51
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Verkhratsky A, Semyanov A, Zorec R. Physiology of Astroglial Excitability. FUNCTION (OXFORD, ENGLAND) 2020; 1:zqaa016. [PMID: 35330636 PMCID: PMC8788756 DOI: 10.1093/function/zqaa016] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 08/29/2020] [Accepted: 09/03/2020] [Indexed: 01/06/2023]
Abstract
Classic physiology divides all neural cells into excitable neurons and nonexcitable neuroglia. Neuroglial cells, chiefly responsible for homeostasis and defense of the nervous tissue, coordinate their complex homeostatic responses with neuronal activity. This coordination reflects a specific form of glial excitability mediated by complex changes in intracellular concentration of ions and second messengers organized in both space and time. Astrocytes are equipped with multiple molecular cascades, which are central for regulating homeostasis of neurotransmitters, ionostasis, synaptic connectivity, and metabolic support of the central nervous system. Astrocytes are further provisioned with multiple receptors for neurotransmitters and neurohormones, which upon activation trigger intracellular signals mediated by Ca2+, Na+, and cyclic AMP. Calcium signals have distinct organization and underlying mechanisms in different astrocytic compartments thus allowing complex spatiotemporal signaling. Signals mediated by fluctuations in cytosolic Na+ are instrumental for coordination of Na+ dependent astrocytic transporters with tissue state and homeostatic demands. Astroglial ionic excitability may also involve K+, H+, and Cl-. The cyclic AMP signalling system is, in comparison to ions, much slower in targeting astroglial effector mechanisms. This evidence review summarizes the concept of astroglial intracellular excitability.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK,Achucarro Center for Neuroscience, Ikerbasque, 48011 Bilbao, Spain,Address correspondence to A.V. (e-mail: )
| | - Alexey Semyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia,Faculty of Biology, Moscow State University, Moscow, Russia,Sechenov First Moscow State Medical University, Moscow, Russia
| | - Robert Zorec
- Celica Biomedical, Ljubljana 1000, Slovenia,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana 1000, Slovenia
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52
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Semyanov A, Henneberger C, Agarwal A. Making sense of astrocytic calcium signals — from acquisition to interpretation. Nat Rev Neurosci 2020; 21:551-564. [DOI: 10.1038/s41583-020-0361-8] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/29/2020] [Indexed: 12/31/2022]
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53
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Astrocyte-mediated switch in spike timing-dependent plasticity during hippocampal development. Nat Commun 2020; 11:4388. [PMID: 32873805 PMCID: PMC7463247 DOI: 10.1038/s41467-020-18024-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 07/31/2020] [Indexed: 01/31/2023] Open
Abstract
Presynaptic spike timing-dependent long-term depression (t-LTD) at hippocampal CA3-CA1 synapses is evident until the 3rd postnatal week in mice, disappearing during the 4th week. At more mature stages, we found that the protocol that induced t-LTD induced t-LTP. We characterized this form of t-LTP and the mechanisms involved in its induction, as well as that driving this switch from t-LTD to t-LTP. We found that this t-LTP is expressed presynaptically at CA3-CA1 synapses, as witnessed by coefficient of variation, number of failures, paired-pulse ratio and miniature responses analysis. Additionally, this form of presynaptic t-LTP does not require NMDARs but the activation of mGluRs and the entry of Ca2+ into the postsynaptic neuron through L-type voltage-dependent Ca2+ channels and the release of Ca2+ from intracellular stores. Nitric oxide is also required as a messenger from the postsynaptic neuron. Crucially, the release of adenosine and glutamate by astrocytes is required for t-LTP induction and for the switch from t-LTD to t-LTP. Thus, we have discovered a developmental switch of synaptic transmission from t-LTD to t-LTP at hippocampal CA3-CA1 synapses in which astrocytes play a central role and revealed a form of presynaptic LTP and the rules for its induction. Presynaptic spike timing-dependent long-term depression at hippocampal CA3-CA1 synapses is evident until the third postnatal week in mice. The authors show that maturation beyond four weeks is associated with a switch to long-term potentiation in which astrocytes play a central role.
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54
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Bijelić DD, Milićević KD, Lazarević MN, Miljković DM, Bogdanović Pristov JJ, Savić DZ, Petković BB, Andjus PR, Momčilović MB, Nikolić LM. Central nervous system-infiltrated immune cells induce calcium increase in astrocytes via astroglial purinergic signaling. J Neurosci Res 2020; 98:2317-2332. [PMID: 32799373 DOI: 10.1002/jnr.24699] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 06/22/2020] [Accepted: 07/07/2020] [Indexed: 12/15/2022]
Abstract
Interaction between autoreactive immune cells and astroglia is an important part of the pathologic processes that fuel neurodegeneration in multiple sclerosis. In this inflammatory disease, immune cells enter into the central nervous system (CNS) and they spread through CNS parenchyma, but the impact of these autoreactive immune cells on the activity pattern of astrocytes has not been defined. By exploiting naïve astrocytes in culture and CNS-infiltrated immune cells (CNS IICs) isolated from rat with experimental autoimmune encephalomyelitis (EAE), here we demonstrate previously unrecognized properties of immune cell-astrocyte interaction. We show that CNS IICs but not the peripheral immune cell application, evokes a rapid and vigorous intracellular Ca2+ increase in astrocytes by promoting glial release of ATP. ATP propagated Ca2+ elevation through glial purinergic P2X7 receptor activation by the hemichannel-dependent nucleotide release mechanism. Astrocyte Ca2+ increase is specifically triggered by the autoreactive CD4+ T-cell application and these two cell types exhibit close spatial interaction in EAE. Therefore, Ca2+ signals may mediate a rapid astroglial response to the autoreactive immune cells in their local environment. This property of immune cell-astrocyte interaction may be important to consider in studies interrogating CNS autoimmune disease.
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Affiliation(s)
- Dunja D Bijelić
- Faculty of Biology, Center for Laser Microscopy, University of Belgrade, Belgrade, Serbia
| | - Katarina D Milićević
- Faculty of Biology, Center for Laser Microscopy, University of Belgrade, Belgrade, Serbia
| | - Milica N Lazarević
- Department of Immunology, Institute for Biological Research Siniša Stanković, National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Djordje M Miljković
- Department of Immunology, Institute for Biological Research Siniša Stanković, National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Jelena J Bogdanović Pristov
- Department of Life Sciences, Institute for Multidisciplinary Research, University of Belgrade, Belgrade, Serbia
| | - Danijela Z Savić
- Department of Neurobiology, Institute for Biological Research Siniša Stanković, National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Branka B Petković
- Department of Neurophysiology, Institute for Biological Research Siniša Stanković, National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Pavle R Andjus
- Faculty of Biology, Center for Laser Microscopy, University of Belgrade, Belgrade, Serbia
| | - Miljana B Momčilović
- Department of Immunology, Institute for Biological Research Siniša Stanković, National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Ljiljana M Nikolić
- Department of Neurophysiology, Institute for Biological Research Siniša Stanković, National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
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55
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Wareham LK, Calkins DJ. The Neurovascular Unit in Glaucomatous Neurodegeneration. Front Cell Dev Biol 2020; 8:452. [PMID: 32656207 PMCID: PMC7325980 DOI: 10.3389/fcell.2020.00452] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 05/15/2020] [Indexed: 12/31/2022] Open
Abstract
Glaucoma is a neurodegenerative disease of the visual system and leading cause of blindness worldwide. The disease is associated with sensitivity to intraocular pressure (IOP), which over a large range of magnitudes stresses retinal ganglion cell (RGC) axons as they pass through the optic nerve head in forming the optic projection to the brain. Despite clinical efforts to lower IOP, which is the only modifiable risk factor for glaucoma, RGC degeneration and ensuing loss of vision often persist. A major contributor to failure of hypotensive regimens is the multifactorial nature of how IOP-dependent stress influences RGC physiology and structure. This stress is conveyed to the RGC axon through interactions with structural, glial, and vascular components in the nerve head and retina. These interactions promote pro-degenerative pathways involving biomechanical, metabolic, oxidative, inflammatory, immunological and vascular challenges to the microenvironment of the ganglion cell and its axon. Here, we focus on the contribution of vascular dysfunction and breakdown of neurovascular coupling in glaucoma. The vascular networks of the retina and optic nerve head have evolved complex mechanisms that help to maintain a continuous blood flow and supply of metabolites despite fluctuations in ocular perfusion pressure. In healthy tissue, autoregulation and neurovascular coupling enable blood flow to stay tightly controlled. In glaucoma patients evidence suggests these pathways are dysfunctional, thus highlighting a potential role for pathways involved in vascular dysfunction in progression and as targets for novel therapeutic intervention.
