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Nishimura M, Taniguchi S, Tamaoki S, Fujita T. Inhibition of compound action potentials in the frog sciatic nerve by inchinkoto, a traditional Japanese medicine used for oral mucositis. J Oral Biosci 2024; 66:420-429. [PMID: 38490561 DOI: 10.1016/j.job.2024.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 03/01/2024] [Accepted: 03/04/2024] [Indexed: 03/17/2024]
Abstract
OBJECTIVE This study aimed to determine the effects of traditional Japanese (Kampo) medicines used to treat oral mucositis on nerve conduction. METHODS The effects of Kampo medicines, crude drugs, and chemical compounds on compound action potentials (CAPs) were analyzed using extracellular recordings in frog sciatic nerves. RESULTS Among the Kampo medicines, inchinkoto demonstrated the most significant reduction in CAP amplitude, with a half-maximal inhibitory concentration (IC50) of 5.4 mg/mL. Hangeshashinto, shosaikoto, hochuekkito, and juzentaihoto also showed a significant reduction. Regarding inchinkoto, Artemisiae Capillari Spica (artemisia) was the most effective crude drug, with an IC50 of 4.2 mg/mL for CAP amplitude reduction, whereas Gardeniae Fructus (gardenia) exerted no significant effect. However, the combined use of artemisia and gardenia reduced the CAP amplitude more effectively than artemisia alone, indicating a synergistic interaction. The chemical ingredient eugenol from artemisia administered at 1 and 3 mmol/L reduced CAP amplitude, whereas other chemical ingredients administered at 0.1 and 1 mmol/L had no significant effects. CONCLUSIONS Inchinkoto exhibited the most effective reduction in CAP amplitude in the sciatic nerve of frogs, primarily through the action of artemisia, with potential synergistic interaction between artemisia and gardenia.
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Affiliation(s)
- Mayuko Nishimura
- Department of Oral Growth and Development, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan; Department of Physiological Science and Molecular Biology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan.
| | - Suguru Taniguchi
- Department of Biochemistry, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan.
| | - Sachio Tamaoki
- Department of Oral Growth and Development, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan.
| | - Tsugumi Fujita
- Department of Physiological Science and Molecular Biology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan.
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2
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Elleman AV, Du Bois J. Chemical and Biological Tools for the Study of Voltage-Gated Sodium Channels in Electrogenesis and Nociception. Chembiochem 2022; 23:e202100625. [PMID: 35315190 PMCID: PMC9359671 DOI: 10.1002/cbic.202100625] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 02/22/2022] [Indexed: 12/17/2022]
Abstract
The malfunction and misregulation of voltage-gated sodium channels (NaV s) underlie in large part the electrical hyperexcitability characteristic of chronic inflammatory and neuropathic pain. NaV s are responsible for the initiation and propagation of electrical impulses (action potentials) in cells. Tissue and nerve injury alter the expression and localization of multiple NaV isoforms, including NaV 1.1, 1.3, and 1.6-1.9, resulting in aberrant action potential firing patterns. To better understand the role of NaV regulation, localization, and trafficking in electrogenesis and pain pathogenesis, a number of chemical and biological reagents for interrogating NaV function have been advanced. The development and application of such tools for understanding NaV physiology are the focus of this review.
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Affiliation(s)
- Anna V Elleman
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - J Du Bois
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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3
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Alles SRA, Smith PA. Peripheral Voltage-Gated Cation Channels in Neuropathic Pain and Their Potential as Therapeutic Targets. FRONTIERS IN PAIN RESEARCH 2022; 2:750583. [PMID: 35295464 PMCID: PMC8915663 DOI: 10.3389/fpain.2021.750583] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 11/10/2021] [Indexed: 11/25/2022] Open
Abstract
The persistence of increased excitability and spontaneous activity in injured peripheral neurons is imperative for the development and persistence of many forms of neuropathic pain. This aberrant activity involves increased activity and/or expression of voltage-gated Na+ and Ca2+ channels and hyperpolarization activated cyclic nucleotide gated (HCN) channels as well as decreased function of K+ channels. Because they display limited central side effects, peripherally restricted Na+ and Ca2+ channel blockers and K+ channel activators offer potential therapeutic approaches to pain management. This review outlines the current status and future therapeutic promise of peripherally acting channel modulators. Selective blockers of Nav1.3, Nav1.7, Nav1.8, Cav3.2, and HCN2 and activators of Kv7.2 abrogate signs of neuropathic pain in animal models. Unfortunately, their performance in the clinic has been disappointing; some substances fail to meet therapeutic end points whereas others produce dose-limiting side effects. Despite this, peripheral voltage-gated cation channels retain their promise as therapeutic targets. The way forward may include (i) further structural refinement of K+ channel activators such as retigabine and ASP0819 to improve selectivity and limit toxicity; use or modification of Na+ channel blockers such as vixotrigine, PF-05089771, A803467, PF-01247324, VX-150 or arachnid toxins such as Tap1a; the use of Ca2+ channel blockers such as TTA-P2, TTA-A2, Z 944, ACT709478, and CNCB-2; (ii) improving methods for assessing “pain” as opposed to nociception in rodent models; (iii) recognizing sex differences in pain etiology; (iv) tailoring of therapeutic approaches to meet the symptoms and etiology of pain in individual patients via quantitative sensory testing and other personalized medicine approaches; (v) targeting genetic and biochemical mechanisms controlling channel expression using anti-NGF antibodies such as tanezumab or re-purposed drugs such as vorinostat, a histone methyltransferase inhibitor used in the management of T-cell lymphoma, or cercosporamide a MNK 1/2 inhibitor used in treatment of rheumatoid arthritis; (vi) combination therapy using drugs that are selective for different channel types or regulatory processes; (vii) directing preclinical validation work toward the use of human or human-derived tissue samples; and (viii) application of molecular biological approaches such as clustered regularly interspaced short palindromic repeats (CRISPR) technology.
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Affiliation(s)
- Sascha R A Alles
- Department of Anesthesiology and Critical Care Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Peter A Smith
- Department of Pharmacology, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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4
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Mechanisms Underlying the Selective Therapeutic Efficacy of Carbamazepine for Attenuation of Trigeminal Nerve Injury Pain. J Neurosci 2021; 41:8991-9007. [PMID: 34446571 DOI: 10.1523/jneurosci.0547-21.2021] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 08/02/2021] [Accepted: 08/03/2021] [Indexed: 11/21/2022] Open
Abstract
Different peripheral nerve injuries cause neuropathic pain through distinct mechanisms. Even the site of injury may impact underlying mechanisms, as indicated by the clinical finding that the antiseizure drug carbamazepine (CBZ) relieves pain because of compression injuries of trigeminal but not somatic nerves. We leveraged this observation in the present study hypothesizing that because CBZ blocks voltage-gated sodium channels (VGSCs), its therapeutic selectivity reflects differences between trigeminal and somatic nerves with respect to injury-induced changes in VGSCs. CBZ diminished ongoing and evoked pain behavior in rats with chronic constriction injury (CCI) to the infraorbital nerve (ION) but had minimal effect in rats with sciatic nerve CCI. This difference in behavior was associated with a selective increase in the potency of CBZ-induced inhibition of compound action potentials in the ION, an effect mirrored in human trigeminal versus somatic nerves. The increase in potency was associated with a selective increase in the efficacy of the NaV1.1 channel blocker ICA-121431 and NaV1.1 protein in the ION, but no change in NaV1.1 mRNA in trigeminal ganglia. Importantly, local ICA-121431 administration reversed ION CCI-induced hypersensitivity. Our results suggest a novel therapeutic target for the treatment of trigeminal neuropathic pain.SIGNIFICANCE STATEMENT This study is based on evidence of differences in pain and its treatment depending on whether the pain is above (trigeminal) or below (somatic) the neck, as well as evidence that voltage-gated sodium channels (VGSCs) may contribute to these differences. The focus of the present study was on channels underlying action potential propagation in peripheral nerves. There were differences between somatic and trigeminal nerves in VGSC subtypes underlying action potential propagation both in the absence and presence of injury. Importantly, because the local block of NaV1.1 in the trigeminal nerve reverses nerve injury-induced mechanical hypersensitivity, the selective upregulation of NaV1.1 in trigeminal nerves suggests a novel therapeutic target for the treatment of pain associated with trigeminal nerve injury.
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5
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Goodwin G, McMahon SB. The physiological function of different voltage-gated sodium channels in pain. Nat Rev Neurosci 2021; 22:263-274. [PMID: 33782571 DOI: 10.1038/s41583-021-00444-w] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/12/2021] [Indexed: 02/01/2023]
Abstract
Evidence from human genetic pain disorders shows that voltage-gated sodium channel α-subtypes Nav1.7, Nav1.8 and Nav1.9 are important in the peripheral signalling of pain. Nav1.7 is of particular interest because individuals with Nav1.7 loss-of-function mutations are congenitally insensitive to acute and chronic pain, and there is considerable hope that phenocopying these effects with a pharmacological antagonist will produce a new class of analgesic drug. However, studies in these rare individuals do not reveal how and where voltage-gated sodium channels contribute to pain signalling, which is of critical importance for drug development. More than a decade of research utilizing rodent genetic models and pharmacological tools to study voltage-gated sodium channels in pain has begun to unravel the role of different subtypes. Here, we review the contribution of individual channel subtypes in three key physiological processes necessary for transmission of sensory information to the CNS: transduction of stimuli at peripheral nerve terminals, axonal transmission of action potentials and neurotransmitter release from central terminals. These data suggest that drugs seeking to recapitulate the analgesic effects of loss of function of Nav1.7 will need to be brain-penetrant - which most of those developed to date are not.
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Affiliation(s)
- George Goodwin
- Pain and Neurorestoration Group, King's College London, London, UK.
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6
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Pathogenic mechanisms of lipid mediator lysophosphatidic acid in chronic pain. Prog Lipid Res 2020; 81:101079. [PMID: 33259854 DOI: 10.1016/j.plipres.2020.101079] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 11/22/2020] [Accepted: 11/23/2020] [Indexed: 02/07/2023]
Abstract
A number of membrane lipid-derived mediators play pivotal roles in the initiation, maintenance, and regulation of various types of acute and chronic pain. Acute pain, comprising nociceptive and inflammatory pain warns us about the presence of damage or harmful stimuli. However, it can be efficiently reversed by opioid analgesics and anti-inflammatory drugs. Prostaglandin E2 and I2, the representative lipid mediators, are well-known causes of acute pain. However, some lipid mediators such as lipoxins, resolvins or endocannabinoids suppress acute pain. Various types of peripheral and central neuropathic pain (NeuP) as well as fibromyalgia (FM) are representatives of chronic pain and refractory owing to abnormal pain processing distinct from acute pain. Accumulating evidence demonstrated that lipid mediators represented by lysophosphatidic acid (LPA) are involved in the initiation and maintenance of both NeuP and FM in experimental animal models. The LPAR1-mediated peripheral mechanisms including dorsal root demyelination, Cavα2δ1 expression in dorsal root ganglion, and LPAR3-mediated amplification of central LPA production via glial cells are involved in the series of molecular mechanisms underlying NeuP. This review also discusses the involvement of lipid mediators in emerging research directives, including itch-sensing, sexual dimorphism, and the peripheral immune system.
