Neonatal estrogen down-regulates prostatic androgen receptor through a proteosome-mediated protein degradation pathway

Estrogens and development of the rete testis, efferent ductules, epididymis and vas deferens

Estrogen has always been considered the female hormone and testosterone the male hormone. However, estrogen's presence in the testis and deleterious effects of estrogen treatment during development have been known for nearly 90 years, long before estrogen receptors (ESRs) were discovered. Eventually it was learned that testes actually synthesize high levels of estradiol (E2) and sequester high concentrations in the reproductive tract lumen, which seems contradictory to the overwhelming number of studies showing reproductive pathology following exogenous estrogen exposures. For too long, the developmental pathology of estrogen has dominated our thinking, even resulting in the "estrogen hypothesis" as related to the testicular dysgenesis syndrome. However, these early studies and the development of an Esr1 knockout mouse led to a deluge of research into estrogen's potential role in and disruption of development and function of the male reproductive system. What is new is that estrogen action in the male cannot be divorced from that of androgen. This paper presents what is known about components of the estrogen pathway, including its synthesis and target receptors, and the need to achieve a balance between androgen- and estrogen-action in male reproductive tract differentiation and adult functions. The review focuses on what is known regarding development of the male reproductive tract, from the rete testis to the vas deferens, and examines the expression of estrogen receptors and presence of aromatase in the male reproductive system, traces the evidence provided by estrogen-associated knockout and transgenic animal models and discusses the effects of fetal and postnatal exposures to estrogens. Hopefully, there will be enough here to stimulate discussions and new investigations of the androgen:estrogen balance that seems to be essential for development of the male reproductive tract.

Developmental estrogenization: Prostate gland reprogramming leads to increased disease risk with aging

While estrogens are involved in normal prostate morphogenesis and function, inappropriate early-life estrogenic exposures, either in type, dose or timing, can reprogram the prostate gland and lead to increased disease risk with aging. This process is referred to as estrogen imprinting or developmental estrogenization of the prostate gland. The present review discusses published and new evidence for prostatic developmental estrogenization that includes extensive research in rodent models combined with epidemiology findings that together have helped to uncover the architectural and molecular underpinnings that promote this phenotype. Complex interactions between steroid receptors, developmental morphoregulatory factors, epigenetic machinery and stem-progenitor cell targets coalesce to hard wire structural, cellular and epigenomic reorganization of the tissue which retains a life-long memory of early-life estrogens, ultimately predisposing the gland to prostatitis, hyperplasia and carcinogenesis with aging.

Effects of 2,4-dichlorophenoxyacetic acid on the ventral prostate of rats during the peri-pubertal, pubertal and adult stage

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is used on a wide variety of terrestrial and aquatic broadleaf weeds. 2,4-D has been shown to produce a wide range of adverse effects on animal and human health. The aim of the current study was to evaluate the effects of pre- and postnatal exposure to 2,4-D on rat ventral prostate (VP). Pregnant rats were exposed daily to oral doses of 70 mg/kg/day of 2,4-D from 16 days of gestation up to 23 days after delivery. Then, the treated groups (n = 8) were fed with a 2,4-D added diet until sacrificed by decapitation on postnatal day (PND) 45, 60, or 90. Morphometric studies were performed and androgen receptor (AR) protein levels in the VP were determined. AR, insulin-like growth factor-I (IGF-1) and insulin-like growth factor-I receptor (IGF-1R) mRNA expression in the VP along with testosterone (T), dihydroxytestosterone (DHT), growth hormone (GH) and IGF-1 serum levels were also determined to ascertain whether these parameters were differentially affected. Results of this study showed that 2,4-D exposure during gestation and until adulthood altered development of the prostate gland in male rats, delaying it at early ages while increasing its size in adults, indicate that 2,4-D could behave as endocrine disruptors (EDs).

Early-life estrogens and prostate cancer in an animal model

While early-life estrogens are thought to play a physiologic role in prostate gland development, inappropriate estrogenic exposures either in dose, type or temporally can reprogram the prostate gland and increase susceptibility to abnormal prostate growth with aging including carcinogenesis. This review discusses the evidence for developmental estrogenic reprogramming that leads to adult prostate disease in a rat model. We propose that estrogen imprinting of the prostate is mediated through both structural reorganization of the gland early in life and epigenomic reprogramming that permits life-long memory of the inappropriate developmental exposures including heightened sensitivity to rising estradiol levels with aging. Complex interactions between early epigenetic programming and later-life experiences results in an emergence of multiple epigenomic outcomes, with some contributing to carcinogenesis with aging.

Conversion of androgen receptor signaling from a growth suppressor in normal prostate epithelial cells to an oncogene in prostate cancer cells involves a gain of function in c-Myc regulation

In normal prostate, androgen-dependent androgen receptor (AR) signaling within prostate stromal cells induces their secretion of paracrine factors, termed “andromedins” which stimulate growth of the epithelial cells. The present studies demonstrate that androgen-dependent andromedin-driven growth stimulation is counter-balanced by androgen-induced AR signaling within normal adult prostate epithelial cells resulting in terminal G₀ growth arrest coupled with terminal differentiation into ΔNp63-negative, PSA-expressing secretory luminal cells. This cell autonomous AR-driven terminal differentiation requires DNA-binding of the AR protein, is associated with decreases in c-Myc m-RNA and protein, are coupled with increases in p21, p27, and SKP-2 protein expression, and does not require functional p53. These changes result in down-regulation of Cyclin D₁ protein and RB phosphoryation. shRNA knockdown documents that neither RB, p21, p27 alone or in combination are required for such AR-induced G₀ growth arrest. Transgenic expression of a constitutive vector to prevent c-Myc down-regulation overrides AR-mediated growth arrest in normal prostate epithelial cells, which documents that AR-induced c-Myc down-regulation is critical in terminal growth arrest of normal prostate epithelial cells. In contrast, in prostate cancer cells, androgen-induced AR signaling paradoxically up-regulates c-Myc expression and stimulates growth as documented by inhibition of both of these responses following exposure to the AR antagonist, bicalutamide. These data document that AR signaling is converted from a growth suppressor in normal prostate epithelial cells to an oncogene in prostate cancer cells during prostatic carcinogenesis and that this conversion involves a gain of function for regulation of c-Myc expression.

Effects of the oestrogen receptor antagonist Fulvestrant on expression of genes that affect organization of the epididymal epithelium

The role of oestrogens in epididymal function is still unclear. Knockout of the oestrogen receptor ESR1 (Esr1(-/-) ) or treatment with the anti-oestrogen Fulvestrant affect epididymal milieu and sperm motility. We investigated the effect of in vivo treatment of rats with Fulvestrant on: (i) expression of genes that may be important for the architecture and function of the epididymal epithelium: prominins 1 and 2, metalloproteinase 7, claudin 7, beta-catenin and cadherin 13, and (ii) levels of oestradiol and testosterone, and expression of oestrogen and androgen receptors, in the initial segment (IS), caput, corpus and cauda epididymis. Fulvestrant (i) reduced gene expression of prominin 1 (variant 1) in the caput, reduced prominin 1 protein content in the caput epididymis and in the efferent ductules, and increased the localization of prominin 1 in microvilli of the caput and corpus; (ii) reduced gene expression of prominin 2 in the corpus and cauda epididymis; (iii) increased the metalloproteinase 7 content in the apical region of principal cells from IS/caput; (iv) reduced in the corpus epididymis, but increased in the efferent ductules, the cadherin 13 mRNA level; (v) reduced testosterone but increased oestradiol levels in the corpus and cauda; (vi) increased the androgen receptor protein content in all regions of the epididymis, and the oestrogen receptor GPER in the corpus and cauda epididymis. In conclusion, treatment with Fulvestrant induced regional-specific changes in hormonal and steroid receptor content, and affected expression of proteins important for epithelial organization and absorption/secretion. The mechanisms of oestrogen action may differ among epididymal regions, which may contribute to determine region-specific sperm functions.

