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Luo M, He J, Yin L, Zhan P, Zhao Z, Xiong H, Mei Z. Borneol exerts its antipruritic effects by inhibiting TRPA1 and activating TRPM8. J Ethnopharmacol 2024; 322:117581. [PMID: 38103845 DOI: 10.1016/j.jep.2023.117581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/28/2023] [Accepted: 12/10/2023] [Indexed: 12/19/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Borneol is a long-established traditional Chinese medicine that has been found to be effective in treating pain and itchy skin. However, whether borneol has a therapeutic effect on chronic itch and its related mechanisms remain unclear. AIM OF THE STUDY To investigate the antipruritic effect of borneol and its molecular mechanism. MATERIALS AND METHODS DrugBAN framework and molecular docking were applied to predict the targets of borneol, and the calcium imaging or patch-clamp recording analysis were used to detect the effects of borneol on TRPA1, TRPM8 or TRPV3 channels in HEK293T cells. In addition, various mouse models of acute itch and chronic itch were established to evaluate the antipruritic effects of borneol on C57BL/6J mice. Then, the borneol-induced pruritic relief was further investigated in Trpa1-/-, Trpm8-/-, or Trpa1-/-/Trpm8-/- mice. The effects of borneol on the activation of TRPM8 and the inhibition of TRPA1 were also measured in dorsal root ganglia neurons of wild-type (WT), Trpm8-/- and Trpv1-/- mice. Lastly, a randomized, double-blind study of adult patients was conducted to evaluate the clinical antipruritic effect of borneol. RESULTS TRPA1, TRPV3 and TRPM8 are the potential targets of borneol according to the results of DrugBAN algorithm and molecular docking. Calcium imaging and patch-clamp recording analysis demonstrated that borneol activates TRPM8 channel-induced cell excitability and inhibits TRPA1 channel-mediated cell excitability in transfected HEK293T cells. Animal behavior analysis showed that borneol can significantly reduce acute and chronic itch behavior in C57BL/6J mice, but this effect was eliminated in Trpa1-/-, Trpm8-/- mice, or at least in Trpa1-/-/Trpm8-/- mice. Borneol elicits TRPM8 channel induced [Ca2+]i responses but inhibits AITC or SADBE-induced activation of TRPA1 channels in dorsal root ganglia neurons of WT and Trpv1-/- mice, respectively. Furthermore, the clinical results indicated that borneol could reduce itching symptoms in patients and its efficacy is similar to that of menthol. CONCLUSION Borneol has therapeutic effects on multiple pruritus models in mice and patients with chronic itch, and the mechanism may be through inhibiting TRPA1 and activating TRPM8.
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Affiliation(s)
- Miao Luo
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, 430074, China
| | - Jinfeng He
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, 430074, China
| | - Liang Yin
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, 430074, China
| | - Ping Zhan
- Dermatology Hospital of Jiangxi Province, Nanchang, 330000, China
| | | | - Hui Xiong
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, 430074, China; Ethnopharmacology Level 3 Laboratory of National Administration of Traditional Chinese Medicine, South-Central Minzu University, Wuhan, 430074, China.
| | - Zhinan Mei
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, 430074, China; College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
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Ständer S, Luger T, Kim B, Lerner E, Metz M, Adiri R, Canosa JM, Cha A, Yosipovitch G. Cutaneous Components Leading to Pruritus, Pain, and Neurosensitivity in Atopic Dermatitis: A Narrative Review. Dermatol Ther (Heidelb) 2024; 14:45-57. [PMID: 38182845 PMCID: PMC10828226 DOI: 10.1007/s13555-023-01081-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 12/05/2023] [Indexed: 01/07/2024] Open
Abstract
Atopic dermatitis (AD) is a chronic, relapsing immunoinflammatory skin condition characterized by sensations such as pruritis, pain, and neuronal hypersensitivity. The mechanisms underlying these sensations are multifactorial and involve complex crosstalk among several cutaneous components. This review explores the role these components play in the pathophysiology of atopic dermatitis. In the skin intercellular spaces, sensory nerves interact with keratinocytes and immune cells via myriad mediators and receptors. These interactions generate action potentials that transmit pruritis and pain signals from the peripheral nervous system to the brain. Keratinocytes, the most abundant cell type in the epidermis, are key effector cells, triggering crosstalk with immune cells and sensory neurons to elicit pruritis, pain, and inflammation. Filaggrin expression by keratinocytes is reduced in atopic dermatitis, causing a weakened skin barrier and elevated skin pH. Fibroblasts are the main cell type in the dermis and, in atopic dermatitis, appear to reduce keratinocyte differentiation, further weakening the skin barrier. Fibroblasts and mast cells promote inflammation while dermal dendritic cells appear to attenuate inflammation. Inflammatory cytokines and chemokines play a major role in AD pathogenesis. Type 2 immune responses typically generate pruritis, and the type 1 and type 3 responses generate pain. Type 2 responses and increased skin pH contribute to barrier dysfunction and promote dysbiosis of the skin microbiome, causing the proliferation of Staphyloccocus aureus. In conclusion, understanding the dynamic interactions between cutaneous components in AD could drive the development of therapies to improve the quality of life for patients with AD.
