Steroidogenic factor 1 differentially regulates basal and inducible steroidogenic gene expression and steroid synthesis in human adrenocortical H295R cells

Local Regulation of Adrenal Steroidogenesis: Subtle in vitro Effects of IL-1β on the Human Cell Line NCI-H295R Steroid Production along with Changes in MicroRNA Profile and Orphan Nuclear Receptors NR4As

INTRODUCTION

IL-1β, a cytokine from the innate immune response, is well known for its proinflammatory effects and stimulating activity on the hypothalamus-pituitary-adrenal axis, leading to the pituitary synthesis of adrenocorticotropic hormone followed by cortisol (and dehydroepiandrosterone - DHEA) release by the adrenal gland. While IL-1β modulates the adrenal steroidogenesis at the central level, it is unclear whether it also exerts an effect on the adrenal gland.

METHOD

We studied the effect of IL-1β on adrenal steroid production and steroidogenic enzyme RNA expression in the human cell line NCI-H295R. We also explored eventual changes in the microRNA (miRNA) profile from IL-1β-treated NCI-H295R cells.

RESULTS

Transcripts encoding IL-1β receptors 1 and 2 were noticeable in the cell line, with cortisol and DHEA production showing a subtle increase after cytokine treatment. Transcripts from key enzymes in the steroidogenic pathway were analyzed, with no noticeable changes on them. The miRNA profile was modified by IL-1β treatment to an extent which bears some relationship with the regulatory mechanisms underlying adrenal steroid production. Since orphan nuclear receptors NR4As have emerged as potential key factors for coordinating inflammatory and metabolic responses, cell expression studies were also carried out to show an NR4As transcript augmentation following IL-1β treatment.

DISCUSSION/CONCLUSIONS

The subtle increase in adrenal steroid production in response to IL-1β stimulation without any modification in the transcription of the steroidogenic enzymes analyzed suggests an additional inflammatory/anti-inflammatory loop, wherein NR4As receptors may participate. Besides its physiological role, this process might be implied in pathological states accompanied by an unbalanced immune-endocrine relationship.

Bile acids increase steroidogenesis in cholemic mice and induce cortisol secretion in adrenocortical H295R cells via S1PR2, ERK and SF-1

BACKGROUND AND AIMS

Bile acids are now accepted as central signalling molecules for the regulation of glucose, amino acid and lipid metabolism. Adrenal gland cortex cells express the bile acid receptors farnesoid X receptor (FXR), the G protein-coupled bile acid receptor (TGR5) and the sphingosine-1-phosphate receptor 2 (S1PR2). We aimed to determine the effects of cholestasis and more specifically of bile acids on cortisol production.

METHODS

FXR and TGR5 knockout mice and controls were subjected to common bile duct ligation (CBDL) or chenodeoxycholic acid (CDCA) feeding to model cholestasis. Human adrenocortical H295R cells were challenged with bile acids for mechanistic studies.

RESULTS

We found that CBDL and CDCA feeding increased the levels of corticosterone, the rodent equivalent to human cortisol and mRNA and protein levels of steroidogenesis-related enzymes in adrenals independent of FXR and TGR5. Taurine-conjugated CDCA (TCDCA) significantly stimulated cortisol secretion, phosphorylation of extracellular signal-regulated kinase (ERK) and expression of steroidogenesis-related genes in human adrenocortical H295R cells. FXR and TGR5 agonists failed to induce cortisol secretion in H295R cells. S1PR2 inhibition significantly abolished TCDCA-induced cortisol secretion, lowered phosphorylation of ERK and abrogated enhanced transcription of steroidogenesis-related genes in H295R cells. Likewise, siRNA S1PR2 treatment reduced the phosphorylation of ERK and cortisol secretion. Steroidogenic factor-1 (SF-1) transactivation activity was increased upon TCDCA treatment suggesting that bile acid signalling is linked to SF-1. Treatment with SF-1 inverse agonist AC45594 also reduced TCDCA-induced steroidogenesis.

CONCLUSIONS

Our findings indicate that supraphysiological bile acid levels as observed in cholestasis stimulate steroidogenesis via an S1PR2-ERK-SF-1 signalling pathway.

