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Kelley MR, Cardarelli RA, Smalley JL, Ollerhead TA, Andrew PM, Brandon NJ, Deeb TZ, Moss SJ. Locally Reducing KCC2 Activity in the Hippocampus is Sufficient to Induce Temporal Lobe Epilepsy. EBioMedicine 2018; 32:62-71. [PMID: 29884458 PMCID: PMC6020795 DOI: 10.1016/j.ebiom.2018.05.029] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 05/22/2018] [Accepted: 05/23/2018] [Indexed: 12/03/2022] Open
Abstract
Mesial temporal lobe epilepsy (mTLE) is the most common form of epilepsy, believed to arise in part from compromised GABAergic inhibition. The neuronal specific K+/Cl- co-transporter 2 (KCC2) is a critical determinant of the efficacy of GABAergic inhibition and deficits in its activity are observed in mTLE patients and animal models of epilepsy. To test if reductions of KCC2 activity directly contribute to the pathophysiology of mTLE, we locally ablated KCC2 expression in a subset of principal neurons within the adult hippocampus. Deletion of KCC2 resulted in compromised GABAergic inhibition and the development of spontaneous, recurrent generalized seizures. Moreover, local ablation of KCC2 activity resulted in hippocampal sclerosis, a key pathological change seen in mTLE. Collectively, our results demonstrate that local deficits in KCC2 activity within the hippocampus are sufficient to precipitate mTLE.
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Affiliation(s)
- Matt R Kelley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Ross A Cardarelli
- AstraZeneca-Tufts University Laboratory for Basic and Translational Neuroscience Research, Boston, MA, USA
| | - Joshua L Smalley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Thomas A Ollerhead
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Peter M Andrew
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Nicholas J Brandon
- AstraZeneca-Tufts University Laboratory for Basic and Translational Neuroscience Research, Boston, MA, USA; Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, MA, USA
| | - Tarek Z Deeb
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA; AstraZeneca-Tufts University Laboratory for Basic and Translational Neuroscience Research, Boston, MA, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA; AstraZeneca-Tufts University Laboratory for Basic and Translational Neuroscience Research, Boston, MA, USA; Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, MA, USA; Department of Neuroscience, Physiology and Pharmacology, University College, London, WC1E, 6BT, UK.
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52
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Di Cristo G, Awad PN, Hamidi S, Avoli M. KCC2, epileptiform synchronization, and epileptic disorders. Prog Neurobiol 2018; 162:1-16. [DOI: 10.1016/j.pneurobio.2017.11.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 11/09/2017] [Accepted: 11/28/2017] [Indexed: 12/31/2022]
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53
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Klein PM, Lu AC, Harper ME, McKown HM, Morgan JD, Beenhakker MP. Tenuous Inhibitory GABAergic Signaling in the Reticular Thalamus. J Neurosci 2018; 38:1232-1248. [PMID: 29273603 PMCID: PMC5792478 DOI: 10.1523/jneurosci.1345-17.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 09/20/2017] [Accepted: 11/03/2017] [Indexed: 11/21/2022] Open
Abstract
Maintenance of a low intracellular Cl- concentration ([Cl-]i) is critical for enabling inhibitory neuronal responses to GABAA receptor-mediated signaling. Cl- transporters, including KCC2, and extracellular impermeant anions ([A]o) of the extracellular matrix are both proposed to be important regulators of [Cl-]i Neurons of the reticular thalamic (RT) nucleus express reduced levels of KCC2, indicating that GABAergic signaling may produce excitation in RT neurons. However, by performing perforated patch recordings and calcium imaging experiments in rats (male and female), we find that [Cl-]i remains relatively low in RT neurons. Although we identify a small contribution of [A]o to a low [Cl-]i in RT neurons, our results also demonstrate that reduced levels of KCC2 remain sufficient to maintain low levels of Cl- Reduced KCC2 levels, however, restrict the capacity of RT neurons to rapidly extrude Cl- following periods of elevated GABAergic signaling. In a computational model of a local RT network featuring slow Cl- extrusion kinetics, similar to those we found experimentally, model RT neurons are predisposed to an activity-dependent switch from GABA-mediated inhibition to excitation. By decreasing the activity threshold required to produce excitatory GABAergic signaling, weaker stimuli are able to propagate activity within the model RT nucleus. Our results indicate the importance of even diminished levels of KCC2 in maintaining inhibitory signaling within the RT nucleus and suggest how this important activity choke point may be easily overcome in disorders such as epilepsy.SIGNIFICANCE STATEMENT Precise regulation of intracellular Cl- levels ([Cl-]i) preserves appropriate, often inhibitory, GABAergic signaling within the brain. However, there is disagreement over the relative contribution of various mechanisms that maintain low [Cl-]i We found that the Cl- transporter KCC2 is an important Cl- extruder in the reticular thalamic (RT) nucleus, despite this nucleus having remarkably low KCC2 immunoreactivity relative to other regions of the adult brain. We also identified a smaller contribution of fixed, impermeant anions ([A]o) to lowering [Cl-]i in RT neurons. Inhibitory signaling among RT neurons is important for preventing excessive activation of RT neurons, which can be responsible for generating seizures. Our work suggests that KCC2 critically restricts the spread of activity within the RT nucleus.
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Affiliation(s)
- Peter M Klein
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Adam C Lu
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Megan E Harper
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Hannah M McKown
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Jessica D Morgan
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Mark P Beenhakker
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
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54
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Boffi JC, Knabbe J, Kaiser M, Kuner T. KCC2-dependent Steady-state Intracellular Chloride Concentration and pH in Cortical Layer 2/3 Neurons of Anesthetized and Awake Mice. Front Cell Neurosci 2018; 12:7. [PMID: 29422838 PMCID: PMC5788967 DOI: 10.3389/fncel.2018.00007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 01/05/2018] [Indexed: 12/31/2022] Open
Abstract
Neuronal intracellular Cl− concentration ([Cl−]i) influences a wide range of processes such as neuronal inhibition, membrane potential dynamics, intracellular pH (pHi) or cell volume. Up to date, neuronal [Cl−]i has predominantly been studied in model systems of reduced complexity. Here, we implemented the genetically encoded ratiometric Cl− indicator Superclomeleon (SCLM) to estimate the steady-state [Cl−]i in cortical neurons from anesthetized and awake mice using 2-photon microscopy. Additionally, we implemented superecliptic pHluorin (SE-pHluorin) as a ratiometric sensor to estimate the intracellular steady-state pH (pHi) of mouse cortical neurons in vivo. We estimated an average resting [Cl−]i of 6 ± 2 mM with no evidence of subcellular gradients in the proximal somato-dendritic domain and an average somatic pHi of 7.1 ± 0.2. Neither [Cl−]i nor pHi were affected by isoflurane anesthesia. We deleted the cation-Cl− co-transporter KCC2 in single identified neurons of adult mice and found an increase of [Cl−]i to approximately 26 ± 8 mM, demonstrating that under in vivo conditions KCC2 produces low [Cl−]i in adult mouse neurons. In summary, neurons of the brain of awake adult mice exhibit a low and evenly distributed [Cl−]i in the proximal somato-dendritic compartment that is independent of anesthesia and requires KCC2 expression for its maintenance.
