary. One tDCS theory regarding "functional targeting" suggests the specificity of tDCS effects are possible by modulating ongoing function (plasticity). Use of animal models of disease are summarized including pain, movement disorders, stroke, and epilepsy.
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Affiliation(s)
- Mark P Jackson
- Department of Biomedical Engineering, The City College of The City University of New York, NY, USA
| | - Asif Rahman
- Department of Biomedical Engineering, The City College of The City University of New York, NY, USA
| | - Belen Lafon
- Department of Biomedical Engineering, The City College of The City University of New York, NY, USA
| | - Gregory Kronberg
- Department of Biomedical Engineering, The City College of The City University of New York, NY, USA
| | - Doris Ling
- Department of Biomedical Engineering, The City College of The City University of New York, NY, USA
| | - Lucas C Parra
- Department of Biomedical Engineering, The City College of The City University of New York, NY, USA
| | - Marom Bikson
- Department of Biomedical Engineering, The City College of The City University of New York, NY, USA.
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114
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Zorec R, Parpura V, Verkhratsky A. Astroglial Vesicular Trafficking in Neurodegenerative Diseases. Neurochem Res 2016; 42:905-917. [DOI: 10.1007/s11064-016-2055-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 08/30/2016] [Accepted: 08/31/2016] [Indexed: 12/20/2022]
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115
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Haydon PG. The Evolving View of Astrocytes. CEREBRUM : THE DANA FORUM ON BRAIN SCIENCE 2016; 2016:cer-12-16. [PMID: 28058092 PMCID: PMC5198755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Did you know that glial cells are more numerous than neurons in the brain? Scientists have found that one type of glial cell that is prevalent in the cortex-the astrocyte-communicates with its brethren, sends information to neurons, and controls blood flow to regions of brain activity. Because of all these properties, and since the cortex is believed responsible for cognition, the role of astrocytes in sleep, learning, and memory is being determined.
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116
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Glia plasma membrane transporters: Key players in glutamatergic neurotransmission. Neurochem Int 2016; 98:46-55. [DOI: 10.1016/j.neuint.2016.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 03/07/2016] [Accepted: 04/06/2016] [Indexed: 12/27/2022]
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117
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Li J, Tang J, Ma J, Du M, Wang R, Wu Y. Dynamic transition of neuronal firing induced by abnormal astrocytic glutamate oscillation. Sci Rep 2016; 6:32343. [PMID: 27573570 PMCID: PMC5004107 DOI: 10.1038/srep32343] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 08/05/2016] [Indexed: 02/01/2023] Open
Abstract
The gliotransmitter glutamate released from astrocytes can modulate neuronal firing by activating neuronal N-methyl-D-aspartic acid (NMDA) receptors. This enables astrocytic glutamate(AG) to be involved in neuronal physiological and pathological functions. Based on empirical results and classical neuron-glial "tripartite synapse" model, we propose a practical model to describe extracellular AG oscillation, in which the fluctuation of AG depends on the threshold of calcium concentration, and the effect of AG degradation is considered as well. We predict the seizure-like discharges under the dysfunction of AG degradation duration. Consistent with our prediction, the suppression of AG uptake by astrocytic transporters, which operates by modulating the AG degradation process, can account for the emergence of epilepsy.
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Affiliation(s)
- Jiajia Li
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China
| | - Jun Tang
- College of Science, China University of Mining and Technology, Xuzhou 221116, China
| | - Jun Ma
- Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China
| | - Mengmeng Du
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China
| | - Rong Wang
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China
| | - Ying Wu
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China
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118
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119
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Mitterauer B, Garvin AM, Dirnhofer R. The Sudden Infant Death Syndrome (SIDS): A Neuro-Molecular Hypothesis. Neuroscientist 2016. [DOI: 10.1177/107385840000600306] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Most of the children who die before age 1 in developed countries do so for unknown reasons, and these deaths are attributed to the sudden infant death syndrome (SIDS). Prospective cardiorespiratory monitoring of infants has revealed that SIDS victims have subtle differences in breathing and heartbeat patterns compared to controls. Because death must involve cardiorespiratory arrest, a straightforward explanation for SIDS is failure on the part of pacemaker neurons controlling the rhythmical processes of breathing or heartbeat. Genes coding for hyperpolarization-activated pacemaker cation channels have recently been isolated and are expressed in the heart and the brain. The authors propose that mutations in these genes and in other genes required for cardiorespiratory pacemaker activity will predispose an individual to SIDS during a window of vulnerability present in the first year of life. Furthermore, mutations in clock genes can alter a variety of rhythmical processes and may indirectly disturb cardiorespiratory function as well.
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Affiliation(s)
- Bernhard Mitterauer
- Institute of Forensic Neuropsychiatry, University of Salzburg, Ignaz-Harrerstrasse 79, 5020 Salzburg, Austria,
| | - Alex M. Garvin
- Department of Biochemistry, Biocentre, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
| | - Richard Dirnhofer
- Institute of Legal Medicine, University of Bern, Buhlstrasse 20, CH-3012 Bern, Switzerland
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120
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Abstract
Neurons and glia are the principal cellular components of the nervous system. Although the glia are 10 times more numerous than neurons, until recently they were thought to be passive cells that monitor and support the active neurons by taking up used neurotransmitters from the synapses. In the past few years, this concept has been challenged by the findings that Ca2+ waves spread from one astrocyte to another via Ca2+-and SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-dependent gliotransmitter release in pure cultures of astrocytes, raising the possibility that glia are not so passive as previously thought. This hypothesis was further advanced by two recent reports, which demonstrated that astrocytes release glutamate via vesicular exocytosis in response to stimuli. The kinetics of single vesicle exocytosis is distinct from its neural equivalent, because in response to physiological stimulation, gliotransmitter release is exclusively in the mode of “kiss and run.” These advances were made possible by newly available techniques for single vesicle recordings, which will also be briefly reviewed here.
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Affiliation(s)
- Xiao-Ke Chen
- Institute of Molecular Medicine, Peking University, 5 Yi-He-Yuan Road, Beijing 100871, China
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121
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Bazargani N, Attwell D. Astrocyte calcium signaling: the third wave. Nat Neurosci 2016; 19:182-9. [PMID: 26814587 DOI: 10.1038/nn.4201] [Citation(s) in RCA: 567] [Impact Index Per Article: 70.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 11/10/2015] [Indexed: 02/06/2023]
Abstract
The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function.
