Objectives To investigate the effect of rhein on endothelial plasminogen activator inhibitor-1 (PAI-1) mRNA expression and protein production induced by transforming growth factor β1 (TGFβ1), and to explore the mechanism of the protective action of rhein on endothelial cells. Methods A human umbilical endothelium derived cell line (ECV-304) from ATCC was used in this study. The PAI-1 mRNA expression and protein synthesis in the endothelial cells were detected by Northern blot and flow cytometry analysis, respectively. The activity of phospho-p44/p42 MAP kinase induced by TGFβ1 was determined by immunoprecipitation analysis and western blot. Results TGFβ1 rapidly increased PAI-1 mRNA expression in the endothelial cells, and this effect lasted at least 24 hours. The upregulation of PAI-1 mRNA expression induced by TGFβ1 in endothelial cells was inhibited by rhein in a dose-dependent manner. In addition, rhein inhibited endothelial PAI-1 protein production. Further study revealed that rhein had a significant inhibitory effect on the activity of phospho-p44/p42 MAP kinase induced by TGFβ1 in human endothelial cells. Conclusions Our results showed that rhein may have a protective effect on the endothelial dysfunction by inhibiting overexpression of PAI-1, indicating a way for the treatment of vascular diseases. Objectives To investigate the effect of rhein on endothelial plasminogen activator inhibitor-1 (PAI-1) mRNA expression and protein production induced by transforming growth factor β1 (TGFβ1), and to explore the mechanism of the protective action of rhein on endothelial cells. The human expression of the human umbilical endothelium derived cell line (ECV-304) from ATCC was used in this study. The PAI-1 mRNA expression and protein synthesis in the endothelial cells were detected by Northern blot and flow cytometry analysis, respectively. The activity of phospho- p44 / p42 MAP kinase induced by TGFβ was determined by immunoprecipitation analysis and western blot. Results TGFβ1 rapidly increased PAI-1 mRNA expression in the endothelial cells, and this effect lasted at least 24 hours. The upregulation of PAI-1 mRNA expression induced by TGFβ1 in endothelial cells was inhibited by rhein in a dose-dependent manner. In addition, rhein inhibited endothelial PAI-1 protein production. that rhein had a significant inhibitory effect on the activity of phospho-p44 / p42 MAP kinase induced by TGFβ1 in human endothelial cells. Conclusions Our results showed that rhein may have a protective effect on endothelial dysfunction by inhibiting overexpression of PAI-1 a way for the treatment of vascular diseases.