Dermatan sulfate released after injury is a potent promoter of fibroblast growth factor-2 function

Amyloid-beta interactions with chondroitin sulfate-derived monosaccharides and disaccharides. implications for drug development

In Alzheimer's disease, the major pathological features are diffuse and senile plaques that are primarily composed of the amyloid-beta (A beta) peptide. It has been proposed that proteoglycans and glycosaminoglycans (GAG) facilitate amyloid fibril formation and/or stabilize the plaque aggregates. To develop effective therapeutics based on A beta-GAG interactions, understanding the A beta binding motif on the GAG chain is imperative. Using electron microscopy, fluorescence spectroscopy, and competitive inhibition ELISAs, we have evaluated the ability of chondroitin sulfate-derived monosaccharides and disaccharides to induce the structural changes in A beta that are associated with GAG interactions. Our results demonstrate that the disaccharides GalNAc-4-sulfate(4S), Delta UA-GalNAc-6-sulfate(6S), and Delta UA-GalNAc-4,6-sulfate(4S,6S), the iduronic acid-2-sulfate analogues, and the monosaccharides d-GalNAc-4S, d-GalNAc-6S, and d-GalNAc-4S,6S, but not d-GalNAc, d-GlcNAc, or Delta UA-GalNAc, induce the fibrillar features of A beta-GAG interactions. The binding affinities of all chondroitin sulfate-derived saccharides mimic those of the intact GAG chains. The sulfated monosaccharides and disaccharides compete with the intact chondroitin sulfate and heparin GAGs for A beta binding, as illustrated by competitive inhibition ELISAs. Therefore, the development of therapeutics based on the model of A beta-chondroitin sulfate binding may lead to effective inhibitors of the GAG-induced amyloid formation that is observed in vitro.

Dermatan sulphate is released by proteinases of common pathogenic bacteria and inactivates antibacterial alpha-defensin

Defensins represent an evolutionarily conserved group of small peptides with potent antibacterial activities. We report here that extracellular proteinases secreted by the human pathogens Pseudomonas aeruginosa, Enterococcus faecalis and Streptococcus pyogenes release dermatan sulphate by degrading dermatan sulphate-containing proteoglycans, such as decorin. Dermatan sulphate was found to bind to neutrophil-derived alpha-defensin, and this binding completely neutralized its bactericidal activity. During infection, proteoglycan degradation and release of dermatan sulphate may therefore represent a previously unknown virulence mechanism, which could serve as a target for novel antibacterial strategies.

Dermatan sulfates of normal and scarred fascia

We evaluated the composition of dermatan sulfates (DS) derived from 23 samples of normal and 23 samples of scarred fascia lata. We analyzed the molecular weight of intact DS chains and the length of chain regions comprising: (1) clusters of L-iduronate-containing disaccharides ("iduronic sections"); (2) clusters of D-glucuronate-containing disaccharides ("glucuronic sections"); and (3) copolymeric sections with both types of disaccharides. A portion of scarred fascia DS chains demonstrated higher molecular weight compared with those from normal tissue. Most disaccharides of DS chains derived from both fascia types form copolymeric segments - heterogeneous in size - with alternatively distributed single disaccharides with glucuronic residues and mainly single ones with iduronate. Only a small number of disaccharides form "glucuronic sections" of heterogeneous size or short "iduronic sections". However, the scarred fascia DS chains demonstrate an increased content of shorter "glucuronic sections" and shorter, often oversulfated, copolymeric segments. It seems that in normal fascia, the DS chain type with a single, long copolymeric region and a single, shorter "glucuronic section" is predominant, while in scarred tissue an increase in multidomain DS chain content may occur.

Decorin is produced by capillary endothelial cells in inflammation-associated angiogenesis

