Inhibition of human CYP19 by azoles used as antifungal agents and aromatase inhibitors, using a new LC–MS/MS method for the analysis of estradiol product formation

Triazoles in Medicinal Chemistry: Physicochemical Properties, Bioisosterism, and Application

Triazole demonstrates distinctive physicochemical properties, characterized by weak basicity, various dipole moments, and significant dual hydrogen bond acceptor and donor capabilities. These features are poised to play a pivotal role in drug-target interactions. The inherent polarity of triazole contributes to its lower logP, suggesting the potential improvement in water solubility. The metabolic stability of triazole adds additional value to drug discovery. Moreover, the metal-binding capacity of the nitrogen atom lone pair electrons of triazole has broad applications in the development of metal chelators and antifungal agents. This Perspective aims to underscore the unique physicochemical attributes of triazole and its application. A comparative analysis involving triazole isomers and other heterocycles provides guiding insights for the subsequent design of triazoles, with the hope of offering valuable considerations for designing other heterocycles in medicinal chemistry.

Exposure to topiramate and acetazolamide causes endocrine disrupting effects in female rats during estrus

BACKGROUND

Idiopathic intracranial hypertension (IIH) is a disease characterized by elevated intracranial pressure (ICP) and is a disease of young females. The first line pharmacological treatments include acetazolamide and topiramate and given the nature of IIH patients and the dosing regimen of these drugs, their effect on the endocrine system is important to evaluate. We aimed to assess the effects of acetazolamide and topiramate on steroid profiles in relevant endocrine tissues.

METHODS

Female Sprague Dawley rats received chronic clinically equivalent doses of acetazolamide or topiramate by oral gavage and were sacrificed in estrus. Tissue specific steroid profiles of lateral ventricle CP, 4th ventricle CP, CSF, serum, uterine horn and fundus, ovaries, adrenal glands and pituitary glands were assessed by quantitative targeted LC-MS/MS. We determined luteinizing hormone (LH) and follicle stimulating hormones (FSH) levels in paired serum by ELISA.

RESULTS

Topiramate increased the concentration of estradiol and decreased the concentration of DHEA in lateral choroid plexus. Moreover, it decreased the concentration of androstenediol in the pituitary gland. Topiramate increased serum LH. Acetazolamide decreased progesterone levels in serum and uterine fundus and increased corticosteroid levels in the adrenal glands.

CONCLUSION

These results demonstrate that both acetazolamide and topiramate have endocrine disrupting effects in rats. Topiramate primarily targeted the choroid plexus and the pituitary gland while acetazolamide had broader systemic effects. Furthermore, topiramate predominantly targeted sex hormones, whereas acetazolamide widely affected all classes of hormones. A similar effect in humans has not yet been documented but these concerning findings warrants further investigations.

Impaired spermatogenesis and associated endocrine effects of azole fungicides in peripubertal Xenopus tropicalis

Early life exposure to endocrine disrupting chemicals (EDCs) has been suggested to adversely affect reproductive health in humans and wildlife. Here, we characterize endocrine and adverse effects on the reproductive system after juvenile exposure to propiconazole (PROP) or imazalil (IMZ), two common azole fungicides with complex endocrine modes of action. Using the frog Xenopus tropicalis, two short-term (2-weeks) studies were conducted. I: Juveniles (2 weeks post metamorphosis (PM)) were exposed to 0, 17 or 178 µg PROP/L. II: Juveniles (6 weeks PM) were exposed to 0, 1, 12 or 154 µg IMZ/L. Histological analysis of the gonads revealed an increase in the number of dark spermatogonial stem cells (SSCs)/testis area, and in the ratio secondary spermatogonia: dark SSCs were increased in all IMZ groups compared to control. Key genes in gametogenesis, retinoic acid and sex steroid pathways were also analysed in the gonads. Testicular levels of 3β-hsd, ddx4 were increased and cyp19 and id4 levels were decreased in the IMZ groups. In PROP exposed males, increased testicular aldh1a2 levels were detected, but no histological effects observed. Although no effects on ovarian histology were detected, ovarian levels of esr1, rsbn1 were increased in PROP groups, and esr1 levels were decreased in IMZ groups. In conclusion, juvenile azole exposure disrupted testicular expression of key genes in retinoic acid (PROP) and sex steroid pathways and in gametogenesis (IMZ). Our results further show that exposure to environmental concentrations of IMZ disrupted spermatogenesis in the juvenile testis, which is a cause for concern as it may lead to impaired fertility. Testicular levels of id4, ddx4 and the id4:ddx4 ratio were associated with the number of dark SSCs and secondary spermatogonia suggesting that they may serve as a molecular markers for disrupted spermatogenesis.

EDC-Predictor: A Novel Strategy for Prediction of Endocrine-Disrupting Chemicals by Integrating Pharmacological and Toxicological Profiles

Identification of endocrine-disrupting chemicals (EDCs) is crucial in the reduction of human health risks. However, it is hard to do so because of the complex mechanisms of the EDCs. In this study, we propose a novel strategy named EDC-Predictor to integrate pharmacological and toxicological profiles for the prediction of EDCs. Different from conventional methods that only focus on a few nuclear receptors (NRs), EDC-Predictor considers more targets. It uses computational target profiles from network-based and machine learning-based methods to characterize compounds, including both EDCs and non-EDCs. The best model constructed by these target profiles outperformed those models by molecular fingerprints. In a case study to predict NR-related EDCs, EDC-Predictor showed a wider applicability domain and higher accuracy than four previous tools. Another case study further demonstrated that EDC-Predictor could predict EDCs targeting other proteins rather than NRs. Finally, a free web server was developed to make EDC prediction easier (http://lmmd.ecust.edu.cn/edcpred/). In summary, EDC-Predictor would be a powerful tool in EDC prediction and drug safety assessment.

Non-target biotransformation enzymes as a target for triazole-zinc mixtures

Triazoles inhibit lanosterol 14α-demethylase and block ergosterol biosynthesis in fungal pathogens. However, they also interact with other cytochrome P450 enzymes and influence non-target metabolic pathways. Disturbingly, triazoles may interact with essential elements. The interaction of penconazole (Pen), cyproconazole (Cyp) and tebuconazole (Teb) with Zn2+ results in the formation of deprotonated ligands in their complexes or in the creation of complexes with Cl- as a counterion or doubly charged complexes. Triazoles, as well as their equimolar cocktails with Zn2+ (10-6 mol/L), decreased the activities of the non-target enzymes CYP19A1 and CYP3A4. Pen most decreased CYP19A1 activity and was best bound to its active centre to block the catalytic cycle in computational analysis. For CYP3A4, Teb was found to be the most effective inhibitor by both, activity assay and interaction with the active centre. Teb/Cyp/Zn2+ and Teb/Pen/Cyp/Zn2+ cocktails also decreased the CYP19A1 activity, which was in correlation with the formation of numerous triazole-Zn2+ complexes.

