Up-regulation of microRNA-503 by high glucose reduces the migration and proliferation but promotes the apoptosis of human umbilical vein endothelial cells by inhibiting the expression of insulin-like growth factor-1 receptor

OBJECTIVE: The present study is aimed to investigate the regulatory effect of microRNA (miRNA or miR)-503 on endothelial functions, as well as the mechanism by which high glucose leads to injury of endothelial cells.

MATERIALS AND METHODS: When reaching 80% confluency, human umbilical vein endothelial cells (HUVECs) were subjected to non-serum synchronization for 12 h, and medium of cells in high-glucose (HG) group was replaced by normal medium supplemented with 25 mmol/L D-glucose. HUVECs cultured in normal glucose (NG) medium were used as control. To overexpress miR-503, HUVECs were transfected with miR-503 mimics. To silence insulin-like growth factor-1 receptor (IGF-1R) mRNA, HUVECs were transfected with small interfering RNA (siRNA). To predict whether miR-503 targets IGF-1R, bioinformatics was performed. Quantitative Real-time polymerase chain reaction was used to determine miR-503 and IGF-1R mRNA expression, and Western blotting was employed to measure IGF-1R protein expression. Cell-Counting Kit 8 assay was used to determine HUVECs proliferation, while wound-healing assay was used to evaluate HUVECs migration. HUVECs apoptosis was investigated by measuring caspase 3 activity.

RESULTS: Expression of IGF-1R in HUVECs in high glucose was decreased compared to that in normal glucose. miR-503 was predicted to target IGF-1R mRNA, and miR-503 expression in HUVECs in high glucose was higher than that in normal glucose. Overexpression of miR-503 inhibited the transcription and the translation of IGF-1R gene reducing migration, suppressed proliferation and promoted apoptosis. Transfection with IGF-1R siRNA decreased IGF-1R protein expression in HUVECs. Down-regulated IGF-1R expression reduced migration and proliferation, but promoted apoptosis of HUVECs.

CONCLUSIONS: The present study demonstrates that miR-503 expression in HUVECs is elevated in high glucose condition. Also, miR-503 reduces migration and proliferation, but promotes apoptosis of HUVECs by inhibiting IGF-1R expression.

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