1
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Chen JL, Kuo CC. Inhibition of resurgent Na + currents by rufinamide. Neuropharmacology 2024; 247:109835. [PMID: 38228283 DOI: 10.1016/j.neuropharm.2024.109835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 12/29/2023] [Accepted: 12/31/2023] [Indexed: 01/18/2024]
Abstract
Na+ channels are essential for the genesis of action potentials in most neurons. After opening by membrane depolarization, Na+ channels enter a series of inactivated states (e.g. the fast, intermediate, and slow inactivated states; or If, Ii, and Is). The inactivated Na+ channel may recover via the open state upon membrane repolarization, giving rise to "resurgent" Na+ currents which could be critical for densely repetitive or burst discharges. We incubated CHO-K1 cells transfected with human NaV1.7 cDNA and measured resurgent currents with whole-cell patch recordings. We found Ii is the major inactivated state responsible for the genesis of resurgent currents. Rufinamide, in therapeutic concentrations, could selectively bind to Ii to slow the recovery process and dose-dependently inhibit resurgent currents. The other Na+ channel-inhibiting antiseizure medications (ASM), such as phenytoin and lacosamide (selectively binds to If and Is, separately), fail to show a similar inhibitory effect in clinically relevant concentrations. Resurgent currents are decreased with lengthening of the prepulse, presumably because of redistribution of the channel from Ii to If. Rufinamide could accentuate the decrease to mimic a use-dependent inhibitory effect. The molecular action of slowing of recovery from inactivation by binding to Ii also explains the highly correlative inhibitory effect of rufinamide on both transient and resurgent Na+ currents. The modest but correlative inhibition of both currents may make a novel synergistic effect and thus strong-enough suppression of pathological repetitive and especially burst discharges. Rufinamide may thus have a unique spectrum of therapeutic applications for disorders with excessive neural excitabilities.
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Affiliation(s)
- Jian-Lin Chen
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.
| | - Chung-Chin Kuo
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan; Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan.
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2
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Thompson AC, Aizenman CD. Characterization of Na + currents regulating intrinsic excitability of optic tectal neurons. Life Sci Alliance 2024; 7:e202302232. [PMID: 37918964 PMCID: PMC10622587 DOI: 10.26508/lsa.202302232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 10/20/2023] [Accepted: 10/23/2023] [Indexed: 11/04/2023] Open
Abstract
Developing neurons adapt their intrinsic excitability to maintain stable output despite changing synaptic input. The mechanisms behind this process remain unclear. In this study, we examined Xenopus optic tectal neurons and found that the expressions of Nav1.1 and Nav1.6 voltage-gated Na+ channels are regulated during changes in intrinsic excitability, both during development and becsuse of changes in visual experience. Using whole-cell electrophysiology, we demonstrate the existence of distinct, fast, persistent, and resurgent Na+ currents in the tectum, and show that these Na+ currents are co-regulated with changes in Nav channel expression. Using antisense RNA to suppress the expression of specific Nav subunits, we found that up-regulation of Nav1.6 expression, but not Nav1.1, was necessary for experience-dependent increases in Na+ currents and intrinsic excitability. Furthermore, this regulation was also necessary for normal development of sensory guided behaviors. These data suggest that the regulation of Na+ currents through the modulation of Nav1.6 expression, and to a lesser extent Nav1.1, plays a crucial role in controlling the intrinsic excitability of tectal neurons and guiding normal development of the tectal circuitry.
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Affiliation(s)
- Adrian C Thompson
- https://ror.org/05gq02987 Department of Neuroscience, Brown University, Providence, RI, USA
| | - Carlos D Aizenman
- https://ror.org/05gq02987 Department of Neuroscience, Brown University, Providence, RI, USA
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3
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Farinato A, Cavalluzzi MM, Altamura C, Campanale C, Laghetti P, Saltarella I, Delre P, Barbault A, Tarantino N, Milani G, Rotondo NP, Di Cesare Mannelli L, Ghelardini C, Pierno S, Mangiatordi GF, Lentini G, Desaphy JF. Development of Riluzole Analogs with Improved Use-Dependent Inhibition of Skeletal Muscle Sodium Channels. ACS Med Chem Lett 2023; 14:999-1008. [PMID: 37465302 PMCID: PMC10350938 DOI: 10.1021/acsmedchemlett.3c00224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Accepted: 06/20/2023] [Indexed: 07/20/2023] Open
Abstract
Several commercially available and newly synthesized riluzole analogs were evaluated in vitro as voltage-gated skeletal muscle sodium-channel blockers. Data obtained from the patch-clamp technique demonstrated that potency is well correlated with lipophilicity and the introduction of a protonatable amino function in the benzothiazole 2-position enhances the use-dependent behavior. The most interesting compound, the 2-piperazine analog of riluzole (14), although slightly less potent than the parent compound in the patch-clamp assay as well as in an in vitro model of myotonia, showed greater use-dependent Nav1.4 blocking activity. Docking studies allowed the identification of the key interactions that 14 makes with the amino acids of the local anesthetic binding site within the pore of the channel. The reported results pave the way for the identification of novel compounds useful in the treatment of cell excitability disorders.
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Affiliation(s)
- Alessandro Farinato
- Section
of Pharmacology, Department of Pharmacy − Drug Sciences, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Maria Maddalena Cavalluzzi
- Section
of Medicinal Chemistry, Department of Pharmacy − Drug Sciences, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Concetta Altamura
- Section
of Pharmacology, Department of Precision and Regenerative Medicine,
School of Medicine, University of Bari Aldo
Moro, 70124 Bari, Italy
| | - Carmen Campanale
- Section
of Pharmacology, Department of Precision and Regenerative Medicine,
School of Medicine, University of Bari Aldo
Moro, 70124 Bari, Italy
| | - Paola Laghetti
- Section
of Pharmacology, Department of Precision and Regenerative Medicine,
School of Medicine, University of Bari Aldo
Moro, 70124 Bari, Italy
| | - Ilaria Saltarella
- Section
of Pharmacology, Department of Precision and Regenerative Medicine,
School of Medicine, University of Bari Aldo
Moro, 70124 Bari, Italy
| | - Pietro Delre
- CNR
− Institute of Crystallography, via Amendola 122/o, 70126 Bari, Italy
| | - Arthur Barbault
- CNR
− Institute of Crystallography, via Amendola 122/o, 70126 Bari, Italy
| | - Nancy Tarantino
- Section
of Pharmacology, Department of Pharmacy − Drug Sciences, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Gualtiero Milani
- Section
of Medicinal Chemistry, Department of Pharmacy − Drug Sciences, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Natalie Paola Rotondo
- Section
of Medicinal Chemistry, Department of Pharmacy − Drug Sciences, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Lorenzo Di Cesare Mannelli
- Department
NEUROFARBA - Pharmaceutical and Nutraceutical Section, University of Firenze, 50139 Florence, Italy
| | - Carla Ghelardini
- Department
NEUROFARBA - Pharmaceutical and Nutraceutical Section, University of Firenze, 50139 Florence, Italy
| | - Sabata Pierno
- Section
of Pharmacology, Department of Pharmacy − Drug Sciences, University of Bari Aldo Moro, 70125 Bari, Italy
| | | | - Giovanni Lentini
- Section
of Medicinal Chemistry, Department of Pharmacy − Drug Sciences, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Jean-François Desaphy
- Section
of Pharmacology, Department of Precision and Regenerative Medicine,
School of Medicine, University of Bari Aldo
Moro, 70124 Bari, Italy
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4
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Tzeplaeff L, Wilfling S, Requardt MV, Herdick M. Current State and Future Directions in the Therapy of ALS. Cells 2023; 12:1523. [PMID: 37296644 PMCID: PMC10252394 DOI: 10.3390/cells12111523] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 05/19/2023] [Accepted: 05/25/2023] [Indexed: 06/12/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disorder affecting upper and lower motor neurons, with death resulting mainly from respiratory failure three to five years after symptom onset. As the exact underlying causative pathological pathway is unclear and potentially diverse, finding a suitable therapy to slow down or possibly stop disease progression remains challenging. Varying by country Riluzole, Edaravone, and Sodium phenylbutyrate/Taurursodiol are the only drugs currently approved in ALS treatment for their moderate effect on disease progression. Even though curative treatment options, able to prevent or stop disease progression, are still unknown, recent breakthroughs, especially in the field of targeting genetic disease forms, raise hope for improved care and therapy for ALS patients. In this review, we aim to summarize the current state of ALS therapy, including medication as well as supportive therapy, and discuss the ongoing developments and prospects in the field. Furthermore, we highlight the rationale behind the intense research on biomarkers and genetic testing as a feasible way to improve the classification of ALS patients towards personalized medicine.
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Affiliation(s)
- Laura Tzeplaeff
- Department of Neurology, Rechts der Isar Hospital, Technical University of Munich, 81675 München, Germany
| | - Sibylle Wilfling
- Department of Neurology, University of Regensburg, 93053 Regensburg, Germany;
- Center for Human Genetics Regensburg, 93059 Regensburg, Germany
| | - Maria Viktoria Requardt
- Formerly: Department of Neurology with Institute of Translational Neurology, Münster University Hospital (UKM), 48149 Münster, Germany;
| | - Meret Herdick
- Precision Neurology, University of Lübeck, 23562 Luebeck, Germany
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5
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The Anti-Epileptic Drugs Lamotrigine and Valproic Acid Reduce the Cardiac Sodium Current. Biomedicines 2023; 11:biomedicines11020477. [PMID: 36831014 PMCID: PMC9953282 DOI: 10.3390/biomedicines11020477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/24/2023] [Accepted: 01/31/2023] [Indexed: 02/10/2023] Open
Abstract
Anti-epileptic drugs (AEDs) are associated with increased risk of sudden cardiac death. To establish whether gabapentin, lamotrigine, levetiracetam, pregabalin, and valproic acid reduce the Nav1.5 current, we conducted whole-cell patch-clamp studies to study the effects of the five AEDs on currents of human cardiac Nav1.5 channels stably expressed in HEK293 cells, and on action potential (AP) properties of freshly isolated rabbit ventricular cardiomyocytes. Lamotrigine and valproic acid exhibited inhibitory effects on the Nav1.5 current in a concentration-dependent manner with an IC50 of 142 ± 36 and 2022 ± 25 µM for lamotrigine and valproic acid, respectively. In addition, these drugs caused a hyperpolarizing shift of steady-state inactivation and a delay in recovery from inactivation. The changes on the Nav1.5 properties were reflected by a reduction in AP upstroke velocity (43.0 ± 6.8% (lamotrigine) and 23.7 ± 10.6% (valproic acid) at 1 Hz) and AP amplitude; in contrast, AP duration was not changed. Gabapentin, levetiracetam, and pregabalin had no effect on the Nav1.5 current. Lamotrigine and valproic acid reduce the Nav1.5 current density and affect its gating properties, resulting in a decrease of the AP upstroke velocity. Gabapentin, levetiracetam, and pregabalin have no effects on the Nav1.5 current.
