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Pavlenko D, Seven ZT, Sanders K, Markan A, Verpile R, Ishida H, Costco D, Akiyama T. Activation of NPY2R-expressing amygdala neurons inhibits itch behavior in mice without lateralization. RESEARCH SQUARE 2024:rs.3.rs-4463812. [PMID: 38826337 PMCID: PMC11142353 DOI: 10.21203/rs.3.rs-4463812/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
The central amygdala (CeA) is a crucial hub in the processing of affective itch, containing a diverse array of neuronal populations. Among these components, Neuropeptide Y (NPY) and its receptors, such as NPY2R, affect various physiological and psychological processes. Despite this broad impact, the precise role of NPY2R+ CeA neurons in itch modulation remains unknown, particularly concerning any potential lateralization effects. To address this, we employed optogenetics to selectively stimulate NPY2R+ CeA neurons in mice, investigating their impact on itch modulation. Optogenetic activation of NPY2R+ CeA neurons reduced scratching behavior elicited by pruritogens without exhibiting any lateralization effects. Electrophysiological recordings confirmed increased neuronal activity upon stimulation. However, this modulation did not affect thermal sensitivity, mechanical sensitivity, or inflammatory pain. Additionally, no alterations in anxiety-like behaviors or locomotion were observed upon stimulation. Projection tracing revealed connections of NPY2R+ CeA neurons to brain regions implicated in itch processing. Overall, this comprehensive study highlights the role of NPY2R+ CeA neurons in itch regulation without any lateralization effects.
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Affiliation(s)
- Darya Pavlenko
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Zeynep Todurga Seven
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Medical Pharmacology, Cerrahpasa Medical Faculty, Istanbul University-Cerrahpasa, Istanbul, Turkey
| | - Kristen Sanders
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Anika Markan
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Rebecca Verpile
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Hirotake Ishida
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Dylan Costco
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Tasuku Akiyama
- Dr. Phillip Frost Department of Dermatology & Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
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2
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Go EJ, Lee JY, Kim YH, Park CK. Site-Specific Transient Receptor Potential Channel Mechanisms and Their Characteristics for Targeted Chronic Itch Treatment. Biomolecules 2024; 14:107. [PMID: 38254707 PMCID: PMC10813675 DOI: 10.3390/biom14010107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 01/10/2024] [Accepted: 01/13/2024] [Indexed: 01/24/2024] Open
Abstract
Chronic itch is a debilitating condition with limited treatment options, severely affecting quality of life. The identification of pruriceptors has sparked a growing interest in the therapeutic potential of TRP channels in the context of itch. In this regard, we provided a comprehensive overview of the site-specific expression of TRP channels and their associated functions in response to a range of pruritogens. Although several potent antipruritic compounds that target specific TRP channels have been developed and have demonstrated efficacy in various chronic itch conditions through experimental means, a more thorough understanding of the potential for adverse effects or interactions with other TRP channels or GPCRs is necessary to develop novel and selective therapeutics that target TRP channels for treating chronic itch. This review focuses on the mechanism of itch associated with TRP channels at specific sites, from the skin to the sensory neuron, with the aim of suggesting specific therapeutic targets for treating this condition.
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Affiliation(s)
- Eun Jin Go
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 21999, Republic of Korea;
| | - Ji Yeon Lee
- Department of Anesthesiology and Pain Medicine, Gil Medical Center, Gachon University, Incheon 21565, Republic of Korea;
| | - Yong Ho Kim
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 21999, Republic of Korea;
| | - Chul-Kyu Park
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 21999, Republic of Korea;
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Kim C, Kim Y, Lim JY, Kim M, Zheng H, Kim M, Hwang SW. Pamoic acid-induced peripheral GPR35 activation improves pruritus and dermatitis. Br J Pharmacol 2023; 180:3059-3070. [PMID: 37501600 DOI: 10.1111/bph.16201] [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: 03/03/2022] [Revised: 07/12/2023] [Accepted: 07/16/2023] [Indexed: 07/29/2023] Open
Abstract
BACKGROUND AND PURPOSE Pruritic dermatitis is a disease with a considerable unmet need for treatment and appears to present with not only epidermal but also peripheral neuronal complications. Here, we propose a novel pharmacological modulation targeting both peripheral dorsal root ganglion (DRG) sensory neurons and skin keratinocytes. GPR35 is an orphan G-protein-coupled receptor expressed in DRG neurons and has been predicted to downregulate neuronal excitability when activated. Modulator information is currently increasing for GPR35, and pamoic acid (PA), a salt-forming agent for drugs, has been shown to be an activator solely specific for GPR35. Here, we investigated its effects on dermatitic pathology. EXPERIMENTAL APPROACH We confirmed GPR35 expression in peripheral neurons and tissues. The effect of PA treatment was pharmacologically evaluated in cultured cells in vitro and in in vivo animal models for acute and chronic pruritus. KEY RESULTS Local PA application mitigated acute non-histaminergic itch and, consistently, obstructed DRG neuronal responses. Keratinocyte fragmentation under dermatitic simulation was also dampened following PA incubation. Chronic pruritus in 1-chloro-2,4-dinitrobenzene and psoriasis models were also moderately but significantly reversed by the repeated applications of PA. Dermatitic scores in the 1-chloro-2,4-dinitrobenzene and psoriatic models were also improved by its application, indicating that it is beneficial for mitigating disease pathology. CONCLUSION AND IMPLICATIONS Our findings suggest that pamoic acid activation of peripheral GPR35 can contribute to the improvement of pruritus and its associated diseases.
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Affiliation(s)
- Chaeeun Kim
- Department of Biomedical Sciences and Department of Physiology, College of Medicine, Korea University, Seoul, Korea
| | - Yerin Kim
- Department of Biomedical Sciences and Department of Physiology, College of Medicine, Korea University, Seoul, Korea
| | - Ji Yeon Lim
- Department of Biomedical Sciences and Department of Physiology, College of Medicine, Korea University, Seoul, Korea
| | - Minseok Kim
- Department of Biomedical Sciences and Department of Physiology, College of Medicine, Korea University, Seoul, Korea
| | - Haiyan Zheng
- Department of Biomedical Sciences and Department of Physiology, College of Medicine, Korea University, Seoul, Korea
| | - Miri Kim
- Department of Biomedical Sciences and Department of Physiology, College of Medicine, Korea University, Seoul, Korea
| | - Sun Wook Hwang
- Department of Biomedical Sciences and Department of Physiology, College of Medicine, Korea University, Seoul, Korea
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Funahashi H, Pavlenko D, Sakai K, Verpile R, Sanders KM, Akiyama T. Dynorphinergic Projections from the Central Amygdala to the Parabrachial Nucleus Regulate Itch. J Neurosci 2023; 43:5340-5349. [PMID: 37399333 PMCID: PMC10359027 DOI: 10.1523/jneurosci.0726-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 06/19/2023] [Accepted: 06/22/2023] [Indexed: 07/05/2023] Open
Abstract
The amygdala plays a key role in the processing of itch and pain signals as well as emotion. A previous study revealed that the central nucleus of the amygdala (CeA)-parabrachial nucleus (PBN) pathway is involved in pain regulation. The same pathway might also control itch. To test this possibility, prodynorphin (Pdyn)-Cre mice were used to optogenetically manipulate Pdyn+ CeA-to-PBN projections. We found that optogenetic stimulation of Pdyn+ amygdala neurons or Pdyn+ CeA-to-PBN projections inhibited histamine-evoked and chloroquine-evoked scratching. The number of Fos-positive neurons in the PBN increased following intradermal injection of chloroquine. Optogenetic stimulation of Pdyn+ CeA-to-PBN projections suppressed the increase in Fos expression in the PBN. Optogenetic stimulation of Pdyn+ CeA-to-PBN projections increased thermal and mechanical thresholds without affecting anxiety-like behavior. These results highlight the importance of dynorphinergic projections from the central amygdala to the parabrachial nucleus in the regulation of itch signaling.SIGNIFICANCE STATEMENT The central nucleus of the amygdala (CeA)-parabrachial nucleus (PBN) pathway regulates pain signaling. Using prodynorphin (Pdyn)-cre mice, we investigated the role of Pdyn+ CeA-to-PBN projections in itch. Optogenetic stimulation of Pdyn+ CeA-to-PBN projections inhibited pruritogen-evoked scratching and neuronal activity (c-Fos expression) in the PBN. Together, dynorphinergic projections from the central amygdala to the parabrachial nucleus are important for regulating itch information.
