DNA and Chromosome Damaging Effects in Mice Exposed to an Estuary Sediment Extract

Abstract

Previous studies have shown that an extract of a sediment sample collected in a fishing area of Sado Estuary, impacted by the urban and industrial pollution from the city of Setúbal, was able to induce cytotoxicity and genotoxicity in a human cell line (HepG2) and in local aquatic species, probably due to the presence of PAHs and metals. However, the assessment of the potential hazard of those contaminants to humans, through extrapolation of the in vitro data, is difficult and thereby in vivo studies are crucial to better reflect human exposure and effects. This study aims to assess the in vivo DNA and chromosome damaging potential of a contaminated sediment sample from a local fishing area of the Sado Estuary. Groups of mice (n=6) were exposed, through drinking water, to two concentrations of a sediment extract (1 and 2 g SEQ/ml), as well as to solvent control, for a 28 day period. The DNA and chromosome damaging effects were monitored at 7 day intervals by the comet assay (coupled with DNA repair endonucleases FPG and ENDO III) and the micronucleus assays, performed in blood leukocytes and immature erythrocytes, respectively. After sacrifice, DNA lesions, oxidative damage and histopathological biomarkers (apoptosis and inflammation) were analysed in liver, spleen and kidney cells. Preliminary results showed that at days 7, 14 and 21, mice exposure to the highest extract dose caused a significant induction on the frequency of micronuclei comparatively to the unexposed group (p < 0.001), while exposure to the lowest dose raised the micronucleus frequency only at day 14 (p = 0.003). No induction of DNA damage or oxidative DNA damage was observed in blood cells, at the 2 first timepoints. The results of DNA damage and micronucleus quantification at the 28 days timepoint, together with data from histopathological biomarkers, will be integrated and discussed in view of the contaminants present in the sediment sample under study. Overall, the results obtained in the present in vivo study are expected to reflect the potential hazard to human health associated to the contamination of estuary water and sediments and to contribute to risk assessment