Structure-activity relationships of 2alpha-substituted androstenedione analogs as aromatase inhibitors and their aromatization reactions

Genetic Variations rs859, rs4646, and rs372883 in the 3'-Untranslated Regions of Genes Are Associated with a Risk of IgA Nephropathy

BACKGROUND

Previous studies indicate that genetic factors play an important role in the pathogenesis of IgA nephropathy (IgAN). To evaluate the association between single nucleotide polymorphisms (SNPs) in the 3'-untranslated region (3'-UTR) of genes and IgAN risk, we performed a case-control study in a Chinese Han population.

MATERIALS

Twelve SNPs were selected and genotyped in 384 IgAN patients and 357 healthy controls. Odds ratio (OR) and 95% confidence intervals (CI) were calculated by logistic regression adjusted for age and gender. Multifactor dimensionality reduction (MDR) was used to analyze the interaction of SNP-SNP with IgAN risk.

RESULTS

Our study demonstrated that IL-16 rs859 (OR = 0.75, p = 0.040) and CYP19A1 rs4646 (OR = 2.58, p = 0.017) polymorphism were related to the risk of IgAN. In stratified analyses by gender, CYP19A1 rs4646 (OR = 2.96, p = 0.015) and BACH1 rs372883 (OR = 1.81, p = 0.038) polymorphisms conferred susceptibility to IgAN in males. Besides, rs372883 reduced IgAN risk in females (OR = 0.44, p = 0.042). We also found rs859 polymorphism was correlated with grade I-II (OR = 0.42, p = 0.028) in subgroup analysis of Lee's classification. Additionally, we found rs4646 polymorphism was correlated with serum creatinine (p = 0.035).

CONCLUSION

Our results suggested that the IL-16 rs859, CYP19A1 rs4646, and BACH1 rs372883 polymorphisms have potential roles in the genetic susceptibility to IgAN in Chinese Han population.

Deep Learning to Predict the Formation of Quinone Species in Drug Metabolism

Many adverse drug reactions are thought to be caused by electrophilically reactive drug metabolites that conjugate to nucleophilic sites within DNA and proteins, causing cancer or toxic immune responses. Quinone species, including quinone-imines, quinone-methides, and imine-methides, are electrophilic Michael acceptors that are often highly reactive and comprise over 40% of all known reactive metabolites. Quinone metabolites are created by cytochromes P450 and peroxidases. For example, cytochromes P450 oxidize acetaminophen to N-acetyl-p-benzoquinone imine, which is electrophilically reactive and covalently binds to nucleophilic sites within proteins. This reactive quinone metabolite elicits a toxic immune response when acetaminophen exceeds a safe dose. Using a deep learning approach, this study reports the first published method for predicting quinone formation: the formation of a quinone species by metabolic oxidation. We model both one- and two-step quinone formation, enabling accurate quinone formation predictions in nonobvious cases. We predict atom pairs that form quinones with an AUC accuracy of 97.6%, and we identify molecules that form quinones with 88.2% AUC. By modeling the formation of quinones, one of the most common types of reactive metabolites, our method provides a rapid screening tool for a key drug toxicity risk. The XenoSite quinone formation model is available at http://swami.wustl.edu/xenosite/p/quinone .

Recent developments in steroidal and nonsteroidal aromatase inhibitors for the chemoprevention of estrogen-dependent breast cancer

Aromatase, a cytochrome P450 enzyme complex present in breast tissues, plays a significant role in the biosynthesis of important endogenous estrogens from androgens. The source of estrogen production in breast cancer tissues is intra-tumoral aromatase, and inhibition of aromatase may inhibit the growth stimulation effect of estrogens in breast cancer tissues. Consequently, aromatase is considered a useful therapeutic target in the treatment and prevention of estrogen-dependent breast cancer. Recently, different natural products and synthetic compounds have been rapidly developed, studied, and evaluated for aromatase inhibitory activity. Aromatase inhibitors are classified into two categories on the basis of their chemical structures, i.e., steroidal and nonsteroidal aromatase inhibitors. This review highlights the synthetic steroidal and nonsteroidal aromatase inhibitors reported in the literature in the last few years and will aid medicinal chemists in the design and synthesis of novel and pharmacologically-potent aromatase inhibitors for the treatment of breast cancer.

