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Li J, Qi H, Chen Y, Zhu X. Epilepsy and demyelination: Towards a bidirectional relationship. Prog Neurobiol 2024; 234:102588. [PMID: 38378072 DOI: 10.1016/j.pneurobio.2024.102588] [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: 01/14/2024] [Accepted: 02/13/2024] [Indexed: 02/22/2024]
Abstract
Demyelination stands out as a prominent feature in individuals with specific types of epilepsy. Concurrently, individuals with demyelinating diseases, such as multiple sclerosis (MS) are at a greater risk of developing epilepsy compared to non-MS individuals. These bidirectional connections raise the question of whether both pathological conditions share common pathogenic mechanisms. This review focuses on the reciprocal relationship between epilepsy and demyelination diseases. We commence with an overview of the neurological basis of epilepsy and demyelination diseases, followed by an exploration of how our comprehension of these two disorders has evolved in tandem. Additionally, we discuss the potential pathogenic mechanisms contributing to the interactive relationship between these two diseases. A more nuanced understanding of the interplay between epilepsy and demyelination diseases has the potential to unveiling the molecular intricacies of their pathological relationships, paving the way for innovative directions in future clinical management and treatment strategies for these diseases.
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Affiliation(s)
- Jiayi Li
- Department of Pharmacology, Medical School of Southeast University, Nanjing, China; Clinical Medicine, Medical School of Southeast University, Nanjing, China
| | - Honggang Qi
- Department of Pharmacology, Medical School of Southeast University, Nanjing, China
| | - Yuzhou Chen
- Department of Pharmacology, Medical School of Southeast University, Nanjing, China; Clinical Medicine, Medical School of Southeast University, Nanjing, China
| | - Xinjian Zhu
- Department of Pharmacology, Medical School of Southeast University, Nanjing, China.
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2
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Enger R, Heuser K. Astrocytes as critical players of the fine balance between inhibition and excitation in the brain: spreading depolarization as a mechanism to curb epileptic activity. FRONTIERS IN NETWORK PHYSIOLOGY 2024; 4:1360297. [PMID: 38405021 PMCID: PMC10884165 DOI: 10.3389/fnetp.2024.1360297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 01/25/2024] [Indexed: 02/27/2024]
Abstract
Spreading depolarizations (SD) are slow waves of complete depolarization of brain tissue followed by neuronal silencing that may play a role in seizure termination. Even though SD was first discovered in the context of epilepsy research, the link between SD and epileptic activity remains understudied. Both seizures and SD share fundamental pathophysiological features, and recent evidence highlights the frequent occurrence of SD in experimental seizure models. Human data on co-occurring seizures and SD are limited but suggestive. This mini-review addresses possible roles of SD during epileptiform activity, shedding light on SD as a potential mechanism for terminating epileptiform activity. A common denominator for many forms of epilepsy is reactive astrogliosis, a process characterized by morphological and functional changes to astrocytes. Data suggest that SD mechanisms are potentially perturbed in reactive astrogliosis and we propose that this may affect seizure pathophysiology.
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Affiliation(s)
- Rune Enger
- Letten Centre and GliaLab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Kjell Heuser
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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3
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Abstract
Astrocyte endfeet enwrap the entire vascular tree within the central nervous system, where they perform important functions in regulating the blood-brain barrier (BBB), cerebral blood flow, nutrient uptake, and waste clearance. Accordingly, astrocyte endfeet contain specialized organelles and proteins, including local protein translation machinery and highly organized scaffold proteins, which anchor channels, transporters, receptors, and enzymes critical for astrocyte-vascular interactions. Many neurological diseases are characterized by the loss of polarization of specific endfoot proteins, vascular dysregulation, BBB disruption, altered waste clearance, or, in extreme cases, loss of endfoot coverage. A role for astrocyte endfeet has been demonstrated or postulated in many of these conditions. This review provides an overview of the development, composition, function, and pathological changes of astrocyte endfeet and highlights the gaps in our knowledge that future research should address.
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Affiliation(s)
- Blanca Díaz-Castro
- UK Dementia Research Institute and Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland, UK;
| | - Stefanie Robel
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, USA;
| | - Anusha Mishra
- Department of Neurology Jungers Center for Neurosciences Research and Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon, USA;
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Smith LA, Chen C, Lax NZ, Taylor RW, Erskine D, McFarland R. Astrocytic pathology in Alpers' syndrome. Acta Neuropathol Commun 2023; 11:86. [PMID: 37259148 DOI: 10.1186/s40478-023-01579-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 05/11/2023] [Indexed: 06/02/2023] Open
Abstract
Refractory epilepsy is the main neurological manifestation of Alpers' syndrome, a severe childhood-onset mitochondrial disease caused by bi-allelic pathogenic variants in the mitochondrial DNA (mtDNA) polymerase gamma gene (POLG). The pathophysiological mechanisms underpinning neuronal hyperexcitabilty leading to seizures in Alpers' syndrome remain unknown. However, pathological changes to reactive astrocytes are hypothesised to exacerbate neural dysfunction and seizure-associated cortical activity in POLG-related disease. Therefore, we sought to phenotypically characterise astrocytic pathology in Alpers' syndrome. We performed a detailed quantitative investigation of reactive astrocytes in post-mortem neocortical tissues from thirteen patients with Alpers' syndrome, eight neurologically normal controls and five sudden unexpected death in epilepsy (SUDEP) patients, to control for generalised epilepsy-associated astrocytic pathology. Immunohistochemistry to identify glial fibrillary acidic protein (GFAP)-reactive astrocytes revealed striking reactive astrogliosis localised to the primary visual cortex of Alpers' syndrome tissues, characterised by abnormal-appearing hypertrophic astrocytes. Phenotypic characterisation of individual GFAP-reactive astrocytes demonstrated decreased abundance of mitochondrial oxidative phosphorylation (OXPHOS) proteins and altered expression of key astrocytic proteins including Kir4.1 (subunit of the inwardly rectifying K+ ion channel), AQP4 (astrocytic water channel) and glutamine synthetase (enzyme that metabolises glutamate). These phenotypic astrocytic changes were typically different from the pathology observed in SUDEP tissues, suggesting alternative mechanisms of astrocytic dysfunction between these epilepsies. Crucially, our findings provide further evidence of occipital lobe involvement in Alpers' syndrome and support the involvement of reactive astrocytes in the pathogenesis of POLG-related disease.
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Affiliation(s)
- Laura A Smith
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
| | - Chun Chen
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Nichola Z Lax
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle University, Newcastle Upon Tyne, Newcastle, NE2 4HH, UK
| | - Daniel Erskine
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
- NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle University, Newcastle Upon Tyne, Newcastle, NE2 4HH, UK.
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Henning L, Unichenko P, Bedner P, Steinhäuser C, Henneberger C. Overview Article Astrocytes as Initiators of Epilepsy. Neurochem Res 2023; 48:1091-1099. [PMID: 36244037 PMCID: PMC10030460 DOI: 10.1007/s11064-022-03773-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 08/22/2022] [Accepted: 09/27/2022] [Indexed: 10/17/2022]
Abstract
Astrocytes play a dual role in the brain. On the one hand, they are active signaling partners of neurons and can for instance control synaptic transmission and its plasticity. On the other hand, they fulfill various homeostatic functions such as clearance of glutamate and K+ released from neurons. The latter is for instance important for limiting neuronal excitability. Therefore, an impairment or failure of glutamate and K+ clearance will lead to increased neuronal excitability, which could trigger or aggravate brain diseases such as epilepsy, in which neuronal hyperexcitability plays a role. Experimental data indicate that astrocytes could have such a causal role in epilepsy, but the role of astrocytes as initiators of epilepsy and the relevant mechanisms are under debate. In this overview, we will discuss the potential mechanisms with focus on K+ clearance, glutamate uptake and homoeostasis and related mechanisms, and the evidence for their causative role in epilepsy.
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Affiliation(s)
- Lukas Henning
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Petr Unichenko
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Peter Bedner
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany.
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany.
- German Center for Neurodegenerative Diseases (DZNE), 53127, Bonn, Germany.
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Curry RN, Aiba I, Meyer J, Lozzi B, Ko Y, McDonald MF, Rosenbaum A, Cervantes A, Huang-Hobbs E, Cocito C, Greenfield JP, Jalali A, Gavvala J, Mohila C, Serin Harmanci A, Noebels J, Rao G, Deneen B. Glioma epileptiform activity and progression are driven by IGSF3-mediated potassium dysregulation. Neuron 2023; 111:682-695.e9. [PMID: 36787748 PMCID: PMC9991983 DOI: 10.1016/j.neuron.2023.01.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 12/11/2022] [Accepted: 01/17/2023] [Indexed: 02/15/2023]
Abstract
Seizures are a frequent pathophysiological feature of malignant glioma. Recent studies implicate peritumoral synaptic dysregulation as a driver of brain hyperactivity and tumor progression; however, the molecular mechanisms that govern these phenomena remain elusive. Using scRNA-seq and intraoperative patient ECoG recordings, we show that tumors from seizure patients are enriched for gene signatures regulating synapse formation. Employing a human-to-mouse in vivo functionalization pipeline to screen these genes, we identify IGSF3 as a mediator of glioma progression and dysregulated neural circuitry that manifests as spreading depolarization (SD). Mechanistically, we discover that IGSF3 interacts with Kir4.1 to suppress potassium buffering and found that seizure patients exhibit reduced expression of potassium handlers in proliferating tumor cells. In vivo imaging reveals that dysregulated synaptic activity emanates from the tumor-neuron interface, which we confirm in patients. Our studies reveal that tumor progression and seizures are enabled by ion dyshomeostasis and identify SD as a driver of disease.
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Affiliation(s)
- Rachel Naomi Curry
- The Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Isamu Aiba
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jochen Meyer
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Brittney Lozzi
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Program in Genetics and Genomics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Yeunjung Ko
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Program in Immunology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Malcolm Ford McDonald
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Program in Development, Disease, Models, and Therapeutics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Anna Rosenbaum
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Alexis Cervantes
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Emmet Huang-Hobbs
- The Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Carolina Cocito
- Department of Pediatric Neurological Surgery, Weill Cornell Medicine, New York, NY 10065, USA
| | | | - Ali Jalali
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jay Gavvala
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Carrie Mohila
- Department of Pathology, Texas Children's Hospital, Houston, TX 77030, USA
| | - Akdes Serin Harmanci
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jeffrey Noebels
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ganesh Rao
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Benjamin Deneen
- The Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA; Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Program in Development, Disease, Models, and Therapeutics, Baylor College of Medicine, Houston, TX 77030, USA; Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA.
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Mulkey DK, Milla BM. Perspectives on the basis of seizure-induced respiratory dysfunction. Front Neural Circuits 2022; 16:1033756. [PMID: 36605420 PMCID: PMC9807672 DOI: 10.3389/fncir.2022.1033756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/28/2022] [Indexed: 12/24/2022] Open
Abstract
Epilepsy is an umbrella term used to define a wide variety of seizure disorders and sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in epilepsy. Although some SUDEP risk factors have been identified, it remains largely unpredictable, and underlying mechanisms remain poorly understood. Most seizures start in the cortex, but the high mortality rate associated with certain types of epilepsy indicates brainstem involvement. Therefore, to help understand SUDEP we discuss mechanisms by which seizure activity propagates to the brainstem. Specifically, we highlight clinical and pre-clinical evidence suggesting how seizure activation of: (i) descending inhibitory drive or (ii) spreading depolarization might contribute to brainstem dysfunction. Furthermore, since epilepsy is a highly heterogenous disorder, we also considered factors expected to favor or oppose mechanisms of seizure propagation. We also consider whether epilepsy-associated genetic variants directly impact brainstem function. Because respiratory failure is a leading cause of SUDEP, our discussion of brainstem dysfunction focuses on respiratory control.