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Affiliation(s)
- Sonja Ständer
- Center for Chronic Pruritus, Münster University Hospital, Münster, Germany.
| | | | - Brian Kim
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, St. Louis, MO, USA
| | - Ethan Lerner
- Massachusetts General Hospital, Charlestown, MA, USA
| | - Martin Metz
- Institute of Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Allergology and Immunology, Berlin, Germany
| | - Roni Adiri
- Pfizer Pharmaceuticals Israel Ltd, Herzliya Pituach, Israel
| | | | - Amy Cha
- Pfizer Inc, New York, NY, USA
| | - Gil Yosipovitch
- Pfizer Inc, New York, NY, USA
- Miami Itch Center, Miller School of Medicine, University of Miami, Miami, FL, USA
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Chen R, Xu X, Wang XY, Jia WB, Zhao DS, Liu N, Pang Z, Liu XQ, Zhang Y. The lateral habenula nucleus regulates pruritic sensation and emotion. Mol Brain 2023; 16:54. [PMID: 37370111 DOI: 10.1186/s13041-023-01045-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 06/14/2023] [Indexed: 06/29/2023] Open
Abstract
Itch is a complex aversive sensory and emotional experience. As a most upsetting symptom in many dermatological and systemic diseases, it lacks efficient treatments. The lateral habenula nucleus (LHb) encodes negative emotions in the epithalamus and has been implicated in pain and analgesia. Nevertheless, the role of the lateral habenula nucleus in the pruritic sensation and emotion remains elusive. Here we defined the crucial role of glutamatergic neurons within the lateral habenula nucleus (GluLHb) in itch modulation in mice. We established histamine-dependent and histamine-independent models of acute pruritus, as well as the acetone-ether-water (AEW) model of chronic pruritus. We first assessed the effects of pruritogen injection on neural activation in both medial and lateral divisions of LHb in vitro. We then demonstrated that the population activity of GluLHb neurons was increased during the acute itch and chronic itch-induced scratching behaviors in vivo. In addition, electrophysiological data showed that the excitability of GluLHb neurons was enhanced by chronic itch. Chemogenetic suppression of GluLHb neurons disrupted both acute and chronic itch-evoked scratching behaviors. Furthermore, itch-induced conditioned place aversion (CPA) was abolished by GluLHb neuronal inhibition. Finally, we dissected the LHb upstream brain regions. Together, these findings reveal the involvement of LHb in processing both the sensational and emotional components of pruritus and may shed new insights into itch therapy.
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Affiliation(s)
- Rui Chen
- Department of Neurology, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, Anhui, 230001, China
| | - Xiang Xu
- Department of Neurology, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, Anhui, 230001, China
| | - Xin-Yue Wang
- Department of Neurology, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, Anhui, 230001, China
| | - Wen-Bin Jia
- Department of Neurology, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, Anhui, 230001, China
| | - De-Shan Zhao
- School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Na Liu
- School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Zhen Pang
- School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Xiao-Qing Liu
- School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Yan Zhang
- Department of Neurology, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, Anhui, 230001, China.
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Li N, Wang C, Zhao Y, Wang Y, Gao T, Yu Y, Wang G, Zhang L. STING controls opioid-induced itch and chronic itch via spinal tank-binding kinase 1-dependent type I interferon response in mice. J Neuroinflammation 2023; 20:101. [PMID: 37122031 PMCID: PMC10150483 DOI: 10.1186/s12974-023-02783-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 04/20/2023] [Indexed: 05/02/2023] Open
Abstract
BACKGROUND Patients receiving epidural or intrathecal opioids administration for neuraxial analgesia frequently suffer from an irritating itch. STING (stimulator of interferon genes), an innate immune modulator, is strongly implicated in pain pathogenesis via neuron-immune modulation. Given that pain and itch share some common neurocircuits, we evaluate the therapeutic potential of STING agonists in opioid-induced itch and chronic itch. METHODS Opioids (morphine, fentanyl and sufentanil) were intrathecally injected to induce acute itch. Chronic itch was induced by dry skin and contact dermatitis. Opioids analgesic effect, itch-induced scratching behavior, spinal expression of STING, phosphorylation of TBK1 (tank-binding kinase 1), IRF3 (interferon regulatory factor-3) and ERK (extracellular signal-regulated kinase), as well as production of IFN-α and IFN-β were examined. STING agonists (DMXAA and ADU-S100), TBK1 inhibitor, recombinant IFN-α and IFN-β elucidated the mechanism and treatment of itch. Whole-brain functional connectivity was evaluated using resting-state fMRI. RESULTS We report the primary expression of STING protein by the spinal dorsal horn neurons. Intraperitoneal injection of DMXAA dose-dependently reduces morphine-induced scratch bouts, without impairing morphine antinociception. Simultaneously, DMXAA alleviates fentanyl- and sufentanil-induced itching-like behavior, and chronic scratching behavior caused by dry skin and contact dermatitis. Furthermore, DMXAA drastically increases spinal phosphorylation of TBK1 and IRF3 following morphine exposure, dry skin and contact dermatitis. DMXAA-induced anti-pruritus effects and spinal productions of IFN-α and IFN-β are compensated by intrathecal delivery of the TBK1 inhibitor. Also, ADU-S100, recombinant IFN-α and IFN-β exhibits remarkable attenuation in scratching behaviors after morphine injection and dermatitis. Recombinant IFN-α inhibits morphine-induced spinal phosphorylation of ERK. Finally, DMXAA prevents dermatitis-induced the increase of cerebral functional connectivity between regions of interests such as primary somatosensory cortex, piriform cortex, retrosplenial cortex, colliculus and ventral thalamus. CONCLUSIONS STING activation confers protection against opioid-induced itch and chronic itch through spinal up-regulation of TBK1-IRF3-type I interferon cascades in mice, suggesting that STING agonists are promising candidates in translational development for pruritus relief.
