Endothelial targeting and enhanced antiinflammatory effects of complement inhibitors possessing sialyl Lewis(x) moieties

The complement inhibitor soluble complement receptor type 1 (sCR1) and a truncated form of sCR1, sCR1[desLHR-A], have been generated with expression of the selectin-reactive oligosaccharide moiety, sialyl Lewis(x) (sLe(x)), as N-linked oligosaccharide adducts. These modified proteins, sCR1sLe(x) and sCR1[desLHR-A]sLe(x), were assessed in the L-selectin- and P-selectin- dependent rat model of lung injury following systemic activation of complement by cobra venom factor and in the L-selectin-, P-selectin-, and E- selectin-dependent model of lung injury following intrapulmonary deposition of IgG immune complexes. In the cobra venom factor model, sCR1sLe(x) and sCR1[desLHR-A]sLe(x) caused substantially greater reductions in neutrophil accumulation and in albumin extravasation in lung when compared with the non- sLe(x)-decorated forms. In this model, increased lung vascular binding of sCR1sLe(x) and sCR1[desLHR-A]sLe(x) occurred in a P-selectin-dependent manner, in contrast to the absence of any increased binding of sCR1 or sCR1[desLHR-A]. In the IgG immune complex model, sCR1[desLHR-A]sLe(x) possessed greater protective effects relative to sCR1[desLHR-A], based on albumin extravasation and neutrophil accumulation. Enhanced protective effects correlated with greater lung vascular binding of sCR1[desLHR-A]sLe(x) as compared with the non-sLe(x)-decorated form. In TNF-α-activated HUVEC, substantial in vitro binding occurred with sCR1[desLHR-A]sLe(x) (but not with sCR1[desLHR-A]). This endothelial cell binding was blocked by anti-E-selectin but not by anti-P-selectin. These data suggest that sLe(x)-decorated complement inhibitors have enhanced antiinflammatory effects and appear to have enhanced ability to localize to the activated vascular endothelium.