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Xu S, Wang Y. Transient Receptor Potential Channels: Multiple Modulators of Peripheral Neuropathic Pain in Several Rodent Models. Neurochem Res 2024; 49:872-886. [PMID: 38281247 DOI: 10.1007/s11064-023-04087-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Revised: 11/22/2023] [Accepted: 12/16/2023] [Indexed: 01/30/2024]
Abstract
Neuropathic pain, a prevalent chronic condition in clinical settings, has attracted widespread societal attention. This condition is characterized by a persistent pain state accompanied by affective and cognitive disruptions, significantly impacting patients' quality of life. However, current clinical therapies fall short of addressing its complexity. Thus, exploring the underlying molecular mechanism of neuropathic pain and identifying potential targets for intervention is highly warranted. The transient receptor potential (TRP) receptors, a class of widely distributed channel proteins, in the nervous system, play a crucial role in sensory signaling, cellular calcium regulation, and developmental influences. TRP ion channels are also responsible for various sensory responses including heat, cold, pain, and stress. This review highlights recent advances in understanding TRPs in various rodent models of neuropathic pain, aiming to uncover potential therapeutic targets for clinical management.
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Affiliation(s)
- Songchao Xu
- Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, No. 95, Yong'an Road, Xicheng District, Beijing, 100050, China
| | - Yun Wang
- Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, No. 95, Yong'an Road, Xicheng District, Beijing, 100050, China.
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2
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Escobar-Sánchez I, Ríos-León M, Taylor J. Long-term bilateral change in pain and sensitivity to high-frequency cutaneous electrical stimulation in healthy subjects depends on stimulus modality: a dermatomal examination. Front Med (Lausanne) 2024; 10:1337711. [PMID: 38293302 PMCID: PMC10825033 DOI: 10.3389/fmed.2023.1337711] [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: 11/13/2023] [Accepted: 12/30/2023] [Indexed: 02/01/2024] Open
Abstract
Introduction Contradictory changes in pain and sensitivity at long-term following cutaneous 100 Hz high frequency stimulation (HFS) have been previously observed. Thus, we aimed to document long-lasting changes in multimodal sensitivity following HFS, and factors influencing them. Methods Long-lasting changes were assessed with mechanical [brush, von Frey filament (588.2 mN)] and thermal [heat (40°C)/cold (25°C)] bedside sensory testing, and electrical TS (0.2 ms single electrical stimuli), at the homotopic (ipsilateral C6 dermatome), adjacent heterotopic (ipsilateral C5 and C7 dermatomes) and contralateral (contralateral C6 dermatomes) dermatomal sites in a single testing session. TS were applied before and after application of 100 Hz HFS at the ipsilateral C6 dermatome. Subjects rated their sensation and pain intensity to TS, and completed questionnaires related to pain descriptors and quality of life. Results Long-lasting changes in mechanical and cold sensitivity was detected up to 45 min after HFS at homotopic C6 dermatome, and a temporary increase in cold sensitivity at 20 min in the contralateral C6 dermatome (p < 0.05). A slow development of bilateral depotentiation to electrical pain TS was also detected from 40 min after HFS (p < 0.05). Higher HFS-induced mechanical and cold sensitivity was identified in women (p < 0.05). Age and quality of life were associated with pain intensity (p < 0.05). Conclusion Long-term unilateral and bilateral changes in sensation and pain following electrical HFS have been found. These findings may suggest a new insight into the development of persistent pain mechanisms. Further studies are now needed.
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Affiliation(s)
- Isabel Escobar-Sánchez
- Sensorimotor Function Group, Hospital Nacional de Parapléjicos (SESCAM), Toledo, Spain
- Alumna de Doctorado (Ciencias de la Salud), Escuela Internacional de Doctorado, Universidad de Castilla-La Mancha, Ciudad Real, Spain
| | - Marta Ríos-León
- Sensorimotor Function Group, Hospital Nacional de Parapléjicos (SESCAM), Toledo, Spain
- Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Toledo, Spain
| | - Julian Taylor
- Sensorimotor Function Group, Hospital Nacional de Parapléjicos (SESCAM), Toledo, Spain
- Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Toledo, Spain
- Harris Manchester College, University of Oxford, Oxford, United Kingdom
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3
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Zhang H, Wang C, Zhang K, Kamau PM, Luo A, Tian L, Lai R. The role of TRPA1 channels in thermosensation. CELL INSIGHT 2022; 1:100059. [PMID: 37193355 PMCID: PMC10120293 DOI: 10.1016/j.cellin.2022.100059] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/05/2022] [Accepted: 10/05/2022] [Indexed: 05/18/2023]
Abstract
Transient receptor potential ankyrin 1 (TRPA1) is a polymodal nonselective cation channel sensitive to different physical and chemical stimuli. TRPA1 is associated with many important physiological functions in different species and thus is involved in different degrees of evolution. TRPA1 acts as a polymodal receptor for the perceiving of irritating chemicals, cold, heat, and mechanical sensations in various animal species. Numerous studies have supported many functions of TRPA1, but its temperature-sensing function remains controversial. Although TRPA1 is widely distributed in both invertebrates and vertebrates, and plays a crucial role in tempreture sensing, the role of TRPA1 thermosensation and molecular temperature sensitivity are species-specific. In this review, we summarize the temperature-sensing role of TRPA1 orthologues in terms of molecular, cellular, and behavioural levels.
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Affiliation(s)
- Hao Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
| | - Chengsan Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Keyi Zhang
- University of Chinese Academy of Sciences, Beijing, 100049, China
- School of Molecular Medicine, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310000, China
| | - Peter Muiruri Kamau
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Sino-African Joint Research Center, Kunming Institute of Zoology, Chinese, Academy of Sciences, Kunming, Yunnan, 650223, China
| | - Anna Luo
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lifeng Tian
- University of Chinese Academy of Sciences, Beijing, 100049, China
- School of Molecular Medicine, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310000, China
| | - Ren Lai
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- Sino-African Joint Research Center, Kunming Institute of Zoology, Chinese, Academy of Sciences, Kunming, Yunnan, 650223, China
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4
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Liu XG. Normalization of Neuroinflammation: A New Strategy for Treatment of Persistent Pain and Memory/Emotional Deficits in Chronic Pain. J Inflamm Res 2022; 15:5201-5233. [PMID: 36110505 PMCID: PMC9469940 DOI: 10.2147/jir.s379093] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Accepted: 08/18/2022] [Indexed: 12/12/2022] Open
Abstract
Chronic pain, which affects around 1/3 of the world population and is often comorbid with memory deficit and mood depression, is a leading source of suffering and disability. Studies in past decades have shown that hyperexcitability of primary sensory neurons resulting from abnormal expression of ion channels and central sensitization mediated pathological synaptic plasticity, such as long-term potentiation in spinal dorsal horn, underlie the persistent pain. The memory/emotional deficits are associated with impaired synaptic connectivity in hippocampus. Dysregulation of numerous endogenous proteins including receptors and intracellular signaling molecules is involved in the pathological processes. However, increasing knowledge contributes little to clinical treatment. Emerging evidence has demonstrated that the neuroinflammation, characterized by overproduction of pro-inflammatory cytokines and glial activation, is reliably detected in humans and animals with chronic pain, and is sufficient to induce persistent pain and memory/emotional deficits. The abnormal expression of ion channels and pathological synaptic plasticity in spinal dorsal horn and in hippocampus are resulting from neuroinflammation. The neuroinflammation is initiated and maintained by the interactions of circulating monocytes, glial cells and neurons. Obviously, unlike infectious diseases and cancer, which are caused by pathogens or malignant cells, chronic pain is resulting from alterations of cells and molecules which have numerous physiological functions. Therefore, normalization (counterbalance) but not simple inhibition of the neuroinflammation is the right strategy for treating neuronal disorders. Currently, no such agent is available in clinic. While experimental studies have demonstrated that intracellular Mg2+ deficiency is a common feature of chronic pain in animal models and supplement Mg2+ are capable of normalizing the neuroinflammation, activation of upregulated proteins that promote recovery, such as translocator protein (18k Da) or liver X receptors, has a similar effect. In this article, relevant experimental and clinical evidence is reviewed and discussed.
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Affiliation(s)
- Xian-Guo Liu
- Pain Research Center and Department of Physiology, Zhongshan School of Medicine of Sun Yat-sen University, Guangzhou, People's Republic of China
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5
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Martínez-Rojas VA, Salinas-Abarca AB, Gómez-Víquez NL, Granados-Soto V, Mercado F, Murbartián J. Interaction of NHE1 and TRPA1 Activity in DRG Neurons Isolated from Adult Rats and its Role in Inflammatory Nociception. Neuroscience 2021; 465:154-165. [PMID: 33957206 DOI: 10.1016/j.neuroscience.2021.04.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 04/01/2021] [Accepted: 04/21/2021] [Indexed: 01/07/2023]
Abstract
Transient receptor potential ankyrin 1 (TRPA1) channel is expressed in a subset of nociceptive neurons. This channel integrates several nociceptive signals. Particularly, it is modulated by intracellular pH (pHi). Na+/H+ exchanger 1 (NHE1) contributes to the maintenance of pHi in nociceptors. However, it is currently unknown whether the interaction between TRPA1 and NHE1 contributes to the nociceptive processing. Thus, the purpose of this study was to assess the functional interaction between NHE1 and TRPA1 in small dorsal root ganglion (DRG) neurons from primary culture obtained from adult rats. Moreover, we also evaluated their possible interaction in acute and inflammatory pain. Zoniporide (selective NHE1 inhibitor) reduced pHi and increased intracellular calcium in a concentration-dependent fashion in DRG neurons. Zoniporide and allyl isothiocyanate (AITC, TRPA1 agonist) increased calcium transients in the same DRG neuron, whereas that A-967079 (TRPA1 antagonist) prevented the effect of zoniporide in DRG neurons. Repeated AITC induced TRPA1 desensitization and this effect was prevented by zoniporide. Both NHE1 and TRPA1 were localized at the membrane surface of DRG neurons in culture. Local peripheral zoniporide enhanced AITC-induced pronociception and this effect was prevented by A-967079. Likewise, zoniporide potentiated Complete Freund's Adjuvant (CFA)-induced hypersensitivity, effect which was prevented by A-967079 in vivo. CFA paw injection increased TRPA1 and decresed NHE1 protein expression in DRG. These results suggest a functional interaction between NHE1 and TRPA1 in DRG neurons in vitro. Moreover, data suggest that this interaction participates in acute and inflamatory pain conditions in vivo.
