AIM:To clarify the effect of miR-519d-3p on high glucose-induced human retinal microvascular endothelial cells(HRMEC)dysfunction and angiogenesis, and to elucidate the regulatory mechanism of miR-519d-3p on hypoxia inducible factor 1 subunit alpha(HIF-1α).METHODS: The normal glucose(NG)and high glucose(HG)cell models were established by inducing HRMEC with 5 and 30 mmol/L glucose, respectively. Control group: HG cell model was transfected with negative control mimics; mannitol group: the control group was added with 25 mmol/L mannitol; miR-519d-3p overexpression group: HG cell model was transfected with miR-519d-3p mimics; miR-519d-3p combined with HIF-1α overexpression group: HG cell model was co-transfected with miR-519d-3p mimics and HIF-1α overexpression vector. The expression of miR-519d-3p in each group was tested by real-time fluorescence quantitative PCR. The expression of HIF-1α protein in each group was tested by Western blotting. The binding sites between miR-519d-3p and HIF-1α were detected by luciferase reporter gene assay. The cell proliferation of each group was detected by CCK-8. The cell apoptosis of each group was tested by Hoechst 33342 staining. The protein expression of extracellular fluid inflammatory factors tumor necrosis factor-α(TNF-α), interleukin(IL)-1β and IL-6 in each group was tested by ELISA. The formation of new capillary lumen-like structures was detected by tubule formation assay.RESULTS: Compared with the NG, miR-519d-3p expression was significantly reduced in the HG cell model, while HIF-1α protein expression was significantly increased in the HG(all P<0.01). Compared with the control group, HIF-1α protein expression was significantly reduced in the miR-519d-3p overexpression group(P<0.01). The “CGUGAAA” sequence of miR-519d-3p could specifically bind to the “GCACUUU” sequence of HIF-1α 3'-untranslated region(3'-UTR). Compared with the control group, the miR-519d-3p overexpression group showed a significant increase in 24, 48 and 72h absorbance values, a significant decrease in cell apoptotic rate, a significant decrease in the concentrations of TNF-α, IL-1β and IL-6, and a significant decrease in the number of new capillary lumen-like structures(all P<0.01). Compared with the miR-519d-3p overexpression group, the miR-519d-3p combined with HIF-1α overexpression group showed a significant decrease in 24, 48 and 72h absorbance values, a significant increase in cell apoptotic rate, a significant increase in the concentrations of TNF-α, IL-1β and IL-6, and a significant increase in the number of new capillary lumen-like structures(all P<0.01). There was no difference between the control group and mannitol group in the comparison of the above indicators(all P>0.05).CONCLUSION: miR-519d-3p expression is down-regulated while HIF-1α protein expression is up-regulated in high glucose induced HRMEC model. HIF-1α is a target gene of miR-519d-3p. The miR-519d-3p targets HIF-1α to increase cell proliferation and reduce cell apoptosis and inflammation, thereby alleviating high glucose-induced HRMEC dysfunction and inhibiting angiogenesis.