Acid Sphingomyelinase-Ceramide Axis Modulation Is Associated with Thymic Stromal Lymphopoietin Release and Epithelial Barrier Dysfunction in an in vitro Type 2 Inflammation Model Relevant to Pediatric Rhinitis

Introduction: Epithelial barrier dysfunction is an early feature of pediatric Rhinitis, but the upstream epithelial events that initiate this process remain incompletely defined. Because lipid remodeling and epithelial-derived alarmins may interact during type 2 inflammation, this study examined whether acid sphingomyelinase (ASM)-ceramide signaling is associated with thymic stromal lymphopoietin (TSLP) release and barrier impairment in a pediatric rhinitis-related nasal epithelial model.

Methods: Primary human nasal epithelial cells were stimulated with interleukin-4 (IL-4)/interleukin-13 (IL-13) (10 ng/mL each, 24 h) to model a type 2 inflammatory epithelial milieu. ARC39 was used to inhibit ASM, and siRNA was used to knockdown TSLP. TSLP was quantified by enzyme-linked immunosorbent assay; barrier function was assessed by FITC-dextran permeability and ZO-1 immunofluorescence; ceramide levels were measured using a commercial kit; and sphingomyelin phosphodiesterase 1 (SMPD1) expression was evaluated by quantitative Real-Time PCR and Western blotting.

Results: IL-4/IL-13 stimulation increased TSLP release and impaired epithelial barrier integrity (p < 0.001). ARC39 reduced ceramide levels and decreased TSLP output (p < 0.001) in a concentration-dependent manner, with an evident effect at approximately 5 μ<sc>m</sc>, whereas SMPD1 expression remained largely unchanged. TSLP knockdown improved barrier function Indicators (p < 0.05), and combined ARC39 treatment did not produce an additional effect beyond TSLP knockdown.

Conclusion: ASM-ceramide axis modulation was associated with TSLP release and epithelial barrier dysfunction in this in vitro model. These findings suggest a possible link among sphingolipid remodeling, epithelial alarmin responses, and barrier injury, but further mechanistic and clinical validation is needed.