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Aiba I, Ning Y, Noebels JL. Persistent Na + current couples spreading depolarization to seizures in Scn8a gain of function mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.10.11.617888. [PMID: 39416109 PMCID: PMC11482884 DOI: 10.1101/2024.10.11.617888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 10/19/2024]
Abstract
Spreading depolarization (SD) is a slowly propagating wave of massive cellular depolarization that transiently impairs the function of affected brain regions. While SD typically arises as an isolated hemispheric event, we previously reported that reducing M-type potassium current (I KM ) by ablation of Kcnq2 in forebrain excitatory neurons results in tightly coupled spontaneous bilateral seizure-SD complexes in the awake mouse cortex. Here we find that enhanced persistent Na + current due to gain-of-function (GOF) mutations in Scn8a (N1768D/+, hereafter D/+) produces a similar compound cortical excitability phenotype. Chronic DC-band EEG recording detected spontaneous bilateral seizure-SD complexes accompanied by seizures with a profound tonic component, which occurs predominantly during the light phase and were detected in the mutant mice across ages between P40-100. Laser speckle contrast imaging of cerebral blood flow dynamics resolved SD as bilateral wave of hypoperfusion and subsequent hour-lasting hypoperfusion in Scn8a D/+ cortex in awake head-restrained mice subjected to a subconvulsive PTZ. Subcortical recordings in freely moving mice revealed that approximately half of the spontaneous cortical seizure-SD complexes arose with concurrent SD-like depolarization in the thalamus and delayed depolarization in the striatum. In contrast, SD-like DC potential shifts were rarely detected in the hippocampus or upper pons. Consistent with the high spontaneous incidence in vivo , cortical slices from Scn8a D/+ mice showed a raised SD susceptibility, and pharmacological inhibition of persistent Na + current (I NaP ), which is enhanced in Scn8a D/+ neurons, inhibited SD generation in cortical slices ex vivo , indicating that I NaP contributes to SD susceptibility. Ex vivo Ca 2+ imaging studies using acute brain slices expressing genetic Ca 2+ sensor (Thy1-GCAMP6s) demonstrated that pharmacological activation of I KM suppressed Ca 2+ spikes and SD, whereas I KM inhibitor drastically increased the frequency of Ca 2+ spikes in the hippocampus of Scn8a D/+ mice, but not in WT, suggesting that I KM restrains the hyperexcitability resulting from Scn8a GOF mutation. Together, our study identifies a cortical SD phenotype in Scn8a GOF mice shared with the Kcnq2 - cKO model of developmental epileptic encephalopathy and reveals that an imbalance of non-inactivating inward and outward membrane currents bidirectionally modulates spatiotemporal SD susceptibility.
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Müller P, Draguhn A, Egorov AV. Persistent sodium currents in neurons: potential mechanisms and pharmacological blockers. Pflugers Arch 2024; 476:1445-1473. [PMID: 38967655 PMCID: PMC11381486 DOI: 10.1007/s00424-024-02980-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2024] [Revised: 06/07/2024] [Accepted: 06/11/2024] [Indexed: 07/06/2024]
Abstract
Persistent sodium current (INaP) is an important activity-dependent regulator of neuronal excitability. It is involved in a variety of physiological and pathological processes, including pacemaking, prolongation of sensory potentials, neuronal injury, chronic pain and diseases such as epilepsy and amyotrophic lateral sclerosis. Despite its importance, neither the molecular basis nor the regulation of INaP are sufficiently understood. Of particular significance is a solid knowledge and widely accepted consensus about pharmacological tools for analysing the function of INaP and for developing new therapeutic strategies. However, the literature on INaP is heterogeneous, with varying definitions and methodologies used across studies. To address these issues, we provide a systematic review of the current state of knowledge on INaP, with focus on mechanisms and effects of this current in the central nervous system. We provide an overview of the specificity and efficacy of the most widely used INaP blockers: amiodarone, cannabidiol, carbamazepine, cenobamate, eslicarbazepine, ethosuximide, gabapentin, GS967, lacosamide, lamotrigine, lidocaine, NBI-921352, oxcarbazepine, phenytoine, PRAX-562, propofol, ranolazine, riluzole, rufinamide, topiramate, valproaic acid and zonisamide. We conclude that there is strong variance in the pharmacological effects of these drugs, and in the available information. At present, GS967 and riluzole can be regarded bona fide INaP blockers, while phenytoin and lacosamide are blockers that only act on the slowly inactivating component of sodium currents.
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Affiliation(s)
- Peter Müller
- Department Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen , Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany.
| | - Andreas Draguhn
- Institute for Physiology and Pathophysiology, Medical Faculty, Heidelberg University, Im Neuenheimer Feld 326, 69120, Heidelberg, Germany
| | - Alexei V Egorov
- Institute for Physiology and Pathophysiology, Medical Faculty, Heidelberg University, Im Neuenheimer Feld 326, 69120, Heidelberg, Germany
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Cho JH, Jang IS. Ibuprofen modulates tetrodotoxin-resistant persistent Na + currents at acidic pH in rat trigeminal ganglion neurons. Eur J Pharmacol 2023; 961:176218. [PMID: 37992887 DOI: 10.1016/j.ejphar.2023.176218] [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: 07/09/2023] [Revised: 11/13/2023] [Accepted: 11/16/2023] [Indexed: 11/24/2023]
Abstract
Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to relieve various symptoms such as headache, arthralgia, and dental pain. While the primary mechanism of NSAID-based pain relief is the inhibition of cyclooxygenase-2, several NSAIDs also modulate other molecular targets related to nociceptive transmission such as voltage-gated Na+ channels. In the present study, we examined the effects of NSAIDs on persistent Na+ current (INaP) mediated by tetrodotoxin-resistant (TTX-R) Na+ channels in small-to medium-sized trigeminal ganglion neurons using a whole-cell patch-clamp technique. At clinically relevant concentrations, all propionic acid derivatives tested (ibuprofen, naproxen, fenoprofen, and flurbiprofen) preferentially inhibited the TTX-R INaP. The inhibition was more potent at acidic extracellular pH (pH 6.5) than at normal pH (pH 7.4). Other NSAIDs, such as ketorolac, piroxicam, and aspirin, had a negligible effect on the TTX-R INaP. Ibuprofen both accelerated the onset of inactivation and retarded the recovery from inactivation of TTX-R Na+ channels at acidic extracellular pH. However, all NSAIDs tested in this study had minor effects on voltage-gated K+ currents, as well as hyperpolarization-activated and cyclic nucleotide-gated cation currents, at both acidic and normal extracellular pH. Under current-clamp conditions, ibuprofen decreased the number of action potentials elicited by depolarizing current stimuli at acidic (pH 6.5) extracellular pH. Considering that extracellular pH falls as low as 5.5 in inflamed tissues, TTX-R INaP inhibition could be a mechanism by which ibuprofen and propionic acid derivative NSAIDs modulate inflammatory pain.
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Affiliation(s)
- Jin-Hwa Cho
- Department of Pharmacology, School of Dentistry, Republic of Korea
| | - Il-Sung Jang
- Department of Pharmacology, School of Dentistry, Republic of Korea; Brain Science & Engineering Institute, Kyungpook National University, Daegu, 41940, Republic of Korea.
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Lapshina MA, Shevtsova EF, Grigoriev VV, Aksinenko AY, Ustyugov AA, Steinberg DA, Maleev GV, Dubrovskaya ES, Goreva TV, Epishina TA, Zamoyski VL, Makhaeva GF, Fisenko VP, Veselov IM, Vinogradova DV, Bachurin SO. New Adamantane-Containing Edaravone Conjugates as Potential Neuroprotective Agents for ALS Treatments. Molecules 2023; 28:7567. [PMID: 38005288 PMCID: PMC10673157 DOI: 10.3390/molecules28227567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 10/31/2023] [Accepted: 11/10/2023] [Indexed: 11/26/2023] Open
Abstract
Currently, there are no effective drugs for the treatment of amyotrophic lateral sclerosis (ALS). Only two drugs-edaravone and riluzole-have been approved, but they have very limited efficacy. The aim of this work was to modify the structural core of the Edaravone-phenylpyrazolone moiety and combine it with aminoadamantane pharmacophore in order to expand the spectrum of its action to a number of processes involved in the pathogenesis of ALS. New conjugates of edaravone derivatives with 1-aminoadamantanes combined with alkylene or hydroxypropylene spacers were synthesized, and their biological activity was investigated. Compounds were found that could inhibit lipid peroxidation and calcium-related mitochondrial permeability, block fast sodium currents of CNS neurons, and reduce aggregation of the mutated form of the FUS-protein typical to ALS. So, the proposed modification of the edaravone molecule has allowed the obtaining of new original structures that combine some prospective therapeutic mechanisms against key chains of the pathogenesis of ALS. The identified lead compounds can be used for further optimization and development of new promising drugs on this basis for the treatment of ALS.
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Affiliation(s)
- Maria A. Lapshina
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Elena F. Shevtsova
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Vladimir V. Grigoriev
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Aleksey Yu. Aksinenko
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Aleksey A. Ustyugov
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Daniil A. Steinberg
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Grigoriy V. Maleev
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Elena S. Dubrovskaya
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Tatiana V. Goreva
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Tatiana A. Epishina
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Vladimir L. Zamoyski
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Galina F. Makhaeva
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Vladimir P. Fisenko
- Department of Pharmacology, Sechenov I. M. First Moscow State Medical University, 8 Build. 2 Trubetskaya Str., 119991 Moscow, Russia;
| | - Ivan M. Veselov
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Daria V. Vinogradova
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
| | - Sergey O. Bachurin
- Institute of Physiologically Active Compounds at the Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, 1 Severnij proezd, 142432 Chernogolovka, Russia; (M.A.L.); (E.F.S.); (V.V.G.); (A.Y.A.); (A.A.U.); (D.A.S.); (G.V.M.); (E.S.D.); (T.V.G.); (T.A.E.); (V.L.Z.); (G.F.M.); (I.M.V.); (D.V.V.)
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Morais A, Qin T, Ayata C, Harriott AM. Inhibition of persistent sodium current reduces spreading depression-evoked allodynia in a mouse model of migraine with aura. Pain 2023; 164:2564-2571. [PMID: 37318029 DOI: 10.1097/j.pain.0000000000002962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 04/18/2023] [Indexed: 06/16/2023]
Abstract
ABSTRACT We investigated the efficacy of inhibiting persistent Na + currents (I NaP ) in acute rodent models of migraine with aura. Cortical spreading depression (SD) is a slow wave of neuronal and glial depolarization that underlies the migraine aura. Minimally invasive optogenetic SD (opto-SD) causes periorbital mechanical allodynia in mice, suggesting SD activates trigeminal nociceptors. Persistent Na + currents contribute to neuronal intrinsic excitability and have been implicated in peripheral and cortical excitation. We examined a preferential inhibitor of I NaP, GS-458967, on SD-induced periorbital allodynia, SD susceptibility, and formalin-induced peripheral pain. Periorbital mechanical allodynia was tested in male and female Thy1-ChR2-YFP mice after a single opto-SD event using manual von Frey monofilaments. GS-458967 (1 mg/kg, s.c.) or vehicle was dosed immediately after opto-SD induction, and allodynia was tested 1 hour later. The electrical SD threshold and KCl-induced SD frequency were examined in the cortex in male Sprague-Dawley rats after 1 hour pretreatment with GS-458967 (3 mg/kg, s.c.) or vehicle. Effects of GS-458967 (0.5-5 mg/kg, p.o.) on spontaneous formalin hind paw behavior and locomotion were also examined in male CD-1 mice. GS-458967 suppressed opto-SD-induced periorbital allodynia and decreased susceptibility to SD. GS-458967 also diminished early and late phase formalin-induced paw-licking behavior with early phase paw licking responding to lower doses. GS-458967 up to 3 mg/kg had no impact on locomotor activity. These data provide evidence that I NaP inhibition can reduce opto-SD-induced trigeminal pain behavior and support I NaP inhibition as an antinociceptive strategy for both abortive and preventive treatment of migraine.
