Inhibition of human leukocyte elastase by chemically and naturally oversulfated galactosaminoglycans

Fucosylated chondroitin sulfates from the body wall of the sea cucumber Holothuria forskali: conformation, selectin binding, and biological activity

Fucosylated chondroitin sulfate (fCS) extracted from the sea cucumber Holothuria forskali is composed of the following repeating trisaccharide unit: → 3)GalNAcβ4,6S(1 → 4) [FucαX(1 → 3)]GlcAβ(1 →, where X stands for different sulfation patterns of fucose (X = 3,4S (46%), 2,4S (39%), and 4S (15%)). As revealed by NMR and molecular dynamics simulations, the fCS repeating unit adopts a conformation similar to that of the Le(x) blood group determinant, bringing several sulfate groups into close proximity and creating large negative patches distributed along the helical skeleton of the CS backbone. This may explain the high affinity of fCS oligosaccharides for L- and P-selectins as determined by microarray binding of fCS oligosaccharides prepared by Cu(2+)-catalyzed Fenton-type and photochemical depolymerization. No binding to E-selectin was observed. fCS poly- and oligosaccharides display low cytotoxicity in vitro, inhibit human neutrophil elastase activity, and inhibit the migration of neutrophils through an endothelial cell layer in vitro. Although the polysaccharide showed some anti-coagulant activity, small oligosaccharide fCS fragments had much reduced anticoagulant properties, with activity mainly via heparin cofactor II. The fCS polysaccharides showed prekallikrein activation comparable with dextran sulfate, whereas the fCS oligosaccharides caused almost no effect. The H. forskali fCS oligosaccharides were also tested in a mouse peritoneal inflammation model, where they caused a reduction in neutrophil infiltration. Overall, the data presented support the action of fCS as an inhibitor of selectin interactions, which play vital roles in inflammation and metastasis progression. Future studies of fCS-selectin interaction using fCS fragments or their mimetics may open new avenues for therapeutic intervention.

Fine structure of glycosaminoglycans from fresh and decellularized porcine cardiac valves and pericardium

Cardiac valves are dynamic structures, exhibiting a highly specialized architecture consisting of cells and extracellular matrix with a relevant proteoglycan and glycosaminoglycan content, collagen and elastic fibers. Biological valve substitutes are obtained from xenogenic cardiac and pericardial tissues. To overcome the limits of such non viable substitutes, tissue engineering approaches emerged to create cell repopulated decellularized scaffolds. This study was performed to determine the glycosaminoglycans content, distribution, and disaccharides composition in porcine aortic and pulmonary valves and in pericardium before and after a detergent-based decellularization procedure. The fine structural characteristics of galactosaminoglycans chondroitin sulfate and dermatan sulfate were examined by FACE. Furthermore, the mechanical properties of decellularized pericardium and its propensity to be repopulated by in vitro seeded fibroblasts were investigated. Results show that galactosaminoglycans and hyaluronan are differently distributed between pericardium and valves and within heart valves themselves before and after decellularization. The distribution of glycosaminoglycans is also dependent from the vascular district and topographic localization. The decellularization protocol adopted resulted in a relevant but not selective depletion of galactosaminoglycans. As a whole, data suggest that both decellularized porcine heart valves and bovine pericardium represent promising materials bearing the potential for future development of tissue engineered heart valve scaffolds.

Synthetic and semi-synthetic chondroitin sulfate oligosaccharides, polysaccharides, and glycomimetics

Chondroitin sulfate (CS) is a sulfated polysaccharide involved in a myriad of biological processes. Due to the variable sulfation pattern of CS polymer chains, the need to study in detail structure-activity relationships regarding CS biomedical features has provoked much interest in obtaining synthetic CS species. This paper reviews two decades of synthetic and semi-synthetic CS oligosaccharides, polysaccharides, and glycomimetics obtained by chemical, chemoenzymatic, enzymatic, and microbiological-chemical strategies.