Steroidogenic factor 1 promotes aggressive growth of castration-resistant prostate cancer cells by stimulating steroid synthesis and cell proliferation

The dependence of prostate cancer on androgens provides a targeted means of treating advanced disease. Unfortunately, androgen deprivation therapies eventually become ineffective, leading to deadly castration-resistant prostate cancer (CRPC). One of many factors implicated in the transition to CRPC is the onset of de novo steroidogenesis. Although reactivation of steroid receptors likely plays a pivotal role in aggressive CRPC, little is understood regarding the mechanisms whereby prostate cancer cells initiate and maintain steroidogenesis. We hypothesize that steroidogenic factor 1 (SF1, NR5A1, AD4BP), a key regulator of steroidogenesis in normal endocrine tissues, is expressed in CRPC where it stimulates aberrant steroidogenesis and fuels aggressive growth. Notably, SF1 is not expressed in normal prostate tissue. Our results indicated that SF1 was absent in benign cells but present in aggressive prostate cancer cell lines. Introduction of ectopic SF1 expression in benign human prostate epithelial cells (BPH-1) stimulated increased steroidogenic enzyme expression, steroid synthesis, and cell proliferation. In contrast, data from an aggressive human prostate cancer cell line (BCaPT10) demonstrated that SF1 was required for steroid-mediated cell growth because BCaPT10 cell growth was diminished by abiraterone treatment and short hairpin RNA-mediated knockdown of SF1 (shSF1). SF1-depleted cells also exhibited defective centrosome homeostasis. Finally, whereas xenograft experiments in castrated hosts with BCaPT10 control transplants grew large, invasive tumors, BCaPT10-shSF1 knockdown transplants failed to grow. Therefore, we conclude that SF1 stimulates steroid accumulation and controls centrosome homeostasis to mediate aggressive prostate cancer cell growth within a castrate environment. These findings present a new molecular mechanism and therapeutic target for deadly CRPC.

Effects of polycyclic musks HHCB and AHTN on steroidogenesis in H295R cells

1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(γ)-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN) are widely used in personal care products. Previous studies showed that HHCB and AHTN can be found in various environmental matrices and have potential endocrine disrupting effects. However, the effects on adrenocortical function of HHCB and AHTN are not fully understood. This study evaluated the influences of HHCB and AHTN on seven steroid hormones (progesterone, aldosterone, cortisol, 17α-OH-progesterone, androstenedione, 17β-estradiol, and testosterone) and 10 genes involved in steroidogenic pathways (HMGR, StAR, CYP11A1, 3βHSD2, CYP17, CYP21, CYP11B1, CYP11B2, 17βHSD, and CYP19) using the H295R cell line in the absence and presence of 8-Br-cAMP. MC2R transcription on the cell membrane was also examined to further investigate the effects of HHCB and AHTN on adrenal steroidogenesis. The results demonstrated that HHCB and AHTN could inhibit progesterone and cortisol production mainly by the suppression of 3βHSD2 and CYP21. Meanwhile, high concentrations of AHTN can affect the sensitivity of H295R cells to ACTH by disrupting MC2R transcription. Overall, the results indicate that high concentrations of HHCB and AHTN can affect steroidogenesis in vitro using the H295R cell line.

Regulation of human CYP11B1 and CYP11B2 promoters by transposable elements and conserved cis elements

CYP11B1 and CYP11B2 responsible for the final steps of cortisol and aldosterone synthesis, respectively, are believed to be duplicate genes with distinctive promoters. Our sequence analysis uncovers that these two genes share great homology in the proximal upstream regions, but insertion of Alu and L1 elements drives promoters divergent. Each CYP11B promoter contains two Alu elements embedded in a truncated L1 element, breaking L1 into three disconnected fragments. Alu functions as an enhancer in both genes regardless of orientation and copy number. Insertion of Alu upstream of a SV40 promoter also elevates promoter activity. However, the effect of Alu on CYP11B1 is blocked by a second L1 element (CYP11B1-L1.2) inserted between the first one and the conserved proximal upstream region. Although CYP11B1-L1.2 is 5'-truncated and lacks a functional ORF, replacing it with a fluorescent gene demonstrates that the element can be transcribed from the CYP11B1 core promoter in an opposite direction and a smaller magnitude compared to CYP11B1. Deletion of CYP11B1-L1.2 greatly increases CYP11B1 promoter activity and restores the enhancing effect of Alu. The Ad5 and SF-1 binding elements conserved in the proximal core promoter play a role in basal expression of both genes. Mutation of the Ad5 site reduces promoter activity to the minimal level. ERRα is the transcription factor interacting with Ad5 during basal expression. The core promoters of both genes are also conserved in mouse and rat despite the fact that the sites corresponding to cre, Ad5, and SF-1 in rodent Cyp11b1 promoters deviate from consensus.