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Affiliation(s)
- Andreia Morais
- Neurovascular Research Unit, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States
| | - Tao Qin
- Neurovascular Research Unit, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States
| | - Cenk Ayata
- Neurovascular Research Unit, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States
- Department of Neurology, Massachusetts General Hospital, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Andrea M Harriott
- Neurovascular Research Unit, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States
- Department of Neurology, Massachusetts General Hospital, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
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Perez-Sanchez J, Middleton SJ, Pattison LA, Hilton H, Awadelkareem MA, Zuberi SR, Renke MB, Hu H, Yang X, Clark AJ, Smith ESJ, Bennett DL. A humanized chemogenetic system inhibits murine pain-related behavior and hyperactivity in human sensory neurons. Sci Transl Med 2023; 15:eadh3839. [PMID: 37792955 PMCID: PMC7615191 DOI: 10.1126/scitranslmed.adh3839] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 09/15/2023] [Indexed: 10/06/2023]
Abstract
Hyperexcitability in sensory neurons is known to underlie many of the maladaptive changes associated with persistent pain. Chemogenetics has shown promise as a means to suppress such excitability, yet chemogenetic approaches suitable for human applications are needed. PSAM4-GlyR is a modular system based on the human α7 nicotinic acetylcholine and glycine receptors, which responds to inert chemical ligands and the clinically approved drug varenicline. Here, we demonstrated the efficacy of this channel in silencing both mouse and human sensory neurons by the activation of large shunting conductances after agonist administration. Virally mediated expression of PSAM4-GlyR in mouse sensory neurons produced behavioral hyposensitivity upon agonist administration, which was recovered upon agonist washout. Stable expression of the channel led to similar reversible suppression of pain-related behavior even after 10 months of viral delivery. Mechanical and spontaneous pain readouts were also ameliorated by PSAM4-GlyR activation in acute and joint pain inflammation mouse models. Furthermore, suppression of mechanical hypersensitivity generated by a spared nerve injury model of neuropathic pain was also observed upon activation of the channel. Effective silencing of behavioral hypersensitivity was reproduced in a human model of hyperexcitability and clinical pain: PSAM4-GlyR activation decreased the excitability of human-induced pluripotent stem cell-derived sensory neurons and spontaneous activity due to a gain-of-function NaV1.7 mutation causing inherited erythromelalgia. Our results demonstrate the contribution of sensory neuron hyperexcitability to neuropathic pain and the translational potential of an effective, stable, and reversible humanized chemogenetic system for the treatment of pain.
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Affiliation(s)
- Jimena Perez-Sanchez
- Nuffield Department of Clinical Neurosciences, University of Oxford; Oxford OX3 9DU, UK
| | - Steven J. Middleton
- Nuffield Department of Clinical Neurosciences, University of Oxford; Oxford OX3 9DU, UK
| | - Luke A. Pattison
- Department of Pharmacology, University of Cambridge; Cambridge CB2 1PD, UK
| | - Helen Hilton
- Department of Pharmacology, University of Cambridge; Cambridge CB2 1PD, UK
| | | | - Sana R. Zuberi
- Nuffield Department of Clinical Neurosciences, University of Oxford; Oxford OX3 9DU, UK
| | - Maria B. Renke
- Nuffield Department of Clinical Neurosciences, University of Oxford; Oxford OX3 9DU, UK
| | - Huimin Hu
- Nuffield Department of Clinical Neurosciences, University of Oxford; Oxford OX3 9DU, UK
| | - Xun Yang
- Nuffield Department of Clinical Neurosciences, University of Oxford; Oxford OX3 9DU, UK
| | - Alex J. Clark
- Blizard Institute, Barts and the London School of Medicine and Dentistry; London E1 2AT, UK
| | | | - David L. Bennett
- Nuffield Department of Clinical Neurosciences, University of Oxford; Oxford OX3 9DU, UK
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Fouda MA, Ghovanloo MR, Ruben PC. Late sodium current: incomplete inactivation triggers seizures, myotonias, arrhythmias, and pain syndromes. J Physiol 2022; 600:2835-2851. [PMID: 35436004 DOI: 10.1113/jp282768] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 04/12/2022] [Indexed: 11/08/2022] Open
Abstract
Acquired and inherited dysfunction in voltage-gated sodium channels underlies a wide range of diseases. "In addition to the defects in trafficking and expression, sodium channelopathies are also caused by dysfunction in one or several gating properties, for instance activation or inactivation. Disruption of the channel inactivation leads to the increased late sodium current, which is a common defect in seizure disorders, cardiac arrhythmias skeletal muscle myotonia and pain. An increase in late sodium current leads to repetitive action potential in neurons and skeletal muscles, and prolonged action potential duration in the heart. In this topical review, we compare the effects of late sodium current in brain, heart, skeletal muscle, and peripheral nerves. Abstract figure legend Shows cartoon illustration of general Nav channel transitions between (1) resting, (2) open, and (3) fast inactivated states. Disruption of the inactivation process exacerbates (4) late sodium currents. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Mohamed A Fouda
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada.,Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt
| | | | - Peter C Ruben
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
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Velasco E, Alvarez JL, Meseguer VM, Gallar J, Talavera K. Membrane potential instabilities in sensory neurons: mechanisms and pathophysiological relevance. Pain 2022; 163:64-74. [PMID: 34086629 DOI: 10.1097/j.pain.0000000000002289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 03/29/2021] [Indexed: 11/25/2022]
Abstract
ABSTRACT Peripheral sensory neurons transduce physicochemical stimuli affecting somatic tissues into the firing of action potentials that are conveyed to the central nervous system. This results in conscious perception, adaptation, and survival, but alterations of the firing patterns can result in pain and hypersensitivity conditions. Thus, understanding the molecular mechanisms underlying action potential firing in peripheral sensory neurons is essential in sensory biology and pathophysiology. Over the past 30 years, it has been consistently reported that these cells can display membrane potential instabilities (MPIs), in the form of subthreshold membrane potential oscillations or depolarizing spontaneous fluctuations. However, research on this subject remains sparse, without a clear conductive thread to be followed. To address this, we here provide a synthesis of the description, molecular bases, mathematical models, physiological roles, and pathophysiological implications of MPIs in peripheral sensory neurons. Membrane potential instabilities have been reported in trigeminal, dorsal root, and Mes-V ganglia, where they are believed to support repetitive firing. They are proposed to have roles also in intercellular communication, ectopic firing, and responses to tonic and slow natural stimuli. We highlight how MPIs are of great interest for the study of sensory transduction physiology and how they may represent therapeutic targets for many pathological conditions, such as acute and chronic pain, itch, and altered sensory perceptions. We identify future research directions, including the elucidation of the underlying molecular determinants and modulation mechanisms, their relation to the encoding of natural stimuli and their implication in pain and hypersensitivity conditions.
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Affiliation(s)
- Enrique Velasco
- Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain
| | - Julio L Alvarez
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Leuven, Belgium
| | - Victor M Meseguer
- Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain
| | - Juana Gallar
- Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain
- Instituto de Investigación Sanitaria y Biomédica de Alicante, San Juan de Alicante, Spain
| | - Karel Talavera
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Leuven, Belgium
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Lauxmann S, Sonnenberg L, Koch NA, Bosselmann C, Winter N, Schwarz N, Wuttke TV, Hedrich UBS, Liu Y, Lerche H, Benda J, Kegele J. Therapeutic Potential of Sodium Channel Blockers as a Targeted Therapy Approach in KCNA1-Associated Episodic Ataxia and a Comprehensive Review of the Literature. Front Neurol 2021; 12:703970. [PMID: 34566847 PMCID: PMC8459024 DOI: 10.3389/fneur.2021.703970] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 07/23/2021] [Indexed: 11/17/2022] Open
Abstract
Introduction: Among genetic paroxysmal movement disorders, variants in ion channel coding genes constitute a major subgroup. Loss-of-function (LOF) variants in KCNA1, the gene coding for KV1.1 channels, are associated with episodic ataxia type 1 (EA1), characterized by seconds to minutes-lasting attacks including gait incoordination, limb ataxia, truncal instability, dysarthria, nystagmus, tremor, and occasionally seizures, but also persistent neuromuscular symptoms like myokymia or neuromyotonia. Standard treatment has not yet been developed, and different treatment efforts need to be systematically evaluated. Objective and Methods: Personalized therapeutic regimens tailored to disease-causing pathophysiological mechanisms may offer the specificity required to overcome limitations in therapy. Toward this aim, we (i) reviewed all available clinical reports on treatment response and functional consequences of KCNA1 variants causing EA1, (ii) examined the potential effects on neuronal excitability of all variants using a single compartment conductance-based model and set out to assess the potential of two sodium channel blockers (SCBs: carbamazepine and riluzole) to restore the identified underlying pathophysiological effects of KV1.1 channels, and (iii) provide a comprehensive review of the literature considering all types of episodic ataxia. Results: Reviewing the treatment efforts of EA1 patients revealed moderate response to acetazolamide and exhibited the strength of SCBs, especially carbamazepine, in the treatment of EA1 patients. Biophysical dysfunction of KV1.1 channels is typically based on depolarizing shifts of steady-state activation, leading to an LOF of KCNA1 variant channels. Our model predicts a lowered rheobase and an increase of the firing rate on a neuronal level. The estimated concentration dependent effects of carbamazepine and riluzole could partially restore the altered gating properties of dysfunctional variant channels. Conclusion: These data strengthen the potential of SCBs to contribute to functional compensation of dysfunctional KV1.1 channels. We propose riluzole as a new drug repurposing candidate and highlight the role of personalized approaches to develop standard care for EA1 patients. These results could have implications for clinical practice in future and highlight the need for the development of individualized and targeted therapies for episodic ataxia and genetic paroxysmal disorders in general.
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Affiliation(s)
- Stephan Lauxmann
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
| | - Lukas Sonnenberg
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
- Bernstein Center for Computational Neuroscience Tübingen, Tübingen, Germany
| | - Nils A. Koch
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
- Bernstein Center for Computational Neuroscience Tübingen, Tübingen, Germany
| | - Christian Bosselmann
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Natalie Winter
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Niklas Schwarz
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Thomas V. Wuttke
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Department of Neurosurgery, University of Tübingen, Tübingen, Germany
| | - Ulrike B. S. Hedrich
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Yuanyuan Liu
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Jan Benda
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
- Bernstein Center for Computational Neuroscience Tübingen, Tübingen, Germany
| | - Josua Kegele
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
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10
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Middleton SJ, Barry AM, Comini M, Li Y, Ray PR, Shiers S, Themistocleous AC, Uhelski ML, Yang X, Dougherty PM, Price TJ, Bennett DL. Studying human nociceptors: from fundamentals to clinic. Brain 2021; 144:1312-1335. [PMID: 34128530 PMCID: PMC8219361 DOI: 10.1093/brain/awab048] [Citation(s) in RCA: 67] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 11/26/2020] [Accepted: 12/08/2020] [Indexed: 12/14/2022] Open
Abstract
Chronic pain affects one in five of the general population and is the third most important cause of disability-adjusted life-years globally. Unfortunately, treatment remains inadequate due to poor efficacy and tolerability. There has been a failure in translating promising preclinical drug targets into clinic use. This reflects challenges across the whole drug development pathway, from preclinical models to trial design. Nociceptors remain an attractive therapeutic target: their sensitization makes an important contribution to many chronic pain states, they are located outside the blood-brain barrier, and they are relatively specific. The past decade has seen significant advances in the techniques available to study human nociceptors, including: the use of corneal confocal microscopy and biopsy samples to observe nociceptor morphology, the culture of human nociceptors (either from surgical or post-mortem tissue or using human induced pluripotent stem cell derived nociceptors), the application of high throughput technologies such as transcriptomics, the in vitro and in vivo electrophysiological characterization through microneurography, and the correlation with pain percepts provided by quantitative sensory testing. Genome editing in human induced pluripotent stem cell-derived nociceptors enables the interrogation of the causal role of genes in the regulation of nociceptor function. Both human and rodent nociceptors are more heterogeneous at a molecular level than previously appreciated, and while we find that there are broad similarities between human and rodent nociceptors there are also important differences involving ion channel function, expression, and cellular excitability. These technological advances have emphasized the maladaptive plastic changes occurring in human nociceptors following injury that contribute to chronic pain. Studying human nociceptors has revealed new therapeutic targets for the suppression of chronic pain and enhanced repair. Cellular models of human nociceptors have enabled the screening of small molecule and gene therapy approaches on nociceptor function, and in some cases have enabled correlation with clinical outcomes. Undoubtedly, challenges remain. Many of these techniques are difficult to implement at scale, current induced pluripotent stem cell differentiation protocols do not generate the full diversity of nociceptor populations, and we still have a relatively poor understanding of inter-individual variation in nociceptors due to factors such as age, sex, or ethnicity. We hope our ability to directly investigate human nociceptors will not only aid our understanding of the fundamental neurobiology underlying acute and chronic pain but also help bridge the translational gap.
