Azzam Edouard I, De Toledo Sonia M, Spitz Douglas R, Little John B
Department of Cancer Cell Biology, Laboratory of Radiobiology, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
Cancer Res. 2002 Oct 1;62(19):5436-42.
The role of oxidative metabolism in the up-regulation/activation of stress-induciblesignaling pathways as well as induction of micronucleus formation in bystander cells was investigated. By immunoblotting and in situ immunofluorescence, active Cu-Zn superoxide dismutase (SOD) enzyme and active catalase enzyme were shown to inhibit the up-regulation of p21(Waf1) as well as the induction of micronucleus formation in bystander cells from confluent cultures of normal human diploid fibroblasts irradiated with 0.3-3 cGy of alpha-particles. Enzyme activity assays indicated that exogenous SOD became significantly associated with the cells. Reactive oxygen species apparently derived from a flavin-containing oxidase enzyme [presumably an NAD(P)H-oxidase] appeared to be major contributors to the bystander-induced up-regulation of p53 and p21(Waf1) as well as micronucleus formation, as evidenced by the inhibition of these effects with diphenyliodonium. Rapid activation of nuclear factor kappaB, Raf-1, extracellular signal-regulated kinase 1/2, c-Jun NH2-terminal kinase, and p38 mitogen-activated protein kinase and their downstream effectors activator protein 1, ELK-1, p90RSK, and activating transcription factor 2 was also observed in cultures exposed to very low fluences of alpha-particles. Significant attenuation in the activation of these kinases and transcription factors occurred in irradiated cultures treated with either SOD or catalase. Overall, these results support the hypothesis that superoxide and hydrogen peroxide produced by flavin-containing oxidase enzymes mediate the activation of several stress-inducible signaling pathways as well as micronucleus formation in bystander cells from cultures of human cells exposed to low fluences of alpha-particles.
研究了氧化代谢在应激诱导信号通路的上调/激活以及旁观者细胞中微核形成诱导方面的作用。通过免疫印迹和原位免疫荧光分析，发现活性铜锌超氧化物歧化酶（SOD）和活性过氧化氢酶可抑制p21（Waf1）的上调以及来自经0.3 - 3 cGy α粒子照射的正常人二倍体成纤维细胞汇合培养物的旁观者细胞中微核的形成。酶活性测定表明外源性SOD与细胞显著结合。显然源自含黄素氧化酶（可能是NAD(P)H氧化酶）的活性氧似乎是旁观者诱导的p53和p21（Waf1）上调以及微核形成的主要促成因素，这一点通过用二苯基碘鎓抑制这些效应得到证明。在暴露于极低剂量α粒子的培养物中还观察到核因子κB、Raf-1、细胞外信号调节激酶1/2、c-Jun氨基末端激酶和p38丝裂原活化蛋白激酶及其下游效应物活化蛋白1、ELK-1、p90RSK和活化转录因子2的快速激活。在用SOD或过氧化氢酶处理的照射培养物中，这些激酶和转录因子的激活显著减弱。总体而言，这些结果支持以下假设：含黄素氧化酶产生的超氧化物和过氧化氢介导了几种应激诱导信号通路的激活以及来自暴露于低剂量α粒子的人类细胞培养物的旁观者细胞中的微核形成。
