Participation of D-galactose-specific receptors of liver macrophages in recognition of fibronectin-opsonized particles

Adjusting the balance between effective loading and vector migration of macrophage vehicles to deliver nanoparticles

The nature of macrophage allows the possibility that this cell type could be used as drug delivery system to track therapeutic drug nanoparticles (NPs) in cancer. However, there is no existing research on the regulation between effective loading of NPs and targeted delivery of macrophages. Here, we investigated the important parameters of intracellular NP quantity and the vector migration rate. Macrophage loading capacity was obtained by comparing the uptake quantity of varisized NPs, and the delivery ability of loaded cells was determined by measuring vector migration rates. We observed a positive correlation between the size of NPs and directed macrophage migration. Our findings suggest that the molecular mechanism of migration vector rate regulation involved increased expression levels of colony-stimulating factor-1 (CSF-1) receptor and integrin induced by 100-nm and 500-nm particles. The ability of macrophages uptake to varisized NPs showed the opposite trend, with the increased vector rate of cell migration influenced by NPs. We are able to demonstrate the important balance between effective macrophage loading and targeted delivery. By adjusting the balance parameters, it will be possible to utilize NPs in macrophage-mediated disease diagnosis and therapy.

The necessity for the coating of perfluorodecalin-filled poly(lactide-co-glycolide) microcapsules in the presence of physiological cholate concentrations: Tetronic-908 as an exemplary polymeric surfactant

Recently, we demonstrated that biodegradable poly(lactide-co-glycolide) (PLGA) micro- and nanocapsules with a liquid content of perfluorodecalin are principally useful for the development of artificial oxygen carriers. In order to solve a decisive and well-known problem with PLGA microcapsules, i.e. the spontaneous agglomeration of the capsules after depletion of the emulsifying agent (i.e. cholate), coating with the ABA block copolymer, Tetronic-908 was studied. After Tetronic-908 treatment at concentrations that were harmless to cultured cells, the clustering of the microcapsules was prevented, the adsorption of opsonins was decreased and the attachment to cells was inhibited, but the oxygen transport capacity of PLGA microcapsules was even increased. The present data clearly show that perfluorodecalin-filled PLGA microcapsules must be coated before decreasing the emulsifying agent cholate to physiological concentrations, in order to develop a solution that has the capabilities to function as a potential artificial oxygen carrier suspension.

Evaluation of hepatotropic targeting properties of allogenic and xenogenic erythrocyte ghosts in normal and liver-injured rats

BACKGROUND/AIMS

Haemoglobin-depleted erythrocyte ghosts have been recommended as vesicle carriers of drugs with hepatotropic properties. However, the influence of liver injury on ghost elimination and targeting has not been reported so far.

METHODS

Human and rat ghosts were prepared and loaded with model substances, and the basic parameters were characterized. Ghosts were injected intravenously into rats with acute, subacute and chronic liver injuries. Elimination from circulation, organ distribution and cellular targeting was measured. The uptake of ghosts by liver macrophages/Kupffer cells was determined in cell culture.

RESULTS

Ghosts are strong hepatotropic carriers with a recovery of 90% in normal liver. Kupffer cells are the almost exclusive target cell type. Hepatotropic properties remain in rats with chronic liver diseases, but are reduced by 60-70% in acute liver damage as a result of decline of phagocytosis of macrophages/Kupffer cells. Although the uptake of ghosts per gram liver tissue in chronic liver injury was also reduced by about 40%, the increase of liver mass and of macrophages/Kupffer cells compensated for the reduced phagocytotic activity. In subacute injury, the uptake per gram liver tissue was only moderately reduced.

CONCLUSION

Drug targeting with ghosts might be feasible in chronic and subacute liver injuries, e.g. fibrogenesis and tumours, because the content of ingested ghosts is released by Kupffer cells into the micro-environment, providing the uptake by and pharmacological effects on adjacent cells.

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.

