TMEM120A/TACAN inhibits mechanically activated Piezo2 channels

John Smith Del Rosario*, Matthew Gabrielle*, Yevgen Yudin and Tibor Rohacs# 

Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, Newark, NJ 08540 

ABSTRACT

Mechanically activated Piezo2 channels are key mediators of light touch and proprioception in mice and humans. Relatively little is known about what other proteins regulate Piezo2 activity in a cellular context. TACAN (TMEM120A) was proposed to act as a high threshold mechanically activated ion channel in nociceptive dorsal root ganglion (DRG) neurons. Here we find that TACAN co-expression robustly reduced mechanically activated Piezo2 currents, but did not inhibit mechanically activated Piezo1 and TREK1 currents. TACAN co-expression did not affect cell surface expression of either Piezo1 or Piezo2 and did not have major effects on the cortical actin or tubulin cytoskeleton. TACAN expression alone did not result in the appearance of mechanically activated currents above background. In addition, TACAN and Piezo2 expression in DRG neurons overlapped, and siRNA mediated knockdown of TACAN did not decrease the proportion of slowly adapting mechanically activated currents, but resulted in an increased proportion of rapidly adapting currents. Our data do not support TACAN being a mechanically activated ion channel, and identify it as a negative modulator of Piezo2 channel activity.

Scutellarein attenuates atopic dermatitis by selectively inhibiting transient receptor potential vanilloid 3 channels

Yujing Wang1 | Liaoxi Tan1 Shan Jiang1 | Younan Ren1 Khalid N. M. Abdelazeem4 | Zhengyu Cao1

| Kejun Jiao1 | Chu Xue1 | Qinglian Tang1 | | Hao Chen2 | Tarek Mohamed Abd El-Aziz3 |

Ye Yu5 | Fang Zhao1 | Michael X. Zhu6 |
1State Key Laboratory of Natural Medicines and Department of TCM Pharmacology, School of Traditional Chinese Pharmacy, China Pharmaceutical University,

Nanjing, China
2Institute of Dermatology, Chinese Academy of Medical Sciences & Peking Union Medical College, Nanjing, China
3Zoology Department, Faculty of Science, Minia University, El-Minia, Egypt
4Radiation Biology Research Department, National Centre for Radiation Research and Technology, Atomic Energy Authority, Cairo, Egypt
5Department of Basic Medicine, School of Basic Medicine and Clinic Pharmacy, China Pharmaceutical University, Nanjing, China
6Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA

Background and Purpose: Atopic dermatitis (AD) is one of the most common chronic inflammatory cutaneous diseases with unmet clinical needs. As a common ingredient found in several medicinal herbs with efficacy on cutaneous inflammatory diseases, Scutellarein (Scu) has been shown to possess anti-inflammatory and anti-proliferative activities. We aimed to evaluate the therapeutic efficacy of Scu against AD and its underlying molecular mechanism.

Experimental Approach: Efficacy of Scu on AD was evaluated in 2,4-dinitrofluorobenzene (DNFB) and carvacrol-induced dermatitis mouse models. Cytokine mRNA and serum IgE levels were examined using qPCR and ELISA, respec- tively. Voltage clamp recordings were used to measure currents mediated by tran- sient receptor potential (TRP) channels. In silico docking, site-direct mutagenesis, and covalent modification were used to explore the binding pocket of Scu on TRPV3.

Key Results: Subcutaneous administration of Scu efficaciously suppresses DNFB and carvacrol-induced pruritus, epidermal hyperplasia and skin inflammation in wild type mice but has no additional benefit in Trpv3 knockout mice in the carvacrol model. Scu is a potent and selective TRPV3 channel allosteric negative modulator with an appar- ent affinity of 1.18 μM. Molecular docking coupled with site-direct mutagenesis and covalent modification of incorporated cysteine residues demonstrate that Scu targets the cavity formed between the pore helix and transmembrane helix S6. Moreover, Scu attenuates endogenous TRPV3 activity in human keratinocytes and inhibits carvacrol-induced proliferative and proinflammatory responses.

Conclusion and Implications: Collectively, these data demonstrate that Scu amelio- rates carvacrol-induced skin inflammation by directly inhibiting TRPV3, and TRPV3 represents a viable therapeutic target for AD treatment.

