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Madeira D, Lopes CR, Simões AP, Canas PM, Cunha RA, Agostinho P. Astrocytic A 2A receptors silencing negatively impacts hippocampal synaptic plasticity and memory of adult mice. Glia 2023. [PMID: 37183905 DOI: 10.1002/glia.24384] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/16/2023]
Abstract
Astrocytes are wired to bidirectionally communicate with neurons namely with synapses, thus shaping synaptic plasticity, which in the hippocampus is considered to underlie learning and memory. Adenosine A2A receptors (A2A R) are a potential candidate to modulate this bidirectional communication, since A2A R regulate synaptic plasticity and memory and also control key astrocytic functions. Nonetheless, little is known about the role of astrocytic A2A R in synaptic plasticity and hippocampal-dependent memory. Here, we investigated the impact of genetic silencing astrocytic A2A R on hippocampal synaptic plasticity and memory of adult mice. The genetic A2A R silencing in astrocytes was accomplished by a bilateral injection into the CA1 hippocampal area of a viral construct (AAV5-GFAP-GFP-Cre) that inactivate A2A R expression in astrocytes of male adult mice carrying "floxed" A2A R gene, as confirmed by A2A R binding assays. Astrocytic A2A R silencing alters astrocytic morphology, typified by an increment of astrocytic arbor complexity, and led to deficits in spatial reference memory and compromised hippocampal synaptic plasticity, typified by a reduction of LTP magnitude and a shift of synaptic long-term depression (LTD) toward LTP. These data indicate that astrocytic A2A R control astrocytic morphology and influence hippocampal synaptic plasticity and memory of adult mice in a manner different from neuronal A2A R.
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Affiliation(s)
- Daniela Madeira
- Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
- Center for Neuroscience and Cell Biology- University of Coimbra (CNC- UC), Coimbra, Portugal
| | - Cátia R Lopes
- Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
- Center for Neuroscience and Cell Biology- University of Coimbra (CNC- UC), Coimbra, Portugal
| | - Ana P Simões
- Center for Neuroscience and Cell Biology- University of Coimbra (CNC- UC), Coimbra, Portugal
| | - Paula M Canas
- Center for Neuroscience and Cell Biology- University of Coimbra (CNC- UC), Coimbra, Portugal
| | - Rodrigo A Cunha
- Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
- Center for Neuroscience and Cell Biology- University of Coimbra (CNC- UC), Coimbra, Portugal
| | - Paula Agostinho
- Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
- Center for Neuroscience and Cell Biology- University of Coimbra (CNC- UC), Coimbra, Portugal
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Tyurikova O, Shih P, Dembitskaya Y, Savtchenko LP, McHugh TJ, Rusakov DA, Semyanov A. K + efflux through postsynaptic NMDA receptors suppresses local astrocytic glutamate uptake. Glia 2022; 70:961-974. [PMID: 35084774 PMCID: PMC9132042 DOI: 10.1002/glia.24150] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 01/14/2022] [Accepted: 01/14/2022] [Indexed: 12/31/2022]
Abstract
Glutamatergic transmission prompts K+ efflux through postsynaptic NMDA receptors. The ensuing hotspot of extracellular K+ elevation depolarizes presynaptic terminal, boosting glutamate release, but whether this also affects glutamate uptake in local astroglia has remained an intriguing question. Here, we find that the pharmacological blockade, or conditional knockout, of postsynaptic NMDA receptors suppresses use-dependent increase in the amplitude and duration of the astrocytic glutamate transporter current (IGluT ), whereas blocking astrocytic K+ channels prevents the duration increase only. Glutamate spot-uncaging reveals that astrocyte depolarization, rather than extracellular K+ rises per se, is required to reduce the amplitude and duration of IGluT . Biophysical simulations confirm that local transient elevations of extracellular K+ can inhibit local glutamate uptake in fine astrocytic processes. Optical glutamate sensor imaging and a two-pathway test relate postsynaptic K+ efflux to enhanced extrasynaptic glutamate signaling. Thus, repetitive glutamatergic transmission triggers a feedback loop in which postsynaptic K+ efflux can transiently facilitate presynaptic release while reducing local glutamate uptake.
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Affiliation(s)
- Olga Tyurikova
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
- Department of Clinical and Experimental EpilepsyUCL Institute of Neurology, Queen SquareLondonUK
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
| | - Pei‐Yu Shih
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
| | - Yulia Dembitskaya
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
| | - Leonid P. Savtchenko
- Department of Clinical and Experimental EpilepsyUCL Institute of Neurology, Queen SquareLondonUK
| | - Thomas J. McHugh
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
- RIKEN Center for Brain Science, Wako‐shiSaitamaJapan
| | - Dmitri A. Rusakov
- Department of Clinical and Experimental EpilepsyUCL Institute of Neurology, Queen SquareLondonUK
| | - Alexey Semyanov
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
- Department of Clinical Pharmacology, Sechenov First Moscow State Medical UniversityMoscowRussia
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Popov A, Denisov P, Bychkov M, Brazhe A, Lyukmanova E, Shenkarev Z, Lazareva N, Verkhratsky A, Semyanov A. Caloric restriction triggers morphofunctional remodeling of astrocytes and enhances synaptic plasticity in the mouse hippocampus. Cell Death Dis 2020; 11:208. [PMID: 32231202 PMCID: PMC7105492 DOI: 10.1038/s41419-020-2406-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 02/15/2020] [Accepted: 02/18/2020] [Indexed: 11/22/2022]
Abstract
Calorie-restricted (CR) diet has multiple beneficial effects on brain function. Here we report morphological and functional changes in hippocampal astrocytes in 3-months-old mice subjected to 1 month of the diet. Whole-cell patch-clamp recordings were performed in the CA1 stratum (str.) radiatum astrocytes of hippocampal slices. The cells were also loaded with fluorescent dye through the patch pipette. CR did not affect the number of astrocytic branches but increased the volume fraction (VF) of distal perisynaptic astrocytic leaflets. The astrocyte growth did not lead to a decrease in the cell input resistance, which may be attributed to a decrease in astrocyte coupling through the gap junctions. Western blotting revealed a decrease in the expression of Cx43 but not Cx30. Immunocytochemical analysis demonstrated a decrease in the density and size of Cx43 clusters. Cx30 cluster density did not change, while their size increased in the vicinity of astrocytic soma. CR shortened K+ and glutamate transporter currents in astrocytes in response to 5 × 50 Hz Schaffer collateral stimulation. However, no change in the expression of astrocytic glutamate transporter 1 (GLT-1) was observed, while the level of glutamine synthetase (GS) decreased. These findings suggest that enhanced enwrapping of synapses by the astrocytic leaflets reduces glutamate and K+ spillover. Reduced spillover led to a decreased contribution of extrasynaptic N2B containing N-methyl-D-aspartate receptors (NMDARs) to the tail of burst-induced EPSCs. The magnitude of long-term potentiation (LTP) in the glutamatergic CA3–CA1 synapses was significantly enhanced after CR. This enhancement was abolished by N2B-NMDARs antagonist. Our findings suggest that astrocytic morphofunctional remodeling is responsible for enhanced synaptic plasticity, which provides a basis for improved learning and memory reported after CR.
