Nectandrin B suppresses the expression of adhesion molecules in endothelial cells: Role of AMP-activated protein kinase activation.

We have previously shown that nectandrin B, a potent natural activator of AMP-activated protein kinase (AMPK) results in endothelium-dependent relaxation via endothelial nitric oxide synthase phosphorylation. This study examined the effects of nectandrin B on monocyte adhesion and on the expression of adhesion molecules in endothelial cells, an initial event in atherogenesis. Nectandrin B inhibited tumor necrosis factor-α (TNFα)-induced monocytoid THP-1 cell adhesion to ECV 304 human endothelial cells. This lignan also suppressed TNFα-induced protein and mRNA expression of two cell adhesion molecules, vascular cell adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1). In addition, expression of cyclooxygenase-2 and inducible nitric oxide synthase were diminished by nectandrin B treatment. Reporter gene and immunoblot analyses revealed that transcription factor activities of nuclear factor-κB (NF-κB), activator protein-1 (AP-1), and cyclic AMP response element binding protein (CREB) were inhibited by nectandrin B. Moreover, nectandrin B activated AMP-activated protein kinase (AMPK) in ECV 304 cells. Transfection of a dominant-negative mutant form of AMPK (DN-AMPK) partially reversed inhibitory effects of nectandrin B on the expression of VCAM-1 and ICAM-1, and on the transcriptional activity of CREB.