Global profiles of gene expression induced by adrenocorticotropin in Y1 mouse adrenal cells

Expression of tryptophan hydroxylase in rat adrenal glands: Upregulation of TPH2 by chronic stress

It has been shown that chronic restraint stress (CRS) increases adrenal 5-HT levels and turnover through a mechanism that appears unrelated to tryptophan hydroxylase (TPH). In the present study we re-analyzed the effects of CRS (20 min/day) for 14 days relative to control (CTRL) conditions on TPH expression, distribution, and activity in rat adrenal glands. On day 15, adrenal glands were collected for TPH1 and TPH2 immunohistochemistry, Western blot, and RT-PCR; TPH activity was estimated by quantification of 5-hydroxytryptophan (5-HTP) and, indirectly, through measurement of 5-HT and 5-hydroxindolacetic acid (5-HIAA) levels and turnover (5-HIAA/5-HT ratio) by HPLC. TPH expression and activity in the dorsal raphe nucleus (DRN) were also determined for comparison. TPH1 and TPH2 immunostaining was observed in the adrenal medulla, and measurable levels of TPH1 and TPH2 protein and mRNA were detected in rat adrenal glands from CTRL animals. CRS exposure noticeably increased TPH2- but not THP1-immunostaining in the medulla and the outer adrenocortical areas of left (LAG) but not of right adrenal glands (RAG). In addition, CRS exposure increased TPH2 protein and mRNA levels in LAG; however, both measures decreased in DRN. Finally, CRS treatment produced an increase and a decrease of TPH activity and 5-HT turnover in LAG and DRN, respectively. Results indicate that TPH is indeed expressed in rat adrenal glands. Exposure to CRS upregulates TPH2 in LAG, while inducing downregulation of it in the DRN. Then, the increased levels of 5-HT in LAG from CRS-exposed animals likely results from TPH2-mediated synthesis.

Non-Canonical Effects of ACTH: Insights Into Adrenal Insufficiency

Introduction

Adrenocorticotropic hormone (ACTH) is produced from proopiomelanocortin, which is predominantly synthetized in the corticotroph and melanotroph cells of the anterior and intermediate lobes of the pituitary gland and the arcuate nucleus of the hypothalamus. Although ACTH clearly has an effect on adrenal homeostasis and maintenance of steroid hormone production, it also has extra-adrenal effects that require further elucidation.

Methods

We comprehensively reviewed English language articles, regardless of whether they reported the presence or absence of adrenal and extra-adrenal ACTH effects.

Results

In the present review, we provide an overview on the current knowledge on adrenal and extra-adrenal effects of ACTH. In the section on adrenal ACTH effects, we focused on corticosteroid rhythmicity and effects on steroidogenesis, mineralocorticoids and adrenal growth. In the section on extra-adrenal effects, we have analyzed the effects of ACTH on the osteoarticular and reproductive systems, adipocytes, immune system, brain and skin. Finally, we focused on adrenal insufficiency.

Conclusions

The role of ACTH in maintaining the function of the hypothalamic-pituitary-adrenal axis is well known. Conversely, if we broaden our vision and analyze its role as a potential treatment strategy in other conditions, it will be evident in the literature that researchers seem to have abandoned this aspect in studies conducted several years ago. We believe it is worth re-evaluating the role of ACTH considering its noncanonical effects on the adrenal gland itself and on extra-adrenal organs and tissues; however, this would not have been possible without the recent advances in the pertinent technologies.

Transcriptome profiles of hypothalamus and adrenal gland linked to haplotype related to coping behavior in pigs

The hypothalamic-pituitary-adrenal (HPA) axis is an important component of neuroendocrine stress regulation and coping behavior. Transcriptome profiles of the hypothalamus and adrenal gland were assessed to identify molecular pathways and candidate genes for coping behavior in pigs. Ten each of high- (HR) and low- (LR) reactive pigs (n = 20) were selected for expression profiling based haplotype information of a prominent QTL-region on SSC12 discovered in our previous genome-wide association study (GWAS) on coping behavior. Comparing the HR and LR pigs showed 692 differentially expressed genes (DEGs) in the adrenal gland and 853 DEGs in the hypothalamus, respectively. Interestingly, 47% (17 out of 36) of DEGs found in both tissues were located in GWAS regions identified on SSC12, indicating that there are significant functional positional candidate genes for coping behaviour. Pathway analysis assigned DEGs to glucocorticoid receptor signaling in the adrenal gland. Furthermore, oxidative phosphorylation, mitochondrial dysfunction, and NGF signaling as well as cholecystokinin/Gastrin-mediated were identified in the hypothalamus. We narrowed the list of candidate genes in GWAS regions by analyzing their DEGs in the HPA axis. The top identified transcripts, including ATP1B2, AURKB, MPDU1 and NDEL1 provide evidence for molecular correlates of coping behavior in GWAS regions.

Transcriptional Regulation of Ovarian Steroidogenic Genes: Recent Findings Obtained from Stem Cell-Derived Steroidogenic Cells

Ovaries represent one of the primary steroidogenic organs, producing estrogen and progesterone under the regulation of gonadotropins during the estrous cycle. Gonadotropins fluctuate the expression of various steroidogenesis-related genes, such as those encoding steroidogenic enzymes, cholesterol deliverer, and electronic transporter. Steroidogenic factor-1 (SF-1)/adrenal 4-binding protein (Ad4BP)/NR5A1 and liver receptor homolog-1 (LRH-1) play important roles in these phenomena via transcriptional regulation. With the aid of cAMP, SF-1/Ad4BP and LRH-1 can induce the differentiation of stem cells into steroidogenic cells. This model is a useful tool for studying the molecular mechanisms of steroidogenesis. In this article, we will provide insight into the transcriptional regulation of steroidogenesis-related genes in ovaries that are revealed from stem cell-derived steroidogenic cells. Using the cells derived from the model, novel SF-1/Ad4BP- and LRH-1-regulated genes were identified by combined DNA microarray and promoter tiling array analyses. The interaction of SF-1/Ad4BP and LRH-1 with transcriptional regulators in the regulation of ovarian steroidogenesis was also revealed.

