Effects of mifepristone on adipocyte differentiation in mouse 3T3-L1 cells.

BACKGROUND: Both glucocorticoid receptor and peroxisome proliferator-activated receptor-γ (PPARγ) play a critical role in adipocyte differentiation. Mifepristone is not only an antagonist of the glucocorticoid receptor but also an agonist of PPARγ. Therefore, the present study investigated the effect of mifepristone on adipocyte differentiation. METHODS: Mouse 3T3-L1 cells were used as a model for adipocyte differentiation. The lipid droplet formation was evaluated with Bodipy493/503 staining and the expression of adipocyte markers [adiponectin and adipocyte fatty acid binding protein-4 (Fabp4)] was evaluated with quantitative PCR and immunoblot analyses for indication of adipocyte differentiation. siRNA and neutralizing antibodies were used to elucidate the molecular mechanism of mifepristone-induced adipocyte differentiation. Luciferase reporter assay was used to examine the effect of mifepristone on the promoter activity of PPAR-response element (PPRE). The DNA microarray analysis was used to characterize the transcriptome of the mifepristone-induced adipocytes. In vivo adipogenic effect of mifepristone was examined in mice. RESULTS: Mifepristone not only enhanced adipocyte differentiation induced by the conventional protocol consisting of insulin, dexamethasone and 3-isobutyl-1-methylxanthine but also induced adipocyte differentiation alone, as evidenced by lipid droplets formation and induction of the expression of adiponectin and Fabp4. These effects were inhibited by an adiponectin-neutralizing antibody and a PPARγ antagonist. Mifepristone activated the promoter activity of PPRE in a manner sensitive to PPARγ antagonist. A principal component analysis (PCA) of DNA microarray data revealed that the mifepristone-induced adipocytes represent some characteristics of the in situ adipocytes in normal adipose tissues to a greater extent than those induced by the conventional protocol. Mifepristone administration induced an increase in the weight of epididymal, perirenal and gluteofemoral adipose tissues. CONCLUSIONS: Mifepristone alone is capable of inducing adipocyte differentiation in 3T3-L1 cells and adipogenesis in vivo. PPARγ plays a critical role in the mifepristone-induced adipocyte differentiation. Mifepristone-induced adipocytes are closer to the in situ adipocytes than those induced by the conventional protocol. The present study proposes a single treatment with mifepristone as a novel protocol to induce more physiologically relevant adipocytes in 3T3-L1 cells than the conventional protocol.

The influence of pharmacological mineralocorticoid and glucocorticoid receptor blockade on the cortisol response to psychological stress.

The glucocorticoid cortisol is the end product of the hypothalamic-pituitary-adrenal (HPA) axis and crucial for the stress response in humans. Cortisol regulates numerous biological functions by binding to two different types of receptors: the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). Both receptors are found in the brain where they are crucially involved in various mental functions and in feedback inhibition of cortisol release. The precise role of both receptors in the human stress response is not completely understood. In this study, we examined the effects of pharmacological blockade of the MR or the GR on stress-induced cortisol release in a sample of 318 healthy young men (M = 25.42, SD = 5.01). Participants received the MR antagonist spironolactone (300 mg), the GR antagonist mifepristone (600 mg), or a placebo and were subjected 90 min later to a social-evaluative stressor (Trier Social Stress Test) or a non-stressful control condition. We found significantly higher stress-induced cortisol release in the spironolactone group, whereas participants after mifepristone administration did not differ from the control groups. These results suggest that MR blockade results in attenuated fast negative feedback processes and emphasize the important role of the MR during the early phase of the stress response.

Effect of 11-Deoxycorticosterone in the Transcriptomic Response to Stress in Rainbow Trout Skeletal Muscle.

