Selectin ligands

Alpha1-acid glycoprotein suppresses rat acute inflammatory paw edema through the inhibition of neutrophils activation and prostaglandin E2 generation

Alpha(1)-acid glycoprotein (AGP) is an acute phase protein. Whereas the expression of AGP in an inflammatory state is enhanced by inflammatory cytokines including interleukin-1, 6 (IL-1 and IL-6), and tumor necrosis factor-alpha (TNF-alpha), the biological significance of AGP remains unclear. In the current study, the anti-inflammatory effect of AGP on the acute inflammatory state was examined in vivo and in vitro. AGP suppressed carrageenan-, dextran- and kaolin-induced paw edema and vascular permeability in rat. These results suggest that both initial inflammatory mediators (serotonin and histamine) and later inflammatory mediators (prostaglandin and bradykinin) are involved in the anti-inflammatory effects of AGP. In fact, prostaglandin E(2) (PGE(2)) generation in plasma was significantly inhibited by AGP. Moreover, AGP inhibited the migration of neutrophils treated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) through membrane filter. In addition, AGP significantly suppressed superoxide generation from neutrophils that has been treated with fMLP or phorbol 12-myristate 13-acetate. These results imply that the anti-inflammatory effect of AGP may involve the inhibition of neutrophils migration. The data obtained in this study support a scenario in which an increase in AGP concentration in pathological conditions suppresses inflammation reactions induced by autacoids and neutrophils activities and that AGP plays an important role in the maintenance in the body.

Sialyl Lewis x expression in canine malignant mammary tumours: correlation with clinicopathological features and E-Cadherin expression

Background

Sialyl Lewis x (sLe^x) antigen is a carbohydrate antigen that is considered not only a marker for cancer but also implicated functionally in the malignant behaviour of cancer cells. Overexpression of sLe^x is associated with enhanced progression and metastases of many types of cancer including those of the mammary gland. Canine mammary tumours can invade and give rise to metastases via either lymphatic or blood vessels.

E-Cadherin is specifically involved in epithelial cell-to-cell adhesion. In cancer, E-Cadherin underexpression is one of the alterations that characterizes the invasive phenotype and is considered an invasion/tumour suppressor gene. Partial or complete loss of E-Cadherin expression correlates with poor prognosis in canine malignant mammary cancer.

The aim of this study was to analyse the sLe^x expression in canine malignant mammary tumours and to evaluate if the presence of sLe^x correlates with the expression of E-Cadherin and with clinicopathological features.

Methods

Fifty-three cases of canine mammary carcinomas were analysed immunohistochemically using monoclonal antibodies against sLe^x (IgM) and E-Cadherin (IgG). The clinicopathological data were then assessed to determine whether there was a correlation with sLe^x tumour expression. Double labelled immunofluorescence staining was performed to analyse the combined expression of sLe^x and E-Cadherin.

Results

sLe^x expression was consistently demonstrated in all cases of canine mammary carcinomas with different levels of expression. We found a significant relationship between the levels of sLe^x expression and the presence of lymph node metastases. We also demonstrated that when E-Cadherin expression was increased sLe^x was reduced and vice-versa. The combined analysis of both adhesion molecules revealed an inverse relationship.

Conclusion

In the present study we demonstrate the importance of sLe^x in the malignant phenotype of canine malignant mammary tumours. Our results support the use of sLe^x as a prognostic tumour marker in canine mammary carcinomas. Furthermore, we showed that sLe^x and E-Cadherin expression were inversely correlated. Future studies are warranted to clarify the molecular mechanism underlying the relation between sLe^x and E-Cadherin in canine mammary carcinoma cells which represents an important comparative model to woman breast cancer.

Mild episodes of tourniquet-induced forearm ischaemia-reperfusion injury results in leukocyte activation and changes in inflammatory and coagulation markers

Background

Monocytes and neutrophils are examples of phagocytic leukocytes, with neutrophils being considered as the 'chief' phagocytic leukocyte. Both monocytes and neutrophils have been implicated to play a key role in the development of ischaemia-reperfusion injury, where they are intrinsically involved in leukocyte-endothelial cell interactions. In this pilot study we hypothesised that mild episodes of tourniquet induced forearm ischaemia-reperfusion injury results in leukocyte activation and changes in inflammatory and coagulation markers.

Methods

Ten healthy human volunteers were recruited after informed consent. None had any history of cardiovascular disease with each subject volunteer participating in the study for a 24 hour period. Six venous blood samples were collected from each subject volunteer at baseline, 10 minutes ischaemia, 5, 15, 30, 60 minutes and 24 hours reperfusion, by means of a cannula from the ante-cubital fossa. Monocyte and neutrophil leukocyte sub-populations were isolated by density gradient centrifugation techniques. Leukocyte trapping was investigated by measuring the concentration of leukocytes in venous blood leaving the arm. The cell surface expression of CD62L (L-selectin), CD11b and the intracellular production of hydrogen peroxide (H₂O₂) were measured via flow cytometry. C-reactive protein (CRP) was measured using a clinical chemistry analyser. Plasma concentrations of D-dimer and von Willebrand factor (vWF) were measured using enzyme-linked fluorescent assays (ELFA).

Results

During ischaemia-reperfusion injury, there was a decrease in CD62L and an increase in CD11b cell surface expression for both monocytes and neutrophils, with changes in the measured parameters reaching statistical significance (p =< 0.05). A significant decrease in peripheral blood leukocyte concentration was observed during this process, which was measured to assess the degree of leukocyte trapping in the micro-circulation (p =< 0.001). There was an increase in the intracellular production of H₂O₂ production by leukocyte sub-populations, which was measured as a marker of leukocyte activation. Intracellular production of H₂O₂ in monocytes during ischaemia-reperfusion injury reached statistical significance (p = 0.014), although similar trends were observed with neutrophils these did not reach statistical significance. CRP was measured to assess the inflammatory response following mild episodes of ischaemia-reperfusion injury and resulted in a significant increase in the CRP concentration (p =< 0.001). There were also increased plasma concentrations of D-dimer and a trend towards elevated vWF levels, which were measured as markers of coagulation activation and endothelial damage respectively. Although significant changes in D-dimer concentrations were observed during ischaemia-reperfusion injury (p = 0.007), measurement of the vWF did not reach statistical significance.