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Affiliation(s)
- Steven J Middleton
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Allison M Barry
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Maddalena Comini
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Yan Li
- Department of Anesthesia and Pain Medicine, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Pradipta R Ray
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Stephanie Shiers
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Andreas C Themistocleous
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.,Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2000, South Africa
| | - Megan L Uhelski
- Department of Anesthesia and Pain Medicine, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Xun Yang
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Patrick M Dougherty
- Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2000, South Africa
| | - Theodore J Price
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX 75080, USA
| | - David L Bennett
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
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11
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Tidball AM, Lopez-Santiago LF, Yuan Y, Glenn TW, Margolis JL, Clayton Walker J, Kilbane EG, Miller CA, Martina Bebin E, Scott Perry M, Isom LL, Parent JM. Variant-specific changes in persistent or resurgent sodium current in SCN8A-related epilepsy patient-derived neurons. Brain 2021; 143:3025-3040. [PMID: 32968789 DOI: 10.1093/brain/awaa247] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 05/27/2020] [Accepted: 06/19/2020] [Indexed: 12/12/2022] Open
Abstract
Missense variants in the SCN8A voltage-gated sodium channel gene are linked to early-infantile epileptic encephalopathy type 13, also known as SCN8A-related epilepsy. These patients exhibit a wide spectrum of intractable seizure types, severe developmental delay, movement disorders, and elevated risk of sudden unexpected death in epilepsy. The mechanisms by which SCN8A variants lead to epilepsy are poorly understood, although heterologous expression systems and mouse models have demonstrated altered sodium current properties. To investigate these mechanisms using a patient-specific model, we generated induced pluripotent stem cells from three patients with missense variants in SCN8A: p.R1872>L (Patient 1); p.V1592>L (Patient 2); and p.N1759>S (Patient 3). Using small molecule differentiation into excitatory neurons, induced pluripotent stem cell-derived neurons from all three patients displayed altered sodium currents. Patients 1 and 2 had elevated persistent current, while Patient 3 had increased resurgent current compared to controls. Neurons from all three patients displayed shorter axon initial segment lengths compared to controls. Further analyses focused on one of the patients with increased persistent sodium current (Patient 1) and the patient with increased resurgent current (Patient 3). Excitatory cortical neurons from both patients had prolonged action potential repolarization. Using doxycycline-inducible expression of the neuronal transcription factors neurogenin 1 and 2 to synchronize differentiation of induced excitatory cortical-like neurons, we investigated network activity and response to pharmacotherapies. Both small molecule differentiated and induced patient neurons displayed similar abnormalities in action potential repolarization. Patient induced neurons showed increased burstiness that was sensitive to phenytoin, currently a standard treatment for SCN8A-related epilepsy patients, or riluzole, an FDA-approved drug used in amyotrophic lateral sclerosis and known to block persistent and resurgent sodium currents, at pharmacologically relevant concentrations. Patch-clamp recordings showed that riluzole suppressed spontaneous firing and increased the action potential firing threshold of patient-derived neurons to more depolarized potentials. Two of the patients in this study were prescribed riluzole off-label. Patient 1 had a 50% reduction in seizure frequency. Patient 3 experienced an immediate and dramatic seizure reduction with months of seizure freedom. An additional patient with a SCN8A variant in domain IV of Nav1.6 (p.V1757>I) had a dramatic reduction in seizure frequency for several months after starting riluzole treatment, but then seizures recurred. Our results indicate that patient-specific neurons are useful for modelling SCN8A-related epilepsy and demonstrate SCN8A variant-specific mechanisms. Moreover, these findings suggest that patient-specific neuronal disease modelling offers a useful platform for discovering precision epilepsy therapies.
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Affiliation(s)
- Andrew M Tidball
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | | | - Yukun Yuan
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Trevor W Glenn
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | | | - J Clayton Walker
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Emma G Kilbane
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | | | - E Martina Bebin
- Department of Neurology, University of Alabama Birmingham School of Medicine, Birmingham, AL, USA.,Department of Pediatrics, University of Alabama Birmingham School of Medicine, Birmingham, AL, USA
| | - M Scott Perry
- Cook Children's Health Care System, Fort Worth, Texas, USA
| | - Lori L Isom
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Jack M Parent
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Ann Arbor VA Healthcare System, Ann Arbor, MI, USA
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12
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Földi MC, Pesti K, Zboray K, Toth AV, Hegedűs T, Málnási-Csizmadia A, Lukacs P, Mike A. The mechanism of non-blocking inhibition of sodium channels revealed by conformation-selective photolabeling. Br J Pharmacol 2021; 178:1200-1217. [PMID: 33450052 DOI: 10.1111/bph.15365] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 12/10/2020] [Accepted: 01/03/2021] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Sodium channel inhibitors can be used to treat hyperexcitability-related diseases, including epilepsies, pain syndromes, neuromuscular disorders and cardiac arrhythmias. The applicability of these drugs is limited by their nonspecific effect on physiological function. They act mainly by sodium channel block and in addition by modulation of channel kinetics. While channel block inhibits healthy and pathological tissue equally, modulation can preferentially inhibit pathological activity. An ideal drug designed to target the sodium channels of pathological tissue would act predominantly by modulation. Thus far, no such drug has been described. EXPERIMENTAL APPROACH Patch-clamp experiments with ultra-fast solution exchange and photolabeling-coupled electrophysiology were applied to describe the unique mechanism of riluzole on Nav1.4 sodium channels. In silico docking experiments were used to study the molecular details of binding. KEY RESULTS We present evidence that riluzole acts predominantly by non-blocking modulation. We propose that, being a relatively small molecule, riluzole is able to stay bound to the binding site, but nonetheless stay off the conduction pathway, by residing in one of the fenestrations. We demonstrate how this mechanism can be recognized. CONCLUSIONS AND IMPLICATIONS Our results identify riluzole as the prototype of this new class of sodium channel inhibitors. Drugs of this class are expected to selectively prevent hyperexcitability, while having minimal effect on cells firing at a normal rate from a normal resting potential.
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Affiliation(s)
- Mátyás C Földi
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Krisztina Pesti
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary.,School of PhD Studies, Semmelweis University, Budapest, Hungary
| | - Katalin Zboray
- Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Adam V Toth
- Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Tamás Hegedűs
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - András Málnási-Csizmadia
- Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | - Peter Lukacs
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Arpad Mike
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary.,Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
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13
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Lai MC, Wu SN, Huang CW. Telmisartan, an Antagonist of Angiotensin II Receptors, Accentuates Voltage-Gated Na + Currents and Hippocampal Neuronal Excitability. Front Neurosci 2020; 14:902. [PMID: 33013297 PMCID: PMC7499822 DOI: 10.3389/fnins.2020.00902] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 08/03/2020] [Indexed: 12/19/2022] Open
Abstract
Telmisartan (TEL), a non-peptide blocker of the angiotensin II type 1 receptor, is a widely used antihypertensive agent. Nevertheless, its neuronal ionic effects and how they potentially affect neuronal network excitability remain largely unclear. With the aid of patch-clamp technology, the effects of TEL on membrane ion currents present in hippocampal neurons (mHippoE-14 cells) were investigated. For additional characterization of the effects of TEL on hippocampal neuronal excitability, we undertook in vivo studies on Sprague Dawley (SD) rats using pilocarpine-induced seizure modeling, a hippocampal histopathological analysis, and inhibitory avoidance testing. In these hippocampal neurons, TEL increased the peak amplitude of INa, with a concomitant decline in the current inactivation rate. The TEL concentration dependently enhanced the peak amplitude of depolarization-elicited INa and lessened the inactivation rate of INa. By comparison, TEL was more efficacious in stimulating the peak INa and in prolonging the inactivation time course of this current than tefluthrin or (-)-epicatechin-3-gallate. In the continued presence of pioglitazone, the TEL-perturbed stimulation of INa remained effective. In addition, cell exposure to TEL shifted the steady-state inactivation INa curve to fewer negative potentials with no perturbations of the slope factor. Unlike chlorotoxin, either ranolazine, eugenol, or KMUP-1 reversed TEL-mediated increases in the strength of non-inactivating INa. In the cell-attached voltage-clamp recordings, TEL shortened the latency in the generation of action currents. Meanwhile, TEL increased the peak INa, with a concurrent decrease in current inactivation in HEKT293T cells expressing SCN5A. Furthermore, although TEL did not aggravate pilocarpine-induced chronic seizures and tended to preserve cognitive performance, it significantly accentuated hippocampal mossy fiber sprouting. Collectively, TEL stimulation of peak INa in combination with an apparent retardation in current inactivation could be an important mechanism through which hippocampal neuronal excitability is increased, and hippocampal network excitability is accentuated following status epilepticus, suggesting further attention to this finding.
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Affiliation(s)
- Ming-Chi Lai
- Department of Pediatrics, Chi-Mei Medical Center, Tainan, Taiwan
| | - Sheng-Nan Wu
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chin-Wei Huang
- Department of Neurology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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14
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Chandra S, Wang Z, Tao X, Chen O, Luo X, Ji RR, Bortsov AV. Computer-aided Discovery of a New Nav1.7 Inhibitor for Treatment of Pain and Itch. Anesthesiology 2020; 133:611-627. [PMID: 32788559 DOI: 10.1097/aln.0000000000003427] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Voltage-gated sodium channel Nav1.7 has been validated as a perspective target for selective inhibitors with analgesic and anti-itch activity. The objective of this study was to discover new candidate compounds with Nav1.7 inhibitor properties. The authors hypothesized that their approach would yield at least one new compound that inhibits sodium currents in vitro and exerts analgesic and anti-itch effects in mice. METHODS In silico structure-based similarity search of 1.5 million compounds followed by docking to the Nav1.7 voltage sensor of Domain 4 and molecular dynamics simulation was performed. Patch clamp experiments in Nav1.7-expressing human embryonic kidney 293 cells and in mouse and human dorsal root ganglion neurons were conducted to test sodium current inhibition. Formalin-induced inflammatory pain model, paclitaxel-induced neuropathic pain model, histamine-induced itch model, and mouse lymphoma model of chronic itch were used to confirm in vivo activity of the selected compound. RESULTS After in silico screening, nine compounds were selected for experimental assessment in vitro. Of those, four compounds inhibited sodium currents in Nav1.7-expressing human embryonic kidney 293 cells by 29% or greater (P < 0.05). Compound 9 (3-(1-benzyl-1H-indol-3-yl)-3-(3-phenoxyphenyl)-N-(2-(pyrrolidin-1-yl)ethyl)propanamide, referred to as DA-0218) reduced sodium current by 80% with a 50% inhibition concentration of 0.74 μM (95% CI, 0.35 to 1.56 μM), but had no effects on Nav1.5-expressing human embryonic kidney 293 cells. In mouse and human dorsal root ganglion neurons, DA-0218 reduced sodium currents by 17% (95% CI, 6 to 28%) and 22% (95% CI, 9 to 35%), respectively. The inhibition was greatly potentiated in paclitaxel-treated mouse neurons. Intraperitoneal and intrathecal administration of the compound reduced formalin-induced phase II inflammatory pain behavior in mice by 76% (95% CI, 48 to 100%) and 80% (95% CI, 68 to 92%), respectively. Intrathecal administration of DA-0218 produced acute reduction in paclitaxel-induced mechanical allodynia, and inhibited histamine-induced acute itch and lymphoma-induced chronic itch. CONCLUSIONS This study's computer-aided drug discovery approach yielded a new Nav1.7 inhibitor that shows analgesic and anti-pruritic activity in mouse models.
