Exposure of the cytoplasm to low-dose X-rays modifies ataxia telangiectasia mutated-mediated DNA damage responses

Munetoshi Maeda,Katsumi Kobayashi,Mika Maeda,Kyo Kume,Hideki Matsumoto,Noriko Usami,Masanori Tomita

doi:10.1038/s41598-021-92213-z

Munetoshi Maeda, Katsumi Kobayashi + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-92213-z

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Abstract

We recently showed that when a low X-ray dose is used, cell death is enhanced in nucleus-irradiated compared with whole-cell-irradiated cells; however, the role of the cytoplasm remains unclear. Here, we show changes in the DNA damage responses with or without X-ray microbeam irradiation of the cytoplasm. Phosphorylated histone H2AX foci, a surrogate marker for DNA double-strand breaks, in V79 and WI-38 cells are not observed in nucleus irradiations at ≤ 2 Gy, whereas they are observed in whole-cell irradiations. Addition of an ataxia telangiectasia mutated (ATM) kinase inhibitor to whole-cell irradiations suppresses foci formation at ≤ 2 Gy. ABL1 and p73 expression is upregulated following nucleus irradiation, suggesting the induction of p73-dependent cell death. Furthermore, CDKN1A (p21) is upregulated following whole-cell irradiation, indicating the induction of cell cycle arrest. These data reveal that cytoplasmic radioresponses modify ATM-mediated DNA damage responses and determine the fate of cells irradiated at low doses.

Highlights

Since the discovery of X-rays by Prof
We demonstrated that in cells exposed to low doses of X-rays, energy deposition in the cytoplasm was required for induction of phosphorylation of H2AX, which occurs during the early stages of the DNA damage response (DDR)
We developed a method to irradiate most areas of the cellular cytoplasm, excluding the nucleus, with X-rays, and assessed the influence of cytoplasmic irradiation on cell death

Summary

Introduction

Since the discovery of X-rays by Prof. Wilhelm Conrad Röntgen in 1895, many scientists have studied the nature of radiation. The biological consequences of radiation exposure, including cell death, are highly influenced by pathways within the DNA damage response (DDR) system. We discuss the intracellular nuclear- and cytoplasmic-ATM responses during a DDR, elicited by local energy deposition in the cell using our SR X-ray microbeam irradiation technique. We demonstrated that in cells exposed to low doses of X-rays, energy deposition in the cytoplasm was required for induction of phosphorylation of H2AX, which occurs during the early stages of the DDR. This cytoplasmic response was inhibited by the addition of a specific ATM inhibitor. The data indicate that low-dose X-ray irradiation of the cytoplasm modifies the ATM-mediated DDR, and determines the fate of the cells

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