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Affiliation(s)
- Daniel K. Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
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Eide PK. Cellular changes at the glia-neuro-vascular interface in definite idiopathic normal pressure hydrocephalus. Front Cell Neurosci 2022; 16:981399. [PMID: 36119130 PMCID: PMC9478415 DOI: 10.3389/fncel.2022.981399] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/17/2022] [Indexed: 11/13/2022] Open
Abstract
Idiopathic normal pressure hydrocephalus (iNPH) is a subtype of dementia with overlap toward Alzheimer's disease. Both diseases show deposition of the toxic metabolites amyloid-β and tau in brain. A unique feature with iNPH is that a subset of patients may improve clinically following cerebrospinal fluid (CSF) diversion (shunt) surgery. The patients responding clinically to shunting are denoted Definite iNPH, otherwise iNPH is diagnosed as Possible iNPH or Probable iNPH, high-lightening that the clinical phenotype and underlying pathophysiology remain debated. Given the role of CSF disturbance in iNPH, the water channel aquaporin-4 (AQP4) has been suggested a crucial role in iNPH. Altered expression of AQP4 at the astrocytic endfeet facing the capillaries could affect glymphatic function, i.e., the perivascular transport of fluids and solutes, including soluble amyloid-β and tau. This present study asked how altered perivascular expression of AQP4 in subjects with definite iNPH is accompanied with cellular changes at the glia-neuro-vascular interface. For this purpose, information was retrieved from a database established by the author, including prospectively collected management data, physiological data and information from brain biopsy specimens examined with light and electron microscopy. Individuals with definite iNPH were included together with control subjects who matched the definite iNPH cohort closest in gender and age. Patients with definite iNPH presented with abnormally elevated pulsatile intracranial pressure measured overnight. Cortical brain biopsies showed reduced expression of AQP4 at astrocytic endfeet both perivascular and toward neuropil. This was accompanied with reduced expression of the anchor molecule dystrophin (Dp71) at astrocytic perivascular endfeet, evidence of altered cellular metabolic activity in astrocytic endfoot processes (reduced number of normal and increased number of pathological mitochondria), and evidence of reactive changes in astrocytes (astrogliosis). Moreover, the definite iNPH subjects demonstrated in cerebral cortex changes in capillaries (reduced thickness of the basement membrane between astrocytic endfeet and endothelial cells and pericytes, and evidence of impaired blood-brain-barrier integrity). Abnormal changes in neurons were indicated by reduced post-synaptic density length, and reduced number of normal mitochondria in pre-synaptic terminals. In summary, definite iNPH is characterized by profound cellular changes at the glia-neurovascular interface, which probably reflect the underlying pathophysiology.
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Affiliation(s)
- Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital—Rikshospitalet, Oslo, Norway
- Faculty of Medicine, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- *Correspondence: Per Kristian Eide
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Proskurina EY, Zaitsev AV. Regulation of Potassium and Chloride Concentrations in Nervous Tissue as a Method of Anticonvulsant Therapy. J EVOL BIOCHEM PHYS+ 2022. [DOI: 10.1134/s0022093022050015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Abstract
Under some pathological conditions, such as pharmacoresistant
epilepsy, status epilepticus or certain forms of genetic abnormalities,
spiking activity of GABAergic interneurons may enhance excitation
processes in neuronal circuits and provoke the generation of ictal
discharges. As a result, anticonvulsants acting on the GABAergic
system may be ineffective or even increase seizure activity. This
paradoxical effect of the inhibitory system is due to ionic imbalances
in nervous tissue. This review addresses the mechanisms of ictal
discharge initiation in neuronal networks due to the imbalance of
chloride and potassium ions, as well as possible ways to regulate
ionic concentrations. Both the enhancement (or attenuation) of the
activity of certain neuronal ion transporters and ion pumps and
their additional expression via gene therapy can be effective in
suppressing seizure activity caused by ionic imbalances. The Na+–K+-pump,
NKCC1 and KCC2 cotransporters are important for maintaining proper
K+ and Cl– concentrations
in nervous tissue, having been repeatedly considered as pharmacological
targets for antiepileptic exposures. Further progress in this direction
is hampered by the lack of sufficiently selective pharmacological
tools and methods for providing effective drug delivery to the epileptic
focus. The use of the gene therapy techniques, such as overexpressing
of the KCC2 transporter in the epileptic focus, seems to be a more promising
approach. Another possible direction could be the use of optogenetic
tools, namely specially designed light-activated ion pumps or ion
channels. In this case, photon energy can be used to create the
required gradients of chloride and potassium ions, although these
methods also have significant limitations which complicate their
rapid introduction into medicine.
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Eide PK, Hansson HA. A New Perspective on the Pathophysiology of Idiopathic Intracranial Hypertension: Role of the Glia-Neuro-Vascular Interface. Front Mol Neurosci 2022; 15:900057. [PMID: 35903170 PMCID: PMC9315230 DOI: 10.3389/fnmol.2022.900057] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Accepted: 06/07/2022] [Indexed: 11/13/2022] Open
Abstract
Idiopathic intracranial hypertension (IIH) is a neurological disease characterized by symptoms and signs of increased intracranial pressure (ICP) of unknown cause. Most attention has been given to the role of cerebrospinal fluid (CSF) disturbance and intracranial venous hypertension caused by sinus vein stenosis. We previously proposed that key pathophysiological processes take place within the brain at the glia-neuro-vascular interface. However, the relative importance of the proposed mechanisms in IIH disease remains unknown. Modern treatment regimens aim to reduce intracranial CSF and venous pressures, but a substantial proportion of patients experience lasting complaints. In 2010, the first author established a database for the prospective collection of information from individuals being assessed for IIH. The database incorporates clinical, imaging, physiological, and biological data, and information about treatment/outcome. This study retrieved information from the database, asking the following research questions: In IIH subjects responding to shunt surgery, what is the occurrence of signs of CSF disturbance, sinus vein stenosis, intracranial hypertension, and microscopic evidence of structural abnormalities at the glia-neuro-vascular interface? Secondarily, do semi-quantitative measures of abnormal ultrastructure at the glia-neurovascular differ between subjects with definite IIH and non-IIH (reference) subjects? The study included 13 patients with IIH who fulfilled the diagnostic criteria and who improved following shunt surgery, i.e., patients with definite IIH. Comparisons were done regarding magnetic resonance imaging (MRI) findings, pulsatile and static ICP scores, and immune-histochemistry microscopy. Among these 13 IIH subjects, 6/13 (46%) of patients presented with magnetic resonance imaging (MRI) signs of CSF disturbance (empty sella and/or distended perioptic subarachnoid spaces), 0/13 (0%) of patients with IIH had MRI signs of sinus vein stenosis, 13/13 (100%) of patients with IIH presented with abnormal preoperative pulsatile ICP [overnight mean ICP wave amplitude (MWA) above thresholds], 3/13 (23%) patients showed abnormal static ICP (overnight mean ICP above threshold), and 12/13 (92%) of patients with IIH showed abnormal structural changes at the glia-neuro-vascular interface. Comparisons of semi-quantitative structural variables between IIH and aged- and gender-matched reference (REF) subjects showed IIH abnormalities in glial cells, neurons, and capillaries. The present data suggest a key role of disease processes affecting the glia-neuro-vascular interface.
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Affiliation(s)
- Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital—Rikshospitalet, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- *Correspondence: Per Kristian Eide
| | - Hans-Arne Hansson
- Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden
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Szu JI, Binder DK. Mechanisms Underlying Aquaporin-4 Subcellular Mislocalization in Epilepsy. Front Cell Neurosci 2022; 16:900588. [PMID: 35734218 PMCID: PMC9207308 DOI: 10.3389/fncel.2022.900588] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
Epilepsy is a chronic brain disorder characterized by unprovoked seizures. Mechanisms underlying seizure activity have been intensely investigated. Alterations in astrocytic channels and transporters have shown to be a critical player in seizure generation and epileptogenesis. One key protein involved in such processes is the astrocyte water channel aquaporin-4 (AQP4). Studies have revealed that perivascular AQP4 redistributes away from astrocyte endfeet and toward the neuropil in both clinical and preclinical studies. This subcellular mislocalization significantly impacts neuronal hyperexcitability and understanding how AQP4 becomes dysregulated in epilepsy is beginning to emerge. In this review, we evaluate the role of AQP4 dysregulation and mislocalization in epilepsy.
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Thompson JA, Miralles RM, Wengert ER, Wagley PK, Yu W, Wenker IC, Patel MK. Astrocyte reactivity in a mouse model of SCN8A epileptic encephalopathy. Epilepsia Open 2022; 7:280-292. [PMID: 34826216 PMCID: PMC9159254 DOI: 10.1002/epi4.12564] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 10/15/2021] [Accepted: 11/23/2021] [Indexed: 11/11/2022] Open
Abstract
OBJECTIVE SCN8A epileptic encephalopathy is caused predominantly by de novo gain-of-function mutations in the voltage-gated sodium channel Nav 1.6. The disorder is characterized by early onset of seizures and developmental delay. Most patients with SCN8A epileptic encephalopathy are refractory to current anti-seizure medications. Previous studies determining the mechanisms of this disease have focused on neuronal dysfunction as Nav 1.6 is expressed by neurons and plays a critical role in controlling neuronal excitability. However, glial dysfunction has been implicated in epilepsy and alterations in glial physiology could contribute to the pathology of SCN8A encephalopathy. In the current study, we examined alterations in astrocyte and microglia physiology in the development of seizures in a mouse model of SCN8A epileptic encephalopathy. METHODS Using immunohistochemistry, we assessed microglia and astrocyte reactivity before and after the onset of spontaneous seizures. Expression of glutamine synthetase and Nav 1.6, and Kir 4.1 channel currents were assessed in astrocytes in wild-type (WT) mice and mice carrying the N1768D SCN8A mutation (D/+). RESULTS Astrocytes in spontaneously seizing D/+ mice become reactive and increase expression of glial fibrillary acidic protein (GFAP), a marker of astrocyte reactivity. These same astrocytes exhibited reduced barium-sensitive Kir 4.1 currents compared to age-matched WT mice and decreased expression of glutamine synthetase. These alterations were only observed in spontaneously seizing mice and not before the onset of seizures. In contrast, microglial morphology remained unchanged before and after the onset of seizures. SIGNIFICANCE Astrocytes, but not microglia, become reactive only after the onset of spontaneous seizures in a mouse model of SCN8A encephalopathy. Reactive astrocytes have reduced Kir 4.1-mediated currents, which would impair their ability to buffer potassium. Reduced expression of glutamine synthetase would modulate the availability of neurotransmitters to excitatory and inhibitory neurons. These deficits in potassium and glutamate handling by astrocytes could exacerbate seizures in SCN8A epileptic encephalopathy. Targeting astrocytes may provide a new therapeutic approach to seizure suppression.
