The ubiquitin ligase FBXW7 regulates epithelial pyroptosis in severe asthma.

Abstract

Background: Severe asthma is characterized by persistent airway inflammation and epithelial injury. Pyroptosis, a Caspase-1-dependent inflammatory cell death pathway, has been implicated in airway inflammation. FBXW7, an E3 ubiquitin ligase involved in inflammatory regulation, may play a role in this process; however, its function in severe asthma remains unclear.

Methods: Human microarray datasets from the Gene Expression Omnibus (GEO) were analyzed to identify differentially expressed genes and potential biomarkers using bioinformatics and machine learning approaches. Experimental validation was performed using murine asthma models, including ovalbumin (OVA)-induced and OVA/LPS-induced models. Airway epithelium-specific FBXW7 conditional knockout mice were generated to assess in vivo function. In vitro, murine lung epithelial (MLE12) cells with FBXW7 knockout or overexpression were used to evaluate pyroptosis and inflammatory responses following LPS/ATP stimulation. Cytokine levels, Caspase-1 expression, and signaling pathways were analyzed using ELISA, Western blotting, and immunofluorescence.

Results: FBXW7 expression was significantly decreased in severe asthma compared with mild-to-moderate asthma, while Caspase-1 expression was increased. Machine learning analyses identified FBXW7 and Caspase-1 as potential biomarkers in severe asthma. In murine models, FBXW7 downregulation was more pronounced in severe asthma and was associated with increased inflammatory cell infiltration and cytokine production. FBXW7-deficient mice exhibited significantly elevated bronchoalveolar lavage fluid (BALF) inflammatory cell counts and increased IL-1β secretion compared with wild-type controls. In vitro experiments using MLE12 cell lines with FBXW7 overexpression, knockout, and wild-type backgrounds exhibited significant differences in Caspase-1 expression and altered secretion of inflammatory cytokines IL-18 and IL-1β under LPS/ATP-induced pyroptotic conditions, while pharmacological inhibition of Caspase-1 corrected aberrant cytokine secretion. However, mRNA levels of these cytokines remained stable, indicating that FBXW7 controls IL-18/IL-1β maturation/secretion via Caspase-1. Thus, the association among FBXW7, Caspase-1 and cGAS-STING was tested.

Conclusions: FBXW7 suppresses airway epithelial pyroptosis and inflammation in severe asthma by regulating Caspase-1, potentially via the cGAS-STING pathway. These findings highlight FBXW7 as a potential biomarker for severe asthma.