| Summary: | 碩士 === 國立陽明大學 === 生物藥學研究所 === 89 === Abstract
Dioscorea spp., a medical herb, has been widely used as a remedy for promotion of health and longevity in China and other Asian countries, but no scientific evidences of their immune-potentiation effects by oral administration have been documented. In our study, immune responses of non-starch polysaccharide components of tubers from Dioscorea spp. by oral administration were examined. In systemic immunity, the cytotoxic activity of natural killers, and the proliferative activity of ConA-induced splenocytes, the proliferative activity of GM-CSF-stimulated bone marrow cells on Dioscorea polysaccharides diet were significantly enhanced.
In mucosal immunity, we used two different antigens： ovalbumin and Pneumovax 23 vaccine to induce humoral immune responses in mice by gastric intubation. Additionally, Dioscorea polysaccharides were supplemented in daily drink for mice as an immunomodulator. For an immunomodulator, a feed of Dioscorea polysaccharides not only abrogated the induction of oral tolerance stimulated by ovalumin feeding in mice but also induced the ovalbumin and Pneumovax-specific serum IgG and mucosal IgA antibody responses.
We attempted to clarify the mechanism of the mucosal immunomodulation of Dioscorea polysaccharides on cytokine responses. Cytokine production by intestinal epithilium lymphocytes, lamina propria and Peyer’s patch of mice orally administrated with Dioscorea polysaccharides was examined. Weak Th1 cytokine IFN-gamma, strong Th2 cytokine IL-4, IL-6 and TGF mRNA expressions were induced. Innate anti-microbial peptide cryptdin (defensin family) mRNA production by intestinal epithilium lymphocytes was also induced. Taken together, our study demonstrated that Dioscorea polysaccharides have differential effects on the expression of various cytokines, which likely contribute to its immunomodulatory activity.
Dioscorea steroid extract is used in commercial steroid synthesis and consumed by people. In our study, methanol extracts of Dioscorea had no obvious effects in systemic immune responses. But when we investigated the effect of methanol extracts of Dioscorea on the progenitor cells, we found that methanol extract of Dioscorea added to neuron progenitor cells and bone marrow cell cultures induced stem cell proliferation and morphological changes.
Bone loss in postmenopausal osteoporosis is mainly due to decreased bone formation or increased bone resorption. Bone formation is mediated by osteoblasts and alkaline phosphatase is a biological marker of osteoblast activity. We proved that methanol extract of Dioscorea stimulation of bone cell proliferation and differentiation, possibly to promote the recruitment and maturation of primitive osteogenic precursors present of bone and marrow.
Stem cells may arise late in development, to act principally in tissue renewal, thus ensuring an organism''''''''s long-term survival. Tissue-specific adult stem cells have the potential to contribute to replenishment of multiple adult tissues. Methanol extracts of Dioscorea may improve cell regeneration to prevent or cure several age-related diseases such as neuron degeneration diseases and osteoporosis.
In this study, we demonstrated that polysaccharides of Dioscorea spp. did have their effects on immunomodulation in both systemic and mucoal immunity. And methanol crude extract of Dioscorea spp. contains bioacitive compounds capable of stimulating the proliferation and differentiation of progenitor cells in brain and bone marrow, in related with their cell regeneration function.
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