TLR3 in Chronic Human Itch: A Keratinocyte-Associated Mechanism of Peripheral Itch Sensitization
Short title: Skin TLR3 and chronic human itch.
Keywords: pruritus, toll-like receptor, endothelin, nerve, keratinocyte
Journal Club 19.06.21. Read More »
Colonization of the skin by Staphylococcus aureus is associated with exacerbation of atopic dermatitis (AD), but any direct mechanism through which dysbiosis of the skin microbiome may influence the development of AD is unknown. Here, we show that proteases and phenol-soluble modulin α (PSMα) secreted by S. aureus lead to endogenous epidermal proteolysis and skin barrier damage that promoted inflammation in mice. We further show that clinical isolates of different coagulase-negative staphylococci (CoNS) species residing on normal skin produced autoinducing peptides that inhibited the S. aureus agr system, in turn decreasing PSMα expression. These autoinducing peptides from skin microbiome CoNS species potently suppressed PSMα expression in S. aureus isolates from subjects with AD without inhibiting S. aureus growth. Metagenomic analysis of the AD skin microbiome revealed that the increase in the relative abundance of S. aureus in patients with active AD correlated with a lower CoNS autoinducing peptides to S. aureus ratio, thus overcoming the peptides’ capacity to inhibit the S. aureus agr system. Characterization of a S. hominis clinical isolate identified an autoinducing peptide (SYNVCGGYF) as a highly potent inhibitor of S. aureus agr activity, capable of preventing S. aureus-mediated epithelial damage and inflammation on murine skin. Together, these findings show how members of the normal human skin microbiome can contribute to epithelial barrier homeostasis by using quorum sensing to inhibit S. aureus toxin production.
Scabies is a common contagious skin disease caused by an infestation of the skin by Sarcoptes scabiei var. hominis. A hallmark symptom of scabies is severe itch.
We sought to determine the generation of a pruritogenic cytokine, interleukin (IL)-31, together with immune profiles in skin lesions of ordinary scabies through immunohistochemical and immunofluorescent studies. To elucidate the pathological mechanisms of IL-31 generation, murine peritoneal macrophages were stimulated with various T helper 2 (Th2) cytokines and proteins ex vivo.
A large number of CCR4(+) Th2 cells, eosinophils, and basophils infiltrated in scabies lesions. Increased generation of IL-31, TSLP, and periostin was also observed. A major population of IL-31(+) cells were Arginase-1(+)/CD163(+) M2 macrophages. Murine peritoneal macrophages showed an M2 phenotype and generated IL-31 when stimulated with TSLP and periostin.
IL-31 appeared to be largely generated by M2 macrophages in ordinary scabies lesions. This IL-31 induction was mediated by TSLP and periostin. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
TSLP ; IL-31; macrophage; periostin; scabies
2019-05-24 Journal Club Read More »
The TRPV4 Agonist GSK1016790A Regulates the Membrane Expression of TRPV4 Channels
The TRPV4 Agonist GSK1016790A Regulates the Membrane Expression of TRPV4 Channels
Sara Baratchi1*, Peter Keov1,2,3, William G. Darby1, Austin Lai1, Khashayar Khoshmanesh4, Peter Thurgood4, Parisa Vahidi1, Karin Ejendal5 and Peter McIntyre1
1 School of Health and Biomedical Sciences, RMIT University, Melbourne, VIC, Australia, 2 Molecular Pharmacology Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia, 3 St Vincent’s Clinical School, University of New South Wales, Darlinghurst, NSW, Australia, 4 School of Engineering, RMIT University, Melbourne, VIC, Australia, 5 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States
TRPV4 is a non-selective cation channel that tunes the function of different tissues including the vascular endothelium, lung, chondrocytes, and neurons. GSK1016790A is the selective and potent agonist of TRPV4 and a pharmacological tool that is used to study the TRPV4 physiological function in vitro and in vivo. It remains unknown how the sensitivity of TRPV4 to this agonist is regulated. The spatial and temporal dynamics of receptors are the major determinants of cellular responses to stimuli. Membrane translocation has been shown to control the response of several members of the transient receptor potential (TRP) family of ion channels to different stimuli. Here, we show that TRPV4 stimulation with GSK1016790A caused an increase in [Ca2+]i that is stable for a few minutes. Single molecule analysis of TRPV4 channels showed that the density of TRPV4 at the plasma membrane is controlled through two modes of membrane trafficking, complete, and partial vesicular fusion. Further, we show that the density of TRPV4 at the plasma membrane decreased within 20min, as they translocate to the recycling endosomes and that the surface density is dependent on the release of calcium from the intracellular stores and is controlled via a PI3K, PKC, and RhoA signaling pathway.
Keywords: TRPV4, membrane trafficking, endothelial cells, GSK1016790A, calcium
Journal Club 19.05.10. Read More »
Transient Receptor Potential Vanilloid 1 (TRPV1) is known to mediate itch and neurogenic inflammation, but the role of TRPV1 in psoriasiform dermal inflammation is poorly understood.