Decorin is a small extracellular chondroitin/dermatan sulfate proteoglycan that has previously been shown to be involved in the angiogenesis-like behavior of endothelial cells (ECs) in vitro. There is also evidence that decorin plays a role in angiogenesis in vivo. In this study we sought to further explore the involvement of decorin in angiogenesis in vivo, especially in that associated with inflammation. We found by CD31 immunostaining of ECs that in giant cell arteritis there are capillary blood vessels not only in the adventitia as in uninvolved temporal artery wall, but also in the media and the external zone of the thickened intima. Localization of decorin by antiserum LF-30 in adjacent sections showed that in normal temporal artery wall decorin resides mainly in the media and the adventitia, whereas in inflamed temporal artery wall decorin is distributed throughout the vessel wall including the intima. Furthermore, the most intense reaction for decorin was evident in ECs of capillary neovessels within the media and the thickened intima of inflamed temporal artery wall. Decorin was also found in capillary ECs in certain pathological and physiological conditions in which the pivotal role of angiogenesis is more generally accepted. Pyogenic granulomas, granulation tissue of healing dermal wounds, and ovaries at different phases of follicle and corpus luteum formation all contained widely distributed CD31-positive capillaries. Decorin, on the other hand, was found in capillary ECs in pyogenic granulomas and granulation tissue, but not in those in the ovaries. The assessment of the degree of inflammation in the specimens with the presence of CD68-positive macrophages showed that the pyogenic granuloma, granulation tissue, and giant cell arteritis specimens were rich in macrophages around the decorin-positive capillaries. In contrast, the ovarian specimens were populated with fewer macrophages and even they were not located in close vicinity of capillaries negative for decorin. Our results confirm that decorin is involved in angiogenesis in vivo and, particularly, in conditions in which the inflammatory component is dominant.

Proteoglycans and cutaneous vascular defense and repair

Proteoglycans are hybrid molecules composed of a core protein and covalently attached glycosaminoglycan chain(s). The structure, location, and processing of these molecules enables them to encode specific information that is used in multiple physiologic processes. Endothelial cells in the skin are influenced by proteoglycans through binding interactions between glycosaminoglycans and extracellular matrix, growth factors, cytokines, adhesion receptors, enzymes, and enzyme inhibitors. In wound repair, proteoglycans such as the syndecans are induced by antimicrobial peptides and can control growth factor responsiveness. The glycosaminoglycans further signal endothelial cells to increase expression of ICAM-1 and other molecules important for leukocyte adhesion. Thus, proteoglycans represent a powerful central regulatory element in skin that influences a wide variety of events and participates in host defense and tissue repair.

Expression of glycosaminoglycans and small proteoglycans in wounds: modulation by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu(2+)

Glycyl-histidyl-lysine-Cu(2+) is a tripeptide-copper complex previously shown to be an activator of wound healing. We have investigated the effects of glycyl-histidyl-lysine-Cu(2+) on the synthesis of glycosaminoglycans and small proteoglycans in a model of rat experimental wounds and in rat dermal fibroblast cultures. Repeated injections of glycyl-histidyl-lysine-Cu(2+) (2 mg per injection) stimulated the wound tissue production, as appreciated by dry weight and total protein measurements. This stimulation was accompanied by an increased production of type I collagen and glycosaminoglycans (assessed, respectively, by hydroxyproline and uronic acid contents of the chamber). Electrophoretic analysis of wound tissue glycosaminoglycans showed an accumulation of chondroitin sulfate and dermatan sulfate in control wound chambers, whereas the proportion of hyaluronic acid decreased with time. The accumulation of chondroitin sulfate and dermatan sulfate was enhanced by glycyl-histidyl-lysine-Cu(2+) treatment. The expression of two small proteoglycans of the dermis, decorin and biglycan, was analyzed by northern blot. The biglycan mRNA steady-state level in the chamber was maximal at day 12, whereas the decorin mRNA increased progressively until the end of the experiment (day 22). Glycyl-histidyl-lysine-Cu(2+) treatment increased the mRNA level of decorin and decreased those of biglycan. In dermal fibroblast cultures, the stimulation of decorin expression by glycyl-histidyl-lysine-Cu(2+) was also found. In contrast, biglycan expression was not modified. These results show that the expression of different proteoglycans in wound tissue are regulated in a different manner during wound healing. The glycyl-histidyl-lysine-Cu(2+) complex is able to modulate the expression of the extracellular matrix macromolecules differently during the wound repair process.

Syntheses of beta-D-GalpNAc4SO3-(1-->4)-L-IdopA2SO3, a disaccharide fragment of dermatan sulfate, and of its methyl alpha-L-glycoside derivative

The syntheses of sodium (sodium 2-acetamido-2-deoxy-4-O-sulfonato-beta-D-galactopyranosyl)-(1-->4)-(sodium 2-O-sulfonato-L-idopyran)uronate, a disaccharide fragment of dermatan sulfate, and of its methyl alpha-L-glycoside derivative are reported for the first time. The use of 4-O-acetyl-3,6-di-O-benzyl-2-deoxy-2-trichloroacetamido-1-O-trichloroacetimidoyl-alpha-D-galactopyranose, readily prepared from a D-gluco precursor, allowed the stereocontrolled and high yielding coupling with the low reactive 4-hydroxyl group of L-iduronic acid ester derivatives. Classical transformation of the disaccharide products into the target molecules was achieved in high yield.

