Hyaluronan-binding proteins on cultured J 774 macrophages

Hyaluronan nanoplatelets exert an intrinsic anti-inflammatory activity in a rat model of bladder painful syndrome/interstitial cystitis

Glycosaminoglycan (GAG) replenishment therapy consists of the instillation of GAG solutions directly in the bladder to alleviate Bladder Painful Syndrome/Interstitial Cystitis (BPS/IC). However, several issues were reported with this strategy because the GAG solutions are rapidly eliminated from the bladder by spontaneous voiding, and GAG have low bioadhesive behaviors. Herein, GAG nanomaterials with typical flattened morphology were obtained by a self-assembly process. The formation mechanism of those nanomaterials, denoted as nanoplatelets, involves the interaction of α-cyclodextrin cavity and alkyl chains covalently grafted on the GAG. Three GAG were used in this investigation, hyaluronan (HA), chondroitin sulfate (CS), and heparin (HEP). HA NP showed the best anti-inflammatory activity in an LPS-induced in vitro inflammation model of macrophages. They also exhibited the best therapeutic efficacy in a BPS/IC rat inflammation model. Histological examinations of the bladders revealed that HA NP significantly reduced bladder inflammation and regenerated the bladder mucosa. This investigation could open new perspectives to alleviate BPS/IC through GAG replenishment therapy.

Hyaluronan Cell Surface Binding Is Induced by Type I Collagen and Regulated by Caveolae in Glioma Cells

Hyaluronan (HA) is a component of the brain extracellular matrix environment that is synthesized and secreted by glioma cells. The primary cell surface receptor for HA is CD44, a membrane glycoprotein that is functionally regulated by a membrane type 1 matrix metalloproteinase (MT1-MMP). Both CD44 and MT1-MMP are partially located in Triton X-100-insoluble domains, but no functional link has yet been established between them. In the present study, we studied the regulation of HA cell surface binding in U-87 glioma cells. We show that an MMP-dependent mechanism regulates the intrinsic cell surface binding of HA as ilomastat, a broad MMP inhibitor, increased HA binding to glioma cells. HA binding was also rapidly and specifically up-regulated by 3-fold by type I collagen in U-87 cells, which also induced a significant morphological reorganization associated with the activation of a latent form of MMP-2 through a MT1-MMP-mediated mechanism. Interestingly, caveolae depletion with a cell surface cholesterol-depleting agent beta-cyclodextrin triggered an additional increase (9-fold) in the binding of HA, in synergy with type I collagen. On the other hand, HA cell surface binding was diminished by the MEK inhibitor PD98059 and by the overexpression of a recombinant, wild type MT1-MMP, whereas its cytoplasmic-deleted form had no effect. Taken together, our results suggest that MT1-MMP regulates, through its cytoplasmic domain, the cell surface functions of CD44 in a collagen-rich pericellular environment. Additionally, we describe a new molecular mechanism regulating the invasive potential of glioma cells involving a MT1-MMP/CD44/caveolin interaction, which could represent a potential target for anti-cancer therapies.

T lymphocyte activation results in an increased expression of beta-1,4-galactosyltransferase: phorbol ester induces a similar enhancement in the absence of mitosis

We previously showed that in vitro activated human T lymphocytes expressed increased amounts of beta-1,6-branched N-linked oligosaccharides (Lemaire S etal. (1994) J Biol Chem269: 8069-74), which have been proposed to participate in the regulation of the immune process. In the present paper, we compared the activity and expression of beta-1,4-galactosyltransferase (GalT), one of the glycosyltransferases involved in the biosynthesis of these beta-1,6-branched N-linked oligosaccharides, before and after in vitro activation of T lymphocytes after a 40h treatment with a mixture of phorbol 12-myristate 13-acetate and Phaseolus vulgaris lectin. After treatment, the enzymatic activity of the GalT was significantly increased and immunoblot experiments performed with a monoclonal antibody to human GalT showed an increased intensity of the GalT band at 49 kDa, attributable to an enhancement of GalT mRNA level, as shown by Northern blots. However, treatment of the same T-lymphocytes by phorbol ester alone, which is unable to induce mitosis, resulted in a comparable increase of the expression of GalT. Moreover, these phorbol ester-treated T lymphocytes, analysed by flow cytometry exhibited a two-fold increase in the expression of GalT. Finally, confocal fluorescence microscopy performed on all T lymphocytes (treated or not) showed that the flow cytometric signal of GalT originates from intracellular, Golgi-associated antigen only since no surface GalT was detected.