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7
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Kushnarev M, Pirvulescu IP, Candido KD, Knezevic NN. Neuropathic pain: preclinical and early clinical progress with voltage-gated sodium channel blockers. Expert Opin Investig Drugs 2020; 29:259-271. [PMID: 32070160 DOI: 10.1080/13543784.2020.1728254] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Introduction: Neuropathic pain is a chronic condition that significantly affects the quality of life of millions of people globally. Most of the pharmacologic treatments currently in use demonstrate modest efficacy and over half of all patients do not respond to medical management. Hence, there is a need for new, efficacious drugs. Evidence points toward voltage-gated sodium channels as a key target for novel analgesics.Area covered: The role of voltage-gated sodium channels in pain pathophysiology is illuminated and the preclinical and clinical data for new sodium channel blockers and toxin-derived lead compounds are examined. The expansion of approved sodium channel blockers is discussed along with the limitations of current research, trends in drug development, and the potential of personalized medicine.Expert opinion: The transition from preclinical to clinical studies can be difficult because of the inherent inability of animal models to express the complexities of pain states. Pain pathways are notoriously intricate and may be pharmacologically modulated at a variety of targets; it is unlikely that action at a single target could completely abolish a pain response because pain is rarely unifactorial. Combination therapy may be necessary and this could further confound the discovery of novel agents.
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Affiliation(s)
- Mikhail Kushnarev
- Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, IL, USA
| | - Iulia Paula Pirvulescu
- Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, IL, USA
| | - Kenneth D Candido
- Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, IL, USA.,Department of Anesthesiology, College of Medicine, University of Illinois, Chicago, IL, USA.,Department of Surgery, College of Medicine, University of Illinois, Chicago, IL, USA
| | - Nebojsa Nick Knezevic
- Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, IL, USA.,Department of Anesthesiology, College of Medicine, University of Illinois, Chicago, IL, USA.,Department of Surgery, College of Medicine, University of Illinois, Chicago, IL, USA
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8
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Tummanapalli SS, Issar T, Kwai N, Poynten A, Krishnan AV, Willcox M, Markoulli M. Association of corneal nerve loss with markers of axonal ion channel dysfunction in type 1 diabetes. Clin Neurophysiol 2020; 131:145-154. [DOI: 10.1016/j.clinph.2019.09.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/29/2019] [Accepted: 09/29/2019] [Indexed: 01/06/2023]
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9
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Spider Knottin Pharmacology at Voltage-Gated Sodium Channels and Their Potential to Modulate Pain Pathways. Toxins (Basel) 2019; 11:toxins11110626. [PMID: 31671792 PMCID: PMC6891507 DOI: 10.3390/toxins11110626] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 10/24/2019] [Accepted: 10/24/2019] [Indexed: 12/15/2022] Open
Abstract
Voltage-gated sodium channels (NaVs) are a key determinant of neuronal signalling. Neurotoxins from diverse taxa that selectively activate or inhibit NaV channels have helped unravel the role of NaV channels in diseases, including chronic pain. Spider venoms contain the most diverse array of inhibitor cystine knot (ICK) toxins (knottins). This review provides an overview on how spider knottins modulate NaV channels and describes the structural features and molecular determinants that influence their affinity and subtype selectivity. Genetic and functional evidence support a major involvement of NaV subtypes in various chronic pain conditions. The exquisite inhibitory properties of spider knottins over key NaV subtypes make them the best lead molecules for the development of novel analgesics to treat chronic pain.
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10
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Kiernan MC, Bostock H, Park SB, Kaji R, Krarup C, Krishnan AV, Kuwabara S, Lin CSY, Misawa S, Moldovan M, Sung J, Vucic S, Wainger BJ, Waxman S, Burke D. Measurement of axonal excitability: Consensus guidelines. Clin Neurophysiol 2019; 131:308-323. [PMID: 31471200 DOI: 10.1016/j.clinph.2019.07.023] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 07/17/2019] [Accepted: 07/24/2019] [Indexed: 12/12/2022]
Abstract
Measurement of axonal excitability provides an in vivo indication of the properties of the nerve membrane and of the ion channels expressed on these axons. Axonal excitability techniques have been utilised to investigate the pathophysiological mechanisms underlying neurological diseases. This document presents guidelines derived for such studies, based on a consensus of international experts, and highlights the potential difficulties when interpreting abnormalities in diseased axons. The present manuscript provides a state-of-the-art review of the findings of axonal excitability studies and their interpretation, in addition to suggesting guidelines for the optimal performance of excitability studies.
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Affiliation(s)
- Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia.
| | - Hugh Bostock
- UCL Queen Square Institute of Neurology, London WC1N 3BG, United Kingdom
| | - Susanna B Park
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Ryuji Kaji
- National Utano Hospital, 8-Narutaki Ondoyamacho, Ukyoku, Kyoto 616-8255, Japan
| | - Christian Krarup
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Satoshi Kuwabara
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Cindy Shin-Yi Lin
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Sonoko Misawa
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Mihai Moldovan
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Jiaying Sung
- Taipei Medical University, Wanfang Hospital, Taipei, Taiwan
| | - Steve Vucic
- Department of Neurology, Westmead Hospital, Western Clinical School, University of Sydney, Australia
| | - Brian J Wainger
- Department of Neurology and Anesthesiology, Critical Care & Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Stephen Waxman
- Department of Neurology, Yale Medical School, New Haven, CT 06510, USA; Neurorehabilitation Research Center, Veterans Affairs Hospital, West Haven, CT 06516, USA
| | - David Burke
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
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11
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Zhang J, Yang X, Zhou Y, Fox H, Xiong H. Direct contacts of microglia on myelin sheath and Ranvier's node in the corpus callosum in rats. J Biomed Res 2019; 33:192-200. [PMID: 30403198 PMCID: PMC6551421 DOI: 10.7555/jbr.32.20180019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Over the recent years, it has been found that microglia pseudopodia contact synapses, detect sick ones and prune them, even in adult animals. Myelinated nerves also carry out plasticity in which microglia remove myelin debris by phagocytosis. However, it remains unknown whether microglia explore structures on nerve fibers, such as Ranvier's node (RN) or myelin sheath, before they become debris. By double or triple staining RNs or myelin sheathes and microglia in healthy rat corpus callosum, this study unveiled direct contacts of microglia pseudopodia with RNs and with para- and inter-nodal myelin sheathes, which was then verified by electron microscopic observations. Our data indicated that microglia also explore unmyelinated nerve fibers. Furthermore, we used the animals with matured white matter; therefore, microglia may be actively involved in plasticity of matured white matter tracts as it does for synapse pruning, instead of only passively phagocytize myelin debris.
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Affiliation(s)
- Jingdong Zhang
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Xinglong Yang
- Department of Clinical and Scientific Training, Affiliated Hospital to Academy of Military Medicine Sciences, Beijing 100071, China
| | - You Zhou
- Center for Biotechnology, University of Nebraska at Lincoln, School of Veterinary Medicine and Biomedical Sciences, Lincoln, NE 68588, USA
| | - Howard Fox
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Huangui Xiong
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
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12
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Israel MR, Tanaka BS, Castro J, Thongyoo P, Robinson SD, Zhao P, Deuis JR, Craik DJ, Durek T, Brierley SM, Waxman SG, Dib-Hajj SD, Vetter I. Na V 1.6 regulates excitability of mechanosensitive sensory neurons. J Physiol 2019; 597:3751-3768. [PMID: 31087362 DOI: 10.1113/jp278148] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 05/08/2019] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Voltage-gated sodium channels are critical for peripheral sensory neuron transduction and have been implicated in a number of painful and painless disorders. The β-scorpion toxin, Cn2, is selective for NaV 1.6 in dorsal root ganglion neurons. NaV 1.6 plays an essential role in peripheral sensory neurons, specifically at the distal terminals of mechanosensing fibres innervating the skin and colon. NaV 1.6 activation also leads to enhanced response to mechanical stimulus in vivo. This works highlights the use of toxins in elucidating pain pathways moreover the importance of non-peripherally restricted NaV isoforms in pain generation. ABSTRACT Peripheral sensory neurons express multiple voltage-gated sodium channels (NaV ) critical for the initiation and propagation of action potentials and transmission of sensory input. Three pore-forming sodium channel isoforms are primarily expressed in the peripheral nervous system (PNS): NaV 1.7, NaV 1.8 and NaV 1.9. These sodium channels have been implicated in painful and painless channelopathies and there has been intense interest in them as potential therapeutic targets in human pain. Emerging evidence suggests NaV 1.6 channels are an important isoform in pain sensing. This study aimed to assess, using pharmacological approaches, the function of NaV 1.6 channels in peripheral sensory neurons. The potent and NaV 1.6 selective β-scorpion toxin Cn2 was used to assess the effect of NaV 1.6 channel activation in the PNS. The multidisciplinary approach included Ca2+ imaging, whole-cell patch-clamp recordings, skin-nerve and gut-nerve preparations and in vivo behavioural assessment of pain. Cn2 facilitates NaV 1.6 early channel opening, and increased persistent and resurgent currents in large-diameter dorsal root ganglion (DRG) neurons. This promotes enhanced excitatory drive and tonic action potential firing in these neurons. In addition, NaV 1.6 channel activation in the skin and gut leads to increased response to mechanical stimuli. Finally, intra-plantar injection of Cn2 causes mechanical but not thermal allodynia. This study confirms selectivity of Cn2 on NaV 1.6 channels in sensory neurons. Activation of NaV 1.6 channels, in terminals of the skin and viscera, leads to profound changes in neuronal responses to mechanical stimuli. In conclusion, sensory neurons expressing NaV 1.6 are important for the transduction of mechanical information in sensory afferents innervating the skin and viscera.
