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Heinle JW, Dalessio S, Janicki P, Ouyang A, Vrana KE, Ruiz-Velasco V, Coates MD. Insights into the voltage-gated sodium channel, Na V1.8, and its role in visceral pain perception. Front Pharmacol 2024; 15:1398409. [PMID: 38855747 PMCID: PMC11158627 DOI: 10.3389/fphar.2024.1398409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Accepted: 04/29/2024] [Indexed: 06/11/2024] Open
Abstract
Pain is a major issue in healthcare throughout the world. It remains one of the major clinical issues of our time because it is a common sequela of numerous conditions, has a tremendous impact on individual quality of life, and is one of the top drivers of cost in medicine, due to its influence on healthcare expenditures and lost productivity in those affected by it. Patients and healthcare providers remain desperate to find new, safer and more effective analgesics. Growing evidence indicates that the voltage-gated sodium channel Nav1.8 plays a critical role in transmission of pain-related signals throughout the body. For that reason, this channel appears to have strong potential to help develop novel, more selective, safer, and efficacious analgesics. However, many questions related to the physiology, function, and clinical utility of Nav1.8 remain to be answered. In this article, we discuss the latest studies evaluating the role of Nav1.8 in pain, with a particular focus on visceral pain, as well as the steps taken thus far to evaluate its potential as an analgesic target. We also review the limitations of currently available studies related to this topic, and describe the next scientific steps that have already been undertaken, or that will need to be pursued, to fully unlock the capabilities of this potential therapeutic target.
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Affiliation(s)
- J. Westley Heinle
- Division of Gastroenterology and Hepatology, Penn State College of Medicine, Hershey, PA, United States
| | - Shannon Dalessio
- Division of Gastroenterology and Hepatology, Penn State College of Medicine, Hershey, PA, United States
| | - Piotr Janicki
- Department of Anesthesiology and Perioperative Medicine, Penn State College of Medicine, Hershey, PA, United States
| | - Ann Ouyang
- Division of Gastroenterology and Hepatology, Penn State College of Medicine, Hershey, PA, United States
| | - Kent E. Vrana
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
| | - Victor Ruiz-Velasco
- Department of Anesthesiology and Perioperative Medicine, Penn State College of Medicine, Hershey, PA, United States
| | - Matthew D. Coates
- Division of Gastroenterology and Hepatology, Penn State College of Medicine, Hershey, PA, United States
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
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Structural basis for high-voltage activation and subtype-specific inhibition of human Na v1.8. Proc Natl Acad Sci U S A 2022; 119:e2208211119. [PMID: 35858452 PMCID: PMC9335304 DOI: 10.1073/pnas.2208211119] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Pain management represents an unmet healthcare need in many countries. Nav1.8 represents a potential target for developing nonaddictive analgesics. Here we present the cryogenic electron microscopy (cryo-EM) structures of human Nav1.8 alone and bound to a selective pore blocker, A-803467. Unlike reported structures of eukaryotic Nav channels wherein the first voltage-sensing domain (VSDI) is well-resolved in one stable conformation, different conformations of VSDI are observed in the cryo-EM maps of Nav1.8. An extracellular interface between VSDI and the pore domain was identified to be a determinant for Nav1.8’s dependence on higher voltage for activation. A-803467 clenches S6IV within the central cavity. Unexpectedly, the channel selectivity for A-803467 is determined by nonligand coordinating residues through an allosteric mechanism. The dorsal root ganglia–localized voltage-gated sodium (Nav) channel Nav1.8 represents a promising target for developing next-generation analgesics. A prominent characteristic of Nav1.8 is the requirement of more depolarized membrane potential for activation. Here we present the cryogenic electron microscopy structures of human Nav1.8 alone and bound to a selective pore blocker, A-803467, at overall resolutions of 2.7 to 3.2 Å. The first voltage-sensing domain (VSDI) displays three different conformations. Structure-guided mutagenesis identified the extracellular interface between VSDI and the pore domain (PD) to be a determinant for the high-voltage dependence of activation. A-803467 was clearly resolved in the central cavity of the PD, clenching S6IV. Our structure-guided functional characterizations show that two nonligand binding residues, Thr397 on S6I and Gly1406 on S6III, allosterically modulate the channel’s sensitivity to A-803467. Comparison of available structures of human Nav channels suggests the extracellular loop region to be a potential site for developing subtype-specific pore-blocking biologics.
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The transition from acute to chronic pain: dynamic epigenetic reprogramming of the mouse prefrontal cortex up to 1 year after nerve injury. Pain 2021; 161:2394-2409. [PMID: 32427748 PMCID: PMC7497614 DOI: 10.1097/j.pain.0000000000001917] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Supplemental Digital Content is Available in the Text. DNA methylation undergoes rapid and large changes in mouse prefrontal cortex at multiple time points postinjury, implicating hundreds of genes in a time-dependent manner. Chronic pain is associated with persistent structural and functional changes throughout the neuroaxis, including in the prefrontal cortex (PFC). The PFC is important in the integration of sensory, cognitive, and emotional information and in conditioned pain modulation. We previously reported widespread epigenetic reprogramming in the PFC many months after nerve injury in rodents. Epigenetic modifications, including DNA methylation, can drive changes in gene expression without modifying DNA sequences. To date, little is known about epigenetic dysregulation at the onset of acute pain or how it progresses as pain transitions from acute to chronic. We hypothesize that acute pain after injury results in rapid and persistent epigenetic remodelling in the PFC that evolves as pain becomes chronic. We further propose that understanding epigenetic remodelling will provide insights into the mechanisms driving pain-related changes in the brain. Epigenome-wide analysis was performed in the mouse PFC 1 day, 2 weeks, 6 months, and 1 year after peripheral injury using the spared nerve injury in mice. Spared nerve injury resulted in rapid and persistent changes in DNA methylation, with robust differential methylation observed between spared nerve injury and sham-operated control mice at all time points. Hundreds of differentially methylated genes were identified, including many with known function in pain. Pathway analysis revealed enrichment in genes related to stimulus response at early time points, immune function at later time points, and actin and cytoskeletal regulation throughout the time course. These results emphasize the importance of considering pain chronicity in both pain research and in treatment optimization.