Multiple noncoding exons 1 of nuclear receptors NR4A family (nerve growth factor-induced clone B, Nur-related factor 1 and neuron-derived orphan receptor 1) and NR5A1 (steroidogenic factor 1) in human cardiovascular and adrenal tissues

OBJECTIVE

Nuclear receptors are involved in a wide variety of functions, including aldosteronogenesis. Nuclear receptor families NR4A [nerve growth factor-induced clone B (NGFIB), Nur-related factor 1 (NURR1) and neuron-derived orphan receptor 1 (NOR1)] and NR2F [chicken ovalbumin upstream promoter-transcription factor 1 (COUP-TFI), COUP-TFII and NR2F6) activate, whereas NR5A1 [steroidogenic factor 1 (SF1)] represses CYP11B2 (aldosterone synthase) gene transcription. The present study was undertaken to elucidate the mechanism of differential regulation of nuclear receptors between cardiovascular and adrenal tissues.

METHODS

We collected tissues of artery (n = 9), cardiomyopathy muscle (n = 9), heart muscle (noncardiomyopathy) (n = 6), adrenal gland (n = 9) and aldosterone-producing adenoma (APA) (n = 9). 5'-rapid amplification of cDNA ends (RACE) identified transcription start sites. Multiplex reverse-transcription PCR (RT-PCR) determined use of alternative noncoding exons 1 (ANEs).

RESULTS

In adrenocortical H295R cells, angiotensin II, KCl or cAMP, all stimulated CYP11B2 transcription and NR4A was upregulated, whereas NR2F and NR5A1 were downregulated. 5'-RACE and RT-PCR revealed four ANEs of NGFIB (NR4A1), three of NURR1 (NR4A2), two of NOR1 (NR4A3) and two of SF1 (NR5A1) in cardiovascular and adrenal tissues. Quantitative multiplex RT-PCR showed NR4A and NR5A1 differentially employed multiple ANEs in a tissue-specific manner. The use of ANEs of NGFIB and NURR1 was significantly different between APA and artery. Changes in use of ANEs of NGFIB and NOR1 were observed between cardiomyopathy and noncardiomyopathy. The NR4A mRNA levels in artery were high compared with cardiac and adrenal tissues, whereas the NR5A1 mRNA level in adrenal tissues was extremely high compared with cardiovascular tissues.

CONCLUSION

NR4A and NR5A1 genes are complex in terms of alternative promoter use. The use of ANEs may be associated with the pathophysiology of the heart and adrenal gland.

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.

Modulation of steroidogenic gene expression and hormone synthesis in H295R cells exposed to PCP and TCP

Chlorophenols (CPs) have been suspected to disrupt the endocrine system and thus affect human and wildlife reproduction but less is known about the underlying mechanism. In this study, we investigated the effects of pentachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP) on human adrenocortical carcinoma cell line (H295R). The H295R cells were exposed to environmentally relevant concentration (0.0, 0.4, 1.1, 3.4μM) of PCP and TCP for 48h, and expression of specific genes involved in steroidogenesis, including cytochrome P450 (CYP11A, CYP17, CYP19), 3βHSD2, 17βHSD4 and StAR was quantitatively measured using real-time polymerase chain reaction. The selected gene expressions were significantly down-regulated compared with those in the control group. Exposure to PCP and TCP significantly decreased production of both testosterone (T) and 17β-estradiol (E2). Furthermore, a dose-dependent decrease of cellular cAMP was observed in H295R cells exposed to both PCP and TCP. A time-course study revealed that the observed selected steroidogenic gene expressions and protein abundance (StAR) are consistent with reduced cellular cAMP concentrations. The results showed that PCP and TCP may inhibit steroidogenesis by disrupting cAMP signaling. The research indicates that H295R cells can be used as an in vitro model for endocrine disruption assay for chlorophenols and the mechanism involvement of disturbing cAMP signaling.