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Affiliation(s)
| | - Ana B Salinas-Abarca
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Cinvestav, South Campus, Mexico City, Mexico
| | | | - Vinicio Granados-Soto
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Cinvestav, South Campus, Mexico City, Mexico
| | - Francisco Mercado
- Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, Mexico City, Mexico
| | - Janet Murbartián
- Departamento de Farmacobiología, Cinvestav, South Campus, Mexico City, Mexico.
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6
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Nazıroğlu M, Öz A, Yıldızhan K. Selenium and Neurological Diseases: Focus on Peripheral Pain and TRP Channels. Curr Neuropharmacol 2021; 18:501-517. [PMID: 31903884 PMCID: PMC7457405 DOI: 10.2174/1570159x18666200106152631] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/26/2019] [Accepted: 01/04/2020] [Indexed: 12/18/2022] Open
Abstract
Pain is a complex physiological process that includes many components. Growing evidence supports the idea that oxidative stress and Ca2+ signaling pathways participate in pain detection by neurons. The main source of endogenous reactive oxygen species (ROS) is mitochondrial dysfunction induced by membrane depolarization, which is in turn caused by Ca2+ influx into the cytosol of neurons. ROS are controlled by antioxidants, including selenium. Selenium plays an important role in the nervous system, including the brain, where it acts as a cofactor for glutathione peroxidase and is incorporated into selenoproteins involved in antioxidant defenses. It has neuroprotective effects through modulation of excessive ROS production, inflammation, and Ca2+ overload in several diseases, including inflammatory pain, hypersensitivity, allodynia, diabetic neuropathic pain, and nociceptive pain. Ca2+ entry across membranes is mediated by different channels, including transient receptor potential (TRP) channels, some of which (e.g., TRPA1, TRPM2, TRPV1, and TRPV4) can be activated by oxidative stress and have a role in the induction of peripheral pain. The results of recent studies indicate the modulator roles of selenium in peripheral pain through inhibition of TRP channels in the dorsal root ganglia of experimental animals. This review summarizes the protective role of selenium in TRP channel regulation, Ca2+ signaling, apoptosis, and mitochondrial oxidative stress in peripheral pain induction.
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Affiliation(s)
- Mustafa Nazıroğlu
- Neuroscience Research Center, Suleyman Demirel University, Isparta, Turkey.,Department of Biophysics, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey.,Drug Discovery Unit, BSN Health, Analysis and Innovation Ltd. Inc. Teknokent, Isparta, Turkey
| | - Ahmi Öz
- Department of Biophysics, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - Kenan Yıldızhan
- Department of Biophysics, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
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Yeh TY, Luo IW, Hsieh YL, Tseng TJ, Chiang H, Hsieh ST. Peripheral Neuropathic Pain: From Experimental Models to Potential Therapeutic Targets in Dorsal Root Ganglion Neurons. Cells 2020; 9:cells9122725. [PMID: 33371371 PMCID: PMC7767346 DOI: 10.3390/cells9122725] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 12/16/2020] [Indexed: 12/12/2022] Open
Abstract
Neuropathic pain exerts a global burden caused by the lesions in the somatosensory nerve system, including the central and peripheral nervous systems. The mechanisms of nerve injury-induced neuropathic pain involve multiple mechanisms, various signaling pathways, and molecules. Currently, poor efficacy is the major limitation of medications for treating neuropathic pain. Thus, understanding the detailed molecular mechanisms should shed light on the development of new therapeutic strategies for neuropathic pain. Several well-established in vivo pain models were used to investigate the detail mechanisms of peripheral neuropathic pain. Molecular mediators of pain are regulated differentially in various forms of neuropathic pain models; these regulators include purinergic receptors, transient receptor potential receptor channels, and voltage-gated sodium and calcium channels. Meanwhile, post-translational modification and transcriptional regulation are also altered in these pain models and have been reported to mediate several pain related molecules. In this review, we focus on molecular mechanisms and mediators of neuropathic pain with their corresponding transcriptional regulation and post-translational modification underlying peripheral sensitization in the dorsal root ganglia. Taken together, these molecular mediators and their modification and regulations provide excellent targets for neuropathic pain treatment.
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Affiliation(s)
- Ti-Yen Yeh
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan;
| | - I-Wei Luo
- Department of Life Science, College of Life Science, National Taiwan University, Taipei 10617, Taiwan;
| | - Yu-Lin Hsieh
- Department of Anatomy, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan;
- School of Post-Baccalaureate Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
- Department of Medical Research, Kaohsiung Medical University Hostpital, Kaohsiung 80708, Taiwan
| | - To-Jung Tseng
- Department of Anatomy, School of Medicine, Chung Shan Medical University, Taichung 40201, Taiwan;
- Department of Medical Education, Chung Shan Medical University Hospital, Taichung 40201, Taiwan
| | | | - Sung-Tsang Hsieh
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan;
- Department of Neurology, National Taiwan University Hospital, Taipei 10002, Taiwan
- Graduate Institute of Brian and Mind Sciences, College of Medicine, National Taiwan University, Taipei 10051, Taiwan
- Center of Precision Medicine, College of Medicine, National Taiwan University, Taipei 10055, Taiwan
- Correspondence: ; Tel.: +886-2-23123456 (ext. 88182); Fax: +886-223915292
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Lin B, Wang Y, Zhang P, Yuan Y, Zhang Y, Chen G. Gut microbiota regulates neuropathic pain: potential mechanisms and therapeutic strategy. J Headache Pain 2020; 21:103. [PMID: 32807072 PMCID: PMC7433133 DOI: 10.1186/s10194-020-01170-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 08/10/2020] [Indexed: 02/08/2023] Open
Abstract
Neuropathic pain (NP) is a sustained and nonreversible condition characterized by long-term devastating physical and psychological damage. Therefore, it is urgent to identify an effective treatment for NP. Unfortunately, the precise pathogenesis of NP has not been elucidated. Currently, the microbiota-gut-brain axis has drawn increasing attention, and the emerging role of gut microbiota is investigated in numerous diseases including NP. Gut microbiota is considered as a pivotal regulator in immune, neural, endocrine, and metabolic signaling pathways, which participates in forming a complex network to affect the development of NP directly or indirectly. In this review, we conclude the current understanding of preclinical and clinical findings regarding the role of gut microbiota in NP and provide a novel therapeutic method for pain relief by medication and dietary interventions.
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Affiliation(s)
- Binbin Lin
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 3 Qingchun East Road, Zhejiang, 310016, Hangzhou, China
| | - Yuting Wang
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 3 Qingchun East Road, Zhejiang, 310016, Hangzhou, China
| | - Piao Zhang
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 3 Qingchun East Road, Zhejiang, 310016, Hangzhou, China
| | - Yanyan Yuan
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 3 Qingchun East Road, Zhejiang, 310016, Hangzhou, China
| | - Ying Zhang
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 3 Qingchun East Road, Zhejiang, 310016, Hangzhou, China
| | - Gang Chen
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 3 Qingchun East Road, Zhejiang, 310016, Hangzhou, China.
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9
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TRPA1 gene variants hurting our feelings. Pflugers Arch 2020; 472:953-960. [PMID: 32444956 DOI: 10.1007/s00424-020-02397-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 05/01/2020] [Accepted: 05/06/2020] [Indexed: 12/13/2022]
Abstract
TRPA1 is a Ca2+-permeable, non-selective cation channel that is activated by thermal and mechanical stimuli, an amazing variety of potentially noxious chemicals, and by endogenous molecules that signal tissue injury. The expression of this channel in nociceptive neurons and epithelial cells puts it at the first line of defense and makes it a key determinant of adaptive protective behaviors. For the same reasons, TRPA1 is implicated in a wide variety of disease conditions, such as acute, neuropathic, and inflammatory pains, and is postulated to be a target for therapeutic interventions against acquired diseases featuring aberrant sensory functions. The human TRPA1 gene can bare mutations that have been associated with painful conditions, such as the N855S that relates to the rare familial episodic pain syndrome, or others that have been linked to altered chemosensation in humans. Here, we review the current knowledge on this field, re-evaluating some available functional data, and pointing out the aspects that in our opinion require attention in future research. We make emphasis in that, although the availability of the human TRPA1 structure provides a unique opportunity for further developments, far more classical functional studies using electrophysiology and analysis of channel gating are also required to understand the structure-function relationship of this intriguing channel.
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Talavera K, Startek JB, Alvarez-Collazo J, Boonen B, Alpizar YA, Sanchez A, Naert R, Nilius B. Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease. Physiol Rev 2019; 100:725-803. [PMID: 31670612 DOI: 10.1152/physrev.00005.2019] [Citation(s) in RCA: 218] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The transient receptor potential ankyrin (TRPA) channels are Ca2+-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH2 terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca2+, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.
