Phenotypic variability and origins of mutations in the gene encoding 3beta-hydroxysteroid dehydrogenase type II

Mutations in HSD3B2, the gene for 3beta-hydroxysteroid dehydrogenase type II (3beta-HSD II) have been detected and activities analysed through the in vitro expression of mutant cDNAs. Two full sibs with male pseudohermaphroditism were found to be double heterozygotes: N100S/266DeltaA. This genotype leads to the most profound loss of 3beta-HSD II enzyme activity (1.3% of normal) described to date in cases without severe salt-loss. One sib (N100S/266DeltaA) is the first reported male case of type II deficiency affected with premature adrenarche. Three apparently independent kindreds had propositi affected with the HSD3B2 mutation A82T/A82T, which is associated with a non salt-losing phenotype with variable expressivity in females. These three families had the same extended HSD3B haplotype and are likely to have inherited the same ancestral mutation. The significance of this finding is discussed in the light of the presence of A82T mutation at a homologous position in pseudogene varphi5 that is present in the HSD3B cluster.

Creation of a fully active, cytosolic form of human type I 3beta-hydroxysteroid dehydrogenase/isomerase by the deletion of a membrane-spanning domain

Human 3beta-hydroxysteroid dehydrogenase/steroid Delta(5)-Delta(4)-isomerase (3beta-HSD/isomerase) is a bifunctional, single enzyme protein that is membrane-bound in the endoplasmic reticulum (microsomes) and mitochondria of cells in the placenta (type I) and in the adrenals and gonads (type II). Two membrane-binding domains (residues 72-89 and 283-310) have been predicted by analyses of hydrophobicity in the type I and II isoenzymes (90% regional homology). These putative membrane domains were deleted in the cDNA by PCR-based mutagenesis, and the two mutant enzymes were expressed by baculovirus in insect Sf9 cells. Differential centrifugation of the Sf9 cell homogenate containing the 283-310 deletion mutant revealed that 94% of the 3beta-HSD and isomerase activities were in the cell cytosol, 6% of the activities were in the microsomes, and no activity was in the mitochondria. This is the opposite of the subcellular distribution of the wild-type enzyme with 94% of the activities in the microsomes and mitochondria and only 6% activity in the cytosol. The organelle distribution of the 72-89 deletion mutant lies between these two extremes with 72% of the enzyme activity in the cytosol and 28% in the microsomes/mitochondria. The integrity of the subcellular organelle preparations was confirmed by electron microscopy. Western immunoblots confirmed the presence of the 283-310 deletion mutant enzyme and the absence of the wild-type enzyme in the insect cell cytosol. The unpurified, cytosolic 383-310 deletion mutant exhibited 3beta-HSD (22 nmol/min per mg) and isomerase (33 nmol/min per mg) specific activities that were comparable with those of the membrane-bound, wild-type enzyme. The isomerase reaction of the cytosolic 283-311 deletion mutant requires activation by NADH just like the isomerase of the microsomal or mitochondrial wild-type enzyme. In contrast, the 72-89 deletion mutant had low 3beta-HSD and isomerase specific activities that were only 12% of the wild-type levels. This innovative study identifies the 283-310 region as the critical membrane domain of 3beta-HSD/isomerase that can be deleted without compromising enzyme function. The shorter 72-89 region is also a membrane domain, but deletion of this NH(2)-terminal region markedly diminishes the enzyme activities. Purification of the active, cytosolic 283-310 deletion mutant will produce a valuable tool for crystallographic studies that may ultimately determine the tertiary/quaternary structure of this key steroidogenic enzyme.

The influence of age and gender on serum dehydroepiandrosterone sulphate (DHEA-S), IL-6, IL-6 soluble receptor (IL-6 sR) and transforming growth factor beta 1 (TGF-beta1) levels in normal healthy blood donors

Dysregulation of IL-6 synthesis is thought to play a role in the development of a number of age-related conditions, such as rheumatoid arthritis, osteoporosis, atherosclerosis, Alzheimer's disease and B cell malignancies. Recently it has been suggested that the production of IL-6 is influenced by the adrenal hormone dehydroepiandrosterone (DHEA) and its sulphated derivative DHEA-S. In humans we investigated the relationship between DHEA-S, IL-6, IL-6 sR and TGF-beta1 in the serum of normal healthy male and female blood donors. Using immunoassay techniques we found that the serum levels of DHEA-S significantly (P = 0.0001) decreased with age in both males and females. Furthermore, mean DHEA-S levels in all age groups were significantly (P = 0.0001) higher in males. Such correlations were not apparent for IL-6 using a standard assay, but a high sensitivity assay revealed that serum IL-6 was significantly (P = 0.0018) positively correlated with age in males only. In addition, serum levels of DHEA-S were significantly (P = 0.048) negatively correlated with serum IL-6, again in male subjects only. In contrast, serum IL-6 sR and TGF-beta1 levels were not correlated with age in either males or females and were not significantly different between the sexes. However, a significant (P = 0.024) negative correlation between DHEA-S and IL-6 sR was found in males. These studies clearly highlight the complex nature of the relationship between these molecules in the ageing process in normal healthy blood donors and demonstrate the need to use high sensitivity assays when measuring IL-6 in apparently healthy individuals under the age of 70 years.

