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Hladky SB, Barrand MA. Alterations in brain fluid physiology during the early stages of development of ischaemic oedema. Fluids Barriers CNS 2024; 21:51. [PMID: 38858667 PMCID: PMC11163777 DOI: 10.1186/s12987-024-00534-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 03/22/2024] [Indexed: 06/12/2024] Open
Abstract
Oedema occurs when higher than normal amounts of solutes and water accumulate in tissues. In brain parenchymal tissue, vasogenic oedema arises from changes in blood-brain barrier permeability, e.g. in peritumoral oedema. Cytotoxic oedema arises from excess accumulation of solutes within cells, e.g. ischaemic oedema following stroke. This type of oedema is initiated when blood flow in the affected core region falls sufficiently to deprive brain cells of the ATP needed to maintain ion gradients. As a consequence, there is: depolarization of neurons; neural uptake of Na+ and Cl- and loss of K+; neuronal swelling; astrocytic uptake of Na+, K+ and anions; swelling of astrocytes; and reduction in ISF volume by fluid uptake into neurons and astrocytes. There is increased parenchymal solute content due to metabolic osmolyte production and solute influx from CSF and blood. The greatly increased [K+]isf triggers spreading depolarizations into the surrounding penumbra increasing metabolic load leading to increased size of the ischaemic core. Water enters the parenchyma primarily from blood, some passing into astrocyte endfeet via AQP4. In the medium term, e.g. after three hours, NaCl permeability and swelling rate increase with partial opening of tight junctions between blood-brain barrier endothelial cells and opening of SUR1-TPRM4 channels. Swelling is then driven by a Donnan-like effect. Longer term, there is gross failure of the blood-brain barrier. Oedema resolution is slower than its formation. Fluids without colloid, e.g. infused mock CSF, can be reabsorbed across the blood-brain barrier by a Starling-like mechanism whereas infused serum with its colloids must be removed by even slower extravascular means. Large scale oedema can increase intracranial pressure (ICP) sufficiently to cause fatal brain herniation. The potentially lethal increase in ICP can be avoided by craniectomy or by aspiration of the osmotically active infarcted region. However, the only satisfactory treatment resulting in retention of function is restoration of blood flow, providing this can be achieved relatively quickly. One important objective of current research is to find treatments that increase the time during which reperfusion is successful. Questions still to be resolved are discussed.
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Affiliation(s)
- Stephen B Hladky
- Department of Pharmacology, Tennis Court Rd., Cambridge, CB2 1PD, UK.
| | - Margery A Barrand
- Department of Pharmacology, Tennis Court Rd., Cambridge, CB2 1PD, UK
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2
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Lia A, Di Spiezio A, Vitalini L, Tore M, Puja G, Losi G. Ion Channels and Ionotropic Receptors in Astrocytes: Physiological Functions and Alterations in Alzheimer's Disease and Glioblastoma. Life (Basel) 2023; 13:2038. [PMID: 37895420 PMCID: PMC10608464 DOI: 10.3390/life13102038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/03/2023] [Accepted: 10/07/2023] [Indexed: 10/29/2023] Open
Abstract
The human brain is composed of nearly one hundred billion neurons and an equal number of glial cells, including macroglia, i.e., astrocytes and oligodendrocytes, and microglia, the resident immune cells of the brain. In the last few decades, compelling evidence has revealed that glial cells are far more active and complex than previously thought. In particular, astrocytes, the most abundant glial cell population, not only take part in brain development, metabolism, and defense against pathogens and insults, but they also affect sensory, motor, and cognitive functions by constantly modulating synaptic activity. Not surprisingly, astrocytes are actively involved in neurodegenerative diseases (NDs) and other neurological disorders like brain tumors, in which they rapidly become reactive and mediate neuroinflammation. Reactive astrocytes acquire or lose specific functions that differently modulate disease progression and symptoms, including cognitive impairments. Astrocytes express several types of ion channels, including K+, Na+, and Ca2+ channels, transient receptor potential channels (TRP), aquaporins, mechanoreceptors, and anion channels, whose properties and functions are only partially understood, particularly in small processes that contact synapses. In addition, astrocytes express ionotropic receptors for several neurotransmitters. Here, we provide an extensive and up-to-date review of the roles of ion channels and ionotropic receptors in astrocyte physiology and pathology. As examples of two different brain pathologies, we focus on Alzheimer's disease (AD), one of the most diffuse neurodegenerative disorders, and glioblastoma (GBM), the most common brain tumor. Understanding how ion channels and ionotropic receptors in astrocytes participate in NDs and tumors is necessary for developing new therapeutic tools for these increasingly common neurological conditions.
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Affiliation(s)
- Annamaria Lia
- Department Biomedical Science, University of Padova, 35131 Padova, Italy; (A.L.); (A.D.S.)
| | - Alessandro Di Spiezio
- Department Biomedical Science, University of Padova, 35131 Padova, Italy; (A.L.); (A.D.S.)
- Neuroscience Institute (CNR-IN), Padova Section, 35131 Padova, Italy
| | - Lorenzo Vitalini
- Department Life Science, University of Modena and Reggio Emilia, 41125 Modena, Italy; (L.V.); (G.P.)
| | - Manuela Tore
- Institute of Nanoscience (CNR-NANO), Modena Section, 41125 Modena, Italy;
- Department Biomedical Science, Metabolic and Neuroscience, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Giulia Puja
- Department Life Science, University of Modena and Reggio Emilia, 41125 Modena, Italy; (L.V.); (G.P.)
| | - Gabriele Losi
- Institute of Nanoscience (CNR-NANO), Modena Section, 41125 Modena, Italy;
- Department Biomedical Science, Metabolic and Neuroscience, University of Modena and Reggio Emilia, 41125 Modena, Italy
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3
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Aten S, Du Y, Taylor O, Dye C, Collins K, Thomas M, Kiyoshi C, Zhou M. Chronic Stress Impairs the Structure and Function of Astrocyte Networks in an Animal Model of Depression. Neurochem Res 2023; 48:1191-1210. [PMID: 35796915 PMCID: PMC9823156 DOI: 10.1007/s11064-022-03663-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 06/18/2022] [Indexed: 01/11/2023]
Abstract
Now astrocytes appear to be the key contributors to the pathophysiology of major depression. Evidence in rodents shows that chronic stress is associated with a decreased expression of astrocytic GFAP-immunoreactivity within the cortex in addition to changes in the complexity and length of astrocyte processes. Furthermore, postmortem brains of individuals with depression have revealed a decrease in astrocyte density. Notably, astrocytes are extensively coupled to one another through gap junctions to form a network, or syncytium, and we have previously demonstrated that syncytial isopotentiality is a mechanism by which astrocytes function as an efficient system with respect to brain homeostasis. Interestingly, the question of how astrocyte network function changes following chronic stress is yet to be elucidated. Here, we sought to examine the effects of chronic stress on network-level astrocyte (dys)function. Using a transgenic aldh1l1-eGFP astrocyte reporter mouse, a six-week unpredictable chronic mild stress (UCMS) paradigm as a rodent model of major depression, and immunohistochemical approaches, we show that the morphology of individual astrocytes is altered by chronic stress exposure. Additionally, in astrocyte syncytial isopotentiality measurement, we found that UCMS impairs the syncytial coupling strength of astrocytes within the hippocampus and prefrontal cortex-two brain regions that have been implicated in the regulation of mood. Together, these findings reveal that chronic stress leads to astrocyte atrophy and impaired gap junction coupling, raising the prospect that both individual and network-level astrocyte functionality are important in the etiology of major depression and other neuropsychiatric disorders.
