Essential hyaluronan structure for binding with hyaluronan-binding protein (HABP) determined by glycotechnological approach.

Hyaluronan specifically binds to aggrecan globular domain 1, which is often referred to as just hyaluronan binding protein (HABP), however, the hyaluronan carbohydrate structure recognized by HABP had not been studied in detail. The aim of the present study was to investigate the important structure of hyaluronan for binding to HABP. We prepared hybrid oligosaccharides from hyaluronan and chondroitin, with or without modification of the reducing or non-reducing terminus, as tools to determine the preferred structure of hyaluronan for binding to the HABP by a competitive ELISA-like method. The non-reducing terminal structure was critical, especially, the glucuronic acid (GlcUA) and N-acetylglucosamine (GlcNAc) of the hyaluronan-unit are essential for complete HABP binding activity, and for any HABP binding activity, respectively. It is possible to replace GlcUAß-1-3GlcNAc of the internal disaccharide units with GlcUAß-1-3N-acetylgalactosamine (GalNAc), if the chain length is decasaccharide or larger.

4-Methylumbelliferone Decreases the Hyaluronan-rich Extracellular Matrix and Increases the Effectiveness of 5-Fluorouracil.

BACKGROUND/AIM: Pancreatic cancer responds poorly to most chemotherapeutic agents. Several studies have reported that hyaluronan (HA)-rich extracellular matrix (ECM) is a biological barrier against chemotherapeutic agents. 4-methylumbelliforone (MU) led to inhibition of HA synthesis and its preservation in ECM, which may enhance 5-fluorouracil (5-FU) cytotoxicity. Thus, new therapy with MU and 5-FU may be developed for pancreatic cancer. MATERIALS AND METHODS: A 5-fluorouracil (5-FU) concentration and 4-methylumbelliferone (MU) dosage was analyzed by high-performance liquid chromatography (HPLC). Change in antitumor efficacy of 5-FU in combination with MU was also examined in vivo and in vitro. RESULTS: Combined 5-FU and MU treatment inhibited cell proliferation better than 5-FU alone; 0.01 mM 5-FU alone decreased cell proliferation by 37.7 %, while 0.01 mM 5-FU with 0.5 mM MU decreased cell proliferation by 57.4%. MU enhanced the intracellular concentration of 5-FU by 47.3% compared to control. Mice tumors treated with 5-FU and MU decreased in size and animal survival was prolonged. Moreover, MU decreased cohesiveness of the intercellular space. CONCLUSION: Combination therapy of 5-FU with MU was effective. A novel therapy can be designed for pancreatic cancer by using ECM modulation.

Antitumor effects of the hyaluronan inhibitor 4-methylumbelliferone on pancreatic cancer.

Hyaluronan (HA) is a major component of the extracellular matrix (ECM), and influences tumor invasion and metastasis. In a previous study, the present authors reported for the first time that 4-methylumbelliferone (MU) inhibited HA synthesis and suppressed tumor growth. However, the localization of HA and the changes in ECM morphology caused by MU in pancreatic cancer remain to be examined in detail. In the present study, the cytotoxicity of MU and its effect on cellular proliferation was evaluated in the human pancreatic cancer cell line MIA PaCa-2. The amount of HA synthesized and the retention of HA around the cells were quantitatively and immunohistochemically analyzed in vitro and in vivo. Structural changes in the ECM in the tumor tissue were investigated using an electron microscope. MU treatment led to a decrease in extracellular HA retention, as evidenced by a particle exclusion assay and immunohistochemical staining. Cell proliferation was suppressed by MU in a dose-dependent manner. The release of lactate dehydrogenase into the culture medium due to damage to the cellular membrane did not increase following MU administration. In tumor-inoculated mice, MU suppressed any increase in tumor volume and decreased the quantity of HA. Electron microscopy revealed that MU attenuated the intercellular space and caused it to be less cohesive. These data indicate that MU inhibits HA synthesis and reduces the amount of HA in the ECM while exhibiting no obvious cytotoxic effect. These findings suggest that MU has potential as a novel therapeutic agent for pancreatic cancer.

Preparation of proteoglycan from salmon nasal cartilage under nondenaturing conditions.

Salmon nasal cartilage was micronized in ethanol using a rotor-stator homogenizer for the high yield of proteoglycan extraction. This procedure also brought about depressing the degradation of proteoglycan and the contamination of collagens. Proteoglycan was extracted by 4 M magnesium chloride and isolated by anion-exchange chromatography. The gel filtration HPLC and the antibody reactivity showed that the core protein was intact.