Ontogeny of 3beta-hydroxysteroid dehydrogenase expression in the rat adrenal gland as studied by immunohistochemistry

The enzyme 3beta-hydroxysteroid dehydrogenase plays a crucial role in the steroidogenic process in the adrenal gland. In the present study we tried to characterize its localization and developmental changes in the rat adrenal cortex during the postnatal period, using immunohistochemical methods. The development of the different zones evidenced specific particularities: the zona glomerulosa almost lacked 3beta-HSD in the first days after birth; then, 3beta-HSD increased, attaining a maximum around day 20 and afterwards it decreased again and remained less intense than the neighbouring zona fasciculata up until adulthood (65 days of age). The zona fasciculata was already intensely stained at birth and the expression of 3beta-HSD increased rapidly reaching a maximum after 2 weeks of life and that level was maintained from then on. The inner part of the zona fasciculata and the zona reticularis both of which develop postnatally were faintly immunostained before day 20. The expression of 3beta-HSD increased after that age to become approximately as intense as in the outer zona fasciculata and so remaining until day 90. The development of the zona glomerulosa was parallel to the secretion of aldosterone. The same did not occur with the zona fasciculata as the intensity of staining during the first 14 postnatal days was accompanied by very low levels of corticosterone.

Adrenarche results from development of a 3beta-hydroxysteroid dehydrogenase-deficient adrenal reticularis

Adrenarche is the increased adrenal production of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) that occurs during the prepubertal period. To date, the exact mechanism initiating adrenarche is unknown, although many factors have been postulated. In the present study, we examined the hypothesis that alterations in intra-adrenal expression of 3beta-hydroxysteroid dehydrogenase (3betaHSD) or 21-hydroxylase (CYP21) within the inner reticularis zone leads to the increased production of 19-carbon (C19) steroids. After conversion of cholesterol to pregnenolone, 17alpha-hydroxylase/17,20-lyase (CYP17) can metabolize pregnenolone through to DHEA. The enzyme 3betaHSD competes for substrate with CYP17 and effectively removes steroid precursor from the pathway leading to DHEA. On the other hand, deficiency in CYP21 expression is known to cause excessive production of adrenal C19 steroids, suggesting that CYP21 could play a role in adrenarche. Thus, a decrease in 3betaHSD or CYP21 expression would allow substrate to flow toward the synthesis of DHEA. To determine whether adrenarche results from a decreased expression of 3betaHSD or CYP21 in the reticularis, immunohistochemical localization of 3betaHSD and CYP21 was performed, and staining intensities compared using adrenal glands from children ages 4 months to 4 yr (n = 12), ages 5-7 yr (n = 9), ages 8-13 yr (n = 9), and adults ages 25-56 yr (n = 8). There were no differences in the zonal expression of CYP21. No difference in 3betaHSD staining was observed between the glomerulosa and fasciculata from any age group. However, children age 8 yr and older show a significant decrease in 3betaHSD expression in reticularis as compared with the fasciculata. No significant difference was noted for 3betaHSD levels between the fasciculata and reticularis for children age 7 yr or younger. The level of 3betaHSD expression in the reticularis continued to decrease in the adult adrenals examined. These findings suggest that as children mature there is a decreased level of 3betaHSD in the adrenal reticularis that may contribute to the increased production of DHEA and DHEAS seen during adrenarche.

Site-directed mutagenesis identifies amino acid residues associated with the dehydrogenase and isomerase activities of human type I (placental) 3beta-hydroxysteroid dehydrogenase/isomerase

3beta-hydroxysteroid dehydrogenase/steroid delta5-->4-isomerase (3beta-HSD/isomerase) was expressed by baculovirus in Spodoptera fungiperda (Sf9) insect cells from cDNA sequences encoding human wild-type I (placental) and the human type I mutants - H261R, Y253F and Y253,254F. Western blots of SDS-polyacrylamide gels showed that the baculovirus-infected Sf9 cells expressed the immunoreactive wild-type, H261R, Y253F or Y253,254F protein that co-migrated with purified placental 3beta-HSD/isomerase (monomeric Mr=42,000 Da). The wild-type, H261R and Y253F enzymes were each purified as a single, homogeneous protein from a suspension of the Sf9 cells (5.01). In kinetic studies with purified enzyme, the H261R mutant enzyme had no 3beta-HSD activity, whereas the Km and Vmax values of the isomerase substrate were similar to the values obtained with the wild-type and native enzymes. The Vmax (88 nmol/min/mg) for the conversion of 5-androstene-3,17-dione to androstenedione by the Y253F isomerase activity was 7.0-fold less than the mean Vmax (620 nmol/min/mg) measured for the isomerase activity of the wild-type and native placental enzymes. In microsomal preparations, isomerase activity was completely abolished in the Y253,254F mutant enzyme, but Y253,254F had 45% of the 3beta-HSD activity of the wild-type enzyme. In contrast, the purified Y253F, wild-type and native enzymes had similar Vmax values for substrate oxidation by the 3beta-HSD activity. The 3beta-HSD activities of the Y253F, Y253,254F and wild-type enzymes reduced NAD+ with similar kinetic values. Although NADH activated the isomerase activities of the H261R and wild-type enzymes with similar kinetics, the activation of the isomerase activity of H261R by NAD+ was dramatically decreased. Based on these kinetic measurements, His261 appears to be a critical amino acid residue for the 3beta-HSD activity, and Tyr253 or Tyr254 participates in the isomerase activity of human type I (placental) enzyme.

