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Combe CL, Gasparini S. I h from synapses to networks: HCN channel functions and modulation in neurons. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:119-132. [PMID: 34181891 DOI: 10.1016/j.pbiomolbio.2021.06.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 05/25/2021] [Accepted: 06/03/2021] [Indexed: 01/16/2023]
Abstract
Hyperpolarization-activated cyclic nucleotide gated (HCN) channels and the current they carry, Ih, are widely and diversely distributed in the central nervous system (CNS). The distribution of the four subunits of HCN channels is variable within the CNS, within brain regions, and often within subcellular compartments. The precise function of Ih can depend heavily on what other channels are co-expressed. In this review, we give an overview of HCN channel structure, distribution, and modulation by cyclic adenosine monophosphate (cAMP). We then discuss HCN channel and Ih functions, where we have parsed the roles into two main effects: a steady effect on maintaining the resting membrane potential at relatively depolarized values, and slow channel dynamics. Within this framework, we discuss Ih involvement in resonance, synaptic integration, transmitter release, plasticity, and point out a special case, where the effects of Ih on the membrane potential and its slow channel dynamics have dual roles in thalamic neurons.
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Affiliation(s)
- Crescent L Combe
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA
| | - Sonia Gasparini
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA.
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2
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Liu W, Lao W, Zhang R, Zhu H. Altered expression of voltage gated sodium channel Nav1.1 is involved in motor ability in MPTP-treated mice. Brain Res Bull 2021; 170:187-198. [PMID: 33610724 DOI: 10.1016/j.brainresbull.2021.02.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 01/12/2021] [Accepted: 02/16/2021] [Indexed: 11/25/2022]
Abstract
Parkinson's disease (PD) is a motor disabling disorder owing to the progressive degeneration of dopaminergic neurons in the substantia nigra (SN). The mechanisms causing motor deficits remain debated. High synchronized oscillations in the basal ganglia (BG) were proposed to be associated with motor symptoms in PD patients and animal models of PD. Voltage-gated sodium channels play a vital role in the initiation and propagation of action potentials. Here, we investigated the expression patterns of a VGSC subtype Nav1.1 in the BG of a PD animal model induced by MPTP intraperitoneal injection. The results showed that Nav1.1 was significantly reduced in tyrosine hydroxylase (TH) positive dopaminergic neurons of the SN. Moreover, Nav1.1 expression was significantly increased in calcium binding protein parvalbumin (PV) positive neurons of the globus pallidus (GP) in MPTP-treated mice compared to the rarely undetectable expression of Nav1.1 in the control GP. Furthermore, the administration of phenytoin, a VGSCs blocker, can effectively improve motor disabilities and reduce the synchronous oscillations in the BG of MPTP-treated mice. These findings suggested that the alterations of Nav1.1 expression may be associated with the high synchronous oscillations in the BG of PD animals.
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Affiliation(s)
- Weitang Liu
- School of Life Science, Shanghai University, Shanghai, China
| | - Wenwen Lao
- School of Life Science, Shanghai University, Shanghai, China
| | - Renxing Zhang
- School of Life Science, Shanghai University, Shanghai, China
| | - Hongyan Zhu
- School of Life Science, Shanghai University, Shanghai, China.
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3
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Yeh TY, Luo IW, Hsieh YL, Tseng TJ, Chiang H, Hsieh ST. Peripheral Neuropathic Pain: From Experimental Models to Potential Therapeutic Targets in Dorsal Root Ganglion Neurons. Cells 2020; 9:cells9122725. [PMID: 33371371 PMCID: PMC7767346 DOI: 10.3390/cells9122725] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 12/16/2020] [Indexed: 12/12/2022] Open
Abstract
Neuropathic pain exerts a global burden caused by the lesions in the somatosensory nerve system, including the central and peripheral nervous systems. The mechanisms of nerve injury-induced neuropathic pain involve multiple mechanisms, various signaling pathways, and molecules. Currently, poor efficacy is the major limitation of medications for treating neuropathic pain. Thus, understanding the detailed molecular mechanisms should shed light on the development of new therapeutic strategies for neuropathic pain. Several well-established in vivo pain models were used to investigate the detail mechanisms of peripheral neuropathic pain. Molecular mediators of pain are regulated differentially in various forms of neuropathic pain models; these regulators include purinergic receptors, transient receptor potential receptor channels, and voltage-gated sodium and calcium channels. Meanwhile, post-translational modification and transcriptional regulation are also altered in these pain models and have been reported to mediate several pain related molecules. In this review, we focus on molecular mechanisms and mediators of neuropathic pain with their corresponding transcriptional regulation and post-translational modification underlying peripheral sensitization in the dorsal root ganglia. Taken together, these molecular mediators and their modification and regulations provide excellent targets for neuropathic pain treatment.
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Affiliation(s)
- Ti-Yen Yeh
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan;
| | - I-Wei Luo
- Department of Life Science, College of Life Science, National Taiwan University, Taipei 10617, Taiwan;
| | - Yu-Lin Hsieh
- Department of Anatomy, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan;
- School of Post-Baccalaureate Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
- Department of Medical Research, Kaohsiung Medical University Hostpital, Kaohsiung 80708, Taiwan
| | - To-Jung Tseng
- Department of Anatomy, School of Medicine, Chung Shan Medical University, Taichung 40201, Taiwan;
- Department of Medical Education, Chung Shan Medical University Hospital, Taichung 40201, Taiwan
| | | | - Sung-Tsang Hsieh
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan;
- Department of Neurology, National Taiwan University Hospital, Taipei 10002, Taiwan
- Graduate Institute of Brian and Mind Sciences, College of Medicine, National Taiwan University, Taipei 10051, Taiwan
- Center of Precision Medicine, College of Medicine, National Taiwan University, Taipei 10055, Taiwan
- Correspondence: ; Tel.: +886-2-23123456 (ext. 88182); Fax: +886-223915292
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4
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Ma RSY, Kayani K, Whyte-Oshodi D, Whyte-Oshodi A, Nachiappan N, Gnanarajah S, Mohammed R. Voltage gated sodium channels as therapeutic targets for chronic pain. J Pain Res 2019; 12:2709-2722. [PMID: 31564962 PMCID: PMC6743634 DOI: 10.2147/jpr.s207610] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 08/02/2019] [Indexed: 01/23/2023] Open
Abstract
Being maladaptive and frequently unresponsive to pharmacotherapy, chronic pain presents a major unmet clinical need. While an intact central nervous system is required for conscious pain perception, nociceptor hyperexcitability induced by nerve injury in the peripheral nervous system (PNS) is sufficient and necessary to initiate and maintain neuropathic pain. The genesis and propagation of action potentials is dependent on voltage-gated sodium channels, in particular, Nav1.7, Nav1.8 and Nav1.9. However, nerve injury triggers changes in their distribution, expression and/or biophysical properties, leading to aberrant excitability. Most existing treatment for pain relief acts through non-selective, state-dependent sodium channel blockage and have narrow therapeutic windows. Natural toxins and developing subtype-specific and molecular-specific sodium channel blockers show promise for treatment of neuropathic pain with minimal side effects. New approaches to analgesia include combination therapy and gene therapy. Here, we review how individual sodium channel subtypes contribute to pain, and the attempts made to develop more effective analgesics for the treatment of chronic pain.
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Affiliation(s)
- Renee Siu Yu Ma
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Kayani Kayani
- Department of Medicine, University of Cambridge, Cambridge, UK
| | | | | | | | | | - Raihan Mohammed
- Department of Medicine, University of Cambridge, Cambridge, UK
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5
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McKinley JW, Shi Z, Kawikova I, Hur M, Bamford IJ, Sudarsana Devi SP, Vahedipour A, Darvas M, Bamford NS. Dopamine Deficiency Reduces Striatal Cholinergic Interneuron Function in Models of Parkinson's Disease. Neuron 2019; 103:1056-1072.e6. [PMID: 31324539 DOI: 10.1016/j.neuron.2019.06.013] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Revised: 03/12/2019] [Accepted: 06/18/2019] [Indexed: 11/30/2022]
Abstract
Motor and cognitive functions depend on the coordinated interactions between dopamine (DA) and acetylcholine (ACh) at striatal synapses. Increased ACh availability was assumed to accompany DA deficiency based on the outcome of pharmacological treatments and measurements in animals that were critically depleted of DA. Using Slc6a3DTR/+ diphtheria-toxin-sensitive mice, we demonstrate that a progressive and L-dopa-responsive DA deficiency reduces ACh availability and the transcription of hyperpolarization-activated cation (HCN) channels that encode the spike timing of ACh-releasing tonically active striatal interneurons (ChIs). Although the production and release of ACh and DA are reduced, the preponderance of ACh over DA contributes to the motor deficit. The increase in striatal ACh relative to DA is heightened via D1-type DA receptors that activate ChIs in response to DA release from residual axons. These results suggest that stabilizing the expression of HCN channels may improve ACh-DA reciprocity and motor function in Parkinson's disease (PD). VIDEO ABSTRACT.
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Affiliation(s)
| | - Ziqing Shi
- Department of Pediatrics, Yale University, New Haven, CT 06510, USA
| | - Ivana Kawikova
- Department of Pediatrics, Yale University, New Haven, CT 06510, USA
| | - Matthew Hur
- Department of Pediatrics, Yale University, New Haven, CT 06510, USA
| | - Ian J Bamford
- Department of Pediatrics, Yale University, New Haven, CT 06510, USA
| | | | - Annie Vahedipour
- Department of Pediatrics, Yale University, New Haven, CT 06510, USA
| | - Martin Darvas
- Department of Pathology, University of Washington, Seattle, WA 98105, USA
| | - Nigel S Bamford
- Department of Pediatrics, Yale University, New Haven, CT 06510, USA; Department of Neurology and Cellular and Molecular Physiology, Yale University, New Haven, CT 06510, USA; Department of Neurology, University of Washington, Seattle, WA 98105, USA.
