Growth inhibition of MCF-7 tumor cell line by phenylacetate linked to functionalized dextran

We investigated the antiproliferative effect of phenylacetate covalently linked to dextran derivatives (DMCBPA conjugates) on human breast cancer MCF-7 cells. We show that free sodium phenylacetate (NaPA) inhibits the cell growth (IC50 = 14 mM), while an important inhibitory effect is observed for DMCBPA conjugates. The IC50 dose of these conjugates is as low as 1.0 mg/ml, corresponding to 1.3 mM of phenylacetate. The precursors, dextran substituted with methylcarboxylate and benzylamide groups, did not affect the growth of MCF-7 tumor cells. We have observed that MCF-7 cell growth inhibition depends on amount of phenylacetate linked to the conjugate. The data indicated that an optimum antiproliferative effect is more significant when the amount of phenylacetate groups present on the dextran backbone is high. Analysis of doubling time by growth kinetics study shows that conjugates have more time-sustained effect than free NaPA. It is noteworthy that the inhibitory effect is observed at non-toxic concentration. Theses conjugates could be considered as acceptable derivatives to prevent tumor progression.

Polystyrene derivatives as candidates for extracorporeal adsorption of Factor VIII antibodies in the management of haemophiliac patients

BACKGROUND AND OBJECTIVES

This article presents a new approach for removing the Factor VIII inhibitors (anti-FVIII) in haemophiliac patients by immunoadsorption using an affinity matrix.

MATERIALS AND METHODS

Ten blood samples from haemophiliac patients with anti-FVIII were assayed for antibodies, total immunoglobulins, procoagulant proteins and complement C3 protein after circulation over one or two columns filled with the polymers under investigation.

RESULTS

These new synthetic sorbents are able to remove in vitro 90% of anti-FVIII from haemophiliac plasma with inhibitors (up to 540 Bethesda Units/ml). Neither coagulation factor adsorption nor effects on complement system activation were observed.

CONCLUSIONS

The data presented clearly show that these polymers allow a rapid and efficient reduction of inhibitor titre. In view of the parameters studied, these polymers fulfil the requirements for use in a blood purification process to decrease high inhibitor titres without losing essential proteins.

Growth inhibition of human melanoma tumor cells by the combination of sodium phenylacetate (NaPA) and substituted dextrans and one NaPA-dextran conjugate

We have studied the cytostatic effects of sodium phenylacetate (NaPA) in association with several substituted dextrans on human tumor melanoma 1205LU cells. We show that NaPA alone inhibits the growth of these cells (IC50 = 3.9 mM) while a weak inhibitory effect appears at a concentration of 37 microM (10 microg/ml) for a dextran methyl carboxylate benzylamide (LS17-DMCB). The precursors of LS17-DMCB [T40 Dextran and carboxymethyl dextran (LS17-DMC)] did not affect the growth of 1205LU cells. To potentiate the inhibitory activity of NaPA at low concentrations (below 5.6 mM), we have tested NaPA and LS17-DMCB in physical mixture (association) or linked together covalently (this conjugate is termed 'LS17-NaPaC'). We have observed an increase of the 1205LU cell growth inhibition effect with NaPA in association (IC50 1.8 mM). For a concentration of 5 mM of NaPA (free in the case of association or linked in the case of conjugate), the association with dextran derivative exhibits a 4.6-fold higher efficacy than with NaPA alone (9 versus 41% surviving fraction), while the conjugate is 1.3-fold smaller (52% growth inhibition). By performing isobologram analysis of the IC50 data, we have shown a synergistic effect for a particular molar ratio of NaPA and LS17-DMCB (NaPA:LS17-DMCB = 0.35).

Sodium phenylacetate enhances the inhibitory effect of dextran derivative on breast cancer cell growth in vitro and in nude mice

Sodium phenylacetate (NaPa) and carboxymethyl benzylamide dextran derivative (CMDB(LS4)) are able to inhibit growth of breast tumour cells. In this study, we explored whether the combination of NaPa and CMDB(LS4)may enhance their respective inhibitory effects on the MCF-7ras cell growth in vitro and in vivo. NaPa inhibited MCF-7ras cell proliferation by reducing the DNA replication concomitantly with a recruitment of cells in G0/G1 phase and by inducing apoptosis in a dose- and time-dependent manner. The addition of CMDB(LS4)potentiated the NaPa antiproliferative effect in the manner dependent on the ratio of CMDB(LS4)and NaPa concentrations. In nude mice, CMDB(LS4)(150 mg kg(-1)) or NaPa (40 mg kg(-1)) administrated twice a week, for 7 weeks inhibited MCF-7ras xenograft growth by 40% and 60%, respectively. The treatment by both, CMDB(LS4)and NaPa, decreased tumour growth by 83% without any toxicity. To better understand the mechanism of NaPa and CMDB(LS4)action we assessed their effect on mitogenic activity of MCF-7ras conditioned medium (CM) on BALBC/3T3 fibroblasts. CMDB(LS4)added to the CM, inhibited its mitogenic activity whereas NaPa had an anti-mitogenic effect when CM was prepared from MCF-7ras cells pretreated with NaPa. Thus, the antiproliferative effects of NaPa and CMDB(LS4)involve 2 different mechanisms explaining, at least in part, the possible synergism between them. Overall, this study points to the potential use of a combination of dextran derivatives with NaPa to inhibit the breast tumour growth.

Anticoagulant properties of dextranmethylcarboxylate benzylamide sulfate (DMCBSu); a new generation of bioactive functionalized dextran

Dextranmethylcarboxylate benzylamide sulfate (DMCBSu), a functionalized dextran, exhibits anticoagulant properties. Its synthesis involves three steps: a carboxymethylation with monochloroacetic acid in alkaline water-iso-propanol, a benzylamidification of some of the methylcarboxylate groups with benzylamine in the presence of a water soluble carbodiimide and a partial sulfation of the remaining hydroxyl groups with SO3-pyridine in dimethylformamide. This procedure yields reproducibly DMCBSu with degrees of substitution in methylcarboxylate (MC), benzylamide (B) and sulfate (Su) groups, respectively, up to 1.61, 0.35 and 1.5, each obtained in one step. For a degree of substitution of methylcarboxylate ca. 1, the presence of sulfate groups is absolutely necessary to confer anticoagulant activities to the samples. In addition, the anticoagulant ability is higher for derivatives bearing benzylamide groups. The anticoagulant ability of DMCBSu increases with the degree of sulfation, reaching 20% of heparin activity for a degree of substitution of Su groups about 1.3.

