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Andersen HH, van Laarhoven AI, Elberling J, Arendt-Nielsen L. Modulation of Itch by Conditioning Itch and Pain Stimulation in Healthy Humans. THE JOURNAL OF PAIN 2017; 18:1437-1450. [DOI: 10.1016/j.jpain.2017.07.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 06/28/2017] [Accepted: 07/03/2017] [Indexed: 12/16/2022]
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Abstract
Introduction Chronic itch has been drawing much attention due to its clinical significance and the complexity of its mechanisms. To facilitate the development of anti-itch strategies, it is necessary to investigate the key players in itch sensation under chronic itch conditions. Several members of the Mrgpr family were identified as itch receptors that detect cutaneous pruritogens in primary sensory neurons. However, the role of Mrgprs in chronic itch conditions has not been well described. Methods Scratching behaviors of WT and Mrgpr-clusterΔ-/- mice were examined in dry skin model and contact dermatitis model to examine the role of Mrgpr genes in mediating chronic itch sensation. Scratching behaviors of the mice were also examined in allergic itch model. Real-time PCR were performed to examine the expression level of MrgprA3 and MrgprC11 under naïve and dry skin conditions. The MrgprA3+ itch-sensing fibers were labeled by tdTomato fluorescence in Mrgpra3GFP-Cre; ROSA26tdTomato mice, and the morphology and density of those fibers in the epidermis were analyzed under dry skin condition. Results We showed that deleting a cluster of Mrgpr genes in mice reduced scratching behavior severely under two chronic itch conditions, namely dry skin and contact dermatitis, and the allergic itch condition. Moreover, the gene expressions of itch receptors MrgprA3 and MrgprC11 in dorsal root ganglia (DRG) were upregulated significantly under dry skin condition. Consistently, the percentage of MrgprA3+ itch-sensing neurons was increased as well. We also observed hyperinnervation of MrgprA3+ itch-sensing fibers in the epidermis of the skin under dry skin condition. Discussion We demonstrate that Mrgprs play important roles in mediating chronic itch and allergic itch. These findings enrich our knowledge of itch mechanism and may lead to the development of novel therapeutic approach to combat itch.
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Haddadi NS, Ostadhadi S, Shakiba S, Afshari K, Rahimi N, Foroutan A, Dehpour AR. Pharmacological evidence of involvement of nitric oxide pathway in anti-pruritic effects of sumatriptan in chloroquine-induced scratching in mice. Fundam Clin Pharmacol 2017; 32:69-76. [DOI: 10.1111/fcp.12317] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 06/30/2017] [Accepted: 08/11/2017] [Indexed: 12/01/2022]
Affiliation(s)
- Nazgol-Sadat Haddadi
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
| | - Sattar Ostadhadi
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Brain and Spinal Cord Injury Research Center; Neuroscience Institute; Tehran University of Medical Sciences; Chamran highway Bagherkhan St., Imam Khomeini Hospital Tehran Iran
| | - Saeed Shakiba
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
| | - Khashayar Afshari
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
| | - Nastaran Rahimi
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
| | - Arash Foroutan
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
| | - Ahmad-Reza Dehpour
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Poorsina St., Enghelab Ave.; Tehran Iran
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Afzal R, Shim WS. Glucosylsphingosine Activates Serotonin Receptor 2a and 2b: Implication of a Novel Itch Signaling Pathway. Biomol Ther (Seoul) 2017; 25:497-503. [PMID: 28208011 PMCID: PMC5590793 DOI: 10.4062/biomolther.2016.207] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 11/01/2016] [Accepted: 12/13/2016] [Indexed: 02/06/2023] Open
Abstract
Recent reports claimed that glucosylsphingosine (GS) is highly accumulated and specifically evoking itch-scratch responses in the skins of atopic dermatitis (AD) patients. However, it was unclear how GS can trigger itch-scratch responses, since there were no known molecular singling pathways revealed yet. In the present study, it was verified for the first time that GS can activate mouse serotonin receptor 2a (mHtr2a) and 2b (mHtr2b), but not 2c (mHtr2c) that are expressed in HEK293T cells. Specifically, effects of GS on all mouse serotonin receptor 2 subfamily were evaluated by calcium imaging techniques. The GS-induced intracellular calcium increase was dose-dependent, and antagonists such as ketanserin (Htr2a antagonist) and RS-127445 (Htr2b antagonist) significantly blocked the GS-induced responses. Moreover, the proposed GS-induced responses appear to be mediated by phospholipase C (PLC), since pretreatment of a PLC inhibitor U-73122 abolished the GS-induced responses. Additionally, the GS-induced calcium influx is probably mediated by endogenous TRPC ion channels in HEK293T cells, since pretreatment of SKF-96365, an inhibitor for TRPC, significantly suppressed GS-induced response. In conclusion, the present study revealed for the first time that GS can stimulate mHtr2a and mHtr2b to induce calcium influx, by utilizing PLC-dependent pathway afterwards. Considering that GS is regarded as a pruritogen in AD, the present study implicates a novel GS-induced itch signaling pathway.
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Affiliation(s)
- Ramsha Afzal
- College of Pharmacy, Gachon University, Incheon 21936, Republic of Korea
| | - Won-Sik Shim
- College of Pharmacy, Gachon University, Incheon 21936, Republic of Korea.,Gachon Institue of Pharmaceutical Sciences, Incheon 21936, Republic of Korea
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Ostadhadi S, Haddadi NS, Foroutan A, Azimi E, Elmariah S, Dehpour AR. Development of resistance to serotonin-induced itch in bile duct ligated mice. Clin Exp Pharmacol Physiol 2017; 44:680-685. [DOI: 10.1111/1440-1681.12752] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 02/14/2017] [Accepted: 02/22/2017] [Indexed: 02/06/2023]
Affiliation(s)
- Sattar Ostadhadi
- Brain and Spinal Cord Injury Research Center; Neurosciences Institute; Tehran University of Medical Sciences; Tehran Iran
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Tehran Iran
| | - Nazgol-Sadat Haddadi
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Tehran Iran
| | - Arash Foroutan
- Brain and Spinal Cord Injury Research Center; Neurosciences Institute; Tehran University of Medical Sciences; Tehran Iran
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Tehran Iran
| | - Ehsan Azimi
- Cutaneous Biology Research Center; Massachusetts General Hospital; Charlestown MA USA
| | - Sarina Elmariah
- Cutaneous Biology Research Center; Massachusetts General Hospital; Charlestown MA USA
| | - Ahmad-Reza Dehpour
- Brain and Spinal Cord Injury Research Center; Neurosciences Institute; Tehran University of Medical Sciences; Tehran Iran
- Experimental Medicine Research Center; Tehran University of Medical Sciences; Tehran Iran
- Department of Pharmacology; School of Medicine; Tehran University of Medical Sciences; Tehran Iran
- Faculty of Pharmacy; Tehran University of Medical Sciences; Tehran Iran
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Abstract
Itch, or pruritus, is a hallmark feature of atopic dermatitis (AD). The impact of AD-related pruritus can range from mildly distressing or distracting to completely disabling. Traditionally, management of itch in AD patients has focused on restoring the altered skin barrier with topical emollients and/or reducing inflammation. A growing emphasis has been placed on directly targeting the neural transmission pathways that mediate itch signaling. Off-label use of neuromodulatory agents has helped reduce this aggravating symptom in atopic patients. This article reviews the current literature on the use of neuromodulatory agents and nonpharmacologic alternative therapies used to treat AD-related pruritus.
