Although much has been determined about the molecular mechanisms of hexavalent chromium [Cr(VI)]-induced hepatotoxicity, more remains to be explored. In particular, explicit epigenetic alterations of microRNAs (miRNAs) which can negatively regulate mRNAs at post transcriptional level remain understudied. In the present study, cell apoptosis was determined using Annexin V/propidium iodide (PI) staining, while proliferative growth was analyzed by colony formation assay and proliferating cell nuclear antigen (PCNA) detection. miRNA microarray was performed to compare the global miRNAs expression patterns. miR-21-5p mimics (mi)/inhibitor (in), and PDCD4-siRNAs were transfected into L02 hepatocytes. Our results revealed that Cr(VI) induced apoptosis and inhibited proliferation in L02 hepatocytes via reactive oxygen species (ROS), the formation of which is closely related to mitochondrial damage, especially the inhibition of mitochondrial respiratory chain complex (MRCC). We also confirmed that ROS-mediated miR-21-5p inhibition participated in cell apoptosis and proliferative inhibition induced by Cr(VI). Furthermore, programmed cell death protein 4 (PDCD4), the up-regulation of which was related to ROS over-production, was predicted and verified as a target of miR-21-5p. Transcription factor PDCD4 silencing suppressed apoptosis and stimulated cell proliferation. In conclusion, from the perspective of epigenetics, the present study revealed that ROS-mediated miR-21-5p regulated the proliferation and apoptosis of Cr(VI)-exposed L02 hepatocytes via targeting PDCD4, which provided the new targets for molecular intervention and treatment of liver damage in Cr(VI)-exposed population.

中文翻译：

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ROS介导的miR-21-5p通过靶向PDCD4调节Cr（VI）暴露的L02肝细胞的增殖和凋亡。

尽管已经对六价铬[Cr（VI）]诱导的肝毒性的分子机制进行了很​​多研究，但仍有更多的探索空间。特别是，仍然可以研究在转录后水平上可以负调控mRNA的microRNA（miRNA）的显性表观遗传学变化。在本研究中，使用膜联蛋白V /碘化丙啶（PI）染色确定细胞凋亡，同时通过菌落形成分析和增殖细胞核抗原（PCNA）检测来分析增殖生长。进行miRNA芯片比较全局miRNA的表达模式。将miR-21-5p模拟物（mi）/抑制剂（in）和PDCD4-siRNA转染到L02肝细胞中。我们的研究结果表明，Cr（VI）通过活性氧（ROS）诱导L02肝细胞凋亡并抑制其增殖，其形成与线粒体损伤特别是抑制线粒体呼吸链复合物（MRCC）密切相关。我们还证实了ROS介导的miR-21-5p抑制参与了由Cr（VI）诱导的细胞凋亡和增殖抑制。此外，预测并证实其上调与ROS过量产生有关的程序性细胞死亡蛋白4（PDCD4）是miR-21-5p的靶标。转录因子PDCD4沉默抑制凋亡并刺激细胞增殖。总之，从表观遗传学的角度来看，本研究表明，ROS介导的miR-21-5p通过靶向PDCD4来调节Cr（VI）暴露的L02肝细胞的增殖和凋亡，