Gestational protein restriction delays prostate morphogenesis in male rats

Maternal malnutrition due to a low-protein diet is associated with functional disorders in adulthood, which may be related to embryonic development failures. The effects of gestational protein restriction on prostate morphogenesis in male offspring were investigated. Pregnant rat dams were divided into normoprotein (NP; fed a normal diet containing 17% protein) and hypoprotein (LP; fed a diet containing 6% protein) groups. On the day of birth (PND1), anogenital distance and bodyweight were measured in male pups. Seven males per experimental group (one male per litter) were killed, and the pelvic urethra was evaluated. LP offspring showed a significant reduction in bodyweight and anogenital distance on PND1. On three-dimensional reconstruction of the prostate, the number of prostatic buds was lower in LP than in NP males. Mesenchymal cells surrounding the buds were androgen-receptor positive, and the quantity and intensity of nucleus immunoreactivity was decreased in LP. The proliferation index was lower in LP than in NP prostatic buds. Immunoreactivity for α-actin in mesenchymal cells and that for epidermal growth factor receptor in epithelial cells was higher in NP than in LP. Our findings demonstrate that maternal protein restriction delays prostatic morphogenesis, probably because of considerable disruption in the epithelium–mesenchyme interaction.

Gender and estradiol as major factors in the expression and dimerization of nNOSα in rats with experimental diabetic gastroparesis

BACKGROUND

The molecular mechanisms of cellular changes responsible for diabetic gastroparesis, primarily seen in middle-aged women, still remain incompletely defined. We hypothesized that a decrease in the expression, dimerization, and post-translational modification of neuronal nitric oxide synthase alpha (nNOSα) is estrogen mediated and responsible for the gender-specific prevalence of this malady.

METHODS

We induced diabetes by injecting male and female rats with streptozotocin. Male diabetic rats without gastroparesis were then injected with estrogen for 3 weeks and evaluated for gastroparesis development. Gastric tissues were analyzed for the elucidation of biochemical events associated with diabetes and gastroparetic dysfunction.

RESULTS

Although male diabetic, gastroparetic (either streptozotocin- or estrogen-induced) rats exhibited similarity in disease pathology to that of females, the molecular mechanisms of development were different. Our results indicate that slow gastric emptying in both male diabetic, gastroparetic rat groups was not associated with the level of expression of nNOSα in gastric tissues. However, nNOSα dimerization, which reflects nNOSα activation, did decline slightly in the antrum of diabetic males with estrogen-induced gastroparesis, suggesting a possible estrogen role. Females with diabetic gastroparesis, in contrast, demonstrated significantly impaired levels and dimerization of nNOSα in the antrum and pylorus. Although the precise mechanism remains unknown, nNOSα dimerization impairment in female antrum is apparently associated with reduced phosphorylation of Ser(1416) in the activation loop of nNOSα.

CONCLUSION

Taken together, these results demonstrate that gender and estrogens may be leading factors, through molecular changes involved in nitric oxide synthesis down-regulation, within the antrum and pylorus of female diabetic, gastroparetic rats.

The industrial chemical bisphenol A (BPA) interferes with proliferative activity and development of steroidogenic capacity in rat Leydig cells

The presence of bisphenol A (BPA) in consumer products has raised concerns about potential adverse effects on reproductive health. Testicular Leydig cells are the predominant source of the male sex steroid hormone testosterone, which supports the male phenotype. The present report describes the effects of developmental exposure of male rats to BPA by gavage of pregnant and lactating Long-Evans dams at 2.5 and 25 μg/kg body weight from Gestational Day 12 to Day 21 postpartum. This exposure paradigm stimulated Leydig cell division in the prepubertal period and increased Leydig cell numbers in the testes of adult male rats at 90 days. Observations from in vitro experiments confirmed that BPA acts directly as a mitogen in Leydig cells. However, BPA-induced proliferative activity in vivo is possibly mediated by several factors, such as 1) protein kinases (e.g., mitogen-activated protein kinases or MAPK), 2) growth factor receptors (e.g., insulin-like growth factor 1 receptor-beta and epidermal growth factor receptors), and 3) the Sertoli cell-secreted anti-Mullerian hormone (also called Mullerian inhibiting substance). On the other hand, BPA suppressed protein expression of the luteinizing hormone receptor (LHCGR) and the 17beta-hydroxysteroid dehydrogenase enzyme (HSD17B3), thereby decreasing androgen secretion by Leydig cells. We interpret these findings to mean that the likely impact of deficits in androgen secretion on serum androgen levels following developmental exposure to BPA is alleviated by increased Leydig cell numbers. Nevertheless, the present results reinforce the view that BPA causes biological effects at environmentally relevant exposure levels and its presence in consumer products potentially has implication for public health.

Harmful effects of carbamazepine on the postnatal development of the rat ventral prostate

BACKGROUND

Carbamazepine (CBZ) is a first-line antiepileptic drug (AED), although it is also used for the treatments of psychiatric disorders and neuropathic pain. The CBZ utilization has been associated with male reproductive damage, including hormonal alterations, sexual dysfunction and reduction of sperm quality. The wide and long-term use of the CBZ is a common schedule in children and adolescents and alters the testosterone level in adult rats and humans. The objective of this work was to evaluate the CBZ side effects on the ventral prostate of rats from pre-puberty to sexual maturation, since the prostate is an androgen-dependent organ.

METHODS

Twenty three day-old male albino Wistar rats received CBZ diluted in propylene glycol (20 mg/Kg/i.p via). The treatment lasted 20, 40 and 70 days, according to the different stages of the rat sexual maturation. At the end of each treatment period, ventral prostates were removed and histologically processed. The prostate sections were submitted to the histopathological, morphological and stereological analyses using image analysis system.

RESULTS

Reductions of the glandular epithelium, glandular lumen and fibromuscular stroma volume of the ventral prostate were observed in adult rats treated with CBZ since the weaning. Triggering and degranulation of mast cells were observed in the fibromuscular stroma of prepubertal and pubertal CBZ treated rats.

CONCLUSIONS

The results suggest a direct effect of the CBZ on rat ventral prostate, evidenced by increase of mast cell and macrophage populations during pre-puberty and puberty causing a ventral prostate accentuated damage in the adult phase.

Possible mechanism of benign prostatic hyperplasia induced by androgen-estrogen ratios in castrated rats

OBJECTIVES

To explore the role of androgen-estrogen balance in benign prostatic hyperplasia (BPH) induced by varying doses of estradiol/testosterone propionate (E(2)/TP) in castrated rats.

MATERIALS AND METHODS

A total of 222 rats were divided into 37 groups at random, including 35 groups of different E(2)/TP, one control, and one castrated group. All 37 groups except the control group were castrated, for eliminating endogenesis of testosterone in rats. The treated groups were administered testosterone propionate (TP; at the dosages of 0.15, 0.74, 3.7, 18.5, and 92.6 mg/kg), combined with estradiol (E(2); at the dosage of 0, 0.4, 2, 10, 50, 250, and 1250 µg/kg) diluted in vegetable oil for 30 days, respectively, whereas the control groups received only vegetable oil. All prostate specimens were removed under anesthesia, then fixed and embedded in paraffin, for measuring the organ quotient, volume, area of prostate glandular cavity, and the height of prostate epithelia.

RESULTS

When the dosages of TP were 0.15, 3.7, 18.5, and 92.6 mg/kg, the degree of prostatic hyperplasia had no obvious dose-effect relationship with E(2). When TP was 0.74 mg/kg, with the increase of the dosage of E(2), the volume and quotient of prostate were increasing. However, when the dosage of E(2)exceeded 50 µg/kg, E(2)/TP was 5/74, the prostatic volume did not increase obviously.

CONCLUSION

The proper levels of E2/TP play an important role in the pathogenesis of BPH. In rats, the balance point of E(2)/TP is 5/74.

AR versus ER (α) expression in the testis and pituitary following chronic estrogen administration in adult rat

Modulation of the testis-pituitary axis has direct relevance to the expression of androgen and estrogen receptors. Androgen receptor (AR) and estrogen receptor (ERα) expression during hypospermatogenesis after chronic estrogen administration to rats was studied in the adult testis and pituitary utilizing immunohistochemistry, western blotting, and RT-PCR. Both organs demonstrated higher AR transcriptional activity gradually increasing from 15 days (d) to 30 d of estrogen treatment. However, the AR protein as measured by either immunostaining or western blotting demonstrated a significant decline. A distinct break down of the AR protein in the pituitary into two specific bands was seen. In contrast, higher ERα transcriptional activity coincided well with the rise in protein and immunoexpression in both organs. FSH and testosterone (serum, intra-testicular testosterone) were found significantly (p < 0.001) lowered compared with raised estradiol levels. Spermatogenesis was adversely affected and was associated with a significant increase in cell apoptosis in both organs. The pituitary demonstrated a higher rate of apoptosis at the end of 30 d of estrogen treatment. Taken together, the above data indicate that chronic estrogenization to adult rats up-regulates ERα but down-regulates AR protein expression in testis and pituitary which probably has a direct association to the marked rise in cell apoptosis in these organs.