Thrombin inhibition by antithrombin in the presence of oversulfated dermatan sulfates

DSS1 and DSS2 are two oversulfated dermatan sulfate derivatives with sulfur contents of 7.8% and 11.5%, respectively. DSS1 and DSS2 both enhanced the rate at which antithrombin (AT) inactivates thrombin according to a concentration dependent manner. The analysis of the experimental data, using our previously described kinetic model [Biomaterials1997, 18, 203] (i) suggested that both DSS1 and DSS2 catalyzed the thrombin-AT reaction according to a mechanism in which the oversulfated derivative quickly formed with AT a complex, which was more reactive towards thrombin than the free inhibitor and (ii) allowed us to determine the dissociation constants of the polysaccharide-inhibitor complexes, which were (1.15 +/- 0.74) x 10(-7) and (7.17 +/- 0.65) x 10(-9) M, and the catalyzed reaction rate constants, which were (2.29 +/- 0.15) x 10(8) and (8.71 +/- 0.08) x 10(8) M(-1) min(-1), for DSS1 and DSS2, respectively. These data suggested that the oversulfation confers an affinity for AT to dermatan sulfate and that the higher the sulfur content the higher the affinity for AT. They also suggested that the reactivities of the polysaccharide-AT complexes formed towards the protease increased with the sulfur content.

A Sensitive and Simple Method for the Determination of Chondroitin Sulfate A with Crystal Violet by Resonance Rayleigh Scattering Technique

Resonance Rayleigh scattering (RRS) spectra resulting from interaction between chondroitin sulfate A (CSA) and crystal violet (CV) have been investigated and applied to the determination of CSA. Though the intensity of RRS has proved very weak for CSA and CV, respectively, it can be greatly enhanced when both interact and form a supramolecular complex. A new RRS spectrum appears with a maximum scattering peak at 328 nm. In this paper, the optimum conditions of the interaction, influencing factors, and the relationship between the relative intensity of RRS (DeltaI) and the concentration of CSA have been thoroughly investigated. A new method of determination for the trace amount of CSA has been developed, which combines a simple procedure, high sensitivity, and a low detection limit of 4.8 ng/mL. It has been applied with satisfactory results to the determination of CSA in CSA injection samples and synthetic samples.

Chondroitins 4 and 6 sulfate in osteoarthritis of the knee: a randomized, controlled trial

OBJECTIVE

To determine whether chondroitin sulfate (CS) is effective in inhibiting cartilage loss in knee osteoarthritis (OA).

METHODS

In this randomized, double-blind, placebo-controlled trial, 300 patients with knee OA were recruited from an outpatient clinic, from private practices, and through advertisements. Study patients were randomly assigned to receive either 800 mg CS or placebo once daily for 2 years. The primary outcome was joint space loss over 2 years as assessed by a posteroanterior radiograph of the knee in flexion; secondary outcomes included pain and function.

RESULTS

Of 341 patients screened, 300 entered the study and were included in the intent-to-treat analysis. The 150 patients receiving placebo had progressive joint space narrowing, with a mean +/- SD joint space loss of 0.14 +/- 0.61 mm after 2 years (P = 0.001 compared with baseline). In contrast, there was no change in mean joint space width for the 150 patients receiving CS (0.00 +/- 0.53 mm; P not significant compared with baseline). Similar results were found for minimum joint space narrowing. The differences in loss of joint space between the two groups were significant for mean joint space width (0.14 +/- 0.57 mm; P = 0.04) and for minimum joint space width (0.12 +/- 0.52 mm; P = 0.05). CS was well tolerated, with no significant differences in rates of adverse events between the two groups.

CONCLUSION

While there was no significant symptomatic effect in this study, long-term treatment with CS may retard radiographic progression in patients with OA of the knee. However, the clinical relevance of the observed structural results has to be further evaluated, and further studies are needed to confirm the structural effects of CS.