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Cohen E, Kumar R, Zinger T, Priel A, Treinin M. GTL-1, a Calcium Activated TRPM Channel, Enhances Nociception. Front Pharmacol 2020; 10:1567. [PMID: 32009965 PMCID: PMC6978279 DOI: 10.3389/fphar.2019.01567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 12/03/2019] [Indexed: 12/23/2022] Open
Abstract
C. elegans PVD neurons are conserved for morphology, function and molecular determinants with mammalian polymodal nociceptors. Functions of polymodal nociceptors require activities of multiple ion channels and receptors including members of the TRP family. GTL-1, a member of the TRPM subclass of TRP channels, was previously shown to amplify PVD-mediated responses to optogenetic stimuli. Here we characterize effects of GTL-1 on PVD-mediated behavioral responses to noxious stimuli. We show that GTL-1 is required within PVD for the immediate and enduring response to thermal (cold) stimuli. But, find no significant reduction in percent animals responding to single or to repeated noxious mechanical stimuli. Nevertheless, PVD specific knockdown of gtl-1expression reduces the magnitude of responses to noxious mechanical stimuli. To understand GTL-1's mechanism of action we expressed it in HEK293 cells. Our results show GTL-1-dependent currents induced by activation of a Gαq-coupled Designer Receptor Exclusively Activated by Designer Drugs (DREADD). In addition, using excised patches we show that GTL-1 can be activated by internal calcium. Our results are consistent with indirect, calcium dependent, activation of GTL-1 by noxious stimuli. This mechanism explains the GTL-1-dependent amplification of responses to multiple stimuli optogenetic and sensory in PVD.
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Affiliation(s)
- Emiliano Cohen
- Department of Medical Neurobiology, Hadassah-Medical School, Jerusalem, Israel
| | - Rakesh Kumar
- Faculty of Medicine, School of Pharmacy, The Institute for Drug Research, Hebrew University, Jerusalem, Israel
| | - Tal Zinger
- Department of Medical Neurobiology, Hadassah-Medical School, Jerusalem, Israel
| | - Avi Priel
- Faculty of Medicine, School of Pharmacy, The Institute for Drug Research, Hebrew University, Jerusalem, Israel
| | - Millet Treinin
- Department of Medical Neurobiology, Hadassah-Medical School, Jerusalem, Israel
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Coates MD, Vrana KE, Ruiz-Velasco V. The influence of voltage-gated sodium channels on human gastrointestinal nociception. Neurogastroenterol Motil 2019; 31:e13460. [PMID: 30216585 DOI: 10.1111/nmo.13460] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 08/01/2018] [Accepted: 08/07/2018] [Indexed: 12/14/2022]
Abstract
BACKGROUND Abdominal pain is a frequent and persistent problem in the most common gastrointestinal disorders, including irritable bowel syndrome and inflammatory bowel disease. Pain adversely impacts quality of life, incurs significant healthcare expenditures, and remains a challenging issue to manage with few safe therapeutic options currently available. It is imperative that new methods are developed for identifying and treating this symptom. A variety of peripherally active neuroendocrine signaling elements have the capability to influence gastrointestinal pain perception. A large and growing body of evidence suggests that voltage-gated sodium channels (VGSCs) play a critical role in the development and modulation of nociceptive signaling associated with the gut. Several VGSC isoforms demonstrate significant promise as potential targets for improved diagnosis and treatment of gut-based disorders associated with hyper- and hyposensitivity to abdominal pain. PURPOSE In this article, we critically review key investigations that have evaluated the potential role that VGSCs play in visceral nociception and discuss recent advances related to this topic. Specifically, we discuss the following: (a) what is known about the structure and basic function of VGSCs, (b) the role that each VGSC plays in gut nociception, particularly as it relates to human physiology, and (c) potential diagnostic and therapeutic uses of VGSCs to manage disorders associated with chronic abdominal pain.
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Affiliation(s)
- Matthew D Coates
- Division of Gastroenterology & Hepatology, Department of Medicine, Penn State University College of Medicine, Hershey, Pennsylvania
| | - Kent E Vrana
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania
| | - Victor Ruiz-Velasco
- Department of Anesthesiology and Perioperative Medicine, Penn State University College of Medicine, Hershey, Pennsylvania
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Patel R, Kucharczyk M, Montagut‐Bordas C, Lockwood S, Dickenson AH. Neuropathy following spinal nerve injury shares features with the irritable nociceptor phenotype: A back-translational study of oxcarbazepine. Eur J Pain 2019; 23:183-197. [PMID: 30091265 PMCID: PMC6396087 DOI: 10.1002/ejp.1300] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 07/24/2018] [Accepted: 07/31/2018] [Indexed: 12/30/2022]
Abstract
BACKGROUND The term 'irritable nociceptor' was coined to describe neuropathic patients characterized by evoked hypersensitivity and preservation of primary afferent fibres. Oxcarbazepine is largely ineffectual in an overall patient population, but has clear efficacy in a subgroup with the irritable nociceptor profile. We examine whether neuropathy in rats induced by spinal nerve injury shares overlapping pharmacological sensitivity with the irritable nociceptor phenotype using drugs that target sodium channels. METHODS In vivo electrophysiology was performed in anaesthetized spinal nerve ligated (SNL) and sham-operated rats to record from wide dynamic range (WDR) neurones in the ventral posterolateral thalamus (VPL) and dorsal horn. RESULTS In neuropathic rats, spontaneous activity in the VPL was substantially attenuated by spinal lidocaine, an effect that was absent in sham rats. The former measure was in part dependent on ongoing peripheral activity as intraplantar lidocaine also reduced aberrant spontaneous thalamic firing. Systemic oxcarbazepine had no effect on wind-up of dorsal horn neurones in sham and SNL rats. However, in SNL rats, oxcarbazepine markedly inhibited punctate mechanical-, dynamic brush- and cold-evoked neuronal responses in the VPL and dorsal horn, with minimal effects on heat-evoked responses. In addition, oxcarbazepine inhibited spontaneous activity in the VPL. Intraplantar injection of the active metabolite licarbazepine replicated the effects of systemic oxcarbazepine, supporting a peripheral locus of action. CONCLUSIONS We provide evidence that ongoing activity in primary afferent fibres drives spontaneous thalamic firing after spinal nerve injury and that oxcarbazepine through a peripheral mechanism exhibits modality-selective inhibitory effects on sensory neuronal processing. SIGNIFICANCE The inhibitory effects of lidocaine and oxcarbazepine in this rat model of neuropathy resemble the clinical observations in the irritable nociceptor patient subgroup and support a mechanism-based rationale for bench-to-bedside translation when screening novel drugs.
