Quantification of glycosaminoglycans by reversed-phase HPLC separation of fluorescent isoindole derivatives

An optimize adaptable method for determining the monosaccharide composition of pectic polysaccharides

Pectic polysaccharides are considered the highly complex natural plant polysaccharides which plays a vital role in plant tissue structure and human health. Detailed characterization of the monosaccharide composition can provide insights into the pectic polysaccharide structure. Nevertheless, when analyzing the monosaccharides of pectic polysaccharide, it is crucial to address the issue of incomplete hydrolysis that can occur due to the formation of acid-induced precipitates. Based on above, the main purpose of this article is to provide an optimized method for monosaccharide analysis of pectic polysaccharides through acid hydrolysis optimization using high-performance anion exchange chromatography (HPAEC) The results indicate that reducing the sample concentration to 0.5 mg/mL effectively reduces the acid gelling phenomenon and promotes the complete hydrolysis of pectin polysaccharides. The optimized parameters for acid hydrolysis involve 110 °C for 6 h in 2 M TFA. Furthermore, the consistency of this method is assessed, along with its ability to analyze pectin polysaccharides from various fruits. This hydrolysis approach holds promise for enabling accurate quantification of monosaccharide composition in pectic polysaccharides.

A novel graphene oxide-based fluorescence method for detection of urine glycosaminoglycans

Glycosaminoglycans (GAGs) serve as a biomarker for mucopolysaccharidoses disease. In this study, a novel fluorometric method was developed to measure total GAGs in urine. Graphene oxide (GO) and rhodamine B (RhB), a cationic fluorescent dye, were employed in the development of the method. RhB attaches to the GO surface via electrostatic attraction, leading to the quenching of its fluorescence upon the establishment of the RhB-GO complex. However, the presence of GAGs prompts a resurgence of intense fluorescence. The linear range of the method is between 5.00 and 70.00 mg/L. The total GAG levels of urine samples analyzed using the method agree with the results of the biochemistry analysis laboratory (65.85 and 79.18 mg/L; 73.30 ± 1.76 and 72.21 ± 2.21). The method is simple, accurate, and sensitive and may be used for both first-step diagnosis of the mucopolysaccharidoses and detection of individual GAGs for studies of GAG-related research and other biological applications.

Quantitative determination of chondroitin sulfate with various molecular weights in raw materials by pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate

A simple and reliable HPLC method was developed for quantification of chondroitin sulfate (CS). The procedure is based on precolumn hydrolysis of CS to liberate galactosamine and subsequent derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. Hydrolysis and derivatization conditions were optimized. A linear correlation coefficient of 0.9999 was calculated within the range of 10-1500 μg/mL from the standard curve. The method produces good precision and good accuracy (100.75 % recovery). An advantage over other common methods is its ability to quantify CS of all molecular weights and structures, as evidenced by the determination of CS fractions with narrow molecular weight distributions obtained through depolymerization by different methods, while enzymatic HPLC was proven to be infeasible. Extraction recoveries of CS from monosaccharide mixed samples were > 93 %. The reliability was also validated by a small difference (-1.95 % to 4.12 %) relative to enzymatic HPLC results in analysing representative CS samples of different animal origins and suppliers.

Sweet but Challenging: Tackling the Complexity of GAGs with Engineered Tailor-Made Biomaterials

