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Yosipovitch G, Kim B, Luger T, Lerner E, Metz M, Adiri R, Canosa JM, Cha A, Ständer S. Similarities and differences in peripheral itch and pain pathways in atopic dermatitis. J Allergy Clin Immunol 2024; 153:904-912. [PMID: 38103700 DOI: 10.1016/j.jaci.2023.10.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 09/22/2023] [Accepted: 10/12/2023] [Indexed: 12/19/2023]
Abstract
Atopic dermatitis (AD) is predominantly characterized by intense itching, but concomitant skin pain is experienced by more than 40% of patients. Patients with AD display considerable somatosensory aberrations, including increased nerve sensitivity to itch stimuli (hyperknesis), perception of itch from innocuous stimuli (alloknesis), or perception of pain from innocuous stimuli (allodynia). This review summarizes the current understanding of the similarities and differences in the peripheral mechanisms underlying itch and pain in AD. These distinct yet reciprocal sensations share many similarities in the peripheral nervous system, including common mediators (such as serotonin, endothelin-1, IL-33, and thymic stromal lymphopoietin), receptors (such as members of the G protein-coupled receptor family and Toll-like receptors), and ion channels for signal transduction (such as certain members of the transient receptor potential [TRP] cation channels). Itch-responding neurons are also sensitive to pain stimuli. However, there are distinct differences between itch and pain signaling. For example, specific immune responses are associated with pain (type 1 and/or type 3 cytokines and certain chemokine C-C [CCL2, CCL5] and C-X-C [CXCL] motif ligands) and itch (type 2 cytokines, including IL-31, and periostin). The TRP melastatin channels TRPM2 and TRPM3 have a role in pain but no known role in itch. Activation of μ-opioid receptors is known to alleviate pain but exacerbate itch. Understanding the connection between itch and pain mechanisms may offer new insights into the treatment of chronic pain and itch in AD.
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Affiliation(s)
- Gil Yosipovitch
- Miami Itch Center, Miller School of Medicine, University of Miami, Miami, Fla.
| | - Brian Kim
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, St Louis, Mo
| | | | - Ethan Lerner
- Massachusetts General Hospital, Charlestown, Mass
| | - Martin Metz
- Institute of Allergology, Charité-Universitätsmedizin Berlin, Berlin, Germany; Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Allergology and Immunology, Berlin, Germany
| | - Roni Adiri
- Pfizer Pharmaceuticals Israel Ltd, Herzliya Pituach, Israel
| | | | | | - Sonja Ständer
- Center for Chronic Pruritus, Münster University Hospital, Münster, Germany
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Li L, Li ZE, Mo YL, Li WY, Li HJ, Yan GH, Qin XZ, Piao LH. Molecular and cellular pruritus mechanisms in the host skin. Exp Mol Pathol 2024; 136:104889. [PMID: 38316203 DOI: 10.1016/j.yexmp.2024.104889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 12/28/2023] [Accepted: 01/31/2024] [Indexed: 02/07/2024]
Abstract
Pruritus, also known as itching, is a complex sensation that involves the activation of specific physiological and cellular receptors. The skin is innervated with sensory nerves as well as some receptors for various sensations, and its immune system has prominent neurological connections. Sensory neurons have a considerable impact on the sensation of itching. However, immune cells also play a role in this process, as they release pruritogens. Disruption of the dermal barrier activates an immune response, initiating a series of chemical, physical, and cellular reactions. These reactions involve various cell types, including keratinocytes, as well as immune cells involved in innate and adaptive immunity. Collective activation of these immune responses confers protection against potential pathogens. Thus, understanding the molecular and cellular mechanisms that contribute to pruritus in host skin is crucial for the advancement of effective treatment approaches. This review provides a comprehensive analysis of the present knowledge concerning the molecular and cellular mechanisms underlying itching signaling in the skin. Additionally, this review explored the integration of these mechanisms with the broader context of itch mediators and the expression of their receptors in the skin.
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Affiliation(s)
- Li Li
- Jilin Key Laboratory for Immune and Targeting Research on Common Allergic Diseases, Yanbian University, Yanji 133002, China; Department of Anatomy, Yanbian University Medical College, Yanji 133002, China
| | - Zhi-En Li
- Clinical Medicine, Yanbian University Medical College, Yanji 133002, China
| | - Yun-Li Mo
- Clinical Medicine, Yanbian University Medical College, Yanji 133002, China
| | - Wan-Yao Li
- Clinical Medicine, Yanbian University Medical College, Yanji 133002, China
| | - Hui-Jing Li
- Clinical Medicine, Yanbian University Medical College, Yanji 133002, China
| | - Guang-Hai Yan
- Jilin Key Laboratory for Immune and Targeting Research on Common Allergic Diseases, Yanbian University, Yanji 133002, China; Department of Anatomy, Yanbian University Medical College, Yanji 133002, China
| | - Xiang-Zheng Qin
- Jilin Key Laboratory for Immune and Targeting Research on Common Allergic Diseases, Yanbian University, Yanji 133002, China; Department of Anatomy, Yanbian University Medical College, Yanji 133002, China.
| | - Li-Hua Piao
- Jilin Key Laboratory for Immune and Targeting Research on Common Allergic Diseases, Yanbian University, Yanji 133002, China; Department of Anatomy, Yanbian University Medical College, Yanji 133002, China.
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Li DJ, Zhong ZJ, Wang XL, Wei N, Zhao SJ, Shan TT, Liu YP, Yu YQ. Chemokine receptor CXCR2 in primary sensory neurons of trigeminal ganglion mediates orofacial itch. Front Mol Neurosci 2023; 16:1279237. [PMID: 37953876 PMCID: PMC10637378 DOI: 10.3389/fnmol.2023.1279237] [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: 09/05/2023] [Accepted: 10/16/2023] [Indexed: 11/14/2023] Open
Abstract
The CXCR2 chemokine receptor is known to have a significant impact on the initiation and control of inflammatory processes. However, its specific involvement in the sensation of itch is not yet fully understood. In this study, we aimed to elucidate the function of CXCR2 in the trigeminal ganglion (TG) by utilizing orofacial itch models induced by incision, chloroquine (CQ), and histamine. Our results revealed a significant up-regulation of CXCR2 mRNA and protein expressions in the primary sensory neurons of TG in response to itch stimuli. The CXCR2 inhibitor SB225002 resulted in notable decrease in CXCR2 protein expression and reduction in scratch behaviors. Distal infraorbital nerve (DION) microinjection of a specific shRNA virus inhibited CXCR2 expression in TG neurons and reversed itch behaviors. Additionally, the administration of the PI3K inhibitor LY294002 resulted in a decrease in the expressions of p-Akt, Akt, and CXCR2 in TG neurons, thereby mitigating pruritic behaviors. Collectively, we report that CXCR2 in the primary sensory neurons of trigeminal ganglion contributes to orofacial itch through the PI3K/Akt signaling pathway. These observations highlight the potential of molecules involved in the regulation of CXCR2 as viable therapeutic targets for the treatment of itch.
