P-selectin reexpresses and supports leukocyte adherence on the endothelial cell surfaces by repetitive stimulations with thrombin

P-selectin is a cell adhesion molecule, which is located on the granele membrane of Weibel-Palade bodies in resting endothelial cells and expressed on the cell surfaces during celiutar activation/ foil owed by internal ization. So we investigated whether P-selectin reexpresses with subsequent cellular activation. Indirect Immunofluorescence and analysis with confocal laser cytometer (ACAS 570) led us to measure the celfular P-selectin content and surface expression of it. The surface expression of P-selectin is increased to the maximum within 2 minutes of thrombin (l U/ml) stimulation and declined to basal level after 180 minutes. Rechallenge with thrombin induced rapid reexpression of P-selectin on the endothelial surfaces. Cellular P-selectin content showed little decline throughout those courses. Moreover, reexpressed P-selectin remained the function for supporting the adherence of promyelocytic cell line HL60 cells. These results demonstrated the recycling mechanism of P-selectin, which is in contrast to cytokine-inducible adhesion molecules such as E-selectin, and provided the possibility that P-selectin might be a candidate even in chronic inflammatory diseases.