Regulation of corticotropin and steroidogenic enzyme mRNAs in human fetal adrenal cells by corticotropin, angiotensin-II and transforming growth factor beta 1

A spatiotemporal steroidogenic regulatory network in human fetal adrenal glands and gonads

Human fetal adrenal glands produce substantial amounts of dehydroepiandrosterone (DHEA), which is one of the most important precursors of sex hormones. However, the underlying biological mechanism remains largely unknown. Herein, we sequenced human fetal adrenal glands and gonads from 7 to 14 gestational weeks (GW) via 10× Genomics single-cell transcriptome techniques, reconstructed their location information by spatial transcriptomics. Relative to gonads, adrenal glands begin to synthesize steroids early. The coordination among steroidogenic cells and multiple non-steroidogenic cells promotes adrenal cortex construction and steroid synthesis. Notably, during the window of sexual differentiation (8-12 GW), key enzyme gene expression shifts to accelerate DHEA synthesis in males and cortisol synthesis in females. Our research highlights the robustness of the action of fetal adrenal glands on gonads to modify the process of sexual differentiation.

Stability and Turnover of the ACTH Receptor Complex

Glucocorticoid production in mammals is principally regulated by the action of the pituitary hormone adrenocorticotropin (ACTH) acting on its cognate membrane receptor on the zona fasciculata cells of the adrenal cortex. The receptor for ACTH consists of two essential components, a small seven transmembrane domain G protein-coupled receptor of the melanocortin receptor subgroup known as the melanocortin 2 receptor (MC2R) and a small single transmembrane domain protein that adopts a antiparallel homodimeric form and which is known as the melanocortin 2 receptor accessory protein (MRAP). MRAP is essential for the trafficking of the MC2R to the cell surface as well as being required for receptor responsiveness to ACTH at physiological concentrations-probably by facilitating ACTH binding, but possibly also by supporting G protein interaction with the MC2R. A number of studies have shown that ACTH stimulates the expression of functional receptor at the cell surface and the transcription of both MC2R and MRAP mRNA. However, the time course of these transcriptional effects differs such that MRAP is expressed relatively rapidly whereas MC2R transcription responds much more slowly. Furthermore, recent data suggests that MRAP protein is turned over with a short half-life whereas MC2R has a significantly longer half-life. These findings imply that these two ACTH receptor proteins have distinct trajectories and that it is likely that MRAP-independent MC2R is present at the cell surface. In such a situation newly transcribed and translated MRAP could enable the rapid recruitment of functional receptor at the plasma membrane without the need for new MC2R translation. This may be advantageous in circumstances of significant stress in that the potentially complex and perhaps inefficient process of de novo MC2R translation, folding, post-translational modification and trafficking can be avoided.

Genetics of primary macronodular adrenal hyperplasia

Recent advances in molecular genetics investigations of primary macronodular adrenal hyperplasia (PMAH) have been providing new insights for the research on this issue. The cAMP-dependent pathway is physiologically triggered by ACTH and its receptor, MC2-R, in adrenocortical cells. Different mechanisms of this cascade may be altered in some functioning adrenal cortical disorders. Activating somatic mutations of the GNAS gene (known as gsp oncogene) which encodes the stimulatory G protein alpha-subunit (Gsα) have been found in a small number of adrenocortical secreting adenomas and rarely in PMAH. Lately, ARMC5 was linked to the cyclic AMP signaling pathway, which could be implicated in all of mechanisms of cortisol-secreting by macronodules adrenal hyperplasia and the molecular defects in: G protein aberrant receptors; MC2R; GNAS; PRKAR1A; PDE11A; PDE8B. Around 50 % of patient's relatives with PMAH and 30 % of apparently sporadic hypercortisolism carried ARMC5 mutations. Therefore, PMAH is genetically determined more frequently than previously believed. This review summarizes the most important molecular mechanisms involved in PMAH.

Transforming growth factor-β1 induces cerebrovascular dysfunction and astrogliosis through angiotensin II type 1 receptor-mediated signaling pathways

Transgenic mice constitutively overexpressing the cytokine transforming growth factor-β1 (TGF-β1) (TGF mice) display cerebrovascular alterations as seen in Alzheimer's disease (AD) and vascular cognitive impairment and dementia (VCID), but no or only subtle cognitive deficits. TGF-β1 may exert part of its deleterious effects through interactions with angiotensin II (AngII) type 1 receptor (AT1R) signaling pathways. We test such interactions in the brain and cerebral vessels of TGF mice by measuring cerebrovascular reactivity, levels of protein markers of vascular fibrosis, nitric oxide synthase activity, astrogliosis, and mnemonic performance in mice treated (6 months) with the AT1R blocker losartan (10 mg/kg per day) or the angiotensin converting enzyme inhibitor enalapril (3 mg/kg per day). Both treatments restored the severely impaired cerebrovascular reactivity to acetylcholine, calcitonin gene-related peptide, endothelin-1, and the baseline availability of nitric oxide in aged TGF mice. Losartan, but not enalapril, significantly reduced astrogliosis and cerebrovascular levels of profibrotic protein connective tissue growth factor while raising levels of antifibrotic enzyme matrix metallopeptidase-9. Memory was unaffected by aging and treatments. The results suggest a pivotal role for AngII in TGF-β1-induced cerebrovascular dysfunction and neuroinflammation through AT1R-mediated mechanisms. Further, they suggest that AngII blockers could be appropriate against vasculopathies and astrogliosis associated with AD and VCID.

The role of ARMC5 in human cell cultures from nodules of primary macronodular adrenocortical hyperplasia (PMAH)

The participation of aberrant receptors and intra-adrenal ACTH in hyperplastic tissue are considered mechanisms that regulate hypercortisolism in PMAH. Additionally, germline ARMC5 mutations have been described as the most frequent genetic abnormality found in patients diagnosed with PMAH. Previous functional studies analyzed ARMC5 role using H295R cells. Therefore, we investigated the role of ARMC5 in cell cultures obtained from PMAH nodules containing steroidogenic cells, aberrant receptors and intra-adrenal ACTH. ARMC5 silencing in non-mutated PMAH cell cultures decreased steroidogenesis-related genes and increased CCNE1 mRNA expression and proliferative capacity without affecting cell viability. Additionally, ARMC5 overexpression induced cell death in PMAH mutated cell cultures, thereby decreasing cell viability. We confirmed the role of ARMC5 as an important pro-apoptotic protein involved in PMAH-related steroidogenesis. We also report for the first time the involvement of ARMC5 in controlling proliferation and regulating cell cycle in PMAH cell cultures; these effects need to be explored further.