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Affiliation(s)
- Narges Bazargani
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
| | - David Attwell
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
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122
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Lossi L, Cocito C, Alasia S, Merighi A. Ex vivo imaging of active caspase 3 by a FRET-based molecular probe demonstrates the cellular dynamics and localization of the protease in cerebellar granule cells and its regulation by the apoptosis-inhibiting protein survivin. Mol Neurodegener 2016; 11:34. [PMID: 27122136 PMCID: PMC4848850 DOI: 10.1186/s13024-016-0101-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 04/22/2016] [Indexed: 01/27/2023] Open
Abstract
Background Apoptosis takes place in naturally occurring neuronal death, but also in aging, neurodegenerative disorders, and traumatic brain injuries. Caspase 3 (Casp3) is the most important effector protease in apoptosis: being inactive inside the cell, it undergoes enzymatic cleavage and - hence - activation once the apoptotic cascade is triggered. Immunological techniques with antibodies against cleaved Casp3 (cCasp3) or assays with colorimetric/fluorogenic substrates are commonly in use, but they do not allow to directly follow the dynamics of activation in alive neurons that may be committed to die. Results By combined biolistic transfection, confocal microscopy, and fluorescence resonance energy transfer (FRET), we have implemented a methodology to dynamically monitor Casp3 activation in organotypic cerebellar slices from postnatal mice. After transfection with pSCAT3 FRET probes, we measured the ratio of the emissions of the donor/acceptor pair (ECFPem/Venusem) in fixed or alive cultures. In so doing, we i. discriminated the cellular compartment(s) of enzyme activation (nucleus, perikaryon, neurites); ii. demonstrated that Casp3 was constitutively active in the granule cells; iii. followed the fluctuations of ECFPem/Venusem, and its response to 25 mM KCl depolarization, or to increased intracellular Ca++ after NMDA (1 mM), kainic acid (1 mM), or A23187 (100–200 μM). The specificity of the active pSCAT3-DEVD probe was confirmed with RNA interference and after inhibition of Casp3 with Ac-DEVD-CMK (100 μM), as both sets of experiments brought ECFPem/Venusem to the values recorded with the control probe pSCAT3-DEVG. After double-transfection with pSCAT3-DEVD + pHcRed1-C1-survivin, we also showed a 44–56 % reduction of basal Casp3 activity in cells overexpressing survivin, a protein-member of the family of apoptosis inhibitors, with augmented survival (2.82 folds). Survivin-rescued cells were sensitive to 5 mM H2O2 oxidative stress but died without intervention of Casp3. Conclusions This ex vivo FRET-based methodology provides quantitative information on the functional and histological dynamics of Casp3 activation in individual neurons at a cell level resolution. Not only it can be combined with experimental manipulation of the apoptotic machinery inside the cell, but offers several advantages over existing protocols for monitoring apoptosis in live mammalian neurons, and has potential to be transferred in vivo. Due to the pivotal role of Casp3 in apoptosis, our approach is relevant for a better comprehension of molecular neurodegeneration in the normal and pathological brain. Electronic supplementary material The online version of this article (doi:10.1186/s13024-016-0101-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Laura Lossi
- University of Turin, Department of Veterinary Sciences, Largo Paolo Braccini 2, I-10095, Grugliasco, TO, Italy
| | - Carolina Cocito
- University of Turin, Department of Veterinary Sciences, Largo Paolo Braccini 2, I-10095, Grugliasco, TO, Italy
| | - Silvia Alasia
- University of Turin, Department of Veterinary Sciences, Largo Paolo Braccini 2, I-10095, Grugliasco, TO, Italy
| | - Adalberto Merighi
- University of Turin, Department of Veterinary Sciences, Largo Paolo Braccini 2, I-10095, Grugliasco, TO, Italy.
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123
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Modulation of Synaptic Plasticity by Glutamatergic Gliotransmission: A Modeling Study. Neural Plast 2016; 2016:7607924. [PMID: 27195153 PMCID: PMC4852535 DOI: 10.1155/2016/7607924] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 02/15/2016] [Indexed: 01/03/2023] Open
Abstract
Glutamatergic gliotransmission, that is, the release of glutamate from perisynaptic astrocyte processes in an activity-dependent manner, has emerged as a potentially crucial signaling pathway for regulation of synaptic plasticity, yet its modes of expression and function in vivo remain unclear. Here, we focus on two experimentally well-identified gliotransmitter pathways, (i) modulations of synaptic release and (ii) postsynaptic slow inward currents mediated by glutamate released from astrocytes, and investigate their possible functional relevance on synaptic plasticity in a biophysical model of an astrocyte-regulated synapse. Our model predicts that both pathways could profoundly affect both short- and long-term plasticity. In particular, activity-dependent glutamate release from astrocytes could dramatically change spike-timing-dependent plasticity, turning potentiation into depression (and vice versa) for the same induction protocol.
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124
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Davidson JM, Wong CT, Rai-Bhogal R, Li H, Crawford DA. Prostaglandin E2 elevates calcium in differentiated neuroectodermal stem cells. Mol Cell Neurosci 2016; 74:71-7. [PMID: 27074429 DOI: 10.1016/j.mcn.2016.03.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 03/21/2016] [Accepted: 03/31/2016] [Indexed: 01/02/2023] Open
Abstract
Lipid mediator prostaglandin E2 (PGE2) is an endogenous signaling molecule that plays an important role during early development of the nervous system. Abnormalities in the PGE2 signaling pathway have been associated with neurodevelopmental disorders such as autism spectrum disorders. In this study we use ratiometric fura-2AM calcium imaging to show that higher levels of PGE2 elevate intracellular calcium levels in the cell soma and growth cones of differentiated neuroectodermal (NE-4C) stem cells. PGE2 also increased the amplitude of calcium fluctuation in the neuronal growth cones and affected the neurite extension length. In summary, our results show that PGE2 may adversely impact intracellular calcium dynamics in differentiated neuronal cells and possibly affect early development of the nervous system.
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Affiliation(s)
- Jennilee M Davidson
- Neuroscience Graduate Diploma Program, York University, Toronto, ON M3J 1P3, Canada; Department of Biology, York University, Toronto, ON M3J 1P3, Canada
| | - Christine T Wong
- School of Kinesiology and Health Science, York University, Toronto, ON M3J 1P3, Canada; Neuroscience Graduate Diploma Program, York University, Toronto, ON M3J 1P3, Canada
| | - Ravneet Rai-Bhogal
- Neuroscience Graduate Diploma Program, York University, Toronto, ON M3J 1P3, Canada; Department of Biology, York University, Toronto, ON M3J 1P3, Canada
| | - Hongyan Li
- School of Kinesiology and Health Science, York University, Toronto, ON M3J 1P3, Canada
| | - Dorota A Crawford
- School of Kinesiology and Health Science, York University, Toronto, ON M3J 1P3, Canada; Neuroscience Graduate Diploma Program, York University, Toronto, ON M3J 1P3, Canada; Department of Biology, York University, Toronto, ON M3J 1P3, Canada.
