Search Results

You are looking at 21 - 30 of 770 items for

  • Abstract: Estrogen x
  • Abstract: Corticosteroids x
  • Abstract: Mineralocorticoid x
  • Abstract: Aldosterone x
  • Abstract: Androgens x
  • Abstract: Testosterone x
  • Abstract: Gonadotropin x
  • Abstract: Cholesterol x
  • Abstract: Adrenal x
  • Abstract: Gonads x
  • Abstract: steroid* x
  • Abstract: glucocorticoids x
Clear All Modify Search
Restricted access

D. D. Brandon, A. J. Markwick, M. Flores, K. Dixon, B. D. Albertson and D. L. Loriaux

ABSTRACT

The neotropical cotton-top marmoset (Saguinus oedipus) is a New World primate known to have markedly increased total and free plasma cortisol concentrations when compared with Old World primates including man. The relative end-organ 'resistance' to glucocorticoids found in various New World primates has been attributed to a glucocorticoid receptor (GR) with diminished affinity for glucocorticoids. It has been demonstrated that the marmoset GR has approximately tenfold lower binding affinity for dexamethasone when compared with the human GR. We have examined the primary structure of the marmoset GR by molecular cloning and sequencing of GR functional domains. A library of cDNA clones was constructed in the phage vector λgt10 using poly(A)+ RNA from a marmoset-derived lymphoid cell line, and screened using the human GR cDNA. DNA sequencing determined 76 individual nucleotide substitutions in the coding region of the marmoset GR. Comparison of the marmoset GR nucleotide sequence with the human GR cDNA coding region indicated an overall sequence homology of about 97%. Thirty of the nucleotide substitutions lead to alterations in the predicted amino acid sequence (28 amino acid substitutions) of the marmoset GR.

The size of the marmoset GR predicted from the 778 amino acids is approximately 90 000 which is in agreement with previous size estimates of the human and marmoset GRs. Alterations of amino acid sequence in the marmoset GR were greatest towards the amino terminus, including the τ1 domain putatively involved in transcriptional activation. The DNA-binding domain contained an additional codon (arginine). Comparison of the DNA-binding domain of the marmoset GR with other members of the steroid receptor superfamily indicates that the additional arginine occurs in the same position as other amino acid insertions within the interfinger region of the human androgen receptor and the erb-A proto-oncogene. There are only four missense substitutions within the steroid-binding domain. Two of these substitutions occur within the transducing site which has been associated with binding of the GR to a 90 kDa heat shock protein. These data suggest that diminished GR affinity for glucocorticoids in the marmoset may be due to alterations in the primary structure of one or more functional domains of the GR gene. In addition, other important regulatory functions, such as transcriptional activation, DNA binding and receptor transduction, may also be affected.

Free access

Amy L Filby, Karen L Thorpe and Charles R Tyler

Complex interrelationships in the signalling of oestrogenic effects mean that environmental oestrogens present in the aquatic environment have the potential to disrupt physiological function in fish in a more complex manner than portrayed in the present literature. Taking a broader approach to investigate the possible effect pathways and the likely consequences of environmental oestrogen exposure in fish, the effects of 17β-oestradiol (E2) were studied on the expression of a suite of genes which interact to mediate growth, development and thyroid and interrenal function (growth hormone GH (gh), GH receptor (ghr ), insulin-like growth factor (IGF-I) (igf1), IGF-I receptor (igf1r ), thyroid hormone receptors-α (thra) and -β (thrb) and glucocorticoid receptor (gr )) together with the expression analyses of sex-steroid receptors and ten other genes centrally involved in sexual development and reproduction in fathead minnow (fhm; Pimephales promelas). Exposure of adult fhm to 35 ng E2/l for 14 days induced classic oestrogen biomarker responses (hepatic oestrogen receptor 1 and plasma vitellogenin), and impacted on the reproductive axis, feminising ‘male’ steroidogenic enzyme expression profiles and suppressing genes involved in testis differentiation. However, E2 also triggered a cascade of responses for gh, ghr, igf1, igf1r, thra, thrb and gr in the pituitary, brain, liver, gonad and gill, with potential consequences for the functioning of many physiological processes, not just reproduction. Molecular responses to E2 were complex, with most genes showing differential responses between tissues and sexes. For example, igf1 expression increased in brain but decreased in gill on exposure to E2, and responded in an opposite way in males compared with females in liver, gonad and pituitary. These findings demonstrate the importance of developing a deeper understanding of the endocrine interactions for unravelling the mechanisms of environmental oestrogen action and predicting the likely health consequences.