Is spaceflight-induced immune dysfunction linked to systemic changes in metabolism?

The Space Shuttle Atlantis launched on its final mission (STS-135) on July 8, 2011. After just under 13 days, the shuttle landed safely at Kennedy Space Center (KSC) for the last time. Female C57BL/6J mice flew as part of the Commercial Biomedical Testing Module-3 (CBTM-3) payload. Ground controls were maintained at the KSC facility. Subsets of these mice were made available to investigators as part of NASA’s Bio-specimen Sharing Program (BSP). Our group characterized cell phenotype distributions and phagocytic function in the spleen, catecholamine and corticosterone levels in the adrenal glands, and transcriptomics/metabolomics in the liver. Despite decreases in most splenic leukocyte subsets, there were increases in reactive oxygen species (ROS)-related activity. Although there were increases noted in corticosterone levels in both the adrenals and liver, there were no significant changes in catecholamine levels. Furthermore, functional analysis of gene expression and metabolomic profiles suggest that the functional changes are not due to oxidative or psychological stress. Despite changes in gene expression patterns indicative of increases in phagocytic activity (e.g. endocytosis and formation of peroxisomes), there was no corresponding increase in genes related to ROS metabolism. In contrast, there were increases in expression profiles related to fatty acid oxidation with decreases in glycolysis-related profiles. Given the clear link between immune function and metabolism in many ground-based diseases, we propose a similar link may be involved in spaceflight-induced decrements in immune and metabolic function.

Endogenous inhibins regulate steroidogenesis in mouse TM3 Leydig cells by altering SMAD2 signalling

This study tested the hypothesis that inhibins act in an autocrine manner on Leydig cells using a pre-pubertal Leydig cell line, TM3, as a model of immature Leydig cells. The expression of Inha, Inhba, and Inhbb in TM3 cells was determined by RT-PCR and the production of the inhibin-alpha subunit was confirmed by western blot. Knockdown of Inha expression resulted in significant decreases in the expression of Leydig cell markers Cyp17a1, Cyp11a1, Nr5a1, and Insl3. Western blot showed that activin A, TGFβ1 and TGFβ2 activated SMAD2, and that knockdown of Inha expression in TM3 cells enhanced both activin A- and TGFβ-induced SMAD2 activation. SB431542, a chemical inhibitor of the TGFβ/activin type I receptors, blocked ligand-induced SMAD2 activation and the downregulation of Cyp17a1 expression. Our findings demonstrate that TGFβs and activin A negatively regulate steroidogenic gene expression in TM3 cells via ALK4/5 and SMAD2 and endogenous inhibins can counter this regulation.

Genetics of androgen metabolism in women with infertility and hypoandrogenism

Hypoandrogenism in women with low functional ovarian reserve (LFOR, defined as an abnormally low number of small growing follicles) adversely affects fertility. The androgen precursor dehydroepiandrosterone (DHEA) is increasingly used to supplement treatment protocols in women with LFOR undergoing in vitro fertilization. Due to differences in androgen metabolism, however, responses to DHEA supplementation vary between patients. In addition to overall declines in steroidogenic capacity with advancing age, genetic factors, which result in altered expression or enzymatic function of key steroidogenic proteins or their upstream regulators, might further exacerbate variations in the conversion of DHEA to testosterone. In this Review, we discuss in vitro studies and animal models of polymorphisms and gene mutations that affect the conversion of DHEA to testosterone and attempt to elucidate how these variations affect female hormone profiles. We also discuss treatment options that modulate levels of testosterone by targeting the expression of steroidogenic genes. Common variants in genes encoding DHEA sulphotransferase, aromatase, steroid 5α-reductase, androgen receptor, sex-hormone binding globulin, fragile X mental retardation protein and breast cancer type 1 susceptibility protein have been implicated in androgen metabolism and, therefore, can affect levels of androgens in women. Short of screening for all potential genetic variants, hormonal assessments of patients with low testosterone levels after DHEA supplementation facilitate identification of underlying genetic defects. The genetic predisposition of patients can then be used to design individualized fertility treatments.

Steroidogenesis-adrenal cell signal transduction

The purpose of this article is to review fundamentals in adrenal gland histophysiology. Key findings regarding the important signaling pathways involved in the regulation of steroidogenesis and adrenal growth are summarized. We illustrate how adrenal gland morphology and function are deeply interconnected in which novel signaling pathways (Wnt, Sonic hedgehog, Notch, β-catenin) or ionic channels are required for their integrity. Emphasis is given to exploring the mechanisms and challenges underlying the regulation of proliferation, growth, and functionality. Also addressed is the fact that while it is now well-accepted that steroidogenesis results from an enzymatic shuttle between mitochondria and endoplasmic reticulum, key questions still remain on the various aspects related to cellular uptake and delivery of free cholesterol. The significant progress achieved over the past decade regarding the precise molecular mechanisms by which the two main regulators of adrenal cortex, adrenocorticotropin hormone (ACTH) and angiotensin II act on their receptors is reviewed, including structure-activity relationships and their potential applications. Particular attention has been given to crucial second messengers and how various kinases, phosphatases, and cytoskeleton-associated proteins interact to ensure homeostasis and/or meet physiological demands. References to animal studies are also made in an attempt to unravel associated clinical conditions. Many of the aspects addressed in this article still represent a challenge for future studies, their outcome aimed at providing evidence that the adrenal gland, through its steroid hormones, occupies a central position in many situations where homeostasis is disrupted, thus highlighting the relevance of exploring and understanding how this key organ is regulated. © 2014 American Physiological Society. Compr Physiol 4:889-964, 2014.

100th anniversary of the discovery of the human adrenal fetal zone by Stella Starkel and Lesław Węgrzynowski: how far have we come?