Short Stature in Chronic Kidney Disease Treated with Growth Hormone and an Aromatase Inhibitor

We describe an alternative strategy for management of severe growth failure in a 14-year-old child who presented with advanced chronic kidney disease close to puberty. The patient was initially treated with growth hormone for a year until kidney transplantation, followed immediately by a year-long course of an aromatase inhibitor, anastrozole, to prevent epiphyseal fusion and prolong the period of linear growth. Outcome was excellent, with successful transplant and anticipated complete correction of height deficit. This strategy may be appropriate for children with chronic kidney disease and short stature who are in puberty.

Current status on development of steroids as anticancer agents

Steroids are important biodynamic agents. Their affinities for various nuclear receptors have been an interesting feature to utilize them for drug development particularly for receptor mediated diseases. Steroid biochemistry and its crucial role in human physiology, has attained importance among the researchers. Recent years have seen an extensive focus on modification of steroids. The rational modifications of perhydrocyclopentanophenanthrene nucleus of steroids have yielded several important anticancer lead molecules. Exemestane, SR16157, fulvestrant and 2-methoxyestradiol are some of the successful leads emerged on steroidal pharmacophores. The present review is an update on some of the steroidal leads obtained during past 25 years. Various steroid based enzyme inhibitors, antiestrogens, cytotoxic conjugates and steroidal cytotoxic molecules of natural as well as synthetic origin have been highlighted. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Molecular docking and QSAR studies of aromatase inhibitor androstenedione derivatives

Objectives

Aromatase (CYP19) inhibitors have emerged as promising candidates for the treatment of estrogen-dependent breast cancer. In this study, a series of androstenedione derivatives with CYP19 inhibitory activity was subjected to a molecular docking study followed by quantitative structure–activity relationship (QSAR) analyses in search of ideal physicochemical characteristics of potential aromatase inhibitors.

Methods

The QSAR studies were carried out using both two-dimensional (topological, and structural) and three-dimesional (spatial) descriptors. We also used thermodynamic parameters along with 2D and 3D descriptors. Genetic function approximation (GFA) and genetic partial least squares (G/PLS) were used as chemometric tools for QSAR modelling.

Key findings

The docking study indicated that the important interacting amino acids in the active site were Met374, Arg115, Ile133, Ala306, Thr310, Asp309, Val370, Leu477 and Ser478. The 17-keto oxygen of the ligands is responsible for the formation of a hydrogen bond with Met374 and the remaining parts of the molecules are stabilized by the hydrophobic interactions with the non-polar amino acids. The C2 and C19 positions in the ligands are important for maintaining the appropriate orientation of the molecules in the active site. The results of docking experiments and QSAR studies supported each other.

Conclusions

The developed QSAR models indicated the importance of some Jurs parameters, structural parameters, topological branching index and E-state indices of different fragments. All the developed QSAR models were statistically significant according to the internal and external validation parameters.

Aromatase inactivation by 2-substituted derivatives of the suicide substrate androsta-1,4-diene-3,17-dione

To gain the structure-activity relationship of Delta(1)-androstenediones (Delta(1)-ADs) as mechanism-based inactivator of aromatase, series of 2-alkyl- and 2-alkoxy-substituted Delta(1)-ADs (6 and 9) as well as 2-bromo-Delta(1)-AD (14) were synthesized and tested. All of the inhibitors examined blocked aromatase in human placental microsomes in a competitive manner. In a series of 2-alkyl-Delta(1)-ADs (6), n-hexyl compound 6f was the most powerful inhibitor with an apparent K(i) value of 31 nM. The inhibitory activities of 2-alkoxy steroids 9 decreased in relation to length of the alkyl chain up to n-hexyloxy group (K(i): 95 nM for methoxy 9a). All of the alkyl steroids 6 along with the alkoxy steroid 9, except for the ethyl and n-propyl compounds 6b and 6c, caused a time-dependent inactivation of aromatase. The inactivation rates (k(inact): 0.020-0.084 min(-1)) were comparable to that of the parent compound Delta(1)-AD. The inactivation was prevented by the substrate AD, and no significant effect of l-cysteine on the inactivation was observed in each case. The results indicate that the 2-hexyl compound 6f act as the most powerful mechanism-based inactivator of aromatase among Delta(1)-AD analogs and may be submitted to the preclinical study in estrogen-dependent breast cancer.

