Determination of Accurate Dose of ã- Irradiation causing Low-Dose Hyper-Radio-Sensitivity by Using Human Fibroblast Cells
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2018, Vol 10, Issue 3
Abstract
Effects of low-dose radiation (LDR) on living organisms including human is still in argument, in spite of the LDR is ubiquitous in our environment. One prominent phenomenon by the LDR is hyper-radio-sensitivity (HRS). The doses causing HRS by LDR varies from 10 to 200 mGy depending on the cell line and the quality of radiation. Before undertaking the research of HRS, to determine the doses conferring the HRS is necessary for each experiment system. Using human normal fibroblast cells, we determined the dose conferring the HRS as 75 mGy, and inferred the border of doses that distinguish from the increased radio-resistance (IRR) between 75 and 100 mGy with y-rays from a 60Co source.While high-dose-radiation (HDR)-induced human diseases are well known, the effects of low-dose radiation (LDR) on human health is still in argument, in spite of the LDR is ubiquitous in our environment, for example, the radioactive substance leakage due to the accident of nuclear power plant, medical exposure such as medical diagnosis and radiotherapy, occupational radiation exposure, frequent-flyer risks and manned space exploration. Researches over the past two decades suggested the biological effects of LDR differ from those observed with HDR. Most cell lines exhibit hyper-radio-sensitivity (HRS) to LDR that is not predicted by back-extrapolating the cell survival response from HDR. As the dose is increased, they exhibit increased radio-resistance (IRR), and the cell survival follows the usual downward-bending curve with increasing dose. One explanation is, with low dose radiation, the induction of DNA repair mechanisms does not work sufficiently, then the cells becomes hypersensitive, while at high doses, the mechanisms can be recruited, then the cells becomes resistant [1-3]. Another mechanism of HRS by LDR was explained as the radiation-induced bystander responses in unirradiated cells that receive signals from the neighboring irradiated cells give carcinogenic risks.In contrast, the LDR sometimes confers beneficial effects, called radiation hormesis, on organisms [4]. Moreover, the adaptive response by the LDR to the following HDR has been studied [5]. The LDR is generally defined as a radiation dose of 100 mSv or less (<100 mGy). However, even if it is limited to researches of human culture cells, the doses causing HRS by LDR are various from 10 to 200 mGy depending on the cell line and quality of radiation [6-8] and most of them utilized wide intervals of doses. Because the IRR occurs at close doses of the HRS, determination of the accurate border of dose that distinguish the HRS and IRR is necessary, especially for analyzing the mechanisms underlying the events of HRS/IRR, by observing the cellular responses by irradiation of gradually increasing doses as much as possible. To accurately determine the dose at which HRS/IRR occurs in various cells by delimiting the dose more finely, will lead to correct coping of the LDR whether it has proper impact as radiation hormesis or harmful effect. In this study, we investigated the dose of y-rays for HRS using human normal fibroblast cells because they are widely utilized for this kind of research and determined border doses distinguishing from doses for supposed IRR, by conventional cell biological methods.
Authors and Affiliations
Yoshiharu Tanaka, Masakazu Furuta
Keywords
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- EP ID EP592317
- DOI 10.26717/BJSTR.2018.10.001958
- Views 186
- Downloads 0
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