Elevated androgens and prolactin in aromatase-deficient mice cause enlargement, but not malignancy, of the prostate gland

Estrogen signaling is not required for prostatic bud patterning or for its disruption by 2,3,7,8-tetrachlorodibenzo-p-dioxin

Estrogens play an important role in prostatic development, health, and disease. While estrogen signaling is essential for normal postnatal prostate development, little is known about its prenatal role in control animals. We tested the hypothesis that estrogen signaling is needed for normal male prostatic bud patterning. Budding patterns were examined by scanning electron microscopy of urogenital sinus epithelium from wild-type mice, mice lacking estrogen receptor (ER)alpha, ERbeta, or both, and wild-type mice exposed to the antiestrogen ICI 182,780. Budding phenotypes did not detectably differ among any of these groups, strongly suggesting that estrogen signaling is not needed to establish the prototypical prostatic budding pattern seen in control males. This finding contributes to our understanding of the effects of low-level estrogen exposure on early prostate development. In utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can greatly alter the pattern in which prostatic buds form and reduce their number. For several reasons, including a prior observation that inhibitory effects of TCDD on prostatic budding in rats depend heavily on the sex of adjacent fetuses, we tested the hypothesis that estrogen signaling is needed for TCDD to disrupt prostatic budding. However, budding did not detectably differ among wild-type mice, or mice lacking ERalpha, ERbeta, or both, that were exposed prenatally to TCDD (5 microg/kg on embryonic day 13.5). Nor did ICI 182,780 detectably affect the response to TCDD. These results strongly suggest that estrogen signaling is not needed for TCDD to inhibit prostatic epithelial budding.

Androgen sensitivity of prostate epithelium is enhanced by postnatal androgen receptor inactivation

Postnatal inactivation of epithelial androgen receptor (AR) in prostate epithelial AR knockout (PEARKO) mice results in hindered differentiation but enhanced proliferation of epithelial cells. As this resembles the precancerous proliferative atrophy of human prostates with undifferentiated but intensively replicating epithelial cells, we utilized the PEARKO mice to characterize the epithelial response to castration-induced involution with a focus on identifying the potential role of stromal AR and responsiveness of the androgen-deprived epithelia to the aromatizable androgen testosterone (T) or its nonaromatizable metabolite dihydrotestosterone (DHT). PEARKO and littermate control mice were orchidectomized at 8 wk of age and treated 2 wk later with subdermal implantation of 1-cm Silastic tubing filled with T or DHT for a week. Following castration, the prostatic involution and epithelial apoptosis did not significantly differ between control (intact AR) and PEARKO (only stromal AR) males, demonstrating that prostate epithelial involution following castration is mediated primarily via stromal AR-dependent apoptotic signals. Androgen replacement (T/DHT) for 7 days induced significant growth and epithelial proliferation in all prostate lobes in both control and PEARKO, but full regrowth was observed only in controls treated with T. In PEARKO, prostate androgen (T and DHT) treatment induced significant epithelial cell "shedding" into the lumen, with T treatment resulting in acinar disorganization, cyst formation, and aberrant epithelial structures, described as a "gland within a gland." These data suggest that epithelial AR inactivation during postnatal prostate development sensitizes prostate epithelial cells to paracrine signaling mediated by stromal AR activity leading to indirectly androgen-induced epithelial hyperproliferation and formation of epithelial hyperplastic cysts by aromatizable androgens.

Long-term inhibition of 5-alpha reductase and aromatase changes the cellular and extracellular compartments in gerbil ventral prostate at different postnatal ages

As local steroid metabolism controls the bioavailability of active steroidal hormones in the prostate, the aim of this study, was to investigate the effects of absence of 5-alpha reductase (5alpha-r) and aromatase (Aro) enzymes on prostatic cellular and extracellular components after long-term inhibition. Young, adult and old male Mongolian gerbils were treated orally, once a day, for 30 consecutive days, with Finasteride (10.0 mg/kg) and Letrozole (1.0 mg/kg) (5alpha-r and Aro enzymes inhibitors respectively) simultaneously or separately. Animals were killed on 1, 7, 14 and 21 days post-treatment. Data obtained after double or single enzymatic inhibition with Finasteride and Letrozole demonstrated marked remodelling of epithelial and stromal compartments. During the post-treatment period, particularly on the first and the last analysed days, prostatic epithelial cells showed decreased cytoplasmic volume and secretory activity. In the stroma, collagen fibres had accumulated in the epithelial base and among smooth muscle cells, which showed reduced diameter and condensed cytoplasm, and some of them had a highly irregular external contour. Also in the sub-epithelial area, some fibroblasts acquired an activated phenotype besides increased deposits of amorphous granular material. In conclusion, the inhibition of 5alpha-r and Aro enzymes affected, in a persistent manner, the structural and ultrastructural morphology of the prostate, irrespective of the gerbil's age. Hence these enzymes appear to be crucial in the maintenance of this gland during postnatal development. Also, these data bring more light to the complex issue of the mechanisms of local steroid metabolism and prostatic histology. Thus, the blockade of the steroid-metabolizing enzymes provided an important novel tool to study the relationship between sex steroids and normal physiology and diseases of the prostate.

Elevated level of inhibin-alpha subunit is pro-tumourigenic and pro-metastatic and associated with extracapsular spread in advanced prostate cancer

The biological function of inhibin-α subunit (INHα) in prostate cancer (PCa) is currently unclear. A recent study associated elevated levels of INHα in PCa patients with a higher risk of recurrence. This prompted us to use clinical specimens and functional studies to investigate the pro-tumourigenic and pro-metastatic function of INHα. We conducted a cross-sectional study to determine a link between INHα expression and a number of clinicopathological parameters including Gleason score, surgical margin, extracapsular spread, lymph node status and vascular endothelial growth factor receptor-3 expression, which are well-established prognostic factors of PCa. In addition, using two human PCa cell lines (LNCaP and PC3) representing androgen-dependent and -independent PCa respectively, we investigated the biological function of elevated levels of INHα in advanced cancer. Elevated expression of INHα in primary PCa tissues showed a higher risk of PCa patients being positive for clinicopathological parameters outlined above. Over-expressing INHα in LNCaP and PC3 cells demonstrated two different and cell-type-specific responses. INHα-positive LNCaP demonstrated reduced tumour growth whereas INHα-positive PC3 cells demonstrated increased tumour growth and metastasis through the process of lymphangiogenesis. This study is the first to demonstrate a pro-tumourigenic and pro-metastatic function for INHα associated with androgen-independent stage of metastatic prostate disease. Our results also suggest that INHα expression in the primary prostate tumour can be used as a predictive factor for prognosis of PCa.