KEYWORDS

atopic dermatitis, keratinocytes, scutellarein, TRPV3

GPR15L is an epithelial inflammation-derived pruritogen

Pang-Yen Tseng and Mark A. Hoon*

Molecular Genetics Section, National Institute of Dental and Craniofacial Research/ NIH, 35 Convent Drive, Bethesda, MD 20892, USA.
*Corresponding author. Email: mark.hoon@nih.gov

Itch is an unpleasant sensation that often accompanies chronic dermatological conditions. Although many of the itch receptors and the neural pathways underlying this sensation are known, the identity of endogenous ligands is still not fully appreciated. Using an unbiased bioinformatic approach, we identified GPR15L as a candidate pruritogen whose expression is robustly up-regulated in psoriasis and atopic dermatitis. Although GPR15L was previously shown to be a cognate ligand of the receptor GPR15, expressed in dermal T cells, here we show that it also contributes to pruritogenesis by activating Mas-related G protein–coupled receptors (MRGPRs). GPR15L can selectively stimulate mouse dorsal root ganglion neurons that express Mrgpra3 and evokes intense itch re- sponses. GPR15L causes mast cell degranulation through stimulation of MRGPRX2 and Mrgprb2. Genetic dis- ruption of GPR15L expression attenuates scratch responses in a mouse model of psoriasis. Our study reveals unrecognized features of GRP15L, showing that it is a potent itch-inducing agent.

The Role of Transient Receptor Potential A1 and G Protein-Coupled Receptor 39 in Zinc-Mediated Acute and Chronic Itch in Mice

Yue Hu^1†, Qing-Yue Fu^1†, Dan-Ni Fu^1†, Xue-Long Wang^2†, Zhi-Hong Wang¹, Jiang-Tao Zhang³, Wen-Jing Xu³, Guo-Kun Zhou³, Li-Hua Chen^4* and Tong Liu^3,5,6*

• ¹Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou, China
• ²Department of Thoracic Surgery, Capital Medical University Electric Power Teaching Hospital Beijing, Beijing, China
• ³Institute of Pain Medicine and Special Environmental Medicine, Nantong University, Nantong, China
• ⁴Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, China
• ⁵College of Life Sciences, Yanan University, Yan’an, China
• ⁶Suzhou Key Laboratory of Intelligent Medicine and Equipment, Soochow University, Suzhou, China

Itching is a common symptom of many skin or systemic diseases and has a negative impact on the quality of life. Zinc, one of the most important trace elements in an organism, plays an important role in the regulation of pain. Whether and how zinc regulates itching is largely unclear. Herein, we explored the role of Zn²⁺ in the regulation of acute and chronic itch in mice. It is found that intradermal injection (i.d.) of Zn²⁺ dose-dependently induced acute itch and transient receptor potential A1 (TRPA1) participated in Zn²⁺-induced acute itch in mice. Moreover, the pharmacological analysis showed the involvement of histamine, mast cells, opioid receptors, and capsaicin-sensitive C-fibers in Zn²⁺-induced acute itch in mice. Systemic administration of Zn²⁺ chelators, such as N,N,N′,N′-Tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), pyrithione, and clioquinol were able to attenuate both acute itch and dry skin-induced chronic itch in mice. Quantitative polymerase chain reaction (Q-PCR) analysis showed that the messenger RNA (mRNA) expression levels of zinc transporters (ZIPs and ZnTs) significantly changed in the dorsal root ganglia (DRG) under dry skin-induced chronic itch condition in mice. Activation of extracellular signal-regulated kinase (ERK) pathway was induced in the DRG and skin by the administration of zinc or under dry skin condition, which was inhibited by systemic administration of Zn²⁺ chelators. Finally, we found that the expression of GPR39 (a zinc-sensing GPCR) was significantly upregulated in the dry skin mice model and involved in the pathogenesis of chronic itch. Together, these results indicated that the TRPA1/GPR39/ERK axis mediated the zinc-induced itch and, thus, targeting zinc signaling may be a promising strategy for anti-itch therapy.

Keywords: GPR39; Itch; TRPA1; Zn2+; p-ERK.

Sensory neuron expressed TRPC3 mediates acute and chronic itch.