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Affiliation(s)
- Mathilde R Israel
- IMB Centre for Pain Research, Institute for Molecular Bioscience, 306 Carmody Rd (Building 80), University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Brian S Tanaka
- Center for Neuroscience and Regeneration Research, Yale School of Medicine, New Haven, CT, 06510, USA.,Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Joel Castro
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, 5042, Australia.,Hopwood Centre for Neurobiology and Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, 5000, Australia
| | - Panumart Thongyoo
- IMB Centre for Pain Research, Institute for Molecular Bioscience, 306 Carmody Rd (Building 80), University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Samuel D Robinson
- IMB Centre for Pain Research, Institute for Molecular Bioscience, 306 Carmody Rd (Building 80), University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Peng Zhao
- Center for Neuroscience and Regeneration Research, Yale School of Medicine, New Haven, CT, 06510, USA.,Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Jennifer R Deuis
- IMB Centre for Pain Research, Institute for Molecular Bioscience, 306 Carmody Rd (Building 80), University of Queensland, Brisbane, Queensland, 4072, Australia
| | - David J Craik
- IMB Centre for Pain Research, Institute for Molecular Bioscience, 306 Carmody Rd (Building 80), University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Thomas Durek
- IMB Centre for Pain Research, Institute for Molecular Bioscience, 306 Carmody Rd (Building 80), University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Stuart M Brierley
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, 5042, Australia.,Hopwood Centre for Neurobiology and Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, 5000, Australia
| | - Stephen G Waxman
- Center for Neuroscience and Regeneration Research, Yale School of Medicine, New Haven, CT, 06510, USA.,Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Sulayman D Dib-Hajj
- Center for Neuroscience and Regeneration Research, Yale School of Medicine, New Haven, CT, 06510, USA.,Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Irina Vetter
- IMB Centre for Pain Research, Institute for Molecular Bioscience, 306 Carmody Rd (Building 80), University of Queensland, Brisbane, Queensland, 4072, Australia.,School of Pharmacy, Pharmacy Australia Centre of Excellence, 20 Cornwall St, Woolloongabba, Queensland, 4102, Australia
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13
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Bennett DL, Clark AJ, Huang J, Waxman SG, Dib-Hajj SD. The Role of Voltage-Gated Sodium Channels in Pain Signaling. Physiol Rev 2019; 99:1079-1151. [DOI: 10.1152/physrev.00052.2017] [Citation(s) in RCA: 256] [Impact Index Per Article: 51.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Acute pain signaling has a key protective role and is highly evolutionarily conserved. Chronic pain, however, is maladaptive, occurring as a consequence of injury and disease, and is associated with sensitization of the somatosensory nervous system. Primary sensory neurons are involved in both of these processes, and the recent advances in understanding sensory transduction and human genetics are the focus of this review. Voltage-gated sodium channels (VGSCs) are important determinants of sensory neuron excitability: they are essential for the initial transduction of sensory stimuli, the electrogenesis of the action potential, and neurotransmitter release from sensory neuron terminals. Nav1.1, Nav1.6, Nav1.7, Nav1.8, and Nav1.9 are all expressed by adult sensory neurons. The biophysical characteristics of these channels, as well as their unique expression patterns within subtypes of sensory neurons, define their functional role in pain signaling. Changes in the expression of VGSCs, as well as posttranslational modifications, contribute to the sensitization of sensory neurons in chronic pain states. Furthermore, gene variants in Nav1.7, Nav1.8, and Nav1.9 have now been linked to human Mendelian pain disorders and more recently to common pain disorders such as small-fiber neuropathy. Chronic pain affects one in five of the general population. Given the poor efficacy of current analgesics, the selective expression of particular VGSCs in sensory neurons makes these attractive targets for drug discovery. The increasing availability of gene sequencing, combined with structural modeling and electrophysiological analysis of gene variants, also provides the opportunity to better target existing therapies in a personalized manner.
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Affiliation(s)
- David L. Bennett
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Alex J. Clark
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Jianying Huang
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Stephen G. Waxman
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Sulayman D. Dib-Hajj
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
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14
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Role of Na V1.6 and Na Vβ4 Sodium Channel Subunits in a Rat Model of Low Back Pain Induced by Compression of the Dorsal Root Ganglia. Neuroscience 2019; 402:51-65. [PMID: 30699332 DOI: 10.1016/j.neuroscience.2019.01.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 01/08/2019] [Accepted: 01/11/2019] [Indexed: 01/18/2023]
Abstract
Low back pain is a common cause of chronic pain and disability. It is modeled in rodents by chronically compressing the lumbar dorsal root ganglia (DRG) with small metal rods, resulting in ipsilateral mechanical and cold hypersensitivity, and hyperexcitability of sensory neurons. Sodium channels are implicated in this hyperexcitability, but the responsible isoforms are unknown. In this study, we used siRNA-mediated knockdown of the pore-forming NaV1.6 and regulatory NaVβ4 sodium channel isoforms that have been previously implicated in a different model of low back pain caused by locally inflaming the L5 DRG. Knockdown of either subunit markedly reduced spontaneous pain and mechanical and cold hypersensitivity induced by DRG compression, and reduced spontaneous activity and hyperexcitability of sensory neurons with action potentials <1.5 msec (predominately cells with myelinated axons, based on conduction velocities measured in a subset of cells) 4 days after DRG compression. These results were similar to those previously obtained in the DRG inflammation model and some neuropathic pain models, in which sensory neurons other than nociceptors seem to play key roles. The cytokine profiles induced by DRG compression and DRG inflammation were also very similar, with upregulation of several type 1 pro-inflammatory cytokines and downregulation of type 2 anti-inflammatory cytokines. Surprisingly, the cytokine profile was largely unaffected by NaVβ4 knockdown in either model. The NaV1.6 channel, and the NaVβ4 subunit that can regulate NaV1.6 to enhance repetitive firing, play key roles in both models of low back pain; targeting the abnormal spontaneous activity they generate may have therapeutic value.
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15
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16
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De Col R, Messlinger K, Hoffmann T. Differential conduction and CGRP release in visceral versus cutaneous peripheral nerves in the mouse. J Neurosci Res 2018; 96:1398-1405. [DOI: 10.1002/jnr.24255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 03/23/2018] [Accepted: 04/16/2018] [Indexed: 01/05/2023]
Affiliation(s)
- Roberto De Col
- Institute for Physiology and Pathophysiology; University of Erlangen-Nuremberg; Erlangen Germany
| | - Karl Messlinger
- Institute for Physiology and Pathophysiology; University of Erlangen-Nuremberg; Erlangen Germany
| | - Tali Hoffmann
- Institute for Physiology and Pathophysiology; University of Erlangen-Nuremberg; Erlangen Germany
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17
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Chen L, Huang J, Zhao P, Persson AK, Dib-Hajj FB, Cheng X, Tan A, Waxman SG, Dib-Hajj SD. Conditional knockout of Na V1.6 in adult mice ameliorates neuropathic pain. Sci Rep 2018; 8:3845. [PMID: 29497094 PMCID: PMC5832877 DOI: 10.1038/s41598-018-22216-w] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/19/2018] [Indexed: 01/09/2023] Open
Abstract
Voltage-gated sodium channels NaV1.7, NaV1.8 and NaV1.9 have been the focus for pain studies because their mutations are associated with human pain disorders, but the role of NaV1.6 in pain is less understood. In this study, we selectively knocked out NaV1.6 in dorsal root ganglion (DRG) neurons, using NaV1.8-Cre directed or adeno-associated virus (AAV)-Cre mediated approaches, and examined the specific contribution of NaV1.6 to the tetrodotoxin-sensitive (TTX-S) current in these neurons and its role in neuropathic pain. We report here that NaV1.6 contributes up to 60% of the TTX-S current in large, and 34% in small DRG neurons. We also show NaV1.6 accumulates at nodes of Ranvier within the neuroma following spared nerve injury (SNI). Although NaV1.8-Cre driven NaV1.6 knockout does not alter acute, inflammatory or neuropathic pain behaviors, AAV-Cre mediated NaV1.6 knockout in adult mice partially attenuates SNI-induced mechanical allodynia. Additionally, AAV-Cre mediated NaV1.6 knockout, mostly in large DRG neurons, significantly attenuates excitability of these neurons after SNI and reduces NaV1.6 accumulation at nodes of Ranvier at the neuroma. Together, NaV1.6 in NaV1.8-positive neurons does not influence pain thresholds under normal or pathological conditions, but NaV1.6 in large NaV1.8-negative DRG neurons plays an important role in neuropathic pain.
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Affiliation(s)
- Lubin Chen
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Jianying Huang
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Peng Zhao
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Anna-Karin Persson
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Fadia B Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Xiaoyang Cheng
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Andrew Tan
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA. .,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA. .,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT, 06516, USA.
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19
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Accessibility of axonal G protein coupled mu-opioid receptors requires conceptual changes of axonal membrane targeting for pain modulation. J Control Release 2017; 268:352-363. [PMID: 29054370 DOI: 10.1016/j.jconrel.2017.10.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 10/07/2017] [Accepted: 10/13/2017] [Indexed: 12/19/2022]
Abstract
The mechanisms of axonal trafficking and membrane targeting are well established for sodium channels, which are the principle targets for perineurally applied local anaesthetics. However, they have not been thoroughly investigated for G protein coupled receptors such as mu-opioid receptors (MOR). Focusing on these axonal mechanisms, we found that axonal MOR functionality is quite distinct in two different pain states, i.e. hindpaw inflammation and nerve injury. We observed axonal membrane MOR binding and functional G protein coupling exclusively at sites of CCI nerve injury. Moreover at these axonal membrane sites, MOR exhibited extensive co-localization with the membrane proteins SNAP and Na/K-ATPase as well as NGF-dependent enhanced lipid rafts and L1CAM anchoring proteins. Silencing endogenous L1CAM with intrathecal L1CAM specific siRNA, disrupting lipid rafts with the perineurial cholesterol-sequestering agent MβCD, as well as suppressing NGF receptor activation with the perineurial NGF receptor inhibitor K252a abrogated MOR axonal membrane integration, functional coupling, and agonist-elicited antinociception at sites of nerve injury. These findings suggest that local conceptual changes resulting from nerve injury are required for the establishment of functional axonal membrane MOR. Axonal integration and subsequent accessibility of functionally coupled MOR are of great relevance particularly for patients suffering from severe pain due to nerve injury or tumour infiltration.
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20
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Taha O, Opitz T, Mueller M, Pitsch J, Becker A, Evert BO, Beck H, Jeub M. Neuropathic pain in experimental autoimmune neuritis is associated with altered electrophysiological properties of nociceptive DRG neurons. Exp Neurol 2017; 297:25-35. [PMID: 28734788 DOI: 10.1016/j.expneurol.2017.07.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 07/02/2017] [Accepted: 07/13/2017] [Indexed: 12/30/2022]
Abstract
Guillain-Barré syndrome (GBS) is an acute, immune-mediated polyradiculoneuropathy characterized by rapidly progressive paresis and sensory disturbances. Moderate to severe and often intractable neuropathic pain is a common symptom of GBS, but its underlying mechanisms are unknown. Pathology of GBS is classically attributed to demyelination of large, myelinated peripheral fibers. However, there is increasing evidence that neuropathic pain in GBS is associated with impaired function of small, unmyelinated, nociceptive fibers. We therefore examined the functional properties of small DRG neurons, the somata of nociceptive fibers, in a rat model of GBS (experimental autoimmune neuritis=EAN). EAN rats developed behavioral signs of neuropathic pain. This was accompanied by a significant shortening of action potentials due to a more rapid repolarization and an increase in repetitive firing in a subgroup of capsaicin-responsive DRG neurons. Na+ current measurements revealed a significant increase of the fast TTX-sensitive current and a reduction of the persistent TTX-sensitive current component. These changes of Na+ currents may account for the significant decrease in AP duration leading to an overall increase in excitability and are therefore possibly directly linked to pathological pain behavior. Thus, like in other animal models of neuropathic and inflammatory pain, Na+ channels seem to be crucially involved in the pathology of GBS and may constitute promising targets for pain modulating pharmaceuticals.
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Affiliation(s)
- Omneya Taha
- Department of Neurology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany; Department of Epileptology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany
| | - Thoralf Opitz
- Department of Epileptology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany
| | - Marcus Mueller
- Department of Neurology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany
| | - Julika Pitsch
- Department of Neuropathology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany
| | - Albert Becker
- Department of Neuropathology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany
| | - Bernd Oliver Evert
- Department of Neurology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany
| | - Heinz Beck
- Department of Epileptology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany
| | - Monika Jeub
- Department of Neurology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany; Department of Epileptology, University of Bonn Medical Center, Sigmund Freud Straße 25, 53105 Bonn, Germany.
