Is hyaluronan deposition in the stroma of pancreatic ductal adenocarcinoma of prognostic significance?

Background

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis and the number of PDAC-related deaths is rising. Recently the tumour stroma and in particular one of its main components, hyaluronan (HA), have attracted considerable attention as intravenous hyaluronidase treatment together with conventional chemotherapy considerably prolonged survival in HA-rich PDA patients. We therefore wanted to investigate the prognostic significance of HA deposition in PDA using both antibodies to HA and hyaluronan binding protein (HABP).

Material and methods

Tissue microarrays of PDAs of 184 patients and pancreatic xenografts tumours were immunohistochemically (IHC) stained for HA using either biotinylated hyaluronic acid binding protein (HABP) or anti-HA antibody.

Results

The pattern of staining with HABP differed significantly from that with antibody IHC. Antibody staining was found both within cancer cells and in the extracellular matrix and staining could not be eliminated by hyaluronidase predigestion of the tissue sections. In contrast, HABP staining was generally confined to the extracellular matrix and was completely abolished by hyaluronidase pretreatment. HA positivity as determined by HABP was associated with larger primary tumours (p = 0.046). There were no correlations between overall survival, disease-free survival and HA expression.

Conclusion

Presence of HA alone is not of prognostic importance in PDAC, and IHC with utilization of antibody detection shows no reliable staining pattern and should not be applied for HA IHC.

Positive side effects of Ca antagonists for osteoarthritic joints-results of an in vivo pilot study

Background

We have shown previously that some calcium antagonists inhibit hyaluronan export, loss of proteoglycans, and degradation of collagen from osteoarthritic cartilage. Clinically approved calcium antagonists normally are prescribed for cardiac arrhythmia. In the present study, we compared the effect of these drugs on osteoarthritic patients which had received no medication and patients which were also diagnosed for cardiac arrhythmias and were treated with calcium antagonists. The effects and the side effects of the used drugs were analyzed.

Method

We used the Lequesne questionnaire to examine patients with osteoarthritis (212 patients, control group receiving no calcium antagonists) and patients with cardiac arrhythmia and osteoarthritis (188 patients treated with various calcium antagonists). The answers of the questionnaires were transformed into the Lequesne scoring system quantifying the severity of the disease. The Lequesne score is a standardized questionnaire focused on osteoarthritis. It is a 24-scale questionary in which low scores indicate low functional activity.

Results

The data showed that the mean score of the control group (6.2) was higher than the treated group (5.2), the drugs differed in their efficiency. Verapamil had a slightly worse score and Azupamil, Escor, Felodipine, and Nifedipine showed no alteration. Adalat, Amlodipine, Carmen, Nitrendipin, and Norvasc lead to an improvement.

Conclusion

These results suggest that inhibition of hyaluronan export may have a beneficial effect on human osteoarthritis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13018-014-0138-8) contains supplementary material, which is available to authorized users.

Curcumin analogue identified as hyaluronan export inhibitor by virtual docking to the ABC transporter MRP5

Hyaluronan is overproduced in many diseases including metastasis, inflammation or ischemia, but there is no drug to attenuate hyaluronan production. Hyaluronan is exported from fibroblasts by the multidrug resistance associated protein 5 (MRP5) which is inhibited by the plant phenols curcumin or xanthohumol. We performed virtual docking and chemical synthesis of analogues to optimize the inhibitors. The AutoDock software was used to identify the binding cavity within the open conformation of MRP5. Inhibitory plant phenols bound to the ATP binding site between the two nucleotide binding domains NBD1 and NBD2. This binding cavity was chosen to screen about 120 derivatives and analogues. The superior hyaluronan export inhibitor was 1,5-bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadien-3-one (hylin). It inhibited hyaluronan export from fibroblasts with an IC50 of 4.9 μM. Hylin is a minor component in natural curcumin preparations and has previously been described as anti-metastatic and anti-inflammatory. Since curcumin itself is unstable under physiological conditions, the active component for many cell biological and pharmaceutical effects of natural curcumin preparations could be hylin that acts by hyaluronan export inhibition.

Recovery of ΔF508-CFTR function by analogs of hyaluronan disaccharide

We recently discovered that hyaluronan was exported from fibroblasts by MRP5 and from epithelial cells by cystic fibrosis (CF) transmembrane conductance regulator (CFTR) that was known as a chloride channel. On this basis we developed membrane permeable analogs of hyaluronan disaccharide as new class of compounds to modify their efflux. We found substances that activated hyaluronan export from human breast cancer cells. The most active compound 2-(2-acetamido-3,5-dihydroxyphenoxy)-5-aminobenzoic acid (Hylout4) was tested for its influence on the activity of epithelial cells. It activated the ion efflux by normal and defective ΔF508-CFTR. It also enhanced the plasma membrane concentration of the ΔF508-CFTR protein and reduced the transepithelial resistance of epithelial cells. In human trials of healthy persons, it caused an opening of CFTR in the nasal epithelium. Thus compound Hylout4 is a corrector that recovered ΔF508-CFTR from intracellular degradation and activated its export function.

Regulation of cell volume by glycosaminoglycans

Cell volume is regulated by a delicate balance between ion distribution across the plasma membrane and the osmotic properties of intra- and extracellular components. Using a fluorescent calcein indicator, we analysed the effects of glycosaminoglycans on the cell volume of hyaluronan producing fibroblasts and hyaluronan deficient HEK cells over a time period of 30 h. Exogenous glycosaminoglycans induced cell blebbing after 2 min and swelling of fibroblasts to about 110% of untreated cell volume at low concentrations which decreased at higher concentrations. HEK cells did not show cell blebbing and responded by shrinking to 65% of untreated cell volume. Heparin induced swelling of both fibroblasts and HEK cells. Hyaluronidase treatment or inhibition of hyaluronan export led to cell shrinkage indicating that the hyaluronan coat maintained fibroblasts in a swollen state. These observations were explained by the combined action of the Donnan effect and molecular crowding.