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Affiliation(s)
- Hideki Funahashi
- Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL 33136
- Department of Psychiatry, Faculty of Medicine, University of Miyazaki, Miyazaki City, Miyazaki 5200, Japan
| | - Darya Pavlenko
- Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Kent Sakai
- Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Rebecca Verpile
- Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Kristen M Sanders
- Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Tasuku Akiyama
- Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery and Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL 33136
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5
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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: 0] [Impact Index Per Article: 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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Steinhoff M, Ahmad F, Pandey A, Datsi A, AlHammadi A, Al-Khawaga S, Al-Malki A, Meng J, Alam M, Buddenkotte J. Neuro-immune communication regulating pruritus in atopic dermatitis. J Allergy Clin Immunol 2022; 149:1875-1898. [PMID: 35337846 DOI: 10.1016/j.jaci.2022.03.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 02/13/2022] [Accepted: 03/10/2022] [Indexed: 11/26/2022]
Abstract
Atopic dermatitis (AD) is a common, chronic-relapsing inflammatory skin disease with significant disease burden. Genetic and environmental trigger factors contribute to AD, activating two of our largest organs, the nervous and immune system. Dysregulation of neuro-immune circuits plays a key role in the pathophysiology of AD causing inflammation, pruritus, pain, and barrier dysfunction. Sensory nerves can be activated by environmental or endogenous trigger factors transmitting itch stimuli to the brain. Upon stimulation, sensory nerve endings also release neuromediators into the skin contributing again to inflammation, barrier dysfunction and itch. Additionally, dysfunctional peripheral and central neuronal structures contribute to neuroinflammation, sensitization, nerve elongation, neuropathic itch, thus chronification and therapy-resistance. Consequently, neuro-immune circuits in skin and central nervous system may be targets to treat pruritus in AD. Cytokines, chemokines, proteases, lipids, opioids, ions excite/sensitize sensory nerve endings not only induce itch but further aggravate/perpetuate inflammation, skin barrier disruption, and pruritus. Thus, targeted therapies for neuro-immune circuits as well as pathway inhibitors (e.g., kinase inhibitors) may be beneficial to control pruritus in AD either in systemic and/or topical form. Understanding neuro-immune circuits and neuronal signaling will optimize our approach to control all pathological mechanisms in AD, inflammation, barrier dysfunction and pruritus.
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Affiliation(s)
- Martin Steinhoff
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar; Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Department of Dermatology, Weill Cornell Medicine-Qatar, Doha, Qatar; Qatar University, College of Medicine, Doha, Qatar; Department of Dermatology, Weill Cornell Medicine, New York, USA.
| | - Fareed Ahmad
- Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Atul Pandey
- Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Angeliki Datsi
- Institute for Transplantational Diagnostics and Cell Therapeutics, University Hospital Düsseldorf, Düsseldorf, Germany
| | - Ayda AlHammadi
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar
| | - Sara Al-Khawaga
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar
| | - Aysha Al-Malki
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar
| | - Jianghui Meng
- National Institute for Cellular Biotechnology, Dublin City University, Dublin, Ireland
| | - Majid Alam
- Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Joerg Buddenkotte
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar; Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar
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7
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Riccio D, Andersen HH, Arendt-Nielsen L. Mild Skin Heating Evokes Warmth Hyperknesis Selectively for Histaminergic and Serotoninergic Itch in Humans. Acta Derm Venereol 2022; 102:adv00649. [PMID: 35083491 PMCID: PMC9558757 DOI: 10.2340/actadv.v102.173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Chronic itch can severely affect quality of life. Patients report that their chronic itch can be exacerbated by exposure to warm conditions (“warmth hyperknesis”). The aim of this mechanistic study was to investigate the effect of mild heating of the skin in humans on various experimental models of itch. A total of 18 healthy subjects were recruited to the study. Itch was provoked by histamine, serotonin, or cowhage in 3 different sessions. The provoked area was heated with an infrared lamp, and the skin temperature was either not altered, or was increased by 4°C or 7°C. Subsequent to induction of itch, the itch intensity was recorded for 10 min while the skin was heated continuously throughout the entire period of itch induction. Heating the skin resulted in a significant increase in itch intensity when provoked by histamine or serotonin. It is possible that thermoception and pruriception interact and selectively produce a higher itch intensity in histaminergic and serotoninergic itch.
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Affiliation(s)
| | | | - Lars Arendt-Nielsen
- Faculty of Medicine, Aalborg University, Fredrik Bajers Vej, D3-212, DK-9220 Aalborg East, Denmark.
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8
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Guo CJ, Grabinski NS, Liu Q. Peripheral Mechanisms of Itch. J Invest Dermatol 2021; 142:31-41. [PMID: 34838258 DOI: 10.1016/j.jid.2021.10.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 10/15/2021] [Accepted: 10/26/2021] [Indexed: 12/30/2022]
Abstract
Itch is a universally experienced sensation, and chronic itch can be as diabolically debilitating as pain. Recent advances have not only identified the neuronal itch sensing circuitry, but also have uncovered the intricate interactions between skin and immune cells that work together with neurons to identify itch-inducing irritants. In this review, we will summarize the fundamental mechanisms of acute itch detection in the skin, as well as highlight the recent discoveries relating to this topic.
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Affiliation(s)
- Changxiong J Guo
- Center for the Study of Itch & Sensory Disorders, Department of Anesthesiology, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Nathaniel S Grabinski
- Center for the Study of Itch & Sensory Disorders, Department of Anesthesiology, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Qin Liu
- Center for the Study of Itch & Sensory Disorders, Department of Anesthesiology, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, USA.
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9
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Gatto G, Bourane S, Ren X, Di Costanzo S, Fenton PK, Halder P, Seal RP, Goulding MD. A Functional Topographic Map for Spinal Sensorimotor Reflexes. Neuron 2021; 109:91-104.e5. [PMID: 33181065 PMCID: PMC7790959 DOI: 10.1016/j.neuron.2020.10.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 06/17/2020] [Accepted: 09/30/2020] [Indexed: 01/02/2023]
Abstract
Cutaneous somatosensory modalities play pivotal roles in generating a wide range of sensorimotor behaviors, including protective and corrective reflexes that dynamically adapt ongoing movement and posture. How interneurons (INs) in the dorsal horn encode these modalities and transform them into stimulus-appropriate motor behaviors is not known. Here, we use an intersectional genetic approach to functionally assess the contribution that eight classes of dorsal excitatory INs make to sensorimotor reflex responses. We demonstrate that the dorsal horn is organized into spatially restricted excitatory modules composed of molecularly heterogeneous cell types. Laminae I/II INs drive chemical itch-induced scratching, laminae II/III INs generate paw withdrawal movements, and laminae III/IV INs modulate dynamic corrective reflexes. These data reveal a key principle in spinal somatosensory processing, namely, sensorimotor reflexes are driven by the differential spatial recruitment of excitatory neurons.
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Affiliation(s)
- Graziana Gatto
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Steeve Bourane
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA; Université de la Réunion, DéTROI, UMR 1188 INSERM, Sainte Clotilde, La Réunion 97490, France
| | - Xiangyu Ren
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA; Biology Graduate Program, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stefania Di Costanzo
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA; Biology Graduate Program, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Peter K Fenton
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Priyabrata Halder
- Departments of Neurobiology and Otolaryngology, Center for Neural Basis of Cognition, and Pittsburgh Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Rebecca P Seal
- Departments of Neurobiology and Otolaryngology, Center for Neural Basis of Cognition, and Pittsburgh Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Martyn D Goulding
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
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10
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Domocos D, Selescu T, Ceafalan LC, Iodi Carstens M, Carstens E, Babes A. Role of 5-HT1A and 5-HT3 receptors in serotonergic activation of sensory neurons in relation to itch and pain behavior in the rat. J Neurosci Res 2020; 98:1999-2017. [PMID: 32537854 DOI: 10.1002/jnr.24633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 03/29/2020] [Accepted: 04/10/2020] [Indexed: 12/21/2022]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) released by platelets, mast cells, and immunocytes is a potent inflammatory mediator which modulates pain and itch sensing in the peripheral nervous system. The serotonergic receptors expressed by primary afferent neurons involved in these sensory functions are not fully identified and appear to be to a large extent species dependent. Moreover, the mechanisms through which 5-HT receptor activation is coupled to changes in neuronal excitability have not been completely revealed. Using a combination of in vitro (calcium and voltage imaging and patch-clamp) and in vivo behavioral methods, we used both male and female Wistar rats to provide evidence for the involvement of two 5-HT receptor subtypes, 5-HT1A and 5-HT3, in mediating the sustained and transient effects, respectively, of 5-HT on rat primary afferent neurons involved in pain and itch processing. In addition, our results are consistent with a model in which sustained serotonergic responses triggered via the 5-HT1A receptor are due to closure of background potassium channels, followed by membrane depolarization and action potentials, during which the activation of voltage-gated calcium channels leads to calcium entry. Our results may provide a better understanding of mammalian serotonergic itch signaling.
