Defect in regulated secretion of P-selectin affects leukocyte recruitment in von Willebrand factor-deficient mice

Stimulation of endothelial cells by various inflammatory mediators leads to release of Weibel-Palade bodies and therefore to exocytosis of both P-sele ctin (adhesion receptor for leukocytes) and von Willebrand factor (vWf) (pl atelet ligand), The potential role of vWf in leukocyte recruitment was inve stigated with the use of vWf-deficient mice. We report a strong reduction o f leukocyte rolling in venules of vWf-deficient mice. Similarly, vWf defici ency led to a decrease in neutrophil recruitment in a cytokine-induced meni ngitis model as well as in early skin wounds. In all instances with an anti body that preferentially recognizes plasma membrane P-selectin, we observed a dramatic reduction in P-selectin expression at the cell surface of vWf-d eficient endothelium, With confocal microscopy, we found that the typical r odlike shape of the Weihel-Palade body is missing in vWf -/- endothelial ce lls and that part of the P-selectin content in the vWf -/- cells colocalize d with LAMP-1, a lysosomal marker. However, intracellular P-selectin levels were similar in tumor necrosis factor alpha- and lipopolysaccharide-activa ted cells of both genotypes, We conclude that the absence of vWf, as found in severe von Willebrand disease, leads to a defect in Weibel-Palade body f ormation. This defect results in decreased P-selectin translocation to the cell surface and reduced leukocyte recruitment in early phases of inflammat ion.