Tributyltin and triphenyltin induce 11ß-hydroxysteroid dehydrogenase 2 expression and activity through activation of retinoid X receptor α.

Exposure to the environmental pollutants organotins is of toxicological concern for the marine ecosystem and sensitive human populations, including pregnant women and their unborn children. Using a placenta cell model, we investigated whether organotins at nanomolar concentrations affect the expression and activity of 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2). 11ß-HSD2 represents a placental barrier controlling access of maternal glucocorticoids to the fetus. The organotins tributyltin (TBT) and triphenyltin (TPT) induced 11ß-HSD2 expression and activity in JEG-3 placenta cells, an effect confirmed at the mRNA level in primary human trophoblast cells. Inhibition/knock-down of retinoid X receptor alpha (RXRα) in JEG-3 cells reduced the effect of organotins on 11ß-HSD2 activity, mRNA and protein levels, revealing involvement of RXRα. Experiments using RNA and protein synthesis inhibitors indicated that the effect of organotins on 11ß-HSD2 expression was direct and caused by increased transcription. Induction of placental 11ß-HSD2 activity by TBT, TPT and other endocrine disrupting chemicals acting as RXRα agonists may affect placental barrier function by altering the expression of glucocorticoid-dependent genes and resulting in decreased availability of active glucocorticoids for the fetus, disturbing development and increasing the risk for metabolic and cardiovascular complications in later life.

Currently available murine Leydig cell lines can be applied to study early steps of steroidogenesis but not testosterone synthesis.

Androgen biosynthesis in males occurs to a large extent in testicular Leydig cells. This study focused on the evaluation of three murine Leydig cell lines as potential screening tool to test xenobiotics interfering with gonadal androgen synthesis. The final step of testosterone (T) production in Leydig cells is catalyzed by the enzyme 17ß-hydroxysteroid dehydrogenase 3 (17ß-hsd3). The endogenous 17ß-hsd3 mRNA expression and Δ4-androstene-3,17-dione (AD) to T conversion were determined in the murine cell lines MA-10, BLTK1 and TM3. Additionally, effects of 8-Br-cAMP and forskolin stimulation on steroidogenesis and T production were analyzed. Steroids were quantified in supernatants of cells using liquid chromatography-tandem mass spectrometry. Unstimulated cells incubated with AD produced only very low T but substantial amounts of the inactive androsterone. Stimulated cells produced low amounts of T, moderate amounts of AD, but high amounts of progesterone. Gene expression analyses revealed barely detectable 17ß-hsd3 levels, absence of 17ß-hsd5 (Akr1c6), but substantial 17ß-hsd1 expression in all three cell lines. Thus, MA-10, BLTK1 and TM3 cells are not suitable to study the expression and activity of the gonadal T synthesizing enzyme 17ß-hsd3. The low T production reported in stimulated MA-10 cells are likely a result of the expression of 17ß-hsd1. This study substantiates that the investigated Leydig cell lines MA-10, BLTK1, and TM3 are not suitable to study gonadal androgen biosynthesis due to altered steroidogenic pathways. Furthermore, this study emphasizes the necessity of mass spectrometry-based steroid quantification in experiments using steroidogenic cells such as Leydig cells.

Accelerated skin wound healing by selective 11ß-Hydroxylase (CYP11B1) inhibitors.

Previous studies have shown that inhibition of cortisol biosynthesis in skin leads to accelerated wound healing. Here, pyridylmethyl pyridine type 11ß-hydroxylase (CYP11B1) inhibitors were optimized for topical application to avoid systemic side effects. The resulting very potent, non-toxic CYP11B1 inhibitor 14 (IC50 = 0.8 nM) exhibited good selectivity over 11ß-HSD1, CYP17A1 and CYP19A1. The compound showed high stability toward human plasma (t1/2= > 150 min, as a substitute for wound fluid) and low stability toward HLS9 (t1/2 = 19 min) for rapid metabolic clearance after absorption. Compound 14 was able to accelerate wound healing in human skin.

Interference of Paraben Compounds with Estrogen Metabolism by Inhibition of 17ß-Hydroxysteroid Dehydrogenases.