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Affiliation(s)
- Lauren K Wareham
- Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN, United States
| | - David J Calkins
- Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN, United States
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56
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Pro-maturational Effects of Human iPSC-Derived Cortical Astrocytes upon iPSC-Derived Cortical Neurons. Stem Cell Reports 2020; 15:38-51. [PMID: 32502466 PMCID: PMC7363746 DOI: 10.1016/j.stemcr.2020.05.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 05/04/2020] [Accepted: 05/04/2020] [Indexed: 12/22/2022] Open
Abstract
Astrocytes influence neuronal maturation and function by providing trophic support, regulating the extracellular environment, and modulating signaling at synapses. The emergence of induced pluripotent stem cell (iPSC) technology offers a human system with which to validate and re-evaluate insights from animal studies. Here, we set out to examine interactions between human astrocytes and neurons derived from a common cortical progenitor pool, thereby recapitulating aspects of in vivo cortical development. We show that the cortical iPSC-derived astrocytes exhibit many of the molecular and functional hallmarks of astrocytes. Furthermore, optogenetic and electrophysiological co-culture experiments reveal that the iPSC-astrocytes can actively modulate ongoing synaptic transmission and exert pro-maturational effects upon developing networks of iPSC-derived cortical neurons. Finally, transcriptomic analyses implicate synapse-associated extracellular signaling in the astrocytes' pro-maturational effects upon the iPSC-derived neurons. This work helps lay the foundation for future investigations into astrocyte-to-neuron interactions in human health and disease. Human astrocytes and neurons are generated from a common cortical progenitor pool Astrocyte-neuron signaling is demonstrated with neurotransmitters and optogenetics Astrocyte co-culture promotes cortical neuron and synaptic network maturation Transcriptomics reveal extracellular astrocytic proteins that interact at synapses
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57
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Rogers RC, Hasser EM, Hermann GE. Thrombin action on astrocytes in the hindbrain of the rat disrupts glycemic and respiratory control. Am J Physiol Regul Integr Comp Physiol 2020; 318:R1068-R1077. [PMID: 32320636 PMCID: PMC7311679 DOI: 10.1152/ajpregu.00033.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/30/2020] [Accepted: 04/21/2020] [Indexed: 02/06/2023]
Abstract
Severe trauma can produce a postinjury "metabolic self-destruction" characterized by catabolic metabolism and hyperglycemia. The severity of the hyperglycemia is highly correlated with posttrauma morbidity and mortality. Although no mechanism has been posited to connect severe trauma with a loss of autonomic control over metabolism, traumatic injury causes other failures of autonomic function, notably, gastric stasis and ulceration ("Cushing's ulcer"), which has been connected with the generation of thrombin. Our previous studies established that proteinase-activated receptors (PAR1; "thrombin receptors") located on astrocytes in the autonomically critical nucleus of the solitary tract (NST) can modulate gastric control circuit neurons to cause gastric stasis. Hindbrain astrocytes have also been implicated as important detectors of low glucose or glucose utilization. When activated, these astrocytes communicate with hindbrain catecholamine neurons that, in turn, trigger counterregulatory responses (CRR). There may be a convergence between the effects of thrombin to derange hindbrain gastrointestinal control and the hindbrain circuitry that initiates CRR to increase glycemia in reaction to critical hypoglycemia. Our results suggest that thrombin acts within the NST to increase glycemia through an astrocyte-dependent mechanism. Blockade of purinergic gliotransmission pathways interrupted the effect of thrombin to increase glycemia. Our studies also revealed that thrombin, acting in the NST, produced a rapid, dramatic, and potentially lethal suppression of respiratory rhythm that was also a function of purinergic gliotransmission. These results suggest that the critical connection between traumatic injury and a general collapse of autonomic regulation involves thrombin action on astrocytes.
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Affiliation(s)
- Richard C Rogers
- Autonomic Neurosciences Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Eileen M Hasser
- Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Gerlinda E Hermann
- Autonomic Neurosciences Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana
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58
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Felix L, Stephan J, Rose CR. Astrocytes of the early postnatal brain. Eur J Neurosci 2020; 54:5649-5672. [PMID: 32406559 DOI: 10.1111/ejn.14780] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 04/30/2020] [Accepted: 05/06/2020] [Indexed: 12/21/2022]
Abstract
In the rodent forebrain, the majority of astrocytes are generated during the early postnatal phase. Following differentiation, astrocytes undergo maturation which accompanies the development of the neuronal network. Neonate astrocytes exhibit a distinct morphology and domain size which differs to their mature counterparts. Moreover, many of the plasma membrane proteins prototypical for fully developed astrocytes are only expressed at low levels at neonatal stages. These include connexins and Kir4.1, which define the low membrane resistance and highly negative membrane potential of mature astrocytes. Newborn astrocytes moreover express only low amounts of GLT-1, a glutamate transporter critical later in development. Furthermore, they show specific differences in the properties and spatio-temporal pattern of intracellular calcium signals, resulting from differences in their repertoire of receptors and signalling pathways. Therefore, roles fulfilled by mature astrocytes, including ion and transmitter homeostasis, are underdeveloped in the young brain. Similarly, astrocytic ion signalling in response to neuronal activity, a process central to neuron-glia interaction, differs between the neonate and mature brain. This review describes the unique functional properties of astrocytes in the first weeks after birth and compares them to later stages of development. We conclude that with an immature neuronal network and wider extracellular space, astrocytic support might not be as demanding and critical compared to the mature brain. The delayed differentiation and maturation of astrocytes in the first postnatal weeks might thus reflect a reduced need for active, energy-consuming regulation of the extracellular space and a less tight control of glial feedback onto synaptic transmission.
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Affiliation(s)
- Lisa Felix
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Jonathan Stephan
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
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59
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L-type Voltage-Gated Calcium Channel Modulators Inhibit Glutamate-Induced Morphology Changes in U118-MG Astrocytoma Cells. Cell Mol Neurobiol 2020; 40:1429-1437. [PMID: 32172458 DOI: 10.1007/s10571-020-00828-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 03/06/2020] [Indexed: 10/24/2022]
Abstract
The excitatory neurotransmitter glutamate evokes physiological responses within the astrocytic network that lead to fine morphological changes. However, the mechanism by which astrocytes couple glutamate sensing with cellular calcium rise remains unclear. We tested a possible connection between L-type voltage-gated calcium channels (Cav) and glutamate-induced response in U118-MG astrocytoma cells. While astrocytoma cells differ from primary astrocytes, they demonstrate the same response to glutamate. In this study, the extension of U118-MG processes upon glutamate exposure was shown to depend on extracellular calcium entry via L-type Cav's. Drugs known to bind to the pore-forming subunit of Cav's decreased the astrocytic filopodia extension caused by glutamate, and ligands of the α2δ auxiliary subunit inhibited all process growth (e.g., gabapentinoids). The observed phenotypic responses suggest that α2δ is a main contributor to the role of Cavs in glutamate-dependent filopodiagenesis, thereby opening new avenues of research on the role of α2δ in astrocytic neurochemical signaling.
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60
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King CM, Bohmbach K, Minge D, Delekate A, Zheng K, Reynolds J, Rakers C, Zeug A, Petzold GC, Rusakov DA, Henneberger C. Local Resting Ca 2+ Controls the Scale of Astroglial Ca 2+ Signals. Cell Rep 2020; 30:3466-3477.e4. [PMID: 32160550 PMCID: PMC7068654 DOI: 10.1016/j.celrep.2020.02.043] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/21/2019] [Accepted: 02/06/2020] [Indexed: 02/07/2023] Open
Abstract
Astroglia regulate neurovascular coupling while engaging in signal exchange with neurons. The underlying cellular machinery is thought to rely on astrocytic Ca2+ signals, but what controls their amplitude and waveform is poorly understood. Here, we employ time-resolved two-photon excitation fluorescence imaging in acute hippocampal slices and in cortex in vivo to find that resting [Ca2+] predicts the scale (amplitude) and the maximum (peak) of astroglial Ca2+ elevations. We bidirectionally manipulate resting [Ca2+] by uncaging intracellular Ca2+ or Ca2+ buffers and use ratiometric imaging of a genetically encoded Ca2+ indicator to establish that alterations in resting [Ca2+] change co-directionally the peak level and anti-directionally the amplitude of local Ca2+ transients. This relationship holds for spontaneous and for induced (for instance by locomotion) Ca2+ signals. Our findings uncover a basic generic rule of Ca2+ signal formation in astrocytes, thus also associating the resting Ca2+ level with the physiological "excitability" state of astroglia.
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Affiliation(s)
- Claire M King
- Institute of Neurology, University College London, London, UK
| | - Kirsten Bohmbach
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Daniel Minge
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Andrea Delekate
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Kaiyu Zheng
- Institute of Neurology, University College London, London, UK
| | - James Reynolds
- Institute of Neurology, University College London, London, UK
| | - Cordula Rakers
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Andre Zeug
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Gabor C Petzold
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany; Department of Neurology, University Hospital Bonn, Bonn, Germany
| | | | - Christian Henneberger
- Institute of Neurology, University College London, London, UK; Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany; German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.
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61
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Cell-to-Cell Communication in Learning and Memory: From Neuro- and Glio-Transmission to Information Exchange Mediated by Extracellular Vesicles. Int J Mol Sci 2019; 21:ijms21010266. [PMID: 31906013 PMCID: PMC6982255 DOI: 10.3390/ijms21010266] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/14/2019] [Accepted: 12/28/2019] [Indexed: 02/06/2023] Open
Abstract
Most aspects of nervous system development and function rely on the continuous crosstalk between neurons and the variegated universe of non-neuronal cells surrounding them. The most extraordinary property of this cellular community is its ability to undergo adaptive modifications in response to environmental cues originating from inside or outside the body. Such ability, known as neuronal plasticity, allows long-lasting modifications of the strength, composition and efficacy of the connections between neurons, which constitutes the biochemical base for learning and memory. Nerve cells communicate with each other through both wiring (synaptic) and volume transmission of signals. It is by now clear that glial cells, and in particular astrocytes, also play critical roles in both modes by releasing different kinds of molecules (e.g., D-serine secreted by astrocytes). On the other hand, neurons produce factors that can regulate the activity of glial cells, including their ability to release regulatory molecules. In the last fifteen years it has been demonstrated that both neurons and glial cells release extracellular vesicles (EVs) of different kinds, both in physiologic and pathological conditions. Here we discuss the possible involvement of EVs in the events underlying learning and memory, in both physiologic and pathological conditions.
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62
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Heuser K, Nome CG, Pettersen KH, Åbjørsbråten KS, Jensen V, Tang W, Sprengel R, Taubøll E, Nagelhus EA, Enger R. Ca2+ Signals in Astrocytes Facilitate Spread of Epileptiform Activity. Cereb Cortex 2019; 28:4036-4048. [PMID: 30169757 PMCID: PMC6188565 DOI: 10.1093/cercor/bhy196] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 07/21/2018] [Indexed: 01/04/2023] Open
Abstract
Epileptic seizures are associated with increased astrocytic Ca2+ signaling, but the fine spatiotemporal kinetics of the ictal astrocyte–neuron interplay remains elusive. By using 2-photon imaging of awake head-fixed mice with chronic hippocampal windows we demonstrate that astrocytic Ca2+ signals precede neuronal Ca2+ elevations during the initial bout of kainate-induced seizures. On average, astrocytic Ca2+ elevations preceded neuronal activity in CA1 by about 8 s. In subsequent bouts of epileptic seizures, astrocytes and neurons were activated simultaneously. The initial astrocytic Ca2+ elevation was abolished in mice lacking the type 2 inositol-1,4,5-trisphosphate-receptor (Itpr2−/−). Furthermore, we found that Itpr2−/− mice exhibited 60% less epileptiform activity compared with wild-type mice when assessed by telemetric EEG monitoring. In both genotypes we also demonstrate that spreading depression waves may play a part in seizure termination. Our findings imply a role for astrocytic Ca2+ signals in ictogenesis.
