Organ/Cell-Selective Intracellular Delivery of Biologics via N-Acetylated Galactosamine-Functionalized Polydisulfide Conjugates

Biologics, including proteins and antisense oligonucleotides (ASOs), face significant challenges when it comes to achieving intracellular delivery within specific organs or cells through systemic administrations. In this study, we present a novel approach for delivering proteins and ASOs to liver cells, both in vitro and in vivo, using conjugates that tether N-acetylated galactosamine (GalNAc)-functionalized, cell-penetrating polydisulfides (PDSs). The method involves the thiol-bearing cargo-mediated ring-opening polymerization of GalNAc-functionalized lipoamide monomers through the so-called aggregation-induced polymerization, leading to the formation of site-specific protein/ASO-PDS conjugates with narrow dispersity. The hepatocyte-selective intracellular delivery of the conjugates arises from a combination of factors, including first GalNAc binding with ASGPR receptors on liver cells, leading to cell immobilization, and the subsequent thiol-disulfide exchange occurring on the cell surface, promoting internalization. Our findings emphasize the critical role of the close proximity of the PDS backbone to the cell surface, as it governs the success of thiol-disulfide exchange and, consequently, cell penetration. These conjugates hold tremendous potential in overcoming the various biological barriers encountered during systemic and cell-specific delivery of biomacromolecular cargos, opening up new avenues for the diagnosis and treatment of a range of liver-targeting diseases.

Optically Manipulated Microtools to Measure Adhesion of the Nanoparticle-Targeting Ligand Glutathione to Brain Endothelial Cells

Targeting nanoparticles as drug delivery platforms is crucial to facilitate their cellular entry. Docking of nanoparticles by targeting ligands on cell membranes is the first step for the initiation of cellular uptake. As a model system, we studied brain microvascular endothelial cells, which form the anatomical basis of the blood-brain barrier, and the tripeptide glutathione, one of the most effective targeting ligands of nanoparticles to cross the blood-brain barrier. To investigate this initial docking step between glutathione and the membrane of living brain endothelial cells, we applied our recently developed innovative optical method. We present a microtool, with a task-specific geometry used as a probe, actuated by multifocus optical tweezers to characterize the adhesion probability and strength of glutathione-coated surfaces to the cell membrane of endothelial cells. The binding probability of the glutathione-coated surface and the adhesion force between the microtool and cell membrane was measured in a novel arrangement: cells were cultured on a vertical polymer wall and the mechanical forces were generated laterally and at the same time, perpendicularly to the plasma membrane. The adhesion force values were also determined with more conventional atomic force microscopy (AFM) measurements using functionalized colloidal probes. The optical trapping-based method was found to be suitable to measure very low adhesion forces (≤ 20 pN) without a high level of noise, which is characteristic for AFM measurements in this range. The holographic optical tweezers-directed functionalized microtools may help characterize the adhesion step of nanoparticles initiating transcytosis and select ligands to target nanoparticles.

Synthesis and immunological evaluation of the unnatural β-linked mucin-1 Thomsen-Friedenreich conjugate

MUC1 glycopeptides are attractive antigens for anti-cancer vaccine development. One potential drawback in using the native MUC1 glycopeptide for vaccine design is the instability of the O-glycosyl linkage between the glycan and the peptide backbone to glycosidase. To overcome this challenge, a MUC1 glycopeptide mimic has been synthesized with the galactose-galactosamine disaccharide linked with threonine (Thomsen-Friedenreich or Tf antigen) through an unnatural β-glycosyl bond. The resulting MUC1-β-Tf had a much-enhanced stability toward a glycosidase capable of cleaving the glycan from the corresponding MUC1 glycopeptide with the natural α-Tf linkage. The MUC1-β-Tf was subsequently conjugated with a powerful carrier bacteriophage Qβ. The conjugate induced high levels of IgG antibodies in clinically relevant human MUC1 transgenic mice, which cross-recognized not only the natural MUC1-α-Tf glycopeptide but also MUC1 expressing tumor cells, supporting the notion that a simple switch of the stereochemistry of the glycan/peptide linkage can be a strategy for anti-cancer vaccine epitope design for glycopeptides.

Quantification of Surface GalNAc Ligands Decorating Nanostructured Lipid Carriers by UPLC-ELSD

Nanoparticles have been extensively studied for drug delivery and targeting to specific organs. The functionalization of the nanoparticle surface by site-specific ligands (antibodies, peptides, saccharides) can ensure efficient recognition and binding with relevant biological targets. One of the main challenges in the development of these decorated nanocarriers is the accurate quantification of the amount of ligands on the nanoparticle surface. In this study, nanostructured lipid carriers (NLC) were functionalized with N-acetyl-D-galactosamine (GalNAc) units, known to target the asialoglycoprotein receptor (ASGPR). Different molar percentages of GalNAc-functionalized surfactant (0%, 2%, 5%, and 14%) were used in the formulation. Based on ultra-high-performance liquid chromatography separation and evaporative light-scattering detection (UPLC-ELSD), an analytical method was developed to specifically quantify the amount of GalNAc units present at the NLC surface. This method allowed the accurate quantification of GalNAc surfactant and therefore gave some insights into the structural parameters of these multivalent ligand systems. Our data show that the GalNAc decorated NLC possess large numbers of ligands at their surface and suitable distances between them for efficient multivalent interaction with the ASGPR, and therefore promising liver-targeting efficiency.

Polyproline Tri-Helix Macrocycles as Nanosized Scaffolds to Control Ligand Patterns for Selective Protein Oligomer Interactions

Multivalent ligand-receptor interactions play essential roles in biological recognition and signaling. As the receptor arrangement on the cell surface can alter the outcome of cell signaling and also provide spatial specificity for ligand binding, controlling the presentation of ligands has become a promising strategy to manipulate or selectively target protein receptors. The lack of adjustable universal tools to control ligand positions at the size of a few nanometers has prompted the development of polyproline tri-helix macrocycles as scaffolds to present ligands in designated patterns. Model lectin Helix pomatia agglutinin has shown selectivity toward the matching GalNAc ligand pattern matching its binding sites arrangement. The GalNAc pattern selectivity is also observed on intact asialoglycoprotein receptor oligomer on human hepatoma cells showing the pattern-selective interaction can be achieved not only on isolated protein oligomers but also the receptors arranged on the cell surface. As the scaffold design allows convenient creation of versatile ligand patterns, it can be expected as a promising tool to probe the arrangement of receptors on the cell surface and as nanomedicine to manipulate signaling or cell recognition.

Effective Increase of Serum Vitamin D3 by IV Application of a Cholecalciferol-N-Acetyl-Galactosamine-Stabilized Dimer: a Clinical Murine Trial Study

BACKGROUND

Pre-clinical toxicology studies of human Gc-protein (vitamin D binding protein) are of special interest as to the transport of vitamin D and its biological activities. We have demonstrated that the oral application of a special dimeric vitamin D complex reduces oxidative stress and increases the quality of life in autistic children. Therefore, safety and toxic effects of two dimeric cholecalciferol-N-acetyl-galactosamine-albumin complexes were evaluated in increasing intravenous (iv.) vitamin D levels administered in a pre-clinical trial in mice over a 5-week period.

METHODS

Over a period of 5 weeks, two times a week, mice received iv. administration of one of the following: (a) 1.2 IE of vitamin D-N-acetyl-galactosamine-albumin (Vitamin D3 NAGA, ImmunoD® group), (b) 1.2 IE of vitamin-D-poly-N-acetyl-galactosamine-albumin (Poly-Nac group), or (c) isotonic saline solution (sham group). Before and after the trial, red and white blood cell panels (RBS, WBC and platelets) were determined. Furthermore, vitamin D levels, electrolytes, and C-reactive protein levels were measured directly before sacrificing.

RESULTS

No toxic effects were observed during iv. injection with dimeric vitamin D complexes, neither in the sham group, nor in the two treatment groups. Vitamin D levels increased significantly within 5 weeks in the Poly-Nac group (26.6 ± 8.8 ng/mL; p = 0.001) compared to the sham group (3.1 ± 0.9 ng/mL), and the Poly-Nac group to the ImmunoD group (7.0 ± 3.6 ng/mL; p = 0.003). A significant increase of vitamin D was also obtained in favor of the ImmunoD group compared to the sham (p = 0.03). Electrolytes (K, Na, Cl, Mg, Ca) and C-reactive protein showed no significant differences after administration in all three mice groups. Also, no significant differences were observed between these three groups in the WBC and RBC blood panels.

