Estrogen receptor-alpha is required by the supporting somatic cells for spermatogenesis

Role for Nongenomic Estrogen Signaling in Male Fertility

Estrogen actions are mediated by both nuclear (n) and membrane (m) localized estrogen receptor 1 (ESR1). Male Esr1 knockout (Esr1KO) mice lacking functional Esr1 are infertile, with reproductive tract abnormalities. Male mice expressing nESR1 but lacking mESR1 (nuclear-only estrogen receptor 1 mice) are progressively infertile due to testicular, rete testis, and efferent ductule abnormalities similar to Esr1KO males, indicating a role for mESR1 in male reproduction. The H2NES mouse expresses only mESR1 but lacks nESR1. The goal of this study was to identify the functions of mESR1 alone in mice where nESR1 was absent. Breeding trials showed that H2NES males are fertile, with decreased litter numbers but normal pup numbers/litter. In contrast to Esr1KO mice, H2NES testicular, and epididymal weights were not reduced, and seminiferous tubule abnormalities were less pronounced. However, Esr1KO and H2NES males both had decreased sperm motility and a high incidence of abnormal sperm morphology. Seminiferous tubule and rete testis dilation and decreased efferent ductule epithelial height characteristic of Esr1KO males were reduced in H2NES. Consistent with this, expression of genes involved in fluid transport and ion movement that were reduced in Esr1KO (Aqp1, Car2, Car14, Cftr) were partially or fully restored to wild-type levels in H2NES. In summary, in contrast to Esr1KO males, H2NES males are fertile and have reduced phenotypic and functional abnormalities in the testis and efferent ductules. Thus, mESR1 alone, in the absence of nESR1, can partially regulate male reproductive tract structure and function, emphasizing its importance for overall estrogen action.

Adverse outcome pathways of PBDEs inducing male reproductive toxicity

Polybrominated diphenyl ethers (PBDEs) are widely used brominated flame retardants, they are easily released into environment and causing adverse effects to the ecosystem and human health. This review aims to summarize the research status of PBDEs-induced male reproductive toxicity and its mechanisms at various levels such as molecular/cellular, tissue/organ and individual/population. The Adverse Outcome Pathways (AOPs) diagram showed that PBDEs-induced reactive oxygen species (ROS) production, disruptions of estrogen receptor-α (ERα) and antagonism of androgen receptor (AR) were defined as critical molecular initiating events (MIEs). They caused key events (KEs) at the molecular and cellular levels, including oxidative stress, increased DNA damage, damaging mitochondria, increased glycolipid levels and apoptosis, depletion of ectoplasmic specialization and decreased Leydig cells numbers. These in turn lead to followed KEs at the tissue or organ levels, such as the impaired spermatogenesis, impaired blood-testis barrier and reduced testosterone synthesis and function. As a result, reproductive system-related adverse outcomes (AOs) were reported, such as the decreased sperm quantity or quality, shorten male anogenital distance and cryptorchidism in individual and reduced reproduction of the population. This review assembled information on the mechanisms of male reproductive toxicity induced by PBDEs, and constructed a causal mechanism relationship diagram from different levels using the an AOP framework to provide theoretical basis for ecological risk assessment and environmental management of PBDEs. The AOP framework makes it possible to develop risk management strategies based on toxicity mechanisms and support for development of Integrated Approach to Testing and Assessment (IATA) which are available for regulatory purposes.

Classical cadherins in the testis: how are they regulated?

Cadherins (CDH) are crucial intercellular adhesion molecules, contributing to morphogenesis and creating tissue barriers by regulating cells' movement, clustering and differentiation. In the testis, classical cadherins such as CDH1, CDH2 and CDH3 are critical to gonadogenesis by promoting the migration and the subsequent clustering of primordial germ cells with somatic cells. While CDH2 is present in both Sertoli and germ cells in rodents, CDH1 is primarily detected in undifferentiated spermatogonia. As for CDH3, its expression is mainly found in germ and pre-Sertoli cells in developing gonads until the establishment of the blood-testis barrier (BTB). This barrier is made of Sertoli cells forming intercellular junctional complexes. The restructuring of the BTB allows the movement of early spermatocytes toward the apical compartment as they differentiate during a process called spermatogenesis. CDH2 is among many junctional proteins participating in this process and is regulated by several pathways. While cytokines promote the disassembly of the BTB by enhancing junctional protein endocytosis for degradation, testosterone facilitates the assembly of the BTB by increasing the recycling of endocytosed junctional proteins. Mitogen-activated protein kinases (MAPKs) are also mediators of the BTB kinetics in many chemically induced damages in the testis. In addition to regulating Sertoli cell functions, follicle stimulating hormone can also regulate the expression of CDH2. In this review, we discuss the current knowledge on regulatory mechanisms of cadherin localisation and expression in the testis.

Ameliorative effect of betulinic acid against zearalenone exposure triggers testicular dysfunction and oxidative stress in mice via p38/ERK MAPK inhibition and Nrf2-mediated antioxidant defense activation

Zearalenone (ZEA) is a nonsteroidal estrogenic mycotoxin, which mainly contaminates grains and has estrogen-like effects on the reproductive system. Betulinic acid (BA), a natural lupane-type pentacyclic triterpene, has anti-oxidative and anti-inflammatory properties. This study aimed to investigate whether BA alleviates ZEA-induced testicular damage and explore the possible mechanism. Here, BA ameliorated testicular damage by mitigating the disordered arrangement of seminiferous tubules, the exfoliation of lumen cells, and the increase of cell apoptosis caused by ZEA. Meanwhile, BA alleviated ZEA-triggered testicular damage by restoring hormone levels and sperm motility, and reconstructing the blood-testis-barrier. Moreover, BA alleviated ZEA-exposed testicular oxidative stress by activating Nrf2 pathway. Furthermore, BA moderated ZEA-evoked testicular inflammation by inhibiting p38/ERK MAPK pathway. Overall, our results revealed that BA has a therapeutic protective effect on ZEA-induced testicular injury and oxidative stress via p38/ERK MAPK inhibition and Nrf2-mediated antioxidant defense activation, which provides a viable alternative to alleviate ZEA-induced male reproductive toxicology.

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

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

Gestational and lactational exposure to triclosan causes impaired fertility of F1 male offspring and developmental defects in F2 generation

Triclosan (5-chloro-2-(2, 4-dichlorophenoxy) phenol, TCS), is a broad-spectrum antimicrobial agent and extensively used in household and daily daycare products. Recently, several reports have demonstrated the endocrine disruptive action of TCS to alter the testicular steroidogenesis. However, the gestational and lactational effects of TCS exposure on F1 offspring has not been studied. Present study aimed to investigate the effect of gestational and lactational exposure to TCS on F1 male progeny and its effect on fertility. Pregnant dams (F0) were administered with different doses of TCS (0.1, 4, 40 and 150 mg/kg b. wt./day) and Diethylstilbestrol (1 μg/kg b. wt./day), as a positive control daily by subcutaneous injection during Gestation Day 6 to Postnatal Day 21. Delayed testicular descent was observed at 150 mg/kg b. wt./day dose group. Dose-dependent decrease in testosterone level, sperm count and motility was observed. Significantly decreased expression of steroid hormone receptors (AR, ERα and ERβ), StAR and aromatase were observed in F1 male rats; indicating its prolonged effect on spermatogenesis and steroidogenesis in adulthood and poor development in F2 fetuses. Further, gestational and lactational exposure to TCS has negative impact on the fertility of F1 male rats. The F1 male rats were found sub-fertile with increased (%) pre- and post-implantation loss (at 40 and 150 mg/kg b.wt./day dose) with a simultaneous decrease in litter size. The significant decrease in mean fetal weight and crown-rump length (CRL) of F2 fetuses were observed at 0.1, 4, 40 and 150 dose groups indicating impaired development of F2 fetuses caused by TCS exposure. Present study emphasizes for the first time that TCS exposure during the vulnerable developmental time point (gestation and lactation) adversely affects reproductive functions and fertility of F1 male rats, which were transmitted to F2 generations leading to reduced CRLs and weights of F2 fetuses.

