Dexamethasone Increased Plasminogen Activator Inhibitor-1 Expression on Human Umbilical Vein Endothelial Cells: An Additive Effect to Tumor Necrosis Factor-α

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Abstract
Objective: In patients with autoimmune diseases, blood vessels may be critically involved at the site of inflammation. For these patients, glucocorticoids (GC) are often used as therapeutics. The aim of this study is to determine the effects of GC on vascular endothelial cells which are under inflammatory conditions. Methods: We examined the molecular expressions in human umbilical vein endothelial cells (HUVEC) induced by dexamethasone (Dex) and tumor necrosis factor (TNF)-α. Live cell number of HUVEC under exposure to Dex and TNF-α was also assayed. Results: The cDNA array analysis showed that a number of genes were upregulated, but only a few were downregulated by Dex and TNF-α, respectively. Among them, thrombomodulin (TM) gene showed the least fold change when HUVEC were stimulated by TNF-α. Since TM inhibits blood coagulation, we took notice of molecules associated with coagulation and fibrinolysis. The quantitative real-time RT-PCR revealed that the expression of plasminogen activator inhibitor-1 (PAI-1) gene increased when HUVEC were exposed to Dex and TNF-α, respectively, and the corresponding augmentation of its protein expression was confirmed by immunohistochemistry. The expression of PAI-1 gene additively increased when Dex and TNF-α were added to stimulate HUVEC. Under our experimental conditions, TNF-α induced proliferation of HUVEC. On the other hand, Dex did not change the number of live cells regardless of stimulation by TNF-α. Conclusion: TNF-α can induce proliferation of vascular endothelial cells with downregulation of the anticoagulation molecule, TM, and upregulation of the anti-fibrinolysis molecule, PAI-1. Dex further increased the expression of PAI-1 gene in the cells stimulated by TNF-α, and did not reduce the effect on cell proliferation induced by TNF-α. These findings suggest that the balance of blood coagulation versus fibrinolysis may incline to coagulation when Dex and TNF-α cooperate on vascular endothelial cells.

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