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)-alpha-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-alpha-induced TF protein expression. In contrast, ouabain did not affect TNF-alpha-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-alpha-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-alpha-induced degradation of IkappaB-alpha. 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.