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Hinzpeter J, Barrientos C, Zamorano Á, Martinez Á, Palet M, Wulf R, Barahona M, Sepúlveda JM, Guerra M, Bustamante T, Del Campo M, Tapia E, Lagos N. Gonyautoxins: First evidence in pain management in total knee arthroplasty. Toxicon 2016; 119:180-5. [PMID: 27317871 DOI: 10.1016/j.toxicon.2016.06.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 06/09/2016] [Accepted: 06/14/2016] [Indexed: 12/19/2022]
Abstract
Improvements in pain management techniques in the last decade have had a major impact on the practice of total knee arthroplasty (TKA). Gonyautoxin are phycotoxins, whose molecular mechanism of action is a reversible block of the voltage-gated sodium channels at the axonal level, impeding nerve impulse propagation. This study was designed to evaluate the clinical efficacy of Gonyautoxin infiltration, as a long acting pain blocker in TKA. Fifteen patients received a total dose of 40 μg of Gonyautoxin during the TKA operation. Postoperatively, all patients were given a standard painkiller protocol: 100 mg of intravenous ketoprofen and 1000 mg of oral acetaminophen every 8 hours for 3 days. The Visual Analog Scale (VAS) pain score and range of motion were recorded 12, 36, and 60 hours post-surgery. All patients reported pain of 2 or less on the VAS 12 and 36 hours post-surgery. Moreover, all scored were less than 4 at 60 hours post-surgery. All patients achieved full knee extension at all times. No side effects or adverse reactions to Gonyautoxin were detected in the follow-up period. The median hospital stay was 3 days. For the first time, this study has shown the effect of blocking the neuronal transmission of pain by locally infiltrating Gonyautoxin during TKA. All patients successfully responded to the pain control. The Gonyautoxin infiltration was safe and effective, and patients experienced pain relief without the use of opioids.
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Affiliation(s)
- Jaime Hinzpeter
- Department of Orthopedic Surgery, University of Chile Clinical Hospital, Santos Dumont 999, Independencia, Santiago, 8380456, Chile
| | - Cristián Barrientos
- Department of Orthopedic Surgery, University of Chile Clinical Hospital, Santos Dumont 999, Independencia, Santiago, 8380456, Chile
| | - Álvaro Zamorano
- Department of Orthopedic Surgery, University of Chile Clinical Hospital, Santos Dumont 999, Independencia, Santiago, 8380456, Chile
| | - Álvaro Martinez
- Department of Orthopedic Surgery, Hospital San José, San José 1196, Independencia, Santiago, 8380419, Chile
| | - Miguel Palet
- Department of Orthopedic Surgery, University of Chile Clinical Hospital, Santos Dumont 999, Independencia, Santiago, 8380456, Chile
| | - Rodrigo Wulf
- Department of Orthopedic Surgery, University of Chile Clinical Hospital, Santos Dumont 999, Independencia, Santiago, 8380456, Chile
| | - Maximiliano Barahona
- Department of Orthopedic Surgery, University of Chile Clinical Hospital, Santos Dumont 999, Independencia, Santiago, 8380456, Chile
| | - Joaquín M Sepúlveda
- Membrane Biochemistry Laboratory, Department of Physiology and Biophysics, Faculty of Medicine, University of Chile, Independencia 1027, Santiago, 8389100, Chile
| | - Matias Guerra
- Membrane Biochemistry Laboratory, Department of Physiology and Biophysics, Faculty of Medicine, University of Chile, Independencia 1027, Santiago, 8389100, Chile
| | - Tamara Bustamante
- Membrane Biochemistry Laboratory, Department of Physiology and Biophysics, Faculty of Medicine, University of Chile, Independencia 1027, Santiago, 8389100, Chile
| | - Miguel Del Campo
- Membrane Biochemistry Laboratory, Department of Physiology and Biophysics, Faculty of Medicine, University of Chile, Independencia 1027, Santiago, 8389100, Chile
| | - Eric Tapia
- Membrane Biochemistry Laboratory, Department of Physiology and Biophysics, Faculty of Medicine, University of Chile, Independencia 1027, Santiago, 8389100, Chile
| | - Nestor Lagos
- Membrane Biochemistry Laboratory, Department of Physiology and Biophysics, Faculty of Medicine, University of Chile, Independencia 1027, Santiago, 8389100, Chile.
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102
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Characterization of Specific Roles of Sodium Channel Subtypes in Regional Anesthesia. Reg Anesth Pain Med 2016; 40:599-604. [PMID: 26236999 DOI: 10.1097/aap.0000000000000294] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND AND OBJECTIVES Commonly used local anesthetics (eg, lidocaine) are nonselective in blocking sodium channel subtypes, potentially resulting in adverse events, such as prolonged muscle paralysis and unstable hemodynamics. Subtype-selective sodium channel block might avoid these unwanted adverse effects while preserving desirable anesthetic effects. The contributions of sodium channel subtypes in different components of regional anesthesia are unclear and this study assumed that selective sodium channel subtype block might produce selective nerve block. METHODS Sciatic nerve block was performed in mice with lidocaine (nonselective sodium channel blocker), tetrodotoxin (TTX, TTX-sensitive sodium channel blocker), and A-803467 (selective Nav1.8 subtype blocker). Tactile sensory, pinprick, and thermal sensory block as well as motor block were evaluated after injection of study drugs. Median effective concentration (EC50) of lidocaine, TTX, and A-803467 as well as their blocking durations were determined. RESULTS Lidocaine produced regional anesthetic effects including tactile, pinprick, and thermal sensory block as well as motor block, with EC50 [mean, 95% confidence intervals (CIs)] of 4.4 (3.7-5.2), 9.4 (8.0-10.9), 5.2 (4.3-6.2), and 3.7 (3.3-4.2) mmol/L, respectively. Tetrodotoxin produced tactile sensory block and motor block with EC50 (mean, 95% CIs) of 7.7 (6.0-11.0) and 8.3 (7.4-9.8) μmol/L, respectively; whereas A-803467 produced tactile sensory block only, with EC50 (mean, 95% CIs) of 12.6 (11.7-15.6) μmol/L. CONCLUSIONS Sodium channel subtype selective blockers could induce selective nerve blocks. Tetrodotoxin-sensitive sodium channel subtypes contribute to low-threshold sensory block (eg, tactile) and motor block. Unexpectedly, selective Nav1.8 subtype block induced low-threshold sensory block rather than nociceptive or motor block.
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103
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van der Pijl EM, van Putten M, Niks EH, Verschuuren JJGM, Aartsma-Rus A, Plomp JJ. Characterization of neuromuscular synapse function abnormalities in multiple Duchenne muscular dystrophy mouse models. Eur J Neurosci 2016; 43:1623-35. [PMID: 27037492 DOI: 10.1111/ejn.13249] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 11/30/2022]
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked myopathy caused by dystrophin deficiency. Dystrophin is present intracellularly at the sarcolemma, connecting actin to the dystrophin-associated glycoprotein complex. Interestingly, it is enriched postsynaptically at the neuromuscular junction (NMJ), but its synaptic function is largely unknown. Utrophin, a dystrophin homologue, is also concentrated at the NMJ, and upregulated in DMD. It is possible that the absence of dystrophin at NMJs in DMD causes neuromuscular transmission defects that aggravate muscle weakness. We studied NMJ function in mdx mice (lacking dystrophin) and wild type mice. In addition, mdx/utrn(+/-) and mdx/utrn(-/-) mice (lacking utrophin) were used to investigate influences of utrophin levels. The three Duchenne mouse models showed muscle weakness when comparatively tested in vivo, with mdx/utrn(-/-) mice being weakest. Ex vivo muscle contraction and electrophysiological studies showed a reduced safety factor of neuromuscular transmission in all models. NMJs had ~ 40% smaller miniature endplate potential amplitudes compared with wild type, indicating postsynaptic sensitivity loss for the neurotransmitter acetylcholine. However, nerve stimulation-evoked endplate potential amplitudes were unchanged. Consequently, quantal content (i.e. the number of acetylcholine quanta released per nerve impulse) was considerably increased. Such a homeostatic compensatory increase in neurotransmitter release is also found at NMJs in myasthenia gravis, where autoantibodies reduce acetylcholine receptors. However, high-rate nerve stimulation induced exaggerated endplate potential rundown. Study of NMJ morphology showed that fragmentation of acetylcholine receptor clusters occurred in all models, being most severe in mdx/utrn(-/-) mice. Overall, we showed mild 'myasthenia-like' neuromuscular synaptic dysfunction in several Duchenne mouse models, which possibly affects muscle weakness and degeneration.
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Affiliation(s)
- Elizabeth M van der Pijl
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
| | - Maaike van Putten
- Department of Human Genetics, Leiden University Medical Centre, Leiden, The Netherlands
| | - Erik H Niks
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
| | - Jan J G M Verschuuren
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
| | - Annemieke Aartsma-Rus
- Department of Human Genetics, Leiden University Medical Centre, Leiden, The Netherlands
| | - Jaap J Plomp
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
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104
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Heine M, Ciuraszkiewicz A, Voigt A, Heck J, Bikbaev A. Surface dynamics of voltage-gated ion channels. Channels (Austin) 2016; 10:267-81. [PMID: 26891382 DOI: 10.1080/19336950.2016.1153210] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Neurons encode information in fast changes of the membrane potential, and thus electrical membrane properties are critically important for the integration and processing of synaptic inputs by a neuron. These electrical properties are largely determined by ion channels embedded in the membrane. The distribution of most ion channels in the membrane is not spatially uniform: they undergo activity-driven changes in the range of minutes to days. Even in the range of milliseconds, the composition and topology of ion channels are not static but engage in highly dynamic processes including stochastic or activity-dependent transient association of the pore-forming and auxiliary subunits, lateral diffusion, as well as clustering of different channels. In this review we briefly discuss the potential impact of mobile sodium, calcium and potassium ion channels and the functional significance of this for individual neurons and neuronal networks.
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Affiliation(s)
- Martin Heine
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Anna Ciuraszkiewicz
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Andreas Voigt
- b Lehrstuhl Systemverfahrenstechnik, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Jennifer Heck
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Arthur Bikbaev
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
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105
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Bosch MK, Nerbonne JM, Townsend RR, Miyazaki H, Nukina N, Ornitz DM, Marionneau C. Proteomic analysis of native cerebellar iFGF14 complexes. Channels (Austin) 2016; 10:297-312. [PMID: 26889602 DOI: 10.1080/19336950.2016.1153203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Intracellular Fibroblast Growth Factor 14 (iFGF14) and the other intracellular FGFs (iFGF11-13) regulate the properties and densities of voltage-gated neuronal and cardiac Na(+) (Nav) channels. Recent studies have demonstrated that the iFGFs can also regulate native voltage-gated Ca(2+) (Cav) channels. In the present study, a mass spectrometry (MS)-based proteomic approach was used to identify the components of native cerebellar iFGF14 complexes. Using an anti-iFGF14 antibody, native iFGF14 complexes were immunoprecipitated from wild type adult mouse cerebellum. Parallel control experiments were performed on cerebellar proteins isolated from mice (Fgf14(-/-)) harboring a targeted disruption of the Fgf14 locus. MS analyses of immunoprecipitated proteins demonstrated that the vast majority of proteins identified in native cerebellar iFGF14 complexes are Nav channel pore-forming (α) subunits or proteins previously reported to interact with Nav α subunits. In contrast, no Cav channel α or accessory subunits were revealed in cerebellar iFGF14 immunoprecipitates. Additional experiments were completed using an anti-PanNav antibody to immunoprecipitate Nav channel complexes from wild type and Fgf14(-/-) mouse cerebellum. Western blot and MS analyses revealed that the loss of iFGF14 does not measurably affect the protein composition or the relative abundance of Nav channel interacting proteins in native adult mouse cerebellar Nav channel complexes.
