Antioxidant system in photoaged skin of hairless mouse

光老化的皮肤变化是由于长期重复光照射而引起的，真皮内可见“日光弹力增殖症”。紫外线照射是氧化应激的代表，长期重复照射是氧化应激的重复。长期暴露在紫外线下会对皮肤造成氧化损伤，而抗氧化系统的改变会影响其他信号转导系统，特别是通过氧化还原调节系统。为了阐明长时间重复UVA(300-420 nm)照射光老化皮肤的机制，我们对白化无毛小鼠进行了12个月的重复UVA照射。这些小鼠被分成7组，每组5只。三组照射时间分别为4、8、12个月，每周照射5天。其余3组均为年龄匹配的对照组。照射组小鼠每日剂量为30J/cm~2/d。为此，我们建立了一种分析人体皮肤光老化的动物模型。取各组小鼠背部皮肤，进行免疫组织化学、酶谱分析、RT-PCR和培养。对原弹性蛋白、基质金属蛋白酶(MMP2)和MMP9进行分析，发现照射后12个月小鼠成纤维细胞MMP9mRNA表达显著增加。在酶谱中，照射组的MMP9活性高于非照射组。提示MMP9在UVA照射后1年皮肤的发育过程中起着重要的调节作用。皮肤光老化的存在意味着慢性紫外线照射的积累，会影响抗氧化系统。接下来，我们对超氧化物歧化酶在转录水平的表达进行了定量分析，超氧化物歧化酶是抗氧化系统和清除O^-2的代表酶。

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.