Yan Liu , Yutong Liu , Nathachit Limjunyawong , Claire Narang , Hanna Jamaldeen, Shimeng Yu , Shivanie Patiram , Hong Nie , Michael J. Caterina , Xinzhong Dong , Lintao Qu

Abstract

Chronic pruritus is a prominent symptom of allergic contact dermatitis(ACD) and represent a huge unmet health problem. However, its underlying cellular and molecular mechanisms remain largely unexplored. TRPC3 is highly expressed in primary sensory neurons and has been implicated in peripheral sensitization induced by proinflammatory mediators. Yet, the role of TRPC3 in acute and chronic itch is still not well defined. Here, we show that, among mouse trigeminal ganglion (TG) neurons, Trpc3 mRNA is predominantly expressed in nonpeptidergic small diameter TG neurons of mice. Moreover, Trpc3 mRNA signal was present in the majority of presumptively itch sensing neurons. TRPC3 agonism induced TG neuronal activation and acute nonhistaminergic itch- and pain-like behaviors in naïve mice. In addition, genetic deletion of Trpc3 attenuated acute itch evoked by certain common nonhistaminergic pruritogens, including endothelin-1 and SLIGRL-NH2. In a murine model of contact hypersensitivity (CHS), Trpc3 mRNA expression level and function were upregulated in the TG following CHS. Pharmacological inhibition and global knockout of Trpc3 significantly alleviated spontaneous scratching behaviors without affecting concurrent cutaneous inflammation in the CHS model. Furthermore, conditional deletion of Trpc3 in primary sensory neurons but not in keratinocytes produced similar antipruritic effects in this model. These findings suggest that TRPC3 expressed in primary sensory neurons may contribute to acute and chronic itch via a histamine independent mechanism and that targeting neuronal TRPC3 might benefit the treatment of chronic itch associated with ACD and other inflammatory skin disorders.

Keywords: TRPC3, itch, pain, primary sensory neurons, dermatitis

Mast cells instruct keratinocytes to produce thymic stromal lymphopoietin: Relevance of the tryptase/protease-activated receptor 2 axis

Davender Redhu, PhD,a Kristin Franke, PhD,a Marina Aparicio-Soto, PhD,a Vandana Kumari, PhD,a Kristijan Pazur, PhD,a Anja Illerhaus, PhD,b Karin Hartmann, MD,c,d Margitta Worm, MD,a and Magda Babina, PhDa Berlin and Cologne, Germany; and Basel, Switzerland

Background: Thymic stromal lymphopoietin (TSLP) promotes TH2 inflammation and is deeply intertwined with inflammatory dermatoses like atopic dermatitis. The mechanisms regulating TSLP are poorly defined.

Objective: We investigated whether and by what mechanisms mast cells (MCs) foster TSLP responses in the cutaneous environment.
Methods: Ex vivo and in vivo skin MC degranulation was induced by compound 48/80 in wild-type protease-activated receptor 2 (PAR-2)- and MC-deficient mice in the presence or absence of neutralizing antibodies, antagonists, or exogenous mouse MC protease 6 (mMCP6). Primary human keratinocytes and murine skin explants were stimulated with lysates/supernatants of human skin MCs, purified tryptase, or MC lysate diminished of tryptase. Chymase and histamine were also used. TSLP was quantified by ELISA, real-time quantitative PCR, and immunofluorescence staining.
Results: Mas-related G protein–coupled receptor X2 (Mrgprb2) activation elicited TSLP in intact skin, mainly in the epidermis. Responses were strictly MC dependent and relied on PAR-2. Complementarily, TSLP was elicited by tryptase in murine skin explants. Exogenous mMCP6 could fully restore responsiveness in MC-deficient murine skin explants. Conversely, PAR-2 knockout mice were unresponsive to mMCP6 while displaying increased responsiveness to other inflammatory pathways, such as IL-1a. Indeed, IL-1a acted in concert with tryptase. In primary human keratinocytes, MC-elicited TSLP generation was likewise abolished by tryptase inhibition or elimination. Chymase and histamine did not affect TSLP production, but histamine triggered IL-6, IL- 8, and stem cell factor.
Conclusion: MCs communicate with kerationocytes more broadly than hitherto suspected. The tryptase/PAR-2 axis is a crucial component of this cross talk, underlying MC-dependent stimulation of TSLP in neighboring kerationocytes. Interference specifically with MC tryptase may offer a treatment option for disorders initiated or perpetuated by aberrant TSLP, such as atopic dermatitis. (J Allergy Clin Immunol 2022;nnn:nnn-nnn.)

