Simultaneous expression of tissue factor and tissue factor pathway inhibitor by human monocytes. A potential mechanism for localized control of blood coagulation.

Abstract

SummaryCells of monocytic lineage can initiate extravascular fibrin deposition via expression of blood coagulation mediators. This report is about experiments on three mechanisms with the potential to modulate monocyte-initiated coagulation. Monocyte procoagulant activity was examined as a function of lipid cofactor, protein cofactor, and specific inhibitor expression during short-term culture in vitro. Lipid cofactor activity was measured as the initial rate of factor X activation by intrinsic-pathway components, the assembly of which depends on this cofactor. Lipid cofactor activity levels changed by <30% during 48-h culture. Protein cofactor, i.e., tissue factor (TF) antigen was measured by enzyme immunoassay. It increased from 461 pg/ml to a maximum value of 3,550 pg/ml at 24 h and remained at 70% of this value. Spedfic TF activity, measured as factor VII-dependent factor X activation rate, decreased from 54 to 18 nM FXa/min between 24 and 48 h. TF activity did not correlate well with either lipid cofactor or TF protein levels. In contrast, the decrease in TF activity coincided in time with maximal expression of tissue factor pathway inhibitor (TFPI) mRNA, which was determined using reverse transcriptase polymerase chain reaction (RT-PCR), and with maximal TFPI protein levels measured by immunoassay. The number of mRNA copies coding for TFPI and TF in fleshly isolated blood monocytes were 46 and 20 copies/cell, respectively. These values increased to 220 and 63 copies/cell during short-term cell culture in the presence of endotoxin. Results demonstrate concomitant expression by monocytes of genes coding for both the essential protein cofactor and the specific inhibitor of the extrinsic coagulation pathway. Together with functional and antigenic analyses, they also imply that the initiation of blood dotting by extravascular monocyte/macrophages can be modulated locally by TFPI independently of plasma sources of the inhibitor.

Specific Regulation of Procoagulant Activity on Monocytes

“…As described previously (McGee et al, 1994), under these conditions both cell types express procoagulant activity with similar time courses. Activity increased rapidly during the first 4 h of culture, afterward slowly reaching maximum levels at 18 -20 h. The increase in procoagulant activity was primarily due to expression of TF on the cytoplasmic membrane.…”

Regulation of monocyte procoagulant activity in acute myocardial infarction: role of tissue factor and tissue factor pathway inhibitor-1

“…Although serum and growth factors have been shown to induce TFPI-1 in smooth muscle and endothelial cells, [17][18][19] conflicting results have been obtained for monocytes. 5,20 In our study, the regulation of monocytic TFPI-1 by inflammatory mediators did not appear to play a major role. Contrary to our findings on TF, we did not observe the up-regulation of monocytic TFPI-1 during reperfusion in AMI.…”

Effect of Glycoprotein IIb/IIIa Antagonist Abciximab on Monocyte-Platelet Aggregates and Tissue Factor Expression

“…19 We additionally studied TFPI expression in 24-hour PBMC-platelet coculture by flow cytometry and RT-PCR, because monocyte TF-induction was shown to be antagonized by delayed induction (24 to 48 hours) of monocyte TFPI. 12 In contrast to LPS, TRA-stimulated monocyte-platelet cross talk did not increase monocyte TFPI mRNA after 24 hours, and preincubation with abciximab or anti-P-selectin did not change TFPI mRNA expression significantly.…”

“…19 We additionally studied TFPI expression in 24-hour PBMC-platelet coculture by flow cytometry and RT-PCR, because monocyte TF-induction was shown to be antagonized by delayed induction (24 to 48 hours) of monocyte TFPI. 12 In contrast to LPS, TRA-stimulated monocyte-platelet cross talk did not increase monocyte TFPI mRNA after 24 hours, and preincubation with abciximab or anti-P-selectin did not change TFPI mRNA expression significantly.In conclusion, our data provide in vitro evidence for a potential regulation of monocyte TF by abciximab interfering with monocyte-platelet cross talk. Abciximab administered as adjunct antithrombotic therapy in percutaneous coronary intervention improved clinical outcome, 7-10 in particular in Figure 2.…”

“…We used whole blood flow cytometry, immunohistochemistry, chromogenic activity assay, and reverse transcriptase-polymerase chain reaction (RT-PCR) to demonstrate this effect of the GP IIb/IIIa-antagonist abciximab on TRA-dependent TF induction and compared it to the extent of monocyte TF suppression achieved by P-selectin. Because TF pathway inhibitor (TFPI) regulates TF activity, 12 we additionally studied monocyte TFPI expression in response to TRA-induced monocyteplatelet cross talk.…”