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Affiliation(s)
- Sydney Aten
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA
- Department of Neurology, Division of Sleep Medicine, and Program in Neuroscience, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Yixing Du
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA
| | - Olivia Taylor
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA
| | - Courtney Dye
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA
| | - Kelsey Collins
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA
| | - Matthew Thomas
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA
| | - Conrad Kiyoshi
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA
- Northern Marianas College, Saipan, MP, USA
| | - Min Zhou
- Department of Neuroscience, Ohio State University Wexner Medical Center, Graves Hall, Rm 4066C, 333 W. 10th Ave, Columbus, OH, 43210, USA.
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4
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Zhong S, Kiyoshi CM, Du Y, Wang W, Luo Y, Wu X, Taylor AT, Ma B, Aten S, Liu X, Zhou M. Genesis of a functional astrocyte syncytium in the developing mouse hippocampus. Glia 2023; 71:1081-1098. [PMID: 36598109 PMCID: PMC10777263 DOI: 10.1002/glia.24327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 12/03/2022] [Accepted: 12/15/2022] [Indexed: 01/05/2023]
Abstract
Astrocytes are increasingly shown to operate as an isopotential syncytium in brain function. Protoplasmic astrocytes acquire this ability to functionally go beyond the single-cell level by evolving into a spongiform morphology, cytoplasmically connecting into a syncytium, and expressing a high density of K+ conductance. However, none of these cellular/functional features exist in neonatal newborn astrocytes, which imposes a basic question of when a functional syncytium evolves in the developing brain. Our results show that the spongiform morphology of individual astrocytes and their spatial organization all reach stationary levels by postnatal day (P) 15 in the hippocampal CA1 region. Functionally, astrocytes begin to uniformly express a mature level of passive K+ conductance by P11. We next used syncytial isopotentiality measurement to monitor the maturation of the astrocyte syncytium. In uncoupled P1 astrocytes, the substitution of endogenous K+ by a Na+ -electrode solution ([Na+ ]p ) resulted in the total elimination of the physiological membrane potential (VM ), and outward K+ conductance as predicted by the Goldman-Hodgkin-Katz (GHK) equation. As more astrocytes are coupled to each other through gap junctions during development, the [Na+ ]p -induced loss of physiological VM and the outward K+ conductance is progressively compensated by the neighboring astrocytes. By P15, a stably established syncytial isopotentiality (-73 mV), and a fully compensated outward K+ conductance appeared in all [Na+ ]p -recorded astrocytes. Thus, in view of the developmental timeframe wherein a singular syncytium is anatomically and functionally established for intra-syncytium K+ equilibration, an astrocyte syncytium becomes fully operational at P15 in the mouse hippocampus.
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Affiliation(s)
- Shiying Zhong
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
- Department of Neurology, Shanghai 10Hospital of Tongji University, School of Medicine, Shanghai, 200072, China
| | - Conrad M. Kiyoshi
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Yixing Du
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Wei Wang
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
- Department of Physiology, Tongji Medical College, Wuhan, 430030, China
| | - Yumeng Luo
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Xiao Wu
- Department of Neurology, Wuhan First Hospital, Wuhan 430022, China
| | - Anne T. Taylor
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Baofeng Ma
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Sydney Aten
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Xueyuan Liu
- Department of Neurology, Shanghai 10Hospital of Tongji University, School of Medicine, Shanghai, 200072, China
| | - Min Zhou
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
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5
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Du Y, Brennan FH, Popovich PG, Zhou M. Microglia maintain the normal structure and function of the hippocampal astrocyte network. Glia 2022; 70:1359-1379. [PMID: 35394085 PMCID: PMC9324808 DOI: 10.1002/glia.24179] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 03/09/2022] [Accepted: 03/28/2022] [Indexed: 12/14/2022]
Abstract
Microglial control of activity‐dependent plasticity and synaptic remodeling in neuronal networks has been the subject of intense research in the past several years. Although microglia–neuron interactions have been extensively studied, less is known about how microglia influence astrocyte‐dependent control over neuronal structure and function. Here, we explored a role for microglia in regulating the structure and function of the astrocyte syncytium in mouse hippocampus. After depleting microglia using a CSF1R antagonist (PLX5622, Plexxikon), we observed severe disruption of astrocyte syncytial isopotentiality and dye coupling. A decrease in astrocyte‐specific gap junction connexin (Cx) 30 and 43 expression, at least partially accounts for these microglia‐dependent changes in astrocytes. Because neuronal function requires intact astrocyte coupling, we also evaluated the effects of microglia depletion on synaptic transmission in the hippocampus. Without microglia, the strength of synaptic transmission was reduced at baseline and after long‐term potentiation (LTP). Conversely, priming microglia with systemic injections of lipopolysaccharide enhanced CA3‐CA1 synaptic transmission. This microglia‐induced scaling of synaptic transmission was associated with increased expression of post‐synaptic scaffold proteins (Homer1) in CA1. However, astrocyte network function was not affected by microglia priming, indicating that microglia‐dependent effects on astrocytes and neurons vary across functional states. Through manipulation of microglia in the brain, our results reveal the importance of microglia in homeostatic regulation of the astrocyte syncytium and scaling of synaptic transmission. These novel mechanisms uncover a new direction for future studies interrogating microglia function in various physiological and pathological contexts.
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Affiliation(s)
- Yixing Du
- Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Faith H Brennan
- Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA.,Center for Brain and Spinal Cord Repair, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Phillip G Popovich
- Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA.,Center for Brain and Spinal Cord Repair, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Min Zhou
- Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
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6
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Chung W, Wang DS, Khodaei S, Pinguelo A, Orser BA. GABA A Receptors in Astrocytes Are Targets for Commonly Used Intravenous and Inhalational General Anesthetic Drugs. Front Aging Neurosci 2022; 13:802582. [PMID: 35087395 PMCID: PMC8787299 DOI: 10.3389/fnagi.2021.802582] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 12/20/2021] [Indexed: 12/14/2022] Open
Abstract
Background: Perioperative neurocognitive disorders (PNDs) occur commonly in older patients after anesthesia and surgery. Treating astrocytes with general anesthetic drugs stimulates the release of soluble factors that increase the cell-surface expression and function of GABAA receptors in neurons. Such crosstalk may contribute to PNDs; however, the receptor targets in astrocytes for anesthetic drugs have not been identified. GABAA receptors, which are the major targets of general anesthetic drugs in neurons, are also expressed in astrocytes, raising the possibility that these drugs act on GABAA receptors in astrocytes to trigger the release of soluble factors. To date, no study has directly examined the sensitivity of GABAA receptors in astrocytes to general anesthetic drugs that are frequently used in clinical practice. Thus, the goal of this study was to determine whether the function of GABAA receptors in astrocytes was modulated by the intravenous anesthetic etomidate and the inhaled anesthetic sevoflurane. Methods: Whole-cell voltage-clamp recordings were performed in astrocytes in the stratum radiatum of the CA1 region of hippocampal slices isolated from C57BL/6 male mice. Astrocytes were identified by their morphologic and electrophysiologic properties. Focal puff application of GABA (300 μM) was applied with a Picospritzer system to evoke GABA responses. Currents were studied before and during the application of the non-competitive GABAA receptor antagonist picrotoxin (0.5 mM), or etomidate (100 μM) or sevoflurane (532 μM). Results: GABA consistently evoked inward currents that were inhibited by picrotoxin. Etomidate increased the amplitude of the peak current by 35.0 ± 24.4% and prolonged the decay time by 27.2 ± 24.3% (n = 7, P < 0.05). Sevoflurane prolonged current decay by 28.3 ± 23.1% (n = 7, P < 0.05) but did not alter the peak amplitude. Etomidate and sevoflurane increased charge transfer (area) by 71.2 ± 45.9% and 51.8 ± 48.9% (n = 7, P < 0.05), respectively. Conclusion: The function of astrocytic GABAA receptors in the hippocampus was increased by etomidate and sevoflurane. Future studies will determine whether these general anesthetic drugs act on astrocytic GABAA receptors to stimulate the release of soluble factors that may contribute to PNDs.