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Affiliation(s)
- Karel Talavera
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Justyna B Startek
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Julio Alvarez-Collazo
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Brett Boonen
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Yeranddy A Alpizar
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Alicia Sanchez
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Robbe Naert
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Bernd Nilius
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven; VIB Center for Brain and Disease Research, Leuven, Belgium
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11
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Startek JB, Boonen B, López-Requena A, Talavera A, Alpizar YA, Ghosh D, Van Ranst N, Nilius B, Voets T, Talavera K. Mouse TRPA1 function and membrane localization are modulated by direct interactions with cholesterol. eLife 2019; 8:e46084. [PMID: 31184584 PMCID: PMC6590989 DOI: 10.7554/elife.46084] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 06/10/2019] [Indexed: 01/04/2023] Open
Abstract
The cation channel TRPA1 transduces a myriad of noxious chemical stimuli into nociceptor electrical excitation and neuropeptide release, leading to pain and neurogenic inflammation. Despite emergent evidence that TRPA1 is regulated by the membrane environment, it remains unknown whether this channel localizes in membrane microdomains or whether it interacts with cholesterol. Using total internal reflection fluorescence microscopy and density gradient centrifugation we found that mouse TRPA1 localizes preferably into cholesterol-rich domains and functional experiments revealed that cholesterol depletion decreases channel sensitivity to chemical agonists. Moreover, we identified two structural motifs in transmembrane segments 2 and 4 involved in mTRPA1-cholesterol interactions that are necessary for normal agonist sensitivity and plasma membrane localization. We discuss the impact of such interactions on TRPA1 gating mechanisms, regulation by the lipid environment, and role of this channel in sensory membrane microdomains, all of which helps to understand the puzzling pharmacology and pathophysiology of this channel.
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Affiliation(s)
- Justyna B Startek
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Brett Boonen
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Alejandro López-Requena
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Ariel Talavera
- Center for Microscopy and Molecular Imaging (CMMI), Laboratory of MicroscopyUniversité Libre de BruxellesGosseliesBelgium
| | - Yeranddy A Alpizar
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Debapriya Ghosh
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Nele Van Ranst
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Bernd Nilius
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Thomas Voets
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
| | - Karel Talavera
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Cellular and Molecular MedicineKU LeuvenLeuvenBelgium
- VIB Center for Brain & Disease ResearchLeuvenBelgium
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12
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Abstract
Voltage-gated potassium (Kv) channels are increasingly recognised as key regulators of nociceptive excitability. Kcns1 is one of the first potassium channels to be associated with neuronal hyperexcitability and mechanical sensitivity in the rat, as well as pain intensity and risk of developing chronic pain in humans. Here, we show that in mice, Kcns1 is predominantly expressed in the cell body and axons of myelinated sensory neurons positive for neurofilament-200, including Aδ-fiber nociceptors and low-threshold Aβ mechanoreceptors. In the spinal cord, Kcns1 was detected in laminae III to V of the dorsal horn where most sensory A fibers terminate, as well as large motoneurons of the ventral horn. To investigate Kcns1 function specifically in the periphery, we generated transgenic mice in which the gene is deleted in all sensory neurons but retained in the central nervous system. Kcns1 ablation resulted in a modest increase in basal mechanical pain, with no change in thermal pain processing. After neuropathic injury, Kcns1 KO mice exhibited exaggerated mechanical pain responses and hypersensitivity to both noxious and innocuous cold, consistent with increased A-fiber activity. Interestingly, Kcns1 deletion also improved locomotor performance in the rotarod test, indicative of augmented proprioceptive signalling. Our results suggest that restoring Kcns1 function in the periphery may be of some use in ameliorating mechanical and cold pain in chronic states.
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13
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Abstract
The transient receptor potential ankyrin 1 (TRPA1) ion channel is expressed in pain-sensing neurons and other tissues and has become a major target in the development of novel pharmaceuticals. A remarkable feature of the channel is its long list of activators, many of which we are exposed to in daily life. Many of these agonists induce pain and inflammation, making TRPA1 a major target for anti-inflammatory and analgesic therapies. Studies in human patients and in experimental animals have confirmed an important role for TRPA1 in a number of pain conditions. Over the recent years, much progress has been made in elucidating the molecular structure of TRPA1 and in discovering binding sites and modulatory sites of the channel. Because the list of published mutations and important molecular sites is steadily growing and because it has become difficult to see the forest for the trees, this review aims at summarizing the current knowledge about TRPA1, with a special focus on the molecular structure and the known binding or gating sites of the channel.
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Affiliation(s)
- Jannis E Meents
- Institute of Physiology, University Hospital RWTH Aachen , Aachen , Germany
| | - Cosmin I Ciotu
- Center for Physiology and Pharmacology, Medical University of Vienna , Vienna , Austria
| | - Michael J M Fischer
- Center for Physiology and Pharmacology, Medical University of Vienna , Vienna , Austria
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Kim YS, Kim SK, Lee JS, Ko SJ, Bae YC. Expression of vesicular glutamate transporters in transient receptor potential ankyrin 1 (TRPA1)-positive neurons in the rat trigeminal ganglion. Brain Res 2018; 1690:31-39. [DOI: 10.1016/j.brainres.2018.04.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 03/16/2018] [Accepted: 04/09/2018] [Indexed: 01/31/2023]
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15
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Nugent M, Yusef YR, Meng J, Wang J, Dolly JO. A SNAP-25 cleaving chimera of botulinum neurotoxin /A and /E prevents TNFα-induced elevation of the activities of native TRP channels on early postnatal rat dorsal root ganglion neurons. Neuropharmacology 2018; 138:257-266. [PMID: 29906413 DOI: 10.1016/j.neuropharm.2018.06.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Revised: 05/29/2018] [Accepted: 06/11/2018] [Indexed: 01/28/2023]
Abstract
Transient receptor potential (TRP) vallinoid 1 (TRPV1) and ankyrin 1 (TRPA1) are two transducing channels expressed on peripheral sensory nerves involved in pain sensation. Upregulation of their expression, stimulated by inflammatory cytokines and growth factors in animal pain models, correlate with the induction of nociceptive hyper-sensitivity. Herein, we firstly demonstrate by immuno-cytochemical labelling that TNFα augments the surface content of these channels on rat cultured dorsal root ganglion (DRG) neurons which, in turn, enhances the electrophysiological and functional responses of the latter to their specific agonists. A molecular basis underlying this TNFα-dependent enhancement was unveiled by pre-treating DRGs with a recently-published chimeric protein, consisting of the protease light chain (LC) of botulinum neurotoxin (BoNT) serotype E fused to full-length BoNT/A (LC/E-BoNT/A). This cleaves synaptosomal-associated protein of Mr 25k (SNAP-25) and reported previously to exhibit anti-nociceptive activity in a rat model of neuropathic pain. Low pM concentrations of this chimera were found to prevent the TNFα-stimulated delivery of TRPV1/A1 to the neuronal plasmalemma and, accordingly, decreased their incremental functional activities relative to those of control cells, an effect accompanied by SNAP-25 cleavage. Advantageously, LC/E-BoNT/A did not reduce the basal surface contents of the two channels or their pharmacological responses. Thus, use of multiple complementary methodologies provides evidence that LC/E-BoNT/A abolishes the TNFα-dependent augmented, but not resting, surface trafficking of TRPV1/A1. As TNFα is known to induce nociceptive hyper-sensitivity in vivo, our observed inhibition by LC/E-BoNT/A of its action in vitro could contribute to its potential alleviation of pain.
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Affiliation(s)
- Marc Nugent
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Yamil R Yusef
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Jianghui Meng
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Jiafu Wang
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - J Oliver Dolly
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland.
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16
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Martínez-Rojas VA, García G, Noriega-Navarro R, Guzmán-Priego CG, Torres-López JE, Granados-Soto V, Murbartián J. Peripheral and spinal TRPA1 channels contribute to formalin-induced long-lasting mechanical hypersensitivity. J Pain Res 2017; 11:51-60. [PMID: 29343980 PMCID: PMC5749559 DOI: 10.2147/jpr.s153671] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Background Transient receptor potential ankyrin 1 (TRPA1) is a non-selective cation channel expressed by a subset of nociceptive neurons that acts as a multimodal receptor. Its activity contributes to modulate nociceptive transmission in acute inflammatory pain. However, the role of this channel in chronic pain has been less studied. The purpose of this study was to investigate the local peripheral and spinal participation of TRPA1 channels in formalin-induced long-lasting hypersensitivity. Materials and methods Formalin (1%)-induced chronic hypersensitivity was determined by the application of von Frey filaments to ipsilateral and contralateral paws and through pharmacological testing using a selective TRPA1 blocker (A-967079). TRPA1 expression in the dorsal root ganglion (DRG) and spinal cord was analyzed by Western blotting. Results Formalin (1%) injection produced acute flinching behavior (1 h) as well as secondary allodynia and hyperalgesia (12 days). Local peripheral pretreatment (10 min before) or posttreatment (6 days later) with A-967079 (1–100 µM) partially prevented and reversed, respectively, in a dose-dependent manner, long-lasting secondary mechanical allodynia and hyperalgesia evoked by 1% formalin. Likewise, intrathecal pretreatment or posttreatment with A-967079 partially prevented and reversed, respectively, formalin-induced long-lasting hypersensitivity. A-967079 (100 µM) completely abolished the pro-nociceptive effect of formalin (adjusted to pH 7.4). Finally, formalin injection increased TRPA1 protein expression in the DRG and spinal cord. Conclusion Results indicate that TRPA1 expressed in the DRG and spinal cord plays a relevant role in formalin-induced long-lasting secondary nociceptive hypersensitivity.