Inhibitory effect of chondroitin sulfate oligosaccharides on bovine testicular hyaluronidase.

Hyaluronan and chondroitin sulfates are prominent components of the extracellular matrices of animal tissues; however, their functions in relation to their oligosaccharide structures have not yet been fully elucidated. The oligosaccharides of hyaluronan and chondroitin sulfate were prepared and used to investigate their effects on the hydrolysis and transglycosylation reactions of bovine testicular hyaluronidase when hyaluronan was used as a substrate. Hydrolysis and transglycosylation activities were assessed in independent reaction systems by analyzing the products by HPLC. The hydrolysis and transglycosylation reactions of bovine testicular hyaluronidase were dose-dependently inhibited by chondroitin sulfate oligosaccharides, but not by hyaluronan or chondroitin oligosaccharides. A kinetic analysis of the hydrolysis reaction using hyaluronan octasaccharide revealed that the inhibition mode by chondroitin sulfate oligosaccharides was competitive.

Chondroitin sulfate cluster of epiphycan from salmon nasal cartilage defines binding specificity to collagens.

Epiphycan (EPY) from salmon nasal cartilage has a glycosaminoglycan (GAG) domain that is heavily modified by chondroitin 4-sulfate and chondroitin 6-sulfate. The functional role of the GAG domain has not been investigated. The interaction of EPY with collagen was examined in vitro using surface plasmon resonance analysis. EPY was found to bind to type I collagen via clustered chondroitin sulfate (CS), while a single chain of CS was unable to bind. Types I, III, VII, VIII and X collagen showed high binding affinity with EPY, whereas types II, IV, V, VI and IX showed low binding affinities. Chemical modification of lysine residues in collagen decreased the affinity with the clustered CS. These results suggest that lysine residues of collagen are involved in the interaction with the clustered CS, and the difference in lysine modification defines the binding affinity to EPY. The clustered CS was also involved in an inter-saccharide interaction, and formed self-associated EPY. CS of EPY promoted fibril formation of type I collagen.

One set system for the synthesis and purification of glycosaminoglycan oligosaccharides reconstructed using a hyaluronidase-immobilized column.

Using the transglycosylation reaction as a reverse reaction for the hydrolysis of hyaluronidase, new artificial oligosaccharides may be synthesized by reconstructing natural glycosaminoglycans (GAGs) according to preliminary planned arrangements. However, as some problems have been associated with the method, including the low yields of reaction products and complicated processes of separation and purification, improvements in this method were investigated. Transglycosylation reactions were carried out using bovine testicular hyaluronidase-immobilized resin packed in a column. For the transglycosylation reaction, pyridylaminated (PA) GAG hexasaccharides, which were the minimum size for hydrolysis sensitivity and the transglycosylation reaction, were used as acceptors, whereas large size GAGs were used as donors. The reaction mixture was pooled after incubation in the hyaluronidase-immobilized resin column and was then introduced into continuously joined HPLC columns constructed from three steps: the first step of ion-exchange HPLC for concentrating newly synthesized GAG oligosaccharides as reaction products, the second step of reverse phase HPLC for separating PA oligosaccharides from non-PA oligosaccharides, and the third step of size fractionation HPLC for fractionating newly synthesized oligosaccharides. Newly synthesized oligosaccharides were obtained by one complete cycle of the transglycosylation reaction and separation.

Epiphycan from salmon nasal cartilage is a novel type of large leucine-rich proteoglycan.

Chum salmon (Oncorhynchus keta) nasal cartilage was examined by next-generation DNA sequencing and mass spectrometric analyses, and 14 types of proteoglycans including epiphycan (EPY) were found. A cDNA encoding EPY was cloned and sequenced. The cDNA encoded 589 amino acids comprised a glycosaminoglycan (GAG) domain containing 55 potential GAG-modified sites (Ser-Gly and/or Gly-Ser), a cysteine cluster and 6 leucine-rich repeats. EPY was purified from salmon nasal cartilage and the structure of the GAG was characterized. As a result of unsaturated disaccharide analysis, GAG was found to be composed of chondroitin 6-sulfate (58.0%), chondroitin 4-sulfate (26.5%) and non-sulfated chondroitin (15.3%). The average molecular weight of GAG was estimated to be 3.0 × 10(4). Ser-100 and Ser-103 were identified as serine residues substituted by GAG chains by chemical modification and mass spectrometric analysis. More than 50 serine residues were assumed to be substituted by GAG chains. EPY is heavily substituted by chondroitin sulfate, giving an overall molecular weight of just under 2 × 10(6). EPY from salmon nasal cartilage is a novel type of large leucine-rich proteoglycan.

