MECHANISMS OF BYSTANDER MUTAGENESIS

描述（由申请人提供）：使用精密带电粒子微束，申请人和他的合作研究者已经证明，在一些已知的细胞核部分被击中的群体中，诱导突变和染色体变化的频率与未被击中的细胞一致，这些细胞对反应有显著贡献。事实上，对10%的哺乳动物细胞群进行单个α粒子的辐照，其结果与对种群中所有细胞进行辐照时所观察到的结果相似。虽然间隙连接通信已被证明在旁观者反应中发挥重要作用，但其确切机制尚不清楚。利用cDNA微阵列，申请人已经证明COX-2酶在旁观者细胞中持续升高。此外，初步证据表明活性氮可能参与信号传递过程。这就提出了以下问题：过亚硝酸盐阴离子是否参与了旁观者效应？自由基生成过程是否涉及线粒体损伤？COX-2酶是如何增加的

DESCRIPTION (provided by applicant): Using a precision charged particle microbeam, the applicant and his co-investigators have shown that the frequencies of induced mutations and chromosomal changes in populations where some known fractions of nuclei were hit are consistent with non-hit cells contributing significantly to the response. In fact, irradiation of 10% of a mammalian cell population with a single alpha particle per cell results in a mutant yield similar to that observed when all of the cells in the population are irradiated. While gap junctional communication has been shown to play an important role in the bystander response, the precise mechanism is not known. Using cDNA microarrays, the applicant has shown that the COX-2 enzyme is consistently elevated in bystander cells. Furthermore, preliminary evidence suggests that reactive nitrogen species may be involved in the signaling process. This raised the following questions: Are peroxynitrite anions involved in the bystander effect? Does this radical generating process involve mitochondrial damage? How does an increase in COX-2 enzymes relate to the bystander process? Can cytoplasmic irradiation induce bystander mutagenic effect in mammalian cells in a manner similar to what the applicant has recently demonstrated with nuclear traversal of normal human bronchial epithelial (NHBE) cells? And finally, can bystander signal induce genomic instability in mammalian cells? To address these issues, a series of 8 inter-related specific aims are proposed to address the 5 testable hypotheses. Mutations will be scored at the CD59 locus of the AL cells and G2PCC will be scored in NHBE cells. The proposed studies will help to address the mechanism of bystander mutagenesis in mammalian cells. Together with the cytoplasmic genotoxicity study, this project will address, in the context of this program project, some of the fundamental issues regarding both the target and radiation dose effect and are likely to have a significant impact on our current understanding of radiation risk assessment.