Functional activity of 3beta-hydroxysteroid dehydrogenase/isomerase

3Beta-hydroxysteroid dehydrogenase/steroid delta5-isomerase (3beta-HSD/isomerase) was expressed by baculovirus in Spodoptera fungiperda (Sf9) insect cells from cDNA sequences encoding the human wild-type I (placental) enzyme and the human type I mutant- Y253F. The wild-type and Y253F enzymes were each purified as a single, homogeneous protein from a suspension of the Sf9 cells. Ultraviolet (UV) spectral analyses showed that the wild-type enzyme induced changes in the UV spectrum of the competitive isomerase inhibitor, 19-nortestosterone, and the Y253F mutant did not. The wild-type isomerase required activation by coenzyme to produce the spectral shift. Activation of isomerase by NADH produced a greater change in the 19-nortestosterone spectrum than activation by NAD+. These observations provide direct evidence that Tyr253 functions as the general acid (proton donor) in the isomerase reaction mechanism. Furthermore, the coenzyme-activation profiles support our proposed two-step enzyme mechanism in which NADH produced by the 3beta-HSD activity induces the enzyme to assume the isomerase conformation.

Battle of the kinases: integration of adrenal responses to cAMP, DG and Ca2+ at the level of steroidogenic cytochromes P450 and 3betaHSD expression in H295R cells

While ACTH receptors (activating the protein kinase A pathway) are expressed throughout the human/bovine/ovine zona glomerulosa (zg) and zona fasciculata (zf), there are clear zonal differences in AII Type-1 receptor levels (activating protein kinase C/Ca2+), as well as resting membrane potential. Thus zg is most responsive to AII and K+ (Ca2+ signalling), while zf is less responsive to AII with no K+ response. Zonal function in turn requires differential expression of CYP17/3betaHSD and CYP11B2/CYP11B1. We have used the H295R cell to study how differential activation of kinase A, kinase C and Ca2+/calmodulin (CaM) kinases may alter the relative expression of the steroidogenic P450s and 3betaHSDII. While CYP11A, CYP17, 3betaHSDII, CYP21, and CYP11B1 are all induced by increases in cAMP, studies with TPA alone or in combination with forskolin reveal subsets of steroidogenic enzymes regulated either positively (CYP21, 3betaHSDII) or negatively (CYP17, CYP11A) by protein kinase C. Thus adrenal 3betaHSDII and CYP21 expression is high in zg and zf, but CYP17 is not expressed in the zg where AII activation of kinase C is highest. In turn both K+ and AII-induced elevation of Ca2+ strongly induces CYP11B2 but not CYP11B1, consistent with preferential expression of CYP11B2 in the zg. We conclude that differential signaling through kinase C and CaM kinases in addition to kinase A underlies zonal differences in both the early and late pathways involved in steroid hormone production within the adrenocortical zones.

The expression of steroidogenic acute regulatory protein (StAR) in bovine adrenocortical cells

StAR protein may facilitate rapid transfer of cholesterol from the outer to the inner mitochondrial membrane, the site at which cholesterol is converted to pregnenolone by the cholesterol side chain cleavage complex. We have studied the effect of ACTH treatment on StAR mRNA and protein levels in bovine adrenocortical cells in primary culture. Cells were initially cultured for 3 days after isolation, and then treated with ACTH (10(-8) M) for various times up to 24 hours. Northern analysis of total BAC mRNA, using a [alpha32P]-labelled cDNA probe encoding a 5' region of bovine StAR mRNA, revealed two principal hybridising species of 1.6 and 3.0 kb. Western immunoblot analysis revealed a principal band at 30 kDa. Levels of both StAR mRNA and protein showed an increase at 1 hour, reached a maximum at around 6 hours and declined to basal levels at 24 hours. Cortisol secretion (measured by RIA) showed a similar change over the same period. From these results it appears that StAR mRNA and protein levels in BAC are acutely regulated in concert with ACTH-stimulated cortisol secretion.

StAR protein is expressed in both medulla and cortex of the bovine and rat adrenal gland

We have employed polyclonal antibodies to a peptide sequence of bovine steroidogenic acute regulatory (StAR) protein and human placental 3beta-hydroxysteroid dehydrogenase (3beta-HSD) to determine the localisation and distribution of these proteins in rat and bovine adrenal glands. Immunohistochemical staining demonstrated the presence of StAR protein in the zona glomerulosa (ZG), zona fasciculata (ZF), zona reticularis (ZR) and in the medulla of both species. For 3beta-HSD, immunostaining was observed in the ZG, ZF and ZR of the rat adrenal and was absent in the medulla. Immunoblotting experiments showed intense bands for StAR protein (30 kDa, 37 kDa) in the mitochondria of bovine ZG, ZF and medulla and a less intense band (30 kDa) in the microsomes. In rat ZG and ZF/R mitochondria only the 30 kDa protein was present. For 3beta-HSD, an intense band (42 kDa) was found in microsomes and mitochondria of rat and bovine ZG and ZFR. A very faint signal for 3beta-HSD was seen in adrenal medulla. In conclusion, StAR (or a closely related) protein is present throughout the adrenal gland in rat and bovine species in contrast to 3beta-HSD which is confined to the steroidogenic zones. The possible function of StAR protein in the adrenal medulla merits investigation.