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6
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Fazia T, Pastorino R, Notartomaso S, Busceti C, Imbriglio T, Cannella M, Gentilini D, Morani G, Ticca A, Bitti P, Berzuini C, Dalmay T, Battaglia G, Bernardinelli L. Acid sensing ion channel 2: A new potential player in the pathophysiology of multiple sclerosis. Eur J Neurosci 2019; 49:1233-1243. [PMID: 30549327 PMCID: PMC6618268 DOI: 10.1111/ejn.14302] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 11/12/2018] [Accepted: 11/23/2018] [Indexed: 12/20/2022]
Abstract
Acid‐sensing ion channels (ASICs) are proton‐gated channels involved in multiple biological functions such as: pain modulation, mechanosensation, neurotransmission, and neurodegeneration. Earlier, we described the genetic association, within the Nuoro population, between Multiple Sclerosis (MS) and rs28936, located in ASIC2 3′UTR. Here we investigated the potential involvement of ASIC2 in MS inflammatory process. We induced experimental autoimmune encephalomyelitis (EAE) in wild‐type (WT), knockout Asic1−/− and Asic2−/− mice and observed a significant reduction of clinical score in Asic1−/− mice and a significant reduction in the clinical score in Asic2−/− mice in a limited time window (i.e., at days 20–23 after immunization). Immunohistochemistry confirmed the reduction in adaptive immune cell infiltrates in the spinal cord of EAE Asic1−/− mice. Analysis of mechanical allodynia, showed a significant higher pain threshold in Asic2−/− mice under physiological conditions, before immunization, as compared to WT mice and Asic1−/−. A significant reduction in pain threshold was observed in all three strains of mice after immunization. More importantly, analysis of human autoptic brain tissue in MS and control samples showed an increase of ASIC2 mRNA in MS samples. Subsequently, in vitro luciferase reporter gene assays, showed that ASIC2 expression is under possible miRNA regulation, in a rs28936 allele‐specific manner. Taken together, these findings suggest a potential role of ASIC2 in the pathophysiology of MS.
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Affiliation(s)
- Teresa Fazia
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Roberta Pastorino
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | | | | | - Tiziana Imbriglio
- I.R.C.C.S. Neuromed, Pozzilli, Italy.,Department of Physiology and Pharmacology, University Sapienza, Roma, Italy
| | | | - Davide Gentilini
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.,Unità di Bioinformatica e Statistica Genomica, Istituto Auxologico Italiano IRCCS, Cusano Milanino, Milano, Italy
| | - Gabriele Morani
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Anna Ticca
- Azienda Tutela Salute Sardegna, ASSL Nuoro, Neurologia e Stroke Unit, Ospedale "San Francesco", Nuoro, Italy
| | - Pierpaolo Bitti
- Azienda Tutela Salute Sardegna, ASSL Nuoro, Immunoematologia e Medicina Trasfusionale, Ospedale "San Francesco", Nuoro, Italy
| | - Carlo Berzuini
- Centre for Biostatistics, University of Manchester, Manchester, UK
| | - Tamas Dalmay
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | | | - Luisa Bernardinelli
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
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A Network Model Reveals That the Experimentally Observed Switch of the Granule Cell Phenotype During Epilepsy Can Maintain the Pattern Separation Function of the Dentate Gyrus. ACTA ACUST UNITED AC 2019. [DOI: 10.1007/978-3-319-99103-0_23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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8
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Neuronal Dysfunction in iPSC-Derived Medium Spiny Neurons from Chorea-Acanthocytosis Patients Is Reversed by Src Kinase Inhibition and F-Actin Stabilization. J Neurosci 2017; 36:12027-12043. [PMID: 27881786 DOI: 10.1523/jneurosci.0456-16.2016] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 09/07/2016] [Accepted: 09/26/2016] [Indexed: 11/21/2022] Open
Abstract
Chorea-acanthocytosis (ChAc) is a fatal neurological disorder characterized by red blood cell acanthocytes and striatal neurodegeneration. Recently, severe cell membrane disturbances based on depolymerized cortical actin and an elevated Lyn kinase activity in erythrocytes from ChAc patients were identified. How this contributes to the mechanism of neurodegeneration is still unknown. To gain insight into the pathophysiology, we established a ChAc patient-derived induced pluripotent stem cell model and an efficient differentiation protocol providing a large population of human striatal medium spiny neurons (MSNs), the main target of neurodegeneration in ChAc. Patient-derived MSNs displayed enhanced neurite outgrowth and ramification, whereas synaptic density was similar to controls. Electrophysiological analysis revealed a pathologically elevated synaptic activity in ChAc MSNs. Treatment with the F-actin stabilizer phallacidin or the Src kinase inhibitor PP2 resulted in the significant reduction of disinhibited synaptic currents to healthy control levels, suggesting a Src kinase- and actin-dependent mechanism. This was underlined by increased G/F-actin ratios and elevated Lyn kinase activity in patient-derived MSNs. These data indicate that F-actin stabilization and Src kinase inhibition represent potential therapeutic targets in ChAc that may restore neuronal function. SIGNIFICANCE STATEMENT Chorea-acanthocytosis (ChAc) is a fatal neurodegenerative disease without a known cure. To gain pathophysiological insight, we newly established a human in vitro model using skin biopsies from ChAc patients to generate disease-specific induced pluripotent stem cells (iPSCs) and developed an efficient iPSC differentiation protocol providing striatal medium spiny neurons. Using patch-clamp electrophysiology, we detected a pathologically enhanced synaptic activity in ChAc neurons. Healthy control levels of synaptic activity could be restored by treatment of ChAc neurons with the F-actin stabilizer phallacidin and the Src kinase inhibitor PP2. Because Src kinases are involved in bridging the membrane to the actin cytoskeleton by membrane protein phosphorylation, our data suggest an actin-dependent mechanism of this dysfunctional phenotype and potential treatment targets in ChAc.
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9
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Kawano R, Horike N, Hijikata Y, Kondo M, Carné-Sánchez A, Larpent P, Ikemura S, Osaki T, Kamiya K, Kitagawa S, Takeuchi S, Furukawa S. Metal-Organic Cuboctahedra for Synthetic Ion Channels with Multiple Conductance States. Chem 2017. [DOI: 10.1016/j.chempr.2017.02.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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10
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Abstract
This review attempts to give a concise and up-to-date overview on the role of potassium channels in epilepsies. Their role can be defined from a genetic perspective, focusing on variants and de novo mutations identified in genetic studies or animal models with targeted, specific mutations in genes coding for a member of the large potassium channel family. In these genetic studies, a demonstrated functional link to hyperexcitability often remains elusive. However, their role can also be defined from a functional perspective, based on dynamic, aggravating, or adaptive transcriptional and posttranslational alterations. In these cases, it often remains elusive whether the alteration is causal or merely incidental. With ∼80 potassium channel types, of which ∼10% are known to be associated with epilepsies (in humans) or a seizure phenotype (in animals), if genetically mutated, a comprehensive review is a challenging endeavor. This goal may seem all the more ambitious once the data on posttranslational alterations, found both in human tissue from epilepsy patients and in chronic or acute animal models, are included. We therefore summarize the literature, and expand only on key findings, particularly regarding functional alterations found in patient brain tissue and chronic animal models.
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Affiliation(s)
- Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
| | - Jakob Wolfart
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
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11
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Bertram KL, Banderali U, Tailor P, Krawetz RJ. Ion channel expression and function in normal and osteoarthritic human synovial fluid progenitor cells. Channels (Austin) 2015; 10:148-57. [PMID: 26632350 DOI: 10.1080/19336950.2015.1116652] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Osteoarthritis (OA) is a chronic disease affecting the cartilage of over 15% of Canadians. Synovial fluid mesenchymal progenitor cells (sfMPCs) are present in joints and are thought to contribute to healing. OA sfMPCs have a greater proliferative ability but decreased chondrogenic potential. However, little is known about the factors influencing/regulating the differences between normal and OA sfMPCs. Recently, our lab has shown that sfMPC chondrogenic differentiation in vitro is favorably biased toward a similar osmotic environment as they experience in vivo. The current study now examines the expression and functionality of a variety of ion channels in sfMPCs derived from normal individuals and early OA patients. Results indicated that there is differential ion channel regulation at the functional level and expression level in early OA sfMPCs. All ion channels were upregulated in early OA compared to normal sfMPCs with the exception of KCNMA1 at the mRNA level. At the protein level, TRPV4 was over expressed in early OA sfMPCs, while KCNJ12 and KCNMA1 were unchanged between normal and early OA sfMPCs. At the functional level, the inward rectifying potassium channel was under expressed in early OA sfMPCs, however the membrane potential was unchanged between normal and early OA sfMPCs. In the synovial environment itself, a number of differences in ion concentration between normal and early OA synovial fluid were observed. These findings suggest that normal and OA progenitor cells demonstrate functional differences in how they interact with the synovial ion environment.
