1
|
Campanale C, Laghetti P, Saltarella I, Altamura C, Canioni E, Iosa E, Maggi L, Brugnoni R, Tacconi P, Desaphy JF. A c.1775C > T Point Mutation of Sodium Channel Alfa Subunit Gene (SCN4A) in a Three-Generation Sardinian Family with Sodium Channel Myotonia. J Neuromuscul Dis 2024; 11:725-734. [PMID: 38427496 DOI: 10.3233/jnd-230134] [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] [Indexed: 03/03/2024]
Abstract
Background The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. Methods Next-generation sequencing including the CLCN1 and SCN4A genes was performed in patients with clinical neuromuscular disorders. Electromyography, Short Exercise Test, in vivo and in vitro electrophysiology, site-directed mutagenesis and heterologous expression were collected. Results A heterozygous point mutation (c.1775C > T, p.Thr592Ile) of muscle voltage-gated sodium channel α subunit gene (SCN4A) has been identified in five female patients over three generations, in a family with non-dystrophic myotonia. The muscle stiffness and myotonia involve mainly the face and hands, but also affect walking and running, appearing early after birth and presenting a clear cold sensitivity. Very hot temperatures, menstruation and pregnancy also exacerbate the symptoms; muscle pain and a warm-up phenomenon are variable features. Neither paralytic attacks nor post-exercise weakness has been reported. Muscle hypertrophy with cramp-like pain and increased stiffness developed during pregnancy. The symptoms were controlled with both mexiletine and acetazolamide. The Short Exercise Test after muscle cooling revealed two different patterns, with moderate absolute changes of compound muscle action potential amplitude. Conclusions The p.Thr592Ile mutation in the SCN4A gene identified in this Sardinian family was responsible of clinical phenotype of myotonia.
Collapse
Affiliation(s)
- Carmen Campanale
- Department of Precision and Regenerative Medicine, Section of Pharmacology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Paola Laghetti
- Department of Precision and Regenerative Medicine, Section of Pharmacology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Ilaria Saltarella
- Department of Precision and Regenerative Medicine, Section of Pharmacology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Precision and Regenerative Medicine, Section of Pharmacology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Eleonora Canioni
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Emanuele Iosa
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Lorenzo Maggi
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Raffaella Brugnoni
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Paolo Tacconi
- Centro Regionale per la Sclerosi Multipla, Ospedale Binaghi, Cagliari, Italy
| | - Jean-François Desaphy
- Department of Precision and Regenerative Medicine, Section of Pharmacology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| |
Collapse
|
2
|
Vicino A, Brugnoni R, Maggi L. Diagnostics in skeletal muscle channelopathies. Expert Rev Mol Diagn 2023; 23:1175-1193. [PMID: 38009256 DOI: 10.1080/14737159.2023.2288258] [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: 08/23/2023] [Accepted: 11/22/2023] [Indexed: 11/28/2023]
Abstract
INTRODUCTION Skeletal muscle channelopathies (SMCs) are a heterogenous group of disorders, caused by mutations in skeletal ion channels leading to abnormal muscle excitability, resulting in either delayed muscle relaxation (myotonia) which characterizes non-dystrophic myotonias (NDMs), or membrane transient inactivation, causing episodic weakness, typical of periodic paralyses (PPs). AREAS COVERED SMCs include myotonia congenita, paramyotonia congenita, and sodium-channel myotonia among NDMs, and hyper-normokalemic, hypokalemic, or late-onset periodic paralyses among PPs. When suspecting an SMC, a structured diagnostic approach is required. Detailed personal and family history and clinical examination are essential, while neurophysiological tests should confirm myotonia and rule out alternative diagnosis. Moreover, specific electrodiagnostic studies are important to further define the phenotype of de novo cases and drive molecular analyses together with clinical data. Definite diagnosis is achieved through genetic testing, either with Sanger sequencing or multigene next-generation sequencing panel. In still unsolved patients, more advanced techniques, as exome-variant sequencing or whole-genome sequencing, may be considered in expert centers. EXPERT OPINION The diagnostic approach to SMC is still mainly based on clinical data; moreover, definite diagnosis is sometimes complicated by the difficulty to establish a proper genotype-phenotype correlation. Lastly, further studies are needed to allow the genetic characterization of unsolved patients.
