The isolation of a rat alveolar macrophage lectin

N-Acetylglucosamine mitigates lung injury and pulmonary fibrosis induced by bleomycin

Lung injury and pulmonary fibrosis contribute to morbidity and mortality, and, in particular, are characterized as leading cause on confirmed COVID-19 death. To date, efficient therapeutic approach for such lung diseases is lacking. N-Acetylglucosamine (NAG), an acetylated derivative of glucosamine, has been proposed as a potential protector of lung function in several types of lung diseases. The mechanism by which NAG protects against lung injury, however, remains unclear. Here, we show that NAG treatment improves pulmonary function in bleomycin (BLM)-induced lung injury model measured by flexiVent system. At early phase of lung injury, NAG treatment results in silenced immune response by targeting ARG1+ macrophages activation, and, consequently, blocks KRT8+ transitional stem cell in the alveolar region to stimulate PDGF Rβ+ fibroblasts hyperproliferation, thereby attenuating the pulmonary fibrosis. This combinational depression of immune response and extracellular matrix deposition within the lung mitigates lung injury and pulmonary fibrosis induced by BLM. Our findings provide novel insight into the protective role of NAG in lung injury.

Targeting anticancer drug delivery to pancreatic cancer cells using a fucose-bound nanoparticle approach

Owing to its aggressiveness and the lack of effective therapies, pancreatic ductal adenocarcinoma has a dismal prognosis. New strategies to improve treatment and survival are therefore urgently required. Numerous fucosylated antigens in sera serve as tumor markers for cancer detection and evaluation of treatment efficacy. Increased expression of fucosyltransferases has also been reported for pancreatic cancer. These enzymes accelerate malignant transformation through fucosylation of sialylated precursors, suggesting a crucial requirement for fucose by pancreatic cancer cells. With this in mind, we developed fucose-bound nanoparticles as vehicles for delivery of anticancer drugs specifically to cancer cells. L-fucose-bound liposomes containing Cy5.5 or Cisplatin were effectively delivered into CA19-9 expressing pancreatic cancer cells. Excess L-fucose decreased the efficiency of Cy5.5 introduction by L-fucose-bound liposomes, suggesting L-fucose-receptor-mediated delivery. Intravenously injected L-fucose-bound liposomes carrying Cisplatin were successfully delivered to pancreatic cancer cells, mediating efficient tumor growth inhibition as well as prolonging survival in mouse xenograft models. This modality represents a new strategy for pancreatic cancer cell-targeting therapy.

Therapeutic potential of nanoparticulate systems for macrophage targeting

The use of non-viral nanoparticulate systems for the delivery of therapeutic agents is receiving considerable attention for medical and pharmaceutical applications. This increasing interest results from the fact that these systems can be designed to meet specific physicochemical requirements, and they display low toxic and immunogenic effects. Among potential cellular targets by drug-loaded nanoparticles, macrophages are considered because they play a central role in inflammation and they act as reservoirs for microorganisms that are involved with deadly infectious diseases. The most common and potent drugs used in macrophage-mediated diseases treatment often induce unwanted side effects, when applied as a free form, due to the necessity of high doses to induce a satisfactory effect. This could result in their systemic spreading, a lack of bioavailability at the desired sites, and a short half-life. Therefore, the use of drug-loaded nanoparticles represents a good alternative to avoid, or at least decrease, side effects and increase efficacy. In this manuscript, we present an overview of the usefulness of nanoparticles for macrophage-mediated therapies in particular. We discuss, though not exhaustively, the potential of therapeutic agent-loaded nanoparticles for some macrophage-mediated diseases. We also underline the most important parameters that affect the interaction mechanisms of the macrophages and the physicochemical aspects of the particulate systems that may influence their performance in macrophage-targeted therapies.

