A Novel circUBR4/miR-491-5p/NRP2 ceRNA Network Regulates Oxidized Low-density Lipoprotein-induced Proliferation and Migration in Vascular Smooth Muscle Cells

Abstract

Vascular smooth muscle cells (VSMCs) play critical roles in the progression of atherosclerosis. Circular RNA (circRNA) ubiquitin protein ligase E3 component n-recognin 4 (circUBR4) has been shown to regulate VSMC migration and proliferation. In this study, we sought to identify the mechanism in the regulation of circUBR4. CircUBR4, microRNA (miR)-491-5p, and Neuropilin-2 (NRP2) were quantified by quantitative real-time polymerase chain reaction (PCR) and western blot. Cell proliferation was evaluated by Cell Counting Kit-8 and 5-Ethynyl-2'-Deoxyuridine assays. Cell migration was examined by wound-healing and transwell invasion assays. The direct relationship between miR-491-5p and circUBR4 or NRP2 was validated by dual-luciferase reporter and RNA immunoprecipitation assays. Our data indicated that in VSMCs, ox-LDL induced circUBR4 expression. Silencing endogenous circUBR4 attenuated VSMC proliferation and migration induced by ox-LDL. Mechanistically, circUBR4 targeted miR-491-5p by pairing to miR-491-5p. Moreover, miR-491-5p was identified as a downstream mediator of circUBR4 function in ox-LDL-treated VSMCs. NRP2 was a direct target of miR-491-5p, and circUBR4 acted as a competing endogenous RNA for miR-491-5p to regulate NRP2 expression. In addition, NRP2 was a functionally downstream effector of miR-491-5p in regulating ox-LDL-evoked VSMC proliferation and migration. Our findings identify a new competing endogenous RNA network, the circUBR4/miR-491-5p/NRP2 axis, for the regulation of circUBR4 in VSMC migration and proliferation.