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Affiliation(s)
- Jeremy A. Thompson
- Department of AnesthesiologyUniversity of Virginia Health SystemCharlottesvilleVAUSA
- Neuroscience Graduate ProgramUniversity of VirginiaCharlottesvilleVAUSA
| | - Raquel M. Miralles
- Department of AnesthesiologyUniversity of Virginia Health SystemCharlottesvilleVAUSA
- Neuroscience Graduate ProgramUniversity of VirginiaCharlottesvilleVAUSA
| | - Eric R. Wengert
- Department of AnesthesiologyUniversity of Virginia Health SystemCharlottesvilleVAUSA
- Neuroscience Graduate ProgramUniversity of VirginiaCharlottesvilleVAUSA
| | - Pravin K. Wagley
- Department of AnesthesiologyUniversity of Virginia Health SystemCharlottesvilleVAUSA
| | - Wenxi Yu
- Department of Human GeneticsUniversity of MichiganAnn ArborMIUSA
| | - Ian C. Wenker
- Department of AnesthesiologyUniversity of Virginia Health SystemCharlottesvilleVAUSA
| | - Manoj K. Patel
- Department of AnesthesiologyUniversity of Virginia Health SystemCharlottesvilleVAUSA
- Neuroscience Graduate ProgramUniversity of VirginiaCharlottesvilleVAUSA
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13
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Lo J, Forst AL, Warth R, Zdebik AA. EAST/SeSAME Syndrome and Beyond: The Spectrum of Kir4.1- and Kir5.1-Associated Channelopathies. Front Physiol 2022; 13:852674. [PMID: 35370765 PMCID: PMC8965613 DOI: 10.3389/fphys.2022.852674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 02/08/2022] [Indexed: 12/13/2022] Open
Abstract
In 2009, two groups independently linked human mutations in the inwardly rectifying K+ channel Kir4.1 (gene name KCNJ10) to a syndrome affecting the central nervous system (CNS), hearing, and renal tubular salt reabsorption. The autosomal recessive syndrome has been named EAST (epilepsy, ataxia, sensorineural deafness, and renal tubulopathy) or SeSAME syndrome (seizures, sensorineural deafness, ataxia, intellectual disability, and electrolyte imbalance), accordingly. Renal dysfunction in EAST/SeSAME patients results in loss of Na+, K+, and Mg2+ with urine, activation of the renin-angiotensin-aldosterone system, and hypokalemic metabolic alkalosis. Kir4.1 is highly expressed in affected organs: the CNS, inner ear, and kidney. In the kidney, it mostly forms heteromeric channels with Kir5.1 (KCNJ16). Biallelic loss-of-function mutations of Kir5.1 can also have disease significance, but the clinical symptoms differ substantially from those of EAST/SeSAME syndrome: although sensorineural hearing loss and hypokalemia are replicated, there is no alkalosis, but rather acidosis of variable severity; in contrast to EAST/SeSAME syndrome, the CNS is unaffected. This review provides a framework for understanding some of these differences and will guide the reader through the growing literature on Kir4.1 and Kir5.1, discussing the complex disease mechanisms and the variable expression of disease symptoms from a molecular and systems physiology perspective. Knowledge of the pathophysiology of these diseases and their multifaceted clinical spectrum is an important prerequisite for making the correct diagnosis and forms the basis for personalized therapies.
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Affiliation(s)
- Jacky Lo
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Anna-Lena Forst
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Richard Warth
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Anselm A. Zdebik
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
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14
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Akyuz E, Koklu B, Uner A, Angelopoulou E, Paudel YN. Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy. J Neurosci Res 2021; 100:413-443. [PMID: 34713909 DOI: 10.1002/jnr.24985] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 09/23/2021] [Accepted: 10/01/2021] [Indexed: 01/29/2023]
Abstract
Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.
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Affiliation(s)
- Enes Akyuz
- Faculty of International Medicine, Department of Biophysics, University of Health Sciences, Istanbul, Turkey
| | - Betul Koklu
- Faculty of Medicine, Namık Kemal University, Tekirdağ, Turkey
| | - Arda Uner
- Faculty of Medicine, Yozgat Bozok University, Yozgat, Turkey
| | - Efthalia Angelopoulou
- Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Yam Nath Paudel
- Neuropharmacology Research Strength, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia
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15
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Twible C, Abdo R, Zhang Q. Astrocyte Role in Temporal Lobe Epilepsy and Development of Mossy Fiber Sprouting. Front Cell Neurosci 2021; 15:725693. [PMID: 34658792 PMCID: PMC8514632 DOI: 10.3389/fncel.2021.725693] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/02/2021] [Indexed: 11/13/2022] Open
Abstract
Epilepsy affects approximately 50 million people worldwide, with 60% of adult epilepsies presenting an onset of focal origin. The most common focal epilepsy is temporal lobe epilepsy (TLE). The role of astrocytes in the presentation and development of TLE has been increasingly studied and discussed within the literature. The most common histopathological diagnosis of TLE is hippocampal sclerosis. Hippocampal sclerosis is characterized by neuronal cell loss within the Cornu ammonis and reactive astrogliosis. In some cases, mossy fiber sprouting may be observed. Mossy fiber sprouting has been controversial in its contribution to epileptogenesis in TLE patients, and the mechanisms surrounding the phenomenon have yet to be elucidated. Several studies have reported that mossy fiber sprouting has an almost certain co-existence with reactive astrogliosis within the hippocampus under epileptic conditions. Astrocytes are known to play an important role in the survival and axonal outgrowth of central and peripheral nervous system neurons, pointing to a potential role of astrocytes in TLE and associated cellular alterations. Herein, we review the recent developments surrounding the role of astrocytes in the pathogenic process of TLE and mossy fiber sprouting, with a focus on proposed signaling pathways and cellular mechanisms, histological observations, and clinical correlations in human patients.
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Affiliation(s)
- Carolyn Twible
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada
| | - Rober Abdo
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada.,Department of Anatomy and Cell Biology, Western University, London, ON, Canada
| | - Qi Zhang
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada.,Department of Pathology and Lab Medicine, London Health Sciences Centre, University Hospital, London, ON, Canada
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16
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Heuser K, Enger R. Astrocytic Ca 2+ Signaling in Epilepsy. Front Cell Neurosci 2021; 15:695380. [PMID: 34335188 PMCID: PMC8320018 DOI: 10.3389/fncel.2021.695380] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 06/16/2021] [Indexed: 01/10/2023] Open
Abstract
Epilepsy is one of the most common neurological disorders – estimated to affect at least 65 million worldwide. Most of the epilepsy research has so far focused on how to dampen neuronal discharges and to explain how changes in intrinsic neuronal activity or network function cause seizures. As a result, pharmacological therapy has largely been limited to symptomatic treatment targeted at neurons. Given the expanding spectrum of functions ascribed to the non-neuronal constituents of the brain, in both physiological brain function and in brain disorders, it is natural to closely consider the roles of astrocytes in epilepsy. It is now widely accepted that astrocytes are key controllers of the composition of the extracellular fluids, and may directly interact with neurons by releasing gliotransmitters. A central tenet is that astrocytic intracellular Ca2+ signals promote release of such signaling substances, either through synaptic or non-synaptic mechanisms. Accruing evidence suggests that astrocytic Ca2+ signals play important roles in both seizures and epilepsy, and this review aims to highlight the current knowledge of the roles of this central astrocytic signaling mechanism in ictogenesis and epileptogenesis.
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Affiliation(s)
- Kjell Heuser
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Rune Enger
- Letten Centre and GliaLab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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17
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Nikitin ES, Vinogradova LV. Potassium channels as prominent targets and tools for the treatment of epilepsy. Expert Opin Ther Targets 2021; 25:223-235. [PMID: 33754930 DOI: 10.1080/14728222.2021.1908263] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
INTRODUCTION K+ channels are of great interest to epilepsy research as mutations in their genes are found in humans with inherited epilepsy. At the level of cellular physiology, K+ channels control neuronal intrinsic excitability and are the main contributors to membrane repolarization of active neurons. Recently, a genetically modified voltage-dependent K+ channel has been patented as a remedy for epileptic seizures. AREAS COVERED We review the role of potassium channels in excitability, clinical and experimental evidence for the association of potassium channelopathies with epilepsy, the targeting of K+ channels by drugs, and perspectives of gene therapy in epilepsy with the expression of extra K+ channels in the brain. EXPERT OPINION Control over K+ conductance is of great potential benefit for the treatment of epilepsy. Nowadays, gene therapy affecting K+ channels is one of the most promising approaches to treat pharmacoresistant focal epilepsy.
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Affiliation(s)
- E S Nikitin
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia
| | - L V Vinogradova
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia
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18
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Eide PK, Hasan‐Olive MM, Hansson H, Enger R. Increased occurrence of pathological mitochondria in astrocytic perivascular endfoot processes and neurons of idiopathic intracranial hypertension. J Neurosci Res 2021; 99:467-480. [PMID: 33105056 PMCID: PMC7821105 DOI: 10.1002/jnr.24743] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 09/29/2020] [Accepted: 10/01/2020] [Indexed: 12/11/2022]
Abstract
Idiopathic intracranial hypertension (IIH) primarily affects fertile, overweight women, and presents with the symptoms of raised intracranial pressure. The etiology is unknown but has been thought to relate to cerebrospinal fluid disturbance or cerebral venous stenosis. We have previously found evidence that IIH is also a disease of the brain parenchyma, evidenced by alterations at the neurogliovascular interface, including astrogliosis, pathological changes in the basement membrane and pericytes, and alterations of perivascular aquaporin-4. The aim of this present electron microscopic study was to examine whether mitochondria phenotype was changed in IIH, particularly focusing on perivascular astrocytic endfeet and neurons (soma and pre- and postsynaptic terminals). Cortical brain biopsies of nine reference individuals and eight IIH patients were analyzed for subcellular distribution and phenotypical features of mitochondria using transmission electron microscopy. We found significantly increased prevalence of pathological mitochondria and reduced number of normal mitochondria in astrocytic endfeet of IIH patients. The degree of astrogliosis correlated negatively with the number of normal mitochondria in astrocytic endfoot processes. Moreover, we found significantly increased number of pathological mitochondria in pre- and postsynaptic neuronal terminals, as well as significantly shortened distance between mitochondria and endoplasmic reticulum contacts. Finally, the length of postsynaptic density, a marker of synaptic strength, was on average reduced in IIH. The present data provide evidence of pathological mitochondria in perivascular astrocytes endfeet and neurons of IIH patients, highlighting that impaired metabolism at the neurogliovascular interface may be a facet of IIH.
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Affiliation(s)
- Per Kristian Eide
- Department of NeurosurgeryOslo University Hospital ‐ RikshospitaletOsloNorway
- Institute of Clinical MedicineFaculty of MedicineUniversity of OsloOsloNorway
| | - Md Mahdi Hasan‐Olive
- Department of NeurosurgeryOslo University Hospital ‐ RikshospitaletOsloNorway
- Institute of Clinical MedicineFaculty of MedicineUniversity of OsloOsloNorway
| | | | - Rune Enger
- GliaLab and Letten CentreDivision of Anatomy and Division of PhysiologyDepartment of Molecular MedicineInstitute of Basic Medical SciencesUniversity of OsloOsloNorway
- Department of NeurologyOslo University Hospital ‐ RikshospitaletOsloNorway
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19
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Kinboshi M, Ikeda A, Ohno Y. Role of Astrocytic Inwardly Rectifying Potassium (Kir) 4.1 Channels in Epileptogenesis. Front Neurol 2020; 11:626658. [PMID: 33424762 PMCID: PMC7786246 DOI: 10.3389/fneur.2020.626658] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/08/2020] [Indexed: 12/25/2022] Open
Abstract
Astrocytes regulate potassium and glutamate homeostasis via inwardly rectifying potassium (Kir) 4.1 channels in synapses, maintaining normal neural excitability. Numerous studies have shown that dysfunction of astrocytic Kir4.1 channels is involved in epileptogenesis in humans and animal models of epilepsy. Specifically, Kir4.1 channel inhibition by KCNJ10 gene mutation or expressional down-regulation increases the extracellular levels of potassium ions and glutamate in synapses and causes hyperexcitation of neurons. Moreover, recent investigations demonstrated that inhibition of Kir4.1 channels facilitates the expression of brain-derived neurotrophic factor (BDNF), an important modulator of epileptogenesis, in astrocytes. In this review, we summarize the current understanding on the role of astrocytic Kir4.1 channels in epileptogenesis, with a focus on functional and expressional changes in Kir4.1 channels and their regulation of BDNF secretion. We also discuss the potential of Kir4.1 channels as a therapeutic target for the prevention of epilepsy.
