Summary
Factor VIIa/tissue factor (FVIIa/TF) interaction has been reported to induce intracellular
signalling in cells constitutively expressing TF, independently of downstream activation
of the coagulation cascade. It is unknown, however, whether binding of FVII to its
cofactor TF alters the gene expression profile in cells which inducible express TF
under inflammatory conditions. To address this issue, gene expression patterns in
cultured LPSstimulated monocyte-derived macrophages with or without exposure to FVIIa
were compared by cDNA macro-array analysis. Of the 1176 genes examined on the array,
a small set of six genes (IL-6, IL-8, TNF-a, GRO-beta alpha-thymosin, cathepsin H)
were consistently up-regulated and one gene suppressed (alpha-antitrypsin) in response
to FVIIa in activated monocyte-derived macrophages. Among the seven genes identified
by array analysis, five genes were finally confirmed by real-time RT-PCR. Interestingly,
all of these genes differentially regulated in response to FVIIa (GRO-beta, IL-6,
IL-8, TNF-α and alpha-antitrypsin) are critical in inflammation. The changes in gene
expression were reflected by corresponding changes in the protein concentrations of
IL-6 and IL-8 as demonstrated by ELISA. Active site-inhibited FVIIa had no effect
on gene expression indicating that FVIIa-induced gene alteration is dependent on the
proteolytic activity of FVIIa. The FVIIa-induced alterations in gene expression were
found to be TF-dependent but independent of downstream coagulation proteins like thrombin
and FXa. In summary, this study demonstrates that binding of FVIIa to its cofactor
TF enhances restricted pro-inflammatory genes in activated monocyte-derived macrophages.
By up-regulation of chemokines critical for leukocyte recruitment, FVIIa/TF interaction
on activated monocyte- derived macrophages could be relevant to prepare monocytes/
macrophages for extravasation and may represent a novel amplification loop of leukocyte
recruitment.
Keywords
Factor VIIa - monocyte - inflammation - coagulation - gene expression