To investigate the function of TRPV1 in imiquimod (IMQ)-induced psoriasiform dermatitis (PsD) in mice.
Following daily treatment of topical IMQ cream for consecutive 5 days in C57BL/6 wide-type (WT) and TRPV1 gene knockout (KO) mice, we assessed the psoriasis severity index (PSI) scores, transepidermal water loss (TEWL), dermal inflammatory infiltrates, as well as gene expression levels for psoriasis related genes in mouse skin lesions.
Compared with WT mice, the clinical and TEWL scores, the extent of skin hyperplasia, the area of Munro microabscesses (MM) and angiogenesis of psoriasis were all significantly decreased in TRPV1 KO mice triggered with IMQ, suggesting a reduction in skin inflammation and barrier defects. In addition, the infiltration of CD45+ leukocytes, mast cells as well as CD3+ T cells was all reduced in the IMQ-treated skin of TRPV1 KO mice. Quantitative Real-time PCR (RT-qPCR) revealed that expression levels of IL-1β, IL-6, IL-23, S100A8 were decreased while IL-10 was increased in TRPV1 KO mice.
In summary, key markers of psoriatic inflammation and epidermal hyperplasia are reduced in TRPV1 KO mice, indicating the involvement of TRPV1 in the psoriasiform inflammation and suggesting its potential as a therapeutic target.
Copyright © 2018 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.
Itch; Pain neuroinflammation; Psoriasis
Itch is an unpleasant skin sensation that can be triggered by exposure to many chemicals, including those released by mast cells. The natriuretic polypeptide b (Nppb)-expressing class of sensory neurons, when activated, elicits scratching responses in mice, but it is unclear which itch-inducing agents stimulate these cells and the receptors involved. Here, we identify receptors expressed by Nppb neurons and demonstrate the functional importance of these receptors as sensors of endogenous pruritogens released by mast cells. Our search for receptors in Nppb neurons reveals that they express leukotriene, serotonin, and sphingosine-1-phosphate receptors. Targeted cell ablation, calcium imaging of primary sensory neurons, and conditional receptor knockout studies demonstrate that these receptors induce itch by the direct stimulation of Nppb neurons and neurotransmission through the canonical gastrin-releasing peptide (GRP)-dependent spinal cord itch pathway. Together, our results define a molecular and cellular pathway for mast cell-induced itch.
To identify itch-related mediators and receptors that are differentially expressed in pruritic skin, we used RNA sequencing to analyze the complete transcriptome in skin from paired itchy, lesional and nonitchy, nonlesional skin biopsies from 25 patients with atopic dermatitis and 25 patients with psoriasis and site-matched biopsies from 30 healthy controls. This analysis identified 18,000 differentially expressed genes common between itchy atopic and psoriatic skin compared with healthy skin. Of those, almost 2,000 genes were differentially expressed between itchy and nonitchy skin in atopic and psoriatic subjects. Overexpression of several genes, such as phospholipase A2 IVD, substance P, voltage-gated sodium channel 1.7, and transient receptor potential (TRP) vanilloid 1, in itchy skin was positively correlated with itch intensity ratings in both atopic dermatitis and psoriasis. Cytokines such as IL-17A, IL-23A, and IL-31 had elevated gene transcript levels in both itchy atopic and psoriatic skin. However, expression of genes for TRP vanilloid 2, TRP ankyrin 1, protease-activated receptor 2, protease-activated receptor 4, and IL-10 was found to be increased only in pruritic atopic skin, whereas expression of genes for TRP melastatin 8, TRP vanilloid 3, phospholipase C, and IL-36α/γ was elevated only in pruritic psoriatic skin. This “itchscriptome” analysis will lead to an increased understanding of the molecular mechanisms of chronic pruritus and provide targets for itch treatment irrespective of disease state.
