Insights into the modes of action of tritium on the early-life stages of zebrafish, Danio rerio, using transcriptomic and proteomic analyses.

In the environment, populations are exposed to different kinds of ionizing radiation. Little is known about their modes of action on non-human species, and whether or not they are similar for alpha, beta and gamma radiations, considered as the reference. In this context, tritium effects (beta emitter) under the form of tritiated water (HTO) were investigated in zebrafish, a common model in toxicology and ecotoxicology with a fully sequenced genome. Experiments were conducted on early life stages, considered to be highly sensitive to pollutants, by exposing eggs to 0.4 mGy/h of HTO until 10 days post fertilization. Tritium internalization was quantified, and effects were investigated using a combined approach of transcriptomic and proteomic analyses. Results highlighted similarities in the biological pathways affected by HTO by both techniques, such as defence response, muscle integrity and contraction, and potential visual alterations. These results correlated well with previous data obtained on earlier developmental stages (1 and 4 dpf). Interestingly, HTO effects were partly overlapping those obtained after gamma irradiation, underlying potential common modes of action. This study, therefore, brought a body of evidence on the effects of HTO observed at the molecular level on zebrafish larvae. Further studies could investigate if the effects persist in adult organisms.