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Affiliation(s)
- Marie K Bosch
- a Department of Developmental Biology , Washington University School of Medicine , St. Louis , MO , USA
| | - Jeanne M Nerbonne
- a Department of Developmental Biology , Washington University School of Medicine , St. Louis , MO , USA.,b Internal Medicine, Washington University School of Medicine , St. Louis , MO , USA
| | - R Reid Townsend
- b Internal Medicine, Washington University School of Medicine , St. Louis , MO , USA.,c Cell Biology & Physiology, Washington University School of Medicine , St. Louis , MO , USA
| | - Haruko Miyazaki
- d Laboratory of Structural Pathology, Doshisha University, Kyotanabe-shi, Kyoto , Japan
| | - Nobuyuki Nukina
- d Laboratory of Structural Pathology, Doshisha University, Kyotanabe-shi, Kyoto , Japan
| | - David M Ornitz
- a Department of Developmental Biology , Washington University School of Medicine , St. Louis , MO , USA
| | - Céline Marionneau
- e L'Institut du Thorax, INSERM UMR1087, CNRS UMR6291, Université de Nantes , Nantes , France
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106
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Sowell MK, Youssef PE. The Comorbidity of Migraine and Epilepsy in Children and Adolescents. Semin Pediatr Neurol 2016; 23:83-91. [PMID: 27017028 DOI: 10.1016/j.spen.2016.01.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Migraine and epilepsy share a number of clinical attributes, including pathophysiology and clinical expression. Both are paroxysmal in nature and thus constitute episodic disorders, yet either may be chronic and/or recurrent. Epileptic seizures and migraine headaches may be mistaken one for the other and may even overlap. In particular, occipital lobe seizures may be misdiagnosed as migraine auras. In this article, we review the relationship between migraine and epilepsy, including the known genetic contributions to both conditions, prodromal, ictal, and postictal headache and shared pathophysiology and treatment options. We describe clinical conditions in which both migraine and epilepsy are prominent features. Lastly, we discuss electronecephaographic abnormalities that have been known to occur in individuals with migraine.
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Affiliation(s)
- Michael K Sowell
- Department of Neurology, University of Louisville School of Medicine, Louisville, KY.
| | - Paul E Youssef
- Division of Child and Adolescent Neurology, Mayo Clinic Rochester, Rochester, MN
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107
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Liu J, Laksman Z, Backx PH. The electrophysiological development of cardiomyocytes. Adv Drug Deliv Rev 2016; 96:253-73. [PMID: 26788696 DOI: 10.1016/j.addr.2015.12.023] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 12/23/2015] [Accepted: 12/31/2015] [Indexed: 02/07/2023]
Abstract
The generation of human cardiomyocytes (CMs) from human pluripotent stem cells (hPSCs) has become an important resource for modeling human cardiac disease and for drug screening, and also holds significant potential for cardiac regeneration. Many challenges remain to be overcome however, before innovation in this field can translate into a change in the morbidity and mortality associated with heart disease. Of particular importance for the future application of this technology is an improved understanding of the electrophysiologic characteristics of CMs, so that better protocols can be developed and optimized for generating hPSC-CMs. Many different cell culture protocols are currently utilized to generate CMs from hPSCs and all appear to yield relatively “developmentally” immature CMs with highly heterogeneous electrical properties. These hPSC-CMs are characterized by spontaneous beating at highly variable rates with a broad range of depolarization-repolarization patterns, suggestive of mixed populations containing atrial, ventricular and nodal cells. Many recent studies have attempted to introduce approaches to promote maturation and to create cells with specific functional properties. In this review, we summarize the studies in which the electrical properties of CMs derived from stem cells have been examined. In order to place this information in a useful context, we also review the electrical properties of CMs as they transition from the developing embryo to the adult human heart. The signal pathways involved in the regulation of ion channel expression during development are also briefly considered.
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108
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Maturing human pluripotent stem cell-derived cardiomyocytes in human engineered cardiac tissues. Adv Drug Deliv Rev 2016; 96:110-34. [PMID: 25956564 DOI: 10.1016/j.addr.2015.04.019] [Citation(s) in RCA: 167] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 04/24/2015] [Accepted: 04/25/2015] [Indexed: 12/19/2022]
Abstract
Engineering functional human cardiac tissue that mimics the native adult morphological and functional phenotype has been a long held objective. In the last 5 years, the field of cardiac tissue engineering has transitioned from cardiac tissues derived from various animal species to the production of the first generation of human engineered cardiac tissues (hECTs), due to recent advances in human stem cell biology. Despite this progress, the hECTs generated to date remain immature relative to the native adult myocardium. In this review, we focus on the maturation challenge in the context of hECTs, the present state of the art, and future perspectives in terms of regenerative medicine, drug discovery, preclinical safety testing and pathophysiological studies.
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109
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Abstract
Life depends on a membrane's ability to precisely control the level of solutes in the aqueous compartments, inside and outside, bathing the membrane. The membrane determines what solutes enter and leave a cell. Transmembrane transport is controlled by complex interactions between membrane lipids, proteins, and carbohydrates. How the membrane accomplishes these tasks is the topic of this chapter.
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110
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Chapter Five - Ubiquitination of Ion Channels and Transporters. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:161-223. [DOI: 10.1016/bs.pmbts.2016.02.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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111
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Feldman CR, Durso AM, Hanifin CT, Pfrender ME, Ducey PK, Stokes AN, Barnett KE, Brodie III ED, Brodie Jr ED. Is there more than one way to skin a newt? Convergent toxin resistance in snakes is not due to a common genetic mechanism. Heredity (Edinb) 2016; 116:84-91. [PMID: 26374236 PMCID: PMC4675877 DOI: 10.1038/hdy.2015.73] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Revised: 06/07/2015] [Accepted: 06/08/2015] [Indexed: 02/08/2023] Open
Abstract
Convergent evolution of tetrodotoxin (TTX) resistance, at both the phenotypic and genetic levels, characterizes coevolutionary arms races between amphibians and their snake predators around the world, and reveals remarkable predictability in the process of adaptation. Here we examine the repeatability of the evolution of TTX resistance in an undescribed predator-prey relationship between TTX-bearing Eastern Newts (Notophthalmus viridescens) and Eastern Hog-nosed Snakes (Heterodon platirhinos). We found that that local newts contain levels of TTX dangerous enough to dissuade most predators, and that Eastern Hog-nosed Snakes within newt range are highly resistant to TTX. In fact, these populations of Eastern Hog-nosed Snakes are so resistant to TTX that the potential for current reciprocal selection might be limited. Unlike all other cases of TTX resistance in vertebrates, H. platirhinos lacks the adaptive amino acid substitutions in the skeletal muscle sodium channel that reduce TTX binding, suggesting that physiological resistance in Eastern Hog-nosed Snakes is conferred by an alternate genetic mechanism. Thus, phenotypic convergence in this case is not due to parallel molecular evolution, indicating that there may be more than one way for this adaptation to arise, even among closely related species.
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Affiliation(s)
- C R Feldman
- Department of Biology, University of Nevada Reno, Reno, NV, USA
| | - A M Durso
- Department of Biology, Utah State University, Logan, UT, USA
| | - C T Hanifin
- Department of Biology, Utah State University, Logan, UT, USA
- Department of Biology, Utah State University, Uintah Basin, Vernal, UT, USA
| | - M E Pfrender
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - P K Ducey
- Department of Biological Sciences, State University of New York–Cortland, Cortland, NY, USA
| | - A N Stokes
- Department of Biology, California State University Bakersfield, Bakersfield, CA, USA
| | - K E Barnett
- New York State Department of Environmental Conservation, Albany, NY, USA
| | - E D Brodie III
- Mountain Lake Biological Station and Department of Biology, University of Virginia, Charlottesville, VA, USA
| | - E D Brodie Jr
- Department of Biology, Utah State University, Logan, UT, USA
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112
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Ditting T, Freisinger W, Rodionova K, Schatz J, Lale N, Heinlein S, Linz P, Ott C, Schmieder RE, Scrogin KE, Veelken R. Impaired excitability of renal afferent innervation after exposure to the inflammatory chemokine CXCL1. Am J Physiol Renal Physiol 2015; 310:F364-71. [PMID: 26697980 DOI: 10.1152/ajprenal.00189.2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 12/15/2015] [Indexed: 01/06/2023] Open
Abstract
Recently, we showed that renal afferent neurons exhibit a unique firing pattern, i.e., predominantly sustained firing, upon stimulation. Pathological conditions such as renal inflammation likely alter excitability of renal afferent neurons. Here, we tested whether the proinflammatory chemokine CXCL1 alters the firing pattern of renal afferent neurons. Rat dorsal root ganglion neurons (Th11-L2), retrogradely labeled with dicarbocyanine dye, were incubated with CXCL1 (20 h) or vehicle before patch-clamp recording. The firing pattern of neurons was characterized as tonic, i.e., sustained action potential (AP) firing, or phasic, i.e., <5 APs following current injection. Of the labeled renal afferents treated with vehicle, 58.9% exhibited a tonic firing pattern vs. 7.8%, in unlabeled, nonrenal neurons (P < 0.05). However, after exposure to CXCL1, significantly more phasic neurons were found among labeled renal neurons; hence the occurrence of tonic neurons with sustained firing upon electrical stimulation decreased (35.6 vs. 58.9%, P < 0.05). The firing frequency among tonic neurons was not statistically different between control and CXCL1-treated neurons. However, the lower firing frequency of phasic neurons was even further decreased with CXCL1 exposure [control: 1 AP/600 ms (1-2) vs. CXCL1: 1 AP/600 ms (1-1); P < 0.05; median (25th-75th percentile)]. Hence, CXCL1 shifted the firing pattern of renal afferents from a predominantly tonic to a more phasic firing pattern, suggesting that CXCL1 reduced the sensitivity of renal afferent units upon stimulation.