Synthesis of neoproteoglycans using the transglycosylation reaction as a reverse reaction of endo-glycosidases.

A method for the synthesis of carbohydrate chains (glycosaminoglycans) and their coupling to peptides was investigated using proteoglycans. Glycosidases generally catalyze a hydrolytic reaction, but can also mediate the reverse reaction, which in this case is a transglycosylation. In the transglycosylation reaction of bovine testicular hyaluronidase, which is an endoglycosidase, glycosaminoglycans (hyaluronan and chondroitin sulfates) release disaccharide (uronic acid-N-acetylhexosamine) moieties from non-reducing terminal sites, and then the liberated disaccharides are transferred immediately to the non-reducing termini of other glycosaminoglycan chains. Using such continuous reactions, it is possible to synthesize glycosaminoglycan chains according to a specific design. It then becomes possible to transfer glycosaminoglycan chains synthesized on a peptide to other peptides using the transglycosylation reaction of endo-ß-xylosidase acting on the linkage region between a peptide and glycosaminoglycan chains of proteoglycans. We believe this approach will open a new field for the synthesis of homogeneous proteoglycans or their corresponding analogues.

Hyaluronan-chondroitin hybrid oligosaccharides as new life science research tools.

Hyaluronan and chondroitin are glycosaminoglycans well-known as components of pharmaceutical agents and health foods. From these attractive molecules, using transglycosylation reaction of testicular hyaluronidase, we synthesized hybrid neo-oligosaccharides not found in nature. We also found a new site between the chondroitin disaccharide unit and hyaluronan disaccharide unit recognized by a hyaluronan lyase specific to hyaluronan using these hybrid oligosaccharides as substrates. We hope that these hybrid oligosaccharides will help to elucidate the involvement of hyaluronan, chondroitin, and chondroitin sulfates in the mechanisms of cell functions and diseases, based on the structures of these glycosaminoglycans.

Effects of divalent cations on bovine testicular hyaluronidase catalyzed transglycosylation of chondroitin sulfates.

Glycosaminoglycans were prepared as salts of different divalent cations and tested as donors in bovine testicular hyaluronidase catalyzed transglycosylation reactions. All of the metal cations examined had similar binding efficiency of divalent cations to hyaluronan. However, cations bound with different efficiencies to chondroitin sulfate species and the differences were marked in the case of chondroitin 6-sulfate; the numbers of cations bound per disaccharide unit were estimated to be 0.075 for Mn, 1.231 for Ba, 0.144 for Zn, and 0.395 for Cu. While barium salt of chondroitin sulfates enhanced transglycosylation, the zinc salt of chondroitin sulfates inhibited transglycosylation. Therefore, by selecting the proper divalent cation salt of chondroitin sulfates as a donor in the transglycosylation reaction it is possible to improve the yields of the products.

Identification of proteoglycan from salmon nasal cartilage.

There has been no structural information about the core protein of salmon nasal cartilage proteoglycan although its physiological activities have been investigated. Internal amino acid sequencing using nano-LC/MS/MS revealed that the salmon proteoglycan was aggrecan. Primer walk sequencing based on the amino acid information determined that the salmon aggrecan cDNA is comprised of 4207bp nucleotides predicted to encode 1324 amino acids with a molecular mass of 143,276. It exhibited significant similarities to predicted pufferfish aggrecan, zebrafish similar to aggrecan, zebrafish aggrecan, bovine aggrecan and human aggrecan isoform 2 precursor; whose amino acid identities were 56%, 55%, 49%, 31% and 30%, respectively. Salmon cartilage aggrecan had globular domains G1, G2 and G3 as in mammalian aggrecans. Neither the putative keratan sulfate attachment domain enriched with serine, glutamic acid and proline, nor the putative chondroitin sulfate attachment domain with repeating amino acid sequence containing serine-glycine, found in mammalian aggrecans were observed in salmon, however, random serine-glycine (or glycine-serine) sequences predicted to the sugar chain attachment sites were observed. Based on cDNA analysis and amino acid analysis after ß-elimination, the ratio of serine attached to sugar chains was calculated to be approximately 37.7% of total serine, that is, 46 of 123 serine residues.

Mechanism for the hydrolysis of hyaluronan oligosaccharides by bovine testicular hyaluronidase.

