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Hladky SB, Barrand MA. Alterations in brain fluid physiology during the early stages of development of ischaemic oedema. Fluids Barriers CNS 2024; 21:51. [PMID: 38858667 PMCID: PMC11163777 DOI: 10.1186/s12987-024-00534-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 03/22/2024] [Indexed: 06/12/2024] Open
Abstract
Oedema occurs when higher than normal amounts of solutes and water accumulate in tissues. In brain parenchymal tissue, vasogenic oedema arises from changes in blood-brain barrier permeability, e.g. in peritumoral oedema. Cytotoxic oedema arises from excess accumulation of solutes within cells, e.g. ischaemic oedema following stroke. This type of oedema is initiated when blood flow in the affected core region falls sufficiently to deprive brain cells of the ATP needed to maintain ion gradients. As a consequence, there is: depolarization of neurons; neural uptake of Na+ and Cl- and loss of K+; neuronal swelling; astrocytic uptake of Na+, K+ and anions; swelling of astrocytes; and reduction in ISF volume by fluid uptake into neurons and astrocytes. There is increased parenchymal solute content due to metabolic osmolyte production and solute influx from CSF and blood. The greatly increased [K+]isf triggers spreading depolarizations into the surrounding penumbra increasing metabolic load leading to increased size of the ischaemic core. Water enters the parenchyma primarily from blood, some passing into astrocyte endfeet via AQP4. In the medium term, e.g. after three hours, NaCl permeability and swelling rate increase with partial opening of tight junctions between blood-brain barrier endothelial cells and opening of SUR1-TPRM4 channels. Swelling is then driven by a Donnan-like effect. Longer term, there is gross failure of the blood-brain barrier. Oedema resolution is slower than its formation. Fluids without colloid, e.g. infused mock CSF, can be reabsorbed across the blood-brain barrier by a Starling-like mechanism whereas infused serum with its colloids must be removed by even slower extravascular means. Large scale oedema can increase intracranial pressure (ICP) sufficiently to cause fatal brain herniation. The potentially lethal increase in ICP can be avoided by craniectomy or by aspiration of the osmotically active infarcted region. However, the only satisfactory treatment resulting in retention of function is restoration of blood flow, providing this can be achieved relatively quickly. One important objective of current research is to find treatments that increase the time during which reperfusion is successful. Questions still to be resolved are discussed.
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Affiliation(s)
- Stephen B Hladky
- Department of Pharmacology, Tennis Court Rd., Cambridge, CB2 1PD, UK.
| | - Margery A Barrand
- Department of Pharmacology, Tennis Court Rd., Cambridge, CB2 1PD, UK
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2
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Bataveljic D, Pivonkova H, de Concini V, Hébert B, Ezan P, Briault S, Bemelmans AP, Pichon J, Menuet A, Rouach N. Astroglial Kir4.1 potassium channel deficit drives neuronal hyperexcitability and behavioral defects in Fragile X syndrome mouse model. Nat Commun 2024; 15:3583. [PMID: 38678030 PMCID: PMC11055954 DOI: 10.1038/s41467-024-47681-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 04/03/2024] [Indexed: 04/29/2024] Open
Abstract
Fragile X syndrome (FXS) is an inherited form of intellectual disability caused by the loss of the mRNA-binding fragile X mental retardation protein (FMRP). FXS is characterized by neuronal hyperexcitability and behavioral defects, however the mechanisms underlying these critical dysfunctions remain unclear. Here, using male Fmr1 knockout mouse model of FXS, we identify abnormal extracellular potassium homeostasis, along with impaired potassium channel Kir4.1 expression and function in astrocytes. Further, we reveal that Kir4.1 mRNA is a binding target of FMRP. Finally, we show that the deficit in astroglial Kir4.1 underlies neuronal hyperexcitability and several behavioral defects in Fmr1 knockout mice. Viral delivery of Kir4.1 channels specifically to hippocampal astrocytes from Fmr1 knockout mice indeed rescues normal astrocyte potassium uptake, neuronal excitability, and cognitive and social performance. Our findings uncover an important role for astrocyte dysfunction in the pathophysiology of FXS, and identify Kir4.1 channel as a potential therapeutic target for FXS.
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Affiliation(s)
- Danijela Bataveljic
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Labex Memolife, Université PSL, Paris, France
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Helena Pivonkova
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Labex Memolife, Université PSL, Paris, France
- Department of Physiology, 2nd Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Vidian de Concini
- Experimental and Molecular Immunology and Neurogenetics, CNRS UMR7355 and Orléans University, Orléans, France
| | - Betty Hébert
- Experimental and Molecular Immunology and Neurogenetics, CNRS UMR7355 and Orléans University, Orléans, France
| | - Pascal Ezan
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Labex Memolife, Université PSL, Paris, France
| | - Sylvain Briault
- Experimental and Molecular Immunology and Neurogenetics, CNRS UMR7355 and Orléans University, Orléans, France
- Department of Genetics, Regional Hospital, Orléans, France
| | - Alexis-Pierre Bemelmans
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de la Recherche Fondamentale, Institut de biologie François Jacob, MIRCen, and CNRS UMR 9199, Université Paris-Sud, Neurodegenerative Diseases Laboratory, Fontenay-aux-Roses, 92260, France
| | - Jacques Pichon
- Experimental and Molecular Immunology and Neurogenetics, CNRS UMR7355 and Orléans University, Orléans, France
| | - Arnaud Menuet
- Experimental and Molecular Immunology and Neurogenetics, CNRS UMR7355 and Orléans University, Orléans, France
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Labex Memolife, Université PSL, Paris, France.
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3
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Nguyen HS, Kang SJ, Kim S, Cha BH, Park KS, Jeong SW. Changes in the expression of satellite glial cell-specific markers during postnatal development of rat sympathetic ganglia. Brain Res 2024; 1829:148809. [PMID: 38354998 DOI: 10.1016/j.brainres.2024.148809] [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: 11/16/2023] [Revised: 01/31/2024] [Accepted: 02/08/2024] [Indexed: 02/16/2024]
Abstract
The sympathetic ganglia represent a final motor pathway that mediates homeostatic "fight and flight" responses in the visceral organs. Satellite glial cells (SGCs) form a thin envelope close to the neuronal cell body and synapses in the sympathetic ganglia. This unique morphological feature suggests that neurons and SGCs form functional units for regulation of sympathetic output. In the present study, we addressed whether SGC-specific markers undergo age-dependent changes in the postnatal development of rat sympathetic ganglia. We found that fatty acid-binding protein 7 (FABP7) is an early SGC marker, whereas the S100B calcium-binding protein, inwardly rectifying potassium channel, Kir4.1 and small conductance calcium-activated potassium channel, SK3 are late SGC markers in the postnatal development of sympathetic ganglia. Unlike in sensory ganglia, FABP7 + SGC was barely detectable in adult sympathetic ganglia. The expression of connexin 43, a gap junction channel gradually increased with age, although it was detected in both SGCs and neurons in sympathetic ganglia. Glutamine synthetase was expressed in sensory, but not sympathetic SGCs. Unexpectedly, the sympathetic SGCs expressed a water-selective channel, aquaporin 1 instead of aquaporin 4, a pan-glial marker. However, aquaporin 1 was not detected in the SGCs encircling large neurons. Nerve injury and inflammation induced the upregulation of glial fibrillary acidic protein, suggesting that this protein is a hall marker of glial activation in the sympathetic ganglia. In conclusion, our findings provide basic information on the in vivo profiles of specific markers for identifying sympathetic SGCs at different stages of postnatal development in both healthy and diseased states.
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Affiliation(s)
- Huu Son Nguyen
- Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea; Mitohormesis Research Center, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Seong Jun Kang
- Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Sohyun Kim
- Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Byung Ho Cha
- Department of Pediatrics, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Kyu-Sang Park
- Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea; Mitohormesis Research Center, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Seong-Woo Jeong
- Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
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4
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Zhou X, Zhao C, Xu H, Xu Y, Zhan L, Wang P, He J, Lu T, Gu Y, Yang Y, Xu C, Chen Y, Liu Y, Zeng Y, Tian F, Chen Q, Xie X, Liu J, Hu H, Li J, Zheng Y, Guo J, Gao Z. Pharmacological inhibition of Kir4.1 evokes rapid-onset antidepressant responses. Nat Chem Biol 2024:10.1038/s41589-024-01555-y. [PMID: 38355723 DOI: 10.1038/s41589-024-01555-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 01/15/2024] [Indexed: 02/16/2024]
Abstract
Major depressive disorder, a prevalent and severe psychiatric condition, necessitates development of new and fast-acting antidepressants. Genetic suppression of astrocytic inwardly rectifying potassium channel 4.1 (Kir4.1) in the lateral habenula ameliorates depression-like phenotypes in mice. However, Kir4.1 remains an elusive drug target for depression. Here, we discovered a series of Kir4.1 inhibitors through high-throughput screening. Lys05, the most potent one thus far, effectively suppressed native Kir4.1 channels while displaying high selectivity against established targets for rapid-onset antidepressants. Cryogenic-electron microscopy structures combined with electrophysiological characterizations revealed Lys05 directly binds in the central cavity of Kir4.1. Notably, a single dose of Lys05 reversed the Kir4.1-driven depression-like phenotype and exerted rapid-onset (as early as 1 hour) antidepressant actions in multiple canonical depression rodent models with efficacy comparable to that of (S)-ketamine. Overall, we provided a proof of concept that Kir4.1 is a promising target for rapid-onset antidepressant effects.
