Steroidogenic factor 1-dependent promoter activity of the human steroidogenic acute regulatory protein (StAR) gene

Dual role of NR4A1 in porcine ovarian granulosa cell differentiation and granulosa-lutein cell regression in vitro

This study aimed to investigate the role of NR4A1 in forskolin (FSK)-induced granulosa cell (GC) differentiation and PGF_2α-induced granulosa-lutein cell (GLC) regression. For experiment 1, primary porcine GCs were pre-cultured for 6 d before induced-differentiation by FSK with or without siNR4A1, and changes in GC proliferation, lipid droplets (LDs), and P₄ level were detected. For experiment 2, the GLC model was established by FSK as in experiment 1, and then PGF_2α was utilized to induce GLC regression with or without siNR4A1, changes in P₄ secretion, apoptosis proteins, and associated signaling pathway members were detected. Results showed that in experiment 1, FSK up-regulated NR4A1 expression during GC differentiation and decreased GC proliferation activity, which was reversed by siNR4A1. siNR4A1 inhibited the FSK-induced decreases in Cyclin B1/D1 and CDK1/2 mRNA abundances, and increases in P21/P27 mRNA abundances, and FSK-induced LD accumulation. FSK up-regulated P₄ secretion and StAR, CYP11A1 and HSD3B expression, decreased CYP19A1 expression, which were reversed by siNR4A1 except for StAR expression. In experiment 2, PGF_2α induced NR4A1 expression and reduced GLC viability, which were reversed by siNR4A1. Compared with PGF_2α group, the levels of P₄ secretion and StAR expression were higher in PGF_2α+siNR4A1 group, while CYP11A1 and HSD3B expressions held at low levels. siNR4A1 inhibited PGF_2α-induced expression of apoptosis proteins (caspase3, Bax, Fas, TNFa), ATF3, and phosphorylated MAPKs (ERK1/2, P38, JNK). In summary, NR4A1 is involved in regulating porcine GC differentiation and GLC regression as well as the changes in cell proliferation, apoptosis, steroidogenesis, and MAPK pathways, which provide a theoretical basis for further understanding of the mechanism of porcine luteal formation and regression.

Inhibition of NR5A1 phosphorylation alleviates a transcriptional suppression defect caused by a novel NR0B1 mutation

Context

Mutations in the NR0B1 gene, also well-known as the DAX1 gene, are known to cause congenital adrenal hypoplasia associated with hypogonadotropic hypogonadism. The abnormal NR0B1 protein fails to suppress the transcription of promoters of steroidogenic enzymes, which are also targets of NR5A1 protein, also well-known as Ad4BP/SF-1 protein. Since NR5A1 and NR0B1 have antagonistic effects on steroidogenesis, the loss of function due to NR0B1 mutations may be compensated by inducing loss of function of NR5A1 protein.

Patient

A middle-aged man was diagnosed with congenital adrenal hypoplasia associated with hypogonadotropic hypogonadism and genetic analysis revealed him to have a novel NR0B1 mutation, c.1222C>T(p.Gln408Ter).

Methods

NR0B1 activity was evaluated in CLK1/4 inhibitor-treated 293T cells via immunoblotting and luciferase assays of the STAR promoter.

Results

TG003 treatment suppressed NR5A1 protein function to compensate for the mutant NR0B1 showing inhibited suppression of transcription. Immunoblotting analyses showed that the phosphorylation status of NR5A1 at Ser203 was attenuated by the CLK1/4 inhibitor.

Conclusion

The specific reduction of NR5A1 phosphorylation by a CLK1/4 inhibitor may alleviate developmental defects in patients with NR0B1 mutations.

Morphological Characteristics and Transcriptome Landscapes of Chicken Follicles during Selective Development

Ovarian follicle selection largely depends on the transition of granulosa cells from an undifferentiated to a fully differentiated state, which is accompanied by morphological and functional changes in follicles. The processes and transcriptional regulation of follicles during follicle selection are unclear; we thus used follicles from the prehierarchal to the hierarchal stage to investigate histology, reproductive endocrinology, and transcription. The morphology of follicles changed markedly during follicle selection. The numbers of large white, small yellow, and large yellow follicles (LWF, SYF, and LYF, respectively) were 11.83 ± 2.79, 6.83 ± 2.23, and 1.00, respectively, per ovary. LYF showed thicker granulosa cell layers than those of other prehierarchal follicles. Progesterone concentrations were significantly higher in LYF than that in LWF and SYF. In total, 16,823 genes were positively expressed in LWF, SYF, and LYF. Among follicle types, 1,290 differentially expressed genes were enriched regarding cell differentiation, blood vessel morphogenesis, and response to steroid hormones. Candidate genes associated with follicle selection participated in the Wnt signaling pathway, steroid hormone biosynthesis, and the TGF-β signaling pathway. We produced insights into crucial morphological characteristics of transcriptional regulation in follicle development. Our results provide an important basis for revealing the mechanism of follicle selection and potential impact on the poultry industry.

Expression and Transcript Localization of star, sf-1, and dax-1 in the Early Brain of the Orange-Spotted Grouper Epinephelus coioides

We investigated the developmental expression and localization of sf-1 and dax-1 transcripts in the brain of the juvenile orange-spotted grouper in response to steroidogenic enzyme gene at various developmental ages in relation to gonadal sex differentiation. The sf-1 transcripts were significantly higher from 110-dah (day after hatching) and gradually increased up to 150-dah. The dax-1 mRNA, on the other hand, showed a decreased expression during this period, in contrast to sf-1 expression. At the same time, the early brain had increased levels of steroidogenic gene (star). sf-1 and star hybridization signals were found to be increased in the ventromedial hypothalamus at 110-dah; however, dax-1 mRNA signals decreased in the early brain toward 150-dah. Furthermore, the exogenous estradiol upregulated star and sf-1 transcripts in the early brain of the grouper. These findings suggest that sf-1 and dax-1 may have an antagonistic expression pattern in the early brain during gonadal sex differentiation. Increased expression of steroidogenic gene together with sf-1 during gonadal differentiation strongly suggests that sf-1 may play an important role in the juvenile grouper brain steroidogenesis and brain development.

Role of the cytoskeleton in steroidogenesis

Steroidogenesis in the adrenal cortex or gonads is a complicated process, modulated by various elements either at the tissue or molecular level. The substrate-cholesterol is first delivered to the outer membrane of mitochondria, undergoing a series of enzymatic reactions along with the material exchange between the mitochondria and the ER (endoplasmic reticulum) and ultimately yield various steroids: aldosterone, cortisol, testosterone and estrone. Several valves are set to adjust the amount of production to the needs. e.g. StAR(steroidogenic acute regulator) is in charge of the rate-limiting step-traffic of cholesterol from outer membrane to inner membrane of mitochondria. And the "needs" is partly reflected by trophic signals like ACTH、LH and downstream pathways-- intracellular cAMP pathway, which represents the endocrinal regulation of steroid synthesis, too. The coordinated activities of these related factors are all associated with another crucial cellular constituent-the cytoskeleton, which plays a crucial role in the cellular architecture and substrate trafficking. Though considerable studies have been performed regarding steroid synthesis, details about the upstream signaling pathways and mechanisms of the regulation by cytoskeleton network still remain unclear. The metabolism and interplays of the pivotal cellular organelles with cytoskeleton are worth exploring as well. In this review, we summarize research of different time span, describing the roles of specific cytoskeleton elements in steroidogenesis and related signaling pathways involved in the steroid synthesis. In addition, we discussed the inner cytoskeletal network involved in steroidogenic processes such as mitochondrial movement, organelle interactions and cholesterol trafficking.