Structural characteristics of anabolic androgenic steroids contributing to binding to the androgen receptor and to their anabolic and androgenic activities. Applied modifications in the steroidal structure

Anabolic androgenic steroids (AAS) are synthetic derivatives of testosterone introduced for therapeutic purposes providing enhanced anabolic potency with reduced androgenic effects. Androgens mediate their action through their binding to the androgen receptor (AR) which is mainly expressed in androgen target tissues, such as the prostate, skeletal muscle, liver and central nervous system. This paper reviews some of the wide spectrum of testosterone and synthetic AAS structure modifications related to the intended enhancement in anabolic activity. The structural features of steroids necessary for effective binding to the AR and those which contribute to the stipulation of the androgenic and anabolic activities are also presented.

Use of aromatase inhibitors in children and adolescents with disorders of growth and adolescent development

Although treatment of children and adolescents who have disorders of growth and adolescent development with aromatase inhibitors is increasingly common, data for or against their use are extremely limited. Precocious puberty, short stature, and gynecomastia are conditions for which inhibition of the enzyme aromatase might prove beneficial to reduce clinical signs of estrogenization and/or estrogen-mediated skeletal maturation. In this report, we summarize the published data regarding the use of aromatase inhibitors in these conditions, and review known and potential benefits, safety concerns, and shortcomings of the available information.

Biochemical aromatization of 2-methyleneandrostenedione: stereochemistry of hydrogen removal at the C-1 position

To explore a stereochemistry of hydrogen removal at C-1 of the powerful aromatase inhibitor 2-methyleneandrostenedione (1), of which the A-ring conformation is markedly different from that of the natural substrate androstenedione (AD), in the course of the aromatase-catalyzed A-ring aromatization producing 2-methylestrone (2), we synthesized [1alpha-2H]labeled steroid 1 and its [1beta-2H]stereoisomer, and the metabolic fate of the C-1 deuterium in aromatization was analyzed by gas chromatography-mass spectrometry (GC-MS) in each. Parallel experiments with the natural substrates [1alpha-2H] and [1beta-2H]ADs were also carried out. The GC-MS analysis indicated that 2-methyl estrogen 2 produced from [1alpha-2H]labeled substrate 1 retained completely the 1alpha-deuterium (1beta-H elimination), while product 2 obtained from [1beta-2H]isomer 1 lost completely the 1beta-deuterium. Stereospecific 1beta-hydrogen elimination was also observed in the parallel experiments with the labeled ADs as established previously. The results indicate that biochemical aromatization of the 2-methylene steroid 1 proceeds through the 1beta-hydrogen removal concomitant with cleavage of the C(10)-C(19) bond, yielding 1(10),4-dienone 9, in a similar manner to that involved in AD aromatization. This would give additional evidence for the stereomechanisms for the last step of aromatization of AD, requiring the stereospecific 1beta-hydrogen abstraction and cleavage of the C(10)-C(19) bond, and for the enolization of a carbonyl group at C-3 in the A-ring aromatization.

Gas chromatography-mass spectrometric study of 19-oxygenation of the aromatase inhibitor 19-methylandrostenedione with human placental microsomes

To gain insight into the catalytic function of aromatase, we studied 19-oxygenation of 19-methyl-substituted derivative of the natural substrate androstenedione (AD), compound 1, with human placental aromatase by use of gas chromatography-mass spectrometry (GC-MS). Incubation of the 19-methyl derivative 1 with human placental microsomes in the presence of NADPH under an aerobic condition did not yield a detectable amount of [19S]19-hydroxy product 2 or its [19R]-isomer 3 when the product was analyzed as the bis-methoxime-trimethylsilyl (TMS) derivative by GC-MS; moreover, the production of estrogen was not detected as the bis-TMS derivative of estradiol (detection limit: about 3 ng and 10 pg per injection for the 19-ol and estradiol, respectively). The results reveal that the 19-methyl steroid 1 does not serve as a substrate of aromatase, although it does serve as a powerful inhibitor of the enzyme.

Steroids: partial synthesis in medicinal chemistry

This article reviews the progress in the chemistry of the steroids that was published between January and December 2005. The reactions and partial synthesis of estrogens, androgens, pregnanes, bile acid derivatives, cholestanes and vitamin D analogues are covered. There are 139 references.