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125
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Longden TA, Hill-Eubanks DC, Nelson MT. Ion channel networks in the control of cerebral blood flow. J Cereb Blood Flow Metab 2016; 36:492-512. [PMID: 26661232 PMCID: PMC4794103 DOI: 10.1177/0271678x15616138] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 09/17/2015] [Accepted: 10/14/2015] [Indexed: 12/26/2022]
Abstract
One hundred and twenty five years ago, Roy and Sherrington made the seminal observation that neuronal stimulation evokes an increase in cerebral blood flow.(1) Since this discovery, researchers have attempted to uncover how the cells of the neurovascular unit-neurons, astrocytes, vascular smooth muscle cells, vascular endothelial cells and pericytes-coordinate their activity to control this phenomenon. Recent work has revealed that ionic fluxes through a diverse array of ion channel species allow the cells of the neurovascular unit to engage in multicellular signaling processes that dictate local hemodynamics.In this review we center our discussion on two major themes: (1) the roles of ion channels in the dynamic modulation of parenchymal arteriole smooth muscle membrane potential, which is central to the control of arteriolar diameter and therefore must be harnessed to permit changes in downstream cerebral blood flow, and (2) the striking similarities in the ion channel complements employed in astrocytic endfeet and endothelial cells, enabling dual control of smooth muscle from either side of the blood-brain barrier. We conclude with a discussion of the emerging roles of pericyte and capillary endothelial cell ion channels in neurovascular coupling, which will provide fertile ground for future breakthroughs in the field.
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Affiliation(s)
- Thomas A Longden
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT, USA Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK
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126
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Kong L, Albano R, Madayag A, Raddatz N, Mantsch JR, Choi S, Lobner D, Baker DA. Pituitary Adenylate cyclase-activating polypeptide orchestrates neuronal regulation of the astrocytic glutamate-releasing mechanism system xc (.). J Neurochem 2016; 137:384-93. [PMID: 26851652 DOI: 10.1111/jnc.13566] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 01/28/2016] [Accepted: 02/01/2016] [Indexed: 12/26/2022]
Abstract
Glutamate signaling is achieved by an elaborate network involving neurons and astrocytes. Hence, it is critical to better understand how neurons and astrocytes interact to coordinate the cellular regulation of glutamate signaling. In these studies, we used rat cortical cell cultures to examine whether neurons or releasable neuronal factors were capable of regulating system xc (-) (Sxc), a glutamate-releasing mechanism that is expressed primarily by astrocytes and has been shown to regulate synaptic transmission. We found that astrocytes cultured with neurons or exposed to neuronal-conditioned media displayed significantly higher levels of Sxc activity. Next, we demonstrated that the pituitary adenylate cyclase-activating polypeptide (PACAP) may be a neuronal factor capable of regulating astrocytes. In support, we found that PACAP expression was restricted to neurons, and that PACAP receptors were expressed in astrocytes. Interestingly, blockade of PACAP receptors in cultures comprised of astrocytes and neurons significantly decreased Sxc activity to the level observed in purified astrocytes, whereas application of PACAP to purified astrocytes increased Sxc activity to the level observed in cultures comprised of neurons and astrocytes. Collectively, these data reveal that neurons coordinate the actions of glutamate-related mechanisms expressed by astrocytes, such as Sxc, a process that likely involves PACAP. A critical gap in modeling excitatory signaling is how distinct components of the glutamate system expressed by neurons and astrocytes are coordinated. In these studies, we found that system xc (-) (Sxc), a glutamate release mechanism expressed by astrocytes, is regulated by releasable neuronal factors including PACAP. This represents a novel form of neuron-astrocyte communication, and highlights the possibility that pathological changes involving astrocytic Sxc may stem from altered neuronal activity.
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Affiliation(s)
- Linghai Kong
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - Rebecca Albano
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - Aric Madayag
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - Nicholas Raddatz
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - John R Mantsch
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - SuJean Choi
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - Doug Lobner
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - David A Baker
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA
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127
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Petrelli F, Bezzi P. Novel insights into gliotransmitters. Curr Opin Pharmacol 2016; 26:138-45. [DOI: 10.1016/j.coph.2015.11.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 11/20/2015] [Accepted: 11/23/2015] [Indexed: 12/13/2022]
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128
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Ochoa-Cortes F, Turco F, Linan-Rico A, Soghomonyan S, Whitaker E, Wehner S, Cuomo R, Christofi FL. Enteric Glial Cells: A New Frontier in Neurogastroenterology and Clinical Target for Inflammatory Bowel Diseases. Inflamm Bowel Dis 2016; 22:433-49. [PMID: 26689598 PMCID: PMC4718179 DOI: 10.1097/mib.0000000000000667] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 08/29/2015] [Indexed: 12/12/2022]
Abstract
The word "glia" is derived from the Greek word "γλoια," glue of the enteric nervous system, and for many years, enteric glial cells (EGCs) were believed to provide mainly structural support. However, EGCs as astrocytes in the central nervous system may serve a much more vital and active role in the enteric nervous system, and in homeostatic regulation of gastrointestinal functions. The emphasis of this review will be on emerging concepts supported by basic, translational, and/or clinical studies, implicating EGCs in neuron-to-glial (neuroglial) communication, motility, interactions with other cells in the gut microenvironment, infection, and inflammatory bowel diseases. The concept of the "reactive glial phenotype" is explored as it relates to inflammatory bowel diseases, bacterial and viral infections, postoperative ileus, functional gastrointestinal disorders, and motility disorders. The main theme of this review is that EGCs are emerging as a new frontier in neurogastroenterology and a potential therapeutic target. New technological innovations in neuroimaging techniques are facilitating progress in the field, and an update is provided on exciting new translational studies. Gaps in our knowledge are discussed for further research. Restoring normal EGC function may prove to be an efficient strategy to dampen inflammation. Probiotics, palmitoylethanolamide (peroxisome proliferator-activated receptor-α), interleukin-1 antagonists (anakinra), and interventions acting on nitric oxide, receptor for advanced glycation end products, S100B, or purinergic signaling pathways are relevant clinical targets on EGCs with therapeutic potential.
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Affiliation(s)
| | - Fabio Turco
- Department of Anesthesiology, The Ohio State University, Columbus, Ohio
- Department of Clinical and Experimental Medicine, Gastroenterological Unit, “Federico II” University of Naples, Naples, Italy; and
| | | | - Suren Soghomonyan
- Department of Anesthesiology, The Ohio State University, Columbus, Ohio
| | - Emmett Whitaker
- Department of Anesthesiology, The Ohio State University, Columbus, Ohio
| | - Sven Wehner
- Department of Surgery, University of Bonn, Bonn, Germany
| | - Rosario Cuomo
- Department of Clinical and Experimental Medicine, Gastroenterological Unit, “Federico II” University of Naples, Naples, Italy; and
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129
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Gordon GRJ, Howarth C, MacVicar BA. Bidirectional Control of Blood Flow by Astrocytes: A Role for Tissue Oxygen and Other Metabolic Factors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 903:209-19. [PMID: 27343099 DOI: 10.1007/978-1-4899-7678-9_15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Altering cerebral blood flow through the control of cerebral vessel diameter is critical so that the delivery of molecules important for proper brain functioning is matched to the activity level of neurons. Although the close relationship of brain glia known as astrocytes with cerebral blood vessels has long been recognized, it is only recently that these cells have been demonstrated to translate information on the activity level and energy demands of neurons to the vasculature. In particular, astrocytes respond to elevations in extracellular glutamate as a consequence of synaptic transmission through the activation of group 1 metabotropic glutamate receptors. These Gq-protein coupled receptors elevate intracellular calcium via IP3 signaling. A close examination of astrocyte endfeet calcium signals has been shown to cause either vasoconstriction or vasodilation. Common to both vasomotor responses is the generation of arachidonic acid in astrocytes by calcium sensitive phospholipase A2. Vasoconstriction ensues from the conversion of arachidonic acid to 20-hydroxyeicosatetraenoic acid, while vasodilation ensues from the production of epoxyeicosatrienoic acids or prostaglandins. Factors that determine whether constrictor or dilatory pathways predominate include brain oxygen, lactate, adenosine as well as nitric oxide. Changing the oxygen level itself leads to many downstream changes that facilitate the switch from vasoconstriction at high oxygen to vasodilation at low oxygen. These findings highlight the importance of astrocytes as sensors of neural activity and metabolism to coordinate the delivery of essential nutrients via the blood to the working cells.
