Neutrophil extracellular traps induced by cigarette smoke contribute to airway inflammation in mice

Neutrophil extracellular traps (NETs) were initially identified as an important antimicrobial barrier to capture and kill microorganisms. Emerging evidence suggests that NETs play a crucial role in chronic airway inflammation induced by cigarette smoke (CS). However, how NETs form and the mechanisms by which NETs function in CS-related airway diseases are still unclear. To explore NET formation and its potential role in CS-related airway diseases, we first established a CS-induced subacute airway inflammation model in mice and verified NET formation in the airways. Moreover, NETs degradation by aerosolized DNase I treatment significantly inhibited the airway inflammation induced by CS in mice. More importantly, by in vitro experiments, we found that cigarette smoke extract (CSE) induces NET formation in an NADPH oxidase-dependent manner, and that macrophages and human bronchial epithelial cells (HBEs) are important targets for the NETs-induced secretion of inflammatory cytokines. Therefore, NETs may represent a critical link among neutrophils, macrophages and HBEs under chronic inflammation conditions induced by CS.