Effect of ACTH and hCG on the Expression of Gonadotropin-Inducible Ovarian Transcription Factor 1 (Giot1) Gene in the Rat Adrenal Gland

Gonadotropin-inducible ovarian transcription factor-1 (Giot1) belongs to a family of fast-responsive genes, and gonadotropins rapidly induce its expression in steroidogenic cells of ovaries and testes of rats. Gonadal Giot1 gene expression is regulated by cyclic adenosine monophosphate (cAMP) -dependent protein kinase A pathway, with essential role of orphan nuclear receptor NR4A1 transcription factor (nuclear receptor subfamily 4, group A, member 1). A recent study reports that Giot1 is also expressed in adrenals, however, the mechanism of its regulation in adrenal gland is yet to be identified. Therefore, the aim of this study was to characterise the changes in Giot1 gene expression in male and female rat adrenals using wide range of in vivo and in vitro experimental models. Special emphasis was directed at the Giot1 gene regulation by ACTH and gonadotropin. In our study, we found that ACTH rapidly stimulates Giot1 expression both in vivo and in vitro. However, gonadotropin does not affect the adrenal Giot1 gene expression, presumably due to the low expression of gonadotropin receptor in adrenals. Both testosterone and estradiol administered in vivo had inhibitory effect on Giot1 gene expression in the adrenals of post-gonadectomized adult rats. Further, our studies revealed that the intracellular mechanism of Giot1 gene regulation in rat adrenals is similar to that of gonads. As in the case of gonads, the expression of Giot1 in adrenal gland is regulated by cAMP-dependent signaling pathway with essential role of the NR4A1 transcription factor. The results of our studies suggest that Giot1 may be involved in the regulation of rat adrenocortical steroidogenesis.

Mitochondrial cAMP exerts positive feedback on mitochondrial Ca2+ uptake via the recruitment of Epac1

We have previously demonstrated in H295R adrenocortical cells that the Ca²⁺-dependent production of mitochondrial cAMP (mt-cAMP) by the matrix soluble adenylyl cyclase (sAC; encoded by ADCY10) is associated with enhanced aldosterone production. Here, we examined whether mitochondrial sAC and mt-cAMP fine tune mitochondrial Ca²⁺ metabolism to support steroidogenesis. Reduction of mt-cAMP formation resulted in decelerated mitochondrial Ca²⁺ accumulation in intact cells during K⁺-induced Ca²⁺ signalling and also in permeabilized cells exposed to elevated perimitochondrial [Ca²⁺]. By contrast, treatment with the membrane-permeable cAMP analogue 8-Br-cAMP, inhibition of phosphodiesterase 2 and overexpression of sAC in the mitochondrial matrix all intensified Ca²⁺ uptake into the organelle. Identical mt-cAMP dependence of mitochondrial Ca²⁺ uptake was also observed in HeLa cells. Importantly, the enhancing effect of mt-cAMP on Ca²⁺ uptake was independent from both the mitochondrial membrane potential and Ca²⁺ efflux, but was reduced by Epac1 (also known as RAPGEF3) blockade both in intact and in permeabilized cells. Finally, overexpression of sAC in the mitochondrial matrix potentiated aldosterone production implying that the observed positive feedback mechanism of mt-cAMP on mitochondrial Ca²⁺ accumulation may have a role in the rapid initiation of steroidogenesis.This article has an associated First Person interview with the first author of the paper.

Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development

This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.

Synthetic High-Density Lipoprotein (sHDL) Inhibits Steroid Production in HAC15 Adrenal Cells

High density lipoprotein (HDL) transported cholesterol represents one of the sources of substrate for adrenal steroid production. Synthetic HDL (sHDL) particles represent a new therapeutic option to reduce atherosclerotic plaque burden by increasing cholesterol efflux from macrophage cells. The effects of the sHDL particles on steroidogenic cells have not been explored. sHDL, specifically ETC-642, was studied in HAC15 adrenocortical cells. Cells were treated with sHDL, forskolin, 22R-hydroxycholesterol, or pregnenolone. Experiments included time and concentration response curves, followed by steroid assay. Quantitative real-time RT-PCR was used to study mRNA of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, lanosterol 14-α-methylase, cholesterol side-chain cleavage enzyme, and steroid acute regulatory protein. Cholesterol assay was performed using cell culture media and cell lipid extracts from a dose response experiment. sHDL significantly inhibited production of cortisol. Inhibition occurred in a concentration- and time-dependent manner and in a concentration range of 3μM-50μM. Forskolin (10μM) stimulated cortisol production was also inhibited. Incubation with 22R-hydroxycholesterol (10μM) and pregnenolone (10μM) increased cortisol production, which was unaffected by sHDL treatment. sHDL increased transcript levels for the rate-limiting cholesterol biosynthetic enzyme, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase. Extracellular cholesterol assayed in culture media showed a positive correlation with increasing concentration of sHDL, whereas intracellular cholesterol decreased after treatment with sHDL. The current study suggests that sHDL inhibits HAC15 adrenal cell steroid production by efflux of cholesterol, leading to an overall decrease in steroid production and an adaptive rise in adrenal cholesterol biosynthesis.