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Affiliation(s)
- Xiaoyu Zhou
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- College of Pharmacy, University of Chinese Academy of Sciences, Beijing, China
| | - Cheng Zhao
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Haiyan Xu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yixiang Xu
- State Key Laboratory of Bioreactor Engineering, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai, China
| | - Li Zhan
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Pei Wang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Jingyi He
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- School of Pharmacy, Henan University, Kaifeng, China
| | - Taotao Lu
- State Key Laboratory of Bioreactor Engineering, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai, China
| | - Yueling Gu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Yan Yang
- Liangzhu Laboratory, Zhejiang University School of Medicine, New Cornerstone Science Laboratory, Zhejiang University, Hangzhou, China
| | - Chanjuan Xu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Yiyang Chen
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Yuxuan Liu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Yue Zeng
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Fuyun Tian
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Zhongshan, China
| | - Qian Chen
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xin Xie
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Jianfeng Liu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Hailan Hu
- Liangzhu Laboratory, Zhejiang University School of Medicine, New Cornerstone Science Laboratory, Zhejiang University, Hangzhou, China
| | - Jian Li
- State Key Laboratory of Bioreactor Engineering, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai, China
| | - Yueming Zheng
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
| | - Jiangtao Guo
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
| | - Zhaobing Gao
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
- College of Pharmacy, University of Chinese Academy of Sciences, Beijing, China.
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, China.
- School of Pharmacy, Henan University, Kaifeng, China.
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Zhongshan, China.
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Olmos-Pastoresa CA, Vázquez-Mendoza E, López-Meraz ML, Pérez-Estudillo CA, Beltran-Parrazal L, Morgado-Valle C. Transgenic rodents as dynamic models for the study of respiratory rhythm generation and modulation: a scoping review and a bibliometric analysis. Front Physiol 2023; 14:1295632. [PMID: 38179140 PMCID: PMC10764557 DOI: 10.3389/fphys.2023.1295632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 11/20/2023] [Indexed: 01/06/2024] Open
Abstract
The pre-Bötzinger complex, situated in the ventrolateral medulla, serves as the central generator for the inspiratory phase of the respiratory rhythm. Evidence strongly supports its pivotal role in generating, and, in conjunction with the post-inspiratory complex and the lateral parafacial nucleus, in shaping the respiratory rhythm. While there remains an ongoing debate concerning the mechanisms underlying these nuclei's ability to generate and modulate breathing, transgenic rodent models have significantly contributed to our understanding of these processes. However, there is a significant knowledge gap regarding the spectrum of transgenic rodent lines developed for studying respiratory rhythm, and the methodologies employed in these models. In this study, we conducted a scoping review to identify commonly used transgenic rodent lines and techniques for studying respiratory rhythm generation and modulation. Following PRISMA guidelines, we identified relevant papers in PubMed and EBSCO on 29 March 2023, and transgenic lines in Mouse Genome Informatics and the International Mouse Phenotyping Consortium. With strict inclusion and exclusion criteria, we identified 80 publications spanning 1997-2022 using 107 rodent lines. Our findings revealed 30 lines focusing on rhythm generation, 61 on modulation, and 16 on both. The primary in vivo method was whole-body plethysmography. The main in vitro method was hypoglossal/phrenic nerve recordings using the en bloc preparation. Additionally, we identified 119 transgenic lines with the potential for investigating the intricate mechanisms underlying respiratory rhythm. Through this review, we provide insights needed to design more effective experiments with transgenic animals to unravel the mechanisms governing respiratory rhythm. The identified transgenic rodent lines and methodological approaches compile current knowledge and guide future research towards filling knowledge gaps in respiratory rhythm generation and modulation.
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Affiliation(s)
| | | | | | | | - Luis Beltran-Parrazal
- Laboratorio de Neurofisiología, Instituto de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Veracruz, Mexico
| | - Consuelo Morgado-Valle
- Laboratorio de Neurofisiología, Instituto de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Veracruz, Mexico
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6
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Extrémet J, Ramirez-Franco J, Fronzaroli-Molinieres L, Boumedine-Guignon N, Ankri N, El Far O, Garrido JJ, Debanne D, Russier M. Rescue of Normal Excitability in LGI1-Deficient Epileptic Neurons. J Neurosci 2023; 43:8596-8606. [PMID: 37863654 PMCID: PMC10727174 DOI: 10.1523/jneurosci.0701-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 09/08/2023] [Accepted: 10/14/2023] [Indexed: 10/22/2023] Open
Abstract
Leucine-rich glioma inactivated 1 (LGI1) is a glycoprotein secreted by neurons, the deletion of which leads to autosomal dominant lateral temporal lobe epilepsy. We previously showed that LGI1 deficiency in a mouse model (i.e., knock-out for LGI1 or KO-Lgi1) decreased Kv1.1 channel density at the axon initial segment (AIS) and at presynaptic terminals, thus enhancing both intrinsic excitability and glutamate release. However, it is not known whether normal excitability can be restored in epileptic neurons. Here, we show that the selective expression of LGI1 in KO-Lgi1 neurons from mice of both sexes, using single-cell electroporation, reduces intrinsic excitability and restores both the Kv1.1-mediated D-type current and Kv1.1 channels at the AIS. In addition, we show that the homeostatic-like shortening of the AIS length observed in KO-Lgi1 neurons is prevented in neurons electroporated with the Lgi1 gene. Furthermore, we reveal a spatial gradient of intrinsic excitability that is centered on the electroporated neuron. We conclude that expression of LGI1 restores normal excitability through functional Kv1 channels at the AIS.SIGNIFICANCE STATEMENT The lack of leucine-rich glioma inactivated 1 (LGI1) protein induces severe epileptic seizures that leads to death. Enhanced intrinsic and synaptic excitation in KO-Lgi1 mice is because of the decrease in Kv1.1 channels in CA3 neurons. However, the conditions to restore normal excitability profile in epileptic neurons remain to be defined. We show here that the expression of LGI1 in KO-Lgi1 neurons in single neurons reduces intrinsic excitability, and restores both the Kv1.1-mediated D-type current and Kv1.1 channels at the axon initial segment (AIS). Furthermore, the homeostatic shortening of the AIS length observed in KO-Lgi1 neurons is prevented in neurons in which the Lgi1 gene has been rescued. We conclude that LGI1 constitutes a critical factor to restore normal excitability in epileptic neurons.
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Affiliation(s)
- Johanna Extrémet
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
| | - Jorge Ramirez-Franco
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
| | - Laure Fronzaroli-Molinieres
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
| | - Norah Boumedine-Guignon
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
| | - Norbert Ankri
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
| | - Oussama El Far
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
| | - Juan José Garrido
- Cajal Institute, Consejo Superior de Investigaciones Cientificas, Madrid, 28002, Spain
| | - Dominique Debanne
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
| | - Michaël Russier
- Unité de Neurobiologie des canaux Ioniques et de la Synapse, Unité Mixte de Recherche 1072, Institut National de la Santé et de la Recherche Médicale, Aix-Marseille Université, Marseille, 13015, France
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7
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Nanclares C, Noriega-Prieto JA, Labrada-Moncada FE, Cvetanovic M, Araque A, Kofuji P. Altered calcium signaling in Bergmann glia contributes to spinocerebellar ataxia type-1 in a mouse model of SCA1. Neurobiol Dis 2023; 187:106318. [PMID: 37802154 PMCID: PMC10624966 DOI: 10.1016/j.nbd.2023.106318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 09/28/2023] [Accepted: 10/04/2023] [Indexed: 10/08/2023] Open
Abstract
Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disease caused by an abnormal expansion of glutamine (Q) encoding CAG repeats in the ATAXIN1 (ATXN1) gene and characterized by progressive cerebellar ataxia, dysarthria, and eventual deterioration of bulbar functions. SCA1 shows severe degeneration of cerebellar Purkinje cells (PCs) and activation of Bergmann glia (BG), a type of cerebellar astroglia closely associated with PCs. Combining electrophysiological recordings, calcium imaging techniques, and chemogenetic approaches, we have investigated the electrical intrinsic and synaptic properties of PCs and the physiological properties of BG in SCA1 mouse model expressing mutant ATXN1 only in PCs. PCs of SCA1 mice displayed lower spontaneous firing rate and larger slow afterhyperpolarization currents (sIAHP) than wildtype mice, whereas the properties of the synaptic inputs were unaffected. BG of SCA1 mice showed higher calcium hyperactivity and gliotransmission, manifested by higher frequency of NMDAR-mediated slow inward currents (SICs) in PC. Preventing the BG calcium hyperexcitability of SCA1 mice by loading BG with the calcium chelator BAPTA restored sIAHP and spontaneous firing rate of PCs to similar levels of wildtype mice. Moreover, mimicking the BG hyperactivity by activating BG expressing Gq-DREADDs in wildtype mice reproduced the SCA1 pathological phenotype of PCs, i.e., enhancement of sIAHP and decrease of spontaneous firing rate. These results indicate that the intrinsic electrical properties of PCs, but not their synaptic properties, were altered in SCA1 mice and that these alterations were associated with the hyperexcitability of BG. Moreover, preventing BG hyperexcitability in SCA1 mice and promoting BG hyperexcitability in wildtype mice prevented and mimicked, respectively, the pathological electrophysiological phenotype of PCs. Therefore, BG plays a relevant role in the dysfunction of the electrical intrinsic properties of PCs in SCA1 mice, suggesting that they may serve as potential targets for therapeutic approaches to treat the spinocerebellar ataxia type 1.
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Affiliation(s)
- Carmen Nanclares
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | - Marija Cvetanovic
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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8
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Brown LN, Barth JL, Jafri S, Rumschlag JA, Jenkins TR, Atkinson C, Lang H. Complement factor B is essential for the proper function of the peripheral auditory system. Front Neurol 2023; 14:1214408. [PMID: 37560455 PMCID: PMC10408708 DOI: 10.3389/fneur.2023.1214408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Accepted: 07/05/2023] [Indexed: 08/11/2023] Open
Abstract
Sensorineural hearing loss is associated with dysfunction of cochlear cells. Although immune cells play a critical role in maintaining the inner ear microenvironment, the precise immune-related molecular mechanisms underlying the pathophysiology of hearing loss remain unclear. The complement cascade contributes to the regulation of immune cell activity. Additionally, activation of the complement cascade can lead to the cellular opsonization of cells and pathogens, resulting in their engulfment and elimination by phagocytes. Complement factor B (fB) is an essential activator protein in the alternative complement pathway, and variations in the fB gene are associated with age-related macular degeneration. Here we show that mice of both sexes deficient in fB functional alleles (fB-/-) demonstrate progressive hearing impairment. Transcriptomic analysis of auditory nerves from adult mice detected 706 genes that were significantly differentially expressed between fB-/- and wild-type control animals, including genes related to the extracellular matrix and neural development processes. Additionally, a subset of differentially expressed genes was related to myelin function and neural crest development. Histological and immunohistochemical investigations revealed pathological alterations in auditory nerve myelin sheathes of fB-/- mice. Pathological alterations were also seen in the stria vascularis of the cochlear lateral wall in these mice. Our results implicate fB as an integral regulator of myelin maintenance and stria vascularis integrity, underscoring the importance of understanding the involvement of immune signaling pathways in sensorineural hearing loss.
