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

Inhibition of the M. tuberculosis 3β-hydroxysteroid dehydrogenase by azasteroids

The cholesterol metabolism pathway in Mycobacterium tuberculosis (M. tb) is a potential source of energy as well as secondary metabolite production that is important for survival of M. tb in the host macrophage. Oxidation and isomerization of 3β-hydroxysterols to 4-en-3-ones is requisite for sterol metabolism and the reaction is catalyzed by 3β-hydroxysteroid dehydrogenase (Rv1106c). Three series of 6-azasteroids and 4-azasteroids were employed to define the substrate preferences of M. tb 3β-hydroxysteroid dehydrogenase. 6-Azasteroids with large, hydrophobic side chains at the C17 position are the most effective inhibitors. Substitutions at C1, C2, C4 and N6 were poorly tolerated. Our structure-activity studies indicate that the 6-aza version of cholesterol is the best and tightest binding competitive inhibitor (K(i)=100 nM) of the steroid substrate and are consistent with cholesterol being the preferred substrate of M. tb 3β-hydroxysteroid dehydrogenase.

Human adrenal cells that express both 3β-hydroxysteroid dehydrogenase type 2 (HSD3B2) and cytochrome b5 (CYB5A) contribute to adrenal androstenedione production

Androstenedione is one of several weak androgens produced in the human adrenal gland. 3β-Hydroxysteroid dehydrogenase type 2 (HSD3B2) and cytochrome b5 (CYB5A) are both required for androstenedione production. However, previous studies demonstrated the expression of HSD3B2 within the zona glomerulosa (ZG) and fasciculata (ZF) but low levels in the zona reticularis. In contrast, CYB5A expression increases in the zona reticularis (ZR) in human adrenal glands. Although their colocalization has been reported in gonadal theca and Leydig cells this has not been studied in the human adrenal. Therefore, we immonolocalized HSD3B2 and CYB5A in normal human adrenal glands and first demonstrated their co-expression in the cortical cells located at the border between the ZF and ZR in normal human adrenal. Results of in vitro studies using the human adrenal H295R cells treated with the HSD3B2 inhibitor, trilostane, also demonstrated a markedly decreased androstenedione production. Decreasing CYB5A mRNA using its corresponding siRNA also resulted in significant inhibition of androstenedione production in the H295R cells. These findings together indicate that there are a group of cells co-expressing HSD3B2 and CYB5A with hybrid features of both ZF and ZR in human adrenal cortex, and these hybrid cortical cells may play an important role in androstenedione production in human adrenal gland.

The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders

Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.

Neurosteroid biosynthesis in the brain of amphibians

Amphibians have been widely used to investigate the synthesis of biologically active steroids in the brain and the regulation of neurosteroid production by neurotransmitters and neuropeptides. The aim of the present review is to summarize the current knowledge regarding the neuroanatomical distribution and biochemical activity of steroidogenic enzymes in the brain of anurans and urodeles. The data accumulated over the past two decades demonstrate that discrete populations of neurons and/or glial cells in the frog and newt brains express the major steroidogenic enzymes and are able to synthesize de novo a number of neurosteroids from cholesterol/pregnenolone. Since neurosteroidogenesis has been conserved during evolution from amphibians to mammals, it appears that neurosteroids must play important physiological functions in the central nervous system of vertebrates.

Characterization of invasive trophoblasts generated from human embryonic stem cells

BACKGROUND

Abnormal human embryo implantation leads to poor foetal development and miscarriage, or pre-eclampsia. Ethical and practical considerations concerning implantation limit its investigation, and it is often difficult to extrapolate findings in laboratory animals when implantation processes show diverse species differences. Therefore, it is important to develop new in vitro models to study the earliest events of human implantation. The aim of this study was to derive trophoblast cell lines from human embryonic stem cells (hESCs) by a robust protocol and co-culture of these cells with an established endometrial cell culture system to validate a model of trophoblast invasion at implantation.

METHODS

Derivation of trophoblast cell lines from hESC lines was established by spontaneous and induced differentiation of embryoid bodies and by initial measurement of hCGβ secretion by enzyme-linked immunosorbent assay and their phenotype investigated using gene- and protein-expression markers. Vesicles formed from an aggregating trophoblast were co-cultured with decidualized human endometrial stromal cells in hypoxic (2% oxygen) and normoxic (20% oxygen) environments.

RESULTS

Derived villous cytotrophoblast cell (CTB) lines further differentiated to invasive, extra-villous CTBs. Eventually, cells lost their proliferative capacity, with some lines acquiring karyotypic changes, such as a gain in the X chromosome. Cell-invasion assays confirmed that the extra-villous CTBs were invasive and erosion of the endometrial stromal layer occurred, particularly under hypoxic conditions in vitro.

CONCLUSIONS

Trophoblast cell lines derived from hESCs differentiate and adapt in vitro and can be used as a model to study the mechanisms of early trophoblast invasion.

"Getting from here to there"--mechanisms and limitations to the activation of the androgen receptor in castration-resistant prostate cancer

Despite the clinical regression that typifies the initial response of advanced prostate cancer to gonadal testosterone depletion, tumors eventually progress. However, evidence supports the concept that signaling via the androgen receptor (AR) is important in progression to castration-resistant prostate cancer (CRPC).Steroid hormones are synthesized from cholesterol in a series of tightly regulated steps involving the cleavage of carbon-carbon bonds, the introduction of functional groups derived from activated molecular oxygen, and the oxidation and reduction of carbon-carbon and carbon-oxygen bonds. In the adrenal cortex and gonads, steroidogenesis is tightly regulated, very efficient, and highly directional. In contrast, steroid metabolism in peripheral tissues is characterized by competing enzymes and pathways, low efficiency, and great variability. Many steps are mechanistically and functionally irreversible, but some are not, and the repertoire of specific enzymes, intracellular redox state, and access to hormone precursors all contribute to steroid flux and accumulation.The investigation of steroid metabolizing enzymes in CRPC often assumes that the pathways and the patterns of metabolism mirror those defined in the adrenals and the gonads and validated by human deficiency syndromes. Unfortunately, several potential pathways using different enzymes might contribute substantially to androgen synthesis in CRPC. Finally, a number of mechanisms have been reported by which the AR is activated independent of ligand. Recent observations have suggested that AR forms with constitutive activity occur in CRPC, stimulating transcription without a requirement for ligand. This overview outlines a broad view of how the mechanisms by which the AR may be activated, whether by alternate pathways of androgen synthesis or the production of alternate forms of the AR, with an emphasis on what aspects must be accounted for when using model systems to explore the biology of human prostate cancer.