Breast carcinoma cell uptake and biodistribution of technetium-99m-carboxymethyl benzylamide dextran

Carboxymethyl Benzylamide Dextran (CMDB7) displayed an in vitro growth inhibitory activity on breast tumor cells. CMDB7 is able to disrupt the interaction of angiogenic growth factors (FGF2, TGF beta and PDGF) with their membrane receptors. This compound blocks the angiogenesis of MDA-MB435 carcinoma xenografted in mammary fat pad and their lung metastases in nude mice. In this work, we studied the uptake of CMDB7 labeled with 99mTc in cultured human breast cancer MCF-7 cell line and the highly tumorigenic MCF-7ras cell line (Ha-ras-transfected MCF-7 cells) and the in vivo distribution in MCF-7ras tumor-bearing mice. The 99mTc-CMDB7 are stable and the intracellular concentration is time-dependent and reaches a plateau at 180 minutes. 99mTc CMDB7 uptake is much higher in MCF-7ras cells than MCF-7 cells. Since CMDB7 is internalized and could also inhibit cell proliferation by acting at nuclear sites, we investigated the MCF-7ras nuclear localization after cell fractionation. Cell fractionation revealed a cytoplasmic and nuclear internalization of CMDB7. The tumor uptakes of 99mTc-CMDB7 were 0.34%, 0.72% and 0.62% of the administrated doses per gram of tumor tissue at 1 hour, 3 hour and 5 hours respectively after their injection. The blood clearance of 99mTc CMDB7 was very rapid and the liver, spleen and kidney uptakes were very weak. These results confirm the absence of toxicity of CMDB7 and the usefulness of CMDB7 in cancer therapy by targeting breast tumors.

Development of a capillary electrophoresis assay based on free sulfate determination for the direct monitoring of sulfoesterase activity

A capillary electrophoresis assay of sulfoesterase activity was developed that overcomes the main drawbacks encountered with the usual methods for sulfate determination in complex biological medium. Conditions are described allowing direct measurement of inorganic sulfate that is enzymatically produced in the reaction mixture. The main features of this method are electrokinetic sample introduction, which allows selective extraction of sulfate from the matrix into the separation capillary, counter-electroosmotic flow migration mode, indirect absorbance detection and use of an internal standard for quantitative performances. Likewise, perfect linearity was obtained for concentrations of sulfate up to 40 ppm. The limits of detection and quantification were 0.2 and 0.6 ppm, respectively. The run-to-run and day-to-day precision are 1 and 4.5%, respectively, for sulfate concentrations varying from 35 ppm down to 1 ppm. The accuracy was established for the synthetic p-nitrocatechol sulfate substrate by comparison with the classical spectrophotometric assay. The method was applied to the kinetic monitoring of the activity of a sulfoesterase extracted from the marine mollusc Pecten maximus on fucoidan, a bioactive sulfated fucose-based polysaccharide derived from brown algae. For the first time, a sulfoesterase activity was shown to be effective on such sulfated polysaccharides.

Carboxymethyl benzylamide sulfonate dextrans (CMDBS), a family of biospecific polymers endowed with numerous biological properties: a review

The functionalized dextrans termed carboxymethyl benzylamide sulfonate dextran (CMDBS) represent a family encompassing a wide range of polymers. These soluble macromolecular compounds, which are substituted with specific chemical functional groups, are designed to interact with living systems. By analogy with glycosaminoglycan heparin, a natural highly charged anionic polysaccharide that exerts a variety of biological effects, we postulated that CMDBS compounds also possess binding sites capable of specific interactions with biological constituents, depending on the overall composition of the polymer. The synthesis and heparin-like properties of these CMDBS have been extensively investigated. Thus, it appears that dextran derivatives can mimic the action of heparin in regard to its interactions with antithrombin and serine proteases involved in blood coagulation. Other derivatives interact with various components of the immune system or with adhesive proteins such as fibronectin in modulating the proliferation of Staphylococcus aureus. Because they are able to stimulate wound healing in various in vivo models, these polysaccharides may also constitute a family of tissue repair agents because of their protecting and potentiating effects with heparin binding growth factors. Moreover, dextran derivatives in contact with cells such as endothelial cells, smooth muscle cells, or tumoral cells can affect both cell proliferation and metabolism. It appears that these bioactive polymers are also efficient tools to investigate the precise mechanism of action of individual biological activities by contrasting their mode of action to that of heparin. In addition to their numerous biological properties and biospecificity, functionalized dextrans are relatively simple to manufacture and exempt of donor contaminant, which make them attractive in a variety of clinical applications.

Effects of the binding of a dextran derivative on fibroblast growth factor 2: secondary structure and receptor-binding studies

CMDB (carboxymethyldextran-benzylamide) are dextrans statistically substituted with carboxymethyl and benzylamide groups which can mimick some of the biological properties of heparin. It has previously been shown that CMDB inhibit autocrine growth of breast tumor cells (Bagheri-Yarmand et al., Biochem. Biophys. Res. Commun. 239: 424-428, 1997) and selectively displace fibroblast growth factor 2 (FGF-2) from its receptor. Here, we used circular dichroism and fluorescence anisotropy measurements to show that the conformation of FGF-2 was significantly altered upon its binding to CMDB and to short CMDB fragments prepared within this study. CMDB and fragments formed a stable 1:1 complex with FGF-2, with affinities being estimated as 20+/-10 nM from fluorescence anisotropy analysis. No such a complex was formed with insulin-like growth factor (IGF-1) or epidermal growth factor (EGF). CMDB competed with the FGF-2 receptor for binding to FGF-2 but did not disturb the binding of IGF-1 and EGF to their receptors. Thus, our results highlight the selectivity of CMDB and their fragments towards FGF-2. Heparin, however, competes with CMDB and their fragments for binding to FGF-2. The carboxymethyl and benzylamide groups of these molecules likely interact directly with a heparin-binding region of FGF-2. The resulting change in conformation disturbs the binding of FGF-2 to its receptor and consecutively its mitogenic activity.

Carboxymethyl benzylamide dextran blocks angiogenesis of MDA-MB435 breast carcinoma xenografted in fat pad and its lung metastases in nude mice

We previously showed that carboxymethyl benzylamide dextran (CMDB7) prevents tumor growth and tumor angiogenesis by binding to angiogenic growth factors, thereby preventing them from reaching their receptors on tumor or stromal cells (Bagheri-Yarmand et al. Br. J. Cancer, 78: 111-118, 1998; Bagheri-Yarmand et al. Cell Growth Differ., 9: 497-504, 1998). In this study, CMDB7 inhibited neovessel formation within the fibroblast growth factor 2-enriched matrigel in mice, and its anticancer effect was then tested in a metastatic breast cancer model. Human MDA-MB435 cells were injected into the mammary fat pad of nude mice, and breast tumors developed within 1 week; all of the mice had lung metastases at 12 weeks. CMDB7 treatment (50, 150, or 300 s.c. or 300 i.v. mg/kg/week for 10 weeks) reduced the incidence of lung metastases to 12%. Histological analysis showed markedly less tumor neovascularization in the CMDB7-treated mice. Pulmonary metastasis incidence was strongly dependent on the intratumoral neoangiogenesis in primary tumors.

