Collectively, the results suggested that 4-OI inhibits the expression of Toll-like receptor 4 (TLR4) in endothelial cells and associated downstream signaling pathways, reduces inflammation, oxidative stress and vascular permeability, and ultimately protects against pulmonary endothelial barrier and lung tissue damage in LPS-induced ALI. Here, TLR4 is linked to acute respiratory distress syndrome.