An endocrine pathway in the prostate, ERbeta, AR, 5alpha-androstane-3beta,17beta-diol, and CYP7B1, regulates prostate growth

Dihydrotestosterone synthesis pathways from inactive androgen 5α-androstane-3β,17β-diol in prostate cancer cells: Inhibition of intratumoural 3β-hydroxysteroid dehydrogenase activities by abiraterone

Intratumoural dihydrotestosterone (DHT) synthesis could be an explanation for castration resistance in prostate cancer (PC). By using liquid chromatography-mass spectrometry, we evaluated the intratumoral DHT synthesis from 5α-androstane-3β,17β-diol (3β-diol), which is inactive androgen metabolized from DHT. 3β-diol had biochemical potential to be converted to DHT via three metabolic pathways and could stimulate PC cell growth. Especially, 3β-diol was not only converted back to upstream androgens such as dehydroepiandrosterone (DHEA) or Δ5-androstenediol but also converted directly to DHT which is the main pathway from 3β-diol to DHT. Abiraterone had a significant influence on the metabolism of DHEA, epiandrosterone and 3β-diol, by the inhibition of the intratumoural 3β-hydroxysteroid dehydrogenase (3β-HSD) activities which is one of key catalysts in androgen metabolic pathway. The direct-conversion of 3β-diol to DHT was catalysed by 3β-HSD and abiraterone could inhibit this activity of 3β-HSD. These results suggest that PC had a mechanism of intratumoural androgen metabolism to return inactive androgen to active androgen and intratumoural DHT synthesis from 3β-diol is important as one of the mechanisms of castration resistance in PC. Additionally, the inhibition of intratumoural 3β-HSD activity could be a new approach to castration-resistant prostate cancer treatment.

MicroRNA-17 induces epithelial-mesenchymal transition consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer

MicroRNA-17 (miRNA-17/miR‑17) expression has been confirmed to be significantly higher in colorectal cancer tissues than in normal tissues. However, its exact role in colorectal cancer has not yet been fully elucidated. In this study, we found that miR-17 not only promoted epithelial-mesenchymal transition (EMT), but also promoted the formation of a stem cell-like population in colon cancer DLD1 cells. We also wished to determine the role of cytochrome P450, family 7, subfamily B, polypeptide 1 (CYP7B1) in CRC. miR-17 was overexpressed using a recombinant plasmid and CYP7B1 was silenced by transfection with shRNA. Western blot analysis was used to determine protein expression in the DLD1 cells and in tumor tissues obtained from patients with colon cancer. Our results revealed that miR‑17 overexpression led to the degradation of CYP7B1 mRNA expression in DLD1 cells. In addition, we found that the silencing of CYB7B1 promoted EMT and the formation of a stem cell-like population in the cells. Thus, our findings demonstrate that miR‑17 induces EMT consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer.

Opposing Effects of Cyclooxygenase-2 (COX-2) on Estrogen Receptor β (ERβ) Response to 5α-Reductase Inhibition in Prostate Epithelial Cells

Current pharmacotherapies for symptomatic benign prostatic hyperplasia (BPH), an androgen receptor-driven, inflammatory disorder affecting elderly men, include 5α-reductase (5AR) inhibitors (i.e. dutasteride and finasteride) to block the conversion of testosterone to the more potent androgen receptor ligand dihydrotestosterone. Because dihydrotestosterone is the precursor for estrogen receptor β (ERβ) ligands, 5AR inhibitors could potentially limit ERβ activation, which maintains prostate tissue homeostasis. We have uncovered signaling pathways in BPH-derived prostate epithelial cells (BPH-1) that are impacted by 5AR inhibition. The induction of apoptosis and repression of the cell adhesion protein E-cadherin by the 5AR inhibitor dutasteride requires both ERβ and TGFβ. Dutasteride also induces cyclooxygenase type 2 (COX-2), which functions in a negative feedback loop in TGFβ and ERβ signaling pathways as evidenced by the potentiation of apoptosis induced by dutasteride or finasteride upon pharmacological inhibition or shRNA-mediated ablation of COX-2. Concurrently, COX-2 positively impacts ERβ action through its effect on the expression of a number of steroidogenic enzymes in the ERβ ligand metabolic pathway. Therefore, effective combination pharmacotherapies, which have included non-steroidal anti-inflammatory drugs, must take into account biochemical pathways affected by 5AR inhibition and opposing effects of COX-2 on the tissue-protective action of ERβ.

Androgen receptor-mediated non-genomic effects of vinclozolin on porcine ovarian follicles and isolated granulosa cells: Vinclozolin and non-genomic effects in porcine ovarian follicles

The present study investigated the influence of the androgen receptor (AR) agonists testosterone (T) and dihydrotestosterone (DHT), and vinclozolin (Vnz), a fungicide with antiandrogenic activity, on non-genomic signal transduction within ovarian follicles. Porcine granulosa cells (GCs) isolated from mature follicles were cultured for 48h. For the last 24h of culture, they were exposed to T (10(-7)M), DHT (10(-7)M), Vnz (1.4×10(-5)M), T and Vnz (T+Vnz), or DHT and Vnz (DHT+Vnz) at the same concentrations. To better imitate in vivo conditions, whole follicles (4-6mm in diameter) were incubated (24h) in an organ culture system with the same factors. Expression of AR mRNA and protein was determined by real-time PCR and western blot analyses. To demonstrate AR localization in cultured GCs and whole follicles, immunocytochemistry and immunohistochemistry were performed, respectively. To elucidate the possible non-genomic action of Vnz in GCs, protein expression and the activity of ERK1/2 and Akt kinases were determined by western blot and ELISA analyses. The immunocytochemistry and immunohistochemistry results showed that exposure of GCs and follicles to Vnz resulted in cytoplasmic and perinuclear AR localization. Real-time PCR and western blot analysis showed that AR mRNA and protein expression increased (P≤0.001) in GC cultures after combined treatment with an androgen and Vnz. In whole follicles, such treatment also increased AR mRNA with a decrease in the respective protein expression (P≤0.001). Moreover, addition of T or DHT with Vnz increased the activity of ERK1/2 and Akt kinases in cultured GCs (P≤0.001). The results suggest a novel mechanism for Vnz action in porcine ovarian follicles on both AR mRNA and protein levels. Thus, this environmental antiandrogen activates non-genomic signaling pathways, as indicated by the increased activity of both investigated kinases observed within minutes of Vnz addition. Given the widespread presence of Vnz in the environment, elucidation of its non-genomic action should be the subject of studies on female fertility.

Estrogens and Male Lower Urinary Tract Dysfunction

Benign prostatic hyperplasia (BPH) and associated lower urinary tract symptoms (LUTS) are common clinical problems in urology and affect the majority of men at some time during their lives. The development of BPH/LUTS is associated with an increased ratio of estrogen to androgen levels, and this ratio, when mimicked in a variety of animals, induces BPH and lower urinary tract dysfunction (LUTD). While the precise molecular etiology remains unclear, estrogens have been implicated in the development and maintenance of BPH. Numerous endogenous and exogenous estrogens exist in humans. These estrogens act via multiple estrogen receptors to promote or inhibit prostatic hyperplasia and other BPH-associated processes. The prostate is an estrogen target tissue, and estrogens directly and indirectly affect growth and differentiation of prostate. The precise role of estrogen action directly affecting prostate growth and differentiation in the context of BPH is an understudied area and remains to be elucidated. Estrogens and selective estrogen receptor modulators (SERMs) have been shown to promote or inhibit prostate proliferation illustrating their potential roles in the development of BPH as therapy. More work will be required to identify estrogen signaling pathways associated with LUTD in order to develop more efficacious drugs for BPH treatment and prevention.