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Affiliation(s)
- Juan C Boffi
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
| | - Johannes Knabbe
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
| | - Michaela Kaiser
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
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55
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Altered Chloride Homeostasis Decreases the Action Potential Threshold and Increases Hyperexcitability in Hippocampal Neurons. eNeuro 2018; 4:eN-NWR-0172-17. [PMID: 29379872 PMCID: PMC5783240 DOI: 10.1523/eneuro.0172-17.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 10/09/2017] [Accepted: 10/31/2017] [Indexed: 11/21/2022] Open
Abstract
Chloride ions play an important role in controlling excitability of principal neurons in the central nervous system. When neurotransmitter GABA is released from inhibitory interneurons, activated GABA type A (GABAA) receptors on principal neurons become permeable to chloride. Typically, chloride flows through activated GABAA receptors into the neurons causing hyperpolarization or shunting inhibition, and in turn inhibits action potential (AP) generation. However, in situations when intracellular chloride concentration is increased, chloride ions can flow in opposite direction, depolarize neurons, and promote AP generation. It is generally recognized that altered chloride homeostasis per se has no effect on the AP threshold. Here, we demonstrate that chloride overload of mouse principal CA3 pyramidal neurons not only makes these cells more excitable through GABAA receptor activation but also lowers the AP threshold, further aggravating excitability. This phenomenon has not been described in principal neurons and adds to our understanding of mechanisms regulating neuronal and network excitability, particularly in developing brain and during pathological situations with altered chloride homeostasis. This finding further broadens the spectrum of neuronal plasticity regulated by ionic compositions across the cellular membrane.
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56
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Conway LC, Cardarelli RA, Moore YE, Jones K, McWilliams LJ, Baker DJ, Burnham MP, Bürli RW, Wang Q, Brandon NJ, Moss SJ, Deeb TZ. N-Ethylmaleimide increases KCC2 cotransporter activity by modulating transporter phosphorylation. J Biol Chem 2017; 292:21253-21263. [PMID: 29092909 PMCID: PMC5766942 DOI: 10.1074/jbc.m117.817841] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 10/27/2017] [Indexed: 11/06/2022] Open
Abstract
K+/Cl- cotransporter 2 (KCC2) is selectively expressed in the adult nervous system and allows neurons to maintain low intracellular Cl- levels. Thus, KCC2 activity is an essential prerequisite for fast hyperpolarizing synaptic inhibition mediated by type A γ-aminobutyric acid (GABAA) receptors, which are Cl--permeable, ligand-gated ion channels. Consistent with this, deficits in the activity of KCC2 lead to epilepsy and are also implicated in neurodevelopmental disorders, neuropathic pain, and schizophrenia. Accordingly, there is significant interest in developing activators of KCC2 as therapeutic agents. To provide insights into the cellular processes that determine KCC2 activity, we have investigated the mechanism by which N-ethylmaleimide (NEM) enhances transporter activity using a combination of biochemical and electrophysiological approaches. Our results revealed that, within 15 min, NEM increased cell surface levels of KCC2 and modulated the phosphorylation of key regulatory residues within the large cytoplasmic domain of KCC2 in neurons. More specifically, NEM increased the phosphorylation of serine 940 (Ser-940), whereas it decreased phosphorylation of threonine 1007 (Thr-1007). NEM also reduced with no lysine (WNK) kinase phosphorylation of Ste20-related proline/alanine-rich kinase (SPAK), a kinase that directly phosphorylates KCC2 at residue Thr-1007. Mutational analysis revealed that Thr-1007 dephosphorylation mediated the effects of NEM on KCC2 activity. Collectively, our results suggest that compounds that either increase the surface stability of KCC2 or reduce Thr-1007 phosphorylation may be of use as enhancers of KCC2 activity.
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Affiliation(s)
- Leslie C Conway
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts 02111
| | - Ross A Cardarelli
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts 02111
| | - Yvonne E Moore
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Karen Jones
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Alderley Park SK10 4TG, United Kingdom
| | - Lisa J McWilliams
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Cambridge CB4 0WG, United Kingdom
| | - David J Baker
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Cambridge CB4 0WG, United Kingdom
| | - Matthew P Burnham
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Alderley Park SK10 4TG, United Kingdom
| | - Roland W Bürli
- Neuroscience, IMED Biotech Unit, AstraZeneca, Cambridge CB21 6GH, United Kingdom, and
| | - Qi Wang
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts 02111
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts 02451
| | - Nicholas J Brandon
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts 02111
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts 02451
| | - Stephen J Moss
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts 02111,
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Tarek Z Deeb
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts 02111
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
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57
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Cardarelli RA, Jones K, Pisella LI, Wobst HJ, McWilliams LJ, Sharpe PM, Burnham MP, Baker DJ, Chudotvorova I, Guyot J, Silayeva L, Morrow DH, Dekker N, Zicha S, Davies PA, Holenz J, Duggan ME, Dunlop J, Mather RJ, Wang Q, Medina I, Brandon NJ, Deeb TZ, Moss SJ. The small molecule CLP257 does not modify activity of the K +-Cl - co-transporter KCC2 but does potentiate GABA A receptor activity. Nat Med 2017; 23:1394-1396. [PMID: 29216042 PMCID: PMC7371006 DOI: 10.1038/nm.4442] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Ross A Cardarelli
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, USA
| | - Karen Jones
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Alderley Park, UK
| | - Lucie I Pisella
- INMED, INSERM, Unité 901, Marseille, France
- Aix-Marseille Université, UMR 901, Marseille, France
| | - Heike J Wobst
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, USA
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | | | - Paul M Sharpe
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Alderley Park, UK
| | - Matthew P Burnham
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Alderley Park, UK
| | - David J Baker
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Cambridge, UK
| | - Ilona Chudotvorova
- INMED, INSERM, Unité 901, Marseille, France
- Aix-Marseille Université, UMR 901, Marseille, France
| | - Justine Guyot
- INMED, INSERM, Unité 901, Marseille, France
- Aix-Marseille Université, UMR 901, Marseille, France
| | - Liliya Silayeva
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, USA
| | - Danielle H Morrow
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Niek Dekker
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Stephen Zicha
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | - Paul A Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Jörg Holenz
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | - Mark E Duggan
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | - John Dunlop
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | - Robert J Mather
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | - Qi Wang
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, USA
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | - Igor Medina
- INMED, INSERM, Unité 901, Marseille, France
- Aix-Marseille Université, UMR 901, Marseille, France
| | - Nicholas J Brandon
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, USA
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, Massachusetts, USA
| | - Tarek Z Deeb
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, USA
| | - Stephen J Moss
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, USA
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
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58
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Agez M, Schultz P, Medina I, Baker DJ, Burnham MP, Cardarelli RA, Conway LC, Garnier K, Geschwindner S, Gunnarsson A, McCall EJ, Frechard A, Audebert S, Deeb TZ, Moss SJ, Brandon NJ, Wang Q, Dekker N, Jawhari A. Molecular architecture of potassium chloride co-transporter KCC2. Sci Rep 2017; 7:16452. [PMID: 29184062 PMCID: PMC5705597 DOI: 10.1038/s41598-017-15739-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 10/27/2017] [Indexed: 01/15/2023] Open
Abstract
KCC2 is a neuron specific K+-Cl− co-transporter that controls neuronal chloride homeostasis, and is critically involved in many neurological diseases including brain trauma, epilepsies, autism and schizophrenia. Despite significant accumulating data on the biology and electrophysiological properties of KCC2, structure-function relationships remain poorly understood. Here we used calixarene detergent to solubilize and purify wild-type non-aggregated and homogenous KCC2. Specific binding of inhibitor compound VU0463271 was demonstrated using surface plasmon resonance (SPR). Mass spectrometry revealed glycosylations and phosphorylations as expected from functional KCC2. We show by electron microscopy (EM) that KCC2 exists as monomers and dimers in solution. Monomers are organized into “head” and “core” domains connected by a flexible “linker”. Dimers are asymmetrical and display a bent “S-shape” architecture made of four distinct domains and a flexible dimerization interface. Chemical crosslinking in reducing conditions shows that disulfide bridges are involved in KCC2 dimerization. Moreover, we show that adding a tag to the C-terminus is detrimental to KCC2 function. We postulate that the conserved KCC2 C-ter may be at the interface of dimerization. Taken together, our findings highlight the flexible multi-domain structure of KCC2 with variable anchoring points at the dimerization interface and an important C-ter extremity providing the first in-depth functional architecture of KCC2.