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Affiliation(s)
- Sarina B Elmariah
- Department of Dermatology, Harvard Medical School, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
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58
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Takai Y, Hiramoto K, Nishimura Y, Ooi K. Relationship between biochemical factors and skin symptoms in chronic venous disease. Arch Dermatol Res 2017; 309:253-258. [DOI: 10.1007/s00403-017-1721-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 01/20/2017] [Accepted: 01/30/2017] [Indexed: 10/20/2022]
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Dutra RC. Kinin receptors: Key regulators of autoimmunity. Autoimmun Rev 2017; 16:192-207. [DOI: 10.1016/j.autrev.2016.12.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 10/25/2016] [Indexed: 01/06/2023]
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Murota H, Katayama I. Exacerbating factors of itch in atopic dermatitis. Allergol Int 2017; 66:8-13. [PMID: 27863904 DOI: 10.1016/j.alit.2016.10.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 10/11/2016] [Accepted: 10/12/2016] [Indexed: 01/01/2023] Open
Abstract
Atopic dermatitis (AD) displays different clinical symptoms, progress, and response to treatment during early infancy and after childhood. After the childhood period, itch appears first, followed by formation of well-circumscribed plaque or polymorphous dermatoses at the same site. When accompanied with dermatitis and dry skin, treatment of skin lesions should be prioritized. When itch appears first, disease history, such as causes and time of appearance of itch should be obtained by history taking. In many cases, itch increases in the evening when the sympathetic nerve activity decreased. Treatment is provided considering that hypersensitivity to various external stimulations can cause itch. Heat and sweating are thought to especially exacerbate itch. Factors causing itch, such as cytokines and chemical messengers, also induce itch mainly by stimulating the nerve. Scratching further aggravates dermatitis. Skin hypersensibility, where other non-itch senses, such as pain and heat, are felt as itch, sometimes occurs in AD. Abnormal elongation of the sensory nerve into the epidermis, as well as sensitizing of the peripheral/central nerve, are possible causes of hypersensitivity, leading to itch. To control itch induced by environmental factors such as heat, treatment for dermatitis is given priority. In the background of itch exacerbated by sweating, attention should be given to the negative impact of sweat on skin homeostasis due to 1) leaving excess sweat on the skin, and 2) heat retention due to insufficient sweating. Excess sweat on the skin should be properly wiped off, and dermatitis should be controlled so that appropriate amount of sweat can be produced. Not only stimulation from the skin surface, but also visual and auditory stimulation can induce new itch. This "contagious itch" can be notably observed in patients with AD. This article reviews and introduces causes of aggravation of itch and information regarding how to cope with such causes.
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Lin SH, Steinhoff M, Ikoma A, Chang YC, Cheng YR, Chandra Kopparaju R, Ishii S, Sun WH, Chen CC. Involvement of TRPV1 and TDAG8 in Pruriception Associated with Noxious Acidosis. J Invest Dermatol 2017; 137:170-178. [DOI: 10.1016/j.jid.2016.07.037] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 06/27/2016] [Accepted: 07/18/2016] [Indexed: 02/06/2023]
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Akiyama T, Nagamine M, Davoodi A, Ivanov M, Carstens MI, Carstens E. Innocuous warming enhances peripheral serotonergic itch signaling and evokes enhanced responses in serotonin-responsive dorsal horn neurons in the mouse. J Neurophysiol 2017; 117:251-259. [PMID: 27784810 PMCID: PMC5220113 DOI: 10.1152/jn.00703.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/19/2016] [Indexed: 11/22/2022] Open
Abstract
Itch is often triggered by warming the skin in patients with itchy dermatitis, but the underlying mechanism is largely unknown. We presently investigated if warming the skin enhances histamine- or serotonin (5-HT)-evoked itch behavior or responses of sensory dorsal root ganglion (DRG) cells, and if responses of superficial dorsal horn neurons to innocuous warming are enhanced by these pruritogens. In a temperature-controlled environmental chamber, mice exhibited greater scratching following intradermal injection of 5-HT, but not histamine, SLIGRL, or BAM8-22, when the skin surface temperature was above 36°C. Calcium imaging of DRG cells in a temperature-controlled bath revealed that responses to 5-HT, but not histamine, were significantly greater at a bath temperature of 35°C vs. lower temperatures. Single-unit recordings revealed a subpopulation of superficial dorsal horn neurons responsive to intradermal injection of 5-HT. Of these, 58% responded to innocuous skin warming (37°C) prior to intradermal injection of 5-HT, while 100% responded to warming following intradermal injection of 5-HT. Warming-evoked responses were superimposed on the 5-HT-evoked elevation in firing and were significantly larger compared with responses pre-5-HT, as long as 30 min after the intradermal injection of 5-HT. Five-HT-insensitive units, and units that either did or did not respond to intradermal histamine, did not exhibit any increase in the incidence of warmth sensitivity or in the mean response to warming following intradermal injection of the pruritogen. The results suggest that 5-HT-evoked responses of pruriceptors are enhanced during skin warming, leading to increased firing of 5-HT-sensitive dorsal horn neurons that signal nonhistaminergic itch. NEW & NOTEWORTHY Skin warming often exacerbates itch in patients with itchy dermatitis. We demonstrate that warming the skin enhanced serotonin-evoked, but not histamine-evoked, itch behavior and responses of sensory dorsal root ganglion cells. Moreover, serotonin, but not histamine, enhanced responses of superficial dorsal horn neurons to innocuous warming. The results suggest that skin warming selectively enhances the responses of serotonin-sensitive pruriceptors, leading to increased firing of serotonin-sensitive dorsal horn neurons that signal nonhistaminergic itch.