In aquaculture, many stressors can negatively affect growth in teleosts. It is believed that cortisol performs glucocorticoid and mineralocorticoid functions because teleosts do not synthesize aldosterone. However, recent data suggest that 11-deoxycorticosterone (DOC) released during stress events may be relevant to modulate the compensatory response. To understand how DOC modifies the skeletal muscle molecular response, we carried out a transcriptomic analysis. Rainbow trout (Oncorhynchus mykiss) were intraperitoneally treated with physiological doses of DOC in individuals pretreated with mifepristone (glucocorticoid receptor antagonist) or eplerenone (mineralocorticoid receptor antagonist). RNA was extracted from the skeletal muscles, and cDNA libraries were constructed from vehicle, DOC, mifepristone, mifepristone plus DOC, eplerenone, and eplerenone plus DOC groups. The RNA-seq analysis revealed 131 differentially expressed transcripts (DETs) induced by DOC with respect to the vehicle group, mainly associated with muscle contraction, sarcomere organization, and cell adhesion. In addition, a DOC versus mifepristone plus DOC analysis revealed 122 DETs related to muscle contraction, sarcomere organization, and skeletal muscle cell differentiation. In a DOC versus eplerenone plus DOC analysis, 133 DETs were associated with autophagosome assembly, circadian regulation of gene expression, and regulation of transcription from RNA pol II promoter. These analyses indicate that DOC has a relevant function in the stress response of skeletal muscles, whose action is differentially modulated by GR and MR and is complementary to cortisol.

Genetically engineered human pituitary corticotroph tumor organoids exhibit divergent responses to glucocorticoid receptor modulators.

Cushing's disease (CD) is a serious endocrine disorder attributed to an adrenocorticotropic hormone (ACTH)-secreting pituitary neuroendocrine tumor (PitNET) that that subsequently leads to chronic hypercortisolemia. PitNET regression has been reported following treatment with the investigational selective glucocorticoid receptor (GR) modulator relacorilant, but the mechanisms behind that effect remain unknown. Human PitNET organoid models were generated from induced human pluripotent stem cells (iPSCs) or fresh tissue obtained from CD patient PitNETs (hPITOs). Genetically engineered iPSC derived organoids were used to model the development of corticotroph PitNETs expressing USP48 (iPSCUSP48) or USP8 (iPSCUSP8) somatic mutations. Organoids were treated with the GR antagonist mifepristone or the GR modulator relacorilant with or without somatostatin receptor (SSTR) agonists pasireotide or octreotide. In iPSCUSP48 and iPSCUSP8 cultures, mifepristone induced a predominant expression of SSTR2 with a concomitant increase in ACTH secretion and tumor cell proliferation. Relacorilant predominantly induced SSTR5 expression and tumor cell apoptosis with minimal ACTH induction. Hedgehog signaling mediated the induction of SSTR2 and SSTR5 in response to mifepristone and relacorilant. Relacorilant sensitized PitNET organoid responsiveness to pasireotide. Therefore, our study identified the potential therapeutic use of relacorilant in combination with somatostatin analogs and demonstrated the advantages of relacorilant over mifepristone, supporting its further development for use in the treatment of Cushing's disease patients.

Exosomes from bone mesenchymal stem cells alleviate mifepristone-induced human endometrial stromal cell injury by inhibiting TLR3 via delivering miR-941.

Objective: We aim to investigate the protective effect and underlying mechanisms of BMSCs-exo on human endometrial stromal cells (HESCs) induced by mifepristone in this study. Methods: BMSCs-exo were extracted and then identified by transmission electron microscopy and western-blot assay. RT-PCR assay was used to determine the level of miR-941. MiR-941 mimics or inhibitor were transfected into BMSCs and the exosomes were extracted. Then, Cell activity, apoptosis rate, cell migration and invasion, as well as the expression of angiogenic proteins were determined in HESCs stimulated by mifepristone and BMSCs-exo. Next, Dual-luciferase reporting assay was used to verify the targeted binding of miR-941 to TLR3, and the TLR3 expression in HESCs was detected by RT-PCR and western-blot. Finally, TLR3 was overexpressed to evaluate the effects of miR-941 from BMSCs-exo on cell apoptosis, cell invasion and angiogenesis in HESCs induced by mifepristone. Results: miR-941 was highly expressed in BMSCs-exo. Exosome miR-941 in BMSCs-exo inhibited the cell apoptosis, and promoted cell activity, cell migration, invasion as well as angiogenesis were also improved in HESCs induced by mifepristone. TLR3 was a target of miR-941, which was up-regulated in mifepristonetreated HESCs. We further found that miR-941 derived from BMSCs-exo down-regulated the expression of TLR3 in HESCs treated by mifepristone. In addition, TLR3 overexpression blocked the inhibition of miR-941 on mifepristone-induced cell apoptosis, as well as cell migration and angiogenesis in HESCs. Conclusions: Thus, we concluded that BMSCs-exo has protective effect on mifepristone-induced cell damage by delivering miR-941 which targeted TLR3 and regulated cell activity, migration, and angiogenesis in HESCs.