Collapse
Affiliation(s)
- Alex Vicino
- Neurology IV Unit, Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
- Nerve-Muscle Unit, Neurology Service, Department of Clinical Neurosciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Raffaella Brugnoni
- Neurology IV Unit, Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Lorenzo Maggi
- Neurology IV Unit, Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| |
Collapse
|
3
|
Altamura C, Saltarella I, Campanale C, Laghetti P, Desaphy JF. Drug repurposing in skeletal muscle ion channelopathies. Curr Opin Pharmacol 2023; 68:102329. [PMID: 36512979 DOI: 10.1016/j.coph.2022.102329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/26/2022] [Accepted: 11/02/2022] [Indexed: 12/14/2022]
Abstract
Skeletal muscle ion channelopathies are rare genetic diseases mainly characterized by myotonia (muscle stiffness) or periodic paralysis (muscle weakness). Here, we reviewed the available therapeutic options in non-dystrophic myotonias (NDM) and periodic paralyses (PP), which consists essentially in drug repositioning to address stiffness or weakness attacks. Empirical use followed by successful randomized clinical trials eventually led to the orphan drug designation and marketing authorization granting of mexiletine for NDM and dichlorphenamide for PP. Yet, these treatments neither consider the genetic cause of the diseases nor address the individual variability in drug response. Thus, ongoing research aims at the identification of repurposed drugs alternative to mexiletine and dichlorphenamide to allow personalization of treatment. This review highlights how drug repurposing may represent an efficient strategy in rare diseases, allowing reduction of drug development time and costs in a context in which the return on investment may be particularly challenging.
Collapse
Affiliation(s)
- Concetta Altamura
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Ilaria Saltarella
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Carmen Campanale
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Paola Laghetti
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Jean-François Desaphy
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy.
| |
Collapse
|
4
|
Altamura C, Conte D, Carratù MR, Desaphy JF. Target mutation-driven drug discovery. Curr Med Chem 2022; 29:5156-5158. [PMID: 35440295 DOI: 10.2174/1389450123666220418111200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 01/10/2022] [Accepted: 02/09/2022] [Indexed: 11/22/2022]
Affiliation(s)
- Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, I-70124 Italy
| | | | - Maria Rosaria Carratù
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, I-70124 Italy
| | - Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, I-70124 Italy
| |
Collapse
|
5
|
Maggi L, Bonanno S, Altamura C, Desaphy JF. Ion Channel Gene Mutations Causing Skeletal Muscle Disorders: Pathomechanisms and Opportunities for Therapy. Cells 2021; 10:cells10061521. [PMID: 34208776 PMCID: PMC8234207 DOI: 10.3390/cells10061521] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/03/2021] [Accepted: 06/10/2021] [Indexed: 02/06/2023] Open
Abstract
Skeletal muscle ion channelopathies (SMICs) are a large heterogeneous group of rare genetic disorders caused by mutations in genes encoding ion channel subunits in the skeletal muscle mainly characterized by myotonia or periodic paralysis, potentially resulting in long-term disabilities. However, with the development of new molecular technologies, new genes and new phenotypes, including progressive myopathies, have been recently discovered, markedly increasing the complexity in the field. In this regard, new advances in SMICs show a less conventional role of ion channels in muscle cell division, proliferation, differentiation, and survival. Hence, SMICs represent an expanding and exciting field. Here, we review current knowledge of SMICs, with a description of their clinical phenotypes, cellular and molecular pathomechanisms, and available treatments.
