Evaluation of Oxidative Damage Induced by Natural Sunlight in Drosophila

抄録

The sunlight that reaches the surface of the earth is composed of polychromatic light with wavelengths ranging from 290 nm to 2500 nm. Ultraviolet (UV) light is a component of sunlight that is harmful to organisms. Although it is known that sunlight induces photoproducts and harmful effects such as major DNA damage caused by UV light in the tissues of many species including human skin, it is not clear whether sunlight induces oxidative damage in organisms. In this study, we investigated whether sunlight causes oxidative damage in exposed organisms using Drosophila. Third instar larvae were exposed to sunlight for an evaluation of viability and 8-hydroxydeoxyguanosine (8-OHdG) content. Urate-null Drosophila mutant larvae (ry⁵⁰⁶), which are sensitive to active oxygen-producing agents, were more sensitive to sunlight lethality than the wild-type strain under limited conditions. This sunlight-induced toxicity in ry⁵⁰⁶ larvae was partially prevented by pretreatment of larvae with 400 mM uric acid. The level of 8-OHdG in DNA showed no significant increase in both strains. In contrast, sunlight was significantly mutagenic for all seasons as reported previously. These results suggest that sunlight is partly responsible for oxidative damage in Drosophila and that 8-OHdG-formation plays little or no role in sunlight-induced mutation and toxicity.