Human steroidogenic factor-1 (hSF-1) regulates progesterone biosynthesis and growth of ovarian surface epithelial cancer cells

The majority of cancers derived from ovarian surface epithelial (OSE) cells are lethal. Estrogens promote proliferation of OSE cells, whereas progesterone inhibits proliferation and promotes apoptosis of OSE cells. Human steroidogenic factor-1 (hSF-1) induction of the steroidogenic acute regulatory protein (StAR) gene, and the steroidogenic enzymes CYP11A1 and HSD3B2 is central to progesterone biosynthesis. Whereas hSF-1 and StAR are expressed in human ovarian surface epithelial (HOSE) cells, hSF-1 and StAR protein were not expressed in a panel of malignant ovarian cancer cell lines (SKOV-3, BG-1, and Caov-3), and in human OSE cells immortalized by SV40 large T antigen (IOSE-121). Transient expression of hSF-1 in SKOV-3 cells activated the expression of StAR, p450scc and 3betaHSD-II mRNAs, and induced progesterone biosynthesis. Additionally, hSF-1 suppressed proliferation and promoted apoptosis of SKOV-3 cells and suppressed SKOV-3 cell growth induced by ERalpha and estradiol. These findings suggest that hSF-1 is central to progesterone biosynthesis in OSE cells. Human SF-1 may decrease OSE cancer cell numbers directly by apoptosis, and indirectly by opposing estradiol-induced proliferation. These findings are consistent with the hypothesis, that down-regulation of hSF-1 contributes to progression of ovarian epithelial cancers.

Prenatal synthetic glucocorticoid exposure alters hypothalamic-pituitary-adrenal regulation and pregnancy outcomes in mature female guinea pigs

Preterm delivery occurs in approximately 10% of all pregnancies. Prenatal exposure to synthetic glucocorticoids (sGCs) reduces the incidence of respiratory distress syndrome (RDS) in these babies. Therefore, administration of multiple courses of sGCs became common practice. Animal and human studies have demonstrated that multiple courses of sGCs can have long-term effects. While the majority of animal studies have been undertaken in male offspring, it is emerging that there are profound sex differences in the consequences of prenatal sGC exposure. To our knowledge, no studies have determined the effects of prenatal sGC exposure on hypothalamic-pituitary-adrenal (HPA) axis function in female offspring while accounting for reproductive cycle status, or determined if there are effects on pregnancy parameters. Pregnant guinea pigs were administered three courses of betamethasone (Beta), dexamethasone (Dex) or vehicle on gestational days 40/41, 50/51 and 60/61. In adulthood (age range: postnatal days 126-165), basal and activated HPA axis function were assessed at various stages of the reproductive cycle. The female offspring were then mated and underwent an undisturbed pregnancy. Females were killed in the luteal phase of the reproductive cycle following litter weaning, and molecular analysis undertaken. In the luteal phase, Beta-exposed females exhibited significantly lower basal salivary cortisol levels (P < 0.05). Dex-exposed females also exhibited significantly lower basal salivary cortisol levels during the luteal phase (P < 0.05), but increased basal salivary cortisol levels during the ostrous phase (P < 0.01). The Beta-exposed females exhibited increased glucocorticoid receptor (GR) mRNA expression in the CA1/2 region of the hippocampus (P < 0.05) and MC2R mRNA in the adrenal cortex (P < 0.05). The Dex-exposed animals exhibited higher hippocampal GR and mineralocorticoid receptor (MR) mRNA levels (P < 0.05). Beta-exposed females showed reduced fecundity (P < 0.05). In Dex-exposed females there was a lower male to female sex ratio. In conclusion, prenatal sGC exposure affects HPA axis activity, in a cycle-dependent manner, and long-term reproductive success. The clinical implications of the findings on endocrine function and pregnancy in females are profound and further follow-up is warranted in human cohorts. Furthermore, we have shown there are considerable difference in phenotypes between the Beta- and Dex-exposed females and the specific endocrine and maternal outcome is contingent on the specific sGCs administered during pregnancy.