Collapse
Affiliation(s)
- Lorenzo Maggi
- Neuroimmunology and Neuromuscular Disorders Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, 20133 Milan, Italy;
- Correspondence:
| | - Silvia Bonanno
- Neuroimmunology and Neuromuscular Disorders Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, 20133 Milan, Italy;
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (C.A.); (J.-F.D.)
| | - Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (C.A.); (J.-F.D.)
| |
Collapse
|
6
|
Desaphy JF, Altamura C, Vicart S, Fontaine B. Targeted Therapies for Skeletal Muscle Ion Channelopathies: Systematic Review and Steps Towards Precision Medicine. J Neuromuscul Dis 2021; 8:357-381. [PMID: 33325393 PMCID: PMC8203248 DOI: 10.3233/jnd-200582] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Skeletal muscle ion channelopathies include non-dystrophic myotonias (NDM), periodic paralyses (PP), congenital myasthenic syndrome, and recently identified congenital myopathies. The treatment of these diseases is mainly symptomatic, aimed at reducing muscle excitability in NDM or modifying triggers of attacks in PP. OBJECTIVE This systematic review collected the evidences regarding effects of pharmacological treatment on muscle ion channelopathies, focusing on the possible link between treatments and genetic background. METHODS We searched databases for randomized clinical trials (RCT) and other human studies reporting pharmacological treatments. Preclinical studies were considered to gain further information regarding mutation-dependent drug effects. All steps were performed by two independent investigators, while two others critically reviewed the entire process. RESULTS For NMD, RCT showed therapeutic benefits of mexiletine and lamotrigine, while other human studies suggest some efficacy of various sodium channel blockers and of the carbonic anhydrase inhibitor (CAI) acetazolamide. Preclinical studies suggest that mutations may alter sensitivity of the channel to sodium channel blockers in vitro, which has been translated to humans in some cases. For hyperkalemic and hypokalemic PP, RCT showed efficacy of the CAI dichlorphenamide in preventing paralysis. However, hypokalemic PP patients carrying sodium channel mutations may have fewer benefits from CAI compared to those carrying calcium channel mutations. Few data are available for treatment of congenital myopathies. CONCLUSIONS These studies provided limited information about the response to treatments of individual mutations or groups of mutations. A major effort is needed to perform human studies for designing a mutation-driven precision medicine in muscle ion channelopathies.
Collapse
Affiliation(s)
- Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Savine Vicart
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
| | - Bertrand Fontaine
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
| |
Collapse
|
7
|
Stunnenberg BC, LoRusso S, Arnold WD, Barohn RJ, Cannon SC, Fontaine B, Griggs RC, Hanna MG, Matthews E, Meola G, Sansone VA, Trivedi JR, van Engelen BG, Vicart S, Statland JM. Guidelines on clinical presentation and management of nondystrophic myotonias. Muscle Nerve 2020; 62:430-444. [PMID: 32270509 PMCID: PMC8117169 DOI: 10.1002/mus.26887] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/01/2020] [Accepted: 04/04/2020] [Indexed: 12/26/2022]
Abstract
The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.
Collapse
Affiliation(s)
- Bas C. Stunnenberg
- Department of Neurology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Samantha LoRusso
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - W. David Arnold
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Richard J. Barohn
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
| | - Stephen C. Cannon
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Bertrand Fontaine
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Robert C. Griggs
- Department of Neurology, University of Rochester, Rochester, New York
| | - Michael G. Hanna
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Emma Matthews
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Giovanni Meola
- Department of Neurorehabilitation Sciences, Casa Cura Policlinico, Milan, Italy
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Valeria A. Sansone
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
- Neurorehabilitation Unit, University of Milan, NEuroMuscular Omnicentre (NEMO), Fondazione Serena Onlus, Milan, Italy
| | - Jaya R. Trivedi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, Texas
| | | | - Savine Vicart
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Jeffrey M. Statland
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
| |
Collapse
|
8
|
Abstract
PURPOSE OF REVIEW This article aims to review the current and upcoming treatment options of primary muscle channelopathies including the non-dystrophic myotonias and periodic paralyses. RECENT FINDINGS The efficacy of mexiletine in the treatment of myotonia is now supported by two randomised placebo-controlled trials, one of which utilised a novel aggregated n-of-1 design. This has resulted in licencing of the drug via orphan drug status. There is also good evidence that mexiletine is well tolerated and safe in this patient group without the need for intensive monitoring. A range of alternative antimyotonic treatment options include lamotrigine, carbamazepine and ranolazine exist with variable evidence base. In vitro studies have shown insight into reasons for treatment failure of some medications with certain genotypes opening the era of mutation-specific therapy such as use of flecainide. In the periodic paralyses, the ability of MRI to distinguish between reversible oedema and irreversible fatty replacement makes it an increasingly useful tool to guide and assess pharmacological treatment. Unfortunately, the striking efficacy of bumetanide in hypokalaemic periodic paralysis animal models was not replicated in a recent pilot study in humans. SUMMARY The treatment of skeletal muscle channelopathies combines dietary and lifestyle advice together with pharmacological interventions. The rarity of these conditions remains a barrier for clinical studies but the example of the aggregated n-of-1 trial of mexiletine shows that innovative trial design can overcome these hurdles. Further research is required to test efficacy of drugs shown to have promising characteristics in preclinical experiments such as safinamide, riluzule and magnesium for myotonia or bumetanide for hypokalaemic periodic paralysis.