Hyaluronan export through plasma membranes depends on concurrent K+ efflux by K(ir) channels

Hyaluronan is synthesized within the cytoplasm and exported into the extracellular matrix through the cell membrane of fibroblasts by the MRP5 transporter. In order to meet the law of electroneutrality, a cation is required to neutralize the emerging negative hyaluronan charges. As we previously observed an inhibiting of hyaluronan export by inhibitors of K⁺ channels, hyaluronan export was now analysed by simultaneously measuring membrane potential in the presence of drugs. This was done by both hyaluronan import into inside-out vesicles and by inhibition with antisense siRNA. Hyaluronan export from fibroblast was particularly inhibited by glibenclamide, ropivacain and BaCl₂ which all belong to ATP-sensitive inwardly-rectifying K_ir channel inhibitors. Import of hyaluronan into vesicles was activated by 150 mM KCl and this activation was abolished by ATP. siRNA for the K⁺ channels K_ir3.4 and K_ir6.2 inhibited hyaluronan export. Collectively, these results indicated that hyaluronan export depends on concurrent K⁺ efflux.

Hyaluronan in intra-operative edema of NF1-associated neurofibromas

The tumor suppressor disorder neurofibromatosis type 1 (NF1) is associated with development of multiple neurofibromas which may grow intraneurally as plexiform neurofibromas (PNF) or intracutaneously (CNF). Upon surgery neurofibromas may show prominent swelling hindering skin-edge approximation. To assess whether the water binding glycosaminoglycan hyaluronan is involved in intra-operative swelling, 51 neurofibromas from 33 NF1-patients were investigated. Hyaluronan was histologically demonstrated and was quantified by ELISA. Molecular weight of hyaluronan was determined by gel filtration. Further, hyaluronan content was measured in cultivated Schwann cells and fibroblasts. Clinically, 67% of PNF were associated with moderate or severe intra-operative swelling, whereas only 36% of CNF showed this feature. Significantly higher levels of hyaluronan content were found in PNF compared to CNF (P < 0.05). Mast cell density did not correlate with any of the parameters. Molecular weight of hyaluronan in PNF and CNF ranged from higher than 10⁶ Da to approximately 10⁵ Da. Fibroblasts produced less hyaluronan than Schwann cells. The findings support the view that hyaluronan plays an important role in intra-operative swelling in neurofibroma surgery.

Depolarization of the membrane potential by hyaluronan

The membrane potential is mainly maintained by the K(+) concentration gradient across the cell membrane between the cytosol and the extracellular matrix. Here, we show that extracellular addition of high-molecular weight hyaluronan depolarized the membrane potential of human fibroblasts, human embryonic kidney cells (HEK), and central nervous system neurons in a concentration-dependent manner, whereas digestion of cell surface hyaluronan by hyaluronidase caused hyperpolarization. This effect could not be achieved by other glycosaminoglycans or hyaluronan oligosaccharides, chondroitin sulfate, and heparin which did not affect the membrane potential. Mixtures of high-molecular weight hyaluronan and bovine serum albumin had a larger depolarization effect than expected as the sum of both individual components. The different behavior of high-molecular weight hyaluronan versus hyaluronan oligosaccharides and other glycosaminoglycans can be explained by a Donnan effect combined with a steric exclusion of other molecules from the water solvated chains of high-molecular weight hyaluronan. Depolarization of the plasma membrane by hyaluronan represents an additional pathway of signal transduction to the classical CD44 signal transduction pathway, which links the extracellular matrix to intracellular metabolism.

Inhibitors of hyaluronan export from hops prevent osteoarthritic reactions

SCOPE

An early reaction in osteoarthritic chondrocytes is hyaluronan overproduction followed by proteoglycan loss and collagen degradation. We recently found that hyaluronan is exported by the ATP-binding cassette transporter multidrug resistance associated protein 5 (MRP5) in competition with cGMP and that some phosphodiesterase 5 inhibitors also inhibited hyaluronan export. These inhibitors also prevented osteoarthritic reactions in cartilage. In an effort to identify the improved inhibitors directed primarily toward MRP5, we analyzed the flavonoids.

METHODS AND RESULTS

Prenylflavonoids from hop xanthohumol, isoxanthohumol and 8-prenylnaringenin inhibited MRP5 export at lower concentrations than phosphodiesterase 5 activity. They were analyzed for their effect on IL-induced osteoarthritic reactions in bovine chondrocytes. Xanthohumol was the superior compound to inhibit hyaluronan export, as well as proteoglycan and collagen loss. It also prevented the shedding of metalloproteases into the culture medium. It directly inhibited MRP5, because it reduced the export of the MRP5 substrate fluorescein immediately and did not influence the hyaluronan synthase activity.

CONCLUSIONS

Xanthohumol may be a natural compound to prevent hyaluronan overproduction and subsequent reactions in osteoarthritis.

Cystic fibrosis transmembrane conductance regulator can export hyaluronan

OBJECTIVES

Hyaluronan, a major water binding component of the extracellular matrix, is synthesised within the cytosol and exported across the plasma membrane by the ABC-transporter MRP5 in fibroblasts. Although its synthesis is vital for embryogenesis, MRP5-deficient mice are without phenotype, suggesting that another transporter had substituted for the MRP5 protein. Thus, we searched for a compensatory exporter in fibroblasts from MRP5 deficient mice and found that cystic fibrosis transmembrane conductance regulator (CFTR) mRNA was upregulated.

METHODS

Hyaluronan export was measured in cell culture. The CFTR transporter was knocked out using si-RNA. Blockers of the ABC-transporter family were used to ascertain the hyaluronan transport capabilities functionally.

RESULTS

CFTR specific siRNA inhibited hyaluronan export. The tetrasaccharide was exported in undegraded form only from normal human epithelial cells and not from human epithelial cells carrying DeltaF508 CFTR. The CFTR inhibitors GlyH-101 and CFTR(172) reduced hyaluronan export from CFTR-expressing mouse fibroblasts and from human breast cancer cell lines. Bronchial secretions from patients with cystic fibrosis that consist mainly of necrotic epithelia contained at least 40-fold higher concentration of hyaluronan than secretions from patients with acute bronchitis.

CONCLUSIONS

CFTR transports hyaluronan across the plasma membrane of epithelial cells and this transport mechanism is defective in cystic fibrosis patients.

Identification and regulation of the eukaryotic hyaluronate synthase

Hyaluronate synthesis is required for fibroblast detachment in mitosis and migration. It is regulated by the activity of the synthase which is localized at the inner side of plasma membranes. The synthase was identified as a 50 kDa protein by immunological cross-reaction with the streptococcal enzyme and by affinity labelling. Transformation of fibroblasts by Rous sarcoma virus activated the synthase by enhanced transcription and phosphorylation. The synthase was a natural target of pp60v-src kinase.

