PRODUCTS OF OZONIZED ARACHIDONIC-ACID POTENTIATE THE FORMATION OF DNASINGLE-STRAND BREAKS IN CULTURED HUMAN LUNG-CELLS

In this study we examined the potential for environmental levels of oz one (O-3) to degrade arachidonic acid (AA), a polyunsaturated fatty ac id abundantly present in the lung, into products that con produce DNA single strand breaks (ssb) in cultured human lung cells. Human lung fi broblasts were incubated with 60 mu M AA that had been previously expo sed to and degraded by 0.4 ppm O-3 (1 hr). incubation of the cells wit h O-3-exposed AA (but not with vehicle alone) for 1 hr at 4 degrees C and 37 degrees C produced 555 and 245 rad-equivalents of DNA ssb, resp ectively, as determined by the DNA alkaline elution technique. These b reaks were completely eliminated when the ozonized AA solution was inc ubated with catalase prior to cell treatment, indicating that H2O2 was solely responsible for damaging DNA. Superoxide dismutase, bovine ser um albumin, or heat-inactivated catalase showed little, if any, inhibi tory activity. The H2O2 content of the ozonized AA (31 +/- 4 mu M) cou ld account for only about 40% of the observed breaks. Potentiation of the H2O2-induced DNA ssb persisted after removal of the carbonyl subst ances by chromatographic procedures, suggesting that the non-carbonyl component of ozonized AA was the responsible component for inducing au gmentation of the observed increases in DNA ssb. Ozonized AA also indu ced DNA ssb in cultures of the human bronchial epithelial cell line BE AS-2B. Again, these breaks were shown to exceed levels that could be a ttributed to the presence of H2O2 alone. These results indicate that p roducts of ozonized AA con interact to potentiate DNA ssb in human lun g cells. (C) 1996 Wiley-Liss, Inc.