1
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Lazar M. [François Gros' laboratory at the Collège de France]. C R Biol 2024; 346:65-68. [PMID: 38127094 DOI: 10.5802/crbiol.135] [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: 09/29/2023] [Accepted: 10/11/2023] [Indexed: 12/23/2023]
Abstract
I was recruited by François Gros as a PhD student in his laboratory at the Institut de Biologie Physico-Chimique in 1965, and continued to work with him after I graduated. In 1973, when he was appointed Professor of Cellular Biochemistry at the Collège de France, François decided to set up a team working on neuronal differentiation. He asked me to take part in this new scientific adventure. Here I'd like to talk about the members of his laboratory and some of their scientific work, in particular that on the cytoskeleton of neurons.
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2
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Hiyama TY. Brain sodium sensing for regulation of thirst, salt appetite, and blood pressure. Physiol Rep 2024; 12:e15970. [PMID: 38479999 PMCID: PMC10937250 DOI: 10.14814/phy2.15970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 02/29/2024] [Indexed: 03/17/2024] Open
Abstract
The brain possesses intricate mechanisms for monitoring sodium (Na) levels in body fluids. During prolonged dehydration, the brain detects variations in body fluids and produces sensations of thirst and aversions to salty tastes. At the core of these processes Nax , the brain's Na sensor, exists. Specialized neural nuclei, namely the subfornical organ (SFO) and organum vasculosum of the lamina terminalis (OVLT), which lack the blood-brain barrier, play pivotal roles. Within the glia enveloping the neurons in these regions, Nax collaborates with Na+ /K+ -ATPase and glycolytic enzymes to drive glycolysis in response to elevated Na levels. Lactate released from these glia cells activates nearby inhibitory neurons. The SFO hosts distinct types of angiotensin II-sensitive neurons encoding thirst and salt appetite, respectively. During dehydration, Nax -activated inhibitory neurons suppress salt-appetite neuron's activity, whereas salt deficiency reduces thirst neuron's activity through cholecystokinin. Prolonged dehydration increases the Na sensitivity of Nax via increased endothelin expression in the SFO. So far, patients with essential hypernatremia have been reported to lose thirst and antidiuretic hormone release due to Nax -targeting autoantibodies. Inflammation in the SFO underlies the symptoms. Furthermore, Nax activation in the OVLT, driven by Na retention, stimulates the sympathetic nervous system via acid-sensing ion channels, contributing to a blood pressure elevation.
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Affiliation(s)
- Takeshi Y. Hiyama
- Department of Integrative PhysiologyTottori University Graduate School and Faculty of MedicineYonagoJapan
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3
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Tsui CT, Lal P, Fox KVR, Churchward MA, Todd KG. The effects of electrical stimulation on glial cell behaviour. BMC Biomed Eng 2022; 4:7. [PMID: 36057631 PMCID: PMC9441051 DOI: 10.1186/s42490-022-00064-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 08/09/2022] [Indexed: 12/05/2022] Open
Abstract
Neural interface devices interact with the central nervous system (CNS) to substitute for some sort of functional deficit and improve quality of life for persons with disabilities. Design of safe, biocompatible neural interface devices is a fast-emerging field of neuroscience research. Development of invasive implant materials designed to directly interface with brain or spinal cord tissue has focussed on mitigation of glial scar reactivity toward the implant itself, but little exists in the literature that directly documents the effects of electrical stimulation on glial cells. In this review, a survey of studies documenting such effects has been compiled and categorized based on the various types of stimulation paradigms used and their observed effects on glia. A hybrid neuroscience cell biology-engineering perspective is offered to highlight considerations that must be made in both disciplines in the development of a safe implant. To advance knowledge on how electrical stimulation affects glia, we also suggest experiments elucidating electrochemical reactions that may occur as a result of electrical stimulation and how such reactions may affect glia. Designing a biocompatible stimulation paradigm should be a forefront consideration in the development of a device with improved safety and longevity.
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Affiliation(s)
- Christopher T Tsui
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Biomedical Engineering, University of Alberta, Edmonton, AB, T6G 2V2, Canada
| | - Preet Lal
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Katelyn V R Fox
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Matthew A Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Biological and Environmental Sciences, Concordia University of Edmonton, Edmonton, AB, T5B 4E4, Canada
| | - Kathryn G Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada. .,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada. .,Department of Biomedical Engineering, University of Alberta, Edmonton, AB, T6G 2V2, Canada.
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4
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Dolivo D, Rodrigues A, Sun L, Li Y, Hou C, Galiano R, Hong SJ, Mustoe T. The Na x (SCN7A) channel: an atypical regulator of tissue homeostasis and disease. Cell Mol Life Sci 2021; 78:5469-5488. [PMID: 34100980 PMCID: PMC11072345 DOI: 10.1007/s00018-021-03854-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/15/2021] [Accepted: 05/08/2021] [Indexed: 12/15/2022]
Abstract
Within an articulately characterized family of ion channels, the voltage-gated sodium channels, exists a black sheep, SCN7A (Nax). Nax, in contrast to members of its molecular family, has lost its voltage-gated character and instead rapidly evolved a new function as a concentration-dependent sensor of extracellular sodium ions and subsequent signal transducer. As it deviates fundamentally in function from the rest of its family, and since the bulk of the impressive body of literature elucidating the pathology and biochemistry of voltage-gated sodium channels has been performed in nervous tissue, reports of Nax expression and function have been sparse. Here, we investigate available reports surrounding expression and potential roles for Nax activity outside of nervous tissue. With these studies as justification, we propose that Nax likely acts as an early sensor that detects loss of tissue homeostasis through the pathological accumulation of extracellular sodium and/or through endothelin signaling. Sensation of homeostatic aberration via Nax then proceeds to induce pathological tissue phenotypes via promotion of pro-inflammatory and pro-fibrotic responses, induced through direct regulation of gene expression or through the generation of secondary signaling molecules, such as lactate, that can operate in an autocrine or paracrine fashion. We hope that our synthesis of much of the literature investigating this understudied protein will inspire more research into Nax not simply as a biochemical oddity, but also as a potential pathophysiological regulator and therapeutic target.
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Affiliation(s)
- David Dolivo
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA
| | - Adrian Rodrigues
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA
| | - Lauren Sun
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA
| | - Yingxing Li
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA
| | - Chun Hou
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA
- Department of Plastic and Cosmetic Surgery, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Robert Galiano
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA
| | - Seok Jong Hong
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA.
- , 300 E. Superior St., Chicago, IL, 60611, USA.
| | - Thomas Mustoe
- Department of Surgery, Northwestern University-Feinberg School of Medicine, Chicago, USA.
- , 737 N. Michigan Ave., Chicago, IL, 60611, USA.
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5
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Tedoldi A, Argent L, Montgomery JM. The role of the tripartite synapse in the heart: how glial cells may contribute to the physiology and pathophysiology of the intracardiac nervous system. Am J Physiol Cell Physiol 2020; 320:C1-C14. [PMID: 33085497 DOI: 10.1152/ajpcell.00363.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
One of the major roles of the intracardiac nervous system (ICNS) is to act as the final site of signal integration for efferent information destined for the myocardium to enable local control of heart rate and rhythm. Multiple subtypes of neurons exist in the ICNS where they are organized into clusters termed ganglionated plexi (GP). The majority of cells in the ICNS are actually glial cells; however, despite this, ICNS glial cells have received little attention to date. In the central nervous system, where glial cell function has been widely studied, glia are no longer viewed simply as supportive cells but rather have been shown to play an active role in modulating neuronal excitability and synaptic plasticity. Pioneering studies have demonstrated that in addition to glia within the brain stem, glial cells within multiple autonomic ganglia in the peripheral nervous system, including the ICNS, can also act to modulate cardiovascular function. Clinically, patients with atrial fibrillation (AF) undergoing catheter ablation show high plasma levels of S100B, a protein produced by cardiac glial cells, correlated with decreased AF recurrence. Interestingly, S100B also alters GP neuron excitability and neurite outgrowth in the ICNS. These studies highlight the importance of understanding how glial cells can affect the heart by modulating GP neuron activity or synaptic inputs. Here, we review studies investigating glia both in the central and peripheral nervous systems to discuss the potential role of glia in controlling cardiac function in health and disease, paying particular attention to the glial cells of the ICNS.