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21
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Sodium Channel Na v1.8 Underlies TTX-Resistant Axonal Action Potential Conduction in Somatosensory C-Fibers of Distal Cutaneous Nerves. J Neurosci 2017; 37:5204-5214. [PMID: 28450535 DOI: 10.1523/jneurosci.3799-16.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium (NaV) channels are responsible for the initiation and conduction of action potentials within primary afferents. The nine NaV channel isoforms recognized in mammals are often functionally divided into tetrodotoxin (TTX)-sensitive (TTX-s) channels (NaV1.1-NaV1.4, NaV1.6-NaV1.7) that are blocked by nanomolar concentrations and TTX-resistant (TTX-r) channels (NaV1.8 and NaV1.9) inhibited by millimolar concentrations, with NaV1.5 having an intermediate toxin sensitivity. For small-diameter primary afferent neurons, it is unclear to what extent different NaV channel isoforms are distributed along the peripheral and central branches of their bifurcated axons. To determine the relative contribution of TTX-s and TTX-r channels to action potential conduction in different axonal compartments, we investigated the effects of TTX on C-fiber-mediated compound action potentials (C-CAPs) of proximal and distal peripheral nerve segments and dorsal roots from mice and pigtail monkeys (Macaca nemestrina). In the dorsal roots and proximal peripheral nerves of mice and nonhuman primates, TTX reduced the C-CAP amplitude to 16% of the baseline. In contrast, >30% of the C-CAP was resistant to TTX in distal peripheral branches of monkeys and WT and NaV1.9-/- mice. In nerves from NaV1.8-/- mice, TTX-r C-CAPs could not be detected. These data indicate that NaV1.8 is the primary isoform underlying TTX-r conduction in distal axons of somatosensory C-fibers. Furthermore, there is a differential spatial distribution of NaV1.8 within C-fiber axons, being functionally more prominent in the most distal axons and terminal regions. The enrichment of NaV1.8 in distal axons may provide a useful target in the treatment of pain of peripheral origin.SIGNIFICANCE STATEMENT It is unclear whether individual sodium channel isoforms exert differential roles in action potential conduction along the axonal membrane of nociceptive, unmyelinated peripheral nerve fibers, but clarifying the role of sodium channel subtypes in different axonal segments may be useful for the development of novel analgesic strategies. Here, we provide evidence from mice and nonhuman primates that a substantial portion of the C-fiber compound action potential in distal peripheral nerves, but not proximal nerves or dorsal roots, is resistant to tetrodotoxin and that, in mice, this effect is mediated solely by voltage-gated sodium channel 1.8 (NaV1.8). The functional prominence of NaV1.8 within the axonal compartment immediately proximal to its termination may affect strategies targeting pain of peripheral origin.
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22
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Duménieu M, Oulé M, Kreutz MR, Lopez-Rojas J. The Segregated Expression of Voltage-Gated Potassium and Sodium Channels in Neuronal Membranes: Functional Implications and Regulatory Mechanisms. Front Cell Neurosci 2017; 11:115. [PMID: 28484374 PMCID: PMC5403416 DOI: 10.3389/fncel.2017.00115] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 04/05/2017] [Indexed: 01/25/2023] Open
Abstract
Neurons are highly polarized cells with apparent functional and morphological differences between dendrites and axon. A critical determinant for the molecular and functional identity of axonal and dendritic segments is the restricted expression of voltage-gated ion channels (VGCs). Several studies show an uneven distribution of ion channels and their differential regulation within dendrites and axons, which is a prerequisite for an appropriate integration of synaptic inputs and the generation of adequate action potential (AP) firing patterns. This review article will focus on the signaling pathways leading to segmented expression of voltage-gated potassium and sodium ion channels at the neuronal plasma membrane and the regulatory mechanisms ensuring segregated functions. We will also discuss the relevance of proper ion channel targeting for neuronal physiology and how alterations in polarized distribution contribute to neuronal pathology.
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Affiliation(s)
- Maël Duménieu
- Research Group Neuroplasticity, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | - Marie Oulé
- Research Group Neuroplasticity, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | - Michael R Kreutz
- Research Group Neuroplasticity, Leibniz Institute for NeurobiologyMagdeburg, Germany.,Leibniz Group "Dendritic Organelles and Synaptic Function", University Medical Center Hamburg-Eppendorf, Center for Molecular Neurobiology (ZMNH)Hamburg, Germany
| | - Jeffrey Lopez-Rojas
- Research Group Neuroplasticity, Leibniz Institute for NeurobiologyMagdeburg, Germany
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23
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Resistance to action potential depression of a rat axon terminal in vivo. Proc Natl Acad Sci U S A 2017; 114:4249-4254. [PMID: 28373550 DOI: 10.1073/pnas.1619433114] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The shape of the presynaptic action potential (AP) has a strong impact on neurotransmitter release. Because of the small size of most terminals in the central nervous system, little is known about the regulation of their AP shape during natural firing patterns in vivo. The calyx of Held is a giant axosomatic terminal in the auditory brainstem, whose biophysical properties have been well studied in slices. Here, we made whole-cell recordings from calyceal terminals in newborn rat pups. The calyx showed a characteristic burst firing pattern, which has previously been shown to originate from the cochlea. Surprisingly, even for frequencies over 200 Hz, the AP showed little or no depression. Current injections showed that the rate of rise of the AP depended strongly on its onset potential, and that the membrane potential after the AP (Vafter) was close to the value at which no depression would occur during high-frequency activity. Immunolabeling revealed that Nav1.6 is already present at the calyx shortly after its formation, which was in line with the fast recovery from AP depression that we observed in slice recordings. Our findings thus indicate that fast recovery from depression and an inter-AP membrane potential that minimizes changes on the next AP in vivo, together enable high timing precision of the calyx of Held already shortly after its formation.
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24
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Petrosyan HA, Alessi V, Sisto SA, Kaufman M, Arvanian VL. Transcranial magnetic stimulation (TMS) responses elicited in hindlimb muscles as an assessment of synaptic plasticity in spino-muscular circuitry after chronic spinal cord injury. Neurosci Lett 2017; 642:37-42. [DOI: 10.1016/j.neulet.2017.01.065] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/17/2017] [Accepted: 01/27/2017] [Indexed: 12/12/2022]
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25
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Inserra MC, Israel MR, Caldwell A, Castro J, Deuis JR, Harrington AM, Keramidas A, Garcia-Caraballo S, Maddern J, Erickson A, Grundy L, Rychkov GY, Zimmermann K, Lewis RJ, Brierley SM, Vetter I. Multiple sodium channel isoforms mediate the pathological effects of Pacific ciguatoxin-1. Sci Rep 2017; 7:42810. [PMID: 28225079 PMCID: PMC5320492 DOI: 10.1038/srep42810] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/13/2017] [Indexed: 01/04/2023] Open
Abstract
Human intoxication with the seafood poison ciguatoxin, a dinoflagellate polyether that activates voltage-gated sodium channels (NaV), causes ciguatera, a disease characterised by gastrointestinal and neurological disturbances. We assessed the activity of the most potent congener, Pacific ciguatoxin-1 (P-CTX-1), on NaV1.1–1.9 using imaging and electrophysiological approaches. Although P-CTX-1 is essentially a non-selective NaV toxin and shifted the voltage-dependence of activation to more hyperpolarising potentials at all NaV subtypes, an increase in the inactivation time constant was observed only at NaV1.8, while the slope factor of the conductance-voltage curves was significantly increased for NaV1.7 and peak current was significantly increased for NaV1.6. Accordingly, P-CTX-1-induced visceral and cutaneous pain behaviours were significantly decreased after pharmacological inhibition of NaV1.8 and the tetrodotoxin-sensitive isoforms NaV1.7 and NaV1.6, respectively. The contribution of these isoforms to excitability of peripheral C- and A-fibre sensory neurons, confirmed using murine skin and visceral single-fibre recordings, reflects the expression pattern of NaV isoforms in peripheral sensory neurons and their contribution to membrane depolarisation, action potential initiation and propagation.
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Affiliation(s)
- Marco C Inserra
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Rd, St Lucia, Queensland 4072, Australia
| | - Mathilde R Israel
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Rd, St Lucia, Queensland 4072, Australia
| | - Ashlee Caldwell
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Joel Castro
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Jennifer R Deuis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Rd, St Lucia, Queensland 4072, Australia
| | - Andrea M Harrington
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Angelo Keramidas
- Queensland Brain Institute, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Sonia Garcia-Caraballo
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Jessica Maddern
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Andelain Erickson
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Luke Grundy
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Grigori Y Rychkov
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Katharina Zimmermann
- Klinik für Anästhesiologie am Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Richard J Lewis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Rd, St Lucia, Queensland 4072, Australia
| | - Stuart M Brierley
- Visceral Pain Group, South Australian Health and Medical Research Institute (SAHMRI), School of Medicine, Flinders University, Adelaide, South Australia 5000, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia 5000, Australia
| | - Irina Vetter
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Rd, St Lucia, Queensland 4072, Australia.,School of Pharmacy, The University of Queensland, 20 Cornwall St, Woolloongabba, Queensland 4102, Australia
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26
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Carrasco DI, Vincent JA, Cope TC. Distribution of TTX-sensitive voltage-gated sodium channels in primary sensory endings of mammalian muscle spindles. J Neurophysiol 2017; 117:1690-1701. [PMID: 28123009 DOI: 10.1152/jn.00889.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 01/24/2017] [Accepted: 01/24/2017] [Indexed: 12/19/2022] Open
Abstract
Knowledge of the molecular mechanisms underlying signaling of mechanical stimuli by muscle spindles remains incomplete. In particular, the ionic conductances that sustain tonic firing during static muscle stretch are unknown. We hypothesized that tonic firing by spindle afferents depends on sodium persistent inward current (INaP) and tested for the necessary presence of the appropriate voltage-gated sodium (NaV) channels in primary sensory endings. The NaV1.6 isoform was selected for both its capacity to produce INaP and for its presence in other mechanosensors that fire tonically. The present study shows that NaV1.6 immunoreactivity (IR) is concentrated in heminodes, presumably where tonic firing is generated, and we were surprised to find NaV1.6 IR strongly expressed also in the sensory terminals, where mechanotransduction occurs. This spatial pattern of NaV1.6 IR distribution was consistent for three mammalian species (rat, cat, and mouse), as was tonic firing by primary spindle afferents. These findings meet some of the conditions needed to establish participation of INaP in tonic firing by primary sensory endings. The study was extended to two additional NaV isoforms, selected for their sensitivity to TTX, excluding TTX-resistant NaV channels, which alone are insufficient to support firing by primary spindle endings. Positive immunoreactivity was found for NaV1.1, predominantly in sensory terminals together with NaV1.6 and for NaV1.7, mainly in preterminal axons. Differential distribution in primary sensory endings suggests specialized roles for these three NaV isoforms in the process of mechanosensory signaling by muscle spindles.NEW & NOTEWORTHY The molecular mechanisms underlying mechanosensory signaling responsible for proprioceptive functions are not completely elucidated. This study provides the first evidence that voltage-gated sodium channels (NaVs) are expressed in the spindle primary sensory ending, where NaVs are found at every site involved in transduction or encoding of muscle stretch. We propose that NaVs contribute to multiple steps in sensory signaling by muscle spindles as it does in other types of slowly adapting sensory neurons.
