Binding properties of androgen receptors. Evidence for identical receptors in rat testis, epididymis, and prostate

Structural perspectives on the androgen receptor, the elusive shape-shifter

The androgen receptor (AR) is a type I nuclear receptor and master transcription factor responsible for development and maintenance of male secondary sex characteristics. Aberrant AR activity is associated with numerous diseases, including prostate cancer, androgen insensitivity syndrome, spinal and bulbar muscular atrophy, and androgenic alopecia. Recent studies have shown that AR adopts numerous conformations that can modulate its ability to bind and transcribe its target DNA substrates, a feature that can be hijacked in the context of cancer. Here, we summarize a series of structural observations describing how this elusive shape-shifter binds to multiple partners, including self-interactions, DNA, and steroid and non-steroidal ligands. We present evidence that AR's pervasive structural plasticity confers an ability to broadly bind and transcribe numerous ligands in the normal and disease state, and explain the structural basis for adaptive resistance mutations to antiandrogen treatment. These evolutionary features are integral to receptor function, and are commonly lost in androgen insensitivity syndrome, or reinforced in cancer.

Generation of a Wt1 conditional deletion, nuclear red fluorescent protein reporter allele in the mouse

A Wt1 conditional deletion, nuclear red fluorescent protein (RFP) reporter allele was generated in the mouse by gene targeting in embryonic stem cells. Upon Cre-mediated recombination, a deletion allele is generated that expresses RFP in a Wt1-specific pattern. RFP expression was detected in embryonic and adult tissues known to express Wt1, including the kidney, mesonephros, and testis. In addition, RFP expression and WT1 co-localization was detected in the adult uterine stroma and myometrium, suggesting a role in uterine function. Crosses with Wnt7a-Cre transgenic mice that express Cre in the Müllerian duct epithelium activate Wt1-directed RFP expression in the epithelium of the oviduct but not the stroma and myometrium of the uterus. This new mouse strain should be a useful resource for studies of Wt1 function and marking Wt1-expressing cells.

Gestodene causes masculinization of the western mosquitofish (Gambusia affinis): Insights from ovary metabolomics

Gestodene (GES) is a common synthetic progesterone frequently detected in aquatic environments. Chronic exposure to GES can cause masculinization of a variety of fish; however, whether metabolism is closely related to the masculinization has yet to be explored. Hence, the ovary metabolome of adult female western mosquitofish (Gambusia affinis) after exposing to GES (0.0, 5.0, 50.0, and 500.0 ng/L) for 40 days was analyzed by using high-performance liquid chromatography ionization with quadrupole time-of-flight tandem mass spectrometry (HPLC-QTOF-MS). The results showed that GES increased the levels of cysteine, taurine, ophthalmic acid and cAMP while decreased methionine, these metabolites changes may owing to the oxidative stress of the ovaries; while taurcholic acid and uric acid were decreased along with induced oocyte apopotosis. Steroids hormone metabolism was also significantly affected, with progesterone and cortisol being the most affected. Enzyme-linked immunoassay results showed that estradiol levels were decreased while testosterone levels were increased with GES exposure. In addition, correlation analysis showed that the differential metabolites of some amino acids (e.g. leucine) were strongly correlated with the levels of steroids hormones secreted by the pituitary gland. The results of this study suggest that GES affects ovarian metabolism via the hypothalamus-pituitary-gonad and hypothalamic-pituitary-adrenal axes, impair antioxidant capacity, induce apoptosis in the ovary of G. affinis, and finally caused masculinization.

The post-finasteride syndrome: possible etiological mechanisms and symptoms

Finasteride and dutasteride, synthetic 5α-reductase inhibitors (5ARIs) are recommended in many guidelines for the treatment of benign prostatic hyperplasia/lower urinary tract symptoms and alopecia despite a variety of side effects like sexual, neurological, psychiatric, endocrinological, metabolic and ophthalmological dysfunctions and the increased incidence of high grade prostate cancer. The sexual side effects are common during the use of the drug but in a small subgroup of patients, they can persist after stopping the drug. This so-called post-finasteride syndrome has serious implications for the quality of life without a clear etiology or therapy. Three types of 5α-reductases are present in many organs in- and outside the brain where they can be blocked by the two 5ARIs. There is increasing evidence that 5ARIs not only inhibit the conversion of testosterone to 5α-dihydrotestosterone (DHT) in the prostate and the scalp but also in many other tissues. The lipophilic 5ARIs can pass the blood-brain barrier and might block many other neurosteroids in the brain with changes in the neurochemistry and impaired neurogenesis. Further research and therapeutic innovations are urgently needed that might cure or relieve these side effects. More awareness is needed for physicians to outweigh these health risks against the benefits of 5ARIs.

Targeting the Androgen Signaling Axis in Prostate Cancer

Activation of the androgen receptor (AR) and AR-driven transcriptional programs is central to the pathophysiology of prostate cancer. Despite successful translational efforts in targeting AR, therapeutic resistance often occurs as a result of molecular alterations in the androgen signaling axis. The efficacy of next-generation AR-directed therapies for castration-resistant prostate cancer has provided crucial clinical validation for the continued dependence on AR signaling and introduced a range of new treatment options for men with both castration-resistant and castration-sensitive disease. Despite this, however, metastatic prostate cancer largely remains an incurable disease, highlighting the need to better understand the diverse mechanisms by which tumors thwart AR-directed therapies, which may inform new therapeutic avenues. In this review, we revisit concepts in AR signaling and current understandings of AR signaling-dependent resistance mechanisms as well as the next frontier of AR targeting in prostate cancer.

Synergistic effects of hormones on structural and functional maturation of cardiomyocytes and implications for heart regeneration

The limited endogenous regenerative capacity of the human heart renders cardiovascular diseases a major health threat, thus motivating intense research on in vitro heart cell generation and cell replacement therapies. However, so far, in vitro-generated cardiomyocytes share a rather fetal phenotype, limiting their utility for drug testing and cell-based heart repair. Various strategies to foster cellular maturation provide some success, but fully matured cardiomyocytes are still to be achieved. Today, several hormones are recognized for their effects on cardiomyocyte proliferation, differentiation, and function. Here, we will discuss how the endocrine system impacts cardiomyocyte maturation. After detailing which features characterize a mature phenotype, we will contemplate hormones most promising to induce such a phenotype, the routes of their action, and experimental evidence for their significance in this process. Due to their pleiotropic effects, hormones might be not only valuable to improve in vitro heart cell generation but also beneficial for in vivo heart regeneration. Accordingly, we will also contemplate how the presented hormones might be exploited for hormone-based regenerative therapies.

Inhibitory effects of Hydrocotyle ramiflora on testosterone-induced benign prostatic hyperplasia in rats

PURPOSE

Benign prostatic hyperplasia (BPH) is a urogenital disorder that affects approximately 85% of males who are over 50 years of age. Hydrocotyle ramiflora (HR), belonging to Apiaceae family, is used to treat urinary system diseases such as urine retention in traditional Chinese herbal medicine. In this study, we evaluated the effects of HR in the BPH animal model.

METHODS

We induced BPH in rats via subcutaneous (sc) injections of testosterone propionate (TP, 3 mg/kg). Rats were also administered HR (150 mg/kg), finasteride (10 mg/kg), or vehicle via oral gavage. After induction, prostate glands were collected, weighed, and processed for further analysis, including histopathological examination and immunohistochemistry. In addition, the mRNA expression of inflammatory cytokines in prostatic tissues was determined by quantitative real-time PCR (qRT-PCR). The protein expression of pro-apoptotic markers was examined using western blotting.