A fish with no sex: gonadal and adrenal functions partition between zebrafish NR5A1 co-orthologs

People with NR5A1 mutations experience testicular dysgenesis, ovotestes, or adrenal insufficiency, but we do not completely understand the origin of this phenotypic diversity. NR5A1 is expressed in gonadal soma precursor cells before expression of the sex-determining gene SRY. Many fish have two co-orthologs of NR5A1 that likely partitioned ancestral gene subfunctions between them. To explore ancestral roles of NR5A1, we knocked out nr5a1a and nr5a1b in zebrafish. Single-cell RNA-seq identified nr5a1a-expressing cells that co-expressed genes for steroid biosynthesis and the chemokine receptor Cxcl12a in 1-day postfertilization (dpf) embryos, as does the mammalian adrenal-gonadal (interrenal-gonadal) primordium. In 2dpf embryos, nr5a1a was expressed stronger in the interrenal-gonadal primordium than in the early hypothalamus but nr5a1b showed the reverse. Adult Leydig cells expressed both ohnologs and granulosa cells expressed nr5a1a stronger than nr5a1b. Mutants for nr5a1a lacked the interrenal, formed incompletely differentiated testes, had no Leydig cells, and grew far larger than normal fish. Mutants for nr5a1b formed a disorganized interrenal and their gonads completely disappeared. All homozygous mutant genotypes lacked secondary sex characteristics, including male breeding tubercles and female sex papillae, and had exceedingly low levels of estradiol, 11-ketotestosterone, and cortisol. RNA-seq showed that at 21dpf, some animals were developing as females and others were not, independent of nr5a1 genotype. By 35dpf, all mutant genotypes greatly under-expressed ovary-biased genes. Because adult nr5a1a mutants form gonads but lack an interrenal and conversely, adult nr5a1b mutants lack a gonad but have an interrenal, the adrenal, and gonadal functions of the ancestral nr5a1 gene partitioned between ohnologs after the teleost genome duplication, likely owing to reciprocal loss of ancestral tissue-specific regulatory elements. Identifying such elements could provide hints to otherwise unexplained cases of Differences in Sex Development.

Co-culture of monocytes and zona fasciculata adrenal cells: An in vitro model to study the immune-adrenal cross-talk

The hypothalamic-pituitary-adrenal axis is the primary neuroendocrine system activated to re-establish homeostasis during periods of stress, including critical illness and major surgery. During critical illness, evidence suggests that locally induced inflammation of the adrenal gland could facilitate immune-adrenal cross-talk and, in turn, modulate cortisol secretion. It has been hypothesized that immune cells are necessary to mediate the effect of inflammatory stimuli on the steroidogenic pathway that has been observed in vivo. To test this hypothesis, we developed and characterized a trans-well co-culture model of THP1 (human monocytic cell)-derived macrophages and ATC7 murine zona fasciculata adrenocortical cells. We found that co-culture of ATC7 and THP1 cells results in a significant increase in the basal levels of IL-6 mRNA in ATC7 cells, and this effect was potentiated by treatment with LPS. Addition of LPS to co-cultures of ATC7 and THP1 significantly decreased the expression of key adrenal steroidogenic enzymes (including StAR and DAX-1), and this was also found in ATC7 cells treated with pro-inflammatory cytokines. Moreover, 24-h treatment with the synthetic glucocorticoid dexamethasone prevented the effects of LPS stimulation on IL-6, StAR and DAX-1 mRNA in ATC7 cells co-cultured with THP1 cells. Our data suggest that the expression of IL-6 and steroidogenic genes in response to LPS depends on the activation of intra-adrenal immune cells. Moreover, we also show that the effects of LPS can be modulated by glucocorticoids in a time- and dose-dependent manner with potential implications for clinical practice.

Prolonged treatment with the synthetic glucocorticoid methylprednisolone affects adrenal steroidogenic function and response to inflammatory stress in the rat

Synthetic glucocorticoids are widely prescribed for the treatment of numerous inflammatory and autoimmune diseases and they can also affect the way the adrenal gland produces endogenous glucocorticoids. Indeed, patients undergoing synthetic glucocorticoid treatment can develop adrenal insufficiency, a condition characterised by reduced responsiveness of the adrenal to ACTH stimulation or stressors (e.g. surgical or inflammatory stress). To better elucidate the long-term effect of synthetic glucocorticoids treatment and withdrawal on adrenal function, we have investigated the long-term effects of prolonged treatment with methylprednisolone on HPA axis dynamics and on the adrenal steroidogenic pathway, both in basal conditions and in response to an inflammatory stress (lipopolysaccharide, LPS). We have found that 5-days treatment with methylprednisolone suppresses basal ACTH and corticosterone secretion, as well as corticosterone secretion in response to a high dose of ACTH, and down-regulates key genes in the adrenal steroidogenic pathway, including StAR, MRAP, CYP11a1 and CYP11b1. These effects were paralleled by changes in the adrenal expression of transcription factors regulating steroidogenic gene expression, as well as changes in the expression of adrenal clock genes. Importantly, 5 days after withdrawal of the treatment, ACTH levels are restored, yet basal levels of corticosterone, as well as most of the key steroidogenic genes and their regulators, remain down regulated. We also show that, although 5-days treatment with methylprednisolone reduces the corticosterone response to LPS, an increase in intra-adrenal pro-inflammatory cytokine gene expression was observed. Our data suggests that the steroidogenic pathway is directly affected by synthetic glucocorticoid treatment in the long-term, presumably via a mechanism involving activation of the glucocorticoid receptor. Furthermore, our data suggests a pro-inflammatory effect of synthetic glucocorticoids treatment in the adrenal gland.

Novel NR5A1 Pathogenic Variants Cause Phenotypic Heterogeneity in 46,XY Disorders of Sex Development

Steroidogenic factor 1 (NR5A1/SF1) is a key transcription factor that is known to regulate the development of adrenal glands and gonads and is also involved in steroidogenesis. Several pathogenic NR5A1 variants have been reported to cause 46,XY disorders of sex development (DSD), with varying clinical phenotypes ranging from hypospadias to complete gonadal dysgenesis. Most often, the primary cause of DSD is due to variants in gene(s) related to gonadal development or the steroidogenic pathway. In the present study, we have analyzed 64 cases of 46,XY DSD for pathogenic NR5A1 variants. We report a total of 3 pathogenic variants of which 2 were novel (p.Gly22Ser and p.Ser143Asn) and 1 was already known (p.Ser32Asn). Functional studies have revealed that the 2 mutations p.Gly22Ser and p.Ser32Asn could significantly affect DNA binding and transactivation abilities. Further, these mutant proteins showed nuclear localization with aggregate formation. The third mutation, p.Ser143Asn, showed unspeckled nuclear localization and normal DNA binding, but the ability of transcriptional activation was significantly reduced. In conclusion, we recommend screening for NR5A1 pathogenic variants in individuals with features of 46,XY DSD for better diagnosis and management.

Dynamics of ACTH-Mediated Regulation of Gene Transcription in ATC1 and ATC7 Adrenal Zona Fasciculata Cell Lines

We tested the hypothesis that mouse ATC1 and ATC7 cells, the first adrenocortical cell lines to exhibit a complete zona fasciculata (ZF) cell phenotype, respond to dynamic ACTH stimulation in a similar manner as the adrenal gland in vivo. Exploiting our previous in vivo observations that gene transcription within the steroidogenic pathway is dynamically regulated in response to a pulse of ACTH, we exposed ATC1 and ATC7 cells to various patterns of ACTH, including pulsatile and constant, and measured the transcriptional activation of this pathway. We show that pulses of ACTH administered to ATC7 cells can reliably stimulate a pulsatile pattern of transcriptional activity that is comparable to that observed in adrenal ZF cells in vivo. Hourly pulses of ACTH stimulate dynamic increases in CREB phosphorylation (pCREB) and transcription of genes involved in critical steps of steroidogenesis including signal transduction (e.g., MRAP), cholesterol delivery (e.g., StAR), and steroid biosynthesis (e.g., CYP11A1), as well as those relating to transcriptional regulation of steroidogenic factors (e.g., SF-1 and Nur-77). In contrast, constant ACTH stimulation results in a prolonged and exaggerated pCREB and steroidogenic gene transcriptional response. We also show that when a large dose of ACTH (100 nM) is applied after these treatment regimens, a significant increase in steroidogenic transcriptional responsiveness is achieved only in cells that have been exposed to pulsatile, rather than constant, ACTH. Our data support our in vivo observations that pulsatile ACTH is important for the optimal transcriptional responsiveness of the adrenal. Importantly, our data suggest that ATC7 cells respond to dynamic ACTH stimulation.

