紫外线诱导小鼠角膜核因子-κB及肿瘤坏死因子-α的表达

目的:探讨紫外线B光(UVB)照射小鼠角膜后核转录因子(NF-κB)、肿瘤坏死因子-α(TNF-α)的表达变化及NF-κB在角膜损伤中的意义。方法:ICR小鼠随机分为对照组、低剂量UVB照射组(300mJ/cm2)及高剂量UVB照射组(1200mJ/cm2),裂隙灯下观察角膜病变,评分以判断角膜损伤程度。UVB照射后不同时间点(6h、24h及72h)分别取角膜,凝胶电泳迁移法(EMSA)检测角膜NF-κB的活性,酶联免疫吸附(ELISA)测定角膜TNF-α的表达水平,光镜及电镜检查角膜的病理改变。结果:低剂量照射组角膜基质轻度水肿,在72h内基本消退,高剂量照射组角膜基质混浊明显增强且持久。正常对照组小鼠角膜NF-κB的活性水平低,照射组角膜组织出现NF-κB表达的活化,并随剂量的增加活性明显增加,不同剂量组间差异有显著统计学意义。同时,照射后角膜组织TNF-α的表达也明显增强,其变化趋势与NF-κB的活性变化类似。电镜显示低剂量组仅角膜上皮及浅层基质细胞受损,高剂量组角膜损伤累积全基质细胞及内皮细胞。结论:UVB照射小鼠角膜后激活NF-κB,并引发促炎性细胞因子TNF-α的表达。随着角膜损伤程度的加重,NF-κB的活性水平增强,提示NF-κB的激活可能在紫外线造成的角膜损伤中起着重要的作用

Ultraviolet B Irradiation Induces NF-κB Activation and Tumor Necrosis Factor-α Production in Mouse Cornea

PURPOSE: To evaluate the activation of nuclear factor-kappaB (NF-kappaB) and expression of tumor necrosis factor (TNF)-alpha in mouse cornea following different doses of ultraviolet-B (UVB) irradiation and to demonstrate the potential role of NF-kappaB in the corneal damage. METHODS: ICR mice were randomly divided into control group, mice irradiated by low dose (300 mJ/cm2) and high dose (1200 mJ/cm2) of UVB group. The mouse corneas were observed under a slit lamp microscope, and corneal opacity was graded to evaluate corneal damage. Then the mice were sacrificed at time points varying from 6 hours to 72 hours after treatment and then corneas were excised. Translocation of NF-kappaB was examined by electrophoretic mobility shift assay (EMSA). TNF-alpha production was measured by enzyme-linked immunosorbant assay (ELISA). Moreover, eyes were harvested for routine histological analysis and electron microscopy. RESULTS: Mild corneal edema was observed after low-dose of UVB irradiation, and resolved after 72 hours.However, significant and persistent corneal edema was observed after high dose of UVB irradiation. EMSA results showed that the marked increased activation of NF-kappaB after UVB irradiation, compared with the control group. The level of activity of NF-kappaB was enhanced as the radiant exposure increased. The significance was statistically different at each time point between groups. ELISA showed rapid production of high levels of TNF-alpha concomitant with the up-regulation of NF-kappaB. Histological findings by electron microscopy demonstrated only damage of corneal epithelial cell and superficial keratocytes in low-dose group. Ultrastructural morphology in high-dose group showed deeper damage including keratocytes throughout the whole stroma and endothelial cells. CONCLUSIONS: These results suggest that acute ultraviolet exposure induces the activation of NF-kappaB which results in the production of proinflammatory cytokines such as TNF-alpha. Moreover, the up-regulated NF-KB activation was concomitant with the enhanced corneal damage. These findings imply that NF-kappaB may play an important role in the pathogenesis of UV-induced damage of cornea.