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6
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Bigsby S, Neapetung J, Campanucci VA. Voltage-gated sodium channels in diabetic sensory neuropathy: Function, modulation, and therapeutic potential. Front Cell Neurosci 2022; 16:994585. [PMID: 36467605 PMCID: PMC9713017 DOI: 10.3389/fncel.2022.994585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 10/11/2022] [Indexed: 10/29/2023] Open
Abstract
Voltage-gated sodium channels (Na V ) are the main contributors to action potential generation and essential players in establishing neuronal excitability. Na V channels have been widely studied in pain pathologies, including those that develop during diabetes. Diabetic sensory neuropathy (DSN) is one of the most common complications of the disease. DSN is the result of sensory nerve damage by the hyperglycemic state, resulting in a number of debilitating symptoms that have a significant negative impact in the quality of life of diabetic patients. Among those symptoms are tingling and numbness of hands and feet, as well as exacerbated pain responses to noxious and non-noxious stimuli. DSN is also a major contributor to the development of diabetic foot, which may lead to lower limb amputations in long-term diabetic patients. Unfortunately, current treatments fail to reverse or successfully manage DSN. In the current review we provide an updated report on Na V channels including structure/function and contribution to DSN. Furthermore, we summarize current research on the therapeutic potential of targeting Na V channels in pain pathologies, including DSN.
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Affiliation(s)
| | | | - Verónica A. Campanucci
- Department of Anatomy, Physiology and Pharmacology (APP), College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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7
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Characterization in Inhibitory Effectiveness of Carbamazepine in Voltage-Gated Na + and Erg-Mediated K + Currents in a Mouse Neural Crest-Derived (Neuro-2a) Cell Line. Int J Mol Sci 2022; 23:ijms23147892. [PMID: 35887240 PMCID: PMC9321339 DOI: 10.3390/ijms23147892] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/15/2022] [Accepted: 07/15/2022] [Indexed: 12/18/2022] Open
Abstract
Carbamazepine (CBZ, Tegretol®) is an anticonvulsant used in the treatment of epilepsy and neuropathic pain; however, several unwanted effects of this drug have been noticed. Therefore, the regulatory actions of CBZ on ionic currents in electrically excitable cells need to be reappraised, although its efficacy in suppressing voltage-gated Na+ current (INa) has been disclosed. This study was undertaken to explore the modifications produced by CBZ on ionic currents (e.g., INa and erg-mediated K+ current [IK(erg)]) measured from Neuro-2a (N2a) cells. In these cells, we found that this drug differentially suppressed the peak (transient, INa(T)) and sustained (late, INa(L)) components of INa in a concentration-dependent manner with effective IC50 of 56 and 18 μM, respectively. The overall current–voltage relationship of INa(T) with or without the addition of CBZ remained unchanged; however, the strength (i.e., ∆area) in the window component of INa (INa(W)) evoked by the short ascending ramp pulse (Vramp) was overly lessened in the CBZ presence. Tefluthrin (Tef), a synthetic pyrethroid, known to stimulate INa, augmented the strength of the voltage-dependent hysteresis (Hys(V)) of persistent INa (INa(P)) in response to the isosceles-triangular Vramp; moreover, further application of CBZ attenuated Tef-mediated accentuation of INa(P)’s Hys(V). With a two-step voltage protocol, the recovery of INa(T) inactivation seen in Neuro-2a cells became progressively slowed by adding CBZ; however, the cumulative inhibition of INa(T) evoked by pulse train stimulation was enhanced during exposure to this drug. Neuro-2a-cell exposure to CBZ (100 μM), the magnitude of erg-mediated K+ current measured throughout the entire voltage-clamp steps applied was mildly inhibited. The docking results regarding the interaction of CBZ and voltage-gate Na+ (NaV) channel predicted the ability of CBZ to bind to some amino-acid residues in NaV due to the existence of a hydrogen bond or hydrophobic contact. It is conceivable from the current investigations that the INa (INa(T), INa(L), INa(W), and INa(P)) residing in Neuro-2a cells are susceptible to being suppressed by CBZ, and that its block on INa(L) is larger than that on INa(T). Collectively, the magnitude and gating of NaV channels produced by the CBZ presence might have an impact on its anticonvulsant and analgesic effects occurring in vivo.
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8
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Jia L, Eroglu TE, Wilders R, Verkerk AO, Tan HL. Carbamazepine Increases the Risk of Sudden Cardiac Arrest by a Reduction of the Cardiac Sodium Current. Front Cell Dev Biol 2022; 10:891996. [PMID: 35721495 PMCID: PMC9204209 DOI: 10.3389/fcell.2022.891996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 05/09/2022] [Indexed: 11/21/2022] Open
Abstract
Aim: To assess the risk of sudden cardiac arrest (SCA) associated with the use of carbamazepine (CBZ) and establish the possible underlying cellular electrophysiological mechanisms. Methods: The SCA risk association with CBZ was studied in general population cohorts using a case–control design (n = 5,473 SCA cases, 21,866 non-SCA controls). Effects of 1–100 µM CBZ on action potentials (APs) and individual membrane currents were determined in isolated rabbit and human cardiomyocytes using the patch clamp technique. Results: CBZ use was associated with increased risk of SCA compared with no use (adjusted odds ratio 1.90 [95% confidence interval: 1.12–3.24]). CBZ reduced the AP upstroke velocity of rabbit and human cardiomyocytes, without prominent changes in other AP parameters. The reduction occurred at ≥30 µM and was frequency-dependent with a more pronounced reduction at high stimulus frequencies. The cardiac sodium current (INa) was reduced at ≥30 μM; this was accompanied by a hyperpolarizing shift in the voltage-dependency of inactivation. The recovery from inactivation was slower, which is consistent with the more pronounced AP upstroke velocity reduction at high stimulus frequencies. The main cardiac K+ and Ca2+ currents were unaffected, except reduction of L-type Ca2+ current by 100 µM CBZ. Conclusion: CBZ use is associated with an increased risk of SCA in the general population. At concentrations of 30 µM and above, CBZ reduces AP upstroke velocity and INa in cardiomyocytes. Since the concentration of 30 µM is well within the therapeutic range (20–40 µM), we conclude that CBZ increases the risk of SCA by a reduction of the cardiac INa.
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Affiliation(s)
- Lixia Jia
- Department of Clinical and Experimental Cardiology, Heart Center, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Talip E. Eroglu
- Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
- Department of Cardiology, Herlev and Gentofte Hospital, University of Copenhagen, Gentofte, Denmark
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Arie O. Verkerk
- Department of Clinical and Experimental Cardiology, Heart Center, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Hanno L. Tan
- Department of Clinical and Experimental Cardiology, Heart Center, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Netherlands Heart Institute, Utrecht, Netherlands
- *Correspondence: Hanno L. Tan,
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9
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Tavares-Ferreira D, Shiers S, Ray PR, Wangzhou A, Jeevakumar V, Sankaranarayanan I, Cervantes AM, Reese JC, Chamessian A, Copits BA, Dougherty PM, Gereau RW, Burton MD, Dussor G, Price TJ. Spatial transcriptomics of dorsal root ganglia identifies molecular signatures of human nociceptors. Sci Transl Med 2022; 14:eabj8186. [PMID: 35171654 PMCID: PMC9272153 DOI: 10.1126/scitranslmed.abj8186] [Citation(s) in RCA: 143] [Impact Index Per Article: 71.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Nociceptors are specialized sensory neurons that detect damaging or potentially damaging stimuli and are found in the dorsal root ganglia (DRG) and trigeminal ganglia. These neurons are critical for the generation of neuronal signals that ultimately create the perception of pain. Nociceptors are also primary targets for treating acute and chronic pain. Single-cell transcriptomics on mouse nociceptors has transformed our understanding of pain mechanisms. We sought to generate equivalent information for human nociceptors with the goal of identifying transcriptomic signatures of nociceptors, identifying species differences and potential drug targets. We used spatial transcriptomics to molecularly characterize transcriptomes of single DRG neurons from eight organ donors. We identified 12 clusters of human sensory neurons, 5 of which are C nociceptors, as well as 1 C low-threshold mechanoreceptors (LTMRs), 1 Aβ nociceptor, 2 Aδ, 2 Aβ, and 1 proprioceptor subtypes. By focusing on expression profiles for ion channels, G protein-coupled receptors (GPCRs), and other pharmacological targets, we provided a rich map of potential drug targets in the human DRG with direct comparison to mouse sensory neuron transcriptomes. We also compared human DRG neuronal subtypes to nonhuman primates showing conserved patterns of gene expression among many cell types but divergence among specific nociceptor subsets. Last, we identified sex differences in human DRG subpopulation transcriptomes, including a marked increase in calcitonin-related polypeptide alpha (CALCA) expression in female pruritogen receptor-enriched nociceptors. This comprehensive spatial characterization of human nociceptors might open the door to development of better treatments for acute and chronic pain disorders.
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Affiliation(s)
- Diana Tavares-Ferreira
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA.,Corresponding author: (T.J.P.); (D.T.-F.)
| | - Stephanie Shiers
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Pradipta R. Ray
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Andi Wangzhou
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Vivekanand Jeevakumar
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Ishwarya Sankaranarayanan
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | | | | | - Alexander Chamessian
- Department of Anesthesiology, Washington University Pain Center, St. Louis, MO 63110, USA
| | - Bryan A. Copits
- Department of Anesthesiology, Washington University Pain Center, St. Louis, MO 63110, USA
| | - Patrick M. Dougherty
- Department of Pain Medicine, Division of Anesthesiology and Critical Care, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Robert W. Gereau
- Department of Anesthesiology, Washington University Pain Center, St. Louis, MO 63110, USA
| | - Michael D. Burton
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Gregory Dussor
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Theodore J. Price
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA.,Corresponding author: (T.J.P.); (D.T.-F.)
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10
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Tavares-Ferreira D, Shiers S, Ray PR, Wangzhou A, Jeevakumar V, Sankaranarayanan I, Cervantes AM, Reese JC, Chamessian A, Copits BA, Dougherty PM, Gereau RW, Burton MD, Dussor G, Price TJ. Spatial transcriptomics of dorsal root ganglia identifies molecular signatures of human nociceptors. Sci Transl Med 2022. [DOI: 10.1126/scitranslmed.abj8186\] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Nociceptors are specialized sensory neurons that detect damaging or potentially damaging stimuli and are found in the dorsal root ganglia (DRG) and trigeminal ganglia. These neurons are critical for the generation of neuronal signals that ultimately create the perception of pain. Nociceptors are also primary targets for treating acute and chronic pain. Single-cell transcriptomics on mouse nociceptors has transformed our understanding of pain mechanisms. We sought to generate equivalent information for human nociceptors with the goal of identifying transcriptomic signatures of nociceptors, identifying species differences and potential drug targets. We used spatial transcriptomics to molecularly characterize transcriptomes of single DRG neurons from eight organ donors. We identified 12 clusters of human sensory neurons, 5 of which are C nociceptors, as well as 1 C low-threshold mechanoreceptors (LTMRs), 1 Aβ nociceptor, 2 Aδ, 2 Aβ, and 1 proprioceptor subtypes. By focusing on expression profiles for ion channels, G protein–coupled receptors (GPCRs), and other pharmacological targets, we provided a rich map of potential drug targets in the human DRG with direct comparison to mouse sensory neuron transcriptomes. We also compared human DRG neuronal subtypes to nonhuman primates showing conserved patterns of gene expression among many cell types but divergence among specific nociceptor subsets. Last, we identified sex differences in human DRG subpopulation transcriptomes, including a marked increase in calcitonin-related polypeptide alpha (
CALCA
) expression in female pruritogen receptor–enriched nociceptors. This comprehensive spatial characterization of human nociceptors might open the door to development of better treatments for acute and chronic pain disorders.
