17beta-hydroxysteroid dehydrogenases: physiological roles in health and disease

Serum progesterone is lower in ovarian stimulation with highly purified HMG compared to recombinant FSH owing to a different regulation of follicular steroidogenesis: a randomized controlled trial

STUDY QUESTION

Does ovarian stimulation with highly purified (hp)-HMG protect from elevated progesterone in the follicular phase compared to recombinant FSH (r-FSH) cycles through a different regulation of follicular steroidogenesis?

SUMMARY ANSWER

hp-HMG enhanced the Δ4 pathway from pregnenolone to androstenodione leading to lower serum progesterone at the end of the cycle, while r-FSH promoted the conversion of pregnenolone to progesterone causing higher follicular phase progesterone levels.

WHAT IS KNOWN ALREADY

Elevated progesterone in the follicular phase has been related to lower clinical outcome in fresh IVF cycles. Progesterone levels are positively correlated to ovarian response, and some studies have shown that when r-FSH alone is used for ovarian stimulation serum progesterone levels on the day of triggering are higher than when hp-HMG is given. Whether this is caused by a lower ovarian response in hp-HMG cycles or to a difference in follicular steroidogenesis in the two ovarian stimulation regimens has not been well characterized.

STUDY DESIGN, SIZE, DURATION

A randomized controlled trial including 112 oocyte donors undergoing ovarian stimulation with GnRH antagonists and 225 IU/day of r-FSH (n = 56) or hp-HMG (n = 56) was carried out in a university-affiliated private infertility clinic. Subjects were recruited between October 2016 and June 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The women were aged 18-35 years with a regular menstrual cycle (25-35 days) and normal ovarian reserve (serum anti-Müllerian hormone (AMH) = 10-30 pMol/l) undergoing ovarian stimulation for oocyte donation. FSH, LH, estradiol (E2), estrone, progesterone, pregnenolone, 17-OH-progesterone, androstenodione, dehidroepiandrostenodione, and testosterone were determined on stimulation Days 1, 4, 6, and 8 and on day of triggering in serum and in follicular fluid. Samples were frozen at -20°C until assay. Total exposures across the follicular phase were compared by polynomic extrapolation.

MAIN RESULTS AND THE ROLE OF CHANCE

Subjects in both groups were comparable in terms of age, BMI, and AMH levels. Ovarian response was also similar: 17.5 ± 7.9 (mean ± SD) versus 16.5 ± 7.5 oocytes with r-FSH and hp-HMG, respectively (P = 0.49). Serum progesterone (ng/ml) on day of trigger was 0.46 ± 0.27 in the hp-HMG group versus 0.68 ± 0.50 in the r-FSH group (P = 0.010). Differences for progesterone were also significant on stimulation days 6 and 8. The pregnenolone: progesterone ratio was significantly increased in the r-FSH group from stimulation day 8 to the day of trigger (P = 0.019). Serum androstenodione (ng/ml) on day of trigger was 3.0 ± 1.4 in the hp-HMG group versus 2.4 ± 1.1 in the r-FSH group (P = 0.015). Differences in adrostenodione were also significant on stimulation Day 8. The pregnenolone:androstenodione ratio was significantly higher in the hp-HMG group (P = 0.012) on Days 6 and 8 and trigger. There were no other significant differences between groups. Follicular fluid E2, FSH, LH, dehidroepioandrostenodione, androstenodione, and testosterone were significantly higher in the hp-HMG than r-FSH group. No differences were observed for progesterone, estrone, 17-OH-progesterone, and pregnenolone in follicular fluid.

LIMITATIONS, REASONS FOR CAUTION

All women included in the study were young, not infertile, and had a normal BMI and a good ovarian reserve. The findings might be different in other patient subpopulations. Hormone analyses with immunoassays are subject to intra-assay variations that may influence the results.

WIDER IMPLICATIONS OF THE FINDINGS

Stimulation with hp-HMG may prevent progesterone elevation at the end of the follicular phase because of a different follicular steroidogenesis pathway, regardless of ovarian response. This should be considered, particularly in patients at risk of having high progesterone levels at the end of the follicular phase when a fresh embryo transfer is planned.