Parabens are effective preservatives widely used in cosmetic products and processed food, with high human exposure. Recent evidence suggests that parabens exert estrogenic effects. This work investigated the potential interference of parabens with the estrogen-activating enzyme 17ß-hydroxysteroid dehydrogenase (17ß-HSD) 1 and the estrogen-inactivating 17ß-HSD2. A ligand-based 17ß-HSD2 pharmacophore model was applied to screen a cosmetic chemicals database, followed by in vitro testing of selected paraben compounds for inhibition of 17ß-HSD1 and 17ß-HSD2 activities. All tested parabens and paraben-like compounds, except their common metabolite p-hydroxybenzoic acid, inhibited 17ß-HSD2. Ethylparaben and ethyl vanillate inhibited 17ß-HSD2 with IC50 values of 4.6 ± 0.8 and 1.3 ± 0.3 µM, respectively. Additionally, parabens size-dependently inhibited 17ß-HSD1, whereby hexyl- and heptylparaben were most active with IC50 values of 2.6 ± 0.6 and 1.8 ± 0.3 µM. Low micromolar concentrations of hexyl- and heptylparaben decreased 17ß-HSD1 activity, and ethylparaben and ethyl vanillate decreased 17ß-HSD2 activity. However, regarding the very rapid metabolism of these compounds to the inactive p-hydroxybenzoic acid by esterases, it needs to be determined under which conditions low micromolar concentrations of these parabens or their mixtures can occur in target cells to effectively disturb estrogen effects in vivo.

Biochemical Analysis of Four Missense Mutations in the HSD17B3 Gene Associated With 46,XY Disorders of Sex Development in Egyptian Patients.

BACKGROUND: Mutations in the HSD17B3 gene are associated with a 46,XY disorder of sexual development (46,XY DSD) as a result of low testosterone production during embryogenesis. AIM: To elucidate the molecular basis of the disorder by chemically analyzing four missense mutations in HSD17B3 (T54A, M164T, L194P, G289S) from Egyptian patients with 46,XY DSD. METHODS: Expression plasmids for wild-type 17ß-hydroxysteroid hydrogenase type 3 (17ß-HSD3) and mutant enzymes generated by site-directed mutagenesis were transiently transfected into human HEK-293 cells. Protein expression was verified by western blotting and activity was determined by measuring the conversion of radiolabeled Δ4-androstene-3,17-dione to testosterone. Application of a homology model provided an explanation for the observed effects of the mutations. OUTCOMES: Testosterone formation by wild-type and mutant 17ß-HSD3 enzymes was compared. RESULTS: Mutations T54A and L194P, despite normal protein expression, completely abolished 17ß-HSD3 activity, explaining their severe 46,XY DSD phenotype. Mutant M164T could still produce testosterone, albeit with significantly lower activity compared with wild-type 17ß-HSD3, resulting in ambiguous genitalia or a microphallus at birth. The substitution G289S represented a polymorphism exhibiting comparable activity to wild-type 17ß-HSD3. Sequencing of the SRD5A2 gene in three siblings bearing the HSD17B3 G289S polymorphism disclosed the homozygous Y91H mutation in the former gene, thus explaining the 46,XY DSD presentations. Molecular modeling analyses supported the biochemical observations and predicted a disruption of cofactor binding by mutations T54A and M164T and of substrate binding by L196P, resulting in the loss of enzyme activity. In contrast, the G289S substitution was predicted to disturb neither the three-dimensional structure nor enzyme activity. CLINICAL TRANSLATION: Biochemical analysis of mutant 17ß-HSD3 enzymes is necessary to understand genotype-phenotype relationships. STRENGTHS AND LIMITATIONS: Biochemical analysis combined with molecular modeling provides insight into disease mechanism. However, the stability of mutant proteins in vivo cannot be predicted by this approach. CONCLUSION: The 17ß-HSD3 G289S substitution, previously reported in other patients with 46,XY DSD, is a polymorphism that does not cause the disorder; thus, further sequence analysis was required and disclosed a mutation in SRD5A2, explaining the cause of 46,XY DSD in these patients. Engeli RT, Tsachaki M, Hassan HA, et al. Biochemical Analysis of Four Missense Mutations in the HSD17B3 Gene Associated With 46,XY Disorders of Sex Development in Egyptian Patients. J Sex Med 2017;14:1165-1174.