Year 2010 marks a centennial anniversary of the description by Stella Starkel and Lesław Węgrzynowski, Polish students of the Faculty of Medicine, University of Lwów, the fetal zone of the human fetal adrenal gland. In 1911 both, Starkel and Węgrzynowski were graduated from the Faculty of Medicine of Lwow University. The paper appeared in the German Arch. Anat. Physiol. and its original title was "Beitrag zur Histologie der Nebeniere bei Feten und Kindern" ("Contribution to histology of adrenals of fetuses and children"). The studies were performed on 100 adrenal glands obtained from fetuses (from 6th month of gestation) and up to 5-year-old children. They described the fetal zone as a "medullary zone", also as "immature cortex", which undergoes involution in first years of life. To commemorate this discovery, this review aimed to present the most important achievements of studies on the development and involution of the human adrenal fetal zone.

The effects of ACTH on steroid metabolomic profiles in human adrenal cells

The adrenal glands are the primary source of mineralocorticoids, glucocorticoids, and the so-called adrenal androgens. Under physiological conditions, cortisol and adrenal androgen synthesis are controlled primarily by ACTH. Although it is well established that ACTH can stimulate steroidogenesis in the human adrenal gland, the effect of ACTH on overall production of different classes of steroid hormones has not been defined. In this study, we examined the effect of ACTH on the production of 23 steroid hormones in adult adrenal primary cultures and 20 steroids in the adrenal cell line, H295R. Liquid chromatography/tandem mass spectrometry analysis revealed that, in primary adrenal cell cultures, cortisol and corticosterone were the two most abundant steroid hormones produced with or without ACTH treatment (48  h). Cortisol production responded the most to ACTH treatment, with a 64-fold increase. Interestingly, the production of two androgens, androstenedione and 11β-hydroxyandrostenedione (11OHA), that were also produced in large amounts under basal conditions significantly increased after ACTH incubation. In H295R cells, 11-deoxycortisol and androstenedione were the major products under basal conditions. Treatment with forskolin increased the percentage of 11β-hydroxylated products, including cortisol and 11OHA. This study illustrates that adrenal cells respond to ACTH through the secretion of a variety of steroid hormones, thus supporting the role of adrenal cells as a source of both corticosteroids and androgens.

Development and function of the human fetal adrenal cortex: a key component in the feto-placental unit

Continuous efforts have been devoted to unraveling the biophysiology and development of the human fetal adrenal cortex, which is structurally and functionally unique from other species. It plays a pivotal role, mainly through steroidogenesis, in the regulation of intrauterine homeostasis and in fetal development and maturation. The steroidogenic activity is characterized by early transient cortisol biosynthesis, followed by its suppressed synthesis until late gestation, and extensive production of dehydroepiandrosterone and its sulfate, precursors of placental estrogen, during most of gestation. The gland rapidly grows through processes including cell proliferation and angiogenesis at the gland periphery, cellular migration, hypertrophy, and apoptosis. Recent studies employing modern technologies such as gene expression profiling and laser capture microdissection have revealed that development and/or function of the fetal adrenal cortex may be regulated by a panoply of molecules, including transcription factors, extracellular matrix components, locally produced growth factors, and placenta-derived CRH, in addition to the primary regulator, fetal pituitary ACTH. The role of the fetal adrenal cortex in human pregnancy and parturition appears highly complex, probably due to redundant and compensatory mechanisms regulating these events. Mounting evidence indicates that actions of hormones operating in the human feto-placental unit are likely mediated by mechanisms including target tissue responsiveness, local metabolism, and bioavailability, rather than changes only in circulating levels. Comprehensive study of such molecular mechanisms and the newly identified factors implicated in adrenal development should help crystallize our understanding of the development and physiology of the human fetal adrenal cortex.

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

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

Leptin infusion and obesity in mouse cause alterations in the hypothalamic melanocortin system

The objectives of this study were to identify potential alterations in gene expression of melanocortin-4 receptor (MC4-R), proopiomelanocortin (POMC), and Agouti-related protein (AgRP) in mouse hypothalamus under a chronic peripheral infusion of leptin or at early (8 weeks) and advanced (16 weeks) phases of diet-induced obesity. Control or diet-induced obesity mice (8 or 16 weeks of high-fat diet) were either treated or not treated with leptin. Metabolic features were analyzed and expression of the genes of interest was measured by quantitative reverse transcriptase-PCR (RT-qPCR) and western blot. We reported that in control mice, but not in obese mice, leptin infusion induced an increase in POMC mRNA level as well as in MC4-R mRNA level suggesting that leptin could act directly and/or through alpha-melanocyte-stimulating hormone (alpha-MSH). This hypothesis was reinforced after in vitro studies, using the mouse hypothalamic GT1-7 cell line, since both leptin and Norleucine(4), D-Phenylalanine(7)-alpha-MSH (NDP-alpha-MSH) treatments increased MC4-R expression. After 8 weeks of high-fat diet, nondiabetic obese mice became resistant to the central action of leptin and their hypothalamic content of POMC and AgRP mRNA were decreased without modification of MC4-R mRNA level. After 16 weeks of high-fat diet, mice exhibited more severe metabolic disorders with type 2 diabetes. Moreover, hypothalamic expression of MC4-R was highly increased. In conclusion, several alterations of the melanocortin system were found in obese mice that are probably consecutive to their central resistance to leptin. Moreover, when the metabolic status is highly degraded (with all characteristics of a type 2 diabetes), other regulatory mechanisms (independent of leptin) can also take place.