STUDY FUNDING/COMPETING INTEREST(S)

Roche Diagnostics provided unrestricted funding for all serum and follicular fluid hormone determinations. J.L.R., M.M., and A.P. have nothing to declare. E.B. has received consulting fees from Ferring, Merck, Gedeon Richter, and Roche and has participated in a research cooperation with Gedeon-Richter. In addition, the author has participated in speakers' bureau and received fees from Ferring, Gedeon Richter, Merck, and Roche. P.A. has received consulting fees from MSD and has participated in speakers' bureau and received fees from Ferring. P.A. also declares travel/meeting support from MSD. E.L. has received consulting fees from Ferring and MSD. In addition, the author has participated in a research cooperation with Gedeon-Richter. Also, the author has participated in speakers' bureau and received fees from Ferring and IBSA, as well as travel/meeting support from IBSA and Gedeon Richter. E.B., P.A., and E.L. also own stocks in IVIRMA Valencia.

TRIAL REGISTRATION NUMBER

NCT: NCT02738580.

TRIAL REGISTER DATE

19 February 2016.

DATE OF FIRST PATIENT’S ENROLMENT

03 October 2016.

Description of Chemical Synthesis, Nuclear Magnetic Resonance Characterization and Biological Activity of Estrane-Based Inhibitors/Activators of Steroidogenesis

Steroid hormones play a crucial role in several aspects of human life, and steroidogenesis is the process by which hormones are produced from cholesterol using several enzymes that work in concert to obtain the appropriate levels of each hormone at the right time. Unfortunately, many diseases, such as cancer, endometriosis, and osteoporosis as examples, are caused by an increase in the production of certain hormones. For these diseases, the use of an inhibitor to block the activity of an enzyme and, in doing so, the production of a key hormone is a proven therapeutic strategy whose development continues. This account-type article focuses on seven inhibitors (compounds 1-7) and an activator (compound 8) of six enzymes involved in steroidogenesis, namely steroid sulfatase, aldo-keto reductase 1C3, types 1, 2, 3, and 12 of the 17β-hydroxysteroid dehydrogenases. For these steroid derivatives, three topics will be addressed: (1) Their chemical synthesis from the same starting material, estrone, (2) their structural characterization using nuclear magnetic resonance, and (3) their in vitro or in vivo biological activities. These bioactive molecules constitute potential therapeutic or mechanistic tools that could be used to better understand the role of certain hormones in steroidogenesis.

Androgen Metabolism and Response in Prostate Cancer Anti-Androgen Therapy Resistance

All aspects of prostate cancer evolution are closely related to androgen levels and the status of the androgen receptor (AR). Almost all treatments target androgen metabolism pathways and AR, from castration-sensitive prostate cancer (CSPC) to castration-resistant prostate cancer (CRPC). Alterations in androgen metabolism and its response are one of the main reasons for prostate cancer drug resistance. In this review, we will introduce androgen metabolism, including how the androgen was synthesized, consumed, and responded to in healthy people and prostate cancer patients, and discuss how these alterations in androgen metabolism contribute to the resistance to anti-androgen therapy.

Congenital Adrenal Hyperplasia-Current Insights in Pathophysiology, Diagnostics, and Management

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders affecting cortisol biosynthesis. Reduced activity of an enzyme required for cortisol production leads to chronic overstimulation of the adrenal cortex and accumulation of precursors proximal to the blocked enzymatic step. The most common form of CAH is caused by steroid 21-hydroxylase deficiency due to mutations in CYP21A2. Since the last publication summarizing CAH in Endocrine Reviews in 2000, there have been numerous new developments. These include more detailed understanding of steroidogenic pathways, refinements in neonatal screening, improved diagnostic measurements utilizing chromatography and mass spectrometry coupled with steroid profiling, and improved genotyping methods. Clinical trials of alternative medications and modes of delivery have been recently completed or are under way. Genetic and cell-based treatments are being explored. A large body of data concerning long-term outcomes in patients affected by CAH, including psychosexual well-being, has been enhanced by the establishment of disease registries. This review provides the reader with current insights in CAH with special attention to these new developments.

