Synthetic glycopeptide substrates for receptor-mediated endocytosis by macrophages

Macrophage-related therapeutic strategies: Regulation of phenotypic switching and construction of drug delivery systems

Macrophages, as highly phenotypic plastic immune cells, play diverse roles in different pathological conditions. Changing and controlling the phenotypes of macrophages is considered a novel potential therapeutic intervention. Meanwhile, specific transmembrane proteins anchoring on the surface of the macrophage membrane are relatively conserved, supporting its functional properties, such as inflammatory chemotaxis and tumor targeting. Thus, a series of drug delivery systems related to specific macrophage membrane proteins are commonly used to treat chronic inflammatory diseases. This review summarizes macrophages-based strategies for chronic diseases, discusses the regulation of macrophage phenotypes and their polarization processes, and presents how to design and apply the site-specific targeted drug delivery systems in vivo based on the macrophages and their derived membrane receptors. It aims to provide a better understanding of macrophages in immunoregulation and proposes macrophages-based targeted therapeutic approaches for chronic diseases.

Multivalent Mannose-Decorated NIR Nanoprobes for Targeting Pan Lymph Nodes

Lymphadenectomy is a prerequisite for most malignancies to define the precise staging of cancer, as well as resect the possible metastases completely. While it improves prognosis, lymphadenectomy often causes postoperative edema or bleeding because of unclear surgical margins. In this study, we synthesized near-infrared (NIR) fluorescent nanoprobes with conjugating various mannose moieties on the surface to target macrophages in the lymph node. Armed with these NIR nanoprobes, we demonstrated the feasibility of intraoperative pan lymph nodes (PLN) mapping and real-time optical imaging under the NIR fluorescence imaging system. We found that even single mannose-conjugated ZW800-1 showed specific uptake in lymph nodes within 4 h, and multiple mannose-employed polyrotaxanes highlighted PLN efficiently with low background signals in major organs. This technology can help surgeons perform lymphadenectomy with ease and safety by identifying all regional lymph nodes proficiently after a single intravenous injection of NIR nanoprobes.

Covalent Binding of Mannosyl Ligand via 6-O Position and Glycolic Arm to Target a PLCA-Type Degradable Drug Carrier toward Macrophages

Mononuclear phagocytes play a central role in the defense against important pathologies. Attempts were made to target drugs toward this cell type by using specific interactions between a mannose ligand and the lectin-type specific receptor present on the macrophage membrane. Basically, the use of a mannosyl radical as a homing device raised several problems: necessity to keep unmodified the part of the molecule which gives rise to lectin recognition, complex protection-deprotection chemistry, and blockage of the aldehyde function to preclude any side reaction. A new method was used to bind α-D-methylmannopy-ranoside, a commercially available precursor, through its primary hydroxyl group to the hydrosoluble bioresorbable drug carrier poly(L-lysine citramide imide). The method consisted of a few steps that did not require special protection of secondary hydroxyl groups. In the resulting conjugate, the pyranose structure of the sugar was retained. In vivo recognition of the conjugate by the lectin of mononuclear phagocytes was preserved.

Uptake of HLA Alloantigens via CD89 and CD206 Does Not Enhance Antigen Presentation by Indirect Allorecognition

In organ transplantation, alloantigens are taken up by antigen presenting cells and presented via the indirect pathway to T-cells which in turn can induce allograft rejection. Monitoring of these T-cells is of major importance; however no reliable assay is available to routinely monitor indirect allorecognition. Recently we showed that HLA monomers can be successfully used to monitor indirect allorecognition. Targeting antigens to endocytic receptors on antigen presenting cells may further enhance the presentation of antigens via HLA class II and improve the efficiency of this assay. In the current study we explored targeting of HLA monomers to either CD89 expressing monocytes or mannose receptor expressing dendritic cells. Monomer-antibody complexes were generated using biotin-labeled monomers and avidin labeling of the antibodies. We demonstrate that targeting the complexes to these receptors resulted in a dose-dependent HLA class II mediated presentation to a T-cell clone. The immune-complexes were efficiently taken up and presented to T-cells. However, the level of T-cell reactivity was similar to that when only exogenous antigen was added. We conclude that HLA-A2 monomers targeted for presentation through CD89 on monocytes or mannose receptor on dendritic cells lead to proper antigen presentation but do not enhance indirect allorecognition via HLA-DR.

