Protection of tea polyphenols on fibrinolytic functions of cultured human umbilical vein endothelial cells in vitro.

Objective To examine the protective effects of tea polyphenols(TP) on fibrinolytic functions of cultured human umbilical vein endothelial cells(HUVEC) in vitro.Method HUVEC cells were administered with homocysteine(Hcy)(0.5 mmol/L),TP(10 μg/ml),and Hcy(0.5 mmol/L) + TP(10 μg/ml) respectively.The control cells were treated with equal volume of solvent.Cell viability was assessed by methyl thiazol tetrazolium(MTT).Tissue-type plasminogen activator(t-PA) and plasminogen activator inhibitor-1(PAI-1) concentration in HUVEC supernatant were determined by ELISA assay,and their mRNA levels were examined by RT-PCR.Results The results showed that Hcy increased PAI-1 expression both at protein and mRNA levels(P0.01);TP and Hcy treatment simultaneously could down-regulate PAI-1/t-PA ratio by decreasing PAI-1 expression which might be regulated by mRNA levels.Conclusion TP could decrease PAI-1 secretion by down-regulating mRNA levels to sustain PAI-1/t-PA ratios access to normal level,which might be related to its protective effects on fibrinolytic functions.