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Affiliation(s)
- Diana Tavares-Ferreira
- 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
| | - Pradipta R. Ray
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Andi Wangzhou
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Vivekanand Jeevakumar
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Ishwarya Sankaranarayanan
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | | | | | - Alexander Chamessian
- Department of Anesthesiology , Washington University Pain Center, St. Louis, MO 63110, USA
| | - Bryan A. Copits
- Department of Anesthesiology , Washington University Pain Center, St. Louis, MO 63110, USA
| | - Patrick M. Dougherty
- Department of Pain Medicine, Division of Anesthesiology and Critical Care, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Robert W. Gereau
- Department of Anesthesiology , Washington University Pain Center, St. Louis, MO 63110, USA
| | - Michael D. Burton
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Gregory Dussor
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
| | - Theodore J. Price
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX 75080, USA
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11
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Wengert ER, Patel MK. One Size Doesn't Fit All: Variant-Specific Effects in SCN8A Encephalopathy. Epilepsy Curr 2021; 21:183-185. [PMID: 34867099 PMCID: PMC8609588 DOI: 10.1177/15357597211002206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Variant-Specific Changes in Persistent or Resurgent Sodium Current in SCN8A-Related Epilepsy Patient-Derived Neurons Tidball AM, Lopez-Santiago LF, Yuan Y, et al. Brain. 2020;143(10):3025-3040. doi:10.1093/brain/awaa247 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 3 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 3 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 3 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 modeling SCN8A-related epilepsy and demonstrate SCN8A variant-specific mechanisms. Moreover, these findings suggest that patient-specific neuronal disease modeling offers a useful platform for discovering precision epilepsy therapies.
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12
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Xenakis MN, Kapetis D, Yang Y, Gerrits MM, Heijman J, Waxman SG, Lauria G, Faber CG, Westra RL, Lindsey PJ, Smeets HJ. Hydropathicity-based prediction of pain-causing NaV1.7 variants. BMC Bioinformatics 2021; 22:212. [PMID: 33892629 PMCID: PMC8063372 DOI: 10.1186/s12859-021-04119-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 04/01/2021] [Indexed: 11/10/2022] Open
Abstract
Background Mutation-induced variations in the functional architecture of the NaV1.7 channel protein are causally related to a broad spectrum of human pain disorders. Predicting in silico the phenotype of NaV1.7 variant is of major clinical importance; it can aid in reducing costs of in vitro pathophysiological characterization of NaV1.7 variants, as well as, in the design of drug agents for counteracting pain-disease symptoms. Results In this work, we utilize spatial complexity of hydropathic effects toward predicting which NaV1.7 variants cause pain (and which are neutral) based on the location of corresponding mutation sites within the NaV1.7 structure. For that, we analyze topological and scaling hydropathic characteristics of the atomic environment around NaV1.7’s pore and probe their spatial correlation with mutation sites. We show that pain-related mutation sites occupy structural locations in proximity to a hydrophobic patch lining the pore while clustering at a critical hydropathic-interactions distance from the selectivity filter (SF). Taken together, these observations can differentiate pain-related NaV1.7 variants from neutral ones, i.e., NaV1.7 variants not causing pain disease, with 80.5\documentclass[12pt]{minimal}
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\begin{document}$$\%$$\end{document}% specificity [area under the receiver operating characteristics curve = 0.872]. Conclusions Our findings suggest that maintaining hydrophobic NaV1.7 interior intact, as well as, a finely-tuned (dictated by hydropathic interactions) distance from the SF might be necessary molecular conditions for physiological NaV1.7 functioning. The main advantage for using the presented predictive scheme is its negligible computational cost, as well as, hydropathicity-based biophysical rationalization. Supplementary Information The online version contains supplementary material available at 10.1186/s12859-021-04119-2.
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Affiliation(s)
- Makros N Xenakis
- Department of Toxicogenomics, Section Clinical Genomics, Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands. .,Research School for Mental Health and Neuroscience (MHeNS), Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands.
| | - Dimos Kapetis
- Neuroalgology Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy
| | - Yang Yang
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University College of Pharmacy, West Lafayette, IN, 47907, USA.,Purdue Institute for Integrative Neuroscience, West Lafayette, IN, 47907, USA
| | - Monique M Gerrits
- Department of Clinical Genetics, Maastricht University Medical Center, PO box 5800, 6202 AZ, Maastricht, The Netherlands
| | - Jordi Heijman
- Department of Cardiology, CARIM School for Cardiovascular Diseases, Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands
| | - Stephen G Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, 06510, USA.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, 06516, USA
| | - Giuseppe Lauria
- Neuroalgology Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy.,Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Via G.B. Grassi 74, 20157, Milan, Italy
| | - Catharina G Faber
- Department of Neurology, Maastricht University Medical Center, PO Box 5800, 6202 AZ, Maastricht, The Netherlands
| | - Ronald L Westra
- Department of Data Science and Knowledge Engineering, Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands
| | - Patrick J Lindsey
- Department of Toxicogenomics, Section Clinical Genomics, Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands.,Research School for Oncology and Developmental Biology (GROW), Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands
| | - Hubert J Smeets
- Department of Toxicogenomics, Section Clinical Genomics, Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands.,Research School for Mental Health and Neuroscience (MHeNS), Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands
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13
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Gambeta E, Chichorro JG, Zamponi GW. Trigeminal neuralgia: An overview from pathophysiology to pharmacological treatments. Mol Pain 2021; 16:1744806920901890. [PMID: 31908187 PMCID: PMC6985973 DOI: 10.1177/1744806920901890] [Citation(s) in RCA: 129] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The trigeminal nerve (V) is the fifth and largest of all cranial nerves, and it is responsible for detecting sensory stimuli that arise from the craniofacial area. The nerve is divided into three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3); their cell bodies are located in the trigeminal ganglia and they make connections with second-order neurons in the trigeminal brainstem sensory nuclear complex. Ascending projections via the trigeminothalamic tract transmit information to the thalamus and other brain regions responsible for interpreting sensory information. One of the most common forms of craniofacial pain is trigeminal neuralgia. Trigeminal neuralgia is characterized by sudden, brief, and excruciating facial pain attacks in one or more of the V branches, leading to a severe reduction in the quality of life of affected patients. Trigeminal neuralgia etiology can be classified into idiopathic, classic, and secondary. Classic trigeminal neuralgia is associated with neurovascular compression in the trigeminal root entry zone, which can lead to demyelination and a dysregulation of voltage-gated sodium channel expression in the membrane. These alterations may be responsible for pain attacks in trigeminal neuralgia patients. The antiepileptic drugs carbamazepine and oxcarbazepine are the first-line pharmacological treatment for trigeminal neuralgia. Their mechanism of action is a modulation of voltage-gated sodium channels, leading to a decrease in neuronal activity. Although carbamazepine and oxcarbazepine are the first-line treatment, other drugs may be useful for pain control in trigeminal neuralgia. Among them, the anticonvulsants gabapentin, pregabalin, lamotrigine and phenytoin, baclofen, and botulinum toxin type A can be coadministered with carbamazepine or oxcarbazepine for a synergistic approach. New pharmacological alternatives are being explored such as the active metabolite of oxcarbazepine, eslicarbazepine, and the new Nav1.7 blocker vixotrigine. The pharmacological profiles of these drugs are addressed in this review.
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Affiliation(s)
- Eder Gambeta
- Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Juliana G Chichorro
- Department of Pharmacology, Biological Sciences Sector, Federal University of Parana, Curitiba, Brazil
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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14
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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: 32] [Impact Index Per Article: 10.7] [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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15
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Toffano AA, Chiarot G, Zamuner S, Marchi M, Salvi E, Waxman SG, Faber CG, Lauria G, Giacometti A, Simeoni M. Computational pipeline to probe NaV1.7 gain-of-function variants in neuropathic painful syndromes. Sci Rep 2020; 10:17930. [PMID: 33087732 PMCID: PMC7578092 DOI: 10.1038/s41598-020-74591-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 09/30/2020] [Indexed: 01/09/2023] Open
Abstract
Applications of machine learning and graph theory techniques to neuroscience have witnessed an increased interest in the last decade due to the large data availability and unprecedented technology developments. Their employment to investigate the effect of mutational changes in genes encoding for proteins modulating the membrane of excitable cells, whose biological correlates are assessed at electrophysiological level, could provide useful predictive clues. We apply this concept to the analysis of variants in sodium channel NaV1.7 subunit found in patients with chronic painful syndromes, by the implementation of a dedicated computational pipeline empowering different and complementary techniques including homology modeling, network theory, and machine learning. By testing three templates of different origin and sequence identities, we provide an optimal condition for its use. Our findings reveal the usefulness of our computational pipeline in supporting the selection of candidates for cell electrophysiology assay and with potential clinical applications.
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Affiliation(s)
- Alberto A Toffano
- Dipartimento di Scienze Molecolari e Nanosistemi, Universitá Ca' Foscari Venezia, Venezia-Mestre, Italy
| | - Giacomo Chiarot
- Dipartimento di Scienze Ambientali, Informatica e Statistica, Universitá Ca' Foscari Venezia, Venezia-Mestre, Italy
| | - Stefano Zamuner
- Laboratory of Statistical Biophysics, Institute of Physics, School of Basic Sciences, Ècole Polytechnique Fèdèrale de Lausanne (EPFL), Lausanne, Switzerland
| | - Margherita Marchi
- Neuroalgology Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Milan, Italy
| | - Erika Salvi
- Neuroalgology Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Milan, Italy
| | - Stephen G Waxman
- Center for Neuroscience and Regeneration Research, VA Connecticut Healthcare System and Yale Medical School, West Haven, USA
| | - Catharina G Faber
- MHeNs school for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands.,Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Giuseppe Lauria
- Neuroalgology Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Milan, Italy.,Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Milan, Italy
| | - Achille Giacometti
- Dipartimento di Scienze Molecolari e Nanosistemi, Universitá Ca' Foscari Venezia, Venezia-Mestre, Italy.,European Centre for Living Technology (ECLT), Venice, Italy
| | - Marta Simeoni
- Dipartimento di Scienze Ambientali, Informatica e Statistica, Universitá Ca' Foscari Venezia, Venezia-Mestre, Italy. .,European Centre for Living Technology (ECLT), Venice, Italy.
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16
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Adney SK, Millichap JJ, DeKeyser JM, Abramova T, Thompson CH, George AL. Functional and pharmacological evaluation of a novel SCN2A variant linked to early-onset epilepsy. Ann Clin Transl Neurol 2020; 7:1488-1501. [PMID: 32750235 PMCID: PMC7480906 DOI: 10.1002/acn3.51105] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/26/2020] [Accepted: 05/28/2020] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVE We identified a novel de novo SCN2A variant (M1879T) associated with infantile-onset epilepsy that responded dramatically to sodium channel blocker antiepileptic drugs. We analyzed the functional and pharmacological consequences of this variant to establish pathogenicity, and to correlate genotype with phenotype and clinical drug response. METHODS The clinical and genetic features of an infant boy with epilepsy are presented. We investigated the effect of the variant using heterologously expressed recombinant human NaV 1.2 channels. We performed whole-cell patch clamp recording to determine the functional consequences and response to carbamazepine. RESULTS The M1879T variant caused disturbances in channel inactivation including substantially depolarized voltage dependence of inactivation, slower time course of inactivation, and enhanced resurgent current that collectively represent a gain-of-function. Carbamazepine partially normalized the voltage dependence of inactivation and produced use-dependent block of the variant channel at high pulsing frequencies. Carbamazepine also suppresses resurgent current conducted by M1879T channels, but this effect was explained primarily by reducing the peak transient current. Molecular modeling suggests that the M1879T variant disrupts contacts with nearby residues in the C-terminal domain of the channel. INTERPRETATION Our study demonstrates the value of conducting functional analyses of SCN2A variants of unknown significance to establish pathogenicity and genotype-phenotype correlations. We also show concordance of in vitro pharmacology using heterologous cells with the drug response observed clinically in a case of SCN2A-associated epilepsy.
