Epigallocatechin-3-O-Gallate, A Green Tea Polyphenol, Induces Expression Of Pim-1 Kinase Via Ppar Gamma In Human Vascular Endothelial Cells

Pim-1 is a serine/threonine kinase and involved in cell survival and proliferation. Recently, it has been shown that pim-1 signaling pathway plays an important role in cardiovascular protection and differentiation. In this study, we sought to explore the expression of pim-1 in human vascular endothelial cells (ECs) and its regulation by epigallocatechin-3-O-gallate (EGCG), a green tea polyphenol which has anti-oxidant, anti-inflammatory and vascular protective effects. By using quantitative reverse transcriptase PCR (qRT-PCR) and Western blotting, we showed that EGCG dose-dependently increased the expression of pim-1 in cultured umbilical vein endothelial cells. Next, we showed that EGCG activated a luciferase reporter driven by peroxisome proliferators-activated receptor (PPAR)-responsive elements. The induced expression of pim-1 was inhibited in ECs pretreated with GW9662, a specific antagonist of PPAR gamma. In addition, pim-1 was also up-regulated in endothelial cells treated with rosiglitazone, a specific agonist for PPAR gamma, or those infected with the adenovirus expressing a constitutively active PPAR gamma. Collectively, our results provided new evidence that pim-1 can be up-regulated by EGCG via a PPAR gamma-mediated mechanism and may mediate its vascular protective effects.