Role of angiotensin II-induced rapid response genes in the regulation of enzymes needed for aldosterone synthesis

Aldosterone is principally synthesized in the zona glomerulosa of the adrenal by a series of enzymatic reactions leading to the conversion of cholesterol to aldosterone. Angiotensin II (Ang II) is the major physiological regulator of aldosterone production acting acutely to stimulate aldosterone biosynthesis and chronically to increase the capacity of the adrenals to produce aldosterone. We previously defined eight transcription factors that are rapidly induced following Ang II treatment using three in vitro adrenocortical cell models. Herein, we investigated the function of these transcription factors in the regulation of the enzymes needed for aldosterone production. H295R adrenal cells were co-transfected with expression vectors for each transcription factor and promoter/reporter constructs prepared for genes encoding the enzymes needed for aldosterone production. NGFI-B family members induced promoter activity of 3-beta-hydroxysteroid-dehydrogenase type 2 (HSD3B2), 21-hydroxylase (CYP21A2), and aldosterone synthase (CYP11B2). The importance of NGFI-B in the regulation of CYP11B2 was also demonstrated by reduced CYP11B2 transcription in the presence of a dominant-negative-NGFI-B. A pharmacological approach was used to characterize the Ang II pathways regulating transcription of NGFI-B family genes. Transcription of NGFI-B members were decreased following inhibition of Ang II type 1 receptor (AT1R), protein kinase C (PKC), calcium/calmodulin-dependent kinases (CaMK), and Src tyrosine kinase (SRC). Taken together, these results suggest that Ang II binding to the AT1R increases activity of PKC, CaMK, and SRC, which act to increase expression of the family of NGFI-B genes as well as CYP11B2. Ang II induction of the NGFI-B family members represents an important pathway to increase the capacity of adrenal cells to produce aldosterone.

Differential effects of high and low steroidogenic factor-1 expression on CYP11B2 expression and aldosterone production in adrenocortical cells

Steroidogenic factor-1 (SF-1/Ad4BP/NR5A1) plays a major role in regulating steroidogenic enzymes. We have previously shown that SF-1 inhibits aldosterone synthase (CYP11B2) reporter gene activity. Herein, we used the H295R/TR/SF-1 adrenal cells that increase SF-1 in a doxycycline-dependent fashion. Cells were incubated with or without doxycycline to induce SF-1 and then treated with angiotensin II (Ang II). Aldosterone was measured by immunoassay. SF-1 mRNA was silenced by small interfering RNA (siRNA) by Nucleofector technology. mRNA levels were measured by real-time RT-PCR. Ang II treatment without doxycycline increased aldosterone production by 11.3-fold and CYP11B2 mRNA by 116-fold. Doxycycline treatment increased SF-1 mRNA levels by 3.7-fold and inhibited Ang II-induced aldosterone by 84%. Doxycycline treatment inhibited Ang II-stimulated CYP11B2 mRNA levels by 86%. Doxycycline decreased basal CYP11B2 promoter activity by 68%. Doxycycline inhibited Ang II stimulation by 85%. Ang II increased CYP21 mRNA expression by 4.6-fold, whereas doxycycline inhibited induction by 69%. In contrast, doxycycline treatment increased CYP11B1 mRNA by 1.7-fold in basal cells and increased Ang II induction by 3.6-fold. SF-1-specific siRNA significantly reduced SF-1 mRNA expression as compared with cells treated with control siRNA. SF-1 siRNA reversed doxycycline stimulation of CYP B1 and its inhibition of CYP11B2. However, in H295R/TR/SF-1 cells without doxycycline treatment, both CYP11B1 and CYP11B2 mRNAs were significantly decreased, suggesting that both enzymes require a minimal level of SF-1 for basal expression. In summary, SF-1 overexpression dramatically inhibited CYP11B2 expression and decreased aldosterone production. The opposing effects of SF-1 on CYP11B1 and CYP11B2 suggest that the regulation of SF-1 activity may play a role that determines the relative ability to produce mineralocorticoid and glucocorticoid.