60 YEARS OF POMC: Adrenal and extra-adrenal functions of ACTH

The pituitary adrenocorticotropic hormone (ACTH) plays a pivotal role in homeostasis and stress response and is thus the major component of the hypothalamo-pituitary-adrenal axis. After a brief summary of ACTH production from proopiomelanocortin (POMC) and on ACTH receptor properties, the first part of the review covers the role of ACTH in steroidogenesis and steroid secretion. We highlight the mechanisms explaining the differential acute vs chronic effects of ACTH on aldosterone and glucocorticoid secretion. The second part summarizes the effects of ACTH on adrenal growth, addressing its role as either a mitogenic or a differentiating factor. We then review the mechanisms involved in steroid secretion, from the classical Cyclic adenosine monophosphate second messenger system to various signaling cascades. We also consider how the interaction between the extracellular matrix and the cytoskeleton may trigger activation of signaling platforms potentially stimulating or repressing the steroidogenic potency of ACTH. Finally, we consider the extra-adrenal actions of ACTH, in particular its role in differentiation in a variety of cell types, in addition to its known lipolytic effects on adipocytes. In each section, we endeavor to correlate basic mechanisms of ACTH function with the pathological consequences of ACTH signaling deficiency and of overproduction of ACTH.

Disruption of steroidogenesis: Cell models for mechanistic investigations and as screening tools

In the modern world, humans are exposed during their whole life to a large number of synthetic chemicals. Some of these chemicals have the potential to disrupt endocrine functions and contribute to the development and/or progression of major diseases. Every year approximately 1000 novel chemicals, used in industrial production, agriculture, consumer products or as pharmaceuticals, are reaching the market, often with limited safety assessment regarding potential endocrine activities. Steroids are essential endocrine hormones, and the importance of the steroidogenesis pathway as a target for endocrine disrupting chemicals (EDCs) has been recognized by leading scientists and authorities. Cell lines have a prominent role in the initial stages of toxicity assessment, i.e. for mechanistic investigations and for the medium to high throughput analysis of chemicals for potential steroidogenesis disrupting activities. Nevertheless, the users have to be aware of the limitations of the existing cell models in order to apply them properly, and there is a great demand for improved cell-based testing systems and protocols. This review intends to provide an overview of the available cell lines for studying effects of chemicals on gonadal and adrenal steroidogenesis, their use and limitations, as well as the need for future improvements of cell-based testing systems and protocols.

Role of EPAC in cAMP-Mediated Actions in Adrenocortical Cells

Adrenocorticotropic hormone regulates adrenal steroidogenesis mainly via the intracellular signaling molecule cAMP. The effects of cAMP are principally relayed by activating protein kinase A (PKA) and the more recently discovered exchange proteins directly activated by cAMP 1 and 2 (EPAC1 and EPAC2). While the intracellular roles of PKA have been extensively studied in steroidogenic tissues, those of EPACs are only emerging. EPAC1 and EPAC2 are encoded by the genes RAPGEF3 and RAPGEF4, respectively. Whereas EPAC1 is ubiquitously expressed, the expression of EPAC2 is more restricted, and typically found in endocrine tissues. Alternative promoter usage of RAPGEF4 gives rise to three different isoforms of EPAC2 that vary in their N-termini (EPAC2A, EPAC2B, and EPAC2C) and that exhibit distinct expression patterns. EPAC2A is expressed in the brain and pancreas, EPAC2B in steroidogenic cells of the adrenal gland and testis, and EPAC2C has until now only been found in the liver. In this review, we discuss current knowledge on EPAC expression and function with focus on the known roles of EPAC in adrenal gland physiology.

Osthole, a coumadin analog from Cnidium monnieri (L.) Cusson, stimulates corticosterone secretion by increasing steroidogenic enzyme expression in mouse Y1 adrenocortical tumor cells

ETHNOPHARMACOLOGICAL RELEVANCE

Osthole is an O-methylated coumadin, which was isolated and purified from the seeds of Cnidium monnieri (L.) Cusson. Osthole is a commonly used traditional Chinese medicine to treat patients with Kidney-Yang deficiency patients, who exhibit clinical signs similar to those of glucocorticoid withdrawal. However, the mechanism of action of osthole is not fully understood.

OBJECTIVE

This study was designed to reveal the effects of osthole on corticosterone production in mouse Y1 cell.

MATERIALS AND METHODS

Mouse Y1 adrenocortical cells were used to evaluate corticosterone production, which was quantified by enzyme-linked immunosorbent assay (ELISA) kits. Cell viability was tested using the MTT assay, and the mRNA and protein expression of genes encoding steroidogenic enzymes and transcription factors was monitored by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) and western blotting, respectively.

RESULTS

Osthole stimulated corticosterone secretion from mouse Y1 cells in a dose- and time-dependent manner, and osthole enhanced the effect of dibutyryl-cAMP (Bu2cAMP) on corticosterone production. Further, osthole also increased StAR and CYP11B1 mRNA expression in a dose-dependent manner and enhanced the expression of transcription factors such as HSD3B1, FDX1, POR and RXRα as well as immediate early genes such as NR4A1. Moreover, osthole significantly increased SCARB1(SRB1) mRNA and StAR protein expression in the presence or absence of Bu2cAMP; these proteins are an important for the transport of the corticosteroid precursor cholesterol transport into mitochondria.

CONCLUSIONS

Our results show that the promotion of corticosterone biosynthesis and secretion is a novel effect of osthole, suggesting that this agent can be utilized for the prevention and treatment of Kidney-Yang deficiency syndrome.

Corticotropin (ACTH) regulates alternative RNA splicing in Y1 mouse adrenocortical tumor cells

The stimulatory effect of ACTH on gene expression is well documented and is thought to be a major mechanism by which ACTH maintains the functional and structural integrity of the gland. Previously, we showed that ACTH regulates the accumulation of over 1200 transcripts in Y1 adrenal cells, including a cluster with functions in alternative splicing of RNA. On this basis, we postulated that some of the effects of ACTH on the transcription landscape of Y1 cells are mediated by alternative splicing. In this study, we demonstrate that ACTH regulates the alternative splicing of four transcripts - Gnas, Cd151, Dab2 and Tia1. Inasmuch as alternative splicing potentially affects transcripts from more than two-thirds of the mouse genome, we suggest that these findings are representative of a genome-wide effect of ACTH that impacts on the mRNA and protein composition of the adrenal cortex.

