ABSTRACT
AIM: To investigate the effect of Chinese propolis on the activity of phosphatidylcholine-specific phospholipase C (PC-PLC) and the expression of Toll-like receptor 4 (TLR4) in LPS-treated vascular endothelial cells (VECs). METHODS: Confluent VECs were stimulated with LPS at the concentration of 100 μg/L in the presence of 0.5% fetal bovine serum. The cells were treated with Chinese propolis at the concentration of 12.5 mg/L for 12 h and 24 h. The viability of VECs and the level of nitric oxide (NO) were detected by sulforhodamine B (SRB) assay and chemical method, respectively. The activity of PC-PLC was measured using L-α-phosphatidylcholine as substrate. The protein levels of TLR4, nuclear factor-Κb p65 (NF-Κb p65) and p53 were determined by Western blotting. The level of intracellular reactive oxygen species (ROS) was examined using a fluorescent probe, 2',7'-dichlorodihydrofluorescin (DCHF). For the measurement of mitochondrial membrane potential, the fluorescent dye JC-1 was used. RESULTS: Treatment with Chinese propolis for 24 h had no effect on the viability of VECs. However, the levels of NO and ROS were significantly decreased by Chinese propolis. PC-PLC activity and NF-Κb p65 expression were significantly depressed by Chinese propolis treated for 12 h, and the expression of TLR4 and p53 were dramatically decreased by Chinese propolis treated for 12 and 24 h. No effect of Chinese propolis on mitochondrial membrane potential was observed. CONCLUSION: Chinese propolis depresses the activity of PC-PLC and the expression of TLR4, and then inhibits the downstream signal molecules such as NF-Κb p65, p53, ROS and NO in VECs.