17-Beta-Estradiol Directly Regulates the Expression of Adrenergic Receptors and Kisspeptin/GPR54 System in GT1-7 GnRH Neurons

Abstract

Estradiol plays a critical role in the feedback regulation of reproduction, in part by modulating the neurosecretory activity of gonadotropin-releasing hormone (GnRH) neurons. While indirect effects of estradiol on GnRH neurons have been clearly demonstrated, direct actions are still controversial. In the current study, we examined direct effects of 17β-estradiol upon the expression of receptors for afferent signals at the level of the GnRH neuron, using immortalized GT1-7 cells. Using RT-PCR, we confirmed the expression of mRNA for the adrenergic receptors (AR) α₁A-, α₁B-, α₁D-, α₂A-, α₂C-, and β₁-AR, and showed for the first time that mRNAs for α₂B-, β₂- and β₃-AR, for kisspeptin and its receptor GPR54 and for the novel estrogenic receptor GPR30 are expressed in GT1-7 cells. After treatment with 10 nM 17β-estradiol, α₁B-AR mRNA was significantly increased (14-fold) after 6 h as determined by real-time PCR, while α₁B- and α₁D-AR mRNA were significantly increased (19- and 23-fold, respectively) after 24 h. The expression of KiSS-1 and GPR54 mRNAs were also significantly increased (8- and 6-fold, respectively) after 24 h treatment of GT1-7 cells with estradiol. GPR30 mRNA expression was not affected by estradiol. Our data also showed that kisspeptin-10 (1–10 nM) can significantly stimulate GnRH release and GnRH mRNA expression in GT1-7 cells. These results suggest that the complex physiologic effects of estradiol on the function of the reproductive axis could be mediated partly through direct modulation of the expression of receptors for afferent signals in GnRH neurons.

Molecular Identification of the Kiss2/Kiss1ra System and Its Potential Function During 17Alpha-Methyltestosterone-Induced Sex Reversal in the Orange-Spotted Grouper, Epinephelus coioides1

“…Although most studies have demonstrated a stimulatory role for KISS1 on GnRH release, KISS-10 (1-10 nM) can significantly stimulate Gnrh mRNA expression in GT1-7 cells [36]. A direct effect of grouper Kiss2-10 on gnrh1 is consistent with the situation in mammals where KISS1 regulates Gnrh1 (mammalian gnrh).…”

Kisspeptin antagonist prevents RF9-induced reproductive changes in female rats

“…Kisspeptin was demonstrated to increase the intracellular calcium concentration [Ca 2C ] i in isolated GnRH neurons (Kroll et al 2011) as well as in hypothalamic GT1-7 immortalized cell lines (Ozcan et al 2011). Furthermore, GnRH secretion was increased in kisspeptin-activated GT1-7 cells (Jacobi et al 2007, Novaira et al 2009, Tonsfeldt et al 2011. Taken together, these findings implicate an important role for kisspeptin/GPR54 for the regulation of sexual maturation and the development of the reproductive system.…”

Kisspeptin Induces Dynamic Chromatin Modifications to Control GnRH Gene Expression

“…Kisspeptin has been shown to be a key component in the regulation of GnRH secretion [14,15,36,37], and investigations have correlated GnRH gene expression to secretion in response to kisspeptin stimulation [17,18]. Our recent studies aimed at elucidating the mechanism of GnRH gene regulation and the activation of the GnRH promoter by kisspeptin have provided new insight into possible mechanisms regulating GnRH gene expression [7,18,38].…”

“…In addition, studies on the role of kisspeptin in the GnRH neuron have largely focused on cellular secretion of GnRH [14][15][16], and interestingly, more recent studies have related GnRH gene expression to secretion in response to kisspeptin stimulation [7,17,18]. Furthermore, in this context, through our previous studies using mouse-derived immortalized GnRH-secreting neuronal cell lines (GT1-7 and GN11) and transgenic mouse models, we have investigated the role of kisspeptin in modulating GnRH transcription/translation activity [7].…”