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Affiliation(s)
- T Akiyama
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
- Departments of Dermatology, Anatomy, and Cell Biology, Temple Itch Center, Temple University, Philadelphia, Pennsylvania
| | - M Nagamine
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - A Davoodi
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - M Ivanov
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - M Iodi Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
| | - E Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
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Rodrigues L, Ekundi-Valentim E, Florenzano J, Cerqueira ARA, Soares AG, Schmidt TP, Santos KT, Teixeira SA, Ribela MTCP, Rodrigues SF, de Carvalho MH, De Nucci G, Wood M, Whiteman M, Muscará MN, Costa SKP. Protective effects of exogenous and endogenous hydrogen sulfide in mast cell-mediated pruritus and cutaneous acute inflammation in mice. Pharmacol Res 2016; 115:255-266. [PMID: 27840098 DOI: 10.1016/j.phrs.2016.11.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 10/20/2016] [Accepted: 11/09/2016] [Indexed: 12/24/2022]
Abstract
The recently described 'gasomediator' hydrogen sulfide (H2S) has been involved in pain mechanisms, but its effect on pruritus, a sensory modality that similarly to pain acts as a protective mechanism, is poorly known and controversial. The effects of the slow-releasing (GYY4137) and spontaneous H2S donors (Na2S and Lawesson's reagent, LR) were evaluated in histamine and compound 48/80 (C48/80)-dependent dorsal skin pruritus and inflammation in male BALB/c mice. Animals were intradermally (i.d.) injected with C48/80 (3μg/site) or histamine (1μmol/site) alone or co-injected with Na2S, LR or GYY4137 (within the 0.3-100nmol range). The involvement of endogenous H2S and KATP channel-dependent mechanism were also evaluated. Pruritus was assessed by the number of scratching bouts, whilst skin inflammation was evaluated by the extravascular accumulation of intravenously injected 125I-albumin (plasma extravasation) and myeloperoxidase (MPO) activity (neutrophil recruitment). Histamine or C48/80 significantly evoked itching behavior paralleled by plasma extravasation and increased MPO activity. Na2S and LR significantly ameliorated histamine or C48/80-induced pruritus and inflammation, although these effects were less pronounced or absent with GYY4137. Inhibition of endogenous H2S synthesis increased both Tyrode and C48/80-induced responses in the skin, whereas the blockade of KATP channels by glibenclamide did not. H2S-releasing donors significantly attenuate C48/80-induced mast cell degranulation either in vivo or in vitro. We provide first evidences that H2S donors confer protective effect against histamine-mediated acute pruritus and cutaneous inflammation. These effects can be mediated, at least in part, by stabilizing mast cells, known to contain multiple mediators and to be primary initiators of allergic processes, thus making of H2S donors a potential alternative/complementary therapy for treating inflammatory allergic skin diseases and related pruritus.
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Affiliation(s)
- L Rodrigues
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - E Ekundi-Valentim
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - J Florenzano
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - A R A Cerqueira
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - A G Soares
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - T P Schmidt
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - K T Santos
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - S A Teixeira
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - M T C P Ribela
- Department of Biotechnology, Institute of Nuclear and Energetic Research (IPEN), Sao Paulo, Brazil
| | - S F Rodrigues
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - M H de Carvalho
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - G De Nucci
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - M Wood
- University of Exeter Medical School, Exeter, UK
| | - M Whiteman
- University of Exeter Medical School, Exeter, UK
| | - M N Muscará
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - S K P Costa
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil.
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Hoeck EA, Marker JB, Gazerani P, H. Andersen H, Arendt-Nielsen L. Preclinical and human surrogate models of itch. Exp Dermatol 2016; 25:750-7. [DOI: 10.1111/exd.13078] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/11/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Emil A. Hoeck
- SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Aalborg E Denmark
| | - Jens B. Marker
- SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Aalborg E Denmark
| | - Parisa Gazerani
- SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Aalborg E Denmark
| | - Hjalte H. Andersen
- SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Aalborg E Denmark
| | - Lars Arendt-Nielsen
- SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Aalborg E Denmark
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Chen Y, Jiang S, Liu Y, Xiong J, Liang J, Ji W. Role of ERK1/2 activation on itch sensation induced by bradykinin B1 activation in inflamed skin. Exp Ther Med 2016; 12:627-632. [PMID: 27446253 PMCID: PMC4950635 DOI: 10.3892/etm.2016.3426] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/11/2016] [Indexed: 12/26/2022] Open
Abstract
It has previously been demonstrated that bradykinin receptor B1 (B1R) agonists evoke an itch-related scratching response in inflamed skin via the B1 receptor; however, the mechanisms responsible for this abnormal itch sensation remain unclear. Therefore, the present study utilized a complete Freund's adjuvant (CFA)-induced mouse model of inflammation to elucidate the mechanisms responsible. Over a period of 30 min, scratching behavior was quantified by the number of hind limb scratches of the area surrounding the drug injection site on the neck. Furthermore, western blot analysis was used to investigate the potential role of extracellular signal-regulated kinase (ERK) 1/2 signaling as a mediator of itch in CFA-treated mice. The results demonstrated that CFA-induced inflammation at the back of the neck is associated with sustained enhancement of ERK1/2 activation in the spinal cord. Moreover, B1R agonist treatment resulted in increased expression of phosphorylated ERK1/2 in the spinal cord, which peaked at 45 min. Consistent with these findings, inhibition of either mitogen-activated protein/ERK kinase or ERK1/2, as well as inhibition of ERK1/2 activation following inflammation, attenuated B1 receptor-mediated scratching responses to a greater extent, as compared with control mice. Collectively, the results of the present study indicated that enhanced and persistent ERK1/2 activation in the spinal cord may be required to induce a scratching response to B1R agonists following CFA-induced inflammation.
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Affiliation(s)
- Yuanzhen Chen
- Postgraduate Institute, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China; Department of Anesthesiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
| | - Shuyan Jiang
- Postgraduate Institute, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China; Division of Anesthesiology, Department of Cardiovascular Surgery, Guangdong Institute of Cardiovascular Diseases, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
| | - Yuying Liu
- Postgraduate Institute, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China; Department of Anesthesiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
| | - Jialing Xiong
- Postgraduate Institute, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China; Division of Anesthesiology, Department of Cardiovascular Surgery, Guangdong Institute of Cardiovascular Diseases, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
| | - Jiexian Liang
- Postgraduate Institute, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China; Division of Anesthesiology, Department of Cardiovascular Surgery, Guangdong Institute of Cardiovascular Diseases, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
| | - Wenjin Ji
- Department of Anesthesiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
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Abstract
Previous studies have revealed that TRPV1 and TRPA1 function downstream of many itch receptors, where they mediate inward current to trigger action potentials in primary afferents. Although other TRP channels, such as TRPV4, are expressed in primary afferents, whether or not they play an analogous role in itch was previously unknown. Now, Akiyama et al. provide evidence that TRPV4 is a key mediator of serotonin-induced itch. This finding is important because it uncovers an unanticipated role for TRPV4 in itch, thereby identifying a novel therapeutic target.
