| Summary: | 碩士 === 國立臺灣大學 === 微生物與生化學研究所 === 94 === The purpose of this study is to evaluate whether the yam may possess an immunomodulation effect. First, the effect of ethyl acetate extract of Taiwanese Yam ( Dioscorea alata L. cv. Tainung No.2 ) ( DAEA ) on in vitro cytokines secretions by RAW 264.7 cell and primary macrophages and splenocytes from BALB/c mice was investigated. The results showed that 50 g/mL and 40 g/mL DAEA significantly inhibited IL-6 secretion in LPS-stimulated RAW264.7 and primary macrophages. ConA-stimulated IFN-, IL-4, IL-10 secretions under DAEA treatment also significantly reduced. Therefore, yam may have an anti-inflammatory and immunoregulatory effect.
Based on the results from cell culture experiments, we further used an in vivo OVA-sensitized mouse model to evaluate the effect of yam on allergic asthma. Female BALB/c mice were first sensitized with ovalbumin (OVA) in Al(OH)3 adjuvant intraperitoneally. After three times of sensitization, mice were divided into four groups by OVA-IgE titers. Four groups of mice were either fed an AIN-76 diet ( control ), AIN-76 diet containing 0.9% cooked yam ( DA-cook ), tube-feeding of 100 ( DAEA-1X ) or 200 g ( DAEA-2X ) EA extracts of yam per day. During the feeding period, mice were challenged with OVA aerosol twice to induce bronchoconstriction. The results showed that DA-cook, DAEA-1X and DAEA-2X groups significantly attenuated methacholine-induced airway hyperresponsiveness. After feeding for fifteen days, mice were sacrificed for further analysis. Compared to the control group, the DA-cook, DAEA-1X and DAEA-2X groups inhibited Th2 cytokines such as IL-4, IL-5, IL-10 secretions by splenocytes and suppressed the IgE productions in serum. The count of total cells and the distribution of eosinoiphil and neutrophil in bronchoalveolar fluid (BALF) were decreased in the DA-cook, DAEA-1X and DAEA-2X groups. The Th2 cytokines and inflammatory indicators of BALF such as IL-4, IL-5, IL-6, IL10, IL-13, PGE2 were all lessened by yam-feeding groups. In conclusion, these results suggest yam extract could alleviate allergic asthma through suppression of Th2 cytokines, pro-inflammatory mediators and serum IgE levels. Dioscorea alata L. cv. Tainung No.2 used in this study may be beneficial for patient of allergic asthma and it need to be further studied.
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