Recombinant dermatan sulfate is a potent activator of heparin cofactor II-dependent inhibition of thrombin.

The glycosaminoglycan dermatan sulfate (DS) is a well-known activator of heparin cofactor II-dependent inactivation of thrombin. In contrast to heparin, dermatan sulfate has never been prepared recombinantly from material of non-animal origin. Here we report on the enzymatic synthesis of structurally well-defined DS with high anticoagulant activity. Using a microbial K4 polysaccharide and the recombinant enzymes DS-epimerase 1, dermatan 4-O-sulfotransferase 1, uronyl 2-O-sulfotransferase and N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase, several new glycostructures have been prepared, such as a homogenously sulfated IdoA-GalNAc-4S polymer and its 2-O-, 6-O- and 2,6-O-sulfated derivatives. Importantly, the recombinant highly 2,4-O-sulfated DS inhibits thrombin via heparin cofactor II, approximately 20 times better than heparin, enabling manipulation of vascular and extravascular coagulation. The potential of this method can be extended to preparation of specific structures that are of importance for binding and activation of cytokines, and control of inflammation and metastasis, involving extravasation and migration.

Sulfated glycosaminoglycan-based block copolymer: preparation of biocompatible chondroitin sulfate-b-poly(lactic acid) micelles.

Despite a growing interest in amphiphilic polysaccharide-based diblock copolymers as functional polymeric drug delivery nanosystems, biologically relevant sulfated glycosaminoglycan systems were not yet investigated. Here, we report the synthesis and the self-assembly properties in water of chondroitin sulfate-b-poly(lactic acid) (CS-b-PLA(n)). The CS-b-PLA(n) were synthesized using click-grafting onto method implying reducing-end alkynation of low-molecular weight depolymerized CS (M(w) = 5000 g·mol(-1)) and azide-terminated functionalization of PLAn (M(w) = 6500 g·mol(-1) (n = 46) and M(w) = 1700 g·mol(-1) (n = 20)). The diblock copolymer self-assembled in water giving rise to spherical micelles that were characterized in solution using dynamic/static light scattering and at dry state by TEM technique. In vitro assays on healthy cells showed that at high concentrations, up to 10 µg·mL(-1), CS-b-PLA(n) were noncytotoxic. Those preliminary studies are promising in the perspective to use them as biocompatible nanovehicles for anticancer drug delivery.

Synthesis of chondroitin/dermatan sulfate-like oligosaccharides and evaluation of their protein affinity by fluorescence polarization.

Here, we present a novel approach for the chemical synthesis of chondroitin and dermatan sulfate oligosaccharides. A key point of this strategy is the preparation and use of an N-trifluoroacetyl galactosamine building block containing a 4,6-O-di-tert-butylsilylene group. Glycosylation reactions proceeded in good yields (74-91%) with our protecting group distribution. Using this approach, we have synthesized, for the first time, a chondroitin/dermatan sulfate-like tetrasaccharide that contains both types of uronic acids, D-glucuronic and L-iduronic acid. Moreover, we have employed a fluorescence polarization competition assay to evaluate the interactions between the synthesized oligosaccharides and FGF-2 (basic fibroblast growth factor). Our results show that this method, using standard instrumentation and minimal sample consumption, is a powerful tool for the rapid analysis of the glycosaminoglycan affinity for proteins in solution.

Aromatic interactions with naphthylalanine in a ß-hairpin peptide.

Stable peptides have been explored as epitope mimics for protein-protein and protein-nucleic acid interactions; however, presentation of a regular structure is critical. Aromatic interactions are ubiquitous and are competent at stabilizing a ß-hairpin fold. The greatest stabilization has been reported from pairs of tryptophan side chains. Naphthylalanine residues are often used as tryptophan replacements, but it is not clear if 1-naphthylalanine or 2-naphthylalanine is adequate at replicating the geometry and stability observed with tryptophan aromatic interactions. Herein, a 12-residue peptide has been constructed with laterally disposed aromatic amino acids. A direct comparison is made between tryptophan and other bicyclic, unnatural amino acids. Significant stabilization is gained from all bicyclic amino acids; however, geometric analysis shows that only 1-naphthylalanine adopts a similar edge to face geometry as tryptophan, whereas the 2-naphthylalanine appears most similar to a substituted phenylalanine.

Polyurethane/dermatan sulfate copolymers as hemocompatible, non-biofouling materials.