Glycosaminoglycans (GAGs) play a crucial role in tissue homeostasis by regulating the activity and diffusion of bioactive molecules. Incorporating GAGs into biomaterials has emerged as a widely adopted strategy in medical applications, owing to their biocompatibility and ability to control the release of bioactive molecules. Nevertheless, immobilized GAGs on biomaterials can elicit distinct cellular responses compared to their soluble forms, underscoring the need to understand the interactions between GAG and bioactive molecules within engineered functional biomaterials. By controlling critical parameters such as GAG type, density, and sulfation, it becomes possible to precisely delineate GAG functions within a biomaterial context and to better mimic specific tissue properties, enabling tailored design of GAG-based biomaterials for specific medical applications. However, this requires access to pure and well-characterized GAG compounds, which remains challenging. This review focuses on different strategies for producing well-defined GAGs and explores high-throughput approaches employed to investigate GAG-growth factor interactions and to quantify cellular responses on GAG-based biomaterials. These automated methods hold considerable promise for improving the understanding of the diverse functions of GAGs. In perspective, the scientific community is encouraged to adopt a rational approach in designing GAG-based biomaterials, taking into account the in vivo properties of the targeted tissue for medical applications.

The investigation of batch-to-batch variabilities in the composition of isolates from fish and mammalian species using different protocols

The aim of this study was to investigate batch-to-batch inconsistencies in the processing of pig and fish collagen isolates processed using two protocols that differed in terms of the acetic acid concentrations applied and the pre- and post-extraction steps, and which were previously tested in our laboratory with the intention of preserving the biological structures and functions of the collagen isolates for biomedical purposes. Both the major and minor components such as the amino acids, lipids, water, glycosaminoglycan and ash contents and elemental content, as well as the structure and morphology of the raw sources and the resulting batches of isolates were subsequently examined in detail applying standardized analytical methods including high perfomance liquid chromatography, ultraviolet-visible and infrared spectrometry, polyacrylamide gel electrophoresis, energy dispersive spectroscopy and scanning electron microscopy. All the fish isolates provided severalfold higher yields (8-45 wt%) than did the pig isolates (3-9 wt%). In addition, the variability of the fish isolate yields (the coefficient of variation for processing A: 16.4-32.9 % and B: 6.8-17.4 %) was significantly lower (p ≤ 0.05, n = 5) than that of the pig isolates (A: 27.7-69.8 %; B: 35.3-87.9 %). In general, the fish skin batches had significantly higher protein contents (˃60 wt%) and lower lipid contents (<10 wt%) than the pig skin batches (<55 wt% protein and up to 66 wt% lipid). In addition, the fish skin batches did not differ significantly in terms of their composition applying the same processing method, whereas the pig skin batches exhibited considerable variations in terms of their compositions, particularly regarding the protein and lipid contents. It can be stated that, concerning the fish isolates, processing B was, in most cases, slightly more efficient and reproducible than processing A. However, concerning the pig isolates, although processing A appeared to be more efficient than processing B in terms of the yield, it resulted in the production of isolates that contained a certain level of contaminants. The study provides a comprehensive discussion on the suitability of the processing protocol in terms of producing batches of reproducible quality according to the specific type of biomaterial processed from different animal species.

Determination of monosaccharide composition in human serum by an improved HPLC method and its application as candidate biomarkers for endometrial cancer

Altered glycan levels in serum have been associated with increased risk of cancer. In this study, we have developed and validated a HPLC-based method to analyze monosaccharide composition (D-mannose, Glucosamine, Galactosamine, Glucuronic acid, D-glucose, D-galactose, D-xylose, L-fucose) in human serum, with L-rhamnose, being used as internal standard. Monosaccharides obtained from hydrolyzed serum samples were derivatized by 1-Phenyl-3-methyl-5-pyrazolone. A ZORBAX XDB-C18 column(150×4.6mm) was used for chromatographic separation with 100 mM ammonium acetate buffer (NH4Ac-HAc, PH=5.5, solvent A), acetonitrile (ACN, solvent B) as a mobile phase. The calibration standard curves for the eight monosaccharides showed good linearity over the range of 2.5-500μg/mL with R² > 0.995. The relative standard deviation values for intra-day and inter-day precision were ≤ 5.49%. Recovery was 69.01-108.96%. We observed that this column exhibited high specificity and selectivity to separate monosaccharides from serum. This method was then applied to quantitatively analyze the serum monosaccharide levels in 30 patients with endometrial cancer and 30 matched healthy controls. Statistical analysis indicated that the serum monosaccharide levels were significantly higher in patients compared with healthy controls (P value< 0.0001). Overall, we report here a simple, reliable, low-cost, and reproducible HPLC method for the separation and quantification monosaccharides in the human serum, which has potential value to serve as a screening marker for endometrial cancer.