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Affiliation(s)
- Angelo Tedoldi
- Department of Physiology, University of Auckland, Auckland, New Zealand.,Manaaki Mānawa Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - Liam Argent
- Department of Physiology, University of Auckland, Auckland, New Zealand.,Manaaki Mānawa Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - Johanna M Montgomery
- Department of Physiology, University of Auckland, Auckland, New Zealand.,Manaaki Mānawa Centre for Heart Research, University of Auckland, Auckland, New Zealand
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6
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Verkhratsky A, Semyanov A, Zorec R. Physiology of Astroglial Excitability. FUNCTION (OXFORD, ENGLAND) 2020; 1:zqaa016. [PMID: 35330636 PMCID: PMC8788756 DOI: 10.1093/function/zqaa016] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 08/29/2020] [Accepted: 09/03/2020] [Indexed: 01/06/2023]
Abstract
Classic physiology divides all neural cells into excitable neurons and nonexcitable neuroglia. Neuroglial cells, chiefly responsible for homeostasis and defense of the nervous tissue, coordinate their complex homeostatic responses with neuronal activity. This coordination reflects a specific form of glial excitability mediated by complex changes in intracellular concentration of ions and second messengers organized in both space and time. Astrocytes are equipped with multiple molecular cascades, which are central for regulating homeostasis of neurotransmitters, ionostasis, synaptic connectivity, and metabolic support of the central nervous system. Astrocytes are further provisioned with multiple receptors for neurotransmitters and neurohormones, which upon activation trigger intracellular signals mediated by Ca2+, Na+, and cyclic AMP. Calcium signals have distinct organization and underlying mechanisms in different astrocytic compartments thus allowing complex spatiotemporal signaling. Signals mediated by fluctuations in cytosolic Na+ are instrumental for coordination of Na+ dependent astrocytic transporters with tissue state and homeostatic demands. Astroglial ionic excitability may also involve K+, H+, and Cl-. The cyclic AMP signalling system is, in comparison to ions, much slower in targeting astroglial effector mechanisms. This evidence review summarizes the concept of astroglial intracellular excitability.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK,Achucarro Center for Neuroscience, Ikerbasque, 48011 Bilbao, Spain,Address correspondence to A.V. (e-mail: )
| | - Alexey Semyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia,Faculty of Biology, Moscow State University, Moscow, Russia,Sechenov First Moscow State Medical University, Moscow, Russia
| | - Robert Zorec
- Celica Biomedical, Ljubljana 1000, Slovenia,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana 1000, Slovenia
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7
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Bogdanovic E, Potet F, Marszalec W, Iyer H, Galiano R, Hong SJ, Leung KP, Wasserstrom JA, George AL, Mustoe TA. The sodium channel Na X : Possible player in excitation-contraction coupling. IUBMB Life 2020; 72:601-606. [PMID: 32027092 DOI: 10.1002/iub.2247] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 01/18/2020] [Indexed: 11/10/2022]
Abstract
The sodium channel NaX (encoded by the SCN7A gene) was originally identified in the heart and skeletal muscle and is structurally similar to the other voltage-gated sodium channels but does not appear to be voltage gated. Although NaX is expressed at high levels in cardiac and skeletal muscle, little information exists on the function of NaX in these tissues. Transcriptional profiling of ion channels in the heart in a subset of patients with Brugada syndrome revealed an inverse relationship between the expression of NaX and NaV 1.5 suggesting that, in cardiac myocytes, the expression of these channels may be linked. We propose that NaX plays a role in excitation-contraction coupling based on our experimental observations. Here we show that in cardiac myocytes, NaX is expressed in a striated pattern on the sarcolemma in regions corresponding to the sarcomeric M-line. Knocking down NaX expression decreased NaV 1.5 mRNA and protein and reduced the inward sodium current (INa+ ) following cell depolarization. When the expression of NaV 1.5 was knocked down, ~85% of the INa+ was reduced consistent with the observations that NaV 1.5 is the main voltage-gated sodium channel in cardiac muscle and that NaX likely does not directly participate in mediating the INa+ following depolarization. Silencing NaV 1.5 expression led to significant upregulation of NaX mRNA. Similar to NaV 1.5, NaX protein levels were rapidly downregulated when the intracellular [Ca2+ ] was increased either by CaCl2 or caffeine. These data suggest that a relationship exists between NaX and NaV 1.5 and that NaX may play a role in excitation-contraction coupling.
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Affiliation(s)
- Elena Bogdanovic
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Franck Potet
- Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - William Marszalec
- Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Hari Iyer
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Robert Galiano
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Seok J Hong
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Kai P Leung
- Department of Dental and Maxillofacial Trauma, Institute of Surgical Research, Texas
| | | | - Alfred L George
- Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Thomas A Mustoe
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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8
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Xie Y, Ng NN, Safrina OS, Ramos CM, Ess KC, Schwartz PH, Smith MA, O'Dowd DK. Comparisons of dual isogenic human iPSC pairs identify functional alterations directly caused by an epilepsy associated SCN1A mutation. Neurobiol Dis 2019; 134:104627. [PMID: 31786370 DOI: 10.1016/j.nbd.2019.104627] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 09/05/2019] [Accepted: 09/26/2019] [Indexed: 02/06/2023] Open
Abstract
Over 1250 mutations in SCN1A, the Nav1.1 voltage-gated sodium channel gene, are associated with seizure disorders including GEFS+. To evaluate how a specific mutation, independent of genetic background, causes seizure activity we generated two pairs of isogenic human iPSC lines by CRISPR/Cas9 gene editing. One pair is a control line from an unaffected sibling, and the mutated control carrying the GEFS+ K1270T SCN1A mutation. The second pair is a GEFS+ patient line with the K1270T mutation, and the corrected patient line. By comparing the electrophysiological properties in inhibitory and excitatory iPSC-derived neurons from these pairs, we found the K1270T mutation causes cell type-specific alterations in sodium current density and evoked firing, resulting in hyperactive neural networks. We also identified differences associated with genetic background and interaction between the mutation and genetic background. Comparisons within and between dual pairs of isogenic iPSC-derived neuronal cultures provide a novel platform for evaluating cellular mechanisms underlying a disease phenotype and for developing patient-specific anti-seizure therapies.
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Affiliation(s)
- Yunyao Xie
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Nathan N Ng
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Olga S Safrina
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Carmen M Ramos
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Kevin C Ess
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Philip H Schwartz
- Children's Hospital of Orange County Research Institute, Orange, CA, United States of America
| | - Martin A Smith
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, United States of America
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America.
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9
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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10
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 928] [Impact Index Per Article: 154.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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11
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Hagiwara T, Yoshida S, Hidaka Y. Gene expression of the concentration-sensitive sodium channel is suppressed in lipopolysaccharide-induced acute lung injury in mice. Exp Lung Res 2017; 43:150-157. [PMID: 28557567 DOI: 10.1080/01902148.2017.1321064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE The concentration-sensitive sodium channel (NaC) is expressed in alveolar type II epithelial cells and pulmonary microvascular endothelial cells in mouse lungs. We recently reported that NaC contributes to amiloride-insensitive sodium transport in mouse lungs (Respiratory Physiology & Neurobiology, 2016). However, details regarding its physiological role in the lung remain unknown. To examine whether NaC is involved in alveolar fluid clearance during an acute lung injury (ALI), we analyzed the relationship between NaC gene expression in the lung and the development of pulmonary edema in lipopolysaccharide (LPS)-induced ALI mice. METHODS LPS-induced ALI mice were prepared by the intratracheal administration of LPS. Bronchoalveolar lavage (BAL) neutrophils and lung water content (LWCs) were used as a marker of ALI and pulmonary edema, respectively. NaC protein production in the lung was detected by immunoblotting and immunofluorescence. The gene expressions of NaC and the epithelial sodium channel (ENaC) of LPS-induced ALI mice were examined by quantitative RT-PCR over a time course of 14 days. RESULTS The BAL neutrophil count increased until day 2 after LPS administration and had nearly recovered by day 6. LWCs in LPS-induced mice gradually increased until day 8 and had recovered by day 14. The expression of the NaC protein in the lungs of LPS-induced mice dramatically decreased from day 2 to day 6, but recovered by day 8. The mRNA expression of NaC decreased in the lung, as well as those for α-, β-, and γ-ENaC during ALI. Thus, NaC expression is suppressed during the development stage of pulmonary edema and then recovers in the convalescent phase. CONCLUSION Our results suggest that suppression of the gene expression of NaC is involved in the development of pulmonary edema in ALI.
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Affiliation(s)
- Teruki Hagiwara
- a Department of Life Science, Faculty of Science and Engineering , Kindai University , Higashi-Osaka , Osaka , Japan
| | - Shigeru Yoshida
- a Department of Life Science, Faculty of Science and Engineering , Kindai University , Higashi-Osaka , Osaka , Japan
| | - Yuji Hidaka
- a Department of Life Science, Faculty of Science and Engineering , Kindai University , Higashi-Osaka , Osaka , Japan
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12
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Zostawa J, Adamczyk J, Sowa P, Adamczyk-Sowa M. The influence of sodium on pathophysiology of multiple sclerosis. Neurol Sci 2017; 38:389-398. [PMID: 28078565 PMCID: PMC5331099 DOI: 10.1007/s10072-016-2802-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Accepted: 12/19/2016] [Indexed: 01/06/2023]
Abstract
Multiple sclerosis (MS) is a chronic, inflammatory, autoimmune disease of the central nervous system, and is an important cause of disability in young adults. In genetically susceptible individuals, several environmental factors may play a partial role in the pathogenesis of MS. Some studies suggests that high-salt diet (>5 g/day) may contribute to the MS and other autoimmune disease development through the induction of pathogenic Th17 cells and pro-inflammatory cytokines in both humans and mice. However, the precise mechanisms of pro-inflammatory effect of sodium chloride intake are not yet explained. The purpose of this review was to discuss the present state of knowledge on the potential role of environmental and dietary factors, particularly sodium chloride on the development and course of MS.