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Affiliation(s)
- Grant R J Gordon
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada.
| | - Clare Howarth
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
| | - Brian A MacVicar
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
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130
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131
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Panatier A, Arizono M, Nägerl UV. Dissecting tripartite synapses with STED microscopy. Philos Trans R Soc Lond B Biol Sci 2015; 369:20130597. [PMID: 25225091 DOI: 10.1098/rstb.2013.0597] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The concept of the tripartite synapse reflects the important role that astrocytic processes are thought to play in the function and regulation of neuronal synapses in the mammalian nervous system. However, many basic aspects regarding the dynamic interplay between pre- and postsynaptic neuronal structures and their astrocytic partners remain to be explored. A major experimental hurdle has been the small physical size of the relevant glial and synaptic structures, leaving them largely out of reach for conventional light microscopic approaches such as confocal and two-photon microscopy. Hence, most of what we know about the organization of the tripartite synapse is based on electron microscopy, which does not lend itself to investigating dynamic events and which cannot be carried out in parallel with functional assays. The development and application of superresolution microscopy for neuron-glia research is opening up exciting experimental opportunities in this regard. In this paper, we provide a basic explanation of the theory and operation of stimulated emission depletion (STED) microscopy, outlining the potential of this recent superresolution imaging modality for advancing our understanding of the morpho-functional interactions between astrocytes and neurons that regulate synaptic physiology.
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Affiliation(s)
- Aude Panatier
- Université de Bordeaux, Bordeaux, France Neurocentre Magendie, Inserm U862, Bordeaux, France
| | - Misa Arizono
- Université de Bordeaux, Bordeaux, France Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, Wako, Japan
| | - U Valentin Nägerl
- Université de Bordeaux, Bordeaux, France Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France
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132
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Navarrete M, Díez A, Araque A. Astrocytes in endocannabinoid signalling. Philos Trans R Soc Lond B Biol Sci 2015; 369:20130599. [PMID: 25225093 DOI: 10.1098/rstb.2013.0599] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Astrocytes are emerging as integral functional components of synapses, responding to synaptically released neurotransmitters and regulating synaptic transmission and plasticity. Thus, they functionally interact with neurons establishing tripartite synapses: a functional concept that refers to the existence of communication between astrocytes and neurons and its crucial role in synaptic function. Here, we discuss recent evidence showing that astrocytes are involved in the endocannabinoid (ECB) system, responding to exogenous cannabinoids as well as ECBs through activation of type 1 cannabinoid receptors, which increase intracellular calcium and stimulate the release of glutamate that modulates synaptic transmission and plasticity. We also discuss the consequences of ECB signalling in tripartite synapses on the astrocyte-mediated regulation of synaptic function, which reveal novel properties of synaptic regulation by ECBs, such as the spatially controlled dual effect on synaptic strength and the lateral potentiation of synaptic efficacy. Finally, we discuss the potential implications of ECB signalling for astrocytes in brain pathology and animal behaviour.
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Affiliation(s)
| | | | - Alfonso Araque
- Instituto Cajal, CSIC, Madrid 28002, Spain Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
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133
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Mohn TC, Koob AO. Adult Astrogenesis and the Etiology of Cortical Neurodegeneration. J Exp Neurosci 2015; 9:25-34. [PMID: 26568684 PMCID: PMC4634839 DOI: 10.4137/jen.s25520] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 10/06/2015] [Accepted: 10/08/2015] [Indexed: 01/09/2023] Open
Abstract
As more evidence points to a clear role for astrocytes in synaptic processing, synaptogenesis and cognition, continuing research on astrocytic function could lead to strategies for neurodegenerative disease prevention. Reactive astrogliosis results in astrocyte proliferation early in injury and disease states and is considered neuroprotective, indicating a role for astrocytes in disease etiology. This review describes the different types of human cortical astrocytes and the current evidence regarding adult cortical astrogenesis in injury and degenerative disease. A role for disrupted astrogenesis as a cause of cortical degeneration, with a focus on the tauopathies and synucleinopathies, will also be considered.
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Affiliation(s)
- Tal C. Mohn
- Biology Department, University of Wisconsin—River Falls, River Falls, Wisconsin, USA
| | - Andrew O. Koob
- Biology Department, University of Wisconsin—River Falls, River Falls, Wisconsin, USA
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134
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Naeem M, McDaid LJ, Harkin J, Wade JJ, Marsland J. On the role of astroglial syncytia in self-repairing spiking neural networks. IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS 2015; 26:2370-80. [PMID: 25576582 DOI: 10.1109/tnnls.2014.2382334] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
It has been shown that brain-like self-repair can arise from the interactions between neurons and astrocytes where endocannabinoids are synthesized and released from active neurons. This retrograde messenger feeds back to local synapses directly and indirectly to distant synapses via astrocytes. This direct/indirect feedback of the endocannabinoid retrograde messenger results in the modulation of the probability of release (PR) at synaptic sites. When synapses fail, there is a corresponding falloff in the firing activity of the associated neurons, and hence the strength of the direct feedback messenger diminishes. This triggers an increase in PR of healthy synapses, due to the indirect messenger from other active neurons, which is the catalyst for the repair process. In this paper, the repair process is implemented by developing a new learning rule that captures the spike-timing-dependent plasticity and Bienenstock, Cooper, and Munro learning rules. The rule is activated by the increase in PR and results in a potentiation of the weight values, which reestablishes the firing activity of neurons. In addition, this self-repairing mechanism is extended to network-level repair where astrocyte to astrocyte communications are implemented using a linear gap junction model. This facilitates the implementation of an astroglial syncytium involving multiple astrocytes, which relays the indirect feedback messenger to distant neurons: each astrocyte is bidirectionally coupled to neurons. A detailed and comprehensive set of results with analysis is presented demonstrating repair at both cellular and network levels.
