Oxidative modification enhances lipoprotein(a)-induced overproduction of plasminogen activator inhibitor-1 in cultured vascular endothelial cells.
Elevated levels of plasma lipoprotein (a) [Lp(a)] have been considered as a strong risk factor for premature cardiovascular diseases. Plasminogen activator inhibitor-1 (PAI-1) is the major physiological inhibitor of plasminogen activators (PA). Increases in PAI-1 levels with or without a reduction in PA levels have been frequently found in coronary artery disease patients. The present paper examined the effects of oxidized Lp(a) on the production of PAI-1 in cultured human umbilical vein endothelial cells (HUVEC). Lp(a) and Lp(a)-free, low density lipoprotein (LDL) were prepared using lysine-Sepharose 4B affinity chromatography. Incubations with 10(-8) M levels of native Lp(a) moderately increased the levels of biologically active PAI-1 in post-culture medium of HUVEC compared to that with equimolar concentrations of native Lp(a)-free LDL. The release of PAI-1 induced by Lp(a) was enhanced by oxidative modification with copper ion. The stimulation of oxidized Lp(a) on PAI-1 production reached plateau in EC treated with 10-20 nM oxidized Lp(a) modified by microM CuSO4. Treatment with 0.2 micrograms/ml of actinomycin D significantly reduced native and oxidized Lp(a)-induced PAI-1 overproduction in EC. Increases in the steady state levels of PAI-1 mRNA were detected in native or oxidized Lp(a)-treated EC. The effect of Lp(a)-free oxidized LDL on PAI-1 production was significantly weaker than the equimolar amount of oxidized Lp(a) but stronger than that of native LDL. Treatments with oxidized Lp(a) increased cell-associated PAI-1 to a similar extent as that in native Lp(a)-treated EC. The results of the present paper demonstrate that oxidative modification enhances Lp(a)-induced PAI-1 production in vascular endothelial cells at RNA transcription level, which suggests that oxidization potentially amplifies the anti-fibrinolytic and thrombotic effect of Lp(a).
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Department of Internal Medicine, University of Manitoba, Winnipeg, Canada.
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D015152:Blotting, Northern; D002478:Cells, Cultured; D019327:Copper Sulfate / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D017270:Lipoprotein(a) / Q000378:metabolism / Q000502:physiology*; D010084:Oxidation-Reduction; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D014471:Umbilical Veins
D017270:Lipoprotein(a); D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D017392:Thiobarbituric Acid Reactive Substances; D019327:Copper Sulfate