Estrogens in Human Male Gonadotropin Secretion and Testicular Physiology From Infancy to Late Puberty

Several reports in humans as well as transgenic mouse models have shown that estrogens play an important role in male reproduction and fertility. Estrogen receptor alpha (ERα) and beta (ERβ) are expressed in different male tissues including the brain. The estradiol-binding protein GPER1 also mediates estrogen action in target tissues. In human testes a minimal ERα expression during prepuberty along with a marked pubertal up-regulation in germ cells has been reported. ERβ expression was detected mostly in spermatogonia, primary spermatocytes, and immature spermatids. In Sertoli cells ERβ expression increases with age. The aromatase enzyme (cP450arom), which converts androgens to estrogens, is widely expressed in human tissues (including gonads and hypothalamus), even during fetal life, suggesting that estrogens are also involved in human fetal physiology. Moreover, cP450arom is expressed in the early postnatal testicular Leydig cells and spermatogonia. Even though the aromatase complex is required for estrogen synthesis, its biological relevance is also related to the regulation of the balance between androgens and estrogens in different tissues. Knockout mouse models of aromatase (ArKO) and estrogen receptors (ERKOα, ERKOβ, and ERKOαβ) provide an important tool to study the effects of estrogens on the male reproductive physiology including the gonadal axis. High basal serum FSH levels were reported in adult aromatase-deficient men, suggesting that estrogens are involved in the negative regulatory gonadotropin feedback. However, normal serum gonadotropin levels were observed in an aromatase-deficient boy, suggesting a maturational pattern role of estrogen in the regulation of gonadotropin secretion. Nevertheless, the role of estrogens in primate testis development and function is controversial and poorly understood. This review addresses the role of estrogens in gonadotropin secretion and testicular physiology in male humans especially during childhood and puberty.

Estrogen in the male: a historical perspective

Estrogens have traditionally been considered female hormones. Nevertheless, the presence of estrogen in males has been known for over 90 years. Initial studies suggested that estrogen was deleterious to male reproduction because exogenous treatments induced developmental abnormalities. However, demonstrations of estrogen synthesis in the testis and high concentrations of 17β-estradiol in rete testis fluid suggested that the female hormone might have a function in normal male reproduction. Identification of estrogen receptors and development of biological radioisotope methods to assess estradiol binding revealed that the male reproductive tract expresses estrogen receptor extensively from the neonatal period to adulthood. This indicated a role for estrogens in normal development, especially in efferent ductules, whose epithelium is the first in the male reproductive tract to express estrogen receptor during development and a site of exceedingly high expression. In the 1990s, a paradigm shift occurred in our understanding of estrogen function in the male, ushered in by knockout mouse models where estrogen production or expression of its receptors was not present. These knockout animals revealed that estrogen's main receptor (estrogen receptor 1 [ESR1]) is essential for male fertility and development of efferent ductules, epididymis, and prostate, and that loss of only the membrane fraction of ESR1 was sufficient to induce extensive male reproductive abnormalities and infertility. This review provides perspectives on the major discoveries and developments that led to our current knowledge of estrogen's importance in the male reproductive tract and shaped our evolving concept of estrogen's physiological role in the male.

An increase of estrogen receptor α protein level regulates BDE-209-mediated blood-testis barrier disruption during spermatogenesis in F1 mice

Deca-bromodiphenyl ether (BDE-209) regulates various aspects of spermatogenesis and male fertility through its effect on estrogen receptor α (ERα), but the underlying mechanism remains unclear. Because molecular mechanisms such as remodeling of the blood-testis barrier (BTB) play crucial roles in spermatogenesis, we investigated the disruptive effects of ERα agonists on the BTB in spermatogenesis. In this study, 0, 300, and 500 mg/kg/day of BDE-209 were administered to pregnant adult mice by oral gavage from gestation day 7 to postnatal day 21. SerW3 cells were treated with methylpiperidino pyrazole (MPP) for 30 min before being treated with 50 μg/mL of BDE-209. BDE-209 increases ERα in time- and dose-dependent manners and decreases formin 1 and BTB-associated protein in F1 male mice. Furthermore, BDE-209 impairs the structure and function of the BTB. Activation of ERα signaling could disrupt the BTB, leading to spermatogenesis dysfunction. The results identified the role of ERα in BTB disruption during spermatogenesis and suggested that BTB disruption occurs because of exposure to BDE-209, which could potentially affect spermatogenesis. In conclusion, Sertoli cells seem to be the primary target of BDE-209 in the perinatal period, and this period constitutes a critical window of susceptibility to BDE-209. Also, the SerW3 cell model may not be a particularly useful cell model for studying the function of the cytoskeleton.

A comparative review on estrogen receptors in the reproductive male tract of non mammalian vertebrates

Estrogen receptors alpha (ERα) and beta (ERβ) are transcription factors known to be involved in the regulation of many complex physiological processes in mammals. They are expressed primarily in the reproductive tract of all vertebrates females, thus indicating important and conserved functions in female reproductive success. ERs are also present in physiological different tissues as bone, brain, liver, skin and adipose tissues, in both females and males. In the latter, ERs have been found also in the genital tract, supporting the findings of a complex role for estrogen in spermatogenesis and, more generally, in male reproduction. This review provides an overview and update on ERα and ERβ expression and synthesis in male reproductive tract of non-mammalian vertebrates, with focus on their role in germ cells proliferation, maturation and survival. Data from studies on fish, amphibians, reptiles and birds were collated and common or species-specific distribution highlighted. The widespread distribution of estrogen receptors in testicular cells and ducts of all vertebrates so far investigated suggests that whatever are the roles that estrogens may exert on these structures, they are phylogenetically conserved and are possibly related to the physiological support given to achieve male reproductive success.

Of Oestrogens and Sperm: A Review of the Roles of Oestrogens and Oestrogen Receptors in Male Reproduction

The crucial role that oestrogens play in male reproduction has been generally accepted; however, the exact mechanism of their action is not entirely clear and there is still much more to be clarified. The oestrogen response is mediated through oestrogen receptors, as well as classical oestrogen receptors’ variants, and their specific co-expression plays a critical role. The importance of oestrogen signalling in male fertility is indicated by the adverse effects of selected oestrogen-like compounds, and their interaction with oestrogen receptors was proven to cause pathologies. The aims of this review are to summarise the current knowledge on oestrogen signalling during spermatogenesis and sperm maturation and discuss the available information on oestrogen receptors and their splice variants. An overview is given of species-specific differences including in humans, along with a detailed summary of the methodology outcome, including all the genetically manipulated models available to date. This review provides coherent information on the recently discovered mechanisms of oestrogens’ and oestrogen receptors’ effects and action in both testicular somatic and germ cells, as well as in mature sperm, available for mammals, including humans.

Membrane-Localized Estrogen Receptor 1 Is Required for Normal Male Reproductive Development and Function in Mice

Estrogen receptor 1 (ESR1) mediates major reproductive functions of 17β-estradiol (E2). Male Esr1 knockout (Esr1KO) mice are infertile due to efferent ductule and epididymal abnormalities. The majority of ESR1 is nuclear/cytoplasmic; however, a small fraction is palmitoylated at cysteine 451 in mice and localized to cell membranes, in which it mediates rapid E2 actions. This study used an Esr1 knock-in mouse containing an altered palmitoylation site (C451A) in ESR1 that prevented cell membrane localization, although nuclear ESR1 was expressed. These nuclear-only estrogen receptor 1 (NOER) mice were used to determine the roles of membrane ESR1 in males. Epididymal sperm motility was reduced 85% in 8-month-old NOER mice compared with wild-type controls. The NOER mice had decreased epididymal sperm viability and greater than 95% of sperm had abnormalities, including coiled midpieces and tails, absent heads, and folded tails; this was comparable to 4-month Esr1KO males. At 8 months, daily sperm production in NOER males was reduced 62% compared with controls. The NOER mice had histological changes in the rete testes, efferent ductules, and seminiferous tubules that were comparable with those previously observed in Esr1KO males. Serum T was increased in NOER males, but FSH, LH, and E2 were unchanged. Critically, NOER males were initially subfertile, becoming infertile with advancing age. These findings identify a previously unknown role for membrane ESR1 in the development of normal sperm and providing an adequate environment for spermatogenesis.