The regulation of adrenocorticotrophic hormone receptor by corticotropin-releasing hormone in human fetal adrenal definitive/transitional zone cells

As gestation progresses, human fetal adrenals (HFA) initiate the production of cortisol, which increases placental corticotropin-releasing hormone (CRH) biosynthesis. While adrenocorticotrophic hormone (ACTH) is important for the onset of cortisol production, the late gestational surge in cortisol production occurs despite falling ACTH levels in the fetal circulation. The authors determine if CRH directly regulates the expression of the ACTH receptor (ACTHR) in HFA definitive/transitional zone (DZ/TZ) cells. DZ/TZ cells isolated from midgestation HFA were cultured before treatment with 0.01 nM to 100 nM CRH or ACTH. Cortisol was measured by radioimmunoassay. Real-time reverse-transcriptase polymerase chain reaction was used to measure ACTHR mRNA. Whole-cell ACTH binding studies were performed using I(125) (Tyr-23) ACTH. CRH produced a dose-dependent rise in cortisol production and caused a time-dependent increase in ACTHR mRNA levels between 12 and 24 hours. As little as 0.1 nM CRH induced ACTHR transcript by 12-fold at 24 hours. Together with ACTH 0.01 nM, 0.03 or 0.1 nM CRH increased ACTHR expression more than ACTH alone. Binding assays demonstrated a 3.5-fold increase in ACTHR protein at 48 hours with combined CRH and ACTH treatment. Physiologic levels of CRH seen in the late-gestation fetus stimulate DZ/TZ ACTHR expression. Since placental CRH production increases strikingly near the end of gestation, the authors suggest that CRH-induced ACTH receptor expression may increase TZ responsiveness to circulating ACTH and contribute to the late gestational rise in cortisol secretion by the HFA, participating in an endocrine cascade that is involved in fetal organ maturation and potentially in the timing of human parturition.

Angiotensin II, corticosteroids, type II diabetes and the metabolic syndrome

Syndrome X, the Metabolic Syndrome, and type II diabetes are closely related diseases that share risk factors and symptoms, notably insulin resistance. Several factors have been proposed either to mediate the disease(s) or to be their causes, and most converge on the endocrine/paracrine functions of the adipocyte. A common feature of such systems is their relative autonomy from systemic negative feedback regulation, for example by the HPA axis. We draw particular attention to two such mechanisms, both of which are associated with, and can cause, insulin resistance: the extra-adrenal production of corticosteroids, and the tissue renin angiotensin system of the adipocyte. These show another feature: the inter-regulation of glucocorticoid action and the RAS by positive feedback. Cortisol enhances the expression of 11 beta-HSD 1, and also of angiotensinogen and angiotensin type 1 receptors. In turn, angiotensin can stimulate further corticosteroid production, from the adrenal and perhaps from extra-adrenal sources. The instability inherent in such positive loops could account for the progressive nature of the disease(s), suggesting ways to break the circle.

Prolactin and the expression of suppressor of cytokine signaling-3 in the sheep adrenal gland before birth

The fetal pituitary-adrenal axis plays a key role in the fetal response to intrauterine stress and in the timing of parturition. The fetal sheep adrenal gland is relatively refractory to stimulation in midgestation (90–120 days) before the prepartum activation, which occurs around 135 days gestation (term = 147 ± 3 days). The mechanisms underlying the switch from adrenal quiescence to activation are unclear. Therefore, we have investigated the expression of suppressor of cytokine signaling-3 (SOCS-3), a putative inhibitor of tissue growth in the fetal sheep adrenal between 50 and 145 days gestation and in the adrenal of the growth-restricted fetal sheep in late gestation. SOCS-3 is activated by a range of cytokines, including prolactin (PRL), and we have, therefore, determined whether PRL administered in vivo or in vitro stimulates SOCS-3 mRNA expression in the fetal adrenal in late gestation. There was a decrease ( P < 0.005) in SOCS-3 expression in the fetal adrenal between 54 and 133 days and between 141 and 144 days gestation. Infusion of the dopaminergic agonist, bromocriptine, which suppressed fetal PRL concentrations but did not decrease adrenal SOCS-3 mRNA expression. PRL administration, however, significantly increased adrenal SOCS-3 mRNA expression ( P < 0.05). Similarly, there was an increase ( P < 0.05) in SOCS-3 mRNA expression in adrenocortical cells in vitro after exposure to PRL (50 ng/ml). Placental and fetal growth restriction had no effect on SOCS-3 expression in the adrenal during late gestation. In summary, the decrease in the expression of the inhibitor SOCS-3 after 133 days gestation may be permissive for a subsequent increase in fetal adrenal growth before birth. We conclude that factors other than PRL act to maintain adrenal SOCS-3 mRNA expression before 133 days gestation but that acute elevations of PRL can act to upregulate adrenal SOCS-3 expression in the sheep fetus during late gestation.

Developmental changes in adrenocorticotrophin (ACTH)-induced expression of ACTH receptor and steroid acute regulatory protein mRNA in ovine fetal adrenal cells

OBJECTIVES

Adrenocorticotrophin (ACTH) plays an important role in mediating the increase in cortisol output in the late gestation sheep fetus. At the adrenal itself, heightened expression of ACTH receptor (ACTH-R) and steroid acute regulatory protein (StAR) appear to be important parallel changes. This study examined how ACTH affects ACTH-R and StAR mRNA expression, and cortisol production in adrenocortical cells isolated from fetuses of varying gestational age (dGA). We hypothesized that the ability of ACTH to stimulate its receptor and StAR mRNA expression would be greater close to term than earlier in development.

METHODS

Adrenals were obtained from fetuses (100-105, 120, or 135-139 dGA), and the cortical cells were dispersed. After 3 days of culture, cells were stimulated with ACTH(1-24), and the cells and medium were collected at different time points (0, 3, 6, 9, 12, and 24 hours) for measurement of cortisol and ACTH-R and StAR mRNA.

RESULTS

Cortisol secretion was increased after ACTH treatment in all three age cohorts. Cells from the 135-139 dGA group secreted the most cortisol, followed by the 100-105 and then the 120 dGA groups (P <.05). ACTH-R mRNA levels before and after ACTH were higher in the late compared to both earlier groups. StAR mRNA levels before and after ACTH were higher in the 100-105 and 135 than in the 120 dGA group. The time to peak ACTH-R mRNA response was age-dependent, with the 100-105 dGA cells taking longer to attain maximum levels. Maximal StAR mRNA levels were not age-related.

CONCLUSION

The data suggest that ACTH-R and StAR are indeed key mediators of fetal adrenocortical responsiveness, and that ACTH is able to up-regulate responsiveness, and hence cortisol production, by increasing their expression.

