Retinoic acid regulates gonadotropin-releasing hormone (GnRH) release and gene expression in the rat hypothalamic fragments and GT1-1 neuronal cells in vitro

Sehyung Cho, Hyeseong Cho, Dongho Geum, Kyungjin Kim

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The present study attempts to examine the possible involvement of retinoic acid (RA) in the regulation of gonadotropin-releasing hormone (GnRH) release and gene expression in the rat hypothalamic fragments and GT1-1 neuronal cells in vitro. During a short-term period (2 h), RA (0.01-1 μM) increased GnRH release in a dose-related manner. Time-course experiments showed that RA rapidly increased GnRH release by 30 min in both cells. RA-induced GnRH release was slowly attenuated in the next incubation period in hypothalamic fragments, but rapidly returned to control levels in GT1-1 cells. In hypothalamic fragments, GnRH mRNA levels decreased, but in GT1-1 cells, no change in GnRH mRNA levels was observed. We then extended the incubation time to see any changes in GnRH mRNA levels by RA in GT1-1 cells. In a long term (up to 48 h), RA increased GnRH mRNA levels in a dose- and time-related manner. Significant increase in GnRH mRNA levels by RA (at higher than 10 nM) was observed within 12 h. Transient transfection experiments with a luciferase reporter vector containing more than 3 kb of the rat GnRH 5'-flanking region ( -3002 to +88) revealed that RA also increased the rat GnRH promoter activity in a similar dose- and time-dependent manner, suggesting that increases in GnRH mRNA levels are attributable, at least in part, to the enhanced gene transcription. The promoter analysis with the 5'-deletional constructs demonstrated that cis-elements responsible for the RA action may reside within -1640/ -1438 of the rat GnRH promoter, where multiple direct or palindromic arrangements of the AGGTCA-related sequences exist. We also showed that GT1-1 cells as well as the hypothalamic tissues express mRNA for multiple subtypes of retinoid receptors, and that reporter plasmids with three copies of the strong retinoic acid response element (RARE) were activated by 80 folds upon treatment with RA in GT1-1 cells, suggesting that retinoid receptors in GT1-1 cells are functional. Taken together, the present study strongly suggests that RA is an important regulator of the GnRH neurons.

Original languageEnglish
Pages (from-to)74-84
Number of pages11
JournalMolecular Brain Research
Volume54
Issue number1
DOIs
Publication statusPublished - 1998 Feb 1
Externally publishedYes

Fingerprint

Tretinoin
Gonadotropin-Releasing Hormone
Gene Expression
Messenger RNA
Retinoids
In Vitro Techniques
5' Flanking Region
Response Elements
Luciferases
Transfection
Plasmids

Keywords

  • GnRH release
  • Gonadotropin-releasing hormone
  • GT1-1 cells
  • Retinoic acid
  • Transcriptional regulation

ASJC Scopus subject areas

  • Molecular Biology
  • Cellular and Molecular Neuroscience

Cite this

Retinoic acid regulates gonadotropin-releasing hormone (GnRH) release and gene expression in the rat hypothalamic fragments and GT1-1 neuronal cells in vitro. / Cho, Sehyung; Cho, Hyeseong; Geum, Dongho; Kim, Kyungjin.

In: Molecular Brain Research, Vol. 54, No. 1, 01.02.1998, p. 74-84.

Research output: Contribution to journalArticle

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