High-Content and Semi-Automated Quantification of Responses to Estrogenic Chemicals Using a Novel Translucent Transgenic Zebrafish

Rapid embryogenesis, together with genetic similarities with mammals, and the desire to reduce mammalian testing, are major incentives for using the zebrafish model in chemical screening and testing. Transgenic zebrafish, engineered for identifying target gene expression through expression of fluorophores, have considerable potential for both high-content and high-throughput testing of chemicals for endocrine activity. Here we generated an estrogen responsive transgenic zebrafish model in a pigment-free "Casper" phenotype, facilitating identification of target tissues and quantification of these responses in whole intact fish. Using the ERE-GFP-Casper model we show chemical type and concentration dependence for green fluorescent protein (GFP) induction and both spatial and temporal responses for different environmental estrogens tested. We also developed a semiautomated (ArrayScan) imaging and image analysis system that we applied to quantify whole body fluorescence responses for a range of different estrogenic chemicals in the new transgenic zebrafish model. The zebrafish model developed provides a sensitive and highly integrative system for identifying estrogenic chemicals, their target tissues and effect concentrations for exposures in real time and across different life stages. It thus has application for chemical screening to better direct health effects analysis of environmental estrogens and for investigating the functional roles of estrogens in vertebrates.

Oestrogen action and male fertility: experimental and clinical findings

A proper balance between androgen and oestrogen is fundamental for normal male reproductive development and function in both animals and humans. This balance is governed by the cytochrome P450 aromatase, which is expressed also under spatio-temporal control. Oestrogen receptors ERα and/or ERβ, together with the membrane-associated G-protein-coupled functional ER (GPER), mediate the effects of oestrogen in the testis. Oestrogen action in male reproduction is more complex than previously predicted. The androgen/oestrogen balance and its regulation in the masculinisation programming window (MPW) during foetal life is the most critical period for the development of the male reproductive system. If this balance is impaired during the MPW, the male reproductive system may be negatively affected. Recent data from genetically modified mice and human infertile patients have shown that oestrogens may promote the engulfment of live Leydig cells by macrophages leading to male infertility. We also discuss recent data on environmental oestrogen exposure in men and rodents, where a rodent-human distinction is crucial and analyse some aspects of male fertility potentially related to impaired oestrogen/androgen balance.

Disruption of estrogen receptor signaling and similar pathways in the efferent ductules and initial segment of the epididymis

Seminiferous tubular atrophy may involve indirectly the disruption of estrogen receptor-α (ESR1) function in efferent ductules of the testis. ESR1 helps to maintain fluid resorption by the ductal epithelium and the inhibition or stimulation of this activity in rodent species will lead to fluid accumulation in the lumen. If not resolved, the abnormal buildup of fluid in the head of the epididymis and efferent ductules becomes a serious problem for the testis, as it leads to an increase in testis weight, tubular dilation and seminiferous epithelial degeneration, as well as testicular atrophy. The same sequence of pathogenesis occurs if the efferent ductule lumen becomes occluded. This review provides an introduction to the role of estrogen in the male reproductive tract but focuses on the various overlapping mechanisms that could induce efferent ductule dysfunction and fluid backpressure histopathology. Although efferent ductules are difficult to find, their inclusion in routine histological evaluations is recommended, as morphological images of these delicate tubules may be essential for understanding the mechanism of testicular injury, especially if dilations are observed in the rete testis and/or seminiferous tubules.

Signature Lesion:

The rete testis and efferent ductules can appear dilated, as if the lumens were greatly expanded with excess fluid or the accumulation of sperm. Because the efferent ductules resorb most of the fluid arriving from the rete testis lumen, one of two mechanisms is likely to be involved: a) reduced fluid uptake, which has been caused by the disruption in estrogen receptor signaling or associated pathways; or b) an increased rate of fluid resorption, which results in luminal occlusion. Both mechanisms can lead to a temporary increase in testicular weight, tubular dilation and atrophy of the seminiferous tubules.

Fsh and Lh direct conserved and specific pathways during flatfish semicystic spermatogenesis

The current view of the control of spermatogenesis by Fsh and Lh in non-mammalian vertebrates is largely based on studies carried out in teleosts with cystic and cyclic spermatogenesis. Much less is known concerning the specific actions of gonadotropins during semicystic germ cell development, a type of spermatogenesis in which germ cells are released into the tubular lumen where they transform into spermatozoa. In this study, using homologous gonadotropins and a candidate gene approach, for which the genes' testicular cell-type-specific expression was established, we investigated the regulatory effects of Fsh and Lh on gene expression during spermatogenesis in Senegalese sole (Solea senegalensis), a flatfish with asynchronous and semicystic germ cell development. During early spermatogenesis, Fsh and Lh upregulated steroidogenesis-related genes and nuclear steroid receptors, expressed in both somatic and germ cells, through steroid-dependent pathways, although Lh preferentially stimulated the expression of downstream genes involved in androgen and progestin syntheses. In addition, Lh specifically promoted the expression of spermatid-specific genes encoding spermatozoan flagellar proteins through direct interaction with the Lh receptor in these cells. Interestingly, at this spermatogenic stage, Fsh primarily regulated genes encoding Sertoli cell growth factors with potentially antagonistic effects on germ cell proliferation and differentiation through steroid mediation. During late spermatogenesis, fewer genes were regulated by Fsh or Lh, which was associated with a translational and posttranslational downregulation of the Fsh receptor in different testicular compartments. These results reveal that conserved and specialized gonadotropic pathways regulate semicystic spermatogenesis in flatfish, which may spatially adjust cell germ development to maintain a continuous reservoir of spermatids in the testis.

Estrogen hormone physiology: reproductive findings from estrogen receptor mutant mice

Estrogen receptors (ERs) play a crucial role in reproduction and normal physiology. The two sub-types of ER (ERα and β) are expressed in various levels in different tissues and selective cell types. Gene targeting technology allowed us to produce lines of mice with disrupted ERα (αERKO) and ERβ genes (βERKO) as well as a compound αβERKO in the whole body. Male and female αERKO mice are infertile. Estrogen, EGF and IGF-1 treatments failed to induce uterine growth and DNA synthesis in αERKO uteri. αERKO females are infertile due to hypoplastic uteri and hyperemic ovaries with no corpora lutea due to persistent LH stimulation from loss of negative feedback. αERKO males are infertile, with testicular atrophy and seminiferous tubule dysmorphogenesis producing decreased spermatogenesis and inactive sperm. βERKO females show arrested folliculogenesis and subfertility. Ovarian analyses indicate differential gene expression related to ovulatory stimulation deficits including lack of LH, PR, Cyp19 and Cox2 expression. A unique ovarian phenotype is found only in αβERKO females showing transdifferentiation of granulosa cells to Sertoli cells. We describe here several novel mouse models which possess ERα gene modification. To understand ERα function in uterine endometrial epithelial cells, we generated a tissue selective ERα gene disrupted mouse model, the uterine epithelial-specific ERα knockout (UtEpiαERKO). To understand the physiological role of ERα functional domains, we generated a mouse model with a mutation in the ligand dependent transcription activation domain of ERα (AF2ERKI). Findings from the ERα mutant mice suggest that the absence of functional ERα is not lethal and results in significant endocrine effects and altered physiological processes.

Subsequent influences of feeding intact green seaweed Ulva lactuca to growing lambs on the seminal and testicular characteristics in rams

The present experiment was designed to investigate the subsequent influences of supplementing different levels of intact green seaweed Ulva lactuca (0%, 3%, and 5% DM) to growing sexually immature lambs during the growth period (74 d) on the seminal and testicular characteristics of sexually mature rams. Ulva lactuca was manually collected, adequately prepared, and then incorporated into lambs' diets. Eighteen male 3-mo-old lambs of the Awassi breed with a mean BW of 22.57 kg (SD = 1.08) were randomly assigned into treatments. The obtained results indicate that offering Ulva lactuca at the level of 3% or 5% DM to lambs during the growth period had no subsequent impacts (P > 0.05) on liver and kidney functions as well as blood water balance in rams, thereby suggesting that Ulva lactuca can be safely supplemented to lambs during growing. However, our findings point out that feeding a lamb diet supplemented with intact Ulva lactuca failed to demonstrate any subsequent benefit (P > 0.05) on the growth performance, thermoregulatory responses, and plasma oxidative status in rams. Above all, it was clearly evident that supplementing intact Ulva lactuca to lambs had demonstrated subsequent negative influences (P < 0.05) on seminal and testicular characteristics of rams, more noticeably observed at the 5% DM inclusion rate than at 3%. These results were manifested by the inferior (P < 0.05) seminal quality, reduced (P < 0.05) testicular morphometry, changes (P < 0.05) in testicular histopathology, defective (P < 0.05) endocrine signaling, and increased (P < 0.05) seminal oxidative stress in rams fed diets supplemented with Ulva lactuca during the growth period compared to control rams. The deleterious impacts of feeding intact Ulva lactuca on spermatogenesis and germ cell loss were proven to be attributed to the dysfunction of Sertoli cells. Collectively, these results provide novel insights on the subsequent influences of dietary supplementation of intact Ulva lactuca to lambs. The consistent evidence of profound negative impacts on seminal and testicular characteristics as well as the resulting data of no improvement of subsequent growth, thermoregulation, and plasma oxidative status in rams prompts us to tentatively recommend the avoidance of feeding intact Ulva lactuca to lambs.