Estrogen and its receptors in cancer

The involvement of estrogen and its receptors in the development of cancer has been known for years. However, the exact mechanism responsible is far from clear. The estrogen-mediated carcinogenic process is complicated by recent findings, which reveal that estrogens have multiple functions in cells, which can be either adverse or beneficial, and that the effects of estrogen may be cell-type or organ dependent. The estrogenic effect may be also greatly influenced by the state of two estrogen receptors, ERalpha and ERbeta. This review will discuss the role and function of estrogens and its receptors in cancers of three categories: (1) Breast cancer and gynecologic cancers, (2) Cancers of endocrine organs, (3) Lung cancer and cancers of digestive system. We will also review some novel treatments aiming to interfere with relevant pathways mediated by estrogens and its receptors.

Inflammation and epithelial alterations in rat prostate: impact of the androgen to oestrogen ratio

Chronic non-bacterial prostatitis may offer new insights into the pathogenesis of human benign prostatic hyperplasia and prostate cancer and the strategies for their treatment and prevention. The potential significance of androgen replacement therapy in terms of the reversal of oestradiol (E(2))-induced inflammatory reaction was studied in the dorsolateral prostate (DLP) of the Noble rat. Castrated Noble rats were treated with E(2) and different doses of androgens [dihydrotestosterone (DHT) and testosterone (T)] to achieve an elevated concentration of E(2) and a wide range of the androgen-to-oestradiol ratios in serum. After the 3-week treatment, inflammatory changes in the DLP were classified and counted. Oestrogen receptor alpha (ER alpha), progesterone receptor (PR), fos-related antigen-2 (Fra2), Ki-67 and P63 were immunocytochemically stained. T, E(2) and prolactin concentrations in serum were measured and the relative weights of the seminal vesicles and pituitary glands and microscopic structures of the DLP and seminal vesicle ducts were determined. Hypoandrogenic doses of DHT (judged on the basis of seminal vesicle weight gain), dose-dependently increased the number of perivascular and stromal inflammatory infiltrates. T and DHT were anti-inflammatory at the doses which normalized or over stimulated the growth of the seminal vesicles. As signs of anti-oestrogenicity, androgens dose-dependently decreased the number and distribution of the ER alpha and PR-positive cells at proinflammatory concentrations. Anti-inflammatory concentrations were needed to reduce the expression of Fra2, E(2)-increased prolactin concentration in serum and pituitary weight. The androgen concentrations required to prevent proinflammatory and epithelial responses to E(2) in the presence of elevated E(2) concentrations may subject the accessory sex glands to more intense androgenic stimulation than is normal for the male. The androgen-resistant endpoints of oestrogen action (body weight reduction and hyperplasia of seminal vesicle ducts) further indicate limitations in the possible preventive effects of androgen-replacement therapy.

ERAP75 functions as a coactivator to enhance estrogen receptor alpha transactivation in prostate stromal cells

BACKGROUND

Estrogen receptor alpha (ER alpha) has been reported to be expressed and function in the prostate stromal cells, and numerous evidences indicated that the stromal ER alpha signal pathway plays critical roles in prostate development and cancer. ER alpha requires distinct coregulators for efficient transcriptional regulation. The goal of this study is to examine physical and functional interaction between ER alpha and ERAP75 in the context of prostate stromal cells.

METHOD

Yeast two-hybrid assays were used to screen novel ER alpha interaction proteins. The interaction between ER alpha and ERAP75 was confirmed by mammalian two-hybrid, GST pull-down, and co-immunoprecipitation methods. The interaction motif was examined by site-directed mutagenesis. The effect of ERAP75 on ER alpha transactivation and the expression of ER alpha target genes were determined by luciferase assay and real-time PCR, respectively.

RESULT

ER alpha can interact with the C terminus of ERAP75 via its ligand binding domain both in vivo and in vitro. The conserved LXXLL motif within the C terminus of ERAP75 is required for the interaction between ER alpha and ERAP75. ERAP75 can enhance ER alpha transactivation in a dose-dependent manner and up-regulate the expression of the endogenous ER alpha target gene, stromal-derived factor-1 (SDF-1), in the prostate stromal cells.

CONCLUSION

ERAP75 functions as a novel coactivator that can modulate ER alpha function in the prostate stromal cells. The understanding of the mechanism of ER alpha transactivation in prostate stromal cells could possibly help in the development of new strategies to control or treat prostate cancer by targeting its transactivation protein complex.

Early-onset endocrine disruptor-induced prostatitis in the rat

BACKGROUND

Androgens are critical for specifying prostate development, with the fetal prostate sensitive to altered hormone levels and endocrine-disrupting chemicals (EDCs) that exhibit estrogenic or antiandrogenic properties. Prostatic inflammation (prostatitis) affects 9% of men of all ages, and > 90% of cases are of unknown etiology.

OBJECTIVES

In this study we aimed to evaluate effects of in utero exposure to the antiandrogenic EDC vinclozolin, during the period of male reproductive tract development, on neonatal, prepubertal, and postpubertal prostate gland function of male offspring.

METHODS

Fetal rats were exposed to vinclozolin (100 mg/kg body weight) or vehicle control (2.5 mL/kg body weight) in utero from gestational day 14 (GD14) to GD19 via oral administration to pregnant dams. Tissue analysis was carried out when male offspring were 0, 4, or 8 weeks of age.

RESULTS

In utero exposure to vinclozolin was insufficient to perturb prostatic development and branching, although expression of androgen receptor and mesenchymal fibroblast growth factor-10 was down-regulated. Prostate histology remained normal until puberty, but 100% of animals displayed prostatitis postpubertally (56 days of age). Prostatic inflammation was associated with phosphorylation and nuclear translocation of nuclear factor-kappa B (NFkappaB) and postpubertal activation of proinflammatory NFkappaB-dependent genes, including the chemokine interleukin-8 and the cytokine transforming growth factor-beta1. Significantly, inflammation arising from vinclozolin exposure was not associated with the emergence of premalignant lesions, such as prostatic intra-epithelial neoplasia or proliferative inflammatory atrophy, and hence mimics nonbacterial early-onset prostatitis that commonly occurs in young men.

CONCLUSIONS

These data are the first to unequivocally implicate EDCs as a causative factor and fill an important knowledge gap on the etiology of prostatitis.

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.

Antiestrogen therapies affect tissue homeostasis of the gerbil (Meriones unguiculatus) female prostate and ovaries

The present work aims to evaluate the response of the adult gerbil female prostate (paraurethral glands) and ovaries to short-term exposure to antiestrogenic agents, consisting of daily oral doses of letrozole (1 mg kg(-1) day(-1)) or intradermal doses of tamoxifen (1 mg/kg) every other day for 21 days. The serum levels of testosterone and estradiol were monitored, and the prostates and ovaries collected for structural, ultrastructural, and immunocytochemical analyses. The letrozole treatment resulted in increases of serum testosterone levels and secretory activity as well as in glandular hyperplasia and dysplastic growth, simulating the effects caused by the exogenous androgens. The effects caused by tamoxifen indicate that this endocrine agent acted as an estrogenic agonist on the prostate, causing glandular hypertrophy, secretory activity decrease, and the development of prostatic lesions. Therefore, it is possible to conclude that the letrozole and tamoxifen therapies result in a series of complex effects that endanger the physiology of hormone-dependent organs, including the female prostate and ovaries. The hormonal imbalance caused by administration of these drugs resulted in considerable changes in prostatic morphology, in a manner very similar to what occurs during the development of prostatic lesions in aged postmenopausal women. Thus, these therapies must be chosen carefully since long-term treatments can result in female prostate dysplasic lesions.