Phenylbenzenesulfonates and -sulfonamides as 17ß-hydroxysteroid dehydrogenase type 2 inhibitors: Synthesis and SAR-analysis.

17ß-Hydroxysteroid dehydrogenase type 2 (17ß-HSD2) converts the potent estrogen estradiol into the weakly active keto form estrone. Because of its expression in bone, inhibition of 17ß-HSD2 provides an attractive strategy for the treatment of osteoporosis, a condition that is often caused by a decrease of the active sex steroids. Currently, there are no drugs on the market targeting 17ß-HSD2, but in multiple studies, synthesis and biological evaluation of promising 17ß-HSD2 inhibitors have been reported. Our previous work led to the identification of phenylbenzenesulfonamides and -sulfonates as new 17ß-HSD2 inhibitors by ligand-based pharmacophore modeling and virtual screening. In this study, new molecules representing this scaffold were synthesized and tested in vitro for their 17ß-HSD2 activity to derive more profound structure-activity relationship rules.

Potential Antiosteoporotic Natural Product Lead Compounds That Inhibit 17ß-Hydroxysteroid Dehydrogenase Type 2.

17ß-Hydroxysteroid dehydrogenase type 2 (17ß-HSD2) converts the active steroid hormones estradiol, testosterone, and 5α-dihydrotestosterone into their weakly active forms estrone, Δ4-androstene-3,17-dione, and 5α-androstane-3,17-dione, respectively, thereby regulating cell- and tissue-specific steroid action. As reduced levels of active steroids are associated with compromised bone health and onset of osteoporosis, 17ß-HSD2 is considered a target for antiosteoporotic treatment. In this study, a pharmacophore model based on 17ß-HSD2 inhibitors was applied to a virtual screening of various databases containing natural products in order to discover new lead structures from nature. In total, 36 hit molecules were selected for biological evaluation. Of these compounds, 12 inhibited 17ß-HSD2 with nanomolar to low micromolar IC50 values. The most potent compounds, nordihydroguaiaretic acid (1), IC50 0.38 ± 0.04 µM, (-)-dihydroguaiaretic acid (4), IC50 0.94 ± 0.02 µM, isoliquiritigenin (6), IC50 0.36 ± 0.08 µM, and ethyl vanillate (12), IC50 1.28 ± 0.26 µM, showed 8-fold or higher selectivity over 17ß-HSD1. As some of the identified compounds belong to the same structural class, structure-activity relationships were derived for these molecules. Thus, this study describes new 17ß-HSD2 inhibitors from nature and provides insights into the binding pocket of 17ß-HSD2, offering a promising starting point for further research in this area.

Novel cases of Tunisian patients with mutations in the gene encoding 17ß-hydroxysteroid dehydrogenase type 3 and a founder effect.

17ß-Hydroxysteroid dehydrogenase type 3 (17ß-HSD3) is expressed almost exclusively in the testis and converts Δ4-androstene-3,17-dione to testosterone. Mutations in the HSD17B3 gene causing 17ß-HSD3 deficiency are responsible for a rare recessive form of 46, XY Disorders of Sex Development (46, XY DSD). We report novel cases of Tunisian patients with 17ß-HSD3 deficiency due to previously reported mutations, i.e. p.C206X and p.G133R, as well as a case with the novel compound heterozygous mutations p.C206X and p.Q176P. Moreover, the previously reported polymorphism p.G289S was identified in a heterozygous state in combination with a novel non-coding variant c.54G>T, also in a heterozygous state, in a male patient presenting with micropenis and low testosterone levels. The identification of four different mutations in a cohort of eight patients confirms the generally observed genetic heterogeneity of 17ß-HSD3 deficiency. Nevertheless, analysis of DNA from 272 randomly selected healthy controls from the same geographic area (region of Sfax) revealed a high carrier frequency for the p.C206X mutation of approximately 1 in 40. Genotype reconstruction of the affected pedigree members revealed that all p.C206X mutation carriers harbored the same haplotype, indicating inheritance of the mutation from a common ancestor. Thus, the identification of a founder effect and the elevated carrier frequency of the p.C206X mutation emphasize the importance to consider this mutation in the diagnosis and genetic counseling of affected 17ß-HSD3 deficiency pedigrees in Tunisia.