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Affiliation(s)
- Kjell Heuser
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Cecilie G Nome
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Klas H Pettersen
- Letten Centre and GliaLab, Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Knut S Åbjørsbråten
- Letten Centre and GliaLab, Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Vidar Jensen
- Letten Centre and GliaLab, Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Wannan Tang
- Letten Centre and GliaLab, Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Rolf Sprengel
- Max Planck Research Group "Molecular Neurobiology" at the Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Erik Taubøll
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Erlend A Nagelhus
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.,Letten Centre and GliaLab, Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Rune Enger
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.,Letten Centre and GliaLab, Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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63
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Faramarzi F, Azad F, Amiri M, Linares-Barranco B. A Neuromorphic Digital Circuit for Neuronal Information Encoding Using Astrocytic Calcium Oscillations. Front Neurosci 2019; 13:998. [PMID: 31649494 PMCID: PMC6794439 DOI: 10.3389/fnins.2019.00998] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 09/03/2019] [Indexed: 01/30/2023] Open
Abstract
Neurophysiological observations are clarifying how astrocytes can actively participate in information processing and how they can encode information through frequency and amplitude modulation of intracellular Ca2+ signals. Consequently, hardware realization of astrocytes is important for developing the next generation of bio-inspired computing systems. In this paper, astrocytic calcium oscillations and neuronal firing dynamics are presented by De Pittà and IF (Integrated & Fire) models, respectively. Considering highly nonlinear equations of the astrocyte model, linear approximation and single constant multiplication (SCM) techniques are employed for efficient hardware execution while maintaining the dynamic of the original models. This low-cost hardware architecture for the astrocyte model is able to show the essential features of different types of Ca2+ modulation such as amplitude modulation (AM), frequency modulation (FM), or both modes (AFM). To show good agreement between the results of original models simulated in MATLAB and the proposed digital circuits executed on FPGA, quantitative, and qualitative analyses including phase plane are done. This new neuromorphic circuit of astrocyte is able to successfully demonstrate AM/FM/AFM calcium signaling in its real operation on FPGA and has applications in self-repairing systems. It also can be employed as a subsystem for linking biological cells to artificial neuronal networks using astrocytic calcium oscillations in future research.
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Affiliation(s)
- Farnaz Faramarzi
- Department of Electronics, Amirkabir University of Technology, Tehran, Iran
| | - Fatemeh Azad
- Medical Technology Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Mahmood Amiri
- Medical Technology Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Bernabé Linares-Barranco
- Instituto de Microelectrónica de Sevilla (IMSE-CNM), CSIC and Univesity of Seville, Sevilla, Spain
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64
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Bedner P, Jabs R, Steinhäuser C. Properties of human astrocytes and NG2 glia. Glia 2019; 68:756-767. [DOI: 10.1002/glia.23725] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 08/09/2019] [Accepted: 08/09/2019] [Indexed: 01/11/2023]
Affiliation(s)
- Peter Bedner
- Institute of Cellular Neurosciences, Medical FacultyUniversity of Bonn Bonn Germany
| | - Ronald Jabs
- Institute of Cellular Neurosciences, Medical FacultyUniversity of Bonn Bonn Germany
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65
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Verkhratsky A, Parpura V, Vardjan N, Zorec R. Physiology of Astroglia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1175:45-91. [PMID: 31583584 DOI: 10.1007/978-981-13-9913-8_3] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Astrocytes are principal cells responsible for maintaining the brain homeostasis. Additionally, these glial cells are also involved in homocellular (astrocyte-astrocyte) and heterocellular (astrocyte-other cell types) signalling and metabolism. These astroglial functions require an expression of the assortment of molecules, be that transporters or pumps, to maintain ion concentration gradients across the plasmalemma and the membrane of the endoplasmic reticulum. Astrocytes sense and balance their neurochemical environment via variety of transmitter receptors and transporters. As they are electrically non-excitable, astrocytes display intracellular calcium and sodium fluctuations, which are not only used for operative signalling but can also affect metabolism. In this chapter we discuss the molecules that achieve ionic gradients and underlie astrocyte signalling.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK. .,Faculty of Health and Medical Sciences, Center for Basic and Translational Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark. .,Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
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Caragher SP, Hall RR, Ahsan R, Ahmed AU. Monoamines in glioblastoma: complex biology with therapeutic potential. Neuro Oncol 2019; 20:1014-1025. [PMID: 29126252 DOI: 10.1093/neuonc/nox210] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Glioblastoma (GBM) is characterized by extremely poor prognoses, despite the use of gross surgical resection, alkylating chemotherapeutic agents, and radiotherapy. Evidence increasingly highlights the role of the tumor microenvironment in enabling this aggressive phenotype. Despite this interest, the role of neurotransmitters, brain-specific messengers underlying synaptic transmission, remains murky. These signaling molecules influence a complex network of molecular pathways and cellular behaviors in many CNS-resident cells, including neural stem cells and progenitor cells, neurons, and glia cells. Critically, available data convincingly demonstrate that neurotransmitters can influence proliferation, quiescence, and differentiation status of these cells. This ability to affect progenitors and glia-GBM-initiating cells-and their availability in the CNS strongly support the notion that neurotransmitters participate in the onset and progression of GBM. This review will focus on dopamine and serotonin, as studies indicate they contribute to gliomagenesis. Particular attention will be paid to how these neurotransmitters and their receptors can be utilized as novel therapeutic targets. Overall, this review will analyze the complex biology governing the interaction of GBM with neurotransmitter signaling and highlight how this interplay shapes the aggressive nature of GBM.
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Affiliation(s)
- Seamus Patrick Caragher
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | | | - Riasat Ahsan
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Atique U Ahmed
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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Sun Y, Yang J, Hu X, Gao X, Li Y, Yu M, Liu S, Lu Y, Wang J, Huang L, Lu X, Jin C, Wu S, Cai Y. Conditioned medium from overly excitatory primary astrocytes induced by La 3+ increases apoptosis in primary neurons via upregulating the expression of NMDA receptors. Metallomics 2019; 10:1016-1028. [PMID: 29989126 DOI: 10.1039/c8mt00056e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Lanthanum (La) can accumulate in the brain and impair learning and memory. However, the underlying mechanism of La-induced neurotoxicity has remained elusive. Under physiological conditions, it has been reported that moderately excitatory astrocytes play an important role in the regulation of neuronal signals and synaptic plasticity. However, under pathological conditions, overly excitatory astrocytes can release excess excitatory transmitters, such as glutamate (Glu) and d-serine, and induce the over-activation of NMDA receptors (NMDAR) in neurons, ultimately leading to neuronal excitotoxicity. To date, limited work has been performed with respect to whether La can induce neuronal excitotoxicity by inducing astrocytes to become overexcited. In this study, in vitro models of primary culture rat cortical astrocytes and neurons were established. First, the astrocytes were treated with 0.125 mM, 0.25 mM and 0.5 mM lanthanum chloride (LaCl3) for 24 h, and the supernatants were collected as a conditioned medium (CM) which is denoted as CM (La3+); then, the neurons were treated with CM (La3+) for 48 h. The results illustrate that LaCl3 treatment significantly upregulated the mRNA and protein expression levels of metabotropic glutamate receptor 5 (mGLUR5), phospholipase C (PLC), connexin 43 (Cx43) and Cx30, increased the concentrations of inositol trisphosphate (IP3) and [Ca2+]i, and promoted the synthesis and release of Glu and d-serine in astrocytes. Moreover, the CM (La3+) could increase the mRNA and protein expression levels of NMDAR subunits (NR1, NR2A, NR2B), the concentration of [Ca2+]i and the rate of apoptosis in neurons. Furthermore, after removal of La, CM (La-free) had a similar effect on neurons which could be antagonized by MK-801, DCKA and DAAO. These results suggest that the neuron apoptosis induced by La is closely related to the excessive release of Glu and d-serine from overly excitatory astrocytes.
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Affiliation(s)
- Yaling Sun
- Department of Toxicology, School of Public Health, China Medical University, No. 77 Puhe road, Shenyang North New Area, Shenyang 110122, Liaoning Province, People's Republic of China.
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Halpern M, Brennand KJ, Gregory J. Examining the relationship between astrocyte dysfunction and neurodegeneration in ALS using hiPSCs. Neurobiol Dis 2019; 132:104562. [PMID: 31381978 DOI: 10.1016/j.nbd.2019.104562] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 06/28/2019] [Accepted: 07/31/2019] [Indexed: 02/07/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a complex and fatal neurodegenerative disease for which the causes of disease onset and progression remain unclear. Recent advances in human induced pluripotent stem cell (hiPSC)-based models permit the study of the genetic factors associated with ALS in patient-derived neural cell types, including motor neurons and glia. While astrocyte dysfunction has traditionally been thought to exacerbate disease progression, astrocytic dysfunction may play a more direct role in disease initiation and progression. Such non-cell autonomous mechanisms expand the potential targets of therapeutic intervention, but only a handful of ALS risk-associated genes have been examined for their impact on astrocyte dysfunction and neurodegeneration. This review summarizes what is currently known about astrocyte function in ALS and suggests ways in which hiPSC-based models can be used to more effectively study the role of astrocytes in neurodegenerative disease.
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Affiliation(s)
- Madeline Halpern
- Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America
| | - Kristen J Brennand
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America; Department of Genetics and Genomics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America; Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America; Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States of America.
| | - James Gregory
- Center for Genomics of Neurodegenerative Disease, New York Genome Center, New York, NY 10013, United States of America.