Glycosaminoglycan Quality Control by Monosaccharide Analysis

Glycosaminoglycans (GAGs) are heterogeneous biomacromolecules made by all animal cells with overlapping molecular weight and high negative charge densities, which make thorough separation of different types of GAGs and elimination of all GAG-binding proteins difficult. Even with the constant challenge of quality control, chondroitin sulfate, dermatan sulfate, heparan sulfate, and heparin glycosaminoglycans (GAGs) have been used as nutraceuticals and modern drugs for many years worldwide. Testing galactosamine in heparin has been added to the USP monograph after contaminated heparin event, but the general monosaccharide composition analysis has not been developed for GAG quality control purposes. Using a PCR-facilitated hydrolysis assay, the hydrolyzed GAG saccharides were labeled with 1-phenyl-3-methyl-5-pyrazolone (PMP) and quantified by high performance liquid chromatography (HPLC) coupled with mass spectrometry (MS). Glucosamine was found in both chondroitin sulfate and dermatan sulfate whereas galactosamine was observed in both heparan sulfate and heparin, indicating the cross contamination among different types of GAGs. Moreover, fucose was detected in chondroitin sulfate, dermatan sulfate, and heparan sulfate, and both fucose and mannose were detected in chondroitin sulfate, suggesting the co-presence of other types of glycans or novel fucosylated GAG structures. Furthermore, both the amount and structure of acid-resistant disaccharides provide distinguishable features for each type of GAGs at the same hydrolysis condition. Thus, monosaccharide analysis provides a practical and quantitative way for GAG quality control.

Determination of glycosaminoglycans in biological matrices using a simple and sensitive reversed-phase HPLC method with fluorescent detection

This paper suggests a sensitive reversed-phase gradient HPLC method combined with fluorescence detection that has been developed, optimized and tested via the quantitative analysis of authentic biological material in an effort to determine and subsequently compare the total content of glycosaminoglycans (GAGs) in various collagen-based biomaterials intended for medical application. The proposed analytical method enabled the identification and separation of the GAGs present from the other components in the samples using commonly-available laboratory equipment; moreover, the very low detection limit of the method permits the determination of GAGs even for very small samples. This study describes the development of the method, including the isolation and processing of the collagen samples prior to HPLC analysis and the optimal parameters applied during the chromatographic analysis. The application of the method in laboratory practice is documented by means of several examples of the determination of GAGs employing both commercial standards and real collagen samples isolated from various animal tissues.

Advances in glycosaminoglycan detection

BACKGROUND

Glycosaminoglycans (GAGs) are negatively charged long linear (highly sulfated) polysaccharides consisting of repeating disaccharide units that are expressed on the surfaces of all nucleated cells. The expression of GAGs is required for embryogenesis, regulation of cell growth and proliferation, maintenance of tissue hydration, and interactions of the cells via receptors. Mucopolysaccharidoses (MPS) are caused by deficiency of specific lysosomal enzymes that result in the accumulation of GAGs in multiple tissues leading to organ dysfunction. Therefore, GAGs are important biomarkers for MPS. Without any treatment, patients with severe forms of MPS die within the first two decades of life.

SCOPE OF REVIEW

Accurate measurement of GAGs is important to understand the diagnosis and pathogenesis of MPS and to monitor therapeutic efficacy before, during, and after treatment of the disease. This review covers various qualitative and quantitative methods for measurement of GAGs, including dye specific, thin layer chromatography (TLC), capillary electrophoresis, high-performance liquid chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-MS/MS), gas chromatography, ELISA, and automated high-throughput mass spectrometry. Major conclusion: There are several methods for GAG detection however, specific GAG detection in the various biological systems requires rapid, sensitive, specific, and cost-effective methods such as LC-MS/MS.