CONCLUSIONS

The two dimeric vitamin D complexes used in this pre-clinical study showed no side or toxic effects after iv. administration in mice, but a sole increase in vitamin D levels without any change in electrolytes or blood cells. Therefore, we assume this newly developed composition to be safe in oral or iv.-administration and further pre-clinical studies can be conducted to evaluate the value in treatment of various diseases related to vitamin D deficiencies.

Barbaloin loaded polydopamine-polylactide-TPGS (PLA-TPGS) nanoparticles against gastric cancer as a targeted drug delivery system: Studies in vitro and in vivo

Gastric cancer is the third leading cause of cancer-associated death worldwide. Although a decrease in its incidence is observed, gastric cancer still poses a major clinical challenge due to poor prognosis and limited treatments. Barbaloin (BBL) is a main medicinal composition of the Chinese traditional medicine aloe vera. BBL has various bioactivities, including anti-oxidant, anti-inflammatory and anti-tumor properties. Polydopamine (pD)-based surface modification is easy to functionalize polymeric nanoparticles (NPs) surfaces with ligands and/or additional polymeric layers. In the present study, BBL-loaded formulations was developed with pD-modified NPs, which was synthesized by polylactide-TPGS (PLA-TPGS) (pD-PLA-TPGS/NPs). And galactosamine (Gal) was conjugated on the prepared NPs (Gal-pD-PLA-TPGS/NPs) for targeting the gastric cancer cells. Here, we found that BBL-loaded Gal-pD-PLA-TPGS/NPs showed the highest cellular uptake efficacy in gastric cancer cells. Gal-pD-PLA-TPGS/NPs more significantly reduced the gastric cancer cell viability. Further, greater apoptosis, autophagy and ROS generation was induced by Gal-pD-PLA-TPGS/NPs in gastric cancer cells. Additionally, compared to the other two NPs, Gal-pD-PLA-TPGS/NPs most markedly decreased ATP levels in gastric cancer cells. In vivo, Gal-pD-PLA-TPGS/NPs were specifically targeted to tumor site. Moreover, Gal-pD-PLA-TPGS/NPs exhibited the most anti-tumor effects, as evidenced by the lowest tumor volume and tumor weight. Of note, there was no significant difference was observed in body and liver weight, as well as the histological changes in major organs isolated from each group of mice. Together, the findings indicated that BBL-loaded Gal-pD-PLA-TPGS/NPs could be targeted to gastric cancer cells to suppress tumor progression without toxicity.

Design, Synthesis, Molecular Docking Analysis, and Carbonic Anhydrase IX Inhibitory Evaluations of Novel N-Substituted-β-d-Glucosamine Derivatives that Incorporate Benzenesulfonamides

A series of novel N-substituted-β-d-glucosamine derivatives that incorporate benzenesulfonamides were designed using a fragment-based drug design strategy. Each derivative was synthesized and evaluated in vitro for its inhibitory activity against human carbonic anhydrase (hCA) IX; several derivatives displayed desirable potency profiles against this enzyme. The molecular docking studies provided the design rationale and predicted potential binding modes for carbonic anhydrase (CA) IX and three target compounds, including the most potent inhibitor, compound 7f (IC50 = 10.01 nM). Moreover, the calculated Log P (cLog P) values showed that all the compounds tended to be hydrophilic. In addition, topological polar surface area (TPSA) value-based predictions highlighted the selectivity of these carbohydrate-based inhibitors for membrane-associated CA IX.

Structural studies of Helix aspersa agglutinin complexed with GalNAc: A lectin that serves as a diagnostic tool

Lectins belong to a differentiated group of proteins known to possess sugar-binding properties. Due to this fact, they are interesting research targets in medical diagnostics. Helix aspersa agglutinin (HAA) is a lectin that recognizes the epitopes containing α-d-N-acetylgalactosamine (GalNAc), which is present at the surface of metastatic cancer cells. Although several reports have already described the use of HAA as a diagnostic tool, this protein was not characterized on the molecular level. Here, we present for the first time the structural information about lectin isolated from mucus of Helix aspersa (garden snail). The amino acid sequence of this agglutinin was determined by Edman degradation and tertiary as well as quaternary structure by X-ray crystallography. The high resolution crystal structure (1.38Å) and MALDI-TOF mass spectrometry analysis provide the detailed information about a large part of the HAA natural glycan chain. The topology of the GalNAc binding cleft and interaction with lectin are very well defined in the structure and fully confirmed by STD HSQC NMR spectroscopy. Together, this provides structural clues regarding HAA specificity and opens possibilities to rational modifications of this important diagnostic tool.

miR-150 Deficiency Protects against FAS-Induced Acute Liver Injury in Mice through Regulation of AKT

Although miR-150 is implicated in the regulation of immune cell differentiation and activation, it remains unknown whether miR-150 is involved in liver biology and disease. This study was performed to explore the potential role of miR-150 in LPS/D-GalN and Fas-induced liver injuries by using wild type and miR-150 knockout (KO) mice. Whereas knockout of miR-150 did not significantly alter LPS/D-GalN-induced animal death and liver injury, it protected against Fas-induced liver injury and mortality. The Jo2-induced increase in serum transaminases, apoptotic hepatocytes, PARP cleavage, as well as caspase-3/7, caspase-8, and caspase-9 activities were significantly attenuated in miR-150 KO mice. The liver tissues from Jo2-treated miR-150 KO mice expressed higher levels of Akt1, Akt2, total Akt, as well as p-Akt(Ser473) compared to the wild type livers. Pretreatment with the Akt inhibitor V reversed Jo2-induced liver injury in miR-150 KO mice. The primary hepatocytes isolated from miR-150 KO mice also showed protection against Fas-induced apoptosis in vitro (characterized by less prominent PARP cleavage, less nuclear fragmentation and less caspase activation) in comparison to hepatocytes from wild type mice. Luciferase reporter assays in hepatocytes transfected with the Akt1 or Akt2 3’-UTR reporter constructs (with or without mutation of miR-150 binding site) established Akt1 and Akt2 as direct targets of miR-150. Tail vein injection of lentiviral particles containing pre-miR-150 enhanced Jo2-induced liver injury in miR-150 KO mice. These findings demonstrate that miR-150 deficiency prevents Fas-induced hepatocyte apoptosis and liver injury through regulation of the Akt pathway.

Synthesis of zwitterionic 1,1'-glycosylphosphodiester: a partial structure of galactosamine-modified Francisella lipid A

Synthesis of a "double glycosidic" phosphodiester comprising anomeric centers of two 2-amino-2-deoxy-sugars is reported. The carbohydrate epitope of Francisella lipid A modified with α-d-galactosamine at the anomerically linked phosphate has been stereoselectively prepared and coupled to maleimide-activated bovine serum albumin via an amide-linked thiol-terminated spacer group. H-Phosphonate and phosphoramidite approaches have been explored for the coupling of 4,6-DTBS-2-azido-protected GalN lactol and peracetylated spacer-equipped reducing βGlcN(1→6)GlcN disaccharide via phosphodiester linkage. Deprotection conditions preserving the integrity of the labile glycosidic zwitterionic phosphodiester were elaborated.

Reduction/pH dual-sensitive PEGylated hyaluronan nanoparticles for targeted doxorubicin delivery

To minimize the side effect of chemotherapy, a novel reduction/pH dual-sensitive drug nanocarrier, based on PEGylated dithiodipropionate dihydrazide (TPH)-modified hyaluronic acid (PEG-SS-HA copolymer), was developed for targeted delivery of doxorubicin (DOX) to hepatocellular carcinoma. The copolymer was synthesized by reductive amination via Schiff's base formation between TPH-modified HA and galactosamine-conjugated poly(ethylene glycol) aldehyde/methoxy poly(ethylene glycol) aldehyde. Conjugation of DOX to PEG-SS-HA copolymer was accomplished through the hydrazone linkage formed between DOX and PEG-SS-HA, and confirmed by FTIR and (1)H NMR spectra. The polymer-DOX conjugate could self-assemble into spherical nanoparticles (~150 nm), as indicated by TEM and DLS. In vitro release studies showed that the DOX-loaded nanoparticles could release DOX rapidly under the intracellular levels of pH and glutathiose. Cellular uptake experiments demonstrated that the nanoparticles could be efficiently internalized by HepG2 cells. These results indicate that the PEG-SS-HA copolymer holds great potential for targeted intracellular delivery of DOX.