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Affiliation(s)
- Alexander Popov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya street 16/10, Moscow, 117997, Russia
| | - Pavel Denisov
- University of Nizhny Novgorod, Gagarin Ave. 23, Nizhny Novgorod, 603950, Russia
| | - Maxim Bychkov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya street 16/10, Moscow, 117997, Russia
| | - Alexey Brazhe
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya street 16/10, Moscow, 117997, Russia.,Faculty of Biology, Moscow State University, Leninskie Gory 1/12, Moscow, 119234, Russia
| | - Ekaterina Lyukmanova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya street 16/10, Moscow, 117997, Russia
| | - Zakhar Shenkarev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya street 16/10, Moscow, 117997, Russia
| | - Natalia Lazareva
- Sechenov First Moscow State Medical University, Bolshaya Pirogovskaya, 19с1, Moscow, 119146, Russia
| | - Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK. .,Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Alexey Semyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya street 16/10, Moscow, 117997, Russia. .,Faculty of Biology, Moscow State University, Leninskie Gory 1/12, Moscow, 119234, Russia. .,Sechenov First Moscow State Medical University, Bolshaya Pirogovskaya, 19с1, Moscow, 119146, Russia.
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Lebedeva A, Plata A, Nosova O, Tyurikova O, Semyanov A. Activity-dependent changes in transporter and potassium currents in hippocampal astrocytes. Brain Res Bull 2018; 136:37-43. [DOI: 10.1016/j.brainresbull.2017.08.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 08/29/2017] [Accepted: 08/30/2017] [Indexed: 01/01/2023]
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Wanke E, Gullo F, Dossi E, Valenza G, Becchetti A. Neuron-glia cross talk revealed in reverberating networks by simultaneous extracellular recording of spikes and astrocytes' glutamate transporter and K+ currents. J Neurophysiol 2016; 116:2706-2719. [PMID: 27683885 PMCID: PMC5133298 DOI: 10.1152/jn.00509.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 09/22/2016] [Indexed: 01/11/2023] Open
Abstract
In neocortex networks, we simultaneously captured spikes and the slower astrocytes' K+and glutamate transporter (GluT) currents with the use of individual MEA electrodes. Inward and outward K+currents in different regions of the glial syncytium suggested that spatial buffering was operant. Moreover, in organotypic slices from ventral tegmental area and prefrontal cortex, the large GluT current amplitudes allowed to measure transporter currents with a single electrode. Our method allows direct study of the dynamic interplay of different cell types in excitable and nonexcitable tissue. Astrocytes uptake synaptically released glutamate with electrogenic transporters (GluT) and buffer the spike-dependent extracellular K+ excess with background K+ channels. We studied neuronal spikes and the slower astrocytic signals on reverberating neocortical cultures and organotypic slices from mouse brains. Spike trains and glial responses were simultaneously captured from individual sites of multielectrode arrays (MEA) by splitting the recorded traces into appropriate filters and reconstructing the original signal by deconvolution. GluT currents were identified by using dl-threo-β-benzyloxyaspartate (TBOA). K+ currents were blocked by 30 μM Ba2+, suggesting a major contribution of inwardly rectifying K+ currents. Both types of current were tightly correlated with the spike rate, and their astrocytic origin was tested in primary cultures by blocking glial proliferation with cytosine β-d-arabinofuranoside (AraC). The spike-related, time-locked inward and outward K+ currents in different regions of the astrocyte syncytium were consistent with the assumptions of the spatial K+ buffering model. In organotypic slices from ventral tegmental area and prefrontal cortex, the GluT current amplitudes exceeded those observed in primary cultures by several orders of magnitude, which allowed to directly measure transporter currents with a single electrode. Simultaneously measuring cell signals displaying widely different amplitudes and kinetics will help clarify the neuron-glia interplay and make it possible to follow the cross talk between different cell types in excitable as well as nonexcitable tissue.