Collapse
Affiliation(s)
- Nantaporn Jitpimolmard
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
- Rehabilitation Medicine Department, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Emma Matthews
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
- Atkinson-Morley Neuromuscular Centre, St George’s University Hospitals Foundation Trust, London, UK
| | - Doreen Fialho
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
| |
Collapse
|
9
|
Modoni A, D'Amico A, Primiano G, Capozzoli F, Desaphy JF, Lo Monaco M. Long-Term Safety and Usefulness of Mexiletine in a Large Cohort of Patients Affected by Non-dystrophic Myotonias. Front Neurol 2020; 11:300. [PMID: 32655465 PMCID: PMC7326038 DOI: 10.3389/fneur.2020.00300] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 03/30/2020] [Indexed: 02/01/2023] Open
Abstract
Objective: The aim of our study was to evaluate the long-term efficacy and safety of mexiletine in 112 patients affected by genetically confirmed non-dystrophic myotonias. The study was performed at the Neurophysiologic Division of Fondazione Policlinico Universitario A. Gemelli Istituto di Ricerca e Cura a Carattere Scientifico (IRCCS), Rome and the Children's Hospital Bambino Gesù, Rome. Methods: The treatment was accepted by 59 patients according to clinical severity, individual needs, and concerns about a chronic medication. Forty-three patients were affected by recessive congenita myotonia, 11 by sodium channel myotonia, and five by dominant congenital myotonia. They underwent clinical examination before and after starting therapy, and Electromyography (EMG). A number of recessive myotonia patients underwent a protocol of repetitive nerve stimulations, for detecting and quantifying the transitory weakness, and a modified version of the Timed Up and Go test, to document and quantify the gait impairment. Results: Treatment duration ranged from 1 month to 20 years and the daily dosages in adults ranged between 200 and 600 mg. No patient developed cardiac arrhythmias causing drug discontinuation. Mexiletine was suspended in 13 cases (22%); in three patients, affected by Sodium Channel myotonia, because flecainide showed better efficacy; in one patient because of a gastric cancer antecedent treatment; in four patients because of untreatable dyspepsia; and five patients considered the treatment not necessary. Conclusions: In our experience, mexiletine is very useful and not expensive. We did not observe any hazarding cardiac arrhythmias. Dyspepsia was the most frequent dose-limiting side effect.