Prenatal undernutrition affects the phenotypes of PCOS model rats

Although polycystic ovary syndrome (PCOS) is among the most common endocrine disorders in women of reproductive age, its etiology remains poorly understood. From the perspective of developmental origins of health and disease, some studies have investigated the relationship between low birth weight and the prevalence of PCOS and/or PCOS phenotypes in humans; however, the results of these studies were inconclusive. Here, we evaluated the effects of prenatal undernutrition on the metabolic and reproductive phenotypes of dihydrotestosterone-induced PCOS model rats. The PCOS model rats showed increased body weight, food intake, fat weight, adipocyte size and upregulation of inflammatory cytokines in adipose tissue; prenatal undernutrition exacerbated these metabolic changes. Prenatal undernutrition also increased the gene expression of hypothalamic orexigenic factor and decreased the gene expression of anorexigenic factor in the PCOS model rats. In addition, the PCOS model rats exhibited irregular cyclicity, polycystic ovaries and disrupted gene expression of ovarian steroidogenic enzymes. Interestingly, prenatal undernutrition attenuated these reproductive changes in the PCOS model rats. Our results suggest that in dihydrotestosterone-induced PCOS model rats, prenatal undernutrition exacerbates the metabolic phenotypes, whereas it improves the reproductive phenotypes and that such phenotypic changes may be induced by the alteration of some peripheral and central factors.

Functional study on new FOXL2 mutations found in Chinese patients with blepharophimosis, ptosis, epicanthus inversus syndrome

BACKGROUND

Blepharophimosis, ptosis, epicanthus inversus syndrome (BPES) is a rare inheritable disease that mainly affects eyelid development associated with (type I) or without (type II) ovarian dysfunction, resulting in premature ovarian failure (POF). Mutations in the gene forkhead box L2 (FOXL2) have been shown to be responsible for BPES. The aim of this study was to determine and functionally validate the FOXL2 mutation in a Chinese BPES family.

METHODS

Twelve individuals including five BPES patients from a Chinese family were enrolled. Genomic DNA was extracted from peripheral blood of enrolled subjects. The coding region of the FOXL2 gene was amplified and mutations were determined by sequencing analyses. Functional analysis was carried out to study changes in expression and transcriptional activity of the mutant FOXL2 protein.

RESULTS

A novel mutation in the FOXL2 gene (c.931C > T) was detected in all five BPES patients, which converts a histidine residue into a tyrosine (p.H311Y) in the FOXL2 protein. Functional analysis revealed that this point mutation reduces FOXL2 protein expression, concomitant with decreased transcriptional activity on the steroidogenic acute regulatory (StAR) gene promotor.

CONCLUSIONS

Our results expand the mutational spectrum of the FOXL2 gene and provide additional insights to the research on the molecular pathogenesis of FOXL2 in BPES.

Ad4BP/SF-1 regulates cholesterol synthesis to boost the production of steroids

Housekeeping metabolic pathways such as glycolysis are active in all cell types. In addition, many types of cells are equipped with cell-specific metabolic pathways. To properly perform their functions, housekeeping and cell-specific metabolic pathways must function cooperatively. However, the regulatory mechanisms that couple metabolic pathways remain largely unknown. Recently, we showed that the steroidogenic cell-specific nuclear receptor Ad4BP/SF-1, which regulates steroidogenic genes, also regulates housekeeping glycolytic genes. Here, we identify cholesterogenic genes as the targets of Ad4BP/SF-1. Further, we reveal that Ad4BP/SF-1 regulates Hummr, a candidate mediator of cholesterol transport from endoplasmic reticula to mitochondria. Given that cholesterol is the starting material for steroidogenesis and is synthesized from acetyl-CoA, which partly originates from glucose, our results suggest that multiple biological processes involved in synthesizing steroid hormones are governed by Ad4BP/SF-1. To our knowledge, this study provides the first example where housekeeping and cell-specific metabolism are coordinated at the transcriptional level.

The Essential Role of GATA6 in the Activation of Estrogen Synthesis in Endometriosis

Endometriotic stromal cells synthesize estradiol via the steroidogenic pathway. Nuclear receptor subfamily 5, group A, member 1 (NR5A1) is critical, but alone not sufficient, in activating this cascade that involves at least 5 genes. To evaluate whether another transcription factor is required for the activation of this pathway, we examined whether GATA Binding Protein 6 (GATA6) can transform a normal endometrial stromal cell (NoEM) into an endometriotic-like cell by conferring an estrogen-producing phenotype. We ectopically expressed GATA6 alone or with NR5A1 in NoEM or silenced these transcription factors in endometriotic stromal cells (OSIS) and assessed the messenger RNAs or proteins encoded by the genes in the steroidogenic cascade. Functionally, we assessed the effects of GATA6 expression or silencing on estradiol formation. In OSIS, GATA6 was necessary for catalyzing the conversion of progesterone to androstenedione (CYP17A1; P < .05). In NoEM, ectopic expression of GATA6 was essential for converting pregnenolone to estrogen (HSD3B2, CYP17A1, and CYP19A1; P < .05). However, simultaneous ectopic expression of both GATA6 and NR5A1 was required and sufficient to confer induction of all 5 genes and their encoded proteins that convert cholesterol to estrogen. Functionally, only simultaneous knockdown of GATA6 and NR5A1 blocked estradiol formation in OSIS ( P < .05). The presence of both transcription factors was required and sufficient to transform endometrial stromal cells into endometriotic-like cells that produced estradiol in large quantities ( P < .05). In summary, GATA6 alone is essential but not sufficient for estrogen formation in endometriosis. However, simultaneous addition of GATA6 and NR5A1 to an endometrial stromal cell is sufficient to transform it into an endometriotic-like cell, manifested by the activation of the estradiol biosynthetic cascade.

Estrogen-regulated expression of P450arom genes in the brain and ovaries of adult female Indian climbing perch, Anabas testudineus

Cytochrome P450arom (CYP19), a product of cyp19a1 gene, catalyzes the conversion of androgens to estrogens and is essential for regulation of reproductive function in vertebrates. In the present study, we isolated partial cDNA encoding the ovarian (cyp19a1a) and brain (cyp19a1b) P450arom genes from adult female perch, Anabas testudineus and investigated their regulation by estrogen in vivo. Results demonstrated that cyp19a1a and cyp19a1b predominate in ovary and brain respectively, with quantity of both attuned to reproductive cycle. To elucidate estrogen-regulated expression of cyp19a1b in brain and cyp19a1a in ovary, dose- and time-dependent studies were conducted with estrogen in vitellogenic-stage fish in the presence or absence of specific aromatase inhibitor fadrozole. Results demonstrated that treatment of fish with 17β-estradiol (E2; 1.0 μM)) for 6 days caused significant upregulation of cyp19a1b transcripts, aromatase B protein, and aromatase activity in brain in a dose- and time-dependent manner. Ovarian cyp19a1a mRNA, aromatase protein, and aromatase activity, however, was less responsive to E2 than brain. Treatment of fish with an aromatase inhibitor fadrozole for 6 days attenuated both brain and ovarian cyp19a1 mRNAs expression and stimulatory effects of E2 was also significantly reduced. These results indicate that expression of cyp19a1b in brain and cyp19a1a in ovary of adult female A. testudineus was closely associated to plasma E2 levels and seasonal reproductive cycle. Results further show apparent differential regulation of cyp19a1a and cyp19a1b expression by E2/fadrozole manipulation.

Role of Ad4-binding protein/steroidogenic factor 1 in regulating NADPH production in adrenocortical Y-1 cells

Ad4-binding protein/steroidogenic factor 1 (Ad4BP/SF-1), a member of the nuclear receptor superfamily, is expressed in steroidogenic cells and regulates all steroidogenic gene expression. We recently employed mRNA and chromatin immunoprecipitation sequence (ChIP-seq) to demonstrate that Ad4BP/SF-1 directly regulates the expression of nearly all glycolytic genes. The pentose phosphate pathway (PPP) contributes to the production of nicotinamide adenine dinucleotide phosphate (NADPH). Although the expression of PPP genes and intracellular NADPH were decreased by Ad4BP/SF-1 knockdown, these genes were not the direct targets of Ad4BP/SF-1. This study therefore investigates whether Ad4BP/SF-1 directly regulates genes implicated in NADPH production. Examination of previously published data sets of mRNA sequence (mRNA-seq) and ChIP-seq strongly suggested a possibility that other NADPH-producing genes, such as malic enzyme 1 (Me1) and methylenetetrahydrofolate dehydrogenase 2 (Mthfd2), are the direct targets of Ad4BP/SF-1. Reporter gene assays and determination of intracellular NADPH concentration supported the notion that Ad4BP/SF-1 regulates NADPH production by regulating these genes. NADPH is required for macromolecule synthesis of compounds such as steroids, and for detoxification of reactive oxygen species. When synthesizing steroid hormones, steroidogenic cells consume NADPH through enzymatic reactions mediated by steroidogenic P450s. NADPH is also consumed through elimination of reactive oxygen species produced as the byproducts of the P450 reactions. Overall, Ad4BP/SF-1 potentially maintains the intracellular NADPH level through cooperative regulation of genes involved in the biological processes for consumption and supply.