Indirect androgen doping by oestrogen blockade in sports

Androgens can increase muscular mass and strength and remain the most frequently abused and widely available drugs used in sports doping. Banning the administration of natural or synthetic androgens has led to a variety of strategies to circumvent the ban of the most effective ergogenic agents for power sports. Among these, a variety of indirect androgen doping strategies aiming to produce a sustained rise in endogenous testosterone have been utilized. These include oestrogen blockade by drugs that act as oestrogen receptor antagonists (antioestrogen) or aromatase inhibitors. The physiological and pharmacological basis for the effects of oestrogen blockade in men, but not women, are reviewed.

Estrogen and prostate cancer: an eclipsed truth in an androgen-dominated scenario

Prostate cancer is the commonest non-skin cancer in men. Incidence and mortality rates of this tumor vary strikingly throughout the world. Although several factors have been implicated to explain this remarkable variation, lifestyle and dietary factors may play a dominant role, with sex hormones behaving as intermediaries between exogenous factors and molecular targets in development and progression of prostate cancer. Human prostate cancer is generally considered a paradigm of androgen-dependent tumor; however, estrogen role in both normal and malignant prostate appears to be equally important. The association between plasma androgens and prostate cancer remains contradictory and mostly not compatible with the androgen hypothesis. Similar evidence apply to estrogens, although the ratio of androgen to estrogen in plasma declines with age. Apart from methodological problems, a major issue is to what extent circulating hormones can be considered representative of their intraprostatic levels. Both nontumoral and malignant human prostate tissues and cells are endowed with key enzymes of steroid metabolism, including 17betahydroxysteroid dehydrogenase (17betaHSD), 5beta-reductase, 3alpha/3betaHSD, and aromatase. A divergent expression and/or activity of these enzymes may eventually lead to a differential prostate accumulation of steroid derivatives having distinct biological activities, as it occurs for hydroxylated estrogens in the human breast. Locally produced or metabolically transformed estrogens may differently affect proliferative activity of prostate cancer cells. Aberrant aromatase expression and activity has been reported in prostate tumor tissues and cells, implying that androgen aromatization to estrogens may play a role in prostate carcinogenesis or tumor progression. Interestingly, many genes encoding for steroid enzymes are polymorphic, although only a few studies have supported their relation with risk of prostate cancer. In animal model systems estrogens, combined with androgens, appear to be required for the malignant transformation of prostate epithelial cells. Although the mechanisms underlying the hormonal induction of prostate cancer in experimental animals remain uncertain, there is however evidence to support the assumption that long term administration of androgens and estrogens results in an estrogenic milieu in rat prostates and in the ensuing development of dysplasia and cancer. Both androgen and estrogen have been reported to stimulate proliferation of cultured prostate cancer cells, primarily through receptor-mediated effects. As for estrogens, the two major receptor types, ERalpha and ERbeta, are expressed in both normal and diseased human prostate, though with a different cellular localization. Since these two receptors are different in terms of ligand binding, heterodimerization, transactivation, and estrogen response element activity, it is likely that an imbalance of their expression may be critical to determine the ultimate estrogen effects on prostate cancer cells. In prostate cancer, ERbeta activation appears to limit cell proliferation directly or through ERalpha inhibition, and loss of ERbeta has been consistently associated with tumor progression. Several splicing variants of both ERalpha and ERbeta exist. Little is known about their expression and function in the human prostate, although reciprocal regulation and interaction with gene promoter both warrant further investigation. In summary, although multiple consistent evidence suggests that estrogens are critical players in human prostate cancer, their role has been only recently reconsidered, being eclipsed for years by an androgen-dominated interest.

Treating prostate cancer: a rationale for targeting local oestrogens

Prostate cancer is the most commonly diagnosed cancer and the second most common cause of cancer-related death in men, and benign prostatic hyperplasia is the most common benign condition known to occur in ageing men. Oestrogen has been implicated in the development of prostate cancer, and offers a promising new avenue for treatment. Despite this, the role of oestrogens in the prostate is complex. This Perspective presents a rationale for a targeted approach for the treatment of prostate disease through the use of selective oestrogen-receptor modulators in conjunction with contemporary androgen-ablation therapy.

Delay of postnatal maturation sensitizes the mouse prostate to testosterone-induced pronounced hyperplasia: protective role of estrogen receptor-beta

The role of estrogens in the etiology of prostate cancer is controversial. To demonstrate the specific effects of estrogens and androgens on the development of the prostatic epithelial hyperplasia, we used luteinizing hormone receptor knockout mice (LuRKO), which are resistant to pituitary regulation mediated by luteinizing hormone, lack postnatal androgen production, and have rudimentary accessory sex glands, the growth of which can be induced with exogenous androgen replacement. This model is thus ideal for the investigation of direct hormonal effects on the prostate. Testosterone, but not 5alpha-dihydrotestosterone, replacement from 21 days of life for 8 weeks induced pronounced hyperplasia and inflammation in the prostates of LuRKO mice. Interestingly, 5alpha-dihydrotestosterone combined with 17beta-estradiol did not induce hyperplasia or inflammation, and treatments with inhibitors of estrogen action, aromatase inhibitor, and ICI 182780 further exacerbated testosterone-induced hyperplastic growth. However, the activation of estrogen receptor (ER)-beta with a specific agonist, DPN [2,3-bis(4-hydroxyphenol)-propionitrile], prevented the development of prostatic hyperplasia and inflammation in testosterone-treated LuRKO mice. Thus, it seems that in the presence of sufficient androgenic stimulation, it is the balance between ER-alpha- and ER-beta-mediated signaling that determines whether estrogens promote hyperplasia or protect the prostate against hyperplastic changes.

17beta-Estradiol differentially regulates androgen-responsive genes through estrogen receptor-beta- and extracellular-signal regulated kinase-dependent pathways in LNCaP human prostate cancer cells

The molecular mechanism underlying the actions of estrogens in normal prostate physiology and prostate cancer development remains unclear. In the present study we tested the hypothesis that estrogens modulate androgen-dependent events in prostate cells by examining the effects of 17beta-estradiol (E2) on androgen-responsive genes (ARGs) in the androgenresponsive LNCaP cells. We found that LNCaP cells express estrogen receptor-beta (ER-beta) as the major form of ER and ER treatment with E2 led to an increase in cell growth. The proliferative effect of E2 correlated with induction of several ARGs by E2. Interestingly, some other ARGs did not respond to E2. Consistent with involvement of ER-beta, the induction of both cell growth and ARG mRNA levels by E2 was attenuated by the pure antiestrogen ICI 182,780. Moreover, we found ER-beta small interfering RNA attenuated induction of ARG mRNAs by E2. However, the effect of E2 on ARG mRNA appeared also to require the androgen receptor and to be mediated through activation of the extracellular-signal regulated kinase (ERK) pathway. These results provide mechanistic evidence supporting a direct effect of estrogen, mediated through ER-beta- and ERK-dependent pathways, on specific molecular targets in human prostate cancer cells.

