New and more efficient multivalent glyco-ligands for asialoglycoprotein receptor of mammalian hepatocytes
ABSTRACT New multi-valent, carbohydrate ligands that contain terminal N-acetylgalactosamine (GalNAc) or lactose (Lac) were prepared using a nitrilotriacetic acid (NTA) derivative of L-lysine as scaffold. Tri-valent structures were prepared by attaching an ω-amino glycoside of GalNAc or Lac to each of the three carboxyl groups of N(ε)-protected N(α)-dicarboxymethyl-L-lysine. In addition, a hexa-valent lactoside was synthesized by attaching N(ε)-deprotected trivalent lactoside to each of the carboxyl group of N(α)-(trifluoroacetamido)hexanoyl L-aspartic acid. Tri-valent GalNAc glycosides and the hexa-valent lactoside had high affinity (dissociation constants approaching nM) for rat hepatocytes. The hexa-valent lactoside, after de-N(ε)-protection, was modified with a chelator, diethylenetriaminepentaacetic acid (DTPA), through which a fluorescent or radioactive tag, such as europium or indium, can be firmly attached. Intravenous infusion of (111)Indium-tagged hexa-valent lactoside to rats and mice resulted in nearly exclusive accumulation of radioactivity in the liver.
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- "In-HL) as an imaging marker of ASGPR. Its physical and chemical properties have been published previously  . "
ABSTRACT: The asialoglycoprotein receptor on hepatocyte membranes recognizes the galactose residues of glycoproteins. We investigated the specificity, accuracy and threshold value of asialoglycoprotein receptor imaging for estimating liver reserve via scintigraphy using (111)In-hexavalent lactoside in mouse models. (111)In-hexavalent lactoside scintigraphy for asialoglycoprotein receptor imaging was performed on groups of normal mice, orthotopic SK-HEP-1-bearing mice, subcutaneous Hep G2-bearing mice, mice with 20-80% partial hepatectomy and mice with acute hepatitis induced by acetaminophen. Liver reserve was measured by relative liver uptake and compared with normal mice. Asialoglycoprotein receptor blockade was performed via an in vivo asialofetuin competitive binding assay. A total of 73.64±7.11% of the injection dose accumulated in the normal liver tissue region, and radioactivity was barely detected in the hepatoma region. When asialoglycoprotein receptor was blocked using asialofetuin, less than 0.41±0.04% of the injection dose was detected as background in the liver. Asialoglycoprotein receptor imaging data revealed a linear correlation between (111)In-hexavalent lactoside binding and residual liver mass (R(2)=0.8548) in 20-80% of partially hepatectomized mice, demonstrating the accuracy of (111)In-hexavalent lactoside imaging for measuring the functional liver mass. Asialoglycoprotein receptor imaging data in mice with liver failure induced using 600 mg/kg acetaminophen revealed 19-45% liver reserve relative to normal mice and a fatal threshold value of 25% liver reserve. The (111)In-hexavalent lactoside imaging method appears to be a good, specific visual and quantitative predictor of functional liver reserve. The diagnostic threshold for survival was at 25% liver reserve in mice. Copyright © 2015. Published by Elsevier B.V.Journal of Hepatology 03/2015; DOI:10.1016/j.jhep.2015.02.052 · 10.40 Impact Factor
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ABSTRACT: Asialoglycoprotein receptor (ASGP-R) has been actively investigated for targeted delivery of therapeutic agents into hepatocytes because this receptor is selectively and highly expressed in liver and has a high internalization rate. Synthetic cluster glycopeptides (e.g., triGalNAc) bind with high affinity to ASGP-R and, when conjugated to a therapeutic agent, can drive receptor-mediated uptake in liver. We developed a novel fluorescent polarization (FP) ASGP-R binding assay to determine the binding affinities of ASGP-R-targeted molecules. The assay was performed in 96-well microplates using membrane preparations from rat liver as a source of ASGP-R and Cy5 fluorophore-labeled triGalNAc synthetic ligand as a tracer. This high-throughput homogeneous assay demonstrates advantages over existing multistep methods in that it minimizes both time and resources spent in determining binding affinities to ASGP-R. At the optimized conditions, a Z' factor of 0.73 was achieved in a 96-well format.Analytical Biochemistry 02/2012; 425(1):43-6. DOI:10.1016/j.ab.2012.02.024 · 2.22 Impact Factor
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ABSTRACT: We have synthesized and characterized doxorubicin (DOX)-loaded galactosylated gelatin nanovectors using in vitro and in vivo for targeting liver cells including hepatocarcinoma cells. Galactosylated and nongalactosylated gelatin nanovectors (GL-GN-DOX and GN-DOX) were spherical in shape and had mean sizes of about 95.1 and 88.3 nm, respectively. In-vitro release of DOX from nanovectors followed first-order kinetics and was pH dependent. Galactosylated formulation released 95.2% of DOX compared with 86.6% by nongalactosylated formulation at pH 5.8. However, the release rate was suppressed at pH 7.4. Further, we showed that GL-GN-DOX had greater growth inhibitory effect on HepG2 in terms of low inhibitory concentration (IC(50); 0.35 µg/ml) compared with GN-DOX (0.75 µg/ml) and induced caspase-3-mediated apoptosis in HepG2 cells. This might be due to efficient internalization of galactosylated nanovectors by HepG2 cells compared with unmodified formulation. Pharmacokinetic and biodistribution analyses show that galactosylated formulation deposits 24.5 µg/g of DOX in targeted tissue (liver) in comparison with heart (0.3 µg/g) at a single dose of 10 mg/kg. These results suggest that DOX-loaded galactosylated gelatin nanovectors warrant future in-depth antitumor study to scale-up technology and may be used for the management of hepatocarcinoma.Anti-cancer drugs 03/2012; 23(8):836-45. DOI:10.1097/CAD.0b013e328351424f · 1.89 Impact Factor