Triazoles as a Potential Threat to the Nutritional Quality of Tomato Fruits

Triazole fungicides can threaten plants as abiotic stressors but can also positively affect plant defense by inducing priming. Thus, plant yield is also both protected and endangered by triazoles that may influence several metabolic pathways during maturation processes, such as the biosynthesis of saccharides or secondary metabolites. Here, Solanum lycopersicum L. plants were exposed to foliar and soil applications of penconazole, tebuconazole, or their combination, and their resulting effect on tomato fruits was followed. The exposure to the equimolar mixture of both triazoles influenced the representation of free proteinogenic amino acids, especially Gln, Glu, Gly, Ile, Lys, Ser and Pro, saccharide content, and led to a significant increase in the contents of total phenolics and flavonoids as well as positive stimulation of the non-enzymatic antioxidant system. Among the identified secondary metabolites, the most abundant was naringenin, followed by chlorogenic acid in tomato peel. In turn, all triazole-treated groups showed a significantly lower content of rosmarinic acid in comparison with the control. Foliar application of penconazole affected the fruit more than other single triazole applications, showing a significant decrease in antioxidant capacity, the total content of secondary metabolites, and the activities of total membrane-bound peroxidases and ascorbate peroxidase.

DectiSomes: C-type lectin receptor-targeted liposomes as pan-antifungal drugs

Combatting the ever-increasing threat from invasive fungal pathogens faces numerous fundamental challenges, including constant human exposure to large reservoirs of species in the environment, the increasing population of immunocompromised or immunosuppressed individuals, the unsatisfactory efficacy of current antifungal drugs and their associated toxicity, and the scientific and economic barriers limiting a new antifungal pipeline. DectiSomes represent a new drug delivery platform that enhances antifungal efficacy for diverse fungal pathogens and reduces host toxicity for current and future antifungals. DectiSomes employ pathogen receptor proteins - C-type lectins - to target drug-loaded liposomes to conserved fungal cognate ligands and away from host cells. DectiSomes represent one leap forward for urgently needed effective pan-antifungal therapy. Herein, we discuss the problems of battling fungal diseases and the state of DectiSome development.

Stereoselective Toxicokinetic and Distribution Study on the Hexaconazole Enantiomers in Mice

Hexaconazole (Hex) has been widely used in agricultural products, and its residues may pose a potential risk to human health. However, the metabolic behavior of Hex enantiomers in mammal organisms is still unknown, which is important for evaluating the differences in their toxicity. In this study, the distribution of S-(+)- and R-(-)-Hex in mice was detected by an ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS), and the mechanism differences in the toxicokinetic behavior were analyzed by molecular docking. Good linearities, accuracies, and precisions were achieved for S-(+)- and R-(-)-Hex, with recoveries of 88.7~104.2% and RSDs less than 9.45% in nine tissues of mice. This established method was then used to detect the toxicokinetic of Hex enantiomers in mice after oral administration within 96 h. The results showed that the half-lives of S-(+)- and R-(-)-Hex were 3.07 and 3.71 h in plasma. Hex was mainly accumulated in the liver, followed by the kidneys, brain, lungs, spleen, and heart. The enantiomeric fraction (EF) values of Hex enantiomers in most of the samples were below 1, indicating that S-(+)-Hex decreased faster than its antipode. The molecular docking showed that the binding of S-(+)-Hex with P450arom was much more stable than R-(-)-Hex, which verified the fact that S-(+)-Hex was prefer to decrease in most of the tissues. The results of this study could be helpful for further evaluating the potential toxic risk of Hex enantiomers and for the development and usage of its pure monomer.

Investigation of Novel Quinoline-Thiazole Derivatives as Antimicrobial Agents: In Vitro and In Silico Approaches

Infectious diseases are a major concern around the world. Today, it is an urgent need for new chemotherapeutics for infectious diseases. Because of that, our group designed, synthesized, and analyzed 14 new quinoline derivatives endowed with the pharmacophore moiety of fluoroquinolones primarily for their antimicrobial effects. Their cytotoxicity effects were tested against six bacterial and four fungal strains and NIH/3T3 cell line. Additionally, their action mechanisms were evaluated against DNA gyrase and lanosterol 14α-demethylase (LMD). Furthermore, to eliminate the potential side effects, the active compounds were evaluated against the aromatase enzyme. The experimental enzymatic results were evaluated for active compounds' binding modes using molecular docking and molecular dynamics simulation studies. The results were utilized to clarify the structure-activity relationship (SAR). Finally, compound 4m was the most potent compound for its antifungal activity with low cytotoxicity against healthy cells and fewer possible side effects, while compounds 4j and 4l can be used alone for special patients who are suffering from fungal infections in addition to the primer disease.

The effect of conazoles on reproductive organs structure and function – a review

Conazoles are azole antifungals used in agricultural and pharmaceutical products. Exposure to conazole fungicides leads to several toxic endpoints, including reproductive and endocrine. The results of animal experiments have shown that various conazole fungicides at high doses affect the structure and functions of reproductive organs. In males, adverse effects of conazole fungicides are manifested in the testes, prostate, sperm viability, fertility and sexual behaviour. Reduced testis weight, testis atrophy and reduced or absent sperm production were frequently observed. In female genitalia, structural changes in the ovaries and uterus have been observed. The extent of the changes depends on the dose and duration of treatment. Triazoles affected the expression of multiple genes involved in steroid hormone metabolism and modulate enzyme activity of multiple cytochrome P450 (CYP) and other metabolic enzymes in mammalian liver and other tissues. Conazole fungicides act as endocrine disruptors. Conazoles have been reported to reduce oestradiol and testosterone production and to increase progesterone concentration, indicating the inhibition of enzymes involved in the conversion of progesterone to testosterone. The reproductive effects are consistent with impairment of testosterone homeostasis. The disruption in steroid homeostasis is a common mode of action, leading to abnormal reproductive development and diminished reproductive function. At high doses, azole fungicides affect reproductive organs and fertility in several species.

