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Objective: To evaluate the protective effect of propyl gallate (PG), an alkyl ester of gallic acid which is an active ingredient of Radix Paeoniae, against oxidized low-density lipoprotein (ox-LDL)-induced apoptosis and death in endothelial cells (ECs) and to find out its preliminary mechanism. Methods: The cultured endothelial cells were divided into normal, model (ox-LDL), control (fetal bovine serum), PG high dose (20 μg/mL), PG middle dose (10 μg/mL), and PG low dose (5 μg/mL) groups, each derived from three different pools of umbilical cords. The model of injured human umbilical vein endothelial cells (HUVECs) was induced by ox-LDL. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, Hoechst 33258 staining, flow cytometry and measurement of nitrogen monoxidum (NO) release were used to evaluate the protective effect of PG against ox-LDL-induced apoptosis and death in HUVECs. To find out the mechanism of this protective effect, the expression of endothelial nitric oxide synthase (eNOS) mRNA, eNOS protein expression, immunofluorescence of intracellular reactive oxygen species (ROS) and activities of malondialdehyde (MDA), superoxidedismutase (SOD) and glutathione peroxidase (GPx) were observed. Results: PG significantly reduced ox-LDL-induced apoptosis and cell death. The percentage of cells death and apoptosis was significantly higher in the ox-LDL group than that in the control group ( P<0.05). Compared with the control group, the cells death and apoptosis of PG group was no different ( P>0.05). As compared with the ox-LDL group, results of the PG high dose group showed that cell viability was significantly increased ( P<0.05), the level of NO release, expression of eNOS mRNA, densitometric value of eNOS protein expression, as well as the activities of SOD and GPx were all significantly higher (all P<0.05). Conclusion: PG could potentially serve as a novel endothelial protective agent against ox-LDL-induced injury of endothelial cell. [ABSTRACT FROM AUTHOR]