Alveolar macrophages bind and phagocytose allergen-containing pollen starch granules via C-type lectin and integrin receptors: implications for airway inflammatory disease

Recent studies suggest that IgE-independent mechanisms of airway inflammation contribute significantly to the pathophysiology of allergic airway inflammatory diseases such as asthma. Such mechanisms may involve direct interactions between inhaled allergens and cells of the respiratory tract such as macrophages, dendritic cells, and epithelial cells. In this study, we investigated receptor-mediated interactions occurring between alveolar macrophages and allergen-containing pollen starch granules (PSG). We report here that PSG are released from a range of grass species and are rapidly bound and phagocytosed by alveolar macrophages. Human monocyte-derived dendritic cells also bound PSG but no internalization was observed. Phagocytosis of PSG was dependent on Mg2+ and Ca2+ and was inhibited by neo-glycoproteins such as galactose-BSA and N-acetylgalactose-BSA. Partial inhibition of phagocytosis was also seen with the Arg-Gly-Asp-Ser (RGDS) motif and with an anti-CD18 mAb (OX42). The combination of both neo-glycoprotein and anti-CD18 achieved the greatest degree of inhibition (>90%). Together, these data suggest a role for both C-type lectins and beta2-integrins in the binding and internalization of PSG. The consequences of this interaction included a rapid up-regulation of inducible NO synthase mRNA and subsequent release of NO by alveolar macrophages. Thus, receptor-mediated recognition of inhaled allergenic particles by alveolar macrophages may represent a potential mechanism for modulating the inflammatory response associated with allergic airway diseases such as asthma.

Biochemical purification and partial characterization of a murine macrophage surface receptor possessing specificity for small aromatic moieties including fluorescein

Binding properties and requirements for internalization of hapten-protein antigens, such as fluorescein-polyderivatized bovine serum albumin (FITC-BSA) and poly-D-lysine (FITC-PDL), by murine macrophage was consistent with surface receptor recognition of fluorescyl moieties (Cherukuri et al., Mol. Immunol. 34, 21-32, 1997; Cherukuri et al., Cytometry 31, 110-124, 1998). Ligand binding properties of the putative macrophage receptor pointed toward specificity for various aromatic moieties including phenylalanine, phenyloxazolone and fluorescein (Cherukuri and Voss, Mol. Immunol. 35, 115-125, 1998). Purification of the hapten-recognizing receptor from J774 macrophage cells involved subcellular fractionation of plasma membrane fractions, and affinity chromatography of solubilized membranes employing a phenyl-Sepharose adsorbent with subsequent specific elution of receptor using fluorescein ligand. The final product was a protein with a molecular mass of approximately 180 kDa. Characterization of the purified receptor involved absorption and fluorescence spectroscopy, circular dichroism, fluorescence quenching analyses, various ligand binding assays and an immunological analysis. Spectroscopic analyses revealed that the receptor possessed aromatic amino acids while circular dichroism suggested significant alpha-helical secondary structure. Binding specificity of the purified receptor was confirmed in a spectrofluorometric assay where the fluorescence of fluorescein ligand was quenched approximately 97%. Finally, specific binding activity of the receptor with FITC-BSA was demonstrated in Western blot analysis under native conditions. Receptor purity was confirmed in amino acid sequencing analysis when the amino-terminal residue was found to be totally blocked. Results are discussed in terms of the possible identity of the isolated macrophage receptor and its biological-immunological role.

Isolation of the SO4-4-GalNAcbeta1,4GlcNAcbeta1,2Manalpha-specific receptor from rat liver