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Affiliation(s)
- Vladimir A Martínez-Rojas
- Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados (Cinvestav), Unidad Coapa, Ciudad de México
| | - Guadalupe García
- Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados (Cinvestav), Unidad Coapa, Ciudad de México
| | - Roxana Noriega-Navarro
- Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados (Cinvestav), Unidad Coapa, Ciudad de México
| | - Crystell G Guzmán-Priego
- Laboratorio Mecanismos del Dolor, Centro de Investigación, División Académica de Ciencias de la Salud, Universidad Juárez Autónoma de Tabasco
| | - Jorge E Torres-López
- Laboratorio Mecanismos del Dolor, Centro de Investigación, División Académica de Ciencias de la Salud, Universidad Juárez Autónoma de Tabasco.,Hospital Regional de Alta Especialidad "Dr. Juan Graham Casasús", Villahermosa, Tabasco
| | - Vinicio Granados-Soto
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Cinvestav, Unidad Coapa, Ciudad de México, México
| | - Janet Murbartián
- Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados (Cinvestav), Unidad Coapa, Ciudad de México
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17
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Palazzo E, Marabese I, Luongo L, Guida F, de Novellis V, Maione S. Nociception modulation by supraspinal group III metabotropic glutamate receptors. J Neurochem 2017; 141:507-519. [DOI: 10.1111/jnc.13725] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 06/15/2016] [Accepted: 06/20/2016] [Indexed: 02/02/2023]
Affiliation(s)
- Enza Palazzo
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Ida Marabese
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Livio Luongo
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Francesca Guida
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Vito de Novellis
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Sabatino Maione
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
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18
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Wei H, Wu HY, Chen Z, Ma AN, Mao XF, Li TF, Li XY, Wang YX, Pertovaara A. Mechanical antihypersensitivity effect induced by repeated spinal administrations of a TRPA1 antagonist or a gap junction decoupler in peripheral neuropathy. Pharmacol Biochem Behav 2016; 150-151:57-67. [DOI: 10.1016/j.pbb.2016.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 09/21/2016] [Accepted: 09/23/2016] [Indexed: 01/06/2023]
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19
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TRP channels: potential drug target for neuropathic pain. Inflammopharmacology 2016; 24:305-317. [PMID: 27757589 DOI: 10.1007/s10787-016-0288-x] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 10/05/2016] [Indexed: 01/06/2023]
Abstract
Neuropathic pain is a debilitating disease which affects central as well as peripheral nervous system. Transient receptor potential (TRP) channels are ligand-gated ion channels that detect physical and chemical stimuli and promote painful sensations via nociceptor activation. TRP channels have physiological role in the mechanisms controlling several physiological responses like temperature and mechanical sensations, response to painful stimuli, taste, and pheromones. TRP channel family involves six different TRPs (TRPV1, TRPV2, TRPV3, TRPV4, TRPM8, and TRPA1) which are expressed in pain sensing neurons and primary afferent nociceptors. They function as transducers for mechanical, chemical, and thermal stimuli into inward currents, an essential first step for provoking pain sensations. TRP ion channels activated by temperature (thermo TRPs) are important molecular players in acute, inflammatory, and chronic pain states. Different degree of heat activates four TRP channels (TRPV1-4), while cold temperature ranging from affable to painful activate two indistinctly related thermo TRP channels (TRPM8 and TRPA1). Targeting primary afferent nociceptive neurons containing TRP channels that play pivotal role in revealing physical stimuli may be an effective target for the development of successful pharmacotherapeutics for clinical pain syndromes. In this review, we highlighted the potential role of various TRP channels in different types of neuropathic pain. We also discussed the pharmacological activity of naturally and synthetically originated TRP channel modulators for pharmacotherapeutics of nociception and neuropathic pain.
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21
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Luo J, Feng J, Liu S, Walters ET, Hu H. Molecular and cellular mechanisms that initiate pain and itch. Cell Mol Life Sci 2015; 72:3201-23. [PMID: 25894692 PMCID: PMC4534341 DOI: 10.1007/s00018-015-1904-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 03/20/2015] [Accepted: 04/07/2015] [Indexed: 12/17/2022]
Abstract
Somatosensory neurons mediate our sense of touch. They are critically involved in transducing pain and itch sensations under physiological and pathological conditions, along with other skin-resident cells. Tissue damage and inflammation can produce a localized or systemic sensitization of our senses of pain and itch, which can facilitate our detection of threats in the environment. Although acute pain and itch protect us from further damage, persistent pain and itch are debilitating. Recent exciting discoveries have significantly advanced our knowledge of the roles of membrane-bound G protein-coupled receptors and ion channels in the encoding of information leading to pain and itch sensations. This review focuses on molecular and cellular events that are important in early stages of the biological processing that culminates in our senses of pain and itch.
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Affiliation(s)
- Jialie Luo
- Department of Anesthesiology, The Center for the Study of Itch, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO, 63110, USA
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22
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Palazzo E, Marabese I, de Novellis V, Rossi F, Maione S. Supraspinal metabotropic glutamate receptors: a target for pain relief and beyond. Eur J Neurosci 2014; 39:444-54. [PMID: 24494684 DOI: 10.1111/ejn.12398] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 09/20/2013] [Accepted: 09/23/2013] [Indexed: 01/09/2023]
Abstract
Glutamate is the main excitatory neurotransmitter in the central nervous system, controlling the majority of synapses. Apart from neurodegenerative diseases, growing evidence suggests that glutamate is involved in psychiatric and neurological disorders, including pain. Glutamate signaling is mediated via ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs). So far, drugs acting via modulation of glutamatergic system are few in number, and all are associated with iGluRs and important side effects. The glutamatergic system may be finely modulated by mGluRs. Signaling via these receptors is slower and longer-lasting, and permits fine-tuning of glutamate transmission. There have been eight mGluRs cloned to date (mGluR1-mGluR8), and these are further divided into three groups on the basis of sequence homology, pharmacological profile, and second messenger signaling. The pattern of expression of mGluRs along the pain neuraxis makes them suitable substrates for the design of novel analgesics. This review will focus on the supraspinal mGluRs, whose pharmacological manipulation generates a variety of effects, which depend on the synaptic location, the cell type on which they are located, and the expression in particular pain modulation areas, such as the periaqueductal gray, which plays a major role in the descending modulation of pain, and the central nucleus of the amygdala, which is an important center for the processing of emotional information associated with pain. A particular emphasis will also be given to the novel selective mGluR subtype ligands, as well as positive and negative allosteric modulators, which have permitted discrimination of the individual roles of the different mGluR subtypes, and subtle modulation of central nervous system functioning and related disorders.
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Affiliation(s)
- Enza Palazzo
- Department of Anaesthesiology, Surgery and Emergency, The Second University of Naples, Piazza Luigi Miraglia 2, 80138, Naples, Italy
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23
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Miyakawa T, Terashima Y, Takebayashi T, Tanimoto K, Iwase T, Ogon I, Kobayashi T, Tohse N, Yamashita T. Transient receptor potential ankyrin 1 in spinal cord dorsal horn is involved in neuropathic pain in nerve root constriction rats. Mol Pain 2014; 10:58. [PMID: 25192906 PMCID: PMC4163170 DOI: 10.1186/1744-8069-10-58] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 09/02/2014] [Indexed: 12/26/2022] Open
Abstract
Background Lumbar radicular pain is categorized as a type of neuropathic pain, but its pathophysiological mechanisms are not fully understood. The substantia gelatinosa (SG) in the spinal cord dorsal horn receives primary afferent inputs and is considered to be a therapeutic target for treating neuropathic pain. In vivo patch-clamp recording is a useful procedure for analyzing the functional properties of synaptic transmission in SG neurons. Transient receptor potential ankyrin 1 (TRPA1) has been widely identified in the central and peripheral nervous systems, such as in the peripheral nociceptor, dorsal root ganglion, and spinal cord dorsal horn and is involved in synaptic transmission of pain. However, its functional role and mechanism of pain transmission in the spinal cord dorsal horn are not well understood. The purpose of this study was to use in vivo patch-clamp analysis to examine changes in the excitatory synaptic transmission of SG neurons treated with TRPA1 antagonist and to clarify the potential role of TRPA1 in the rat spinal cord dorsal horn. Results The rats with root constriction (RC) showed mechanical hypersensitivity, hyperalgesia, and thermal hyperalgesia. In addition, pin pricks elicited pain-related behavior even in the sham and naïve rats. These pain-related behaviors were significantly attenuated by intrathecal injection of a TRPA1 antagonist. The degrees of intrathecal injection efficacy were equivalent among the 3 groups (RC, sham, and naïve groups). In an electrophysiological study, the frequencies and amplitudes of excitatory postsynaptic currents (EPSCs) were significantly increased in the RC rats compared with those in the sham and naïve rats. Spontaneous EPSCs and evoked-EPSCs by non-noxious and noxious stimuli were significantly decreased by TRPA1 antagonist. As in the behavioral study, there were no statistically significant differences among the 3 groups. Conclusion These data showed that the TRPA1 antagonist had an inhibitory effect on mechanical hypersensitivity and hyperalgesia as well as on physiological pain transmission in the spinal cord dorsal horn. This suggests that TRPA1 is consistently involved in excitatory synaptic transmission even in the physiological state and has a role in coordinating pain transmission.
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Affiliation(s)
- Tsuyoshi Miyakawa
- Department of Orthopaedic Surgery, Sapporo Medical University School of Medicine, S1 W16, Sapporo, Hokkaido 060-8543, Japan.
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Nilius B, Szallasi A. Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine. Pharmacol Rev 2014; 66:676-814. [DOI: 10.1124/pr.113.008268] [Citation(s) in RCA: 348] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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25
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Luo J, Walters ET, Carlton SM, Hu H. Targeting Pain-evoking Transient Receptor Potential Channels for the Treatment of Pain. Curr Neuropharmacol 2014; 11:652-63. [PMID: 24396340 PMCID: PMC3849790 DOI: 10.2174/1570159x113119990040] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 06/19/2013] [Accepted: 06/19/2013] [Indexed: 02/06/2023] Open
Abstract
Chronic pain affects billions of lives globally and is a major public health problem in the United States. However, pain management is still a challenging task due to a lack of understanding of the fundamental mechanisms of pain. In the past decades transient receptor potential (TRP) channels have been identified as molecular sensors of tissue damage and inflammation. Activation/sensitization of TRP channels in peripheral nociceptors produces neurogenic inflammation and contributes to both somatic and visceral pain. Pharmacological and genetic studies have affirmed the role of TRP channels in multiple forms of inflammatory and neuropathic pain. Thus pain-evoking TRP channels emerge as promising therapeutic targets for a wide variety of pain and inflammatory conditions.
