Inhibition of DNA double strand break repair by uranium and links with effects on reproduction of the zebrafish

Transcription

1 Inhibition of DNA double strand break repair by uranium and links with effects on reproduction of the zebrafish C. Adam-Guillermin, S. Pereira, S. Bourrachot, S. Barillet, I. Cavalié, V. Camilleri, M. Floriani, J. Garnier-Laplace Institut de Radioprotection et de Sûreté Nucléaire, Laboratoire d ECOtoxicologie des radionucléides (LECO), Cadarache, France

2 Uranium nuclear fuel cycle, military, industrial & agricultural applications Contamination of aquatic ecosystems Background [U] surface water : ~ ng/l to 6 µg/l Vicinity of former uranium mines : ~ tens 100 µg/l U drinking water guideline : 15 µg/l WHO Environmental Quality Standards range from 1 µg/l to 100 µg/l C. Adam, IRPA13, Glasgow, May 16th, /14

3 Biological endpoints Ecosystem Population Organism Tissue Ecological relevance Genotoxicity DNA is the 1 st cellular target for radionuclides DNA damages in : somatic cells : carcinogenesis germ cells : teratogenesis and reprotoxicity Cell Molecule Mechanisms Objective Assess genotoxicity markers as predictive biomarkers for U effects on individuals or populations 3/14 2

4 Zebrafish Easy breeding (mature in 3 month) Fully sequenced genome Model for developmental studies v 24 hpf hpf hpf 32 C. Adam, IRPA13, Glasgow, May 16th, /14

5 Zebrafish exposure to to uranium (20 (20 days) days) and and reproduction DNA damages and reproduction Comet assay (gonads after 20 d exposure) ADN dans la queue des comètes (%) Mean DNA tail (%) Dommages à l ADN * ** control Témoin 20 µg/l µg.l µg/l µm female male Contrôle témoin 20 µg.l 20 µg/l -1 Uapp µg.l µg/l -1 Uapp femelle mâle Spawning Nombre events de pontes per female par femelle for pendant 16 days 16 jours Bourrachot, 2009 control Témoin 20 µg/l 250 µg/l µg/l Significant increase of DNA damage in males and females gonads Decrease of fecundity & of egg and larvae viability 5 C. Adam, IRPA13, Glasgow, May 16th, /14

6 Reversible DNA damages? Comet assay in male gonad cells Exposure of zebrafish to 20 µg/l of uranium during 27 days U depuration during 28 days Mean DNA tail (%) * p<0.05 ** p<0.01 U accumulation * Témoin control U depuration ** ** ** Exposé exposed Time (d) C.Adam, 2012 DNA damages are still observed after 28 days of depuration occurence of DNA Double Strand breaks (DSBs)? correlation with the decrease of fertility? C. Adam, IRPA13, Glasgow, May 16th, /14

7 Does U induce DNA DSBs in zebrafish? Cells in G0/G1 DNA Double Strand Breaks DSB repair DSB detection Time-response Experiments P P P Dose-response experiments DNApK H2AX DNA repair kinetics Number of foci at 10min, 1h,2h, 4h, 24h ATM P Ku70 Ku80 P NHEJ repair Pathway DNApK Cytogenetic abnormalities MRE11 MRE11 dependant recombination Pathway Micronuclei number 7 C. Adam, IRPA13, Glasgow, May 16th, /14

8 ZF4 cells (embryonic fibroblasts) Uranium induces DSB in ZF4 cells 5 µm QuickTime et un décompresseur sont requis pour visionner cette image. Pereira et al, Aquatic Toxicology, 2011 No cytotoxicity up to 500 µm Increase of the nb of γ-h2ax foci per cell up to 100 µm 8 C. Adam, IRPA13, Glasgow, May 16th, /14

9 Occurrence of SSBs concomitant to DBSs formation Alkaline comet assay Pereira et al, Aquatic Toxicology, 2011 C. Adam, IRPA13, Glasgow, May 16th, /14

10 Genotoxicity of uranium on ZF4 cells Increasing of U precipitates with the decrease of DSBs QuickTime et un décompresseur sont requis pour visionner cette image. U QuickTime et un décompresseur sont requis pour visionner cette image. U C. Adam, IRPA13, Glasgow, May 16th, /14 Pereira et al, AquaticToxicology, 2011

11 Genotoxicity of uranium on ZF4 cells Urchins-like thin needle-shaped uranium structures, mainly concentrated in lyzosome-like vesicles M. Floriani C. Adam, IRPA13, Glasgow, May 16th, /14 Pereira et al, Aquatic Toxicology,

12 Unrepaired DBSs at low U concentrations QuickTime et un décompresseur sont requis pour visionner cette image. Pereira et al, Aquatic Toxicology, 2011 NHEJ repair was disrupted in uranium contaminated ZF4 cells: no DNApK foci was observed after 24 h of 10 µm uranium exposure C. Adam, IRPA13, Glasgow, May 16th, /14

13 Conclusions Uranium induces DNA SSBs, DSBs and micronuclei These damages are probably linked to U reprotoxicity (similar internal [U] concentrations for in vivo & in vitro studies) UO µg/l ZF4 cells gonad cells H2AX Uranium detoxication in lyzosome-like structures may explain the low cytotoxicity (< 10 %) Inhibition of NHEJ (DNA PK) complemented by another non specific DNA repair mechanism? C. Adam, IRPA13, Glasgow, May 16th, /14

14 Thank you for your attention ANR HEMI-BREAKS Envirhom project 14 C. Adam, IRPA13, Glasgow, May 16th, /14