Collapse
Affiliation(s)
- Anna Modoni
- Department of Geriatric, Neurologic, Orthopedics and Head-Neck Science, Area of Neuroscience, Institute of Neurology, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Adele D'Amico
- Unit of Neuromuscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Department of Neurosciences, Bambino Gesú Children's Hospital, Rome, Italy
| | - Guido Primiano
- Department of Geriatric, Neurologic, Orthopedics and Head-Neck Science, Area of Neuroscience, Institute of Neurology, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | | | - Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Polyclinic, Bari, Italy
| | - Mauro Lo Monaco
- Department of Geriatric, Neurologic, Orthopedics and Head-Neck Science, Area of Neuroscience, Institute of Neurology, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy.,MiA Onlus ("Miotonici in Associazione"), Portici, Italy
| |
Collapse
|
10
|
Malak OA, Abderemane-Ali F, Wei Y, Coyan FC, Pontus G, Shaya D, Marionneau C, Loussouarn G. Up-regulation of voltage-gated sodium channels by peptides mimicking S4-S5 linkers reveals a variation of the ligand-receptor mechanism. Sci Rep 2020; 10:5852. [PMID: 32246066 PMCID: PMC7125111 DOI: 10.1038/s41598-020-62615-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 03/12/2020] [Indexed: 11/09/2022] Open
Abstract
Prokaryotic NaV channels are tetramers and eukaryotic NaV channels consist of a single subunit containing four domains. Each monomer/domain contains six transmembrane segments (S1-S6), S1-S4 being the voltage-sensor domain and S5-S6 the pore domain. A crystal structure of NaVMs, a prokaryotic NaV channel, suggests that the S4-S5 linker (S4-S5L) interacts with the C-terminus of S6 (S6T) to stabilize the gate in the open state. However, in several voltage-gated potassium channels, using specific S4-S5L-mimicking peptides, we previously demonstrated that S4-S5L/S6T interaction stabilizes the gate in the closed state. Here, we used the same strategy on another prokaryotic NaV channel, NaVSp1, to test whether equivalent peptides stabilize the channel in the open or closed state. A NaVSp1-specific S4-S5L peptide, containing the residues supposed to interact with S6T according to the NaVMs structure, induced both an increase in NaVSp1 current density and a negative shift in the activation curve, consistent with S4-S5L stabilizing the open state. Using this approach on a human NaV channel, hNaV1.4, and testing 12 hNaV1.4 S4-S5L peptides, we identified four activating S4-S5L peptides. These results suggest that, in eukaryotic NaV channels, the S4-S5L of DI, DII and DIII domains allosterically modulate the activation gate and stabilize its open state.
Collapse
Affiliation(s)
- Olfat A Malak
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.,Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, California, 94945, USA
| | - Fayal Abderemane-Ali
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.,Cardiovascular Research Institute, University of California, San Francisco, California, 941158-9001, USA
| | - Yue Wei
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.,Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fabien C Coyan
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France
| | - Gilyane Pontus
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France
| | - David Shaya
- Cardiovascular Research Institute, University of California, San Francisco, California, 941158-9001, USA
| | - Céline Marionneau
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France
| | - Gildas Loussouarn
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.
| |
Collapse
|
11
|
Desaphy JF, Farinato A, Altamura C, De Bellis M, Imbrici P, Tarantino N, Caccia C, Melloni E, Padoani G, Vailati S, Keywood C, Carratù MR, De Luca A, Conte D, Pierno S. Safinamide's potential in treating nondystrophic myotonias: Inhibition of skeletal muscle voltage-gated sodium channels and skeletal muscle hyperexcitability in vitro and in vivo. Exp Neurol 2020; 328:113287. [PMID: 32205118 DOI: 10.1016/j.expneurol.2020.113287] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/14/2020] [Accepted: 03/19/2020] [Indexed: 12/26/2022]
Abstract