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Affiliation(s)
- Enzo Wanke
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
| | - Francesca Gullo
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
| | - Elena Dossi
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
| | - Gaetano Valenza
- Research Centre "E. Piaggio" and Department of Information Engineering, School of Engineering, University of Pisa, Pisa, Italy
| | - Andrea Becchetti
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
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Activity-Dependent Plasticity of Astroglial Potassium and Glutamate Clearance. Neural Plast 2015; 2015:109106. [PMID: 26346563 PMCID: PMC4539499 DOI: 10.1155/2015/109106] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 04/17/2015] [Indexed: 12/21/2022] Open
Abstract
Recent evidence has shown that astrocytes play essential roles in synaptic transmission and plasticity. Nevertheless, how neuronal activity alters astroglial functional properties and whether such properties also display specific forms of plasticity still remain elusive. Here, we review research findings supporting this aspect of astrocytes, focusing on their roles in the clearance of extracellular potassium and glutamate, two neuroactive substances promptly released during excitatory synaptic transmission. Their subsequent removal, which is primarily carried out by glial potassium channels and glutamate transporters, is essential for proper functioning of the brain. Similar to neurons, different forms of short- and long-term plasticity in astroglial uptake have been reported. In addition, we also present novel findings showing robust potentiation of astrocytic inward currents in response to repetitive stimulations at mild frequencies, as low as 0.75 Hz, in acute hippocampal slices. Interestingly, neurotransmission was hardly affected at this frequency range, suggesting that astrocytes may be more sensitive to low frequency stimulation and may exhibit stronger plasticity than neurons to prevent hyperexcitability. Taken together, these important findings strongly indicate that astrocytes display both short- and long-term plasticity in their clearance of excess neuroactive substances from the extracellular space, thereby regulating neuronal activity and brain homeostasis.
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Sibille J, Zapata J, Teillon J, Rouach N. Astroglial calcium signaling displays short-term plasticity and adjusts synaptic efficacy. Front Cell Neurosci 2015; 9:189. [PMID: 26074766 PMCID: PMC4444818 DOI: 10.3389/fncel.2015.00189] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 04/29/2015] [Indexed: 01/14/2023] Open
Abstract
Astrocytes are dynamic signaling brain elements able to sense neuronal inputs and to respond by complex calcium signals, which are thought to represent their excitability. Such signaling has been proposed to modulate, or not, neuronal activities ranging from basal synaptic transmission to epileptiform discharges. However, whether calcium signaling in astrocytes exhibits activity-dependent changes and acutely modulates short-term synaptic plasticity is currently unclear. We here show, using dual recordings of astroglial calcium signals and synaptic transmission, that calcium signaling in astrocytes displays, concomitantly to excitatory synapses, short-term plasticity in response to prolonged repetitive and tetanic stimulations of Schaffer collaterals. We also found that acute inhibition of calcium signaling in astrocytes by intracellular calcium chelation rapidly potentiates excitatory synaptic transmission and short-term plasticity of Shaffer collateral CA1 synapses, i.e., paired-pulse facilitation and responses to tetanic and prolonged repetitive stimulation. These data reveal that calcium signaling of astrocytes is plastic and down-regulates basal transmission and short-term plasticity of hippocampal CA1 glutamatergic synapses.
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Affiliation(s)
- Jérémie Sibille
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France ; Université Paris Diderot, Sorbonne Paris Cité Paris, France
| | - Jonathan Zapata
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France
| | - Jérémie Teillon
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050 Paris, France
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Protein mutated in paroxysmal dyskinesia interacts with the active zone protein RIM and suppresses synaptic vesicle exocytosis. Proc Natl Acad Sci U S A 2015; 112:2935-41. [PMID: 25730884 DOI: 10.1073/pnas.1501364112] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Paroxysmal nonkinesigenic dyskinesia (PNKD) is an autosomal dominant episodic movement disorder precipitated by coffee, alcohol, and stress. We previously identified the causative gene but the function of the encoded protein remains unknown. We also generated a PNKD mouse model that revealed dysregulated dopamine signaling in vivo. Here, we show that PNKD interacts with synaptic active zone proteins Rab3-interacting molecule (RIM)1 and RIM2, localizes to synapses, and modulates neurotransmitter release. Overexpressed PNKD protein suppresses release, and mutant PNKD protein is less effective than wild-type at inhibiting exocytosis. In PNKD KO mice, RIM1/2 protein levels are reduced and synaptic strength is impaired. Thus, PNKD is a novel synaptic protein with a regulatory role in neurotransmitter release.
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Lee J, Favorov OV, Tommerdahl M, Lee CJ, Whitsel BL. Attenuated Glial K(+) Clearance Contributes to Long-Term Synaptic Potentiation Via Depolarizing GABA in Dorsal Horn Neurons of Rat Spinal Cord. Exp Neurobiol 2014; 23:53-64. [PMID: 24737940 PMCID: PMC3984957 DOI: 10.5607/en.2014.23.1.53] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 03/05/2014] [Accepted: 03/05/2014] [Indexed: 11/19/2022] Open
Abstract
It has been reported that long-term enhancement of superficial dorsal horn (DHs) excitatory synaptic transmission underlies central sensitization, secondary hyperalgesia, and persistent pain. We tested whether impaired clearance of K(+) and glutamate by glia in DHs may contribute to initiation and maintenance of the CNS pain circuit and sensorimotor abnormalities. Transient exposure of the spinal cord slice to fluorocitrate (FC) is shown to be accompanied by a protracted decrease of the DHs optical response to repetitive electrical stimulation of the ipsilateral dorsal root, and by a similarly protracted increase in the postsynaptic response of the DHs like LTP. It also is shown that LTPFC does not occur in the presence of APV, and becomes progressively smaller as [K(+)]o in the perfusion solution decreased from 3.0 mM to 0.0 mM. Interestingly LTPFC is reduced by bath application of Bic. Whole-cell patch recordings were carried out to evaluate the effects of FC on the response of DHs neurons to puffer-applied GABA. The observations reveal that transient exposure to FC is reliably accompanied by a prolonged (>1 hr) depolarizing shift of the equilibrium potential for the DHs neuron transmembrane ionic currents evoked by GABA. Considered collectively, the findings demonstrate that LTPFC involves (1) elevation of [K(+)]o in the DHs, (2) NMDAR activation, and (3) conversion of the effect of GABA on DHs neurons from inhibition to excitation. It is proposed that a transient impairment of astrocyte energy production can trigger the cascade of dorsal horn mechanisms that underlies hyperalgesia and persistent pain.
