Ellagic Acid Inhibits Oxidized Low-Density Lipoprotein (OxLDL)-Induced Metalloproteinase (MMP) Expression by Modulating the Protein Kinase C-α/Extracellular Signal-Regulated Kinase/Peroxisome Proliferator-Activated Receptor γ/Nuclear Factor-κB (PKC-α/ERK/PPAR-γ/NF-κB) Signaling Pathway in Endothelial Cells

Previous studies have shown that vascular endothelium-derived matrix metalloproteinases (MMPs) contribute to the destabilization of atherosclerotic plaques, a key event triggering acute myocardial infarction. In addition, studies have reported that the PKC-MEK-PPAR gamma signaling pathway is involved in oxidized low-density lipoprotein (oxLDL)-induced expression of MMPs. Ellagic acid, a phenolic compound found in fruits and nuts, has potent antioxidant, anti-inflammatory, and anticancerous properties. However, the molecular mechanisms underlying its antiatherogenic effects remain to be clarified. This study aimed to assess whether the effects of ellagic acid on the fibrotic markers MMP-1 and MMP-3 are modulated by the PKC-ERK-PPAR-gamma signaling pathway in human umbilical vein endothelial cells (HUVECs) that have been exposed to oxLDL. It was found that ellagic acid significantly inhibited oxLDL-induced expressions of MMP-1 and MMP-3. Pretreatment with ellagic acid and DPI, a well-known ROS inhibitor, attenuated the oxLDL-induced expression and activity of PKC-alpha. In addition, ellagic acid as well as pharmacological inhibitors of ROS, calcium, and PKC strongly suppressed the oxLDL-induced phosphorylation of extracellular signal-regulated kinase (ERK) and NF-kappa B activation. Moreover, ellagic acid ameliorated the oxLDL-induced suppression of PPAR-gamma expression. In conclusion, the data suggest that ellagic acid elicits its protective effects by modulating the PKC-alpha/ERK/PPAR-gamma/NF-kappa B pathway, resulting in the suppression of ROS generation and, ultimately, inhibition of MMP-1 and MMP-3 expression in HUVECs exposed to oxLDL.