Graphene oxide enhanced the endocrine disrupting effects of bisphenol A in adult male zebrafish: Integrated deep learning and metabolomics studies

In our previous studies, it was found that graphene oxide (GO) reduced the endocrine disruption of bisphenol A (BPA) in zebrafish embryo and larvae, but through different mechanisms. In this study, adult male zebrafish were selected to further understand the interactions between GO and BPA considering that adult zebrafish have different uptake pathways and metabolism from embryo and larvae. BPA was predicted to bind with the estrogen receptor α (ERα) with a probability of 98.1% by training a directed-message passing deep neural network model, and was confirmed by molecular docking analysis. The results were in accordance with the significantly increased vitellogenin (VTG) and estradiol (E2) levels, while decreased testosterone (T) and follicle-stimulating hormone (FSH) levels in the adult male zebrafish after 7 d exposure to 500 μg/L BPA. Compared to BPA single exposure group, the presence of GO led to significantly lower T and FSH levels and fewer spermatozoa, indicating that GO enhanced the endocrine disruption effects of BPA in the adult zebrafish. Metabolomics analysis revealed that 5 μg/L BPA could elicit changes in the metabolome, and the responses were correlated with BPA concentrations. Metabolic pathway analysis revealed more disturbance was caused by the mixture of GO and BPA compared to BPA alone, including three additional pathways and stronger perturbations on carbohydrate, lipid, and amino acid metabolism, fortifying that GO exaggerated the toxic effects of BPA. This was opposite to the depression effect observed in zebrafish embryo and larvae, magnifying that the joint effects of exposure to nanomaterials and endocrine disrupting chemicals are relevant to the life stages of organisms.