Tissue Effects in a Randomized Controlled Trial of Short-term Finasteride in Early Prostate Cancer

BACKGROUND

In the Prostate Cancer Prevention Trial, finasteride selectively suppressed low-grade prostate cancer and significantly reduced the incidence of prostate cancer in men treated with finasteride compared with placebo. However, an apparent increase in high-grade disease was also observed among men randomized to finasteride. We aimed to determine why and hypothesized that there is a grade-dependent response to finasteride.

METHODS

From 2007 to 2012, we randomized dynamically by intranet-accessible software 183 men with localized prostate cancer to receive 5mg finasteride or placebo daily in a double-blind study during the 4-6weeks preceding prostatectomy. As the primary end point, the expression of a predefined molecular signature (ERβ, UBE2C, SRD5A2, and VEGF) differentiating high- and low-grade tumors in Gleason grade (GG) 3 areas of finasteride-exposed tumors from those in GG3 areas of placebo-exposed tumors, adjusted for Gleason score (GS) at prostatectomy, was compared. We also determined androgen receptor (AR) levels, Ki-67, and cleaved caspase 3 to evaluate the effects of finasteride on the expression of its downstream target, cell proliferation, and apoptosis, respectively. The expression of these markers was also compared across grades between and within treatment groups. Logistic regression was used to assess the expression of markers.

FINDINGS

We found that the predetermined molecular signature did not distinguish GG3 from GG4 areas in the placebo group. However, AR expression was significantly lower in the GG4 areas of the finasteride group than in those of the placebo group. Within the finasteride group, AR expression was also lower in GG4 than in GG3 areas, but not significantly. Expression of cleaved caspase 3 was significantly increased in both GG3 and GG4 areas in the finasteride group compared to the placebo group, although it was lower in GG4 than in GG3 areas in both groups.

INTERPRETATION

We showed that finasteride's effect on apoptosis and AR expression is tumor grade dependent after short-term intervention. This may explain finasteride's selective suppression of low-grade tumors observed in the PCPT.

Flaxseed reduces epithelial proliferation but does not affect basal cells in induced benign prostatic hyperplasia in rats

PURPOSE

This study aimed to quantitatively and qualitatively evaluate the effects of a flaxseed-based diet on the histoarchitecture of the prostate of normal Wistar rats and of rats with induced BPH.

METHODS

The study included four experimental groups of ten animals each: casein control group (CCG), who were fed a casein-based diet; flaxseed control group (FCG), who were fed a flaxseed-based diet; hyperplasia-induced casein group (HICG), who were fed a casein-based diet; and hyperplasia-induced flaxseed group (HIFG), who were fed a flaxseed-based diet. Hyperplasia was induced by the subcutaneous implantation of silicone pellets containing testosterone propionate. After 20 weeks, the rats were euthanized and their prostate fixed in buffered formalin. Tissue sections were stained with HE, picrosirius red and immunostained for nuclear antigen p63. Histomorphometric analysis evaluated the epithelial thickness, epithelial area, individual luminal area, and total area of prostatic alveoli.

RESULTS

The mean epithelial thickness obtained for HIFG and HICG was 16.52 ± 1.65 and 20.58 ± 2.86 µm, respectively. The mean epithelial thickness in HICG was greater than that in the other groups tested. HIFG had a smaller epithelial thickness and lower percentage of papillary projections in the prostatic alveoli. No significant difference was observed between CCG and FCG. The total area and mean alveolar area showed no significant differences between the groups. The number of cells immunostained for p63 was not significantly different between the groups evaluated.

CONCLUSION

These results suggest that flaxseed has a protective effect on the prostate epithelium in BPH-induced animals.

Neonatal Estrogen Receptor β Is Important in the Permanent Inhibition of Epithelial Cell Proliferation in the Mouse Uterus

Estrogen receptor α (ERα) plays a pivotal role in the mouse uterine and vaginal epithelial cell proliferation stimulated by estrogen, whereas ERβ inhibits cell proliferation. ERβ mRNA is expressed in neonatal uteri and vaginae; however, its functions in neonatal tissues have not been ascertained. In this study, we investigated the ontogenic mRNA expression and localization of ERβ, and its roles in cell proliferation in neonatal uteri and vaginae of ERβ knockout (βERKO) mice. ERβ mRNA and protein were abundant in the uterine and vaginal epithelia of 2-day-old mice and decreased with age. In uterine and vaginal epithelia of 2-day-old βERKO mice, cell proliferation was greater than that in wild-type animals and in uterine epithelia of 90- and 365-day-old βERKO mice. In addition, p27 protein, known as a cyclin-dependent kinase inhibitor, was decreased in the uteri of 90- and 365-day-old βERKO mice. Inhibition of neonatal ERs by ICI 182780 (an ER antagonist) treatment stimulated cell proliferation and decreased p27 protein in the uterine luminal epithelium of 90-day-old mice but not in the vaginal epithelium. These results suggest that neonatal ERβ is important in the persistent inhibition of epithelial cell proliferation with accumulation of p27 protein in the mouse uterus. Thus, suppression of ERβ function in the uterine epithelium during the neonatal period may be responsible for a risk for proliferative disease in adults.

Resveratrol reduces the levels of circulating androgen precursors but has no effect on, testosterone, dihydrotestosterone, PSA levels or prostate volume. A 4-month randomised trial in middle-aged men

BACKGROUND

Resveratrol is a naturally occurring polyphenol with purported inhibitory effects on prostate growth and cancer development. A number of studies have demonstrated that resveratrol reduces prostate growth in animal models and reduces prostate cell growth in vitro. Based on these pre-clinical findings, interest in resveratrol is increasing in relation to the management of benign prostate hyperplasia (BPH) and prostate cancer. So far, no human trials have evaluated the effects of resveratrol on circulating androgens, prostate size, or biochemical markers of prostate size.

METHODS

In a randomized placebo controlled clinical study using two doses of resveratrol (150 mg or 1,000 mg resveratrol daily) for 4 months, we evaluated the effects on prostate size, prostate specific antigen (PSA) and sex steroid hormones in 66 middle-aged men suffering from the metabolic syndrome(MetS).

RESULTS

At baseline, prostate size and PSA were positively correlated (R = 0.34, P < 0.007) as was prostate size and age (R = 0.37, P < 0.003). Prostate size did not correlate with testosterone, free testosterone, dihydrotestosterone (DHT), or any other androgen precursor at baseline. The highest dose of resveratrol lowered the serum level of androstenedione 24% (P = 0.052), dehydroepiandrosterone (DHEA) 41% (P < 0.01), and dehydroepiandrosterone-sulphate (DHEAS) 50% (p<0.001), compared to the control group. However, prostate size and levels of PSA, testosterone, free testosterone and DHT remained unchanged.

CONCLUSION

In this population of middle-aged men suffering from MetS, high dose resveratrol (1,000 mg daily) administration for 4 months significantly lowered serum levels of the androgen precursors androstenedione, DHEA and DHEAS, whereas prostate size and circulating levels of PSA, testosterone, free testosterone, and dihydrotestosterone were unaffected. The present study suggests that resveratrol does not affect prostate volume in healthy middle-aged men as measured by PSA levels and CT acquired prostate volumes. Consequently, we find no support for the use of resveratrol in the treatment of benign prostate hyperplasia.