On the adsorption of hyaluronan and ICAM-1 to modified hydrophobic resins

Hyaluronan is a negatively charged glycosaminoglycan that occurs in connective tissue and has a wide range of mechanical and cell biological functions. The purpose of this study was to utilize affinity chromatography resins for purification of detergent (Triton X-100) solubilized hyaluronan binding proteins from liver, the major organ of hyaluronan clearance from the blood. However, during these studies we made the unexpected finding that hyaluronan binds to Sepharose substituted with a hexamethylene chain, a commonly used spacer arm in affinity chromatography resins, capped with either a terminal primary amine or a terminal acetoamido group. Hyaluronan did not bind the hydrophobic resins hexyl- or octyl-Sepharose under the same conditions. It was also found that rat liver intercellular adhesion molecule-1 binds to resins containing the hexamethylene spacer arm, an interaction which could be inhibited with free hyaluronan oligosaccharides. Finally, we have determined that resins with ethylene spacer arms show no affinity for hyaluronan and can therefore be used to immobilize hyaluronan for chromatography of hyaluronan binding proteins. By using this resin we have purified two proteins of approximately 200 and 400 kDa from rat liver endothelial cells. In summary, this study demonstrates the efficacy of certain "capped-hydrophobic" resins for binding hyaluronan; these resins may provide a novel means for the study and/or purification of this glycosaminoglycan. This study further demonstrates the importance of the careful design of appropriate affinity columns for the specific purification of hyaluronan binding proteins.

Adherence of Borrelia burgdorferi to granulocytes of different animal species

Adherence of 4 Borrelia (B.) burgdorferi strains (z7/22, z7/27, z7/41, PBi) to polymorphonuclear granulocytes from different domestic animals (horses, cattle, sheep, dogs) was investigated. All 4 strains adhered to the granulocytes. Binding assays indicated that the adherence occurred between structures on the surface of the borreliae ("binding-sites") and on the membranes of the granulocytes ("receptors"). The "receptors" consisted of 4 fractions (A, B, C, and D) with components differing in molecular weight (MW) and binding activity for proteins on the surface of B. burgdorferi. Fraction A (MW 80000) had the highest binding activity for B. burgdorferi.

Purification of a cell-surface receptor for surfactant protein A

In the present report we have characterized the binding of surfactant protein A (SP-A) to bone marrow-derived macrophages, U937 cells, alveolar macrophages, and type II epithelial cells. The binding of SP-A to all cell types is Ca2+-dependent and trypsin-sensitive, but type II cells express distinct Ca2+-independent binding sites. The binding of SP-A to macrophages is independent of known cell surface carbohydrate-specific receptors and of glycoconjugate binding sites on the surface of the cells and is distinct from binding to C1q receptors. Based on ligand blot analysis, both type II cells and macrophages express a 210-kDa SP-A-binding protein. The 210-kDa protein was purified to apparent homogeneity from U937 macrophage membranes using affinity chromatography with noncovalently immobilized surfactant protein A, and was purified from rat lung by differential detergent and salt extraction of isolated rat lung membranes. Polyclonal antibodies against the rat lung SP-A-binding protein inhibit binding of SP-A to both type II cells and macrophages, indicating that the 210-kDa protein is expressed on the cell surface. The polyclonal antibodies also block the SP-A-mediated inhibition of phospholipid secretion by type II cells, indicating that the 210-kDa protein is a functional cell-surface receptor on type II cells. In a separate report we have determined that antibodies to the SP-A receptor block the SP-A-mediated uptake of Mycobacterium bovis, indicating that the macrophage SP-A receptor is involved in SP-A-mediated clearance of pathogens.

