Blockade of PAR2 Signaling by Punicalagin as a Therapeutic Strategy for Atopic Dermatitis

Atopic dermatitis is a chronic inflammatory skin disorder characterized by persistent inflammation and severe pruritus. Current anti-inflammatory agents carry risks of long-term adverse effects, while antihistamines provide limited relief of pruritus. Protease-activated receptor 2 (PAR2) has emerged as a critical mediator of both inflammation and pruritus, representing a promising therapeutic target. In this study, we investigated the therapeutic potential of punicalagin (PCG), a potent PAR2 antagonist, in atopic dermatitis. PCG fully and potently inhibited trypsin-induced PAR2 activation in HaCaT cells with an IC₅₀ of 1.30 µM, exhibiting over 40-fold greater selectivity over PAR1. PCG significantly inhibited PAR2-induced phosphorylation of ERK1/2 and NF-κB in both HaCaT and human dermal fibroblast cells and reduced IL-8 secretion in HaCaT cells. In addition, PCG did not significantly affect other pruritus-related GPCRs including H1R, H4R, TGR5, 5HT2A, 5HT2B, and MRGPRX2 at 30 µM. Notably, PCG strongly blocked PAR2-AP-induced scratching in mice. In addition, PCG improved skin lesions, reduced dermatitis severity scores, and alleviated scratching behavior in a DNFB-induced atopic dermatitis model. These effects were associated with reduced epidermal thickness, decreased serum TSLP levels, and inhibition of PAR2-dependent calcium signaling in dorsal root ganglion neurons. These findings demonstrate that PCG is a selective PAR2 antagonist that effectively alleviates both inflammatory and pruritic symptoms of atopic dermatitis, suggesting its potential as a novel therapeutic agent.