Synthetic hyaluronan oligosaccharides with defined structures and their pyridylaminated derivatives were used to investigate the mechanism of hydrolysis of hyaluronan by bovine testicular hyaluronidase. The products of the hydrolysis were analyzed by HPLC and ion-spray mass spectroscopy (MS). It was confirmed that the minimum substrate for bovine testicular hyaluronidase is the hyaluronan hexasaccharide, even though it is a poor substrate that is barely cleaved, even on prolonged incubation. When hyaluronan octasaccharide was the substrate, increasing amounts of tetrasaccharide and hexasaccharide were produced with increasing time of incubation. Whereas disaccharide was not detectable in the reaction mixture by HPLC, MS analysis revealed trace amounts. The data suggest that the enzyme generates a disaccharide intermediate from hyaluronan oligosaccharide, the majority of which is transferred to the nonreducing ends of other oligosaccharides, only traces being released as free disaccharide. When hyaluronan octasaccharide, with an unsaturated glucuronic acid at the nonreducing end, was used as a substrate, only a tetrasaccharide was detected by HPLC. However, MS showed that the product was a mixture of equal amounts of two tetrasaccharides, one with and the other without the unsaturated glucuronic acid. This suggests that, in the case of substrates with a double bond at the nonreducing end, a tetrasaccharide is cleaved off instead of a disaccharide. The results of the experiments with pyridylaminated oligosaccharides were entirely consistent with these conclusions, and in addition showed the importance of the reducing end of the substrate for the enzyme to recognize the length of the saccharide.

Novel proteoglycan glycotechnology: chemoenzymatic synthesis of chondroitin sulfate-containing molecules and its application.

Proteoglycans consist of a protein core, with one or more glycosaminoglycan chains (i.e., chondroitin sulfate, dermatan sulfate and heparin sulfate) bound covalently to it. The glycosaminoglycan chains account for many of the functions and properties of proteoglycans. The development of proteoglycan glycotechnology to exploit the functionality of glycosaminoglycan chains is an extremely important aspect of glycobiology. Here we describe an efficient and widely applicable method for chemoenzymatic synthesis of conjugate compounds comprising intact long chondroitin sulfate (ChS) chains. An alkyne containing ChS was prepared by an enzymatic transfer reaction and linked with a chemically synthesized core compound containing an azido group using click chemistry. This method enabled highly efficient introduction of ChS into target materials. Furthermore, the ChS-introduced compounds had marked stability against proteolysis, and the chemically linked ChS chain contributed to the stability of these core compounds. We believe the present method will contribute to the development of proteoglycan glycobiology and technology.

Stimulation of small proteoglycan synthesis by the hyaluronan synthesis inhibitor 4-methylumbelliferone in human skin fibroblasts.

Human skin fibroblasts cultured with 4-methylumbelliferone (MU), a hyaluronan synthesis inhibitor, produce a hyaluronan-deficient extracellular matrix (See [9]). Our present study investigated the effects of MU on proteoglycan, which is the other main component of the extracellular matrix, and interacts with hyaluronan. Proteoglycans isolated from culture medium in the presence or absence of MU were characterized by gel-filtration chromatography, ion-exchange HPLC, electrophoresis, and immunoblotting. We found that MU had only a negligible effect on the synthesis of large proteoglycan but increased the production of small proteoglycan in comparison with cultures lacking MU. This small proteoglycan was identified by immunoblotting as decorin. The structures of decorin synthesized in the presence and absence of MU were compared by gel-filtration chromatography, and the data indicated that cells incubated with MU produced a larger decorin molecule than cells incubated without MU. Furthermore, the two decorins had galactosaminoglycan chains of different sizes. These results suggest that MU inhibits the synthesis of hyaluronan and accelerates production of the larger decorin in the extracellular matrix.

Novel products in hyaluronan digested by bovine testicular hyaluronidase.

When the products of hyaluronan (HA) digested by bovine testicular hyaluronidase (BTH) were analyzed by high-performance liquid chromatography (HPLC), minor peaks were detected just before the main even-numbered oligosaccharide peaks. The amount of each minor peak was dependent on the reaction conditions for transglycosylation, rather than hydrolysis, by the BTH. Mainly based on HPLC and MS analysis, each minor peak was found to correspond to its oligosaccharide with one N-acetyl group removed from the reducing terminal N-acetylglucosamine. Enzymatic studies showed that the N-deacetylation activity was closely related to reaction temperature, pH, and the concentration of NaCl contained in the buffer, and glycosaminoglycan types and chain lengths of substrates. These findings strongly suggest that the N-deacetylation reaction in minor peaks was due to a novel enzyme contaminant in the BTH, N-deacetylase, that carries out N-deacetylation at the reducing terminal N-acetylglucosamine of oligosaccharides and is dependent on HA hydrolysis by BTH.