Hyaluronan export by the ABC transporter MRP5 and its modulation by intracellular cGMP

Hyaluronan must be exported from its site of synthesis, the inner side of plasma membrane, to the extracellular matrix. Here, we identified the multidrug-associated protein MRP5 as the principle hyaluronan exporter from fibroblasts. The expression of the MRP5 (ABC-C5) transporter was silenced in fibroblasts using RNA interference, and a dose-dependent inhibition of hyaluronan export was observed. Hyaluronan oligosaccharides introduced into the cytosol competed with the export of endogenously labeled hyaluronan and the MRP5 substrate fluorescein. Because cGMP is a physiological substrate of MRP5, the intracellular concentrations of cGMP were modulated by the drugs 3-isobutyl-1-methylxanthin, propentofyllin, L-NAME, zaprinast, and bromo-cGMP, and the effects on hyaluronan export were analyzed. Increasing the cGMP levels inhibited hyaluronan export and decreasing it afforded higher concentrations of zaprinast to inhibit the export. Thus, cGMP may be a physiological regulator of hyaluronan export at the level of the export MRP5.

Biosynthesis of hyaluronan: direction of chain elongation

The mechanism of hyaluronan biosynthesis in vertebrates had been proposed to occur at the reducing end of growing chains. This mechanism was questioned because a recombinant synthase appeared to add new monosaccharides to the non-reducing end. I reinvestigated this problem with membranes from the eukaryotic B6 cell line. The membranes were incubated with UDP-[3H]GlcNAc and UDP-[14C]GlcA to yield differentially labelled reducing terminal and non-reducing terminal domains. Digestion of the product with a mixture of the exoglycosidases beta-glucuronidase and beta-N-acetylglucosaminidase truncated the hyaluronan chain strictly from the non-reducing end. The change in 3H/14C ratio of the remaining hyaluronan fraction, during the course of exoglycosidase digestion, confirmed the original results that the native eukaryotic synthase extended hyaluronan at the reducing end. This mechanism demands that the UDP-hyaluronan terminus is bound to the active site within the synthase and should compete with the substrates for binding. Accordingly, increasing substrate concentrations enhanced hyaluronan release from the synthase. A model is proposed that explains the direction of chain elongation at the reducing end by the native synthase and at the non-reducing end by the recombinant synthase based on a loss of binding affinity of the synthase towards the growing UDP-hyaluronan chain.

Hyaluronate and its receptors in bone marrow

Cell-cell and cell-matrix interactions, which are mediated by cell adhesion molecules, play a fundamental role during many cellular processes including growth, differentiation, cell migration and cancer metastasis. One molecule playing a major role in these processes is the CD44 surface receptor, which is expressed in a wide range of cells including many cells of the hemopoietic system, where it mediates the interaction with its major ligand, hyaluronate. However, little is known about CD44 and hyaluronate in bone marrow and this was investigated immunohistochemically in trephine biopsies and in cultivated human bone marrow stromal cells. In biopsy specimens, patches of hyaluronate deposition were detected in the extracellular matrix (ECM). However, most of the areas of the ECM were devoid of hyaluronate. Single mast cells and lymphocytes scattered throughout the marrow were CD44 immunopositive. Marrow-derived stromal cells (MDSC) expanded in cell culture were immunopositive for CD44, hyaluronate synthase, and hyaluronate. Hence, a marked difference between CD44 immunolocalisation and hyaluronate deposition can be observed between in situ and under cell culture conditions. Since in normal marrow in situ the number of CD44 immunopositive cells was low, interactions of CD44 and hyaluronate would appear to not to play a major role in cell adhesion in the normal bone marrow.

Inhibitors of hyaluronan export prevent proteoglycan loss from osteoarthritic cartilage

OBJECTIVE

Osteoarthritis (OA) is characterized by cartilage erosion, proteolysis of aggrecan and collagen, and disturbed synthesis rates of aggrecan and hyaluronan by chondrocytes. The hypothesis is tested that hyaluronan overproduction contributes to aggrecan loss from osteoarthritic cartilage.

METHODS

Human chondrocytes or bovine cartilage explants were incubated with interleukin 1beta (IL-1beta) to induce upregulation of hyaluronan and downregulation of aggrecan. OA was induced by injection of iodoacetate into the synovial cavity in rat knees. Hyaluronan export was inhibited by ATP-binding cassette transporter inhibitors such as the multidrug resistance (MDR) inhibitors valspodar or verapamil. The concentration of aggrecan was measured in cell culture media or visualized histochemically in cartilage tissue sections.

RESULTS

Valspodar inhibited hyaluronan export from human chondrocytes in cell culture selectively without reducing aggrecan secretion. Valspodar and other MDR inhibitors prevented loss of aggrecan from osteoarthritic cartilage explants in culture. Verapamil prevented loss of aggrecan from cartilage in osteoarthritic rat knees.

CONCLUSION

Hyaluronan is synthesized at plasma membranes and exported out of the cell. We recently identified an ATP-binding cassette transport system that is responsible for hyaluronan export. A number of ATP-binding cassette transport inhibitors are known and are in use clinically. These inhibitors were used here to inhibit hyaluronan export and to prevent aggrecan loss from arthritic cartilage. New drugs for treatment of arthritis are suggested by these studies.

The expression pattern of hyaluronan synthase during human tooth development

In previous studies, hyaluronan (HA) and its major cell surface receptor CD44 have been suggested to play an important role during tooth development. HA synthases (HASs) are the enzymes that polymerize hyaluronan. Data on the expression pattern of HASs during tooth development is lacking and the aim of the present study was to investigate the localisation of HAS by immunohistochemistry in human tooth germs from different developmental stages. The distribution pattern of HAS in the various tissues of the "bell stage" tooth primordia corresponded to that of hyaluronan in most locations: positive HAS immunoreactivity was observed in the dental lamina cells, inner- and outer-enamel epithelium. On the stellate reticulum cells, moderate HAS signal was observed, similar to the layers of the oral epithelium, where faint HAS immunoreactivity was detected. At the early phase of dental hard tissues mineralization, strong HAS immunoreactivity was detected in the odontoblasts and their processes, as well as in the secretory ameloblasts and their apical processes and also, the pulpal mesenchymal cells. The HAS signals observed in odontoblasts and ameloblasts gradually decreased with age. Our results demonstrate that hyaluronan synthesised locally by different dental cells and these results provide additional indirect support to the suggestion that HA may contribute both to the regulation of tooth morphogenesis and dental hard tissue formation.

