Maternal di-n-butyl phthalate exposure promotes renal fibrosis in IUGR offspring rats via HBB downregulation and Nrf2 pathway activation

Di-n-butyl phthalate (DBP) is an environmental endocrine disruptor with developmental nephrotoxicity, but its long-term effects on renal fibrotic remodeling in offspring remain incompletely understood. In this study, a maternal DBP exposure model was established in pregnant Sprague-Dawley rats (750 mg/kg/day, GD14-GD18), and adult male offspring were examined at postnatal day 42. DBP-exposed offspring showed intrauterine growth restriction, reduced relative kidney weight, renal collagen deposition, and epithelial-mesenchymal transition (EMT)-related molecular changes. Transcriptomic analysis identified hemoglobin subunit beta (HBB) as a prominently downregulated gene in renal tissues of DBP-exposed offspring. HBB expression was reduced by approximately four-fold and was accompanied by increased oxidative stress, including elevated reactive oxygen species and malondialdehyde levels and decreased total superoxide dismutase activity. DBP exposure was also associated with increased expression of NRF2 and its downstream antioxidant targets HO-1 and NQO1. In HK-2 cells, HBB overexpression attenuated DBP-induced oxidative stress and EMT-related marker changes, while N-acetylcysteine (NAC) reduced oxidative stress and restored HBB and EMT-related protein expression. In adult male offspring, renal AAV-HBB delivery partially restored HBB expression and reduced DBP-associated collagen deposition, oxidative stress, and EMT-related changes. These findings indicate that maternal DBP exposure is associated with adult renal fibrotic remodeling in male offspring, with HBB downregulation, oxidative stress, NRF2-related antioxidant responses, and EMT-related alterations as key molecular features. HBB may serve as a candidate biomarker and intervention target for DBP-associated developmental nephrotoxicity, pending further validation.