Fucoidan is a non-anticoagulant inhibitor of intimal hyperplasia

Fucoidan for cardiovascular application and the factors mediating its activities

Fucoidan is a sulfated polysaccharide with various bioactivities. The application of fucoidan in cancer treatment, wound healing, and food industry has been extensively studied. However, the therapeutic value of fucoidan in cardiovascular diseases has been less explored. Increasing number of investigations in the past years have demonstrated the effects of fucoidan on cardiovascular system. In this review, we will focus on the bioactivities related to cardiovascular applications, for example, the modulation functions of fucoidan on coagulation system, inflammation, and vascular cells. Factors mediating those activities will be discussed in detail. Current therapeutic strategies and future opportunities and challenges will be provided to inspire and guide further research.

Isolation and purification of fucoidan fraction in Turbinaria ornata from the Maldives; Inflammation inhibitory potential under LPS stimulated conditions in in-vitro and in-vivo models

Fucoidan, referred to as fucose containing sulfated polysaccharides (FCSP), is a polymer from brown algae cell wall that is reported to exhibit potential anti-inflammatory activity. In the present study, the fucoidans are extracted from Turbinaria ornata (TO) from the Maldives. The method involves enzyme assisted extraction and is modified in order to improve the effectiveness and purity of final product. Purified fucoidan fraction was identified as F10, and its chemical properties were verified via FTIR, 1H NMR and monosaccharide analysis. Selected inflammatory mediators were studied to evaluate the anti-inflammatory potential using RAW 264.7 macrophages. F10 successfully inhibited NO production (IC50 = 30.83 ± 1.02 μg mL-1). F10 dose-dependently down-regulated iNOS, COX-2, and pro-inflammatory cytokines including PGE2 levels. The in vivo experiments were assisted by zebrafish embryo model. This exhibited reduction in ROS, NO expression levels. To our knowledge, this is the first report to illustrate potential anti-inflammatory activity of FCSPs' extracted from the brown algae T. ornata. Concisely, the results suggest that fucoidan purified from T. ornata increases the macrophage cellular and zebrafish embryo resistance against LPS-induced inflammation. Based on the observations, the fucoidans are promising candidates to be used in the pharmaceutical and cosmeceutical sectors.

Fucoidan suppresses excessive phagocytic capacity of porcine peripheral blood polymorphonuclear cells by modulating production of tumor necrosis factor-alpha by lipopolysaccharide-stimulated peripheral blood mononuclear cells

We examined the effect of fucoidan, an immune modulator, on the phagocytic capacity of porcine peripheral blood polymorphonuclear cells (PMNs) exposed to culture supernatant from lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMCs). For this purpose, we evaluated the phagocytic capacity of porcine PMNs by flow cytometry and measured levels of tumor necrosis factor-alpha (TNF-α) protein and mRNA in porcine PBMCs by enzyme-linked immunosorbent assay (ELISA) and real time-polymerase chain reaction (PCR), respectively. Fucoidan or LPS alone did not affect the phagocytic capacity of PMNs, but phagocytosis by these cells was increased by exposure to culture supernatant from PBMCs treated with fucoidan or LPS. In particular, the culture supernatant from PBMCs treated with LPS revealed excessive phagocytosis of PMNs. This excessive phagocytic capacity was diminished by co-treatment LPS with fucoidan. Production of TNF-α mRNA and protein increased upon treatment of PBMCs with either fucoidan or LPS, but this effect was also diminished by co-treatment LPS with fucoidan. The ability of culture supernatant from PBMCs treated with LPS and/or fucoidan to increase the phagocytic capacity of PMNs was inhibited by anti-recombinant porcine TNF-α polyclonal antibody. These results suggested that fucoidan suppresses the phagocytic capacity of PMNs by modulating TNF-α production by LPS-stimulated PBMCs.

Detection of Fucoidan in Urine after Oral Intake of Traditional Japanese Seaweed, Okinawa mozuku (Cladosiphon okamuranus Tokida)

Seaweed has been considered an indigestible food. Fucoidan, which is found abundantly in seaweed, especially in Cladosiphon okamuranus (Okinawa mozuku), has a high molecular weight and has been long believed to be hardly absorbed in the human digestive system due to a lack of certain digestive enzymes. We previously reported that fucoidan can be detected in serum and urine after oral intake of purified fucoidan in humans and rats. However, it is unclear whether the fucoidan in mozuku can be absorbed after digestion of mozuku. Therefore, we attempted to detect fucoidan in urine before and after mozuku intake. We determined the fucoidan concentration in urine after oral intake of Okinawa mozuku and urinary fucoidan was detected in several volunteers. In conclusion, these results suggest that fucoidan in mozuku can be absorbed after ingestion of mozuku.