Liposomes coated with chemically modified dextran interact with human endothelial cells

Some liposomal formulations are now in clinical use. New applications in biology and medicine using targeted liposomes remain an intensive research area. In this context, liposomes constituted of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol (70/10/20 mol %) were prepared by detergent dialysis and coated with dextran (Dx) or functionalized dextran (FDx), both hydrophobized by a cholesterol anchor which penetrates the lipid bilayer during the vesicle formation. The coating of liposomes with these polysaccharides was performed because chemically modified dextran but not native Dx interacted with vascular cells. The liposome uptake by human endothelial cells was followed using uncoated and coated liposomes radiolabeled with a neutral lipid (3H-cholesterol) and a polar phospholipid (14C-PC). The results indicated for both radiolabels a preferential uptake by endothelial cells of FDx-coated liposomes compared to uncoated or Dx-coated liposomes. Addition to the culture medium of calcium up to 10 mM further enhanced the level and rate of incorporation of FDx-coated liposomes, whereas interaction of endothelial cells with uncoated liposomes or liposomes coated with Dx was poorly affected. Liposome membranes were then labeled with N-(lissamine rhodamine B sulfonyl)diacyl-PE and liposome uptake by endothelial cells was observed by fluorescence microscopy. The punctate intracellular fluorescence of cells incubated at 37 degrees C with fluorolabeled liposomes is indicative of the liposome localization within the endocytotic pathway of the cells. Altogether, these data demonstrate that coating of liposomes with FDx enable specific interactions with human endothelial cells in culture. Consequently, these liposomes coated with bioactive polymers represent an attractive approach as materials for use as drug delivery vehicles targeting vascular cells.

The suppression of fibroblast growth factor 2/fibroblast growth factor 4-dependent tumour angiogenesis and growth by the anti-growth factor activity of dextran derivative (CMDB7)

Our previous studies showed that carboxymethyl benzylamide dextran (CMDB7) blocks basic fibroblast growth factor (FGF-2)-dependent cell proliferation of a human breast epithelial line (HBL100), suggesting its potential role as a potent antiangiogenic substance. The derived cell line (HH9), which was transformed with the hst/FGF4 gene, has been shown to be highly proliferative in vitro and to induce angiogenic tumours in nude mice. We show here that CMDB7 inhibits the mitogenic activities of the conditioned media from HBL 100 and HH9 cells in a dose-dependent manner. When HH9 cells were injected s.c. into nude mice, CMDB7 treatment (300 mg kg(-1) week(-1)) suppressed the tumour take and the tumour growth by about 50% and 80% respectively. Immunohistochemical analysis showed a highly significant decrease, by more than threefold, in the endothelial density of viable tumour regions, together with a significant increase in the necrosis area. This antiangiogenic activity of CMDB7 was further demonstrated by direct inhibition of calf pulmonary artery (CPAE) and human umbilical vein (HUVEC) endothelial cell proliferation and migration in vitro. In addition, we showed that CMDB7 inhibits specifically the mitogenic effects of the growth factors that bind to heparin such as FGF-2, FGF-4, platelet-derived growth factor (PDGF-BB) and transforming growth factor (TGF-beta1), but not those of epidermal growth factor (EGF) and insulin-like growth factor (IGF-1). These results demonstrate that CMDB7 inhibits FGF-2/FGF-4-dependent tumour growth and angiogenesis, most likely by disrupting the autocrine and paracrine effects of growth factors released from the tumour cells.

Inhibition of MCF-7ras tumor growth by carboxymethyl benzylamide dextran: blockage of the paracrine effect and receptor binding of transforming growth factor beta1 and platelet-derived growth factor-BB

The highly tumorigenic human breast cancer MCF-7ras line (Ha-ras-transfected MCF-7 cell line) loses estrogen dependence and secretes diffusible growth factors that support its own tumor growth in vivo. Our previous studies showed that carboxymethyl benzylamide dextran (CMDB7) inhibits the growth of breast MCF-7 and MCF-7ras cell lines. In this study, we have shown that conditioned medium (CM) from MCF-7 and MCF-7ras cells stimulated the DNA synthesis of BALB/c3T3 fibroblasts and that CMDB7 strongly inhibited these mitogenic effects in a dose-dependent manner. Neutralizing antibodies against platelet-derived growth factor (PDGF) partially inhibited the mitogenic effect of MCF-7ras CM. The flow cytometry analysis of the cell cycle showed that the CM of tumor cells increased the percentage of fibroblasts in S phase and that CMDB7 blocked them in G0/G1 phase. CMDB7 inhibited the mitogenic effect of PDGF-BB and transforming growth factor (TGF) beta1 but not those of epidermal growth factors and insulin-like growth factor on BALB/c3T3 fibroblasts. CMDB7 increased the electrophoretic mobility of radiolabeled PDGF-BB and TGF-beta1, apparently by forming a stable complex with these factors. On intact BALB/c3T3 fibroblasts, binding of iodinated growth factors (125I-TGF-beta1 and 125I-PDGF) to their receptors was completely displaced by CMDB7. In vivo studies demonstrated that s.c. injection of CMDB7 inhibited by 66% the tumor growth of MCF-7ras xenografts in nude mice. These results showed that CMDB7 inhibits the mitogenic effect of growth factors released from MCF-7 and MCF-7ras cells and suppresses tumor growth in the MCF-7ras model.

Fluorescent and radiolabeling of polysaccharides: binding and internalization experiments on vascular cells

Glycosaminoglycans (GAGs) such as heparan sulfates are complex carbohydrate polymers. These structural components of the extracellular matrix are essential for the adhesion, migration, and regulation of cellular growth. To understand the physiological role of GAGs and GAG analogues, a practical approach consists of labeling and detecting them in cell extracts, or analyzing binding domains and their distributions into the cells. We propose a convenient and reliable method for preparing and labeling amino-enriched, polysaccharides with the fluorescent derivative 5-[(4,6-dichlorotriazine-2-yl)amino]-fluorescein (DTAF). Radioiodination is then performed on the DTAF moiety. This method was applied to polysaccharides known to inhibit vascular smooth-muscle cell (SMC) proliferation such as functionalized dextrans derived from poly(alpha 1-6 glucose) and fucan, poly(L-fucose 4-sulfate) extracted from brown seaweed. Using autoradiography and confocal microscopy, we observed the fixation and internalization of labeled antiproliferative products in SMCs from rat aorta. These probes can be useful for the understanding of polysaccharide-cell interactions. In addition, the method presented here can be applied to various synthetic or natural biomedical materials.

Temperature-responsive size-exclusion chromatography using poly(N-isopropylacrylamide) grafted silica

Silica-based packing materials induce non-specific interactions with proteins in aqueous media because of the nature of their surface, mainly silanol groups. Therefore, the silica surface has to be modified in order to be used as stationary phase for the High Performance Size-Exclusion Chromatography (HPSEC) of proteins. For this purpose, porous silica beads were coated with hydrophilic polymer gels (dextrans of different molecular weights) carrying a calculated amount of diethyl-aminoethyl groups (DEAE). Actually, as shown by HPSEC, these dextran modified supports minimize non-specific adsorption for proteins and pullulans in aqueous solution. Then, in order to change the pore size in response to temperature, temperature responsive polymer of poly(N-isopropylacrylamide) (PIPAAm) was introduced into the surface of dextran-DEAE on porous silica beads. The structure of these supports before and after modification was alternately studied by Scanning Electronic Microscopy (SEM) and Scanning Force Microscopy (SFM). An adsorption of radiolabelled albumin was performed to complete our study. Silica modifications by dextran-DEAE and PIPAAm improve the neutrality of the support and minimize the non-specific interactions between the solid support and proteins in solution. At low temperature, the support having PIPAAm exhibits a high resolution domain in HPSEC and finally permits a better resolution of proteins and pullulans. At higher temperature, hydrophobic properties of PIPAAm produce interactions with some proteins and trigger off a slight delay of their elution time.

