Sulfatides activate platelets through P-selectin and enhance platelet and platelet-leukocyte aggregation.
OBJECTIVE
Sulfatides are sulfated glycosphingolipids present on the surface of a variety of cells; however, their exact physiological function is not known. Recently, we have shown that the inhibition of sulfatide-P-selectin interactions leads to disaggregation of platelet aggregates.


RESULTS
In this study, we show that sulfatides activated platelets as they increased activation of GPIIb/IIIa (PAC-1 epitope) and expression of P-selectin on the platelet surface. Furthermore, sulfatides aggregated washed platelets in a dose-dependent manner and enhanced platelet aggregation in platelet-rich plasma. Previous activation of platelets was necessary for this effect. Monoclonal anti-P-selectin antibodies inhibited not only sulfatide-induced PAC-1 binding to platelets but also sulfatide-induced platelet aggregation, suggesting that sulfatides activate platelet GPIIb/IIIa via signaling through P-selectin. The proaggegatory effect of sulfatides was also observed in an ex vivo thrombosis model using whole blood and pulsatile flow at 37 degrees C. In this model, sulfatides significantly enhanced platelet aggregation and the formation of platelet-leukocyte aggregates.


CONCLUSIONS
We show that sulfatide-P-selectin interactions lead to subsequent platelet activation and P-selectin expression, forming a positive feedback loop that can potentiate formation of stable platelet aggregates. In addition, sulfatides enhance the aggregation of platelet-leukocyte aggregates. These mechanisms may play a significant role in hemostasis and thrombosis.
Merten
Michael
M
Division of Cardiology, Department of Internal Medicine, University Hospital Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany. michael_merten@yahoo.com
Beythien
Christian
C
Gutensohn
Kai
K
Kühnl
Peter
P
Meinertz
Thomas
T
Thiagarajan
Perumal
P
D000244:Adenosine Diphosphate / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism*; D002449:Cell Aggregation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D019007:P-Selectin / Q000235:genetics / Q000378:metabolism*; D015539:Platelet Activation / Q000502:physiology*; D010974:Platelet Aggregation / Q000187:drug effects*; D010979:Platelet Function Tests / Q000379:methods; D013433:Sulfoglycosphingolipids / Q000494:pharmacology*; D013927:Thrombosis / Q000378:metabolism / Q000473:pathology
D019007:P-Selectin; D013433:Sulfoglycosphingolipids; D000244:Adenosine Diphosphate