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Affiliation(s)
- Nan Li
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China
| | - Chunyan Wang
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China
| | - Yuying Zhao
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China
| | - Yigang Wang
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China
| | - Tianyu Gao
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China
| | - Yonghao Yu
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China
| | - Guolin Wang
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China
| | - Linlin Zhang
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China.
- Tianjin Research Institute of Anesthesiology, Tianjin, 300052, China.
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Yang N, Shao H, Deng J, Yang Y, Tang Z, Wu G, Liu Y. Dictamnine ameliorates chronic itch in DNFB-induced atopic dermatitis mice via inhibiting MrgprA3. Biochem Pharmacol 2023; 208:115368. [PMID: 36493846 DOI: 10.1016/j.bcp.2022.115368] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 11/24/2022] [Accepted: 11/29/2022] [Indexed: 12/12/2022]
Abstract
Chronic itch is the most prominent feature of atopic dermatitis (AD), and antihistamine treatment is often less effective in reducing clinical pruritus severity in AD. Multiple studies have shown that histamine-independent itch pathway is thought to predominate in AD-induced chronic itch. Mas-related G-protein-coupled receptor (Mrgpr) A3+ sensory neurons have been identified as one of the major itch-sensing neuron populations, and transient receptor potential (TRP) channel A1 is the key downstream of MrgprA3-mediated histamine-independent itch. MrgprA3-TRPA1 signal pathway is necessary for the development of chronic itch and may be the potentially promising target of chronic itch in AD. Dictamnine is one of the main quinoline alkaloid components of Cortex Dictamni (a traditional Chinese medicine widely used in clinical treatment of skin diseases). However, the anti-inflammatory and anti-pruritic effect of dictamnine on AD have not been reported. In this study, we used the 2,4-dinitrofluorobenzene (DNFB)-induced AD mouse model to observe the scratching behavior, inflammatory manifestations, and to detect the expression of MrgprA3 and TRPA1 in skin and DRG. The data demonstrated that dictamnine effectively inhibited AD-induced chronic itch, inflammation symptoms, epidermal thickening, inflammatory cell infiltration, and downregulated the expression of MrgprA3 and TRPA1. Furthermore, dictamnine restrained the excitability of MrgprA3+ and TRPA1+ neurons. Molecular docking also indicated that dictamnine has better binding affinity with MrgprA3. These results suggest that dictamnine may inhibit chronic itch caused by AD through the MrgprA3-TRPA1 mediated histamine-independent itch pathway, and may have a potential utility in AD treatment.
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Affiliation(s)
- Niuniu Yang
- Department of Traditional Chinese and Western Medicine, Medical College, Yangzhou University, Yangzhou 225009, China; The Key Laboratory of Syndrome Differentiation and Treatment of Gastric Cancer of the State Administration of Traditional Chinese Medicine, Yangzhou University, Yangzhou 225009, China; Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou 225002, China.
| | - Haifeng Shao
- Department of Traditional Chinese and Western Medicine, Medical College, Yangzhou University, Yangzhou 225009, China; The Key Laboratory of Syndrome Differentiation and Treatment of Gastric Cancer of the State Administration of Traditional Chinese Medicine, Yangzhou University, Yangzhou 225009, China; Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou 225002, China
| | - Jialin Deng
- Department of Traditional Chinese and Western Medicine, Medical College, Yangzhou University, Yangzhou 225009, China; The Key Laboratory of Syndrome Differentiation and Treatment of Gastric Cancer of the State Administration of Traditional Chinese Medicine, Yangzhou University, Yangzhou 225009, China; Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou 225002, China
| | - Yan Yang
- School of Medicine and Holistic Integrative Medicine, Nanjing University of Chinese Medicine, Nanjing 210023, China; Key Laboratory for Chinese Medicine of Prevention and Treatment in Neurological Diseases, Nanjing University of Chinese Medicine, Nanjing 210023, China
| | - Zongxiang Tang
- School of Medicine and Holistic Integrative Medicine, Nanjing University of Chinese Medicine, Nanjing 210023, China; Key Laboratory for Chinese Medicine of Prevention and Treatment in Neurological Diseases, Nanjing University of Chinese Medicine, Nanjing 210023, China
| | - Guanyi Wu
- College of Basic Medicine, Guangxi University of Chinese Medicine, Nanning 530299, China
| | - Yanqing Liu
- Department of Traditional Chinese and Western Medicine, Medical College, Yangzhou University, Yangzhou 225009, China; The Key Laboratory of Syndrome Differentiation and Treatment of Gastric Cancer of the State Administration of Traditional Chinese Medicine, Yangzhou University, Yangzhou 225009, China; Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou 225002, China
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Abstract
Astrocytes, the most abundant type of glial cell, are electrically non-excitable cells that use intracellular calcium (Ca2+) for functional regulation. Changes in intracellular Ca2+ concentration play important roles in the central nervous system (CNS), as they are involved in the release of gliotransmitters and the control of extracellular ion concentrations, thereby affecting the regulation of neuronal excitability, CNS homeostasis, and behavior. Intracellular calcium mobilization in astrocytes is known to be mediated via inositol 1,4,5-trisphosphate receptors (IP3Rs), particularly IP3R2, and its association with CNS pathogenesis has been widely reported. In addition, the existence of IP3R2-independent calcium signaling has recently been postulated; however, the detailed mechanisms and its role in astrocyte functions and CNS pathogenesis are still poorly understood. In this paper, we describe the putative mechanisms underlying IP3R1-dependent calcium signaling in astrocytes and its effects on the reactive state, compare this signaling with IP3R2-dependent calcium signaling, and discuss its contribution to chronic itch-like behavior.