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Affiliation(s)
- Jaekwang Lee
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. ; WCI Center for Functional Connectomics, Institute of Science and Technology (KIST), Seoul, Korea
| | - Oleg V Favorov
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Mark Tommerdahl
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - C Justin Lee
- WCI Center for Functional Connectomics, Institute of Science and Technology (KIST), Seoul, Korea. ; KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, Korea
| | - Barry L Whitsel
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. ; Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Diversity of astroglial functions alludes to subcellular specialisation. Trends Neurosci 2014; 37:228-42. [PMID: 24631033 DOI: 10.1016/j.tins.2014.02.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Revised: 02/12/2014] [Accepted: 02/13/2014] [Indexed: 01/23/2023]
Abstract
Rapid signal exchange between astroglia and neurons has emerged as an essential element of neural circuits of the brain. However, the increasing variety of mechanisms contributing to this signalling appears to be facing a conceptual stalemate. The communication medium of astroglia involves intracellular [Ca(2+)] waves, which until recently have been associated with slow, global [Ca(2+)] rises. How such a uniform trigger could handle fast and diverse molecular messages remains unexplained. Recent studies have, however, revealed a variety of apparently independent Ca(2+) activities within individual astrocytic compartments, also indicating the prevalence of subcellular segregation for some signalling mechanisms. These signs of intracellular compartmentalisation might provide the key to the multitude of adaptive roles played by astroglia.
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Retrograde Synaptic Signaling Mediated by K+ Efflux through Postsynaptic NMDA Receptors. Cell Rep 2013; 5:941-51. [DOI: 10.1016/j.celrep.2013.10.026] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 09/03/2013] [Accepted: 10/16/2013] [Indexed: 11/18/2022] Open
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Dallérac G, Chever O, Rouach N. How do astrocytes shape synaptic transmission? Insights from electrophysiology. Front Cell Neurosci 2013; 7:159. [PMID: 24101894 PMCID: PMC3787198 DOI: 10.3389/fncel.2013.00159] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 09/02/2013] [Indexed: 02/01/2023] Open
Abstract
A major breakthrough in neuroscience has been the realization in the last decades that the dogmatic view of astroglial cells as being merely fostering and buffering elements of the nervous system is simplistic. A wealth of investigations now shows that astrocytes actually participate in the control of synaptic transmission in an active manner. This was first hinted by the intimate contacts glial processes make with neurons, particularly at the synaptic level, and evidenced using electrophysiological and calcium imaging techniques. Calcium imaging has provided critical evidence demonstrating that astrocytic regulation of synaptic efficacy is not a passive phenomenon. However, given that cellular activation is not only represented by calcium signaling, it is also crucial to assess concomitant mechanisms. We and others have used electrophysiological techniques to simultaneously record neuronal and astrocytic activity, thus enabling the study of multiple ionic currents and in depth investigation of neuro-glial dialogues. In the current review, we focus on the input such approach has provided in the understanding of astrocyte-neuron interactions underlying control of synaptic efficacy.
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Affiliation(s)
- Glenn Dallérac
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, CNRS UMR 7241, INSERM U1050, Collège de France Paris, France
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Sibille J, Pannasch U, Rouach N. Astroglial potassium clearance contributes to short-term plasticity of synaptically evoked currents at the tripartite synapse. J Physiol 2013; 592:87-102. [PMID: 24081156 DOI: 10.1113/jphysiol.2013.261735] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Astroglial processes enclose ∼60% of CA1 hippocampal synapses to form the tripartite synapse. Although astrocytes express ionic channels, neurotransmitter receptors and transporters to detect neuronal activity, the nature, plasticity and impact of the currents induced by neuronal activity on short-term synaptic plasticity remain elusive in hippocampal astrocytes. Using simultaneous electrophysiological recordings of astrocytes and neurons, we found that single stimulation of Schaffer collaterals in hippocampal slices evokes in stratum radiatum astrocytes a complex prolonged inward current synchronized to synaptic and spiking activity in CA1 pyramidal cells. The astroglial current is composed of three components sensitive to neuronal activity, i.e. a long-lasting potassium current mediated by Kir4.1 channels, a transient glutamate transporter current and a slow residual current, partially mediated by GABA transporters and Kir4.1-independent potassium channels. We show that all astroglial membrane currents exhibit activity-dependent short-term plasticity. However, only the astroglial glutamate transporter current displays neuronal-like dynamics and plasticity. As Kir4.1 channel-mediated potassium uptake contributes to 80% of the synaptically evoked astroglial current, we investigated in turn its impact on short-term synaptic plasticity. Using glial conditional Kir4.1 knockout mice, we found that astroglial potassium uptake reduces synaptic responses to repetitive stimulation and post-tetanic potentiation. These results show that astrocytes integrate synaptic activity via multiple ionic channels and transporters and contribute to short-term plasticity in part via potassium clearance mediated by Kir4.1 channels.
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Affiliation(s)
- Jérémie Sibille
- N. Rouach: Neuroglial Interactions in Cerebral Physiopathology, Collège de France, CIRB, CNRS UMR 7241, INSERM U1050, 11, place Marcelin Berthelot, 75005 Paris, France.