The effects of mifepristone on the structure of human decidua and chorion and Bax and Bcl-2 expression at early stage of pregnancy.

BACKGROUND: As a progesterone receptor antagonist, mifepristone combined with misoprostol is widely used to terminate early pregnancy in clinical practice. It has also been reported that mifepristone may cause cell death in decidual cells and result in hemorrhage of the decidua and insufficient blood supply. However, little is known about the histological effects of mifepristone on human decidua and chorion. METHODS: Histological and subcellular structural changes of decidua and chorionic villi from women taking mifepristone at early pregnancy times were examined by Hematoxylin and eosin (H&E) staining and transmission Electron microscope. The expression of apoptosis-related proteins Bax/Bcl-2 was examined by immunohistochemistry. RESULTS: After 48 h of mifepristone administration, the decidua tissue and chorionic villus structures were altered in women within 39-49 days of gestation and displayed varying degrees of degeneration and necrosis-like features. Apoptotic events were observed in the decidua and chorionic villi of early pregnancy, and mifepristone treatment significantly increases the number of apoptotic cells. The increased apoptotic events were concomitant with the increased expression of Bax and decreased expression of Bcl-2. CONCLUSION: This study provides evidence that mifepristone induces histological and subcellular changes in decidua and chorionic villi. Mifepristone modulates the relative ratio of Bax/Bcl-2 and the increased apoptosis contributes to the pregnancy termination at early stage of pregnancy.

Dexamethasone, a Synthetic Glucocorticoid, Induces the Activity of Androgen Receptor in Human Dermal Papilla Cells.

Psychosocial stress stimulates the secretion of glucocorticoids (GCs), which are stress-related neurohormones. GCs are secreted from hair follicles and promote hair follicle regression by inducing cellular apoptosis. Moreover, the androgen receptor (AR) is abundant in the balding scalp, and androgens suppress hair growth by binding to AR in androgenetic alopecia. First, by using immunofluorescence, we investigated whether the treatment of dermal papilla (DP) cells with dexamethasone (DEX), a synthetic GC, causes the translocation of the glucocorticoid receptor (GR) into the nucleus. DEX treatment causes the translocation of the GR into the nucleus. Next, we investigated whether stress-induced GCs affect the AR, a key factor in male pattern baldness. In this study, we first assessed that DEX increases the expression of AR mRNA in non-balding DP cells, which rarely express AR without androgen. RU486, a GR antagonist, attenuated DEX-inducible AR mRNA expression and AR activation in human non-balding DP cells. In addition, AR translocated into the nucleus after DEX treatment. Furthermore, we indeed showed that the expression of AR was induced in the nucleus by DEX in DP cells of human and mouse hair follicles. Our results first suggest that stress-associated hair loss may be due to increased AR expression and activity induced by DEX. These results demonstrate that hair loss occurs in non-balding scalps with low AR expression.

The Alterations and Significance of Intercellular Adhesion Molecule-1 in Mouse Brainstem During Herpes Simplex Virus Type 1-Induced Facial Palsy.

Herpes simplex virus type 1 (HSV-1) results in the development of Bell's pals but still, the pathophysiology of the facial nerve paralysis is still not fully studied. The main objective is to establish an animal model of type 1 herpes simplex virus (HSV-1)-induced face paralysis in the mouse and to investigate the pattern of changes in intercellular adhesion molecule -1(ICAM-1) expression in the facial nucleus of the brain stem in mice with facial paralysis as well as the effects of glucocorticoids on intercellular adhesion molecule -1(ICAM-1) expression. A total of 170 4-week-old Balb/c male mice were randomly divided into the virus inoculation group (n = 135), saline control group (n = 26), and blank control group (n = 9). Mice in the virus inoculation group that showed facial paralysis were divided into A, B, and C subgroups. The A group did not receive any treatments, the B group received methylprednisolone sodium succinate (MPSS) intervention, and the C group received MPSS + RU486 treatment. The mouse model of facial paralysis was established by inoculating HSV-1 to the skin at the back of the ears. The facial nerve function of mice was assessed, and real-time PCR and western blot were used to assess ICAM-1 expression in the facial nucleus of the brain stem in mice with facial paralysis after drug intervention. In the virus inoculation group, 95 mice (55.88%) showed varying degrees of facial paralysis symptoms within 2-5 days after inoculation. The ICAM-1 gene and protein expression levels remained at low levels in the facial nucleus of the brain stem of mice in the saline group, which showed no significant difference compared to the normal control group (P > 0.05). However, for mice of the virus inoculation group, ICAM-1 expression increased at 6 h after the occurrence of facial paralysis and peaked after 2 days, differing significantly from the blank control group (P < 0.01). ICAM-1 expression subsequently decreased gradually. In the HSV-1 + MPSS group, ICAM-1 protein expression decreased significantly on the 2nd day after facial paralysis. In the HSV-1 + MPSS + RU486 group, MPSS inhibition of ICAM-1 protein expression was reduced. The results suggested that ICAM-1 is involved in the pathological processes by which HSV-1 induces facial paralysis in mice, and the treatment effects of MPSS for Bell's palsy can be achieved by the inhibition of MCP-1.