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Affiliation(s)
- Miho Shiratori-Hayashi
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
| | - Makoto Tsuda
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan; Kyushu University Institute for Advanced Study, Fukuoka, Japan.
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Li C, Kim HJ, Back SK, Na HS. Common and discrete mechanisms underlying chronic pain and itch: peripheral and central sensitization. Pflugers Arch 2021. [PMID: 34245379 DOI: 10.1007/s00424-021-02599-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 05/26/2021] [Accepted: 06/22/2021] [Indexed: 12/30/2022]
Abstract
Normally, an obvious antagonism exists between pain and itch. In normal conditions, painful stimuli suppress itch sensation, whereas pain killers often generate itch. Although pain and itch are mediated by separate pathways under normal conditions, most chemicals are not highly specific to one sensation in chronic pathologic conditions. Notably, in patients with neuropathic pain, histamine primarily induces pain rather than itch, while in patients with atopic dermatitis, bradykinin triggers itch rather than pain. Accordingly, repetitive scratching even enhances itch sensation in chronic itch conditions. Physicians often prescribe pain relievers to patients with chronic itch, suggesting common mechanisms underlying chronic pain and itch, especially peripheral and central sensitization. Rather than separating itch and pain, studies should investigate chronic itch and pain including neuropathic and inflammatory conditions. Here, we reviewed chronic sensitization leading to chronic pain and itch at both peripheral and central levels. Studies investigating the connection between pain and itch facilitate the development of new therapeutics against both chronic dysesthesias based on the underlying pathophysiology.
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Ingrasci G, El-Kashlan N, Alexis A, Yosipovitch G. Chronic itch in African Americans: an unmet need. Arch Dermatol Res 2021. [PMID: 34129098 DOI: 10.1007/s00403-021-02255-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 06/05/2021] [Indexed: 10/21/2022]
Abstract
Chronic pruritus carries a significant burden of disease and is associated with a negative impact on quality of life. African Americans are disproportionately burdened by chronic pruritic disorders, including but not limited to atopic dermatitis, prurigo nodularis, inflammatory scalp dermatoses, pathologic scarring, and HIV-related dermatoses. Racial differences in skin structure and function may contribute to the pathogenesis of itch in African Americans. Itch perception and response to treatment in African Americans remain understudied and not well understood. As such, there is a large unmet need with regard to the knowledge and management of pruritus in African Americans. This review highlights notable differences in the epidemiology, pathophysiology, genetic predisposition, clinical presentation, and response to treatment for select pruritic skin conditions. By addressing itch as an unmet need in African Americans, we hope to improve patient outcomes and lessen disparities in dermatologic care.
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Wang Y, Gao D, Cui B, Yu B, Fang J, Wang Z, Tang R, Cao Z, Song W, Song P, Li S. Increased grey matter volume and associated resting-state functional connectivity in chronic spontaneous urticaria: A structural and functional MRI study. J Neuroradiol 2021; 48:236-42. [PMID: 33549611 DOI: 10.1016/j.neurad.2021.01.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 12/28/2020] [Accepted: 01/26/2021] [Indexed: 01/13/2023]
Abstract
BACKGROUND AND PURPOSE Chronic itch is one of the most common irritating sensations, yet its mechanisms have not been fully elucidated. Although some studies have revealed relationships between itching and brain function, the structural changes in the brain induced by chronic itching, such as those accompanying chronic spontaneous urticaria (CSU), remain unclear. In this study, we aimed to explore the potential changes in brain structure and the associated functional circuitry in CSU patients to generate insights to aid chronic itch management. METHODS Forty CSU patients and forty healthy controls (HCs) were recruited. Seven-day urticaria activity score (UAS7) values were collected to evaluate clinical symptoms. Voxel-based morphometry (VBM) and seed-based resting-state functional connectivity (rs-FC) analysis were used to assess structural changes in the brain and associated changes in functional circuitry. RESULTS Compared with HCs, CSU patients had significantly increased grey matter (GM) volume in the right premotor cortex, left fusiform cortex, and cerebellum. UAS7 values were positively associated with GM volume in the left fusiform cortex. In CSU patients relative to HCs, the left fusiform cortex as extracted by VBM analysis demonstrated decreased functional connectivity with the right orbitofrontal cortex, medial prefrontal cortex (mPFC), premotor cortex, primary motor cortex (MI), and cerebellum and increased functional connectivity with the right posterior insular cortex, primary somatosensory cortex (SI), and secondary somatosensory cortex (SII). The left cerebellum as extracted from VBM analysis demonstrated decreased functional connectivity with the right supplementary motor area (SMA) and MI in CSU patients relative to HCs. CONCLUSIONS Our findings indicate that patients suffering from chronic itching conditions, such as CSU, are likely to demonstrate altered GM volume in some brain regions. These changes may affect not only the sensorimotor area but also brain regions associated with cognitive function.
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Haruta-Tsukamoto A, Miyahara Y, Funahashi H, Nishimori T, Ishida Y. Perampanel attenuates scratching behavior induced by acute or chronic pruritus in mice. Biochem Biophys Res Commun 2020; 533:1102-1108. [PMID: 33028486 DOI: 10.1016/j.bbrc.2020.09.109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 09/24/2020] [Indexed: 11/28/2022]
Abstract
An itch is defined as an unpleasant sensation that evokes a desire to scratch. Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system and has a crucial role in pruriceptive processing in the spinal dorsal horn. It is well known that glutamate exerts its effects by binding to various glutamate receptors including α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, and that AMPA/kainate receptors play a crucial role in pruriceptive processing; however, the precise role of AMPA receptors remains uncertain. Perampanel, an antiepileptic drug, is an antagonist of AMPA receptors. Pretreatment with perampanel dose-dependently attenuated the induction of scratching, a behavior typically associated with pruritus, by intradermal administration of the pruritogen chloroquine. In addition, the induction of scratching in mice painted with diphenylcyclopropenone and NC/Nga mice treated with Biostir AD, animal models of contact dermatitis and atopic dermatitis, respectively, was dose-dependently alleviated by administration of perampanel. These findings indicate that AMPA receptors play a crucial role in pruriceptive processing in mice with acute or chronic pruritus.