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Afzalov R, Pryazhnikov E, Shih PY, Kondratskaya E, Zobova S, Leino S, Salminen O, Khiroug L, Semyanov A. Low micromolar Ba(2+) potentiates glutamate transporter current in hippocampal astrocytes. Front Cell Neurosci 2013; 7:135. [PMID: 24009556 PMCID: PMC3755269 DOI: 10.3389/fncel.2013.00135] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 08/06/2013] [Indexed: 11/13/2022] Open
Abstract
Glutamate uptake, mediated by electrogenic glutamate transporters largely localized in astrocytes, is responsible for the clearance of glutamate released during excitatory synaptic transmission. Glutamate uptake also determines the availability of glutamate for extrasynaptic glutamate receptors. The efficiency of glutamate uptake is commonly estimated from the amplitude of transporter current recorded in astrocytes. We recorded currents in voltage-clamped hippocampal CA1 stratum radiatum astrocytes in rat hippocampal slices induced by electrical stimulation of the Schaffer collaterals. A Ba(2+)-sensitive K(+) current mediated by inward rectifying potassium channels (Kir) accompanied the transporter current. Surprisingly, Ba(2+) not only suppressed the K(+) current and changed holding current (presumably, mediated by Kir) but also increased the transporter current at lower concentrations. However, Ba(2+) did not significantly increase the uptake of aspartate in cultured astrocytes, suggesting that increase in the amplitude of the transporter current does not always reflect changes in glutamate uptake.
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Affiliation(s)
- Ramil Afzalov
- Neuroscience Center, University of Helsinki Helsinki, Finland ; RIKEN Brain Science Institute Wako-shi, Japan
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Inhibition of glycogen synthase kinase-3β by lithium chloride suppresses 6-hydroxydopamine-induced inflammatory response in primary cultured astrocytes. Neurochem Int 2013; 63:345-53. [PMID: 23871716 DOI: 10.1016/j.neuint.2013.07.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 06/29/2013] [Accepted: 07/07/2013] [Indexed: 11/21/2022]
Abstract
An increasing amount of evidence has emerged to suggest that neuroinflammatory process is involved in the pathogenesis of Parkinson's disease (PD). Activated microglia and astrocytes are found in the substantia nigra (SN) of Parkinson's disease brains as well as in animal models of Parkinson's disease. Although reactive astrocytes are involved in the progression of PD, the role of reactive astrocytes in neuroinflammation of PD has received limited attention to date. Recently, Glycogen synthase kinase-3β (GSK-3β) was identified as a crucial regulator of the inflammatory response. The purpose of this study was to explore the mechanism by which 6-hydroxydopamine (6-OHDA) induces inflammatory response in astrocytes and observe the anti-inflammatory effect of lithium chloride (LiCl) on 6-OHDA-treated astrocytes. In the present study, we found that glial fibrillary acidic protein (GFAP) was markedly upregulated in the presence of 6-OHDA. Moreover, our results revealed that proinflammatory molecules including inducible nitric oxide synthase (iNOS), nitric oxide (NO), cyclooxygenase-2(COX-2), prostaglandins E2 (PGE2), and tumor necrosis factor-α (TNF-α) were obviously increased in astrocytes exposed to 6-OHDA. Western blot analysis revealed that 6-OHDA significantly increased dephosphorylation/activation of GSK-3β as well as the nuclear translocation of nuclear factor-κB (NF-κB) p65. Besides, GSK-3β inhibitor LiCl and SB415286 inhibited the GSK-3β/NF-κB signaling pathway, leading to the reduction of proinflammatory molecules in 6-OHDA-activated astrocytes. These results confirmed that GSK-3β inhibitor LiCl and SB415286 provide protection against neuroinflammation in 6-OHDA-treated astrocytes. Therefore, GSK-3β may be a potential therapeutic target for the treatment of PD.
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Devaraju P, Sun MY, Myers TL, Lauderdale K, Fiacco TA. Astrocytic group I mGluR-dependent potentiation of astrocytic glutamate and potassium uptake. J Neurophysiol 2013; 109:2404-14. [PMID: 23427307 DOI: 10.1152/jn.00517.2012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
One of the most important functions of astrocytes is removal of glutamate released during synaptic transmission. Surprisingly, the mechanisms by which astrocyte glutamate uptake is acutely modulated remain to be clarified. Astrocytes express metabotropic glutamate receptors (mGluRs) and other G protein-coupled receptors (GPCRs), which are activated during neuronal activity. Here, we test the hypothesis that astrocytic group I mGluRs acutely regulate glutamate uptake by astrocytes in situ. This hypothesis was tested in acute mouse hippocampal slices. Activation of astrocytic mGluRs, using a tetanic high-frequency stimulus (HFS) applied to Schaffer collaterals, led to potentiation of the amplitude of the synaptically evoked glutamate transporter currents (STCs) and associated charge transfer without changes in kinetics. Similar potentiation of STCs was not observed in the presence of group I mGluR antagonists or the PKC inhibitor, PKC 19-36, suggesting that HFS-induced potentiation of astrocyte glutamate uptake is astrocytic group I mGluR and PKC dependent. Pharmacological stimulation of a transgenic GPCR (MrgA1R), expressed exclusively in astrocytes, also potentiated STC amplitude and charge transfer, albeit quicker and shorter lasting compared with HFS-induced potentiation. The amplitude of the slow, inward astrocytic current due to potassium (K(+)) influx was also enhanced following activation of the endogenous mGluRs or the astrocyte-specific MrgA1 Gq GPCRs. Taken together, these findings suggest that astrocytic group I mGluR activation has a synergistic, modulatory effect on the uptake of glutamate and K(+).
