Oxidized low-density lipoprotein contributes to injury of endothelial cells via the circ_0090231/miR-9-5p/TXNIP axis

Atherosclerosis (AS) has been reported to induce severe clinical complications. Circular RNA (circRNA) circ_0090231 was found to be aberrantly overexpressed in oxidized low-density lipoprotein (ox-LDL)-induced endothelial cells. This study was designed to explore the role and mechanism of circ_0090231 in ox-LDL-triggered endothelial cell injury in AS. Circ_0090231, microRNA-9-5p (miR-9-5p), and thioredoxin interacting protein (TXNIP) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, angiogenesis, and apoptosis were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), tube formation, and flow cytometry assay. Bcl-2, Bax, and TXNIP protein levels were gauged by western blot assay. Malondialdehyde (MDA), lactate dehydrogenase (LDH), and superoxide dismutase (SOD) activity were determined by special kits. Tumor necrosis factor  (TNF-), interleukin-1 (IL-1), and interleukin 6 (IL-6) levels were analyzed using enzyme-linked immunosorbent assay (ELISA) kits. The binding relationship between miR-9-5p and circ_0090231 or TXNIP was predicted by starBase, and then verified by a dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Circ_0090231 and TXNIP were increased, and miR-9-5p was decreased in ox-LDL-treated HUVECs. Moreover, circ_0090231 knockdown mitigated ox-LDL-induced HUVEC injury by boosting angiogenesis, oxidative stress, and inflammation, and hindering apoptosis. The mechanical analysis revealed that circ_0090231 acted as a sponge of miR-9-5p to regulate TXNIP expression. Circ_0090231 could attenuate ox-LDL-mediated HUVEC damage by the miR-9-5p/TXNIP axis, providing a promising therapeutic strategy for AS treatment.