Intrinsic and Regulated Gonadotropin-Releasing Hormone Receptor Gene Transcription in Mammalian Pituitary Gonadotrophs

Transcriptome analysis revealed the characteristics and functions of long non-coding RNAs in the hypothalamus during sexual maturation in goats

The hypothalamus is an essential neuroendocrine area in animals that regulates sexual development. Long non-coding RNAs (lncRNAs) are hypothesized to regulate physiological processes related to animal reproduction. However, the regulatory mechanism by which lncRNAs participate in sexual maturity in goats is poorly known, particularly from birth to sexual maturation. In this study, RNAseq analysis was conducted on the hypothalamus of four developmental stages (1day (D1, n = 5), 2 months (M2, n = 5), 4 months (M4, n = 5), and 6 months (M6, n = 5)) of Jining grey goats. The results showed that a total of 237 differentially expressed lncRNAs (DELs) were identified in the hypothalamus. Among these, 221 DELs exhibited cis-regulatory effects on 693 target genes, while 24 DELs demonstrated trans-regulatory effects on 63 target genes. The target genes of these DELs are mainly involved in biological processes related to energy metabolism, signal transduction and hormone secretion, such as sphingolipid signaling pathway, adipocytokine signaling pathway, neurotrophic signaling pathway, glutamatergic synapse, P53 signaling pathway and GnRH signaling pathway. In addition, XR_001918477.1, TCONS_00077463, XR_001918760.1, and TCONS_00029048 and their potential target genes may play a crucial role in the process of goat sexual maturation. This study advances our understanding of lncRNA in hypothalamic tissue during sexual maturation in goats and will give a theoretical foundation for improving goat reproductive features.

A decade's overview of 2-aminothiophenes and their fused analogs as promising anticancer agents

Over the past decades, cancer has been a challenging domain for medicinal chemists as it is an international health concern. In association, small molecules such as 2-aminothiophenes and their derivatives showed significant antitumor activity through variable modes of action. Therefore, this article aims to review the advances regarding these core scaffolds over the past 10 years, where 2-aminothiophenes and their fused analogs are classified and discussed according to their biological activity and mode of action, in the interest of boosting new design pathways for medicinal chemists to develop targeted antitumor candidates.

Unraveling Hypothalamus-Pituitary dysregulation: Hypergonadotropism in F1 progeny due to prenatal exposure to hexavalent chromium

The endocrine disruptor hexavalent chromium [Cr(VI)] is a proven reproductive toxicant. We recently demonstrated that prenatal Cr(VI) exposure causes testicular resistance to gonadotropins, resulting in hypergonadotropic hypoandrogenism in F1 rats. However, the mechanism driving hypergonadotropism in F1 rats exposed to Cr(VI) prenatally remains an enigma. Therefore, we hypothesized that 'Prenatal Cr(VI) exposure may disrupt steroid hormones-mediated negative feedback regulation of the hypothalamic GnRH, and its receptor in the pituitary of F1 rats, leading to hypergonadotropism.' We administered potassium dichromate (50, 100, or 200 mg/L) to pregnant rats through drinking water between days 9 and 14, and their male F1 offspring were euthanized at 60 days of age. Prenatal Cr(VI) exposure in F1 rats resulted in the accumulation of Cr in the hypothalamus and pituitary. Western blot detected decreased hypothalamic GnRH, Kisspeptin1, and its receptor GPR54, along with diminished ERα, AR, aromatase, and 5α reductase, and GnRH regulatory transcription factors Pit-1 and GATA-4 proteins. Immunohistochemical studies revealed increased immunopositivity of GnRH receptor, AR, 5α reductase, ERα, ERβ, and aromatase proteins in the pituitary, whereas decreased Kisspeptin1, GPR54, and inhibin β. Our findings imply that Cr(VI) exposure during the prenatal period disrupts the hypothalamic Kisspeptin-GPR54-Pit-1/GATA4-GnRH network, boosting the pituitary GnRH receptor. We conclude that prenatal exposure to Cr(VI) alters GnRH expression in the hypothalamus and its receptor in the pituitary of F1 progeny through interfering with the negative feedback effect of androgens and estrogens.

