Chronic hypoxia is a common inducer of end-stage cardiovascular disease. In cells under hypoxia, the hypoxia-inducible factor-1 (HIF-1) plays a vital role in regulating downstream target genes. However, the mechanism of hypoxia in cardiomyocytes is still unclear. In this study, we aimed to identify novel downstream epigenetic targets of HIF-1α in cardiomyocytes under hypoxia. H9c2 cells were exposed to hypoxia condition, and quantitative real-time PCR analysis was performed to evaluate the expression of miR-20b-5p. The results indicated that the expression of miR-20b-5p was down-regulated in H9c2 cells under low oxygen condition. Meanwhile, HIF-1α overexpression further down-regulated the miR-20b-5p expression in H9c2 cells transfected with HIF-1α plasmids. In addition, Annexin-V-FITC/PI flow cytometry analysis suggested that overexpression of miR-20b-5p attenuated cell apoptosis under hypoxia condition in H9c2 cells. Western blot analysis showed that the hypoxia apparently increased Bax and cleaved-caspase-3, but decreased Bcl-2 expression in H9c2 cells, indicating that hypoxia-induced NF-κB signaling pathway activation is mediated by miR-20b-5p. Hypoxia-induced H9c2 cell apoptosis was reduced after HIF-1α knockdown as shown by the flow cytometry analysis. In conclusion, we identified that miR-20b-5p plays an important role in mediating cardiomyocytes apoptosis under hypoxia, which is mediated by the HIF-1/NF-κB signaling pathway.

中文翻译：

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miR-20b-5p通过HIF-1α/NF-κB途径减弱缺氧诱导的心肌细胞凋亡。

慢性低氧是终末期心血管疾病的常见诱因。在低氧条件下的细胞中，低氧诱导因子-1（HIF-1）在调节下游靶基因中起着至关重要的作用。但是，心肌细胞缺氧的机制仍不清楚。在这项研究中，我们旨在确定缺氧条件下心肌细胞中HIF-1α的新型下游表观遗传学靶标。将H9c2细胞暴露于缺氧条件下，并进行定量实时PCR分析以评估miR-20b-5p的表达。结果表明在低氧条件下，miR-20b-5p在H9c2细胞中的表达下调。同时，HIF-1α的过表达进一步下调了转染HIF-1α质粒的H9c2细胞中miR-20b-5p的表达。此外，Annexin-V-FITC / PI流式细胞仪分析表明，miR-20b-5p的过表达减弱了H9c2细胞在缺氧条件下的细胞凋亡。Western印迹分析表明，低氧明显增加了Haxc9细胞中的Bax和裂解的caspase-3，但降低了Bcl-2的表达，表明低氧诱导的NF-κB信号通路的激活是由miR-20b-5p介导的。流式细胞术分析显示，HIF-1α敲低后，低氧诱导的H9c2细胞凋亡减少。总之，我们确定miR-20b-5p在缺氧条件下介导心肌细胞凋亡中起重要作用，缺氧是由HIF-1 /NF-κB信号通路介导的。但在H9c2细胞中Bcl-2表达降低，表明低氧诱导的NF-κB信号通路激活是由miR-20b-5p介导的。流式细胞术分析显示，HIF-1α敲低后，低氧诱导的H9c2细胞凋亡减少。总之，我们确定miR-20b-5p在缺氧条件下介导心肌细胞凋亡中起重要作用，缺氧是由HIF-1 /NF-κB信号通路介导的。但在H9c2细胞中Bcl-2表达降低，表明低氧诱导的NF-κB信号通路激活是由miR-20b-5p介导的。流式细胞术分析显示，HIF-1α敲低后，低氧诱导的H9c2细胞凋亡减少。总之，我们确定miR-20b-5p在缺氧条件下介导心肌细胞凋亡中起重要作用，缺氧是由HIF-1 /NF-κB信号通路介导的。