Antioxidant system in photoaged skin of hairless mouse

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The cutaneous change of photoaging is caused by long-term repetitive photo-irradiation and "solar elastosis" is observed in the dermis. UV irradiation is the representative of oxidative stress and long-term repetitive irradiation is the repeat of oxidative stress. The chronic exposure to UV ray is harmful to the skin which can cause oxidative damage, and the change of antioxidant system would affect the other signal transduction system, especially through the redox regulation system. To clarify the mechanism of long-term repetitive UVA (300-420nm) irradiation in photoaged skin, we evaluated albino hairless mice by repetitive UVA irradiation for 12 months. The mice were divided into 7 groups of five individuals. Three groups were irradiated for 5 days per week for 4, 8 and 12 months. The other 3 groups were treated as age-matched controls. Mice in the irradiated groups received a daily dose of 30 J/cm^2/day. For this purpose, we established an animal model to analyze the cutaneous photoaging in human. The dorsal skins of mice were taken from each group and applied to immunohistochemistry, zymography, RT-PCR and culture. The analysis of tropoelastin, matrix metalloproteinase (MMP) 2 and MMP9 was performed and the expression of MMP9 mRNA was found to be significantly increased in cultured fibroblast derived from irradiated mice at 12 month. In zymograph, MMP9 activity was higher in irradiated group than that in non-irradiated group. These results suggest that MMP9 is an important mediator in the development of UVA irradiated skin for one-year. The existence of cutaneous photoaging means the accumulation of chronic UV exposure which can influence the antioxidant system. Next, we performed the quantitative analysis of the expression of superoxide dismutase in the transcription level, which was the representative enzyme of antioxidant system and scavenged O^-_2.