Allergy. 2024 Mar 13. doi: 10.1111/all.16086. 

RNA-sequencing of paired tape-strips and skin biopsies in atopic dermatitis reveals key differences

Blaine Fritz ¹, Anne-Sofie Halling ², Isabel Díaz-Pinés Cort ¹, Maria Oberländer Christensen ², Amalie Thorsti Møller Rønnstad ², Caroline Meyer Olesen ², Mette Hjorslev Knudgaard ³, Claus Zachariae ^3 4, Steffen Heegaard ⁴, Jacob P Thyssen ^2 4, Thomas Bjarnsholt ^1 5

• PMID: 38477552
• DOI: 10.1111/all.16086

Abstract

Background: Skin tape-strips and biopsies are widely used methods for investigating the skin in atopic dermatitis (AD). Biopsies are more commonly used but can cause scarring and pain, whereas tape-strips are noninvasive but sample less tissue. The study evaluated the performance of skin tape-strips and biopsies for studying AD.

Methods: Whole-transcriptome RNA-sequencing was performed on paired tape-strips and biopsies collected from lesional and non-lesional skin from AD patients (n = 7) and non-AD controls (n = 5). RNA yield, mapping efficiency, and differentially expressed genes (DEGs) for the two methods (tape-strip/biopsy) and presence of AD (AD/non-AD) were compared.

Results: Tape-strips demonstrated a lower RNA yield (22 vs. 4596 ng) and mapping efficiency to known genes (28% vs. 93%) than biopsies. Gene-expression profiles of paired tape-strips and biopsies demonstrated a medium correlation (R² = 0.431). Tape-strips and biopsies demonstrated systematic differences in measured expression levels of 6483 genes across both AD and non-AD samples. Tape-strips preferentially detected many itch (CCL3/CCL4/OSM) and immune-response (CXCL8/IL4/IL5/IL22) genes as well as markers of epidermal dendritic cells (CD1a/CD207), while certain cytokines (IL18/IL37), skin-barrier genes (KRT2/FLG2), and dermal fibroblasts markers (COL1A/COL3A) were preferentially detected by biopsies. Tape-strips identified more DEGs between AD and non-AD (3157 DEGs) then biopsies (44 DEGs). Tape-strips also detected higher levels of bacterial mRNA than biopsies.

Conclusions: This study concludes that tape-strips and biopsies each demonstrate respective advantages for measuring gene-expression changes in AD. Thus, the specific skin layers and genes of interest should be considered before selecting either method.

Keywords: RNA sequencing; atopic dermatitis; biopsies; inflammation; tape-strips.

© 2024 The Authors. Allergy published by European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.

20-HETE mediated TRPV1 activation drives allokinesis via MrgprA3+ neurons in chronic dermatitis

Guang Yu1,2*, Pei Liu1*, Xiaobao Huang3*, Mingxin Qi2, Xue Li2, Weimeng Feng1, Erxin Shang1, Yuan Zhou2, Changming Wang2, Yan Yang2, Chan Zhu2, Fang Wang3, Zongxiang Tang2, Jinao Duan1

1. Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, Jiangsu Key Laboratory for High Technology Research of TCM Formulae, Nanjing University of Chinese Medicine, Nanjing, China.
2. Key Laboratory for Chinese Medicine of Prevention and Treatment in Neurological Diseases, School of Medicine, Nanjing University of Chinese Medicine, Nanjing, China.
3. Department of Dermatology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.

* Guang Yu, Pei Liu and Xiaobao Huang are co-first authors.

Corresponding author: Guang Yu, E-mail: yuguang@njucm.edu.cn; Zongxiang Tang, E-mail: tangzxlab@njucm.edu.cn; Jinao Duan, E-mail: dja@njucm.edu.cn (J.D.).

© The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions.

Received: 2023.04.12; Accepted: 2024.01.26; Published: 2024.02.04

Abstract
Rationale: Noxious stimuli are often perceived as itchy in patients with chronic dermatitis (CD); however, itch and pain mechanisms of CD are not known.

Methods: TRPV1 involvement in CD was analyzed using a SADBE induced CD-like mouse model, and several loss- and gain-of-function mouse models. T rigeminal TRPV1 channel and Mrgpr A3+ neuron functions were analyzed by calcium imaging and whole-cell patch-clamp recordings. Lesional CD-like skin from mice were analyzed by unbiased metabolomic analysis. 20-HETE availability in human and mouse skin were determined by LC/MS and ELISA. And finally, HET0016, a selective 20-HETE synthase inhibitor, was used to evaluate if blocking skin TRPV1 activation alleviates CD-associated chronic itch or pain.

