Neutrophil extracellular traps activate IL-8 and IL-1 expression in human bronchial epithelia.

INTRODUCTION: Neutrophil extracellular traps (NETs) provide host defense, but can contribute to the pathobiology of diverse human diseases. We sought to determine the extent and mechanism by which NETs contribute to human airway cell inflammation. METHODS: Primary normal human bronchial epithelia (HBEs) grown at air liquid interface and wtCFBE41o- cells (expressing wtCFTR) were exposed to cell-free NETs from unrelated healthy volunteers for 18 hours in vitro. Cytokines were measured in the apical supernatant by Luminex and the effect on the HBE transcriptome was assessed by RNA seq. RESULTS: NETs consistently stimulated IL-8, TNF-alpha and IL-1alpha secretion by HBEs from multiple donors, with variable effects on other cytokines (IL-6, G-CSF, GM-CSF). HBE RNAs encoding IL-1 family cytokines, particularly IL-36 subfamily members, were increased in response to NETs. NET exposure in the presence of anakinra (recombinant human IL-1RA) dampened NET-induced changes in IL-8 and TNF-alpha proteins as well as IL-36alpha RNA. RhIL-36RA limited the increase in proinflammatory cytokine RNAs in HBEs exposed to NETs. CONCLUSION: NETs selectively upregulate an IL-1 family cytokine response in HBEs, which enhances IL-8 production and is limited by rhIL-1RA. Present findings describe a unique mechanism by which NETs may contribute to inflammation in human lung disease in vivo. NET-driven IL-1 signaling may represent a novel target for modulating inflammation in diseases characterized by a substantial NET burden.