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Affiliation(s)
- Jacek Zostawa
- Department of Neurology in Zabrze, Medical University of Silesia, ul. 3-go Maja 13-15, 41-800, Zabrze, Poland
| | - Jowita Adamczyk
- Department of Neurology in Zabrze, Medical University of Silesia, ul. 3-go Maja 13-15, 41-800, Zabrze, Poland.
| | - Paweł Sowa
- Department of Otorhinolaryngology and Oncological Laryngology, Medical University of Silesia, ul. C. Skłodowskiej 10, 41-800, Zabrze, Poland
| | - Monika Adamczyk-Sowa
- Department of Neurology in Zabrze, Medical University of Silesia, ul. 3-go Maja 13-15, 41-800, Zabrze, Poland
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13
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Masocha W. Gene expression profile of sodium channel subunits in the anterior cingulate cortex during experimental paclitaxel-induced neuropathic pain in mice. PeerJ 2016; 4:e2702. [PMID: 27896032 PMCID: PMC5119229 DOI: 10.7717/peerj.2702] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 10/19/2016] [Indexed: 12/19/2022] Open
Abstract
Paclitaxel, a chemotherapeutic agent, causes neuropathic pain whose supraspinal pathophysiology is not fully understood. Dysregulation of sodium channel expression, studied mainly in the periphery and spinal cord level, contributes to the pathogenesis of neuropathic pain. We examined gene expression of sodium channel (Nav) subunits by real time polymerase chain reaction (PCR) in the anterior cingulate cortex (ACC) at day 7 post first administration of paclitaxel, when mice had developed paclitaxel-induced thermal hyperalgesia. The ACC was chosen because increased activity in the ACC has been observed during neuropathic pain. In the ACC of vehicle-treated animals the threshold cycle (Ct) values for Nav1.4, Nav1.5, Nav1.7, Nav1.8 and Nav1.9 were above 30 and/or not detectable in some samples. Thus, comparison in mRNA expression between untreated control, vehicle-treated and paclitaxel treated animals was done for Nav1.1, Nav1.2, Nav1.3, Nav1.6, Nax as well as Navβ1–Navβ4. There were no differences in the transcript levels of Nav1.1–Nav1.3, Nav1.6, Nax, Navβ1–Navβ3 between untreated and vehicle-treated mice, however, vehicle treatment increased Navβ4 expression. Paclitaxel treatment significantly increased the mRNA expression of Nav1.1, Nav1.2, Nav1.6 and Nax, but not Nav1.3, sodium channel alpha subunits compared to vehicle-treated animals. Treatment with paclitaxel significantly increased the expression of Navβ1 and Navβ3, but not Navβ2 and Navβ4, sodium channel beta subunits compared to vehicle-treated animals. These findings suggest that during paclitaxel-induced neuropathic pain (PINP) there is differential upregulation of sodium channels in the ACC, which might contribute to the increased neuronal activity observed in the area during neuropathic pain.
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Affiliation(s)
- Willias Masocha
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Kuwait University , Safat , Kuwait
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14
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Abstract
Ion channels no longer belong to students of the neuron. The development of the patch- clamp technique has triggered an avalanche of ion channel studies extending far beyond the initial investigations that tended to focus on neuronal excitability. Studies of basic cell properties, even in cells other than neurons, now routinely include the evaluation of a cell's electrophysiological features and have yielded a large and growing database con cerning the electrophysiological properties of inexcitable cells. These include such cells as fibroblasts, macrophages, glial cells, bone cells, epithelial cells, and even plant cells, to name but a few, and the electrophysiological properties of these cells are as wide ranging as their cell functions and tissue origins. The Neuroscientist 1:64-67, 1995
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Contribution of concentration-sensitive sodium channels to the absorption of alveolar fluid in mice. Respir Physiol Neurobiol 2016; 231:45-54. [PMID: 27259686 DOI: 10.1016/j.resp.2016.05.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 04/29/2016] [Accepted: 05/29/2016] [Indexed: 01/11/2023]
Abstract
The concentration-sensitive sodium channel (Nac) is activated by an increase in the extracellular sodium concentration. Although the expression of Nac in alveolar type II epithelial cells (AEC II) has been reported previously, the physiological role of Nac in the lung has not been established. We characterized Nac expression and examined amiloride-insensitive sodium transport mediated by Nac in mouse lung. Immunofluorescence studies revealed that Nac did not colocalize with either aquaporin 5 or cystic fibrosis transmembrane conductance regulator, but partially colocalized with the epithelial sodium channel γ-subunit. Immunoelectron microscopy studies showed that Nac localized at the basolateral membrane of pulmonary microvascular endothelial cells (PMVECs). Nac mRNA and protein were expressed in PMVECs isolated from the lungs of mice. Image analysis indicated that sodium influx into the alveolar wall was dependent on increases in extracellular sodium concentration. We conclude that Nac expressed in PMVECs and AEC II contributes to the reabsorption of sodium via an amiloride-insensitive pathway during alveolar fluid clearance.
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Matsumoto M, Hiyama TY, Kuboyama K, Suzuki R, Fujikawa A, Noda M. Channel properties of Nax expressed in neurons. PLoS One 2015; 10:e0126109. [PMID: 25961826 PMCID: PMC4427406 DOI: 10.1371/journal.pone.0126109] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 03/19/2015] [Indexed: 12/19/2022] Open
Abstract
Nax is a sodium-concentration ([Na+])-sensitive Na channel with a gating threshold of ~150 mM for extracellular [Na+] ([Na+]o) in vitro. We previously reported that Nax was preferentially expressed in the glial cells of sensory circumventricular organs including the subfornical organ, and was involved in [Na+] sensing for the control of salt-intake behavior. Although Nax was also suggested to be expressed in the neurons of some brain regions including the amygdala and cerebral cortex, the channel properties of Nax have not yet been adequately characterized in neurons. We herein verified that Nax was expressed in neurons in the lateral amygdala of mice using an antibody that was newly generated against mouse Nax. To investigate the channel properties of Nax expressed in neurons, we established an inducible cell line of Nax using the mouse neuroblastoma cell line, Neuro-2a, which is endogenously devoid of the expression of Nax. Functional analyses of this cell line revealed that the [Na+]-sensitivity of Nax in neuronal cells was similar to that expressed in glial cells. The cation selectivity sequence of the Nax channel in cations was revealed to be Na+ ≈ Li+ > Rb+ > Cs+ for the first time. Furthermore, we demonstrated that Nax bound to postsynaptic density protein 95 (PSD95) through its PSD95/Disc-large/ZO-1 (PDZ)-binding motif at the C-terminus in neurons. The interaction between Nax and PSD95 may be involved in promoting the surface expression of Nax channels because the depletion of endogenous PSD95 resulted in a decrease in Nax at the plasma membrane. These results indicated, for the first time, that Nax functions as a [Na+]-sensitive Na channel in neurons as well as in glial cells.
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Affiliation(s)
- Masahito Matsumoto
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
| | - Takeshi Y. Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
- School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan
| | - Kazuya Kuboyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
| | - Ryoko Suzuki
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
| | - Akihiro Fujikawa
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
| | - Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
- School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan
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Abstract
Sodium (Na) homeostasis is crucial for life, and the Na(+) level ([Na(+)]) of body fluids is strictly maintained at a range of 135-145 mM. However, the existence of a [Na(+)] sensor in the brain has long been controversial until Nax was identified as the molecular entity of the sensor. This review provides an overview of the [Na(+)]-sensing mechanism in the brain for the regulation of salt intake by summarizing a series of our studies on Nax. Nax is a Na channel expressed in the circumventricular organs (CVOs) in the brain. Among the CVOs, the subfornical organ (SFO) is the principal site for the control of salt intake behavior, where Nax populates the cellular processes of astrocytes and ependymal cells enveloping neurons. A local expression of endothelin-3 in the SFO modulates the [Na(+)] sensitivity for Nax activation, and thereby Nax is likely to be activated in the physiological [Na(+)] range. Nax stably interacts with Na(+)/K(+)-ATPase whereby Na(+) influx via Nax is coupled with activation of Na(+)/K(+)-ATPase associated with the consumption of ATP. The consequent activation of anaerobic glucose metabolism of Nax-positive glial cells upregulates the cellular release of lactate, and this lactate functions as a gliotransmitter to activate GABAergic neurons in the SFO. The GABAergic neurons presumably regulate hypothetic neurons involved in the control of salt intake behavior. Recently, a patient with essential hypernatremia caused by autoimmunity to Nax was found. In this case, the hypernatremia was considered to be induced by the complement-mediated cell death in the CVOs, where Nax specifically populates.
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Affiliation(s)
- Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology, 5-1 Higashiyama, Myodaiji-cho, Okazaki, 444-8787, Japan,
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Zhang B, Li M, Wang L, Li C, Lou Y, Liu J, Liu Y, Wang Z, Wen S. The association between the polymorphisms in a sodium channel gene SCN7A and essential hypertension: a case-control study in the Northern Han Chinese. Ann Hum Genet 2014; 79:28-36. [PMID: 25393565 DOI: 10.1111/ahg.12085] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Accepted: 09/03/2014] [Indexed: 11/29/2022]
Abstract
Nax , an α-subunit of the sodium channel encoded by the SCN7A gene, has been deemed to be a sensor of the concentration of sodium in the brain and may be involved in salt intake behavior. We inferred that Nax /SCN7A may participate in the regulation of blood pressure and the pathogenesis of essential hypertension (EH). The present case-control study involving 615 hypertensives and 617 normotensives was performed to investigate the association between SCN7A polymorphisms and EH in the Northern Han Chinese population. The three common single nucleotide polymorphisms (SNPs) (rs3791251, rs6738031, rs7565062) in the exons of SCN7A were genotyped with the TaqMan assay. Significant association between SNP rs7565062 and EH was found under the addictive and dominant genetic models (P = 0.024, OR = 1.283, 95%CI [1.033-1.592]; P = 0.013, OR = 1.203, 95%CI [1.040-1.392]; respectively). The three SNPs were in close pair-wise linkage disequilibrium with each other and the haplotype analyses indicated that haplotype G-A-T was significantly associated with increased risk of EH (P = 0.023, OR = 1.290). In conclusion, our data showed that SNP rs7565062 of SCN7A was significantly associated with EH and the allele T of rs7565062 or the related haplotype G-A-T will be a genetic risk factor for EH in the Northern Han Chinese population.
