Salidroside protects against ox-LDL-induced endothelial injury by enhancing autophagy mediated by SIRT1-FoxO1 pathway

Background: Atherosclerosis is a condition with the vascular accumulation of lipid plaques, and its main major contributing factor is endothelial injury induced by oxidized low-density lipoprotein (ox-LDL). Salidroside (SAL) is the primary active ingredient of Rhodiola rosea, and exhibits antioxidant properties on endothelial cells and alleviates atherosclerosis. However, the effect of SAL on autophagy in ox-LDL-induced vascular endothelial injury remains unclear. Here, we investigated the effect and underlying mechanisms of SAL on autophagy in human umbilical vein endothelial cells (HUVECs). Methods: HUVECs were incubated with ox-LDL to induce in vitro atherosclerosis model. The cell viability and injury were evaluated by cell counting kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) release assay. The oxidative stress was evaluated by NADPH oxidase, malondialdehyde (MDA) and superoxide dismutase (SOD) activities. Immunofluorescence was performed to detect autophagy using LC3 beta antibody. Quantitative real-time PCR (qRT-PCR) and western blot were performed to measure the mRNA expressions of SIRT1 and Forkhead box O1 (FOXO1). Nicotinamide (NAM) and AS1842856 were used to inhibit activities of SIRT1 and FOXO1, respectively. Results: Exposure of HUVECs to ox-LDL (100 mu g/mL) reduced cell viability, increased cellular MDA, and reduced SOD in a concentration-dependent manner. The pretreatment with SAL (20, 50 and 100 mu M) significantly enhanced the cell viability and decreased LDH release in HUVECs exposed to ox-LDL (100 mu g/mL). ox-LDL induced autophagy in HUVECs, which was further enhanced by pretreatment with SAL. However, SAL attenuated increase in oxidative stress in HUVECs induced by ox-LDL. ox-LDL reduced mRNA and protein expressions of SIRT1 and FOXO1, which could be reversed by SAL. The protective, anti-oxidative and pro-autophagic effects of SAL could be obviously abolished by cotreatment with SIRT1 inhibitor or FOXO1 inhibitor. Conclusion: Salidroside shows protective effect on endothelial cell induced by ox-LDL, and the mechanisms might be related to autophagy induction via increasing SIRT1 and FoxO1 expressions.