Studies on radiation induced defensive cellular signaling using SPICE-NIRS microbeam

In classical radiation biology, it is described that initial DNA damages induced directly by the energy deposition of radiation are the main cause for the varieties of radiobiological consequences, thus the DNA is considered to be the primary target of radiation. However, in the past several decades, there are many phenomena were reported that cannot be explained by this classical dogma. These findings indicated the existence of non-DNA/secondary targets, that may affect the fate of irradiated and nearby non-irradiated cells. Hence, this non-DNA/secondary target may be activated by direct energy deposition in the cytoplasm, or may be indirectly activated through signaling the surrounding non-irradiated cells, such as radiation induced bystander effect. Our aim is to provide answers to questions such as what is the non-DNA/secondary target and how does it involve with the damages in the primary target, and microbeam technology would be the effective method to fulfill our demands.Microbeam is a powerful tool that enables us to target cell nucleus or cytoplasm or even both with several micrometer resolutions. Also, it is possible to distinguish the non-targeted cells from the targeted cells, which is essential for radiation induced bystander effect studies. Our microbeam irradiation system, the Single-Particle Irradiation system to CEll (SPICE-NIRS microbeam) provides a 3.4 MeV proton microbeam focused with a quadrupole magnetic lens on an upward vertical beam line. At present, SPICE is the only proton microbeam facility in Asia on which a single-ion/single-cell irradiation can be performed on mammalian cells with stability and high throughput using an upward vertical beam of below 2-micrometer in diameter. In this research core, we have set two specific topics to investigate the underlying mechanisms of this secondary target in cells. First is the investigation of cytoplasmic damage induced cellular response. In this part, we focused on the activation of oxidative stress response pathway, which are triggered by a transcriptional factor Nuclear factor erythroid 2-related factor 2 (Nrf2), which is known as an important regulator of cellular oxidative status through controlling the expression of the large amount of detoxifying enzymes, including enzymes participating in maintaining cell oxidative equilibrium. The second topic is the bi-directional response resulting “rescue” in the targeted cells, which takes place in radiation induced bystander effects. In addition, we determine the characteristics of radiation induced cell signaling between two different types of cell lines; normal and cancer cell lines. In this part of the project, our aim is to characterize bystander signaling molecules underlying cellular response to radiation exposures.The overall strategy of this research core is to establish an international collaboration network on radiation biology in Asia based on advanced microbeam technology to expand our studies of radiation induced cellular signaling. To have this collaborative network in continual and not only as in part of NIRS-IOL program in the near future, we would like to establish a “microbeam training course” in NIRS to recruit the young investigators in Asia to be participate in the studies of microbeam biology.International Open Laboratory Symposium 201