Involvement of leukotriene B4 in spontaneous itch-related behaviour in NC mice with atopic dermatitis-like skin lesions

Tsugunobu Andoh, Satomi Haza, Ayumi Saito and Yasushi Kuraishi

Abstract

To elucidate the mechanisms of severe itch in atopic dermatitis, we investigated the role of leukotriene B4, a potent itch mediator, in spontaneous itch-related behaviour in NC mice with atopic dermatitis-like skin lesions. Topical application of the BLT leukotriene B4 receptor antagonist ONO-4057 inhibited
spontaneous itch-related behaviour. The concentration of leukotriene B4 was significantly increased in the lesional skin. The expression levels of 5-lipoxygenase were also elevated in the lesional skin, yet present throughout the epidermis of both healthy and lesional skin. These results suggest a role for leukotriene B4 in chronic dermatitis-related itch. Sphingosylphosphorylcholine (SPC) was increased in the epidermis of the lesional skin. Moreover, intradermal injection of SPC elicited itch-related behaviours in healthy mice. Because SPC induces itch-related responses through the production of leukotriene B4 in keratinocytes (J Invest Dermatol, 129, 2009, 2854), these results suggest that an increase in SPC induces
leukotriene B4-mediated itching in chronic dermatitis. BLT1 receptor and 5-lipoxygenase in the skin may be effective pharmacological targets for the treatment of itch in atopic dermatitis.

Key words: atopic dermatitis – itch – leukotriene B4 – scratching – sphingosylphosphorylcholine

The G protein-coupled estrogen receptor of the trigeminal ganglion regulates acute and chronic itch in mice

Jun Li1,2,3 | Po Gao2,3 | Siyu Zhang2,3,4 | Xiaoqi Lin2,3 | Junhui Chen2,3 | Song Zhang2,3 | Yingfu Jiao2,3 | Weifeng Yu2,3 | Xiaoqiong Xia1 | Liqun Yang2,3

Abstract
Aims: Itch is an unpleasant sensation that severely impacts the patient’s quality of life. Recent studies revealed that the G protein-coupled estrogen receptor (GPER) may play a crucial role in the regulation of pain and itch perception. However, the contribution of the GPER in primary sensory neurons to the regulation of itch perception remains elusive. This study aimed to investigate whether and how the GPER participates in the regulation of itch perception in the trigeminal ganglion (TG).
Methods and Results: Immunofluorescence staining results showed that GPERpositive (GPER+) neurons of the TG were activated in both acute and chronic itch. Behavioral data indicated that the chemogenetic activation of GPER+ neurons of the TG of Gper-Cre mice abrogated scratching behaviors evoked by acute and chronic itch. Conversely, the chemogenetic inhibition of GPER+ neurons resulted in increased itch
responses. Furthermore, the GPER expression and function were both upregulated in the TG of the dry skin-induced chronic itch mouse model. Pharmacological inhibition of GPER (or Gper deficiency) markedly increased acute and chronic itch-related scratching behaviors in mouse. Calcium imaging assays further revealed that Gper deficiency in TG neurons led to a marked increase in the calcium responses evoked by agonists of the transient receptor potential ankyrin A1 (TRPA1) and transient receptor potential vanilloid V1 (TRPV1).
Conclusion: Our findings demonstrated that the GPER of TG neurons is involved in the regulation of acute and chronic itch perception, by modulating the function of TRPA1 and TRPV1. This study provides new insights into peripheral itch sensory signal processing mechanisms and offers new targets for future clinical antipruritic therapy.

Presenter: Ji Eun Cha

Involucrin Modulates Vitamin D Receptor Activity in the Epidermis

Alina D. Schmidt1,2,3, Charlene Miciano1,2,3, Qi Zheng4, Mary Elizabeth Mathyer1,2,3, Elizabeth A. Grice4 and Cristina de Guzman Strong1,2,3,5,6,7