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Affiliation(s)
- Lindsey M Snyder
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; The Pittsburgh Center for Pain Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Marissa S Kuzirian
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; The Pittsburgh Center for Pain Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Sarah E Ross
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; The Pittsburgh Center for Pain Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Anesthesiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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67
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Akiyama T, Ivanov M, Nagamine M, Davoodi A, Carstens MI, Ikoma A, Cevikbas F, Kempkes C, Buddenkotte J, Steinhoff M, Carstens E. Involvement of TRPV4 in Serotonin-Evoked Scratching. J Invest Dermatol 2016; 136:154-160. [PMID: 26763435 PMCID: PMC4731048 DOI: 10.1038/jid.2015.388] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 08/26/2015] [Accepted: 09/05/2015] [Indexed: 01/13/2023]
Abstract
Several thermo-sensitive TRP channels (TRPV1, -3; TRPA1) have been implicated in itch. In contrast, the role of transient receptor potential vanilloid type-4 (TRPV4) in itch is unknown. Therefore, we investigated if TRPV4, a temperature-sensitive cation channel, plays an important role in acute itch in mice. Four different pruritogens including serotonin (5-hydroxytrytamine, 5-HT), histamine, SLIGRL (PAR2/MrgprC11 agonist) and chloroquine (MrgprA3 agonist) were intradermally injected and itch-related scratching behavior was assessed. TRPV4 knockout (TRPV4KO) mice exhibited significantly fewer 5-HT-evoked scratching bouts compared to wild-type (WT) mice. Notably, no differences between TRPV4KO and WT mice were observed in the number of scratch bouts elicited by SLIGRL and histamine. Pretreatment with a TRPV4 antagonist significantly attenuated 5-HT-evoked scratching in vivo. Using calcium imaging in cultured primary murine dorsal root ganglion (DRG) neurons, the response of neurons after 5-HT application, but not other pruritogens, was significantly lower in TRPV4KO compared to WT mice. A TRPV4 antagonist significantly suppressed 5-HT-evoked responses in DRG cells from WT mice. Approximately 90% of 5-HT-sensitive DRG neurons were immunoreactive for an antibody to TRPV4, as assessed by calcium imaging. These results indicate that serotonin-induced itch is linked to TRPV4.
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Affiliation(s)
- Tasuku Akiyama
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, USA; Department of Dermatology, Department of Anatomy & Cell Biology, Temple Itch Center, Temple University, Philadelphia, Pennsylvania, USA.
| | - Margaret Ivanov
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, USA
| | - Masaki Nagamine
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, USA
| | - Auva Davoodi
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, USA
| | - Mirela I Carstens
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, USA
| | - Akihiko Ikoma
- Departments of Dermatology and Surgery, University of California, San Francisco, USA
| | - Ferda Cevikbas
- Departments of Dermatology and Surgery, University of California, San Francisco, USA
| | - Cordula Kempkes
- Departments of Dermatology and Surgery, University of California, San Francisco, USA
| | - Joerg Buddenkotte
- Departments of Dermatology and Surgery, University of California, San Francisco, USA; U Dept. of Dermatology and UCD Charles Institute for Translational Dermatology, University College Dublin, Dublin, Ireland
| | - Martin Steinhoff
- Departments of Dermatology and Surgery, University of California, San Francisco, USA; U Dept. of Dermatology and UCD Charles Institute for Translational Dermatology, University College Dublin, Dublin, Ireland.
| | - E Carstens
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, USA.
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68
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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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69
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Yu G, Yang N, Li F, Chen M, Guo CJ, Wang C, Hu D, Yang Y, Zhu C, Wang Z, Shi H, Gegen T, Tang M, He Q, Liu Q, Tang Z. Enhanced itch elicited by capsaicin in a chronic itch model. Mol Pain 2016; 12:12/0/1744806916645349. [PMID: 27118771 PMCID: PMC4956172 DOI: 10.1177/1744806916645349] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/20/2016] [Indexed: 11/17/2022] Open
Abstract
Chronic itch (pruritus) is an important clinical problem. However, the underlying molecular basis has yet to be understood. The Transient Receptor Potential Vanilloid 1 channel is a heat-sensitive cation channel expressed in primary sensory neurons and involved in both thermosensation and pain, but its role in chronic itch remains elusive. Here, we for the first time revealed an increased innervation density of Transient Receptor Potential Vanilloid 1-expressing sensory fibers in the skin afflicted with chronic itch. Further analysis indicated that this phenomenon is due to an expansion of Transient Receptor Potential Vanilloid 1-expressing sensory neurons under chronic itch conditions. As a functional correlates of this neuronal expansion, we observed an enhanced neuronal responsiveness to capsaicin under the dry skin conditions. Importantly, the neuronal hypersensitivity to capsaicin results in itch, rather than pain sensation, suggesting that the up-regulated Transient Receptor Potential Vanilloid 1 underlies the pain-to-itch switch under chronic itchy conditions. The study shows that there are different mechanisms of chronic pain and itching, and Transient Receptor Potential Vanilloid 1 plays an important role in chronic itch.
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Affiliation(s)
- Guang Yu
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Niuniu Yang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Fengxian Li
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA Department of Anesthesiology, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong, China
| | - Meijuan Chen
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Changxiong J Guo
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Changming Wang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Danyou Hu
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Yan Yang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Chan Zhu
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Zhongli Wang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Hao Shi
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Tana Gegen
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Ming Tang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Qian He
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Qin Liu
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Zongxiang Tang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
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70
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Bourane S, Duan B, Koch SC, Dalet A, Britz O, Garcia-Campmany L, Kim E, Cheng L, Ghosh A, Ma Q, Goulding M. Gate control of mechanical itch by a subpopulation of spinal cord interneurons. Science 2015; 350:550-4. [PMID: 26516282 DOI: 10.1126/science.aac8653] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Light mechanical stimulation of hairy skin can induce a form of itch known as mechanical itch. This itch sensation is normally suppressed by inputs from mechanoreceptors; however, in many forms of chronic itch, including alloknesis, this gating mechanism is lost. Here we demonstrate that a population of spinal inhibitory interneurons that are defined by the expression of neuropeptide Y::Cre (NPY::Cre) act to gate mechanical itch. Mice in which dorsal NPY::Cre-derived neurons are selectively ablated or silenced develop mechanical itch without an increase in sensitivity to chemical itch or pain. This chronic itch state is histamine-independent and is transmitted independently of neurons that express the gastrin-releasing peptide receptor. Thus, our studies reveal a dedicated spinal cord inhibitory pathway that gates the transmission of mechanical itch.
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Affiliation(s)
- Steeve Bourane
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Bo Duan
- Dana-Farber Cancer Institute and Department of Neurobiology, Harvard Medical School, 1 Jimmy Fund Way, Boston, MA 02115, USA
| | - Stephanie C Koch
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Antoine Dalet
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Olivier Britz
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Lidia Garcia-Campmany
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Euiseok Kim
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, CA 92093, USA
| | - Longzhen Cheng
- Dana-Farber Cancer Institute and Department of Neurobiology, Harvard Medical School, 1 Jimmy Fund Way, Boston, MA 02115, USA. Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Anirvan Ghosh
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, CA 92093, USA
| | - Qiufu Ma
- Dana-Farber Cancer Institute and Department of Neurobiology, Harvard Medical School, 1 Jimmy Fund Way, Boston, MA 02115, USA.
