Effects of radionuclide contamination on leaf litter decomposition in the Chernobyl exclusion zone

The effects of radioactive contamination on ecosystem processes such as litter decomposition remain largely un- known. Because radionuclides accumulated in soil and plant biomass can be harmful for organisms, the function- ing of ecosystems may be altered by radioactive contamination. Here, we tested the hypothesis that decomposition is impaired by increasing levels of radioactivity in the environment by exposing uncontaminated leaf litter from silver birch and black alder at (i) eleven distant forest sites differing in ambient radiation levels (0.22–15 μGy h−1) and (ii) along a short distance gradient of radioactive contamination (1.2–29 μGy h−1) within a single forest in the Chernobyl exclusion zone. In addition to measuring ambient external dose rates, we estimat- ed the average total dose rates (ATDRs) absorbed by decomposers for an accurate estimate of dose-induced eco- logical consequences of radioactive pollution. Taking into account potential confounding factors (soil pH, moisture, texture, and organic carbon content), the results from the eleven distant forest sites, and from the single forest, showed increased litter mass loss with increasing ATDRs from 0.3 to 150 μGy h−1. This unexpected result may be due to (i) overcompensation of decomposer organisms exposed to radionuclides leading to a higher decomposer abundance (hormetic effect), and/or (ii) from preferred feeding by decomposers on the un- contaminated leaf litter used for our experiment compared to locally produced, contaminated leaf litter. Our data indicate that radio-contamination of forest ecosystems over more than two decades does not necessarily have detrimental effects on organic matter decay. However, further studies are needed to unravel the underlying mechanisms of the results reported here, in order to draw firmer conclusions on how radio-contamination affects decomposition and associated ecosystem processes

Current evidence for a role of epigenetic mechanisms in response to ionizing radiation in an ecotoxicological context

The issue of potential long-term or hereditary effects for both humans and wildlife exposed to low doses (or dose rates) of ionising radiation is a major concern. Chronic exposure to ionising radiation, defined as an exposure over a large fraction of the organism's lifespan or even over several generations, can possibly have consequences in the progeny. Recent work has begun to show that epigenetics plays an important role in adaptation of organisms challenged to environmental stimulae. Changes to so-called epigenetic marks such as histone modifications, DNA methylation and non-coding RNAs result in altered transcriptomes and proteomes, without directly changing the DNA sequence. Moreover, some of these environmentally-induced epigenetic changes tend to persist over generations, and thus, epigenetic modifications are regarded as the conduits for environmental influence on the genome. Here, we review the current knowledge of possible involvement of epigenetics in the cascade of responses resulting from environmental exposure to ionising radiation. In addition, from a comparison of lab and field obtained data, we investigate evidence on radiation-induced changes in the epigenome and in particular the total or locus specific levels of DNA methylation. The challenges for future research and possible use of changes as an early warning (biomarker) of radiosensitivity and individual exposure is discussed. Such a biomarker could be used to detect and better understand the mechanisms of toxic action and inter/intra-species susceptibility to radiation within an environmental risk assessment and management context

RETRATO SIN IDENTIFICAR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Brain Damage and Repair: From Molecular Effects to Central Nervous System Disorders

International audienceChronical exposures to biological, chemical and physical stressors can be particularly detrimental during the early phase of embryonic development, increasing the risk of brain dysfunctions after birth. Major advances have been made in our understanding of the mechanisms driving the development of a fully functional brain from a limited pool of stem cells, as well as how this organ can respond after injuries. However, further knowledge is required to understand how these processes are altered by environmental stressors, such as ionizing radiations, chemicals, stroke or viral infectious agents, and therefore be able to predict the etiology of neurological disorders

Whole transcriptome data of zebrafish exposed to chronic dose of depleted uranium