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Affiliation(s)
- Dario I Carrasco
- School of Biological Science, Georgia Institute of Technology, Atlanta Georgia
| | - Jacob A Vincent
- School of Biological Science, Georgia Institute of Technology, Atlanta Georgia
| | - Timothy C Cope
- School of Biological Science, Georgia Institute of Technology, Atlanta Georgia; .,Biomedical Engineering, Georgia Institute of Technology, Atlanta Georgia; and
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Upregulation of the sodium channel NaVβ4 subunit and its contributions to mechanical hypersensitivity and neuronal hyperexcitability in a rat model of radicular pain induced by local dorsal root ganglion inflammation. Pain 2017; 157:879-891. [PMID: 26785322 DOI: 10.1097/j.pain.0000000000000453] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
High-frequency spontaneous firing in myelinated sensory neurons plays a key role in initiating pain behaviors in several different models, including the radicular pain model in which the rat lumbar dorsal root ganglia (DRG) are locally inflamed. The sodium channel isoform NaV1.6 contributes to pain behaviors and spontaneous activity in this model. Among all isoforms in adult DRG, NaV1.6 is the main carrier of tetrodotoxin-sensitive resurgent Na currents that allow high-frequency firing. Resurgent currents flow after a depolarization or action potential, as a blocking particle exits the pore. In most neurons, the regulatory β4 subunit is potentially the endogenous blocker. We used in vivo siRNA-mediated knockdown of NaVβ4 to examine its role in the DRG inflammation model. NaVβ4 but not control siRNA almost completely blocked mechanical hypersensitivity induced by DRG inflammation. Microelectrode recordings in isolated whole DRG showed that NaVβ4 siRNA blocked the inflammation-induced increase in spontaneous activity of Aβ neurons and reduced repetitive firing and other measures of excitability. NaVβ4 was preferentially expressed in larger diameter cells; DRG inflammation increased its expression, and this was reversed by NaVβ4 siRNA, based on immunohistochemistry and Western blotting. NaVβ4 siRNA also reduced immunohistochemical NaV1.6 expression. Patch-clamp recordings of tetrodotoxin-sensitive Na currents in acutely cultured medium diameter DRG neurons showed that DRG inflammation increased transient and especially resurgent current, effects blocked by NaVβ4 siRNA. NaVβ4 may represent a more specific target for pain conditions that depend on myelinated neurons expressing NaV1.6.
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Israel MR, Tay B, Deuis JR, Vetter I. Sodium Channels and Venom Peptide Pharmacology. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 79:67-116. [PMID: 28528674 DOI: 10.1016/bs.apha.2017.01.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Venomous animals including cone snails, spiders, scorpions, anemones, and snakes have evolved a myriad of components in their venoms that target the opening and/or closing of voltage-gated sodium channels to cause devastating effects on the neuromuscular systems of predators and prey. These venom peptides, through design and serendipity, have not only contributed significantly to our understanding of sodium channel pharmacology and structure, but they also represent some of the most phyla- and isoform-selective molecules that are useful as valuable tool compounds and drug leads. Here, we review our understanding of the basic function of mammalian voltage-gated sodium channel isoforms as well as the pharmacology of venom peptides that act at these key transmembrane proteins.
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Affiliation(s)
- Mathilde R Israel
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Bryan Tay
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Jennifer R Deuis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia.
| | - Irina Vetter
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia; School of Pharmacy, The University of Queensland, Brisbane, QLD, Australia.
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A Novel Approach for Studying the Physiology and Pathophysiology of Myelinated and Non-Myelinated Axons in the CNS White Matter. PLoS One 2016; 11:e0165637. [PMID: 27829055 PMCID: PMC5102346 DOI: 10.1371/journal.pone.0165637] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 10/14/2016] [Indexed: 11/19/2022] Open
Abstract
Advances in brain connectomics set the need for detailed knowledge of functional properties of myelinated and non-myelinated (if present) axons in specific white matter pathways. The corpus callosum (CC), a major white matter structure interconnecting brain hemispheres, is extensively used for studying CNS axonal function. Unlike another widely used CNS white matter preparation, the optic nerve where all axons are myelinated, the CC contains also a large population of non-myelinated axons, making it particularly useful for studying both types of axons. Electrophysiological studies of optic nerve use suction electrodes on nerve ends to stimulate and record compound action potentials (CAPs) that adequately represent its axonal population, whereas CC studies use microelectrodes (MEs), recording from a limited area within the CC. Here we introduce a novel robust isolated "whole" CC preparation comparable to optic nerve. Unlike ME recordings where the CC CAP peaks representing myelinated and non-myelinated axons vary broadly in size, "whole" CC CAPs show stable reproducible ratios of these two main peaks, and also reveal a third peak, suggesting a distinct group of smaller caliber non-myelinated axons. We provide detailed characterization of "whole" CC CAPs and conduction velocities of myelinated and non-myelinated axons along the rostro-caudal axis of CC body and show advantages of this preparation for comparing axonal function in wild type and dysmyelinated shiverer mice, studying the effects of temperature dependence, bath-applied drugs and ischemia modeled by oxygen-glucose deprivation. Due to the isolation from gray matter, our approach allows for studying CC axonal function without possible "contamination" by reverberating signals from gray matter. Our analysis of "whole" CC CAPs revealed higher complexity of myelinated and non-myelinated axonal populations, not noticed earlier. This preparation may have a broad range of applications as a robust model for studying myelinated and non-myelinated axons of the CNS in various experimental models.
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Age-Related Changes in Axonal and Mitochondrial Ultrastructure and Function in White Matter. J Neurosci 2016; 36:9990-10001. [PMID: 27683897 DOI: 10.1523/jneurosci.1316-16.2016] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/02/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED The impact of aging on CNS white matter (WM) is of general interest because the global effects of aging on myelinated nerve fibers are more complex and profound than those in cortical gray matter. It is important to distinguish between axonal changes created by normal aging and those caused by neurodegenerative diseases, including multiple sclerosis, stroke, glaucoma, Alzheimer's disease, and traumatic brain injury. Using three-dimensional electron microscopy, we show that in mouse optic nerve, which is a pure and fully myelinated WM tract, aging axons are larger, have thicker myelin, and are characterized by longer and thicker mitochondria, which are associated with altered levels of mitochondrial shaping proteins. These structural alterations in aging mitochondria correlate with lower ATP levels and increased generation of nitric oxide, protein nitration, and lipid peroxidation. Moreover, mitochondria-smooth endoplasmic reticulum interactions are compromised due to decreased associations and decreased levels of calnexin and calreticulin, suggesting a disruption in Ca(2+) homeostasis and defective unfolded protein responses in aging axons. Despite these age-related modifications, axon function is sustained in aging WM, which suggests that age-dependent changes do not lead to irreversible functional decline under normal conditions, as is observed in neurodegenerative diseases. SIGNIFICANCE STATEMENT Aging is a common risk factor for a number of neurodegenerative diseases, including stroke. Mitochondrial dysfunction and oxidative damage with age are hypothesized to increase risk for stroke. We compared axon-myelin-node-mitochondrion-smooth endoplasmic reticulum (SER) interactions in white matter obtained at 1 and 12 months. We show that aging axons have enlarged volume, thicker myelin, and elongated and thicker mitochondria. Furthermore, there are reduced SER connections to mitochondria that correlate with lower calnexin and calreticulin levels. Despite a prominent decrease in number, elongated aging mitochondria produce excessive stress markers with reduced ATP production. Because axons maintain function under these conditions, our study suggests that it is important to understand the process of normal brain aging to identify neurodegenerative changes.
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Tanaka BS, Zhao P, Dib-Hajj FB, Morisset V, Tate S, Waxman SG, Dib-Hajj SD. A gain-of-function mutation in Nav1.6 in a case of trigeminal neuralgia. Mol Med 2016; 22:338-348. [PMID: 27496104 DOI: 10.2119/molmed.2016.00131] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/18/2016] [Indexed: 01/29/2023] Open
Abstract
Idiopathic trigeminal neuralgia (TN) is a debilitating pain disorder characterized by episodic unilateral facial pain along the territory of branches of the trigeminal nerve. Human painful disorders, but not TN, have been linked to gain-of-function mutations in peripheral voltage-gated sodium channels (NaV1.7, NaV1.8 and NaV1.9). Gain-of-function mutations in NaV1.6, which is expressed in myelinated and unmyelinated CNS and peripheral nervous system neurons and supports neuronal high-frequency firing, have been linked to epilepsy but not to pain. Here, we describe an individual who presented with evoked and spontaneous paroxysmal unilateral facial pain, and carried a diagnosis of TN. Magnetic resonance imaging showed unilateral neurovascular compression, consistent with pain in areas innervated by the second branch of the trigeminal nerve. Genetic analysis as part of a phase 2 clinical study in patients with TN conducted by Convergence Pharmaceuticals Ltd revealed a previously undescribed de novo missense mutation in NaV1.6 (c.A406G; p.Met136Val). Whole-cell voltage-clamp recordings show that the Met136Val mutation significantly increases peak current density (1.5-fold) and resurgent current (1.6-fold) without altering gating properties. Current-clamp studies in trigeminal ganglion (TRG) neurons showed that Met136Val increased the fraction of high-firing neurons, lowered the current threshold and increased the frequency of evoked action potentials in response to graded stimuli. Our results demonstrate a novel NaV1.6 mutation in TN, and show that this mutation potentiates transient and resurgent sodium currents and leads to increased excitability in TRG neurons. We suggest that this gain-of-function NaV1.6 mutation may exacerbate the pathophysiology of vascular compression and contribute to TN.
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Affiliation(s)
- Brian S Tanaka
- Department of Neurology.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT 06510.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516
| | - Peng Zhao
- Department of Neurology.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT 06510.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516
| | - Fadia B Dib-Hajj
- Department of Neurology.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT 06510.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516
| | - Valerie Morisset
- Convergence Pharmaceuticals Ltd, a Biogen company, Cambridge, United Kingdom
| | - Simon Tate
- Convergence Pharmaceuticals Ltd, a Biogen company, Cambridge, United Kingdom
| | - Stephen G Waxman
- Department of Neurology.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT 06510.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516
| | - Sulayman D Dib-Hajj
- Department of Neurology.,Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT 06510.,Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516
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Ramachandra R, Elmslie KS. EXPRESS: Voltage-dependent sodium (NaV) channels in group IV sensory afferents. Mol Pain 2016; 12:12/0/1744806916660721. [PMID: 27385723 PMCID: PMC4956173 DOI: 10.1177/1744806916660721] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Patients with intermittent claudication suffer from both muscle pain and an exacerbated exercise pressor reflex. Excitability of the group III and group IV afferent fibers mediating these functions is controlled in part by voltage-dependent sodium (NaV) channels. We previously found tetrodotoxin-resistant NaV1.8 channels to be the primary type in muscle afferent somata. However, action potentials in group III and IV afferent axons are blocked by TTX, supporting a minimal role of NaV1.8 channels. To address these apparent differences in NaV channel expression between axon and soma, we used immunohistochemistry to identify the NaV channels expressed in group IV axons within the gastrocnemius muscle and the dorsal root ganglia sections. Positive labeling by an antibody against the neurofilament protein peripherin was used to identify group IV neurons and axons. We show that >67% of group IV fibers express NaV1.8, NaV1.6, or NaV1.7. Interestingly, expression of NaV1.8 channels in group IV somata was significantly higher than in the fibers, whereas there were no significant differences for either NaV1.6 or NaV1.7. When combined with previous work, our results suggest that NaV1.8 channels are expressed in most group IV axons, but that, under normal conditions, NaV1.6 and/or NaV1.7 play a more important role in action potential generation to signal muscle pain and the exercise pressor reflex.