Developmental exposures of male rats to soy isoflavones impact Leydig cell differentiation

Testicular Leydig cells, which are the predominant source of the male sex steroid hormone testosterone, express estrogen receptors (ESRs) and are subject to regulation by estrogen. Following ingestion, the two major isoflavones in soybeans, genistin and daidzin, are hydrolyzed by gut microflora to form genistein and daidzein, which have the capacity to bind ESRs and affect gene expression. Thus, the increasing use of soy-based products as nondairy sources of protein has raised concerns about the potential of these products to cause reproductive toxicity. In the present study, perinatal exposure of male rats to isoflavones induced proliferative activity in Leydig cells. Isoflavones have the capacity to act directly as mitogens in Leydig cells, because genistein treatment induced Leydig cell division in vitro. Genistein action regulating Leydig cell division involved ESRs, acting in concert with signaling molecules in the transduction pathway mediated by protein kinase B (AKT) and mitogen-activated protein kinase (MAPK). Enhanced proliferative activity in the prepubertal period increased Leydig cell numbers, which alleviated deficits in androgen biosynthesis and/or augmented serum and testicular testosterone concentrations in adulthood. Together, these observations indicate that the perinatal exposures of male rats to isoflavones affected Leydig cell differentiation, and they imply that including soy products in the diets of neonates has potential implications for testis function.

The ubiquitin-proteasome system in prostate cancer and its transition to castration resistance

Prostate cancer is the most common carcinoma in the male population. In its initial stage, the disease is androgen-dependent and responds therapeutically to androgen deprivation treatment but it usually progresses after a few years to an androgen-independent phase that is refractory to hormonal manipulations. The proteasome is a multi-unit protease system that regulates the abundance and function of a significant number of cell proteins, and its inhibition results in cancer cell growth inhibition and apoptosis and is already exploited in the clinic with the use of proteasome inhibitor bortezomib in multiple myeloma. In order to be recognized by the proteasome, a target protein needs to be linked to a chain of the small protein ubiquitin. In this paper, we review the role of ubiquitin-proteasome system (UPS) in androgen receptor-dependent transcription as well as in the castration resistant stage of the disease, and we discuss therapeutic opportunities that UPS inhibition offers in prostate cancer.

Gestational and neonatal-onset hypothyroidism alters androgen receptor status in rat prostate glands at adulthood

BACKGROUND

Infertility associated with congenital and early childhood hypothyroidism is an important reproductive health problem in men. Nevertheless, the exact mechanism underlying hypothyroidism-induced changes in the prostate gland, an androgen-dependent organ that contributes a significant portion of the seminal plasma remains obscure. The present study tested the hypothesis "transient gestational- or neonatal-onset hypothyroidism may have duration dependent and lobe specific effect on androgen receptor (AR) status in the prostate glands of adult rats."

METHODS

Hypothyroidism was induced in pregnant and lactating rats by feeding 0.05% methimazole (MMI) through drinking water during fetal and neonatal milestones of testicular and prostatic development. Pregnant dams had MMI exposure from 9th day post-coitum (dpc) to 14 dpc (group II) or 21 dpc (group III). Lactating mothers had MMI exposure from day 1 post-partum (dpp) to 14 dpp (group IV) or up to 29 dpp (group V). AR status in the dorsolateral and ventral prostate lobes (DLP and VP) of the pups was assessed by RT-PCR, western blot and radio receptor assay.

RESULTS

AR mRNA expression consistently decreased in the DLP of all groups, whereas it increased in VP of group III and V rats. AR protein consistently decreased in both DLP and VP of all experimental rats. AR nuclear ligand-binding activity diminished in groups II and IV, whereas it increased in groups III and V.

CONCLUSION

The results obtained support the proposed hypothesis and indicate that an optimum thyroid activity during pre- and neonatal period determines AR status in the prostate glands at adulthood.

Mechanism underlying transient gestational-onset hypothyroidism-induced impairment of posttesticular sperm maturation in adult rats

OBJECTIVE

To understand the mechanism underlying gestational-onset hypothyroidism-induced male infertility.

DESIGN

Controlled laboratory study.

SETTING

Research laboratory in a university department of endocrinology.

ANIMAL(S)

Wistar rat.

INTERVENTION(S)

Pregnant rats were exposed to methimazole from embryonic days 9 to 14, 18, and 21, covering specific fetal periods of differentiation and development of male reproductive tract organs.

MAIN OUTCOME MEASURE(S)

Fertility of male rats was assessed by testing sperm count, forward motility, and in vivo fertilizing ability. Secretory activity of the epididymis was evaluated by quantifying sialic acid, carnitine, and glycerylphosphorylcholine. Bioavailability of androgens was assessed by quantifying testosterone in serum and testicular interstitial fluid and epididymal 5alpha-reductase activity/mRNA expression. Androgen receptor (AR) status in the epididymis was tested by detecting the expression levels of its mRNA and protein, as well as ligand binding activity. Data were analyzed statistically by one-way analysis of variance.

RESULT(S)

Gestational exposure to methimazole decreased sperm forward motility, in vivo fertilizing ability, bioavailability of androgens, AR status, and secretory activity of the epididymis in adult rats.

CONCLUSION(S)

Transient gestational-onset hypothyroidism affects male fertility by impairing posttesticular sperm maturation process in the epididymis, owing to subnormal androgen(s) bioavailability, AR expression, and AR functional activity.

Oestrogen imprinting causes nuclear changes in epithelial cells and overall inhibition of gene transcription and protein synthesis in rat ventral prostate

Oestrogen exposure during the early post-natal period affects male growth, physiology, and susceptibility to disease in adult life. The prostate gland is susceptible to this oestrogen imprinting, showing a reduced expression of the androgen receptor and inability to respond to androgen stimulus. In this context, we decided to study key signalling regulators of ventral prostate (VP) functioning after early postnatal exposure to high-dose oestrogen. Our results showed a decrease of mTOR phosphorylation and its direct downstream target 4EBP. It is known that mTOR-induced signalling is a pivotal pathway of cell metabolism, which is able to control gene transcription and protein synthesis. We then decided to investigate other indicators of a reduced metabolism in the oestrogenized prostate, and found that the luminal epithelial cells were shorter, less polarized and had smaller nuclei containing more compacted chromatin, suggesting that a general mechanism of regulating gene expression and protein synthesis could be installed in the epithelium of the oestrogenized VP. To evaluate this idea, we analysed nucleolar morphology, and measured the amount of ribosomes and the level of methylation of the 45S ribosomal RNA promoter region. These data indicated that the nucleolus was dismantled and that the methylation at the 45S promoter was increased ( approximately five-fold). Taken together, the results support the idea that the oestrogenized prostate maintains a very low transcriptional level and protein turnover by affecting canonical signalling pathways and promoting nuclear and nucleolar changes.

Novel biomarkers for risk of prostate cancer: results from a case-control study

BACKGROUND

Although the estrogens estrone and estradiol are recognized to play very important roles in the risk of developing prostate cancer (Pca), the molecular mechanism by which estrogens initiate and/or promote Pca is still unknown. Substantial evidence supports that specific metabolites of estrogens, catechol estrogen quinones, can react with DNA to form depurinating estrogen-DNA adducts. Apurinic sites derived from depurination of these adducts can induce mutations leading to cancer. Once released from DNA, depurinating estrogen-DNA adducts are shed from cells into the bloodstream and excreted in urine. By analyzing profiles of estrogen metabolites, conjugates, and depurinating DNA adducts in urine from men with and without prostate cancer, potential biomarkers of Pca can be detected. The goal of this case-control study was to detect and identify potential biomarkers of Pca.

METHODS

Urine samples from fourteen cases, men diagnosed with Pca, and 125 controls, men who had not been diagnosed with Pca, were partially purified by solid phase extraction and analyzed by ultraperformance liquid chromatography/tandem mass spectrometry. The urinary levels of androgens, estrogens, estrogen metabolites, conjugates and depurinating DNA adducts were measured.

RESULTS

The ratio of depurinating estrogen-DNA adducts to the sum of the corresponding estrogen metabolites and conjugates was significantly higher in cases (median: 57.34) compared to controls (median: 23.39) (P < 0.001).