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Affiliation(s)
- Bei Zhang
- Department of Hypertension Research, Beijing Anzhen Hospital, Capital Medical University and Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing, People's Republic of China
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Abstract
Na x, which is preferentially expressed in the glial cells of sensory circumventricular organs in the brain, is a sodium channel that is poorly homologous to voltage-gated sodium channels. We previously reported that Na x is a sodium concentration ([Na+])-sensitive, but not a voltage-sensitive channel that is critically involved in body-fluid homeostasis. Nax-knockout mice do not stop ingesting salt even when dehydrated and transiently develop hypernatremia. [Na+] in body fluids is strictly controlled at 135 to 145 mM in mammals. Although the set point must be within this range, Na x was shown to have a threshold value of ~150 mM for extracellular [Na+] ([Na+]o) for activation in vitro. Therefore, the [Na+]o dependency of Na x in vivo is presumably modified by an as yet unidentified mechanism. We recently demonstrated that the [Na+]o dependency of Na x in the subfornical organ was adjusted to the physiological range by endothelin-3. Pharmacological experiments revealed that endothelin receptor B signaling was involved in this modulation of Na x gating through protein kinase C and ERK1/2 activation. In addition, we identified a case of essential hypernatremia caused by autoimmunity to Na x. Occurrence of a ganglioneuroma composed of Schwann-like cells that robustly expressed Na x was likely to induce the autoimmune response in this patient. An intravenous injection of the immunoglobulin fraction of the patient’s serum, which contained anti-Na x antibodies, into mice reproduced the patient’s symptoms. This review provides an overview of the physiological functions of Na x by summarizing our recent studies.
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Affiliation(s)
- Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
- School of Life Science, The Graduate University for Advanced Studies, Okazaki, Japan
| | - Takeshi Y. Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
- School of Life Science, The Graduate University for Advanced Studies, Okazaki, Japan
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Unezaki S, Katano T, Hiyama TY, Tu NH, Yoshii S, Noda M, Ito S. Involvement of Naxsodium channel in peripheral nerve regeneration via lactate signaling. Eur J Neurosci 2013; 39:720-9. [DOI: 10.1111/ejn.12436] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Sawako Unezaki
- Department of Medical Chemistry; Kansai Medical University; 2-5-1 Shinmachi Hirakata 573-1010 Japan
| | - Tayo Katano
- Department of Medical Chemistry; Kansai Medical University; 2-5-1 Shinmachi Hirakata 573-1010 Japan
| | - Takeshi Y. Hiyama
- Division of Molecular Neurobiology; National Institute for Basic Biology; Okazaki 444-8787 Japan
- School of Life Science; The Graduate University for Advanced Studies; Okazaki 444-8787 Japan
| | - Nguyen H. Tu
- Department of Medical Chemistry; Kansai Medical University; 2-5-1 Shinmachi Hirakata 573-1010 Japan
| | - Satoru Yoshii
- Department of Rehabilitation; Osaka Red Cross Hospital; Osaka 543-8555 Japan
| | - Masaharu Noda
- Division of Molecular Neurobiology; National Institute for Basic Biology; Okazaki 444-8787 Japan
- School of Life Science; The Graduate University for Advanced Studies; Okazaki 444-8787 Japan
| | - Seiji Ito
- Department of Medical Chemistry; Kansai Medical University; 2-5-1 Shinmachi Hirakata 573-1010 Japan
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Xu J, Song D, Xue Z, Gu L, Hertz L, Peng L. Requirement of Glycogenolysis for Uptake of Increased Extracellular K+ in Astrocytes: Potential Implications for K+ Homeostasis and Glycogen Usage in Brain. Neurochem Res 2012; 38:472-85. [DOI: 10.1007/s11064-012-0938-3] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/09/2012] [Accepted: 11/20/2012] [Indexed: 11/29/2022]
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Nehmé B, Henry M, Mouginot D, Drolet G. The Expression Pattern of the Na(+) Sensor, Na(X) in the Hydromineral Homeostatic Network: A Comparative Study between the Rat and Mouse. Front Neuroanat 2012; 6:26. [PMID: 22833716 PMCID: PMC3400090 DOI: 10.3389/fnana.2012.00026] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/21/2012] [Indexed: 12/19/2022] Open
Abstract
The Scn7a gene encodes for the specific sodium channel NaX, which is considered a primary determinant of sodium sensing in the brain. Only partial data exist describing the NaX distribution pattern and the cell types that express NaX in both the rat and mouse brain. To generate a global view of the sodium detection mechanisms in the two rodent brains, we combined NaX immunofluorescence with fluorescent cell markers to map and identify the NaX-expressing cell populations throughout the network involved in hydromineral homeostasis. Here, we designed an anti-NaX antibody targeting the interdomain 2–3 region of the NaX channel’s α-subunit. In both the rat and mouse, NaX immunostaining was colocalized with vimentin positive cells in the median eminence and with magnocellular neurons immunopositive for neurophysin associated with oxytocin or vasopressin in both the supraoptic and paraventricular nuclei. NaX immunostaining was also detected in neurons of the area postrema. In addition to this common NaX expression pattern, several differences in NaX immunostaining for certain structures and cell types were found between the rat and mouse. NaX was present in both NeuN and vimentin positive cells in the subfornical organ and the vascular organ of the lamina terminalis of the rat whereas NaX was only colocalized with vimentin positive cells in the mouse circumventricular organs. In addition, NaX immunostaining was specifically observed in NeuN immunopositive cells in the median preoptic nucleus of the rat. Overall, this study characterized the NaX-expressing cell types in the network controlling hydromineral homeostasis of the rat and mouse. NaX expression pattern was clearly different in the nuclei of the lamina terminalis of the rat and mouse, indicating that the mechanisms involved in systemic and central Na+ sensing are specific to each rodent species.
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Affiliation(s)
- Benjamin Nehmé
- Axe Neurosciences du CRCHUQ (CHUL), Faculté de Médecine, Université Laval Québec, QC, Canada
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Qi FH, Zhou YL, Xu GY. Targeting voltage-gated sodium channels for treatment for chronic visceral pain. World J Gastroenterol 2011; 17:2357-64. [PMID: 21633634 PMCID: PMC3103787 DOI: 10.3748/wjg.v17.i19.2357] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 03/16/2011] [Accepted: 03/23/2011] [Indexed: 02/06/2023] Open
Abstract
Voltage-gated sodium channels (VGSCs) play a fundamental role in controlling cellular excitability, and their abnormal activity is related to several pathological processes, including cardiac arrhythmias, epilepsy, neurodegenerative diseases, spasticity and chronic pain. In particular, chronic visceral pain, the central symptom of functional gastrointestinal disorders such as irritable bowel syndrome, is a serious clinical problem that affects a high percentage of the world population. In spite of intense research efforts and after the dedicated decade of pain control and research, there are not many options to treat chronic pain conditions. However, there is a wealth of evidence emerging to give hope that a more refined approach may be achievable. By using electronic databases, available data on structural and functional properties of VGSCs in chronic pain, particularly functional gastrointestinal hypersensitivity, were reviewed. We summarize the involvement and molecular bases of action of VGSCs in the pathophysiology of several organic and functional gastrointestinal disorders. We also describe the efficacy of VGSC blockers in the treatment of these neurological diseases, and outline future developments that may extend the therapeutic use of compounds that target VGSCs. Overall, clinical and experimental data indicate that isoform-specific blockers of these channels or targeting of their modulators may provide effective and novel approaches for visceral pain therapy.
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25
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Adámek S, Vyskočil F. Potassium-selective microelectrode revealed difference in threshold potassium concentration for cortical spreading depression in female and male rat brain. Brain Res 2010; 1370:215-9. [PMID: 21075087 DOI: 10.1016/j.brainres.2010.11.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 11/02/2010] [Accepted: 11/05/2010] [Indexed: 12/19/2022]
Abstract
It has been found with potassium-selective microelectrodes that the threshold extracellular concentration of potassium [K(+)](e) for eliciting fast spreading depression from the site of administration 1.5mm away is 80% lower in the rat female cortex (8.0 ± 0.6 mM) than in the male cortex (14.4 ± 0.4mM). The rate of the first slow phase of [K(+)](e) rise before reaching the threshold and speed of SD propagation were similar for both sexes as well as the rise of the second active fast phase of the [K(+)](e) increase. Lower [K(+)](e) threshold in females can facilitate the rapid K(+) release from the nerve tissue cells that may cause a cerebrovascular vasodilatation and the attack of migraine pain.