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Affiliation(s)
- Prakash Devaraju
- Department of Cell Biology and Neuroscience, University of California, Riverside, CA, USA
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17
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Acute antidepressant treatment differently modulates ERK/MAPK activation in neurons and astrocytes of the adult mouse prefrontal cortex. Neuroscience 2012; 232:161-8. [PMID: 23238574 DOI: 10.1016/j.neuroscience.2012.11.061] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 11/13/2012] [Accepted: 11/30/2012] [Indexed: 01/20/2023]
Abstract
The onset of action of antidepressants (ADs) usually takes several weeks, but first molecular responses to these drugs may appear already after acute administration. The Extracellular Signal-regulated Kinase/Mitogen-Activated Protein Kinase (ERK/MAPK) signaling pathway is a target of ADs and an important pathway involved in cellular plasticity. In major depressive disorder (MDD), especially the prefrontal cortex (PFC) and hippocampus (Hip) are most likely affected in depressive patients and recent work revealed a hyperactivated ERK signaling in the rat PFC after chronic stress, a precipitating factor for MDD. Strong evidences support that not only neurons but also astrocytes participate in neuronal activity and may therefore additionally be a substrate of AD action. In this study, we show by Western blot that neither fluoxetine (FLX) nor desipramine (DMI) preferentially affects the activation of one of the two ERK isoforms, ERK1 and ERK2, with respect to the other. Further immunohistochemical analysis in the PFC revealed that basal levels of phospho-activated ERK (pERK) are mostly found in neurons in contrast to very few astrocytes. Both ADs can inhibit neuronal pERK as early as 15 min after drug administration with peculiar regional and layer specificities. Contrarily, at this time point none of the two ADs shows a clear modulation of astrocytic pERK. We propose that this mechanism of action of ADs may be protective against an exacerbated cortical ERK activity that may exert detrimental effects on susceptible neuronal populations. Our findings on acute effects of AD treatment in the adult mouse PFC encourage to examine further how this treatment might influence pERK in animal models of depression to identify early targets of AD action.
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18
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Abstract
Rapid signal exchange between astroglia and neurons has emerged as a key player in neural communication in the brain. To understand the mechanisms involved, it is often important to have access to individual astrocytes while monitoring the activity of nearby synapses. Achieving this with standard electrophysiological tools is not always feasible. The protocol presented here enables the monitoring of synaptic activity using whole-cell current-clamp recordings from a local astrocyte. This approach takes advantage of the fact that the low input resistance of electrically passive astroglia allows extracellular currents to pass through the astrocytic membrane with relatively little attenuation. Once the slice preparation is ready, it takes ~30 min to several hours to implement this protocol, depending on the experimental design, which is similar to other patch-clamp techniques. The technique presented here can be used to directly access the intracellular medium of individual astrocytes while examining synapses functioning in their immediate proximity.
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19
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Local generation of glia is a major astrocyte source in postnatal cortex. Nature 2012; 484:376-80. [PMID: 22456708 DOI: 10.1038/nature10959] [Citation(s) in RCA: 335] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 02/14/2012] [Indexed: 12/21/2022]
Abstract
Glial cells constitute nearly 50% of the cells in the human brain. Astrocytes, which make up the largest glial population, are crucial to the regulation of synaptic connectivity during postnatal development. Because defects in astrocyte generation are associated with severe neurological disorders such as brain tumours, it is important to understand how astrocytes are produced. Astrocytes reportedly arise from two sources: radial glia in the ventricular zone and progenitors in the subventricular zone, with the contribution from each region shifting with time. During the first three weeks of postnatal development, the glial cell population, which contains predominantly astrocytes, expands 6-8-fold in the rodent brain. Little is known about the mechanisms underlying this expansion. Here we show that a major source of glia in the postnatal cortex in mice is the local proliferation of differentiated astrocytes. Unlike glial progenitors in the subventricular zone, differentiated astrocytes undergo symmetric division, and their progeny integrate functionally into the existing glial network as mature astrocytes that form endfeet with blood vessels, couple electrically to neighbouring astrocytes, and take up glutamate after neuronal activity.
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20
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Shavit E, Michaelson DM, Chapman J. Anatomical localization of protease-activated receptor-1 and protease-mediated neuroglial crosstalk on peri-synaptic astrocytic endfeet. J Neurochem 2011; 119:460-73. [PMID: 21854391 DOI: 10.1111/j.1471-4159.2011.07436.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We studied the localization, activation and function of protease-activated receptor 1 (PAR-1) at the CNS synapse utilizing rat brain synaptosomes and slices. Confocal immunofluoresence and transmission electron microscopy in brain slices with pre-embedding diaminobenzidine (DAB) immunostaining found PAR-1 predominantly localized to the peri-synaptic astrocytic endfeet. Structural confocal immunofluorescence microscopy studies of isolated synaptosomes revealed spherical structures stained with anti-PAR-1 antibody which co-stained mainly for glial-filament acidic protein compared with the neuronal markers synaptophysin and PSD-95. Immunoblot studies of synaptosomes demonstrated an appropriate major band corresponding to PAR-1 and activation of the receptor by a specific agonist peptide (SFLLRN) significantly modulated phosphorylated extracellular signal-regulated kinase. A significant membrane potential depolarization was produced by thrombin (1 U/mL) and the PAR-1 agonist (100 μM) and depolarization by high K(+) elevated extracellular thrombin-like activity in the synaptosomes preparation. The results indicate PAR-1 localized to the peri-synaptic astrocytic endfeet is most likely activated by synaptic proteases and induces cellular signaling and modulation of synaptic electrophysiology. A protease mediated neuron-glia pathway may be important in both physiological and pathological regulation of the synapse.
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Affiliation(s)
- Efrat Shavit
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv, Israel
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21
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Honsek SD, Walz C, Kafitz KW, Rose CR. Astrocyte calcium signals at Schaffer collateral to CA1 pyramidal cell synapses correlate with the number of activated synapses but not with synaptic strength. Hippocampus 2010; 22:29-42. [DOI: 10.1002/hipo.20843] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2010] [Indexed: 11/08/2022]
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22
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Abstract
There is a growing body of evidence suggesting a functional relationship between Ca2+ signals generated in astroglia and the functioning of nearby excitatory synapses. Interference with endogenous Ca2+ homeostasis inside individual astrocytes has been shown to affect synaptic transmission and its use-dependent changes. However, establishing the causal link between source-specific, physiologically relevant intracellular Ca2+ signals, the astrocytic release machinery and the consequent effects on synaptic transmission has proved difficult. Improved methods of Ca2+ monitoring in situ will be essential for resolving the ambiguity in understanding the underlying Ca2+ signalling cascades.