Development of a fucoidan-specific antibody and measurement of fucoidan in serum and urine by sandwich ELISA

Fucoidan exhibits various biological properties. We raised a novel antibody against fucoidan extracted from Cladosiphon okamuranus and developed a sandwich ELISA method to measure fucoidan. The fucoidan antibody was specific and did not cross-react with other polysulfated polysaccharides. Fucoidan recovery from serum and urine by ELISA was 86-113%. Intra- and inter-assay CVs were 1.5-13.4%. Assay linearity was maintained after 3-fold dilution of each sample with phosphate-buffer saline (PBS). In the serum and urine of healthy volunteers (n=10), fucoidan was not detected before administration, and the levels markedly increased 6 and 9 h after oral administration. The molecular weight of the serum fucoidan determined by HPLC gel filtration remained unchanged, whereas that of urine fucoidan was significantly reduced. This is the first ELISA method of measuring serum and urine fucoidan levels after oral administration. The method is simple, reliable, and practical for the analysis of samples, especially urine samples.

Characterization of meFucoidan as a selective inhibitor for secretory phospholipase A2-IIA and the phosphorylation of meFucoidan-binding proteins by A-kinase in vitro

The direct interaction of Mekabu fucoidan (meFucoidan) with four functional basic proteins (sPLA2-IIA, bFGF, histone H2B and HBV core protein) and three synthetic FGF-BP peptides (sp5, GE13 and RS6) was characterized in vitro. It was found that (i) meFucoidan inhibited dose-dependently the activity of sPLA2-IIA, but not pPLA2, through its direct binding to the enzyme; (ii) sPLA2-IIA activity was sensitive to meFucoidan rather than heparin, but significantly stimulated by sulfatide; (iii) the A-kinase-mediated phosphorylation of these basic proteins, except sPLA2-IIA, and synthetic peptides, containing potent phosphorylation sites for A-kinase, was inhibited dose-dependently by meFucoidan; and (iv) two consensus meFucoidan-binding motifs (B-B-B-B-X and B-X-B-B-X; B, basic amino acid) in these basic proteins and synthetic peptides could be overlapping to the potent phosphorylation site (B-B-X-S/T) for the kinase in vitro. These results presented here suggest that meFucoidan functions as a selective inhibitor for sPLA2-IIA and the A-kinase-mediated phosphorylation of cellular meFucoidan-binding functional basic proteins in vitro.

A comparative study of the anti-inflammatory, anticoagulant, antiangiogenic, and antiadhesive activities of nine different fucoidans from brown seaweeds

The anti-inflammatory, antiangiogenic, anticoagulant, and antiadhesive properties of fucoidans obtained from nine species of brown algae were studied in order to examine the influence of fucoidan origin and composition on their biological activities. All fucoidans inhibited leucocyte recruitment in an inflammation model in rats, and neither the content of fucose and sulfate nor other structural features of their polysaccharide backbones significantly affected the efficacy of fucoidans in this model. In vitro evaluation of P-selectin-mediated neutrophil adhesion to platelets under flow conditions revealed that only polysaccharides from Laminaria saccharina, L. digitata, Fucus evanescens, F. serratus, F. distichus, F. spiralis, and Ascophyllum nodosum could serve as P-selectin inhibitors. All fucoidans, except that from Cladosiphon okamuranus carrying substantial levels of 2-O-alpha-D-glucuronopyranosyl branches in the linear (1-->3)-linked poly-alpha-fucopyranoside chain, exhibited anticoagulant activity as measured by activated partial thromboplastin time whereas only fucoidans from L. saccharina, L. digitata, F. serratus, F. distichus, and F. evanescens displayed strong antithrombin activity in a platelet aggregation test. The last fucoidans potently inhibited human umbilical vein endothelial cell (HUVEC) tubulogenesis in vitro and this property correlated with decreased levels of plasminogen-activator inhibitor-1 in HUVEC supernatants, suggesting a possible mechanism of fucoidan-induced inhibition of tubulogenesis. Finally, fucoidans from L. saccharina, L. digitata, F. serratus, F. distichus, and F. vesiculosus strongly blocked MDA-MB-231 breast carcinoma cell adhesion to platelets, an effect which might have critical implications in tumor metastasis. The data presented herein provide a new rationale for the development of potential drugs for thrombosis, inflammation, and tumor progression.

Low Molecular Weight Fucoidan Increases VEGF165-induced Endothelial Cell Migration by Enhancing VEGF165 Binding to VEGFR-2 and NRP1