Seminal androgens, oestradiol and progesterone in oligoasthenoteratozoospermic men with varicocele

This study aimed to assess seminal androgens, oestradiol, progesterone levels in oligoasthenoteratozoospermic (OAT) men with varicocele (Vx). In all, 154 men with matched age and body mass index were investigated that were divided into healthy fertile controls (n = 35), OAT men with Vx (n = 55), OAT men without Vx (n = 64). They were subjected to assessment of semen parameters, seminal levels of testosterone (T), androstenedione (A), 5α-androstane-3 α,17 β-diol (3 α-diol), oestradiol (E2 ), 17-hydroxyprogesterone (17-OHP) and progesterone (P). Seminal levels of T and A were significantly decreased where seminal levels of 3 α-diol, E2 , 17-OHP, P were significantly higher in OAT men with/without Vx compared with fertile controls. Sperm count, sperm motility and sperm normal forms percentage demonstrated significant positive correlation with seminal T and A and significant negative correlation with seminal 3 α-diol, E2 , P. It is concluded that in fertile men, seminal T and A are significantly increased and seminal 3 α-diol, E2 , 17-OHP, P are significantly decreased compared with infertile OAT men with/without Vx. Association of Vx demonstrated a nonsignificant influence on these hormonal levels in OAT cases. Sperm count, sperm motility and sperm normal forms demonstrated significant positive correlation with seminal T, A and significant negative correlation with seminal 3 α-diol, E2 , P.

Ketamine attenuates cytochrome p450 aromatase gene expression and estradiol-17β levels in zebrafish early life stages

Ketamine, a dissociative anesthetic, is a noncompetitive antagonist of N-methyl-D-aspartate-type glutamate receptors. In rodents and non-human primates as well as in zebrafish embryos, ketamine has been shown to be neurotoxic. In cyclic female rats, ketamine has been shown to decrease serum estradiol-17β (E2) levels. E2 plays critical roles in neurodevelopment and neuroprotection. Cytochrome p450 (CYP) aromatase catalyzes E2 synthesis from androgens. Although ketamine down-regulates a number of CYP enzymes in rodents, its effect on the CYP aromatase (CYP19) is not known. Zebrafish have been used as a model system for examining mechanisms underlying drug effects. Here, using wild-type (WT) zebrafish (Danio rerio) embryos, we demonstrate that ketamine significantly reduced E2 levels compared with the control. However, the testosterone level was elevated in ketamine-treated embryos. These results are concordant with data from mammalian studies. Ketamine also attenuated the expression of the ovary form of CYP aromatase (cyp19a1a) at the transcriptional level but not the brain form of aromatase, cyp19a1b. Exogenous E2 potently induced the expression of cyp19a1b and vtg 1, both validated biomarkers of estrogenicity and endocrine disruption, but not cyp19a1a expression. Attenuation of activated ERK/MAPK levels, reportedly responsible for reduced human cyp19 transcription, was also observed in ketamine-treated embryos. These results suggest that reduced E2 levels in ketamine-treated embryos may have resulted from the suppression of cyp19a1a transcription.

Transactivating function (AF) 2-mediated AF-1 activity of estrogen receptor α is crucial to maintain male reproductive tract function

Estrogen receptor alpha (ERα) is a ligand-dependent transcription factor containing two transcriptional activation function (AF) domains. AF-1 is in the N terminus of the receptor protein, and AF-2 activity is dependent on helix 12 of the C-terminal ligand-binding domain. We recently showed that two point mutations converting leucines 543 and 544 to alanines in helix 12 (AF2ER) minimized estrogen-dependent AF-2 transcriptional activation. A characteristic feature of AF2ER is that the estrogen antagonists ICI182780 and tamoxifen (TAM) act as agonists through intact AF-1, but not through mutated AF-2. Here we report the reproductive phenotype of male AF2ER knock-in (AF2ERKI) mice and demonstrate the involvement of ERα in male fertility. The AF2ERKI male homozygotes are infertile because of seminiferous tubular dysmorphogenesis in the testis, similar to ERα KO males. Sperm counts and motility did not differ at age 6 wk in AF2ERKI and WT mice, but a significant testis defect was observed in adult AF2ERKI male mice. The expression of efferent ductal genes involved in fluid reabsorption was significantly lower in AF2ERKI males. TAM treatment for 3 wk beginning at age 21 d activated AF-2-mutated ERα (AF2ER) and restored expression of efferent ductule genes. At the same time, the TAM treatment reversed AF2ERKI male infertility compared with the vehicle-treated group. These results indicate that the ERα AF-2 mutation results in male infertility, suggesting that the AF-1 is regulated in an AF-2-dependent manner in the male reproductive tract. Activation of ERα AF-1 is capable of rescuing AF2ERKI male infertility.

Biosensor zebrafish provide new insights into potential health effects of environmental estrogens

BACKGROUND

Environmental estrogens alter hormone signaling in the body that can induce reproductive abnormalities in both humans and wildlife. Available testing systems for estrogens are focused on specific systems such as reproduction. Crucially, however, the potential for significant health impacts of environmental estrogen exposures on a variety of body systems may have been overlooked.

OBJECTIVE

Our aim was to develop and apply a sensitive transgenic zebrafish model to assess real-time effects of environmental estrogens on signaling mechanisms in a whole body system for use in integrated health assessments.

METHODS

We created a novel transgenic biosensor zebrafish containing an estrogen-inducible promoter derived with multiple tandem estrogen responsive elements (EREs) and a Gal4ff-UAS system for enhanced response sensitivity.

RESULTS

Using our novel estrogen-responsive transgenic (TG) zebrafish, we identified target tissues for environmental estrogens; these tissues have very high sensitivity even at environmentally relevant concentrations. Exposure of the TG fish to estrogenic endocrine-disrupting chemicals (EDCs) induced specific expression of green fluorescent protein (GFP) in a wide variety of tissues including the liver, heart, skeletal muscle, otic vesicle, forebrain, lateral line, and ganglions, most of which have not been established previously as targets for estrogens in fish. Furthermore, we found that different EDCs induced GFP expression with different tissue response patterns and time trajectories, suggesting different potential health effects.

CONCLUSION

We have developed a powerful new model for understanding toxicological effects, mechanisms, and health impacts of environmental estrogens in vertebrates.