Hypoxia modifies the effect of PDGF on glycosaminoglycan synthesis by primary human lung cells

Hypoxia, a consequence of interstitial lung diseases, may lead to secondary pulmonary hypertension and pulmonary vascular remodeling. Hypoxia induces activation and proliferation of lung cells and enhances the deposition of extracellular matrix including glycosaminoglycans (GAGs). To elucidate the cell biological mechanisms underlying the development of secondary pulmonary hypertension, we studied the effect of hypoxia on GAG synthesis by human lung cells. GAG synthesis was measured by incorporation of [(3)H]glucosamine; GAGs were isolated, purified, and characterized with GAG-degrading enzymes. Fibroblasts and vascular smooth muscle cells (VSMCs) synthesized hyaluronic acid, heparan sulfate, and chondroitin sulfates, whereas dermatan sulfate was found only in fibroblasts. Hypoxia did not influence the size or charge of the individual GAGs. However, hypoxia inhibited platelet-derived growth factor-induced [(3)H]glucosamine incorporation in secreted GAGs, especially hyaluronic acid, in VSMCs. In contrast, it stimulated GAG secretion, specifically heparan sulfate, by fibroblasts. Our results indicate that hypoxia induces modifications in GAG synthesis by human lung VSMCs and fibroblasts that may be correlated to pathophysiological manifestations in lung diseases causing hypoxia.

Inhibition of human dermal fibroblast proliferation by removal of dermatan sulfate

In the current study, a glycosaminoglycan lyase, chondroitinase B, was used to study the role of dermatan sulfate proteoglycans on human dermal fibroblast proliferation. Pretreatment with chondroitinase B significantly decreased fibroblast proliferative responses to serum (20% to 55%). In contrast, heparinase III and chondroitinase AC were less effective in inhibiting fibroblast proliferation to serum. Analysis of glycosaminoglycans on chondroitinase B-treated fibroblasts confirmed that dermatan sulfate was removed from fibroblasts by this enzyme. Chondroitinase B treatment also decreased proliferation to basic fibroblast growth factor (bFGF) by 20% and reduced receptor binding by 25%. Heparinase III inhibited bFGF binding by 73%, but decreased proliferation to bFGF by only 21%. Chondroitinase AC had no effect on bFGF proliferation or binding. These data suggest that dermatan sulfate proteoglycans play a significant role in the control of human dermal fibroblast proliferation.

Functions of cell surface heparan sulfate proteoglycans

The heparan sulfate on the surface of all adherent cells modulates the actions of a large number of extracellular ligands. Members of both cell surface heparan sulfate proteoglycan families, the transmembrane syndecans and the glycosylphosphoinositide-linked glypicans, bind these ligands and enhance formation of their receptor-signaling complexes. These heparan sulfate proteoglycans also immobilize and regulate the turnover of ligands that act at the cell surface. The extracellular domains of these proteoglycans can be shed from the cell surface, generating soluble heparan sulfate proteoglycans that can inhibit interactions at the cell surface. Recent analyses of genetic defects in Drosophila melanogaster, mice, and humans confirm most of these activities in vivo and identify additional processes that involve cell surface heparan sulfate proteoglycans. This chapter focuses on the mechanisms underlying these activities and on the cellular functions that they regulate.

Benign hyperplasia of the human prostate is associated with tissue enrichment in chondroitin sulphate of wide size distribution

BACKGROUND

Benign prostatic hyperplasia (BPH) involves qualitative and quantitative alterations in extracellular matrix (ECM) components affecting stromal-epithelial interactions. Glycosaminoglycans (GAGs) are polysaccharide components of the ECM whose role in the development of BPH is under investigation.

METHODS

GAGs were extracted from human prostates of normal and BPH origin and were subsequently fractionated through DEAE-sephacel anion exchange chromatography. The isolated GAG fractions were identified through electrophoresis on cellulose acetate membranes and treatment with GAG-degrading enzymes of known specificity. Their size distribution was determined through gradient polyacrylamide gel electrophoresis.

RESULTS

Isolated prostatic GAGs included hyaluronic acid (HA), heparan sulphate (HS), and a mixture of dermatan sulphate (DS) and chondroitin sulphate (CS). The CS/DS ratio was significantly higher in hyperplastic as compared to normal prostates. A difference was also observed with respect to the apparent molecular mass of the DS-CS mixture, which reflects the CS enrichment in BPH. GAGs isolated from hyperplastic prostates were more diverse in size as compared to the corresponding glycans from normal prostates.