Therapeutic induction of angiogenesis is a potential treatment for chronic ischemia. Heparan sulfate proteoglycans are known to play an important role by their interactions with proangiogenic growth factors such as vascular endothelial growth factor (VEGF). Low molecular weight fucoidan (LMWF), a sulfated polysaccharide from brown seaweeds that mimic some biological activities of heparin, has been shown recently to promote revascularization in rat critical hindlimb ischemia. In this report, we first used cultured human endothelial cells (ECs) to investigate the possible ability of LMWF to enhance the actions of VEGF(165). Data showed that LMWF greatly enhances EC tube formation in growth factor reduced matrigel. LMWF is a strong enhancer of VEGF(165)-induced EC chemotaxis, but not proliferation. In addition, LMWF has no effect on VEGF(121)-induced EC migration, a VEGF isoform that does not bind to heparan sulfate proteoglycans. Then, with binding studies using (125)I-VEGF(165), we observed that LMWF enhances the binding of VEGF(165) to recombinant VEGFR-2 and Neuropilin-1 (NRP1), but not to VEGFR-1. Surface plasmon resonance analysis showed that LMWF binds with high affinity to VEGF(165) (1.2 nm) and its receptors (5-20 nm), but not to VEGF(121). Pre-injection of LMWF on immobilized receptors shows that VEGF(165) has the highest affinity for VEGFR-2 and NRP1, as compared with VEGFR-1. Overall, the effects of LMWF were much more pronounced than those of LMW heparin. These findings suggested an efficient mechanism of action of LMWF by promoting VEGF(165) binding to VEGFR-2 and NRP1 on ECs that could help in stimulating therapeutic revascularization.

Exopolysaccharides produced by the recently described halophilic bacteria Halomonas ventosae and Halomonas anticariensis

We studied exopolysaccharides (EPSs) produced by Halomonas ventosae and Halomonas anticariensis, two novel species of halophilic bacteria. Under optimum environmental and nutritional conditions, H. ventosae strains Al12(T) and Al16 excreted 28.35 mg and 28.95 mg of EPS per 100 ml of culture medium (34.55 and 38.6 mg of EPS per gram of dry cell weight) respectively. The molecular masses of the polymers were about 50 kDa and their main components were glucose, mannose and galactose. They had high protein fractions and showed emulsifying activity on several hydrophobic substrates. Under optimum environmental and nutritional conditions, H. anticariensis strains FP35(T) and FP36 excreted about 29.65 and 49.95 mg of EPS per 100 ml of culture medium (43.6 and 50.95 mg of EPS per gram of dry cell weight) respectively. The molecular masses of the polymers were about 20 and 46 kDa respectively and were composed mainly of glucose, mannose and galacturonic acid. All EPSs produced solutions of low viscosity and pseudoplastic behaviour. They also had a high capacity for binding cations and incorporated considerable quantities of sulphates, which is highly unusual in bacterial polysaccharides. All strains assayed formed biofilms both in polystyrene wells and borosilicate test tubes.

Isolation and culture of a marine bacterium degrading the sulfated fucans from marine brown algae

Fucoidans are matrix polysaccharides from marine brown algae, consisting of an alpha-L-fucose backbone substituted by sulfate-ester groups and masked with ramifications containing other monosaccharide residues. In spite of their interest as biologically active compounds in a number of homologous and heterologous systems, no convenient sources with fucanase activity are available yet for the degradation of the fucalean algae. We here report on the isolation, characterization, and culture conditions of a bacterial strain capable of degrading various brown algal fucoidans. This bacterium, a member of the family Flavobacteriaceae, was shown to secrete fucoidan endo-hydrolase activity. An extracellular enzyme preparation was used to degrade the fucoidan from the brown alga Pelvetia canaliculata. End products included a tetrasaccharide and a hexasaccharide made of the repetition of disaccharidic units consisting of alpha-1-->3-L-fucopyranose-2-sulfate-alpha-1-->4-L-fucopyranose-2,3-disulfate, with the 3-linked residues at the nonreducing end.

Toxicological evaluation of fucoidan extracted from Laminaria japonica in Wistar rats

Fucoidans, the sulfated polysacchrides extracted from brown algae, have been extensively studied for their diverse biological activities. However, there is no detailed report investigating the toxicity of fucoidan. In this study, the acute and subchronic (6 months) toxicity of varying levels of fucoidan extracted from Laminaria japonica was investigated in Wistar rats after oral administration. The results showed that no significant toxicological changes were observed when 300 mg/kg body weight per day fucoidan was administered to rats. But when the dose was increased to 900 and 2500 mg/kg body weight per day, the clotting time was significantly prolonged. Besides this, no other signs of toxicity were observed. Based on these results, it can be concluded that the no adverse effect level of fucoidan from L. japonica is 300 mg/kg body weight per day.

Expression of stromal cell-derived factor-1 and of its receptor CXCR4 in liver regeneration from oval cells in rat

Stromal cell-derived factor-1 is a chemokine that plays a major role during embryogenesis. Since stromal cell-derived factor-1 and its unique receptor CXCR4 are involved in the differentiation of progenitor cells, we studied the expression of this chemokine and of its receptor in hepatic regeneration from precursor oval cells. Hepatic regeneration was induced by treating rats with 2-acetylaminofluorene, and followed by partial hepatectomy. Oval cell accumulation, which predominated in periportal regions, reached a maximum at days 9 to 14 after hepatectomy and declined thereafter. Oval cells strongly expressed stromal cell-derived factor-1 protein and mRNA. CXCR4 mRNA hepatic level paralleled the number of oval cells and in situ hybridization showed CXCR4 mRNA expression by these cells. Treatment of rats with fucoidan, a sulfated polysaccharide which binds to stromal cell-derived factor-1 and blocks its biological effects, markedly decreased oval cell accumulation in five of the seven treated rats. In conclusion, our data demonstrate an expression of stromal cell-derived factor-1 and of its receptor CXCR4 in oval cells during hepatic regeneration and strongly suggest that stromal cell-derived factor-1 stimulates the proliferation of these precursor cells through an autocrine/paracrine pathway.