Conclusion

Tourniquet induced forearm ischaemia-reperfusion injury results in increased adhesiveness, trapping and activation of leukocytes. We report that, even following a mild ischaemic insult, this leukocyte response is immediately followed by evidence of increased inflammatory response, coagulation activity and endothelial damage. These results may have important implications and this pilot study may lead to a series of trials that shed light on the mechanisms of ischaemia-reperfusion injury, including potential points of therapeutic intervention for pathophysiological conditions.

Glycan-based interactions involving vertebrate sialic-acid-recognizing proteins

All cells in nature are covered by a dense and complex array of carbohydrates. Given their prominence on cell surfaces, it is not surprising that these glycans mediate and/or modulate many cellular interactions. Proteins that bind sialic acid, a sugar that is found on the surface of the cell and on secreted proteins in vertebrates, are involved in a broad range of biological processes, including intercellular adhesion, signalling and microbial attachment. Studying the roles of such proteins in vertebrates has improved our understanding of normal physiology, disease and human evolution.

Vesicle size and stability of biomimetic liposomes from 3'-sulfo-Lewis a (SuLea) containing glycolipids

We report on the use of a natural Lewis type saccharide ligand, 3'-sulfo-Lewis a (SuLe(a)) for glycocalyx-mimetic surface modification of liposomes. Two SuLe(a)-containing glycolipids, monovalent SuLe(a)-lipid and trivalent SuLe(a) (TSuLe(a))-lipid, were synthesized, and used with 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol to prepare unilaminar vesicles (ULVs) by a freeze-thaw and extrusion method. The effects of the glycolipid concentrations and the pore sizes of extrusion membranes on vesicle size and stability were investigated by photon correlation spectroscopy (PCS). Glycoliposomes, with 5% SuLe(a)- or TSuLe(a)-lipids obtained by 50 nm extrusion, had 25-30% more vesicles less than 100 nm in diameter compared with the 100 nm extrusion. TSuLe(a)-liposomes always produced larger vesicle size than SuLe(a)-liposomes, which we attribute to the larger TSuLe(a) headgroup. Both SuLe(a)- and TSuLe(a)-liposomes increased their vesicle size with increasing glycolipid concentration from 5% to 15%, and demonstrated good stability at room temperature for over 1 month. Further increasing the glycolipid concentration to 20% resulted in large vesicle aggregation after 5 days for TSuLe(a)-liposomes, while the SuLe(a)-liposomes remained stable for 10 days. SuLe(a)- and TSuLe(a)-liposomes with 15% glycolipids demonstrated better stability due to the electrostatic effect from the negatively charged SuLe(a) and TSuLe(a) headgroups. The results indicate that the biomimetic liposomes with SuLe(a)- and TSuLe(a)-lipids with 5 to 15% incorporation are sufficiently stable for the potential applications in targeted drug delivery.

Anti-ganglioside complex antibodies associated with severe disability in GBS

Ganglioside complexes (GSCs) are known as target antigens in Guillain-Barré syndrome (GBS). To elucidate the clinical importance of the anti-GSC antibodies in GBS, we investigated serum antibodies to GSCs containing two of the gangliosides, GM1, GD1a, GD1b and GT1b, and analyzed clinical features of anti-GSC-positive GBS patients. Thirty-nine (17%) of 234 GBS patients had IgG anti-GSC antibodies. Anti-GSC-positive GBS had antecedent gastrointestinal infection and lower cranial nerve deficits more frequently than control GBS. The presence of antibody specificity to GD1a/GD1b and/or GD1b/GT1b was significantly associated with severe disability and a requirement for mechanical ventilation.

Circulating KL-6/MUC1 mucin carrying sialyl Lewisa oligosaccharide is an independent prognostic factor in patients with lung adenocarcinoma

MUC1 mucin is frequently observed in adenocarcinomas, and its association with metastasis has been postulated through the interaction between sialyl Lewis oligosaccharides present on this glycoprotein and selectins. Levels of soluble MUC1 recognized by anti-KL-6 monoclonal antibody were also frequently elevated in the sera of lung adenocarcinoma patients. The aim of this study was to demonstrate the presence of KL-6/MUC1 carrying sialyl Lewis(a) oligosaccharide, designated as SLAK, and subsequently evaluate the clinical significance of circulating SLAK in patients with lung adenocarcinoma. We developed a sandwich ELISA system using anti-sialyl Lewis(a) and anti-KL-6 antibodies to detect SLAK, and also measured circulating SLAK levels in 97 healthy controls and 103 patients with lung adenocarcinoma. Circulating SLAK levels were measured in the sera taken before treatment and then were evaluated to clarify whether such levels were related to the clinical outcomes. Levels of circulating SLAK were significantly higher in lung adenocarcinoma patients than in healthy subjects, and a higher serum SLAK level was correlated with the presence of distant metastasis. The overall survival rate for patients with high serum SLAK levels was significantly poorer than that of patients with low serum SLAK levels. The survival analysis restricted to the patients with distant metastasis also showed the same trend. In a multivariate survival analysis in lung adenocarcinoma patients, a high serum SLAK level was indicated as an independent prognostic factor. In conclusion, the circulating SLAK level at diagnosis is useful for predicting a poor prognosis in patients with lung adenocarcinoma.