Sex hormone metabolism in lung development and maturation

Sex hormones are increasingly recognized as regulators of lung development. Respiratory distress syndrome (RDS) is the leading cause of morbidity in preterm neonates and occurs with a higher incidence in males. The mechanisms underlying the effects of androgens on lung development and the occurrence of RDS are only partially deciphered, and positive roles of estrogens on surfactant production and alveologenesis are relevant to our understanding of pulmonary diseases. This manuscript reviews current knowledge on androgen and estrogen metabolism and on relevant hormone targets in the fetal lung. Further investigations are needed to elucidate mechanisms orchestrating sex hormone effects on lung development. These studies aim to decrease mortality and morbidity associated with RDS and other pathologies related to lung immaturity at birth.

Semicomprehensive analysis of the postnatal age-related changes in the mRNA expression of sex steroidogenic enzymes and sex steroid receptors in the male rat hippocampus

Although sex steroids play a crucial role in the postnatal brain development, the age-related changes in the hippocampal steroidogenesis remain largely unknown. We performed comprehensive investigations for the mRNA expressions of 26 sex steroidogenic enzymes/proteins and three sex steroid receptors in the male rat hippocampus, at the ages of postnatal day (PD) 1, PD4, PD7, PD10, PD14, 4 wk, and 12 wk (adult), by RT-PCR/Southern blotting analysis. The relative expression levels of these enzymes/receptors at PD1 were Srd5a1 > Star > Ar ∼ Hsd17b4 ∼ Hsd17b1 ∼ Hsd17b7 ∼ Esr1 ∼ Srd5a2 > Hsd17b3 > Esr2 > Cyp11a1 > Cyp17a1 > Cyp19a1 ∼ Hsd17b2 > 3β-hydroxysteroid dehydrogenase I. The mRNA levels of essential enzymes for progesterone/testosterone/estradiol metabolisms (Cyp17a1, Hsd17b7, and Cyp19a1) were approximately constant between PD1 and PD14 and then declined toward the adult levels. Cyp11a1 increased during PD4-PD14 and then considerably decreased toward the adult level (∼8% of PD1). Hsd17b1, Hsd17b2, and 3β-hydroxysteroid dehydrogenase I mRNA decreased approximately monotonously. Hsd17b3 increased to approximately 200% of PD1 during PD4-PD14 and was maintained at this high level. The 5α-reductase mRNA was maintained constant (Srd5a1) or decreased monotonically (Srd5a2) toward the adult level. The Esr1 level peaked at PD4 and decreased toward the adult level, whereas Ar greatly increased during PD1-PD14 and was maintained at this high level. The Star and Hsd17b4 levels were maintained constant from neonate to adult. These results suggest that the hippocampal sex steroidogenic properties are substantially altered during the postnatal development processes, which might contribute to brain sexual maturation.

Expression of the ACTH receptor, steroidogenic acute regulatory protein, and steroidogenic enzymes in canine cortisol-secreting adrenocortical tumors

Studies of human adrenocortical tumors (ATs) causing Cushing's syndrome suggest that hypersecretion of cortisol is caused by altered expression of steroidogenic enzymes and that steroidogenesis can only be maintained when there is expression of the ACTH receptor (ACTH-R). Here we report the screening for the mRNA expression of the ACTH-R, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase, 21-hydroxylase (all in 38 cortisol-secreting ATs), 17α-hydroxylase, and 11β-hydroxylase (both in 28 cortisol-secreting ATs). Real-time PCR (RT-PCR) was applied in all samples and was compared with that in normal canine adrenal glands. Messenger-RNA encoding StAR, steroidogenic enzymes, and ACTH-R were present in both normal adrenal glands and cortisol-secreting ATs. The amounts of mRNA encoding StAR and enzymes of the steroidogenic cluster needed for cortisol production did not differ significantly between either adenomas or carcinomas and normal adrenal glands. The amount of mRNA encoding ACTH-R was significantly lower in carcinomas than in normal adrenal glands (P = 0.008). In conclusion, RT-PCR analysis revealed no overexpression of StAR and steroidogenic enzymes in canine cortisol-secreting ATs. Significant downregulation of ACTH-R in carcinomas might be associated with the malignant character of the AT.

Estradiol, progesterone, testosterone profiles in human follicular fluid and cultured granulosa cells from luteinized pre-ovulatory follicles

BACKGROUND

The production of sex steroids by follicular cells is proposed to be influenced by the maturity of the incumbent oocyte. Thus steroid levels may reflect suitability of an oocyte for IVF. We examined follicular fluids and granulosa cell production of steroid from IVF patients in order to test the relationship between steroid levels and fertilization.

METHODS

Follicular fluid and granulosa cells were extracted from 206 follicles of 35 women undergoing controlled ovarian stimulation. Follicular fluid was assayed for estradiol, progesterone and testosterone. Granulosa cells were cultured from individual follicles and their culture media assayed for production of these hormones after 24 hrs in vitro. Levels of steroids were correlated with follicular diameter, oocyte recovery and subsequent fertilization.

