Cardiac Glycosides Regulate Endothelial Tissue Factor Expression in Culture

Abstract

Background— Tissue factor (TF) plays an important role in acute coronary syndromes and stent thrombosis. This study investigates whether Na + /K + -ATPase regulates TF expression in human endothelial cells. Methods and Results— Ouabain inhibited tumor necrosis factor (TNF)-α–induced endothelial TF protein expression; maximal inhibition occurred at 10 −5 mol/L, reached more than 70%, and was observed throughout the 5 hours stimulation period. The decrease in protein expression was paralleled by a reduced TF surface activity. Similarly, lowering of extracellular potassium concentration inhibited TNF-α–induced TF protein expression. In contrast, ouabain did not affect TNF-α–induced expression of full-length TF mRNA for up to 5 hours of stimulation; instead, expression of alternatively-spliced TF mRNA was upregulated after 3 and 5 hours of stimulation. Ouabain did not affect TNF-α–induced activation of the MAP kinases p38, extracellular signal-regulated kinase (ERK), and c-Jun terminal NH 2 kinase; activation of Akt and p70S6 kinase remained unaltered as well. Similar to the MAP kinases, ouabain did not affect TNF-α–induced degradation of IκB-α. Ouabain had no effect on TF protein degradation. Conclusions— Na + /K + -ATPase is required for protein translation of endothelial TF in culture. This observation provides novel insights into posttranscriptional regulation of TF expression.