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Affiliation(s)
- LaShardai N. Brown
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States
| | - Jeremy L. Barth
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, United States
| | - Shabih Jafri
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States
| | - Jeffrey A. Rumschlag
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States
| | - Tyreek R. Jenkins
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States
| | - Carl Atkinson
- Division of Pulmonary Medicine, University of Florida, Gainesville, FL, United States
| | - Hainan Lang
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States
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9
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Li X, Li Q, Xu L, Ma Z, Shi Y, Zhang X, Yang Y, Wang J, Fan L, Wu L. Involvement of Kir4.1 in pain insensitivity of the BTBR mouse model of autism spectrum disorder. Biochim Biophys Acta Mol Basis Dis 2023; 1869:166700. [PMID: 36990129 DOI: 10.1016/j.bbadis.2023.166700] [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: 12/30/2022] [Revised: 03/19/2023] [Accepted: 03/21/2023] [Indexed: 03/30/2023]
Abstract
Autism spectrum disorder (ASD) is a severe neurodevelopmental disorder. Abnormal pain sensation is a common clinical symptom of ASD that seriously affects the quality of life of patients with ASD and their families. However, the underlying mechanism is unclear. It is believed to be related to the excitability of neurons and the expression of ion channels. Herein, we confirmed that baseline pain and Complete Freund's adjuvant (CFA)-induced chronic inflammatory pain were impaired in the BTBR T+ Itpr3tf/J (BTBR) mouse model of ASD. RNA sequencing (RNA-seq) analyses of the dorsal root ganglia (DRG), which are closely related to pain in ASD model mice, revealed that high expression of KCNJ10 (encoding Kir4.1) might be an important factor in ASD pain sensation abnormalities. The levels of Kir4.1 were further verified by western blotting, RT-qPCR, and immunofluorescence. By inhibiting Kir4.1, the pain insensitivity of BTBR mice improved, confirming that a high expression level of Kir4.1 was highly correlated with decreased pain sensitivity in ASD. Meanwhile, we found that the anxiety behaviours and the social novelty recognition were changed after CFA induced inflammatory pain. And after inhibiting Kir4.1, the stereotyped behaviours and social novelty recognition of BTBR mice were also improved. Further, we found that the expression levels of glutamate transporters, excitatory amino acid transporter 1 (EAAT1), and excitatory amino acid transporter 2 (EAAT2) were increased in the DRG of BTBR mice but decreased after inhibiting Kir4.1. This suggests that Kir4.1 may play a key role in the improvement of pain insensitivity in ASD by regulating glutamate transporters. In conclusion, our findings revealed the possible mechanism and role of Kir4.1 in the pain insensitivity in ASD, using bioinformatics analyses and animal experiments, and provided a theoretical basis for clinically targeted intervention in ASD.
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Affiliation(s)
- Xiang Li
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Qi Li
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Lisha Xu
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Zhe Ma
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Yaxin Shi
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Xirui Zhang
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Yuan Yang
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Jia Wang
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Lili Fan
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China.
| | - Lijie Wu
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China.
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10
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Krämer-Albers EM, Werner HB. Mechanisms of axonal support by oligodendrocyte-derived extracellular vesicles. Nat Rev Neurosci 2023:10.1038/s41583-023-00711-y. [PMID: 37258632 DOI: 10.1038/s41583-023-00711-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2023] [Indexed: 06/02/2023]
Abstract
Extracellular vesicles (EVs) have recently emerged as versatile elements of cell communication in the nervous system, mediating tissue homeostasis. EVs influence the physiology of their target cells via horizontal transfer of molecular cargo between cells and by triggering signalling pathways. In this Review, we discuss recent work revealing that EVs mediate interactions between oligodendrocytes and neurons, which are relevant for maintaining the structural integrity of axons. In response to neuronal activity, myelinating oligodendrocytes release EVs, which are internalized by neurons and provide axons with key factors that improve axonal transport, stress resistance and energy homeostasis. Glia-to-neuron transfer of EVs is thus a crucial facet of axonal preservation. When glial support is impaired, axonal integrity is progressively lost, as observed in myelin-related disorders, other neurodegenerative diseases and with normal ageing. We highlight the mechanisms that oligodendroglial EVs use to sustain axonal integrity and function.
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Affiliation(s)
- Eva-Maria Krämer-Albers
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany.
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
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11
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Lim D, Tapella L, Dematteis G, Talmon M, Genazzani AA. Calcineurin Signalling in Astrocytes: From Pathology to Physiology and Control of Neuronal Functions. Neurochem Res 2023; 48:1077-1090. [PMID: 36083398 PMCID: PMC10030417 DOI: 10.1007/s11064-022-03744-4] [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: 07/31/2022] [Revised: 07/31/2022] [Accepted: 08/29/2022] [Indexed: 10/14/2022]
Abstract
Calcineurin (CaN), a Ca2+/calmodulin-activated serine/threonine phosphatase, acts as a Ca2+-sensitive switch regulating cellular functions through protein dephosphorylation and activation of gene transcription. In astrocytes, the principal homeostatic cells in the CNS, over-activation of CaN is known to drive pathological transcriptional remodelling, associated with neuroinflammation in diseases such as Alzheimer's disease, epilepsy and brain trauma. Recent reports suggest that, in physiological conditions, the activity of CaN in astrocytes is transcription-independent and is required for maintenance of basal protein synthesis rate and activation of astrocytic Na+/K+ pump thereby contributing to neuronal functions such as neuronal excitability and memory formation. In this contribution we overview the role of Ca2+ and CaN signalling in astroglial pathophysiology focusing on the emerging physiological role of CaN in astrocytes. We propose a model for the context-dependent switch of CaN activity from the post-transcriptional regulation of cell proteostasis in healthy astrocytes to the CaN-dependent transcriptional activation in neuroinflammation-associated diseases.
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Affiliation(s)
- Dmitry Lim
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "Amedeo Avogadro", Via Bovio 6, 28100, Novara, Italy.
| | - Laura Tapella
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "Amedeo Avogadro", Via Bovio 6, 28100, Novara, Italy
| | - Giulia Dematteis
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "Amedeo Avogadro", Via Bovio 6, 28100, Novara, Italy
| | - Maria Talmon
- Department of Health Sciences, School of Medicine, Università del Piemonte Orientale "Amedeo Avogadro", Via Solaroli 17, 28100, Novara, Italy
| | - Armando A Genazzani
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "Amedeo Avogadro", Via Bovio 6, 28100, Novara, Italy.
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12
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McGinnis A, Ji RR. The Similar and Distinct Roles of Satellite Glial Cells and Spinal Astrocytes in Neuropathic Pain. Cells 2023; 12:965. [PMID: 36980304 PMCID: PMC10047571 DOI: 10.3390/cells12060965] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Revised: 03/19/2023] [Accepted: 03/20/2023] [Indexed: 03/30/2023] Open
Abstract
Preclinical studies have identified glial cells as pivotal players in the genesis and maintenance of neuropathic pain after nerve injury associated with diabetes, chemotherapy, major surgeries, and virus infections. Satellite glial cells (SGCs) in the dorsal root and trigeminal ganglia of the peripheral nervous system (PNS) and astrocytes in the central nervous system (CNS) express similar molecular markers and are protective under physiological conditions. They also serve similar functions in the genesis and maintenance of neuropathic pain, downregulating some of their homeostatic functions and driving pro-inflammatory neuro-glial interactions in the PNS and CNS, i.e., "gliopathy". However, the role of SGCs in neuropathic pain is not simply as "peripheral astrocytes". We delineate how these peripheral and central glia participate in neuropathic pain by producing different mediators, engaging different parts of neurons, and becoming active at different stages following nerve injury. Finally, we highlight the recent findings that SGCs are enriched with proteins related to fatty acid metabolism and signaling such as Apo-E, FABP7, and LPAR1. Targeting SGCs and astrocytes may lead to novel therapeutics for the treatment of neuropathic pain.
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Affiliation(s)
- Aidan McGinnis
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Ru-Rong Ji
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
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13
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Dystrophin Short Product, Dp71, Interacts with AQP4 and Kir4.1 Channels in the Mouse Cerebellar Glial Cells in Contrast to Dp427 at Inhibitory Postsynapses in the Purkinje Neurons. Mol Neurobiol 2023; 60:3664-3677. [PMID: 36918517 DOI: 10.1007/s12035-023-03296-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 03/01/2023] [Indexed: 03/16/2023]
Abstract
Dystrophin is the causative gene for Duchenne and Becker muscular dystrophy (DMD/BMD), and it produces full-length and short dystrophin, Dp427 and Dp71, respectively, in the brain. The existence of the different dystrophin molecular complexes has been known for a quarter century, so it is necessary to derive precise expression profiles of the molecular complexes in the brain to elucidate the mechanism of cognitive symptoms in DMD/BMD patients. In order to investigate the Dp71 expression profile in cerebellum, we employed Dp71-specific tag-insertion mice, which allowed for the specific detection of endogenous Dp71 in the immunohistochemical analysis and found its expressions in the glial cells, Bergmann glial (BG) cells, and astrocytes, whereas Dp427 was exclusively expressed in the inhibitory postsynapses within cerebellar Purkinje cells (PCs). Interestingly, we found different cell-type dependent dystrophin molecular complexes; i.e., glia-associated Dp71 was co-expressed with dystroglycan (DG) and dystrobrevinα, whereas synapse-associated Dp427 was co-expressed with DG and dystrobrevinβ. Furthermore, we investigated the molecular relationship of Dp71 to the AQP4 water channel and the Kir4.1 potassium channel, and found biochemical associations of Dp71 with AQP4 and Kir4.1 in both the cerebellum and cerebrum. Immunohistochemical and cytochemical investigations revealed partial co-localizations of Dp71 with AQP4 and Kir4.1 in the glial cells, indicating Dp71 interactions with the channels in the BG cells and astrocytes. Taken together, different cell-types, glial cells and Purkinje neurons, in the cerebellum express different dystrophin molecular complexes, which may contribute to pathological and physiological processes through the regulation of the water/ion channel and inhibitory postsynapses.