Results: While normally a pain inducing chemical, capsaicin induced both itch and pain in mice with CD condition. DREADD silencing of MrgprA3+ primary sensory neurons in these mice selectively decreased capsaicin induced scratching, but not pain-related wiping behavior. In the mice with CD condition, MrgprA3+ neurons showed elevated ERK phosphorylation. Further experiments showed that MrgprA3+ neurons from MrgprA3;Braf mice, which have constitutively active BRAF in MrgprA3+ neurons, were significantly more excitable and responded more strongly to capsaicin. Importantly, capsaicin induced both itch and pain in MrgprA3;Braf mice in an MrgprA3+ neuron dependent manner. Finally, the arachidonic acid metabolite 20-HETE, which can activate TRPV1, was significantly elevated in the lesional skin of mice and patients with CD. Treatment with the selective 20-HETE synthase inhibitor HET0016 alleviated itch in mice with CD condition.

Conclusion: Our results demonstrate that 20-HETE activates TRPV1 channels on sensitized MrgprA3+ neurons, and induces allokinesis in lesional CD skin. Blockade of 20-HETE synthesis or silencing of TRPV1-MrgprA3+ neuron signaling offers promising therapeutic strategies for alleviating CD-associated chronic itch.

Keywords: 20-HETE, TRPV1, allokinesis, MrgprA3+ neurons, chronic dermatitis

Vitexin inhibits pain and itch behavior via modulating TRPV4 activity in mice

Zhiqiang Qin ^a1, Lan Xiang ^a1, Siyu Zheng ^a1, Yuchen Zhao ^b, Yanyan Qin ^a, Lei Zhang ^a, Lanlan Zhou ^a

^aSchool of Medical Technology and Nursing, Shenzhen Polytechnic, Shenzhen 518055, China ^bDepartment of Mathematics, University of California, Los Angeles, CA 90095, USA Received 6 March 2023, Revised 27 June 2023, Accepted 28 June 2023, Available online 3 July 2023, Version of Record 3 July 2023.

https://doi.org/10.1016/j.biopha.2023.115101

Abstract
Itching and pain are distinct unpleasant sensations. The transient receptor potential cation channel subfamily V member 4 (TRPV4) pathway is regarded as a shared pathway that mediates pain and itching. Vitexin (Mujingsu, MJS), a C-glycosylflavonoid, is an effective analgesic. This study aimed to explore the antinociceptive and anti-pruritic effects of MJS and whether its effects are mediated via the TRPV4 pathway. Mice were treated with MJS (7.5 mg/kg) 0.5 h prior to the initiation of the pain or itch modeling process. The results showed that MJS suppressed pain-like behavior in hot plate, thermal infiltration, glacial acetic acid twisting, and formalin tests. Administration of MJS decreased the pruritus response induced by histamine, C48/80, chloroquine and BAM8-22 within 30 min. MJS reduced scratching bouts and lessened the wiping reaction of mice under TRPV4 activation by GSK101 (10 µg/5 μl). MJS inhibited scratching behavior in acetone–ether–water (AEW)-treated mice within 60 min. An H1 receptor antagonist—chlorpheniramine (CLP, 400 mg/kg)—and a TRPV4 antagonist—HC067047 (250 ng/kg), exhibited similar effects to those of MJS. Moreover, MJS ameliorated dry skin itch-associated cutaneous barrier disruption in mice. MJS did not inhibit the expression of TRPV4 in the dorsal root ganglion neurons at L2–L3 in AEW mice. These results indicate that the analgesic and anti-pruritic effects of MJS in acute and chronic pain and itching, as well as itching caused by TRPV4 activation, could be attributed to the TRPV4 pathway modulation.

IL-31–generating network in atopic dermatitis comprising macrophages, basophils, thymic stromal lymphopoietin, and periostin

Takashi Hashimoto, MD, PhD,a Hiroo Yokozeki, MD, PhD,b Hajime Karasuyama, MD, PhD,c and Takahiro Satoh, MD, PhDa Tokorozawa and Tokyo, Japan

From a the Department of Dermatology, National Defense Medical College, Tokorozawa, and b the Department of Dermatology, Graduate School of Medical and Dental Sciences, and c the Inflammation, Infection and Immunity Laboratory, Advanced Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo. This study was partially supported by Japan Society for the Promotion of Science (JSPS) KAKENHI Grant-in-Aid for Scientific Research (C) (grant numbers 17K16328, 19K08743, and 22K08395 to T.H. and 19K08805 and 22K08444 to T.S.). Disclosure of potential conflict of interest: The authors declare that they have no relevant conflicts of interest. Received for publication July 18, 2022; revised October 22, 2022; accepted for publication November 11, 2022. Available online November 19, 2022. Corresponding author: Takashi Hashimoto, MD, PhD, Department of Dermatology, National Defense Medical College, 3-2, Namiki, Tokorozawa, Saitama 359-8513, Japan. E-mail: hashderm@ndmc.ac.jp. The CrossMark symbol notifies online readers when updates have been made to the article such as errata or minor corrections 0091-6749/$36.00 2022 American Academy of Allergy, Asthma & Immunology https://doi.org/10.1016/j.jaci.2022.11.009