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Affiliation(s)
- Morgane Agez
- CALIXAR, 60 avenue Rockefeller, 69008, Lyon, France
| | - Patrick Schultz
- Department of Integrated Structural Biology, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire) INSERM, U964; CNRS/Strasbourg University, UMR7104 1, rue Laurent Fries, BP10142, 67404, Illkirch, France
| | | | - David J Baker
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Cambridge, UK
| | - Matthew P Burnham
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Alderley Park, UK
| | - Ross A Cardarelli
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, 02111, USA
| | - Leslie C Conway
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, 02111, USA
| | | | | | - Anders Gunnarsson
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Eileen J McCall
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Cambridge, UK
| | - Alexandre Frechard
- Department of Integrated Structural Biology, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire) INSERM, U964; CNRS/Strasbourg University, UMR7104 1, rue Laurent Fries, BP10142, 67404, Illkirch, France
| | - Stéphane Audebert
- Aix Marseille Univ, CNRS, INSERM, Institut Paoli-Calmettes, CRCM, Marseille Protéomique, Marseille, France
| | - Tarek Z Deeb
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, 02111, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, 02111, USA.,Department of Neuroscience, Physiology and Pharmacology, University College, London, WC1E, 6BT, UK
| | - Nicholas J Brandon
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, 02111, USA.,Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, MA, USA
| | - Qi Wang
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, Massachusetts, 02111, USA.,Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, MA, USA
| | - Niek Dekker
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden.
| | - Anass Jawhari
- CALIXAR, 60 avenue Rockefeller, 69008, Lyon, France.
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59
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Estradiol modulates the efficacy of synaptic inhibition by decreasing the dwell time of GABA A receptors at inhibitory synapses. Proc Natl Acad Sci U S A 2017; 114:11763-11768. [PMID: 29078280 PMCID: PMC5676881 DOI: 10.1073/pnas.1705075114] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Estrogen plays a critical role in many physiological processes and exerts profound effects on behavior by regulating neuronal excitability. While estrogen has been established to exert effects on dendritic morphology and excitatory neurotransmission its role in regulating neuronal inhibition is poorly understood. Fast synaptic inhibition in the adult brain is mediated by specialized populations of γ-c aA receptors (GABAARs) that are selectively enriched at synapses, a process dependent upon their interaction with the inhibitory scaffold protein gephyrin. Here we have assessed the role that estradiol (E2) plays in regulating the dynamics of GABAARs and stability of inhibitory synapses. Treatment of cultured cortical neurons with E2 reduced the accumulation of GABAARs and gephyrin at inhibitory synapses. However, E2 exposure did not modify the expression of either the total or the plasma membrane GABAARs or gephyrin. Mechanistically, single-particle tracking revealed that E2 treatment selectively reduced the dwell time and thereby decreased the confinement of GABAARs at inhibitory synapses. Consistent with our cell biology measurements, we observed a significant reduction in amplitude of inhibitory synaptic currents in both cultured neurons and hippocampal slices exposed to E2, while their frequency was unaffected. Collectively, our results suggest that acute exposure of neurons to E2 leads to destabilization of GABAARs and gephyrin at inhibitory synapses, leading to reductions in the efficacy of GABAergic inhibition via a postsynaptic mechanism.
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60
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Pelkey KA, Chittajallu R, Craig MT, Tricoire L, Wester JC, McBain CJ. Hippocampal GABAergic Inhibitory Interneurons. Physiol Rev 2017; 97:1619-1747. [PMID: 28954853 DOI: 10.1152/physrev.00007.2017] [Citation(s) in RCA: 490] [Impact Index Per Article: 70.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/16/2017] [Accepted: 05/26/2017] [Indexed: 12/11/2022] Open
Abstract
In the hippocampus GABAergic local circuit inhibitory interneurons represent only ~10-15% of the total neuronal population; however, their remarkable anatomical and physiological diversity allows them to regulate virtually all aspects of cellular and circuit function. Here we provide an overview of the current state of the field of interneuron research, focusing largely on the hippocampus. We discuss recent advances related to the various cell types, including their development and maturation, expression of subtype-specific voltage- and ligand-gated channels, and their roles in network oscillations. We also discuss recent technological advances and approaches that have permitted high-resolution, subtype-specific examination of their roles in numerous neural circuit disorders and the emerging therapeutic strategies to ameliorate such pathophysiological conditions. The ultimate goal of this review is not only to provide a touchstone for the current state of the field, but to help pave the way for future research by highlighting where gaps in our knowledge exist and how a complete appreciation of their roles will aid in future therapeutic strategies.
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Affiliation(s)
- Kenneth A Pelkey
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Ramesh Chittajallu
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Michael T Craig
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Ludovic Tricoire
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Jason C Wester
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Chris J McBain
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
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Moore YE, Kelley MR, Brandon NJ, Deeb TZ, Moss SJ. Seizing Control of KCC2: A New Therapeutic Target for Epilepsy. Trends Neurosci 2017; 40:555-571. [PMID: 28803659 DOI: 10.1016/j.tins.2017.06.008] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 06/20/2017] [Accepted: 06/22/2017] [Indexed: 11/17/2022]
Abstract
Deficits in GABAergic inhibition result in the abnormal neuronal activation and synchronization that underlies seizures. However, the molecular mechanisms responsible for transforming a normal brain into an epileptic one remain largely unknown. Hyperpolarizing inhibition mediated by type A GABA (GABAA) receptors is dependent on chloride extrusion by the neuron-specific type 2K+-Cl- cotransporter (KCC2). Loss-of-function mutations in KCC2 are a known cause of infantile epilepsy in humans and KCC2 dysfunction is present in patients with both idiopathic and acquired epilepsy. Here we discuss the growing evidence that KCC2 dysfunction has a central role in the development and severity of the epilepsies.
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Affiliation(s)
- Yvonne E Moore
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Matt R Kelley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Nicholas J Brandon
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA; AstraZeneca Neuroscience, Innovative Medicines and Early Development Biotech Unit, R&D Boston, Waltham, MA 024515, USA
| | - Tarek Z Deeb
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA
| | - Stephen J Moss
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA.