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Affiliation(s)
- Scott K Adney
- Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA
| | - John J Millichap
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA.,Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, 60611, USA
| | - Jean-Marc DeKeyser
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Tatiana Abramova
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Christopher H Thompson
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Alfred L George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
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17
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Andrews JA, Jackson CE, Heiman-Patterson TD, Bettica P, Brooks BR, Pioro EP. Real-world evidence of riluzole effectiveness in treating amyotrophic lateral sclerosis. Amyotroph Lateral Scler Frontotemporal Degener 2020; 21:509-518. [PMID: 32573277 DOI: 10.1080/21678421.2020.1771734] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To compare the effect of riluzole on median survival in population studies of patients with amyotrophic lateral sclerosis (ALS) with that observed in clinical trials. Methods: Two independent PubMed searches were conducted, to identify population studies that reported median survival for ALS patients who were either treated with riluzole or remained riluzole-free. Results: We identified 14 studies that met the inclusion criteria of reporting median survival and an additional study that reported mean survival of both riluzole and riluzole-free patients. Analysis of the 15 studies found that a majority reported increased survival of riluzole vs. riluzole-free patients. In 8 studies, the median survival for patients treated with riluzole was 6-19 months longer compared with patients not treated with riluzole (p < 0.05). Three additional studies reported a clinically meaningful treatment effect (range 3-5.9 months) but did not meet statistical significance. The remaining 4 studies did not show a meaningful treatment effect between riluzole and riluzole-free groups (<3 months), and differences among the groups were not significant. Also, 5 of the studies used multivariate regression analysis to investigate the level of association between treatment with riluzole and survival; these analyses supported the positive effect of riluzole on survival. Conclusions: A majority of population studies that compared riluzole vs. riluzole-free ALS patients found significant differences in median survival between the two groups, ranging from 6 to 19 months. This is substantially longer than the 2- to 3-month survival benefit observed in the pivotal clinical trials of riluzole.
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Affiliation(s)
- Jinsy A Andrews
- Neurological Institute of New York, Columbia University, New York, NY, USA
| | | | | | | | - Benjamin Rix Brooks
- Atrium Health Neurosciences Institute, Carolinas Medical Center, University of North Carolina School of Medicine, Charlotte, NC, USA, and
| | - Erik P Pioro
- Neuromuscular Centre, Neurological Institute, Cleveland Clinic, Cleveland, OH, USA
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18
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Zhang X, Gao Y, Wang Q, Du S, He X, Gu N, Lu Y. Riluzole induces LTD of spinal nociceptive signaling via postsynaptic GluR2 receptors. J Pain Res 2018; 11:2577-2586. [PMID: 30464577 PMCID: PMC6209077 DOI: 10.2147/jpr.s169686] [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] [Indexed: 12/13/2022] Open
Abstract
Purpose Riluzole - a major therapeutic medicine for patients with amyotrophic lateral sclerosis - reportedly has anti-nociceptive and anti-allodynic efficacies in neuropathic pain models. However, little is known about its effect on neurotransmission in the spinal superficial dorsal horn (SDH). The present study aims to investigate the effects of riluzole on the synaptic transmission of SDH nociceptive pathways in both physiological and pathological conditions. Materials and methods Spinal nerve ligation was used to produce a neuropathic pain model. Mechanical allodynia behavior was assessed with Von Frey filaments. Riluzole's effects on nociceptive synaptic transmission under both physiological and pathological conditions were examined by patch-clamp recordings in rat SDH neurons. Results The principal findings of the present study are three-fold. First, we affirm that riluzole has a remarkable long-lasting analgesic effect on both in vitro and in vivo pathological pain models. Second, the prolonged inhibitory effects of riluzole on spinal nociceptive signaling are mediated by both presynaptic and postsynaptic mechanisms. Finally, endocytosis of post-synaptic GluR2 contributes to the riluzole-induced long-term depression (LTD) of the spinal nociceptive pathway. Conclusion The present study finds that riluzole induces LTD of nociceptive signaling in the SDH and produces long-lasting anti-allodynia effects in nerve injury-induced neuropathic pain conditions via postsynaptic AMPA receptors associated with the endocytosis of GluR2.
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Affiliation(s)
- Xiao Zhang
- Department of Pain Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China, ;
| | - Yandong Gao
- Department of Anesthesiology, First Hospital of Yulin City, Yulin 719000, China
| | - Qun Wang
- Department of Pain Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China, ;
| | - Shibin Du
- Department of Pain Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China, ;
| | - Xiaolan He
- Department of Pain Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China, ;
| | - Nan Gu
- Department of Pain Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China, ;
| | - Yan Lu
- Department of Pain Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China, ;
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19
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Zheng YM, Wang WF, Li YF, Yu Y, Gao ZB. Enhancing inactivation rather than reducing activation of Nav1.7 channels by a clinically effective analgesic CNV1014802. Acta Pharmacol Sin 2018; 39:587-596. [PMID: 29094728 PMCID: PMC5888685 DOI: 10.1038/aps.2017.151] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 09/03/2017] [Indexed: 12/16/2022] Open
Abstract
The Nav1.7 channel represents a promising target for pain relief. In the recent decades, a number of Nav1.7 channel inhibitors have been developed. According to the effects on channel kinetics, these inhibitors could be divided into two major classes: reducing activation or enhancing inactivation. To date, however, only several inhibitors have moved forward into phase 2 clinical trials and most of them display a less than ideal analgesic efficacy, thus intensifying the controversy regarding if an ideal candidate should preferentially affect the activation or inactivation state. In the present study, we investigated the action mechanisms of a recently clinically confirmed inhibitor CNV1014802 using both electrophysiology and site-directed mutagenesis. We found that CNV1014802 inhibited Nav1.7 channels through stabilizing a nonconductive inactivated state. When the cells expressing Nav1.7 channels were hold at 70 mV or 120 mV, the half maximal inhibitory concentration (IC50) values (with 95% confidence limits) were 1.77 (1.20-2.33) and 71.66 (46.85-96.48) μmol/L, respectively. This drug caused dramatic hyperpolarizing shift of channel inactivation but did not affect activation. Moreover, CNV1014802 accelerated the onset of inactivation and delayed the recovery from inactivation. Notably, application of CNV1014802 (30 μmol/L) could rescue the Nav1.7 mutations expressed in CHO cells that cause paroxysmal extreme pain disorder (PEPD), thereby restoring the impaired inactivation to those of the wild-type channel. Our study demonstrates that CNV1014802 enhances the inactivation but does not reduce the activation of Nav1.7 channels, suggesting that identifying inhibitors that preferentially affect inactivation is a promising approach for developing drugs targeting Nav1.7.
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Affiliation(s)
- Yue-ming Zheng
- CAS Key Laboratory of Receptor Research, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Wan-fu Wang
- CAS Key Laboratory of Receptor Research, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Yan-fen Li
- CAS Key Laboratory of Receptor Research, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
- Shanghai Key Laboratory of Bio-Energy Crops, School of Life Sciences, Shanghai University, Shanghai 200444, China
| | - Yong Yu
- Department of Neurosurgery, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Zhao-bing Gao
- CAS Key Laboratory of Receptor Research, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
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Foadi N. Modulation of sodium channels as pharmacological tool for pain therapy-highlights and gaps. Naunyn Schmiedebergs Arch Pharmacol 2018; 391:481-488. [PMID: 29572558 DOI: 10.1007/s00210-018-1487-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 03/14/2018] [Indexed: 02/06/2023]
Abstract
Voltage-gated sodium channels are crucially involved in the transduction and transmission of nociceptive signals and pathological pain states. In the past decades, a lot of effort has been spent examining and characterizing biophysical properties of the different sodium channels and their role in signaling pathways. Several gains of function mutations of the sodium channels Nav1.7, Nav1.8, and Nav1.9 are associated with pain disorders. Due to their critical role in nociceptive pathways voltage-gated sodium channels are regarded interesting targets for pharmacological pain treatment. However we still need to fill the gap that exists in the translation of efficacy in preclinical in vitro experiments and in models of pain into the clinic. This review summarizes biological and electrophysiological properties of voltage-gated sodium channels and aims to discuss limitations and promising pharmacological strategies in sodium channel research in the context of pain therapy.
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Affiliation(s)
- Nilufar Foadi
- Clinic for Anaesthesia and Critical Care Medicine, Hannover Medical School, 30625, Hannover, Germany.
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Farinato A, Altamura C, Desaphy JF. Effects of Benzothiazolamines on Voltage-Gated Sodium Channels. Handb Exp Pharmacol 2018; 246:233-250. [PMID: 28939972 DOI: 10.1007/164_2017_46] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Benzothiazole is a versatile fused heterocycle that aroused much interest in drug discovery as anticonvulsant, neuroprotective, analgesic, anti-inflammatory, antimicrobial, and anticancer. Two benzothiazolamines, riluzole and lubeluzole, are known blockers of voltage-gated sodium (Nav) channels. Riluzole is clinically used as a neuroprotectant in amyotrophic lateral sclerosis. Inhibition of Nav channels by riluzole is voltage-dependent due to preferential binding to inactivated sodium channels. Yet the drug exerts little use-dependent block, probably because it lacks protonable amine. One important property is riluzole ability to inhibit persistent Na+ currents, which likely contributes to its neuroprotective activity. Lubeluzole showed promising neuroprotective effects in animal stroke models, but failed to show benefits in acute ischemic stroke in humans. One important concern is its propensity to prolong the cardiac QT interval, due to hERG K+ channel block. Lubeluzole very potently inhibits Nav channels in a voltage- and use-dependent manner, due to its great preferential affinity for inactivated channels and the presence of a protonable amine group. Patch-clamp experiments suggest that the binding sites of both drugs overlap the local anesthetic receptor within the ion-conducting pathway. Riluzole and lubeluzole displayed very potent antimyotonic activity in a rat model of myotonia, a pathological skeletal muscle condition characterized by high-frequency runs of action potentials. Such results well support the repurposing of riluzole as an antimyotonic drug, allowing the launch of a pilot study in myotonic patients. Riluzole, lubeluzole, and new Nav channel blockers built on the benzothiazolamine scaffold will certainly continue to be investigated for possible clinical applications.
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Affiliation(s)
- Alessandro Farinato
- Section of Pharmacology, Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Policlinico, Piazza G. Cesare 11, 70124, Bari, Italy
| | - Concetta Altamura
- Section of Pharmacology, Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Policlinico, Piazza G. Cesare 11, 70124, Bari, Italy
| | - Jean-François Desaphy
- Section of Pharmacology, Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Policlinico, Piazza G. Cesare 11, 70124, Bari, Italy.
