Structural characterization of the neutral polysaccharides (FALP-A1) from bran-fried Atractylodes lancea and its role in alleviating immune suppression and intestinal damage

ABSTRACT Polysaccharides, such as bran-fried Atractylodes lancea rhizome polysaccharide (FALP), enhance intestinal immunity; however, the structures of the immunoregulation homogenous polysaccharides of bran-fried A. lancea rhizome (FAL) and their specific mechanisms in enhancing intestinal mucosal immunity are unclear. Here, the immunoregulation homogenous polysaccharides of FAL were structurally characterized and their potential mechanisms in the polarization of macrophages and enhancement of intestinal mucosal immunity were elucidated. The homogeneous polysaccharide FALP-A1 composed of fructose and glucose in a 97.58:2.42 molar ratio. Structural analysis confirmed that FALP-A1 was mainly composed of →1)-β- d -Fru f -(2→ and a small amount of β- d -Fru f -(2→, α- d -Glc p -(1→ interconnected, indicating it to be an inulin fructan. FALP-A1 enhanced the phagocytic activity of macrophages in vitro and in vivo and alleviated cyclophosphamide (Cy)-induced immune suppression and intestinal mucosal damage. FALP-A1 repaired the damaged intestinal mechanical barriers by increasing zonula occludens-1 and Claudin-1 expression. It enhanced intestinal immunity by promoting the expression of IgA-secreting cells and increasing secretory IgA levels. Its mechanism may be attributed to activation of the TLR4/MyD88/NF-κB signaling pathway to promote macrophage polarization toward the M1 type. To our knowledge, this study is the first to isolate and purify FALP-A1 from FAL. The mechanisms of FALP-A1 in alleviating Cy-induced immune suppression and enhancing intestinal mucosal immunity by regulating macrophage phenotype were also studied. Our findings highlight the potential of FALP-A1 as a food-based immunomodulatory agent in alleviating immunosuppression and intestinal mucosal damage.