| | - Martyn Goulding
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
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71
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Intracellular signaling pathways involved in the release of IL-4 and VEGF from human keratinocytes by activation of kinin B1 receptor: functional relevance to angiogenesis. Arch Dermatol Res 2015; 307:803-17. [PMID: 26338700 DOI: 10.1007/s00403-015-1595-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 08/04/2015] [Accepted: 08/20/2015] [Indexed: 12/11/2022]
Abstract
The injured skin produces a number of mediators that directly or indirectly modulate cell chemotaxis, migration, proliferation, and angiogenesis. Components of the kinin pathway including the kinin B1 receptor (B1R) have been found to occur in the human skin, but information about its role on keratinocyte biology is still scarce. Our aim was to determine whether stimulation of B1R causes the secretion of IL-4 and/or VEGF from human keratinocytes and to evaluate the role of the B1R agonist Lys-des[Arg(9)]bradykinin and IL-4 on various stages of angiogenesis, such as cell migration, proliferation, and release of metalloproteases. By using ELISA and Western blotting, we showed that HaCaT keratinocytes stimulated with the B1R agonist release IL-4 and VEGF. Stimulation of B1R also caused transient c-JunN-terminal kinase phosphorylation and JunB nuclear translocation, transcription factor that regulates IL-4 expression. The 3D-angiogenesis assay, performed on spheroids of EA.hy923 endothelial cells embedded in a collagen matrix, showed that their cumulative sprout area increased significantly following stimulation with either IL-4 or B1R agonist. Furthermore, these ligands produced significant endothelial cell migration and release of metalloproteases 2 and 9, but did not increase endothelial cell proliferation as measured by 5-bromo-2'-deoxyuridine incorporation. Our results provide experimental evidence that establishes IL-4 and B1R agonist as important angiogenic factors of relevance for skin repair.
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72
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Fostini AC, Girolomoni G. Experimental elicitation of itch: Evoking and evaluation techniques. J Dermatol Sci 2015; 80:13-7. [PMID: 26095137 DOI: 10.1016/j.jdermsci.2015.06.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 06/10/2015] [Indexed: 01/20/2023]
Abstract
Itch is a very common symptom of many skin diseases. Chronic itch may be very troublesome and may strongly impact on work ability, sleep and on the quality of life. Many studies have been conducted to define peripheral and central itch pathways, and to test the anti-pruritic effect of drugs, in which pruritus was experimentally evoked by chemical mediators and by physical stimuli. However, no objective methods to reproduce and to evaluate itch has been standardized. In this review we summarize the experimental techniques used to induce pruritus and to quantify it both in animal models and in humans.
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Affiliation(s)
- Anna Chiara Fostini
- Department of Medicine, Section of Dermatology and Venereology, University of Verona, 37126, Verona, Italy.
| | - Giampiero Girolomoni
- Department of Medicine, Section of Dermatology and Venereology, University of Verona, 37126, Verona, Italy
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73
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Pall PS, Hurwitz OE, King BA, LaMotte RH. Psychophysical measurements of itch and nociceptive sensations in an experimental model of allergic contact dermatitis. THE JOURNAL OF PAIN 2015; 16:741-9. [PMID: 26002605 DOI: 10.1016/j.jpain.2015.04.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 04/25/2015] [Accepted: 04/28/2015] [Indexed: 11/25/2022]
Abstract
UNLABELLED Allergic contact dermatitis (ACD) is a common condition that can significantly affect the quality of life. Contact with allergens results in delayed hypersensitivity reactions involving T lymphocytes, with associated skin inflammation and spontaneous itch and nociceptive sensations. However, psychophysical studies of these sensations are lacking. In the present study, we sensitized 8 healthy volunteers to squaric acid dibutyl ester (SADBE). Two weeks later, 1 volar forearm was challenged with SADBE, and the other with acetone vehicle control. Subsequently, participants rated the maximal perceived intensity of spontaneous itch, pricking/stinging, and burning every 6 to 12 hours for 1 week, using the generalized Labeled Magnitude Scale. In the laboratory, they judged stimulus-evoked sensations within and outside the chemically treated area. The SADBE- but not the acetone-treated skin resulted in 1) localized inflammation, with spontaneous itch and nociceptive sensations peaking at 24 to 48 hours after challenge, 2) alloknesis, hyperknesis, and hyperalgesia to mechanical stimuli that were reduced or eliminated by anesthetic cooling of the SADBE-treated area and restored on rewarming, suggesting that sensations and dysesthesias are dependent on ongoing peripheral neural activity, and 3) enhanced itch to intradermal injection of histamine, BAM8-22, or β-alanine. This experimental model of T-cell-mediated inflammation may prove useful in evaluating potential treatments of itch from ACD. PERSPECTIVE In a model of allergic contact dermatitis, experimentally applied in humans, psychophysical measurements were obtained of persistent, spontaneous itch and enhanced stimulus-evoked itch and pain sensations. These sensory measurements will be useful in the identification of the neural mechanisms underlying inflammatory itch and pain.
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Affiliation(s)
- Parul S Pall
- Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut
| | - Olivia E Hurwitz
- Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut
| | - Brett A King
- Department of Dermatology, Yale University School of Medicine, New Haven, Connecticut
| | - Robert H LaMotte
- Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut.
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74
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Placebo Effects on Itch: A Meta-Analysis of Clinical Trials of Patients with Dermatological Conditions. J Invest Dermatol 2015; 135:1234-1243. [DOI: 10.1038/jid.2014.522] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 10/31/2014] [Accepted: 12/01/2014] [Indexed: 01/21/2023]
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75
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Church MK, Maurer M. H1-Antihistamines and itch in atopic dermatitis. Exp Dermatol 2015; 24:332-3. [DOI: 10.1111/exd.12626] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/29/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Martin K Church
- Department of Dermatology and Allergy; Allergie-Centrum-Charité; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Marcus Maurer
- Department of Dermatology and Allergy; Allergie-Centrum-Charité; Charité - Universitätsmedizin Berlin; Berlin Germany
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76
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Abstract
Itch is a complex sensory modality that can be evoked by an extremely diverse set of stimuli and has multiple components of disease etiology. Thus, determining the basic molecular and cellular players is essential before we can tackle the more complex aspects of itch. The identification of novel itch receptors has been extremely fruitful and has uncovered novel signaling pathways and pruritogens. Mrgprs encode a family of G protein-coupled receptors, many of which are expressed specifically in sensory nerves and function as itch receptors in mediating histamine-independent itch. In this chapter, we will review the discovery of the receptor family, their specific expression, their roles as itch receptors, and the itch-inducing agonists. Furthermore, we will summarize the results indicating that Mrgpr-expressing sensory neurons are itch-sensing neurons. In the end we will discuss the role of Mrgprs and Mrgpr-positive neurons in chronic itch.
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Affiliation(s)
- Qin Liu
- The Center for the Study of Itch, Washington University Pain Center, St. Louis, MO, 63110, USA,
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77
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Abstract
Histamine is one of the best-characterized pruritogens in humans. It is known to play a role in pruritus associated with urticaria as well as ocular and nasal allergic reactions. Histamine mediates its effect via four receptors. Antihistamines that block the activation of the histamine H₁receptor, H₁R, have been shown to be effective therapeutics for the treatment of pruritus associated with urticaria, allergic rhinitis, and allergic conjunctivitis. However, their efficacy in other pruritic diseases such as atopic dermatitis and psoriasis is limited. The other histamine receptors may also play a role in pruritus, with the exception of the histamine H₂receptor, H₂R. Preclinical evidence indicates that local antagonism of the histamine H₃receptor, H₃R, can induce scratching perhaps via blocking inhibitory neuronal signals. The histamine H₄receptor, H₄R, has received a significant amount of attention as to its role in mediating pruritic signals. Indeed, it has now been shown that a selective H₄R antagonist can inhibit histamine-induced itch in humans. This clinical result, in conjunction with efficacy in various preclinical pruritus models, points to the therapeutic potential of H₄R antagonists for the treatment of pruritus not controlled by antihistamines that target the H₁R.
