Department of Automatics, Silesian University of Technology, Gliwice, Poland.
Mutat Res. 2012 Mar 1;731(1-2):117-24. doi: 10.1016/j.mrfmmm.2011.12.007. Epub 2011 Dec 21.
The radiation-induced bystander effect is a well-established phenomenon which results in damage in non-irradiated cells in response to signaling from irradiated cells. Since communication between irradiated and bystander cells could be reciprocal, we examined the mutual bystander response between irradiated cells and co-cultured with them non-irradiated recipients. Using a transwell culture system, irradiated human melanoma (Me45) cells were co-cultured with non-irradiated Me45 cells or normal human dermal fibroblasts (NHDF) and vice versa. The frequency of micronuclei and of apoptosis, ROS level, and mitochondrial membrane potential were used as the endpoints. Irradiated Me45 and NHDF cells induced conventional bystander effects detected as modest increases of the frequency of micronuclei and apoptosis in both recipient neighbors; the increase of apoptosis was especially high in NHDF cells co-cultured with irradiated Me45 cells. However, the frequencies of micronuclei and apoptosis in irradiated Me45 cells co-cultured with NHDF cells were significantly reduced in comparison with those cultured alone. This protective effect was not observed when irradiated melanomas were co-cultured with non-irradiated cells of the same line, or when irradiated NHDF fibroblasts were co-cultured with bystander melanomas. The increase of micronuclei and apoptosis in irradiated Me45 cells was paralleled by an increase in the level of intracellular reactive oxygen species (ROS), which was reduced significantly when they were co-cultured for 24h with NHDF cells. A small but significant elevation of ROS level in NHDF cells shortly after irradiation was also reduced by co-culture with non-irradiated NHDF cells. We propose that in response to signals from irradiated cells, non-irradiated NHDF cells trigger rescue signals, whose nature remains to be elucidated, which modify the redox status in irradiated cells. This inverse bystander effect may potentially have implications in clinical radiotherapy.
辐射诱导的旁观者效应是一种已被证实的现象，它会导致非照射细胞在受到照射细胞信号的作用下受到损伤。由于照射细胞和旁观者细胞之间的通讯可能是相互的，我们研究了照射细胞与与之共培养的未照射受者细胞之间的相互旁观者反应。使用 Transwell 培养系统，将照射的人黑色素瘤（Me45）细胞与未照射的 Me45 细胞或正常人类真皮成纤维细胞（NHDF）共培养，并进行了相反的实验。使用微核和细胞凋亡、ROS 水平和线粒体膜电位作为终点。照射的 Me45 和 NHDF 细胞诱导了常规旁观者效应，表现为微核和细胞凋亡频率适度增加，在两个受者邻居中均有观察到；在与照射的 Me45 细胞共培养的 NHDF 细胞中，细胞凋亡的增加尤其高。然而，与单独培养相比，与 NHDF 细胞共培养的照射 Me45 细胞的微核和细胞凋亡频率显著降低。当照射的黑色素瘤与相同系的未照射细胞共培养时，或者当照射的 NHDF 成纤维细胞与旁观者黑色素瘤共培养时，没有观察到这种保护作用。照射的 Me45 细胞的微核和细胞凋亡增加与细胞内活性氧物种（ROS）水平的增加平行，当它们与 NHDF 细胞共培养 24 小时时，ROS 水平显著降低。照射后 NHDF 细胞中 ROS 水平的短暂升高也因与未照射的 NHDF 细胞共培养而降低。我们提出，非照射的 NHDF 细胞在接收到照射细胞的信号后，触发了尚未阐明的拯救信号，这些信号改变了照射细胞的氧化还原状态。这种反向旁观者效应可能对临床放射治疗具有潜在意义。
