Allergens abrogate anti-inflammatory DNA effects and unmasks macrophage-driven neutrophilic asthma via ILC2/STING/TNF signaling.

Abstract

The mechanism of neutrophilic and mixed neutrophilic-eosinophilic asthma is poorly understood. We found that extracellular DNA and nucleosomes (Nuc) were elevated in the airways from neutrophilic-eosinophilic asthma patients and correlated with bronchoalveolar lavage neutrophils. Bronchial tissue from neutrophilic-eosinophilic asthma expressed increased DNA sensor-positive cells. Intranasally administered DNA did not induce airway hyperreactivity (AHR) or any pathology but induced AHR and neutrophilic-eosinophilic inflammation when co- administered with the allergen Alternaria (Alt). Nuc alone induced anti-inflammatory/defensive genes whereas the Nuc-Alt combo increased TNF and innate cytokines. The Alt-Nuc phenotype was abolished in Cgas-/-, ALR-/-, Sting-/-, LysMCre:Stingf/f, IL7RCre:Rorαf/f and Tnfr2-/- mice. Alt, unexpectedly, played an essential role in the Nuc-induced phenotype. It abrogated Nuc-induction of anti-inflammatory genes, facilitated Nuc uptake, induced ILC2s, which, in presence of Nuc, produced high levels of TNFα and promoted neutrophilic infiltration. We established a paradigm where allergens inhibit the anti-inflammatory effects of DNA/Nuc and facilitate STING-TNFα-driven neutrophilic-eosinophilic inflammation in asthma.