International audienceThe concentration of depleted uranium (DU) in the environment is expected to increase due to anthropogenic activities, posing potential risks on ecosystems. The effects of chronic exposure to DU at concentration close to the environmental standards (0.3–30 µg DU/L) are scarcely characterised. Genomic alterations caused by low doses of pollutants can potentially propagate over generations, but how these effects may affect the health of the progeny remain uncertain for the vast majority of toxicants. The present dataset describes the transcriptomic effects of a chronic exposure to 20 µg DU/L during 10 days on adult zebrafish (Danio rerio) organs, the brain, the testis and the ovaries. The potential multigenerational effects of DU were assessed on the progeny of the adult exposed fish at the two-cells stage and after four days of development. We describe in this article the summary statistics of the differential gene expression analysis and focus on key molecular pathways affected by an exposure to a low concentration of DU. The data presented in this study supports the observation made in Armant et al. (2017) [1] (https://doi.org/10.1016/j.dib.2016.05.007) that DU can induce a molecular stress in both adult zebrafish and their progeny. The raw dataset has been deposited at the Gene Expression Omnibus (GEO) repository under the accession number GEO: GSE96603

Réponse celluliare à l'exposition aux éléments chimiques stables ou radioacttifs

International audienc

Réponse celluliare à l'exposition aux éléments chimiques stables ou radioacttifs

International audienc

Effects of uranium on the metabolism of zebrafish, Danio rerio

International audienceThe increasing demand for nuclear energy results in heightened levels of uranium (U) in aquatic systems which present a potential health hazard to resident organisms. The aim of this study was to mechanistically assess how chronic exposure to environmentally relevant concentrations of U perturbs the complex interplay between feeding, growth, maintenance, maturation and reproduction throughout the life-cycle of an individual. To this end we analysed literature-based and original zebrafish toxicity data within a same mass and energy balancing conceptual framework. U was found to increase somatic maintenance leading to inhibition of spawning as well as increase hazard rate and costs for growth during the early life stages. The fish's initial conditions and elimination through reproduction greatly affected toxicokinetics and effects. We demonstrate that growth and reproduction should be measured on specific individuals since mean values were hardly interpretable. The mean food level differed between experiments, conditions and individuals. This last 'detail' contributed substantially to the observed variability by its combined effect on metabolism, toxic effects and toxico-kinetics. The significance of this work is that we address exactly how these issues are related and derive conclusions which are independent of experimental protocol and coherent with a very large body of literature on zebrafish eco-physiology

Ionising Radiation Induces Promoter DNA Hypomethylation and Perturbs Transcriptional Activity of Genes Involved in Morphogenesis during Gastrulation in Zebrafish

International audienceEmbryonic development is particularly vulnerable to stress and DNA damage, as mutationscan accumulate through cell proliferation in a wide number of cells and organs. However, the biologicaleffects of chronic exposure to ionising radiation (IR) at low and moderate dose rates (<6 mGy/h)remain largely controversial, raising concerns for environmental protection. The present study focuseson the molecular effects of IR (0.005 to 50 mGy/h) on zebrafish embryos at the gastrula stage (6 hpf),at both the transcriptomics and epigenetics levels. Our results show that exposure to IR modifies theexpression of genes involved in mitochondrial activity from 0.5 to 50 mGy/h. In addition, importantdevelopmental pathways, namely, the Notch, retinoic acid, BMP and Wnt signalling pathways,were altered at 5 and 50 mGy/h. Transcriptional changes of genes involved in the morphogenesisof the ectoderm and mesoderm were detected at all dose rates, but were prominent from 0.5 to50 mGy/h. At the epigenetic level, exposure to IR induced a hypomethylation of DNA in the promoterof genes that colocalised with both H3K27me3 and H3Kme4 histone marks and correlated withchanges in transcriptional activity. Finally, pathway enrichment analysis demonstrated that theDNA methylation changes occurred in the promoter of important developmental genes, includingmorphogenesis of the ectoderm and mesoderm. Together, these results show that the transcriptionalprogram regulating morphogenesis in gastrulating embryos was modified at dose rates greater than orequal to 0.5 mGy/h, which might predict potential neurogenesis and somitogenesis defects observedat similar dose rates later in development