Novel non-steroidal inhibitors of human 11beta-hydroxysteroid dehydrogenase type 1

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) regulates glucocorticoid action at the pre-receptor stage by converting cortisone to cortisol. 11β-HSD1 is selectively expressed in many tissues including the liver and adipose tissue where metabolic events are important. Metabolic syndrome relates to a number of metabolic abnormalities and currently has a prevalence of >20% in adult Americans. 11β-HSD1 inhibitors are being investigated by many major pharmaceutical companies for type 2 diabetes and other abnormalities associated with metabolic syndrome. In this area of intense interest a number of structural types of 11β-HSD1 inhibitor have been identified. It is important to have an array of structural types as the physicochemical properties of the compounds will determine tissue distribution, HPA effects, and ultimately clinical utility. Here we report the discovery and synthesis of three structurally different series of novel 11β-HSD1 inhibitors that inhibit human 11β-HSD1 in the low micromolar range. Docking studies with 1–3 into the crystal structure of human 11β-HSD1 reveal how the molecules may interact with the enzyme and cofactor and give further scope for structure based drug design in the optimisation of these series.     

Piperidine amides as 11beta-hydroxysteroid dehydrogenase type 1 inhibitors

A series of piperidine amide inhibitors of human 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) were identified via modifications of the HTS hit compound 1. The synthesis, in vitro biological evaluation, and structure-activity relationship of these compounds are presented.     

Androsterone 3beta-substituted derivatives as inhibitors of type 3 17beta-hydroxysteroid dehydrogenase

Androsterone derivatives substituted at position 3 were synthesized starting from dihydrotestosterone in a short sequence of reactions. They proved to be potent inhibitors (IC50 = 57-147 nM) of type 3 17beta-hydroxysteroid dehydrogenase, a key enzyme of steroidogenesis, which catalyzes the transformation of androstenedione to steroid active androgen testosterone.     

Phytoestrogens as inhibitors of fungal 17beta-hydroxysteroid dehydrogenase

Different phytoestrogens were tested as inhibitors of 17beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17beta-HSDcl), a member of the short-chain dehydrogenase/reductase superfamily. Phytoestrogens inhibited the oxidation of 100microM 17beta-hydroxyestra-4-en-3-one and the reduction of 100microM estra-4-en-3,17-dione, the best substrate pair known. The best inhibitors of oxidation, with IC(50) below 1microM, were flavones hydroxylated at positions 3, 5 and 7: 3-hydroxyflavone, 3,7-dihydroxyflavone, 5,7-dihydroxyflavone (chrysin) and 5-hydroxyflavone, together with 5-methoxyflavone. The best inhibitors of reduction were less potent; 3-hydroxyflavone, 5-methoxyflavone, coumestrol, 3,5,7,4'-tetrahydroxyflavone (kaempferol) and 5-hydroxyflavone, all had IC(50) values between 1 and 5microM. Docking the representative inhibitors chrysin and kaempferol into the active site of 17beta-HSDcl revealed the possible binding mode, in which they are sandwiched between the nicotinamide moiety and Tyr212. The structural features of phytoestrogens, inhibitors of both oxidation and reduction catalyzed by the fungal 17beta-HSD, are similar to the reported structural features of phytoestrogen inhibitors of human 17beta-HSD types 1 and 2.     

Oxazolones as potent inhibitors of 11beta-hydroxysteroid dehydrogenase type 1

2,5,5-Trisubstituted oxazolones were identified as potent inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). The synthesis, structure-activity relationship and metabolic stability of these compounds are presented.     