Changes in Estrogen Receptor ERβ (ESR2) Expression without Changes in the Estradiol Levels in the Prostate of Aging Rats

Although the prostate is androgen-dependent, it is also influenced by estrogens, which act via the estrogen receptors ERα and ERβ. In the prostate, ERβ is highly expressed in the epithelium and appears to participate in the regulation of cell proliferation, apoptosis and differentiation. Evidence shows that ERβ is decreased in malignant prostate, suggesting that it plays an important role in protecting this tissue. Despite the relationship between reductions in ERβ and abnormal growth of the gland, little is known about the age-dependent variation of this receptor. Therefore, we aimed to investigate ERβ expression in the prostatic lobes of aging Wistar rats (3 to 24 months). Histopathological alterations, including hyperplasia, intraluminal concretions, nuclear atypia and prostate intraepithelial neoplasias (PIN), were observed in the prostates of aging rats. Epithelial proliferation led to cribriform architecture in some acini, especially in the ventral prostate (VP). In the VP, areas of epithelial atrophy were also observed. Furthermore, in the lateral prostate, there was frequent prostatitis. Immunohistochemistry revealed that the expression of ERβ is reduced in specific areas related to PIN, atrophic abnormalities and cellular atypia in the prostate epithelium of senile rats. Corroborating the involvement of the receptor with proliferative activity, the punctual reduction in ERβ paralleled the increase in cell proliferation especially in areas of PIN and nuclear atypies. The decrease in ERβ reactivity occurred in a hormonal milieu characterized by a constant concentration of estradiol and decreased plasmatic and tissue DHT. This paper is a pioneering study that reveals focal ERβ reduction in the prostate of aging rats and indicates a potential disorder in the ERβ pathway. These data corroborate previous data from humans and dogs that silencing of this receptor may be associated with premalignant or malignant conditions in the prostate.

Population pharmacokinetic/pharmacodynamic assessment of pharmacological effect of a selective estrogen receptor β agonist on total testosterone in healthy men

BACKGROUND

LY500307 is a highly selective estrogen receptor β (ERβ) agonist, which loses its selectivity at high dose and leads to undesirable suppression of total testosterone (TT) concentration. The objective of the present analysis was to define the LY500307 dose with minimal effect on TT METHODS: LY500307 and TT concentrations were obtained from a single ascending-dose study in a total of 30 healthy male subjects. LY500307 (in the range of 0.5 to 500 mg) or placebo was administered orally as a single dose on 2 occasions with a 3-week washout period. A population pharmacokinetics/pharmacodynamics (PK/PD) model that integrated Fourier series in an indirect response model was developed to describe the circadian rhythm of TT and the exposure-response relationship of LY500307 on TT.

RESULTS

The maximum TT suppression (Emax ) was approximately 28.6%. The potency (EC50 ) of LY500307 on TT suppression was approximately 1.69 ng/mL with a 95%CI of 0.871 to 4.44 ng/mL. This model could provide inferences on LY500307 dose levels that would result in various magnitudes of TT suppression.

CONCLUSIONS

Population PK/PD modeling is a highly sensitive tool to detect exposure-response relationships on top of the complicated and highly variable circadian rhythm of TT.

CYP7B1 Enzyme Deletion Impairs Reproductive Behaviors in Male Mice

In addition to androgenic properties mediated via androgen receptors, dihydrotestosterone (DHT) also regulates estrogenic functions via an alternate pathway. These estrogenic functions of DHT are mediated by its metabolite 5α-androstane-3β, 17β-diol (3β-diol) binding to estrogen receptor β (ERβ). CYP7B1 enzyme converts 3β-diol to inactive 6α- or 7α-triols and plays an important role as a regulator of estrogenic functions mediated by 3β-diol. Using a mutant mouse carrying a null mutation for the CYP7B1 gene (CYP7B1KO), we examined the contribution of CYP7B1 on physiology and behavior. Male, gonadectomized (GDX) CYP7B1KO and their wild type (WT) littermates were assessed for their behavioral phenotype, anxiety-related behavioral measures, and hypothalamic pituitary adrenal axis reactivity. No significant effects of genotype were evident in anxiety-like behaviors in open field (OFA), light-dark (L/D) exploration, and elevated plus maze (EPM). T significantly reduced open arm time on the EPM while not affecting L/D exploratory and OFA behaviors in CYP7B1KO and WT littermates. T also attenuated the corticosterone response to EPM in both genotypes. In GDX animals, T was able to reinstate male-specific reproductive behaviors (latencies and number of mounts, intromission, and ejaculations) in the WT but not in the CYP7B1KO mice. The male reproductive behavior defect in CYP7B1KO seems to be due to their inability to distinguish olfactory cues from a behavioral estrus female. CYP7B1KO mice also showed a reduction in androgen receptor mRNA expression in the olfactory bulb. Our findings suggest a novel role for the CYP7B1 enzyme in the regulation of male reproductive behaviors.

Clinical significance of estrogen receptor β in breast and prostate cancer from biological aspects

Breast and prostate cancers are among the most common of all cancers. They are referred to as hormone-dependent cancers, because estrogen and androgen are involved in their development and growth. The effects of these hormones are mediated by their respective receptors, estrogen receptor (ER) α and androgen receptor. Around 18 years ago, a second ER, ERβ, which has a very similar structure to ERα, was discovered. Its function has been investigated using a variety of methods and biological systems, leading to our present understanding that ERβ can interact with or inhibit ERα and androgen receptor function directly and/or indirectly, suppress cell growth, and influence responsiveness to endocrine therapy. In order to apply the “inhibition of cell growth” function to cancer treatment, several specific ERβ agonists have been synthesized and are being tested for effectiveness in cancer treatment. We need to keep our eyes on ERβ.

Estrogen receptor β and Liver X receptor β: biology and therapeutic potential in CNS diseases

In the last decade of the twentieth century, two nuclear receptors were discovered in our laboratory and, very surprisingly, were found to have key roles in the central nervous system. These receptors have provided some novel insights into the etiology and progression of neurodegenerative diseases and anxiety disorders. The two receptors are estrogen receptor beta (ERβ) and liver X receptor beta (LXRβ). Both ERβ and LXRβ have potent anti-inflammatory activities and, in addition, LXRβ is involved in the genesis of dopaminergic neurons during development and protection of these neurons against neurodegeneration in adult life. ERβ is involved in migration of cortical neurons and calretinin-positive GABAergic interneurons during development and maintenance of serotonergic neurons in adults. Both receptors are present in magnocellular neurons of the hypothalamic preoptic area including those expressing vasopressin and oxytocin. As both ERβ and LXRβ are ligand-activated transcription factors, their ligands hold great potential in the treatment of diseases of the CNS.

Perinatal exposure to mixtures of anti-androgenic chemicals causes proliferative lesions in rat prostate

BACKGROUND

Elevated levels of endogenous or exogenous estrogens during fetal life can induce permanent disturbances in prostate growth and predispose to precancerous lesions. Recent studies have indicated that also early anti-androgen exposure may affect prostate cancer risk.

METHODS

We examined the influence of perinatal exposure to mixtures of anti-androgenic and estrogenic chemicals on prostate development. Wistar rats were exposed from gestation day 7 to postnatal day 22 to a mixture of 8 anti-androgenic compounds (AAMix), a mixture of four estrogenic compounds (EMix), or paracetamol or a mixture of all 13 compounds (TotalMix) in mixture ratios reflecting human exposure levels.

