小剂量长波紫外线多次照射对人体皮肤的影响

Effects of repeated low-dose UVA irradiation on human skin

目的:研究小剂量长波紫外线(UVA)辐射对人体皮肤的累积效应。方法:以10名志愿者的臀部作为受试部位,共分为3个区域:阴性对照区域,不进行照射;小剂量照射区域和阳性对照区域分别进行UVA照射,每周照射3次,连续13周,共39次。其中小剂量照射区域的累积剂量为50 J/cm^2;阳性对照区域的累积剂量为1 000J/cm^2。照射前后测定皮肤角质层含水量、经皮水分丢失(transepidermal water loss,TEWL)、pH值、皮肤颜色的L~*a~*b~*值和M、E值。取照射区皮肤组织进行苏木精-伊红染色、弹性纤维染色和免疫组化染色,观察表皮、角质层厚度、胶原纤维、弹性纤维的变化、基质金属蛋白酶(MMP)-1和人类长寿基因SIRT1的蛋白表达产物在UVA照射后的变化。结果:小剂量照射区域角质层含水量有下降趋势,TEWL有增加趋势,L~*值下降、M、a~*、E值升高,pH值无明显变化。皮肤的角质层和表皮厚度增加,真皮中的胶原纤维细碎、淡染,弹性纤维片断化。MMP-1和SIRT1的表达增加。结论:小剂量UVA照射可以引起皮肤光老化。

Objective： To investigate the accumulative effects of low-dose UVA irradiation on human skin. Methods： Ten subjects were tested on three sites of the buttocks：negative control sites,without UVA exposure; low-dose UVA exposure sites, with an accumulative dose of 50 J/cruZ; and positive control sites with an accumulative dose of 1 000 J/cm^2.Each UVA exposure site was exposed to UVA irradiation three times a week for 13 weeks. The water content of stratum eorneum, transepidermal water loss （TEWL）, skin pH, and the indices for skin color （value L^＊a^＊b^＊, value M, and value E） were measured before and after UVA irradiation. Skin biopsies were taken for H-E staining, elastic fiber staining, and immunohistochemistry staining after the final UVA irradiation to investigate the thickness of the stratum corneum and the epidermis, the changes of collagen and elastic fibers and the expression of MMP-1 and SIRT1. Results： After long term low-dose UVA irradiation, the water content of stratum eornemn and the value L^＊ were decreased. Meanwhile, there was an increase of value M, value a^＊ and value E, as well as TEWL, but no significant change of pH value. Histologically, thickened stratum corneum and epidermis, lightly stained collagen fibers and broken elastic fibers were seen in the dermis. The expression of MMP-1 and SIRT1 increased. Conclusion： Low -dose UVA irradiation could result in the photo aging of the skin.