Inhibition of hyaluronan export from human fibroblasts by inhibitors of multidrug resistance transporters

In a previous report we described the export of hyaluronan from Streptococcus pyogenes by an ABC transporter. Extending these findings a sequence homology search against human proteins revealed a strong homology to the multidrug resistance transporter ABC-B (MDR-1) and ABC-C (MRP 5). Using several inhibitors directed against these and other transporters, a decreased hyaluronan production in cell culture as well as in hyaluronan synthase activity in purified membrane fractions was observed. The inhibitory capacity (IC(50) concentrations) was compared the with reported IC(50)- or the K(i)-concentrations for individual transporters. These analyses revealed that hyaluronan is synthesized within the cytoplasm of mammalian cells and actively secreted into the pericellular space by energy dependent transport proteins. While inhibition of several transport proteins resulted in a decrease of hyaluronan export, inhibition of the MRP5 transporter was the most effective one to decrease hyaluronan in the cell culture supernatant indicating that hyaluronan export is one physiological role of this transport protein.

Hyaluronan release from Streptococcus pyogenes: export by an ABC transporter

Capsular hyaluronan of Streptococcus pyogenes is synthesized at the protoplast membrane. It is widely assumed that hyaluronan is exported by the synthase itself and that no additional protein is required for transfer through plasma membranes. However, we produced an insertional mutation that reduced the mucoid phenotype, hyaluronan production, and capsule formation. Nucleotide sequence analysis of the insertion site identified a gene coding for a protein with an ATP-binding cassette (ABC) that belonged to an ABC transporter system and was located next to the hyaluronan synthesis genes. The mucoid phenotype was reconstituted by complementation with DNA encoding the ABC transporter system. These results indicated that an ABC transporter was required for efficient capsule production.

CD44H and the isoforms CD44v5 and CD44v6 in the synovial fluid of the osteoarthritic human knee joint

OBJECTIVE

To determine whether the concentrations of CD44H and v5 and v6 in the synovial fluid are correlated with the presence of accompanying synovitis in the osteoarthritic joint and with the grade of osteoarthritis.

DESIGN

Using antero-posterior and lateral X-rays of the knee joint and patellar view of 46 patients were graded with the Kellgren & Lawrence scale. Synovial fluid from these patients with different grades of primary osteoarthritis of the knee joint with and without synovial inflammation (synovitis) was collected during surgical procedures. A horseradish peroxidase conjugated anti-CD44H-, anti-sCD44v5- or anti-sCD44v6-antibody was added and labeled with tetramethylbenzidine. The absorbance was measured at wavelengths of 450/620 nm. Regression analysis was performed and the statistical significance was assessed, using the Student t-test for unequal variance.

RESULTS

CD44H and v5 and v6 were detected in the synovial fluid of all 46 patients. Osteoarthritic patients with synovial inflammation showed significantly higher levels of CD44H and v6, but not v5, than osteoarthritic patients without synovial inflammation. With progression of osteoarthritis from Kellgren grade II to III, CD44v5 decreased significantly. All other isoform concentrations remained statistically unchanged.

CONCLUSIONS

CD44H and the isoforms v5 and v6 were present in the synovial fluid of osteoarthritic patients. Their concentrations do not reflect the osteoarthritic stage in the Kellgren grading scale. CD44H and CD44v6, but not CD44v5, are significantly up-regulated in osteoarthritic synovial inflammation.

Extracellular matrix components in nasal polyposis

OBJECTIVE

Macroscopically, tissue hydration in nasal polyps seems to be a phenomenon of unknown etiology. As the macromolecular composition of extracellular matrix (ECM) determines to a large extent tissue hydration, which in turn determines tissue volume, we investigated ECM components in nasal polyps (NP) in comparison to nasal mucosa of the inferior turbinate (TM) and sinus mucosa from patients with chronic sinusitis without polyps (CS).

MATERIAL AND METHODS

The following parameters were determined: (i) the dry weight of freeze-dried NP, TM and CS; (ii) the total protein content (Bio-Rad Protein Assay) of the tissue; (iii) the quality of proteins, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE); (iv) the amount of albumin, using nephelometry; and (v) the amount of hyaluronic acid, using a chemical method: deaminative hydrolysis with carbazole.

RESULTS

In 20 NP we found a significantly elevated total protein content compared to TM (n = 20) and CS (n = 15), referred to 0.1 g dry of tissue. In SDS-PAGE of NP (n = 20) a protein band at approximately 70 kDa, representing albumin, dominated, in comparison to TM. The amount of albumin was significantly increased in NP compared to CS and TM. In contrast, the amount of the glycosaminoglycan, hyaluronic acid, was not elevated in NP or CS.

CONCLUSION

Albumin was significantly increased in NP and CS, possibly as a result of inflammatory plasma exudation mechanisms. Hyaluronic acid seems to play no role in the tissue hydration of NP.

Supramolecular organization in streptococcal pericellular capsules is based on hyaluronan tertiary structures

Supramolecular organization involving a polyanionic glycan in a bacterial capsule (hyaluronan, HA, in streptococcal capsules) is revealed, for the first time, by electron-histochemical methodology previously used to elucidate ultrastructure in extracellular matrix. Capsular HA filaments thereby revealed closely resemble aligned linear structures demonstrated by similar technology in HA solution. These parallel arrays, spontaneously formed, are based on HA tertiary structures (beta sheet-like) which are stabilized by hydrophobic and hydrogen bonds. HA tertiary structures in aqueous solutions resist shear stress as shown by rheo-NMR. Thus, supramolecular HA wrapping covering many cells probably stabilizes chains of bacteria. Streptococci possibly templated the ordered structures since eukaryotic B6 cell HA did not produce similarly organized envelopes. Supramolecular organization in streptococcal and pneumococcal capsules are compared. Their glycans are very similar but the potential for HA-like tertiary structures is not present in the pneumococcal type 3 polysaccharide and chains of cells are not formed to the same extent by pneumococci. We suggest that the streptococcal capsule exemplifies a simple extracellular matrix analogous to those in animal connective tissues, which contain glycans (chondroitin, keratan, and dermochondan sulfates) of the HA family, capable of undergoing aggregation to similar tertiary structures.