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Affiliation(s)
- Dong-Jin Li
- College of Life Sciences, Northwest University, Xi’an, China
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
| | - Zhen-Juan Zhong
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
| | - Xiao-Liang Wang
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
| | - Na Wei
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
| | - Si-Jia Zhao
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
| | - Ting-Ting Shan
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
| | - Ya-Ping Liu
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
| | - Yao-Qing Yu
- College of Life Sciences, Northwest University, Xi’an, China
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, Air Force Medical University, Xi’an, China
- Key Laboratory of Brain Stress and Behavior, People’s Liberation Army, Xi’an, China
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da Silva CN, Miot HA, Grassi TF, Dias-Melício LA, Santos L, Espósito ACC. Expression of Endothelin-1, Endothelin Receptor-A, and Endothelin Receptor-B in facial melasma compared to adjacent skin. Clin Cosmet Investig Dermatol 2023; 16:2847-2853. [PMID: 37850109 PMCID: PMC10578179 DOI: 10.2147/ccid.s402168] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 09/28/2023] [Indexed: 10/19/2023]
Abstract
Background/Objectives Although melasma is highly prevalent, its pathogenesis is not yet fully understood. In the skin, endothelin-1 (ET-1) is primarily produced by keratinocytes in response to UVB exposure, which is mediated by an increase in IL-1α or reactive oxygen species. ET-1 plays a role in melanogenesis by binding to specific receptor B (ERB) or receptor A (ERA). However, the expression of ET-1, ERA, and ERB in melasma has not been systematically investigated. The objective of this study was to evaluate the expression of ET-1, ERA, and ERB in facial melasma compared to the adjacent unaffected skin. Methods Cross-sectional study, with 40 skin samples (20: facial melasma; 20: adjacent unaffected skin) from women with facial melasma without treatment for 30 days except for sunscreen. A triple staining immunofluorescence technique was performed for anti-vimentin, DAPI, plus one of the following antibodies: (a) anti-ET1, (b) anti-ERA; (c) anti-ERB. Interfollicular areas on the slides of each topography (melasma; unaffected skin) were photographed in triplicate under confocal laser microscopy. The mean staining intensities of the image histograms (0-255 pixels intensity) were estimated for different types of cells (suprabasal keratinocytes, basal layer, and upper dermis) and were blindly compared between topographies. Results The mean (SD) age of the participants was 44.9 (9.2). The expression of ET-1 was increased in the whole epidermis with melasma when compared to the adjacent skin, being 32.8% (CI95% 14.7%-52.6%) higher in the spinous layer (p=0.013), 30.4% (CI95% 13.7%-47.9%) higher in the basal layer (p=0.014), and 29.7% (CI95% 11.4%-49.7%) higher in the melanocytes (p=0.006). There was no noticeable expression of ET-1 within the cells on the upper dermis. Neither ERA nor ERB resulted in differential epidermal expression between melasma and unaffected skin (p≥0.1). Conclusion ET-1 is expressed more intensely on the epidermis from the skin with facial melasma compared to the unaffected adjacent skin.
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Affiliation(s)
- Carolina Nunhez da Silva
- Department of Dermatology, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
| | - Hélio Amante Miot
- Department of Dermatology, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
| | - Tony Fernando Grassi
- UNIPEX - Experimental Research Unit, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
| | - Luciane Alarcão Dias-Melício
- UNIPEX - Experimental Research Unit, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
- Laboratory of Immunopathology and Infectious Agents – LIAI, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
- Department of Pathology, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
| | - Leandro Santos
- UNIPEX - Experimental Research Unit, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
- Laboratory of Immunopathology and Infectious Agents – LIAI, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
| | - Ana Cláudia Cavalcante Espósito
- Department of Dermatology, São Paulo State University (UNESP) - Medical School of Botucatu, Botucatu, São Paulo State, Brazil
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Koumaki D, Gregoriou S, Evangelou G, Krasagakis K. Pruritogenic Mediators and New Antipruritic Drugs in Atopic Dermatitis. J Clin Med 2023; 12:2091. [PMID: 36983094 PMCID: PMC10054239 DOI: 10.3390/jcm12062091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/27/2023] [Accepted: 03/01/2023] [Indexed: 03/30/2023] Open
Abstract
Atopic dermatitis (AD) is a common highly pruritic chronic inflammatory skin disorder affecting 5-20% of children worldwide, while the prevalence in adults varies from 7 to 10%. Patients with AD experience intense pruritus that could lead to sleep disturbance and impaired quality of life. Here, we analyze the pathophysiology of itchiness in AD. We extensively review the histamine-dependent and histamine-independent pruritogens. Several receptors, substance P, secreted molecules, chemokines, and cytokines are involved as mediators in chronic itch. We also, summarize the new emerging antipruritic drugs in atopic dermatitis.
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Affiliation(s)
- Dimitra Koumaki
- Dermatology Department, University Hospital of Heraklion, 71110 Heraklion, Greece
| | - Stamatios Gregoriou
- Department of Dermatology and Venereology, Andreas Sygros Hospital, Medical School of Athens, National and Kapodistrian University of Athens, 16121 Athens, Greece
| | - George Evangelou
- Dermatology Department, University Hospital of Heraklion, 71110 Heraklion, Greece
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Hiroyasu S, Barit JVJG, Hiroyasu A, Tsuruta D. Pruritogens in pemphigoid diseases: Possible therapeutic targets for a burdensome symptom. J Dermatol 2023; 50:150-161. [PMID: 36477831 PMCID: PMC10108135 DOI: 10.1111/1346-8138.16652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 12/12/2022]
Abstract
Pruritus is a hallmark feature in pemphigoid diseases, where it can be severe and greatly impact the quality of life of affected patients. Despite being a key symptom, the exact pathophysiological mechanisms involved in pruritus in pemphigoid are yet to be fully elucidated and effective therapies addressing them are limited. This review summarizes the present understanding of pruritus specific to pemphigoid diseases, especially the pruritogens that induce it, and the therapeutic options that have been explored so far. The majority of the available evidence is on bullous pemphigoid and epidermolysis bullosa acquisita. Histamine derived from basophils correlates with pruritus severity, with omalizumab demonstrating promising efficacy in pruritus for bullous pemphigoid. IL-4/-13 contribute to itch in bullous pemphigoid with dupilumab being evaluated in clinical trials. Other pruritogens of interest include substance P, tryptase, and thymic stromal lymphopoetin, with therapies targeting them requiring further investigation. Scratching behaviors contribute directly to blister formation through various mechanisms, such as pathological autoantibody recruitment, T helper cell type 1 polarization, and exposure of intracellular autoantigens. Treatments addressing these pathways may contribute to decreasing disease severity. Additional studies are needed to fully characterize how pruritus is regulated in pemphigoid diseases, to help pave the way to develop novel and effective therapeutics that will not only address pruritic symptoms but also decrease disease severity.
