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The present study investigated the effects of a homogeneous Dendrobium huoshanense polysaccharide (GXG) on mucosal barrier function and microbiota composition in different intestinal regions of mice. Results exhibited, besides changing the intestinal physiological status, orally administrated GXG could improve the intestinal physical barrier function by modulating mucosal structures and up-regulating the expression of tight junction proteins, reinforce the intestinal biochemical barrier function by elevating the expression and secretion of mucin-2, β-defensins and sIgA, and regulate the intestinal immunological barrier function by stimulating the production of cytokines and the functional development of immune cells. Simultaneously, GXG could differentially impact the composition and metabolism of microbiota along intestinal tract. In addition, the immune response in spleen and peripheral blood were effectively regulated by GXG. These results indicated that GXG might be used as functional agent to improve host health., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

With fluorescent end-labeling method, a homogenous Dendrobium huoshanense polysaccharide (GXG) that was orally administrated to mice was found to be degraded into a stable fragment (dGXG) in the stomach, where dGXG was propelled into the small intestine and absorbed into the systemic circulation. The residual GXG in the stomach could pass through the gastrointestinal tract and was excreted into faeces with a very slow fermentation in the large intestine. The simulated digestion of GXG indicated that the acidic pH condition in the gastric fluid was responsible for GXG degradation, which was supported by the oral digestion of dGXG. Chemical analysis not only showed a change in the molar ratio of monosaccharide compositions and glycosidic linkage types, but also found the loss of the sugar residue (1→4)-linked Galp after the acid treatment of GXG, suggesting that the cleavage of glycosidic linkage, especially (1→4)-linked Galp linkage, resulted in GXG degradation in the gastrointestinal tract., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The present work aimed at investigating the pattern recognition receptor (PRR) and immunostimulatory mechanism of a purified Dendrobium huoshanense polysaccharide (DHP). We found that DHP could bind to the surface of macrophages and stimulate macrophages to secrete NO, TNF-α and IL-1β. To unravel the mechanism for the binding of DHP to macrophages, flow cytometry, confocal laser-scanning microscopy, affinity electrophoresis, SDS-PAGE and western blotting were employed to verify the type of PRR responsible for the recognition of DHP by RAW264.7 macrophages and peritoneal macrophages of C3H/HeN and C3H/HeJ macrophages. Results showed that toll-like receptor 4 (TLR4) was an essential receptor for macrophages to directly bind DHP. Further, the phosphorylation of ERK, JNK, Akt and p38 were observed to be time-dependently promoted by DHP, as well as the nuclear translocation of NF-κB p65. These results suggest that DHP activates macrophages via its direct binding to TLR4 to trigger TLR4 signaling pathways., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

A homogeneous polysaccharide fraction (DOP-W3-b) with a high intestinal immunomodulating activity was obtained from the stems of Dendrobium officinale through a bioactivity-guided sequential isolation procedure based on the screening of Peyer's patch-mediated immunomodulating activity. Oral administration experiments of mice showed that DOP-W3-b could effectively regulate intestinal mucosal immune activity by changing intestinal mucosal structures, promoting the secretions of cytokines from Peyer's patches (PPs) and mesenteric lymph nodes (MLNs), and increasing the production of secretory immunoglobulin A (sIgA) in the lamina propria. Structure analysis indicated that DOP-W3-b was composed of mannose and glucose in a molar ratio of 4.5 with a relatively low molecular weight of 1.543 × 10(4) Da, and its repeat unit contained a backbone consisting of β-(1→4)-d-Manp, β-(1→4)-d-Glcp and β-(1→3,6)-d-Manp residues, a branch consisting of β-(1→4)-d-Manp, β-(1→4)-d-Glcp and terminal β-d-Glcp, and O-acetyl groups attached to O-2 of β-(1→4)-d-Manp. These results suggested that DOP-W3-b was a new polysaccharide with an essential potential for modulating body's immune functions.