Azole Fungicides and Their Endocrine Disrupting Properties: Perspectives on Sex Hormone-Dependent Reproductive Development

Azoles are antifungal agents used in both agriculture and medicine. They typically target the CYP51 enzyme in fungi and, by so doing, disrupt cell membrane integrity. However, azoles can also target various CYP enzymes in mammals, including humans, which can disrupt hormone synthesis and signaling. For instance, several azoles can inhibit enzymes of the steroidogenic pathway and disrupt steroid hormone biosynthesis. This is of particular concern during pregnancy, since sex hormones are integral to reproductive development. In other words, exposure to azole fungicides during fetal life can potentially lead to reproductive disease in the offspring. In addition, some azoles can act as androgen receptor antagonists, which can further add to the disrupting potential following exposure. When used as pharmaceuticals, systemic concentrations of the azole compounds can become significant as combatting fungal infections can be very challenging and require prolonged exposure to high doses. Although most medicinal azoles are tightly regulated and used as prescription drugs after consultations with medical professionals, some are sold as over-the-counter drugs. In this review, we discuss various azole fungicides known to disrupt steroid sex hormone biosynthesis or action with a focus on what potential consequences exposure during pregnancy can have on the life-long reproductive health of the offspring.

Development of a validated HPTLC-bioautographic method for evaluation of aromatase inhibitory activity of plant extracts and their constituents

INTRODUCTION

Aromatase is a CYP450 enzyme that catalyses the conversion of androgens into oestrogens, where the decrease in the production of oestrogens aided by aromatase inhibitors is considered a target in post-menopausal breast cancer therapy. TLC-bioautography is a technique employed for combining chromatographic separations on TLC plates with bioassays. This is the first report to evaluate aromatase inhibitory activity using this technique.

OBJECTIVES

The aim of this study is to develop and validate a new TLC-bioautographic method for determination of aromatase inhibitory activity in 14 plant extracts. Two quantitation methods, the peak area method and reciprocal iso-inhibition volume (RIV) method, were compared and investigated to attain reliable results. Factors affecting the enzymatic reaction (temperature, pH, enzyme and substrate concentrations … etc.) were also investigated to attain the optimum parameters.

METHODOLOGY

TLC assisted by digital image processing was implemented for quantitative estimation of the aromatase inhibition of 14 plant extracts using chrysin as positive control. The fluorometric substrate dibenzyl fluorescein (DBF) was utilised for the assay, where inhibitory compounds were visualised as dark spots against a blue fluorescent background. Two software programs, Sorbfil® videodensitometer (in the peak area method) and ImageJ® (in the RIV method), were thoroughly validated using the International Council on Harmonisation (ICH) guideline and used for quantitation.

RESULTS

The RIV method showed superiority over the peak area method in the quantitation results of the tracks with non-homogenous background with %RSD values of 0.98 and 1.49 compared with 2.86 and 3.58, respectively. Further, the methods allow the comparison of the activity of different unknown inhibitory compounds without the need for a reference or a positive control.

CONCLUSION

Using the TLC-bioautographic method by image processing combined with the RIV quantitation method, simultaneous separation and quantitation of aromatase inhibitory components could be applied to estimate the relative activity of various plant extracts.

Endpoints as human biomarkers in exposure assessment of triazoles fungicides

Potential endpoint biomarkers were evaluated in the assessment of exposure to triazoles, in the southern region of Minas Gerais, Brazil. Volunteers were divided into three groups: occupationally exposed and rural residents (n = 21), non-occupationally exposed and rural residents (n = 35) and non-occupationally exposed and urban residents (n = 30). Of all endpoints evaluated, plasma concentration of androstenedione (p < 0.001) and glycine-conjugated bile acids presented statistical differences in the three studied groups (p < 0.05). However, our findings concerning oxidative stress and testosterone levels, plus that related to unconjugated and taurine conjugated bile acids, suggested that more studies are necessary to evaluate their potential as biomarkers for triazole exposure, as statistical significance was not attained between the groups. Our human population data contributes to the development of triazole exposure risk assessment with respect to these potential effect biomarkers, in potentially vulnerable groups and individuals.

Human-relevant concentrations of the antifungal drug clotrimazole disrupt maternal and fetal steroid hormone profiles in rats

Clotrimazole is a non-prescription and broad-spectrum antifungal drug sold under brand names such as Canesten® and Lotrimin®. It is used to treat different types of fungal infections, from oral thrush to athlete's foot and vaginal mycosis. The level of exposure to clotrimazole is uncertain, as the exact usage amongst self-medicating patients is unclear. Recent studies have raised potential concern about the unsupervised use of clotrimazole during pregnancy, especially since it is a potent inhibitor of CYP enzymes of the steroidogenesis pathway. To address some of these concerns, we have assessed the effects of intrauterine exposure to clotrimazole on developing rat fetuses. By exposing pregnant rats to clotrimazole 25 or 75 mg/kg bw/day during gestation days 7-21, we obtained internal fetal concentrations close to those observed in humans. These in vivo data are in strong agreement with our physiologically-based pharmacokinetic (PBK)-modelled levels. At these doses, we observed no obvious morphological changes to the reproductive system, nor shorter male anogenital distance; a well-established morphometric marker for anti-androgenic effects in male offspring. However, steroid hormone profiles were significantly affected in both maternal and fetal plasma, in particular pronounced suppression of estrogens was seen. In fetal testes, marked up-concentration of hydroxyprogesterone was observed, which indicates a specific action on steroidogenesis. Since systemic clotrimazole is rapidly metabolized in humans, relevant exposure levels may not in itself cause adverse changes to the reproductive systems. Its capacity to significantly alter steroid hormone concentrations, however, suggests that clotrimazole should be used with caution during pregnancy.

Synthesis, Optimization, Antifungal Activity, Selectivity, and CYP51 Binding of New 2-Aryl-3-azolyl-1-indolyl-propan-2-ols

A series of 2-aryl-3-azolyl-1-indolyl-propan-2-ols was designed as new analogs of fluconazole (FLC) by replacing one of its two triazole moieties by an indole scaffold. Two different chemical approaches were then developed. The first one, in seven steps, involved the synthesis of the key intermediate 1-(1H-benzotriazol-1-yl)methyl-1H-indole and the final opening of oxiranes by imidazole or 1H-1,2,4-triazole. The second route allowed access to the target compounds in only three steps, this time with the ring opening by indole and analogs. Twenty azole derivatives were tested against Candida albicans and other Candida species. The enantiomers of the best anti-Candida compound, 2-(2,4-dichlorophenyl)-3-(1H-indol-1-yl)-1-(1H-1,2,4-triazol-1-yl)-propan-2-ol (8g), were analyzed by X-ray diffraction to determine their absolute configuration. The (−)-8g enantiomer (Minimum inhibitory concentration (MIC) = IC₈₀ = 0.000256 µg/mL on C. albicans CA98001) was found with the S-absolute configuration. In contrast the (+)-8g enantiomer was found with the R-absolute configuration (MIC = 0.023 µg/mL on C. albicans CA98001). By comparison, the MIC value for FLC was determined as 0.020 µg/mL for the same clinical isolate. Additionally, molecular docking calculations and molecular dynamics simulations were carried out using a crystal structure of Candida albicans lanosterol 14α-demethylase (CaCYP51). The (−)-(S)-8g enantiomer aligned with the positioning of posaconazole within both the heme and access channel binding sites, which was consistent with its biological results. All target compounds have been also studied against human fetal lung fibroblast (MRC-5) cells. Finally, the selectivity of four compounds on a panel of human P450-dependent enzymes (CYP19, CYP17, CYP26A1, CYP11B1, and CYP11B2) was investigated.

