Antiandrogenic effect of RU-486 in the mouse kidney

Mifepristone (RU486) inhibits dietary lipid digestion by antagonizing the role of glucocorticoid receptor on lipase transcription

Lipid digestion and absorption are tightly regulated to cope with metabolic demands among tissues. How these processes are coordinated is not well characterized. Here, we found that mifepristone (RU486) prevents lipid digestion both in flies and mice. In flies, RU486 administration suppresses lipid digestion by transcriptional downregulating Magro in guts. Similarly, intestinal lipid uptake in mice was also suppressed by RU486 through the glucocorticoid receptor (GR). Further studies showed that the pancreatic lipase Pnlip is a direct transcriptional target of GR in pancreas tissues. Glucocorticoid levels in mice fed a high fat diet (HFD) are significantly lower than those fed on a conventional diet, and RU486 administration inhibits HFD-induced obesity both in mice and flies. Our findings identified a novel mechanism of RU486 functions as a GR antagonist systematically regulating lipid metabolism, providing new insight on the role of Glucocorticoid/GR in Cushing disease, diabetes, and other related metabolic syndromes.

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RU486 suppresses lipid digestion both in mice and flies.

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In flies, lipase Magro is transcriptionally suppressed by RU486 through dERR.

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In mice, intestinal lipid digestion is inhibited by RU486 through (GR)/PTL pathway in pancreas.

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RU486 alleviates high fat diet-induced obesity both in flies and mice.

Screening of some anti-androgenic endocrine disruptors using a recombinant cell-based in vitro bioassay

The present work describes the development and optimization of a cell-based androgen reporter assay using the Chinese hamster ovarian cell line (CHO K1) in the 96-well format. The recent reports on increasing exposure of humans and wild-life to environmental endocrine disrupting chemicals (ED) prompt the need for high throughput screening systems for such compounds in environmental and biological samples. To this end, CHO cells were cotransfected with plasmids encoding mouse mammary tumour virus-neomycin-luciferase and human androgen receptor (hAR), and a stable cell line was established. After selection with neomycin, a highly active clone was obtained which stably expressed both the hAR and the androgen-responsive luciferase reporter. Stimulation of the cells with androgens for 24 h resulted in about 15-fold stimulation of luciferase activity, with the minimum effective dose of testosterone being 0.1 nmol/l. Potent steroidal and non-steroidal anti-androgens, such as hydroxyflutamide and cyproterone acetate, significantly inhibited the androgen-induced transactivation. Non-androgenic steroids like estradiol, progesterone, dexamethasone and cortisol showed weak activity at high concentrations. RT-PCR and western blot confirmed proper transcription and translation as well as stable expression of the AR gene in the cells. About 60 different chemicals (mostly pesticides or their metabolites, and common industrial chemicals) were screened with the cell line for their ability to stimulate luciferase activity or inhibit that evoked by 0.1 nmol/l R1881, used as a positive androgenic control. About 10 highly potent anti-androgenic chemicals were identified. The most potent anti-androgenic compounds identified in our assay included bisphenol A, alpha-hexachlorocyclohexane, vinclozolin and 4,4-DDE. These compounds had alone either no effect or were weak agonists (with cytotoxic effects at very high concentrations), but none showed any significant agonistic activity. In conclusion, we demonstrate that the bioassay based on this cell line provides a reliable test for detecting androgenic and anti-androgenic compounds. The 96-well plate format makes the assay suitable for high throughput screening.

Beta-catenin binds to the activation function 2 region of the androgen receptor and modulates the effects of the N-terminal domain and TIF2 on ligand-dependent transcription