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Affiliation(s)
- Masato Kinboshi
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan.,Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yukihiro Ohno
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
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20
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Putra M, Puttachary S, Liu G, Lee G, Thippeswamy T. Fyn-tau Ablation Modifies PTZ-Induced Seizures and Post-seizure Hallmarks of Early Epileptogenesis. Front Cell Neurosci 2020; 14:592374. [PMID: 33363455 PMCID: PMC7752812 DOI: 10.3389/fncel.2020.592374] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 11/16/2020] [Indexed: 12/22/2022] Open
Abstract
Both Fyn and tau have been associated with neuronal hyperexcitability and neurotoxicity in many tauopathies, including Alzheimer's disease (AD). Individual genetic ablation of fyn or tau appears to be protective against aberrant excitatory neuronal activities in AD and epilepsy models. It is, however, still unknown whether ablation of both Fyn and tau can likely elicit more profound anti-seizure and neuroprotective effects. Here, we show the effects of genetic deletion of Fyn and/or tau on seizure severity in response to pentylenetetrazole (PTZ)-induced seizure in mouse models and neurobiological changes 24 h post-seizures. We used Fyn KO (fyn -/-), tau KO (tau -/-), double knockout (DKO) (fyn -/- / tau -/-), and wild-type (WT) mice of the same genetic background. Both tau KO and DKO showed a significant increase in latency to convulsive seizures and significantly decreased the severity of seizures post-PTZ. Although Fyn KO did not differ significantly from WT, in response to PTZ, Fyn KO still had 36 ± 8% seizure reduction and a 30% increase in seizure latency compared to WT. Surprisingly, in contrast to WT, Fyn KO mice showed higher mortality in <20 min of seizure induction; these mice had severe hydrocephalous. None of the tau -/- and DKO died during the study. In response to PTZ, all KO groups showed a significant reduction in neurodegeneration and gliosis, in contrast to WT, which showed increased neurodegeneration [especially, parvalbumin (PV)-GABAergic interneurons] and gliosis. DKO mice had the most reduced gliosis. Immunohistochemically, phospho-tau (AT8, pS199/S202), Fyn expression, as well as Fyn-tau interaction as measured by PLA increased in WT post-PTZ. Moreover, hippocampal Western blots revealed increased levels of AT8, tyrosine phospho-tau (pY18), and phosphorylated Src tyrosine family kinases (pSFK) in PTZ-treated WT, but not in KO, compared to respective controls. Furthermore, PV interneurons were protected from PTZ-induced seizure effects in all KO mice. The levels of inwardly rectifying potassium (Kir 4.1) channels were also downregulated in astrocytes in the WT post-PTZ, while its levels did not change in KO groups. Overall, our results demonstrated the role of Fyn and tau in seizures and their impact on the mediators of early epileptogenesis in PTZ model.
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Affiliation(s)
- Marson Putra
- Neuroscience Interdepartmental Program, Iowa State University, Ames, IA, United States
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, United States
| | - Sreekanth Puttachary
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, United States
| | - Guanghao Liu
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Gloria Lee
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Thimmasettappa Thippeswamy
- Neuroscience Interdepartmental Program, Iowa State University, Ames, IA, United States
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, United States
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21
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Verhoog QP, Holtman L, Aronica E, van Vliet EA. Astrocytes as Guardians of Neuronal Excitability: Mechanisms Underlying Epileptogenesis. Front Neurol 2020; 11:591690. [PMID: 33324329 PMCID: PMC7726323 DOI: 10.3389/fneur.2020.591690] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/26/2020] [Indexed: 12/11/2022] Open
Abstract
Astrocytes are key homeostatic regulators in the central nervous system and play important roles in physiology. After brain damage caused by e.g., status epilepticus, traumatic brain injury, or stroke, astrocytes may adopt a reactive phenotype. This process of reactive astrogliosis is important to restore brain homeostasis. However, persistent reactive astrogliosis can be detrimental for the brain and contributes to the development of epilepsy. In this review, we will focus on physiological functions of astrocytes in the normal brain as well as pathophysiological functions in the epileptogenic brain, with a focus on acquired epilepsy. We will discuss the role of astrocyte-related processes in epileptogenesis, including reactive astrogliosis, disturbances in energy supply and metabolism, gliotransmission, and extracellular ion concentrations, as well as blood-brain barrier dysfunction and dysregulation of blood flow. Since dysfunction of astrocytes can contribute to epilepsy, we will also discuss their role as potential targets for new therapeutic strategies.
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Affiliation(s)
- Quirijn P. Verhoog
- Leiden Academic Center for Drug Research, Leiden University, Leiden, Netherlands
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Linda Holtman
- Leiden Academic Center for Drug Research, Leiden University, Leiden, Netherlands
| | - Eleonora Aronica
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, Netherlands
| | - Erwin A. van Vliet
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
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22
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Cohen-Salmon M, Slaoui L, Mazaré N, Gilbert A, Oudart M, Alvear-Perez R, Elorza-Vidal X, Chever O, Boulay AC. Astrocytes in the regulation of cerebrovascular functions. Glia 2020; 69:817-841. [PMID: 33058289 DOI: 10.1002/glia.23924] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 09/18/2020] [Accepted: 09/21/2020] [Indexed: 12/18/2022]
Abstract
Astrocytes are the most numerous type of neuroglia in the brain and have a predominant influence on the cerebrovascular system; they control perivascular homeostasis, the integrity of the blood-brain barrier, the dialogue with the peripheral immune system, the transfer of metabolites from the blood, and blood vessel contractility in response to neuronal activity. These regulatory processes occur in a specialized interface composed of perivascular astrocyte extensions that almost completely cover the cerebral blood vessels. Scientists have only recently started to study how this interface is formed and how it influences cerebrovascular functions. Here, we review the literature on the astrocytes' role in the regulation of the cerebrovascular system. We cover the anatomy and development of the gliovascular interface, the known gliovascular functions, and molecular factors, the latter's implication in certain pathophysiological situations, and recent cutting-edge experimental tools developed to examine the astrocytes' role at the vascular interface. Finally, we highlight some open questions in this field of research.
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Affiliation(s)
- Martine Cohen-Salmon
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
| | - Leila Slaoui
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
| | - Noémie Mazaré
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
| | - Alice Gilbert
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
| | - Marc Oudart
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
| | - Rodrigo Alvear-Perez
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
| | - Xabier Elorza-Vidal
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
| | - Oana Chever
- Normandie University, UNIROUEN, INSERM, DC2N, IRIB, Rouen, France
| | - Anne-Cécile Boulay
- Physiology and Physiopathology of the Gliovascular Unit Research Group, Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS Unité Mixte de Recherche 724, INSERM Unité 1050, Labex Memolife, PSL Research University, Paris, France
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23
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Boni JL, Kahanovitch U, Nwaobi SE, Floyd CL, Olsen ML. DNA methylation: A mechanism for sustained alteration of KIR4.1 expression following central nervous system insult. Glia 2020; 68:1495-1512. [PMID: 32068308 PMCID: PMC8665281 DOI: 10.1002/glia.23797] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 01/29/2020] [Accepted: 01/31/2020] [Indexed: 12/22/2022]
Abstract
Kir4.1, a glial-specific inwardly rectifying potassium channel, is implicated in astrocytic maintenance of K+ homeostasis. Underscoring the role of Kir4.1 in central nervous system (CNS) functioning, genetic mutations in KCNJ10, the gene which encodes Kir4.1, causes seizures, ataxia and developmental disability in humans. Kir4.1 protein and mRNA loss are consistently observed in CNS injury and neurological diseases linked to hyperexcitability and neuronal dysfunction, leading to the notion that Kir4.1 represents an attractive therapeutic target. Despite this, little is understood regarding the mechanisms that underpin this downregulation. Previous work by our lab revealed that DNA hypomethylation of the Kcnj10 gene functions to regulate mRNA levels during astrocyte maturation whereas hypermethylation in vitro led to decreased promoter activity. In the present study, we utilized two vastly different injury models with known acute and chronic loss of Kir4.1 protein and mRNA to evaluate the methylation status of Kcnj10 as a candidate molecular mechanism for reduced transcription and subsequent protein loss. Examining whole hippocampal tissue and isolated astrocytes, in a lithium-pilocarpine model of epilepsy, we consistently identified hypermethylation of CpG island two, which resides in the large intronic region spanning the Kcnj10 gene. Strikingly similar results were observed using the second injury paradigm, a fifth cervical (C5) vertebral hemi-contusion model of spinal cord injury. Our previous work indicates the same gene region is significantly hypomethylated when transcription increases during astrocyte maturation. Our results suggest that DNA methylation can bidirectionally modulate Kcnj10 transcription and may represent a targetable molecular mechanism for the restoring astroglial Kir4.1 expression following CNS insult.
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Affiliation(s)
- Jessica L Boni
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
- School of Neuroscience, Virginia Polytechnic and State University, Blacksburg, Virginia
| | - Uri Kahanovitch
- School of Neuroscience, Virginia Polytechnic and State University, Blacksburg, Virginia
| | - Sinifunanya E Nwaobi
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
- Division of Pediatric Neurology, UCLA Mattel Children's Hospital, University of California Los Angeles, Los Angeles, California
| | - Candace L Floyd
- Department of Physical Medicine and Rehabilitation, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Physical Medicine and Rehabilitation, University of Utah Health, Salt Lake City, Utah
| | - Michelle L Olsen
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
- School of Neuroscience, Virginia Polytechnic and State University, Blacksburg, Virginia
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24
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Liu J, Qu C, Han C, Chen MM, An LJ, Zou W. Potassium channels and their role in glioma: A mini review. Mol Membr Biol 2020; 35:76-85. [PMID: 32067536 DOI: 10.1080/09687688.2020.1729428] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
K+ channels regulate a multitude of biological processes and play important roles in a variety of diseases by controlling potassium flow across cell membranes. They are widely expressed in the central and peripheral nervous system. As a malignant tumor derived from nerve epithelium, glioma has the characteristics of high incidence, high recurrence rate, high mortality rate, and low cure rate. Since glioma cells show invasive growth, current surgical methods cannot completely remove tumors. Adjuvant chemotherapy is still needed after surgery. Because the blood-brain barrier and other factors lead to a lower effective concentration of chemotherapeutic drugs in the tumor, the recurrence rate of residual lesions is extremely high. Therefore, new therapeutic methods are needed. Numerous studies have shown that different K+ channel subtypes are differentially expressed in glioma cells and are involved in the regulation of the cell cycle of glioma cells to arrest them at different stages of the cell cycle. Increasing evidence suggests that K+ channels express in glioma cells and regulate glioma cell behaviors such as cell cycle, proliferation and apoptosis. This review article aims to summarize the current knowledge on the function of K+ channels in glioma, suggests K+ channels participating in the development of glioma.