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Affiliation(s)
- Christian Henneberger
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 2BG, UK.
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23
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Sharif A, Prevot V. ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system. Neurochem Int 2010; 57:344-58. [PMID: 20685225 DOI: 10.1016/j.neuint.2010.05.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 03/29/2010] [Accepted: 05/18/2010] [Indexed: 10/19/2022]
Abstract
Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.
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Affiliation(s)
- Ariane Sharif
- Inserm, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the postnatal Brain, Lille, France.
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24
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Reyes-Haro D, Müller J, Boresch M, Pivneva T, Benedetti B, Scheller A, Nolte C, Kettenmann H. Neuron-astrocyte interactions in the medial nucleus of the trapezoid body. ACTA ACUST UNITED AC 2010; 135:583-94. [PMID: 20479112 PMCID: PMC2888059 DOI: 10.1085/jgp.200910354] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The calyx of Held (CoH) synapse serves as a model system to analyze basic mechanisms of synaptic transmission. Astrocyte processes are part of the synaptic structure and contact both pre- and postsynaptic membranes. In the medial nucleus of the trapezoid body (MNTB), midline stimulation evoked a current response that was not mediated by glutamate receptors or glutamate uptake, despite the fact that astrocytes express functional receptors and transporters. However, astrocytes showed spontaneous Ca2+ responses and neuronal slow inward currents (nSICs) were recorded in the postsynaptic principal neurons (PPNs) of the MNTB. These currents were correlated with astrocytic Ca2+ activity because dialysis of astrocytes with BAPTA abolished nSICs. Moreover, the frequency of these currents was increased when Ca2+ responses in astrocytes were elicited. NMDA antagonists selectively blocked nSICs while D-serine degradation significantly reduced NMDA-mediated currents. In contrast to previous studies in the hippocampus, these NMDA-mediated currents were rarely synchronized.
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Affiliation(s)
- Daniel Reyes-Haro
- Cellular Neuroscience, Max Delbrück Center for Molecular Medicine, 13092 Berlin, Germany
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25
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Zhang X, Poo MM. Progress in neural plasticity. SCIENCE CHINA-LIFE SCIENCES 2010; 53:322-329. [DOI: 10.1007/s11427-010-0062-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Accepted: 01/19/2010] [Indexed: 11/25/2022]
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26
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Progress in glial cell studies in some laboratories in China. SCIENCE CHINA-LIFE SCIENCES 2010; 53:330-337. [DOI: 10.1007/s11427-010-0067-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 02/26/2010] [Indexed: 01/12/2023]
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27
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Henneberger C, Papouin T, Oliet SHR, Rusakov DA. Long-term potentiation depends on release of D-serine from astrocytes. Nature 2010; 463:232-6. [PMID: 20075918 PMCID: PMC2807667 DOI: 10.1038/nature08673] [Citation(s) in RCA: 961] [Impact Index Per Article: 68.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Accepted: 11/11/2009] [Indexed: 11/08/2022]
Abstract
Long-term potentiation (LTP) of synaptic transmission provides an experimental model for studying mechanisms of memory. The classical form of LTP relies on N-methyl-D-aspartate receptors (NMDARs), and it has been shown that astroglia can regulate their activation through Ca(2+)-dependent release of the NMDAR co-agonist D-serine. Release of D-serine from glia enables LTP in cultures and explains a correlation between glial coverage of synapses and LTP in the supraoptic nucleus. However, increases in Ca(2+) concentration in astroglia can also release other signalling molecules, most prominently glutamate, ATP and tumour necrosis factor-alpha, whereas neurons themselves can synthesize and supply D-serine. Furthermore, loading an astrocyte with exogenous Ca(2+) buffers does not suppress LTP in hippocampal area CA1 (refs 14-16), and the physiological relevance of experiments in cultures or strong exogenous stimuli applied to astrocytes has been questioned. The involvement of glia in LTP induction therefore remains controversial. Here we show that clamping internal Ca(2+) in individual CA1 astrocytes blocks LTP induction at nearby excitatory synapses by decreasing the occupancy of the NMDAR co-agonist sites. This LTP blockade can be reversed by exogenous D-serine or glycine, whereas depletion of D-serine or disruption of exocytosis in an individual astrocyte blocks local LTP. We therefore demonstrate that Ca(2+)-dependent release of D-serine from an astrocyte controls NMDAR-dependent plasticity in many thousands of excitatory synapses nearby.