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Kapetis D, Sassone J, Yang Y, Galbardi B, Xenakis MN, Westra RL, Szklarczyk R, Lindsey P, Faber CG, Gerrits M, Merkies ISJ, Dib-Hajj SD, Mantegazza M, Waxman SG, Lauria G. Network topology of NaV1.7 mutations in sodium channel-related painful disorders. BMC SYSTEMS BIOLOGY 2017; 11:28. [PMID: 28235406 PMCID: PMC5324268 DOI: 10.1186/s12918-016-0382-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 12/20/2016] [Indexed: 11/30/2022]
Abstract
BACKGROUND Gain-of-function mutations in SCN9A gene that encodes the voltage-gated sodium channel NaV1.7 have been associated with a wide spectrum of painful syndromes in humans including inherited erythromelalgia, paroxysmal extreme pain disorder and small fibre neuropathy. These mutations change the biophysical properties of NaV1.7 channels leading to hyperexcitability of dorsal root ganglion nociceptors and pain symptoms. There is a need for better understanding of how gain-of-function mutations alter the atomic structure of Nav1.7. RESULTS We used homology modeling to build an atomic model of NaV1.7 and a network-based theoretical approach, which can predict interatomic interactions and connectivity arrangements, to investigate how pain-related NaV1.7 mutations may alter specific interatomic bonds and cause connectivity rearrangement, compared to benign variants and polymorphisms. For each amino acid substitution, we calculated the topological parameters betweenness centrality (B ct ), degree (D), clustering coefficient (CC ct ), closeness (C ct ), and eccentricity (E ct ), and calculated their variation (Δ value = mutant value -WT value ). Pathogenic NaV1.7 mutations showed significantly higher variation of |ΔB ct | compared to benign variants and polymorphisms. Using the cut-off value ±0.26 calculated by receiver operating curve analysis, we found that ΔB ct correctly differentiated pathogenic NaV1.7 mutations from variants not causing biophysical abnormalities (nABN) and homologous SNPs (hSNPs) with 76% sensitivity and 83% specificity. CONCLUSIONS Our in-silico analyses predict that pain-related pathogenic NaV1.7 mutations may affect the network topological properties of the protein and suggest |ΔB ct | value as a potential in-silico marker.
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Affiliation(s)
- Dimos Kapetis
- Bioinformatics Unit, IRCCS Foundation “Carlo Besta” Neurological Institute, Milan, Italy
- Neuroalgology Unit, IRCCS Foundation “Carlo Besta” Neurological Institute, Milan, Italy
| | - Jenny Sassone
- Neuroalgology Unit, IRCCS Foundation “Carlo Besta” Neurological Institute, Milan, Italy
- Present address: San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
| | - Yang Yang
- Department of Neurology, Yale University School of Medicine, New Haven, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, USA
| | - Barbara Galbardi
- Bioinformatics Unit, IRCCS Foundation “Carlo Besta” Neurological Institute, Milan, Italy
| | - Markos N. Xenakis
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
| | - Ronald L. Westra
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
| | - Radek Szklarczyk
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Patrick Lindsey
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Catharina G. Faber
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Monique Gerrits
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Ingemar S. J. Merkies
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Neurology, Spaarne Hospital, Hoofddorp, The Netherlands
| | - Sulayman D. Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, USA
| | - Massimo Mantegazza
- Laboratory of Excellence Ion Channel Science and Therapeutics, Institute of Molecular and Cellular Pharmacology, CNRS UMR7275 & University of Nice-Sophia Antipolis, Valbonne, France
| | - Stephen G. Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, USA
| | - Giuseppe Lauria
- Neuroalgology Unit, IRCCS Foundation “Carlo Besta” Neurological Institute, Milan, Italy
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Upregulation of the sodium channel NaVβ4 subunit and its contributions to mechanical hypersensitivity and neuronal hyperexcitability in a rat model of radicular pain induced by local dorsal root ganglion inflammation. Pain 2017; 157:879-891. [PMID: 26785322 DOI: 10.1097/j.pain.0000000000000453] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
High-frequency spontaneous firing in myelinated sensory neurons plays a key role in initiating pain behaviors in several different models, including the radicular pain model in which the rat lumbar dorsal root ganglia (DRG) are locally inflamed. The sodium channel isoform NaV1.6 contributes to pain behaviors and spontaneous activity in this model. Among all isoforms in adult DRG, NaV1.6 is the main carrier of tetrodotoxin-sensitive resurgent Na currents that allow high-frequency firing. Resurgent currents flow after a depolarization or action potential, as a blocking particle exits the pore. In most neurons, the regulatory β4 subunit is potentially the endogenous blocker. We used in vivo siRNA-mediated knockdown of NaVβ4 to examine its role in the DRG inflammation model. NaVβ4 but not control siRNA almost completely blocked mechanical hypersensitivity induced by DRG inflammation. Microelectrode recordings in isolated whole DRG showed that NaVβ4 siRNA blocked the inflammation-induced increase in spontaneous activity of Aβ neurons and reduced repetitive firing and other measures of excitability. NaVβ4 was preferentially expressed in larger diameter cells; DRG inflammation increased its expression, and this was reversed by NaVβ4 siRNA, based on immunohistochemistry and Western blotting. NaVβ4 siRNA also reduced immunohistochemical NaV1.6 expression. Patch-clamp recordings of tetrodotoxin-sensitive Na currents in acutely cultured medium diameter DRG neurons showed that DRG inflammation increased transient and especially resurgent current, effects blocked by NaVβ4 siRNA. NaVβ4 may represent a more specific target for pain conditions that depend on myelinated neurons expressing NaV1.6.
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Michiels JJ. Aspirin responsive erythromelalgia in JAK2-thrombocythemia and incurable inherited erythrothermalgia in neuropathic Nav1.7 sodium channelopathy: from Mitchell 1878 to Michiels 2017. Expert Opin Orphan Drugs 2016. [DOI: 10.1080/21678707.2017.1270822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Jan Jacques Michiels
- Department of Hematology & Coagulation, Academic Hospital Dijkzigt and Erasmus University, Rotterdam, The Netherlands
- Department of Blood and Coagulation Disorders, University Hospital Antwerp, Edegem, Belgium
- Blood, Coagulation and Vascular Medicine Research Center, Goodheart Institute & Foundation in Nature Medicine & Health, Freedom of Science and Education, European Free University, Erasmus Tower, Rotterdam
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25
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Huang CW, Lai HJ, Huang PY, Lee MJ, Kuo CC. The Biophysical Basis Underlying Gating Changes in the p.V1316A Mutant Nav1.7 Channel and the Molecular Pathogenesis of Inherited Erythromelalgia. PLoS Biol 2016; 14:e1002561. [PMID: 27653502 PMCID: PMC5031448 DOI: 10.1371/journal.pbio.1002561] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 08/24/2016] [Indexed: 12/16/2022] Open
Abstract
The Nav1.7 channel critically contributes to the excitability of sensory neurons, and gain-of-function mutations of this channel have been shown to cause inherited erythromelalgia (IEM) with neuropathic pain. In this study, we report a case of a severe phenotype of IEM caused by p.V1316A mutation in the Nav1.7 channel. Mechanistically, we first demonstrate that the Navβ4 peptide acts as a gating modifier rather than an open channel blocker competing with the inactivating peptide to give rise to resurgent currents in the Nav1.7 channel. Moreover, there are two distinct open and two corresponding fast inactivated states in the genesis of resurgent Na+ currents. One is responsible for the resurgent route and practically existent only in the presence of Navβ4 peptide, whereas the other is responsible for the “silent” route of recovery from inactivation. In this regard, the p.V1316A mutation makes hyperpolarization shift in the activation curve, and depolarization shift in the inactivation curve, vividly uncoupling inactivation from activation. In terms of molecular gating operation, the most important changes caused by the p.V1316A mutation are both acceleration of the transition from the inactivated states to the activated states and deceleration of the reverse transition, resulting in much larger sustained as well as resurgent Na+ currents. In summary, the genesis of the resurgent currents in the Nav1.7 channel is ascribable to the transient existence of a distinct and novel open state promoted by the Navβ4 peptide. In addition, S4–5 linker in domain III where V1316 is located seems to play a critical role in activation–inactivation coupling, chiefly via direct modulation of the transitional kinetics between the open and the inactivated states. The sustained and resurgent Na+ currents may therefore be correlatively enhanced by specific mutations involving this linker and relevant regions, and thus marked hyperexcitability in corresponding neural tissues as well as IEM symptomatology. Mutations in the Nav1.7 sodium channel cause idiopathic erythromelalgia. This study shows that the pathogenic resurgent sodium currents arise via modification of gating behavior rather than via competing pore block by the Navβ4 peptide. The gain-of-function mutation (p.V1316A) of the Nav1.7 channel causes inherited erythromelalgia (IEM), a disease characterized by extremely enhanced activity in relevant neural tissues that results in neuropathic pain. We found that the p.V1316A mutation alters the basic gating properties of the channel, leading to increased sustained currents during membrane depolarization and resurgent currents during repolarization. Neurons expressing these mutant channels are more difficult to maintain in a hyperpolarized state and are thus more excitable. We demonstrate that there is very likely a distinct set of open/inactivated (O/I) states responsible for the genesis of resurgent currents. We show that the p.V1316A mutation chiefly accelerates the I to O transition in this set, but also decelerates the transitions between different sets of O/I states, to cause the channel gating and cellular excitability changes. Contrary to the conventional view, we find that the Navβ4 peptide, a key element responsible for sizable resurgent currents, does not seem to act as a pore blocker that competes with the inactivation peptide. Instead, we show that it acts as a gating modifier of the Nav1.7 channel. Thus, the DIII/S4–5 linker, where V1316 is located, may play a critical role not only in O/I coupling but also in the couplings between different sets of O/I in the Nav1.7 channel.
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Affiliation(s)
- Chiung-Wei Huang
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Hsing-Jung Lai
- Department of Neurology, National Taiwan University Hospital Jinshan Branch, New Taipei City, Taiwan
| | - Po-Yuan Huang
- Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan
| | - Ming-Jen Lee
- Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan
- * E-mail: (MJL); (CCK)
| | - Chung-Chin Kuo
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan
- * E-mail: (MJL); (CCK)
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27
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Winters JJ, Isom LL. Developmental and Regulatory Functions of Na(+) Channel Non-pore-forming β Subunits. CURRENT TOPICS IN MEMBRANES 2016; 78:315-51. [PMID: 27586289 DOI: 10.1016/bs.ctm.2016.07.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Voltage-gated Na(+) channels (VGSCs) isolated from mammalian neurons are heterotrimeric complexes containing one pore-forming α subunit and two non-pore-forming β subunits. In excitable cells, VGSCs are responsible for the initiation of action potentials. VGSC β subunits are type I topology glycoproteins, containing an extracellular amino-terminal immunoglobulin (Ig) domain with homology to many neural cell adhesion molecules (CAMs), a single transmembrane segment, and an intracellular carboxyl-terminal domain. VGSC β subunits are encoded by a gene family that is distinct from the α subunits. While α subunits are expressed in prokaryotes, β subunit orthologs did not arise until after the emergence of vertebrates. β subunits regulate the cell surface expression, subcellular localization, and gating properties of their associated α subunits. In addition, like many other Ig-CAMs, β subunits are involved in cell migration, neurite outgrowth, and axon pathfinding and may function in these roles in the absence of associated α subunits. In sum, these multifunctional proteins are critical for both channel regulation and central nervous system development.
