Azzam E I, de Toledo S M, Little J B
Department of Cancer Cell Biology, Laboratory of Radiobiology, Harvard School of Public Health, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 2001 Jan 16;98(2):473-8. doi: 10.1073/pnas.98.2.473. Epub 2001 Jan 9.
It has generally been considered that important biological effects of ionizing radiation arise as a direct consequence of DNA damage occurring in irradiated cells. We have examined this hypothesis by exposing cells to very low fluences of alpha-particles, similar to those emitted by radon gas, such that as few as 1% of the cells in a population are traversed by a particle and thus receive any radiation exposure. By using the endpoints of changes in gene expression and induction of DNA damage, we show that nonirradiated "bystander" cells participate in the overall response of confluent density-inhibited populations of cultured fibroblast and epithelial cells. By in situ immunofluorescence techniques and the use of cells genetically compromised in their ability to perform gap junction intercellular communication, we present direct evidence for the involvement of connexin43-mediated intercellular communication in the transmission of damage signals to nonirradiated cells. Induction of the stress-inducible p21(Waf1) protein in aggregates of neighboring cells far exceeding the fraction of cells whose nucleus has been traversed occurred in gap junction-competent cells only. These changes in p21(Waf1) expression correlated with both the induction of DNA damage (as measured by micronucleus formation) as well as increased Ser-15 phosphorylation of p53.
一般认为，电离辐射的重要生物学效应是受辐射细胞中发生的DNA损伤的直接后果。我们通过将细胞暴露于非常低通量的α粒子（类似于氡气发射的粒子）来检验这一假设，使得群体中只有1%的细胞被粒子穿过并因此受到任何辐射暴露。通过使用基因表达变化和DNA损伤诱导的终点指标，我们表明未受辐射的“旁观者”细胞参与了汇合密度抑制的培养成纤维细胞和上皮细胞群体的整体反应。通过原位免疫荧光技术以及使用在进行间隙连接细胞间通讯能力上存在基因缺陷的细胞，我们提供了直接证据，证明连接蛋白43介导的细胞间通讯参与了损伤信号向未受辐射细胞的传递。仅在具有间隙连接能力的细胞中，相邻细胞聚集体中应激诱导的p21（Waf1）蛋白的诱导远远超过其细胞核被穿过的细胞比例。p21（Waf1）表达的这些变化与DNA损伤的诱导（通过微核形成测量）以及p53的Ser-15磷酸化增加相关。