Sex steroids and prostate carcinogenesis: integrated, multifactorial working hypothesis

Androgens are thought to cause prostate cancer, but there is little epidemiological support for this notion. Animal studies, however, demonstrate that androgens are very strong tumor promotors for prostate carcinogenesis after tumor-initiating events. Even treatment with low doses of testosterone alone can induce prostate cancer in rodents. Because testosterone can be converted to estradiol-17beta by the enzyme aromatase, expressed in human and rodent prostate, estrogen may be involved in prostate cancer induction by testosterone. When estradiol is added to testosterone treatment of rats, prostate cancer incidence is markedly increased and even a short course of estrogen treatment results in a high incidence of prostate cancer. The active testosterone metabolite 5alpha-dihydrotestosterone cannot be aromatized to estrogen and hardly induces prostate cancer, supporting a critical role of estrogen in prostate carcinogenesis. Estrogen receptors are expressed in the prostate and may mediate some or all of the effects of estrogen. However, there is also evidence that in the rodent and human prostate conversion occurs of estrogens to catecholestrogens. These can be converted to reactive intermediates that can adduct to DNA and cause generation of reactive oxygen species, and thus estradiol can be a weak DNA damaging (genotoxic) carcinogen. In the rat prostate DNA damage can result from estrogen treatment; this occurs prior to cancer development and at exactly the same location. Inflammation may be associated with prostate cancer risk, but no environmental carcinogenic risk factors have been definitively identified. We postulate that endogenous factors present in every man, sex steroids, are responsible for the high prevalence of prostate cancer in aging men, androgens acting as strong tumor promoters in the presence of a weak, but continuously present genotoxic carcinogen, estradiol-17beta.

Sex steroid hormones in young manhood and the risk of subsequent prostate cancer: a longitudinal study in African-Americans and Caucasians (United States)

OBJECTIVE

To investigate the relation of sex hormone levels in young adults to subsequent prostate cancer risk.

METHODS

From 1959 to 1967, the Child Health and Development Studies collected sera from 10,442 men (median age: 34 years) and followed them for a median of 32 years. In this analysis, we selected 119 African-Americans and 206 Caucasians diagnosed with prostate cancer during the follow-up period. Two prostate cancer-free men were chosen to match each prostate cancer case on race and birth year. We compared the levels of testosterone, estradiol, and sex hormone-binding globulin in cases to those of their matched controls using conditional logistic regression.

RESULTS

There was no significant association between absolute levels of sex hormones in youth and prostate cancer risk in either race. However, among Caucasians, but not African-Americans, prostate cancer risk was positively associated with the ratio of total testosterone to total estradiol (odds ratio relating the fourth to the first quartile: 3.01; 95% confidence interval: 1.42-6.39).

CONCLUSIONS

The association between testosterone to estradiol ratio and prostate cancer risk in young Caucasians is consistent with similar findings in older Caucasians. The absence of this association in African-Americans needs confirmation in other data involving larger numbers of African-Americans.

Estrogens and Antiestrogens as Etiological Factors and Therapeutics for Prostate Cancer

Mounting evidence supports a key role played by estrogen or estrogen in synergy with an androgen, in the pathogenesis of prostate cancer (PCa). New experimental data suggest that this process could begin as early as prenatal life. During adulthood, estrogen carcinogenicity is believed to be mediated by the combined effects of hormone-induced, unscheduled cell proliferation and bioactivation of estrogens to genotoxic carcinogens. Increased bioavailability of estrogen through age-dependent increases in conversion from androgen could also be a contributing factor. Individual variations and race-/ethnic-based differences in circulating or locally formed estrogens or in tissue estrogen responsiveness may explain differential PCa risk among individuals or different populations. Estrogen receptor (ER)-alpha and ER-beta are the main mediators of estrogen action in the prostate. However, ER-beta is the first ER subtype expressed in the fetal prostate. During cancer development, ER-beta expression is first lost as tumors progress into high grade in the primary site. Yet, its reexpression occurs in all metastatic cases of PCa. A change in cytosine methylation in a regulatory CpG island located in the proximal promoter of ER-beta may constitute an "on/off" switch for reversible regulation of ER-beta expression. A variety of estrogenic/antiestrogenic/selective estrogen receptor modulator (SERM)-like compounds have been shown to use non-ERE pathways, such as tethering of ER-beta to NF-kappaB binding proteins, Sp2, or Ap1 for gene transactivation. These findings open new avenues for drug design that now focuses on developing a new generation of estrogen-based PCa therapies with maximal proapoptotic action but few or no side effects.

Oestrogen modulation of the effect of 8-OH-DPAT on prepulse inhibition: effects of aromatase deficiency and castration in mice

OBJECTIVE

The aim of this study was to investigate the interaction of sex steroid hormones, particularly oestrogen, in the regulation of prepulse inhibition (PPI) by serotonin-1A (5-HT1A) receptors.

MATERIALS AND METHODS

We studied aromatase knockout (ArKO) mice, which are unable to produce oestrogen but have high levels of testosterone, and the effects of castration.

RESULTS AND DISCUSSION

Treatment of male ArKO mice with the 5-HT1A receptor agonist, 8-hydroxy-dipropyl-aminotetralin (8-OH-DPAT), caused an increase in PPI that was significantly greater than in male wild-type controls. Castration of male mice caused a significant enhancement of the effect of 8-OH-DPAT in control mice; however, there was no change in the effect of this drug in ArKO mice. There was no significant effect of 8-OH-DPAT on PPI in either female ArKO or wild-type controls. In all experiments, the effects of 8-OH-DPAT on startle were not different between the groups. [3H]8-OH-DPAT autoradiography showed no differences in 5-HT1A receptor binding densities in areas of the forebrain, hippocampus or raphe region that could explain the PPI results. These data show that the absence of oestrogen in male ArKO mice leads to a greater effect of 5-HT1A receptor stimulation on PPI. This effect can be mimicked in male control mice by castration. The differential involvement of oestrogen and testosterone in these animal models is discussed.

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.