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Affiliation(s)
- Svatopluk Adámek
- Third Surgical Department, First Faculty of Medicine, Charles University, Prague, Czech Republic
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26
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Gorter JA, Zurolo E, Iyer A, Fluiter K, Van Vliet EA, Baayen JC, Aronica E. Induction of sodium channel Nax (SCN7A) expression in rat and human hippocampus in temporal lobe epilepsy. Epilepsia 2010; 51:1791-800. [DOI: 10.1111/j.1528-1167.2010.02678.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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27
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Moignot B, Lemaire C, Quinchard S, Lapied B, Legros C. The discovery of a novel sodium channel in the cockroach Periplaneta americana: evidence for an early duplication of the para-like gene. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2009; 39:814-823. [PMID: 19800971 DOI: 10.1016/j.ibmb.2009.09.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 09/23/2009] [Accepted: 09/24/2009] [Indexed: 05/28/2023]
Abstract
Voltage-gated sodium channels (Na(v) channels) belong to a superfamily of ion channels which play an essential role in membrane excitability. Only one gene encoding Na(v) channels has been characterized so far in insects. Here, we have cloned one full-length cDNA encoding a conventional insect Na(v) channel (PaNa(v)1) and two full-length cDNAs encoding putative insect Na(v) channels (PaFPC1 and PaFPC2) in Periplaneta americana, a model insect for neurophysiological studies. The ORFs of PaFPC1 and PaFPC2 contained 4662 bp and encoded 1553 amino acid residues, and the ORF of PaNa(v)1 contained 6153 bp and encoded 2051 amino acid residues. PaFPC1 and PaFPC2 are two isoforms, which differ by eight single amino acid substitutions. PaFPC1 shares 37.5-55% protein identities with known insect Na(v) channels, while PaNa(v)1 shares 70-97.5% protein identities with these latter. Both PaFPC1 and PaFPC2 possess the molecular hallmarks of Na(v) channels except the motif involved in fast inactivation. Contrary to PaNa(v)1 transcripts which are expressed mainly in the central nervous system, those ones of PaFPC are also expressed in non-neuronal tissues (muscles, gut and mushroom-shaped accessory glands). A detailed phylogenetic analysis confirmed that PaNa(v)1 and PaFPC are evolutionarily closely related to insect Na(v) channel genes.
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Affiliation(s)
- Bénédicte Moignot
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM), UPRES EA 2647/USC INRA 2023, IFR 149 QUASAV, Université d'Angers, UFR Sciences, 2 boulevard Lavoisier, Angers cedex, France
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García-Villegas R, López-Alvarez LE, Arni S, Rosenbaum T, Morales MA. Identification and functional characterization of the promoter of the mouse sodium-activated sodium channel Na(x) gene (Scn7a). J Neurosci Res 2009; 87:2509-19. [PMID: 19326446 DOI: 10.1002/jnr.22069] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Na(x) is a sodium channel, thought to be a descendant of the voltage-gated sodium channel family. Nevertheless, Na(x) is not activated by voltage but rather by augmentation of extracellular sodium over 150 mM. In the brain, it is localized to the circumventricular organs, important regions for salt and water homeostasis in mammals, where it operates as a sodium-level sensor of body fluid. Na(x) channel is expressed in lung, uterus, and heart, and it is also found in trigeminal and dorsal root ganglia and in nonmyelinating Schwann cells, where its physiological role remains unclarified. Here we identified the promoter and transcription start sites of Na(x) sodium channel in dorsal root ganglia neurons from mouse. We report a characterization of the basal TATA-less promoter and the sequence requirements for promoter activity in Neuro 2A neuroblastoma cells and in dorsal root ganglia neurons, where basal promoter activity seems to require NGFI-C and Ebox DNA elements. Finally, we provide evidence that a repression mechanism that inhibits Na(x) expression may be present in certain tissues. These findings provide the basis with which to understand tissue-specific regulation of Na(x) sodium channel gene (Scn7a) expression.
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Affiliation(s)
- Refugio García-Villegas
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, D.F., México.
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Brackenbury WJ, Isom LL. Voltage-gated Na+ channels: potential for beta subunits as therapeutic targets. Expert Opin Ther Targets 2008; 12:1191-203. [PMID: 18694383 DOI: 10.1517/14728222.12.9.1191] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Voltage gated Na(+) channels (VGSCs) contain a pore-forming alpha subunit and one or more beta subunits. VGSCs are involved in a wide variety of pathophysiologies, including epilepsy, cardiac arrhythmia, multiple sclerosis, periodic paralysis, migraine, neuropathic and inflammatory pain, Huntington's disease and cancer. Increasing evidence implicates the beta subunits as key players in these disorders. OBJECTIVE To review the recent literature describing the multifunctional roles of VGSC beta subunits in the context of their role(s) in disease. METHODS An extensive review of the literature on beta subunits. RESULTS/CONCLUSION beta subunits are multifunctional. As components of VGSC complexes, beta subunits mediate signaling processes regulating electrical excitability, adhesion, migration, pathfinding and transcription. beta subunits may prove useful in disease diagnosis and therapy.
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Affiliation(s)
- William J Brackenbury
- University of Michigan, School of Medicine, Department of Pharmacology, 1150 W. Medical Center Dr, 1301 MSRB III, Ann Arbor, MI 48109-0632, USA
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Brackenbury WJ, Djamgoz MBA, Isom LL. An emerging role for voltage-gated Na+ channels in cellular migration: regulation of central nervous system development and potentiation of invasive cancers. Neuroscientist 2008; 14:571-83. [PMID: 18940784 DOI: 10.1177/1073858408320293] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Voltage-gated Na(+) channels (VGSCs) exist as macromolecular complexes containing a pore-forming alpha subunit and one or more beta subunits. The VGSC alpha subunit gene family consists of 10 members, which have distinct tissue-specific and developmental expression profiles. So far, four beta subunits (beta1-beta4) and one splice variant of beta1 (beta1A, also called beta1B) have been identified. VGSC beta subunits are multifunctional, serving as modulators of channel activity, regulators of channel cell surface expression, and as members of the immunoglobulin superfamily, cell adhesion molecules (CAMs). beta subunits are substrates of beta-amyloid precursor protein-cleaving enzyme (BACE1) and gamma-secretase, yielding intracellular domains (ICDs) that may further modulate cellular activity via transcription. Recent evidence shows that beta1 regulates migration and pathfinding in the developing postnatal CNS in vivo. The alpha and beta subunits, together with other components of the VGSC signaling complex, may have dynamic interactive roles depending on cell/tissue type, developmental stage, and pathophysiology. In addition to excitable cells like nerve and muscle, VGSC alpha and beta subunits are functionally expressed in cells that are traditionally considered nonexcitable, including glia, vascular endothelial cells, and cancer cells. In particular, the alpha subunits are up-regulated in line with metastatic potential and are proposed to enhance cellular migration and invasion. In contrast to the alpha subunits, beta1 is more highly expressed in weakly metastatic cancer cells, and evidence suggests that its expression enhances cellular adhesion. Thus, novel roles are emerging for VGSC alpha and beta subunits in regulating migration during normal postnatal development of the CNS as well as during cancer metastasis.
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Affiliation(s)
- William J Brackenbury
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109-0632, USA
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Voltage-gated Na+ channel II immunoreactivity is selectively up-regulated in hippocampal interneurons of seizure sensitive gerbils. Neurosci Lett 2008; 438:295-9. [PMID: 18487017 DOI: 10.1016/j.neulet.2008.04.079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Revised: 04/23/2008] [Accepted: 04/23/2008] [Indexed: 11/20/2022]
Abstract
In the present study, we investigated the distribution of voltage-gated Na(+) channels (VGSCs) in the normal and epileptic hippocampus of gerbils (a genetic epilepsy model) in order to confirm the relationship between VGSC and seizure activity in these animals. There was no difference of VGSC I immunoreactivity in the hippocampus between seizure-resistant (SR) and seizure sensitive (SS) gerbils. VGSC II immunoreactivity was rarely detected in the perikarya of principal neurons and interneurons in the SR gerbil hippocampus. However, in the SS gerbil hippocampus, VGSC II immunoreactivity was densely observed in the somata of interneurons located in the stratum radiatum and stratum lacunosum-moleculare. Double immunofluorescent study showed immunoreactivity for calretinin (approximately 80% in VGSC II-positive neurons) or calbindin D-28k (approximately 20% in VGSC II-positive neurons) in VGSC II-immunoreactive neurons. VGSC II-immunoreactive neurons did not show parvalbumin immunoreactivity. These findings suggest that seizure activity in SS gerbils may be related to the selective hyperactivation of interneurons in stratum lacunosum-moleculare via the up-regulation of VGSC II expression, which leads to the disinhibition of CA1 pyramidal cells.
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Shimizu H, Watanabe E, Hiyama TY, Nagakura A, Fujikawa A, Okado H, Yanagawa Y, Obata K, Noda M. Glial Nax Channels Control Lactate Signaling to Neurons for Brain [Na+] Sensing. Neuron 2007; 54:59-72. [PMID: 17408578 DOI: 10.1016/j.neuron.2007.03.014] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 02/08/2007] [Accepted: 03/19/2007] [Indexed: 11/25/2022]
Abstract
Sodium (Na) homeostasis is crucial for life, and Na levels in body fluids are constantly monitored in the brain. The subfornical organ (SFO) is the center of the sensing responsible for the control of salt-intake behavior, where Na(x) channels are expressed in specific glial cells as the Na-level sensor. Here, we show direct interaction between Na(x) channels and alpha subunits of Na(+)/K(+)-ATPase, which brings about Na-dependent activation of the metabolic state of the glial cells. The metabolic enhancement leading to extensive lactate production was observed in the SFO of wild-type mice, but not of the Na(x)-knockout mice. Furthermore, lactate, as well as Na, stimulated the activity of GABAergic neurons in the SFO. These results suggest that the information on a physiological increase of the Na level in body fluids sensed by Na(x) in glial cells is transmitted to neurons by lactate as a mediator to regulate neural activities of the SFO.