Key words: Atopic dermatitis, interleukin 1, keratinocytes, mast cells, PAR-2, TSLP, tryptase

Anoctamin 1/TMEM16A in pruritoceptors is essential for Mas-related G protein receptor-dependent itch

Kim, Hyesu^1,3,7; Kim, Hyungsup^1,7; Cho, Hawon²; Lee, Byeongjun¹; Lu, Huan-Jun¹; Kim, Kyungmin¹; Chung, Sooyoung¹; Shim, Won-Sik⁴; Shin, Young Kee³; Dong, Xinzhong⁵; Wood, John N⁶; Oh, Uhtaek^1,3,*Author InformationPAIN: February 08, 2022 – Volume – Issue –doi: 10.1097/j.pain.0000000000002611

Abstract

Itch is an unpleasant sensation that evokes a desire to scratch. Pathologic conditions such as allergy or atopic dermatitis produce severe itching sensation. Mas-related G protein receptors (Mrgprs) are receptors for many endogenous pruritogens. However, signaling pathways downstream to these receptors in dorsal root ganglion (DRG) neurons are not yet understood. We found that Anoctamin 1 (ANO1), a Ca²⁺-activated chloride channel, is a transduction channel mediating Mrgprs-dependent itch signals. Genetic ablation of Ano1 in DRG neurons displayed a significant reduction in scratching behaviors in response to acute and chronic Mrgprs-dependent itch models and the epidermal hyperplasia induced by dry skin. In-vivo Ca²⁺ imaging and electrophysiological recording revealed that chloroquine and other agonists of Mrgpr receptors excited DRG neurons via ANO1. More importantly, the overexpression of Ano1 in DRG neurons of Ano1-deficient mice rescued the impaired itching observed in Ano1-deficient mice. These results demonstrate that ANO1 mediates the Mrgprs-dependent itch signaling in pruriceptors and provides clues to treating pathologic itch syndromes.

MrgprB4 in trigeminal neurons expressing TRPA1 modulates unpleasant sensations

Shota Tobori a, 1, Haruka Hiyama a, 1, Takahito Miyake a, b, Yuichi Yano a, Kazuki Nagayasu a, Hisashi Shirakawa a, *, Takayuki Nakagawa c, Yasuo Mori d, Shuji Kaneko a

a Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
b Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimoadachi-cho, Sakyo-ku, Kyoto 606- 8501, Japan

c Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, 54 Shogoin -Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
d Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Building A4, Katsura Campus, Nishikyo-ku, Kyoto 615-8510, Japan

ABSTRACT

Gentle touch such as stroking of the skin produces a pleasant feeling, which is detected by a rare subset of sensory neurons that express Mas-related G protein-coupled receptor B4 (MrgprB4) in mice. We examined small populations of MrgprB4-positive neurons in the trigeminal ganglion and the dorsal root ganglion, and most of these were sensitive to transient receptor potential ankyrin 1 (TRPA1) agonist but not TRPV1, TRPM8, or TRPV4 agonists. Deficiency of MrgprB4 did not affect noxious pain or itch be- haviors in the hairless plantar and hairy cheek. Although behavior related to acetone-induced cold sensing in the hind paw was not changed, unpleasant sensory behaviors in response to acetone appli- cation or sucrose splash to the cheek were significantly enhanced in Mrgprb4-knockout mice as well as in TRPA1-knockout mice. These results suggest that MrgprB4 in the trigeminal neurons produces pleasant sensations in cooperation with TRPA1, rather than noxious or cold sensations. Pleasant sensa- tions may modulate unpleasant sensations on the cheek via MrgprB4.

