Phenotype-related differential alpha-2,6- or alpha-2,3-sialylation of glycoprotein N-glycans in human chondrocytes.

OBJECTIVE: Sialic acids frequently occur at the terminal positions of glycoprotein N-glycans present at chondrocyte surfaces or in the cartilage matrix. Sialic acids are transferred to glycoproteins in either alpha-2,3 or alpha-2,6 linkage by specific sialyltransferases (SiaTs) and can potentially affect cell functions and cell-matrix interactions. The present study aimed to assess the relationship between the expression of the human chondrocyte phenotype and the sialylation of chondrocyte glycoprotein N-glycans. METHODS: The transcription of 5 SiaT was quantified using real-time Reverse transcription polymerase chain reaction (RT-PCR) assays. N-glycan analysis was performed using LC-ESI-MS. Primary human chondrocytes were cultured in monolayer or alginate beads and compared to the chondrocyte cell lines C-28/I2 and SW1353. In addition, effects of interleukin-1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha) on primary cells were assessed. RESULTS: Primary human chondrocytes predominantly express alpha-2,6-specific SiaTs and accordingly, alpha-2,6-linked sialic acid residues in glycoprotein N-glycans. In contrast, the preponderance of alpha-2,3-linked sialyl residues and, correspondingly, reduced levels of alpha-2,6-specific SiaTs are associated with the altered chondrocyte phenotype of C-28/I2 and SW1353 cells. Importantly, a considerable shift towards alpha-2,3-linked sialic acids and alpha-2,3-specific SiaT mRNA levels occurred in primary chondrocytes treated with IL-1beta or tumour necrosis factor-alpha (TNF-alpha). CONCLUSION: The expression of the differentiated chondrocyte phenotype is linked to the ratio of alpha-2,6- to alpha-2,3-linked sialic acids in chondrocyte glycoprotein N-glycans. A shift towards altered sialylation might contribute to impaired cell-matrix interactions in disease conditions.

Lectin binding patterns reflect the phenotypic status of in vitro chondrocyte models.

In vitro studies using chondrocyte cell cultures have increased our understanding of cartilage physiology and the altered chondrocytic cell phenotype in joint diseases. Beside the use of primary cells isolated from cartilage specimens of donors, immortalized chondrocyte cell lines such as C-28/I2 and T/C-28a2 have facilitated reproducible and standardized experiments. Although carbohydrate structures appear of significance for cartilage function, the contribution of the chondrocyte glycocalyx to matrix assembly and alterations of the chondrocyte phenotype is poorly understood. Therefore, the present study aimed to evaluate the glycoprofile of primary human chondrocytes as well as of C-28/I2 and T/C-28a2 cells in culture. First, the chondrocytic phenotype of primary and immortalized cells was assessed using real-time reverse transcriptase polymerase chain reaction, immunofluorescence, and glycosaminoglycans staining. Then, a panel of lectins was selected to probe for a range of oligosaccharide sequences determining specific products of the O-glycosylation and N-glycosylation pathways. We found that differences in the molecular phenotype between primary chondrocytes and the immortalized chondrocyte cell models C-28/I2 and T/C-28a2 are reflected in the glycoprofile of the cells. In this regard, the glycocalyx of immortalized chondrocytes was characterized by reduced levels of high-mannose type and sialic acid-capped N-glycans as well as increased fucosylated O-glycosylation products. In summary, the present report emphasizes the glycophenotype as an integral part of the chondrocyte phenotype and points at a significant role of the glycophenotype in chondrocyte differentiation.

Comparison between chondroprotective effects of glucosamine, curcumin, and diacerein in IL-1beta-stimulated C-28/I2 chondrocytes.