RESULTS

HR treatment significantly reduced the prostate weight, epithelial thickness, and proliferating cell nuclear antigen (PCNA) expression, with the levels of cleaved caspase-3 and Bcl-2-associated X (Bax) protein considerably increased compared to BPH group. HR also decreased inflammatory cell infiltration and pro-inflammatory cytokine levels compared with BPH group. Furthermore, the expression of phosphor-nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) were reduced by HR treatment.

CONCLUSION

These results indicate that HR suppresses the development of BPH associated with anti-proliferative, pro-apoptotic, and anti-inflammatory effects, suggesting it is a potential alternative therapeutic agent for BPH.

Androgens and Non-Genomic vascular responses in hypertension

Arterial hypertension is a global public health concern. In the last few years, the interest in androgen deficiency has been growing, and the association between androgens and high blood pressure (BP) is still controversial. One purpose of this review was to summarize the available findings in order to clarify whether male sex steroid hormones have beneficial or harmful effect on BP. The second purpose was to enhance the recognition of the acute non-genomic sex-independent vasorelaxing effect of androgens. Remarkably, BP variation is expected to be a consequence of the androgen-induced vasorelaxation which reduces systemic BP; hence the in vivo vasodepressor, hypotensive, and antihypertensive responses of androgens were also analyzed. This article reviews the current understanding of the physiological regulation of vascular smooth muscle contractility by androgens. Additionally, it summarizes older and more recent data on androgens, and some of the possible underlying mechanisms of relaxation, structural-functional differences in the androgen molecules, and their designing ability to induce vasorelaxation. The clinical relevance of these findings in terms of designing future therapeutics mainly the 5-reduced metabolite of testosterone, 5β-dihydrotestosterone, is also highlighted. Literature collected through a PubMed database search, as well as our experimental work, was used for the present review.

Membrane-Initiated Estrogen, Androgen, and Progesterone Receptor Signaling in Health and Disease

Rapid effects of steroid hormones were discovered in the early 1950s, but the subject was dominated in the 1970s by discoveries of estradiol and progesterone stimulating protein synthesis. This led to the paradigm that steroid hormones regulate growth, differentiation, and metabolism via binding a receptor in the nucleus. It took 30 years to appreciate not only that some cellular functions arise solely from membrane-localized steroid receptor (SR) actions, but that rapid sex steroid signaling from membrane-localized SRs is a prerequisite for the phosphorylation, nuclear import, and potentiation of the transcriptional activity of nuclear SR counterparts. Here, we provide a review and update on the current state of knowledge of membrane-initiated estrogen (ER), androgen (AR) and progesterone (PR) receptor signaling, the mechanisms of membrane-associated SR potentiation of their nuclear SR homologues, and the importance of this membrane-nuclear SR collaboration in physiology and disease. We also highlight potential clinical implications of pathway-selective modulation of membrane-associated SR.

Manipulation of Dietary Intake on Changes in Circulating Testosterone Concentrations

Elevations in the circulating concentration of androgens are thought to have a positive effect on the anabolic processes leading to improved athletic performance. Anabolic-androgenic steroids have often been used by competitive athletes to augment this effect. Although there has been concerted effort on examining how manipulating training variables (e.g., intensity and volume of training) can influence the androgen response to exercise, there has been much less effort directed at understanding how changes in both macronutrient and micronutrient intake can impact the androgen response. Thus, the focus of this review is to examine the effect that manipulating energy and nutrient intake has on circulating concentrations of testosterone and what the potential mechanism is governing these changes.

Androgens in prostate cancer: A tale that never ends

Androgens play an essential role in prostate cancer. Clinical treatments that target steroidogenesis and the androgen receptor (AR) successfully postpone disease progression. Abiraterone and enzalutamide, the next-generation androgen receptor pathway inhibitors (ARPI), emphasize the function of the androgen-AR axis even in castration-resistant prostate cancer (CRPC). However, with the increased incidence in neuroendocrine prostate cancer (NEPC) showing resistance to ARPI, the importance of androgen-AR axis in further disease management remains elusive. Herein we review the steroidogenic pathways associated with different disease stages and discuss the potential targets for disease management after manifesting resistance to abiraterone and enzalutamide.

Combined MD and QM/MM Investigations of Hydride Reduction of 5α-Dihydrotestosterone Catalyzed by Human 3α-Hydroxysteroid Dehydrogenase Type 3: Importance of Noncovalent Interactions

3α-Hydroxysteroid dehydrogenase (3α-HSD) is an enzyme that is essential in the regulation of the concentration of 5α-dihydrotestosterone (5α-DHT) in the prostate. It catalyzes the hydride reduction of 5α-DHT to 3α-androstanediol, which activates androgen receptors. Elucidating details about the hydride reduction of 5α-DHT by 3α-HSD and the environment around the active site of the enzyme could lead to the development of effective drugs for the treatment of prostate cancer. In this study, the X-ray crystal structure of human 3α-HSD type 3 was comprehensively evaluated. Moreover, molecular dynamics (MD) simulations and hybrid ONIOM-type quantum mechanics/molecular mechanics (QM/MM) calculations were performed using a large QM region (maximum 232 atoms). It was determined that the reaction proceeded in a single step without the formation of an alkoxide ion owing to the direct hydride reduction of the substrate by nicotinamide adenine dinucleotide phosphate (NADPH) and concerted proton transfer by Tyr55 and Lys84. Noncovalent interaction (NCI) analysis highlighted the roles of Tyr216 and Trp227 in 3α-HSD. Specifically, Tyr216 assisted the reaction by π/π interactions with the neighboring nicotinamide ring of NADP(H), whereas Trp227 played an important role in recognition of the size of the substrate by CH/π interactions.

Investigation into Adaptation in Genes Associated with Response to Estrogenic Pollution in Populations of Roach (Rutilus rutilus) Living in English Rivers

Exposure of male fish to estrogenic substances from wastewater treatment works (WwTWs) results in feminization and reduced reproductive fitness. Nevertheless, self-sustaining populations of roach (Rutilus rutilus) inhabit river stretches polluted with estrogenic WwTW effluents. In this study, we examine whether such roach populations have evolved adaptations to tolerate estrogenic pollution by comparing frequency differences in single-nucleotide polymorphisms (SNPs) between populations sampled from rivers receiving either high- or low-level WwTW discharges. SNPs within 36 "candidate" genes, selected for their involvement in estrogenic responses, and 120 SNPs in reference genes were genotyped in 465 roaches. There was no evidence for selection in highly estrogen-dependent candidate genes, including those for the estrogen receptors, aromatases, and vitellogenins. The androgen receptor (ar) and cytochrome P450 1A genes were associated with large shifts in allele frequencies between catchments and in individual populations, but there is no clear link to estrogen pollution. Selection at ar in the effluent-dominated River Lee may have resulted from historical contamination with endocrine-disrupting pesticides. Critically, although our results suggest population-specific selection including at genes related to endocrine disruption, there was no strong evidence that the selection resulted from exposure to estrogen pollution.

ARe we there yet? Understanding androgen receptor signaling in breast cancer

The role of androgen receptor (AR) activation and expression is well understood in prostate cancer. In breast cancer, expression and activation of AR is increasingly recognized for its role in cancer development and its importance in promoting cell growth in the presence or absence of estrogen. As both prostate and breast cancers often share a reliance on nuclear hormone signaling, there is increasing appreciation of the overlap between activated cellular pathways in these cancers in response to androgen signaling. Targeting of the androgen receptor as a monotherapy or in combination with other conventional therapies has proven to be an effective clinical strategy for the treatment of patients with prostate cancer, and these therapeutic strategies are increasingly being investigated in breast cancer. This overlap suggests that targeting androgens and AR signaling in other cancer types may also be effective. This manuscript will review the role of AR in various cellular processes that promote tumorigenesis and metastasis, first in prostate cancer and then in breast cancer, as well as discuss ongoing efforts to target AR for the more effective treatment and prevention of cancer, especially breast cancer.