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Affiliation(s)
- Robin L Thurmond
- Janssen Research and Development, L.L.C., San Diego, CA, 92121, USA,
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78
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Tóth BI, Szallasi A, Bíró T. Transient receptor potential channels and itch: how deep should we scratch? Handb Exp Pharmacol 2015; 226:89-133. [PMID: 25861776 DOI: 10.1007/978-3-662-44605-8_6] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Over the past 30 years, transient receptor potential (TRP) channels have evolved from a somewhat obscure observation on how fruit flies detect light to become the center of drug discovery efforts, triggering a heated debate about their potential as targets for therapeutic applications in humans. In this review, we describe our current understanding of the diverse mechanism of action of TRP channels in the itch pathway from the skin to the brain with focus on the peripheral detection of stimuli that elicit the desire to scratch and spinal itch processing and sensitization. We predict that the compelling basic research findings on TRP channels and pruritus will be translated into the development of novel, clinically useful itch medications.
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Affiliation(s)
- Balázs I Tóth
- DE-MTA "Lendület" Cellular Physiology Research Group, Department of Physiology, University of Debrecen, Debrecen, 4032, Hungary
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79
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Abstract
Protease-activated receptors (PARs) have been implicated in a variety of physiological functions, as well as somatosensation and particularly itch and pain. Considerable attention has focused on PARs following the finding they are upregulated in the skin of atopic dermatitis patients. The present review focuses on recent studies showing that PARs are critically involved in itch and sensitization of itch. PARs are expressed by diverse cell types including primary sensory neurons, keratinocytes, and immune cells and are activated by proteases that expose a tethered ligand. Endogenous proteases are also released from diverse cell types including keratinocytes and immune cells. Exogenous proteases released from certain plants and insects contacting the skin can also induce itch. Increased levels of proteases in the skin contribute to inflammation that is often accompanied by chronic itch which is not predominantly mediated by histamine. The neural pathway signaling itch induced by activation of PARs is distinct from that mediating histamine-induced itch. In addition, there is evidence that PARs play an important role in sensitization of itch signaling under conditions of chronic itch. These recent findings suggest that PARs and other molecules involved in the itch-signaling pathway are good targets to develop novel treatments for most types of chronic itch that are poorly treated with antihistamines.
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Affiliation(s)
- Tasuku Akiyama
- Department of Dermatology, Anatomy and Cell Biology/Temple Itch Center, Temple University School of Medicine, Philadelphia, PA, 19140, USA
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80
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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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81
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Kollmeier A, Francke K, Chen B, Dunford PJ, Greenspan AJ, Xia Y, Xu XL, Zhou B, Thurmond RL. The Histamine H 4Receptor Antagonist, JNJ 39758979, Is Effective in Reducing Histamine-Induced Pruritus in a Randomized Clinical Study in Healthy Subjects. J Pharmacol Exp Ther 2014; 350:181-187. [DOI: 10.1124/jpet.114.215749] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
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82
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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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83
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Understanding the switch from pain-to-itch in dermatitis. Neurosci Lett 2014; 579:188-9. [PMID: 24905172 DOI: 10.1016/j.neulet.2014.05.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 05/07/2014] [Indexed: 11/22/2022]
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84
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Itch elicited by intradermal injection of serotonin, intracisternal injection of morphine, and their synergistic interactions in rats. Neuroscience 2014; 274:119-27. [PMID: 24875173 DOI: 10.1016/j.neuroscience.2014.05.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 05/09/2014] [Accepted: 05/13/2014] [Indexed: 12/19/2022]
Abstract
We used the cheek model of itch and pain in rats to determine the dose-response relationships for intradermal injection of serotonin and α methylserotonin on scratching behavior. We also determined the dose-related effects of intracisternally injected morphine on scratching, effects that were greatly reduced by administration of the opiate antagonist naloxone. We then examined the interactions of intradermal injection of serotonin and intracisternal injection of morphine on scratching and found that the two procedures act synergistically to increase itch. These results suggest that morphine applied to the CNS is capable of producing itch and greatly increasing itch originating in the skin (hyperknesis).
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85
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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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86
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Fu K, Qu L, Shimada SG, Nie H, LaMotte RH. Enhanced scratching elicited by a pruritogen and an algogen in a mouse model of contact hypersensitivity. Neurosci Lett 2014; 579:190-4. [PMID: 24704378 DOI: 10.1016/j.neulet.2014.03.062] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 03/24/2014] [Accepted: 03/26/2014] [Indexed: 02/08/2023]
Abstract
Chemical pruritogens and algogens evoke primarily itch and pain, respectively, when administered to the skin of healthy human subjects. However, the dominant sensory quality elicited by an algesic chemical stimulus may change in patients with chronic itch where bradykinin, elicits itch in addition to pain. Here we tested whether normally pruritic and algesic chemicals evoked abnormal itch- or pain-like behaviors in the mouse after the development of contact hypersensitivity (CHS), an animal model of allergic contact dermatitis. Mice previously sensitized to a hapten (squaric acid dibutylester) applied to the abdomen, exhibited spontaneous itch-like scratching and pain-like wiping directed to the site on the cheek of the CHS elicited by a subsequent challenge with the same hapten. In comparison with responses of control mice, CHS mice exhibited a significant increase in the scratching evoked by bovine adrenal medulla 8-22, a peptide that elicits a histamine-independent itch, but did not alter the scratching to histamine. Bradykinin, an algogen that elicited only wiping in control mice, additionally evoked significant scratching in CHS mice. Thus, within an area of CHS, histamine-independent itch is enhanced and chemically evoked pain is accompanied by itch.
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Affiliation(s)
- Kai Fu
- Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520, USA; Guangdong Province Key Laboratory of Pharmacodynamic Constituents of TCM and New Drugs Research, College of Pharmacy, Jinan University, Guangzhou 510632, Guangdong, China
| | - Lintao Qu
- Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Steven G Shimada
- Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Hong Nie
- Guangdong Province Key Laboratory of Pharmacodynamic Constituents of TCM and New Drugs Research, College of Pharmacy, Jinan University, Guangzhou 510632, Guangdong, China.
| | - Robert H LaMotte
- Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520, USA.