GENERAL SIGNIFICANCE

This review will describe different methods for GAG detection and analysis, including their advantages and limitation.

Glycosaminoglycans from fresh water fish processing discard - Isolation, structural characterization, and osteogenic activity

Glycosaminoglycans (GAGs) play an important role in various biological activities. A lot of them are present in fish processing discards from abattoirs and fish processing industries which can serve as a valuable source of GAGs. We have, in this paper, isolated and characterized GAGs from fish processing discard (head) generated from the processing of Labeo rohita (L. rohita) and Piaractus brachypomus (P. brachypomus) and have determined their ability to promote osteogenic activity. Isolated GAGs showed higher amounts of chondroitin sulfate/dermatan sulfate (CS/DS) than heparan sulfate (HS). CS/DS from both the fish have a distinct disaccharide composition indicating differences in their structure. Biological activity, in terms of promoting osteogenesis, evaluated in MC3T3-E1 cells and primary cells of the calvaria showed that early mineralization, characterized by alkaline phosphatase staining and activity, and late mineralization, was supported by both the GAGs.

Analysis of Sulfated Glycosaminoglycans in ECM Scaffolds for Tissue Engineering Applications: Modified Alcian Blue Method Development and Validation

Accurate determination of the amount of glycosaminoglycans (GAGs) in a complex mixture of extracellular matrix (ECM) is important for tissue morphogenesis and homeostasis. The aim of the present study was to investigate an accurate, simple and sensitive alcian blue (AB) method for quantifying heparin in biological samples. A method for analyzing heparin was developed and parameters such as volume, precipitation time, solvent component, and solubility time were evaluated. The AB dye and heparin samples were allowed to react at 4 ℃ for 24 h. The heparin-AB complex was dissolved in 25 N NaOH and 2-Aminoethanol (1:24 v/v). The optical density of the solution was analyzed by UV-Vis spectrometry at 620 nm. The modified AB method was validated in accordance with U.S. Food and Drug Administration guidelines. The limit of detection was found to be 2.95 µg/mL. Intraday and interday precision ranged between 2.14–4.83% and 3.16–7.02% (n = 9), respectively. Overall recovery for three concentration levels varied between 97 ± 3.5%, confirming good accuracy. In addition, this study has discovered the interdisciplinary nature of protein detection using the AB method. The basis for this investigation was that the fibrous protein inhibits heparin-AB complex whereas globular protein does not. Further, we measured the content of sulfated GAGs (sGAGs; expressed as heparin equivalent) in the ECM of decellularized porcine liver. In conclusion, the AB method may be used for the quantitative analysis of heparin in ECM scaffolds for tissue engineering applications.

Optimizing microwave-assisted hydrolysis conditions for monosaccharide composition analyses of different polysaccharides

Releasing all monosaccharides during acid hydrolysis for composition analysis of polysaccharides has been a time consuming process. In current study, an efficient (10 μL sample + 10 μL acid), sensitive, and quick monosaccharide composition analysis of polysaccharides was accomplished by using microwave-assisted HCl hydrolysis (10 min) of the polysaccharides followed by high-performance anion-exchange chromatography (HPAEC) combined with pulsed amperometric detection (PAD) analysis. Compared to the conventional hydrolysis procedure, this method is an efficient approach for monosaccharide composition analysis of acidic, basic, and neutral polysaccharides and particularly suited to polysaccharides that are difficult to hydrolyse fully such as chitosan, heparin and chondroitin sulfates.

Differential calixarene receptors create patterns that discriminate glycosaminoglycans

A well-designed fluorescence displacement sensing array based on calixarene receptors realizes the discrimination of glycosaminoglycans.