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Affiliation(s)
- Sho Hiroyasu
- Department of Dermatology, Osaka Metropolitan University Graduate School of Medicine, Osaka, Japan
| | - Jay-V James G Barit
- Department of Dermatology, Osaka Metropolitan University Graduate School of Medicine, Osaka, Japan
| | - Aoi Hiroyasu
- Department of Dermatology, Osaka Metropolitan University Graduate School of Medicine, Osaka, Japan
| | - Daisuke Tsuruta
- Department of Dermatology, Osaka Metropolitan University Graduate School of Medicine, Osaka, Japan
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Sensory neuron-expressed TRPC3 mediates acute and chronic itch. Pain 2023; 164:98-110. [PMID: 35507377 DOI: 10.1097/j.pain.0000000000002668] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 04/20/2022] [Indexed: 01/09/2023]
Abstract
ABSTRACT Chronic pruritus is a prominent symptom of allergic contact dermatitis (ACD) and represents a huge unmet health problem. However, its underlying cellular and molecular mechanisms remain largely unexplored. TRPC3 is highly expressed in primary sensory neurons and has been implicated in peripheral sensitization induced by proinflammatory mediators. Yet, the role of TRPC3 in acute and chronic itch is still not well defined. Here, we show that, among mouse trigeminal ganglion (TG) neurons, Trpc3 mRNA is predominantly expressed in nonpeptidergic small diameter TG neurons of mice. Moreover, Trpc3 mRNA signal was present in most presumptively itch sensing neurons. TRPC3 agonism induced TG neuronal activation and acute nonhistaminergic itch-like and pain-like behaviors in naive mice. In addition, genetic deletion of Trpc3 attenuated acute itch evoked by certain common nonhistaminergic pruritogens, including endothelin-1 and SLIGRL-NH2. In a murine model of contact hypersensitivity (CHS), the Trpc3 mRNA expression level and function were upregulated in the TG after CHS. Pharmacological inhibition and global knockout of Trpc3 significantly alleviated spontaneous scratching behaviors without affecting concurrent cutaneous inflammation in the CHS model. Furthermore, conditional deletion of Trpc3 in primary sensory neurons but not in keratinocytes produced similar antipruritic effects in this model. These findings suggest that TRPC3 expressed in primary sensory neurons may contribute to acute and chronic itch through a histamine independent mechanism and that targeting neuronal TRPC3 might benefit the treatment of chronic itch associated with ACD and other inflammatory skin disorders.
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8
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Critical Players and Therapeutic Targets in Chronic Itch. Int J Mol Sci 2022; 23:ijms23179935. [PMID: 36077340 PMCID: PMC9456029 DOI: 10.3390/ijms23179935] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/28/2022] [Accepted: 08/29/2022] [Indexed: 12/04/2022] Open
Abstract
Chronic itch is one of the most prominent clinical characteristics of diverse systematic diseases. It is a devastating sensation in pathological diseases. Despite its importance, there are no FDA-labelled drugs specifically geared toward chronic itch. The associated complex pathogenesis and diverse causes escalate chronic itch to being one of the top challenges in healthcare. Humanized antibodies against IL-13, IL-4, and IL-31 proved effective in treatment of itch-associated atopic dermatitis but remain to be validated in chronic itch. There are still no satisfactory anti-itch therapeutics available toward itch-related neuropeptides including GRP, BNP, SST, CGRP, and SP. The newly identified potential itch targets including OSM, NMB, glutamate, periostin, and Serpin E1 have opened new avenues for therapeutic development. Proof-of-principle studies have been successfully performed on antagonists against these proteins and their receptors in itch treatment in animal models. Their translational interventions in humans need to be evaluated. It is of great importance to summarize and compare the newly emerging knowledge on chronic itch and its pathways to promote the development of novel anti-itch therapeutics. The goal of this review is to analyze the different physiologies and pathophysiologies of itch mediators, whilst assessing their suitability as new targets and discussing future therapeutic development.
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Tominaga M, Takamori K. Peripheral itch sensitization in atopic dermatitis. Allergol Int 2022; 71:265-277. [PMID: 35624035 DOI: 10.1016/j.alit.2022.04.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Accepted: 04/06/2022] [Indexed: 02/07/2023] Open
Abstract
Atopic dermatitis is a skin disorder caused by skin dryness and barrier dysfunction, resulting in skin inflammation and chronic itch (or pruritus). The pathogenesis of atopic dermatitis is thought to be initiated by a lowering of the itch threshold due to dry skin. This lowering of the itch threshold is at least partially due to the increase in intraepidermal nerve fibers and sensitization of sensory nerves by interleukin (IL)-33 produced and secreted by keratinocytes. Such skin is easily prone to itch due to mechanical stimuli, such as rubbing of clothing and chemical stimuli from itch mediators. In patients with atopic dermatitis, once itch occurs, further itch is induced by scratching, and the associated scratching breaks down the skin barrier. Disruption of the skin barrier allows entry into the epidermis of external foreign substances, such as allergens derived from house dust mites, leading to an increased induction of type 2 inflammatory responses. As a result, type 2 cytokines IL-4, IL-13, and IL-31 are mainly secreted by Th2 cells, and their action on sensory nerve fibers causes further itch sensitization. These sequences of events are thought to occur simultaneously in patients with atopic dermatitis, leading to a vicious itch-scratch cycle. This vicious cycle becomes a negative spiral that leads to disease burden. Therefore, controlling itch is essential for the treatment of atopic dermatitis. In this review, we summarize and discuss advances in the mechanisms of peripheral itch sensitization in atopic dermatitis, focusing on skin barrier-neuro-immune triadic connectivity.
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Szöllősi AG, Oláh A, Lisztes E, Griger Z, Tóth BI. Pruritus: A Sensory Symptom Generated in Cutaneous Immuno-Neuronal Crosstalk. Front Pharmacol 2022; 13:745658. [PMID: 35321329 PMCID: PMC8937025 DOI: 10.3389/fphar.2022.745658] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 02/07/2022] [Indexed: 12/21/2022] Open
Abstract
Pruritus or itch generated in the skin is one of the most widespread symptoms associated with various dermatological and systemic (immunological) conditions. Although many details about the molecular mechanisms of the development of both acute and chronic itch were uncovered in the last 2 decades, our understanding is still incomplete and the clinical management of pruritic conditions is one of the biggest challenges in daily dermatological practice. Recent research revealed molecular interactions between pruriceptive sensory neurons and surrounding cutaneous cell types including keratinocytes, as well as resident and transient cells of innate and adaptive immunity. Especially in inflammatory conditions, these cutaneous cells can produce various mediators, which can contribute to the excitation of pruriceptive sensory fibers resulting in itch sensation. There also exists significant communication in the opposite direction: sensory neurons can release mediators that maintain an inflamed, pruritic tissue-environment. In this review, we summarize the current knowledge about the sensory transduction of pruritus detailing the local intercellular interactions that generate itch. We especially emphasize the role of various pruritic mediators in the bidirectional crosstalk between cutaneous non-neuronal cells and sensory fibers. We also list various dermatoses and immunological conditions associated with itch, and discuss the potential immune-neuronal interactions promoting the development of pruritus in the particular diseases. These data may unveil putative new targets for antipruritic pharmacological interventions.
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Affiliation(s)
- Attila Gábor Szöllősi
- Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Attila Oláh
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Erika Lisztes
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zoltán Griger
- Division of Clinical Immunology, Department of Internal Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs István Tóth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- *Correspondence: Balázs István Tóth,
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11
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Toyama S, Tominaga M, Takamori K. Connections between Immune-Derived Mediators and Sensory Nerves for Itch Sensation. Int J Mol Sci 2021; 22:12365. [PMID: 34830245 PMCID: PMC8624544 DOI: 10.3390/ijms222212365] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/09/2021] [Accepted: 11/15/2021] [Indexed: 12/28/2022] Open
Abstract
Although histamine is a well-known itch mediator, histamine H1-receptor blockers often lack efficacy in chronic itch. Recent molecular and cellular based studies have shown that non-histaminergic mediators, such as proteases, neuropeptides and cytokines, along with their cognate receptors, are involved in evocation and modulation of itch sensation. Many of these molecules are produced and secreted by immune cells, which act on sensory nerve fibers distributed in the skin to cause itching and sensitization. This understanding of the connections between immune cell-derived mediators and sensory nerve fibers has led to the development of new treatments for itch. This review summarizes current knowledge of immune cell-derived itch mediators and neuronal response mechanisms, and discusses therapeutic agents that target these systems.
