Objective
To investigate the protective effect and underlying mechanism(s) of icariin (ICA) in preventing hydrogen peroxide (H₂O₂)-induced vascular endothelial cell injury via endoplasmic reticulum stress (ERS).
Methods
To study the effects of ICA on H₂O₂-induced damage, we used the cell counting kit-8 assay to detect cell viability and the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay to determine cell adhesion and apoptosis, respectively. Spectrophotometry and enzyme-linked immunosorbent assay were used to measure the expression levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Subsequently, glucose-regulated protein 78 (GRP78), activating transcription factor-4 (ATF4) and eukaryotic initiation factor-2α (eIF2α) were detected using Western blotting.
Results
In human umbilical vein endothelial cells, different concentrations of ICA exhibited multiple effects, including reduced H₂O₂ damage, improved cell viability and adhesion, reduced cell apoptosis and increased SOD and GSH-Px activity. Among the ICA concentrations used, only the H₂O₂ + 100 μmol/L ICA group had significant differences compared to the H₂O₂ group. ERS activators H₂O₂ and dl-dithiothreitol (DTT) significantly increased GRP78, ATF4 and eIF2α expressions, decreased cell activity and reduced SOD and GSH-Px activity. In contrast, the H₂O₂ + 100 μmol/L ICA and H₂O₂ + 100 μmol/L ICA + DTT groups had significant inhibitory effects on the expressions of GRP78, ATF4 and eIF2α proteins, showing enhanced cell viability and SOD and GSH-Px activity.
Conclusion
The results showed the dose-dependent effects of ICA against H₂O₂-induced injury in vascular endothelial cells. The inhibition of GRP78, ATF4 and eIF2α protein expressions in the ERS, and the subsequent alleviation of oxidative stress damage, might be the molecular mechanism.

Key words: Icariin, Endoplasmic reticulum stress, Human umbilical vein endothelial cells, Oxidative stress