Tissue targeting of multivalent Le(x)-terminated N-linked oligosaccharides in mice

Major Genetic Drivers of Statin Treatment Response in African Populations and Pharmacogenetics of Dyslipidemia Through a One Health Lens

A One Health lens is increasingly significant to address the intertwined challenges in planetary health concerned with the health of humans, nonhuman animals, plants, and ecosystems. A One Health approach can benefit the public health systems in Africa that are overburdened by noncommunicable, infectious, and environmental diseases. Notably, the COVID-19 pandemic revealed the previously overlooked two-fold importance of pharmacogenetics (PGx), for individually tailored treatment of noncommunicable diseases and environmental pathogens. For example, dyslipidemia, a common cardiometabolic risk factor, has been identified as an independent COVID-19 severity risk factor. Observational data suggest that patients with COVID-19 infection receiving lipid-lowering therapy may have better outcomes. However, among African patients, the response to these drugs varies from patient to patient, pointing to the possible contribution of genetic variation in important pharmacogenes. The PGx of lipid-lowering therapies may underlie differences in treatment responses observed among dyslipidemia patients as well as patients comorbid with COVID-19 and dyslipidemia. Genetic variations in APOE, ABCB1, CETP, CYP2C9, CYP3A4, CYP3A5, HMGCR, LDLR, NPC1L1, and SLCO1B1 genes affect the pharmacogenomics of statins, and they have individually been linked to differential responses to dyslipidemia and COVID-19 treatment. African populations are underrepresented in PGx research. This leads to poor accounting of additional diverse genetic variants that could be important in understanding interindividual and between-population variations in therapeutic responses to dyslipidemia and COVID-19. This expert review examines and synthesizes the salient and priority PGx variations, as seen through a One Health lens in Africa, to improve and inform personalized medicine in both dyslipidemia and COVID-19.

Rationally Designed Galactose Dendrimer for Hepatocyte-Specific Targeting and Intracellular Drug Delivery for the Treatment of Liver Disorders

Over two million people die of liver disorders every year globally. Hepatocytes are the key cells affected in several acute and chronic liver diseases. The current clinical outcomes of liver-targeted nanoparticles are limited, necessitating the need to develop smart hepatocyte-targeted drug delivery systems. Here, we present the rational design and development of a hepatocyte-targeting glycodendrimer (GAL-24) built from biocompatible building blocks, using expedite and facile chemical methodology. GAL-24 is designed to inherently target asialoglycoprotein receptor 1 (ASGP-R) on hepatocytes and shows significant accumulation in the liver (20% of injected dose), just 1 h after systemic administration. This is highly specific to hepatocytes, with over 80% of hepatocytes showing GAL-24-Cy5 signal at 24 h. GAL-24-Cy5 maintains hepatocyte-targeting capabilities in both a mouse model of severe acetaminophen poisoning-induced hepatic necrosis and a rat model of nonalcoholic steatohepatitis (NASH). This GAL-24 nanoplatform holds great promise for improved drug delivery to hepatocytes to combat many liver disorders.

Efficient Liver Targeting by Polyvalent Display of a Compact Ligand for the Asialoglycoprotein Receptor

A compact and stable bicyclic bridged ketal was developed as a ligand for the asialoglycoprotein receptor (ASGPR). This compound showed excellent ligand efficiency, and the molecular details of binding were revealed by the first X-ray crystal structures of ligand-bound ASGPR. This analogue was used to make potent di- and trivalent binders of ASGPR. Extensive characterization of the function of these compounds showed rapid ASGPR-dependent cellular uptake in vitro and high levels of liver/plasma selectivity in vivo. Assessment of the biodistribution in rodents of a prototypical Alexa647-labeled trivalent conjugate showed selective hepatocyte targeting with no detectable distribution in nonparenchymal cells. This molecule also exhibited increased ASGPR-directed hepatocellular uptake and prolonged retention compared to a similar GalNAc derived trimer conjugate. Selective release in the liver of a passively permeable small-molecule cargo was achieved by retro-Diels-Alder cleavage of an oxanorbornadiene linkage, presumably upon encountering intracellular thiol. Therefore, the multicomponent construct described here represents a highly efficient delivery vehicle to hepatocytes.

