Monocyte tissue factor response is decreased in patients with hyperlipidemia

A Simplified and High-Throughput Chromogenic Assay for Testing Tissue Factor–Dependent Procoagulant Activity

Tissue factor (TF), the primary initiator of the coagulation cascade, plays a critical role in hemostasis and thrombosis, and inhibition of TF activity appears to be an attractive target for the treatment of cardiovascular diseases. However, few selective small-molecule inhibitors of TF are available, and the present assays for measuring TF activity are relatively expensive and complex. The authors present a simple and high-throughput chromogenic assay for screening TF inhibitors based on using commercial human prothrombin complex instead of purified coagulation factors, reducing the dosage, and performing with a one-stage procedure. In the optimized assay, <45 µL cell lysates was incubated with Tris-CaCl2 buffer (pH 7.3) containing human prothrombin complex at 37°C for 15 min in 96-well or 384-well plates. Tris-EDTA buffer (pH 8.4) containing chromogenic substrate Xa was then added and the absorbance measured at 405 nm. This simplified assay was more sensitive or precise than some reported methods for TF procoagulant activities. Two known active compounds (curcumin and simvastatin) inhibiting TF activity were tested by the simplified assay to validate the screening method. Furthermore, berberine and cryptotanshinone suppressed TF activity induced by lipopolysaccharides in human monocytes by this assay and might be promising new TF inhibitors.

Dietary lipid lowering modifies plaque phenotype in rabbit atheroma after angioplasty: a potential role of tissue factor

BACKGROUND

Tissue factor (TF), the main initiator of blood coagulation, is involved in cellular migration and angiogenesis processes. TF is expressed strongly in lipid-rich plaques and probably plays an important role in the thrombotic complications of plaque rupture. This study analyzes the effect of dietary lipid lowering on TF expression and cellular modifications in angioplasty-induced rabbit plaque rupture.

METHODS AND RESULTS

After experimental plaque rupture by balloon angioplasty in atheromatous rabbits, animals were assigned a 0.2% or a 2% cholesterol diet, and the TF content of arterial wall and the associated histological modifications were analyzed after 4 weeks. Early effects of lipid lowering were observed: The increase of TF expression in the vascular wall was stronger in the 2% than in the 0.2% cholesterol diet group (iliac arteries: 1226+/-308 versus 72+/-29 mU TF/g artery, P<0.005). Immunohistochemistry indicated that TF expression was associated with sprout of neovessels, which was more pronounced in the 2% than in the 0.2% cholesterol group.

CONCLUSIONS

This study shows that dietary lipid lowering decreases the thrombotic potential of ruptured atherosclerotic plaques through TF decrease. Moreover, high TF expression is associated with marked angiogenesis in the vascular wall, which is reduced by lipid lowering. These results provide further arguments for strong dietary lipid lowering to reduce plaque instability and thrombogenicity.

Level of plasma tissue factor pathway inhibitor is inversely correlated with intraarterial diastolic pressure in subjects who underwent coronary angiography

There are only a few studies of the relationship between hemostatic abnormalities and intraarterial pressure, so the present study investigated the association of various newer lipid and hemostatic variables with intraarterial pressure levels. Levels of total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, triglyceride, lipoprotein-(a), remnant-like particle cholesterol, cholesteryl ester transfer protein, uric acid, blood glucose, fibrinogen, free form of tissue factor pathway inhibitor (TFPI), C-reactive protein, serum amyloid A protein, anti-Chlamydia pneumoniae immunoglobulin G and immunoglobulin A, and apolipoproteins (apo) A-I, B, and E were measured in 176 patients who underwent diagnostic coronary angiography. Intraarterial blood pressure was determined from central aortic pressure using a standard fluid-filled catheter-external transducer system. Multivariate regression analyses showed that TFPI level was the only independent factor associated with aortic diastolic pressure. The linear regression equation demonstrated a significant negative correlation of TFPI level with aortic diastolic pressure (r=-0.395, p=0.0011). With respect to the association with other parameters, the TFPI level showed significant correlations between the HDL-C level and the apo A-I level, both in the overall patients and in the patients with coronary artery stenosis. This is the first evidence that the level of the plasma free form of TFPI is inversely correlated to aortic diastolic pressure.