Evaluation of mutagenic effects of hyperbaric oxygen (HBO) in vitro

Hyperbaric oxygen (HBO) treatment as used therapeutically (i.e., exposure t o 100% oxygen at a pressure of 1.5 bar for a total of 60 min) has been show n to induce DNA damage in the alkaline comet assay with leukocytes from tes t subjects. Under these conditions, HBO did not lead to an induction of gen e- and chromosome mutations. Due to known toxic effects, exposure of humans to HBO is limited and possible genetic consequences of HBO could not be co mpletely evaluated in vivo. We thus established an in vitro HBO model, wher e human blood cells or V79 cells were exposed to hyperbaric oxygen (98% O-2 and 2% CO2 at a pressure of either 1.5 or 3 bar) for up to 3 hr in a tempe rature-controlled hyperbaric chamber. Using the comet assay, we found expos ure-related genotoxic effects in V79 cells, whole blood, and isolated lymph ocytes. V79 cells showed the highest sensitivity toward HBO-induced DNA dam age, and the exposure conditions applied to blood in vitro, to induce DNA m igration, had to be higher than those used in vivo. We could also show that prolonged HBO treatment clearly increased the frequency of micronuclei in V79 cells, whereas it exerted only a marginal effect on the frequency of hp rt mutations. These results demonstrate that HBO treatment of cell cultures is a well-suited model for investigating the biological significance of ox idative stress. The relationship between oxygen-induced DNA lesions and the formation of gene- and chromosome mutations is discussed. (C) 1999 Wiley-L iss, Inc.