RESULTS

Ventral prostate weights were reduced by the TotalMix and AAMix in pre-pubertal rats. Histological changes in prostate appeared with increasing age and indicated a shift from the normal age-dependent epithelial atrophy towards hyperplasia. These lesions showed similarities to pre-cancerous lesions in humans. Increased proliferation was observed already in pre-puberty and it was hypothesized that this could be associated with reduced ERβ signaling, but no clear conclusions could be made from gene expression studies on ERβ-related pathways. The influences of the estrogenic chemicals and paracetamol on prostate morphology were minor, but in young adulthood the estrogen mixture reduced ventral prostate mRNA levels of Igf1 and paracetamol reduced the mRNA level ofPbpc3.

CONCLUSIONS

Mixtures of endocrine disrupters relevant for human exposure was found to elicit persistent effects on the rat prostate following perinatal exposure, suggesting that human perinatal exposure to environmental chemicals may increase the risk of prostate cancer later in life.

DHEA - a precursor of ERβ ligands

What is DHEA and why is there so much public interest in this steroid which has been touted as the fountain of youth and is supposed to have all kinds of health benefits? Endocrinologists have been fascinated with DHEA for a long time because of its high production in the fetal adrenals and its continued high levels until the 7th decade of life. Yet there is still little agreement about its physiological functions. In its simplest terms endocrinology is the communication between at least three organs: one sends a message, one releases a hormone into the blood in response to the message and one responds to the hormone. DHEA is produced by a specific zone of the adrenal cortex, the zona reticularis, whose sole function is to produce this steroid. Glucocorticoids and mineralocorticoids which are C21 steroids are produced in two other zones of the adrenal cortex called the zona fasicularis and the zona glomerulosa, respectively. Being C21 steroids, they cannot be synthesized from DHEA which is a C19 steroid. To date there is no known hormone which specifically stimulates the zona reticularis and there is no known specific receptor for DHEA. Thus DHEA does not qualify as a hormone. DHEA could have autocrine or paracrine effects but, so far, there is no known effect of DHEA on either the cells of the zona glomerulosa or the zona fasicularis. Of course DHEA could have functions as a local precursor of androgens or estrogens and many studies have reported on the beneficial effects of transdermal or transvaginal administration of DHEA in postmenopausal women. This review will consider two of the potential functions of DHEA as a precursor of estrogen receptor beta (ERβ) ligands.

The intracrinology of breast cancer

The importance of intracrinology, or in situ production of steroids from circulating precursors, in breast cancer has been firmly established in estrogen actions on postmenopausal patients. Expression levels of various steroid synthesizing and/or metabolizing enzymes have been examined in human breast cancer tissues by a number of groups. The enzymes examined include those capable of converting circulating DHEA-S to sex steroids (STS and 3βHSDΔ4-5 isomerase), the group of enzymes that modulate the strength of both androgens and estrogens (17βHSD family) as well as the androgenic 5αR enzymes and the estrogenic aromatase enzyme. In addition to these DHEA-related metabolism pathways, other intracrine pathways involving progesterone and cholesterol have also been examined. Some risk factors of breast cancer development, including obesity, have also been postulated to interact with steroid metabolising pathways. In this review, we aimed to summarise the current state of knowledge regarding intracrine metabolism including expression levels of various enzymes and receptors, focusing particularly upon the importance of the production of biologically potent steroids from circulating sulfated precursors such as DHEA-S. In addition, we attempted to summarise the factors, both steroidal and non-steroidal, involved in the regulation of these enzymes and propose future directions for research in this particular field. The concept of intracrinology was first proposed over 20 years ago but there still remain many unanswered questions which could open new horizons for the understanding of intracrine metabolism in the breast. This article is part of a Special Issue entitled 'Essential role of DHEA'.

The interaction between metabolism, cancer and cardiovascular disease, connected by 27-hydroxycholesterol

Oxysterols are metabolites of cholesterol that are produced in liver and other peripheral tissues as a means to eliminate cholesterol to bile acid. Recent studies have revealed that the most abundant circulating oxysterol 27-hydroxycholesterol (27HC) is the first identified endogenous selective estrogen receptor modulator. 27HC levels correlate well with that of cholesterol, and also rise progressively with age. 27HC affects estrogen receptor function by the antagonism of estrogen action and also by the direct modulation of the receptor function, and similar to estrogen/estrogen receptors, 27HC has many actions in various tissues. This review article introduces the recent progress in the understanding of the role of 27HC in breast cancer and cardiovascular dysfunction.

The role of androgens in experimental rodent mammary carcinogenesis

Breast cancer is currently the most frequent, fatal cancer of women in western countries. While estrogens have a widely understood involvement in breast cancer, a significant but not yet fully understood role for androgens has also been suggested. The principal androgen, testosterone, is the obligate steroidal precursor of estradiol, but can equally be metabolized into dihydrotestosterone, a more potent, pure androgen. Both androgens exert their distinctive biological effects via the androgen receptor, which is coexpressed with estrogen receptor alpha in 80 to 90% of breast cancers. The hormonal control of breast development and pathology has been examined experimentally through the use of animal models, notably mice and rats. This review summarizes the data from experimental rodent models on the effects of androgens in experimental breast cancer, aiming to address the importance of androgens and the androgen receptor in the origins and pathogenesis of breast cancers, as well as to discuss potential biomarker and therapeutic opportunities arising from novel insights based on the experimental research.

Estrogen receptor beta agonist LY500307 fails to improve symptoms in men with enlarged prostate secondary to benign prostatic hypertrophy

BACKGROUND

To assess the efficacy and safety of LY500307, a selective estrogen receptor beta agonist, on lower urinary tract symptoms (LUTS) in patients with enlarged prostate secondary to BPH.

METHODS

In a randomized, double-blind, placebo-controlled, parallel phase 2, efficacy and safety study, eligible patients with moderate to severe LUTS and prostatic enlargement (⩾30 ml) were randomized to placebo or LY500307 at 1, 3, 10 and 25 mg once daily for 24 weeks. Primary efficacy end point was change in total International Prostate Symptoms Score (IPSS) after 24 weeks. Secondary end points included changes in total prostate volume (TPV) that served as a proof of concept end point, as well as IPSS quality of life, maximum peak urine flow rate (Qmax) and PSA and safety (adverse events, laboratory test).

RESULTS

A total of 414 patients were randomized when the study was terminated because of insufficient TPV reduction, based on a priori defined interim analysis. The IPSS mean change from baseline to end point was -3.4±6.8 in the placebo group and -1.3±6.6, -2.6±7.0, -3.7±6.7 and -4.4±5.7 in the 1, 3, 10 and 25 mg LY500307-treated groups, respectively (P>0.05). Similarly, no treatment effect was observed for any of the secondary efficacy measures. Incidence of adverse events was comparable between treatment groups, and no clinically meaningful changes in laboratory tests were observed.

CONCLUSIONS

LY500307 was well tolerated in BPH patients with LUTS at doses up to 25 mg once daily for 24 weeks. The study was terminated early because of inadequate efficacy.

Effects of sex hormones on inflammatory response in male and female vascular endothelial cells

PURPOSE

Gender-related differences in sex hormones might have a key role in the development of atherosclerosis though direct vascular effects of sex hormones are not yet well understood. Thus, the main purpose of this study was to compare the effects of sex hormones on inflammatory response in Human Umbilical Vein Endothelial Cells (HUVECs) obtained from both male and female donors.