The glycosaminoglycans in cultures of stimulated rat peritoneal macrophages. 2. Gel chromatographic studies and the behaviour of heparan sulfate

The molecular weight distribution of pMP-derived glycosaminoglycans (GAG), i.e. non-sulfated GAG, chondroitin sulfate (CS), and heparin sulfate (HS)-like material was determined. The peritoneal macrophages (pMP) were harvested from rats normal or stimulated by i.p. injection of thioglycolate, carrageenan or BCG, and maintained in culture. The GAG of cell layer and medium were isolated separately after labeling with 35S-sulfate and 3H-acetate. Treatment with nitrous acid served to remove HS-like material. Labeling with 3H-acetate served to detect synthesis of the high m. w. hyaluronic acid (HA). Gel chromatic separation was done using Sephadex G-200 columns. The maximal size of 35S-labeled GAG, especially HS (36 kDa), was reduced in cultural medium and cell layer after stimulation in vivo. Reduction was most pronounced after application of carrageenan followed by thioglycolate and BCG/LPS stimulation. The extracellular GAG of BCG-stimulated pMP were smallest, probably due to degradation. Heparan sulfate-like material made up a larger proportion in monolayer and medium, comprising the total m.w. range up to 36 kDa. The GAG sensitive to nitrous acid were maximal in cultures of carrageenan-stimulated pMP and minimal in those of thioglycolate-stimulated pMP. This type of HS was sensitive to hyaluronidase, too. Any synthesis of high molecular hyaluronic acid was not found in normal or stimulated rat pMP. Therefore MP-associated HA must be adsorbed from other sources or synthesized by early forms of macrophages.

CD44 in human placenta: localization and binding to hyaluronic acid

CD44, a receptor for hyaluronic acid (HA), has been identified in the stroma of stem and terminal chorionic villi of human term placenta. The CD44 glycoprotein antigen, isolated from placenta by affinity to monoclonal antibody (mAb) 50B4, consisted mainly of species of M(r) 85,000 and 200,000. Radiolabelled CD44 bound specifically to HA attached to plastic, predominantly via the M(r) 85,000 species; this binding was inhibited by soluble HA and hyaluronidase. The binding of CD44 to HA was also inhibited by mAb 50B4 and IM7.8.1, which recognize epitopes of cluster I and II respectively, but was not blocked by a polyclonal antibody to peptide 18-30 of the B loop (residues 12-101). These results suggest that the portion of the B loop of CD44 implicated in the binding to HA is between amino acids 31-101 and that epitopes located outside the B loop, such as that recognized by mAb IM7.8.1 (between residues 132-215), contribute to this interaction. The presence of a functional CD44 molecule in the human term placenta suggest a role for this molecule in situ in the stabilization and orientation of HA network important in the maintenance of the structural integrity of the placenta.

Endocytosis of hyaluronan in rat Kupffer cells

The binding, uptake and degradation of hyaluronan (HA) labelled with 3H in its acetyl group were studied in cultured rat Kupffer cells (KC). At 4 degrees C the binding increased with increasing concentrations of HA in the culture medium up to at least 1 microgram/ml, when saturation occurred. Binding could be prevented efficiently by the addition of an excess of unlabelled HA, and to a lesser extent by chondroitin sulphate and oligosaccharide fragments of HA, consisting of four sugars or more. The labelled HA bound to the cells could be removed by incubating the cells with Streptomyces hyaluronidase, or trypsin, indicating that the HA-binding sites are located on the cell surface. At 37 degrees C HA was internalized in a concentration-dependent manner, and degradation products appeared in the supernatant after 1-5 h, depending on the concentration applied. At 50 ng of free HA/ml, each KC accumulated 60 ag of the polysaccharide/min in the first 1 h, and degraded a total amount of 10 fg of HA during an 8 h period. Addition of the negatively charged polysaccharide dextran sulphate reduced binding, and to an even greater extent internalization, of HA in KC, while no effect was observed with dextran. Depletion of intracellular potassium caused a marked reduction in the rate of endocytosis of cell-membrane-associated HA into KC, without affecting binding. Addition of KCl to the culture medium returned endocytosis of [3H]HA to normal levels. There was no effect on binding and a partial effect on internalization by depletion of bivalent cations or in the presence of EDTA. The degradation of [3H]HA by KC cultures was abolished in the presence of weak bases, NH4Cl and chloroquine, supporting the idea that HA is endocytosed into lysosomes prior to degradation. The fluid-phase marker [14C]sucrose was internalized in the cells at much lower rate than was HA. Rates of binding, internalization and degradation of HA in KC point therefore to a specific endocytosis followed by an intracellular degradation to low-M(r) compounds. It was estimated that, under physiological conditions, KC only clear a minor proportion of circulating HA.