Low Dose-Rate Irradiation of Gamma-Rays-Induced Cytotoxic and Genotoxic Alterations in Peripheral Erythrocytes of p53-Deficient Medaka (Oryzias latipes)

Alaa El-Din H Sayed,Junya Kobayashi,Shoji Oda,Hiroshi Mitani,Kento Nagata,Takuya Nakazawa

doi:10.3389/fmars.2021.773481

Alaa El-Din H Sayed, Junya Kobayashi + Show 4 more

Open Access

https://doi.org/10.3389/fmars.2021.773481

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Abstract

Morphological alterations and nuclear abnormalities in fish erythrocytes have been used in many studies as bioindicators of environmental mutagens including ionizing radiation. In this study, adult Japanese medaka (Oryzias latipes) were irradiated with gamma rays at a low dose rate (9.92 μGy/min) for 7 days, giving a total dose of 100 mGy; and morphological alterations, nuclear abnormalities, and apoptotic cell death induced in peripheral erythrocytes were investigated 8 h and 7 days after the end of the irradiation. A variety of abnormalities, such as tear-drop cell, crenated cell, acanthocyte, sickled cell, micronucleated cell, eccentric nucleus, notched nucleus, and schistocyte, were induced in the peripheral erythrocytes of the wild-type fish, and a less number of abnormalities and apoptotic cell death were induced in the p53-deficient fish. These results indicate that low dose-rate chronic irradiation of gamma rays can induce cytotoxic and genotoxic effects in the peripheral erythrocytes of medaka, and p53-deficient medaka are tolerant to the gamma-ray irradiation than the wild type on the surface.

Highlights

Gamma irradiation induces ionization and cellular damage, including morphological alterations, nuclear abnormalities, DNA damage, and apoptosis (Muslimovic et al, 2012; Sayed et al, 2014, 2016b; Mohamed et al, 2016)
After the low dose-rate irradiation (100 mGy in total at 9.92 μGy/min) of gamma rays, morphological alterations and nuclear abnormalities were induced in the erythrocytes of the wild-type and p53-deficient medaka, such as micronucleated cell (Mn; Figure 1B), acanthocyte (Ac; Figures 1C,H,I), crenated cell (Cr; Figures 1C,H,I), sickled cell (Sk; Figures 1C,E,I,K), cell with notched nucleus (Nn; Figures 1E,K), tear-drop cell (Tr; Figures 1F,I), cell with eccentric nucleus (Ecn; Figure 1H), and schistocyte (Sch; Figure 1L)
The erythrocytes of the irradiated wild-type fish showed more serious morphological alterations than the erythrocytes of the irradiated p53-deficient fish. These results clearly demonstrated that the gamma-ray irradiation of low dose (100 mGy in total) at low dose-rate (9.92 μGy/min) for 7 days can induce various types of morphological abnormalities in peripheral erythrocytes of medaka fish

Summary

Introduction

Gamma irradiation induces ionization and cellular damage, including morphological alterations, nuclear abnormalities, DNA damage, and apoptosis (Muslimovic et al, 2012; Sayed et al, 2014, 2016b; Mohamed et al, 2016). In medaka fish blood cells, Sayed et al (2014) reported that gamma radiation induces DNA aberrations such as nuclear abnormalities. In the case where the dose of radiation is low and the induced DNA lesions are repaired by the cells, it has been considered that the risk of carcinogenesis can be negligible (International Commission on Radiological Protection [ICRP], 2007). Since 100 mGy is the dose for the lower limit of epidemiologically evaluated carcinogenic risk (International Commission on Radiological Protection [ICRP], 2007), IR exposure at doses lower than 100 mGy is considered not to increase carcinogenic risk, and its biological effects have not been emphasized

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