Inflammation elevated IL-33 originating from the lung mediates inflammation in acute lung injury

Excessive inflammatory reactions occur with acute respiratory distress syndrome (ARDS), however, the underlying mechanisms of ARDS remain incompletely understood. Here we investigated whether interleukin (IL)-33 was elevated in ARDS patients. Serum samples were obtained from 14 ARDS patients and 24 control healthy volunteers. ELISA was used to measure the concentrations of IL-33. Besides, we established pulmonary ARDS and extrapulmonary ARDS models in mice, and serum and lung tissue samples were collected for analyses. The results showed that serum IL-33 concentrations were significantly higher in pulmonary ARDS patients compared to controls. Also, the levels of IFN-γ and IL-2 were positively correlated with IL-33 levels. We also showed that there were increased IL-33 levels in both the serum and lungs in the pulmonary ARDS model. This was not the case, however, in the extrapulmonary ARDS model. Pulmonary inflammation and injury in the pulmonary ARDS model was reduced with IL-33 neutralizing antibody treatment.