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14
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Wiese BM, Alvarez Reyes A, Vanderah TW, Largent-Milnes TM. The endocannabinoid system and breathing. Front Neurosci 2023; 17:1126004. [PMID: 37144090 PMCID: PMC10153446 DOI: 10.3389/fnins.2023.1126004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 03/16/2023] [Indexed: 05/06/2023] Open
Abstract
Recent changes in cannabis accessibility have provided adjunct therapies for patients across numerous disease states and highlights the urgency in understanding how cannabinoids and the endocannabinoid (EC) system interact with other physiological structures. The EC system plays a critical and modulatory role in respiratory homeostasis and pulmonary functionality. Respiratory control begins in the brainstem without peripheral input, and coordinates the preBötzinger complex, a component of the ventral respiratory group that interacts with the dorsal respiratory group to synchronize burstlet activity and drive inspiration. An additional rhythm generator: the retrotrapezoid nucleus/parafacial respiratory group drives active expiration during conditions of exercise or high CO2. Combined with the feedback information from the periphery: through chemo- and baroreceptors including the carotid bodies, the cranial nerves, stretch of the diaphragm and intercostal muscles, lung tissue, and immune cells, and the cranial nerves, our respiratory system can fine tune motor outputs that ensure we have the oxygen necessary to survive and can expel the CO2 waste we produce, and every aspect of this process can be influenced by the EC system. The expansion in cannabis access and potential therapeutic benefits, it is essential that investigations continue to uncover the underpinnings and mechanistic workings of the EC system. It is imperative to understand the impact cannabis, and exogenous cannabinoids have on these physiological systems, and how some of these compounds can mitigate respiratory depression when combined with opioids or other medicinal therapies. This review highlights the respiratory system from the perspective of central versus peripheral respiratory functionality and how these behaviors can be influenced by the EC system. This review will summarize the literature available on organic and synthetic cannabinoids in breathing and how that has shaped our understanding of the role of the EC system in respiratory homeostasis. Finally, we look at some potential future therapeutic applications the EC system has to offer for the treatment of respiratory diseases and a possible role in expanding the safety profile of opioid therapies while preventing future opioid overdose fatalities that result from respiratory arrest or persistent apnea.
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Affiliation(s)
- Beth M. Wiese
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
| | - Angelica Alvarez Reyes
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
- College of Medicine, University of Arizona, Tucson, AZ, United States
| | - Todd W. Vanderah
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
| | - Tally M. Largent-Milnes
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
- *Correspondence: Tally M. Largent-Milnes,
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15
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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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16
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Young CJ, Lyons D, Piggins HD. Circadian Influences on the Habenula and Their Potential Contribution to Neuropsychiatric Disorders. Front Behav Neurosci 2022; 15:815700. [PMID: 35153695 PMCID: PMC8831701 DOI: 10.3389/fnbeh.2021.815700] [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: 11/15/2021] [Accepted: 12/27/2021] [Indexed: 12/13/2022] Open
Abstract
The neural circadian system consists of the master circadian clock in the hypothalamic suprachiasmatic nuclei (SCN) communicating time of day cues to the rest of the body including other brain areas that also rhythmically express circadian clock genes. Over the past 16 years, evidence has emerged to indicate that the habenula of the epithalamus is a candidate extra-SCN circadian oscillator. When isolated from the SCN, the habenula sustains rhythms in clock gene expression and neuronal activity, with the lateral habenula expressing more robust rhythms than the adjacent medial habenula. The lateral habenula is responsive to putative SCN output factors as well as light information conveyed to the perihabenula area. Neuronal activity in the lateral habenula is altered in depression and intriguingly disruptions in circadian rhythms can elevate risk of developing mental health disorders including depression. In this review, we will principally focus on how circadian and light signals affect the lateral habenula and evaluate the possibility that alteration in these influences contribute to mental health disorders.
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17
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Dynamic expression of homeostatic ion channels in differentiated cortical astrocytes in vitro. Pflugers Arch 2021; 474:243-260. [PMID: 34734327 PMCID: PMC8766406 DOI: 10.1007/s00424-021-02627-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 09/02/2021] [Accepted: 09/24/2021] [Indexed: 11/16/2022]
Abstract
The capacity of astrocytes to adapt their biochemical and functional features upon physiological and pathological stimuli is a fundamental property at the basis of their ability to regulate the homeostasis of the central nervous system (CNS). It is well known that in primary cultured astrocytes, the expression of plasma membrane ion channels and transporters involved in homeostatic tasks does not closely reflect the pattern observed in vivo. The individuation of culture conditions that promote the expression of the ion channel array found in vivo is crucial when aiming at investigating the mechanisms underlying their dynamics upon various physiological and pathological stimuli. A chemically defined medium containing growth factors and hormones (G5) was previously shown to induce the growth, differentiation, and maturation of primary cultured astrocytes. Here we report that under these culture conditions, rat cortical astrocytes undergo robust morphological changes acquiring a multi-branched phenotype, which develops gradually during the 2-week period of culturing. The shape changes were paralleled by variations in passive membrane properties and background conductance owing to the differential temporal development of inwardly rectifying chloride (Cl−) and potassium (K+) currents. Confocal and immunoblot analyses showed that morphologically differentiated astrocytes displayed a large increase in the expression of the inward rectifier Cl− and K+ channels ClC-2 and Kir4.1, respectively, which are relevant ion channels in vivo. Finally, they exhibited a large diminution of the intermediate filaments glial fibrillary acidic protein (GFAP) and vimentin which are upregulated in reactive astrocytes in vivo. Taken together the data indicate that long-term culturing of cortical astrocytes in this chemical-defined medium promotes a quiescent functional phenotype. This culture model could aid to address the regulation of ion channel expression involved in CNS homeostasis in response to physiological and pathological challenges.
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18
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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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19
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In Vivo Neocortical [K]o Modulation by Targeted Stimulation of Astrocytes. Int J Mol Sci 2021; 22:ijms22168658. [PMID: 34445364 PMCID: PMC8395460 DOI: 10.3390/ijms22168658] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/05/2021] [Accepted: 08/09/2021] [Indexed: 11/17/2022] Open
Abstract
A normally functioning nervous system requires normal extracellular potassium ion concentration ([K]o). Throughout the nervous system, several processes, including those of an astrocytic nature, are involved in [K]o regulation. In this study we investigated the effect of astrocytic photostimulation on [K]o. We hypothesized that in vivo photostimulation of eNpHR-expressing astrocytes leads to a decreased [K]o. Using optogenetic and electrophysiological techniques we showed that stimulation of eNpHR-expressing astrocytes resulted in a significantly decreased resting [K]o and evoked K responses. The amplitude of the concomitant spreading depolarization-like events also decreased. Our results imply that astrocytic membrane potential modification could be a potential tool for adjusting the [K]o.
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20
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Price BR, Johnson LA, Norris CM. Reactive astrocytes: The nexus of pathological and clinical hallmarks of Alzheimer's disease. Ageing Res Rev 2021; 68:101335. [PMID: 33812051 PMCID: PMC8168445 DOI: 10.1016/j.arr.2021.101335] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 01/21/2021] [Accepted: 03/20/2021] [Indexed: 02/06/2023]
Abstract
Astrocyte reactivity is a hallmark of neuroinflammation that arises with Alzheimer’s disease (AD) and nearly every other neurodegenerative condition. While astrocytes certainly contribute to classic inflammatory processes (e.g. cytokine release, waste clearance, and tissue repair), newly emerging technologies for measuring and targeting cell specific activities in the brain have uncovered essential roles for astrocytes in synapse function, brain metabolism, neurovascular coupling, and sleep/wake patterns. In this review, we use a holistic approach to incorporate, and expand upon, classic neuroinflammatory concepts to consider how astrocyte dysfunction/reactivity modulates multiple pathological and clinical hallmarks of AD. Our ever-evolving understanding of astrocyte signaling in neurodegeneration is not only revealing new drug targets and treatments for dementia but is suggesting we reimagine AD pathophysiological mechanisms.
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Affiliation(s)
- Brittani R Price
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA, 02111, USA
| | - Lance A Johnson
- Sanders-Brown Center on Aging, University of Kentucky, 800 S. Limestone St., Lexington, KY, 40356, USA; Department of Physiology, University of Kentucky, College of Medicine, UK Medical Center MN 150, Lexington, KY, 40536, USA
| | - Christopher M Norris
- Sanders-Brown Center on Aging, University of Kentucky, 800 S. Limestone St., Lexington, KY, 40356, USA; Department of Pharmacology and Nutritional Sciences, University of Kentucky, College of Medicine, UK Medical Center MN 150, Lexington, KY, 40536, USA.
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21
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Yuan Q, Xu J, Chen H. Dynamics Analysis of Firing Patterns in Pre-Bötzinger Complex Neurons Model. Front Comput Neurosci 2021; 15:591037. [PMID: 34211383 PMCID: PMC8239244 DOI: 10.3389/fncom.2021.591037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 05/25/2021] [Indexed: 11/29/2022] Open
Abstract
Pre-Bötzinger complex (PBC) neurons located in mammalian brain are the necessary conditions to produce respiratory rhythm, which has been widely verified experimentally and numerically. At present, one of the two different types of bursting mechanisms found in PBC mainly depends on the calcium-activated of non-specific cation current (ICaN). In order to study the influence of ICaN and stimulus current Iexc in PBC inspiratory neurons, a single compartment model was simplified, and firing patterns of the model was discussed by using stability theory, bifurcation analysis, fast, and slow decomposition technology combined with numerical simulation. Under the stimulation of different somatic applied currents, the firing behavior of neurons are studied and exhibit multiple mix bursting patterns, which is helpful to further understand the mechanism of respiratory rhythms of PBC neurons.
