Effects of novel sulfated-rhamnoglucuronan isolated from Korean seaweed Ulva pertusa on IgA-mediated intestinal-immune system activation in naïve C3H/HeN mice

A previous study identified a novel sulfated-rhamnoglucuronan structure in Ulva pertusa polysaccharide (UPP). The present study evaluates the intestinal immunostimulatory effects of UPP in naïve C3H/HeN mice. Oral administration of UPP significantly enhanced the secretion of IgA and associated cytokines, including interleukin (IL)-6, IL-10, and transforming growth factor (TGF)-β, from Peyer's patch (PP) cells in vivo. Additionally, the supernatant from PP cell cultures stimulated the proliferation of bone marrow cells. Histological analysis revealed strong stimulation of PP by UPP, as evidenced by hematoxylin and eosin staining. Serum analysis indicated that UPP triggered TGF-β secretion, which subsequently promoted IgA production. Furthermore, UPP administration enhanced IgA-related cytokine production in ileum tissues and was linked to the activation of the mitogen-activated protein kinase and nuclear factor kappa B signaling pathways. The secretion of A proliferation-inducing ligand (tumor necrosis factor superfamily member 13; TNFSF13) and B-cell activating factor (TNFSF13B) was also upregulated in the ileum. Additionally, fecal analysis demonstrated an increase in short-chain fatty acids, including acetic, propionic, and butyric acids, in a dose- and administration period-dependent manner. These findings suggest that UPP administration contributes IgA-related immune responses and intestinal immune system modulation via PP cells.