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Affiliation(s)
- Karri L Bertram
- a Department of Cell Biology and Anatomy , University of Calgary , Calgary , Alberta , Canada.,b McCaig Institute for Bone and Joint Health , Faculty of Medicine, University of Calgary, Calgary , Alberta , Canada
| | - Umberto Banderali
- c Faculty of Kinesiology , University of Calgary , Calgary , Alberta , Canada
| | - Pankaj Tailor
- a Department of Cell Biology and Anatomy , University of Calgary , Calgary , Alberta , Canada.,b McCaig Institute for Bone and Joint Health , Faculty of Medicine, University of Calgary, Calgary , Alberta , Canada
| | - Roman J Krawetz
- a Department of Cell Biology and Anatomy , University of Calgary , Calgary , Alberta , Canada.,b McCaig Institute for Bone and Joint Health , Faculty of Medicine, University of Calgary, Calgary , Alberta , Canada
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12
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van Loo KMJ, Schaub C, Pitsch J, Kulbida R, Opitz T, Ekstein D, Dalal A, Urbach H, Beck H, Yaari Y, Schoch S, Becker AJ. Zinc regulates a key transcriptional pathway for epileptogenesis via metal-regulatory transcription factor 1. Nat Commun 2015; 6:8688. [PMID: 26498180 PMCID: PMC4846312 DOI: 10.1038/ncomms9688] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 09/18/2015] [Indexed: 11/29/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is the most common focal seizure disorder in adults. In many patients, transient brain insults, including status epilepticus (SE), are followed by a latent period of epileptogenesis, preceding the emergence of clinical seizures. In experimental animals, transcriptional upregulation of CaV3.2 T-type Ca(2+)-channels, resulting in an increased propensity for burst discharges of hippocampal neurons, is an important trigger for epileptogenesis. Here we provide evidence that the metal-regulatory transcription factor 1 (MTF1) mediates the increase of CaV3.2 mRNA and intrinsic excitability consequent to a rise in intracellular Zn(2+) that is associated with SE. Adeno-associated viral (rAAV) transfer of MTF1 into murine hippocampi leads to increased CaV3.2 mRNA. Conversely, rAAV-mediated expression of a dominant-negative MTF1 abolishes SE-induced CaV3.2 mRNA upregulation and attenuates epileptogenesis. Finally, data from resected human hippocampi surgically treated for pharmacoresistant TLE support the Zn(2+)-MTF1-CaV3.2 cascade, thus providing new vistas for preventing and treating TLE.
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Affiliation(s)
- Karen M. J. van Loo
- Section for Translational Epilepsy Research, Department of Neuropathology, University of Bonn Medical Center, Bonn 53105, Germany
| | - Christina Schaub
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn Medical Center, Bonn 53105, Germany
- Department of Neurology, University of Bonn Medical Center, Bonn 53105, Germany
| | - Julika Pitsch
- Section for Translational Epilepsy Research, Department of Neuropathology, University of Bonn Medical Center, Bonn 53105, Germany
| | - Rebecca Kulbida
- Section for Translational Epilepsy Research, Department of Neuropathology, University of Bonn Medical Center, Bonn 53105, Germany
| | - Thoralf Opitz
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn Medical Center, Bonn 53105, Germany
| | - Dana Ekstein
- Department of Medical Neurobiology, IMRIC, Hebrew University–Hadassah School of Medicine, Jerusalem 91120, Israel
- Department of Neurology, Hadassah—Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Adam Dalal
- Department of Medical Neurobiology, IMRIC, Hebrew University–Hadassah School of Medicine, Jerusalem 91120, Israel
| | - Horst Urbach
- Department of Neuroradiology, Medical Center University of Freiburg, Freiburg 79106, Germany
| | - Heinz Beck
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn Medical Center, Bonn 53105, Germany
| | - Yoel Yaari
- Department of Medical Neurobiology, IMRIC, Hebrew University–Hadassah School of Medicine, Jerusalem 91120, Israel
| | - Susanne Schoch
- Section for Translational Epilepsy Research, Department of Neuropathology, University of Bonn Medical Center, Bonn 53105, Germany
| | - Albert J. Becker
- Section for Translational Epilepsy Research, Department of Neuropathology, University of Bonn Medical Center, Bonn 53105, Germany
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13
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Wolfart J, Laker D. Homeostasis or channelopathy? Acquired cell type-specific ion channel changes in temporal lobe epilepsy and their antiepileptic potential. Front Physiol 2015; 6:168. [PMID: 26124723 PMCID: PMC4467176 DOI: 10.3389/fphys.2015.00168] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/19/2015] [Indexed: 01/16/2023] Open
Abstract
Neurons continuously adapt the expression and functionality of their ion channels. For example, exposed to chronic excitotoxicity, neurons homeostatically downscale their intrinsic excitability. In contrast, the “acquired channelopathy” hypothesis suggests that proepileptic channel characteristics develop during epilepsy. We review cell type-specific channel alterations under different epileptic conditions and discuss the potential of channels that undergo homeostatic adaptations, as targets for antiepileptic drugs (AEDs). Most of the relevant studies have been performed on temporal lobe epilepsy (TLE), a widespread AED-refractory, focal epilepsy. The TLE patients, who undergo epilepsy surgery, frequently display hippocampal sclerosis (HS), which is associated with degeneration of cornu ammonis subfield 1 pyramidal cells (CA1 PCs). Although the resected human tissue offers insights, controlled data largely stem from animal models simulating different aspects of TLE and other epilepsies. Most of the cell type-specific information is available for CA1 PCs and dentate gyrus granule cells (DG GCs). Between these two cell types, a dichotomy can be observed: while DG GCs acquire properties decreasing the intrinsic excitability (in TLE models and patients with HS), CA1 PCs develop channel characteristics increasing intrinsic excitability (in TLE models without HS only). However, thorough examination of data on these and other cell types reveals the coexistence of protective and permissive intrinsic plasticity within neurons. These mechanisms appear differentially regulated, depending on the cell type and seizure condition. Interestingly, the same channel molecules that are upregulated in DG GCs during HS-related TLE, appear as promising targets for future AEDs and gene therapies. Hence, GCs provide an example of homeostatic ion channel adaptation which can serve as a primer when designing novel anti-epileptic strategies.
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Affiliation(s)
- Jakob Wolfart
- Oscar Langendorff Institute of Physiology, University of Rostock Rostock, Germany
| | - Debora Laker
- Oscar Langendorff Institute of Physiology, University of Rostock Rostock, Germany
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14
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Zhao HW, Gu XQ, Chailangkarn T, Perkins G, Callacondo D, Appenzeller O, Poulsen O, Zhou D, Muotri AR, Haddad GG. Altered iPSC-derived neurons' sodium channel properties in subjects with Monge's disease. Neuroscience 2015; 288:187-99. [PMID: 25559931 DOI: 10.1016/j.neuroscience.2014.12.039] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 12/22/2014] [Accepted: 12/23/2014] [Indexed: 12/17/2022]
Abstract
Monge's disease, also known as chronic mountain sickness (CMS), is a disease that potentially threatens more than 140 million highlanders during extended time living at high altitudes (over 2500m). The prevalence of CMS in Andeans is about 15-20%, suggesting that the majority of highlanders (non-CMS) are rather healthy at high altitudes; however, CMS subjects experience severe hypoxemia, erythrocytosis and many neurologic manifestations including migraine, headache, mental fatigue, confusion, and memory loss. The underlying mechanisms of CMS neuropathology are not well understood and no ideal treatment is available to prevent or cure CMS, except for phlebotomy. In the current study, we reprogrammed fibroblast cells from both CMS and non-CMS subjects' skin biopsies into the induced pluripotent stem cells (iPSCs), then differentiated into neurons and compared their neuronal properties. We discovered that CMS neurons were much less excitable (higher rheobase) than non-CMS neurons. This decreased excitability was not caused by differences in passive neuronal properties, but instead by a significantly lowered Na(+) channel current density and by a shift of the voltage-conductance curve in the depolarization direction. Our findings provide, for the first time, evidence of a neuronal abnormality in CMS subjects as compared to non-CMS subjects, hoping that such studies can pave the way to a better understanding of the neuropathology in CMS.
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Affiliation(s)
- H W Zhao
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA
| | - X Q Gu
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA
| | - T Chailangkarn
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - G Perkins
- National Center for Microscopy and Imaging Research, University of California San Diego, La Jolla, CA, USA
| | - D Callacondo
- Laboratorios de Investigación y Desarrollo, Universidad Peruana Cayetano Heredia, Lima 36, Peru
| | - O Appenzeller
- New Mexico Health Enhancement and Marathon Clinics Research Foundation, Albuquerque, NM 87122, USA
| | - O Poulsen
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA
| | - D Zhou
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA
| | - A R Muotri
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA; The Rady Children's Hospital, San Diego, CA 92123, USA
| | - G G Haddad
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA; The Rady Children's Hospital, San Diego, CA 92123, USA.
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15
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Karlsson P, Nyengaard JR, Polydefkis M, Jensen TS. Structural and functional assessment of skin nerve fibres in small-fibre pathology. Eur J Pain 2014; 19:1059-70. [PMID: 25546653 DOI: 10.1002/ejp.645] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2014] [Indexed: 01/19/2023]
Abstract
Damage to nociceptor nerve fibres may give rise to peripheral neuropathies, some of which are pain free and some are painful. A hallmark of many peripheral neuropathies is the loss of small nerve fibres in the epidermis, a condition called small-fibre neuropathy (SFN) when it is predominantly the small nerve fibres that are damaged. Historically, SFN has been very difficult to diagnose as clinical examination and nerve conduction studies mainly detect large nerve fibres, and quantitative sensory testing is not sensitive enough to detect small changes in small nerve fibres. However, taking a 3-mm punch skin biopsy from the distal leg and quantification of the nerve fibre density has proven to be a useful method to diagnose SFN. However, the correlation between the nerve fibre loss and other test results varies greatly. Recent studies have shown that it is possible not only to extract information about the nerve fibre density from the biopsies but also to get an estimation of the nerve fibre length density using stereology, quantify sweat gland innervation and detect morphological changes such as axonal swelling, all of which may be additional parameters indicating diseased small fibres relating to symptoms reported by the patients. In this review, we focus on available tests to assess structure and function of the small nerve fibres, and summarize recent advances that have provided new possibilities to more specifically relate structural findings with symptoms and function in patients with SFN.
