Abstract
The mechanisms of neutrophilic and mixed neutrophilic-eosinophilic asthma are poorly understood. We found that extracellular DNA and nucleosomes (Nucs) were elevated in the airways of patients with neutrophilic-eosinophilic asthma and correlated with bronchoalveolar lavage neutrophils. Bronchial tissue from neutrophilic-eosinophilic asthma had more DNA sensor-positive cells. Intranasally administered DNA did not induce airway hyperreactivity (AHR) or any pathology but induced AHR and neutrophilic-eosinophilic inflammation when coadministered with the allergen Alternaria (Alt). Nuc alone induced antiinflammatory/defensive genes, whereas the Nuc-Alt combination increased levels of TNF-α and innate cytokines. The Alt-Nuc phenotype was abolished in Cgas-/-, ALR-/-, Sting-/-, LysMCre:Stingfl/fl, IL7RCre:Rorαfl/fl, and Tnfr2-/- mice. Alt, unexpectedly, played an essential role in the Nuc-induced phenotype. It abrogated Nuc induction of antiinflammatory genes, facilitated Nuc uptake, induced type 2 innate lymphoid cells, which, in the presence of Nuc, produced high levels of TNF-α, and promoted neutrophilic infiltration. We established a paradigm whereby allergens inhibit the antiinflammatory effects of DNA/Nuc and facilitate STING-TNF-α-driven neutrophilic-eosinophilic inflammation in asthma.