CONCLUSIONS

This study suggests that depurinating estrogen-DNA adducts could serve as potential biomarkers to predict risk of Pca. They also could be useful tools for early clinical diagnosis and development of suitable strategies to prevent Pca.

Estrogen-regulated development and differentiation of the prostate

Both androgens and estrogens play a significant role in the prostate and are critical for normal prostate growth and development, as well as the maintenance of adult prostatic homeostasis throughout life. It is the balance of these two hormones, rather than each individually, that is important for prostatic development and differentiation. Estrogen action is mediated by the estrogen receptors, ERalpha and ERbeta. ERalpha is expressed throughout the prostatic tissue during fetal and early neonatal life, and if activated inappropriately, produces late-life disease, including inflammation and emergence of pre-malignant pathologies. In contrast, ERbeta expression is initiated after ERalpha, is localized primarily to the epithelium, and appears to be important during later periods of development such as puberty and adulthood, acting to regulate cellular proliferation and differentiation in the adult tissue. Therefore, there is also a spatial and temporal balance between ERalpha and ERbeta that is critical for development. Together with the shifting balance between androgens and estrogens themselves, the subtle, yet critical, balance between the activity of ERalpha and ERbeta is what ultimately determines the response of the prostate to estrogen, and is crucial for prostate health.

Transgenerational effects of the endocrine disruptor vinclozolin on the prostate transcriptome and adult onset disease

PURPOSE

The ability of an endocrine disruptor exposure during gonadal sex determination to promote a transgenerational prostate disease phenotype was investigated in the current study.

METHODS

Exposure of an F0 gestating female rat to the endocrine disruptor vinclozolin during F1 embryo gonadal sex determination promoted a transgenerational adult onset prostate disease phenotype. The prostate disease phenotype and physiological parameters were determined for males from F1 to F4 generations and the prostate transcriptome was assessed in the F3 generation.

RESULTS

Although the prostate in prepubertal animals develops normally, abnormalities involving epithelial cell atrophy, glandular dysgenesis, prostatitis, and hyperplasia of the ventral prostate develop in older animals. The ventral prostate phenotype was transmitted for four generations (F1-F4). Analysis of the ventral prostate transcriptome demonstrated 954 genes had significantly altered expression between control and vinclozolin F3 generation animals. Analysis of isolated ventral prostate epithelial cells identified 259 genes with significantly altered expression between control and vinclozolin F3 generation animals. Characterization of regulated genes demonstrated several cellular pathways were influenced, including calcium and WNT. A number of genes identified have been shown to be associated with prostate disease and cancer, including beta-microseminoprotein (Msp) and tumor necrosis factor receptor superfamily 6 (Fadd).

CONCLUSIONS

The ability of an endocrine disruptor to promote transgenerational prostate abnormalities appears to involve an epigenetic transgenerational alteration in the prostate transcriptome and male germ-line. Potential epigenetic transgenerational alteration of prostate gene expression by environmental compounds may be important to consider in the etiology of adult onset prostate disease.

Neonatal exposure to estrogen in the Wistar rat decreases estrogen receptor-beta and induces epithelial proliferation of the prostate in the adult

BACKGROUND/AIMS

The effects of environmental endocrine disruptors on the male reproductive system have received much attention. We attempted to assess the responsible reproduction period vulnerable to decrease in ER beta mRNA by exposing neonate rats to disruptors.

METHODS

Each of 64 male Wistar rats was given an injection of estradiol at a dose of 25 mug or oil on days 1, 3 and 5 after birth. These rats were sacrificed on days 80, 120, 160 and 180 and then subjected to measurements of both serum and tissue testosterone levels. Real-time quantitative polymerase chain reaction (PCR) was used to measure the levels of androgen receptor (AR) and estrogen receptor-beta (ER beta) mRNA of the ventral prostate. Histological compositions were analyzed by quantitative morphometry. Immunohistochemical analysis of proliferating cell nuclear antigen (PCNA) was determined.

RESULTS

The incidence of epithelial components by histomorphometry and the expression of PCNA was significantly higher in the estrogen group in the mature adult (day 160). Levels of AR and ER beta mRNAs in the estrogen group were significantly lower in middle-aged rats (day 180).

CONCLUSION

Estrogen exposure in the neonatal period to Wistar rats decreases the number of ER beta in the mature adult and accelerates cell proliferation.

5alpha-Androstane-3beta,17beta-diol (3beta-diol), an estrogenic metabolite of 5alpha-dihydrotestosterone, is a potent modulator of estrogen receptor ERbeta expression in the ventral prostrate of adult rats

Prostate is one of the major targets for dihydrotestosterone (DHT), however this gland is also recognized as a nonclassical target for estrogen as it expresses both types of estrogen receptors (ER), especially ERbeta. Nevertheless, the concentrations of aromatase and estradiol in the prostate are low, indicating that estradiol may not be the only estrogenic molecule to play a role in the prostate. It is known that DHT can be metabolized to 5alpha-androstane-3beta,17beta-diol (3beta-diol), a hormone that binds to ERbeta but not to AR. The concentration of 3beta-diol in prostate is much higher than that of estradiol. Based on the high concentration of 3beta-diol and since this metabolite is a physiological ERbeta ligand, we hypothesized that 3beta-diol would be involved in the regulation of ERbeta expression. To test this hypothesis, adult male rats were submitted to castration followed by estradiol, DHT or 3beta-diol replacement. ERbeta and AR protein levels in the prostate were investigated by immunohistochemistry and Western blotting assays. The results showed that after castration, the structure of the prostate was dramatically changed and ERbeta and AR protein levels were decreased. Estradiol had just minor effects on the parameters analyzed. DHT-induced partial recovery of ERbeta while it was the most effective inductor of AR expression. Replacement with 3beta-diol-induced the highest levels of ERbeta, but was comparatively less effective in recovering the AR expression and the gland structure. These results offer evidence that one functional role of 3beta-diol in the prostate may be autoregulation of its natural receptor, ERbeta.

Estrogen sensitivity of target genes and expression of nuclear receptor co-regulators in rat prostate after pre- and postnatal exposure to the ultraviolet filter 4-methylbenzylidene camphor

BACKGROUND AND OBJECTIVES

In previous studies, we found that the ultraviolet filter 4-methyl-benzylidene camphor (4-MBC) exhibits estrogenic activity, is a preferential estrogen receptor (ER)-beta ligand, and interferes with development of female reproductive organs and brain of both sexes in rats. Here, we report effects on male development.

METHODS

4-MBC (0.7, 7, 24, 47 mg/kg/day) was administered in chow to the parent generation before mating, during gestation and lactation, and to offspring until adulthood. mRNA was determined in prostate lobes by real-time reverse transcription-polymerase chain reaction and protein was determined by Western blot analysis.

RESULTS

4-MBC delayed male puberty, decreased adult prostate weight, and slightly increased testis weight. Androgen receptor (AR), insulin-like growth factor-1 (IGF-1), ER-alpha, and ER-beta expression in prostate were altered at mRNA and protein levels, with stronger effects in dorsolateral than ventral prostate. To assess sensitivity of target genes to estrogens, offspring were castrated on postnatal day 70, injected with 17beta-estradiol (E(2); 10 or 50 microg/kg, sc) or vehicle on postnatal day 84, and sacrificed 6 hr later. Acute repression of AR and IGF-1 mRNAs by E(2), studied in ventral prostate, was reduced by 4-MBC exposure. This was accompanied by reduced co-repressor N-CoR (nuclear receptor co-repressor) protein in ventral and dorsolateral prostate, whereas steroid receptor coactivator-1 (SRC-1) protein levels were unaffected.

CONCLUSIONS

Our data indicate that 4-MBC affects development of male reproductive functions and organs, with a lowest observed adverse effect level of 0.7 mg/kg. Nuclear receptor coregulators were revealed as targets for endocrine disruptors, as shown for N-CoR in prostate and SRC-1 in uterus. This may have widespread effects on gene regulation.