Assembly, postsynthetic modification and hepatocyte targeting by multiantennary, galactosylated soft structures

Enzyme modifiable, hollow self-assembled structures offer an excellent scope for multiantennary delivery vectors.

Imiglucerase in the treatment of Gaucher disease: a history and perspective

The scientific and therapeutic development of imiglucerase (Cerezyme(®)) by the Genzyme Corporation is a paradigm case for a critical examination of current trends in biotechnology. In this article the authors argue that contemporary interest in treatments for rare diseases by major pharmaceutical companies stems in large part from an exception among rarities: the astonishing commercial success of Cerezyme. The fortunes of the Genzyme Corporation, latterly acquired by global giant Sanofi SA, were founded on the evolution of a blockbuster therapy for a single but, as it turns out, propitious ultra-orphan disorder: Gaucher disease.

Carrier-based strategies for targeting protein and peptide drugs to the lungs

With greater interest in delivery of protein and peptide-based drugs to the lungs for topical and systemic activity, a range of new devices and formulations are being investigated. While a great deal of recent research has focused on the development of novel devices, attention must now be paid to the formulation of these macromolecular drugs. The emphasis in this review will be on targeting of protein/peptide drugs by inhalation using carriers and ligands.

99mtc-labeled mannosyl-neoglycoalbumin for sentinel lymph node identification

99mTc-labeled mannosyl-neoglycoalbumin (NMA) was prepared and evaluated as a radiopharmaceutical for sentinel lymph node (SLN) identification, since 99mTc-labeled human serum albumin (HSA) rapidly cleared from injection sites. NMA was conjugated with 6-hydrazinopyridine-3-carboxylic acid (HYNIC) and reacted with [99mTc](tricine)2 to prepare [99mTc](HYNIC-NMA)(tricine)2. After subcutaneous injection of [99mTc](HYNIC-NMA)(tricine)2 from murine foot pad, radioactivity levels in the popliteal and lumbar lymph nodes, the injection site and other tissues were compared with those of [99mTc](HYNIC-HSA)(tricine)2 and 99mTc-labeled colloidal rhenium sulfate ([99mTc]colloid). [99mTc](HYNIC-NMA)(tricine)2 demonstrated significantly higher radioactivity levels in the popliteal lymph node, the SLN in this model, than did [99mTc](HYNIC-HSA)(tricine)2 and [99mTc]colloid at 0.5, 1, and 6 h post-injection. [99mTc](HYNIC-NMA)(tricine)2 showed a dose-dependent decrease in the popliteal accumulation while the radioactivity levels in the blood, liver and spleen increased with an increase in the molar dose of NMA. [99mTc]colloid registered a decrease in the radioactivity levels in the popliteal lymph node, blood, liver, and spleen with dilution. However, the radioactivity levels at the injection site increased with dilution of [99mTc] colloid. Both [99mTc](HYNIC-NMA)(tricine)2 and [99mTc](HYNIC-HSA)(tricine)2 showed the radioactivity levels at the injection site similar each other. These findings indicated that an addition of a macrophage binding function to 99mTc-labeled HSA provided high and selective accumulation of the radioactivity in the SLN without affecting the elimination rate from the injection site. Such characteristics render [99mTc](HYNIC-NMA)(tricine)2 attractive as a radiopharmaceutical for SLN identification. This study also demonstrated that the number of non-radiolabeled colloidal particles and the molar dose of mannosylated compounds play a crucial role in the SLN accumulation.

Physical characterization and macrophage cell uptake of mannan-coated nanoparticles

