S1P/S1PR3 axis drives epithelial dysfunction and type 2 inflammation in chronic rhinosinusitis with nasal polyps.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by epithelial barrier dysfunction and type 2-dominant inflammation, yet the upstream regulatory mechanisms linking epithelial remodeling and immune activation remain poorly understood, and reliable biomarkers for eosinophilic CRSwNP (EOS CRSwNP) are limited. This study investigated the role of the sphingosine-1-phosphate (S1P)/S1P receptor (S1PR) axis in epithelial barrier dysfunction and immune inflammation, and assess its potential as an adjunctive biomarker. S1P levels were significantly elevated in both serum and nasal tissues of CRSwNP patients, especially in the eosinophilic subtype, and correlated with disease severity and epithelial-mesenchymal transition (EMT) marker expression. In vitro experiments using human nasal epithelial cells (HNEpCs and primary HNECs) showed that S1P induced EMT and impaired barrier function predominantly through S1PR3. Pharmacological inhibition and lentiviral knockdown of S1PR3 attenuated these effects. Transcriptomic analysis identified PI3K-AKT signaling as a key downstream pathway mediating S1P/S1PR3-driven epithelial dysfunction. Multiplex immunofluorescence revealed increased S1PR3 expression in epithelial cells as well as in eosinophils and group 2 innate lymphoid cells (ILC2) in human nasal polyp tissues. In a murine nasal polyp model, pharmacological inhibition of S1PR3 attenuated polyp formation, restored epithelial junction proteins, reduced eosinophil and ILC2 infiltration, and suppressed Th2-associated cytokines (IL-4, IL-5, and IL-13). Moreover, serum S1P levels closely reflected tissue expression and disease severity, when combined with peripheral eosinophil percentage, improved diagnostic performance for identifying EOS CRSwNP. Collectively, these findings demonstrate that the S1P/S1PR3 axis links epithelial barrier dysfunction with type 2 immune inflammation in CRSwNP and may represent a promising therapeutic target and adjunctive biomarker for disease stratification.