Sylvia Colliec-Jouault

A disaccharide repeat unit is the major structure in fucoidans from two species of brown algae

The predominant repeating structure of a fraction of the fucoidan from Ascophyllum nodosum prepared by acid hydrolysis and centrifugal partition chromatography (LMWF) was established as: [-->3)-alpha-L-Fuc(2SO3-)-(1-->4)-alpha-L-Fuc(2,3diSO3-)-(1]n by NMR spectroscopy and methylation analysis. The proton and carbon NMR spectra of this unit have been assigned and found to correspond with features in the spectra of the whole purified fucan from A. nodosum which account for most of the integrated intensity. The same structure has also been recognised in the fucoidan of Fucus vesiculosus. The fraction LMWF has in vitro anticoagulant activity, indicating that the above structure may be partly responsible for biological activity in the native fucoidan.

Marine Polysaccharides: A Source of Bioactive Molecules for Cell Therapy and Tissue Engineering

The therapeutic potential of natural bioactive compounds such as polysaccharides, especially glycosaminoglycans, is now well documented, and this activity combined with natural biodiversity will allow the development of a new generation of therapeutics. Advances in our understanding of the biosynthesis, structure and function of complex glycans from mammalian origin have shown the crucial role of this class of molecules to modulate disease processes and the importance of a deeper knowledge of structure-activity relationships. Marine environment offers a tremendous biodiversity and original polysaccharides have been discovered presenting a great chemical diversity that is largely species specific. The study of the biological properties of the polysaccharides from marine eukaryotes and marine prokaryotes revealed that the polysaccharides from the marine environment could provide a valid alternative to traditional polysaccharides such as glycosaminoglycans. Marine polysaccharides present a real potential for natural product drug discovery and for the delivery of new marine derived products for therapeutic applications.

Low Molecular Weight Fucoidan Prevents Neointimal Hyperplasia in Rabbit Iliac Artery In-Stent Restenosis Model

Objective—Smooth muscle cell (SMC) proliferation within the intima is regulated by heparan sulfates. We studied a low molecular weight (LMW) fucoidan (sulfated polysaccharide from brown seaweed) on SMC proliferation in vitro and intimal hyperplasia in vivo. Methods and Results—In vitro study revealed that LMW fucoidan reduces rabbit SMC proliferation and is internalized in SMC perinuclear vesicles. On rabbit iliac arteries perfused in vivo with fluorolabeled LMW fucoidan after angioplasty, the labeling was mainly located on sites of injury. Pharmacokinetic studies showed that LMW fucoidan exhibited in rats an elimination half-life of 56±25 minutes (n=8) after intravenous administration and a constant plasma rate for ≥6 hours after intramuscular administration. After stent implantation in their iliac arteries, rabbits were also treated with LMW fucoidan (5 mg/kg IM twice a day). Histomorphometric analysis at day 14 indicated that LMW fucoidan reduced intimal hyperplasia by 59% (1.79±0.4 versus 0.73±0.2 mm2, P <0.0001) and luminal cross-sectional area narrowing by 58% (0.38±0.08 versus 0.16±0.04, P <0.0001). Blood samples showed no anticoagulant activity due to LMW fucoidan. Conclusions—This natural polysaccharide with high affinity for SMCs and sustained plasma concentration markedly reduced intimal hyperplasia, suggesting its use for the prevention of human in-stent restenosis.

Antiviral activities of sulfated polysaccharides isolated from Sphaerococcus coronopifolius (Rhodophytha, Gigartinales) and Boergeseniella thuyoides (Rhodophyta, Ceramiales).

Water-soluble sulfated polysaccharides isolated from two red algae Sphaerococcus coronopifolius (Gigartinales, Sphaerococcaceae) and Boergeseniella thuyoides (Ceramiales, Rhodomelaceae) collected on the coast of Morocco inhibited in vitro replication of the Human Immunodeficiency Virus (HIV) at 12.5 μg/mL. In addition, polysaccharides were capable of inhibiting the in vitro replication of Herpes simplex virus type 1 (HSV-1) on Vero cells values of EC50 of 4.1 and 17.2 μg/mL, respectively. The adsorption step of HSV-1 to the host cell seems to be the specific target for polysaccharide action. While for HIV-1, these results suggest a direct inhibitory effect on HIV-1 replication by controlling the appearance of the new generations of virus and potential virucidal effect. The polysaccharides from S. coronopifolius (PSC) and B. thuyoides (PBT) were composed of galactose, 3,6-anhydrogalactose, uronics acids, sulfate in ratios of 33.1, 11.0, 7.7 and 24.0% (w/w) and 25.4, 16.0, 3.2, 7.6% (w/w), respectively.