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135
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Li H, Xie Y, Zhang N, Yu Y, Zhang Q, Ding S. Disruption of IP₃R2-mediated Ca²⁺ signaling pathway in astrocytes ameliorates neuronal death and brain damage while reducing behavioral deficits after focal ischemic stroke. Cell Calcium 2015; 58:565-76. [PMID: 26433454 DOI: 10.1016/j.ceca.2015.09.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 09/19/2015] [Accepted: 09/21/2015] [Indexed: 12/12/2022]
Abstract
Inositol trisphosphate receptor (IP3R)-mediated intracellular Ca(2+) increase is the major Ca(2+) signaling pathway in astrocytes in the central nervous system (CNS). Ca(2+) increases in astrocytes have been found to modulate neuronal function through gliotransmitter release. We previously demonstrated that astrocytes exhibit enhanced Ca(2+) signaling in vivo after photothrombosis (PT)-induced ischemia, which is largely due to the activation of G-protein coupled receptors (GPCRs). The aim of this study is to investigate the role of astrocytic IP3R-mediated Ca(2+) signaling in neuronal death, brain damage and behavior outcomes after PT. For this purpose, we conducted experiments using homozygous type 2 IP3R (IP3R2) knockout (KO) mice. Histological and immunostaining studies showed that IP3R2 KO mice were indeed deficient in IP3R2 in astrocytes and exhibited normal brain cytoarchitecture. IP3R2 KO mice also had the same densities of S100β+ astrocytes and NeuN+ neurons in the cortices, and exhibited the same glial fibrillary acidic protein (GFAP) and glial glutamate transporter (GLT-1) levels in the cortices and hippocampi as compared with wild type (WT) mice. Two-photon (2-P) imaging showed that IP3R2 KO mice did not exhibit ATP-induced Ca(2+) waves in vivo in the astrocytic network, which verified the disruption of IP3R-mediated Ca(2+) signaling in astrocytes of these mice. When subject to PT, IP3R2 KO mice had smaller infarction than WT mice in acute and chronic phases of ischemia. IP3R2 KO mice also exhibited less neuronal apoptosis, reactive astrogliosis, and tissue loss than WT mice. Behavioral tests, including cylinder, hanging wire, pole and adhesive tests, showed that IP3R2 KO mice exhibited reduced functional deficits after PT. Collectively, our study demonstrates that disruption of astrocytic Ca(2+) signaling by deleting IP3R2s has beneficial effects on neuronal and brain protection and functional deficits after stroke. These findings reveal a novel non-cell-autonomous neuronal and brain protective function of astrocytes in ischemic stroke, whereby suggest that the astrocytic IP3R2-mediated Ca(2+) signaling pathway might be a promising target for stroke therapy.
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Affiliation(s)
- Hailong Li
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States; Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Yicheng Xie
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States; Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Nannan Zhang
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States
| | - Yang Yu
- Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Qiao Zhang
- Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States
| | - Shinghua Ding
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211, United States; Department of Bioengineering, University of Missouri-Columbia, MO 65211, United States.
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136
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Vardjan N, Parpura V, Zorec R. Loose excitation-secretion coupling in astrocytes. Glia 2015; 64:655-67. [PMID: 26358496 DOI: 10.1002/glia.22920] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/26/2015] [Indexed: 12/19/2022]
Abstract
Astrocytes play an important housekeeping role in the central nervous system. Additionally, as secretory cells, they actively participate in cell-to-cell communication, which can be mediated by membrane-bound vesicles. The gliosignaling molecules stored in these vesicles are discharged into the extracellular space after the vesicle membrane fuses with the plasma membrane. This process is termed exocytosis, regulated by SNARE proteins, and triggered by elevations in cytosolic calcium levels, which are necessary and sufficient for exocytosis in astrocytes. For astrocytic exocytosis, calcium is sourced from the intracellular endoplasmic reticulum store, although its entry from the extracellular space contributes to cytosolic calcium dynamics in astrocytes. Here, we discuss calcium management in astrocytic exocytosis and the properties of the membrane-bound vesicles that store gliosignaling molecules, including the vesicle fusion machinery and kinetics of vesicle content discharge. In astrocytes, the delay between the increase in cytosolic calcium activity and the discharge of secretions from the vesicular lumen is orders of magnitude longer than that in neurons. This relatively loose excitation-secretion coupling is likely tailored to the participation of astrocytes in modulating neural network processing.
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Affiliation(s)
- Nina Vardjan
- Celica Biomedical, Ljubljana, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Vladimir Parpura
- Department of Neurobiology, Center for Glial Biology in Medicine, Civitan International Research Center, Atomic Force Microscopy & Nanotechnology Laboratories, Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Robert Zorec
- Celica Biomedical, Ljubljana, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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137
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Abstract
Neuroglia, the "glue" that fills the space between neurons in the central nervous system, takes active part in nerve cell signaling. Neuroglial cells, astroglia, oligodendroglia, and microglia, are together about as numerous as neurons in the brain as a whole, and in the cerebral cortex grey matter, but the proportion varies widely among brain regions. Glial volume, however, is less than one-fifth of the tissue volume in grey matter. When stimulated by neurons or other cells, neuroglial cells release gliotransmitters by exocytosis, similar to neurotransmitter release from nerve endings, or by carrier-mediated transport or channel flux through the plasma membrane. Gliotransmitters include the common neurotransmitters glutamate and GABA, the nonstandard amino acid d-serine, the high-energy phosphate ATP, and l-lactate. The latter molecule is a "buffer" between glycolytic and oxidative metabolism as well as a signaling substance recently shown to act on specific lactate receptors in the brain. Complementing neurotransmission at a synapse, neuroglial transmission often implies diffusion of the transmitter over a longer distance and concurs with the concept of volume transmission. Transmission from glia modulates synaptic neurotransmission based on energetic and other local conditions in a volume of tissue surrounding the individual synapse. Neuroglial transmission appears to contribute significantly to brain functions such as memory, as well as to prevalent neuropathologies.
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Affiliation(s)
- Vidar Gundersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Jon Storm-Mathisen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Linda Hildegard Bergersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
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138
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Motor-Skill Learning Is Dependent on Astrocytic Activity. Neural Plast 2015; 2015:938023. [PMID: 26346977 PMCID: PMC4539503 DOI: 10.1155/2015/938023] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 02/24/2015] [Indexed: 12/26/2022] Open
Abstract
Motor-skill learning induces changes in synaptic structure and function in the primary motor cortex through the involvement of a long-term potentiation- (LTP-) like mechanism. Although there is evidence that calcium-dependent release of gliotransmitters by astrocytes plays an important role in synaptic transmission and plasticity, the role of astrocytes in motor-skill learning is not known. To test the hypothesis that astrocytic activity is necessary for motor-skill learning, we perturbed astrocytic function using pharmacological and genetic approaches. We find that perturbation of astrocytes either by selectively attenuating IP3R2 mediated astrocyte Ca2+ signaling or using an astrocyte specific metabolic inhibitor fluorocitrate (FC) results in impaired motor-skill learning of a forelimb reaching-task in mice. Moreover, the learning impairment caused by blocking astrocytic activity using FC was rescued by administration of the gliotransmitter D-serine. The learning impairments are likely caused by impaired LTP as FC blocked LTP in slices and prevented motor-skill training-induced increases in synaptic AMPA-type glutamate receptor in vivo. These results support the conclusion that normal astrocytic Ca2+ signaling during a reaching task is necessary for motor-skill learning.