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Martín-Aragón Baudel MAS, Poole AV, Darlison MG. Chloride co-transporters as possible therapeutic targets for stroke. J Neurochem 2016; 140:195-209. [PMID: 27861901 DOI: 10.1111/jnc.13901] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/08/2016] [Accepted: 11/08/2016] [Indexed: 02/06/2023]
Abstract
Stroke is one of the major causes of death and disability worldwide. The major type of stroke is an ischaemic one, which is caused by a blockage that interrupts blood flow to the brain. There are currently very few pharmacological strategies to reduce the damage and social burden triggered by this pathology. The harm caused by the interruption of blood flow to the brain unfolds in the subsequent hours and days, so it is critical to identify new therapeutic targets that could reduce neuronal death associated with the spread of the damage. Here, we review some of the key molecular mechanisms involved in the progression of neuronal death, focusing on some new and promising studies. In particular, we focus on the potential of the chloride co-transporter (CCC) family of proteins, mediators of the GABAergic response, both during the early and later stages of stroke, to promote neuroprotection and recovery. Different studies of CCCs during the chronic and recovery phases post-stroke reveal the importance of timing when considering CCCs as potential neuroprotective and/or neuromodulator targets. The molecular regulatory mechanisms of the two main neuronal CCCs, NKCC1 and KCC2, are further discussed as an indirect approach for promoting neuroprotection and neurorehabilitation following an ischaemic insult. Finally, we mention the likely importance of combining different strategies in order to achieve more effective therapies.
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Affiliation(s)
| | - Amy V Poole
- School of Applied Sciences, Edinburgh Napier University, Sighthill Campus, Sighthill Court, Edinburgh, UK
| | - Mark G Darlison
- School of Applied Sciences, Edinburgh Napier University, Sighthill Campus, Sighthill Court, Edinburgh, UK
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Riffault B, Kourdougli N, Dumon C, Ferrand N, Buhler E, Schaller F, Chambon C, Rivera C, Gaiarsa JL, Porcher C. Pro-Brain-Derived Neurotrophic Factor (proBDNF)-Mediated p75NTR Activation Promotes Depolarizing Actions of GABA and Increases Susceptibility to Epileptic Seizures. Cereb Cortex 2016; 28:510-527. [DOI: 10.1093/cercor/bhw385] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 11/17/2016] [Indexed: 12/16/2022] Open
Affiliation(s)
- Baptiste Riffault
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- INSERM—Institut National de la Santé et de la Recherche Médicale, Unité 901, Marseille, Parc Scientifique de Luminy, 13273 Marseille, France
- INMED—Institut de Neurobiologie de la Méditerranée, Parc Scientifique de Luminy, 13273 Marseille, France
| | - Nazim Kourdougli
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- INSERM—Institut National de la Santé et de la Recherche Médicale, Unité 901, Marseille, Parc Scientifique de Luminy, 13273 Marseille, France
- INMED—Institut de Neurobiologie de la Méditerranée, Parc Scientifique de Luminy, 13273 Marseille, France
| | - Camille Dumon
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- INSERM—Institut National de la Santé et de la Recherche Médicale, Unité 901, Marseille, Parc Scientifique de Luminy, 13273 Marseille, France
- INMED—Institut de Neurobiologie de la Méditerranée, Parc Scientifique de Luminy, 13273 Marseille, France
| | - Nadine Ferrand
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- INSERM—Institut National de la Santé et de la Recherche Médicale, Unité 901, Marseille, Parc Scientifique de Luminy, 13273 Marseille, France
- INMED—Institut de Neurobiologie de la Méditerranée, Parc Scientifique de Luminy, 13273 Marseille, France
| | - Emmanuelle Buhler
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- Plateforme Post-Génomique, INMED, 13273 Marseille, France
| | - Fabienne Schaller
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- Plateforme Post-Génomique, INMED, 13273 Marseille, France
| | - Caroline Chambon
- Aix-Marseille University, Département de Biologie, NIA, UMR 7260 CNRS, 13331 cedex 03, Marseille, France
| | - Claudio Rivera
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- INSERM—Institut National de la Santé et de la Recherche Médicale, Unité 901, Marseille, Parc Scientifique de Luminy, 13273 Marseille, France
- INMED—Institut de Neurobiologie de la Méditerranée, Parc Scientifique de Luminy, 13273 Marseille, France
| | - Jean-Luc Gaiarsa
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- INSERM—Institut National de la Santé et de la Recherche Médicale, Unité 901, Marseille, Parc Scientifique de Luminy, 13273 Marseille, France
- INMED—Institut de Neurobiologie de la Méditerranée, Parc Scientifique de Luminy, 13273 Marseille, France
| | - Christophe Porcher
- Aix-Marseille University, Département de Biologie, Parc Scientifique de Luminy, 13273 Marseille, France
- INSERM—Institut National de la Santé et de la Recherche Médicale, Unité 901, Marseille, Parc Scientifique de Luminy, 13273 Marseille, France
- INMED—Institut de Neurobiologie de la Méditerranée, Parc Scientifique de Luminy, 13273 Marseille, France
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Kahle KT, Khanna AR, Duan J, Staley KJ, Delpire E, Poduri A. The KCC2 Cotransporter and Human Epilepsy: Getting Excited About Inhibition. Neuroscientist 2016; 22:555-562. [PMID: 27130838 DOI: 10.1177/1073858416645087] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The cation-Cl- cotransporter KCC2, encoded by SLC12A5, is required for the emergence and maintenance of GABAergic fast synaptic inhibition in organisms across evolution. These findings have suggested that KCC2 deficiency might play a role in the pathogenesis human epilepsy, but this has only recently been substantiated by two lines of genetic evidence. The first is the discovery of heterozygous missense polymorphisms in SLC12A5, causing decreased KCC2-dependent Cl- extrusion capacity, in an Australian family with inherited febrile seizures and in a French-Canadian cohort with severe genetic generalized epilepsy (GGE). The second is the discovery of recessive loss-of-function mutations in SLC12A5 in patients with a severe, early-onset Mendelian disease termed "epilepsy of infancy with migrating focal seizures" (EIMFS). These findings collectively support the paradigm that precisely regulated KCC2 activity is required for synaptic inhibition in humans, and that genetically encoded impairment of KCC2 function, due to effects on gene dosage, intrinsic activity, or extrinsic regulation, can influence epilepsy phenotypes in patients. Accordingly, KCC2 could be a target for a novel antiepileptic strategies that aims to restore GABA inhibition by facilitating Cl- extrusion. Such drugs could have relevance for pharmaco-resistant epilepsies and possibly other diseases characterized by synaptic hyperexcitability, such as the spectrum autism disorders.
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Affiliation(s)
- Kristopher T Kahle
- Departments of Neurosurgery, Pediatrics, and Cellular and Molecular Physiology, Yale Program in Neurogenetics, and Centers for Mendelian Genomics, Yale University School of Medicine, New Haven, CT, USA
| | - Arjun R Khanna
- Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - JingJing Duan
- Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Kevin J Staley
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Annapurna Poduri
- Division of Epilepsy and Clinical Electrophysiology, Department of Neurology, Boston Children's Hospital, Boston, MA, USA
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Alfonsa H, Lakey JH, Lightowlers RN, Trevelyan AJ. Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons. Nat Commun 2016; 7:13495. [PMID: 27853135 PMCID: PMC5118542 DOI: 10.1038/ncomms13495] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 10/10/2016] [Indexed: 01/11/2023] Open
Abstract
Chloride regulation affects brain function in many ways, for instance, by dictating the GABAergic reversal potential, and thereby influencing neuronal excitability and spike timing. Consistent with this, there is increasing evidence implicating chloride in a range of neurological conditions. Investigations about these conditions, though, are made difficult by the limited range of tools available to manipulate chloride levels. In particular, there has been no way to actively remove chloride from neurons; we now describe an optogenetic strategy, ‘Cl-out', to do exactly this. Cl-out achieves its effect by the cooperative action of two different component opsins: the proton pump, Archaerhodopsin and a chloride channel opsin. The removal of chloride happens when both are activated together, using Archaerhodopsin as an optical voltage clamp to provide the driving force for chloride removal through the concurrently opened, chloride channels. We further show that this novel optogenetic strategy can reverse an in vitro epileptogenic phenotype. Chloride regulation is important for setting GABAergic reversal potential, though tools to manipulate chloride levels are limited. Here, the authors combine Archaerhodopsin with a chloride channel opsin to generate an optogenetic chloride extrusion strategy, ‘Cl-out', which they demonstrate in hippocampal slices.
