Immunostaining of UVA-induced DNA damage in erythrocytes of medaka (Oryzias latipes).

Some authors have recently reported that UVA induces double-strand breaks (DSBs) in DNA. Only a few researchers have reported on the induction of DSBs upon UVA exposure, as measured using the Comet assay and γ-H2AX as markers of DSB formation. In the present study, we have investigated for the first time the dose-dependent induction of DSBs by UVA in medaka (Oryzias latipes) erythrocytes. Adult female medaka fish were exposed to UVA for 15, 30, and 60min/day for three continuous days; an unirradiated control group was kept in the same laboratory conditions. At 0h and 24h after UVA exposure, blood was collected to detect DNA damage and repair. The number of γ-H2AX foci was higher than the control value at 0h after UVA exposure and decreased within a 24h. the comet assay showed that DNA repair began during the recovery period. These findings confirm our pervious findings of genotoxic effects after UVA exposure in medaka erythrocytes and suggest that the replication-independent formation of UVA-induced DSBs is mediated through the generation of reactive oxygen species. In conclusion, these results suggest that DNA damage and repair occur after UVA exposure in medaka fish. UVA is the main component of solar UV radiation and is used for artificial UV exposure. Our results may have implications for skin cancer research.