Narayanan P K, Goodwin E H, Lehnert B E
Cell and Molecular Biology Group, Life Sciences Division, Los Alamos National Laboratory, New Mexico 87545, USA.
Cancer Res. 1997 Sep 15;57(18):3963-71.
The mechanism(s) by which high-linear energy transfer a particles, like those emitted by inhaled radon and radon daughters, cause lung cancer has not been elucidated. Conceivably, DNA damage that is induced by a particles may be mediated by the metabolic generation of reactive oxygen species (ROS), in addition to direct a particle-DNA interactions and hydroxyl radical-DNA interactions. Using normal human lung fibroblasts, we investigated the hypothesis that densely ionizing alpha particles may induce the intracellular generation of superoxide (O2.-) and hydrogen peroxide (H2O2). Ethidium bromide and 2',7'-dichlorofluorescein, fluorescent products of the membrane-permeable dyes hydroethidine and 2',7'-dichlorofluorescin diacetate, respectively, were used to monitor the intracellular production of O2.- and H2O2, respectively, by flow cytometry. Compared to sham-irradiated cells, fibroblasts that were exposed to alpha particles (0.4-19 cGy) had significant increases in intracellular O2.- production, along with concomitant increases in H2O2 production. Further analyses suggest that the plasma membrane-bound NADPH-oxidase is primarily responsible for this increased intracellular generation of ROS and that the ROS response does not require direct nuclear or cellular "hits" by the a particles. In this latter regard, we additionally report that unirradiated cells also show the ROS response when they are incubated with serum-containing culture medium that has been exposed to a particles or when they are incubated with supernatants from a-irradiated cells. Our overall results support the possibility that a particles, at least in part, may mediate their DNA-damaging effects indirectly via a ROS-related mechanism.
高传能线密度的α粒子（如吸入的氡及其子体所发射的那些粒子）引发肺癌的机制尚未阐明。可以想象，除了直接的α粒子 - DNA相互作用和羟基自由基 - DNA相互作用外，α粒子诱导的DNA损伤可能由活性氧（ROS）的代谢生成介导。我们使用正常人肺成纤维细胞，研究了密集电离的α粒子可能诱导细胞内超氧阴离子（O2.-）和过氧化氢（H2O2）生成的假说。分别使用溴化乙锭和2',7'-二氯荧光素（分别为膜通透性染料氢化乙锭和2',7'-二氯荧光素二乙酸酯的荧光产物），通过流式细胞术监测细胞内O2.-和H2O2的生成。与假照射细胞相比，暴露于α粒子（0.4 - 19 cGy）的成纤维细胞细胞内O2.-生成显著增加，同时H2O2生成也随之增加。进一步分析表明，质膜结合的NADPH氧化酶是细胞内ROS生成增加的主要原因，并且ROS反应不需要α粒子对细胞核或细胞的直接“撞击”。在这后一点上，我们还报告说，未照射的细胞在与暴露于α粒子的含血清培养基一起孵育时，或与α照射细胞的上清液一起孵育时，也会显示出ROS反应。我们的总体结果支持α粒子至少部分可能通过与ROS相关的机制间接介导其DNA损伤作用的可能性。