The antiarrhythmic sodium-channel blocker mexiletine is used to treat patients with myotonia. However, around 30% of patients do not benefit from mexiletine due to poor tolerability or suboptimal response. Safinamide is an add-on therapy to levodopa for Parkinson's disease. In addition to MAOB inhibition, safinamide inhibits neuronal sodium channels, conferring anticonvulsant activity in models of epilepsy. Here, we investigated the effects of safinamide on skeletal muscle hNav1.4 sodium channels and in models of myotonia, in-vitro and in-vivo. Using patch-clamp, we showed that safinamide reversibly inhibited sodium currents in HEK293T cells transfected with hNav1.4. At the holding potential (hp) of -120 mV, the half-maximum inhibitory concentrations (IC50) were 160 and 33 μM at stimulation frequencies of 0.1 and 10 Hz, respectively. The calculated affinity constants of safinamide were dependent on channel state: 420 μM for closed channels and 9 μM for fast-inactivated channels. The p.F1586C mutation in hNav1.4 greatly impaired safinamide inhibition, suggesting that the drug binds to the local anesthetic receptor site in the channel pore. In a condition mimicking myotonia, i.e. hp. of -90 mV and 50-Hz stimulation, safinamide inhibited INa with an IC50 of 6 μM, being two-fold more potent than mexiletine. Using the two-intracellular microelectrodes current-clamp method, action potential firing was recorded in vitro in rat skeletal muscle fibers in presence of the chloride channel blocker, 9-anthracene carboxylic acid (9-AC), to increase excitability. Safinamide counteracted muscle fiber hyperexcitability with an IC50 of 13 μM. In vivo, oral safinamide was tested in the rat model of myotonia. In this model, intraperitoneal injection of 9-AC greatly increased the time of righting reflex (TRR) due to development of muscle stiffness. Safinamide counteracted 9-AC induced TRR increase with an ED50 of 1.2 mg/kg, which is 7 times lower than that previously determined for mexiletine. In conclusion, safinamide is a potent voltage and frequency dependent blocker of skeletal muscle sodium channels. Accordingly, the drug was able to counteract abnormal muscle hyperexcitability induced by 9-AC, both in vitro and in vivo. Thus, this study suggests that safinamide may have potential in treating myotonia and warrants further preclinical and human studies to fully evaluate this possibility.
Collapse
Affiliation(s)
- Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy.
| | - Alessandro Farinato
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Michela De Bellis
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Paola Imbrici
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Nancy Tarantino
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Carla Caccia
- Open R&D Department, Zambon S.p.A., Bresso, MI, Italy
| | - Elsa Melloni
- Open R&D Department, Zambon S.p.A., Bresso, MI, Italy
| | | | | | | | - Maria Rosaria Carratù
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Annamaria De Luca
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Diana Conte
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Sabata Pierno
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| |
Collapse
|
12
|
Suetterlin KJ, Raja Rayan D, Matthews E, Hanna MG. Mexiletine (NaMuscla) for the treatment of myotonia in non-dystrophic myotonic disorders. Expert Opin Orphan Drugs 2020. [DOI: 10.1080/21678707.2020.1739519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Karen J. Suetterlin
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Dipa Raja Rayan
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Emma Matthews
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Michael G Hanna
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| |
Collapse
|
13
|
Matthews E, Balestrini S, Sisodiya SM, Hanna MG. Muscle and brain sodium channelopathies: genetic causes, clinical phenotypes, and management approaches. THE LANCET CHILD & ADOLESCENT HEALTH 2020; 4:536-547. [PMID: 32142633 DOI: 10.1016/s2352-4642(19)30425-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/29/2019] [Accepted: 12/12/2019] [Indexed: 01/26/2023]
Abstract
Voltage-gated sodium channels are essential for excitability of skeletal muscle fibres and neurons. An increasing number of disabling or fatal paediatric neurological disorders linked to mutations of voltage-gated sodium channel genes are recognised. Muscle phenotypes include episodic paralysis, myotonia, neonatal hypotonia, respiratory compromise, laryngospasm or stridor, congenital myasthenia, and myopathy. Evidence suggests a possible link between sodium channel dysfunction and sudden infant death. Increasingly recognised phenotypes of brain sodium channelopathies include several epilepsy disorders and complex encephalopathies. Together, these early-onset muscle and brain phenotypes have a substantial morbidity and a considerable mortality. Important advances in understanding the pathophysiological mechanisms underlying these channelopathies have helped to identify effective targeted therapies. The availability of effective treatments underlines the importance of increasing clinical awareness and the need to achieve a precise genetic diagnosis. In this Review, we describe the expanded range of phenotypes of muscle and brain sodium channelopathies and the underlying knowledge regarding mechanisms of sodium channel dysfunction. We also outline a diagnostic approach and review the available treatment options.