Abstract

Terminally differentiated keratinocytes are critical for epidermal function and are surrounded by involucrin (IVL). Increased IVL expression is associated with a near-selective sweep in European populations compared with those in Africa. This positive selection for increased IVL in the epidermis identifies human adaptation outside of Africa. The functional significance is unclear. We hypothesize that IVL modulates the environmentally sensitive vitamin D receptor (VDR) in the epidermis. We investigated VDR activity in Ivl‒/‒ and wildtype mice using vitamin D agonist (MC903) treatment and comprehensively determined the inflammatory response using single-cell RNA sequencing and associated skin microbiome changes using 16S bacterial phylotyping. VDR activity and target gene expression were reduced in Ivl‒/‒ mouse skin, with decreased MC903-mediated skin inflammation and significant reductions in CD4þ T cells, basophils, macrophages, monocytes, and type II basal keratinocytes and an increase in suprabasal keratinocytes. Coinciding with the dampened MC903-mediated inflammation, the skin microbiota of Ivl‒/‒ mice was more stable than that of the wild-type mice, which exhibited an MC903-responsive increase in Bacteroidetes and a decrease in Firmicutes. Together, our studies in Ivl‒/‒ mice identify a functional role for IVL to positively impact VDR activity and suggest an emerging IVL/VDR paradigm for adaptation in the human epidermis.

Presenter: Ju hee Ryu

Eun Ju Kim ^abc, Dong Hun Lee ^abc, Yeon Kyung Kim ^abc, Min-Kyoung Kim ^abc, Jung Yun Kim ^abc, Min Jung Lee ^abc, Won Woo Choi ^abc, Hee Chul Eun ^abc, Jin Ho Chung ^abc

Summary

Background

Sensitive skin represents hyperactive sensory symptoms showing exaggerated reactions in response to internal stimulants or external irritants. Although sensitive skin is a very common condition affecting an estimated 50% of the population, its pathophysiology remains largely elusive, particularly with regard to its metabolic aspects.

Objective

The objective of our study was to investigate the pathogenesis of sensitive skin.

Methods

We recruited healthy participants with ‘sensitive’ or ‘non-sensitive’ skin based on standardized questionnaires and 10% lactic acid stinging test, and obtained skin samples for microarray analysis and subsequent experiments.

Results

Microarray transcriptome profiling revealed that genes involved in muscle contraction, carbohydrate and lipid metabolism, and ion transport and balance were significantly decreased in sensitive skin. These altered genes could account for the abnormal muscle contraction, decreased ATP amount in sensitive skin. In addition, pain-related transcripts such as TRPV1, ASIC3 and CGRP were significantly up-regulated in sensitive skin, compared with non-sensitive skin.

Conclusions

Our findings suggest that sensitive skin is closely associated with the dysfunction of muscle contraction and metabolic homeostasis.

The Delta-Opioid Receptor Bidirectionally Modulates Itch

Kelly M Smith, Eileen Nguyen, Sarah E Ross

Abstract

Opioid signaling has been shown to be critically important in the neuromodulation of sensory circuits in the superficial spinal cord. Agonists of the mu-opioid receptor (MOR) elicit itch, whereas agonists of the kappa-opioid receptor (KOR) have been shown to inhibit itch. Despite the clear roles of MOR and KOR for the modulation itch, whether the delta-opioid receptor (DOR) is involved in the regulation of itch remained unknown. Here, we show that intrathecal administration of DOR agonists suppresses chemical itch and that intrathecal application of DOR antagonists is sufficient to evoke itch. We identify that spinal enkephalin neurons co-express neuropeptide Y (NPY), a peptide previously implicated in the inhibition of itch. In the spinal cord, DOR overlapped with both the NPY receptor (NPY1R) and KOR, suggesting that DOR neurons represent a site for convergent itch information in the dorsal horn. Lastly, we found that neurons co-expressing DOR and KOR showed significant Fos induction following pruritogen-evoked itch. These results uncover a role for DOR in the modulation of itch in the superficial dorsal horn. PERSPECTIVE: This article reveals the role of the delta-opioid receptor in itch. Intrathecal administration of delta agonists suppresses itch whereas the administration of delta antagonists is sufficient to induce itch. These studies highlight the importance of delta-opioid signaling for the modulation of itch behaviors, which may represent new targets for the management of itch disorders.

Keywords: DOR; Itch; delta opioid; pruritus; spinal cord.