Chondroitin sulphate structure affects its immunological activities on murine splenocytes sensitized with ovalbumin

Chondroitin sulphate (CS) is a glycosaminoglycan widely distributed in animal tissues, which has anti-inflammatory and chondroprotective properties. We reported previously that chondroitin 4-sulphate (CS-A) up-regulates the antigen-specific Th1 immune response of murine splenocytes sensitized with ovalbumin in vitro, and that CS suppresses the antigen-specific IgE responses. We now demonstrate that a specific sulphation pattern of the CS polysaccharide is required for the Th1-promoted activity, as other polysaccharides such as dextran and dextran sulphate do not significantly induce this activity. While the presence of some O-sulpho groups appear to be essential for activity, CS-A, and synthetically prepared, partially O-sulphonated CS, induce higher Th1-promoted activity than synthetically prepared, fully O-sulphonated CS. CS-A induces an activity greater than chondroitin sulphate B (CS-B) or chondroitin 6-sulphate (CS-C). In addition, chondroitin sulphate E (CS-E) induces greater activity than CS-A or CS-D. These results suggest that the GlcA(beta1-3)GalNAc(4,6-O-disulpho) sequence in CS-E is important for Th1-promoted activity. Furthermore, rat anti-mouse CD62L antibody, an antibody to L-selectin, inhibits the Th1-promoting activity of CS. These results suggest that the Th1-promoted activity could be associated with L-selectin on lymphocytes. These findings describe a new mechanism for the anti-inflammatory and chondroprotective properties of CS that may be useful in designing new therapeutic applications for CS used in the treatment of immediate-type hypersensitivity.

Biosensor analysis of the molecular interactions of pentosan polysulfate and of sulfated glycosaminoglycans with immobilized elastase, hyaluronidase and lysozyme using surface plasmon resonance (SPR) technology

Pentosan polysulfate (NaPPS) and chondroitin sulfates (ChSs) have recently been shown to exhibit both symptom and disease modifying activities in osteoarthritis (OA), but their respective mechanisms of action are still the subject of conjecture. Excessive catabolism of joint articular cartilage is considered to be responsible for the initiation and progression of OA but the abilities of these drugs to mitigate this process has received only limited attention. Human neutrophil elastase (HNE) is a proteinase, which can degrade the collagens and proteoglycans (PGs) of the cartilage directly or indirectly by activating latent matrix metalloproteinases. Hyaluronidase (HAase) is an endoglycosidase, which degrades glycosaminoglycans including hyaluronan, which provides the aggregating component of the PG aggrecan complex. In the present study the molecular interactions between the NaPPS, ChSs and some other sulfated polysaccharides with immobilized HNE, HAase or lysozyme (a cationic protein implicated in PG metabolism) were studied using a SPR biosensor device-BIAcore2000. The above three enzymes were covalently immobilized to a biosensor chip CM5 separately using amine coupling. The binding affinity of each sulfated polysaccharide and the kinetics of NaPPS over the concentration range of 0.3-5.0 microg/ml were determined. The inhibition of HNE by the sulfated polysaccharides as determined using the synthetic substrate succinyl-Ala-Ala-Val-nitroanilide (SAAVNA) in a functional assay was compared with their respective binding affinities for this proteinase using the BIAcore system. The results obtained with the two independent techniques showed good correlation and indicated that the degree and ring positions of oligosaccharide sulfation were major determinants of enzyme inhibitory activity. The observed difference in order of binding affinities of the drugs to the immobilized HNE, HAase and lysozyme suggests a conformational relationship, in addition to the charge interactions between the sulfate esters of the polysaccharides and the cationic amino acids of the enzymes. Significantly, the SPR biosensor technology demonstrated that small differences among sulfated polysaccharides, even subtle variations among different NaPPS batches, could be readily detected. The SPR technology therefore offers not only a sensitive and reproducible method for ranking noncompetitive enzyme inhibitors for drug discovery but a rapid and quantitative bioassay for monitoring batch consistency of manufacture.