Sex-related gene expression profiles in the adrenal cortex in the mature rat: microarray analysis with emphasis on genes involved in steroidogenesis

Notable sex-related differences exist in mammalian adrenal cortex structure and function. In adult rats, the adrenal weight and the average volume of zona fasciculata cells of females are larger and secrete greater amounts of corticosterone than those of males. The molecular bases of these sex-related differences are poorly understood. In this study, to explore the molecular background of these differences, we defined zone- and sex-specific transcripts in adult male and female (estrous cycle phase) rats. Twelve-week-old rats of both genders were used and samples were taken from the zona glomerulosa (ZG) and zona fasciculata/reticularis (ZF/R) zones. Transcriptome identification was carried out using the Affymetrix^® Rat Gene 1.1 ST Array. The microarray data were compared by fold change with significance according to moderated t-statistics. Subsequently, we performed functional annotation clustering using the Gene Ontology (GO) and Database for Annotation, Visualization and Integrated Discovery (DAVID). In the first step, we explored differentially expressed transcripts in the adrenal ZG and ZF/R. The number of differentially expressed transcripts was notably higher in the female than in the male rats (702 vs. 571). The differentially expressed genes which were significantly enriched included genes involved in steroid hormone metabolism, and their expression levels in the ZF/R of adult female rats were significantly higher compared with those in the male rats. In the female ZF/R, when compared with that of the males, prevailing numbers of genes linked to cell fraction, oxidation/reduction processes, response to nutrients and to extracellular stimuli or steroid hormone stimuli were downregulated. The microarray data for key genes involved directly in steroidogenesis were confirmed by qPCR. Thus, when compared with that of the males, in the female ZF/R, higher expression levels of genes involved directly in steroid hormone synthesis were accompanied by lower expression levels of genes regulating basal cell functions.

Cell-to-cell communication in bilateral macronodular adrenal hyperplasia causing hypercortisolism

It has been well established that, in the human adrenal gland, cortisol secretion is not only controlled by circulating corticotropin but is also influenced by a wide variety of bioactive signals, including conventional neurotransmitters and neuropeptides, released within the cortex by various cell types such as chromaffin cells, neurons, cells of the immune system, adipocytes, and endothelial cells. These different types of cells are present in bilateral macronodular adrenal hyperplasia (BMAH), a rare etiology of primary adrenal Cushing's syndrome, where they appear intermingled with adrenocortical cells in the hyperplastic cortex. In addition, the genetic events, which cause the disease, favor abnormal adrenal differentiation that results in illicit expression of paracrine regulatory factors and their receptors in adrenocortical cells. All these defects constitute the molecular basis for aberrant autocrine/paracrine regulatory mechanisms, which are likely to play a role in the pathophysiology of BMAH-associated hypercortisolism. The present review summarizes the current knowledge on this topic as well as the therapeutic perspectives offered by this new pathophysiological concept.

Expression of selected genes involved in steroidogenesis in the course of enucleation-induced rat adrenal regeneration

The enucleation-induced (EI) rapid proliferation of adrenocortical cells is followed by their differentiation, the degree of which may be characterized by the expression of genes directly and indirectly involved in steroid hormone biosynthesis. In this study, out of 30,000 transcripts of genes identified by means of Affymetrix Rat Gene 1.1 ST Array, we aimed to select genes (either up- or downregulated) involved in steroidogenesis in the course of enucleation-induced adrenal regeneration. On day 1, we found 32 genes with altered expression levels, 15 were upregulated and 17 were downregulated [i.e., 3β-hydroxysteroid dehydrogenase (Hsd3β), nuclear receptor subfamily 0, group B, member 1 (Nr0b1), cytochrome P450 aldosterone synthase (Cyp11b2) and sterol O-acyltransferase 1 (Soat1)]. On day 15, the expression of only 2 genes was increased and that of 3 was decreased. The investigated genes were clustered according to an hierarchical clustering algorithm and 4 clusters were obtained. Quantitative PCR (qPCR) confirmed the much lower mRNA expression levels of steroidogenic acute regulatory protein (StAR) during the regeneration process compared to the control, while the cholesterol side-chain cleavage enzyme (cholesterol desmolase; Cyp11a1) and Hsd3β genes presented similar expression profiles throughout the entire regeneration process. Cyp11b2 mRNA levels remained very low during the whole regeneration period. Fatty acid binding protein 6 (Fabp6) was markedly upregulated, whereas hormone-sensitive lipase (Lipe) was downregulated. The expression of Soat1 was lowest on regeneration day 1 and, subsequently, its expression increased from there on, reaching levels higher than the control. Dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 (Dax-1) mRNA levels were lowest on day 1 of the experiment; however, throughout the entire experimental period, there were no statistically significant differences observed. After the initial decrease in steroidogenic factor 1 (Sf-1) mRNA levels observed on the 1st day of the experiment, a marked upregulation in its expression was observed from there on. Data from the current study strongly suggest the role of Fabp6, Lipe and Soat1 in supplying substrates of regenerating adrenocortical cells for steroid synthesis. Our results indicate that during the first days of adrenal regeneration, intense synthesis of cholesterol may occur, which is then followed by its conversion into cholesteryl esters. Moreover, our data demonstrated that in enucleation-induced regeneration, the restoration of genes involved in glucocorticoid synthesis is notably shorter than that of those involved in aldosterone synthesis.

