Increased Levels of 8-Hydroxy-2′-Deoxyguanosine in Drosophila Larval DNA after Irradiation with 364-nm Laser Light but not with X-rays

Abstract

Exposure to UVA light causes damage to cellular components such as DNA and membrane lipids. We showed previously that UVA irradiation can induce mutations in Drosophila larvae and that the major lesions responsible for mutations were not thymidine dimers when wavelengths tested became longer. The use of a longer wavelength with UVA laser apparatus (364 nm) has made it possible to test the effects of this powerful light in biological organisms. In the present study, we irradiated third instar larvae of the urate-null Drosophila mutant strain y v ma-l, which is sensitive to oxidative stress, and compared the effects of 364 nm light irradiation with the effects of X-rays. To assay viability, some of the larvae were kept at 25 degrees C until they eclosed in order to obtain a measure of viability. The remaining larvae were used to measure the amount of 8-hydroxydeoxyguanosine (8-OHdG), an indicator of oxidative DNA damage. The amount of 8-OHdG increased and viability decreased in response to increased UV dose in both the y v ma-l and wild-type strains. With irradiation of 600 kJ m(-2), 8-OHdG/10(6)dG was 7.2 +/- 3.2 and 6.2 +/- 2.0 in y v ma-l and wild-type strains, respectively, whereas the respective levels were 2.2 +/- 0.6 and 2.3 +/- 0.8 without irradiation. Our results indicated that irradiation with a 364-nm laser light caused significant oxidative damage in Drosophila larval DNA; however, induction of the damage was not prohibited by urate. To the best of our knowledge, this is the first report of a study in whole animals that shows increased levels of 8-OHdG in response to 364-nm UVA. X-ray ionizing radiation is also thought to generate reactive oxygen species in irradiated cells. We found that the amount of 8-OHdG in DNA following X-ray radiation remained unchanged in both strains, though survival rates were affected. X-ray-generated oxidative damage in Drosophila cells was followed by cell death but not DNA base oxidation, and the damage was suppressed by urate. The overall results suggest significant differences in the major in vivo oxidative damage caused by 364-nm light and X-rays.

Increase of somatic cell mutations in oxidative damage-sensitive drosophila

“…Third-instar larvae were placed on the medium containing the test compound, and kept at 25 °C until the individuals reached the adult stage. For observing the effects of X-ray irradiation (0.5 Gy/min), larvae were soaked in a 0.25 M sucrose solution on petri dishes (PD-47 50 ϕ × 11 mm; Advantic, Tokyo, Japan) with a hole for air exchange, and were irradiated with 3 or 10 Gy of X-ray, as described previously [ 15 ]. To observe the co-treatment effects of NDMA and uric acid, 126 mg of uric acid was mixed with 1.5 g of instant medium and 5 ml of 0.5 mM NDMA in aqueous solution.…”

Oxidatively Generated Damage to Cellular DNA by UVB and UVA Radiation,

“…Additional support for the UVA‐mediated oxidation of cellular DNA is provided by the specific measurement of 8‐oxodGuo in the DNA of mammalian cells that was achieved by either HPLC‐ECD or HPLC‐ESI‐MS/MS . The formation of 8‐oxodGuo that was shown to be linear with the applied doses of UVA radiation within the 0–200 J cm −2 dose range is more efficient in human fibroblasts than in keratinocytes.…”

Hypersensitivity of a Urate-null Strain of Drosophila melanogaster to the Toxic Effects of Environmental Cigarette Smoke

“…Each type of cross for the urate-null and wild-type strains was performed three replicates in both series of experiments. Measurement of 8-hydroxydeoxyguanosine in larval DNA: Immediately after ECS exposure, some larvae were frozen, stored at -759 C until DNA extraction, and subjected to HPLC measurement of the 8hydroxydeoxyguanosine (8-OHdG) content, as described previously (13,14).…”

“…In human plasma, the concentration of urate is estimated to be about 300 mM. The urate-null strain of Drosophila used in the present study is known to be sensitive to oxidative stress such as that caused by X-rays and paraquat (12)(13)(14). In the present study, we examined the toxicity of ECS by exposing Drosophila larvae from urate-null and wild-type strains.…”