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Affiliation(s)
- Ryan Patel
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonLondonUK
| | - Mateusz Kucharczyk
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonLondonUK
| | | | - Stevie Lockwood
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonLondonUK
| | - Anthony H. Dickenson
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonLondonUK
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Akiyama T, Nagamine M, Davoodi A, Ivanov M, Carstens MI, Carstens E. Innocuous warming enhances peripheral serotonergic itch signaling and evokes enhanced responses in serotonin-responsive dorsal horn neurons in the mouse. J Neurophysiol 2017; 117:251-259. [PMID: 27784810 PMCID: PMC5220113 DOI: 10.1152/jn.00703.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/19/2016] [Indexed: 11/22/2022] Open
Abstract
Itch is often triggered by warming the skin in patients with itchy dermatitis, but the underlying mechanism is largely unknown. We presently investigated if warming the skin enhances histamine- or serotonin (5-HT)-evoked itch behavior or responses of sensory dorsal root ganglion (DRG) cells, and if responses of superficial dorsal horn neurons to innocuous warming are enhanced by these pruritogens. In a temperature-controlled environmental chamber, mice exhibited greater scratching following intradermal injection of 5-HT, but not histamine, SLIGRL, or BAM8-22, when the skin surface temperature was above 36°C. Calcium imaging of DRG cells in a temperature-controlled bath revealed that responses to 5-HT, but not histamine, were significantly greater at a bath temperature of 35°C vs. lower temperatures. Single-unit recordings revealed a subpopulation of superficial dorsal horn neurons responsive to intradermal injection of 5-HT. Of these, 58% responded to innocuous skin warming (37°C) prior to intradermal injection of 5-HT, while 100% responded to warming following intradermal injection of 5-HT. Warming-evoked responses were superimposed on the 5-HT-evoked elevation in firing and were significantly larger compared with responses pre-5-HT, as long as 30 min after the intradermal injection of 5-HT. Five-HT-insensitive units, and units that either did or did not respond to intradermal histamine, did not exhibit any increase in the incidence of warmth sensitivity or in the mean response to warming following intradermal injection of the pruritogen. The results suggest that 5-HT-evoked responses of pruriceptors are enhanced during skin warming, leading to increased firing of 5-HT-sensitive dorsal horn neurons that signal nonhistaminergic itch. NEW & NOTEWORTHY Skin warming often exacerbates itch in patients with itchy dermatitis. We demonstrate that warming the skin enhanced serotonin-evoked, but not histamine-evoked, itch behavior and responses of sensory dorsal root ganglion cells. Moreover, serotonin, but not histamine, enhanced responses of superficial dorsal horn neurons to innocuous warming. The results suggest that skin warming selectively enhances the responses of serotonin-sensitive pruriceptors, leading to increased firing of serotonin-sensitive dorsal horn neurons that signal nonhistaminergic itch.
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Affiliation(s)
- T Akiyama
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
- Departments of Dermatology, Anatomy, and Cell Biology, Temple Itch Center, Temple University, Philadelphia, Pennsylvania
| | - M Nagamine
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - A Davoodi
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - M Ivanov
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - M Iodi Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - E Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
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Ye P, Hua L, Jiao Y, Li Z, Qin S, Fu J, Jiang F, Liu T, Ji Y. Functional up-regulation of Nav1.8 sodium channel on dorsal root ganglia neurons contributes to the induction of scorpion sting pain. Acta Biochim Biophys Sin (Shanghai) 2016; 48:132-44. [PMID: 26764239 DOI: 10.1093/abbs/gmv123] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 08/02/2015] [Indexed: 12/19/2022] Open
Abstract
BmK I, purified from the venom of scorpion Buthus martensi Karsch (BmK), is a receptor site-3-specific modulator of voltage-gated sodium channels (VGSCs) and can induce pain-related behaviors in rats. The tetrodotoxin-resistant (TTX-R) sodium channel Nav1.8 contributes to most of the sodium current underlying the action potential upstroke in dorsal root ganglia (DRG) neurons and may serve as a critical ion channel targeted by BmK I. Herein, using electrophysiological, molecular, and behavioral approaches, we investigated whether the aberrant expression of Nav1.8 in DRG contributes to generation of pain induced by BmK I. The expression of Nav1.8 was found to be significantly increased at both mRNA and protein levels following intraplantar injection of BmK I in rats. In addition, the current density of TTX-R Nav1.8 sodium channel is significantly increased and the gating kinetics of Nav1.8 is also altered in DRG neurons from BmK I-treated rats. Furthermore, spontaneous pain and mechanical allodynia, but not thermal hyperalgesia induced by BmK I, are significantly alleviated through either blockade of the Nav1.8 sodium channel by its selective blocker A-803467 or knockdown of the Nav1.8 expression in DRG by antisense oligodeoxynucleotide (AS-ODN) targeting Nav1.8 in rats. Finally, BmK I was shown to induce enhanced pain behaviors in complete freund's adjuvant (CFA)-inflamed rats, which was partly due to the over-expression of Nav1.8 in DRG. Our results suggest that functional up-regulation of Nav1.8 channel on DRG neurons contributes to the development of BmK I-induced pain in rats.