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Affiliation(s)
- Hannah Alfonsa
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Jeremy H Lakey
- Institute for Cell and Molecular Biosciences, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Robert N Lightowlers
- Institute for Cell and Molecular Biosciences, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
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Buchin A, Chizhov A, Huberfeld G, Miles R, Gutkin BS. Reduced Efficacy of the KCC2 Cotransporter Promotes Epileptic Oscillations in a Subiculum Network Model. J Neurosci 2016; 36:11619-11633. [PMID: 27852771 PMCID: PMC6231544 DOI: 10.1523/jneurosci.4228-15.2016] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 08/04/2016] [Accepted: 08/07/2016] [Indexed: 12/17/2022] Open
Abstract
Pharmacoresistant epilepsy is a chronic neurological condition in which a basal brain hyperexcitability results in paroxysmal hypersynchronous neuronal discharges. Human temporal lobe epilepsy has been associated with dysfunction or loss of the potassium-chloride cotransporter KCC2 in a subset of pyramidal cells in the subiculum, a key structure generating epileptic activities. KCC2 regulates intraneuronal chloride and extracellular potassium levels by extruding both ions. Absence of effective KCC2 may alter the dynamics of chloride and potassium levels during repeated activation of GABAergic synapses due to interneuron activity. In turn, such GABAergic stress may itself affect Cl- regulation. Such changes in ionic homeostasis may switch GABAergic signaling from inhibitory to excitatory in affected pyramidal cells and also increase neuronal excitability. Possibly these changes contribute to periodic bursting in pyramidal cells, an essential component in the onset of ictal epileptic events. We tested this hypothesis with a computational model of a subicular network with realistic connectivity. The pyramidal cell model explicitly incorporated the cotransporter KCC2 and its effects on the internal/external chloride and potassium levels. Our network model suggested the loss of KCC2 in a critical number of pyramidal cells increased external potassium and intracellular chloride concentrations leading to seizure-like field potential oscillations. These oscillations included transient discharges leading to ictal-like field events with frequency spectra as in vitro Restoration of KCC2 function suppressed seizure activity and thus may present a useful therapeutic option. These simulations therefore suggest that reduced KCC2 cotransporter activity alone may underlie the generation of ictal discharges. SIGNIFICANCE STATEMENT Ion regulation in the brain is a major determinant of neural excitability. Intracellular chloride in neurons, a partial determinant of the resting potential and the inhibitory reversal potentials, is regulated together with extracellular potassium via kation chloride cotransporters. During temporal lobe epilepsy, the homeostatic regulation of intracellular chloride is impaired in pyramidal cells, yet how this dysregulation may lead to seizures has not been explored. Using a realistic neural network model describing ion mechanisms, we show that chloride homeostasis pathology provokes seizure activity analogous to recordings from epileptogenic brain tissue. We show that there is a critical percentage of pathological cells required for seizure initiation. Our model predicts that restoration of the chloride homeostasis in pyramidal cells could be a viable antiepileptic strategy.
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Affiliation(s)
- Anatoly Buchin
- École normale supérieure, Paris Sciences et Lettres University, Laboratoire de Neurosciences Cognitives, Institute national de la santé et de la recherche médicale U960, Group for Neural Theory, 75005 Paris, France,
- Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251, Russia
- National Research University Higher School of Economics, Center for Cognition and Decision Making, Moscow 109316, Russia
| | - Anton Chizhov
- Ioffe Institute, Computational Physics Laboratory, St. Petersburg 194021, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg 194223, Russia
| | - Gilles Huberfeld
- Université Pierre et Marie Curie, Pitié-Salpêtrière Hôpital, Assistance Publique-Hôpitaux de Paris, Neurophysiology Department, 75013 Paris, France
- Institute national de la santé et de la recherche médicale U1129 "Infantile Epilepsies and Brain Plasticity," Paris Descartes University, Pôle de recherche et d'enseignement supérieur Sorbonne Paris Cité, 75015 Paris, France, and
| | - Richard Miles
- Institut du Cerveau et de la Moelle Epinière, Cortex et Epilepsie Group, 75013 Paris, France
| | - Boris S Gutkin
- École normale supérieure, Paris Sciences et Lettres University, Laboratoire de Neurosciences Cognitives, Institute national de la santé et de la recherche médicale U960, Group for Neural Theory, 75005 Paris, France
- National Research University Higher School of Economics, Center for Cognition and Decision Making, Moscow 109316, Russia
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67
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MacKenzie G, O'Toole KK, Moss SJ, Maguire J. Compromised GABAergic inhibition contributes to tumor-associated epilepsy. Epilepsy Res 2016; 126:185-96. [PMID: 27513374 PMCID: PMC5308901 DOI: 10.1016/j.eplepsyres.2016.07.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 05/02/2016] [Accepted: 07/26/2016] [Indexed: 10/21/2022]
Abstract
Glioblastoma Multiforme (GBM) is the most common form of primary brain tumor with 30-50% of patients presenting with epilepsy. These tumor-associated seizures are often resistant to traditional antiepileptic drug treatment and persist after tumor resection. This suggests that changes in the peritumoral tissue underpin epileptogenesis. It is known that glioma cells extrude pathological concentrations of glutamate which is thought to play a role in tumor progression and the development of epilepsy. Given that pathological concentrations of glutamate have been shown to dephosphorylate and downregulate the potassium chloride cotransporter KCC2, we hypothesized that glioma-induced alterations in KCC2 in the peritumoral region may play a role in tumor-associated epilepsy. Consistent with this hypothesis, we observe a decrease in total KCC2 expression and a dephosphorylation of KCC2 at residue Ser940 in a glioma model which exhibits hyperexcitability and the development of spontaneous seizures. To determine whether the reduction of KCC2 could potentially contribute to tumor-associated epilepsy, we generated mice with a focal knockdown of KCC2 by injecting AAV2-Cre-GFP into the cortex of floxed KCC2 mice. The AAV2-Cre-mediated knockdown of KCC2 was sufficient to induce the development of spontaneous seizures. Further, blocking NKCC1 with bumetanide to offset the loss of KCC2 reduced the seizure susceptibility in glioma-implanted mice. These findings support a mechanism of tumor-associated epilepsy involving downregulation of KCC2 in the peritumoral region leading to compromised GABAergic inhibition and suggest that modulating chloride homeostasis may be useful for seizure control.
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Affiliation(s)
- Georgina MacKenzie
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Kate K O'Toole
- Training in Education and Critical Research Skills (TEACRS) Program, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Jamie Maguire
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, United States.