Facilitation of MrgprD by TRP-A1 promotes neuropathic pain
Facilitation of MrgprD by TRP-A1 promotes neuropathic pain
Changming Wang,*,†,‡,§ Leying Gu,*,†,‡,§ Yonglan Ruan,*,†,‡,§ Xiao Geng,*,†,‡,§ Miao Xu,{ Niuniu Yang,*,k Lei Yu,*,† Yucui Jiang,*,† Chan Zhu,*,†,‡,§ Yan Yang,*,†,‡,§
Yuan Zhou,*,†,‡,§ Xiaowei Guan,*,†,‡,§ Wenqin Luo,# Qin Liu,**,††,‡‡ Xinzhong Dong,§§,{{ Guang Yu,*,†,‡,§,1 Lei Lan,{,2 and Zongxiang Tang*,†,‡,§
*School of Medicine and Life Sciences, †Key Laboratory of Chinese Medicine for Prevention and Treatment of Neurological Diseases, ‡State Key Laboratory Cultivation Base for Traditional Chinese Medicine Quality and Efficacy, and §Key Laboratory of Drug Target and Drug for Degenerative Disease of Jiangsu Province, Nanjing University of Chinese Medicine, Nanjing, China; {Jiangsu Province Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China; kDepartment of Traditional Chinese and Western Medicine, Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou, China; #Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; **Department of Anesthesiology, ††Center for the Study of Itch, and ‡‡Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA; and §§The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, and {{Howard Hughes Medical Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
ABSTRACT: Neuropathic pain remains a therapeutic challenge because of its complicated mechanisms. Mas-related GPCR D (MrgprD) is specifically expressed in small-diameter, nociceptive neurons of dorsal root ganglia (DRGs) and is implicated in pain modulation. However, the underlying mechanism of MrgprD involved in neuropathic pain remains elusive. In this study, we used behavioral experiments and physiologic examination methods to investigate the role of MrgprD in chronic constriction injury (CCI)–induced neuropathic pain. We found that MrgprD is necessary for the initiation of mechanical hypersensitivity and cold allodynia, but not for heat allodynia. Moreover, we demonstrated that transient receptor potential cation channel (TRP)-A1 was the ion channel down- stream of MrgprD, and the b-alanine–induced calcium signal was attributed mostly to TRP-A1 function. We further showed that PKA serves as a downstream mediator of b-alanine–activated MrgprD signaling to activate TRP-A1 in DRG neurons and in human embryonic kidney 293 cells, to coexpress MrgprD and TRP-A1 plasmids. Finally, we found that the b-alanine–induced pain behavior was increased, whereas the itching behavior was unchanged in CCI models compared with sham-injured animals. Knockout of TRPA1 also attenuated the b-alanine–induced pain behavior in CCI models. In conclusion, MrgprD is essential in cold allodynia in CCI-induced neuropathic pain through the PKA–TRP-A1 pathway. TRP-A1 facilitates MrgprD to development of neuropathic pain. Our findings reveal a novel mechanism of neuropathic pain formation and highlight MrgprD as a promising drug target for the treatment of neuropathic pain.—Wang, C., Gu, L., Ruan, Y., Geng, X., Xu, M., Yang, N., Yu, L., Jiang, Y., Zhu, C., Yang, Y., Zhou, Y., Guan, X., Luo, W., Liu, Q., Dong, X., Yu, G., Lan, L., Tang, Z. Facilitation of MrgprD by TRP-A1 promotes neuropathic pain. FASEB J. 33, 1360–1373 (2019). www.fasebj.org
KEY WORDS: MrgprA1 • dorsal root ganglia (DRG) • protein kinase A (PKA)
Journal Club 19.03.22. Read More »
Various pathologic conditions result in jaundice, a yellowing of the skin due to a buildup of bilirubin. Patients with jaundice commonly report experiencing an intense non-histaminergic itch. Despite this association, the pruritogenic capacity of bilirubin itself has not been described, and no bilirubin receptor has been identified. Here, we demonstrate that pathophysiologic levels of bilirubin excite peripheral itch sensory neurons and elicit pruritus through MRGPRs, a family of G-protein coupled receptors expressed in primary sensory neurons. Bilirubin binds and activates two MRGPRs, mouse MRGPRA1 and human MRGPRX4. In two mouse models of pathologic hyperbilirubinemia, we show that genetic deletion of either Mrgpra1 or Blvra, the gene that encodes the bilirubin-producing enzyme biliverdin reductase, attenuates itch. Similarly, plasma isolated from hyperbilirubinemic patients evoked itch in wild-type animals but not Mrgpra1-/- animals. Removing bilirubin decreased the pruritogenic capacity of patient plasma. Based on these data, targeting MRGPRs is a promising strategy for alleviating jaundice-associated itch.
Mrgpr; bilirubin; cholestasis; itch; mouse; neuroscience; sensory neuron
Identification of a bilirubin receptor that may mediate a component of cholestatic itch
Increasing evidence suggests that cytokines and chemokines play crucial roles in chronic itch. In the present study, we evaluated the roles of tumor necrosis factor-alpha (TNF-α) and its receptors TNF receptor subtype-1 (TNFR1) and TNFR2 in acute and chronic itch in mice. Compared to wild-type (WT) mice, TNFR1-knockout (TNFR1-KO) and TNFR1/R2 double-KO (DKO), but not TNFR2-KO mice, exhibited reduced acute itch induced by compound 48/80 and chloroquine (CQ). Application of the TNF-synthesis inhibitor thalidomide and the TNF-α antagonist etanercept dose-dependently suppressed acute itch. Intradermal injection of TNF-α was not sufficient to evoke scratching, but potentiated itch induced by compound 48/80, but not CQ. In addition, compound 48/80 induced TNF-α mRNA expression in the skin, while CQ induced its expression in the dorsal root ganglia (DRG) and spinal cord. Furthermore, chronic itch induced by dry skin was reduced by administration of thalidomide and etanercept and in TNFR1/R2 DKO mice. Dry skin induced TNF-α expression in the skin, DRG, and spinal cord and TNFR1 expression only in the spinal cord. Thus, our findings suggest that TNF-α/TNFR1 signaling is required for the full expression of acute and chronic itch via peripheral and central mechanisms, and targeting TNFR1 may be beneficial for chronic itch treatment.
2019.03.08 journal club Read More »