Asteris Radix et Rhizoma suppresses testosterone-induced benign prostatic hyperplasia in rats by regulating apoptosis and inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Asteris Radix et Rhizoma (AR) refers to the roots and rhizomes of Aster tataricus L., which is widely distributed throughout East Asia. AR has been consumed as a traditional medicine in Korea, Japan and China for the treatment of urologic symptoms. To date, however, the therapeutic effect of AR on benign prostatic hyperplasia (BPH) has not been investigated.

AIM OF THE STUDY

The present study evaluated the therapeutic effects of AR on a testosterone-induced BPH rats.

MATERIALS AND METHODS

We induced BPH to rats by subcutaneous injections (s.c) of testosterone propionate (TP) daily for four weeks. Rats were also administered daily oral gavage of AR (150 mg/kg) or vehicle. After four weeks of induction, all animals were euthanized humanely and their prostate glands were removed, weighed and processed for further analysis, including histopathological examination, real-time PCR, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and Western blot analysis.

RESULTS

Administration of AR to TP-induced BPH rats considerably reduced prostate weight and concentrations of serum testosterone and prostate dihydrotestosterone (DHT). Epithelial thickness and expression of proliferating cell nuclear antigen (PCNA) were markedly suppressed by AR-treatment in the rats. Furthermore, the expression of the B-cell lymphoma 2 (Bcl-2) were reduced and expression of the Bcl-2-associated X protein (Bax) increased, resulting in significant reduction in Bcl-2/Bax ratio. In addition, AR decreased the level of pro-inflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). The expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were reduced by AR treatment in a TP-induced BPH rat model.

CONCLUSIONS

AR alleviates BPH by promoting apoptosis and suppressing inflammation, indicating that AR may be used clinically to treat BPH accompanied by inflammation.

Physiopathological role of the enzymatic complex 5α-reductase and 3α/β-hydroxysteroid oxidoreductase in the generation of progesterone and testosterone neuroactive metabolites

The enzymatic complex 5α-reductase (5α-R) and 3α/3β-hydroxysteroid oxidoreductase (HSOR) is expressed in the nervous system, where it transforms progesterone (PROG) and testosterone (T) into neuroactive metabolites. These metabolites regulate myelination, brain maturation, neurotransmission, reproductive behavior and the stress response. The expression of 5α-R and 3α-HSOR and the levels of PROG and T reduced metabolites show regional and sex differences in the nervous system and are affected by changing physiological conditions as well as by neurodegenerative and psychiatric disorders. A decrease in their nervous tissue levels may negatively impact the course and outcome of some pathological events. However, in other pathological conditions their increased levels may have a negative impact. Thus, the use of synthetic analogues of these steroids or 5α-R modulation have been proposed as therapeutic approaches for several nervous system pathologies. However, further research is needed to fully understand the consequences of these manipulations, in particular with 5α-R inhibitors.

Health Risks Associated with Long-Term Finasteride and Dutasteride Use: It's Time to Sound the Alarm

5α-dihydrotestosterone (5α-DHT) is the most potent natural androgen. 5α-DHT elicits a multitude of physiological actions, in a host of tissues, including prostate, seminal vesicles, hair follicles, skin, kidney, and lacrimal and meibomian glands. However, the physiological role of 5α-DHT in human physiology, remains questionable and, at best, poorly appreciated. Recent emerging literature supports a role for 5α-DHT in the physiological function of liver, pancreatic β-cell function and survival, ocular function and prevention of dry eye disease and kidney physiological function. Thus, inhibition of 5α-reductases with finasteride or dutasteride to reduce 5α-DHT biosynthesis in the course of treatment of benign prostatic hyperplasia (BPH) or male pattern hair loss, known as androgenetic alopecia (AGA) my induces a novel form of tissue specific androgen deficiency and contributes to a host of pathophysiological conditions, that are yet to be fully recognized. Here, we advance the concept that blockade of 5α-reductases by finasteride or dutasteride in a mechanism-based, irreversible, inhabitation of 5α-DHT biosynthesis results in a novel state of androgen deficiency, independent of circulating testosterone levels. Finasteride and dutasteride are frequently prescribed for long-term treatment of lower urinary tract symptoms in men with BPH and in men with AGA. This treatment may result in development of non-alcoholic fatty liver diseases (NAFLD), insulin resistance (IR), type 2 diabetes (T2DM), dry eye disease, potential kidney dysfunction, among other metabolic dysfunctions. We suggest that long-term use of finasteride and dutasteride may be associated with health risks including NAFLD, IR, T2DM, dry eye disease and potential kidney disease.

Androgen receptor co-regulation in prostate cancer

Prostate cancer (PCa) progression relies on androgen receptor (AR) action. Preventing AR's ligand-activation is the frontline treatment for metastatic PCa. Androgen deprivation therapy (ADT) that inhibits AR ligand-binding initially induces remission but eventually fails, mainly because of adaptive PCa responses that restore AR action. The vast majority of castration-resistant PCa (CRPC) continues to rely on AR activity. Novel therapeutic strategies are being explored that involve targeting other critical AR domains such as those that mediate its constitutively active transactivation function, its DNA binding ability, or its interaction with co-operating transcriptional regulators. Considerable molecular and clinical variability has been found in AR's interaction with its ligands, DNA binding motifs, and its associated coregulators and transcription factors. Here, we review evidence that each of these levels of AR regulation can individually and differentially impact transcription by AR. In addition, we examine emerging insights suggesting that each can also impact the other, and that all three may collaborate to induce gene-specific AR target gene expression, likely via AR allosteric effects. For the purpose of this review, we refer to the modulating influence of these differential and/or interdependent contributions of ligands, cognate DNA-binding motifs and critical regulatory protein interactions on AR's transcriptional output, which may influence the efficiency of the novel PCa therapeutic approaches under consideration, as co-regulation of AR activity.

Androgen Receptor Signaling in the Development of Castration-Resistant Prostate Cancer

Most prostate cancers are androgen-sensitive malignancies whose growths depend on the transcriptional activity of the androgen receptor (AR). In the 1940s, Charles Huggins demonstrated that the surgical removal of testes in men can result in a dramatic improvement in symptoms and can induce prostate cancer regression. Since then, androgen deprivation therapies have been the standard first-line treatment for advanced prostate cancer, including: surgical castration, medical castration, antiandrogens, and androgen biosynthesis inhibitors. These therapies relieve symptoms, reduce tumor burden, and prolong patient survival, while having relatively modest side effects. Unfortunately, hormone deprivation therapy rarely cures the cancer itself. Prostate cancer almost always recurs, resulting in deadly castration-resistant prostate cancer. The underlying escape mechanisms include androgen receptor gene/enhancer amplification, androgen receptor mutations, androgen receptor variants, coactivator overexpression, intratumoral de novo androgen synthesis, etc. Whereas, the majority of the castration-resistant prostate cancers continuously rely on the androgen axis, a subset of recurrent cancers have completely lost androgen receptor expression, undergone divergent clonal evolution or de-differentiation, and become truly androgen receptor-independent small-cell prostate cancers. There is an urgent need for the development of novel targeted and immune therapies for this subtype of prostate cancer, when more deadly small-cell prostate cancers are induced by thorough androgen deprivation and androgen receptor ablation.

