Murine Model of Acute Lung Injury

Wild-type (WT) C57BL/6 male mice aged 6–8 weeks were purchased from the Laboratory Animal Center of Chongqing Medical University, and IL-33 knockout (IL-33^−/−) mice (NM-KO-190436) on a C57BL/6 background were purchased from Shanghai Model Organisms Center (Shanghai, China). All mice were housed under specific pathogen-free conditions with free access to water and chow. After anaesthetization with an intraperitoneal injection of sodium pentobarbital (50 mg/kg), the mice were subjected to intratracheal (i.t.) instillation of 3 mg/kg lipopolysaccharide (LPS, Escherichia coli serotype O111: B4; Sigma-Aldrich, St. Louis, MO, USA) dissolved in sterile phosphate-buffered saline (PBS). A sham operation was performed in a similar manner with the same volume of PBS instead of LPS. For IL-33 injection experiments, 1000 ng of recombinant mouse IL-33 (rmIL-33) per mouse was dissolved in sterile PBS (rmIL-33, 3236-ML-010; R&D Systems) and injected intraperitoneally following intratracheal instillation of PBS [16 (link)]. Control mice received the same volume of PBS at the same time point. After 2 days of LPS insult, the mice were sacrificed for further analysis according to the Interdisciplinary Principles and Institutional Animal Care and Use Committee guidelines.