Impact and mechanism for oxidized and glycated lipoproteins on generation of fibrinolytic regulators from vascular endothelial cells

Abstract

Thrombogenesis depends on the balance between coagulation and fibrinolysis in vasculature. Vascular endothelial cells (EC) synthesize activators and inhibitors for fibrinolysis, tissue and urokinase plasminogen activators (tPA and uPA) and plasminogen activator inhibitor-1 (PAI-1). Increased levels of PAI-1 with various levels of tPA have been frequently found in plasma of patients with coronary heart disease (CHD) or diabetes mellitus (DM). Dyslipidemia is common feature in patients with CHD or DM, which is characterized by elevated levels of total cholesterol, triglycerides, low or very low density lipoproteins (LDL or VLDL) and decreased levels of high density lipoprotein (HDL). LDL and VLDL stimulated the generation of PAI-1 from cultured EC. LDL and lipoprotein(a) [Lp(a)], another lipoprotein risk factor for CHD, reduced the generation of tPA from EC. HDL did not greatly alter the release of PAI-1 from EC. Oxidative modification by copper, ultraviolet or long exposure to EC enhanced the effect of LDL on the generation of PAI-1 and tPA from EC. Glycation amplified the effect of LDL and Lp(a) on the changes in the generation of the fibrinolytic regulators from EC. Treatment with antioxidants or HDL normalized glycated LDL-induced changes in the generation of fibrinolytic regulators from EC. Activation of protein kinase C is required for oxidized LDL or Lp(a)-induced PAI-1 production in EC. VLDL, but not LDL or its oxidized form, stimulated PAI-1 production through the activation of the VLDL-responsive element in the PAI-1 promoter. Plasma levels of fibrinolytic regulators in CHD or DM patients may be normalized by HMG-CoA reductase inhibitors and angiotensin II converting enzyme inhibitors. This review summarizes the up-to-date information on effects, mechanism and management for disorders in EC-derived fibrinolytic regulators induced by modified lipoproteins.