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Affiliation(s)
- Ayaka Haruta-Tsukamoto
- Department of Psychiatry, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki-city, Miyazaki, 889-1692, Japan
| | - Yu Miyahara
- Department of Psychiatry, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki-city, Miyazaki, 889-1692, Japan
| | - Hideki Funahashi
- Department of Psychiatry, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki-city, Miyazaki, 889-1692, Japan
| | - Toshikazu Nishimori
- Department of Psychiatry, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki-city, Miyazaki, 889-1692, Japan
| | - Yasushi Ishida
- Department of Psychiatry, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki-city, Miyazaki, 889-1692, Japan.
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Janmohamed SR, Gwillim EC, Yousaf M, Patel KR, Silverberg JI. The impact of prurigo nodularis on quality of life: a systematic review and meta-analysis. Arch Dermatol Res 2020; 313:669-677. [PMID: 33108524 DOI: 10.1007/s00403-020-02148-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/11/2020] [Accepted: 10/09/2020] [Indexed: 12/29/2022]
Abstract
Prurigo nodularis (PN) is a chronic, pruritic, debilitating disease. Previous studies found that chronic pruritus in general negatively affects patients' quality of life (QoL). However, results about the impact of PN on QoL are conflicting. Our objective was to assess the QoL burden of PN. A systematic review was conducted of all published studies that assessed QoL measures in PN. OVID MEDLINE, EMBASE, SCOPUS, and Web of Science were searched. Pooled meta-analysis (means) was performed using random-effects weighting. Overall, 13 studies met inclusion criteria. All studies identified QoL reductions in patients suffering from PN compared to control groups. The most common QoL instrument used was the Dermatology Life Quality Index [n = 9 studies; pooled mean (95% confidence interval): 13.8 (10.6-16.9), denoting a very large effect]. In particular, PN was associated with substantial impact on multiple domains of QoL. No publication bias was detected. In conclusion, QoL is negatively impacted in PN. Future studies are necessary to determine the best instruments of measuring QoL in PN patients, better understand this association, and assess the impact in males and females separately. PROSPERO CRD42019136193.
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Affiliation(s)
- Sherief R Janmohamed
- Department of Dermatology, Universitair Ziekenhuis Brussel (UZB), Vrije Universiteit Brussel (VUB), Laarbeeklaan 101, 1090, Jette, Belgium
| | - Eran C Gwillim
- Department of Dermatology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - Muhammad Yousaf
- Department of Dermatology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - Kevin R Patel
- Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Jonathan I Silverberg
- Department of Dermatology, George Washington University School of Medicine, 2150 Pennsylvania Avenue, Suite 2B-430, Washington, DC, 20037, USA.
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12
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Shiratori-Hayashi M, Tsuda M. Role of reactive astrocytes in the spinal dorsal horn under chronic itch conditions. J Pharmacol Sci 2020; 144:147-50. [PMID: 32800684 DOI: 10.1016/j.jphs.2020.07.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 07/02/2020] [Accepted: 07/27/2020] [Indexed: 12/25/2022] Open
Abstract
Astrocytes are the most abundant glial cells in the central nervous system (CNS), including the spinal cord. Neuronal damage induces astrocytes to become reactive and contribute to various CNS pathologies. Recent studies have demonstrated that astrocytes in the spinal dorsal horn (SDH) become reactive in a transcription factor signal transducer and activator of transcription 3-dependent manner without neuronal damage under chronic itch conditions, causing release of the factor lipocalin-2, leading to induction of sensitization of gastrin releasing peptide-induced chemical itch signaling in the SDH. In this review, we describe recent advances in our understanding of SDH neuronal pathways for itch transmission, the mechanisms of SDH astrocytic activation and its contribution to abnormal itch processing and discuss the role of reactive astrocytes in the SDH in abnormal sensory processing under chronic itch conditions.
