N- and 6-O-sulfated heparan sulfates mediate internalization of coxsackievirus B3 variant PD into CHO-K1 cells

Recently, it was demonstrated that the coxsackievirus B3 variant PD (CVB3 PD) is able to infect coxsackievirus-adenovirus receptor (CAR)-lacking cells by using heparan sulfates (HS) as additional receptors (A. E. Zautner, U. Korner, A. Henke, C. Badorff, and M. Schmidtke, J. Virol. 77:10071-10077, 2003). For this study, competition experiments with growth factors binding to known HS sequences as well as with specifically desulfated heparins were performed with Chinese hamster ovary cells (CHO-K1) to determine the structural requirements of HS for interaction with CVB3. Hepatocyte growth factor interacting with HS sequences containing [IdUA-GlcNSO(3)(6OSO(3))](n), but not basic fibroblast growth factor binding to [HexUA-GlcNSO(3)-HexUA-GlcNSO(3)-IdUA(2OSO(3))](n), was shown to compete effectively with CVB3 PD for cell surface HS. Whereas unmodified heparin and 2-O-desulfated heparin strongly inhibited the CVB3 PD-induced cytopathic effect, the antiviral activity was markedly reduced after N-, O- and 6-O-desulfation of heparin. Taken together, these results indicate that 6-O- and N-sulfation of GlcNAc of HS is crucial for HS interaction with CVB3 PD and that the disaccharide [IdUA-GlcNSO(3)(6OSO(3))](n) is involved in viral binding. Results from experiments with various inhibitors of endocytic pathways suggest that HS-mediated virus internalization is pH dependent. Despite the fact that CVB3 PD initiates infection about four times slower by making use of HS as a receptor than by using CAR, the time required for a complete viral life cycle in Chinese hamster ovary cells was independent of the utilized receptor.

The 37-kDa/67-kDa laminin receptor acts as a receptor for infectious prions and is inhibited by polysulfated glycanes

BACKGROUND

Recently, we showed that the 37-kDa/67-kDa laminin receptor (LRP/LR) acts as the receptor of the cellular prion protein.

METHODS

For the present study, we investigated the binding of the murine scrapie prion protein (moPrP27-30) to baby hamster kidney (BHK) cells, using the Semliki Forest virus system.

RESULTS

The enhanced binding of moPrP27-30 to BHK cells expressing moLRP::FLAG was inhibited by the LRP/LR-specific antibody W3, which suggests that LRP/LR acts as a receptor for the scrapie form of the prion protein, PrP(Sc). This finding was confirmed by a parallel study that showed that bovine prions are internalized by human enterocytes via LRP/LR. The heparan sulfate mimetics HM5004 and HM2602 reduced PrP27-30 binding to moLRP-expressing cells to approximately 30% and approximately 20%, respectively, at a concentration of 10 microg/mL, whereas pentosan polysulfate (SP54) and phycarin sulfate (PS3) both reduced the binding to approximately 40% at a concentration of 100 microg/mL.

CONCLUSIONS

We suggest that the inhibition reported elsewhere of PrP(Sc) synthesis and the incubation times prolonged in rodent models by these sulfated glycans are due to the inhibition of the LRP/LR-dependent binding of prions to the target cells.

Glycosaminoglycans increase levels of free and bioactive IGF-I in vitro

BACKGROUND

It is unclear how IGFs become separated from their IGF-binding proteins (IGFBPs) in vivo. However, the IGFBPs possess binding sites for glycosaminoglycans (GAGs) and interaction with GAGs alters IGFBP ligand affinity. Accordingly, GAGs may control IGF bioavailability. To test this hypothesis, we investigated the effect of GAGs on serum levels of free and bioactive IGF-I, total IGF-I, and IGFBPs in vitro.

METHODS

Serum was incubated with increasing concentrations of six different GAGs (heparin, tinzaparin (Innohep), dermatan sulfate, heparan sulfate, non-anticoagulant (nac) heparin, and nac low-molecular weight heparin). To investigate for reversibility, heparin was co-incubated with protamine sulfate (PS). Finally, the effect of heparin was studied in serum from pregnant and post partum women, normal subjects and patients with type 1 diabetes.