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Affiliation(s)
- Pin Ye
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
| | - Liming Hua
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
| | - Yunlu Jiao
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
| | - Zhenwei Li
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
| | - Shichao Qin
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
| | - Jin Fu
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
| | - Feng Jiang
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
| | - Tong Liu
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and Institute of Neuroscience, Soochow University, Suzhou 215021, China
| | - Yonghua Ji
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200436, China
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Role for monocyte chemoattractant protein-1 in the induction of chronic muscle pain in the rat. Pain 2014; 155:1161-1167. [PMID: 24637038 DOI: 10.1016/j.pain.2014.03.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 02/27/2014] [Accepted: 03/06/2014] [Indexed: 01/25/2023]
Abstract
While raised levels of monocyte chemoattractant protein 1 (MCP-1) have been observed in patients with chronic muscle pain, direct evidence for its role as an algogen in skeletal muscle is still lacking. In the rat, MCP-1 induces a dose-dependent mechanical hyperalgesia lasting for up to 6weeks. Following recovery, rats exhibited a markedly prolonged hyperalgesia to an intramuscular injection of prostaglandin E2, hyperalgesic priming. Intrathecal pretreatment with isolectin B4 (IB4)-saporin, which selectively destroys IB4-positive (IB4+) nociceptors, markedly decreased MCP-1-induced hyperalgesia and prevented the subsequent development of priming. To evaluate the involvement of MCP-1 in stress-induced chronic pain we administered, intrathecally, antisense (AS) or mismatch oligodeoxynucleotides directed against CCR2 (the canonical receptor for MCP-1) mRNA, during the exposure to water-avoidance stress, a model of stress-induced persistent muscle pain. The AS treatment attenuated this hyperalgesia, whereas IB4-saporin abolished water-avoidance stress-induced muscle hyperalgesia and prevented stress-induced hyperalgesic priming. These results indicate that MCP-1 induces persistent muscle hyperalgesia and a state of latent chronic sensitization to other algogens, by action on its cognate receptor on IB4+ nociceptors. Because MCP-1 also contributes to stress-induced widespread chronic muscle pain, it should be considered as a player in chronic musculoskeletal pain syndromes.
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Blockade of Nav1.8 Currents in Nociceptive Trigeminal Neurons Contributes to Anti-trigeminovascular Nociceptive Effect of Amitriptyline. Neuromolecular Med 2013; 16:308-21. [DOI: 10.1007/s12017-013-8282-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 11/08/2013] [Indexed: 01/22/2023]
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Kalezic I, Steffens H. Changes in tetrodotoxin-resistant C-fibre activity during fatiguing isometric contractions in the rat. PLoS One 2013; 8:e73980. [PMID: 24040134 PMCID: PMC3764014 DOI: 10.1371/journal.pone.0073980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Accepted: 08/01/2013] [Indexed: 11/18/2022] Open
Abstract
It is by now well established that tetrodotoxin-resistant (TTX-R) afferent fibres from muscle in the rat exhibit a multisensitive profile, including nociception. TTX-R afferent fibres play an important role in motor control, via spinal and supraspinal loops, but their activation and function during muscle exercise and fatigue are still unknown. Therefore, the specific effect of isometric fatiguing muscle contraction on the responsiveness of TTX-R C-fibres has been investigated in this study. To quantify the TTX-R afferent input we recorded the cord dorsum potential (CDP), which is the result of the electrical fields set up within the spinal cord by the depolarisation of the interneurons located in the dorsal horn, activated by an incoming volley of TTX-R muscle afferents. The changes in TTX-R CDP size before, during and after fatiguing electrical stimulation of the gastrocnemius-soleus (GS) muscle have been taken as a measure of TTX-R C-unit activation. At the end of the fatiguing protocol, following an exponential drop in force, TTX-R CDP area decreased in the majority of trials (9/14) to 0.75±0.03% (mean ± SEM) of the pre-fatigue value. Recovery to the control size of the TTX-R CDP was incomplete after 10 min. Furthermore, fatiguing trials could sensitise a fraction of the TTX-R C-fibres responding to muscle pinch. The results suggest a long-lasting activation of the TTX-R muscle afferents after fatiguing stimulation. The role of this behaviour in chronic muscle fatigue in connection with pain development is discussed. Accumulation of metabolites released into the interstitium during fatiguing stimulation might be one of the reasons underlying the C-fibres’ long-lasting activation.
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Affiliation(s)
- Ivana Kalezic
- Department of Surgical and Perioperative Science, Sport Medicine Unit, Umeå University, Umeå, Sweden
- Centre for Musculoskeletal Research, University of Gävle, Umeå, Sweden
- * E-mail:
| | - Heinz Steffens
- Institute of Physiology, University of Göttingen, Göttingen, Germany
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12
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Pristerà A, Baker MD, Okuse K. Association between tetrodotoxin resistant channels and lipid rafts regulates sensory neuron excitability. PLoS One 2012; 7:e40079. [PMID: 22870192 PMCID: PMC3411591 DOI: 10.1371/journal.pone.0040079] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 06/05/2012] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) play a key role in the initiation and propagation of action potentials in neurons. NaV1.8 is a tetrodotoxin (TTX) resistant VGSC expressed in nociceptors, peripheral small-diameter neurons able to detect noxious stimuli. NaV1.8 underlies the vast majority of sodium currents during action potentials. Many studies have highlighted a key role for NaV1.8 in inflammatory and chronic pain models. Lipid rafts are microdomains of the plasma membrane highly enriched in cholesterol and sphingolipids. Lipid rafts tune the spatial and temporal organisation of proteins and lipids on the plasma membrane. They are thought to act as platforms on the membrane where proteins and lipids can be trafficked, compartmentalised and functionally clustered. In the present study we investigated NaV1.8 sub-cellular localisation and explored the idea that it is associated with lipid rafts in nociceptors. We found that NaV1.8 is distributed in clusters along the axons of DRG neurons in vitro and ex vivo. We also demonstrated, by biochemical and imaging studies, that NaV1.8 is associated with lipid rafts along the sciatic nerve ex vivo and in DRG neurons in vitro. Moreover, treatments with methyl-β-cyclodextrin (MβCD) and 7-ketocholesterol (7KC) led to the dissociation between rafts and NaV1.8. By calcium imaging we demonstrated that the lack of association between rafts and NaV1.8 correlated with impaired neuronal excitability, highlighted by a reduction in the number of neurons able to conduct mechanically- and chemically-evoked depolarisations. These findings reveal the sub-cellular localisation of NaV1.8 in nociceptors and highlight the importance of the association between NaV1.8 and lipid rafts in the control of nociceptor excitability.
