Cytotoxicity and genotoxicity of lanthanides for Vicia faba L. are mediated by their chemical speciation in different exposure media

A comprehensive study of the toxicity of lanthanides (LN) in relation to the media composition will enhance the prediction of their potential adverse effects for living organisms. Here we examined the effect of different media on the V. faba root elongation and on the cytotoxic (mitotic index) and the genotoxic (micronucleated cell number) effects from toxicity tests with Ce, Gd and Lu (100, 800 and 6400 μg L^-1). Three different exposure media were selected: the standard Hoagland media (SH); an alternative SH, without phosphates (SH-P); and distilled water (DW). In the SH no cyto-genotoxic effects were observed and even, for low LN content, potential root elongation stimulation was reported. The absence of toxic effects was explained by a drastic decrease of the total dissolved LN concentration due to the presence of phosphates causing LN precipitation. In SH-P, LN remained largely soluble and inhibition of root elongation was observed mainly for the highest treatments. While in the tests done in DW, toxic effects were obtained for all treatments. Our results showed that in absence of phosphorous, LN appear mainly as free form and complexed in carbonates and sulphates, and can cause toxic effects, whereas toxicity is not expected when phosphorous is available in aquatic media. The highest LN root contents were observed for the tests using distilled water, possibly due to the absence of competition by Ca²⁺ for uptake. The present work demonstrated that media composition has a great impact in assessing the ecotoxicology of lanthanides.

Very low concentration of cerium dioxide nanoparticles induce DNA damage, but no loss of vitality, in human spermatozoa

Cerium dioxide nanoparticles (CeO₂NP) are widely used for industrial purposes, as in diesel, paint, wood stain and as potential therapeutic applications. The Organization for Economic Cooperation and Development included CeO₂NP in the priority list of nanomaterials requiring urgent evaluation. As metal nanoparticles can cross the blood-testis barrier, CeO₂NP could interact with spermatozoa. The genotoxicity of CeO₂NP was demonstrated in vitro on human cell lines and mouse gametes. However, the effects of CeO₂NP on human spermatozoa DNA remain unknown. We showed significant DNA damage induced in vitro by CeO₂NP on human spermatozoa using Comet assay. The genotoxicity was inversely proportional to the concentration (0.01 to 10 mg·L^-1). TEM showed no internalization of CeO₂NP into the spermatozoa. This study shows for the first time that in vitro exposure to very low concentrations of cerium dioxide nanoparticles can induce significant DNA damage in human spermatozoa. These results add new and important insights regarding the reproductive toxicity of priority nanomaterials, which require urgent evaluation.

A new approach for the oocyte genotoxicity assay: adaptation of comet assay on mouse cumulus–oocyte complexes

Conventional genotoxicity tests are technically difficult to apply to oocytes, and results obtained on somatic cells cannot be extrapolated to gametes. We have previously described a comet assay (original–CA) on denuded mouse oocytes, but, in vivo, oocytes are not isolated from their surrounding follicular cells. Our objective was to develop a comet assay on cumulus–oocyte complexes (COC–CA) for a more physiological approach to study the genotoxicity of environmental factors on oocytes. For COC–CA, whole COC were exposed directly to exogenous agents after ovulation and removal from oviducts. Three conditions were studied: a negative control group, and two positive control groups, one of which was exposed to hydrogen peroxide (H2O2) and the other group was incubated with cerium dioxide nanoparticles (CeO2 NPs). With both tests, DNA damage was significant in the presence of both H2O2 and CeO2 NPs compared with the negative control. COC–CA offers an interesting tool for assaying the genotoxicity of environmental agents towards germinal cells. Furthermore, COC–CA is less time-consuming and simplifies the protocol of the original–CA, because COC-CA is easier to perform without the washing-out procedure.