RESULTS

All GAGs increased free IGF-I in a dose-dependent manner (P<0.0001), whereas total IGF-I and IGFBP levels remained unchanged. However, the potency of the GAGs differed significantly (P<0.0001) and did not relate to their anti-coagulating activity. The effect of heparin on free IGF-I was fully reversed by PS. Heparin increased free and bioactive IGF-I in all tested sera (P<0.0001), but the increase was most pronounced in samples from pregnant women (P<0.0001).

CONCLUSION

All tested GAGs stimulated the release of free and bioactive IGF-I in several types of serum, most likely by reversible interaction with the IGFBPs. The effect was most pronounced in pregnancy sera, which are characterized by extensive IGFBP-3 proteolysis. Our findings support the view that GAGs localized in the vessel wall and attached to the extracellular matrix control IGF-I tissue accessibility and bioactivity.

Heparan sulfate in trans potentiates VEGFR-mediated angiogenesis

Several receptor tyrosine kinases require heparan sulfate proteoglycans (HSPGs) as coreceptors for efficient signal transduction. We have studied the role of HSPGs in the development of blood capillary structures from embryonic stem cells, a process strictly dependent on signaling via vascular endothelial growth factor receptor-2 (VEGFR-2). We show, by using chimeric cultures of embryonic stem cells defective in either HS production or VEGFR-2 synthesis, that VEGF signaling in endothelial cells is fully supported by HS expressed in trans by adjacent perivascular smooth muscle cells. Transactivation of VEGFR-2 leads to prolonged and enhanced signal transduction due to HS-dependent trapping of the active VEGFR-2 signaling complex. Our data imply that direct signaling via HSPG core proteins is dispensable for a functional VEGF response in endothelial cells. We propose that transactivation of tyrosine kinase receptors by HSPGs constitutes a mechanism for crosstalk between adjacent cells.

A comparison of the effects of unfractionated heparin, dalteparin and danaparoid on vascular endothelial growth factor-induced tumour angiogenesis and heparanase activity

Disseminated intravascular coagulation (DIC) is the most common complication of solid tumours. In this study, the effectiveness of three polysaccharide anticoagulants (PSAs), at therapeutic doses, at inhibiting solid tumour growth was investigated. Mice with tumour xenografts were subcutaneously injected with either unfractionated heparin (UFH; 200 units kg(-1) day(-1)), dalteparin (75 units kg(-1) day(-1)) or danaparoid (50 units kg(-1) day(-1)). At these concentrations, these PSAs are equieffective at inhibiting blood coagulation activated factor X. In mice with Lewis lung carcinoma (LLC) tumours dalteparin and, to a lesser extent, UFH inhibited both tumour growth and angiogenesis, whereas danaparoid did not. In contrast, in mice with KLN205 tumours, all the PSAs inhibited tumour growth and angiogenesis. All the PSAs significantly inhibited proliferation, migration of endothelial cells and vessel formation in matrigel plugs containing vascular endothelial growth factor (VEGF) and there were no significant differences between these effects of the PSAs. The PSAs had no effect on endothelial cell tubular formation in vitro. Although all the PSAs inhibited VEGF production in KLN205 tumours in vivo and cells in vitro, in LLC tumours and cells only UFH and dalteparin inhibited VEGF production, whereas danaparoid did not. In both LLC and KLN205 tumours in vivo, heparanase activity was inhibited by UFH and dalteparin, but not by danaparoid. Hence, UFH and dalteparin may be more effective than danaparoid at inhibiting cancer progression in DIC patients with solid tumours, due at least in part to their ability to suppress VEGF and heparanase in tumours.

Probing the impact of valency on the routing of arginine-rich peptides into eukaryotic cells