Glycoproteins, such as the glycoprotein hormone lutropin (LH), bear oligosaccharides terminating with the sequence SO4-4GalNAcbeta1, 4GlcNAcbeta1,2Manalpha (S4GGnM) and are rapidly removed from the circulation by a receptor present in hepatic endothelial cells and Kupffer cells. Rapid removal from the circulation is essential for attaining maximal hormone activity in vivo. We have isolated a protein from rat liver which has the properties expected for the S4GGnM-specific receptor (S4GGnM-R). The S4GGnM-R is closely related to the macrophage mannose receptor (Man-R) both antigenically and structurally. At least 12 peptides prepared from the S4GGnM-R have amino acid sequences that are identical to those of the Man-R. Nonetheless, the ligand binding properties of the S4GGnM-R and the Man-R differ in a number of respects. The S4GGnM-R binds to immobilized LH but not to immobilized mannose, whereas the Man-R binds to immobilized mannose but not to immobilized LH. When analyzed using a binding assay that precipitates receptor ligand complexes with polyethylene glycol, the S4GGnM-R is able to bind S4GGnM-bovine serum albumin (S4GGnM-BSA) conjugates whereas the Man-R is not. In contrast both the S4GGnM-R and the Man-R are able to bind Man-BSA. Monosaccharides that inhibit binding of Man-BSA by the Man-R enhance binding by the S4GGnM-R. Oligosaccharides terminating with S4GGnM and those terminating with Man are bound at independent sites on the S4GGnM-R. The S4GGnM-R present in hepatic endothelial cells may account for clearance of glycoproteins bearing oligosaccharides terminating with S4GGnM and glycoproteins bearing oligosaccharides terminating with either mannose, fucose, or N-acetylglucosamine.

Receptor-mediated endocytosis of fucosylated neoglycoprotein by macrophages

The characteristics of the recognition system involved in the receptor mediated endocytosis of the neoglycoprotein, fucose-human serum albumin (HSA) were studied. It was found that (i) fucose-HSA showed strong affinity binding and uptake by various macrophages; (ii) binding was specific for L-fucose and D-mannose; (iii) binding was found to be inhibited by oxidant like H2O2 and swainsonine whereas it was elevated by dexamethasone; (iv) clearance of 125I-fucose-HSA was rapid and strongly inhibited by unlabelled fucose-HSA. Greater than 70% of fucose-HSA was found in liver and more than 60% of this was found in liver lysosomes; (v) uptake of fucose-HSA was thirty-fold more efficient in liver macrophages (Kupffer cells) than in hepatocytes; (vi) moreover, mannose-HSA and ovalbumin which are potent inhibitors of mannose/N-acetylglucosamine receptors inhibited clearance and uptake of fucose-HSA by liver as well as by isolated Kupffer cells suggesting the involvement of both fucose and mannose receptors or a single type of receptor having greater affinity for fucose-HSA than for mannose-HSA. These results emphasize the important role of fucose-terminated glycoproteins in site-specific drug targeting.

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

The target site for N-linked biantennary and triantennary oligosaccharides containing multiple terminal Le(x) determinants was analyzed in mice. N-linked oligosaccharides containing a single tert-butoxycarbonyl-tyrosine attached to the reducing end were used as synthons for human milk alpha-3/4-fucosyltransferase to prepare multivalent Le(x) (Gal beta 1-4[Fuc alpha 1-3]GlcNAc) terminated tyrosinamide oligosaccharides. The oligosaccharides were radioiodinated and examined for their pharmacokinetics and biodistribution in mice. The liver was the major target site in mice at 30 min, which accumulated 18% of the dose for Le(x) biantennary compared with 6% for a nonfucosylated Gal biantennary. By comparison, Le(x)- and Gal-terminated triantennary accumulated in the liver with a targeting efficiency of 66 and 59%, respectively. The liver targeting of Le(x)-biantennary was partially blocked by co-administration with either galactose or L-fucose whereas Le(x) triantennary targeting was only reduced by co-administration with galactose. In contrast to these results in mice, in vivo experiments performed in rats established that both Le(x) and Gal terminated biantennary target the liver with nearly identical efficiency (6-7%). It is concluded that the asialoglycoprotein receptor in mice preferentially recognize Le(x) biantennary over Gal biantennary, whereas little or no differentiation exists in rats. Thereby, the mouse asialoglycoprotein receptor apparently possesses additional binding pockets that accommodate a fucose residue when presented as Le(x).