Substituted Aryl Benzylamines as Potent and Selective Inhibitors of 17β-Hydroxysteroid Dehydrogenase Type 3

17β-Hydroxysteroid dehydrogenase type 3 (17β-HSD3) is expressed at high levels in testes and seminal vesicles; it is also present in prostate tissue and involved in gonadal and non-gonadal testosterone biosynthesis. The enzyme is membrane-bound, and a crystal structure is not yet available. Selective aryl benzylamine-based inhibitors were designed and synthesised as potential agents for prostate cancer therapeutics through structure-based design, using a previously built homology model with docking studies. Potent, selective, low nanomolar IC₅₀ 17β-HSD3 inhibitors were discovered using N-(2-([2-(4-chlorophenoxy)phenylamino]methyl)phenyl)acetamide (1). The most potent compounds have IC₅₀ values of approximately 75 nM. Compound 29, N-[2-(1-Acetylpiperidin-4-ylamino)benzyl]-N-[2-(4-chlorophenoxy)phenyl]acetamide, has an IC₅₀ of 76 nM, while compound 30, N-(2-(1-[2-(4-chlorophenoxy)-phenylamino]ethyl)phenyl)acetamide, has an IC₅₀ of 74 nM. Racemic C-allyl derivative 26 (IC₅₀ of 520 nM) was easily formed from 1 in good yield and, to determine binding directionality, its enantiomers were separated by chiral chromatography. Absolute configuration was determined using single crystal X-ray crystallography. Only the S-(+)-enantiomer (32) was active with an IC₅₀ of 370 nM. Binding directionality was predictable through our in silico docking studies, giving confidence to our model. Importantly, all novel inhibitors are selective over the type 2 isozyme of 17β-HSD2 and show <20% inhibition when tested at 10 µM. Lead compounds from this series are worthy of further optimisation and development as inhibitors of testosterone production by 17β-HSD3 and as inhibitors of prostate cancer cell growth.

Indel mutations within the bovine HSD17B3 gene are significantly associated with ovary morphological traits and mature follicle number

Given the intensive selection for increased milk production, it is imperative that the problem of declining fertility in dairy cows be reversed. In female mammals their reproductive traits and functioning is controlled by a finely tuned process balancing estrogens and androgens, in which androgens (e.g., testosterone) as a precursor substance can participate in estrogen synthesis by activating 17β-hydroxysteroid dehydrogenase (17betaHSD). Being a key catalyst for testosterone synthesis, we hypothesized HSD17B3 gene is involved in the ovary's development and thereby capable of influencing cows' fecundity. Herein, to investigate the relationship between polymorphisms of the HSD17B3 gene and cow fertility, we characterized three insertion/deletion (indels) polymorphisms of this gene in 1110 healthy bovine ovaries. Their respective minimum allelic frequency (MAF) ranged from 0.180 to 0.482. For the ovary morphological traits, correlations revealed that both P1-D_15-bp and P4-D_19-bp demonstrated significant associations with ovarian height (P = 0.007 and 0.004, respectively), while P5-I_5-bp was found to be significantly associated with the ovarian weight (P = 0.024). For ovarian volume, a significant correlation was uncovered between it and both polymorphisms of P4-D_19-bp (P = 0.036) and P5-I_5-bp (P = 0.045). Cows with either the DD genotype of P4-D_19-bp or P5-I_5-bp tended to have greater ovarian volume, a result consistent with their relationship to ovarian weight (P5-I_5-bp) or height (P4-D_19-bp). For the mature follicle traits, polymorphisms of P4-D_19-bp were found significantly associated with the number of mature follicles (P = 0.045). Furthermore, expression levels of HSD17B3 differed significantly between the maximal and minimum groups of ovarian weight or volume, and the transcription factors GATA-1 and USF were predicted to bind P1-D_15-bp and P4-D_19-bp, respectively. This suggested the detected intron mutations could affect HSD17B3's transcription by regulating the binding of transcription factors, thereby affecting ovarian weight and other reproductive traits. As a potential effective molecular marker loci significantly related to traits of ovary and follicle, these three indels could be used in practical molecular marker-assisted selection (MAS) breeding programs, to optimize female fertility and enhance economic efficiency in the dairy cow industry.