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Affiliation(s)
- Sharat Chandra
- From the Center for Translational Pain Medicine, Department of Anesthesiology, Duke University School of Medicine, Durham, North Carolina (S.C., Z.W., X.T., O.C., X.L., R.-R.J., A.V.B.) the Departments of Cell Biology (O.C., R.-R.J.) Neurobiology (R.-R.J.), Duke University Medical Center, Durham, North Carolina
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15
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Fatoyinbo HO, Brown RG, Simpson DJW, van Brunt B. Numerical Bifurcation Analysis of Pacemaker Dynamics in a Model of Smooth Muscle Cells. Bull Math Biol 2020; 82:95. [PMID: 32676881 DOI: 10.1007/s11538-020-00771-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 06/26/2020] [Indexed: 11/26/2022]
Abstract
Evidence from experimental studies shows that oscillations due to electro-mechanical coupling can be generated spontaneously in smooth muscle cells. Such cellular dynamics are known as pacemaker dynamics. In this article, we address pacemaker dynamics associated with the interaction of [Formula: see text] and [Formula: see text] fluxes in the cell membrane of a smooth muscle cell. First we reduce a pacemaker model to a two-dimensional system equivalent to the reduced Morris-Lecar model and then perform a detailed numerical bifurcation analysis of the reduced model. Existing bifurcation analyses of the Morris-Lecar model concentrate on external applied current, whereas we focus on parameters that model the response of the cell to changes in transmural pressure. We reveal a transition between Type I and Type II excitabilities with no external current required. We also compute a two-parameter bifurcation diagram and show how the transition is explained by the bifurcation structure.
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Affiliation(s)
- H O Fatoyinbo
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
| | - R G Brown
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - D J W Simpson
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - B van Brunt
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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16
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Nakamura M, Cho JH, Shin H, Jang IS. Effects of cenobamate (YKP3089), a newly developed anti-epileptic drug, on voltage-gated sodium channels in rat hippocampal CA3 neurons. Eur J Pharmacol 2019; 855:175-182. [PMID: 31063770 DOI: 10.1016/j.ejphar.2019.05.007] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 04/30/2019] [Accepted: 05/03/2019] [Indexed: 11/26/2022]
Abstract
New, more effective pharmacologic treatments for epilepsy are needed, as a substantial portion of patients (>30%) are refractory to currently available anti-epileptic drugs. Cenobamate (YKP3089) is an investigational anti-epileptic drug in clinical development. Two completed adequate and well-controlled studies demonstrated a significant reduction in focal seizures with cenobamate in patients with epilepsy. In this study, we characterized the effects of cenobamate on voltage-gated Na+ channels in acutely isolated rat hippocampal CA3 neurons using a whole-cell patch-clamp technique. While cenobamate had little effect on the peak component of transient Na+ current (INaT) induced by brief depolarizing step pulses, it potently inhibited the non-inactivating persistent component of INa (INaP). In addition, cenobamate potently inhibited the current by slow voltage-ramp stimuli. Cenobamate significantly shifted the steady-state fast inactivation relationship toward a hyperpolarizing range, indicating that cenobamate binds to voltage-gated Na+ channels at the inactivated state with a higher affinity. Cenobamate also accelerated the development of inactivation and retarded recovery from inactivation of voltage-gated Na+ channels. In current clamp experiments, cenobamate hyperpolarized membrane potentials in a concentration-dependent manner, and these effects were mediated by inhibiting the INaP. Cenobamate also increased the threshold for generation of action potentials, and decreased the number of action potentials elicited by depolarizing current injection. Given that the INaP plays a pivotal role in the repetitive and/or burst generation of action potentials, the cenobamate-mediated preferential blockade of INaP might contribute to anti-epileptic activity.
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Affiliation(s)
- Michiko Nakamura
- Department of Pharmacology, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 700-412, Republic of Korea; Brain Science & Engineering Institute, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 700-412, Republic of Korea.
| | - Jin-Hwa Cho
- Department of Pharmacology, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 700-412, Republic of Korea.
| | - Hyewon Shin
- Department of Pharmacology, SK Biopharmaceuticals, Co., Ltd., 221 Pangyoyeok-ro, Seongnam, Gyeonggi, 305-712, Republic of Korea.
| | - Il-Sung Jang
- Department of Pharmacology, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 700-412, Republic of Korea; Brain Science & Engineering Institute, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 700-412, Republic of Korea.
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17
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Howells J, Matamala JM, Park SB, Garg N, Vucic S, Bostock H, Burke D, Kiernan MC. In vivo evidence for reduced ion channel expression in motor axons of patients with amyotrophic lateral sclerosis. J Physiol 2018; 596:5379-5396. [PMID: 30175403 DOI: 10.1113/jp276624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 08/31/2018] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS The progressive loss of motor units in amyotrophic lateral sclerosis (ALS) is initially compensated for by the reinnervation of denervated muscle fibres by surviving motor axons. A disruption in protein homeostasis is thought to play a critical role in the pathogenesis of ALS. The changes in surviving motor neurons were studied by comparing the nerve excitability properties of moderately and severely affected single motor axons from patients with ALS with those from single motor axons in control subjects. A mathematical model indicated that approximately 99% of the differences between the ALS and control units could be explained by a non-selective reduction in the expression of all ion channels. These changes in ALS patients are best explained by a failure in the supply of ion channel and other membrane proteins from the diseased motor neuron. ABSTRACT Amyotrophic lateral sclerosis (ALS) is characterised by a progressive loss of motor units and the reinnervation of denervated muscle fibres by surviving motor axons. This reinnervation preserves muscle function until symptom onset, when some 60-80% of motor units have been lost. We have studied the changes in surviving motor neurons by comparing the nerve excitability properties of 31 single motor axons from patients with ALS with those from 21 single motor axons in control subjects. ALS motor axons were classified as coming from moderately or severely affected muscles according to the compound muscle action potential amplitude of the parent muscle. Compared with control units, thresholds were increased, and there was reduced inward and outward rectification and greater superexcitability following a conditioning impulse. These abnormalities were greater in axons from severely affected muscles, and were correlated with loss of fine motor skills. A mathematical model indicated that 99.1% of the differences between the moderately affected ALS and control units could be explained by a reduction in the expression of all ion channels. For the severely affected units, modelling required, in addition, an increase in the current leak through and under the myelin sheath. This might be expected if the anchoring proteins responsible for the paranodal seal were reduced. We conclude that changes in axonal excitability identified in ALS patients are best explained by a failure in the supply of ion channel and other membrane proteins from the diseased motor neuron, a conclusion consistent with recent animal and in vitro human data.
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Affiliation(s)
- James Howells
- Brain & Mind Centre, University of Sydney, Sydney, Australia
| | | | - Susanna B Park
- Brain & Mind Centre, University of Sydney, Sydney, Australia
| | - Nidhi Garg
- Brain & Mind Centre, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
| | - Steve Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital and University of Sydney, Sydney, Australia
| | - Hugh Bostock
- MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK.,Institute of Neurology, UCL, Queen Square, London, WC1N 3BG, UK
| | - David Burke
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
| | - Matthew C Kiernan
- Brain & Mind Centre, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
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18
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North RY, Lazaro TT, Dougherty PM. Ectopic Spontaneous Afferent Activity and Neuropathic Pain. Neurosurgery 2018; 65:49-54. [PMID: 31076785 DOI: 10.1093/neuros/nyy119] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 04/04/2018] [Indexed: 12/17/2022] Open
Affiliation(s)
- Robert Y North
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas
| | - Tyler T Lazaro
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas
| | - Patrick M Dougherty
- The Departments of Pain Medicine Research, The Division of Anesthesia, Critical Care and Pain Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
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19
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Differences in Functional Expression of Connexin43 and Na V1.5 by Pan- and Class-Selective Histone Deacetylase Inhibition in Heart. Int J Mol Sci 2018; 19:ijms19082288. [PMID: 30081552 PMCID: PMC6121244 DOI: 10.3390/ijms19082288] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Revised: 08/01/2018] [Accepted: 08/02/2018] [Indexed: 12/22/2022] Open
Abstract
Class-selective histone deacetylase (HDAC) inhibitors were designed to improve safety profiles and therapeutic effectiveness in the treatment of multiple cancers relative to pan-HDAC inhibitors. However, the underlying mechanisms for their therapeutic and cardiotoxic potentials remain poorly understood. Cardiac sodium currents (INa) and gap junction conductance (gj) were measured by whole cell patch clamp techniques on primary cultures of neonatal cardiomyocytes. Cardiac NaV1.5 sodium channel and connexin43 (Cx43) gap junction protein levels were assessed by Western blot analyses. Panobinostat produced concentration-dependent reductions in ventricular gj, peak INa density, and NaV1.5 protein expression levels. Membrane voltage (Vm)-dependent activation of INa was shifted by +3 to 6 mV with no effect on inactivation. Entinostat (1 μM) did not affect ventricular gj, peak INa density, or INa activation. However, the INa half-inactivation voltage (V½) was shifted by −3.5 mV. Ricolinostat had only minor effects on ventricular gj and INa properties, though INa activation was shifted by −4 mV. Cx43 and NaV1.5 protein expression levels were not altered by class-selective HDAC inhibitors. The lack of effects of class-selective HDAC inhibitors on ventricular gj and INa may help explain the improved cardiac safety profile of entinostat and ricolinostat.
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20
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Djouhri L, Smith T, Alotaibi M, Weng X. Membrane potential oscillations are not essential for spontaneous firing generation in L4 Aβ-afferent neurons after L5 spinal nerve axotomy and are not mediated by HCN channels. Exp Physiol 2018; 103:1145-1156. [PMID: 29860719 DOI: 10.1113/ep087013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/23/2018] [Indexed: 01/01/2023]
Abstract
NEW FINDINGS What is the central question of this study? Is spontaneous activity (SA) in L4 dorsal root ganglion (DRG) neurons induced by L5 spinal nerve axotomy associated with membrane potential oscillations in these neurons, and if so, are these membrane oscillations mediated by HCN channels? What is the main finding and its importance? Unlike injured L5 DRG neurons, which have been shown to be incapable of firing spontaneously without membrane potential oscillations, membrane potential oscillations are not essential for SA generation in conducting 'uninjured' L4 neurons, and they are not mediated by HCN channels. These findings suggest that the underlying cellular mechanisms of SA in injured and 'uninjured' DRG neurons induced by spinal nerve injury are distinct. ABSTRACT The underlying cellular and molecular mechanisms of peripheral neuropathic pain are not fully understood. However, preclinical studies using animal models suggest that this debilitating condition is driven partly by aberrant spontaneous activity (SA) in injured and uninjured dorsal root ganglion (DRG) neurons, and that SA in injured DRG neurons is triggered by subthreshold membrane potential oscillations (SMPOs). Here, using in vivo intracellular recording from control L4-DRG neurons, and ipsilateral L4-DRG neurons in female Wistar rats that had previously undergone L5 spinal nerve axotomy (SNA), we examined whether conducting 'uninjured' L4-DRG neurons in SNA rats exhibit SMPOs, and if so, whether such SMPOs are associated with SA in those L4 neurons, and whether they are mediated by hyperpolarization-activated cyclic nucleotide gated (HCN) channels. We found that 7 days after SNA: (a) none of the control A- or C-fibre DRG neurons showed SMPOs or SA, but 50%, 43% and 0% of spontaneously active cutaneous L4 Aβ-low threshold mechanoreceptors, Aβ-nociceptors and C-nociceptors exhibited SMPOs, respectively, in SNA rats with established neuropathic pain behaviors; (b) neither SMPOs nor SA in L4 Aβ-neurons was suppressed by blocking HCN channels with ZD7288 (10 mg kg-1 , i.v.); and (c) there is a tendency for female rats to show greater pain hypersensitivity than male rats. These results suggest that SMPOs are linked to SA only in some of the conducting L4 Aβ-neurons, that such oscillations are not a prerequisite for SA generation in those L4 A- or C-fibre neurons, and that HCN channels are not involved in their electrogenesis.
