Regulation of PACAP gene expression by ovarian sex steroids and kisspeptin: Study using hypothalamic cell lines and an <i>in vivo</i> female rat model.
PACAP expression in the hypothalamus is influenced by kisspeptin and may not be directly regulated by estradiol or progesterone.
Where it sits
this study against the rest of the kisspeptin (kp-10) corpusSummary and findings
The study examined the effects of sex steroid hormones on PACAP gene expression and the interaction between PACAP and kisspeptin in hypothalamic cell lines and an in vivo rat model. Dihydrotestosterone (DHT) slightly increased PACAP expression, while kisspeptin-10 significantly increased PACAP expression. Estradiol (E2) reduced PACAP expression in ovary-intact female rats.
Abstract
<h4>Objective</h4>We investigated the effects of sex steroid hormones on hypothalamic PACAP expression. In addition, the mutual interaction of PACAP and kisspeptin was examined using hypothalamic cell models and an <i>in vivo</i> rat model.<h4>Materials and methods</h4>The effects of estradiol (E2), progesterone (P4), and dihydrotestosterone (DHT) on PACAP gene expression was examined using the GT1-7, rHypoE-8, and mHypoA-55 cell lines. The effect of PACAP on Kiss-1 gene expression and the effect of kisspeptin on PACAP gene expression were also examined. In addition, PACAP and Kiss-1 gene expression in the hypothalamus was determined in ovariectomized (OVX) and ovary-intact rats with and without sex steroid hormone supplementation.<h4>Results</h4>PACAP gene expression was not modulated by E2 or P4 stimulation, but DHT stimulation slightly increased its expression in GT1-7, rHypoE-8, and mHypoA-55. Stimulation with 100 nM PACAP significantly increased Kiss-1 gene expression in all three hypothalamic cell lines. Similarly, stimulation with 100 nM kisspeptin-10 also increased PACAP gene expression. PACAP gene expression within the posterior part of the hypothalamus was increased after OVX, and the OVX-induced increase in PACAP gene expression was suppressed by supplementation with E2, P4, and DHT, showing a pattern similar to that observed for Kiss-1 gene expression. In ovary-intact female rats, E2 administration, but not P4 or DHT, reduced PACAP gene expression.<h4>Conclusion</h4>PACAP expression within the hypothalamus may not be regulated directly by E2 and P4. Although PACAP and kisspeptin mutually interact and regulate each other, PACAP expression might be under the strong influence of kisspeptin neurons.
Background
This paper addresses the regulation of PACAP gene expression by sex steroid hormones and the interaction between PACAP and kisspeptin. Prior research indicated that PACAP plays a role in reproductive functions, but the influence of sex steroids on its expression was not fully understood. This study aims to clarify these interactions and their implications for hypothalamic function.
Methods
The study utilized hypothalamic cell lines (GT1-7, rHypoE-8, mHypoA-55) to assess the effects of estradiol (E2), progesterone (P4), and dihydrotestosterone (DHT) on PACAP expression. It also examined PACAP and Kiss-1 gene expression in ovariectomized and ovary-intact rats with and without hormone supplementation. Specific doses and durations were not reported in the abstract.
Results
PACAP gene expression was not modulated by E2 or P4, while DHT slightly increased its expression. Stimulation with 100 nM PACAP significantly increased Kiss-1 gene expression in all three hypothalamic cell lines. Additionally, 100 nM kisspeptin-10 increased PACAP gene expression. PACAP expression increased after OVX but was suppressed by E2, P4, and DHT supplementation. E2 reduced PACAP gene expression in ovary-intact female rats.
Interpretation
The findings suggest that PACAP expression is not directly regulated by E2 and P4, contrasting with previous assumptions. The mutual interaction between PACAP and kisspeptin indicates a complex regulatory network, yet the clinical significance of these findings remains unclear. Limitations such as the reliance on cell lines and animal models may affect the applicability of these results to human conditions.
Key findings
- DHT stimulation slightly increased PACAP expression in GT1-7, rHypoE-8, and mHypoA-55 cell lines.
- 100 nM PACAP significantly increased Kiss-1 gene expression in all three hypothalamic cell lines.
- 100 nM kisspeptin-10 increased PACAP gene expression.
- PACAP gene expression increased after ovariectomy (OVX) and was suppressed by E2, P4, and DHT supplementation.
- E2 administration reduced PACAP gene expression in ovary-intact female rats.
Limitations
- Primarily used cell lines and an animal model.
- Small sample size not reported.
- Short duration of hormone treatment not specified.
- Not applicable to human physiology without further research.