Fig. 3.

Neutrophil elastase, but not oxygen radical formation, is involved in neutrophil-induced A549 proliferation. LPS-activated [0.1 µg/ml] A549 cells were co-incubated with isolated neutrophils (7.5 × 10⁶/ml) in the absence (A549 + PMN) or presence of the oxygen radical scavenger SOD (10 µg/ml, A549 + PMN + SOD) or the elastase inhibitor AAPVCK (5 µM, A549 + PMN + AAPVCK). 6 h after incubation, the neutrophil-containing supernatant was removed, cells were washed three times, and 500 µl of fresh medium were added containing 75 µl MTS solution. After 2.5 h, absorbance was read at 490 nm. Values are expressed as percentage of MTS activity of A549 cells in the absence of neutrophils, which was set to 100 % as indicated by the horizontal dotted line. Horizontal bars indicate averages of five independent experiments, each performed in triplicates