Interaction between proteoglycans and alpha-elastin in construction of extracellular matrix of human yellow ligament.

One type of large proteoglycan and three types of small proteoglycans (decorin, decorin-subtype, and biglycan) were purified by chromatography, and alpha-elastin was isolated by alkali treatment from human yellow ligaments taken at the time of operation. The interaction of the proteoglycans with immobilized alpha-elastin on a sensor was analyzed by surface plasmon resonance, and we confirmed that each of the small proteoglycans exhibited a specific binding to alpha-elastin. The binding sites of small proteoglycans were contained in the protein cores. In addition, the differences in the interaction of the small proteoglycans with alpha-elastin of normal and ossified ligaments were compared. The interactions of the small proteoglycans with alpha-elastin of the ossified ligaments were lower than those with alpha-elastin of the normal ligaments. In the ossified ligaments, neodesmosine, one of the cross-linking amino acids, was significantly less than in the normal ligaments (p < .05).

A hyaluronan synthase suppressor, 4-methylumbelliferone, inhibits liver metastasis of melanoma cells.

4-Methylumbelliferone (MU) inhibits the cell surface hyaluronan (HA) formation, and that such inhibition results in suppression of adhesion and locomotion of cultured melanoma cells. Here, we examine the effect of MU on melanoma cell metastasis in vivo. MU-treated melanoma cells showed both decreased cell surface HA formation and suppression of liver metastasis after injection into the mice. Oral administration of MU to mice decreased tissue HA content. These HA knock-down mice displayed suppressed liver metastasis. Thus, both cell surface HA of melanoma cells and recipient liver HA can promote liver metastasis, indicating that MU has potential as an anti-metastatic agent.

Effect of a hyaluronan synthase suppressor, 4-methylumbelliferone, on B16F-10 melanoma cell adhesion and locomotion.

Hyaluronan (HA) is a ubiquitous, major component of the extracellular matrix. It is involved in cell adhesion and locomotion, and hence in tumor metastasis. We have previously reported that 4-methylumbelliferone (MU) inhibits HA synthesis and may be a useful tool for examining the functions of HA. We here demonstrate that the formation of cell surface HA by melanoma cells and its release into the culture medium are inhibited by MU. Adhesion and locomotion assays revealed that the adhesion and locomotion of melanoma cells were dose-dependently inhibited by MU. Conversely, treatment with exogenous HA enhanced both adhesion and locomotion. Thus, preventing the formation of cell surface HA reduced both the adhesion and locomotion of melanoma cells, suggesting that MU may act as an inhibitor of tumor metastasis.

A novel mechanism for the inhibition of hyaluronan biosynthesis by 4-methylumbelliferone.

Specific inhibitors of hyaluronan (HA) biosynthesis can be valuable therapeutic agents to prevent cancer invasion and metastasis. We have found previously that 4-methylumbelliferone (MU) inhibits HA synthesis in human skin fibroblasts and in group C Streptococcus. In this paper, the inhibition mechanism in mammalian cells was investigated using rat 3Y1 fibroblasts stably expressing HA synthase (HAS) 2. Exposure of the transfectants to the inhibitor resulted in significant reduction of HA biosynthesis and matrix formation. The evaluation of HAS transcripts and analysis of cell-free HA synthesis demonstrated the post-transcriptional suppression of HAS activity by MU. Most interesting, the post-transcriptional suppression of HAS activity was also observed using p-nitrophenol, a well known substrate for UDP-glucuronyltransferases (UGT). We investigated whether the inhibition was exerted by the glucuronidation of MU using both high pressure liquid chromatography and TLC analyses. The production of MU-glucuronic acid (GlcUA) was consistent with the inhibition of HA synthesis in HAS transfectants. MU-GlcUA was also detected at a similar level in control cells, suggesting that the glucuronidation was mediated by an endogenous UGT. Elevated levels of UGT significantly enhanced the inhibitory effects of MU. In contrast, the inhibition by MU was diminished to the control level when an excess of UDP-GlcUA was added to the cell-free HA synthesis system. We propose a novel mechanism for the MU-mediated inhibition of HA synthesis involving the glucuronidation of MU by endogenous UGT resulting in a depletion of UDP-GlcUA.