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Affiliation(s)
- Jialie Luo
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin Street, Houston, TX 77030
| | - Edgar T Walters
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin Street, Houston, TX 77030
| | - Susan M Carlton
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1069
| | - Hongzhen Hu
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin Street, Houston, TX 77030
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26
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Abstract
The transient receptor potential ankyrin subtype 1 protein (TRPA1) is a nonselective cation channel permeable to Ca(2+), Na(+), and K(+). TRPA1 is a promiscuous chemical nocisensor that is also involved in noxious cold and mechanical sensation. It is present in a subpopulation of Aδ- and C-fiber nociceptive sensory neurons as well as in other sensory cells including epithelial cells. In primary sensory neurons, Ca(2+) and Na(+) flowing through TRPA1 into the cell cause membrane depolarization, action potential discharge, and neurotransmitter release both at peripheral and central neural projections. In addition to being activated by cysteine and lysine reactive electrophiles and oxidants, TRPA1 is indirectly activated by pro-inflammatory agents via the phospholipase C signaling pathway, in which cytosolic Ca(2+) is an important regulator of channel gating. The finding that non-electrophilic compounds, including menthol and cannabinoids, activate TRPA1 may provide templates for the design of non-tissue damaging activators to fine-tune the activity of TRPA1 and raises the possibility that endogenous ligands sharing binding sites with such non-electrophiles exist and regulate TRPA1 channel activity. TRPA1 is promising as a drug target for novel treatments of pain, itch, and sensory hyperreactivity in visceral organs including the airways, bladder, and gastrointestinal tract.
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Affiliation(s)
- Peter M Zygmunt
- Clinical and Experimental Pharmacology, Clinical Chemistry, Department of Laboratory Medicine, Lund University, Skåne University Hospital, SE-221 85, Lund, Sweden,
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27
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Targeting TRP channels for pain relief. Eur J Pharmacol 2013; 716:61-76. [DOI: 10.1016/j.ejphar.2013.03.003] [Citation(s) in RCA: 227] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 03/04/2013] [Indexed: 11/23/2022]
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28
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Barabas ME, Stucky CL. TRPV1, but not TRPA1, in primary sensory neurons contributes to cutaneous incision-mediated hypersensitivity. Mol Pain 2013; 9:9. [PMID: 23497345 PMCID: PMC3602024 DOI: 10.1186/1744-8069-9-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 02/21/2013] [Indexed: 12/22/2022] Open
Abstract
Background Mechanisms underlying postoperative pain remain poorly understood. In rodents, skin-only incisions induce mechanical and heat hypersensitivity similar to levels observed with skin plus deep incisions. Therefore, cutaneous injury might drive the majority of postoperative pain. TRPA1 and TRPV1 channels are known to mediate inflammatory and nerve injury pain, making them key targets for pain therapeutics. These channels are also expressed extensively in cutaneous nerve fibers. Therefore, we investigated whether TRPA1 and TRPV1 contribute to mechanical and heat hypersensitivity following skin-only surgical incision. Results Behavioral responses to mechanical and heat stimulation were compared between skin-incised and uninjured, sham control groups. Elevated mechanical responsiveness occurred 1 day post skin-incision regardless of genetic ablation or pharmacological inhibition of TRPA1. To determine whether functional changes in TRPA1 occur at the level of sensory neuron somata, we evaluated cytoplasmic calcium changes in sensory neurons isolated from ipsilateral lumbar 3–5 DRGs of skin-only incised and sham wild type (WT) mice during stimulation with the TRPA1 agonist cinnamaldehyde. There were no changes in the percentage of neurons responding to cinnamaldehyde or in their response amplitudes. Likewise, the subpopulation of DRG somata retrogradely labeled specifically from the incised region of the plantar hind paw showed no functional up-regulation of TRPA1 after skin-only incision. Next, we conducted behavior tests for heat sensitivity and found that heat hypersensitivity peaked at day 1 post skin-only incision. Skin incision-induced heat hypersensitivity was significantly decreased in TRPV1-deficient mice. In addition, we conducted calcium imaging with the TRPV1 agonist capsaicin. DRG neurons from WT mice exhibited sensitization to TRPV1 activation, as more neurons (66%) from skin-incised mice responded to capsaicin compared to controls (46%), and the sensitization occurred specifically in isolectin B4 (IB4)-positive neurons where 80% of incised neurons responded to capsaicin compared to just 44% of controls. Conclusions Our data suggest that enhanced TRPA1 function does not mediate the mechanical hypersensitivity that follows skin-only surgical incision. However, the heat hypersensitivity is dependent on TRPV1, and functional up-regulation of TRPV1 in IB4-binding DRG neurons may mediate the heat hypersensitivity after skin incision injury.
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Affiliation(s)
- Marie E Barabas
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226-0509, USA
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29
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Duraku LS, Hossaini M, Schüttenhelm BN, Holstege JC, Baas M, Ruigrok TJ, Walbeehm ET. Re-innervation patterns by peptidergic Substance-P, non-peptidergic P2X3, and myelinated NF-200 nerve fibers in epidermis and dermis of rats with neuropathic pain. Exp Neurol 2013; 241:13-24. [DOI: 10.1016/j.expneurol.2012.11.029] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 11/24/2012] [Accepted: 11/29/2012] [Indexed: 12/27/2022]
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Barabas ME, Kossyreva EA, Stucky CL. TRPA1 is functionally expressed primarily by IB4-binding, non-peptidergic mouse and rat sensory neurons. PLoS One 2012; 7:e47988. [PMID: 23133534 PMCID: PMC3485059 DOI: 10.1371/journal.pone.0047988] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 09/19/2012] [Indexed: 11/23/2022] Open
Abstract
Subpopulations of somatosensory neurons are characterized by functional properties and expression of receptor proteins and surface markers. CGRP expression and IB4-binding are commonly used to define peptidergic and non-peptidergic subpopulations. TRPA1 is a polymodal, plasma membrane ion channel that contributes to mechanical and cold hypersensitivity during tissue injury, making it a key target for pain therapeutics. Some studies have shown that TRPA1 is predominantly expressed by peptidergic sensory neurons, but others indicate that TRPA1 is expressed extensively within non-peptidergic, IB4-binding neurons. We used FURA-2 calcium imaging to define the functional distribution of TRPA1 among peptidergic and non-peptidergic adult mouse (C57BL/6J) DRG neurons. Approximately 80% of all small-diameter (<27 µm) neurons from lumbar 1–6 DRGs that responded to TRPA1 agonists allyl isothiocyanate (AITC; 79%) or cinnamaldehyde (84%) were IB4-positive. Retrograde labeling via plantar hind paw injection of WGA-Alexafluor594 showed similarly that most (81%) cutaneous neurons responding to TRPA1 agonists were IB4-positive. Additionally, we cultured DRG neurons from a novel CGRP-GFP mouse where GFP expression is driven by the CGRPα promoter, enabling identification of CGRP-expressing live neurons. Interestingly, 78% of TRPA1-responsive neurons were CGRP-negative. Co-labeling with IB4 revealed that the majority (66%) of TRPA1 agonist responders were IB4-positive but CGRP-negative. Among TRPA1-null DRGs, few small neurons (2–4%) responded to either TRPA1 agonist, indicating that both cinnamaldehyde and AITC specifically target TRPA1. Additionally, few large neurons (≥27 µm diameter) responded to AITC (6%) or cinnamaldehyde (4%), confirming that most large-diameter somata lack functional TRPA1. Comparison of mouse and rat DRGs showed that the majority of TRPA1-responsive neurons in both species were IB4-positive. Together, these data demonstrate that TRPA1 is functionally expressed primarily in the IB4-positive, CGRP-negative subpopulation of small lumbar DRG neurons from rodents. Thus, IB4 binding is a better indicator than neuropeptides for TRPA1 expression.
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Affiliation(s)
- Marie E. Barabas
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Elena A. Kossyreva
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Cheryl L. Stucky
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- * E-mail:
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Abstract
Tissue damage evokes an inflammatory response that promotes the removal of harmful stimuli, tissue repair, and protective behaviors to prevent further damage and encourage healing. However, inflammation may outlive its usefulness and become chronic. Chronic inflammation can lead to a host of diseases, including asthma, itch, rheumatoid arthritis, and colitis. Primary afferent sensory neurons that innervate target organs release inflammatory neuropeptides in the local area of tissue damage to promote vascular leakage, the recruitment of immune cells, and hypersensitivity to mechanical and thermal stimuli. TRPA1 channels are required for neuronal excitation, the release of inflammatory neuropeptides, and subsequent pain hypersensitivity. TRPA1 is also activated by the release of inflammatory agents from nonneuronal cells in the area of tissue injury or disease. This dual function of TRPA1 as a detector and instigator of inflammatory agents makes TRPA1 a gatekeeper of chronic inflammatory disorders of the skin, airways, and gastrointestinal tract.
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Affiliation(s)
- Diana M Bautista
- Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, USA.