RESULTS

Follicular fluid levels of progesterone were 6100 times higher than that of estradiol, and 16,900 times higher that of testosterone. Despite the size of follicle triggered after controlled luteinization, the levels of progesterone and testosterone were maintained at relatively constant levels (median 98.1 micromoles/L for progesterone, and 5.8 nanomoles/L for testosterone). However, estradiol levels were slightly lower in the larger follicles (follicular diameter 10-15 mm, median 25.3 nanomoles/L; follicles > = 15 mm, median 15.1 nanomoles/L; linear correlation r = -0.47, p < 0.0001). With respect to oocyte recovery, no steroid showed a significant association in follicular fluid levels. Similarly no difference in follicular fluid steroid levels was found for those oocytes that did or did not fertilize. Significant quantities of progesterone were produced by the granulosa cells but production was constant regardless of the size of follicle from which the cells originated. Estradiol levels were only detectable in 10 of 121 cultures examined, and testosterone in none. Interestingly, when an oocyte was present follicular estradiol levels correlated with progesterone levels. However, when absent, follicular estradiol levels correlated with testosterone levels but not with progesterone.

CONCLUSIONS

The principle steroid product of luteinized pre-ovulatory granulosa is progesterone, a differentiation triggered by the gonadotropin surge. However, absolute steroid levels are associated with follicular size, not oocyte maturation/ability to fertilize.

Steroid hormone metabolizing enzymes in benign and malignant human bone tumors

IMPORTANCE IN THE FIELD: Primary bone tumors are considered as (sex steroid) hormone-dependent tumors. Osteosarcoma, osteoblastoma and bone cysts are preferentially found in males, while giant cell tumors are more common in females. Indeed, bone tumor development and progression are influenced by sex steroid hormones derived from in situ synthesis in bone cells.

AREAS COVERED IN THIS REVIEW

This review describes intracrine mechanisms for local formation of the biologically most active estrogen, 17beta-estradiol (E2), from circulating steroid precursors through the 'aromatase' (aromatization of androgens) and the 'sulfatase' (conversion of inactive estrone-sulfate) pathway.

WHAT THE READER WILL GAIN

The reader gains knowledge on both pathways and the enzymes, which contribute to the in situ availability of active hormones, namely 3beta-hydroxysteroid dehydrogenases, 17beta-hydroxysteroid dehydrogenases, aromatase, steroid sulfatases and sulfotransferases. An overview is given and the expression and function of these enzymes in bone tumors are discussed.

TAKE HOME MESSAGE

Knowledge on pathways for the in situ formation of E2 in bone cells may allow the identification of potential targets for i) novel endocrine therapeutic options in primary bone tumors and ii) future preventive interventions.

Porcine glutathione transferase Alpha 2-2 is a human GST A3-3 analogue that catalyses steroid double-bond isomerization

A primary role of GSTs (glutathione transferases) is detoxication of electrophilic compounds. In addition to this protective function, hGST (human GST) A3-3, a member of the Alpha class of soluble GSTs, has prominent steroid double-bond isomerase activity. The isomerase reaction is an obligatory step in the biosynthesis of steroid hormones, indicating a special role of hGST A3-3 in steroidogenic tissues. An analogous GST with high steroid isomerase activity has so far not been found in any other biological species. In the present study, we characterized a Sus scrofa (pig) enzyme, pGST A2-2, displaying high steroid isomerase activity. High levels of pGST A2-2 expression were found in ovary, testis and liver. In its functional properties, other than steroid isomerization, pGST A2-2 was most similar to hGST A3-3. The properties of the novel porcine enzyme lend support to the notion that particular GSTs play an important role in steroidogenesis.

The intracrine sex steroid biosynthesis pathways

There is an increasing number of differences reported between the steroidogenesis pathways described in the traditional literature related to gonadal steroidogenesis and the more recent observations achieved using new technologies, especially molecular cloning, pangenomic expression studies, precise quantification of mRNA expression using real-time PCR, use of steroidogenic enzymes stably transfected in cells, detailed enzymatic activity analysis in cultured cell lines and mass spectrometry analysis of steroids. The objective of this chapter is to present steroidogenesis in the light of new findings that demonstrate pathways of biosynthesis of estradiol (E(2)) and dihydrotestosterone (DHT) from adrenal dehydroepiandrosterone (DHEA) in peripheral intracrine tissues which do not involve testosterone as intermediate as classically found in the testis and ovary. Steroidogenic enzymes different from those of the ovary and testis act in a tissue-specific manner to catalyze the transformation of DHEA into active sex steroids. These new pathways are especially important in post-menopausal women where all estrogens and practically all androgens are made at their site of action in peripheral tissues from DHEA, the precursor of adrenal origin. In men, on the other hand, from 40 to 50% of androgens are made in peripheral tissues from adrenal DHEA, thus indicating the major importance of the intracrine pathways in both men and women. We also examine the molecular evolution of steroidogenic enzymes which explains the major differences in steroid metabolism observed between laboratory animals and humans.

3beta-hydroxysteroid dehydrogenase is a possible pharmacological target in the treatment of castration-resistant prostate cancer

Prostate cancer usually responds to androgen deprivation therapy, although the response in metastatic disease is almost always transient and tumors eventually progress as castration-resistant prostate cancer (CRPC). CRPC continues to be driven by testosterone or dihydrotestosterone from intratumoral metabolism of 19-carbon adrenal steroids from circulation, and/or de novo intratumoral steroidogenesis. Both mechanisms require 3beta-hydroxysteroid dehydrogenase (3betaHSD) metabolism of Delta(5)-steroids, including dehydroepiandrosterone (DHEA) and Delta(5)-androstenediol (A5diol), to testosterone. In contrast, reports that DHEA and A5diol directly activate the androgen receptor (AR) suggest that 3betaHSD metabolism is not required and that 3betaHSD inhibitors would be ineffective in the treatment of CRPC. We hypothesized that activation of AR in prostate cancer by DHEA and A5diol requires their conversion via 3betaHSD to androstenedione and testosterone, respectively. Here, we show that DHEA and A5diol induce AR chromatin occupancy and AR-regulated genes. Furthermore, we show that Delta(5)-androgens undergo 3beta-dehydrogenation in prostate cancer and that induction of AR nuclear translocation, AR chromatin occupancy, transcription of PSA, TMPRSS2, and FKBP5, as well as cell proliferation by DHEA and A5diol, are all blocked by inhibitors of 3betaHSD. These findings demonstrate that DHEA and A5diol must be metabolized by 3betaHSD to activate AR in these models of CRPC. Furthermore, this work suggests that 3betaHSD may be exploited as a pharmacologic target in the treatment of CRPC.

