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/).

MRGPR-mediated activation of local mast cells clears cutaneous bacterial infection and protects against reinfection

Mohammad Arifuzzaman, Yuvon R. Mobley, HAE WOONG CHOI,

PRADEEP BISTCRISTINA A. SALINASZACHARY D. BROWNSWAINE L. CHEN, HERMAN F. STAATS, SOMAN N. ABRAHAM 

Published in Science advances, 2 Jan 2019

Abstract

Mast cells (MCs) are strategically distributed at barrier sites and prestore various immunocyte-recruiting cytokines, making them ideal targets for selective activation to treat peripheral infections. Here, we report that topical treatment with mastoparan, a peptide MC activator (MCA), enhances clearance of Staphylococcus aureus from infected mouse skins and accelerates healing of dermonecrotic lesions. Mastoparan functions by activating connective tissue MCs (CTMCs) via the MRGPRX2 (Mas-related G protein-coupled receptor member X2) receptor. Peripheral CTMC activation, in turn, enhances recruitment of bacteria-clearing neutrophils and wound-healing CD301b⁺ dendritic cells. Consistent with MCs playing a master coordinating role, MC activation also augmented migration of various antigen-presenting dendritic cells to draining lymph nodes, leading to stronger protection against a second infection challenge. MCAs therefore orchestrate both the innate and adaptive immune arms, which could potentially be applied to combat peripheral infections by a broad range of pathogens.

ZBTB20 in nociceptive neurons of the trigeminal ganglia regulates pruritus

Xin Jia, Meng-Han Dai, An-Jing Ren, Ting-Ting Wang, Weiping J. Zhang and Ling Zhang

Published in :-Frontiers of Medicine (2021.Mar.04) Impact factor:-5.02

Abstract

Recent studies have shown that ZBTB20, a zinc-finger protein containing transcription factor, is highly expressed in small-diameter primary sensory neurons in mice, and modulates pain through regulating TRP channels. However, whether ZBTB20 regulates itch sensation has not been demonstrated. In this study, small-diameter primary sensory
neuron-specific ZBTB20 knockout (PN-ZB20KO) mice were used to investigate the role of ZBTB20 in the regulation of itch sensation. First, both histamine-dependent and non-histamine-dependent itch behaviors induced by injection of histamine and chloroquine (CQ) into the cheek were significantly diminished in PN-ZB20KO mice. Second, double immunohistochemistry showed that ZBTB20 was mainly expressed in CGRP-labeled small peptidergic neurons and was expressed at low levels in IB4-labeled small non-peptidergic and NF200-labeled large neurons in the trigeminal ganglia (TG). ZBTB20 was also expressed in most TRPV1+ and TRPA1+ neurons and to a lesser extent in TRPM8+ neurons in the TG. Furthermore, cheek injection of histamine and CQ enhanced the mRNA expression of TRPV1 and TRPA1 but not TRPM8 in the TG. Moreover, TRPV1 and TRPA1 knockout (KO) mice exhibited attenuation of itch behavior induced by histamine and CQ, respectively. Finally, silencing endogenous ZBTB20 with recombinant lentivirus expressing a short hairpin RNA against ZBTB20 (LV-shZBTB20) in TG neurons attenuated histamine- and non-histamine-induced itch and downregulated TRP channels in the TG. Our study suggests that ZBTB20 plays an important role in mediating itch in small primary sensory neurons.

Keywords: itch, TRPA1, TRPV1, ZBTB20, trigeminal ganglia, pain, pruritus

Histamine enhances ATP-induced itching and responsiveness to ATP in keratinocytes

Yoshihiro Inami, Miki Fukushima, Toshiaki Kume, Daisuke Uta

Abstract

Mechanical stimulation of cultured keratinocytes and a living epidermis increases intracellular calcium ion concentrations ([Ca²⁺]_i) in stimulated cells. This action propagates a Ca²⁺ wave to neighboring keratinocytes via ATP/P2Y₂ receptors. Recent behavioral, pharmacological studies revealed that exogenous ATP induces itching via P2X₃ receptors in mice. We previously showed that alloknesis occurs when an external stimulus is applied to the skin with increased epidermal histamine in the absence of spontaneous pruritus. Based on these results, we investigated the effects of histamine at a concentration that does not cause itching on ATP-induced itching. The mean number of scratching events induced by the mixture of ATP and histamine increased by 28% over the sum of that induced by histamine alone or ATP alone. A317491, a P2X₃ receptor antagonist, suppressed the mixture-induced scratching more often than the ATP-induced scratching. Next, we examined the ATP-induced [Ca²⁺]_i change before and after histamine stimulation using normal human epidermal keratinocytes. Some cells did not respond to ATP before histamine stimulation but responded to ATP afterward, the phenomenon suppressed by chlorpheniramine maleate. These findings suggest that histamine enhances ATP-induced itching and that a potential mechanism could involve increased responsiveness to ATP in keratinocytes.