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Affiliation(s)
- P Karlsson
- Danish Pain Research Center and Stereology & EM Laboratory, Aarhus University Hospital, Denmark.,Stereology and Electron Microscopy Laboratory and Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University Hospital, Denmark
| | - J R Nyengaard
- Stereology and Electron Microscopy Laboratory and Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University Hospital, Denmark
| | - M Polydefkis
- Department of Neurology, The Johns Hopkins Hospital, Baltimore, MD, USA
| | - T S Jensen
- Danish Pain Research Center and Stereology & EM Laboratory, Aarhus University Hospital, Denmark.,Department of Neurology, Aarhus University Hospital, Denmark
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16
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Thompson A, Vo D, Comfort C, Zakon HH. Expression evolution facilitated the convergent neofunctionalization of a sodium channel gene. Mol Biol Evol 2014; 31:1941-55. [PMID: 24782440 DOI: 10.1093/molbev/msu145] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Ion channels have played a substantial role in the evolution of novel traits across all of the domains of life. A fascinating example of a novel adaptation is the convergent evolution of electric organs in the Mormyroid and Gymnotiform electric fishes. The regulated currents that flow through ion channels directly generate the electrical signals which have evolved in these fish. Here, we investigated how the expression evolution of two sodium channel paralogs (Scn4aa and Scn4ab) influenced their convergent molecular evolution following the teleost-specific whole-genome duplication. We developed a reliable assay to accurately measure the expression stoichiometry of these genes and used this technique to analyze relative expression of the duplicate genes in a phylogenetic context. We found that before a major shift in expression from skeletal muscle and neofunctionalization in the muscle-derived electric organ, Scn4aa was first downregulated in the ancestors of both electric lineages. This indicates that underlying the convergent evolution of this gene, there was a greater propensity toward neofunctionalization due to its decreased expression relative to its paralog Scn4ab. We investigated another derived muscle tissue, the sonic organ of Porichthys notatus, and show that, as in the electric fishes, Scn4aa again shows a radical shift in expression away from the ancestral muscle cells into the evolutionarily novel muscle-derived tissue. This study presents evidence that expression downregulation facilitates neofunctionalization after gene duplication, a pattern that may often set the stage for novel trait evolution after gene duplication.
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Affiliation(s)
- Ammon Thompson
- Department of Integrative Biology, University of Texas at AustinDepartment of Neuroscience, University of Texas at Austin
| | - Derek Vo
- Department of Integrative Biology, University of Texas at Austin
| | - Caitlin Comfort
- Department of Integrative Biology, University of Texas at Austin
| | - Harold H Zakon
- Department of Integrative Biology, University of Texas at AustinDepartment of Neuroscience, University of Texas at AustinJosephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA
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17
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Tamura R, Nemoto T, Maruta T, Onizuka S, Yanagita T, Wada A, Murakami M, Tsuneyoshi I. Up-regulation of NaV1.7 sodium channels expression by tumor necrosis factor-α in cultured bovine adrenal chromaffin cells and rat dorsal root ganglion neurons. Anesth Analg 2014; 118:318-324. [PMID: 24445633 DOI: 10.1213/ane.0000000000000085] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Tumor necrosis factor-α (TNF-α) is not only a key regulator of inflammatory response but also an important pain modulator. TNF-α enhances both tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant Na channel currents in dorsal root ganglion (DRG) neurons. However, it remains unknown whether TNF-α affects the function and expression of the TTX-S NaV1.7 Na channel, which plays crucial roles in pain generation. METHODS We used cultured bovine adrenal chromaffin cells expressing the NaV1.7 Na channel isoform and compared them with cultured rat DRG neurons. The expression of TNF receptor 1 and 2 (TNFR1 and TNFR2) in adrenal chromaffin cells was studied by Semiquantitative reverse transcription-polymerase chain reaction. The effects of TNF-α on the expression of NaV1.7 were examined with reverse transcription-polymerase chain reaction and Western blot analysis. Results were expressed as mean ± SEM. RESULTS TNFR1 and TNFR2 were expressed in adrenal chromaffin cells, as well as reported in DRG neurons. TNF-α up-regulated NaV1.7 mRNA by 132% ± 9% (N = 5, P = 0.004) in adrenal chromaffin cells, as well as 117% ± 2% (N = 5, P < 0.0001) in DRG neurons. Western blot analysis showed that TNF-α increased NaV1.7 protein up to 166% ± 24% (N = 5, corrected P < 0.0001) in adrenal chromaffin cells, concentration- and time-dependently. CONCLUSIONS TNF-α up-regulated NaV1.7 mRNA in both adrenal chromaffin cells and DRG neurons. In addition, TNF-α up-regulated the protein expression of the TTX-S NaV1.7 channel in adrenal chromaffin cells. Our findings may contribute to understanding the peripheral nociceptive mechanism of TNF-α.
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Affiliation(s)
- Ryuji Tamura
- From the Departments of Anesthesiology and Intensive Care and Pharmacology, Miyazaki Medical College, University of Miyazaki, Miyazaki, Japan; Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, Missouri; Department of Sports Health and Welfare, Faculty of Social Welfare, Kyusyu University of Health and Welfare, Miyazaki, Japan
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18
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Cummins TR, Rush AM. Voltage-gated sodium channel blockers for the treatment of neuropathic pain. Expert Rev Neurother 2014; 7:1597-612. [DOI: 10.1586/14737175.7.11.1597] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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19
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Moldovan M, Alvarez S, Romer Rosberg M, Krarup C. Axonal voltage-gated ion channels as pharmacological targets for pain. Eur J Pharmacol 2013; 708:105-12. [PMID: 23500193 DOI: 10.1016/j.ejphar.2013.03.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 03/04/2013] [Indexed: 12/19/2022]
Abstract
Upon peripheral nerve injury (caused by trauma or disease process) axons of the dorsal root ganglion (DRG) somatosensory neurons have the ability to sprout and regrow/remyelinate to reinnervate distant target tissue or form a tangled scar mass called a neuroma. This regenerative response can become maladaptive leading to a persistent and debilitating pain state referred to as chronic pain corresponding to the clinical description of neuropathic/chronic inflammatory pain. There is little agreement to what causes peripheral chronic pain other than hyperactivity of the nociceptive DRG neurons which ultimately depends on the function of voltage-gated ion channels. This review focuses on the pharmacological modulators of voltage-gated ion channels known to be present on axonal membrane which represents by far the largest surface of DRG neurons. Blockers of voltage-gated Na(+) channels, openers of voltage-gated K(+) channels and blockers of hyperpolarization-activated cyclic nucleotide-gated channels that were found to reduce neuronal activity were also found to be effective in neuropathic and inflammatory pain states. The isoforms of these channels present on nociceptive axons have limited specificity. The rationale for considering axonal voltage-gated ion channels as targets for pain treatment comes from the accumulating evidence that chronic pain states are associated with a dysregulation of these channels that could alter their specificity and make them more susceptible to pharmacological modulation. This drives the need for further development of subtype-specific voltage-gated ion channels modulators, as well as clinically available neurophysiological techniques for monitoring axonal ion channel function in peripheral nerves.
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Affiliation(s)
- Mihai Moldovan
- Institute of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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20
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Chang KJ, Rasband MN. Excitable domains of myelinated nerves: axon initial segments and nodes of Ranvier. CURRENT TOPICS IN MEMBRANES 2013; 72:159-92. [PMID: 24210430 DOI: 10.1016/b978-0-12-417027-8.00005-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Neurons are highly polarized cells. They can be subdivided into at least two structurally and functionally distinct domains: somatodendritic and axonal domains. The somatodendritic domain receives and integrates upstream input signals, and the axonal domain generates and relays outputs in the form of action potentials to the downstream target. Demand for quick response to the harsh surroundings prompted evolution to equip vertebrates' neurons with a remarkable glia-derived structure called myelin. Not only Insulating the axon, myelinating glia also rearrange the axonal components and elaborate functional subdomains along the axon. Proper functioning of all theses domains and subdomains is vital for a normal, efficient nervous system.
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Affiliation(s)
- Kae-Jiun Chang
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, USA
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21
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Hoeijmakers JGJ, Merkies ISJ, Gerrits MM, Waxman SG, Faber CG. Genetic aspects of sodium channelopathy in small fiber neuropathy. Clin Genet 2012; 82:351-8. [PMID: 22803682 DOI: 10.1111/j.1399-0004.2012.01937.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 07/11/2012] [Accepted: 07/11/2012] [Indexed: 12/12/2022]
Abstract
Small fiber neuropathy (SFN) is a disorder typically dominated by neuropathic pain and autonomic dysfunction, in which the thinly myelinated Aδ-fibers and unmyelinated C-fibers are selectively injured. The diagnosis SFN is based on a reduced intraepidermal nerve fiber density and/or abnormal thermal thresholds in quantitative sensory testing. The etiologies of SFN are diverse, although no apparent cause is frequently seen. Recently, SCN9A-gene variants (single amino acid substitutions) have been found in ∼30% of a cohort of idiopathic SFN patients, producing gain-of-function changes in sodium channel Na(V)1.7, which is preferentially expressed in small diameter peripheral axons. Functional testing showed that these variants altered fast inactivation, slow inactivation or resurgent current and rendered dorsal root ganglion neurons hyperexcitable. In this review, we discuss the role of Na(V)1.7 in pain and highlight the molecular genetics and pathophysiology of SCN9A-gene variants in SFN. With increasing knowledge regarding the underlying pathophysiology in SFN, the development of specific treatment in these patients seems a logical target for future studies.