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Affiliation(s)
- Woosuk Chung
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Anesthesiology and Pain Medicine, Chungnam National University, Daejeon, South Korea
| | - Dian-Shi Wang
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Shahin Khodaei
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Arsene Pinguelo
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Beverley A Orser
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Anesthesiology and Pain Medicine, University of Toronto, Toronto, ON, Canada.,Department of Anesthesia, Sunnybrook Health Sciences Centre, Toronto, ON, Canada
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7
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Mulkey DK, Olsen ML, Ou M, Cleary CM, Du G. Putative Roles of Astrocytes in General Anesthesia. Curr Neuropharmacol 2022; 20:5-15. [PMID: 33588730 PMCID: PMC9199541 DOI: 10.2174/1570159x19666210215120755] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/29/2021] [Accepted: 02/06/2021] [Indexed: 02/08/2023] Open
Abstract
General anesthetics are a mainstay of modern medicine, and although much progress has been made towards identifying molecular targets of anesthetics and neural networks contributing to endpoints of general anesthesia, our understanding of how anesthetics work remains unclear. Reducing this knowledge gap is of fundamental importance to prevent unwanted and life-threatening side-effects associated with general anesthesia. General anesthetics are chemically diverse, yet they all have similar behavioral endpoints, and so for decades, research has sought to identify a single underlying mechanism to explain how anesthetics work. However, this effort has given way to the 'multiple target hypothesis' as it has become clear that anesthetics target many cellular proteins, including GABAA receptors, glutamate receptors, voltage-independent K+ channels, and voltagedependent K+, Ca2+ and Na+ channels, to name a few. Yet, despite evidence that astrocytes are capable of modulating multiple aspects of neural function and express many anesthetic target proteins, they have been largely ignored as potential targets of anesthesia. The purpose of this brief review is to highlight the effects of anesthetic on astrocyte processes and identify potential roles of astrocytes in behavioral endpoints of anesthesia (hypnosis, amnesia, analgesia, and immobilization).
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Affiliation(s)
- Daniel K. Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, StorrsCT, USA;,Address correspondence to this author at the Department of Physiology and Neurobiology, University of Connecticut, Storrs CT, USA; E-mail:
| | | | | | - Colin M. Cleary
- Department of Physiology and Neurobiology, University of Connecticut, StorrsCT, USA
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8
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Schmaul S, Hanuscheck N, Bittner S. Astrocytic potassium and calcium channels as integrators of the inflammatory and ischemic CNS microenvironment. Biol Chem 2021; 402:1519-1530. [PMID: 34455729 DOI: 10.1515/hsz-2021-0256] [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: 05/10/2021] [Accepted: 08/13/2021] [Indexed: 12/24/2022]
Abstract
Astrocytes are key regulators of their surroundings by receiving and integrating stimuli from their local microenvironment, thereby regulating glial and neuronal homeostasis. Cumulating evidence supports a plethora of heterogenic astrocyte subpopulations that differ morphologically and in their expression patterns of receptors, transporters and ion channels, as well as in their functional specialisation. Astrocytic heterogeneity is especially relevant under pathological conditions. In experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS), morphologically distinct astrocytic subtypes were identified and could be linked to transcriptome changes during different disease stages and regions. To allow for continuous awareness of changing stimuli across age and diseases, astrocytes are equipped with a variety of receptors and ion channels allowing the precise perception of environmental cues. Recent studies implicate the diverse repertoire of astrocytic ion channels - including transient receptor potential channels, voltage-gated calcium channels, inwardly rectifying K+ channels, and two-pore domain potassium channels - in sensing the brain state in physiology, inflammation and ischemia. Here, we review current evidence regarding astrocytic potassium and calcium channels and their functional contribution in homeostasis, neuroinflammation and stroke.
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Affiliation(s)
- Samantha Schmaul
- Department of Neurology, Focus Program Translational Neuroscience (FTN) and Immunotherapy (FZI), Rhine Main Neuroscience Network (rmn2), University Medical Centre of the Johannes Gutenberg University Mainz, Langenbeckstraße 1, D-55131 Mainz, Germany
| | - Nicholas Hanuscheck
- Department of Neurology, Focus Program Translational Neuroscience (FTN) and Immunotherapy (FZI), Rhine Main Neuroscience Network (rmn2), University Medical Centre of the Johannes Gutenberg University Mainz, Langenbeckstraße 1, D-55131 Mainz, Germany
| | - Stefan Bittner
- Department of Neurology, Focus Program Translational Neuroscience (FTN) and Immunotherapy (FZI), Rhine Main Neuroscience Network (rmn2), University Medical Centre of the Johannes Gutenberg University Mainz, Langenbeckstraße 1, D-55131 Mainz, Germany
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9
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Zhou M, Du Y, Aten S, Terman D. On the electrical passivity of astrocyte potassium conductance. J Neurophysiol 2021; 126:1403-1419. [PMID: 34525325 DOI: 10.1152/jn.00330.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Predominant expression of leak-type K+ channels provides astrocytes a high membrane permeability to K+ ions and a hyperpolarized membrane potential that are crucial for astrocyte function in brain homeostasis. In functionally mature astrocytes, the expression of leak K+ channels creates a unique membrane K+ conductance that lacks voltage-dependent rectification. Accordingly, the conductance is named ohmic or passive K+ conductance. Several inwardly rectifying and two-pore domain K+ channels have been investigated for their contributions to passive conductance. Meanwhile, gap junctional coupling has been postulated to underlie the passive behavior of membrane conductance. It is now clear that the intrinsic properties of K+ channels and gap junctional coupling can each act alone or together to bring about a passive behavior of astrocyte conductance. Additionally, while the passive conductance can generally be viewed as a K+ conductance, the actual representation of this conductance is a combined expression of multiple known and unknown K+ channels, which has been further modified by the intricate morphology of individual astrocytes and syncytial gap junctional coupling. The expression of the inwardly rectifying K+ channels explains the inward-going component of passive conductance disobeying Goldman-Hodgkin-Katz constant field outward rectification. However, the K+ channels encoding the outward-going passive currents remain to be determined in the future. Here, we review our current understanding of ion channels and biophysical mechanisms engaged in the passive astrocyte K+ conductance, propose new studies to resolve this long-standing puzzle in astrocyte physiology, and discuss the functional implication(s) of passive behavior of K+ conductance on astrocyte physiology.