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Kim YS, Jung HK, Kwon TK, Kim CS, Cho JH, Ahn DK, Bae YC. Expression of Transient Receptor Potential Ankyrin 1 in Human Dental Pulp. J Endod 2012; 38:1087-92. [DOI: 10.1016/j.joen.2012.04.024] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 04/18/2012] [Accepted: 04/27/2012] [Indexed: 01/11/2023]
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An ultrastructural evidence for the expression of transient receptor potential ankyrin 1 (TRPA1) in astrocytes in the rat trigeminal caudal nucleus. J Chem Neuroanat 2012; 45:45-9. [PMID: 22813698 DOI: 10.1016/j.jchemneu.2012.07.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 07/09/2012] [Accepted: 07/09/2012] [Indexed: 01/03/2023]
Abstract
The transient receptor potential ankyrin 1 (TRPA1) is implicated in the mechanical and cold hyperalgesia following inflammation and nerve injury. Its expression has been presumed to be confined to primary afferent terminals. Here, we show that TRPA1 is expressed in astrocytes in the superficial laminae of the rat trigeminal caudal nucleus by use of electron microscopic immunoperoxidase and immunogold labeling techniques. Immunoreactivity for TRPA1 was consistently observed in somata and process of astrocytes and was weaker than that in presumed nociceptive primary afferent terminals, but increased significantly in the fine process of astrocyte in rats with experimental inflammation of the temporomandibular joint. Thus, we provide ultrastructural evidence that TRPA1 is expressed in astrocytes in the brain stem and propose a novel pathway of its involvement in the central mechanism of inflammatory hyperalgesia.
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Eberhardt MJ, Filipovic MR, Leffler A, de la Roche J, Kistner K, Fischer MJ, Fleming T, Zimmermann K, Ivanovic-Burmazovic I, Nawroth PP, Bierhaus A, Reeh PW, Sauer SK. Methylglyoxal activates nociceptors through transient receptor potential channel A1 (TRPA1): a possible mechanism of metabolic neuropathies. J Biol Chem 2012; 287:28291-306. [PMID: 22740698 DOI: 10.1074/jbc.m111.328674] [Citation(s) in RCA: 159] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Neuropathic pain can develop as an agonizing sequela of diabetes mellitus and chronic uremia. A chemical link between both conditions of altered metabolism is the highly reactive compound methylglyoxal (MG), which accumulates in all cells, in particular neurons, and leaks into plasma as an index of the severity of the disorder. The electrophilic structure of this cytotoxic ketoaldehyde suggests TRPA1, a receptor channel deeply involved in inflammatory and neuropathic pain, as a molecular target. We demonstrate that extracellularly applied MG accesses specific intracellular binding sites of TRPA1, activating inward currents and calcium influx in transfected cells and sensory neurons, slowing conduction velocity in unmyelinated peripheral nerve fibers, and stimulating release of proinflammatory neuropeptides from and action potential firing in cutaneous nociceptors. Using a model peptide of the N terminus of human TRPA1, we demonstrate the formation of disulfide bonds based on MG-induced modification of cysteines as a novel mechanism. In conclusion, MG is proposed to be a candidate metabolite that causes neuropathic pain in metabolic disorders and thus is a promising target for medicinal chemistry.
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Affiliation(s)
- Mirjam J Eberhardt
- Institute of Physiology and Pathophysiology Friedrich-Alexander University Erlangen-Nuremberg, Universitaetsstrasse 17, 91054 Erlangen, Germany
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35
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Cho JH, Jeong MY, Choi IS, Lee HJ, Jang IS. TRPA1-like channels enhance glycinergic transmission in medullary dorsal horn neurons. J Neurochem 2012; 122:691-701. [PMID: 22671314 DOI: 10.1111/j.1471-4159.2012.07817.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effect of icilin, a potent agonist of transient receptor potential ankyrin 1 (TRPA1) and TRPM8, on glycinergic transmission was examined in mechanically isolated rat medullary dorsal horn neurons by use of the conventional whole-cell patch-clamp technique. Icilin increased the frequency of glycinergic spontaneous miniature inhibitory post-synaptic currents (mIPSCs) in a dose-dependent manner. Either allyl isothiocyanate(AITC) or cinnamaldehyde, other TRPA1 agonists, also increased mIPSC frequency, but the extent of facilitation induced by AITC or cinnamaldehyde was less than that induced by icilin. However, menthol, a TRPM8 agonist, had no facilitatory effect on glycinergic mIPSCs. The icilin-induced increase in mIPSC frequency was significantly inhibited by either HC030031, a selective TRPA1 antagonist, or ruthenium red, a non-selective transient receptor potential channel blocker. Icilin failed to increase glycinergic mIPSC frequency in the absence of extracellular Ca(2+), suggesting that the icilin-induced increase in mIPSC frequency is mediated by the Ca(2+) influx from the extracellular space. In contrast, icilin still increased mIPSC frequency either in the Na(+) -free external solution or in the presence of Cd(2+), a general voltage-dependent Ca(2+) channel blocker. The present results suggest that icilin acts on pre-synaptic TRPA1-like ion channels, which are permeable to Ca(2+), to enhance glycinergic transmission onto medullary dorsal horn neurons. The TRPA1-like channel-mediated enhancement of glycinergic transmission in medullary dorsal horn neurons would contribute to the regulation of pain information from the peripheral tissues.
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Affiliation(s)
- Jin-Hwa Cho
- Department of Pharmacology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
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Hulse RP, Donaldson LF, Wynick D. Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor. Mol Pain 2012; 8:41. [PMID: 22672616 PMCID: PMC3404965 DOI: 10.1186/1744-8069-8-41] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Accepted: 06/06/2012] [Indexed: 12/11/2022] Open
Abstract
Background Galanin is expressed in a small percentage of intact small diameter sensory neurons of the dorsal root ganglia and in the afferent terminals of the superficial lamina of the dorsal horn of the spinal cord. The neuropeptide modulates nociception demonstrating dose-dependent pro- and anti-nociceptive actions in the naïve animal. Galanin also plays an important role in chronic pain, with the anti-nociceptive actions enhanced in rodent neuropathic pain models. In this study we compared the role played by galanin and its receptors in mechanical and cold allodynia by identifying individual rat C-fibre nociceptors and characterising their responses to mechanical or acetone stimulation. Results Mechanically evoked responses in C-fibre nociceptors from naive rats were sensitised after close intra-arterial infusion of galanin or Gal2-11 (a galanin receptor-2/3 agonist) confirming previous data that galanin modulates nociception via activation of GalR2. In contrast, the same dose and route of administration of galanin, but not Gal2-11, inhibited acetone and menthol cooling evoked responses, demonstrating that this inhibitory mechanism is not mediated by activation of GalR2. We then used the partial saphenous nerve ligation injury model of neuropathic pain (PSNI) and the complete Freund’s adjuvant model of inflammation in the rat and demonstrated that close intra-arterial infusion of galanin, but not Gal2-11, reduced cooling evoked nociceptor activity and cooling allodynia in both paradigms, whilst galanin and Gal2-11 both decreased mechanical activation thresholds. A previously described transgenic mouse line which inducibly over-expresses galanin (Gal-OE) after nerve injury was then used to investigate whether manipulating the levels of endogenous galanin also modulates cooling evoked nociceptive behaviours after PSNI. Acetone withdrawal behaviours in naive mice showed no differences between Gal-OE and wildtype (WT) mice. 7-days after PSNI Gal-OE mice demonstrated a significant reduction in the duration of acetone-induced nociceptive behaviours compared to WT mice. Conclusions These data identify a novel galaninergic mechanism that inhibits cooling evoked neuronal activity and nociceptive behaviours via a putative GalR1 mode of action that would also be consistent with a TRP channel-dependent mechanism.
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Affiliation(s)
- Richard P Hulse
- School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol BS8 1TD, UK
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May D, Baastrup J, Nientit MR, Binder A, Schünke M, Baron R, Cascorbi I. Differential expression and functionality of TRPA1 protein genetic variants in conditions of thermal stimulation. J Biol Chem 2012; 287:27087-94. [PMID: 22665484 DOI: 10.1074/jbc.m112.341776] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of genetic modifications of the TRPA1 receptor has been well documented in inflammatory and neuropathic pain. We recently reported that the E179K variant of TRPA1 appears to be crucial for the generation of paradoxical heat sensation in pain patients. Here, we describe the consequences of the single amino acid exchange at position 179 in the ankyrin repeat 4 of human TRPA1. TRPA1 wild type Lys-179 protein expressed in HEK cells exhibited intact biochemical properties, inclusive trafficking into the plasma membrane, formation of large protein complexes, and the ability to be activated by cold. Additionally, a strong increase of Lys-179 protein expression was observed in cold (4 °C) and heat (49 °C)-treated cells. In contrast, HEK cells expressing the variant Lys-179 TRPA1 failed to get activated by cold possibly due to the loss of ability to interact with other proteins or other TRPA1 monomers during oligomerization. In conclusion, the detailed understanding of TRPA1 genetic variants might provide a fruitful strategy for future development of pain treatments.
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Affiliation(s)
- Denisa May
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein, Campus Kiel, 24105 Kiel, Germany
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Garrison SR, Stucky CL. The dynamic TRPA1 channel: a suitable pharmacological pain target? Curr Pharm Biotechnol 2012; 12:1689-97. [PMID: 21466445 DOI: 10.2174/138920111798357302] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2010] [Accepted: 07/02/2010] [Indexed: 01/13/2023]
Abstract
Acute pain detection is vital to navigate and survive in one's environment. Protection and preservation occur because primary afferent nociceptors transduce adverse environmental stimuli into electrical impulses that are transmitted to and interpreted within high levels of the central nervous system. Therefore, it is critical that the molecular mechanisms that convert noxious information into neural signals be identified, and their specific functional roles delineated in both acute and chronic pain settings. The Transient Receptor Potential (TRP) channel family member TRP ankyrin 1 (TRPA1) is an excellent candidate molecule to explore and intricately understand how single channel properties can tailor behavioral nociceptive responses. TRPA1 appears to dynamically respond to an amazingly wide range of diverse stimuli that include apparently unrelated modalities such as mechanical, chemical and thermal stimuli that activate somatosensory neurons. How such dissimilar stimuli activate TRPA1, yet result in modality-specific signals to the CNS is unclear. Furthermore, TRPA1 is also involved in persistent to chronic painful states such as inflammation, neuropathic pain, diabetes, fibromyalgia, bronchitis and emphysema. Yet how TRPA1's role changes from an acute sensor of physical stimuli to its contribution to these diseases that are concomitant with implacable, chronic pain is unknown. TRPA1's involvement in the nociceptive machinery that relays the adverse stimuli during painful disease states is of considerable interest for drug delivery and design by many pharmaceutical entities. In this review, we will assess the current knowledge base of TRPA1 in acute nociception and persistent inflammatory pain states, and explore its potential as a therapeutic pharmacological target in chronic pervasive conditions such neuropathic pain, persistent inflammation and diabetes.