Consideration of breast cancer subtype in targeting the androgen receptor

The androgen receptor (AR) is a drug target in breast cancer, and AR-targeted therapies have induced tumor responses in breast cancer patients. In this review, we summarized the role of AR in breast cancer based on preclinical and clinical data. Response to AR-targeted therapies in unselected breast cancer populations is relatively low. Preclinical and clinical data show that AR antagonists might have a role in estrogen receptor (ER)-negative/AR-positive tumors. The prognostic value of AR for patients remains uncertain due to the use of various antibodies and cut-off values for immunohistochemical assessment. To get more insight into the role of AR in breast cancer, we additionally performed a retrospective pooled analysis to determine the prognostic value of the AR using mRNA profiles of 7270 primary breast tumors. Our analysis shows that a higher AR mRNA level is associated with improved disease outcome in patients with ER-positive/human epidermal growth factor receptor 2 (HER2)-negative tumors, but with worse disease outcome in HER2-positive subgroups. In conclusion, next to AR expression, incorporation of additional tumor characteristics will potentially make AR targeting a more valuable therapeutic strategy in breast cancer.

Supraphysiological androgens suppress prostate cancer growth through androgen receptor-mediated DNA damage

Prostate cancer (PC) is initially dependent on androgen receptor (AR) signaling for survival and growth. Therapeutics designed to suppress AR activity serve as the primary intervention for advanced disease. However, supraphysiological androgen (SPA) concentrations can produce paradoxical responses leading to PC growth inhibition. We sought to discern the mechanisms by which SPA inhibits PC and to determine if molecular context associates with anti-tumor activity. SPA produced an AR-mediated, dose-dependent induction of DNA double-strand breaks (DSBs), G0/G1 cell cycle arrest and cellular senescence. SPA repressed genes involved in DNA repair and delayed the restoration of damaged DNA which was augmented by PARP1 inhibition. SPA-induced DSBs were accentuated in BRCA2-deficient PCs, and combining SPA with PARP or DNA-PKcs inhibition further repressed growth. Next-generation sequencing was performed on biospecimens from PC patients receiving SPA as part of ongoing Phase II clinical trials. Patients with mutations in genes mediating homology-directed DNA repair were more likely to exhibit clinical responses to SPA. These results provide a mechanistic rationale for directing SPA therapy to PCs with AR amplification or DNA repair deficiency, and for combining SPA therapy with PARP inhibition.

Adrenal androgens rescue prostatic dihydrotestosterone production and growth of prostate cancer cells after castration

Adrenal androgens dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS) are potential substrates for intracrine production of testosterone (T) and dihydrotestosterone (DHT), or directly to DHT, by prostate cancer (PCa) cells. Production of DHT from DHEAS and DHEA, and the role of steroid sulfatase (STS), were evaluated ex vivo using fresh human prostate tissue and in vitro using human PCa cell lines. STS was expressed in benign prostate tissue and PCa tissue. DHEAS at a physiological concentration was converted to DHT in prostate tissue and PCa cell lines, which was STS-dependent. DHEAS activation of androgen receptor (AR) and stimulation of PCa cell growth were STS-dependent. DHEA at a physiological concentration was not converted to DHT ex vivo and in vitro, but stimulated in vivo tumor growth of the human PCa cell line, VCaP, in castrated mice. The findings suggest that targeting metabolism of DHEAS and DHEA may enhance androgen deprivation therapy.

Autism spectrum disorders, endocrine disrupting compounds, and heavy metals in amniotic fluid: a case-control study

Background

Evidence has indicated that some non-inherited factors such as exposure to environmental pollutants are associated with neurodevelopment disorders like autism spectrum disorder (ASD). Studies report that endocrine disrupting compounds (EDCs), including polychlorinated biphenyls, organochlorine pesticides, perfluoroalkyl substances (PFAS), and some metals, have adverse effects on the fetal neurodevelopment. The aim of this study was to measure the amniotic fluid (AF) levels of EDCs and metals as well as the receptor transactivities induced by AF and investigate the possible link between prenatal exposure to EDCs and heavy metals and ASD risk.

Methods

In this case-control study, we included AF samples of 75 ASD cases and 135 frequency-matched controls and measured the levels of the endogenous sex hormones, PFAS, and elements including heavy metals. The combined effect of endogenous hormones and EDCs on the receptor of estrogen (ER), androgen (AR), aryl hydrocarbon (AhR), and thyroid hormone-like activity were also determined and expressed as receptor ligand equivalents. We assessed the associations of AF levels of chemicals, sex hormones, and receptor activities with ASD risk using unconditional logistical regression analyses. To control for multiple comparisons, the false discovery rate (FDR) was used and q values less than 0.25 were designated as statistical significance.

Results

PFAS and metals were detectable in AF samples. The ASD cases had significantly lower AF levels of PFAS than controls, and the adjusted odds ratio (OR) was 0.410 (95% CI 0.174, 0.967; p = 0.042; FDR q _value = 0.437) for perfluorooctane sulfonate (PFOS). The principal component, including PFAS congeners, copper, iron, and estrogenic activity, was significantly inversely associated with ASD risk (adjusted OR = 0.100; 95% CI 0.016, 0.630; p = 0.014; FDR q _value = 0.098).Testosterone level in AF weakly associated with ASD risk (adjusted OR = 1.002; 95% CI 1.000, 1.004; p = 0.05). However, after multiple comparison correction, the association was not significant (FDR q _value = 0.437). No significant associations between AF-induced receptor transactivities and ASD risk were observed. The adjusted OR was 2.176 (95%CI 0.115, 41.153) for the ratio of the combined androgenic activity to combined estrogenic activity.

Conclusions

The presence of PFAS and heavy metals in AF indicates that they can cross the placenta. The inverse association between levels of PFAS congeners in AF and ASD risk might relate to the weak estrogenic activities and anti-androgenic activities of PFAS.The observed tendency of positive association between the ratio of combined androgenic effect to the combined estrogenic effect and ASD risk needs further studies to explore whether EDCs together with endogenous hormones play a role in the development of ASD.

Muscle Androgen Receptor Content but Not Systemic Hormones Is Associated With Resistance Training-Induced Skeletal Muscle Hypertrophy in Healthy, Young Men

The factors that underpin heterogeneity in muscle hypertrophy following resistance exercise training (RET) remain largely unknown. We examined circulating hormones, intramuscular hormones, and intramuscular hormone-related variables in resistance-trained men before and after 12 weeks of RET. Backward elimination and principal component regression evaluated the statistical significance of proposed circulating anabolic hormones (e.g., testosterone, free testosterone, dehydroepiandrosterone, dihydrotestosterone, insulin-like growth factor-1, free insulin-like growth factor-1, luteinizing hormone, and growth hormone) and RET-induced changes in muscle mass (n = 49). Immunoblots and immunoassays were used to evaluate intramuscular free testosterone levels, dihydrotestosterone levels, 5α-reductase expression, and androgen receptor content in the highest- (HIR; n = 10) and lowest- (LOR; n = 10) responders to the 12 weeks of RET. No hormone measured before exercise, after exercise, pre-intervention, or post-intervention was consistently significant or consistently selected in the final model for the change in: type 1 cross sectional area (CSA), type 2 CSA, or fat- and bone-free mass (LBM). Principal component analysis did not result in large dimension reduction and principal component regression was no more effective than unadjusted regression analyses. No hormone measured in the blood or muscle was different between HIR and LOR. The steroidogenic enzyme 5α-reductase increased following RET in the HIR (P < 0.01) but not the LOR (P = 0.32). Androgen receptor content was unchanged with RET but was higher at all times in HIR. Unlike intramuscular free testosterone, dihydrotestosterone, or 5α-reductase, there was a linear relationship between androgen receptor content and change in LBM (P < 0.01), type 1 CSA (P < 0.05), and type 2 CSA (P < 0.01) both pre- and post-intervention. These results indicate that intramuscular androgen receptor content, but neither circulating nor intramuscular hormones (or the enzymes regulating their intramuscular production), influence skeletal muscle hypertrophy following RET in previously trained young men.