Hepatoprotective iridoid glycosides from the roots of Rehmannia glutinosa

Eleven new iridoid glycosides, rehmaglutosides A-K (1-11), together with 20 known analogues were isolated from the air-dried roots of Rehmannia glutinosa. The structures of these compounds were elucidated on the basis of spectroscopic data analysis and chemical evidence. Furthermore, in in vitro assays, compounds 3, 7, and 9-11 (10 μM) exhibited moderate hepatoprotective activities against D-galactosamine-induced HL-7702 cell damage.

A variety of novel lipid A structures obtained from Francisella tularensis live vaccine strain

F. tularensis is a Gram-negative coccobacillus that causes tularemia. Its LPS has nominal biological activity. Currently, there is controversy regarding the structure of the lipid A obtained from F. tularensis live vaccine strain (LVS). Therefore, to resolve this controversy, the purification and structural identification of this LPS was crucial. To achieve this, LPS from F. tularensis LVS was acid hydrolyzed to obtain crude lipid A that was methylated and purified by HPLC and the fractions were analyzed by MALDI-TOF MS. The structure of the major lipid A species was composed of a glucosamine disaccharide backbone substituted with four fatty acyl groups and a phosphate (1-position) with a molecular mass of 1505. The major lipid A component contained 18:0[3-O(16:0)] in the distal subunit and two 18:0(3-OH) fatty acyl chains at the 2- or 3-positions of the reducing subunit. Additional variations in the lipid A species include: heterogeneity in fatty acyl groups, a phosphate or a phosphoryl galactosamine at the 1-position, and a hexose at the 4' or 6' position, some of which have not been previously described for F. tularensis LVS. This analysis revealed that lipid A from F. tularensis LVS is far more complex than originally believed.

Elucidation of the sugar recognition ability of the lectin domain of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 3 by using unnatural glycopeptide substrates

Mucin-type glycosylation [α-N-acetyl-D-galactosamine (α-GalNAc)-O-Ser/Thr] on proteins is initiated biosynthetically by 16 homologous isoforms of GalNAc-Ts (uridine diphosphate-GalNAc:polypeptide N-acetylgalactosaminyltransferases). All the GalNAc-Ts consist of a catalytic domain and a lectin domain. Previous reports of GalNAc-T assays toward peptides and α-GalNAc glycopeptides showed that the lectin domain recognized the sugar on the substrates and affected the reaction; however, the details are not clear. Here, we report a new strategy to give insight on the sugar recognition ability and the function of the GalNAc-T3 lectin domain using chemically synthesized natural-type (α-GalNAc-O-Thr) and unnatural-type [β-GalNAc-O-Thr, α-Fuc-O-Thr and β-GlcNAc-O-Thr] MUC5AC glycopeptides. GalNAc-T3 is one of isoforms expressed in various organs, its substrate specificity extensively characterized and its anomalous expression has been identified in several types of cancer (e.g. pancreas and stomach). The glycopeptides used in this study were designed based on a preliminary peptide assay with a sequence derived from the MUC5AC tandem repeat. Through GalNAc-T3 and lectin-inactivated GalNAc-T3, competition assays between the glycopeptide substrates and product analyses (MALDI-TOF MS, RP-HPLC and ETD-MS/MS), we show that the lectin domain strictly recognized GalNAc on the substrate and this specificity controlled the glycosylation pathway.

Involvement of HSP70 in the protection of bicyclol on apoptosis of HepG2 cells intoxicated by d-galactosamine

Heat shock proteins (HSPs), the best known endogenous factors, play important roles in the cytoprotection and repair of cells and tissues against the harmful effects of stress and insults. In this study, RNAi technology was used to identify whether HSP70 was involved in the protection of bicyclol against d-galactosamine (d-GaIN)-induced apoptosis in HepG2 cells. As a result, bicyclol induced HSP70 in a time- and dose-dependent manner in HepG2 cells. Bicyclol markedly alleviated apoptosis and caspase-3 activity in HepG2 cells intoxicated by d-GaIN. The degradation of inhibitory kappa B, phosphorylation of inhibitory kappa B kinase, nuclear factor kappa B (NF-kappaB) nuclear translocation, and DNA-binding activity were all inhibited by bicyclol in HepG2 cells intoxicated by d-GaIN. In addition, bicyclol decreased the nitric oxide production and inducible nitric oxide synthase (iNOS) expression. The inhibitory effects of bicyclol on all the above biomarkers were attenuated when the HSP70 gene was silenced accordingly. Our data also showed that MG132 (inhibitor of NF-kappaB) and NG-nitro-l-arginine methyl ester (inhibitor of iNOS) inhibited hepatocyte apoptosis induced by d-GaIN. These in vitro results suggested that HSP70 partially contributed to the hepatoprotection of bicyclol through suppressing the NF-kappaB-iNOS pathway.

Molecular interaction of imino sugars with human alpha-galactosidase: Insight into the mechanism of complex formation and pharmacological chaperone action in Fabry disease

Enzyme enhancement therapy (EET) for Fabry disease involving imino sugars has been developed and attracted interest. It is thought that imino sugars act as pharmacological chaperones for wild-type and mutant alpha-galactosidases (GLAs) in cells, but the mechanisms underlying the molecular interactions between the imino sugars and the enzyme have not been clarified yet. We examined various kinds of imino sugars and found that galactostatin bisulfite (GBS) inhibited GLA in vitro and increased the enzyme activity in cultured Fabry fibroblasts as in the case of 1-deoxygalactonojirimycin (DGJ). Then, we analyzed the molecular interactions between the imino sugars and recombinant human GLA by means of isothermal titration calorimetry and surface plasmon resonance biosensor assays, and first determined the thermodynamic and binding-kinetics parameters of imino sugar and GLA complex formation. The results revealed that DGJ bound to the enzyme more strongly than GBS, the binding of DGJ to the enzyme protein being enthalpy-driven. In the case of GBS, the reaction was mainly enthalpy-driven, but there was a possibility that entropy-driven factors were involved in the binding. Structural analysis in silico revealed that both the chemicals fit into the active-site pocket and undergo hydrogen bonding with residues comprising the active-site pocket including the catalytic ones. The side chain of GBS was oriented towards the entrance of the active-site pocket, and thus it could be in contact with residues comprising the wall of the active-site pocket. Thermodynamic, kinetic and structural studies should provide us with a lot of information for improving EET for Fabry disease.

Glucosamine hydrochloride specifically inhibits COX-2 by preventing COX-2 N-glycosylation and by increasing COX-2 protein turnover in a proteasome-dependent manner

COX-2 and its products, including prostaglandin E(2), are involved in many inflammatory processes. Glucosamine (GS) is an amino monosaccharide and has been widely used for alternative regimen of (osteo) arthritis. However, the mechanism of action of GS on COX-2 expression remains unclear. Here we describe a new action mechanism of glucosamine hydrochloride (GS-HCl) to tackle endogenous and agonist-driven COX-2 at protein level. GS-HCl (but not GS sulfate, N-acetyl GS, or galactosamine HCl) resulted in a shift in the molecular mass of COX-2 from 72-74 to 66-70 kDa and concomitant inhibition of prostaglandin E(2) production in a concentration-dependent manner in interleukin (IL)-1beta-treated A549 human lung epithelial cells. Remarkably, GS-HCl-mediated decrease in COX-2 molecular mass was associated with inhibition of COX-2 N-glycosylation during translation, as assessed by the effect of tunicamycin, the protein N-glycosylation inhibitor, or of cycloheximide, the translation inhibitor, on COX-2 modification. Specifically, the effect of low concentration of GS-HCl (1 mM) or of tunicamycin (0.1 microg/ml) to produce the aglycosylated COX-2 was rescued by the proteasomal inhibitor MG132 but not by the lysosomal or caspase inhibitors. However, the proteasomal inhibitors did not show an effect at 5 mM GS-HCl, which produced the aglycosylated or completely deglycosylated form of COX-2. Notably, GS-HCl (5 mM) also facilitated degradation of the higher molecular species of COX-2 in IL-1beta-treated A549 cells that was retarded by MG132. GS-HCl (5 mM) was also able to decrease the molecular mass of endogenous and IL-1beta- or tumor necrosis factor-alpha-driven COX-2 in different human cell lines, including Hep2 (bronchial) and H292 (laryngeal). However, GS-HCl did not affect COX-1 protein expression. These results demonstrate for the first time that GS-HCl inhibits COX-2 activity by preventing COX-2 co-translational N-glycosylation and by facilitating COX-2 protein turnover during translation in a proteasome-dependent manner.

