In acute
myocardial infarction (AMI),
monocyte procoagulant activity is increased and may contribute to the risk for recurrence and other thrombotic events. This study sought to investigate the role
tissue factor (TF) and
tissue factor pathway inhibitor-1 (TFPI-1) in the regulation of
monocyte procoagulant activity in AMI. Serial venous blood samples were obtained from 40 patients with AMI undergoing revascularization by
stent placement. Twenty patients with elective stenting for
stable angina served as control subjects. TF proteolytic activity was measured with
spectrozyme factor Xa (FXa), TF and TFPI-1 surface expression on monocytes by flow cytometry,
RNA expression in whole blood by reverse transcription-polymerase chain reaction, and concentrations of plasma
prothrombin fragments F(1 + 2) by immunoassay. Forty-eight hours after AMI, an increase was found in TF
RNA, followed by an increase in TF surface expression by 24% +/- 4% and in plasma concentration of F(1 + 2) by 103% +/- 17% (P <.05). These changes could not be attributed to the intervention because they did not occur in the control group. TFPI-1
RNA and binding to the monocyte surface remained unchanged. FXa generation by monocytes of patients with AMI increased 53.6% +/- 9% in the presence of polyclonal
antibodies to TFPI-1, indicating that cell-associated TFPI-1 inhibits monocyte TF activity. The increased
monocyte procoagulant activity in AMI was caused by an up-regulation of TF that was partially inhibited by surface-bound TFPI-1.
Anticoagulant therapy by direct inhibition of TF activity may, thus, be particularly effective in AMI. (Blood. 2001;97:3721-3726)