Phytoestrogens as inhibitors of fungal 17beta-hydroxysteroid dehydrogenase

Different phytoestrogens were tested as inhibitors of 17beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17beta-HSDcl), a member of the short-chain dehydrogenase/reductase superfamily. Phytoestrogens inhibited the oxidation of 100 microM 17beta-hydroxyestra-4-en-3-one and the reduction of 100 microM estra-4-en-3,17-dione, the best substrate pair known. The best inhibitors of oxidation, with IC(50) below 1 microM, were flavones hydroxylated at positions 3, 5 and 7: 3-hydroxyflavone, 3,7-dihydroxyflavone, 5,7-dihydroxyflavone (chrysin) and 5-hydroxyflavone, together with 5-methoxyflavone. The best inhibitors of reduction were less potent; 3-hydroxyflavone, 5-methoxyflavone, coumestrol, 3,5,7,4'-tetrahydroxyflavone (kaempferol) and 5-hydroxyflavone all had IC(50) values between 1 and 5 microM. Docking the representative inhibitors chrysin and kaempferol into the active site of 17beta-HSDcl revealed the possible binding mode, in which they are sandwiched between the nicotinamide moiety and Tyr212. The structural features of phytoestrogens, inhibitors of both oxidation and reduction catalyzed by the fungal 17beta-HSD, are similar to the reported structural features of phytoestrogen inhibitors of human 17beta-HSD types 1 and 2.     

Novel enzymological profiles of human 11beta-hydroxysteroid dehydrogenase type 1

The human enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD) catalyzes the reversible oxidoreduction of 11beta-OH/11-oxo groups of glucocorticoid hormones. Besides this important endocrinological property, the type 1 isozyme (11beta-HSD1) mediates reductive phase I reactions of several carbonyl group bearing xenobiotics, including drugs, insecticides and carcinogens. The aim of this study was to explore novel substrate specificities of human 11beta-HSD1, using heterologously expressed protein in the yeast system Pichia pastoris. In addition to established phase I xenobiotic substrates, it is now demonstrated that transformed yeast strains catalyze the reduction of ketoprofen to its hydroxy metabolite, and the oxidation of the prodrug DFU-lactol to the pharmacologically active lactone compound. Purified recombinant 11beta-HSD1 mediated oxidative reactions, however, the labile reductive activity component could not be maintained. In conclusion, evidence is provided that human 11beta-HSD1 in vitro is involved in phase I reactions of anti-inflammatory non-steroidal drugs like ketoprofen and DFU-lactol.     

Characterization of type 12 17beta-hydroxysteroid dehydrogenase, an isoform of type 3 17beta-hydroxysteroid dehydrogenase responsible for estradiol formation in women

A novel 17beta-hydroxysteroid dehydrogenase (17beta-HSD) chronologically named type 12 17beta-HSD (17beta-HSD12), that transforms estrone (E1) into estradiol (E2) was identified by sequence similarity with type 3 17beta-HSD (17beta-HSD3) that catalyzes the formation of testosterone from androstenedione in the testis. Both are encoded by large genes spanning 11 exons, most of them showing identical size. Using human embryonic kidney-293 cells stably expressing 17beta-HSD12, we have found that the enzyme catalyzes selectively and efficiently the transformation of E1 into E2, thus identifying its role in estrogen formation, in contrast with 17beta-HSD3, the enzyme involved in the biosynthesis of the androgen testosterone in the testis. Using real-time PCR to quantify mRNA in a series of human tissues, the expression levels of 17beta-HSD12 as well as two other enzymes that perform the same transformation of E1 into E2, namely type 1 17beta-HSD and type 7 17beta-HSD, it was found that 17beta-HSD12 mRNA is the most highly expressed in the ovary and mammary gland. To obtain a better understanding of the structural basis of the difference in substrate specificity between 17beta-HSD3 and 17beta-HSD12, we have performed tridimensional structure modelization using the coordinates of type 1 17beta-HSD and site-directed mutagenesis. The results show the potential role of bulky amino acid F234 in 17beta-HSD12 that blocks the entrance of androstenedione. Overall, our results strongly suggest that 17beta-HSD12 is the major estrogenic 17beta-HSD responsible for the conversion of E1 to E2 in women, especially in the ovary, the predominant source of estrogens before menopause.     

Bis-aryl triazoles as selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1

3-Aryl-5-phenyl-(1,2,4)-triazoles were identified as selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). They are active in both in vitro and an in vivo mouse pharmacodynamic (PD) model. The synthesis and structure activity relationships are presented.     

Adamantyl triazoles as selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1

Adamantyl triazoles were identified as selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). They are active both in in vitro and in in vivo pharmacodynamic models. The synthesis and structure-activity relationships of these inhibitors are presented.     