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Affiliation(s)
- Jia Liu
- School of Life Science and Biotechnology, Faculty of Chemical, Environmental and Biological Science, Technology, Dalian University of Technology, Dalian, China.,College of Life Science, Liaoning Normal University, Dalian, China
| | - Chao Qu
- College of Life Science, Liaoning Normal University, Dalian, China
| | - Chao Han
- Regenerative Medicine Center, First Affiliated Hospital of Dalian Medical University, Dalian, China
| | - Meng-Meng Chen
- Company of Qingdao Re-Store Life Sciences, Qingdao, China
| | - Li-Jia An
- School of Life Science and Biotechnology, Faculty of Chemical, Environmental and Biological Science, Technology, Dalian University of Technology, Dalian, China
| | - Wei Zou
- College of Life Science, Liaoning Normal University, Dalian, China.,Company of Qingdao Re-Store Life Sciences, Qingdao, China
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Zhu H, Zhang M, Fu Y, Long H, Xiao W, Feng L, Xiao B, Zhou L. Effects of AQP4 and KCNJ10 Gene Polymorphisms on Drug Resistance and Seizure Susceptibility in Chinese Han Patients with Focal Epilepsy. Neuropsychiatr Dis Treat 2020; 16:119-129. [PMID: 32021205 PMCID: PMC6957104 DOI: 10.2147/ndt.s231352] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Accepted: 12/23/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND PURPOSE Epilepsy is a common chronic neurological disorder. About one third of epilepsy patients will suffer from drug resistance after rational selection of antiepileptic drug treatment. The formation of drug-resistant epilepsy has quite a few causes of which genetic factors are considered to be the most important. Previous studies have suggested that the aquaporin 4(AQP4) and inward rectifier potassium ion channel Kir4.1 (encoded by gene KCNJ10) may act in concert to adjust water homeostasis and concentration of potassium ions in extracellular spaces of the central nervous system. Therefore, these two molecules would play a major role in the regulation of the excitability of neurons. In order to explore the potential mechanism of genetic factors related to AQP4 and Kir4.1, we conducted a study to analyze the effects of the AQP4 and KCNJ10 genes' single nucleotide polymorphisms (SNPs) on epileptic drug resistance and seizure susceptibility in a group of Chinese Han patients with focal epilepsy. MATERIALS AND METHODS In total, 510 patients with focal-onset seizures and 206 healthy controls were recruited. Among the patients, 222 were drug resistant and 288 were responsive. The selection of tag SNPs was based on the Hapmap database and Haploview software. Genotyping of three loci of the AQP4 gene (rs1058424, rs3763043 and rs35931) and nine loci of the KCNJ10 gene (rs12122979, rs1186685, rs6690889, rs2486253, rs1186675, rs12402969, rs12729701, rs1890532 and rs3795339) was conducted on the Sequenom MassARRAY iPLEX platform. RESULTS The distribution of genotype and allele frequencies of selected SNP loci of AQP4 and KCNJ10 genes showed no significant difference between the drug-resistant and drug-responsive groups (p>0.05), and no significant difference between all the idiopathic focal epilepsy patients and healthy controls either. CONCLUSION AQP4 and KCNJ10 genetic polymorphisms may not be associated with drug resistance or seizure susceptibility of focal epilepsy in the Chinese Han population.
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Affiliation(s)
- Haoyue Zhu
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Mengqi Zhang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Yujiao Fu
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Hongyu Long
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Wenbiao Xiao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Li Feng
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Bo Xiao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Luo Zhou
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
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26
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Berger TC, Vigeland MD, Hjorthaug HS, Etholm L, Nome CG, Taubøll E, Heuser K, Selmer KK. Neuronal and glial DNA methylation and gene expression changes in early epileptogenesis. PLoS One 2019; 14:e0226575. [PMID: 31887157 PMCID: PMC6936816 DOI: 10.1371/journal.pone.0226575] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 11/28/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND AIMS Mesial Temporal Lobe Epilepsy is characterized by progressive changes of both neurons and glia, also referred to as epileptogenesis. No curative treatment options, apart from surgery, are available. DNA methylation (DNAm) is a potential upstream mechanism in epileptogenesis and may serve as a novel therapeutic target. To our knowledge, this is the first study to investigate epilepsy-related DNAm, gene expression (GE) and their relationship, in neurons and glia. METHODS We used the intracortical kainic acid injection model to elicit status epilepticus. At 24 hours post injection, hippocampi from eight kainic acid- (KA) and eight saline-injected (SH) mice were extracted and shock frozen. Separation into neurons and glial nuclei was performed by flow cytometry. Changes in DNAm and gene expression were measured with reduced representation bisulfite sequencing (RRBS) and mRNA-sequencing (mRNAseq). Statistical analyses were performed in R with the edgeR package. RESULTS We observed fulminant DNAm- and GE changes in both neurons and glia at 24 hours after initiation of status epilepticus. The vast majority of these changes were specific for either neurons or glia. At several epilepsy-related genes, like HDAC11, SPP1, GAL, DRD1 and SV2C, significant differential methylation and differential gene expression coincided. CONCLUSION We found neuron- and glia-specific changes in DNAm and gene expression in early epileptogenesis. We detected single genetic loci in several epilepsy-related genes, where DNAm and GE changes coincide, worth further investigation. Further, our results may serve as an information source for neuronal and glial alterations in both DNAm and GE in early epileptogenesis.
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Affiliation(s)
- Toni C. Berger
- Department of Neurology, Oslo University Hospital, Oslo, Norway
- University of Oslo, Oslo, Norway
- * E-mail:
| | - Magnus D. Vigeland
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Hanne S. Hjorthaug
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Lars Etholm
- National Center for Epilepsy, Oslo University Hospital, Sandvika, Norway
- Department of Neurology, Section for Neurophysiology, Oslo University Hospital, Oslo, Norway
| | | | - Erik Taubøll
- Department of Neurology, Oslo University Hospital, Oslo, Norway
- University of Oslo, Oslo, Norway
| | - Kjell Heuser
- Department of Neurology, Oslo University Hospital, Oslo, Norway
- University of Oslo, Oslo, Norway
| | - Kaja K. Selmer
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, Oslo, Norway
- National Center for Epilepsy, Oslo University Hospital, Sandvika, Norway
- Division of Clinical Neuroscience, Department of Research and Development, Oslo University Hospital, Oslo, Norway
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Szu JI, Chaturvedi S, Patel DD, Binder DK. Aquaporin-4 Dysregulation in a Controlled Cortical Impact Injury Model of Posttraumatic Epilepsy. Neuroscience 2019; 428:140-153. [PMID: 31866558 DOI: 10.1016/j.neuroscience.2019.12.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/25/2019] [Accepted: 12/03/2019] [Indexed: 11/15/2022]
Abstract
Posttraumatic epilepsy (PTE) is a long-term negative consequence of traumatic brain injury (TBI) in which recurrent spontaneous seizures occur after the initial head injury. PTE develops over an undefined period during which circuitry reorganization in the brain causes permanent hyperexcitability. The pathophysiology by which trauma leads to spontaneous seizures is unknown and clinically relevant models of PTE are key to understanding the molecular and cellular mechanisms underlying the development of PTE. In the present study, we used the controlled-cortical impact (CCI) injury model of TBI to induce PTE in mice and to characterize changes in aquaporin-4 (AQP4) expression. A moderate-severe TBI was induced in the right frontal cortex and video-electroencephalographic (vEEG) recordings were performed in the ipsilateral hippocampus to monitor for spontaneous seizures at 14, 30, 60, and 90 days post injury (dpi). The percentage of mice that developed PTE were 13%, 20%, 27%, and 14% at 14, 30, 60, and 90 dpi, respectively. We found a significant increase in AQP4 in the ipsilateral frontal cortex and hippocampus of mice that developed PTE compared to those that did not develop PTE. Interestingly, AQP4 was found to be mislocalized away from the perivascular endfeet and towards the neuropil in mice that developed PTE. Here, we report for the first time, AQP4 dysregulation in a model of PTE which may carry significant implications for epileptogenesis after TBI.
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Affiliation(s)
- Jenny I Szu
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, CA, USA
| | - Som Chaturvedi
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, CA, USA
| | - Dillon D Patel
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, CA, USA
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, CA, USA.
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28
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Patel DC, Tewari BP, Chaunsali L, Sontheimer H. Neuron-glia interactions in the pathophysiology of epilepsy. Nat Rev Neurosci 2019; 20:282-297. [PMID: 30792501 DOI: 10.1038/s41583-019-0126-4] [Citation(s) in RCA: 226] [Impact Index Per Article: 45.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Epilepsy is a neurological disorder afflicting ~65 million people worldwide. It is caused by aberrant synchronized firing of populations of neurons primarily due to imbalance between excitatory and inhibitory neurotransmission. Hence, the historical focus of epilepsy research has been neurocentric. However, the past two decades have enjoyed an explosion of research into the role of glia in supporting and modulating neuronal activity, providing compelling evidence of glial involvement in the pathophysiology of epilepsy. The mechanisms by which glia, particularly astrocytes and microglia, may contribute to epilepsy and consequently could be harnessed therapeutically are discussed in this Review.
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Affiliation(s)
- Dipan C Patel
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA
| | - Bhanu P Tewari
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA
| | - Lata Chaunsali
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA
| | - Harald Sontheimer
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA. .,School of Neuroscience, Virginia Tech, Blacksburg, VA, USA.
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29
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Nikolic L, Nobili P, Shen W, Audinat E. Role of astrocyte purinergic signaling in epilepsy. Glia 2019; 68:1677-1691. [DOI: 10.1002/glia.23747] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 10/08/2019] [Accepted: 10/25/2019] [Indexed: 12/26/2022]
Affiliation(s)
- Ljiljana Nikolic
- Institute for Biological Research Siniša Stanković, University of Belgrade Serbia
| | | | - Weida Shen
- Zhejiang University City College Zhejiang Hangzhou China
| | - Etienne Audinat
- Institute for Functional Genomics (IGF), University of Montpellier, CNRS, INSERM Montpellier France
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30
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Eid T, Lee TSW, Patrylo P, Zaveri HP. Astrocytes and Glutamine Synthetase in Epileptogenesis. J Neurosci Res 2019; 97:1345-1362. [PMID: 30022509 PMCID: PMC6338538 DOI: 10.1002/jnr.24267] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 05/15/2018] [Accepted: 05/22/2018] [Indexed: 12/31/2022]
Abstract
The cellular, molecular, and metabolic mechanisms that underlie the development of mesial temporal lobe epilepsy are incompletely understood. Here we review the role of astrocytes in epilepsy development (a.k.a. epileptogenesis), particularly astrocyte pathologies related to: aquaporin 4, the inwardly rectifying potassium channel Kir4.1, monocarboxylate transporters MCT1 and MCT2, excitatory amino acid transporters EAAT1 and EAAT2, and glutamine synthetase. We propose that inhibition, dysfunction or loss of astrocytic glutamine synthetase is an important causative factor for some epilepsies, particularly mesial temporal lobe epilepsy and glioblastoma-associated epilepsy. We postulate that the regulatory mechanisms of glutamine synthetase as well as the downstream effects of glutamine synthetase dysfunction, represent attractive, new targets for antiepileptogenic interventions. Currently, no antiepileptogenic therapies are available for human use. The discovery of such interventions is important as it will fundamentally change the way we approach epilepsy by preventing the disease from ever becoming manifest after an epileptogenic insult to the brain.
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Affiliation(s)
- Tore Eid
- Department of Laboratory Medicine, Yale School of Medicine
- Department of Molecular Medicine, University of Oslo
| | | | - Peter Patrylo
- Department of Physiology, Southern Illinois University School of Medicine
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31
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Aoki Y, Hanai S, Sukigara S, Otsuki T, Saito T, Nakagawa E, Kaido T, Kaneko Y, Takahashi A, Ikegaya N, Iwasaki M, Sugai K, Sasaki M, Goto Y, Oka A, Itoh M. Altered Expression of Astrocyte-Related Receptors and Channels Correlates With Epileptogenesis in Hippocampal Sclerosis. Pediatr Dev Pathol 2019; 22:532-539. [PMID: 31166880 DOI: 10.1177/1093526619855488] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND Hippocampal sclerosis (HS) is one of the major causes of intractable epilepsy. Astrogliosis in epileptic brain is a peculiar condition showing epileptogenesis and is thought to be different from the other pathological conditions. The aim of this study is to investigate the altered expression of astrocytic receptors, which contribute to neurotransmission in the synapse, and channels in HS lesions. METHODS We performed immunohistochemical and immunoblotting analyses of the P2RY1, P2RY2, P2RY4, Kir4.1, Kv4.2, mGluR1, and mGluR5 receptors and channels with the brain samples of 20 HS patients and 4 controls and evaluated the ratio of immunopositive cells and those expression levels. RESULTS The ratio of each immunopositive cell per glial fibrillary acidic protein-positive astrocytes and the expression levels of all 7 astrocytic receptors and channels in HS lesions were significantly increased. We previously described unique astrogliosis in epileptic lesions similar to what was observed in this study. CONCLUSION This phenomenon is considered to trigger activation of the related signaling pathways and then contribute to epileptogenesis. Thus, astrocytes in epileptic lesion may show self-hyperexcitability and contribute to epileptogenesis through the endogenous astrocytic receptors and channels. These findings may suggest novel astrocytic receptor-related targets for the pharmacological treatment of epilepsy.
