Identification of Bronchial Epithelial Genes Associated with Type-2 Eosinophilic Inflammation in Asthma

Airway inflammation has a critical role in asthma pathogenesis and pathophysiology. Yet, the molecular pathways contributing to airway inflammation are not fully known, particularly Type-2 (T2) inflammation characterized by both eosinophilia and FeNO levels. Here, we seek to identify genes whose level of expression in epithelial brushing samples is associated with both bronchoalveolar lavage (BAL) eosinophilia and generation of FeNO. We used a segmental allergen bronchoprovocation (SBP-Ag) procedure in asthma subjects, and RNA-sequencing (RNA-seq) analyses of BAL cells and brushing samples before and 48 h after SBP-Ag. Allergen bronchoprovocation increased FeNO levels which correlated with eosinophilia but not neutrophilia. Thirteen genes were identified in brushing samples, whose expression changed in response to SBP-Ag and correlated with both airway eosinophilia and FeNO levels after SBP-Ag. Among these 13 genes, the epithelial cell product, CDH26 was a candidate to contribute to the amplification of T2 inflammation as reflected by eosinophilia and FeNO, and causal mediation analyses with pro-T2 and pro-eosinophilic cytokine mediators in BAL fluids. Among the genes associated with reduced eosinophila and FeNO, HEY2 is known to enhance cell proliferation, migration, invasion, and EMT, as well as to reduce apoptosis. This unbiased RNA-seq analysis in subjects with allergic asthma has revealed several epithelial cell genes that may be critical for the development or augmentation of T2 inflammation in asthma, particularly CDH26. Overall design: Segmental bronchial provocation with allergen (SBP-Ag) was used to provoke airway inflammation and retrieve airway cells to characterize cellular responses by RNA-sequencing to determine gene-expression profiles. This sample set includes bronchoalveolar brushings (BE). Differential gene-expression was assessed by linear modeling of post vs pre SBP-Ag gene expression as well as post SBP-Ag expression associated with FeNO, FEV1, eosinophils, and neutrophils.