Distinctive molecular inhibition mechanisms for selective inhibitors of human 11beta-hydroxysteroid dehydrogenase type 1

11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) catalyzes the NADPH dependent interconversion of inactive cortisone to active cortisol. Excess 11beta-HSD1 or cortisol leads to insulin resistance and metabolic syndrome in animal models and in humans. Inhibiting 11beta-HSD1 activity signifies a promising therapeutic strategy in the treatment of Type 2 diabetes and related diseases. Herein, we report two highly potent and selective small molecule inhibitors of human 11beta-HSD1. While compound 1, a sulfonamide, functions as a simple substrate competitive inhibitor, compound 2, a triazole, shows the kinetic profile of a mixed inhibitor. Co-crystal structures reveal that both compounds occupy the 11beta-HSD1 catalytic site, but present distinct molecular interactions with the protein. Strikingly, compound 2 interacts much closer to the cofactor NADP+ and likely modifies its binding. Together, the structural and kinetic analyses demonstrate two distinctive molecular inhibition mechanisms, providing valuable information for future inhibitor design.     

Oxidative 3alpha-hydroxysteroid dehydrogenase activity of human type 10 17beta-hydroxysteroid dehydrogenase

In vitro enzyme assays have demonstrated that human type 10 17beta-hydroxysteroid dehydrogenase (17beta-HSD10) catalyzes the oxidation of 5alpha-androstane-3alpha,17beta-diol (adiol), an almost inactive androgen, to dihydrotestosterone (DHT) rather than androsterone or androstanedione. To further investigate the role of this steroid-metabolizing enzyme in intact cells, we produced stable transfectants expressing 17beta-HSD10 or its catalytically inactive Y168F mutant in human embryonic kidney (HEK) 293 cells. It was found that DHT levels in HEK 293 cells expressing 17beta-HSD10, but not its catalytically inactive mutant, will dramatically increase if adiol is added to culture media. Moreover, certain malignant prostatic epithelial cells have more 17beta-HSD10 than normal controls, and can generate DHT, the most potent androgen, from adiol. This event might promote prostate cancer growth. Analysis of the 17beta-HSD10 sequence shows that this enzyme does not have any ER retention signal or transmembrane segments and has not originated by divergence from a retinol dehydrogenase. The data suggest that the unique mitochondrial location of this HSD [Eur. J. Biochem. 268 (2001) 4899] does not prevent it from oxidizing the 3alpha-hydroxyl group of a C19 sterol in living cells. The experimental results lead to the conclusion that mitochondrial 17beta-HSD10 plays a significant part in a non-classical androgen synthesis pathway along with microsomal retinol dehydrogenases.     

Rational design of novel mutants of fungal 17beta-hydroxysteroid dehydrogenase

Reduction of 17-ketosteroids is a biocatalytic process of economic significance for the production of steroid drugs. This reaction can be catalyzed by different microbial 17beta-hydroxysteroid dehydrogenases (17beta-HSD), like the 17beta-HSD activity of Saccharomyces cerevisiae, Pichia faranosa and Mycobacterium sp., and by purified 3beta,17beta-HSD from Pseudomonas testosteroni. In addition to the bacterial 3beta,17beta-HSD the 17beta-HSD of the filamentous fungus Cochliobolus lunatus is the only microbial 17beta-HSD that has been expressed as a recombinant protein and fully characterized. On the basis of its modeled 3D structure, we selected several positions for the replacement of amino acids by site-directed mutagenesis to change substrate specificity, alter coenzyme requirements, and improve overall catalytic activity. Replacement of Val161 and Tyr212 in the substrate-binding region by Gly and Ala, respectively, increased the initial rates for the conversion of androstenedione to testosterone. Replacement of Tyr49 within the coenzyme binding site by Asp changed the coenzyme specificity of the enzyme. This latter mutant can convert the steroids not only in the presence of NADP(+) and NADPH, but also in the presence of NADH and NAD(+). The replacement of His164, located in the non-flexible part of the 'lid' covering the active center resulted in a conformation of the enzyme that possessed a higher catalytic activity.     

