REGULATION OF PLASMINOGEN ACTIVATOR INHIBITOR TYPE-1 BY ACETYL-LDL IN HUMAN UMBIUCAL VEIN ENDOTIIELIAL CELLS

Acetyl-LDL concentration-dependently increase the PAI-1 antigen levels in conditioned medium of human umbilical vein endothelial cells (HUVEC) and this effect is due to "de-novo" protein synthesis. In this study we have evaluated whether the effect of acetyl-LDL on PAI-1 biosynthesis by HUVEC was mediated by the interaction of the lipoprotein with the "scavenger" receptor. Fucoidan and dextran sulphate but not condroitin sulfate concentration-dependently prevented the effect of acetyl-LDL (25 µg/ml) on PAI-1 antigen release by HUVEC. Since the interaction of acetyl-LDL with the scavenger receptor is followed by intracellular lipid accumulation, experiments were carried out with free exogenous non-lipoprotein cholesterol and triglycerides rich particles, isolated from Intralipid 20% . PAI-1 levels were not affected by either cholesterol or triglyceride enrichment of cells. 1t is concluded that the activation of the scavenger receptor by acetyl-LDL in endothelial cells is, at least partially, involved in the induction of PAI-1 biosynthesis.