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Affiliation(s)
- Sumika Toyama
- Juntendo Itch Research Center (JIRC), Institute for Environmental and Gender-Specific Medicine, Juntendo University Graduate School of Medicine, 2-1-1 Tomioka, Chiba 279-0021, Japan; (S.T.); (M.T.)
| | - Mitsutoshi Tominaga
- Juntendo Itch Research Center (JIRC), Institute for Environmental and Gender-Specific Medicine, Juntendo University Graduate School of Medicine, 2-1-1 Tomioka, Chiba 279-0021, Japan; (S.T.); (M.T.)
- Anti-Aging Skin Research Laboratory, Juntendo University Graduate School of Medicine, 2-1-1 Tomioka, Chiba 279-0021, Japan
| | - Kenji Takamori
- Juntendo Itch Research Center (JIRC), Institute for Environmental and Gender-Specific Medicine, Juntendo University Graduate School of Medicine, 2-1-1 Tomioka, Chiba 279-0021, Japan; (S.T.); (M.T.)
- Anti-Aging Skin Research Laboratory, Juntendo University Graduate School of Medicine, 2-1-1 Tomioka, Chiba 279-0021, Japan
- Department of Dermatology, Juntendo University Urayasu Hospital, 2-1-1 Tomioka, Chiba 279-0021, Japan
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Kido‐Nakahara M, Wang B, Ohno F, Tsuji G, Ulzii D, Takemura M, Furue M, Nakahara T. Inhibition of mite-induced dermatitis, pruritus, and nerve sprouting in mice by the endothelin receptor antagonist bosentan. Allergy 2021; 76:291-301. [PMID: 32535962 DOI: 10.1111/all.14451] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 05/09/2020] [Accepted: 05/19/2020] [Indexed: 01/18/2023]
Abstract
BACKGROUND Endothelin-1 (EDN1) can evoke histamine-independent pruritus in mammals and is upregulated in the lesional epidermis of atopic dermatitis (AD). EDN1 increases the production of interleukin 25 (IL-25) from keratinocytes to accelerate T helper type 2 immune deviation. Plasma EDN1 levels are positively correlated with the clinical severity and itch intensity of AD. Therefore, we hypothesized that the inhibition of EDN1 might be useful for treating atopic inflammation and itch and investigated the effects of the topical application of the EDN1 receptor antagonist bosentan on the skin inflammation and itch in a murine AD model. METHODS We analyzed the mite-induced AD-like NC/Nga murine model, which was topically applied with bosentan or ethanol control every day for 3 weeks. We also subjected in vitro primary sensory neuron culture systems to nerve elongation and branching assays after EDN1 stimulation. RESULTS Topical application of bosentan significantly attenuated the development of mite-induced AD-like skin inflammation, dermatitis scores, ear thickness, scratching bouts, and serum level of thymus and activation-regulated chemokine in NC/Nga mice. Bosentan application also significantly reduced the gene expression of Il13, Il17, and Ifng in the treated lesions. Histologically, the number of infiltrated dermal cells, the epidermal EDN1 expression, and the number of intraepidermal nerve fibers were significantly inhibited upon bosentan application. While EDN1 significantly elongated the neurites of dorsal root ganglion cells in a dose- and time-dependent manner, bosentan treatment attenuated this. CONCLUSIONS EDN1 plays a significant role in mite-induced inflammation and itch. Topical bosentan is a potential protective candidate for AD.
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Affiliation(s)
- Makiko Kido‐Nakahara
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
| | - Bing Wang
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
| | - Fumitaka Ohno
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
| | - Gaku Tsuji
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
- Research and Clinical Center for Yusho and Dioxin Kyushu University Hospital Fukuoka Japan
| | - Dugarmaa Ulzii
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
- Department of Dermatology National Dermatology Center of Mongolia Ulaanbaatar Mongolia
| | - Masaki Takemura
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
| | - Masutaka Furue
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
- Research and Clinical Center for Yusho and Dioxin Kyushu University Hospital Fukuoka Japan
- Division of Skin Surface Sensing Graduate School of Medical Sciences Kyushu University Fukuoka Japan
| | - Takeshi Nakahara
- Department of Dermatology Graduate School of Medical Sciences Kyushu University Fukuoka Japan
- Division of Skin Surface Sensing Graduate School of Medical Sciences Kyushu University Fukuoka Japan
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Kelemen B, Pinto S, Kim N, Lisztes E, Hanyicska M, Vládar A, Oláh A, Pénzes Z, Shu B, Vriens J, Bíró T, Rohács T, Voets T, Tóth BI. The TRPM3 ion channel mediates nociception but not itch evoked by endogenous pruritogenic mediators. Biochem Pharmacol 2021; 183:114310. [PMID: 33130130 PMCID: PMC8086171 DOI: 10.1016/j.bcp.2020.114310] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 10/22/2020] [Accepted: 10/27/2020] [Indexed: 02/06/2023]
Abstract
During the molecular transduction of itch, the stimulation of pruriceptors on sensory fibers leads to the activation or sensitization of ion channels, which results in a consequent depolarization of the neurons. These ion channels mostly belong to the transient receptor potential (TRP) channels, which are involved in nociception and thermosensation. In particular, TRPV1 and TRPA1 were described in the transduction of both thermal nociception as well as histaminergic and non-histaminergic itch. The thermosensitive TRPM3 plays an indispensable role in heat nociception together with TRPV1 and TRPA1. However, the role of TRPM3 in the development of pruritus has not been studied yet. Therefore, in this study we aimed at investigating the potential role of TRPM3 in the transduction of pruritus and pain by investigating itch- and nociception-related behavior of Trpm3+/+ and Trpm3-/- mice, and by studying the activation of somatosensory neurons isolated from trigeminal ganglia upon application of algogenic and pruritogenic substances. Activators of TRPM3 evoked only nocifensive responses, but not itch in Trpm3+/+ animals, and these nocifensive responses were abolished in the Trpm3-/- strain. Histamine and endogenous non-histaminergic pruritogens induced itch in both Trpm3+/+ and Trpm3-/- mice to a similar extent. Genetic deletion or pharmacological blockade diminished TRPM3 mediated Ca2+ responses of sensory neurons, but did not affect responses evoked by pruritogenic substances. Our results demonstrate that, in contrast to other thermosensitive TRP channels, TRPM3 selectively mediates nociception, but not itch sensation, and suggest that TRPM3 is a promising candidate to selectively target pain sensation.