Previously, we reported on a cationic nanoparticle-based DNA vaccine delivery system engineered from warm oil-in-water microemulsion precursors. In these present studies, the feasibility of lyophilizing the nanoparticles and their thermal properties were investigated. Also, the binding and uptake of the nanoparticles by a macrophage cell line were studied. The nanoparticles (prior to pDNA coating) were freeze-dried with lactose or sucrose as cryoprotectants. The stability of lyophilized nanoparticles at room temperature was monitored and compared to that of the aqueous nanoparticle suspension. The thermal properties of the nanoparticles were investigated using differential scanning calorimetry (DSC). The nanoparticles, coated or uncoated with mannan as a ligand, were incubated with a mannose receptor positive (MR+) mouse macrophage cell line (J774E), at either 4 degrees C or 37 degrees C to study the binding and uptake of the nanoparticles by the cells. It was found that lactose or sucrose (1-5%, w/v) was required for successful lyophilization of the nanoparticles. After 4 months of storage, the size of lyophilized nanoparticles did not significantly increase while those in aqueous suspension grew by over 900%. Unlike its individual components, emulsifying wax (m.p., approximately 55 degrees C) and hexadecyltrimethyl ammonium bromide, the nanoparticles showed a melting point of approximately 90 degrees C. Moreover, the DSC profile of the nanoparticles was different from that of the physical mixture of emulsifying wax and CTAB. After 1 hour incubation at 37 degrees C, the uptake of mannan-coated nanoparticles was 50% higher than that of the uncoated nanoparticles. At 4 degrees C and after one hour, the binding of the mannan-coated nanoparticles by J774E was over 2-fold higher than that of the uncoated nanoparticles. This increase in J774E binding could be abolished by preincubating the cells with free mannan, suggesting that the binding and uptake were receptor-mediated. In conclusion, the nanoparticles were lyophilizable, and lyophilization was shown to enhance the stability of the nanoparticles. DSC provided evidence that the nanoparticles were not a physical mixture of their individual components. Finally, cell binding and uptake studies demonstrated that the nanoparticles have potential application for cell-specific targeting.

Oligolysine-based saccharide clusters: synthesis and specificity

In search of specific and highly selective sugar clusters for cell receptors, such as membrane lectins, various disaccharides were coupled to small peptide cores through an amide bond. In a first step, the reducing disaccharides, i.e. lactose and three different dimannoses, were converted into glycosyl-pyroglutamyl-beta-alanine derivatives. The free carboxylic group of these conjugates was then coupled to the alpha and epsilon amino groups of the core peptide (Lys( n )-Ala-Cys-NH2) with n =1 to 5, with complete substitution leading to homogeneous glycoclusters. The thiol group of the cysteine residue was used to tag the glycosylated oligolysines upon reaction with fluorescein iodoacetamide. The affinity of these glycoclusters towards two plant lectins was assessed by surface plasmon resonance. The selectivity of their cell uptake was investigated by flow cytometry using two types of cells: a human hepatoma cell line (HepG2 cells) expressing the plasma membrane galactose-specific lectin, and monocyte-derived dendritic cells expressing the plasma membrane mannose-specific lectin. The glycoclusters containing four or five disaccharides were shown to bind plant lectins and cell surface membrane lectins with a narrow selectivity and with a high affinity.

Synthesis of clustered glycoside-antigen conjugates by two one-pot, orthogonal, chemoselective ligation reactions: scope and limitations

Major histocompatibility class II antigens have been bound to clustered glycosides for selective targeting of the dendritic cell mannose receptor. Di-, tetra-, and octavalent glycoside-antigen conjugates have been obtained after two, orthogonal, hydrazone/thioether ligations, performed by using thio derivatives of D-mannose, D-galactose, or D(-)-quinic acid, glyoxylyl (or hydrazino)-N-chloroacetylated lysinyl trees, and N-terminal hydrazino (or glyoxylyl) peptide antigens. Successful one-pot condensations have been developed to account for the nature of the antigens and the valency of the trees.

Antagonists of the mannose receptor and the LDL receptor-related protein dramatically delay the clearance of tissue plasminogen activator

BACKGROUND

Clinical application of tissue plasminogen activator (TPA) as a fibrinolytic agent is complicated by its rapid clearance from the bloodstream, which is caused by TPA liver uptake. The mannose receptor on endothelial liver cells and the LDL receptor-related protein (LRP) on parenchymal liver cells were reported to contribute to liver uptake.