Keywords: ATP, Histamine, Keratinocytes, Itch, Calcium

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.

A plant-derived TRPV3 inhibitor suppresses pain and itch

PUBLISHED IN:- JOURNAL OF BRITISH PHARMACOLOGY. DOI: 10.1111/BPH.15390

Abstract

Background and Purpose: Itching is the most frequent pathology in dermatology that has significant impacts on people’s mental health and social life. Transient receptor potential vanilloid 3 (TRPV3) channel is a promising target for treating pruritus. However, few selecetive and potent antagonists have been reported. This study was designed to identify selective TRPV3 antagonist and elucidate its anti-pruritus pharmacology.

Experimental Approach: FlexStation and calcium fluorescence imaging were conducted to track the functional compounds. Whole-cell patch clamp was used to record itch-related ion channel currents. Homologous recombination and site-directed mutagenesis were employed to construct TRPV3 channel chimeras and point mutations for exploring pharmacological mechanism. Mouse models were used for in vivo anti-pruritus assay.

Key Results: An acridone alkaloid (citrusinine-II) was purified and characterized from Atalantia monophylla. It directly interacts with Y564 within S4 helix of TRPV3 to selectively inhibit the channel with a half maximal inhibitory concentration (IC50) of 12.43 μM. Citrusinine-II showed potential efficacy to attenuate both chronic and acute itch. Intradermal administration of citrusinine-II (143 ng/skin site) nearly completely inhibited itch behaviours. It also shows significant analgesic effects. Little side effects of the compound are observed.

Conclusion and Implications: By acting as a selective and potent inhibitor of TRPV3 channel, citrusinine-II shows valuable therapeutic effects in pruritus animal models and is a promising candidate drug and/or lead molecule for the development of anti- pruritus drugs.

KEYWORDS: citrusinine-II, Inhibition, Itch, Pain, TRPV3

Lancet. 2021 Oct 30;398(10311):1581-1592. doi: 10.1016/S0140-6736(21)01256-3.Epub 2021 Oct 28.

Efficacy and safety of maralixibat treatment in patients with Alagille syndrome and cholestatic pruritus (ICONIC): a randomised phase 2 study

Emmanuel Gonzales ¹, Winita Hardikar ², Michael Stormon ³, Alastair Baker ⁴, Loreto Hierro ⁵, Dorota Gliwicz ⁶, Florence Lacaille ⁷, Alain Lachaux ⁸, Ekkehard Sturm ⁹, Kenneth D R Setchell ¹⁰, Ciara Kennedy ¹¹, Alejandro Dorenbaum ¹², Jana Steinmetz ¹³, Nirav K Desai ¹⁴, Andrew J Wardle ¹⁵, Will Garner ¹⁵, Pamela Vig ¹⁵, Thomas Jaecklin ¹⁶, Etienne M Sokal ¹⁷, Emmanuel Jacquemin ¹⁸Affiliations expand

• PMID: 34755627
• DOI: 10.1016/S0140-6736(21)01256-3

Abstract

Background: Alagille syndrome is a rare genetic disease that often presents with severe cholestasis and pruritus. There are no approved drugs for management. Maralixibat, an apical, sodium-dependent, bile acid transport inhibitor, prevents enterohepatic bile acid recirculation. We evaluated the safety and efficacy of maralixibat for children with cholestasis in Alagille syndrome.

Methods: ICONIC was a placebo-controlled, randomised withdrawal period (RWD), phase 2b study with open-label extension in children (aged 1-18 years) with Alagille syndrome (NCT02160782). Eligible participants had more than three times the normal serum bile acid (sBA) levels and intractable pruritus. After 18 weeks of maralixibat 380 μg/kg once per day, participants were randomly assigned (1:1) to continue maralixibat or receive placebo for 4 weeks. Subsequently, all participants received open-label maralixibat until week 48. During the long-term extension (204 weeks reported), doses were increased up to 380 μg/kg twice per day. The primary endpoint was the mean sBA change during the RWD in participants with at least 50% sBA reduction by week 18. Cholestastic pruritus was assessed using observer-rated, patient-rated, and clinician-rated 0-4 scales. The safety population was defined as all participants who had received at least one dose of maralixibat. This trial was registered with ClinicalTrials.gov, NCT02160782, and is closed to recruitment.