The blood-testis barrier and its implications for male contraception

The blood-testis barrier (BTB) is one of the tightest blood-tissue barriers in the mammalian body. It divides the seminiferous epithelium into the basal and the apical (adluminal) compartments. Meiosis I and II, spermiogenesis, and spermiation all take place in a specialized microenvironment behind the BTB in the apical compartment, but spermatogonial renewal and differentiation and cell cycle progression up to the preleptotene spermatocyte stage take place outside of the BTB in the basal compartment of the epithelium. However, the BTB is not a static ultrastructure. Instead, it undergoes extensive restructuring during the seminiferous epithelial cycle of spermatogenesis at stage VIII to allow the transit of preleptotene spermatocytes at the BTB. Yet the immunological barrier conferred by the BTB cannot be compromised, even transiently, during the epithelial cycle to avoid the production of antibodies against meiotic and postmeiotic germ cells. Studies have demonstrated that some unlikely partners, namely adhesion protein complexes (e.g., occludin-ZO-1, N-cadherin-β-catenin, claudin-5-ZO-1), steroids (e.g., testosterone, estradiol-17β), nonreceptor protein kinases (e.g., focal adhesion kinase, c-Src, c-Yes), polarity proteins (e.g., PAR6, Cdc42, 14-3-3), endocytic vesicle proteins (e.g., clathrin, caveolin, dynamin 2), and actin regulatory proteins (e.g., Eps8, Arp2/3 complex), are working together, apparently under the overall influence of cytokines (e.g., transforming growth factor-β3, tumor necrosis factor-α, interleukin-1α). In short, a "new" BTB is created behind spermatocytes in transit while the "old" BTB above transiting cells undergoes timely degeneration, so that the immunological barrier can be maintained while spermatocytes are traversing the BTB. We also discuss recent findings regarding the molecular mechanisms by which environmental toxicants (e.g., cadmium, bisphenol A) induce testicular injury via their initial actions at the BTB to elicit subsequent damage to germ-cell adhesion, thereby leading to germ-cell loss, reduced sperm count, and male infertility or subfertility. Moreover, we also critically evaluate findings in the field regarding studies on drug transporters in the testis and discuss how these influx and efflux pumps regulate the entry of potential nonhormonal male contraceptives to the apical compartment to exert their effects. Collectively, these findings illustrate multiple potential targets are present at the BTB for innovative contraceptive development and for better delivery of drugs to alleviate toxicant-induced reproductive dysfunction in men.

Quantitative trait analysis suggests polymorphisms of estrogen-related genes regulate human sperm concentrations and motility

BACKGROUND

Human spermatogenesis is regulated by complex networks, and estrogens are recognized as one of the significant regulators of spermatogenesis. We tested the associations between variants of estrogen-related genes and semen parameters.

METHODS

We performed genotyping for genetic variants of estrogen-related genes and quantitative trait analysis of fertile and infertile men with well-characterized reproductive phenotypes. Men with known semen parameters (n= 677) were enrolled, including 210 fertile men and 467 infertile men. A total of 17 genetic markers from 10 genes, including 2 estrogen receptors (ER-α, ER-β), 7 estrogen synthesizing/metabolizing genes (CYP19A1, HSD17B1, CYP1A1, CYP1B1, COMT, GSTM1, GSTT1) and 1 transport gene (SHBG) were genotyped. Sperm concentration, motility and morphology were taken as quantitative traits to correlate with genetic variants in the estrogen-related genes.

RESULTS

Five genes (rs1801132 and rs2228480 of the ER-α gene, rs1256049 and rs4986938 of the ER-β gene, rs605059 of the HSD17B1 gene, rs1799941 of the SHBG gene and rs1048943 and rs4646903 of the CYP1A1 gene) were found to be significantly associated with sperm concentration (P< 0.01), while five genes (rs1801132 of the ER-a gene, rs1256049 of the ER-β gene, rs1048943 of the CYP1A1 gene, rs605059 of the HSD17B1 gene and rs1799941 along with rs6259 of the SHBG gene) were associated with sperm motility (P< 0.01). None of the estrogen-related genes were associated with sperm morphology. With an increasing number of risk alleles, sperm concentration and motility tended to deteriorate and show a loci-dosage effect.

CONCLUSIONS

Quantitative trait analysis based on a limited number of genetic markers suggests that estrogen-related genes mainly regulate sperm concentration and motility.

Ex3αERKO male infertility phenotype recapitulates the αERKO male phenotype

Disruption of the Esr1 gene encoding estrogen receptor α (ERα) by insertion of a neomycin resistance gene (neo) into exon 2 (αERKO mice) was shown previously to cause infertility in male mice. While full-length ERα protein was not expressed in αERKO mice, alternative splicing resulted in the low-level expression of a truncated form lacking the N-terminus A/B domain and containing the DNA- and ligand-binding domains. Thus, it was unclear whether the reproductive phenotype in αERKO males was only due to the lack of full-length ERα or was affected by the presence of the variant ERα isoform. The present study examined male mice with deletion of exon 3 of Esr1 gene, lacking the DNA-binding domain, and null for ERα (Ex3αERKO). Dilation of some seminiferous tubules was apparent in male Ex3αERKO mice as early as postnatal day 10 and was pronounced in all tubules from day 20 onward. At 6 weeks of age, sperm numbers and sperm motility were lower in Ex3αERKO mice than in wild-type (WT) mice, and the rete testis and efferent ductules were dilated. Mating studies determined that adult Ex3αERKO males were infertile and failed to produce copulatory plugs. Serum testosterone levels and Hsd17b3 and Cyp17a1 transcript levels were significantly higher, but serum estradiol, progesterone, LH, and FSH levels and Cyp19a1 transcript levels were not significantly different from those in WT mice. These results confirm and extend those seen in other studies on male mice with deletion of exon 3 of Esr1 gene. In addition, the reproductive phenotype of male Ex3αERKO mice recapitulated the phenotype of αERKO mice, strongly suggesting that the αERKO male infertility was not due to the presence of the DNA-binding domain in the truncated form of ERα and that full-length ERα is essential for maintenance of male fertility.

Oestrogens and spermatogenesis

The role of oestrogens in male reproductive tract physiology has for a long time been a subject of debate. The testis produces significant amounts of oestrogenic hormones, via aromatase, and oestrogen receptors (ERs)alpha (ESR1) and ERbeta (ESR2) are selectively expressed in cells of the testis as well as the epididymal epithelium, depending upon species. This review summarizes the current knowledge concerning the presence and activity of aromatase and ERs in testis and sperm and the potential roles that oestrogens may have in mammalian spermatogenesis. Data show that physiology of the male gonad is in part under the control of a balance of androgens and oestrogens, with aromatase serving as a modulator.

Estradiol induction of spermatogenesis is mediated via an estrogen receptor-{alpha} mechanism involving neuroendocrine activation of follicle-stimulating hormone secretion

Both testosterone and its nonaromatizable metabolite dihydrotestosterone (DHT) induce spermatogenesis in gonadotropin-deficient hpg mice. Surprisingly, because aromatization is not required, estradiol (E2) also induces spermatogenesis and increases circulating FSH in hpg mice, but the mechanism remains unclear. We studied E2-induced spermatogenesis in hpg mice on an estrogen receptor (ER)-alpha (hpg/alphaERKO) or ERbeta (hpg/betaERKO) knockout or wild-type ER (hpg/WT) background treated with subdermal E2 or DHT implants for 6 wk. In hpg/WT and hpg/betaERKO, but not hpg/alphaERKO mice, E2 increased testis and epididymal weight, whereas DHT-induced increases were unaffected by ERalpha or ERbeta inactivation. E2 but not DHT treatment increased serum FSH (but not LH) in hpg/WT and hpg/betaERKO but not hpg/alphaERKO hpg mice. DHT or E2 alone increased (premeiotic) spermatogonia and (meiotic) spermatocytes without significant change in Sertoli cell numbers. DHT alone increased postmeiotic spermatids, regardless of ER presence, compared with variable ERalpha-dependent E2 postmeiotic responses. An ERalpha-mediated effect was confirmed by treating hpg mice for 6 wk by subdermal selective ER-alpha (16alpha-LE(2)) or ERbeta (8beta-VE(2)) agonist implants. ERalpha (but not ERbeta) agonist increased testis and epididymal weight, Sertoli cell, spermatogonia, meiotic, and postmeiotic germ cell numbers. Only ERalpha agonist markedly increased serum FSH, whereas either agonist induced small rises in serum LH. Administration of ERalpha agonist or E2 in the presence of functional ERalpha induced prominent gene expression of specific Sertoli (Eppin, Rhox5) and Leydig cell (Cyp11a1, Hsd3b1) markers. We conclude that E2-induced spermatogenesis in hpg mice involves an ERalpha-dependent neuroendocrine mechanism increasing blood FSH and Sertoli cell function.