Human Milk Oligosaccharides (HMOS): Structure, Function, and Enzyme-Catalyzed Synthesis

The important roles played by human milk oligosaccharides (HMOS), the third major component of human milk, in the health of breast-fed infants have been increasingly recognized, as the structures of more than 100 different HMOS have now been elucidated. Despite the recognition of the various functions of HMOS as prebiotics, antiadhesive antimicrobials, and immunomodulators, the roles and the applications of individual HMOS species are less clear. This is mainly due to the limited accessibility to large amounts of individual HMOS in their pure forms. Current advances in the development of enzymatic, chemoenzymatic, whole-cell, and living-cell systems allow for the production of a growing number of HMOS in increasing amounts. This effort will greatly facilitate the elucidation of the important roles of HMOS and allow exploration into the applications of HMOS both as individual compounds and as mixtures of defined structures with desired functions. The structures, functions, and enzyme-catalyzed synthesis of HMOS are briefly surveyed to provide a general picture about the current progress on these aspects. Future efforts should be devoted to elucidating the structures of more complex HMOS, synthesizing more complex HMOS including those with branched structures, and developing HMOS-based or HMOS-inspired prebiotics, additives, and therapeutics.

Cross-linked low molecular weight glycopeptide-mediated gene delivery: relationship between DNA metabolic stability and the level of transient gene expression in vivo

DNA co-condensates were formed by reacting [125I]DNA with an admixture of a high-mannose glycopeptide (Man9-CWK(18)) and either of two poly(ethylene glycol) peptides (PEG-VS-CWK(18) or PEG-SS-CWK(18)) followed by cross-linking with 6-50 mol equiv of glutaraldehyde. [125I]DNA co-condensates were administered intravenously in mice to determine the influence of peptide DNA formulation parameters on specific targeting to Kupffer cells. Optimal targeting to Kupffer cells required the combined use of 50 mol % Man9-CWK(18) and PEG-CWK(18) to mediate specific recognition by the mannose receptor to Kupffer cells. The cellular uptake of cross-linked Man9-CWK(18)/PEG-CWK(18) DNA co-condensates was receptor mediated since Kupffer cell targeting was inhibited by pre-administration of Man-bovine serum albumin (BSA) but not BSA. An optimized formulation targeted 60% of the dose to the liver, with 80% of the liver-targeted DNA localized to Kupffer cells. Cross-linking with either 6, 15, or 50 mol equiv of glutaraldehyde led to a corresponding decrease in the metabolism rate of DNA in liver as measured by half-live- of 4, 6, and 39 h, respectively. Tail vein dosing of 50 microg of DNA co-condensates cross-linked with 6 mol equiv of glutaraldehyde produced detectable levels of human alpha1-antitrypsin in blood after 12 h, which peaked at day six and persisted for 10 days. The level of human alpha1-antitrypsin was elevated two-fold each day when dosing with DNA co-condensates cross-linked with 15 mol equiv of glutaraldehyde, revealing a correlation between the metabolic stability of the DNA in liver and level of gene expression. In addition to possessing greater metabolic stability, DNA co-condensates cross-linked with 50 mol equiv of glutaraldehyde, but lacking a targeting ligand, avoided rapid liver uptake and possessed a prolonged pharmacokinetic half-life, providing insight into a means to target DNA condensates to peripheral tissues.

Tissue targeting of multivalent GalNAc Le(x) terminated N-glycans in mice

N-Linked biantennary and triantennary oligosaccharides containing multiple terminal GalNAc Le(x) (GalNAcss1-4[Fuc-alpha1-3]GlcNAc) determinants were radioiodinated and their pharmacokinetics, biodistribution, and hepatic cellular localization were determined in mice. Pharmacokinetic analysis revealed GalNAc Le(x) biantennary and triantennary oligosaccharides had a similar mean residence time and steady-state volume of distribution but differed in their total body clearance rate due a shorter alpha half-life for GalNAc Le(x) triantennary. Biodistribution and whole-body-autoradiography studies revealed that both GalNAc Le(x) terminated biantennary and triantennary oligosaccharides predominately targeted to the liver, which accumulated 72% and 79% of the dose 30 min after administration, respectively. Separation of mouse liver parenchymal from non-parenchymal cells demonstrated both N-glycans were almost exclusively (94%) taken up by the parenchymal cells. By comparison, GalNAc terminated biantennary and triantennary N-glycans accumulated in the liver with a targeting efficiency of 73% and 81%, respectively. It is concluded that GalNAc and GalNAc Le(x) terminated N-glycans are recognized in vivo with equivalent affinity by the murine hepatic asialoglycoprotein receptor.

