Comparative genotoxicity of aluminium and cadmium in embryonic zebrafish cells

Aluminium is a toxic metal whose genotoxicity has been scarcely studied in aquatic species and more generally in mammals. Recently, human and ecological disaster caused by the discharge of red mud in Hungary has revived questions about the toxicity of this metal particularly for the environment. On the contrary, cadmium is a highly toxic metal whose genotoxicity has been well characterized in various mammalian cells. However on non-human cells, little is known about its impact on DNA damage and repair. In this study, the genotoxic potential of both metals on embryonic zebrafish cells ZF4 was analyzed and particularly the impairment of the major DNA double strand breaks (DSB)-repair pathway, i.e. non-homologous end-joining (NHEJ). To this aim, DNA single strand breaks (SSB) and DSB were evaluated using the comet assay and the immunodetection of γ-H2AX proteins, respectively, in AlCl(3) or CdCl(2) exposed ZF4 cells. These exposures result in the production of DSBs a few hours after incubation. The DNA-PK kinase activity, essential for NHEJ, is more affected by the presence of aluminium than cadmium. Altogether our data provide evidence of the high toxicity induced by aluminium in zebrafish and indicates the pertinence of genotoxicity evaluation in organisms living in contaminated water.