Collapse
Affiliation(s)
- Emma Matthews
- Department of Neuromuscular Diseases, Medical Research Council Centre for Neuromuscular Diseases, University College London Queen Square Institute of Neurology, London, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK.
| | - Simona Balestrini
- Department of Clinical and Experimental Epilepsy, University College London Queen Square Institute of Neurology, London, UK; Chalfont Centre for Epilepsy, Buckinghamshire, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
| | - Sanjay M Sisodiya
- Department of Clinical and Experimental Epilepsy, University College London Queen Square Institute of Neurology, London, UK; Chalfont Centre for Epilepsy, Buckinghamshire, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
| | - Michael G Hanna
- Department of Neuromuscular Diseases, Medical Research Council Centre for Neuromuscular Diseases, University College London Queen Square Institute of Neurology, London, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
| |
Collapse
|
14
|
Affiliation(s)
- Michela De Bellis
- Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Bari, Italy
| | - Diana Conte Camerino
- Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Bari, Italy
| | - Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Bari, Italy
| |
Collapse
|
15
|
Pharmacogenetics of myotonic hNav1.4 sodium channel variants situated near the fast inactivation gate. Pharmacol Res 2019; 141:224-235. [DOI: 10.1016/j.phrs.2019.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 01/02/2019] [Accepted: 01/02/2019] [Indexed: 12/13/2022]
|
16
|
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.
Collapse
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.
| |
Collapse
|
17
|
Symonds JD, Zuberi SM. Genetics update: Monogenetics, polygene disorders and the quest for modifying genes. Neuropharmacology 2017; 132:3-19. [PMID: 29037745 DOI: 10.1016/j.neuropharm.2017.10.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 10/09/2017] [Accepted: 10/11/2017] [Indexed: 12/19/2022]
Abstract
The genetic channelopathies are a broad collection of diseases. Many ion channel genes demonstrate wide phenotypic pleiotropy, but nonetheless concerted efforts have been made to characterise genotype-phenotype relationships. In this review we give an overview of the factors that influence genotype-phenotype relationships across this group of diseases as a whole, using specific individual channelopathies as examples. We suggest reasons for the limitations observed in these relationships. We discuss the role of ion channel variation in polygenic disease and highlight research that has contributed to unravelling the complex aetiological nature of these conditions. We focus specifically on the quest for modifying genes in inherited channelopathies, using the voltage-gated sodium channels as an example. Epilepsy related to genetic channelopathy is one area in which precision medicine is showing promise. We will discuss the successes and limitations of precision medicine in these conditions. This article is part of the Special Issue entitled 'Channelopathies.'
Collapse
Affiliation(s)
- Joseph D Symonds
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Queen Elizabeth University Hospitals, Glasgow, UK; School of Medicine, University of Glasgow, Glasgow, UK
| | - Sameer M Zuberi
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Queen Elizabeth University Hospitals, Glasgow, UK; School of Medicine, University of Glasgow, Glasgow, UK.
| |
Collapse
|
18
|
Maggi L, Ravaglia S, Farinato A, Brugnoni R, Altamura C, Imbrici P, Camerino DC, Padovani A, Mantegazza R, Bernasconi P, Desaphy JF, Filosto M. Coexistence of CLCN1 and SCN4A mutations in one family suffering from myotonia. Neurogenetics 2017; 18:219-225. [PMID: 28993909 DOI: 10.1007/s10048-017-0525-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 10/01/2017] [Indexed: 01/28/2023]
Abstract
Non-dystrophic myotonias are characterized by clinical overlap making it challenging to establish genotype-phenotype correlations. We report clinical and electrophysiological findings in a girl and her father concomitantly harbouring single heterozygous mutations in SCN4A and CLCN1 genes. Functional characterization of N1297S hNav1.4 mutant was performed by patch clamp. The patients displayed a mild phenotype, mostly resembling a sodium channel myotonia. The CLCN1 c.501C>G (p.F167L) mutation has been already described in recessive pedigrees, whereas the SCN4A c.3890A>G (p.N1297S) variation is novel. Patch clamp experiments showed impairment of fast and slow inactivation of the mutated Nav1.4 sodium channel. The present findings suggest that analysis of both SCN4A and CLCN1 genes should be considered in myotonic patients with atypical clinical and neurophysiological features.