Discovery of Novel GR Ligands toward Druggable GR Antagonist Conformations Identified by MD Simulations and Markov State Model Analysis.

Binding of different ligands to glucocorticoid receptor (GR) may induce different conformational changes and even trigger completely opposite biological functions. To understand the allosteric communication within the GR ligand binding domain, the folding pathway of helix 12 (H12) induced by the binding of the agonist dexamethasone (DEX), antagonist RU486, and modulator AZD9567 are explored by molecular dynamics simulations and Markov state model analysis. The ligands can regulate the volume of the activation function-2 through the residues Phe737 and Gln738. Without ligand or with agonist binding, H12 swings from inward to outward to visit different folding positions. However, the binding of RU486 or AZD9567 perturbs the structural state, and the passive antagonist state appears more stable. Structure-based virtual screening and in vitro bioassays are used to discover novel GR ligands that bias the conformation equilibria toward the passive antagonist state. HP-19 exhibits the best anti-inflammatory activity (IC50 = 0.041 ± 0.011 µm) in nuclear factor-kappa B signaling pathway, which is comparable to that of DEX. HP-19 also does not induce adverse effect-related transactivation functions of GR. The novel ligands discovered here may serve as promising starting points for the development of GR modulators.

Late glucocorticoid receptor antagonism changes the outcome of adult life stress.

BACKGROUND: Stressors activate a wide spectrum of interacting hormonal and neuronal systems resulting in behavioral and physiological responses, with consequences for the development of psychopathology. Several recent studies demonstrated that treatment with the glucocorticoid receptor (GR) antagonist RU486 during adulthood normalized effects of early life stress. We aimed to evaluate the potential of RU486 to reverse stress-induced changes in an animal model of adult stress. METHOD: We employed the single-prolonged stress (SPS) model as a multimodal stress exposure protocol in male rats. SPS rats and unstressed controls were treated with RU486 on days 8, 9, 10 after stress exposure and the effects of treatment were evaluated after another 4 days. We determined body weight gain, corticosterone levels, behavioral reactivity in anxiety tests, and brain gene expression of c-fos, corticosteroid receptors, drivers of the stress response and genes (epi-)genitally linked to PTSD. RESULTS: RU486 affected body weight gain, corticosterone levels and open field behavior only in SPS rats. RU486 had history-independent effects in reducing fear in the elevated plus maze and fear conditioning behavior. Gene expression analysis showed a diversity of in- and interdependent effects of stress and RU486. CONCLUSION: The effects of RU486 applied 1 week after stress and measured 4 days after treatment demonstrate that in the state of post-SPS the GR-dependence of homeostatic processes has changed. This suggests that GR-mediated processes are part of allostatic regulation after adult stress. The normalization of a number of SPS-effects after RU486 treatment reinforces the potential of targeting GR for treatment of stress-related psychopathologies.

A bile acid derivative with PPARγ-mediated anti-inflammatory activity.

During our search for bioactive secondary metabolites in the jellyfish-derived fungus Penicillium chrysogenum J08NF-4, several bile acid derivatives (2-6) were isolated along with a new steroidal artifact (1). An in vitro anti-inflammatory assay showed that pretreatment with 1 suppressed NO production and the gene expressions of the pro-inflammatory mediators iNOS and TNF-α in LPS-induced RAW 264.7 macrophages. Docking analysis of 1 revealed that it might bind to the ligand binding domain (LBD) of PPARγ in a manner similar to that of the synthetic steroid mifepristone (7), which is used clinically to treat hypercortisolism and was recently reported to be a PPARγ agonist. Compound 1 activated PPARγ in murine Ac2F liver cells and suppressed the LPS-induced phosphorylation of the NF-κB p65 subunit leading to downregulation of pro-inflammatory mediators. Our findings suggest that 1 acts as a steroidal PPARγ activator that downregulates the expressions of pro-inflammatory mediators by suppressing the NF-κB signaling pathway.

