The Effects of Tetrachlorobisphenol a on Puberty Initiation in Wistar Rats and the Molecular Mechanism

Abstract

Humans are widely exposed to tetrachlorobisphenol A (TCBPA) which has a negative impact on the reproduction. However, few studies have investigated the neuroendocrine interference mechanism of the reproductive toxicity of TCBPA. This study investigated the influence of TCBPA (0, 50, 100 and 200 mg/kg bw/day) on the onset time of puberty in Wistar rats and the related molecular mechanisms by combing in vitro GT1-7 cells and molecular docking. TCBPA at 100 and 200 mg/kg bw/day markedly advanced the vaginal opening time of rats and increased the serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and gonadotropin-releasing hormone (GnRH) involved in puberty initiation. TCBPA exposure elevated the expression of kisspeptin/G protein-coupled receptor 54 (GPR54)/GnRH (KGG)-related proteins and genes in GT1-7 cells. Similarly, the relative gene expression of LH receptor (LHR), GnRH1 and FSH receptor (FSHR) also increased in hypothalamus/pituitary/gonadal (HPG) axis-related tissues of rats. Furthermore, TCBPA activated the extracellular-regulated protein kinase 1/2 (Erk1/2) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) pathways by G protein-coupled estrogen membrane receptor 1 (GPER1) and estrogen receptor alpha (ERα). The specific inhibitors related to ERα and GPER1-modulated PI3K/Akt and Erk1/2 signals reversed the expression of the GnRH1, FSHR, and LHR genes induced by TCBPA. Together, these findings demonstrated that TCBPA-induced advance of puberty initiation primarily resulted from the secretion increase of LH, GnRH, and FSH, and the upregulation of GnRH1, FSHR, and LHR genes in female Wistar rats. In addition, ERα and GPER1-modulated Erk1/2 and PI3K/Akt signals played pivotal roles in this process. This study is the first to provide a comprehensive understanding of the neuroendocrine toxicity of TCBPA and the associated molecular mechanisms by using in vitro and in vivo experiments, and molecular docking methods.

Keywords: GT1-7 neuronal cells, neuroendocrine toxicity, molecular docking, kisspeptin/GPR54-GnRH system, molecular mechanism