Expression of hyaluronate and hyaluronate synthase in human primary tumours and their metastases in scid mice

Hyaluronate and hyaluronate synthase expression were examined in primary tumours and if present in metastatic deposits of human breast, colon, ovarian and small-cell lung cancer cell lines transplanted into scid mice using biotinylated hyaluronectin and immunohistochemical staining of hyaluronate synthase. Very intensive hyaluronate and hyaluronate synthase expression could be observed in peripheral areas of tumours derived from highly metastatic cell lines (HT29, MCF-7). Even smaller lung metastases of up to 15 cells showed typically a focal binding of hyaluronectin predominantly at the host-tumour interface of the metastases, indicating that increased expression is closely correlated with the degree of invasiveness and metastatic potential of malignant tumours.

Hyaluronan reduces migration and proliferation in CHO cells

Expression of the hyaluronan synthase gene in hyaluronan-deficient CHO cells changed the cell morphology from a spindle shape to a flattened epithelial-type form. Hyaluronan producing CHO cells showed reduced initial cell adhesion, migration, proliferation and density at contact inhibition, but no difference in random migration determined by the Boyden chamber assay. Addition of hyaluronan to the medium of CHO cells reduced migration, proliferation and initial cell adhesion. In contrast, coating the plastic dish with hyaluronan enhanced initial cell adhesion. These results are discussed in the context of the perplexing properties of hyaluronan on cellular functions.

Oligosaccharides of hyaluronan are potent activators of dendritic cells

The extracellular matrix component hyaluronan (HA) exists physiologically as a high m.w. polymer but is cleaved at sites of inflammation, where it will be contacted by dendritic cells (DC). To determine the effects of HA on DC, HA fragments of different size were established. Only small HA fragments of tetra- and hexasaccharide size (sHA), but not of intermediate size (m.w. 80, 000-200,000) or high m.w. HA (m.w. 1,000,000-600,000) induced immunophenotypic maturation of human monocyte-derived DC (up-regulation of HLA-DR, B7-1/2, CD83, down-regulation of CD115). Likewise, only sHA increased DC production of the cytokines IL-1beta, TNF-alpha, and IL-12 as well as their allostimulatory capacity. These effects were highly specific for sHA, because they were not induced by other glycosaminoglycans such as chondroitin sulfate or heparan sulfate or their fragmentation products. Interestingly, sHA-induced DC maturation does not involve the HA receptors CD44 or the receptor for hyaluronan-mediated motility, because DC from CD44-deficient mice and wild-type mice both responded similarly to sHA stimulation, whereas the receptor for hyaluronan-mediated motility is not detectable in DC. However, TNF-alpha is an essential mediator of sHA-induced DC maturation as shown by blocking studies with a soluble TNFR1. These findings suggest that during inflammation, interaction of DC with small HA fragments induce DC maturation.

Synthesis and shedding of hyaluronan from plasma membranes of human fibroblasts and metastatic and non-metastatic melanoma cells

The regulation of hyaluronan synthesis and shedding was analysed in human fibroblasts and in two melanoma cells that differed in the metastatic potential and proteolysis of the hyaluronan receptor CD44. Dissociation of nascent hyaluronan from plasma membranes isolated from fibroblasts by high salt concentrations led to activation of hyaluronan synthase. Hyaluronan synthesis was also enhanced in plasma membranes from fibroblasts that had been treated with hyaluronidase or trypsin. Hyaluronan oligosaccharides stimulated hyaluronan production in fibroblast cultures. These results indicated that nascent high-molecular-mass hyaluronan inhibited its own chain elongation, if it was retained in the vicinity of the synthase by cell-surface receptors. The results also indicated that increased hyaluronan synthesis and shedding correlated with proteolysis of CD44 on the melanoma cell lines, which has been observed by others.

An ectoprotein kinase of group C streptococci binds hyaluronan and regulates capsule formation

A 56-kDa protein had been isolated and cloned from protoplast membranes of group C streptococci that had erroneously been identified as hyaluronan synthase. The function of this protein was reexamined. When streptococcal membranes were separated on an SDS-polyacrylamide gel and renatured, a 56-kDa protein was detected that had kinase activity for a casein substrate. When this recombinant protein was expressed in Escherichia coli and incubated in the presence of [32P]ATP, it was responsible for phosphorylation of two proteins with 30 and 56 kDa that were not present in the control lysate. The 56-kDa protein was specifically phosphorylated in an immunoprecipitate of a detergent extract of the recombinant E. coli lysate with antibodies against the 56-kDa protein, indicating that it was autophosphorylated. The E. coli lysate containing the recombinant protein could bind hyaluronan, and hyaluronan binding was abolished by the addition of ATP. Kinetic analysis of hyaluronan synthesis and release from isolated protoplast membranes indicated that phosphorylation by ATP stimulated hyaluronan release and synthesis. Incubation of membranes with antibodies to the 56-kDa protein increased hyaluronan release. The addition of [32P]ATP to intact streptococci led to rapid phosphorylation of two proteins, 56 and 75 kDa each at threonine residues. This phosphorylation was neither observed with [32P]phosphate nor in the presence of trypsin, indicating that the kinase was localized extracellularly. The addition of ATP to growing group C streptococci led to increased hyaluronan synthesis and release. However marked differences were found between group A and group C streptococci. Antibodies against the 56-kDa protein from group C streptococci did not recognize proteins from group A strains, and a homologous DNA sequence could not be detected by polymerase chain reaction or Southern blotting. In addition, Group A streptococci did not retain a large hyaluronan capsule like group C strains. These results indicated that the 56-kDa protein is an ectoprotein kinase specific for group C streptococci that regulates hyaluronan capsule shedding by phosphorylation.