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Affiliation(s)
- Quan Yuan
- School of Mathematics and Information Science, Guangxi University, Guangxi, China
| | - Jieqiong Xu
- School of Mathematics and Information Science, Guangxi University, Guangxi, China
| | - Huiying Chen
- School of Mathematics and Information Science, Guangxi University, Guangxi, China
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22
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Leo M, Schmitt LI, Steffen R, Kutritz A, Kleinschnitz C, Hagenacker T. Modulation of Glutamate Transporter EAAT1 and Inward-Rectifier Potassium Channel K ir4.1 Expression in Cultured Spinal Cord Astrocytes by Platinum-Based Chemotherapeutics. Int J Mol Sci 2021; 22:6300. [PMID: 34208258 PMCID: PMC8230757 DOI: 10.3390/ijms22126300] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/06/2021] [Accepted: 06/09/2021] [Indexed: 12/26/2022] Open
Abstract
Platinum-based chemotherapeutics still play an essential role in cancer treatment. Despite their high effectiveness, severe side effects such as chemotherapy-induced neuropathy (CIPN) occur frequently. The pathophysiology of CIPN by platinum-based chemotherapeutics is not fully understood yet, but primarily the disturbance of dorsal root ganglion cells is discussed. However, there is increasing evidence of central nervous system involvement with activation of spinal cord astrocytes after treatment with chemotherapeutics. We investigated the influence of cis- or oxaliplatin on the functionality of cultured rat spinal cord astrocytes by using immunocytochemistry and patch-clamp electrophysiology. Cis- or oxaliplatin activated spinal astrocytes and led to downregulation of the excitatory amino acid transporter 1 (EAAT1) expression. Furthermore, the expression and function of potassium channel Kir4.1 were modulated. Pre-exposure to a specific Kir4.1 blocker in control astrocytes led to a reduced immune reactivity (IR) of EAAT1 and a nearly complete block of the current density. When spinal astrocytes were pre-exposed to antibiotic minocycline, all effects of cis- or oxaliplatin were abolished. Taken together, the modulation of Kir4.1 and EAAT1 proteins in astrocytes could be linked to the direct impact of cis- or oxaliplatin, identifying spinal astrocytes as a potential target in the prevention and treatment of chemotherapy-induced neuropathy.
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Affiliation(s)
- Markus Leo
- Department of Neurology, Center for Translational Neuro- and Behavioral Sciences (C-TNBS), University Hospital Essen, 45147 Essen, Germany; (L.-I.S.); (R.S.); (A.K.); (C.K.); (T.H.)
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23
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Abstract
Myelination of axons provides the structural basis for rapid saltatory impulse propagation along vertebrate fiber tracts, a well-established neurophysiological concept. However, myelinating oligodendrocytes and Schwann cells serve additional functions in neuronal energy metabolism that are remarkably similar to those of axon-ensheathing glial cells in unmyelinated invertebrates. Here we discuss myelin evolution and physiological glial functions, beginning with the role of ensheathing glia in preventing ephaptic coupling, axoglial metabolic support, and eliminating oxidative radicals. In both vertebrates and invertebrates, axoglial interactions are bidirectional, serving to regulate cell fate, nerve conduction, and behavioral performance. One key step in the evolution of compact myelin in the vertebrate lineage was the emergence of the open reading frame for myelin basic protein within another gene. Several other proteins were neofunctionalized as myelin constituents and help maintain a healthy nervous system. Myelination in vertebrates became a major prerequisite of inhabiting new ecological niches.
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Affiliation(s)
- Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany; ,
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany; ,
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24
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Göppner C, Soria AH, Hoegg-Beiler MB, Jentsch TJ. Cellular basis of ClC-2 Cl - channel-related brain and testis pathologies. J Biol Chem 2021; 296:100074. [PMID: 33187987 PMCID: PMC7949093 DOI: 10.1074/jbc.ra120.016031] [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: 09/13/2020] [Revised: 11/11/2020] [Accepted: 11/13/2020] [Indexed: 12/11/2022] Open
Abstract
The ClC-2 chloride channel is expressed in the plasma membrane of almost all mammalian cells. Mutations that cause the loss of ClC-2 function lead to retinal and testicular degeneration and leukodystrophy, whereas gain-of-function mutations cause hyperaldosteronism. Leukodystrophy is also observed with a loss of GlialCAM, a cell adhesion molecule that binds to ClC-2 in glia. GlialCAM changes the localization of ClC-2 and opens the channel by altering its gating. We now used cell type-specific deletion of ClC-2 in mice to show that retinal and testicular degeneration depend on a loss of ClC-2 in retinal pigment epithelial cells and Sertoli cells, respectively, whereas leukodystrophy was fully developed only when ClC-2 was disrupted in both astrocytes and oligodendrocytes. The leukodystrophy of Glialcam-/- mice could not be rescued by crosses with Clcn2op/op mice in which a mutation mimics the "opening" of ClC-2 by GlialCAM. These data indicate that GlialCAM-induced changes in biophysical properties of ClC-2 are irrelevant for GLIALCAM-related leukodystrophy. Taken together, our findings suggest that the pathology caused by Clcn2 disruption results from disturbed extracellular ion homeostasis and identifies the cells involved in this process.
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Affiliation(s)
- Corinna Göppner
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Audrey H Soria
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Maja B Hoegg-Beiler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Thomas J Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany.
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25
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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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26
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Smith KE, Murphy P, Jagger DJ. Divergent membrane properties of mouse cochlear glial cells around hearing onset. J Neurosci Res 2020; 99:679-698. [PMID: 33099767 DOI: 10.1002/jnr.24744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 09/21/2020] [Accepted: 10/05/2020] [Indexed: 11/11/2022]
Abstract
Spiral ganglion neurons (SGNs) are the primary afferent neurons of the auditory system, and together with their attendant glia, form the auditory nerve. Within the cochlea, satellite glial cells (SGCs) encapsulate the cell body of SGNs, whereas Schwann cells (SCs) wrap their peripherally- and centrally-directed neurites. Despite their likely importance in auditory nerve function and homeostasis, the physiological properties of auditory glial cells have evaded description. Here, we characterized the voltage-activated membrane currents of glial cells from the mouse cochlea. We identified a prominent weak inwardly rectifying current in SGCs within cochlear slice preparations (postnatal day P5-P6), which was also present in presumptive SGCs within dissociated cultures prepared from the cochleae of hearing mice (P14-P15). Pharmacological block by Ba2+ and desipramine suggested that channels belonging to the Kir4 family mediated the weak inwardly rectifying current, and post hoc immunofluorescence implicated the involvement of Kir4.1 subunits. Additional electrophysiological profiles were identified for glial cells within dissociated cultures, suggesting that glial subtypes may have specific membrane properties to support distinct physiological roles. Immunofluorescence using fixed cochlear sections revealed that although Kir4.1 is restricted to SGCs after the onset of hearing, these channels are more widely distributed within the glial population earlier in postnatal development (i.e., within both SGCs and SCs). The decrease in Kir4.1 immunofluorescence during SC maturation was coincident with a reduction of Sox2 expression and advancing neurite myelination. The data suggest a diversification of glial properties occurs in preparation for sound-driven activity in the auditory nerve.
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Affiliation(s)
- Katie E Smith
- UCL Ear Institute, University College London, London, UK
| | - Phoebe Murphy
- UCL Ear Institute, University College London, London, UK
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27
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Moroni RF, Regondi MC, de Curtis M, Frassoni C, Librizzi L. Kir4.1 RNA Interference by In Utero Electroporation Fails to Affect Ictogenesis and Reveals a Possible role of Kir4.1 in Corticogenesis. Neuroscience 2020; 441:65-76. [PMID: 32590038 DOI: 10.1016/j.neuroscience.2020.06.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 04/24/2020] [Accepted: 06/15/2020] [Indexed: 11/26/2022]
Abstract
Astrocyte dysfunction, and in particular impaired extracellular potassium spatial buffering, has been postulated to have a potential role in seizure susceptibility and ictogenesis. Inwardly rectifying potassium (Kir) channels, and specifically KIR4.1, have a predominant role in K+ homeostasis and their involvement in neuronal excitability control have been hypothesized. To avoid the severe side effects observed in Kir4.1 cKO, we studied the effects of Kir4.1 down-regulation in cortical astrocytes by using Kir4.1 RNA interference (RNAi) technique combined with in utero electroporation (IUE) at E16 and a piggyBac transposon system. Kir4.1 down-regulation was confirmed by immunohistochemistry and field fraction analysis. To investigate if Kir4.1 silencing affects 4AP-induced seizure threshold and extracellular potassium homeostasis, simultaneous in vitro field potential and extracellular K+ recordings were performed on somatosensory cortex slices obtained from rats electroporated with a piggyBac-Kir4.1-shRNA (Kir4.1-) and scrambled shRNA (Kir4.1Sc). Electrophysiological data revealed no significant differences in terms of seizure onset and seizure-induced extracellular K+ changes between Kir4.1- and Kir4.1Sc rats. Intriguingly, immunohistochemical analysis performed on slices studied with electrophysiology revealed a reduced number of neurons generated from radial glial cells in Kir4.1- rats. We conclude that focal down-regulation of Kir4.1 channel in cortical astrocytes by Kir4.1 RNAi technique combined with IUE is not effective in altering potassium homeostasis and seizure susceptibility. This technique revealed a possible role of Kir4.1 during corticogenesis.