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Affiliation(s)
- Min Zhou
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Yixing Du
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Sydney Aten
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - David Terman
- Department of Mathematics, Ohio State University, Columbus, Ohio
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10
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Contribution of Neuronal and Glial Two-Pore-Domain Potassium Channels in Health and Neurological Disorders. Neural Plast 2021; 2021:8643129. [PMID: 34434230 PMCID: PMC8380499 DOI: 10.1155/2021/8643129] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/03/2021] [Indexed: 02/05/2023] Open
Abstract
Two-pore-domain potassium (K2P) channels are widespread in the nervous system and play a critical role in maintaining membrane potential in neurons and glia. They have been implicated in many stress-relevant neurological disorders, including pain, sleep disorder, epilepsy, ischemia, and depression. K2P channels give rise to leaky K+ currents, which stabilize cellular membrane potential and regulate cellular excitability. A range of natural and chemical effectors, including temperature, pressure, pH, phospholipids, and intracellular signaling molecules, substantially modulate the activity of K2P channels. In this review, we summarize the contribution of K2P channels to neuronal excitability and to potassium homeostasis in glia. We describe recently discovered functions of K2P channels in glia, such as astrocytic passive conductance and glutamate release, microglial surveillance, and myelin generation by oligodendrocytes. We also discuss the potential role of glial K2P channels in neurological disorders. In the end, we discuss current limitations in K2P channel researches and suggest directions for future studies.
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11
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McNeill J, Rudyk C, Hildebrand ME, Salmaso N. Ion Channels and Electrophysiological Properties of Astrocytes: Implications for Emergent Stimulation Technologies. Front Cell Neurosci 2021; 15:644126. [PMID: 34093129 PMCID: PMC8173131 DOI: 10.3389/fncel.2021.644126] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 04/26/2021] [Indexed: 12/12/2022] Open
Abstract
Astrocytes comprise a heterogeneous cell population characterized by distinct morphologies, protein expression and function. Unlike neurons, astrocytes do not generate action potentials, however, they are electrically dynamic cells with extensive electrophysiological heterogeneity and diversity. Astrocytes are hyperpolarized cells with low membrane resistance. They are heavily involved in the modulation of K+ and express an array of different voltage-dependent and voltage-independent channels to help with this ion regulation. In addition to these K+ channels, astrocytes also express several different types of Na+ channels; intracellular Na+ signaling in astrocytes has been linked to some of their functional properties. The physiological hallmark of astrocytes is their extensive intracellular Ca2+ signaling cascades, which vary at the regional, subregional, and cellular levels. In this review article, we highlight the physiological properties of astrocytes and the implications for their function and influence of network and synaptic activity. Furthermore, we discuss the implications of these differences in the context of optogenetic and DREADD experiments and consider whether these tools represent physiologically relevant techniques for the interrogation of astrocyte function.
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Affiliation(s)
- Jessica McNeill
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | | | | | - Natalina Salmaso
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
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12
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Shrestha S, Shrestha BK, Joong OK, Park CH, Kim CS. Para-substituted sulfonic acid-doped protonated emeraldine salt nanobuds: a potent neural interface targeting PC12 cell interactions and promotes neuronal cell differentiation. Biomater Sci 2021; 9:1691-1704. [PMID: 33410823 DOI: 10.1039/d0bm01034k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Structural parameters, such as metal-like semiconductor and electrochemical properties of functionalized polyaniline, hold great potential especially for the development of the cell-substrate interface due to its ion/electron transfer ability. We report the one-step synthesis of sulfonic acid-doped polyaniline nanobuds (s-PANINbs) with controlled shape/size under various oxidation potentials. The different oxidation states of s-PANINbs are used to investigate the cell-specific platform for the induction of neuronal networks in PC12 cells, including the growth, proliferation, and differentiation of cells. The unique structure of one-dimensional (1-D) s-PANINbs enhances its intrinsic conductive properties, and facilitates the dispersibility and electrochemical activity via covalent bonding with dopants. The protonated emeraldine salt nanobuds of s-PANINbs synthesized at 0.18 V anodic potential demonstrated low resistivity (∼81.18 mΩ) and charge transfer resistance (∼3253 Ω). The most biologically compatible protonated emeraldine salt was used in vitro to induce PC12 cells associated with neurite outgrowth, contributing to the electrophysiology of neuronal cells under an external electrical stimulation. The western blotting analysis and qRT-PCR results show that β-III Tubulin, synapsin I, and TREK-1 are highly expressed in PC12 cells, confirming their successful differentiation into neural-specific cells. Our approach demonstrates the promising role of the self-standing framework based on the s-PANINbs of the protonated emeraldine salt in peripheral nerve repair for the future in vivo cell-interface.
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Affiliation(s)
- Sita Shrestha
- Department of Bionanotechnology and Bioconvergence Engineering, Graduate School, Jeonbuk National University, Jeonju, Republic of Korea. and Department of Bionanosystem Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea
| | - Bishnu Kumar Shrestha
- Department of Bionanotechnology and Bioconvergence Engineering, Graduate School, Jeonbuk National University, Jeonju, Republic of Korea. and Department of Bionanosystem Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea and Mechanical Design Engineering, Jeonbuk National University, Jeonju 561-756, Republic of Korea
| | - Oh Kwang Joong
- Department of chemistry, Jeonbuk National University, Jeonju 561-756, Republic of Korea
| | - Chan Hee Park
- Department of Bionanotechnology and Bioconvergence Engineering, Graduate School, Jeonbuk National University, Jeonju, Republic of Korea. and Department of Bionanosystem Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea and Mechanical Design Engineering, Jeonbuk National University, Jeonju 561-756, Republic of Korea
| | - Cheol Sang Kim
- Department of Bionanotechnology and Bioconvergence Engineering, Graduate School, Jeonbuk National University, Jeonju, Republic of Korea. and Department of Bionanosystem Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea and Mechanical Design Engineering, Jeonbuk National University, Jeonju 561-756, Republic of Korea
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13
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Khoubza L, Chatelain FC, Feliciangeli S, Lesage F, Bichet D. Physiological roles of heteromerization: focus on the two-pore domain potassium channels. J Physiol 2021; 599:1041-1055. [PMID: 33347640 DOI: 10.1113/jp279870] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/07/2020] [Indexed: 12/28/2022] Open
Abstract
Potassium channels form the largest family of ion channels with more than 80 members involved in cell excitability and signalling. Most of them exist as homomeric channels, whereas specific conditions are required to obtain heteromeric channels. It is well established that heteromerization of voltage-gated and inward rectifier potassium channels affects their function, increasing the diversity of the native potassium currents. For potassium channels with two pore domains (K2P ), homomerization has long been considered the rule, their polymodal regulation by a wide diversity of physical and chemical stimuli being responsible for the adaptation of the leak potassium currents to cellular needs. This view has recently evolved with the accumulation of evidence of heteromerization between different K2P subunits. Several functional intragroup and intergroup heteromers have recently been identified, which contribute to the functional heterogeneity of this family. K2P heteromerization is involved in the modulation of channel expression and trafficking, promoting functional and signalling diversity. As illustrated in the Abstract Figure, heteromerization of TREK1 and TRAAK provides the cell with more possibilities of regulation. It is becoming increasingly evident that K2P heteromers contribute to important physiological functions including neuronal and cardiac excitability. Since heteromerization also affects the pharmacology of K2P channels, this understanding helps to establish K2P heteromers as new therapeutic targets for physiopathological conditions.