Repurposing steroidogenesis inhibitors for the therapy of neuropsychiatric disorders: Promises and caveats

Steroids exert a profound influence on behavioral reactivity, by modulating the functions of most neurotransmitters and shaping the impact of stress and sex-related variables on neural processes. This background - as well as the observation that most neuroactive steroids (including sex hormones, glucocorticoids and neurosteroids) are synthetized and metabolized by overlapping enzymatic machineries - points to steroidogenic pathways as a powerful source of targets for neuropsychiatric disorders. Inhibitors of steroidogenic enzymes have been developed and approved for a broad range of genitourinary and endocrine dysfunctions, opening to new opportunities to repurpose these drugs for the treatment of mental problems. In line with this idea, preliminary clinical and preclinical results from our group have shown that inhibitors of key steroidogenic enzymes, such as 5α-reductase and 17,20 desmolase-lyase, may have therapeutic efficacy in specific behavioral disorders associated with dopaminergic hyperfunction. While the lack of specificity of these effects raises potential concerns about endocrine adverse events, these initial findings suggest that steroidogenesis modulators with greater brain specificity may hold significant potential for the development of alternative therapies for psychiatric problems. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

Corpora lutea of pregnant and pseudopregnant domestic cats reveal similar steroidogenic capacities during the luteal life span

In domestic cats, luteal phases of pregnancy and pseudopregnancy (non-pregnant luteal phase) differ in the course and level of plasma progesterone (P4). Therefore, we assumed differences in luteal steroidogenic capacities. Here we present a comprehensive analysis of intraluteal steroid biogenesis in the domestic cat. We quantitatively measured relative mRNA levels of steroidogenic acute regulatory protein (STAR), cytochrome P450 oxidases (CYP), hydroxysteroid dehydrogenases (HSD), steroid reductase (SRD) and enzymes involved in sulfoconjugation of steroids, i.e. sulfotransferase (SULT) and sulfatase (STS). Protein expression was analysed by Western Blot for HSD3B. Additionally, intraluteal steroid contents were determined. During the pseudopregnant luteal phase, expression of STAR (p=0.005), HSD3B1 (p<0.0001), CYP19A1 (p<0.0001) and HSD17B7 (p=0.008) decreased from formation of the corpus luteum (CL) onwards. HSD3B protein expression was highest in the development/maintenance stage of CL and declined during the subsequent luteal phase of pregnancy and pseudopregnancy. This was in accordance with decreasing intraluteal levels of P4, oestrogens and androgens. In contrast, expression of SRD5A1 (p<0.001) increased with progression through stages of the pseudopregnant CL, being indicative of P4 metabolism via an alternate pathway to dihydrotestosterone (DHT). Compared to the formation stage, expression of SULT1E1 was higher in all other luteal stages of pseudopregnancy (p=0.004), implying a potential sulfoconjugation of oestrogens. Expression of CYP11A1 and CYP17A1 was unaffected by the luteal stage (p>0.05), suggesting a permanent capacity of cat CL to convert progestogens via androgen and oestrogen pathways. In general, mRNA expression profiles of steroidogenic enzymes during the pregnant luteal phase reflected the pseudopregnancy profiles. Intraluteal oestrogen (p<0.0001) and androgen (p=0.008) levels were higher in the formation stage compared to the following luteal stages of pseudopregnancy. Concentrations of P4 were higher in the development/maintenance compared to the regression stages (p=0.01). We conclude that cat CL of the same histomorphological stage are characterised by identical steroidogenic capacities independently of an on-going pregnancy.

SIRT3 positively regulates the expression of folliculogenesis- and luteinization-related genes and progesterone secretion by manipulating oxidative stress in human luteinized granulosa cells

SIRT3 is a member of the sirtuin family and has recently emerged as a vital molecule in controlling the generation of reactive oxygen species (ROS) in oocytes. Appropriate levels of ROS play pivotal roles in human reproductive medicine. The aim of the present study was to investigate SIRT3 expression and analyze the SIRT3-mediated oxidative response in human luteinized granulosa cells (GCs). Human ovarian tissues were subjected to immunohistochemical analysis to localize SIRT3 expression. Hydrogen peroxide and human chorionic gonadotropin were used to analyze the relationship between ROS and SIRT3 by quantitative RT-PCR and Western blotting. Intracellular levels of ROS were investigated by fluorescence after small interfering RNA-mediated knockdown of SIRT3 in human GCs. To uncover the role of SIRT3 in folliculogenesis and luteinization, mRNA levels of related genes and the progesterone concentration were analyzed by quantitative RT-PCR and immunoassays, respectively. We detected the expression of SIRT3 in the GCs of the human ovary. The mRNA levels of SIRT3, catalase, and superoxide dismutase 1 were up-regulated by hydrogen peroxide in both COV434 cells and human GCs and down-regulated by human chorionic gonadotropin. Knockdown of SIRT3 markedly elevated ROS generation in human GCs. In addition, SIRT3 depletion resulted in decreased mRNA expression of aromatase, 17β-hydroxysteroid dehydrogenase 1, steroidogenic acute regulatory protein, cholesterol side-chain cleavage enzyme, and 3β-hydroxysteroid dehydrogenase in GCs and thus resulted in decreased progesterone secretion. These results have the important clinical implication that SIRT3 might play a positive role in the folliculogenesis and luteinization processes in GCs, possibly by sensing and regulating the generation of ROS. Activation of SIRT3 function might help to sustain human reproduction by maintaining GCs as well as oocytes.

