图1 免疫印迹检测OGG1的过表达及OGG1对beas-2b细胞ROS的影响
注:A:荧光显微镜拍摄单细胞凝胶电泳荧光图,彗星尾巴的长度和体积代表DNA损伤程度。B:彗星实验统计结果(结果重复三次),OGG1对PM2.5造成的beas-2b细胞DNA损伤具有显著的修复作用(vs NC+PM2.5 * *p<001)
图2 彗星实验检测OGG1对PM2.5造成beas-2b细胞DNA损伤的修复作用
3 讨论
近些年来,随着工业的发展和机动车的增加,空气污染越来越严重。作为空气质量最重要的指标,PM2.5指数已经在全国各大城市实行了实时监测。国内最近统计研究表明,恶性肿瘤中肺癌的死亡病例数排第一位[14],越来越多的研究表明,PM2.5与哮喘、肺癌等一系列的肺部疾病的产生存在相关性。本实验研究表明,PM2.5能够诱导细胞内活性氧的产生,能够导致细胞DNA的损伤,这与之前的研究报道一致[15-16]。不同来源的PM2.5的成分已经被研究得非常清楚,主要是多环芳烃(PAHs)和过渡金属元素[17],随着对PM2.5研究的深入,如何保护机体、减少PM2.5对机体造成的损伤显得非常重要。
OGG1是非常重要的碱基切除修复酶之一,在清除8-oxoG,保护细胞功能方面发挥重要的作用。研究表明细胞核中的OGG1的表达和蛋白活性都高于线粒体,线粒体中的氧化损伤和突变积累比细胞核更快。
致癌物苯并芘Bap是多环芳烃的重要成分之一,有研究表明Bap能够降低OGG1的活性,诱导肺癌的产生[18],也有研究表重金属导致的基因突变与OGG1的活性降低有关[19],因此PM2.5的致癌很可能与PM2.5降低OGG1的活性相关。
本研究表明,OGG1的过表达对PM2.5造成的DNA损伤有明显的修复和减轻作用,但对于该修复和保护作用的具体分子机制还没有研究清楚,可能是和清除细胞内的ROS、保护线粒体的功能相关,PM2.5是如何对线粒体造成的损伤以及OGG1保护线粒体功能的分子机制需要后续试验进行验证。而基于OGG1对PM2.5造成的DNA损伤有明显的修复和减轻作用,OGG1可能成为PM2.5导致的肺部疾病的一个治疗靶点。
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