Enantioselective maternal transfer of chiral pesticide metabolite o,p’-DDD in zebrafish (Danio rerio): Implications for intergenerational thyroid disruption

Recent studies show that pesticides can induce intergenerational toxicity, posing threats to wildlife populations. However, the intergenerational effects of chiral pesticide metabolites remain understudied despite their known enantioselective bioactivities. We evaluated the maternal transfer and intergenerational impacts of chiral metabolite o,p’ - dichlorodiphenyldichloroethane ( o,p’ -DDD) in zebrafish ( Danio rerio ). Adult zebrafish (F0) were fed diets spiked with racemic o,p’ -DDD ( Rac -DDD) and its isolated S - and R -enantiomers ( S- DDD and R- DDD) at 5 and 50 ng/g for 28 days. Significant accumulation of o,p' -DDD in both F0 and their offspring (F1) was observed, with F1 larvae exhibiting higher tissue residues, indicating efficient maternal transfer. The S -enantiomer showed higher bioaccumulation, with 134–176 % higher in F0 and 103–118 % higher in F1 than R -DDD. Offspring exhibited more severe developmental abnormalities, including mortality, malformations, and reduced hatching success, in S- DDD groups. Levels of thyroid hormones triiodothyronine (T3) and thyroxine (T4) were significantly altered in F0 and F1 in an enantiomer-dependent manner. Cluster and principal component analyses (PCA) of hypothalamic-pituitary-thyroid (HPT) axis gene expression revealed enantiomer-specific regulation in both generations. In silico molecular docking further indicated stronger binding of S- DDD to proteins critical for thyroid hormone biosynthesis, development, and metabolism. These findings underscore the importance of incorporating stereochemistry when estimating the long-term ecological impacts of chiral contaminants. The zebrafish was created in BioRender. Niu, L. (2025) https://BioRender.com/guejfff • Significant maternal transfer was observed for o,p’ -DDD and its enantiomers. • S- DDD bioaccumulated 134–176 % more than R -DDD in F0 and 103–118 % more in F1. • Thyroid hormones were altered enantiomer-dependently in both F0 and F1 zebrafish. • In silico docking showed higher S -DDD affinity for key HPT-axis proteins. • Stereoselective regulation of HPT-axis gene expression was observed in zebrafish.