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.