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Affiliation(s)
- J G J Hoeijmakers
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
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22
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Cotrina ML, Nedergaard M. Brain connexins in demyelinating diseases: therapeutic potential of glial targets. Brain Res 2012; 1487:61-8. [PMID: 22789906 DOI: 10.1016/j.brainres.2012.07.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Revised: 06/29/2012] [Accepted: 07/03/2012] [Indexed: 12/23/2022]
Abstract
Several demyelinating syndromes have been linked to mutations in glial gap junction proteins, the connexins. Although mutations in connexins of the myelinating cells, Schwann cells and oligodendrocytes, were initially described, recent data have shown that astrocytes also play a major role in the demyelination process. Alterations in astrocytic proteins directly affect the oligodendrocytes' ability to maintain myelin structure, and associated astrocytic proteins that regulate water and ionic fluxes, including aquaporins, can also regulate myelin integrity. Here, we will review the main evidence from human disorders and transgenic mouse models that implicate glial gap junction proteins in demyelinating diseases and the therapeutic potential of some of these targets. This article is part of a Special Issue entitled Electrical Synapses.
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Affiliation(s)
- Maria Luisa Cotrina
- Division of Glia Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester Medical School, Rochester, NY 14640, USA.
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23
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Steinlein OK. Ion channel mutations in neuronal diseases: a genetics perspective. Chem Rev 2012; 112:6334-52. [PMID: 22607259 DOI: 10.1021/cr300044d] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ortrud K Steinlein
- Institute of Human Genetics, University Hospital, Ludwig-Maximilians-University , Goethestr. 29, D-80336 Munich, Germany
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24
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Abstract
The axon initial segment (AIS), with its dense clusters of voltage-gated ion channels decorating the axonal membrane, regulates action potential initiation and modulation. The AIS also functions as a barrier to maintain axodendritic polarity, and its precise axonal location contributes to the fine-tuning of neuronal excitability. Therefore, it is not surprising that mutations in AIS-related genes, disruption of the molecular organization of the AIS and altered AIS ion channel expression, function, location and/or density are emerging as key players in neurological disorders. Here, we consider the role of the AIS in nervous system disease and injury.
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Affiliation(s)
- Shelly A Buffington
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, BCM295, Houston, TX 77030, USA
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25
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Tetrodotoxin (TTX) as a therapeutic agent for pain. Mar Drugs 2012; 10:281-305. [PMID: 22412801 PMCID: PMC3296997 DOI: 10.3390/md10020281] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 01/19/2012] [Accepted: 01/19/2012] [Indexed: 12/19/2022] Open
Abstract
Tetrodotoxin (TTX) is a potent neurotoxin that blocks voltage-gated sodium channels (VGSCs). VGSCs play a critical role in neuronal function under both physiological and pathological conditions. TTX has been extensively used to functionally characterize VGSCs, which can be classified as TTX-sensitive or TTX-resistant channels according to their sensitivity to this toxin. Alterations in the expression and/or function of some specific TTX-sensitive VGSCs have been implicated in a number of chronic pain conditions. The administration of TTX at doses below those that interfere with the generation and conduction of action potentials in normal (non-injured) nerves has been used in humans and experimental animals under different pain conditions. These data indicate a role for TTX as a potential therapeutic agent for pain. This review focuses on the preclinical and clinical evidence supporting a potential analgesic role for TTX. In addition, the contribution of specific TTX-sensitive VGSCs to pain is reviewed.
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26
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Yeon KY, Chung G, Kim YH, Hwang JH, Davies AJ, Park MK, Ahn DK, Kim JS, Jung SJ, Oh SB. Eugenol reverses mechanical allodynia after peripheral nerve injury by inhibiting hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Pain 2011; 152:2108-2116. [DOI: 10.1016/j.pain.2011.05.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 04/28/2011] [Accepted: 05/17/2011] [Indexed: 01/23/2023]
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27
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Guillouet M, Gueret G, Rannou F, Giroux-Metges MA, Gioux M, Arvieux CC, Pennec JP. Tumor necrosis factor-α downregulates sodium current in skeletal muscle by protein kinase C activation: involvement in critical illness polyneuromyopathy. Am J Physiol Cell Physiol 2011; 301:C1057-63. [PMID: 21795525 DOI: 10.1152/ajpcell.00097.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Sepsis is involved in the decrease of membrane excitability of skeletal muscle, leading to polyneuromyopathy. This effect is mediated by alterations of the properties of voltage-gated sodium channels (Na(V)), but the exact mechanism is still unknown. The aim of the present study was to check whether tumor necrosis factor (TNF-α), a cytokine released during sepsis, exerts a rapid effect on Na(V). Sodium current (I(Na)) was recorded by macropatch clamp in skeletal muscle fibers isolated from rat peroneus longus muscle, in control conditions and after TNF-α addition. Analyses of dose-effect and time-effect relationships were carried out. Effect of chelerythrine, a PKC inhibitor, was also studied to determine the way of action of TNF-α. TNF-α induced a reversible dose- and time-dependent inhibition of I(Na). A maximum inhibition of 75% of the control current was observed. A shift toward more negative potentials of activation and inactivation curves of I(Na) was also noticed. These effects were prevented by chelerythrine pretreatment. TNF-α is a cytokine released in the early stages of sepsis. Besides a possible transcriptional role, i.e., modification of the channel type and/or number, we demonstrated the existence of a rapid, posttranscriptional inhibition of Na(V) by TNF-α. The downregulation of the sodium current could be mediated by a PKC-induced phosphorylation of the sodium channel, thus leading to a significant decrease in muscle excitability.
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Affiliation(s)
- Maité Guillouet
- Faculté de Médecine et des Sciences de la Santé, Laboratoire de Physiologie, Université de Brest, Brest, France
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28
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Dexmedetomidine and clonidine inhibit the function of Na(v)1.7 independent of α(2)-adrenoceptor in adrenal chromaffin cells. J Anesth 2011; 25:549-57. [PMID: 21607767 DOI: 10.1007/s00540-011-1168-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 04/28/2011] [Indexed: 12/19/2022]
Abstract
PURPOSE Besides being administered systemically for sedation and analgesia, α(2)-agonists such as dexmedetomidine and clonidine have been administered with intrathecal, epidural, or perineural injections, leading to an antinociceptive effect at the spinal cord or peripheral nerve level. However, the mechanism for this remains unclear. In the present study, we examined whether dexmedetomidine and clonidine could inhibit the function of tetrodotoxin-sensitive Na(+) channels, which play important roles in the generation of pain. METHODS Cultured bovine adrenal chromaffin cells expressing the tetrodotoxin-sensitive Na(v)1.7 Na(+) channel isoform were incubated in KRP buffer containing 2 μCi (22)NaCl for 5 min without or with dexmedetomidine or clonidine in the absence or presence of veratridine, α-scorpion venom, β-scorpion venom, Ptychodiscus brevis toxin-3 or ouabain. Cells were then washed and counted radioactively. RESULTS Dexmedetomidine and clonidine reduced veratridine-induced (22)Na(+) influx via Na(v)1.7 in a concentration-dependent manner (EC(50) = 50 μM and 530 μM), even in the presence of ouabain, an inhibitor of Na(+), K(+)-ATPase. Dexmedetomidine and clonidine shifted the concentration-response curve of veratridine for (22)Na(+) influx downward without altering the EC(50) of veratridine. Atipamezole and yohimbine, α(2)-antagonists, did not prevent the inhibition of veratridine-induced (22)Na(+) influx by dexmedetomidine. Dexmedetomidine and clonidine combined with lidocaine induced more inhibition of veratridine-induced (22)Na(+) influx than each drug did individually. Atipamezole and yohimbine did not prevent the lidocaine-enhancing effect of dexmedetomidine and clonidine. CONCLUSION Dexmedetomidine and clonidine inhibit the function of Na(v)1.7 independent of α(2)-adrenoceptor. These results may lead to a deeper understanding of the peripheral antinociceptive effects of α (2)-agonists.
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29
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Ion channels in autoimmune neurodegeneration. FEBS Lett 2011; 585:3836-42. [DOI: 10.1016/j.febslet.2011.03.065] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 03/26/2011] [Accepted: 03/28/2011] [Indexed: 11/23/2022]
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30
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Deng GF, Qin JM, Sun XS, Kuang ZY, Su T, Zhao QH, Shi YW, Liu XR, Yu MJ, Yi YH, Liao WP, Long YS. Promoter analysis of mouse Scn3a gene and regulation of the promoter activity by GC box and CpG methylation. J Mol Neurosci 2011; 44:115-21. [PMID: 21271300 DOI: 10.1007/s12031-011-9492-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 01/11/2011] [Indexed: 01/04/2023]
Abstract
Voltage-gated sodium channel α-subunit type III (Na(v)1.3) is mainly expressed in the central nervous system and is associated with neurological disorders. The expression of mouse Scn3a product (Na(v)1.3) mainly occurs in embryonic and early postnatal brain but not in adult brain. Here, we report for the first time the identification and characterization of the mouse Scn3a gene promoter region and regulation of the promoter activity by GC box and CpG methylation. Luciferase assay showed that the promoter region F1.2 (nt -1,049 to +157) had significantly higher activity in PC12 cells, comparing with that in SH-SY5Y cells and HEK293 cells. A stepwise 5' truncation of the promoter region found that the minimal functional promoter located within the region nt -168 to +157. Deletion of a GC box (nt -254 to -258) in the mouse Scn3a promoter decreased the promoter activity. CpG methylation of the F1.2 without the GC box completely repressed the promoter activity, suggesting that the GC box is a critical element in the CpG-methylated Scn3a promoter. These results suggest that the GC box and CpG methylation might play important roles in regulating mouse Scn3a gene expression.