Low-molecular-weight fucoidan promotes therapeutic revascularization in a rat model of critical hindlimb ischemia

The therapeutic potential of low-molecular-weight (LMW) fucoidan, a sulfated polysaccharide extracted from brown seaweed devoid of direct antithrombin effect, was investigated in vitro and in a model of critical hindlimb ischemia in rat. In vitro results showed that LMW fucoidan enhanced fibroblast growth factor (FGF)-2-induced [(3)H]thymidine incorporation in cultured rat smooth muscle cells. Intravenous injection in rats of LMW fucoidan significantly increased the stromal-derived factor (SDF)-1 level from 1.2 +/- 0.1 to 6.5 +/- 0.35 ng/ml in plasma. The therapeutic effect of LMW fucoidan (5 mg/kg/day), FGF-2 (1 micro g/kg/day), and LMW fucoidan combined with FGF-2 was assessed 14 days after induction of ischemia by 1) clinical evaluation of claudication, 2) tissue blood flow analysis, 3) histoenzymology of muscle metabolic activity, and 4) quantification of capillary density. Both LMW fucoidan and FGF-2 similarly improved residual muscle blood flow (62.5 +/- 6.5 and 64.5 +/- 4.5%, respectively) compared with the control group (42 +/- 3.5%, p < 0.0001). The combination of FGF-2 and LMW fucoidan showed further significant improvement in tissue blood flow (90.5 +/- 3%, p < 0.0001). These results were confirmed by phosphorylase activity, showing muscle regeneration in rats treated with the combination of FGF-2 and LMW fucoidan. Capillary density count increased from 9.6 +/- 0.7 capillaries/muscle section in untreated ischemic controls to 14.3 +/- 0.9 with LMW fucoidan, 14.5 +/- 0.9 with FGF-2, and 19.1 +/- 0.9 in combination (p < 0.001). Thus, LMW fucoidan potentiates FGF-2 activity, mobilizes SDF-1, and facilitates angiogenesis in a rat model. This natural compound could be of interest as an alternative for conventional treatment in critical ischemia.

Partial synthetic glucan sulfates as potential new antithrombotics: a review

Structurally defined sulfated polysaccharides were produced by partial synthesis to develop new antithrombotics as potential heparin alternatives. Glucans of different natural origins were used as starting polymers. The resulting glucan sulfates display pronounced anticoagulant effects; some of them are as active as heparin. According to studies on the structure-activity relationships, besides the molecular weight (MW) and the degree of sulfation (DS), the sulfation pattern and the polysaccharide basic structure are crucial parameters for their anticoagulant potency. Their mode of action differs from that of heparin. Depending on their individual structure, they specifically interfere with various stages of the coagulation process. In vivo, they partly exhibit antithrombotic activity similar to that of heparin. But the in vivo efficacy is not just based on their anticoagulant activity. Their profibrinolytic actions and their strong TFPI-releasing effect may considerably contribute to this overall effect. Due to their manifold interactions with the system of hemostasis, each glucan sulfate shows a structure-dependent, individual action profile. From the investigated glucan sulfates, mainly C2- and C4-sulfated, linear beta-1,3-glucan sulfates with DS > 1.0 and MW between 18 and 50 kDa proved to be most suitable for a potential use as heparin alternatives. The results of this study demonstrate the impact of the various structural parameters on the antithrombotic activity of sulfated polysaccharides. However, the biological actions of sulfated polysaccharides are not limited to hemostasis, but they also show manifold modulating effects on other biological systems. Therefore, the approach of using highly sophisticated carbohydrate drug design might be a possibility to obtain new drugs with specific action profiles.

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 > or =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.

Development of SPC-ELISA: a new assay principle for the study of sulfated polysaccharide-protein interactions

A sulfated polysaccharide-coating enzyme-linked immunosorbent assay (SPC-ELISA), a new screening assay for the study of interactions between sulfated polysaccharides and proteins, has been developed. Fibrinogen was used as representative for the protein. A microplate is coated with the sulfated polysaccharide to be tested and then incubated with various concentrations of fibrinogen. The bound fibrinogen is quantified by ELISA technique. The assay has been optimized with respect to coating procedure, incubation times, antibody concentrations, and detection conditions. Its capacity was demonstrated using three different sulfated polysaccharides: heparin, a sulfated glucuronogalactan extracted from a red algae, and a semisynthetic xanthan sulfate. Furthermore, the fibrinogen binding of semisynthetic laminarin sulfates with different degrees of sulfation showed good correlation with their anticoagulant effect as measured by fibrinogen clotting time. The intraassay as well as the interassay variations were lower than 8%. The binding properties observed in the SPC-ELISA correlated well with those found utilizing conventional gel permeation chromatography and fibrinogen affinity gel electrophoresis. Compared to these methods, the SPC-ELISA has several advantages: It is more rapid and far easier to perform, allows high throughput screening, and is suitable for automation. Furthermore, it is inexpensive, highly sensitive, and reproducible and has no special equipment requirements. Finally, the method represents the basis for multiple variations with regard to the target proteins as well as the detection methods.