Salivary non-immunoglobulin agglutinin inhibits human leukocyte elastase digestion of acidic proline-rich salivary proteins

Saliva contains acidic proline-rich salivary proteins that are involved in the formation of the salivary pellicle coating supragingival tooth surfaces. However, human leukocyte elastase, arriving in gingival exudates from inflamed periodontal tissues, degrades the acidic proline-rich salivary proteins, preventing binding to hydroxylapatite surfaces. Here it is reported that high-molecular-weight non-immunoglobulin salivary agglutinin inhibited the proteolytic action of human leukocyte elastase on purified acidic proline-rich salivary proteins. Inhibition was eliminated with monoclonal antibody to a protein determinant on the salivary agglutinin. The addition of antibody against salivary agglutinin blocked the inhibitory effect of parotid saliva on exogenously applied human leukocyte elastase, allowing for the elastase-mediated digestion of the salivary acidic proline-rich salivary proteins. Salivary agglutinin, therefore, is a physiologically important inhibitor of human leukocyte elastase and is able to inhibit elastase-mediated digestion of salivary acidic proline-rich proteins.

Preparation and anticoagulant activity of fully O-sulphonated glycosaminoglycans

Glycosaminoglycans including dermatan sulphate, hyaluronan, heparan sulphate and heparin were chemically modified by O-sulphonation. By altering the reaction conditions, products having a different degree of O-sulphonation could be obtained. Glycosaminoglycan derivatives were prepared having no free hydroxyl groups, with sulphoester group/disaccharide unit ratios of 4.0 for dermatan sulphate and hyaluronan, and sulphoester and sulphamide group/disaccharide unit ratios of 4.22 and 4.88 for heparan sulphate and heparin, respectively. 1H NMR spectroscopy showed that the fully O-sulphonated hyaluronan derivative had a glucuronate residue with an altered conformation. Since glycosaminiglycans and their derivatives are often used as anticoagulant/antithrombotic agents, their anti-amidolytic activities were determined. The anti-factor IIa activity of fully O-sulphonated dermatan sulphate, hyaluronan and heparan sulphate ranged from 40 to 80 units/mg, while no anti-factor Xa activity of the fully O-sulphonated glycosaminoglycans was detected. These values are lower than those reported for low-molecular-weight heparins and are consistent with the requirement of an antithrombin III pentasaccharide binding site for anti-factor Xa activity. Interestingly, the anti-factor Xa of heparin is lost by chemical O-sulphonation.

Semisynthetic chondroitins as chiral buffer additives in capillary electrophoresis

Chemically oversulfated galactosaminoglycans with potential as therapeutic agents (inhibitors of human leukocyte elastase) were tested as chiral selectors in capillary electrophoresis of basic racemates. The high anionic character of these compounds provides them with anodic mobility in acidic buffer; using uncoated capillaries, the enantioresolution of racemic basic drugs was obtained at pH 2.5. Dimethindene, chloroquine and chlorpheniramine were enantioresolved applying negative voltage (-15 kV) while the other analytes (propranolol, pindolol, tetrahydrozoline and cloperastine) exhibited catodic migration. The addition of organic solvents to the running buffer was evaluated in order to increase the resolution; methanol provides the best results and in general, baseline separation of the analytes was reached. The studied oversulfated mucopolysaccharide, shows the same ionic character of heparin but presents different stereochemistry and sites of sulfation. A comparison with heparin, used in the same acidic conditions, may underline the role of ionic, spatial and steric features of glycosaminoglycans in the enantiorecognition.

Fractions of chemically oversulphated galactosaminoglycan sulphates inhibit three enveloped viruses: human immunodeficiency virus type 1, herpes simplex virus type 1 and human cytomegalovirus

A series of chemically oversulphated galactosaminoglycans (SO3H:COOH ratio > or = 2) were tested in vitro as antiviral agents against human immunodeficiency virus type 1 (HIV-1), the aetiological agent of AIDS, and against herpes simplex virus type 1 and human cytomegalovirus, two agents responsible for opportunistic infections in HIV-infected people. The oversulphated derivatives displayed an increase in activity ranging from one to four orders of magnitude against the three viruses, as compared to the natural parent compounds (SO3H:COOH, ratio approx. 1). The antiviral activity of these polyanions appears to be favoured by a high degree of sulphation and a high molecular mass. An oversulphated dermatan, with a SO3H:COOH ratio of 2.86 and molecular mass of 23.2 kDa, was the most potent anti-HIV-1 compound (EC50 0.04 microgram/ml). A second oversulphated dermatan, with a SO3H:COOH ratio of 2.40 and molecular mass of 25 kDa, displayed the highest activity against HSV-1 (EC50 0.01 microgram/ml). An oversulphated chondroitin, with a SO3H:COOH ratio of 2.80 and molecular mass of 17.3 kDa, was the strongest anti-HCMV agent (EC50 0.4 microgram/ml). In view of the absence of the side-effects typical of heparin-like compounds, a combination of these derivatives could have therapeutic potential.