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Affiliation(s)
- Lamyaa Khoubza
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, 660 route des Lucioles 06650 Valbonne, France
| | - Franck C Chatelain
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, 660 route des Lucioles 06650 Valbonne, France
| | - Sylvain Feliciangeli
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, 660 route des Lucioles 06650 Valbonne, France.,Inserm, 101 rue de Tolbiac, 75013, Paris, France
| | - Florian Lesage
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, 660 route des Lucioles 06650 Valbonne, France.,Inserm, 101 rue de Tolbiac, 75013, Paris, France
| | - Delphine Bichet
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, 660 route des Lucioles 06650 Valbonne, France
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14
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Bae Y, Choi JH, Ryoo K, Kim A, Kwon O, Jung HG, Hwang EM, Park JY. Spadin Modulates Astrocytic Passive Conductance via Inhibition of TWIK-1/TREK-1 Heterodimeric Channels. Int J Mol Sci 2020; 21:ijms21249639. [PMID: 33348878 PMCID: PMC7765948 DOI: 10.3390/ijms21249639] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 12/09/2020] [Accepted: 12/15/2020] [Indexed: 12/11/2022] Open
Abstract
Astrocytes, the most abundant cell type in the brain, are non-excitable cells and play critical roles in brain function. Mature astrocytes typically exhibit a linear current-voltage relationship termed passive conductance, which is believed to enable astrocytes to maintain potassium homeostasis in the brain. We previously demonstrated that TWIK-1/TREK-1 heterodimeric channels mainly contribute to astrocytic passive conductance. However, the molecular identity of astrocytic passive conductance is still controversial and needs to be elucidated. Here, we report that spadin, an inhibitor of TREK-1, can dramatically reduce astrocytic passive conductance in brain slices. A series of gene silencing experiments demonstrated that spadin-sensitive currents are mediated by TWIK-1/TREK-1 heterodimeric channels in cultured astrocytes and hippocampal astrocytes from brain slices. Our study clearly showed that TWIK-1/TREK-1-heterodimeric channels can act as the main molecular machinery of astrocytic passive conductance, and suggested that spadin can be used as a specific inhibitor to control astrocytic passive conductance.
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Affiliation(s)
- Yeonju Bae
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea; (Y.B.); (K.R.); (O.K.); (H.-G.J.)
| | - Jae Hyouk Choi
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea; (J.H.C.); (A.K.)
| | - Kanghyun Ryoo
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea; (Y.B.); (K.R.); (O.K.); (H.-G.J.)
| | - Ajung Kim
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea; (J.H.C.); (A.K.)
| | - Osung Kwon
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea; (Y.B.); (K.R.); (O.K.); (H.-G.J.)
| | - Hyun-Gug Jung
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea; (Y.B.); (K.R.); (O.K.); (H.-G.J.)
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea; (J.H.C.); (A.K.)
| | - Eun Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea; (J.H.C.); (A.K.)
- Correspondence: (E.M.H.); (J.-Y.P.)
| | - Jae-Yong Park
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea; (Y.B.); (K.R.); (O.K.); (H.-G.J.)
- Correspondence: (E.M.H.); (J.-Y.P.)
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15
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Ou M, Kuo FS, Chen X, Kahanovitch U, Olsen ML, Du G, Mulkey DK. Isoflurane inhibits a Kir4.1/5.1-like conductance in neonatal rat brainstem astrocytes and recombinant Kir4.1/5.1 channels in a heterologous expression system. J Neurophysiol 2020; 124:740-749. [PMID: 32727273 PMCID: PMC7509298 DOI: 10.1152/jn.00358.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 07/29/2020] [Accepted: 07/29/2020] [Indexed: 02/08/2023] Open
Abstract
All inhalation anesthetics used clinically including isoflurane can suppress breathing; since this unwanted side effect can persist during the postoperative period and complicate patient recovery, there is a need to better understand how isoflurane affects cellular and molecular elements of respiratory control. Considering that astrocytes in a brainstem region known as the retrotrapezoid nucleus (RTN) contribute to the regulation of breathing in response to changes in CO2/H+ (i.e., function as respiratory chemoreceptors), and astrocytes in other brain regions are highly sensitive to isoflurane, we wanted to determine whether and how RTN astrocytes respond to isoflurane. We found that RTN astrocytes in slices from neonatal rat pups (7-12 days postnatal) respond to clinically relevant levels of isoflurane by inhibition of a CO2/H+-sensitive Kir4.1/5.1-like conductance [50% effective concentration (EC50) = 0.8 mM or ~1.7%]. We went on to confirm that similar levels of isoflurane (EC50 = 0.53 mM or 1.1%) inhibit recombinant Kir4.1/5.1 channels but not homomeric Kir4.1 channels expressed in HEK293 cells. We also found that exposure to CO2/H+ occluded subsequent effects of isoflurane on both native and recombinant Kir4.1/5.1 currents. These results identify Kir4.1/5.1 channels in astrocytes as novel targets of isoflurane. These results suggest astrocyte Kir4.1/5.1 channels contribute to certain aspects of general anesthesia including altered respiratory control.NEW & NOTEWORTHY An unwanted side effect of isoflurane anesthesia is suppression of breathing. Despite this clinical significance, effects of isoflurane on cellular and molecular elements of respiratory control are not well understood. Here, we show that isoflurane inhibits heteromeric Kir4.1/5.1 channels in a mammalian expression system and a Kir4.1/5.1-like conductance in astrocytes in a brainstem respiratory center. These results identify astrocyte Kir4.1/5.1 channels as novel targets of isoflurane and potential substrates for altered respiratory control during isoflurane anesthesia.
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Affiliation(s)
- Mengchan Ou
- Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu City, China
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Fu-Shan Kuo
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Xinnian Chen
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Uri Kahanovitch
- School of Neuroscience, Virginia Polytechnic and State University, Blacksburg, Virginia
| | - Michelle L Olsen
- School of Neuroscience, Virginia Polytechnic and State University, Blacksburg, Virginia
| | - Guizhi Du
- Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu City, China
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
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16
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Epileptiform Neuronal Discharges Impair Astrocyte Syncytial Isopotentiality in Acute Hippocampal Slices. Brain Sci 2020; 10:brainsci10040208. [PMID: 32252295 PMCID: PMC7226063 DOI: 10.3390/brainsci10040208] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 03/21/2020] [Accepted: 03/31/2020] [Indexed: 12/25/2022] Open
Abstract
Astrocyte syncytial isopotentiality is a physiological mechanism resulting from a strong electrical coupling among astrocytes. We have previously shown that syncytial isopotentiality exists as a system-wide feature that coordinates astrocytes into a system for high efficient regulation of brain homeostasis. Neuronal activity is known to regulate gap junction coupling through alteration of extracellular ions and neurotransmitters. However, the extent to which epileptic neuronal activity impairs the syncytial isopotentiality is unknown. Here, the neuronal epileptiform bursts were induced in acute hippocampal slices by removal of Mg2+ (Mg2+ free) from bath solution and inhibition of γ-aminobutyric acid A (GABAA) receptors by 100 µM picrotoxin (PTX). The change in syncytial coupling was monitored by using a K+ free-Na+-containing electrode solution ([Na+]p) in the electrophysiological recording where the substitution of intracellular K+ by Na+ ions dissipates the physiological membrane potential (VM) to ~0 mV in the recorded astrocyte. However, in a syncytial coupled astrocyte, the [Na+]p induced VM loss can be compensated by the coupled astrocytes to a quasi-physiological membrane potential of ~73 mV. After short-term exposure to this experimental epileptic condition, a significant closure of syncytial coupling was indicated by a shift of the quasi-physiological membrane potential to −60 mV, corresponding to a 90% reduction of syncytial coupling strength. Consequently, the closure of syncytial coupling significantly decreased the ability of the syncytium for spatial redistribution of K+ ions. Altogether, our results show that epileptiform neuronal discharges weaken the strength of syncytial coupling and that in turn impairs the capacity of a syncytium for spatial redistribution of K+ ions.