Fucoidan inhibits smooth muscle cell proliferation and reduces mitogen-activated protein kinase activity

OBJECTIVES AND DESIGN

fucoidan has previously been shown to inhibit the proliferation of arterial smooth muscle cells both in animal models and in vitro. However, the mechanisms behind the anti-proliferative effects of this polysulfated polysaccharide are not known in detail. Here, the inhibitory effect of fucoidan on rat aortic smooth muscle cell proliferation was examined and compared with the effects of heparin after stimulation with fetal calf serum, platelet-derived growth factor BB, basic fibroblast growth factor, heparin-binding epidermal growth factor, and angiotensin II.

MATERIALS AND METHODS

the cultures were analysed with respect to cell proliferation and DNA synthesis by cell counting and measurement of(3)H-thymidine incorporation. Phosphorylation of mitogen-activated protein kinase and nuclear translocation of phosphorylated mitogen-activated protein kinase were studied by immunoblotting and immunocytochemistry.

RESULTS

fucoidan was shown to be a more potent inhibitor of smooth muscle cell proliferation than heparin. Fucoidan also reduced growth factor-induced activation of mitogen-activated protein kinase and prevented nuclear translocation of phosphorylated mitogen-activated protein kinase.

CONCLUSION

fucoidan is a more potent anti-proliferative polysulphated polysaccharide than heparin and may mediate its effects through inhibition of the mitogen-activated protein kinase pathway in a similar manner as heparin.

Inhibition of platelet-neutrophil interactions by Fucoidan reduces adhesion and vasoconstriction after acute arterial injury by angioplasty in pigs

The selectin family of cell-adhesion molecules contributes to the interactions of leukocytes and platelets at the site of vascular injury. Such interactions enhance inflammatory reactions and thrombus formation during the arterial response to injury. In this study, we investigated the effects of a selectin inhibitor (Fucoidan) on platelet and neutrophil interactions after arterial injury produced by angioplasty in pigs. [51Cr]-platelet deposition and [111In]-neutrophil adhesion were quantified on intact, mildly, and deeply injured carotid arterial segments, produced by balloon dilation in control (saline, n = 7) and Fucoidan-treated (i.v.; 1 mg/kg, n = 6; 5 mg/kg, n = 5) pigs. In the control group, platelet deposition (x10(6)/cm2) was influenced by the severity of injury and increased significantly (p < 0.05) from 0.06+/-0.06 on intact endothelium to 3.8+/-0.6 and 33.6+/-4.9 on mildly and deeply injured segments, respectively. Fucoidan, 1 mg/kg, had no significant effect, although doses of 5 mg/kg reduced platelet deposition by 73% on deeply injured segments. The level of neutrophil adhesion (x10(3)/cm2) was also influenced by the severity of injury: it increased in the control group from 8.8+/-2.5 on intact endothelium to 226.6+/-45.5 and 397.4+/-61.3 on mildly and deeply injured arterial segments, respectively (p < 0.05). Again, 1 mg/kg Fucoidan had no effect, although doses of 5 mg/kg reduced neutrophil adhesion by 92% and by 84% on mildly and deeply injured segments, respectively. The effects of Fucoidan were associated with a 51% decrease in the vasoconstrictive response at the site of arterial injury. However, Fucoidan had no significant effect on either platelet aggregation or activated clotting time (ACT). In the in vitro perfusion experiments, Fucoidan inhibited both isolated platelet, and neutrophil, adhesion to damaged arterial surfaces. This inhibition was more pronounced in experiments using mixed cell preparations, indicating that Fucoidan interferes with platelet and neutrophil interactions. These results highlight the importance of selectins in the acute physiopathologic reactions related to platelet-neutrophil interactions after arterial injury.

Structure and anticoagulant activity of sulfated fucans. Comparison between the regular, repetitive, and linear fucans from echinoderms with the more heterogeneous and branched polymers from brown algae

Sulfated fucans are among the most widely studied of all the sulfated polysaccharides of non-mammalian origin that exhibit biological activities in mammalian systems. Examples of these polysaccharides extracted from echinoderms have simple structures, composed of oligosaccharide repeating units within which the residues differ by specific patterns of sulfation among different species. In contrast the algal fucans may have some regular repeating structure but are clearly more heterogeneous when compared with the echinoderm fucans. The structures of the sulfated fucans from brown algae also vary from species to species. We compared the anticoagulant activity of the regular and repetitive fucans from echinoderms with that of the more heterogeneous fucans from three species of brown algae. Our results indicate that different structural features determine not only the anticoagulant potency of the sulfated fucans but also the mechanism by which they exert this activity. Thus, the branched fucans from brown algae are direct inhibitors of thrombin, whereas the linear fucans from echinoderms require the presence of antithrombin or heparin cofactor II for inhibition of thrombin, as reported for mammalian glycosaminoglycans. The linear sulfated fucans from echinoderms have an anticoagulant action resembling that of mammalian dermatan sulfate and a modest action through antithrombin. A single difference of one sulfate ester per tetrasaccharide repeating unit modifies the anticoagulant activity of the polysaccharide markedly. Possibly the spatial arrangements of sulfate esters in the repeating tetrasaccharide unit of the echinoderm fucan mimics the site in dermatan sulfate with high affinity for heparin cofactor II.