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87
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Moser HR, Giesler GJ. Characterization of pruriceptive trigeminothalamic tract neurons in rats. J Neurophysiol 2014; 111:1574-89. [PMID: 24478156 PMCID: PMC4035772 DOI: 10.1152/jn.00668.2013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 01/22/2014] [Indexed: 11/22/2022] Open
Abstract
Rodent models of facial itch and pain provide a valuable tool for distinguishing between behaviors related to each sensation. In rats, pruritogens applied to the face elicit scratching using the hindlimb while algogens elicit wiping using the forelimb. We wished to determine the role of trigeminothalamic tract (VTT) neurons in carrying information regarding facial itch and pain to the forebrain. We have characterized responses to facially applied pruritogens (serotonin, BAM8-22, chloroquine, histamine, capsaicin, and cowhage) and noxious stimuli in 104 VTT neurons recorded from anesthetized rats. Each VTT neuron had a mechanically sensitive cutaneous receptive field on the ipsilateral face. All pruriceptive VTT neurons also responded to noxious mechanical and/or thermal stimulation. Over half of VTT neurons responsive to noxious stimuli also responded to at least one pruritogen. Each tested pruritogen, with the exception of cowhage, produced an increase in discharge rate in a subset of VTT neurons. The response to each pruritogen was characterized, including maximum discharge rate, response duration, and spike timing dynamics. Pruriceptive VTT neurons were recorded from throughout superficial and deep layers of the spinal trigeminal nucleus and were shown to project via antidromic mapping to the ventroposterior medial nucleus or posterior thalamic nuclei. These results indicate that pruriceptive VTT neurons are a subset of polymodal nociceptive VTT neurons and characterize a system conducive to future experiments regarding the similarities and differences between facial itch and pain.
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Affiliation(s)
- Hannah R Moser
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
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88
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Akiyama T, Nagamine M, Carstens MI, Carstens E. Behavioral model of itch, alloknesis, pain and allodynia in the lower hindlimb and correlative responses of lumbar dorsal horn neurons in the mouse. Neuroscience 2014; 266:38-46. [PMID: 24530451 DOI: 10.1016/j.neuroscience.2014.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 02/02/2014] [Accepted: 02/04/2014] [Indexed: 12/01/2022]
Abstract
We have further developed a behavioral model of itch and pain in the lower hindlimb (calf) originally reported by LaMotte et al. (2011) that allows comparisons with responses of lumbar dorsal horn neurons to pruritic and noxious stimuli. Intradermal (id) microinjection of the pruritogens histamine, SLIGRL-NH2 (agonist of PAR-2 and MrgprC11) and chloroquine (agonist of MrgprA3) into the calf of the lower limb elicited significant biting and a small amount of licking directed to the injection site, over a 30-min time course. Following id injection of histamine, low-threshold mechanical stimuli reliably elicited discrete episodes of biting (alloknesis) over a longer time course; significantly less alloknesis was observed following id injection of SLIGRL-NH2. Capsaicin injections elicited licking but little biting. Following id injection of capsaicin, low-threshold mechanical stimuli elicited discrete hindlimb flinches (allodynia) over a prolonged (>2h) time course. In single-unit recordings from superficial lumbar dorsal horn neurons, low-threshold mechanically evoked responses were significantly enhanced, accompanied by receptive field expansion, following id injection of histamine in histamine-responsive neurons. This was not observed in histamine-insensitive neurons, or following id injection of saline or SLIGRL-NH2, regardless of whether the latter activated the neuron or not. These results suggest that itch-responsive neurons are selectively sensitized by histamine but not SLIGRL-NH2 to account for alloknesis. The presently described "calf" model appears to distinguish between itch- and pain-related behavioral responses, and provides a basis to investigate lumbar spinal neural mechanisms underlying itch, alloknesis, pain and allodynia.
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Affiliation(s)
- T Akiyama
- University of California, Davis, Department of Neurobiology, Physiology & Behavior, 1 Shields Avenue, Davis, CA 95616, USA
| | - M Nagamine
- University of California, Davis, Department of Neurobiology, Physiology & Behavior, 1 Shields Avenue, Davis, CA 95616, USA
| | - M I Carstens
- University of California, Davis, Department of Neurobiology, Physiology & Behavior, 1 Shields Avenue, Davis, CA 95616, USA
| | - E Carstens
- University of California, Davis, Department of Neurobiology, Physiology & Behavior, 1 Shields Avenue, Davis, CA 95616, USA.
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89
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Abstract
The itch-scratch reflex serves as a protective mechanism in everyday life. However, chronic persistent itching can be devastating. Despite the clinical importance of the itch sensation, its mechanism remains elusive. In the past decade, substantial progress has been made to uncover the mystery of itching. Here, we review the molecules, cells, and circuits known to mediate the itch sensation, which, coupled with advances in understanding the pathophysiology of chronic itching conditions, will hopefully contribute to the development of new anti-itch therapies.
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Affiliation(s)
- Liang Han
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205;
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205;
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205;
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90
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Sölle A, Bartholomäus T, Worm M, Klinger R. How to Psychologically Minimize Scratching Impulses. ZEITSCHRIFT FUR PSYCHOLOGIE-JOURNAL OF PSYCHOLOGY 2014. [DOI: 10.1027/2151-2604/a000183] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Research in recent years, especially in the analgesic field, has intensively studied the placebo effect and its mechanisms. It has been shown that physical complaints can be efficiently reduced via learning and cognitive processes (conditioning and expectancies). However, despite evidence demonstrating a large variety of physiological similarities between pain and itch, the possible transfer of the analgesic placebo model to itch has not yet been widely discussed in research. This review therefore aims at highlighting potential transfers of placebo mechanisms to itch processes by demonstrating the therapeutic issues in pharmacological treatments for pruritus on a physiological basis and by discussing the impact of psychological mechanisms and psychological factors influencing itch sensations.
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Affiliation(s)
- Ariane Sölle
- Outpatient Clinic of Behavior Therapy, Department of Psychology, University of Hamburg, Germany
| | - Theresa Bartholomäus
- Hospital for Dermatology, Venereology und Allergology, Allergy Center, Charité University Medicine, Berlin, Germany
| | - Margitta Worm
- Hospital for Dermatology, Venereology und Allergology, Allergy Center, Charité University Medicine, Berlin, Germany
| | - Regine Klinger
- Outpatient Clinic of Behavior Therapy, Department of Psychology, University of Hamburg, Germany
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91
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Affiliation(s)
- Kapsok Li
- Department of Dermatology, Chung-Ang University College of Medicine, Seoul, Korea
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92
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The kinin B1 receptor mediates alloknesis in a murine model of inflammation. Neurosci Lett 2013; 560:31-5. [PMID: 24355361 DOI: 10.1016/j.neulet.2013.12.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Revised: 12/04/2013] [Accepted: 12/09/2013] [Indexed: 01/02/2023]
Abstract
Noxious stimuli and non-noxious mechanical stimuli elicit itch (alloknesis) instead of pain on skin lesions of patients with atopic dermatitis. We previously found that bradykinin evokes an itch-related scratching response through activation of kinin B1 receptor in skin inflamed using complete Freund's adjuvant. In this study we investigated whether alloknesis is evoked in CFA-inflamed skin and the involvement of kinin receptors. In our results, alloknesis was elicited four days after CFA-inflammation. Furthermore, pretreatment with a B1 receptor antagonist or μ-opioid receptor antagonist significantly reduced alloknesis. In contrast, treatment with a B2 receptor antagonist significantly increased alloknesis. These results suggest that the alloknesis response is mediated by the activation of kinin B1 receptor but antagonized by the B2 receptor in CFA-inflamed mice.