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Affiliation(s)
- Sheldon R Garrison
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Andrade EL, Meotti FC, Calixto JB. TRPA1 antagonists as potential analgesic drugs. Pharmacol Ther 2011; 133:189-204. [PMID: 22119554 DOI: 10.1016/j.pharmthera.2011.10.008] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 10/29/2011] [Indexed: 12/16/2022]
Abstract
The necessity of safe and effective treatments for chronic pain has intensified the search for new analgesic drugs. In the last few years, members of a closely-related family of ion channels, called transient receptor potential (TRP) have been identified in different cell types and their functions in physiological and pathological conditions have been characterized. The transient receptor potential ankyrin 1 (TRPA1), originally called ANKTM1 (ankyrin-like with transmembrane domains protein 1), is a molecule that has been conserved in different species during evolution; TRPA1 is a cation channel that functions as a cellular sensor, detecting mechanical, chemical and thermal stimuli, being a component of neuronal, epithelial, blood and smooth muscle tissues. In mammals, TRPA1 is largely expressed in primary sensory neurons that mediate somatosensory processes and nociceptive transmission. Recent studies have described the role of TRPA1 in inflammatory and neuropathic pain. However, its participation in cold sensation has not been agreed in different studies. In this review, we focus on data that support the relevance of the activation and blockade of TRPA1 in pain transmission, as well as the mechanisms underlying its activation and modulation by exogenous and endogenous stimuli. We also discuss recent advances in the search for new analgesic medicines targeting the TRPA1 channel.
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Affiliation(s)
- E L Andrade
- Departamento de Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
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Carlton SM, Zhou S, Govea R, Du J. Group II/III metabotropic glutamate receptors exert endogenous activity-dependent modulation of TRPV1 receptors on peripheral nociceptors. J Neurosci 2011; 31:12727-37. [PMID: 21900552 PMCID: PMC3209953 DOI: 10.1523/jneurosci.6558-10.2011] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 07/07/2011] [Accepted: 07/14/2011] [Indexed: 12/13/2022] Open
Abstract
There is pharmacological evidence that group II and III metabotropic glutamate receptors (mGluRs) function as activity-dependent autoreceptors, inhibiting transmission in supraspinal sites. These receptors are expressed by peripheral nociceptors. We investigated whether mGluRs function as activity-dependent autoreceptors inhibiting pain transmission to the rat CNS, particularly transient receptor potential vanilloid 1 (TRPV1)-induced activity. Blocking peripheral mGluR activity by intraplantar injection of antagonists LY341495 [(2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid] (LY) (20, 100 μm, group II/III), APICA [(RS)-1-amino-5-phosphonoindan-1-carboxylic acid] (100 μm, group II), or UBP1112 (α-methyl-3-methyl-4-phosphonophenylglycine) (30 μm, group III) increased capsaicin (CAP)-induced nociceptive behaviors and nociceptor activity. In contrast, group II agonist APDC [(2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate] (0.1 μm) or group III agonist l-(+)-2-amino-4-phosphonobutyric acid (l-AP-4) (10 μm) blocked the LY-induced increase. Ca(2+) imaging in dorsal root ganglion (DRG) cells confirmed LY enhanced CAP-induced Ca(2+) mobilization, which was blocked by APDC and l-AP-4. We hypothesized that excess glutamate (GLU) released by high intensity and/or prolonged stimulation endogenously activated group II/III, dampening nociceptor activation. In support of this, intraplantar GLU + LY produced heat hyperalgesia, and exogenous GLU + LY applied to nociceptors produced enhanced nociceptor activity and thermal sensitization. Intraplantar Formalin, known to elevate extracellular GLU, enhanced pain behaviors in the presence of LY. LY alone produced no pain behaviors, no change in nociceptor discharge rate or heat-evoked responses, and no change in cytosolic Ca(2+) in DRG cells, demonstrating a lack of tonic inhibitory control. Group II/III mGluRs maintain an activity-dependent autoinhibition, capable of significantly reducing TRPV1-induced activity. They are endogenously activated after high-frequency and/or prolonged nociceptor stimulation, acting as built-in negative modulators of TRPV1 and nociceptor function, reducing pain transmission to the CNS.
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Affiliation(s)
- Susan M Carlton
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA.
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41
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Sawynok J, Reid AR. Reduction of formalin-evoked responses and maintenance of peripheral antinociception by morphine against formalin in the spared nerve injury model. Neurosci Lett 2011; 494:99-103. [DOI: 10.1016/j.neulet.2011.02.067] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 02/18/2011] [Accepted: 02/23/2011] [Indexed: 10/18/2022]
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Abstract
TRPA1 is a nonselective cation channel expressed by nociceptors. Although it is widely accepted that TRPA1 serves as a broad irritancy receptor for a variety of reactive chemicals, its role in cold sensation remains controversial. Here, we demonstrate that mild cooling markedly increases agonist-evoked rat TRPA1 currents. In the absence of an agonist, even noxious cold only increases current amplitude slightly. These results suggest that TRPA1 is a key mediator of cold hypersensitivity in pathological conditions in which reactive oxygen species and proinflammatory activators of the channel are present, but likely plays a comparatively minor role in acute cold sensation. Supporting this, cold hypersensitivity can be induced in wild-type but not Trpa1(-/-) mice by subcutaneous administration of a TRPA1 agonist. Furthermore, the selective TRPA1 antagonist HC-030031 [2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide] reduces cold hypersensitivity in rodent models of inflammatory and neuropathic pain.
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Takahashi T, Aoki Y, Okubo K, Maeda Y, Sekiguchi F, Mitani K, Nishikawa H, Kawabata A. Upregulation of Ca(v)3.2 T-type calcium channels targeted by endogenous hydrogen sulfide contributes to maintenance of neuropathic pain. Pain 2010; 150:183-191. [PMID: 20546998 DOI: 10.1016/j.pain.2010.04.022] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Revised: 04/09/2010] [Accepted: 04/20/2010] [Indexed: 11/28/2022]
Abstract
Hydrogen sulfide (H(2)S) formed from l-cysteine by multiple enzymes including cystathionine-gamma-lyase (CSE) is now considered a gasotransmitter in the mammalian body. Our previous studies have shown that H(2)S activates/sensitizes Ca(v)3.2 T-type Ca(2+) channels, leading to facilitation of somatic and visceral nociception, and that CSE-derived endogenous H(2)S participates in inflammatory pain. Here, we show novel evidence for involvement of the endogenous H(2)S-Ca(v)3.2 pathway in neuropathic pain. In the rat subjected to the right L5 spinal nerve cutting (L5SNC), a neuropathic pain model, i.p. administration of dl-propargylglycine (PPG) and beta-cyanoalanine, irreversible and reversible CSE inhibitors, respectively, strongly suppressed the neuropathic hyperalgesia/allodynia. The anti-hyperalgesic effect of PPG was reversed by intraplantar administration of NaHS, a donor for H(2)S, in the L5SNC rat. Intraplantar administration or topical application of mibefradil, a T-type Ca(2+) channel blocker, reversed hyperalgesia in the L5SNC rat. The protein levels of Ca(v)3.2, but not CSE, in the ipsilateral L4, L5 and L6 dorsal root ganglia were dramatically upregulated in the L5SNC rat. Finally, silencing of Ca(v)3.2 in DRG by repeated intrathecal administration of Ca(v)3.2-targeting siRNA significantly attenuated the neuropathic hyperalgesia in the L5SNC rat. In conclusion, our data suggest that Ca(v)3.2 T-type Ca(2+) channels in sensory neurons are upregulated and activated/sensitized by CSE-derived endogenous H(2)S after spinal nerve injury, contributing to the maintenance of neuropathic pain. We thus propose that Ca(v)3.2 and CSE could be targets for the development of therapeutic drugs for the treatment of neuropathic pain.
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Affiliation(s)
- Tomoko Takahashi
- Division of Pharmacology & Pathophysiology, Kinki University School of Pharmacy, Higashi-Osaka 577-8502, Japan
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Kim YS, Son JY, Kim TH, Paik SK, Dai Y, Noguchi K, Ahn DK, Bae YC. Expression of transient receptor potential ankyrin 1 (TRPA1) in the rat trigeminal sensory afferents and spinal dorsal horn. J Comp Neurol 2010; 518:687-98. [PMID: 20034057 DOI: 10.1002/cne.22238] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Transient receptor potential ankyrin 1 (TRPA1), responding to noxious cold and pungent compounds, is implicated in the mediation of nociception, but little is known about the processing of the TRPA1-mediated nociceptive information within the trigeminal sensory nuclei (TSN) and the spinal dorsal horn (DH). To address this issue, we characterized the TRPA1-positive (+) neurons in the trigeminal ganglion (TG) and investigated the distribution of TRPA1(+) afferent fibers and their synaptic connectivity within the rat TSN and DH by using light and electron microscopic immunohistochemistry. In the TG, TRPA1 was expressed in unmyelinated and small myelinated axons and also occasionally in large myelinated axons. Many TRPA1(+) neurons costained for the marker for peptidergic neurons substance P (26.8%) or the marker for nonpeptidergic neurons IB4 (44.5%). In the CNS, small numbers of axons and terminals were immunopositive for TRPA1 throughout the rostral TSN, in contrast to the dense network of positive fibers and terminals in the superficial laminae of the trigeminal caudal nucleus (Vc) and DH. The TRPA1(+) terminals contained clear round vesicles, were presynaptic to one or two dendrites, and rarely participated in axoaxonic contacts, suggesting involvement in relatively simple synaptic circuitry with a small degree of synaptic divergence and little presynaptic modulation. Immunoreactivity for TRPA1 was also occasionally observed in postsynaptic dendrites. These results suggest that TRPA1-dependent orofacial and spinal nociceptive input is processed mainly in the superficial laminae of the Vc and DH in a specific manner and may be processed differently between the rostral TSN and Vc.