Absence of estrogen receptor alpha leads to physiological alterations in the mouse epididymis and consequent defects in sperm function

Male mice deficient in ESR1 (ERalpha) (Esr1KO mice) are infertile, and sperm recovered from the cauda epididymis exhibit reduced motility and fail to fertilize eggs in vitro. These effects on sperm appear to result from defective epididymal function and not a direct effect on spermatogenesis, as Esr1KO germ cells transplanted into wild-type testes yield normal offspring. We hypothesized that the previously described defect in efferent duct fluid reabsorption would lead to alterations in the epididymal fluid milieu, which would negatively impact sperm function. Analysis of the epididymal fluid revealed that the Esr1KO maintains a higher luminal pH throughout the epididymis, confirming an inability of the efferent ducts and/or epididymis to properly acidify the luminal contents. Subsequent studies showed that these abnormalities were not the result of global defects in epididymal function since protein secretion by the Esr1KO epididymis appeared normal as judged by SDS-PAGE of total secreted proteins and by immunoblotting of candidate secreted proteins. To gain insight into the basis of the aberrant fluid homeostasis in the Esr1KO epididymis, the expression of several enzymes and transporters known to be involved in acid/base regulation were analyzed. The levels of SLC9A3 (NHE3) as well as carbonic anhydrase XIV and SLC4A4 (NBC1) were all reduced in the proximal portion of the Esr1KO epididymis, while other components appeared unaffected, including other ion transporters and ATP6V0A1 (V-ATPase). The altered luminal milieu of the Esr1KO epididymis was shown to lead to a corresponding increase in the intracellular pH of Esr1KO sperm, relative to sperm from control animals. Since pH and bicarbonate ions are critical regulators of sperm cAMP levels and motility, we attempted to bypass the abnormal luminal and intracellular environment by supplementing sperm with exogenous cAMP. This treatment rescued all defective motility parameters, as assayed by CASA, further showing that motility defects are not intrinsic to the sperm but, rather, result from the abnormal epididymal milieu.

QUANTITATIVE ANALYSIS OF CCR5 CHEMOKINE RECEPTOR AND CYTOCHROME P450 AROMATASE TRANSCRIPTS IN SWIM-UP SPERMATOZOA ISOLATED FROM FERTILE AND INFERTILE MEN

We determined the CCR5 chemokine receptor and cytochrome P450 aromatase (P450arom) transcript copies number in swim-up sperm isolated from fertile and infertile men. The ejaculates were purified by centrifugation through discontinuous Percoll density gradient and swim-up techniques. RNA was isolated from sperm, treated with DNase I and reverse-transcribed into cDNA. Quantitative analysis of CCR5 and P450arom cDNA were performed by real-time quantitative (RQ-PCR) SYBR Green I analysis. There was a higher content of CCR5 and P450arom transcripts copy number in swim-up sperm of fertile than from infertile donors. The decrease in CCR5 and P450arom transcripts in swim-up sperm may be associated with male infertility.

Spermatogonial culture medium: an effective and efficient nutrient mixture for culturing rat spermatogonial stem cells

An economical and simplified procedure to derive and propagate fully functional lines of undifferentiated rat spermatogonia in vitro is presented. The procedure is based on the formulation of a new spermatogonial culture medium termed SG medium. The SG medium is composed of a 1:1 mixture of Dulbecco modified Eagle medium:Ham F12 nutrient, 20 ng/ml of GDNF, 25 ng/ml of FGF2, 100 microM 2-mercaptoethanol, 6 mM l-glutamine, and a 1x concentration of B27 Supplement Minus Vitamin A solution. Using SG medium, six individual spermatogonial lines were derived from the testes of six separate Sprague-Dawley rats. After proliferating over a 120-day period in SG medium, stem cells within the spermatogonial cultures effectively regenerated spermatogenesis in testes of busulfan-treated recipient rats, which transmitted the donor cell haplotype to more than 75% of progeny by natural breeding. Subculturing in SG medium did not require protease treatment and was achieved by passaging the loosely bound spermatogonial cultures at 1:3 dilutions onto fresh monolayers of irradiated DR4 mouse fibroblasts every 12 days. Spermatogonial lines derived and propagated using SG medium were characterized as homogeneous populations of ZBTB16(+) DAZL(+) cells endowed with spermatogonial stem cell potential.

Oestradiol-induced spermatogenesis requires a functional androgen receptor

Spermatogenesis requires androgen but, paradoxically, oestradiol (E2) treatment stimulates spermatogenic development in gonadotrophin- and androgen-deficient hypogonadal (hpg) mice. The mechanisms of E2-induced spermatogenesis were investigated by determining intratesticular E2 levels and testis cell populations in E2-treated hpg male mice, and E2 spermatogenic actions were determined in androgen receptor-knockout (ARKO) mice. Despite increased serum E2 concentrations (150-300 pmol L(-1)), intratesticular E2 concentrations declined fivefold (P < 0.001) in E2-treated v. untreated hpg male mice. Serum FSH reached 40% of normal and total testicular numbers of known FSH-responsive Sertoli, spermatogonia and meiotic spermatocyte populations were significantly (P < 0.001) elevated 1.7-, 4- and 13-fold, respectively. However, E2 administration also increased androgen-dependent pachytene spermatocytes and post-meiotic spermatids to levels comparable with testosterone-treated hpg testes. Selective investigation of androgen receptor involvement used E2-treated ARKO mice, which were found to exhibit increased (1.6-fold; P < 0.05) intratesticular E2 concentrations and suppression of the elevated serum gonadotrophins, although FSH remained twofold higher than normal. However, testis size and total Sertoli, spermatogonia and spermatocyte numbers were not increased in E2-treated ARKO male mice. Therefore, E2-stimulated murine spermatogenic development occurs with markedly suppressed and not elevated intratesticular E2 levels and displays an absolute requirement for functional androgen receptors. We propose that this paradoxical E2 spermatogenic response is explained by predominantly extratesticular E2 actions, increasing FSH to combine with residual androgen activity in hpg testes to stimulate pre- to post-meiotic development.

The novel estrogen receptor, G protein-coupled receptor 30, mediates the proliferative effects induced by 17beta-estradiol on mouse spermatogonial GC-1 cell line

Many studies have indicated that estrogens could have a role in the regulation of testicular function. However, it remains uncertain whether estrogens are able to directly activate signaling pathways in male germ cells. Estrogens are synthesized by the enzyme aromatase and classically act by binding to estrogen receptors (ERs)-alpha and ERbeta. Knockout mice for both receptor isoforms exhibit a testicular phenotype that is less severe than aromatase knockout mice, suggesting the existence of an estrogen-binding receptor that may compensate for the lack of ERs. Recently studies using estrogen-sensitive tumor cell lines have demonstrated that the G-protein-coupled receptor (GPR)-30 binds and mediates estrogen action through the activation of the epidermal growth factor receptor (EGFR)/ERK/fos transduction pathway. The present study investigated the ability of 17beta-estradiol (E2) to activate this pathway in the mouse spermatogonial cell line (GC-1). Using the GC-1 cell line as a model system, we demonstrated that GC-1 cells express GPR30 and ERalpha but not ERbeta. E2, the selective GPR30 agonist G1, and the selective ERalpha agonist 4,4',4''-(4-propyl-[1H]pyrazole-1,3,5-triyl) trisphenol activated the rapid ERK1/2-fos signaling cascade. This response was abrogated by the EGFR inhibitor AG1478, ERK inhibitor PD98059 and ER inhibitor ICI 182780, or by silencing GPR30 expression. Moreover, E2 and G1 up-regulated cyclin D1 expression and GC-1 cell proliferation. Our results indicate for the first time that estrogens, through a cross talk between GPR30 and ERalpha, activate the rapid EGFR/ERK/fos pathway, which in turn stimulate mouse GC-1 cell proliferation. Further studies to elucidate the involvement of rapid estrogen signaling pathways in the regulation of male fertility are warranted.