Acidolysis-based component mapping of glycosaminoglycans by reversed-phase high-performance liquid chromatography with off-line electrospray ionization-tandem mass spectrometry: evidence and tags to distinguish different glycosaminoglycans

Diverse monosaccharide analysis methods have been established for a long time, but few methods are available for a complete monosaccharide analysis of glycosaminoglycans (GAGs) and certain acidolysis-resistant components derived from GAGs. In this report, a reversed-phase high-performance liquid chromatography (RP-HPLC) method with pre-column 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization was established for a complete monosaccharide analysis of GAGs. Good separation of glucosamine/mannosamine (GlcN/ManN) and glucuronic acid/iduronic acid (GlcA/IdoA) was achieved. This method can also be applied to analyze the acidolysis-resistant disaccharides derived from GAGs, and the sequences of these disaccharides were confirmed by electrospray ionization-collision-induced dissociation-tandem mass spectrometry (ESI-CID-MS/MS). These unique disaccharides could be used as markers to distinguish heparin/heparan sulfate (HP/HS), chondroitin sulfate/dermatan sulfate (CS/DS), and hyaluronic acid (HA).

Monoclonal antibodies to sea cucumber polysaccharide and their use in a sandwich ELISA assay

Antigen was synthesized with L-SCP, a sea cucumber polysaccharide isolated from Pearsonothuria graeffei (Semper) and bovine serum albumin (BSA) as a carrier protein. Spleen cells with high titer antibody producing ability were removed and fused with myeloma cells of SP2/0-Ag14 origin. Three stable murine monoclonal antibodies (MAb ascites) producing cell lines to L-SCP were generated according to a conventional immunization protocol. Their epitope mapping and binding specificity, which was characterized by blocking and inhibition enzyme-linked immunosorbent assay (ELISA) indicated that these specific MAb ascites have similar binding patterns. A sandwich ELISA was developed on the basis of employing L-SCP specific antibodies including MAb 3G6 as capture antibody and HRP-3G6 as detection antibody. The working range for L-SCP in aqueous solution from this method was 100-10,000 ng/mL with good sensitivity, specificity, and precision (relative standard deviation ≤7.9%). Thus the developed ELISA can be used as a convenient tool for the rapid detection of L-SCP in biological examples in the future.

Heparan sulfate modification of the transmembrane receptor CD47 is necessary for inhibition of T cell receptor signaling by thrombospondin-1

Cell surface proteoglycans on T cells contribute to retroviral infection, binding of chemokines and other proteins, and are necessary for some T cell responses to the matricellular glycoprotein thrombospondin-1. The major cell surface proteoglycans expressed by primary T cells and Jurkat T cells have an apparent M(r) > 200,000 and are modified with chondroitin sulfate and heparan sulfate chains. Thrombospondin-1 bound in a heparin-inhibitable manner to this proteoglycan and to a soluble form released into the medium. Based on mass spectrometry, knockdown, and immunochemical analyses, the proteoglycan contains two major core proteins as follows: amyloid precursor-like protein-2 (APLP2, apparent M(r) 230,000) and CD47 (apparent M(r) > 250,000). CD47 is a known thrombospondin-1 receptor but was not previously reported to be a proteoglycan. This proteoglycan isoform of CD47 is widely expressed on vascular cells. Mutagenesis identified glycosaminoglycan modification of CD47 at Ser(64) and Ser(79). Inhibition of T cell receptor signaling by thrombospondin-1 was lost in CD47-deficient T cells that express the proteoglycan isoform of APLP2, indicating that binding to APLP2 is not sufficient. Inhibition of CD69 induction was restored in CD47-deficient cells by re-expressing CD47 or an S79A mutant but not by the S64A mutant. Therefore, inhibition of T cell receptor signaling by thrombospondin-1 is mediated by CD47 and requires its modification at Ser(64).