Neoangiogenesis Induced by Progenitor Endothelial Cells: Effect of Fucoidan from Marine Algae

Fucoidans--sulphated polysaccharides extracted from brown algae--could be beneficial in patients with ischemic diseases. Their antithrombotic and proangiogenic properties promote in animals, neovascularization and angiogenesis which prevent necrosis of ischemic tissue. In 1997, endothelial progenitor cells were first identified in human peripheral blood. They are recruited from bone marrow and contribute to neovascularization after ischemic injury. Mobilization of these cells in ischemic sites is an important step in new vessel formation. It is thought that the progenitors interact with endothelial cells, then extravasate and reach ischemic sites, where they proliferate and differentiate into new blood vessels. Although chemokines, cytokines and adhesion molecules are thought to be involved, the precise mechanism of progenitor mobilization is not fully understood. Recent studies suggest that stromal-derived factor 1 plays a critical role at several steps of progenitor mobilization. Given the role of proteoglycans within bone marrow, at the endothelium surface, and in growth factor and chemokine binding, fucoidans might influence the mobilization of endothelial progenitor cells and their incorporation in ischemic tissue. This review provides an update on circulating endothelial progenitors and their role in neovascularization. It focuses on recent advances in our understanding of interactions between these progenitor cells and exogenous sulphated polysaccharides, and their implications for understanding the fucoidan mechanism of action.

Sulfation and depolymerization of a bacterial exopolysaccharide of hydrothermal origin

An unusual exopolysaccharide produced by Alteromonas infernus, a heterotrophic aerobic bacteria originating from a deep-sea hydrothermal vent, was chemically modified by sulfation and acidic depolymerization in order to promote biological activity and to evaluate its potential applications in the pharmaceutical area. Two experimental processes, sulfation prior to depolymerization (method 1) and depolymerization prior to sulfation (method 2), were applied to this high-molecular-weight bacterial polymer. Both methods led to the recovery of highly sulfated (33–40%) low-molecular-weight, low-viscous exopolysaccharides with yields ranging from 25 to 50%. Similar chemical compositions were obtained for all depolymerized fractions. These fractions are expected to show biological activity and their evaluation is in progress.

Capillary electrophoresis determination of the binding affinity of bioactive sulfated polysaccharides to proteins: study of the binding properties of fucoidan to antithrombin

The interaction of proteins with polysaccharides represents a major and challenging topic in glycobiology, since such complexes mediate fundamental biological mechanisms. An affinity capillary electrophoresis method has been developed to evidence the complex formation and to determine the binding properties between an anticoagulant polysaccharide of marine origin, fucoidan, and a potential target protein, antithrombin. This method is a variant of zonal electrophoresis in the mobility shift format. A fixed amount of protein was injected into a capillary filled with a background electrolyte containing the polysaccharide in varying concentrations. The effective mobility data of the protein were processed according to classical linearization treatments to obtain the binding constant for the polysaccharide/antithrombin complex. The results indicate that fucoidan binds to antithrombin in a 1:1 stoichiometry and with an affinity depending on the molecular weight of the polysaccharide. For heparin, the binding constant obtained similarly is in accordance with the literature. This is the first report showing the implementation of a capillary electrophoresis method contributing to the mechanistic understanding of the biological activities of fucoidan and providing evidence for the complex formation between fucoidan and the protein inhibitor of the coagulation antithrombin.