FOXL2 Is an Essential Activator of SF-1-Induced Transcriptional Regulation of Anti-Müllerian Hormone in Human Granulosa Cells

Anti-Müllerian hormone (AMH) is required for proper sexual differentiation by regulating the regression of the Müllerian ducts in males. Recent studies indicate that AMH could be an important factor for maintaining the ovarian reserve. However, the mechanisms of AMH regulation in the ovary are largely unknown. Here, we provide evidence that AMH is an ovarian target gene of steroidogenic factor-1 (SF-1), an orphan nuclear receptor required for proper follicle development. FOXL2 is an evolutionally conserved transcription factor, and its mutations cause blepharophimosis, ptosis, and epicanthus inversus syndrome (BPES), wherein affected females display eyelid defects and premature ovarian failure (POF). Notably, we found that functional FOXL2 is essential for SF-1-induced AMH regulation, via protein–protein interactions between FOXL2 and SF-1. A BPES-inducing mutant of FOXL2 (290–291delCA) was unable to interact with SF-1 and failed to mediate the association between SF-1 and the AMH promoter. Therefore, this study identified a novel regulatory circuit for ovarian AMH production; specifically, through the coordinated interplay between FOXL2 and SF-1 that could control ovarian follicle development.

Modulatory role of leptin on ovarian functions in water buffalo (Bubalus bubalis)

The aim of the present study was to demonstrate the modulatory role of leptin on bubaline granulosa cells (GCs) and luteal cells (LCs) functions using an in vitro cell culture system and to establish a cross talk between leptin and insulin-like growth factor-1 (IGF-1). GCs were collected from group IV follicles (>13 mm size) and LCs from mid-luteal phase corpus luteum and were grown in serum-containing media supplemented with leptin at three different dose rates (0.1, 1, and 10 ng/mL) and time durations (24, 48, and 72 hours). We evaluated the production and secretion of estradiol (E2) and progesterone (P4) using RIA and the mRNA expression of steroidogenic acute regulatory protein (STARD1), cytochrome P450 cholesterol side-chain cleavage (CYP11A1), 3β-hydroxysteroid dehydrogenase (3β-HSD), cytochrome P450 aromatase (CYP19A1), sterol regulatory element-binding protein 1 (SREBP1), steroidogenic factor-1 (SF1), anti-apoptotic gene PCNA, pro-apoptotic gene caspase 3 and endothelial cell marker, Von Willebrand factor (vWF), using quantitative real-time polymerase chain reaction. The results depicted a direct inhibitory action of leptin on GCs steroidogenesis in a time-dependent manner (P < 0.05), whereas in the presence of IGF-1 the inhibitory effect was reverted. Furthermore, leptin augmented both cellular proliferation (PCNA) and apoptosis (caspase 3). On the other hand, in LCs, leptin alone showed an apparent stimulatory effect on steroidogenesis (P < 0.05); however, in the presence of IGF-1, an antagonistic effect was witnessed. Moreover, leptin had an inhibitory effect on apoptosis while promoted cellular proliferation and angiogenesis. These findings were further strengthened by immunocytochemistry. To conclude, these observations for the first time reported that in buffaloes leptin has a direct dose-, time-, and tissue-dependent effect on ovarian steroidogenesis, angiogenesis, and cytoprotection, and furthermore, it can regulate the effect of systemic factors like IGF-1. Hence, this in vitro study provides an insight into the putative roles of leptin alone and its interactions in vivo.

Gonadotropin and sf-1 regulation of cyp19a1a gene and aromatase activity during oocyte development in the rohu, L. rohita

Cytochrome P450 aromatase (P450arom), a product of cyp19a1 gene, plays pivotal roles in vertebrate steroidogenesis and reproduction. In this study, we isolated partial cDNA encoding the ovarian (cyp19a1a) and brain (cyp19a1b) P450arom genes from adult female rohu, Labeo rohita and investigated the regulation of cyp19a1a by gonadotropin and SF-1. The cyp19a1a and cyp19a1b were expressed predominantly in the ovary and brain respectively, with quantity of the former attuned to reproductive cycle. To elucidate gonadotropin regulation of cyp19a1a mRNA expression and P450 aromatase activity for 17β-estradiol (E2) biosynthesis in vitro by the vitellogenic ovarian follicles, time- and dose-dependent studies were conducted with HCG and porcine FSH. Results demonstrated that HCG stimulated significantly higher expression of cyp19a1a mRNA and aromatase activity leading to increased biosynthesis of E2 than FSH. To understand the involvement of SF-1 to in the regulation of cyp19a1a and aromatase activity, ovarian follicles were incubated with increasing concentrations of HCG and expression of sf1gene and activation of SF-1 protein were measured. Results demonstrated that HCG significantly induced expression of sf-1 gene and activation of SF-1 protein suggesting a link between SF-1 and P450 aromatase activation in this fish ovary during gonadotropin-induced steroidogenesis.

Impact of ACTH Signaling on Transcriptional Regulation of Steroidogenic Genes

The trophic peptide hormone adrenocorticotropic (ACTH) stimulates steroid hormone biosynthesis evoking both a rapid, acute response and a long-term, chronic response, via the activation of cAMP/protein kinase A (PKA) signaling. The acute response is initiated by the mobilization of cholesterol from lipid stores and its delivery to the inner mitochondrial membrane, a process that is mediated by the steroidogenic acute regulatory protein. The chronic response results in the increased coordinated transcription of genes encoding steroidogenic enzymes. ACTH binding to its cognate receptor, melanocortin 2 receptor (MC2R), stimulates adenylyl cyclase, thus inducing cAMP production, PKA activation, and phosphorylation of specific nuclear factors, which bind to target promoters and facilitate coactivator protein recruitment to direct steroidogenic gene transcription. This review provides a general view of the transcriptional control exerted by the ACTH/cAMP system on the expression of genes encoding for steroidogenic enzymes in the adrenal cortex. Special emphasis will be given to the transcription factors required to mediate ACTH-dependent transcription of steroidogenic genes.

Regulation of Steroidogenesis, Development, and Cell Differentiation by Steroidogenic Factor-1 and Liver Receptor Homolog-1

Steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1) belong to the nuclear receptor superfamily and are categorized as orphan receptors. In addition to other nuclear receptors, these play roles in various physiological phenomena by regulating the transcription of target genes. Both factors share very similar structures and exhibit common functions. Of these, the roles of SF-1 and LRH-1 in steroidogenesis are the most important, especially that of SF-1, which was originally discovered and named to reflect such roles. SF-1 and LRH-1 are essential for steroid hormone production in gonads and adrenal glands through the regulation of various steroidogenesis-related genes. As SF-1 is also necessary for the development of gonads and adrenal glands, it is also considered a master regulator of steroidogenesis. Recent studies have clearly demonstrated that LRH-1 also represents another master regulator of steroidogenesis, which similarly to SF-1, can induce differentiation of non-steroidogenic stem cells into steroidogenic cells. Here, we review the functions of both factors in these steroidogenesis-related phenomena.

Effects of monobutyl phthalate on steroidogenesis through steroidogenic acute regulatory protein regulated by transcription factors in mouse Leydig tumor cells

OBJECTIVE

Dibutyl phthalate (DBP) is one of the most widely used phthalate esters, and it is ubiquitous in the environment. DBP and its major metabolite, monobutyl phthalate (MBP), change steroid biosynthesis and impair male reproductive function. However, the regulatory mechanism underlying the steroid biosynthesis disruption by MBP is still unclear.

METHODS

We analyzed the progesterone production, steroidogenic acute regulatory protein (StAR) mRNA, protein expression, and DNA-binding affinity of transcription factors (SF-1 and GATA-4).

RESULTS

Our results reveal that MBP inhibited progesterone production. At the same time, StAR mRNA and protein were decreased after MBP exposure. Furthermore, electrophoretic mobility shift assay showed that DNA-binding affinity of transcription factors (SF-1 and GATA-4) was decreased in a dose-dependent manner after MBP treatments. Western blot tests next confirmed that protein of SF-1 was decreased, but GATA-4 protein was unchanged. However, phosphorylated GATA-4 protein was decreased with 800 μM of MBP.