Evaluation of Strategies for the Assessment of Drug-Drug Interactions Involving Cytochrome P450 Enzymes.

BACKGROUND AND OBJECTIVES: Drug-drug interactions (DDIs) can occur when one drug alters the metabolism of another drug. Drug metabolism mediated by cytochrome P450 enzymes (CYPs) is responsible for the majority of metabolism of known drugs and inhibition of CYP enzymes is a well-known cause of DDIs. In the current study, the use of various human liver microsomes (HLM)-based methods to determine occurrence of CYP-mediated metabolism-dependent inhibition (MDI) and possible follow-up studies were evaluated. METHODS: Human CYP inhibition was studied using the following methodologies: direct inhibition and (non-diluted) IC50-shift assays, a ferricyanide-based reversibility assay, a spectrophotometric metabolic intermediate complex (MIC) assay, and recording of reduced carbon monoxide (CO)-difference spectra. HLM incubations in the presence and absence of NADPH and glutathione (GSH) were performed to study the possible formation of CYP-dependent GSH adducts. HLM incubations with the radiolabeled inhibitors mifepristone and paroxetine were performed to study CYP-mediated covalent binding. RESULTS: Dihydralazine and furafylline displayed irreversible MDI of CYP1A2. Paroxetine displayed both quasi-irreversible and irreversible MDI of CYP2D6, formation of CYP-dependent GSH adducts was observed, while CYP-mediated covalent binding occurred which was decreased in the presence of GSH. Mifepristone displayed irreversible MDI of CYP3A4, formation of CYP-dependent GSH adducts was observed, while CYP-mediated covalent binding occurred which was decreased in the presence of GSH. Troleandomycin and verapamil displayed quasi-irreversible MDI of CYP3A4; MIC formation was observed, while no formation of CYP-dependent GSH adducts occurred. CONCLUSIONS: This study gives a representative overview of current methodologies that can be used to study CYP inhibition. The here presented strategy can be applied as a tool during risk evaluation of CYP-mediated DDIs.

Pharmacokinetic differences of mifepristone between sexes in animals.

Mifepristone (RU486) is developed originally as a contraceptive used by hundreds of millions of women world-wide, and also reported as a safe and long-term psychotic depressant, or as a cancer chemotherapeutic agent used by both sexes. In our preliminary study aimed at developing mifepristone as a cancer metastatic chemopreventive, we coincidentally observed that blood mifepristone concentrations in female rats seem to be higher than those in male ones post administration. To substantiate if the pharmacokinetic differences between sexes exist, we established a fast UPLC-MS/MS method to determine mifepristone concentrations in plasma, and analyzed blood concentrations of mifepristone over time in rats and dogs of both sexes. Mifepristone in plasma or incubation liquid was recovered by liquid-liquid extraction using 1 mL of ethyl acetate. Chromatographic separation was performed on a C18 column at 35 °C, with a gradient elution consisting of methanol and water containing 0.1% (v/v) formic acid at a flow rate of 0.3 mL/min. And pharmacokinetic parameters such as elimination half-life, and mean residence time were calculated by using the non-compartmental pharmacokinetics data analysis software. In this work, administrations of mifepristone to rats and beagle dogs revealed that the plasma concentrations of mifepristone (AUC, Cmax) were significantly higher (P < 0.05) in females than that in males. In vitro liver microsomal incubation experiments showed that the metabolic rate of mifepristone in males was higher than that in females, which was consistent with the results of in vivo experiments. In general, we first found the sex-related differences about pharmacokinetic properties of mifepristone and revealed the metabolism difference of hepatic microsomal enzyme is the main reason.

Choline acetyltransferase and TrkA expression, as well as the improvement in cognition produced by E2 and P4 in ovariectomized rats, are blocked by ICI 182 780 and RU486.