Development of a prioritization method for chemical-mediated effects on steroidogenesis using an integrated statistical analysis of high-throughput H295R data

Synthesis of 11 steroid hormones in human adrenocortical carcinoma cells (H295R) was measured in a high-throughput steroidogenesis assay (HT-H295R) for 656 chemicals in concentration-response as part of the US Environmental Protection Agency's ToxCast program. This work extends previous analysis of the HT-H295R dataset and model by examining the utility of a novel prioritization metric based on the Mahalanobis distance that reduced these 11-dimensional data to 1-dimension via calculation of a mean Mahalanobis distance (mMd) at each chemical concentration screened for all hormone measures available. Herein, we evaluated the robustness of mMd values, and demonstrate that covariance and variance of the hormones measured appear independent of the chemicals screened and are inherent to the assay; the Type I error rate of the mMd method is less than 1%; and, absolute fold changes (up or down) of 1.5 to 2-fold have sufficient power for statistical significance. As a case study, we examined hormone responses for aromatase inhibitors in the HT-H295R assay and found high concordance with other ToxCast assays for known aromatase inhibitors. Finally, we used mMd and other ToxCast cytotoxicity data to demonstrate prioritization of the most selective and active chemicals as candidates for further in vitro or in silico screening.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Azoles additively inhibit cytochrome P450 1 (EROD) and 19 (aromatase) in rainbow trout (Oncorhynchus mykiss)

Antifungal azoles are widely used in medicine, agriculture, and material protection and several antifungal azoles have been found in environmental samples. Although these compounds were designed to inhibit fungal enzymes such as lanosterol-14-demethylase (cytochrome P450 (CYP) 51), it is well established that the inhibitory actions of azoles are not specific for fungal CYP isozymes. We refined a gill filament assay to determine the inhibition of CYP1, measured as reduced 7-ethoxyresorufin-O-deethylase (EROD) activity, in rainbow trout (Oncorhynchus mykiss) gill tissue ex vivo. The advantage of this method is that both induction and inhibition of EROD are performed ex vivo. Among thirteen azoles studied, the five that caused the strongest inhibition of gill EROD activity at a concentration of 5 μM were selected for concentration-response assessment. These compounds (bifonazole, clotrimazole, imazalil, miconazole, and prochloraz) showed IC₅₀ values ranging from 0.1 to 1.5 μM. CYP19 (aromatase) inhibition was measured using microsomes from rainbow trout brains. Concentration-response curves for CYP19 inhibition were determined for letrozole, bifonazole, clotrimazole, imazalil, miconazole and prochloraz, which gave IC₅₀ values ranging from 0.02 to 3.3 μM. It was further found that mixtures of the five most potent azoles reduced both CYP1 and 19 catalytic activity in an additive fashion (IC₅₀ = 0.7 μM and 0.6 μM, in the respective assay). Bifonazole (IC₅₀ = 0.1 μM) is not previously known to inhibit CYP1 activity. The additive inhibition of CYP1 and CYP19 catalytic activity is an important finding of the present study. We conclude that this additive action of azoles could mediate adverse impacts on CYP regulated physiological functions in environmentally exposed fish.

The use of aromatase inhibitors in boys with short stature: what to know before prescribing?

Aromatase is a cytochrome P450 enzyme (CYP19A1 isoform) able to catalyze the conversion of androgens to estrogens. The aromatase gene mutations highlighted the action of estrogen as one of the main regulators of bone maturation and closure of bone plate. The use of aromatase inhibitors (AI) in boys with short stature has showed its capability to improve the predicted final height. Anastrozole (ANZ) and letrozole (LTZ) are nonsteroidal inhibitors able to bind reversibly to the heme group of cytochrome P450. In this review, we describe the pharmacokinetic profile of both drugs, discussing possible drug interactions between ANZ and LTZ with other drugs. AIs are triazolic compounds that can induce or suppress cytochrome P450 enzymes, interfering with metabolism of other compounds. Hydroxilation, N-dealkylation and glucoronidation are involved in the metabolism of AIs. Drug interactions can occur with azole antifungals, such as ketoconazole, by inhibiting CYP3A4 and by reducing the clearance of AIs. Antiepileptic drugs (lamotrigine, phenobarbital, and phenytoin) also inhibit aromatase. Concomitant use of phenobarbital or valproate has a synergistic effect on aromatase inhibition. Therefore, it is important to understand the pharmacokinetics of AIs, recognizing and avoiding possible drug interactions and offering a safer prescription profile of this class of aromatase inhibitors. Arch Endocrinol Metab. 2017;61(3):391-7.

Effects of triazole fungicides on androgenic disruption and CYP3A4 enzyme activity

Triazole fungicides are widely used as broad-spectrum fungicides, non-steroidal antiestrogens and for various industrial applications. Their residues have been frequently detected in multiple environmental and human matrices. The increasingly reported toxicity incidents have led triazole fungicides as emerging contaminants of environmental and public health concern. However, whether triazole fungicides behave as endocrine disruptors by directly mimicking environmental androgens/antiandrogens or exerting potential androgenic disruption indirectly through the inhibition of cytochrome P450 (CYP450) enzyme activity is yet an unresolved question. We herein evaluated five commonly used triazole fungicides including bitertanol, hexaconazole, penconazole, tebuconazole and uniconazole for the androgenic and anti-androgenic activity using two-hybrid recombinant human androgen receptor (AR) yeast bioassay and comparatively evaluated their effects on enzymatic activity of CYP3A4 by P450-Glo™ CYP3A4 bioassay. All five fungicides showed moderate anti-androgenic activity toward human AR with the IC₅₀ ranging from 9.34 μM to 79.85 μM. The anti-androgenic activity remained no significant change after the metabolism mediated by human liver microsomes. These fungicides significantly inhibited the activity of CYP3A4 at the environmental relevant concentrations and the potency ranks as tebuconazole > uniconazole > hexaconazole > penconazole > bitertanol with the corresponding IC₅₀ of 0.81 μM, 0.93 μM, 1.27 μM, 2.22 μM, and 2.74 μM, respectively. We found that their anti-androgenic activity and the inhibition potency toward CYP3A4 inhibition was significantly correlated (R² between 0.83 and 0.97, p < 0.001). Our results indicated that the risk assessment of triazole pesticides and structurally similar chemicals should fully consider potential androgenic disrupting effects and the influences on the activity of CYP450s.