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Affiliation(s)
- Alessandro Pristerà
- Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
| | - Mark D. Baker
- Neuroscience and Trauma Centre, Blizard Institute, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, London, United Kingdom
| | - Kenji Okuse
- Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
- * E-mail:
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Abstract
PURPOSE OF REVIEW Visceral pain represents a major clinical problem, yet far less is known about its mechanisms compared with somatic pains, for example, from cutaneous and muscular structures. RECENT FINDINGS In this review, we describe the neuroanatomical bases of visceral pain signalling in the peripheral and central nervous system, comparing to somatic pains and also the channels and receptors involved in these events. We include an overview of potential new targets in the context of mechanisms of visceral pain and hypersensitivity. SUMMARY This review should inform on the recognition of what occurs in patients with visceral pain, why comorbidities are common and how analgesic treatments work.
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Affiliation(s)
- Shafaq Sikandar
- Department of Neuroscience, Physiology and Pharmacology University College London, London UK.
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Jennings EA, Williams MC, Staikopoulos V, Ivanusic JJ. Neurobiology of Temporomandibular Joint Pain: Therapeutic Implications. Semin Orthod 2012. [DOI: 10.1053/j.sodo.2011.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Moon JY, Song S, Yoon SY, Roh DH, Kang SY, Park JH, Beitz AJ, Lee JH. The differential effect of intrathecal Nav1.8 blockers on the induction and maintenance of capsaicin- and peripheral ischemia-induced mechanical allodynia and thermal hyperalgesia. Anesth Analg 2011; 114:215-23. [PMID: 22127815 DOI: 10.1213/ane.0b013e318238002e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND It has been reported that the selective blockade of Nav1.8 sodium channels could be a possible target for the development of analgesics without unwanted side effects. However, the precise role of spinal Nav1.8 in the induction and maintenance of persistent pain, e.g., mechanical allodynia (MA) and thermal hyperalgesia (TH), is not clear. We designed this study to investigate whether spinal Nav1.8 contributes to capsaicin-induced and peripheral ischemia-induced MA and TH. METHODS The Nav1.8 blockers, A-803467 or ambroxol, were injected intrathecally either before or after intraplantar capsaicin injection. To evaluate capsaicin-induced neuronal activation in the spinal cord, we quantified the number of Fos-immunoreactive cells in the dorsal horn. In the thrombus-induced ischemic pain model, we determined the differential effect of A-803467 on the induction phase or maintenance phase of MA. RESULTS Intrathecal injection of A-803467 (10, 30, 100 nmol) or ambroxol (241, 724, 2410 nmol) before intraplantar injection of capsaicin dose dependently prevented the induction of both MA and TH. However, posttreatment with A-803467 (100 nmol) and ambroxol (2410 nmol) did not reduce the MA that had already developed, but did significantly suppress capsaicin-induced TH. Moreover, the capsaicin-induced increase of spinal Fos-immunoreactive cells was significantly diminished by pretreatment, but not posttreatment with Nav1.8 blockers. In thrombus-induced ischemic pain rats, repetitive treatments of A-803467 during the induction period also prevented the development of MA, whereas A-803467 treatments during the maintenance period were ineffective in preventing or reducing MA. CONCLUSIONS These results demonstrate that spinal activation of Nav1.8 mediates the early induction of MA, but not the maintenance of MA. However, both the induction and maintenance of TH are modulated by the intrathecal injection of Nav1.8 blockers. These findings suggest that early treatment with a Nav1.8 blocker can be an important factor in the clinical management of chronic MA associated with inflammatory and ischemic pain.
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Affiliation(s)
- Ji-Young Moon
- Department of Veterinary Physiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, South Korea
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16
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Fukuoka T, Noguchi K. Comparative study of voltage-gated sodium channel α-subunits in non-overlapping four neuronal populations in the rat dorsal root ganglion. Neurosci Res 2011; 70:164-71. [PMID: 21303679 DOI: 10.1016/j.neures.2011.01.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/20/2011] [Accepted: 01/28/2011] [Indexed: 12/23/2022]
Abstract
Voltage-gated sodium channel α-subunit (Nav) is the major determinant of neuronal electrophysiological characters. In order to compare the composition of Navs among neurochemically different neurons in the rat dorsal root ganglion (DRG), we examined the expression of Nav transcripts in four non-overlapping neuronal populations, with (+) or without (-) N52 immunoreactivity, a marker of neurons with myelinated axons, and TrkA mRNA identified by in situ hybridization histochemistry. Both N52-/TrkA+ and N52-/TrkA- populations had high levels of signals for Nav1.7, Nav1.8, and Nav1.9 mRNAs, but rarely expressed Nav1.1 or Nav1.6. There was no significant difference in these signals, suggesting that C-fiber peptidergic and non-peptidergic neurons have similar electrophysiological characters with regard to sodium currents. N52+/TrkA+ neurons (putative A-fiber nociceptors) had similar high levels of signals for Nav1.7 and Nav1.8, but a significantly lower level of Nav1.9 signals, as compared to N52- neurons. Although, almost no N52+/TrkA- neurons had Nav1.8 or Nav1.9, half of this population expressed Nav1.7 at similar levels to other three populations and the other half completely lacked this channel. These data suggest that Nav1.8 is a common channel for both C- and A-fiber nociceptors, and Nav1.9 is rather selective for C-fiber nociceptors. Nav1.7 is the most universal channel while some functionally unknown N52+/TrkA- subpopulation selectively lacks it.
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Affiliation(s)
- Tetsuo Fukuoka
- Department of Anatomy & Neuroscience, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan.
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17
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Abstract
Nociception is essential for survival whereas pathological pain is maladaptive and often unresponsive to pharmacotherapy. Voltage-gated sodium channels, Na(v)1.1-Na(v)1.9, are essential for generation and conduction of electrical impulses in excitable cells. Human and animal studies have identified several channels as pivotal for signal transmission along the pain axis, including Na(v)1.3, Na(v)1.7, Na(v)1.8, and Na(v)1.9, with the latter three preferentially expressed in peripheral sensory neurons and Na(v)1.3 being upregulated along pain-signaling pathways after nervous system injuries. Na(v)1.7 is of special interest because it has been linked to a spectrum of inherited human pain disorders. Here we review the contribution of these sodium channel isoforms to pain.