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Affiliation(s)
- Tilmann Ditting
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Wolfgang Freisinger
- Department of Internal Medicine 1, Nephrology Johannes-Guttenberg University, Mainz, Germany
| | - Kristina Rodionova
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Johannes Schatz
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Nena Lale
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Sonja Heinlein
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Peter Linz
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Christian Ott
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Roland E Schmieder
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany
| | - Karie E Scrogin
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago Stritch School of Medicine, Chicago, Illinois
| | - Roland Veelken
- Department of Internal Medicine 4, Nephrology and Hypertension, Friedrich-Alexander University, Erlangen, Germany;
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113
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Effects of the β1 auxiliary subunit on modification of Rat Na(v)1.6 sodium channels expressed in HEK293 cells by the pyrethroid insecticides tefluthrin and deltamethrin. Toxicol Appl Pharmacol 2015; 291:58-69. [PMID: 26708501 DOI: 10.1016/j.taap.2015.12.007] [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: 09/30/2015] [Revised: 12/09/2015] [Accepted: 12/16/2015] [Indexed: 11/22/2022]
Abstract
We expressed rat Nav1.6 sodium channels with or without the rat β1 subunit in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on whole-cell sodium currents. In assays with the Nav1.6 α subunit alone, both pyrethroids prolonged channel inactivation and deactivation and shifted the voltage dependence of channel activation and steady-state inactivation toward hyperpolarization. Maximal shifts in activation were ~18 mV for tefluthrin and ~24 mV for deltamethrin. These compounds also caused hyperpolarizing shifts of ~10-14 mV in the voltage dependence of steady-state inactivation and increased in the fraction of sodium current that was resistant to inactivation. The effects of pyrethroids on the voltage-dependent gating greatly increased the size of sodium window currents compared to unmodified channels; modified channels exhibited increased probability of spontaneous opening at membrane potentials more negative than the normal threshold for channel activation and incomplete channel inactivation. Coexpression of Nav1.6 with the β1 subunit had no effect on the kinetic behavior of pyrethroid-modified channels but had divergent effects on the voltage-dependent gating of tefluthrin- or deltamethrin-modified channels, increasing the size of tefluthrin-induced window currents but decreasing the size of corresponding deltamethrin-induced currents. Unexpectedly, the β1 subunit did not confer sensitivity to use-dependent channel modification by either tefluthrin or deltamethrin. We conclude from these results that functional reconstitution of channels in vitro requires careful attention to the subunit composition of channel complexes to ensure that channels in vitro are faithful functional and pharmacological models of channels in neurons.
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114
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Mohammed FH, Khajah MA, Yang M, Brackenbury WJ, Luqmani YA. Blockade of voltage-gated sodium channels inhibits invasion of endocrine-resistant breast cancer cells. Int J Oncol 2015; 48:73-83. [PMID: 26718772 PMCID: PMC4734602 DOI: 10.3892/ijo.2015.3239] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 09/24/2015] [Indexed: 12/18/2022] Open
Abstract
Voltage-gated Na+ channels (VGSCs) are membrane proteins which are normally expressed in excitable cells but have also been detected in cancer cells, where they are thought to be involved in malignancy progression. In this study we examined the ion current and expression profile of VGSC (Nav1.5) in estrogen receptor (ER)-positive (MCF-7) and silenced (pII) breast cancer cells and its possible influence on their proliferation, motility and invasion. VGSC currents were analysed by whole cell patch clamp recording. Nav1.5 expression and localization, in response to EGF stimulation, was examined by western blotting and immunofluorescence respectively. Cell invasion (under-agarose and Matrigel assays), motility (wound healing assay) and proliferation (MTT assay) were assessed in pII cells in response to VGSC blockers, phenytoin (PHT) and tetrodotoxin (TTX), or by siRNA knockdown of Nav1.5. The effect of PHT and TTX on modulating EGF-induced phosphorylation of Akt and ERK1/2 was determined by western blotting. Total matrix metalloproteinase (MMP) was determined using a fluorometric-based activity assay. The level of various human proteases was detected by using proteome profiler array kit. VGSC currents were detected in pII cells, but were absent in MCF-7. Nav1.5 showed cytoplasmic and perinuclear expression in both MCF-7 and pII cells, with enhanced expression upon EGF stimulation. Treatment of pII cells with PHT, TTX or siRNA significantly reduced invasion towards serum components and EGF, in part through reduction of P-ERK1/2 and proteases such as cathepsin E, kallikrein-10 and MMP-7, as well as total MMP activity. At high concentrations, PHT inhibited motility while TTX reduced cell proliferation. Pharmacological or genetic blockade of Nav1.5 may serve as a potential anti-metastatic therapy for breast cancer.
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Affiliation(s)
| | | | - Ming Yang
- Department of Biology, University of York, Heslington, York, YO10 5DD, UK
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115
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Laedermann CJ, Abriel H, Decosterd I. Post-translational modifications of voltage-gated sodium channels in chronic pain syndromes. Front Pharmacol 2015; 6:263. [PMID: 26594175 PMCID: PMC4633509 DOI: 10.3389/fphar.2015.00263] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 10/23/2015] [Indexed: 02/06/2023] Open
Abstract
In the peripheral sensory nervous system the neuronal expression of voltage-gated sodium channels (Navs) is very important for the transmission of nociceptive information since they give rise to the upstroke of the action potential (AP). Navs are composed of nine different isoforms with distinct biophysical properties. Studying the mutations associated with the increase or absence of pain sensitivity in humans, as well as other expression studies, have highlighted Nav1.7, Nav1.8, and Nav1.9 as being the most important contributors to the control of nociceptive neuronal electrogenesis. Modulating their expression and/or function can impact the shape of the AP and consequently modify nociceptive transmission, a process that is observed in persistent pain conditions. Post-translational modification (PTM) of Navs is a well-known process that modifies their expression and function. In chronic pain syndromes, the release of inflammatory molecules into the direct environment of dorsal root ganglia (DRG) sensory neurons leads to an abnormal activation of enzymes that induce Navs PTM. The addition of small molecules, i.e., peptides, phosphoryl groups, ubiquitin moieties and/or carbohydrates, can modify the function of Navs in two different ways: via direct physical interference with Nav gating, or via the control of Nav trafficking. Both mechanisms have a profound impact on neuronal excitability. In this review we will discuss the role of Protein Kinase A, B, and C, Mitogen Activated Protein Kinases and Ca++/Calmodulin-dependent Kinase II in peripheral chronic pain syndromes. We will also discuss more recent findings that the ubiquitination of Nav1.7 by Nedd4-2 and the effect of methylglyoxal on Nav1.8 are also implicated in the development of experimental neuropathic pain. We will address the potential roles of other PTMs in chronic pain and highlight the need for further investigation of PTMs of Navs in order to develop new pharmacological tools to alleviate pain.
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Affiliation(s)
- Cedric J. Laedermann
- F.M. Kirby Neurobiology Research Center, Boston Children’s Hospital, Harvard Medical School, BostonMA, USA
| | - Hugues Abriel
- Department of Clinical Research, University of BernBern, Switzerland
| | - Isabelle Decosterd
- Pain Center, Department of Anesthesiology, Lausanne University Hospital (CHUV) and University of LausanneLausanne, Switzerland
- Department of Fundamental Neurosciences, University of LausanneLausanne, Switzerland
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116
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Murray JK, Biswas K, Holder JR, Zou A, Ligutti J, Liu D, Poppe L, Andrews KL, Lin FF, Meng SY, Moyer BD, McDonough SI, Miranda LP. Sustained inhibition of the Na V 1.7 sodium channel by engineered dimers of the domain II binding peptide GpTx-1. Bioorg Med Chem Lett 2015; 25:4866-4871. [DOI: 10.1016/j.bmcl.2015.06.033] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 06/06/2015] [Accepted: 06/08/2015] [Indexed: 11/15/2022]
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117
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Age-dependent alterations of voltage-gated Na(+) channel isoforms in rat sinoatrial node. Mech Ageing Dev 2015; 152:80-90. [PMID: 26528804 DOI: 10.1016/j.mad.2015.10.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2015] [Revised: 10/08/2015] [Accepted: 10/26/2015] [Indexed: 02/06/2023]
Abstract
Multiple isoforms of voltage-gated Na(+) channels (NaChs) have been identified in sinoatrial node (SAN) and contribute to a rapid intrinsic heart rate. However, their roles in aging remain unclear. Here, we sought to clarify whether the age-related expression of NaChs contributes to the impaired SAN function during aging. Blockade of the tetrodotoxin (TTX)-sensitive Na(+) current with nanomolar concentrations of TTX prolonged the cycle length (CL) in both the rat intact heart and SAN. The effect of nanomolar concentrations of TTX on SAN pacemaking was lessened in adulthood compared with that in youth. Interestingly, the pacemaking became more sensitive to TTX and TTX-induced sinus arrhythmias occurred more frequently in the senescent group. The presences of NaCh α subunit isoforms Nav1.1, Nav1.6 as well as β subunit isoforms Navβ1 and Navβ3 in SAN were confirmed by immunohistochemistry. Western blot revealed a declination of Nav1.1, Nav1.6, Navβ1 and Navβ3 proteins during aging. Furthermore, laser captured SAN cells were used for further real-time quantitative RT-PCR analysis, which also confirmed the presences of Nav1.1, Nav1.6, Navβ1 and Navβ3 mRNA and their reduced levels in rat SAN during aging. These results indicated an age-dependent alterations in expression and relative function of NaCh in rat SAN.
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118
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Gu H, Fang YJ, Liu DD, Chen P, Mei YA. cAMP/PKA Pathways and S56 Phosphorylation Are Involved in AA/PGE2-Induced Increases in rNaV1.4 Current. PLoS One 2015; 10:e0140715. [PMID: 26485043 PMCID: PMC4618696 DOI: 10.1371/journal.pone.0140715] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 09/28/2015] [Indexed: 12/19/2022] Open
Abstract
Arachidonic acid (AA) and its metabolites are important second messengers for ion channel modulation. The effects of extracellular application of AA and its non-metabolized analogue on muscle rNaV1.4 Na+ current has been studied, but little is known about the effects of intracellular application of AA on this channel isoform. Here, we report that intracellular application of AA significantly augmented the rNaV1.4 current peak without modulating the steady-state activation and inactivation properties of the rNaV1.4 channel. These results differed from the effects of extracellular application of AA on rNaV1.4 current. The effects of intracellular AA were mimicked by prostaglandin E2 but not eicosatetraynoic acid (ETYA), the non-metabolized analogue of AA, and were eliminated by treatment with cyclooxygenase inhibitors, flufenamic acid, or indomethacin. AA/PGE2-induced activation of rNaV1.4 channels was mimicked by a cAMP analogue (db-cAMP) and eliminated by a PKA inhibitor, PKAi. Furthermore, inhibition of EP2 and EP4 (PGE2 receptors) with AH6809 and AH23848 reduced the intracellular AA/PGE2-induced increase of rNaV1.4 current. Two mutated channels, rNaV1.4S56A and rNaV1.4T21A, were designed to investigate the role of predicted phosphorylation sites in the AA/PGE2–mediated regulation of rNaV1.4 currents. In rNaV1.4S56A, the effects of intracellular db-cAMP, AA, and PGE2 were significantly reduced. The results of the present study suggest that intracellular AA augments rNaV1.4 current by PGE2/EP receptor-mediated activation of the cAMP/PKA pathway, and that the S56 residue on the channel protein is important for this process.
