Dexamethasone-Mediated Up-Regulation of the Mannose Receptor Improves the Delivery of Recombinant Glucocerebrosidase to Gaucher Macrophages

Abstract

Enzyme replacement therapy for Gaucher disease uses a recombinant glucocerebrosidase (Cerezyme) whose oligosaccharide chains have been remodeled to expose the core mannose residues. This modification promotes the uptake of the hydrolase by Gaucher-affected macrophages via mannose receptor-mediated endocytosis. However, studies revealed that amounts of the infused enzyme were also delivered to other mannose receptor-bearing cells such as the liver sinusoidal endothelial cells. To maximize the delivery of Cerezyme to macrophages, agents that increased the cell surface levels of the mannose receptor specifically on macrophages were examined. Treatment with dexamethasone improved the in vitro uptake of Cerezyme by a macrophage but not by liver sinusoidal endothelial or hepatocyte cell lines. The enhanced uptake by the macrophages was due to an increase in surface mannose receptors because the activity could be blocked by the addition of mannans. Pretreatment of rats with the glucocorticoid also preferentially enhanced the delivery of Cerezyme to the Kupffer cells and splenic macrophages. This effect of dexamethasone also applied to substrate-laden macrophages isolated from Niemann-Pick A mice. Together, these data suggest that pretreatment with dexamethasone could specifically enhance the presentation of mannose receptors on Gaucher macrophages with resultant improvement in delivery of the enzyme to the affected cells.

Characterization of functional mannose receptor in a continuous hybridoma cell line

“…Previous studies have shown that agents and cytokines such as dexamethasone, IL-4 and GM-CSF that promote a mature “deactivated” macrophage phenotype result in the induction of MR expression and altered MR. For example, Cowan et al reported that treatment with dexamethasone increased MR expression on rodent macrophages by as much as 2.5 fold in a time and dose-dependent fashion [69]. Chakraborty et al reported that dexamethasone-induced increases in the MR resulted in increased uptake of Leishmania parasites [29], and Zhu et al demonstrated that dexamethasone treatment increased clearance of glucocerebrocidase by the MR [78]. In data not presented, we examined the effect of positive regulators (dexamethasone, GM-CSF, and IL-4) on MR expression in 43 MR cells.…”

Glycosylation and functionality of recombinant β-glucocerebrosidase from various production systems

“…The cells were then washed twice with ice cold PBS enriched with Mannan (1 mg/ml). This step is used to inhibit the uptake of the enzyme molecules through the MR [17]. To further ensure release of any proteins bound non-specifically to the membrane half of the cells were washed with ice cold glycine buffer: (0.8% NaCl, 0.038% KCl, 0.01% MgCl2, 0.01% CaCl2, 0.7% glycine [pH 3]) [18] followed by two additional cold PBS washes.…”

Carbohydrate-remodelled acid α-glucosidase with higher affinity for the cation-independent mannose 6-phosphate receptor demonstrates improved delivery to muscles of Pompe mice

“…The procedures used to assay enzyme uptake into the rat alveolar macrophage cells (NR8383) were the same as those reported previously except that rhGAA was used in lieu of Cerezyme [29]. Cells were lysed in GAA assay buffer (0.2 M sodium acetate and 0.4 M potassium chloride, pH 4.3) containing 0.1 % Triton X-100.…”