The
proliferation and migration of
vascular smooth muscle cells (
VSMCs) is one of the major mechanisms of intimal thickening in atherosclerosis and post-angioplasty restenosis. Elevated plasma levels of low-density lipoprotein (LDL) have been implicated in the pathogenesis of atherosclerotic vascular diseases. The purpose of this study was to determine the effects of green
tea polyphenols on the proliferation and p44/42 mitogen-activated protein kinase (
MAPK) activity in rat VSMCs simulated by native LDL. Rat aortic VSMCs were cultured and treated with LDL (100 μg/ml) in the absence or presence of green tea polyphenols, and the
cell proliferation was subsequently quantified by non-radioactive MTS/PES assay and the cell cycle analyzed by flow cytometry. The p44/42 MAPK activity was evaluated by immunoblotting using anti-p44/42 phospho-MAPK antibody. Compared with the cells without polyphenol treatment, the proliferation of the VSMCs induced by LDL was dose-dependently inhibited by green tea polyphenols (P<0.05), with more numerous cells in G0/G1 phase (P<0.05) as shown by flow cytometry analysis. LDL significantly enhanced the p44/42 MAPK activity, an effect obviously inhibited by green tea polyphenols (at 100 μg/ml). These results suggest that green tea polyphenols can inhibit high levels of LDL-induced proliferation of phosphorylated p44/42 MAPK expression in rat VSMCs. Green tea polyphenols may, therefore, offer vascular protection by inhibiting VSMC growth in response to hypercholesterolemia.