Impact of Antioxidants and HDL on Glycated LDL–Induced Generation of Fibrinolytic Regulators From Vascular Endothelial Cells

Abstract

Abstract-Hyperglycemia and dyslipoproteinemia are biochemical markers of diabetes mellitus (DM). Elevated levels of plasminogen activator inhibitor-1 (PAI-1) with and without reduction of tissue plasminogen activator (tPA) in plasma have been frequently found in patients with DM. Our previous studies indicated that glycation enhances low density lipoprotein (LDL)-induced production of PAI-1 and further decreases tPA generation in vascular endothelial cells (ECs). The present study demonstrated that treatment with antioxidants, butylated hydroxytoluene or vitamin E, blocked native LDL-and glycated LDL-induced changes in PAI-1 and tPA generation in ECs. Native or glycated high density lipoprotein (HDL) did not significantly alter tPA generation in ECs. Glycated but not native HDL (Ն100 g/mL) moderately increased PAI-1 release from ECs. Cotreatment with native or glycated HDL inhibited LDL-induced or glycated LDL-induced changes in PAI-1 and tPA generation in ECs. The abundance of conjugated dienes was increased in glycated or EC-modified LDL. Treatment with butylated hydroxytoluene, vitamin E, or HDL reduced the abundance of conjugated dienes in glycated or EC-modified LDL. The effects of antioxidants and HDL on LDL-induced or its glycated LDL-induced changes in the generation of PAI-1 and tPA were also found in cultured human coronary artery ECs. The findings of the present study suggest that antioxidants and HDL may attenuate native LDL-or glycated LDL-induced changes in the generation of fibrinolytic regulators from vascular ECs, which possibly results from their inhibition on the lipid peroxidation of LDL particles. Treatment with antioxidants or hypolipidemic agents potentially improves fibrinolytic activity and reduces thrombotic tendencies in patients with DM. Key Words: LDL Ⅲ glycation Ⅲ antioxidants Ⅲ HDL Ⅲ plasminogen activator inhibitor-1 H yperglycemia and dyslipoproteinemia, 2 major biochemical markers in diabetes mellitus (DM), have been implicated in the development of cardiovascular complications in patients with DM. Intravascular thrombosis plays a critical role in the development of ischemic events with and without the presence of atherosclerotic lesions. The formation of thrombus in the vasculature mainly depends on the balance between coagulation and fibrinolysis. The release of fibrinolytic activity from the vascular wall responding to temporary occlusion was impaired in patients with DM. 1,2 The production of plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) in vascular endothelial cells (ECs) is modulated by thrombin, 3 glucose, 4 proinsulin, 5 growth factors, 6 and several types of plasma lipoproteins. [7][8][9][10][11][12][13] Elevated levels of glycated LDL were detected in the plasma of patients with DM. 14,15 Previous studies by our group demonstrated that glycation enhanced LDL-induced overproduction of PAI-1 and further reduced the generation of tPA from cultured vascular ECs. 13 Glycation increases the oxidative stress of lipoproteins. 16 Treatment with...

Involvement of NADPH oxidase in oxidized LDL-induced upregulation of heat shock factor-1 and plasminogen activator inhibitor-1 in vascular endothelial cells

“…Our previous studies indicated that the LDL-induced moderate increase in PAI-1 generation from EC may be attenuated by an antioxidant (21), which is an indication that cell-mediated oxidative modification contributes to PAI-1 upregulation in EC induced by LDL. The combination of the present and previous findings suggests that oxidative modification plays critical roles in LDL or its modified forms induced upregulation of HSF1 and PAI-1 in cultured vascular EC.…”

“…We previously reported that CLDL increased the release of PAI-1 from cultured HUVEC or HCAEC (21). The influence of other types of oxidized LDLs on PAI-1 expression, or that of CLDL on cell-associated PAI-1 abundance in EC, remains uncharacterized.…”

Involvement of Heat Shock Factor-1 in Glycated LDL–Induced Upregulation of Plasminogen Activator Inhibitor-1 in Vascular Endothelial Cells

“…LDL may be oxidatively modified by a prolonged incubation with endothelial cells (44). A previous study in our group demonstrated that antioxidants reduced the abundance of lipid peroxides in LDL and prevented LDL-induced release of PAI-1 from endothelial cells (15). The effects of LDL on HSF1 and PAI-1 after a prolonged incubation with endothelial cells may result, at least in part, from cell-mediated oxidative modification on LDL.…”

“…Seed human umbilical vein endothelial cells (HUVECs) were obtained from American Type Culture Collection (Manassas, VA). Cells were grown in F12K medium (Gibco, Burlington, ON, Canada) containing 10% FCS, 0.1 mg/ml heparin, and 30 g/ml endothelial cell growth supplements (Sigma) (15). Seed human coronary arterial endothelial cells (HCAECs) and cultured supplements were obtained from Clonetics (San Diego, CA).…”

“…Previous studies in our laboratory demonstrated that glycated LDL increased the production of PAI-1 in cultured venous or arterial endothelial cells. LDL isolated from diabetic patients or glycated LDL modified in vitro enhanced the activity of PAI-1 promoter in endothelial cells (12)(13)(14)(15). Glycated LDL stimulated the generation of reactive oxygen species (ROS) and decreased the abundance of reduced glutathione in endothelial cells (16).…”