Electrostatic interactions between human leukocyte elastase and sulfated glycosaminoglycans: physiological implications

The influence of ionic strength and composition on the binding and inhibition of human leukocyte elastase by glycosaminoglycans with variable degree and position of sulfation was investigated. The kinetic mechanism of inhibition had a hyperbolic, mixed-type character with a competitive component that was promoted by low ionic strength, reduced by phosphate ions, and which also depended on the substrate and glycosaminoglycan structure. Enzyme binding was a cooperative phenomenon that varied with ionic strength and composition. The inhibition patterns correlated with the cationic character of elastase and with the distribution of arginines on its molecular surface, most notably with residues located in the vicinity of the substrate binding region. The order of affinity for elastase binding was chondroitin 4-sulfate < chondroitin 6-sulfate < dermatan sulfate, iduronate-containing derivatives being superior with respect to the glucuronate-containing counterparts. Additional sulfation at both the 4- and 6- positions or at the N- and 4-positions of the N-acetylgalactosamine moiety decidedly improved the inhibitory efficiency. The results highlight a fundamental physiological role of enzyme-glycosaminoglycan interactions. In the azurophil granule of the human polymorphonuclear neutrophil, elastase and other enzymes are bound to a matrix of chondroitin 4-sulfate because this is the only glycosaminoglycan that simultaneously offers good binding for enzyme compartmentalization together with prompt release from the bound state at the onset of phagocytosis.

Inhibition of human leukocyte elastase activity by chondroitin sulfates

Chondroitin sulfates with different properties and devoid of appreciable anticoagulant activity were evaluated for their capacity to inhibit human leukocyte elastase activity in vitro by using a chromogenic substrate. Fractions with various mass and the same charge density were tested. The chondroitin sulfates with a molecular mass greater than about 2000 inhibited human leukocyte elastase activity to the same extent, whilst the fractions with a molecular mass of 1960 and 1020 were much less effective. The percentage inhibition of human leukocyte elastase activity increased based on the charge density of chondroitin sulfates. In particular, the inhibition of the enzymatic activity decreased with the percentage of non-sulfated disaccharide and increased with the amount of disaccharide-2,6-disulfated.

Active site for heparin cofactor II in low molecular mass dermatan sulfate. Contribution to the antithrombotic activity of fractions with high affinity for heparin cofactor II

Dermatan sulfate (DS) is currently under clinical investigation as new antithrombotic agent. Unlike heparin, DS does not act through Antithrombin III (ATIII) but primarily through thrombin on Heparin Cofactor II (HCII). HCII is activated by the oversulfated sequence (IdoA2SO3-GalNAc4SO3)4 or by both the sequences (IdoA2SO3-GalNAc4SO3)n and (IdoA-GalNAc-4,6SO3)n, [n > or = 2]. A Low Molecular Mass Dermatan Sulfate (LMM-DS), endowed with a bioavailability three-four times higher than DS, by subcutaneous route, was obtained by chemical depolymerization of DS. The LMM-DS was fractionated by anion exchange and size exclusion chromatography. Fractions with high and low charge densities, high and low molecular masses, and high (2.66) and low (0.07) potencies on HCII were isolated. A relationship between the in vitro HCII-mediated inhibition of thrombin and the chain length of DS fractions containing oversulfated sequences was found [by a multiple regression test]. The in vivo activity increased until it reached a plateau. The important influence on the HCII activity of natural IdoA-GalNAc-4,6SO3 disaccharide was confirmed by investigation on oversulfated DS obtained by a limited and selective chemical 6-O-sulfation in GalNAc4SO3 units of DS.