【作者】 李艳春；

【导师】 景永奎；

【作者基本信息】 沈阳药科大学 ， 药理学， 2010， 博士

【摘要】 葫芦素E是由葫芦科植物瓜蒂中提取出来的有效单体,最近的研究发现葫芦素E对多种肿瘤细胞均有生长抑制作用。我们应用人白血病细胞和肝癌细跑对葫芦素E的抗肿瘤作用及作用机制进行了研究。葫芦素E低剂量抑制白血病HL-60细胞、K562细胞及肝癌Bel7402、HepG2细胞生长。细胞周期进程研究显示葫芦素的增殖抑制作用与细胞周期阻滞于G2/M期有关。蛋白分析显示葫芦素E下调CDK1蛋白表达,上调p21蛋白表达,但是不影响cyclin A, cyclin B1和Cdc25C蛋白表达。葫芦素E在高剂量通过活化caspase-3, caspase-8,和caspase-9而诱导HL-60细胞凋亡。葫芦素E不能增加活性氧的含量,抗氧化剂N-乙酰半胱氨酸和过氧化氢酶也不能抑制葫芦素E所诱导的HL-60细胞凋亡。葫芦素E能减少抗凋亡蛋白XIAP, survivin和Mcl-1蛋白的表达,增加促进凋亡蛋白Bax蛋白表达。葫芦素E诱导eIF2α(真核翻译起动因子2)磷酸化。我们的数据提示葫芦素E引起HL-60细胞增殖抑制和细胞凋亡诱导可能是由于诱导eIF2α的磷酸化,eIF2a的磷酸化将抑制Cdk1、c-FLIP、Mcl-1、survivin和XIAP蛋白的合成,然后诱发G2/M周期阻滞和线粒体途径的细胞凋亡激活。葫芦素E作用于K562细胞时间延长将导致细胞衰老。葫芦素E抑制小鼠移植性肝癌H22的体内生长。高浓度葫芦素E在不同的细胞显示不同的作用：在HL-60细胞中具有凋亡诱导作用,在K562细胞中具有诱导衰老作用,其不同的作用机制值得进一步研究。更多还原

【Abstract】 Cucurbitacin E is a natural product isolated from Cucurbitaceae which has been reported to have antitumor effects. We determined the antiproliferative effects and explored its mechanisms of action in leukemia and hepatoma cells. Cucurbitacin E at low concentrations inhibited growth of leukemia cells, HL-60 and K562, and hepatoma cells, Bel7402 and HepG2. Cell cycle analyses revealed that cucurbitacin E induced G2/M cell cycle arrest in all of the tested cell lines. Western blot analyses indicated that cucurbitacin E decreased the levels of Cdk1 and increased the levels of p21waf1 but did influence the levels of cyclin A, cyclin B1 and Cdc25C protein. These data suggest the G2/M cell cycle arrest may be caused by the decreased levels of Cdk1 and/or increased levels of p21waf1. Cucurbitacin E at high concentrations induced apoptosis of HL-60 cells with the activation of caspase-3, caspase-8, and caspase-9 as determined by Western blot analysis. Cucurbitacin E did not increase the levels of reactive oxygen species and that the antioxidants did not block cucurbitacin E-induced apoptosis. Cucurbitacin E decreased the levels of the antiapoptotic proteins XIAP, survivin and Mcl-1, but increased the level of the proapoptotic protein Bax. The levels of phosphorylated eukaryotic translation initiation factor 2 subunit (eIF2α) were induced in cells undergoing both apoptosis and cell cycle arrest. Since phosphorylated eIF2αis an inhibitor of protein translation initiation, our data suggest that cucurbitacin E induces cell growth arrest and apoptosis probably through induction of eIF2αphosphorylation which leads to inhibition of Cdk1, p21, Mcl-1, survivin and/or XIAP protein synthesis and that cucurbitacin E induces apoptosis mainly through a mitochondrial-mediated pathway in HL-60 cells. Senescence but not apoptosis was detected in K562 cells after treatment with cucurbitacin E at high concentrations. It seems that cucurbitacin E induces cell death in different cell lines through different pathways that need to be further investigated.更多还原