Benzo[a]pyrene enhances the formation of 8-hydroxy-2'-deoxyguanosine by ultraviolet A radiation in calf thymus DNA and human epidermoid carcinoma cells.
The objective of this study is to investigate if benzo[a]pyrene (BaP) and ultraviolet (UV) radiation synergistically induce oxidative DNA damage. Calf thymus DNA was incubated with BaP and irradiated with UVB (280-320 nm) and UVA (335-400 nm). BaP substantially enhanced the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) by UVA, but only moderately increased the level of 8-OHdG by UVB. Formation of 8-OHdG proportionally correlated with both UV dose and BaP concentration. Human epidermoid carcinoma cells were incubated with 10 microg of BaP/mL for 24 h and then exposed to 10 kJ/m2 UVB and 25 kJ/m2 UVA. UVB plus BaP did not affect the level of 8-OHdG in cultured cells, whereas UVA plus BaP substantially increased 8-OHdG by over 4-fold compared to BaP and UVA controls. To confirm what reactive oxygen species (ROS) are involved in BaP plus UVA-induced oxidative DNA damage, less or more specific ROS quenchers were added to DNA solution. The results showed that only superoxide dismutase and genistein significantly quenched BaP plus UVA-induced 8-OHdG, whereas catalase, sodium azide, and mannitol exhibited no effect. Our studies suggest that BaP enhances the formation of 8-OHdG in purified DNA and cultured cells by UVA, but not by UVB, and that superoxide anion plays an important role in the synergistic induction of oxidative DNA damage.
Liu
Z
Z
Department of Dermatology, Community Medicine and Radiation Oncology, Mount Sinai School of Medicine, New York 10029, USA.
Lu
Y
Y
Rosenstein
B
B
Lebwohl
M
M
Wei
H
H
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D001564:Benzo(a)pyrene / Q000378:metabolism / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism; D002417:Cattle; D004247:DNA / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects*; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D017382:Reactive Oxygen Species / Q000378:metabolism; D013950:Thymus Gland; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
D017382:Reactive Oxygen Species; D001564:Benzo(a)pyrene; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D003849:Deoxyguanosine