Interaction of immobilized recombinant mouse C-type macrophage lectin with glycopeptides and oligosaccharides

Inflammatory and tumoricidal macrophages express galactose- and N-acetylgalactosamine-specific Ca(2+)-dependent lectins on their surfaces. This lectin is a family member of membrane-bound C-type animal lectins and consists of 304 amino acid residues (molecular weight 34,595). In the present study, expression vectors containing a nucleotide sequence corresponding to the carbohydrate-binding domain of mouse macrophage lectin cDNA have been prepared. The carbohydrate-binding specificity of the recombinant macrophage lectin expressed in Escherichia coli was investigated by comparing elution profiles of various glycopeptides having defined carbohydrate structures on immobilized lectins. When elution profiles of high mannose-type and complex-type Asn-linked carbohydrate chains were compared, the degree of retardation from immobilized macrophage lectin column was in the order tetraantennary complex-type with terminal galactosyl residues > triantennary complex-type with terminal galactosyl residues > biantennary complex-type with terminal galactosyl residues > high mannose-type glycopeptides. N-Terminal octapeptides from human glycophorin A that bore three NeuAc alpha 2-3Gal beta 1-3(NeuAc alpha 2-6)GalNAc serine/threonine-linked tetrasaccharide chains and their sequentially deglycosylated derivatives were also applied to this column. Glycopeptides carrying three constitutive GalNAc-Ser/Thr(Tn-antigen) had the strongest affinity, whereas those with fully sialylated carbohydrate tetrasaccharide chains showed weak interaction. The association kinetics of Asn-linked glycopeptides from bovine asialofetuin to recombinant macrophage lectin was determined by surface plasmon resonance spectroscopy. The results indicate k(assoc) value of 1.63 x 10(4) M-1 s-1. The calculated value for Ka was 6.20 x 10(7) M.

Dual function of macrophage galactose/N-acetylgalactosamine-specific lectins: glycoprotein uptake and tumoricidal cellular recognition

We investigated whether the interaction of peritoneal macrophages with extracellular ligands is mediated by C-type lectins specific for galactose and N-acetylgalactosamine. The carbohydrate-binding domain of mouse galactose/N-acetylgalactosamine-specific lectin was prepared in a recombinant form. The purified recombinant lectins were tested for competitive inhibition against glycoprotein uptake and against tumoricidal effect. Thioglycolate-elicited macrophages internalized galactosylated bovine serum albumin in vitro. The internalization was blocked by recombinant macrophage lectins. Activated macrophages obtained after intraperitoneal injection of a nonspecific immune potentiator, OK432, did not internalize galactosylated bovine serum albumin. These cells elicited a cytotoxic effect against P815 murine mastocytoma cells, and the effect was blocked by recombinant macrophage lectins. These results indicated that galactose/N-acetylgalactosamine-specific C-type lectins expressed on the surface of inflammatory macrophages and on activated tumoricidal macrophages mediate two distinct functions, i.e. glycoprotein uptake and tumoricidal effector mechanisms.

Studies on a glucose-binding lectin from peripheral blood lymphocytes

Lectin-carbohydrate interactions have been found to be important in many of the steps of lymphocyte recirculation and inflammatory responses. A D-glucose-specific lectin was isolated from goat peripheral blood lymphocytes by affinity chromatography on N-acetyl-D-glucosamine agarose and gave a single band corresponding to 112 kDa in SDS-PAGE, irrespective of treatment with 2-mercaptoethanol. The lymphocyte lectin agglutinated rabbit and human ABO erythrocytes, the hemagglutinating activity being Ca2+ dependent. It appears to be a member of type C animal lectins.