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Affiliation(s)
- Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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18
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Governing role of primary afferent drive in increased excitation of spinal nociceptive neurons in a model of sciatic neuropathy. Exp Neurol 2008; 214:219-28. [PMID: 18773893 DOI: 10.1016/j.expneurol.2008.08.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 07/31/2008] [Accepted: 08/10/2008] [Indexed: 01/07/2023]
Abstract
Previously we reported that the cuff model of peripheral neuropathy, in which a 2 mm polyethylene tube is implanted around the sciatic nerve, exhibits aspects of neuropathic pain behavior in rats similar to those in humans and causes robust hyperexcitation of spinal nociceptive dorsal horn neurons. The mechanisms mediating this increased excitation are not known and remain a key unresolved question in models of peripheral neuropathy. In anesthetized adult male Sprague-Dawley rats 2-6 weeks after cuff implantation we found that elevated discharge rate of single lumbar (L(3-4)) wide dynamic range (WDR) neurons persists despite acute spinal transection (T9) but is reversed by local conduction block of the cuff-implanted sciatic nerve; lidocaine applied distal to the cuff (i.e. between the cuff and the cutaneous receptive field) decreased spontaneous baseline discharge of WDR dorsal horn neurons approximately 40% (n=18) and when applied subsequently proximal to the cuff, i.e. between the cuff and the spinal cord, it further reduced spontaneous discharge by approximately 60% (n=19; P<0.05 proximal vs. distal) to a level that was not significantly different from that of naive rats. Furthermore, in cuff-implanted rats WDR neurons (n=5) responded to mechanical cutaneous stimulation with an exaggerated afterdischarge which was reversed entirely by proximal nerve conduction block. These results demonstrate that the hyperexcited state of spinal dorsal horn neurons observed in this model of peripheral neuropathy is not maintained by tonic descending facilitatory mechanisms. Rather, on-going afferent discharges originating from the sciatic nerve distal to, at, and proximal to the cuff maintain the synaptically-mediated gain in discharge of spinal dorsal horn WDR neurons and hyperresponsiveness of these neurons to cutaneous stimulation. Our findings reveal that ectopic afferent activity from multiple regions along peripheral nerves may drive CNS changes and the symptoms of pain associated with peripheral neuropathy.
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19
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Abrahamsen B, Zhao J, Asante CO, Cendan CM, Marsh S, Martinez-Barbera JP, Nassar MA, Dickenson AH, Wood JN. The cell and molecular basis of mechanical, cold, and inflammatory pain. Science 2008; 321:702-5. [PMID: 18669863 DOI: 10.1126/science.1156916] [Citation(s) in RCA: 372] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Peripheral pain pathways are activated by a range of stimuli. We used diphtheria toxin to kill all mouse postmitotic sensory neurons expressing the sodium channel Nav1.8. Mice showed normal motor activity and low-threshold mechanical and acute noxious heat responses but did not respond to noxious mechanical pressure or cold. They also showed a loss of enhanced pain responses and spontaneous pain behavior upon treatment with inflammatory insults. In contrast, nerve injury led to heightened pain sensitivity to thermal and mechanical stimuli indistinguishable from that seen with normal littermates. Pain behavior correlates well with central input from sensory neurons measured electrophysiologically in vivo. These data demonstrate that Na(v)1.8-expressing neurons are essential for mechanical, cold, and inflammatory pain but not for neuropathic pain or heat sensing.
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Affiliation(s)
- Bjarke Abrahamsen
- Molecular Nociception Group, University College London (UCL), Gower Street, London, WC1E 6BT, UK
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20
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Martinez V, Melgar S. Lack of colonic-inflammation-induced acute visceral hypersensitivity to colorectal distension in Na(v)1.9 knockout mice. Eur J Pain 2008; 12:934-44. [PMID: 18280187 DOI: 10.1016/j.ejpain.2007.12.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 12/10/2007] [Accepted: 12/28/2007] [Indexed: 02/06/2023]
Abstract
Tetrodotoxin-resistant voltage-gated sodium channels subtype 9 (Na(v)1.9) are expressed in small-diameter dorsal root ganglion neurons and have been involved in persistent somatic hyperalgesic responses associated with inflammation. We assessed the role of Na(v)1.9 channels on acute colonic inflammation-induced visceral hypersensitivity in conscious mice, using Na(v)1.9 knockout (KO) mice. Colorectal distension (CRD)-induced visceral pain was assessed in conscious wild-type and Na(v)1.9 KO mice (C57Bl/6 background). The mechanical activity of the abdominal muscles during isobaric colorectal distension was used as a measure of visceral pain. Acute colonic inflammation was induced by intracolonic administration of the toll-like receptor (TLR) 7 activator, R-848 (40mug/animal). CRD was performed 5h later, thereafter animals were euthanized and the colonic content of inflammatory mediators assessed. Normal pain responses were similar in Na(v)1.9 KO and wild-type mice. In wild-type mice, R-848 administration increased the response to phasic CRD by 62% compared with vehicle-treated animals (vehicle: 0.16+/-0.04, R-848: 0.26+/-0.03, n=6-7, P<0.05). However, in Na(v)1.9 KO mice, intracolonic R-848 did not affect the response to CRD (0.11+/-0.02, n=7) compared to animals treated with vehicle (0.17+/-0.03, n=5; P>0.05). After R-848 administration, the colonic content of pro-inflammatory cytokines was increased in similar proportion in wild type and Na(v)1.9 KO mice, suggesting the presence of a similar acute inflammatory reaction in both groups of animals. These results suggest that Na(v)1.9 channels do not significantly contribute to normal visceral pain responses to acute colonic mechanical stimulation but may be important for the development of inflammation-related acute visceral hyperalgesic responses.
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Affiliation(s)
- V Martinez
- Integrative Pharmacology, Gastrointestinal Biology, AstraZeneca R&D Mölndal, Mölndal, Sweden.
