Aluminum exposure alters oocytes spindle, and tadpole behavior with modifications of proteasome and oxidative stress markers in Xenopus laevis

Abstract

Aluminum, a non-essential metal, identified as potentially toxic to organisms, is increasingly released and accumulated into the aquatic ecosystems as a result of human activities. However, only a few data are available regarding its action in aquatic vertebrates during their early stages of development. In order to further investigate the toxicity mechanisms induced by this metal, we used a relevant model in ecotoxicology Xenopus laevis. Oocytes and embryos were exposed to aluminum sulfate (Al₂(SO₄)₃), at various concentrations, ranging from environmentally relevant levels to those known to cause toxicity. The results indicate that during oocyte maturation, abnormalities in meiotic spindles were observed at concentrations ranging from 0.05 to 50 mg/L. At these exposure concentrations, the fertilization efficiency, phenotypes and cardiac rhythms of tadpoles were not affected. On the contrary, at 50 mg/L, the behavior of 6 days tadpoles was modified towards a longer hypoactivity. Concomitantly, Western blot analysis showed that heat shock Hsp70 and proteasome Rpn10 were increased, while, oxidative stress markers Sod1, Gst, and Nrf2 were decreased. Our work identifies aluminum as a threat to oocyte maturation and tadpole behavior in Xenopus laevis potentially impacting their population dynamics. Moreover, Nrf2 and Rpn10 are uncovered as potential toxicity markers for this early tadpole period and could serve to evaluate aluminum exposure in aquatic species.