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Affiliation(s)
- Hua Gu
- School of Life Science and Technology, Tongji University, Shanghai 200092, PR China
- * E-mail: (HG); (YAM)
| | - Yan-Jia Fang
- School of Life Sciences, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200433, PR China
| | - Dong-Dong Liu
- School of Life Sciences, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200433, PR China
| | - Ping Chen
- School of Life Science and Technology, Tongji University, Shanghai 200092, PR China
| | - Yan-Ai Mei
- School of Life Sciences, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200433, PR China
- * E-mail: (HG); (YAM)
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119
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Brodie III ED, Brodie Jr. ED. Predictably Convergent Evolution of Sodium Channels in the Arms Race between Predators and Prey. BRAIN, BEHAVIOR AND EVOLUTION 2015; 86:48-57. [DOI: 10.1159/000435905] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Evolution typically arrives at convergent phenotypic solutions to common challenges of natural selection. However, diverse molecular and physiological mechanisms may generate phenotypes that appear similar at the organismal level. How predictable are the molecular mechanisms of adaptation that underlie adaptive convergence? Interactions between toxic prey and their predators provide an excellent avenue to investigate the question of predictability because both taxa must adapt to the presence of defensive poisons. The evolution of resistance to tetrodotoxin (TTX), which binds to and blocks voltage-gated sodium channels (NaV1) in nerves and muscle, has been remarkably parallel across deep phylogenetic divides. In both predators and prey, representing three major vertebrate groups, TTX resistance has arisen through structural changes in NaV1 proteins. Fish, amphibians and reptiles, though they differ in the total number of NaV1 paralogs in their genomes, have each evolved common amino acid substitutions in the orthologous skeletal muscle NaV1.4. Many of these substitutions involve not only the same positions in the protein, but also the identical amino acid residues. Similarly, predictable convergence is observed across the family of sodium channel genes expressed in different tissues in puffer fish and in garter snakes. Trade-offs between the fundamental role of NaV1 proteins in selective permeability of Na+ and their ability to resist binding by TTX generate a highly constrained adaptive landscape at the level of the protein.
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120
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Upregulation of Nav1.8 in demyelinated facial nerves might be relevant to the generation of hemifacial spasm. J Craniofac Surg 2015; 25:1334-6. [PMID: 24892416 DOI: 10.1097/scs.0000000000000802] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Our previous studies demonstrated that the abnormal muscle response could vanish when the ipsilateral superior cervical ganglion was removed and reappear when norepinephrine was dripped at the neurovascular conflict site. Evidentially, we believed that the mechanism of hemifacial spasm should involve emersion of ectopical action potential in the compressed facial nerve fibers. As the action potential is ignited by ion channel opening, we focused on Nav1.8 that has been found overexpressed in peripheral nerve while damaged. In this study, Moller model was adopted, 20 Sprague-Dawley rats underwent drip of norepinephrine, and the abnormal muscle response wave was monitored in 14 rats. Antibodies against unique epitopes of the α subunit of sodium channel isoforms were used to detect the Nav1.8 neuronal isoforms, and the immunohistochemistry showed strong staining in 13 rats, which were all in the abnormal muscle response positive group (P < 0.05). Accordingly, we concluded that the substance of hemifacial spasm is an ectopic action potential that emerged on the damaged facial nerve, which might be coupled by Nav1.8.
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121
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Crestey F, Frederiksen K, Jensen HS, Dekermendjian K, Larsen PH, Bastlund JF, Lu D, Liu H, Yang CR, Grunnet M, Svenstrup N. Identification and electrophysiological evaluation of 2-methylbenzamide derivatives as Nav1.1 modulators. ACS Chem Neurosci 2015; 6:1302-8. [PMID: 26114759 DOI: 10.1021/acschemneuro.5b00147] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (Nav) are crucial to the initiation and propagation of action potentials (APs) in electrically excitable cells, and during the past decades they have received considerable attention due to their therapeutic potential. Here, we report for the first time the synthesis and the electrophysiological evaluation of 16 ligands based on a 2-methylbenzamide scaffold that have been identified as Nav1.1 modulators. Among these compounds, N,N'-(1,3-phenylene)bis(2-methylbenzamide) (3a) has been selected and evaluated in ex-vivo experiments in order to estimate the activation impact of such a compound profile. It appears that 3a increases the Nav1.1 channel activity although its overall impact remains moderate. Altogether, our preliminary results provide new insights into the development of small molecule activators targeting specifically Nav1.1 channels to design potential drugs for treating CNS diseases.
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Affiliation(s)
- François Crestey
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
| | - Kristen Frederiksen
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
| | - Henrik S. Jensen
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
| | - Kim Dekermendjian
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
| | - Peter H. Larsen
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
| | - Jesper F. Bastlund
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
| | - Dunguo Lu
- ChemPartner Co.
Ltd., 998 Halei Road, Zhangjiang Hi-Tech
Park, Shanghai 201203, P. R. China
| | - Henry Liu
- ChemPartner Co.
Ltd., 998 Halei Road, Zhangjiang Hi-Tech
Park, Shanghai 201203, P. R. China
| | - Charles R. Yang
- ChemPartner Co.
Ltd., 998 Halei Road, Zhangjiang Hi-Tech
Park, Shanghai 201203, P. R. China
| | - Morten Grunnet
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
| | - Niels Svenstrup
- Neuroscience Drug
Discovery, H. Lundbeck A/S, Ottiliavej
9, 2500 Valby, Denmark
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122
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Castro Fonseca MD, Da Silva JH, Ferraz VP, Gomez RS, Guatimosim C. Comparative presynaptic effects of the volatile anesthetics sevoflurane and isoflurane at the mouse neuromuscular junction. Muscle Nerve 2015; 52:876-84. [DOI: 10.1002/mus.24589] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/25/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Matheus De Castro Fonseca
- Departamento de Morfologia, Instituto de Ciências Biológicas; Universidade Federal de Minas Gerais; Av. Antônio Carlos, 6627 Belo Horizonte MG 31270-901 Brasil
| | - Janice Henriques Da Silva
- Departamento de Morfologia, Instituto de Ciências Biológicas; Universidade Federal de Minas Gerais; Av. Antônio Carlos, 6627 Belo Horizonte MG 31270-901 Brasil
| | - Vany Perpetua Ferraz
- Departamento de Química, Instituto de Ciências Exatas; Universidade Federal de Minas Gerais; MG Brasil
| | - Renato Santiago Gomez
- Departamento de Cirurgia, Faculdade de Medicina; Universidade Federal de Minas Gerais; Belo Horizonte MG Brasil
| | - Cristina Guatimosim
- Departamento de Morfologia, Instituto de Ciências Biológicas; Universidade Federal de Minas Gerais; Av. Antônio Carlos, 6627 Belo Horizonte MG 31270-901 Brasil
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123
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Wang CF, Russell G, Strichartz GR, Wang GK. The Local and Systemic Actions of Duloxetine in Allodynia and Hyperalgesia Using a Rat Skin Incision Pain Model. Anesth Analg 2015; 121:532-44. [DOI: 10.1213/ane.0000000000000794] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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124
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Miceli F, Soldovieri MV, Ambrosino P, De Maria M, Manocchio L, Medoro A, Taglialatela M. Molecular pathophysiology and pharmacology of the voltage-sensing module of neuronal ion channels. Front Cell Neurosci 2015; 9:259. [PMID: 26236192 PMCID: PMC4502356 DOI: 10.3389/fncel.2015.00259] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 06/22/2015] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated ion channels (VGICs) are membrane proteins that switch from a closed to open state in response to changes in membrane potential, thus enabling ion fluxes across the cell membranes. The mechanism that regulate the structural rearrangements occurring in VGICs in response to changes in membrane potential still remains one of the most challenging topic of modern biophysics. Na+, Ca2+ and K+ voltage-gated channels are structurally formed by the assembly of four similar domains, each comprising six transmembrane segments. Each domain can be divided into two main regions: the Pore Module (PM) and the Voltage-Sensing Module (VSM). The PM (helices S5 and S6 and intervening linker) is responsible for gate opening and ion selectivity; by contrast, the VSM, comprising the first four transmembrane helices (S1–S4), undergoes the first conformational changes in response to membrane voltage variations. In particular, the S4 segment of each domain, which contains several positively charged residues interspersed with hydrophobic amino acids, is located within the membrane electric field and plays an essential role in voltage sensing. In neurons, specific gating properties of each channel subtype underlie a variety of biological events, ranging from the generation and propagation of electrical impulses, to the secretion of neurotransmitters and to the regulation of gene expression. Given the important functional role played by the VSM in neuronal VGICs, it is not surprising that various VSM mutations affecting the gating process of these channels are responsible for human diseases, and that compounds acting on the VSM have emerged as important investigational tools with great therapeutic potential. In the present review we will briefly describe the most recent discoveries concerning how the VSM exerts its function, how genetically inherited diseases caused by mutations occurring in the VSM affects gating in VGICs, and how several classes of drugs and toxins selectively target the VSM.
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Affiliation(s)
- Francesco Miceli
- Department of Neuroscience, University of Naples Federico II Naples, Italy
| | | | - Paolo Ambrosino
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Michela De Maria
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Laura Manocchio
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Alessandro Medoro
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Maurizio Taglialatela
- Department of Neuroscience, University of Naples Federico II Naples, Italy ; Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
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125
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Pucca MB, Cerni FA, Peigneur S, Bordon KCF, Tytgat J, Arantes EC. Revealing the Function and the Structural Model of Ts4: Insights into the "Non-Toxic" Toxin from Tityus serrulatus Venom. Toxins (Basel) 2015; 7:2534-50. [PMID: 26153865 PMCID: PMC4516927 DOI: 10.3390/toxins7072534] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 06/20/2015] [Accepted: 06/25/2015] [Indexed: 01/21/2023] Open
Abstract
The toxin, previously described as a "non-toxic" toxin, was isolated from the scorpion venom of Tityus serrulatus (Ts), responsible for the most severe and the highest number of accidents in Brazil. In this study, the subtype specificity and selectivity of Ts4 was investigated using six mammalian Nav channels (Nav1.2→Nav1.6 and Nav1.8) and two insect Nav channels (DmNav1 and BgNav). The electrophysiological assays showed that Ts4 specifically inhibited the fast inactivation of Nav1.6 channels, the most abundant sodium channel expressed in the adult central nervous system, and can no longer be classified as a "non-toxic peptide". Based on the results, we could classify the Ts4 as a classical α-toxin. The Ts4 3D-structural model was built based on the solved X-ray Ts1 3D-structure, the major toxin from Ts venom with which it shares high sequence identity (65.57%). The Ts4 model revealed a flattened triangular shape constituted by three-stranded antiparallel β-sheet and one α-helix stabilized by four disulfide bonds. The absence of a Lys in the first amino acid residue of the N-terminal of Ts4 is probably the main responsible for its low toxicity. Other key amino acid residues important to the toxicity of α- and β-toxins are discussed here.
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Affiliation(s)
- Manuela B Pucca
- Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Av. do Café, s/n, Ribeirão Preto, SP 14040-903, Brazil.
| | - Felipe A Cerni
- Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Av. do Café, s/n, Ribeirão Preto, SP 14040-903, Brazil.
| | - Steve Peigneur
- Toxicology and Pharmacology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, Leuven 3000, Belgium.
| | - Karla C F Bordon
- Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Av. do Café, s/n, Ribeirão Preto, SP 14040-903, Brazil.
| | - Jan Tytgat
- Toxicology and Pharmacology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, Leuven 3000, Belgium.
| | - Eliane C Arantes
- Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Av. do Café, s/n, Ribeirão Preto, SP 14040-903, Brazil.