Alpha 1,3-fucosyltransferase-VII regulates the signaling molecules of the insulin receptor pathway

Two H7721 human hepatocarcinoma cell lines showing moderate and high expression of alpha1,3-fucosyltransferase (FucT)-VII cDNA were established and designated FucTVII-M and FucTVII-H, respectively. In alpha1,3-FucT-VII-transfected cells, expression of insulin receptor (InR) alpha- and beta subunits and epidermal growth factor receptor (EGFR) on the cell surface and in cells, as well as the sialyl Lewis X (SLe(x), the product of alpha1,3-FucT-VII) content of the EGFR were unchanged. However the level of SLe(x) on the InR alpha subunit (InR-alpha) was increased dramatically. Tyrosine autophosphorylation of InR-beta , but not EGFR, was elevated. Concomitantly, tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), Ser/Thr phosphorylation of protein kinase B (PKB; Akt), p42/44 mitogen-activated protein kinase (MAPK), MAPK kinase (MEK), and the protein of some other signaling molecules, such as phosphoinositide-dependent kinase-1 (PDK-1), novel protein kinase (PKN), c-Raf-1 and beta-catenin were also upregulated. The activities of PKB and transcription factor TCF were concomitantly stimulated. Upregulation of InR signaling molecules and their phosphorylation was correlated with the level of SLe(x) on InR-alpha and alpha1,3-FucT-VII expression in cells. In addition, the phosphorylation intensity and difference in phosphorylation intensity between cells with different levels of alpha1,3-FucT-VII expression were attenuated significantly by the inhibitor of InR tyrosine kinase and by the mAb to SLe(x). Furthermore, insulin-induced signaling was facilitated in alpha1,3-FucT-VII-transfected cells, particularly FucTVII-H. These findings provide strong evidence that alpha1,3-FucT-VII may affect insulin signaling by upregulating the phosphorylation and expression of some signaling molecules involved in the InR-signaling pathway. These effects are likely mediated by its product, SLe(x), on the glycans of the InR. This is the first study to report that changes in the terminal structure of glycans on a surface receptor can modify cell signaling.

P-selectin mediates metastatic progression through binding to sulfatides on tumor cells

Hematogenous carcinoma metastasis is associated with tumor cell emboli formation, which is now known to be facilitated by selectins. P-selectin-mediated interactions of platelets with cancer cells are based mostly on mucin- and glycosaminoglycan-type selectin ligands. We previously showed that mouse colon carcinoma cells (MC-38) carry P-selectin ligands of nonmucin origin, which were not identified. Here we show that P-selectin ligands recognized on MC-38 cells are sulfated glycolipids, thereby facilitating experimental metastasis in a syngeneic mouse model. Metabolic inhibition of sulfation by incubation of cells with sodium chlorate almost completely abrogated P-selectin binding. Metabolic labeling of MC-38 cells with (35)S sulfate revealed only a single band as detected by high-performance thin layer chromatography analysis of a total lipid extract. Matrix-assisted laser desorption/ionization tandem time-of-flight/time-of-flight analysis (MALDI-TOF-TOF) analysis of the purified sulfate-containing lipid fraction identified the selectin ligand to be a sulfated galactosylceramide SM4 (HSO(3)-3Galbeta-1Cer). Modulation of glycolipid biosynthesis in MC-38 cells altered P-selectin binding, thereby confirming sulfoglycolipids to be major P-selectin ligands. In addition, P-selectin was also found to recognize lactosylceramide sulfate SM3 (HSO(3)-3Galbeta-4Glcbeta-1Cer) and gangliotriaosylceramide sulfate SM2 [GalNAcbeta-4(HSO(3)-3)Galbeta-4Glcbeta-1Cer] in human hepatoma cells. Finally, the enzymatic removal of sulfation from the cell surface of MC-38 cells resulted in decreased P-selectin binding and led to attenuation of metastasis. Thus, SM4 sulfatide serves as a native ligand for P-selectin contributing to cell-cell interactions and to facilitation of metastasis.

Diminished lymphocyte adhesion and alleviation of allergic responses by small-molecule- or antibody-mediated inhibition of L-selectin functions

Selectins are attractive targets for specific anti-inflammatory therapies. Using human lymphocytes as well as an L-selectin-transfected pre-B-cell line in dynamic flow chamber experiments, we could demonstrate that the small-molecule compound efomycine M blocks L-selectin-mediated lymphocyte rolling on sialylated Lewis(X), an action that was confirmed by plasmon resonance spectroscopy. Recruitment of naive lymphocytes to peripheral lymph nodes depends on L-selectin-mediated adhesion to high endothelial venules. We performed intravital microscopy studying lymphocyte rolling in peripheral lymph nodes and showed a 53% reduction (P=0.0006) of lymphocyte rolling in mice treated with efomycine M or a function-blocking antibody against L-selectin. In addition, the number of lymph node-homing T cells was reduced by >60% using either efomycine M or L-selectin-blocking antibodies. As recruitment of naive lymphocytes is a prerequisite for sensitization in T-cell-mediated immune reactions and allergic responses, mice were treated with efomycine M or an L-selectin-specific antibody during contact sensitization with DNFB. After adoptive transfer of corresponding T cells into non-sensitized recipient mice, the capacity of these cells to induce contact hypersensitivity was significantly reduced (P=0.0002 and P=0.0001, respectively). Our data demonstrate that it is possible, in principle, to diminish T-cell-mediated allergic reactions through interference with L-selectin functions during the early sensitization phase.

Heterologous expression and site-directed mutagenesis studies of two Trichoderma harzianum chitinases, Chit33 and Chit42, in Escherichia coli

Heterologous expression of two fungal chitinases, Chit33 and Chit42, from Trichoderma harzianum was tested in the different compartments and on the surface of Escherichia coli cells. Our goal was to find a fast and efficient expression system for protein engineering and directed evolution studies of the two fungal enzymes. Cytoplasmic overexpression resulted in both cases in inclusion body formation, where active enzyme could be recovered after refolding. Periplasmic expression of Chit33, and especially of Chit42, proved to be better suited for mutagenesis purposes. Recombinant chitinases from the periplasmic expression system showed activity profiles similar to those of the native proteins. Both chitinases also degraded a RET (resonance energy transfer) based bifunctionalized chitinpentaose substrate in a similar manner as reported for some putative exochitinases in the glycosyl hydrolase family 18, offering a sensitive way to assay their activities. We further demonstrated that Chit42 can also be displayed on E. coli surface and the enzymatic activity can be measured directly from the whole cells using methylumbelliferyl-chitinbioside as a substrate. The periplasmic expression and the surface display of Chit42, both offer a suitable expression system for protein engineering and activity screening in a microtiter plate scale. As a first mutagenesis approach we verified the essential role of the two carboxylic acid residues E172 (putative proton donor) and D170 (putative stabilizer) in the catalytic mechanism of Chit42, and additionally the role of the carboxylic acid E145 (putative proton donor) in the catalytic mechanism of Chit33.

