目的 研究载脂蛋白2(lipocalin 2,Lcn 2)对缺氧诱导视网膜神经节细胞-5(retinal ganglion cells,RGC-5)损伤的抑制作用及可能机制.方法 将RGC-5细胞置于缺氧环境下处理(0h、4h、8h、12 h、24 h、48 h),采用实时定量PCR和Western blot 法检测Lcn 2的表达水平.将细胞分为4组:对照组、缺氧组、siNC+缺氧组(转染siRNA阴性对照后进行缺氧处理24 h)和siL-cn2+缺氧组(细胞转染Lcn 2 siRNA后进行缺氧处理24 h).ELISA检测细胞凋亡率和Caspase-3活性,DCFH-DA试剂盒检测活性氧(reactive oxygen speciesin,ROS)产生情况,线粒体膜电位检测试剂盒评价线粒体膜电势,Western blot检测半胱氨酸天冬氨酸蛋白酶3(cleaved-Caspase-3,c-Caspase-3)、聚腺苷二磷酸核糖聚合酶(cleaved-PARP,c-PARP)、Bax、Bcl-2和细胞色素C(cytochrome C,Cyto C)蛋白表达.结果 与0h组相比,缺氧组(4h、8h、12h、24 h和48 h)Lcn 2 mRNA表达水平均升高(均为P＜0.05),同时缺氧组(12 h、24h和48 h)的Lcn 2蛋白表达水平均较0h组升高(均为P＜0.05).与对照组细胞凋亡率(99.66％±2.86％)比较,缺氧组(138.33％±13.76％)显著升高(P＜0.05);siLcn 2+缺氧组细胞凋亡率(105.02％±8.60％)较siNC+缺氧组(142.33％±6.54％)显著下降(P＜0.05).此外,缺氧组较对照组Caspase-3相对活性增强、c-Caspase-3和c-PARP表达均上调(均为P＜0.05),与siNC+缺氧组比较,siLcn 2+缺氧组Caspase-3相对活性水平、c-Caspase-3和c-PARP相对表达水平均降低(均为P＜0.05).与对照组ROS相对荧光强度(1.03±0.11)比较,缺氧组(4.26±0.63)增强(P＜0.05),siLcn 2+缺氧组ROS相对荧光强度(3.10±0.24)较siNC+缺氧组(4.73±0.26)显著减弱(P＜0.05).且siLen 2+缺氧组较siNC+缺氧组线粒体膜电势增加、Cyto C蛋白表达水平及Bax和Bcl-2相对比率减少(均为P＜0.05).结论 沉默Lcn 2抑制缺氧诱导的细胞凋亡及ROS产生,可能是通过抑制线粒体凋亡信号通路实现的.%Objective To investigate the roles and mechanisms of siRNA targeted lipocalin 2 (Lcn 2) gene silencing on hypoxia-induced cell apoptosis in retinal ganglion cells (RGC-5).Methods RGC-5 cells were subjected to hypoxic condition for various time duration (0 h,4 h,8 h,12 h,24 h,48 h),and quantitative real-time PCR and Western blot were used to evaluate the expression of Lcn 2 in mRNA and protein levels.Cells were divided into 4 groups:control group,hypoxia group,siNC + hypoxia group,in which cells were transfected with negative control for siRNA,and then subjected to hypoxic condition for 24 h,and siLcn 2 + hypoxia group,in which cells were transfected with Lcn 2 siRNA,and then subjected to hypoxic condition for 24 h).Next,cell apoptotic rate and Caspase-3 activity were detected using ELISA.The fluorescence intensity of reactive oxygen species (ROS) was assayed using DCFH-DA kit,and mitochondrial membrane potential assay kit was used to evaluate the mitochondrial membrane potential.Finally,the expression levels of cleaved-Caspase-3 (c-Caspase-3),cleaved-PARP (c-PARP),Bax,Bcl-2 and cytochrome C (Cyto C) were detected using Western blot.Results In the hypoxia group,Lcn 2 mRNA level at 4 h,8 h,12 h,24 h and 48 h was higher than that at 0 h (all P ＜0.05).Meanwhile,Lcn 2 protein level at 12 h,24 h and 48 h was also higher than that at 0 h (all P ＜ 0.05).Cell apoptotic rate in the hypoxia group (138.33％ ± 13.76％) was significantly higher than that in the control group (99.66％ ± 2.86％) (P ＜ 0.05),and siLcn 2 + hypoxia group (105.02％ ± 8.60％) was lower than siNC + hypoxia group (142.33％ ± 6.54％) (P ＜ 0.05).In addition,compared with the control group,the relative activity of Caspase-3 and the relative expression of c-Caspase-3 and c-PARP in the hypoxia group were all upregulated (all P ＜ 0.05);whereas the relative activity of Caspase-3 and the relative expression of c-Caspase-3 and c-PARP in the siLcn2 + hypoxia group were downregulated compared with the siNC + hypoxia group (all P ＜ 0.05).Moreover,the fluorescence intensity of ROS in the hypoxia group (4.26 0.63) was more enhanced than that in the control group (1.03 ± 0.11) (P ＜ 0.05),and the siLcn2 + hypoxia group (3.10 ± 0.24) was lower than siNC + hypoxia group (4.73 ± 0.26) (P ＜ 0.05).Furthermore,mitochondrial membrane potential,Cyto C expression and the relative ratio of Bax to Bcl-2 in the siLcn2 + hypoxia group was lower than those in the siNC + hypoxia group.Conclusion Lcn 2 Lcn2 gene silencing can inhibit cell apoptosis and ROS production induced by hypoxia,which may be achieved by suppressing mitochondrial apoptosis signaling pathway.
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