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13
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Fan JJ, Gao B, Song AQ, Zhu YJ, Zhou J, Li WZ, Yin YY, Wu WN. Spinal cord NLRP1 inflammasome contributes to dry skin induced chronic itch in mice. J Neuroinflammation 2020; 17:122. [PMID: 32312281 PMCID: PMC7168883 DOI: 10.1186/s12974-020-01807-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 04/08/2020] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Dry skin itch is one of the most common skin diseases and elderly people are believed to be particularly prone to it. The inflammasome has been suggested to play an important role in chronic inflammatory disorders including inflammatory skin diseases such as psoriasis. However, little is known about the role of NLRP1 inflammasome in dry skin-induced chronic itch. METHODS Dry skin-induced chronic itch model was established by acetone-ether-water (AEW) treatment. Spontaneous scratching behavior was recorded by video monitoring. The expression of nucleotide oligomerization domain (NOD)-like receptor protein 1 (NLRP1) inflammasome complexes, transient receptor potential vanilloid type 1 (TRPV1), and the level of inflammatory cytokines were determined by western blot, quantitative real-time PCR, and enzyme-linked immunosorbent assay (ELISA) kits. Nlrp1a knockdown was performed by an adeno-associated virus (AAV) vector containing Nlrp1a-shRNA-eGFP infusion. H.E. staining was used to evaluate skin lesion. RESULTS AEW treatment triggers spontaneous scratching and significantly increases the expression of NLRP1, ASC, and caspase-1 and the levels of IL-1β, IL-18, IL-6, and TNF-α in the spinal cord and the skin of mice. Spinal cord Nlrp1a knockdown prevents AEW-induced NLRP1 inflammasome assembly, TRPV1 channel activation, and spontaneous scratching behavior. Capsazepine, a specific antagonist of TRPV1, can also inhibit AEW-induced inflammatory response and scratching behavior. Furthermore, elderly mice and female mice exhibited more significant AEW-induced scratching behavior than young mice and male mice, respectively. Interestingly, AEW-induced increases in the expression of NLRP1 inflammasome complex and the levels of inflammatory cytokines were more remarkable in elderly mice and female mice than in young mice and male mice, respectively. CONCLUSIONS Spinal cord NLRP1 inflammasome-mediated inflammatory response contributes to dry skin-induced chronic itch by TRPV1 channel, and it is also involved in age and sex differences of chronic itch. Inhibition of NLRP1 inflammasome may offer a new therapy for dry skin itch.
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Affiliation(s)
- Jun-Juan Fan
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, People's Republic of China
| | - Bo Gao
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, People's Republic of China
| | - Ao-Qi Song
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, People's Republic of China
| | - Ya-Jing Zhu
- Department of Pharmacy, Xi'an Chest Hospital, Shaanxi University of Chinese Medicine, Xi'an, 710100, People's Republic of China
| | - Jun Zhou
- Department of Pharmacy, Xi'an Chest Hospital, Shaanxi University of Chinese Medicine, Xi'an, 710100, People's Republic of China
| | - Wei-Zu Li
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, People's Republic of China.,Key Laboratory of Anti-inflammatory and Immunopharmacology, Anhui Medical University, Hefei, 230032, People's Republic of China
| | - Yan-Yan Yin
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, People's Republic of China.,Key Laboratory of Anti-inflammatory and Immunopharmacology, Anhui Medical University, Hefei, 230032, People's Republic of China
| | - Wen-Ning Wu
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, People's Republic of China. .,Key Laboratory of Anti-inflammatory and Immunopharmacology, Anhui Medical University, Hefei, 230032, People's Republic of China.
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14
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Abstract
Chronic itch is a clinically challenging yet scientifically remarkable and complex process. Increasing understanding of the pathophysiology of chronic itch is leading to targeted therapeutic approaches that are now dramatically improving quality of life. This improvement will accelerate as the tools of basic and clinical research continue to be applied to this previously intractable problem.
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Affiliation(s)
- Ethan A Lerner
- Department of Dermatology, Harvard Medical School, Massachusetts General Hospital, Boston, MA 02114, USA.
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15
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Abstract
Chronic pruritus is a common condition that has a detrimental impact on quality of life. As the molecular pathogenesis of itch is elucidated, novel therapies that disrupt itch pathways are being investigated. Emerging treatments include drugs targeting the neural system, drugs targeting the immune system, antihistamines, bile acid transport inhibitors, and topical drugs that work through a variety of mechanisms such as phosphodiesterase-4 inhibition or targeting of nerve ion channels. Many of these therapies show promising results in the treatment of chronic itch of various etiologies, such as atopic dermatitis, psoriasis, uremic pruritus, and cholestatic pruritus.
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Affiliation(s)
- Matthew W McEwen
- Kaplan-Amonette Department of Dermatology, College of Medicine, University of Tennessee Health Science Center, 930 Madison Avenue, Suite 840, Memphis, TN 38163, USA
| | - Elizabeth M Fite
- Department of Dermatology, University of Tennessee Health Science Center, 930 Madison Avenue, Suite 840, Memphis, TN 38163, USA
| | - Gil Yosipovitch
- Department of Dermatology, Miami Itch Center, University of Miami, Miller School of Medicine, 1600 Northwest 10th Avenue, Rosenstiel Medical Science Building - Room 2023, Miami, FL 33136, USA
| | - Tejesh Patel
- Kaplan-Amonette Department of Dermatology, University of Tennessee Health Science Center, 930 Madison Avenue, Suite 840, Memphis, TN 38163, USA.
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16
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Abstract
Introduction Chronic itch has been drawing much attention due to its clinical significance and the complexity of its mechanisms. To facilitate the development of anti-itch strategies, it is necessary to investigate the key players in itch sensation under chronic itch conditions. Several members of the Mrgpr family were identified as itch receptors that detect cutaneous pruritogens in primary sensory neurons. However, the role of Mrgprs in chronic itch conditions has not been well described. Methods Scratching behaviors of WT and Mrgpr-clusterΔ-/- mice were examined in dry skin model and contact dermatitis model to examine the role of Mrgpr genes in mediating chronic itch sensation. Scratching behaviors of the mice were also examined in allergic itch model. Real-time PCR were performed to examine the expression level of MrgprA3 and MrgprC11 under naïve and dry skin conditions. The MrgprA3+ itch-sensing fibers were labeled by tdTomato fluorescence in Mrgpra3GFP-Cre; ROSA26tdTomato mice, and the morphology and density of those fibers in the epidermis were analyzed under dry skin condition. Results We showed that deleting a cluster of Mrgpr genes in mice reduced scratching behavior severely under two chronic itch conditions, namely dry skin and contact dermatitis, and the allergic itch condition. Moreover, the gene expressions of itch receptors MrgprA3 and MrgprC11 in dorsal root ganglia (DRG) were upregulated significantly under dry skin condition. Consistently, the percentage of MrgprA3+ itch-sensing neurons was increased as well. We also observed hyperinnervation of MrgprA3+ itch-sensing fibers in the epidermis of the skin under dry skin condition. Discussion We demonstrate that Mrgprs play important roles in mediating chronic itch and allergic itch. These findings enrich our knowledge of itch mechanism and may lead to the development of novel therapeutic approach to combat itch.
