Epidermal PAR2-TRPV3-IL-33 Signaling Promotes Mast Cell Recruitment and Sensory Nerve-Mast Cell Interactions in Atopic Dermatitis

Jiahui Zhao 1,2 | Lingxuan Zhou 1 | Chenyu Wang 2,3,4 | Ziyan Rao 5,6 | Xiaohui Yuan 1 | Jun Cui 7 | Dongyu Zhao 5,6 | Ying Sun 8 | Yan Chen 8 | Ruoyu Li 1 | Miao Jing 2,3,4

1 Department of Dermatology, Peking University First Hospital, Beijing Key Laboratory of Molecular Diagnosis on Dermatoses, National Clinical Research
Center for Skin and Immune Disease, NMPA Key Laboratory for Quality Control and Evaluation of Cosmetics, Beijing, China | 2 Chinese Institute for
Brain Research, Beijing, China | 3 Beijing Institute for Brain Research, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing,
China | 4 Basic Medical Sciences, Capital Medical University, Beijing, China | 5 Department of Biomedical Informatics, School of Basic Medical Sciences,
Peking University, Beijing, China | 6 State Key Laboratory of Vascular Homeostasis and Remodeling, Peking University, Beijing, China | 7 National
Institute of Biological Sciences, Beijing, China | 8Department of Immunology, School of Basic Medical Sciences, Capital Medical University, Beijing, China

Keywords: atopic dermatitis | dermatology | mast cells

In silico discovery of nanobody binders to a G protein coupled receptor using AlphaFold Multimer

Edward P. Harvey^1,* , Jeffrey S. Smith^{1,2, *}, Joseph D. Hurley^1,*, Alyana Granados³, Ernst W. Schmid¹, Jason G. Liang-Lin¹, Huyang Zhang¹, Emily M. Meara^1,2, Elizabeth K. Wren¹, Steffanie Paul^4,5, Matthew P. Ferguson¹, Victor G. Calvillo-Miranda¹, Miguel A. Alcantar^1,6, Debora S. Marks^4,5, Johannes C. Walter^1,7, Andrew C. Kruse^1,†, Katherine J. Susa^3,†

¹Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
²Department of Dermatology, Brigham and Women’s Hospital, Boston, MA, 02115,USA.
³Department of Pharmaceutical Chemistry, University of California, San Francisco, CA94158, USA
⁴Department of Systems Biology, Harvard Medical School, Boston, MA, 02115, USA
⁵Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
⁶Department of Biomedical Engineering, University of California, Irvine, CA, 92697, USA
⁷Howard Hughes Medical Institute, Boston, MA, USA
^*These authors contributed equally.
^†Correspondence to: Andrew C. Kruse (Andrew_kruse@hms.harvard.edu) and Katherine J. Susa (Katherine.Susa@ucsf.edu)

• Received02 October 2025
• Accepted03 April 2026
• Published23 April 2026

https://doi.org/10.1038/s41467-026-72093-5

Neuropsin, TRPV4 and intracellular calcium mediate intrinsic photosensitivity in corneal epithelial cells

Luka Lapajne ¹, Monika Lakk ², Christopher N Rudzitis ³, Shruti Vemaraju ⁴, Richard A Lang ⁴, Marko Hawlina ⁵, David Križaj ⁶

• ¹Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA; Department of Ophthalmology, University Medical Center, Ljubljana, Slovenia.
• ²Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA.
• ³Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA; Interdepartmental Program in Neuroscience, University of Utah, USA.
• ⁴Department of Ophthalmology, College of Medicine, University of Cincinnati, Cincinnati, OH, USA.
• ⁵Department of Ophthalmology, University Medical Center, Ljubljana, Slovenia.
• ⁶Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA; Interdepartmental Program in Neuroscience, University of Utah, USA; Department of Bioengineering, University of Utah, Salt Lake City, UT, USA; Department of Neurobiology, University of Utah, Salt Lake City, UT, USA. Electronic address: david.krizaj@hsc.utah.edu.

Abstract

Purpose: To investigate intrinsic phototransduction in the corneal epithelium and its role in intracellular and inflammatory signaling.

Methods: Optical imaging in isolated corneal epithelial cells (CECs) and debrided epithelia was combined with molecular, biochemical, pharmacological assays and gene deletion studies to track UVB-induced calcium signaling and release of cytokines, chemokines and matrix remodeling enzymes. Results from wild type mouse CECs were compared to data obtained from Opn5^-/- and Trpv4^-/- cells.

Results: UVB stimuli and TRPV4 activity induced epithelial release of IL-1β, IL-17, matrix metalloproteinases MMP-3/MMP-9, and thymic stromal lymphopoietin (TSLP). UVB stimuli evoked [Ca²⁺]_i elevations in dissociated mouse CECs that were partially reduced by inhibition of TRPV4 channels, Trpv4 knockdown and replacement of control saline with Ca²⁺-free saline. UVB-induced Ca²⁺ responses were significantly suppressed by OPN5 deletion and by inhibition of phospholipase C signaling, and responses were abrogated in cells with depleted intracellular Ca²⁺ stores.