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126
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Torregrosa R, Yang XF, Dustrude ET, Cummins TR, Khanna R, Kohn H. Chimeric derivatives of functionalized amino acids and α-aminoamides: compounds with anticonvulsant activity in seizure models and inhibitory actions on central, peripheral, and cardiac isoforms of voltage-gated sodium channels. Bioorg Med Chem 2015; 23:3655-66. [PMID: 25922183 PMCID: PMC4461516 DOI: 10.1016/j.bmc.2015.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/26/2015] [Accepted: 04/03/2015] [Indexed: 10/23/2022]
Abstract
Six novel 3″-substituted (R)-N-(phenoxybenzyl) 2-N-acetamido-3-methoxypropionamides were prepared and then assessed using whole-cell, patch-clamp electrophysiology for their anticonvulsant activities in animal seizure models and for their sodium channel activities. We found compounds with various substituents at the terminal aromatic ring that had excellent anticonvulsant activity. Of these compounds, (R)-N-4'-((3″-chloro)phenoxy)benzyl 2-N-acetamido-3-methoxypropionamide ((R)-5) and (R)-N-4'-((3″-trifluoromethoxy)phenoxy)benzyl 2-N-acetamido-3-methoxypropionamide ((R)-9) exhibited high protective indices (PI=TD50/ED50) comparable with many antiseizure drugs when tested in the maximal electroshock seizure test to mice (intraperitoneally) and rats (intraperitoneally, orally). Most compounds potently transitioned sodium channels to the slow-inactivated state when evaluated in rat embryonic cortical neurons. Treating HEK293 recombinant cells that expressed hNaV1.1, rNaV1.3, hNaV1.5, or hNaV1.7 with (R)-9 recapitulated the high levels of sodium channel slow inactivation.
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Affiliation(s)
- Robert Torregrosa
- NeuroGate Therapeutics, Inc., 150 Fayetteville Street, Suite 2300, Raleigh, NC 27601, United States
| | - Xiao-Fang Yang
- Department of Pharmacology and Neuroscience Graduate Interdisciplinary Program, College of Medicine, University of Arizona, Tucson, AZ 85742, United States
| | - Erik T Dustrude
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, United States
| | - Theodore R Cummins
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, United States; Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, United States
| | - Rajesh Khanna
- Department of Pharmacology and Neuroscience Graduate Interdisciplinary Program, College of Medicine, University of Arizona, Tucson, AZ 85742, United States
| | - Harold Kohn
- NeuroGate Therapeutics, Inc., 150 Fayetteville Street, Suite 2300, Raleigh, NC 27601, United States; Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, United States; Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, United States
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127
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Kroll JR, Saras A, Tanouye MA. Drosophila sodium channel mutations: Contributions to seizure-susceptibility. Exp Neurol 2015; 274:80-7. [PMID: 26093037 DOI: 10.1016/j.expneurol.2015.06.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Revised: 06/14/2015] [Accepted: 06/16/2015] [Indexed: 01/10/2023]
Abstract
This paper reviews Drosophila voltage-gated Na(+) channel mutations encoded by the para (paralytic) gene and their contributions to seizure disorders in the fly. Numerous mutations cause seizure-sensitivity, for example, para(bss1), with phenotypes that resemble human intractable epilepsy in some aspects. Seizure phenotypes are also seen with human GEFS+ spectrum mutations that have been knocked into the Drosophila para gene, para(GEFS+) and para(DS) alleles. Other para mutations, para(ST76) and para(JS) act as seizure-suppressor mutations reverting seizure phenotypes in other mutants. Seizure-like phenotypes are observed from mutations and other conditions that cause a persistent Na(+) current through either changes in mRNA splicing or protein structure.
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Affiliation(s)
- Jason R Kroll
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Arunesh Saras
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA
| | - Mark A Tanouye
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA; Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA.
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128
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Wakita M, Kotani N, Akaike N. Tetrodotoxin abruptly blocks excitatory neurotransmission in mammalian CNS. Toxicon 2015; 103:12-8. [PMID: 25959619 DOI: 10.1016/j.toxicon.2015.05.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 04/28/2015] [Accepted: 05/06/2015] [Indexed: 10/23/2022]
Abstract
The present study utilised a 'synaptic bouton' preparation of mechanically isolated rat hippocampal CA3 pyramidal neurons, which permits direct physiological and pharmacological quantitative analyses at the excitatory and inhibitory single synapse level. Evoked excitatory and inhibitory postsynaptic currents (eEPSCs and eIPSCs) were generated by focal paired-pulse electrical stimulation of single boutons. The sensitivity of eEPSC to tetrodotoxin (TTX) was higher than that of the voltage-dependent Na(+) channel whole-cell current (INa) in the postsynaptic CA3 soma membrane. The synaptic transmission was strongly inhibited by 3 nM TTX, at which concentration the INa was hardly suppressed. The IC50 values of eEPSC and INa for TTX were 2.8 and 37.9 nM, respectively, and complete inhibition was 3-10 nM for eEPSC and 1000 nM for INa. On the other hand, both eEPSC and eIPSC were equally and gradually inhibited by decreasing the external Na(+) concentration ([Na]o), which decreases the Na(+)gradient across the cell membrane. The results indicate that TTX at 3-10 nM could block most of voltage-dependent Na(+) channels on presynaptic nerve terminal, resulting in abruptly inhibition of action potential dependent excitatory neurotransmission.
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Affiliation(s)
- Masahito Wakita
- Research Division for Clinical Pharmacology, Medical Corporation, Jyuryokai, Kumamoto Kinoh Hospital, 6-8-1 Yamamuro, Kitaku, Kumamoto, 860-8518, Japan; Research Division for Life Science, Kumamoto Health Science University, 325 Izumi-machi, Kitaku, Kumamoto, 861-5598, Japan
| | - Naoki Kotani
- Research Division of Neurophysiology, Kitamoto Hospital, 3-7-6 Kawarasone, Koshigaya, 343-0821, Japan
| | - Norio Akaike
- Research Division for Clinical Pharmacology, Medical Corporation, Jyuryokai, Kumamoto Kinoh Hospital, 6-8-1 Yamamuro, Kitaku, Kumamoto, 860-8518, Japan; Research Division for Life Science, Kumamoto Health Science University, 325 Izumi-machi, Kitaku, Kumamoto, 861-5598, Japan; Research Division of Neurophysiology, Kitamoto Hospital, 3-7-6 Kawarasone, Koshigaya, 343-0821, Japan.
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129
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Krause U, Alflen C, Steinmetz M, Müller MJ, Quentin T, Paul T. Characterization of maturation of neuronal voltage-gated sodium channels SCN1A and SCN8A in rat myocardium. Mol Cell Pediatr 2015; 2:5. [PMID: 26542295 PMCID: PMC4530575 DOI: 10.1186/s40348-015-0015-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/19/2015] [Indexed: 12/17/2022] Open
Abstract
Background Sodium channels predominantly expressed in brain are expressed in myocardial tissue and play an important role in cardiac physiology. Alterations of sodium channels are known to result in neurological disease in infancy and childhood. It will be of interest to study the expression of brain-type sodium channels in the developing myocardium. Methods The expression of neuronal sodium channels (SCN1A, SCN8A) and the cardiac isoform SCN5A in the developing rat myocardium was studied by rtPCR, Western blot, and immunohistochemistry at different stages of antenatal and postnatal development. Results Significant changes of sodium channel expression during development were detected. Whereas SCN5A RNA increased to maximum levels on day 21 after birth, the highest SCN1A RNA levels were detected on day 1 to 7 after birth. SCN8A RNA was maximally expressed during embryonic development. At the protein level, the amount of SCN5A protein increased along with the RNA level. SCN1A protein level decreased after birth in contrast to RNA expression. Western blot could not detect SCN8A protein in the myocardium at any stage of development. Immunohistochemistry however proved the presence of SCN8A protein in the developing rat myocardium. Conclusions Heart- and brain-type sodium channels are differentially expressed during ontogenesis. The high expression level of SCN1A in the perinatal period and early infancy indicates its importance in preserving a regular cardiac rhythm in this early phase of life. Altered regulation of sodium channels might result in severe cardiac rhythm disturbances.
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Affiliation(s)
- Ulrich Krause
- Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University, Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany.
| | - Christian Alflen
- Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University, Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany.
| | - Michael Steinmetz
- Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University, Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany.
| | - Matthias J Müller
- Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University, Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany.
| | - Thomas Quentin
- Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University, Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany.
| | - Thomas Paul
- Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University, Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany.
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130
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Murray JK, Ligutti J, Liu D, Zou A, Poppe L, Li H, Andrews KL, Moyer BD, McDonough SI, Favreau P, Stöcklin R, Miranda LP. Engineering Potent and Selective Analogues of GpTx-1, a Tarantula Venom Peptide Antagonist of the NaV1.7 Sodium Channel. J Med Chem 2015; 58:2299-314. [DOI: 10.1021/jm501765v] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
| | | | | | | | | | | | | | | | | | - Philippe Favreau
- Atheris Laboratories, Case Postale
314, CH-1233 Bernex, Geneva, Switzerland
| | - Reto Stöcklin
- Atheris Laboratories, Case Postale
314, CH-1233 Bernex, Geneva, Switzerland
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131
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Park KD, Yang XF, Dustrude ET, Wang Y, Ripsch MS, White FA, Khanna R, Kohn H. Chimeric agents derived from the functionalized amino acid, lacosamide, and the α-aminoamide, safinamide: evaluation of their inhibitory actions on voltage-gated sodium channels, and antiseizure and antinociception activities and comparison with lacosamide and safinamide. ACS Chem Neurosci 2015; 6:316-30. [PMID: 25418676 PMCID: PMC4372064 DOI: 10.1021/cn5002182] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
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The functionalized amino acid, lacosamide
((R)-2), and the α-aminoamide,
safinamide ((S)-3), are neurological
agents that have been extensively
investigated and have displayed potent anticonvulsant activities in
seizure models. Both compounds have been reported to modulate voltage-gated
sodium channel activity. We have prepared a series of chimeric compounds,
(R)-7–(R)-10, by merging key structural units in these two clinical
agents, and then compared their activities with (R)-2 and (S)-3. Compounds
were assessed for their ability to alter sodium channel kinetics for
inactivation, frequency (use)-dependence, and steady-state activation
and fast inactivation. We report that chimeric compounds (R)-7–(R)-10 in catecholamine A-differentiated (CAD) cells and embryonic rat
cortical neurons robustly enhanced sodium channel inactivation at
concentrations far lower than those required for (R)-2 and (S)-3, and that
(R)-9 and (R)-10, unlike (R)-2 and (S)-3, produce sodium channel frequency (use)-dependence
at low micromolar concentrations. We further show that (R)-7–(R)-10 displayed
excellent anticonvulsant activities and pain-attenuating properties
in the animal formalin model. Of these compounds, only (R)-7 reversed mechanical hypersensitivity in the tibial-nerve
injury model for neuropathic pain in rats.