Intracrine androgen biosynthesis, metabolism and action revisited

Androgens play an important role in metabolic homeostasis and reproductive health in both men and women. Androgen signalling is dependent on androgen receptor activation, mostly by testosterone and 5α-dihydrotestosterone. However, the intracellular or intracrine activation of C19 androgen precursors to active androgens in peripheral target tissues of androgen action is of equal importance. Intracrine androgen synthesis is often not reflected by circulating androgens but rather by androgen metabolites and conjugates. In this review we provide an overview of human C19 steroid biosynthesis including the production of 11-oxygenated androgens, their transport in circulation and uptake into peripheral tissues. We conceptualise the mechanisms of intracrinology and review the intracrine pathways of activation and inactivation in selected human tissues. The contribution of liver and kidney as organs driving androgen inactivation and renal excretion are also highlighted. Finally, the importance of quantifying androgen metabolites and conjugates to assess intracrine androgen production is discussed.

Androgen Signaling in Prostate Cancer

The androgen-signaling axis plays a pivotal role in the pathogenesis of prostate cancer. Since the landmark discovery by Huggins and Hodges, gonadal depletion of androgens has remained a mainstay of therapy for advanced disease. However, progression to castration-resistant prostate cancer (CRPC) typically follows and is largely the result of restored androgen signaling. Efforts to understand the mechanisms behind CRPC have revealed new insights into dysregulated androgen signaling and intratumoral androgen synthesis, which has ultimately led to the development of several novel androgen receptor (AR)-directed therapies for CRPC. However, emergence of resistance to these newer agents has also galvanized new directions in investigations of prereceptor and postreceptor AR regulation. Here, we review our current understanding of AR signaling as it pertains to the biology and natural history of prostate cancer.

Dihydrotestosterone: Biochemistry, Physiology, and Clinical Implications of Elevated Blood Levels

Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicates that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/testosterone (T) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. Although the primary focus of this review is about DHT in men, we also provide a brief overview of DHT in women. The available published data are limited by the lack of large, well-controlled studies of long duration that are sufficiently powered to expose subtle safety signals. Nonetheless, the preponderance of available clinical data indicates that modest elevations in circulating levels of DHT in response to androgen therapy should not be of concern in clinical practice. Elevated DHT has not been associated with increased risk of prostate disease (e.g., cancer or benign hyperplasia) nor does it appear to have any systemic effects on cardiovascular disease safety parameters (including increased risk of polycythemia) beyond those commonly observed with available T preparations. Well-controlled, long-term studies of transdermal DHT preparations have failed to identify safety signals unique to markedly elevated circulating DHT concentrations or signals materially different from T.

Androgen-mediated regulation of skeletal muscle protein balance

Androgens significantly alter muscle mass in part by shifting protein balance in favor of net protein accretion. During various atrophic conditions, the clinical impact of decreased production or bioavailability of androgens (termed hypogonadism) is important as a loss of muscle mass is intimately linked with survival outcome. While androgen replacement therapy increases muscle mass in part by restoring protein balance, this is not a comprehensive treatment option due to potential side effects. Therefore, an understanding of the mechanisms by which androgens alter protein balance is needed for the development of androgen-independent therapies. While the data in humans suggest androgens alter protein balance (both synthesis and breakdown) in the fasted metabolic state, a predominant molecular mechanism(s) behind this observation is still lacking. This failure is likely due in part to inconsistent experimental design between studies including failure to control nutrient/feeding status, the method of altering androgens, and the model systems utilized.

Sex differences in Gadd45b expression and methylation in the developing rodent amygdala

Precise spatiotemporal epigenetic regulation of the genome facilitates species-typical development; sexual differentiation of the brain by gonadal hormones and sex chromosomes causes extensive epigenetic reprogramming of many cells in the body, including the brain, and may indirectly predispose males and females to different psychiatric conditions. We and others have demonstrated sex differences in DNA methylation, as well as in the enzymes that form, or 'write', this epigenetic modification. However, while a growing body of evidence suggests that DNA methylation undergoes rapid turnover and is dynamically regulated in vivo, to our knowledge no studies have been done investigating whether sex differences exist in the epigenetic 'erasers' during postnatal development. Here we report sex differences in the expression of growth arrest and DNA damage inducible factor β (Gadd45b), but not family members α (a) or γ (g), in the neonatal and juvenile rodent amygdala.

Fibroblast Growth Factor 8 Expression in GT1-7 GnRH-Secreting Neurons Is Androgen-Independent, but Can Be Upregulated by the Inhibition of DNA Methyltransferases

Fibroblast growth factor 8 (FGF8) is a potent morphogen that regulates the embryonic development of hypothalamic neuroendocrine cells. Indeed, using Fgf8 hypomorphic mice, we showed that reduced Fgf8 mRNA expression completely eliminated the presence of gonadotropin-releasing hormone (GnRH) neurons. These findings suggest that FGF8 signaling is required during the embryonic development of mouse GnRH neurons. Additionally, in situ hybridization studies showed that the embryonic primordial birth place of GnRH neurons, the olfactory placode, is highly enriched for Fgf8 mRNA expression. Taken together these data underscore the importance of FGF8 signaling for GnRH emergence. However, an important question remains unanswered: How is Fgf8 gene expression regulated in the developing embryonic mouse brain? One major candidate is the androgen receptor (AR), which has been shown to upregulate Fgf8 mRNA in 60-70% of newly diagnosed prostate cancers. Therefore, we hypothesized that ARs may be involved in the regulation of Fgf8 transcription in the developing mouse brain. To test this hypothesis, we used chromatin-immunoprecipitation (ChIP) assays to elucidate whether ARs interact with the 5'UTR region upstream of the translational start site of the Fgf8 gene in immortalized mouse GnRH neurons (GT1-7) and nasal explants. Our data showed that while AR interacts with the Fgf8 promoter region, this interaction was androgen-independent, and that androgen treatment did not affect Fgf8 mRNA levels, indicating that androgen signaling does not induce Fgf8 transcription. In contrast, inhibition of DNA methyltransferases (DNMT) significantly upregulated Fgf8 mRNA levels indicating that Fgf8 transcriptional activity may be dependent on DNA methylation status.

Association Between Endogenous Sex Hormones and Liver Fat in a Multiethnic Study of Atherosclerosis

BACKGROUND & AIMS

Levels of circulating of sex hormones are associated with glucose metabolism and adiposity, but little is known about their association with ectopic fat. We aimed to characterize the association between circulating sex hormones and liver fat.

METHODS

We conducted a cross-sectional analysis by using data from the Multiethnic Study of Atherosclerosis to assess the association of the circulating levels of bioavailable testosterone, estradiol, dehydroepiandrosterone, and sex hormone binding globulin (SHBG) with fatty liver. Fatty liver was defined as a reduction of ≤40 Hounsfield units, measured by computed tomography, in 2835 postmenopausal women and 2899 men (45-84 years old; white, black, Hispanic, or Chinese) at 6 centers in the United States.

RESULTS

Women in the highest tertile of bioavailable testosterone were significantly more likely to have fatty liver than women in the lowest tertile (odds ratio, 1.77; 95% confidence interval, 1.07-2.92). We found an even greater difference for level of estradiol (odds ratio, 2.49; 95% confidence interval, 1.41-4.39) after adjusting for age, race/ethnicity, waist-to-hip ratio, hypertension, total and high-density lipoprotein cholesterol, smoking, insulin sensitivity, and hormone replacement therapy use. Men in the highest tertile of estradiol level were significantly more likely to have fatty liver than men in the lowest tertile (odds ratio, 2.10; 95% confidence level, 1.29-3.40). Men in the highest tertile of SHBG were less likely to have fatty liver than those in the lowest tertile (odds ratio, 0.46; 95% confidence interval, 0.27-0.77). Other associations between hormone levels and fatty liver were not statistically significant.