CONCLUSIONS

The apparent increase in CS and decrease in DS content in prostates of patients with BPH is in good agreement with the pathological manifestation of increased cell proliferation in hyperplastic prostate tissue, since these glycan molecules have been reported to increase and decrease cell proliferation, respectively. Identification of the responsible enzymes involved in the homeostasis of CS and DS may provide alternative targets for pharmacological intervention.

Matrix glycosaminoglycans in the growth phase of fibroblasts: more of the story in wound healing

BACKGROUND

Understanding wound healing and ways to accelerate the healing process includes understanding the factors that influence the synthesis of granulation tissue, which fills the wound before epithelialization. An important phase of early wound healing involves secretion of glycosaminoglycans (GAGs) by fibroblasts which form a hydrophilic matrix suitable for remodeling during healing. The complexity of GAG structure and function in the extracellular matrix (ECM) remains poorly studied in wound healing. There is no established model for cutaneous wound healing due to variations in donor age, anatomic site, or stage of organ development. Rat embryo fibroblasts (REF) developed as a model to study malignant changes in fibroblasts were used as a model for fibroblasts in early wound healing because they lack the confounding variations based on age, site, and stage present in other fibroblasts used to study early wound healing. The purpose of this study was to identify and characterize the sulfated GAGs synthesized by REF-D.

MATERIALS AND METHODS

Rat embryo fibroblasts (REF-D) were cultured in serum-based medium and radiolabeled during their growth phase with (35)S to identify the GAG chains usually associated with proteoglycans (PGs). The sites of attachment (ECM-rich) were collected with detergent in sodium acetate buffer, pH 5.8, in the presence of protease inhibitors. Sulfated molecules were collected by ion-exchange chromatography and then assayed for GAGs. Nitrous acid deamination was used to determine heparan sulfate GAGs, and chondroitinase was used for chondroitin/dermatan sulfate GAGs. The proportion of individual GAGs was expressed with respect to sulfated molecules isolated. In addition, RNA was isolated from subconfluent REF-D, and core proteins for proteoglycans (decorin, biglycan, syndecan-2, and perlecan) were assayed by reverse transcription polymerase chain reaction.

RESULTS

There were two major configurations of GAGs: free GAG chains (79.7% of sulfated molecules) and GAGs attached to the core protein of a proteoglycan (15.6%). The free GAG chains were composed of chondroitin sulfate (79.1% +/- 3.5) and heparan sulfate (28.7% +/- 2.1). In the smaller group of PGs, both heparan sulfate (94.8% +/- 7.3) and chondroitin sulfate (88.9% +/- 3.2) chains were attached to a core protein. REF-D expressed mRNA for biglycan and decorin, which are chondroitin sulfate-containing PGs. In addition, REF-D expressed mRNA for syndecan-2 and perlecan, which are PGs that contain primarily heparan sulfate chains.

CONCLUSIONS

A majority of GAG chains synthesized by subconfluent REF-D are chondroitin sulfate. A smaller proportion of chondroitin sulfate chains associate with a core protein as part of a PG (e.g., biglycan, decorin, syndecan-2). Heparan sulfate chains are also present, with a small proportion associated with a core protein (e.g., the PGs syndecan-2, perlecan). The greater presence of free GAG chains forming weak interactions with surrounding molecules may assist fibroblasts that are moving and replicating during this phase. Therefore, REF-D are particularly well suited to study early wound healing by their expression of chondroitin sulfate chains and associated PGs without the influence of donor age, stage, or anatomic site.

Impaired elastogenesis in Hurler disease: dermatan sulfate accumulation linked to deficiency in elastin-binding protein and elastic fiber assembly

Hurler disease resulting from a deficiency in alpha-L-iduronidase, which causes an accumulation of dermatan sulfate and heparan sulfate glycosaminoglycans, is characterized by connective tissue and skeletal deformations, cardiomyopathy, cardiac valve defects, and progressive coronary artery stenosis. In this report, we present evidence that accumulation of dermatan sulfate but not heparan sulfate moieties is linked to impaired elastic fiber assembly that, in turn, contributes substantially to the development of the clinical phenotype in Hurler disease. Our data suggest that dermatan sulfate-bearing moieties bind to and cause functional inactivation of the 67-kd elastin-binding protein, a molecular chaperone for tropoelastin, which normally facilitates its secretion and assembly into elastic fibers. We demonstrate that, in contrast to normal skin fibroblasts and cells from Sanfilippo disease, which accumulate heparan sulfate, Hurler fibroblasts show reduced expression of elastin-binding protein and do not assemble elastic fibers, despite an adequate synthesis of tropoelastin and sufficient production of a microfibrillar scaffold of elastic fibers. Because cultured Hurler fibroblasts proliferate more quickly than their normal counterparts and the addition of exogenous insoluble elastin reduces their proliferation, we suggest that cell contacts with insoluble elastin play an important role in controlling their proliferation.