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Affiliation(s)
| | - Xiao-Fang Yang
- Department
of Pharmacology and Neuroscience Graduate Interdisciplinary Program,
College of Medicine, University of Arizona, Tucson, Arizona 85742, United States
| | | | - Yuying Wang
- Department
of Pharmacology and Neuroscience Graduate Interdisciplinary Program,
College of Medicine, University of Arizona, Tucson, Arizona 85742, United States
| | | | | | - Rajesh Khanna
- Department
of Pharmacology and Neuroscience Graduate Interdisciplinary Program,
College of Medicine, University of Arizona, Tucson, Arizona 85742, United States
| | - Harold Kohn
- NeuroGate Therapeutics, Inc., 150
Fayetteville Street, Suite 2300, Raleigh, North Carolina 27601, United States
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132
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Gorelova N, Seamans JK. Cell-attached single-channel recordings in intact prefrontal cortex pyramidal neurons reveal compartmentalized D1/D5 receptor modulation of the persistent sodium current. Front Neural Circuits 2015; 9:4. [PMID: 25729354 PMCID: PMC4325928 DOI: 10.3389/fncir.2015.00004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Accepted: 01/08/2015] [Indexed: 11/28/2022] Open
Abstract
The persistent Na+ current (INap) is believed to be an important target of dopamine modulation in prefrontal cortex (PFC) neurons. While past studies have tested the effects of dopamine on INap, the results have been contradictory largely because of difficulties in measuring INap using somatic whole-cell recordings. To circumvent these confounds we used the cell-attached patch-clamp technique to record single Na+ channels from the soma, proximal dendrite (PD) or proximal axon (PA) of intact prefrontal layer V pyramidal neurons. Under baseline conditions, numerous well resolved Na+ channel openings were recorded that exhibited an extrapolated reversal potential of 73 mV, a slope conductance of 14–19 pS and were blocked by tetrodotoxin (TTX). While similar in most respects, the propensity to exhibit prolonged bursts lasting >40 ms was many fold greater in the axon than the soma or dendrite. Bath application of the D1/D5 receptor agonist SKF81297 shifted the ensemble current activation curve leftward and increased the number of late events recorded from the PD but not the soma or PA. However, the greatest effect was on prolonged bursting where the D1/D5 receptor agonist increased their occurrence 3 fold in the PD and nearly 7 fold in the soma, but not at all in the PA. As a result, D1/D5 receptor activation equalized the probability of prolonged burst occurrence across the proximal axosomatodendritic region. Therefore, D1/D5 receptor modulation appears to be targeted mainly to Na+ channels in the PD/soma and not the PA. By circumventing the pitfalls of previous attempts to study the D1/D5 receptor modulation of INap, we demonstrate conclusively that D1/D5 receptor activation can increase the INap generated proximally, however questions still remain as to how D1/D5 receptor modulates Na+ currents in the more distal initial segment where most of the INap is normally generated.
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Affiliation(s)
- Natalia Gorelova
- Department of Psychiatry and Brain Research Centre, University of British Columbia Vancouver, BC, Canada
| | - Jeremy K Seamans
- Department of Psychiatry and Brain Research Centre, University of British Columbia Vancouver, BC, Canada
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133
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Teramoto N, Yotsu-Yamashita M. Selective blocking effects of 4,9-anhydrotetrodotoxin, purified from a crude mixture of tetrodotoxin analogues, on NaV1.6 channels and its chemical aspects. Mar Drugs 2015; 13:984-95. [PMID: 25686275 PMCID: PMC4344613 DOI: 10.3390/md13020984] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 01/30/2015] [Accepted: 02/03/2015] [Indexed: 12/19/2022] Open
Abstract
Tetrodotoxin (TTX) is a potent neurotoxin found in a number of marine creatures including the pufferfish, where it is synthesized by bacteria and accumulated through the food chain. It is a potent and selective blocker of some types of voltage-gated Na+ channel (NaV channel). 4,9-Anhydrotetrodotoxin (4,9-anhydroTTX) was purified from a crude mixture of TTX analogues (such as TTX, 4-epiTTX, 6-epiTTX, 11-oxoTTX and 11-deoxyTTX) by the use of liquid chromatography-fluorescence detection (LC-FLD) techniques. Recently, it has been reported that 4,9-anhydroTTX selectively blocks the activity of NaV1.6 channels with a blocking efficacy 40–160 times higher than that for other TTX-sensitive NaV1.x channel isoforms. However, little attention has been paid to the molecular properties of the α-subunit in NaV1.6 channels and the characteristics of binding of 4,9-anhydroTTX. From a functional point of view, it is important to determine the relative expression of NaV1.6 channels in a wide variety of tissues. The aim of this review is to discuss briefly current knowledge about the pharmacology of 4,9-anhydroTTX, and provide an analysis of the molecular structure of native NaV1.6 channels. In addition, chemical aspects of 4,9-anhydroTTX are briefly covered.
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Affiliation(s)
- Noriyoshi Teramoto
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga 849-8501, Japan.
- Laboratory of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, Sendai 980-8575, Japan.
| | - Mari Yotsu-Yamashita
- Laboratory of Bioorganic Chemistry of Natural Products, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan.
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134
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Lin WH, He M, Baines RA. Seizure suppression through manipulating splicing of a voltage-gated sodium channel. ACTA ACUST UNITED AC 2015; 138:891-901. [PMID: 25681415 PMCID: PMC5014079 DOI: 10.1093/brain/awv012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Voltage-gated persistent sodium current (INaP) is a tractable target for antiepileptic drugs. Using a strategy focused on INaP reduction, Lin et al. identify 95 regulators of voltage-gated sodium channel splicing for which RNAi knockdown reduces seizure duration in Drosophila. Manipulation of splicing regulators could improve control of epilepsy. Seizure can result from increased voltage-gated persistent sodium current expression. Although many clinically-approved antiepileptic drugs target voltage-gated persistent sodium current, none exclusively repress this current without also adversely affecting the transient voltage-gated sodium current. Achieving a more selective block has significant potential for the treatment of epilepsy. Recent studies show that voltage-gated persistent sodium current amplitude is regulated by alternative splicing offering the possibility of a novel route for seizure control. In this study we identify 291 splicing regulators that, on knockdown, alter splicing of the Drosophila voltage-gated sodium channel to favour inclusion of exon K, rather than the mutually exclusive exon L. This change is associated with both a significant reduction in voltage-gated persistent sodium current, without change to transient voltage-gated sodium current, and to rescue of seizure in this model insect. RNA interference mediated knock-down, in two different seizure mutants, shows that 95 of these regulators are sufficient to significantly reduce seizure duration. Moreover, most suppress seizure activity in both mutants, indicative that they are part of well conserved pathways and likely, therefore, to be optimal candidates to take forward to mammalian studies. We provide proof-of-principle for such studies by showing that inhibition of a selection of regulators, using small molecule inhibitors, is similarly effective to reduce seizure. Splicing of the Drosophila sodium channel shows many similarities to its mammalian counterparts, including altering the amplitude of voltage-gated persistent sodium current. Our study provides the impetus to investigate whether manipulation of splicing of mammalian voltage-gated sodium channels may be exploitable to provide effective seizure control.
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Affiliation(s)
- Wei-Hsiang Lin
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - Miaomiao He
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - Richard A Baines
- Faculty of Life Sciences, University of Manchester, Manchester, UK
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135
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Pugsley MK, Curtis MJ, Hayes ES. Biophysics and Molecular Biology of Cardiac Ion Channels for the Safety Pharmacologist. Handb Exp Pharmacol 2015; 229:149-203. [PMID: 26091640 DOI: 10.1007/978-3-662-46943-9_7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cardiac safety pharmacology is a continuously evolving discipline that uses the basic principles of pharmacology in a regulatory-driven process to generate data to inform risk/benefit assessment of a new chemical entity (NCE). The aim of cardiac safety pharmacology is to characterise the pharmacodynamic/pharmacokinetic (PK/PD) relationship of a drug's adverse effects on the heart using continuously evolving methodology. Unlike Toxicology, safety pharmacology includes within its remit a regulatory requirement to predict the risk of rare cardiotoxic (potentially lethal) events such as torsades de pointes (TdP), which is statistically associated with drug-induced changes in the QT interval of the ECG due to blockade of I Kr or K v11.1 current encoded by hERG. This gives safety pharmacology its unique character. The key issues for the safety pharmacology assessment of a drug on the heart are detection of an adverse effect liability, projection of the data into safety margin calculation and clinical safety monitoring. This chapter will briefly review the current cardiac safety pharmacology paradigm outlined in the ICH S7A and ICH S7B guidance documents and the non-clinical models and methods used in the evaluation of new chemical entities in order to define the integrated risk assessment for submission to regulatory authorities. An overview of how the present cardiac paradigm was developed will be discussed, explaining how it was based upon marketing authorisation withdrawal of many non-cardiovascular compounds due to unanticipated proarrhythmic effects. The role of related biomarkers (of cardiac repolarisation, e.g. prolongation of the QT interval of the ECG) will be considered. We will also provide an overview of the 'non-hERG-centric' concepts utilised in the evolving comprehensive in vitro proarrhythmia assay (CIPA) that details conduct of the proposed ion channel battery test, use of human stem cells and application of in silico models to early cardiac safety assessment. The summary of our current understanding of the triggers of TdP will include the interplay between action potential (AP) prolongation, early and delayed afterdepolarisation and substrates for re-entry arrhythmias.
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Affiliation(s)
- Michael K Pugsley
- Global Safety Pharmacology and Toxicology/Pathology, Janssen Pharmaceuticals LLC, 1000 Route 202 South, Raritan, NJ, 08869, USA,
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136
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Zimmer T, Haufe V, Blechschmidt S. Voltage-gated sodium channels in the mammalian heart. Glob Cardiol Sci Pract 2014; 2014:449-63. [PMID: 25780798 PMCID: PMC4355518 DOI: 10.5339/gcsp.2014.58] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 12/11/2014] [Indexed: 12/19/2022] Open
Abstract
Mammalian species express nine functional voltage-gated Na(+) channels. Three of them, the cardiac-specific isoform Nav1.5 and the neuronal isoforms Nav1.8 and Nav1.9, are relatively resistant to the neurotoxin tetrodotoxin (TTX; IC50 ≥ 1 μM). The other six isoforms are highly sensitive to TTX with IC50 values in the nanomolar range. These isoforms are expressed in the central nervous system (Nav1.1, Nav1.2, Nav1.3, Nav1.6), in the skeletal muscle (Nav1.4), and in the peripheral nervous system (Nav1.6, Nav1.7). The isoform Nav1.5, encoded by the SCN5A gene, is responsible for the upstroke of the action potential in the heart. Mutations in SCN5A are associated with a variety of life-threatening arrhythmias, like long QT syndrome type 3 (LQT3), Brugada syndrome (BrS) or cardiac conduction disease (CCD). Previous immunohistochemical and electrophysiological assays demonstrated the cardiac expression of neuronal and skeletal muscle Na(+) channels in the heart of various mammals, which led to far-reaching speculations on their function. However, when comparing the Na(+) channel mRNA patterns in the heart of various mammalian species, only minute quantities of transcripts for TTX-sensitive Na(+) channels were detectable in whole pig and human hearts, suggesting that these channels are not involved in cardiac excitation phenomena in higher mammals. This conclusion is strongly supported by the fact that mutations in TTX-sensitive Na(+) channels were associated with epilepsy or skeletal muscle diseases, rather than with a pathological cardiac phenotype. Moreover, previous data from TTX-intoxicated animals and from cases of human tetrodotoxication showed that low TTX dosages caused at most little alterations of both the cardiac output and the electrocardiogram. Recently, genome-wide association studies identified SCN10A, the gene encoding Nav1.8, as a determinant of cardiac conduction parameters, and mutations in SCN10A have been associated with BrS. These novel findings opened a fascinating new research area in the cardiac ion channel field, and the on-going debate on how SCN10A/Nav1.8 affects cardiac conduction is very exciting.