Multivalency represents a critical parameter in cell biology responsible for the overall avidity of low-affinity interactions and the triggering of cellular events. Functions such as catalytic activity, cellular uptake, or localization are frequently linked to the oligomeric state of a protein. This study explores the impact of multivalency on the import and routing of peptides into cells. Specifically, cationic import sequences such as decaarginine, decalysine, and the HIV Tat peptide (GRKKRRQRRRAP, residues 48-59) as well as the nuclear localization sequence from SV40 large T-antigen were assembled into defined peptide oligomers by fusing them to the tetramerization domain of human p53 (residues 325-355, hp53(tet) domain). The resulting tetravalent peptides typically displayed between 10- and 100-fold enhancements in cellular import and intracellular routing properties in relation to their monomeric homologues. These peptides were not toxic to cells. Flow cytometry results and transfection assays indicated that tetravalent decaarginyl peptides (10R-p53(tet) and NLS-10R-p53(tet)) were the peptides most efficiently routed into cells. Their mechanism of import was subsequently examined on unfixed, viable cells using a combination of metabolic inhibitors, flow cytometry, and microscopy techniques. These studies revealed that tetravalent arginine-rich peptides bind to heparan sulfate on the cell surface, are internalized at 37 degrees C, but not at 4 degrees C, via a clathrin-mediated pathway, and accumulate into endosome-like acidic compartments. A fraction of these tetravalent peptides access the cytosol and accumulate in the nucleus of cells. This study concludes that the oligomerization of proteins harboring arginine-rich peptide chains may profoundly influence their ability to enter and be routed into cells.

The use of heparan sulfate to augment fracture repair in a rat fracture model

Fracture healing is a complex process regulated by numerous growth and adhesive factors expressed at specific stages during healing. The naturally occurring, cell surface-expressed sugar, heparan sulfate (HS), is known to bind to and potentiate the effects of many classes of growth factors, and as such, may be a potential candidate therapy for enhancing bone repair. This study investigated the local application of bone-derived HS in the repair of rat femoral fractures. After 2 weeks, there was a significant increase in the callus size of rats administered with 5 microg HS compared to the control and 50 microg HS groups, presumably due to increased trabecular bone volume rather than increased cartilage production. In addition, 5 microg HS increased the expression of ALP, Runx2, FGF-1, IGF-II, TGF-beta1, and VEGF. It is hypothesized that these increases resulted from changes in HS-mediated receptor/ligand interactions that increase local growth factor production to augment bone formation. The findings of this study demonstrate the anabolic potential of HS in bone repair by recruiting and enhancing the production of endogenous growth factors at the site of injury.

Chazin W, Yui S. Regulation of S100A8/A9 (calprotectin) binding to tumor cells by zinc ion and its implication for apoptosis-inducing activity

S100A8/A9 (calprotectin), which is released by neutrophils under inflammatory conditions, has the capacity to induce apoptosis in various cells. We previously reported that S100A8/A9 induces apoptosis of EL-4 lymphoma cells via the uptake of extracellular zinc in a manner similar to DTPA, a membrane-impermeable zinc chelator. In this study, S100A8/A9-induced apoptosis was examined in several cell lines that are weakly sensitive to DTPA, suggesting S100A8/A9 is directly responsible for apoptosis in these cells. Since zinc inhibits apoptosis of MM46, one of these cells, the regulation by zinc of the capacity of S100A8/A9 to bind MM46 cells was studied. When MM46 cells were incubated with S100A8/A9 in standard or zinc-depleted medium, the amounts of S100A8/A9 bound to cells was markedly lower at 3 h than at 1 h. In contrast, when MM46 cells were incubated with S100A8/A9 in the presence of high levels of zinc, binding to cells was the same at 1 and 3 h. When the cells were permeabilized with saponin prior to analysis, a larger amount of cell-associated S100A8/A9 was detected at 3 h. The amount was further increased in cells treated with chloroquine, suggesting that S100A8/A9 was internalized and degraded in lysosomes. Although it has been reported that S100A8/A9 binds to heparan sulfate on cell membranes, the amount of S100A8/A9 bound to MM46 cells was not reduced by heparinase treatment, but was reduced by trypsin treatment. These results suggest that S100A8/A9 induces apoptosis by direct binding to MM46 cells, and that this activity is regulated by zinc.

Effective targeting of liposomes to liver and hepatocytes in vivo by incorporation of a Plasmodium amino acid sequence

PURPOSE

Several species of the protozoan Plasmodium effectively target mammalian liver during the initial phase of host invasion. The purpose of this study was to demonstrate that a Plasmodium targeting amino acid sequence can be engineered into therapeutic nanoparticle delivery systems.

METHODS

A 19-amino peptide from the circumsporozoite protein of Plasmodium berghei was prepared containing the conserved region I as well as a consensus heparan sulfate proteoglycan binding sequence. This peptide was attached to the distal end of a lipid-polyethylene glycol bioconjugate. The bioconjugate was incorporated into phosphatidylcholine liposomes containing fluorescently labeled lipids to follow blood clearance and organ distribution in vivo.

