A22-22 Dual Role of the EGFR in Airway Dysfunction and Epithelial Regeneration in Mice Following Chlorine Exposure

Rationale Chlorine (Cl2) is a common cause of irritant-induced asthma (IIA), a predominantly neutrophilic, T2-low phenotype with few targeted therapies. While epidermal growth factor receptor (EGFR) signaling regulates epithelial repair and inflammation in allergic asthma, its role in Cl2-induced airway injury and dysfunction is undefined. This study investigated the role of EGFR in airway dysfunction and epithelial regeneration following Cl2 exposure in mice. Methods Wild-type BALB/c mice were exposed to Cl2 gas and treated with EGFR tyrosine kinase inhibitors (TKIs) gefitinib or afatinib. We assessed airway hyperresponsiveness (AHR) to methacholine using the flexiVent system, cytokines in bronchoalveolar lavage (BAL) fluid (CXCL1, IL-6, IL-33), BAL cell counts, and epithelial apoptosis (TUNEL) and proliferation (Ki-67). Lung EGFR pathway activation (p-EGFR, p-STAT3, p-ERK, p-Akt) and NRF2 nuclear translocation were evaluated by immunoblotting/immunostaining. A STAT3 inhibitor was used to dissect IL-6/STAT3 contributions.RNA sequencing of lung tissue was performed to identify gene expression alterations associated with EGFR inhibition. Results Cl2 rapidly increased EGFR ligands (HB-EGF, amphiregulin) and EGFR activation in lungs. EGFR inhibition attenuated AHR and reduced pro-inflammatory cytokines (CXCL1, IL-6 and IL-33) in BAL fluid, but did not decreased total inflammatory cell counts. Afatinib suppressed downstream STAT3/ERK/Akt phosphorylation, yet direct STAT3 blockade reduced BAL cellularity without improving AHR, suggesting that EGFR-dependent AHR modulation is not explained by IL-6/STAT3 alone. Notably, EGFR inhibition impaired NRF2 nuclear translocation, suppressing antioxidant response (Hmox1, Nfe2l2) and prolonging epithelial apoptosis. Transcriptomic analysis revealed EGFR inhibition altered pathways linked to muscle contraction and extracellular matrix remodeling genes. Conclusions EGFR inhibition attenuates AHR and cytokine production, while it simultaneously impairs epithelial repair and oxidative defenses. EGFR plays harmful and protective roles in Cl2-induced airway injury, contributing to both AHR and epithelial repair. This abstract is funded by: MSD Life Science Foundation