The aggregation of pig articular chondrocyte and synthesis of extracellular matrix by a lactose-modified chitosan

A reductive amination reaction (N-alkylation) obtained exploiting the aldheyde group of lactose and the amino group of the glucosamine residues of chitosan (d.a. 89%) afforded a highly soluble engineered polysaccharide (chitlac) for a potential application in the repair of the articular cartilage. Chitosan derivatives with 9% and 64% of side chain groups introduced have been prepared and characterized by means of potentiometric titration, (1)H-NMR and intrinsic viscosity. Both polymers, with respect to the unmodified chitosan, induce cell aggregation when in contact with a primary culture of pig chondrocytes, leading to the formation of nodules of considerable dimensions (up to 0.5-1 mm in diameter). The nodules obtained from chondrocytes treated with chitlac with the higher degree of substitution have been studied by means of optical and electron microscopy (SEM, TEM) and the production of glycosaminoglycans (GAGs) and collagen has been measured by means of colorimetric assays. The chondro-specificity of GAG and collagen was determined by RT-PCR. The results show that the lactose-modified chitosan is non-toxic and stimulates the production of aggrecan and type II collagen.

Specificity studies of an antibody developed against a mucin-type glycoprotein

The specificity of a new anti-epiglycanin antibody (AE-3) which recognizes a mucin-type glycoprotein, the Human Carcinoma Antigen, found in the blood of patients with carcinomas, was studied. Information regarding the chemical nature of the antibody binding site was obtained by altering the structure of epiglycanin by chemical or enzymic means and testing the product in a competitive binding assay for inhibition of the binding of AE-3 to epiglycanin. The need for a high molecular weight antigen containing clustered T disaccharide, Gal,1-3GalNAc, was demonstrated. The specificity was further explored by inhibition studies with glycopeptides having one to three mono- to disaccharides. The results were interpreted using computer graphics molecular modeling which predicted the specific recognition of hydroxyl groups on oligosaccharides on adjacent amino acids. Thus T antigen O-linked glycopeptide tumour markers can be designed to be distinguished by antibodies by the amount of clustering of their oligosaccharides.

Expression of membrane-associated C-reactive protein by human monocytes: indications for a selectin-like activity participating in adhesion

We have shown previously that rat liver macrophages (Kupffer cells) express a membrane-bound form of C-reactive protein (mCRP) on their surface which is identical to a galactose-specific particle receptor activity. We now establish the presence of mCRP on human monocyte-macrophages using immunocytochemistry with an anti-neoCRP specific monoclonal antibody and RNA-RNA in situ hybridization to demonstrate the presence of CRP-specific mRNA. Concomitant with mCRP expression, cells exhibit galactose-dependent uptake of particles coated with lactosylated bovine serum albumin. Adhesion experiments on fibronectin-coated surfaces that mCRP on human blood monocytes may act as a selectin-like adhesion molecule, mediating initial carbohydrate-specific contacts which are followed by peptide-specific recognition via integrin receptors.

Characterization of the interaction of galactose-exposing particles with rat Kupffer cells

The characteristics of the recognition system involved in the binding of galactose-exposing particles to freshly isolated rat Kupffer cells were determined. For this purpose we used iodinated lactosylated low-density lipoprotein (125I-Lac-LDL) as a ligand for the galactose receptor on Kupffer cells. The affinity of the binding of 125I-Lac-LDL to Kupffer cells was saturable (23,500 galactose-specific binding sites per cell) and of high affinity (2.4 +/- 0.3 nM). The order of potency of various carbohydrates in inhibiting the association of 125I-Lac-LDL with Kupffer cells was as follows: N-acetylgalactosamine > L-fucose >> N-acetylglucosamine/mannan. Association of 125I-Lac-LDL with Kupffer cells in the absence of Ca2+ was at the same level as in the presence of 50 mM N-acetylgalactosamine. A polyclonal antibody raised against the rat asialoglycoprotein receptor inhibited the binding of 125I-Lac-LDL to Kupffer cells and reacted in a Western blot with two proteins (molecular mass 88 and 77 kDa), which correspond to the molecular mass of the fucose receptor [Lehrman, Haltiwanger and Hill (1986) J. Biol. Chem. 261, 7426-7432]. Furthermore, the ability of fucosylated neoglycoproteins to displace 125I-Lac-LDL from Kupffer cells was equally dependent on the extent of fucosylation as previously reported for the fucose receptor. We conclude that the fucose receptor and not the C-reactive protein, as recently proposed [Kempka, Roos and Kolb-Bachofen (1990) J. Immunol. 144, 1004-1009], functions as the galactose-particle receptor on the Kupffer cell. The binding of galactose-exposing particles to the fucose receptor is a previously unknown property of this receptor.