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Zhang Y, Wu S, Xie L, Yu S, Zhang L, Liu C, Zhou W, Yu T. Ketamine Within Clinically Effective Range Inhibits Glutamate Transmission From Astrocytes to Neurons and Disrupts Synchronization of Astrocytic SICs. Front Cell Neurosci 2019; 13:240. [PMID: 31244607 PMCID: PMC6581012 DOI: 10.3389/fncel.2019.00240] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 05/14/2019] [Indexed: 01/07/2023] Open
Abstract
Background Astrocytes are now considered as crucial modulators of neuronal synaptic transmission. General anesthetics have been found to inhibit astrocytic activities, but it is not clear whether general anesthetics within the clinical concentration range affects the astrocyte-mediated synaptic regulation. Methods The effects of propofol, dexmedetomidine, and ketamine within clinically effective ranges on the slow inward currents (SICs) were tested by using the whole-cell recording in acute prefrontal cortex (PFC) slice preparations of rats. Astrocytes culture and HPLC were used to measure the effects of different anesthetics on the glutamate release of astrocytes. Results Propofol and dexmedetomidine showed no significant effect on the amplitude or frequency of SICs. Ketamine was found to inhibit the frequency of SICs in a concentration-dependent manner. The SICs synchronization rate of paired neurons was inhibited by 30 μM ketamine (from 42.5 ± 1.4% to 9.6 ± 0.8%) and was abolished by 300 μM ketamine. The astrocytic glutamate release induced by DHPG, an agonist of astrocytic type I metabotropic glutamate receptors, was not affected by ketamine, and ifenprodil, a selective antagonist of GluN1/GluN2B receptor, blocked all SICs and enhanced the inhibitory effect of 30 μM ketamine on the frequency of SICs. Ketamine at low concentration (3 μM) could inhibit the frequency of SICs, not the miniature excitatory postsynaptic currents (mEPSCs), and the inhibition rate of SICs was significantly higher than mEPSCs with 30 μM ketamine (44.5 ± 3% inhibition vs. 28.3 ± 6% inhibition). Conclusion Our data indicated that ketamine, not propofol and dexmedetomidine, within clinical concentration range inhibits glutamatergic transmission from astrocytes to neurons, which is likely mediated by the extrasynaptic GluN1/GluN2B receptor activation.
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Affiliation(s)
- Yu Zhang
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical University, Guizhou, China.,The Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Sisi Wu
- The Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Liwei Xie
- The Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Shouyang Yu
- The Key Laboratory of Brain Science, Zunyi Medical University, Guizhou, China
| | - Lin Zhang
- The Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Chengxi Liu
- The Key Laboratory of Brain Science, Zunyi Medical University, Guizhou, China
| | - Wenjing Zhou
- The Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Tian Yu
- The Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
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70
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Rogers RC, Hermann GE. Hindbrain astrocytes and glucose counter-regulation. Physiol Behav 2019; 204:140-150. [PMID: 30797812 PMCID: PMC7145321 DOI: 10.1016/j.physbeh.2019.02.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 02/11/2019] [Accepted: 02/20/2019] [Indexed: 12/31/2022]
Abstract
Hindbrain astrocytes are emerging as critical components in the regulation of homeostatic functions by either modulating synaptic activity or serving as primary detectors of physiological parameters. Recent studies have suggested that the glucose counter-regulation response (CRR), a critical defense against hypoglycemic emergencies, is dependent on glucoprivation-sensitive astrocytes in the hindbrain. This subpopulation of astrocytes produces a robust calcium signal in response to glucopenic stimuli. Both ex vivo and in vivo evidence suggest that low-glucose sensitive astrocytes utilize purinergic gliotransmission to activate catecholamine neurons in the hindbrain that are critical to the generation of the integrated CRR. Lastly, reports in the clinical literature suggest that an uncontrolled activation of CRR may as part of the pathology of severe traumatic injury. Work in our laboratory also suggests that this pathological hyperglycemia resulting from traumatic injury may be caused by the action of thrombin (generated by tissue trauma or bleeding) on hindbrain astrocytes. Similar to their glucopenia-sensitive neighbors, these hindbrain astrocytes may trigger hyperglycemic responses by their interactions with catecholaminergic neurons.
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Affiliation(s)
- Richard C Rogers
- Pennington Biomedical Research Center, 6400 Perkins Rd, Baton Rouge, LA 70808, USA
| | - Gerlinda E Hermann
- Pennington Biomedical Research Center, 6400 Perkins Rd, Baton Rouge, LA 70808, USA.
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Glutamate affects the CYP1B1- and CYP2U1-mediated hydroxylation of arachidonic acid metabolism via astrocytic mGlu5 receptor. Int J Biochem Cell Biol 2019; 110:111-121. [DOI: 10.1016/j.biocel.2019.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 01/27/2019] [Accepted: 03/01/2019] [Indexed: 01/10/2023]
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Weiss S, Melom JE, Ormerod KG, Zhang YV, Littleton JT. Glial Ca 2+signaling links endocytosis to K + buffering around neuronal somas to regulate excitability. eLife 2019; 8:44186. [PMID: 31025939 PMCID: PMC6510531 DOI: 10.7554/elife.44186] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 04/25/2019] [Indexed: 12/30/2022] Open
Abstract
Glial-neuronal signaling at synapses is widely studied, but how glia interact with neuronal somas to regulate their activity is unclear. Drosophila cortex glia are restricted to brain regions devoid of synapses, providing an opportunity to characterize interactions with neuronal somas. Mutations in the cortex glial NCKXzydeco elevate basal Ca2+, predisposing animals to seizure-like behavior. To determine how cortex glial Ca2+ signaling controls neuronal excitability, we performed an in vivo modifier screen of the NCKXzydeco seizure phenotype. We show that elevation of glial Ca2+ causes hyperactivation of calcineurin-dependent endocytosis and accumulation of early endosomes. Knockdown of sandman, a K2P channel, recapitulates NCKXzydeco seizures. Indeed, sandman expression on cortex glial membranes is substantially reduced in NCKXzydeco mutants, indicating enhanced internalization of sandman predisposes animals to seizures. These data provide an unexpected link between glial Ca2+ signaling and the well-known role of glia in K+ buffering as a key mechanism for regulating neuronal excitability.
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Affiliation(s)
- Shirley Weiss
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Jan E Melom
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Kiel G Ormerod
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Yao V Zhang
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - J Troy Littleton
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
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73
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Ventral tegmental area astrocytes orchestrate avoidance and approach behavior. Nat Commun 2019; 10:1455. [PMID: 30926783 PMCID: PMC6440962 DOI: 10.1038/s41467-019-09131-y] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 02/22/2019] [Indexed: 12/28/2022] Open
Abstract
The ventral tegmental area (VTA) is a heterogeneous midbrain structure, containing neurons and astrocytes, that coordinates behaviors by integrating activity from numerous afferents. Within neuron-astrocyte networks, astrocytes control signals from distinct afferents in a circuit-specific manner, but whether this capacity scales up to drive motivated behavior has been undetermined. Using genetic and optical dissection strategies we report that VTA astrocytes tune glutamatergic signaling selectively on local inhibitory neurons to drive a functional circuit for learned avoidance. In this circuit, astrocytes facilitate excitation of VTA GABA neurons to increase inhibition of dopamine neurons, eliciting real-time and learned avoidance behavior that is sufficient to impede expression of preference for reward. Loss of one glutamate transporter (GLT-1) from VTA astrocytes selectively blocks these avoidance behaviors and spares preference for reward. Thus, VTA astrocytes selectively regulate excitation of local GABA neurons to drive a distinct avoidance circuit that opposes approach behavior. Astrocytes can dynamically control glutamate availability at specific active synapses through the glutamate transporter, GLT-1. Here, the authors show that astrocytes in the VTA selectively facilitate excitation of VTA GABAergic neurons to inhibit dopamine neurons and drive avoidance behavior via GLT-1.
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74
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Ashhad S, Narayanan R. Stores, Channels, Glue, and Trees: Active Glial and Active Dendritic Physiology. Mol Neurobiol 2019; 56:2278-2299. [PMID: 30014322 PMCID: PMC6394607 DOI: 10.1007/s12035-018-1223-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 07/03/2018] [Indexed: 02/07/2023]
Abstract
Glial cells and neuronal dendrites were historically assumed to be passive structures that play only supportive physiological roles, with no active contribution to information processing in the central nervous system. Research spanning the past few decades has clearly established this assumption to be far from physiological realities. Whereas the discovery of active channel conductances and their localized plasticity was the turning point for dendritic structures, the demonstration that glial cells release transmitter molecules and communicate across the neuroglia syncytium through calcium wave propagation constituted path-breaking discoveries for glial cell physiology. An additional commonality between these two structures is the ability of calcium stores within their endoplasmic reticulum (ER) to support active propagation of calcium waves, which play crucial roles in the spatiotemporal integration of information within and across cells. Although there have been several demonstrations of regulatory roles of glial cells and dendritic structures in achieving common physiological goals such as information propagation and adaptability through plasticity, studies assessing physiological interactions between these two active structures have been few and far. This lacuna is especially striking given the strong connectivity that is known to exist between these two structures through several complex and tightly intercoupled mechanisms that also recruit their respective ER structures. In this review, we present brief overviews of the parallel literatures on active dendrites and active glial physiology and make a strong case for future studies to directly assess the strong interactions between these two structures in regulating physiology and pathophysiology of the brain.
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Affiliation(s)
- Sufyan Ashhad
- Department of Neurobiology, University of California at Los Angeles, Los Angeles, CA, 90095, USA
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India.
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Durkee CA, Covelo A, Lines J, Kofuji P, Aguilar J, Araque A. G i/o protein-coupled receptors inhibit neurons but activate astrocytes and stimulate gliotransmission. Glia 2019; 67:1076-1093. [PMID: 30801845 DOI: 10.1002/glia.23589] [Citation(s) in RCA: 125] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 12/06/2018] [Accepted: 12/26/2018] [Indexed: 12/31/2022]
Abstract
G protein-coupled receptors (GPCRs) play key roles in intercellular signaling in the brain. Their effects on cellular function have been largely studied in neurons, but their functional consequences on astrocytes are less known. Using both endogenous and chemogenetic approaches with DREADDs, we have investigated the effects of Gq and Gi/o GPCR activation on astroglial Ca2+ -based activity, gliotransmitter release, and the functional consequences on neuronal electrical activity. We found that while Gq GPCR activation led to cellular activation in both neurons and astrocytes, Gi/o GPCR activation led to cellular inhibition in neurons and cellular activation in astrocytes. Astroglial activation by either Gq or Gi/o protein-mediated signaling stimulated gliotransmitter release, which increased neuronal excitability. Additionally, activation of Gq and Gi/o DREADDs in vivo increased astrocyte Ca2+ activity and modified neuronal network electrical activity. Present results reveal additional complexity of the signaling consequences of excitatory and inhibitory neurotransmitters in astroglia-neuron network operation and brain function.