AKR1C3 as a target in castrate resistant prostate cancer

Aberrant androgen receptor (AR) activation is the major driver of castrate resistant prostate cancer (CRPC). CRPC is ultimately fatal and more therapeutic agents are needed to treat this disease. Compounds that target the androgen axis by inhibiting androgen biosynthesis and or AR signaling are potential candidates for use in CRPC treatment and are currently being pursued aggressively. Aldo-keto reductase 1C3 (AKR1C3) plays a pivotal role in androgen biosynthesis within the prostate. It catalyzes the 17-ketoreduction of weak androgen precursors to give testosterone and 5α-dihydrotestosterone. AKR1C3 expression and activity has been implicated in the development of CRPC, making it a rational target. Selective inhibition of AKR1C3 will be important, however, due to the presence of closely related isoforms, AKR1C1 and AKR1C2 that are also involved in androgen inactivation. We examine the evidence that supports the vital role of AKR1C3 in CRPC and recent developments in the discovery of potent and selective AKR1C3 inhibitors. This article is part of a Special Issue entitled 'CSR 2013'.

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.

The design of novel 17beta-hydroxysteroid dehydrogenase type 3 inhibitors

17beta-Hydroxysteroid dehydrogenase type 3 (17beta-HSD3) is expressed at high levels in the testes and seminal vesicles but has also been shown to be present in prostate tissue, suggesting its potential involvement in both gonadal and non-gonadal testosterone biosynthesis. The role of 17beta-HSD3 in testosterone biosynthesis makes this enzyme an attractive molecular target for small molecule inhibitors for the treatment of prostate cancer. Here we report the design of selective inhibitors of 17beta-HSD3 as potential anti-cancer agents. Due to 17beta-HSD3 being a membrane-bound protein a crystal structure is not yet available. A homology model of 17beta-HSD3 has been built to aid structure-based drug design. This model has been used with docking studies to identify a series of lead compounds that may give an insight as to how inhibitors interact with the active site. Compound 1 was identified as a potent selective inhibitor of 17beta-HSD3 with an IC(50)=700nM resulting in the discovery of a novel lead series for further optimisation. Using our homology model as a tool for inhibitor design compound 5 was discovered as a novel potent and selective inhibitor of 17beta-HSD3 with an IC(50) approximately 200nM.

Androgen synthesis in adrenarche

The enzymes and pathways of steroidogenesis are central to an understanding of adrenarche. The quantitative regulation of steroidogenesis occurs at the first step, the conversion of cholesterol to pregnenolone. Chronic quantitative regulation is principally at the level of transcription of the CYP11A1 gene encoding P450scc, which is the enzymatically rate-limiting step. Acute regulation is mediated by the steroidogenic acute regulatory protein (StAR), which facilitates the rapid influx of cholesterol into mitochondria, where P450scc resides. Qualitative regulation, which determines the type of steroid produced in a cell, is principally at the level of P450c17 (CYP17). In the absence of P450c17 in the zona glomerulosa, C21 deoxy steroids are produced, leading to the mineralocorticoid, aldosterone. In the presence of the 17alpha-hydroxylase but not the 17,20 lyase activity of P450c17 in the zona fasciculata, C21, 17-hydroxy steroids are produced, leading to the glucocorticoid, cortisol. When both the 17alpha-hydroxylase and 17,20 lyase activities of P450c17 are present in the zona reticularis, the androgen precursor DHEA is produced. The discrimination between 17alpha-hydroxylase and 17,20 lyase activities is regulated by two post-translational events, the serine phosphorylation of P450c17 and the allosteric action of cytochrome b5, both of which act to optimize the interaction of P450c17 with its obligatory electron donor, P450 oxidoreductase. In the adrenal zona reticularis, the abundant expression of P450 oxidoreductase and cytochrome b5, and the low expression of 3beta-hydroxysteroid dehydrogenase (HSD3B2) result in the production of the large amounts of DHEA that characterize adrenarche.