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Affiliation(s)
- Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, AT Still University of Health Sciences, Kirksville, MO, USA
- Renuka Ramachandra, The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, AT Still University of Health Sciences, Kirksville, MO 63501, USA.
| | - Keith S Elmslie
- The Baker Laboratory of Pharmacology, Department of Pharmacology, AT Still University of Health Sciences, Kirksville, MO, USA
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33
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Sodium Channels, Mitochondria, and Axonal Degeneration in Peripheral Neuropathy. Trends Mol Med 2016; 22:377-390. [DOI: 10.1016/j.molmed.2016.03.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 03/21/2016] [Accepted: 03/22/2016] [Indexed: 12/19/2022]
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Hong H, Rollman L, Feinstein B, Sanchez JT. Developmental Profile of Ion Channel Specializations in the Avian Nucleus Magnocellularis. Front Cell Neurosci 2016; 10:80. [PMID: 27065805 PMCID: PMC4811932 DOI: 10.3389/fncel.2016.00080] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 03/14/2016] [Indexed: 11/18/2022] Open
Abstract
Ultrafast and temporally precise action potentials (APs) are biophysical specializations of auditory brainstem neurons; properties necessary for encoding sound localization and communication cues. Fundamental to these specializations are voltage dependent potassium (KV) and sodium (NaV) ion channels. Here, we characterized the functional development of these ion channels and quantified how they shape AP properties in the avian cochlear nucleus magnocellularis (NM). We report that late developing NM neurons (embryonic [E] days 19–21) generate fast APs that reliably phase lock to sinusoidal inputs at 75 Hz. In contrast, early developing neurons (<E12) have slower and less reliable APs that preferentially fire to lower frequencies (5–10 Hz). With development, the membrane time constant of NM neurons became faster, while input resistance and capacitance decreased. Change in input resistance was due to a 2-fold increase in KV current from E10 to E21 and when high-voltage activated potassium (K+HVA) channels were blocked, APs for all ages became significantly slower. This was most evident for early developing neurons where the ratio of K+HVA current accounted for ~85% of the total KV response. This ratio dropped to ~50% for late developing neurons, suggesting a developmental upregulation of low-voltage activated potassium (K+LVA) channels. Indeed, blockade of K+LVA eliminated remaining current and increased neural excitability for late developing neurons. We also report developmental changes in the amplitude, kinetics and voltage dependence of NaV currents. For early developing neurons, increase in NaV current amplitude was due to channel density while channel conductance dominated for late developing neurons. From E10 to E21, NaV channel currents became faster but differed in their voltage dependence; early developing neurons (<E16) had similar NaV channel inactivation voltages while late developing NM neurons (>E19) contained NaV channels that inactivate at more negative voltages, suggesting alterations in NaV channel subtypes. Taken together, our results indicate that the refinement of passive and active ion channel properties operate differentially in order to develop fast and reliable APs in the avian NM.
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Affiliation(s)
- Hui Hong
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, The Hugh Knowles Hearing Research Center, School of Communication, Northwestern University Evanston, IL, USA
| | - Lisia Rollman
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, The Hugh Knowles Hearing Research Center, School of Communication, Northwestern University Evanston, IL, USA
| | - Brooke Feinstein
- Department of Neurobiology and Interdepartmental Neuroscience Program, Weinberg College of Arts and Sciences, Northwestern University Evanston, IL, USA
| | - Jason Tait Sanchez
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, The Hugh Knowles Hearing Research Center, School of Communication, Northwestern UniversityEvanston, IL, USA; Department of Neurobiology and Interdepartmental Neuroscience Program, Weinberg College of Arts and Sciences, Northwestern UniversityEvanston, IL, USA
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Bao L. Trafficking regulates the subcellular distribution of voltage-gated sodium channels in primary sensory neurons. Mol Pain 2015; 11:61. [PMID: 26423360 PMCID: PMC4590712 DOI: 10.1186/s12990-015-0065-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 09/23/2015] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (Navs) comprise at least nine pore-forming α subunits. Of these, Nav1.6, Nav1.7, Nav1.8 and Nav1.9 are the most frequently studied in primary sensory neurons located in the dorsal root ganglion and are mainly localized to the cytoplasm. A large pool of intracellular Navs raises the possibility that changes in Nav trafficking could alter channel function. The molecular mediators of Nav trafficking mainly consist of signals within the Navs themselves, interacting proteins and extracellular factors. The surface expression of Navs is achieved by escape from the endoplasmic reticulum and proteasome degradation, forward trafficking and plasma membrane anchoring, and it is also regulated by channel phosphorylation and ubiquitination in primary sensory neurons. Axonal transport and localization of Navs in afferent fibers involves the motor protein KIF5B and scaffold proteins, including contactin and PDZ domain containing 2. Localization of Nav1.6 to the nodes of Ranvier in myelinated fibers of primary sensory neurons requires node formation and the submembrane cytoskeletal protein complex. These findings inform our understanding of the molecular and cellular mechanisms underlying Nav trafficking in primary sensory neurons.
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Affiliation(s)
- Lan Bao
- State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai, 200031, China.
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36
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Barbosa C, Tan ZY, Wang R, Xie W, Strong JA, Patel RR, Vasko MR, Zhang JM, Cummins TR. Navβ4 regulates fast resurgent sodium currents and excitability in sensory neurons. Mol Pain 2015; 11:60. [PMID: 26408173 PMCID: PMC4582632 DOI: 10.1186/s12990-015-0063-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/10/2015] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Increased electrical activity in peripheral sensory neurons including dorsal root ganglia (DRG) and trigeminal ganglia neurons is an important mechanism underlying pain. Voltage gated sodium channels (VGSC) contribute to the excitability of sensory neurons and are essential for the upstroke of action potentials. A unique type of VGSC current, resurgent current (INaR), generates an inward current at repolarizing voltages through an alternate mechanism of inactivation referred to as open-channel block. INaRs are proposed to enable high frequency firing and increased INaRs in sensory neurons are associated with pain pathologies. While Nav1.6 has been identified as the main carrier of fast INaR, our understanding of the mechanisms that contribute to INaR generation is limited. Specifically, the open-channel blocker in sensory neurons has not been identified. Previous studies suggest Navβ4 subunit mediates INaR in central nervous system neurons. The goal of this study was to determine whether Navβ4 regulates INaR in DRG sensory neurons. RESULTS Our immunocytochemistry studies show that Navβ4 expression is highly correlated with Nav1.6 expression predominantly in medium-large diameter rat DRG neurons. Navβ4 knockdown decreased endogenous fast INaR in medium-large diameter neurons as measured with whole-cell voltage clamp. Using a reduced expression system in DRG neurons, we isolated recombinant human Nav1.6 sodium currents in rat DRG neurons and found that overexpression of Navβ4 enhanced Nav1.6 INaR generation. By contrast neither overexpression of Navβ2 nor overexpression of a Navβ4-mutant, predicted to be an inactive form of Navβ4, enhanced Nav1.6 INaR generation. DRG neurons transfected with wild-type Navβ4 exhibited increased excitability with increases in both spontaneous activity and evoked activity. Thus, Navβ4 overexpression enhanced INaR and excitability, whereas knockdown or expression of mutant Navβ4 decreased INaR generation. CONCLUSION INaRs are associated with inherited and acquired pain disorders. However, our ability to selectively target and study this current has been hindered due to limited understanding of how it is generated in sensory neurons. This study identified Navβ4 as an important regulator of INaR and excitability in sensory neurons. As such, Navβ4 is a potential target for the manipulation of pain sensations.
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Affiliation(s)
- Cindy Barbosa
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, USA. .,Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, 320 West 25th Street, NB-414F, Indianapolis, IN, 46202-2266, USA.
| | - Zhi-Yong Tan
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, USA. .,Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, 320 West 25th Street, NB-414F, Indianapolis, IN, 46202-2266, USA.
| | - Ruizhong Wang
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, USA.
| | - Wenrui Xie
- Department of Anesthesiology, University of Cincinnati, Cincinnati, OH, USA.
| | - Judith A Strong
- Department of Anesthesiology, University of Cincinnati, Cincinnati, OH, USA.
| | - Reesha R Patel
- Medical Neuroscience Graduate Program, Indiana University School of Medicine, Indianapolis, IN, USA. .,Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, 320 West 25th Street, NB-414F, Indianapolis, IN, 46202-2266, USA.
| | - Michael R Vasko
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, USA. .,Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, 320 West 25th Street, NB-414F, Indianapolis, IN, 46202-2266, USA.
| | - Jun-Ming Zhang
- Department of Anesthesiology, University of Cincinnati, Cincinnati, OH, USA.
| | - Theodore R Cummins
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, USA. .,Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, 320 West 25th Street, NB-414F, Indianapolis, IN, 46202-2266, USA.
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37
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Hoeijmakers JG, Faber CG, Merkies IS, Waxman SG. Painful peripheral neuropathy and sodium channel mutations. Neurosci Lett 2015; 596:51-9. [DOI: 10.1016/j.neulet.2014.12.056] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Revised: 12/22/2014] [Accepted: 12/29/2014] [Indexed: 12/19/2022]
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38
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Xie W, Strong JA, Zhang JM. Local knockdown of the NaV1.6 sodium channel reduces pain behaviors, sensory neuron excitability, and sympathetic sprouting in rat models of neuropathic pain. Neuroscience 2015; 291:317-30. [PMID: 25686526 DOI: 10.1016/j.neuroscience.2015.02.010] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 01/21/2015] [Accepted: 02/05/2015] [Indexed: 11/15/2022]
Abstract
In the spinal nerve ligation (SNL) model of neuropathic pain, as in other pain models, abnormal spontaneous activity of myelinated sensory neurons occurs early and is essential for establishing pain behaviors and other pathologies. Sympathetic sprouting into the dorsal root ganglion (DRG) is observed after SNL, and sympathectomy reduces pain behavior. Sprouting and spontaneous activity may be mutually reinforcing: blocking neuronal activity reduces sympathetic sprouting, and sympathetic spouts functionally increase spontaneous activity in vitro. However, most studies in this field have used nonspecific methods to block spontaneous activity, methods that also block evoked and normal activity. In this study, we injected small inhibitory (si) RNA directed against the NaV1.6 sodium channel isoform into the DRG before SNL. This isoform can mediate high-frequency repetitive firing, like that seen in spontaneously active neurons. Local knockdown of NaV1.6 markedly reduced mechanical pain behaviors induced by SNL, reduced sympathetic sprouting into the ligated sensory ganglion, and blocked abnormal spontaneous activity and other measures of hyperexcitability in myelinated neurons in the ligated sensory ganglion. Immunohistochemical experiments showed that sympathetic sprouting preferentially targeted NaV1.6-positive neurons. Under these experimental conditions, NaV1.6 knockdown did not prevent or strongly alter single evoked action potentials, unlike previous less specific methods used to block spontaneous activity. NaV1.6 knockdown also reduced pain behaviors in another pain model, chronic constriction of the sciatic nerve, provided the model was modified so that the lesion site was relatively close to the siRNA-injected lumbar DRGs. The results highlight the relative importance of abnormal spontaneous activity in establishing both pain behaviors and sympathetic sprouting, and suggest that the NaV1.6 isoform may have value as a therapeutic target.
