Circ_GRN Promotes the Proliferation, Migration, and Inflammation of Vascular Smooth Muscle Cells in Atherosclerosis Through miR-214-3p/FOXO1 Axis

Dysfunction of vascular smooth muscle cells (VSMCs) assumes a fundamental part in the pathogenesis of atherosclerosis (AS). Circular RNA granulin precursor (circ_GRN) was identified to promote the proliferation and invasion of human VSMCs (HVSMCs) in an in vitro AS model. However, the underlying mechanisms remain unclear. Levels of circ_GRN, microRNA (miR)-214-3p, and forkhead box protein O1 (FOXO1) were detected using quantitative real-time polymerase chain reaction and Western blot assays. The proliferation, migration, and inflammatory response of HVSMCs were evaluated by using flow cytometry, colony formation, Cell Counting Kit-8, Western blot, transwell assays, and enzyme-linked immunosorbent assay, respectively. The binding interaction between miR-214-3p and circ_GRN or FOXO1 was detected by dual-luciferase reporter assay. In this study, we found that circ_GRN was elevated in the serum of AS and oxidized low-density lipoprotein (ox-LDL)-induced HVSMCs. The in vitro AS model was established by exposing HVSMCs to ox-LDL, and we found circ_GRN knockdown reversed ox-LDL-evoked cell proliferation, migration, and inflammation. In a mechanical study, miR-214-3p directly bound to circ_GRN or FOXO1, and circ_GRN could regulate FOXO1 expression by competitively binding to miR-214-3p. Importantly, we demonstrated that miR-214-3p inhibition attenuated the protective effects of circ_GRN knockdown on ox-LDL-induced HVSMCs; besides that, miR-214-3p overexpression abolished ox-LDL-triggered HVSMC proliferation, migration, and inflammation, which were counteracted by FOXO1 upregulation. In conclusion, circ_GRN promoted the proliferation, migration, and inflammation of HVSMCs through miR-214-3p/FOXO1 axis in ox-LDL-induced AS model in vitro, suggesting the potential involvement in an AS process, which provided a potential candidate for future clinic intervention in AS.