PUVA (8-methoxy-psoralen plus ultraviolet A) induces the formation of 8-hydroxy-2 '-deoxyguanosine and DNA fragmentation in calf thymus DNA and humanepidermoid carcinoma cells

The objective of this study is to investigate if 8-methoxy-psoralen (8-MOP) plus ultraviolet A (UVA) radiation (PUVA) induces oxidative DNA damage. Wh en calf thymus DNA was incubated with 8-MOP and irradiated with UVA (335-40 0 nm), the level of 8-hydroxy-2'-deoxyguanosine (8-OHdG) was substantially increased by approximately 6-fold. Formation of 8-OHdG proportionally corre lated with both UVA fluence and 8-MOP concentrations. Human epidermoid carc inoma cells were incubated with 10 mu g 8-MOP per milliliter, followed by i rradiation of 25 kJ/m(2) WA. The level of 8-OHdG increased by nearly 3-fold in PUVA-treated cells compared to 8-MOP and UVA controls. The formation of 8-OHdG correlated with DNA fragmentation as determined by spectrofluoromet ry. To investigate the reactive oxygen species (ROS) involved in PUVA-induc ed oxidative DNA damage, less or more specific ROS quenchers were added to DNA solution prior to PUVA treatment. The results showed that only sodium a zide and genistein significantly quenched PUVA-induced 8-OHdG, whereas cata lase, superoxide dismutase, and mannitol exhibited no effect. The quencher study with cultured cells indicated that N-acetyl-cysteine and genistein pr otected oxidative DNA damage as well as DNA fragmentation by PUVA treatment . Our studies show that PUVA treatment is able to induce the formation of 8 -OHdG in purified DNA and cultured cells and suggest that singlet oxygen is the principle reactive oxygen species involved in oxidative DNA damage by PUVA treatment. (C) 1999 Elsevier Science Inc.