The use of levoglucosenone and isolevoglucosenone as templates for the construction of C-linked disaccharides

Because of their functionalities (enone, ketone, and acetal) and their bicyclic structure (steric factors), levoglucosenone (1,6-anhydro-3,4-dideoxy-beta-D-glycero-hex-3-enopyran-2-ulose) and isolevoglucosenone (1,6-anhydro-2,3-dideoxy-beta-D-glycero-hex-3-enopyran-4-ulose) are useful templates for the convergent and combinatorial synthesis of (1-->2), (1-->3), and (1-->4)-linked C-disaccharides in reactions combining them with sugar-derived carbaldehydes. Synthetic methods relying on conjugate nucleophilic additions of these enones, their combination with aluminum reagents and aldehydes (Baylis-Hillman reaction) and modified Takai-Hiyama-Nozaki-Kishi couplings of enol triflates derived from them with sugar-derived aldehydes are reviewed. Highly stereoselective methods have thus been developed. These allow the generation of disaccharide mimetics with a high molecular diversity.

System-wide genomic and biochemical comparisons of sialic acid biology among primates and rodents: Evidence for two modes of rapid evolution

Numerous vertebrate genes are involved in the biology of the oligosaccharide chains attached to glycoconjugates. These genes fall into diverse groups within the conventional Gene Ontology classification. However, they should be evaluated together from functional and evolutionary perspectives in a "biochemical systems" approach, considering each monosaccharide unit's biosynthesis, activation, transport, modification, transfer, recycling, degradation, and recognition. Sialic acid (Sia) residues are monosaccharides at the outer end of glycans on the cell-surface and secreted molecules of vertebrates, mediating recognition by intrinsic or extrinsic (pathogen) receptors. The availability of multiple genome sequences allows a system-wide comparison among primates and rodents of all genes directly involved in Sia biology. Taking this approach, we present further evidence for accelerated evolution in Sia-binding domains of CD33-related Sia-recognizing Ig-like lectins. Other gene classes are more conserved, including those encoding the sialyltransferases that attach Sia residues to glycans. Despite this conservation, tissue sialylation patterns are shown to differ widely among these species, presumably because of rapid evolution of sialyltransferase expression patterns. Analyses of N- and O-glycans of erythrocyte and plasma glycopeptides from these and other mammalian taxa confirmed this phenomenon. Sia modifications on these glycopeptides also appear to be undergoing rapid evolution. This rapid evolution of the sialome presumably results from the ongoing need of organisms to evade microbial pathogens that use Sia residues as receptors. The rapid evolution of Sia-binding domains of the inhibitory CD33-related Sia-recognizing Ig-like lectins is likely to be a secondary consequence, as these inhibitory receptors presumably need to keep up with recognition of the rapidly evolving "self"-sialome.

Lymphocyte trafficking to inflamed skin--molecular mechanisms and implications for therapeutic target molecules

Tissue-selective recruitment of lymphocytes to peripheral organs, such as the skin, is crucial for spatial compartmentalisation within the immune system as well as immune surveillance under normal conditions. In addition, this process plays a key role for the pathogenesis of various diseases including common inflammatory disorders such as atopic dermatitis or psoriasis, but also malignancies such as cutaneous T cell lymphomas. Recruitment of lymphocytes to the skin is a highly complex process that involves adhesion to the endothelial lining, extravasation, migration through the connective tissue, and, finally, localisation of a subpopulation of lymphocytes to the epithelial compartment, the epidermis. An intertwined network of constitutively expressed and inducible cytokines, chemokines and other mediators provides guidance for lymphocyte migration, and a large number of adhesion receptors mediate sequential steps of cell-cell- and cell-substrate-interactions resulting in tissue-specific localisation of immune cells. Selectively targeting the functions of one or several key molecules involved in this complex cascade promises exciting new therapeutic options for treating inflammatory disorders, but at the same time, bears considerable imponderables which will be discussed in this article.

Serum P-selectin, soluble vascular cell adhesion molecule-I (s-VCAM-I) and soluble intercellular adhesion molecule-I (s-ICAM-I) levels in bladder carcinoma patients with different stages

Adhesion molecules are thought to have a role in the host defense against carcinogenesis. In this study, we measured serum platelet-(P-) selectin, soluble vascular cell adhesion molecule-I (s-VCAM-I), and soluble intercellular adhesion molecule-I (s-ICAM-I) levels in 51 sequential bladder cancer patients at our urology clinic and 8 controls. Serum levels of P-selectin, s-VCAM-I and s-ICAM-I were significantly higher in all patients than controls. Serum P-selectin and s-ICAM-I levels did not differ based on tumor (T) stage and tumor grade, whereas serum levels of s-VCAM-I were significantly higher in patients with muscle invasive tumors than those with superficial tumors. Further, s-VCAM-I levels correlated with T stage. In conclusion, significantly increased P-selectin, s-VCAM-I, and s-ICAM-I levels were observed in patients with bladder cancer, and s-VCAM-I levels correlated with T stage. Thus, we suggest that the analysis of serum s-VCAM-I levels may provide a prognostic test for T stage and bladder cancer progression during and/or following therapy.

