Rationale: In many organs, hypoxic cell death triggers sterile neutrophilic inflammation via IL-1R signaling. Although hypoxia is common in airways from patients with cystic fibrosis (CF), its role in neutrophilic inflammation remains unknown. We recently demonstrated that hypoxic epithelial necrosis caused by airway mucus obstruction precedes neutrophilic inflammation in Scnn1b-transgenic (Scnn1b-Tg) mice with CF-like lung disease.
Objectives: To determine the role of epithelial necrosis and IL-1R signaling in the development of neutrophilic airway inflammation, mucus obstruction, and structural lung damage in CF lung disease.
Methods: We used genetic deletion and pharmacologic inhibition of IL-1R in Scnn1b-Tg mice and determined effects on airway epithelial necrosis; levels of IL-1α, keratinocyte chemoattractant, and neutrophils in bronchoalveolar lavage; and mortality, mucus obstruction, and structural lung damage. Furthermore, we analyzed lung tissues from 21 patients with CF and chronic obstructive pulmonary disease and 19 control subjects for the presence of epithelial necrosis.
Measurements and main results: Lack of IL-1R had no effect on epithelial necrosis and elevated IL-1α, but abrogated airway neutrophilia and reduced mortality, mucus obstruction, and emphysema in Scnn1b-Tg mice. Treatment of adult Scnn1b-Tg mice with the IL-1R antagonist anakinra had protective effects on neutrophilic inflammation and emphysema. Numbers of necrotic airway epithelial cells were elevated and correlated with mucus obstruction in patients with CF and chronic obstructive pulmonary disease.
Conclusions: Our results support an important role of hypoxic epithelial necrosis in the pathogenesis of neutrophilic inflammation independent of bacterial infection and suggest IL-1R as a novel target for antiinflammatory therapy in CF and potentially other mucoobstructive airway diseases.
Keywords: airway epithelium; airway inflammation; chronic obstructive pulmonary disease; cystic fibrosis; mucus obstruction.