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Affiliation(s)
- W Xie
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA.
| | - J A Strong
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA.
| | - J-M Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA.
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39
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Teramoto N, Yotsu-Yamashita M. Selective blocking effects of 4,9-anhydrotetrodotoxin, purified from a crude mixture of tetrodotoxin analogues, on NaV1.6 channels and its chemical aspects. Mar Drugs 2015; 13:984-95. [PMID: 25686275 PMCID: PMC4344613 DOI: 10.3390/md13020984] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 01/30/2015] [Accepted: 02/03/2015] [Indexed: 12/19/2022] Open
Abstract
Tetrodotoxin (TTX) is a potent neurotoxin found in a number of marine creatures including the pufferfish, where it is synthesized by bacteria and accumulated through the food chain. It is a potent and selective blocker of some types of voltage-gated Na+ channel (NaV channel). 4,9-Anhydrotetrodotoxin (4,9-anhydroTTX) was purified from a crude mixture of TTX analogues (such as TTX, 4-epiTTX, 6-epiTTX, 11-oxoTTX and 11-deoxyTTX) by the use of liquid chromatography-fluorescence detection (LC-FLD) techniques. Recently, it has been reported that 4,9-anhydroTTX selectively blocks the activity of NaV1.6 channels with a blocking efficacy 40–160 times higher than that for other TTX-sensitive NaV1.x channel isoforms. However, little attention has been paid to the molecular properties of the α-subunit in NaV1.6 channels and the characteristics of binding of 4,9-anhydroTTX. From a functional point of view, it is important to determine the relative expression of NaV1.6 channels in a wide variety of tissues. The aim of this review is to discuss briefly current knowledge about the pharmacology of 4,9-anhydroTTX, and provide an analysis of the molecular structure of native NaV1.6 channels. In addition, chemical aspects of 4,9-anhydroTTX are briefly covered.
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Affiliation(s)
- Noriyoshi Teramoto
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga 849-8501, Japan.
- Laboratory of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, Sendai 980-8575, Japan.
| | - Mari Yotsu-Yamashita
- Laboratory of Bioorganic Chemistry of Natural Products, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan.
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Moore S, Khalaj AJ, Patel R, Yoon J, Ichwan D, Hayardeny L, Tiwari-Woodruff SK. Restoration of axon conduction and motor deficits by therapeutic treatment with glatiramer acetate. J Neurosci Res 2014; 92:1621-36. [PMID: 24989965 PMCID: PMC4305217 DOI: 10.1002/jnr.23440] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 05/25/2014] [Accepted: 05/27/2014] [Indexed: 12/20/2022]
Abstract
Glatiramer acetate (GA; Copaxone) is an approved drug for the treatment of multiple sclerosis (MS). The underlying multifactorial anti-inflammatory, neuroprotective effect of GA is in the induction of reactive T cells that release immunomodulatory cytokines and neurotrophic factors at the injury site. These GA-induced cytokines and growth factors may have a direct effect on axon function. Building on previous findings that suggest a neuroprotective effect of GA, we assessed the therapeutic effects of GA on brain and spinal cord pathology and functional correlates using the chronic experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Therapeutic regimens were utilized based on promising prophylactic efficacy. More specifically, C57BL/6 mice were treated with 2 mg/mouse/day GA for 8 days beginning at various time points after EAE post-induction day 15, yielding a thorough, clinically relevant assessment of GA efficacy within the context of severe progressive disease. Therapeutic treatment with GA significantly decreased clinical scores and improved rotorod motor performance in EAE mice. These functional improvements were supported by an increase in myelinated axons and fewer amyloid precursor protein-positive axons in the spinal cords of GA-treated EAE mice. Furthermore, therapeutic GA decreased microglia/macrophage and T cell infiltrates and increased oligodendrocyte numbers in both the spinal cord and corpus callosum of EAE mice. Finally, GA improved callosal axon conduction and nodal protein organization in EAE. Our results demonstrate that therapeutic GA treatment has significant beneficial effects in a chronic mouse model of MS, in which its positive effects on both myelinated and non-myelinated axons results in improved axon function.
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Affiliation(s)
- Spencer Moore
- Department of Neurology, UCLA School of MedicineLos Angeles, California
| | - Anna J Khalaj
- Department of Neurology, UCLA School of MedicineLos Angeles, California
| | - Rhusheet Patel
- Department of Neurology, UCLA School of MedicineLos Angeles, California
| | - JaeHee Yoon
- Department of Neurology, UCLA School of MedicineLos Angeles, California
| | - Daniel Ichwan
- Department of Neurology, UCLA School of MedicineLos Angeles, California
| | - Liat Hayardeny
- Pharmacology Unit, Global Innovative Research and Development, Teva Pharmaceutical IndustriesNetanya, Israel
| | - Seema K Tiwari-Woodruff
- Department of Neurology, UCLA School of MedicineLos Angeles, California
- Brain Research Institute, UCLA School of MedicineLos Angeles, California
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Escalona MP, Batista CV, Cassulini RR, Rios MS, Coronas FI, Possani LD. A proteomic analysis of the early secondary molecular effects caused by Cn2 scorpion toxin on neuroblastoma cells. J Proteomics 2014; 111:212-23. [DOI: 10.1016/j.jprot.2014.04.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 04/20/2014] [Accepted: 04/22/2014] [Indexed: 01/16/2023]
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Neishabouri A, Faisal AA. Saltatory conduction in unmyelinated axons: clustering of Na(+) channels on lipid rafts enables micro-saltatory conduction in C-fibers. Front Neuroanat 2014; 8:109. [PMID: 25352785 PMCID: PMC4195365 DOI: 10.3389/fnana.2014.00109] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Accepted: 09/15/2014] [Indexed: 11/17/2022] Open
Abstract
THE ACTION POTENTIAL (AP), THE FUNDAMENTAL SIGNAL OF THE NERVOUS SYSTEM, IS CARRIED BY TWO TYPES OF AXONS: unmyelinated and myelinated fibers. In the former the action potential propagates continuously along the axon as established in large-diameter fibers. In the latter axons the AP jumps along the nodes of Ranvier-discrete, anatomically specialized regions which contain very high densities of sodium ion (Na(+)) channels. Therefore, saltatory conduction is thought as the hallmark of myelinated axons, which enables faster and more reliable propagation of signals than in unmyelinated axons of same outer diameter. Recent molecular anatomy showed that in C-fibers, the very thin (0.1 μm diameter) axons of the peripheral nervous system, Nav1.8 channels are clustered together on lipid rafts that float in the cell membrane. This localized concentration of Na(+) channels resembles in structure the ion channel organization at the nodes of Ranvier, yet it is currently unknown whether this translates into an equivalent phenomenon of saltatory conduction or related-functional benefits and efficiencies. Therefore, we modeled biophysically realistic unmyelinated axons with both conventional and lipid-raft based organization of Na(+) channels. We find that APs are reliably conducted in a micro-saltatory fashion along lipid rafts. Comparing APs in unmyelinated fibers with and without lipid rafts did not reveal any significant difference in either the metabolic cost or AP propagation velocity. By investigating the efficiency of AP propagation over Nav1.8 channels, we find however that the specific inactivation properties of these channels significantly increase the metabolic cost of signaling in C-fibers.
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Affiliation(s)
- Ali Neishabouri
- Brain and Behaviour Lab, Department of Computing, Imperial College LondonLondon, UK
- Brain and Behaviour Lab, Department of Bioengineering, Imperial College LondonLondon, UK
| | - A. Aldo Faisal
- Brain and Behaviour Lab, Department of Computing, Imperial College LondonLondon, UK
- Brain and Behaviour Lab, Department of Bioengineering, Imperial College LondonLondon, UK
- Faculty of Medicine, MRC Clinical Sciences CentreLondon, UK
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Persson AK, Estacion M, Ahn H, Liu S, Stamboulian-Platel S, Waxman SG, Black JA. Contribution of sodium channels to lamellipodial protrusion and Rac1 and ERK1/2 activation in ATP-stimulated microglia. Glia 2014; 62:2080-95. [PMID: 25043721 DOI: 10.1002/glia.22728] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 06/11/2014] [Accepted: 07/08/2014] [Indexed: 12/19/2022]
Abstract
Microglia are motile resident immune cells of the central nervous system (CNS) that continuously explore their territories for threats to tissue homeostasis. Following CNS insult (e.g., cellular injury, infection, or ischemia), microglia respond to signals such as ATP, transform into an activated state, and migrate towards the threat. Directed migration is a complex and highly-coordinated process involving multiple intersecting cellular pathways, including signal transduction, membrane adhesion and retraction, cellular polarization, and rearrangement of cytoskeletal elements. We previously demonstrated that the activity of sodium channels contributes to ATP-induced migration of microglia. Here we show that TTX-sensitive sodium channels, specifically NaV 1.6, participate in an initial event in the migratory process, i.e., the formation in ATP-stimulated microglia of polymerized actin-rich membrane protrusions, lamellipodia, containing accumulations of Rac1 and phosphorylated ERK1/2. We also examined Ca(2+) transients in microglia and found that blockade of sodium channels with TTX produced a downward shift in the level of [Ca(2+) ]i during the delayed, slower recovery of [Ca(2+) ]i following ATP stimulation. These observations demonstrate a modulatory role of sodium channels on Ca(2+) transients in microglia that are likely to affect down-stream signaling cascades. Consistent with these observations, we demonstrate that ATP-induced microglial migration is mediated via Rac1 and ERK1/2, but not p38α/β and JNK, dependent pathways, and that activation of both Rac1 and ERK1/2 is modulated by sodium channel activity. Our results provide evidence for a direct link between sodium channel activity and modulation of Rac1 and ERK1/2 activation in ATP-stimulated microglia, possibly by regulating Ca(2+) transients.