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Affiliation(s)
- Balázs Kelemen
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Laboratory of Ion Channel Research (VIB-KU Leuven Center for Brain & Disease Research) Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
- Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Doctoral School of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Silvia Pinto
- Laboratory of Ion Channel Research (VIB-KU Leuven Center for Brain & Disease Research) Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Nawoo Kim
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Erika Lisztes
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Martin Hanyicska
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Doctoral School of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Anita Vládar
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Doctoral School of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Attila Oláh
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zsófia Pénzes
- Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Doctoral School of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Brian Shu
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Joris Vriens
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
| | - Tamás Bíró
- Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tibor Rohács
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Thomas Voets
- Laboratory of Ion Channel Research (VIB-KU Leuven Center for Brain & Disease Research) Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Balázs István Tóth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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Rosenbaum T, Benítez-Angeles M, Sánchez-Hernández R, Morales-Lázaro SL, Hiriart M, Morales-Buenrostro LE, Torres-Quiroz F. TRPV4: A Physio and Pathophysiologically Significant Ion Channel. Int J Mol Sci 2020; 21:ijms21113837. [PMID: 32481620 PMCID: PMC7312103 DOI: 10.3390/ijms21113837] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 05/23/2020] [Accepted: 05/24/2020] [Indexed: 02/07/2023] Open
Abstract
Transient Receptor Potential (TRP) channels are a family of ion channels whose members are distributed among all kinds of animals, from invertebrates to vertebrates. The importance of these molecules is exemplified by the variety of physiological roles they play. Perhaps, the most extensively studied member of this family is the TRPV1 ion channel; nonetheless, the activity of TRPV4 has been associated to several physio and pathophysiological processes, and its dysfunction can lead to severe consequences. Several lines of evidence derived from animal models and even clinical trials in humans highlight TRPV4 as a therapeutic target and as a protein that will receive even more attention in the near future, as will be reviewed here.
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Affiliation(s)
- Tamara Rosenbaum
- Departamento de Neurociencia Cognitiva, División Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (M.B.-A.); (R.S.-H.); (S.L.M.-L.); (M.H.)
- Correspondence: ; Tel.: +52-555-622-56-24; Fax: +52-555-622-56-07
| | - Miguel Benítez-Angeles
- Departamento de Neurociencia Cognitiva, División Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (M.B.-A.); (R.S.-H.); (S.L.M.-L.); (M.H.)
| | - Raúl Sánchez-Hernández
- Departamento de Neurociencia Cognitiva, División Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (M.B.-A.); (R.S.-H.); (S.L.M.-L.); (M.H.)
| | - Sara Luz Morales-Lázaro
- Departamento de Neurociencia Cognitiva, División Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (M.B.-A.); (R.S.-H.); (S.L.M.-L.); (M.H.)
| | - Marcia Hiriart
- Departamento de Neurociencia Cognitiva, División Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (M.B.-A.); (R.S.-H.); (S.L.M.-L.); (M.H.)
| | - Luis Eduardo Morales-Buenrostro
- Departamento de Nefrología y Metabolismo Mineral, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City 14080, Mexico;
| | - Francisco Torres-Quiroz
- Departamento de Bioquímica y Biología Estructural, División Investigación Básica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico;
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15
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Magnúsdóttir EI, Grujic M, Bergman J, Pejler G, Lagerström MC. Mouse connective tissue mast cell proteases tryptase and carboxypeptidase A3 play protective roles in itch induced by endothelin-1. J Neuroinflammation 2020; 17:123. [PMID: 32321525 PMCID: PMC7175568 DOI: 10.1186/s12974-020-01795-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 03/30/2020] [Indexed: 11/17/2022] Open
Abstract
Background Itch is an unpleasant sensation that can be debilitating, especially if it is chronic and of non-histaminergic origin, as treatment options are limited. Endothelin-1 (ET-1) is a potent endogenous vasoconstrictor that also has the ability to induce a burning, non-histaminergic pruritus when exogenously administered, by activating the endothelin A receptor (ETAR) on primary afferents. ET-1 is released endogenously by several cell-types found in the skin, including macrophages and keratinocytes. Mast cells express ETARs and can thereby be degranulated by ET-1, and mast cell proteases chymase and carboxypeptidase A3 (CPA3) are known to either generate or degrade ET-1, respectively, suggesting a role for mast cell proteases in the regulation of ET-1-induced itch. The mouse mast cell proteases (mMCPs) mMCP4 (chymase), mMCP6 (tryptase), and CPA3 are found in connective tissue type mast cells and are the closest functional homologs to human mast cell proteases, but little is known about their role in endothelin-induced itch. Methods In this study, we evaluated the effects of mast cell protease deficiency on scratching behavior induced by ET-1. To investigate this, mMCP knock-out and transgenic mice were injected intradermally with ET-1 and their scratching behavior was recorded and analyzed. Results CPA3-deficient mice and mice lacking all three proteases demonstrated highly elevated levels of scratching behavior compared with wild-type controls. A modest increase in the number of scratching bouts was also seen in mMCP6-deficient mice, while mMCP4-deficiency did not have any effect. Conclusion Altogether, these findings identify a prominent role for the mast cell proteases, in particular CPA3, in the protection against itch induced by ET-1.
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Affiliation(s)
- Elín I Magnúsdóttir
- Department of Neuroscience, Uppsala University, Husargatan 3, Box 593, 751 24, Uppsala, Sweden
| | - Mirjana Grujic
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Jessica Bergman
- Department of Neuroscience, Uppsala University, Husargatan 3, Box 593, 751 24, Uppsala, Sweden
| | - Gunnar Pejler
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.,Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Malin C Lagerström
- Department of Neuroscience, Uppsala University, Husargatan 3, Box 593, 751 24, Uppsala, Sweden.
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16
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Meng J, Wang J, Buddenkotte J, Buhl T, Steinhoff M. Role of SNAREs in Atopic Dermatitis–Related Cytokine Secretion and Skin-Nerve Communication. J Invest Dermatol 2019; 139:2324-2333. [DOI: 10.1016/j.jid.2019.04.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 04/08/2019] [Accepted: 04/23/2019] [Indexed: 01/11/2023]
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17
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IL-17A Induces Endothelin-1 Expression through p38 Pathway in Prurigo Nodularis. J Invest Dermatol 2019; 140:702-706.e2. [PMID: 31476318 DOI: 10.1016/j.jid.2019.08.438] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 07/26/2019] [Accepted: 08/07/2019] [Indexed: 12/17/2022]
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18
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Nakahara T, Kido-Nakahara M, Furue M. Potential Role of Endothelin-1 in Atopic Dermatitis. CURRENT TREATMENT OPTIONS IN ALLERGY 2019. [DOI: 10.1007/s40521-019-00206-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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19
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Nakahara T, Kido-Nakahara M, Ohno F, Ulzii D, Chiba T, Tsuji G, Furue M. The pruritogenic mediator endothelin-1 shifts the dendritic cell-T-cell response toward Th17/Th1 polarization. Allergy 2018; 73:511-515. [PMID: 28960333 DOI: 10.1111/all.13322] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/21/2017] [Indexed: 01/13/2023]
Abstract
Endothelin-1 (ET-1) is associated with skin diseases such as atopic dermatitis (AD) and psoriasis. ET-1 is enhanced in the skin of patients AD and psoriasis. In addition, plasma levels of ET-1 are elevated in AD and psoriasis. Although both AD and psoriasis are T-cell-mediated skin diseases, the association between ET-1 and the T-cell immune response has not been clarified. To evaluate the role of ET-1 in inflammatory skin disease, we sought to investigate the effects of ET-1 on the functions of dendritic cells (DCs) and subsequent immune responses. For this purpose, we immunohistochemically confirmed the upregulation of ET-1 in the epidermis of patients with AD or psoriasis. ET-1 directly induced phenotypic maturation of bone marrow-derived DCs (BMDCs). In addition, ET-1 augmented the production of several cytokines and allogeneic stimulatory capacity of BMDCs. Interestingly, ET-1-activated BMDCs primed T cells to produce Th1 and Th17 cytokines, but not Th2 cytokines. These findings indicate that ET-1 polarizes the DC-T-cell response toward Th17/1 differentiation and may augment the persistent course of inflammatory skin diseases.