17beta-hydroxysteroid dehydrogenase-3 deficiency: a rare endocrine cause of male-to-female sex reversal

Deficiency of 17beta-hydroxysteroid dehydrogenase type 3 (17beta-HSD3), due to mutations in the gene encoding the enzyme, results in a rare autosomal recessive form of male-to-female sex reversal. Mutated genes encode an abnormal enzyme with absent or reduced ability to convert Delta4-androstenedione to testosterone in the testis. Affected individuals are genetically males who developed internal male Wolffian structures but female external genitalia. Such individuals are usually raised as females and diagnosis is made at puberty, when they show virilization. Correct diagnosis is mandatory to optimize treatment and follow-up. In the present paper we report the clinical history, endocrine evaluation and molecular genetics of a prepubertal girl affected by 17beta-HSD3 deficiency, in whom an erroneous diagnosis of androgen insensitivity syndrome was made. The clinical, endocrine and genetic features of 17beta-HSD3 deficiency are also reviewed.

Androsterone 3alpha-ether-3beta-substituted and androsterone 3beta-substituted derivatives as inhibitors of type 3 17beta-hydroxysteroid dehydrogenase: chemical synthesis and structure-activity relationship

Type 3 17beta-hydroxysteroid dehydrogenase (17beta-HSD) is involved in the biosynthesis of androgen testosterone. To produce potent inhibitors of this key steroidogenic enzyme, we prepared a series of androsterone (ADT) derivatives by adding a variety of substituents at position 3. The 3beta-substituted ADT derivatives proved to be good inhibitors (IC(50) = 57-147 nM) with better inhibitory activities obtained for compounds bearing a propyl, s-butyl, cyclohexylalkyl, or phenylalkyl group. With an IC(50) value of 57 nM, the 3beta-phenylmethyl-ADT was 6-fold more potent than ADT, the lead compound, and 13-fold more potent than 4-androstene-3,17-dione, the natural enzyme substrate used itself as inhibitor. The 3alpha-ether-3beta-substituted ADT derivatives had a lower inhibitory activity compared to the 3beta-substituted ADT analogues except for the 3beta-phenylethyl-3alpha-methl-O-ADT (IC(50) = 73 nM), which proved to be a more potent inhibitor than 3beta-phenylethyl-ADT (IC(50) = 99 nM). The results of our study identified potent type 3 17beta-HSD inhibitors for potential use in the treatment of androgen-sensitive diseases.

Amino acid substitution of arginine 80 in 17beta-hydroxysteroid dehydrogenase type 3 and its effect on NADPH cofactor binding and oxidation/reduction kinetics

17beta-Hydroxysteroid dehydrogenase type 3 (17beta-HSD-3) is a member of the short-chain dehydrogenase/reductase (SDR) family and is essential for the reductive conversion of inactive C(19)-steroid, androstenedione, to the biologically active androgen, testosterone, which plays a central role in the development of the male phenotype. Mutations that inactivate this enzyme give rise to a rare form of male pseudohermaphroditism, referred to as 17beta-HSD-3 deficiency. One such mutation is the replacement of arginine at position 80 with glutamine, compromising enzyme activity by increasing the cofactor binding constant 60-fold. In the absence of a 17beta-HSD-3 crystal structure, we have grafted its amino acid sequence for the NADPH binding site on the X-ray crystal structures of glutathione reductase (Protein Data Bank code 1gra) and 17beta-HSD type 1 (Protein Data Bank codes 1fdv and 1fdu) where we find the trunk of the arginine 80 side chain forms part of the hydrophobic pocket for the purine ring of adenosine while its guanidinium moiety interacts with the 2'-phosphate to both stabilize cofactor binding and neutralize its intrinsic negative charge through two hydrogen bonds. To qualitatively assess the role arginine 80 plays in both selecting and stabilizing NADPH binding, it was replaced with each amino acid and the mutant enzymes subjected to enzymatic analysis. There are only seven enzymes exhibiting any measurable enzymatic activity with arginine approximately lysine>leucine>glutamine>methionine>tyrosine>isoleucine. With an aspartic acid at position 58 in 17beta-HSD-3 occupying the equivalent space in the cofactor binding pocket as arginine 224 in glutathione reductase or serine 12 in 17beta-HSD-1, there was an expectation that some of the mutants might use NADH as a cofactor. In no case was NADH found to substitute for NADPH.