Protein kinase A, protein kinase C, and Ca(2+)-regulated expression of 21-hydroxylase cytochrome P450 in H295R human adrenocortical cells

The physiological importance of adrenal 21-hydroxylase cytochrome P450 (CYP21) expression is clearly demonstrated by 21-hydroxylase deficiency, which results in adrenal hyperplasia and over-production of C19 steroids, leading to virilization. The mechanisms regulating normal expression of this key enzyme in human adrenocortical cells are ill defined. Herein we examine the role of the calcium, protein kinase C, and protein kinase A signaling pathways in the expression of CYP21 messenger ribonucleic acid (mRNA) using the H295R human adrenocortical cell model. Forskolin (10 mumol/L) treatment caused a progressive increase in CYP21 mRNA levels (maximum, 4-fold; P < 0.05) over 36 h of treatment, whereas angiotensin II (AII; 10 nmol/L) produced a smaller, biphasic rise (maximum, 1.8-fold at 12 h; P < 0.05). K+ (14 mmol/L) also induced a time-dependent (maximal, 1.5-fold at 12 h; P < 0.05) and dose-dependent (P < 0.05 12 mmol/L or above at 20 h) rise in CYP21 mRNA levels. The action of forskolin was reproduced by dibutyryl cAMP, confirming the involvement of cAMP in this response. The action of AII was greater than that of K+ or the calcium channel agonist BAYK8644, suggesting that AII action was not solely through the Ca2+ signaling pathway. The action of AII was reproduced and indeed exceeded by the protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA; 10 nmol/L; 5.5-fold increase; P < 0.05). The actions of forskolin alone were not significantly increased by combined treatment with AII, suggesting neither synergy nor attenuation of the effects of protein kinase A activation. This was further demonstrated at the level of mRNA and 21-hydroxylase activity by the observation that the effect of forskolin and TPA in combination did not exceed that of TPA alone. Inhibition of protein synthesis with cycloheximide blocked induction of CYP21 as well as type II 3 beta-hydroxysteroid dehydrogenase (3 beta HSDII) mRNA expression in response to AII, forskolin, and dibutyryl cAMP, but had no effect on 17 alpha-hydroxylase cytochrome P450 (CYP17) or cholesterol side-chain cleavage cytochrome P450 (CYP11A) mRNA. Together, these findings were remarkably similar to those of our previous studies regarding mechanisms regulating 3 beta HSDII expression and underline the existence of a subset of steroidogenic enzymes regulated positively (CYP21 and 3 beta HSDII) as opposed to negatively (CYP17 and CYP11A) by the protein kinase C signaling pathway. The additional finding of a small induction of CYP21 expression in response to increased Ca2+, as previously reported for CYP17, but not 3 beta HSDII, expression, also demonstrates that the mechanisms of control of CYP21 and 3 beta HSDII are not identical. This latter finding may also relate to how CYP21 as well as CYP17 expression continues in the zona reticularis after adrenarche, whereas 3 beta HSD expression declines.

Corticosteroid metabolism in human granulosa-lutein cells

OBJECTIVE

The aims of this study were to determine the type and level of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) in human granulosa-leutein cells (GLE) shortly before ovulation and to correlate activity with the outcome of treatment in patients undergoing in vitro fertilization and embryo transfer (IVF/ET).

DESIGN

GLC from 32 patients undergoing IVF/ET were tested for type and level of 11 beta HSD activity in relation to treatment outcome.

PATIENTS

Periovulatory follicles were aspirated by ultrasound guided transvaginal puncture following a standard controlled ovarian stimulation protocol, approximately 36 h after administering an ovulation-inducing dose of human chorionic gonadotrophin (HCG). GLC were separated from follicular fluid by density-gradient centrifugation and taken for measurement of 11 beta HSD activity in vitro; oocytes were used for IVF/ET.

MEASUREMENTS

Interconversion of cortisol (F) and cortisone (E), and dexamethasone (D) and 11-dehydrodexamethasone (DHD) was measured in standardized assays comprising incubation of GLC with 3H-labelled substrate, with separation of substrate and product by thin-layer radiochromatography.

RESULTS

Conversion of F to E varied from 10.5 to 30.9% while that of E to F was between 2.4 and 44.6%. In the GLC of 25 patients in whom both activities were measured, dehydrogenase (F to E) activity predominated in 13 and reductase (E to F) in 12. By contrast, D (substrate for 11 beta HSD2 but not 11 beta HSD1) showed less than 1% metabolism in this system while DHD (substrate for 11 beta HSD1 and 11 beta HSD2) was converted significantly (65.6-90.5%) to D in the four patients tested. There was no significant difference in the interconversion of F and E between patients who became pregnant and those who did not.