Extending insulin action in vivo by conjugation to carboxymethyl dextran

The biochemical and pharmacological properties of bioactive peptides and proteins can be altered by conjugation with polymers. This report describes site-specific attachment of insulin to activated carboxyl groups of carboxymethyl dextran (CMD, MW=51000) through the GlyA1 insulin amino group. On average, three or four insulin molecules were grafted to a CMD linear chain. Coupled insulin molecules were properly folded, and the bioactivity of conjugated insulin in the blood glucose depression assay was 9.6 IU/mg, which was only 2.6 times less than that for native insulin. The cell growth study indicated that the CMD-insulin conjugate was as mitogenic as insulin on vascular smooth muscle cells, whereas the starting CMD polymer was not. The insulin receptor binding constant of the conjugate (3.6 x 10[9] M[-1]) compared well with that of native insulin (7.6 x 10[9] M[-1]), indicating that the CMD chain does not present any major constraints to binding. Plasma clearance of CMD-insulin obeyed a two-compartment pharmacokinetic (PK) model with a CMD-insulin conjugate plasma elimination half-life of 114.1 min, which was significantly longer than that of soluble Zn-insulin (12.4 min). In contrast, pharmacodynamic (PD) profiles (blood glucose lowering effects) after intravenous (iv) administration of the conjugate or insulin in rats were not different. Subcutaneous (sc) administration of the conjugate resulted in a significantly prolonged plasma profile with a noncompartmental PK parameter mean residence time (MRT) of 103.5 min which was significantly longer than that of soluble Zn-insulin (40.5 min). This was reflected in the protracted PD effect of sc administered conjugate with time needed to reach minimum glucose concentration Tnadir of 95.7 min, which was significantly longer than that of insulin (62 min). We conclude that the conjugation of insulin to CMD leads to a bioactive conjugate with a delayed sc PD profile showing prolonged response, resembling intermediate acting insulin preparations.

Influence of the nature of coupling agents on insulin adsorption on supports grafted with sialic acid for high-performance affinity chromatography

Porous silica exhibits excellent mechanical properties for use as a stationary phase for high-performance liquid chromatography. However, negative surface charges make it unusable in its native state. For this reason, silica beads are coated with dextran polymers carrying a calculated amount of diethylaminoethyl groups. Both the minimization of non-specific interactions and the hydrophilic character of such supports allow their functionalization with biospecific ligands and finally their use in high-performance affinity chromatography of biological products. The use of these modified supports in high-performance affinity chromatography requires a better understanding of various characteristics of stationary phases. For this purpose, several techniques were utilized, in particular, size-exclusion chromatography and adsorption of radiolabelled albumin. These methods provided complementary information on the structure of these supports. Coated silica-based supports were functionalized with sialic acid by means of different coupling agents. The affinity of these supports for insulin was determined by the establishment of adsorption isotherms and by high-performance affinity chromatography, to evidence the relationships between structural characteristics of the supports and their separation properties. The study of interactions between these supports and insulin allowed us to show the importance of the coupling method on the performances of supports in affinity chromatography.

High-performance affinity chromatography for the purification of heparin-binding proteins from detergent-solubilized smooth muscle cell membranes

Heparin and heparan sulfates are regulators of cellular events including adhesion, proliferation and migration. In particular, the antiproliferative effect of heparin on smooth muscle cell (SMC) growth is well described. However, its mechanism of action remains unclear. Numerous results suggest an endocytosis mediated by a still unknown heparin receptor on vascular SMCs. In order to identify a putative heparin receptor on SMCs that could be involved in heparin signalling, affinity chromatography supports were developed. In this paper, we describe high-performance liquid affinity chromatography (HPLAC) supports obtained from silica beads coated with dextran polymer substituted by a calculated amount of diethylaminoethyl functions. With a polysaccharide dextran layer, this type of support can be grafted with specific ligands, such as heparin, using conventional coupling methods. In a previous work, we demonstrated, using butanedioldiglycidyl ether, that silica stationary phases coupled to heparin could be used for the fast elution and good peak resolution of heparin-binding proteins. In the present work, an affinity chromatographic fraction of SMC membrane extracts was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and six heparin-binding proteins from dodecyloctaethyleneglycol monoether-solubilized SMCs were observed. Their Mr values were between 40 and 70 kDa, with three major protein bands at 66, 45 and 41 kDa. These results indicate the usefulness of the chromatographic method for purifying heparin binding proteins from SMC membrane.

Insulin bound to chiral polymer with N-acetyl-D-glucosaminyl units. Lacks of mitogenic activity on rat aorta smooth muscle cell proliferation

Insulin was covalently attached to two terpolymers of N-(2-hydroxypropyl) methacrylamide, N-methacryloyldiglycine and a) R-(-)-1-methyl-2-methacryloylamidoethyl 2-acetamido-2-deoxy-beta-D-glucopyranoside or b) S-(+)-1-methyl-2-methacryloylamidoethyl 2-acetamido-2-deoxy-beta-D-glucopyranoside. The mitogenic effect of both conjugates on vascular smooth muscle cell proliferation was investigated. The results indicated that insulin bound to both carriers with pendant N-acetylglucosaminyl groups possesses hypoglycemic activity but not the mitogenic effect of native insulin. This study shows that for these insulin conjugates, the effect does not depend on the steric configuration of the sugar-containing monomer units incorporated in the terpolymer. A hypothesis is developed that some competition is taking place between N-acetylglucosaminyl groups on the polymeric insulin carrier and the same moieties in the insulin receptor expressed on the surface of smooth muscle cells leading to a lack of mitogenic activity.

Fucans, sulfated polysaccharides extracted from brown seaweeds, inhibit vascular smooth muscle cell proliferation. I. Comparison with heparin for antiproliferative activity, binding and internalization

Smooth muscle cell (SMC) proliferation is inhibited both in vivo and in vitro by heparin. However, the precise mechanisms of action are still not understood. The analogy between two sulfated polysaccharides, heparin and fucan, has led us to compare in detail their effects on SMC growth. We have prepared and characterized a 19 kDa fucan fraction from brown seaweed, Ascophyllum nodosum. Fucan affects the growth of SMCs in a time- and dose-dependent, reversible and non-toxic fashion. As determined by cell counting, [3H]thymidine incorporation, and microcytofluorimetry analysis, heparin was less active than fucan in inhibiting SMC growth. Fucan and heparin act by preferential blocking of G0/G1, thus decreasing the G0/S transition. Binding experiments with [125I]fucan indicated saturable, unlabeled-fucan displaceable binding sites with an apparent Kd of 30 nM. Moreover, displacement experiments performed with various polysaccharides revealed that antiproliferative compounds interacted with these membrane sites, but non-antiproliferative polysaccharides (dextran, chondroitin sulfate) did not, providing evidence of a correlation between binding to SMCs and their antiproliferative activity. When cells were exposed at 37 degrees C to a fluorescent 5-([4,6-dichlorotriazin-2-yl]-amino)fluorescein (DTAF)-fucan, internalization occurred and punctate vesicles were observed which accumulated rapidly in the perinuclear region as previously reported for heparin. Nuclear preparations (membranes + contents) of cultured SMCs previously incubated with radiolabeled heparin or fucan indicated the presence of radioactivity, suggesting an antiproliferative action of both polysaccharides at the nuclear level. Collectively, these observations indicated that fucan and heparin share some similar mechanisms of action, such as SMC growth inhibition, binding, and internalization. In the accompanying paper (Logeart et al., Eur. J. Cell Biol. 74, 1997, this issue), we describe the effect of fucans of different molecular weights and conclude that there is no direct link between polysaccharide degradation and the antiproliferative effect on SMCs.

