Enhancement of radiation-induced apoptosis by 6-formylpterin
Enhancement of radiation-induced apoptosis by 6-formylpterin
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DOI：
10.1080/1071576042000191754
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发表时间：
2004-04-01
影响因子：
3.3
通讯作者：
Makino, K
中科院分区：
文献类型：
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作者：
Cui, ZG;Kondo, T;Makino, K
研究了叶酸代谢物6-甲酰蝶呤（6-FP）在人骨髓单核细胞淋巴瘤U937细胞中辐射诱导的细胞凋亡及其可能的增强。6-FP以300 muM的无毒浓度处理细胞，然后暴露于10 Gy剂量的x射线下，通过观察核形态变化、磷脂酰丝氨酸（PS）外化和DNA片段化，观察到辐射诱导的细胞凋亡显著增强。流式细胞术检测细胞内过氧化氢（H2O2）的结果显示，6-FP增加了细胞内过氧化氢（H2O2）的形成，当细胞辐照后，过氧化氢的形成进一步增加。联合处理后，线粒体跨膜电位（MMP）降低，线粒体细胞色素c释放，caspase-3活化增强。在联合治疗中检测到蛋白激酶Cdelta （PKCdelta）的显著活化及其从细胞质到线粒体的易位。细胞内Ca2+浓度（[Ca2+](i)）的增加也被观察到，然而，calpain i和calpain II都不能抑制细胞凋亡。此外，联合治疗未增强c-Jun nh2末端激酶（JNK）的激活。一种参与caspase非依赖性凋亡通路的蛋白，凋亡诱导因子（apoptosis inducing factor， AIF），在治疗3小时后仍保持不变。这些结果表明，在PKCdelta的积极参与下，6-FP产生的细胞内H2O2通过线粒体介导的caspase依赖途径增强辐射诱导的细胞凋亡。
Radiation-induced apoptosis and its possible enhancement in the presence of 6-formylpterin (6-FP), a metabolite of folic acid, were examined in human myelomonocytic lymphoma U937 cells. When cells were treated with 6-FP at a nontoxic concentration of 300 muM, and then exposed to X-rays at a dose of 10 Gy, significant enhancement of radiation-induced apoptosis as determined by nuclear morphological change, phosphatidylserine (PS) externalization and DNA fragmentation were observed. Flow cytometry for the detection of intracellular hydrogen peroxide (H2O2) revealed that 6-FP increased the formation of intracellular H2O2 , which further increased when the cells were irradiated. Decrease of mitochondria trans-membrane potential (MMP), release of cytochrome c from mitochondria, and activation of caspase-3 were enhanced after the combined treatment. Remarkable activation of protein kinase Cdelta (PKCdelta) and its translocation from cytosol to mitochondria were detected in combined treatment. Increase of intracellular Ca2+ concentrations ([Ca2+](i)) was also observed, however, neither calpain I nor calpain II could inhibit the apoptosis. In addition, c-Jun NH2-terminal kinase (JNK) activation was not enhanced in the combined treatment. A protein involved in a caspase-independent apoptosis pathway, apoptosis inducing factor (AIF), remained unchanged even 3 h after treatment. These results indicate that intracellular H2O2 generated by 6-FP enhances radiation-induced apoptosis via the mitochondria-mediated caspase-dependent pathway, with the active involvement of PKCdelta.