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Affiliation(s)
- Hidetada Shimizu
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Aichi 444-8787, Japan
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33
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Gorter JA, van Vliet EA, Aronica E, Breit T, Rauwerda H, Lopes da Silva FH, Wadman WJ. Potential new antiepileptogenic targets indicated by microarray analysis in a rat model for temporal lobe epilepsy. J Neurosci 2006; 26:11083-110. [PMID: 17065450 PMCID: PMC6674659 DOI: 10.1523/jneurosci.2766-06.2006] [Citation(s) in RCA: 248] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
To get insight into the mechanisms that may lead to progression of temporal lobe epilepsy, we investigated gene expression during epileptogenesis in the rat. RNA was obtained from three different brain regions [CA3, entorhinal cortex (EC), and cerebellum (CB)] at three different time points after electrically induced status epilepticus (SE): acute phase [group D (1 d)], latent period [group W (1 week)], and chronic epileptic period [group M (3-4 months)]. A group that was stimulated but that had not experienced SE and later epilepsy was also included (group nS). Gene expression analysis was performed using the Affymetrix Gene Chip System (RAE230A). We used GENMAPP and Gene Ontology to identify global biological trends in gene expression data. The immune response was the most prominent process changed during all three phases of epileptogenesis. Synaptic transmission was a downregulated process during the acute and latent phases. GABA receptor subunits involved in tonic inhibition were persistently downregulated. These changes were observed mostly in both CA3 and EC but not in CB. Rats that were stimulated but that did not develop spontaneous seizures later on had also some changes in gene expression, but this was not reflected in a significant change of a biological process. These data suggest that the targeting of specific genes that are involved in these biological processes may be a promising strategy to slow down or prevent the progression of epilepsy. Especially genes related to the immune response, such as complement factors, interleukins, and genes related to prostaglandin synthesis and coagulation pathway may be interesting targets.
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Affiliation(s)
- Jan A Gorter
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam, The Netherlands.
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Watanabe E, Hiyama TY, Shimizu H, Kodama R, Hayashi N, Miyata S, Yanagawa Y, Obata K, Noda M. Sodium-level-sensitive sodium channel Na(x) is expressed in glial laminate processes in the sensory circumventricular organs. Am J Physiol Regul Integr Comp Physiol 2005; 290:R568-76. [PMID: 16223844 DOI: 10.1152/ajpregu.00618.2005] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Na(x) is an atypical sodium channel that is assumed to be a descendant of the voltage-gated sodium channel family. Our recent studies on the Na(x)-gene-targeting mouse revealed that Na(x) channel is localized to the circumventricular organs (CVOs), the central loci for the salt and water homeostasis in mammals, where the Na(x) channel serves as a sodium-level sensor of the body fluid. To understand the cellular mechanism by which the information sensed by Na(x) channels is transferred to the activity of the organs, we dissected the subcellular localization of Na(x) in the present study. Double-immunostaining and immunoelectron microscopic analyses revealed that Na(x) is exclusively localized to perineuronal lamellate processes extended from ependymal cells and astrocytes in the organs. In addition, glial cells isolated from the subfornical organ, one of the CVOs, were sensitive to an increase in the extracellular sodium level, as analyzed by an ion-imaging method. These results suggest that glial cells bearing the Na(x) channel are the first to sense a physiological increase in the level of sodium in the body fluid, and they regulate the neural activity of the CVOs by enveloping neurons. Close communication between inexcitable glial cells and excitable neural cells thus appears to be the basis of the central control of the salt homeostasis.
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Affiliation(s)
- Eiji Watanabe
- Laboratory of Neurophysiology, National Institute for Basic Biology, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan
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35
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Grob M, Drolet G, Mouginot D. Specific Na+ sensors are functionally expressed in a neuronal population of the median preoptic nucleus of the rat. J Neurosci 2004; 24:3974-84. [PMID: 15102913 PMCID: PMC6729411 DOI: 10.1523/jneurosci.3720-03.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Whole-cell patch-clamp recordings were performed on acute brain slices of male rats to investigate the ability of the neurons of the median preoptic nucleus (MnPO) to detect fluctuation in extracellular osmolarity and sodium concentration ([Na+]out). Local application of hypotonic and hypertonic artificial CSF hyperpolarized and depolarized the neurons, respectively. Similar responses obtained under synaptic isolation (0.5 microM TTX) highlighted the intrinsic ability of the MnPO neurons to detect changes in extracellular osmolarity and [Na+]out. Manipulating extracellular osmolarity, [Na+]out, and [Cl-]out showed in an independent manner that the MnPO neurons responded to a change in [Na+]out exclusively. The specific Na+ response was voltage insensitive and depended on the driving force for Na+ ions, indicating that a sustained background Na+ permeability controlled the membrane potential of the MnPO neurons. This specific response was not reduced by Gd3+, amiloride, or benzamil, ruling out the participation of mechanosensitive cationic channels, specific epithelial Na+ channels, and Phe-Met-Arg-Phe-gated Na+ channels, respectively. Combination of in situ hybridization, using a riboprobe directed against the atypical Na+ channel (Na(X)), and immunohistochemistry, using an antibody against neuron-specific nuclei protein, revealed that a substantial population of MnPO neurons expressed the Na(X) channel, which was characterized recently as a concentration-sensitive Na+ channel. This study shows that a neuronal population of the MnPO acts as functional Na+ sensors and that the Na(X) channel might represent the molecular basis for the extracellular sodium level sensing in these neurons.
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Affiliation(s)
- Magali Grob
- Centre de Recherche en Neurosciences, Centre Hospitalier de l'Université Laval, Québec G1V 4G2, Canada
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Dave JR, Lin Y, Ved HS, Koenig ML, Clapp L, Hunter J, Tortella FC. RS-100642-198, a novel sodium channel blocker, provides differential neuroprotection against hypoxia/hypoglycemia, veratridine or glutamate-mediated neurotoxicity in primary cultures of rat cerebellar neurons. Neurotox Res 2004; 3:381-95. [PMID: 14715468 DOI: 10.1007/bf03033199] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The present study investigated the effects of RS-100642-198 (a novel sodium channel blocker), and two related compounds (mexiletine and QX-314), in in vitro models of neurotoxicity. Neurotoxicity was produced in primary cerebellar cultures using hypoxia/hypoglycemia (H/H), veratridine or glutamate where, in vehicle-treated neurons, 65%, 60% and 75% neuronal injury was measured, respectively. Dose-response neuroprotection experiments were carried out using concentrations ranging from 0.1-500 micro M. All the sodium channel blockers were neuroprotective against H/H-induced injury, with each exhibiting similar potency and efficacy. However, against veratridine-induced neuronal injury only RS-100642-198 and mexiletine were 100% protective, whereas QX-314 neuroprotection was limited (i.e. only 54%). In contrast, RS-100642-198 and mexiletine had no effect against glutamate-induced injury, whereas QX-314 produced a consistent, but very limited (i.e. 25%), neuroprotection. Measurements of intraneuronal calcium [Ca(2+)]i) mobilization revealed that glutamate caused immediate and sustained increases in [Ca(2+)]i which were not affected by RS-100642-198 or mexiletine. However, both drugs decreased the initial amplitude and attenuated the sustained rise in [Ca(2+)]i mobilization produced by veratridine or KCl depolarization. QX-314 produced similar effects on glutamate-, veratridine- or KCl-induced [Ca(2+)]i dynamics, effectively decreasing the amplitude and delaying the initial spike in [Ca(2+)]i, and attenuating the sustained increase in [Ca(2+)]i mobilization. By using different in vitro models of excitotoxicity, a heterogeneous profile of neuroprotective effects resulting from sodium channel blockade has been described for RS-100642-198 and related drugs, suggesting that selective blockade of neuronal sodium channels in pathological conditions may provide therapeutic neuroprotection against depolarization/excitotoxicity via inhibition of voltage-dependent Na(+) channels.
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Affiliation(s)
- J R Dave
- Division of Neurosciences, Walter Reed Army Inst of Research, Silver Spring, MD 20910, USA.
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Abstract
Voltage-dependent sodium channels (VDSC) are an important class of ion channels in excitable cells, where they are responsible for the generation and conduction of action potential. In addition, the release of neurotransmitters from nerve terminals is influenced by sodium channel activity. The function of VDSC is subject to modulation by various neurotoxins, such as scorpion toxins, which have long been used as tools in the investigation of neurotransmitter release. This opens an interesting perspective concerning modulation of neurotransmission via pharmacological manipulation of sodium channel properties, which can lead to a better understanding of their physiological and pathological roles. Here we briefly review the studies of neurotoxins acting on sodium channels, focusing primarily on the view of the mechanisms of neurotransmitter release.