Effect of aromatase inhibition on bone metabolism in elderly hypogonadal men

Both estrogens and androgens play important roles in skeletal development and maintenance in men. The relative importance of estrogens and androgens in male bone metabolism, however, remains undefined. Anastrozole is an oral aromatase inhibitor that decreases estrogen production and increases androgen production in men. Currently, anastrozole is being investigated as a potential agent for the treatment of hypogonadism in aging men. Because anastrozole lowers estrogen levels and raises androgen levels, its effect on bone metabolism is difficult to predict. To assess the effects of anastrozole on bone turnover, we randomized 37 elderly (ages 62-74) mildly hypogonadal men (serum testosterone <350 ng/dl) to receive either anastrozole 1 mg daily (n=12), anastrozole 1 mg twice weekly (n=11), or daily placebo (n=14) for 12 weeks. Serum gonadal steroid levels, serum and urine biochemical markers of bone turnover, serum osteoprotegerin, and total body bone mineral density were measured at baseline and week 12. Mean serum levels of total and bioavailable testosterone increased substantially in both treated groups. Specifically, mean +/- SD bioavailable testosterone levels increased from 99+/-31 ng/dl to 207+/-65 ng/dl in the group receiving 1 mg of anastrozole daily and from 115+/-37 ng/dl to 178+/-55 ng/dl in the subjects receiving 1 mg of anastrozole twice weekly ( p <0.001 vs placebo for both groups). Serum estradiol levels decreased modestly in both treated groups (from 26+/-8 pg/ml to 17+/-6 pg/ml in the daily treatment group and from 27+/-8 pg/ml to 17+/-5 pg/ml in the twice-weekly treatment group, p <0.001 vs placebo for both groups). Despite these hormonal changes, no increases in biochemical markers of bone resorption were observed. Specifically, mean serum N-telopeptide and urinary deoxypyridinoline concentrations remained stable in both treated groups over the 12-week treatment period. Similarly, serum biochemical markers of bone formation (osteocalcin and amino-terminal propeptide of type 1 collagen), serum osteoprotegerin, and total body bone mineral density did not change. These data demonstrate that although short-term administration of anastrozole decreases serum estradiol levels in elderly men with mild hypogonadism, this intervention does not adversely affect bone metabolism over a 12-week period. This lack of an effect may be due to the concomitant increase in testosterone production, the relative modest effect on estradiol production, or a combination of both factors. These results suggest that anastrozole therapy is unlikely to have an adverse effect on bone metabolism when taken over extended periods and may prove to be a valuable method of normalizing testosterone production in older men.

Early effects of estrogen on the rat ventral prostate

Complex interactions between androgen and estrogen (E2) regulate prostatic development and physiology. We analyzed the early effects of a high single dose of E2 (25 mg/kg body weight) and castration (separately or combined) on the adult 90-day-old male Wistar rat ventral prostate. Androgen levels, prostate weight, and the variation in the relative and absolute volume of tissue compartments and apoptotic indices were determined for 7 days. Castration and exogenous E2 markedly reduced ventral prostate weight (about 50% of the control), with a significant reduction in the epithelial compartment and increased stroma. The final volume of the epithelium was identical at day 7 for all treatments (58.5% of the control). However, E2 had an immediate effect, causing a reduction in epithelial volume as early as day 1. An increase in smooth muscle cell volume resulted from the concentration of these cells around the regressing epithelium. The treatments resulted in differential kinetics in epithelial cell apoptosis. Castration led to a peak in apoptosis at day 3, with 5% of the epithelial cells presenting signs of apoptosis, whereas E2 caused an immediate increase (observed on day 1) and a sustained (up to day 7) effect. E2 administration to castrated rats significantly increased the level of apoptosis by day 3, reaching 9% of the epithelial cells. The divergent kinetics between treatments resulted in the same levels of epithelial regression after 7 days (approximately 30% of control). These results show that E2 has an immediate and possibly direct effect on the prostate, and anticipates epithelial cell death before reducing testosterone to levels as low as those of castrated rats. In addition, E2 and androgen deprivation apparently cause epithelial cell death by distinct and independent pathways.

High incidence of central precocious puberty in a bounded geographic area of northwest Tuscany: an estrogen disrupter epidemic?

The potential health consequences of human exposure to environmental estrogen disrupters are not known. Because many chemical compounds are environmentally persistent, toxic and estrogen-active, they can dysregulate the hypothalamic-pituitary-gonadal axis, potentially inducing reproductive disorders such as central precocious puberty (CPP). We performed a multi-center analysis of CPP distribution in northwest Tuscany (NWT), an area of 5990 km2 with 1,280,895 inhabitants. Study criteria consisted of recorded CPP diagnoses and prescriptions of gonadotropin-releasing hormone analogs from January 1, 1998 to December 1, 2003. Although similar CPP prevalences were found in four major cities of NWT (Livorno, Lucca, Massa and Pisa) (mean 30.4 per 100,000 children, standard deviation 18.6; p > 0.05), Viareggio area (< 300 km2) with 19,219 child inhabitants (0-14 years of age) had the highest CPP prevalence: more than 161 CPP cases per 100,000 children. Living in Viareggio area significantly increased the risk of CPP (relative risk (RR) 5.73, 95% confidence interval (CI) 3.5-9.3; rate/risk difference 0.133%, p < 0.05). Annual CPP incidence in the Viareggio area was relatively constant and significantly higher than in other NWT areas (RR 5.04, 95% CI 2.3-11.2; rate/risk difference 0.03%, p < 0.05). Indeed, 47% of total NWT cases were distributed in the countryside (300?km2) surrounding Viareggio. Specifically, three villages - Camaiore, Pietrasanta and Stazzema - in Viareggio presented the highest CPP frequency: 216.1, 393.5 and 274.0 CPP cases per 100,000 children, respectively (RR 9.59, 95% CI 1.71-16.6; rate/risk difference 0.26%, p < 0.05). Owing to the definite geographic distribution of CPP and because increasing distance (km) from Pietrasanta rarefied CPP frequency, we suggest environmental factors (e.g. estrogen disrupter pollution) as major CPP determinants in NWT.

Dietary influences on endocrine-inflammatory interactions in prostate cancer development

Prostate cancer is the most frequently diagnosed non-cutaneous cancer and is the second leading cause of cancer death in American men. The focus of this review is to define the relationship between hormonal (testosterone/estrogens) stimulation of chronic inflammation, generation of reactive oxygen species (ROS), and uncontrolled prostate cell proliferation, and review putative dietary chemoprevention strategies that focus on these processes. It has been proposed that elevated estrogen in men who already have high blood testosterone are at high risk for prostate cancer. We hypothesized that elevated estrogen, in the presence of testosterone, causes prolonged activation of a redox-sensitive transcription factor, nuclear factor kappa B (NF kappa B), that initiates and amplifies an inflammatory cascade within the prostate and results in sustained oxidative and nitrative damage. The inflammatory cascade is proposed to link with uncontrolled proliferation through up-regulated Wnt signal and abnormal catenin accumulation in the prostate. Finally, a strategy that emphasizes a "whole food" based approach to cancer prevention by selecting food products that bear anti-inflammatory and anti-proliferative properties may be most promising as an effective dietary chemopreventive strategy.

