REGULATION OF PROTEINASE-ACTIVATED RECEPTOR 1 BY INFLAMMATORY MEDIATORS IN HUMAN VASCULAR ENDOTHELIAL CELLS

Abstract Thrombin plays a critical role in haemostasis, inflammation, and cell proliferation, mediated by proteinase-activated receptor 1 (PAR-1; thrombin receptor). The physiological and pathological regulation of PAR-1 by inflammatory mediators has not yet been fully elucidated. The aim of this study is to investigate the effects of inflammatory mediators on mRNA and protein expression of PAR-1 in early passage human vascular endothelial cells. Endothelial cells were activated by inflammatory mediators, such as tumour necrosis factor α (TNFα), interferon γ (IFNγ), and bacterial substance lipopolysaccharide (LPS), and the PAR-1 expression was verified by flow cytometry or RT–PCR. By stimulating endothelial cells with TNFα, IFNγ, and LPS, the PAR-1 expression on the cell surface remained almost unchanged for 48 h. After stimulation with 20–300 U/ml TNFα, the total cellular PAR-1 expression (both on cell surface and in the cytoplasm) significantly decreased at 24 h and thereafter recovered to the basal level at 48 h. The stimulation with 100 U/ml TNFα transiently down-regulated the PAR-1 mRNA expression to approximately 0.3-fold of the basal level at 30 min, but it rebounded 3-fold above the basal level at 6 h, and again decreased to 0.5-fold of the basal level at 12 h, and finally returned to the basal level at 24 h. In contrast, IFNγ or LPS did not affect the PAR-1 mRNA expression.