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Affiliation(s)
- J J Winters
- University of Michigan Neuroscience Program, Ann Arbor, MI, United States
| | - L L Isom
- University of Michigan Neuroscience Program, Ann Arbor, MI, United States; University of Michigan Medical School, Ann Arbor, MI, United States
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28
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Wolff M, Czorlich P, Nagaraj C, Schnöbel-Ehehalt R, Li Y, Kwapiszewska G, Olschewski H, Heschl S, Olschewski A. Amitriptyline and carbamazepine utilize voltage-gated ion channel suppression to impair excitability of sensory dorsal horn neurons in thin tissue slice: An in vitro study. Neurosci Res 2016; 109:16-27. [DOI: 10.1016/j.neures.2016.02.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 02/15/2016] [Accepted: 02/18/2016] [Indexed: 11/27/2022]
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Patel RR, Barbosa C, Brustovetsky T, Brustovetsky N, Cummins TR. Aberrant epilepsy-associated mutant Nav1.6 sodium channel activity can be targeted with cannabidiol. Brain 2016; 139:2164-81. [PMID: 27267376 DOI: 10.1093/brain/aww129] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 04/15/2016] [Indexed: 11/12/2022] Open
Abstract
Mutations in brain isoforms of voltage-gated sodium channels have been identified in patients with distinct epileptic phenotypes. Clinically, these patients often do not respond well to classic anti-epileptics and many remain refractory to treatment. Exogenous as well as endogenous cannabinoids have been shown to target voltage-gated sodium channels and cannabidiol has recently received attention for its potential efficacy in the treatment of childhood epilepsies. In this study, we further investigated the ability of cannabinoids to modulate sodium currents from wild-type and epilepsy-associated mutant voltage-gated sodium channels. We first determined the biophysical consequences of epilepsy-associated missense mutations in both Nav1.1 (arginine 1648 to histidine and asparagine 1788 to lysine) and Nav1.6 (asparagine 1768 to aspartic acid and leucine 1331 to valine) by obtaining whole-cell patch clamp recordings in human embryonic kidney 293T cells with 200 μM Navβ4 peptide in the pipette solution to induce resurgent sodium currents. Resurgent sodium current is an atypical near threshold current predicted to increase neuronal excitability and has been implicated in multiple disorders of excitability. We found that both mutations in Nav1.6 dramatically increased resurgent currents while mutations in Nav1.1 did not. We then examined the effects of anandamide and cannabidiol on peak transient and resurgent currents from wild-type and mutant channels. Interestingly, we found that cannabidiol can preferentially target resurgent sodium currents over peak transient currents generated by wild-type Nav1.6 as well as the aberrant resurgent and persistent current generated by Nav1.6 mutant channels. To further validate our findings, we examined the effects of cannabidiol on endogenous sodium currents from striatal neurons, and similarly we found an inhibition of resurgent and persistent current by cannabidiol. Moreover, current clamp recordings show that cannabidiol reduces overall action potential firing of striatal neurons. These findings suggest that cannabidiol could be exerting its anticonvulsant effects, at least in part, through its actions on voltage-gated sodium channels, and resurgent current may be a promising therapeutic target for the treatment of epilepsy syndromes.
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Affiliation(s)
- Reesha R Patel
- 1 Program in Medical Neuroscience, Neuroscience Research Building, 320 West 15th St, Indianapolis, IN, 46202, USA 2 Paul and Carole Stark Neurosciences Research Institute, 320 West 15th St, Indianapolis, IN, 46202, USA
| | - Cindy Barbosa
- 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Tatiana Brustovetsky
- 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Nickolay Brustovetsky
- 1 Program in Medical Neuroscience, Neuroscience Research Building, 320 West 15th St, Indianapolis, IN, 46202, USA 2 Paul and Carole Stark Neurosciences Research Institute, 320 West 15th St, Indianapolis, IN, 46202, USA 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Theodore R Cummins
- 1 Program in Medical Neuroscience, Neuroscience Research Building, 320 West 15th St, Indianapolis, IN, 46202, USA 2 Paul and Carole Stark Neurosciences Research Institute, 320 West 15th St, Indianapolis, IN, 46202, USA 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
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Abstract
Voltage-gated sodium channels (VGSCs) are fundamentally important for the generation and coordinated transmission of action potentials throughout the nervous system. It is, therefore, unsurprising that they have been shown to play a central role in the genesis and alleviation of epilepsy. Genetic studies on patients with epilepsy have identified more than 700 mutations among the genes that encode for VGSCs attesting to their role in pathogenesis. Further, many common antiepileptic drugs act on VGSCs to suppress seizure activity. Here, we present an account of the role of VGSCs in epilepsy, both through their pathogenic dysfunction and as targets for pharmacotherapy.
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31
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Sodium channel slow inactivation interferes with open channel block. Sci Rep 2016; 6:25974. [PMID: 27174182 PMCID: PMC4865801 DOI: 10.1038/srep25974] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 04/20/2016] [Indexed: 11/17/2022] Open
Abstract
Mutations in the voltage-gated sodium channel Nav1.7 are linked to inherited pain syndromes such as erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD). PEPD mutations impair Nav1.7 fast inactivation and increase persistent currents. PEPD mutations also increase resurgent currents, which involve the voltage-dependent release of an open channel blocker. In contrast, IEM mutations, whenever tested, leave resurgent currents unchanged. Accordingly, the IEM deletion mutation L955 (ΔL955) fails to produce resurgent currents despite enhanced persistent currents, which have hitherto been considered a prerequisite for resurgent currents. Additionally, ΔL955 exhibits a prominent enhancement of slow inactivation (SI). We introduced mutations into Nav1.7 and Nav1.6 that either enhance or impair SI in order to investigate their effects on resurgent currents. Our results show that enhanced SI is accompanied by impaired resurgent currents, which suggests that SI may interfere with open-channel block.
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32
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Báldi R, Ghose D, Grueter BA, Patel S. Electrophysiological Measurement of Cannabinoid-Mediated Synaptic Modulation in Acute Mouse Brain Slices. CURRENT PROTOCOLS IN NEUROSCIENCE 2016; 75:6.29.1-6.29.19. [PMID: 27063786 PMCID: PMC4866814 DOI: 10.1002/cpns.8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Endocannabinoids (eCBs) are a class of bioactive lipids that mediate retrograde synaptic modulation at central and peripheral synapses. The highly lipophilic nature of eCBs and the pharmacological tools available to interrogate this system require unique methodological consideration, especially when applied to ex vivo systems such as electrophysiological analysis in acute brain slices. This unit provides protocols for measuring cannabinoid and eCB-mediated synaptic signaling in mouse brain slices, including analysis of short-term, long-term, and tonic eCB signaling modes, and the unique considerations for working with eCBs and TRPV1/cannabinoid ligands in acute brain slices.
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Affiliation(s)
- Rita Báldi
- Department of Psychiatry, 2213 Garland Avenue, 8415 MRBIV, Vanderbilt University Medical Center, Nashville, TN 37232-0413, Tel. 615-936-7768, Fax. 615-936-4075
| | - Dipanwita Ghose
- Department of Anesthesiology, 2213 Garland Avenue, P445 MRBIV, Vanderbilt University Medical Center, Nashville, TN 37232-0413, Tel. 615-936-1684, Fax. 615-936-0456
| | - Brad A. Grueter
- Department of Anesthesiology, 2213 Garland Avenue, P435H MRBIV, Vanderbilt University Medical Center, Nashville, TN 37232-0413, Tel. 615-936-2586, Fax. 615-936-0456
| | - Sachin Patel
- Departments of Psychiatry and Molecular Physiology & Biophysics, 2213 Garland Avenue, 8425B MRBIV, Vanderbilt University Medical Center, Nashville, TN 37232-0413, Tel. 615-936-7768, Fax. 615-936-4075
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Barbosa C, Cummins TR. Unusual Voltage-Gated Sodium Currents as Targets for Pain. CURRENT TOPICS IN MEMBRANES 2016; 78:599-638. [PMID: 27586296 DOI: 10.1016/bs.ctm.2015.12.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Pain is a serious health problem that impacts the lives of many individuals. Hyperexcitability of peripheral sensory neurons contributes to both acute and chronic pain syndromes. Because voltage-gated sodium currents are crucial to the transmission of electrical signals in peripheral sensory neurons, the channels that underlie these currents are attractive targets for pain therapeutics. Sodium currents and channels in peripheral sensory neurons are complex. Multiple-channel isoforms contribute to the macroscopic currents in nociceptive sensory neurons. These different isoforms exhibit substantial variations in their kinetics and pharmacology. Furthermore, sodium current complexity is enhanced by an array of interacting proteins that can substantially modify the properties of voltage-gated sodium channels. Resurgent sodium currents, atypical currents that can enhance recovery from inactivation and neuronal firing, are increasingly being recognized as playing potentially important roles in sensory neuron hyperexcitability and pain sensations. Here we discuss unusual sodium channels and currents that have been identified in nociceptive sensory neurons, describe what is known about the molecular determinants of the complex sodium currents in these neurons. Finally, we provide an overview of therapeutic strategies to target voltage-gated sodium currents in nociceptive neurons.
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Affiliation(s)
- C Barbosa
- Indiana University School of Medicine, Indianapolis, IN, United States
| | - T R Cummins
- Indiana University School of Medicine, Indianapolis, IN, United States
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34
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Gawali V, Todt H. Mechanism of Inactivation in Voltage-Gated Na+ Channels. CURRENT TOPICS IN MEMBRANES 2016; 78:409-50. [DOI: 10.1016/bs.ctm.2016.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Abstract
Voltage-gated sodium channels (VGSCs) are responsible for the initiation and propagation of action potentials in excitable cells. VGSCs in mammalian brain are heterotrimeric complexes of α and β subunits. Although β subunits were originally termed auxiliary, we now know that they are multifunctional signaling molecules that play roles in both excitable and nonexcitable cell types and with or without the pore-forming α subunit present. β subunits function in VGSC and potassium channel modulation, cell adhesion, and gene regulation, with particularly important roles in brain development. Mutations in the genes encoding β subunits are linked to a number of diseases, including epilepsy, sudden death syndromes like SUDEP and SIDS, and cardiac arrhythmia. Although VGSC β subunit-specific drugs have not yet been developed, this protein family is an emerging therapeutic target.
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Affiliation(s)
- Heather A O'Malley
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109;
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Abstract
• Individual variability in pain perception and differences in the efficacy of analgesic drugs are complex phenomena and are partly genetically predetermined. • Analgesics act in various ways on the peripheral and central pain pathways and are regarded as one of the most valuable but equally dangerous groups of medications. • While pharmacokinetic properties of drugs, metabolism in particular, have been scrutinised by genotype–phenotype correlation studies, the clinical significance of inherited variants in genes governing pharmacodynamics of analgesics remains largely unexplored (apart from the µ-opioid receptor). • Lack of replication of the findings from one study to another makes meaningful personalised analgesic regime still a distant future. • This narrative review will focus on findings related to pharmacogenetics of commonly used analgesic medications and highlight authors’ views on future clinical implications of pharmacogenetics in the context of pharmacological treatment of chronic pain.