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Affiliation(s)
- Dan Domocos
- Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania
| | - Tudor Selescu
- Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania
| | - Laura Cristina Ceafalan
- Cell Biology, Neuroscience and Experimental Myology Laboratory, 'Victor Babeș' National Institute of Pathology, Bucharest, Romania.,Department of Cellular & Molecular Biology and Histology, School of Medicine, 'Carol Davila' University of Medicine and Pharmacy, Bucharest, Romania
| | - Mirela Iodi Carstens
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, CA, USA
| | - Earl Carstens
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, CA, USA
| | - Alexandru Babes
- Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania
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11
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Hassler SN, Kume M, Mwirigi JM, Ahmad A, Shiers S, Wangzhou A, Ray PR, Belugin SN, Naik DK, Burton MD, Vagner J, Boitano S, Akopian AN, Dussor G, Price TJ. The cellular basis of protease-activated receptor 2-evoked mechanical and affective pain. JCI Insight 2020; 5:137393. [PMID: 32352932 PMCID: PMC7308051 DOI: 10.1172/jci.insight.137393] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 04/24/2020] [Indexed: 12/31/2022] Open
Abstract
Protease-activated receptor 2 (PAR2) has long been implicated in inflammatory and visceral pain, but the cellular basis of PAR2-evoked pain has not been delineated. Although PAR2-evoked pain has been attributed to sensory neuron expression, RNA-sequencing experiments show ambiguous F2rl1 mRNA detection. Moreover, many pharmacological tools for PAR2 are nonspecific, acting also on the Mas-related GPCR family (Mrg) that are highly enriched in sensory neurons. We sought to clarify the cellular basis of PAR2-evoked pain. We developed a PAR2-conditional knockout mouse and specifically deleted PAR2 in all sensory neurons using the PirtCre mouse line. Our behavioral findings show that PAR2 agonist-evoked mechanical hyperalgesia and facial grimacing, but not thermal hyperalgesia, are dependent on PAR2 expression in sensory neurons that project to the hind paw in male and female mice. F2rl1 mRNA is expressed in a discrete population (~4%) of mostly small-diameter sensory neurons that coexpress the Nppb and IL31ra genes. This cell population has been implicated in itch, but our work shows that PAR2 activation in these cells causes clear pain-related behaviors from the skin. Our findings show that a discrete population of DRG sensory neurons mediate PAR2-evoked pain.
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Affiliation(s)
- Shayne N. Hassler
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Moeno Kume
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Juliet M. Mwirigi
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Ayesha Ahmad
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Stephanie Shiers
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Andi Wangzhou
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Pradipta R. Ray
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Serge N. Belugin
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, San Antonio, Texas, USA
| | - Dhananjay K. Naik
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Michael D. Burton
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | | | - Scott Boitano
- BIO5 Research Institute and
- Department of Physiology, Asthma & Airway Disease Research Center, University of Arizona, Tucson, Arizona, USA
| | - Armen N. Akopian
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, San Antonio, Texas, USA
| | - Gregory Dussor
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
| | - Theodore J. Price
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Dallas, Texas, USA
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12
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A Subpopulation of Amygdala Neurons Mediates the Affective Component of Itch. J Neurosci 2019; 39:3345-3356. [PMID: 30819800 DOI: 10.1523/jneurosci.2759-18.2019] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/19/2019] [Accepted: 02/21/2019] [Indexed: 01/01/2023] Open
Abstract
Itch consists of both sensory and affective components. For chronic itch patients, the affective component of itch affects both quality of life (leading to psychological comorbidities) and disease prognosis (by promoting scratching of itchy skin). We found that acute itch stimuli, such as histamine, induced anxiety-like behavior and increased activity (c-Fos expression) in the amygdala in adult male C57BL/6 mice. Itch stimuli also increased activity in projection areas to the amygdala, suggesting that these regions form a circuit for affective itch processing. Electrophysiological characterization of histamine-responsive amygdala neurons showed that this population was active on a behaviorally relevant timescale and partially overlapped with pain signaling. Selective optogenetic activation of histamine-responsive amygdala neurons in adult male and female Fos:CreERT2;R26Ai14 mice using the Targeted Recombination in Active Populations system enhanced both scratching and anxiety-like behavior. These results highlight the importance of itch-responsive amygdala neurons in modulating itch-related affect and behavior.SIGNIFICANCE STATEMENT The sensation of itch includes an affective component that leads to stress and anxiety in chronic itch patients. We investigated the neuronal basis of affective itch in mice, with a focus on the amygdala, the key brain region for the generation of anxiety. A subpopulation of amygdala neurons responded to itch stimuli such as histamine. Optogenetic activation of histamine-responsive amygdala neurons affected both scratching and anxiety-like behavior. Therefore, this population appears to be important for mediating the affective component of itch.
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Itch induced by peripheral mu opioid receptors is dependent on TRPV1-expressing neurons and alleviated by channel activation. Sci Rep 2018; 8:15551. [PMID: 30341332 PMCID: PMC6195532 DOI: 10.1038/s41598-018-33620-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 09/28/2018] [Indexed: 12/16/2022] Open
Abstract
Opioids remain the gold standard for the treatment of moderate to severe pain. However, their analgesic properties come with important side effects, including pruritus, which occurs frequently after systemic or neuraxial administration. Although part of the opioid-induced itch is mediated centrally, recent evidence shows that the opioid receptor system in the skin also modulates itch. The goal of our study was to identify the peripherally located transducer mechanisms involved in opioid-induced pruritus. Scratching behaviors in response to an intradermal injection of the mu-opioid receptor (MOR) agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) was quantified in mast cell-, PAR2- and TRPV1-deficient mice or following ablation of TRPV1+ sensory neurons. We found that mast cells−/−, PAR-2−/−, or TRPV1−/− mice still exhibit DAMGO-induced itch responses. However, we show that ablation of TRPV1+ neurons or acute TRPV1 activation by capsaicin abolishes DAMGO-induced itch. Overall, our work shows that peripheral DAMGO-induced itch is dependent on the presence of TRPV1-expressing pruriceptors, but not the TRPV1 channel itself. Activation of these fibers by capsaicin prevents the opioid-induced itch.
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Abstract
Chronic, persistent itch is a devastating symptom that causes much suffering. In recent years, there has been great progress made in understanding the molecules, cells, and circuits underlying itch sensation. Once thought to be carried by pain-sensing neurons, itch is now believed to be capable of being transmitted by dedicated sensory labeled lines. Members of the Mas-related G protein-coupled receptor (Mrgpr) family demarcate an itch-specific labeled line in the peripheral nervous system. In the spinal cord, the expression of other proteins identifies additional populations of itch-dedicated sensory neurons. However, as evidence for labeled-line coding has mounted, studies promoting alternative itch-coding strategies have emerged, complicating our understanding of the neural basis of itch. In this review, we cover the molecules, cells, and circuits related to understanding the neural basis of itch, with a focus on the role of Mrgprs in mediating itch sensation.
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Affiliation(s)
- James Meixiong
- The Solomon H. Snyder Department of Neuroscience and the Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA; ,
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience and the Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA; , .,Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Jiang YM, Huang C, Peng Z, Han SL, Li WG, Zhu MX, Xu TL. Acidosis counteracts itch tachyphylaxis to consecutive pruritogen exposure dependent on acid-sensing ion channel 3. Mol Pain 2018; 13:1744806917721114. [PMID: 28745101 PMCID: PMC5533257 DOI: 10.1177/1744806917721114] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Tachyphylaxis of itch refers to a markedly reduced scratching response to consecutive exposures of a pruritogen, a process thought to protect against tissue damage by incessant scratching and to become disrupted in chronic itch. Here, we report that a strong stimulation of the Mas-related G-protein-coupled receptor C11 by its agonist, Ser-Leu-Ile-Gly-Arg-Leu-NH2 (SL-NH2) or bovine adrenal medulla 8-22 peptide, via subcutaneous injection in mice induces tachyphylaxis to the subsequent application of SL-NH2 to the same site. Notably, co-application of acid and SL-NH2 following the initial injection of the pruritogen alone counteracted itch tachyphylaxis by augmenting the scratching behaviors in wild-type but not in acid-sensing ion channel 3-null, animals. Using an activity-dependent silencing strategy, we identified that acid-sensing ion channel 3-mediated itch enhancement mainly occurred via the Mas-related G-protein-coupled receptor C11-responsive sensory neurons. Together, our results indicate that acid-sensing ion channel 3, activated by concomitant acid and certain pruritogens, constitute a novel signaling pathway that counteracts itch tachyphylaxis to successive pruritogenic stimulation, which likely contributes to chronic itch associated with tissue acidosis.