RESULTS

When administered intravenously into mice, the peptide-containing liposomes were rapidly cleared from the circulation and were recovered almost entirely in the liver. Fluorescence and electron microscopy demonstrated that the liposomes were accumulated both by nonparenchymal cells and hepatocytes, with the majority of the liposomal material associated with hepatocytes. Accumulation of liposomes in the liver was several hundredfold higher compared to heart, lung, and kidney, and more than 10-fold higher compared to spleen. In liver slice experiments, liposome binding was specific to sites sensitive to heparinase.

CONCLUSIONS

Incorporation of amino acid sequences that recognize glycosaminoglycans is an effective strategy for the development of targeted drug delivery systems.

Structural and Thermodynamic Aspects of the Interaction between Heparan Sulfate and Analogues of Melittin

Melittin is an amphipathic cationic peptide derived from honeybee venom with well-known cytolytic and antimicrobial properties. When coupled to cationic polymers or lipid molecules, it forms conjugates with high transfection efficiency and low toxicity with promising applications in gene therapy. A first step in the internalization of melittin and its conjugates is their binding to the cell surface, a reaction likely to involve heparan sulfate proteoglycans (HSPG). In the present work, we characterize the binding equilibrium of heparan sulfate (HS) with two melittin analogues, [Cys(1)]melittin (mel-SH) and retro-inverso [Cys(1)]melittin (ri-mel-SH). The terminal cysteine found in these peptides replaces the N-terminal glycine present in native melittin and allows covalent binding to other molecules. Isothermal titration calorimetry (ITC) reveals a high affinity of each melittin analogue to HS. Association constants of 4.7 x 10(4) and 3.5 x 10(5) M(-)(1) are found at physiological ionic strength and 15 degrees C for ri-mel-SH and mel-SH, respectively. The reaction enthalpy measured under these conditions is DeltaH(degrees)pep= 4.2 kcal/mol for ri-mel-SH and DeltaH(degrees)pep= 1.1 kcal/mol for mel-SH. The peptide-to-HS stoichiometry is approximately 20 for ri-mel-SH and approximately 14 for mel-SH under the same conditions. Temperature dependence studies using ri-mel-SH (mel-SH) show that DeltaH(degrees)pep decreases in magnitude upon increase in temperature, which results in a molar heat capacity of DeltaH(degrees)pep= -322 cal mol(-)(1) K(-)(1) (-45 cal mol(-)(1) K(-)(1)). Such a negative heat capacity change is not expected for a purely electrostatic interaction and indicates that hydrophobic and other interactions are also involved in the binding equilibrium. Salt dependence studies of the binding constants confirm that nonelectrostatic forces are an important component of the HS-melittin interaction. Binding to HS induces conformational changes in both peptides, with ri-mel-SH showing a 6-fold increase of the alpha-helix content when incubated with HS under saturation conditions.

Using change in the National Institutes of Health Stroke Scale to measure treatment effect in acute stroke trials

BACKGROUND AND PURPOSE

Outcome measures in acute stroke trials are being refined. Changes in neurological deficits might be useful outcome measures because they can measure the entire spectrum of deficits.

METHODS

We analyzed data from the acute stroke treatment trial Trial of Org 10172 in Acute Stroke Treatment (TOAST). Using logistic regression analysis, we modeled the probability of the TOAST predefined very favorable outcome (VFO; both Glasgow Outcome Scale 1 and modified Barthel Index 19 to 20) at 3 months. Within-subject changes (baseline-3 months) on the National Institutes of Health Stroke Scale (NIHSS) was the main predictor of interest.

RESULTS

The baseline median NIHSS for the entire TOAST cohort was 7, and it improved by 4 points (interquartile range 3 to 6) among 603 patient with VFO and by 2 points (interquartile range -1 to 5) among 638 patients without a VFO (P<0.001). The odds for VFO increased by 2.29 (95% CI, 2.06 to 2.54; P<0.001) for each 1-point improvement on the NIHSS. In receiver operating characteristic analysis, final NIHSS < or =2 was a good predictor of VFO, but no single NIHSS change cut point was a good predictor of VFO.