Postnatal Development and Maintenance of Functional Pituitary Gonadotrophs Is Dependent on PI4-Kinase A

Postnatal development of functional pituitary gonadotrophs is necessary for maturation of the hypothalamic-pituitary-gonadal axis, puberty, and reproduction. Here we examined the role of PI4-kinase A, which catalyzes the biosynthesis of PI4P in mouse reproduction by knocking out this enzyme in cells expressing the gonadotropin-releasing hormone (GnRH) receptor. Knockout (KO) mice were infertile, reflecting underdeveloped gonads and reproductive tracts and lack of puberty. The number and distribution of hypothalamic GnRH neurons and Gnrh1 expression in postnatal KOs were not affected, whereas Kiss1/kisspeptin expression was increased. KO of PI4-kinase A also did not alter embryonic establishment and neonatal development and function of the gonadotroph population. However, during the postnatal period, there was a progressive loss of expression of gonadotroph-specific genes, including Fshb, Lhb, and Gnrhr, accompanied by low gonadotropin synthesis. The postnatal gonadotroph population also progressively declined, reaching approximately one-third of that observed in controls at 3 months of age. In these residual gonadotrophs, GnRH-dependent calcium signaling and calcium-dependent membrane potential changes were lost, but intracellular administration of inositol-14,5-trisphosphate rescued this signaling. These results indicate a key role for PI4-kinase A in the postnatal development and maintenance of a functional gonadotroph population.

Musashi Exerts Control of Gonadotrope Target mRNA Translation During the Mouse Estrous Cycle

The anterior pituitary controls key biological processes, including growth, metabolism, reproduction, and stress responses through distinct cell types that each secrete specific hormones. The anterior pituitary cells show a remarkable level of cell type plasticity that mediates the shifts in hormone-producing cell populations that are required to meet organismal needs. The molecular mechanisms underlying pituitary cell plasticity are not well understood. Recent work has implicated the pituitary stem cell populations and specifically, the mRNA binding proteins of the Musashi family in control of pituitary cell type identity. In this study we have identified the target mRNAs that mediate Musashi function in the adult mouse pituitary and demonstrate the requirement for Musashi function in vivo. Using Musashi RNA immunoprecipitation, we identify a cohort of 1184 mRNAs that show specific Musashi binding. Identified Musashi targets include the Gnrhr mRNA, which encodes the gonadotropin-releasing hormone receptor (GnRHR), and the Fshb mRNA, encoding follicle-stimulating hormone (FSH). Reporter assays reveal that Musashi functions to exert repression of translation of the Fshb mRNA, in addition to the previously observed repression of the Gnrhr mRNA. Importantly, mice engineered to lack Musashi in gonadotropes demonstrate a failure to repress translation of the endogenous Gnrhr and Fshb mRNAs during the estrous cycle and display a significant heterogeneity in litter sizes. The range of identified target mRNAs suggests that, in addition to these key gonadotrope proteins, Musashi may exert broad regulatory control over the pituitary proteome in a cell type-specific manner.

Discovery of the thieno[2,3-d]pyrimidine-2,4-dione derivative 21a: A potent and orally bioavailable gonadotropin-releasing hormone receptor antagonist

The gonadotropin releasing hormone receptor (GnRH-R) is a G protein-coupled receptor (GPCR) belonging to the rhodopsin family. GnRH-R antagonists suppress testosterone to castrate level more rapidly than gonadotropin releasing hormone agonists but lack the flare phenomenon often seen during the early period of GnRH-R agonist treatment. Recently orgovyx (relugolix) was approved as the first oral GnRH-R antagonist for the treatment of advanced prostate cancer. However, orgovyx has demonstrated poor pharmacokinetic profile with low oral bioavailability and high efflux. Here, we rationally designed and synthesized a series of derivatives (13a-m, 21a-i) through the modification and structure-activity relationship study of relugolix, which led to the discovery of 21a as a highly potent GnRH-R antagonist (IC₅₀ = 2.18 nM) with improved membrane permeability (Papp, A-B = 0.98 × 10^-6 cm/s) and oral bioavailability (F % = 44.7). Compound 21a showed high binding affinity (IC₅₀ = 0.57 nM) and potent in vitro antagonistic activity (IC₅₀ = 2.18 nM) at GnRH-R. 21a was well tolerated and efficacious in preclinical studies to suppress blood testosterone levels, which merits further investigation as a candidate novel GnRH-R antagonist for clinical studies.