Exposure of young rats to high estrogen doses leads to degeneration of elongated spermatids

Single high doses of estrogen (35 mg/kg body weight) were administered to young rats aiming to exacerbate its effects on germ cell populations. The short-term (1 week) and medium-term (7 weeks) consequences of this estrogenic treatment (ET) on the testis were evaluated using light and electron microscopies, quantitative methods and TUNEL reaction. Short-term ET led to 50% atrophy of the testis, however, in the medium term the gonado-somatic index was recovered. No histopathological alterations were found at seminiferous epithelium except for short-term severe degeneration of elongated spermatids (EL) and low frequency of these cells in both time intervals. Two morphologically distinct patterns of degeneration were observed: (1) clusters of EL which were TUNEL-negative and exhibited bizarre appearance and nuclear fragmentation, (2) isolated apoptotic EL within the cytoplasm of Sertoli cells (SC). Both degenerative phenomena were more frequent in stages III-VIII of seminiferous cycle, whereas at stages I and II only coiling of flagellum was observed. One week after ET, small amounts of EL were detected in stages IX-XII, suggesting spermiation failure. Signs of functional SC damage such as an accumulation of myelin-like inclusions in their cytoplasm were observed in the short but not medium-term. However, the apoptotic rates still remained five times higher and the number of elongated spermatids was three-fold lower. Our data indicate that exposure to a high dose of estrogen around puberty has stage-specific effects on the testis and causes massive degeneration of elongated spermatids.

17beta-estradiol induces the translocation of the estrogen receptors ESR1 and ESR2 to the cell membrane, MAPK3/1 phosphorylation and proliferation of cultured immature rat Sertoli cells

The aim of the present study was to determine the mechanisms involved in estrogen actions in cultured rat Sertoli cells. RT-PCR detected transcripts for the estrogen receptors ESR1 and ESR2 in cultured immature Sertoli cells and in the testis of 15-, 28-, and 120-day-old rats. The expression of ESR1 and ESR2 was confirmed in Sertoli cells by immunofluorescence and Western blot. Immunohistochemistry with cryosections of testes from immature and adult rats revealed that ESR1 is present in Sertoli, Leydig, and some peritubular myoid cells, and ESR2 is present in multiple cell types, including germ cells. Treatment of Sertoli cells with 17beta-estradiol (E(2)) induced a translocation of ESR1 and ESR2 to the plasma membrane and a concomitant phosphorylation of MAPK3/1. Both effects reached a maximum after 10 min and were blocked by PP2, an inhibitor of the SRC family of protein tyrosine kinases, and by the antiestrogen ICI 182,780 (ICI). MAPK3/1 phosphorylation was also decreased in the presence of AG 1478, an inhibitor of the epidermal growth factor receptor (EGFR) kinase, and in the presence of MAP2K1/2 inhibitor UO126. Treatment with E(2) for 24 h increased the incorporation of [methyl-(3)H]thymidine, which was blocked by ICI. These results indicate that E(2) activates an SRC-mediated translocation of estrogen receptors to the plasma membrane, which results in the activation of EGFR and the mitogen-activated protein kinase signaling pathway. In addition, activation of ESR1 and/or ESR2 by E(2) is involved in proliferation of immature Sertoli cells. The estrogen actions in Sertoli cells might be a key step mediating cellular events important for spermatogenesis and fertility.

17Beta-Estradiol Triggers Postspawning in Spermatogenically Active Gilthead Seabream (Sparus aurata L.) Males1

The testis is a tightly controlled dynamic tissue. In mammals, there is growing evidence that estrogen plays a role in the regulation of testicular functions. In teleosts, high levels of 17beta-estradiol (E2) in serum correlate with the end of spermatogenesis, spawning, and the initiation of postspawning stages when spermatogonia are the main cell types in the testis. Moreover, E2 modulates leukocyte functions in several teleost species. We hypothesized, therefore, that E2 would induce the infiltration of acidophilic granulocytes and cause a resumption of testicular cell proliferation in spermatogenically active gilthead seabream males. Several studies of this species have reported that supraphysiological doses of E2 are needed to induce histological and developmental changes in males. In fact, as gilthead seabream is a protandrous hermaphrodite teleost, long exposures (6-14 wk) to high doses of E2 result in feminization of the males. Taking all this into account, we sharply increased E2 levels during short times by i.p. injecting E2 diluted in coconut oil as the vehicle and sampled the fish after 7, 13, and 18 days to assess the effects that E2 had on spermatogenesis. It was observed that E2 levels in plasma increased, while 11-ketotestosterone (11-KT) and testosterone (T) levels remained unaltered. However, 11-KT and T levels strongly increased in control fish 18 days postinjection. The most relevant result of our study was that E2 accelerates the final events of spermatogenesis, inhibits the proliferation of spermatogonia in early stages, and induces some of the processes that usually occur during postspawning, such as the infiltration of acidophilic granulocytes and the apoptosis of primary spermatogonia. Strikingly, neither the shedding of spermatozoa nor an increase in the proliferative rate of spermatogonia stem cells was observed, probably because of the lack of other necessary stimuli, such as the increase in T levels that takes place during normal postspawning.

Effect of antispermatogenic agents on cell marker enzymes of rat Sertoli cells in vitro

OBJECTIVE

To examine the role of Sertoli cells in the antispermatogenic action of two nonsteroidal male contraceptive compounds (CDRI-84/35 and gossypol) by evaluating their effect on some key parameters of Sertoli cell function in vitro.

METHODS

Primary cultures of Sertoli cell were established from 18-day-old rat testis and treated on day 5 with different concentrations (1.0, 0.1, 0.01, and 0.001 mM) of either CDRI-84/35 or gossypol in vitro. Lactate (secretion), along with beta-glucuronidase, gamma-glutamyl transpeptidase, lactate dehydrogenase (LDH) and aromatase activities, was measured in these cells to examine the functions targeted by antispermatogenic agents in Sertoli cells.

RESULTS

CDRI-84/35 significantly affected Sertoli cell parameters (stimulation in most of the cases) that are important for germ cell development like lactate secretion, LDH activity, aromatase activity (estradiol secretion) and so on. Gossypol in comparison to CDRI-84/35 had a more severe effect on Sertoli cells with complete inhibition of enzyme activities at higher concentrations.

CONCLUSION

It is probable that the antispermatogenic action of CDRI-84/35 and gossypol is routed through Sertoli cells by disruption of important cell functions that support spermatogenesis in vivo. However, the two compounds appear to have different course of action in Sertoli cells, ultimately leading to spermatogenic failure.

Estrogen regulation of testicular function

Evidence supporting a role for estrogen in male reproductive tract development and function has been collected from rodents and humans. These studies fall into three categories: i) localization of aromatase and the target protein for estrogen (ER-alpha and ER-beta) in tissues of the reproductive tract; ii) analysis of testicular phenotypes in transgenic mice deficient in aromatase, ER-alpha and/or ER-beta gene; and, iii) investigation of the effects of environmental chemicals on male reproduction. Estrogen is thought to have a regulatory role in the testis because estrogen biosynthesis occurs in testicular cells and the absence of ERs caused adverse effects on spermatogenesis and steroidogenesis. Moreover, several chemicals that are present in the environment, designated xenoestrogens because they have the ability to bind and activate ERs, are known to affect testicular gene expression. However, studies of estrogen action are confounded by a number of factors, including the inability to dissociate estrogen-induced activity in the hypothalamus and pituitary from action occurring directly in the testis and expression of more than one ER subtype in estrogen-sensitive tissues. Use of tissue-specific knockout animals and administration of antiestrogens and/or aromatase inhibitors in vivo may generate additional data to advance our understanding of estrogen and estrogen receptor biology in the developing and mature testis.

Estrogens in males: what have we learned in the last 10 years?

This review focuses on the role of estrogen in men, mainly in male reproduction. The continuing increase in data obtained, and recent discoveries in this area will enable a better understanding of male physiology; these, in turn, will have important clinical implications.

Gene expression changes induced in the testis by transplacental exposure to high and low doses of 17{alpha}-ethynyl estradiol, genistein, or bisphenol A

The purpose of this study was to determine (1) the transcriptional program elicited by exposure to three estrogen receptor (ER) agonists: 17 alpha-ethynyl estradiol (EE), genistein (Ges), and bisphenol A (BPA) during fetal development of the rat testis and epididymis; and (2) whether very low dosages of estrogens (evaluated over five orders of magnitude of dosage) produce unexpected changes in gene expression (i.e., a non-monotonic dose-response curve). In three independently conducted experiments, Sprague-Dawley rats were dosed (sc) with 0.001-10 microg EE/kg/day, 0.001-100 mg Ges/kg/day, or 0.002-400 mg BPA/kg/day. While morphological changes in the developing reproductive system were not observed, the gene expression profile of target tissues were modified in a dose-responsive manner. Independent dose-response analyses of the three studies identified 59 genes that are significantly modified by EE, 23 genes by Ges, and 15 genes by BPA (out of 8740), by at least 1.5 fold (up- or down-regulated). Even more genes were observed to be significantly changed when only the high dose is compared with all lower doses: 141, 46, and 67 genes, respectively. Global analyses aimed at detecting genes consistently modified by all of the chemicals identified 50 genes whose expression changed in the same direction across the three chemicals. The dose-response curve for gene expression changes was monotonic for each chemical, with both the number of genes significantly changed and the magnitude of change, for each gene, decreasing with decreasing dose. Using the available annotation of the gene expression changes induced by ER-agonist, our data suggest that a variety of cellular pathways are affected by estrogen exposure. These results indicate that gene expression data are diagnostic of mode of action and, if they are evaluated in the context of traditional toxicological end-points, can be used to elucidate dose-response characteristics.