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Affiliation(s)
- André Ricardo Massensini
- Núcleo de Neurociências, Departamento de Fisiologia e Biofisica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Carlos 6627, Belo Horizonte-MG, Brazil
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Schaller KL, Caldwell JH. Expression and distribution of voltage-gated sodium channels in the cerebellum. CEREBELLUM (LONDON, ENGLAND) 2003; 2:2-9. [PMID: 12882229 DOI: 10.1080/14734220309424] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In order to understand the effects of sodium channels on synaptic signaling and response in the cerebellum, it is essential to know for each class of neuron what sodium channel isoforms are present, and the properties and distribution of each. Sodium channels are heteromultimeric membrane proteins, consisting of a large alpha subunit that forms the pore, and one or more beta subunits. Ten genes encode an alpha subunit in mammals, and of these, four are expressed in the cerebellum: Nav1.1, Nav1.2, Nav1.3 and Nav1.6. Three genes encode beta subunits (Nabeta1-3), and all three are expressed in the cerebellum. However, Nav1.3 and Nabeta3 have been found only in the developing cerebellum. All sodium channels recorded in the cerebellum are TTX-sensitive with similar kinetics, making it difficult to identify the isoforms electrically. Thus, most of the expression studies have relied on techniques that allow visualization of sodium channel subtypes at the level of mRNA and protein. In situ hybridization and immunolocalization studies demonstrated that granule cells predominantly express Nav1.2, Nav1.6, Nabeta1, and Nabeta2. Protein for Nav1.2 and Nav1.6 is localized primarily in granule cell parallel fibers. Purkinje cells express Nav1.1, Nav1.6, Nabeta1 and Nabeta2. The somato-dendritic localization of Nav1.1 and Nav1.6 in Purkinje cells suggests that these isoforms are involved in the integration of synaptic input. Deep cerebellar nuclei neurons expressed Nav1.1 and Nav1.6 as well as Nabeta1. Bergmann glia expressed Nav1.6, but not granule cell layer astrocytes. Some sodium channel isoforms that are not expressed normally in the adult cerebellum are expressed in animals with mutations or disease. Electrophysiological studies suggest that Nav1.6 is responsible for spontaneous firing and bursting features in Purkinje cells, but the specialized functions of the other subunits in the cerebellum remain unknown.
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Affiliation(s)
- Kristin L Schaller
- Department of Cellular and Structural Biology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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39
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Yao C, Williams AJ, Lu XCM, Price RA, Cunningham BS, Berti R, Tortella FC, Dave JR. The sodium channel blocker RS100642 reverses down-regulation of the sodium channel alpha-subunit Na(v) 1.1 expression caused by transient ischemic brain injury in rats. Neurotox Res 2003; 5:245-53. [PMID: 12835116 DOI: 10.1007/bf03033382] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In this study we evaluated the expression of five sodium channel (NaCh) Alpha-subunit genes after transient middle cerebral artery occlusion (MCAo) in the rat and the effects of treatment with the NaCh blocker and experimental neuroprotective agent RS100642 as compared to the prototype NaCh blocker mexiletine. The expression of Na(v) 1.1, Na(v) 1.2, Na(v) 1.3, Na(v) 1.7, Na(v) 1.8 and the housekeeping gene beta-actin were studied in vehicle or drug-treated rats at 6, 24 and 48 h post-MCAo using real-time quantitative RT-PCR. RS100642 (1 mg/kg), mexiletine (10 mg/kg), or vehicle (1 ml/kg) was injected (i.v.) at 30 min, 2, 4, and 6 h post-injury. Following MCAo only the Na(v) 1.1 and Na(v) 1.2 genes were significantly down-regulated in the ipsilateral hemisphere of the injured brains. RS100642 treatment significantly reversed the down-regulation of Na(v) 1.1 (but not Na(v) 1.2) at 24-48 h post-injury. Mexiletine treatment, on the other hand, had no significant effect on the down-regulation of either gene. These findings demonstrate that treatment with a neuroprotective dose of RS100642 significantly reverses the down-regulation of Na(v) 1.1 caused by ischemic brain injury and suggests that RS100642 selectively targets the Na(v) 1.1 Alpha-subunit of the NaCh. Furthermore, our findings strengthen the hypothesis that ischemic injury may produce selective depletion of voltage-gated NaChs, and suggest that the Na(v) 1.1 NaCh Alpha-subunit may play a key role in the neuronal injury/recovery process.
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Affiliation(s)
- C Yao
- Division of Neurosciences, Walter Reed Army Institute of Research, 503 Robert Grant Ave. Rm. 2W14, Silver Spring, MD 20910-7500, USA
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40
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Dave JR, Yao C, Moffett JR, Berti R, Koenig M, Tortella FC. Down regulation of sodium channel Na(v)1.1 expression by veratridine and its reversal by a novel sodium channel blocker, RS100642, in primary neuronal cultures. Neurotox Res 2003; 5:213-20. [PMID: 12835125 DOI: 10.1007/bf03033141] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
This study investigated the effects of veratridine-induced neuronal toxicity on sodium channel gene (NaCh) expression in primary forebrain cultures enriched in neurons, and its reversal by a novel sodium channel blocker, RS100642. Using quantitative RT-PCR, our findings demonstrated the expression ratio of NaCh genes in normal fetal rat forebrain neurons to be Na(v)1.2 > Na(v)1.3 > Na(v)1.8 > Na(v)1.1 > Na(v)1.7 (rBII > rBIII > PN3 > rBI > PN1). Veratridine treatment of neuronal cells produced neurotoxicity in a dose-dependent manner (0.25-20 micro M). Neuronal injury caused by a dose of veratridine producing 80% cell death (2.5 micro M) significantly, and exclusively down-regulated the Na(v)1.1 gene. However, treatment of neurons with RS100642 (200 micro M) reversed the down-regulation of the Na(v)1.1 gene expression caused by veratridine. Our findings document for the first time quantitative and relative changes in the expression of various NaCh genes in neurons following injury produced by selective activation of voltage-gated sodium channels, and suggest that the Na(v)1.1 sodium channel gene may play a key role in the neuronal injury/recovery process.
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Affiliation(s)
- Jitendra R Dave
- Department of Neuropharmacology and Molecular Biology, Division of Neurosciences, Walter Reed Army Institute of Research, 503 Robert Grant Ave., Silver Spring, MD 20910-7500, USA.
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41
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Schrey M, Codina C, Kraft R, Beetz C, Kalff R, Wölfl S, Patt S. Molecular characterization of voltage-gated sodium channels in human gliomas. Neuroreport 2002; 13:2493-8. [PMID: 12499855 DOI: 10.1097/00001756-200212200-00023] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Voltage-sensitive sodium channels appear to be an electrophysiological hallmark of gliomas. However, the expression of channel subtypes is unclear in these tumors. In this study different gliomas were investigated for the expression of sodium channel subtypes Na(v)1.1, Na(v)1.2, Na(v)1.3, Na(v)1.4, Na(v)1.6, and Na(x)(Na(v)2.1) using RT-PCR. At least one subtype of channels could be detected in each tumor. High-grade gliomas expressed fewer sodium channel subtypes and these at weaker levels than low-grade tumors. Expression of Na(v)1.6, the most abundant isoform in the CNS, was almost absent in the gliomas except the pilocytic variant. Our study gives clear evidence for a differential expression of sodium channel subtypes in gliomas and indicates a predominant expression of channels related to malignancy grades.
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Affiliation(s)
- Michael Schrey
- Institute of Pathology (Neuropathology), Friedrich Schiller University-Jena, Bachstrasse 18, D-07740 Jena, Germany
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42
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Abstract
Animal experiments, and particularly functional investigations on human chronically epileptic tissue as well as genetic studies in epilepsy patients and their families strongly suggest that some forms of epilepsy may share a pathogenetic mechanism: an alteration of voltage-gated sodium channels. This review summarizes recent data on changes of sodium channel expression, molecular structure and function associated with epilepsy, as well as on the interaction of new and established antiepileptic drugs with sodium currents. Although it remains to be determined precisely how and to what extent altered sodium-channel functions play a role in different epilepsy syndromes, future promising therapy approaches may include drugs modulating sodium currents, and particularly substances changing their inactivation characteristics.
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Affiliation(s)
- Rüdiger Köhling
- Institut für Physiologie, Westfälische Wilhelms-Universität Münster, Münster, Germany.
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43
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Bicalho AFX, Guatimosim C, Prado MAM, Gomez MV, Romano-Silva MA. Investigation of the modulation of glutamate release by sodium channels using neurotoxins. Neuroscience 2002; 113:115-23. [PMID: 12123690 DOI: 10.1016/s0306-4522(02)00139-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The modulation of neurotransmitter release by calcium channels is well established, yet, sodium channels were regarded mainly as charge carriers. Many lines of evidence suggest a more fine-tuning role played by sodium channels. Using rat cerebrocortical isolated nerve endings (synaptosomes) and two toxins that have separate sites of action on sodium channels and provoke distinct changes in channel kinetics, we were able to show that depending on the rate of increase in channel conductance, the outcome in terms of neurotransmitter release and calcium channel types coupled to that event are different. Mainly, our study focused on veratridine, an alkaloid from lilaceous plants that binds to sodium channel toxin site 2, and tityustoxin, a toxin purified from the venom of the Brazilian yellow scorpion Tityus serrulatus that binds to site 3. Veratridine induces a slower increase in intrasynaptosomal sodium and calcium concentrations, slower depolarization, delayed exocytosis and a slower and predominantly calcium-independent glutamate release, when compared to tityustoxin.Thus, we have used these two toxins to investigate the events that start with sodium entry and culminate with the release of glutamate in isolated nerve endings (synaptosomes) from rat cerebral cortex. With that in mind we measured intrasynaptosomal free sodium concentration [Na(+)](i), intrasynaptosomal free calcium concentration [Ca(2+)](i), membrane potential, exocytosis and glutamate release using fluorescent probes.