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Affiliation(s)
- Roman Cregg
- UCL Centre for Anaesthesia, Critical Care & Pain Medicine, London, UK ; Royal Marsden NHS Foundation Trust, London, UK
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Alessi C, Raspanti A, Magistretti J. Two distinct types of depolarizing afterpotentials are differentially expressed in stellate and pyramidal-like neurons of entorhinal-cortex layer II. Hippocampus 2015; 26:380-404. [PMID: 26342161 DOI: 10.1002/hipo.22529] [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] [Accepted: 09/03/2015] [Indexed: 11/09/2022]
Abstract
Two types of principal neurons, stellate cells and pyramidal-like cells, are found in medial entorhinal-cortex (mEC) layer II, and are believed to represent two distinct channels of information processing and transmission in the entorhinal cortex-hippocampus network. In this study, we found that depolarizing afterpotentials (DAPs) that follow single action potentials (APs) evoked from various levels of holding membrane voltage (Vh ) show distinct properties in the two cells types. In both, an evident DAP followed the AP at near-threshold Vh levels, and was accompanied by an enhancement of excitability and spike-timing precision. This DAP was sensitive to voltage-gated Na(+)-channel block with TTx, but not to partial removal of extracellular Ca(2+). Application of 5-μM anandamide, which inhibited the resurgent and persistent Na(+) -current components in a relatively selective way, significantly reduced the amplitude of this particular DAP while exerting poor effects on the foregoing AP. In the presence of background hyperpolarization, DAPs showed an opposite behavior in the two cell types, as in stellate cells they became even more prominent, whereas in pyramidal-like cells their amplitude was markedly reduced. The DAP observed in stellate cells under this condition was strongly inhibited by partial extracellular-Ca(2+) removal, and was sensitive to the low-voltage-activated Ca(2+)-channel blocker, NNC55-0396. This Ca(2+) dependence was not observed in the residual DAP evoked in pyramidal-like cells from likewise negative Vh levels. These results demonstrate that two distinct mechanism of DAP generation operate in mEC layer-II neurons, one Na(+)-dependent and active at near-threshold Vh levels in both stellate and-pyramidal-like cells, the other Ca(2+)-dependent and only expressed by stellate cells in the presence of background membrane hyperpolarization.
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Affiliation(s)
- Camilla Alessi
- Department of Biology and Biotechnology, "L. Spallanzani,", University of Pavia, Pavia, Italy
| | - Alessandra Raspanti
- Department of Biology and Biotechnology, "L. Spallanzani,", University of Pavia, Pavia, Italy
| | - Jacopo Magistretti
- Department of Biology and Biotechnology, "L. Spallanzani,", University of Pavia, Pavia, Italy
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38
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Kwong K, Carr MJ. Voltage-gated sodium channels. Curr Opin Pharmacol 2015; 22:131-9. [PMID: 26043074 DOI: 10.1016/j.coph.2015.04.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 04/21/2015] [Accepted: 04/29/2015] [Indexed: 12/11/2022]
Abstract
Voltage-gated sodium channels play a key role in the transmission of sensory information about the status of organs in the periphery. Sensory fibers contain a heterogeneous yet specific distribution of voltage-gated sodium channel isoforms. Major efforts by industry and academic groups are underway to develop medicines that interrupt inappropriate signaling for a number of clinical indications by taking advantage of this specific distribution of channel isoforms. This review highlights recent advances in the study of human channelopathies, animal toxins and channel structure that may facilitate the development of selective voltage-gated sodium channel blockers.
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Al Kury LT, Voitychuk OI, Yang KHS, Thayyullathil FT, Doroshenko P, Ramez AM, Shuba YM, Galadari S, Howarth FC, Oz M. Effects of the endogenous cannabinoid anandamide on voltage-dependent sodium and calcium channels in rat ventricular myocytes. Br J Pharmacol 2015; 171:3485-98. [PMID: 24758718 DOI: 10.1111/bph.12734] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 02/17/2014] [Accepted: 03/14/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE The endocannabinoid anandamide (N-arachidonoyl ethanolamide; AEA) exerts negative inotropic and antiarrhythmic effects in ventricular myocytes. EXPERIMENTAL APPROACH Whole-cell patch-clamp technique and radioligand-binding methods were used to analyse the effects of anandamide in rat ventricular myocytes. KEY RESULTS In the presence of 1-10 μM AEA, suppression of both Na(+) and L-type Ca(2+) channels was observed. Inhibition of Na(+) channels was voltage and Pertussis toxin (PTX) - independent. Radioligand-binding studies indicated that specific binding of [(3) H] batrachotoxin (BTX) to ventricular muscle membranes was also inhibited significantly by 10 μM metAEA, a non-metabolized AEA analogue, with a marked decrease in Bmax values but no change in Kd . Further studies on L-type Ca(2+) channels indicated that AEA potently inhibited these channels (IC50 0.1 μM) in a voltage- and PTX-independent manner. AEA inhibited maximal amplitudes without affecting the kinetics of Ba(2+) currents. MetAEA also inhibited Na(+) and L-type Ca(2+) currents. Radioligand studies indicated that specific binding of [(3) H]isradipine, was inhibited significantly by metAEA. (10 μM), changing Bmax but not Kd . CONCLUSION AND IMPLICATIONS Results indicate that AEA inhibited the function of voltage-dependent Na(+) and L-type Ca(2+) channels in rat ventricular myocytes, independent of CB1 and CB2 receptor activation.
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Affiliation(s)
- Lina T Al Kury
- Laboratory of Functional Lipidomics, Department of Pharmacology, UAE University, Al Ain, UAE
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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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Abstract
Voltage-gated sodium channels (NaV) play a crucial role in development and propagation of action potentials in neurons and muscle cells. NaV1.7 channels take a special place in modern science since it is believed that they contribute to nerve hyperexcitability. Mutations of the gene SCN9A, which codes the α subunit of NaV1.7 channels, are associated with pain perception disorders (primary erythermalgia, congenital analgesia, and paroxysmal pain disorder). It is considered that the SCN9A gene mutations may cause variations in sensitivity to pain, from complete insensitivity to extreme sensitivity. Further research of the SCN9A gene polymorphism influence on pain sensitivity is essential for the understanding of the pathophysiology of pain and the development of the appropriate targeted pain treatment.
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López-Pérez SJ, Morales-Villagrán A, Medina-Ceja L. Effect of perinatal asphyxia and carbamazepine treatment on cortical dopamine and DOPAC levels. J Biomed Sci 2015; 22:14. [PMID: 25889791 PMCID: PMC4335632 DOI: 10.1186/s12929-015-0117-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 01/23/2015] [Indexed: 01/29/2023] Open
Abstract
Background One of the most important manifestations of perinatal asphyxia is the occurrence of seizures, which are treated with antiepileptic drugs, such as carbamazepine. These early seizures, combined with pharmacological treatments, may influence the development of dopaminergic neurotransmission in the frontal cortex. This study aimed to determine the extracellular levels of dopamine and its main metabolite DOPAC in 30-day-old rats that had been asphyxiated for 45 min in a low (8%) oxygen chamber at a perinatal age and treated with daily doses of carbamazepine. Quantifications were performed using microdialysis coupled to a high-performance liquid chromatography (HPLC) system in basal conditions and following the use of the chemical stimulus. Results Significant decreases in basal and stimulated extracellular dopamine and DOPAC content were observed in the frontal cortex of the asphyxiated group, and these decreases were partially recovered in the animals administered daily doses of carbamazepine. Greater basal dopamine concentrations were also observed as an independent effect of carbamazepine. Conclusions Perinatal asphyxia plus carbamazepine affects extracellular levels of dopamine and DOPAC in the frontal cortex and stimulated the release of dopamine, which provides evidence for the altered availability of dopamine in cortical brain areas during brain development.
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Affiliation(s)
- Silvia J López-Pérez
- Laboratorio de Neurofisiología y Neuroquímica, Departamento de Biología Celular y Molecular, CUCBA, Universidad de Guadalajara, Camino Ing. Ramón Padilla Sánchez #2100, Predio Las Agujas, Zapopan, Jalisco, C.P 44600, Mexico.
| | - Alberto Morales-Villagrán
- Laboratorio de Neurofisiología y Neuroquímica, Departamento de Biología Celular y Molecular, CUCBA, Universidad de Guadalajara, Camino Ing. Ramón Padilla Sánchez #2100, Predio Las Agujas, Zapopan, Jalisco, C.P 44600, Mexico.
| | - Laura Medina-Ceja
- Laboratorio de Neurofisiología y Neuroquímica, Departamento de Biología Celular y Molecular, CUCBA, Universidad de Guadalajara, Camino Ing. Ramón Padilla Sánchez #2100, Predio Las Agujas, Zapopan, Jalisco, C.P 44600, Mexico.
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Protein kinase C enhances human sodium channel hNav1.7 resurgent currents via a serine residue in the domain III-IV linker. FEBS Lett 2014; 588:3964-9. [PMID: 25240195 DOI: 10.1016/j.febslet.2014.09.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 08/30/2014] [Accepted: 09/02/2014] [Indexed: 11/20/2022]
Abstract
Resurgent sodium currents likely play a role in modulating neuronal excitability. Here we studied whether protein kinase C (PKC) activation can increase resurgent currents produced by the human sodium channel hNav1.7. We found that a PKC agonist significantly enhanced hNav1.7-mediated resurgent currents and this was prevented by PKC antagonists. The enhancing effects were replicated by two phosphorylation-mimicking mutations and were prevented by a phosphorylation-deficient mutation at a conserved PKC phosphorylation site (Serine 1479). Our results suggest that PKC can increase sodium resurgent currents through phosphorylation of a conserved Serine residue located in the domain III-IV linker of sodium channels.
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44
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Due MR, Yang XF, Allette YM, Randolph AL, Ripsch MS, Wilson SM, Dustrude ET, Khanna R, White FA. Carbamazepine potentiates the effectiveness of morphine in a rodent model of neuropathic pain. PLoS One 2014; 9:e107399. [PMID: 25221944 PMCID: PMC4164621 DOI: 10.1371/journal.pone.0107399] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 08/13/2014] [Indexed: 01/05/2023] Open
Abstract
Approximately 60% of morphine is glucuronidated to morphine-3-glucuronide (M3G) which may aggravate preexisting pain conditions. Accumulating evidence indicates that M3G signaling through neuronal Toll-like receptor 4 (TLR4) may be central to this proalgesic signaling event. These events are known to include elevated neuronal excitability, increased voltage-gated sodium (NaV) current, tactile allodynia and decreased opioid analgesic efficacy. Using an in vitro ratiometric-based calcium influx analysis of acutely dissociated small and medium-diameter neurons derived from lumbar dorsal root ganglion (DRG), we observed that M3G-sensitive neurons responded to lipopolysaccharide (LPS) and over 35% of these M3G/LPS-responsive cells exhibited sensitivity to capsaicin. In addition, M3G-exposed sensory neurons significantly increased excitatory activity and potentiated NaV current as measured by current and voltage clamp, when compared to baseline level measurements. The M3G-dependent excitability and potentiation of NaV current in these sensory neurons could be reversed by the addition of carbamazepine (CBZ), a known inhibitor of several NaV currents. We then compared the efficacy between CBZ and morphine as independent agents, to the combined treatment of both drugs simultaneously, in the tibial nerve injury (TNI) model of neuropathic pain. The potent anti-nociceptive effects of morphine (5 mg/kg, i.p.) were observed in TNI rodents at post-injury day (PID) 7–14 and absent at PID21–28, while administration of CBZ (10 mg/kg, i.p.) alone failed to produce anti-nociceptive effects at any time following TNI (PID 7–28). In contrast to either drug alone at PID28, the combination of morphine and CBZ completely attenuated tactile hyperalgesia in the rodent TNI model. The basis for the potentiation of morphine in combination with CBZ may be due to the effects of a latent upregulation of NaV1.7 in the DRG following TNI. Taken together, our observations demonstrate a potential therapeutic use of morphine and CBZ as a combinational treatment for neuropathic pain.