Effect of Low Molecular Weight Fucoidan and Low Molecular Weight Heparin in a Rabbit Model of Arterial Thrombosis

Background: Therapeutic use of unfractionated heparin and low molecular weight heparins (LMWHs) is limited by hemorrhagic adverse effects. We compared the antithrombotic effect of LMW fucoidan (LMWF) and LMWH in an experimental model. Methods: Thrombosis was induced in femoral arteries of male New Zealand White rabbits by in situ induction of endothelial apoptosis with staurosporine (10–5M for 30 min). Starting the day before apoptosis induction, the animals received subcutaneous LMWF (15 mg/kg), LMWH (enoxaparin 2.5 mg/kg) or saline solution (control group) twice a day for 4 days. Results: The degrees of apoptosis and endothelial denudation were similar in the 3 groups. The thrombotic score was significantly lower in the LMWF group than in the LMWH and control groups (p = 0.01). Tissue factor expression was significantly lower in the LMWF group than in the control and LMWH groups (p = 0.01). The plasma concentration of tissue factor pathway inhibitor was significantly increased after LMWF injection (137 ± 28 vs. 102 ± 17; p = 0.01), whereas no change was observed after LMWH treatment. LMWF did not prolong the bleeding time or decrease platelet aggregation. Conclusions: LMWF appeared to be more effective than LMWH for preventing arterial thrombosis in this experimental model. LMWF also had a lower hemorrhagic risk than LMWH.

Exopolysaccharides produced by marine bacteria and their applications as glycosaminoglycan-like molecules

Although polysaccharides are ubiquitous and the most abundant renewable bio-components, their studies, covered by the glycochemistry and glycobiology fields, remain a challenge due to their high molecular diversity and complexity. Polysaccharides are industrially used in food products; human therapeutics fall into a more recent research field and pharmaceutical industry is looking for more and more molecules with enhanced activities. Glycosaminoglycans (GAGs) found in animal tissues play a critical role in cellular physiological and pathological processes as they bind many cellular components. Therefore, they present a great potential for the design and preparation of therapeutic drugs. On the other hand, microorganisms producing exopolysaccharides (EPS) are renewable resources meeting well the actual industrial demand. In particular, the diversity of marine microorganisms is still largely unexplored offering great opportunities to discover high value products such as new molecules and biocatalysts. EPS-producing bacteria from the marine environment will be reviewed with a focus on marine-derived EPS from bacteria isolated from deep-sea hydrothermal vents. Information on chemical and structural features, putative pathways of biosynthesis, novel strategies for chemical and enzymatic modifications and potentialities in the biomedical field will be provided. An integrated approach should be used to increase the basic knowledge on these compounds and their applications; new clean environmentally friendly processes for the production of carbohydrate bioactive compounds should also be proposed for a sustainable industry.

Osteoprotegerin, a new actor in vasculogenesis, stimulates endothelial colony-forming cells properties.

Summary.  Background: Osteoprotegerin (OPG), a soluble receptor of the tumour necrosis factor family, and its ligand, the receptor activator of nuclear factor‐κB ligand (RANKL), are emerging as important regulators of vascular pathophysiology. Objectives: We evaluated their effects on vasculogenesis induced by endothelial colony‐forming cells (ECFC) and on neovessel formation in vivo. Methods: Effects of OPG and RANKL on in vitro angiogenesis were evaluated after ECFC incubation with OPG or RANKL (0–50 ng mL−1). Effects on microvessel formation were evaluated with an in vivo murin Matrigel plug assay. Vascularization was evaluated by measuring plug hemoglobin and vascular endothelial growth factor (VEGF)‐R2 content 14 days after implantation. Results: We found that ECFC expressed OPG and RANK but not RANKL mRNA. Treatment of ECFC with VEGF or stromal cell‐derived factor‐1 (SDF‐1) upregulated OPG mRNA expression. OPG stimulated ECFC migration (P < 0.05), chemotaxis (P < 0.05) and vascular cord formation on Matrigel® (P < 0.01). These effects were correlated with SDF‐1 mRNA overexpression, which was 30‐fold higher after 4 h of OPG stimulation (P < 0.01). OPG‐mediated angiogenesis involved the MAPK signaling pathway as well as Akt or mTOR cascades. RANKL also showed pro‐vasculogenic effects in vitro. OPG combined with FGF‐2 promoted neovessel formation in vivo, whereas RANKL had no effect. Conclusions: OPG induces ECFC activation and is a positive regulator of microvessel formation in vivo. Our results suggest that the OPG/RANK/RANKL axis may be involved in vasculogenesis and strongly support a modulatory role in tissue revascularization.