ristocetin and Arteriosclerosis

VCL, fragment Leu504 to Lys728 of von Willebrand factor (vWF) expressed in Escherichia coli, contains the glycoprotein (GP) Ib-binding domain of vWF. This fragment inhibited ristocetin-induced platelet aggregation with an IC50 of 0.2 mumol/L and botrocetin-induced platelet aggregation with an IC50 of 0.08 mumol/L. We studied the antiadhesive profile of VCL by adding it to blood that was circulated over various adhesive surfaces. VCL inhibited adhesion to endothelial cell matrix, which served as a model of the vessel wall. Maximal inhibition at a high shear rate of 1600 s-1 was stronger (60%) than at a low shear rate of 300 s-1 (40%). Half maximal inhibition was found to be 1.5 mumol/L at both shear rates. The role of various adhesive molecules was investigated in more detail by coating glass coverslips with collagen type I, laminin, fibronectin, or vWF. Fibrinogen was studied as well. Platelet adhesion to laminin and vWF was not inhibited by VCL. Adhesion to collagen, fibronectin, and fibrinogen was particularly inhibited at a high shear rate. VCL coated to a coverslip caused a concentration-dependent adhesion that was blocked by antibodies against GPIb, which block interaction with vWF. Binding studies showed a nonsaturable ristocetin binding of VCL to platelets that was blocked by vWF or inhibitory antibodies against GPIb. Binding to collagen was weak, and VCL did not inhibit binding of vWF at a 5000-fold excess. From these data, we conclude that VCL inhibits adhesion in all cases in which adhesion is vWF dependent by competing for vWF binding to activated GPIb. The lack of inhibition of adhesion to vWF as a single molecule may be explained by assuming that this adhesion is determined by interaction of nonactivated GPIb with vWF that has been changed in conformation by adsorption. Studies investigating thrombus formation on the connective tissue of an atherosclerotic plaque in a human coronary artery showed that VCL was able to partially prevent this thrombus formation. VCL may be of value in preventing adhesion and thrombus formation under conditions in which these processes are dependent on vWF.

Topics: Animals; Arteriosclerosis; Collagen; Crotalid Venoms; Endothelium, Vascular; Escherichia coli; Fibrinogen; Fibronectins; Humans; Laminin; Mice; Peptide Fragments; Platelet Adhesiveness; Platelet Aggregation; Platelet Aggregation Inhibitors; Recombinant Proteins; Ristocetin; von Willebrand Factor

Topics: Arteriosclerosis; Blood Coagulation Tests; Blood Transfusion; Deamino Arginine Vasopressin; Factor VIII; Humans; Platelet Aggregation; Prenatal Diagnosis; Ristocetin; von Willebrand Diseases; von Willebrand Factor

Topics: Animals; Arteriosclerosis; Blood Platelets; Cardiovascular Diseases; Humans; Hyperlipoproteinemias; Liver Cirrhosis; Lysophosphatidylcholines; Phosphatidylcholine-Sterol O-Acyltransferase; Platelet Adhesiveness; Platelet Aggregation; Rabbits; Ristocetin; Thrombosis; von Willebrand Factor

Von Willebrand pigs have all the manifestations of the severe human disease. The role of Willebrand antigen (VIII R:AG) and ristocetin cofactor (VIII: RWF) was assessed in these pigs by (1) transfusion and (2) "in vitro" bleeding time assay. The skin bleeding time became normal when the level of transfused Willebrand factor (VIII R:AG/RWF) was raised in the plasma above 30 U/dl. After single or repeated transfusions, skin capillary endothelium and platelets were still distinguished from normal by VIII R:AG deficiency. When incisions in excised porcine skin ("in vitro" bleeding time) were perfused with blood and plasma fractions, haemostasis occurred when plasmatic Willebrand factor exceeded 30 U/dl whether the skin or platelets came from normal or from von Willebrand pigs. The platelet plug occluding the skin incision contained VIII R:AG by immunofluorescence. Willebrand factor appears to coat surfaces and to serve as a platelet attachment protein. These bleeder pigs are resistant to atherosclerosis. If platelets are involved in early atherosclerotic lesions, the role of Willebrand factor in platelet - blood vessel interaction may be important.

Topics: Animals; Arteriosclerosis; Blood Coagulation Factors; Blood Platelets; Disease Models, Animal; Endothelium; Hemostasis; Platelet Adhesiveness; Ristocetin; Swine; von Willebrand Factor

Topics: Adult; Antigens; Arteriosclerosis; Cholesterol; Diabetes Complications; Diabetes Mellitus; Diabetic Retinopathy; Factor VIII; Fibrinogen; Fibrinolysis; Humans; Lipoproteins, HDL; Male; Middle Aged; Ristocetin

Topics: Animals; Antigens; Arteriosclerosis; Factor VIII; Hemostasis; Humans; Ristocetin; von Willebrand Diseases