Hyphenated techniques for the analysis of heparin and heparan sulfate

The elucidation of the structure of glycosaminoglycan has proven to be challenging for analytical chemists. Molecules of glycosaminoglycan have a high negative charge and are polydisperse and microheterogeneous, thus requiring the application of multiple analytical techniques and methods. Heparin and heparan sulfate are the most structurally complex of the glycosaminoglycans and are widely distributed in nature. They play critical roles in physiological and pathophysiological processes through their interaction with heparin-binding proteins. Moreover, heparin and low-molecular weight heparin are currently used as pharmaceutical drugs to control blood coagulation. In 2008, the health crisis resulting from the contamination of pharmaceutical heparin led to considerable attention regarding their analysis and structural characterization. Modern analytical techniques, including high-performance liquid chromatography, capillary electrophoresis, mass spectrometry, and nuclear magnetic resonance spectroscopy, played critical roles in this effort. A successful combination of separation and spectral techniques will clearly provide a critical advantage in the future analysis of heparin and heparan sulfate. This review focuses on recent efforts to develop hyphenated techniques for the analysis of heparin and heparan sulfate.

Glycosaminoglycans and activated contact system in cancer patient plasmas

Oncogenic mutations create cancer cells. Cancer cells require thrombin for growth, angiogenesis, and metastasis. All cancer patients display a hypercoagulable state, which includes platelet activation, blood coagulation, complement activation, vasodilatation, and inflammation. This often results in thrombosis, the second leading cause of death in cancer patients. It is established that chemically oversulfated glycosaminoglycans (GAGs) induce thrombin generation through contact system activation in human plasma. Thrombin is responsible for thrombosis. In this chapter, we show that plasmas from lung cancer patients contain activated contact systems apparent by the absence of high molecular weight kininogen and processed C1inh, by abnormal kallikrein and thrombin activities, and by increased glucosamine, galactosamine, and GAG levels. Activated contact systems were also evident in plasmas from breast, colon, and pancreatic cancer patients. These data suggest that GAGs or other molecules produced by tumors induce abnormal thrombin generation through contact system activation. Therefore, the contact system and glycans represent new targets for cancer diagnosis, prevention, and treatment.

Analysis of a gain-of-function FGFR2 Crouzon mutation provides evidence of loss of function activity in the etiology of cleft palate

Cleft palate is a common birth defect in humans and is a common phenotype associated with syndromic mutations in fibroblast growth factor receptor 2 (Fgfr2). Cleft palate occurred in nearly all mice homozygous for the Crouzon syndrome mutation C342Y in the mesenchymal splice form of Fgfr2. Mutant embryos showed delayed palate elevation, stage-specific biphasic changes in palate mesenchymal proliferation, and reduced levels of mesenchymal glycosaminoglycans (GAGs). Reduced levels of feedback regulators of FGF signaling suggest that this gain-of-function mutation in FGFR2 ultimately resembles loss of FGF function in palate mesenchyme. Knowledge of how mesenchymal FGF signaling regulates palatal shelf development may ultimately lead to pharmacological approaches to reduce cleft palate incidence in genetically predisposed humans.

Activated contact system and abnormal glycosaminoglycans in lupus and other auto- and non-autoimmune diseases