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.

Anticoagulant fucoidan fractions from Fucus vesiculosus induce platelet activation in vitro

Anticoagulant fucoidan fractions of different molecular weight and sulfate content were prepared and investigated for their effects on platelet function in vitro. The fucoidan fractions were incubated with human platelet rich plasma (PRP) at concentrations of 5, 10 and 50 micrograms/ml. Platelet activation was subsequently studied by a standard aggregation assay and flow cytometric determination of the activation dependent platelet-surface markers CD62p (P-selectin, GMP-140) and CD63 (GP53). All fucoidan fractions induced irreversible platelet aggregation in a dose-dependent manner. Comparing fractions of identical molecular weight (100 kDa) the low sulfate content fucoidan FF5 (S = 7.6%) exerted a significantly greater effect than the highly sulfated fucoidan FF7 (S = 10.2%) over the whole concentration range (n = 5, P < 0.05). Among fractions of identical sulfate content fucoidan-induced platelet aggregation was also found to depend on the molecular weight of the fucoidan. At concentrations of 10 and 50 micrograms/ml the high molecular weight fraction FF7/1 (150 kDa) showed a significantly greater effect than the 50 kDa fraction FF7/3 (24.8 +/- 6.7 vs. 7.0 +/- 3.5 and 54.6 +/- 13.5 vs. 15.0 +/- 9.0%, respectively; mean +/- SD, n = 5, P < 0.05). The molecular weight dependence of the fucoidan effect was also reflected by the flow cytometric data. Coincubation of FF7/1 and FF7/3 (10 micrograms/ml) with PRP increased the number of CD62p and CD63 positive platelets by 9.0 +/- 3.3 vs. 2 +/- 1.9 and 7.1 +/- 2.4 vs. 3.2 +/- 2.6% over control values, respectively (n = 5, P < 0.05). In conclusion, our results show that the low molecular weight fucoidan FF7/3 combines potent anticoagulant and fibrinolytic properties with only minor platelet activating effects and is therefore a suitable substance for further pharmacological studies.

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.

Heparin binding, internalization, and metabolism in vascular smooth muscle cells: I. Upregulation of heparin binding correlates with antiproliferative activity

Vascular smooth muscle cell (SMC) hyperplasia is an important component in the pathogenesis of arteriosclerotic lesions and is responsible for the failure of many vascular surgical procedures. SMC proliferation is inhibited by the glycosaminoglycan heparin; however, the precise mechanisms of action are still not understood. One important question in this regard is whether binding, internalization, and metabolism of heparin are necessary for the antiproliferative activity. In this study, we have analyzed SMC rendered resistant to the antiproliferative effect of heparin by drug selection and retroviral infection of SMC. We first examined the ability of heparin to bind to SMC. Experiments using [3H]heparin indicate the presence of saturable, heparin-displaceable, protease-sensitive binding sites on both sensitive and resistant SMC. The affinity of heparin binding does not correlate with the antiproliferative response. Using fluorescent and radiolabeled heparin probes, we observed that early heparin internalization kinetics in both sensitive and resistant SMC is similar, indicating that resistance to heparin is not due to changes in the ability of cells to take up heparin. In contrast, we observed during the continuous incubation with heparin that binding to resistant SMC is rapidly downregulated, whereas sensitive cells continue to bind and internalize heparin. These results suggest that upregulation of heparin binding to the SMC surface is required for an antiproliferative response. In an accompanying paper (Letourneur et al. [1995] J. Cell Physiol., 165:687-695, this issue), we describe the degradation and secretion of internalized heparin in both sensitive and resistant SMC.