Species differences in lectin binding to pulmonary cells: Soybean agglutinin (SBA) as a marker of type I alveolar epithelial cells and alveolar macrophages in mini pigs

We compared lectin staining patterns in rat and mini pig tissues of normal and fibrotic (irradiation-induced) lungs. Two lectins were studied: Dolichos biflorus (DBA) and Soybean (SBA). Both lectins strongly stained a subpopulation of alveolar macrophages. In the rat, DBA positive macrophages were a subpopulation of the SBA binding cells. In mini pig lungs, a further specific binding of DBA and SBA was observed: DBA reacted with endothelia, and SBA stained the alveolar type I cells. Double immunofluorescence experiments using a type II cell-specific cytokeratin antibody confirmed the selective reactivity of SBA with type I cells, which was also present in fibrotic areas with epithelial cell proliferation.

Coating particles with a block co-polymer (poloxamine-908) suppresses opsonization but permits the activity of dysopsonins in the serum

The surfaces of polystyrene microspheres (60 nm in diameter) and colloidal gold particles (17 nm in diameter) were coated with a polyoxyethylene (POE)/polyoxypropylene (POP) block co-polymer; poloxamine-908. The polymer adsorb strongly to the microspheres via its relatively hydrophobic POP segments. This leaves the POE chains in a mobile state as they extend outward from the surface and thereby provide stability to the particle suspension by suppressing aggregation. The blood clearance and biodistribution of uncoated vs. poloxamine-908-coated 125I-labelled polystyrene microspheres were compared 1 h after intravenous administration into rats. Poloxamine coating dramatically reduced liver accumulation of microspheres and kept them within the systemic circulation. These observations were further confirmed by electron microscopy, demonstrating that Kupffer cells were loaded with uncoated latex but had ingested few if any of the poloxamine-908-coated particles. The interaction of uncoated and poloxamine-coated gold particles with freshly isolated rat liver sinusoidal cells was examined by electron microscopy. The accumulation in Kupffer cells of gold particles after opsonization with autologous plasma was in accordance with previous observations where the dominant opsonizing activity had been identified as fibronectin. In contrast, coating of gold particles with poloxamine-908 prior to plasma opsonization prevented the adsorption of fibronectin onto their surface. Simultaneously, Kupffer cells failed to recognize poloxamine-908-coated gold particles before and after opsonization. Unlike Kupffer cells, liver endothelial cells endocytosed poloxamine-908-coated gold particles prior to opsonization but failed to recognize them after the opsonization process. This was taken as an indication of the presence of dysopsonic activity in plasma. This dysopsonic activity was studied using polystyrene latex microspheres, where the uptake of such particles by phagocytes is known to be independent of opsonization. The coating of 125I-labelled polystyrene microspheres with poloxamine-908 dramatically reduced their interaction with liver sinusoidal cells. This interaction was further reduced in the presence of either autologous plasma or serum. A heat-stable (60 degrees C for 15 min) serum component of molecular mass > 100 kDa was found to mediate this suppressive effect. Thus, we demonstrate that organ-specific receptors, opsonin activities and plasma dysopsonins regulate the in vivo clearance of particulate materials from the circulation. Poloxamine-908 coating modulates particle clearance by effectively blocking opsonization but still allowing for dysopsonization.

Uptake of toxic silica particles by isolated rat liver macrophages (Kupffer cells) is receptor mediated and can be blocked by competition

Silica particles (quartz dust) are toxic to macrophages after their uptake into these cells. These experiments describe the opsonization mechanism(s) and macrophage receptor(s) involved in silica uptake. Freshly isolated rat liver macrophages (Kupffer cells) were incubated at 37 degrees C with silica particles in the presence or absence of autologous or heterologous plasma or purified plasma fibronectin and cell viability was assessed at various times. Within 60 min of coincubation, > 80% of macrophages were lysed in the presence of plasma or purified fibronectin but not in their absence (viability > 90%). Lysis was slower with defibronectinized plasma (28% in 60 min). Macrophages could be protected from lysis by addition of the monosaccharide N-acetyl-D-galactosamine but not by N-acetyl-D-glucosamine. Galactosylated serum albumin but not mannosylated albumin or native albumin exerted full protection from lysis. The pentapeptide GRGDS also prevented macrophage lysis in synergy with N-acetyl-galactosamine. Enzymatic deglycosylation of fibronectin reduced lysis significantly. These findings indicate an important opsonizing activity for fibronectin and dual recognition via the lectin-like galactose-specific binding activity of membrane-associated C-reactive protein and by integrin receptor(s). Binding experiments (at 4 degrees C) revealed initial binding as primarily galactose-inhibitable, suggesting integrin-mediated binding as a later event necessary for effective uptake.