Synergistic Induction of Plasminogen Activator Inhibitor Type-1 in HEP G2 Cells by Thrombin and Transforming Growth Factor-β

• Published in: Blood Vol. 79; no. 1; pp. 75 - 81
• Main Authors: William, E. Hopkins, Satoshi, Fujii, Burton, E. Sobel
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01.01.1992; The Americain Society of Hematology
• Subjects: Antithrombin III - pharmacology; Biological and medical sciences; Blood Platelets - metabolism; Blotting, Northern; Carcinoma, Hepatocellular - metabolism; Drug Synergism; Gastroenterology. Liver. Pancreas. Abdomen; Hirudins - pharmacology; Humans; Liver - drug effects; Liver - metabolism; Liver Neoplasms - metabolism; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Medical sciences; Plasminogen Inactivators - metabolism; RNA, Messenger - metabolism; Thrombin - pharmacology; Transforming Growth Factor beta - pharmacology; Tumor Cells, Cultured; Tumors; Human; Enzyme; Transforming growth factor; Cytokine; Enzyme inhibitor; Hepatic disease; Plasminogen activator; Thrombin; Activation; Biosynthesis; Malignant tumor; Hepatocyte; Liver cell carcinoma; Digestive diseases
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V79.1.75.75

Plasminogen activator inhibitor type-1 (PAl-1) is a physiologic modulator of the fibrinolytic system. Its activity in plasma increases in diverse thrombotic states. The large synthetic capacity of the liver make it a source of potentially large amounts of PAl-1. Because thrombin activity increases in association with thrombotic disorders and because specific binding sites for thrombin have been identified on hepatocytes, we characterized the effect of thrombin on hepatocyte PAl-1. production. Incubation of Hep G2 cells with human a-thrombin resulted in a dose- and time-dependent increase in the concentration of  PAl-1. in conditioned media. This effect was inhibited completely by hirudin and by antithrombin III. Steady-state levels of both the 3.2-kb and 2.2-kb forms of PAl-1. mRNA increased after stimulation of the cells with thrombin, indicating that thrombin influences PAl-1 expression in Hep G2 cells at the pretranslational level. Incubation of Hep G2 cells with a-thrombin and either platelet lysates or purified transforming growth factor-β (TGF-β ), both previously shown to augment hepatocyte PAl-1 expression, resulted in a synergistic increase in the concentration of PAl-1 in conditioned media. PAl-1 mRNA appeared to be synergistically increased as well. Thus, thrombin increases expression of both PAl-1 protein and mRNA in Hep G2 cells and exerts synergistic effects with TGF-β. These results underscore the potential importance of inhibition of thrombin under conditions in which thrombolysis is induced pharmacolooically. © 1992 by The American Society of Hematology. 0006-4971/92/7901-0003$3.00/0