Presentation of IFN-gamma to nitric oxide-producing cells: a novel function for mast cells

We report that mast cells can bind and present IFN-gamma in a functionally active form to macrophages. Flow-cytometric analysis revealed that biotinylated IFN-gamma bound equally well to purified peritoneal mast cells from both IFN-gammaR knockout and wild-type mice, indicating a non-IFN-gammaR binding site. Purified peritoneal mast cells, loaded with IFN-gamma for 30 min and washed, were able to induce NO synthesis by peritoneal macrophages. This response required cell contact and expression of IFN-gammaR on the responding macrophages, but not the mast cells. Human HMC-1 mast cells were also able to present IFN-gamma to mouse macrophages. Enzyme treatment of mouse mast cells revealed that binding of IFN-gamma was predominantly to chondroitin sulfate B (dermatan sulfate). Binding of IFN-gamma to dermatan sulfate was confirmed by inhibition ELISA. This study demonstrates for the first time that mast cells can present IFN-gamma to other cells via glycosaminoglycans. Mast cells may act as a reservoir of surface-stored functionally active cytokines.

Dermatan sulfate activates nuclear factor-kappab and induces endothelial and circulating intercellular adhesion molecule-1

Proteoglycans (PGs) can influence cell behaviors through binding events mediated by their glycosaminoglycan (GAG) chains. This report demonstrates that chondroitin sulfate B, also known as dermatan sulfate (DS), a major GAG released during the inflammatory phase of wound repair, directly activates cells at the physiologic concentrations of DS found in wounds. Cultured human dermal microvascular endothelial cells exposed to DS responded with rapid nuclear translocation of nuclear factor-kappaB (NF-kappaB), increased expression of intercellular adhesion molecule-1 (ICAM-1) mRNA, and increased ICAM-1 cell surface protein. Heparan sulfate and chondroitin sulfates A and C had no effect on activation of NF-kappaB or induction of ICAM-1. Inhibition of NF-kappaB activation blocked the effect of DS. The increase in cell surface ICAM-1 did not involve TNF-alpha or IL-1 release by endothelial cells, but it was facilitated by autocrine factors whose release was initiated by DS. The ICAM-1-inductive activity of DS was confirmed in vivo. Injection of DS, but not heparin or other chondroitin sulfates, into mice greatly increased circulating levels of soluble ICAM. These data provide evidence that DS, but not other GAGs, initiates a previously unrecognized cell signaling event that can act during the response to injury.

Molecular cloning and characterization of a human uronyl 2-sulfotransferase that sulfates iduronyl and glucuronyl residues in dermatan/chondroitin sulfate

A partial-length human cDNA with a predicted amino acid sequence homologous to a previously described heparan sulfate iduronyl 2-sulfotransferase (Kobayashi, M., Habuchi, H., Yoneda, M., Habuchi, O., and Kimata, K. (1997) J. Biol. Chem. 272, 13980-13985) was obtained by searching the expressed sequence-tagged data bank. Northern blot analysis was performed using this homologous cDNA as a probe, which demonstrated ubiquitous expression of messages of 5.1 and 2.0 kilobases in a number of human tissues and in several human cancer cell lines. Since the human lymphoma Raji cell line had the highest level of expression, it was used to isolate a full-length cDNA clone. The full-length cDNA was found to contain an open reading frame that predicted a type II transmembrane protein composed of 406 amino acid residues. The cDNA in a baculovirus expression vector was expressed in Sf9 insect cells, and cell extracts were then incubated together with 3'-phosphoadenosine 5'-phospho[35S]sulfate and potential glycosaminoglycan acceptors. This demonstrated substantial sulfotransferase activity with dermatan sulfate, a small degree of activity with chondroitin sulfate, but no sulfotransferase activity with desulfated N-resulfated heparin. Analysis of [35S]sulfate-labeled disaccharide products of chondroitin ABC, chondroitin AC, and chondroitin B lyase treatment demonstrated that the enzyme only transferred sulfate to the 2-position of uronyl residues, which were preponderantly iduronyl residues in dermatan sulfate, but some lesser transfer to glucuronyl residues of chondroitin sulfate.