Studies on the Immunomodulatory Activities of Mushrooms from Boletaceae Family, with Special Emphasis on Rubinoboletus ballouii.

摘要

Edible Mushrooms come from many fungal species and are widely distributed all around the world. Some of them were not only used as food but also as a source of physiologically beneficial bioactive components. Rubinoboletus ballouii (RB) is an edible mushroom belonging to Boletaceae family, wildly grown in Yunnan province, China. Up till now, very little is known about the biological activities of this species and Boletaceae family. The present study aimed at investigating the immunomodulatory activities of Rubinoboletus ballouii and comparing the immunological effects of seven common edible mushroom species from Boletaceae family.;Firstly, the immunomodulatory activities of the ethanolic extract of RB were evaluated using human peripheral blood mononuclear cells (PBMC). Our results demonstrated that the ethanolic extract of RB showed immunosuppressive activities in phytohemagglutinin (PHA)-stimulated PBMC by inhibiting the proliferative responses and the productions of inflammatory cytokines. Two single compounds were isolated from the ethanolic extract of RB using bioactivity-guided fractionation. They showed significant inhibition of cell proliferation and cytokines productions of TNF-alpha, IL-10, IFN-gamma and IL-1beta in PHA-stimulated PBMC, and the suppression levels were comparable with dexamethasone. Furthermore, their structures were elucidated as pistillarin and 1-ribofuranosyl-s-triazin-2(1H)-one. This is the first time to show the isolation of pistillarin and 1-ribofuranosyl-s-triazin-2(1H)-one from Boletaceae family, and their immunosuppressive effects in human immune cells.;Secondly, the water-soluble polysaccharides of RB were evaluated for the immunomodulatory effects in human PBMC and monocytes-derived dendritic cells (moDC). Our results demonstrated that the crude polysaccharides of RB (RBP), characterized as polysaccharide-protein complex, showed significant stimulatory effects on the cytokines production of TNF-alpha and IL-1beta in human PBMC. Two purified polysaccharide fractions, namely RBP-A and RBP-B, were isolated from RBP using bioactivity-guided fractionation by gel chromatography. They could induce the maturation of human moDC, induce the production of IL-12p40, IL-10 and TNF-alpha, as well as down-regulate the endocytotic activities. Further studies demonstrated that the more potent RBP-A mainly induced the IkappaB kinase (IKK) activity by phosphorylation of IkappaBalpha and mitogen-activated protein (MAP) kinases activities by phosphorylation of p38 MAPK and c-Jun N-terminal kinases (JNK) in human moDC through toll-like receptor (TLR)-4.;Thirdly, RBP and RBP-A showed immunostimulatory effects in cyclophosphamide (Cy)-induced immunosuppressive mouse model. They remarkably recovered the lose of CD34brightCD45dim cells from bone marrow of Cytreated mice. They also showed direct mitogenic and co-mitogenic activities on splenocytes and significantly up-regulated IL-2 production in in sera and splenocytes culture medium in Cy-treated mice. Based on the above results, RB polysaccharides exhibited potential in recovering the myelosuppression and immunosuppression caused by Cy.;On the other hand, the crude polysaccharides of the selected seven mushrooms species from Boletaceae family were compared for their chemical compositions and immunological activaties. The present results demonstrated that all the crude polysaccharides were characterized as polysaccharide-protein complex. They contained a variety of essential amino acids for human health. In addition, among these tested mushrooms, the crude polysaccharides from Boletus edulis exhibited the most potent stimulatory effects on the productions of TNF-alpha and IL-1beta in human PBMC.;In conclusion, RB showed bi-directional modulating activities in the immune system. RB and other species from Boletaceae family deserved to be further studied and developed as health supplements.