Estrogen receptor alpha mediates estrogen-inducible abnormalities in the developing penis

Previously, we reported an association between estrogen receptor-alpha (ERalpha) upregulation and detrimental effects of neonatal diethylstilbestrol (DES) exposure in the rat penis. The objective of this study was to employ the ERalpha knockout (ERalphaKO) mouse model to test the hypothesis that ERalpha mediates DES effects in the developing penis. ERalphaKO and wild-type C57BL/6 mice received oil or DES at a dose of 0.2 microg/pup per day (0.1 mg/kg) on alternate days from postnatal days 2 to 12. Fertility was tested at 80-240 days of age and tissues were examined at 96-255 days of age. DES caused malformation of the os penis, significant reductions in penile length, diameter, and weight, accumulation of fat cells in the corpora cavernosa penis, and significant reductions in weight of the bulbospongiosus and levator ani muscles in wild-type mice. Conversely, ERalphaKO mice treated with DES developed none of the above abnormalities. While nine out of ten male mice sired pups in the wild-type/control group, none did in the wild-type/DES group. ERalphaKO mice, despite normal penile development, are inherently infertile. Both plasma and intratesticular testosterone levels were unaltered in the DES-treated wild-type or DES-treated ERalphaKO mice when compared with controls, although testosterone concentration was much higher in the ERalphaKO mice. Hence, the resistance of ERalphaKO mice to developing penile abnormalities provides unequivocal evidence of an obligatory role for ERalpha in mediating the harmful effects of neonatal DES exposure in the developing penis.

Estrogen receptors: how do they signal and what are their targets

During the past decade there has been a substantial advance in our understanding of estrogen signaling both from a clinical as well as a preclinical perspective. Estrogen signaling is a balance between two opposing forces in the form of two distinct receptors (ER alpha and ER beta) and their splice variants. The prospect that these two pathways can be selectively stimulated or inhibited with subtype-selective drugs constitutes new and promising therapeutic opportunities in clinical areas as diverse as hormone replacement, autoimmune diseases, prostate and breast cancer, and depression. Molecular biological, biochemical, and structural studies have generated information which is invaluable for the development of more selective and effective ER ligands. We have also become aware that ERs do not function by themselves but require a number of coregulatory proteins whose cell-specific expression explains some of the distinct cellular actions of estrogen. Estrogen is an important morphogen, and many of its proliferative effects on the epithelial compartment of glands are mediated by growth factors secreted from the stromal compartment. Thus understanding the cross-talk between growth factor and estrogen signaling is essential for understanding both normal and malignant growth. In this review we focus on several of the interesting recent discoveries concerning estrogen receptors, on estrogen as a morphogen, and on the molecular mechanisms of anti-estrogen signaling.

Risk factors for hypospadias in the estrogen receptor 2 gene

CONTEXT

Hypospadias is a common inborn error of the male genitalia of complex, and still elusive, etiology. The presence of active estrogen receptors (ESRs) in the developing male urethra, predominantly the ESR2, has suggested a role of estrogens in the otherwise androgen-dependent male genital differetiation. Moreover, imbalances between these two steroid hormones have been suggested to disturb the external genital development. This has been supported by the association between longer (CA)n variants in the ESR2 gene with lower androgen levels as well as with hypospadias.

OBJECTIVE

The aim of this study was to analyze the effect of ESR2 gene variants on the risk to hypospadias.

DESIGN, PARTICIPANTS, AND METHODS

Four haplotype-tagging single nucleotide polymorphisms (rs2987983, rs1887994, rs1256040, and rs1256062), the (CA)n polymorphism, and two additional promoter single nucleotide polymorphisms (rs10483774 and rs1271572), mapping to a transcription factor binding region, were typed and analyzed in a Swedish cohort of 354 boys with nonsyndromic hypospadias and 380 healthy controls.

RESULTS

Association was identified with longer variants of the (CA)n polymorphism in intron 6 and with a region of intense transcription factor binding, in the putative promoter region, mapping to rs2987983 and rs10483774. The two regions are in low-linkage disequilibrium, meaning that they are not necessarily inherited together as a haplotype; logistic regression analysis indicates that these two risk effects are not independent.

CONCLUSIONS

The present study evidences two nonindependent risk factors for hypospadias in the ESR2 gene. We discuss possible mechanisms that explain how these variants may affect male urethral development.

Role of estrogen in induction of penile dysmorphogenesis: a review

In this review, we report permanent dysmorphogenesis of the penis and loss of fertility in adult rats treated neonatally with estrogen. Specifically, we report replacement of smooth muscle cells and cavernous spaces by fat cells in the corpus cavernosum penis, but not in the adjoining corpus spongiosum. Induction of these novel, region-specific phenotypes is dose-dependent, requires a critical window of exposure and associated with decreased testosterone and up-regulation of estrogen receptor α (ERα). The resistance of ERα knockout mice to develop these abnormalities implies an unequivocal role for ERα in mediating maldevelopment of the penis. Additionally, the prevention of estrogen-inducible penile abnormalities by ER antagonist ICI 182 780 implies that a functional ER-mediated pathway is essential for inducing penile abnormalities. Likewise, the ability of testosterone or dihydrotestosterone to negate these abnormalities suggests a role for an androgen receptor (AR)-mediated pathway. Taken together, these observations led us to hypothesize that neonatal estrogen exposure, via an ER-mediated pathway (direct action) or an AR-mediated pathway (indirect action through decreased testosterone) or both pathways, up-regulates ERα expression in stromal cells of the penis, which are then reprogrammed such that their differentiation into smooth muscle cells is inhibited and their differentiation into adipocytes is stimulated.

Estradiol and Bisphenol A stimulate androgen receptor and estrogen receptor gene expression in fetal mouse prostate mesenchyme cells

BACKGROUND

Hormonal alterations during development have lifelong effects on the prostate gland. Endogenous estrogens, including 17beta-estradiol (E(2)), and synthetic estrogenic endocrine disruptors, such as bisphenol A (BPA), have similar effects on prostate development. Increasing exposure to estrogens within the low-dose, physiologic range results in permanent increases in the size and androgen responsiveness of the prostate, whereas exposure within the high-dose, pharmacologic range has the opposite effects.

OBJECTIVES

We tested the hypothesis that the low-dose effects of estrogens on the developing prostate are associated with increased expression of androgen receptor (Ar) and estrogen receptor 1 (alpha) (Esr1) genes in mesenchyme cells.

METHODS

Ar and Esr1 mRNA levels were quantified in primary cultures of fetal mouse prostate mesenchyme cells treated with E(2) and BPA.

DISCUSSION

Ar and Esr1 mRNA expression increased in response to E(2), with thresholds of 0.001 and 0.037 nM, respectively; and in response to BPA, with a threshold of 1 nM for both mRNAs. We did not observe the expected inhibition of Ar mRNA expression by pharmacologic levels of E(2) relative to unexposed cells.

CONCLUSIONS

The observed induction of gene expression occurred at concentrations within the range of free E(2) previously shown to permanently increase prostate size, thus supporting the involvement of direct effects of estrogens on gene expression in prostate mesenchyme. The effects of BPA occurred within the range of concentrations currently measured in human serum, demonstrating the vulnerability of developing tissues to xenoestrogens.

Developmental estrogen exposures predispose to prostate carcinogenesis with aging

Prostate morphogenesis occurs in utero in humans and during the perinatal period in rodents. While largely driven by androgens, there is compelling evidence for a permanent influence of estrogens on prostatic development. If estrogenic exposures are abnormally high during the critical developmental period, permanent alterations in prostate morphology and function are observed, a process referred to as developmental estrogenization. Using the neonatal rodent as an animal model, it has been shown that early exposure to high doses of estradiol results in an increased incidence of prostatic lesions with aging which include hyperplasia, inflammatory cell infiltration and prostatic intraepithelial neoplasia or PIN, believed to be the precursor lesion for prostatic adenocarcinoma. The present review summarizes research performed in our laboratory to characterize developmental estrogenization and identify the molecular pathways involved in mediating this response. Furthermore, recent studies performed with low-dose estradiol exposures during development as well as exposures to environmentally relevant doses of the endocrine disruptor bisphenol A show increased susceptibility to PIN lesions with aging following additional adult exposure to estradiol. Gene methylation analysis revealed a potential epigenetic basis for the estrogen imprinting of the prostate gland. Taken together, our results suggest that a full range of estrogenic exposures during the postnatal critical period - from environmentally relevant bisphenol A exposure to low-dose and pharmacologic estradiol exposures - results in an increased incidence and susceptibility to neoplastic transformation of the prostate gland in the aging male which may provide a fetal basis for this adult disease.