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Affiliation(s)
- Yi-Ming Jiang
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chen Huang
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhong Peng
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shao-Ling Han
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei-Guang Li
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Michael Xi Zhu
- 2 Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, TX, USA
| | - Tian-Le Xu
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Andersen HH, Akiyama T, Nattkemper LA, van Laarhoven A, Elberling J, Yosipovitch G, Arendt-Nielsen L. Alloknesis and hyperknesis—mechanisms, assessment methodology, and clinical implications of itch sensitization. Pain 2018; 159:1185-1197. [DOI: 10.1097/j.pain.0000000000001220] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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17
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Sakai K, Sanders KM, Youssef MR, Yanushefski KM, Jensen LE, Yosipovitch G, Akiyama T. Role of neurturin in spontaneous itch and increased nonpeptidergic intraepidermal fiber density in a mouse model of psoriasis. Pain 2017; 158:2196-2202. [PMID: 28825602 PMCID: PMC5676563 DOI: 10.1097/j.pain.0000000000001025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Psoriasis is often accompanied by itch, but the mechanisms behind this symptom remain elusive. Dynamic changes in epidermal innervation have been observed under chronic itch conditions. Therefore, we investigated whether epidermal innervation is altered in the imiquimod-induced psoriasis mouse model, whether blockade of neurotrophic growth factor signaling can reduce these changes, and whether this system can impact psoriatic itch. Over the 7-day time course of imiquimod treatment, the density of epidermal nonpeptidergic nerves significantly increased, whereas the density of peptidergic nerves significantly decreased. The nonpeptidergic epidermal nerves expressed glial cell line-derived neurotrophic factor (GDNF) family receptor GFRα-1 and GFRα-2, the ligand-binding domains for GDNF and neurturin (NRTN). The NRTN mRNA expression was elevated in the skin of imiquimod-treated mice, whereas the GDNF mRNA expression was decreased. Treatment of imiquimod-challenged mice with an NRTN-neutralizing antibody significantly reduced nonpeptidergic nerve density as well as spontaneous scratching. These results indicate that NRTN contributes to an increase in the epidermal density of nonpeptidergic nerves in the imiquimod-induced psoriasis model, and this increase may be a factor in chronic itch for these mice. Therefore, inhibition of NRTN could be a potential treatment for chronic itch in psoriasis.
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Affiliation(s)
- Kent Sakai
- Department of Dermatology and Cutaneous Surgery, Miami Itch Center, University of Miami, Miami, FL
| | - Kristen M. Sanders
- Department of Dermatology and Cutaneous Surgery, Miami Itch Center, University of Miami, Miami, FL
| | | | | | - Liselotte E. Jensen
- Department of Microbiology and Immunology, Temple University Lewis Katz School of Medicine, Philadelphia, PA
| | - Gil Yosipovitch
- Department of Dermatology and Cutaneous Surgery, Miami Itch Center, University of Miami, Miami, FL
| | - Tasuku Akiyama
- Department of Dermatology and Cutaneous Surgery, Miami Itch Center, University of Miami, Miami, FL
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18
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Liu BW, Li ZX, He ZG, Liu C, Xiong J, Xiang HB. Altered expression of target genes of spinal cord in different itch models compared with capsaicin assessed by RT-qPCR validation. Oncotarget 2017; 8:74423-74433. [PMID: 29088797 PMCID: PMC5650352 DOI: 10.18632/oncotarget.20148] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 05/23/2017] [Indexed: 11/25/2022] Open
Abstract
Spinal cord plays a central role in the development and progression of pathogenesis of obstinate pruritus. In the current study, four groups of adult male C57Bl/6 mice were investigated; one group treated with saline, while the other groups intradermally injected with compound 48/80, histamine, α-Me-5-HT and capsaicin (algogenic substance), respectively. The intradermal microinjection of pruritic and algogenic compound resulted in a dramatic increase in the itch/algogenic behavior. Analysis of the microarray data showed that 15 genes in spinal cord (C5-C8) were differentially expressed between control group and 48/80 group, in which 9 genes were up-regulated and 6 genes were down-regulated. Furthermore, the results of RT-qPCR validation studies in C5-C8 spinal cord revealed that the 9 mRNA (Sgk1, Bag4, Fos, Ehd2, Edn3, Wdfy, Corin, 4921511E18Rik and 4930423020Rik) showed very different patterns for these different drugs, especially when comparing α-Me-5-HT and capsaicin. In three itch models, Fos and Ehd2 were up-regulated whereas Corin, 4921511E18Rik and 4930423020Rik were down-regulated. Furthermore, Corin and 4930423020Rik were down-regulated in itch model group compared to capsaicin group. Thus the application of microarray technique, coupled with RT-qPCR validation, further explain the mechanism behind itching evoked by pruritic compounds. It can contribute to our understanding of pharmacological methods for prevention or treatment of obstinate pruritus.
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Affiliation(s)
- Bao-Wen Liu
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhi-Xiao Li
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhi-Gang He
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Cheng Liu
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jun Xiong
- Hepatobiliary Surgery Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hong-Bing Xiang
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Liu T, He Z, Tian X, Kamal GM, Li Z, Liu Z, Liu H, Xu F, Wang J, Xiang H. Specific patterns of spinal metabolites underlying α-Me-5-HT-evoked pruritus compared with histamine and capsaicin assessed by proton nuclear magnetic resonance spectroscopy. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1222-1230. [PMID: 28344131 DOI: 10.1016/j.bbadis.2017.03.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 03/22/2017] [Accepted: 03/22/2017] [Indexed: 12/29/2022]
Abstract
The mechanism behind itching is not well understood. Proton nuclear magnetic resonance (1H-NMR) spectroscopic analysis of spinal cord extracts provides a quick modality for evaluating the specific metabolic activity of α-Me-5-HT-evoked pruritus mice. In the current study, four groups of young adult male C57Bl/6 mice were investigated; one group treated with saline, while the other groups intradermally injected with α-Me-5-HT (histamine independent pruritogen), histamine (histamine dependent pruritogen) and capsaicin (algogenic substance), respectively. The intradermal microinjection of α-Me-5-HT and histamine resulted in a dramatic increase in the itch behavior. Furthermore, the results of NMR studies of the spinal cord extracts revealed that the metabolites show very different patterns for these different drugs, especially when comparing α-Me-5-HT and capsaicin. All the animals in the groups of α-Me-5-HT and capsaicin were completely separated using the metabolite parameters and principal component analysis. For α-Me-5-HT, the concentrations of glutamate, GABA, glycine and aspartate increased significantly, especially for GABA (increased 17.2%, p=0.008). Furthermore, the concentration of NAA increased, but there was no significant difference (increased 11.3%, p=0.191) compared to capsaicin (decreased 29.1%, p=0.002). Thus the application of magnetic resonance spectroscopy technique, coupled with statistical analysis, could further explain the mechanism behind itching evoked by α-Me-5-HT or other drugs. It can thus improve our understanding of itch pathophysiology and pharmacological therapies which may contribute to itch relief.
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Affiliation(s)
- Taotao Liu
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China; Department of Anesthesiology, Peking University Third Hospital, Beijing 100191, China
| | - Zhigang He
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China
| | - Xuebi Tian
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China
| | - Ghulam Mustafa Kamal
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Zhixiao Li
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China
| | - Zeyuan Liu
- College of Life Science, Wuhan University, Wuhan, Hubei 430076, PR China
| | - Huili Liu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China
| | - Fuqiang Xu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Jie Wang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
| | - Hongbing Xiang
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China.