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Affiliation(s)
- Yun Sook Kim
- Department of Oral Anatomy and Neurobiology, Kyungpook National University, Daegu, Korea
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45
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Abstract
Neuropathic pain remains a serious medical problem because of patient morbidity and the absence of effective therapeutic interventions. Recent evidence suggests that this type of pain may be particularly difficult to manage because underlying mechanisms are influenced by a variety of factors, including type of injury, site of injury, and time after injury. This situation is exacerbated by the fact that different mechanisms may contribute to unique aspects of neuropathic pain, including ongoing pain as well as mechanical and thermal hypersensitivity. The different ion channels present in primary afferent neurons implicated in each of these aspects of neuropathic pain are reviewed.
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Dunham J, Leith J, Lumb B, Donaldson L. Transient receptor potential channel A1 and noxious cold responses in rat cutaneous nociceptors. Neuroscience 2010; 165:1412-9. [PMID: 19961905 PMCID: PMC2860241 DOI: 10.1016/j.neuroscience.2009.11.065] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 11/24/2009] [Accepted: 11/24/2009] [Indexed: 01/25/2023]
Abstract
The role of transient receptor potential channel A1 (TRPA1) in noxious cold sensation remains unclear. Some data support the hypothesis that TRPA1 is a transducer of noxious cold whilst other data contest it. In this study we investigated the role of TRPA1 in cold detection in cutaneous nociceptors in vivo using complementary experimental approaches. We used noxious withdrawal reflex electromyography, and single fibre recordings in vivo, to test the hypothesis that TRPA1-expressing primary afferents mediate noxious cold responses in anaesthetised rats. TRPV1 and TRPM8 agonists sensitise their cognate receptors to heat and cold stimuli respectively. Herein we show that the TRPA1 agonist cinnamaldehyde applied to the skin in anaesthetised rats did not sensitise noxious cold evoked hind limb withdrawal. In contrast, cinnamaldehyde did sensitise the C fibre-mediated noxious heat withdrawal, indicated by a significant drop in the withdrawal temperature. TRPA1 agonist thus sensitised the noxious reflex withdrawal to heat, but not cold. Thermal stimuli also sensitise transient receptor potential (TRP) channels to agonist. Activity evoked by capsaicin in teased primary afferent fibres showed a significant positive correlation with receptive field temperature, in both normal and Freund's complete adjuvant-induced cutaneous inflammation. Altering the temperature of the receptive field did not modulate TRPA1 agonist evoked-activity in cutaneous primary afferents, in either normal or inflamed skin. In addition, block of the TRPA1 channel with Ruthenium Red did not inhibit cold evoked activity in either cinnamaldehyde sensitive or insensitive cold responsive nociceptors. In cinnamaldehyde-sensitive-cold-sensitive afferents, although TRPA1 agonist-evoked activity was totally abolished by Ruthenium Red, cold evoked activity was unaffected by channel blockade. We conclude that these results do not support the hypothesis that TRPA1-expressing cutaneous afferents play an important role in noxious cold responses.
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Affiliation(s)
| | | | | | - L.F. Donaldson
- Department of Physiology and Pharmacology, University of Bristol, School of Medical Sciences, University Walk, Bristol, BS8 1TD, UK
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Schmidt M, Dubin AE, Petrus MJ, Earley TJ, Patapoutian A. Nociceptive signals induce trafficking of TRPA1 to the plasma membrane. Neuron 2009; 64:498-509. [PMID: 19945392 DOI: 10.1016/j.neuron.2009.09.030] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/16/2009] [Indexed: 11/18/2022]
Abstract
Transient receptor potential A1 (TRPA1) ion channel senses a variety of noxious stimuli and is involved in nociception. Many TRPA1 agonists covalently modify the channel, which can lead to desensitization. The fate of modified TRPA1 and the mechanism of preserving its response to subsequent stimuli are not understood. Moreover, inflammatory signals sensitize TRPA1 by involving protein kinase A (PKA) and phospholipase C (PLC) through unknown means. We show that TRPA1-mediated nocifensive behavior can be sensitized in vivo via PKA/PLC signaling and by activating TRPA1 with the ligand mustard oil (MO). Interestingly, both stimuli increased TRPA1 membrane levels in vitro. Tetanus toxin attenuated the response to the second of two pulses of MO in neurons, suggesting that vesicle fusion increases functional surface TRPA1. Capacitance recordings suggest that MO can induce exocytosis. We propose that TRPA1 translocation to the membrane might represent one of the mechanisms controlling TRPA1 functionality upon acute activation or inflammatory signals.
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Affiliation(s)
- Manuela Schmidt
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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48
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Carlton SM, Du J, Tan HY, Nesic O, Hargett GL, Bopp AC, Yamani A, Lin Q, Willis WD, Hulsebosch CE. Peripheral and central sensitization in remote spinal cord regions contribute to central neuropathic pain after spinal cord injury. Pain 2009; 147:265-76. [PMID: 19853381 DOI: 10.1016/j.pain.2009.09.030] [Citation(s) in RCA: 187] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 09/22/2009] [Accepted: 09/23/2009] [Indexed: 12/13/2022]
Abstract
Central neuropathic pain (CNP) developing after spinal cord injury (SCI) is described by the region affected: above-level, at-level and below-level pain occurs in dermatomes rostral, at/near, or below the SCI level, respectively. People with SCI and rodent models of SCI develop above-level pain characterized by mechanical allodynia and thermal hyperalgesia. Mechanisms underlying this pain are unknown and the goals of this study were to elucidate components contributing to the generation of above-level CNP. Following a thoracic (T10) contusion, forelimb nociceptors had enhanced spontaneous activity and were sensitized to mechanical and thermal stimulation of the forepaws 35 days post-injury. Cervical dorsal horn neurons showed enhanced responses to non-noxious and noxious mechanical stimulation as well as thermal stimulation of receptive fields. Immunostaining dorsal root ganglion (DRG) cells and cord segments with activating transcription factor 3 (ATF3, a marker for neuronal injury) ruled out neuronal damage as a cause for above-level sensitization since few C8 DRG cells expressed AFT3 and cervical cord segments had few to no ATF3-labeled cells. Finally, activated microglia and astrocytes were present in thoracic and cervical cord at 35 days post-SCI, indicating a rostral spread of glial activation from the injury site. Based on these data, we conclude that peripheral and central sensitization as well as reactive glia in the uninjured cervical cord contribute to CNP. We hypothesize that reactive glia in the cervical cord release pro-inflammatory substances which drive chronic CNP. Thus a complex cascade of events spanning many cord segments underlies above-level CNP.
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Affiliation(s)
- Susan M Carlton
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555-1069, USA.
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49
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Morgan CR, Bird EV, Robinson PP, Boissonade FM. TRPA1 expression in human lingual nerve neuromas in patients with and without symptoms of dysaesthesia. Neurosci Lett 2009; 465:189-93. [PMID: 19715741 DOI: 10.1016/j.neulet.2009.08.055] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/17/2009] [Accepted: 08/21/2009] [Indexed: 11/15/2022]
Abstract
The TRPA1 receptor is a member of the ankyrin family and is found in both spinal and trigeminal neurones. There is evidence to suggest that this receptor may be a sensor of noxious thermal stimuli in normal animals. After nerve injury, TRPA1 shows increased expression in uninjured axons, and has been implicated in the development and maintenance of hyperalgesia. We examined expression of TRPA1 in lingual nerve neuromas and investigated any potential correlation with the presence or absence of symptoms of dysaesthesia. Thirteen neuroma-in-continuity specimens were obtained from patients undergoing repair of a lingual nerve that had previously been damaged during lower third molar removal. Visual analogue scales (VAS) were used to record the degree of pain, tingling and discomfort. Tissue was processed for indirect immunofluorescence and the percentage area of PGP 9.5-immunoreactive neuronal tissue also labelled for TRPA1 was quantified. No significant difference between levels of TRPA1 in neuromas from patients with or without symptoms of dysaesthesia and no relationship between TRPA1 expression and VAS scores for pain, tingling or discomfort were observed. TRPA1 expression and the time after initial injury that the specimen was obtained also showed no correlation. These data show that TRPA1 is expressed in lingual nerve neuromas, but, it appears that, at this site, TRPA1 does not play a principal role in the development of neuropathic pain.
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Affiliation(s)
- Claire R Morgan
- Department of Oral and Maxillofacial Medicine and Surgery, University of Sheffield, United Kingdom.
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Tsunozaki M, Bautista DM. Mammalian somatosensory mechanotransduction. Curr Opin Neurobiol 2009; 19:362-9. [PMID: 19683913 PMCID: PMC4044613 DOI: 10.1016/j.conb.2009.07.008] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 07/10/2009] [Accepted: 07/13/2009] [Indexed: 11/22/2022]
Abstract
In the mammalian somatosensory system, mechanosensitive neurons mediate the senses of touch and pain. Among sensory modalities, mechanosensation has been the most elusive with regard to the identification of transduction molecules. One factor that has hindered the identification of transduction molecules is the diversity of neurons; physiological studies have revealed many subtypes of neurons, specialized to detect a variety of mechanical stimuli. Do different subtypes use the same transduction molecules that are modified by cellular context? Or, are there multiple mechanotransducers that specialize in sensing different mechanical stimuli? This review highlights recent progress in identifying and characterizing candidate molecular force transducers, as well as the development of new tools to characterize touch transduction at the molecular, cellular, and behavioral levels.
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Affiliation(s)
- Makoto Tsunozaki
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA
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