Dexamethasone treatment decreases hyaluronan-formation by primate trabecular meshwork cells in vitro

The functional significance of Hyaluronan (HA) present in the cribriform layer of Schlemm's canal is not known. It may contribute to the actual outflow resistance but the relatively inert molecule might also be necessary to prevent adherence of larger molecules to the cribriform network. Thus HA might rather prevent an increase in outflow resistance. It is well known that treatment with Dexamethasone (DM) in a number of patients leads to an increase in intraocular pressure presumably due to an increase in outflow resistance. To clarify whether an imbalance in HA formation might be involved in these changes we have treated confluent cultures of human trabecular cells as well as control cell lines (ciliary muscle cells, scleral fibroblasts) with 500 nM DM for 24 hr or 12 days and have measured HA-synthesis using incorporation assays with 0.05 m D-[6-3H] Glucosamine hydrochloride. In all six cell lines investigated there was a significant decrease in HA-synthesis following short and long term treatment with DM when compared with the untreated controls. This reaction of trabecular cells to DM treatment is different from the DM effect reported on the synthesis of many other components of the extracellular matrix like fibronectin and elastin which increase after DM treatment. If the DM-effect seen in cell cultures plays a role in vivo decreased formation in HA could result in impaired function of the outflow pathways.

A mild purification method for polysaccharide binding membrane proteins: phase separation of digitonin extracts to isolate the hyaluronate synthase from Streptococcus sp. in active form

A new method was developed to purify the streptococcal hyaluronate synthase in active form to electrophoretic homogeneity. The method is based on the extraction of protoplast membranes with digitonin and a phase separation into an aqueous and a detergent phase induced by addition of polyethylene glycol 6000 at 0 degree C. Proteins bound to hyaluronate were enriched in the aqueous phase, whereas other membrane proteins resided in the detergent phase. Final purification of the hyaluronate synthase was achieved by ion exchange chromatography.

CD44 exon variant 6 epitope and hyaluronate synthase are expressed on HT29 human colorectal carcinoma cells in a SCID mouse model of metastasis formation

The factors which lead to the formation of metastases are generally poorly understood; however the expression of a particular variant of the cell adhesion molecule CD44 may be important in facilitating metastasis formation in colon cancer. The aim of the present study was to investigate the expression of CD44 exon v 6 (CD44v6), hyaluronate (one of its ligands), and hyaluronate synthase, in a clinically relevant animal model of metastatic colon carcinoma. HT29 human colon carcinoma cells were injected subcutaneously between the scapulae of severe combined immunodeficient (SCID) mice and left for 3 weeks (by which time the tumours had produced metastases in the lungs). Morphological observations at the tumour-host interface were consistent with the dissociation of neoplastic cells from the primary tumours, and the ability of these cells to migrate through the extracellular matrix facilitating metastasis formation. Immunohistochemically detectable hyaluronate synthase expression was increased in vivo compared with the parent cell line in vitro. CD44v6 expression and hyaluronate were increased around single cells at the periphery of tumours compared with the central regions. CD44v6 and hyaluronate snythase expression were co-expressed in the same cells. Indeed, the present study is the first to demonstrate hyaluronate synthase expression by an epithelial cell type.

Antibodies against proteins of streptococcal hyaluronate synthase bind to human fibroblasts and are present in patients with rheumatic fever

Antibodies directed against the streptococcal 42 kDa hyaluronate synthase and a 56 kDa auxiliary protein bound to the surface of intact human fibroblasts in vitro. Staining was most prominent during the detachment phase of mitosis. In eukaryotic plasma membranes a 52 kDa protein was recognized by the antiserum against the 56 kDa streptococcal protein. Since the cross-reacting proteins could be involved in immunological mimicry between streptococcal and human antigens leading to heart cell necrosis, the reactivity of sera from patients with rheumatic fever was compared with that of sera from healthy or streptococcal infected persons. The sera from patients with rheumatic fever showed a higher reactivity against the 56 kDa protein than those from healthy persons or from patients with an antibiotic treated streptococcal infection. This difference was not observed for the 42 kDa protein. These sera were able to lead to cell lysis in the presence of complement.

Synovial hyaluronate in rheumatoid arthritis binds C1q and is covalently bound to antibodies: a model for chronicity

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Synthesis and degradation of hyaluronate by synovia from patients with rheumatoid arthritis

OBJECTIVE

Hyaluronate degradation was analyzed in cultures of healthy tissue and tissue obtained from patients with rheumatoid arthritis.

METHODS

Arthritic and healthy synovial tissues were incubated in culture with [3H]glucosamine. Labelled hyaluronate was extracted and its size determined by gel filtration. The production of low molecular weight hyaluronate was analyzed by pulse-chase experiments. Radical production was measured by a cytochrome C reduction assay.

RESULTS

Healthy tissues and some arthritic tissues that did not contain significant amounts of granulocytes produced high molecular weight hyaluronate. In contrast, arthritic tissue infiltrated with granulocytes released low molecular weight hyaluronate. Pulse-chase experiments suggested that hyaluronate was degraded in these arthritic tissues. Exogenous hyaluronate was degraded only by intact tissue, but not by cells in culture obtained from synovial membranes of synovial fluids. Hyaluronate degradation was accompanied by massive oxygen radical production. Radical scavengers protected hyaluronate from degradation in synovial tissue. Some protection was achieved by superoxide and catalase or by methionine and complete protection by the iron chelators diethyltriaminepentacetic acid or deferoxamine mesylate.

CONCLUSION

Degradation of hyaluronate in arthritic synovial tissue may be inhibited in tissue culture by radical scavengers.

Alterations in hyaluronan synthesis during developing joint cavitation

The mechanisms essential for generating diarthrodial joint cavities between skeletal elements in developing limbs remain enigmatic. Histochemical localization of hyaluronan (HA) at joint interzones concomitant with cavitation led to the postulation that HA may be pivotal in this process. HA synthesis involves the transfer of UDP-glucuronate and UDP-N-acetyl glucosamine to nascent HA by HA synthase. Uridine diphosphoglucose dehydrogenase (UDPGD) activity is responsible for the prior conversion of UDP-glucose to UDP-glucuronate. We have assessed the relationship between the appearance of HA and enzyme activities (quantitatively where possible) involved in HA synthesis during metatarsophalangeal joint development in embryonic chicks. Microspectrophotometric assessment of UDPGD activity using an in situ biochemical assay indicated that cells immediately adjacent to forming cavities contained increased UDPGD activity, which was subsequently maintained after cavitation. Immunocytochemistry showed that high levels of expression of HA synthase were localized to these same cells. In addition, radiolabeled sulfate autoradiography showed that cells bordering developing cavities incorporated relatively little sulfate, suggesting that UDP-glucuronate is utilized in the synthesis of undersulfated or non-sulfated glycosaminoglycans. These results indicate that the differentiation of cells bordering presumptive spaces may involve alterations associated specifically with differential synthesis of HA, which appears to be a primary event in joint cavity formation.