CONCLUSIONS

This study reveals an important and novel mechanism whereby SF-1 and GATA-4 may regulate StAR during MBP-induced steroidogenesis disruption.

Dynamics of adrenal glucocorticoid steroidogenesis in health and disease

The activity of the hypothalamic-pituitary-adrenal (HPA) axis is characterized by an ultradian (pulsatile) pattern of hormone secretion. Pulsatility of glucocorticoids has been found critical for optimal transcriptional, neuroendocrine and behavioral responses. This review will focus on the mechanisms underlying the origin of the glucocorticoid ultradian rhythm. Our recent research shows that the ultradian rhythm of glucocorticoids depends on highly dynamic processes within adrenocortical steroidogenic cells. Furthermore, we have evidence that disruption of these dynamics leads to abnormal glucocorticoid secretion observed in disease and critical illness in both humans and rats.

Retinoic acid receptor beta and angiopoietin-like protein 1 are involved in the regulation of human androgen biosynthesis

Androgens are essential for sexual development and reproduction. However, androgen regulation in health and disease is poorly understood. We showed that human adrenocortical H295R cells grown under starvation conditions acquire a hyperandrogenic steroid profile with changes in steroid metabolizing enzymes HSD3B2 and CYP17A1 essential for androgen production. Here we studied the regulatory mechanisms underlying androgen production in starved H295R cells. Microarray expression profiling of normal versus starved H295R cells revealed fourteen differentially expressed genes; HSD3B2, HSD3B1, CYP21A2, RARB, ASS1, CFI, ASCL1 and ENC1 play a role in steroid and energy metabolism and ANGPTL1, PLK2, DUSP6, DUSP10 and FREM2 are involved in signal transduction. We discovered two new gene networks around RARB and ANGPTL1, and show how they regulate androgen biosynthesis. Transcription factor RARB stimulated the promoters of genes involved in androgen production (StAR, CYP17A1 and HSD3B2) and enhanced androstenedione production. For HSD3B2 regulation RARB worked in cooperation with Nur77. Secretory protein ANGPTL1 modulated CYP17A1 and DUSP6 expression by inducing ERK1/2 phosphorylation. By contrast, our studies revealed no evidence for hormones or cell cycle involvement in regulating androgen biosynthesis. In summary, these studies establish a firm role for RARB and ANGPTL1 in the regulation of androgen production in H295R cells.

Dynamic pituitary-adrenal interactions in response to cardiac surgery

OBJECTIVES

To characterize the dynamics of the pituitary-adrenal interaction during the course of coronary artery bypass grafting both on and off pump. Since our data pointed to a major change in adrenal responsiveness to adrenocorticotropic hormone, we used a reverse translation approach to investigate the molecular mechanisms underlying this change in a rat model of critical illness.

DESIGN

CLINICAL STUDIES

Prospective observational study.

ANIMAL STUDIES

Controlled experimental study.

SETTING

CLINICAL STUDIES

Cardiac surgery operating rooms and critical care units.

ANIMAL STUDIES

University research laboratory.

SUBJECTS

CLINICAL STUDIES

Twenty, male patients.

ANIMAL STUDIES

Adult, male Sprague-Dawley rats.

INTERVENTIONS

CLINICAL STUDIES

Coronary artery bypass graft-both on and off pump.

ANIMAL STUDIES

Injection of either lipopolysaccharide or saline (controls) via a jugular vein cannula.

MEASUREMENTS AND MAIN RESULTS

CLINICAL STUDIES

Blood samples were taken for 24 hours from placement of the first venous access. Cortisol and adrenocorticotropic hormone were measured every 10 and 60 minutes, respectively, and corticosteroid-binding globulin was measured at the beginning and end of the 24-hour period and at the end of operation. There was an initial rise in both levels of adrenocorticotropic hormone and cortisol to supranormal values at around the end of surgery. Adrenocorticotropic hormone levels then returned toward preoperative values. Ultradian pulsatility of both adrenocorticotropic hormone and cortisol was maintained throughout the perioperative period in all individuals. The sensitivity of the adrenal gland to adrenocorticotropic hormone increased markedly at around 8 hours after surgery maintaining very high levels of cortisol in the face of "basal" levels of adrenocorticotropic hormone. This sensitivity began to return toward preoperative values at the end of the 24-hour sampling period.

ANIMAL STUDIES

Adult, male Sprague-Dawley rats were given either lipopolysaccharide or sterile saline via a jugular vein cannula. Hourly blood samples were subsequently collected for adrenocorticotropic hormone and corticosterone measurement. Rats were killed 6 hours after the injection, and the adrenal glands were collected for measurement of steroidogenic acute regulatory protein, steroidogenic factor 1, and dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 messenger RNAs and protein using real-time quantitative polymerase chain reaction and Western immunoblotting, respectively. Adrenal levels of the adrenocorticotropic hormone receptor (melanocortin type 2 receptor) messenger RNA and its accessory protein (melanocortin type 2 receptor accessory protein) were also measured by real-time quantitative polymerase chain reaction. In response to lipopolysaccharide, rats showed a pattern of adrenocorticotropic hormone and corticosterone that was similar to patients undergoing coronary artery bypass grafting. We were also able to demonstrate increased intra-adrenal corticosterone levels and an increase in steroidogenic acute regulatory protein, steroidogenic factor 1, and melanocortin type 2 receptor accessory protein messenger RNAs and steroidogenic acute regulatory protein, and a reduction in dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 and melanocortin type 2 receptor messenger RNAs, 6 hours after lipopolysaccharide injection.

CONCLUSIONS

Severe inflammatory stimuli activate the hypothalamic-pituitary-adrenal axis resulting in increased steroidogenic activity in the adrenal cortex and an elevation of cortisol levels in the blood. Following coronary artery bypass grafting, there is a massive increase in both adrenocorticotropic hormone and cortisol secretion. Despite a subsequent fall of adrenocorticotropic hormone to basal levels, cortisol remains elevated and coordinated adrenocorticotropic hormone-cortisol pulsatility is maintained. This suggested that there is an increase in adrenal sensitivity to adrenocorticotropic hormone, which we confirmed in our animal model of immune activation of the hypothalamic-pituitary-adrenal axis. Using this model, we were able to show that this increased adrenal sensitivity results from changes in the regulation of both stimulatory and inhibitory intra-adrenal signaling pathways. Increased understanding of the dynamics of normal hypothalamic-pituitary-adrenal responses to major surgery will provide us with a more rational approach to glucocorticoid therapy in critically ill patients.

Transcriptional regulation of genes related to progesterone production

Steroid hormones are synthesized from cholesterol in various tissues, mainly in the adrenal glands and gonads. Because these lipid-soluble steroid hormones immediately diffuse through the cells in which they are produced, their secretion directly reflects the activity of the genes related to their production. Progesterone is important not only for luteinization and maintenance of pregnancy, but also as a substrate for most other steroids. Steroidogenic acute regulatory protein (STAR), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), and 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4) isomerase (3β-HSD) are well-known proteins essential for progesterone production. In addition to them, glutathione S-transferase A1-1 and A3-3 are shown to exert Δ(5)-Δ(4) isomerization activity to produce progesterone in a cooperative fashion with 3β-HSD. 5-Aminolevulinic acid synthase 1, ferredoxin 1, and ferredoxin reductase also play a role in steroidogenesis as accessory factors. Members of the nuclear receptor 5A (NR5A) family (steroidogenic factor 1 and liver receptor homolog 1) play a crucial role in the transcriptional regulation of these genes. The NR5A family activates these genes by binding to NR5A responsive elements present within their promoter regions, as well as to the elements far from their promoters. In addition, various NR5A-interacting proteins including peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear receptor subfamily 0, group B, member 1 (DAX-1), and CCAAT/enhancer-binding proteins (C/EBP) are involved in the transcription of NR5A target genes and regulate the transcription either positively or negatively under both basal and tropic hormone-stimulated conditions. In this review, we describe the transcriptional regulation of genes related to progesterone production.