Molecular regulation of the hypothalamic-pituitary-adrenal axis in adult male guinea pigs after prenatal stress at different stages of gestation

Studies in humans and animals have demonstrated that maternal stress during fetal development can lead to altered hypothalamic-pituitary-adrenal (HPA) axis function and behaviour postnatally. We have previously shown adult male guinea pigs that were born to mothers exposed to a stressor during the phase of rapid fetal brain growth (gestational days (GD) 50, 51 and 52; prenatal stress (PS)50) exhibit significantly increased basal plasma cortisol levels. In contrast, male guinea pig offspring whose mothers were exposed to stress later in gestation (GD60, 61 and 62; PS60) exhibited a significantly higher plasma cortisol response to activation of the HPA axis. In the present study, we hypothesized that the endocrine changes in HPA axis function observed in male guinea pig offspring would be reflected by altered molecular regulation of the HPA axis. Corticosteroid receptors in the hippocampus, hypothalamus and pituitary were measured, as well as corticotropin-releasing hormone (CRH), pro-opiomelanocortin (POMC) and adrenal enzymes in the paraventricular nucleus, pituitary and adrenal cortex, respectively, by in situ hybridization and Western blot. PS50 male offspring exhibited a significant reduction in glucocorticoid receptor (GR) mRNA (P <0.01) in the CA3 region of the hippocampus and significantly increased POMC mRNA (P <0.05) in the pituitary, consistent with the increase in basal HPA axis activity observed. In line with elevated activity of the HPA axis, both PS50 and PS60 male offspring exhibited significantly higher steroidogenic factor (SF)-1 (P <0.001) and melanocortin 2 receptor (MC2-R) mRNA (P <0.001) in the adrenal cortex. This study demonstrates that short periods of prenatal stress during critical windows of neuroendocrine development affect the expression of key regulators of HPA axis activity leading to the changes in endocrine function observed in prenatally stressed male offspring. Further, these changes are dependent on the timing of the maternal stressor, a pattern that is emerging in human studies.

Identification of the first synthetic steroidogenic factor 1 inverse agonists: pharmacological modulation of steroidogenic enzymes

Steroidogenic factor SF-1, a constitutively active nuclear hormone receptor, is essential to the development of adrenal and gonadal glands and acts as a shaping factor of sexual determination and differentiation. Its effects are exerted primarily through the control of the synthesis of steroid hormones. The functional cell-based assay Receptor Selection and Amplification Technology (R-SAT) was used to identify potent and selective SF-1 inverse agonists through the screening of a chemical library of drug-like small-molecule entities. Among them, 4-(heptyloxy)phenol (AC-45594), a prototype inverse agonist lead, was used to show that SF-1 constitutive activity can be pharmacologically modulated by a synthetic ligand. In a physiological system of endocrine function, the expression of several reported SF-1 target genes, including SF-1 itself, was inhibited by treatment with AC-45594 and analogs. Thus, pharmacological modulation of SF-1 is critical to its function as an endocrine master regulator and has potentially important consequences to diseases in which SF-1 activity is critical.

Increased steroidogenic factor-1 dosage triggers adrenocortical cell proliferation and cancer