Beta-catenin is a multifunctional molecule that is activated by signaling through WNT receptors. beta-Catenin can also enhance the transcriptional activity of some steroid hormone receptors such as the androgen receptor and retinoic acid receptor alpha. Androgens can affect nuclear translocation of beta-catenin and influence its subcellular distribution. Using mammalian two-hybrid binding assays, analysis of reporter gene transcription, and coimmunoprecipitation, we now show that beta-catenin binds to the androgen receptor ligand-binding domain (LBD) and modulates the transcriptional effects of TIF2 and the androgen receptor N-terminal domain (NTD). In functional assays, beta-catenin bound to androgen receptor only in the presence of ligand agonists, not antagonists. Beta-catenin binding to the androgen receptor LBD was independent of and cooperative with the androgen receptor NTD and the p160 coactivator TIF2, both of which bind to the activation function 2 (AF-2) region of the androgen receptor. Different mutations of androgen receptor helix 3 amino acids disrupted binding of androgen receptor NTD and beta-catenin. beta-Catenin, androgen receptor NTD, and TIF2 binding to the androgen receptor LBD were affected similarly by a subset of helix 12 mutations, but disruption of two sites on helix 12 affected only binding of beta-catenin and not of TIF2 or the androgen receptor NTD. Mutational disruption of each of five LXXLL peptide motifs in the beta-catenin armadillo repeats did not disrupt either binding to androgen receptor or transcriptional coactivation. ICAT, an inhibitor of T-cell factor 4 (TCF-4), and E-cadherin binding to beta-catenin also blocked binding of the androgen receptor LBD. We also demonstrated cross talk between the WNT and androgen receptor signaling pathways because excess androgen receptor could interfere with WNT signaling and excess TCF-4 inhibited the interaction of beta-catenin and androgen receptor. Taken together, the data show that beta-catenin can bind to the androgen receptor LBD and modulate the effects of the androgen receptor NTD and TIF2 on transcription.

Androgen and estrogen stimulation of ornithine decarboxylase activity in mouse kidney

In the present work, the activity of mouse renal ornithine decarboxylase (ODC) from CBA female mice was used as a biological marker to detect (anti)androgenic activity of different groups of endocrine disruptors and steroids. Daily injections of testosterone or dihydrotestosterone (DHT) into 60 day old female mice for 4 days increased renal ODC activity in a dose-dependent manner that reached up to 100-fold (testosterone) or 250-fold (DHT) above the baseline when the highest dose, 200 microg/mouse, was used. Administration of flutamide concurrently with testosterone (75 microg/mouse) caused a potent decrease of ODC induction in a dose-dependent manner, suppressing the enzyme activity at the doses of 0.1 and 0.5 mg/mouse by about 88 and 95%, respectively. In contrast, estradiol at the doses of 0.5 and 1 mg/mouse induced a significant stimulation of renal ODC activity in a dose-dependent manner when it was given alone or in combination with testosterone. Using a sensitive increase in ODC activity in response to androgens as an end point, we did not detect an antiandrogenic effect of several antiandrogens, such as cyproterone acetate, spironolactone, p,p'DDE and vinclozolin. Also, none of these antiandrogens were able to change the basal level of renal ODC activity, with the exception of cyproterone acetate that at a dose of 0.1 mg/mouse stimulated ODC activity. The data obtained suggest that mouse renal ODC from CBA females is not strictly androgen-specific and cannot be used for estimation of antiandrogenic effects of compounds having an affinity to different types of receptors.

A stable prostatic bioluminescent cell line to investigate androgen and antiandrogen effects

We developed a new stable prostatic cell line expressing the human androgen receptor (AR) and the AR-responsive reporter gene to generate a powerful tool for investigating androgen action and for rapid screening of agonists and antagonists. The AR-deficient PC-3 cells were stably transfected with pSG(5)-puro-hAR and pMMTV-neo-Luc. After selection with puromycin and neomycin, one highly inducible clone was isolated and named PALM, for PC-3-Androgen receptor-Luciferase-MMTV. The expression of hAR was confirmed by western blot and steroid-binding assays on the whole cells. The transcriptional activity of the clone was measured after incubation of cells with increasing concentrations of synthetic R1881 or natural androgens (DHT and testosterone). The three agonists had the same maximal activity at 0.1 microM and the fold induction was equal to 20. The agonist and antagonist activities of the steroidal antiandrogens (cyproterone acetate and RU2956) and the non-steroidal antiandrogens (nilutamide, bicalutamide, inocoterone and hydroxyflutamide) measured with the PALM cells were in good correlation with the results obtained with transiently transfected cells. The selectivity in steroid transactivation was demonstrated with estradiol, progesterone, cortisol, dexamethasone and aldosterone. Spironolactone and RU486 showed partial agonist and antagonist activities, whereas R5020 presented only a partial antagonist activity. We here demonstrate that this stable transfectant provides an accurate tool for studying wild-type human AR activation and its regulation by androgens and antiandrogens in a human prostatic epithelial cell, which is routinely available and remains androgen-responsive in vitro.