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Affiliation(s)
- Caitlin A Durkee
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Ana Covelo
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Justin Lines
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Juan Aguilar
- Laboratory of Experimental Neurophysiology, Hospital Nacional de Parapléjicos, Toledo, Spain
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
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Poberezhnyi VI, Marchuk OV, Shvidyuk OS, Petrik IY, Logvinov OS. Fundamentals of the modern theory of the phenomenon of "pain" from the perspective of a systematic approach. Neurophysiological basis. Part 1: A brief presentation of key subcellular and cellular ctructural elements of the central nervous system. PAIN MEDICINE 2019. [DOI: 10.31636/pmjua.v3i4.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The phenomenon of “pain” is a psychophysiological phenomenon that is actualized in the mind of a person as a result of the systemic response of his body to certain external and internal stimuli. The heart of the corresponding mental processes is certain neurophysiological processes, which in turn are caused by a certain form of the systemic structural and functional organization of the central nervous system (CNS). Thus, the systemic structural and functional organization of the central nervous system of a person, determining the corresponding psychophysiological state in a specific time interval, determines its psycho-emotional states or reactions manifested by the pain phenomenon. The nervous system of the human body has a hierarchical structure and is a morphologically and functionally complete set of different, interconnected, nervous and structural formations. The basis of the structural formations of the nervous system is nervous tissue. It is a system of interconnected differentials of nerve cells, neuroglia and glial macrophages, providing specific functions of perception of stimulation, excitation, generation of nerve impulses and its transmission. The neuron and each of its compartments (spines, dendrites, catfish, axon) is an autonomous, plastic, active, structural formation with complex computational properties. One of them – dendrites – plays a key role in the integration and processing of information. Dendrites, due to their morphology, provide neurons with unique electrical and plastic properties and cause variations in their computational properties. The morphology of dendrites: 1) determines – a) the number and type of contacts that a particular neuron can form with other neurons; b) the complexity, diversity of its functions; c) its computational operations; 2) determines – a) variations in the computational properties of a neuron (variations of the discharges between bursts and regular forms of pulsation); b) back distribution of action potentials. Dendritic spines can form synaptic connection – one of the main factors for increasing the diversity of forms of synaptic connections of neurons. Their volume and shape can change over a short period of time, and they can rotate in space, appear and disappear by themselves. Spines play a key role in selectively changing the strength of synaptic connections during the memorization and learning process. Glial cells are active participants in diffuse transmission of nerve impulses in the brain. Astrocytes form a three-dimensional, functionally “syncytia-like” formation, inside of which there are neurons, thus causing their specific microenvironment. They and neurons are structurally and functionally interconnected, based on which their permanent interaction occurs. Oligodendrocytes provide conditions for the generation and transmission of nerve impulses along the processes of neurons and play a significant role in the processes of their excitation and inhibition. Microglial cells play an important role in the formation of the brain, especially in the formation and maintenance of synapses. Thus, the CNS should be considered as a single, functionally “syncytia-like”, structural entity. Because the three-dimensional distribution of dendritic branches in space is important for determining the type of information that goes to a neuron, it is necessary to consider the three-dimensionality of their structure when analyzing the implementation of their functions.
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Durkee CA, Araque A. Diversity and Specificity of Astrocyte-neuron Communication. Neuroscience 2018; 396:73-78. [PMID: 30458223 DOI: 10.1016/j.neuroscience.2018.11.010] [Citation(s) in RCA: 191] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 11/08/2018] [Accepted: 11/09/2018] [Indexed: 01/30/2023]
Abstract
Astrocytes are emerging as important players in synaptic function, and, consequently, on brain function and animal behavior. According to the Tripartite Synapse concept, astrocytes are integral elements involved in synaptic function. They establish bidirectional communication with neurons, whereby they respond to synaptically released neurotransmitters and, in turn, release gliotransmitters that influence neuronal and synaptic activity. Accumulating evidence is revealing that the mechanisms and functional consequences of astrocyte-neuron signaling are more complex than originally thought. Furthermore, astrocyte-neuron signaling is not based on broad, unspecific interaction; rather, it is a synapse-, cell- and circuit-specific phenomenon that presents a high degree of complexity. This diversity and complexity of astrocyte-synapse interactions greatly enhance the degrees of freedom of the neural circuits and the consequent computational power of the neural systems.
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Affiliation(s)
- Caitlin A Durkee
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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Bar El Y, Kanner S, Barzilai A, Hanein Y. Activity changes in neuron-astrocyte networks in culture under the effect of norepinephrine. PLoS One 2018; 13:e0203761. [PMID: 30332429 PMCID: PMC6192555 DOI: 10.1371/journal.pone.0203761] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 08/27/2018] [Indexed: 11/26/2022] Open
Abstract
The concerted activity of neuron-glia networks is responsible for the fascinating dynamics of brain functions. Although these networks have been extensively investigated using a variety of experimental (in vivo and in vitro) and theoretical models, the manner by which neuron-glia networks interact is not fully understood. In particular, how neuromodulators influence network-level signaling between neurons and astrocytes was poorly addressed. In this work, we investigated global effects of the neuromodulator norepinephrine (NE) on neuron-astrocyte network communication in co-cultures of neurons and astrocytes and in isolated astrocyte networks. Electrical stimulation was used to activate the neuron-astrocyte glutamate-mediated pathway. Our results showed dramatic changes in network activity under applied global perturbations. Under neuromodulation, there was a marked rise in calcium signaling in astrocytes, neuronal spontaneous activity was reduced, and the communication between neuron-astrocyte networks was perturbed. Moreover, in the presence of NE, we observed two astrocyte behaviors based on their coupling to neurons. There were also morphological changes in astrocytes upon application of NE, suggesting a physical cause underlies the change in signaling. Our results shed light on the role of NE in controlling sleep-wake cycles.
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Affiliation(s)
- Yasmin Bar El
- School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv, Israel
| | - Sivan Kanner
- Department of Neurobiology, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel
| | - Ari Barzilai
- Department of Neurobiology, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel
- Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel
| | - Yael Hanein
- Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel
- School of Electrical Engineering, Tel-Aviv University, Tel-Aviv, Israel
- * E-mail:
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Christensen RK, Delgado-Lezama R, Russo RE, Lind BL, Alcocer EL, Rath MF, Fabbiani G, Schmitt N, Lauritzen M, Petersen AV, Carlsen EM, Perrier JF. Spinal dorsal horn astrocytes release GABA in response to synaptic activation. J Physiol 2018; 596:4983-4994. [PMID: 30079574 DOI: 10.1113/jp276562] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 08/01/2018] [Indexed: 02/02/2023] Open
Abstract
KEY POINTS GABA is an essential molecule for sensory information processing. It is usually assumed to be released by neurons. Here we show that in the dorsal horn of the spinal cord, astrocytes respond to glutamate by releasing GABA. Our findings suggest a novel role for astrocytes in somatosensory information processing. ABSTRACT Astrocytes participate in neuronal signalling by releasing gliotransmitters in response to neurotransmitters. We investigated if astrocytes from the dorsal horn of the spinal cord of adult red-eared turtles (Trachemys scripta elegans) release GABA in response to glutamatergic receptor activation. For this, we developed a GABA sensor consisting of HEK cells expressing GABAA receptors. By positioning the sensor recorded in the whole-cell patch-clamp configuration within the dorsal horn of a spinal cord slice, we could detect GABA in the extracellular space. Puff application of glutamate induced GABA release events with time courses that exceeded the duration of inhibitory postsynaptic currents by one order of magnitude. Because the events were neither affected by extracellular addition of nickel, cadmium and tetrodotoxin nor by removal of Ca2+ , we concluded that they originated from non-neuronal cells. Immunohistochemical staining allowed the detection of GABA in a fraction of dorsal horn astrocytes. The selective stimulation of A∂ and C fibres in a dorsal root filament induced a Ca2+ increase in astrocytes loaded with Oregon Green BAPTA. Finally, chelating Ca2+ in a single astrocyte was sufficient to prevent the GABA release evoked by glutamate. Our results indicate that glutamate triggers the release of GABA from dorsal horn astrocytes with a time course compatible with the integration of sensory inputs.
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Affiliation(s)
- Rasmus Kordt Christensen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Rodolfo Delgado-Lezama
- Departamento de Fisiología, Biofísica y Neurociencias Cinvestav-IPN Avenida IPN 2508, Col. Zacatenco México City, CP, 07300, Mexico
| | - Raúl E Russo
- Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, 11600, Montevideo, Uruguay
| | - Barbara Lykke Lind
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Emanuel Loeza Alcocer
- Departamento de Fisiología, Biofísica y Neurociencias Cinvestav-IPN Avenida IPN 2508, Col. Zacatenco México City, CP, 07300, Mexico
| | - Martin Fredensborg Rath
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Gabriela Fabbiani
- Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, 11600, Montevideo, Uruguay
| | - Nicole Schmitt
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Martin Lauritzen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Anders Victor Petersen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Eva Meier Carlsen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Jean-François Perrier
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
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80
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Interactions between astrocytes and the reward-attention circuit: A model for attention focusing in the presence of nicotine. COGN SYST RES 2018. [DOI: 10.1016/j.cogsys.2018.03.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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81
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Hegyi Z, Oláh T, Kőszeghy Á, Piscitelli F, Holló K, Pál B, Csernoch L, Di Marzo V, Antal M. CB 1 receptor activation induces intracellular Ca 2+ mobilization and 2-arachidonoylglycerol release in rodent spinal cord astrocytes. Sci Rep 2018; 8:10562. [PMID: 30002493 PMCID: PMC6043539 DOI: 10.1038/s41598-018-28763-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 06/29/2018] [Indexed: 01/26/2023] Open
Abstract
Accumulating evidence supports the role of astrocytes in endocannabinoid mediated modulation of neural activity. It has been reported that some astrocytes express the cannabinoid type 1 receptor (CB1-R), the activation of which is leading to Ca2+ mobilization from internal stores and a consecutive release of glutamate. It has also been documented that astrocytes have the potential to produce the endocannabinoid 2-arachidonoylglycerol, one of the best known CB1-R agonist. However, no relationship between CB1-R activation and 2-arachidonoylglycerol production has ever been demonstrated. Here we show that rat spinal astrocytes co-express CB1-Rs and the 2-arachidonoylglycerol synthesizing enzyme, diacylglycerol lipase-alpha in close vicinity to each other. We also demonstrate that activation of CB1-Rs induces a substantial elevation of intracellular Ca2+ concentration in astrocytes. Finally, we provide evidence that the evoked Ca2+ transients lead to the production of 2-arachidonoylglycerol in cultured astrocytes. The results provide evidence for a novel cannabinoid induced endocannabinoid release mechanism in astrocytes which broadens the bidirectional signaling repertoire between astrocytes and neurons.