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21
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McGaraughty S, Chu KL, Scanio MJC, Kort ME, Faltynek CR, Jarvis MF. A selective Nav1.8 sodium channel blocker, A-803467 [5-(4-chlorophenyl-N-(3,5-dimethoxyphenyl)furan-2-carboxamide], attenuates spinal neuronal activity in neuropathic rats. J Pharmacol Exp Ther 2007; 324:1204-11. [PMID: 18089840 DOI: 10.1124/jpet.107.134148] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We have recently reported that systemic delivery of A-803467 [5-(4-chlorophenyl-N-(3,5-dimethoxyphenyl)furan-2-carboxamide], a selective Na(v)1.8 sodium channel blocker, reduces behavioral measures of chronic pain. In the current study, the effects of A-803467 on evoked and spontaneous firing of wide dynamic range (WDR) neurons were measured in uninjured and rats with spinal nerve ligations (SNLs). Administration of A-803467 (10-30 mg/kg i.v.) reduced mechanically evoked (10-g von Frey hair) and spontaneous WDR neuronal activity in SNL rats. In uninjured rats, A-803467 (20 mg/kg i.v.) transiently reduced evoked but not spontaneous firing of WDR neurons. The systemic effects of A-803467 in SNL rats were not altered by spinal transection or by systemic pretreatment with the transient receptor potential vanilloid type 1 (TRPV1) receptor agonist, resiniferatoxin, at doses that impair the function of TRPV1-expressing fibers. To determine sites of action, A-803467 was administered into spinal tissue, into the uninjured L4 dorsal root ganglion (DRG), or into the neuronal receptive field. Injections of A-803467 into the L4 DRG (30-100 nmol/1 mul) or into the hindpaw receptive field (300 nmol/50 mul) reduced evoked but not spontaneous WDR firing. In contrast, intraspinal (50-150 nmol/0.5 mul) injection of A-803467 decreased both evoked and spontaneous discharges of WDR neurons. Thus, Na(v)1.8 sodium channels on the cell bodies/axons within the L4 DRG as well as on peripheral and central terminals of primary afferent neurons regulate the inflow of low-intensity mechanical signals to spinal WDR neurons. However, Na(v)1.8 sodium channels on central terminals seem to be key to the modulation of spontaneous firing in SNL rats.
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Affiliation(s)
- Steve McGaraughty
- Neuroscience Research, Abbott Laboratories, R4PM, AP9-1, 100 Abbott Park Rd., Abbott Park, IL 60064-6118, USA.
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22
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Zimmermann K, Leffler A, Babes A, Cendan CM, Carr RW, Kobayashi JI, Nau C, Wood JN, Reeh PW. Sensory neuron sodium channel Nav1.8 is essential for pain at low temperatures. Nature 2007; 447:855-8. [PMID: 17568746 DOI: 10.1038/nature05880] [Citation(s) in RCA: 299] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 04/25/2007] [Indexed: 12/19/2022]
Abstract
Sensory acuity and motor dexterity deteriorate when human limbs cool down, but pain perception persists and cold-induced pain can become excruciating. Evolutionary pressure to enforce protective behaviour requires that damage-sensing neurons (nociceptors) continue to function at low temperatures. Here we show that this goal is achieved by endowing superficial endings of slowly conducting nociceptive fibres with the tetrodotoxin-resistant voltage-gated sodium channel (VGSC) Na(v)1.8 (ref. 2). This channel is essential for sustained excitability of nociceptors when the skin is cooled. We show that cooling excitable membranes progressively enhances the voltage-dependent slow inactivation of tetrodotoxin-sensitive VGSCs. In contrast, the inactivation properties of Na(v)1.8 are entirely cold-resistant. Moreover, low temperatures decrease the activation threshold of the sodium currents and increase the membrane resistance, augmenting the voltage change caused by any membrane current. Thus, in the cold, Na(v)1.8 remains available as the sole electrical impulse generator in nociceptors that transmits nociceptive information to the central nervous system. Consistent with this concept is the observation that Na(v)1.8-null mutant mice show negligible responses to noxious cold and mechanical stimulation at low temperatures. Our data present strong evidence for a specialized role of Na(v)1.8 in nociceptors as the critical molecule for the perception of cold pain and pain in the cold.
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Affiliation(s)
- Katharina Zimmermann
- Department of Physiology and Pathophysiology, Faculty of Medicine, Friedrich-Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany.
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23
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Abstract
Light touch, a sense of muscle position, and the responses to tissue-damaging levels of pressure all involve mechanosensitive sensory neurons that originate in the dorsal root or trigeminal ganglia. A variety of mechanisms of mechanotransduction are proposed. These ranges from direct activation of mechanically activated channels at the tips of sensory neurons to indirect effects of intracellular mediators, or chemical signals released from distended tissues, or specialized mechanosensory end organs. This chapter describes the properties of mechanosensitive channels present in sensory neurons and the potential molecular candidates that may underlie. Mechanically regulated electrical activity by touch and tissue damaging levels of pressure in sensory neurons seems to involve a variety of direct and indirect mechanisms and ion channels, and the involvement of specialized end organs in mechanotransduction complicates matters even more. Imaging studies are providing useful information about the events in the central nervous system associated with touch pain and allodynia (a pathological state where touch becomes painful this type of activity).
