Nuclear factor kappaB-mediated down-regulation of adhesion molecules: Possible mechanism for inhibitory activity of bigelovin against inflammatory monocytes adhesion to endothelial cells

The flowers of Inula britannica L. var. chinensis (Rupr.) Reg. (Compositae) are used in traditional medicine to treat asthma, chronic bronchitis, and acute pleurisy in China and Korea. However, the pharmacological actions of Inula britannica L. var. chinensis on endothelial cells and inflammatory monocytes are not clear. In this study, we investigated whether bigelovin, a sesquiterpene lactone isolated from the flowers of Inula britannica L. var. chinensis, inhibits monocyte adhesion and adhesion molecule expression in brain endothelial cells. We measured tumor necrosis factor-α (TNF-α)-enhanced Raw264.7 monocyte binding to brain endothelial cells and the levels of cell adhesion molecules, including vascular adhesion molecule-1 (VCAM-1), intracellular adhesion molecule-1 (ICAM-1), and endothelial-selectin (E-selectin) on the surface of brain endothelial cells. Bigelovin significantly inhibited these in a dose-dependent manner without affecting cell viability. Furthermore, bigelovin suppressed the nuclear factor kappaB (NF-κB) promoter-driven luciferase activity, NF-κB activation, and degradation of NF-κB inhibitor protein alpha (IκBα). These results indicate that bigelovin inhibits inflammatory monocyte adhesion to endothelial cells and the expression of VCAM-1, ICAM-1, and E-selectin by blocking IκBα degradation and NF-κB activation.