Estrogen receptor beta regulates epithelial cellular differentiation in the mouse ventral prostate

We have previously reported epithelial cellular hyperplasia in ventral prostates (VP) of mice lacking estrogen receptor beta (ER beta). To investigate the causes of this phenomenon, we measured cellular proliferation and apoptosis in VP of ER beta(-/-) and WT mice. With BrdUrd labeling, the number of proliferating cells was 3.6-fold higher in ER beta(-/-) mice. There was also a decrease in apoptosis as measured by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay and an increase in expression of the anti-apoptotic bcl-2. The state of differentiation of the epithelial cells of the VP was studied by immunohistochemical staining, Western blotting, and fluorescence-activated cell sorting (FACS). In ER beta(-/-) mouse VP, the number of p63-positive cells (basal phenotype) was 2.6-fold higher, and expression level of cytokeratin (CK) 8, a luminal cell marker, was lower. FACS analysis with p63 showed that in WT mice the ratio of basal to intermediate/luminal cell populations expressing p63 was 1:2.5, whereas in ER beta(-/-) mice it was 1:9. The expression of basal/intermediate marker CK 19 in three FACS areas, g1, g2, and g3, gated according to cellular size and granularity, was 1:0.6:2 in WT and 1:4:6.7 in ER beta(-/-) mice, showing a shift of CK 19-positive cells toward a cell population of intermediate size and granularity. We conclude that, in ER beta(-/-) mouse VP, there is increased epithelial proliferation, decreased apoptosis, and accumulation of incompletely differentiated cells in an intermediate pool. The continued proliferation of intermediate cells leads to the prostatic epithelial hyperplasia observed in the absence of ER beta signaling.

Effects of aromatase inhibition in elderly men with low or borderline-low serum testosterone levels

As men age, serum testosterone levels decrease, a factor that may contribute to some aspects of age-related physiological deterioration. Although androgen replacement has been shown to have beneficial effects in frankly hypogonadal men, its use in elderly men with borderline hypogonadism is controversial. Furthermore, current testosterone replacement methods have important limitations. We investigated the ability of the orally administered aromatase inhibitor, anastrozole, to increase endogenous testosterone production in 37 elderly men (aged 62-74 yr) with screening serum testosterone levels less than 350 ng/dl. Subjects were randomized in a double-blind fashion to the following 12-wk oral regimens: group 1: anastrozole 1 mg daily (n = 12); group 2: anastrozole 1 mg twice weekly (n = 11); and group 3: placebo daily (n = 14). Hormone levels, quality of life (MOS Short-Form Health Survey), sexual function (International Index of Erectile Function), benign prostate hyperplasia severity (American Urological Association Symptom Index Score), prostate-specific antigen, and measures of safety were compared among groups. Mean +/- SD bioavailable testosterone increased from 99 +/- 31 to 207 +/- 65 ng/dl in group 1 and from 115 +/- 37 to 178 +/- 55 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.054 group 1 vs. group 2). Total testosterone levels increased from 343 +/- 61 to 572 +/- 139 ng/dl in group 1 and from 397 +/- 106 to 520 +/- 91 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.012 group 1 vs. group 2). Serum estradiol levels decreased from 26 +/- 8 to 17 +/- 6 pg/ml in group 1 and from 27 +/- 8 to 17 +/- 5 pg/ml in group 2 (P < 0.001 vs. placebo for both groups and P = NS group 1 vs. group 2). Serum LH levels increased from 5.1 +/- 4.8 to 7.9 +/- 6.5 U/liter and from 4.1 +/- 1.6 to 7.2 +/- 2.8 U/liter in groups 1 and 2, respectively (P = 0.007 group 1 vs. placebo, P = 0.003 group 2 vs. placebo, and P = NS group 1 vs. group 2). Scores for hematocrit, MOS Short-Form Health Survey, International Index of Erectile Function, and American Urological Association Symptom Index Score did not change. Serum prostate-specific antigen levels increased in group 2 only (1.7 +/- 1.0 to 2.2 +/- 1.5 ng/ml, P = 0.031, compared with placebo). These data demonstrate that aromatase inhibition increases serum bioavailable and total testosterone levels to the youthful normal range in older men with mild hypogonadism. Serum estradiol levels decrease modestly but remain within the normal male range. The physiological consequences of these changes remain to be determined.

Androgen Replacement Therapy

The major goal of androgen substitution is to replace testosterone at levels as close to physiological levels as is possible. For some androgen-dependent functions testosterone is a pro-hormone, peripherally converted to 5alpha-dihydrotestosterone (DHT) and 17beta-estradiol (E2), of which the levels preferably should be within normal physiological ranges. Furthermore, androgens should have a good safety profile without adverse effects on the prostate, serum lipids, liver or respiratory function, and they must be convenient to use and patient-friendly, with a relative independence from medical services. Natural testosterone is viewed as the best androgen for substitution in hypogonadal men. The reason behind the selection is that testosterone can be converted to DHT and E2, thus developing the full spectrum of testosterone activities in long-term substitution. The mainstays of testosterone substitution are parenteral testosterone esters (testosterone enantate and testosterone cipionate) administered every 2-3 weeks. A major disadvantage is the strongly fluctuating levels of plasma testosterone, which are not in the physiological range at least 50% of the time. Also, the generated plasma E2 is usually supraphysiological. A major improvement is parenteral testosterone undecanoate producing normal plasma levels of testosterone for 12 weeks, with normal plasma levels of DHT and E2 also. Subcutaneous testosterone implants provide the patient, depending on the dose of implants, with normal plasma testosterone for 3-6 months. However, their use is not widespread. Oral testosterone undecanoate dissolved in castor oil bypasses the liver via its lymphatic absorption. At a dosage of 80 mg twice daily, plasma testosterone levels are largely in the normal range, but plasma DHT tends to be elevated. For two decades transdermal testosterone preparations have been available and have an attractive pharmacokinetic profile. Scrotal testosterone patches generate supraphysiological plasma DHT levels, which is not the case with the nonscrotal testosterone patches. Transdermal testosterone gel produces fewer skin irritations than the patches and offers greater flexibility in dosage. Oromucosal testosterone preparations have recently become available. Testosterone replacement is usually of long duration and so patient compliance is of utmost importance. Therefore, the patient must be involved in the selection of type of testosterone preparation. Administration of testosterone to young individuals has almost no adverse effects. With increasing age the risk of adverse effects on the prostate, the cardiovascular system and erythropoiesis increases. Consequently, short-acting testosterone preparations are better suited for aging androgen-deficient men.

