Oxidative stress plays a critical role in endothelial injury and the pathogenesis of diverse cardiovascular diseases, including atherosclerosis. Isoquercitrin (quercetin-3-glucoside), a flavonoid distributed widely in plants, exhibits many biological activities, including anti-allergic, anti-viral, anti-inflammatory, and anti-oxidative effects. In the present study, the inhibitory effect of isoquercitrin on H₂O₂-induced apoptosis of EA.hy926 cells was evaluated. MTT assays showed that isoquercitrin significantly inhibited H₂O₂-induced loss of viability in EA.hy926 cells. Hoechst33342/PI and Annexin V-FITC/PI fluorescent double staining indicated that isoquercitrin inhibited H₂O₂-induced apoptosis of EA.hy926 cells. Western blotting demonstrated that isoquercitrin prevented H₂O₂-induced increases in cleaved caspase-9 and cleaved caspase-3 expression, while increasing expression of anti-apoptotic protein Mcl-1. Additionally, isoquercitrin significantly increased the expression of p-Akt and p-GSK3β in a dose-dependent manner in EA.hy926 cells. LY294002, a PI3K/Akt inhibitor, inhibited isoquercitrin-induced GSK3β phosphorylation and increase of Mcl-1 expression, which indicated that regulation of isoquercitrin on Mcl-1 expression was likely related to the modulation of Akt activation. These results demonstrated that the anti-apoptotic effect of isoquercitrin on H₂O₂-induced EA.hy926 cells was likely associated with the regulation of isoquercitrin on Akt/GSK3β signaling pathway and that isoquercitrin could be used clinically to interfere with the progression of endothelial injury-associated cardiovascular disease.

Vascular inflammation is directly responsible for atherosclerosis. 5,2′-Dibromo-2,4′,5′-trihydroxydiphenylmethanone (TDD), a synthetic bromophenol derivative, exhibits anti-atherosclerosis and anti-inflammatory effects. However, the underlying pathways are not yet clear. In this study, we first examined the effects of TDD on toll-like receptor-4 (TLR4) activity, the signaling receptor for lipopolysaccharide (LPS), and found that TDD does not inhibit LPS-induced TLR4 expression in EA.hy926 cells and the vascular wall in vivo. Next, we investigated the global protein alterations and the mechanisms underlying the action of TDD in LPS-treated EA.hy926 cells using an isobaric tag for the relative and absolute quantification technique. Western blot analysis revealed that TDD inhibited NF-κB activation by regulating the phosphorylation and subsequent degradation IκBα. Among the differentially expressed proteins, TDD concentration-dependently inhibited Caveolin 1(Cav1) expression. The interaction between Cav1 and TDD was determined by using biolayer interference assay, UV-vis absorption spectra, fluorescence spectrum, and molecular docking. We found that TDD can directly bind to Cav1 through hydrogen bonds and van der Waals forces. In conclusion, our results showed that TDD inhibited LPS-induced vascular inflammation and the NF-κB signaling pathway by specifically targeting the Cav1 protein. TDD may be a novel anti-inflammatory compound, especially for the treatment of atherosclerosis.

Vascular endothelial cells produce reactive oxygen species (ROS) during the process of energy metabolism in aerobic respiration. A growing body of evidence indicates that excessive ROS is implicated in the pathogenesis of cardiovascular diseases including atherosclerosis. The newly synthesized halophenol, 2,4′,5′-trihydroxyl-5,2′-dibromo diphenylmethanone (TDD), exhibits antioxidative and cytoprotective activities in vitro. In this study, the protective effect of TDD against hydrogen peroxide (H₂O₂)-induced oxidative injury of EA.hy926 cells was investigated. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-dephenyltetrazolium bromide (MTT) assay, while the effect of TDD on the transcription profile of EA.hy926 cells subjected to H₂O₂-induced oxidative injury was evaluated by microarray analysis. Several signaling pathways, including apoptosis, were significantly associated with TDD. Flow cytometric analysis was used to evaluate anti-apoptotic effect of TDD. Subsequently, RT-PCR and Western blot were used to detect the expressions of the apoptosis-associated protein, Bcl-2 and Bax. Meanwhile the expression of cleaved caspase-3, an executioner of apoptosis, was also detected by Western blot. The results showed that pretreatment of EA.hy926 cells with TDD prevented the decrease of cell viability induced by H₂O₂, and attenuated H₂O₂-induced elevation of Bax and cleaved caspase-3 while increased Bcl-2 expressions. In summary, TDD inhibited H₂O₂-induced oxidative injury of EA.hy926 cells through negative regulation of apoptosis. These findings suggest that TDD is a potential candidate for therapeutic intervention in oxidative stress-associated cardiovascular diseases.