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Affiliation(s)
- Anna-Karin Persson
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, Connecticut
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Lesniak DR, Marshall KL, Wellnitz SA, Jenkins BA, Baba Y, Rasband MN, Gerling GJ, Lumpkin EA. Computation identifies structural features that govern neuronal firing properties in slowly adapting touch receptors. eLife 2014; 3:e01488. [PMID: 24448409 PMCID: PMC3896213 DOI: 10.7554/elife.01488] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Touch is encoded by cutaneous sensory neurons with diverse morphologies and physiological outputs. How neuronal architecture influences response properties is unknown. To elucidate the origin of firing patterns in branched mechanoreceptors, we combined neuroanatomy, electrophysiology and computation to analyze mouse slowly adapting type I (SAI) afferents. These vertebrate touch receptors, which innervate Merkel cells, encode shape and texture. SAI afferents displayed a high degree of variability in touch-evoked firing and peripheral anatomy. The functional consequence of differences in anatomical architecture was tested by constructing network models representing sequential steps of mechanosensory encoding: skin displacement at touch receptors, mechanotransduction and action-potential initiation. A systematic survey of arbor configurations predicted that the arrangement of mechanotransduction sites at heminodes is a key structural feature that accounts in part for an afferent’s firing properties. These findings identify an anatomical correlate and plausible mechanism to explain the driver effect first described by Adrian and Zotterman. DOI:http://dx.doi.org/10.7554/eLife.01488.001 Sensory receptors in the skin supply us with information about objects in the world around us, including their shape and texture. These receptors also detect pressure, temperature, and pain, enabling us to respond appropriately to stimuli that could be potentially harmful. The activation of a touch receptor—for example, due to the movement of a hair—causes ions to flow into the cell, changing the electric charge inside it. When the charge exceeds a threshold value, the cell fires action potentials, which travel along its axon to the central nervous system. The patterns of these action potentials from a population of touch receptors carry all the information about a touch stimulus to the brain. Different types of sensory receptors have unique anatomical structures and distinct signaling patterns; however, little is known about how the structures of sensory receptors influence action potential firing. Now Lesniak and Marshall et al. have revealed that structure determines function in a type of mammalian touch receptor called the slowly adapting type I receptor, which is concentrated in fingertips and other areas of high tactile acuity. With the aid of high-resolution microscopy, the complex branching structure of the receptor and its network of nerve endings were mapped in three dimensions. Experiments revealed highly variable structures and firing patterns between individual touch receptors, and computational modeling showed that changing either the number or the arrangement of receptor endings influenced the neuron’s firing properties. This is the first computational model that captures touch encoding by combining skin properties, sensory transduction, and spike initiation. As well as providing new information on how structure permits function, this work opens up new possibilities for exploring how the skin maintains its sensory capabilities during routine maintenance and after injury. DOI:http://dx.doi.org/10.7554/eLife.01488.002
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Affiliation(s)
- Daine R Lesniak
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, United States
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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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Xie W, Strong JA, Ye L, Mao JX, Zhang JM. Knockdown of sodium channel NaV1.6 blocks mechanical pain and abnormal bursting activity of afferent neurons in inflamed sensory ganglia. Pain 2013; 154:1170-80. [PMID: 23622763 DOI: 10.1016/j.pain.2013.02.027] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 02/06/2013] [Accepted: 02/26/2013] [Indexed: 11/15/2022]
Abstract
Inflammatory processes in the sensory ganglia contribute to many forms of chronic pain. We previously showed that local inflammation of the lumbar sensory ganglia rapidly leads to prolonged mechanical pain behaviors and high levels of spontaneous bursting activity in myelinated cells. Abnormal spontaneous activity of sensory neurons occurs early in many preclinical pain models and initiates many other pathological changes, but its molecular basis is not well understood. The sodium channel isoform NaV1.6 can underlie repetitive firing and excitatory persistent and resurgent currents. We used in vivo knockdown of this channel via local injection of siRNA to examine its role in chronic pain after local inflammation of the rat lumbar sensory ganglia. In normal dorsal root ganglion (DRG), quantitative polymerase chain reaction showed that cells capable of firing repetitively had significantly higher relative expression of NaV1.6. In inflamed DRG, spontaneously active bursting cells expressed high levels of NaV1.6 immunoreactivity. In vivo knockdown of NaV1.6 locally in the lumbar DRG at the time of DRG inflammation completely blocked development of pain behaviors and abnormal spontaneous activity, while having only minor effects on unmyelinated C cells. Current research on isoform-specific sodium channel blockers for chronic pain is largely focused on NaV1.8 because it is present primarily in unmyelinated C fiber nociceptors, or on NaV1.7 because lack of this channel causes congenital indifference to pain. However, the results suggest that NaV1.6 may be a useful therapeutic target for chronic pain and that some pain conditions may be mediated primarily by myelinated A fiber sensory neurons.
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Affiliation(s)
- Wenrui Xie
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
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Eijkelkamp N, Linley JE, Baker MD, Minett MS, Cregg R, Werdehausen R, Rugiero F, Wood JN. Neurological perspectives on voltage-gated sodium channels. Brain 2012; 135:2585-612. [PMID: 22961543 PMCID: PMC3437034 DOI: 10.1093/brain/aws225] [Citation(s) in RCA: 251] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The activity of voltage-gated sodium channels has long been linked to disorders of neuronal excitability such as epilepsy and chronic pain. Recent genetic studies have now expanded the role of sodium channels in health and disease, to include autism, migraine, multiple sclerosis, cancer as well as muscle and immune system disorders. Transgenic mouse models have proved useful in understanding the physiological role of individual sodium channels, and there has been significant progress in the development of subtype selective inhibitors of sodium channels. This review will outline the functions and roles of specific sodium channels in electrical signalling and disease, focusing on neurological aspects. We also discuss recent advances in the development of selective sodium channel inhibitors.
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Affiliation(s)
- Niels Eijkelkamp
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK.
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Cachemaille M, Laedermann CJ, Pertin M, Abriel H, Gosselin RD, Decosterd I. Neuronal expression of the ubiquitin ligase Nedd4-2 in rat dorsal root ganglia: modulation in the spared nerve injury model of neuropathic pain. Neuroscience 2012; 227:370-80. [PMID: 23022218 DOI: 10.1016/j.neuroscience.2012.09.044] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 09/13/2012] [Accepted: 09/19/2012] [Indexed: 10/27/2022]
Abstract
Neuronal hyperexcitability following peripheral nerve lesions may stem from altered activity of voltage-gated sodium channels (VGSCs), which gives rise to allodynia or hyperalgesia. In vitro, the ubiquitin ligase Nedd4-2 is a negative regulator of VGSC α-subunits (Na(v)), in particular Na(v)1.7, a key actor in nociceptor excitability. We therefore studied Nedd4-2 in rat nociceptors, its co-expression with Na(v)1.7 and Na(v)1.8, and its regulation in pathology. Adult rats were submitted to the spared nerve injury (SNI) model of neuropathic pain or injected with complete Freund's adjuvant (CFA), a model of inflammatory pain. L4 dorsal root ganglia (DRG) were analyzed in sham-operated animals, seven days after SNI and 48 h after CFA with immunofluorescence and Western blot. We observed Nedd4-2 expression in almost 50% of DRG neurons, mostly small and medium-sized. A preponderant localization is found in the non-peptidergic sub-population. Additionally, 55.7 ± 2.7% and 55.0 ± 3.6% of Nedd4-2-positive cells are co-labeled with Na(v)1.7 and Na(v)1.8 respectively. SNI significantly decreases the proportion of Nedd4-2-positive neurons from 45.9 ± 1.9% to 33.5 ± 0.7% (p<0.01) and the total Nedd4-2 protein to 44% ± 0.13% of its basal level (p<0.01, n=4 animals in each group, mean ± SEM). In contrast, no change in Nedd4-2 was found after peripheral inflammation induced by CFA. These results indicate that Nedd4-2 is present in nociceptive neurons, is downregulated after peripheral nerve injury, and might therefore contribute to the dysregulation of Na(v)s involved in the hyperexcitability associated with peripheral nerve injuries.
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Affiliation(s)
- M Cachemaille
- Pain Center, Department of Anesthesiology, University Hospital Center (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.
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An ankyrinG-binding motif is necessary and sufficient for targeting Nav1.6 sodium channels to axon initial segments and nodes of Ranvier. J Neurosci 2012; 32:7232-43. [PMID: 22623668 DOI: 10.1523/jneurosci.5434-11.2012] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Neurons are highly polarized cells with functionally distinct axonal and somatodendritic compartments. Voltage-gated sodium channels Na(v)1.2 and Na(v)1.6 are highly enriched at axon initial segments (AISs) and nodes of Ranvier, where they are necessary for generation and propagation of action potentials. Previous studies using reporter proteins in unmyelinated cultured neurons suggest that an ankyrinG-binding motif within intracellular loop 2 (L2) of sodium channels is sufficient for targeting these channels to the AIS, but mechanisms of channel targeting to nodes remain poorly understood. Using a CD4-Na(v)1.2/L2 reporter protein in rat dorsal root ganglion neuron-Schwann cell myelinating cocultures, we show that the ankyrinG-binding motif is sufficient for protein targeting to nodes of Ranvier. However, reporter proteins cannot capture the complexity of full-length channels. To determine how native, full-length sodium channels are clustered in axons, and to show the feasibility of studying these channels in vivo, we constructed fluorescently tagged and functional mouse Na(v)1.6 channels for in vivo analysis using in utero brain electroporation. We show here that wild-type tagged-Na(v)1.6 channels are efficiently clustered at nodes and AISs in vivo. Furthermore, we show that mutation of a single invariant glutamic acid residue (E1100) within the ankyrinG-binding motif blocked Na(v)1.6 targeting in neurons both in vitro and in vivo. Additionally, we show that caseine kinase phosphorylation sites within this motif, while not essential for targeting, can modulate clustering at the AIS. Thus, the ankyrinG-binding motif is both necessary and sufficient for the clustering of sodium channels at nodes of Ranvier and the AIS.
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Vasylyev DV, Waxman SG. Membrane properties and electrogenesis in the distal axons of small dorsal root ganglion neurons in vitro. J Neurophysiol 2012; 108:729-40. [DOI: 10.1152/jn.00091.2012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Although it is generally thought that sensory transduction occurs at or close to peripheral nerve endings, with action potentials subsequently propagating along the axons of dorsal root ganglia (DRG) neurons toward the central nervous system, the small diameter of nociceptive axons and their endings have made it difficult to estimate their membrane properties and electrogenic characteristics. Even the resting potentials of nociceptive axons are unknown. In this study, we developed the capability to record directly with patch-clamp electrodes from the small-diameter distal axons of DRG neurons in vitro. We showed using current-clamp recordings that 1) these sensory axons have a resting potential of −60.2 ± 1 mV; 2) both tetrodotoxin (TTX)-sensitive (TTX-S) and TTX-resistant (TTX-R) Na+ channels are present and available for activation at resting potential, at densities that can support action potential electrogenesis in these axons; 3) TTX-sensitive channels contribute to the amplification of small depolarizations that are subthreshold with respect to the action potential in these axons; 4) TTX-R channels can support the production of action potentials in these axons; and 5) these TTX-R channels can produce repetitive firing, even at depolarized membrane potentials where TTX-S channels are inactivated. Finally, using voltage-clamp recordings with an action potential as the command, we confirmed the presence of both TTX-S and TTX-R channels, which are activated sequentially during action potential in these axons. These results provide direct evidence for the presence of TTX-S and TTX-R Na+ channels that are functionally available at resting potential and contribute to electrogenesis in small-diameter afferent axons.
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Affiliation(s)
- Dmytro V. Vasylyev
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Stephen G. Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
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