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Affiliation(s)
- Michael R. Due
- Department of Anesthesia, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Xiao-Fang Yang
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Yohance M. Allette
- Department of Cell Biology and Anatomy, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Aaron L. Randolph
- Department of Anesthesia, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Matthew S. Ripsch
- Department of Anesthesia, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Sarah M. Wilson
- Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Erik T. Dustrude
- Department of Cell Biology and Anatomy, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Rajesh Khanna
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona, United States of America
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Fletcher A. White
- Department of Anesthesia, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- * E-mail:
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Meglič A, Perkovič-Benedik M, Trebušak Podkrajšek K, Bertok S. Painful micturition in a small child: an unusual clinical picture of paroxysmal extreme pain disorder. Pediatr Nephrol 2014; 29:1643-6. [PMID: 24817410 DOI: 10.1007/s00467-014-2819-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 02/03/2023]
Abstract
BACKGROUND Paroxysmal extreme pain disorder (PEPD) is a rare autosomal dominant pain disorder linked to a mutation in the SCN9A gene, which encodes voltage-gated sodium channel Nav1.7. Abnormal pain sensitivity occurs because of changes in the properties of voltage-gated sodium channels. Different mutations in SCN9A and a spectrum of clinical expressions have been described. CASE-DIAGNOSIS/TREATMENT Here we describe a 3-year-old child with a rare clinical picture of PEPD. Extremely painful voiding had been present since the child's birth. The diagnosis was confirmed by the detection of a heterozygous pathogenic mutation in the SCN9A gene, c.554G>A (p.Arg185His) inherited paternally. The same mutation was also found in the girl's father, who has occasionally had some pain in his jaw while yawning since childhood. Significant reduction of the pain was achieved with carbamazepine. CONCLUSIONS The case is interesting because the same mutation as that found in the girl and her father has been found in patients with small fiber sensory neuropathy. These data do not correlate with the clinical picture of our case and her father, but intra- and interfamily phenotypic diversity in symptoms associated with a gain-of-function variant of Na(V)1.7 are also described and may explain our case.
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Affiliation(s)
- Anamarija Meglič
- Department of Pediatric Nephrology, Division of Pediatrics, University Children's Hospital, University Medical Centre Ljubljana, Bohoričeva ulica 20, 1000, Ljubljana, Slovenia,
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Abstract
Resurgent Na(+) current results from a distinctive form of Na(+) channel gating, originally identified in cerebellar Purkinje neurons. In these neurons, the tetrodotoxin-sensitive voltage-gated Na(+) channels responsible for action potential firing have specialized mechanisms that reduce the likelihood that they accumulate in fast inactivated states, thereby shortening refractory periods and permitting rapid, repetitive, and/or burst firing. Under voltage clamp, step depolarizations evoke transient Na(+) currents that rapidly activate and quickly decay, and step repolarizations elicit slower channel reopening, or a 'resurgent' current. The generation of resurgent current depends on a factor in the Na(+) channel complex, probably a subunit such as NaVβ4 (Scn4b), which blocks open Na(+) channels at positive voltages, competing with the fast inactivation gate, and unblocks at negative voltages, permitting recovery from an open channel block along with a flow of current. Following its initial discovery, resurgent Na(+) current has been found in nearly 20 types of neurons. Emerging research suggests that resurgent current is preferentially increased in a variety of clinical conditions associated with altered cellular excitability. Here we review the biophysical, molecular and structural mechanisms of resurgent current and their relation to the normal functions of excitable cells as well as pathophysiology.
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Affiliation(s)
- Amanda H Lewis
- Ion Channel Research Unit & Department of Neurobiology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Indira M Raman
- Department of Neurobiology, Northwestern University, Evanston, IL, 60208, USA
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Lee H, Park KD, Torregrosa R, Yang XF, Dustrude ET, Wang Y, Wilson SM, Barbosa C, Xiao Y, Cummins TR, Khanna R, Kohn H. Substituted N-(biphenyl-4'-yl)methyl (R)-2-acetamido-3-methoxypropionamides: potent anticonvulsants that affect frequency (use) dependence and slow inactivation of sodium channels. J Med Chem 2014; 57:6165-82. [PMID: 25004277 PMCID: PMC4111400 DOI: 10.1021/jm500707r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
We
prepared 13 derivatives of N-(biphenyl-4′-yl)methyl
(R)-2-acetamido-3-methoxypropionamide that differed
in type and placement of a R-substituent in the terminal aryl unit.
We demonstrated that the R-substituent impacted the compound’s
whole animal and cellular pharmacological activities. In rodents,
select compounds exhibited excellent anticonvulsant activities and
protective indices (PI = TD50/ED50) that compared
favorably with clinical antiseizure drugs. Compounds with a polar,
aprotic R-substituent potently promoted Na+ channel slow
inactivation and displayed frequency (use) inhibition of Na+ currents at low micromolar concentrations. The possible advantage
of affecting these two pathways to decrease neurological hyperexcitability
is discussed.
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Affiliation(s)
- Hyosung Lee
- Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, and ‡Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599, United States
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Tetrodotoxin-resistant sodium channels in sensory neurons generate slow resurgent currents that are enhanced by inflammatory mediators. J Neurosci 2014; 34:7190-7. [PMID: 24849353 DOI: 10.1523/jneurosci.5011-13.2014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Resurgent sodium currents contribute to the regeneration of action potentials and enhanced neuronal excitability. Tetrodotoxin-sensitive (TTX-S) resurgent currents have been described in many different neuron populations, including cerebellar and dorsal root ganglia (DRG) neurons. In most cases, sodium channel Nav1.6 is the major contributor to these TTX-S resurgent currents. Here we report a novel TTX-resistant (TTX-R) resurgent current recorded from rat DRG neurons. The TTX-R resurgent currents are similar to classic TTX-S resurgent currents in many respects, but not all. As with TTX-S resurgent currents, they are activated by membrane repolarization, inhibited by lidocaine, and enhanced by a peptide-mimetic of the β4 sodium channel subunit intracellular domain. However, the TTX-R resurgent currents exhibit much slower kinetics, occur at more depolarized voltages, and are sensitive to the Nav1.8 blocker A803467. Moreover, coimmunoprecipitation experiments from rat DRG lysates indicate the endogenous sodium channel β4 subunits associate with Nav1.8 in DRG neurons. These results suggest that slow TTX-R resurgent currents in DRG neurons are mediated by Nav1.8 and are generated by the same mechanism underlying TTX-S resurgent currents. We also show that both TTX-S and TTX-R resurgent currents in DRG neurons are enhanced by inflammatory mediators. Furthermore, the β4 peptide increased excitability of small DRG neurons in the presence of TTX. We propose that these slow TTX-R resurgent currents contribute to the membrane excitability of nociceptive DRG neurons under normal conditions and that enhancement of both types of resurgent currents by inflammatory mediators could contribute to sensory neuronal hyperexcitability associated with inflammatory pain.
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Foadi N, Berger C, Pilawski I, Stoetzer C, Karst M, Haeseler G, Wegner F, Leffler A, Ahrens J. Inhibition of voltage-gated Na⁺ channels by the synthetic cannabinoid ajulemic acid. Anesth Analg 2014; 118:1238-45. [PMID: 24755846 DOI: 10.1213/ane.0000000000000188] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND The synthetic cannabinoid ajulemic acid has been demonstrated to alleviate pain in patients suffering from chronic neuropathic pain. Cannabinoids interact with several molecules within the pain circuit, including a potent inhibition of voltage-gated sodium channels. In this study, we closely characterized this property on neuronal and nonneuronal sodium channels. METHODS The inhibition of sodium inward currents by ajulemic acid was studied in vitro. Human embryonic kidney 293t cells were used as the expression system for Nav1.2, 1.3, 1.4, 1.5, 1.5N406K, 1.5F1760A, and 1.7; Nav1.8 was transiently expressed in ND7/23 cells. Nav1.2, Nav1.3, and Nav 1.8 were from rats, and Nav1.4, Nav1.5, and Nav1.7 were of human origin. Sodium currents were analyzed by means of the whole cell patch-clamp technique. The investigated concentrations of ajulemic acid were 0.1, 0.3, 1, 3, 10, and 30 μmol/L. RESULTS Ajulemic acid reversibly and concentration-dependently inhibited all voltage-gated sodium channel (Nav) isoforms investigated in this study, including Nav1.2, 1.3, 1.4, 1.5, 1.7, and 1.8. Tonic block of resting channels yielded half-maximal inhibitory concentration values between 2 and 9 μmol/L and was strongly enhanced on inactivated channels, suggesting state-dependent inhibition by ajulemic acid. Tonic block did not differ significantly when comparing Nav1.2 and Nav1.3, Nav1.4 and Nav1.5, and Nav1.7 and Nav1.8. Statistical analysis of other combinations of subunits (e.g., Nav1.2 and Nav1.4) by analysis of variance yielded a significant difference in block. Although we did not observe any relevant use-dependent block, ajulemic acid induced a strong hyperpolarizing shift of the voltage dependency of fast inactivation and modest shift of slow inactivation. The local anesthetic-insensitive Nav1.5 constructs N406K and F1760A displayed a preserved sensitivity to block by ajulemic acid. Finally, we found that low concentrations of ajulemic acid efficiently inhibited Navβ4 peptide-mediated resurgent currents in Nav1.5. CONCLUSIONS Our data suggest that block of sodium channels can be a relevant mechanism by which ajulemic acid alleviates neuropathic pain. The potent inhibition of resurgent currents and the preserved block on local anesthetic-insensitive channels indicates that ajulemic acid interacts with a conserved but yet unknown site of sodium channels.
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Affiliation(s)
- Nilufar Foadi
- From the *Department of Anesthesia and Critical Care Medicine, and † Department of Neurology and Clinical Neurophysiology, Medizinische Hochschule Hannover, Hannover, Germany
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50
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Lu W, Wen B, Zhang F, Wang JH. Voltage-independent sodium channels emerge for an expression of activity-induced spontaneous spikes in GABAergic neurons. Mol Brain 2014; 7:38. [PMID: 24886791 PMCID: PMC4039334 DOI: 10.1186/1756-6606-7-38] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 05/13/2014] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Cerebral overexcitation needs inhibitory neurons be functionally upregulated to rebalance excitation vs. inhibition. For example, the intensive activities of GABAergic neurons induce spontaneous spikes, i.e., activity-induced spontaneous spikes (AISS). The mechanisms underlying AISS onset remain unclear. We investigated the roles of sodium channels in AISS induction and expression at hippocampal GABAergic neurons by electrophysiological approach. RESULTS AISS expression includes additional spike capability above evoked spikes, and the full spikes in AISS comprise early phase (spikelets) and late phase, implying the emergence of new spikelet component. Compared with the late phase, the early phase is characterized as voltage-independent onset, less voltage-dependent upstroke and sensitivity to TTX. AISS expression and induction are independent of membrane potential changes. Therefore, AISS's spikelets express based on voltage-independent sodium channels. In terms of AISS induction, the facilitation of voltage-gated sodium channel (VGSC) activation accelerates AISS onset, or vice versa. CONCLUSION AISS expression in GABAergic neurons is triggered by the spikelets based on the functional emergence of voltage-independent sodium channels, which is driven by intensive VGSCs' activities.
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Affiliation(s)
- Wei Lu
- State Key lab for Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
- Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
| | - Bo Wen
- State Key lab for Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
- Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
| | - Fengyu Zhang
- State Key lab for Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Jin-Hui Wang
- State Key lab for Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
- Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
- Qingdao University, Medical College, 38, Dengzhou, Shandong 266021, China
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