A predictive data-driven framework for endocrine prioritization: a triazole fungicide case study

The US Environmental Protection Agency Endocrine Disruptor Screening Program (EDSP) is a tiered screening approach to determine the potential for a chemical to interact with estrogen, androgen, or thyroid hormone systems and/or perturb steroidogenesis. Use of high-throughput screening (HTS) to predict hazard and exposure is shifting the EDSP approach to (1) prioritization of chemicals for further screening; and (2) targeted use of EDSP Tier 1 assays to inform specific data needs. In this work, toxicology data for three triazole fungicides (triadimefon, propiconazole, and myclobutanil) were evaluated, including HTS results, EDSP Tier 1 screening (and other scientifically relevant information), and EPA guideline mammalian toxicology study data. The endocrine-related bioactivity predictions from HTS and information that satisfied the EDSP Tier 1 requirements were qualitatively concordant. Current limitations in the available HTS battery for thyroid and steroidogenesis pathways were mitigated by inclusion of guideline toxicology studies in this analysis. Similar margins (3-5 orders of magnitude) were observed between HTS-predicted human bioactivity and exposure values and between in vivo mammalian bioactivity and EPA chronic human exposure estimates for these products' registered uses. Combined HTS hazard and human exposure predictions suggest low priority for higher-tiered endocrine testing of these triazoles. Comparison with the mammalian toxicology database indicated that this HTS-based prioritization would have been protective for any potential in vivo effects that form the basis of current risk assessment for these chemicals. This example demonstrates an effective, human health protective roadmap for EDSP evaluation of pesticide active ingredients via prioritization using HTS and guideline toxicology information.

Fetal safety profile of aromatase inhibitors: Animal data

Aromatase inhibitors (AIs) are a class of drugs that act by blocking the production of estrogens from androgens. The current review concentrates on the prenatal developmental toxicity of AIs in experimental models. Available data indicate that AIs may affect pregnancy at human therapeutic or lower doses. The window of vulnerability to AIs is not limited to organogenesis, but also includes the preimplantation stage and fetal periods. Decreased embryo/fetal survival was the prominent treatment-related effect. Morphological anomalies noted in fetuses exposed to AIs included skeletal anomalies, abnormal head morphology, increased ano-genital distance in female fetuses, and minor urinary tract system anomalies. Placental enlargement was consistently reported in rats and non-human primates after maternal treatment with several AIs. In conclusion, data from basic scientific research suggest that low intensity exposure to AIs applied during a wide gestational window can profoundly affect prenatal development.

Developmental exposures to an azole fungicide triadimenol at environmentally relevant concentrations cause reproductive dysfunction in females of medaka fish

Triadimenol is an effective meatabolite derived from the triazole fungicide triadimenfon. It is an agriculturally important reagent of environmentally emerging concern because of its broad use, persistent occurrence in the environment and greater fungicidal or toxic potency than the parent compound. However, the ecotoxicological impact of triadimenol on fish populations remains unclear. In this study, we investigated developmental toxicity and endocrine disruption effects in medaka fish (Oryzias latipes) exposed at an early life stage to triadimenol. First, mortality, gross development and oxidative stress responses were assessed with triadimenol exposure (3-3000 μg/L) during the embryonic stage. Then, medaka at a sensitive stage of early sexual development underwent 35-day continuous chronic exposure to triadimenol, and the endocrine disruption effects were assessed in adulthood and the next generation. Embryonic exposure to triadimenol did not induce significant teratogenic effects or oxidative stress in embryos or hatchlings. However, early-life exposure to triadimenol under environmentally relevant concentrations (3-30 μg/L) and 300 μg/L persistently altered ovary development and reproduction in female adults and skewed the sex ratio in progeny. As well, triadimenol exposure interrupted the hormone balance, as seen by the expression of genes responsible for estrogen metabolism and egg reproduction. Environmentally relevant triadimenol exposure in medaka fish at early life stages may have ecotoxicological impact in aquatic environments. Along with previous studies, we suggest that conazoles share similar modes of action in disrupting hormone homeostasis and reproduction in fish and mammals.

Tebuconazole disrupts steroidogenesis in Xenopus laevis

A 27-day controlled exposure study of adult male African clawed frogs (Xenopus laevis) was conducted to examine the mechanism by which tebuconazole may disrupt steroidogenesis. The fungicide was measured by LC-MS/MS in tank water and in target tissues (adipose, kidney, liver, and brain), and we observed tissue-specific bioconcentration with BCF up to 238. Up to 10 different steroid hormones were quantified in gonads using LC-MS/MS and in plasma using GC-MS/MS and a radioimmunoassay was performed for further measurement of androgens. In order to assess whether effects increased with exposure or animals adapted to the xenobiotic, blood samples were collected 12 days into the study and at termination (day 27). After 12 days of exposure to 100 and 500μgL(-1) tebuconazole, plasma levels of testosterone (T) and dihydrotestosterone (DHT) were increased, while plasma 17β-estradiol (E2) concentrations were greatly reduced. Exposure to 0.1μgL(-1), on the other hand, resulted in decreased levels of T and DHT, with no effects observed for E2. After 27 days of exposure, effects were no longer observed in circulating androgen levels while the suppressive effect on E2 persisted in the two high-exposure groups (100 and 500μgL(-1)). Furthermore, tebuconazole increased gonadal concentrations of T and DHT as well as expression of the enzyme CYP17 (500μgL(-1), 27 days). These results suggest that tebuconazole exposure may supress the action of CYP17 at the lowest exposure (0.1μgL(-1)), while CYP19 suppression dominates at higher exposure concentrations (increased androgens and decreased E2). Increased androgen levels in plasma half-way into the study and in gonads at termination may thus be explained by compensatory mechanisms, mediated through increased enzymatic expression, as prolonged exposure had no effect on circulating androgen levels.

Gender differences in cadmium and cotinine levels in prepubertal children

Susceptibility to environmental stressors has been described for fetal and early childhood development. However, the possible susceptibility of the prepubertal period, characterized by the orchestration of the organism towards sexual maturation and adulthood has been poorly investigated and exposure data are scarce. In the current study levels of cadmium (Cd), cotinine and creatinine in urine were analyzed in a subsample 216 children from 12 European countries within the DEMOCOPHES project. The children were divided into six age-sex groups: boys (6-8 years, 9-10 years and 11 years old), and girls (6-7 years, 8-9 years, 10-11 years). The number of subjects per group was between 23 and 53. The cut off values were set at 0.1 µg/L for Cd, and 0.8 µg/L for cotinine defined according to the highest limit of quantification. The levels of Cd and cotinine were adjusted for creatinine level. In the total subsample group, the median level of Cd was 0.180 µg/L (range 0.10-0.69 µg/L), and for cotinine the median wet weight value was 1.50 µg/L (range 0.80-39.91 µg/L). There was no significant difference in creatinine and cotinine levels between genders and age groups. There was a significant correlation between levels of cadmium and creatinine in all children of both genders. This shows that even at such low levels the possible effect of cadmium on kidney function was present and measurable. An increase in Cd levels was evident with age. Cadmium levels were significantly different between 6-7 year old girls, 11 year old boys and 10-11 year old girls. As there was a balanced distribution in the number of subjects from countries included in the study, bias due to data clustering was not probable. The impact of low Cd levels on kidney function and gender differences in Cd levels needs further investigation.

