Expression of tissue factor pathway inhibitor-2 in murine and human liver regulation during inflammation.

Abstract

Tissue factor pathway inhibitor-2 (TFPI-2) is a recently described serine proteinase inhibitor. Human and murine TFPI-2 share about 50% homology. The aim of this study was to investigate the cellular localization of human and murine TFPI-2 in the liver and the regulation of their expression during acute inflammation. Northern blot, in situ hybridization and studies on isolated hepatocytes demonstrated a high-level expression of TFPI-2 in murine hepatocytes. On the other hand, very little TFPI-2 mRNA expression could be detected in human liver. Studies with isolated human liver cells suggested that TFPI-2 expression in human liver was mainly observed in liver sinusoidal endothelial cells rather than hepatocytes. Liver murine TFPI-2 expression was greatly increased after lipopolysaccharide administration with a delayed kinetics as compared to alpha1-acid glycoprotein, a classical acute-phase reactant. Accordingly, studies with isolated cells showed that the increase in TFPI-2 transcripts occurred in non-hepatocytic cells. Moreover, the LPS response was abolished in mice with a hepatocyte-specific KO for the gp130 receptor, thus indicating that a mediator from hepatocytes is involved in the up-regulation of TFPI-2 in non-parenchymal cells. In conclusion, murine TFPI-2 is highly expressed in hepatocytes in the normal murine liver and is upregulated in non-parenchymal cells in the context of inflammation. The large difference in the level of liver expression of human and murine TFPI-2 suggests that despite significant sequence similarities, these proteins presumably have different functions in the two species.