Regulation of IL ‐13 Signaling by Retinoic Acid in Airway Epithelial Cells

Dysregulated vitamin A signaling, characterized by reduced all-trans retinoic acid (ATRA), is associated with asthma severity, and restoration of ATRA signaling may alleviate asthma symptoms. However, the molecular changes induced by inflammatory cytokines such as IL-13 that are central to asthma pathology and the retinoic acid receptor (RAR) agonists in airway cells are not well established. This study investigates the effects of IL-13 and RAR agonists on lung epithelial cells using a mass spectrometry-based proteomics approach. A549 alveolar and BEAS-2B bronchial epithelial cells were treated with IL-13 in the presence of vehicle, ATRA (pan-RAR agonist), or CD1530 (RARγ agonist). Proteomic profiling revealed significant changes in proteins relevant to asthma pathogenesis in IL-13-treated cells. IL-13 upregulated pro-inflammatory signaling kinases JAK1 and AXL, cytoskeletal-associated proteins CLDN2 and ACTN4, and inflammatory proteins CD44 and HLAs in A549 cells. In BEAS-2B cells, IL-13 upregulated barrier dysfunction-related proteins P-Cadherin and α-catenin, immune activation marker ICAM-1, and pro-fibrosis marker TGF-β. Notably, IL-13 significantly reduced ATRA biosynthesis enzymes RDH10 and ALDH1A1 which were accompanied by reduced ATRA levels and reduced ATRA biosynthesis in A549 cells as quantified by liquid chromatography-multistage-tandem mass spectrometry. RAR agonists mitigated IL-13-induced upregulation of proteins involved in epithelial integrity, inflammation, epithelial-to-mesenchymal transition (EMT), and extracellular matrix (ECM) production. CD1530 produced more pronounced changes than ATRA, underscoring the relevance of the RARγ subtype-specific activation in mitigating pathological changes in epithelial cells. These findings suggest that activating RAR restores ATRA signaling in airway cells and mitigates the pathological features of asthma.