Conclusions: Mammalian CECs are intrinsically and constitutively photosensitive. UVB photons are transduced by neuropsin, phospholipase C and CICR signaling, with mouse but not human CE transduction exhibiting a UVB-sensitive TRPV4 component. TRPV4 activity and UVB transduction are linked to cell-autonomous release of proinflammatory, matrix remodeling and nociceptive interleukins and MMPS. TRPV4-induced cytokine release may contribute to the pain induced by mechanical injury of the cornea and CEC photosensing may alert and protect the visual system from ultraviolet B (UVB) radiation -induced snow blindness, injury, vision loss and cancer.

Keywords: Corneal epithelium; Neuropsin; Phototransduction; Snow blindness; TRPV4.

Journal Club (2026.05.08)

Abstract
The Mas-related G protein-coupled receptor (MRGPR) X2 is expressed on skin mast cells
and can be stimulated by an unusually broad spectrum of ligands, including specific drugs
and even endogenous peptides. MRGPRX2 activation can induce mast cell degranulation
and consequently mediator release, leading to inflammatory and hypersensitivity reactions.
In addition, MRGPRX2 mediates pain and itching sensations, leading to increased efforts
to identify MRGPRX2 inhibitors, including plant-derived compounds. Components within
oat extracts have been shown to mediate anti-inflammatory and itch-relieving properties,
but a possible inhibitory effect on MRGPRX2 activation has not yet been investigated. We
aimed to fill this gap and explored whether an oat kernel extract can modulate MRGPRX2
activation. For this purpose, we established a mast cell model with the human LAD2
cell line and used it to investigate the consequences of exposure to oat extract. While
we did not observe any influence on cell viability, we analyzed the impact of oat extract
on MRGPRX2-mediated mast cell activation and degranulation initiated by the three
confirmed MRGPRX2 ligands c48/80, substance P, and cortistatin 14. Exposure to oat
extract resulted in a significant reduction in mast cell degranulation for all three ligands, as
assessed by the release of β-hexosaminidase, tryptase, cell surface expression of CD63 and
CD107a, and phosphorylation of ERK. All results were confirmed with primary human
mast cells. Thus, we demonstrated for the first time that oat extract leads to a significant
reduction in MRGPRX2 activation, pointing to a previously unrecognized capacity of
natural compounds to modulate this pathway.
Keywords: mast cells; MRGPRX2; oat extract

Chaeeun Lee

Can aged Camellia oleifera Abel oil truly be used to treat atopic dermatitis?

Abstract

Xi-Lin Ouyang1, Zhang-Lin Yuan1, Xiao-Bing Chen1, Hong-Wan Gan2, Sen-Hui Guo1, Juan Cai1 and Jing-Jing Zhong2
1Department of Pharmacy, Gannan Healthcare Vocational College, Ganzhou, China, 2Department of
Dermatology, Ganzhou People’s Hospital, Ganzhou, China

Atopic dermatitis is an inflammatory skin condition characterized by erythema,
eruption, lichenification, and pruritus. Aged Camellia oleifera Abel oil, an effective
empirical plant oil utilized by the Gannan Hakka people in China to alleviate the
symptomsofatopicdermatitis.However,noscientificstudieshavebeenreported
to prove whether this oil is truly effective. We conducted this study to confirm
whether aged C. oleifera oil could alleviate the symptoms of 2,4
dinitrochlorobenzene (DNCB)-induced atopic dermatitis in mice. Differences
in the thickness and weight of the right and left ears were measured. ELISA
wasusedtodeterminetheserumlevelsoftheinflammatoryfactorsIL-4,IgE,IFN
γ, and TNF-α. HEstaining was performed to observe inflammatory cell infiltration
in the mouseskinlesions.Inaddition, themetabolitesofagedC.oleiferaoils were
analyzed, and molecular docking was used to assess the binding affinity of the
major metabolites to filaggrin, a protein involved in skin barrier function. Animal
studies showed that aged C. oleifera oil significantly improved the symptoms of
atopic dermatitis. HE staining and measurement of inflammatory factor levels
revealed similar results. A total of 41 metabolites were tentatively identified in the
oil, with fatty acids emerging as the major metabolites. Molecular docking
confirmed that the three most abundant fatty acids, i.e., oleic acid,
n-hexadecanoic acid, and octadecanoic acid, bind well to filaggrin. Our
results suggest that aged C. oleifera oils can be used to ameliorate the
symptoms of atopic dermatitis. Fatty acids may be the major active
metabolites responsible for the observed therapeutic effects by reducing
transdermal water loss, increasing skin hydration, alleviating DNCB-induced
skin barrier alterations, and eliminating itchy scratching caused by dry skin.

Tussilagone inhibits MRGPRX2-mediated mast cell degranulation and suppresses pseudo-allergic reactions

Highlights

• •Tussilagone attenuates Tween 80 and Substance P-induced pseudoallergic reactions.
• •Tussilagone targets the downstream signaling pathway of MRGPRX2.
• •Tussilagone suppresses pseudo-allergic reactions via Lyn-Btk-PLCγ-Ca²⁺ and p38/NF-κB pathways.

