Anti-neutrophil cytoplasmic antibodies contribute to airway inflammation via induction of neutrophil extracellular traps in children with bronchiolitis obliterans

Abstract Objective: It was found that the level of anti-neutrophil cytoplasmic antibodies (ANCA) in children with bronchiolitis obliterans (BO) was increased and was related to the severity of the disease previously. This study aims to explore the mechanism of ANCA in the process of BO. Methods: ANCA and components of neutrophil extracellular traps (NETs) were detected in plasma from patients with BO (n=40) and age- and sex-matched healthy children (n=11). Plasma IgG was extracted from ANCA-positive BO children and normal controls to stimulate neutrophils, and the production of reactive oxygen species (ROS) and NETs were detected. Small airway epithelial cells (SAECs) were treated directly with NETs of various concentrations. Cell viability was determined by CCK8, and secreted inflammatory cytokines were detected by ELISA. The IgG treated neutrophils were co-cultured with SAECs and the levels of cytokines in the culture supernatants were detected by ELISA. Results: The levels of ANCA and NETs components including dsDNA, neutrophil elastase (NE) and myeloperoxidase (MPO) in the plasma of BO children were significantly higher than those of healthy controls. ANCA-positive IgG induced neutrophils produce ROS and NETs. The cell viability of SAECs was significantly reduced upon treatment with NETs in a concentration-dependent manner. The levels of IL-8, IL-17, TNF-α and TGF-β secreted by SAECs treated with NETs were increased significantly, and the degree of increase was positively correlated with the concentration of NETs. The co-culture of neutrophils stimulated by ANCA IgG with SAECs significantly increased the expression of cytokines including IL-8, IL-17, TNF-α and TGF-β. Conclusions: NETs induced by ANCA may exacerbate airway inflammation in children with BO.