Fucans, sulfated polysaccharides extracted from brown seaweeds, inhibit vascular smooth muscle cell proliferation. II. Degradation and molecular weight effect

Fucan, a sulfated polysaccharide extracted from brown seaweeds, inhibits smooth muscle cell (SMC) proliferation with a higher antiproliferative activity than heparin (Logeart et al., Eur. J. Cell Biol. 74, 1997, this issue). In order to investigate the structure-activity relationship of fucan on SMC growth, we have prepared by size exclusion chromatography fucan fractions of various molecular masses ranging from 5.5 to 556 kDa. Our experiments showed that the antiproliferative activity is dependent on the molecular weight of the polysaccharide. The molecular weight threshold indicated that about 30 saccharidic units on fucan were necessary to give the antiproliferative activity on SMCs. A kinetics study of DNA synthesis using tritiated thymidine uptake was also performed with different molecular weight fucan fractions. Although all tested fractions acted as soon as the cells enter the first cell cycle, the duration and potency of action varied. Moreover, displacement experiments of iodinated fucan revealed that the low molecular fucan fraction interacted weakly with the binding sites. Finally, gel permeation chromatography of internalized radiolabeled heparin and fucans was performed with SMCs. A rapid degradation of internalized heparin was observed, whereas only low molecular weight fucan fractions were partially degraded by SMCs. Together, these results indicate the significance of molecular weight on the antiproliferative activity of fucans on SMCs, and might help to understand their mechanism of action. In addition, the degradation experiments with internalized heparin and fucans ruled out a direct link between polysaccharide degradation and the antiproliferative effect on SMCs.

Randomness and biospecificity: random copolymers are capable of biospecific molecular recognition in living systems

Biospecific molecular recognition in living systems is known to be based on the lock and key principle as proposed by Emil Fischer. Based on this concept, biospecific polymers have been produced synthetically by attaching biospecific 'keys' to the polymer chain. We postulate that biospecificity can be achieved by alternative means, namely random substitution of a preformed polymer with suitable chemical groups or random copolymerization of suitable functional monomers. Such polymers, we suggest, will contain arrangements of the chemical functions which mimic natural biospecific sites and the probability of occurrence of such arrangements will depend on the average composition of the polymer. In support of this principle, we have developed several functional random copolymer systems which possess a variety of biological properties depending on the type of chemical function. Examples are: polymers possessing anticoagulant properties similar to those of heparin; polymers which interact specifically with components of the immune system; and polymers which, in contact with cells, affect their growth and metabolism. In the case of statistical copolymers possessing 'DNA-like' properties obtained by phosphorylation of hydroxylated polystyrene derivatives, Monte Carlo simulations were used to determine the distribution of phosphodiester (PDE) groups along the chains and to compute the probabilities of occurrence of particular arrangements of PDE found in the 'DNA-like' sites. The results showed that these sites are made up of PDE groups separated by distances that closely match those between the same groups along a generatrix of the DNA double-helix cylinder. These findings offer the prospect of manufacturing polymeric biomaterials endowed with biomimetic character. Moreover, they provide the basis for a hypothesis regarding the appearance of biospecificity at the origin of life, suggesting that biospecific structures may have evolved by natural selection from purely random copolymers. It is likely therefore that biospecificity is a continuous function of randomness, arising from purely statistical distributions of reactivity and evolving into precisely defined structures such as those involved in ligand-receptor interactions.

Antiviral activity of derivatized dextrans on HIV-1 infection of primary macrophages and blood lymphocytes

The present study demonstrates at the molecular level that dextran derivatives carboxymethyl dextran benzylamine (CMDB) and carboxymethyl dextran benzylamine sulfonate (CMDBS), characterized by a statistical distribution of anionic carboxylic groups, hydrophobic benzylamide units, and/or sulfonate moieties, interact with HIV-1 LAI gp120 and V3 consensus clades B domain. Only limited interaction was observed with carboxy-methyl dextran (CMD) or dextran (D) under the same conditions. CMDBS and CMDB (1 microM) strongly inhibited HIV-1 infection of primary macrophages and primary CD4+ lymphocytes by macrophage-tropic and T lymphocyte-tropic strains, respectively, while D or CMD had more limited effects on M-tropic infection of primary macrophages and exert no inhibitory effect on M- or T-tropic infection of primary lymphocytes. CMDBS and CMDB (1 microM) had limited but significant effect on oligomerized soluble recombinant gp120 binding to primary macrophages while they clearly inhibit (> 50%) such binding to primary lymphocytes. In conclusion, the inhibitory effect of CMDB and the CMDBS, is observed for HIV M- and T-tropic strain infections of primary lymphocytes and macrophages which indicates that these compounds interfere with steps of HIV replicative cycle which neither depend on the virus nor on the cell.

Adsorption of immunoglobulin G and anti-factor VIII inhibitory antibody from haemophiliac plasma to derivatized polystyrenes

Modified polystyrene resins containing sulphonate groups and tyrosyl sulphamide or tyrosyl methyl ester sulphamide groups have been investigated with respect to their potential for selective binding of anti-Factor VIII inhibitory antibodies from plasma. Adsorption of total immunoglobulin G and of a monoclonal antibody to Factor VIII was measured following addition of the radioiodinated proteins to normal plasma, plasma depleted of Factor VIII by adsorption on a resin coupled to anti-Factor VIII antibody, and haemophiliac plasma containing various levels of inhibitory anti-Factor VIII antibody. Depletion of anti-Factor VIII antibody from the haemophiliac plasmas by incubation with the resins was also measured by Bethesda assay. The modified resins and their corresponding unmodified "controls' showed similar binding of total immunoglobulin G. However, only resins containing either sulphonate or a combination of sulphonate and tyrosyl sulphamide groups showed evidence of selective adsorption of anti-Factor VIII antibody from plasma.

