title: Gamma rays induce DNA damage and oxidative stress associated with impaired growth and reproduction in the copepod Tigriopus japonicus.
abstract: Nuclear radioisotope accidents are potentially ecologically devastating due to their impact on marine organisms. To examine the effects of exposure of a marine organism to radioisotopes, we irradiated the intertidal copepod Tigriopus japonicus with several doses of gamma radiation and analyzed the effects on mortality, fecundity, and molting by assessing antioxidant enzyme activities and gene expression patterns. No mortality was observed at 96h, even in response to exposure to a high dose (800Gy) of radiation, but mortality rate was significantly increased 120h (5 days) after exposure to 600 or 800Gy gamma ray radiation. We observed a dose-dependent reduction in fecundity of ovigerous females; even the group irradiated with 50Gy showed a significant reduction in fecundity, suggesting that gamma rays are likely to have a population level effect. In addition, we observed growth retardation, particularly at the nauplius stage, in individuals after gamma irradiation. In fact, nauplii irradiated with more than 200Gy, though able to molt to copepodite stage 1, did not develop into adults. Upon gamma radiation, T. japonicus showed a dose-dependent increase in reactive oxygen species (ROS) levels, the activities of several antioxidant enzymes, and expression of double-stranded DNA break damage genes (e.g. DNA-PK, Ku70, Ku80). At a low level (sub-lethal dose) of gamma irradiation, we found dose-dependent upregulation of p53, implying cellular damage in T. japonicus in response to sub-lethal doses of gamma irradiation, suggesting that T. japonicus is not susceptible to sub-lethal doses of gamma irradiation. Additionally, antioxidant genes, phase II enzyme (e.g. GSTs), and cellular chaperone genes (e.g. Hsps) that are involved in cellular defense mechanisms also showed the same expression patterns for sublethal doses of gamma irradiation (50-200Gy). These findings indicate that sublethal doses of gamma radiation can induce oxidative stress-mediated DNA damage and increase the expression of antioxidant enzymes and proteins with chaperone-related functions, thereby significantly affecting life history parameters such as fecundity and molting in the copepod T. japonicus.
authors.affiliation: Department of Biological Sciences, College of Science, Sungkyunkwan University, Suwon 440-746, South Korea.
authors.forename: Jeonghoon
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of Biological Sciences, College of Science, Sungkyunkwan University, Suwon 440-746, South Korea.
authors.forename: Eun-Ji
authors.initials: EJ
authors.lastname: Won
authors.affiliation: Department of Biological Sciences, College of Science, Sungkyunkwan University, Suwon 440-746, South Korea.
authors.forename: Bo-Young
authors.initials: BY
authors.lastname: Lee
authors.affiliation: Marine Ecological Risk Assessment Center, West Sea Fisheries Research Institute, National Fisheries Research & Development Institute, Incheon 400-420, South Korea.
authors.forename: Un-Ki
authors.initials: UK
authors.lastname: Hwang
authors.affiliation: Division of Life Sciences, Korea Polar Research Institute, Incheon 406-840, South Korea.
authors.forename: Il-Chan
authors.initials: IC
authors.lastname: Kim
authors.affiliation: Division of Life Sciences, Korea Polar Research Institute, Incheon 406-840, South Korea.
authors.forename: Joung Han
authors.initials: JH
authors.lastname: Yim
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Kenneth Mei Yee
authors.initials: KM
authors.lastname: Leung
authors.affiliation: Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul 133-791, South Korea.
authors.forename: Yong Sung
authors.initials: YS
authors.lastname: Lee
authors.affiliation: Department of Biological Sciences, College of Science, Sungkyunkwan University, Suwon 440-746, South Korea. Electronic address: jslee2@skku.edu.
authors.forename: Jae-Seong
authors.initials: JS
authors.lastname: Lee
mesh_terms: D000818:Animals; D033342:Copepoda / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects*; D005260:Female; D005720:Gamma Rays; D005786:Gene Expression Regulation / Q000528:radiation effects; D008018:Life Cycle Stages / Q000528:radiation effects; D018384:Oxidative Stress / Q000528:radiation effects*; D010088:Oxidoreductases / Q000235:genetics; D017382:Reactive Oxygen Species / Q000032:analysis; D012098:Reproduction / Q000528:radiation effects; D016019:Survival Analysis
chemical_list: D017382:Reactive Oxygen Species; D010088:Oxidoreductases
keywords: Copepod; DNA repair; Gamma rays; In vivo endpoints; Oxidative stress; Tigriopus japonicus