The in vivo kinetics of tissue factor messenger RNA expression during human endotoxemia: relationship with activation of coagulation

Triggering of the tissue factor (TF)-dependent coagulation pathway is consi dered to underlie the generation of a procoagulant state during endotoxemia , To determine the in vivo pattern of monocytic TF messenger RNA (mRNA) exp ression during endotoxemia, 10 healthy volunteers were injected with lipopo lysaccharide (LPS, 4 ng/kg) and blood was collected before and 0.5, 1, 2, 3 , 4, 6, 8, and 24 hours after LPS administration. Total blood RNA was isola ted and amplified by NASBA (nucleic acid sequence-based amplification), fol lowed by quantitation of TF mRNA by an electrochemiluminescence (ECL) assay , To com-pare the pattern of coagulation activation with the kinetics of mo nocytic TF mRNA expression, we measured plasma levels of markers of thrombi n generation, thrombin-antithrombin (TAT) complexes, and prothrombin fragme nt 1 + 2 (F1 + 2). Baseline value (mean +/- SEM) of the number of TF mRNA m olecules per monocytic cell was 0.08 +/- 0.02. A progressive and significan t (P < .0001) increase in TF expression was observed after LPS Injection (0.5 hour: 0.3 +/- 0.1, +1 hour: 1.3 +/- 0.9, +2 hours: 4.1 +/- 0.9), peakin g at +3 hours (10 +/- 1.9 TF mRNA molecules per monocyte), As TF mRNA level s Increased, thrombin generation was augmented, Peak levels of TAT and F1 2 were reached later (at t +4 hours) than those of TF mRNA. TF mRNA, TAT, and F1 + 2 levels returned to baseline after 24 hours. In conclusion, we us ed a NASBA/ECL-based technique to quantify TF mRNA in whole blood during hu man endotoxemia and observed a 125-fold increase in TF mRNA levels, Our dat a demonstrate a pivotal role for enhanced TF gene activity in the activatio n of coagulation after LPS challenge. (C) 2000 by The American Society of H ematology.