The range of application of polyurethanes has been limited by their poor hemocompatibility and inability to resist non-specific binding of biomolecules and cells. In this work, a non-adhesive PU-based material was synthesized via the copolymerization of PU with dermatan sulfate. Incorporation of DS into the PU backbone dramatically increased material hydrophilicity and decreased protein adsorption. The in vitro adhesion of several cell types, including platelets, also significantly decreased with increasing DS content. Both the physical and biological properties of the DS contributed to the anti-adhesive properties of the PU/DS copolymer, and this anti-adhesive nature of PU/DS renders this new biomaterial attractive for blood-contacting or non-fouling applications.

Recent chemical and enzymatic approaches to the synthesis of glycosaminoglycan oligosaccharides.

Glycosaminoglycans, highly charged polycarboxylated, polysulfated polysaccharides, are an important class of therapeutic agents and investigational drug candidates. Heparin has been widely used as a clinical anticoagulant for over 60 years. Low molecular weight heparins have begun to displace heparin and recently a synthetic heparin pentasaccharide was approved for clinical use in Europe. In addition to heparin (and the related heparan sulfate glycosaminoglycan), dermatan sulfate, chondroitin sulfate, hyaluronan and their derivatives are all in various stages of clinical evaluation. This review focuses on the chemical and chemoenzymatic synthesis of glycosaminoglycan oligosaccharides. Recent advances in functional group protection chemistry, conversion of D-gluco to L-ido or D-galacto configurations, glycosylation reactions and the preparation and use of novel starting materials in acidic oligosaccharide synthesis are discussed.

Synthesis and biological effects of N-alkylamine-labeled low-molecular-mass dermatan sulfate.

Dermatan sulfate (DS) is a component of connective tissue and catalyzes the heparin cofactor II-mediated inhibition of thrombin. Low-molecular-mass dermatan sulfates (LMMDS) are produced to prolong the antithrombotic activity of this substance. Cleavage of DS by nitrous acid leads to an LMMDS with a terminal 2,5-anhydrotalose (At) group at the reducing end which can react with primary amines. Tyramine (Tyr) was bound to the terminal At of LMMDS using reductive amination. LMMDS-tyr is produced using DS. LMMDS desacetglated were produced using totally deaminated DS. These compounds were employed as a model for the characterization of DS using NMR spectroscopy. The purity of the compounds was checked using capillary electrophoresis. The structure of the products was proven by 1H- and 13C-NMR spectroscopy. LMMDS-Tyr was radiolabeled with 125I for use in a radioimmunoassay. The anti-Xa activity and antithrombin activity of the tyramine-labeled DS are very low. The clotting assays Heptest, aPTT, thrombin time, and ecarin time indicate a highly anticoagulant-active substance. The heparin cofactor II-mediated inhibition of thrombin is similar to the parent compound. LMMDS were labeled "endpoint-attached." They are a new tool to understand the actions of DS in biologic systems.

Low molecular weight dermatan sulfate as an antithrombotic agent. Structure-activity relationship studies.

A structure-activity relationship of low molecular weight dermatan sulfate was undertaken to understand better this new non-heparin, glycosaminoglycan-based antithrombotic agent. A dermatan sulfate prepared from bovine intestinal mucosa [average molecular weight (MWavg) 25,000], and currently in clinical trials as an antithrombotic agent, was used in this study. Dermatan sulfate was partially depolymerized using hydrogen peroxide and copper(II) as catalyst to MWavg 5600 to obtain a low molecular weight dermatan sulfate. This low molecular weight dermatan sulfate was then fractionated by gel permeation chromatography to obtain four subfractions having MWavg 7800, 5500, 4200 and 1950. The dermatan sulfate, low molecular weight dermatan sulfate and its subfractions showed substantially different optical rotations. The 1H-NMR spectroscopic analysis of dermatan sulfate samples showed some differences including increased content of GalpNAc4S6S residues and improved resolution in ring resonances for low molecular weight dermatan sulfate fractions, primarily the result of reduced molecular weight and lowered heterogeneity. Saccharide compositional analysis relied on chondroitin ABC lyase treatment followed by capillary electrophoresis. Polyacrylamide gel-based oligosaccharide mapping was also performed by treating dermatan sulfate samples with chondroitin B, AC and ABC lysases. These analyses showed increased amounts of sulfation as the MWavg decreased. In vitro bioassay showed maximum anti-Xa activity in the 4.2 kDa fraction and maximum heparin cofactor II-mediated anti-IIa activity in the 5.5 kDa fraction. The in vivo antithrombotic activity of these fractions was measured using a modified Wessler stasis thrombosis model. The 4.2 kDa fraction showed greater antithrombotic activity than the other low molecular weight dermatan sulfate fractions, dermatan sulfate, and low molecular weight dermatan sulfate. This enhanced activity may result from several structural features of the 4.2 kDa fraction including: a high content of 4,6- and 2,4-disulfated disaccharide sequences; the requirement of specific chain length; a change in the ratio of iduronic to glucuronic acid; and the presence of chondroitin ABC lyase resistant material.