METHODS

We analyzed the expression of receptors and enzymes relevant to the action of androgens (AR, 5α-reductase 1 and 5α-reductase 2) and estrogens (ERα, ERβ, and aromatase) in male and female HUVECs. Furthermore, we analyzed the effect of testosterone (T), 17β-estradiol (E2), dihydrotestosterone (DHT), and several androgenic-anabolic steroids (AAS) on VCAM-1, ICAM-1, and E-selectin gene expression and on adhesion of U937 cells to TNF-α-stimulated male and female HUVECs.

RESULTS

Our results reveal that in HUVECs, regardless of gender, the components involved in the androgen action pathway are predominant as compared to those of estrogen action pathway. In both HUVEC genders, the inflammatory effect of TNF-α was amplified by co-administration of T or DHT and several AAS frequently used in doping, while E2 had no effect.

CONCLUSIONS

This is the first study analyzing, under identical culture conditions, the key components of sex hormone response in male and female HUVECs and the possible role of sex hormones in regulating the endothelial inflammatory response. The data obtained in our experimental system showed a pro-inflammatory effect of androgens, while conclusively excluding any protective effect for all the tested hormones.

Estrogen receptor β upregulates FOXO3a and causes induction of apoptosis through PUMA in prostate cancer

Estrogen receptor β (ERβ) is emerging as a critical factor in understanding prostate cancer biology. Although reduced in prostate cancer above Gleason grade 3, ERβ is a potential drug target at the initial stage of the disease. In human prostate cancer cells, we found that ERβ causes apoptosis by increasing the expression of pro-apoptotic factor p53-upregulated modulator of apoptosis (PUMA), independent of p53, but dependent on the forkhead transcription factor class-O family member, FOXO3a. FOXO3a has previously been shown to induce PUMA after growth factor withdrawal and inhibition of the Akt pathway. Surprisingly, the phosphorylation of FOXO3a remained unchanged, while the mRNA and total protein levels of FOXO3a were increased in response to ERβ expression or treatment of PC3, 22Rv1 and LNCaP cells with the ERβ-specific ligands 3β-Adiol (5α-androstane-3β,17β-diol), DPN (diarylpropionitrile) or 8β-VE2 (8-vinylestra-1,3,5 (10)-triene-3,17β-diol). Knockdown of FOXO3a or ERβ expression abolished the increase of PUMA in response to 3β-Adiol in LNCaP and PC3 cells, suggesting that FOXO3a mediates the apoptotic effect of 3β-Adiol-activated ERβ. Moreover, the ventral prostate of ERβ-/- mice had decreased expression of FOXO3a and PUMA compared with the ERβ+/+ mice, indicating a relationship between ERβ and FOXO3a expression. The regulation of FOXO3a by ERβ in normal basal epithelial cells indicates a function of ERβ in cell differentiation and maintenance of cells in a quiescent state. In addition, the expression of ERβ, FOXO3a and PUMA is comparable and higher in benign prostatic hyperplasia than in prostate cancer Gleason grade 4 or higher, where there is substantial loss of ERβ, FOXO3a and PUMA. We conclude that ERβ induces apoptosis of prostate cancer cells by increasing transcription of FOXO3a, leading to an increase of PUMA and subsequent triggering of apoptosis via the intrinsic pathway involving caspase-9. Furthermore, we conclude that ligands specifically activating ERβ could be useful pharmaceuticals in the treatment of prostate cancer.

Dehydroepiandrosterone-induces miR-21 transcription in HepG2 cells through estrogen receptor β and androgen receptor

Although oncomiR miR-21 is highly expressed in liver and overexpressed in hepatocellular carcinoma (HCC), its regulation is uncharacterized. We examined the effect of physiologically relevant nanomolar concentrations of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) on miR-21 expression in HepG2 human hepatoma cells. 10nM DHEA and DHEA-S increase pri-miR-21 transcription in HepG2 cells. Dietary DHEA increased miR-21 in vivo in mouse liver. siRNA and inhibitor studies suggest that DHEA-S requires desulfation for activity and that DHEA-induced pri-miR-21 transcription involves metabolism to androgen and estrogen receptor (AR and ER) ligands. Activation of ERβ and AR by DHEA metabolites androst-5-ene-3,17-dione (ADIONE), androst-5-ene-3β,17β-diol (ADIOL), dihydrotestosterone (DHT), and 5α-androstane-3β,17β-diol (3β-Adiol) increased miR-21 transcription. DHEA-induced miR-21 increased cell proliferation and decreased Pdcd4 protein, a bona fide miR-21. Estradiol (E2) inhibited miR-21 expression via ERα. DHEA increased ERβ and AR recruitment to the miR-21 promoter within the VMP1/TMEM49 gene, with possible significance in hepatocellular carcinoma.

Transcriptional analysis of endocrine disruption using zebrafish and massively parallel sequencing

Endocrine-disrupting chemicals (EDCs), including plasticizers, pesticides, detergents, and pharmaceuticals, affect a variety of hormone-regulated physiological pathways in humans and wildlife. Many EDCs are lipophilic molecules and bind to hydrophobic pockets in steroid receptors, such as the estrogen receptor and androgen receptor, which are important in vertebrate reproduction and development. Indeed, health effects attributed to EDCs include reproductive dysfunction (e.g. reduced fertility, reproductive tract abnormalities, and skewed male:female sex ratios in fish), early puberty, various cancers, and obesity. A major concern is the effects of exposure to low concentrations of endocrine disruptors in utero and post partum, which may increase the incidence of cancer and diabetes in adults. EDCs affect transcription of hundreds and even thousands of genes, which has created the need for new tools to monitor the global effects of EDCs. The emergence of massive parallel sequencing for investigating gene transcription provides a sensitive tool for monitoring the effects of EDCs on humans and other vertebrates, as well as elucidating the mechanism of action of EDCs. Zebrafish conserve many developmental pathways found in humans, which makes zebrafish a valuable model system for studying EDCs, especially on early organ development because their embryos are translucent. In this article, we review recent advances in massive parallel sequencing approaches with a focus on zebrafish. We make the case that zebrafish exposed to EDCs at different stages of development can provide important insights on EDC effects on human health.

Steroid signaling: ligand-binding promiscuity, molecular symmetry, and the need for gating

Steroid/sterol-binding receptors and enzymes are remarkably promiscuous in the range of ligands they can bind to and, in the case of enzymes, modify - raising the question of how specific receptor activation is achieved in vivo. Estrogen receptors (ER) are modulated by 27-hydroxycholesterol and 5α-androstane-3β,17β-diol (Adiol), in addition to estradiol (E2), and respond to diverse small molecules such as bisphenol A. Steroid-modifying enzymes are also highly promiscuous in ligand binding and metabolism. The specificity problem is compounded by the fact that the steroid core (hydrogenated cyclopentophenanthrene ring system) has several planes of symmetry. Ligand binding can be in symmetrical East-West (rotation) and North-South (inversion) orientations. Hydroxysteroid dehydrogenases (HSDs) can modify symmetrical 7 and 11, also 3 and 17/20, positions, exemplified here by yeast 3α,20β-HSD and mammalian 11β-HSD and 17β-HSD enzymes. Faced with promiscuity and symmetry, other strategies are clearly necessary to promote signaling selectivity in vivo. Gating regulates hormone access via enzymes that preferentially inactivate (or activate) a subclass of ligands, thereby governing which ligands gain receptor access - exemplified by 11β-HSD gating cortisol access to the mineralocorticoid receptor, and P450 CYP7B1 gating Adiol access to ER. Counter-intuitively, the specificity of steroid/sterol action is achieved not by intrinsic binding selectivity but by the combination of local metabolism and binding affinity.