Systemic lupus erythematosus (SLE), heparin-induced thrombocytopenia (HIT), rheumatoid arthritis (RA) are marked by the presence of autoantibodies against negatively changed DNA, phospholipids, heparin, and chondroitin sulfate, respectively. Heparin/protein complexes induce contact system activation in HIT patient plasmas. The activated contact system generates thrombin. Thrombin is responsible for thrombosis, a common cause of death and disabilities for both HIT and SLE. In this chapter, we analyze plasma contact system proteins, thrombin- and kallikrein-like activities, glucosamine and galactosamine content from SLE-, RA-, osteoarthritis (OA)-, and psoriasis (Ps)-patient plasmas in addition to pooled 30+ healthy patient plasmas. We found that all SLE patient plasmas exhibited abnormal contact systems marked by the absence of high molecular weight kininogen, the presence of processed C1 inhibitor (C1inh), the display of abnormal thrombin- and kallikrein-like activities, and increased levels of plasma glucosamine and galactosamine. Different patterns of contact system activation distinguish SLE, RA, and Ps whereas no contact system activation is observed in normal and OA patient plasmas. The presence of paradoxical "lupus anticoagulants" in certain thrombosis-prone SLE patient plasmas, marked by delayed clotting in clinical plasma test, was explained by the consumption of contact system proteins, especially high molecular weight kininogen. Finally, we discovered that mouse and human SLE autoantibodies bind to cell surface GAGs with structural selectivity. In conclusion, markers of abnormal contact system activation represent potential new targets for autoimmune disease diagnosis, prevention, and treatment. These markers might also be useful in monitoring SLE activity/severity and in pinpointing patients with SLE-associated arthritis and psoriasis.

Production of monoclonal antibodies for detecting marine fungal polysaccharide isolated from the Phoma herbarum YS4108

Seven monoclonal antibodies (MAbs) specific for marine fungal polysaccharide YCP isolated from the Phoma herbarum YS4108 were obtained after immunization of BALB/c mice with the conjugate of YCP coupled to bovine serum albumin (BSA). Their epitope mapping and binding specificity characterized by blocking and inhibition Enzyme-linked immunosorbent assay (ELISA) indicated that these specific MAbs have similar binding patterns. An immuno-capture ELISA has been developed on the basis of employing the MAbs N(3)F and P(12)B specific for YCP as the capture antibody and the detecting antibody, respectively. The working range for YCP in aqueous solution was 1-10,000 ng/ml with a good reproducibility (relative standard deviation <or=7.2%). Subsequently, the extraction process of YCP from Phoma herbarum YS4108 was successfully optimized by the method.

High affinity glycosaminoglycan and autoantigen interaction explains joint specificity in a mouse model of rheumatoid arthritis

In the K/BxN mouse model of rheumatoid arthritis, autoantibodies specific for glucose-6-phosphate isomerase (GPI) can transfer joint-specific inflammation to most strains of normal mice. Binding of GPI and autoantibody to the joint surface is a prerequisite for joint-specific inflammation. However, how GPI localizes to the joint remains unclear. We show that glycosaminoglycans (GAGs) are the high affinity (83 nm) joint receptors for GPI. The binding affinity and structural differences between mouse paw/ankle GAGs and elbows/knee GAGs correlated with the distal to proximal disease severity in these joints. We found that cartilage surface GPI binding was greatly reduced by either chondroitinase ABC or beta-glucuronidase treatment. We also identified several inhibitors that inhibit both GPI/GAG interaction and GPI enzymatic activities, which suggests that the GPI GAG-binding domain overlaps with the active site of GPI enzyme. Our studies raise the possibility that GAGs are the receptors for other autoantigens involved in joint-specific inflammatory responses.

The Quantification of Glycosaminoglycans: A Comparison of HPLC, Carbazole, and Alcian Blue Methods

Glycosaminoglycans (GAGs) are linear polysaccharides that are found in the extracellular matrix and biological fluids of animals where they interact with hundreds of proteins and perform a variety of critical roles. There are five classes of animal GAGs: heparan sulfate (HS), chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS), and hyaluronan (HA). Many biological functions can be monitored directly by their impact on GAG quantity. Thus, simple, sensitive, and robust GAG quantification methods are needed for the development of biomarkers. We have systematically compared three available GAG quantification assays including an HPLC-based assay, a simplified Alcian Blue assay, and a miniaturized carbazole assay. The carbazole and Alcian Blue assays were reproducible and simple to perform in general lab settings, but had important limitations: The carbazole assay could not detect KS and it overestimated GAGs that were contaminated with salts or dissolved in PBS. The Alcian Blue assay detected only those GAGs that were sulfated. In contrast, while the HPLC method was time-consuming, it was a robust and sensitive assay that not only detected all GAGs but also quantified glucosamine-GAGs and galactosamine-GAGs simultaneously. The HPLC assay was not affected by salt or level of GAG sulfation and it yielded reproducible values for all types of GAGs tested. These results suggest that an automated HPLC assay would be generally useful for the routine measurement of a panel of GAG-based biomarkers while the carbazole assay and the Alcian Blue assays could prove valuable for more specific purposes.

