Platelet-monocyte cross talk and tissue factor expression in stable angina vs. unstable angina/non ST-elevation myocardial infarction.

Tissue factor (TF), the major procoagulant in vivo, is usually absent from blood cells. However, since both monocyte TF (MoTF) expression and platelet activation are present in acute coronary syndrome we hypothesized that MoTF expression may in part depend on monocyte platelet aggregate (MPA) formation in coronary artery disease (CAD). Patients with unstable angina/non-ST-elevation myocardial infarction (UA/NSTEMI, n = 20) had significantly higher levels of MoTF (17.4 ± 3.1MFI) and MPAs (CD42b:273 ± 183MFI; CD62P:256.3 ± 48.5MFI) than patients with stable angina (SA, n = 40; MoTF:13.2 ± 2.2MFI, p = 0.001; CD42b:160 ± 113MFI, p = 0.025; CD62P:118.7 ± 24.5MFI, p = 0.018) as measured by whole blood flow cytometry on CD14+-cells. TF-activity of isolated mononuclear cells (MNC) was elevated in UA/NSTEMI (75 ± 27 pg/mL) in comparison to SA (47 ± 17 pg/mL, p = 0.001) as determined by chromogenic assay, and TF mRNA expression in isolated MNC was more frequent in UA/NSTEMI than in SA (50% vs. 18.2%; p = 0.017). MoTF expression significantly correlated with the constitutive platelet marker CD42b (r = 0.69, p < 0.001) and the platelet activation marker CD62P (r = 0.47, p = 0.001) on CD14+-cells suggesting its association with MPAs in UA/NSTEMI. In addition, MoTF expression correlated with MoTF activity of isolated MNC (r = 0.41, p = 0.01) and plasma levels of the F1.2 prothrombin fragment (r = 0.35, p = 0.02). In conclusion, MoTF and MPAs are elevated in UA/NSTEMI compared with SA. MoTF expression correlates with platelet mass and activity attached to monocytes.