Using Small-Angle Neutron Scattering to Study the Solution Conformation of N-(2-Hydroxypropyl)methacrylamide Copolymer−Doxorubicin Conjugates

Our past research developed two N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-doxorubicin (Dox) conjugates that became the first synthetic polymer-anticancer conjugates to be evaluated clinically. The first, FCE28068, contained Dox bound to the polymeric carrier via a tetrapeptidic linker (glycine-phenylalanine-leucine-glycine (GFLG)) (Mw approximately 30,000 g/mol; approximately 8 wt % drug), and the second, FCE28069, contained additionally galactosamine (Gal) (Mw approximately 30,000 g/mol; approximately 7.5 wt % Dox) again bound by a GFLG linker. Galactosamine was included to promote hepatocyte/hepatoma targeting via the asialoglycoprotein receptor. Both conjugates showed antitumor activity and were clinically less toxic than free Dox (2-5 fold). However, despite their similar chemical characteristics, the conjugates displayed a significantly different maximum-tolerated dose (MTD) in patients. The aim of this study, therefore, was to use small-angle neutron scattering (SANS) to explore the solution behavior of a small library of HPMA polymer conjugates including FCE28068, FCE28069, and their pharmaceutical formulations, plus as reference compounds HPMA copolymer-GFLG conjugates containing aminopropanol (Ap) or galactosamine (Gal) alone (i.e., without Dox). The SANS data obtained showed that HPMA copolymer-GFLG-Ap conjugates (containing 5 and 10 mol % side chains) showed evidence of polymer aggregation, however, no indication of aggregation was observed for FCE28068 and FCE28069 over the concentration range studied (2.5-50 mg/mL). Clear differences in the scattering behavior for the two conjugates were observed at equivalent concentration. Data were best fitted by a model for polydisperse Gaussian coils, and the HPMA copolymer-Dox conjugate with Gal (FCE28069) exhibited a larger radius of gyration (Rg) (by approximately 2.5 nm) compared to FCE28068. In conclusion, we have shown that SANS will be a valuable tool to elucidate conformation-performance relationships for polymer-drug conjugates.

Hydrogen peroxide derived from amine oxidation mediates the interaction between aminosugars and semicarbazide-sensitive amine oxidase

Semicarbazide-sensitive amine oxidase (SSAO) also functions as a vascular-adhesion protein (VAP-1). The nature of the target site on lymphocytes to which endothelial-cell SSAO/VAP-1 binds is unknown. We have shown that amino sugars (galactosamine, glucosamine and mannosamine), which are not SSAO substrates, can bind to the enzyme as reversible inhibitors. Thus, they serve as a model system in which to study the interaction process. Binding occurred during substrate (benzylamine) oxidation but not when the amino sugar was incubated, for extended periods, with SSAO alone. These results suggest that one, or more of the products of the SSAO-catalysed amine oxidation might be necessary for the inhibitory process to occur. Two of the reaction products of benzylamine oxidation, benzaldehyde and ammonia were found to have no effect on the inhibition of SSAO by galactosamine. Preincubation of the enzyme with galactosamine plus H(2)O(2) was, however, found to result in time-dependent inhibition. This is not a result of the non-enzymic reaction between H(2)O(2) and the amino sugar, since preincubation of galactosamine with H(2)O(2) alone, for extended periods, did not give rise to an inhibitory species. The amount of exogenously added H(2)O(2) necessary for inhibition was very much greater than that formed during substrate oxidation. These results suggest that the H(2)O(2) formed as a product of the SSAO-catalysed oxidation reaction is more efective in promoting the binding of amino sugars.

Structure and biosynthesis of free lipid A molecules that replace lipopolysaccharide in Francisella tularensis subsp. novicida

Francisella tularensis subsp. novicida U112 phospholipids, extracted without hydrolysis, consist mainly of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, and two lipid A species, designated A1 and A2. These lipid A species, present in a ratio of 7:1, comprise 15% of the total phospholipids, as judged by 32Pi labeling. Although lipopolysaccharide is detectable in F. tularensis subsp. novicida U112, less than 5% of the total lipid A is covalently linked to it. A1 and A2 were analyzed by electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry, gas chromatography/mass spectrometry, and NMR spectroscopy. Both compounds are disaccharides of glucosamine, acylated with primary 3-hydroxystearoyl chains at positions 2, 3, and 2' and a secondary palmitoyl residue at position 2'. Minor isobaric species and some lipid A molecules containing a 3-hydroxypalmitoyl chain in place of 3-hydroxystearate are also present. The 4'- and 3'-positions of A1 and A2 are not derivatized, and 3-deoxy-d-manno-octulosonic acid (Kdo) is not detectable. The 1-phosphate groups of both A1 and A2 are modified with an alpha-linked galactosamine residue, as shown by NMR spectroscopy and gas chromatography/mass spectrometry. An alpha-linked glucose moiety is attached to the 6'-position of A2. The lipid A released by mild acid hydrolysis of F. tularensis subsp. novicida lipopolysaccharide consists solely of component A1. F. tularensis subsp. novicida mutants lacking the arnT gene do not contain a galactosamine residue on their lipid A. Formation of free lipid A in F. tularensis subsp. novicida might be initiated by an unusual Kdo hydrolase present in the membranes of this organism.

Identification of the Origin of Chondroitin Sulfate in "Health Foods"

Twelve "health foods" products containing chondroitin sulfate (CS) were purchased from the Japanese market and the origin of the CS was investigated by conducting disaccharide compositional analysis after enzymatic depolymerization and by 1H-NMR spectroscopy. Nine of the 12 products had labels indicating that the origin of the CS was shark cartilage. However, two of them were found to contain mammalian CS. Next, we compared the ratio of the sulfate group to the galactosamine residue after the acid hydrolysis of CS. The results suggest that all of the CS from sharks had a ratio of more than 1.0, while the CS from mammals had a ratio of less than 1.0. Since this comparative analysis does not require expensive purified enzyme, it would be an economical way to identify the origin of CS in "health foods." Being able to determine the origin of the ingredients in natural products is very important for ensuring their quality, safety, and efficacy. Therefore, we think that regulatory requirements for accurately indicating the origin of "health foods" and effective enforcement of these requirements are needed.

Sequencing of oligoarabinosyl units released from mycobacterial arabinogalactan by endogenous arabinanase: identification of distinctive and novel structural motifs

The mycobacterial D-arabinofuran is a common constituent of both cell wall mycolyl-arabinogalactan (AG) and the associated lipoarabinomannan (LAM), and is thus accorded critical structural and immunological roles. Despite a well-recognized importance, progress in understanding its full structural characteristics beyond the nonreducing terminal motifs has hitherto been limited by available analytical tools. An endogenous arabinanase activity recently isolated from Mycobacterium smegmatis was previously shown to be capable of releasing large oligoarabinosyl units from AG. Advanced tandem mass spectrometry utilizing both low and high energy collision induced dissociation now afforded a facile way to map and directly sequence the digestion products which were dominated by distinctive Ara18 and Ara19 structural units, together with Ara7 and lesser amount of Ara11 and Ara12. Significantly, evidence was obtained for the first time which validated the linkages and branching pattern of the previously inferred Ara22 structural motif of AG, on which the preferred cleavage sites of the novel arabinanase could be localized. The established linkage-specific MS/MS fragmentation characteristics further led to identification of a galactosamine substituent on the C2 position of a portion of the internal 3,5-branched Ara residue of the AG of Mycobacterium tuberculosis, but not that of the nonpathogenic, fast growing M. smegmatis.