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Kelley MR, Deeb TZ, Brandon NJ, Dunlop J, Davies PA, Moss SJ. Compromising KCC2 transporter activity enhances the development of continuous seizure activity. Neuropharmacology 2016; 108:103-10. [PMID: 27108931 PMCID: PMC5337122 DOI: 10.1016/j.neuropharm.2016.04.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 04/05/2016] [Accepted: 04/20/2016] [Indexed: 11/17/2022]
Abstract
Impaired neuronal inhibition has long been associated with the increased probability of seizure occurrence and heightened seizure severity. Fast synaptic inhibition in the brain is primarily mediated by the type A γ-aminobutyric acid receptors (GABAARs), ligand-gated ion channels that can mediate Cl(-) influx resulting in membrane hyperpolarization and the restriction of neuronal firing. In most adult brain neurons, the K(+)/Cl(-) co-transporter-2 (KCC2) establishes hyperpolarizing GABAergic inhibition by maintaining low [Cl(-)]i. In this study, we sought to understand how decreased KCC2 transport function affects seizure event severity. We impaired KCC2 transport in the 0-Mg(2+) ACSF and 4-aminopyridine in vitro models of epileptiform activity in acute mouse brain slices. Experiments with the selective KCC2 inhibitor VU0463271 demonstrated that reduced KCC2 transport increased the duration of SLEs, resulting in non-terminating discharges of clonic-like activity. We also investigated slices obtained from the KCC2-Ser940Ala (S940A) point-mutant mouse, which has a mutation at a known functional phosphorylation site causing behavioral and cellular deficits under hyperexcitable conditions. We recorded from the entorhinal cortex of S940A mouse brain slices in both 0-Mg(2+) ACSF and 4-aminopyridine, and demonstrated that loss of the S940 residue increased the susceptibility of continuous clonic-like discharges, an in vitro form of status epilepticus. Our experiments revealed KCC2 transport activity is a critical factor in seizure event duration and mechanisms of termination. Our results highlight the need for therapeutic strategies that potentiate KCC2 transport function in order to decrease seizure event severity and prevent the development of status epilepticus.
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Affiliation(s)
- Matthew R Kelley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Tarek Z Deeb
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA
| | - Nicholas J Brandon
- AstraZeneca Neuroscience, Innovative Medicines and Early Development Biotech Unit, 141, Portland St, Cambridge, MA, USA
| | - John Dunlop
- AstraZeneca Neuroscience, Innovative Medicines and Early Development Biotech Unit, 141, Portland St, Cambridge, MA, USA
| | - Paul A Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA; Department of Neuroscience, Physiology and Pharmacology, University College, London, WC1E 6BT, UK.
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69
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Tighilet B, Dutheil S, Siponen MI, Noreña AJ. Reactive Neurogenesis and Down-Regulation of the Potassium-Chloride Cotransporter KCC2 in the Cochlear Nuclei after Cochlear Deafferentation. Front Pharmacol 2016; 7:281. [PMID: 27630564 PMCID: PMC5005331 DOI: 10.3389/fphar.2016.00281] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/16/2016] [Indexed: 12/26/2022] Open
Abstract
While many studies have been devoted to investigating the homeostatic plasticity triggered by cochlear hearing loss, the cellular and molecular mechanisms involved in these central changes remain elusive. In the present study, we investigated the possibility of reactive neurogenesis after unilateral cochlear nerve section in the cochlear nucleus (CN) of cats. We found a strong cell proliferation in all the CN sub-divisions ipsilateral to the lesion. Most of the newly generated cells survive up to 1 month after cochlear deafferentation in all cochlear nuclei (except the dorsal CN) and give rise to a variety of cell types, i.e., microglial cells, astrocytes, and neurons. Interestingly, many of the newborn neurons had an inhibitory (GABAergic) phenotype. This result is intriguing since sensory deafferentation is usually accompanied by enhanced excitation, consistent with a reduction in central inhibition. The membrane potential effect of GABA depends, however, on the intra-cellular chloride concentration, which is maintained at low levels in adults by the potassium chloride co-transporter KCC2. The KCC2 density on the plasma membrane of neurons was then assessed after cochlear deafferentation in the cochlear nuclei ipsilateral and contralateral to the lesion. Cochlear deafferentation is accompanied by a strong down-regulation of KCC2 ipsilateral to the lesion at 3 and 30 days post-lesion. This study suggests that reactive neurogenesis and down-regulation of KCC2 is part of the vast repertoire involved in homeostatic plasticity triggered by hearing loss. These central changes may also play a role in the generation of tinnitus and hyperacusis.
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Affiliation(s)
- Brahim Tighilet
- Laboratoire de Neurosciences Intégratives et Adaptatives, UMR 7260 - Comportement, Cerveau, Cognition (Behavior, Brain, and Cognition) - Aix-Marseille Université - Centre National de la Recherche Scientifique Marseille, France
| | - Sophie Dutheil
- Department of Psychiatry, School of Medicine, Yale University, New Haven CT, USA
| | - Marina I Siponen
- Laboratoire de Neurosciences Intégratives et Adaptatives, UMR 7260 - Comportement, Cerveau, Cognition (Behavior, Brain, and Cognition) - Aix-Marseille Université - Centre National de la Recherche Scientifique Marseille, France
| | - Arnaud J Noreña
- Laboratoire de Neurosciences Intégratives et Adaptatives, UMR 7260 - Comportement, Cerveau, Cognition (Behavior, Brain, and Cognition) - Aix-Marseille Université - Centre National de la Recherche Scientifique Marseille, France
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Awad PN, Sanon NT, Chattopadhyaya B, Carriço JN, Ouardouz M, Gagné J, Duss S, Wolf D, Desgent S, Cancedda L, Carmant L, Di Cristo G. Reducing premature KCC2 expression rescues seizure susceptibility and spine morphology in atypical febrile seizures. Neurobiol Dis 2016; 91:10-20. [PMID: 26875662 DOI: 10.1016/j.nbd.2016.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/26/2016] [Accepted: 02/09/2016] [Indexed: 11/23/2022] Open
Abstract
Atypical febrile seizures are considered a risk factor for epilepsy onset and cognitive impairments later in life. Patients with temporal lobe epilepsy and a history of atypical febrile seizures often carry a cortical malformation. This association has led to the hypothesis that the presence of a cortical dysplasia exacerbates febrile seizures in infancy, in turn increasing the risk for neurological sequelae. The mechanisms linking these events are currently poorly understood. Potassium-chloride cotransporter KCC2 affects several aspects of neuronal circuit development and function, by modulating GABAergic transmission and excitatory synapse formation. Recent data suggest that KCC2 downregulation contributes to seizure generation in the epileptic adult brain, but its role in the developing brain is still controversial. In a rodent model of atypical febrile seizures, combining a cortical dysplasia and hyperthermia-induced seizures (LHS rats), we found a premature and sustained increase in KCC2 protein levels, accompanied by a negative shift of the reversal potential of GABA. In parallel, we observed a significant reduction in dendritic spine size and mEPSC amplitude in CA1 pyramidal neurons, accompanied by spatial memory deficits. To investigate whether KCC2 premature overexpression plays a role in seizure susceptibility and synaptic alterations, we reduced KCC2 expression selectively in hippocampal pyramidal neurons by in utero electroporation of shRNA. Remarkably, KCC2 shRNA-electroporated LHS rats show reduced hyperthermia-induced seizure susceptibility, while dendritic spine size deficits were rescued. Our findings demonstrate that KCC2 overexpression in a compromised developing brain increases febrile seizure susceptibility and contribute to dendritic spine alterations.