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Affiliation(s)
- Zoltán Hegyi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary
| | - Tamás Oláh
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary
| | - Áron Kőszeghy
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary.,Department of Cognitive Neurobiology, Center for Brain Research, Medical University of Vienna, 1090, Vienna, Austria
| | - Fabiana Piscitelli
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, Consiglio Nazionale delle Ricerche, 80078, Pozzuoli, Naples, Italy
| | - Krisztina Holló
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary
| | - Balázs Pál
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary
| | - László Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary
| | - Vincenzo Di Marzo
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, Consiglio Nazionale delle Ricerche, 80078, Pozzuoli, Naples, Italy
| | - Miklós Antal
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary. .,MTA-DE Neuroscience Research Group, University of Debrecen, 4032, Debrecen, Hungary.
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82
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Liu CY, Yang Y, Ju WN, Wang X, Zhang HL. Emerging Roles of Astrocytes in Neuro-Vascular Unit and the Tripartite Synapse With Emphasis on Reactive Gliosis in the Context of Alzheimer's Disease. Front Cell Neurosci 2018; 12:193. [PMID: 30042661 PMCID: PMC6048287 DOI: 10.3389/fncel.2018.00193] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Accepted: 06/14/2018] [Indexed: 01/09/2023] Open
Abstract
Astrocytes, which are five-fold more numerous than neurons in the central nervous system (CNS), are traditionally viewed to provide simple structural and nutritional supports for neurons and to participate in the composition of the blood brain barrier (BBB). In recent years, the active roles of astrocytes in regulating cerebral blood flow (CBF) and in maintaining the homeostasis of the tripartite synapse have attracted increasing attention. More importantly, astrocytes have been associated with the pathogenesis of Alzheimer's disease (AD), a major cause of dementia in the elderly. Although microglia-induced inflammation is considered important in the development and progression of AD, inflammation attributable to astrogliosis may also play crucial roles. A1 reactive astrocytes induced by inflammatory stimuli might be harmful by up-regulating several classical complement cascade genes thereby leading to chronic inflammation, while A2 induced by ischemia might be protective by up-regulating several neurotrophic factors. Here we provide a concise review of the emerging roles of astrocytes in the homeostasis maintenance of the neuro-vascular unit (NVU) and the tripartite synapse with emphasis on reactive astrogliosis in the context of AD, so as to pave the way for further research in this area, and to search for potential therapeutic targets of AD.
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Affiliation(s)
- Cai-Yun Liu
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Yu Yang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Wei-Na Ju
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Xu Wang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Hong-Liang Zhang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
- Department of Life Sciences, The National Natural Science Foundation of China, Beijing, China
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83
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Robin LM, Oliveira da Cruz JF, Langlais VC, Martin-Fernandez M, Metna-Laurent M, Busquets-Garcia A, Bellocchio L, Soria-Gomez E, Papouin T, Varilh M, Sherwood MW, Belluomo I, Balcells G, Matias I, Bosier B, Drago F, Van Eeckhaut A, Smolders I, Georges F, Araque A, Panatier A, Oliet SHR, Marsicano G. Astroglial CB 1 Receptors Determine Synaptic D-Serine Availability to Enable Recognition Memory. Neuron 2018; 98:935-944.e5. [PMID: 29779943 DOI: 10.1016/j.neuron.2018.04.034] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 03/20/2018] [Accepted: 04/24/2018] [Indexed: 12/22/2022]
Abstract
Bidirectional communication between neurons and astrocytes shapes synaptic plasticity and behavior. D-serine is a necessary co-agonist of synaptic N-methyl-D-aspartate receptors (NMDARs), but the physiological factors regulating its impact on memory processes are scantly known. We show that astroglial CB1 receptors are key determinants of object recognition memory by determining the availability of D-serine at hippocampal synapses. Mutant mice lacking CB1 receptors from astroglial cells (GFAP-CB1-KO) displayed impaired object recognition memory and decreased in vivo and in vitro long-term potentiation (LTP) at CA3-CA1 hippocampal synapses. Activation of CB1 receptors increased intracellular astroglial Ca2+ levels and extracellular levels of D-serine in hippocampal slices. Accordingly, GFAP-CB1-KO displayed lower occupancy of the co-agonist binding site of synaptic hippocampal NMDARs. Finally, elevation of D-serine levels fully rescued LTP and memory impairments of GFAP-CB1-KO mice. These data reveal a novel mechanism of in vivo astroglial control of memory and synaptic plasticity via the D-serine-dependent control of NMDARs.
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Affiliation(s)
- Laurie M Robin
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - José F Oliveira da Cruz
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France; Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, 95123 Catania, Italy
| | - Valentin C Langlais
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | | | - Mathilde Metna-Laurent
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France; Aelis Farma, 33077 Bordeaux, France
| | - Arnau Busquets-Garcia
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Luigi Bellocchio
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Edgar Soria-Gomez
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France; Department of Neurosciences, University of the Basque Country UPV/EHU, 48940 Leioa, Spain; IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Thomas Papouin
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Marjorie Varilh
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Mark W Sherwood
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Ilaria Belluomo
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Georgina Balcells
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Isabelle Matias
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Barbara Bosier
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Filippo Drago
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, 95123 Catania, Italy
| | - Ann Van Eeckhaut
- Vrije Universiteit Brussel, Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Research group Experimental Pharmacology, Center for Neurosciences (C4N), Laarbeeklaan 103, 1090 Brussels, Belgium
| | - Ilse Smolders
- Vrije Universiteit Brussel, Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Research group Experimental Pharmacology, Center for Neurosciences (C4N), Laarbeeklaan 103, 1090 Brussels, Belgium
| | - Francois Georges
- University of Bordeaux, 33077 Bordeaux, France; Centre National de la Recherche Scientifique, Neurodegenerative Diseases Institute, UMR 5293, 33076 Bordeaux, France
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Aude Panatier
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Stéphane H R Oliet
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France
| | - Giovanni Marsicano
- INSERM U1215, NeuroCentre Magendie, 33077 Bordeaux, France; University of Bordeaux, 33077 Bordeaux, France.
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84
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Manninen T, Havela R, Linne ML. Computational Models for Calcium-Mediated Astrocyte Functions. Front Comput Neurosci 2018; 12:14. [PMID: 29670517 PMCID: PMC5893839 DOI: 10.3389/fncom.2018.00014] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 02/28/2018] [Indexed: 12/16/2022] Open
Abstract
The computational neuroscience field has heavily concentrated on the modeling of neuronal functions, largely ignoring other brain cells, including one type of glial cell, the astrocytes. Despite the short history of modeling astrocytic functions, we were delighted about the hundreds of models developed so far to study the role of astrocytes, most often in calcium dynamics, synchronization, information transfer, and plasticity in vitro, but also in vascular events, hyperexcitability, and homeostasis. Our goal here is to present the state-of-the-art in computational modeling of astrocytes in order to facilitate better understanding of the functions and dynamics of astrocytes in the brain. Due to the large number of models, we concentrated on a hundred models that include biophysical descriptions for calcium signaling and dynamics in astrocytes. We categorized the models into four groups: single astrocyte models, astrocyte network models, neuron-astrocyte synapse models, and neuron-astrocyte network models to ease their use in future modeling projects. We characterized the models based on which earlier models were used for building the models and which type of biological entities were described in the astrocyte models. Features of the models were compared and contrasted so that similarities and differences were more readily apparent. We discovered that most of the models were basically generated from a small set of previously published models with small variations. However, neither citations to all the previous models with similar core structure nor explanations of what was built on top of the previous models were provided, which made it possible, in some cases, to have the same models published several times without an explicit intention to make new predictions about the roles of astrocytes in brain functions. Furthermore, only a few of the models are available online which makes it difficult to reproduce the simulation results and further develop the models. Thus, we would like to emphasize that only via reproducible research are we able to build better computational models for astrocytes, which truly advance science. Our study is the first to characterize in detail the biophysical and biochemical mechanisms that have been modeled for astrocytes.
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Affiliation(s)
- Tiina Manninen
- Computational Neuroscience Group, BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, Tampere, Finland
| | | | - Marja-Leena Linne
- Computational Neuroscience Group, BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, Tampere, Finland
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85
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Activity dependent internalization of the glutamate transporter GLT-1 requires calcium entry through the NCX sodium/calcium exchanger. Neurochem Int 2018; 123:125-132. [PMID: 29574129 DOI: 10.1016/j.neuint.2018.03.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/20/2018] [Accepted: 03/20/2018] [Indexed: 12/13/2022]
Abstract
GLT-1 is the main glutamate transporter in the brain and its trafficking controls its availability at the cell surface, thereby shaping glutamatergic neurotransmission under physiological and pathological conditions. Extracellular glutamate is known to trigger ubiquitin-dependent GLT-1 internalization from the surface of the cell to the intracellular compartment, yet here we show that internalization also requires the participation of calcium ions. Consistent with previous studies, the addition of glutamate (1 mM) to mixed primary cultures (containing neurons and astrocytes) promotes GLT-1 internalization, an effect that was suppressed in the absence of extracellular Ca2+. The pathways of Ca2+ mobilization by astrocytes were analyzed in these mixed cultures using the genetically encoded calcium sensor GCaMP6f. A complex pattern of calcium entry was activated by glutamate, with a dramatic and rapid rise in the intracellular Ca2+ concentration partially driven by glutamate transporters, especially in the initial stages after exposure to glutamate. The Na+/Ca2+ exchanger (NCX) plays a dominant role in this Ca2+ mobilization and its blockade suppresses the glutamate induced internalization of GLT-1, both in astrocytes and in a more straightforward experimental system like HEK293 cells transiently transfected with GLT-1. This regulatory mechanism might be relevant to control the amount of GLT-1 transporter at the cell surface in conditions like ischemia or traumatic brain injury, where extracellular concentrations of glutamate are persistently elevated and they promote rapid Ca2+ mobilization.