Syntheses of α-d-galactosamine neoglycolipids

Several N-acetyl-alpha-d-galactosamine neoglycolipids, as well as hydrophobized T and T(N) antigen analogues, were prepared for embedment onto liposomes. Three different lipidic structures were used for the anchoring, that is cholesterol, 1,3-bis(undecyloxy)propan-2-ol and 1,3-bis(3,7,11,15-tetramethylhexadecyloxy)propan-2-ol. Oligoethyleneglycol spacers were used to link the carbohydrate and the hydrophobic moieties; their lengths were varied in order to obtain model compounds for the selective recognition by sialyl transferases involved in cancer processes. Glycosylation reactions were optimized to sluggish amphiphilic acceptor alcohols, in order to reach good 1,2-cis-stereoselectivities and acceptable yields. This aim was achieved by using 3,4,6-tri-O-acetyl-2-azido-2-deoxy-d-galactopyranosyl trichloroacetimidate as the donor, trimethylsilyl trifluoromethanesulfonate as the promoter and diethyl ether or mixtures of diethyl ether and dichloromethane as solvents.

Paclitaxel-Loaded Poly(γ-glutamic acid)-poly(lactide) Nanoparticles as a Targeted Drug Delivery System against Cultured HepG2 Cells

The study was to develop paclitaxel-loaded formulations using a novel type of self-assembled nanoparticles that was composed of block copolymers synthesized from poly(gamma-glutamic acid) and poly(lactide) via a simple coupling reaction. The nanoparticles (the NPs) were prepared with various feed weight ratios of paclitaxel to block copolymer (the P/BC ratio). The morphology of all prepared nanoparticles was spherical and the surfaces were smooth. Increasing the P/BC ratio significantly increased the drug loading content of the prepared nanoparticles, but remarkably reduced the drug loading efficiency. The release rate of paclitaxel from the NPs decreased significantly as the P/BC ratio increased. For the potential of targeting liver cancer cells, galactosamine was further conjugated on the prepared nanoparticles (the Gal-NPs) as a targeting moiety. It was found that the activity in inhibiting the growth of HepG2 cells (a liver cancer cell line) by the Gal-NPs was comparable to that of a clinically available paclitaxel formulation, while the NPs displayed a significantly less activity. This may be attributed to the fact that the Gal-NPs had a specific interaction with HepG2 cells via ligand-receptor recognition. Cells treated with distinct paclitaxel formulations resulted in arrest in the G2/M phase. The arrest of cells in the G2/M phase was highly suggestive of interference by paclitaxel with spindle formation and was consistent with the morphological findings presented herein. In conclusion, the active targeting nature of the Gal-NPs prepared in the study may be used as a potential drug delivery system for the targeted delivery to liver cancers.

Synthesis of a polymer-bound galactosylamine and its application as an immobilized chiral auxiliary in stereoselective syntheses of piperidine and amino acid derivatives

A 2,3,4-tri-O-pivaloylated beta-D-galactopyranosyl azide bearing a hydroxy-functionalized spacer unit at the C-6 position of the galactose was synthesized and immobilized on the solid phase by using a polymer-bound chlorosilane. The azide was reduced to the corresponding galactopyranosylamine, which served as a versatile chiral auxiliary in highly diastereoselective Ugi four-component condensation reactions at ambient temperature. Fluoride-induced cleavage from the polymeric support furnished N-glycosylated N-acylated alpha-amino acid amides. The reaction of the immobilized galactosylamine with aldehydes gave rise to the corresponding aldimines, which underwent a domino Mannich-Michael condensation reaction with Danishefsky's diene at ambient temperature to yield 2-substituted 5,6-didehydropiperidin-4-ones on the solid phase. Subsequent cleavage with tetra-n-butylammonium fluoride delivered the N-glycosylated products in high yields, purities, and diastereoselectivities. A chemoselective 1,4-hydride addition to the polymer-bound dehydropiperidinones was achieved in the presence of the bulky oxygenophilic Lewis acid methylaluminum [bis(2,6-di-tert-butyl-4-methylphenoxide)]. The conjugate addition of cyano-modified Gilman reagents to the immobilized dehydropiperidinones furnished 2,6-cis-substituted piperidine derivatives as the major diastereomers that were isolated after cleavage from the support.

Monodisperse Protein-Based Glycopolymers via a Combined Biosynthetic and Chemical Approach

Helical protein polymers with sequences comprising primarily alanine and glutamine have been designed to contain glutamic acid residues at distances that are targeted to match the receptor spacing of certain toxins and lectins. These proteins are readily expressed and purified from E. coli and are highly helical under a variety of solution conditions. The helical artificial proteins are also competent for chemical modification with saccharides for inhibition of select bacterial toxins and lectins. In the investigations reported here, multivalent artificial glycoproteins bearing galactose moieties as pendant groups have been prepared via the coupling reaction of amine-functionalized galactose with the glutamic acid functional groups of the protein polymer. Glycosylation of proteins was confirmed via mass spectrometry, NMR spectroscopy, SDS-PAGE, and photometric methods. CD spectroscopy shows that the resulting glycosylated proteins maintain a highly helical structure, and competitive ELISA assays suggest the efficient binding of these glycoproteins to cholera toxin. These results demonstrate that the integration of biological and chemical approaches in the synthesis of well-defined polymeric structures offers significant opportunities in the purposeful design of glycopolymers for applications in biology.

Allosteric activation of protein phosphatase 2C by D-chiro-inositol-galactosamine, a putative mediator mimetic of insulin action

Insulin-stimulated glucose disposal in skeletal muscle proceeds predominantly through a nonoxidative pathway with glycogen synthase as a rate-limiting enzyme, yet the mechanisms for insulin activation of glycogen synthase are not understood despite years of investigation. Isolation of putative insulin second messengers from beef liver yielded a pseudo-disaccharide consisting of pinitol (3-O-methyl-d-chiro-inositol) beta-1,4 linked to galactosamine chelated with Mn(2+) (called INS2). Here we show that chemically synthesized INS2 has biological activity that significantly enhances insulin reduction of hyperglycemia in streptozotocin diabetic rats. We used computer modeling to dock INS2 onto the known three-dimensional crystal structure of protein phosphatase 2C (PP2C). Modeling and FlexX/CScore energy minimization predicted a unique favorable site on PP2C for INS2 in a surface cleft adjacent to the catalytic center. Binding of INS2 is predicted to involve formation of multiple H-bonds, including one with residue Asp163. Wild-type PP2C activity assayed with a phosphopeptide substrate was potently stimulated in a dose-dependent manner by INS2. In contrast, the D163A mutant of PP2C was not activated by INS2. The D163A mutant and wild-type PP2C in the absence of INS2 had the same Mn(2+)-dependent phosphatase activity with p-nitrophenyl phosphate as a substrate, showing that this mutation did not disrupt the catalytic site. We propose that INS2 allosterically activates PP2C, fulfilling the role of a putative mediator mimetic of insulin signaling to promote protein dephosphorylation and metabolic responses.

Structural analysis of the sheath of a sheathed bacterium, Leptothrix cholodnii

Leptothrix cholodnii is an aerobic sheath-forming bacterium often found in oligotrophic and metal-rich aquatic environments. The sheath of this bacterium was isolated by selectively lysing the cells. Glycine and cysteine were the major amino acids of the sheath. The sheath was readily dissolved in hydrazine, and a polysaccharide substituted with cysteine was recovered from the solution. Galactosamine, glucosamine and galacturonic acid were detected in the hydrazinolysate by gas liquid chromatography analysis. FAB-MS analysis of the hydrazinolysate suggested a sugar sequence of HexN-GalA-HexN-HexN. Methylation linkage analysis revealed the presence of 4-linked GalA, 3-linked HexN and 4-linked HexN. The sulfhydryl groups of the sheath were used for labeling with the fluorogenic reagent, 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (ABD-F). The labeled sheath (ABD-sheath) was partially hydrolyzed and three fluorescent fragments were purified by HPLC. One of them was identified as ABD-cysteine. The second one was found to be the ABD-cysteine tetramer. Another fragment was indicated to be a pentasaccharide substituted with ABD-cysteine by nuclear magnetic resonance (NMR) analysis. It can be assumed that the polysaccharide and peptide moieties of the sheath are connected by a cysteine residue. NMR analysis of the hydrazinolysate revealed that the polysaccharide moiety of the sheath was constructed from a pentasaccharide repeating unit containing 2-amino-2-deoxygalacturonic acid (GalNA), as shown below. -->4)-alpha-GalNA-(1-->4)-alpha-D-GalN(p)-(1-->4)-alpha-D-GalA(p)-(1-->4)-beta-D-GlcN(p)-(1-->3)-beta-D-GalN(p)-(1-->.