Endogenous lectins as targets for drug delivery

To minimize side effects of drugs it would be ideal to target them exclusively to those cell types which require treatment. As a means to this end prototypical cellular recognition systems pique our interest to devise biomimetic strategies. Since oligosaccharides of glycoconjugates outmatch other information-carrying biomolecules (proteins, nucleic acids) in theoretical storage capacity by far, work on the sugar code can spark off development of effective targeting devices. Conjugation of custom-made glycan epitopes to proteins or biocompatible non-immunogenic polymeric scaffolds produces neoglycoconjugates with purpose-adaptable properties. In the interplay with endogenous receptors such as lectins, suitable oligosaccharides such as histo-blood group trisaccharides as parts of neoglycoconjugates have already proven their practical applications in histopathology. Elucidation of the structure of cell lectins with currently five main families aids to tailor ligand characteristics rationally. They include the types of functional groups and their topological presentation to optimize the bimolecular binding as well as the optimal spatial clustering and spacer characteristics to exploit cooperativity. Indeed, the potent trivalent cluster glycosides designed for the C-type asialoglycoprotein receptors furnish an instructive example how to turn the theoretical guideline on ligand modification into nM-affinity. By placing emphasis on tissue lectins as targets of neoglycoconjugate-mediated drug delivery, the long-term perspective is opened to likewise test members of these families themselves for routing of therapeutic payloads, aiming at cell addressins. This review illustrates the conceivable potential which work on the sugar code with custom-made neoglycoconjugates and tissue lectins can have in store for drug delivery.

In vivo ligand specificity of E-selectin binding to multivalent sialyl Lewisx N-linked oligosaccharides

The in vivo specificity for E-selectin binding to a panel of N-linked oligosaccharides containing a clustered array of one to four sialyl Lewisx (SLex; NeuAcalpha2-3Gal[Fucalpha1-3]beta1-4GlcNAc) determinants was studied in mice. Following intraperitoneal dosing with lipopolysaccharide, radioiodinated tyrosinamide N-linked oligosaccharides were dosed i.v. and analyzed for their pharmacokinetics and biodistribution. Specific targeting was determined from the degree of SLex oligosaccharide targeting relative to a sialyl oligosaccharide control. Oligosaccharides targeted the kidney with the greatest selectivity after a 4-h induction period following lipopolysaccharide dosing. Unique pharmacokinetic profiles were identified for SLex biantennary and triantennary oligosaccharides but not for monovalent and tetraantennary SLex oligosaccharides or sialyl oligosaccharide controls. Biodistribution studies established that both SLex biantennary and triantennary oligosaccharides distributed to the kidney with 2-3-fold selectivity over sialyl oligosaccharide controls, whereas monovalent and tetraantennary SLex oligosaccharides failed to mediate specific kidney targeting. Simultaneous dosing of SLex biantennary or triantennary oligosaccharide with a mouse anti-E-selectin monoclonal antibody blocked kidney targeting, whereas co-administration with anti-P-selectin monoclonal antibody did not significantly block kidney targeting. The results suggest that SLex biantennary and triantennary are N-linked oligosaccharide ligands for E-selectin and implicate E-selectin as a bivalent receptor in the murine kidney endothelium.

Site-specific gene delivery in vivo through engineered Sendai viral envelopes

Inspite of several stimulating developments in gene therapy, the formulation of a targeted gene delivery "vector" is still far from ideal. We have demonstrated the potential of reconstituted Sendai viral envelopes containing only the fusion glycoprotein (F-virosomes) in targeted delivery of reporter genes to liver cells of BALB/c mouse in vivo. The membrane fusion-mediated high efficiency of gene transfer to liver cells was ascertained following a critical evaluation of the level of the DNA, mRNA, and relevant proteins. Furthermore, the involvement of viral glycoprotein both as a unique natural ligand and as a membrane fusogen could lead to preferential transfection of parenchymal cell types of liver. The integration of transgenes in the mouse chromosomal DNA and its stable expression up to 4 mo after single i.v. administration of this gene carrier has bolstered its efficiency and novelty. Moreover, the F-virosomes did not elicit significant humoral immune response against the fusion protein in the injected animal. The findings reported here open up the possibility for considering "F-virosomes" as a promising "vehicle" for site-specific DNA delivery in gene therapy.

