Effects of Zearalenone on the Kiss1/GPR54 System and Related Genes Expression in the Hypothalamus and Pituitary Gland of Weaned Gilts

Zearalenone (ZEA) is a potent estrogenic mycotoxin known to disrupt reproductive functions, but its precise central neuroendocrine mechanisms remain unclear. This study investigated the effects of ZEA on the hypothalamic-pituitary Kiss1/GPR54 signaling pathway in weaned gilts. A total of 32 gilts were randomly assigned to four dietary treatments contained with 0, 0.15, 1.5, or 3.0 mg/kg ZEA for a 32-day feeding trial. Histopathology, immunohistochemistry, and mRNA/protein expression analyses of GPR30, Kiss1, GPR54, GnRH, and GnRHR in the hypothalamus and pituitary gland were conducted. ZEA exposure induced significant histological damage in both tissues. In the hypothalamus, Kiss1, GPR54, GnRH, and GnRHR exhibited a non-linear response, increasing at moderate doses and decreasing at 3.0 mg/kg ZEA, whereas GPR30 expression was continuously upregulated. In the pituitary gland, GnRHR showed a similar non-linear pattern. Furthermore, high-dose ZEA down-regulated pituitary Kiss1 and GPR54 while up-regulating GnRH and GPR30 expressions. In conclusion, ZEA induces reproductive neuroendocrine toxicity through a complex, dose-dependent modulation of the Kiss1/GPR54 signaling axis. The persistent upregulation of GPR30 suggests it acts as a crucial mediator in disrupting this endocrine feedback loop within the hypothalamus and pituitary gland.