CONCLUSIONS

The dehydrogenase and oxoreductase reactions catalysed by 11 beta HSD both occur in granulosa-lutein cells at the time of follicular rupture, probably due to 11 beta HSD1. A lack of measurable conversion of dexamethasone to 11-dehydrodexamethasone suggests that dehydrogenation due to 11 beta HSD2 is low or absent. Neither type nor level of 11 beta HSD activity measured under the present assay conditions correlates with IVF outcome.

Characterization of cDNAs encoding isoforms of hamster 3 beta-hydroxysteroid dehydrogenase/delta 5-->4 isomerase

Western blot analyses of various hamster tissues reveal high levels of expression of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in adrenal and liver, and moderate levels of expression in kidney. The expression in liver is sexually dimorphic; very high levels of protein are observed in adult male liver but very low levels are seen in the female liver. Three distinct cDNAs encoding isoforms of 3 beta-HSD were isolated from hamster cDNA libraries. The type 1 isoform is a high-affinity dehydrogenase/isomerase expressed in adrenal and male kidney. The type 2 isoform is also a high-affinity dehydrogenase/isomerase expressed in kidney and male liver. The type 3 enzyme is a 3-ketosteroid reductase expressed predominantly in kidney. Sequencing of the clones showed that all three are structurally very similar, although types 1 and 2 share the greatest degree of similarity. Immunohistochemical staining for 3 beta-HSD in the adrenal was found throughout the adrenal cortex. In the kidney staining was confined to tubules, and in the liver, heavy staining was found in hepatocytes. The cloning of cDNAs for 3 beta-HSD from the liver and kidney should help in elucidating the function of this enzyme in these tissues.

Direct stimulation of cortisol secretion from the human NCI H295 adrenocortical cell line by vasoactive intestinal polypeptide

OBJECTIVE

To investigate a possible direct action of vasoactive intestinal polypeptide (VIP) on adrenal cortisol secretion and to define its mechanism of action.

DESIGN

The human adrenocortical carcinoma cell line NCI H295, which is not contaminated by medullary chromaffin cells, was used to aid distinction between a direct action of VIP on adrenocortical cells and an indirect mechanism involving VIP-stimulated release of catecholamines.

METHODS

NCI H295 cells were challenged with 10(-11)-10(-7) mol/l VIP for 4 h, with or without prior exposure for 72 h to 10 micromol/l forskolin. Cortisol and cyclic AMP contents of the overlying media were measured using in-house radioimmunoassays. Cells were treated with 10(-8)-10(-6) mol/l adrenaline or 3.3 x 10(-8) mol/l VIP with and without 10(-8)-10(-6) mol/l propranolol to exclude the possibility that an indirect mechanism of action involving beta-adrenoceptors was operating.

RESULTS

VIP treatment produced an increase in cortisol secretion without pre-incubation, but this was markedly enhanced by prior exposure of cells to forskolin. VIP was potent, with a threshold of 10(-11) mol/l (n = 4), reaching a maximum 3.9+/-0.9-fold increase in effect on cells pre-exposed to forskolin (n = 4) by 3.3 x 10(-8) mol/l. This increase matched the 4 h response to 10 micromol/l forskolin. Cortisol secretion was accompanied by a parallel, dose-dependent increase in accumulation of cAMP.

CONCLUSIONS

VIP potently and directly stimulates secretion of cortisol from these adrenocortical cells of human origin via an adenylate cyclase-coupled VIP receptor. These findings raise the possibility of a significant and direct effect of VIP in the control of steroid secretion from the adrenal cortex in humans.

Alternate splicing of the RNA for hamster type 2 3 beta-hydroxysteroid dehydrogenase/delta 5-->4isomerase

Complementary DNAs encoding the hamster type 2 3 beta-hydroxysteroid dehydrogenase/delta 5-->4 isomerase were isolated from liver and kidney cDNA libraries. Nine clones were isolated containing identical coding and 3' untranslated sequences. However, six of the clones contained a 68-nucleotide stretch in the 5' untranslated region that was missing in the other three clones. Primers were designed to flank this region and the polymerase chain reaction (PCR) was performed on hamster liver and adrenal RNA. Two PCR products were amplified of the predicted molecular sizes and with the expected sequence. Primers were then designed to amplify sequences encompassing this region from hamster genomic DNA. Sequencing of the resultant PCR products demonstrated that the 68-nucleotide stretch missing in some transcripts corresponded exactly to the second of three exons identified. We conclude that the 5' untranslated region of this mRNA is transcribed from at least three exons, and that the sequence of the second of these exons is spliced out of some of the RNA transcripts.

