Adhesive interaction between P-selectin and sialyl Lewisx plays an important role in recurrent coronary arterial thrombosis in dogs

Cell adhesion molecules may play an important role in the disease process of acute coronary syndromes. We have shown a neutralizing anti-P-selectin monoclonal antibody and a sialyl Lewis(x)-containing oligosaccharide (SLe(x)-OS), an analogue of selectin ligand on leukocytes, reduce cyclic flow variations (CFVs) in a canine model of recurrent coronary arterial thrombosis, suggesting the important interaction between P-selectin and SLe(x) for the pathophysiology of these syndromes. However, the functional role of these adhesion molecules in the thrombotic process remains unclear. Therefore, we investigated effects of SLe(x)-OS on CFVs, platelet P-selectin expression, and morphology of the stenotic site in the same model. Anesthetized open-chest dogs (n=34) were randomly divided into 4 groups after developing CFVs. Dogs intravenously received saline or graded doses of SLe(x)-OS (5, 20, or 40 mg/kg bolus) infusion followed by a continuous infusion (5 mg . kg(-1) . h(-1)) for 60 minutes. By flow cytometric analysis, P-selectin expression on platelets after CFVs was significantly upregulated during CFVs. Immunohistochemical analysis revealed the incorporation of platelets with upregulated P-selectin within thrombi at the stenotic site. Microscopic observations revealed the presence of numerous platelets adhered to leukocytes at the stenotic site on the damaged endothelium. SLe(x)-OS significantly reduced CFVs, inhibited the P-selectin expression on platelets, and prevented the adherence of platelets and leukocytes. These findings further support the notion that the adhesive interaction between P-selectin on platelets and SLe(x) on leukocytes plays an important role in platelet-mediated thrombus formation in this model.