N-Butyl-N-methyl-11-(3'-hydroxy-21', 17'-carbolactone-19'-nor-17'alpha-pregna-1',3', 5'(10')-trien-7'alpha-yl)-undecanamide: an inhibitor of type 2 17beta-hydroxysteroid dehydrogenase that does not have oestrogenic or androgenic activity

It is well known that 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) play a key role in the formation and inactivation, from circulating precursors, of several active androgens and oestrogens. These enzymes can thus regulate tumoural cell proliferation in androgen- and oestrogen-dependent cancers. Recently, we discovered that adding a spiro-gamma-lactone to the oestradiol nucleus results in a novel inhibitor of type 2 17beta-HSD, an enzyme that catalyses the interconversions between 4-androstene-3,17-dione and testosterone, and between oestrone and oestradiol. This finding motivated our introducing the spiro-gamma-lactone moiety onto an anti-oestrogenic nucleus. The N-butyl-N-methyl-11-(3'-hydroxy-21', 17'-carbolactone-19'-nor-17'alpha-pregna-1',3', 5'(10')-trien-7'alpha-yl)-undecanamide (4) was then efficiently synthesized and its biological activity was assessed in vitro. Despite the presence of a bulky alkylamide side chain, the spiro-gamma-lactone function conserved its ability to inhibit type 2 17beta-HSD (IC(50) = 0.35 and 0.25 microM, with and without side chain, respectively). Furthermore, the selective inhibition by lactone 4 toward type 2 17beta-HSD (microsomal fraction of human placenta) was demonstrated by the absence of inhibitory activity toward type 1 17beta-HSD (cytosolic fraction of human placenta). Cell proliferation assays indicated that compound 4 had no oestrogenic activity but did show anti-oestrogenic activity on ER(+) cell line ZR-75-1. No androgenic activity could be detected when assayed on the AR(+) cell line Shionogi either. Based on these facts, we report the synthesis of a new steroidal derivative, one that inhibits type 2 17beta-HSD while possessing anti-oestrogenic activity.

The rat 17beta-hydroxysteroid dehydrogenase type III: molecular cloning and gonadotropin regulation

17Beta-hydroxysteroid dehydrogenase (17betaHSD), the enzyme that catalyzes the final step of testosterone biosynthesis in the testis, was cloned from a rat Leydig cell complementary DNA library to gain insights into the functional requirements, activation mechanisms, and molecular regulation. The 17betaHSD complementary DNA encoded 306 amino acids (molecular mass of 33.7 kDa) and displayed 75% and 85% amino acid sequence homology to the human and mouse 17betaHSD type III enzymes, respectively. Northern analysis revealed a single 1.4-kb messenger RNA (mRNA) species in rat Leydig cells, whereas ovarian mRNA was detected only by RT-PCR amplification. The cloned 17betaHSD expressed in mammalian cell lines specifically catalyzed the reductive reaction in androgen formation with androstenedione as the preferred substrate. This reaction was significantly reduced in the absence of glucose. Expression of the endogenous 17betaHSD gene in rat Leydig cells was inhibited by a single dose of hCG in vivo, with maximum reduction of steady state mRNA levels at 24 h and recovery at 9 days. Such agonist-induced down-regulation of 17betaHSD expression, which preceded the marked reduction of LH receptors, resulted from changes at the transcriptional level and was accompanied by loss of enzymatic activity. These studies have demonstrated a glucose requirement for optimal activity of the enzyme in vitro and for a role of gonadotropin in regulating the expression of 17betaHSD gene in vivo. Cloning of the 17betaHSD type III enzyme from rat Leydig cells will facilitate further investigation of the molecular regulation of its activity in the testis.