Correlation Between Apelin and Collateral Circulation in Patients with Middle Cerebral Artery Occlusion and Moyamoya Disease

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.

RUNX3-activated apelin signaling inhibits cell proliferation and fibrosis in diabetic nephropathy by regulation of the SIRT1/FOXO pathway

BACKGROUND

Diabetic nephropathy is a major secondary cause of end-stage renal disease. Apelin plays an important role in the development of DN. Understanding the exact mechanism of Apelin can help expand the means of treating DN.

METHODS

Male C57BL/6 mice was used and STZ treatment was implemented for DN model establishment. Lentivirus systems including Lv-sh-RUNX3 and Lv-Apelin were obtained to knockdown RUNX3 and overexpress Apelin, respectively. A total of 36 mice were divided into 6 groups (n = 6 in each group): control, DN, DN + LV-Vector, DN + Lv-Apelin, DN + LV-Apelin + LV-sh-NC and DN + Lv-Apelin + Lv-sh-RUNX3 group. In vitro studies were performed using mesangial cells. Cell viability and proliferation was assessed through CCK8 and EDU analysis. Hematoxylin and eosin staining as well as Masson staining was implemented for histological evaluation. RT-qPCR was conducted for measuring relative mRNA levels, and protein expression was detected by western blotting. The interaction between SIRT1 and FOXO were verified by co-immunoprecipitations, and relations between RUNX3 and Apelin were demonstrated by dual luciferase report and chromatin immunoprecipitation.

RESULTS

The DN group exhibited significantly lower Apelin expression compared to control (p < 0.05). Apelin overexpression markedly improved blood glucose, renal function indicators, ameliorated renal fibrosis and reduced fibrotic factor expression (p < 0.05) in the DN group, accompanied by elevated sirt1 levels and diminished acetylated FOXO1/FOXO3a (p < 0.05). However, RUNX3 knockdown combined with Apelin overexpression abrogated these beneficial effects, leading to impaired renal function, exacerbated fibrosis, increased fibrotic factor expression and acetylated FOXO1/FOXO3a versus Apelin overexpression alone (p < 0.05). In mesangial cells under high glucose, Apelin overexpression significantly inhibited cell proliferation and fibrotic factor production (p < 0.05). Conversely, RUNX3 interference enhanced cell proliferation and the secretion of fibrotic factors. (p < 0.05). Remarkably, combining Apelin overexpression with RUNX3 interference reversed the proliferation and fibrosis induced by RUNX3 interference (p < 0.05). Mechanistic studies revealed RUNX3 binds to the Apelin promoter, with the 467-489 bp site1 as the primary binding region, and SIRT1 physically interacts with FOXO1 and FOXO3a in mesangial cells.

CONCLUSION

RUNX3 activated Apelin and regulated the SIRT1/FOXO signaling pathway, resulting in the suppressed cell proliferation and fibrosis in diabetic nephropathy. Apelin is a promising endogenous therapeutic target for anti-renal injury and anti-fibrosis in diabetic nephropathy. RUNX3 may serve as an endogenous intervention target for diseases related to Apelin deficiency.

The beneficial roles of apelin-13/APJ system in cerebral ischemia: Pathogenesis and therapeutic strategies

The incidence of cerebral ischemia has increased in the past decades, and the high fatality and disability rates seriously affect human health. Apelin is a bioactive peptide and the ligand of the G protein-coupled receptor APJ. Both are ubiquitously expressed in the peripheral and central nervous systems, and regulate various physiological and pathological process in the cardiovascular, nervous and endocrine systems. Apelin-13 is one of the subtypes of apelin, and the apelin-13/APJ signaling pathway protects against cerebral ischemia by promoting angiogenesis, inhibiting excitotoxicity and stabilizing atherosclerotic plaques. In this review, we have discussed the role of apelin-13 in the regulation of cerebral ischemia and the underlying mechanisms, along with the therapeutic potential of the apelin-13/APJ signaling pathway in cerebral ischemia.