ALPHA-GALACTOSYL EPITOPE-MEDIATED ACTIVATION OF PORCINE AORTIC ENDOTHELIAL-CELLS - TYPE-I ACTIVATION

Background. The galactose alpha(1-3)galactose (alpha-gal) epitope asso ciated with membrane glycoproteins and glycolipids represents a major determinant recognized on porcine cells by human xenoreactive natural antibodies (XNA), Together, bound XNA and complement rapidly induce po rcine aortic endothelial cell (PAEC) activation; this process is assoc iated with cellular shape changes, transient development of intercellu lar gaps, and loss of ATDPase and thrombomodulin, with release of hepa ran sulfate. The aim of this study was to evaluate patterns of type I endothelial cell activation (i,e,, activation that does not require pr otein synthesis) following ligation of alpha-gal epitopes with anti-Ga l antibodies and alpha-gal-specific lectins, Methods and Results. PAEC incubated in the presence of the alpha-gal binding, Bandeiraea simpli cifolia lectin (BS-I) underwent cellular shape changes associated with the formation of intercellular gaps. PAEC exposure to BS-I was also a ssociated with the tyrosine phosphorylation of a protein (apparent mol ecular mass of approximately 130 kDa), not observed following lipopoly saccharide, tumor necrosis factor, or XNA stimulation, This lectin-ind uced tyrosine phosphorylation was not affected by cytochalasin D (inhi bitor of actin filament polymerization), by genistein (inhibitor of ty rosine kinases), or by staurosporine (inhibitor of tyrosine phosphoryl ation and protein kinase C), In addition, incubation of PAEC with BS-I and monoclonal anti-Gal IgM induced p42/44 map kinase and activated t he transcription factor NF-kappa B. Conclusions, Agonist binding of al pha-gal can evoke endothelial cell activation independently of complem ent activation. These observations have implications for the survival Of xenografts.