Differential expression of messenger ribonucleic acids encoding 11beta-hydroxysteroid dehydrogenase types 1 and 2 in human granulosa cells

In glucocorticoid target organs 11beta-hydroxysteroid dehydrogenase (11betaHSD) regulates the levels of active glucocorticoids available to glucocorticoid receptors. To date two isoforms of 11betaHSD, NADP-dependent type 1 11betaHSD (11betaHSD1) with predominant reductase activity and NAD-dependent type 2 11betaHSD (11betaHSD2) with dehydrogenase activity have been identified. Human ovarian granulosa cells have been shown to possess both dehydrogenase and reductase 11betaHSD activities and express 11betaHSD1 mRNA. However, whether 11betaHSD2 mRNA is also present or if the expression of either mRNA is developmentally regulated in the human ovary is unknown. We therefore used northern analysis to examine 11betaHSD1 and 11betaHSD2 mRNA levels in non-luteinized and luteinizing granulosa cells, corpora lutea (CL) and ovarian stroma obtained from human ovaries. Here we show that non-luteinized granulosa cells express relatively high levels of 11betaHSD2 mRNA but not 11betaHSD1. Conversely, luteinizing granulosa cells abundantly express 11betaHSD1 mRNA but not 11betaHSD2. CL also expresses 11betaHSD2 to lesser extent. Neither 11betaHSD mRNA is detectable in ovarian stroma. These results indicate that mRNAs encoding both 1lbetaHSD isozymes are present in human granulosa cells and they are developmentally--but differentially--regulated during preovulatory follicular development. The existence of developmentally regulated 11betaHSD in human granulosa cells is important new evidence that glucocorticoids, acting directly on the ovary, serve physiologically significant roles in the regulation of folliculogenesis.

Synergistic activation of the human type II 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase promoter by the transcription factor steroidogenic factor-1/adrenal 4-binding protein and phorbol ester

Steroidogenic factor-1/adrenal 4-binding protein (SF-1/Ad4BP) is an orphan nuclear receptor/transcription factor known to regulate the P450 steroid hydroxylases; however, mechanisms that regulate the activity of SF-1/Ad4BP are not well defined. In addition, little is known about the mechanisms that regulate the human steroidogenic enzyme, type II 3beta-hydroxysteroid dehydrogenase (3beta-HSD II), the major gonadal and adrenal isoform. Regulation of the 3beta-HSD II promoter was examined using human adrenal cortical (H295R; steroidogenic) and cervical (HeLa; non-steroidogenic) carcinoma cells. H295R cells were transfected with a series of 5' deletions of 1251 base pairs (bp) of the 3beta-HSD II 5'-flanking region fused to a chloramphenicol acetyltransferase (CAT) reporter gene followed by treatment with or without phorbol ester (phorbol 12-myristate 13-acetate; PMA). CAT assay data indicated that the region from -101 to -52 bp of the promoter was required for PMA-induced expression. A putative SF-1/Ad4BP regulatory element, TCAAGGTAA, was identified by sequence homology at -64 to -56 bp of the promoter. Cotransfection of HeLa cells with the -101 3beta-HSD-CAT construct and an expression vector for SF-1/Ad4BP increased CAT activity 49-fold. Subsequent treatment with PMA induced an unexpected synergistic increase in transcriptional activity 540-fold over basal. Mutation of the putative response element (TCAAGGTAA to TCAATTTAA) abolished SF-1-induced CAT activity and the synergistic response to PMA. Gel mobility shift assays confirmed that SF-1/Ad4BP interacts with the putative element and transcripts for SF-1/Ad4BP were detected in H295R cells by Northern analysis. These data are the first to demonstrate 1) regulation of a non-cytochrome P450 steroidogenic enzyme promoter by SF-1/Ad4BP, 2) a powerful synergistic effect of PMA on SF-1/Ad4BP-induced transcription, and 3) the importance of the SF-1/Ad4BP regulatory element in the regulation of the 3beta-HSD II promoter.

Characterization of the adrenal cytochrome P450C17 in the hamster, a small animal model for the study of adrenal dehydroepiandrosterone biosynthesis

The hamster, like the human produces cortisol as its major glucocorticoid, rather than corticosterone, typical of most enzyme rodents. It is not known, however, if the hamster cytochrome P450C17 (P450C17), a key enzyme for cortisol formation, also exhibits 17,20-lyase activity and if it catalyzes the formation of dehydroepiandrosterone (DHEA) at the adrenal level. To study this, we isolated the cDNA of P450C17 from a hamster adrenal library. This cDNA was sequenced and was found to have an open reading frame for a protein of 511 amino acids, as compared to the human P450C17, which contains 508 amino acids. The hamster P450C17 cDNA, in the coding region, is 76% homologous with the human P450C17 cDNA. The cDNA was then cloned in the expression vector pSV-SPORT 1, which was transiently transfected into COS 1 cells. The transfected cells were used for temporal studies on the transformation of radiolabeled C21-delta5- and C21-delta4-precursors. When transfected cells were incubated with [14C]pregnenolone, rapid formation of [14C]DHEA occurred. The intermediate 17alpha-hydroxypregnenolone accumulated initially with subsequent metabolism to DHEA. Likewise, when incubated with C21-delta4-steroids, [14C]progesterone and [3H]17alpha-hydroxyprogesterone, the 17,20-lyase product androstenedione was produced efficiently. In these studies, with respect to the delta5 pathway, the expressed hamster P450C17 gave similar results to bovine P450C17 cDNA inserted in the same expression vector. However, in contrast to the bovine enzyme, which converted low amounts of progesterone to androstenedione, the expressed hamster P450C17 enzyme showed an active metabolism via the delta4 pathway. Northern blot analysis, using the complete alpha-32P labeled hamster P450C17 cDNA as the probe, demonstrated a strong presence of P450C17 mRNA in hamster adrenals, a weaker presence in testes and ovaries, and no detectable species in brain, mesentery, and kidney. Immunoblotting analysis using an anti-rat P450C17 antibody demonstrated the presence of P450C17 protein in hamster adrenals, testes, and ovaries. Hamster adrenal cell suspensions and microsomal preparations were used to demonstrate the biosynthesis of [14C]17alpha-hydroxypregnenolone and [14C]DHEA from [14C]pregnenolone; both metabolites were formed during incubations. However, the ratio of [14C]DHEA/[14C]17alpha-hydroxypregnenolone was much lower in adrenal cells than in transfected COS 1 cells, indicating the presence of putative factors in hamster adrenal cells, favoring the 17alpha-hydroxylase activity rather than that of the 17,20-lyase. In conclusion, these studies demonstrate that the hamster adrenal is both a DHEA and a cortisol producer, and, therefore, this animal could be a suitable small animal model for the study of the role of DHEA in relation to human biochemistry and physiology.