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17
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Wang W, Kiyoshi CM, Du Y, Taylor AT, Sheehan ER, Wu X, Zhou M. TREK-1 Null Impairs Neuronal Excitability, Synaptic Plasticity, and Cognitive Function. Mol Neurobiol 2020; 57:1332-1346. [PMID: 31728930 PMCID: PMC8808335 DOI: 10.1007/s12035-019-01828-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 10/30/2019] [Indexed: 02/07/2023]
Abstract
TREK-1, a two-pore-domain K+ channel, is highly expressed in the central nervous system. Although aberrant expression of TREK-1 is implicated in cognitive impairment, the cellular and functional mechanism underlying this channelopathy is poorly understood. Here we examined TREK-1 contribution to neuronal morphology, excitability, synaptic plasticity, and cognitive function in mice deficient in TREK-1 expression. TREK-1 immunostaining signal mainly appeared in hippocampal pyramidal neurons, but not in astrocytes. TREK-1 gene knockout (TREK-1 KO) increases dendritic sprouting and the number of immature spines in hippocampal CA1 pyramidal neurons. Functionally, TREK-1 KO increases neuronal excitability and enhances excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs). The increased EPSCs appear to be attributed to an increased release probability of presynaptic glutamate and functional expression of postsynaptic AMPA receptors. TREK-1 KO decreased the paired-pulse ratio and severely occluded the long-term potentiation (LTP) in the CA1 region. These altered synaptic transmission and plasticity are associated with recognition memory deficit in TREK-1 KO mice. Although astrocytic expression of TREK-1 has been reported in previous studies, TREK-1 KO does not alter astrocyte membrane K+ conductance or the syncytial network function in terms of syncytial isopotentiality. Altogether, TREK-1 KO profoundly affects the cellular structure and function of hippocampal pyramidal neurons. Thus, the impaired cognitive function in diseases associated with aberrant expression of TREK-1 should be attributed to the failure of this K+ channel in regulating neuronal morphology, excitability, synaptic transmission, and plasticity.
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Affiliation(s)
- Wei Wang
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Conrad M Kiyoshi
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Yixing Du
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Anne T Taylor
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Erica R Sheehan
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Xiao Wu
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Min Zhou
- Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
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18
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Chilian WM, Yin L, Ohanyan V. Step by Step: Advancing the Understanding of Local Vascular Control. Arterioscler Thromb Vasc Biol 2020; 40:498-499. [PMID: 32101473 DOI: 10.1161/atvbaha.120.313811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- William M Chilian
- From the Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH
| | - Liya Yin
- From the Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH
| | - Vahagn Ohanyan
- From the Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH
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19
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Kim A, Jung HG, Kim SC, Choi M, Park JY, Lee SG, Hwang EM. Astrocytic AEG-1 regulates expression of TREK-1 under acute hypoxia. Cell Biochem Funct 2019; 38:167-175. [PMID: 31782179 DOI: 10.1002/cbf.3469] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 08/29/2019] [Accepted: 10/13/2019] [Indexed: 12/16/2022]
Abstract
TREK-1 (TWIK-related K+ channel), a member of the two-pore domain K+ (K2P) channel family, is highly expressed in astrocytes, where it plays a key role in glutamate release and passive conductance. In addition, TREK-1 is induced to protect neurons under pathological conditions such as hypoxia. However, the upstream regulation of TREK-1 remains poorly understood. In this study, we found that AEG-1 (astrocyte elevated gene-1) regulates the expression of astrocytic TREK-1 under hypoxic conditions. Upregulation of AEG-1 increased expression of TREK-1 in astrocytes, and knockdown of AEG-1 dramatically decreased the mRNA and protein levels of TREK-1, which were restored by expression of shRNA-insensitive AEG-1. In addition, expression of TREK-1 was not regulated in the absence of AEG-1, even when HIF1α was present. Together, these results suggest that AEG-1 acts as a major upstream regulator of TREK-1 channels in astrocytes under hypoxia. SIGNIFICANCE OF THE STUDY: Previous studies have reported that hypoxia increases the expression of astrocytic TREK-1 and that increased TREK-1 expression protects neuronal cells from apoptosis. However, its cellular mechanism is not clear. In this study we first showed that AEG-1 is a major mediator of hypoxic-regulated TREK-1 expression in normal astrocytes independently of HIF-1α.
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Affiliation(s)
- Ajung Kim
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea.,KHU-KIST Department of Converging Science and Technology, Graduate School, Kyung Hee University, Seoul, Republic of Korea
| | - Hyun-Gug Jung
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea.,School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, Republic of Korea
| | - Seung-Chan Kim
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea.,School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, Republic of Korea
| | - Minji Choi
- Department of Science in Korean Medicine, Kyung Hee University, Seoul, Republic of Korea
| | - Jae-Yong Park
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, Republic of Korea
| | - Seok-Geun Lee
- KHU-KIST Department of Converging Science and Technology, Graduate School, Kyung Hee University, Seoul, Republic of Korea.,Department of Science in Korean Medicine, Kyung Hee University, Seoul, Republic of Korea
| | - Eun Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea.,KHU-KIST Department of Converging Science and Technology, Graduate School, Kyung Hee University, Seoul, Republic of Korea
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20
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Pineda RH, Hypolite J, Lee S, Carrasco A, Iguchi N, Meacham RB, Malykhina AP. Altered detrusor contractility and voiding patterns in mice lacking the mechanosensitive TREK-1 channel. BMC Urol 2019; 19:40. [PMID: 31113422 PMCID: PMC6528348 DOI: 10.1186/s12894-019-0475-3] [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: 04/23/2018] [Accepted: 05/13/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Previously published results from our laboratory identified a mechano-gated two-pore domain potassium channel, TREK-1, as a main mechanosensor in the smooth muscle of the human urinary bladder. One of the limitations of in vitro experiments on isolated human detrusor included inability to evaluate in vivo effects of TREK-1 on voiding function, as the channel is also expressed in the nervous system, and may modulate micturition via neural pathways. Therefore, in the present study, we aimed to assess the role of TREK-1 channel in bladder function and voiding patterns in vivo by using TREK-1 knockout (KO) mice. METHODS Adult C57BL/6 J wild-type (WT, N = 32) and TREK-1 KO (N = 33) mice were used in this study. The overall phenotype and bladder function were evaluated by gene and protein expression of TREK-1 channel, in vitro contractile experiments using detrusor strips in response to stretch and pharmacological stimuli, and cystometry in unanesthetized animals. RESULTS TREK-1 KO animals had an elevated basal muscle tone and enhanced spontaneous activity in the detrusor without detectable changes in bladder morphology/histology. Stretch applied to isolated detrusor strips increased the amplitude of spontaneous contractions by 109% in the TREK-1 KO group in contrast to a 61% increase in WT mice (p ≤ 0.05 to respective baseline for each group). The detrusor strips from TREK-1 KO mice also generated more contractile force in response to electric field stimulation and high potassium concentration in comparison to WT group (p ≤ 0.05 for both tests). However, cystometric recordings from TREK-1 KO mice revealed a significant increase in the duration of the intermicturition interval, enhanced bladder capacity and increased number of non-voiding contractions in comparison to WT mice. CONCLUSIONS Our results provide evidence that global down-regulation of TREK-1 channels has dual effects on detrusor contractility and micturition patterns in vivo. The observed differences are likely due to expression of TREK-1 channel not only in detrusor myocytes but also in afferent and efferent neural pathways involved in regulation of micturition which may underly the "mixed" voiding phenotype in TREK-1 KO mice.