A review of the effects of azole compounds in fish and their possible involvement in masculinization of wild fish populations

Endocrine-mediated effects in fish populations have been widely documented. Most attention has been focused on feminization caused by estrogenic substances, but this paper reviews evidence for the effects of a group of fungicides and pharmaceuticals, the azoles, which have been reported to cause masculinization in fish. The paper considers information from laboratory studies on the effects of azole compounds on fish endocrinology, and on the potential existence of such effects in wild fish. The occurrence of some azoles in effluents and surface waters has also been briefly reviewed. Under laboratory conditions, many azoles are able to cause masculinization or defeminization in fish by inhibition of the P450 enzyme aromatase (CYP19). However, in no case where such effects have been observed in the field has a link been established with this group of substances. In most instances, other more convincing explanations have been proposed. Peak concentrations of some azoles in surface waters can approach those which, under continuous long-term exposure in the laboratory, might lead to some aromatase inhibition. However, available data on exposure and effects provide reassurance that the concentrations of azoles found in surface waters are too low to cause adverse effects in fish by interference with their endocrine system. Compared to the widespread observations of feminization and estrogenic effects in (male) fish, there are relatively few papers describing masculinization or defeminization in (female) wild fish populations, suggesting that this is quite a rare phenomenon. The significance of this result is emphasized by the fact that fish are among the best studied organisms in the environment.

Mechanism of inhibition of estrogen biosynthesis by azole fungicides

Biosynthesis of estrogens from androgens is catalyzed by cytochrome P450 aromatase. Aromatase inhibition by the triazole compounds letrozole (LTZ) and anastrozole is a prevalent therapy for estrogen-dependent postmenopausal breast cancer. Azoles are widely used as agricultural fungicides and antimycotic drugs that target 14α-demethylase. Some were previously shown to inhibit aromatase, thereby raising the possibility of endocrine disruptive effects. However, mechanistic analysis of their inhibition has never been undertaken. We have evaluated the inhibitory effects of 3 common fungicides, bifonazole, imazalil, and flusilazole, in human aromatase purified from placenta and compared them with LTZ, the most potent inhibitor of aromatase. Bifonazole exhibits strong inhibitory effects with an IC50 of 270nM and Ki (Michaeles-Menten inhibition constant) of 68nM, compared with 10nM and 13nM, respectively, for LTZ. The IC50 and Ki are 1100nM and 278nM for imazilil and 3200nM and 547nM for flusilazole, respectively. Analyses of inhibition kinetics suggest that the modes of inhibition by azole fungicides are mixed or competitive, whereas LTZ inhibition could be noncompetitive or mixed. We interpret the inhibition mechanism in the context of the x-ray structure of aromatase-androstenedione complex. Structural data show that aromatase has 3 binding pockets in relation to the heme. The substrate-binding cavity at the heme-distal site closely compliments the structures of the natural substrate, androstenedione, and steroidal aromatase inhibitors. Because the structures of LTZ and the azole fungicides are entirely dissimilar to the androstenedione backbone, the azoles possibly inhibit by binding to a structurally rearranged active site, the 2 other catalytically important sites, or both, in agreement with the kinetics data.

Modulation of estradiol synthesis and aromatase activity in human choriocarcinoma JEG-3 cells exposed to tetrabromobisphenol A

The goal of the present study was to investigate the impact of tetrabromobisphenol A (TBBPA) on human choriocarcinoma-derived placental JEG-3 cells in vitro. We determined the effect of this compound on estradiol secretion, aromatase protein expression and activity in vitro in the JEG-3 cell line. We assessed the ability of TBBPA to increase intracellular levels of cAMP as well as its effect on cell viability and proliferation. Our results indicated that TBBPA, at a wide range of concentrations (1×10(-8)-5×10(-5)M), significantly induced estradiol secretion by JEG-3 cells compared to that of controls after 24, 48 or 72 h of exposure. This effect was accompanied by an increase in the aromatase protein expression in JEG-3 cells treated with 100 nM and 10 μM of TBBPA for 24 h. Additionally, in our study, we confirmed that TBBPA-induced changes in aromatase protein expression were associated w ith the up-regulation of aromatase activity and cAMP levels. No tested doses of TBBPA inhibited JEG-3 cell proliferation, except for the highest dose of 100 μM, which had a toxic effect on cell viability at all time points. The present study clearly indicates that TBBPA alters JEG-3 cells estrogen synthesis due to its action on CYP19 protein expression and thus this compound may interfere with normal placental development during early pregnancy.

Discovery of novel aromatase inhibitors using a homogeneous time-resolved fluorescence assay

AIM

Aromatase is an important target for drugs to treat hormone-dependent diseases, including breast cancer. The aim of this study was to develop a homogeneous time-resolved fluorescence (HTRF) aromatase assay suitable for high-throughput screening (HTS).

METHODS

A 384-well aromatase HTRF assay was established, and used to screen about 7000 compounds from a compound library. Anti-proliferation activity of the hit was evaluated using alamarBlue(R) assay in a hormone-dependent breast cancer cell line T47D. Molecular docking was conducted to elucidate the binding mode of the hit using the Discovery Studio program.

RESULTS

The Z' value and signal to background (S/B) ratio were 0.74 and 5.4, respectively. Among the 7000 compounds, 4 hits (XHN22, XHN26, XHN27 and triptoquinone A) were found to inhibit aromatase with IC50 values of 1.60±0.07, 2.76±0.24, 0.81±0.08 and 45.8±11.3 μmol /L, respectively. The hits XHN22, XHN26 and XHN27 shared the same chemical scaffold of 4-imidazolyl quinoline. Moreover, the most potent hit XHN27 at 10 and 50 μmol/L inhibited the proliferation of T47D cells by 45.3% and 35.2%, respectively. The docking study revealed that XHN27 docked within the active site of aromatase and might form a hydrogen bond and had a π-cation interaction with amino acid residues of the protein.

CONCLUSION

XHN27, an imidazolyl quinoline derivative of flavonoid, is a potent aromatase inhibitor with anti-proliferation activity against breast cancer in vitro. The established assay can be used in HTS for discovering novel aromatase inhibitor.

