To understand the role of oxidized low density lipoprotein (OX LDL) in the pathogenesis of thrombotic complications in atherogenesis Methods Low density lipoprotein was isolated from normal heparinized blood by density gradient ultracentrifugation and oxidized by CuCl 2 Total RNA was extracted from human umbilical vein endothelial cells (HUVECs) exposed to LDL or OX LDL, using the guanidinium isothiocyanate method The quantification of tissue factor pathway inhibitor (TFPI) mRNA in HUVECs was carried out by reverse transcriptase polymerase chain reaction (RT PCR) Results HUVECs were able to express TFPI mRNA constitutively The expression was not affected by LDL but was effectively inhibited by OX LDL in a time and dose dependent manner Conclusions The results suggest that oxidized LDL may play an important role in inducing coagulation in atherosclerotic lesions by the inhibition of expression of TFPI in vascular endothelial cells To understand the role of oxidized low density lipoprotein (OX LDL) in the pathogenesis of thrombotic complications in atherogenesis Methods Low density lipoprotein was isolated from normal heparinized blood by density gradient ultracentrifugation and oxidized by CuCl 2 Total RNA was extracted from human umbilical vein endothelial cells (HUVECs) exposed to LDL or OX LDL, using the guanidinium isothiocyanate method The quantification of tissue factor pathway inhibitor (TFPI) mRNA in HUVECs was carried out by reverse transcriptase polymerase chain reaction (RT PCR) Results HUVECs were able to express TFPI mRNA constitutively The expression was not affected by LDL but was effectively inhibited by OX LDL in a time and dose dependent manner by OX LDL in a time and dose dependent manner Conclusions The results suggest that oxidized LDL may play an important role in inducing coagulation in atherosclerotic lesions by the inhibition of expression of TFPI in vascular endothelial cells