Preparation of nanoparticles composed of poly(gamma-glutamic acid)-poly(lactide) block copolymers and evaluation of their uptake by HepG2 cells

In the study, poly(gamma-glutamic acid) (gamma-PGA) and poly(lactide) (PLA) were used to synthesize block copolymers via a simple coupling reaction between gamma-PGA and PLA to prepare self-assembled nanoparticles. For the potential of targeting liver cancer cells, galactosamine was further conjugated on the prepared nanoparticles as a targeting moiety. gamma-PGA, a water-soluble, biodegradable, and non-toxic compound, was produced by microbial fermentation (Bacillus licheniformis, ATCC 9945a) and then was hydrolyzed. The hydrolyzed gamma-PGA with a molecular weight of 4 kDa and a polydispersity of 1.3 was used, together with PLA (10 kDa, polydispersity 1.1), to synthesize block copolymers. The prepared nanoparticles had a mean particle size of about 140 nm with a zeta potential of about -20 mV. The results obtained by the TEM and AFM examinations showed that the morphology of the prepared nanoparticles was spherical in shape with a smooth surface. In the stability study, no aggregation or precipitation of nanoparticles was observed during storage for up to 1 month, as a result of the electrostatic repulsion between the negatively charged nanoparticles. With increasing the galactosamine content conjugated on the rhodamine-123-containing nanoparticles, the intensity of fluorescence observed in HepG2 cells increased significantly. Additionally, the intensity of fluorescence observed in HepG2 cells incubated with the nanoparticles with or without galactosamine conjugated increased approximately linearly with increasing the duration of incubation. In contrast, there was no fluorescence observed in Hs68 cells (without ASGP receptors) incubated with the nanoparticles with galactosamine conjugated. The aforementioned results indicated that the galactosylated nanoparticles prepared in the study had a specific interaction with HepG2 cells via ligand-receptor recognition.

Expression of mannose receptor and ligands for its cysteine-rich domain in venous sinuses of human spleen

The mannose receptor (MR) is a type I membrane molecule with two lectin activities. Mannose recognition takes place through the C-type lectin-like carbohydrate recognition domains, while recognition of sulphated glycans is mediated by the cysteine-rich domain (CR). In murine spleen CR ligands are present in a subpopulation of macrophages (Mphi) placed in the marginal zone whereas MR-expressing cells consisting of Mphi and nonvascular endothelia are located in the red pulp. No colocalisation of MR with CR ligands has been observed in murine tissues. In this manuscript we describe the distribution of MR and CR ligands in human spleen. In this organ we have detected a perfect colocalisation of MR with CR ligands in Lyve-1+ cells lining venous sinuses. These cells form a physical barrier for blood cells as they need to migrate through the sinuses in order to exit the splenic parenchyma and, in this way, contribute to the unique filtration function of this organ. Furthermore, unlike murine spleen, CD68+ red pulp Mphi lack MR expression. Our results suggest an unexpected contribution of MR to splenic function through the recognition of sulphated ligands that could influence the filtering capability of this organ.

Synthetic alpha-mannosyl ceramide as a potent stimulant for an NKT cell repertoire bearing the invariant Valpha19-Jalpha26 TCR alpha chain

A NKT cell repertoire is characterized by the expression of the Valpha19-Jalpha26 invariant TCR alpha chain (Valpha19 NKT cell). This repertoire, as well as a well-established Valpha14-Jalpha281 invariant TCR alpha(+) NKT cell subset (Valpha14 NKT cell), has been suggested to have important roles in the regulation of the immune system and, thus, is a major therapeutic target. Here, we attempted to find specific antigens for Valpha19 NKT cells. Valpha19 as well as Valpha14 NKT cells exhibited reactivity to alpha-galactosyl ceramide (alpha-GalCer). Thus, a series of monoglycosyl ceramides with an axially oriented glycosidic linkage between the sugar and ceramide moiety were synthesized and their antigenicity to Valpha19 NKT cells was determined by measuring their immune responses in culture with glycolipids. Comprehensive examinations revealed substantial antigenic activity for Valpha19 NKT cells by alpha-mannosyl ceramide.

An alternative high yielding and highly stereoselective method for preparing an α-Neu5NAc-(2,6)-d-GalN3 building block suitable for further glycosylation

This paper deals with new approaches to alpha-Neu5NAc-(2,6)-D-GalN3 building blocks, suitable as glycosylation donors. The major improvement, by comparison with the results of the literature, lies in the glycosylation step of a new d-galactosamine acceptor (tert-butyldimethylsilyl 3-O-acetyl-2-azido-2-deoxy-beta-D-galactopyranoside) with O-methyl-S-[methyl(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto-non-2-ulopyranosyl)onate] dithiocarbonate as the N-acetylneuraminic acid donor. The reaction affords the expected disaccharide in high yield (85%) and a complete alpha-Neu5NAc stereoselectivity. A subsequent oxidation step, eliminating the glycal by-product allows an easier purification. Afterwards, the tert-butyldimethylsilyl disaccharide can be transformed into a donor, after cleavage of the anomeric group in smooth conditions.

A solid-state NMR application of the anomeric effect in carbohydrates: galactosamine, glucosamine, and N-acetyl-glucosamine

Simple 2D 13C/15N heteronuclear correlation solid-state NMR spectroscopy was implemented to resolve the 15N resonances of the alpha and beta anomers of three amino monosaccharides: galactosamine (GalN), glucosamine hydrochloride (GlcN), and N-acetyl-glucosamine (GlcNAc) labeled specifically with 13C1/15N spin pairs. Although the 15N resonances could not be distinguished in normal 1D spectra, they were well resolved in 2D double CP/MAS correlation spectra by taking advantage of the 13C spectral resolution. The alpha and beta resonances shifted apart by 3-5 ppm in their 13C chemical shifts, and differed by 1-2 ppm in the extended 15N dimension. Aside from this, the detection of other 13C/15N correlations over short distances was also achieved arising from the C2, C3 and CO carbons present in natural abundance. 2D double CP/MAS chemical shift correlation NMR spectroscopy is a simple and powerful technique to characterize the anomeric effect of amino monosaccharides. Applications of the 2D method reveal well-resolved 15N and 13C chemical shifts might be useful for structural determination on carbohydrates of biological significance, such as glycopeptide or glycolipids.

Conformational Analysis of Chirally Deuterated Tunicamycin as an Active Site Probe of UDP-N-Acetylhexosamine:Polyprenol-P N-Acetylhexosamine-1-P Translocases

Tunicamycins are potent inhibitors of UDP-N-acetyl-D-hexosamine:polyprenol-phosphate N-acetylhexosamine-1-phosphate translocases (D-HexNAc-1-P translocases), a family of enzymes involved in bacterial cell wall synthesis and eukaryotic protein N-glycosylation. Structurally, tunicamycins consist of an 11-carbon dialdose core sugar called tunicamine that is N-linked at C-1' to uracil and O-linked at C-11' to N-acetylglucosamine (GlcNAc). The C-11' O-glycosidic linkage is highly unusual because it forms an alpha/beta anomeric-to-anomeric linkage to the 1-position of the GlcNAc residue. We have assigned the (1)H and (13)C NMR spectra of tunicamycin and have undertaken a conformational analysis from rotating angle nuclear Overhauser effect (ROESY) data. In addition, chirally deuterated tunicamycins produced by fermentation of Streptomyces chartreusis on chemically synthesized, monodeuterated (S-6)-[(2)H(1)]glucose have been used to assign the geminal H-6'a, H-6'b methylene bridge of the 11-carbon dialdose sugar, tunicamine. The tunicamine residue is shown to assume pseudo-D-ribofuranose and (4)C(1) pseudo-D-galactopyranosaminyl ring conformers. Conformation about the C-6' methylene bridge determines the relative orientation of these rings. The model predicts that tunicamycin forms a right-handed cupped structure, with the potential for divalent metal ion coordination at 5'-OH, 8'-OH, and the pseudogalactopyranosyl 7'-O ring oxygen. The formation of tunicamycin complexes with various divalent metal ions was confirmed experimentally by MALDI-TOF mass spectrometry. Our data support the hypothesis that tunicamycin is a structural analogue of the UDP-D-HexNAc substrate and is reversibly coordinated to the divalent metal cofactor in the D-HexNAc-1-P translocase active site.

