Dibutyl phthalate promotes central precocious puberty through primordial follicle activation by downregulating BMP15

Dibutyl phthalate (DBP) has been reported to induce central precocious puberty (CPP). However, the mechanism by which DBP accelerates primordial follicle activation and contributes to CPP has not been studied. This study aims to explore the effects of DBP on puberty onset and the role of primordial follicle activation in DBP-related CPP. Female ICR pups (developed by the Institute of Cancer Research, USA) were exposed to DBP from PND5 to PND20. Vaginal opening, a marker of puberty onset, was monitored daily staring from PND20. The involvement of the hypothalamus-pituitary-ovary axis (HPOA) was evaluated, and the activation of primordial follicles was analysed. To investigate the role of primordial follicle activation in CPP development, masitinib was used to establish a model of primordial follicle silencing. Additionally, a neonatal ovary in vitro culture model was developed to explore the mechanism by which DBP accelerates primordial follicle activation. Compared to the control group, the DBP-exposed group exhibited significantly earlier vaginal opening. The hypothalamic gene expression of KISS1, GPR54, as well as serum levels of LH and E2, were elevated. Moreover, the activation of primordial follicle was accelerated in the DBP group. However, these effects were blocked by masitinib treatment. In vitro culture of neonatal ovaries revealed that DBP downregulates AMH expression via the BMP15/p38-MAPK pathway. In conclusion, our study firstly demonstrates that the activation of primordial follicles is essential for CPP development, and DBP contributes to CPP by accelerating primordial follicle activation through the BMP15/p38-MAPK/AMH pathway.