Tumor necrosis factor- α–induced production of plasminogen activator inhibitor 1 and its regulation by pioglitazone and cerivastatin in a nonmalignant human hepatocyte cell line

Abstract

Plasminogen activator inhibitor 1 (PAI-1) is an important mediator of atherosclerosis and liver fibrosis in insulin resistance. Circulating levels of PAI-1 are elevated in obese individuals, and PAI-1 messenger RNA is significantly higher in the livers of obese type 2 diabetic individuals than in nonobese type 2 diabetic individuals. To address the mechanism underlying the up-regulation of hepatic PAI-1 in obesity, we tested the effects of tumor necrosis factor α (TNF- α), an important link between obesity and insulin resistance, on PAI-1 production in the nonmalignant human hepatocyte cell line, THLE-5b. Incubation of THLE-5b cells with TNF- α stimulated PAI-1 production via protein kinase C–, mitogen-activated protein kinase–, protein tyrosine kinase–, and nuclear factor- κB–dependent pathways. A thiazolidinedione, pioglitazone, reduced TNF- α–induced PAI-1 production by 32%, via protein kinase C– and nuclear factor- κB–dependent pathways. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor cerivastatin inhibited TNF- α–induced PAI-1 production by 59%, which was reversed by coincubation with mevalonic acid. In conclusion, obesity and TNF- α up-regulation of PAI-1 expression in human hepatocytes may contribute to the impairment of the fibrinolytic system, leading to the development of atherosclerosis and liver fibrosis in insulin-resistant individuals. A thiazolidinedione and a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor may thus be candidate drugs to inhibit obesity-associated hepatic PAI-1 production.