OBJECTIVE: To compare the effects of glucosamine (GlcN), curcumin, and diacerein in immortalized human C-28/I2 chondrocytes at the cellular and the gene expression level. This study aimed to provide insights into the proposed beneficial effects of these agents and to assess the applicability of the C-28/I2 cell line as a model for the evaluation of chondroprotective action. METHODS: Interleukin-1beta (IL-1beta)-stimulated C-28/I2 cells were cultured in the presence of GlcN, curcumin, and diacerein prior to the evaluation of parameters such as viability, morphology and proliferation. The impact of GlcN, curcumin, and diacerein on gene expression was determined using quantitative real-time RT-PCR (qPCR). RESULTS: At the transcriptional level, 5 mM GlcN and 50 microM diacerein increased the expression of cartilage-specific genes such as aggrecan (AGC) and collagen type II (COL2), while reducing collagen type I (COL1) mRNA levels. Moreover, the IL-1beta-mediated shift in gene expression pattern was antagonized by GlcN and diacerein. These effects were associated with a significant reduction in cellular proliferation and the development of chondrocyte-specific cell morphology. In contrast, curcumin was not effective at lower concentrations but even damaged the cells at higher amounts. CONCLUSIONS: Both GlcN and diacerein promoted a differentiated chondrocytic phenotype of immortalized human C-28/I2 chondrocytes by altering proliferation, morphology, and COL2/COL1 mRNA ratios. Moreover, both agents antagonized inhibitory effects of IL-1beta by enhancing AGC and COL2 as well as by reducing COL1 mRNA levels.

Lectin binding studies on C-28/I2 and T/C-28a2 chondrocytes provide a basis for new tissue engineering and drug delivery perspectives in cartilage research.

The present study was performed to evaluate the applicability of plant lectins as mediators of bioadhesion in cartilage research using human chondrocyte cell lines C-28/I2 and T/C-28a2. The bioadhesive properties of fluorescein-labelled lectins with different carbohydrate specificities were investigated by flow cytometry. Specificity of the lectin-cell interactions was ascertained by competitive inhibition using complementary carbohydrates. As compared to that of other lectins, the interaction between wheat germ agglutinin (WGA) and chondrocytic cells was characterised by remarkable cytoadhesion, adequate binding strength and a high degree of specificity for N-acetyl-glucosamine as contained in hyaluronan chains. We therefore suggest WGA to be a promising candidate for mediating bioadhesion to low-adhesive scaffolds in cartilage tissue engineering. Moreover, the WGA-association rate of C-28/I2 and T/C-28a2 cells was dependent on temperature indicating cellular uptake of membrane-bound WGA. Intracellular enrichment was confirmed by confocal microscopy. Equilibration of intracellular pH gradients with monensin resulted in the reversal of quenching effects indicating accumulation of WGA within acid compartments of chondrocytic cells. Thus, WGA might be internalised into chondrocytes together with hyaluronan via the CD44 receptor-mediated endocytosis pathway and accumulated within lysosomes. This physiological process could represent a feasible pathway to target WGA-functionalised drug delivery devices into chondrocytes.

Synthesis and binding to plant lectins of sulfur-containing analogues of betaGal1,3 alphaGalNAc (T-antigen).

Analogues of the tumor-associated T-antigen (betaGal1,3 alphaGalNAc) containing 4,6-epidithio and 4,6-thietan modifications were synthesized from the alpha-allyl glycoside of betaGal alpha1,3GlcNAc via suitable thiocyanate derivatives. Binding to three leguminous lectins as model systems was investigated in an enzyme-linked lectin assay (ELLA) and IC50 values comparable to the corresponding natural disaccharides T-antigen, lactose and N-acetyllactosamine were found.

Applications of S-layers.

The wealth of information existing on the general principle of S-layers has revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from many organisms are capable of recrystallizing as closed monolayers onto solid supports at the air-water interface, on lipid monolayers or onto the surface of liposomes. Particularly their repetitive physicochemical properties down to the subnanometer scale make S-layers unique structures for functionalization of surfaces and interfaces down to the ultimate resolution limit. The following review focuses on selected applications in biotechnology, diagnostics, vaccine development, biomimetic membranes, supramolecular engineering and nanotechnology. Despite progress in the characterization of S-layers and the exploitation of S-layers for the applications described in this chapter, it is clear that the field lags behind others (e.g. enzyme engineering) in applying recent advances in protein engineering. Genetic modification and targeted chemical modification would allow several possibilities including the manipulation of pore permeation properties, the introduction of switches to open and close the pores, and the covalent attachment to surfaces or other macromolecules through defined sites on the S-layer protein. The application of protein engineering to S-layers will require the development of straightforward expression systems, the development of simple assays for assembly and function that are suitable for the rapid screening of numerous mutants and the acquisition of structural information at atomic resolution. Attention should be given to these areas in the coming years.

Bet v 1, the major birch pollen allergen, conjugated to crystalline bacterial cell surface proteins, expands allergen-specific T cells of the Th1/Th0 phenotype in vitro by induction of IL-12.