Structure–Function Relation of Efomycines, a Family of Small-Molecule Inhibitors of Selectin Functions

Selectin-mediated leukocyte adhesion to endothelia, the crucial first step initiating the pathogenic cascade of inflammation, is an attractive target for specific therapies. The small-molecule macrolide, efomycine M, inhibits selectin-mediated leukocyte adhesion in vitro and in vivo, and effectively alleviates inflammatory disorders in vivo. To define the molecular basis of the therapeutically relevant antiadhesive properties of efomycines, several new species of this family were purified and/or synthesized. Efomycines E and G were isolated from Steptomyces BS1261. Efomycine O was synthesized by Lewis acid-catalyzed acetalization and efomycine M was generated by base-catalyzed deglycosylation. Efomycine S resulted from ester cleavage of the macrolide ring system, and efomycine T represents the peracetylated form of efomycine M. When the functional activity of efomycines on adhesion of leukocytes to vascular endothelium was studied, some remarkable differences between the compounds became apparent, inasmuch as efomycines E, G, M, and O significantly inhibited adhesion of both human and porcine leukocytes to the vascular endothelium, whereas efomycines S and T did not show any biological activity. A novel docking engine (ProPose), generating an improved, fully configurable protein-ligand interaction model, demonstrated that biological activities of efomycines can be predicted in silico, thus highlighting the utility of such combinatorial approaches.

Alterations of CD43 expression in transfusion-dependent myelodysplastic syndromes

CD43 is a sialylated glycoprotein expressed on the surface of most haemopoietic cells and has been implicated in cell adhesion and signaling. It has previously been shown that CD43 expression is altered in patients with myelodysplastic syndrome (MDS). This raised the question of whether the alteration is associated with transfusions in these patients. We studied the expression of this antigen on peripheral blood leucocytes in two groups of patients with refractory anaemia, 22 transfused and 20 non-transfused. We found decreased expression of CD43 on the monocytes and neutrophils of patients receiving transfusions. Other activation molecules were studied (CD11b, CD18) and were found up-regulated suggesting the existence of activated leucocytes in these patients. The increased levels of soluble vascular cellular endothelial molecule after transfusions in these patients suggested vascular endothelial activation in the absence of infection. Given together, these results show that decreased CD43 in the transfused group of MDS patients is associated with an activated endothelial phenotype.

Differential metastasis inhibition by clinically relevant levels of heparins--correlation with selectin inhibition, not antithrombotic activity

PURPOSE

Unfractionated heparin reduces metastasis in many murine models. Multiple mechanisms are proposed, particularly anticoagulation and/or inhibition of P-selectin and L-selectin. However, the doses used are not clinically tolerable and other heparins are now commonly used. We studied metastasis inhibition by clinically relevant levels of various heparins and investigated the structural basis for selectin inhibition differences.

EXPERIMENTAL DESIGN

Five clinically approved heparins were evaluated for inhibition of P-selectin and L-selectin binding to carcinoma cells. Pharmacokinetic studies determined optimal dosing for clinically relevant anticoagulant levels in mice. Experimental metastasis assays using carcinoma and melanoma cells investigated effects of a single injection of various heparins. Heparins were compared for structural relationships to selectin inhibition.

RESULTS

One (Tinzaparin) of three low molecular weight heparins showed increased selectin inhibitory activity, and the synthetic pentasaccharide, Fondaparinux, showed none when normalized to anticoagulant activity. Experimental metastasis models showed attenuation with unfractionated heparin and Tinzaparin, but not Fondaparinux, at clinically relevant anticoagulation levels. Tinzaparin has a small population of high molecular weight fragments not present in other low molecular weight heparins, enriched for selectin inhibitory activity.

CONCLUSIONS

Heparin can attenuate metastasis at clinically relevant doses, likely by inhibiting selectins. Equivalent anticoagulation alone with Fondaparinux is ineffective. Clinically approved heparins have differing abilities to inhibit selectins, likely explained by size distribution. It should be possible to size fractionate heparins and inhibit selectins at concentrations that do not have a large effect on coagulation. Caution is also raised about the current preference for smaller heparins. Despite equivalent anticoagulation, hitherto unsuspected benefits of selectin inhibition in various clinical circumstances may be unwittingly discarded.

Expression of Lea in gastric cancer cell lines depends on FUT3 expression regulated by promoter methylation

Aberrant expression of Lewis antigens has been demonstrated in gastric lesions, namely gastritis, intestinal metaplasia (IM) and gastric carcinoma (GC), and can be partly due to overexpression of the Lewis (FUT3) enzyme. Our aim was to evaluate the role of promoter methylation in FUT3 and Le(a) expression in gastric carcinoma cell lines. MKN45 cell line showed low amounts of Le(a), in the absence of FUT3; GP220 expressed high levels of Le(a) and FUT3. After 5aza-2'deoxycytidine MKN45 showed increased levels of FUT3 and Le(a), by immunohistochemistry and Real-Time PCR, whereas GP220 showed an increase in FUT3 without increase of Le(a). Enzyme activity assays confirmed an increase in alpha-1,4 fucosyltransferase activity in both cell lines by 5aza-2'deoxycytidine. Luciferase reporter gene assays, using methylated and unmethylated deletion constructs of FUT3 promoter, showed that FUT3 expression is regulated by methylation. Summing up, we showed that FUT3 overexpression in gastric cells depends upon promoter hypomethylation and that FUT3 is responsible for overexpression of Le(a) in gastric cells, in vitro. FUT3, Lea, Methylation.

The involvement of selectins and their ligands in tumor-progression

About 70 years ago, Peyton Rous described the progression of cancer towards metastasis formation as "the process whereby tumors go from bad to worse". The interactions of tumor cells with endothelium are pivotal steps in this process. This review focuses on the role played by the selectins and their ligands in these interactions and especially in tumor cell extravasation. The working hypothesis of researchers studying tumor cell extravasation is that the tumor cells follow the extravasation strategy of leukocytes in their migration towards inflammatory sites. A significant portion of this review is, therefore, dedicated to the molecular mechanisms underlying leukocyte extravasation and to a comparison between the extravasation strategy employed by leukocytes and tumor cells. The review also summarizes some of the available data on signals generated by selectin-selectin ligand interactions.

