Selective PAR2 Inhibition Attenuates HDM-Induced Th1/Th2 Responses in Human Epithelial and Murine Models of Allergic Rhinitis and Asthma.

Background: Allergic rhinitis (AR) and asthma are involved in complex interactions between Th1 and Th2 inflammatory pathways. House dust mite (HDM) activates protease-activated receptor 2 (PAR2) to trigger inflammatory responses, but current treatments often provide inadequate control.

Objective: This study aimed to investigate the effects of selective PAR2 inhibition on Th1 and Th2 responses in human nasal epithelial (HNE) cells and murine models of AR and asthma.

Methods: We examined the effects of selective PAR2 inhibition using primary HNE cells and HDM-induced mouse models (PAR2-wild-type [PAR2-wt] and knockout [PAR2-ko]). Analyses included inflammatory signaling pathways, cytokine profiles, airway responses, histopathology, and transcriptomics.

Results: In HNE cells, PAR2 inhibition suppressed Th2 (interleukin [IL]-33, TSLP) and Th1 (TNF-α, IL-6) inflammatory cytokines while inhibiting calcium mobilization and ERK/NF-κB signaling cascades. In PAR2-wt mice, treatment with the PAR2 inhibitor reduced HDM-specific Immunoglobulin E (IgE), airway hyperresponsiveness, and allergic inflammation in both nasal and bronchial tissues, matching the anti-inflammatory profile of PAR2-ko mice. Bulk RNA sequencing confirmed comprehensive suppression of inflammatory gene expression.

Conclusions: Selective PAR2 inhibition effectively attenuates HDM-induced allergic inflammation by modulation of Th1 and Th2 pathways in human airway epithelium and murine models. We suggest that PAR2 can be a possible target for AR and asthma.