Non-stereo-selective cytosolic human brain tissue 3-ketosteroid reductase is refractory to inhibition by AKR1C inhibitors

Cerebral 3α-hydroxysteroid dehydrogenase (3α-HSD) activity was suggested to be responsible for the local directed formation of neuroactive 5α,3α-tetrahydrosteroids (5α,3α-THSs) from 5α-dihydrosteroids. We show for the first time that within human brain tissue 5α-dihydroprogesterone and 5α-dihydrotestosterone are converted via non-stereo-selective 3-ketosteroid reductase activity to produce the respective 5α,3α-THSs and 5α,3β-THSs. Apart from this, we prove that within the human temporal lobe and limbic system cytochrome P450c17 and 3β-HSD/Δ(5-4) ketosteroid isomerase are not expressed. Thus, it appears that these brain regions are unable to conduct de novo biosynthesis of Δ(4)-3-ketosteroids from Δ(5)-3β-hydroxysteroids. Consequently, the local formation of THSs will depend on the uptake of circulating Δ(4)-3-ketosteroids such as progesterone and testosterone. 3α- and 3β-HSD activity were (i) equally enriched in the cytosol, (ii) showed equal distribution between cerebral neocortex and subcortical white matter without sex- or age-dependency, (iii) demonstrated a strong and significant positive correlation when comparing 46 different specimens and (iv) exhibited similar sensitivities to different inhibitors of enzyme activity. These findings led to the assumption that cerebral 3-ketosteroid reductase activity might be catalyzed by a single enzyme and is possibly attributed to the expression of a soluble AKR1C aldo-keto reductase. AKR1Cs are known to act as non-stereo-selective 3-ketosteroid reductases; low AKR1C mRNA expression was detected. However, the cerebral 3-ketosteroid reductase was clearly refractory to inhibition by AKR1C inhibitors indicating the expression of a currently unidentified enzyme. Its lack of stereo-selectivity is of physiological significance, since only 5α,3α-THSs enhance the effect of GABA on the GABA(A) receptor, whereas 5α,3β-THSs are antagonists.

New frontiers in androgen biosynthesis and metabolism

PURPOSE OF REVIEW

To summarize recent advances in androgen biosynthesis and metabolism in peripheral tissues (e.g., liver and prostate) and how these can be exploited therapeutically.

RECENT FINDINGS

Human liver catalyzes the reduction of circulating testosterone to yield four stereoisomeric tetrahydrosteroids. Recent advances have assigned the enzymes responsible for these reactions and elucidated their structural biology. Data also suggest that for 5alpha-dihydrotestosterone (5alpha-DHT), conjugation reactions (phase II) may precede ketosteroid reduction (phase I) reactions. Human prostate is the site of benign prostatic hyperplasia and prostate cancer, which occur in the aging male. Although the importance of local androgen biosynthesis in these diseases is accepted, recent advances have identified enzymes that regulate ligand access to the androgen-receptor; a 'backdoor pathway' to 5alpha-DHT that does not require testosterone acting as an intermediate; and the finding that castrate-resistant prostate cancer (CRPC) has undergone an adaptive response to androgen deprivation, which involves intratumoral testosterone and 5alpha-DHT biosynthesis that can be targeted using inhibitors of (CYP17-hydroxylase/17,20-lyase), aldo-keto reductase 1C3, and 5alpha-reductase type 1 and type 2.

SUMMARY

Enzyme isoforms responsible for the biosynthesis and metabolism of androgens in liver and prostate have been identified and those responsible for the biosynthesis of androgens in CRPC can be therapeutically targeted.

Mice lacking Mrp1 have reduced testicular steroid hormone levels and alterations in steroid biosynthetic enzymes

The multidrug resistance-associated protein 1 (MRP1/ABCC1) is a member of the ABC active transporter family that can transport several steroid hormone conjugates, including 17beta-estradiol glucuronide, dehydroepiandrosterone sulfate (DHEAS), and estrone 3-sulfate. The present study investigated the role that MRP1 plays in maintaining proper hormone levels in the serum and testes. Serum and testicular steroid hormone levels were examined in both wild-type mice and Mrp1 null mice. Serum testosterone levels were reduced 5-fold in mice lacking Mrp1, while testicular androstenedione, testosterone, estradiol, and dehydroepiandrosterone (DHEA) were significantly reduced by 1.7- to 4.5-fold in Mrp1 knockout mice. Investigating the mechanisms responsible for the reduction in steroid hormones in Mrp1-/- mice revealed no differences in the expression or activity of enzymes that inactivate steroids, the sulfotransferases or glucuronosyltransferases. However, steroid biosynthetic enzyme levels in the testes were altered. Cyp17 protein levels were increased by 1.6-fold, while Cyp17 activity using progesterone as a substrate was also increased by 1.4- to 2.0-fold in mice lacking Mrp1. Additionally, the ratio of 17beta-hydroxysteroid dehydrogenase to 3beta-hydroxysteroid dehydrogenase, and steroidogenic factor 1 to 3beta-hydroxysteroid dehydrogenase were significantly increased in the testes of Mrp1-/- mice. These results indicate that Mrp1-/- mice have lowered steroid hormones levels, and suggests that upregulation of steroid biosynthetic enzymes may be an attempt to maintain proper steroid hormone homeostasis.