T-2 toxin regulates steroid hormone secretion of rat ovarian granulosa cells through cAMP-PKA pathway

T-2 toxin is a secondary metabolite produced by Fusarium genus and is a common contaminant in food and feedstuffs of cereal origin. In porcine granulosa cells(GC), T-2 toxin has been shown to inhibit the steroidogenesis; however, the mechanism has not been well understood. Gonadotropin-stimulated steroidogenesis is regulated by the cAMP-PKA pathway. In this study, we investigated potential mechanisms for T-2 toxin-induced reproductive toxicity focusing on the critical steps of the cAMP-PKA pathway affected by T-2 toxin. We first analyzed the effects of T-2 toxin on progesterone and estrogen production in rat granulosa cells. For this purpose the granulosa cells were cultured for 48 h in 10% fetal bovine serum-containing medium followed by 24h in serum-free medium containing FSH (10 ng/ml) and androstenedione (3 ng/ml), both are required for normal steroidogenesis. Treatment of these cells with T-2 toxin dose-dependently inhibited the growth of cells and the steroid hormone production. Cellular cyclic AMP levels were dose-dependently inhibited by T-2 toxin (0, 1, 10 and 100 nM, 24 h). Furthermore, we found that although the induction of progesterone by 8-Br-cAMP (a FSH mimetic) and 22R-HC (substrate for progesterone) could both be inhibited by T-2 toxin treatment, the T-2-imposed inhibitory effects could be reversed by increasing doses of 22R-HC, while increasing 8-Br-cAMP had no effects, suggesting that T2 toxin targeted at distinct mechanisms. cAMP-stimulated steroidogenic acute regulatory protein (StAR) is a rate limiting protein in progesterone synthesis. Exposure to T2 toxin caused significant suppression of StAR expression as determined by Western blotting and semi-quantitative RT-PCR suggesting StAR is a sensitive target for T-2 toxin. Taken together, our results strongly suggest that T2 toxin inhibits steroidogenesis by suppressing cAMP-PKA pathway and StAR is a target for T-2-toxin. The antisteroidogenesis effects were observable at low T-2 dose (1 ng/ml) suggesting T-2 toxin has an endocrine disruptive effect.

Low-dose bisphenol A disrupts gonad development and steroidogenic genes expression in adult female rare minnow Gobiocypris rarus

Bisphenol A (BPA), an estrogenic monomer, has attracted many researchers to study its adverse effects in animal reproduction, especially in fish. To explore the effects of low dose BPA on adult female rare minnow Gobiocypris rarus, we exposed the fish to BPA at nominal concentrations of 5, 15, and 50 μg L(-1) for 14 and 35 d. The 35-d BPA exposure at 50 μg L(-1) had obviously suppressive effects on oocyte development, and BPA at all the three concentrations in both exposure durations of 14 and 35 d had stimulative effects on hepatic vitellogenin (vtg) transcription. BPA at lower concentrations (5 and 15 μg L(-1)) exhibited stimulative effects on the expressions of ovarian steroidogenic genes while at higher concentration (50 μg L(-1)) displayed inhibitive effects. Analysis of ovarian steroidogenic genes 5'-flanking regions and mRNA expressions of their potential regulatory factors revealed that the BPA-mediated actions on steroidogenesis in G. rarus ovary probably involve estrogen receptor (Esr) and androgen receptor (Ar) signaling, nuclear receptor subfamily 5, group A, number 1 (Nr5a1) pathway, and epigenetic regulation.

The nuclear receptor NR2F2 activates star expression and steroidogenesis in mouse MA-10 and MLTC-1 Leydig cells

Testosterone production is dependent on cholesterol transport within the mitochondrial matrix, an essential step mediated by a protein complex containing the steroidogenic acute regulatory (STAR) protein. In steroidogenic Leydig cells, Star expression is hormonally regulated and involves several transcription factors. NR2F2 (COUP-TFII) is an orphan nuclear receptor that plays critical roles in cell differentiation and lineage determination. Conditional NR2F2 knockout prior to puberty leads to male infertility due to insufficient testosterone production, suggesting that NR2F2 could positively regulate steroidogenesis and Star expression. In this study we found that NR2F2 is expressed in the nucleus of some peritubular myoid cells and in interstitial cells, mainly in steroidogenically active adult Leydig cells. In MA-10 and MLTC-1 Leydig cells, small interfering RNA (siRNA)-mediated NR2F2 knockdown reduces basal steroid production without affecting hormone responsiveness. Consistent with this, we found that STAR mRNA and protein levels were reduced in NR2F2-depleted MA-10 and MLTC-1 cells. Transient transfections of Leydig cells revealed that a -986 bp mouse Star promoter construct was activated 3-fold by NR2F2. Using 5' progressive deletion constructs, we mapped the NR2F2-responsive element between -131 and -95 bp. This proximal promoter region contains a previously uncharacterized direct repeat 1 (DR1)-like element to which NR2F2 is recruited and directly binds. Mutations in the DR1-like element that prevent NR2F2 binding severely blunted NR2F2-mediated Star promoter activation. These data identify an essential role for the nuclear receptor NR2F2 as a direct activator of Star gene expression in Leydig cells, and thus in the control of steroid hormone biosynthesis.

Glycolytic genes are targets of the nuclear receptor Ad4BP/SF-1

Genetic deficiencies in transcription factors can lead to the loss of certain types of cells and tissue. The steroidogenic tissue-specific nuclear receptor Ad4BP/SF-1 (NR5A1) is one such gene, because mice in which this gene is disrupted fail to develop the adrenal gland and gonads. However, the specific role of Ad4BP/SF-1 in these biological events remains unclear. Here we use chromatin immunoprecipitation sequencing to show that nearly all genes in the glycolytic pathway are regulated by Ad4BP/SF-1. Suppression of Ad4BP/SF-1 by small interfering RNA reduces production of the energy carriers ATP and nicotinamide adenine dinucleotide phosphate, as well as lowers expression of genes involved in glucose metabolism. Together, these observations may explain tissue dysgenesis as a result of Ad4BP/SF-1 gene disruption in vivo. Considering the function of estrogen-related receptor α, the present study raises the possibility that certain types of nuclear receptors regulate sets of genes involved in metabolic pathways to generate energy carriers.

Thyroid and male reproduction

Male reproduction is governed by the classical hypothalamo-hypophyseal testicular axis: Hypothalamic gonadotropin releasing hormone (GnRH), pituitary luteinizing hormone (LH) and follicle stimulating hormone (FSH) and the gonadal steroid, principally, testosterone. Thyroid hormones have been shown to exert a modulatory influence on this axis and consequently the sexual and spermatogenic function of man. This review will examine the modulatory influence of thyroid hormones on male reproduction.

Characterization of four nr5a genes and gene expression profiling for testicular steroidogenesis-related genes and their regulatory factors in response to bisphenol A in rare minnow Gobiocypris rarus

Bisphenol A (BPA) widely used in the manufacture of numerous products is ubiquitous in aquatic environment. To explore the mechanisms of BPA-mediated actions, male rare minnow Gobiocypris rarus were exposed to BPA at concentrations of 5, 15, and 50 μg/L for 14 and 35 days in the present study. Four subtypes of nr5a gene encoding important transcription factors for steroidogenesis were characterized, and tissue distribution analysis demonstrated distinct expression profiling of the four genes in G. rarus. BPA at environmentally relevant concentration (5 μg/L) caused increase of gonadosomatic index (GSI) of male fish. In response to BPA, no obvious changes on the testis development were observed. Modulation of vtg mRNA expression by BPA suggests estrogenic and/or anti-estrogenic effects of BPA were dependent on exposed duration (14 or 35 days). Gene expression profiling for testicular steroidogenesis-related genes, sexual steroid receptors, gonadotropin receptors, and transcription factors indicates differential regulation was dependent on exposure duration and dose of BPA. The correlation analysis at mRNA level demonstrates that the BPA-mediated actions on testicular steroidogenesis might involve sex steroid hormone receptor signaling, gonadotropin/gonadotropin receptor pathway, and transcription factors such as nuclear receptor subfamily 5, group A (Nr5a), fork head box protein L2 (Foxl2).

Low-dose monobutyl phthalate stimulates steroidogenesis through steroidogenic acute regulatory protein regulated by SF-1, GATA-4 and C/EBP-beta in mouse Leydig tumor cells

BACKGROUND

The ubiquitous use of dibutyl phthalate (DBP), one of the most widely used plasticizers, results in extensive exposure to humans and the environment. DBP and its major metabolite, monobutyl phthalate (MBP), may alter steroid biosynthesis and their exposure may lead to damage to male reproductive function. Low-doses of DBP/MBP may result in increased steroidogenesis in vitro and in vivo. However, the mechanisms of possible effects of low-dose MBP on steroidogenesis remain unclear. The aim of present study was to elaborate the role of transcription factors and steroidogenic acute regulatory protein in low-dose MBP-induced distruption of steroidogenesis in mouse Leydig tumor cells (MLTC-1 cells).