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Affiliation(s)
- Guang-Fei Deng
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China, Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University, 250 Chang-gang-dong Road, Guangzhou, China
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31
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Sandoval R, Runft B, Roddey T. Pilot Study: Does Lower Extremity Night Splinting Assist in the Management of Painful Peripheral Neuropathy in the HIV/AIDS Population? ACTA ACUST UNITED AC 2010; 9:368-81. [DOI: 10.1177/1545109710373828] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Introduction: The pain associated with peripheral neuropathy (PN) observed in patients living with HIV/AIDS represents a difficult complication to manage. Participants: A total of 22 participants with a diagnosis of PN were recruited to assess the effects of using night splints on pain and sleep quality. Methods: For 3 weeks, the participants were instructed to use bilateral night splints and given an exercise regimen for 3 additional weeks. Scores from pain and sleep questionnaires were analyzed using repeated measures analysis of variance (ANOVA). Results: The change in pain scores (F(1.16) = 13.41,η2 =.456, P = .002) and sleep index scores (z = -2.69, P = .004, 1-tailed) was found to be significant following the use of night splints. No difference was found with the use of the exercises. Discussion: The use of night splints in HIV-infected patients with PN represents an additional tool for managing pain and improving sleep.
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Affiliation(s)
- Roberto Sandoval
- Harris County Hospital District, Rehabilitation Services Department, Thomas Street Health Center, 2015 Thomas St, Houston, TX, USA,
| | - Britt Runft
- Harris County Hospital District, Rehabilitation Services Department, Thomas Street Health Center, 2015 Thomas St, Houston, TX, USA
| | - Toni Roddey
- Texas Woman's University, School of Physical Therapy, Houston, TX, USA
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32
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Abstract
Inherited episodic neurological disorders are often due to mutations in ion channels or their interacting proteins, termed channelopathies. There are a wide variety of such disorders, from those causing paralysis, to extreme pain, to ataxia. A common theme in these is alteration of action potential properties or synaptic transmission and a resulting increased propensity of the resulting tissue to enter into or stay in an altered excitability state. Manifestations of these disorders are triggered by an array of precipitants, all of which stress the particular affected tissue in some way and aid in propelling its activity into an aberrant state. Study of these disorders has aided in the understanding of disease risk factors and elucidated the cause of clinically related sporadic disorders. The findings from study of these disorders will aid in the diagnosis and efficient targeted treatment of affected patients.
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Affiliation(s)
- Devon P Ryan
- Neuroscience Graduate Program, University of California-San Francisco, San Francisco, CA 94158, USA
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Rasband MN. The axon initial segment and the maintenance of neuronal polarity. Nat Rev Neurosci 2010; 11:552-62. [PMID: 20631711 DOI: 10.1038/nrn2852] [Citation(s) in RCA: 329] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ion channel clustering at the axon initial segment (AIS) and nodes of Ranvier has been suggested to be a key evolutionary innovation that enabled the development of the complex vertebrate nervous system. This innovation epitomizes a signature feature of neurons, namely polarity. The mechanisms that establish neuronal polarity, channel clustering and axon-dendrite identity during development are becoming clearer. However, much less is known about how polarity is maintained throughout life. Here, I review the role of the AIS in the development and maintenance of neuronal polarity and discuss how disrupted polarity may be a common component of many diseases and injuries that affect the nervous system.
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Affiliation(s)
- Matthew N Rasband
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
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Graef JD, Godwin DW. Intrinsic plasticity in acquired epilepsy: too much of a good thing? Neuroscientist 2010; 16:487-95. [PMID: 20407126 DOI: 10.1177/1073858409358776] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mechanisms of plasticity are important to the astounding capacity of the brain to adapt and learn. Ion channels are significant contributors to neuronal plasticity, but their dysfunction has been implicated in several nervous system diseases from movement disorders to epilepsy. Although many inherited ion channel mutations have been associated with these disorders, it has been recently recognized that channelopathies can also include aberrant ion channel function that is acquired after an insult or injury to the brain. These acquired alterations are being investigated in animal models of temporal lobe epilepsy, where studies have shown functional changes in voltage-gated ion channels that lead to increases in excitability. Studies of these hyperexcitable neurons have included recordings in the hippocampus, entorhinal cortex, and thalamus and support the existence of an extended seizure network with several nodes of altered activity that are established during epileptogenesis. A better understanding of the key ion channels and brain regions that are responsible for the development of this hyperexcitability, along with the molecular mechanisms involved, may provide novel treatment strategies for epilepsy.
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Affiliation(s)
- John D Graef
- Neuroscience Program, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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35
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Abstract
Nociception is essential for survival whereas pathological pain is maladaptive and often unresponsive to pharmacotherapy. Voltage-gated sodium channels, Na(v)1.1-Na(v)1.9, are essential for generation and conduction of electrical impulses in excitable cells. Human and animal studies have identified several channels as pivotal for signal transmission along the pain axis, including Na(v)1.3, Na(v)1.7, Na(v)1.8, and Na(v)1.9, with the latter three preferentially expressed in peripheral sensory neurons and Na(v)1.3 being upregulated along pain-signaling pathways after nervous system injuries. Na(v)1.7 is of special interest because it has been linked to a spectrum of inherited human pain disorders. Here we review the contribution of these sodium channel isoforms to pain.
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Affiliation(s)
- Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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36
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Nieoullon A. Neurobiologia cellulare e molecolare. Neurologia 2010. [DOI: 10.1016/s1634-7072(10)70491-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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37
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Benfenati V, Ferroni S. Water transport between CNS compartments: functional and molecular interactions between aquaporins and ion channels. Neuroscience 2009; 168:926-40. [PMID: 20026249 DOI: 10.1016/j.neuroscience.2009.12.017] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2009] [Revised: 12/04/2009] [Accepted: 12/05/2009] [Indexed: 12/16/2022]
Abstract
The physiological ability of the mammalian CNS to integrate peripheral stimuli and to convey information to the body is tightly regulated by its capacity to preserve the ion composition and volume of the perineuronal milieu. It is well known that astroglial syncytium plays a crucial role in such process by controlling the homeostasis of ions and water through the selective transmembrane movement of inorganic and organic molecules and the equilibration of osmotic gradients. Astrocytes, in fact, by contacting neurons and cells lining the fluid-filled compartments, are in a strategic position to fulfill this role. They are endowed with ion and water channel proteins that are localized in specific plasma membrane domains facing diverse liquid spaces. Recent data in rodents have demonstrated that the precise dynamics of the astroglia-mediated homeostatic regulation of the CNS is dependent on the interactions between water channels and ion channels, and their anchoring with proteins that allow the formation of macromolecular complexes in specific cellular domains. Interplay can occur with or without direct molecular interactions suggesting the existence of different regulatory mechanisms. The importance of molecular and functional interactions is pinpointed by the numerous observations that as consequence of pathological insults leading to the derangement of ion and volume homeostasis the cell surface expression and/or polarized localization of these proteins is perturbed. Here, we critically discuss the experimental evidence concerning: (1) molecular and functional interplay of aquaporin 4, the major aquaporin protein in astroglial cells, with potassium and gap-junctional channels that are involved in extracellular potassium buffering. (2) the interactions of aquaporin 4 with chloride and calcium channels regulating cell volume homeostasis. The relevance of the crosstalk between water channels and ion channels in the pathogenesis of astroglia-related acute and chronic diseases of the CNS is also briefly discussed.
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Affiliation(s)
- V Benfenati
- Istituto per lo Studio dei Materiali Nanostrutturati, ISMN, National Research Council, Via Gobetti 101, 40129 Bologna, Italy
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38
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Dib-Hajj SD, Black JA, Waxman SG. Voltage-Gated Sodium Channels: Therapeutic Targets for Pain. PAIN MEDICINE 2009; 10:1260-9. [DOI: 10.1111/j.1526-4637.2009.00719.x] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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39
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Biel M, Wahl-Schott C, Michalakis S, Zong X. Hyperpolarization-activated cation channels: from genes to function. Physiol Rev 2009; 89:847-85. [PMID: 19584315 DOI: 10.1152/physrev.00029.2008] [Citation(s) in RCA: 719] [Impact Index Per Article: 47.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels comprise a small subfamily of proteins within the superfamily of pore-loop cation channels. In mammals, the HCN channel family comprises four members (HCN1-4) that are expressed in heart and nervous system. The current produced by HCN channels has been known as I(h) (or I(f) or I(q)). I(h) has also been designated as pacemaker current, because it plays a key role in controlling rhythmic activity of cardiac pacemaker cells and spontaneously firing neurons. Extensive studies over the last decade have provided convincing evidence that I(h) is also involved in a number of basic physiological processes that are not directly associated with rhythmicity. Examples for these non-pacemaking functions of I(h) are the determination of the resting membrane potential, dendritic integration, synaptic transmission, and learning. In this review we summarize recent insights into the structure, function, and cellular regulation of HCN channels. We also discuss in detail the different aspects of HCN channel physiology in the heart and nervous system. To this end, evidence on the role of individual HCN channel types arising from the analysis of HCN knockout mouse models is discussed. Finally, we provide an overview of the impact of HCN channels on the pathogenesis of several diseases and discuss recent attempts to establish HCN channels as drug targets.
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Affiliation(s)
- Martin Biel
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Pharmakologie für Naturwissenschaften, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, Munich D-81377, Germany.