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Affiliation(s)
- Ramona Frida Moroni
- Epilepsy Unit, Fondazione I.R.C.C.S. Istituto Neurologico "C. Besta", via Celoria 11, 20133 Milan, Italy.
| | - Maria Cristina Regondi
- Epilepsy Unit, Fondazione I.R.C.C.S. Istituto Neurologico "C. Besta", via Celoria 11, 20133 Milan, Italy.
| | - Marco de Curtis
- Epilepsy Unit, Fondazione I.R.C.C.S. Istituto Neurologico "C. Besta", via Celoria 11, 20133 Milan, Italy.
| | - Carolina Frassoni
- Epilepsy Unit, Fondazione I.R.C.C.S. Istituto Neurologico "C. Besta", via Celoria 11, 20133 Milan, Italy.
| | - Laura Librizzi
- Epilepsy Unit, Fondazione I.R.C.C.S. Istituto Neurologico "C. Besta", via Celoria 11, 20133 Milan, Italy.
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28
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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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29
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Rivera-Aponte DE, Melnik-Martínez KV, Malpica-Nieves CJ, Tejeda-Bayron F, Méndez-González MP, Skatchkov SN, Eaton MJ. Kir4.1 potassium channel regulation via microRNA-205 in astrocytes exposed to hyperglycemic conditions. Neuroreport 2020; 31:450-455. [PMID: 32168096 PMCID: PMC7127973 DOI: 10.1097/wnr.0000000000001427] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Protecting neurons from neurotoxicity is a job mainly performed by astrocytes through glutamate uptake and potassium buffering. These functions are aided principally by the Kir4.1 inwardly rectifying potassium channels located in the membrane of astrocytes. Astrocytes grown in hyperglycemic conditions have decreased levels of Kir4.1 potassium channels as well as impaired potassium and glutamate uptake. Previous studies performed in a human corneal epithelial cell injury model demonstrated a mechanism of regulation of Kir4.1 expression via the binding of microRNA-250 (miR-205) to the Kir4.1 3´ untranslated region. Our purpose is to test if astrocytes express miR-205 and elucidate its role in regulating Kir4.1 expression in astrocytes grown in hyperglycemic conditions. We used quantitative-PCR to assess the levels of miR-205 in astrocytes grown in high glucose (25 mM) medium compared to astrocytes grown in normal glucose (5 mM). We found that not only was miR-205 expressed in astrocytes grown in normal glucose, but its expression was increased up to six-fold in astrocytes grown in hyperglycemic conditions. Transfection of miR-205 mimic or inhibitor was performed to alter the levels of miR-205 in astrocytes followed by western blot to assess Kir4.1 channel levels in these cells. Astrocytes treated with miR-205 mimic had a 38.6% reduction of Kir4.1 protein levels compared to control (mock-transfected) cells. In contrast, astrocytes transfected with miR-205 inhibitor were significantly upregulated compared to mock by 47.4%. Taken together, our data indicate that miR-205 negatively regulates the expression of Kir4.1 in astrocytes grown in hyperglycemic conditions.
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Affiliation(s)
| | | | | | - Flavia Tejeda-Bayron
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico
| | - Miguel P. Méndez-González
- Department of Natural Sciences, University of Puerto Rico, Aguadilla, Puerto Rico
- Department of Sciences and Technology, Antilles Adventist University, Mayagüez, Puerto Rico
| | - Serguei N. Skatchkov
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico
- Department of Physiology, Universidad Central del Caribe, Bayamón, Puerto Rico
| | - Misty J. Eaton
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico
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30
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MacAulay N. Molecular mechanisms of K + clearance and extracellular space shrinkage-Glia cells as the stars. Glia 2020; 68:2192-2211. [PMID: 32181522 DOI: 10.1002/glia.23824] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/28/2020] [Accepted: 03/04/2020] [Indexed: 12/17/2022]
Abstract
Neuronal signaling in the central nervous system (CNS) associates with release of K+ into the extracellular space resulting in transient increases in [K+ ]o . This elevated K+ is swiftly removed, in part, via uptake by neighboring glia cells. This process occurs in parallel to the [K+ ]o elevation and glia cells thus act as K+ sinks during the neuronal activity, while releasing it at the termination of the pulse. The molecular transport mechanisms governing this glial K+ absorption remain a point of debate. Passive distribution of K+ via Kir4.1-mediated spatial buffering of K+ has become a favorite within the glial field, although evidence for a quantitatively significant contribution from this ion channel to K+ clearance from the extracellular space is sparse. The Na+ /K+ -ATPase, but not the Na+ /K+ /Cl- cotransporter, NKCC1, shapes the activity-evoked K+ transient. The different isoform combinations of the Na+ /K+ -ATPase expressed in glia cells and neurons display different kinetic characteristics and are thereby distinctly geared toward their temporal and quantitative contribution to K+ clearance. The glia cell swelling occurring with the K+ transient was long assumed to be directly associated with K+ uptake and/or AQP4, although accumulating evidence suggests that they are not. Rather, activation of bicarbonate- and lactate transporters appear to lead to glial cell swelling via the activity-evoked alkaline transient, K+ -mediated glial depolarization, and metabolic demand. This review covers evidence, or lack thereof, accumulated over the last half century on the molecular mechanisms supporting activity-evoked K+ and extracellular space dynamics.
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Affiliation(s)
- Nanna MacAulay
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
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31
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Zupanc GKH. Development of a sexual dimorphism in a central pattern generator driving a rhythmic behavior: The role of glia-mediated potassium buffering in the pacemaker nucleus of the weakly electric fish Apteronotus leptorhynchus. Dev Neurobiol 2020; 80:6-15. [PMID: 32090501 DOI: 10.1002/dneu.22736] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Revised: 01/24/2020] [Accepted: 02/20/2020] [Indexed: 01/09/2023]
Abstract
Central pattern generators play a critical role in the neural control of rhythmic behaviors. One of their characteristic features is the ability to modulate the oscillatory output. An important yet little-studied type of modulation involves the generation of oscillations that are sexually dimorphic in frequency. In the weakly electric fish Apteronotus leptorhynchus, the pacemaker nucleus serves as a central pattern generator that drives the electric organ discharge of the fish in a one-to-one fashion. Males discharge at higher frequencies than females-a sexual dimorphism that develops under the influence of steroid hormones. The two principal neurons that constitute the oscillatory network of the pacemaker nucleus are the pacemaker and relay cells. Whereas the number and size of the pacemaker and relay cells are sexually monomorphic, pronounced sex-dependent differences exist in the morphology, and subcellular properties of astrocytes, which form a syncytium closely associated with these neurons. In females, compared to males, the astrocytic syncytium covers a larger area surrounding the pacemaker and relay cells and exhibits higher levels of expression of connexin-43 expression. The latter indicates a strong gap-junction coupling of the individual cells within the syncytium. It is hypothesized that these sex-specific differences result in an increased capacity for buffering of extracellular potassium ions, thereby lowering the potassium equilibrium potential, which, in turn, leads to a decrease in the oscillation frequency. This hypothesis has received strong support from simulations based on computational models of individual neurons and the whole neural network of the pacemaker nucleus.
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Affiliation(s)
- Günther K H Zupanc
- Laboratory of Neurobiology, Department of Biology, Northeastern University, Boston, Massachusetts, USA
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32
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Nadella RK, Chellappa A, Subramaniam AG, More RP, Shetty S, Prakash S, Ratna N, Vandana VP, Purushottam M, Saini J, Viswanath B, Bindu PS, Nagappa M, Mehta B, Jain S, Kannan R. Identification and functional characterization of two novel mutations in KCNJ10 and PI4KB in SeSAME syndrome without electrolyte imbalance. Hum Genomics 2019; 13:53. [PMID: 31640787 PMCID: PMC6805350 DOI: 10.1186/s40246-019-0236-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 08/23/2019] [Indexed: 12/27/2022] Open
Abstract
Background Dysfunction in inwardly rectifying potassium channel Kir4.1 has been implicated in SeSAME syndrome, an autosomal-recessive (AR), rare, multi-systemic disorder. However, not all neurological, intellectual disability, and comorbid phenotypes in SeSAME syndrome can be mechanistically linked solely to Kir4.1 dysfunction. Methods We therefore performed whole-exome sequencing and identified additional genetic risk-elements that might exert causative effects either alone or in concert with Kir4.1 in a family diagnosed with SeSAME syndrome. Results Two variant prioritization pipelines based on AR inheritance and runs of homozygosity (ROH), identified two novel homozygous variants in KCNJ10 and PI4KB and five rare homozygous variants in PVRL4, RORC, FLG2, FCRL1, NIT1 and one common homozygous variant in HSPA6 segregating in all four patients. The novel mutation in KCNJ10 resides in the cytoplasmic domain of Kir4.1, a seat of phosphatidylinositol bisphosphate (PIP2) binding. The mutation altered the subcellular localization and stability of Kir4.1 in patient-specific lymphoblastoid cells (LCLs) compared to parental controls. Barium-sensitive endogenous K+ currents in patient-specific LCLs using whole-cell patch-clamp electrophysiology revealed membrane depolarization and defects in inward K+ ion conductance across the membrane, thereby suggesting a loss-of-function effect of KCNJ10 variant. Conclusion Altogether, our findings implicate the role of new genes in SeSAME syndrome without electrolyte imbalance and thereby speculate the regulation of Kir4.1 channel activity by PIP2 and integrin-mediated adhesion signaling mechanisms. Electronic supplementary material The online version of this article (10.1186/s40246-019-0236-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ravi K Nadella
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - Anirudh Chellappa
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - Anand G Subramaniam
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - Ravi Prabhakar More
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore, India
| | - Srividya Shetty
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - Suriya Prakash
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - Nikhil Ratna
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - V P Vandana
- Department of Speech Pathology and Audiology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Meera Purushottam
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - Jitender Saini
- Department of Neuroimaging and Interventional Radiology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Biju Viswanath
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India
| | - P S Bindu
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Madhu Nagappa
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Bhupesh Mehta
- Department of Biophysics, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Sanjeev Jain
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India.,National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore, India
| | - Ramakrishnan Kannan
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, 560029, India.