Sophorolipid inhibits histamine‐induced itch by decreasing PLC/IP3R signaling pathway activation and modulating TRPV1 activity

Rui-Qi Xu ¹, Ling Ma ², Timson Chen ³, Wei-Xiong Zhang ³, Kuan Chang ⁴, Jing Wang ⁵

• ¹Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, 214122, China.
• ²Adolph Innovation Laboratory, Guangzhou Degu Personal Care Products Co., Ltd., Guangzhou, 510000, China. maling@adolph.cn.
• ³Adolph Innovation Laboratory, Guangzhou Degu Personal Care Products Co., Ltd., Guangzhou, 510000, China.
• ⁴Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, 214122, China. changkuan@jiangnan.edu.cn.
• ⁵Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, 214122, China. jingwang@jiangnan.edu.cn.

Biosurfactants are attracting much interest due to their potential application as therapeutic agents in the medical and cosmetic field. Previous studies have demonstrated that biosurfactant such as sophorolipid (SL) exhibits immunomodulatory effects. In this article, we found the potential of sophorolipid for inhibiting histamine‐induced itch and preliminarily explored its molecular basis. First, behavioral tests indicated that SL can remit the histamine‐induced scratching behaviors of mice. Second, SL can suppress the the calcium influx induced by histamine, HTMT and VUF8430 in HaCaT cells. RT‐PCR analysis showed that the histamine‐induced upregulation of mRNA levels of phospholipase Cγ1, 1,4,5‐trisphosphate receptor (IP3R), and protein kinase Cα can be inhibted by SL, suggesting that SL may impede the PLC/IP3R signaling pathway activated by histamine. In further tests, the capsaicin‐induced calcium influx can also be inhibited by SL. The and molecular docking analysis indicated that SL acts as an inhibitor of transient receptor potential vanilloid‐1 (TRPV1) activation to decrease calcium influx against stimuli. In summary, these results revealed that SL may inhibit histamine‐induced itch by decreasing PLC/IP3R signaling pathway activation and modulating TRPV1 activity. This paper indicates that SL can be a useful treatment for histamine‐dependent itch.immunofluorescence

Activation of the Melastatin-Related Cation Channel TRPM3 by D-erythro-Sphingosine

Mol Pharmacol. 2005 Mar;67(3):798-805. doi: 10.1124/mol.104.006734. Epub 2004 Nov 18.

Christian Grimm, Robert Kraft, Gunter Schultz, and Christian Harteneck

Abstract

TRPM3, a member of the melastatin-like transient receptor potential channel subfamily (TRPM), is predominantly expressed in human kidney and brain. TRPM3 mediates spontaneous Ca2+ entry and nonselective cation currents in transiently transfected human embryonic kidney 293 cells. Using measurements with the Ca2+-sensitive fluorescent dye fura-2 and the whole-cell patch-clamp technique, we found that D-erythro-sphingosine, a metabolite arising during the de novo synthesis of cellular sphingolipids, activated TRPM3. Other transient receptor potential (TRP) channels tested [classic or canonical TRP (TRPC3, TRPC4, TRPC5), vanilloid-like TRP(TRPV4, TRPV5, TRPV6), and melastatin-like TRP (TRPM2)] did not significantly respond to application of sphingosine. Sphingosine-induced TRPM3 activation was not mediated by inhibition of protein kinase C, depletion of intracellular Ca2+ stores, and intracellular conversion of sphingosine to sphingosine-1-phosphate. Although sphingosine-1-phosphate and ceramides had no effect, two structural analogs of sphingosine, dihydro-D-erythro-sphingosine and N,N-dimethyl-D-erythro-sphingosine, also activated TRPM3. Sphingolipids, including sphingosine, are known to have inhibitory effects on a variety of ion channels. Thus, TRPM3 is the first ion channel activated by sphingolipids.

Cell Immunol 2021 Oct;368:104422. doi: 10.1016/j.cellimm.2021.104422. Epub 2021 Aug 8.