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Affiliation(s)
- Ricardo H Pineda
- Division of Urology, Department of Surgery, University of Colorado Denver,Anschutz Medical Campus, 12700 E 19th Ave, M/S C317, Aurora, CO, 80045, USA
| | - Joseph Hypolite
- Division of Urology, Department of Surgery, University of Colorado Denver,Anschutz Medical Campus, 12700 E 19th Ave, M/S C317, Aurora, CO, 80045, USA
| | - Sanghee Lee
- Department of Urology, University of California San Diego, 3855 Health Science Drive, Room 4345, Bay 4LL, La Jolla, CA, 92093, USA
| | - Alonso Carrasco
- Children's Mercy Hospital, 2401 Gillham Rd, Kansas City, MO, 64108, USA
| | - Nao Iguchi
- Division of Urology, Department of Surgery, University of Colorado Denver,Anschutz Medical Campus, 12700 E 19th Ave, M/S C317, Aurora, CO, 80045, USA
| | - Randall B Meacham
- Division of Urology, Department of Surgery, University of Colorado Denver, Academic Office One Bldg., Rm 5602, 12631 East 17th Ave., M/S C319, Aurora, CO, 80045, USA
| | - Anna P Malykhina
- Division of Urology, Department of Surgery, University of Colorado Denver,Anschutz Medical Campus, 12700 E 19th Ave, M/S C317, Aurora, CO, 80045, USA.
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21
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Abstract
Brain waves are rhythmic voltage oscillations emerging from the synchronization of individual neurons into a neuronal network. These oscillations range from slow to fast fluctuations, and are classified by power and frequency band, with different frequency bands being associated with specific behaviours. It has been postulated that at least ten distinct mechanisms are required to cover the frequency range of neural oscillations, however the mechanisms that gear the transition between distinct oscillatory frequencies are unknown. In this study, we have used electrophysiological recordings to explore the involvement of astrocytic K+ clearance processes in modulating neural oscillations at both network and cellular levels. Our results indicate that impairment of astrocytic K+ clearance capabilities, either through blockade of K+ uptake or astrocytic connectivity, enhance network excitability and form high power network oscillations over a wide range of frequencies. At the cellular level, local increases in extracellular K+ results in modulation of the oscillatory behaviour of individual neurons, which underlies the network behaviour. Since astrocytes are central for maintaining K+ homeostasis, our study suggests that modulation of their inherent capabilities to clear K+ from the extracellular milieu is a potential mechanism to optimise neural resonance behaviour and thus tune neural oscillations.
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22
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Xin W, Bonci A. Functional Astrocyte Heterogeneity and Implications for Their Role in Shaping Neurotransmission. Front Cell Neurosci 2018; 12:141. [PMID: 29896091 PMCID: PMC5987431 DOI: 10.3389/fncel.2018.00141] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 05/08/2018] [Indexed: 12/20/2022] Open
Abstract
In recent years, the role of astrocytes in shaping neuronal signaling has come to the forefront of neuroscience research. The development of genetic tools that enable targeted manipulation of astrocytes has revealed a wealth of mechanisms by which they can alter the synaptic strength and intrinsic excitability of neurons in behaviorally relevant ways. In parallel, several studies have demonstrated significant variability in the gene expression and physiology of astrocytes within and between brain regions. Thus, to form an accurate understanding of how astrocytes contribute to neuronal transmission, we must take into consideration the diversity that exists in their intrinsic properties. In this review, we will summarize recent findings on astrocyte heterogeneity and discuss the implications for their interactions with neurons and their effects on neuronal transmission.
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Affiliation(s)
- Wendy Xin
- Synaptic Plasticity Section, Cellular Neurobiology Branch, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, United States.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Antonello Bonci
- Synaptic Plasticity Section, Cellular Neurobiology Branch, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, United States.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Department of Neuroscience, Georgetown University Medical Center, School of Medicine, Washington, DC, United States.,Department of Psychiatry, University of Maryland, School of Medicine, Baltimore, MD, United States
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23
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Modulation of the inwardly rectifying potassium channel Kir4.1 by the pro-invasive miR-5096 in glioblastoma cells. Oncotarget 2018; 8:37681-37693. [PMID: 28445150 PMCID: PMC5514940 DOI: 10.18632/oncotarget.16949] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 03/22/2017] [Indexed: 12/19/2022] Open
Abstract
Inwardly rectifying potassium channels (Kir), and especially the barium-sensitive Kir4.1 encoded by KCNJ10, are key regulators of glial functions. A lower expression or mislocation of Kir4.1 is detected in human brain tumors. MicroRNAs participate in the regulation of ionic channels and associated neurologic disorders. Here, we analyze effects of miR-5096 on the Kir4.1 expression and function in two glioblastoma cell lines, U87 and U251. Using whole-cell patch-clamp and western-blot analysis, we show that cell loading with miR-5096 decreases the Kir4.1 protein level and associated K+ current. Cell treatment with barium, a Kir4.1 blocker, or cell loading of miR-5096 both increase the outgrowth of filopodia in glioma cells, as observed by time-lapse microscopy. Knocking-down Kir4.1 expression by siRNA transfection similarly increased both filopodia formation and invasiveness of glioma cells as observed in Boyden chamber assay. MiR-5096 also promotes the release of extracellular vesicles by which it increases its own transfer to surrounding cells, in a Kir4.1-dependent manner in U251 but not in U87. Altogether, our results validate Kir4.1 as a miR-5096 target to promote invasion of glioblastoma cells. Our data highlight the complexity of microRNA effects and the role of K+ channels in cancer.
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Hover S, Foster B, Fontana J, Kohl A, Goldstein SAN, Barr JN, Mankouri J. Bunyavirus requirement for endosomal K+ reveals new roles of cellular ion channels during infection. PLoS Pathog 2018; 14:e1006845. [PMID: 29352299 PMCID: PMC5805358 DOI: 10.1371/journal.ppat.1006845] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 02/08/2018] [Accepted: 12/28/2017] [Indexed: 11/18/2022] Open
Abstract
In order to multiply and cause disease a virus must transport its genome from outside the cell into the cytosol, most commonly achieved through the endocytic network. Endosomes transport virus particles to specific cellular destinations and viruses exploit the changing environment of maturing endocytic vesicles as triggers to mediate genome release. Previously we demonstrated that several bunyaviruses, which comprise the largest family of negative sense RNA viruses, require the activity of cellular potassium (K+) channels to cause productive infection. Specifically, we demonstrated a surprising role for K+ channels during virus endosomal trafficking. In this study, we have used the prototype bunyavirus, Bunyamwera virus (BUNV), as a tool to understand why K+ channels are required for progression of these viruses through the endocytic network. We report three major findings: First, the production of a dual fluorescently labelled bunyavirus to visualize virus trafficking in live cells. Second, we show that BUNV traffics through endosomes containing high [K+] and that these K+ ions influence the infectivity of virions. Third, we show that K+ channel inhibition can alter the distribution of K+ across the endosomal system and arrest virus trafficking in endosomes. These data suggest high endosomal [K+] is a critical cue that is required for virus infection, and is controlled by cellular K+ channels resident within the endosome network. This highlights cellular K+ channels as druggable targets to impede virus entry, infection and disease.