Modulation of allergic immune responses by using adequate adjuvants is a promising concept for future immunotherapy of type I hypersensitivity. In the present study, recombinant Bet v 1 (rBet v 1, the major birch pollen allergen) was conjugated to cross-linked crystalline surface layer proteins (SL) derived from Gram-positive eubacteria. T cell lines (TCL) and clones (TCC) were established from peripheral blood of birch pollen-allergic patients. TCL and TCC were induced either using rBet v 1 alone or rBet v 1/SL conjugates (rBet v 1/SL) as initial antigen stimulus. Cytokine production after re-stimulation with rBet v 1 was investigated. TCL initiated with rBet v 1/SL showed significantly increased IFN-gamma production as compared to rBet v 1 -selected TCL. TCC were established from TCL of five patients. As expected, the majority of CD4+ TCC induced by rBet v 1 (55%) displayed a Th2-like pattern of cytokine production. However, only 21% of Bet v 1-specific TCC isolated from TCL established with the Bet v 1/SL revealed this phenotype. The majority of SL-specific TCC (80%) belonged to the Th1 phenotype. In cultures of peripheral blood mononuclear cells, both, SL and Bet v 1/SL (but not rBet v 1) stimulated the production of high levels of IL-12, a pivotal mediator of Th1 responses. Moreover, stimulation of rBet v 1-induced TCC with rBet v 1/SL led to an increased IFN-gamma production. This effect could be reversed by neutralizing anti-IL-12 mAb. Together these results indicate an adjuvant effect of SL mediated by IL-12. Our results indicate that bacterial components, such as SL, displaying adjuvant effects may be suitable for immunotherapeutical vaccines for type I allergy.

Immunoreactivity of allergen (Bet v 1) conjugated to crystalline bacterial cell surface layers (S-layers).

BACKGROUND: Crystalline cell surface layers (S-layers) from Gram-positive eubacteria had been demonstrated as carrier/adjuvants for chemically synthesized tumor-associated oligosaccharide haptens and capsular polysaccharide antigens of Streptococcus pneumoniae strains. OBJECTIVES: The applicability of S-layers as vaccine carrier for treatment of Type I allergy was investigated. STUDY DESIGN: Native or cross-linked S-layer self-assembly products and cell wall preparations from Bacillus sphaericus CCM 2177 and Thermoanaerobacter thermohydrosulfuricus L111-69 and L110-69 were used for immobilization of recombinant major birch pollen allergen Bet v 1. RESULTS AND CONCLUSIONS: Depending on the carrier used, amounts of approximately 20-40 micrograms allergen per mg conjugate could be immobilized. By application of L-glutamic acid dimethyl ester as a spacer, this value could be increased approximately 10-fold. The functionality of the rBet v 1-conjugates was assessed in immunological systems. (i) The presence of intact B-cell epitopes was demonstrated in inhibition experiments using human Bet v 1-specific IgE. (ii) The rBet v 1-S-layer conjugates were immunogenic in mice. (iii) The proliferation of rBet v 1-specific T-cell clones suggested that the peptides created by processing of immobilized Bet v 1 were similar to those derived from natural allergen. (iv) Stimulation of human allergen-specific TH2 lymphocytes with S-layer-conjugated Bet v 1 led to a modulation of the cytokine production pattern from TH2 to TH0/TH1. This study indicates that S-layers may be suitable carriers for few immunotherapeutical vaccines for Type 1 hypersensitivity.

Toward selective elicitation of TH1-controlled vaccination responses: vaccine applications of bacterial surface layer proteins.

Bacterial surface layer proteins have been utilized as combined vaccine carrier/adjuvants and offer a number of advantages in these applications. The crystalline protein arrays contain functional groups in precisely defined orientations for coupling of haptens. Conventional applications of S-layer vaccines do not cause observable trauma or side effects. Depending on the nature of the S-layer preparations, antigenic conjugates will induce immune responses of a predominantly cellular or predominantly humoral nature. Immune responses to S-layer-hapten conjugates are also observed following oral/nasal application. In the present contribution, the status of investigations with S-layer conjugates in three main immunological projects is reviewed. In a project aimed at immunotherapy of cancer, conjugates of S-layer with small, tumor-associated oligosaccharides have been found to elicit hapten-specific DTH responses. An enlarged program of chemical synthesis has now been initiated to prepare a complete set of mucin-derived, tumor-associated oligosaccharides and their chemically modified analogues for elicitation of cell-mediated immune responses to certain tumors in humans. In another application, oligosaccharides derived from capsules of Streptococcus pneumoniae type 8 have been linked to S-layer proteins and have been found to elicit protective antibody responses in animals. Most recently, allergen S-layer conjugates have been prepared with the intention to suppress the TH2-directed, IgE-mediated allergic responses to Bet nu 1, the major allergen of birch pollen. In the former two applications, the S-layer vaccine technology appears to offer the versatility needed to direct vaccination responses toward predominant control by TH1 or TH2 lymphocytes to meet the different therapeutic or prophylactic requirements in each case. In the third application, work has progressed to a preliminary stage only.