Monocyte recruitment and foam cell formation in atherosclerosis

Atherosclerosis is a chronic immune-inflammatory disease in which the interactions of monocytes with activated endothelium are crucial events leading to atherosclerotic alteration of the arterial intima. In early atherosclerosis, monocytes migrate into the subendothelial layer of the intima where they differentiate into macrophages or dendritic cells. In the subendothelial space enriched with atherogenic lipoproteins, most macrophages transform into foam cells. Foam cells aggregate to form the atheromatous core and as this process progresses, the atheromatous centres of plaques become necrotic, consisting of lipids, cholesterol crystals and cell debris. This review highlights some aspects of monocyte recruitment and foam cell formation in atherosclerosis.

Regulation of metastasis-suppressive gene Nm23-H1 on glycosyl-transferases involved in the synthesis of sialyl Lewis antigens

By using reverse transcriptase-polymerase chain reaction (RT-PCR), the mRNA expressions of three families of glycosyltransferases involved in the synthesis of sialyl Lewis antigens were determined in H7721 human hepatocarcinoma cell line before and after the transfection of metastasis-suppressive gene nm23-H1. These glycosyltransferases included alpha1,3fucosyltransferase (alpha1,3FucT)-III, -IV, -VI, -VII, and -IX, alpha2,3-sialyltransferase (ST3Gal)-I, -II, -III, and -IV as well as O-glycan core 2 beta1,6 N-acetylglucosaminyltransferase (C2GnT)-I and -II. In mock cells transfected with the vector, the expression-order of alpha1,3FucTs was IV>VI>III>VII>IX, that of ST3Gals was IV>I>II>III, and that of C2GnT was I>II. Nm23-H1 downregulated the mRNA expressions of all five subtypes of alpha1,3FucT and -I, -III, -IV subtypes of ST3Gal, but not ST3Gal-II and C2GnT-I, II. On the other hand, the expressions of cell surface sialyl Lewis X (SLe(x)) and alpha2,3 sialyl residues were decreased on nm23-H1 transfected cells as detected with monoclonal antibody of SLe(x) and enzyme-labeled lectins, respectively. Since SLe(x) was reported to be a metastasis-associated glycan structure, the reduced expressions of SLe(x) and some enzymes related to its synthesis may be one of the mechanisms to explain the metastasis-suppressive effect of nm23-H1.

Inhibitors of selectin functions in the treatment of inflammatory skin disorders

Selectins mediate tethering and rolling of leukocytes to the vascular endothelium, the first adhesive step in the recruitment of immune cells to inflamed tissues. Thus, selectins play a key role in the pathogenesis of common inflammatory skin disorders such as atopic dermatitis or psoriasis. As a consequence of their key functions, selectins have received much attention as potential target structures for new therapies. Indeed, a number of agents including small-molecule as well as peptide compounds interfering with selectin functions have been developed to treat inflammatory disorders. However, many of the selectin-directed compounds have not held up to the high expectations, in some cases due to overlapping and mutually compensating functions of selectins or suboptimal pharmacokinetic properties of the compounds, while other agents appear to be more promising candidates and have already entered clinical trials. Selectively targeting the functions of one or several selectins involved in the cascade of leukocyte recruitment promises exciting new therapeutic options, but, at the same time, bears considerable imponderables, which will be discussed in this review article.

Evolution of human-chimpanzee differences in malaria susceptibility: relationship to human genetic loss of N-glycolylneuraminic acid

Chimpanzees are the closest evolutionary cousins of humans, sharing >99% identity in most protein sequences. Plasmodium falciparum is the major worldwide cause of malaria mortality. Plasmodium reichenowi, a morphologically identical and genetically very similar parasite, infects chimpanzees but not humans. Conversely, experimental P. falciparum infection causes brief moderate parasitization and no severe infection in chimpanzees. This surprising host specificity remains unexplained. We modified and enhanced traditional methods for measuring sialic acid (Sia)-dependent recognition of glycophorins by merozoite erythrocyte-binding proteins, eliminating interference caused by endogenous Sias on transfected cells, and by using erythroleukemia cells to allow experimental manipulation of Sia content. We present evidence that these remarkable differences among such closely related host-parasite pairs is caused by species-specific erythrocyte-recognition profiles, apparently related to the human-specific loss of the common primate Sia N-glycolylneuraminic acid. The major merozoite-binding protein erythrocyte-binding antigen-175 of P. falciparum apparently evolved to take selective advantage of the excess of the Sia N-acetylneuraminic acid (the precursor of N-glycolylneuraminic acid) on human erythrocytes. The contrasting preference of P. reichenowi erythrocyte-binding antigen-175 for N-glycolylneuraminic acid is likely the ancestral condition. The surprising ability of P. falciparum to cause disease in New World Aotus monkeys (geographically isolated from P. falciparum until arrival of peoples from the Old World) can be explained by parallel evolution of a human-like Sia expression pattern in these distantly related primates. These results also have implications for the prehistory of hominids and for the genetic origins and recent emergence of P. falciparum as a major human pathogen.

Chiasmatic neurons in the ventral diencephalon of mouse embryos--changes in arrangement and heterogeneity in surface antigen expression

We have investigated the changes in arrangement of the SSEA-1 immunoreactive chiasmatic neurons in the mouse ventral diencephalon from embryonic day (E) 9 to the end of gestation. A regionally specific staining of SSEA-1 was first detected in the ventricular layer of the caudal diencephalon at E10 and later at E11 on the cells in the subventricular layer. At E12, these cells formed the characteristic V-shaped configuration caudal to the optic axons in the chiasm. At E13-E15, this neuronal array changes gradually to a configuration that facilitates contact with the optic axons only at the midline and the initial segment of the optic tract. Colocalization studies showed that CD44 was localized strongly on the neurons in the central but not lateral domains of the array, suggesting existence of heterogeneity in these neurons in terms of surface antigen presentation. This difference between the central and lateral domains raises the possibility that the chiasmatic neurons may regulate the patterning of axon orders at the midline and the optic tract through presentation of distinct combination of guidance cues at these strategic positions in the optic pathway. Furthermore, exogenous Lewis-x/SSEA-1 inhibited neurite outgrowth from the E14 retinal explants; this inhibition was observed in neurites from both ventral temporal and dorsal nasal retina. These findings suggest an action of this surface carbohydrate on the control of axon growth and guidance in the mouse optic pathway.