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Affiliation(s)
- Samantha Hover
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Becky Foster
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Juan Fontana
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Steve A. N. Goldstein
- Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, United States of America
| | - John N. Barr
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
- * E-mail: (JNB); (JM)
| | - Jamel Mankouri
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
- * E-mail: (JNB); (JM)
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25
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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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26
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 899] [Impact Index Per Article: 149.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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27
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Fang Y, Huang X, Wan Y, Tian H, Tian Y, Wang W, Zhu S, Xie M. Deficiency of TREK-1 potassium channel exacerbates secondary injury following spinal cord injury in mice. J Neurochem 2017; 141:236-246. [PMID: 28192611 DOI: 10.1111/jnc.13980] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 01/09/2017] [Accepted: 02/03/2017] [Indexed: 12/31/2022]
Affiliation(s)
- Yongkang Fang
- Department of Neurology; Tongji Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - Xiaojiang Huang
- Department of Neurology; Tongji Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - Yue Wan
- Department of Neurology; The Third People's Hospital of Hubei Province; Wuhan China
| | - Hao Tian
- Department of Neurology; Tongji Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - Yeye Tian
- Department of Neurology; Tongji Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - Wei Wang
- Department of Neurology; Tongji Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
- Key Laboratory of Neurological Diseases of Chinese Ministry of Education; The School of Basic Medicine; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - Suiqiang Zhu
- Department of Neurology; Tongji Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - Minjie Xie
- Department of Neurology; Tongji Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
- Key Laboratory of Neurological Diseases of Chinese Ministry of Education; The School of Basic Medicine; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
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28
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Hülsmann S, Hagos L, Heuer H, Schnell C. Limitations of Sulforhodamine 101 for Brain Imaging. Front Cell Neurosci 2017; 11:44. [PMID: 28293173 PMCID: PMC5328990 DOI: 10.3389/fncel.2017.00044] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 02/09/2017] [Indexed: 11/19/2022] Open
Abstract
Since 2004, the red fluorescent dye Sulforhodamine 101 (SR101) has been boosting the functional analysis of astrocytes in a functional environment in an unprecedented way. However, two major limitations have been challenging the usefulness of this tool for cellular imaging: (i) SR101 is not as specific for astrocytes as previously reported; and (ii) discoveries of severe excitatory side effects of SR101 are bearing the risk of unwanted alteration of the system of interest. In this article, we summarize the current knowledge about SR101-labeling protocols and discuss the problems that arise from varying of the staining protocols. Furthermore, we provide a testable hypothesis for the observed hyper-excitability that can be observed when using SR101.
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Affiliation(s)
- Swen Hülsmann
- Clinic for Anesthesiology, University Hospital GöttingenGöttingen, Germany; DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB)Göttingen, Germany
| | - Liya Hagos
- Clinic for Anesthesiology, University Hospital GöttingenGöttingen, Germany; DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB)Göttingen, Germany
| | - Heike Heuer
- Leibniz-Institut für Umweltmedizinische Forschung GmbH Düsseldorf, Germany
| | - Christian Schnell
- DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB) Göttingen, Germany
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29
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Miller SJ, Zhang PW, Glatzer J, Rothstein JD. Astroglial transcriptome dysregulation in early disease of an ALS mutant SOD1 mouse model. J Neurogenet 2016; 31:37-48. [DOI: 10.1080/01677063.2016.1260128] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Sean J. Miller
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- The Brain Science Institute, Johns Hopkins University, Baltimore, MD, USA
- Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ping-wu Zhang
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- The Brain Science Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Jenna Glatzer
- The Brain Science Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Jeffrey D. Rothstein
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- The Brain Science Institute, Johns Hopkins University, Baltimore, MD, USA
- Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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30
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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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31
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Zhong S, Du Y, Kiyoshi CM, Ma B, Alford CC, Wang Q, Yang Y, Liu X, Zhou M. Electrophysiological behavior of neonatal astrocytes in hippocampal stratum radiatum. Mol Brain 2016; 9:34. [PMID: 27004553 PMCID: PMC4802662 DOI: 10.1186/s13041-016-0213-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 03/12/2016] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Neonatal astrocytes are diverse in origin, and undergo dramatic change in gene expression, morphological differentiation and syncytial networking throughout development. Neonatal astrocytes also play multifaceted roles in neuronal circuitry establishment. However, the extent to which neonatal astrocytes differ from their counterparts in the adult brain remains unknown. RESULTS Based on ALDH1L1-eGFP expression or sulforhodamine 101 staining, neonatal astrocytes at postnatal day 1-3 can be reliably identified in hippocampal stratum radiatum. They exhibit a more negative resting membrane potential (V M), -85 mV, than mature astrocytes, -80 mV and a variably rectifying whole-cell current profile due to complex expression of voltage-gated outward transient K(+) (IKa), delayed rectifying K(+) (IKd) and inward K(+) (IKin) conductances. Differing from NG2 glia, depolarization-induced inward Na(+) currents (INa) could not be detected in neonatal astrocytes. A quasi-physiological V M of -69 mV was retained when inwardly rectifying Kir4.1 was inhibited by 100 μM Ba(2+) in both wild type and TWIK-1/TREK-1 double gene knockout astrocytes, indicating expression of additional leak K(+) channels yet unknown. In dual patch recording, electrical coupling was detected in 74 % (14/19 pairs) of neonatal astrocytes with largely variable coupling coefficients. The increasing gap junction coupling progressively masked the rectifying K(+) conductances to account for an increasing number of linear voltage-to-current relationship passive astrocytes (PAs). Gap junction inhibition, by 100 μM meclofenamic acid, substantially reduced membrane conductance and converted all the neonatal PAs to variably rectifying astrocytes. The low density expression of leak K(+) conductance in neonatal astrocytes corresponded to a ~50 % less K(+) uptake capacity compared to adult astrocytes. CONCLUSIONS Neonatal astrocytes predominantly express a variety of rectifying K(+) conductances, form discrete cell-to-cell gap junction coupling and are deficient in K(+) homeostatic capacity.
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Affiliation(s)
- Shiying Zhong
- />Department of Neurology, Shanghai 10th Hospital of Tongji University, School of Medicine, 301 Yan Chang Zhong Road, Shanghai, 200072 China
- />Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210 USA
| | - Yixing Du
- />Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210 USA
| | - Conrad M. Kiyoshi
- />Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210 USA
| | - Baofeng Ma
- />Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210 USA
| | - Catherine C. Alford
- />Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210 USA
| | - Qi Wang
- />Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210 USA
| | - Yongjie Yang
- />Department of Neuroscience, Tufts University School of Medicine, Boston, MA USA
| | - Xueyuan Liu
- />Department of Neurology, Shanghai 10th Hospital of Tongji University, School of Medicine, 301 Yan Chang Zhong Road, Shanghai, 200072 China
| | - Min Zhou
- />Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210 USA
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