CONCLUSIONS

NIHSS change appears to be a useful outcome measure for acute stroke trials and is not fully comparable to dichotomized functional outcomes.

Surface modifying substances that reduce apparent yeast cell hydrophobicity

OBJECTIVE: To determine whether several topical compounds and other chemical entities are able to diminish the surface hydrophobicity of yeast cells. METHOD: Hydrophobicity of yeast cells was determined by binding styrene microspheres to the surface of untreated yeast or yeast pre-incubated with various substances with potential for cell surface modification. The degree of microsphere adherence to yeast cells was measured by flow cytometry. RESULTS: A significant reduction in cell surface hydrophobicity was observed when yeast was incubated in protein-containing media. Other compounds that effectively reduced microsphere binding were various formulations of K-Y and heparin. Divalent cations (Ca+ + , Mg+ + , Zn+ + , Cu + + ) were also potent inhibitors of microsphere adherence. It was possible to remove substances contributing to microsphere binding by chemical extraction of the yeast. Yeast having reduced microsphere binding activity also showed diminished binding of concanavalin A. CONCLUSIONS: Several commercially available compounds were able to block binding of styrene microspheres to yeast. Some of the binding activity appeared to be attributable to mannose-containing surface components. These findings have implications for formulating therapeutic products that might block yeast binding to tissues.

Antiviral effect of the heparan sulfate mimetic, PI-88, against dengue and encephalitic flaviviruses

Many viruses, including flaviviruses, display affinity for cell surface heparan sulfate (HS) proteoglycans with biological relevance in virus attachment/entry. This raises the possibility of the application of HS mimetics in antiviral therapy. We have evaluated the antiviral effect of the sulfated polysaccharides, suramin, pentosan polysulfate (PPS) and PI-88, which are currently approved or in trial for clinical use, against dengue virus (DEN) and the encephalitic flaviviruses, Japanese encephalitis virus, West Nile virus, and Murray Valley encephalitis virus. A flow cytometry-based method for the measurement of inhibition of virus infectivity was developed, which showed the in vitro antiviral activity of the three compounds, albeit with differences in efficiency which were virus-dependent. The 50% effective concentration (EC(50)) values for DEN inhibition were in the order: PPS<suramin<PI-88, and for Japanese encephalitis virus, PPS<PI-88<or=suramin. Heparin inhibited the DEN infectivity 30-fold more efficiently than the best of the test compounds, which was not the case for encephalitic flaviviruses. The in vitro anti-flaviviral effectiveness of the HS mimetics did not reliably predict their in vivo therapeutic activity. In mouse models for DEN and flaviviral encephalitis, only PI-88 demonstrated a significant beneficial effect in disease outcome.

Bone-specific heparan sulfates induce osteoblast growth arrest and downregulation of retinoblastoma protein

The heparan sulfate (HSs) sugars of the extracellular matrix (ECM) play a key role during both development and wound repair in regulating the flow of growth and adhesive factors across their cell surface receptors. The aim of this study was to assess the structural and functional differences of HS chains extracted from the conditioned media (soluble), cell surface, and ECM of primary human osteoblast cultures, and to analyze their effects on osteoblast cell growth. HS chains from these compartments were characterized through a combination of enzymatic degradation, anion exchange chromatography, and molecular sieving. Although the chains were all approximately the same size, they varied systematically in their sulfate content, suggesting differences in their protein-binding domains. When added to pre-confluent hFOB1.19 osteoblast cultures, HS doses exceeding 500 ng/ml inhibited proliferation, without affecting viability, irrespective of their origin. Furthermore, HS doses of 500 ng/ml also downregulated retinoblastoma, Cyclin A and CDK1 protein expression, indicating that high doses of osteoblast HS negatively regulate cell cycle, resulting in growth arrest; when high doses of HS were withdrawn after a prolonged period, linear cell growth was reestablished. Thus, despite differences in sulfation, HS from either the soluble, cell surface, or matrix compartments of primary human osteoblast cultures are functionally similar with respect to their effects on growth. Binding assays revealed that the HS chains bound TGFbeta1, a known inhibitor of osteoprogenitor growth, at higher affinity than a suite of other bone-related, heparin-binding growth factors. Overcoming such sugar-mediated inhibition may prove important for wound repair.