Steroidogenic factor-1 (SF-1/Ad4BP; NR5A1), a nuclear receptor transcription factor, has a pivotal role in adrenal and gonadal development in humans and mice. A frequent feature of childhood adrenocortical tumors is SF-1 amplification and overexpression. Here we show that an increased SF-1 dosage can by itself augment human adrenocortical cell proliferation through concerted actions on the cell cycle and apoptosis. This effect is dependent on an intact SF-1 transcriptional activity. Gene expression profiling showed that an increased SF-1 dosage regulates transcripts involved in steroid metabolism, the cell cycle, apoptosis, and cell adhesion to the extracellular matrix. Consistent with these results, increased SF-1 levels selectively modulate the steroid secretion profile of adrenocortical cells, reducing cortisol and aldosterone production and maintaining dehydroepiandrosterone sulfate secretion. As a model to understand the mechanisms of transcriptional regulation by increased SF-1 dosage, we studied FATE1, coding for a cancer-testis antigen implicated in the control of cell proliferation. Increased SF-1 levels increase its binding to a consensus site in FATE1 promoter and stimulate its activity through modulation of the recruitment of specific cofactors. On the other hand, sphingosine, which can compete with phospholipids for binding to SF-1, had no effect on the SF-1 dosage-dependent increase of adrenocortical cell proliferation and expression of the FATE1 promoter. In mice, increased Sf-1 dosage produces adrenocortical hyperplasia and formation of tumors expressing gonadal markers (Amh, Gata-4), which originate from the subcapsular region of the adrenal cortex. Gene expression profiling revealed that genes involved in cell adhesion and the immune response and transcription factor signal transducer and activator of transcription-3 (Stat3) are differentially expressed in Sf-1 transgenic mouse adrenals compared with wild-type adrenals. Our studies reveal a critical role for SF-1 dosage in adrenocortical tumorigenesis and constitute a rationale for the development of drugs targeting SF-1 transcriptional activity for adrenocortical tumor therapy.

SF-1 (nuclear receptor 5A1) activity is activated by cyclic AMP via p300-mediated recruitment to active foci, acetylation, and increased DNA binding

Steroidogenic factor 1 (SF-1) is a nuclear receptor essential for steroidogenic gene expression, but how its activity is regulated is unclear. Here we demonstrate that p300 plays an important role in regulating SF-1 function. SF-1 was acetylated in vitro and in vivo by p300 at the KQQKK motif in the Ftz-F1 (Fushi-tarazu factor 1) box adjacent to its DNA-binding domain. Mutation of the KQQKK motif reduced the DNA-binding activity and p300-dependent activation of SF-1. When stimulated with cyclic AMP (cAMP), adrenocortical Y1 cells expressed more p300, leading to additional SF-1 association with p300 and increased SF-1 acetylation and DNA binding. It also increased SF-1 colocalization with p300 in nuclear foci. Collectively, these results indicate that SF-1 transcriptional activity is regulated by p300 in response to the cAMP signaling pathway by way of increased acetylation, DNA binding, and recruitment to nuclear foci.

PCB126 induces differential changes in androgen, cortisol, and aldosterone biosynthesis in human adrenocortical H295R cells

Dioxins and polychlorinated biphenyls (PCBs) have been shown to accumulate in the adrenal glands when incorporated into the body. However, the impacts of exposure on adrenal steroidogenesis have not been thoroughly investigated. In this study, we demonstrated that dioxin-like PCB126 altered androgen, cortisol, and aldosterone biosynthesis differentially in human adrenocortical H295R cells. PCB126 diminished basal and cAMP-induced androstenedione production as well as CYP17 mRNA expression in a dose-dependent and time-dependent manner. The CYP17 repression was accompanied with decreases in the encoded 17 alpha-hydroxylase and 17,20-lyase activities, particularly the latter. In contrast, high concentrations of PCB126 stimulated basal cortisol and aldosterone biosynthesis, including induction of CYP21B, CYP11B1, and CYP11B2 mRNA expression and elevation of the conversion of cortisol from 17-OH-progesterone and aldosterone from progesterone. cAMP abolished the positive effect of PCB126 on cortisol synthesis, while it synergistically enhanced PCB126 stimulation on CYP11B2 expression and aldosterone production. It seemed likely that the downregulation of CYP21B caused by the combination of PCB126 and cAMP counteracted the CYP11B1 induction stimulated by the co-treatment. In addition, high concentrations of PCB126 might sensitize the regulation of adrenocorticotropin (ACTH) on the adrenocortical cells by increasing ACTH receptor levels. Because adrenal steroids have profound influences on glucose tolerance, insulin sensitivity, lipid metabolism, obesity, vascular function, and cardiac remodeling, this article also discusses the potential association of the detected adrenocortical alterations with increased diabetic and cardiovascular risk found among highly exposed people.