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Affiliation(s)
| | - Thomas Papouin
- Inserm U862, Neurocentre Magendie, Bordeaux F-33077, France
- Université de Bordeaux, F-33077, France
| | - Stéphane H. R. Oliet
- Inserm U862, Neurocentre Magendie, Bordeaux F-33077, France
- Université de Bordeaux, F-33077, France
| | - Dmitri A. Rusakov
- UCL Institute of Neurology, University College London, London WC1N 3BG
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28
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Zhang H, Xin W, Dougherty PM. Synaptically evoked glutamate transporter currents in Spinal Dorsal Horn Astrocytes. Mol Pain 2009; 5:36. [PMID: 19570219 PMCID: PMC2713213 DOI: 10.1186/1744-8069-5-36] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 07/01/2009] [Indexed: 12/02/2022] Open
Abstract
Background Removing and sequestering synaptically released glutamate from the extracellular space is carried out by specific plasma membrane transporters that are primarily located in astrocytes. Glial glutamate transporter function can be monitored by recording the currents that are produced by co-transportation of Na+ ions with the uptake of glutamate. The goal of this study was to characterize glutamate transporter function in astrocytes of the spinal cord dorsal horn in real time by recording synaptically evoked glutamate transporter currents. Results Whole-cell patch clamp recordings were obtained from astrocytes in the spinal substantia gelatinosa (SG) area in spinal slices of young adult rats. Glutamate transporter currents were evoked in these cells by electrical stimulation at the spinal dorsal root entry zone in the presence of bicuculline, strychnine, DNQX and D-AP5. Transporter currents were abolished when synaptic transmission was blocked by TTX or Cd2+. Pharmacological studies identified two subtypes of glutamate transporters in spinal astrocytes, GLAST and GLT-1. Glutamate transporter currents were graded with stimulus intensity, reaching peak responses at 4 to 5 times activation threshold, but were reduced following low-frequency (0.1 – 1 Hz) repetitive stimulation. Conclusion These results suggest that glutamate transporters of spinal astrocytes could be activated by synaptic activation, and recording glutamate transporter currents may provide a means of examining the real time physiological responses of glial cells in spinal sensory processing, sensitization, hyperalgesia and chronic pain.
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Affiliation(s)
- Haijun Zhang
- Department of Anesthesiology and Pain Medicine, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
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29
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Activity-dependent neuron-glial signaling by ATP and leukemia-inhibitory factor promotes hippocampal glial cell development. ACTA ACUST UNITED AC 2009; 4:43-55. [PMID: 19267953 DOI: 10.1017/s1740925x09000076] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Activity-dependent signaling between neurons and astrocytes contributes to experience-dependent plasticity and development of the nervous system. However, mechanisms responsible for neuron-glial interactions and the releasable factors that underlie these processes are not well understood. The pro-inflammatory cytokine, leukemia-inhibitory factor (LIF), is transiently expressed postnatally by glial cells in the hippocampus and rapidly up-regulated by enhanced neural activity following seizures. To test the hypothesis that spontaneous neural activity regulates glial development in hippocampus via LIF signaling, we blocked spontaneous activity with the sodium channel blocker tetrodotoxin (TTX) in mixed hippocampal cell cultures in combination with blockers of LIF and purinergic signaling. TTX decreased the number of GFAP-expressing astrocytes in hippocampal cell culture. Furthermore, blocking purinergic signaling by P2Y receptors contributed to reduced numbers of astrocytes. Blocking activity or purinergic signaling in the presence of function-blocking antibodies to LIF did not further decrease the number of astrocytes. Moreover, hippocampal cell cultures prepared from LIF -/- mice had reduced numbers of astrocytes and activity-dependent neuron-glial signaling promoting differentiation of astrocytes was absent. The results show that endogenous LIF is required for normal development of hippocampal astrocytes, and this process is regulated by spontaneous neural impulse activity through the release of ATP.
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30
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Dividing glial cells maintain differentiated properties including complex morphology and functional synapses. Proc Natl Acad Sci U S A 2008; 106:328-33. [PMID: 19104058 DOI: 10.1073/pnas.0811353106] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is generally believed that dividing cells gain complex features of differentiation only after exiting the cell cycle because cell division and differentiation are both under such tight regulation that their coexistence is deemed unlikely. As the major proliferating cell type in the mammalian CNS, NG2 glial cells (NG2 cells) account for 5-8% of the glial cell population and form synaptic contacts with neurons. Here we report that NG2 cells divide while maintaining their differentiation, including morphological features, such as the elaboration of multiple complex cellular processes and physiological features including active glutamatergic and GABAergic synaptic responses. Not only do NG2 cells continue to receive excitatory and inhibitory synaptic inputs as they undergo mitosis, a subpopulation of dividing NG2 cells can fire action potentials upon depolarization, thereby revealing that these dividing NG2 cells retain voltage-gated ion channels as well as transmitter receptors for signal processing. These findings provide a clear counterexample of the widely perceived incompatibility between cell division and differentiation.
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31
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Wang LP, Cheung G, Kronenberg G, Gertz K, Ji S, Kempermann G, Endres M, Kettenmann H. Mild brain ischemia induces unique physiological properties in striatal astrocytes. Glia 2008; 56:925-34. [PMID: 18442086 DOI: 10.1002/glia.20660] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We studied the properties of GFAP-expressing cells in adult mouse striatum using acute brain slices from transgenic animals expressing EGFP under GFAP promoter. Under physiological conditions, two distinct populations of GFAP-EGFP cells could be identified: (1) brightly fluorescent cells had bushy processes, passive membrane properties, glutamate transporter activity, and high gap junction coupling rate typical for classical astrocytes; (2) weakly fluorescent cells were characterized by thin, clearly distinguishable processes, voltage-gated currents, complex responses to kainate, and low coupling rate reminiscent of an astrocyte subtype recently described in the hippocampus. Mild focal cerebral ischemia confers delayed neuronal cell death and astrogliosis in the striatum. Following middle cerebral artery occlusion and reperfusion, brightly fluorescent cells were the dominant GFAP-EGFP population observed within the ischemic lesion. Interestingly, the majority of these cells expressed voltage-gated channels, showed complex responses to kainate, and a high coupling rate exceeding that of brightly fluorescent control cells. A minority of cells had passive membrane properties and was coupled less compared with passive control cells. We conclude that, in the adult striatum, astrocytes undergo distinct pathophysiological changes after ischemic insults. The dominant population in the ischemic lesion constitutes a novel physiological phenotype unlike any normal astrocyte and generates a large syncytium which might be a neuroprotective response of reactive astrocytes.
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Affiliation(s)
- Li-Ping Wang
- Department of Cellular Neurosciences, Max-Delbrueck-Center for Molecular Medicine, Berlin, Germany
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