Background. Platelet-activating factor (PAF) is a phospholipid mediator of inflammation which has been implicated in rejection. The interaction of anti-α-galactosyl natural antibodies (anti-α gal Abs) with endothelial cells is the initial step for the development of xenograft rejection. In our study, we stimulated porcine aorthic endothelial cells (PAEC) with anti-α gal IgG to investigate the synthesis of PAF from PAEC and its biological consequences. Methods and Results. PAF was extracted and chromatografically purified from cultured PAEC stimulated with baboon anti-α gal Abs. The Abs induced a dose-dependent synthesis of PAF peaking after 39 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-α gal Abs showed reduced cell contraction and motility compared with empty vector-transfected cells. Moreover, in PAEC stimulated with anti-α 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-α gal Abs, and this increase was prevented by PAF-inactivation and by PAF-receptor blockade. Conclusions. These results demonstrate that on stimulation with anti-α gal Abs, PAEC synthetize PAF which can contribute to several vascular events involved in xenograft rejection.
|Number of pages||8|
|Publication status||Published - Oct 27 2000|
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