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Affiliation(s)
- L Djouhri
- Department of Physiology, College of Medicine, Alfaisal University, PO Box 50927, Riyadh, 11533, Saudi Arabia
| | - T Smith
- Wolfson CARD, Neurorestoration Group, Hodgkin Building, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - M Alotaibi
- Department of Physiology, College of Medicine, King Saud University, PO Box 7805, Riyadh, 11472, Saudi Arabia
| | - X Weng
- Department of Neurobiology and State Key Laboratory of Proteomics, Beijing Institute of Basic Medical Sciences, Beijing, 100850, China
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21
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Takkala P, Prescott SA. Using dynamic clamp to quantify pathological changes in the excitability of primary somatosensory neurons. J Physiol 2018; 596:2209-2227. [PMID: 29601637 PMCID: PMC5983269 DOI: 10.1113/jp275580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 03/21/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Primary somatosensory neurons normally respond to somatic depolarization with transient spiking but can switch to repetitive spiking under pathological conditions. This switch in spiking pattern reflects a qualitative change in spike initiation dynamics and contributes to the hyperexcitability associated with chronic pain. Neurons can be converted to repetitive spiking by adding a virtual conductance using dynamic clamp. By titrating the conductance to determine how much must be added to cause repetitive spiking, we found that small cells are more susceptible to switching (i.e. required less added conductance) than medium-large cells. By measuring how much less conductance is required to cause repetitive spiking when dynamic clamp was combined with other pathomimetic manipulations (e.g. application of inflammatory mediators), we measured how much each manipulation facilitated repetitive spiking. Our results suggest that many pathological factors facilitate repetitive spiking but that the switch to repetitive spiking requires the cumulative effect of many co-occurring factors. ABSTRACT Primary somatosensory neurons become hyperexcitable in many chronic pain conditions. Hyperexcitability can include a switch from transient to repetitive spiking during sustained somatic depolarization. This switch results from diverse pathological processes that impact ion channel expression or function. Because multiple pathological processes co-occur, isolating how much each contributes to switching the spiking pattern is difficult. Our approach to this challenge involves adding a virtual sodium conductance via dynamic clamp. The magnitude of that conductance was titrated to determine the minimum required to enable rheobasic stimulation to evoke repetitive spiking. The minimum required conductance, termed g¯ Na ∗, was re-measured before and during manipulations designed to model various pathological processes in vitro. The reduction in g¯ Na ∗ caused by each pathomimetic manipulation reflects how much the modelled process contributes to switching the spiking pattern. We found that elevating extracellular potassium or applying inflammatory mediators reduced g¯ Na ∗ whereas direct hyperpolarization had no effect. Inflammatory mediators reduced g¯ Na ∗ more in medium-large (>30 μm diameter) neurons than in small (⩽30 μm diameter) neurons, but had equivalent effects in cutaneous and muscle afferents. The repetitive spiking induced by dynamic clamp was also found to differ between small and medium-large neurons, thus revealing latent differences in adaptation. Our study demonstrates a novel way to determine to what extent individual pathological factors facilitate repetitive spiking. Our results suggest that most factors facilitate but do not cause repetitive spiking on their own, and, therefore, that a switch to repetitive spiking results from the cumulative effect of many co-occurring factors.
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Affiliation(s)
- Petri Takkala
- Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada, M5G 0A4.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada, M5S 1A8
| | - Steven A Prescott
- Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada, M5G 0A4.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada, M5S 1A8.,Department of Physiology and Institute of Biomaterials and Biomedical Engineering, University of Toronto, Ontario, Canada, M5S 1A8
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22
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Xie RG, Chu WG, Hu SJ, Luo C. Characterization of Different Types of Excitability in Large Somatosensory Neurons and Its Plastic Changes in Pathological Pain States. Int J Mol Sci 2018; 19:ijms19010161. [PMID: 29303989 PMCID: PMC5796110 DOI: 10.3390/ijms19010161] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 12/30/2017] [Accepted: 01/02/2018] [Indexed: 12/16/2022] Open
Abstract
Sensory neuron types have been distinguished by distinct morphological and transcriptional characteristics. Excitability is the most fundamental functional feature of neurons. Mathematical models described by Hodgkin have revealed three types of neuronal excitability based on the relationship between firing frequency and applied current intensity. However, whether natural sensory neurons display different functional characteristics in terms of excitability and whether this excitability type undergoes plastic changes under pathological pain states have remained elusive. Here, by utilizing whole-cell patch clamp recordings, behavioral and pharmacological assays, we demonstrated that large dorsal root ganglion (DRG) neurons can be classified into three classes and four subclasses based on their excitability patterns, which is similar to mathematical models raised by Hodgkin. Analysis of hyperpolarization-activated cation current (Ih) revealed different magnitude of Ih in different excitability types of large DRG neurons, with higher Ih in Class 2-1 than that in Class 1, 2-2 and 3. This indicates a crucial role of Ih in the determination of excitability type of large DRG neurons. More importantly, this pattern of excitability displays plastic changes and transition under pathological pain states caused by peripheral nerve injury. This study sheds new light on the functional characteristics of large DRG neurons and extends functional classification of large DRG neurons by integration of transcriptomic and morphological characteristics.
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Affiliation(s)
- Rou-Gang Xie
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, Fourth Military Medical University, Xi'an 710032, China.
| | - Wen-Guang Chu
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, Fourth Military Medical University, Xi'an 710032, China.
| | - San-Jue Hu
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, Fourth Military Medical University, Xi'an 710032, China.
| | - Ceng Luo
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, Fourth Military Medical University, Xi'an 710032, China.
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23
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Parker SL, Guerra Valero YC, Lipman J, Weiss S, Smith C, Russell L, Smith P, Roberts JA, Wallis SC. A validated UHPLC-MS/MS method for the measurement of riluzole in plasma and myocardial tissue samples. Biomed Chromatogr 2017. [PMID: 28623867 DOI: 10.1002/bmc.4030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Through blocking the cardiac persistent sodium current, riluzole has the potential to prevent myocardial damage post cardiac bypass surgery. A sensitive UHPLC-MS/MS method was developed and validated for quantitation of riluzole and 5-methoxypsoralen in human plasma and myocardial tissue homogenate using a liquid-liquid extraction with dichloromethane. The chromatographic separation was achieved using Shimadzu Shim-pack XR-ODS III, 2.0 × 50 mm, 1.6 μm column with a gradient mobile phase comprising methanol and ammonium acetate buffer pH 3.6 in purified water. The analyte and internal standard were separated within 3.5 min. Riluzole quantitation was achieved using the mass transitions of 235-138 for riluzole and 217-156 for 5-methoxypsoralen. The method was linear for riluzole plasma concentrations from 0.2 to 500 ng/mL and myocardial tissue homogenate concentrations from 0.2 to 100 ng/mL. The method developed was successfully applied to a clinical study for patients receiving riluzole while undergoing cardiac bypass surgery.
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Affiliation(s)
- Suzanne L Parker
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia
| | - Yarmarly C Guerra Valero
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia
| | - Jeffrey Lipman
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia.,Department of Intensive Care Medicine, Royal Brisbane & Women's Hospital, Brisbane, Australia.,Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Steven Weiss
- Medical School, College of Medicine, Biology and Environment, Australian National University, Canberra, Australia
| | - Camilla Smith
- Trauma and Orthopaedic Research Unit, Canberra Hospital, Canberra, Australia
| | - Lyndal Russell
- Trauma and Orthopaedic Research Unit, Canberra Hospital, Canberra, Australia
| | - Paul Smith
- Trauma and Orthopaedic Research Unit, Canberra Hospital, Canberra, Australia
| | - Jason A Roberts
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia.,Department of Intensive Care Medicine, Royal Brisbane & Women's Hospital, Brisbane, Australia.,School of Pharmacy, The University of Queensland, Brisbane, Australia.,Department of Pharmacy, Royal Brisbane & Women's Hospital, Brisbane, Australia
| | - Steven C Wallis
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia
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24
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Jia B, Gu H, Xue L. A basic bifurcation structure from bursting to spiking of injured nerve fibers in a two-dimensional parameter space. Cogn Neurodyn 2017; 11:189-200. [PMID: 28348650 DOI: 10.1007/s11571-017-9422-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 12/22/2016] [Accepted: 01/24/2017] [Indexed: 10/20/2022] Open
Abstract
Two different bifurcation scenarios of firing patterns with decreasing extracellular calcium concentrations were observed in identical sciatic nerve fibers of a chronic constriction injury (CCI) model when the extracellular 4-aminopyridine concentrations were fixed at two different levels. Both processes proceeded from period-1 bursting to period-1 spiking via complex or simple processes. Multiple typical experimental examples manifested dynamics closely matching those simulated in a recently proposed 4-dimensional model to describe the nonlinear dynamics of the CCI model, which included most cases of the bifurcation scenarios. As the extracellular 4-aminopyridine concentrations is increased, the structure of the bifurcation scenario becomes more complex. The results provide a basic framework for identifying the relationships between different neural firing patterns and different bifurcation scenarios and for revealing the complex nonlinear dynamics of neural firing patterns. The potential roles of the basic bifurcation structures in identifying the information process mechanism are discussed.
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Affiliation(s)
- Bing Jia
- State Key Laboratory of Medical Neurobiology, Department of Physiology and Biophysics, School of Life Sciences and Collaborative Innovation Centre for Brain Science, Fudan University, Shanghai, 200438 People's Republic of China
| | - Huaguang Gu
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, 200092 People's Republic of China
| | - Lei Xue
- State Key Laboratory of Medical Neurobiology, Department of Physiology and Biophysics, School of Life Sciences and Collaborative Innovation Centre for Brain Science, Fudan University, Shanghai, 200438 People's Republic of China
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25
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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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26
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Vincent JA, Wieczerzak KB, Gabriel HM, Nardelli P, Rich MM, Cope TC. A novel path to chronic proprioceptive disability with oxaliplatin: Distortion of sensory encoding. Neurobiol Dis 2016; 95:54-65. [PMID: 27397106 DOI: 10.1016/j.nbd.2016.07.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 06/06/2016] [Accepted: 07/03/2016] [Indexed: 02/08/2023] Open
Abstract
Persistent neurotoxic side effects of oxaliplatin (OX) chemotherapy, including sensory ataxia, limit the efficacy of treatment and significantly diminish patient quality of life. The common explanation for neurotoxicity is neuropathy, however the degree of neuropathy varies greatly among patients and appears insufficient in some cases to fully account for disability. We recently identified an additional mechanism that might contribute to sensory ataxia following OX treatment. In the present study, we tested whether that mechanism, selective modification of sensory signaling by muscle proprioceptors might result in behavioral deficits in rats. OX was administered once per week for seven weeks (cumulative dose i.p. 70mg/kg) to adult female Wistar rats. Throughout and for three weeks following treatment, behavioral analysis was performed daily on OX and sham control rats. Compared to controls, OX rats demonstrated errors in placing their hind feet securely and/or correctly during a horizontal ladder rung task. These behavioral deficits occurred together with modification of proprioceptor signaling that eliminated sensory encoding of static muscle position while having little effect on encoding of dynamic changes in muscle length. Selective inability to sustain repetitive firing in response to static muscle stretch led us to hypothesize that OX treatment impairs specific ionic currents, possibly the persistent inward Na currents (NaPIC) that are known to support repetitive firing during static stimulation in several neuron types, including the class of large diameter dorsal root ganglion cells that includes muscle proprioceptors. We tested this hypothesis by determining whether the chronic effects of OX on the firing behavior of muscle proprioceptors in vivo were mimicked by acute injection of NaPIC antagonists. Both riluzole and phenytoin, each having multiple drug actions but having only antagonist action on NaPIC in common, reproduced selective modification of proprioceptor signaling observed in OX rats. Taken together, these findings lead us to propose that OX chemotherapy contributes to movement disability by modifying sensory encoding, possibly via a chronic neurotoxic effect on NaPIC in the sensory terminals of muscle proprioceptors.
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Affiliation(s)
- Jacob A Vincent
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Krystyna B Wieczerzak
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Hanna M Gabriel
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Paul Nardelli
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, United States
| | - Mark M Rich
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Timothy C Cope
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, United States.