CONCLUSIONS

On the basis of a cross-sectional study, postmenopausal women with high levels of bioavailable testosterone are at greater risk for fatty liver. In men, higher levels of SHBG are associated with reduced risk for fatty liver. Higher levels of estradiol are associated with fatty liver in both sexes. This pattern is consistent with the sex-specific associations of sex hormones with other cardiometabolic risk factors.

Current state of practice regarding testosterone supplementation therapy in men with prostate cancer

Hypogonadal men are characterized by low serum testosterone and symptoms of low energy, decreased libido, and muscle mass as well as impaired concentration and sexual functioning. Men with prostate cancer (PCa) currently on active surveillance or post-therapy, have traditionally been excluded from management paradigms given the decade-old concern that testosterone caused PCa growth. However, there appears to be little or no relationship between serum testosterone concentration and PCa. Androgen action in the prostate has long been known to be affected by the kinetics of receptor saturation and, as such, testosterone beyond a certain baseline is unable to stimulate prostatic growth due to complete intra-prostatic androgen receptor binding. Given this physiologic concept, many clinical investigators have begun to promote testosterone supplementation therapy (TST) as safe in men with PCa. This review examines the basics of testosterone physiology and summarizes the most recent findings on the use of TST in men with PCa on active surveillance and following treatment with external beam radiotherapy, brachytherapy and radical prostatectomy.

Androgens block outward potassium currents and decrease spontaneous action potentials in GH3 cells

Androgens produce nongenomic effects in several cells by different mechanisms, including ion channel modulation. Adenohypophyseal cells express several K(+) channels, including voltage and Ca(2+)-dependent K(+) (BK) channels, which might be the target of androgens to modulate cellular action potentials and hormonal secretion. Androgen effects were studied in GH3 cells (from anterior pituitary rat tumor) by means of the patch-clamp technique. Cells were continuously perfused with saline solution, in the absence or presence of the androgens studied, while applying 40 mV pulses of 400 ms from a holding potential of -60 mV in whole-cell configuration with nystatin-perforated patches. Androgens reversibly blocked noninactivating K(+) currents in a concentration-dependent manner without a latency period and with an order of efficacy of: 5β-dihydrotestosterone (DHT)>testosterone>5α-DHT. RT-PCR showed two isoforms of the α-pore forming subunits of BK channels. These channels are responsible for one third of the noninactivating current, according to the blockade of paxilline, a selective BK antagonist. Androgens seem to directly interact with BK channels since they were blocked in excised inside-out patches and independent of the whole-cell configuration and the NO-cGMP-dependent pathway. Testosterone, but not 5α- or 5β-DHT, increased BK currents in HEK-293 cells overexpressing the short isoform, suggesting a cellular selectivity based on the α-subunits. The effect on noninactivating currents may be responsible for the decrease of spontaneous action potential frequency. Long-term cellular incubation with testosterone did not modify noninactivating currents density in GH3 cells. It is remarkable that 5β-DHT, a reductase metabolite with weak androgenic activity, was the most efficient blocker.

The regulation of aromatase and androgen receptor expression during gonad development in male and female European eel

This research investigated the regulation of aromatase and androgen receptor gene expression in the brain-pituitary-gonad (BPG) axis of male and female European eels (Anguilla anguilla) during induced sexual maturation. Complete A. anguilla aromatase (aa-cyp19a1) and partial androgen receptor α and β (aa-ara and aa-arb) sequences were isolated, and qPCR assays were validated and used for quantification of transcript levels for these three genes. Expression levels of the genes varied with sex, tissue and stage of maturation. aa-arb was expressed at higher levels than aa-ara in the pituitary and gonad in both sexes, suggesting aa-arb is the physiologically most important androgen receptor in these tissues. In the female brain, a decrease in aa-ara and an increase in aa-cyp19a1 were observed at the vitellogenic stage. In contrast, a progressive increase in all three genes was observed in the pituitary and ovaries throughout gonadal development, with aa-arb and aa-cyp19a1 reaching significantly higher levels at the vitellogenic stage. In the male pituitary, a decrease in aa-arb and an increase in aa-cyp19a1 were observed at the beginning of spermatogenesis, and thereafter remained low and high, respectively. In the testis, the transcript levels of androgen receptors and aa-cyp19a1 were higher during the early stages of spermatogenesis and decreased thereafter. These sex-dependent differences in the regulation of the expression of aa-ara, aa-arb and cyp19a1 are discussed in relation to the role of androgens and their potential aromatization in the European eel during gonadal maturation.

Prostate cancer cells differ in testosterone accumulation, dihydrotestosterone conversion, and androgen receptor signaling response to steroid 5α-reductase inhibitors

BACKGROUND

Blocking 5α-reductase-mediated testosterone conversion to dihydrotestosterone (DHT) with finasteride or dutasteride is the driving hypothesis behind two prostate cancer prevention trials. Factors affecting intracellular androgen levels and the androgen receptor (AR) signaling axis need to be examined systematically in order to fully understand the outcome of interventions using these drugs.

METHODS

The expression of three 5α-reductase isozymes, as determined by immunohistochemistry and qRT-PCR, was studied in five human prostate cancer cell lines. Intracellular testosterone and DHT were analyzed using mass spectrometry. A luciferase reporter assay and AR-regulated genes were used to evaluate the modulation of AR activity.

RESULTS

Prostate cancer cells were capable of accumulating testosterone to a level 15-50 times higher than that in the medium. The profile and expression of 5α-reductase isozymes did not predict the capacity to convert testosterone to DHT. Finasteride and dutasteride were able to depress testosterone uptake in addition to lowering intracellular DHT. The inhibition of AR activity following drug treatment often exceeded the expected response due to reduced availability of DHT. The ability to maintain high intracellular testosterone might compensate for the shortage of DHT.

CONCLUSIONS

The biological effect of finasteride or dutasteride appears to be complex and may depend on the interplay of several factors, which include testosterone turnover, enzymology of DHT production, ability to use testosterone and DHT interchangeably, and propensity of cells for off-target AR inhibitory effect.

Interaction of Androst-5-ene-3β,17β-diol and 5α-androstane-3β,17β-diol with estrogen and androgen receptors: a combined binding and cell study

Androst-5-ene-3β,17β-diol (ADIOL) and 5α-androstane-3β,17β-diol (3β-DIOL), metabolites of dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT), respectively, are known to possess estrogenic properties. To better understand their hormonal action and roles in the proliferation of breast cancer (BC) cells, we studied their binding to sex-hormone receptors in estrogen receptor (ER)-positive (ZR-75-1 and T-47D) and ER-negative (MDA-MB-231) human BC cells. The results demonstrated that estradiol (E2), ADIOL and 3β-DIOL stimulated the proliferation of ZR-75-1 and T-47D cells, but had no effect on ER-negative cells. In the presence of estradiol, ADIOL and 3β-DIOL inhibited the estrogen-stimulated BC cell growth. This inhibition was counteracted by anti-androgens, which were unable to affect the ADIOL and 3β-DIOL stimulatory effects in E2-free medium. On the other hand, in the presence of tamoxifen, ADIOL and 3β-DIOL showed an additional anti-proliferative activity on hormone-sensitive BC cells compared with tamoxifen treatment alone. These results are similar to previous reports obtained using MCF-7 cells, which confirmed that ADIOL and 3β-DIOL stimulated estrogen-dependent BC cell growth via ERs, but inhibited growth via androgen receptors (ARs). Several steroids bind to both ER and AR in a different preference and degree, i.e. E2>estrone (E1)>ADIOL>3β-DIOL>testosterone (T)>DHT for ER and DHT>T>3β-DIOL>ADIOL>E1>E2 for AR. The relative binding affinities of ADIOL, 3β-DIOL, and E2 corresponded well to their respective potential in stimulating cell proliferation of ZR-75-1 and T-47D cells in our results. The intrinsic relationship between cell proliferation effects and binding affinities for receptors of several steroids was revealed here by a combined binding and cell study. This article is part of a Special Issue entitled 'Synthesis and biological testing of steroid derivatives as inhibitors'.

