Evidence for autocrine inhibition of gonadotropin-releasing hormone (GnRH) gene transcription by GnRH in hypothalamic GT1-1 neuronal cells

Abstract

To examine whether an ultrashort feedback mechanism of gonadotropin-releasing hormone (GnRH) operates at the level of gene transcription, we studied the effects of GnRH analogs on GnRH promoter activity and GnRH mRNA level in hypothalamic GT1–1 neuronal cells. Treatment of GT1–1 cells with buserelin, a GnRH agonist, or native GnRH for 24 h significantly decreased GnRH promoter activity and its mRNA level, whereas that with GnRH antagonists, antide or [ D-Phe 2, D-Ala 6]-GnRH, showed no effect. The inhibitory effects of buserelin on GnRH gene transcription and GnRH mRNA level were dose-related, and a significant inhibition was observed in cells treated with buserelin at concentrations higher than 0.1 μM. Time-course experiments showed that significant decreases in GnRH promoter-driven luciferase activity and GnRH mRNA level were observed within 12 h and sustained up to 48 h. Moreover, treatment with GnRH agonist for 12 h significantly decreased the transcription rate of the mouse GnRH gene, as revealed by nuclear run-on transcription assay. The promoter analysis with the 5′-deletional constructs demonstrated that cis-acting elements important for GnRH autoregulation by GnRH agonist reside within −854 bp upstream from the transcription start site. These data clearly demonstrate that GnRH can exert autocrine regulation at the level of GnRH gene transcription.