The role of heparan sulphate in the generation of Abeta

Alzheimer's disease is a fatal neurodegenerative disorder for which there are currently few treatments and no cure. Heparan sulfate, a heterogeneously sulfated glycosaminoglycan, has been identified as the first naturally occurring inhibitor of beta secretase, the rate-limiting step in the formation of Abeta, the peptide core of the amyloid plaques that cause Alzheimer's disease. Though heparan sulfate has frequently been implicated in the formation of fibrils, only fairly recently has its role as an inhibitor of beta secretase been recognized. This inhibitory activity is dependent on the structure and size of the heparan sulfate chain, with emphasis placed on the position of the sulfates. Heparan sulfate directly binds to beta secretase and causes a closed configuration of the catalytic site. Regulation of amyloid precursor protein (APP) beta secretase cleavage could occur at a number of cellular locations, including the Golgi complex, endosomal system and cell surface. Heparan sulfate also binds to APP and may sequester it away from beta secretase. These findings have led to the examination of heparan sulfate analogues, such as beta-secretase inhibitors, as a potential therapeutic approach to treat Alzheimer's disease.

Heparan sulfate regulates the anabolic activity of MC3T3-E1 preosteoblast cells by induction of Runx2

The transcription factor Runx2 can be controlled by a number of upstream regulators involved in intracellular signalling, including the activation ERK1/2 signaling by fibroblast growth factor-2 (FGF-2). FGFs interact with their cell surface receptors (FGFRs) through an obligate cross-binding interaction with heparan sulfate proteoglycan (HSPG) co-receptors; exogenous HS sugar chains have been shown to potently modulate changes in cell phenotype depending on the stage of tissue differentiation when the HS is harvested, suggesting that HS chain structure and function varies depending on the stage of cell maturity. This study examined the potential of bone-derived heparan sulfate (HS), harvested from differentiating osteoblasts, for the enhancement of preosteoblast growth and differentiation. HS was harvested from conditioned media, cell surface and matrix compartments of postconfluent (differentiating) MC3T3-E1 osteoblasts and dosed back onto preconfluent MC3T3-E1 cells. We show that HS can increase the expression Runx2, ALP, and OPN in preosteoblast cells, suggesting the potential for exogenous HS to shift cells from proliferative to differentiative phenotypes. In line with their structural differences, only HS released into the media was found to co-stimulate the mitogenic effect of FGF-2, whilst exogenous application of all the HSs together with FGF-2 served to increase the expression of OPN. Only the application of cell surface-derived HS triggered a synergistic increase in FGFR1 expression together with FGF-2, although all three HS preparations could trigger transient increases in PI3K, ERK1/2, and stat3 phosphorylation levels. These findings demonstrate that the compartmentally distinct HS species expressed by differentiating MC3T3-E1 cells act in complex ways to coordinate the extracellular conditions that lead to osteoblast differentiation, with the cell surface species coordinating the FGF response.

Modulation of the homophilic interaction between the first and second Ig modules of neural cell adhesion molecule by heparin

The second Ig module (IgII) of the neural cell adhesion molecule (NCAM) is known to bind to the first Ig module (IgI) of NCAM (so-called homophilic binding) and to interact with heparan sulfate and chondroitin sulfate glycoconjugates. We here show by NMR that the heparin and chondroitin sulfate-binding sites (HBS and CBS, respectively) in IgII coincide, and that this site overlaps with the homophilic binding site. Using NMR and surface plasmon resonance (SPR) analyses we demonstrate that interaction between IgII and heparin indeed interferes with the homophilic interaction between IgI and IgII. Accordingly, we show that treatment of cerebellar granule neurons (CGNs) with heparin inhibits NCAM-mediated outgrowth. In contrast, treatment with heparinase III or chondroitinase ABC abrogates NCAM-mediated neurite outgrowth in CGNs emphasizing the importance of the presence of heparan/chondroitin sulfates for proper NCAM function. Finally, a peptide encompassing HBS in IgII, termed the heparin-binding peptide (HBP), is shown to promote neurite outgrowth in CGNs. These observations indicate that neuronal differentiation induced by homophilic NCAM interaction is modulated by interactions with heparan/chondroitin sulfates.