Ligand recognition by purified human mannose receptor

In this work we examine the carbohydrate binding properties of human placental mannose receptor (HMR) using a rapid and sensitive enzyme-linked immunosorbent microplate assay. The assay is based on the inhibition of binding of highly purified receptor to yeast mannan-coated 96-well plates. The specificity of ligand binding was inferred from the potency of different saccharides in blocking HMR binding to the mannan-coated wells. The relative inhibitory potency of monosaccharides was L-Fuc greater than D-Man greater than D-Glc greater than D-GlcNAc greater than Man-6-P much greater than D-Gal much greater than L-Rha much greater than GalNAc. The inhibitory potency of mannose increased by two orders of magnitude when linear oligomers were used. Oligomers containing alpha-1-3- and alpha-1-6-linked mannose residues were more inhibitory than those containing alpha-1-2- and alpha-1-4-linked mannoses. Linear or branched oligomannosides larger than three units did not have a significant influence on their inhibitory potency; rather, potency was found to decrease in comparison with oligomannosides with three units. Compared to linear oligomers, inhibition of binding was the best using branched mannose oligosaccharides, alpha-D-Man-bovine serum albumin conjugates, or mannan. A model is discussed in which branched ligand is bound to spatially distinct sites on the HMR.

Purification and characterization of the D-mannose receptor from J774 mouse macrophage cells

Macrophages display on their cell surface a D-mannose-specific receptor which facilitates the scavenging of certain pathogens and deleterious macromolecules from the extracellular fluid as part of the host defense mechanism. The mouse D-mannose receptor was purified from J774 E macrophages and an antiserum was generated against the receptor protein. In mouse macrophages, the newly synthesized receptor has an Mr of 157,000 Da and rapidly matures to a protein with an Mr of 172,000 Da. Both forms of the receptor protein are tightly associated with cell membranes. The receptor is found in a number of mouse macrophage cell types but is not present in mouse fibroblasts. An assay was developed to characterize D-mannose receptor-ligand binding based on immunoprecipitation of the detergent-solubilized receptor protein. The dissociation constant, determined for receptor and the neoglycoprotein D-mannose-BSA, was 1.67nM. Receptor-ligand binding was calcium and pH dependent. Monosaccharides, such as D-mannose and L-fucose, partially inhibited receptor binding to the ligand D-mannose-BSA.

Characterization and isolation of an intracellular D-mannose-specific receptor from human promyelocytic HL60 cells

Most mammalian macrophages express D-mannose-specific receptor (membrane lectin, Mr 175,000) allowing endocytosis of their ligands, but cells of the monocytic lineage (HL60, U937, monocyte) lack this receptor. However, after permeabilization, promyelocytic, promonocytic cells and monocytes bound fluoresceinylated D-mannose-terminated neoglycoproteins as evidenced by flow cytometry. Under these conditions, confocal analysis confirmed the intracellular membrane localization of the labeling and the absence of nuclear binding. An intracellular D-mannose-specific receptor was isolated from the human promyelocytic cell line HL60, by affinity chromatography on 4-isothiocyanatophenyl alpha-D-mannopyranoside-substituted Affi-gel as a 60,000-Mr membrane protein requiring divalent cations for the ligand binding. Under the same conditions, mouse macrophages were shown to express a 175,000-Mr D-mannose-specific receptor but not the 60,000-Mr receptor.

Binding and uptake of ligands for mannose-specific receptors in liver cells: an electron microscopic study during development and aging in rat

The binding and uptake of mannose exposing ligands in rat liver cells during development and aging was studied. The mannose-specific receptors are visualized using 5-nm diameter colloidal gold particles coated with invertase or mannan. It was found that the binding sites are present on sinusoidal liver cells since prenatal life but their quantitative and qualitative cell surface expression changes with age. The number of receptors affects the endocytotic capacity of Kupffer cells which is low during perinatal and aging periods and reaches the values of adult animals between the 11th and the 15th day after birth. Our results indicate that the expression and the activity of mannose-specific receptors on sinusoidal rat liver cells is related to the differentiative stage of the organ.