Regulatory mechanism of DDX5 in ox-LDL-induced endothelial cell injury through the miR-640/SOX6 axis.

Background: Endothelial dysfunction is an early and pre-clinical manifestation of coronary heart disease (CHD).

Objective: This study investigates the role of DDX5 in oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell injury to confer novel targets for the treatment of CHD.

Methods: Endothelial cells were induced by ox-LDL. DDX5, pri-miR-640, pre-miR-640, miR-640, and SOX6 expressions were analyzed by RT-qPCR and Western blot. DDX5 expression was intervened by shRNA, followed by CCK-8 analysis of proliferation, flow cytometry detection of apoptosis, and tube formation assay analysis of angiogenic potential of cells. The binding between DDX5 and pri-miR-640 was determined by RIP, and the pri-miR-640 RNA stability was measured after actinomycin D treatment. Dual-luciferase assay verified the targeting relationship between miR-640 and SOX6.

Results: DDX5 and miR-640 were highly expressed while SOX6 was poorly expressed in ox-LDL-induced endothelial cells. Silence of DDX5 augmented cell proliferation, abated apoptosis, and facilitated angiogenesis. Mechanistically, RNA binding protein DDX5 elevated miR-640 expression by weakening the degradation of pri-miR-640, thereby reducing SOX6 expression. Combined experimental results indicated that overexpression of miR-640 or low expression of SOX6 offset the protective effect of DDX5 silencing on cell injury.

Conclusion: DDX5 elevates miR-640 expression by repressing the degradation of pri-miR-640 and then reduces SOX6 expression, thus exacerbating ox-LDL-induced endothelial cell injury.