Mechanism of thrombin inhibition by heparin cofactor II in the presence of dermatan sulphates, native or oversulphated, and a heparin-like dextran derivative

The kinetics of thrombin inhibition by heparin cofactor II (HC II) in the presence of dermatan sulphates, native (DS), or oversulphated (DSS 1 and DSS 2) and a biospecific dextran derivative substituted with carboxymethyl, carboxymethyl-benzylamide and carboxymethyl benzylamide-sulphonate functional groups (CMDBS), has been studied as a function of the sulphated polysaccharide concentration. The initial HC II and thrombin concentrations were set at equimolar levels. Analysis of the experimental data obtained for DS, DSS1 and DSS2 was performed using a previously described model which allows computation of the dissociation constant (KPS,HC) of the polysaccharide-HC II complex and the rate constant of thrombin inhibition by the polysaccharide-HC II complex (k). A KPS.HC of 9.6 x'10(-7) M and a k of 4.5 x 10(9) M-1 min-1 were found for DS, whereas KPS,HC 2.1 x 10(-6) M, k 1.1 x 10(10) M-1 min-1 and KPS,HC 4.3 x 10(-7) M, k 1.4 x 10(10) M-1 min-1 were found for DSS1 and DSS2, respectively. Knowing that DSS1 has a sulphur content per disaccharide of 7.8%, compared with 11.5% for DSS2, these results indicate that the polysaccharide affinity for HC II is increased only in the case of DSS 2, whereas the oversulphation increases the reactivities towards thrombin of both complexes DSS1-HC II and DSS2-HC II. A better conformation of these complexes may favour a faster interaction with the protease. Unlike heparin, DS at concentrations higher than 10(-5) M does not modify the reaction rate of thrombin inhibition, a fact which can be explained by the absence of complex formation between DS and thrombin. The experimental data obtained for CMDBS fit a kinetic model in which the biospecific dextran derivative rapidly forms a complex with thrombin which is more reactive towards HC II than the free protease. The reaction rate remained unchanged for CMDBS concentrations equal to or higher than 10(-5) M, whereas CMDBS was found to interfere strongly with the fibrinogen-thrombin interaction. These data suggest that CMDBS has a strong affinity for the protease and no affinity for HC II. The computed dissociation constant of the CMDBS-thrombin complex (KPS,E) was 2.4 x 10(-7) M and the rate constant of the reaction of this complex with HC II (k) was 1.7 x 10(8) M-1 min-1. These findings indicate that CMDBS exerts its catalytic effect through a unique mechanism of action and may constitute a new class of anticoagulant drugs.

Lipid composition of cultured endothelial cells in relation to their growth

Human endothelial cells in culture were examined in different growth conditions. The human endothelial cell line, EA.hy 926 cell line, was used and cells were studied either in exponential growth phase, at confluence, or growth-arrested by serum deprivation. Phospholipids were separated and analyzed by high-performance thin-layer chromatography, and their fatty acids were quantified by gas-liquid chromatography. No significant differences in the phospholipid distributions were found between exponentially growing and confluent endothelial cells in which phosphatidylcholine (PC) represented the major phospholipid. In comparison, serum-deprived cells exhibited higher proportions of sphingomyelin and lower content of PC. We also found that among the total lipids, cholesterol level for dividing endothelial cells was lower than for cells growth-arrested either by serum deprivation or by contact inhibition at confluence. The global fatty acid distribution was not affected by the growth conditions. Thus, oleate (18:1 n-9 and 18:1 n-7), palmitate (C16:0), and stearate (C18:0) were the main components of endothelial cell membranes. However, the fatty acid distributions obtained from each phospholipid species differed with the growth status. Altogether, the data indicated that subtle modulations of endothelial cell metabolism appear upon cell growth. The resulting membrane-dependent cellular functions such as cholesterol transport and receptor activities can be expected to be relevant for lipid trafficking within the vessel wall in vitro and in vivo.

Affinity chromatography of human anti-dextran antibodies. Isolation of two distinct populations

Affinity chromatography is a very efficient method for antibody purification. Two affinity chromatography supports were prepared to analyze the specificity of anti-dextran antibodies. Silica beads were grafted with native dextran or with functionalized dextran. The anti-dextran antibodies present in some human sera were analyzed by enzyme-linked immunosorbent assay method. These antibodies play an important role in severe dextran-induced anaphylactic reactions in humans by forming immune complexes with clinical dextran. The results indicated that two distinct populations of anti-dextran antibodies were purified from human serum, using dextran-coated silica beads. Elution from this support with an oligo-dextran of 4000 g/mol allowed the isolation of one population that only recognized native dextran as antigen. Functionalized dextran coated on dextran silica beads led to the purification, with a glycine-HCl buffer, of another subclass of antibodies that recognized substituted dextran derivatives. Furthermore, these antibodies could be useful tools for in vitro and in vivo investigations using dextran derivatives as bio-active polysaccharides.

Affinity of human anti-factor VIII antibodies for functional polystyrene supports

Human anti-factor VIII antibodies (anti-FVIII) neutralize Factor VIII (FVIII) procoagulant activity. These antibodies appear in about 5-15 per cent of severely affected patients with haemophilia A treated with FVIII concentrates (Mannucci, 1993). In order to obtain non-thrombogenic materials able to interact specifically with anti-FVIII, amino acids residues that mimic part of the FVIII molecule recognized by anti-FVIII have been grafted. Several cross-linked polystyrenes were functionalized with sulphonate and tyrosine sulphamide groups or tyrosine derivatives sulphamide groups such as methyl ester tyrosine, or the peptides aspartic acid methyl amide tyrosine, tyrosine aspatic acid methyl amide or aspartic acid aspatic acid methyl amide tyrosine. The in vitro removal of anti-FVIII from haemophilic A plasma was performed on different supports. These polymers exhibit strong and selective affinity for the anti-FVIII. The amount of adsorbed anti-FVIII varies with the composition of the polymer and a maximum is achieved for 15-35 per cent of amino acid sulphamide groups. The influence of different chemical groups on the surface of the polymeric solid supports on the adsorption of anti-FVIII was also studied.

Affinity of mouse immunoglobulin G subclasses for sialic acid derivatives immobilized on dextran-coated supports

High-performance liquid affinity chromatography is a powerful method for the purification of biological compounds owing to its specificity, rapidity and high resolution. In our laboratory, we develop chromatographic supports based on porous silica beads. However, in order to minimize non-specific interactions between the inorganic surface and proteins in aqueous solution, the silica beads are coated with modified dextran. As previously reported, many affinity ligands can be covalently grafted onto dextran-coated silica. In this study, N-acetylneuramic acid, which belongs to the sialic acid family and is present in immunoglobulin G (IgG) epitopes, is used as an active ligand. The interactions of this affinity support and IgG subclasses are analyzed. This immobilized ligand enables purification of IgG3 antibodies.