Influence of the oversulfation method and the degree of sulfation on the anticoagulant properties of dermatan sulfate derivatives.

Six oversulfated dermatan sulfate (DS) derivatives, differing in their tissue origin (porcine skin, bovine and porcine intestinal mucosa), and the oversulfation method of preparation, have been tested for their anticoagulant properties. In the first method, the SO3-trimethylamine complex is added to a DS sodium salt dissolved in formamide while it is added to a DS-benzethonium salt dissolved in dimethyl formamide in the second method. The rate of sulfation of these compounds ranged from 7.8 to 11.5 percent of sulfur on a weight basis, whereas it is 6% and 12% for natural DS and for heparin respectively. The anticoagulant potency was assessed by determining the catalytic effect of each glycosaminoglycan on the inhibition of thrombin added to (i) plasma (ii) purified heparin cofactor II(HC II) or (iii) purified antithrombin III(AT III). The catalytic effect on Factor Xa inhibition in the presence of AT III has also been investigated. The increased sulfation is found to enhance the antithrombin activity of the native dermatan sulfate whatever the method used, while the Factor Xa inhibition by AT III could be catalysed only by the most sulfated derivative obtained by the second method. The two derivatives which were less oversulfated, by the first oversulfation method, exhibit equal or even higher catalytic effects on thrombin inhibition when compared to the four other derivatives. The use of the first oversulfation method provides slightly oversulfated derivatives which exhibit strong anticoagulant properties and may constitute effective antithrombotic drugs with no bleeding tendency, a side effect perhaps related to a high rate of sulfation.

Synthesis of disaccharide fragments of dermatan sulfate.

Condensation of crystalline methyl 2-azido-4,6-O-benzylidene-2-deoxy-beta-D-galactopyranoside with methyl (2,3,4-tri-O-acetyl-alpha-L-idopyranosyl bromide)uronate in dichloromethane, in the presence of silver triflate and molecular sieve, provided 54% of methyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-alpha-L-idopyranosyluronate)-beta-D-galactopyranoside . The use of methyl (2,3,4-tri-O-acetyl-alpha-L-idopyranosyl trichloroacetimidate)uronate as glycosyl donor, in the presence of trimethylsilyl triflate, improved the yield to 68%. Regioselective opening of the benzylidene group with sodium cyanoborohydride followed successively by O-sulfation with the sulfur trioxide-trimethylamine complex, saponification, catalytic hydrogenolysis and selective N-acetylation gave the disodium salt of methyl 2-acetamido-2-deoxy-3-O-(alpha-L-idopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside. Condensation of methyl 2-azido-4,6-O-benzylidene-2-deoxy-beta-D-galactopyranoside with methyl (2,3,4-tri-O-acetyl-alpha-D-glucopyranosyl bromide)uronate in dichloromethane, in the presence of silver triflate and molecular sieve, gave methyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-beta-D-glucopyranosyluronate)-beta-D-galactopryano side in 85% yield. The sequence already described then gave the disodium salt of methyl 2-acetamido-2-deoxy-3-O-(beta-D-glucopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside.

[Synthesis of xylose-containing glycopeptides that contain the amino acid sequence 4 bis 7 des NH2-terminus of the protein core structure of cattle skin proteodermatan sulfates]. / Synthese eines Xylose-haltigen Glycopeptides, das die Aminosäure-Sequenz 4 bis 7 des NH2-terminus der Protein-Core-Struktur des Rinderhaut-Proteodermatan-Sulfats enthalt.

The synthesis is described of alpha-beta-D-xylopyranosyl-L-serylglycyl-L-isoleucyl-glycine (7), a glycopeptide containing the amino acid sequence of the protein core-structure of beef-skin proteodermatan sulfate; coupling of N-protected O-XylpSer with protected GlyIleuGly followed by deprotection afforded 7.