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Affiliation(s)
- Yoshinori Aoki
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Pediatrics, The University of Tokyo, Tokyo, Japan
| | - Sae Hanai
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Sayuri Sukigara
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Taisuke Otsuki
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Neurosurgery, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Takashi Saito
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan.,Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Eiji Nakagawa
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Takanobu Kaido
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Neurosurgery, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Yuu Kaneko
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Neurosurgery, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Akio Takahashi
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Neurosurgery, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Naoki Ikegaya
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Neurosurgery, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Masaki Iwasaki
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Neurosurgery, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Kenji Sugai
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Masayuki Sasaki
- Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan.,Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Yuichi Goto
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan.,Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
| | - Akira Oka
- Department of Pediatrics, The University of Tokyo, Tokyo, Japan
| | - Masayuki Itoh
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan.,Epilepsy Center, National Center Hospital, National Center of Neurology and Psychiatry, Kodaira, Japan
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32
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González OC, Krishnan GP, Timofeev I, Bazhenov M. Ionic and synaptic mechanisms of seizure generation and epileptogenesis. Neurobiol Dis 2019; 130:104485. [PMID: 31150792 DOI: 10.1016/j.nbd.2019.104485] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 05/23/2019] [Accepted: 05/27/2019] [Indexed: 01/09/2023] Open
Abstract
The biophysical mechanisms underlying epileptogenesis and the generation of seizures remain to be better understood. Among many factors triggering epileptogenesis are traumatic brain injury breaking normal synaptic homeostasis and genetic mutations disrupting ionic concentration homeostasis. Impairments in these mechanisms, as seen in various brain diseases, may push the brain network to a pathological state characterized by increased susceptibility to unprovoked seizures. Here, we review recent computational studies exploring the roles of ionic concentration dynamics in the generation, maintenance, and termination of seizures. We further discuss how ionic and synaptic homeostatic mechanisms may give rise to conditions which prime brain networks to exhibit recurrent spontaneous seizures and epilepsy.
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Affiliation(s)
- Oscar C González
- Neurosciences Graduate Program, University of California, San Diego, CA 92093, United States of America; Department of Medicine, University of California, San Diego, CA 92093, United States of America
| | - Giri P Krishnan
- Department of Medicine, University of California, San Diego, CA 92093, United States of America
| | - Igor Timofeev
- Centre de recherche de l'Institut universitaire en santé mentale de Québec (CRIUSMQ), 2601 de la Canardière, Québec, QC, Canada; Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada
| | - Maxim Bazhenov
- Neurosciences Graduate Program, University of California, San Diego, CA 92093, United States of America; Department of Medicine, University of California, San Diego, CA 92093, United States of America.
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33
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ECS Dynamism and Its Influence on Neuronal Excitability and Seizures. Neurochem Res 2019; 44:1020-1036. [DOI: 10.1007/s11064-019-02773-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 03/07/2019] [Accepted: 03/07/2019] [Indexed: 02/08/2023]
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34
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Down-Regulation of Astrocytic Kir4.1 Channels during the Audiogenic Epileptogenesis in Leucine-Rich Glioma-Inactivated 1 ( Lgi1) Mutant Rats. Int J Mol Sci 2019; 20:ijms20051013. [PMID: 30813600 PMCID: PMC6429235 DOI: 10.3390/ijms20051013] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 02/14/2019] [Accepted: 02/21/2019] [Indexed: 02/07/2023] Open
Abstract
The dysfunction of astrocytic inwardly rectifying potassium (Kir) 4.1 channels, which mediate the spatial potassium-buffering function of astrocytes, is known to be involved in the development of epilepsy. Here, we analyzed the Kir4.1 expressional changes in Leucine-Rich Glioma-Inactivated 1 (Lgi1) mutant rats, which is a model of autosomal dominant lateral temporal lobe epilepsy in humans, to clarify the role of astrocytic Kir4.1 channels in Lgi1-related epileptogenesis. Priming acoustic stimulation (at postnatal day 16) conferred seizure susceptibility on Lgi1 mutant rats, which evoked audiogenic seizures with test stimulation at eight weeks. In the seizure-susceptible Lgi1 mutant rats (before test stimulation), astrocytic Kir4.1 expression was down-regulated region-specifically in the cerebral cortex, hippocampus, and amygdala. In addition, prophylactic treatments of Lgi1 mutant rats with valproic acid (VPA, 30 mg/kg and 200 mg/kg) for two weeks prevented both the development of seizure susceptibility and the down-regulation of Kir4.1 expression in astrocytes. The present study demonstrated for the first time that the astrocytic Kir4.1 expression was reduced in the Lgi1-related seizure model, suggesting that the down-regulation of Kir4.1 channels in astrocytes is involved in audiogenic epileptogenesis caused by Lgi1 mutation. In addition, VPA seemed to have a prophylactic effect on Lgi1-related seizures.
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35
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Ohno Y, Kinboshi M, Shimizu S. Inwardly Rectifying Potassium Channel Kir4.1 as a Novel Modulator of BDNF Expression in Astrocytes. Int J Mol Sci 2018; 19:ijms19113313. [PMID: 30356026 PMCID: PMC6274740 DOI: 10.3390/ijms19113313] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 10/19/2018] [Accepted: 10/22/2018] [Indexed: 12/02/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) is a key molecule essential for neural plasticity and development, and is implicated in the pathophysiology of various central nervous system (CNS) disorders. It is now documented that BDNF is synthesized not only in neurons, but also in astrocytes which actively regulate neuronal activities by forming tripartite synapses. Inwardly rectifying potassium (Kir) channel subunit Kir4.1, which is specifically expressed in astrocytes, constructs Kir4.1 and Kir4.1/5.1 channels, and mediates the spatial potassium (K+) buffering action of astrocytes. Recent evidence illustrates that Kir4.1 channels play important roles in bringing about the actions of antidepressant drugs and modulating BDNF expression in astrocytes. Although the precise mechanisms remain to be clarified, it seems likely that inhibition (down-regulation or blockade) of astrocytic Kir4.1 channels attenuates K+ buffering, increases neuronal excitability by elevating extracellular K+ and glutamate, and facilitates BDNF expression. Conversely, activation (up-regulation or opening) of Kir4.1 channels reduces neuronal excitability by lowering extracellular K+ and glutamate, and attenuates BDNF expression. Particularly, the former pathophysiological alterations seem to be important in epileptogenesis and pain sensitization, and the latter in the pathogenesis of depressive disorders. In this article, we review the functions of Kir4.1 channels, with a focus on their regulation of spatial K+ buffering and BDNF expression in astrocytes, and discuss the role of the astrocytic Kir4.1-BDNF system in modulating CNS disorders.
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Affiliation(s)
- Yukihiro Ohno
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
| | - Masato Kinboshi
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
| | - Saki Shimizu
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
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36
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Mukai T, Kinboshi M, Nagao Y, Shimizu S, Ono A, Sakagami Y, Okuda A, Fujimoto M, Ito H, Ikeda A, Ohno Y. Antiepileptic Drugs Elevate Astrocytic Kir4.1 Expression in the Rat Limbic Region. Front Pharmacol 2018; 9:845. [PMID: 30127740 PMCID: PMC6088221 DOI: 10.3389/fphar.2018.00845] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Accepted: 07/13/2018] [Indexed: 11/20/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channel subunits Kir4.1 are specifically expressed in astrocytes and regulate neuronal excitability by mediating spatial potassium buffering. In addition, it is now known that astrocytic Kir4.1 channels are closely involved in the pathogenesis of epilepsy. Here, to explore the role of Kir4.1 channels in the treatment of epilepsy, we evaluated the effects of the antiepileptic drugs, valproate, phenytoin, phenobarbital and ethosuximide, on Kir4.1 expression in astrocytes using immunohistochemical techniques. Repeated treatment of rats with valproate (30–300 mg/kg, i.p., for 1–10 days) significantly elevated the Kir4.1 expression levels in the cerebral cortex, amygdala and hippocampus. Up-regulation of Kir4.1 expression by valproate occurred in a dose- and treatment period-related manner, and did not accompany an increase in the number of astrocytes probed by glial fibrillary acidic protein (GFAP). In addition, repeated treatment with phenytoin (30 mg/kg, i.p., for 10 days) or phenobarbital (30 mg/kg, i.p., for 10 days) also elevated Kir4.1 expression region-specifically in the amygdala. However, ethosuximide (100 mg/kg, i.p., for 10 days), which can alleviate absence but not convulsive seizures, showed no effects on the astrocytic Kir4.1 expression. The present results demonstrated for the first time that the antiepileptic drugs effective for convulsive seizures (valproate, phenytoin, and phenobarbital) commonly elevate the astrocytic Kir4.1 channel expression in the limbic regions, which may be related to their antiepileptic actions.
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Affiliation(s)
- Takahiro Mukai
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| | - Masato Kinboshi
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan.,Department of Neurology, Wakayama Medical University, Wakayama, Japan.,Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yuki Nagao
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| | - Saki Shimizu
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| | - Asuka Ono
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| | - Yoshihisa Sakagami
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| | - Aoi Okuda
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| | - Megumi Fujimoto
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| | - Hidefumi Ito
- Department of Neurology, Wakayama Medical University, Wakayama, Japan
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yukihiro Ohno
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
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Expression of Kir2.1 Inward Rectifying Potassium Channels in Optic Nerve Glia: Evidence for Heteromeric Association with Kir4.1 and Kir5.1. ACTA ACUST UNITED AC 2018. [DOI: 10.3390/neuroglia1010012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Inward rectifying potassium (Kir) channels comprise a large family with diverse biophysical properties. A predominant feature of central nervous system (CNS) glia is their expression of Kir4.1, which as homomers are weakly rectifying channels, but form strongly rectifying channels as heteromers with Kir2.1. However, the extent of Kir2.1 expression and their association with Kir4.1 in glia throughout the CNS is unclear. We have examined this in astrocytes and oligodendrocytes of the mouse optic nerve, a typical CNS white matter tract. Western blot and immunocytochemistry demonstrates that optic nerve astrocytes and oligodendrocytes express Kir2.1 and that it co-localises with Kir4.1. Co-immunoprecipitation analysis provided further evidence that Kir2.1 associate with Kir4.1 and, moreover, Kir2.1 expression was significantly reduced in optic nerves and brains from Kir4.1 knock-out mice. In addition, optic nerve glia express Kir5.1, which may associate with Kir2.1 to form silent channels. Immunocytochemical and co-immunoprecipitation analyses indicate that Kir2.1 associate with Kir5.1 in optic nerve glia, but not in the brain. The results provide evidence that astrocytes and oligodendrocytes may express heteromeric Kir2.1/Kir4.1 and Kir2.1/Kir5.1 channels, together with homomeric Kir2.1 and Kir4.1 channels. In astrocytes, expression of multiple Kir channels is the biophysical substrate for the uptake and redistribution of K+ released during neuronal electrical activity known as ‘potassium spatial buffering’. Our findings suggest a similar potential role for the diverse Kir channels expressed by oligodendrocytes, which by way of their myelin sheaths are intimately associated with the sites of action potential propagation and axonal K+ release.