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20
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Distribution of hemokinin-1 in the rat trigeminal ganglion and trigeminal sensory nuclear complex. Arch Oral Biol 2017; 79:62-69. [PMID: 28301818 DOI: 10.1016/j.archoralbio.2017.03.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 01/18/2017] [Accepted: 03/05/2017] [Indexed: 11/24/2022]
Abstract
OBJECTIVE A new mammalian tachykinin peptide encoded in a TAC4 gene was identified and designated as hemokinin-1 (HK-1). A representative of the tachykinin peptide family is substance P (SP), and the function of SP has been well characterized as a pain transmitter or modulator, while it is possible that HK-1 is involved in pruriceptive processing, but, as yet, the distribution of HK-1 peptide in the trigeminal sensory system is still unknown. Thus, the aim of the present study was to elucidate the distribution of HK-1, while comparing the expression of SP, in the trigeminal ganglion and trigeminal sensory nuclear complex. DESIGN The trigeminal ganglion and the brain stem of male SD rats were used in the immunohistochemical study. Since the amino acid sequence in the carboxyl-terminal regions of HK-1 and SP is common, polyclonal antibodies of HK-1 and SP derived from 6 amino acids consisting of amino-terminal regions of these peptides were produced in guinea pig and rabbit, respectively. The immunohistochemical staining of HK-1 and SP was conducted using frozen sections of the trigeminal ganglion and brain stem in rats. RESULTS Immunohistochemical studies revealed the expression of HK-1 in small- and medium-sized trigeminal ganglion neurons, in the paratrigeminal nucleus, and in lamina I of the trigeminal nucleus caudalis, while there was no immunoreactivity of HK-1 in the trigeminal nucleus principalis, trigeminal nucleus oralis, and trigeminal nucleus interpolaris. CONCLUSION These findings indicate that HK-1 is a target molecule for treatment of itch in the orofaicial regions.
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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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23
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Sakai K, Sanders KM, Youssef MR, Yanushefski KM, Jensen L, Yosipovitch G, Akiyama T. Mouse model of imiquimod-induced psoriatic itch. Pain 2016; 157:2536-2543. [PMID: 27437787 PMCID: PMC5069152 DOI: 10.1097/j.pain.0000000000000674] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Itch is a major indicator of psoriasis, but the underlying mechanisms behind this symptom are largely unknown. To investigate the neuronal mechanisms of psoriatic itch, we tested whether mice subjected to the imiquimod-induced psoriasis model exhibit itch-associated behaviors. Mice received daily topical applications of imiquimod to the rostral back skin for 7 days. Imiquimod-treated mice exhibited a significant increase in spontaneous scratching behavior directed to the treated area as well as touch-evoked scratching (alloknesis). To characterize this model, we measured the mRNA expression levels of pruritogens and itch-relevant receptors/channels using real-time reverse transcription PCR. The mRNA expression of MrgprA3, MrgprC11, and MrgprD decreased gradually over time in the dorsal root ganglion (DRG) cells. There was no significant change in the mRNA expression of TRPV1 or TRPA1 in DRG cells. TRPV4 mRNA expression was transiently increased in the DRG cells, whereas TRPM8 mRNA was significantly decreased. The mRNA expression levels of histidine decarboxylase and tryptophan hydroxylase 1, as well as the intensity of histamine and serotonin immunoreactivity, were transiently increased in the skin on day 2, returning to baseline by day 7. Histamine H1-receptor antagonists, chlorpheniramine and olopatadine, significantly inhibited spontaneous scratching on day 2, but not day 7. Neither chlorpheniramine nor olopatadine affected alloknesis on day 2 or day 7. These results may reflect the limited antipruritic effects of histamine H1-receptor antagonists on human psoriasis. The imiquimod-induced psoriasis model seems to be useful for the investigation of itch and its sensitization in psoriasis.
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Affiliation(s)
- Kent Sakai
- Department of Dermatology, Temple Itch Center, Temple University, Philadelphia, PA, USA
| | - Kristen M Sanders
- Department of Dermatology, Temple Itch Center, Temple University, Philadelphia, PA, USA
| | - Marina R Youssef
- Department of Dermatology, Temple Itch Center, Temple University, Philadelphia, PA, USA
| | - Kevin M Yanushefski
- Department of Dermatology, Temple Itch Center, Temple University, Philadelphia, PA, USA
| | - Liselotte Jensen
- Department of Microbiology and Immunology, Temple Autoimmunity Center, Temple University, Philadelphia, PA, USA
| | - Gil Yosipovitch
- Department of Dermatology, Temple Itch Center, Temple University, Philadelphia, PA, USA
| | - Tasuku Akiyama
- Department of Dermatology, Temple Itch Center, Temple University, Philadelphia, PA, USA
- Department of Anatomy and Cell Biology, Temple University, Philadelphia, PA, USA
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24
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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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25
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Bell AM, Gutierrez-Mecinas M, Polgár E, Todd AJ. Spinal neurons that contain gastrin-releasing peptide seldom express Fos or phosphorylate extracellular signal-regulated kinases in response to intradermal chloroquine. Mol Pain 2016; 12:12/0/1744806916649602. [PMID: 27270268 PMCID: PMC4937990 DOI: 10.1177/1744806916649602] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 04/08/2016] [Indexed: 12/25/2022] Open
Abstract
Background Gastrin-releasing peptide (GRP) is thought to play a role in the itch evoked by intradermal injection of chloroquine. Although some early studies suggested that GRP was expressed in pruriceptive primary afferents, it is now thought that GRP in the spinal cord is derived mainly from a population of excitatory interneurons in lamina II, and it has been suggested that these are involved in the itch pathway. To test this hypothesis, we used the transcription factor Fos and phosphorylation of extracellular signal-regulated kinases (ERK) to look for evidence that interneurons expressing GRP were activated following intradermal injection of chloroquine into the calf, in mice that express enhanced green fluorescent protein (EGFP) in these cells. Results Injection of chloroquine resulted in numerous Fos- or phospho-ERK (pERK) positive cells in the somatotopically appropriate part of the superficial dorsal horn. The proportion of all neurons in this region that showed Fos or pERK was 18% and 21%, respectively. However, among the GRP–EGFP, only 7% were Fos-positive and 3% were pERK-positive. As such, GRP–EGFP cells were significantly less likely than other neurons to express Fos or to phosphorylate ERK. Conclusions Both expression of Fos and phosphorylation of ERK can be used to identify dorsal horn neurons activated by chloroquine injection. However, these results do not support the hypothesis that interneurons expressing GRP are critical components in the itch pathway.
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Affiliation(s)
- Andrew M Bell
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK School of Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Maria Gutierrez-Mecinas
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Erika Polgár
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Andrew J Todd
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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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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Abstract
In this chapter we will first introduce the pathophysiological process of several skin diseases including allergic dermatitis, a common skin disease, including chronic allergic contact dermatitis (CACD), and atopic dermatitis (AD). In CACD and AD patients, repeated skin exposure to antigens contributes to the development of chronic eczematous lesions. Repeated application of haptens on mice allows emulation of the development of CACD in humans. Further, we will focus on H1, H2, and H4 histamine receptors and their effects on CACD and AD. Histamine-deficient mice, with a knockout histidine decarboxylase (HDC) gene, were used to investigate the role of histamine in CACD and AD. Histamine induces infiltration of inflammatory cells, including mast cells and eosinophils, and elevates Th2 cytokine levels in CACD. Histamine promotes the development of eczematous lesions, elevates IgE serum levels, and induces scratching behavior in CACD. The administration of H1 or H4 receptor antagonists was effective to ameliorate these symptoms in murine CACD models. The combination of H1 and H4 receptor antagonists is a potential therapeutic target for chronic inflammatory skin diseases such as CACD and AD, since combined therapy proved to be more effective than monotherapy.
