Prenatal amoxicillin exposure impairs mouse alveolar development via Tet3-mediated hypo-hydroxymethylation of Nkx2-1 promoter.

Prenatal exposure to antibiotics is an emerging environmental risk factor for fetal development; however, the impact of amoxicillin (Amo)-one of the most frequently prescribed antibiotics-on alveolarization remains poorly understood. In the present study, we established a mouse model of maternal Amo exposure to investigate its developmental toxicity and underlying mechanisms. Histological and ultrastructural examinations revealed that prenatal Amo exposure resulted in marked alveolar simplification and injury to alveolar type II (AT2) epithelial cells, characterized by mitochondrial swelling and compromised lamellar bodies. Mechanistically, we demonstrated that Amo exposure disrupted the Tet3-Nkx2-1 axis. Specifically, Amo exposure downregulated the DNA dioxygenase Tet3, leading to a reduction in 5-hydroxymethylcytosine (5-hmC) (hypo-hydroxymethylation) levels at the Nkx2-1 promoter region, thereby silencing the transcription of Nkx2-1 and its downstream target Sftpc. Notably, administration of Vitamin C, a cofactor for Tet enzymes, effectively reinstated Tet3-mediated hydroxymethylation, restored Nkx2-1 expression, and alleviated the observed pulmonary defects both in vitro and in vivo. These findings uncover a novel epigenetic mechanism linking maternal Amo exposure to impaired alveolar development and suggest Vitamin C supplementation as a potential therapeutic strategy to mitigate antibiotic-induced developmental toxicity.