Background: IL-31 is a type 2 cytokine involved in the itch sensation in atopic dermatitis (AD). The cellular origins of IL-31 are generally considered to be TH2 cells. Macrophages have also been implicated as cellular sources of IL-31. Objective: We sought to determine the expression of IL-31 by macrophages and to elucidate the productive mechanisms and contributions to itch in AD skin lesions. Methods: Expression of IL-31 by macrophages, expressions of thymic stromal lymphopoietin (TSLP) and periostin, and presence of infiltrating basophils in human AD lesions were examined through immunofluorescent staining, and correlations were assessed. Furthermore, mechanisms of inducing IL-31– expressing macrophages were analyzed in an MC903-induced murine model for AD in vivo and in mouse peritoneal macrophages ex vivo.

Results: A significant population of IL-311 cells in human AD lesions was that of CD681 cells expressing CD163, an M2 macrophage marker. The number of IL-311/CD681 cells correlated with epidermal TSLP, dermal periostin, and the number of dermal-infiltrating basophils. In the MC903-induced murine AD model, significant scratching behaviors with enhanced expressions of TSLP and periostin were observed, accompanied by massive infiltration of basophils and IL-311/ MOMA-21/Arg-11 cells. Blockade of IL-31 signaling with anti– IL-31RA antibody or direct depletion of macrophages by clodronate resulted in attenuation of scratching behaviors. Toeffectively reduce lesional IL-311 macrophages and itch, basophil depletion was essential in combination with TSLP- and periostin-signal blocking. Murine peritoneal macrophages produced IL-31 when stimulated with TSLP, periostin, and basophils.

Conclusions: A network comprising IL-31–expressing macrophages, TSLP, periostin, and basophils plays a significant role in AD itch. (J Allergy Clin Immunol 2023;151:737-46.)

Key words: Atopic dermatitis, basophil, IL-31, itch, macrophage, periostin, thymic stromal lymphopoietin

Propionate alleviates itch in murine models of atopic dermatitis by modulating sensory TRP channels of dorsal root ganglion

Yao Xu, Zhuoqiong Qiu, Chaoying Gu, Su Yu, Shangshang Wang, Changlin Li, Xu Yao, Wei Li

First published: 02 January 2024

https://doi.org/10.1111/all.1599

Pain. 2024 Feb 28.  doi: 10.1097/j.pain.0000000000003189.

ATF4 inhibits TRPV4 function and controls itch perception in rodents and nonhuman primate

Man-Xiu Xie ¹, Jun-Hua Rao ², Xiao-Yu Tian ³, Jin-Kun Liu ^3 4, Xiao Li ⁵, Zi-Yi Chen ⁶, Yan Cao ⁵, An-Nan Chen ⁶, Hai-Hua Shu ⁷, Xiao-Long Zhang 

• PMID: 38422489
• DOI: 10.1097/j.pain.0000000000003189

Abstract

Acute and chronic itch are prevalent and incapacitating, yet the neural mechanisms underlying both acute and chronic itch are just starting to be unraveled. Activated transcription factor 4 (ATF4) belongs to the ATF/CREB transcription factor family and primarily participates in the regulation of gene transcription. Our previous study has demonstrated that ATF4 is expressed in sensory neurons. Nevertheless, the role of ATF4 in itch sensation remains poorly understood. Here, we demonstrate that ATF4 plays a significant role in regulating itch sensation. The absence of ATF4 in dorsal root ganglion (DRG) neurons enhances the itch sensitivity of mice. Overexpression of ATF4 in sensory neurons significantly alleviates the acute and chronic pruritus in mice. Furthermore, ATF4 interacts with the transient receptor potential cation channel subfamily V member 4 (TRPV4) and inhibits its function without altering the expression or membrane trafficking of TRPV4 in sensory neurons. In addition, interference with ATF4 increases the itch sensitivity in nonhuman primates and enhances TRPV4 currents in nonhuman primates DRG neurons; ATF4 and TRPV4 also co-expresses in human sensory neurons. Our data demonstrate that ATF4 controls pruritus by regulating TRPV4 signaling through a nontranscriptional mechanism and identifies a potential new strategy for the treatment of pathological pruritus.