Treatment with 17-ß estradiol and progesterone improves the performance of ovariectomized rats in an autoshaping learning task, representing cognitive improvement. To test whether this is attributable to genomic mechanisms, the antiestrogen ICI 182 780 or antiprogesterone RU486 was injected into ovariectomized animals primed previously with estrogen or progesterone, respectively. Compared with the vehicle control, each hormone administered alone produced an elevated expression of choline acetyltransferase and TrkA, along with an improvement in performance on the behavioral test. E2+ICI reverted the increase in these two proteins. However, RU alone elicited higher ChAT expression. With this exception, there was a clear linear regression between the number of conditioned responses and the level of ChAT and TrkA in the basal forebrain. The results suggest that TrkA may be more important than ChAT for regulating autoshaping learning tasks, and that genomic mechanisms in the basal forebrain could possibly underlie hormonal improvement of cognition.

Fluocinolone Acetonide Is a Potent Synergistic Factor of TGF-ß3-Associated Chondrogenesis of Bone Marrow-Derived Mesenchymal Stem Cells for Articular Surface Regeneration.

Articular cartilage repair remains a challenging problem. Based on a high-throughput screening and functional analysis, we found that fluocinolone acetonide (FA) in combination with transforming growth factor beta 3 (TGF-ß3) strongly potentiated chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs). In an in vivo cartilage defect model in knee joints of immunocompromised mice, transplantation of FA/TGF-ß3-treated hBMSCs could completely repair the articular surface. Analysis of the intracellular pathways revealed that FA enhanced TGF-ß3-induced phosphorylation of Smad2 and Smad3. Additionally, we performed a pathway array and found that FA activates the mTORC1/AKT pathway. Chemical inhibition of mTORC1 with rapamycin substantially suppressed FA effect, and inhibition of AKT completely repressed chondrogenesis of hBMSCs. Inhibition of glucocorticoid receptor with mifepristone also suppressed FA effect, suggesting that FA involves binding to the glucocorticoid receptor. Comparative analysis with other glucocorticoids (triamcinolone acetonide [TA] and dexamethasone [DEX]) revealed the unique ability of FA to repair articular cartilage surgical defects. Analysis of intracellular pathways showed that the mTORC1/AKT pathway and the glucocorticoid receptor was highly activated with FA and TA, but to a lesser extent with DEX. Collectively, these results show a unique ability of FA to enhance TGF-ß3-associated chondrogenesis, and suggest that the FA/TGF-ß3 combination may be used as major inducer of chondrogenesis in vitro. Additionally, FA/TGF-ß3 could be potentially applied in a clinical setting to increase the efficiency of regenerative approaches based on chondrogenic differentiation of stem cells.

Influence of domain interactions on conformational mobility of the progesterone receptor detected by hydrogen/deuterium exchange mass spectrometry.

Structural and functional details of the N-terminal activation function 1 (AF1) of most nuclear receptors are poorly understood due to the highly dynamic intrinsically disordered nature of this domain. A hydrogen/deuterium exchange (HDX) mass-spectrometry-based investigation of TATA box-binding protein (TBP) interaction with various domains of progesterone receptor (PR) demonstrate that agonist-bound PR interaction with TBP via AF1 impacts the mobility of the C-terminal AF2. Results from HDX and other biophysical studies involving agonist- and antagonist-bound full-length PR and isolated PR domains reveal the molecular mechanism underlying synergistic transcriptional activation mediated by AF1 and AF2, dominance of PR-B isoform over PR-A, and the necessity of AF2 for full AF1-mediated transcriptional activity. These results provide a comprehensive picture elaborating the underlying mechanism of PR-TBP interactions as a model for studying nuclear receptor (NR)-transcription factor functional interactions.

X-ray crystal structure of the ancestral 3-ketosteroid receptor-progesterone-mifepristone complex shows mifepristone bound at the coactivator binding interface.