IL-6, DHEA and the ageing process

The age-related increase in circulating IL-6 levels in humans which has been attributed to a decline in DHEA production by the adrenal gland is currently attracting attention because of its possible relevance to the aetiology and management of a number of age-related clinical disorders. The potential importance of these observations and suggestions has prompted us to perform more detailed studies on the relationship between IL-6 and DHEA. Using immunoassay techniques we have found in normal healthy individuals over the age of 40 an inverse relationship between plasma DHEA levels and the presence of detectable levels of IL-6 (more than 1 pg/ml). In vitro, studies also revealed that low dose (10(-6)-10(-8) M) of DHEA and DHEAS inhibited the production of IL-6 in unstimulated human spleen cell suspension cultures whilst enhancing its release by explant cultures of the same tissue. In contrast they had no effect on immunoglobulin production. These studies suggest that there is a real, but complex relationship between IL-6 production and DHEA levels which warrants further investigation.

The regulation of 3 beta-hydroxysteroid dehydrogenase expression

3 beta-Hydroxysteroid dehydrogenasel delta 5-->4-isomerase (3 beta-HSD) catalyzes the formation of delta 4-3-ketosteroids from delta 5-3 beta-hydroxysteroids, an obligate step in the biosynthesis not only of androgens and estrogens but also of mineralocorticoids and glucocorticoids. The enzyme is expressed in the adrenal cortex and in steroidogenic cells of the gonads, consistent with this role. However, 3 beta-HSD is also expressed in many other tissues, such as the liver and kidney, where its function is not entirely clear. It is established that a family of closely related genes encode for 3 beta-HSD. The various 3 beta-HSD isoforms are expressed in a tissue-specific manner involving separate mechanisms of regulation. The human type I 3 beta-HSD is expressed at high levels in syncytial trophoblast and in sebaceous glands, and the type II isoform is almost exclusively expressed in the adrenal cortex and gonads. An important feature in liver and kidney (at least of hamster, mouse, rabbit, and rat) is the sexual dimorphic nature of 3 beta-HSD expression. We briefly review studies on the regulation of the human 3 beta-HSD I and II genes in human trophoblast and adrenal cortex and extend this to discuss the rat 3 beta-HSD I gene expressed in adrenals and gonads. The complexity of 3 beta-HSD expression through multiple signaling pathways acting on a multigene family of enzymes may contribute importantly to the diverse patterns and locations of steroid hormone biosynthesis.

Seasonal changes in spermatogenesis and testicular steroidogenesis in the male black bear Ursus americanus

American black bears, Ursus americanus, are seasonal breeders with a mating season in late spring to early summer. The objectives of this study were to determine whether there are seasonal changes in spermatogenesis and immunolocalization of testicular steroidogenic enzymes, and to correlate these changes with peripheral steroid concentrations. Three captive mature bears were maintained in open cages during the summer season and provided with chambers for denning during the winter. Testicular biopsies and blood samples were obtained from anaesthetized bears on 12 March, 15 June, 12 October and 15 January. Steroidogenic enzymes were immunolocalized using polyclonal antisera raised against bovine adrenal cholesterol side-chain cleavage cytochrome P450 (P450scc), human placental 3 beta-hydroxysteroid dehydrogenase (3 beta HSD), porcine testicular 17 alpha-hydroxylase cytochrome P450 (P450c17) and human placental aromatase cytochrome P450 (P450arom). Spermatogenesis changed seasonally: spermatogonia and degenerating spermatocytes were observed in October; spermatogonia and primary spermatocytes were present in January; spermatogonia, spermatocytes and round spermatids were present in March; and spermatogonia through spermatozoa were present in June. P450scc and P450c17 were immunolocalized in spermatids and Leydig cells in June, whereas in October these enzymes were present only in Leydig cells. 3 beta HSD was localized in Leydig cells in June and October with more intense staining in June. Localization of P450arom changed seasonally: no immunostaining in October; positive immunostaining in Sertoli cells in January; more extensive immunostaining in Sertoli cells, peritubular-myoid cells and round spermatids in March; and strong immunostaining in Sertoli cells and round and elongating spermatids in June. Serum testosterone and oestradiol concentrations changed seasonally: testosterone and oestrogen were low in October and January, slightly higher in March, and high in June. The present study demonstrates that in the black bear seasonal changes in spermatogenesis are accompanied by changes in the immunolocalization of testicular steroidogenic enzymes that are correlated with changes in serum testosterone and oestradiol concentrations. The presence of P450arom in Sertoli cells at the beginning of testicular recrudescence suggests that aromatase and oestrogen may play a role in re-initiating spermatogenesis.