Induction of T-cell immunity to oligosaccharide antigens immobilized on crystalline bacterial surface layers (S-layers).

Immunization of Balb/c mice with conjugates of oligosaccharide haptens and crystalline bacterial surface-layer proteins (S-layers) primed the mice for a strong, hapten-specific, delayed-type hypersensitivity (DTH) response. Conjugates of haptens with bovine serum albumin produced only weak DTH responses but, when mixed with aluminium hydroxide, elicited DTH responses comparable to those against S-layer conjugates. Surface-layer conjugates also elicited strong anti-hapten DTH responses when administered by an oral/nasal route. Apparently, the natural assembly of S-layer proteins into large, two-dimensional arrays endows them with intrinsic adjuvant properties.

Artificial antigens. Synthetic carbohydrate haptens immobilized on crystalline bacterial surface layer glycoproteins.

The crystalline surface-layer glycoproteins of Clostridium thermohydrosulfuricum L111-69, Bacillus stearothermophilus NRS 2004/3a and Bacillus alvei CCM 2051 were used for immobilization of spacer-linked blood group A-trisaccharide (alpha GalNAc(1----3)[alpha Fuc(1----2)]beta Gal) and of the spacer-linked, tumor-associated T-disaccharide [beta Gal(1----3)alpha GalNAc]. The immobilization involved the glycan portions of surface-layer glycoproteins. Different activation methods were used, namely, periodate oxidation, or treatment with epichlorohydrin or divinyl sulfone, followed by coupling of the hapten under appropriate conditions. The resulting conjugates are useful for assessing the application potential of haptenated surface layer preparations as carrier/adjuvants for the induction of immunity to poorly immunogenic molecules.

Autosomal recessive cerebellar hypoplasia and endosteal sclerosis: a newly recognized syndrome.

We describe a brother and sister and an unrelated boy with congenital cerebellar hypoplasia and endosteal sclerosis. All 3 children presented with ataxia and developmental delay, and were found to have microcephaly, short stature, oligodontia, strabismus, nystagmus, and congenital hip dislocation. A previously published case is reviewed. The disorder appears to represent a newly recognized autosomal recessive syndrome.

Synthesis and bioactivity of copolymers with fragments of heparin.

A new type of biocompatible copolymer comprising small fragments of heparin, (octa- to dodecasaccharides) copolymerized with a synthetic monomeric component, viz. acrylamide, has been prepared. The heparin fragments are produced by enzymatic or chemical means and are copolymerized, directly or after suitable derivatization, with acrylamide as the major polymerizable component. The polymeric material incorporates the heparin segments as pendant moieties such that their essential functional groups and structural features for specific binding with the selective serine protease coagulation factor inhibitor antithrombin III are preserved. An important feature of this copolymer is its biocompatibility which relates specifically to its antithrombotic and antithrombogenic activity derived from those of heparin fragments. The biological activity of heparin fragments and copolymers thereof are determined in terms of APTT and anti-Xa activity, their antithrombotic potential being expressed as a ratio of anti-Xa activity to APTT. The copolymers reported have biological activities similar to equivalent amounts of respective heparin fragments, and show higher antithrombotic activity compared to intact heparin or commercially available low-molecular-weight heparin (4,000-6,000 Da).

Synthesis of trisaccharides containing 3-deoxy-D-manno-2-octulosonic acid residues related to the KDO-region of enterobacterial lipopolysaccharides.