Conjugates of insulin with copolymers of N-(2-hydroxypropyl) methacrylamide: effects on smooth muscle cell proliferation

The hypothesis that an elevated plasma insulin level contributes to an increase in coronary heart disease has led to studies of the mitogenic effect of native insulin and its conjugates on smooth muscle cells (SMC). In this study, insulin was covalently attached to two water-soluble polymers containing N-(2-hydroxypropyl)methacrylamide using the mixed anhydride method. The first polymer was a copolymer of N-(2-hydroxypropyl)methacrylamide and N-methacryloyldiglycine. The second one was a terpolymer of two of the above-given monomers and R-(-)-1-methyl-2-methacryloylamidoethyl 2-acetamido-2-deoxy-beta-D-glucopyranoside. Insulin conjugates were isolated and characterized, and the mitogenic effect on SMC was investigated. The results showed that only conjugates of insulin and terpolymers bearing pendant N-acetyl-glucosamine groups do not have a mitogenic effect on SMC while maintaining the hypoglycemic activity of insulin. This finding suggests that some inter- or intramolecular interactions of coupled insulin with the sugar moiety(ies) attached to the polymer backbone contribute to the observed effects.

Sulfonated dextran inhibits complement activation and complement-dependent cytotoxicity in an in vitro model of hyperacute xenograft rejection

In the present study, we demonstrate that a substituted soluble dextran derivative bearing 73% carboxylic groups and 15% benzylamide sulfonate groups, termed CMDBS25, inhibits complement activation and complement-mediated damage in an in vitro model of xenogeneic rejection. Incubation of porcine aortic endothelial cells with normal human serum resulted in time-dependent complement consumption as assessed by C3a generation in the fluid phase and deposition of activated complement fragments C3, C5 and of C5b-9 on target cells. The presence of C5b-9 membrane attack complex was associated with 51Cr release from prelabelled endothelial cells. The addition of 5-25 mg of CMDBS25/ml under the experimental conditions used, inhibited complement activation and C3a generation in a dose-dependent fashion. CMDBS25 (25 mg/ml) totally suppressed iC3b, C5 and C5b-9 cytolytic complex deposition on cells and inhibits by 42% lysis of target endothelial cells. Native dextran had no effect. Our observations document the anti-complementary properties of sulfonated dextran derivatives and their potential as therapeutic agents for the prevention of complement-dependent hyperacute xenograft rejection.

Collagen synthesis by vascular smooth muscle cells in the presence of antiproliferative polysaccharides

Production of various components of the extracellular matrix (ECM) modulates biological functions of the vascular tissue. This process is generally amplified in pathologic states as atherosclerosis. Atheroma originates from smooth muscle cells (SMC) which have migrated and proliferated in the vascular intima. In this study we investigated protein synthesis, collagen synthesis, and types I, III, and V collagen distribution by SMC in the presence of three families of watersoluble polysaccharides, heparin, fucans, and derivatized dextrans. We observed that fucan and derivatized dextran were able, as was heparin, to inhibit rat aortic SMC growth in culture. We then analyzed collagen modulation by measuring the incorporation of the radiolabeled precursor (3H)-proline into vascular SMC. Our results showed uncoupling of the antiproliferative capacity with collagen biosynthesis. However, fucan, the most antiproliferative polysaccharide, was also the most active in inhibiting protein and collagen synthesis. In addition, compounds that decreased total collagen synthesis preferentially increased the proportion of cell-associated collagen. Interestingly, only the antiproliferative polysaccharides inhibited significantly type V collagen biosynthesis. These new biomaterials appear to be valuable tools to study and control extracellular-matrix interactions with cells from the vascular walls.

Relationships between chemical characteristics and anticomplementary activity of fucans

We have shown previously that a low-molecular-weight fucan extracted from the brown seaweed Ascophylum nodosum strongly inhibited human complement activation in vitro and its mechanism of action was largely elucidated. We further investigated the influence of molecular weight and chemical composition of fucan on its anticomplementary activity. The capacity of 12 fragments of fucan (ranging from a molecular weight of 4100 to 214,000) to prevent complement-mediated haemolysis of sheep erythrocytes (classical pathway) and of rabbit erythrocytes (alternative pathway) increased with increasing molecular weight, and reached a plateau for 40,000 and 13,500, respectively. The most potent fucan fractions were 40-fold more active than heparin in inhibiting the classical pathway. They were, however, as active as heparin in inhibiting the alternative pathway. In addition, we have developed a haemolytic test based on the CH50 protocol, which allows discrimination between activators and inhibitors of complement proteins. Although the mannose content within the different fucan fragments did not vary, the galactose and glucuronic acid contents increased with increasing activity, suggesting that these residues should be essential for full anticomplementary activity. Meanwhile, sulphate groups appeared to be necessary, but were clearly not a sufficient requirement for anticomplementary activity of fucans. Taken together, these data illustrate the prospects for the use of fucans as potential anti-inflammatory agents.

Effect of substituted dextran derivative on complement activation in vivo

A soluble dextran derivatized with carboxylic groups (73%) and benzylamide sulphonate groups (15%), termed CMDBS 25, exhibited significant anticomplementary activity in the absence of anticoagulant activity. The polysaccharide inhibited both classical and alternative pathway-dependent complement activation in human and rat serum in vitro. Simultaneous administration of CMDBS 25 (100 mg) and crushed Sephadex G25 (20 mg) into normal Lewis rats suppressed systematic complement consumption that was induced by Sephadex in the animals by 98% for 1 h. Two consecutive injections of 100 mg of CMDBS at 1 h interval resulted in total suppression of systemic complement activation for 2 h and in 50% suppression for an additional 2 h. Infusion of CMDBS alone was well tolerated and had no effect on CH50 in serum in vivo. Our results demonstrate that CMDBS 25 exhibits anticomplementary properties in vivo and suggest that the polymer represents a potential therapeutic agent for pathological conditions associated with complement activation.

Purification of monoclonal antibodies on dextran-coated silica support grafted by thiophilic ligand

Coated silica beads are promising supports for high-performance liquid chromatography (HPLC) of proteins; they combine the excellent mechanical properties of silica with minimal non-specific interactions with proteins in solution due to the presence of hydrophilic dextran polymers adsorbed at the silica surface. So, dextran-coated porous silica beads can be grafted with beta-mercaptoethanol by using divinylsulfone as coupling reagent to obtain new thiophilic supports usable in HPLC. The affinity of monoclonal IgG subclasses from mouse ascitic fluids for the active phases can be analysed. These dextran-coated silica supports grafted with thiophilic ligands allow a one-step purification of these antibodies. Moreover, the chromatographic separation of two subclasses, immunoglobulin G1 (IgG1) and IgG3, is observed and can be correlated to the high resolution of these new HPLC thiophilic supports.

Interaction mechanisms between insulin and N-acetylneuraminic acid in affinity chromatography

Silica beads are coated with dextran carrying a calculated amount of positively charged diethylaminoethyl (DEAE) groups in order to neutralize negatively charged silanol groups at the silica surface and in this way to minimize non-specific interactions between silica and proteins in solution. Dextran-coated silica supports are potentially excellent stationary phases for high-performance liquid chromatography of proteins. These supports combine the advantages of polysaccharide phases with the excellent mechanical characteristics of silica. These supports [silica-dextran-DEAE (SID)] are easily functionalized by grafting N-acetylneuramic acid (NANA), extracted from edible birds' nests, using conventional coupling methods. The performance of supports bearing NANA was studied by high-performance liquid affinity chromatography of insulin, the hypoglycaemic peptide hormone of the human organism. The study showed that these supports exhibit a reversible and specific affinity towards insulin and allow separations with high purification yields. The influence of different physico-chemical parameters (pH, temperature and insulin concentration) on insulin retention on the support was studied. This allowed the optimization of the conditions of adsorption and a better understanding of the interaction mechanisms between insulin and NANA as a biospecific ligand.