Steroid 5α-reductase in adult rat brain after neonatal dihydrotestosterone administration

Testosterone (T) is known to play an important masculinizing role in the developing brain of rat, including the regulation of 5α-reductase (5α-R) isozymes. However, the effects of dihydrotesterone (DHT), a more potent androgen than T, have not been elucidated. In this study, DHT was administered from day 5 through day 20 of postnatal life (period of postnatal sexual differentiation of the central nervous system) at doses of: 12 mg/kg/d on days 5, 6, 7, 8, 19, and 20; 15 mg/kg/d on days 9, 10, 11, 12, 16, 17, and 18; and 18 mg/kg/d on days 13, 14, and 15. In adulthood, quantitative RT-PCR was used to measure mRNA levels of 5α-R1 and 5α-R2 isozymes in the prefrontal cortex (PFC) of male and female rats with varied androgenic status. Under our study conditions, neonatal DHT administration influenced on adult PFC 5α-R isozymes levels and their regulation pattern by androgens, and this pattern was the inverse of that reported in adult neonatally T-treated rats.

Subdomain structure of the co-chaperone SGTA and activity of its androgen receptor client

Ligand-dependent activity of steroid receptors is affected by tetratricopeptide repeat (TPR)-containing co-chaperones, such as small glutamine-rich tetratricopeptide repeat-containing alpha (SGTA). However, the precise mechanisms by which the predominantly cytoplasmic TPR proteins affect downstream transcriptional outcomes of steroid signaling remain unclear. In this study, we assessed how SGTA affects ligand sensitivity and action of the androgen receptor (AR) using a transactivation profiling approach. Deletion mapping coupled with structural prediction, transcriptional assays, and in vivo regulation of AR-responsive promoters were used to assess the role of SGTA domains in AR responses. At subsaturating ligand concentrations of ≤ 0.1 nM 5α-dihydrotestosterone, SGTA overexpression constricted AR activity by an average of 32% (P<0.002) across the majority of androgen-responsive loci tested, as well as on endogenous promoters in vivo. The strength of the SGTA effect was associated with the presence or absence of bioinformatically predicated transcription factor motifs at each site. Homodimerizaion of SGTA, which is thought to be necessary for chaperone complex formation, was found to be dependent on the structural integrity of amino acids 1-80, and a core evolutionary conserved peptide within this region (amino acids 21-40) necessary for an effect of SGTA on the activity of both exogenous and endogenous AR. This study provides new insights into the subdomain structure of SGTA and how SGTA acts as a regulator of AR ligand sensitivity. A change in AR:SGTA ratio will impact the cellular and molecular response of prostate cancer cells to maintain androgenic signals, which may influence tumor progression.

Feed-forward inhibition of androgen receptor activity by glucocorticoid action in human adipocytes

We compared transcriptomes of terminally differentiated mouse 3T3-L1 and human adipocytes to identify cell-specific differences. Gene expression and high content analysis (HCA) data identified the androgen receptor (AR) as both expressed and functional, exclusively during early human adipocyte differentiation. The AR agonist dihydrotestosterone (DHT) inhibited human adipocyte maturation by downregulation of adipocyte marker genes, but not in 3T3-L1. It is interesting that AR induction corresponded with dexamethasone activation of the glucocorticoid receptor (GR); however, when exposed to the differentiation cocktail required for adipocyte maturation, AR adopted an antagonist conformation and was transcriptionally repressed. To further explore effectors within the cocktail, we applied an image-based support vector machine (SVM) classification scheme to show that adipocyte differentiation components inhibit AR action. The results demonstrate human adipocyte differentiation, via GR activation, upregulates AR but also inhibits AR transcriptional activity.

Effects of androgens on cardiovascular remodeling

Androgens, the male sex hormones, exert various biological effects on many target organs through the transcriptional effects of the nuclear androgen receptor (AR). ARs are expressed not only in classical target organs, such as the brain, genital organs, bone, and skeletal muscles, but also in the cardiovascular system. Because the female sex hormones estrogens are well-known to protect against cardiovascular disease, sex has been considered to have a significant clinical impact on cardiovascular mortality. However, the influence of androgens on the cardiovascular system has not been fully elucidated. To clarify this issue, we analyzed the effects of administration of angiotensin II and doxorubicin, an anticancer agent, in a loading model in male wild-type and AR-deficient mice. In this review, we focus on the actions of androgens as potential targets for the prevention of cardiovascular diseases in males.

Androgen receptor exon 1 mutation causes androgen insensitivity by creating phosphorylation site and inhibiting melanoma antigen-A11 activation of NH2- and carboxyl-terminal interaction-dependent transactivation

Naturally occurring germ line mutations in the X-linked human androgen receptor (AR) gene cause incomplete masculinization of the external genitalia by disrupting AR function in males with androgen insensitivity syndrome. Almost all AR missense mutations that cause androgen insensitivity syndrome are located in the highly structured DNA and ligand binding domains. In this report we investigate the functional defect associated with an AR exon 1 missense mutation, R405S, that caused partial androgen insensitivity. The 46,XX heterozygous maternal carrier had a wild-type Arg-405 CGC allele but transmitted an AGC mutant allele coding for Ser-405. At birth, the 46,XY proband had a bifid scrotum, hypospadias, and micropenis consistent with clinical stage 3 partial androgen insensitivity. Androgen-dependent transcriptional activity of AR-R405S expressed in CV1 cells was less than wild-type AR and refractory in androgen-dependent AR NH(2)- and carboxyl interaction transcription assays that depend on the coregulator effects of melanoma antigen-A11. This mutation created a Ser-405 phosphorylation site evident by the gel migration of an AR-R405S NH(2)-terminal fragment as a double band that converted to the wild-type single band after treatment with λ-phosphatase. Detrimental effects of the R405S mutation were related to the proximity of the AR WXXLF motif (433)WHTLF(437) required for melanoma antigen-A11 and p300 to stimulate transcriptional activity associated with the AR NH(2)- and carboxyl-terminal interaction. We conclude that the coregulator effects of melanoma antigen-A11 on the AR NH(2)- and carboxyl-terminal interaction amplify the androgen-dependent transcriptional response to p300 required for normal human male sex development in utero.

5α-Reduced glucocorticoids: a story of natural selection

5α-Reduced glucocorticoids (GCs) are formed when one of the two isozymes of 5α-reductase reduces the Δ(4-5) double bond in the A-ring of GCs. These steroids are largely viewed inert, despite the acceptance that other 5α-dihydro steroids, e.g. 5α-dihydrotestosterone, retain or have increased activity at their cognate receptors. However, recent findings suggest that 5α-reduced metabolites of corticosterone have dissociated actions on GC receptors (GRs) in vivo and in vitro and are thus potential candidates for safer anti-inflammatory steroids. 5α-Dihydro- and 5α-tetrahydro-corticosterone can bind with GRs, but interest in these compounds had been limited, since they only weakly activated metabolic gene transcription. However, a greater understanding of the signalling mechanisms has revealed that transactivation represents only one mode of signalling via the GR and recently the abilities of 5α-reduced GCs to suppress inflammation have been demonstrated in vitro and in vivo. Thus, the balance of parent GC and its 5α-reduced metabolite may critically affect the profile of GR signalling. 5α-Reduction of GCs is up-regulated in liver in metabolic disease and may represent a pathway that protects from both GC-induced fuel dyshomeostasis and concomitant inflammatory insult. Therefore, 5α-reduced steroids provide hope for drug development, but may also act as biomarkers of the inflammatory status of the liver in metabolic disease. With these proposals in mind, careful attention must be paid to the possible adverse metabolic effects of 5α-reductase inhibitors, drugs that are commonly administered long term for the treatment of benign prostatic hyperplasia.