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Affiliation(s)
- Liam J Drew
- Molecular Nociception Group, Biology Department, University College London, London WC1E 6BT, United Kingdom
| | - Francois Rugiero
- Molecular Nociception Group, Biology Department, University College London, London WC1E 6BT, United Kingdom
| | - John N Wood
- Molecular Nociception Group, Biology Department, University College London, London WC1E 6BT, United Kingdom
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24
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Foulkes T, Nassar MA, Lane T, Matthews EA, Baker MD, Gerke V, Okuse K, Dickenson AH, Wood JN. Deletion of annexin 2 light chain p11 in nociceptors causes deficits in somatosensory coding and pain behavior. J Neurosci 2006; 26:10499-507. [PMID: 17035534 PMCID: PMC6674704 DOI: 10.1523/jneurosci.1997-06.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The S100 family protein p11 (S100A10, annexin 2 light chain) is involved in the trafficking of the voltage-gated sodium channel Na(V)1.8, TWIK-related acid-sensitive K+ channel (TASK-1), the ligand-gated ion channels acid-sensing ion channel 1a (ASIC1a) and transient receptor potential vanilloid 5/6 (TRPV5/V6), as well as 5-hydroxytryptamine receptor 1B (5-HT1B), a G-protein-coupled receptor. To evaluate the role of p11 in peripheral pain pathways, we generated a loxP-flanked (floxed) p11 mouse and used the Cre-loxP recombinase system to delete p11 exclusively from nociceptive primary sensory neurons in mice. p11-null neurons showed deficits in the expression of Na(V)1.8, but not of annexin 2. Damage-sensing primary neurons from these animals show a reduced tetrodotoxin-resistant sodium current density, consistent with a loss of membrane-associated Na(V)1.8. Noxious coding in wide-dynamic-range neurons in the dorsal horn was markedly compromised. Acute pain behavior was attenuated in certain models, but no deficits in inflammatory pain were observed. A significant deficit in neuropathic pain behavior was also apparent in the conditional-null mice. These results confirm an important role for p11 in nociceptor function.
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Affiliation(s)
| | | | - Tim Lane
- Molecular Nociception Group, Department of Biology, and
| | - Elizabeth A. Matthews
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Mark D. Baker
- Molecular Nociception Group, Department of Biology, and
| | - Volker Gerke
- Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, University of Muenster, 48149 Muenster, Germany, and
| | - Kenji Okuse
- Division of Cell and Molecular Biology, Imperial College, London SW7 2AZ, United Kingdom
| | - Anthony H. Dickenson
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - John N. Wood
- Molecular Nociception Group, Department of Biology, and
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25
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Abstract
Our knowledge of the ion channels, receptors and signalling mechanisms involved in pain pathophysiology, and which specific channels play a role in subtypes of pain such as neuropathic and inflammatory pain, has expanded considerably in recent years. It is now clear that in the neuropathic state the expression of certain channels is modified, and that these changes underlie the plasticity of responses that occur to generate inappropriate pain signals from normally trivial inputs. Pain is modulated by a subset of the voltage-gated sodium channels, including Nav1.3, Nav1.7, Nav1.8 and Nav1.9. These isoforms display unique expression patterns within specific tissues, and are either up- or down-regulated upon injury to the nervous system. Here we describe our current understanding of the roles of sodium channels in pain and nociceptive information processing, with a particular emphasis on neuropathic pain and drugs useful for the treatment of neuropathic pain that act through mechanisms involving block of sodium channels. One of the future challenges in the development of novel sodium channel blockers is to design and synthesise isoform-selective channel inhibitors. This should provide substantial benefits over existing pain treatments.
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Affiliation(s)
- Marc Rogers
- Xention Ltd., Iconix Park, Pampisford, Cambridge CB2 4EF, United Kingdom
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26
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Hillsley K, Lin JH, Stanisz A, Grundy D, Aerssens J, Peeters PJ, Moechars D, Coulie B, Stead RH. Dissecting the role of sodium currents in visceral sensory neurons in a model of chronic hyperexcitability using Nav1.8 and Nav1.9 null mice. J Physiol 2006; 576:257-67. [PMID: 16857712 PMCID: PMC1995629 DOI: 10.1113/jphysiol.2006.113597] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Tetrodotoxin-resistant (TTX-R) sodium currents have been proposed to underlie sensory neuronal hyperexcitability in acute inflammatory models, but their role in chronic models is unknown. Since no pharmacological tools to separate TTX-R currents are available, this study employs Na(v)1.8 and Na(v)1.9 null mice to evaluate these currents roles in a chronic hyperexcitability model after the resolution of an inflammatory insult. Transient jejunitis was induced by infection with Nippostrongylus brasiliensis (Nb) in Na(v)1.9 and Na(v)1.8 null, wild-type and naïve mice. Retrogradely labelled dorsal root ganglia (DRG) neurons were harvested on day 20-24 post-infection for patch clamp recording. Rheobase and action potential (AP) parameters were recorded as measures of excitability, and Na(v)1.9 and Na(v)1.8 currents were recorded. DRG neuronal excitability was significantly increased in post-infected mice compared to sham animals, despite the absence of ongoing inflammation (sham = 1.9 +/- 0.3, infected = 3.6 +/- 0.7 APs at 2x rheobase, P = 0.02). Hyperexcitability was associated with a significantly increased amplitude of TTX-R currents. Hyperexcitability was maintained in Na(v)1.9(-/-) mice, but hyperexcitability was absent and APs were blunted in Na(v)1.8(-/-) mice. This study identifies a critical role for Na(v)1.8 in chronic post-infectious visceral hyperexcitability, with no contribution from Na(v)1.9. Nb infection-induced hyperexcitability is not observed in Na(v)1.8(-/-) mice, but is still present in Na(v)1.9(-/-) mice. It is not clear whether hyperexcitability is due to a change in the function of Na(v)1.8 channels or a change in the number of Na(v)1.8 channels.
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MESH Headings
- Action Potentials/drug effects
- Action Potentials/physiology
- Amino Acid Sequence
- Anesthetics, Local/pharmacology
- Animals
- Cells, Cultured
- Electrophysiology
- Ganglia, Spinal/metabolism
- Ganglia, Spinal/pathology
- Ganglia, Spinal/physiology
- Ganglia, Spinal/physiopathology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Knockout
- Molecular Sequence Data
- NAV1.8 Voltage-Gated Sodium Channel
- NAV1.9 Voltage-Gated Sodium Channel
- Neurons, Afferent/metabolism
- Neurons, Afferent/pathology
- Neurons, Afferent/physiology
- Neuropeptides/analysis
- Neuropeptides/drug effects
- Neuropeptides/genetics
- Neuropeptides/physiology
- Nippostrongylus
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Sodium Channels/analysis
- Sodium Channels/drug effects
- Sodium Channels/genetics
- Sodium Channels/physiology
- Strongylida Infections/pathology
- Strongylida Infections/physiopathology
- Tetrodotoxin/pharmacology
- Viscera/innervation
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Affiliation(s)
- Kirk Hillsley
- Holburn Group, 1100 Bennett Road, Bowmanville, Canada ON L1C 3K5
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