Sulfated Polysaccharides of <i>Potamogeton lucens</i> as a Promising Immunostimulatory Agent in Activation of <scp>RAW264.7</scp> and <scp>NK</scp> Cells

Sulfated polysaccharides are naturally occurring biomacromolecules with complex structures and promising therapeutic effects, the mechanism of which remains to be fully understood. This study isolated a novel sulfated polysaccharide from <i>Potamogeton lucens</i>, followed by fractionation by a DAEA Sepharose FF column to assess its immunostimulatory effects on NK-92 and RAW264.7 cells. The primary components within the crude polysaccharides and fractions (PLF1, PLF2 and PLF3) were predominantly neutral sugars, with comparatively lower proportions of sulfate and uronic acids. The isolated polysaccharides exhibited a range of weight average molecular weights (<i>M</i> _w) from 488.7 to 918.9 × 10³ g/mol. Polysaccharide composition included glucose, galactose, arabinose, rhamnose, mannose, and xylose units linked through various glycosidic linkages, including (1 → 4)-Gal<i>p</i>, (1 → 6)-Gal<i>p</i>, (1 → 3)-Gal<i>p</i>, (1 → 3)-Ara<i>p</i>, (1 → 2,4)-Rha<i>p</i>, (1 → 2)-Glc<i>p</i> and (1 → 4)-Glc<i>p</i> residues. The PLF2 polysaccharide showed remarkable efficacy by activating RAW264.7 macrophage cells to synthesize NO, TNF-α, IL-1β and IL-6, while also activating NK-92 cells to synthesize TNF-α, INF-γ, granzyme-B, perforin, NKG2D, and FasL via the NF-κB and MAPKs signaling pathways. Collective findings indicated that polysaccharides derived from <i>P. lucens</i> have the potential to serve as potent immunostimulatory compounds in functional foods, capable of eliciting responses in both RAW264.7 and NK cells.