Neutrophils Injure Bronchial Epithelium after Ozone Exposure

Neutrophil (PMN) influx is an early, prominent finding in the airways of humans after experimental inhalation of ozone (O3), however the potential for PMN to contribute to epithelial injury in this setting is unknown. Bronchial epithelial cells of the human BEAS 2B R1.4 cell line or primary human bronchial epithelial cells underwent DNA labeling by incubation with BrdU. Monolayers were exposed to O3 (0.05 to 1 ppm) or filtered air for 60 min., and subsequently incubated with PMN for 2 h. Epithelial cell cytolysis was significant only in BEAS exposed to O3 and co-cultured with PMN. Apoptosis was maximal in BEAS exposed to O3 + PMN. Primary bronchial epithelial cells were resistant to injury; no cytolysis was detected, and apoptosis was detected only after treatment with 10 mM H₂O₂. Neutrophils may increase damage to the respiratory epithelium after O3 exposure, but primary bronchial epithelial cells are resistant to PMN and ozone induced injury.