Free access

Karine Steketee, Angelique C J Ziel-van der Made, Hetty A G M van der Korput, Adriaan B Houtsmuller and Jan Trapman

We characterized the specifically androgen-regulated gene (SARG), which is expressed in the androgen receptor (AR) and glucocorticoid receptor (GR) positive cell line lymph node carcinoma of the prostate-1F5 (LNCaP-1F5). SARG mRNA expression can be up-regulated by androgens, but not by glucocorticoids. SARG mRNA expression is high in prostate tissue. SARG is composed of four exons and spans a region of 14.5 kbp on chromosome 1q32.2. Transcripts of 5.5, 3.3 and 2.3 kb are the result of alternative polyadenylation. SARG mRNA splice variants lack exon 2 and vary in length of exon 1. The SARG protein has a length of 601 amino acids and is located in the cytoplasm. By screening the 18 kbp genomic sequence flanking the transcription start site we identified the imperfect direct repeat 5′-TGTGCTaacTGTTCT-3′in intron 1 as an active androgen response element (ARE-SARG+4.6). A 569 bp genomic DNA fragment containing this element functioned as an androgen-specific enhancer in transiently transfected LNCaP-1F5 cells. ARE-SARG+4.6 cooperated with flanking sequences for optimal activity. Inactivation of ARE-SARG+4.6 completely abolished the androgen response of the enhancer. Chromatin immunoprecipitation (ChIP) experiments showed chromatin structural changes of the enhancer in the presence of R1881. ARE-SARG+4.6 was able to bind to the androgen receptor, but not to the glucocorticoid receptor, correlating with its androgen-specific activity in transfections.

Free access

Laura E Ellestad, Stefanie A Malkiewicz, H David Guthrie, Glenn R Welch and Tom E Porter

The expression profile of glucocorticoid-induced leucine zipper (GILZ) in the anterior pituitary during the second half of embryonic development in the chick is consistent with in vivo regulation by circulating corticosteroids. However, nothing else has been reported about the presence of GILZ in the neuroendocrine system. We sought to characterize expression and regulation of GILZ in the chicken embryonic pituitary gland and determine the effect of GILZ overexpression on anterior pituitary hormone levels. Pituitary GILZ mRNA levels increased during embryogenesis to a maximum on the day of hatch, and decreased through the first week after hatch. GILZ expression was rapidly upregulated by corticosterone in embryonic pituitary cells. To determine whether GILZ regulates hormone gene expression in the developing anterior pituitary, we overexpressed GILZ in embryonic pituitary cells and measured mRNA for the major pituitary hormones. Exogenous GILZ increased prolactin mRNA above basal levels, but not as high as that in corticosterone-treated cells, indicating that GILZ may play a small role in lactotroph differentiation. The largest effect we observed was a twofold increase in FSH β subunit in cells transfected with GILZ but not treated with corticosterone, suggesting that GILZ may positively regulate gonadotroph development in a manner not involving glucocorticoids. In conclusion, this is the first report to characterize avian GILZ and examine its regulation in the developing neuroendocrine system. We have shown that GILZ is upregulated by glucocorticoids in the embryonic pituitary gland and may regulate expression of several pituitary hormones.

Restricted access

P. Davies and N. K. Rushmere

ABSTRACT

Ventral prostate glands of intact normal rats contained low levels (2500 molecules/cell) of high-affinity (dissociation constant (K d) 0·57 nmol/l) glucocorticoid receptors (GR). Levels of GR increased 2·8-fold 1 day after castration, and 4·3-fold 3 days after castration. Nuclear GR increased from a normal value of 1150 molecules/nucleus to 5200 molecules/nucleus 3 days after castration. The greater increase in intranuclear GR was in that associated with oligomeric chromatin. Although nuclear GR never approached the normal population of nuclear androgen receptors (AR; approximately 16000 molecules/nucleus), the selective rise in chromatin-associated receptors ensured that almost 60% of chromatin sites remained occupied. GR associated with prostate nuclear structures in a similar manner to AR, and exogenous GR bound saturably and with high affinity (K d 100 pmol/1) to a similar number of sites as did AR. Both steroid receptors apparently competed for the same sites. In DNA—cellulose competition analyses, synthetic oligonucleotides containing glucocorticoid response elements or putative androgen response elements competed similarly against immobilized non-specific DNA for both AR and GR. In view of these data and information from other sources, it is probable that the role of GR in the prostate should be assessed with a view to understanding its action under conditions of androgen deprivation.

