Proinflammatory cytokines such as TNF-α have been shown to contribute to the progressive development of hypertension. In the endothelium, TNF-α induces upregulation of cell adhesion molecule expressions and actin cytoskeleton rearrangement, thereby promotes endothelial hyperpermeability. Centella asiatica is a traditional medicinal herb which has been shown to reduce the permeability of microcirculation in venous hypertensive patients. Asiatic acid, an active constituent derived from C. asiatica, has also been demonstrated to reduce blood pressure in L-NAME-induced hypertensive rats. Yet, the underlying mechanisms by which asiatic acid suppresses vascular hyperpermeability and endothelial dysfunction are poorly understood. The purpose of this study was to evaluate the effects of asiatic acid on TNF-α-induced endothelial barrier dysfunction using human aortic endothelial cells (HAECs).Design and Method:
FITC-dextran permeability assay was used to measure the cell monolayer's permeability. The concentrations of soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) were measured by using flow cytometry. Western blot analysis was used to examine the expression of ICAM-1 and VCAM-1. F-actin distribution was stained using rhodamine-phalloidin and viewed under a confocal microscope.Results:
20–40 μM of asiatic acid significantly suppressed TNF-α-induced increased HAECs permeability and increased secretion of sICAM-1 and sVCAM-1. However, asiatic acid selectively suppressed TNF-α-induced increased VCAM-1 expression, but not ICAM-1. Besides, pretreatment of asiatic acid also prevented F-actin redistribution and stress fiber formation triggered by TNF-α.Conclusions:
Asiatic acid improves TNF-α-stimulated endothelial barrier impairment. This is associated with inhibition of cytoskeletal rearrangement and VCAM-1 expression induced by TNF-α. Furthermore, asiatic acid also suppresses the production of sICAM-1 and sVCAM-1, which are soluble biomarkers commonly used to assess endothelial function and to predict the risk of future cardiovascular events. These data support the use of asiatic acid as a potential therapeutic agent against TNF-α-induced endothelial dysfunction.