Blocking of monocyte chemoattractant protein-1 during tubulointerstitial nephritis resulted in delayed neutrophil clearance

The chemokine monocyte chemoattractant protein (MCP)-1 has been implicated in the monocyte/macrophage infiltration that occurs during tubulointerstitial nephritis (TIN). We investigated the role of MCP-1 in rats with TIN by administering a neutralizing anti-MCP-1 antibody (Ab). We observed significantly reduced macrophage infiltration and delayed neutrophil clearance in the kidneys of TIN model rats treated with the anti-MCP-1 Ab. To exclude the possibility that an observed immune complex could affect the resolution of apoptotic neutrophils via the Fc receptor, TIN model rats were treated with a peptide-based MCP-1 receptor antagonist (RA). The MCP-1 RA had effects similar to those of the anti-MCP-1 Ab. In addition, MCP-1 did not affect macrophage-mediated phagocytosis of neutrophils in vitro. Deposition of the anti-MCP-1 Ab in rat kidneys resulted from its binding to heparan sulfate-immobilized MCP-1, as demonstrated by the detection of MCP-1 in both pull-down and immunoprecipitation assays. We conclude that induction of chemokines, specifically MCP-1, in TIN corresponds with leukocyte infiltration and that the anti-MCP-1 Ab formed an immune complex with heparan sulfate-immobilized MCP-1 in the kidney. Antagonism of MCP-1 in TIN by Ab or RA may alter the pathological process, most likely through delayed removal of apoptotic neutrophils in the inflammatory loci.

Pharmacologic approaches to butterfly wing patterning: sulfated polysaccharides mimic or antagonize cold shock and alter the interpretation of gradients of positional information

Butterflies produce complex and diverse wing patterns by mechanisms that are generally unknown. We have employed a pharmacological approach to explore the molecular mechanisms of pattern formation. In a screen of over 200 compounds injected into developing Junonia coenia pupae, we identified several specific sulfated polysaccharides that caused widespread, dose-dependent effects on adult wing patterns. These compounds were well tolerated and permitted butterflies to eclose normally and take flight at moderate levels of effect. Heparin and closely related chondroitin sulfates caused stage-specific expansion of distal and proximal band systems and reduction and repatterning of eyespots. Dextran sulfate and fucoidan, whose structures are widely divergent from heparin and one another, caused contraction of distal and proximal systems, but had no effect on eyespots. Nonsulfated or nonpolymeric saccharides were without effect. Pattern alterations were indistinguishable from those reported for extreme cold shock and exposure to sodium tungstate and "molsin". When administered after cold shock or coinjected with heparin, dextran sulfate reversed all patterning effects. We suggest that the primary effect of polysaccharide treatments is to alter the interpretation of gradients of positional information along the proximodistal axis of the pupal wing.

Novel heparan sulphate analogues: inhibition of β-secretase cleavage of amyloid precursor protein

The role of HS (heparan sulphate) in the pathology of AD (Alzheimer's disease) is multifaceted. HS and other glycosaminoglycans have been widely reported to be associated with neuritic plaques. HS has also been shown to promote the aggregation of Abeta (amyloid beta-peptide), the proteinaceous component of neuritic plaques. Recently, we described a novel and contrasting role for HS in the pathology of AD: HS can inhibit the formation of Abeta, by directly interacting with the protease BACE1 (beta-site amyloid precursor protein cleaving enzyme 1; beta-secretase 1), that cleaves the amyloid precursor protein and is the rate limiting step in the generation of Abeta. Here, we review the current roles of HS and the potential for HS-derivatives in the treatment of AD.

Some structural determinants of the antiproliferative effect of heparin-like molecules on human airway smooth muscle