In utero exposure to dipentyl phthalate disrupts fetal and adult Leydig cell development

Phthalates as plasticizers are widely used in many consumer products. Dipentyl phthalate (DPeP) is one of phthalates. However, there are currently few data on whether DPeP exposure affects rat Leydig cell development. In this study, we investigated the effects of in utero DPeP exposure on Leydig cell development in the testes of male newborn and adult rats. From gestational days 14 to 21, Sprague-Dawley pregnant rats were gavaged vehicle (corn oil, control) or DPeP (10, 50, 100, and 500 mg/kg body weight/day). Testosterone and the expression of Leydig cell genes and proteins in the testis at birth and at postnatal day 56 were examined. DPeP dose-dependently reduced serum testosterone levels of male offspring at birth and at postnatal day 56 at 100 and 500 mg/kg and lowered serum luteinizing hormone levels at adult males at ≥10 mg/kg when compared with the control. In addition, DPeP increased number of fetal Leydig cells by inducing their proliferation but down-regulated the expression of Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, and Insl3 in fetal Leydig cells per se. DPeP reduced number of adult Leydig cells by inducing cell apoptosis and down-regulated the expression of Lhcgr and Star in adult Leydig cells at postnatal day 56. DPeP lowered SIRT1 and BCL2 levels in the testis of adult rats. In conclusion, DPeP adversely affects both fetal and adult Leydig cell development after in utero exposure.

Dissecting the Hormonal Signaling Landscape in Castration-Resistant Prostate Cancer

Understanding the molecular mechanisms underlying prostate cancer (PCa) progression towards its most aggressive, castration-resistant (CRPC) stage is urgently needed to improve the therapeutic options for this almost incurable pathology. Interestingly, CRPC is known to be characterized by a peculiar hormonal landscape. It is now well established that the androgen/androgen receptor (AR) axis is still active in CRPC cells. The persistent activity of this axis in PCa progression has been shown to be related to different mechanisms, such as intratumoral androgen synthesis, AR amplification and mutations, AR mRNA alternative splicing, increased expression/activity of AR-related transcription factors and coregulators. The hypothalamic gonadotropin-releasing hormone (GnRH), by binding to its specific receptors (GnRH-Rs) at the pituitary level, plays a pivotal role in the regulation of the reproductive functions. GnRH and GnRH-R are also expressed in different types of tumors, including PCa. Specifically, it has been demonstrated that, in CRPC cells, the activation of GnRH-Rs is associated with a significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic activity. This antitumor activity is mainly mediated by the GnRH-R-associated Gαi/cAMP signaling pathway. In this review, we dissect the molecular mechanisms underlying the role of the androgen/AR and GnRH/GnRH-R axes in CRPC progression and the possible therapeutic implications.

Post-Transcriptional Regulation of Gnrhr: A Checkpoint for Metabolic Control of Female Reproduction

The proper expression of gonadotropin-releasing hormone receptors (GnRHRs) by pituitary gonadotropes is critical for maintaining maximum reproductive capacity. GnRH receptor expression must be tightly regulated in order to maintain the normal pattern of expression through the estrous cycle in rodents, which is believed to be important for interpreting the finely tuned pulses of GnRH from the hypothalamus. Much work has shown that Gnrhr expression is heavily regulated at the level of transcription. However, researchers have also discovered that Gnrhr is regulated post-transcriptionally. This review will discuss how RNA-binding proteins and microRNAs may play critical roles in the regulation of GnRHR expression. We will also discuss how these post-transcriptional regulators may themselves be affected by metabolic cues, specifically with regards to the adipokine leptin. All together, we present evidence that Gnrhr is regulated post-transcriptionally, and that this concept must be further explored in order to fully understand the complex nature of this receptor.

Perfluoroundecanoic acid inhibits Leydig cell development in pubertal male rats via inducing oxidative stress and autophagy

Perfluoroundecanoic acid (PFUnA) is one of long-chain perfluoroalkyl carboxylic acids. However, the effect of PFUnA on pubertal development of Leydig cells remains unclear. The goal of this study was to investigate the effect of PFUnA on Leydig cell development in pubertal male rats. We orally dosed male Sprague-Dawley rats (age 35 days) with PFUnA at doses of 0, 1, 5, and 10 mg/kg/day from postnatal day (PND) 35 to PND 56. Serum testosterone and luteinizing hormone levels were remarkably reduced by PFUnA at ≥1 mg/kg while serum follicle-stimulating hormone levels were lowered at 5 and 10 mg/kg. PFUnA down-regulated the expression of Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Hsd11b1, Insl3, Nr5a1, Fshr, Dhh, Sod1, and Sod2 and their proteins in the testis and the expression of Lhb and Fshb in the pituitary. PFUnA reduced Leydig cell number at 5 and 10 mg/kg. PFUnA induced oxidative stress and increased autophagy. These may result from the inhibition of phosphorylation of mTOR, AKT1, AKT2, and ERK1/2 in the testis. In conclusion, PFUnA exhibits inhibitory effects on pubertal Leydig cell development possibly via inducing oxidative stress and increasing autophagy.