Molecular biology of the 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase gene family

The 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) isoenzymes are responsible for the oxidation and isomerization of Delta(5)-3beta-hydroxysteroid precursors into Delta(4)-ketosteroids, thus catalyzing an essential step in the formation of all classes of active steroid hormones. In humans, expression of the type I isoenzyme accounts for the 3beta-HSD activity found in placenta and peripheral tissues, whereas the type II 3beta-HSD isoenzyme is predominantly expressed in the adrenal gland, ovary, and testis, and its deficiency is responsible for a rare form of congenital adrenal hyperplasia. Phylogeny analyses of the 3beta-HSD gene family strongly suggest that the need for different 3beta-HSD genes occurred very late in mammals, with subsequent evolution in a similar manner in other lineages. Therefore, to a large extent, the 3beta-HSD gene family should have evolved to facilitate differential patterns of tissue- and cell-specific expression and regulation involving multiple signal transduction pathways, which are activated by several growth factors, steroids, and cytokines. Recent studies indicate that HSD3B2 gene regulation involves the orphan nuclear receptors steroidogenic factor-1 and dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1 (DAX-1). Other findings suggest a potential regulatory role for STAT5 and STAT6 in transcriptional activation of HSD3B2 promoter. It was shown that epidermal growth factor (EGF) requires intact STAT5; on the other hand IL-4 induces HSD3B1 gene expression, along with IL-13, through STAT 6 activation. However, evidence suggests that multiple signal transduction pathways are involved in IL-4 mediated HSD3B1 gene expression. Indeed, a better understanding of the transcriptional factors responsible for the fine control of 3beta-HSD gene expression may provide insight into mechanisms involved in the functional cooperation between STATs and nuclear receptors as well as their potential interaction with other signaling transduction pathways such as GATA proteins. Finally, the elucidation of the molecular basis of 3beta-HSD deficiency has highlighted the fact that mutations in the HSD3B2 gene can result in a wide spectrum of molecular repercussions, which are associated with the different phenotypic manifestations of classical 3beta-HSD deficiency and also provide valuable information concerning the structure-function relationships of the 3beta-HSD superfamily. Furthermore, several recent studies using type I and type II purified enzymes have elegantly further characterized structure-function relationships responsible for kinetic differences and coenzyme specificity.

Hypothalamic-pituitary disconnection in fetal sheep blocks the peripartum increases in adrenal responsiveness and adrenal ACTH receptor expression

Although it has been recognized for over a decade that hypothalamic-pituitary disconnection (HPD) in fetal sheep prevents the late gestation rise in plasma cortisol concentrations, the underlying mechanisms remain unclear. We hypothesized that reductions in adrenal responsiveness and ACTH receptor (ACTH-R) expression may be mediating factors. HPD or sham surgery was performed at 120 days of gestation, and catheters were placed for blood sampling. At approximately 138 days of gestation, fetuses were killed, and adrenals were removed for cell culture and analyses of ACTH-R mRNA and protein. After 48 h, adrenocortical cells were stimulated with ACTH for 2 h, and the medium was collected for cortisol measurement. The same cells were incubated overnight with medium or medium containing ACTH or forskolin (FSK), followed by ACTH stimulation (as above) and cortisol and cellular ACTH-R mRNA analyses. HPD prevented the late gestation increase in plasma cortisol and bioactive ACTH and reduced adrenal ACTH-R mRNA and protein levels by over 35%. HPD cells secreted significantly less cortisol than sham cells (3.2 +/- 1.2 vs. 47.3 +/- 11.1 ng.ml(-1).2 h(-1)) after the initial ACTH stimulation. Overnight incubation of HPD cells with ACTH or FSK restored cortisol responses to acute stimulation to levels seen in sham cells initially. ACTH-R mRNA levels in cells isolated from HPD fetuses were decreased by over 60%, whereas overnight incubation with ACTH or FSK increased levels by approximately twofold. Our findings indicate that the absence of the cortisol surge in HPD fetuses is a consequence, at least in part, of decreased ACTH-R expression and adrenal responsiveness.

Adrenal TGFbeta1 mRNA levels fall during late gestation and are not regulated by cortisol in the sheep fetus

During mammalian development there are periods when the fetal adrenal is either relatively refractory or increasingly sensitive to trophic stimulation. This pattern of regulation of adrenal growth and function ensures that the fetal lungs, liver, brain and kidney are exposed in a programmed temporal sequence to the genomic actions of circulating glucocorticoids. The factors which act to maintain periods of adrenal quiescence are not known. In the present study we have measured the level of messenger RNA (mRNA) expression of a putative inhibitor of adrenal steroidogenesis, transforming growth factor beta 1 (TGFbeta1), and a key steroidogenic enzyme, cytochrome P450 17alpha hydroxylase (CYP17), during periods of adrenal quiescence and activation in the sheep fetus. We have also investigated the relative roles of the fetal hypothalamic-pituitary axis and cortisol in the regulation of expression of adrenal TGFbeta1 and CYP17 mRNA during late gestation. Adrenal expression of TGFbeta1 was greatest at around 100 days gestation, at a time when the fetal sheep adrenal is relatively refractory to trophic stimulation and there was an inverse relationship between the expression of TGFbeta1 and CYP17 mRNA in the adrenal gland during the peripartum period. Whilst disconnection of the fetal hypothalamic-pituitary disconnection (HPD) axis resulted in a decrease in adrenal CYP 17 mRNA expression, there was no effect of fetal HPD, with or without cortisol replacement, on adrenal TGFbeta1 mRNA expression in late gestation. Thus TGFbeta1 may play a role in inhibiting adrenal steroidogenesis and ensuring that the adrenal remains relatively refractory to trophic stimulation during mid gestation. The maintenance of low adrenal TGFbeta1 expression during late gestation is not dependent, however, on stimulation by the fetal hypothalamic-pituitary axis.