Meesum Syed ¹, Ananth K Kammala ¹, Brianna Callahan ¹, Carole A Oskeritzian ², Hariharan Subramanian ³Affiliations expand

• PMID: 34399172
• PMCID: PMC8428143
• DOI: 10.1016/j.cellimm.2021.104422

Abstract

MAS related G-protein coupled receptor X2 (MRGPRX2) is a G-protein coupled receptor (GPCR) expressed in human mast cells that has been implicated to play an important role in causing pseudo-allergic reactions as well as exacerbating inflammation during asthma and other allergic diseases. Lactic acid, a byproduct of glucose metabolism, is abundantly present in inflamed tissues and has been shown to regulate functions of several immune cells. Because the endogenous ligands for MRGPRX2 (substance P and LL-37) are elevated during pathologic conditions, such as cancer and asthma, and given that lactic acid levels are also enhanced in these patients, we explored the role of lactic acid in regulating mast cells response via MRGPRX2 and MrgprB2, the mouse orthologue of the human receptor. We found that lactic acid suppressed both the early (Ca²⁺ mobilization and degranulation) and late (chemokine/cytokine release) phases of mast cell activation; this data was confirmed in LAD2, human skin and mouse peritoneal mast cells. In LAD2 cells, the reduction in degranulation and chemokine/cytokine production mediated by lactic acid was dependent on pH. In agreement with our in vitro studies, lactic acid also reduced passive systemic anaphylaxis to compound 48/80 (a known MRGPRX2/MrgprB2 ligand) and skin inflammation in a mouse model of rosacea that is dependent on MrgprB2 expression on skin mast cells. Our data thus suggest that lactic acid may serve to inhibit mast cell-mediated inflammation during asthma and reduce immune response during cancer by affecting mast cell activation through MRGPRX2.

Keywords: Lactic acid; MAS-related G-protein coupled receptor-X2 (MRGPRX2); Mast cells; MrgprB2; Pseudo-allergic reactions.

Copyright © 2021 Elsevier Inc. All rights reserved.

MrgprA3-expressing pruriceptors drive pruritogen-induced alloknesis through mechanosensitive Piezo2 channel

Ping Lu ¹, Yonghui Zhao ², Zili Xie ², Huan Zhou ³, Xinzhong Dong ⁴, Gregory F Wu ⁵, Brian S Kim ⁶, Jing Feng ⁷, Hongzhen Hu ⁸

Abstract

Although touch and itch are coded by distinct neuronal populations, light touch also provokes itch in the presence of exogenous pruritogens, resulting in a phenomenon called alloknesis. However, the cellular and molecular mechanisms underlying the initiation of pruritogen-induced mechanical itch sensitization are poorly understood. Here, we show that intradermal injections of histamine or chloroquine (CQ) provoke alloknesis through activation of TRPV1- and MrgprA3-expressing prurioceptors, and functional ablation of these neurons reverses pruritogen-induced alloknesis. Moreover, genetic ablation of mechanosensitive Piezo2 channel function from MrgprA3-expressing prurioceptors also dampens pruritogen-induced alloknesis. Mechanistically, histamine and CQ sensitize Piezo2 channel function, at least in part, through activation of the phospholipase C (PLC) and protein kinase C-δ (PKCδ) signaling. Collectively, our data find a TRPV1⁺/MrgprA3⁺ prurioceptor-Piezo2 signaling axis in the initiation of pruritogen-induced mechanical itch sensitization in the skin.

Keywords: CP: Neuroscience; PKCδ; PLC; Piezo2; alloknesis; pruriceptor; pruritogens.

SpiCee: A Genetic Tool for Subcellular and Cell-Specific Calcium Manipulation

Oriol Ros,1,6 Sarah Baudet,1,6 Yvrick Zagar,1 Karine Loulier,1 Fiona Roche,1 Sandrine Couvet,1 Alain Aghaie,2
Melody Atkins,3 Alice Louail,1 Christine Petit,2,4 Christine Metin,3 Yves Mechulam,5 and Xavier Nicol1,7,*

Abstract

Calcium is a second messenger crucial to a myriad of cellular processes ranging from regulation of metabolism and cell survival to vesicle release and motility. Current strategies to directly manipulate endogenous calcium signals lack cellular and subcellular specificity. We introduce SpiCee, a versatile and genetically encoded chelator combining low- and high-affinity sites for calcium. This scavenger enables altering endogenous calcium signaling and functions in single cells in vitro and in vivo with biochemically controlled subcellular resolution. SpiCee paves the way to investigate local calcium signaling in vivo and directly manipulate
this second messenger for therapeutic use.

Presenter: Ju hee Ryu