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Du M, Li J, Chen L, Yu Y, Wu Y. Astrocytic Kir4.1 channels and gap junctions account for spontaneous epileptic seizure. PLoS Comput Biol 2018; 14:e1005877. [PMID: 29590095 PMCID: PMC5891073 DOI: 10.1371/journal.pcbi.1005877] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 04/09/2018] [Accepted: 11/06/2017] [Indexed: 01/30/2023] Open
Abstract
Experimental recordings in hippocampal slices indicate that astrocytic dysfunction may cause neuronal hyper-excitation or seizures. Considering that astrocytes play important roles in mediating local uptake and spatial buffering of K+ in the extracellular space of the cortical circuit, we constructed a novel model of an astrocyte-neuron network module consisting of a single compartment neuron and 4 surrounding connected astrocytes and including extracellular potassium dynamics. Next, we developed a new model function for the astrocyte gap junctions, connecting two astrocyte-neuron network modules. The function form and parameters of the gap junction were based on nonlinear regression fitting of a set of experimental data published in previous studies. Moreover, we have created numerical simulations using the above single astrocyte-neuron network module and the coupled astrocyte-neuron network modules. Our model validates previous experimental observations that both Kir4.1 channels and gap junctions play important roles in regulating the concentration of extracellular potassium. In addition, we also observe that changes in Kir4.1 channel conductance and gap junction strength induce spontaneous epileptic activity in the absence of external stimuli. Astrocytes are critical regulators of normal physiological activity in the central nervous system, and one of their key functions is removing extracellular K+. In recent years, numerous biological studies have shown that astrocytic Kir4.1 channels and gap junctions between astrocytes act as major K+ clearance mechanisms. Dysfunction of either of these regulatory mechanisms may cause generation of K+-induced seizures. However, it is unclear how and to what extent these two K+-regulating processes lead to spontaneous epileptic activity. These questions were addressed in the present study by constructing novel single astrocyte-neuron network models and a coupled astrocyte-neuron module network connected by an astrocyte gap junction based on existing experimental observations and previous theoretical reports. Simulation results first verified that either down-regulation of astrocytic Kir4.1 channels or a decrease of the gap junction strength between astrocytes causes neuropathological hyper-excitability and spontaneous epileptic activity. These results imply that dysfunctional astrocytes should be considered as targets for therapeutic strategies in epilepsy.
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Affiliation(s)
- Mengmeng Du
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an, China
- State Key Laboratory of Medical Neurobiology, School of Life Science and Human Phenome Institute, Institutes of Brain Science, Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China
| | - Jiajia Li
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an, China
| | - Liang Chen
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yuguo Yu
- State Key Laboratory of Medical Neurobiology, School of Life Science and Human Phenome Institute, Institutes of Brain Science, Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China
- * E-mail: (YY); (YW)
| | - Ying Wu
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an, China
- Key Laboratory for NeuroInformation of Ministry of Education, University of Electronic Science and Technology of China, Chengdu, China
- * E-mail: (YY); (YW)
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Kitaura H, Shirozu H, Masuda H, Fukuda M, Fujii Y, Kakita A. Pathophysiological Characteristics Associated With Epileptogenesis in Human Hippocampal Sclerosis. EBioMedicine 2018; 29:38-46. [PMID: 29478873 PMCID: PMC5925580 DOI: 10.1016/j.ebiom.2018.02.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 02/07/2018] [Accepted: 02/15/2018] [Indexed: 12/29/2022] Open
Abstract
Mesial temporal lobe epilepsy (MTLE) is the most frequent focal epileptic syndrome in adults, and the majority of seizures originate primarily from the hippocampus. The resected hippocampal tissue often shows severe neuronal loss, a condition referred to as hippocampal sclerosis (HS). In order to understand hippocampal epileptogenesis in MTLE, it seems important to clarify any discrepancies between the clinical and pathological features of affected patients. Here we investigated epileptiform activities ex vivo using living hippocampal tissue taken from patients with MTLE. Flavoprotein fluorescence imaging and local field potential recordings revealed that epileptiform activities developed from the subiculum. Moreover, physiological and morphological experiments revealed possible impairment of K+ clearance in the subiculum affected by HS. Stimulation of mossy fibers induced recurrent trans-synaptic activity in the granule cell layer of the dentate gyrus, suggesting that mossy fiber sprouting in HS also contributes to the epileptogenic mechanism. These results indicate that pathophysiological alterations involving the subiculum and dentate gyrus could be responsible for epileptogenesis in patients with MTLE.
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Affiliation(s)
- Hiroki Kitaura
- Department of Pathology, Brain Research Institute, Niigata University, 1 Asahimachi, Chuo-ku, Niigata 951-8585, Japan.
| | - Hiroshi Shirozu
- Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 1 Masago, Nishi-ku, Niigata 950-2085, Japan
| | - Hiroshi Masuda
- Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 1 Masago, Nishi-ku, Niigata 950-2085, Japan
| | - Masafumi Fukuda
- Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 1 Masago, Nishi-ku, Niigata 950-2085, Japan
| | - Yukihiko Fujii
- Department of Neurosurgery, Brain Research Institute, Niigata University, 1 Asahimachi, Chuo-ku, Niigata 951-8585, Japan
| | - Akiyoshi Kakita
- Department of Pathology, Brain Research Institute, Niigata University, 1 Asahimachi, Chuo-ku, Niigata 951-8585, Japan
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Kinboshi M, Mukai T, Nagao Y, Matsuba Y, Tsuji Y, Tanaka S, Tokudome K, Shimizu S, Ito H, Ikeda A, Inanobe A, Kurachi Y, Inoue S, Ohno Y. Inhibition of Inwardly Rectifying Potassium (Kir) 4.1 Channels Facilitates Brain-Derived Neurotrophic Factor (BDNF) Expression in Astrocytes. Front Mol Neurosci 2017; 10:408. [PMID: 29358904 PMCID: PMC5768989 DOI: 10.3389/fnmol.2017.00408] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/24/2017] [Indexed: 11/16/2022] Open
Abstract
Inwardly rectifying potassium (Kir) 4.1 channels in astrocytes regulate neuronal excitability by mediating spatial potassium buffering. Although dysfunction of astrocytic Kir4.1 channels is implicated in the development of epileptic seizures, the functional mechanisms of Kir4.1 channels in modulating epileptogenesis remain unknown. We herein evaluated the effects of Kir4.1 inhibition (blockade and knockdown) on expression of brain-derived neurotrophic factor (BDNF), a key modulator of epileptogenesis, in the primary cultures of mouse astrocytes. For blockade of Kir4.1 channels, we tested several antidepressant agents which reportedly bound to and blocked Kir4.1 channels in a subunit-specific manner. Treatment of astrocytes with fluoxetine enhanced BDNF mRNA expression in a concentration-dependent manner and increased the BDNF protein level. Other antidepressants (e.g., sertraline and imipramine) also increased the expression of BDNF mRNA with relative potencies similar to those for inhibition of Kir4.1 channels. In addition, suppression of Kir4.1 expression by the transfection of small interfering RNA (siRNA) targeting Kir4.1 significantly increased the mRNA and protein levels of BDNF. The BDNF induction by Kir4.1 siRNA transfection was suppressed by the MEK1/2 inhibitor U0126, but not by the p38 MAPK inhibitor SB202190 or the JNK inhibitor SP600125. The present results demonstrated that inhibition of Kir4.1 channels facilitates BDNF expression in astrocytes primarily by activating the Ras/Raf/MEK/ERK pathway, which may be linked to the development of epilepsy and other neuropsychiatric disorders.
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Affiliation(s)
- Masato Kinboshi
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan.,Department of Neurology, Wakayama Medical University, Wakayama, Japan.,Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takahiro Mukai
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yuki Nagao
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yusuke Matsuba
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yoshimi Tsuji
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Shiho Tanaka
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Kentaro Tokudome
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan.,Department of Molecular and Cellular Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Saki Shimizu
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Hidefumi Ito
- Department of Neurology, Wakayama Medical University, Wakayama, Japan
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Atsushi Inanobe
- Department of Molecular and Cellular Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Yoshihisa Kurachi
- Department of Molecular and Cellular Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Seiji Inoue
- Education and Research Center for Fundamental Pharmaceutical Sciences, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yukihiro Ohno
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
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41
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Hattingen E, Enkirch SJ, Jurcoane A, Kruse M, Delev D, Grote A, Becker A. Hippocampal "gliosis only" on MR imaging represents a distinct entity in epilepsy patients. Neuroradiology 2017; 60:161-168. [PMID: 29085967 DOI: 10.1007/s00234-017-1939-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 10/17/2017] [Indexed: 10/18/2022]
Abstract
PURPOSE The purpose of this study is to evaluate whether patients with drug-resistant mesial temporal lobe epilepsy (TLE) due to hippocampal "gliosis only" have different MRI features than those with hippocampal sclerosis (HS). Most TLE patients have HS corresponding to severe neuronal loss and gliosis, but a few have "gliosis only" without significant reduction of neuronal density. METHODS We analyzed the morphology of cerebral 3 T MRIs (T1, T2, and FLAIR) of 103 patients with HS and 20 with "gliosis only" concerning hippocampal and amygdala aspect, volumes, and signal intensity (SI) using Fisher's exact test, Student's t test, and principal component analysis. RESULTS Visually, the ipsilateral hippocampus was hyperintense in both groups, but SI was markedly increased in 74% of HS and in 25% of "gliosis only" patients; the ipsilateral hippocampus was smaller in 92% of HS and in 50% of "gliosis only" patients, and its internal architecture was lost in 57% of HS and 5% of "gliosis only" patients; the contralateral hippocampal SI was altered in 25% of HS and in 70% of "gliosis only" patients (all p < 0.001). Ipsilateral hippocampus of HS patients had lower volume (mean ± SD 2.86 ± 0.87 ml) compared with that of "gliosis only" patients (3.4 ± 1.02 ml) and had higher SI than the contralateral hippocampus of HS patients and then the hippocampus of "gliosis only" patients (all p < 0.01). CONCLUSION "Gliosis only" has different MRI hippocampal characteristics than HS: less volume loss, less increase of the T2-w signal intensity, preservation of internal architecture, and more contralateral affection.
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Affiliation(s)
- Elke Hattingen
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany.
| | - Simon Jonas Enkirch
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany
| | - Alina Jurcoane
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany
| | - Maximilian Kruse
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany
| | - Daniel Delev
- Department of Neurosurgery, University Clinics Bonn, Bonn, Germany.,Department of Neurosurgery, University Clinics Freiburg, Freiburg, Germany
| | - Alexander Grote
- Department of Neurosurgery, University Clinics Bonn, Bonn, Germany.,Department of Neurosurgery, Evangelic Hospital of Bethel, Bielefeld, Germany
| | - Albert Becker
- Institute of Neuropathology, University Clinics Bonn, Bonn, Germany
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42
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Eto K, Kim SK, Takeda I, Nabekura J. The roles of cortical astrocytes in chronic pain and other brain pathologies. Neurosci Res 2017; 126:3-8. [PMID: 28870605 DOI: 10.1016/j.neures.2017.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 08/01/2017] [Accepted: 08/18/2017] [Indexed: 01/21/2023]
Abstract
Astrocytes are the most abundant cell type in the brain. Several decades ago, they were considered to be only support cells in the central nervous system. Recent studies using advanced technologies have clarified that astrocytes play more active roles in regulating neuronal function and remodeling synaptic structures by releasing molecules called gliotransmitters. In addition to various physiological functions, astrocytes are activated under disease conditions, such as chronic pain, releasing molecules that in turn cause reorganization of the central nervous system microstructure and disrupt behavior in pathological conditions. In the present review, we summarize cortical astrocyte function in chronic pain and other neurological disorders and discuss the role of astrocytes in brain pathologies.
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Affiliation(s)
- Kei Eto
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; Department of Physiological Sciences, The Graduate School for Advanced Studies, Hayama, Kanagawa 240-0193, Japan
| | - Sun Kwang Kim
- Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Ikuko Takeda
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; Department of Physiological Sciences, The Graduate School for Advanced Studies, Hayama, Kanagawa 240-0193, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Tokyo 102-0076, Japan.
