Purification, structural analysis and mechanism of murine macrophage cell activation by sulfated polysaccharides from Cystoseira indica

Sulfated polysaccharides were isolated and purified from the water extract of Cystoseira indica using DEAE Sepharose Fast Flow column to evaluate their structure and macrophage stimulating capacity. Crude and fractionated polysaccharides, CIF₁ and CIF₂, were mostly composed of neutral sugars (73.1%-78.6%) with relatively lower amounts of acidic sugars (1.3%-9.0%) and sulfate esters (6.9%-9.7%). The polymer chains of polysaccharides were mainly built of different levels of glucose (2.1%-30.8%), fucose (17.2%-24.4%), mannose (17.8%-20.6%) and galactose (16.7%-17.3%). The weight average molecular weight (M_w) of polysaccharides varied between 573.1 × 10³ g/mol to 1146.6 × 10³ g/mol. The CIF₂ polysaccharide, as the most immunostimulating polysaccharide, remarkably induced the release of nitric oxide and inflammatory cytokines including TNF-α, IL-1β, IL-6 and IL-10 from RAW264.7 murine macrophage cells through NF-κB and PAMKs transduction signaling pathways via cell surface TLR4. The interconnections of sugars in CIF₂ polysaccharide were complex with (1→3)-fucopyranose, (1→2,3,4)-glucopyranose, (→1)-galactopyranose, (→1)-xylopyranose, (1→2)-rhamnopyranose and (1→2,3)-mannopyranose units being the most predominant residues.