© 2021 The Authors. Production and hosting by Elsevier B.V. on behalf of Japanese Pharmacological Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Tentonin 3/TMEM150C regulates glucose-stimulated insulin secretion in pancreatic b-cells

Jungwon Wee,1,4,5 Sungmin Pak,2,4,5 Tahnbee Kim,4 Gyu-Sang Hong,4 Ji Seon Lee,3 Jinyan Nan,3 Hyungsup Kim,4 Mi-Ock Lee,2 Kyong Soo Park,1,3,* and Uhtaek Oh1,4,6,*
1Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 03080, Korea

2College of Pharmacy, Seoul National University, Seoul 08826, Korea
3Department of Internal Medicine, College of Medicine, Seoul National University, Seoul 03080, Korea 4Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea 5These authors contributed equally
6Lead contact
*Correspondence: kspark@snu.ac.kr (K.S.P.), utoh@kist.re.kr (U.O.)

SUMMARY

Glucose homeostasis is initially regulated by the pancreatic hormone insulin. Glucose-stimulated insulin secretion in b-cells is composed of two cellular mechanisms: a high glucose concentration not only depolar- izes the membrane potential of the b-cells by ATP-sensitive K+ channels but also induces cell inflation, which is sufficient to release insulin granules. However, the molecular identity of the stretch-activated cation chan- nel responsible for the latter pathway remains unknown. Here, we demonstrate that Tentonin 3/TMEM150C (TTN3), a mechanosensitive channel, contributes to glucose-stimulated insulin secretion by mediating cation influx. TTN3 is expressed specifically in b-cells and mediates cation currents to glucose and hypotonic stim- ulations. The glucose-induced depolarization, firing activity, and Ca2+ influx of b-cells were significantly lower in Ttn3/ mice. More importantly, Ttn3/ mice show impaired glucose tolerance with decreased insulin secretion in vivo. We propose that TTN3, as a stretch-activated cation channel, contributes to glucose-stim- ulated insulin secretion.

IL-33 Signaling in Sensory Neurons Promotes Dry Skin Itch

Abstract

Background

Chronic pruritus, or itch, is common and debilitating, but the neuro-immune mechanisms that drive chronic itch are only starting to be elucidated. Recent studies demonstrate that the IL-33 receptor (IL-33R) is expressed by sensory neurons. However, whether sensory neuron-restricted activity of IL-33 is necessary for chronic itch remains poorly understood.

Objectives

We sought to determine if IL-33 signaling in sensory neurons is critical for the development of chronic itch in two divergent pruritic disease models.

Methods

Plasma levels of IL-33 were assessed in patients with atopic dermatitis (AD) and chronic pruritus of unknown origin (CPUO). Mice were generated to conditionally delete IL-33R from sensory neurons. The contribution of neuronal IL-33R signaling to chronic itch development was tested in mouse models that recapitulate key pathologic features of AD and CPUO, respectively.

Results

IL-33 was elevated in both AD and CPUO as well as their respective mouse models. While neuron-restricted IL-33R signaling was dispensable for itch in AD-like disease, it was required for the development of dry skin itch in a mouse model that mirrors key aspects of CPUO pathology.

Conclusion

These data highlight how IL-33 may be a predominant mediator of itch in certain contexts, depending on the tissue microenvironment. Further, this study provides insight for future therapeutic strategies targeting the IL-33 pathway for chronic itch.

Key Words

• Atopic dermatitis
• chronic pruritus of unknown origin
• dry skin
• IL-33
• itch
• neuroimmunology
• pruriceptor
• pruritogen

Abbreviations:

Ab ((antibody)), AD ((atopic dermatitis)), AEW ((acetone/ether plus water)), bp ((base pair)), Cap ((Capsaicin)), CPUO ((chronic pruritus of unknown origin)), CQ ((chloroquine)), DRG ((dorsal root ganglia)), DT ((diphtheria toxin)), epidermis ((Epi)), EtOH ((ethanol)), HC ((healthy control)), His ((histamine)), i.d ((intradermal)), ILC2s ((group 2 innate lymphoid cells)), IL-33R ((IL-33 receptor)), i.p ((intraperitoneal)), KCl ((potassium chloride)), LM ((littermate)), loxP ((locus of X-over P1)), mAb ((monoclonal antibody)), MACS ((magnetic-activated cell sorting)), MasTRECK ((mast cell-specific enhancer-mediated toxin receptor-mediated conditional cell knockout)), NS ((no significance)), rh ((recombinant human)), rm ((recombinant mouse)), RNA-seq ((RNA sequencing)), stratum corneum ((SC)), Veh ((Vehicle)), WT ((wild-type))