Effects of neonatal administration of 17beta-estradiol, beta-estradiol 3-benzoate, or bisphenol A on mouse and rat spermatogenesis

Bisphenol A (BPA) is a global environmental contaminant that has been implicated as a potential endocrine disruptor. In the present study, newborn rats and mice were injected subcutaneously with BPA to determine the potential developmental effects on the testis. Testes were examined by light and electron microscopy at 15 weeks of age. Other groups of newborn mice and rats were injected with 17beta-estradiol (E2) or beta-estradiol 3-benzoate (E2B) in a similar manner. BPA, E2, and E2B had similar effects on testes. When treated animals reached puberty and spermiogenesis began, the first sign of the effects was detected in the steps 2-3 spermatids: the acrosomal granule and nucleus were deformed. Henceforth, abnormalities in the acrosome and nucleus were observed in older spermatids and spermatozoa. Ectoplasmic specialization between the Sertoli cell and spermatids was also affected: some specializations were partially or totally deleted. When animals fully matured, the effects of the agents were not found in the testes, and the animals were found to be fertile. The results of the present study show that BPA acts as an estrogen, and causes changes which appear to revert in adults.

Adverse effects of bisphenol A to spermiogenesis in mice and rats

Either a 20 or 200 microg/kg body weight/injection of bisphenol A (BPA) was subcutaneously administered to adult mice and rats for 6 days, and the effects on the testes were investigated by electron and light microscopy. Abnormalities were observed in the spermatids: acrosomal vesicles, acrosomal caps, acrosomes and nuclei of the spermatids were severely deformed. The ectoplasmic specialization between the Sertoli cell and spermatids were also affected: incomplete specialization, redundant ectopic specialization and aplasia were observed. Rats and mice responded similarly to BPA. There were no dose dependencies between the 20- and 200 microg/kg body weight/injection groups. The ectoplasmic specialization between adjoining Sertoli cells, or blood-testis barrier, was not affected. Since similar adverse effects were observed when adult mice were treated with beta-estradiol 3-benzoate, the effects of BPA reported here seem to reflect the estrogenic effects on the testes. Animals kept for an additional two months after cessation of the administration were shown to be fertile and the testes showed normal histology, indicating that the adverse effects were transitory.

Lessons in estrogen biology from knockout and transgenic animals

Tremendous progress has been made in elucidating numerous critical aspects of estrogen signaling. New tools and techniques have enabled detailed molecular analysis of components that direct estrogen responses. At the other end of the spectrum, generation of a multiplicity of transgenic animals has allowed analysis of the physiological roles of the estrogen-signaling components in biologically relevant models. Here, we review the ever-increasing body of knowledge in the field of estrogen biology, especially as applied to the female reproductive processes.

Intraspecific variation in estrogen receptor alpha and the expression of male sociosexual behavior in two populations of prairie voles

Estrogen (E) regulates a variety of male sociosexual behaviors. We hypothesize that there is a relationship between the distribution of estrogen receptor alpha (ERalpha) and the degree of male social behavior. To test this hypothesis, ERalpha immunoreactivity (IR) was compared in prairie voles (Microtus ochrogaster) from Illinois (IL), which are highly social, and Kansas (KN), which are less social. The expression of androgen receptors (AR) in males also was compared between populations. The expression of ERalpha and AR were compared in brains from KN and IL males and females using immunocytochemistry (ICC). There were significant intrapopulational differences, with males expressing less ERalpha-IR than females in the medial preoptic area, ventromedial nucleus, ventrolateral portion of the hypothalamus, and bed nucleus of the stria terminalis (BST). IL males also displayed less ERalpha-IR in the medial amygdala (MeA) than IL females. While IL males expressed significantly less ERalpha-IR in the BST and MeA than KN males, there was no difference in AR-IR. Differences in the pattern of ERalpha-IR between KN and IL males were behaviorally relevant, as low levels of testosterone (T) were more effective in restoring sexual activity in castrated KN males than IL males. The lack of difference in AR combined with lower expression of ERalpha-IR in IL males suggests that behavioral differences in response to T are associated with aromatization of T to E and that reduced sensitivity to E may facilitate prosocial behavior in males.

The antiestrogen ICI 182,780 induces early effects on the adult male mouse reproductive tract and long-term decreased fertility without testicular atrophy

BACKGROUND

Estrogen receptors (ER) have important physiological roles in both the female and male reproductive systems. Previous studies using the estrogen receptor-alpha knockout mouse (alphaERKO) or antiestrogen treatment in adult rodents have shown that ERalpha is essential for normal function of the male reproductive tract. In the present study, time-response effects of the antiestrogen ICI 182,780 were determined to better understand ERalpha function in the adult male.

METHODS

Adult male mice, 30 days old, were injected subcutaneously with ICI 182,780 (5 mg) once per week for 17 weeks. Tissues were fixed by vascular perfusion to study the time responses from day 2 to 125 post treatment.

RESULTS

No difference was seen in body weight due to treatment. Testis weight was decreased 18% on day 59 and 21.4% on day 125. Other significant treatment-related effects included the following: 1) dilation of rete testis and efferent ductule lumen; 2) decreased height of the rete testis and efferent ductule epithelium; 3) decreased height of the supranuclear epithelial cytoplasm in efferent ductules; 4) decreased height of the efferent ductule epithelial microvilli, particularly in the proximal ductules; 5) decrease in the PAS-positive granules and endocytotic vesicles in nonciliated epithelial cells of efferent ductules; 6) capping and vesiculation of narrow cells in the initial segment of the epididymis; 7) accumulation of PAS-positive granules in apical cells of the caput epididymis; 8) increase in lysosomal granules in clear cells of the corpus and cauda epididymis; 9) limited induction of atrophic seminiferous tubules and abnormal spermatogenesis; and 10) decreases in the concentration of cauda sperm, progressive sperm motility and decreased fertility.

CONCLUSIONS

Antiestrogen treatment of the pubertal male mouse resulted in reproductive effects similar to those observed in the alphaERKO mouse as early as day 4; however, testis weight did not increase substantially and total atrophy was not observed with extended treatment.

Estrogen in the adult male reproductive tract: a review

Testosterone and estrogen are no longer considered male only and female only hormones. Both hormones are important in both sexes. It was known as early as the 1930's that developmental exposure to a high dose of estrogen causes malformation of the male reproductive tract, but the early formative years of reproductive biology as a discipline did not recognize the importance of estrogen in regulating the normal function of the adult male reproductive tract. In the adult testis, estrogen is synthesized by Leydig cells and the germ cells, producing a relatively high concentration in rete testis fluid. Estrogen receptors are present in the testis, efferent ductules and epididymis of most species. However, estrogen receptor-alpha is reported absent in the testis of a few species, including man. Estrogen receptors are abundant in the efferent ductule epithelium, where their primary function is to regulate the expression of proteins involved in fluid reabsorption. Disruption of the alpha-receptor, either in the knockout (alphaERKO) or by treatment with a pure antiestrogen, results in dilution of cauda epididymal sperm, disruption of sperm morphology, inhibition of sodium transport and subsequent water reabsorption, increased secretion of Cl-, and eventual decreased fertility. In addition to this primary regulation of luminal fluid and ion transport, estrogen is also responsible for maintaining a differentiated epithelial morphology. Thus, we conclude that estrogen or its alpha-receptor is an absolute necessity for fertility in the male.