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Patricio ES, Costa R, Figueiredo CP, Gers-Barlag K, Bicca MA, Manjavachi MN, Segat GC, Gentry C, Luiz AP, Fernandes ES, Cunha TM, Bevan S, Calixto JB. Mechanisms Underlying the Scratching Behavior Induced by the Activation of Proteinase-Activated Receptor-4 in Mice. J Invest Dermatol 2015; 135:2484-2491. [DOI: 10.1038/jid.2015.183] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 04/20/2015] [Accepted: 04/27/2015] [Indexed: 02/08/2023]
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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, Curtis E, Nguyen T, Carstens MI, Carstens E. Anatomical evidence of pruriceptive trigeminothalamic and trigeminoparabrachial projection neurons in mice. J Comp Neurol 2015; 524:244-56. [PMID: 26099199 DOI: 10.1002/cne.23839] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Revised: 06/05/2015] [Accepted: 06/08/2015] [Indexed: 11/06/2022]
Abstract
Itch is relayed to higher centers by projection neurons in the spinal and medullary dorsal horn. We employed a double-label method to map the ascending projections of pruriceptive and nociceptive trigeminal and spinal neurons. The retrograde tracer fluorogold (FG) was stereotaxically injected into the right thalamus or lateral parabrachial area (LPb) in mice. Seven days later, mice received intradermal (id) microinjection of histamine, chloroquine, capsaicin, or vehicle into the left cheek. Histamine, chloroquine, and capsaicin intradermally elicited similar distributions of Fos-positive neurons in the medial aspect of the superficial medullary and spinal dorsal horn from the trigeminal subnucleus caudalis to C2. Among neurons retrogradely labeled from the thalamus, 43%, 8%, and 22% were Fos-positive following id histamine, chloroquine, or capsaicin. Among the Fos-positive neurons following pruritic or capsaicin stimuli, ∼1-2% were retrogradely labeled with FG. Trigeminoparabrachial projection neurons exhibited a higher incidence of double labeling in the superficial dorsal horn. Among the neurons retrogradely labeled from LPb, 36%, 29%, and 33% were Fos positive following id injection of histamine, chloroquine, and capsaicin, respectively. Among Fos-positive neurons elicited by id histamine, chloroquine, and capsaicin, respectively, 3.7%, 4.3%, and 4.1% were retrogradely labeled from LPb. The present results indicate that, overall, relatively small subpopulations of pruriceptive and/or nociceptive neurons innervating the cheek project to thalamus or LPb. These results imply that the vast majority of pruritogen- and algogen-responsive spinal neurons are likely to function as interneurons relaying information to projection neurons and/or participating in segmental nocifensive circuits.
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Affiliation(s)
- Tasuku Akiyama
- Temple Itch Center, Department of Dermatology, Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, Pennsylvania, 19140
| | - Eric Curtis
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, California, 95616
| | - Tony Nguyen
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, California, 95616
| | - Mirela Iodi Carstens
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, California, 95616
| | - E Carstens
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, California, 95616
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Pradhananga S, Shim WS. Caffeic acid exhibits anti-pruritic effects by inhibition of multiple itch transmission pathways in mice. Eur J Pharmacol 2015; 762:313-21. [PMID: 26057691 DOI: 10.1016/j.ejphar.2015.06.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 06/01/2015] [Accepted: 06/02/2015] [Indexed: 01/09/2023]
Abstract
Itch is an unpleasant sensation that evokes a desire to scratch. Although often regarded as a trivial 'alarming' sensation, itch may be debilitating and exhausting, leading to reduction in quality of life. In the current study, the question of whether caffeic acid can be used to alleviate itch sensation induced by various pruritic agents, including histamine, chloroquine, SLIGRL-NH2, and β-alanine was investigated. It turned out that histamine-induced intracellular calcium increase was significantly blocked by caffeic acid in HEK293T cells that express H1R and TRPV1, molecules required for transmission of histamine-induced itch in sensory neurons. In addition, inhibition of histamine-induced intracellular calcium increase by caffeic acid was demonstrated in primary cultures of mouse dorsal root ganglion (DRG). When chloroquine, an anti-malaria agent known to induce histamine-independent itch - was used, it was also found that caffeic acid inhibits the induced response in both DRG and HEK293T cells that express MRGPRA3 and TRPA1, underlying molecular entities responsible for chloroquine-mediated itch. Likewise, intracellular calcium changes by SLIGRL-NH2 - an itch-inducing agent via PAR2 and MRGPRC11 - were decreased by caffeic acid as well. However, it was found that caffeic acid is not capable of inhibiting β-alanine-induced responses via its specific receptor MRGPRD. Finally, in vivo scratching behavior tests showed that caffeic acid indeed has anti-scratching effects against histamine, chloroquine, and SLIGRL-NH2 administration but not by β-alanine. Overall, the current study demonstrated that caffeic acid has anti-itch effects by inhibition of multiple itch mechanisms induced by histamine, chloroquine and SLIGRL-NH2.
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Affiliation(s)
- Sabindra Pradhananga
- College of Pharmacy, Gachon University, Hambakmoeiro 191, Yeonsu-gu, Incheon 406-799, Republic of Korea
| | - Won-Sik Shim
- College of Pharmacy, Gachon University, Hambakmoeiro 191, Yeonsu-gu, Incheon 406-799, Republic of Korea.
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32
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Wilson AD. Immune responses to ectoparasites of horses, with a focus on insect bite hypersensitivity. Parasite Immunol 2015; 36:560-72. [PMID: 25180696 DOI: 10.1111/pim.12142] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 08/18/2014] [Indexed: 12/24/2022]
Abstract
Horses are affected by a wide variety of arthropod ectoparasites, ranging from lice which spend their entire life on the host, through ticks which feed over a period of days, to numerous biting insects that only transiently visit the host to feed. The presence of ectoparasites elicits a number of host responses including innate inflammatory responses, adaptive immune reactions and altered behaviour; all of which can reduce the severity of the parasite burden. All of these different responses are linked through immune mechanisms mediated by mast cells and IgE antibodies which have an important role in host resistance to ectoparasites, yet immune responses also cause severe pathological reactions. One of the best described examples of such pathological sequelae is insect bite hypersensitivity (IBH) of horses; an IgE-mediated type 1 hypersensitivity to the salivary proteins of Culicoides spp. associated with T-helper-2 production of IL4 and IL13. Importantly, all horses exposed to Culicoides have an expanded population of Culicoides antigen-specific T cells with this pattern of cytokine production, but in those which remain healthy, the inflammatory reaction is tempered by the presence of FoxP3+ CD4+ regulatory T cells that express IL10 and TGF-beta, which suppresses the IL4 production by Culicoides antigen-activated T cells.
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Affiliation(s)
- A D Wilson
- School of Clinical Veterinary Science, University of Bristol, Bristol, UK
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33
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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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34
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Funahashi H, Naono-Nakayama R, Ebihara K, Koganemaru G, Kuramashi A, Ikeda T, Nishimori T, Ishida Y. Hemokinin-1 mediates pruriceptive processing in the rat spinal cord. Neuroscience 2014; 277:206-16. [DOI: 10.1016/j.neuroscience.2014.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2014] [Revised: 06/28/2014] [Accepted: 07/01/2014] [Indexed: 11/16/2022]
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Maciel I, Azevedo V, Pereira T, Bogo M, Souza A, Gomez M, Campos M. The spinal inhibition of N-type voltage-gated calcium channels selectively prevents scratching behavior in mice. Neuroscience 2014; 277:794-805. [DOI: 10.1016/j.neuroscience.2014.07.065] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 07/02/2014] [Accepted: 07/29/2014] [Indexed: 11/27/2022]
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36
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Tominaga M, Takamori K. Itch and nerve fibers with special reference to atopic dermatitis: Therapeutic implications. J Dermatol 2014; 41:205-12. [DOI: 10.1111/1346-8138.12317] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 01/10/2023]
Affiliation(s)
- Mitsutoshi Tominaga
- Institute for Environmental and Gender Specific Medicine; Juntendo University Graduate School of Medicine; Urayasu Chiba Japan
| | - Kenji Takamori
- Institute for Environmental and Gender Specific Medicine; Juntendo University Graduate School of Medicine; Urayasu Chiba Japan
- Department of Dermatology; Juntendo University Urayasu Hospital; Urayasu Chiba Japan
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Descalzi G, Chen T, Koga K, Li XY, Yamada K, Zhuo M. Cortical GluK1 kainate receptors modulate scratching in adult mice. J Neurochem 2013; 126:636-50. [DOI: 10.1111/jnc.12351] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 06/05/2013] [Accepted: 06/12/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Giannina Descalzi
- Department of Physiology; Faculty of Medicine; University of Toronto; 1 King's College Circle; University of Toronto Center for the study of Pain; Toronto Ontario Canada
| | - Tao Chen
- Department of Physiology; Faculty of Medicine; University of Toronto; 1 King's College Circle; University of Toronto Center for the study of Pain; Toronto Ontario Canada
- Center for Neuron and Disease; Frontier Institutes of Life Science, and Science and Technology; Xi'an Jiaotong University; Xian Shanxi China
| | - Kohei Koga
- Department of Physiology; Faculty of Medicine; University of Toronto; 1 King's College Circle; University of Toronto Center for the study of Pain; Toronto Ontario Canada
| | - Xiang-Yao Li
- Department of Physiology; Faculty of Medicine; University of Toronto; 1 King's College Circle; University of Toronto Center for the study of Pain; Toronto Ontario Canada
- Center for Neuron and Disease; Frontier Institutes of Life Science, and Science and Technology; Xi'an Jiaotong University; Xian Shanxi China
| | - Kaori Yamada
- Department of Physiology; Faculty of Medicine; University of Toronto; 1 King's College Circle; University of Toronto Center for the study of Pain; Toronto Ontario Canada
| | - Min Zhuo
- Department of Physiology; Faculty of Medicine; University of Toronto; 1 King's College Circle; University of Toronto Center for the study of Pain; Toronto Ontario Canada
- Center for Neuron and Disease; Frontier Institutes of Life Science, and Science and Technology; Xi'an Jiaotong University; Xian Shanxi China
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NAKAGAWA H, HIURA A. Four Possible Itching Pathways Related to the TRPV1 Channel, Histamine, PAR-2 and Serotonin. Malays J Med Sci 2013; 20:5-12. [PMID: 24043991 PMCID: PMC3773347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/06/2013] [Indexed: 06/02/2023] Open
Abstract
The following four possible pathways for itching sensation have been suggested by recent reports. 1) Histaminergic TRPV1-positive pathway: Although histamine-positive nerve fibers cannot strictly be classified as "itch specific" due to their excitation also by pure algogens (making them itch-selective), the existence of a subpopulation of nociceptors responsible for itching is strongly suggested. Moreover, the TRPV1-expressing neurons have been suggested to be the main sensors and mediators of itching. 2) Histaminergic TRPV1-negative pathway: The scratching behavior caused by itching was not different between capsaicin-pre-treated and vehicle-treated (control) mast cell-rich NC mice. This result suggests the existence of a capsaicin-insensitive (TRPV1-negative) histaminergic pathway. 3) Non-histaminergic PAR-2 pathway: Protease-activated receptor 2 (PAR-2) has been shown to play a role in the itching of atopic dermatitis (AD). The itch evoked by cowhage (a non-histaminergic pruritogen that activates PAR-2) is very similar in characteristics to the itch evoked by conditions such as AD. 4) Non-histaminergic serotonin (5-HT) pathway: 5-HT alone applied to the human skin evokes an itching sensation and has been suggested to be involved in the itching associated with pruritic diseases, such as polycythemia vera and cholestasis.
