Thrombin Suppresses Endothelial Nitric Oxide Synthase and Upregulates Endothelin-Converting Enzyme-1 Expression by Distinct Pathways

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Abstract
— An imbalance of nitric oxide and endothelin plays an important role in cardiovascular disease. Thrombin exerts profound effects on endothelial function. The present study investigated the molecular mechanisms by which thrombin regulates endothelial nitric oxide synthase (eNOS) and endothelin-converting enzyme (ECE)-1 expression in human endothelial cells. Incubation of human umbilical vein endothelial cells with thrombin (0.01 to 4 U/mL) for 15 to 24 hours markedly downregulated eNOS and increased ECE-1 protein level in a dose-dependent manner. Thrombin also decreased eNOS mRNA and increased ECE-1 mRNA level. In mRNA stability assay, thrombin shortened the half-life of eNOS mRNA but not that of ECE-1 mRNA. Activation of protease-activated receptor 1 by the agonist (SFLLRN, 10 to 100 μmol/L) had no effect on eNOS expression but increased ECE-1 level as thrombin. Thrombin activated Rho A and extracellular signal–regulated kinase (ERK)1 and ERK2. Inhibition of Rho A by C3 exoenzyme (20 μg/mL) and R...