Tissue Factor-603 A–G promoter polymorphism is associated with human monocyte constitutive but not with LPS induced gene expression

Abstract number: OC236

Reny^* J. L., Laurendeau† I., Fontana^* P., Bieche† I., Remones‡ V., Emmerich^* J., Aiach^* M., Gaussem^* P.

^*AP-HP Inserm, France; ‡AP-HP, France †Universite Paris 5, France;

The TF-603 A–G gene promoter polymorphism, in complete linkage disequilibrium with 3 other polymorphic sites, has been associated with venous thromboembolic disease. The aim of the present study was to explore the involvement of this polymorphism in monocyte TF gene expression. Using an ex vivo approach, we quantified monocyte TF mRNA and measured a whole-blood clotting time (WBCT) in 100 healthy Caucasian volunteers. The study was approved by the local ethic committee. Two blood samples were obtained one week apart (day1 and day7) to assess the intra and interindividual differences. TF mRNA levels were quantified in peripheral blood mononuclear cells (PBMC) with real time quantitative PCR after adjustment on ubiquitous gene (RPLP0) and a monocyte specific (CD14) gene expression. The WBCT was performed with a modified recalcification test using a Hemochron apparatus. TF mRNA and WBCT were evaluated on unstimulated PBMC and whole blood (H0 condition) as well as after 4 h of incubation with lipopolysaccharide (H4LPS condition). TF mRNA levels within each individual subject were concordant one week apart and values in the group displayed an important interindividual variability with differences of 3- to 4-fold between the lower and upper quartiles. The TF-603 A haplotype was associated with 40% lower TF mRNA levels at H0 (anovaP = 0.0002). In H4LPS samples, TF mRNA levels were increased 70-fold (P < 0.0001) but the increase was not significantly associated with the TF-603 A–G promoter polymorphism. The WBCT is a global test, only partially reflecting functional TF expression. Indeed, at H0, WBCT significantly correlated with FVIIIc, monocyte count and F1 + 2 but not with monocyte TFmRNA or plasma TF concentration. Moreover, WBCT values at day1 and day7 were not significantly concordant suggesting that uncontrolled acquired factors account for intraindividual variations. In contrast, WBCT values at H4LPS were concordant one week apart and were independently associated with monocyte TF mRNA levels (P = 0.0003); however, H4LPS WBCTs were not associated with the TF-603 A–G polymorphism. In conclusion, the TF-603 A–G gene promoter polymorphism weakly but significantly influenced TF constitutive gene expression in monocytes but the 40% difference has no detectable effect on WBCT. The polymorphism was not associated with LPS induced TF gene expression but was, as expected, correlated with WBCT shortening