Adrenocorticotrophin-induced hypertension: effects of mineralocorticoid and glucocorticoid receptor antagonism

OBJECTIVE

To examine whether the increase of blood pressure in adrenocorticotrophin-treated rats is mediated through mineralocorticoid or glucocorticoid receptors or corticosterone 6 beta-hydroxylation inhibition.

DESIGN

Rats were randomly allocated to 14 treatment groups for 10 days. The treatments included sham injection (n = 35), adrenocorticotrophin (5, 100, 500 micrograms/kg per day, subcutaneously, n = 5, 15 and 15, respectively), spironolactone (100 mg/kg per day, subcutaneously, n = 15), standard-dose or high-dose RU 486 (70 mg/kg every 3 days or 70 mg/kg per day, subcutaneously, n = 5 and 10, respectively), spironolactone + adrenocorticotrophin (100 micrograms/kg per day, n = 5, or 500 micrograms/kg per day, n = 10), standard-dose RU 486 + adrenocorticotrophin (500 micrograms/kg per day, n = 5), high-dose RU 486 + adrenocorticotrophin (100 micrograms/kg per day, n = 10), troleandomycin (40 mg/kg per day, subcutaneously, n = 5) and troleandomycin + adrenocorticotrophin (5 micrograms/kg per day, n = 5). Systolic blood pressure and metabolic parameters were measured every second day.

RESULTS

Adrenocorticotrophin treatment increased systolic blood pressure dose-dependently (5 micrograms/kg per day: +14 +/- 2 mmHg; 100 micrograms/kg per day: +20 +/- 2 mmHg; 500 micrograms/kg per day: +28 +/- 2 mmHg, all P < 0.001). Adrenocorticotrophin at 100 and 500 micrograms/kg per day increased plasma sodium and decreased plasma potassium concentrations. Spironolactone did not block adrenocorticotrophin-induced systolic blood pressure changes but did block changes in plasma sodium and potassium levels. Standard-dose RU 486 did not modify the adrenocorticotrophin-induced (500 micrograms/kg per day) systolic blood pressure rise but blocked the effect of adrenocorticotrophin on body weight. High-dose RU 486 partially blocked the adrenocorticotrophin-induced (100 micrograms/kg per day) systolic blood pressure increase (adrenocorticotrophin at 100 micrograms/kg per day: 143 +/- 3 mmHg; high-dose RU 486 + adrenocorticotrophin at 100 micrograms/kg per day: 128 +/- 5 mmHg, P < 0.001) and body-weight loss. Troleandomycin did not alter the development of adrenocorticotrophin-induced hypertension.

CONCLUSIONS

Spironolactone and standard-dose RU 486 did not modify adrenocorticotrophin-induced hypertension despite demonstrable antimineralocorticoid and antiglucocorticoid actions. High-dose RU 486 partially blocked adrenocorticotrophin-induced (100 micrograms/kg per day) hypertension, suggesting either a permissive effect of glucocorticoid on blood pressure or other antihypertensive actions of RU 486. Inhibition of glucocorticoid 6 beta-hydroxylation by troleandomycin did not modify adrenocorticotrophin-induced hypertension, suggesting that effects of corticosterone 6 beta-hydroxylation in adrenocorticotrophin-induced hypertension are negligible.

Interference of the antihormone RU486 in the determination of testosterone and estradiol by enzyme-immunoassay

The antihormone RU486 (mifepristone, 11beta-(4-dimethylaminophenyl)-17beta-hydroxy-17alpha-(prop- 1-ynyl)-estra-4,9-dien-3-one) is currently used in many endocrinological studies and in clinical practice as a contraceptive agent. The results presented here indicate that the synthetic steroid RU486 may interfere in determinations of testosterone and estradiol when using some commercial kits. Although the cross reactivity is low (0.30% for testosterone and 0.16% for estradiol), in animal experiments RU486 doses higher than 5 mg/kg may produce false positive results in the estimation of plasma testosterone (specially in castrated male or female mice) or estradiol concentrations, even in samples obtained 48 h after the administration of this antihormone.