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

Abstract

Triggering of the tissue factor (TF)-dependent coagulation pathway is considered to underlie the generation of a procoagulant state during endotoxemia. To determine the in vivo pattern of monocytic TF messenger RNA (mRNA) expression during endotoxemia, 10 healthy volunteers were injected with lipopolysaccharide (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 isolated and amplified by NASBA (nucleic acid sequence-based amplification), followed by quantitation of TF mRNA by an electrochemiluminescence (ECL) assay. To compare the pattern of coagulation activation with the kinetics of monocytic TF mRNA expression, we measured plasma levels of markers of thrombin generation, thrombin-antithrombin (TAT) complexes, and prothrombin fragment 1 + 2 (F1 + 2). Baseline value (mean ± SEM) of the number of TF mRNA molecules per monocytic cell was 0.08 ± 0.02. A progressive and significant (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), peaking at +3 hours (10 ± 1.9 TF mRNA molecules per monocyte). As TF mRNA levels 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 used a NASBA/ECL-based technique to quantify TF mRNA in whole blood during human endotoxemia and observed a 125-fold increase in TF mRNA levels. Our data demonstrate a pivotal role for enhanced TF gene activity in the activation of coagulation after LPS challenge.

Procoagulant microparticles promote coagulation in a factor XI‐dependent manner in human endotoxemia

“…Another potential limitation was the fact that we focused exclusively on MPs and did not concurrently measure cell-associated procoagulant activity. However, we [28] and others [18] have previously shown that TF mRNA and activity [48] in the mononuclear cell fraction increase dramatically in the human endotoxemia model.…”

“…Increased intracellular and surface expression of TF on circulating monocytes is detectable after ex vivo LPS stimulation [17]. Similarly, total whole blood TF mRNA is increased in human endotoxemia [18,19], in addition to MP-TF and whole-blood TF activity [20]. Perhaps most convincingly, it has been shown that inhibition of the extrinsic pathway, using anti-TF antibodies [21][22][23], active site-inactivated FVIIa [24], tissue factor pathway inhibitor (TFPI) [25] or genetically altered animals with either low TF [26] or low FVII levels [27], have attenuated coagulopathy and improved survival in animal models of endotoxemia and sepsis.…”

Recombinant human antithrombin inhibits thrombin formation and interleukin 6 release in human endotoxemia

“…Human endotoxemia is a well-standardized model of systemic inflammation 13,14 and tissue factor (TF)-induced coagulation activation. 17,20,21 Detailed study procedures of the LPS model have been outlined previously. 22 In our study volunteers were randomly assigned to receive either a bolus-primed continuous infusion of recombinant human antithrombin (a generous gift from GTC Biotherapeutics, Framingham, Mass) 23 (500% or 200% antithrombin target level) or an equal volume of placebo (0.9% sodium chloride) over a period of 4 hours.…”

COVID-19 for the Cardiologist

“…The exact mechanism of DIC in the setting of sepsis and ARDS is complex, but is generally thought to be related to an immunemediated exhaustion of the coagulation and fibrinolytic systems promoting bleeding and thrombosis in the same patient (83). Endothelial injury and inflammatory cytokines, such as IL-6 and TNF-alpha, upregulate tissue factor expression, driving a pro-thombotic state (84)(85)(86)(87).…”