Enzymatic synthesis of N-linked oligosaccharides terminating in multiple sialyl-Lewis(x) and GalNAc-Lewis(x) determinants: clustered glycosides for studying selectin interactions

Galactosyltransferase, sialyltransferase, and fucosyltransferase were used to create a panel of complex oligosaccharides that possess multiple terminal sialyl-Le(x) (NeuAc alpha 2-3Gal[Fuc alpha 1-3] beta 1-4GlcNAc) and GalNAc-Le(x) (GalNAc[Fuc alpha 1-3]beta 1-4GlcNAc). The enzymatic synthesis of tyrosinamide biantennary, triantennary, and tetraantennary N-linked oligosaccharides bearing multiple terminal sialyl-Le(x) was accomplished on the 0.5 mumol scale and the purified products were characterized by electrospray MS and 1H NMR. Likewise, biantennary and triantennary tyrosinamide oligosaccharides bearing multiple terminal GalNAc-Le(x) determinants were synthesized and similarly characterized. The transfer kinetics of human milk alpha 3/4-fucosyltransferase were compared for biantennary oligosaccharide acceptor substrates possessing Gal beta 1-4GlcNAc, GalNAc beta 1-4GlcNAc, and NeuAc alpha 2-3Gal beta 1-4GlcNAc which established NeuAc alpha 2-3Gal beta 1-4GlcNAc as the most efficient acceptor substrate. The resulting complex oligosaccharides were chemically tethered through the tyrosinamide aglycone to the surface of liposomes containing phosphatidylthioethanol, resulting in the generation of glycoliposomes probe which will be useful to study relationships between binding affinity and the micro- and macro-clustering of selectin ligand.

Chemoenzymatic synthesis of a sialylated diantennary N-glycan linked to asparagine

A partial structure of many glycoproteins, a glycosylated asparagine carrying a complex type undecasaccharide N-glycan (Neu5Ac(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-2)Man alpha 1-3) [Neu5Ac(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-6)]Man(beta 1-4) GlcNAc(beta 1-4)GlcNAc-Asn) was obtained by total synthesis. As a starting material served a chemically synthesized diantennary heptasaccharide azide which was deprotected in a three-step sequence in high yield. The reduction of the anomeric azide was accomplished with propanedithiol in methanol-ethyldiisopropylamine. Coupling of the glycosyl amine to an activated aspartic acid gave the benzyl protected asparagine conjugate. After removal of the six benzyl functions the resulting free heptasaccharide asparagine was elongated enzymatically in the oligosaccharide part. The use of beta-1,4-galactosyltransferase and alpha-2,6-sialytransferase in the presence of alkaline phosphatase allowed the efficient transfer of four sugar units to the acceptor resulting in a full length N-glycan, a sialyated diantennary undecasaccharide-asparagine of the complex type.

Tyramine-containing poly(4-nitrophenylacrylate) as iodinatable ligand carrier in biodistribution analysis

PURPOSE

Targeted label or drug delivery requires access to convenient carrier systems and methods for efficient ligand conjugation. The main purpose of this study is to design an iodinatable synthetic polymer, whose application in vivo in tumor-bearing mice is tested with several related carbohydrate ligands, namely ABH and Lewis blood group epitopes.

METHODS

Tyramine and aminopropyl derivatives of the synthetic oligosaccharides were attached to poly(4-nitrophenylacrylate). Following iodination, the biodistribution of the sugar-free and the substituted polymers was determined in tumor-bearing mice. Flow cytofluorimetric analysis assessed tumor cell binding of further ligand types to human tumor cells in vitro.

RESULTS

Quantitative ligand incorporation was achieved under mild conditions. Whereas the ligand-free poly[N-(2-hydroxyethyl)acrylamide] (MW 30 kDa) showed preferential accumulation in kidney, neoglycopolymers were found in substantial amounts in liver, kidney or spleen. The nature of the carbohydrate structure quantitatively influenced the distribution pattern. Tumor cell binding of blood group determinants and three further ligand types revealed non-uniform intensity in labeling and percentage of positive cells even in comparison between lines with identical histogenetic origin.

CONCLUSIONS

Carbohydrate-exposing poly[N-(2-hydroxyethyl)acrylamide] polymers with tyramine as an iodine acceptor distribute in mice with a profile which is quantitatively influenced by small structural variations of the ligand part. Further refinement of the ligand structure may increase the level of selectivity for organ and tumor accumulation.

