POLYMORPHONUCLEAR LEUKOCYTE ADHESION TRIGGERS THE DISORGANIZATION OF ENDOTHELIAL CELL-TO-CELL ADHERENS JUNCTIONS

Polymorphonuclear leukocytes (PMN) infiltration into tissues is freque ntly accompanied by increase in vascular permeability. This suggests t hat PMN adhesion and transmigration could trigger modifications in the architecture of endothelial cell-to-cell junctions. In the present pa per, using indirect immunofluorescence, we found that PMN adhesion to tumor necrosis factor-activated endothelial cells (EC) induced the dis appearance from endothelial cell-to-cell contacts of adherens junction (AJ) components: vascular endothelial (VE)-cadherin, alpha-catenin, b eta-catenin, and plakoglobin. Immunoprecipitation and Western blot ana lysis of the VE-cadherin/catenin complex showed that the amount of bet a-catenin and plakoglobin was markedly reduced from the complex and fr om total cell extracts. In contrast, VE-cadherin and alpha-catenin wer e only partially affected. Disorganization of endothelial AJ by PMN wa s not accompanied by EC retraction or injury and was specific for VE-c adherin/catenin complex, since platelet/endothelial cell adhesion mole cule 1 (PECAM-1) distribution at cellular contacts was unchanged. PMN adhesion to EC seems to be a prerequisite for VE-cadherin/catenin comp lex disorganization. This phenomenon could be fully inhibited by block ing PMN adhesion with an anti-integrin beta(2) mAb, while it could be reproduced by any condition that induced increase of PMN adhesion, suc h as addition of PMA or an anti-beta(2)-activating mAb. The effect on endothelial AJ was specific for PMN since adherent activated lymphocyt es did not induce similar changes. High concentrations of protease inh ibitors and oxygen metabolite scavengers were unable to prevent AJ dis organization mediated by PMN. PMN adhesion to EC was accompanied by in crease in EC permeability in vitro. This effect was dependent on PMN a dhesion, was not mediated by proteases and oxygen-reactive metabolites , and could be reproduced by EC treatment with EGTA. Finally, immunohi stochemical analysis showed that VE-cadherin distribution was affected by PMN adhesion to the vessel wall in vivo too. This work suggests th at PMN adhesion could trigger intracellular signals in EC that possibl y regulate VE-cadherin/catenin complex disorganization. This effect co uld increase EC permeability and facilitate PMN transmigration during the acute inflammatory reaction.