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27
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Estes S, Zhong L, Artinian L, Rehder V. Regulation of electrical activity and neuronal excitability in Helisoma trivolvis by carbon monoxide. Neuroscience 2015; 311:453-63. [DOI: 10.1016/j.neuroscience.2015.10.056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 10/23/2015] [Accepted: 10/28/2015] [Indexed: 11/30/2022]
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28
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Wang XC, Wang S, Zhang M, Gao F, Yin C, Li H, Zhang Y, Hu SJ, Duan JH. Α-Dendrotoxin-sensitive Kv1 channels contribute to conduction failure of polymodal nociceptive C-fibers from rat coccygeal nerve. J Neurophysiol 2015; 115:947-57. [PMID: 26609114 DOI: 10.1152/jn.00786.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 11/23/2015] [Indexed: 01/20/2023] Open
Abstract
It is known that some patients with diabetic neuropathy are usually accompanied by abnormal painful sensations. Evidence has accumulated that diabetic neuropathic pain is associated with the hyperexcitability of peripheral nociceptors. Previously, we demonstrated that reduced conduction failure of polymodal nociceptive C-fibers and enhanced voltage-dependent sodium currents of small dorsal root ganglion (DRG) neurons contribute to diabetic hyperalgesia. To further investigate whether and how potassium channels are involved in the conduction failure, α-dendrotoxin (α-DTX), a selective blocker of the low-threshold sustained Kv1 channel, was chosen to examine its functional capability in modulating the conduction properties of polymodal nociceptive C-fibers and the excitability of sensory neurons. We found that α-DTX reduced the conduction failure of C-fibers from coccygeal nerve in vivo accompanied by an increased initial conduction velocity but a decreased activity-dependent slowing of conduction velocity. In addition, the number of APs evoked by step currents was significantly enhanced after the treatment with α-DTX in small-diameter sensory neurons. Further study of the mechanism indicates α-DTX-sensitive K(+) current significantly reduced and the activation of this current in peak and steady state shifted to depolarization for diabetic neurons. Expression of Kv channel subunits Kv1.2 and Kv1.6 was downregulated in both small dorsal root ganglion neurons and peripheral C-fibers. Taken together, these results suggest that α-DTX-sensitive Kv1 channels might play an important role in regulating the conduction properties of polymodal nociceptive C-fibers and firing properties of sensory neurons.
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Affiliation(s)
- Xiu-Chao Wang
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China; Department of Psychology, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Shan Wang
- State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Ming Zhang
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Fang Gao
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Chun Yin
- Team Nine, Brigade of Cadets, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Hao Li
- Team Nine, Brigade of Cadets, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Ying Zhang
- Department of Cardiovascular Surgery, Xijing Hospital, Xi'an, People's Republic of China; and
| | - San-Jue Hu
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Jian-Hong Duan
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China; State Key Laboratory of Military Stomatology, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China
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Xu ZZ, Kim YH, Bang S, Zhang Y, Berta T, Wang F, Oh SB, Ji RR. Inhibition of mechanical allodynia in neuropathic pain by TLR5-mediated A-fiber blockade. Nat Med 2015; 21:1326-31. [PMID: 26479925 DOI: 10.1038/nm.3978] [Citation(s) in RCA: 251] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 09/22/2015] [Indexed: 12/19/2022]
Abstract
Mechanical allodynia, induced by normally innocuous low-threshold mechanical stimulation, represents a cardinal feature of neuropathic pain. Blockade or ablation of high-threshold, small-diameter unmyelinated group C nerve fibers (C-fibers) has limited effects on mechanical allodynia. Although large, myelinated group A fibers, in particular Aβ-fibers, have previously been implicated in mechanical allodynia, an A-fiber-selective pharmacological blocker is still lacking. Here we report a new method for targeted silencing of A-fibers in neuropathic pain. We found that Toll-like receptor 5 (TLR5) is co-expressed with neurofilament-200 in large-diameter A-fiber neurons in the dorsal root ganglion (DRG). Activation of TLR5 with its ligand flagellin results in neuronal entry of the membrane-impermeable lidocaine derivative QX-314, leading to TLR5-dependent blockade of sodium currents, predominantly in A-fiber neurons of mouse DRGs. Intraplantar co-application of flagellin and QX-314 (flagellin/QX-314) dose-dependently suppresses mechanical allodynia after chemotherapy, nerve injury, and diabetic neuropathy, but this blockade is abrogated in Tlr5-deficient mice. In vivo electrophysiology demonstrated that co-application of flagellin/QX-314 selectively suppressed Aβ-fiber conduction in naive and chemotherapy-treated mice. TLR5-mediated Aβ-fiber blockade, but not capsaicin-mediated C-fiber blockade, also reduced chemotherapy-induced ongoing pain without impairing motor function. Finally, flagellin/QX-314 co-application suppressed sodium currents in large-diameter human DRG neurons. Thus, our findings provide a new tool for targeted silencing of Aβ-fibers and neuropathic pain treatment.
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Affiliation(s)
- Zhen-Zhong Xu
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.,Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Yong Ho Kim
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.,Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, USA.,Pain Cognitive Function Research Center, Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea
| | - Sangsu Bang
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.,Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Yi Zhang
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Temugin Berta
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.,Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Fan Wang
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Seog Bae Oh
- Pain Cognitive Function Research Center, Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.,Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Ru-Rong Ji
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.,Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, USA
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30
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Hosier H, Peterson D, Tsymbalyuk O, Keledjian K, Smith BR, Ivanova S, Gerzanich V, Popovich PG, Simard JM. A Direct Comparison of Three Clinically Relevant Treatments in a Rat Model of Cervical Spinal Cord Injury. J Neurotrauma 2015; 32:1633-44. [PMID: 26192071 PMCID: PMC4638208 DOI: 10.1089/neu.2015.3892] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Recent preclinical studies have identified three treatments that are especially promising for reducing acute lesion expansion following traumatic spinal cord injury (SCI): riluzole, systemic hypothermia, and glibenclamide. Each has demonstrated efficacy in multiple studies with independent replication, but there is no way to compare them in terms of efficacy or safety, since different models were used, different laboratories were involved, and different outcomes were evaluated. Here, using a model of lower cervical hemicord contusion, we compared safety and efficacy for the three treatments, administered beginning 4 h after trauma. Treatment-associated mortality was 30% (3/10), 30% (3/10), 12.5% (1/8), and 0% (0/7) in the control, riluzole, hypothermia, and glibenclamide groups, respectively. For survivors, all three treatments showed overall favorable efficacy, compared with controls. On open-field locomotor scores (modified Basso, Beattie, and Bresnahan scores), hypothermia- and glibenclamide-treated animals were largely indistinguishable throughout the study, whereas riluzole-treated rats underperformed for the first two weeks; during the last four weeks, scores for the three treatments were similar, and significantly different from controls. On beam balance, hypothermia and glibenclamide treatments showed significant advantages over riluzole. After trauma, rats in the glibenclamide group rapidly regained a normal pattern of weight gain that differed markedly and significantly from that in all other groups. Lesion volumes at six weeks were: 4.8±0.7, 3.5±0.4, 3.1±0.3 and 2.5±0.3 mm3 in the control, riluzole, hypothermia, and glibenclamide groups, respectively; measurements of spared spinal cord tissue confirmed these results. Overall, in terms of safety and efficacy, systemic hypothermia and glibenclamide were superior to riluzole.
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Affiliation(s)
- Hillary Hosier
- 1 Department of Neurosurgery, University of Maryland , Baltimore, Maryland
| | - David Peterson
- 1 Department of Neurosurgery, University of Maryland , Baltimore, Maryland
| | - Orest Tsymbalyuk
- 1 Department of Neurosurgery, University of Maryland , Baltimore, Maryland
| | - Kaspar Keledjian
- 1 Department of Neurosurgery, University of Maryland , Baltimore, Maryland
| | - Bradley R Smith
- 1 Department of Neurosurgery, University of Maryland , Baltimore, Maryland
| | - Svetlana Ivanova
- 1 Department of Neurosurgery, University of Maryland , Baltimore, Maryland
| | | | - Phillip G Popovich
- 2 Center for Brain and Spinal Cord Repair, the Ohio State University , Columbus, Ohio
| | - J Marc Simard
- 3 Departments of Neurosurgery, Pathology and Physiology, University of Maryland , Baltimore, Maryland
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31
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Coggan JS, Sejnowski TJ, Prescott SA. Cooperativity between remote sites of ectopic spiking allows afterdischarge to be initiated and maintained at different locations. J Comput Neurosci 2015; 39:17-28. [PMID: 25929191 DOI: 10.1007/s10827-015-0562-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 04/08/2015] [Accepted: 04/13/2015] [Indexed: 12/22/2022]
Abstract
Many symptoms of nerve damage arise from ectopic spiking caused by hyperexcitability. Ectopic spiking can originate at the site of axonal damage and elsewhere within affected neurons. This raises the question of whether localized damage elicits cell-wide changes in excitability and/or if localized changes in excitability can drive abnormal spiking at remote locations. Computer modeling revealed an example of the latter involving afterdischarge (AD)--stimulus-evoked spiking that outlasts stimulation. We found that AD originating in a hyperexcitable region of axon could shift to the soma where it was maintained. This repositioning of ectopic spike initiation was independent of distance between the two sites but relied on the rate and number of ectopic spikes originating from the first site. Nonlinear dynamical analysis of a reduced model demonstrated that properties which rendered the axonal site prone to initiating AD discouraged it from maintaining AD, whereas the soma had the inverse properties thus enabling the two sites to interact cooperatively. A first phase of AD originating in the axon could, by providing sufficient drive to trigger somatic AD, give way to a second phase of AD originating in the soma such that spiking continued when axonal AD failed. Ectopic spikes originating from the soma during phase 2 AD propagated successfully through the defunct site of axonal spike initiation. This novel mechanism whereby ectopic spiking at one site facilitates ectopic spiking at another site is likely to contribute to the chronification of hyperexcitability in conditions such as neuropathic pain.
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Affiliation(s)
- Jay S Coggan
- NeuroLinx Research Institute, PO Box 13668, La Jolla, CA, 92039, USA,
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32
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Huaguang G, Zhiguo Z, Bing J, Shenggen C. Dynamics of on-off neural firing patterns and stochastic effects near a sub-critical Hopf bifurcation. PLoS One 2015; 10:e0121028. [PMID: 25867027 PMCID: PMC4395087 DOI: 10.1371/journal.pone.0121028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 02/07/2015] [Indexed: 11/18/2022] Open
Abstract
On-off firing patterns, in which repetition of clusters of spikes are interspersed with epochs of subthreshold oscillations or quiescent states, have been observed in various nervous systems, but the dynamics of this event remain unclear. Here, we report that on-off firing patterns observed in three experimental models (rat sciatic nerve subject to chronic constrictive injury, rat CA1 pyramidal neuron, and rabbit blood pressure baroreceptor) appeared as an alternation between quiescent state and burst containing multiple period-1 spikes over time. Burst and quiescent state had various durations. The interspike interval (ISI) series of on-off firing pattern was suggested as stochastic using nonlinear prediction and autocorrelation function. The resting state was changed to a period-1 firing pattern via on-off firing pattern as the potassium concentration, static pressure, or depolarization current was changed. During the changing process, the burst duration of on-off firing pattern increased and the duration of the quiescent state decreased. Bistability of a limit cycle corresponding to period-1 firing and a focus corresponding to resting state was simulated near a sub-critical Hopf bifurcation point in the deterministic Morris-Lecar (ML) model. In the stochastic ML model, noise-induced transitions between the coexisting regimes formed an on-off firing pattern, which closely matched that observed in the experiment. In addition, noise-induced exponential change in the escape rate from the focus, and noise-induced coherence resonance were identified. The distinctions between the on-off firing pattern and stochastic firing patterns generated near three other types of bifurcations of equilibrium points, as well as other viewpoints on the dynamics of on-off firing pattern, are discussed. The results not only identify the on-off firing pattern as noise-induced stochastic firing pattern near a sub-critical Hopf bifurcation point, but also offer practical indicators to discriminate bifurcation types and neural excitability types.
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Affiliation(s)
- Gu Huaguang
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
- * E-mail:
| | - Zhao Zhiguo
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
| | - Jia Bing
- Centre for Computational Systems Biology, Fudan University, Shanghai 200433, China
| | - Chen Shenggen
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
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33
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Han C, Estacion M, Huang J, Vasylyev D, Zhao P, Dib-Hajj SD, Waxman SG. Human Na(v)1.8: enhanced persistent and ramp currents contribute to distinct firing properties of human DRG neurons. J Neurophysiol 2015; 113:3172-85. [PMID: 25787950 DOI: 10.1152/jn.00113.2015] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 03/13/2015] [Indexed: 12/19/2022] Open
Abstract
Although species-specific differences in ion channel properties are well-documented, little has been known about the properties of the human Nav1.8 channel, an important contributor to pain signaling. Here we show, using techniques that include voltage clamp, current clamp, and dynamic clamp in dorsal root ganglion (DRG) neurons, that human Na(v)1.8 channels display slower inactivation kinetics and produce larger persistent current and ramp current than previously reported in other species. DRG neurons expressing human Na(v)1.8 channels unexpectedly produce significantly longer-lasting action potentials, including action potentials with half-widths in some cells >10 ms, and increased firing frequency compared with the narrower and usually single action potentials generated by DRG neurons expressing rat Na(v)1.8 channels. We also show that native human DRG neurons recapitulate these properties of Na(v)1.8 current and the long-lasting action potentials. Together, our results demonstrate strikingly distinct properties of human Na(v)1.8, which contribute to the firing properties of human DRG neurons.