Estrogens and anti-estrogens: Key mediators of prostate carcinogenesis and new therapeutic candidates

Despite the historical use of estrogens in the treatment of prostate cancer (PCa) little is known about their direct biological effects on the prostate, their role in carcinogenesis, and what mechanisms mediate their therapeutic effects on PCa. It is now known that estrogens alone, or in synergism with an androgen, are potent inducers of aberrant growth and neoplastic transformation in the prostate. The mechanisms of estrogen carcinogenicity could be mediated via induction of unscheduled cell proliferation or through metabolic activation of estrogens to genotoxic metabolites. Age-related changes and race-/ethnic-based differences in circulating or locally formed estrogens may explain differential PCa risk among different populations. Loss of expression of estrogen receptor (ER)-beta expression during prostate carcinogenesis and prevention of estrogen-mediated oxidative damage could be exploited in future PCa prevention strategies. Re-expression of ER-beta in metastatic PCa cells raises the possibility of using ER-beta-specific ligands in triggering cell death in these malignant cells. A variety of new estrogenic/anti-estrogenic/selective estrogen receptor modulator (SERM)-like compounds, including 2-methoxyestradiol, genistein, resveratrol, licochalcone, Raloxifene, ICI 182,780, and estramustine are being evaluated for their potential in the next generation of PCa therapies. Increasing numbers of patients self-medicate with herbal formulations such as PC-SPES. Some of these compounds are selective ER-beta ligands, while most of them have minimal interaction with ER-alpha. Although many may inhibit testosterone production by blockade of the hypothalamal-pituitary-testis axis, the most effective agents also exhibit direct cytostatic, cytotoxic, or apoptotic action on PCa cells. Some of them are potent in interfering with tubulin polymerization, blocking angiogenesis and cell motility, suppressing DNA synthesis, and inhibiting specific kinase activities. Further discovery of other compounds with potent apoptotic activities but minimal estrogen action should promote development of a new generation of effective PCa preventive or treatment regimens with few or no side-effects due to estrogenicity. Further advancement of our knowledge of the role of estrogens in prostate carcinogenesis through metabolic activation of estrogens and/or ER-mediated pathways will certainly result in better preventive or therapeutic modalities for PCa.

Impaired spatial reference memory in aromatase-deficient (ArKO) mice

Previous studies indicate an important role for estrogen in memory and learning. Aromatase-knockout (ArKO) mice are unable to produce estrogen because they lack a functional Cyp 19 gene that encodes for aromatase, the enzyme that converts testosterone into estrogen. Using a Y-maze test for short-term spatial reference memory, we found that both male and female ArKO mice performed significantly worse than wildtype controls. Gonadectomy reduced Y-maze responses in male and female wildtype controls, but had no effect in ArKO mice. After gonadectomy, there was no significant difference between wildtype and ArKO mice. For the first time using ArKO mice, our findings confirm the importance of estrogen in memory in both males and females.

Update on estrogen signaling

Our understanding of estrogen signaling has undergone a true paradigm shift over recent years, following the discovery in 1995 of a second estrogen receptor, estrogen receptor beta (ERbeta). In many contexts ERbeta appears to antagonize the actions of ERalpha (yin/yang relationship) although there also exist genes that are specifically regulated by one of the two receptors. Studies of ERbeta knockout mice have shown that ERbeta exerts important functions in the ovary, central nervous system, mammary gland, prostate gland, hematopoiesis, immune system, vessels and bone. The use of ERbeta-specific ligands against certain forms of cancer represents one of the many pharmaceutical possibilities that have been created thanks to the discovery of ERbeta.

Anti-androgenic action by red clover-derived dietary isoflavones reduces non-malignant prostate enlargement in aromatase knockout (ArKo) mice

BACKGROUND

Red clover (RC)-derived dietary isoflavones have been implicated as potential preventative agents for the development and prevalence of non-malignant prostate diseases. This study investigated whether dietary isoflavones inhibit prostate growth in vivo in the aromatase knock-out (ArKO) mouse that exhibits lifelong elevation of androgens leading to prostate enlargement.

METHODS

Adult (11-week-old) wild-type (WT) and ArKO mice were fed on protein matched isoflavones free (IF) and RC (isoflavone rich) diets for 28 days. Individual prostate lobes and testes were weighed and collected for histological analysis and serum androgens were measured. Responses were compared to castration and estrogen administration to ArKO mice to determine the mechanism of action.

RESULTS

ArKO mice fed on IF diet exhibited enlarged prostate lobes and elevated serum androgens compared to WT mice. Following 28 days of RC diet, ArKO VP, AP, and SV weights were reduced to WT weights, although testis and body weights remained unaltered. Stereological analysis of VPs revealed a reduction in all components of the tissue, particularly the lumen. The RC diet reduced ArKO serum testosterone and dihydrotestosterone to WT levels. In comparison to castration and estrogen administration, the dietary isoflavones were shown to be anti-androgenic rather than weakly estrogenic, mimicking responses observed in the castrated ArKO, rather than estrogen treated ArKOs.

CONCLUSIONS

This study demonstrates that RC-derived isoflavones have a significant effect on prostatic growth, and are capable of reducing the enlarged non-malignant prostate phenotype of the adult ArKO mouse, by acting as anti-androgenic agents rather than weak estrogenic substances.

Prostate hyperplasia in a transgenic mouse with prostate-specific expression of prolactin

Prolactin (PRL) is one of several polypeptide factors known to exert trophic effects on the prostate. We have previously reported a dramatic prostate enlargement with concurrent chronic hyperprolactinemia and elevated serum androgen levels in a PRL transgenic mouse (Mt-PRL) with ubiquitous expression of the transgene. To address the role of local PRL action in the prostate, a new transgenic mouse model (Pb-PRL) was generated using the prostate-specific rat probasin (Pb) minimal promoter to drive expression of the rat PRL gene. Pb-PRL transgenic males developed a significant enlargement of both the dorsolateral and ventral prostate lobes evident from 10 wk of age and increasing with age. Expression of the transgene was restricted to the prostate and detected from 4 wk of age. Low levels of transgenic rat PRL were detectable in the serum of adult Pb-PRL animals. Serum androgen levels were normal. The Pb-PRL prostate displayed significant stromal hyperplasia, ductal dilation, and focal areas of epithelial dysplasia. Quantitative analysis of prostatic tissue cellularity demonstrated a marked increase in the stromal to epithelial ratio in all lobes of Mt-PRL and Pb-PRL transgenic prostates compared with controls. Microdissections demonstrated an increased ductal morphogenesis in dorsolateral and ventral prostate lobes of Mt-PRL prostate vs. Pb-PRL and controls. In conclusion, this study indicates the ability of PRL to promote, directly or indirectly, ductal morphogenesis in the developing prostate and further to induce abnormal growth primarily of the stroma in the adult gland in a setting of normal androgen levels.

Prepulse inhibition of acoustic startle in aromatase knock-out mice: effects of age and gender

Estrogen has been suggested to play a neuromodulatory and neuroprotective role on the brain dopamine system. We used aromatase knockout (ArKO) mice that lack a functional aromatase enzyme and are unable to convert testosterone into estrogen, and assessed prepulse inhibition of acoustic startle, locomotor hyperactivity to amphetamine treatment and rotarod performance. Mice were tested at either 1 month, 4-5 months or 12-18 months of age. In male, but not female ArKO mice, there was an age-related reduction of prepulse inhibition. The 12-18 months old male ArKO mice also showed significantly greater amphetamine-induced hyperactivity. Mice heterozygous for the mutation showed no deficits or were in-between wildtype mice and ArKO mice. We postulate that these data indicate a neuroprotective role of estrogen, particularly in male mice, on ageing of brain mechanisms involved in pre-pulse inhibition and locomotor activity regulation. It is likely that these brain mechanisms are or include dopaminergic activity.