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139
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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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140
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Plasticity of Neuron-Glial Transmission: Equipping Glia for Long-Term Integration of Network Activity. Neural Plast 2015; 2015:765792. [PMID: 26339509 PMCID: PMC4539116 DOI: 10.1155/2015/765792] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 06/11/2015] [Indexed: 01/28/2023] Open
Abstract
The capacity of synaptic networks to express activity-dependent changes in strength and connectivity is essential for learning and memory processes. In recent years, glial cells (most notably astrocytes) have been recognized as active participants in the modulation of synaptic transmission and synaptic plasticity, implicating these electrically nonexcitable cells in information processing in the brain. While the concept of bidirectional communication between neurons and glia and the mechanisms by which gliotransmission can modulate neuronal function are well established, less attention has been focussed on the computational potential of neuron-glial transmission itself. In particular, whether neuron-glial transmission is itself subject to activity-dependent plasticity and what the computational properties of such plasticity might be has not been explored in detail. In this review, we summarize current examples of plasticity in neuron-glial transmission, in many brain regions and neurotransmitter pathways. We argue that induction of glial plasticity typically requires repetitive neuronal firing over long time periods (minutes-hours) rather than the short-lived, stereotyped trigger typical of canonical long-term potentiation. We speculate that this equips glia with a mechanism for monitoring average firing rates in the synaptic network, which is suited to the longer term roles proposed for astrocytes in neurophysiology.
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141
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mGluR5 protect astrocytes from ischemic damage in postnatal CNS white matter. Cell Calcium 2015; 58:423-30. [PMID: 26189008 PMCID: PMC4634333 DOI: 10.1016/j.ceca.2015.06.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Revised: 06/26/2015] [Accepted: 06/28/2015] [Indexed: 11/21/2022]
Abstract
Astrocytes perform essential neuron-supporting functions in the central nervous system (CNS) and their disruption has devastating effects on neuronal integrity in multiple neuropathologies. Although astrocytes are considered resistant to most pathological insults, ischemia can result in astrocyte injury and astrocytes in postnatal white matter are particularly vulnerable. Metabotropic glutamate receptors (mGluR) are neuroprotective in ischemia and are widely expressed by astrocytes throughout CNS grey matter, but their potential cytoprotective role in astrocytes had not been determined. Here, we identify functional expression of group I mGluR in white matter astrocytes and demonstrate their activation protects astrocytes from ischemic damage in the postnatal mouse optic nerve. Optic nerve astrocytes are shown to express mGluR5 using immunolabelling of sections and explant cultures from transgenic reporter mice in which GFAP drives expression of EGFP. In addition, using Fluo-4 calcium imaging in isolated intact optic nerves, we show that the group I/II mGluR agonist ACPD and the specific group I mGluR agonist DHPG evoke glial Ca(2+) signals that were significantly inhibited by the group I mGluR antagonist AIDA. A key finding is that activation of group I mGluR protects astrocytes against oxygen-glucose deprivation (OGD) in situ, in isolated intact optic nerves from GFAP-EGFP mice. This study identifies a role for group I mGluR in protecting astrocytes against ischemia in postnatal white matter and suggests this may be a strategy for limiting damage in neuropathologies involving excitotoxity.
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142
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Vecino E, Rodriguez FD, Ruzafa N, Pereiro X, Sharma SC. Glia-neuron interactions in the mammalian retina. Prog Retin Eye Res 2015; 51:1-40. [PMID: 26113209 DOI: 10.1016/j.preteyeres.2015.06.003] [Citation(s) in RCA: 493] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 05/18/2015] [Accepted: 06/02/2015] [Indexed: 02/07/2023]
Abstract
The mammalian retina provides an excellent opportunity to study glia-neuron interactions and the interactions of glia with blood vessels. Three main types of glial cells are found in the mammalian retina that serve to maintain retinal homeostasis: astrocytes, Müller cells and resident microglia. Müller cells, astrocytes and microglia not only provide structural support but they are also involved in metabolism, the phagocytosis of neuronal debris, the release of certain transmitters and trophic factors and K(+) uptake. Astrocytes are mostly located in the nerve fibre layer and they accompany the blood vessels in the inner nuclear layer. Indeed, like Müller cells, astrocytic processes cover the blood vessels forming the retinal blood barrier and they fulfil a significant role in ion homeostasis. Among other activities, microglia can be stimulated to fulfil a macrophage function, as well as to interact with other glial cells and neurons by secreting growth factors. This review summarizes the main functional relationships between retinal glial cells and neurons, presenting a general picture of the retina recently modified based on experimental observations. The preferential involvement of the distinct glia cells in terms of the activity in the retina is discussed, for example, while Müller cells may serve as progenitors of retinal neurons, astrocytes and microglia are responsible for synaptic pruning. Since different types of glia participate together in certain activities in the retina, it is imperative to explore the order of redundancy and to explore the heterogeneity among these cells. Recent studies revealed the association of glia cell heterogeneity with specific functions. Finally, the neuroprotective effects of glia on photoreceptors and ganglion cells under normal and adverse conditions will also be explored.
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Affiliation(s)
- Elena Vecino
- Department of Cell Biology and Histology, University of the Basque Country UPV/EHU, Leioa 48940, Vizcaya, Spain
| | - F David Rodriguez
- Department of Biochemistry and Molecular Biology, E-37007, University of Salamanca, Salamanca, Spain
| | - Noelia Ruzafa
- Department of Cell Biology and Histology, University of the Basque Country UPV/EHU, Leioa 48940, Vizcaya, Spain
| | - Xandra Pereiro
- Department of Cell Biology and Histology, University of the Basque Country UPV/EHU, Leioa 48940, Vizcaya, Spain
| | - Sansar C Sharma
- Department of Ophthalmology, Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA; IKERBASQUE, Basque Foundation for Science at Dept. Cell Biology and Histology, UPV/EHU, Spain
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143
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Abstract
Astrocytes exhibit cellular excitability through variations in their intracellular calcium (Ca²⁺) levels in response to synaptic activity. Astrocyte Ca²⁺ elevations can trigger the release of neuroactive substances that can modulate synaptic transmission and plasticity, hence promoting bidirectional communication with neurons. Intracellular Ca²⁺ dynamics can be regulated by several proteins located in the plasma membrane, within the cytosol and by intracellular organelles such as mitochondria. Spatial dynamics and strategic positioning of mitochondria are important for matching local energy provision and Ca²⁺ buffering requirements to the demands of neuronal signalling. Although relatively unresolved in astrocytes, further understanding the role of mitochondria in astrocytes may reveal more about the complex bidirectional relationship between astrocytes and neurons in health and disease. In the present review, we discuss some recent insights regarding mitochondrial function, transport and turnover in astrocytes and highlight some important questions that remain to be answered.
