Xanthoangelol Prevents Ox-LDL-Induced Endothelial Cell Injury by Activating Nrf2/ARE Signaling

Atherosclerosis (AS) contributes to the development of several cardiovascular diseases such as myocardial infarction and stroke. Oxidized low-density lipoprotein (Ox-LDL)-induced endothelial cell injury plays a key role in the pathogenesis of AS. Thus, this study was conducted to examine the effects of a naturally occurring flavonoid compound, xanthoangelol (XAG), on Ox-LDL-induced cell injury.

Human umbilical vein endothelial cells (HUVECs) were used as the in vitro cell model. The number of viable cells was determined using CCK-8 assay. Cell apoptosis was detected using Hoechst staining. Percentage of apoptotic cells was quantified by flow cytometry. The cellular levels of malondialdehyde (MDA), superoxide dismutase, catalase (CAT), and glutathione peroxidase were determined using enzyme-linked immunosorbent assays. The cellular reactive oxygen species level was detected by flow cytometry after fluorescence staining. The mRNA expression levels of nuclear factor-E2-related factor-2 (Nrf2), heme oxygenase-1 (HO-1), and NQO-1 were determined using quantitative real-time polymerase chain reaction assay. The protein levels of cleaved caspase-3, cleaved poly ADP-ribose polymerase, Bax, Bcl-2, Nrf2, Keap1, HO-1, and NQO-1 were measured by using Western blot assay. The HUVECs were transfected with Nrf2 siRNA to reduce the expression of Nrf2.

XAG could effectively protect against Ox-LDL-stimulated cell death in HUVECs. These cytoprotective effects were due to its anti-apoptotic and anti-oxidant activities, as supported by the increase of SOD, CAT, and glutathione peroxidase activities, and the decrease of MDA and reactive oxygen species levels in injured HUVECs induced by Ox-LDL. Moreover, the results showed that XAG activated Nrf2/ARE signaling in a dose-dependent manner. Importantly, blockade of Nrf2 signaling using siRNA or specific inhibitor notably abolished the cytoprotective activities of XAG.

These data suggest that XAG cytoprotects against Ox-LDL-induced cell injury through activating Nrf2/ARE-mediated antioxidative stress. Cumulatively, these findings show that EX has the potential to prevent and treat AS.