Collapse
Affiliation(s)
- Lorenzo Maggi
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy.
| | | | - Alessandro Farinato
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Raffaella Brugnoni
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy
| | - Concetta Altamura
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Paola Imbrici
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Diana Conte Camerino
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Alessandro Padovani
- Center for Neuromuscular Diseases and Neuropathies, Unit of Neurology ASST "Spedali Civili", University of Brescia, Brescia, Italy
| | - Renato Mantegazza
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy
| | - Pia Bernasconi
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy
| | - Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Bari, Italy
| | - Massimiliano Filosto
- Center for Neuromuscular Diseases and Neuropathies, Unit of Neurology ASST "Spedali Civili", University of Brescia, Brescia, Italy
| |
Collapse
|
19
|
Symonds JD, Zuberi SM. WITHDRAWN: Genetics update: Monogenetics, polygene disorders and the quest for modifying genes. Neuropharmacology 2017:S0028-3908(17)30347-7. [PMID: 28757052 DOI: 10.1016/j.neuropharm.2017.07.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 07/17/2017] [Indexed: 11/15/2022]
Abstract
The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.neuropharm.2017.10.013. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
Collapse
Affiliation(s)
- Joseph D Symonds
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Queen Elizabeth University Hospitals, Glasgow, UK; School of Medicine, University of Glasgow, Glasgow, UK
| | - Sameer M Zuberi
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Queen Elizabeth University Hospitals, Glasgow, UK; School of Medicine, University of Glasgow, Glasgow, UK
| |
Collapse
|
20
|
Increased sodium channel use-dependent inhibition by a new potent analogue of tocainide greatly enhances in vivo antimyotonic activity. Neuropharmacology 2016; 113:206-216. [PMID: 27743929 PMCID: PMC5154332 DOI: 10.1016/j.neuropharm.2016.10.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 10/08/2016] [Accepted: 10/11/2016] [Indexed: 01/19/2023]
Abstract
Although the sodium channel blocker, mexiletine, is the first choice drug in myotonia, some myotonic patients remain unsatisfied due to contraindications, lack of tolerability, or incomplete response. More therapeutic options are thus needed for myotonic patients, which require clinical trials based on solid preclinical data. In previous structure-activity relationship studies, we identified two newly-synthesized derivatives of tocainide, To040 and To042, with greatly enhanced potency and use-dependent behavior in inhibiting sodium currents in frog skeletal muscle fibers. The current study was performed to verify their potential as antimyotonic agents. Patch-clamp experiments show that both compounds, especially To042, are greatly more potent and use-dependent blockers of human skeletal muscle hNav1.4 channels compared to tocainide and mexiletine. Reduced effects on F1586C hNav1.4 mutant suggest that the compounds bind to the local anesthetic receptor, but that the increased hindrance and lipophilia of the N-substituent may further strengthen drug-receptor interaction and use-dependence. Compared to mexiletine, To042 was 120 times more potent to block hNav1.4 channels in a myotonia-like cellular condition and 100 times more potent to improve muscle stiffness in vivo in a previously-validated rat model of myotonia. To explore toxicological profile, To042 was tested on hERG potassium currents, motor coordination using rotarod, and C2C12 cell line for cytotoxicity. All these experiments suggest a satisfactory therapeutic index for To042. This study shows that, owing to a huge use-dependent block of sodium channels, To042 is a promising candidate drug for myotonia and possibly other membrane excitability disorders, warranting further preclinical and human studies. To040 and To042 are potent use-dependent hNav1.4 sodium channel blockers. The compounds strengthen the molecular interaction at the local anesthetic receptor. To042 is 120-fold more potent than mexiletine in vitro in myotonia-like conditions. To042 is 100-fold more potent than mexiletine in vivo in a rat model of myotonia. To042 is a promising antimyotonic drug deserving further investigation.
Collapse
|