- 學位論文
微量元素硒誘導人類血癌細胞凋亡機制之探討
Study the Mechanisms of Selenium on Growth Inhibition and Apoptosis Induction of Human Leukemia Cells
摘要
中文摘要 微量元素硒 (Selenium)，為身體中抗氧化酵素重要之輔因子，可預防惡性腫瘤的發生及具有抗氧化的效果。有文獻指出，硒能夠促使前列腺癌細胞 (Prostate cancer)、肺癌細胞 (Lung cancer) 及血癌細胞HL-60 (Leukemia cancer) 之細胞凋亡，且已證實可做為預防性化學藥物，但對於其毒殺細胞的機制尚不清楚。因此，本研究探討硒在血癌細胞株U937、Jurkat和Raji cells 之毒殺作用，更進一步的探討硒對U937的毒殺作用機制。首先我們利用Trypan blue exclusion來分析硒對細胞毒殺的能力，從研究結果得知，隨著硒濃度的增加，細胞死亡情形越顯著。以DNA fragmentation及AnnexinⅤ staining做進一步分析，其結果顯示，在高濃度硒的作用下，血癌細胞株U937呈現細胞凋亡的情形，並且與劑量呈正相關現象。而以Western blotting分析抗凋亡蛋白Bcl-2、Bcl-XL與凋亡蛋白酵素Caspase-3、PARP〔Poly (ADP-ribose) polymerase〕之表現得知，硒對Bcl-2和Bcl-XL蛋白的表現量沒有影響，但會誘導Bcl-XL蛋白之isoform Bcl-Xs (pro-apoptotic protein) 蛋白的表現量增加，且在高濃度硒的作用下NF kappa B (NF-κB) 蛋白的表現量降低。更進一步，以 RT-PCR偵測TNF-α及Fas ligand (FasL) 之mRNA的表現，結果得知硒元素對於TNF-α表現是不顯著的，反而對FasL作用明顯增加。綜合研究結果發現，硒對於血癌細胞株U937所誘導之細胞凋亡，是藉由活化Fas ligand及抑制下游蛋白NF-κB的表現量，並且活化下游凋亡蛋白酵素Caspase-3及PARP，而導致細胞凋亡。綜合上述研究結果證實，硒能抑制血癌細胞U937增生及誘導細胞凋亡的能力。
並列摘要
英文摘要 Selenium (Se), an essential trace element, acts as a cofactor of antioxidant enzymes, such as glutathione peroxidase. It has been shown to have anticancer and antioxidant effects. Previously, we showed Se induced apoptosis of cancer cells of prostate, lung, and leukemia cells. In chemoprevention, Se was effective, however, it is not known whether it is effective on leukemia cell lines of U937, Jurkat, or Raji cells. In the present study, we investigated the effects of sodium selenite (Na2SeO3) on U937 and the underline mechanisms. Our results showed sodium selenite induced cytotoxicities of U937, Jurkat, and Raji cells in a dose-dependent manner as measured by Trypan blue exclusion. Analysis of Annexin Ⅴ staining and DNA fragmentation demonstrated that sodium selenite caused U937 cell death by apoptosis. Western blotting analysis showed that anti-apoptosis protein of Bcl-2 and Bcl-XL were not affected, but pro-apoptotic proteins of Bcl-Xs, caspase-3 and PARP〔poly (ADP-ribose) polymerase〕 were increased in U937 cells by treatment of sodium selenite. The NF kappa B (NF-κB) protein expression was degraded in U937 after high dose sodium selenite treatment. RT-PCR analysis was used to detect TNF-α and Fas ligand (FasL) mRNA expression, and results showed TNF-α expression was not apparently increased but FasL mRNA expression was increased by high dose sodium selenite treatment. Theses results suggested that sodium selenite induced U937 cell’s death by apoptosis via activation of Fas ligand, caspase-3, and PARP and inhibition of NF-κB expression.
參考文獻
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