A study of the prostate, androgens and sexual activity of male rats

BACKGROUND

The prostate is a sexual gland that produces important substances for the potency of sperm to fertilize eggs within the female reproductive tract, and is under complex endocrine control. Taking advantage of the peculiar behavioral pattern of copulating male rats, we developed experimental paradigms to determine the influence of sexual behavior on the level of serum testosterone, prostate androgen receptors, and mRNA for androgen receptors in male rats displaying up to four consecutive ejaculations.

METHODS

The effect of four consecutive ejaculations was investigated by determining levels of (i) testosterone in serum by solid phase RIA, (ii) androgen receptors at the ventral prostate with Western Blots, and (iii) androgen receptors-mRNA with RT-PCR. Data were analyzed with a one-way ANOVA followed by a post hoc application of Dunnett's test if required.

RESULTS

The constant execution of sexual behavior did not produce any change in the weight of the ventral prostate. Serum testosterone increased after the second ejaculation, and remained elevated even after four ejaculations. The androgen receptor at the ventral prostate was higher after the first to third ejaculations, but returned suddenly to baseline levels after the fourth ejaculation. The level of mRNA increased after the first ejaculation, continued to increase after the second, and reached the highest peak after the third ejaculation; however, it returned suddenly to baseline levels after the fourth ejaculation.

CONCLUSION

Four consecutive ejaculations by sexually experienced male rats had important effects on the physiological responses of the ventral prostate. Fast responses were induced as a result of sexual behavior that involved an increase and decrease in androgen receptors after one and four ejaculations, respectively. However, a progressive response was observed in the elevation of mRNA for androgen receptors, which also showed a fast decrease after four ejaculations. All of these changes with the prostate gland occurred in the presence of a sustained elevation of testosterone in the serum that started after two ejaculations. A consideration of these fast-induced changes suggests that the nerve supply plays a key role in prostate physiology during the sexual behavior of male rats.

The role of estrogens in normal and abnormal development of the prostate gland

Estrogens play a physiologic role during prostate development with regard to programming stromal cells and directing early morphogenic events. However, if estrogenic exposures are abnormally high during the critical developmental period, permanent alterations in prostate branching morphogenesis and cellular differentiation will result, a process referred to as neonatal imprinting or developmental estrogenization. These perturbations are associated with an increased incidence of prostatic lesions with aging, which include hyperplasia, inflammation, and dysplasia. To understand how early estrogenic exposures can permanently alter the prostate and predispose it to neoplasia, we examined the effects of estrogens on prostatic steroid receptors and key developmental genes. Transient and permanent alterations in prostatic AR, ERalpha, ERbeta, and RARs are observed. We propose that estrogen-induced alterations in these critical transcription factors play a fundamental role in initiating prostatic growth and differentiation defects by shifting the prostate from an androgen-dominated gland to one whose development is regulated by estrogens and retinoids. This in turn leads to specific disruptions in the expression patterns of key prostatic developmental genes that normally dictate morphogenesis and differentiation. Specifically, we find transient reductions in Nkx3.1 and permanent reductions in Hoxb-13, which lead to differentiation defects particularly within the ventral lobe. Prolonged developmental expression of Bmp-4 contributes to hypomorphic growth throughout the prostatic complex. Reduced expression of Fgf10 and Shh and their cognate receptors in the dorsolateral lobes leads to branching defects in those specific regions in response to neonatal estrogens. We hypothesize that these molecular changes initiated early in life predispose the prostate to the neoplastic state upon aging.

Mepartricin long-term administration regulates steroid hormone and adrenergic receptor concentrations in the prostate of aged rats

Mepartricin is a semi-synthetic macrolide antibiotic developed as a drug for the treatment of benign prostatic hyperplasia (BPH) in human patients. In the present study, aged rats are used as an experimental model to evaluate the effects of mepartricin on circulating hormone concentrations and prostate receptor concentrations, to compare these possible effects with clinical findings observed in long-term treated dogs. Fifty-six aged male rats were randomly divided into four experimental groups treated orally with 0 (group 1), 2 mg (group 2), 5 mg (group 3) and 20 mg (group 4) mepartricin/kg of body weight. for 28 days respectively. Serum oestradiol and testosterone concentrations were measured by radio-immune-assays methods. Binding assays were used to measure the prostate concentrations of oestrogen receptors (ER), androgen receptors (AnR), alpha(1)-adrenergic receptor (alpha(1)-AR), and beta-adrenerergic receptor (beta-AR) subtypes. Mepartricin induced a significant reduction of prostate weight and serum oestradiol concentrations. Serum testosterone concentrations were unaffected. The treatment induced a significant down-regulation of ER concentrations (P < 0.05) and a significant up-regulation of AnR (P < 0.05) in rat prostate. Mepartricin induced a significant (P < 0.05) dose-dependent up-regulation of alpha(1)-AR and beta(2)-AR. In contrast, the concentration of beta(3)-ARs was significantly decreased (P < 0.05) in treated animals. The increase in prostate beta(2)-AR concentrations observed in subjects treated with mepartricin may be a favourable element in the evolution of BPH, because of the role exerted by these receptors in the control of prostatic smooth muscle relaxation. Curiously, beta(3)-AR concentrations were significantly reduced in treated animals. Data collected suggest that the prostatic beta-AR expression might be strongly influenced by oestrogen deprivation (mepartricin treatment); therefore, the combination of oestrogen suppression (mepartricin) and adrenergic suppression (alpha(1)-AR blockers) may be proposed as a possible nonhormonal therapeutic strategy for the treatment of benign prostatic hyperplasia in dogs.

Transient neonatal estrogen exposure to estrogen-deficient mice (aromatase knockout) reduces prostate weight and induces inflammation in late life

Exposure of newborn male mice to estrogens is associated with age-related changes in prostate size and induction of epithelial hyperplasia and dysplasia. Whether these changes directly result from systemic estrogen administration or indirect effects of estrogens on systemic testosterone levels is unclear. We have addressed this question using aromatase-knockout (ArKO) mice that are estrogen-deficient during their lifespan but have elevated androgen levels and develop prostate enlargement and hyperplasia (McPherson SJ, Wang H, Jones ME, Pedersen J, Iismaa TP, Wreford N, Simpson ER, Risbridger GP: Endocrinology 2001, 142:2458-2467). Circulating testosterone and dihydrotestosterone levels were significantly decreased by neonatal diethylstilbestrol treatment, remained suppressed in adult wild-type mice, but rapidly returned to control levels in ArKO animals. However, adult prostate weight and luminal size were reduced in both wild-type and ArKO animals. Because both wild-type and ArKO mice developed epithelial hyperplasia and inflammation following neonatal diethylstilbestrol treatment, this validates that estrogens directly cause prostatic inflammation and epithelial hyperplasia. Furthermore, because ArKO mice are estrogen-deficient, this study demonstrates the sensitivity of the neonatal period to estrogen exposure and the long range and permanent nature of the prostatic responses that occur. Finally, this study establishes the ArKO mouse model of estrogen deficiency as a unique approach to study the effects of estrogens, estrogenic factors, and endocrine disruptors on prostate development.

Fulvestrant (ICI 182,780) down-regulates androgen receptor expression and diminishes androgenic responses in LNCaP human prostate cancer cells

The androgen receptor (AR) plays a key role in the development and progression of prostate cancer. Targeting the AR for down-regulation would be a useful strategy for treating prostate cancer, especially hormone-refractory or androgen-independent prostate cancer. In the present study, we showed that the antiestrogen fulvestrant [ICI 182,780 (ICI)] effectively suppressed AR expression in several human prostate cancer cells, including androgen-independent cells. In LNCaP cells, ICI (10 micromol/L) treatment decreased AR mRNA expression by 43% after 24 hours and AR protein expression by approximately 50% after 48 hours. We further examined the mechanism of AR down-regulation by ICI in LNCaP cells. ICI did not bind to the T877A-mutant AR present in the LNCaP cells nor did it promote proteasomal degradation of the AR. ICI did not affect AR mRNA or protein half-life. However, ICI decreased the activity of an AR promoter-luciferase reporter plasmid transfected into LNCaP cells, suggesting a direct repression of AR gene transcription. As a result of AR down-regulation by ICI, androgen induction of prostate-specific antigen mRNA and protein expression were substantially attenuated. Importantly, LNCaP cell proliferation was significantly inhibited by ICI treatment. Following 6 days of ICI treatment, a 70% growth inhibition was seen in androgen-stimulated LNCaP cells. These data show that the antiestrogen ICI is a potent AR down-regulator that causes significant inhibition of prostate cancer cell growth. Our study suggests that AR down-regulation by ICI would be an effective strategy for the treatment of all prostate cancer, especially AR-dependent androgen-independent prostate cancer.