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Affiliation(s)
- A F X Bicalho
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, ICB, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Belo Horizonte 31270-901, MG, Brazil
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Grauert M, Bechtel WD, Weiser T, Stransky W, Nar H, Carter AJ. Synthesis and structure-activity relationships of 6,7-benzomorphan derivatives as use-dependent sodium channel blockers for the treatment of stroke. J Med Chem 2002; 45:3755-64. [PMID: 12166948 DOI: 10.1021/jm020875j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have synthesized a series of 6,7-benzomorphan derivatives and determined their ability to bind to voltage-dependent sodium channels. We have also compared the functional consequences of this blockade in vitro and in vivo. The ability of the compounds to displace [(3)H]batrachotoxin from voltage-dependent sodium channels was compared with their ability to inhibit [(3)H]glutamate release in rat brain slices and block convulsions in the maximal electroshock test in mice. We found that the hydroxyl function in the 4'-position is crucial for improving the sodium channel blocking properties. Moreover, the stereochemistry and the topology of the N-linked side chain also influence this interaction. Indeed, the affinity is improved by an aromatic substitution in the side chain. By modifying the N substituent and the substitution pattern of the hydroxyl function, we were able to discover (2R)-[2alpha,3(S),6alpha]-1,2,3,4,5,6-hexahydro-6,11,11-tri-methyl-3-[2-(phenylmethoxy)propyl]-2,6-methano-3-benzazocin-10-ol hydrochloride. This compound was chosen as the best candidate for further pharmacological investigations.
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Affiliation(s)
- Matthias Grauert
- Department of Medicinal Chemistry, Boehringer Ingelheim Pharma KG, 88397 Biberach an der Riss, and Corporate Development, Boehringer Ingelheim GmbH, 55216 Ingelheim am Rhein, Germany.
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45
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Ogata N, Ohishi Y. Molecular diversity of structure and function of the voltage-gated Na+ channels. JAPANESE JOURNAL OF PHARMACOLOGY 2002; 88:365-77. [PMID: 12046980 DOI: 10.1254/jjp.88.365] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A variety of different isoforms of voltage-sensitive Na+ channels have now been identified. The recent three-dimensional analysis of Na+ channels has unveiled a unique and unexpected structure of the Na+ channel protein. Na+ channels can be classified into two categories on the basis of their amino acid sequence, Nav1 isoforms currently comprising nine highly homologous clones and Nax that possesses structure diverging from Nav1, especially in several critical functional motifs. Although the functional role of Nav1 isoforms is primarily to form an action potential upstroke in excitable cells, recent biophysical studies indicate that some of the Nav1 isoforms can also influence subthreshold electrical activity through persistent or resurgent Na+ currents. Nav1.8 and Nav1.9 contain an amino acid sequence common to tetrodotoxin resistant Na+ channels and are localized in peripheral nociceptors. Recent patch-clamp experiments on dorsal root ganglion neurons from Nav1.8-knock-out mice unveiled an additional tetrodotoxin-resistant Na+ current. The demonstration of its dependence on Nav1.9 provides evidence for a specialized role of Nav1.9, together with Nav1.8, in pain sensation. Although Nax has not been successfully expressed in an exogenous system, recent investigations using relevant native tissues combined with gene-targeting have disclosed their unique "concentration"-sensitive but not voltage-sensitive roles. In this context, these emerging views of novel functions mediated by different types of Na+ channels are reviewed, to give a perspective for future research on the expanding family of Na+ channel clones.
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Affiliation(s)
- Nobukuni Ogata
- Department of Physiology, Hiroshima University School of Medicine, Japan.
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46
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Abstract
SUMMARY
Voltage-gated Na+ channels play important functional roles in the generation of electrical excitability in most vertebrate and invertebrate species. These channels are members of a superfamily that includes voltage-gated K+, voltage-gated Ca2+ and cyclic-nucleotide-gated channels. There are nine genes encoding voltage-gated Na+ channels in mammals, with a tenth homologous gene that has not been shown to encode a functional channel. Other vertebrate and invertebrate species have a smaller number of Na+ channel genes. The mammalian genes can be classified into five branches in a phylogenetic tree, and they are localized on four chromosomes. Four of the branches representing the four chromosomal locations probably resulted from the chromosomal duplications that led to the four Hox gene clusters. These duplications occurred close to the emergence of the first vertebrates. The fifth branch probably evolved from a separate ancestral Na+ channel gene. There are two branches in the invertebrate tree, although members of only one of those branches have been demonstrated to encode functional voltage-gated Na+ channels. It is possible that the other branch may have diverged, so that its members do not represent true voltage-gated Na+ channels. Vertebrate and invertebrate Na+ channels appear to be derived from a single primordial channel that subsequently evolved independently in the two lineages.
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Affiliation(s)
- Alan L Goldin
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA.
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47
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Yao C, Williams AJ, Cui P, Berti R, Hunter JC, Tortella FC, Dave JR. Differential pattern of expression of voltage-gated sodium channel genes following ischemic brain injury in rats. Neurotox Res 2002; 4:67-75. [PMID: 12826495 DOI: 10.1080/10298420290007646] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
This study investigated the effects of brain ischemia on sodium channel gene (NaCh) expression in rats. Using quantitative RT-PCR, our findings demonstrated the expression ratio of NaCh genes in normal rat brain to be Na(v)1.1 > Na(v)1.8 > Na(v)1.3 > Na(v)1.7 (rBI > PN3 > rBIII > PN1). In contrast, brain injury caused by middle cerebral artery occlusion (MCAo) for 2 h followed by reperfusion significantly down-regulated Na(v)1.3 and Na(v)1.7 genes in both injured and contralateral hemispheres; whereas the Na(v)1.8 gene was down regulated in only the injured hemisphere (though only acutely at 2 or 2-6 h post-MCAo). However, the time-course of NaCh gene expression revealed a significant down-regulation of Na(v)1.1 only in the ischemic hemisphere beginning 6 h post-MCAo and measured out to 48 h post-MCAo. In a separate preliminary study Na(v)1.2 (rBII) gene was found to be expressed at levels greater than that of Na(v)1.1 in normal rats and was significantly down regulated at 24 h post-MCAo). Our findings document, for the first time, quantitative and relative changes in the expression of various NaCh genes following ischemic brain injury and suggest that the Na(v)1.1 sodium channel gene may play a key role in ischemic injury/recovery.
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Affiliation(s)
- C Yao
- Division of Neurosciences, Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500, USA.
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48
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Baker MD. Electrophysiology of mammalian Schwann cells. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2002; 78:83-103. [PMID: 12429109 DOI: 10.1016/s0079-6107(02)00007-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Schwann cells are the satellite cell of the peripheral nervous system, and they surround axons and motor nerve terminals. The review summarises evidence for the ion channels expressed by mammalian Schwann cells, their molecular nature and known or speculated functions. In addition, the recent evidence for gap junctions and cytoplasmic diffusion pathways within the myelin and the functional consequences of a lower-resistance myelin sheath are discussed. The main types of ion channel expressed by Schwann cells are K(+) channels, Cl(-) channels, Na(+) channels and Ca(2+) channels. Each is represented by a variety of sub-types. The molecular and biophysical characteristics of the cation channels expressed by Schwann cells are closely similar or identical to those of channels expressed in peripheral axons and elsewhere. In addition, Schwann cells express P(2)X ligand-gated ion channels. Possible in vivo roles for each ion channel type are discussed. Ion channel expression in culture could have a special function in driving or controlling cell proliferation and recent evidence indicates that some Ca(2+) channel and Kir channel expression in culture is dependent upon the presence of neurones and local electrical activity.
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Affiliation(s)
- Mark D Baker
- Molecular Nociception Group, Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.
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Abstract
An important aspect of Na+ channel regulation is their distribution on neuronal membranes within the nervous system. The complexity of this process is brought by the molecular diversity of Na+ channels and differential regulation of their distribution. In addition, Na+ channel localization is a highly dynamic process depending on the status of the cell in vitro, and (patho)physiological condition of the organism in vivo. Nonetheless, the pharmacological manipulation of Na+ channel distribution should be possible and will hopefully bring safer and more-potent medicines in the future.
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50
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Abstract
A variety of isoforms of mammalian voltage-gated sodium channels have been described. Ten genes encoding sodium channel alpha subunits have been identified, and nine of those isoforms have been functionally expressed in exogenous systems. The alpha subunit is associated with accessory beta subunits in some tissues, and three genes encoding different beta subunits have been identified. The alpha subunit isoforms have distinct patterns of development and localization in the nervous system, skeletal and cardiac muscle. In addition, many of the isoforms demonstrate subtle differences in their functional properties. However, there are no clear subfamilies of the channels, unlike the situation with potassium and calcium channels. The subtle differences in the functional properties of the sodium channel isoforms result in unique conductances in specific cell types, which have important physiological effects for the organism. Small alterations in the electrophysiological properties of the channel resulting from mutations in specific isoforms cause human diseases such as periodic paralysis, long QT syndrome, and epilepsy.
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Affiliation(s)
- A L Goldin
- Department of Microbiology and Molecular Genetics, University of California Irvine, California 92697-4025, USA.
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