Steroid receptors are a subfamily of nuclear receptors found throughout all metazoans. They are highly important in the regulation of development, inflammation, and reproduction and their misregulation has been implicated in hormone insensitivity syndromes and cancer. Steroid binding to SRs drives a conformational change in the ligand binding domain that promotes nuclear localization and subsequent interaction with coregulator proteins to affect gene regulation. SRs are important pharmaceutical targets, yet most SR-targeting drugs have off-target pharmacology leading to unwanted side effects. A better understanding of the structural mechanisms dictating ligand specificity and the evolution of the forces that created the SR-hormone pairs will enable the design of better pharmaceutical ligands. In order to investigate this relationship, we attempted to crystallize the ancestral 3-ketosteroid receptor (ancSR2) with mifepristone, a SR antagonist. Here, we present the x-ray crystal structure of the ancestral 3-keto steroid receptor (ancSR2)-progesterone complex at a resolution of 2.05 Å. This improves upon our previously reported structure of the ancSR2-progesterone complex, permitting unambiguous assignment of the ligand conformation within the binding pocket. Surprisingly, we find mifepristone, fortuitously docked at the protein surface, poised to interfere with coregulator binding. Recent attention has been given to generating pharmaceuticals that block the coregulator binding site in order to obstruct coregulator binding and achieve tissue-specific SR regulation independent of hormone binding. Mifepristone's interaction with the coactivator cleft of this SR suggests that it may be a useful molecular scaffold for further coactivator binding inhibitor development.

Dexamethasone rapidly increases GABA release in the dorsal motor nucleus of the vagus via retrograde messenger-mediated enhancement of TRPV1 activity.

Glucocorticoids influence vagal parasympathetic output to the viscera via mechanisms that include modulation of neural circuitry in the dorsal vagal complex, a principal autonomic regulatory center. Glucocorticoids can modulate synaptic neurotransmitter release elsewhere in the brain by inducing release of retrograde signalling molecules. We tested the hypothesis that the glucocorticoid agonist dexamethasone (DEX) modulates GABA release in the rat dorsal motor nucleus of the vagus (DMV). Whole-cell patch-clamp recordings revealed that DEX (1-10 µM) rapidly (i.e. within three minutes) increased the frequency of tetrodotoxin-resistant, miniature IPSCs (mIPSCs) in 67% of DMV neurons recorded in acutely prepared slices. Glutamate-mediated mEPSCs were also enhanced by DEX (10 µM), and blockade of ionotropic glutamate receptors reduced the DEX effect on mIPSC frequency. Antagonists of type I or II corticosteroid receptors blocked the effect of DEX on mIPSCs. The effect was mimicked by application of the membrane-impermeant BSA-conjugated DEX, and intracellular blockade of G protein function with GDP ßS in the recorded cell prevented the effect of DEX. The enhancement of GABA release was blocked by the TRPV1 antagonists, 5'-iodoresiniferatoxin or capsazepine, but was not altered by the cannabinoid type 1 receptor antagonist AM251. The DEX effect was prevented by blocking fatty acid amide hydrolysis or by inhibiting anandamide transport, implicating involvement of the endocannabinoid system in the response. These findings indicate that DEX induces an enhancement of GABA release in the DMV, which is mediated by activation of TRPV1 receptors on afferent terminals. The effect is likely induced by anandamide or other 'endovanilloid', suggesting activation of a local retrograde signal originating from DMV neurons to enhance synaptic inhibition locally in response to glucocorticoids.

Fluorescent ligand for human progesterone receptor imaging in live cells.

We employed molecular modeling to design and then synthesize fluorescent ligands for the human progesterone receptor. Boron dipyrromethene (BODIPY) or tetramethylrhodamine were conjugated to the progesterone receptor antagonist RU486 (Mifepristone) through an extended hydrophilic linker. The fluorescent ligands demonstrated comparable bioactivity to the parent antagonist in live cells and triggered nuclear translocation of the receptor in a specific manner. The BODIPY labeled ligand was applied to investigate the dependency of progesterone receptor nuclear translocation on partner proteins and to show that functional heat shock protein 90 but not immunophilin FKBP52 activity is essential. A tissue distribution study indicated that the fluorescent ligand preferentially accumulates in tissues that express high levels of the receptor in vivo. The design and properties of the BODIPY-labeled RU486 make it a potential candidate for in vivo imaging of PR by positron emission tomography through incorporation of (18)F into the BODIPY core.

Pharmacological interference with the glucocorticoid system influences symptoms and lifespan in a mouse model of Rett syndrome.

Rett syndrome (RTT) is caused by loss-of-function mutations in the X-linked gene MECP2 coding for methyl CpG-binding protein 2 (MeCP2). This protein can act as transcriptional repressor, and we showed in a previous study that glucocorticoid-inducible genes are up-regulated in an RTT mouse model and that these genes are direct MeCP2 targets. Here, we report that pharmacological intervention with the glucocorticoid system has an impact on the symptoms and lifespan in an RTT mouse model. Our data support a functional implication of the stress hormone system in RTT and suggest this hormone system as potential therapeutic target.