Findings: Between Oct 28, 2014, and Aug 14, 2015, 31 participants (mean age 5·4 years [SD 4·25]) were enrolled and 28 analysed at week 48. Of the 29 participants who entered the randomised drug withdrawal period, ten (34%) were female and 19 (66%) were male. In the RWD, participants switched to placebo had significant increases in sBA (94 μmol/L, 95% CI 23 to 164) and pruritus (1·7 points, 95% CI 1·2 to 2·2), whereas participants who continued maralixibat maintained treatment effect. This study met the primary endpoint (least square mean difference -117 μmol/L, 95% CI -232 to -2). From baseline to week 48, sBA (-96 μmol/L, -162 to -31) and pruritus (-1·6 pts, -2·1 to -1·1) improved. In participants who continued to week 204 (n=15) all improvements were maintained. Maralixibat was generally safe and well tolerated throughout. The most frequent adverse events were gastrointestinal related. Most adverse events were self-limiting in nature and mild-to-moderate in severity.

Interpretation: In children with Alagille syndrome, maralixibat is, to our knowledge, the first agent to show durable and clinically meaningful improvements in cholestasis. Maralixibat might represent a new treatment paradigm for chronic cholestasis in Alagille syndrome.

Funding: Mirum Pharmaceuticals.

Copyright © 2021 Elsevier Ltd. All rights reserved.

presentation by Jong hyun

Type I hypersensitivity promotes Aedes aegypti blood feeding

Michael J. Conway, published in Scientific reports

Abstract:

Mosquitoes play a major role in human disease by serving as vectors of pathogenic microorganisms. Mosquitoes inject saliva into host skin during the probing process. Mosquito saliva contains a number of proteins that facilitate blood feeding by preventing hemostasis. Mosquito saliva also contains potent allergens that induce type I hypersensitivity reactions in some individuals. Type I hypersensitivity reactions in skin involve IgE-mediated degranulation of mast cells, which leads to vasodilation and an itch sensation. We hypothesized that hypersensitivity to mosquito saliva influences blood feeding. To test this hypothesis, we recruited human subjects who consented to Aedes aegypti bites. We measured their first sensation of itch, the strength of their itch sensation, the number of times mosquitoes attempted to feed, the number of times mosquitoes probed their skin, feeding time, engorgement status, and wheal diameter. Here we show that hypersensitive subjects had a stronger itch sensation, and that the time to first itch sensation was inversely correlated with wheal diameter; however, mosquitoes tended to probe less and engorge more on these subjects. Follow-up experiments testing the impact of oral antihistamine treatment on mosquito feeding parameters failed to reveal a statistically significant result. Histamine also failed to promote blood feeding on an artificial membrane feeder. This study suggests that mosquito saliva-induced type
I hypersensitivity promotes blood feeding but that this may be independent from histamine or histamine signaling.

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))

TRPC3 Antagonizes Pruritus in A Mouse Contact Dermatitis Model

Katherine Beattie , Haowu Jiang , Mayank Gautam , Mary K MacVittie , Barbara Miller , Minghong Ma , Qin Liu , Wenqin Luo 

Abstract

Contact dermatitis (CD), including allergic and irritant CD, are common dermatological diseases and characterized by an erythematous rash and severe itch. In this study, we investigated the function of TRPC3, a canonical TRP channel highly expressed in type 1 non-peptidergic (NP1) nociceptive primary afferents and other cell types, in a mouse CD model. Though TrpC3 null mice had little deficits in acute somatosensation, they showed significantly increased scratching with CD. In addition, TrpC3 null mice displayed no differences in mechanic and thermal hypersensitivity in an inflammatory pain model, suggesting that this channel preferentially functions to antagonize CD-induced itch. Using dorsal root ganglia (DRG) and pan-immune-specific TrpC3 conditional KO (CKO) mice, we determined that TrpC3 in DRG neurons, but not in immune cells, is required for this phenotype. Furthermore, the number of MRGPRD⁺ NP1 afferents in CD-affected DRGs is significantly reduced in TrpC3 mutant mice. Taken together, our results suggest that TrpC3 plays a critical role in NP1 afferents to cope with CD-induced excitotoxicity, and that degeneration of NP1 fibers may lead to an increased itch of CD. Our study identified a role of TrpC3 and NP1 afferents in CD pathology.

Keywords: Contact dermatitis; DRG; MRGPRD; TRPC3; non-peptidergic nociceptors; pruritus.