Vascular cell adhesion molecule-1 (VCAM-1) is involved in several diseases, including chronic inflammation and atherosclerosis. Inhibition of the expression of this adhesion molecule is one of the key targets of anti-inflammatory, anti-cancer and anti-atherosclerotic drugs. Gynostemma pentaphyllum is a traditional medicine widely used in the treatment of respiratory inflammation, hyperlipidemia and atherosclerosis. However, its molecular mechanisms of action are still largely unknown. Gypenoside XLIX, a dammarane-type glycoside, is a prominent component of G. pentaphyllum. We have recently demonstrated Gypenoside XLIX to be a selective peroxisome proliferator-activated receptor (PPAR)-alpha activator. Here we demonstrate that Gypenoside XLIX concentration-dependently (0-300 microM) inhibited VCAM-1 promoter activity after induction by cytokine tumor necrosis factor (TNF)-alpha in human umbilical vein endothelial cells (HUVECs) transfected with promoter-reporter construct pVCAM-1-LUC. Furthermore, Gypenoside XLIX inhibited TNF-alpha-induced VCAM-1 mRNA and protein overexpression in HUVECs. The result of the enzyme immunoassay demonstrated that Gypenoside XLIX inhibited TNF-alpha-induced increase in cell surface VCAM-1 protein levels in HUVECs. In the present study we show that activities of Gypenoside XLIX are similar to those of Wy-14643, a potent synthetic PPAR-alpha activator. Furthermore, Gypenoside XLIX-induced inhibition on TNF-alpha-stimulated VCAM-1 promoter hyperactivity was completely abolished by a selective blocker of PPAR-alpha, MK-886. Thus, our findings suggest that Gypenoside XLIX inhibits cytokine-induced VCAM-1 overexpression and hyperactivity in human endothelial cells via a PPAR-alpha-dependent pathway. These data provide new insight into the rational basis of the use of the traditional Chinese herbal medicine G. pentaphyllum in the treatment of inflammatory and cardiovascular diseases, including atherosclerosis.