Accumulation of airway smooth muscle (ASM) and its infiltration by mast cells are key pathological features of airway remodelling in asthma. Heparin, a major component of mast cell granules, inhibits ASM proliferation by an unknown mechanism. Here, unfractionated heparins and related glycosaminoglycans having structurally heterogeneous polysaccharide side chains that varied in molecular weight, sulphation and anionic charge were used to identify features of the heparin molecule that were required for its antiproliferative activity in cultured human ASM cells. Proliferation induced by 10% fetal bovine serum (FBS) was abrogated by two unfractionated commercial heparin preparations (Sigma and Multiparin) and this effect was reproduced with each of three low-molecular weight heparin preparations (3, 5 and 6 kDa, respectively), demonstrating that antiproliferative activity resided in at least a 3 kDa heparin fraction. N-desulphated 20% re-acetylated (N-de) heparin (anticoagulant) and O-desulphated heparin (O-de) (non-anticoagulant) fractions also inhibited FBS-dependent proliferation (rank potency: Sigma heparin > O-de > N-de) suggesting that the antiproliferative action of heparin involved N-sulphation but was independent of its anticoagulant activity. Other sulphated molecules with variable anionic charge (dextran sulphate, fucoidan, chondroitin sulphates A or B, heparan sulphate) inhibited proliferation to varying degrees, as did the non-sulphated molecules hyaluronic acid and poly-L-glutamic acid. However, nonsulphated dextran had no effect. In summary, attenuation of FBS-dependent proliferation of human ASM by heparin involves but does not depend upon sulphation, although loss of N-sulphation reduces antiproliferative activity. This antiproliferative effect is independent of anionic charge and the anticoagulant actions of heparin.

pH-specific sequestration of phosphoglucose isomerase/autocrine motility factor by fibronectin and heparan sulphate

Phosphoglucose isomerase (PGI) is a glycolytic enzyme that moonlights as a cytokine under the aliases autocrine motility factor (AMF), neuroleukin and maturation factor. The cytokine function of PGI/AMF targets multiple cell types however mechanisms that regulate and sequester this ubiquitous, circulating cytokine remain largely unidentified. PGI/AMF is shown here to exhibit fibronectin (FN)-dependent cell surface association at both neutral and acid pH. Direct PGI/AMF binding to FN and fluorescence resonance energy transfer (FRET) between PGI/AMF and FN were detected only at pH 5. At neutral pH, the interaction of PGI/AMF with FN is receptor-mediated requiring prior clathrin-dependent endocytosis. PGI/AMF and FN do not co-internalize and PGI/AMF undergoes a second round of endocytosis upon recycling to the plasma membrane indicating that recycling PGI/AMF receptor complexes associate with FN fibrils. Heparan sulphate does not affect cell association of PGI/AMF at neutral pH but enhances the FN-independent cell surface association of PGI/AMF at acid pH identifying two distinct mechanisms for PGI/AMF sequestration under acidic conditions. However, only PGI/AMF sequestration by FN at acid pH was able to stimulate cell motility upon pH neutralization identifying FN as a pH-dependent cytokine trap for PGI/AMF. The multiple ways of cellular association of PGI/AMF may represent acquired mechanisms to regulate and harness the cytokine function of PGI/AMF.

A functional heparan sulfate mimetic implicates both heparanase and heparan sulfate in tumor angiogenesis and invasion in a mouse model of multistage cancer

Heparan sulfate proteoglycans are integral components of the extracellular matrix that surrounds all mammalian cells. In addition to providing structural integrity, they act as a storage depot for a variety of heparan sulfate (HS)-binding proteins, including growth factors and chemokines. Heparanase is a matrix-degrading enzyme that cleaves heparan sulfate side chains from the core proteoglycans, thus liberating such HS-binding proteins, as well as potentially contributing to extracellular matrix degradation. Here, we report that heparanase mRNA and protein expression are increased in the neoplastic stages progressively unfolding in a mouse model of multistage pancreatic islet carcinogenesis. Notably, heparanase is delivered to the neoplastic lesions in large part by infiltrating Gr1+/Mac1+ innate immune cells. A sulfated oligosaccharide mimetic of heparan sulfate, PI-88, was used to inhibit simultaneously both heparanase activity and HS effector functions. PI-88 had significant effects at distinct stages of tumorigenesis, producing a reduction in the number of early progenitor lesions and an impairment of tumor growth at later stages. These responses were associated with decreased cell proliferation, increased apoptosis, impaired angiogenesis, and a substantive reduction in the number of invasive carcinomas. In addition, we show that the reduction in tumor angiogenesis is correlated with a reduced association of VEGF-A with its receptor VEGF-R2 on the tumor endothelium, implicating heparanase in the mobilization of matrix-associated VEGF. These data encourage clinical applications of inhibitors such as PI-88 for the many human cancers where heparanase expression is elevated or mobilization of HS-binding regulatory factors is implicated.