Gonadotropin-Releasing Hormone Receptors in Prostate Cancer: Molecular Aspects and Biological Functions

Pituitary Gonadotropin-Releasing Hormone receptors (GnRH-R) mediate the activity of the hypothalamic decapeptide GnRH, thus playing a key role in the regulation of the reproductive axis. Early-stage prostate cancer (PCa) is dependent on serum androgen levels, and androgen-deprivation therapy (ADT), based on GnRH agonists and antagonists, represents the standard therapeutic approach for PCa patients. Unfortunately, the tumor often progresses towards the more aggressive castration-resistant prostate cancer (CRPC) stage. GnRH receptors are also expressed in CRPC tissues, where their binding to both GnRH agonists and antagonists is associated with significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic effects, mediated by the Gαi/cAMP signaling cascade. GnRH agonists and antagonists are now considered as an effective therapeutic strategy for CRPC patients with many clinical trials demonstrating that the combined use of these drugs with standard therapies (i.e., docetaxel, enzalutamide, abiraterone) significantly improves disease-free survival. In this context, GnRH-based bioconjugates (cytotoxic drugs covalently linked to a GnRH-based decapeptide) have been recently developed. The rationale of this treatment is that the GnRH peptide selectively binds to its receptors, delivering the cytotoxic drug to CRPC cells while sparing nontumor cells. Some of these compounds have already entered clinical trials.

The role of the hypothalamus and pituitary epigenomes in central activation of the reproductive axis at puberty

Puberty is programmed through a multifactorial gene network which works to activate the pulsatile secretion of the gonadotropin releasing hormone (GnRH), and subsequently elevate circulating levels of the pituitary gonadotropins that stimulate gonadal activity. Although this developmental transition normally occurs at a limited age-range in individuals of the same genetic background and environment, pubertal onset can occur prematurely or be delayed following changes in ambient conditions, or due to genetic variations or mutations, many of which have remained elusive due to their location in distal regulatory elements. Growing evidence is pointing to a pivotal role for the epigenome in regulating key genes in the reproductive hypothalamus and pituitary at this time, which might mediate some of the plasticity of pubertal timing. This review will address epigenetic mechanisms which have been demonstrated in the KNDy neurons that increase the output of pulsatile GnRH, and those involved in activation of the GnRH gene and its receptor, and describes how GnRH utilizes epigenetic mechanisms to stimulate transcription of the pituitary gonadotropin genes in the context of the chromatin landscape.

Cytogenetic, Genomic, and Functional Characterization of Pituitary Gonadotrope Cell Lines

LβT2 and αT3-1 are important, widely studied cell line models for the pituitary gonadotropes that were generated by targeted tumorigenesis in transgenic mice. LβT2 cells are more mature gonadotrope precursors than αT3-1 cells. Microsatellite authentication patterns, chromosomal characteristics, and their intercellular variation have not been reported. We performed microsatellite and cytogenetic analysis of both cell types at early passage numbers. Short tandem repeat (STR) profiling was consistent with a mixed C57BL/6J × BALB/cJ genetic background, with distinct patterns for each cell type. Spectral karyotyping in αT3-1 cells revealed cell-to-cell variation in chromosome composition and pseudodiploidy. In LβT2 cells, chromosome counting and karyotyping demonstrated pseudotriploidy and high chromosomal variation among cells. Chromosome copy number variation was confirmed by single-cell DNA sequencing. Chromosomal compositions were consistent with a male sex for αT3-1 and a female sex for LβT2 cells. Among LβT2 stocks used in multiple laboratories, we detected two genetically similar but distinguishable lines via STR authentication, LβT2a and LβT2b. The two lines differed in morphological appearance, with LβT2a having significantly smaller cell and nucleus areas. Analysis of immediate early gene and gonadotropin subunit gene expression revealed variations in basal expression and responses to continuous and pulsatile GnRH stimulation. LβT2a showed higher basal levels of Egr1, Fos, and Lhb but lower Fos induction. Fshb induction reached significance only in LβT2b cells. Our study highlights the heterogeneity in gonadotrope cell line genomes and provides reference STR authentication patterns that can be monitored to improve experimental reproducibility and facilitate comparisons of results within and across laboratories.