METHODS

In the present study, MLTC-1 cells were cultured in RPMI 1640 medium supplemented with 2 g/L sodium bicarbonate. Progesterone level was examined by I125-pregesterone Coat-A-Count radioimmunoassay (RIA) kits. mRNA and protein levels were assessed by reverse transcription-polymerase chain reaction (RT-PCR) and western blot, respectively. DNA-binding of several transcription factors was examined by electrophoretic mobility shift assay (EMSA).

RESULTS

In this study, various doses of MBP (0, 10(-9), 10(-8), 10(-7), or 10(-6) M) were added to the medium followed by stimulation of MLTC-1 cells with human chorionic gonadotrophin (hCG). The results showed that MBP increased progesterone production and steroidogenic acute regulatory protein (StAR) mRNA and protein levels. However, the protein levels of cytochrome P450scc and 3 beta-hydroxy-steroid dehydrogenase (3 beta-HSD) were unchanged after MBP treatment. EMSA assay showed that DNA-binding of steroidogenic factors 1(SF-1), GATA-4 and CCAAT/enhancer binding protein-beta (C/EBP-beta) was increased in a dose-dependent manner after MBP exposure. Western blot tests were next employed and confirmed that the protein levels of SF-1, GATA-4 and C/EBP-beta were also increased. Additionally, western blot tests confirmed the expression of DAX-1, negative factor of SF-1, was dose-dependently down regulated after MBP exposure, which further confirmed the role of SF-1 in MBP-stimulated steroid biosynthesis.

CONCLUSIONS

In conclusion, we firstly delineated the regulation of StAR by transcription factors including SF-1, GATA-4 and C/EBP-beta maybe critical mechanism involved in low-dose MBP-stimulated steroidogenesis.

Constant light disrupts the circadian rhythm of steroidogenic proteins in the rat adrenal gland

The circadian rhythm of corticosterone (CORT) secretion from the adrenal cortex is regulated by the suprachiasmatic nucleus (SCN), which is entrained to the light-dark cycle. Since the circadian CORT rhythm is associated with circadian expression of the steroidogenic acute regulatory (StAR) protein, we investigated the 24h pattern of hormonal secretion (ACTH and CORT), steroidogenic gene expression (StAR, SF-1, DAX1 and Nurr77) and the expression of genes involved in ACTH signalling (MC2R and MRAP) in rats entrained to a normal light-dark cycle. We found that circadian changes in ACTH and CORT were associated with the circadian expression of all gene targets; with SF-1, Nurr77 and MRAP peaking in the evening, and DAX1 and MC2R peaking in the morning. Since disruption of normal SCN activity by exposure to constant light abolishes the circadian rhythm of CORT in the rat, we also investigated whether the AM-PM variation of our target genes was also disrupted in rats exposed to constant light conditions for 5weeks. We found that the disruption of the AM-PM variation of ACTH and CORT secretion in rats exposed to constant light was accompanied by a loss of AM-PM variation in StAR, SF-1 and DAX1, and a reversed AM-PM variation in Nurr77, MC2R and MRAP. Our data suggest that circadian expression of StAR is regulated by the circadian expression of nuclear receptors and proteins involved in both ACTH signalling and StAR transcription. We propose that ACTH regulates the secretion of CORT via the circadian control of steroidogenic gene pathways that become dysregulated under the influence of constant light.

Phospholipid--driven gene regulation

Phospholipids (PLs), well known for their fundamental role in cellular structure, play critical signaling roles via their derivatives and cleavage products acting as second messengers in signaling cascades. Recent work has shown that intact PLs act as signaling molecules in their own right by modulating the activity of nuclear hormone transcription factors responsible for tuning genes involved in metabolism, lipid flux, steroid synthesis and inflammation. As such, PLs have been classified as novel hormones. This review highlights recent work in PL-driven gene regulation with a focus on the unique structural features of phospholipid-sensing transcription factors and what sets them apart from well known soluble phospholipid transporters.

Inhibitory effect of bufalin and cinobufagin on steroidogenesis via the activation of ERK in human adrenocortical cells

BACKGROUND AND PURPOSE

Bufalin and cinobufagin exhibit cardiotonic and natriuretic activities. The aim of this study was to evaluate the effects of bufalin and cinobufagin on aldosterone and cortisol secretion and their mechanisms of action in human adrenocortical cells (NCI-H295).

EXPERIMENTAL APPROACH

H295 cells were incubated with bufalin or cinobufagin in the presence or absence of angiotensin II (Ang II), forskolin, 8-Br-cAMP, corticosterone or deoxycortisol. The role of ERK1/2 was studied by use of the inhibitor of MEK (U0126). The binding of transcription factor steroidogenic factor 1 (SF-1) to steroidogenic acute regulatory (StAR) gene promoter was analysed by EMSA.

KEY RESULTS

Bufalin and cinobufagin markedly inhibited basal, Ang II-, forskolin- or 8-Br-cAMP-stimulated aldosterone and cortisol secretion, and the conversions of corticosterone to aldosterone and deoxycortisol to cortisol. Bufalin and cinobufagin also inhibited StAR protein expression and SF-1 binding to StAR gene promoter. They both increased phosphorylation of ERK1/2, and U0126 fully abolished these effects on ERK1/2 in H295 cells. Furthermore, U0126 reversed the inhibitory effects of bufalin and cinobufagin on StAR protein expression and the binding of SF-1 to StAR gene promoter. However, U0126 did not completely reverse their inhibitory effects on aldosterone and cortisol release.

CONCLUSIONS AND IMPLICATIONS

The inhibitory effects of bufalin and cinobufagin on steroidogenesis of aldosterone and cortisol were associated with inhibition of aldosterone synthase and 11β-hydroxylase, as well as the suppression of StAR protein expression and SF-1 binding to StAR promoter via the phosphorylation of ERK1/2 in H295 cells.

Angiotensin II-dependent transcriptional activation of human steroidogenic acute regulatory protein gene by a 25-kDa cAMP-responsive element modulator protein isoform and Yin Yang 1

Transcriptional activation of the steroidogenic acute regulatory protein (STAR) gene is a critical component in the angiotensin II (Ang II)-dependent increase in aldosterone biosynthesis in the adrenal gland. The purpose of this study was to define the molecular mechanisms that mediate the Ang II-dependent increase in STARD1 gene (STAR) expression in H295R human adrenocortical cells. Mutational analysis of the STAR proximal promoter revealed that a nonconsensus cAMP-responsive element located at -78 bp relative to the transcription start site (-78CRE) is required for the Ang II-stimulated STAR reporter gene activity. DNA immunoaffinity chromatography identified a 25-kDa cAMP-responsive element modulator isoform and Yin Yang 1 (YY1) as -78CRE DNA-binding proteins, and Ang II treatment of H295R cells increased expression of that 25-kDa CREM isoform. Small interfering RNA silencing of CREM and YY1 attenuated the Ang II-dependent increases in STAR reporter gene activity and STAR mRNA levels. Conversely, overexpression of CREM and YY1 in COS-1 cells resulted in transactivation of STAR reporter gene activity. Chromatin immunoprecipitation analysis demonstrated recruitment of CREM and YY1 to the STAR promoter along with increased association of the coactivator cAMP response element-binding protein-binding protein (CBP) and increased phosphorylated RNA polymerase II after Ang II treatment. Together our data reveal that the Ang II-stimulated increase in STAR expression in H295R cells requires 25 kDa CREM and YY1. The recruitment of these transcription factors to the STAR proximal promoter results in association of CBP and activation of RNA polymerase II leading to increased STAR transcription.