Effects of genistein and equol on human and rat testicular 3beta-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase 3 activities

The objective of the present study was to investigate the effects of genistein and equol on 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase 3 (17beta-HSD3) in human and rat testis microsomes. These enzymes (3beta-HSD and 17beta-HSD3), along with two others (cytochrome P450 side-chain cleavage enzyme and cytochrome P450 17alpha-hydroxylase/17-20 lyase), catalyze the reactions that convert the steroid cholesterol into the sex hormone testosterone. Genistein inhibited 3beta-HSD activity (0.2 micromol L(-1) pregnenolone) with half-maximal inhibition or a half-maximal inhibitory concentration (IC(50)) of 87 +/- 15 (human) and 636 +/- 155 nmol L(-1) (rat). Genistein's mode of action on 3beta-HSD activity was competitive for the substrate pregnenolonrge and noncompetitive for the cofactor NAD(+). There was no difference in genistein's potency of 3beta-HSD inhibition between intact rat Leydig cells and testis microsomes. In contrast to its potent inhibition of 3beta-HSD, genistein had lesser effects on human and rat 17beta-HSD3 (0.1 micromol L(-1) androstenedione), with an IC(50) >or= 100 micromol L(-1). On the other hand, equol only inhibited human 3beta-HSD by 42%, and had no effect on 3beta-HSD and 17beta-HSD3 in rat tissues. These observations imply that the ability of soy isoflavones to regulate androgen biosynthesis in Leydig cells is due in part to action on Leydig cell 3beta-HSD activity. Given the increasing intake of soy-based food products and their potential effect on blood androgen levels, these findings are greatly relevant to public health.

Mineralocorticoid deficiency and treatment in congenital adrenal hyperplasia

Approximately 75%–80% of patients with Congenital Adrenal Hyperplasia (CAH) fail to synthesize sufficient mineralocorticoids to maintain salt and water balance. In most instances genotype can predict mineralocorticoid deficiency in CAH. Early recognition and replacement with 9α-fludrocortisone and salt supplements will prevent development of potentially lethal salt losing crises. In infancy a relative state of aldosterone resistance exists and replacement dose of 9α-fludrocortisone based on body surface area is higher during infancy compared to childhood and adults. Salt supplementation is generally not required after weaning is started. Regular monitoring of blood pressure and measurements of plasma electrolytes and renin are required to prevent complications of under or over dosage.

Genomic and neural analysis of the estradiol-synthetic pathway in the zebra finch

Background

Steroids are small molecule hormones derived from cholesterol. Steroids affect many tissues, including the brain. In the zebra finch, estrogenic steroids are particularly interesting because they masculinize the neural circuit that controls singing and their synthesis in the brain is modulated by experience. Here, we analyzed the zebra finch genome assembly to assess the content, conservation, and organization of genes that code for components of the estrogen-synthetic pathway and steroid nuclear receptors. Based on these analyses, we also investigated neural expression of a cholesterol transport protein gene in the context of song neurobiology.

Results

We present sequence-based analysis of twenty steroid-related genes using the genome assembly and other resources. Generally, zebra finch genes showed high homology to genes in other species. The diversity of steroidogenic enzymes and receptors may be lower in songbirds than in mammals; we were unable to identify all known mammalian isoforms of the 3β-hydroxysteroid dehydrogenase and 17β-hydroxysteroid dehydrogenase families in the zebra finch genome assembly, and not all splice sites described in mammals were identified in the corresponding zebra finch genes. We did identify two factors, Nobox and NR1H2-RXR, that may be important for coordinated transcription of multiple steroid-related genes. We found very little qualitative overlap in predicted transcription factor binding sites in the genes for two cholesterol transport proteins, the 18 kDa cholesterol transport protein (TSPO) and steroidogenic acute regulatory protein (StAR). We therefore performed in situ hybridization for TSPO and found that its mRNA was not always detected in brain regions where StAR and steroidogenic enzymes were previously shown to be expressed. Also, transcription of TSPO, but not StAR, may be regulated by the experience of hearing song.

Conclusions

The genes required for estradiol synthesis and action are represented in the zebra finch genome assembly, though the complement of steroidogenic genes may be smaller in birds than in mammals. Coordinated transcription of multiple steroidogenic genes is possible, but results were inconsistent with the hypothesis that StAR and TSPO mRNAs are co-regulated. Integration of genomic and neuroanatomical analyses will continue to provide insights into the evolution and function of steroidogenesis in the songbird brain.

Characterization of the oestrogenic activity of non-aromatic steroids: are there male-specific endogenous oestrogen receptor modulators?

BACKGROUND AND PURPOSE

The endogenous oestrogens have important biological functions in men as well as in women. Because 17beta-oestradiol and oestrone are also formed in the male body, these aromatic oestrogens are generally thought to be responsible for exerting the required oestrogenic functions in the male. In the present study, we tested the hypothesis that some of the non-aromatic steroids that are androgen precursors or metabolites with hydroxyl groups at C-3 and/or C-17 positions may also be able to serve as ligands for the oestrogen receptors (ER) in the male.

EXPERIMENTAL APPROACH

A total of sixty non-aromatic steroids (selected from families of androstens, androstans, androstadiens, oestrens and oestrans) were analysed for their ability to bind and activate the human ERalpha and ERbetain vitro and in cultured cells.

KEY RESULTS

Six of the non-aromatic steroids, that is, 5-androsten-3beta,17beta-diol, 5alpha-androstan-3beta,17beta-diol, 5(10)-oestren-3alpha,17beta-diol, 5(10)-oestren-3beta,17beta-diol, 4-oestren-3beta,17beta-diol and 5alpha-oestran-3beta,17beta-diol, were found to have physiologically relevant high binding affinity ( approximately 50% of that of oestrone) for human ERalpha and ERbeta. These non-aromatic steroids also activated the transcriptional activity of human ERs and elicited biological responses (such as growth stimulation) in two representative ER-positive human cancer cell lines (MCF-7 and LNCaP) with physiologically relevant potency and efficacy. Molecular docking analysis of these six active compounds showed that they could bind to ERalpha and ERbeta in a manner similar to that of 17beta-oestradiol.