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Affiliation(s)
- T. Nakahara
- Division of Skin Surface Sensing; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - M. Kido-Nakahara
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - F. Ohno
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - D. Ulzii
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - T. Chiba
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - G. Tsuji
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - M. Furue
- Division of Skin Surface Sensing; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
- Research and Clinical Center for Yusho and Dioxin; Kyushu University; Fukuoka Japan
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20
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Taylor JC, Dewberry LS, Totsch SK, Yessick LR, DeBerry JJ, Watts SA, Sorge RE. A novel zebrafish-based model of nociception. Physiol Behav 2017; 174:83-88. [DOI: 10.1016/j.physbeh.2017.03.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 03/07/2017] [Accepted: 03/09/2017] [Indexed: 12/21/2022]
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21
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Lee JS, Han JS, Lee K, Bang J, Lee H. The peripheral and central mechanisms underlying itch. BMB Rep 2017; 49:474-87. [PMID: 27418284 PMCID: PMC5227140 DOI: 10.5483/bmbrep.2016.49.9.108] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Indexed: 12/20/2022] Open
Abstract
Itch is one of the most distressing sensations that substantially impair quality of life. It is a cardinal symptom of many skin diseases and is also caused by a variety of systemic disorders. Unfortunately, currently available itch medications are ineffective in many chronic itch conditions, and they often cause undesirable side effects. To develop novel therapeutic strategies, it is essential to identify primary afferent neurons that selectively respond to itch mediators as well as the central nervous system components that process the sensation of itch and initiate behavioral responses. This review summarizes recent progress in the study of itch, focusing on itch-selective receptors, signaling molecules, neuronal pathways from the primary sensory neurons to the brain, and potential decoding mechanisms based on which itch is distinguished from pain. [BMB Reports 2016; 49(9): 474-487]
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Affiliation(s)
- Jae Seung Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | | | - Kyeongho Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Juwon Bang
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Hyosang Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
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22
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Sanders KM, Nattkemper LA, Yosipovitch G. Advances in understanding itching and scratching: a new era of targeted treatments. F1000Res 2016; 5. [PMID: 27610225 PMCID: PMC4995681 DOI: 10.12688/f1000research.8659.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/15/2016] [Indexed: 01/14/2023] Open
Abstract
Chronic itch is a significant health burden with few effective treatments. As such, itch researchers seek to understand the mechanisms behind itch and to find potential targets for treatment. The field of itch research is dynamic, and many advances have been made so far this decade. In particular, major steps forward include the identification of new peripheral and central itch mediators and modulators, the discovery of greater roles for immune cells and glia in itch transmission, and a focus on the brain processing of itching and scratching. Finally, several new therapeutic interventions for itch have shown success in clinical trials.
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Affiliation(s)
- Kristen M Sanders
- Department of Dermatology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, 19140, USA
| | - Leigh A Nattkemper
- Department of Dermatology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, 19140, USA
| | - Gil Yosipovitch
- Department of Dermatology and Itch Center, Miller School of Medicine, University of Miami, Miami, FL, USA
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Abstract
Itch is a unique sensation associated with the scratch reflex. Although the scratch reflex plays a protective role in daily life by removing irritants, chronic itch remains a clinical challenge. Despite urgent clinical need, itch has received relatively little research attention and its mechanisms have remained poorly understood until recently. The goal of the present review is to summarize our current understanding of the mechanisms of acute as well as chronic itch and classifications of the primary itch populations in relationship to transient receptor potential (Trp) channels, which play pivotal roles in multiple somatosensations. The convergent involvement of Trp channels in diverse itch signaling pathways suggests that Trp channels may serve as promising targets for chronic itch treatments.
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Affiliation(s)
- Shuohao Sun
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA.
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA.
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25
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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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Akiyama T, Nagamine M, Davoodi A, Iodi Carstens M, Cevikbas F, Steinhoff M, Carstens E. Intradermal endothelin-1 excites bombesin-responsive superficial dorsal horn neurons in the mouse. J Neurophysiol 2015; 114:2528-34. [PMID: 26311187 DOI: 10.1152/jn.00723.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 08/24/2015] [Indexed: 01/21/2023] Open
Abstract
Endothelin-1 (ET-1) has been implicated in nonhistaminergic itch. Here we used electrophysiological methods to investigate whether mouse superficial dorsal horn neurons respond to intradermal (id) injection of ET-1 and whether ET-1-sensitive neurons additionally respond to other pruritic and algesic stimuli or spinal superfusion of bombesin, a homolog of gastrin-releasing peptide (GRP) that excites spinal itch-signaling neurons. Single-unit recordings were made from lumbar dorsal horn neurons in pentobarbital-anesthetized C57BL/6 mice. We searched for units that exhibited elevated firing after id injection of ET-1 (1 μg/μl). Responsive units were further tested with mechanical stimuli, bombesin (spinal superfusion, 200 μg·ml(-1)·min(-1)), heating, cooling, and additional chemicals [histamine, chloroquine, allyl isothiocyanate (AITC), capsaicin]. Of 40 ET-1-responsive units, 48% responded to brush and pinch [wide dynamic range (WDR)] and 52% to pinch only [high threshold (HT)]. Ninety-three percent responded to noxious heat, 50% to cooling, and >70% to histamine, chloroquine, AITC, and capsaicin. Fifty-seven percent responded to bombesin, suggesting that they participate in spinal itch transmission. That most ET-1-sensitive spinal neurons also responded to pruritic and algesic stimuli is consistent with previous studies of pruritogen-responsive dorsal horn neurons. We previously hypothesized that pruritogen-sensitive neurons signal itch. The observation that ET-1 activates nociceptive neurons suggests that both itch and pain signals may be generated by ET-1 to result in simultaneous sensations of itch and pain, consistent with observations that ET-1 elicits both itch- and pain-related behaviors in animals and burning itch sensations in humans.