Free access

GM Hargrove, A Junco and NC Wong

Apolipoprotein AI (apo AI) is the major protein component of the serum high-density lipoprotein (HDL) particles. The antiatherogenic properties of apo AI alone or as part of HDL and their inverse correlation with the incidence of coronary heart disease underlie the clinical importance of the protein. A detailed understanding of the mechanisms by which apo AI is regulated will help us develop new and better ways to manipulate expression of the protein. Although there are many factors that influence apo AI expression, endogenous hormones are attractive because simple changes in abundance of these compounds will alter gene activity. Hormones belonging to the thyroid/steroid family that influence activity of the gene include thyroid hormone, glucocorticoids, gender-specific steroids and retinoic acid. Whereas thyroid, glucocorticoid and estradiol enhance activity of the gene, retinoic acid and androgens decrease it. The mechanisms that mediate the effects of the hormones include direct effects of the ligand and nuclear receptor complex on gene activity. However, indirect means involving the participation of transcription factors other than the hormone receptors are also possible. In summary, members of the same hormone family may have different mechanisms that mediate their activities on apo AI gene activity.

Open access

Rebecca J Gorrigan, Leonardo Guasti, Peter King, Adrian J Clark and Li F Chan

The melanocortin-2-receptor (MC2R)/MC2R accessory protein (MRAP) complex is critical to the production of glucocorticoids from the adrenal cortex. Inactivating mutations in either MC2R or MRAP result in the clinical condition familial glucocorticoid deficiency. The localisation of MC2R together with MRAP within the adrenal gland has not previously been reported. Furthermore, MRAP2, a paralogue of MRAP, has been shown in vitro to have a similar function to MRAP, facilitating MC2R trafficking and responsiveness to ACTH. Despite similar MC2R accessory functions, in vivo, patients with inactivating mutations of MRAP fail to be rescued by a functioning MRAP2 gene, suggesting differences in adrenal expression, localisation and/or function between the two MRAPs. In this study on the rat adrenal gland, we demonstrate that while MRAP and MC2R are highly expressed in the zona fasciculata, MRAP2 is expressed throughout the adrenal cortex in low quantities. In the developing adrenal gland, both MRAP and MRAP2 are equally well expressed. The MC2R/MRAP2 complex requires much higher concentrations of ACTH to activate compared with the MC2R/MRAP complex. Interestingly, expression of MC2R and MRAP in the undifferentiated zone would support the notion that ACTH may play an important role in adrenal cell differentiation and maintenance.

Free access

Hannah E Lapp, Andrew A Bartlett and Richard G Hunter

Glucocorticoids have long been recognized for their role in regulating the availability of energetic resources, particularly during stress. Furthermore, bidirectional connections between glucocorticoids and the physiology and function of mitochondria have been discovered over the years. However, the precise mechanisms by which glucocorticoids act on mitochondria have only recently been explored. Glucocorticoids appear to regulate mitochondrial transcription via activation of glucocorticoid receptors (GRs) with elevated circulating glucocorticoid levels following stress. While several mechanistic questions remain, GR and other nuclear transcription factors appear to have the capacity to substantially alter mitochondrial transcript abundance. The regulation of mitochondrial transcripts by stress and glucocorticoids will likely prove functionally relevant in many stress-sensitive tissues including the brain.

Restricted access

M Shimojo, C B Whorwood and P M Stewart

ABSTRACT

11β-Hydroxysteroid dehydrogenase (11β-HSD) catalyses the interconversion of biologically active cortisol to inactive cortisone in man, and corticosterone to 11-dehydrocorticosterone in rodents. As such, this enzyme has been shown to confer aldosterone-selectivity on the mineralocorticoid receptor and to modulate cortisol/corticosterone access to the glucocorticoid receptor (GR). Two kinetically distinct isoforms of this enzyme have been characterized in both rodents and man; a low-affinity NADP(H)-dependent enzyme (11β-HSD1) which predominantly acts as an oxo-reductase and, more recently, a high-affinity NAD-dependent uni-directional dehydrogenase (11β-HSD2). In this study we have analysed the expression of both 11β-HSD1 and 11β-HSD2 isoforms in rat adrenal cortex and medulla and have investigated their possible roles with respect to glucocorticoid-regulated enzymes mediating catecholamine biosynthesis in adrenal medullary chromaffin cells.