Aggregation and proteasome: the case of elongated polyglutamine aggregation in spinal and bulbar muscular atrophy

Aggregates, a hallmark of most neurodegenerative diseases, may have different properties, and possibly different roles in neurodegeneration. We analysed ubiquitin-proteasome pathway functions during cytoplasmic aggregation in polyglutamine (polyQ) diseases, using a unique model of motor neuron disease, the SpinoBulbar Muscular Atrophy. The disease, which is linked to a polyQ tract elongation in the androgen receptor (ARpolyQ), has the interesting feature that ARpolyQ aggregation is triggered by the AR ligand, testosterone. Using immortalized motor neurons expressing ARpolyQ, we found that a proteasome reporter, YFPu, accumulated in absence of aggregates; testosterone treatment, which induced ARpolyQ aggregation, allowed the normal clearance of YFPu, suggesting that aggregation contributed to proteasome de-saturation, an effect not related to AR nuclear translocation. Using AR antagonists to modulate the kinetic of ARpolyQ aggregation, we demonstrated that aggregation, by removing the neurotoxic protein from the soluble compartment, protected the proteasome from an excess of misfolded protein to be processed.

Toremifene--a promising therapy for the prevention of prostate cancer and complications of androgen deprivation therapy

Deregulation of the estrogen axis in humans prompts a series of tissue-specific events. In the breast and prostate, alterations in estrogen signalling lead to genotypic and phenotypic molecular alterations that result in dysplastic cellular appearance, deregulated cell growth and carcinoma. In bone, decreased estrogen leads to increased osteoclastogenesis and bone resorption, decreased bone mineral density and a significant fracture risk. Toremifene is a selective estrogen receptor modulator that exerts pharmacological activity in the breast, bone and prostate. An intense interest in developing this agent for prostate cancer chemoprevention is based on the reduction of premalignant and malignant prostate lesions in a transgenic model of prostate cancer. Biological and clinical activity was demonstrated in Phase II trials by the prevention of progression to prostate cancer in men with high-grade prostate intraepithelial neoplasia and through suppression of bone turnover biomarkers and increased bone mineral density in men on androgen deprivation therapy for prostate cancer.

Pathways of endocrine disruption during male sexual differentiation and masculinization

After testis formation, further development of a male phenotype (masculinization) is driven by three hormones from the foetal testis: anti-Müllerian hormone, insulin-like factor 3, and testosterone. These hormones divert the development of reproductive and other organs from female to male and also play a role in testis development. The hormone dependence of masculinization renders this process inherently susceptible to disruption by factors that interfere with hormone production, bioavailability, metabolism, or action. This susceptibility is illustrated by the high prevalence of congenital masculinization disorders (cryptorchidism, hypospadias) and disorders in young adult men (low sperm counts, testis cancer), which may also stem from maldevelopment (dysgenesis) of the foetal testis. Testicular dysgenesis occurring in humans, or which is induced in animal models by foetal exposure to certain phthalates, is associated with impaired hormone production by the foetal testis. There is currently no definitive evidence that exposure of humans to environmental chemicals can induce testicular dysgenesis and/or impair masculinization, though pathways via which this could potentially occur are established.

Anabolic responsiveness of skeletal muscles correlates with androgen receptor protein but not mRNA

Anabolic effects of androgens on skeletal muscle are well documented, but the physiological and biochemical bases of these effects are poorly understood. Skeletal muscles that differ in their androgen responsiveness can be used to examine these mechanisms. We compared androgen receptor mRNA and protein levels of the rat levator ani, a perineal skeletal muscle that depends on androgens for its normal maintenance and function with that of the rat extensor digitorum longus, a limb muscle that does not require androgens. Western immunoblotting indicated that androgen receptor protein is significantly elevated in the levator ani relative to the extensor digitorum longus. Surprisingly, steady state androgen receptor mRNA levels were equivalent in these muscles, as determined by Northern blot analysis and quantitative RT-PCR. These results suggest that androgen responsiveness of skeletal muscles is determined by the level of androgen receptor protein in a particular muscle and that androgen receptor protein content is regulated by translational or post-translational mechanisms.

17beta-estradiol induces apoptosis in the developing rodent prostate independently of ERalpha or ERbeta

Estrogens induce both proliferative and antiproliferative responses in the prostate gland. To date, antiproliferative effects of estrogens are generally considered to be due to systemic antiandrogenic actions. However, estrogen action mediated through estrogen receptor (ER) beta was recently suggested as another mechanism of induction of apoptosis in the prostate. This study aimed to explore the hypothesis that the antiproliferative effects of estrogen are directly mediated through ERbeta using a prostate organ culture system. We previously reported effects of 17beta-estradiol (E2) using rat ventral prostate (VP) tissues, and adapted the system for culturing mouse tissues. In both rat and mouse models, estrogen-induced apoptosis was detected that was spatially and regionally localized to the epithelium of the distal tips. Using organ cultures of alphaER knockout (alphaERKO) and betaERKO prostates, we failed to demonstrate that apoptosis induced by E2 was mediated through either receptor subtype. Activation of ER-selective ligands (ERalpha, propyl pyrazole triol, ERbeta, diaryl-proprionitrile, and 5alpha-androstane-3beta,17beta-diol) in organ culture experiments failed to induce apoptosis, as did the membrane impermeable conjugate E2:BSA, discounting the possibility of nongenomic effects. Consequently, E2 regulation of androgen receptor (AR) expression was examined and, in the presence of nanomolar testosterone levels, E2 caused a specific reduction in AR protein expression in wild-type, alphaERKO, and betaERKO mice, particularly in the distal region where apoptosis was detected. This down-regulation of AR protein provides a possible mechanism for the proapoptotic action of E2 that is independent of ERs or nongenomic effects.

Endocrine disrupting compounds and prostate cancer

Prostate cancer is a major health concern and is treated based on its hormone dependence. Agents that alter hormone action can have substantial biological effects on prostate cancer development and progression. As such, there is significant interest in uncovering the potential effects of endocrine disrupting compound (EDC) exposure on prostate cancer. The present review is focused on agents that alter hormone action in the prostate and how they may impact cancer growth or treatment.

Breast cancer resistance protein-mediated efflux of androgen in putative benign and malignant prostate stem cells

Malignantly transformed stem cells represent a potential common nidus for the primary cancer and the recurrent cancer that arises after treatment failure. Putative prostate stem cells and prostate tumor stem cells in benign and malignant human prostate tissue, in primary human prostate xenografts, and in the transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse model of prostate cancer, are defined by expression of breast cancer resistance protein (BCRP), a marker of pluripotent hematopoietic, muscle, and neural stem cells, and by an absence of androgen receptor (AR) protein. Inhibition of BCRP-mediated efflux of dihydrotestosterone by novobiocin or fumitremorgin C in a rat prostate progenitor cell line that expresses BCRP and AR mRNAs, but minimal AR protein, results in stabilization and nuclear translocation of AR protein, providing a mechanism for lack of AR protein in BCRP-expressing stem cells. In both benign and malignant human prostate tissue, the rare epithelial cells that express BCRP and lack AR protein are localized in the basal cell compartment, survive androgen deprivation, and maintain proliferative potential in the hypoxic, androgen-deprived prostate. Putative prostate tumor stem cells that express BCRP but not AR protein in TRAMP are the source of a BCRP-negative and AR-negative, Foxa2- and SV40Tag-expressing, transit amplifying compartment that progresses to the poorly differentiated carcinomas that arise rapidly after castration. Therefore, BCRP expression isolates prostate stem/tumor stem cells from the prostate tissue microenvironment through constitutive efflux of androgen, protecting the putative tumor stem cells from androgen deprivation, hypoxia, or adjuvant chemotherapy, and providing the nidus for recurrent prostate cancer.