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Affiliation(s)
- Chongyang Han
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Jianying Huang
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Dymtro Vasylyev
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Peng Zhao
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
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34
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Ren SC, Shao H, Ji WG, Jiang HH, Xu F, Chen PZ, Mi Z, Wen B, Zhu GX, Zhu ZR. Riluzole prevents soluble Aβ1-42 oligomers-induced perturbation of spontaneous discharge in the hippocampal CA1 region of rats. Amyloid 2015; 22:36-44. [PMID: 25472656 DOI: 10.3109/13506129.2014.990558] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Abnormal accumulation of soluble amyloid beta (Aβ) is believed to cause malfunction of neurons in Alzheimer's disease (AD). The hippocampus is one of the earliest affected brain regions in AD. However, little effort has been made to investigate the effects of soluble Aβ1-42 oligomers on discharge properties of hippocampal neurons in vivo. This study was designed to examine the effects of soluble Aβ1-42 oligomers on the discharge properties of hippocampal CA1 neurons using extracellular single-unit recordings in vivo. The protective effects of riluzole (RLZ) were also investigated for the prevention of soluble oligomers of Aβ1-42-induced alterations in the spontaneous discharge of hippocampal neurons. The results showed that (1) the mean frequency of spontaneous discharge was increased by the local application of 100 μM Aβ1-42 oligomers; (2) Aβ1-42 oligomers also induced alterations of the neuronal firing patterns in the hippocampal CA1 region; and (3) pretreatment with 20 μM RLZ effectively inhibited the Aβ1-42-induced enhancement of spontaneous discharge and alterations of neuronal firing patterns in CA1 neurons. Our study suggested that Aβ1-42 oligomers induced hyperactivity and perturbed the firing patterns in hippocampal neurons. RLZ may provide neuroprotective effects on the Aβ1-42-induced perturbation of neuronal activities in the hippocampal region of rats.
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35
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Contribution of persistent sodium currents to the excitability of tonic firing substantia gelatinosa neurons of the rat. Neurosci Lett 2015; 591:192-196. [PMID: 25703221 DOI: 10.1016/j.neulet.2015.02.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 02/11/2015] [Accepted: 02/15/2015] [Indexed: 11/21/2022]
Abstract
The roles of persistent Na(+) currents (INaP) in intrinsic membrane properties were examined in rat substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis using a conventional whole-cell patch clamp technique. In a voltage-clamp mode, riluzole inhibited the slow voltage ramp-induced INaP but had little effect on the peak amplitude of transient Na(+) currents in SG neurons. In a current-clamp mode, most SG neurons exhibited spontaneous action potentials and tonic firing pattern. Riluzole reduced both spontaneous and elicited action potentials in a concentration-dependent manner. The present results suggest that the riluzole-sensitive INaP plays an important role in the excitability of SG neurons and are thus, likely to contribute to the modulation of nociceptive transmission from the orofacial tissues.
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36
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Huang CW, Hung TY, Wu SN. The inhibitory actions by lacosamide, a functionalized amino acid, on voltage-gated Na+ currents. Neuroscience 2015; 287:125-36. [DOI: 10.1016/j.neuroscience.2014.12.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Revised: 06/18/2014] [Accepted: 07/01/2014] [Indexed: 12/19/2022]
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37
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Yan Z, Xu Y, Liang M, Ren X. Expression and functional role of Nav1.9 sodium channel in cartwheel cells of the dorsal cochlear nucleus. Mol Med Rep 2014; 11:1833-6. [PMID: 25385328 DOI: 10.3892/mmr.2014.2922] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 06/17/2014] [Indexed: 11/06/2022] Open
Abstract
In the central auditory system, cartwheel cells (CWCs) are a group of interneurons in the dorsal cochlear nucleus (DCN). While other DCN neurons respond to stimuli with a simple discharge pattern of single action potentials (SAPs), CWCs respond with complex action potentials (CAPs), consisting of SAPs superimposed on a slow depolarization. The CAPs in CWCs may participate in various auditory or non‑auditory signaling processing but its intrinsic mechanisms are largely unknown. In the present study, in vitro whole‑cell current clamp recordings on neonatal mice brain slices were used to demonstrate that CWCs respond to brief voltage stimulation with CAPs. Western blotting and immunohistochemistry were also utilized to demonstrate that Nav1.9 was expressed in the CWCs. Finally, when Nav1.9 was genetically silenced, CWCs responded to voltage stimulation with SAPs, not CAPs. The results strongly suggested that Nav1.9 was expressed and functionally contributed to the signaling processing in the central auditory pathway.
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Affiliation(s)
- Zhiyu Yan
- Depatment of Otolaryngology, Beijing Military General Hospital, Beijing 100700, P.R. China
| | - Yanjun Xu
- Depatment of Otolaryngology, Beijing Military General Hospital, Beijing 100700, P.R. China
| | - Min Liang
- Depatment of Otolaryngology, Beijing Military General Hospital, Beijing 100700, P.R. China
| | - Xiaowei Ren
- Depatment of Otolaryngology, Beijing Military General Hospital, Beijing 100700, P.R. China
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38
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Dou NN, Zhong J, Zhou QM, Zhu J, Wang YN, Xia L, Yang XS, Ying TT, Zheng XS, Li ST. The mechanism of hemifacial spasm: a new understanding of the offending artery. Neurol Res 2014; 37:184-8. [DOI: 10.1179/1743132814y.0000000424] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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39
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Lee JH, Park CK, Chen G, Han Q, Xie RG, Liu T, Ji RR, Lee SY. A monoclonal antibody that targets a NaV1.7 channel voltage sensor for pain and itch relief. Cell 2014; 157:1393-1404. [PMID: 24856969 DOI: 10.1016/j.cell.2014.03.064] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/25/2014] [Accepted: 03/25/2014] [Indexed: 12/26/2022]
Abstract
Voltage-gated sodium (NaV) channels control the upstroke of the action potentials in excitable cells. Multiple studies have shown distinct roles of NaV channel subtypes in human physiology and diseases, but subtype-specific therapeutics are lacking and the current efforts have been limited to small molecules. Here, we present a monoclonal antibody that targets the voltage-sensor paddle of NaV1.7, the subtype critical for pain sensation. This antibody not only inhibits NaV1.7 with high selectivity, but also effectively suppresses inflammatory and neuropathic pain in mice. Interestingly, the antibody inhibits acute and chronic itch despite well-documented differences in pain and itch modulation. Using this antibody, we discovered that NaV1.7 plays a key role in spinal cord nociceptive and pruriceptive synaptic transmission. Our studies reveal that NaV1.7 is a target for itch management, and the antibody has therapeutic potential for suppressing pain and itch. Our antibody strategy may have broad applications for voltage-gated cation channels.
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Affiliation(s)
- Jun-Ho Lee
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Chul-Kyu Park
- Departments of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Gang Chen
- Departments of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Qingjian Han
- Departments of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Rou-Gang Xie
- Departments of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Tong Liu
- Departments of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Ru-Rong Ji
- Departments of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
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40
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Ratté S, Zhu Y, Lee KY, Prescott SA. Criticality and degeneracy in injury-induced changes in primary afferent excitability and the implications for neuropathic pain. eLife 2014; 3:e02370. [PMID: 24692450 PMCID: PMC3970756 DOI: 10.7554/elife.02370] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Neuropathic pain remains notoriously difficult to treat despite numerous drug targets. Here, we offer a novel explanation for this intractability. Computer simulations predicted that qualitative changes in primary afferent excitability linked to neuropathic pain arise through a switch in spike initiation dynamics when molecular pathologies reach a tipping point (criticality), and that this tipping point can be reached via several different molecular pathologies (degeneracy). We experimentally tested these predictions by pharmacologically blocking native conductances and/or electrophysiologically inserting virtual conductances. Multiple different manipulations successfully reproduced or reversed neuropathic changes in primary afferents from naïve or nerve-injured rats, respectively, thus confirming the predicted criticality and its degenerate basis. Degeneracy means that several different molecular pathologies are individually sufficient to cause hyperexcitability, and because several such pathologies co-occur after nerve injury, that no single pathology is uniquely necessary. Consequently, single-target-drugs can be circumvented by maladaptive plasticity in any one of several ion channels. DOI:http://dx.doi.org/10.7554/eLife.02370.001 Although the pain associated with an injury is unpleasant, it normally serves an important purpose: to make you avoid its source. However, some pain appears to arise from nowhere. Frustratingly, this type of pain, known as neuropathic pain, does not respond to common painkillers and is thus very difficult to treat. The neurons that transmit pain and other sensory information do so using electrical signals. In response to a stimulus, ions travel through channels in the membrane of a neuron, which leads to a change in the electrical potential of the membrane. When this change is large enough, a voltage spike is produced: this signal is ultimately transmitted to the brain. When certain neurons fire too easily or too often, neuropathic pain can arise. This hyperexcitability can make something painful feel even worse, or it can make things hurt that shouldn’t. To prevent this, extensive research has been devoted to identify drugs that target particular types of ion channels and block them. However, despite the discovery of many promising drugs, those drugs have been frustratingly ineffective in clinical trials. Using simulations and experiments, Ratté et al. have examined the behavior of a type of neuron that normally conducts information about touch, but the brain sometimes misinterprets this information as pain. Increasing the flow of ions through the cell membrane in these simulations eventually causes a ‘tipping point’ to be crossed, which triggers a dramatic, discontinuous change in spiking pattern. However, as several different types of ion channels contribute to the current, there are several different ways in which the tipping point can be crossed. This ability to produce the same result by multiple means is a common feature of complex systems. Known as degeneracy, it makes systems more robust, as a given result can still be achieved if one particular attempt to achieve this result fails. The work of Ratté et al. helps to explain why drugs that target just one type of ion channel may fail to relieve neuropathic pain: maladaptive changes in any one of several other ion channels may circumvent the therapeutic effect. DOI:http://dx.doi.org/10.7554/eLife.02370.002
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Affiliation(s)
- Stéphanie Ratté
- Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Canada
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41
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Bourinet E, Altier C, Hildebrand ME, Trang T, Salter MW, Zamponi GW. Calcium-permeable ion channels in pain signaling. Physiol Rev 2014; 94:81-140. [PMID: 24382884 DOI: 10.1152/physrev.00023.2013] [Citation(s) in RCA: 221] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.
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42
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Strong JA, Xie W, Bataille FJ, Zhang JM. Preclinical studies of low back pain. Mol Pain 2013; 9:17. [PMID: 23537369 PMCID: PMC3617092 DOI: 10.1186/1744-8069-9-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 03/18/2013] [Indexed: 12/12/2022] Open
Abstract
Chronic low back pain is a major cause of disability and health care costs. Current treatments are inadequate for many patients. A number of preclinical models have been developed that attempt to mimic aspects of clinical conditions that contribute to low back pain. These involve application of nucleus pulposus material near the lumbar dorsal root ganglia (DRG), chronic compression of the DRG, or localized inflammation of the DRG. These models, which are primarily implemented in rats, have many common features including behavioral hypersensitivity of the hindpaw, enhanced excitability and spontaneous activity of sensory neurons, and locally elevated levels of inflammatory mediators including cytokines. Clinically, epidural injection of steroids (glucocorticoids) is commonly used when more conservative treatments fail, but clinical trials evaluating these treatments have yielded mixed results. There are relatively few preclinical studies of steroid effects in low back pain models. One preclinical study suggests that the mineralocorticoid receptor, also present in the DRG, may have pro-inflammatory effects that oppose the activation of the glucocorticoid receptor. Although the glucocorticoid receptor is the target of anti-inflammatory steroids, many clinically used steroids activate both receptors. This could be one explanation for the limited effects of epidural steroids in some patients. Additional preclinical research is needed to address other possible reasons for limited efficacy of steroids, such as central sensitization or presence of an ongoing inflammatory stimulus in some forms of low back pain.
