低剂量长波紫外线诱导培养人皮肤角质形成细胞适应性反应观察

The adaptation reaction of human keratinocytes induced by low dose UVA irradiation

目的:观察低剂量长波紫外线(UVA)诱导培养人皮肤角质形成细胞适应性反应的程度及特点,探讨其对皮肤可能的保护作用。方法:以具有致死作用的86.4J/cm2UVA照射经7.2J/cm2低剂量UVA单次或多次预照射培养的人皮肤角质形成细胞,并在光镜、电镜下观察细胞形态学变化,用流式细胞仪检测细胞凋亡的比例,单细胞凝胶电泳检测DNA损伤的程度。结果:单次或多次7.2J/cm2UVA预照射处理后的培养人皮肤角质形成细胞,对随后86.4J/cm2UVA照射诱导的相应细胞在形态学上的毒性反应减轻,细胞凋亡的比例下降、DNA链断裂减少及修复加快,和未经预处理的86.4J/cm2UVA照射的相应细胞比较差异均有显著性(P<0.01或P<0.001);单次7.2J/cm2的UVA预照射诱导培养的人皮肤角质形成细胞的适应性反应在预照射12h后消失,而当低剂量UVA预照射的累积剂量>28.8J/cm2时,预照射的培养细胞即使是14d后,对86.4J/cm2UVA照射仍有明显的防护作用。结论:低剂量UVA照射可诱导培养的人皮肤角质形成细胞出现对随后高剂量UVA照射的适应性反应,其滞留期及强度与低剂量UVA预照射的累积剂量有关。

Objective: To investigate the extent and features of the adaptation reaction induced by low dose UVA irradiation. Methods: Cultured skin keratinocytes were irradiated by a lethal dose of UVA (86.4 J/cm2) with or without pre-irradiation of single or repetitive low dose of UVA (7.2 J/cm2). The cellular morphology was observed by light microscope and electron microscope. Proportion of cellular apoptosis was assayed by flow cytometer. The extent of DNA damage was determined by single cell gel electrophoresis (SCGE). Results: In cultured skin keratinocytes, pretreatment with single or repetitive irradiation of 7.2 J/cm2 UVA could relieve toxic reaction of cellular morphology, decrease apoptosis ratio, reduce DNA chain breakages and accelerate DNA repair caused by sequential 86.4J/cm2 UVA irradiation. Compared with non-pretreatment groups, the differences were statistically significant(P < 0.01 or P < 0.001). The adaptation reaction induced by pretreatment of single irradiation of 7.2 J/cm2 UVA eliminated 12h after pretreatment. However, when low dose of UVA irradiation was accumulated to 28.8 J/cm2 ,the cells pretreated with such a low dose of UVA irradiation could prevent photodamage of 86.4 J/cm2 UVA irradiation even 14 d after the irradiation. Conclusions: Low dose UVA irradiation could induce adaptation reaction and protect cultured skin keratinocytes from the subsequent challenge dose of UVA damages. The duration and protective capability of the adaptive reaction are obviously related to the accumulated dose of low dose UVA irradiation.