Human adrenocortical carcinoma cell lines

The human adrenal cortex secretes mineralocorticoids, glucocorticoids and adrenal androgens. These steroids are produced from unique cell types located within the three distinct zones of the adrenal cortex. Disruption of adrenal steroid production results in a variety of diseases that can lead to hypertension, metabolic syndrome, infertility and androgen excess. The adrenal cortex is also a common site for the development of adenomas, and rarely the site for the development of carcinomas. The adenomas can lead to diseases associated with adrenal steroid excess, while the carcinomas are particularly aggressive and have a poor prognosis. In vitro cell culture models provide important tools to examine molecular and cellular mechanisms controlling both the normal and pathologic function of the adrenal cortex. Herein, we discuss currently available human adrenocortical carcinoma cell lines and their use as model systems for adrenal studies.

Steroidogenic factor-1 (SF-1)-driven differentiation of murine embryonic stem (ES) cells into a gonadal lineage

Steroidogenic factor 1 (SF-1) is essential for the development and function of steroidogenic tissues. Stable incorporation of SF-1 into embryonic stem cells (SF-1-ES cells) has been shown to prime the cells for steroidogenesis. When provided with exogenous cholesterol substrate, and after treatment with retinoic acid and cAMP, SF-1-ES cells produce progesterone but do not produce other steroids such as cortisol, estradiol, or testosterone. In this study, we explored culture conditions that optimize SF-1-mediated differentiation of ES cells into defined steroidogenic lineages. When embryoid body formation was used to facilitate cell lineage differentiation, SF-1-ES cells were found to be restricted in their differentiation, with fewer cells entering neuronal pathways and a larger fraction entering the steroidogenic lineage. Among the differentiation protocols tested, leukemia inhibitory factor (LIF) removal, followed by prolonged cAMP treatment was most efficacious for inducing steroidogenesis in SF-1-ES cells. In this protocol, a subset of SF-1-ES cells survives after LIF withdrawal, undergoes morphologic differentiation, and recovers proliferative capacity. These cells are characterized by induction of steroidogenic enzyme genes, use of de novo cholesterol, and production of multiple steroids including estradiol and testosterone. Microarray studies identified additional pathways associated with SF-1 mediated differentiation. Using biotinylated SF-1 in chromatin immunoprecipitation assays, SF-1 was shown to bind directly to multiple target genes, with induction of binding to some targets after steroidogenic treatment. These studies indicate that SF-1 expression, followed by LIF removal and treatment with cAMP drives ES cells into a steroidogenic pathway characteristic of gonadal steroid-producing cells.

Contributions of steroidogenic factor 1 to the transcription landscape of Y1 mouse adrenocortical tumor cells

The contribution of steroidogenic factor 1 (SF-1) to the gene expression profile of Y1 mouse adrenocortical cells was evaluated using short hairpin RNAs to knockdown SF-1. The reduced level of SF-1 RNA was associated with global changes that affected the accumulation of more than 2000 transcripts. Among the down-regulated transcripts were several with functions in steroidogenesis that were affected to different degrees--i.e., Mc2r>Scarb1>Star≥Hsd3b1>Cyp11b1. For Star and Cyp11b1, the different levels of expression correlated with the amount of residual SF-1 bound to the proximal promoter regions. The knockdown of SF-1 did not affect the accumulation of Cyp11a1 transcripts even though the amount of SF-1 bound to the proximal promoter of the gene was reduced to background levels. Our results indicate that transcripts with functions in steroidogenesis vary in their dependence on SF-1 for constitutive expression. On a more global scale, SF-1 knockdown affects the accumulation of a large number of transcripts, most of which are not recognizably involved in steroid hormone biosynthesis.

ACTH is a potent regulator of gene expression in human adrenal cells

The adrenal glands are the primary source of minerocorticoids, glucocorticoids, and the so-called adrenal androgens. Under physiological conditions, cortisol and adrenal androgen synthesis are controlled primarily by ACTH. Although it has been established that ACTH can stimulate steroidogenesis, the effects of ACTH on overall gene expression in human adrenal cells have not been established. In this study, we defined the effects of chronic ACTH treatment on global gene expression in primary cultures of both adult adrenal (AA) and fetal adrenal (FA) cells. Microarray analysis indicated that 48 h of ACTH treatment caused 30 AA genes and 84 FA genes to increase by greater than fourfold, with 20 genes common in both cell cultures. Among these genes were six encoding enzymes involved in steroid biosynthesis, the ACTH receptor and its accessory protein, melanocortin 2 receptor accessory protein (ACTH receptor accessory protein). Real-time quantitative PCR confirmed the eight most upregulated and one downregulated common genes between two cell types. These data provide a group of ACTH-regulated genes including many that have not been previously studied with regard to adrenal function. These genes represent candidates for regulation of adrenal differentiation and steroid hormone biosynthesis.

Regulation of G protein-coupled receptor signaling: specific dominant-negative effects of melanocortin 2 receptor accessory protein 2

Heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs), which constitute the largest family of membrane proteins, mediate responses to diverse physiological stimuli. The presence of melanocortin 2 receptors (MC2Rs) on the plasma membrane requires the presence of either MC2R accessory protein (MRAP) or MRAP2, which are homologous accessory proteins. Here, we show that, whereas MRAP was essential for activation of MC2R signaling, MRAP2 was an endogenous inhibitor that competed with MRAP for binding to MC2R and decreased the potency of adrenocorticotropic hormone (ACTH), the endogenous agonist for MC2Rs, in stimulating the production of adenosine 3',5'-monophosphate (cAMP). ACTH bound with high affinity to MC2Rs in the presence of MRAP, but not MRAP2. The ability of MRAP and MRAP2 to influence ligand-binding affinity was specific to MC2R, because these proteins had little effect on the binding of NDP-alpha-melanocyte-stimulating hormone to MC4R or on its stimulation of cAMP responses. These results demonstrate that the balance of stimulatory and inhibitory accessory proteins can control the sensitivity of a GPCR to its natural agonist.