Differential antiviral activity of derivatized dextrans

The antiviral activity of water-soluble dextrans derivatized with varying percentages of carboxymethyl, benzylamide, and sulfonate groups was evaluated. Several of the polymers exhibited potent antiviral activity against a variety of enveloped viruses, but not against non-enveloped viruses, and only when present during virus adsorption. The mechanism of activity against retroviruses [i.e. human immunodeficiency virus (HIV)] and herpes viruses (i.e. human cytomegalovirus) could be ascribed to inhibition of virus binding to the cells. An absolute requirement for anti-HSV activity appeared to be a sufficiently high percentage of benzylamide and benzylamide sulfonate groups. This did not, however, apply for human cytomegalovirus, respiratory syncytial virus, and HIV. The sensitivity of the latter viruses appeared to be influenced by factors other than the global chemical composition, which leads us to assume that physical factors such as the distribution and sequence of the substituents on the sugar backbone play an important role in the antiviral activity of the derivatized dextrans.

Derivatized dextrans modulate collagen synthesis in aortic smooth muscle cells

The effect of specifically derivatized dextrans, with or without antiproliferative activity on smooth muscle cells (SMC), was investigated on type I and type III collagen biosynthesis and mRNA levels in post-confluent SMC cultures. Our results indicate that dextran derivatives decreased total protein and collagen synthesis independently of their antiproliferative activities. However, the most substituted dextran, the one exhibiting the strongest antiproliferative activity towards SMC, was the most active in modulating type III collagen expression. In addition, only the two dextran derivatives bearing benzylamide groups inhibited collagen excretion.

Interactions of HIV-1 envelope glycoproteins with derivatized dextrans

The present study demonstrates that derivatized dextrans, such as carboxylmethyl dextran benzylamide and carboxymethyl dextran benzylamide sulfonate, specifically interact with HIV-1 envelope glycoproteins (rgp160 and rgp41) with significantly higher affinities than those observed for dextran sulfate (MW 8 kDa). These results suggest the possible involvement in HIV infectivity of surface membrane molecules which may bind the virus at pre or post-CD4 binding steps. They also suggest the possible use of these compounds in anti-HIV therapy.

High-performance affinity chromatography of insulin on coated silica grafted with sialic acid

High-performance liquid affinity chromatography (HPLAC) is a powerful method for the purification of biological compounds, owing to its specificity, speed and high resolution. We developed new chromatographic supports based on porous silica beads. In order to minimize non-specific interaction between the silanol groups at the silica surface and biological molecules, the beads are coated with dextran carrying a calculated amount of positively charged functions. Such supports have the mechanical properties of the starting inorganic material. Moreover, they can be easily activated and functionalized by active ligands using conventional coupling methods. In the present study, N-acetylneuraminic acid (NANA), a member of the sialic acid family, is coupled to dextran coated silica beads to obtain affinity supports. This class of compounds seems to play an important role in the cell recognition mechanism. In particular, sialic acids are present in the structure of the cellular receptors for insulin. By HPLAC, we can study the interactions between coated silica grafted with NANA and insulin. It is also possible to use these active supports to purify the compounds by affinity chromatography. However, it is important to determine and optimize the conditions for adsorption and desorption of insulin on supports grafted with sialic acid and to estimate the chromatographic performances of these active phases.

Tyrosyl sulfamide derivatives as ligands for affinity adsorption of anti FVIII antibodies

Human anti factor VIII (anti FVIII) antibodies neutralize factor VIII procoagulant activity. These antibodies appear in about 5-10% of severely affected haemophiliac A patients treated with FVIII concentrates. In order to obtain non-thrombogenic materials able to interact specifically with anti FVIII, we have grafted amino acid residues which mimic part of the epitope of the FVIII molecule recognized by the anti FVIII. For this purpose, crosslinked polystyrenes functionalized with sulfonate and tyrosyl or methyl ester tyrosyl sulfamide groups have been synthesized and characterized. The in vitro removal of anti FVIII from haemophiliac patient plasma with antibodies, was performed on these different active supports. These polymers exhibit strong and selective affinity for the anti FVIII. The adsorption of the antibodies vary with the percentage of units bearing methyl ester tyrosyl sulfamide groups and present a maximum at 25% grafting rate. For the more efficient resin, the affinity constant, determined for the adsorption isotherm for the anti FVIII is about 10(9) M-1, whereas the affinity constant for the IgG in the same experimental conditions, is low (10(5) M-1). The influence of different chemical groups on the polymeric phase, on their affinity for the inhibitors was also studied. The most active resins can be selected and used in an extracorporeal circulation to reduce the concentration of anti FVIII in a blood epuration process.

Effect of a derivatized dextran on human osteoblast growth and phenotype expression

Water soluble derivatized dextran named E9 with a molecular weight of 45,000 g l-1 containing 58% methyl carboxylic acid unit, 19% benzylamide unit, and 26% sulfonate with a specific anticoagulant activity of 0.29 IU mg-1 was studied for its effects on human osteoblast growth and phenotype expression for short-term treatment. At concentrations between 1 ng ml-1 and 1 microgram ml-1 E9 has no effect on DNA synthesis whereas at higher concentrations DNA synthesis is inhibited in a dose related fashion (87% for 400 micrograms ml-1). For concentrations which do not modify osteoblast growth, E9 promotes alkaline phosphatase activity, type I collagen and osteocalcin synthesis with a maximum effect for 0.1-1 microgram ml-1. It has a synergistic effect with hPTH increasing AMPc. Moreover, osteonectin synthesis was enhanced in a dose-dependent manner between 0.1 and 5 micrograms ml-1. These results seem to indicate that E9 is able to stimulate human osteoblast phenotype expression and could be useful in clinical applications.

Inhibition of complement activation by natural sulfated polysaccharides (fucans) from brown seaweed

In the present study, we demonstrate that natural sulfated polysaccharides (fucans) isolated from brown seaweed are potent inhibitors of human complement activation. A fucan fraction of chromatographic molecular weight 22,600, termed BS8, was found to inhibit classical and alternative pathway activation in whole serum in a dose-dependent fashion. Fucan BS8 inhibited formation of the classical pathway C3 convertase by interfering with C1 activation or by inhibiting C4 cleavage and the interaction between C4b and C2. The fucan also inhibited formation/function of the alternative pathway C3 convertase by suppressing the binding of B to C3b and by interfering with the stabilizing function of Properdin. The inhibitory effect of fucans on formation of the C3 convertases was dependent on the molecular weight of the polysaccharide for compounds of chromatographic molecular weight below 16,600. Fucan had no effect on the function of the terminal complex. Since fucans were more efficient than heparin in inhibiting activation of the classical pathway in whole serum and exhibited a lesser specific anticoagulant activity on a molar basis, our results suggest that these natural sulfated polysaccharides have a potential for use as anti-complementary and anti-inflammatory agents.