Apelin-13 Inhibits the Adhesion of Monocytes to Endothelial Cells via the Gfi1/NF-κB Signaling Pathway.

Oxidized low-density lipoprotein (ox-LDL)-induced endothelial dysregulation and the abnormal interaction between monocytes have been considered key risk factors for atherosclerosis. The study investigated the effects of apelin-13 on ox-LDL-induced endothelial dysfunction in human aortic endothelial cells (HAECs). Cells were stimulated with ox-LDL (100 mg/L), either alone or in combination with apelin-13 at concentrations of 3 and 6 µM. Multiple techniques, including real-time PCR, Western blot analysis, enzyme-linked immunosorbent assay (ELISA), cell attachment assays, and luciferase activity assays, were employed. Our results showed that ox-LDL reduced the expression of the G-protein-coupled apelin receptor (APJ) in HAECs. However, treatment with apelin-13 reduced the expression of lectin-like ox-LDL receptor 1 (LOX-1) against ox-LDL and inhibited the expression of pro-inflammatory cytokines in HAECs. Real-time PCR and ELISA assay demonstrated that apelin-13 also inhibited the expression of cell adhesion molecules intercellular cell adhesion molecule-1 (ICAM-1) and E-selectin. The calcein AM staining method displayed that apelin-13 mitigated ox-LDL-induced attachment of THP-1 monocytes to HAECs. Furthermore, apelin-13 prevented the reduction of growth factor independence-1 (Gfi1) and the activation of NF-κB in HAECs, as evidenced by the luciferase activity assay. Knockdown of Gfi1 counteracted the inhibitory effects of apelin-13 on the attachment of THP-1 monocytes to HAECs, suggesting that the protective effects of apelin-13 in endothelial dysfunction are mediated by the Gfi1/ NF-κB signaling pathway. These findings suggest that apelin-13 may have therapeutic potential in preventing atherosclerosis by improving endothelial function and reducing inflammation.