Intracellular signal transduction for serum activation of the hyaluronan synthase in eukaryotic cell lines

Hyaluronan synthase was activated in B6 cells or 3T3 fibroblasts by foetal calf serum with maximal activity after 6 h. Activation was inhibited by cycloheximide or by the protein kinase inhibitors H-7 or H-8, indicating that transcription as well as phosphorylation was required for activation. The activation by serum was markedly prolonged, when serum was added together with cholera toxin or theophylline. Without serum stimulation the hyaluronan synthase could also be activated by phorbol-12-myristate-13-acetate, by dibutyryl-c-AMP, or by forskolin. Increasing the intracellular Ca-ion concentration with a Ca-ionophore also led to an activation. The activation of the drugs was not synergistic. In isolated plasma membranes the synthase activity could be decreased by phosphatase treatment and enhanced by ATP in B6 cells and by ATP in the presence of phorbol-12-myristate-13-acetate in 3T3 fibroblasts. Stimulation correlated with increased transcription and phosphorylation of the 52 kD hyaluronan synthase at serine residues. The results led to the conclusion that hyaluronan synthase is induced by transcription and activated by phosphorylation by protein kinase C, c-AMP-dependent protein kinases, or Ca-ion-dependent protein kinases.

CD44 variant isoforms are preferentially expressed in basal epithelial of non-malignant human fetal and adult tissues

CD44 is a transmembrane glycoprotein, which can exist in a multitude of isoforms due to alternative splicing of the pre-mRNA. We have generated monoclonal antibodies to several of these variant regions, which are encoded by 10 additional exons in the extracellular part of the molecule. CD44 variant isoforms have been reported to be involved in the malignant progression of rat and human tumours. The precise localization of CD44 variant isoforms in normal developmental and morphogenetic processes is essential for diagnostic studies of human tumorigenesis. Therefore, we have analysed a large number of different human tissues by immunohistochemistry for the expression of CD44 isoforms containing either exons 4v, 6v or 9v. Expression of exon 9v-isoforms was detected in almost all epithelia analysed, with a few exceptions. Exon 6v isoforms are expressed only in squamous and glandular epithelial, e.g. skin epidermis, sweat and sebaceous glands, oesophagus, ducts of the mammary gland, salivary and prostate glands. Detection of exon 4v-encoded isoforms was restricted to the epidermis and the oesophagus. Similar tissue distributions of CD44 variant isoforms were observed in 10-week-old fetal tissues. Since one of the ligands of CD44 is hyaluronic acid (HA), we also analysed the tissue distribution of HA synthetase. HA synthetase was detected in all tissues analysed, showing good correlation with the expression of the standard form of CD44, CD44s.

Immunoelectrophoretic pattern of native mucosal intracellular glycoproteins of hog healthy and drug-intoxicated stomachs and of hog body fluids

Naturally occurring glycoproteins have been extracted from fundic and antral mucosal tissue of the hog stomach by means of nondegrading techniques. Major and retarded glycoprotein fractions separated by gel filtration were further dissociated from appreciable amounts of noncovalently bound proteins by CsCl density gradient centrifugation. Antisera to glycoprotein fractions of fundic and antral regions of the stomach were prepared in rabbits. The major fractions from both gastric regions have similar molecular mass (approximately 2 x 10(6)), sedimentation coefficient (approximately 31.5 s), and specific viscosity (approximately 1.6). Purified fractions from each region were further separated into two subfractions by affinity chromatography on wheat germ lectin. Glycoprotein subfractions from antrum and fundus differ appreciably in their carbohydrate and amino acids content, share antigenic determinants, but do not cross-react with anti-hog serum protein antisera. Further diversity in native mucin glycoproteins was observed by the use of one-(D) and two-dimensional (2D) immunoelectrophoresis; subfractions that cross-react with specific anti-hog gastric glycoproteins were found to contain three or more components. D-Immunoelectrophoretic analyses demonstrated (1) in vivo degradation of glycoprotein components of the major fundic fraction isolated from mucosal tissue of alcohol/acetyl salicylate-intoxicated hog stomachs and (2) in vitro catabolism of major fundic glycoproteins by corresponding mitochondrial lysosomal (ML) acid hydrolases. Furthermore, 2D-immunoelectrophoretic analyses showed that (1) hog synovial fluid and plasma proteins have similar prosthetic moieties as either reacted with anti-hog serum proteins antisera. Nonetheless, locations, shapes, and staining intensities of the immunoprecipitate lines differed, which is indicative of different structures of the carbohydrate moieties of components of synovial fluid and plasma proteins, and (2) only a minor fraction of hog cerebrospinal fluid cross-reacted with anti-hog serum protein antisera. This is contrary to the generally accepted deduction based on high-resolution 2D-electrophoresis, indicative of different compositional patterns of plasma and cerebrospinal fluids.

Hyaluronan synthase immunoreactivity in the anterior segment of the primate eye

The anterior segment of human and cynomolgus monkey eyes was investigated for the presence of hyaluronan (HA) synthesizing cells using a polyclonal antibody against the enzyme HA synthase (HAS). In the chamber angle region the most intense staining was seen in the cell membranes of the corneal endothelium and in monkey eyes in the cells covering the posterior extension of the cornea (the operculum). The trabecular meshwork cells of the uveal and inner corneoscleral lamellae were also intensely stained. On the other hand, no staining was observed in the trabecular cells of the outer corneoscleral and the cribriform meshwork. The cell membranes of the inner wall endothelium of Schlemm's canal were labelled only at their luminal surface. In the iris stroma and the trabeculum ciliare (the ciliary body band), labelled cells were also found, whereas the connective tissue of the ciliary muscle and the muscle itself did not contain HAS-positive cells. In the ciliary processes immunoreactivity was seen in the non-pigmented epithelial cells (NPE) covering the anterior tips of the processes, suggesting that HA found in the aqueous humor is produced by these cells. The pars plana NPE showed the most intense staining in the cells directly adjacent to the ora serrata region. The hyalocytes found in the neighborhood of the pars plana also showed intense HAS immunoreactivity. It is likely that both hyalocytes and NPE cells of the posterior pars plana release HA into the vitreous.

