COMPARISON OF THE TOXIC EFFECTS OF HYDROGEN-PEROXIDE AND OZONE ON CULTURED HUMAN BRONCHIAL EPITHELIAL-CELLS

In this study, we compared the cytotoxic and genotoxic effects of hydr ogen peroxide and ozone on cultured human airway epithelial cells in p rimary culture. Both agents caused a dose-dependent loss in the replic ative ability of epithelial cells and at higher levels of exposure cau sed acute cytotoxicity as measured by release of lactate dehydrogenase . Differences were seen, however, between the agents' effects with reg ard to induction of DNA single-strand breaks as measured by alkaline e lution: whereas single-strand breaks were detected in significant amou nts at concentrations of hydrogen peroxide that caused acute cytotoxic ity, none were detected at any of the levels of ozone exposure examine d. A difference was also seen in the ability of the iron chelator defe roxamine to protect cells from the effects of the two oxidants. Preinc ubation of cultures with deferoxamine appreciably attenuated the toxic ity of hydrogen peroxide but not of ozone. These data suggest that ozo ne has significant toxic effects on bronchial epithelial cells not med iated through the generation of hydrogen peroxide or hydroxyl radical. Furthermore, the data indicate that the inhibiting action of ozone on cell replicative ability is not mediated through a mechanism related to DNA single-strand breaks.