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Investigations on the anti-leukemia and immunomodulatory effects of Agaricus blazei extracts. / 姬松茸提取物在抗白血病和免疫調節作用上的研究 / CUHK electronic theses & dissertations collection / Ji song rong ti qu wu zai kang bai xue bing he mian yi tiao jie zuo yong shang de yan jiuJanuary 2008 (has links)
No direct stimulation of human peripheral blood mononuclear cells proliferation could be detected with incubation of various AB extracts including JAB80E70 in vitro. However, ex vivo assay performed using BALB/c mice orally fed with either water (control) or JAB80E70 for 28 days indicated for the first time that extract-treated groups significantly lowered the ex vivo mitogen-stimulated lymphocyte proliferation. / Our study started with the preparations of different AB extracts using various solvent systems with or without heating. Among all AB extracts tested, the extract JAB80E70 (extracted with 70% v/v ethanol at 80°C) showed the strongest selective suppression on the growth of human leukemia NB-4 and K-562 cells. The anti-leukemia effect of JAB80E70 was also confirmed in vivo using xenografted NB-4 bearing athymic nude mice model. / Phytochemical studies suggested that the selective anti-leukemia activity of JAB80E70-W-B-1 was retained in a relatively polar sub-fraction. One compound was isolated and identified as adenosine from JAB80E70-W-B-1. To the best of our knowledge, this is the first report of the presence of adenosine in AB, even though it exhibited no anti-leukemia activity in vitro. / The mushroom Agaricus blazei (AB) is traditionally used as a remedy against various cancers, infections and immune-related diseases. In the present study, the underlying mechanisms of the anti-tumor and immunomodulatory effects of AB extracts on human leukemia cells were systematically investigated. / With bioassay-guided fractionation, a sub-fraction (JAB80E70-W-B-1) with almost 5-fold improved selective cytotoxicity towards NB-4 cells was obtained. Both JAB80E70 and JAB80E70-W-B-1 could induce apoptosis characteristic DNA fragmentation and nucleosomes enrichment in NB-4 cells. An increase in the pro-apoptotic and a decrease in the anti-apoptotic Bcl-2 family proteins expression were observed in NB-4 cells treated with JAB80E70-W-B-1. JAB80E70-W-B-1 was also found to enhance activities of caspases 3, 8 and 9 in NB-4 cells. However, the activation of caspases 3 and 9 was not affected by the inhibition of caspase 8. Furthermore, JAB80E70-W-B-1 induced apoptosis in NB-4 cells was accompanied by a significant reduction in mitochondria membrane potential and telomerase activity. These results demonstrated that JAB80E70-W-B-1 induced apoptosis in NB-4 cells was dependent on caspase activity, and involved multiple molecular pathways. / Jiang, Jingjing. / Adviser: Lau Bik San Clara. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3454. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 224-250). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
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