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Affiliation(s)
- Thomas Zimmer
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Kollegiengasse 9, 07743 Jena, Germany
| | | | - Steve Blechschmidt
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Kollegiengasse 9, 07743 Jena, Germany
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137
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Yang L, Li L. Actions of the pyrethroid insecticide bifenthrin on sodium channels expressed in rat cerebral cortical neurons. Toxicol Mech Methods 2014; 25:63-9. [DOI: 10.3109/15376516.2014.985355] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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138
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Kirchhof P, Tal T, Fabritz L, Klimas J, Nesher N, Schulte JS, Ehling P, Kanyshkova T, Budde T, Nikol S, Fortmueller L, Stallmeyer B, Müller FU, Schulze-Bahr E, Schmitz W, Zlotkin E, Kirchhefer U. First report on an inotropic peptide activating tetrodotoxin-sensitive, "neuronal" sodium currents in the heart. Circ Heart Fail 2014; 8:79-88. [PMID: 25424392 DOI: 10.1161/circheartfailure.113.001066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND New therapeutic approaches to improve cardiac contractility without severe risk would improve the management of acute heart failure. Increasing systolic sodium influx can increase cardiac contractility, but most sodium channel activators have proarrhythmic effects that limit their clinical use. Here, we report the cardiac effects of a novel positive inotropic peptide isolated from the toxin of the Black Judean scorpion that activates neuronal tetrodotoxin-sensitive sodium channels. METHODS AND RESULTS All venoms and peptides were isolated from Black Judean Scorpions (Buthotus Hottentotta) caught in the Judean Desert. The full scorpion venom increased left ventricular function in sedated mice in vivo, prolonged ventricular repolarization, and provoked ventricular arrhythmias. An inotropic peptide (BjIP) isolated from the full venom by chromatography increased cardiac contractility but did neither provoke ventricular arrhythmias nor prolong cardiac repolarization. BjIP increased intracellular calcium in ventricular cardiomyocytes and prolonged inactivation of the cardiac sodium current. Low concentrations of tetrodotoxin (200 nmol/L) abolished the effect of BjIP on calcium transients and sodium current. BjIP did not alter the function of Nav1.5, but selectively activated the brain-type sodium channels Nav1.6 or Nav1.3 in cellular electrophysiological recordings obtained from rodent thalamic slices. Nav1.3 (SCN3A) mRNA was detected in human and mouse heart tissue. CONCLUSIONS Our pilot experiments suggest that selective activation of tetrodotoxin-sensitive neuronal sodium channels can safely increase cardiac contractility. As such, the peptide described here may become a lead compound for a new class of positive inotropic agents.
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Affiliation(s)
- Paulus Kirchhof
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.).
| | - Tzachy Tal
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Larissa Fabritz
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Jan Klimas
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Nir Nesher
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Jan S Schulte
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Petra Ehling
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Tatayana Kanyshkova
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Thomas Budde
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Sigrid Nikol
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Lisa Fortmueller
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Birgit Stallmeyer
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Frank U Müller
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Eric Schulze-Bahr
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Wilhelm Schmitz
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Eliahu Zlotkin
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
| | - Uwe Kirchhefer
- From the Department of Cardiovascular Medicine (P.K., L.F., S.N., L.F.), Department of Pharmacology and Toxicology (J.K., J.S.S., F.U.M., W.S., U.K.), and Department of Cardiovascular Medicine, Institute for Genetics of Heart Disease (IfGH) (B.S., E.S.-B.), Hospital of the University of Muenster, Muenster, Germany; Center for Cardiovascular Sciences, School of Clinical and Experimental Medicine, and SWBH NHS Trust, University of Birmingham, Birmingham, United Kingdom (P.K., L.F.); Technion Israel Institute of Technology, Haifa, Israel (T.T.); Department of Animal and Cell Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (T.T., N.N., E.Z.); Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovak Republic (J.K.); Department of Neurology, and Division of Neuropathophysiology, Institute of Physiology I (P.E.) and Institute of Physiology I (T.K., T.B.), University of Muenster, Muenster, Germany; and Department of Clinical and Interventional Angiology, Asklepios Clinic St. Georg, Hamburg, Germany (S.N.)
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139
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Zhang B, Li M, Wang L, Li C, Lou Y, Liu J, Liu Y, Wang Z, Wen S. The association between the polymorphisms in a sodium channel gene SCN7A and essential hypertension: a case-control study in the Northern Han Chinese. Ann Hum Genet 2014; 79:28-36. [PMID: 25393565 DOI: 10.1111/ahg.12085] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Accepted: 09/03/2014] [Indexed: 11/29/2022]
Abstract
Nax , an α-subunit of the sodium channel encoded by the SCN7A gene, has been deemed to be a sensor of the concentration of sodium in the brain and may be involved in salt intake behavior. We inferred that Nax /SCN7A may participate in the regulation of blood pressure and the pathogenesis of essential hypertension (EH). The present case-control study involving 615 hypertensives and 617 normotensives was performed to investigate the association between SCN7A polymorphisms and EH in the Northern Han Chinese population. The three common single nucleotide polymorphisms (SNPs) (rs3791251, rs6738031, rs7565062) in the exons of SCN7A were genotyped with the TaqMan assay. Significant association between SNP rs7565062 and EH was found under the addictive and dominant genetic models (P = 0.024, OR = 1.283, 95%CI [1.033-1.592]; P = 0.013, OR = 1.203, 95%CI [1.040-1.392]; respectively). The three SNPs were in close pair-wise linkage disequilibrium with each other and the haplotype analyses indicated that haplotype G-A-T was significantly associated with increased risk of EH (P = 0.023, OR = 1.290). In conclusion, our data showed that SNP rs7565062 of SCN7A was significantly associated with EH and the allele T of rs7565062 or the related haplotype G-A-T will be a genetic risk factor for EH in the Northern Han Chinese population.
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Affiliation(s)
- Bei Zhang
- Department of Hypertension Research, Beijing Anzhen Hospital, Capital Medical University and Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing, People's Republic of China
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140
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Mazet B. Gastrointestinal motility and its enteric actors in mechanosensitivity: past and present. Pflugers Arch 2014; 467:191-200. [PMID: 25366494 DOI: 10.1007/s00424-014-1635-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 10/14/2014] [Accepted: 10/19/2014] [Indexed: 12/14/2022]
Abstract
Coordinated contractions of the smooth muscle layers of the gastrointestinal (GI) tract are required to produce motor patterns that ensure normal GI motility. The crucial role of the enteric nervous system (ENS), the intrinsic ganglionated network located within the GI wall, has long been recognized in the generation of the main motor patterns. However, devising an appropriate motility requires the integration of informations emanating from the lumen of the GI tract. As already found more than half a century ago, the ability of the GI tract to respond to mechanical forces such as stretch is not restricted to neuronal mechanisms. Instead, mechanosensitivity is now recognized as a property of several non-neuronal cell types, the excitability of which is probably involved in shaping the motor patterns. This brief review gives an overview on how mechanosensitivity of different cell types in the GI tract has been established and, whenever available, on what ionic conductances are involved in mechanotransduction and their potential impact on normal GI motility.
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Affiliation(s)
- Bruno Mazet
- Aix Marseille Université, CNRS, CRN2M UMR 7286, CS80011 Bd Pierre Dramard, 13344, Marseille Cedex 15, France,
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141
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Zeberg H, Robinson HPC, Århem P. Density of voltage-gated potassium channels is a bifurcation parameter in pyramidal neurons. J Neurophysiol 2014; 113:537-49. [PMID: 25339708 DOI: 10.1152/jn.00907.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Several types of intrinsic dynamics have been identified in brain neurons. Type 1 excitability is characterized by a continuous frequency-stimulus relationship and, thus, an arbitrarily low frequency at threshold current. Conversely, Type 2 excitability is characterized by a discontinuous frequency-stimulus relationship and a nonzero threshold frequency. In previous theoretical work we showed that the density of Kv channels is a bifurcation parameter, such that increasing the Kv channel density in a neuron model transforms Type 1 excitability into Type 2 excitability. Here we test this finding experimentally, using the dynamic clamp technique on Type 1 pyramidal cells in rat cortex. We found that increasing the density of slow Kv channels leads to a shift from Type 1 to Type 2 threshold dynamics, i.e., a distinct onset frequency, subthreshold oscillations, and reduced latency to first spike. In addition, the action potential was resculptured, with a narrower spike width and more pronounced afterhyperpolarization. All changes could be captured with a two-dimensional model. It may seem paradoxical that an increase in slow K channel density can lead to a higher threshold firing frequency; however, this can be explained in terms of bifurcation theory. In contrast to previous work, we argue that an increased outward current leads to a change in dynamics in these neurons without a rectification of the current-voltage curve. These results demonstrate that the behavior of neurons is determined by the global interactions of their dynamical elements and not necessarily simply by individual types of ion channels.
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Affiliation(s)
- Hugo Zeberg
- Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; and Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Hugh P C Robinson
- Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Peter Århem
- Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; and
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142
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The voltage-gated sodium channel: a major target of marine neurotoxins. Toxicon 2014; 91:84-95. [PMID: 25305552 DOI: 10.1016/j.toxicon.2014.09.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 09/18/2014] [Accepted: 09/30/2014] [Indexed: 12/16/2022]
Abstract
Voltage-gated sodium channels (Nav) are key components for nerve excitability. They initiate and propagate the action potential in excitable cells, throughout the central and peripheral nervous system, thus enabling a variety of physiological functions to be achieved. The rising phase of the action potential is driven by the opening of Nav channels which activate rapidly and carry Na(+) ions in the intracellular medium, and ends with the Na(+) current inactivation. The biophysical properties of these channels have been elucidated, through the use of pharmacological agents that disrupt the molecular mechanism of the channel functioning. Among them, marine toxins produced by venomous animals or microorganisms have been crucial to map the different allosteric binding sites of the channels, understand their mode of action and represent an emerging source of therapeutic agents to alleviate or cure Na(+) channels-linked human diseases. In this article, we review recent discoveries on the molecular and biophysical properties of the Na(+) channel as a target for marine neurotoxins, and present the ongoing developments of pharmacological agents as therapeutic tools.
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143
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Gould HJ, Soignier RD, Cho SR, Hernandez C, Diamond I, Taylor BK, Paul D. Ranolazine Attenuates Mechanical Allodynia Associated with Demyelination Injury. PAIN MEDICINE 2014; 15:1771-80. [DOI: 10.1111/pme.12516] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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144
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Abstract
Voltage-gated sodium channels initiate action potentials in brain neurons, mutations in sodium channels cause inherited forms of epilepsy, and sodium channel blockers-along with other classes of drugs-are used in therapy of epilepsy. A mammalian voltage-gated sodium channel is a complex containing a large, pore-forming α subunit and one or two smaller β subunits. Extensive structure-function studies have revealed many aspects of the molecular basis for sodium channel structure, and X-ray crystallography of ancestral bacterial sodium channels has given insight into their three-dimensional structure. Mutations in sodium channel α and β subunits are responsible for genetic epilepsy syndromes with a wide range of severity, including generalized epilepsy with febrile seizures plus (GEFS+), Dravet syndrome, and benign familial neonatal-infantile seizures. These seizure syndromes are treated with antiepileptic drugs that offer differing degrees of success. The recent advances in understanding of disease mechanisms and sodium channel structure promise to yield improved therapeutic approaches.