AroER tri-screen is a biologically relevant assay for endocrine disrupting chemicals modulating the activity of aromatase and/or the estrogen receptor

Endocrine disrupting chemicals (EDCs) interfere with the biosynthesis, metabolism, and functions of steroid hormones, including estrogens and androgens. Aromatase enzyme converts androgen to estrogen. Thus, EDCs against aromatase significantly impact estrogen- and/or androgen-dependent functions, including the development of breast cancer. The current study aimed to develop a biologically relevant cell-based high-throughput screening assay to identify EDCs that act as aromatase inhibitors (AIs), estrogen receptor (ER) agonists, and/or ER antagonists. The AroER tri-screen assay was developed by stable transfection of ER-positive, aromatase-expressing MCF-7 breast cancer cells with an estrogen responsive element (ERE) driven luciferase reporter plasmid. The AroER tri-screen can identify: estrogenic EDCs, which increase luciferase signal without 17β-estradiol (E2); anti-estrogenic EDCs, which inhibit the E2-induced luciferase signal; and AI-like EDCs, which suppress a testosterone-induced luciferase signal. The assay was first optimized in a 96-well plate format and then miniaturized into a 1536-well plate format. The AroER tri-screen was demonstrated to be suitable for high-throughput screening in the 1536-well plate format, with a 6.9-fold signal-to-background ratio, a 5.4% coefficient of variation, and a screening window coefficient (Z-factor) of 0.78. The assay suggested that bisphenol A (BPA) functions mainly as an ER agonist. Results from screening the 446 drugs in the National Institutes of Health Clinical Collection revealed 106 compounds that modulated ER and/or aromatase activities. Among these, two AIs (bifonazole and oxiconazole) and one ER agonist (paroxetine) were confirmed through alternative aromatase and ER activity assays. These findings indicate that AroER tri-screen is a useful high-throughput screening system for identifying ER ligands and aromatase-inhibiting chemicals.

Clotrimazole, but not dexamethasone, is a potent in vitro inhibitor of cytochrome P450 isoforms CYP1A and CYP3A in rainbow trout

The effects of clotrimazole (CLO) and dexamethasone (DEX), both detected in the aquatic environment, were assessed on inhibition of cytochrome P450 (CYP450) in hepatic microsomes of rainbow trout. Activity of three CYP450 isoforms: ethoxyresorufin O-deethylase (EROD; CYP1A), 7-benzyloxy-4-trifluoromethylcoumarin O-debenzylase (BFCOD; CYP3A) and p-nitrophenol hydroxylase (PNPH; CYP2E1-like protein) was investigated in the presence of four concentrations of CLO and DEX. Clotrimazole in a concentration range of 1-100μM decreased the activity of EROD and BFCOD. The inhibition was reversible, as pre-incubation of the microsomes with CLO, before addition of the substrate, had no effect. EROD activity was non-competitively inhibited with a Ki of 0.5μM, and BFCOD activity revealed competitive inhibition with a Ki of 0.04μM. The relatively low Ki for CLO inhibition of EROD and BFCOD activity may indicate that the ability of CYP1A and CYP3A to metabolize xenobiotics is reduced in the presence of CLO. PNPH activity was not affected by CLO. DEX showed no inhibitory potency on any investigated reaction. CLO, but not DEX, inhibited EROD and BFCOD activity by different mechanisms.

Currently used pesticides and their mixtures affect the function of sex hormone receptors and aromatase enzyme activity

The endocrine-disrupting potential of pesticides is of health concern, since they are found ubiquitously in the environment and in food items. We investigated in vitro effects on estrogen receptor (ER) and androgen receptor (AR) transactivity, and aromatase enzyme activity, of the following pesticides: 2-methyl-4-chlorophenoxyacetic acid (MCPA), terbuthylazine, iodosulfuron-methyl-sodium, mesosulfuron-methyl, metsulfuron-methyl, chlormequat chloride, bitertanol, propiconazole, prothioconazole, mancozeb, cypermethrin, tau fluvalinate, malathion and the metabolite ethylene thiourea (ETU). The pesticides were analyzed alone and in selected mixtures. Effects of the pesticides on ER and AR function were assessed in human breast carcinoma MVLN cells and hamster ovary CHO-K1 cells, respectively, using luciferase reporter gene assays. Effects on aromatase enzyme activity were analyzed in human choriocarcinoma JEG-3 cells, employing the classical [(3)H](2)O method. Five pesticides (terbuthylazine, propiconazole, prothioconazole, cypermethrin and malathion) weakly induced the ER transactivity, and three pesticides (bitertanol, propiconazole and mancozeb) antagonized the AR activity in a concentration-dependent manner. Three pesticides (terbuthylazine, propiconazole and prothioconazole) weakly induced the aromatase activity. In addition, two mixtures, consisting of three pesticides (bitertanol, propiconazole, cypermethrin) and five pesticides (terbuthylazine, bitertanol, propiconazole, cypermethrin, malathion), respectively, induced the ER transactivity and aromatase activity, and additively antagonized the AR transactivity. In conclusion, our data suggest that currently used pesticides possess endocrine-disrupting potential in vitro which can be mediated via ER, AR and aromatase activities. The observed mixture effects emphasize the importance of considering the combined action of pesticides in order to assure proper estimations of related health effect risks.

Cryptococcosis: epidemiology, fungal resistance, and new alternatives for treatment

Cryptococcosis is an important systemic mycosis and the third most prevalent disease in human immunodeficiency virus (HIV)-positive individuals. The incidence of cryptococcosis is high among the 25 million people with HIV/acquired immunodeficiency syndrome (AIDS), with recent estimates indicating that there are one million cases of cryptococcal meningitis globally per year in AIDS patients. In Cryptococcus neoformans, resistance to azoles may be associated with alterations in the target enzyme encoded by the gene ERG11, lanosterol 14α-demethylase. These alterations are obtained through mutations, or by overexpressing the gene encoding. In addition, C. gattii and C. neoformans present a heteroresistance phenotype, which may be related to increased virulence. Other species beyond C. neoformans and C. gattii, such as C. laurentii, have been diagnosed mainly in patients with immunosuppression. Infections of C. albidus have been isolated in cats and marine mammals. Recent evidence suggests that the majority of infections produced by this pathogen are associated with biofilm growth, which is also related with increased resistance to antifungal agents. Therefore, there is a great need to search for alternative antifungal agents for these fungi. The search for new molecules is currently occurring from nanoparticle drugs of plant peptide origin. This article presents a brief review of the literature regarding the epidemiology of cryptococcosis, as well as fungal resistance and new alternatives for treatment.