Secreted NS1 of dengue virus attaches to the surface of cells via interactions with heparan sulfate and chondroitin sulfate E

Dengue virus (DENV) nonstructural protein-1 (NS1) is a secreted glycoprotein that is absent from viral particles but accumulates in the supernatant and on the plasma membrane of cells during infection. Immune recognition of cell surface NS1 on endothelial cells has been hypothesized as a mechanism for the vascular leakage that occurs during severe DENV infection. However, it has remained unclear how NS1 becomes associated with the plasma membrane, as it contains no membrane-spanning sequence motif. Using flow cytometric and ELISA-based binding assays and mutant cell lines lacking selective glycosaminoglycans, we show that soluble NS1 binds back to the surface of uninfected cells primarily via interactions with heparan sulfate and chondroitin sulfate E. DENV NS1 binds directly to the surface of many types of epithelial and mesenchymal cells yet attaches poorly to most peripheral blood cells. Moreover, DENV NS1 preferentially binds to cultured human microvascular compared to aortic or umbilical cord vein endothelial cells. This binding specificity was confirmed in situ as DENV NS1 bound to lung and liver but not intestine or brain endothelium of mouse tissues. Differential binding of soluble NS1 by tissue endothelium and subsequent recognition by anti-NS1 antibodies could contribute to the selective vascular leakage syndrome that occurs during severe secondary DENV infection.

Dengue virus (DENV) is a mosquito-transmitted virus that infects humans and has become a global emerging infectious disease threat. Four serotypes of DENV exist, and the most severe cases are associated with secondary infection with a different virus serotype. Clinical deterioration is characterized by bleeding and selective vascular leakage from endothelium in specific tissue sites. An increased understanding of how DENV proteins contribute to this phenotype is vital to developing novel vaccines and identifying individuals at risk for severe disease. DENV nonstructural protein-1 (NS1) is one such protein: during infection, it is secreted and accumulates in the supernatant and on the surface of cells. In this study, we demonstrate that soluble DENV NS1 attaches to subsets of cells, including some but not all endothelial cells, primarily via an interaction with specific glycosaminoglycans (heparan sulfate and chondroitin sulfate E). This was confirmed in tissue binding studies as DENV NS1 bound to lung and liver but not intestine or brain endothelium. Our findings suggest that the selective vascular leakage that occurs in severe DENV infection may be related to the relative ability of endothelial cells in different tissues to bind soluble NS1 and to be targeted by cross-reactive anti-NS1 antibodies during secondary infection.

Inhibition or Activation of Apert Syndrome FGFR2 (S252W) Signaling by Specific Glycosaminoglycans

Most Apert syndrome patients harbor a single amino acid mutation (S252W) in fibroblast growth factor (FGF) receptor 2 (FGFR2), which leads to abnormal FGF/FGFR2 signaling. Here we show that specific combinations of FGFs and glycosaminoglycans activate both alternative splice forms of the mutant but not of the wild-type FGF receptors. More importantly, 2-O- and N-sulfated heparan sulfate, prepared by a combined chemical and enzymatic synthesis, antagonized the over-activated FGFR2b (S252W) to basal levels at nanomolar concentrations. These studies demonstrated that specific glycosaminoglycans could be useful in treating ligand-dependent FGFR signaling-related diseases, such as Apert syndrome and cancer.