Enhancement of DNA damage and involvement of reactive oxygen species afterexposure to bitumen with UVA irradiation

This study was carried out to evaluate whether bitumen cytotoxicity is enha nced when bitumen treatment is combined with WA exposure. We also evaluated the oxidative processes in bitumen-induced DNA damage, and attempted to id entify the DNA damage caused by bitumen and UVA exposures, either alone or in combination. The effects of bitumen and UVA on cell proliferation were e xamined using HL 60 cells. DNA-protein crosslinks (DPCs) were assessed usin g a K-SDS assay, and reactive oxygen species formation was detected by 8-OH -dG formation. We evaluated the formations of double-strand breaks (DSB) us ing lambda DNA/HindIII and single-strand breaks (SSB) using PM2 DNA. The cy totoxicity assay showed enhanced suppression of cell proliferation when bit umen exposure acid UVA exposure were combined. Combined exposure caused sig nificant increases in DPCs over either exposure alone. Incubation of deoxyg uanosine (dG) with bitumen or UVA showed an increase in 8-hydroxy-2'-deoxyg uanosine (8-OH-dG) levels when compared with controls, and combined exposur e enhanced this effect. An evaluation of agarose gel bands showed that DSB and SSB were not formed following exposure to bitumen and UVA. This fact in dicates that bitumen and UVA may be involved in genotoxic processes by prod ucing oxygen free radicals and that combined exposure enhances these effect s. (C) 1999 Elsevier Science B.V. All rights reserved.