The hyaluronate synthase from a eukaryotic cell line

The hyaluronate synthase complex was identified in plasma membranes from B6 cells. It contained two subunits of molecular masses 52 kDa and 60 kDa which bound the precursor UDP-GlcA in digitonin solution and partitioned into the aqueous phase, together with nascent hyaluronate upon Triton X-114 phase separation. The 52 kDa protein cross-reacted with poly- and monoclonal antibodies raised against the streptococcal hyaluronate synthase and the 60 kDa protein was recognized by monoclonal antibodies raised against a hyaluronate receptor. The 52 kDa protein was purified to homogeneity by affinity chromatography with monoclonal anti-hyaluronate synthase.

Hyaluronate synthase: cloning and sequencing of the gene from Streptococcus sp

The complete nucleotide sequence of hyaluronate synthase from Streptococcus sp. and its flanking regions is presented. The gene locus was designated has. Southern-blotting results suggested that the gene was conserved in hyaluronate-producing streptococci. A putative translation-initiation codon was identified and the open reading frame consists of 1566 bp, specifying a protein of 56 kDa. Sequences resembling the promoter and ribosome-binding site of Gram-positive organisms are found upstream of the synthase. The predicted amino-acid sequence reveals the presence of a 35-residue signal peptide. The sequence has some similarity to bacterial peptide-binding proteins.

Immunohistochemical localization of hyaluronan synthase in cornea and conjunctive of cynomolgus monkey

Distribution of hyaluronan synthase was investigated in cornea and conjunctiva of Cynomolgus monkeys (Macaca fascicularis) using polyclonal antibodies against the streptococcal enzyme. Strong immunoreaction was found in the cell membranes of the corneal endothelium, corneal epithelium, and most of the conjunctival epithelium. In the corneal epithelium all cells except the basal ones stained. In the conjunctiva all cylindrical cells stained, whereas among the goblet cells one type showed intense membrane staining, the other remained unstained. In the limbal portion of the conjunctival epithelium, which in many other respects differs morphologically and functionally from the remaining conjunctiva, all membranes of the different layers of the stratified epithelium except the most superficial ones, appeared unstained. Staining was also seen in all stromal fibroblasts and capillary endothelial cells.

Release of hyaluronate from eukaryotic cells

The mechanism of hyaluronate shedding from eukaryotic cell lines was analysed. All cell lines shed identical sizes of hyaluronate as were retained on the surface. They differed in the amount of hyaluronate synthesized and in the proportions of hyaluronate which were released and retained. A method was developed which could discriminate between shedding due to intramolecular degradation and that due to dissociation as intact macromolecules. This method was applied to B6 and SV3T3 cells in order to study the mechanism of hyaluronate release in more detail. The cells were pulse-labelled to form hyaluronate chains with labelled and unlabelled segments, and the sizes of labelled hyaluronate released into the medium during the pulse extension period were determined by gel filtration. B6 cells released identical sizes of hyaluronate at all labelled segment lengths, indicating that no intramolecular degradation occurred. When chain elongation was blocked by periodate-oxidized UDP-glucuronic acid, hyaluronate release was simultaneously inhibited. These results indicated that B6 cells dissociated hyaluronate as an intact macromolecule. In contrast, SV3T3 cells released hyaluronate of varying molecular mass distributions during extension of the labelled segment, suggesting partial degradation. Exogenous hyaluronate added to SV3T3 cultures was also degraded. This degradation could be prevented by the presence of radical scavengers such as superoxide dismutase and tocopherol. Degradation of endogenous hyaluronate could be inhibited by salicylate. These results led to the conclusion that SV3T3 cells released hyaluronate not only by dissociation, but also by radical-induced degradation.

Shedding of hyaluronate synthase from streptococci

Hyaluronate synthase was shed into the culture medium from growing streptococci (group C) together with nascent hyaluronate. The mechanism of solubilization was analysed using isolated protoplast membranes. Solubilization increased when membranes were suspended in larger volumes, but it was temperature-independent and was not inhibited by protease inhibitors. Increased hyaluronate chain length enhanced solubilization. The soluble synthase could re-integrate into Streptococcal membranes in a saturable manner. The soluble synthase behaved like an integral membrane protein, although it was not integrated into phospholipid vesicles. In sucrose velocity centrifugation the synthase had a higher sedimentation rate in detergent-free solution, indicating that it existed in an aggregated state.

Increased hyaluronate synthesis is required for fibroblast detachment and mitosis

Human-embryo fibroblasts were synchronized by means of colchicine and cytochalasin, and the production of hyaluronate was determined by [3H]glucosamine incorporation and ion-exchange chromatography. Cells arrested by colchicine synthesized small amounts of hyaluronate, whereas cells blocked by cytochalasin were stimulated in hyaluronate production. When the colchicine block was released, there was an increased synthesis of hyaluronate, which appeared first in the cellular fraction and was then shed into the culture medium. After release of the cytochalasin block, the hyaluronate production declined to that found with unsynchronized cells. A comparable increase of hyaluronate synthase activity was observed during mitosis. When hyaluronate synthesis was blocked by periodate-oxidized UDP-glucuronic acid, the cells were arrested in mitosis before rounding of cells. These results suggest that hyaluronate synthesis is required for detachment and rounding of cells during mitosis.

Isolation of streptococcal hyaluronate synthase

Hyaluronate synthase was isolated from protoblast membranes of streptococci by Triton X-114 extraction and cetylpyridinium chloride precipitation. It was identified as a 52,000-Mr protein, which bound to nascent hyaluronate and was affinity-labelled by periodate-oxidized UDP-glucuronic acid and UDP-N-acetylglucosamine. Antibodies directed against the 52,000-Mr protein inhibited hyaluronate synthesis. Mutants defective in hyaluronate synthase activity lacked the 52,000-Mr protein in membrane extracts. Synthase activity was solubilized from membranes by cholate in active form and purified by ion-exchange chromatography.