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33
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Papanikolaou M, Lewis A, Butt AM. Glial and neuronal expression of the Inward Rectifying Potassium Channel Kir7.1 in the adult mouse brain. J Anat 2019; 235:984-996. [PMID: 31309576 PMCID: PMC6794205 DOI: 10.1111/joa.13048] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/29/2019] [Indexed: 01/01/2023] Open
Abstract
Inward Rectifying Potassium channels (Kir) are a large family of ion channels that play key roles in ion homeostasis and neuronal excitability. The most recently described Kir subtype is Kir7.1, which is known as a K+ transporting subtype. Earlier studies localised Kir7.1 to subpopulations of neurones in the brain. However, the pattern of Kir7.1 expression across the brain has not previously been examined. Here, we have determined neuronal and glial expression of Kir7.1 in the adult mouse brain, using immunohistochemistry and transgenic mouse lines expressing reporters specific for astrocytes [glial fibrillary acidic protein‐enhanced green fluorescent protein (GFAP‐EGFP], myelinating oligodendrocytes (PLP‐DsRed), oligodendrocyte progenitor cells (OPC, Pdgfra‐creERT2/Rosa26‐YFP double‐transgenic mice) and all oligodendrocyte lineage cells (SOX10‐EGFP). The results demonstrate significant neuronal Kir7.1 immunostaining in the cortex, hippocampus, cerebellum and pons, as well as the striatum and hypothalamus. In addition, astrocytes are shown to be immunopositive for Kir7.1 throughout grey and white matter, with dense immunostaining on cell somata, primary processes and perivascular end‐feet. Immunostaining for Kir7.1 was observed in oligodendrocytes, myelin and OPCs throughout the brain, although immunostaining was heterogeneous. Neuronal and glial expression of Kir7.1 is confirmed using neurone‐glial cortical cultures and optic nerve glial cultures. Notably, Kir7.1 have been shown to regulate the excitability of thalamic neurones and our results indicate this may be a widespread function of Kir7.1 in neurones throughout the brain. Moreover, based on the function of Kir7.1 in multiple transporting epithelia, Kir7.1 are likely to play an equivalent role in the primary glial function of K+ homeostasis. Our results indicate Kir7.1 are far more pervasive in the brain than previously recognised and have potential importance in regulating neuronal and glial function.
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Affiliation(s)
- Maria Papanikolaou
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Science, University of Portsmouth, Portsmouth, UK
| | - Anthony Lewis
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Science, University of Portsmouth, Portsmouth, UK
| | - Arthur M Butt
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Science, University of Portsmouth, Portsmouth, UK
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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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Sparks JT, Botsko G, Swale DR, Boland LM, Patel SS, Dickens JC. Membrane Proteins Mediating Reception and Transduction in Chemosensory Neurons in Mosquitoes. Front Physiol 2018; 9:1309. [PMID: 30294282 PMCID: PMC6158332 DOI: 10.3389/fphys.2018.01309] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 08/30/2018] [Indexed: 12/17/2022] Open
Abstract
Mosquitoes use chemical cues to modulate important behaviors such as feeding, mating, and egg laying. The primary chemosensory organs comprising the paired antennae, maxillary palps and labial palps are adorned with porous sensilla that house primary sensory neurons. Dendrites of these neurons provide an interface between the chemical environment and higher order neuronal processing. Diverse proteins located on outer membranes interact with chemicals, ions, and soluble proteins outside the cell and within the lumen of sensilla. Here, we review the repertoire of chemosensory receptors and other membrane proteins involved in transduction and discuss the outlook for their functional characterization. We also provide a brief overview of select ion channels, their role in mammalian taste, and potential involvement in mosquito taste. These chemosensory proteins represent targets for the disruption of harmful biting behavior and disease transmission by mosquito vectors.
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Affiliation(s)
- Jackson T Sparks
- Biology Department, High Point University, High Point, NC, United States
| | - Gina Botsko
- Biology Department, High Point University, High Point, NC, United States
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, United States
| | - Linda M Boland
- Department of Biology, University of Richmond, Richmond, VA, United States
| | - Shriraj S Patel
- Department of Biology, University of Richmond, Richmond, VA, United States
| | - Joseph C Dickens
- Department of Biology, University of Richmond, Richmond, VA, United States
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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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Rivera-Pagán AF, Méndez-González MP, Rivera-Aponte DE, Malpica-Nieves CJ, Melnik-Martínez KV, Zayas-Santiago A, Maldonado-Martínez G, Shuba YM, Skatchkov SN, Eaton MJ. A-Kinase-Anchoring Protein (AKAP150) is expressed in Astrocytes and Upregulated in Response to Ischemia. Neuroscience 2018; 384:54-63. [PMID: 29800717 DOI: 10.1016/j.neuroscience.2018.05.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/11/2018] [Accepted: 05/14/2018] [Indexed: 10/16/2022]
Abstract
A-kinase-anchoring proteins, AKAPs, are scaffolding proteins that associate with kinases and phosphatases, and direct them to a specific submembrane site to coordinate signaling events. AKAP150, a rodent ortholog of human AKAP79, has been extensively studied in neurons, but very little is known about the localization and function of AKAP150 in astrocytes, the major cell type in brain. Thus, in this study, we assessed the localization of AKAP150 in astrocytes and elucidated its role during physiological and ischemic conditions. Herein, we demonstrate that AKAP150 is localized in astrocytes and is up-regulated during ischemia both in vitro and in vivo. Knock-down of AKAP150 by RNAi depolarizes the astrocytic membrane potential and substantially reduces by 80% the ability of astrocytes to take up extracellular potassium during ischemic conditions. Therefore, upregulation of AKAP150 during ischemia preserves potassium conductance and the associated hyperpolarized membrane potential of astrocytes; properties of astrocytes needed to maintain extracellular brain homeostasis. Taken together, these data suggest that AKAP150 may play a pivotal role in the neuroprotective mechanism of astrocytes during pathological conditions.
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Affiliation(s)
- Aixa F Rivera-Pagán
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States
| | - Miguel P Méndez-González
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States; University of Puerto Rico, Natural Sciences Department, Aguadilla, PR, United States
| | - David E Rivera-Aponte
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States
| | | | | | - Astrid Zayas-Santiago
- Department of Pathology and Laboratory Medicine, Universidad Central del Caribe, Bayamón, PR, United States
| | | | - Yaroslav M Shuba
- Bogomoletz Institute of Physiology and International Center of Molecular Physiology of the National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Serguei N Skatchkov
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States; Department of Physiology, Universidad Central del Caribe, Bayamón, PR, United States.
| | - Misty J Eaton
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States.
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Larson VA, Mironova Y, Vanderpool KG, Waisman A, Rash JE, Agarwal A, Bergles DE. Oligodendrocytes control potassium accumulation in white matter and seizure susceptibility. eLife 2018; 7:34829. [PMID: 29596047 PMCID: PMC5903864 DOI: 10.7554/elife.34829] [Citation(s) in RCA: 95] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 03/28/2018] [Indexed: 12/19/2022] Open
Abstract
The inwardly rectifying K+ channel Kir4.1 is broadly expressed by CNS glia and deficits in Kir4.1 lead to seizures and myelin vacuolization. However, the role of oligodendrocyte Kir4.1 channels in controlling myelination and K+ clearance in white matter has not been defined. Here, we show that selective deletion of Kir4.1 from oligodendrocyte progenitors (OPCs) or mature oligodendrocytes did not impair their development or disrupt the structure of myelin. However, mice lacking oligodendrocyte Kir4.1 channels exhibited profound functional impairments, including slower clearance of extracellular K+ and delayed recovery of axons from repetitive stimulation in white matter, as well as spontaneous seizures, a lower seizure threshold, and activity-dependent motor deficits. These results indicate that Kir4.1 channels in oligodendrocytes play an important role in extracellular K+ homeostasis in white matter, and that selective loss of this channel from oligodendrocytes is sufficient to impair K+ clearance and promote seizures.
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Affiliation(s)
- Valerie A Larson
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Yevgeniya Mironova
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Kimberly G Vanderpool
- Department of Biomedical Sciences, Colorado State University, Fort Collins, United States
| | - Ari Waisman
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - John E Rash
- Department of Biomedical Sciences, Colorado State University, Fort Collins, United States
| | - Amit Agarwal
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Dwight E Bergles
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
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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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MeCP2 Deficiency Leads to Loss of Glial Kir4.1. eNeuro 2018; 5:eN-NWR-0194-17. [PMID: 29464197 PMCID: PMC5818552 DOI: 10.1523/eneuro.0194-17.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 02/01/2018] [Accepted: 02/08/2018] [Indexed: 01/05/2023] Open
Abstract
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder usually caused by mutations in methyl-CpG-binding protein 2 (MeCP2). RTT is typified by apparently normal development until 6-18 mo of age, when motor and communicative skills regress and hand stereotypies, autonomic symptoms, and seizures present. Restoration of MeCP2 function selectively to astrocytes reversed several deficits in a murine model of RTT, but the mechanism of this rescue is unknown. Astrocytes carry out many essential functions required for normal brain functioning, including extracellular K+ buffering. Kir4.1, an inwardly rectifying K+ channel, is largely responsible for the channel-mediated K+ regulation by astrocytes. Loss-of-function mutations in Kir4.1 in human patients result in a severe neurodevelopmental disorder termed EAST or SESAME syndrome. Here, we evaluated astrocytic Kir4.1 expression in a murine model of Rett syndrome. We demonstrate by chromatin immunoprecipitation analysis that Kir4.1 is a direct molecular target of MeCP2. Astrocytes from Mecp2-deficient mice express significantly less Kir4.1 mRNA and protein, which translates into a >50% deficiency in Ba2+-sensitive Kir4.1-mediated currents, and impaired extracellular potassium dynamics. By examining astrocytes in isolation, we demonstrate that loss of Kir4.1 is cell autonomous. Assessment through postnatal development revealed that Kir4.1 expression in Mecp2-deficient animals never reaches adult, wild-type levels, consistent with a neurodevelopmental disorder. These are the first data implicating a direct MeCP2 molecular target in astrocytes and provide novel mechanistic insight explaining a potential mechanism by which astrocytic dysfunction may contribute to RTT.