CONCLUSIONS AND IMPLICATIONS

These results provide evidence for the possibility that some of the endogenous androgen precursors or metabolites could serve as male-specific ER ligands.

Genetic variation in androgen disposition: implications in clinical medicine including testosterone abuse

BACKGROUND

Testosterone replacement therapy in hypogonadal men has been used for > 60 years. The use of testosterone substitution is continuously growing and is given to aging men to improve the quality of life. Because testosterone use is associated with muscle strength enhancing effects, it has become a popular drug to abuse. Doping with anabolic steroids, such as testosterone, is a severe challenge to the vision, moral and ethics in sports and has also become a significant and increasing problem in society.

OBJECTIVE

The primary aim of this review is to summarize and discuss the contribution of genetic components to inter-individual variation in androgen disposition.

CONCLUSION

Genetic variation has a large impact on androgen disposition. This variation is of the utmost importance for the interpretation of doping test results and may modulate the effects of testosterone replacement therapy and testosterone doping.

Hypocortisolism in the South African angora goat: the role of 3betaHSD

South African Angora goats are susceptible to cold stress, due to their inability to produce sufficient levels of cortisol. During adrenal steroidogenesis the production of cortisol relies on the activity of two key enzymes, namely cytochrome P450 17alpha-hydroxylase and 3beta-hydroxysteroid dehydrogenase. Cytochrome P450 17alpha-hydroxylase has previously been identified as a factor contributing to hypocortisolism in the South African Angora goat. In this comparative study, the catalytic activity of Angora and ovine 3beta-hydroxysteroid dehydrogenase, which differ by five amino acid residues, was characterized. The conversion of 17-hydroxypregnenolone and dehydroepiandosterone to their corresponding products, 17-hydroxyprogesterone and androstenedione, by the two enzymes differed significantly. The enzymes were subsequently co-expressed with Angora P450 17alpha-hydroxylase. Major differences were observed in pregnenolone metabolism with a significant reduction in the formation of the cortisol precursor, 17-hydroxyprogesterone, by cells expressing Angora 3beta-hydroxysteroid dehydrogenase, implicating 3beta-hydroxysteroid dehydrogenase as an additional factor contributing to hypocortisolism in the South African Angora goat.

Salt-sensitive hypertension in circadian clock-deficient Cry-null mice involves dysregulated adrenal Hsd3b6

Malfunction of the circadian clock has been linked to the pathogenesis of a variety of diseases. We show that mice lacking the core clock components Cryptochrome-1 (Cry1) and Cryptochrome-2 (Cry2) (Cry-null mice) show salt-sensitive hypertension due to abnormally high synthesis of the mineralocorticoid aldosterone by the adrenal gland. An extensive search for the underlying cause led us to identify type VI 3beta-hydroxyl-steroid dehydrogenase (Hsd3b6) as a new hypertension risk factor in mice. Hsd3b6 is expressed exclusively in aldosterone-producing cells and is under transcriptional control of the circadian clock. In Cry-null mice, Hsd3b6 messenger RNA and protein levels are constitutively high, leading to a marked increase in 3beta-hydroxysteroid dehydrogenase-isomerase (3beta-HSD) enzymatic activity and, as a consequence, enhanced aldosterone production. These data place Hsd3b6 in a pivotal position through which circadian clock malfunction is coupled to the development of hypertension. Translation of these findings to humans will require clinical examination of human HSD3B1 gene, which we found to be functionally similar to mouse Hsd3b6.

Down-regulation of murine testicular 17β-HSD3 and hepatic CYP1A2 enzymes by a bovine testes extract

Purpose

We investigated the effects of a bovine testes extract (BTE), which was developed as an alternative product for andropausal men, on expression of testicular enzymes responsible for sex hormone synthesis genes and a carcinogen activation related gene.

Methods

Expression of testicular CYP1A2, CYP11A1, CYP17, 3β-HSD, and 17β-HSD3 mRNAs as well as hepatic CYP1A2 mRNA were semi-quantitatively determined by RT-PCR. In addition, expression of hepatic CYP1A2 protein and methoxyresorufin O-demethylase activity were carried out.

Results

Bovine testes extract did not alter the testicular expression of CYP11A1, CYP17, and 3β-HSD mRNAs, while that of CYP11A1 was significantly down-regulated by testosterone. Interestingly, administration of BTE for 3 weeks significantly suppressed testicular 17β-HSD3 and hepatic CYP1A2 mRNA. Correspondingly, methoxyresorufin O-demethylase (MROD) activity and expression of hepatic CYP1A2 protein were significantly decreased.

Conclusions

These findings strongly suggested considering risks versus benefits and raised concerns regarding the use of BTE as an alternative medication or health supplement in andropausal men due to its potential for suppressing expression of both 17β-HSD3 and CYP1A2 mRNAs, testicular enzymes responsible for sex hormone gene synthesis.

MouseCyc: a curated biochemical pathways database for the laboratory mouse

Linking biochemical genetic data to the reference genome for the laboratory mouse is important for comparative physiology and for developing mouse models of human biology and disease. We describe here a new database of curated metabolic pathways for the laboratory mouse called MouseCyc http://mousecyc.jax.org. MouseCyc has been integrated with genetic and genomic data for the laboratory mouse available from the Mouse Genome Informatics database and with pathway data from other organisms, including human.

