ABSTRACT
Marine organisms such as brown and red seaweeds are rich sources222 of sulfated polysaccharides fucans or fucoidans and galactans, respectively. These polysaccharides are structural components of the extra-cellular matrix. Their structures vary among species of seaweeds. Usually, fucoidans are composed essentially of sulfated α-L-fucose. They may also contain galactose, mannose, xylose, uronic acids and acetyl groups. The biological activities of these polysaccharides depend on the degree of sulfation, molecular structure, types of constituent monosaccharides and degree of branching. Sulfated galactans of red algae contain sulfated β-galactoses and a regular repetitive structure. However, structural variations in sulfated galactans occur among different species of red algae. Anti-inflammatory, anticoagulant, immune-modulating, antioxidant, antiproliferative, antitumor and antiangiogenic actions are described for these polymers. The blood vessel formation can occur as vasculogenesis and angiogenesis, in which different cellular mechanisms such as migration and differentiation are involved. In this chapter, the effect of anionic polysaccharides extracted from brown and red algae, fucans and galactans, on angiogenesis are discussed. Angiogenesis is the formation of new capillary vessels from pre-existing vasculature, being regulated by complex interactions between stimulatory and inhibitory factors, including growth factors, cytokines, proteolytic enzymes, integrins and extra-cellular matrix components. The lack of control in angiogenesis has been implicated in the growth of tumors and metastasis. The action of polysaccharides from brown and red seaweed may directly interfere with the binding of growth factors to their specific cognate receptors, such as vascular endothelial growth factor (VEGF). These polysacchari des could modulate the activity of heparin-binding vascular such as basic fibroblast growth factors (bFGF) interfering with heparan sulfate, a proteoglycan, during microvessel formation. We used chick-embryo chorioallantoic membrane (CAM) assay for the in vivo study of angiogenesis using these polysaccharides.
