Signal transduction of p53-independent apoptotic pathway induced by hexavalent chromium in U937 cells
Signal transduction of p53-independent apoptotic pathway induced by hexavalent chromium in U937 cells
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DOI：
10.1016/j.taap.2004.02.011
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发表时间：
2004-06-01
影响因子：
3.8
通讯作者：
Kasuya, M
中科院分区：
文献类型：
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作者：
Hayashi, Y;Kondo, T;Kasuya, M
据报道，六价铬化合物（Cr(VI)）可以诱导p53依赖性和p53非依赖性细胞凋亡。虽然关于p53依赖通路的信息相当多，但对p53不依赖通路知之甚少。为了阐明p53不依赖的机制，我们研究了Ca2+-calpain-和线粒体-caspase-依赖通路在Cr（VI）诱导的细胞凋亡中的作用。20mum Cr（VI）作用于p53突变的人淋巴瘤细胞U937细胞24 h后，观察到细胞核形态变化和DNA断裂。在Cr（VI）处理的细胞中，电子顺磁共振（EPR）自旋捕获显示羟基自由基的产生，并通过数字成像监测细胞内钙离子浓度的增加。细胞内Ca2+螯合剂、BAPTA-AM和钙蛋白酶抑制剂抑制Cr（VI）诱导的DNA断裂。低线粒体膜电位（MMP）、高超氧阴离子自由基（O-2）、高caspase-3活性（线粒体-caspase依赖通路指标）的细胞数量在Cr（VI）处理的细胞中显著增加。抗氧化剂n -乙酰- l-半胱氨酸（NAC）减少DNA断裂，抑制Cr（VI）诱导的MMP、O-2（-）形成和caspase-3活化的变化。Cr（VI）处理后，Fas和磷酸化JNK的表达未见增加。细胞周期分析显示，处理24 h后，G2/M期比例有增加的趋势，提示Cr（VI）诱导细胞凋亡与G2阻滞有关。这些结果表明，Ca2+-calpain-和线粒体-caspase-依赖通路通过G2阻滞在Cr（VI）诱导的细胞凋亡中发挥重要作用，而不依赖于JNK和Fas的激活。NAC对细胞凋亡及其所有信号转导的抑制表明，细胞内活性氧（ROS）在Cr（VI）诱导的U937细胞凋亡的两种途径中都起重要作用。(C) 2004爱思唯尔公司版权所有。
It has been reported that the hexavalent chromium compound (Cr(VI)) can induce both p53-dependent and p53-independent apoptosis. While a considerable amount of information is available on the p53-dependent pathway, only little is known About the p53-independent pathway. To elucidate the p53-independent mechanism, the roles of the Ca2+-calpain- and mitochondria-caspase-dependent pathways in apoptosis induced by Cr(VI) were investigated. When human lymphoma U937 cells, p53 mutated cells, were treated with 20 muM Cr(VI) for 24 h, nuclear morphological changes and DNA fragmentation were observed. Production of hydroxyl radicals revealed by electron paramagnetic resonance (EPR)-spin trapping, and increase of intracellular calcium ion concentration monitored by digital imaging were also observed in Cr(VI)-treated cells. An intracellular Ca2+ chelator, BAPTA-AM, and calpain inhibitors suppressed the Cr(VI)-induced DNA fragmentation. The number of cells showing low mitochondrial membrane potential (MMP), high level of superoxide anion radicals (O-2(-)), and high activity of caspase-3, which are indicators of mitochondria-caspase-dependent pathway, increased significantly in Cr(VI)-treated cells. An antioxidant, N-acetyl-L-cysteine (NAC), decreased DNA fragmentation and inhibited the changes in MMP, O-2(-) formation, and activation of caspase-3 induced by Cr(VI). No increase of the expressions of Fas and phosphorylated JNK was observed after Cr(VI) treatment. Cell cycle analysis revealed that the fraction of G2/M phase tended to increase after 24 h of treatment, suggesting that Cr(VI)induced apoptosis is related to the G2 block. These results indicate that Ca2+-calpain- and mitochondria-caspase-dependent pathways play significant roles in the Cr(VI)-induced apoptosis via the G2 block, which are independent of JNK and Fas activation. The inhibition of apoptosis and all its signal transductions by NAC suggests that intracellular reactive oxygen species (ROS) are important for both pathways in Cr(VI)-induced apoptosis of U937 cell. (C) 2004 Elsevier Inc. All rights reserved.