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40
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Meuth SG, Melzer N, Kleinschnitz C, Budde T, Wiendl H. [Multiple sclerosis -- a channelopathy? Targeting ion channels and transporters in inflammatory neurodegeneration]. DER NERVENARZT 2009; 80:422-9. [PMID: 19011824 DOI: 10.1007/s00115-008-2599-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Multiple sclerosis (MS) has traditionally been regarded as an inflammatory demyelinating disorder of the CNS in which clinical symptoms result from axon conduction block caused by myelin degradation. However, typical accumulation of permanent neurological deficits during the clinical course of MS cannot be explained solely by de- and remyelinating processes. It is considered to be rather due to neuronal degeneration, for which several reasons could be identified depending on the state of the disease. First, neurons and their axons can be damaged by infiltrating lymphocytes and macrophages either directly by cell-to-cell contact or by the release of harmful mediators such as nitric oxide or glutamate. Second, indirect injury to neurons and axons may occur through the loss of trophic support by neighbouring oligodendrocytes due to destruction of both the myelin sheath and the oligodendrocyte itself. Third, redistribution of certain voltage- and ligand-gated ion channels and transporters along naked demyelinated axons restores axonal conduction but also leads to excessive spatially restricted electrical activity of the axonal membrane, intracellular calcium accumulation, impairment of mitochondrial function, and subsequent neuronal degeneration. The neuroprotective potential of pharmacological modulation of these channels and transporters using already approved drugs has been demonstrated in several animal studies, is the subject of current clinical trials and will be the topic of this review.
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Affiliation(s)
- S G Meuth
- Klinik für Neurologie, Klinische Forschungsgruppe für Neuroimmunologie, Julius-Maximilians-Universität, Würzburg, Germany.
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41
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Kahn R, Karbat I, Ilan N, Cohen L, Sokolov S, Catterall WA, Gordon D, Gurevitz M. Molecular requirements for recognition of brain voltage-gated sodium channels by scorpion alpha-toxins. J Biol Chem 2009; 284:20684-91. [PMID: 19509294 DOI: 10.1074/jbc.m109.021303] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The scorpion alpha-toxin Lqh2 (from Leiurus quinquestriatus hebraeus) is active at various mammalian voltage-gated sodium channels (Na(v)s) and is inactive at insect Na(v)s. To resolve the molecular basis of this preference we used the following strategy: 1) Lqh2 was expressed in recombinant form and key residues important for activity at the rat brain channel rNa(v)1.2a were identified by mutagenesis. These residues form a bipartite functional surface made of a conserved "core domain" (residues of the loops connecting the secondary structure elements of the molecule core), and a variable "NC domain" (five-residue turn and the C-tail) as was reported for other scorpion alpha-toxins. 2) The functional role of the two domains was validated by their stepwise construction on the similar scaffold of the anti-insect toxin LqhalphaIT. Analysis of the activity of the intermediate constructs highlighted the critical role of Phe(15) of the core domain in toxin potency at rNa(v)1.2a, and has suggested that the shape of the NC-domain is important for toxin efficacy. 3) Based on these findings and by comparison with other scorpion alpha-toxins we were able to eliminate the activity of Lqh2 at rNa(v)1.4 (skeletal muscle), hNa(v)1.5 (cardiac), and rNa(v)1.6 channels, with no hindrance of its activity at Na(v)1.1-1.3. These results suggest that by employing a similar approach the design of further target-selective sodium channel modifiers is imminent.
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Affiliation(s)
- Roy Kahn
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat-Aviv 69978, Tel Aviv, Israel
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42
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Novak KR, Nardelli P, Cope TC, Filatov G, Glass JD, Khan J, Rich MM. Inactivation of sodium channels underlies reversible neuropathy during critical illness in rats. J Clin Invest 2009; 119:1150-8. [PMID: 19425168 DOI: 10.1172/jci36570] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Neuropathy and myopathy can cause weakness during critical illness. To determine whether reduced excitability of peripheral nerves, rather than degeneration, is the mechanism underlying acute neuropathy in critically ill patients, we prospectively followed patients during the acute phase of critical illness and early recovery and assessed nerve conduction. During the period of early recovery from critical illness, patients recovered from neuropathy within days. This rapidly reversible neuropathy has not to our knowledge been previously described in critically ill patients and may be a novel type of neuropathy. In vivo intracellular recordings from dorsal root axons in septic rats revealed reduced action potential amplitude, demonstrating that reduced excitability of nerve was the mechanism underlying neuropathy. When action potentials were triggered by hyperpolarizing pulses, their amplitudes largely recovered, indicating that inactivation of sodium channels was an important contributor to reduced excitability. There was no depolarization of axon resting potential in septic rats, which ruled out a contribution of resting potential to the increased inactivation of sodium channels. Our data suggest that a hyperpolarized shift in the voltage dependence of sodium channel inactivation causes increased sodium inactivation and reduced excitability. Acquired sodium channelopathy may be the mechanism underlying acute neuropathy in critically ill patients.
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Affiliation(s)
- Kevin R Novak
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, Ohio 45435, USA
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43
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Gargus JJ. Genetic calcium signaling abnormalities in the central nervous system: seizures, migraine, and autism. Ann N Y Acad Sci 2009; 1151:133-56. [PMID: 19154521 DOI: 10.1111/j.1749-6632.2008.03572.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The calcium ion is one of the most versatile, ancient, and universal of biological signaling molecules, known to regulate physiological systems at every level from membrane potential and ion transporters to kinases and transcription factors. Disruptions of intracellular calcium homeostasis underlie a host of emerging diseases, the calciumopathies. Cytosolic calcium signals originate either as extracellular calcium enters through plasma membrane ion channels or from the release of an intracellular store in the endoplasmic reticulum (ER) via inositol triphosphate receptor and ryanodine receptor channels. Therefore, to a large extent, calciumopathies represent a subset of the channelopathies, but include regulatory pathways and the mitochondria, the major intracellular calcium repository that dynamically participates with the ER stores in calcium signaling, thereby integrating cellular energy metabolism into these pathways, a process of emerging importance in the analysis of the neurodegenerative and neuropsychiatric diseases. Many of the calciumopathies are common complex polygenic diseases, but leads to their understanding come most prominently from rare monogenic channelopathy paradigms. Monogenic forms of common neuronal disease phenotypes-such as seizures, ataxia, and migraine-produce a constitutionally hyperexcitable tissue that is susceptible to periodic decompensations. The gene families and genetic lesions underlying familial hemiplegic migraine, FHM1/CACNA1A, FHM2/ATP1A2, and FHM3/SCN1A, and monogenic mitochondrial migraine syndromes, provide a robust platform from which genes, such as CACNA1C, which encodes the calcium channel mutated in Timothy syndrome, can be evaluated for their role in autism and bipolar disease.
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Affiliation(s)
- J Jay Gargus
- Department of Physiology & Biophysics, Section of Human Genetics, School of Medicine, University of California-Irvine, Irvine, CA 92697, USA.
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44
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Vleggeert-Lankamp CLAM, Wolfs J, Pêgo AP, van den Berg R, Feirabend H, Lakke E. Effect of nerve graft porosity on the refractory period of regenerating nerve fibers. J Neurosurg 2008; 109:294-305. [PMID: 18671643 DOI: 10.3171/jns/2008/109/8/0294] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT In the present study the authors consider the influence of the porosity of synthetic nerve grafts on peripheral nerve regeneration. METHODS Microporous (1-13 microm) and nonporous nerve grafts made of a copolymer of trimethylene carbonate and epsilon-caprolactone were tested in an animal model. Twelve weeks after surgery, nerve and muscle morphological and electrophysiological results of regenerated nerves that had grown through the synthetic nerve grafts were compared with autografted and untreated (control) sciatic nerves. Based on the observed changes in the number and diameter of the nerve fibers, the predicted values of the electrophysiological parameters were calculated. RESULTS The values of the morphometric parameters of the peroneal nerves and the gastrocnemius and anterior tibial muscles were similar if not equal in the rats receiving synthetic nerve grafts. The refractory periods, however, were shorter in porous compared with nonporous grafted nerves, and thus were closer to control values. CONCLUSIONS A shorter refractory period enables the axon to follow the firing frequency of the neuron more effectively and allows a more adequate target organ stimulation. Therefore, porous are preferred over nonporous nerve grafts.
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45
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Ng K, Howells J, Pollard JD, Burke D. Up-regulation of slow K(+) channels in peripheral motor axons: a transcriptional channelopathy in multiple sclerosis. ACTA ACUST UNITED AC 2008; 131:3062-71. [PMID: 18697908 DOI: 10.1093/brain/awn180] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Spinal lesions produce plastic changes in motoneuron properties. We have documented the excitability of motor axons in the median nerve of 12 patients with multiple sclerosis and 50 normal subjects, hypothesizing that plastic changes in the properties of spinal motoneurons might be reflected in the properties of peripheral motor axons and be demonstrable in vivo. In the patients, there were changes in physiological measures of axonal excitability attributable to increased slow K(+) channel activity. Other measures were within control limits. These changes could be modelled by an 11% increase in slow K(+) current, with compensatory changes in membrane potential, suggesting increased expression of the responsible channels. The changes cannot be explained solely by changes in membrane potential and are not those expected if peripheral nerve axons were involved in the inflammatory process of multiple sclerosis. They probably represent a transcriptional channelopathy, due to up-regulation of channel expression. The abnormalities do not imply that peripheral nerve function has been significantly compromised, but they do suggest that the properties of the parent motoneurons have changed. This study thus provides evidence for plasticity in motoneuronal properties at a molecular level, the first such evidence for intact human subjects.
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Affiliation(s)
- Karl Ng
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and The University of Sydney, Sydney, NSW, Australia.