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17
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Abstract
Chronic itch is a hallmark symptom of inflammatory skin conditions, such as atopic dermatitis. Existing treatment for chronic itch is largely ineffective. Despite recent progress in our understanding of the neuronal basis for itch sensation in the peripheral and central nervous systems, the mechanisms underlying how itch turns into a pathological chronic state remain poorly understood. Recent studies have uncovered the causal role of astrocytes in the spinal dorsal horn using mouse models of chronic itch, including atopic dermatitis. Understanding the key roles of astrocytes may provide us with exciting insights into the mechanisms for the chronicity of itch sensation and clues to develop novel therapeutic agents for treating chronic itch.
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18
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Jing PB, Cao DL, Li SS, Zhu M, Bai XQ, Wu XB, Gao YJ. Chemokine Receptor CXCR3 in the Spinal Cord Contributes to Chronic Itch in Mice. Neurosci Bull 2017; 34:54-63. [PMID: 28401489 DOI: 10.1007/s12264-017-0128-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 03/01/2017] [Indexed: 12/30/2022] Open
Abstract
Recent studies have shown that the chemokine receptor CXCR3 and its ligand CXCL10 in the dorsal root ganglion mediate itch in experimental allergic contact dermatitis (ACD). CXCR3 in the spinal cord also contributes to the maintenance of neuropathic pain. However, whether spinal CXCR3 is involved in acute or chronic itch remains unclear. Here, we report that Cxcr3 -/- mice showed normal scratching in acute itch models but reduced scratching in chronic itch models of dry skin and ACD. In contrast, both formalin-induced acute pain and complete Freund's adjuvant-induced chronic inflammatory pain were reduced in Cxcr3 -/- mice. In addition, the expression of CXCR3 and CXCL10 was increased in the spinal cord in the dry skin model induced by acetone and diethyl ether followed by water (AEW). Intrathecal injection of a CXCR3 antagonist alleviated AEW-induced itch. Furthermore, touch-elicited itch (alloknesis) after compound 48/80 or AEW treatment was suppressed in Cxcr3 -/- mice. Finally, AEW-induced astrocyte activation was inhibited in Cxcr3 -/- mice. Taken together, these data suggest that spinal CXCR3 mediates chronic itch and alloknesis, and targeting CXCR3 may provide effective treatment for chronic pruritus.
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Affiliation(s)
- Peng-Bo Jing
- Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, 226019, China
| | - De-Li Cao
- Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, 226019, China
| | - Si-Si Li
- Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, 226019, China
| | - Meixuan Zhu
- Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, 226019, China
| | - Xue-Qiang Bai
- Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, 226019, China
| | - Xiao-Bo Wu
- Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, 226019, China
| | - Yong-Jing Gao
- Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, 226019, China. .,Co-innovation Center of Neuroregeneration, Nantong University, Nantong, 226001, China.
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19
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Abstract
Chronic pain and itch are a pathological operation of the somatosensory system at the levels of primary sensory neurons, spinal cord and brain. Pain and itch are clearly distinct sensations, and recent studies have revealed the separate neuronal pathways that are involved in each sensation. However, the mechanisms by which these sensations turn into a pathological chronic state are poorly understood. A proposed mechanism underlying chronic pain and itch involves abnormal excitability in dorsal horn neurons in the spinal cord. Furthermore, an increasing body of evidence from models of chronic pain and itch has indicated that synaptic hyperexcitability in the spinal dorsal horn might not be a consequence simply of changes in neurons, but rather of multiple alterations in glial cells. Thus, understanding the key roles of glial cells may provide us with exciting insights into the mechanisms of chronicity of pain and itch, and lead to new targets for treating chronic pain and itch.
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20
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Zhang TT, Shen FY, Ma LQ, Wen W, Wang B, Peng YZ, Wang ZR, Zhao X. Potentiation of synaptic transmission in Rat anterior cingulate cortex by chronic itch. Mol Brain 2016; 9:73. [PMID: 27472923 PMCID: PMC4966729 DOI: 10.1186/s13041-016-0251-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 07/19/2016] [Indexed: 12/26/2022] Open
Abstract
Itch and pain share similar mechanisms. It has been well documented that the anterior cingulate cortex (ACC) is important for pain-related perception. ACC has also been approved to be a potential pruritus-associated brain region. However, the mechanism of sensitization in pruriceptive neurons in the ACC is not clear. In current study, a chronic itch model was established by diphenylcyclopropenone (DCP) application. We found that both the frequency and amplitude of miniature excitatory postsynaptic currents in the ACC were enhanced after the formation of chronic itch. The paired-pulse ratio in ACC neurons recorded from the DCP group were smaller than those recorded in control group at the 50-ms interval. We also observe a significant increase in the AMPA/NMDA ratio in the DCP group. Moreover, an increased inward rectification of AMPARs in ACC pyramidal neurons was observed in the DCP group. Interestingly, the calculated ratio of silent synapses was significantly reduced in the DCP group compared with controls. Taken together, we conclude that a potentiation of synaptic transmission in the ACC can be induced by chronic itch, and unsilencing silent synapses, which probably involved recruitment of AMPARS, contributed to the potentiation of postsynaptic transmission.