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Affiliation(s)
- William A Catterall
- Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280;
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145
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McGlothlin JW, Chuckalovcak JP, Janes DE, Edwards SV, Feldman CR, Brodie ED, Pfrender ME, Brodie ED. Parallel evolution of tetrodotoxin resistance in three voltage-gated sodium channel genes in the garter snake Thamnophis sirtalis. Mol Biol Evol 2014; 31:2836-46. [PMID: 25135948 PMCID: PMC4209135 DOI: 10.1093/molbev/msu237] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Members of a gene family expressed in a single species often experience common selection pressures. Consequently, the molecular basis of complex adaptations may be expected to involve parallel evolutionary changes in multiple paralogs. Here, we use bacterial artificial chromosome library scans to investigate the evolution of the voltage-gated sodium channel (Nav) family in the garter snake Thamnophis sirtalis, a predator of highly toxic Taricha newts. Newts possess tetrodotoxin (TTX), which blocks Nav’s, arresting action potentials in nerves and muscle. Some Thamnophis populations have evolved resistance to extremely high levels of TTX. Previous work has identified amino acid sites in the skeletal muscle sodium channel Nav1.4 that confer resistance to TTX and vary across populations. We identify parallel evolution of TTX resistance in two additional Nav paralogs, Nav1.6 and 1.7, which are known to be expressed in the peripheral nervous system and should thus be exposed to ingested TTX. Each paralog contains at least one TTX-resistant substitution identical to a substitution previously identified in Nav1.4. These sites are fixed across populations, suggesting that the resistant peripheral nerves antedate resistant muscle. In contrast, three sodium channels expressed solely in the central nervous system (Nav1.1–1.3) showed no evidence of TTX resistance, consistent with protection from toxins by the blood–brain barrier. We also report the exon–intron structure of six Nav paralogs, the first such analysis for snake genes. Our results demonstrate that the molecular basis of adaptation may be both repeatable across members of a gene family and predictable based on functional considerations.
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Affiliation(s)
- Joel W McGlothlin
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA Department of Biology, University of Virginia
| | - John P Chuckalovcak
- Department of Biology, University of Virginia Bio-Rad Laboratories, Hercules, CA
| | - Daniel E Janes
- Department of Organismic and Evolutionary Biology, Harvard University Division of Genetics and Developmental Biology, National Institutes of Health, Bethesda, MD
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Harvard University
| | | | | | - Michael E Pfrender
- Department of Biological Sciences and Environmental Change Initiative, University of Notre Dame
| | - Edmund D Brodie
- Department of Biology, University of Virginia Mountain Lake Biological Station, University of Virginia
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146
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Liu Y, Tang J, Zhang Y, Xun X, Tang D, Peng D, Yi J, Liu Z, Shi X. Synthesis and analgesic effects of μ-TRTX-Hhn1b on models of inflammatory and neuropathic pain. Toxins (Basel) 2014; 6:2363-78. [PMID: 25123556 PMCID: PMC4147587 DOI: 10.3390/toxins6082363] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 07/17/2014] [Accepted: 07/18/2014] [Indexed: 01/26/2023] Open
Abstract
μ-TRTX-Hhn1b (HNTX-IV) is a 35-amino acid peptide isolated from the venom of the spider, Ornithoctonus hainana. It inhibits voltage-gated sodium channel Nav1.7, which has been considered as a therapeutic target for pain. The goal of the present study is to elucidate the analgesic effects of synthetic μ-TRTX-Hhn1b on animal models of pain. The peptide was first synthesized and then successfully refolded/oxidized. The synthetic peptide had the same inhibitory effect on human Nav1.7 current transiently expressed in HEK 293 cells as the native toxin. Furthermore, the analgesic potentials of the synthetic peptide were examined on models of inflammatory pain and neuropathic pain. μ-TRTX-Hhn1b produced an efficient reversal of acute nociceptive pain in the abdominal constriction model, and significantly reduced the pain scores over the 40-min period in the formalin model. The efficiency of μ-TRTX-Hhn1b on both models was equivalent to that of morphine. In the spinal nerve model, the reversal effect of μ-TRTX-Hhn1b on allodynia was longer and higher than mexiletine. These results demonstrated that μ-TRTX-Hhn1b efficiently alleviated acute inflammatory pain and chronic neuropathic pain in animals and provided an attractive template for further clinical analgesic drug design.
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Affiliation(s)
- Yu Liu
- College of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China.
| | - Jianguang Tang
- The Second Xiangya Hospital of Central South University, Changsha 410008, Hunan, China.
| | - Yunxiao Zhang
- College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China.
| | - Xiaohong Xun
- College of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China.
| | - Dongfang Tang
- College of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China.
| | - Dezheng Peng
- College of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China.
| | - Jianming Yi
- College of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China.
| | - Zhonghua Liu
- College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China.
| | - Xiaoliu Shi
- The Second Xiangya Hospital of Central South University, Changsha 410008, Hunan, China.
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147
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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
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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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148
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Frenz CT, Hansen A, Dupuis ND, Shultz N, Levinson SR, Finger TE, Dionne VE. NaV1.5 sodium channel window currents contribute to spontaneous firing in olfactory sensory neurons. J Neurophysiol 2014; 112:1091-104. [PMID: 24872539 DOI: 10.1152/jn.00154.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Olfactory sensory neurons (OSNs) fire spontaneously as well as in response to odor; both forms of firing are physiologically important. We studied voltage-gated Na(+) channels in OSNs to assess their role in spontaneous activity. Whole cell patch-clamp recordings from OSNs demonstrated both tetrodotoxin-sensitive and tetrodotoxin-resistant components of Na(+) current. RT-PCR showed mRNAs for five of the nine different Na(+) channel α-subunits in olfactory tissue; only one was tetrodotoxin resistant, the so-called cardiac subtype NaV1.5. Immunohistochemical analysis indicated that NaV1.5 is present in the apical knob of OSN dendrites but not in the axon. The NaV1.5 channels in OSNs exhibited two important features: 1) a half-inactivation potential near -100 mV, well below the resting potential, and 2) a window current centered near the resting potential. The negative half-inactivation potential renders most NaV1.5 channels in OSNs inactivated at the resting potential, while the window current indicates that the minor fraction of noninactivated NaV1.5 channels have a small probability of opening spontaneously at the resting potential. When the tetrodotoxin-sensitive Na(+) channels were blocked by nanomolar tetrodotoxin at the resting potential, spontaneous firing was suppressed as expected. Furthermore, selectively blocking NaV1.5 channels with Zn(2+) in the absence of tetrodotoxin also suppressed spontaneous firing, indicating that NaV1.5 channels are required for spontaneous activity despite resting inactivation. We propose that window currents produced by noninactivated NaV1.5 channels are one source of the generator potentials that trigger spontaneous firing, while the upstroke and propagation of action potentials in OSNs are borne by the tetrodotoxin-sensitive Na(+) channel subtypes.
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Affiliation(s)
| | - Anne Hansen
- Department of Cellular and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Anschutz Medical Center, Aurora, Colorado; and
| | | | - Nicole Shultz
- Department of Cellular and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Anschutz Medical Center, Aurora, Colorado; and
| | - Simon R Levinson
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Anschutz Medical Center, Aurora, Colorado
| | - Thomas E Finger
- Department of Cellular and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Anschutz Medical Center, Aurora, Colorado; and
| | - Vincent E Dionne
- Department of Biology, Boston University, Boston, Massachusetts;
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149
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Ono T, Hayashida M, Tezuka A, Hayakawa H, Ohno Y. Antagonistic effects of tetrodotoxin on aconitine-induced cardiac toxicity. J NIPPON MED SCH 2014; 80:350-61. [PMID: 24189353 DOI: 10.1272/jnms.80.350] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Aconitine, well-known for its high cardiotoxicity, causes severe arrhythmias, such as ventricular tachycardia and ventricular fibrillation, by opening membrane sodium channels. Tetrodotoxin, a membrane sodium-channel blocker, is thought to antagonize aconitine activity. Tetrodotoxin is a potent blocker of the skeletal muscle sodium-channel isoform Na(v)1.4 (IC50 10 nM), but micromolar concentrations of tetrodotoxin are required to inhibit the primary cardiac isoform Na(v)1.5. This suggests that substantial concentrations of tetrodotoxin are required to alleviate the cardiac toxicity caused by aconitine. To elucidate the interaction between aconitine and tetrodotoxin in the cardiovascular and respiratory systems, mixtures of aconitine and tetrodotoxin were simultaneously administered to mice, and the effects on electrocardiograms, breathing rates, and arterial oxygen saturation were examined. Compared with mice treated with aconitine alone, some mice treated with aconitine-tetrodotoxin mixtures showed lower mortality rates and delayed appearance of arrhythmia. The decreased breathing rates and arterial oxygen saturation observed in mice receiving aconitine alone were alleviated in mice that survived after receiving the aconitine-tetrodotoxin mixture; this result suggests that tetrodotoxin is antagonistic to aconitine. When the tetrodotoxin dose is greater than the dose that can block tetrodotoxin-sensitive sodium channels, which are excessively activated by aconitine, tetrodotoxin toxicity becomes prominent, and the mortality rate increases because of the respiratory effects of tetrodotoxin. In terms of cardiotoxicity, mice receiving the aconitine-tetrodotoxin mixture showed minor and shorter periods of change on electrocardiography. This finding can be explained by the recent discovery of tetrodotoxin-sensitive sodium-channel cardiac isoforms (Na(v)1.1, 1.2, 1.3, 1.4 and 1.6).
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150
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Lin WH, Baines RA. Regulation of membrane excitability: a convergence on voltage-gated sodium conductance. Mol Neurobiol 2014; 51:57-67. [PMID: 24677068 PMCID: PMC4309913 DOI: 10.1007/s12035-014-8674-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 03/11/2014] [Indexed: 11/30/2022]
Abstract
The voltage-gated sodium channel (Nav) plays a key role in regulation of neuronal excitability. Aberrant regulation of Nav expression and/or function can result in an imbalance in neuronal activity which can progress to epilepsy. Regulation of Nav activity is achieved by coordination of a multitude of mechanisms including RNA alternative splicing and translational repression. Understanding of these regulatory mechanisms is complicated by extensive genetic redundancy: the mammalian genome encodes ten Navs. By contrast, the genome of the fruitfly, Drosophila melanogaster, contains just one Nav homologue, encoded by paralytic (DmNa v ). Analysis of splicing in DmNa v shows variants exhibit distinct gating properties including varying magnitudes of persistent sodium current (INaP). Splicing by Pasilla, an identified RNA splicing factor, alters INaP magnitude as part of an activity-dependent mechanism. Enhanced INaP promotes membrane hyperexcitability that is associated with seizure-like behaviour in Drosophila. Nova-2, a mammalian Pasilla homologue, has also been linked to splicing of Navs and, moreover, mouse gene knockouts display seizure-like behaviour.Expression level of Navs is also regulated through a mechanism of translational repression in both flies and mammals. The translational repressor Pumilio (Pum) can bind to Na v transcripts and repress the normal process of translation, thus regulating sodium current (INa) density in neurons. Pum2-deficient mice exhibit spontaneous EEG abnormalities. Taken together, aberrant regulation of Nav function and/or expression is often epileptogenic. As such, a better understanding of regulation of membrane excitability through RNA alternative splicing and translational repression of Navs should provide new leads to treat epilepsy.
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Affiliation(s)
- Wei-Hsiang Lin
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK
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