Sphingosine-1-phosphate rapidly increases cortisol biosynthesis and the expression of genes involved in cholesterol uptake and transport in H295R adrenocortical cells

In the acute phase of adrenocortical steroidogenesis, adrenocorticotrophin (ACTH) activates a cAMP/PKA-signaling pathway that promotes the transport of free cholesterol to the inner mitochondrial membrane. We have previously shown that ACTH rapidly stimulates the metabolism of sphingolipids and the secretion of sphingosine-1-phosphate (S1P) in H295R cells. In this study, we examined the effect of S1P on genes involved in the acute phase of steroidogenesis. We show that S1P increases the expression of steroidogenic acute regulatory protein (StAR), 18-kDa translocator protein (TSPO), low-density lipoprotein receptor (LDLR), and scavenger receptor class B type I (SR-BI). S1P-induced StAR mRNA expression requires Gα(i) signaling, phospholipase C (PLC), Ca(2+)/calmodulin-dependent kinase II (CamKII), and ERK1/2 activation. S1P also increases intracellular Ca(2+), the phosphorylation of hormone sensitive lipase (HSL) at Ser(563), and cortisol secretion. Collectively, these findings identify multiple roles for S1P in the regulation of glucocorticoid biosynthesis.

Inverse agonist activity of steroidogenic factor SF-1

Steroidogenic factor 1 (SF-1) is a key regulator of endocrine function, especially steroidogenesis and reproduction. Unlike most nuclear receptors, SF-1 is constitutively activated and still remains an orphan receptor. To study its function, it is imperative to have reliable assays that can assess potential pharmacological modulators. Here we describe in detail three different cell-based assays that evaluate distinct aspects of SF-1 function: a cellular proliferation assay R-SAT® that monitors events far downstream of the receptor/ligand interaction, a transcriptional assay that focuses on the gene-modulating properties of SF-1, and an assay in adrenocortical cultures that constitutes a surrogate measure of SF-1 function in native tissues.

Aromatase is a direct target of FOXL2: C134W in granulosa cell tumors via a single highly conserved binding site in the ovarian specific promoter

Background

Granulosa cell tumors (GCT) of the ovary often express aromatase and synthesize estrogen, which in turn may influence their progression. Recently a specific point mutation (C134W) in the FOXL2 protein was identified in >94% of adult-type GCT and it is likely to contribute to their development. A number of genes are known to be regulated by FOXL2, including aromatase/CYP19A1, but it is unclear which are direct targets and whether the C134W mutation alters their regulation. Recently, it has been reported that FOXL2 forms a complex with steroidogenic factor 1 (SF-1) which is a known regulator of aromatase in granulosa cells.

Methodology/Principal Findings

In this work, the human GCT-derived cell lines KGN and COV434 were heterozygous and wildtype for the FOXL2:C134W mutation, respectively. KGN had abundant FOXL2 mRNA expression but it was not expressed in COV434. Expression of exogenous FOXL2:C134W in COV434 cells induced higher expression of a luciferase reporter for the ovarian specific aromatase promoter, promoter II (PII) (−516bp) than expression of wildtype FOXL2, but did not alter induction of a similar reporter for the steroidogenic acute regulatory protein (StAR) promoter (−1300bp). Co-immunoprecipitation confirmed that FOXL2 bound SF-1 and that it also bound its homologue, liver receptor homologue 1 (LRH-1), however, the C134W mutation did not alter these interactions or induce a selective binding of the proteins. A highly conserved putative binding site for FOXL2 was identified in PII. FOXL2 was demonstrated to bind the site by electrophoretic mobility shift assays (EMSA) and site-directed mutagenesis of this element blocked its differential induction by wildtype FOXL2 and FOXL2:C134W.

Conclusions/Significance

These findings suggest that aromatase is a direct target of FOXL2:C134W in adult-type GCT via a single distinctive and highly conserved binding site in PII and therefore provide insight into the pathogenic mechanism of this mutation.

Stimulatory effects of propylthiouracil on pregnenolone production through upregulation of steroidogenic acute regulatory protein expression in rat granulosa cells

Propylthiouracil (PTU) is a common and effective clinical medicine for the treatment of hyperthyroidism. Our previous study demonstrated that short-term treatment with PTU inhibits progesterone production in rat granulosa cells. However, our present results indicate that a 16-h treatment with PTU was able to stimulate pregnenolone production in rat granulosa cells, although progesterone production was diminished by PTU through inhibition of 3β-hydroxysteroid dehydrogenase. Notably, we found that PTU treatment enhanced the conversion of cholesterol into pregnenolone, whereas the protein level of the cytochrome P450 side-chain cleavage enzyme (P450scc, which is the enzyme responding to this conversion) was not affected. Interestingly, the levels of steroidogenic acute regulatory protein (StAR) in both total cell lysate and the mitochondrial fraction were significantly increased by PTU treatment. Furthermore, the binding of steroidogenic factor-1 (SF-1) to the StAR promoter region was also enhanced by PTU treatment, which suggests that PTU could upregulate StAR gene expression. In addition to SF-1 regulation, we found that mitogen-activated protein (MAP) kinase kinase activation is an important regulator of PTU-stimulated StAR protein expression, based on the effects of the MEK inhibitor PD98059. In conclusion, these results indicate that PTU plays opposite roles in the production of progesterone and its precursor, pregnenolone. The regulation of negative feedback on speeding the cholesterol transportation and pregnenolone conversion after a 16-h PTU treatment may be the mechanism explaining PTU's inhibition of progesterone production in rat granulosa cells.

Synergistic activation of the Mc2r promoter by FOXL2 and NR5A1 in mice

Forkhead box protein L2 (FOXL2) is the earliest ovarian marker and plays an important role in the regulation of cholesterol and steroid metabolism, inflammation, apoptosis, and ovarian development and function. Mutations and deficiencies of the human FOXL2 gene have been shown to cause blepharophimosis-ptosis-epicanthus inversus syndrome as well as premature ovarian failure. Although Foxl2 interacts with steroidogenic factor 1 (Nr5a1) and up-regulates cyp19a1a gene transcription in fish, FOXL2 represses the transcriptional activity of the gene that codes for steroidogenic acute regulatory protein (Star) in mice. Most of the recent studies have heavily focused on the FOXL2 target genes (Star and Cyp19a1) in the ovaries. Hence, it is of importance to search for other downstream targets of FOXL2 and for the possibility of FOXL2 expression in nonovarian tissues. Herein, we demonstrate that the interplay between FOXL2 and NR5A1 regulates Star and melanocortin 2 receptor (Mc2r) gene expression in mammalian systems. Both FOXL2 and NR5A1 are expressed in ovarian and adrenal gland tissues. As expected, FOXL2 represses and NR5A1 enhances the promoter activity of Star. Notably, the promoter activity of Mc2r is activated by FOXL2 in a dose-dependent manner. Surprisingly, we found that FOXL2 and NR5A1 synergistically up-regulate the transcriptional activity of Mc2r. By mapping the Mc2r promoter, we provide evidence that distal NR5A1 response elements (-1410 and -975) are required for synergistic activation by FOXL2 and NR5A1. These results suggest that the interplay between FOXL2 and NR5A1 on the Mc2r promoter functions as a novel mechanism for regulating MC2R-mediated cell signaling as well as steroidogenesis in adrenal glands.

Identification of a novel distal control region upstream of the human steroidogenic acute regulatory protein (StAR) gene that participates in SF-1-dependent chromatin architecture

StAR (steroidogenic acute regulatory protein) mediates the transport of cholesterol from the outer to the inner mitochondrial membrane, the process of which is the rate-limiting step for steroidogenesis. Transcriptional regulation of the proximal promoter of the human StAR gene has been well characterized, whereas analysis of its distal control region has not. Recently, we found that SF-1 (steroidogenic factor 1) induced the differentiation of mesenchymal stem cells (MSCs) into steroidogenic cells with the concomitant strong induction of StAR expression. Here, we show, using differentiated MSCs, that StAR expression is regulated by a novel distal control region. Using electrophoretic mobility shift (EMSA) and chromatin immunoprecipitation (ChIP) assays, we identified novel SF-1 binding sites between 3,000 and 3,400 bp upstream of StAR. A luciferase reporter assay revealed that the region worked as a strong regulator to exert maximal transcription of StAR. ChIP analysis of histone H3 revealed that upon SF-1 expression, nucleosome eviction took place at the SF-1 binding sites, not only in the promoter but also in the distal SF-1 binding sites. Chromosome conformation capture analysis revealed that the region upstream of StAR formed a chromatin loop both in the differentiated MSCs and in KGN cells, a human granulosa cell tumor cell line, where SF-1 is endogenously expressed. Finally, SF-1 knockdown resulted in disrupted formation of this chromatin loop in KGN cells. These results indicate that the novel distal control region participate in StAR activation through SF-1 dependent alterations of chromatin structure, including histone eviction and chromatin loop formation.