XO increases neutrophil adherence to endothelial cells by a dual ICAM-1 and P-selectin-mediated mechanism

Lance S. Terada, Brooks M. Hybertson, Kevin G. Connelly, David Weill, Dale Piermattei, and John E. Repine Webb-Waring Institute for Biomedical Research and Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262 Received 2 April 1996; accepted in final form 20 September 1996. Terada, Lance S., Brooks M. Hybertson, Kevin G. Connelly, David Weill, Dale Piermattei, and John E. Repine. XO increases neutrophil adherence to endothelial cells by a dual ICAM-1 and P-selectin-mediated mechanism. J. Appl. Physiol. 82(3): 866-873, 1997. Circulating xanthine oxidase (XO) can modify adhesive interactions between neutrophils and the vascular endothelium, although the mechanisms underlying this effect are not clear. We found that treatment with XO of bovine pulmonary artery endothelial cells (EC), but not neutrophils or plasma, increased adherence, suggesting that XO had its primary effect on EC. The mechanism by which XO increased neutrophil adherence to EC involved binding of XO to EC and production of H 2 O 2 . XO also increased platelet-activating factor production by EC by a H 2 O 2 -dependent mechanism. Similarly, the platelet-activating factor-receptor antagonist WEB-2086 completely blocked XO-mediated neutrophil EC adherence. In addition, neutrophil adherence was dependent on the 2 -integrin Mac-1 (CD11b/CD18) but not on leukocyte functional antigen-1 (CD11a/CD18). Treatment of EC with XO for 30 min did not alter intercellular adhesion molecule-1 surface expression but increased expression of P-selectin and release of von Willibrand factor. Antibodies against P-selectin (CD62) did not affect XO-mediated neutrophil adherence under static conditions but decreased both rolling and firm adhesive interactions under conditions of shear. We conclude that extracellular XO associates with the endothelium and promotes neutrophil-endothelial cell interactions through dual intercellular adhesion molecule-1 and P-selectin ligation, by a mechanism that involves platelet-activating factor and H 2 O 2 as intermediates. xanthine oxidase; platelet activating factor; CD18; CD11b; Mac-1; CD11a; leukocyte functional antigen-1; heparin; hydrogen peroxide; multiorgan failure; acute respiratory distress syndrome 0161-7567/97 $5.00 Copyright © 1997 the American Physiological Society