Structural characterization of a novel polysaccharide from Panax notoginseng residue and its immunomodulatory activity on bone marrow dendritic cells

This study isolated and characterized a novel polysaccharide (PNPS-0.3) from the residue of Panax notoginseng by gradient elution. PNPS-0.3 mainly consisted of a backbone of →4)- α-D-GalAp-(1 → 4-β-L-Rhap-1 → 4)-β-D-Galp-(1 → residues, with an α-L-Araf-1 → 5)-α-L-Araf-(1 → branch connecting to the backbone at O-3 of →4-β-L-Rhap-1 → and a molecular weight of 76,655 Da. Furthermore, the adjuvant potential of PNPS-0.3 with bone marrow dendritic cells (BMDCs) was investigated. The results suggested that PNPS-0.3 could induce maturation of BMDCs by reshaping the morphology, upregulating the CD40, CD80, CD86 and MHC II membrane phenotypic markers, and by promoting the secretion of TNF-α and IL-12 proinflammatory cytokines. Moreover, PNPS-0.3 can trigger the DC-induced T-cell immune response, as indicated by the higher expressions of CD4, CD8, CD69, and MHC II in T cells with increased secretion of INF-β. Furthermore, PNPS-0.3 can bind to the pattern recognition receptors (PRR) of Toll-like receptor 4 (TLR 4), Toll-like receptor 2 (TLR 2), and mannose receptor (MR) on BMDCs. PNPS-0.3 also upregulated the expressions of Myd88, IKKβ, PP65, T-P65, and NF-κB, suggesting that the TLR4/TLR2-NF-κB signaling pathway was involved in the immunomodulatory mechanism. In conclusion, the immunoadjuvant potential of novel PNPS-0.3 was characterized, which is beneficial for the future utilization and development of P. notoginseng.