Using a rat 11β-HSD1 probe and a recently cloned in-house mouse 11β-HSD2 cDNA probe, Northern blot analyses revealed expression of mRNA species encoding both 11β-HSD1 (1·4kb) and 11β-HSD2 (1·9kb) in the whole adrenal. Consistent with this, 11β-dehydrogenase activity (pmol 11-dehydrocorticosterone formed/mg protein per h, mean ± s.e.m.) in adrenal homogenates, when incubated with 50 nm corticosterone in the presence of 200 μm NAD, was 97·0 ± 9·0 and with 500 nm corticosterone in the presence of 200 μm NADP, was 98·0 ± 1·4 11-Oxoreductase activity (pmol corticosterone formed/mg protein per h) with 500 nm 11-dehydrocorticosterone in the presence of 200 μm NADPH, was 187·7 ± 31·2. In situ hybridization studies of rat adrenal cortex and medulla using 35S-labelled antisense 11β-HSD1 cRNA probe revealed specific localization of 11β-HSD1 mRNA expression predominantly to cells at the corticomedullary junction, most likely within the inner cortex. In contrast, 11β-HSD2 mRNA was more abundant in cortex versus medulla, and was more uniformly distributed over the adrenal gland. Negligible staining was detected using control sense probes.

Ingestion of the 11β-HSD inhibitor, glycyrrhizic acid (>100mg/kg body weight per day for 4 days) resulted in significant inhibition of adrenal NADP-dependent (98·0 ± 1·4 vs 42·5 ± 0·4) and NAD-dependent (97·0 ± 9·0 vs 73·2 ± 6·7) 11β-dehydrogenase activity and 11-oxoreductase activity (187·7 ± 31·2 vs 67·7 ± 15·3). However, while levels of 11β-HSD1 mRNA were similarly reduced (0·85 ± 0·07 vs 0·50 ± 0·05 arbitrary units), those for 11β-HSD2 remained unchanged (0·44 ± 0·03 vs 0·38 ± 0·01). Levels of mRNA encoding the glucocorticoid-dependent enzyme phenylethanolamine N-methyltransferase which catalyses the conversion of noradrenaline to adrenaline, were also significantly reduced in those rats given glycyrrhizic acid (1·12 ± 0·04 vs 0·78 ± 0·04), while those for the glucocorticoid-independent enzyme tyrosine hydroxylase (1·9 kb), which catalyses the conversion of tyrosine to DOPA, were unchanged (0·64 ± 0·04 vs 0·61 ± 0·04).

In conclusion, the rat adrenal gland expresses both 11β-HSD1 and 11β-HSD2 isoforms. 11β-HSDl gene expression is localized to the adrenal cortico-medullary junction, where it is ideally placed to regulate the supply of cortex-derived corticosterone to the medullary chromaffin cells. This, together with our in vivo studies, suggests that 11β-HSD1 may play an important role with respect to adrenocorticosteroid regulation of adrenaline biosynthesis. The role of 11β-HSD2 in the adrenal remains to be elucidated.

Free access

Tomoko Tanaka, Shigeki Gondo, Taijiro Okabe, Kenji Ohe, Hisao Shirohzu, Hidetaka Morinaga, Masatoshi Nomura, Kenzaburo Tani, Ryoichi Takayanagi, Hajime Nawata and Toshihiko Yanase

Abstract

Steroidogenic factor 1/adrenal 4 binding protein (SF-1/Ad4BP) is an essential nuclear receptor for steroidogenesis as well as for adrenal and gonadal gland development. Mesenchymal bone marrow cells (BMCs) contain pluripotent progenitor cells, which differentiate into multiple lineages. In a previous study, we reported that adenovirus-mediated forced expression of SF-1 could transform mouse primary long-term cultured BMCs into steroidogenic cells. For future clinical application, trials using human BMCs would be indispensable. In this study, we examined whether SF-1 could transform human BMCs into steroidogenic cells and compared the steroid profile of these cellswith that of mouse steroidogenic BMCs. Primary cultured human BMCs infected with adenovirus containing bovine SF-1 cDNA could produce progesterone, corticosterone, cortisol, dehydroepiandrosterone, testosterone, and estradiol. Such a mixed character of adrenal and gonadal steroid production in human BMCs was supported by the expressions of P450scc, 3β-hydroxysteroid dehydrogenase (3β-HSD), P450c21, P450c11, P450c17, 17β-HSD, and P450arom mRNAs. Unlike mouse steroidogenic BMCs, introduction of SF-1 into human BMCs caused dramatic inductions of both ACTH and LH receptors, thus leading to good responsiveness of the cells to ACTH and LH respectively. Importantly, among several factors that are known to be closely associated with adrenal and/or gonadal development, introduction of only SF-1 enabled the human BMCs to express P450scc and to produce cortisol and testosterone, suggesting that SF-1 is truly a master regulator for the production of steroidogenic cells from human BMCs.