Regulation of androgen receptor levels: implications for prostate cancer progression and therapy

Androgen deprivation has been the standard therapy for advanced and metastatic prostate cancer for over half a century, as prostate tumors are initially dependent on androgens for growth and survival. Unfortunately, in most patients undergoing androgen ablation, relapse (recurrent tumor growth) eventually occurs. The actions of the principal androgens, testosterone and dihydrotestosterone (DHT), are mediated via androgen receptors (ARs), ligand-activated transcription factors that belong to the nuclear receptor superfamily. Because of the presence of transcriptionally active ARs in tumors from recurrent or androgen-independent disease, there is a heightened interest in new therapeutic paradigms that target the AR and its regulatory pathways. The regulation of AR levels is highly complex with control exerted by several pathways and in a cell-, tissue-, and developmental-stage specific manner. Androgens are important regulators of AR mRNA and protein through transcriptional and post-transcriptional mechanisms. This article reviews the evidence implicating the AR in recurrent prostate cancer and discusses the multiple mechanisms that regulate AR levels in normal and neoplastic cells. The complexity of AR regulation suggests that there will be an ample array of potential new drug targets for modulating levels of this receptor, a key signaling molecule in prostate cancer.

Metastases of prostate cancer express estrogen receptor-beta

OBJECTIVES

To examine estrogen receptor-beta (ERbeta) expression in prostate cancer (CaP) metastases, thereby providing a basis for conducting estrogen therapy studies in patients with metastatic CaP. Advanced androgen-independent CaP is a serious health problem with no effective treatment at present. Estrogens have been reported to inhibit the growth of CaP cells in androgen-free environments. Recent reports have shown that the prostatic epithelium and primary CaP cells express ERbeta, with decreased expression of ERbeta accompanying CaP progression. It has been proposed that ERbeta may play a role in the growth regulation of prostate cells. The targeting of ERs by selective ER modulators might be an effective method of treating advanced CaP.

METHODS

The anti-ERbeta antibody GC17 was used in immunohistochemistry to characterize the expression of ERbeta in CaP metastasis specimens (n = 60) obtained from 20 patients who had died of CaP. Statistical analyses were performed to evaluate the association of ERbeta expression with clinical parameters, including prostate-specific antigen levels, radiotherapy, and estrogen exposure.

RESULTS

Nuclear ERbeta staining was detected in all bone CaP metastases (33 of 33) and nonosseous CaP metastases (27 of 27). However, a large variability in the percentage of immunoreactive cells (5% to 100%) was found among patients, as well as among individual patient samples. A statistically significant negative association between nuclear ERbeta staining and estrogen exposure (P = 0.05) was detected.

CONCLUSIONS

Our data have shown that ERbeta is expressed in CaP metastases, validating the initiation of studies to evaluate selective ER modulators for treatment of advanced CaP.

Neonatal treatment of rats with diethylstilboestrol (DES) induces stromal-epithelial abnormalities of the vas deferens and cauda epididymis in adulthood following delayed basal cell development

This study investigated whether transient, neonatal (days 2-12) treatment of rats with the potent oestrogen, diethylstilboestrol (DES), altered the structure of the cauda epididymis/vas deferens in adulthood, and if the changes observed related to altered development of basal cells in early puberty. Neonatal treatment with 10 microg DES resulted in the following during adulthood: (a) coiling of the normally straight initial vas deferens, (b) gross epithelial abnormalities, (c) 4-fold widening of the periductal non-muscle layer, (d) infiltration of immune cells across the epithelium into the lumen, and (e) reduction/absence of sperm from the vas deferens lumen. Amongst affected animals>75% exhibited reduced epithelial immunoexpression of androgen receptor and aberrant oestrogen receptor-alpha immunoexpression and 63% exhibited multi-layering of basal cells coincident with increased epithelial cell proliferation. None of the aforementioned changes occurred in rats treated neonatally with 0.1 microg DES. As basal cells play a key role in the development of epithelia such as that in the epididymis and vas deferens, we went on to investigate if neonatal DES treatment affected basal cell development. In controls, basal cells were first evident at day 10 (vas deferens) or day 18 (cauda). Rats treated with 10 microg, but not those treated with 0.1 microg, DES, showed approximately 90% reduction (P<0.001) in basal cell numbers at day 15 and day 18. This decrease coincided with gross suppression of testosterone levels; co-treatment of rats with 10 microg DES+testosterone maintained basal cell numbers at control levels at day 18. However, suppression of testosterone production (GnRH antagonist treatment) or action (flutamide treatment) did not alter basal cell numbers. It is concluded that neonatal exposure to high oestrogen levels coincident with reduced testosterone action results in abnormal changes in the adult cauda/vas deferens that are preceded by delayed differentiation of basal cells. These findings imply a role for androgens and oestrogens in basal cell development and suggest that this may be pivotal in determining normal epithelial (and stromal) development of the cauda/vas deferens.

Estrogen-induced abnormal accumulation of fat cells in the rat penis and associated loss of fertility depends upon estrogen exposure during critical period of penile development

We previously reported that diethylstilbestrol (DES) or estradiol valerate (EV) exposure at a dose of 0.10-0.12 mg/kg, or higher, per day, on alternate days, from postnatal days 2-12, resulted in abnormal penis development and infertility (H. O. Goyal et al., 2005, J. Androl. 26, 32-43). The objective of this study was to identify a critical developmental period(s) during which EV exposure results in the observed penile abnormalities. Male pups received EV at a dose of 0.10-0.12 mg/kg on postnatal day(s) 1, 1-3, 4-6, 1-6, 7-12, 13-18, 19-24, or 25-30. Fertility was tested at 102-115 days of age and tissues were examined at 117-137 days. Both penile morphology and fertility were unaltered in rats treated with EV after 12 days of age. Conversely, except in rats treated on postnatal day 1 only, none of the males treated prior to 12 days of age sired pups, and all had abnormal penises, including varying degrees of abnormal accumulation of fat cells and loss of cavernous spaces and smooth muscle cells in the corpora cavernosa penis, which were maximal in the 1-6-day group. Also, the preputial sheath was partially released or its release was delayed, and the weight of the bulbospongiosus muscle was significantly reduced. Plasma testosterone (T) in the 1-6- and 4-6-day groups and intratesticular T in the 4-6-day group were significantly lower. The testosterone surge, characteristic of controls in the first week of life, was suppressed in the 1-3-day group. Estrogen receptor alpha mRNA expression was enhanced in the body of the penis in the 1-3-day group, but not in the 13-18-day group. Hence, EV exposure prior to 12 days of age (as short as 1-3 days postnatal), but not after 12 days of age, results in long-term abnormal penile morphology, characterized by abnormal accumulation of fat cells in the corpora cavernosa penis and, consequently, loss of fertility.

The role of Fgf10 signaling in branching morphogenesis and gene expression of the rat prostate gland: lobe-specific suppression by neonatal estrogens

Brief exposure of rats to high-dose estrogen during the neonatal period interrupts prostate development in a lobe-specific manner and predisposes the gland to dysplasia with aging, a phenomenon referred to as developmental estrogenization. Our previous studies have revealed that these effects are initiated through altered steroid receptor expression; however, the immediate downstream targets remain unclear. We have recently shown that developmental expression of Shh-ptc-gli is downregulated in the dorsolateral prostate following estrogenization, and this is responsible, in part, for branching deficits observed in that prostatic region specifically. In the present study, we examine the role of Fgf10 signaling during rat prostate development and as a mediator of the developmental estrogenized phenotype. Fgf10 and FgfR2iiib localize to the distal signaling center of elongating and branching ducts in separate prostate lobes where they regulate the expression of multiple morphoregulatory genes including Shh, ptc, Bmp7, Bmp4, Hoxb13, and Nkx3.1. Ventral and lateral lobe organ cultures and mesenchyme-free ductal cultures demonstrate a direct role for Fgf10/FgfR2iiib in ductal elongation, branching, epithelial proliferation, and differentiation. Based on these findings, a model is proposed depicting the localized expression and feedback loops between several morphoregulatory factors in the developing prostate that contribute to tightly regulated branching morphogenesis. Similar to Shh-ptc-gli, neonatal estrogen exposure downregulates Fgf10, FgfR2iiib, and Bmp7 expression in the dorsolateral prostate while ventral lobe expression of these genes is unaffected. Lateral prostate organ culture experiments demonstrate that growth and branching inhibition as well as Fgf10/FgfR2iiib suppression are mediated directly at the prostatic level. Furthermore, exogenous Fgf10 fully rescues the growth and branching deficits due to estrogen exposure. Together, these studies demonstrate that alterations in Fgf10 signaling are a proximate cause of Shh-ptc-gli and Bmp7 downregulation that together result in branching inhibition of the dorsolateral prostate following neonatal estrogen exposure.