Anti-inflammatory and Antioxidant Effects of Pluchea indica Leaf Extract in TNF-α-Induced Human Endothelial Cells

Abstract

Pluchea indica is a shrub plant found in mangrove forests. The leaves are consumed as food and herbal tea and exhibit various biological effects, such as antioxidant and anti-inflammatory activities, in macrophages and animal models. However, the inhibitory activity of P. indica leaf extract on vascular inflammation remains unknown. Therefore, this study investigated the effect of an ethanol extract from P. indica herbal tea leaves (PIE) on tumor necrosis factor-α (TNF-α)-induced human vascular endothelial EA.hy926 cells. The cytotoxic effect of PIE was determined by thiazolyl blue tetrazolium bromide assays. PIE at concentrations of 12.5 - 50 µg/mL did not show significant cytotoxicity, whereas PIE at concentrations ≥ 100 µg/mL decreased cell viability. PIE inhibited the production of reactive oxygen species (ROS) in TNF-α-stimulated endothelial cells. To evaluate the PIE’s anti-vascular inflammatory activity, the protein expression of cell adhesion molecules, including intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), was determined by western blot. PIE significantly decreased TNF-α-induced ICAM-1 and VCAM-1 expression in a concentration-dependent manner. Furthermore, PIE upregulated heme oxygenase-1 (HO-1) in a concentration- and time-dependent manner. Inhibiting the activity of HO-1 by tin protoporphyrin IX significantly blocked the suppressive effect of PIE on ICAM-1 but not VCAM-1 expression. Therefore, PIE exerts anti-inflammatory activity on vascular endothelial cells, at least in part, by suppressing ROS production and the induction of HO-1. The obtained data suggest that PIE is a promising substance for developing therapeutic agents or as an ingredient of functional food. HIGHLIGHTS Pluchea indica leaf extract (PIE) at non-toxic doses inhibited ICAM-1 and VCAM-1 in TNF-α-induced human vascular endothelial cells PIE suppressed the production of ROS in TNF-α-stimulated endothelial cells PIE exerts anti-inflammatory activity on vascular endothelial cells mediated partly through the upregulation of HO-1