Salidroside inhibits endothelial‑mesenchymal transition via the KLF4/eNOS signaling pathway

Homocysteine (Hcy) was discovered to be an independent risk factor for the development of atherosclerosis (AS). Moreover, endothelial‑mesenchymal transition (EndMT) was found to be one of main mechanisms contributing to the pathogenesis of AS. Salidroside (SAL) has diverse pharmacological activities, including anti‑inflammatory, anti‑cancer, anti‑oxidative and anti‑fibrosis properties. However, whether SAL serves a beneficial role in Hcy‑induced EndMT remains unknown. The present study aimed to investigate whether SAL exerted its effects on Hcy‑induced EndMT via the Kruppel‑like factor 4 (KLF4)/endothelial nitric oxide (NO) synthase (eNOS) signaling pathway. HUVECs were pretreated with high and low doses (10 or 50 µmol/l) of SAL for 2 h, followed by 1 mmol/l Hcy for 48 h to induce EndMT. Western blotting was used to analyze the protein expression levels of the endothelial marker, VE‑cadherin, the mesenchymal cell marker, α‑smooth muscle actin (SMA), and the nuclear transcription factors, KLF4 and eNOS. Wound healing assays were used to determine the cell migratory ability, and the levels of NO in the cell culture supernatants were measured using a nitrate reductase assay. Cellular immunofluorescence was used to analyze the expression and localization of KLF4. Small interfering (si)RNA targeting KLF4 (siKLF4) was used to knock down KLF4 expression in HUVECs. The results of the present study revealed that treatment with SAL upregulated the expression levels of VE‑cadherin, downregulated the expression levels of α‑SMA, reduced cell migration and activated the eNOS/NO signaling axis, as well as downregulated KLF4 expression and translocation to the nucleus. Compared with the SAL + siKLF4 co‑administration group, no significant differences were observed in the expression levels of the phenotypic markers in the SAL or siKLF4 groups. In conclusion, the findings of the present study revealed that SAL may inhibit Hcy‑induced EndMT via regulation of the KLF4/eNOS signaling pathway.