Gonadal steroid hormones and the hypothalamo-pituitary-adrenal axis

The hypothalamo-pituitary-adrenal (HPA) axis represents a complex neuroendocrine feedback loop controlling the secretion of adrenal glucocorticoid hormones. Central to its function is the paraventricular nucleus of the hypothalamus (PVN) where neurons expressing corticotropin releasing factor reside. These HPA motor neurons are a primary site of integration leading to graded endocrine responses to physical and psychological stressors. An important regulatory factor that must be considered, prior to generating an appropriate response is the animal's reproductive status. Thus, PVN neurons express androgen and estrogen receptors and receive input from sites that also express these receptors. Consequently, changes in reproduction and gonadal steroid levels modulate the stress response and this underlies sex differences in HPA axis function. This review examines the make up of the HPA axis and hypothalamo-pituitary-gonadal (HPG) axis and the interactions between the two that should be considered when exploring normal and pathological responses to environmental stressors.

Human steroid and oxysterol 7α-hydroxylase CYP7B1: substrate specificity, azole binding and misfolding of clinically relevant mutants

Oxysterols and neurosteroids are important signaling molecules produced by monooxygenases of the cytochrome P450 family that realize their effect through nuclear receptors. CYP7B1 catalyzes the 6- or 7-hydroxylation of both steroids and oxysterols and thus is involved in the metabolism of neurosteroids and bile acid synthesis, respectively. The dual physiological role of CYP7B1 is evidenced from different diseases, liver failure and progressive neuropathy, caused by enzyme malfunction. Here we present biochemical characterization of CYP7B1 at the molecular level to understand substrate specificity and susceptibility to azole drugs. Based on our experiments with purified enzyme, the requirements for CYP7B1 hydroxylation of steroid molecules are as follows: C5 hydrogen in the α-configuration (or double bond at C5), a polar group at C17, a hydroxyl group at C3, and the absence of the hydroxyl group at C20-C24 in the C27-sterol side chain. 21-hydroxy-pregnenolone was identified as a new substrate, and overall low activity toward pregnanes could be related to the increased potency of 7-hydroxy derivatives produced by CYP7B1. Metabolic conversion (deactivation) of oxysterols by CYP7B1 in a reconstituted system proceeds via two sequential hydroxylations. Two mutations that are found in patients with diseases, Gly57Arg and Phe216Ser, result in apo-P450 (devoid of heme) protein formation. Our CYP7B1 homology model provides a rationale for understanding clinical mutations and relatively broad substrate specificity for steroid hydroxylase.

Alterations in sensitivity to estrogen, dihydrotestosterone, and xenogens in B-lymphocytes from children with autism spectrum disorder and their unaffected twins/siblings

It has been postulated that androgen overexposure in a susceptible person leads to excessive brain masculinization and the autism spectrum disorder (ASD) phenotype. In this study, the responses to estradiol (E2), dihydrotestosterone (DHT), and dichlorodiphenyldichloroethylene (DDE) on B-lymphocytes from ASD subjects and controls are compared. B cells were obtained from 11 ASD subjects, their unaffected fraternal twins, and nontwin siblings. Controls were obtained from a different cell bank. Lactate dehydrogenase (LDH) and sodium 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction levels were measured after incubation with different concentrations of E2, DHT, and DDE. XTT/LDH ratio, representative of mitochondria number per cell, was calculated. E2, DHT, and DDE all cause “U”-shaped growth curves, as measured by LDH levels. ASD B cells show less growth depression compared to siblings and controls (P < 0.01). They also have reduced XTT/LDH ratios (P < 0.01) when compared to external controls, whereas siblings had values of XTT/LDH between ASD and external controls. B-lymphocytes from people with ASD exhibit a differential response to E2, DHT, and hormone disruptors in regard to cell growth and mitochondrial upregulation when compared to non-ASD siblings and external controls. Specifically, ASD B-lymphocytes show significantly less growth depression and less mitochondrial upregulation when exposed to these effectors. A mitochondrial deficit in ASD individuals is implied.

Fertility and developmental toxicity assessment in rats and rabbits with LY500307, a selective estrogen receptor beta (ERβ) agonist

LY500307 is a selective estrogen receptor beta (ERβ) agonist that was developed for the treatment of benign prostatic hyperplasia. The in vitro functional selectivity of LY500307 for ERβ agonist activity is 32-fold above the activity at the alpha receptor (ERα). LY500307 was evaluated in a series of male (M) and female (F) rat fertility and rat and rabbit embryo-fetal development (EFD) studies, using 20 or 25 animals/group. LY500307 was administered daily by oral gavage starting 2 weeks (F) or 10 weeks (M) before mating, during cohabitation, until necropsy (M) or through gestation day (GD) 6 (F) in the fertility studies and from GD 6 to 17 (rats) or GD 7 to 19 (rabbits) in the EFD studies. Dosage levels of LY500307 ranged from 0.03 to 10 mg/kg/day for rats and from 1 to 25 mg/kg/day for rabbits. Fertility, estrous, maternal reproductive endpoints, conceptus viability, sperm parameters, organ weights, and histopathology were evaluated in the fertility studies. Maternal reproductive endpoints and fetal viability, weight, and morphology were evaluated in the EFD studies. Toxicokinetics were assessed in satellite animals. At 10 mg/kg/day in the male fertility study, findings included decreased body weight (BW); food consumption (FC); fertility, mating, and conception indices; sperm concentration; and reproductive tissue weight (associated with atrophic histologic changes). In the female fertility study, effects included decreased BW and FC at ≥0.3 mg/kg/day and persistent diestrus, delayed mating, and reduced fertility/conception indices at 3 mg/kg/day. In the rat EFD study, findings included decreased maternal BW and FC and increased incidences of adverse clinical signs, abortion, maternal mortality/moribundity, postimplantation loss, and fetal skeletal variations at 3 mg/kg/day. Effects in the rabbit EFD study were limited to decreases in maternal BW and FC at 25 mg/kg/day. In general, systemic maternal exposure increased proportionally with dosage in rats, but less than proportionally in rabbits. In conclusion, the no-observed adverse effect levels following LY500307 administration were 1 mg/kg/day for male rat fertility, 0.3 mg/kg/day for female rat fertility and EFD, and 25 mg/kg/day for rabbit EFD. Adverse reproductive and developmental effects only occurred at or above parentally toxic dosage levels and were considered predominantly due to off-target ERα effects.

Insight into the mechanisms of action of estrogen receptor β in the breast, prostate, colon, and CNS

Estrogen and its receptors (ERs) influence many biological processes in physiology and pathology in men and women. ERs are involved in the etiology and/or progression of cancers of the prostate, breast, uterus, ovary, colon, lung, stomach, and malignancies of the immune system. In estrogen-sensitive malignancies, ERβ usually is a tumor suppressor and ERα is an oncogene. ERβ regulates genes in several key pathways including tumor suppression (p53, PTEN); metabolism (PI3K); survival (Akt); proliferation pathways (p45(Skp2), cMyc, and cyclin E); cell-cycle arresting factors (p21(WAF1), cyclin-dependent kinase inhibitor 1 (CDKN1A)), p27(Kip1), and cyclin-dependent kinases (CDKs); protection from reactive oxygen species, glutathione peroxidase. Because they are activated by small molecules, ERs are excellent targets for pharmaceuticals. ERα antagonists have been used for many years in the treatment of breast cancer and more recently pharmaceutical companies have produced agonists which are very selective for ERα or ERβ. ERβ agonists are being considered for preventing progression of cancer, treatment of anxiety and depression, as anti-inflammatory agents and as agents, which prevent or reduce the severity of neurodegenerative diseases.