Androgen regulation of 5α-reductase isoenzymes in prostate cancer: implications for prostate cancer prevention

The enzyme 5α-reductase, which converts testosterone to dihydrotestosterone (DHT), performs key functions in the androgen receptor (AR) signaling pathway. The three isoenzymes of 5α-reductase identified to date are encoded by different genes: SRD5A1, SRD5A2, and SRD5A3. In this study, we investigated mechanisms underlying androgen regulation of 5α-reductase isoenzyme expression in human prostate cells. We found that androgen regulates the mRNA level of 5α-reductase isoenzymes in a cell type-specific manner, that such regulation occurs at the transcriptional level, and that AR is necessary for this regulation. In addition, our results suggest that AR is recruited to a negative androgen response element (nARE) on the promoter of SRD5A3 in vivo and directly binds to the nARE in vitro. The different expression levels of 5α-reductase isoenzymes may confer response or resistance to 5α-reductase inhibitors and thus may have importance in prostate cancer prevention.

Potential prostate cancer drug target: bioactivation of androstanediol by conversion to dihydrotestosterone

High-affinity binding of dihydrotestosterone (DHT) to the androgen receptor (AR) initiates androgen-dependent gene activation, required for normal male sex development in utero, and contributes to prostate cancer development and progression in men. Under normal physiologic conditions, DHT is synthesized predominantly by 5α-reduction of testosterone, the major circulating androgen produced by the testis. During androgen deprivation therapy, intratumoral androgen production is sufficient for AR activation and prostate cancer growth, even though circulating testicular androgen levels are low. Recent studies indicate that the metabolism of 5α-androstane-3α, 17β-diol by 17β-hydroxysteroid dehydrogenase 6 in benign prostate and prostate cancer cells is a major biosynthetic pathway for intratumoral synthesis of DHT, which binds AR and initiates transactivation to promote prostate cancer growth during androgen deprivation therapy. Drugs that target the so-called backdoor pathway of DHT synthesis provide an opportunity to enhance clinical response to luteinizing-hormone-releasing hormone (LHRH) agonists or antagonists, AR antagonists, and inhibitors of 5α-reductase enzymes (finasteride or dutasteride), and other steroid metabolism enzyme inhibitors (ketoconazole or the recently available abiraterone acetate).

Reduced bone mass and muscle strength in male 5α-reductase type 1 inactivated mice

Androgens are important regulators of bone mass but the relative importance of testosterone (T) versus dihydrotestosterone (DHT) for the activation of the androgen receptor (AR) in bone is unknown. 5α-reductase is responsible for the irreversible conversion of T to the more potent AR activator DHT. There are two well established isoenzymes of 5α-reductase (type 1 and type 2), encoded by separate genes (Srd5a1 and Srd5a2). 5α-reductase type 2 is predominantly expressed in male reproductive tissues whereas 5α-reductase type 1 is highly expressed in liver and moderately expressed in several other tissues including bone. The aim of the present study was to investigate the role of 5α-reductase type 1 for bone mass using Srd5a1^−/− mice. Four-month-old male Srd5a1^−/− mice had reduced trabecular bone mineral density (−36%, p<0.05) and cortical bone mineral content (−15%, p<0.05) but unchanged serum androgen levels compared with wild type (WT) mice. The cortical bone dimensions were reduced in the male Srd5a1^−/− mice as a result of a reduced cortical periosteal circumference compared with WT mice. T treatment increased the cortical periosteal circumference (p<0.05) in orchidectomized WT mice but not in orchidectomized Srd5a1^−/− mice. Male Srd5a1^−/− mice demonstrated a reduced forelimb muscle grip strength compared with WT mice (p<0.05). Female Srd5a1^−/− mice had slightly increased cortical bone mass associated with elevated circulating levels of androgens. In conclusion, 5α-reductase type 1 inactivated male mice have reduced bone mass and forelimb muscle grip strength and we propose that these effects are due to lack of 5α-reductase type 1 expression in bone and muscle. In contrast, the increased cortical bone mass in female Srd5a1^−/− mice, is an indirect effect mediated by elevated circulating androgen levels.

Testosterone, not 5α-dihydrotestosterone, stimulates LRH-1 leading to FSH-independent expression of Cyp19 and P450scc in granulosa cells

Androgens are crucial for normal folliculogenesis and female fertility as evidenced in androgen receptor-null and granulosa cell conditional knockout mice. It is thought, however, that the multiple effects of androgens in the ovary are mainly complementary to the actions of gonadotropins. Using primary rat granulosa cells, we demonstrated that in the absence of gonadotropins, testosterone (T) increases aromatase (Cyp19) and P450 side-change cleavage expression, two enzymes crucial for normal ovarian function. T can be converted into estradiol, a classical estrogen, by Cyp19 and into 5α-dihydrotestosterone, a pure androgen, by 5α-reductase. However, inhibition of Cyp19 and/or 5α-reductase did not prevent the stimulatory effects of T. In contrast, the effect of this steroid was potentiated by blocking 5α-reductase. Additionally, T, not 5α-dihydrotestosterone, stimulates liver receptor homolog-1 (LRH-1) expression, whereas the expression of steroidogenic factor-1 (SF-1) was not affected by either steroid. LRH-1 and SF-1 are transcription factors known to be involved in the regulation of Cyp19. Accordingly, small interference RNA against LRH-1 prevented Cyp19 and P450 side-change cleavage up-regulation whereas anti-SF-1 small interference RNA had no effects. Chromatin immunoprecipitation demonstrated that T stimulation of LRH-1 leads to the recruitment of LRH-1 to the native Cyp19 promoter, which was not affected by cotreatment with 5α-reductase and Cyp19 inhibitors. Finally, gel shift and supershift analysis demonstrated that the androgen receptor binds to an androgen response element located within the LRH-1 promoter. These results provide novel evidence that T has a direct effect on the expression of genes involved in granulosa cell differentiation.

Analysis of interdomain interactions of the androgen receptor

High-affinity binding of testosterone or dihydrotestosterone to the androgen receptor (AR) triggers the androgen-dependent AR NH2- and carboxyl-terminal (N/C) interaction between the AR NH2-terminal FXXLF motif and the activation function 2 (AF2) hydrophobic binding surface in the ligand-binding domain. The functional importance of the AR N/C interaction is supported by naturally occurring loss-of-function AR AF2 mutations where AR retains high-affinity androgen binding but is defective in AR FXXLF motif binding. Ligands with agonist activity in vivo such as testosterone, dihydrotestosterone, and the synthetic anabolic steroids induce the AR N/C interaction and increase AR transcriptional activity in part by slowing the dissociation rate of bound ligand and stabilizing AR against degradation. AR ligand-binding domain competitive antagonists inhibit the agonist-dependent AR N/C interaction. Although the human AR N/C interaction is important for transcriptional activity, it has an inhibitory effect on transcriptional activity from AF2 by competing for p160 coactivator LXXLL motif binding. The primate-specific AR coregulatory protein, melanoma antigen gene protein-A11 (MAGE-A11), modulates the AR N/C interaction through a direct interaction with the AR FXXLF motif. Inhibition of AF2 transcriptional activity by the AR N/C interaction is relieved by AR FXXLF motif binding to the F-box region of MAGE-11. Described here are methods to measure the androgen-dependent AR N/C interdomain interaction and the influence of transcriptional coregulators.