Adrenarche is associated with decreased 3 beta-hydroxysteroid dehydrogenase expression in the adrenal reticularis

The increased production of adrenal dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS) which occurs during the prepubertal period is known as adrenarche. One hypothesis for adrenarche is that alterations in intra-adrenal expression of steroidogenic enzymes within the inner reticularis zone leads to the increased production of 19-carbon steroids. We tested the hypothesis that at the time of adrenarche there is decreased expression of 3 beta HSD in the reticularis. Immunohistochemical localization of 3 beta HSD was performed and staining intensities compared between adrenal glands from children ages 4 months to 7 years (N = 11) and ages 8 to 11 years (N = 6). No difference was observed between the levels of staining in the glomerulosa and fasciculata from either age group. However, the reticularis from the older children exhibited diminished 3 beta HSD immunoreactivity. These findings suggest that as children mature there is a decreased level of 3 beta HSD in the adrenal reticularis which may contribute to the increased production of DHEA and DHEAS seen during adrenarche.

Forskolin treatment directs steroid production towards the androgen pathway in the NCI-H295R adrenocortical tumour cell line

The human adrenocortical tumour cell line, NCI-H295, secretes steroids on the mineralocorticoid, glucocorticoid and adrenal androgen pathways. We have investigated the effects of 96 h treatment of cells in monolayer culture with either forskolin (10 microM) (a direct activator of adenylate cyclase), angiotensin II (10 nM) or no agonist ('control') on the steroidogenic phenotype of this cell line. Androstenedione, cortisol and corticosterone secreted into the medium in response to a subsequent 4 hour treatment with angiotensin II (10nM) indicated that the steroidogenic phenotype of NCI-H295 cells changes away from 17-deoxysteroid biosynthesis towards adrenal androgen production in response to forskolin. The NCI-H295R cell line therefore serves as a useful model for investigation of the differential regulation of the steroidogenic pathways in the human adrenal cortex.

Functional maturation of the primate fetal adrenal in vivo. II. Ontogeny of corticosteroid synthesis is dependent upon specific zonal expression of 3 beta-hydroxysteroid dehydrogenase/isomerase

Cortisol, produced by the primate fetal adrenal, regulates the maturation of organ systems necessary for extrauterine life. During most of primate pregnancy, however, the fetal adrenal lacks the enzyme 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta HSD), which is essential for cortisol synthesis. Therefore, we used immunohistochemistry and in situ hybridization techniques to investigate the developmental expression of 3 beta HSD in the fetal rhesus monkey adrenal from 109 days' gestation until term (165 +/- 5 days) and assessed the role of ACTH in the induction of its expression and localization. We also examined whether ACTH regulates the expression of two other steroidogenic enzymes, cytochrome P450 cholesterol side-chain cleavage (P450scc) and P450 17 alpha-hydroxylase, 17/20-lyase (P450c17), in the fetal rhesus monkey adrenal. To stimulate ACTH secretion from the fetal pituitary in vivo, we administered metyrapone to late gestation fetal rhesus monkeys for 3-7 days. Adrenals were collected from untreated fetuses at 109-125 days (n = 5), 130-148 days (n = 7), 155-172 days (n = 4), and after metyrapone treatment at 135-137 days (n = 4). The cortical width and total amount of 3 beta HSD staining were measured using an image analysis system. 3 beta HSD was localized primarily in the definitive zone cells of the adrenal from fetuses between 109-148 days, whereas at term (155-172 days), 3 beta HSD was localized in both definitive and transitional zone cells. The cortical width and total amount of 3 beta HSD staining in the adrenal increased significantly (P < 0.05) between 148 days (137 +/- 14 microns and 3,689 +/- 522 grains) and 155 days (315 +/- 61 microns and 7,321 +/- 2,008 grains). Interestingly, in metyrapone-treated fetuses at 135-137 days, 3 beta HSD messenger RNA (mRNA) and protein were localized extensively in both the definitive and transitional zones, a pattern seen only in term fetal adrenals in untreated animals. In addition, metyrapone treatment significantly (P < 0.05) increased cortical width (386 +/- 95 microns) and total 3 beta HSD immunostaining (29,063 +/- 13,692 grains) compared with age-matched controls. In contrast to 3 beta HSD, P450scc mRNA was detected in the definitive, transitional, and fetal zones, and its expression was not altered after metyrapone treatment. P450c17 mRNA was detected in the transitional and fetal zones, and the relative abundance was greater in the transitional zone. The relative abundance of P450c17 mRNA was increased in the fetal zone after metyrapone treatment. In summary, at term or after metyrapone treatment, expression of 3 beta HSD is induced in the transitional zone of the fetal rhesus monkey adrenal gland, an indication of functional maturation of the primate adrenal cortex. These data suggest that the ontogenetic increase in fetal pituitary ACTH secretion plays an important role in the induction of 3 beta HSD expression in the transitional zone.