Glycosylation of methyl (allyl 7,8-O-carbonyl-3-deoxy-alpha-D-manno-2-octulo-pyranosid)o nate with an alpha-(2----4) linked per-O-acetylated KDO-disaccharide bromide derivative under Helferich conditions afforded a 2:1 mixture of the alpha- and beta-linked trisaccharide derivatives in 50% yield. Removal of the protecting groups gave sodium O-[sodium (3-deoxy-alpha-D-manno-2-octulopyranosyl)onate]-(2----4)-O-[ sodium (3-deoxy-alpha- and -beta-D-manno-2-octulopyranosyl)onate]-(2----4)-sodium (allyl 3-deoxy-alpha-D-manno-2-octulopyranosid)onate. Radical copolymerization of the allyl glycosides afforded artificial antigens, suitable for defining antibody specificities directed against the KDO-region of enterobacterial lipopolysaccharides.

Isolation and structure determination of a diacetamidodideoxyuronic acid-containing glycan chain from the S-layer glycoprotein of Bacillus stearothermophilus NRS 2004/3a.

A glycan isolated from the surface-layer glycoprotein of Bacillus stearothermophilus strain NRS 2004/3a was shown by 1H- and 13C-n.m.r. spectroscopy to have the tetrasaccharide repeating-unit ----4)-beta-ManpA2,3(NAc)2-(1----3)-alpha-GlcpNAc-(1----4)-beta- ManpA2,3(NAc)-(1----6)-alpha-Glcp(1----.

Artificial antigens. Synthesis of polyacrylamide copolymers containing 3-deoxy-D-manno-2-octulopyranosylonic acid (KDO) residues.

Starting from an anomeric mixture of methyl (allyl 4,5,7,8-tetra-O-acetyl-3-deoxy-alpha- and -beta-D-manno-2-octulopyranosid)onates, the glycosides sodium (allyl 3-deoxy-alpha- and -beta-D-manno-2-octulopyranosid)onate, sodium O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----4)-[allyl 3-deoxy-alpha-D-manno-2-octulopyranosid]onate and sodium (allyl 3-deoxy-7-O-beta-D-ribofuranosyl-beta-D-manno-2-octulopyranosid)++ +onate were prepared in several steps. Radical copolymerization of the allyl glycosides with acrylamide afforded linear macromolecular antigens containing mono- and di-saccharide residues corresponding to the KDO-region of Salmonella minnesota rough-form lipopolysaccharide and to partial structures of the capsular polysaccharide from Escherichia coli K 23, respectively. The copolymers were substituted by KDO-residues in a ratio of 1:18 +/- 2 (based on acrylamide) and had molecular masses of 60-100 kdaltons.

Two additional bacteriophage-associated glycan hydrolases cleaving ketosidic bonds of 3-deoxy-D-manno-octulosonic acid in capsular polysaccharides of Escherichia coli.

Two bacteriophages degrading 3-deoxy-D-manno-2-octulosonic acid-(KDO)-containing capsules of Escherichia coli strains were identified. Using modifications of the thiobarbituric acid assay, it was shown that each phage contains a glycan hydrolase activity cleaving one type of ketosidic linkage of KDO. Thus, the enzyme from phage phi 95 catalyzes the hydrolysis of beta-octulofuranosidonic linkages of the K95 glycan; and phi 1092, the alpha-octulopyranosidonic linkages of the K? antigen of E. coli LP1092. No cross-reactivity of the phage enzymes with other KDO-containing capsular polysaccharides was observed.

Structure of a rhamnan from the surface-layer glycoprotein of Bacillus stearothermophilus strain NRS 2004/3a.

The structure of a glycan from the surface-layer glycoprotein of Bacillus stearothermophilus strain NRS 2004/3a has been studied by 1H- and 13C-n.m.r. spectroscopy. The results indicate the glycan to be a polymer of the trisaccharide repeating-unit ----2)-alpha-L-Rhap-(1----2)-alpha-L-Rhap-(1----3)-beta-L-++ +Rhap-(1----.

Radiologic and real time echocardiographic evaluation of the cyanotic newborn.

Prior to echocardiography, the recognition of serious heart disease in the cyanotic newborn or young infant could be extremely difficult. The profound hemodynamic changes taking place in the heart and lungs after birth influence the clinical manifestations of many cardiac disorders, and sometimes suggest the existence of a cardiac disorder when none is present. Real time echocardiography has revolutionalized the diagnosis of the cyanotic infant. If the reason for the infant's cyanosis or respiratory distress is not apparent from the history, physical examination, laboratory values, and chest radiograph; real time echocardiography should be performed to exclude or diagnose cyanotic congenital heart disease and persistent fetal circulation. This will prevent misdiagnosis in cyanotic infants and assure rapid and appropriate treatment.