In vivo Targeting of Sialyl-Lewis X Conjugated Liposome to Inflamed Site

Abstract

Purpose:: E-selectin, which is expressed on activated endothelial cells, is shown to mediate endothelial cell-leukocyte adhesion by binding a sialylated carbohydrate structure, sialyl-Lewis X (SLX), found on leukocyte. The aim of this study was to evaluate the potential of SLX-conjugate liposome (sLe^XL) as a site-directed delivery system to activated endothelial cells in vivo using murine experimental autoimmune uveoretinitis (EAU) model.

Methods:: Four experiments were undertaken in this study. (Exp 1) Fluorescein isothiocyanate (FITC) labeled sLe^XL (F-sLe^XL) or its vehicle (F-L) was given intravenously as a bolus to EAU mice. Unimmunized normal mice were served as controls. Sequential tissue accumulation of both compounds was examined. (Exp2) Expression of E-selectin in EAU mice or normal mice was studied using immunohistochemistry. (Exp3) Anti-E-selectin antibody, as a blocking antibody, was given intravenously to EAU mice prior to the injection of F-sLe^XL. Effect of the antibody as of inhibition of the accumulation of F-sLe^XL in inflamed eye was examined. (Exp4) 2µg-dexamethasone encapsulating sLe^XL (d- sLe^XL) was injected intravenously as a bolus to EAU mice. Mice injected free dexamethasone solution (1mg) were served as control. Concentration of dexamethasone in several organs was measured by radioimmunoassay.

Results:: The localization of E-selectin, whose expression was not detected in normal mice, was at the same site as where FITC accumulated. Accumulation of FITC was only observed in F-sLe^XL treated EAU mice. F-sLe^XL accumulated at activated endothelial cells within five minutes, which was inhibited using anti-selectin antibody. The FITC color was dispersed sequentially to the entire retina. The d-sLe^XL showed selective targeting to inflamed eye, where nearly two folds higher dexamethasone concentration was achieved in the eye of EAU mice compare to that with 1mg free dexamethasone.

Conclusions:: sLe^XL may be an efficient in vivo targeting delivery system to inflammatory sites.

Keywords: uveitis-clinical/animal model • inflammation • drug toxicity/drug effects