Role of selectins in the intestinal epithelial migration of eosinophils

Understanding the mechanisms by which eosinophils migrate into and across the intestinal epithelium can provide alternative therapeutic targets for conditions characterized by eosinophilic cryptitis and crypt abscesses. Eosinophil migration is dependent on adhesion molecules such as selectins. Human eosinophils express L-selectin and P-selectin counterligand P-selectin glycoprotein ligand-1 (PSGL-1). The tetrasaccharide sialyl Lewis(x) (sLe(x)) binds to all three selectins, so compounds that mimic sLe(x), such as TBC1269, are potential antagonists. We hypothesized that eosinophils migrate from the basolateral to the apical surface of intestinal epithelium through the orchestrated effects of selectins. TBC1269 was added to fluorescently labeled HL-60 clone 15 eosinophils as well as human blood eosinophils, in incremental amounts. Subsequently, blocking antibodies toward L-selectin and PSGL-1 were used in a similar manner. HL-60 eosinophils were allowed to migrate into T-84 monolayers. The number of migrated HL-60 cells was calculated by comparing fluorescence with known cell densities. HL-60 and human eosinophils that were undergoing migration were significantly lower in the presence of TBC1269. This effect was concentration dependent, and near complete inhibition of migration was seen at a TBC1269 concentration of 10 mg/mL. In addition, HL-60 eosinophil migration was significantly lower in the presence of the blocking antibodies to PSGL-1 and L-selectin (39.2 and 51.6% inhibition, respectively). Simultaneous blocking of PSGL-1 and L-selectin resulted in inhibition of 76.0% of the migration. The results of this study suggest a major role for selectins in the intestinal epithelial migration of differentiated eosinophils. sLe(x), L-selectin, and the P-selectin counterligand PSGL-1 can be potential therapeutic targets.