Downregulation of miRNA-328 promotes the angiogenesis of HUVECs by regulating the PIM1 and AKT/mTOR signaling pathway under high glucose and low serum condition

Vascular complications are the primary reason for disability and mortality associated with diabetes mellitus (DM), and numerous microRNAs (miRNAs/miRs) are involved in the process, such as miR-122, miR-24 and miR-423. It has been reported that miR-328 regulates DM and cardiovascular disease; however, the role and mechanism of action underlying miR-328 in HUVECs is not completely understood. The present study aimed to investigate the role and mechanism of action underlying the effects of miR-328 on the functions of HUVECs. To simulate hyperglycemia combined with ischemia-induced tissue starvation, HUVECs were cultured in endothelial cell medium with 25 mmol/l D-glucose and 2% FBS for 24 h [high glucose (HG) + 2% FBS group]. HUVEC miR-328 expression levels were detected by reverse transcription-quantitative PCR. Cell migration, cytotoxicity and tube-like structure formation were analyzed using wound healing, Cell Counting Kit-8 and tube formation assays, respectively. Following transfection with miR-328 inhibitor, miR-328 expression was downregulated in HUVECs. Protein expression levels were determined by western blotting. Compared with the control group, the migration and tube-like structure formation of HUVECs were decreased, and cell cytotoxicity was increased in the HG + 2% FBS group. The protein expression levels of vascular endothelial growth factor were also decreased, and the expression levels of miRNA-328 in the HG + 2% FBS group were increased compared with the control group. However, miRNA-328 downregulation reversed the aforementioned effects. Further experiments indicated that the AKT signaling pathway was inhibited in the HG + 2% FBS group; however, miR-328 downregulation activated the AKT/mTOR signaling pathway, which was blocked by the AKT signaling pathway inhibitor, perifosine. Gene prediction and western blotting demonstrated that miR-328 displayed a regulatory role via Pim-1 proto-oncogene, serine/threonine kinase (PIM1). In conclusion, miR-328 expression was upregulated and angiogenesis was inhibited when HUVECs were subjected to high glucose and low serum conditions. miR-328 downregulation enhanced angiogenesis by increasing PIM1 expression and activating the AKT/mTOR signaling pathway in HUVECs under high glucose and low serum conditions.