Gene array analysis of adrenal glands in broiler chickens following ACTH treatment

BACKGROUND

Difference in adaptability responses to stress has been observed amongst bird species, strains, and individuals. Components of the HPA axis, one of the internal systems involved in homeostasis re-establishment following stress, could play a role in this variability of responses. The aim of the present study was 1) to identify genes involved in the regulation of adrenal activity following ACTH stimulation and 2) to examine adrenal genes differentially expressed in individuals with high and low plasma corticosterone response following ACTH treatment.

RESULTS

Analysis with 21 K poultry oligo microarrays indicated that ACTH treatment affected the expression of 134 genes. Several transcripts assigned to genes involved in the adrenal ACTH signaling pathway and steroidogenic enzymes were identified as differentially expressed by ACTH treatment. Real-time PCR on 18 selected genes confirmed changes in transcript levels of 11 genes, including MC2R, CREM, Cry, Bmal1, Sqle, Prax1, and StAR. Only 4 genes revealed to be differentially expressed between higher and lower adrenal responders to ACTH treatment.

CONCLUSION

The results from the present study reveal putative candidate genes; their role in regulation of adrenal functions and adaptability to stress should be further investigated.

Regulation of P450 oxidoreductase by gonadotropins in rat ovary and its effect on estrogen production

BACKGROUND

P450 oxidoreductase (POR) catalyzes electron transfer to microsomal P450 enzymes. Its deficiency causes Antley-Bixler syndrome (ABS), and about half the patients with ABS have ambiguous genitalia and/or impaired steroidogenesis. POR mRNA expression is up-regulated when mesenchymal stem cells (MSCs) differentiate into steroidogenic cells, suggesting that the regulation of POR gene expression is important for steroidogenesis. In this context we examined the regulation of POR expression in ovarian granulosa cells by gonadotropins, and its possible role in steroidogenesis.

METHODS

Changes in gene expression in MSCs during differentiation into steroidogenic cells were examined by DNA microarray analysis. Changes in mRNA and protein expression of POR in the rat ovary or in granulosa cells induced by gonadotropin treatment were examined by reverse transcription-polymerase chain reaction and western blotting. Effects of transient expression of wild-type or mutant (R457H or V492E) POR proteins on the production of estrone in COS-7 cells were examined in vitro. Effects of POR knockdown were also examined in estrogen producing cell-line, KGN cells.

RESULTS

POR mRNA was induced in MSCs following transduction with the SF-1 retrovirus, and was further increased by cAMP treatment. Expression of POR mRNA, as well as Cyp19 mRNA, in the rat ovary were induced by equine chorionic gonadotropin and human chorionic gonadotropin. POR mRNA and protein were also induced by follicle stimulating hormone in primary cultured rat granulosa cells, and the induction pattern was similar to that for aromatase. Transient expression of POR in COS-7 cells, which expressed a constant amount of aromatase protein, greatly increased the rate of conversion of androstenedione to estrone, in a dose-dependent manner. The expression of mutant POR proteins (R457H or V492E), such as those found in ABS patients, had much less effect on aromatase activity than expression of wild-type POR proteins. Knockdown of endogenous POR protein in KGN human granulosa cells led to reduced estrone production, indicating that endogenous POR affected aromatase activity.

CONCLUSION

We demonstrated that the expression of POR, together with that of aromatase, was regulated by gonadotropins, and that its induction could up-regulate aromatase activity in the ovary, resulting in a coordinated increase in estrogen production.

Failure of adrenal corticosterone production in POMC-deficient mice results from lack of integrated effects of POMC peptides on multiple factors

Production of corticosteroids from the adrenal gland is a multistep process in which corticosterone is enzymatically processed from its precursor cholesterol. The main hormone regulating the production of corticosterone is the proopiomelanocortin (POMC)-derived adrenocorticotropic hormone (ACTH). Adrenals of POMC-deficient (POMC(-/-)) mice do not produce corticosterone either at basal levels or in response to acute stimulation with ACTH. However, pharmacological amounts of ACTH delivered continuously elicit corticosterone production over time. To define the relative effects of ACTH on individual factors involved in corticosterone production, parameters of adrenal cholesterol metabolism and steroidogenesis were examined in POMC(-/-) mice compared with wild-type and ACTH-treated mutant mice. POMC(-/-) adrenals lack cholesterol esters (CE); adrenal CE is restored with ACTH treatment. However, discontinuation of ACTH treatment stops corticosterone production despite the presence of adrenal CE. Failure of corticosterone production by POMC(-/-) adrenals occurs despite the constitutive presence of transcripts of genes required for cholesterol metabolism and steroidogenesis. Levels of key proteins involved in selective cholesterol uptake and steroidogenesis were attenuated; ACTH treatment increased these protein levels, most significantly those of the receptor responsible for selective uptake of CE, scavenger receptor class B, type I (SR-BI). Our studies reveal that failure of corticosterone production of POMC(-/-) adrenal glands and its pharmacological reconstitution by ACTH are not mediated by any one individual protein, but rather as an integrated effect on multiple factors from import of the substrate cholesterol to its conversion to corticosterone.

