角膜基质细胞Nrf2-ARE信号通路活化缺陷在圆锥角膜发病中的作用

摘要

Background Recent researches show that oxidative stress is involved in the progress of keratoconus.Nuclear factor-E2-related factor 2-antioxidant response element (Nrf2-ARE) pathway plays a critical role in the defense against oxidative stress,but its function in keratoconus is unclear.Objective To investigate the differences of Nrf2-ARE signaling activation and matrix degenerating enzymes between keratoconus and normal corneal stromal cells.Methods Corneal stromal cells were isolated from keratoconus and normal cornea by using dispase and collagenase digestion.The cells were treated with hydrogen peroxide (H2O2) to mimic in vivo oxidative stress condition.Reactive oxygen species (ROS) production was measured by fluorescence substrate DCHF-DA incubation.Nrf2 level and the expression of Nrf2-ARE downstream antioxidant genes were analyzed by Western blot and real-time quantitative-PCR(RT-qPCR).The activity of matrix degenerating enzymes,including urokinase-type plasminogen activator (uPA)-uPA receptor (uPAR) system and matrix metalloproteinase-2 (MMP-2) were assessed by Western blot and gelatin zymography respectively.Results In normal culture,keratoconus corneal stromal cells assumed increased basal ROS and Nrf2 level when compared with normal cells(t =18.155,P＜0.01).However,after H2O2 treatment,the keratoconus corneal stromal cells showed increased ROS production,while decreased Nrf2 translocation and no significant difference in expression levels of Nrf2-ARE downstream antioxidant genes (Nrf2:t =62.123,P＜ 0.01 ; (nicotinamide adenine dinucleotide phosphate quinine oxidoreductase-1 [NQO-1]:t =2.209,P =0.092 ; hemo oxygenase-1 [HO-1]:t =0.293,P =0.784 ; superoxide dismutase [SOD2]:t =0.749,P =0.495).The contents of uPA-uPAR and the activity of MMP-2 also showed a higher level in keratoconus corneal stromal cells than normal cells,with significant differences between them (t =19.164,15.458,4.818,all at P＜0.01).Conclusions The defect of Nrf2-ARE signaling activation exists in the keratoconus corneal stromal cells,and correlats with the abnormal expression level of stromal degeneration enzymes,which suggests that the defect of Nrf2-ARE signaling activation may be involved in the progression of keratoconus.%背景 氧化应激在圆锥角膜发病过程中具有重要的作用,核因子E2相关因子2-抗氧化反应元件(Nrf2-ARE)信号通路是介导细胞氧化应激反应的关键通路,但其在圆锥角膜发病中的作用及其机制鲜见报道. 目的 研究正常角膜与圆锥角膜基质细胞中Nrf2-ARE信号通路活化的区别及Nrf2-ARE通路对角膜基质降解酶表达水平的影响,探讨圆锥角膜发病的具体机制.方法 于2012年11月至2013年6月在青岛眼科医院收集圆锥角膜患者术中的角膜组织样本和正常供体角膜样本,采用中性蛋白酶和胶原蛋白酶联合消化法分离角膜基质细胞并用含质量分数10％胎牛血清的DMEM/F12培养基培养细胞,待细胞80％融合后在培养基中加入200 μmol/L H2O2处理1h以模拟氧化应激微环境.采用DCFH-DA荧光底物孵育法检测细胞内活性氧簇(ROS)含量,分别采用Western blot和实时定量PCR法检测细胞核内Nrf2mRNA及其蛋白、Nrf2-ARE信号通路下游抗氧化蛋白、尿激酶型纤溶酶原激活物(uPA)、uPA受体(uPAR) mRNA及其蛋白的相对表达水平,采用明胶酶谱法检测细胞中基质金属蛋白酶2(MMP-2)活性.结果 正常培养条件下,圆锥角膜基质细胞中ROS荧光强于正常角膜基质细胞,细胞核内Nrf2蛋白表达水平均明显高于正常角膜基质细胞,差异有统计学意义(t=18.155,P＜0.01),但在H2O2处理条件下,圆锥角膜基质细胞中ROS荧光强度明显强于正常角膜基质细胞,且圆锥角膜基质细胞核内Nrf2表达水平明显低于正常培养条件下的圆锥角膜基质细胞,差异有统计学意义(t=62.123,P＜0.01).正常培养条件下,圆锥角膜基质细胞间还原型烟酰胺腺嘌呤二核苷酸磷酸氧化还原酶1(NQO-1)、血红素氧合酶1(HO-1)、超氧化物歧化酶2(SOD2) mRNA及其蛋白的相对表达量明显低于正常角膜基质细胞,差异均有统计学意义(均P＜0.01);但在H2O2培养条件下2种细胞间未见明显变化(NQO-1:t=2.209,P=0.092;HO-1:t=0.293,P=0.784;SOD2:t=0.749,P=0.495);圆锥角膜基质细胞uPA、uPAR表达量和MMP-2活性均明显高于正常角膜基质细胞,差异均有统计学意义(t=19.164、15.458、4.818,均P＜0.01). 结论 圆锥角膜基质细胞在Nrf2-ARE信号通路活化方面存在缺陷,且这种缺陷与其表达基质降解酶的水平密切相关,说明该通路异常可能是圆锥角膜发病的机制之一.