Calin from Hirudo medicinalis, an inhibitor of von Willebrand factor binding to collagen under static and flow conditions.
Calin from the saliva of the medicinal leech, Hirudo medicinalis, is a potent inhibitor of collagen mediated platelet adhesion and activation. In addition to inhibition of the direct platelet-collagen interaction, we presently demonstrate that binding of von Willebrand to coated collagen can be prevented by Calin, both under static and flow conditions in agreement with the occurrence of binding of Calin to collagen, confirmed by Biospecific Interaction Analysis. To define whether Calin acted by inhibiting the platelet-collagen or the platelet-von Willebrand factor (vWF)-collagen-mediated thrombus formation, platelet adhesion to different types of collagens was studied in a parallel-plate flow chamber perfused with whole blood at different shear rates. Calin dose-dependently prevented platelet adhesion to the different collagens tested both at high- and low-shear stress. The concentration of Calin needed to cause 50% inhibition of platelet adhesion at high-shear stress was some fivefold lower than that needed for inhibition of vWF-binding under similar conditions, implying that at high-shear stress, the effect of Calin on the direct platelet-collagen interactions, suffices to prevent thrombus formation. Platelet adhesion to extracellular matrix (ECM) of cultured human umbilical vein endothelial cells was only partially prevented by Calin, and even less so at a high-shear rather than a low-shear rate, whereas the platelet binding to coated vWF and fibrinogen were minimally affected at both shear rates. Thus, Calin interferes with both the direct platelet-collagen interaction and the vWF-collagen binding. Both effects may contribute to the inhibition of platelet adhesion in flowing conditions, although the former seems to predominate.
Center for Molecular and Vascular Biology, University of Leuven, Belgium.
J
J
Harsfalvi
J M
JM
Stassen
M F
MF
Hoylaerts
E
E
Van Houtte
R T
RT
Sawyer
J
J
Vermylen
H
H
Deckmyn
D000818:Animals; D003094:Collagen / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007447:Invertebrate Hormones / Q000494:pharmacology*; D007700:Kinetics; D007865:Leeches; D010973:Platelet Adhesiveness / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011485:Protein Binding; D012471:Salivary Proteins and Peptides / Q000494:pharmacology*; D013314:Stress, Mechanical; D013997:Time Factors; D014841:von Willebrand Factor / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*
D007447:Invertebrate Hormones; D010975:Platelet Aggregation Inhibitors; D012471:Salivary Proteins and Peptides; D014841:von Willebrand Factor; C072490:calin; D003094:Collagen