Introduction: In thrombotic processes, during the association of leukocytes with platelets and endothelial cells, P-selectin glycoprotein ligand-1 (PSGL-1) binds to P-selectin, expressed on activated platelets and endothelial cells. Our aim was to establish the role of PSGL-1 in thrombus formation by evaluating the response to thrombotic stimuli in wild type and PSGL-1 knockout mice. Materials and methods: Mice were challenged by tail vein injection of (i) 15 μg collagen plus 3 μg epinephrine (coll/epi) (ii) 7.5 μg collagen plus 1.5 μg epinephrine or (iii) saline. Retro-orbital blood samples were collected in ACD anticoagulaed tubes and platelet and leukocyte counts were measured. In addition, kidneys, liver, spleen and lungs were investigated for fibrin deposition by immunohistochemistry and Western-blotting. Frozen sections were analysed for double labeling for platelet and leukocyte presence. Results: After coll/epi challenge, the number of platelets and leukocytes decreased significantly in both genotypes. Lower agonist concentration resulted in an attenuated platelet decrease in PSGL-1 knockout mice compared to the controls, however changes in leukocyte and neutrophil counts were not significantly different in the two strains. In knockout mice considerably less fibrin deposition has been observed in the lungs by Western-blotting and immunohistochemistry. After coll/epi challenge the lungs of the PSGL-1 knockout animals contained both platelets and leukocytes but less thrombi has been detected than in wild-type mice. Conclusions: Our results indicate that the deficiency of PSGL-1 results in milder thrombocytopenia, less fibrin deposition and lower number of thrombosed blood vessels, suggesting that this molecule is essential for multicellular interactions during thrombus formation.
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