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Affiliation(s)
- Hiroshi NAKAGAWA
- Dentistry for Persons with Disability, Tokushima University Hospital, 3-18-15 Kuramoto cho, Tokushima 770, Japan
| | - Akio HIURA
- Dentistry for Persons with Disability, Tokushima University Hospital, 3-18-15 Kuramoto cho, Tokushima 770, Japan
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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: 20] [Impact Index Per Article: 1.8] [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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Belghiti M, Estévez-Herrera J, Giménez-Garzó C, González-Usano A, Montoliu C, Ferrer-Montiel A, Felipo V, Planells-Cases R. Potentiation of the transient receptor potential vanilloid 1 channel contributes to pruritogenesis in a rat model of liver disease. J Biol Chem 2013; 288:9675-9685. [PMID: 23408423 DOI: 10.1074/jbc.m113.455162] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Persistent pruritus is a common disabling dermatologic symptom associated with different etiologic factors. These include primary skin conditions, as well as neuropathic, psychogenic, or systemic disorders like chronic liver disease. Defective clearance of potential pruritogenic substances that activate itch-specific neurons innervating the skin is thought to contribute to cholestatic pruritus. However, because the underlying disease-specific pruritogens and itch-specific neuronal pathways and mechanism(s) are unknown, symptomatic therapeutic intervention often leads to no or only limited success. In the current study, we aimed to first validate rats with bile duct ligation (BDL) as a model for hepatic pruritus and then to evaluate the contribution of inflammation, peripheral neuronal sensitization, and specific signaling pathways and subpopulations of itch-responsive neurons to scratching behavior and thermal hypersensitivity. Chronic BDL rats displayed enhanced scratching behavior and thermal hyperalgesia indicative of peripheral neuroinflammation. BDL-induced itch and hypersensitivity involved a minor contribution of histaminergic/serotonergic receptors, but significant activation of protein-activated receptor 2 (PAR2) receptors, prostaglandin PGE2 formation, and potentiation of transient receptor potential vanilloid 1 (TRPV1) channel activity. The sensitization of dorsal root ganglion nociceptors in BDL rats was associated with increased surface expression of PAR2 and TRPV1 proteins and an increase in the number of PAR2- and TRPV1-expressing peptidergic neurons together with a shift of TRPV1 receptor expression to medium sized dorsal root ganglion neurons. These results suggest that pruritus and hyperalgesia in chronic cholestatic BDL rats are associated with neuroinflammation and involve PAR2-induced TRPV1 sensitization. Thus, pharmacological modulation of PAR2 and/or TRPV1 may be a valuable therapeutic approach for patients with chronic liver pruritus refractory to conventional treatments.
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Affiliation(s)
| | | | | | | | - Carmina Montoliu
- Fundación Investigación Hospital Clínico de Valencia, INCLIVA, 46010 Valencia, Spain
| | - Antonio Ferrer-Montiel
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche, Spain
| | - Vicente Felipo
- Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Rosa Planells-Cases
- Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain; Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), 13125 Berlin, Germany.
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41
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Role of nociceptive arcuate nucleus neurons in chloroquine-induced pruritic behaviors in mice. ACTA ACUST UNITED AC 2012; 32:919-922. [DOI: 10.1007/s11596-012-1058-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Indexed: 10/27/2022]
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Oxidative stress induces itch via activation of transient receptor potential subtype ankyrin 1 in mice. Neurosci Bull 2012; 28:145-54. [PMID: 22466125 DOI: 10.1007/s12264-012-1207-9] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
OBJECTIVE To investigate the role of oxidative stress in itch-indicative scratching behavior in mice, and furthermore, to define the cellular and molecular mechanisms underlying oxidative stress-mediated itch. METHODS Scratching behavior was induced by intradermal injection of the oxidants hydrogen peroxide (H₂O₂) or tert-butylhydroperoxide (tBHP) into the nape of the neck in mice. The mice were observed for 30 min. RESULTS Intradermal H₂O₂ (0.03%-1%) or tBHP (1-30 μmol) elicited robust scratching behavior, displaying an inverted U-shaped dose-response curve. Naloxone, an opioid receptor antagonist, but not morphine, largely suppressed the oxidant-induced scratching. Chlorpheniramine, a histamine H1 receptor antagonist, blocked histamine- but not oxidant-induced scratching, indicating the involvement of a histamine-independent mechanism in oxidant-evoked itch. Further, resiniferatoxin treatment abolished oxidant-induced scratching, suggesting an essential role of C-fibers. Notably, blockade of transient receptor potential subtype ankyrin 1 (TRPA1) with the selective TRPA1 antagonist HC-030031, or genetic deletion of Trpa1 but not Trpv1 (subfamily V, member 1) resulted in a profound reduction in H₂O₂-evoked scratching. Finally, systemic administration of the antioxidant N-acetyl-L-cysteine or trolox (a water-soluble vitamin E analog) attenuated scratching induced by the oxidants. CONCLUSION Oxidative stress by different oxidants induces profound scratching behavior, which is largely histamine- and TRPV1-independent but TRPA1-dependent. Antioxidants and TRPA1 antagonists may be used to treat human itch conditions associated with oxidative stress.
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Akiyama T, Tominaga M, Davoodi A, Nagamine M, Blansit K, Horwitz A, Carstens MI, Carstens E. Roles for substance P and gastrin-releasing peptide as neurotransmitters released by primary afferent pruriceptors. J Neurophysiol 2012; 109:742-8. [PMID: 23155177 DOI: 10.1152/jn.00539.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent studies support roles for neurokinin-1 (NK-1) and gastrin-releasing peptide (GRP) receptor-expressing spinal neurons in itch. We presently investigated expression of substance P (SP) and GRP in pruritogen-responsive primary sensory neurons and roles for these neuropeptides in itch signaling. Responses of dorsal root ganglion (DRG) cells to various pruritogens were observed by calcium imaging. DRG cells were then processed for SP, GRP, and isolectin B-4 (IB4; a marker for nonpeptidergic neurons) immunofluorescence. Of pruritogen-responsive DRG cells, 11.8-26.8%, 21.8-40.0%, and 21.4-26.8% were immunopositive for SP, GRP, and IB4, respectively. In behavioral studies, both systemic and intrathecal administration of a NK-1 receptor antagonist significantly attenuated scratching evoked by chloroquine and a protease-activated receptor 2 agonist, SLIGRL, but not histamine, bovine adrenal medulla peptide 8-22 (BAM8-22), or serotonin. Systemic or intrathecal administration of a GRP receptor antagonist attenuated scratching evoked by chloroquine and SLIGRL but not BAM8-22 or histamine. The GRP receptor antagonist enhanced scratching evoked by serotonin. These results indicate that SP and GRP expressed in primary sensory neurons are partially involved as neurotransmitters in histamine-independent itch signaling from the skin to the spinal cord.