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Milton M, Smith PD. It's All about Timing: The Involvement of Kir4.1 Channel Regulation in Acute Ischemic Stroke Pathology. Front Cell Neurosci 2018; 12:36. [PMID: 29503609 PMCID: PMC5820340 DOI: 10.3389/fncel.2018.00036] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 01/30/2018] [Indexed: 01/28/2023] Open
Abstract
An acute ischemic stroke is characterized by the presence of a blood clot that limits blood flow to the brain resulting in subsequent neuronal loss. Acute stroke threatens neuronal survival, which relies heavily upon proper function of astrocytes. Neurons are more susceptible to cell death when an astrocyte is unable to carry out its normal functions in supporting the neuron in the area affected by the stroke (Rossi et al., 2007; Takano et al., 2009). For example, under normal conditions, astrocytes initially swell in response to changes in extracellular osmotic pressure and then reduce their regulatory volume in response to volume-activated potassium (K+) and chloride channels (Vella et al., 2015). This astroglial swelling may be overwhelmed, under ischemic conditions, due to the increased levels of glutamate and extracellular K+ (Lai et al., 2014; Vella et al., 2015). The increase in extracellular K+ contributes to neuronal damage and loss through the initiation of harmful secondary cascades (Nwaobi et al., 2016). Reducing the amount of extracellular K+ could, in theory, limit or prevent neuronal damage and loss resulting in an improved prognosis for individuals following ischemic stroke. Kir4.1, an inwardly rectifying K+ channel, has demonstrated an ability to regulate the rapid reuptake of this ion to return the cell to basal levels allowing it to fire again in rapid transmission (Sibille et al., 2015). Despite growing interest in this area, the underlying mechanism suggesting that neuroprotection could occur through modification of the Kir4.1 channel's activity has yet to be described. The purpose of this review is to examine the current literature and propose potential underlying mechanisms involving Kir4.1, specially the mammalian target of rapamycin (mTOR) and/or autophagic pathways, in the pathogenesis of ischemic stroke. The hope is that this review will instigate further investigation of Kir4.1 as a modulator of stroke pathology.
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Affiliation(s)
| | - Patrice D. Smith
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
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43
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Astroglial Kir4.1 in the lateral habenula drives neuronal bursts in depression. Nature 2018; 554:323-327. [DOI: 10.1038/nature25752] [Citation(s) in RCA: 267] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 01/12/2018] [Indexed: 02/08/2023]
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Wu W, Yao H, Zhao HW, Wang J, Haddad GG. Down-regulation of Inwardly Rectifying K + Currents in Astrocytes Derived from Patients with Monge's Disease. Neuroscience 2018; 374:70-79. [PMID: 29355592 DOI: 10.1016/j.neuroscience.2018.01.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 01/04/2018] [Indexed: 12/25/2022]
Abstract
Chronic mountain sickness (CMS) or Monge's disease is a disease in highlanders. These patients have a variety of neurologic symptoms such as migraine, mental fatigue, confusion, dizziness, loss of appetite, memory loss and neuronal degeneration. The cellular and molecular mechanisms underlying CMS neuropathology is not understood. In the previous study, we demonstrated that neurons derived from CMS patients' fibroblasts have a decreased expression and altered gating properties of voltage-gated sodium channel. In this study, we further characterize the electrophysiological properties of iPSC-derived astrocytes from CMS patients. We found that the current densities of the inwardly rectifying potassium (Kir) channels in CMS astrocytes (-5.7 ± 2.2 pA/pF at -140 mV) were significantly decreased as compared to non-CMS (-28.4 ± 3.4 pA/pF at -140 mV) and sea level subjects (-28.3 ± 5.3 pA/pF at -140 mV). We further demonstrated that the reduced Kir current densities in CMS astrocytes were caused by their decreased protein expression of Kir4.1 and Kir2.3 channels, while single channel properties (i.e., Po, conductance) of Kir channel in CMS astrocytes were not altered. In addition, we found no significant differences of outward potassium currents between CMS and non-CMS astrocytes. As compared to non-CMS and sea level subjects, the K+ uptake ability in CMS astrocytes was significantly decreased. Taken together, our results suggest that down-regulation of Kir channels and the resulting decreased K+ uptake ability in astrocytes could be one of the major molecular mechanisms underlying the neurologic manifestations in CMS patients.
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Affiliation(s)
- Wei Wu
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States
| | - Hang Yao
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States
| | - Helen W Zhao
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States
| | - Juan Wang
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States
| | - Gabriel G Haddad
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States; Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, United States; Rady Children's Hospital-San Diego, San Diego, CA 92123, United States.
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45
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Chen R, Swale DR. Inwardly Rectifying Potassium (Kir) Channels Represent a Critical Ion Conductance Pathway in the Nervous Systems of Insects. Sci Rep 2018; 8:1617. [PMID: 29371678 PMCID: PMC5785497 DOI: 10.1038/s41598-018-20005-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 01/10/2018] [Indexed: 12/13/2022] Open
Abstract
A complete understanding of the physiological pathways critical for proper function of the insect nervous system is still lacking. The recent development of potent and selective small-molecule modulators of insect inward rectifier potassium (Kir) channels has enabled the interrogation of the physiological role and toxicological potential of Kir channels within various insect tissue systems. Therefore, we aimed to highlight the physiological and functional role of neural Kir channels the central nervous system, muscular system, and neuromuscular system through pharmacological and genetic manipulations. Our data provide significant evidence that Drosophila neural systems rely on the inward conductance of K+ ions for proper function since pharmacological inhibition and genetic ablation of neural Kir channels yielded dramatic alterations of the CNS spike discharge frequency and broadening and reduced amplitude of the evoked EPSP at the neuromuscular junction. Based on these data, we conclude that neural Kir channels in insects (1) are critical for proper function of the insect nervous system, (2) represents an unexplored physiological pathway that is likely to shape the understanding of neuronal signaling, maintenance of membrane potentials, and maintenance of the ionic balance of insects, and (3) are capable of inducing acute toxicity to insects through neurological poisoning.
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Affiliation(s)
- Rui Chen
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, 70803, USA
| | - Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, 70803, USA.
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Price BR, Norris CM, Sompol P, Wilcock DM. An emerging role of astrocytes in vascular contributions to cognitive impairment and dementia. J Neurochem 2018; 144:644-650. [PMID: 29222909 DOI: 10.1111/jnc.14273] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 10/30/2017] [Accepted: 11/23/2017] [Indexed: 01/15/2023]
Abstract
Vascular contributions to cognitive impairment and dementia (VCID) is understood to be the second most common cause of dementia after Alzheimer's disease, and is also a frequent comorbidity with Alzheimer's disease. While VCID is widely acknowledged as a key contributor to dementia, the mechanistic underpinnings of VCID remain poorly understood. In this review, we address the potential role of astrocytes in the pathophysiology of VCID. The vast majority of the blood vessels in the brain are surrounded by astrocytic end-feet. Given that astrocytes make up a significant proportion of the cells in the brain, and that astrocytes are usually passively connected to one another through gap junctions, we hypothesize that astrocytes are key mediators of cognitive impairment because of cerebrovascular disease. In this review, we discuss the existing body of literature regarding the role of astrocytes at the vasculature in the brain, and the known consequences of their dysfunction, as well as our hypotheses regarding the role astrocytes play in VCID. This article is part of the Special Issue "Vascular Dementia".
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Affiliation(s)
- Brittani R Price
- Department of Physiology, Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
| | - Christopher M Norris
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Pradoldej Sompol
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Donna M Wilcock
- Department of Physiology, Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
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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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González-Castillo C, Muñoz-Ortiz E, Guzmán-Brambila C, Rojas-Mayorquín AE, Beltran-Parrazal L, Ortuño-Sahagún D, Morgado-Valle C. Differential Expression of Ion Channels in Adult and Neonatal Rat Ventral Respiratory Column. J Mol Neurosci 2017; 64:51-61. [DOI: 10.1007/s12031-017-1001-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 11/10/2017] [Indexed: 12/14/2022]
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Aréchiga-Figueroa IA, Marmolejo-Murillo LG, Cui M, Delgado-Ramírez M, van der Heyden MAG, Sánchez-Chapula JA, Rodríguez-Menchaca AA. High-potency block of Kir4.1 channels by pentamidine: Molecular basis. Eur J Pharmacol 2017; 815:56-63. [PMID: 28993158 DOI: 10.1016/j.ejphar.2017.10.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Revised: 10/03/2017] [Accepted: 10/05/2017] [Indexed: 02/06/2023]
Abstract
Inward rectifier potassium (Kir) channels are expressed in almost all mammalian tissues and contribute to a wide range of physiological processes. Kir4.1 channel expression is found in the brain, inner ear, eye, and kidney. Loss-of-function mutations in the pore-forming Kir4.1 subunit cause an autosomal recessive disorder characterized by epilepsy, ataxia, sensorineural deafness and tubulopathy (SeSAME/EST syndrome). Despite its importance in physiological and pathological conditions, pharmacological research of Kir4.1 is limited. Here, we characterized the effect of pentamidine on Kir4.1 channels using electrophysiology, mutagenesis and computational methods. Pentamidine potently inhibited Kir4.1 channels when applied to the cytoplasmic side under inside-out patch clamp configuration (IC50 = 97nM). The block was voltage dependent. Molecular modeling predicted the binding of pentamidine to the transmembrane pore region of Kir4.1 at aminoacids T127, T128 and E158. Mutation of each of these residues reduced the potency of pentamidine to block Kir4.1 channels. A pentamidine analog (PA-6) inhibited Kir4.1 with similar potency (IC50 = 132nM). Overall, this study shows that pentamidine blocks Kir4.1 channels interacting with threonine and glutamate residues in the transmembrane pore region. These results can be useful to design novel compounds with major potency and specificity over Kir4.1 channels.
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Affiliation(s)
- Iván A Aréchiga-Figueroa
- CONACYT, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, SLP, Mexico
| | | | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Mayra Delgado-Ramírez
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, SLP, Mexico
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands
| | - José A Sánchez-Chapula
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Col, Mexico
| | - Aldo A Rodríguez-Menchaca
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, SLP, Mexico.
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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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