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Affiliation(s)
- T Akiyama
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California
| | - M Nagamine
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California
| | - A Davoodi
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California
| | - M Iodi Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California
| | - F Cevikbas
- Departments of Dermatology and Surgery, University of California, San Francisco, California; and
| | - M Steinhoff
- Department of Dermatology and Charles Institute for Translational Dermatology, University College Dublin, Dublin, Ireland
| | - E Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California;
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27
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Aktar MK, Kido-Nakahara M, Furue M, Nakahara T. Mutual upregulation of endothelin-1 and IL-25 in atopic dermatitis. Allergy 2015; 70:846-54. [PMID: 25903653 DOI: 10.1111/all.12633] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2015] [Indexed: 01/11/2023]
Abstract
BACKGROUND Endothelin-1 (ET-1) has been reported to evoke histamine-independent pruritus in mammals. However, its association with pruritus or inflammation of atopic dermatitis (AD) has not been clarified. We sought to investigate the role of ET-1 in the skin inflammation of AD. METHODS To examine the role of ET-1 in AD, we investigated the expression of ET-1 and IL-25 in the skin of an AD mouse model and patients with AD and examined the mutual regulatory relationship between ET-1 and IL-25, one of the important cytokines in AD, using the human HaCaT keratinocyte cell line. RESULTS We immunohistochemically confirmed the upregulation of ET-1 and IL-25 expression in the epidermis of both the AD mouse model and patients with AD. In vitro, IL-25 upregulated ET-1 mRNA and protein expression in a concentration- and time-dependent fashion in HaCaT cells. This IL-25-induced ET-1 expression was inhibited by ERK1/2 or JNK inhibitor. In a reciprocal manner, ET-1 also induced IL-25 upregulation. The enhancing effect of ET-1 on IL-25 was inhibited by an endothelin A receptor antagonist, ERK1/2 inhibitor, or p38 inhibitor, but not by an endothelin B receptor antagonist or JNK inhibitor. CONCLUSION These findings suggest that mutual upregulation of ET-1 and IL-25 takes place in the epidermis of AD, which may be a future target for antipruritic agents.
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Affiliation(s)
- M. K. Aktar
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - M. Kido-Nakahara
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - M. Furue
- Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
- Division of Skin Surface Sensing; Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
| | - T. Nakahara
- Division of Skin Surface Sensing; Department of Dermatology; Graduate School of Medical Sciences; Kyushu University; Fukuoka Japan
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28
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Schwendinger-Schreck J, Wilson SR, Bautista DM. Interactions between keratinocytes and somatosensory neurons in itch. Handb Exp Pharmacol 2015; 226:177-90. [PMID: 25861780 DOI: 10.1007/978-3-662-44605-8_10] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Keratinocytes are epithelial cells that make up the stratified epidermis of the skin. Recent studies suggest that keratinocytes promote chronic itch. Changes in skin morphology that accompany a variety of chronic itch disorders and the multitude of inflammatory mediators secreted by keratinocytes that target both sensory neurons and immune cells highlight the importance of investigating the connection between keratinocytes and chronic itch. This chapter addresses some of the most recent data and models for the role keratinocytes play in the development and maintenance of chronic itch.
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Affiliation(s)
- Jamie Schwendinger-Schreck
- Department of Molecular and Cellular Biology, University of California Berkeley, 355 LSA MC#3200, Berkeley, CA, 94720-3200, USA
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29
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Zhang X. Targeting TRP ion channels for itch relief. Naunyn Schmiedebergs Arch Pharmacol 2014; 388:389-99. [PMID: 25418889 DOI: 10.1007/s00210-014-1068-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 11/11/2014] [Indexed: 12/13/2022]
Abstract
Acute itch (pruritus) is unpleasant and acts as an alerting mechanism for removing irritants. However, severe chronic itch is debilitating and impairs the quality of life. Rapid progress has been made in recent years in our understanding of the fundamental neurobiology of itch. Notably, several temperature-sensitive transient receptor potential (thermo-TRP) ion channels have emerged as critical players in many types of itch, in addition to pain. They serve as markers that define the itch neural pathway. Thermo-TRP ion channels are thus becoming attractive targets for developing effective anti-pruritic therapies.
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Affiliation(s)
- Xuming Zhang
- Rowett Institute of Nutrition and Health & Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK,
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30
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Smith TP, Haymond T, Smith SN, Sweitzer SM. Evidence for the endothelin system as an emerging therapeutic target for the treatment of chronic pain. J Pain Res 2014; 7:531-45. [PMID: 25210474 PMCID: PMC4155994 DOI: 10.2147/jpr.s65923] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Many people worldwide suffer from pain and a portion of these sufferers are diagnosed with a chronic pain condition. The management of chronic pain continues to be a challenge, and despite taking prescribed medication for pain, patients continue to have pain of moderate severity. Current pain therapies are often inadequate, with side effects that limit medication adherence. There is a need to identify novel therapeutic targets for the management of chronic pain. One potential candidate for the treatment of chronic pain is therapies aimed at modulating the vasoactive peptide endothelin-1. In addition to vasoactive properties, endothelin-1 has been implicated in pain transmission in both humans and animal models of nociception. Endothelin-1 directly activates nociceptors and potentiates the effect of other algogens, including capsaicin, formalin, and arachidonic acid. In addition, endothelin-1 has been shown to be involved in inflammatory pain, cancer pain, neuropathic pain, diabetic neuropathy, and pain associated with sickle cell disease. Therefore, endothelin-1 may prove a novel therapeutic target for the relief of many types of chronic pain.
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Affiliation(s)
- Terika P Smith
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina, Columbia, SC, USA
| | - Tami Haymond
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina, Columbia, SC, USA
| | - Sherika N Smith
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina, Columbia, SC, USA
| | - Sarah M Sweitzer
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina, Columbia, SC, USA ; Department of Pharmaceutical and Administrative Sciences, Presbyterian College School of Pharmacy, Clinton, SC, USA
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31
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Receptors, cells and circuits involved in pruritus of systemic disorders. Biochim Biophys Acta Mol Basis Dis 2014; 1842:869-92. [DOI: 10.1016/j.bbadis.2014.02.007] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 02/16/2014] [Accepted: 02/18/2014] [Indexed: 12/12/2022]
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32
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Kido-Nakahara M, Buddenkotte J, Kempkes C, Ikoma A, Cevikbas F, Akiyama T, Nunes F, Seeliger S, Hasdemir B, Mess C, Buhl T, Sulk M, Müller FU, Metze D, Bunnett NW, Bhargava A, Carstens E, Furue M, Steinhoff M. Neural peptidase endothelin-converting enzyme 1 regulates endothelin 1-induced pruritus. J Clin Invest 2014; 124:2683-95. [PMID: 24812665 DOI: 10.1172/jci67323] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
In humans, pruritus (itch) is a common but poorly understood symptom in numerous skin and systemic diseases. Endothelin 1 (ET-1) evokes histamine-independent pruritus in mammals through activation of its cognate G protein-coupled receptor endothelin A receptor (ETAR). Here, we have identified neural endothelin-converting enzyme 1 (ECE-1) as a key regulator of ET-1-induced pruritus and neural signaling of itch. We show here that ETAR, ET-1, and ECE-1 are expressed and colocalize in murine dorsal root ganglia (DRG) neurons and human skin nerves. In murine DRG neurons, ET-1 induced internalization of ETAR within ECE-1-containing endosomes. ECE-1 inhibition slowed ETAR recycling yet prolonged ET-1-induced activation of ERK1/2, but not p38. In a murine itch model, ET-1-induced scratching behavior was substantially augmented by pharmacological ECE-1 inhibition and abrogated by treatment with an ERK1/2 inhibitor. Using iontophoresis, we demonstrated that ET-1 is a potent, partially histamine-independent pruritogen in humans. Immunohistochemical evaluation of skin from prurigo nodularis patients confirmed an upregulation of the ET-1/ETAR/ECE-1/ERK1/2 axis in patients with chronic itch. Together, our data identify the neural peptidase ECE-1 as a negative regulator of itch on sensory nerves by directly regulating ET-1-induced pruritus in humans and mice. Furthermore, these results implicate the ET-1/ECE-1/ERK1/2 pathway as a therapeutic target to treat pruritus in humans.