Discovery of a Small Molecule Activator of Slack (Kcnt1) Potassium Channels That Significantly Reduces Scratching in Mouse Models of Histamine-Independent and Chronic Itch

Annika Balzulat, W. Felix Zhu, Cathrin Flauaus, Victor Hernandez-Olmos, Jan Heering, Sunesh Sethumadhavan, Mariam Dubiel, Annika Frank, Amelie Menge,
Maureen Hebchen, Katharina Metzner, Ruirui Lu, Robert Lukowski, Peter Ruth,
Stefan Knapp, Susanne Müller, Dieter Steinhilber, Inga Hänelt, Holger Stark, Ewgenij Proschak,* and Achim Schmidtko*

ABSTRACT
Various disorders are accompanied by histamine-independent itching, which is often resistant to the currently available therapies. Here, it is reported that the pharmacological activation of Slack (Kcnt1, KNa1.1), a potassium channel highly expressed in itch-sensitive sensory neurons, has therapeutic potential for the treatment of itching. Based on the Slack-activating antipsychotic drug, loxapine, a series of new derivatives with improved pharmacodynamic and pharmacokinetic profiles is designed that enables to validate Slack as a pharmacological target in vivo. One of these new Slack activators, compound 6, exhibits negligible dopamine D2 and D3 receptor binding, unlike loxapine. Notably, compound 6 displays potent on-target antipruritic activity in multiple mouse models of acute histamine-independent and chronic itch without motor side effects. These properties make compound 6 a lead molecule for the development of new antipruritic therapies targeting Slack.

Sphingosylphosphorylcholine down-regulates filaggrin gene transcription through NOX5-based NADPH oxidase and cyclooxygenase-2 in human keratinocytes

Abstract

Sphingosylphosphorylcholine (SPC) mediates various inflammatory and behavioral responses in atopic dermatitis. Recent studies have shown that dysfunction of the epidermal permeability barrier itself plays a primary role in the etiology of atopic dermatitis. However, the effects of SPC on major proteins essential to the development of the epidermal permeability barrier such as filaggrin, loricrin, involucrin, keratin 1, keratin 10 and small proline-rich proteins are still unclear. In this study, we demonstrated that SPC significantly reduces filaggrin gene transcription, implying that SPC plays a pivotal role in impairment of the epidermal permeability barrier in atopic dermatitis lesional skin. In cultured normal human keratinocytes (NHKs), SPC increases the intracellular level of reactive oxygen species (ROS) and upregulates NADPH oxidase 5 (NOX5) gene transcription. SPC also stimulates prostaglandin (PG) E2 production by increasing cyclooxygenase (COX)-2 expression in NHK. The effects of the prostanoid EP receptor agonists, limaprost, butaprost, and sulprostone on filaggrin gene expression in NHK suggest that the prostanoid EP2 receptor plays a significant role in the PGE2-mediated filaggrin down-regulation. In contrast, limaprost and butaprost do not affect NOX5 expression in NHK, implying that the NOX5-regulated ROS pathway stimulated by SPC may be upstream of the COX-2 pathway. We propose that the increase in SPC levels further aggravates dermatological symptoms of atopic dermatitis through SPCinduced down-regulation of filaggrin in NHK.

Abstract

Background: Itch is a common symptom that can greatly diminish quality of life. Histamine is a potent endogenous pruritogen, and while antihistamines are often the first-line treatment for itch, in conditions like chronic spontaneous urticaria (CSU), many patients remain symptomatic while receiving maximal doses. Mechanisms that drive resistance to antihistamines are poorly defined.
Objectives: Signaling of the alarmin cytokine IL-33 in sensory neurons is postulated to drive chronic itch by inducing neuronal sensitization to pruritogens. Thus, we sought to determine if IL-33 can augment histamine-induced (histaminergic) itch.
Methods: Itch behavior was assessed in response to histamine after IL-33 or saline administration. Various stimuli and conditional and global knockout mice were utilized to dissect cellular mechanisms. Multiple existing transcriptomic data sets were evaluated, including single-cell RNA sequencing of human and mouse skin, microarrays of isolated mouse mast cells at steady state and after stimulation with IL-33, and microarrays of skin biopsy samples from subjects with CSU and healthy controls.
Results: IL-33 amplifies histaminergic itch independent of IL-33 signaling in sensory neurons. Mast cells are the top expressors of the IL-33 receptor in both human and mouse skin. When stimulated by IL-33, mouse mast cells significantly increase IL-13 levels. Enhancement of histaminergic itch by IL-33 relies on a mast cell– and IL-13-dependent mechanism. IL-33 receptor expression is increased in lesional skin of subjects with CSU compared to healthy controls.

Presenter: Ju Hee Ryu