Effect of DEP on the expression of IL-1β-induced IL-8 mRNA in A549 cells. A549 cells were stimulated with 50 pg/ml IL-1β for 1 h and then treated with 1–200 μg/ml of DEP for 20 h. Total RNA was extracted as described in Methods. The mRNA levels of IL-8 and β-tubulin were analyzed by RT-PCR (A) and real-time quantification PCR (B). The IL-8 signals were normalized to β-tubulin and are presented in arbitrary units (A.U.).