LAUSR

RATIONALE Indirect airway hyperresponsiveness (AHR) is a highly specific feature of asthma but the underlying mechanisms responsible for driving indirect AHR remain incompletely understood. OBJECTIVES Identify differences in gene expression in epithelial brushings obtained from individuals with asthma who were characterized for indirect AHR in the form of exercise-induced bronchoconstriction (EIB). METHODS RNA-sequencing (RNA-seq) analysis was performed on epithelial brushings obtained from asthmatic individuals with (n=11) and without EIB (n = 9). Differentially expressed genes (DEGs) were correlated with measures of airway physiology, sputum inflammatory markers, and airway wall immunopathology. Based on these relationships, we examined the effects of primary airway epithelial cells (AECs) and specific epithelial-derived cytokines on both mast cells (MCs) and eosinophils (EOS). RESULTS We identified 120 DEGs between individuals with and without EIB. Network analyses suggested critical roles for IL-33-, IL-18-, and IFN--related signaling amongst these DEGs. IL1RL1 expression was positively correlated with the density of MCs in the epithelial compartment and IL1RL1, IL18R1, and IFNG were positively correlated with the density of intraepithelial EOS. Subsequent ex vivo modeling demonstrated that AECs promote sustained T2 inflammation in MCs and enhance IL-33-induced T2 gene expression. Further, EOS increase expression of IFNG and IL13 in response to both IL-18 and IL-33 as well as exposure to AECs. CONCLUSIONS Circuits involving epithelial interactions with MCs and EOS are closely associated with indirect AHR. Ex vivo modeling indicates that epithelial-dependent regulation of these innate cells may be critical in indirect AHR and modulating T2 and non-T2 inflammation in asthma.