APLNR and acute respiratory distress syndrome: After preventive and therapeutic treatment of ALI mice with exogenous apelin, Fli-1, APJ, VE-cadherin, phosphorylated-VE-cadherin (p-VE-cadherin) and β-catenin were up-regulated, while SRC, phosphorylated-SRC (p-SRC), VEGF and VEGF-R were down-regulated, which indicated that the stability of vascular endothelial barrier was enhanced.