Abstract： Objective To investigate the effect of seawater on expression of protease-activated receptor 2 (PAR-2) in adenocarcinoma of lung cell line A549 cells,and the inflammatory injury on A549 cells induced by seawater. Methods A549 cells were randomly divided into four groups: control group,2 hours group,4 hours group,8 hours group,in which cells were treated with seawater for 2,4 and 8 hours respectively. After seawater treatment,cells were collected for real-time quantitative reverse transcrition-polymerase chain reaction (RT-PCR) and Western blotting analysis to determine the expression of PAR-2 mRNA and its protein. Supernatant were collected for tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8) which were determined by enzyme-linked immunosobent assy (ELISA). Results The expression of PAR-2 mRNA and protein of A549 cells increased in a time-dependent manner after seawater treatment,significantly so after 2 hours in all groups (both P<0.05),and peaked at 4 hours after seawater treatment (1.8-fold and 2.2-fold respectively,both P<0.01),followed by a decrease though still higher than those of control group significantly (both P<0.01). TNF-α and IL-8 in supernatant increased significantly after seawater treatment,peaking at 2 hours after seawater treatment [(214.35±20.85) ng/L,(55.86±5.65) ng/L] and then followed by a slight decrease though still significantly higher than those of control group [(25.86±3.85) ng/L,(6.97±1.77) ng/L,all P<0.01]. Conclusion Seawater can induce significant inflammation of A549 cells and up-regulate the expression of PAR-2 on A549 cells.