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Fibrate-modulated expression of fibrinogen, plasminogen activator inhibitor-1 and apolipoprotein A-I in cultured cynomolgus monkey hepatocytes. Role of the peroxisome proliferator-activated receptor-α

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Author: Kockx, M. · Princen, H.M.G. · Kooistra, T.
Institution: Gaubius Instituut TNO
Source:Thrombosis and Haemostasis, 6, 80, 942-948
Identifier: 234742
Keywords: Health · Animals · Antilipemic Agents · Apolipoprotein A-I · Cells, Cultured · Clofibrate · Clofibric Acid · Dimerization · Female · Fibrinogen · Gemfibrozil · Gene Expression Regulation · Genes, Reporter · Liver · Macaca fascicularis · Male · Peroxisome Proliferators · Plasminogen Activator Inhibitor 1 · Procetofen · Pyrimidines · Receptors, Cytoplasmic and Nuclear · Receptors, Retinoic Acid · Retinoid X Receptors · Trans-Activation (Genetics) · Transcription Factors · Tretinoin


Fibrates are used to lower plasma triglycerides and cholesterol levels in hyperlipidemic patients. In addition, fibrates have been found to alter the plasma concentrations of fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and apolipoprotein A-I (apo A-I). We have investigated the in vitro effects of fibrates on fibrinogen, PAI-1 and apo A-I synthesis and the underlying regulatory mechanisms in primary monkey hepatocytes. We show that fibrates time- and dose-dependently increase fibrinogen and apo A-I expression and decrease PAI-1 expression in cultured cynomolgus monkey hepatocytes, the effects demonstrating different potency for different fibrates. After three consecutive periods of 24 h the most effective fibrate, ciprofibrate (at 1 mmol/l), increased fibrinogen and apo A-I synthesis to 356% and 322% of control levels, respectively. Maximum inhibition of PAI-1 synthesis was about 50% of control levels and was reached by 1 mmol/l gemfibrozil or ciprofibrate after 48 h. A ligand for the retinoid-X-receptor (RXR), 9-cis retinoic acid, and specific activators of the peroxisome proliferator-activated receptor-α (PPARα), Wy14,643 and ETYA, influenced fibrinogen, PAI-1 and apo A-I expression in a similar fashion, suggesting a role for the PPARα/RXRα heterodimer in the regulation of these genes. When comparing the effects of the various compounds on PPARα transactivation activity as determined in a PPARα-sensitive reporter gene system and the ability of the compounds to affect fibrinogen, PAI-1 and apo A-I antigen production, a good correlation (r = 0.80; p < 0.01) between PPARα transactivation and fibrinogen expression was found. Apo A-I expression correlated only weakly with PPARα transactivation activity (r = 0.47; p = 0.24), whereas such a correlation was absent for PAI-1 (r = 0.03; p = 0.95). These results strongly suggest an involvement of PPARα in the regulation of fibrinogen gene expression.