Zinc oxide nitrogen oxide crosses the placental barrier and induces fetal malformations through activation of the Wnt/β-catenin signaling pathway

In the recent years, zinc oxide nanoparticles (ZnO NPs) exhibit attractive attention due to their special physical and chemical properties. With the wide applications of ZnO NPs in nanoproducts, the potential risk increased more concerns. Previous studies have revealed that ZnO NPs induced oxidative stress and eventually the cancer process. However, critical knowledge on the adverse effects of ZnO NPs was associated with fetal toxicity. Here, we conducted a systematic investigation to observe the ZnO NP-induced reproductive and developmental toxicity and explore the potential toxic mechanisms. Based on the vital role of Wnt pathway in embryonic development, we supposed that Wnt/β-catenin pathway might contribute to ZnO NP-induced fetal toxicity. After oral administration of ZnO NPs (100 and 200 mg/kg) and ZnCl 2 (20 mg/kg) for 14 consecutive days by gavage, we observed ZnO NP-accumulation in maternal and fetal organs as well as fetal growth and development. Meanwhile, we also observed several protein expressions related to the Wnt pathway. We found that after crossing the placental barrier, ZnO NPs accumulated in the fetal liver and induced fetal malformations. Furthermore, the protein expressions of clathrin, caveolae, Wnt-1, and β-catenin were dose-dependent increase. These results demonstrated that ZnO NPs might cross the placental barrier via clathrin and caveolae-mediated endocytosis. In addition, the activation of Wnt/β-catenin pathway might play a role in ZnO NPs inducing fetal growth restriction and malformations. Overall, our study provided a basic understanding of the reproductive toxicity of ZnO NPs to pregnant mice and indicated that the pregnancy was vulnerable to nanotoxicity.