Pyridine amides as potent and selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1

Several series of pyridine amides were identified as selective and potent 11beta-HSD1 inhibitors. The most potent inhibitors feature 2,6- or 3,5-disubstitution on the pyridine core. Various linkers (CH(2)SO(2), CH(2)S, CH(2)O, S, O, N, bond) between the distal aryl and central pyridyl groups are tolerated, and lipophilic amide groups are generally favored. On the distal aryl group, a number of substitutions are well tolerated. A crystal structure was obtained for a complex between 11beta-HSD1 and the most potent inhibitor in this series.     

Chalcones are potent inhibitors of aromatase and 17beta-hydroxysteroid dehydrogenase activities

Chalcones were tested for estimating anti-aromatase, anti-3beta-hydroxysteroid dehydrogenase delta5/delta4 isomerase (3beta-HSD) and anti-17beta-hydroxysteroid dehydrogenase (17beta-HSD) activities in human placental microsomes. In the present study, we have demonstrated for the first time that chalcones are potent inhibitors of aromatase and 17beta-hydroxysteroid dehydrogenase activities: these enzymes being considered as important targets in the metabolic pathways of human mammary hormone-dependent cells. Our results showed that naringenin chalcone and 4-hydroxychalcone were the most effective aromatase and 17beta-hydroxysteroid dehydrogenase inhibitors with IC50 values of 2.6 and 16 microM respectively. In addition, inhibitory effects of some flavones and flavanones were compared to those of the corresponding chalcones. A structure-activity relationship was established and regions or/and substituents essential for these inhibitory activities were determined.     

4,5-Disubstituted cis-pyrrolidinones as inhibitors of type II 17beta-hydroxysteroid dehydrogenase. Part 2. SAR

4,5-Disubstituted cis-pyrrolidinones were investigated as inhibitors of type II 17beta-hydroxysteroid dehydrogenase (17beta-HSD). Early structure-activity relationship patterns for this class of compounds are discussed.     

Evidence for sulfatase and 17beta-hydroxysteroid dehydrogenase type 1 activities in equine epididymis and uterus

Our previous work showed that stallion testis produces high amounts of estrogens which are subsequently found in the ejaculate. These estrogens are mainly synthesized by testicular aromatase, and the major estrogen produced is estrone sulfate (E1S). The objective of this study was to investigate the potential role of E1S as a source of estrogens in the male and female horse reproductive tracts by determining whether both estrone sulfatase (Sulf) and 17beta-hydroxysteroid dehydrogenase type I (17beta-HSD1) activities were present in equine testes, epididymis and uterus. We assessed E1S bioconversion into estrone (E1) and estradiol (E2) in these tissues. Both Sulf and 17beta-HSD1 activities were well detected in the cauda epididymis and uterus. Additionally, Sulf activity was present in the distal corpus of the epididymis, and 17beta-HSDI in the proximal corpus. In contrast, aromatase gene expression, measured as an internal control of endogenous estrogen production, had high activity only in the testis. We found that seminal E1S of testicular origin can be metabolized to E2, especially in the cauda epididymis and uterus. Because E2 appears to play a major role in male and female reproduction, we propose that the bioconversion of seminal E1S could affect male and female fertility.     

Characterization and localization of human type10 17beta-hydroxysteroid dehydrogenase.

The tissue distribution, subcellular localization, and metabolic functions of human 17beta-hydroxysteroid dehydrogenase type 10/short chain L-3-hydroxyacyl-CoA dehydrogenase have been investigated. Human liver and gonads are abundant in this enzyme, but it is present in only negligible amounts in skeletal muscle. Its N-terminal sequence is a mitochondrial targeting sequence, but is not required for directing this protein to mitochondria. Immunocytochemical studies demonstrate that this protein, which has been referred to as ER-associated amyloid beta-binding protein (ERAB), is not detectable in the ER of normal tissues. We have established that protocols employed to investigate the subcellular distribution of ERAB yield ER fractions rich in mitochondria. Mitochondria-associated membrane fractions believed to be ER fractions were employed in ERAB/Abeta-binding alcohol dehydrogenase studies. The present studies establish that in normal tissues this protein is located in mitochondria. This feature distinguishes it from all known 17beta-hydroxysteroid dehydrogenases, and endows mitochondria with the capability of modulating intracellular levels of the active forms of sex steroids.