Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor that regulates tissue factor-triggered blood coagulation. It has previously been reported that TFPI inhibits the proliferation of human umbilical vein endothelial cells (HUVECs), suggesting that TFPI may act as more than just a mediator of coagulation through changes in gene expression. By using DNA-array techniques and Northern blot analysis, we here revealed that TFPI transiently induced the mRNA expression of JUNB and GADD45B. The inducible effects were not observed in TFPIDeltaC (lacking the C-terminal basic region) or antithrombin (heparin-binding anticoagulant protease inhibitor). Moreover, the TFPI-induced expression of GADD45B was blocked by receptor-associated protein, which masks the ligand-binding domain of very low density lipoprotein receptor (VLDL-R). In conclusion, this is the first report to show an effect of TFPI on mRNA expression, and suggests that TFPI modulates cellular functions by inducing JUNB and GADD45B expression through binding to VLDL-R. (C) 2002 Elsevier Science (USA). All rights reserved.