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46
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Shi XZ, Sarna SK. Gene therapy of Cav1.2 channel with VIP and VIP receptor agonists and antagonists: a novel approach to designing promotility and antimotility agents. Am J Physiol Gastrointest Liver Physiol 2008; 295:G187-G196. [PMID: 18467505 PMCID: PMC2494720 DOI: 10.1152/ajpgi.00047.2008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Recent findings show that the enteric neurotransmitter VIP enhances gene transcription of the alpha1C subunit of Cav1.2 (L-type) Ca2+ channels in the primary cultures of human colonic circular smooth muscle cells and circular smooth muscle strips. In this study, we investigated whether systemic infusion of VIP in intact animals enhances the gene transcription and protein expression of these channels to accelerate colonic transit. We also investigated whether similar systemic infusions of VPAC1/2 receptor antagonist retards colonic transit by repressing the constitutive gene expression of the alpha1C subunit. We found that the systemic infusion of VIP for 7 days by a surgically implanted osmotic pump enhances the gene and protein expression of the alpha1C subunit and circular muscle contractility in the proximal and the middle rat colons, but not in the distal colon. A similar systemic infusion of VPAC1/2 receptor antagonist represses the expression of the alpha1C subunit and circular smooth muscle contractility in the proximal and the middle colons. The VIP infusion accelerates colonic transit and pellet defecation by rats, whereas the infusion of VPAC1/2 receptor antagonist retards colonic transit and pellet defecation. VPAC1 receptors, but not VPAC2 receptors, mediate the above gene transcription-induced promotility effects of VIP. We conclude that VIP and VPAC(1) receptor agonists may serve as potential promotility agents in constipation-like conditions, whereas VPAC receptor antagonists may serve as potential antimotility agents in diarrhea-like conditions produced by enhanced motility function.
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Affiliation(s)
- Xuan-Zheng Shi
- Enteric Neuromuscular Disorders and Visceral Pain Center, Division of Gastroenterology, Department of Internal Medicine, and Department of Neuroscience and Cell Biology, The University of Texas Medical Branch at Galveston, Galveston, Texas
| | - Sushil K. Sarna
- Enteric Neuromuscular Disorders and Visceral Pain Center, Division of Gastroenterology, Department of Internal Medicine, and Department of Neuroscience and Cell Biology, The University of Texas Medical Branch at Galveston, Galveston, Texas
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47
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Lampert A, O'Reilly AO, Dib-Hajj SD, Tyrrell L, Wallace BA, Waxman SG. A pore-blocking hydrophobic motif at the cytoplasmic aperture of the closed-state Nav1.7 channel is disrupted by the erythromelalgia-associated F1449V mutation. J Biol Chem 2008; 283:24118-27. [PMID: 18550534 DOI: 10.1074/jbc.m802900200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sodium channel Na(v)1.7 has recently elicited considerable interest as a key contributor to human pain. Gain-of-function mutations of Na(v)1.7 produce painful disorders, whereas loss-of-function Na(v)1.7 mutations produce insensitivity to pain. The inherited erythromelalgia Na(v)1.7/F1449V mutation, within the C terminus of domain III/transmembrane helix S6, shifts channel activation by -7.2 mV and accelerates time to peak, leading to nociceptor hyperexcitability. We constructed a homology model of Na(v)1.7, based on the KcsA potassium channel crystal structure, which identifies four phylogenetically conserved aromatic residues that correspond to DIII/F1449 at the C-terminal end of each of the four S6 helices. The model predicted that changes in side-chain size of residue 1449 alter the pore's cytoplasmic aperture diameter and reshape inter-domain contact surfaces that contribute to closed state stabilization. To test this hypothesis, we compared activation of wild-type and mutant Na(v)1.7 channels F1449V/L/Y/W by whole cell patch clamp analysis. All but the F1449V mutation conserve the voltage dependence of activation. Compared with wild type, time to peak was shorter in F1449V, similar in F1449L, but longer for F1449Y and F1449W, suggesting that a bulky, hydrophobic residue is necessary for normal activation. We also substituted the corresponding aromatic residue of S6 in each domain individually with valine, to mimic the naturally occurring Na(v)1.7 mutation. We show that DII/F960V and DIII/F1449V, but not DI/Y405V or DIV/F1752V, regulate Na(v)1.7 activation, consistent with well established conformational changes in DII and DIII. We propose that the four aromatic residues contribute to the gate at the cytoplasmic pore aperture, and that their ring side chains form a hydrophobic plug which stabilizes the closed state of Na(v)1.7.
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Affiliation(s)
- Angelika Lampert
- Department of Neurology and Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
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48
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Puhl HL, Ikeda SR. Identification of the sensory neuron specific regulatory region for the mouse gene encoding the voltage-gated sodium channel NaV1.8. J Neurochem 2008; 106:1209-24. [PMID: 18466327 DOI: 10.1111/j.1471-4159.2008.05466.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Voltage-gated sodium channels (VGSC) are critical membrane components that participate in the electrical activity of excitable cells. The type one VGSC family includes the tetrodotoxin insensitive sodium channel, Na(V)1.8, encoded by the Scn10a gene. Na(V)1.8 expression is restricted to small and medium diameter nociceptive sensory neurons of the dorsal root ganglia and cranial sensory ganglia. To understand the stringent transcriptional regulation of the Scn10a gene, the sensory neuron specific promoter was functionally identified. While identifying the mRNA 5'-end, alternative splicing within the 5'-UTR was observed to create heterogeneity in the RNA transcript. Four kilobases of upstream genomic DNA was cloned and the presence of tissue specific promoter activity was tested by microinjection and adenoviral infection of fluorescent protein reporter constructs into primary mouse and rat neurons, and cell lines. The region contained many putative transcription factor-binding sites and strong homology with the predicted rat ortholog. Homology to the predicted human ortholog was limited to the proximal end and several conserved cis elements were noted. Two regulatory modules were identified by microinjection of reporter constructs into dorsal root ganglia and superior cervical ganglia neurons: a neuron specific proximal promoter region between -1.6 and -0.2 kb of the transcription start site cluster, and a distal sensory neuron switch region beyond -1.6 kb that restricted fluorescent protein expression to a subset of primary sensory neurons.
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Affiliation(s)
- Henry L Puhl
- Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892-9411, USA.
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Hilber K. Skeletal myocyte plasticity: basis for improved therapeutic potential? Curr Opin Pharmacol 2008; 8:327-32. [PMID: 18329336 DOI: 10.1016/j.coph.2008.01.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 01/18/2008] [Accepted: 01/25/2008] [Indexed: 12/25/2022]
Abstract
Skeletal muscle tissue exhibits a remarkable capacity to regenerate after injury and to adapt its properties in response to altered functional demands or environmental pressure. This potential renders skeletal myocytes especially attractive candidates to be used in therapeutic strategies. Besides the well-described adaptability of skeletal myocytes in terms of contractile function and metabolic profile, more recent research has revealed that the electrophysiological properties of myocytes are also subject to significant changes both under physiological conditions and in pathophysiological situations. A better understanding of skeletal myocyte plasticity, its regulation and its forced induction could improve existing therapeutic approaches and may pave the way for new therapeutic strategies.
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Affiliation(s)
- Karlheinz Hilber
- Center of Biomolecular Medicine and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13A, 1090 Vienna, Austria.
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50
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Richichi C, Brewster AL, Bender RA, Simeone TA, Zha Q, Yin HZ, Weiss JH, Baram TZ. Mechanisms of seizure-induced 'transcriptional channelopathy' of hyperpolarization-activated cyclic nucleotide gated (HCN) channels. Neurobiol Dis 2008; 29:297-305. [PMID: 17964174 PMCID: PMC2292123 DOI: 10.1016/j.nbd.2007.09.003] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 09/13/2007] [Accepted: 09/16/2007] [Indexed: 12/20/2022] Open
Abstract
Epilepsy may result from abnormal function of ion channels, such as those caused by genetic mutations. Recently, pathological alterations of the expression or localization of normal channels have been implicated in epilepsy generation, and termed 'acquired channelopathies'. Altered expression levels of the HCN channels - that conduct the hyperpolarization-activated current, I(h) - have been demonstrated in hippocampus of patients with severe temporal lobe epilepsy as well as in animal models of temporal lobe and absence epilepsies. Here we probe the mechanisms for the altered expression of HCN channels which is provoked by seizures. In organotypic hippocampal slice cultures, seizure-like events selectively reduced HCN type 1 channel expression and increased HCN2 mRNA levels, as occurs in vivo. The mechanisms for HCN1 reduction involved Ca(2+)-permeable AMPA receptor-mediated Ca(2+) influx, and subsequent activation of Ca(2+)/calmodulin-dependent protein kinase II. In contrast, upregulation of HCN2 expression was independent of these processes. The data demonstrate an orchestrated program for seizure-evoked transcriptional channelopathy involving the HCN channels that may contribute to certain epilepsies.
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Affiliation(s)
- Cristina Richichi
- Dept. Anatomy & Neurobiology, University of California, Irvine, CA 92697-4475
| | - Amy L. Brewster
- Dept. Anatomy & Neurobiology, University of California, Irvine, CA 92697-4475
| | - Roland A. Bender
- Dept. Pediatrics, University of California, Irvine, CA 92697-4475
| | - Timothy A. Simeone
- Dept. Anatomy & Neurobiology, University of California, Irvine, CA 92697-4475
| | - Qinqin Zha
- Dept. Pediatrics, University of California, Irvine, CA 92697-4475
| | - Hong Z. Yin
- Dept. Neurology, University of California, Irvine, CA 92697-4475
| | - John H. Weiss
- Dept. Anatomy & Neurobiology, University of California, Irvine, CA 92697-4475
- Dept. Neurology, University of California, Irvine, CA 92697-4475
| | - Tallie Z. Baram
- Dept. Anatomy & Neurobiology, University of California, Irvine, CA 92697-4475
- Dept. Pediatrics, University of California, Irvine, CA 92697-4475
- Dept. Neurology, University of California, Irvine, CA 92697-4475
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