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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.