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Affiliation(s)
- Patricia N Awad
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Nathalie T Sanon
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Bidisha Chattopadhyaya
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Josianne Nunes Carriço
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Mohamed Ouardouz
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Jonathan Gagné
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Sandra Duss
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Daniele Wolf
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Sébastien Desgent
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Laura Cancedda
- Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, via Morego, 30, 16163 Genova, Italy
| | - Lionel Carmant
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada.
| | - Graziella Di Cristo
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada.
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Robinson S, Winer JL, Berkner J, Chan LAS, Denson JL, Maxwell JR, Yang Y, Sillerud LO, Tasker RC, Meehan WP, Mannix R, Jantzie LL. Imaging and serum biomarkers reflecting the functional efficacy of extended erythropoietin treatment in rats following infantile traumatic brain injury. J Neurosurg Pediatr 2016; 17:739-55. [PMID: 26894518 PMCID: PMC5369240 DOI: 10.3171/2015.10.peds15554] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Traumatic brain injury (TBI) is a leading cause of death and severe morbidity for otherwise healthy full-term infants around the world. Currently, the primary treatment for infant TBI is supportive, as no targeted therapies exist to actively promote recovery. The developing infant brain, in particular, has a unique response to injury and the potential for repair, both of which vary with maturation. Targeted interventions and objective measures of therapeutic efficacy are needed in this special population. The authors hypothesized that MRI and serum biomarkers can be used to quantify outcomes following infantile TBI in a preclinical rat model and that the potential efficacy of the neuro-reparative agent erythropoietin (EPO) in promoting recovery can be tested using these biomarkers as surrogates for functional outcomes. METHODS With institutional approval, a controlled cortical impact (CCI) was delivered to postnatal Day (P)12 rats of both sexes (76 rats). On postinjury Day (PID)1, the 49 CCI rats designated for chronic studies were randomized to EPO (3000 U/kg/dose, CCI-EPO, 24 rats) or vehicle (CCI-veh, 25 rats) administered intraperitoneally on PID1-4, 6, and 8. Acute injury (PID3) was evaluated with an immunoassay of injured cortex and serum, and chronic injury (PID13-28) was evaluated with digitized gait analyses, MRI, and serum immunoassay. The CCI-veh and CCI-EPO rats were compared with shams (49 rats) primarily using 2-way ANOVA with Bonferroni post hoc correction. RESULTS Following CCI, there was 4.8% mortality and 55% of injured rats exhibited convulsions. Of the injured rats designated for chronic analyses, 8.1% developed leptomeningeal cyst-like lesions verified with MRI and were excluded from further study. On PID3, Western blot showed that EPO receptor expression was increased in the injured cortex (p = 0.008). These Western blots also showed elevated ipsilateral cortex calpain degradation products for αII-spectrin (αII-SDPs; p < 0.001), potassium chloride cotransporter 2 (KCC2-DPs; p = 0.037), and glial fibrillary acidic protein (GFAP-DPs; p = 0.002), as well as serum GFAP (serum GFAP-DPs; p = 0.001). In injured rats multiplex electrochemiluminescence analyses on PID3 revealed elevated serum tumor necrosis factor alpha (TNFα p = 0.01) and chemokine (CXC) ligand 1 (CXCL1). Chronically, that is, in PID13-16 CCI-veh rats, as compared with sham rats, gait deficits were demonstrated (p = 0.033) but then were reversed (p = 0.022) with EPO treatment. Diffusion tensor MRI of the ipsilateral and contralateral cortex and white matter in PID16-23 CCI-veh rats showed widespread injury and significant abnormalities of functional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD); MD, AD, and RD improved after EPO treatment. Chronically, P13-P28 CCI-veh rats also had elevated serum CXCL1 levels, which normalized in CCI-EPO rats. CONCLUSIONS Efficient translation of emerging neuro-reparative interventions dictates the use of age-appropriate preclinical models with human clinical trial-compatible biomarkers. In the present study, the authors showed that CCI produced chronic gait deficits in P12 rats that resolved with EPO treatment and that chronic imaging and serum biomarkers correlated with this improvement.
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MESH Headings
- Age Factors
- Animals
- Animals, Newborn
- Biomarkers/blood
- Brain Injuries, Traumatic/blood
- Brain Injuries, Traumatic/complications
- Brain Injuries, Traumatic/diagnostic imaging
- Brain Injuries, Traumatic/drug therapy
- Calpain/metabolism
- Cerebral Cortex/drug effects
- Cerebral Cortex/metabolism
- Cytokines/blood
- Diffusion Magnetic Resonance Imaging
- Disease Models, Animal
- Epoetin Alfa/metabolism
- Erythropoietin/therapeutic use
- Female
- Gait Disorders, Neurologic/drug therapy
- Gait Disorders, Neurologic/etiology
- Gene Expression Regulation, Developmental/drug effects
- Glial Fibrillary Acidic Protein/metabolism
- Image Processing, Computer-Assisted
- Male
- Rats
- Receptors, Erythropoietin/metabolism
- Statistics, Nonparametric
- Symporters
- Time Factors
- K Cl- Cotransporters
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Affiliation(s)
- Shenandoah Robinson
- Brain Injury Center, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Neurosurgery, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- F. M. Kirby Center for Neurobiology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Jesse L. Winer
- Brain Injury Center, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Neurosurgery, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Justin Berkner
- Brain Injury Center, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Emergency Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Lindsay A. S. Chan
- Brain Injury Center, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Neurosurgery, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Jesse L. Denson
- Department of Pediatrics, University of New Mexico School of Medicine, Albuquerque, New Mexico
| | - Jessie R. Maxwell
- Department of Pediatrics, University of New Mexico School of Medicine, Albuquerque, New Mexico
| | - Yirong Yang
- Department of Neurology, University of New Mexico School of Medicine, Albuquerque, New Mexico
| | - Laurel O. Sillerud
- Department of Neurology, University of New Mexico School of Medicine, Albuquerque, New Mexico
| | - Robert C. Tasker
- Brain Injury Center, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Anesthesiology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - William P. Meehan
- Brain Injury Center, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Sports Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Rebekah Mannix
- Brain Injury Center, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Emergency Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Lauren L. Jantzie
- Department of Pediatrics, University of New Mexico School of Medicine, Albuquerque, New Mexico
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, New Mexico
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72
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Mahadevan V, Woodin MA. Regulation of neuronal chloride homeostasis by neuromodulators. J Physiol 2016; 594:2593-605. [PMID: 26876607 PMCID: PMC4865579 DOI: 10.1113/jp271593] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 01/10/2016] [Indexed: 01/23/2023] Open
Abstract
KCC2 is the central regulator of neuronal Cl(-) homeostasis, and is critical for enabling strong hyperpolarizing synaptic inhibition in the mature brain. KCC2 hypofunction results in decreased inhibition and increased network hyperexcitability that underlies numerous disease states including epilepsy, neuropathic pain and neuropsychiatric disorders. The current holy grail of KCC2 biology is to identify how we can rescue KCC2 hypofunction in order to restore physiological levels of synaptic inhibition and neuronal network activity. It is becoming increasingly clear that diverse cellular signals regulate KCC2 surface expression and function including neurotransmitters and neuromodulators. In the present review we explore the existing evidence that G-protein-coupled receptor (GPCR) signalling can regulate KCC2 activity in numerous regions of the nervous system including the hypothalamus, hippocampus and spinal cord. We present key evidence from the literature suggesting that GPCR signalling is a conserved mechanism for regulating chloride homeostasis. This evidence includes: (1) the activation of group 1 metabotropic glutamate receptors and metabotropic Zn(2+) receptors strengthens GABAergic inhibition in CA3 pyramidal neurons through a regulation of KCC2; (2) activation of the 5-hydroxytryptamine type 2A serotonin receptors upregulates KCC2 cell surface expression and function, restores endogenous inhibition in motoneurons, and reduces spasticity in rats; and (3) activation of A3A-type adenosine receptors rescues KCC2 dysfunction and reverses allodynia in a model of neuropathic pain. We propose that GPCR-signals are novel endogenous Cl(-) extrusion enhancers that may regulate KCC2 function.