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93
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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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94
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Abstract
Chronic itch is a debilitating condition that affects one in 10 people. Little is known about the molecules that mediate chronic itch in primary sensory neurons and skin. We demonstrate that the ion channel TRPA1 is required for chronic itch. Using a mouse model of chronic itch, we show that scratching evoked by impaired skin barrier is abolished in TRPA1-deficient animals. This model recapitulates many of the pathophysiological hallmarks of chronic itch that are observed in prevalent human diseases such as atopic dermatitis and psoriasis, including robust scratching, extensive epidermal hyperplasia, and dramatic changes in gene expression in sensory neurons and skin. Remarkably, TRPA1 is required for both transduction of chronic itch signals to the CNS and for the dramatic skin changes triggered by dry-skin-evoked itch and scratching. These data suggest that TRPA1 regulates both itch transduction and pathophysiological changes in the skin that promote chronic itch.
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95
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van Laarhoven AIM, Kraaimaat FW, Wilder-Smith OH, van Riel PLCM, van de Kerkhof PCM, Evers AWM. Sensitivity to itch and pain in patients with psoriasis and rheumatoid arthritis. Exp Dermatol 2013; 22:530-4. [DOI: 10.1111/exd.12189] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2013] [Indexed: 01/21/2023]
Affiliation(s)
| | - Floris W. Kraaimaat
- Department of Medical Psychology; Radboud University Nijmegen Medical Centre; Nijmegen; The Netherlands
| | - Oliver H. Wilder-Smith
- Pain and Nociception Neuroscience Research Group; Department of Anaesthesiology, Pain and Palliative Medicine; Radboud University Nijmegen Medical Centre; Nijmegen; The Netherlands
| | - Piet L. C. M. van Riel
- Department of Rheumatology; Radboud University Nijmegen Medical Centre; Nijmegen; The Netherlands
| | | | - Andrea W. M. Evers
- Department of Medical Psychology; Radboud University Nijmegen Medical Centre; Nijmegen; The Netherlands
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96
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Sensitized pain response to bradykinin after sunburn - a human model for ongoing inflammatory pain? Pain 2013; 154:769-770. [DOI: 10.1016/j.pain.2013.03.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 03/12/2013] [Indexed: 01/26/2023]
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97
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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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98
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Moser HR, Giesler GJ. Itch and analgesia resulting from intrathecal application of morphine: contrasting effects on different populations of trigeminothalamic tract neurons. J Neurosci 2013; 33:6093-101. [PMID: 23554490 PMCID: PMC3668454 DOI: 10.1523/jneurosci.0216-13.2013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 02/22/2013] [Accepted: 02/23/2013] [Indexed: 11/21/2022] Open
Abstract
Intrathecal application of morphine is among the most powerful methods used to treat severe chronic pain. However, this approach commonly produces itch sufficiently severe that patients are forced to choose between relief of pain or itch. The neuronal populations responsible for processing and transmitting information underlying itch caused by intrathecal application of morphine have not been identified and characterized. We describe two populations of antidromically identified trigeminothalamic tract (VTT) neurons in anesthetized rats that are differentially affected by morphine and explain several aspects of opioid-induced itch and analgesia. We found that intrathecal application of morphine increased ongoing activity of itch-responsive VTT neurons. In addition, intrathecal application of morphine increased responses to pruritogens injected into the skin and greatly heightened responses to innocuous mechanical stimuli. In contrast, the ongoing activity and responses to noxious pinches in nociceptive VTT neurons were frequently inhibited by the same dose of morphine. These results reveal that i.t. application of morphine affects specific subpopulations of VTT neurons in ways that may produce itch, hyperknesis, alloknesis, and analgesia.
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Affiliation(s)
- Hannah R Moser
- Graduate Program in Neuroscience and Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, 55455, USA
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99
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Lavinka PC, Dong X. Molecular signaling and targets from itch: lessons for cough. COUGH 2013; 9:8. [PMID: 23497684 PMCID: PMC3630061 DOI: 10.1186/1745-9974-9-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 02/08/2013] [Indexed: 01/05/2023]
Abstract
Itch is described as an unpleasant sensation that elicits the desire to scratch, which results in the removal of the irritant from the skin. The cough reflex also results from irritation, with the purpose of removing said irritant from the airway. Could cough then be similar to itch? Anatomically, both pathways are mediated by small-diameter sensory fibers. These cough and itch sensory fibers release neuropeptides upon activation, which leads to inflammation of the nerves. Both cough and itch also involve mast cells and their mediators, which are released upon degranulation. This common inflammation and interaction with mast cells are involved in the development of chronic conditions of itch and cough. In this review, we examine the anatomy and molecular mechanisms of itch and compare them to known mechanisms for cough. Highlighting the common aspects of itch and cough could lead to new thoughts and perspectives in both fields.
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Affiliation(s)
- Pamela Colleen Lavinka
- The Solomon H, Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University School of Medicine, 725 N Wolfe Street, Baltimore, MD, 21205, USA.
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100
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Fukuoka M, Miyachi Y, Ikoma A. Mechanically evoked itch in humans. Pain 2013; 154:897-904. [PMID: 23582153 DOI: 10.1016/j.pain.2013.02.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2012] [Revised: 01/23/2013] [Accepted: 02/22/2013] [Indexed: 11/30/2022]
Abstract
When a newly developed experimental method to vibrate vellus hairs on human skin was applied to the face and arm in healthy subjects, intense itch was reproducibly induced on the face, but not on the arm, without any flare reactions. In contrast to histamine-induced itch, mechanically evoked itch was not characterized as burning or stinging by any subjects, and was resistant to histamine H1-receptor antagonists. When the stimulation was continued for 10 min, mechanically evoked itch reached the maximum intensity within 10 s, but gradually attenuated after 60 to 90 s and was rarely perceivable at the end of stimulation. When the stimulation was discontinued at 90 s, mechanically evoked itch rapidly attenuated after the end of stimulation, but took more than 10 min before it completely diminished. These results indicate a possible involvement of C-tactile neurons in mechanically evoked itch because they have consistent characteristics such as low mechanical thresholds, intermediate adaptation, after discharge, favorable response to slowly moving stimuli, and fatigue during repeated mechanical stimulation, although it needs to be confirmed by future microneurographic studies. Touch-alloknesis was present in the adjacent skin area until mechanically evoked itch completely diminished, supporting the hypothesis that itch sensitization can be caused by a continuous activation of peripheral itch neurons whether or not they are histamine-sensitive C nerves. In conclusion, this study provides direct evidence of mechanosensitive nerves involved in itch in human skin. The purity of mechanically evoked itch without any pain-related sensory components is a major advantage for investigating the differentiation of itch from pain.
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Affiliation(s)
- Miyuki Fukuoka
- Department of Dermatology, Graduate School of Medicine, Kyoto University, Japan
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