A crude polysaccharide fraction (termed cLEP) and two derived fractions (termed LEP1 and LEP2) from Lentinus edodes mycelia were purified and characterized. LEP1/-2 were classified as α-type heteropolysaccharides with 1 → 2, 1 → 3, 1 → 4, 1 → 6 linkages. Their monosaccharide components were respectively Gal, Glc, Man, Ara, Fuc, and Rha (molar ratio 10.17:9.75:9.01:1.61:1.26:1), and Glc, Man, Fuc, Rha, and Gal (molar ratio 5.18:4.69:2.85:1.43:1). In vitro culture experiments with macrophage RAW264.7 cells showed no cytotoxic effects of the polysaccharides. Phagocytosis (neutral red uptake) was significantly enhanced by LEP1/-2. Levels of NO, TNF-α and IL-6 were higher in LEP1/-2-treated groups than in cLEP-treated group. qRT-PCR analysis showed that LEP1/-2 had greater enhancing effect on mRNA transcription of iNOS, TNF-α, and IL-6 genes. Western blotting analysis revealed that LEP1/-2 strongly promoted phosphorylation of kinases ERK and JNK, and suggested that they exert immunoenhancing effects via MAPK signaling pathway.
Wang, T., et al. (2019). “Mycelial polysaccharides of Lentinus edodes (shiitake mushroom) in submerged culture exert immunoenhancing effect on macrophage cells via MAPK pathway.” International Journal of Biological Macromolecules 130: 745-754.