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Affiliation(s)
- Vivek Mahadevan
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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Abstract
Although the majority of seizures are brief and cause no long-term consequences, a subset is sufficiently prolonged that long-term consequences can result. These very prolonged seizures are termed "status epilepticus" (SE) and are considered a neurological emergency. The clinical presentation of SE can be diverse. SE can occur at any age but most commonly occurs in the very young and the very old. There are numerous studies on SE in animals in which the pathophysiology, medication responses, and pathology can be rigorously studied in a controlled fashion. Human data are consistent with the animal data. In particular, febrile status epilepticus (FSE), a form of SE common in young children, is associated with injury to the hippocampus and subsequent temporal lobe epilepsy (TLE) in both animals and humans.
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Affiliation(s)
- Syndi Seinfeld
- Virginia Commonwealth University, Richmond, Virginia 23298-0211
| | | | - Shlomo Shinnar
- Comprehensive Epilepsy Management Center, Montefiore Medical Center, Albert Einstein College of Medicine, New York, New York 10467
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74
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Jantzie LL, Getsy PM, Denson JL, Firl DJ, Maxwell JR, Rogers DA, Wilson CG, Robinson S. Prenatal Hypoxia-Ischemia Induces Abnormalities in CA3 Microstructure, Potassium Chloride Co-Transporter 2 Expression and Inhibitory Tone. Front Cell Neurosci 2015; 9:347. [PMID: 26388734 PMCID: PMC4558523 DOI: 10.3389/fncel.2015.00347] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 08/20/2015] [Indexed: 12/19/2022] Open
Abstract
Infants who suffer perinatal brain injury, including those with encephalopathy of prematurity, are prone to chronic neurological deficits, including epilepsy, cognitive impairment, and behavioral problems, such as anxiety, inattention, and poor social interaction. These deficits, especially in combination, pose the greatest hindrance to these children becoming independent adults. Cerebral function depends on adequate development of essential inhibitory neural circuits and the appropriate amount of excitation and inhibition at specific stages of maturation. Early neuronal synaptic responses to γ-amino butyric acid (GABA) are initially excitatory. During the early postnatal period, GABAAR responses switch to inhibitory with the upregulation of potassium-chloride co-transporter KCC2. With extrusion of chloride by KCC2, the Cl− reversal potential shifts and GABA and glycine responses become inhibitory. We hypothesized that prenatal hypoxic–ischemic brain injury chronically impairs the developmental upregulation of KCC2 that is essential for cerebral circuit formation. Following late gestation hypoxia–ischemia (HI), diffusion tensor imaging in juvenile rats shows poor microstructural integrity in the hippocampal CA3 subfield, with reduced fractional anisotropy and elevated radial diffusivity. The loss of microstructure correlates with early reduced KCC2 expression on NeuN-positive pyramidal neurons, and decreased monomeric and oligomeric KCC2 protein expression in the CA3 subfield. Together with decreased inhibitory post-synaptic currents during a critical window of development, we document for the first time that prenatal transient systemic HI in rats impairs hippocampal CA3 inhibitory tone. Failure of timely development of inhibitory tone likely contributes to a lower seizure threshold and impaired cognitive function in children who suffer perinatal brain injury.
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Affiliation(s)
- Lauren L Jantzie
- Department of Pediatrics, University of New Mexico , Albuquerque, NM , USA ; Department of Neurosciences, University of New Mexico , Albuquerque, NM , USA ; Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School , Boston, MA , USA ; Department of Neurology, Boston Children's Hospital, Harvard Medical School , Boston, MA , USA
| | - Paulina M Getsy
- Department of Pediatrics, Case Western Reserve University School of Medicine , Cleveland, OH , USA
| | - Jesse L Denson
- Department of Pediatrics, University of New Mexico , Albuquerque, NM , USA ; Department of Neurosciences, University of New Mexico , Albuquerque, NM , USA
| | - Daniel J Firl
- Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School , Boston, MA , USA ; Department of Neurology, Boston Children's Hospital, Harvard Medical School , Boston, MA , USA
| | - Jessie R Maxwell
- Department of Pediatrics, University of New Mexico , Albuquerque, NM , USA ; Department of Neurosciences, University of New Mexico , Albuquerque, NM , USA
| | - Danny A Rogers
- Department of Pediatrics, University of New Mexico , Albuquerque, NM , USA ; Department of Neurosciences, University of New Mexico , Albuquerque, NM , USA
| | - Christopher G Wilson
- Department of Pediatrics, Center for Perinatal Biology, Loma Linda University , Loma Linda, CA , USA
| | - Shenandoah Robinson
- Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School , Boston, MA , USA ; Department of Neurology, Boston Children's Hospital, Harvard Medical School , Boston, MA , USA ; F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School , Boston, MA , USA
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Uwera J, Nedergaard S, Andreasen M. A novel mechanism for the anticonvulsant effect of furosemide in rat hippocampus in vitro. Brain Res 2015; 1625:1-8. [PMID: 26301821 DOI: 10.1016/j.brainres.2015.08.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 07/15/2015] [Accepted: 08/14/2015] [Indexed: 11/25/2022]
Abstract
Though both in vivo and in vitro studies have demonstrated an anticonvulsant effect of the loop diuretic furosemide, the precise mechanism behind this effect is still debated. The current study investigates the effect of furosemide on Cs-induced epileptiform activity (Cs-FP) evoked in area CA1 of rat hippocampal slices in the presence of Cs(+) (5mM) and ionotropic glutamatergic and GABAergic receptor antagonists. As this model diverges in several respects from other epilepsy models it can offer new insight into the mechanism behind the anticonvulsive effect of furosemide. The present study shows that furosemide suppresses the Cs-FP in a dose-dependent manner with a near complete block at concentrations ≥ 1.25 mM. Because furosemide targets several types of ion transporters we examined the effect of more selective antagonists. Bumetanide (20 μM), which selectively inhibits the Na-K-2Cl co-transporter (NKCC1), had no significant effect on the Cs-FP. VU0240551 (10 μM), a selective antagonist of the K-Cl co-transporter (KCC2), reduced the ictal-like phase by 51.73 ± 8.5% without affecting the interictal-like phase of the Cs-FP. DIDS (50 μM), a nonselective antagonist of Cl(-)/HCO3(-)-exchangers, Na(+)-HCO3(-)-cotransporters, chloride channels and KCC2, suppressed the ictal-like phase by 60.8 ± 8.1% without affecting the interictal-like phase. At 500 μM, DIDS completely suppressed the Cs-FP. Based on these results we propose that the anticonvulsant action of furosemide in the Cs(+)-model is exerted through blockade of the neuronal KCC2 and Na(+)-independent Cl(-)/HCO3(-)-exchanger (AE3) leading to stabilization of the activity-induced intracellular acidification in CA1 pyramidal neurons.
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Affiliation(s)
- Josiane Uwera
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Steen Nedergaard
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Mogens Andreasen
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.
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