Direct response of the murine prostate gland and seminal vesicles to estradiol

In the prostate, testosterone action depends on conversion to bioactive metabolites dihydrotestosterone and 17beta-estradiol (E2) via the 5alpha-reductase and aromatase enzymes, respectively. Exogenous estrogen inhibits prostate growth by indirect effects caused by suppression of pituitary gonadotropins and testicular testosterone output, but direct effects are less well known. Direct effects of estrogens were evaluated using the hypogonadal (hpg) mouse model, which has postnatal deficiency in gonadotropins and testosterone but remains hormone sensitive. Mature hpg mice were implanted sc with implants filled with E2. After 6 wk, prostate lobe [anterior prostate (AP) and ventral prostate (VP)] and seminal vesicle (SV) organ volumes were significantly increased (P < 0.05) but remained smaller than wild-type mice. Analysis of the relative volumes (the proportional composition) of each tissue compartment in these organs showed significant increases in cellular and luminal volumes (P < 0.05) in AP (but not VP) and in SVs. Stromal fibroblasts proliferated, whereas smooth muscle cells were reduced in the AP and SVs. In the epithelia, basal cells proliferated and became metaplastic in the AP and VP. In the AP, luminal debris accumulated, together with an inflammatory response, but there was no evidence of malignant changes. The current study unequivocally demonstrates direct proliferative responses to E2 in the hpg mouse AP and VP lobes and SVs, characterized by discrete lobe-specific changes, including smooth-muscle regression, fibroblast proliferation, inflammation, and basal epithelial cell proliferation and metaplasia.

Induction of reproductive tract developmental abnormalities in the male rat by lowering androgen production or action in combination with a low dose of diethylstilbestrol: evidence for importance of the androgen-estrogen balance

This study tested the hypothesis that testis/reproductive tract abnormalities induced in the rat by neonatal treatment with diethylstilbestrol (DES) result from disturbance of the androgen-estrogen balance. Male rats were treated neonatally with a dose of DES (0.1 micro g) that induced either no or small effects on its own or with a dose (10 micro g) that induced major reproductive tract abnormalities. To allow quantification, the abnormalities chosen for study were distension of the rete testis and efferent ducts and reduction in epithelial cell height in the efferent ducts and vas deferens. To alter the androgen-estrogen balance, other rats were treated with DES (0.1 micro g) in combination with a treatment to suppress either androgen production [GnRH antagonist (GnRHa)] or androgen action (flutamide); other rats were treated with GnRHa or flutamide alone. Testosterone levels were measured to verify the effects of treatment. Combined administration of DES (0.1 micro g) plus GnRHa or flutamide induced significantly greater distension/overgrowth of the rete testis and efferent ducts (ED) and a reduction in epithelial cell height of the ED than did DES (0.1 micro g) administered alone. Neither GnRHa nor flutamide affected rete or ED distension when administered alone, but both significantly reduced ED epithelial cell height. Neonatal treatment with bisphenol-A (100 micro g) with or without GnRHa had no significant effect on any of these parameters. In contrast to the ED, a reduction in cell height of the vas deferens was induced to an equal extent by DES (10 micro g), DES (0.1 micro g) with GnRHa, and GnRHa alone, suggesting greater sensitivity of this tissue to both androgen and estrogen action. The induction of major abnormalities in rats treated with DES (10 micro g) was coincident with loss of androgen receptor immunoexpression in affected tissues. Reduced androgen receptor immunoexpression was also induced by combined treatment with DES (0.1 micro g) plus GnRHa or flutamide, whereas treatment with any of these compounds alone had no or only minor effects. These findings suggest that reduced androgen action sensitizes the reproductive tract to estrogens, demonstrating that the balance in action between androgens and estrogens, rather than their absolute levels, may be of fundamental importance in determining normal or abnormal development of some regions of the male reproductive tract.

Progressive prostate hyperplasia in adult prolactin transgenic mice is not dependent on elevated serum androgen levels

BACKGROUND

Transgenic mice overexpressing the rat prolactin (PRL) gene under control of the metallothionein-1 promoter (Mt-1) develop a dramatic prostatic enlargement. These animals also display significantly elevated testosterone serum levels. In this study, we aim to clarify the role of circulating androgen levels in the promotion of abnormal prostate growth in the adult PRL transgenic mouse prostate.

METHODS

Prostate morphology and androgen-receptor distribution patterns were analyzed in castrated and testosterone substituted adult PRL transgenic and in wild-type males.

RESULTS

Progressive prostatic hyperplasia in adult PRL transgenic males was not affected by substitution to serum testosterone levels corresponding to wild-type. Furthermore, prolonged testosterone treatment in adult wild-type males did not produce any significant changes in prostate growth or morphology compared with wild-type controls. Immunohistochemical studies revealed a significantly increased proportion of androgen receptor positive epithelial cells in all lobes of the PRL transgenic prostate versus wild-type.

CONCLUSION

The present study demonstrates that progressive prostate hyperplasia in adult PRL transgenic mice is not dependent on elevated serum androgen levels. Furthermore, prolonged androgen treatment in adult wild-type male mice appears to have no significant effect on prostate growth. In addition, our results suggest that prolonged hyperprolactinemia results in changes in prostate epithelial and stromal cell androgen receptor distribution.

Targeted disruption of the mouse estrogen sulfotransferase gene reveals a role of estrogen metabolism in intracrine and paracrine estrogen regulation

Elicitation of biological responses by estrogen in target tissues requires the presence of ER as well as receptor-active ligand in the local microenvironment. Though much attention has been devoted to the study of the receptor in estrogen target tissues, the concept is emerging that tissue estrogen sensitivity may also be regulated by ligand availability through metabolic transformation in situ. Here, we show that targeted disruption, in the mouse, of an estrogen metabolic enzyme, estrogen sulfotransferase (EST), causes structural and functional lesions in the male reproductive system. EST catalyzes the sulfoconjugation and inactivation of estrogen and is expressed abundantly in testicular Leydig cells. Although knockout males were fertile and phenotypically normal initially, they developed age-dependent Leydig cell hypertrophy/hyperplasia and seminiferous tubule damage. Development of these lesions in the testis could be recapitulated by exogenous E2 administration in younger knockout mice, suggesting that they arose in older knockout mice from chronic estrogen stimulation. Older knockout mice were also found to have reduced testis and epididymis weights but increased seminal vesicle/coagulating gland weight because of tissue swelling. Furthermore, total and forward sperm motility of older knockout mice was reduced by 60% and 80%, respectively, and these mice produced smaller litters compared with age-matched wild-type males. These findings establish a role for EST in the male reproductive system and indicate that intracrine and paracrine estrogen activity can be modulated by a ligand transformation enzyme under a physiological setting. Thus, inhibition of estrogen metabolic enzymes by environmental chemicals, as has been demonstrated recently for the human EST, may constitute a novel mechanism of endocrine disruption in vivo.