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144
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Chinchalongporn V, Koppensteiner P, Prè D, Thangnipon W, Bilo L, Arancio O. Connectivity and circuitry in a dish versus in a brain. ALZHEIMERS RESEARCH & THERAPY 2015; 7:44. [PMID: 26045718 PMCID: PMC4456047 DOI: 10.1186/s13195-015-0129-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In order to understand and find therapeutic strategies for neurological disorders, disease models that recapitulate the connectivity and circuitry of patients’ brain are needed. Owing to many limitations of animal disease models, in vitro neuronal models using patient-derived stem cells are currently being developed. However, prior to employing neurons as a model in a dish, they need to be evaluated for their electrophysiological properties, including both passive and active membrane properties, dynamics of neurotransmitter release, and capacity to undergo synaptic plasticity. In this review, we survey recent attempts to study these issues in human induced pluripotent stem cell-derived neurons. Although progress has been made, there are still many hurdles to overcome before human induced pluripotent stem cell-derived neurons can fully recapitulate all of the above physiological properties of adult mature neurons. Moreover, proper integration of neurons into pre-existing circuitry still needs to be achieved. Nevertheless, in vitro neuronal stem cell-derived models hold great promise for clinical application in neurological diseases in the future.
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Affiliation(s)
- Vorapin Chinchalongporn
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032 USA ; Taub Institute for Research on Alzheimer's Disease and the Aging Brain P&S Bldg, Room 12-420D, Columbia University, New York, NY 10032 USA ; Columbia Stem Cell Initiative, CUMC, New York, NY 10032 USA ; Research Center for Neuroscience, Institute of Molecular Biosciences, Mahidol University, Salaya, Nakhonpathom 73170 Thailand
| | - Peter Koppensteiner
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032 USA ; Taub Institute for Research on Alzheimer's Disease and the Aging Brain P&S Bldg, Room 12-420D, Columbia University, New York, NY 10032 USA ; Columbia Stem Cell Initiative, CUMC, New York, NY 10032 USA ; Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Deborah Prè
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032 USA ; Taub Institute for Research on Alzheimer's Disease and the Aging Brain P&S Bldg, Room 12-420D, Columbia University, New York, NY 10032 USA ; Columbia Stem Cell Initiative, CUMC, New York, NY 10032 USA
| | - Wipawan Thangnipon
- Research Center for Neuroscience, Institute of Molecular Biosciences, Mahidol University, Salaya, Nakhonpathom 73170 Thailand
| | - Leonilda Bilo
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032 USA ; Taub Institute for Research on Alzheimer's Disease and the Aging Brain P&S Bldg, Room 12-420D, Columbia University, New York, NY 10032 USA ; Columbia Stem Cell Initiative, CUMC, New York, NY 10032 USA ; Department of Neurosciences, Reproductive and Odontostomatological Sciences, Federico II University of Naples, 80131 Naples, Italy
| | - Ottavio Arancio
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032 USA ; Taub Institute for Research on Alzheimer's Disease and the Aging Brain P&S Bldg, Room 12-420D, Columbia University, New York, NY 10032 USA ; Columbia Stem Cell Initiative, CUMC, New York, NY 10032 USA
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Sibille J, Zapata J, Teillon J, Rouach N. Astroglial calcium signaling displays short-term plasticity and adjusts synaptic efficacy. Front Cell Neurosci 2015; 9:189. [PMID: 26074766 PMCID: PMC4444818 DOI: 10.3389/fncel.2015.00189] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 04/29/2015] [Indexed: 01/14/2023] Open
Abstract
Astrocytes are dynamic signaling brain elements able to sense neuronal inputs and to respond by complex calcium signals, which are thought to represent their excitability. Such signaling has been proposed to modulate, or not, neuronal activities ranging from basal synaptic transmission to epileptiform discharges. However, whether calcium signaling in astrocytes exhibits activity-dependent changes and acutely modulates short-term synaptic plasticity is currently unclear. We here show, using dual recordings of astroglial calcium signals and synaptic transmission, that calcium signaling in astrocytes displays, concomitantly to excitatory synapses, short-term plasticity in response to prolonged repetitive and tetanic stimulations of Schaffer collaterals. We also found that acute inhibition of calcium signaling in astrocytes by intracellular calcium chelation rapidly potentiates excitatory synaptic transmission and short-term plasticity of Shaffer collateral CA1 synapses, i.e., paired-pulse facilitation and responses to tetanic and prolonged repetitive stimulation. These data reveal that calcium signaling of astrocytes is plastic and down-regulates basal transmission and short-term plasticity of hippocampal CA1 glutamatergic synapses.
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Affiliation(s)
- Jérémie Sibille
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France ; Université Paris Diderot, Sorbonne Paris Cité Paris, France
| | - Jonathan Zapata
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France
| | - Jérémie Teillon
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France
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146
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Liang J, Kulasiri D, Samarasinghe S. Ca2+ dysregulation in the endoplasmic reticulum related to Alzheimer's disease: A review on experimental progress and computational modeling. Biosystems 2015; 134:1-15. [PMID: 25998697 DOI: 10.1016/j.biosystems.2015.05.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 05/12/2015] [Accepted: 05/12/2015] [Indexed: 12/12/2022]
Abstract
Alzheimer's disease (AD) is a devastating, incurable neurodegenerative disease affecting millions of people worldwide. Dysregulation of intracellular Ca(2+) signaling has been observed as an early event prior to the presence of clinical symptoms of AD and is believed to be a crucial factor contributing to its pathogenesis. The progressive and sustaining increase in the resting level of cytosolic Ca(2+) will affect downstream activities and neural functions. This review focuses on the issues relating to the increasing Ca(2+) release from the endoplasmic reticulum (ER) observed in AD neurons. Numerous research papers have suggested that the dysregulation of ER Ca(2+) homeostasis is associated with mutations in the presenilin genes and amyloid-β oligomers. These disturbances could happen at many different points in the signaling process, directly affecting ER Ca(2+) channels or interfering with related pathways, which makes it harder to reveal the underlying mechanisms. This review paper also shows that computational modeling is a powerful tool in Ca(2+) signaling studies and discusses the progress in modeling related to Ca(2+) dysregulation in AD research.
