Functional roles of NR4A transcription factors in GnRH regulation of gonadotropin gene expression and secretion in rat primary pituitary cells

Gonadotropin-releasing hormone (GnRH) tightly regulates the synthesis and the release of gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), while the intracellular molecular mechanisms following GnRH signal for the regulation of transcription remain incompletely understood. In this study, we used primary culture of rat anterior pituitary cells to investigate the role of NR4A transcription factors (NR4A1, NR4A2, and NR4A3) in GnRH regulation of gonadotropin secretion. GnRH agonist stimulation rapidly and transiently increased Nr4a1, Nr4a2, and Nr4a3 expression within one hour, accompanied by a time-dependent increase in Fshb mRNA levels and the secretion of both FSH and LH. The knockdown of each Nr4a gene using siRNA significantly reduced Fshb expression under GnRH stimulation. Nr4a1 knockdown caused the most pronounced decrease in FSH secretion. Although Lhb and Cga mRNA levels were largely unaffected, LH secretion was consistently reduced following NR4A knockdown. These findings suggest that NR4A transcription factors act downstream of GnRH signaling to promote Fshb transcription and facilitate gonadotropin secretion, thereby modulating GnRH-dependent control of FSH and LH secretion.