Generation of hydrogen peroxide primarily contributes to the induction of Fe(II)-dependent apoptosis in Jurkat cells by (-)-epigallocatechin gallate
Generation of hydrogen peroxide primarily contributes to the induction of Fe(II)-dependent apoptosis in Jurkat cells by (-)-epigallocatechin gallate
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DOI：
10.1093/carcin/bgh168
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发表时间：
2004-09-01
期刊：
影响因子：
4.7
通讯作者：
Wachi, M
中科院分区：
文献类型：
--
作者：
Nakagawa, H;Hasumi, K;Wachi, M
虽然(-)-表没食子儿茶素没食子酸酯（EGCG）已被报道可诱导多种肿瘤细胞凋亡，但其具体机制仍有待探索。本研究利用人t细胞急性淋巴母细胞白血病Jurkat细胞，研究EGCG的抗肿瘤作用机制。我们关注活性氧的参与，因为我们之前发现EGCG导致破骨细胞凋亡，主要是由于促进Fe（III）还原为Fe（II）触发Fenton反应，该反应从过氧化氢[H2O2 + Fe(II) -> (OH)- o -提供羟基自由基。+ OH- + Fe(III)]。EGCG （12.5-50 muM）降低Jurkat细胞活力，并引起细胞caspase-3活性升高。过氧化氢酶和Fe（II）螯合试剂邻菲罗啉抑制了EGCG的作用，表明H2O2和Fe（II）参与了这一机制。出乎意料的是，表儿茶素没食子酸酯（ECG）具有与EGCG相当的铁（III）还原能力，但未能降低Jurkat细胞的活力，而表没食子儿茶素（EGC）具有较低的铁（III）还原能力，却表现出与EGCG相似的细胞毒性作用。这些结果表明，与破骨细胞不同，在儿茶素介导的Jurkat细胞死亡中，铁（III）还原以外的机制起作用。我们发现EGCG导致Jurkat细胞培养、无细胞培养基和磷酸钠缓冲液中H2O2水平升高。产生H2O2能力越强的儿茶素对Jurkat细胞的细胞毒性越强。过氧化氢本身发挥铁（II）依赖的细胞毒性。在肿瘤和正常细胞系中，清除h2o2活性较低的细胞对EGCG更敏感。根据这些发现，我们提出使儿茶素在某些肿瘤细胞中具有细胞毒性的机制是由于其产生H2O2的能力，并且由此导致的H2O2水平的增加触发铁（II）依赖性高毒性羟基自由基的形成，从而诱导凋亡细胞死亡。
Although (-)-epigallocatechin gallate (EGCG) has been reported to induce apoptosis in a variety of tumor cells, detailed mechanisms remain to be explored. In the present study, we investigated the antitumor mechanism of EGCG by using human T-cell acute lymphoblastic leukemia Jurkat cells. We focused on the involvement of reactive oxygen species, as we found previously that EGCG caused apoptotic cell death in osteoclastic cells due mainly to promotion of the reduction of Fe(III) to Fe(II) to trigger Fenton reaction, which affords hydroxyl radical from hydrogen peroxide [H2O2 + Fe(II) --> (OH)-O-. + OH- + Fe(III)]. EGCG (12.5-50 muM) decreased the viability of Jurkat cells and caused concomitant increase in cellular caspase-3 activity. Catalase and the Fe(II)-chelating reagent o-phenanthroline suppressed the EGCG effects, indicating involvements of both H2O2 and Fe(II) in the mechanism. Unexpectedly, epicatechin gallate (ECG), which has Fe(III)-reducing potency comparable with EGCG, failed to decrease the viability of Jurkat cells, while epigallocatechin (EGC), which has low capacity to reduce Fe(III), showed cytotoxic effects similar to EGCG. These results suggest that, unlike in osteoclastic cells, a mechanism other than Fe(III) reduction plays a role in catechin-mediated Jurkat cell death. We found that EGCG causes an elevation of H2O2 levels in Jurkat cell culture, in cell-free culture medium and sodium phosphate buffer. Catechins with a higher ability to produce H2O2 were more cytotoxic to Jurkat cells. Hydrogen peroxide itself exerted Fe(II)-dependent cytotoxicity. Amongst tumor and normal cell lines tested, cells exhibiting lower H2O2-eliminating activity were more sensitive to EGCG. From these findings, we propose the mechanism that make catechins cytotoxic in certain tumor cells is due to their ability to produce H2O2 and that the resulting increase in H2O2 levels triggers Fe(II)-dependent formation of highly toxic hydroxyl radical, which in turn induces apoptotic cell death.