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43
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Salman MM, Sheilabi MA, Bhattacharyya D, Kitchen P, Conner AC, Bill RM, Woodroofe MN, Conner MT, Princivalle AP. Transcriptome analysis suggests a role for the differential expression of cerebral aquaporins and the MAPK signalling pathway in human temporal lobe epilepsy. Eur J Neurosci 2017; 46:2121-2132. [PMID: 28715131 DOI: 10.1111/ejn.13652] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 07/10/2017] [Accepted: 07/11/2017] [Indexed: 01/12/2023]
Abstract
Epilepsies are common disorders of the central nervous system (CNS), affecting up to 2% of the global population. Pharmaco-resistance is a major clinical challenge affecting about 30% of temporal lobe epilepsy (TLE) patients. Water homeostasis has been shown crucial for regulation of neuronal excitability. The control of water movement is achieved through a family of small integral membrane channel proteins called aquaporins (AQPs). Despite the fact that changes in water homeostasis occur in sclerotic hippocampi of people with TLE, the expression of AQPs in the epileptic brain is not fully characterised. This study uses microarray and ELISA methods to analyse the mRNA and protein expression of the human cerebral AQPs in sclerotic hippocampi (TLE-HS) and adjacent neocortex tissue (TLE-NC) of TLE patients. The expression of AQP1 and AQP4 transcripts was significantly increased, while that of the AQP9 transcript was significantly reduced in TLE-HS compared to TLE-NC. AQP4 protein expression was also increased while expression of AQP1 protein remained unchanged, and AQP9 was undetected. Microarray data analysis identified 3333 differentially regulated genes and suggested the involvement of the MAPK signalling pathway in TLE pathogenesis. Proteome array data validated the translational profile for 26 genes and within the MAPK pathway (e.g. p38, JNK) that were identified as differentially expressed from microarray analysis. ELISA data showed that p38 and JNK inhibitors decrease AQP4 protein levels in cultured human primary cortical astrocytes. Elucidating the mechanism of selective regulation of different AQPs and associated regulatory proteins may provide a new therapeutic approach to epilepsy treatment.
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Affiliation(s)
- Mootaz M Salman
- Biomolecular Sciences Research Centre (BMRC), Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK
| | - Mariam A Sheilabi
- Biomolecular Sciences Research Centre (BMRC), Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK
| | | | - Philip Kitchen
- School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK
| | - Alex C Conner
- School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK
| | - Roslyn M Bill
- School of Life and Health Sciences, Aston University, Birmingham, UK
| | - M Nicola Woodroofe
- Biomolecular Sciences Research Centre (BMRC), Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK
| | - Matthew T Conner
- Biomolecular Sciences Research Centre (BMRC), Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK.,Research Institute of Health Sciences, School of Sciences, University of Wolverhampton, Wolverhampton, UK
| | - Alessandra P Princivalle
- Biomolecular Sciences Research Centre (BMRC), Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK
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44
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Eide PK, Hansson HA. Astrogliosis and impaired aquaporin-4 and dystrophin systems in idiopathic normal pressure hydrocephalus. Neuropathol Appl Neurobiol 2017. [PMID: 28627088 DOI: 10.1111/nan.12420] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
AIMS Idiopathic normal pressure hydrocephalus (iNPH) is one subtype of dementia that may improve following drainage of cerebrospinal fluid (CSF). This prospective observational study explored whether expression of the water channel aquaporin-4 (AQP4) and the anchoring molecule dystrophin 71 (Dp71) are altered at astrocytic perivascular endfeet and in adjacent neuropil of iNPH patient. Observations were related to measurements of pulsatile and static intracranial pressure (ICP). METHODS The study included iNPH patients undergoing overnight monitoring of the pulsatile/static ICP in whom a biopsy was taken from the frontal cerebral cortex during placement of the ICP sensor. Reference (Ref) biopsies were sampled from 13 patients who underwent brain surgery for epilepsy, tumours or cerebral aneurysms. The brain tissue specimens were examined by light microscopy, immunohistochemistry, densitometry and morphometry. RESULTS iNPH patients responding to surgery (n = 44) had elevated pulsatile ICP, indicative of impaired intracranial compliance. As compared to the Ref patients, the cortical biopsies of iNPH patients revealed prominent astrogliosis and reduced expression of AQP4 and Dp71 immunoreactivities in the astrocytic perivascular endfeet and in parts of the adjacent neuropil. There was a significant correlation between degree of astrogliosis and reduction of AQP4 and Dp71 at astrocytic perivascular endfeet. CONCLUSIONS Idiopathic normal pressure hydrocephalus patients responding to CSF diversion present with abnormal pulsatile ICP, indicative of impaired intracranial compliance. A main histopathological finding was astrogliosis and reduction of AQP4 and of Dp71 in astrocytic perivascular endfeet. We propose that the altered AQP4 and Dp71 complex contributes to the subischaemia prevalent in the brain tissue of iNPH.
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Affiliation(s)
- P K Eide
- Department of Neurosurgery, Oslo University Hospital - Rikshospitalet, Oslo, Norway.,Faculty of Medicine, University of Oslo, Oslo, Norway
| | - H-A Hansson
- Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden
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45
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Turning down the volume: Astrocyte volume change in the generation and termination of epileptic seizures. Neurobiol Dis 2017; 104:24-32. [PMID: 28438505 DOI: 10.1016/j.nbd.2017.04.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 04/18/2017] [Accepted: 04/20/2017] [Indexed: 12/20/2022] Open
Abstract
Approximately 1% of the global population suffers from epilepsy, a class of disorders characterized by recurrent and unpredictable seizures. Of these cases roughly one-third are refractory to current antiepileptic drugs, which typically target neuronal excitability directly. The events leading to seizure generation and epileptogenesis remain largely unknown, hindering development of new treatments. Some recent experimental models of epilepsy have provided compelling evidence that glial cells, especially astrocytes, could be central to seizure development. One of the proposed mechanisms for astrocyte involvement in seizures is astrocyte swelling, which may promote pathological neuronal firing and synchrony through reduction of the extracellular space and elevated glutamate concentrations. In this review, we discuss the common conditions under which astrocytes swell, the resultant effects on neural excitability, and how seizure development may ultimately be influenced by these effects.
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46
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Astrocytic modulation of neuronal excitability through K + spatial buffering. Neurosci Biobehav Rev 2017; 77:87-97. [PMID: 28279812 DOI: 10.1016/j.neubiorev.2017.03.002] [Citation(s) in RCA: 133] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 03/05/2017] [Accepted: 03/05/2017] [Indexed: 11/22/2022]
Abstract
The human brain contains two major cell populations, neurons and glia. While neurons are electrically excitable and capable of discharging short voltage pulses known as action potentials, glial cells are not. However, astrocytes, the prevailing subtype of glia in the cortex, are highly connected and can modulate the excitability of neurons by changing the concentration of potassium ions in the extracellular environment, a process called K+ clearance. During the past decade, astrocytes have been the focus of much research, mainly due to their close association with synapses and their modulatory impact on neuronal activity. It has been shown that astrocytes play an essential role in normal brain function including: nitrosative regulation of synaptic release in the neocortex, synaptogenesis, synaptic transmission and plasticity. Here, we discuss the role of astrocytes in network modulation through their K+ clearance capabilities, a theory that was first raised 50 years ago by Orkand and Kuffler. We will discuss the functional alterations in astrocytic activity that leads to aberrant modulation of network oscillations and synchronous activity.
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47
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Dossi E, Vasile F, Rouach N. Human astrocytes in the diseased brain. Brain Res Bull 2017; 136:139-156. [PMID: 28212850 PMCID: PMC5766741 DOI: 10.1016/j.brainresbull.2017.02.001] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/08/2017] [Accepted: 02/09/2017] [Indexed: 12/23/2022]
Abstract
Astrocytes are key active elements of the brain that contribute to information processing. They not only provide neurons with metabolic and structural support, but also regulate neurogenesis and brain wiring. Furthermore, astrocytes modulate synaptic activity and plasticity in part by controlling the extracellular space volume, as well as ion and neurotransmitter homeostasis. These findings, together with the discovery that human astrocytes display contrasting characteristics with their rodent counterparts, point to a role for astrocytes in higher cognitive functions. Dysfunction of astrocytes can thereby induce major alterations in neuronal functions, contributing to the pathogenesis of several brain disorders. In this review we summarize the current knowledge on the structural and functional alterations occurring in astrocytes from the human brain in pathological conditions such as epilepsy, primary tumours, Alzheimer's disease, major depressive disorder and Down syndrome. Compelling evidence thus shows that dysregulations of astrocyte functions and interplay with neurons contribute to the development and progression of various neurological diseases. Targeting astrocytes is thus a promising alternative approach that could contribute to the development of novel and effective therapies to treat brain disorders.
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Affiliation(s)
- Elena Dossi
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France.
| | - Flora Vasile
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France.
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France.
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48
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Abstract
Many mutations of genes for ion channels result in some epilepsies. Their electrophysiological studies reveal pathophysiological mechanisms underlining epilepsy and also mechanism of action of several antiepileptic drugs. In this review, We briefly summarize pathophysiology of epilepsy and the mechanisms of antiepileptic drugs.
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Affiliation(s)
- Yoshihiro Sugiura
- Department of Neurology, Fukushima Medical University School of Medicine
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49
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Seifert G, Henneberger C, Steinhäuser C. Diversity of astrocyte potassium channels: An update. Brain Res Bull 2016; 136:26-36. [PMID: 27965079 DOI: 10.1016/j.brainresbull.2016.12.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 12/08/2016] [Accepted: 12/09/2016] [Indexed: 01/08/2023]
Abstract
Astrocyte K+ channels and the K+ currents they mediate dwarf all other transmembrane conductances in these cells. This defining feature of astrocytes and its functional implications have been investigated intensely over the past decades. Nonetheless, many aspects of astrocyte K+ handling and signaling remain incompletely understood. In this review, we provide an update on the diversity of K+ channels expressed by astrocytes and new functional implications. We focus on inwardly-rectifying K+ channels (particularly Kir4.1), two-pore K+ channels and voltage and Ca2+-dependent K+ channels. We further discuss new insights into the involvement of these K+ channels in K+ buffering, control of synaptic transmission, regulation of the vasculature and in diseases of the central nervous system.
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Affiliation(s)
- Gerald Seifert
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany.
| | - Christian Henneberger
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany; German Center of Neurodegenerative Diseases (DZNE), Bonn, Germany; Institute of Neurology, University College London, London, United Kingdom
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany.
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Gu C. KIR4.1: K + Channel Illusion or Reality in the Autoimmune Pathogenesis of Multiple Sclerosis. Front Mol Neurosci 2016; 9:90. [PMID: 27729847 PMCID: PMC5037192 DOI: 10.3389/fnmol.2016.00090] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 09/12/2016] [Indexed: 01/12/2023] Open
Abstract
Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Many believe autoimmune pathogenesis plays a key role in MS, but its target(s) remains elusive. A recent study detected autoantibodies against KIR4.1, an ATP-sensitive, inward rectifier potassium channel, in nearly half of the MS patients examined. KIR4.1 channels are expressed in astrocytes. Together with aquaporin 4 (AQP4) water channels, they regulate astrocytic functions vital for myelination. Autoantibodies against AQP4 have been established as a key biomarker for neuromyelitis optica (NMO) and contributed to diagnostic and treatment strategy adjustments. Similarly, identification of KIR4.1 autoantibodies could have high therapeutic values in treating MS. Consistent with its potential role in MS, KIR4.1 dysfunction is implicated in several neurological disorders. However, the enrichment of KIR4.1 autoantibodies in MS patients is questioned by follow-up studies. Further, investigations are needed to clarify this controversy and unravel the underlying mechanisms of MS pathogenesis.
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Affiliation(s)
- Chen Gu
- Department of Biological Chemistry and Pharmacology, The Ohio State University Columbus, OH, USA
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