Role of platelet-activating factor in functional alterations induced by xenoreactive antibodies in porcine endothelial cells.
BACKGROUND
Platelet-activating factor (PAF) is a phospholipid mediator of inflammation which has been implicated in rejection. The interaction of anti-alpha-galactosyl natural antibodies (anti-alpha gal Abs) with endothelial cells is the initial step for the development of xenograft rejection. In our study, we stimulated porcine aortic endothelial cells (PAEC) with anti-alpha gal IgG to investigate the synthesis of PAF from PAEC and its biological consequences.


RESULTS
PAF was extracted and chromatographically purified from cultured PAEC stimulated with baboon anti-alpha gal Abs. The Abs induced a dose-dependent synthesis of PAF peaking after 30 min of incubation, and decreasing thereafter. Concomitant cell shape change, motility, and cytoskeleton redistribution were observed. These events were prevented by addition of a panel of PAF-receptor antagonists. An SV40 T-large antigen-immortalized PAEC line was engineered to express PAF acetyl-hydrolase (PAF-AH) cDNA, the major PAF-inactivating enzyme. These transfected cells exposed to anti-alpha gal Abs showed reduced cell contraction and motility compared with empty vector-transfected cells. Moreover, in PAEC stimulated with anti-alpha gal Abs, the synthesis of PAF promoted the adhesion of a monocytic cell line as shown by the inhibitory effect of PAF-receptor antagonists and of PAF-AH expression. Finally, studies on cell monolayer demonstrated an enhanced permeability 48 hr after exposure to anti-alpha gal Abs, and this increase was prevented by PAF-inactivation and by PAF-receptor blockade.


CONCLUSIONS
These results demonstrate that on stimulation with anti-alpha gal Abs, PAEC synthetize PAF which can contribute to several vascular events involved in xenograft rejection.
Biancone
L
L
Department of Internal Medicine, University of Torino, Italy.
Cantaluppi
V
V
Segoloni
G
G
Boccellino
M
M
Del Sorbo
L
L
Conaldi
P G
PG
Tjoelker
L W
LW
Maruyama
S
S
Cantu
E
E
Stern
D
D
Andres
G
G
Camussi
G
G
D000818:Animals; D000910:Antibodies, Heterophile / Q000494:pharmacology*; D002448:Cell Adhesion; D002460:Cell Line; D002463:Cell Membrane Permeability; D004730:Endothelium, Vascular / Q000166:cytology* / Q000276:immunology; D006801:Humans; D010972:Platelet Activating Factor / Q000502:physiology*; D013552:Swine; D020298:U937 Cells / Q000166:cytology
D000910:Antibodies, Heterophile; D010972:Platelet Activating Factor