The impact of ACTH receptor knockdown on fetal and adult ovine adrenocortical cell function

Preparing the mammalian fetus for birth requires an increase in fetal plasma glucocorticoid levels. The mechanisms facilitating this increase are not fully known. It has been shown in sheep that the prepartum elevation in fetal plasma cortisol is accompanied by increases in adrenocorticotropin receptor (ACTH-R) expression in the fetal adrenal and in the adrenal responsiveness to stimulation. To determine the significance of the upregulation in ACTH-R expression on fetal adrenal function, the authors used small interfering RNA targeted to the ovine ACTH-R to reduce receptor expression and studied responses to stimulation in ovine adrenal cells. They studied fetal cells from late gestation after responsiveness had increased. They also studied adult cells to determine if maturation would influence the impact of receptor expression suppression on responsiveness. Fetal and adult cells were obtained, dispersed, transfected with receptor-targeted small interfering RNA or scrambled small interfering RNA, and subsequently stimulated with ACTH. Cells and media were harvested for measurements of gene and protein expression and cyclic adenosine monophosphate (cAMP) and cortisol levels. The ability of ACTH to upregulate its receptor or steroid acute regulatory protein was attenuated in fetal (P < .01) and adult cells (P < .01) by small interfering RNA treatment; the blockade was more pronounced in the adult cells (P < .01). The small interfering RNA treatment also blocked the cAMP response to ACTH in fetal (P < .001) and adult (P < .05) cells. This was accompanied by marked reductions in cortisol responses in both (P < .001 and P < .01, respectively). These data suggest that upregulation of the ACTH-R expression in late gestation is essential for the increase in adrenal steroidogenic capacity occurring then. The data also indicate that a reduction in the ACTH-R expression blocks the ability of the peptide to stimulate early steps in the steroidogenic pathway event after maturation is complete.

How the new tools to analyze the human genome are opening new perspectives: the use of gene expression in investigations of the adrenal cortex

With the promise of state-of-the-art molecular technologies and the tools provided by the human genome project, a number of investigators are trying to identify molecular targets of adrenocortical tumorigenesis. One path in this endeavor was the identification by positional cloning of genes that are mutated in rare adrenocortical tumors. The subject of this article is an update of the results of experiments in the second path that was followed by us and others: that of using genome-wide expression analysis of adrenocortical cells in normal and various disease states. Transcriptomic analysis is a rapidly evolving technology; this article summarizes some data on the adrenal cortex and points out how these new technologies can be used in the identification of important genes and molecular pathways in both normal and diseased adrenal cortex.

Gene array and real time PCR analysis of the adrenal sensitivity to adrenocorticotropic hormone in pig

Background

Variability in hypothalamic-pituitary-adrenal (HPA) axis activity has been shown to be influenced by genetic factors and related to great metabolic differences such as obesity. The aim of this study was to investigate molecular bases of genetic variability of the adrenal sensitivity to ACTH, a major source of variability, in Meishan (MS) and Large White (LW) pigs, MS being reported to exhibit higher basal cortisol levels, response to ACTH and fatness than LW. A pig cDNA microarray was used to identify changes in gene expression in basal conditions and in response to ACTH stimulation.

Results

Genotype and/or ACTH affected the expression of 211 genes related to transcription, cell growth/maintenance, signal transduction, cell structure/adhesion/extra cellular matrix and protein kinase/phosphatase activity. No change in the expression of known key regulator proteins of the ACTH signaling pathway or of steroidogenic enzymes was found. However, Mdh2, Sdha, Suclg2, genes involved in the tricarboxylic acid (TCA) pathway, were over-expressed in MS pigs. Higher TCA cycle activity in MS than in LW may thus result in higher steroidogenic activity and thus explain the typically higher cortisol levels in MS compared to LW. Moreover, up-regulation of Star and Ldlr genes in MS and/or in response to ACTH suggest that differences in the adrenal function between MS and LW may also involve mechanisms requisite for cholesterol supply to steroidogenesis.

Conclusion

The present study provides new potential candidate genes to explain genetic variations in the adrenal sensitivity to ACTH and better understand relationship between HPA axis activity and obesity.

The regulated cell surface zymogen activation of the proprotein convertase PC5A directs the processing of its secretory substrates

The proprotein convertases are synthesized as zymogens that acquire activity upon autocatalytic removal of their NH(2)-terminal prosegment. Based on the convertase furin, to fold properly and gain activity, the convertases PC5A, PACE4, and PC7 are presumed to undergo two sequential prosegment cleavages in the endoplasmic reticulum and then in the trans-Golgi network. However, biochemical and immunocytochemical experiments revealed that mouse PC5A is complexed to its prosegment at the plasma membrane. This labeling is lost upon treatment with heparin and is increased by overexpressing members of the syndecan family and CD44, suggesting attachment of secreted PC5A-prosegment complex to heparan sulfate proteoglycans. Following stimulation of Y1 cells with adrenocorticotropic hormone or 8-bromo-cyclic AMP, the cell surface labeling of the prosegment of PC5A is greatly diminished, whereas the signal for mature PC5A is increased. Moreover, after stimulation, the protease activity of PC5A is enhanced, as evidenced by the cleavage of the PC5A substrates Lefty, ADAMTS-4, endothelial lipase, and PCSK9. Our data suggest a novel mechanism for PC5A activation and substrate cleavage at the cell surface, through a regulated removal of its prosegment. A similar mechanism may also apply to the convertase PACE4, thereby extending our knowledge of the molecular details of the zymogen activation and functions of these heparan sulfate proteoglycan-bound convertases.

Role of calcium messenger systems in ACTH-induced cortisol production in bovine adrenal fasciculo-reticularis cells

We investigated the regulation of each intracellular signal transduction system including cyclic AMP (cAMP)-dependent and calcium (Ca2+) messenger systems in bovine adrenal fasciculo-reticularis cells to clarify the exact mode of action of ACTH. Pretreatment with primaquine and quinacrine, which are phospholipase A2 inhibitors, significantly inhibited cortisol production activated by both low and high concentrations of ACTH. Therefore, it seems that metabolites induced by phospholipase A2 are quite essential for cortisol synthesis induced by ACTH, either at low or high concentrations. At low concentrations of ACTH (10(-13)-10(-12) M), significant increases of cytosolic calcium ([Ca2+]i), but not of cAMP, were observed. Calphostin C, a specific protein kinase C inhibitor, apparently suppressed cortisol production activated by low concentrations of ACTH, while H-89, a specific inhibitor of cAMP-dependent protein kinase, did not. These findings suggest that, at physiologically low concentrations, ACTH activates [Ca2+]i and phospholipase A2 without affecting cAMP formation, resulting in an increased biosynthesis of cortisol, partly via protein kinase C-dependent processes. At high concentrations, ACTH (10(-9)-10(-7) M) induced an increase of cAMP and [Ca2+]i. The cortisol production induced by high concentrations of ACTH was significantly inhibited by pretreatment with calphostin C, H-89 and H-7, suggesting the participation of cAMP-dependent protein kinase and protein kinase C systems in the regulation of cortisol production in the presence of high concentrations of ACTH. In conclusion, cytosolic calcium is biphasically enhanced by ACTH, although cAMP accumulation is increased only by high concentrations of ACTH. A phospholipase A2-dependent process may partly play a crucial role in the regulation of cortisol biosynthesis, when stimulated by low and high concentrations of ACTH.

