TBBPA downregulates thyroid receptor and estrogen receptor mRNA levels in goldfish gonadal tissue

Tetrabromobisphenol A (TBBPA) is a brominated flame retardant that has been shown to be a potential thyroid disrupting chemical. Currently, TBBPA is not included in the UN's list of endocrine disruptors and adverse effects of TBBPA in mammals has not been fully investigated. However, there is clear evidence that TBBPA exerts adverse health effects on reproduction of aquatic species. Therefore, it is important to provide more information on potential endocrine disruptive effects of TBBPA in vertebrate species. In this study we investigated the effect of TBBPA on transcript levels of estrogen receptors (ERs) and thyroid receptors (TRs) in the gonadal tissue of goldfish in vivo and in vitro. ERβ mRNA levels were significantly lower in testis and ovary following exposure to TBBPA. TRα mRNA levels were also downregulated in testis tissue. Importantly, these phenotypic effects occurred at lower, environmentally relevant, concentrations in vivo. Furthermore, exposure to TBBPA also reduced ERβ and TRα mRNA abundance in goldfish testes and ovaries in vivo, which is similar to previously observed T3 responses in these tissues. These findings suggest that TBBPA may be a thyroid hormone mimic, capable of disrupting reproduction by affecting steroid hormone receptors. Our findings suggest that it is important to study TBBPA as an endocrine disruptor in aquatic organisms as it may have implications for both conservation and aquaculture.