IL-1R signaling enhances neutrophil extracellular traps (NETs) formation and leads to increase lung permeability and hypoxemia in LPS/mechanical ventilation-induced acute lung injury mouse model

Abstract

Abstract Although neutrophils extracellular traps (NETs) play a role in host defense against invading microorganisms, NETs alone play a role in pathogenesis of human acute respiratory distress syndrome (ARDS) either with or without infection. However, the mechanism of NET formation and its functional implications in alveolar space during acute lung injury are not less understood. We created a two-hit lung injury mouse model using intratracheal LPS (0.2 mg/kg), followed by 2.5 hours high-volume mechanical ventilation (30 ml/kg). We observed significant hypoxemia along with increased alveolar leakage, neutrophil infiltration, and NET formation using this model. Neutrophil depletion using (Ly6G[1A8]) monoclonal antibody inhibited these effects. Intriguingly, Il1r1−/− mice were significantly protected from hypoxemia and alveolar leakage despite similar alveolar neutrophil infiltration. We also found that Il1r1−/− mice had reduced levels of cell-free DNA and MPO-DNA complexes in bronchoalveolar lavage fluid (BALF), suggesting that NETs were involved in inducing lung vascular permeability and that IL-1R signaling was involved in inducing NET formation in alveolar space. Inhibition of NET formation via Cl-amidine or removal of NET DNA via DNase I led to reduced hypoxemia and alveolar leakage despite unaltered neutrophil infiltration. Additionally we found that recombinant IL-1β treatment of mouse neutrophils induces NETs, and this was inhibited by IL-1R antagonist (Anakinra). Taken together, we have found that IL-1R signaling-induced NETs play a critical role in development of lung injury, and may offer a new target for therapeutics.