IL-5 signaling in asthmatic derived fibroblasts exacerbates airway remodeling through ECM dysregulation and apoptosis resistance.

BACKGROUND: Airway remodelling, a critical feature of severe asthma, involves fibroblast-driven extracellular matrix (ECM) dysregulation. While IL-5 is pivotal in eosinophilic inflammation, its direct role in fibroblast-mediated fibrosis remains undefined. METHODS: Primary lung fibroblasts from asthmatic and healthy donors were stimulated with 0.5 ng/ml of IL-5 for several time points. ECM components, Matrix metalloproteinases (MMPs), Tissue inhibitor of metalloproteinases (TIMPs), and cytokines were analysed via quantitative real time-PCR (qRT-PCR), Western blot, ELISA, and flow cytometry. RNA sequencing and absolute gene set enrichment analysis (absGSEA) identified signaling pathways. Apoptosis was assessed using Annexin V/PI staining. RESULTS: IL-5 shown to markedly increase the expression of ECM proteins, including collagen I and fibronectin, in asthmatic fibroblasts. It also upregulated MMP-2 and MMP-3 expression, alongside increased levels of TIMP-1 and TIMP-2. Moreover, IL-5 promoted the secretion of IL-6 and TGF-β. RNA-seq analysis identified 472 differentially expressed genes in asthmatic fibroblasts, highlighting activation of the MAPK pathway and suppression of apoptosis through NR4A1 upregulation. IL-5 further reduced fibroblast apoptosis and enhanced IL-5Rα expression, indicating potential autocrine signalling. CONCLUSION: IL-5 directly activates lung fibroblasts to drive airway remodelling in severe asthma through ECM deposition, MMP/TIMP imbalance, and pro-fibrotic cytokine secretion, positioning it as a dual mediator of inflammation and fibrosis with novel therapeutic potential.