Changes in quinolinic acid production and its related enzymes following D-galactosamine and lipopolysaccharide-induced hepatic injury

Increases in quinolinic acid (QUIN), a neurotoxic L-tryptophan metabolite, have been observed in human serum and cerebrospinal fluid and in animal models of severe hepatic injury. The aim of this study was to evaluate the changes in QUIN accumulation and its related enzymes after acute hepatic injury induced by D-galactosamine and endotoxin. Gerbils were given an intraperitoneal injection of pyrogen-free saline alone as control, lipopolysaccharide (LPS) alone (150 ng/kg), D-galactosamine alone (500 mg/kg) or a combination of D-galactosamine with LPS. Concentrations of QUIN, its related metabolites, and related enzyme activities were determined. D-Galactosamine treatment significantly decreased activities of hepatic aminocarboxymuconate-semialdehyde decarboxylase (ACMSDase) resulting in increased QUIN concentrations in serum and tissues. The magnitude of QUIN responses was markedly increased by endotoxin due to the increased availability of L-kynurenine, a rate-limiting substrate for QUIN synthesis. Further, infiltration of monocytes/macrophages, which is a possible major source of QUIN production in the liver, was shown by immunohistochemistry after hepatic injury induced by D-galactosamine and endotoxin. Increased serum QUIN concentrations are probably due to the increased substrate availability and the decreased activity of aminocarboxymuconate-semialdehyde decarboxylase in the liver, accompanying the increased monocyte/macrophage infiltration into the liver after hepatic injury.

Improved borate method for the rapid distinction of glucosamine and galactosamine in an exopolysaccharide produced by Citrobacter sp

An improved borate method for the quantitative distinction of glucosamine (GlcN) and galactosamine (GalN) in a mixture is presented which is based on the Elson-Morgan method with addition of sodium borate to differentiate colour formation by the two hexosamines. The r2 value and maximum deviation of the method based on calculations derived in this study were 0.9979 and 5.1 %, respectively. Using this method, the GlcN/GalN ratio in an exopolysaccharide (EPS) produced by Citrobacter sp. was found to change with time during the production process, with a maximum value at 9.8:1.

Microencapsulated hepatocytes and islets as in vivo bioartificial liver support system

AIM: To confirm the xenotransplantation of microencapsulated hepatocytes and islets as a temporary bioartificial liver support system for mice with acute liver failure (ALF).

METHODS: Mice were rendered ALF by a single intra-peritoneal injection of D-galactosamine (D-gal) and their tail blood was sampled to examine differences in blood ALT, albumin (ALB), total bilirubin (TB) and glucose (GLU) between 4 experimental groups. Rat hepatocytes and islets were collected and microencapsulated referring to both Sun’s and Fritschy’s methods. Mice were grouped into control group (CG), free hepatocyte group (FHG), microencapsulated hepatocyte group (MHG) and microencapsulated hepatocyte plus islet group (HIG). Tissue samples were subjected to microscopic and electron microscopic (EM) examinations.

RESULTS: The highest survival was observed in HIG, surprisingly at 100% (16/16), while the lowest was in CG at 12.5% (2/16), with inter-group statistical difference P < 0.05. ALT levels revealed no statistical difference between groups but the ALB level of HIG descended by the slightest margin {q = (0.54, 0.24, 1.33), P < 0.05} at the time when it reached the lowest point in all groups. TB of HIG returned to normal reference range (NRR) statistically sooner than that of others after a fierce elevation. No statistical inter-group difference was observed in GLU levels. Fusion between hepatocytes and beta cells was demonstrated giving rise to theoretical assumptions.

CONCLUSION: Hepatocytes to be microencapsulated together with islets should be a preferred in vivo hepatic functional supporting system, which can dramatically prolong survival and improve living status.

Changes of gut flora and endotoxin in rats with D-galactosamine-induced acute liver failure

AIM: To investigate the changes of gut microflora and endotoxin levels in rats with acute liver failure (ALF) induced by D-galactosamine (GalN).

METHODS: Flora and endotoxin levels in the jejunum, ileum and colon in normal rats (group A) and rats with GalN-induced ALF were determined at 24 h (group B) or 48 h (group C) after GalN injection, as well as the endotoxin level in portal venous blood (PVB) and right ventricle blood (RVB) were determined by chromogenic limulus amoebocyte assay.

RESULTS: Intestinal (jejunum, ileum, colon) lactobacillus count was statistically reduced in group B compared with those in group A (3.4 ± 0.3 vs 4.9 ± 0.3, 6.1 ± 0.4 vs 8.0 ± 0.3, 8.1 ± 0.2 vs 9.3 ± 0.2, P < 0.001, P < 0.001 and P < 0.001 respectively) and recovered partially in the group C compared with those in the group B, whereas the count of Enterobacteriaceae in the jejunum, ileum and colon in group B was increased markedly compared with those in the group A (5.1 ± 0.3 vs 3.6 ± 0.2, 6.9 ± 0.5 vs 5.3 ± 0.3, 8.7 ± 0.2 vs 7.6 ± 0.1, P < 0.001, P < 0.05 and P < 0.05 respectively) and restored partially in the group C compared with those in the group B. The endotoxin level in ileum was increased in the group B compared with those in the group A (111.3 ± 22.8 vs 51.5 ± 8.9, P < 0.05). In addition, the endotoxin level in PVB was obviously increased in group B compared with that in the group A (76.8 ± 9.1 vs 40.6 ± 7.3, P < 0.01) and reduced to the baseline at 48 h (group C).

CONCLUSION: Severely disturbed gut flora in rats with GalN-induced acute liver failure plays an important role in the elevation of endotoxin level in PVB.

Connexin 32 dominant-negative mutant transgenic rats are resistant to hepatic damage by chemicals

Connexins are subunits of gap junction channels, which allow direct transfer of ions, secondary messenger molecules, and other metabolites between contacting cells. Gap junctions are believed to be involved in tissue homeostasis, embryonic development, and control of cell proliferation. Several studies have shown that cell damage signals are transmitted through gap junctions when cells are irradiated or when cells bearing the herpes simplex virus-thymidine kinase (HSV-TK) gene are treated with ganciclovir. We established 2 lines of transgenic rats with a dominant-negative mutant of connexin 32 gene under control of the albumin promoter. In the livers of transgenic rats, membrane localization of normal endogenous connexin 32 protein is disturbed, and gap junction capacity measured by scrape dye-transfer assay in vivo is markedly decreased when compared with wild-type rats. The present investigation concerned susceptibility to the liver-toxic substances D-galactosamine and carbon tetrachloride. These toxicants induced massive liver cell death and elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the wild-type rats; however, much fewer liver cells were damaged and serum enzyme elevation was much lower in the transgenic rats. In conclusion, gap junctional intercellular communication (GJIC) plays an important role in toxic effects of chemicals; damage or death signals may pass through gap junctions in the rat liver in vivo.

Solution and solid-state structure of N-acetamido-3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-d-galactopyranosylamine

High resolution 1H NMR and 13C NMR spectroscopic and single crystal X-ray structural analyses of N-acetamido-3,4,6-tri-O-acetyl-2-azido-2-deoxy-alpha-D-galactopyranosylamine (1), a minor product of azidonitration reaction of 3,4,6-tri-O-acetyl galactal, are reported. The solution phase studies of 1 reflect that the compound exists in 4C1 conformation with cis-orientation of the substituents at C-1 and C-2. The solid-state structure of 1 reveals that a molecule of water is entrapped in the solid state of 1 and this water molecule serves to mediate N-H...O and C-H...O interactions.

