Inhibitory effect of reinioside C on monocyte–endothelial cell adhesion induced by oxidized low-density lipoprotein via inhibiting NADPH oxidase/ROS/NF-κB pathway

Monocyte adhesion to activated vascular endothelial cells is the critical event in the initiation of atherosclerosis. Adhesion molecules are inflammatory markers, which are upregulated by oxidized low-density lipoprotein (ox-LDL) and play a pivotal role in atherogenesis. In present study, the effect of reinioside C, a major compound of Polygala fallax Hemsl., on adhesion of monocytes to endothelial cells induced by ox-LDL was investigated. The results showed that incubation of endothelial cells with ox-LDL (100 µg/mL) for 24 h markedly increased the expression of ICAM-1 and P-selectin and enhanced the adhesion of monocytes to endothelial cells. Pretreatment with reinioside C (1, 3, or 10 µM) dose-dependently decreased ox-LDL-induced upregulation of expression of ICAM-1 and P-selectin and the enhanced adhesion of monocytes to endothelial cells. To determine the role of NADPH oxidase/reactive oxygen species (ROS)/nuclear factor-κB (NF-κB) pathway, endothelial cells were treated with ox-LDL (100 µg/mL) for 2 h, and NADPH oxidase subunit (Nox 2 and p22phox) mRNA expression, intracellular ROS level, and NF-κB activity were measured. The results showed that reinioside C attenuated ox-LDL-induced NADPH oxidase subunit (Nox 2 and p22phox) mRNA expression, generation of ROS, and activation of NF-κB in endothelial cells in a dose-dependent manner; the two latter effects were inhibited by pyrollidine dithiocarbamate, the inhibitor of NF-κB. These findings suggest that reinioside C attenuates ox-LDL-induced expression of adhesion molecules (P-selectin and ICAM-1) and the adhesion of monocytes to endothelial cells by inhibiting NADPH oxidase/ROS/NF-κB pathway.