Modulators of estrogen receptor inhibit proliferation and migration of prostate cancer cells

In the initial stages, human prostate cancer (PC) is an androgen-sensitive disease, which can be pharmacologically controlled by androgen blockade. This therapy often induces selection of androgen-independent PC cells with increased invasiveness. We recently demonstrated, both in cells and mice, that a testosterone metabolite locally synthetized in prostate, the 5α-androstane-3β, 17β-diol (3β-Adiol), inhibits PC cell proliferation, migration and invasion, acting as an anti-proliferative/anti-metastatic agent. 3β-Adiol is unable to bind androgen receptor (AR), but exerts its protection against PC by specifically interacting with estrogen receptor beta (ERβ). Because of its potential retro-conversion to androgenic steroids, 3β-Adiol cannot be used "in vivo", thus, the aims of this study were to investigate the capability of four ligands of ERβ (raloxifen, tamoxifen, genistein and curcumin) to counteract PC progression by mimicking the 3β-Adiol activity. Our results demonstrated that raloxifen, tamoxifen, genistein and curcumin decreased DU145 and PC3 cell proliferation in a dose-dependent manner; in addition, all four compounds significantly decreased the detachment of cells seeded on laminin or fibronectin. Moreover, raloxifen, tamoxifen, genistein and curcumin-treated DU145 and PC3 cells showed a significant decrease in cell migration. Notably, all these effects were reversed by the anti-estrogen, ICI 182,780, suggesting that their actions are mediated by the estrogenic pathway, via the ERβ, the only isoform present in these PCs. In conclusion, these data demonstrate that by selectively activating the ERβ, raloxifen, tamoxifen, genistein and curcumin inhibit human PC cells proliferation and migration favoring cell adesion. These synthetic and natural modulators of ER action may exert a potent protective activity against the progression of PC even in its androgen-independent status.

Androgen deprivation promotes intratumoral synthesis of dihydrotestosterone from androgen metabolites in prostate cancer

Intratumoral synthesis of dihydrotestosterone (DHT) from precursors cannot completely explain the castration resistance of prostate cancer. We showed that DHT was intratumorally synthesized from the inactive androgen metabolites 5α-androstane-3α/β,17β-diol (3α/β-diol) in prostate cancer cells via different pathways in a concentration-dependent manner. Additionally, long-term culture in androgen-deprived media increased transcriptomic expression of 17β-hydroxysteroid dehydrogenase type 6 (HSD17B6), a key enzyme of oxidative 3α-HSD that catalyzes the conversion of 3α-diol to DHT in prostate cancer cells. Correspondingly, the score for HSD17B6 in tissues of 42 prostate cancer patients undergoing androgen deprivation therapy (ADT) was about 2-fold higher than that in tissues of 100 untreated individuals. In men receiving ADT, patients showing biochemical progression had a higher HSD17B6 score than those without progression. These results suggested that 3α/β-diol also represent potential precursors of DHT, and the back conversion of DHT from androgen derivatives can be a promising target for combination hormone therapy.

AC-186, a selective nonsteroidal estrogen receptor β agonist, shows gender specific neuroprotection in a Parkinson's disease rat model

Drugs that selectively activate estrogen receptor β (ERβ) are potentially safer than the nonselective estrogens currently used in hormonal replacement treatments that activate both ERβ and ERα. The selective ERβ agonist AC-186 was evaluated in a rat model of Parkinson's disease induced through bilateral 6-hydroxydopamine lesions of the substantia nigra. In this model, AC-186 prevented motor, cognitive, and sensorimotor gating deficits and mitigated the loss of dopamine neurons in the substantia nigra, in males, but not in females. Furthermore, in male rats, 17β-estradiol, which activates ERβ and ERα with equal potency, did not show the same neuroprotective benefits as AC-186. Hence, in addition to a beneficial safety profile for use in both males and females, a selective ERβ agonist has a differentiated pharmacological profile compared to 17β-estradiol in males.

Effects of platelet-activating factor and its differential regulation by androgens and steroid hormones in prostate cancers

Background:

Platelet-activating factor (PAF) is an arachidonic acid metabolite that plays an important role in cell proliferation, migration and neoangiogenesis, but whether it is involved in the progression of prostate cancer remains undiscovered.

Methods:

Clinical prostate specimens were investigated with immunohistochemistry method and in vitro cell experiments referred to MTS cell proliferation assay, invasion and migration experiment, quantitative real-time RT–PCR assay, western blotting analysis and ELISA assay.

Results:

Platelet-activating factor synthetase, lyso-PAF acetyl transferase (LPCAT1), increased significantly in castration-resistant prostate cancer (CRPC) specimens and CRPC PC-3 cells than that in controls. Intriguingly, PAF induced invasion and migration of PC-3 cells but not LNCaP cells. The PAF receptor antagonist inhibited proliferation of LNCaP and PC-3 cells. Dihydrotestosterone (DHT) treatment caused a decrease in LPCAT1 expression and PAF release in LNCaP cells, which could be blocked by androgen receptor antagonists. Finally, DHT increased LPCAT1 expression and PAF release in PC-3 cells in a Wnt/β-catenin-dependent manner.

Conclusion:

For the first time, our data supported that PAF might play pivotal roles in the progression of prostate cancer, which might throw a new light on the treatment of prostate cancer and the prevention of the emergence of CRPC.

Central 5-alpha reduction of testosterone is required for testosterone's inhibition of the hypothalamo-pituitary-adrenal axis response to restraint stress in adult male rats

In rodents, the hypothalamo-pituitary-adrenal (HPA) axis is controlled by a precise regulatory mechanism that is influenced by circulating gonadal and adrenal hormones. In males, gonadectomy increases the adrenocorticotropic hormone (ACTH) and corticosterone (CORT) response to stressors, and androgen replacement returns the response to that of the intact male. Testosterone (T) actions in regulating HPA activity may be through aromatization to estradiol, or by 5α-reduction to the more potent androgen, dihydrotestosterone (DHT). To determine if the latter pathway is involved, we assessed the function of the HPA axis response to restraint stress following hormone treatments, or after peripheral or central treatment with the 5α-reductase inhibitor, finasteride. Initially, we examined the timecourse whereby gonadectomy alters the CORT response to restraint stress. Enhanced CORT responses were evident within 48 h following gonadectomy. Correspondingly, treatment of intact male rats with the 5α-reductase inhibitor, finasteride, for 48 h, enhanced the CORT and ACTH response to restraint stress. Peripheral injections of gonadectomized male rats with DHT or T for 48 h reduced the ACTH and CORT response to restraint stress. The effects of T, but not DHT, could be blocked by the third ventricle administration of finasteride prior to stress application. These data indicate that the actions of T in modulating HPA axis activity involve 5α-reductase within the central nervous system. These results further our understanding of how T acts to modulate the neuroendocrine stress responses and indicate that 5α reduction to DHT is a necessary step for T action.

Selective estrogen receptor modulators for BPH: new factors on the ground

As the current management of BPH/lower urinary tract symptoms by traditionally involved pharmacological agents such as 5alpha-reductase inhibitors and α1-adrenoceptor antagonists is suboptimal, there is definite need of new therapeutic strategies. There is ample evidence in literature that suggests the role of estrogens in BPH development and management through the different tissue and cell-specific receptors. This article reviews the beneficial actions of selective estrogen receptor modulator (SERM) and ERβ-selective ligands, which have been demonstrated through in vitro studies using human prostate cell lines and in vivo animal studies. SERMs have anti-proliferative, anti-inflammatory and pro-apoptotic mechanisms in BPH, and also act by inhibiting various growth factors, and thus represent a unique and novel approach in BPH management directed at estrogen receptors or estrogen metabolism.