Disruption of steroidogenesis: Cell models for mechanistic investigations and as screening tools.

In the modern world, humans are exposed during their whole life to a large number of synthetic chemicals. Some of these chemicals have the potential to disrupt endocrine functions and contribute to the development and/or progression of major diseases. Every year approximately 1000 novel chemicals, used in industrial production, agriculture, consumer products or as pharmaceuticals, are reaching the market, often with limited safety assessment regarding potential endocrine activities. Steroids are essential endocrine hormones, and the importance of the steroidogenesis pathway as a target for endocrine disrupting chemicals (EDCs) has been recognized by leading scientists and authorities. Cell lines have a prominent role in the initial stages of toxicity assessment, i.e. for mechanistic investigations and for the medium to high throughput analysis of chemicals for potential steroidogenesis disrupting activities. Nevertheless, the users have to be aware of the limitations of the existing cell models in order to apply them properly, and there is a great demand for improved cell-based testing systems and protocols. This review intends to provide an overview of the available cell lines for studying effects of chemicals on gonadal and adrenal steroidogenesis, their use and limitations, as well as the need for future improvements of cell-based testing systems and protocols.

Biochemical analyses and molecular modeling explain the functional loss of 17ß-hydroxysteroid dehydrogenase 3 mutant G133R in three Tunisian patients with 46, XY Disorders of Sex Development.

Mutations in the HSD17B3 gene resulting in 17ß-hydroxysteroid dehydrogenase type 3 (17ß-HSD3) deficiency cause 46, XY Disorders of Sex Development (46, XY DSD). Approximately 40 different mutations in HSD17B3 have been reported; only few mutant enzymes have been mechanistically investigated. Here, we report novel compound heterozygous mutations in HSD17B3, composed of the nonsense mutation C206X and the missense mutation G133R, in three Tunisian patients from two non-consanguineous families. Mutants C206X and G133R were constructed by site-directed mutagenesis and expressed in HEK-293 cells. The truncated C206X enzyme, lacking part of the substrate binding pocket, was moderately expressed and completely lost its enzymatic activity. Wild-type 17ß-HSD3 and mutant G133R showed comparable expression levels and intracellular localization. The conversion of Δ4-androstene-3,17-dione (androstenedione) to testosterone was almost completely abolished for mutant G133R compared with wild-type 17ß-HSD3. To obtain further mechanistic insight, G133 was mutated to alanine, phenylalanine and glutamine. G133Q and G133F were almost completely inactive, whereas G133A displayed about 70% of wild-type activity. Sequence analysis revealed that G133 on 17ß-HSD3 is located in a motif highly conserved in 17ß-HSDs and other short-chain dehydrogenase/reductase (SDR) enzymes. A homology model of 17ß-HSD3 predicted that arginine or any other bulky residue at position 133 causes steric hindrance of cofactor NADPH binding, whereas substrate binding seems to be unaffected. The results indicate an essential role of G133 in the arrangement of the cofactor binding pocket, thus explaining the loss-of-function of 17ß-HSD3 mutant G133R in the patients investigated.

Ligand-based pharmacophore modeling and virtual screening for the discovery of novel 17ß-hydroxysteroid dehydrogenase 2 inhibitors.

17ß-Hydroxysteroid dehydrogenase 2 (17ß-HSD2) catalyzes the inactivation of estradiol into estrone. This enzyme is expressed only in a few tissues, and therefore its inhibition is considered as a treatment option for osteoporosis to ameliorate estrogen deficiency. In this study, ligand-based pharmacophore models for 17ß-HSD2 inhibitors were constructed and employed for virtual screening. From the virtual screening hits, 29 substances were evaluated in vitro for 17ß-HSD2 inhibition. Seven compounds inhibited 17ß-HSD2 with low micromolar IC50 values. To investigate structure-activity relationships (SAR), 30 more derivatives of the original hits were tested. The three most potent hits, 12, 22, and 15, had IC50 values of 240 nM, 1 µM, and 1.5 µM, respectively. All but 1 of the 13 identified inhibitors were selective over 17ß-HSD1, the enzyme catalyzing conversion of estrone into estradiol. Three of the new, small, synthetic 17ß-HSD2 inhibitors showed acceptable selectivity over other related HSDs, and six of them did not affect other HSDs.