Presentation Enhanced DSB repair triggered by cytoplasmic damage induced by proton microbeam irradiation

Konishi, Teruaki  ,  wang, Jun  ,  Ahbrizal Farizal Tengku Ahmad, Tengku  ,  Autsavapromporn, Narongchai  ,  Kobayashi, Alisa  ,  Oikawa, Masakazu  ,  Furusawa, Yoshiya

Direct hits in the nucleus by radiation are known as the primary cause of the various radio-biological effects. However, the cells will have equal chances of being exposed in the cytoplasm, and results in damages that may activate various signaling pathways that mediates defensive response. We examined the velocity of DNA double-strand break (DSB) repair in microbeam irradiated WI-38 human normal fibroblast cells that were targeted in the nucleus, cytoplasm, or both nucleus/cytoplasm using SPICE-NIRS microbeam. Cells were fixed at various time points of 1hr to 24hr post hours irradiation, then immuno-stained against g-H2AX to quantify the residual DSB/nucleus from the obtained microscopic images. Microbeam irradiation significantly induced g-H2AX, which were proportional to the number of protons per nucleus. With the cells irradiated with 500 protons per nucleus, we found less residual g-H2AX in the cells with additional 200 protons in the cytoplasm at 8hr and 16hr post irradiation. In contrary, cytoplasm irradiation alone showed higherγ-H2AX level at 1, 4, 8 hr post irradiation, but decreased to level equivalent to the controls. Taken together, cytoplasmic damage induces g-H2AX, however it also enhances repair of DSB induced by nucleus irradiation.
5th International Symposium on Space Radiation and Particle Radiotherapy

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