Cytochromes p450: roles in diseases

The cytochrome P450 superfamily consists of a large number of heme-containing monooxygenases. Many human P450s metabolize drugs used to treat human diseases. Others are necessary for synthesis of endogenous compounds essential for human physiology. In some instances, alterations in specific P450s affect the biological processes that they mediate and lead to a disease. In this minireview, we describe medically significant human P450s (from families 2, 4, 7, 11, 17, 19, 21, 24, 27, 46, and 51) and the diseases associated with these P450s.

Estradiol and testosterone regulate arginine-vasopressin expression in SH-SY5Y human female neuroblastoma cells through estrogen receptors-α and -β

The expression of arginine-vasopressin (AVP) is regulated by estradiol and testosterone (T) in different neuronal populations by mechanisms that are not yet fully understood. Estrogen receptors (ERs) have been shown to participate in the regulation of AVP neurons by estradiol. In addition, there is evidence of the participation of ERβ in the regulation of AVP expression exerted by T via its metabolite 5α-dihydrotestosterone (5α-DHT) and its further conversion in the androgen metabolite and ERβ ligand 3β-diol. In this study we have explored the role of ERs in the regulation exerted by estradiol and T on AVP expression, using the human neuroblastoma cell line SH-SY5Y. Estradiol treatment increased AVP mRNA levels in SH-SY5Y cells in comparison with cells treated with vehicle. The stimulatory effect of estradiol on AVP expression was imitated by the ERα agonist 4,4',4',-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol and blocked by the ER antagonist, ICI 182,780, and the ERα antagonist 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1hpyrazoledihydrochloride. In contrast, the ERβ agonist 2,3-bis(4-hydroxyphenyl)-propionitrile reduced AVP expression, whereas the ERβ antagonist 4-[2-phenyl-5,7-bis(trifluoromethyl) pyrazolo[1,5-a]pyrimidin-3-yl]phenol enhanced the action of estradiol on AVP expression. T increased AVP expression in SH-SY5Y cells by a mechanism that was dependent on aromatase but not on 5α-reductase activity. The T effect was not affected by blocking the androgen receptor, was not imitated by the T metabolite 5α-DHT, and was blocked by the ERα antagonist 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1hpyrazoledihydrochloride. In contrast, 5α-DHT had a similar effect as the ERβ agonists 2,3-bis(4-hydroxyphenyl)-propionitrile and 3β-diol, reducing AVP expression. These findings suggest that estradiol and T regulate AVP expression in SH-SY5Y cells through ERs, exerting a stimulatory action via ERα and an inhibitory action via ERβ.

Estrogen receptor alpha single nucleotide polymorphism as predictor of diabetes type 2 risk in hypogonadal men

Estradiol (E2) is, apart from its role as a reproductive hormone, also important for cardiac function and bone maturation in both genders. It has also been shown to play a role in insulin production, energy expenditure and in inducing lipolysis. The aim of the study was to investigate if low circulating testosterone or E2 levels in combination with variants in the estrogen receptor alpha (ESR1) and estrogen receptor beta (ESR2) genes were of importance for the risk of type-2 diabetes. The single nucleotide polymorphisms rs2207396 and rs1256049, in ESR1 and ESR2, respectively, were analysed by allele specific PCR in 172 elderly men from the population-based Tromsø study. The results were adjusted for age. In individuals with low total (≤11 nmol/L) or free testosterone (≤0.18 nmol/L) being carriers of the variant A-allele in ESR1 was associated with 7.3 and 15.9 times, respectively, increased odds ratio of being diagnosed with diabetes mellitus type 2 (p = 0.025 and p = 0.018, respectively). Lower concentrations of E2 did not seem to increase the risk of being diagnosed with diabetes. In conclusion, in hypogonadal men, the rs2207396 variant in ESR1 predicts the risk of type 2 diabetes.

The androgen metabolite, 5α-androstane-3β,17β-diol (3β-diol), activates the oxytocin promoter through an estrogen receptor-β pathway

Testosterone has been shown to suppress the acute stress-induced activation of the hypothalamic-pituitary-adrenal axis; however, the mechanisms underlying this response remain unclear. The hypothalamic-pituitary-adrenal axis is regulated by a neuroendocrine subpopulation of medial parvocellular neurons in the paraventricular nucleus of the hypothalamus (PVN). These neurons are devoid of androgen receptors (ARs). Therefore, a possibility is that the PVN target neurons respond to a metabolite in the testosterone catabolic pathway via an AR-independent mechanism. The dihydrotestosterone metabolite, 5α-androstane-3β,17β-diol (3β-diol), binds and activates estrogen receptor-β (ER-β), the predominant ER in the PVN. In the PVN, ER-β is coexpressed with oxytocin (OT). Therefore, we tested the hypothesis that 3β-diol regulates OT expression through ER-β activation. Treatment of ovariectomized rats with estradiol benzoate or 3β-diol for 4 days increased OT mRNA selectively in the midcaudal, but not rostral PVN compared with vehicle-treated controls. 3β-Diol treatment also increased OT mRNA in the hypothalamic N38 cell line in vitro. The functional interactions between 3β-diol and ER-β with the human OT promoter were examined using an OT promoter-luciferase reporter construct (OT-luc). In a dose-dependent manner, 3β-diol treatment increased OT-luc activity when cells were cotransfected with ER-β, but not ER-α. The 3β-diol-induced OT-luc activity was reduced by deletion of the promoter region containing the composite hormone response element (cHRE). Point mutations of the cHRE also prevented OT-luc activation by 3β-diol. These results indicate that 3β-diol induces OT promoter activity via ER-β-cHRE interactions.

Estrogen receptor β sustains epithelial differentiation by regulating prolyl hydroxylase 2 transcription

Estrogen receptor β (ERβ) promotes the degradation of hypoxia inducible factor 1α (HIF-1α), which contributes to the ability of this hormone receptor to sustain the differentiation of epithelial and carcinoma cells. Although the loss of ERβ and consequent HIF-1 activation occur in prostate cancer with profound consequences, the mechanism by which ERβ promotes the degradation of HIF-1α is unknown. We report that ERβ regulates the ligand (3β-adiol)-dependent transcription of prolyl hydroxylase 2 (PHD2) also known as Egl nine homolog 1 (EGLN1), a 2-oxoglutarate-dependent dioxygenase that hydroxylates HIF-1α and targets it for recognition by the von Hippel-Lindau tumor suppressor and consequent degradation. ERβ promotes PHD2 transcription by interacting with a unique estrogen response element in the 5' UTR of the PHD2 gene that functions as an enhancer. PHD2 itself is critical for maintaining epithelial differentiation. Loss of PHD2 expression or inhibition of its function results in dedifferentiation with characteristics of an epithelial-mesenchymal transition, and exogenous PHD2 expression in dedifferentiated cells can restore an epithelial phenotype. Moreover, expression of HIF-1α in cells that express PHD2 does not induce dedifferentiation but expression of HIF-1α containing mutations in the proline residues that are hydroxylated by PHD2 induces dedifferentiation. These data describe a unique mechanism for the regulation of HIF-1α stability that involves ERβ-mediated transcriptional regulation of PHD2 and they highlight an unexpected role for PHD2 in maintaining epithelial differentiation.