Host: The Japan Radiation Research Society
Co-host: Asian Association for Radiation Research
Purpose : Tetrahydrobiopterin (BH4) is a cofactor of nitric oxide synthase (NOS) and has an antioxidant activity. In our previous study, it is found that various antioxidants and NO reduce γ-ray-induced chromosome aberrations. The effect of BH4 on γ-ray-induced micronucleus (MN) frequency of RAW264.7 cells was investigated in this study.
Methods : Mouse macrophage-like RAW264.7 cells were irradiated with 5Gy γ-ray in the presence or absence of sepiapterin (SP), a precursor of BH4 biosynthesis. To determine MN frequency, cells were fixed to a microscope slide and stained with Giemsa and the number of MN per 500 binucleated cells was scored under a light microscope. Intracellular BH4 concentration was measured by using reversed-phase high performance liquid chromatography (HPLC).
Results and Discussion : Treatment of RAW264.7 cells with 1μM SP, a precursor of BH4, reduced the 5Gy γ-ray-induced MN frequency by 65% at 18 and 24h post-treatment. This effect was blocked by N-acetyl-5-hydroxytryptamine and methotrexate, inhibitors of BH4 biosynthesis. Intracellular BH4 concentrations were peaked at 6h and kept on a high level until 24h after SP treatment. These results suggest that the reduction of γ-ray induced MN frequency by SP would be not necessary due to an antioxidant activity of BH4 and also other protective mechanisms would be included.