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86
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mGlu5-mediated signalling in developing astrocyte and the pathogenesis of autism spectrum disorders. Curr Opin Neurobiol 2018; 48:139-145. [DOI: 10.1016/j.conb.2017.12.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 12/18/2017] [Accepted: 12/22/2017] [Indexed: 11/24/2022]
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87
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Rose CR, Felix L, Zeug A, Dietrich D, Reiner A, Henneberger C. Astroglial Glutamate Signaling and Uptake in the Hippocampus. Front Mol Neurosci 2018; 10:451. [PMID: 29386994 PMCID: PMC5776105 DOI: 10.3389/fnmol.2017.00451] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 12/22/2017] [Indexed: 12/22/2022] Open
Abstract
Astrocytes have long been regarded as essentially unexcitable cells that do not contribute to active signaling and information processing in the brain. Contrary to this classical view, it is now firmly established that astrocytes can specifically respond to glutamate released from neurons. Astrocyte glutamate signaling is initiated upon binding of glutamate to ionotropic and/or metabotropic receptors, which can result in calcium signaling, a major form of glial excitability. Release of so-called gliotransmitters like glutamate, ATP and D-serine from astrocytes in response to activation of glutamate receptors has been demonstrated to modulate various aspects of neuronal function in the hippocampus. In addition to receptors, glutamate binds to high-affinity, sodium-dependent transporters, which results in rapid buffering of synaptically-released glutamate, followed by its removal from the synaptic cleft through uptake into astrocytes. The degree to which astrocytes modulate and control extracellular glutamate levels through glutamate transporters depends on their expression levels and on the ionic driving forces that decrease with ongoing activity. Another major determinant of astrocytic control of glutamate levels could be the precise morphological arrangement of fine perisynaptic processes close to synapses, defining the diffusional distance for glutamate, and the spatial proximity of transporters in relation to the synaptic cleft. In this review, we will present an overview of the mechanisms and physiological role of glutamate-induced ion signaling in astrocytes in the hippocampus as mediated by receptors and transporters. Moreover, we will discuss the relevance of astroglial glutamate uptake for extracellular glutamate homeostasis, focusing on how activity-induced dynamic changes of perisynaptic processes could shape synaptic transmission at glutamatergic synapses.
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Affiliation(s)
- Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Lisa Felix
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Andre Zeug
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Dirk Dietrich
- Department of Neurosurgery, University of Bonn Medical School, Bonn, Germany
| | - Andreas Reiner
- Cellular Neurobiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany.,German Center for Degenerative Diseases (DZNE), Bonn, Germany.,Institute of Neurology, University College London, London, United Kingdom
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88
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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89
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 916] [Impact Index Per Article: 152.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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90
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Eto K, Kim SK, Takeda I, Nabekura J. The roles of cortical astrocytes in chronic pain and other brain pathologies. Neurosci Res 2017; 126:3-8. [PMID: 28870605 DOI: 10.1016/j.neures.2017.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 08/01/2017] [Accepted: 08/18/2017] [Indexed: 01/21/2023]
Abstract
Astrocytes are the most abundant cell type in the brain. Several decades ago, they were considered to be only support cells in the central nervous system. Recent studies using advanced technologies have clarified that astrocytes play more active roles in regulating neuronal function and remodeling synaptic structures by releasing molecules called gliotransmitters. In addition to various physiological functions, astrocytes are activated under disease conditions, such as chronic pain, releasing molecules that in turn cause reorganization of the central nervous system microstructure and disrupt behavior in pathological conditions. In the present review, we summarize cortical astrocyte function in chronic pain and other neurological disorders and discuss the role of astrocytes in brain pathologies.
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Affiliation(s)
- Kei Eto
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; Department of Physiological Sciences, The Graduate School for Advanced Studies, Hayama, Kanagawa 240-0193, Japan
| | - Sun Kwang Kim
- Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Ikuko Takeda
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; Department of Physiological Sciences, The Graduate School for Advanced Studies, Hayama, Kanagawa 240-0193, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Tokyo 102-0076, Japan.
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91
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Importance of Autophagy in Mediating Human Immunodeficiency Virus (HIV) and Morphine-Induced Metabolic Dysfunction and Inflammation in Human Astrocytes. Viruses 2017; 9:v9080201. [PMID: 28788100 PMCID: PMC5580458 DOI: 10.3390/v9080201] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 07/24/2017] [Accepted: 07/24/2017] [Indexed: 12/11/2022] Open
Abstract
Under physiological conditions, the function of astrocytes in providing brain metabolic support is compromised under pathophysiological conditions caused by human immunodeficiency virus (HIV) and opioids. Herein, we examined the role of autophagy, a lysosomal degradation pathway important for cellular homeostasis and survival, as a potential regulatory mechanism during pathophysiological conditions in primary human astrocytes. Blocking autophagy with small interfering RNA (siRNA) targeting BECN1, but not the Autophagy-related 5 (ATG5) gene, caused a significant decrease in HIV and morphine-induced intracellular calcium release. On the contrary, inducing autophagy pharmacologically with rapamycin further enhanced calcium release and significantly reverted HIV and morphine-decreased glutamate uptake. Furthermore, siBeclin1 caused an increase in HIV-induced nitric oxide (NO) release, while viral-induced NO in astrocytes exposed to rapamycin was decreased. HIV replication was significantly attenuated in astrocytes transfected with siRNA while significantly induced in astrocytes exposed to rapamycin. Silencing with siBeclin1, but not siATG5, caused a significant decrease in HIV and morphine-induced interleukin (IL)-8 and tumor necrosis factor alpha (TNF-α) release, while secretion of IL-8 was significantly induced with rapamycin. Mechanistically, the effects of siBeclin1 in decreasing HIV-induced calcium release, viral replication, and viral-induced cytokine secretion were associated with a decrease in activation of the nuclear factor kappa B (NF-κB) pathway.
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92
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Abstract
STUDY DESIGN Literature review. OBJECTIVE A review of the literature that presents a perspective on mechanisms of actions behind spinal cord stimulation (SCS) therapy for chronic pain. SUMMARY OF BACKGROUND DATA SCS is an effective therapeutic alternative for the treatment of intractable chronic pain. Its application has been mostly based on the gate control theory of pain. Computational models have been fundamental on the understanding of clinical observations and the design of therapies that provide optimal neuromodulation. Research has provided insight into the involvement of specific neurotransmitters that support segmental and supraspinal mechanisms of action. METHODS A literature review was performed with emphasis on mechanisms of action for SCS including the effects of electrical fields on spinal cord structures based on computational models and preclinical and clinical explorations. RESULTS This review provides background on the development of SCS, which has been driven around a paresthesia-based paradigm as a result of the gate control theory. A review of computational models emphasizes their importance on our current understanding of the mechanism of action and clinical optimization of therapy. Electrophysiology and molecular biology have provided a closer, yet narrow, view of the effect of SCS on neurotransmitters and their receptors, which have led to the formulation of segmental and supraspinal mechanisms. Literature supporting the involvement of glial cells in chronic pain and their characteristic response to electrical fields should motivate further investigation of mechanisms involving neuroglia. Finally, a review of recent results paresthesia-free strategies should encourage research on mechanisms of action. CONCLUSION The mechanisms of SCS have been extensively studied and several consistent phenomena have emerged. The activation of A-beta fibers to induce paresthesia also involve neurotransmitter release via segmental and supraspinal pathways. Despite advancements, much remains to be understood, particularly as new stimulation strategies are developed. LEVEL OF EVIDENCE N /A.
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93
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Forero-Quintero LS, Deitmer JW, Becker HM. Reduction of epileptiform activity in ketogenic mice: The role of monocarboxylate transporters. Sci Rep 2017; 7:4900. [PMID: 28687765 PMCID: PMC5501801 DOI: 10.1038/s41598-017-05054-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 05/23/2017] [Indexed: 02/05/2023] Open
Abstract
Epilepsy is a chronic neurological disorder that affects approximately 50 million people worldwide. Ketogenic diet (KD) can be a very effective treatment for intractable epilepsy. Potential mechanisms of action for KD have been proposed, including the re-balance among excitatory and inhibitory neurotransmission and decrease in the glycolytic rate in brain cells. KD has been shown to have an effect on the expression pattern of monocarboxylate transporters (MCT), however, it is unknown whether MCT transport activity is affected by KD and linked to the reduction of seizures during KD. Therefore, we studied the influence of KD on MCT transport activity and the role of MCTs during epileptiform activity. Our results showed a decrease in the epileptiform activity in cortical slices from mice fed on KD and in the presence of beta-hydroxybutyrate. KD increased transport capacity for ketone bodies and lactate in cortical astrocytes by raising the MCT1 expression level. Inhibition of MCT1 and MCT2 in control conditions decreases epileptiform activity, while in KD it induced an increase in epileptiform activity. Our results suggest that MCTs not only play an important role in the transport of ketone bodies, but also in the modulation of brain energy metabolism under normal and ketogenic conditions.
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Affiliation(s)
- Linda S Forero-Quintero
- Division of General Zoology, Department of Biology, University of Kaiserslautern, P.O. Box 3049, D-67653, Kaiserslautern, Germany
| | - Joachim W Deitmer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, P.O. Box 3049, D-67653, Kaiserslautern, Germany
| | - Holger M Becker
- Division of General Zoology, Department of Biology, University of Kaiserslautern, P.O. Box 3049, D-67653, Kaiserslautern, Germany.
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94
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Adamsky A, Goshen I. Astrocytes in Memory Function: Pioneering Findings and Future Directions. Neuroscience 2017; 370:14-26. [PMID: 28571720 DOI: 10.1016/j.neuroscience.2017.05.033] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/05/2017] [Accepted: 05/19/2017] [Indexed: 12/29/2022]
Abstract
Astrocytes have been generally believed to perform mainly homeostatic and supportive functions for neurons in the central nervous system. Recently, a growing body of evidence suggests previously unrecognized and surprising functions for astrocytes, including regulation of synaptic formation, transmission and plasticity, all of which are considered as the infrastructure for information processing and memory formation and stabilization. This review discusses the involvement of astrocytes in memory functions and the possible mechanisms that may underlie it. We review the important breakthroughs obtained in this field, as well as some of the controversies that arose from the past difficulty to manipulate these cells in a cell type-specific and non-invasive manner. Finally, we present new research avenues based on the advanced tools becoming available in recent years: optogenetics and chemogenetics, and the potential ways in which these tools may further illuminate the role of astrocytes in memory processes.
