SYNTHESIS AND IN-VITRO ACTIVITIES OF A SPACER-CONTAINING GLYCOPHOSPHOLIPID LIGAND OF A LIPOPOLYSACCHARIDE RECEPTOR INVOLVED IN ENDOTOXIN TOLERANCE

A glycophospholipid consisting in a derivative of N,N'-acylated and bi sphosphorylated 2,3-dideoxy-2,3-diamino-D-glucose, bearing a 6-aminoca proyl side chain as spacer arm at carbon 6 (PPDm2-B), has been synthes ized and its effect on murine macrophages evaluated. The synthesis sta rted from 2,3-diamino-D-glucose, which was best obtained from glucosam ine essentially by known procedures, since attempts to use another kno wn precursor (3-nitroglycoside) led to unexpected results. Selective N -acylation was performed with the hydroxysuccinimide ester of (D)-3-be nzyloxymyritic acid followed by esterification of the sole primary hyd roxyl function by 6-azidocaproylchloride and phosphorylation of the re sulting 1,4-diol by treatment with tetrabenzyl pyrophosphate. Hydrogen ation on a Pd on carbon catalyst permitted the isolation of eoxy-2,3-d i-[(R)-3-hydroxy-tetradecanamido]-alpha- D-glucopyranose 1,4-diphospha te (PPDm2-B). In mouse macrophages, PPDm2-B enhanced the lipopolysacch aride (LPS)-dependent secretion of tumor necrosis factor alpha (TNF-al pha), and inhibited the LPS-induced desensitization of these cells. Th e data suggest that PPDm2-B interacts in a serum-independent way with an LPS receptor different froth CD14, and involved in endotoxin tolera nce. Binding studies of a fluorescent derivative of PPDm2-B indicated that the expression of this unknown receptor is down-regulated during in vitro culture of the cells. Owing to its spacer arm, PPDm2-B could thus be a promising tool for future studies of this receptor. (C) 1998 Elsevier Science Ltd. All rights reserved.