Plasma cytokine profiles in elderly humans

It is known that as we age, immune dysregulation often occurs, leading to failing health, and increased susceptibility to a number of different diseases. In this study we have investigated plasma cytokine profiles in order to identify immune markers of ageing. Plasma samples were obtained from 138 participants of the Swedish longitudinal NONA study (aged 86, 90 and 94 years) and 18 healthy Swedish volunteers (aged between 32 and 59 years). Our results show significantly increased levels of the pro-inflammatory cytokine interleukin-6 (P<0.0001) and soluble intercellular adhesion molecule-1 (P<0.0001) in the elderly group. The anti-inflammatory cytokine interleukin-10 did not alter with age whereas active (naturally processed) transforming growth factor-beta levels were significantly (P<0.0001) increased in the elderly group. No difference was observed between males and females. These data suggest that there are measurable changes in cytokine profiles with ageing with increased levels of potentially harmful molecules, which may contribute to immune alterations and declining health in the elderly population.

Influence of cytokines and growth factors on distinct steroidogenic enzymes in vitro: a short tabular data collection

Cytokines (IL-1, IL-6, IL-8, IL-11, TNF, IFN-gamma, and TGF-beta) and growth factors (EGF, bFGF, aFGF, and KGF) play an important role in modulation of hormone secretion by directly influencing specific enzyme steps of steroidogenesis in various endocrine cell types. For this tabular data collection, the following enzyme steps were considered: steroidogenic acute regulatory protein (StAR), side chain cleavage enzyme (P450scc), 3 beta-hydroxysteroid dehydrogenase, 17-alpha-hydroxylase/17,20-lyase (P450c17), 17-beta-hydroxysteroid-dehydrogenase, aromatase complex, 5-alpha-reductase, P450c21, DHEAS sulfatase, and DHEA sulfotransferase. This collection summarizes the current information on how the mentioned cytokines and growth factors influence particular enzyme steps.

Regulation by adrenocorticotropin (ACTH), angiotensin II, transforming growth factor-beta, and insulin-like growth factor I of bovine adrenal cell steroidogenic capacity and expression of ACTH receptor, steroidogenic acute regulatory protein, cytochrome P450c17, and 3beta-hydroxysteroid dehydrogenase

The purpose of this study was to evaluate the time-course effect of a 36-h treatment with ACTH (10(-8) M), transforming growth factor-beta1 (TGFbeta1; 10(-10) M), angiotensin II (AngII; 10 (-7) M), and insulin-like growth factor I (IGF-I; 10(-8) M) on the steroidogenic capacity of bovine adrenocortical cells (BAC) and on messenger RNA (mRNA) levels of ACTH receptor, cytochrome P450c17, 3beta-hydroxysteroid dehydrogenase (3betaHSD), steroidogenic acute regulatory protein (StAR), and StAR protein. ACTH and IGF-I enhanced, in a time-dependent manner, the acute 2-h ACTH-induced cortisol production, whereas TGFbeta 1 and AngII markedly reduced it. ACTH, IGF-I, and AngII increased ACTH receptor mRNA, but the opposite was observed after TGFbeta1 treatment. ACTH and IGF-I increased P450c17 and 3betaHSD mRNAs, whereas AngII and TGFbeta1 had the opposite effects. However, the effects of the four peptides on ACTH-induced cortisol production appeared before any significant alterations of the mRNA levels occurred. The most marked and rapid effect of the four peptides was on StAR mRNA. The stimulatory effect of ACTH was seen within 1.5 h, peaked at 4-6 h, and declined thereafter, but at the end of the 36-h pretreatment, the levels of StAR mRNA and protein were higher than those in control cells. IGF-I also enhanced StAR mRNA levels within 1.5 h, and these levels remained fairly constant. The effects of AngII on StAR mRNA expression were biphasic, with a peak within 1.5-3 h, followed by a rapid decline to almost undetectable levels of both mRNA and protein. TGFbeta1 had no significant effect during the first 3 h, but thereafter StAR mRNA declined, and at the end of the experiment the StAR mRNA and protein were almost undetectable. Similar results were observed when cells were treated with ACTH plus TGFbeta1. A 2-h acute ACTH stimulation at the end of the 36-h pretreatment caused a higher increase in StAR mRNA and protein in ACTH- or IGF-I-pretreated cells than in control cells, which, in turn, had higher levels than cells pretreated with TGFbeta1, ACTH plus TGFbeta1, or AngII. These results and the fact that the stimulatory (IGF-I) or inhibitory (AngII and TGFbeta1) effects on ACTH-induced cortisol production were more pronounced than those on the ability of cells to transform pregnenolone into cortisol strongly suggest that regulation of StAR expression is one of the main factors, but not the only one, involved in the positive (IGF-I) or negative (TGFbeta1 and AngII) regulation of BAC for ACTH steroidogenic responsiveness. A high correlation between steady state mRNA level and acute ACTH-induced cortisol production favors this conclusion.

Expression and regulation of melanocortin receptor-5 (MC5-R) in the bovine adrenal cortex

Among the five members of the melanocortin receptor (MC-R) family, MC2 and MC5 are expressed in peripheral tissues. The receptor MC2 (ACTH receptor) almost exclusively expressed in the adrenal cortex whereas MC5-R is expressed in several organs including the adrenal cortex. Both receptors bind ACTH and activate adenylate cyclase. The aim of this work was to study the spatial distribution of MC5-R among the different zones of the bovine adrenal cortex and to analyze the regulation of its expression by its own ligands, ACTH and alpha-MSH and by angiotensin II (AII). Using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and RNase protection assay, MC5-R was detected only in the glomerulosa zone whereas MC2-R was present in both glomerulosa and fasciculata zones of adult adrenal cortex. Treatments by ACTH, alpha-MSH, or AII increased the MC5-R mRNA level in glomerulosa cells by factors 7, 5, and 4.5, respectively. However, although potentially regulated by hormones, MC5-R is expressed at a level at least 100 times less than MC2-R, suggesting that MC5-R expression might only be at trace levels in grown adults, but could be much higher during embryogenesis.

