INOSITOL POLYANIONS - NONCARBOHYDRATE INHIBITORS OF L-SELECTIN AND P-SELECTIN THAT BLOCK INFLAMMATION

Selectins are cell adhesion molecules known to support the initial att achment of leukocytes to inflamed vascular endothelium through their r ecognition of carbohydrate ligands such as the tetrasaccharide sialyl Lewis(x) (NeuSAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc-). In the present study, we describe the inhibition of L- and P-selectin functio n by inositol polyanions, simple 6-carbon ring structures that have mu ltiple ester-linked phosphate or sulfate groups. In a purified compone nt competition assay, binding of L- and P-selectin-Ig fusion proteins to immobilized bovine serum albumin-sialyl Lewis(x) neoglycoprotein wa s inhibited by inositol hexakisphosphate (InsP(6) IC50 = 2.1 +/- 1.4 m u M and 160 +/- 40 mu M), by inositol pentakisphosphate (InsP(5), IC50 = 1.4 +/- 0.2 and 260 +/- 40 mu M), and by inositol hexakissulfate (I nsS(6),, IC50 = 210 +/- 80 mu M and 2.8 +/- 0.9 mM); E-selectin-Ig bin ding was unaffected. Inositol polyanions diminished the adhesion of LS 180 colon carcinoma cells to plates coated with L- and P-selectin-Ig b ut not with E-selectin-Ig. Inositol polyanions blocked polymorphonucle ar leukocyte (PMN) adhesion to COS cells expressing recombinant transm embrane P-selectin but not to those expressing E-selectin. In addition , inositol polyanions diminished PMN adhesion to activated endothelial cells under rotation-induced shear stress, a process known to require L-selectin function. In vivo, the effects of inositol polyanions were studied in two murine models of acute inflammation. Intravenously adm inistered InsP(6), (two doses of 40 mu mol/kg) inhibited PMN accumulat ion in thioglycolate-induced inflammation (55 +/- 10% inhibition) and in zymosan-induced inflammation (61 L 4% inhibition), InsP(5) and Ins( 6), also inhibited inflammation in these models, although higher doses were required for InsS(6). In conclusion, inositol polyanions are non carbohydrate small molecules that inhibit L- and P-selectin function i n vitro and inflammation in vivo.