Abstract

BACKGROUND Allergic asthma is a chronic inflammatory airway disease characterized by epithelial barrier dysfunction and dysregulated immune responses. Emerging evidence indicates that gut microbiota dysbiosis contributes to asthma pathogenesis through the gut-lung axis, with microbial metabolites such as tryptamine (TRP) playing critical immunomodulatory roles. However, the precise mechanisms linking gut microbiota-derived tryptophan metabolites to airway epithelial barrier integrity remain incompletely understood. OBJECTIVE This study aims to investigate the role of gut microbiota-dependent tryptamine-aryl hydrocarbon receptor (AhR)-nuclear factor erythroid 2-related factor 2 (NRF2) signaling in regulating airway epithelial barrier function in house dust mite (HDM)-induced allergic asthma. METHODS HDM-induced allergic airway inflammation was established in C57BL/6 mice through intratracheal sensitization followed by intranasal challenge. Airway hyperresponsiveness (AHR) was measured using an Animal Lung Function System with methacholine challenge. Gut microbiota composition was analyzed by 16S rRNA gene sequencing, and functional prediction was performed using PICRUSt2. Fecal tryptophan metabolites were quantified by targeted metabolomics. The effects of exogenous TRP administration (10 mg/kg/day) on airway inflammation, AhR-NRF2 signaling, and tight junction protein expression were evaluated in vivo and in vitro using human bronchial epithelial cells (16HBE). NRF2-specific siRNA was employed to validate the necessity of NRF2 in the AhR-NRF2 axis. RESULTS