Can high maternal melatonin concentrations be responsible for inducing fetal pathologies, and can melatonin participate in immunohormonal homeostasis by determining prohormone convertase activity?--Hypothesis and facts

The hypothesis proposed here presents a mechanism of melatonin action, which may explain the role of this neurohormone in the genesis of various human pathologies, including fetal abnormalities. It assumes that monomeric or dimeric forms of indoloderived compounds such as melatonin and precursors of melanin have the ability to selectively stimulate the synthesis of prohormone 1 convertase (PC1) or prohormone 2 convertase (PC2), in proportion to their concentrations in the body. Thus, the mean circadian level of melatonin, by determining the manner and rapidity of proopiomelanocortin (POMC) cleavage, would also determine the mean proopiomelanocortin (POMC) level, maintained in dynamic equilibrium as a result of the simultaneous influence of testosterone, estradiol and cortisol on the intensity of POMC mRNA synthesis. The correlative proportions between the activity of PC1 and PC2 would therefore shape the character of hormonal balance in the organism, and in particular the mean ACTH concentration that determines the level of cyclic adenosine monophosphate (cAMP) concentration in its cells. The hypothesis also suggests that melatonin, by influencing the concentration of ACTH and beta-endorphin and their relative proportion could determine the stimulation or suppression of the immune system, thereby confirming its role as an immunomodulator. A disturbance in the above model of immunohormonal equilibrium, resulting from, for example, decreased pineal efficiency, would lead to stimulation of an alternative mode of achieving homeostasis, i.e. increase in concentration of melanin monomers and dimers, with concomitant high activity of tyrosine kinase and high cyclic guanosine monophosphate (cGMP) concentration in the cells. According to the proposed hypothesis, the risk of bearing a developmentally handicapped child would be highest in a woman with a high circadian secretion of melatonin, i.e. with domination of melatonin dimers and high PC1 activity, a condition which may be additionally aggravated by the exposure of the mother to adverse environmental factors or by immunohormonal disturbances. The hypothetical break-up of maternal melatonin dimers when crossing placenta would be the cause of excessive concentration of melatonin monomers and high PC2 activity in the fetus, and thus it should be the reason for very low levels of vimentin filaments and cAMP concentration in embryonal cells, the latter being directly responsible for inducing fetal pathologies.

Effect of fibroblastic growth factors (FGF) on steroid UDP-glucuronosyltransferase expression and activity in the LNCaP cell line

It is now widely accepted that factors other than androgens are crucial in the normal and abnormal growth of the prostate. In addition to hormones, many polypeptide growth factors, including the fibroblast growth factor family (FGF), can act as potent mitogens on cell proliferation. The FGF family of growth factors are essential factors for both normal and abnormal proliferation of prostate cells. To study the effect of FGFs on steroid glucuronidation, we used the human prostate cancer LNCaP cell line which is known to be stimulated by FGF resulting in increased cell proliferation. LNCaP cells express steroid metabolizing enzymes including uridine diphosphoglucuronosyltransferases (UGTs). In addition, LNCaP cells treated with dihydrotestosterone (DHT) and epidermal growth factor (EGF) express differential levels of the human UGT2B15 and UGT2B17 transcripts. In the present study, we examined the possible interaction between FGF and steroid UGT enzymes. Results show a dose dependent inhibition of DHT glucuronide (DHT-G) formation following treatment (6 days) with acidic FGF (aFGF) and basic FGF (bFGF). When cells were treated with 10 ng/ ml of FGFs, we observed 33 and 51% inhibition of glucuronidation activity using aFGF and bFGF respectively. Ribonuclease protection analyses revealed a 2 and 3 fold increase of UGT2B15 mRNA expression following treatment with aFGF (50 ng/ml) and bFGF (10 ng/ml) respectively. However, a slight decrease in UGT2B17 transcripts was observed, demonstrating a differential regulation. Since a reduction in the glucuronidation of DHT or its 5alpha-reduced metabolites may contribute to an increase in intraprostatic androgen levels, down-regulation of UGTs by growth factors such as FGFs may increase the proliferation of androgen-dependent tumors.

Developmental and functional biology of the primate fetal adrenal cortex

The unique characteristics of the primate (particularly human) fetal adrenal were first realized in the early 1900s when its morphology was examined in detail and compared with that of other species. The unusual architecture of the human fetal adrenal cortex, with its unique and disproportionately enlarged fetal zone, its compact definitive zone, and its dramatic remodeling soon after birth captured the interest of developmental anatomists. Many detailed anatomical studies describing the morphology of the developing human fetal adrenal were reported between 1920 and 1960, and these morphological descriptions have not changed significantly. More recently, it has become clear that fetal adrenal cortical growth involves cellular hypertrophy, hyperplasia, apoptosis, and migration and is best described by the migration theory, i.e. cells proliferate in the periphery, migrate centripetally, differentiate during their migration to form the functional cortical zones, and then likely undergo apoptosis in the center of the cortex. Consistent with this model, cells of intermediate phenotype, arranged in columnar cords typical of migration, have been identified between the definitive and fetal zones. This cortical area has been referred to as the transitional zone and, based on the expression of steroidogenic enzymes, we consider it to be a functionally distinct cortical zone. Elegant experiments during the 1950s and 1960s demonstrated the central role of the primate fetal adrenal cortex in establishing the estrogenic milieu of pregnancy. Those findings were among the first indications of the function and physiological role of the human fetal adrenal cortex and led Diczfalusy and co-workers to propose the concept of the feto-placental unit, in which DHEA-S produced by the fetal adrenal cortex is used by the placenta for estrogen synthesis. Tissue and cell culture techniques, together with improved steroid assays, revealed that the fetal zone is the primary source of DHEA-S, and that its steroidogenic activity is regulated by ACTH. In recent years, function of the human and rhesus monkey fetal adrenal cortical zones has been reexamined by assessing the localization and ontogeny of steroidogenic enzyme expression. The primate fetal adrenal cortex is composed of three functionally distinct zones: 1) the fetal zone, which throughout gestation does not express 3 beta HSD but does express P450scc and P450c17 required for DHEA-S synthesis; 2) the transitional zone, which early in gestation is functionally identical to the fetal zone but late in gestation (after 25-30 weeks) expresses 3 beta HSD, P450scc, and P450c17, and therefore is the likely site of glucocorticoid synthesis, and 3) the definitive zone, which lacks P450c17 throughout gestation but late in gestation (after 22-24 weeks) expresses 3 beta HSD and P450scc, and therefore is the likely site of mineralocorticoid synthesis. Indirect evidence, based on effects of P450c21 deficiency and maternal estriol concentrations, indicate that the fetal adrenal cortex produces cortisol and DHEA-S early in gestation (6-12 weeks). However, controversy exists as to whether cortisol is produced de novo or derived from the metabolism of progesterone, as data regarding the expression of 3 beta HSD in the fetal adrenal cortex early in gestation are conflicting. During the 1960s, Liggins and colleagues demonstrated that in the sheep, cortisol secreted by the fetal adrenal cortex late in gestation regulates maturation of the fetus and initiates the cascade of events leading to parturition. Those pioneering discoveries provided insight into the mechanism underlying the timing of parturition and therefore were of particular interest to obstetricians and perinatologists confronted with the problems of preterm labor. However, although cortisol emanating from the fetal adrenal cortex promotes fetal maturation in primates as it does in sheep, its role in the regulation of primate parturition, unlike that in sheep