Ni(II) complexes with Schiff bases derived from amino sugars

It was found by 1H and 13C NMR spectroscopy that the Schiff base, 2-deoxy-2-(2-hydroxybenzaldimino)-D-glucopyranose exhibits enol-imine-keto-amine and anomeric equilibria in methanolic, and in dimethyl sulfoxide solutions. The reaction of the Schiff base with nickel acetate gave the bidentate, mononuclear Ni(II) complex that was characterized by spectroscopic methods and by cyclic voltammetry. The coordination of the Schiff base to the metal is through the enol-imine tautomeric form, and the anomeric equilibrium remains in dimethyl sulfoxide solutions. This complex was also obtained by reaction of D-glucosamine with Ni(II) salicylaldehydate. The same reaction was employed for the synthesis of bis-N-[2-deoxy-D-galactopyranosyl-2-(2-hydroxybenzaldiminate)]Ni(II). The small paramagnetic shifts of the 1H NMR resonances of the complexes suggest that paramagnetic species are present in low proportions.

Biosynthesis of tunicamycin and metabolic origin of the 11-carbon dialdose sugar, tunicamine

Tunicamycin is a reversible inhibitor of polyprenol-phosphate: N-acetylhexosamine-1-phosphate translocases and is produced by several Streptomyces species. We have examined tunicamycin biosynthesis, an important but poorly characterized biosynthetic pathway. Biosynthetic precursors have been identified by incorporating radioactive and stable isotopes, and by determining the labeling pattern using electrospray ionization-collision induced dissociation-mass spectrometry (ESI-CID-MS), and proton, deuterium, and C-13 nuclear magnetic resonance (NMR) spectroscopy. Preparation and analysis of [uracil-5-(2)H]-labeled tunicamycin established the complete ESI-CID-MS fragmentation pathway for the major components of the tunicamycin complex. Competitive metabolic experiments indicate that 7 deuteriums incorporate into tunicamycin from [6,6'-(2)H,(2)H]-labeled D-glucose, 6 of which arise from D-GlcNAc and 1 from uridine and/or D-ribose. Inverse correlation NMR experiments (heteronuclear single-quantum coherence (HSQC)) of (13)C-labeled tunicamycin enriched from D-[1-(13)C]glucose suggest that the unique tunicamine 11-carbon dialdose sugar backbone arises from a 5-carbon furanose precursor derived from uridine and a 6-carbon N-acetylamino-pyranose precursor derived from UDP-D-N-acetylglucosamine. The equivalent incorporation of (13)C into both the alpha-1" and beta-11' anomeric carbons of tunicamycin supports a direct biosynthesis via 6-carbon metabolism. It also indicates that the tunicamine motif and the alpha-1"-linked GlcNAc residue are both derived from the same metabolic pool of UDP-GlcNAc, without significant differential metabolic processing. A biosynthetic pathway is therefore proposed for tunicamycin for the first time: an initial formation of the 11-carbon tunicamine sugar motif from uridine and UDP-GlcNAc via uridine-5'-aldehyde and UDP-4-keto-6-ene-N-acetylhexosamine, respectively, and subsequent formation of the anomeric-to-anomeric alpha, beta-1",11'-glycosidic bond.

N-alkyl-3-decarboxy-3-hydroxymethylsiastatin B, a new family of glycosidase inhibitors of gem-diamine 1-N-iminosugars

N-Alkyl-3-decarboxy-3-hydroxymethylsiastatin B, N-alkyl analogues of gem-diamine 1-N-iminosugars, is a new family of glycosidase inhibitors that have been synthesized from siastatin B isolated from Streptomyces culture. These compounds were evaluated as glycosidase inhibitors.

N-(2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-galactopyranosyloxy)succinimide

The crystal structure of the title compound, C18H24N2O11, a GalNAc mimic containing an alpha-glycosyloxysuccinimide linkage, has been determined. The pyranose ring geometry is an almost perfect (4)C(1) chair. The torsion angle of the exocyclic hydroxymethyl group is shown to be gauche-trans with respect to O1 and C4, respectively.

Molecular orbital considerations in probing the stereoselective dissociations of cobalt-coordinated hexosamine monosaccharides

The mechanisms for the stereoselective dissociation pathways of isomeric [CoIII(diaminopropane)2(hexosamine-2H)]+ complexes are studied by ion trap and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The exact masses of product ions were measured in order to determine the composition of each loss, and isotopic labeling experiments were used to determine which atoms were lost during dissociation. MS3 studies were used to probe the structures of the product ions from MS2 experiments. Based on the experimental evidence obtained, mechanisms explaining the dissociations are postulated. In deciphering the mechanisms, careful attention was paid to the molecular orbital alignment of the reacting bonds, and based on the molecular orbitals, transition state conformations were postulated. These transition states suggest how the observed stereoselectivity occurs. In each case, the carbohydrate/metal interaction was crucial in the dissociation processes.

Radical-mediated synthesis of alpha-C-glycosides based on N-acyl galactosamine

[structure] C-Glycosides of N-acyl 2-amino-2-deoxygalactose (acyl = MeCO, CF(3)CO, t-BuOCO) are available in a stereoselective manner by trapping of an anomeric radical with an activated alkene. Using anomeric selenides, radical generation and trapping is carried out under conditions that avoid competitive reduction, and this chemistry has been applied to the synthesis of the novel C-glycoside analogue of O-benzyl alpha-D-GalNAc.

Dermatan is a better substrate for 4-O-sulfation than chondroitin: implications in the generation of 4-O-sulfated, L-iduronate-rich galactosaminoglycans

The biosynthesis of dermatan sulfate is a complex process that involves, inter alia, formation of L-iduronic acid residues by C5-epimerization of D-glucuronic acid residues already incorporated into the growing polymer. It has been shown previously that this reaction is promoted by the presence of the sulfate donor 3'-phosphoadenosine-5'-phosphosulfate. In the present investigation, the role of sulfation in the biosynthesis of L-iduronic acid-rich galactosaminoglycans was examined more closely by a study of the substrate specificities and kinetic properties of the sulfotransferases involved in dermatan sulfate biosynthesis. Comparison of the acceptor reactivities of oligosaccharides from chondroitin and dermatan, in an in vitro system containing microsomes from cultured human skin fibroblasts and 3'-phosphoadenosine-5'-phosphosulfate, showed that Km values for the dermatan fragments were substantially lower than those for their chondroitin counterparts. Calculation of Vmax values likewise showed that dermatan was the better substrate. Whereas dermatan incorporated [35S]sulfate exclusively at the C4 position of N-acetylgalactosamine residues, approximately equal amounts of radioactivity were found at the C4 and C6 positions in the labelled chondroitin. Under standard assay conditions, the 4-O-sulfation of dermatan proceeded about six times faster than the 4-O-sulfation of chondroitin. On the basis of these results, we propose that L-iduronic acids, formed in the course of the biosynthesis of dermatan sulfates, enhance sulfation of their adjacent N-acetylgalactosamine residues, and will thereby be locked in the L-ido configuration.

Fluorometric determination of mucin-type glycoproteins by the galactose oxidase-peroxidase method

We developed a convenient and specific method for the determination of mucin-type glycoproteins using galactose oxidase and horseradish peroxidase on the basis of the contents of galactosyl and N-acetylgalactosaminyl residues in glycoproteins. Galactose and galactosamine residues released from glycoproteins after hydrolysis were oxidized with galactose oxidase and subsequently the resultant hydrogen peroxide was determined by a combination of horseradish peroxidase and 3-(p-hydroxyphenyl) propionic acid as a fluorogenic substrate. The contents of galactose/galactosamine residues in N- and O-glycans, as determined by the galactose oxidase-peroxidase method, were in good agreement with those described in the previous reports. We applied the present method to determine mucin-type glycoproteins secreted from rat gastric mucosa by stimulation with misoprostol, a prostaglandin E(1) analogue in vivo. Thus, the galactose oxidase-peroxidase method is useful for the determination of mucin-type glycoproteins in biological materials.