Tissue targeting and plasma clearance of cobra venom factor in mice

The tissue targeting and rate of clearance of cobra venom factor (CVF) from the circulation was studied in mice by intravenous or intraperitoneal injection of radioiodinated CVF. In both modes of administrations, CVF was targeted mainly to liver. CVF injected directly into the blood was cleared from the circulation with a plasma half life of about 10 h, whereas CVF injected into the peritoneal cavity was slowly absorbed into the blood stream reaching a maximum level at approximately 6 h, and it was then cleared from the circulation with a plasma half life of about 18 h. The rate of plasma clearance of CVF was markedly decreased upon removal of the terminal alpha-galactosyl residues of the oligosaccharide chains; the plasma half lives for intravenously and intraperitoneally administered de-alpha-galactosylated CVF were approximately 5 and approximately 10 h, respectively. However, the clearance rate was not affected by complete deglycosylation using N-glycanase or by chemical modification of the terminal galactosyl residues. Together, these data demonstrate that the terminal alpha-galactosyl residues of CVF mask the Lewis X-dependent uptake of CVF by liver.

Clearance of circulating gamma-glutamyltransferase by the asialoglycoprotein receptor. Enzyme forms with different sialic acid content are eliminated at different clearance rates and without apparent desialylation

gamma-Glutamyltransferase is eliminated from the circulation via the asialoglycoprotein receptor in liver. After purifying the enzyme from human liver, a subfractionation into differently sialylated forms was obtained using MonoQ ion exchange chromatography. The uptake of such forms from rat circulation was studied and the slowest rate was measured for the most sialylated form. To test if the uptake of the sialylated enzymes was dependent on prior desialylation in the circulation the enzyme was recovered from liver after uptake and from serum after inhibiting the uptake with asialofetuin. Analysis of these recovered forms showed no apparent alteration in charge. The enzyme is apparently eliminated without prior desialylation through available galactose units which bind with low affinity to the receptor.

Immobilized Lotus tetragonolobus agglutinin binds oligosaccharides containing the Le(x) determinant

A defined set of oligosaccharides and glycopeptides containing alpha-linked fucose were used to examine the specificity of the immobilized fucose-binding lectin Lotus tetragonolobus agglutinin (LTA1), also known as lotus lectin. Glycans containing the Lewis x determinant (Le(x)) Gal beta 1-4[Fuc alpha 1-3]GlcNAc beta 1-3-R were significantly retarded in elution from high density LTA-Emphaze columns. The lectin also bound the fucosylated lacdiNAc trisaccharide GalNAc beta 1-4[Fuc alpha 1-3]GlcNAc. The lectin did not bind glycans containing either sialylLe(x) or VIM-2 determinants, nor did it bind the isomeric Le(x), Gal beta 1-3[Fuc alpha 1-4]GlcNAc-R. Although 2'-fucosyllactose Fuc alpha 1-2Gal beta 1-4Glc) was retarded in elution from the columns, larger glycans containing the H-antigen Fuc alpha 1-2Gal beta 1-3(4)GlcNAc-R interacted poorly with immobilized LTA. Our results demonstrate that immobilized LTA is effective in isolating glycans containing the Le(x) antigen and is useful in analyzing specific fucosylation of glycoconjugates.

Glycobiology in Medicine

Glycoconjugates play important roles in biological reactions (for example sialyl Lewis(x) in 'homing' of leukocytes and mannose-6-phosphate in targeting of lysosomal enzymes) and thus aberration in carbohydrate structures in glycoconjugates can lead to abnormal biological behaviors. In fact, glycoconjugates expressed on the surfaces of tumor and cancer cells are considerably different from those of the normal cells, at least quantitatively. There are many known carbohydrate-deficient glycoprotein syndromes. As recognition of carbohydrate groups is mostly performed by carbohydrate-binding proteins, aberration in these proteins also results in disease status (for example I-cell disease). Many pathogens use carbohydrates as recognition markers for invasion (examples are influenza virus and cholera toxin). The carbohydrate receptors in various organs can be used for targeting drugs, antibodies and even DNAs. Conjugation of polysaccharides derived from pathogenic micro-organisms with appropriate proteins provides effective vaccines against the micro-organisms. Copyright 1996 S. Karger AG, Basel