Critical role of P-selectin-dependent rolling in tumor necrosis factor-alpha-induced leukocyte adhesion and extravascular recruitment in vivo.

Leukocyte-endothelium interactions are dependent on a coordinated expression and function of specific adhesion molecules. The objective of the present study was to examine the role of selectin function and leukocyte rolling in tumor necrosis factor-alpha (TNF-alpha)-induced leukocyte adhesion and extravasation in venules in vivo. For this purpose, we used intravital microscopy in the mouse cremaster muscle stimulated for 2-3 h with TNF-alpha intrascrotally. Pretreatment with fucoidan, which inhibits P- and L-selectin, and a P-selectin monoclonal antibody (RB40.34) abolished TNF-alpha-stimulated leukocyte rolling. This great reduction in rolling caused a marked attenuation of firm adhesion and extravascular accumulation of leukocytes. When fucoidan and RB40.34 were administrated after stimulation with TNF-alpha, it was found that leukocyte rolling was greatly reduced whereas the number of firmly adherent leukocytes was completely unchanged, suggesting that the inhibitory effect of blocking P-selectin function on firm leukocyte adhesion and recruitment was due to the reduction in leukocyte rolling along the endothelium. Moreover, pretreatment with a monoclonal antibody against intercellular adhesion molecule-1 (ICAM-1) and a platelet-activating factor (PAF)-receptor antagonist had no effect of TNF-alpha-induced leukocyte rolling and adhesion, indicating that molecules other than ICAM-1 and PAF mediate firm adhesion and recruitment of leukocytes in TNF-alpha-activated tissues. Taken together, our data demonstrate that P-selectin function plays an important role in TNF-alpha-induced inflammatory cell recruitment by mediating leukocyte rolling as a precondition for cytokine-provoked firm adhesion and transmigration in vivo. These findings, thus, suggest that inhibition of P-selectin may be a central target for pharmacological intervention in inflammatory diseases.