Thematic Review Series: The Immune System and Atherogenesis. Molecular mechanisms regulating monocyte recruitment in atherosclerosis

Cardiovascular disease, a progressive disorder characterized by the accumulation of lipids in the artery wall, is a leading cause of death in Western societies. One of the initial events in atherogenesis involves the recruitment of inflammatory cells from the circulation into the developing lesion. Studies during the past decade have underscored the role of inflammatory mediators in disease initiation and progression. Critical progress has been made in our understanding of the complex mechanisms by which monocytes, macrophages, and T-cells accumulate in atherosclerotic plaques. Experimental research has identified several candidate adhesion proteins and chemokines that are critically involved in the recruitment process, and encouraging data provide a mechanistic framework for new therapeutic targets. This review provides an overview of our current understanding of the mechanisms that direct the recruitment of monocytes to, and their retention in, atherosclerotic lesions.

Glycans in cancer and inflammation--potential for therapeutics and diagnostics

Changes in glycosylation are often a hallmark of disease states. For example, cancer cells frequently display glycans at different levels or with fundamentally different structures than those observed on normal cells. This phenomenon was first described in the early 1970s, but the molecular details underlying such transformations were poorly understood. In the past decade advances in genomics, proteomics and mass spectrometry have enabled the association of specific glycan structures with disease states. In some cases, the functional significance of disease-associated changes in glycosylation has been revealed. This review highlights changes in glycosylation associated with cancer and chronic inflammation and new therapeutic and diagnostic strategies that are based on the underlying glycobiology.

Optical molecular imaging of lymph nodes using a targeted vascular contrast agent

We develop a highly specific antibody-dye conjugate for optical imaging of peripheral lymph nodes. The contrast agent consists of the monoclonal antibody recognizing endothelial ligands for the lymphocyte homing receptor L-selectin, MECA-79, and a near-infrared (near-IR) fluorescent indotricarbocyanine dye. The targeting and biodistribution behavior of MECA-79 is studied after radio-iodination and intravenous injection into mice demonstrating specific uptake in lymph nodes and accumulation in high endothelial venules (HEV). After conjugation of MECA-79 with indotricarbocyanine dye, the fluorescence imaging properties of the MECA-79 dye conjugate are examined by intravenous injection in nude mice and laser-induced fluorescence whole-body imaging in vivo. The MECA-79 antibody-dye conjugate accumulates in peripheral lymph nodes, whereas an isotype antibody-dye conjugate does not. Specific lymph node near-IR fluorescent signals become detectable within minutes after injection, and stable imaging persists for more than 24 h. The results demonstrate that vascular targeting of endothelial expression of glyocproteins is feasible to visualize the accumulation of near-IR fluorescent MECA-79 in lymph nodes, making this technology potentially useful to characterize processes of inflammation.

A solid-state NMR application of the anomeric effect in carbohydrates: galactosamine, glucosamine, and N-acetyl-glucosamine

Simple 2D 13C/15N heteronuclear correlation solid-state NMR spectroscopy was implemented to resolve the 15N resonances of the alpha and beta anomers of three amino monosaccharides: galactosamine (GalN), glucosamine hydrochloride (GlcN), and N-acetyl-glucosamine (GlcNAc) labeled specifically with 13C1/15N spin pairs. Although the 15N resonances could not be distinguished in normal 1D spectra, they were well resolved in 2D double CP/MAS correlation spectra by taking advantage of the 13C spectral resolution. The alpha and beta resonances shifted apart by 3-5 ppm in their 13C chemical shifts, and differed by 1-2 ppm in the extended 15N dimension. Aside from this, the detection of other 13C/15N correlations over short distances was also achieved arising from the C2, C3 and CO carbons present in natural abundance. 2D double CP/MAS chemical shift correlation NMR spectroscopy is a simple and powerful technique to characterize the anomeric effect of amino monosaccharides. Applications of the 2D method reveal well-resolved 15N and 13C chemical shifts might be useful for structural determination on carbohydrates of biological significance, such as glycopeptide or glycolipids.

Chemokines bind to sulfatides as revealed by surface plasmon resonance

Chemokines bind to sulfated cell surface glycosaminoglycans and thereby modulate signaling mediated by G-protein-coupled seven-transmembrane domain chemokine receptors. Similar to glycosaminoglycans, sulfated oligosaccharides are also exposed on the cell surface by sulfatides, a class of glycosphingolipids. We have now identified sulfated glycosphingolipids (sulfatides) as novel binding partners for chemokines. Using surface plasmon resonance (SPR), the binding of proinflammatory and homeostatic chemokines to glycosphingolipids, in particular sulfatides, was investigated. Chemokines were immobilized while glycosphingolipids or additional phospholipids incorporated into liposomes were applied as soluble analytes. A specific affinity of the chemokines MCP-1/CCL2, IL-8/CXCL8, SDF-1alpha/CXCL12, MIP-1alpha/CCL3 and MIP-1beta/CCL4 to the sulfatides SM4s, SM3, SM2a and SB2, SB1a was detected. No significant interactions with the chemokines were observed for gangliosides, neutral glycosphingolipids or phospholipids. Chemokine receptors have been associated with the detergent-insoluble fraction supposed to contain 'rafts', i.e., glycosphingolipid enriched microdomains of the cell surface. Accordingly, the data suggest that early chemokine receptor signaling may take place in the vicinity of sulfated glycosphingolipids on the cell surface, whereby these sulfatides could modulate the chemokine receptor-mediated cell activation signal.

