Abstract 682: Hepatocyte Growth Factor Regulates E Box-Dependent Plasminogen Activator Inhibitor Type 1 Expression in Hepatocytes Through Statin-Sensitive Pathway: Implications for Clinical Effects
Hemostasis initiates angiogenesis-dependent wound healing. During regeneration plasminogen activator inhibitor (PAI)-1, the physiologic inhibitor of fibrinolysis, preserves extracellular matrix scaffold for cell migration. Thus, PAI-1 is critical in angiogenesis and subsequent wound repair. Patients with acute coronary syndrome exhibit increased serum levels of hepatocyte growth factor (HGF), which stimulates angiogenesis. We have previously shown that HGF stimulates PAI-1 expression using HepG2 human liver cell line. The molecular mechanism was elucidated. HGF increased PAI-1 accumulation in media after 12hrs (2.3 ± 1.3 fold over control at 0.5ng/ml, 7.9 ± 2.7 fold at 50ng/ml, Western, n = 3). HGF induced PAI-1 mRNA expression (1.7 ± 0.4 fold at 0.5ng/ml and 3.3 ± 0.9 fold at 50ng/ml, n = 3, Northern). Increase of PAI-1 mRNA was attenuated by U0126, a specific inhibitor of ERK/MAPK pathway, and genistein, an inhibitor of tyrosine kinase. In contrast, GF109203X, an inhibitor of the PKC pathway, and LY294002, an inhibitor of PI3-kinase, exerted no effects. Intravenous injection of HGF (100 μg/kg) increased hepatic PAI-1 mRNA in mice (1.4 fold, real-time PCR). Transient transfection assay of the human PAI-1 promoter-luciferase construct showed that HGF increased PAI-1 promoter (−829 to +36bp region) activity by 2.0 ± 0.3 fold (n = 5). Deletion and mutation analyses uncovered functional E box motif (5′-CACATG-3′) at −158 to −153bp. Electrophoretic mobility shift assay demonstrated that this E box motif binds heterodimers of upstream stimulatory factor (USF)-1 and -2. HGF phosphorylated USFs through MAPK and tyrosine kinase pathways. Co-transfection of USF1 expression vector increased PAI-1 promoter activity. Sterol regulatory element-binding protein (SREBP)-1 attenuated HGF-inducible PAI-1 promoter activity by replacing USFs bound to the promoter. Simvastatin (10 μM), which translocates membrane-bound SREBP to nuclei, also attenuated PAI-1. Because USFs regulate carbohydrate and lipid metabolism, HGF-mediated PAI-1 production provides a novel link between atherothrombosis and metabolic syndrome. Statins may attenuate PAI-1 increase through SREBP translocation, thus reducing thrombotic risk in patients with metabolic derangements.