Angiotensin II receptors in cortical and medullary adrenal tumors

Several pieces of evidences suggest that angiotensin II (Ang II) has mitogenic effects, and a link between Ang II receptors and adrenal tumors can be suggested. In various adrenal tumors, aldosterone-producing adenoma (APA), Cushing's adrenal adenomas (Cush), pheochromocytomas (Pheo), and adrenal carcinomas, we studied the density, affinity, and subtype of Ang II receptors. Ang II binding was tested in cell membrane homogenates. [125I]Ang II was used as ligand, and Losartan and CGP 42112 were used as selective Ang II type 1 and type 2 antagonists, respectively. In APA, Ang II receptor density was 178.5 +/- 82.7 fmol/mg: however, due to the high degree of variability, the receptor density was not significantly higher than that in nontumorous adrenal cortex (59.3 +/- 8.4 fmol/mg). In Cush, the receptor density (27.6 +/- 8.2 fmol/mg; P < 0.05) was significantly lower than that in controls, whereas in Pheo and cortical carcinoma, Ang II binding was very low and in several cases almost undetectable. There was no remarkable difference in the Ang II receptor affinity among all tissues tested. The ratio between type 1 and type 2 Ang II receptors showed a large prevalence of type 1 in controls, APA, and three cases of Cush; in two cases of Cush, this ratio was reversed. In conclusion, our data indicate that Ang II receptors are normally expressed in APA and can also be detected in Cush, whereas they have a very low density in Pheo and adrenal carcinoma. Therefore, Ang II receptors are not involved in the lack of response to Ang II that is characteristic of APA; additionally, a reduction of Ang II receptors can be associated with dedifferentiation or malignancy of adrenal tumors. Further investigation of the expression and functional characterization of Ang II receptors is required to better clarify their possible role in adrenal tumorigenesis.

Role of growth factors in the developmental regulation of the human fetal adrenal cortex

Development of the human fetal adrenals is characterized by rapid growth and high levels of steroidogenic activity during the latter two-thirds of pregnancy. By midgestation, the human fetal adrenals are composed of two distinct cortical zones: the predominant fetal zone, which occupies 80-90% of the cortical volume and produces large amounts of the delta 5-steroid dehydroepiandrosterone sulfate, and the narrow definitive zone, which surrounds the fetal zone. Late in gestation, the peripheral portion of the fetal zone develops into a third, functionally distinct compartment, the transitional zone, which is the likely site of cortisol synthesis. Soon after birth, the adrenal cortex is remodeled and the fetal zone disappears. The adult cortical zones are thought to arise from the definitive zone, which persists postnatally. Development of the human fetal adrenals is regulated primarily by corticortropin (ACTH) secreted from the fetal pituitary. However, as ACTH is not a mitogen per se, its proliferative actions on human fetal adrenal cortical cells are thought to be mediated by autocrine/paracrine growth factors produced by adrenal cortical cells in response to ACTH. In addition, these growth factors appear to modulate the functional response of fetal adrenal cortical cells to ACTH. The roles of several growth factors, including the insulin like growth factors I and II (IGF-I and IGF-II), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), activin, inhibin, and the transforming growth factors alpha and beta (TGF-alpha and TGF-beta) have been examined. In cultured human fetal adrenal cortical cells, EGF, bFGF, and IGF-I and -II are mitogenic, whereas activin and TGF-beta inhibit proliferation. IGF-II, activin, and TGF-beta also modulate ACTH-stimulated steroidogenesis. Human fetal adrenal cortical cells express IGF-II, bFGF and the activin/inhibin subunits, and the abundance of mRNAs for each of these factors is up-regulated by ACTH, suggesting that these growth factors are autocrine/paracrine mediators of ACTH action. Thus, although human adrenal development is primarily regulated by ACTH, its actions appear to be mediated/modulated by a cohort of locally expressed growth factors, the net effect of which results in the unique growth and steroidogenic activity of the human fetal adrenal cortex.

Regulation of primary response and specific genes in adrenal cells by peptide hormones and growth factors

Using cultured bovine adrenal fasciculata cells (BAC), we investigated the effects of two hormones, corticotropin (ACTH) and angiotensin II (Ang-II) and two growth factors, insulin-like growth factors I (IGF-I) and transforming growth factor beta 1 (TGF beta 1), on the mRNA levels of nuclear proto-oncogenes of the Fos and Jun families and on the mRNA levels of genes expressed in BAC coding for ACTH and AT1 receptors, cytochrome P450scc and P450 17 alpha and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). ACTH and IGF-1 increased c-fos and jun-B mRNA levels early with later increases in the levels of mRNA for the ACTH receptor and the three steroidogenic enzymes, and enhanced steroidogenic responses to both ACTH and Ang-II. In contrast, Ang-II increased mRNA coding for the three proto-oncogenes (cfos, c-jun, and jun-B), decreased those for P450 17 alpha and 3 beta-HSD, and caused marked homologous and heterologous steroidogenic desensitization. TGF beta 1 increased only jun-B mRNA and markedly reduced BAC-differentiated functions and steroidogenic responsiveness to both ACTH and Ang-II. The long-term effects of ACTH on human adrenal fasciculata cells were comparable with those observed in BAC, whereas the long term effects of Ang-II and TGF beta 1 were different from those observed in BAC. Whether these species-specific differences are related to a different effect of these factors on proto-oncogene expression is not yet known.