Effects of a thromboxane A2-receptor antagonist, a thromboxane synthetase inhibitor and aspirin on prostaglandin I2 production in endothelium-intact and -injured aorta of guinea pigs

We examined the effects of KW-3635, a thromboxane (TX) A2-receptor antagonist, and OKY-046, a TX synthetase inhibitor, on the prostaglandin (PG) I2 production in endothelium-intact and -injured guinea pig aorta and compared them with those of aspirin. In the endothelium-intact aorta, both the low (3 mg/kg) and the high (100 mg/kg) dose of aspirin similarly reduced the PGI2 production, as measured ex vivo 1 hr after the injury. In contrast, neither KW-3635 (10 mg/kg) nor OKY-046 (30 mg/kg) inhibited the PGI2 production. The endothelial injury, induced by balloon catheterization, caused a reduction of PGI2 production in the aorta and decline of plasma PGI2/TXA2 ratio. In the endothelium-injured animals, the high dose of aspirin further reduced the PGI2 production in the aorta, whereas KW-3635 and OKY-046 did not affect it. KW-3635 and OKY-046 also ameliorated the reduced ratio of PGI2/TXA2 in the plasma. The present results demonstrate that aspirin, but not KW-3635 or OKY-046, reduces the PGI2 production in the aorta either in the endothelium-intact or -injured state. It is thus suggested that the TXA2-receptor antagonist and the TX synthetase inhibitor have some advantages over aspirin when used for the prevention of acute thrombosis after percutaneous transluminal angioplasty.

Protection of transforming growth factor-beta 1 activity by heparin and fucoidan

The transforming growth factor-beta (TGF-beta) family of proteins exert diverse and potent effects on proliferation, differentiation, and extracellular matrix synthesis. However, relatively little is known about the stability or processing of endogenous TGF-beta activity in vitro or in vivo. Our previous work indicated that 1) TGF-beta 1 has strong heparin-binding properties that were not previously recognized because of neutralization by iodination, and 2) heparin, and certain other polyanions, could block the binding of TGF-beta 1 to alpha 2-macroglobulin (alpha 2-M). The present studies investigated the influence of heparin-like molecules on the stability of the TGF-beta 1 signal in the pericellular environment. The results indicate that heparin and fucoidan, a naturally occurring sulfated L-fucose polymer, suppress the formation of an initial non-covalent interaction between 125I-TGF-beta 1 and activated alpha 2-M. Electrophoresis of 125I-TGF-beta 1 showed that fucoidan protects TGF-beta 1 from proteolytic degradation by plasmin and trypsin. While plasmin caused little, if any, activation of latent TGF-beta derived from vascular smooth muscle cells (SMC), plasmin degraded acid-activated TGF-beta, and purified TGF-beta 1, and this degradation was inhibited by fucoidan. In vitro, heparin and fucoidan tripled the half-life of 125I-TGF-beta 1 and doubled the amount of cell-associated 125I-TGF-beta 1. Consistent with this protective effect, heparin- and fucoidan-treated SMC demonstrated elevated levels of active, but not latent, TGF-beta activity.

Heparin-inhibitable lectin activity of the filamentous hemagglutinin adhesin of Bordetella pertussis

Bordetella pertussis, the etiologic agent of whooping cough, produces an outer membrane-associated filamentous hemagglutinin (FHA) which is the major adhesin of this organism. FHA exhibits a lectin-like activity for heparin and dextran sulfate. By using in vitro adherence assays to cultured epithelial cells, the attachment of B. pertussis was reduced in the presence of sulfated polysaccharides such as heparin and dextran sulfate but not in the presence of dextran, indicating the crucial role of polysaccharide sulfation. In addition, inhibition of cellular sulfation by chlorate treatment of the cells resulted in a reduction of B. pertussis adherence, suggesting that epithelial cell surface-exposed sulfated glycoconjugates may serve as receptors for the microorganism. B. pertussis mutant strains deficient in FHA production expressed residual adherence that was no longer inhibited by sulfated polysaccharides. In addition, purified FHA displayed heparin-inhibitable binding to epithelial cells. Mapping experiments of the heparin-binding site of FHA indicated that this site is different from the RGD site and the recently proposed carbohydrate-binding site involved in the interaction of FHA with lactosylceramide. This result demonstrates that FHA contains at least three different binding sites, a feature unusual for bacterial adhesions but similar to features of eukaryotic adhesins and extracellular matrix proteins.

The influence of low molecular weight heparin on neointimal proliferation in cultured human saphenous vein

OBJECTIVES

To investigate the effect of low molecular weight heparin (LMWH) on neointimal proliferation in cultured human saphenous vein, a model of human vein graft intimal hyperplasia.

DESIGN

Dose ranging LMWH concentration study.

SETTING

Culture Laboratory, Department of Surgery.

MATERIALS

Fifteen segments of human long saphenous vein were incubated at 37 degrees C for 14 days in culture medium with 30% foetal calf serum. LMWH was added to one of the paired segments at 1, 10 and 100 micrograms/ml (five veins each dose). 5-bromo-2-deoxyuridine (Brd-U) was used to label proliferating cells.

CHIEF OUTCOME MEASURES

Neointimal thickness (micron and proliferation index (% labelled neointimal cells).

MAIN RESULTS

Neointimal thickness and proliferation index were both significantly reduced by LMWH at 100 micrograms/ml [control vs. LMWH, reduction in thickness 21 microns vs. 7 microns (median difference 12 microns, 95% conf. int. 6-18), reduction in proliferation index 33% to 6% (median difference 19%, 95% C.I. 4-32)].

