Bisphenol A enhances retinoic acid-HOX genes signaling disrupting brain development: human

Plastic pollution and exposure to endocrine- disrupting chemicals (EDCs) like Bisphenol A (BPA) are emerging environmental concerns with potential impacts on human health and development. Despite evidence from epidemiological studies linking chemical exposure1,2 to neurodevelopmental disorders such as autism spectrum disorder and attention deficit hyperactivity disorder, the underlying causal mechanisms remain unclear3. Here, we show quantitative evidence that chemical exposure and detrimental outcomes are mechanistically linked to interference with retinoic acid (RA) signaling, a critical pathway in brain and neuronal development. Utilizing human induced pluripotent stem cells and zebrafish embryos, we found that BPA potentiated exogenous RA effects on 3′HOX gene expression and brain patterning, resulting in abnormalities such as duplication of Mauthner cell and abnormal craniofacial cartilage defects. Crucially, this potentiation effect was abolished by retinoic acid receptor antagonists but not estrogen receptor antagonists, suggesting a direct interaction with RA signaling pathways. Notably, the phenomenon was also observed with other chemicals, indicating a potential generalizable mechanism for a broader range of EDCs. Our findings provide a causal link between chemical exposure and neurodevelopmental impairments, contributing to the potential adverse effects of plastic pollution on development processes. Human iPS cells (409B2, RBRC-HPS0076) were maintained on mitomycin C-treated SNL cell monolayer on gelatin-coated 6 cm dishes in human iPS medium consisting of DMEM/HAM-F12 (Nacalai Tesque) supplemented with 20% KnockOutTM Serum Replacement (Thermo Fisher Scientific), 2 mM L-Alanyl-L-Glutamine (Wako Pure Chemical Industries), 0.11 mM β-mercaptoethanol (Sigma-Aldrich), 1% non-essential amino acids (Nacalai Tesque), 5 ng/mL human recombinant basic fibroblast growth factor (hbFGF; Wako Pure Chemical Industries), and 0.5% penicillin-streptomycin (Nacalai Tesque). Before differentiation, iPS cells were transferred onto feeder-free conditions using E8 medium (Thermo Fisher Scientific) and reseeded onto a 24-well plate with 1.5 × 10^5 cells/well. The next day, the medium was replaced with E6 medium (Gibco), and chemicals were added for 3 d from the following day. The medium was changed every day, and the cells were collected on the fourth day after addition. To treat cells with 100 nM RA, we prepared 1 µM RA in E6 medium from 1 mM RA stock solution in DMSO by diluting 1:1000 with E6 medium. One-tenth volume (100 µL) of 1 µM RA solution was added into the well to make the final concentration to 100 nM. As a control, the same amount of DMSO solution (0.1% in medium) was added.