绿茶多酚抑制LDL诱导的血管平滑肌细胞增殖

观察绿茶多酚对低密度脂蛋白(LDL)刺激下离体大鼠胸主动脉血管平滑肌细胞增殖和p44/42MAPK表达的影响。体外培养大鼠胸主动脉血管平滑肌细胞,在LDL(100 μg/ml)刺激时,应用不同剂量的绿茶多酚作用24 h后,采用MTS/PES法确定血管平滑肌细胞的增殖状态。应用流式细胞术测定细胞周期,p44/42磷酸化抗MAPK抗体的蛋白免疫印迹法测定MAPK蛋白表达。与未经LDL处理的平滑肌细胞相比,LDL可以明显刺激大鼠血管平滑肌细胞的增殖,绿茶多酚对LDL刺激下的大鼠血管平滑肌细胞增殖具有明显的抑制作用(P<0.05),并呈现剂量依赖性。流式细胞术检测表明,绿茶多酚可以使LDL刺激下的大鼠血管平滑肌细胞大部分处于G0/G1期,与LDL组相比有明显差异(P<0.05)。LDL对磷酸化p44/42MAPK蛋白表达有显著的增强作用,此作用可被绿茶多酚抑制。绿茶多酚可明显抑制LDL刺激下的大鼠血管平滑肌细胞增殖和磷酸化p44/42丝裂素活化蛋白激酶的表达。

Green tea polyphenols inhibit low-density lipoprotein-induced proliferation of rat vascular smooth muscle cells

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.