Human serum-induced expression of E-selectin on porcine aortic endothelial cells in vitro is totally complement mediated.
BACKGROUND
Whereas complement is a key mediator of hyperacute xenograft rejection, its role in acute vascular rejection (AVR) is a matter of controversy. AVR is associated with de novo synthesis of endothelial cell-derived inflammatory mediators, including the leukocyte-recruiting adhesion molecule E-selectin. Here we investigate the role and mechanism of complement in human serum-induced porcine endothelial cell activation.


METHODS
An in vitro xenotransplantation method was designed using porcine aortic endothelial cells stimulated with human serum in microculture wells. E-selectin expression was measured by cell-enzyme immunoassay. Complement inhibitors acting at different levels in the cascade were investigated for their effect on E-selectin expression.


RESULTS
E-selectin was strongly induced by normal human serum but not by heat-inactivated serum. Compstatin, a synthetic C3 inhibitor, markedly reduced human serum-induced E-selectin expression. Purified C1-inhibitor suppressed E-selectin induction completely, indicating activation through the classical or lectin pathway. Furthermore, a monoclonal antibody (mAb) that inhibits cleavage of C5 or another mAb that blocks the function of C7, completely inhibited the expression of serum-induced E-selectin, consistent with the terminal C5b-9 complement complex being the mediator of the endothelial cell activation. Inhibition of the alternative pathway using a novel antifactor D mAb did not reduce E-selectin expression.


CONCLUSIONS
Human serum-induced expression of porcine E-selectin is totally complement dependent, induced by a C1-inhibitor regulated pathway and mediated through the terminal complement complex. The data may have implications for therapeutic strategies, particularly of C1-inhibitor and anti-C5 mAb, to protect against endothelial cell activation and subsequent AVR of porcine xenografts.
Sølvik
U Ø
UØ
Institute of Immunology, The National Hospital, University of Oslo, Norway.
Haraldsen
G
G
Fiane
A E
AE
Boretti
E
E
Lambris
J D
JD
Fung
M
M
Thorsby
E
E
Mollnes
T E
TE
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001011:Aorta / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D001790:Blood Physiological Phenomena; D002478:Cells, Cultured; D003172:Complement C1 / Q000187:drug effects; D003182:Complement C5 / Q000276:immunology; D003184:Complement C7 / Q000276:immunology; D003169:Complement Inactivator Proteins / Q000494:pharmacology; D015938:Complement Membrane Attack Complex / Q000502:physiology; D003165:Complement System Proteins / Q000502:physiology*; D019040:E-Selectin / Q000187:drug effects / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D010456:Peptides, Cyclic / Q000494:pharmacology; D013552:Swine / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D003172:Complement C1; D003182:Complement C5; D003184:Complement C7; D003169:Complement Inactivator Proteins; D015938:Complement Membrane Attack Complex; D019040:E-Selectin; D010456:Peptides, Cyclic; C111828:compstatin; D003165:Complement System Proteins