Development of a high-performance liquid chromatographic method for determination of letrozole in wistar rat serum and its application in pharmacokinetic studies

A fast, sensitive, and specific reversed-phase high-performance liquid chromatographic (RP–HPLC) method for the determination of letrozole in Wistar rat serum was developed. In this method, liquid–liquid extraction of letrozole was achieved using diethyl ether as the extracting solvent. The analysis was carried out on a reversed-phase C18 (250 mm × 4.6 mm, 5 μm) column with an isocratic mobile phase of methanol–water (70:30,v/v), at a flow rate of 1.0 mL min⁻¹. Detection was carried out at 239 nm with a UV–visible spectrophoto-metric detector. The method was shown to be selective and linear over the concentration range of 0.15–100 μg mL⁻¹. The intra-day and inter-day precision studies showed good reproducibility with coefficients of variation less than 11% for the analyte. The relative errors of intra– and inter–day accuracy were within −11.52 to −2.26%. The limit of quantification was evaluated to be 0.15 μg mL⁻¹. The method was successfully applied for the pharmacokinetic study of letrozole after oral administration of 10 mg kg⁻¹ of letrozole in six healthy Wistar rats.

CYP1A inhibition in fish gill filaments: a novel assay applied on pharmaceuticals and other chemicals

The gill filament 7-ethoxyresorufin O-deethylase (EROD) assay was originally developed as a biomarker for cytochrome P4501A (CYP1A) induction by Ah-receptor agonists in water. In this study, the assay was adapted to measure inhibition of CYP1A activity in fish gill filaments ex vivo. The experiments were carried out using gill arch filaments from beta-naphthoflavone (betaNF)-exposed three-spined stickleback (Gasterosteus aculeatus). Candidate CYP1A inhibitors were added to the assay buffer. Nine selected pharmaceuticals and five known or suspected CYP1A-modulating chemicals were examined with regard to their ability to reduce EROD activity in gill filaments. Ellipticine, a well characterized CYP1A inhibitor, was the most effective inhibitor of the compounds tested. At a concentration in the assay buffer of 1 microM the antifungal azoles ketoconazole, miconazole and bitertanol, and the plant flavonoid acacetin reduced gill EROD activity by more than 50%, implying IC50 values below 1 microM. These compounds have previously been shown to inhibit EROD activity in liver microsomes from fish and mammals at similar concentrations. The proton pump inhibitor omeprazole reduced the gill EROD activity by 39% at 10 microM. It is concluded that the modified gill filament EROD assay is useful to screen for waterborne pollutants that inhibit catalytic CYP1A activity in fish gills.

Tissue-selective regulation of aromatase expression by calcitriol: implications for breast cancer therapy

Aromatase, the enzyme that catalyzes estrogen synthesis, is critical for the progression of estrogen receptor-positive breast cancer (BCa) in postmenopausal women. We show that calcitriol, the hormonally active form of vitamin D, regulates the expression of aromatase in a tissue-selective manner. Calcitriol significantly decreased aromatase expression in human BCa cells and adipocytes and caused substantial increases in human osteosarcoma cells (a bone cell model exhibiting osteoblast phenotype in culture) and modest increases in ovarian cancer cells. Calcitriol administration to immunocompromised mice bearing human BCa xenografts decreased aromatase mRNA levels in the tumors and the surrounding mammary adipose tissue but did not alter ovarian aromatase expression. In BCa cells, calcitriol also reduced the levels of prostaglandins (PGs), major stimulators of aromatase transcription, by suppressing the expression of cyclooxygenase-2 (which catalyzes PG synthesis) and increasing that of 15-hydroxyprostaglandin dehydrogenase (which catalyzes PG degradation). The mechanism of aromatase down-regulation by calcitriol in BCa cells is therefore 2-fold: a direct repression of aromatase transcription via promoter II through the vitamin D-response elements identified in this promoter and an indirect suppression by reducing the levels of PGs. Combinations of calcitriol with three different aromatase inhibitors (AIs) caused enhanced inhibition of BCa cell growth. The combination of calcitriol and an AI may have potential benefits for BCa therapy. In addition to augmenting the ability of AIs to inhibit BCa growth, calcitriol acting as a selective aromatase modulator that increases aromatase expression in bone would reduce the estrogen deprivation in bone caused by the AIs, thus ameliorating the AI-induced side effect of osteoporosis.

In situ hybridization to detect spatial gene expression in medaka

A whole-animal tissue section in situ hybridization (ISH) system with radio-labeled probes was developed to detect differential gene expression among tissues of the small, oviparous teleost fish, Japanese medaka (Oryzias latipes). Because of its tissue- and gender-specific expression, gonadal aromatase (CYP19a) was selected as a model gene to demonstrate the potential of the system. The ISH system was validated with a 7d exposure to the model aromatase inhibitor, fadrozole. Fadrozole did not affect the magnitude of gene expression in testes, but significantly up-regulated CYP19a gene expression in ovaries. These results were confirmed with quantitative real-time-polymerase chain reaction (RT-PCR). Histological evaluation revealed that females exposed to 100microg/L fadrozole lacked mature oocytes. Male gonadal morphology was normal in all treatments. The ISH method developed in this study allowed tissue-specific resolution of gene expression in a whole animal model, as well as the ability to analyze cellular morphological detail in the same organism.

Molecular basis for the interaction of four different classes of substrates and inhibitors with human aromatase

Aromatase cytochrome P450 (CYP19) converts androgen to estrogen. In this study, the interactions of four classes of compounds, 17beta-estradiol (the product of aromatase), 17-methyltestosterone (a synthetic androgen), dibenzylfluorescein (a synthetic substrate of aromatase), and coumestrol (a phytoestrogen), with aromatase were investigated through spectral analysis using purified human recombinant aromatase and site-directed mutagenesis studies using CHO cells expressing wild-type human aromatase or five aromatase mutants, E302D, D309A, T310S, S478T and H480Q. Spectral analysis showed that a type I binding spectrum was produced by the binding of 17-methyltestosterone to aromatase and a novel binding spectrum of aromatase was induced by dibenzylfluorescein. Mutagenesis experiments demonstrated that residues S478 and H480 in the beta-4 sheet play an important role in the binding of all four compounds. Computer-assisted docking of these compounds into the three-dimensional model of aromatase revealed that: (1) weak interaction between 17beta-estradiol and the beta-4 sheet of aromatase facilitates the release of 17beta-estradiol from the active site of aromatase; (2) 17-methyl group of 17-methyltestosterone affects its binding to aromatase; (3) dibenzylfluorescein binds to the active site of aromatase with its O-dealkylation site near the heme iron and residue T310; and (4) coumestrol binds to aromatase in a manner such that rings A and C of coumestrol mimic rings A and B of steroid. These structure-function studies help us to evaluate the structural model of aromatase, and to accelerate the structure-based design for new aromatase inhibitors.