Estrogen metabolism and action in endometriosis

Endometriosis is a complex estrogen-dependent disease that is defined as the presence of endometrial glands and stroma outside the uterine cavity. The etiology of endometriosis is multifactorial and includes complex interactions of genetic, immunological, hormonal and environmental factors. Many theories have been proposed, but no single theory can explain all aspects of endometriosis, suggesting that endometriosis is a heterogeneous disease. This review presents the current theories on the pathogenesis of endometriosis, followed by an overview on estrogen metabolism in normal endometrium and diseased endometrium of endometriosis patients. The potential role of aberrant expression of individual estrogen-metabolizing enzymes is discussed, and a model mechanism for increased formation of estradiol is presented separately for different types of endometriosis. The disturbed expression of estrogen receptors in endometriosis is detailed, and the estrogen biosynthetic enzymes and receptors are discussed as novel therapeutic targets for the treatment of endometriosis.

Global gene expression analysis reveals evidence for decreased lipid biosynthesis and increased innate immunity in uninvolved psoriatic skin

Psoriasis is a genetically determined inflammatory skin disease. Although the transition from uninvolved into lesional skin is accompanied by changes in the expression of multiple genes, much less is known about the difference between uninvolved skin from psoriatic patients as opposed to skin from normal individuals. Multiple biochemical and morphological changes were reported decades ago in uninvolved psoriatic skin but remain poorly understood. Here, we show dysregulation of 223 transcripts representing 179 unique genes in uninvolved psoriatic skin, 178 of which were not previously known to be altered in their expression. The proteins encoded by these transcripts are involved in lipid metabolism, antimicrobial defenses, epidermal differentiation, and control of cutaneous vasculature. Cluster analysis of transcripts with significantly altered expression identified a group of genes involved in lipid metabolism with highly correlated gene expression. Promoter analysis showed enrichment for binding sites of three transcription factors; peroxisome proliferator-activator receptor alpha (PPARA), sterol regulatory element-binding protein (SREBF), and estrogen receptor 2 (ESR2), suggesting that the coordinate regulation of lipid metabolic genes may be related to the action of these factors. Taken together, our results identify a "pre-psoriatic" gene expression signature, suggesting decreased lipid biosynthesis and increased innate immunity in uninvolved psoriatic skin.

Global gene expression analysis reveals evidence for decreased lipid biosynthesis and increased innate immunity in uninvolved psoriatic skin

Psoriasis is a genetically determined inflammatory skin disease. Although the transition from uninvolved into lesional skin is accompanied by changes in the expression of multiple genes, much less is known about the difference between uninvolved skin from psoriatic patients as opposed to skin from normal individuals. Multiple biochemical and morphological changes were reported decades ago in uninvolved psoriatic skin but remain poorly understood. Here, we show dysregulation of 223 transcripts representing 179 unique genes in uninvolved psoriatic skin, 178 of which were not previously known to be altered in their expression. The proteins encoded by these transcripts are involved in lipid metabolism, antimicrobial defenses, epidermal differentiation, and control of cutaneous vasculature. Cluster analysis of transcripts with significantly altered expression identified a group of genes involved in lipid metabolism with highly correlated gene expression. Promoter analysis showed enrichment for binding sites of three transcription factors; peroxisome proliferator-activator receptor alpha (PPARA), sterol regulatory element-binding protein (SREBF), and estrogen receptor 2 (ESR2), suggesting that the coordinate regulation of lipid metabolic genes may be related to the action of these factors. Taken together, our results identify a "pre-psoriatic" gene expression signature, suggesting decreased lipid biosynthesis and increased innate immunity in uninvolved psoriatic skin.

Independent elaboration of steroid hormone signaling pathways in metazoans

Steroid hormones regulate many physiological processes in vertebrates, nematodes, and arthropods through binding to nuclear receptors (NR), a metazoan-specific family of ligand-activated transcription factors. The main steps controlling the diversification of this family are now well-understood. In contrast, the origin and evolution of steroid ligands remain mysterious, although this is crucial for understanding the emergence of modern endocrine systems. Using a comparative genomic approach, we analyzed complete metazoan genomes to provide a comprehensive view of the evolution of major enzymatic players implicated in steroidogenesis at the whole metazoan scale. Our analysis reveals that steroidogenesis has been independently elaborated in the 3 main bilaterian lineages, and that steroidogenic cytochrome P450 enzymes descended from those that detoxify xenobiotics.

Transcriptional regulation of steroidogenic genes: STARD1, CYP11A1 and HSD3B

Expression of the genes that mediate the first steps in steroidogenesis, the steroidogenic acute regulatory protein (STARD1), the cholesterol side-chain cleavage enzyme, cytochrome P450scc (CYP11A1) and 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (HSD3B), is tightly controlled by a battery of transcription factors in the adrenal cortex, the gonads and the placenta. These genes generally respond to the same hormones that stimulate steroid production through common pathways such as cAMP signaling and common actions on their promoters by proteins such as NR5A and GATA family members. However, there are distinct temporal, tissue and species-specific differences in expression between the genes that are defined by combinatorial regulation and unique promoter elements. This review will provide an overview of the hormonal and transcriptional regulation of the STARD1, CYP11A1 and specific steroidogenic HSD3B genes in the adrenal, testis, ovary and placenta and discuss the current knowledge regarding the key transcriptional factors involved.

Genetics of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is one of the most common inherited metabolic disorders. It comprises a group of autosomal recessive disorders caused by the deficiency of one of four steroidogenic enzymes involved in cortisol biosynthesis or in the electron donor enzyme P450 oxidoreductase (POR) that serves as electron donor to steroidogenic cytochrome P450 (CYP) type II enzymes. The biochemical and clinical phenotype depends on the specific enzymatic defect and the impairment of specific enzyme activity. Defects of steroid 21-hydroxylase (CYP21A2) and 11beta-hydroxylase (CYP11B1) only affect adrenal steroidogenesis, whereas 17alpha-hydroxylase (CYP17A1) and 3beta-hydroxysteroid dehydrogenase type 2 (HSD3B2) deficiency also impact on gonadal steroid biosynthesis. Inactivating POR gene mutations are the cause of CAH manifesting with apparent combined CYP17A1-CYP21A2 deficiency. P450 oxidoreductase deficiency (ORD) has a complex phenotype including two unique features not observed in any other CAH variant: skeletal malformations and severe genital ambiguity in both sexes.