Adrenal transcription regulatory genes modulated by angiotensin II and their role in steroidogenesis

Transcription regulatory genes are crucial modulators of cell physiology and metabolism whose intracellular levels are tightly controlled to respond to extracellular stimuli. We studied transcription regulatory genes modulated by angiotensin II, one of the most important regulators of adrenal cortical cell function, and their role in adrenal steroidogenesis in H295R human adrenocortical cells. Angiotensin II-modulated transcription regulatory genes were identified with high-density oligonucleotide microarrays and the results validated by real-time RT-PCR. Cotransfection reporter assays were performed in H295R cells to analyze the role of these transcription regulatory genes in the control of the expression of 11beta-hydroxylase and aldosterone synthase, the last and unique enzymes of the glucocorticoid and mineralocorticoid biosynthetic pathways, respectively. We selected a subset of the most regulated genes for reporter plasmid studies to determine the effect on these enzymes. BHLHB2, BTG2, and SALL1 decreased expression of both enzymes, whereas CITED2, EGR2, ELL2, FOS, FOSB, HDAC5, MAFF, MITF, NFIL3, NR4A1, NR4A2, NR4A3, PER1, and VDR increased expression for both enzymes. By the ratio of aldosterone synthase to 11beta-hydroxylase expression, NFIL3, NR4A1, NR4A2, and NR4A3 show the greatest selectivity toward upregulating expression of the mineralocorticoid biosynthetic pathway preferentially. In summary, this study reports for the first time a set of transcription regulatory genes that are modulated by angiotensin II and their role in adrenal gland steroidogenesis. Abnormal regulation of the mineralocorticoid or glucocorticoid biosynthesis pathways is involved in several pathophysiological conditions; hence the modulated transcription regulatory genes described may correlate with adrenal steroidogenesis pathologies.

A genome-wide assessment of adrenocorticotropin action in the Y1 mouse adrenal tumor cell line

This report summarizes the genome-wide effects of ACTH on transcript accumulation in mouse adrenal Y1 cells and the relative contributions of the cAMP-, protein kinase C- and Ca(2+)-dependent signaling pathways to these actions of the hormone. ACTH affected the accumulation of 1386 transcripts, a much larger number than previously appreciated. The cAMP signaling pathway accounted for approximately 56% of the ACTH effects whereas the protein kinase C- and Ca(2+)-dependent pathways made smaller contributions to ACTH action. Approximately 38% of the ACTH-affected transcripts could not be assigned to these signaling pathways and thus represent candidates for regulation via other mechanisms. The set of ACTH-regulated transcripts included clusters with functions in steroid metabolism, cell proliferation and alternative splicing. Collectively, our results suggest that Y1 adrenal cells undergo extensive remodeling upon prolonged stimulation with ACTH. The functional implications of ACTH on alternative splicing are explored.

Dephosphorylation of TORC initiates expression of the StAR gene

Cyclic AMP responsive element (CRE) binding protein (CREB) is known to activate transcription when its Ser133 is phosphorylated. However, transducer of regulated CREB activity (TORC), a CREB specific co-activator, upregulates CREB activity in a phospho-Ser133-independent manner. Interestingly, TORC is also regulated by phosphorylation; the phospho-form is inactive, and the dephospho-form active. When PKA phosphorylates CREB, it inhibits TORC kinases simultaneously and accelerates dephosphorylation of TORC. We show in this report that staurosporine, a kinase inhibitor, induces the expression of the StAR gene in Y1 adrenocortical cells, possibly a result of an increase in the population of dephospho-TORC. The expression of the StAR gene is known to be regulated by SF-1 and CREB, and the co-activators CBP/p300 may mediate the actions of both factors. Our experiments using KG501, a disruptor of the interaction between phospho-CREB and CBP/p300, also support the importance of TORC in the regulation of StAR gene expression.

Regulation of alternative splicing by signal transduction pathways

Alternative splicing is now recognized as a ubiquitous mechanism for controlling gene expression in a tissue-specific manner. A growing body of work from the past few years as begun to also highlight the existence of networks of signal-responsive alternative splicing in a variety of cell types. While the mechanisms by which signal transduction pathways influence the splicing machinery are relatively poorly understood, a few themes have begun to emerge for how extracellular stimuli can be communicated to specific RNA-binding proteins that control splice site selection by the spliceosome. This chapter describes our current understanding of signal-induced alternative splicing with an emphasis on these emerging themes and the likely directions for future research.

Cellular transcriptomics -- the next phase of endocrine expression profiling

Transcriptome analysis, or global gene expression profiling, has become a commonly used and valuable tool in both basic and clinical endocrine research. Novel endocrine regulators have 'surfaced' and greater consideration is now given to understanding function at the level of gene networks. Recent developments have shown that the transcriptome is considerably larger and more divergently expressed than was previously thought. Endocrine cells express a great variety of coding and noncoding RNAs in a highly cell-specific manner. If further value is to be taken from this research area, then steps towards defined cellular transcriptomics must be taken. New sampling techniques that utilize novel genetic models are a key first step.