METHODS AND RESULTS

In this study, we addressed whether TPA clearance can be delayed by inhibiting receptor-mediated endocytosis of TPA. A series of cluster mannosides was synthesized, and their affinity for the mannose receptor was determined. A cluster mannoside carrying six mannose groups (M6L5) displayed a subnanomolar affinity for the mannose receptor (Ki = 0.41 +/- 0.09 nmol/L). Preinjection of M6L5 (1.2 mg/kg) reduced the clearance of 125I-TPA in rats by 60% because of specific inhibition of the endothelial cell uptake. The low toxicity of M6L5, combined with its accessible synthesis and high specificity for the mannose receptor, makes it a promising agent to improve the pharmacokinetics of TPA. Blockade of LRP by 39-kD receptor-associated protein (GST-RAP) also inhibited TPA clearance by 60%. Finally, combined preinjection of M6L5 and GST-RAP almost completely abolished reduced liver uptake of TPA and delayed its clearance by a factor of 10.

CONCLUSIONS

It can be concluded that (1) the mannose receptor and LRP appear to be the sole major receptors responsible for TPA clearance and (2) therapeutic levels of TPA can be maintained for a prolonged time span by coadministration of the aforementioned receptor antagonists.

Lysine-based cluster mannosides that inhibit ligand binding to the human mannose receptor at nanomolar concentration

In search of synthetic high affinity ligands for the mannose receptor, we synthesized a series of lysine-based oligomannosides containing two (M2L) to six (M6L5) terminal alpha-D-mannose groups that are connected with the backbone by flexible elongated spacers (16 A). The synthesized cluster mannosides were all able to displace binding of biotinylated ribonuclease B and tissue-type plasminogen activator to isolated human mannose receptor. The affinity of these cluster mannosides for the mannose receptor was continuously enhanced from 18-23 microM to 0.5-2.6 nM, with mannose valencies increasing from two to six. On average, expansion of the cluster mannoside with an additional alpha-D-mannose group resulted in a 10-fold increase in its affinity for the mannose receptor. M3L2 to M6L5 displayed negative cooperative inhibition of ligand binding to the mannose receptor, suggesting that binding of these mannosides involves multiple binding sites. The nanomolar affinity of the most potent ligand, the hexamannoside M6L5 makes it the most potent synthetic cluster mannoside for the mannose receptor yet developed. As a result of its high affinity and accessible synthesis, M6L5 not only is a powerful tool to study the mechanism of ligand binding by the mannose receptor, but it is also a promising targeting device to accomplish cell-specific delivery of genes and drugs to liver endothelial cells or macrophages in bone marrow, lungs, spleen, and atherosclerotic plaques.

Synthesis of neoglycopeptides and analyses of their biodistribution in vivo to identify tissue specific uptake and novel putative membrane lectins

Complex type N-linked oligosaccharides derived from fetuin, fibrinogen and thyroglobulin were coupled to acetyltyrosine affording a series of neoglycopeptides with retention of terminal structures and the beta-anomeric configuration of their reducing end N-acetylglycosamine residue. The neoglycopeptides thus synthesized could be labelled to high specific activities with 125I in the aromatic side chain of tyrosine. Analysis of the fate of these neoglycopeptides in conjunction with inhibition with asialofetuin and oligosaccharides of defined structure in mice in vivo revealed the uptake of galactosylated biantennary compound by kidneys, in addition to the known itinerary of triantennary galactosylated complex oligosaccharide from fetuin to liver and the galactosylated biantennary chain with fucosylation in the core to bone marrows. On the other hand, the agalacto, aglucosamino biantennary chains with and without fucosylation in the core region are taken up by submaxillary glands while the conserved trimannosyl core with fucose is primarily concentrated in stomach tissue. These studies thus define new routes for the uptake of complex N-linked glycans and also subserve to identify lectins presumably involved in their recognition.

Chain-length dependence for secondary structure formation of homo-oligopeptides from epsilon-tert.-butyloxycarbonyl-L-lysine with a lipophilic C-terminal group

A solid-state and solution analysis of the homo-oligopeptides from epsilon-tert.-butyloxycarbonyl-L-lysine with p-oxymethylbenzylcholestan-3 beta-yl succinate as C-terminal group, using infrared absorption and circular dichroism, is described. The occurrence of intermolecular beta-structure is seen in the solid state and in solvents of low polarity, e.g. methylene chloride, for peptides of intermediate size (from pentamer to decamer). Conversely, the eicosapeptide exhibits a high percentage of alpha-helical structure both in the solid state and in 2,2,2-trifluoroethanol. The influence of the C-terminal group on the conformational preferences of the epsilon-blocked homo-oligolysines in the solid state and in organic solvents appears negligible.