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Affiliation(s)
- Ting-Ting Zhang
- Department of Anesthesiology and Intensive Care Medicine, Xinhua Hospital, College of Medicine, Shanghai Jiaotong University, Shanghai, 200092, China
| | - Feng-Yan Shen
- Department of Anesthesiology, Huashan Hosptital, Fudan University, Shanghai, 200040, China
| | - Li-Qing Ma
- Department of Anesthesiology, Huashan Hosptital, Fudan University, Shanghai, 200040, China
| | - Wen Wen
- Department of Anesthesiology and Intensive Care Medicine, Xinhua Hospital, College of Medicine, Shanghai Jiaotong University, Shanghai, 200092, China
| | - Bin Wang
- Department of Anesthesiology and Intensive Care Medicine, Xinhua Hospital, College of Medicine, Shanghai Jiaotong University, Shanghai, 200092, China
| | - Yuan-Zhi Peng
- Department of Anesthesiology and Intensive Care Medicine, Xinhua Hospital, College of Medicine, Shanghai Jiaotong University, Shanghai, 200092, China
| | - Zhi-Ru Wang
- Institute of Brain Functional Genomics, East China Normal University, Shanghai, 200062, China
| | - Xuan Zhao
- Department of Anesthesiology and Intensive Care Medicine, Xinhua Hospital, College of Medicine, Shanghai Jiaotong University, Shanghai, 200092, China.
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21
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Yu G, Yang N, Li F, Chen M, Guo CJ, Wang C, Hu D, Yang Y, Zhu C, Wang Z, Shi H, Gegen T, Tang M, He Q, Liu Q, Tang Z. Enhanced itch elicited by capsaicin in a chronic itch model. Mol Pain 2016; 12:12/0/1744806916645349. [PMID: 27118771 PMCID: PMC4956172 DOI: 10.1177/1744806916645349] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/20/2016] [Indexed: 11/17/2022] Open
Abstract
Chronic itch (pruritus) is an important clinical problem. However, the underlying molecular basis has yet to be understood. The Transient Receptor Potential Vanilloid 1 channel is a heat-sensitive cation channel expressed in primary sensory neurons and involved in both thermosensation and pain, but its role in chronic itch remains elusive. Here, we for the first time revealed an increased innervation density of Transient Receptor Potential Vanilloid 1-expressing sensory fibers in the skin afflicted with chronic itch. Further analysis indicated that this phenomenon is due to an expansion of Transient Receptor Potential Vanilloid 1-expressing sensory neurons under chronic itch conditions. As a functional correlates of this neuronal expansion, we observed an enhanced neuronal responsiveness to capsaicin under the dry skin conditions. Importantly, the neuronal hypersensitivity to capsaicin results in itch, rather than pain sensation, suggesting that the up-regulated Transient Receptor Potential Vanilloid 1 underlies the pain-to-itch switch under chronic itchy conditions. The study shows that there are different mechanisms of chronic pain and itching, and Transient Receptor Potential Vanilloid 1 plays an important role in chronic itch.
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Affiliation(s)
- Guang Yu
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Niuniu Yang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Fengxian Li
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA Department of Anesthesiology, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong, China
| | - Meijuan Chen
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Changxiong J Guo
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Changming Wang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Danyou Hu
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Yan Yang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Chan Zhu
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Zhongli Wang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Hao Shi
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Tana Gegen
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Ming Tang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Qian He
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Qin Liu
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Zongxiang Tang
- College of Basic Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
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22
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Ji RR. Neuroimmune interactions in itch: Do chronic itch, chronic pain, and chronic cough share similar mechanisms? Pulm Pharmacol Ther 2015; 35:81-6. [PMID: 26351759 DOI: 10.1016/j.pupt.2015.09.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 08/27/2015] [Accepted: 09/01/2015] [Indexed: 12/30/2022]
Abstract
Itch and pain are closely related but also clearly distinct sensations. Pain is known to suppress itch, while analgesics such as morphine can provoke itch. However, in pathological and chronic conditions, pain and itch also have similarities. Dysfunction of the nervous system, as manifested by neural plastic changes in primary sensory neurons of the peripheral nervous system (peripheral sensitization) and spinal cord and brain stem neurons in the central nervous system (central sensitization) will result in chronic pain and itch. Importantly, these diseases also result from immune dysfunction, since inflammatory mediators can directly activate or sensitize nociceptive and pruriceptive neurons in the peripheral and central nervous system, leading to pain and itch hypersensitivity. In this mini-review, I discuss the roles of Toll-like receptors (TLRs), transient receptor potential ankyrin 1 (TRPA1) ion channel, and Nav1.7 sodium channel in regulating itch and inflammation, with special emphasis of neuronal TLR signaling and the interaction of TLR7 and TRPA1. Chronic pain and chronic itch are debilitating diseases and dramatically impact the life quality of patients. Targeting TLRs for the control of inflammation, neuroinflammation (inflammation restricted in the nervous system), and hyperexcitability of nociceptors and pruriceptors will lead to new therapeutics for the relief of chronic pain and chronic itch. Finally, given the shared mechanisms among chronic cough, chronic pain, and chronic itch and the demonstrated efficacy of the neuropathic pain drug gabapentin in treating chronic cough, novel therapeutics targeting TRPA1, Nav1.7, and TLRs may also help to alleviate refractory cough via modulating neuron-immune interaction.
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Affiliation(s)
- Ru-Rong Ji
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, 27710, USA; Department of Neurobiology, Duke University Medical Center, Durham, NC, 27710, USA.
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