Carbohydrate-carbohydrate interaction as a major force initiating cell-cell recognition

Sponges were the earliest multicellular organisms to evolve through the development of cell recognition and adhesion processes mediated by cell surface proteoglycans. Information on sponges has an extra added value because, as a group, they are the oldest Metazoans alive and contribute more to our understanding of life on earth than knowledge of other animal groups. Although the proteoglycans are emerging as key players in various physiological and pathophysiological cellular events, little is known about the carbohydrate moiety of the proteoglycan molecule. Until recently there was no evidence provided for the existence of specific and biologically significant carbohydrate-carbohydrate interaction. We show here that the interaction between single oligosaccharides of surface proteoglycans is relatively strong (in the 200-300 piconewtons range) and in the same range as other relevant biological interactions, like those between antibodies and antigens. This carbohydrate-carbohydrate recognition is highly species-specific and perfectly mimics specific cell-cell recognition. Both the strength and the species-specificity of the carbohydrate-carbohydrate interaction are guaranteed by polyvalency, by compositional and architectural differences between carbohydrates, and by the arrangement of the carbohydrate chain in a three-dimensional context. Ca(2+)-ions are essential and probably provide coordinating forces. Our findings confirm the existence and character of species-specific carbohydrate-carbohydrate recognition fundamental to cell recognition and adhesion events.

Inhibition of CD62L+ T-cell response in vitro via a novel sulfo-glycolipid, beta-SQAG9 liposome that binds to CD62L molecule on the cell surface

We previously reported that synthetic sulfo-glycolipid, 3-O-(6-deoxy-6-sulfono-beta-D-glucopyranosyl)-1,2-di-O-acylglycerol (beta-SQDG(18:0)) which was deduced from sulfonoquinovosyl-diacylglycerols of sea urchin possessed immunosuppressive effects, such as human mixed lymphocyte reaction (MLR) and skin allograft in rat, and that these effects were caused by contact inhibition between T-cells and antigen presenting cells (APCs). Here, we investigated the mechanism of these immunosuppressive effects on human MLR by beta-SQAG9 which had been newly synthesized from beta-SQDG(18:0) to improve structural stability in water solution. CD62L+ T-cells in peripheral blood predominantly respond to APCs, and beta-SQAG9 inhibited the response of CD62L+ T-cell subset in human allogeneic MLR. Surprisingly, it was demonstrated that beta-SQAG9 bound to L- and P-selectin (CD62L and P) molecule in vitro. Meanwhile, beta-SQAG9 efficiently formed liposome structure and bound to L-selectin on the cell surface of CD62L+ T-cell subset but might not be incorporated into the cells. Because the immunosuppressive effects of beta-SQAG9 disappeared when beta-SQAG9 liposome was changed to soluble form by detergent, the liposome structure of beta-SQAG9 was presumed to be essential for these effects. These findings suggested beta-SQAG9 to be a novel drug with a unique immunosuppressive action.

L-Selectin ligands in lymphoid tissues and models of inflammation

Both lymphocyte recirculation through the lymphoid tissues and leukocyte recruitment to sites of inflammation are essential components of immune surveillance, and are necessary for sustained protection against pathogens. This process is mediated by the leukocyte-endothelial adhesion cascade of which the interaction of leukocyte L-Selectin with its endothelial ligand initiates the first critical tethering and rolling step. As well as discussing the constitutive L-Selectin ligands in lymphoid tissues, this review examines the literature regarding their induction in inflammation, and draws attention to recent findings regarding soluble L-Selectin ligands that suggest an emerging multifunctional role in leukocyte recirculation and inflammation.

Mucin biosynthesis: upregulation of core 2 beta 1,6 N-acetylglucosaminyltransferase by retinoic acid and Th2 cytokines in a human airway epithelial cell line

Vitamin A and the T helper 2 cytokines IL-4 and IL-13 play important roles in the induction of mucin gene expression and mucus hypersecretion. However, the effects of these agents on enzymes responsible for mucin glycosylation have received little attention. Here, we report the upregulation of core 2 beta1,6 N-acetylglucosaminyltransferase (C2GnT) activity both by all-trans retinoic acid (RA) and by IL-4 and IL-13 in the H292 airway epithelial cell line. Northern blotting analysis showed that the M isoform of C2GnT, which is expressed in mucus-secreting tissues and can form all mucin glycan beta1,6-branched structures, including core 2, core 4, and blood group I antigen, was upregulated by both RA and IL-4/13. The L isoform, which forms only the core 2 structure, was moderately upregulated by IL-4/13 but not by RA. Enhancement of the M isoform of C2GnT by RA was abolished by an inhibitor of RA receptor alpha, implicating RA receptor alpha in the effect of RA. Likewise, an inhibitor of the Janus kinase 3 pathway blocked the enhancing effects of IL-4/13 on the L and M isoforms of C2GnT, suggesting a role of this pathway in the upregulation of these two C2GnTs by these cytokines. Taken together, the results suggest that IL-4/13 T helper 2 cytokines and RA can alter the activity of enzymes that synthesize branching mucin carbohydrate structure in airway epithelial cells, potentially leading to altered mucin carbohydrate structure and properties.

Antitumor and antimetastatic effect of warfarin and heparins

Experimental and clinical studies have shown an anticancer effect of anticoagulant drugs. The aim of this study is to review the mechanisms by which the common types of anticoagulants influence the primary tumor and metastatic processes of solid tumors. The review evaluates the interference of unfractionated heparin (UFH), low molecular weight heparin (LMWH) and warfarin on the growth of primary tumors and on the development of metastases. The first part of the review evaluates the effect on the growth and development of primary tumors. Attention is paid to the interference with proliferation of cancer cells, tumor angiogenesis and to the interference with the immune system. The second part of the review describes the metastatic process and the effect of anticoagulants on the cell motility and cancer cell adhesion. The third part refers to the outcomes of clinical studies with anticoagulant treatment in patients with cancer. The problem of thromboembolic disease in patients with advanced cancer is also mentioned. The anticoagulants are more effective in inhibition of stages of the metastatic cascade than in the influence on primary tumors. They can interfere with tumor angiogenesis, immunity system, cancer cell motility and adhesion. The first clinical trials showed an effect on the development of primary tumors and survival of patients namely with lung cancer.