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Affiliation(s)
- Judith A Strong
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA
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43
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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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Gabapentin reduces allodynia and hyperalgesia in painful diabetic neuropathy rats by decreasing expression level of Nav1.7 and p-ERK1/2 in DRG neurons. Brain Res 2013. [DOI: 10.1016/j.brainres.2012.11.032] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Simard JM, Woo SK, Aarabi B, Gerzanich V. The Sur1-Trpm4 Channel in Spinal Cord Injury. ACTA ACUST UNITED AC 2013; Suppl 4. [PMID: 24834370 DOI: 10.4172/2165-7939.s4-002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Spinal cord injury (SCI) is a major unsolved challenge in medicine. Impact trauma to the spinal cord shears blood vessels, causing an immediate 'primary hemorrhage'. During the hours following trauma, the region of hemorrhage enlarges progressively, with delayed or 'secondary hemorrhage' adding to the primary hemorrhage, and effectively doubling its volume. The process responsible for the secondary hemorrhage that results in early expansion of the hemorrhagic lesion is termed 'progressive hemorrhagic necrosis' (PHN). PHN is a dynamic process of auto destruction whose molecular underpinnings are only now beginning to be elucidated. PHN results from the delayed, progressive, catastrophic failure of the structural integrity of capillaries. The resulting 'capillary fragmentation' is a unique, pathognomonic feature of PHN. Recent work has implicated the Sur1-Trpm4 channel that is newly upregulated in penumbral microvessels as being required for the development of PHN. Targeting the Sur1-Trpm4 channel by gene deletion, gene suppression, or pharmacological inhibition of either of the two channel subunits, Sur1 or Trpm4, yields exactly the same effects histologically and functionally, and exactly the same unique, pathognomonic phenotype - the prevention of capillary fragmentation. The potential advantage of inhibiting Sur1-Trpm4 channels using glibenclamide is a highly promising strategy for ameliorating the devastating sequelae of spinal cord trauma in humans.
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Affiliation(s)
- J Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA ; Department of Pathology, University of Maryland School of Medicine, Baltimore, USA ; Department of Physiology, University of Maryland School of Medicine, Baltimore, USA
| | - Seung Kyoon Woo
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA
| | - Bizhan Aarabi
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA
| | - Volodymyr Gerzanich
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA
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Enhanced SCN7A/Nax expression contributes to bone cancer pain by increasing excitability of neurons in dorsal root ganglion. Neuroscience 2012; 227:80-9. [PMID: 23026072 DOI: 10.1016/j.neuroscience.2012.09.046] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 09/19/2012] [Accepted: 09/20/2012] [Indexed: 11/21/2022]
Abstract
Bone pain is one of the most common complications in cancer patients with bone metastases, and has the most significant impact on quality of life for patients. Patients with bone cancer pain may be difficult to treat due to the poor understanding of the mechanisms; therefore, the mechanisms of bone cancer pain required elucidation for developing new therapeutics. Recent studies show that SCN7A/Nax channel serves as a sodium-level sensor of the body fluid that controls the Na-intake behavior by changing the excitability of neurons. In the current study, the expression of SCN7A/Nax and the excitability of primary sensory neurons in bone cancer pain rats were examined. The analgesic effects of knockdown SCN7A/Nax channel using RNAi lentivirus intrathecal treatment were evaluated with a behavioral test. The results showed that implantation of sarcoma induced ongoing and movement-evoked pain behaviors, whereas SCN7A/Nax knockdown prevented the onset of these hyperalgesia. Immunohistochemistry showed that SCN7A/Nax was located in the medium- to large-sized neurons in dorsal root ganglions (DRGs). The proportion of SCN7A/Nax-positive cells was significantly increased in DRGs ipsilateral to sarcoma implantation. Immunostaining results were further confirmed by Western blot and real time-polymerase chain reaction (RT-PCR) analyses. Recording from primary sensory neurons in excised rat dorsal root ganglias, we found that most of SCN7A/Nax-positive neurons exhibited subthreshold oscillations, depolarized resting membrane potential and more negative threshold of action potential. These electrophysiological changes of neurons increased ectopic spike discharge which was thought to be an important generator of chronic pain, however, the hyperexcitability was completely reversed by SCN7A/Nax knockdown. These results demonstrate that enhanced expression of SCN7A/Nax channel within distinct subpopulation of DRG neurons contributes to bone cancer pain by increasing the excitability of these neurons. These findings may lead to novel strategies for the treatment of bone cancer pain.
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Yu N, Morris CE, Joós B, Longtin A. Spontaneous excitation patterns computed for axons with injury-like impairments of sodium channels and Na/K pumps. PLoS Comput Biol 2012; 8:e1002664. [PMID: 23028273 PMCID: PMC3441427 DOI: 10.1371/journal.pcbi.1002664] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 07/13/2012] [Indexed: 11/28/2022] Open
Abstract
In injured neurons, “leaky” voltage-gated sodium channels (Nav) underlie dysfunctional excitability that ranges from spontaneous subthreshold oscillations (STO), to ectopic (sometimes paroxysmal) excitation, to depolarizing block. In recombinant systems, mechanical injury to Nav1.6-rich membranes causes cytoplasmic Na+-loading and “Nav-CLS”, i.e., coupled left-(hyperpolarizing)-shift of Nav activation and availability. Metabolic injury of hippocampal neurons (epileptic discharge) results in comparable impairment: left-shifted activation and availability and hence left-shifted INa-window. A recent computation study revealed that CLS-based INa-window left-shift dissipates ion gradients and impairs excitability. Here, via dynamical analyses, we focus on sustained excitability patterns in mildly damaged nodes, in particular with more realistic Gaussian-distributed Nav-CLS to mimic “smeared” injury intensity. Since our interest is axons that might survive injury, pumps (sine qua non for live axons) are included. In some simulations, pump efficacy and system volumes are varied. Impacts of current noise inputs are also characterized. The diverse modes of spontaneous rhythmic activity evident in these scenarios are studied using bifurcation analysis. For “mild CLS injury”, a prominent feature is slow pump/leak-mediated EIon oscillations. These slow oscillations yield dynamic firing thresholds that underlie complex voltage STO and bursting behaviors. Thus, Nav-CLS, a biophysically justified mode of injury, in parallel with functioning pumps, robustly engenders an emergent slow process that triggers a plethora of pathological excitability patterns. This minimalist “device” could have physiological analogs. At first nodes of Ranvier and at nociceptors, e.g., localized lipid-tuning that modulated Nav midpoints could produce Nav-CLS, as could co-expression of appropriately differing Nav isoforms. Nerve cells damaged by trauma, stroke, epilepsy, inflammatory conditions etc, have chronically leaky sodium channels that eventually kill. The usual job of sodium channels is to make brief voltage signals –action potentials– for long distance propagation. After sodium channels open to generate action potentials, sodium pumps work harder to re-establish the intracellular/extracellular sodium imbalance that is, literally, the neuron's battery for firing action potentials. Wherever tissue damage renders membranes overly fluid, we hypothesize, sodium channels become chronically leaky. Our experimental findings justify this. In fluidized membranes, sodium channel voltage sensors respond too easily, letting channels spend too much time open. Channels leak, pumps respond. By mathematical modeling, we show that in damaged channel-rich membranes the continual pump/leak counterplay would trigger the kinds of bizarre intermittent action potential bursts typical of injured neurons. Arising ectopically from injury regions, such neuropathic firing is unrelated to events in the external world. Drugs that can silence these deleterious electrical barrages without blocking healthy action potentials are needed. If fluidized membranes house the problematic leaky sodium channels, then drug side effects could be diminished by using drugs that accumulate most avidly into fluidized membranes, and that bind their targets with highest affinity there.
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Affiliation(s)
- Na Yu
- Department of Physics, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Béla Joós
- Department of Physics, University of Ottawa, Ottawa, Ontario, Canada
- * E-mail:
| | - André Longtin
- Department of Physics, University of Ottawa, Ottawa, Ontario, Canada
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Nardi A, Damann N, Hertrampf T, Kless A. Advances in targeting voltage-gated sodium channels with small molecules. ChemMedChem 2012; 7:1712-40. [PMID: 22945552 DOI: 10.1002/cmdc.201200298] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 07/30/2012] [Indexed: 12/19/2022]
Abstract
Blockade of voltage-gated sodium channels (VGSCs) has been used successfully in the clinic to enable control of pathological firing patterns that occur in conditions as diverse as chronic pain, epilepsy, and arrhythmias. Herein we review the state of the art in marketed sodium channel inhibitors, including a brief compendium of their binding sites and of the cellular and molecular biology of sodium channels. Despite the preferential action of this drug class toward over-excited cells, which significantly limits potential undesired side effects on other cells, the need to develop a second generation of sodium channel inhibitors to overcome their critical clinical shortcomings is apparent. Current approaches in drug discovery to deliver novel and truly innovative sodium channel inhibitors is next presented by surveying the most recent medicinal chemistry breakthroughs in the field of small molecules and developments in automated patch-clamp platforms. Various strategies aimed at identifying small molecules that target either particular isoforms of sodium channels involved in specific diseases or anomalous sodium channel currents, irrespective of the isoform by which they have been generated, are critically discussed and revised.
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Affiliation(s)
- Antonio Nardi
- Global Drug Discovery, Department of Medicinal Chemistry, Grünenthal, Zieglerstrasse 6, 52078 Aachen, Germany.
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Ono K, Xu S, Hitomi S, Inenaga K. Comparison of the electrophysiological and immunohistochemical properties of acutely dissociated and 1-day cultured rat trigeminal ganglion neurons. Neurosci Lett 2012; 523:162-6. [DOI: 10.1016/j.neulet.2012.06.069] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 06/22/2012] [Accepted: 06/23/2012] [Indexed: 01/21/2023]
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Sun W, Miao B, Wang XC, Duan JH, Ye X, Han WJ, Wang WT, Luo C, Hu SJ. Gastrodin inhibits allodynia and hyperalgesia in painful diabetic neuropathy rats by decreasing excitability of nociceptive primary sensory neurons. PLoS One 2012; 7:e39647. [PMID: 22761855 PMCID: PMC3382466 DOI: 10.1371/journal.pone.0039647] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 05/24/2012] [Indexed: 01/29/2023] Open
Abstract
Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus and adversely affects the patients' quality of life. Evidence has accumulated that PDN is associated with hyperexcitability of peripheral nociceptive primary sensory neurons. However, the precise cellular mechanism underlying PDN remains elusive. This may result in the lacking of effective therapies for the treatment of PDN. The phenolic glucoside, gastrodin, which is a main constituent of the Chinese herbal medicine Gastrodia elata Blume, has been widely used as an anticonvulsant, sedative, and analgesic since ancient times. However, the cellular mechanisms underlying its analgesic actions are not well understood. By utilizing a combination of behavioral surveys and electrophysiological recordings, the present study investigated the role of gastrodin in an experimental rat model of STZ-induced PDN and to further explore the underlying cellular mechanisms. Intraperitoneal administration of gastrodin effectively attenuated both the mechanical allodynia and thermal hyperalgesia induced by STZ injection. Whole-cell patch clamp recordings were obtained from nociceptive, capsaicin-sensitive small diameter neurons of the intact dorsal root ganglion (DRG). Recordings from diabetic rats revealed that the abnormal hyperexcitability of neurons was greatly abolished by application of GAS. To determine which currents were involved in the antinociceptive action of gastrodin, we examined the effects of gastrodin on transient sodium currents (I(NaT)) and potassium currents in diabetic small DRG neurons. Diabetes caused a prominent enhancement of I(NaT) and a decrease of potassium currents, especially slowly inactivating potassium currents (I(AS)); these effects were completely reversed by GAS in a dose-dependent manner. Furthermore, changes in activation and inactivation kinetics of I(NaT) and total potassium current as well as I(AS) currents induced by STZ were normalized by GAS. This study provides a clear cellular basis for the peripheral analgesic action of gastrodin for the treatment of chronic pain, including PDN.
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Affiliation(s)
- Wei Sun
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
- Institute for Biomedical Sciences of Pain and Institute for Functional Brain Disorders, Tangdu Hospital, the Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Bei Miao
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
- Jiangsu Province Key Laboratory of Anesthesiology and Center for Pain Research and Treatment, Xuzhou Medical College, Xuzhou, People’s Republic of China
| | - Xiu-Chao Wang
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Jian-Hong Duan
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Xin Ye
- Department of Endocrinology, The 451th Hospital of People’s Liberation Army, Xi’an, People’s Republic of China
| | - Wen-Juan Han
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Wen-Ting Wang
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Ceng Luo
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - San-Jue Hu
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
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