The farnesoid X receptor regulates transcription of 3beta-hydroxysteroid dehydrogenase type 2 in human adrenal cells

Recent studies have shown that the adrenal cortex expresses high levels of farnesoid X receptor (FXR), but its function remains unknown. Herein, using microarray technology, we tried to identify candidate FXR targeting genes in the adrenal glands, and showed that FXR regulated 3beta-hydroxysteroid dehydrogenase type 2 (HSD3B2) expression in human adrenocortical cells. We further demonstrated that FXR stimulated HSD3B2 promoter activity and have defined the cis-element responsible for FXR regulation of HSD3B2 transcription. Transfection of H295R adrenocortical cells with FXR expression vector effectively increased FXR expression levels and additional treatment with chenodeoxycholic acid (CDCA) caused a 25-fold increase in the mRNA for organic solute transporter alpha (OSTalpha), a known FXR target gene. HSD3B2 mRNA levels also increased following CDCA treatment in a concentration-dependent manner. Cells transfected with a HSD3B2 promoter construct and FXR expression vector responded to CDCA with a 20-fold increase in reporter activity compared to control. Analysis of constructs containing sequential deletions of the HSD3B2 promoter suggested a putative regulatory element between -166 and -101. Mutation of an inverted repeat between -137 and -124 completely blocked CDCA/FXR induced reporter activity. Chromatin immunoprecipitation assays further confirmed the presence of a FXR response element in the HSD3B2 promoter. In view of the emerging role of FXR agonists as therapeutic treatment of diabetes and certain liver diseases, the effects of such agonists on other FXR expressing tissues should be considered. Our findings suggest that in human adrenal cells, FXR increases transcription and expression of HSD3B2. Alterations in this enzyme would influence the capacity of the adrenal gland to produce corticosteroids.

Novel 3beta-hydroxysteroid dehydrogenases from gonads of the Nile tilapia: phylogenetic significance and expression during reproductive cycle

Multiple forms of 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD) and their differential tissue expression pattern have not been shown in any lower vertebrates. In the present study, we report cloning of two novel 3beta-HSDs and two variants from gonads of the Nile tilapia. 3beta-HSD cDNAs encode two peptides of 375 (3beta-HSD type-I/variant 1) and 367 (3beta-HSD type-II/variant 1) amino acid residues that share 31.9% homology. 3beta-HSD type-I/variant 1 shared high homology with other piscine counterparts while 3beta-HSD type-II/variant 1 exhibited homology to mammalian DeltaC27-3beta-HSD and multifunctional viral 3beta-HSD. The latter seems to be ancient form among vertebrates. Transiently transfected 3beta-HSDs' open reading frames in COS-7 cells converted exogenous pregnenolone/androsta-5-ene-3beta-17beta-diol to progesterone/testosterone. Tissue distribution pattern of 3beta-HSDs by RT-PCR revealed varied expression pattern. Northern blot analysis of 3beta-HSDs demonstrated steady or gradual rise in transcripts level at different gonadal stages. These data revealed the importance of novel 3beta-HSDs in teleosts and also provided phylogenetic significance.

46,XY disorders of sex development (DSD)

The term disorders of sex development (DSD) includes congenital conditions in which development of chromosomal, gonadal or anatomical sex is atypical. Mutations in genes present in X, Y or autosomal chromosomes can cause abnormalities of testis determination or disorders of sex differentiation leading to 46,XY DSD. Detailed clinical phenotypes allow the identification of new factors that can alter the expression or function of mutated proteins helping to understand new undisclosed biochemical pathways. In this review we present an update on 46,XY DSD aetiology, diagnosis and treatment based on extensive review of the literature and our three decades of experience with these patients.

Molecular determinants for the stereospecific reduction of 3-ketosteroids and reactivity towards all-trans-retinal of a short-chain dehydrogenase/reductase (DHRS4)

DHRS4, a member of the short-chain dehydrogenase/reductase superfamily, reduces all-trans-retinal and xenobiotic carbonyl compounds. Human DHRS4 differs from other animal enzymes in kinetic constants for the substrates, particularly in its low reactivity to retinoids. We have found that pig, rabbit and dog DHRS4s reduce benzil and 3-ketosteroids into S-benzoin and 3alpha-hydroxysteroids, respectively, in contrast to the stereoselectivity of human DHRS4 which produces R-benzoin and 3beta-hydroxysteroids. Among substrate-binding residues predicted from the crystal structure of pig DHRS4, F158 and L161 in the animal DHRS4 are serine and phenylalanine, respectively, in the human enzyme. Double mutation (F158S/L161F) of pig DHRS4 led to an effective switch of its substrate affinity and stereochemistry into those similar to human DHRS4. The roles of the two residues in determining the stereospecificity in 3-ketosteroid reduction were confirmed by reverse mutation (S158F/F161L) in the human enzyme. The stereochemical control was evaluated by comparison of the 3D models of pig wild-type and mutant DHRS4s with the modeled substrates. Additional mutation of T177N into the human S158F/F161L mutant resulted in almost complete kinetic conversion into a pig DHRS4-type form, suggesting a role of N177 in forming the substrate-binding cavity through an intersubunit interaction in pig and other animal DHRS4s, and explaining why the human enzyme shows low reactivity towards retinoids.

Immunohistochemical study of 3 beta-hydroxysteroid dehydrogenase in dog's perianal sinus

In this study, the localization of 3 beta-hydroxysteroid dehydrogenase (3beta-HSD) activity in the wall of canine perianal sinus (PS) was determined. The 3 beta-HSD activity was found out both in the cytoplasm of cells, situated in the propria and forming clusters adjacently to apocrine glands and in the cytoplasm of some epithelial cells in apocrine cells' glands. The results obtained about the 3 beta-HSD activity allowed us to propose a role of this enzyme in PS development and possibly, in tumourogenesis.