The toxic effects and possible mechanisms of Brusatol on mouse oocytes.

Brusatol is a natural quassinoid that shows a potential therapeutic use in cancer models by the inhibition of Nuclear factor erythroid 2-related factor 2 (Nrf2) and is capable of inducing a variety of biological effects. The effects of Brusatol on oocyte meiosis has not been addressed. In this study, we investigated the impact of Brusatol treatment on mouse oocyte maturation and its possible mechanism. Our data demonstrated that Brusatol treatment disrupted oocyte maturation and spindle/chromosome organization by modulating Nrf2-Cyclin B1 pathway, as the influence of Brusatol was compensated by the addition of Nrf2 activation plasmid, and the mRNA and protein levels of Cyclin B1 were severely reduced in oocytes following Nrf2 decline. In summary, our data support a model that Brusatol, through the inhibition of Nrf2, modulate Cyclin B1 levels, consequently disturbing proper spindle assembly and chromosome condensation in meiotic oocytes.