Effect of serine proteinases and agonist peptides of PARs on the expression of IL-8 mRNA in A549 cells. Total cellular RNA was isolated, reverse transcribed to cDNA, and the cDNA was used for real-time PCR. Cells were treated with the testing compounds at 37°C for 2 (open bars), 8 (left hatched bars) and 16 h (right hatched bars), respectively. The data were normalized to the housekeeping gene (β-actin gene) and were expressed as mean ± SE fold of control for three separate experiments performed in duplicate. *p < 0.05 compared with the baseline control.