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Affiliation(s)
- Adar Adamsky
- Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Givat Ram, Jerusalem 91904, Israel
| | - Inbal Goshen
- Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Givat Ram, Jerusalem 91904, Israel.
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95
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Acosta C, Anderson HD, Anderson CM. Astrocyte dysfunction in Alzheimer disease. J Neurosci Res 2017; 95:2430-2447. [PMID: 28467650 DOI: 10.1002/jnr.24075] [Citation(s) in RCA: 155] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/07/2017] [Accepted: 04/10/2017] [Indexed: 12/11/2022]
Abstract
Astrocytes are glial cells that are distributed throughout the central nervous system in an arrangement optimal for chemical and physical interaction with neuronal synapses and brain blood supply vessels. Neurotransmission modulates astrocytic excitability by activating an array of cell surface receptors and transporter proteins, resulting in dynamic changes in intracellular Ca2+ or Na+ . Ionic and electrogenic astrocytic changes, in turn, drive vital cell nonautonomous effects supporting brain function, including regulation of synaptic activity, neuronal metabolism, and regional blood supply. Alzheimer disease (AD) is associated with aberrant oligomeric amyloid β generation, which leads to extensive proliferation of astrocytes with a reactive phenotype and abnormal regulation of these processes. Astrocytic morphology, Ca2+ responses, extracellular K+ removal, glutamate transport, amyloid clearance, and energy metabolism are all affected in AD, resulting in a deleterious set of effects that includes glutamate excitotoxicity, impaired synaptic plasticity, reduced carbon delivery to neurons for oxidative phosphorylation, and dysregulated linkages between neuronal energy demand and regional blood supply. This review summarizes how astrocytes are affected in AD and describes how these changes are likely to influence brain function. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Crystal Acosta
- Department of Pharmacology and Therapeutics, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada.,Canadian Centre for Agri-food Research in Health and Medicine, St. Boniface Hospital Research, Winnipeg, Manitoba, Canada
| | - Hope D Anderson
- Canadian Centre for Agri-food Research in Health and Medicine, St. Boniface Hospital Research, Winnipeg, Manitoba, Canada.,College of Pharmacy, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
| | - Christopher M Anderson
- Department of Pharmacology and Therapeutics, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada.,Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, Winnipeg, Manitoba, Canada
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96
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Copeland CS, Wall TM, Sims RE, Neale SA, Nisenbaum E, Parri HR, Salt TE. Astrocytes modulate thalamic sensory processing via mGlu2 receptor activation. Neuropharmacology 2017; 121:100-110. [PMID: 28416443 PMCID: PMC5480778 DOI: 10.1016/j.neuropharm.2017.04.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 03/27/2017] [Accepted: 04/13/2017] [Indexed: 11/27/2022]
Abstract
Astrocytes possess many of the same signalling molecules as neurons. However, the role of astrocytes in information processing, if any, is unknown. Using electrophysiological and imaging methods, we report the first evidence that astrocytes modulate neuronal sensory inhibition in the rodent thalamus. We found that mGlu2 receptor activity reduces inhibitory transmission from the thalamic reticular nucleus to the somatosensory ventrobasal thalamus (VB): mIPSC frequencies in VB slices were reduced by the Group II mGlu receptor agonist LY354740, an effect potentiated by mGlu2 positive allosteric modulator (PAM) LY487379 co-application (30 nM LY354740: 10.0 ± 1.6% reduction; 30 nM LY354740 & 30 μM LY487379: 34.6 ± 5.2% reduction). We then showed activation of mGlu2 receptors on astrocytes: astrocytic intracellular calcium levels were elevated by the Group II agonist, which were further potentiated upon mGlu2 PAM co-application (300 nM LY354740: ratio amplitude 0.016 ± 0.002; 300 nM LY354740 & 30 μM LY487379: ratio amplitude 0.035 ± 0.003). We then demonstrated mGlu2-dependent astrocytic disinhibition of VB neurons in vivo: VB neuronal responses to vibrissae stimulation trains were disinhibited by the Group II agonist and the mGlu2 PAM (LY354740: 156 ± 12% of control; LY487379: 144 ± 10% of control). Presence of the glial inhibitor fluorocitrate abolished the mGlu2 PAM effect (91 ± 5% of control), suggesting the mGlu2 component to the Group II effect can be attributed to activation of mGlu2 receptors localised on astrocytic processes within the VB. Gating of thalamocortical function via astrocyte activation represents a novel sensory processing mechanism. As this thalamocortical circuitry is important in discriminative processes, this demonstrates the importance of astrocytes in synaptic processes underlying attention and cognition. Thalamic inhibition is mediated by both neuronal and astrocytic mechanisms. Group II mGlu receptor (mGlu2/3) activation can modulate this thalamic inhibition. Thalamic astrocytes can be activated upon mGlu2 receptor stimulation. This process may enable relevant activity to be discerned from background noise. Targeting astrocytic mGlu2 receptors may therefore affect attention and cognition.
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Affiliation(s)
- C S Copeland
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK; St George's, University of London, Cranmer Terrace, London, SW17 0RE, UK.
| | - T M Wall
- Eli Lilly and Company, 893 S Delaware Street, Indianapolis, IN 46285, USA.
| | - R E Sims
- School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK.
| | - S A Neale
- Neurexpert Limited, Kemp House, 152-160 City Road, London, EC1V 2NX, UK.
| | - E Nisenbaum
- Eli Lilly and Company, 893 S Delaware Street, Indianapolis, IN 46285, USA.
| | - H R Parri
- School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK.
| | - T E Salt
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK.
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97
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Vergouts M, Doyen PJ, Peeters M, Opsomer R, Michiels T, Hermans E. PKC epsilon-dependent calcium oscillations associated with metabotropic glutamate receptor 5 prevent agonist-mediated receptor desensitization in astrocytes. J Neurochem 2017; 141:387-399. [PMID: 28266711 DOI: 10.1111/jnc.14007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 01/26/2017] [Accepted: 02/20/2017] [Indexed: 12/16/2022]
Abstract
A critical role has been assigned to protein kinase C (PKC)ε in the control of intracellular calcium oscillations triggered upon activation of type 5 metabotropic glutamate receptor (mGluR5) in cultured astrocytes. Nevertheless, the physiological significance of this particular signalling profile in the response of astrocytes to glutamate remains largely unknown. Considering that kinases are frequently involved in the regulation of G protein-coupled receptors, we have examined a putative link between the nature of the calcium signals and the response regulation upon repeated exposures of astrocytes to the agonist (S)-3,5-dihydroxyphenylglycine. We show that upon repeated mGluR5 activations, a robust desensitization was observed in astrocytes grown in culture conditions favouring the peak-plateau-type response. At variance, in cell cultures where calcium oscillations were predominating, the response was fully preserved even during repeated challenges with the agonist. Pharmacological inhibition of PKCε or genetic suppression of this isoform using shRNA was found to convert an oscillatory calcium profile to a sustained calcium mobilization and this latter profile was subject to desensitization upon repetitive mGluR5 activation. Our results suggest a yet undocumented scheme in which the activity of PKCε contributes to preserve the receptor sensitivity upon repeated or sustained activations. Cover Image for this issue: doi: 10.1111/jnc.13797.
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Affiliation(s)
- Maxime Vergouts
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Avenue Hippocrate B1.54.10, Brussels, Belgium
| | - Pierre J Doyen
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Avenue Hippocrate B1.54.10, Brussels, Belgium
| | - Michael Peeters
- Laboratory of virology, De Duve Institute, Université catholique de Louvain, Avenue Hippocrate B1.74.07, Brussels, Belgium
| | - Remi Opsomer
- Alzheimer Dementia Group, Institute of Neuroscience, Université catholique de Louvain, Avenue Mounier B1.53.02, Brussels, Belgium
| | - Thomas Michiels
- Laboratory of virology, De Duve Institute, Université catholique de Louvain, Avenue Hippocrate B1.74.07, Brussels, Belgium
| | - Emmanuel Hermans
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Avenue Hippocrate B1.54.10, Brussels, Belgium
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98
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Singh A, Abraham WC. Astrocytes and synaptic plasticity in health and disease. Exp Brain Res 2017; 235:1645-1655. [PMID: 28299411 DOI: 10.1007/s00221-017-4928-1] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 02/20/2017] [Indexed: 12/22/2022]
Abstract
Activity-dependent synaptic plasticity phenomena such as long-term potentiation and long-term depression are candidate mechanisms for storing information in the brain. Regulation of synaptic plasticity is critical for healthy cognition and learning and this is provided in part by metaplasticity, which can act to maintain synaptic transmission within a dynamic range and potentially prevent excitotoxicity. Metaplasticity mechanisms also allow neurons to integrate plasticity-associated signals over time. Interestingly, astrocytes appear to be critical for certain forms of synaptic plasticity and metaplasticity mechanisms. Synaptic dysfunction is increasingly viewed as an early feature of AD that is correlated with the severity of cognitive decline, and the development of these pathologies is correlated with a rise in reactive astrocytes. This review focuses on the contributions of astrocytes to synaptic plasticity and metaplasticity in normal tissue, and addresses whether astroglial pathology may lead to aberrant engagement of these mechanisms in neurological diseases such as Alzheimer's disease.
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Affiliation(s)
- A Singh
- Department of Psychology, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Box 56, Dunedin, 9054, New Zealand
| | - Wickliffe C Abraham
- Department of Psychology, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Box 56, Dunedin, 9054, New Zealand.
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99
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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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100
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Effects of astrocytic dynamics on spatiotemporal hemodynamics: Modeling and enhanced data analysis. Neuroimage 2017; 147:994-1005. [DOI: 10.1016/j.neuroimage.2016.10.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 10/12/2016] [Accepted: 10/13/2016] [Indexed: 12/11/2022] Open
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