CONCLUSIONS

High dose LMWH reduces neointimal proliferation in cultured human saphenous vein. The practical clinical application of these results may require the use of non anticoagulant heparin-like molecules and/or local drug delivery systems.

Tamoxifen decreases the rate of proliferation of rat vascular smooth-muscle cells in culture by inducing production of transforming growth factor beta

Tamoxifen selectively and reversibly decreased the rate of proliferation of adult rat aortic vascular smooth-muscle cells (VSMCs). Half-maximal inhibition of proliferation occurred at 2-5 microM tamoxifen for VSMCs and at > 50 microM for adventitial fibroblasts. The cell cycle time for all the VSMCs in the population was increased from 35 +/- 2 h to 54 +/- 4 h in the presence of 33 microM tamoxifen. Tamoxifen did not affect the time of entry into DNA synthesis, but delayed arrival at mitosis by > 24 h. It therefore extended the duration of the G2-to-M phase of the cell cycle. However, the rate of proliferation of VSMCs was not decreased by tamoxifen (at concentrations up to 50 microM) in the presence of neutralizing antibody to transforming growth factor beta (TGF-beta). The level of mRNA for TGF-beta 1 in VSMCs was strongly induced by 10 microM tamoxifen, and TGF-beta activity in conditioned medium from tamoxifen-treated cells was more than 50-fold higher than from control cells. Tamoxifen therefore extended the G2-to-M phase of the cell cycle in VSMCs by increasing TGF-beta activity in the culture.

Evidence for an age-related dysfunction in the antiproliferative response to transforming growth factor-beta in vascular smooth muscle cells

Previous studies have indicated that aged animals show an increased intimal hyperplasia after arterial injury. The present studies examined the hypothesis that the increased serum-free proliferation of aged smooth muscle cells (SMC), in vitro, was due to a loss of an antiproliferative signal, such as transforming growth factor-beta 1 (TGF-beta 1). Northern blot analysis of the mRNA derived from old (> 19 mo) or young (3-4 mo) rat aortic SMC indicated that both groups had an equivalent level of the 2.5 kB TGF-beta 1 message. Metabolic labeling with 35S-methionine and immunoprecipitation for TGF-beta 1 confirmed the de novo synthesis of TGF-beta 1 in rat SMC. Old and young SMC supernatants showed equal levels of active or latent (acid-activated) TGF-beta activity. Despite the similarities in the production of TGF-beta 1, old SMC were refractory to inhibition by TGF-beta 1, whereas young SMC were markedly inhibited (80%) by low levels of TGF-beta 1 (IC50 < 5 pg/ml). Binding studies at 4 degrees C indicated that old SMC exhibited reduced binding capacity for 125I-TGF-beta 1. Cross-linking studies confirmed that old SMC showed reduced binding of 125I-TGF-beta 1 to membrane sites corresponding to the high molecular weight type III receptor, as well as the 85-kDa type II and 65-kDa type I receptor. However, at 37 degrees C, old SMC degraded 125I-TGF-beta 1 more rapidly than young SMC. Combined, this data suggests that SMC derived from older animals are capable of normal production of TGF-beta 1 but fail to respond to the autocrine growth inhibitory effects of this agent, thereby leading to enhanced proliferation.

Transforming growth factor-beta 1 is a heparin-binding protein: identification of putative heparin-binding regions and isolation of heparins with varying affinity for TGF-beta 1

Previous studies indicated that a major factor in heparin's ability to suppress the proliferation of vascular smooth muscle cells is an interaction with transforming growth factor-beta 1 (TGF-beta 1). Heparin appeared to bind directly to TGF-beta 1 and to prevent the association of TGF-beta 1 with alpha 2-macroglobulin (alpha 2-M). The present studies indicate that 20-70% of iodinated TGF-beta 1 binds to heparin-Sepharose and the retained fraction is eluted with approximately 0.37 M NaCl. Native, unlabelled platelet TGF-beta 1, however, is completely retained by heparin-Sepharose and eluted with 0.9-1.2 M NaCl. Using synthetic peptides, the regions of TGF-beta 1 that might be involved in the binding of heparin and other polyanions were examined. Sequence analysis of TGF-beta 1 indicated three regions with a high concentration of basic residues. Two of these regions had the basic residues arranged in a pattern homologous to reported consensus heparin-binding regions of other proteins. The third constituted a structurally novel pattern of basic residues. Synthetic peptides homologous to these three regions, but not to other regions of TGF-beta 1, were found to bind to heparin-Sepharose and were eluted with 0.15 M-0.30 M NaCl. Only two of these regions were capable of blocking the binding of heparin to 125I-TGF-beta. Immobilization of these peptides, followed by affinity purification of heparin, indicated that one peptide was capable of isolating subspecies of heparin with high and low affinity for authentic TGF-beta 1. The ability of TGF-beta 1 to bind to heparin or related proteoglycans under physiological conditions may be useful in understanding the biology of this pluripotent growth and metabolic signal. Conversely, a subspecies of heparin molecules with high affinity for TGF-beta 1 may be a factor in some of the diverse biological actions of heparin.