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Affiliation(s)
- Tasuku Akiyama
- Dept. of Neurobiology, Physiology & Behavior, Univ. of California, Davis, Davis, CA 95616, USA
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Akiyama T, Tominaga M, Davoodi A, Nagamine M, Blansit K, Horwitz A, Carstens MI, Carstens E. Cross-sensitization of histamine-independent itch in mouse primary sensory neurons. Neuroscience 2012; 226:305-12. [PMID: 23000623 DOI: 10.1016/j.neuroscience.2012.09.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 08/10/2012] [Accepted: 09/08/2012] [Indexed: 10/27/2022]
Abstract
Overexpression of pruritogens and their precursors may contribute to the sensitization of histamine-dependent and -independent itch-signaling pathways in chronic itch. We presently investigated self- and cross-sensitization of scratching behavior elicited by various pruritogens, and their effects on primary sensory neurons. The MrgprC11 agonist BAM8-22 exhibited self- and reciprocal cross-sensitization of scratching evoked by the protease-activated receptor-2 (PAR-2) agonist SLIGRL. The MrgprA3 agonist chloroquine unidirectionally cross-sensitized BAM8-22-evoked scratching. Histamine unidirectionally cross-sensitized scratching evoked by chloroquine and BAM8-22. SLIGRL unidirectionally cross-sensitized scratching evoked by chloroquine. Dorsal root ganglion (DRG) cells responded to various combinations of pruritogens and algogens. Neither chloroquine, BAM8-22 nor histamine had any effect on responses of DRG cell responses to subsequently applied pruritogens, implying that their behavioral self- and cross-sensitization effects are mediated indirectly. SLIGRL unilaterally cross-sensitized responses of DRG cells to chloroquine and BAM8-22, consistent with the behavioral data. These results indicate that unidirectional cross-sensitization of histamine-independent itch-signaling pathways might occur at a peripheral site through PAR-2. PAR-2 expressed in pruriceptive nerve endings is a potential target to reduce sensitization associated with chronic itch.
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Affiliation(s)
- T Akiyama
- University of California, Davis, Department of Neurobiology, Physiology & Behavior, 1 Shields Avenue, Davis, CA 95616, USA
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Abstract
Lightly touching normal skin near a site of itch can elicit itch sensation, a phenomenon known as alloknesis. To investigate the neural mechanisms of alloknesis, we have developed an animal model. Low-threshold mechanical stimulation of the skin normally does not elicit any response in naïve C57/BL6 mice. Following acute intradermal (id) injection of histamine in the rostral back, mechanical stimulation 7 mm from the injection site elicited discrete hindlimb scratch bouts directed toward the stimulus. This began at 10 min and peaked 20–40 min post-histamine, declining over the next hour. Histamine itself elicited bouts of scratching not associated with the mechanical stimulus, that ceased after 30 min. Histamine- and touch-evoked scratching was inhibited by the μ-opiate antagonist naltrexone. Touch-evoked scratching was observed following id 5-HT, a PAR-4 agonist and a MrgprC11 agonist BAM8-22, but not chloroquine or a PAR-2 agonist. The histamine H1 receptor antagonist terfenadine prevented scratching and alloknesis evoked by histamine, but not 5-HT, a PAR-4 agonist or a MrgprC11 agonist. In mice with experimental dry skin, there was a time-dependent increase in spontaneous and touch-evoked scratching. This animal model, which to our knowledge is previously unreported, appears to be useful to investigate neural mechanisms of itch and alloknesis.
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Abstract
In psychophysical experiments, humans use different verbal responses to pruritic and algesic chemical stimuli to indicate the different qualities of sensation they feel. A major challenge for behavioural models in the mouse of chemical itch and pain in humans is to devise experimental protocols that provide the opportunity for the animal to exhibit a multiplicity of responses as well. One basic criterion is that chemicals that evoke primarily itch or pain in humans should elicit different types of responses when applied in the same way to the mouse. Meeting this criterion is complicated by the fact that the type of behavioural responses exhibited by the mouse depends in part on the site of chemical application such as the nape of the neck that evokes only scratching with the hind paw versus the hind limb that elicits licking and biting. Here, we review to what extent mice behaviourally differentiate chemicals that elicit itch versus pain in humans.
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Affiliation(s)
- Robert H LaMotte
- Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520, USA.
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Horvath G, Joo G, Kekesi G, Farkas I, Tuboly G, Petrovszki Z, Benedek G. Inhibition of itch-related responses at spinal level in rats. ACTA ACUST UNITED AC 2011; 98:480-90. [DOI: 10.1556/aphysiol.98.2011.4.12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Pereira PJS, Lazarotto LF, Leal PC, Lopes TG, Morrone FB, Campos MM. Inhibition of phosphatidylinositol-3 kinase γ reduces pruriceptive, inflammatory, and nociceptive responses induced by trypsin in mice. Pain 2011; 152:2861-2869. [DOI: 10.1016/j.pain.2011.09.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 08/14/2011] [Accepted: 09/16/2011] [Indexed: 10/16/2022]
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Transmitters and pathways mediating inhibition of spinal itch-signaling neurons by scratching and other counterstimuli. PLoS One 2011; 6:e22665. [PMID: 21818363 PMCID: PMC3144926 DOI: 10.1371/journal.pone.0022665] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 06/28/2011] [Indexed: 12/12/2022] Open
Abstract
Scratching relieves itch, but the underlying neural mechanisms are poorly understood. We presently investigated a role for the inhibitory neurotransmitters GABA and glycine in scratch-evoked inhibition of spinal itch-signaling neurons in a mouse model of chronic dry skin itch. Superficial dorsal horn neurons ipsilateral to hindpaw dry skin treatment exhibited a high level of spontaneous firing that was significantly attenuated by cutaneous scratching, pinch and noxious heat. Scratch-evoked inhibition was nearly abolished by spinal delivery of the glycine antagonist, strychnine, and was markedly attenuated by respective GABAA and GABAB antagonists bicuculline and saclofen. Scratch-evoked inhibition was also significantly attenuated (but not abolished) by interruption of the upper cervical spinal cord, indicating the involvement of both segmental and suprasegmental circuits that engage glycine- and GABA-mediated inhibition of spinal itch-signaling neurons by noxious counterstimuli.
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Glutamate acts as a neurotransmitter for gastrin releasing peptide-sensitive and insensitive itch-related synaptic transmission in mammalian spinal cord. Mol Pain 2011; 7:47. [PMID: 21699733 PMCID: PMC3132725 DOI: 10.1186/1744-8069-7-47] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 06/24/2011] [Indexed: 12/19/2022] Open
Abstract
Itch sensation is one of the major sensory experiences of human and animals. Recent studies have proposed that gastrin releasing peptide (GRP) is a key neurotransmitter for itch in spinal cord. However, no direct evidence is available to indicate that GRP actually mediate responses between primary afferent fibers and dorsal horn neurons. Here we performed integrative neurobiological experiments to test this question. We found that a small population of rat dorsal horn neurons responded to GRP application with increases in calcium signaling. Whole-cell patch-clamp recordings revealed that a part of superficial dorsal horn neurons responded to GRP application with the increase of action potential firing in adult rats and mice, and these dorsal horn neurons received exclusively primary afferent C-fiber inputs. On the other hands, few Aδ inputs receiving cells were found to be GRP positive. Finally, we found that evoked sensory responses between primary afferent C fibers and GRP positive superficial dorsal horn neurons are mediated by glutamate but not GRP. CNQX, a blocker of AMPA and kainate (KA) receptors, completely inhibited evoked EPSCs, including in those Fos-GFP positive dorsal horn cells activated by itching. Our findings provide the direct evidence that glutamate is the principal excitatory transmitter between C fibers and GRP positive dorsal horn neurons. Our results will help to understand the neuronal mechanism of itch and aid future treatment for patients with pruritic disease.
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