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33
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Bautista DM, Wilson SR, Hoon MA. Why we scratch an itch: the molecules, cells and circuits of itch. Nat Neurosci 2014; 17:175-82. [PMID: 24473265 PMCID: PMC4364402 DOI: 10.1038/nn.3619] [Citation(s) in RCA: 235] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 12/03/2013] [Indexed: 12/17/2022]
Abstract
Itch is described as an irritating sensation that triggers a desire to scratch. However, this definition hardly seems fitting for the millions of people who suffer from intractable itch. Indeed, the Buddhist philosopher Nāgārjuna more aptly stated, "There is pleasure when an itch is scratched. But to be without an itch is more pleasurable still." Chronic itch is widespread and very difficult to treat. In this review we focus on the molecules, cells and circuits in the peripheral and central nervous systems that drive acute and chronic itch transmission. Understanding the itch circuitry is critical to developing new therapies for this intractable disease.
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Affiliation(s)
- Diana M Bautista
- 1] Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, USA. [2] Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, USA
| | - Sarah R Wilson
- 1] Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, USA. [2] Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, USA
| | - Mark A Hoon
- Molecular Genetics Unit, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research/NIH, Bethesda, Maryland, USA
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Abstract
This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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35
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Cerebral activation during von Frey filament stimulation in subjects with endothelin-1-induced mechanical hyperalgesia: a functional MRI study. BIOMED RESEARCH INTERNATIONAL 2013; 2013:610727. [PMID: 24151613 PMCID: PMC3789290 DOI: 10.1155/2013/610727] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 08/14/2013] [Indexed: 11/17/2022]
Abstract
Endothelin-1 (ET-1) is an endogenously expressed potent peptide vasoconstrictor. There is growing evidence that ET-1 plays a role in the pain signaling system and triggers overt nociception in humans. The underlying neuronal pathways are still a matter of great debate. In the present study, we applied an intradermal ET-1 sensitization model to induce mechanical hyperalgesia in healthy subjects. Functional magnetic resonance imaging (fMRI) was used to tease out the cortical regions associated with the processing of ET-1-induced punctate hyperalgesia, as compared to a nonnoxious mechanical stimulation of the contralateral arm. Von Frey hair testing revealed the presence of increased responsiveness to punctate stimulation in all subjects. Activational patterns between nonpainful control stimulation and hyperalgesic stimulation were compared. Two major observations were made: (1) all cortical areas that showed activation during the control stimulation were also present during hyperalgesic stimulation, but in addition, some areas showed bilateral activation only during hyperalgesic stimulation, and (2) some brain areas showed significantly higher signal changes during hyperalgesic stimulation. Our findings suggest that injection of ET-1 leads to a state of punctate hyperalgesia, which in turn causes the activation of multiple brain regions. This indicates that ET-1 activates an extended neuronal pathway.
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Abstract
While considerable effort has been made to investigate the neural mechanisms of pain, much less effort has been devoted to itch, at least until recently. However, itch is now gaining increasing recognition as a widespread and costly medical and socioeconomic issue. This is accompanied by increasing interest in the underlying neural mechanisms of itch, which has become a vibrant and rapidly-advancing field of research. The goal of the present forefront review is to describe the recent progress that has been made in our understanding of itch mechanisms.
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Affiliation(s)
- Tasuku Akiyama
- University of California, Davis, Department of Neurobiology, Physiology & Behavior, 1 Shields Avenue, Davis, CA 95616, United States
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37
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Electroacupuncture Attenuates 5'-Guanidinonaltrindole-Evoked Scratching and Spinal c-Fos Expression in the Mouse. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:319124. [PMID: 23878596 PMCID: PMC3708416 DOI: 10.1155/2013/319124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/25/2013] [Accepted: 04/26/2013] [Indexed: 12/13/2022]
Abstract
The present study was undertaken to investigate the influence of electroacupuncture (EA) on compulsive scratching in mice and c-Fos expression elicited by subcutaneous (s.c.) administration of a known puritogen, 5'-guanidinonaltrindole (GNTI) to the neck. Application of EA to Hegu (LI4) and Quchi (LI11) acupoints at 2 Hz, but not 100 Hz, attenuated GNTI-evoked scratching. In mice pretreated with the µ opioid receptor antagonist naloxone, EA 2 Hz did not attenuate GNTI-evoked scratching, whereas EA at 2 Hz did attenuate GNTI-evoked scratching in mice pretreated with the κ opioid receptor antagonist nor-binaltorphimine. Moreover, intradermal (i.d.) administration of the selective µ opioid receptor agonist [d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin acetate (DAMGO) attenuated GNTI-evoked scratching behavior, while s.c. administration of DAMGO was ineffective. GNTI provoked c-Fos expression on the lateral side of the superficial layer of the dorsal horn of the cervical spinal cord. Application of 2 Hz EA to LI4 and LI11 decreased the number of c-Fos positive nuclei induced by GNTI. It may be concluded that application of 2 Hz EA to LI4 and LI11 attenuates scratching behavior induced by GNTI in mice and that the peripheral µ opioid system is involved, at least in part, in the anti-pruritic effects of EA.
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38
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Liu T, Ji RR. New insights into the mechanisms of itch: are pain and itch controlled by distinct mechanisms? Pflugers Arch 2013; 465:1671-85. [PMID: 23636773 DOI: 10.1007/s00424-013-1284-2] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Revised: 04/13/2013] [Accepted: 04/14/2013] [Indexed: 12/30/2022]
Abstract
Itch and pain are closely related but distinct sensations. They share largely overlapping mediators and receptors, and itch-responding neurons are also sensitive to pain stimuli. Itch-mediating primary sensory neurons are equipped with distinct receptors and ion channels for itch transduction, including Mas-related G protein-coupled receptors (Mrgprs), protease-activated receptors, histamine receptors, bile acid receptor, toll-like receptors, and transient receptor potential subfamily V1/A1 (TRPV1/A1). Recent progress has indicated the existence of an itch-specific neuronal circuitry. The MrgprA3-expressing primary sensory neurons exclusively innervate the epidermis of skin, and their central axons connect with gastrin-releasing peptide receptor (GRPR)-expressing neurons in the superficial spinal cord. Notably, ablation of MrgprA3-expressing primary sensory neurons or GRPR-expressing spinal cord neurons results in selective reduction in itch but not pain. Chronic itch results from dysfunction of the immune and nervous system and can manifest as neural plasticity despite the fact that chronic itch is often treated by dermatologists. While differences between acute pain and acute itch are striking, chronic itch and chronic pain share many similar mechanisms, including peripheral sensitization (increased responses of primary sensory neurons to itch and pain mediators), central sensitization (hyperactivity of spinal projection neurons and excitatory interneurons), loss of inhibitory control in the spinal cord, and neuro-immune and neuro-glial interactions. Notably, painful stimuli can elicit itch in some chronic conditions (e.g., atopic dermatitis), and some drugs for treating chronic pain are also effective in chronic itch. Thus, itch and pain have more similarities in pathological and chronic conditions.
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Affiliation(s)
- Tong Liu
- Pain Signaling and Plasticity Laboratory, Department of Anesthesiology and Neurobiology, Duke University Medical Center, 595 LaSalle Street, GSRB-I, Room 1027A, DUMC 3094, Durham, NC, 27710, USA,
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