Abstract

Mas-related G protein-coupled receptor X2 (MRGPRX2) is a crucial target in pseudo-allergic reactions. Tussilagone (Tus), the main bioactive component derived from Tussilago farfara, has anti-inflammatory effects, but its potential inhibitory effects on pseudo-allergic responses remain unclear. This research aimed to evaluate the inhibitory role of Tus on pseudo-allergic reactions and its underlying mechanism. In vivo Systemic pseudo-allergic reactions and passive cutaneous anaphylaxis (PCA) models were established to assess the effects of Tus. In vitro, mast cell (LAD2) degranulation, inflammatory cytokine release, and signaling pathway protein expression were assessed. Calcium influx was measured in MRGPRX2-expressing HEK293 cells. The results showed that Tus significantly attenuated Tween 80- and substance P (SP)-induced systemic pseudo-allergy and PCA reactions. It also suppressed mast cell degranulation and decreased production of tumor necrosis factor-alpha (TNF-α), Interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1). In MRGPRX2-expressing HEK293 cells, Tus suppressed Tween 80- and SP-induced Ca²⁺ influx. Mechanistically, Tus inhibited tolimidone-induced Lyn kinase activation and suppressed SP-and Tween 80-induced β-hexosaminidase release, exhibiting an inhibitory profile comparable to that of the Lyn/Btk antagonist bosutinib. Additionally, Tus attenuated the phosphorylation levels of MRGPRX2 downstream signal molecules, including Btk, PLCγ1, PKC, p38 MAPK, IκB-α and NF-κB (p65). In conclusion, Tus attenuates SP-and Tween 80-induced mast cell activation and pseudo-allergic reactions by targeting the Lyn/Btk/PLCγ1 and p38/NF-κB pathways, highlighting its therapeutic potential for pseudo-allergy.

Keywords

pseudo-allergic reactions; Tussilagone; Mast cell; Lyn; MRGPRX2

https://doi.org/10.1016/j.taap.2026.117763

Oxidative stress induced TSLP production via TRPV4 regulates type 2 inflammation and pruritus in MC903 induced atopic dermatitis mouse model

Author links open overlay panelKeiji Kosaka ^a, Akihiko Uchiyama ^a, Yuta Inoue ^a, Mai Ishikawa ^a, Takeshi Araki ^a, Shintaro Saito ^a, Akiko Sekiguchi ^a, Yoko Yokoyama ^a, Sachiko Ogino ^a, Ryoko Torii ^a, Yuki Watanuki ^a, Sei-ichiro Motegi ^a

^aDepartment of Dermatology, Gunma University Graduate School of Medicine, Maebashi, Japan^bLaboratory of Neurochemistry, Department of Nutrition Science, University of Nagasaki, Nagasaki, Japan

Received 3 September 2025, Revised 4 December 2025, Accepted 28 January 2026, Available online 31 January 2026.

Abstract

Background

Transient receptor potential vanilloid 4 (TRPV4) is a calcium ion channel that is widely expressed in various cells, and it regulates multiple physiological and pathological processes. In skin, TRPV4 senses temperature, mechanical and chemical stimuli. Although TRPV4 has been shown to regulate inflammatory in psoriasis, its role in atopic dermatitis (AD) remains unclear.

Objective

We aimed to elucidate the role of TRPV4 is AD pathogenesis and its potential as therapeutic target.

Methods

We used human skin samples from healthy and patients with AD for immunostaining. TRPV4 knock out (KO) mice and MC903-induced AD mouse models were used in vivo. HaCaT cells were used in vitro.

Results

TRPV4 was highly expressed in keratinocytes in lesional skin site of AD. TRPV4 KO mice had less severe dermatitis, barrier dysfunction and pruritus than WT mice in MC903-treated mouse model. TRPV4 KO mice had significantly decreased mRNA expression of type 2 inflammatory cytokines, including TSLP, interleukin (IL)-4, IL-13, and IL-31 via qPCR, and reduced protein levels of TSLP and IL-4 by ELISA. In vitro, oxidative stress promoted expression and activation of TRPV4, following enhanced TSLP expression in HaCaT cells. However, stimulation with IL-4 and IL-13 inhibited TRPV4 activation in HaCaT cells. Finally, treatment with selective TRPV4 antagonist HC-067047 significantly reduced the severity of MC903-induced AD-like dermatitis.

Conclusion

Our findings showed that TRPV4 mediates the expression of keratinocyte-derived TSLP and increases Th2 immunity and pruritus, highlighting TRPV4 as a novel therapeutic strategy for the treatment of AD.

Key words

Atopic dermatitis, Th2, TRPV4, TSLP, Keratinocyte

Azelaic acid potentiates TRPV3 activity as a mechanism for skin irritation

Diwas Rawal ^{1 2}, Wook-Joo Lee ^{1 2}, Won-Sik Shim ^{1 2*}

¹College of Pharmacy, Gachon University, Incheon, Republic of Korea ²Gachon Institute of Pharmaceutical Sciences, Incheon, Republic of Korea

*Corresponding author e-mail: wsshim@gachon.ac.kr

https://doi.org/10.1016/j.jid.2026.01.022