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Affiliation(s)
- Jingyi Liang
- Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand; Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - Don Kulasiri
- Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand; Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand.
| | - Sandhya Samarasinghe
- Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand; Department of Informatics and Enabling Technologies, Lincoln University, Christchurch, New Zealand
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147
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Fleischer W, Theiss S, Slotta J, Holland C, Schnitzler A. High-frequency voltage oscillations in cultured astrocytes. Physiol Rep 2015; 3:3/5/e12400. [PMID: 25969464 PMCID: PMC4463829 DOI: 10.14814/phy2.12400] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Because of their close interaction with neuronal physiology, astrocytes can modulate brain function in multiple ways. Here, we demonstrate a yet unknown astrocytic phenomenon: Astrocytes cultured on microelectrode arrays (MEAs) exhibited extracellular voltage fluctuations in a broad frequency spectrum (100–600 Hz) after electrical stimulation. These aperiodic high-frequency oscillations (HFOs) could last several seconds and did not spread across the MEA. The voltage-gated calcium channel antagonist cilnidipine dose-dependently decreased the power of the oscillations. While intracellular calcium was pivotal, incubation with bafilomycin A1 showed that vesicular release of transmitters played only a minor role in the emergence of HFOs. Gap junctions and volume-regulated anionic channels had just as little functional impact, which was demonstrated by the addition of carbenoxolone (100 μmol/L) and NPPB (100 μmol/L). Hyperpolarization with low potassium in the extracellular solution (2 mmol/L) dramatically raised oscillation power. A similar effect was seen when we added extra sodium (+50 mmol/L) or if we replaced it with NMDG+ (50 mmol/L). The purinergic receptor antagonist PPADS suppressed the oscillation power, while the agonist ATP (100 μmol/L) had only an increasing effect when the bath solution pH was slightly lowered to pH 7.2. From these observations, we conclude that astrocytic voltage oscillations are triggered by activation of voltage-gated calcium channels and driven by a downstream influx of cations through channels that are permeable for large ions such as NMDG+. Most likely candidates are subtypes of pore-forming P2X channels with a low affinity for ATP.
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Affiliation(s)
- Wiebke Fleischer
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Stephan Theiss
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany RESULT Medical GmbH, Düsseldorf, Germany
| | - Johannes Slotta
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Christine Holland
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Alfons Schnitzler
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
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148
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Morquette P, Verdier D, Kadala A, Féthière J, Philippe AG, Robitaille R, Kolta A. An astrocyte-dependent mechanism for neuronal rhythmogenesis. Nat Neurosci 2015; 18:844-54. [PMID: 25938883 DOI: 10.1038/nn.4013] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/02/2015] [Indexed: 12/22/2022]
Abstract
Communication between neurons rests on their capacity to change their firing pattern to encode different messages. For several vital functions, such as respiration and mastication, neurons need to generate a rhythmic firing pattern. Here we show in the rat trigeminal sensori-motor circuit for mastication that this ability depends on regulation of the extracellular Ca(2+) concentration ([Ca(2+)]e) by astrocytes. In this circuit, astrocytes respond to sensory stimuli that induce neuronal rhythmic activity, and their blockade with a Ca(2+) chelator prevents neurons from generating a rhythmic bursting pattern. This ability is restored by adding S100β, an astrocytic Ca(2+)-binding protein, to the extracellular space, while application of an anti-S100β antibody prevents generation of rhythmic activity. These results indicate that astrocytes regulate a fundamental neuronal property: the capacity to change firing pattern. These findings may have broad implications for many other neural networks whose functions depend on the generation of rhythmic activity.
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Affiliation(s)
- Philippe Morquette
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Dorly Verdier
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Aklesso Kadala
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - James Féthière
- Faculté de Pharmacie, Université de Montréal, Montréal, Québec, Canada
| | - Antony G Philippe
- 1] Faculté des Sciences du Sport, Université Montpellier 1, Montpellier, France. [2] Institut National de la Recherche Agronomique, UMR866 Dynamique Musculaire Et Métabolisme, Montpellier, France
| | - Richard Robitaille
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Arlette Kolta
- 1] Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada. [2] Faculté de Médecine Dentaire and Réseau de Recherche en Santé Bucco-dentaire et Osseuse du Fonds de Recherche Québec-Santé, Université de Montréal, Montréal, Québec, Canada
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149
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Astrocyte physiopathology: At the crossroads of intercellular networking, inflammation and cell death. Prog Neurobiol 2015; 130:86-120. [PMID: 25930681 DOI: 10.1016/j.pneurobio.2015.04.003] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/15/2015] [Accepted: 04/20/2015] [Indexed: 12/11/2022]
Abstract
Recent breakthroughs in neuroscience have led to the awareness that we should revise our traditional mode of thinking and studying the CNS, i.e. by isolating the privileged network of "intelligent" synaptic contacts. We may instead need to contemplate all the variegate communications occurring between the different neural cell types, and centrally involving the astrocytes. Basically, it appears that a single astrocyte should be considered as a core that receives and integrates information from thousands of synapses, other glial cells and the blood vessels. In turn, it generates complex outputs that control the neural circuitry and coordinate it with the local microcirculation. Astrocytes thus emerge as the possible fulcrum of the functional homeostasis of the healthy CNS. Yet, evidence indicates that the bridging properties of the astrocytes can change in parallel with, or as a result of, the morphological, biochemical and functional alterations these cells undergo upon injury or disease. As a consequence, they have the potential to transform from supportive friends and interactive partners for neurons into noxious foes. In this review, we summarize the currently available knowledge on the contribution of astrocytes to the functioning of the CNS and what goes wrong in various pathological conditions, with a particular focus on Amyotrophic Lateral Sclerosis, Alzheimer's Disease and ischemia. The observations described convincingly demonstrate that the development and progression of several neurological disorders involve the de-regulation of a finely tuned interplay between multiple cell populations. Thus, it seems that a better understanding of the mechanisms governing the integrated communication and detrimental responses of the astrocytes as well as their impact towards the homeostasis and performance of the CNS is fundamental to open novel therapeutic perspectives.
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150
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Panatier A, Robitaille R. Astrocytic mGluR5 and the tripartite synapse. Neuroscience 2015; 323:29-34. [PMID: 25847307 DOI: 10.1016/j.neuroscience.2015.03.063] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 03/19/2015] [Accepted: 03/26/2015] [Indexed: 11/27/2022]
Abstract
In the brain, astrocytes occupy a key position between vessels and synapses. Among their numerous functions, these glial cells are key partners of neurons during synaptic transmission. Astrocytes detect transmitter release through receptors and transporters at the level of their processes, which are in close proximity to the tow neuronal elements of synapses. In response to transmitter-mediated activation, glial cells in turn regulate synaptic transmission and neuronal excitability. This process has been reported to involve several glial receptors. One of the best known of such receptors is the metabotropic glutamatergic receptor subtype 5 (mGluR5). In the present review we will discuss the implication of mGluR5s as detectors of synaptic transmission. In particular, we will discuss how the functional properties and localization of these receptors permit the detection of the synaptic signal in a defined temporal window and a given spatial area around the synapse. Furthermore, we will review the impact of their activation on synaptic transmission.
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Affiliation(s)
- A Panatier
- Neurocentre Magendie, INSERM U862, Bordeaux, France; Université de Bordeaux, Bordeaux, France.
| | - R Robitaille
- Groupe de recherche sur le système nerveux central, Université de Montréal, Canada; Département de neurosciences, Université de Montréal, PO Box 6128, Station centre-ville, Montréal, Québec H3C 3J7, Canada
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