[Platelet adhesion mediated by von Willebrand factor in patients with premature coronary artery disease].

Aim    To study platelet adhesion mediated by von Willebrand factor (VWF) in patients with premature ischemic heart disease (IHD).Material and methods    This study enrolled 58 patients with stable IHD, including 45 men younger than 55 years with the first manifestation of IHD at the age of <50 years and 13 women younger than 65 years with the first manifestation of IHD at the age of <60 years. The control group consisted of 33 patients, 13 men younger than 55 years and 20 women younger than 65 years without IHD. Platelet adhesion to the collagen surface at the shear rate of 1300 s-1 was studied by evaluating the intensity of scattered laser light from the collagen-coated optical substrate in a flow chamber of a microfluidic device after 15-min circulation of whole blood in the chamber. Decreases in platelet adhesion after addition to the blood of monoclonal antibodies (mAb) to platelet receptors glycoproteins Ib (GPIb) to inhibit the receptor interaction with VWF were compared for patients of both groups. Results    In patients with premature IHD, the decrease in platelet adhesion following the platelet GPIb receptor inhibition was significantly less than in patients of the control group (74.8 % (55.6; 82.7) vs. 28.9 % (-9.8; 50,5), p <0.001). For the entire sample, the median decrease in platelet adhesion following the GPIb receptor inhibition was 62.8 % (52.2; 71.2). With an adjustment for traditional risk factors of IHD, a decrease in platelet adhesion of >62.8% after blocking GPIb receptors increased the likelihood of premature IHD (OR=9.84, 95 % CI: 2.80-34.59; p <0.001).Conclusion    Blocking the interaction of GPIb receptors with VWF in patients with premature IHD and increased shear rate induced a greater decrease in platelet adhesion than in patients without this disease. This suggested that an excessive interaction of VWF with platelets might contribute to the pathogenesis of premature IHD.

Monomeric form of C-reactive protein in the assessment of the residual inflammatory cardiovascular risk in patients with subclinical carotid atherosclerosis.

Aim      To study the relationship between monomeric C-reactive protein (mCRP) and the progression of asymptomatic carotid atherosclerosis in patients with a moderate risk for cardiovascular diseases (CVD) as assessed with the SCORE model.Material and methods  The study included 80 men and women aged 53.1±5.8 years assigned to the category of a moderate risk for CVDs by the SCORE model with a low-density lipoprotein cholesterol (LDL-C) level of 2.7-4.8 mmol/l and asymptomatic, hemodynamically insignificant (<50% luminal narrowing) carotid atherosclerosis according to ultrasonic data. All patients were prescribed atorvastatin to achieve a LDL-C level <2.6 mmol/l. After 7 years of follow-up, ultrasonic examination of carotid arteries was performed, and concentrations of high-sensitivity C-reactive protein (hsCRP) and mCRP were measured.Results A concentration of LDL-C <2.6 mmol/l was achieved in all patients. The progression of atherosclerosis as determined by an increased number of atherosclerotic plaques (ASPs), was observed in 45 (56 %) patients. At 7 months of follow-up, concentrations of cCRP were higher in the group of patients with progressive carotid atherosclerosis, while the levels of hsCRP did not differ between the groups. Increased mCRP concentrations were associated with changes in variables of the "atherosclerotic load", including the number of ASPs, total ASP height, and the intima-media thickness (IMT). In patients with a median mCRP concentration of 5.2 [3.3; 7.1] µg/l and more, the increases in mean ACP number and total ASP height were considerably higher than in patients with mCRP concentrations lower than the median (3.9 and 2.7 times, respectively), whereas the odds ratio for the progression of asymptomatic carotid atherosclerosis was 5.5 (95 % confidence interval, CI: 2.1-14.6; p=0.001). ROC analysis showed that the concentration of hsCRP had no predictive value for prognosis of asymptomatic carotid atherosclerosis (p=0.16), while the area under the ROC curve (AUC) for mCRP was 0.75±0.056 (95 % CI: 0.64-0.86; p=0.001).Conclusion      According to the results of 7-year follow-up, the plasma concentration of mCRP was significantly higher in patients with an increased number of ASPs than in patients without this increase. An increased level of mCRP may indicate a higher inflammatory risk of CVD.

Complex Interaction of Platelets, von Willebrand Factor and Leukocytes, in Whole Blood at High Shear Rates Is Mediated by Platelet GPIIb/IIIa Receptor.

We studied the contribution of von Willebrand factor (vWF) into blood cell adhesion to collagen-coated surfaces in whole blood of healthy volunteers. Adhesion of blood cells to collagen I was measured at shear rate of 2300 sec-1. The interaction of platelet GPIIb/IIIa receptor with vWF was blocked with monoclonal anti-GPIIb/IIIa antibodies. The degree of cell adhesion was quantified by measuring the intensity of scattered light after 15-min perfusion: in samples with blocked GPIIb/IIIa it decreased to 0.39±0.13 V vs 0.06±0.03 V in control samples (p=0.002). Under a fluorescence microscope, intensively stained structures consisting of vWF, platelets, and leukocytes attached to the collagen surface were observed. After blockade of GPIIb/IIIa, these structures were absent. Leukocyte recruitment at high shear rates is a time-dependent process sensitive to complex interaction of vWF, leukocytes, and platelets, in which the platelet GPIIb/IIIa receptor is essential.

Kinetics of Platelet Adhesion to Protein-Coated Surface in Whole Blood Samples at High Flow Rates.

We studied platelet adhesion to fibrinogen-coated surface in whole blood samples under conditions of high flow rates. The degree of platelet adhesion was evaluated by the intensity of laser light scattered from protein-coated optical surface with adhered platelets. The intensity of adhesion in whole blood samples at high flow rates was by 2.7 (2.4; 4.1) times higher than in platelet-rich plasma samples. Among the factors intensifying platelet adhesion in the whole blood at high flow rates, von Willebrand factor is of utmost importance. At low flow rates, platelet adhesion almost totally depends on platelet-fibrinogen interaction. At high flow rates, the interactions of platelets with both fibrinogen and von Willebrand factor become equally important.

Real-Time Recording of Platelet Adhesion to Fibrinogen-Coated Surface under Flow Conditions.

We present a testing system allowing real-time recording of the kinetics of platelet adhesion to fibrinogen-coated surface under flow conditions. The system consists of an optical flow chamber, semiconductor laser, two photodetectors, analog-to-digital converter, computer, and peristaltic pump. Platelet adhesion to fibrinogen-coated surface is recorded with two photodetectors and analyzed by the intensity of total internal reflection and scattered laser radiation at the boundary of the blood sample and fibrinogen-coated optical surface. Kinetics of platelet adhesion was studied as a function of shear rate and platelet concentration. The specificity of platelet adhesion with proteins on the surface of the flow chamber was verified by blocking IIb/IIIa glycoprotein complex on platelets with Fab2 fragments of monoclonal antibodies.